U.S. patent application number 11/425832 was filed with the patent office on 2007-01-04 for methods for improved power transmission performance and compositions therefor.
Invention is credited to Ramnath N. Iyer, Tze-Chi Jao, Samuel H. Tersigni.
Application Number | 20070004603 11/425832 |
Document ID | / |
Family ID | 37124162 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070004603 |
Kind Code |
A1 |
Iyer; Ramnath N. ; et
al. |
January 4, 2007 |
METHODS FOR IMPROVED POWER TRANSMISSION PERFORMANCE AND
COMPOSITIONS THEREFOR
Abstract
Advanced methods are provided for achieving improved power
transmission performance, and unique fluid compositions useful for
practicing such methods are also presented. In particular a method
and related composition is provided for improving anti-NVH
durability in aged transmission fluids.
Inventors: |
Iyer; Ramnath N.; (Glen
Allen, VA) ; Tersigni; Samuel H.; (Glen Allen,
VA) ; Jao; Tze-Chi; (Glen Allen, VA) |
Correspondence
Address: |
NEW MARKET SERVICES CORPORATION;(FORMERLY ETHYL CORPORATION)
330 SOUTH 4TH STREET
RICHMOND
VA
23219
US
|
Family ID: |
37124162 |
Appl. No.: |
11/425832 |
Filed: |
June 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60695165 |
Jun 30, 2005 |
|
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|
Current U.S.
Class: |
508/441 ;
508/545 |
Current CPC
Class: |
C10M 2207/046 20130101;
C10N 2030/08 20130101; C10N 2040/042 20200501; C10M 2207/021
20130101; C10M 2215/02 20130101; C10M 2219/104 20130101; C10M
2207/028 20130101; C10M 2215/28 20130101; C10M 141/10 20130101;
C10M 2209/104 20130101; C10M 2215/042 20130101; C10M 2223/049
20130101; C10M 2219/046 20130101; C10N 2060/12 20130101; C10M
2207/262 20130101; C10N 2030/76 20200501; C10M 169/047 20130101;
C10N 2030/02 20130101; F16H 57/04 20130101; C10M 2215/04 20130101;
C10N 2030/06 20130101; C10M 163/00 20130101; C10M 2209/104
20130101; C10M 2209/109 20130101; C10M 2215/28 20130101; C10N
2060/12 20130101; C10M 2215/28 20130101; C10N 2060/12 20130101 |
Class at
Publication: |
508/441 ;
508/545 |
International
Class: |
C10M 133/06 20060101
C10M133/06; C10M 137/04 20060101 C10M137/04 |
Claims
1. A fluid composition, comprising: (1) a major amount of a base
oil, and (2) a minor amount of an additive composition comprising
alkoxylated amine, dihydrocarbyl phosphite, metallic detergent,
phosphorylated succinimide, tertiary fatty amine, and ethoxylated
alcohol, in respective amounts effective for providing sustained
anti-NVH durability upon aging in a power transmission lubricated
therewith.
2. The fluid composition of claim 1, comprising 0.002-0.5 wt %
alkoxylated amine, 0.001-0.5 wt % dihydrocarbyl phosphite, 0.01-1.0
wt % metallic detergent, 0.01-12 wt % phosphorylated succinimide,
0.005-1.0 wt % long chain tertiary amine, and 0.01-0.7 ethoxylated
alcohol.
3. The fluid composition of claim 1, comprising 0.01-0.25 wt %
alkoxylated amine, 0.01-0.2 wt % dihydrocarbyl phosphite, 0.01-0.7
wt % metallic detergent, 0.01-10 wt % phosphorylated succinimide,
0.01-0.7 wt % long chain tertiary amine, and 0.01-0.5 ethoxylated
alcohol.
4. The fluid composition of claim 1, wherein the additive
composition is present in an amount of about 3 wt % to about 20 wt
%, based on the fluid composition.
5. The fluid composition of claim 1, wherein the additive
composition is present in an amount of about 5 wt % to about 15 wt
%, based on the fluid composition.
6. The fluid composition of claim 1, wherein the fluid composition
is formulated such that the fluid composition comprises a viscosity
at 100.degree. C. of <6 cSt, a viscosity at 40.degree. C. of
<30 cSt, and a Brookfield Viscosity at -40.degree. C. of
<10,000 cP, and wherein the fluid, when aged at 150.degree. C.
for 200 hours, has a variation in coefficient of friction at
testing rpm ranging from 50 to 300 of less than about 0.015 as
determined from measurements taken on an SAE #2 Machine using a
paper friction material lined clutch plate and testing conditions
of 0.79N/mm.sup.2.
7. The fluid composition of claim 1, wherein the fluid composition
is formulated such that the fluid composition comprises a viscosity
at 100.degree. C. of <6 cSt, a viscosity at 40.degree. C. of
<30 cSt, and a Brookfield Viscosity at -40.degree. C. of
<10,000 cP, and wherein the fluid has a quasistatic friction
greater than 0.098 and static friction of 0.123 or greater as
measured on a ZF GK rig.
8. The fluid composition of claim 1, wherein the fluid composition
is formulated such that the fluid composition comprises a viscosity
at 100.degree. C. of <6 cSt, a viscosity at 40.degree. C. of
<30 cSt, and a Brookfield Viscosity at -40.degree. C. of
<10,000 cP, and wherein an NVH characteristic of the fluid
composition has a threshold pressure value greater in value than
0.8N/mm.sup.2 as measured on a ZF GK rig.
9. The fluid composition of claim 8, wherein the NVH characteristic
is squawk.
10. The fluid composition of claim 1, wherein the fluid composition
is formulated such that the fluid composition comprises a viscosity
at 100.degree. C. of <6 cSt, a viscosity at 40.degree. C. of
<30 cSt, and a Brookfield Viscosity at -40.degree. C. of
<10,000 cP, and wherein an NVH characteristic of the fluid after
exposure to oxidizing conditions does not decrease in value below
the initial value of the NVH characteristic value before the
exposure as measured on a ZF GK rig.
11. The fluid composition of claim 1, wherein the base oil
comprises one or more of a natural oil, a mixture of natural oils,
a synthetic oil, a mixture of synthetic oils, a mixture of natural
and synthetic oils, and a base oil derived from a Fischer-Tropsch
or gas-to-liquid process.
12. The fluid composition of claim 1, wherein the additive
composition further comprises one or more of a additional friction
modifier, an additional detergent, an additional dispersant, an
antioxidant, an antiwear agent, an antifoam agent, a viscosity
index improver, a copper corrosion inhibitor, an anti-rust
additive, a seal swell agent, a metal deactivator, and an air
expulsion additive.
13. An additive composition comprising an alkoxylated amine,
dihydrocarbyl phosphite, metallic detergent, phosphorylated
succinimide, tertiary fatty amine, and ethoxylated alcohol, in
respective amounts effective for providing sustained anti-NVH
durability upon aging in a power transmission apparatus lubricated
therewith.
14. A method of improving anti-NVH durability in a power
transmission apparatus having a friction torque transfer apparatus,
comprising lubricating the friction torque transfer apparatus with
a fluid composition comprising alkoxylated amine, dihydrocarbyl
phosphite, metallic detergent, phosphorylated succinimide, tertiary
fatty amine, and ethoxylated alcohol, in respective amounts
effective for providing sustained anti-NVH durability upon aging in
the power transmission lubricated therewith.
15. The method of claim 14, wherein the friction torque transfer
apparatus is selected from the group consisting of a shifting
clutch, a starting clutch, a torque converter clutch, a band
clutch, disk or plate clutch, and a limited slip differential
clutch.
16. The method of claim 14, wherein the friction torque transfer
apparatus comprises a shifting clutch.
17. A method for improving anti-NVH durability performance in a
power transmitting apparatus comprising: 1) adding a fluid to a
power transmitting apparatus, said fluid comprising (a) a base oil,
and (b) an additive package comprising alkoxylated amine,
dihydrocarbyl phosphite, metallic detergent, phosphorylated
succinimide, tertiary fatty amine, and ethoxylated alcohol; and 2)
operating the fluid in the power transmitting apparatus, wherein
the additive package being present in an amount effective for
providing improved anti-NVH durability upon aging in the power
transmission lubricated therewith.
18. The method of claim 17, wherein the fluid composition is
formulated such that the fluid composition comprises a viscosity at
100.degree. C. of <6 cSt, a viscosity at 40.degree. C. of <30
cSt, and a Brookfield Viscosity at -40.degree. C. of <10,000 cP,
and wherein the fluid, when aged at 150.degree. C. for 200 hours,
has a variation in coefficient of friction at testing rpm ranging
from 50 to 300 of less than about 0.015 as determined from
measurements taken on an SAE #2 Machine using a paper friction
material lined clutch plate and testing conditions of
0.79N/mm.sup.2 at 150.degree. C. for 200 hours, and wherein an NVH
characteristic of the fluid after exposure to oxidizing conditions
does not decrease in value below the initial value of the NVH
characteristic before the exposure as measured on a ZF GK rig.
19. A transmission containing the fluid composition of claim 1.
20. The transmission of claim 19, wherein the transmission
comprises a continuously variable transmission.
21. The transmission of claim 19, wherein the transmission
comprises a dual clutch transmission.
22. The transmission of claim 19, wherein the transmission
comprises an automatic transmission.
23. The transmission of claim 19, wherein the transmission
comprises a manual transmission.
24. The transmission of claim 19, wherein the transmission
comprises one or more of an electronically controlled converter
clutch, a slipping torque converter, a lock-up torque converter, a
starting clutch, and one or more shifting clutches.
25. The transmission of claim 19, wherein the transmission
comprises a belt, chain, or disk-type continuously variable
transmission, a 4-speed or more automatic transmission, a manual
transmission, an automated manual transmission, or a dual clutch
transmission.
26. A vehicle comprising an engine and a transmission, the
transmission including the fluid composition of claim 1.
Description
[0001] This application claims the benefit of priority of U.S.
Provisional Application No. 60/695,165, filed on Jun. 30, 2006.
FIELD OF THE INVENTION
[0002] The present disclosure relates to methods for providing
improved power transmission performance and fluid compositions
suitable for use in power transmission applications.
BACKGROUND OF THE INVENTION
[0003] An automatic transmission in a vehicle generally includes a
multiple disk clutch in which a plurality of friction plates, each
having a friction material bonded to a surface of a metal substrate
(core plate), and a plurality of separator plates, each constituted
by a single plate or more, are arranged in an alternating sequence.
In an automatic transmission lubricated with transmission fluid,
these plates are frictionally connected/disconnected to/from one
another so that driving force is transmitted/released. Wet friction
materials used in transmission clutches have included paper
friction materials, carbon fiber friction materials, elastomeric
friction materials, sintered friction metals, and so forth. The
term "wet", in this general context, refers to a friction material
wetted with transmission fluid.
[0004] New and advanced transmission systems are being developed by
the automotive industry. These new systems often involve
high-energy requirements. Component protection technology must be
developed to meet the increasing energy requirements of these
advanced systems. Commercially, it is known to add various additive
packages to automatic transmission fluid, including, among other
things, extreme pressure agents, antiwear agents, antioxidant
systems, corrosion inhibitor systems, metal deactivators, anti-rust
agents, friction modifiers, dispersants, detergents, anti-foam
agents, and/or viscosity index improvers. However, not all
additives interact predictably or well with one another. The
friction properties are particularly important in clutches that
need more friction to transfer torque but less friction in gears,
bearings and seals. As a lubricant in a transmission, the fluid
used in the clutches is also in the gears. Reducing friction in the
gears, bearings and seals increases the lives of these components
and improves fuel mileage, but reduces torque capacity of the
clutch and the ability to transmit power. When friction is reduced,
higher clutch forces are needed to achieve sufficient torque
capacity, which can lead to mechanical failures.
[0005] An important performance requirement for an automatic
transmission fluid is the ability to prevent noise, vibration, and
harshness, i.e., "NVH" for purposes herein, from occurring in the
clutches of a transmission. Automotive power transmission fluids
are being called upon to provide specific frictional properties
under very demanding conditions of temperature and pressure. For
instance, multiple plate disk clutches are used extensively for
shifting gears in automatic transmissions under high static and
quasi-static friction conditions. During shifting, one or more
clutches is engaging or disengaging. In these active clutches the
automatic transmission fluid and friction material experience
substantial changes in pressure, temperature, and sliding speed.
The frictional interaction of the automatic transmission fluid and
friction material is a function of these variables, so the
coefficient of friction has tended to change during clutch
engagement. Changes in a fluid's frictional properties as a
function of relative sliding speed, temperature, or pressure as a
result of these conditions may lead to performance degradation in
the vehicle "feel" that is readily discernible to the vehicle
operator and passengers. Such discernible effects may include shift
chatter or squawk in the shifting clutches, shudder or vibration in
slipping torque converter clutches, and/or harsh shifts ("gear
change shock"), collectively referred to as "NVH" herein.
Frictional properties of a fluid ideally would be selected to
suppress NVH in the clutches. Moreover, an automatic transmission
fluid ideally would reduce occurrence of NVH without compromising
the frictional properties needed for good shifting performance. For
instance, the static friction level is important in an automatic
transmission where the clutch pack must have sufficient holding
capacity to transmit power from the engine to the wheels. In
addition, conventional automatic transmission fluids can be highly
susceptible to significant loss of the desired frictional
properties as they age, and an ideal fluid would address that
consideration as well.
[0006] There is a need for transmission fluids that reduce NVH
while maintaining high static and quasi-static friction, and/or
which have improved anti-NVH durability upon aging, especially
under conditions of high temperatures and pressures. Such fluids
would minimize equipment and performance problems while maximizing
the interval between fluid changes. By enabling smooth engagement
of torque converter and shifting clutches, these fluids would
minimize NVH, and in some cases improve fuel economy, over a longer
fluid lifetime.
SUMMARY OF THE INVENTION
[0007] The present invention relates to the advanced methods for
providing enhanced power transmission performance, and unique fluid
compositions useful for practicing such methods.
[0008] In one embodiment, there is a fluid composition and
associated method of using same for improving anti-NVH durability
in aging or aged fluids used in the operation of a power
transmission apparatus having a friction torque transfer apparatus,
wherein the friction torque transfer apparatus is lubricated with a
unique fluid composition comprising alkoxylated amine,
dihydrocarbyl phosphite, metallic detergent, phosphorylated
succinimide, tertiary fatty amine, and ethoxylated alcohol, in
respective amounts effective therefor. In one particular
embodiment, this fluid composition comprises about 0.002 to about
0.5 wt % alkoxylated amine, about 0.001 to about 0.5 wt %
dihydrocarbyl phosphite, about 0.01 about to 1.0 wt % overbased
metal salt, about 0.01 to about 12 wt % phosphorylated succinimide,
about 0.005 to about 1.0 wt % long chain tertiary amine, and about
0.01 to about 0.7 ethoxylated alcohol. This unique composition
maintains a relatively uniform frictional interaction at a friction
plate of a clutch even after being aged.
[0009] In a particular embodiment, where the above-described unique
fluid is aged as tested on a SAE #2 Machine using a paper friction
material lined clutch plate and testing conditions at 150.degree.
C. for 200 hours, the fluid has a variation in coefficient of
friction at test rpm values ranging from 50 to 300 of less than
about 0.015. By contrast, the effects of aging on a comparable
commercial reference ATF product tested under similar conditions
have been observed to be significantly greater, wherein it
experiences approximately twice the variation in the coefficient of
friction than that of the inventive formulation. In one embodiment,
the fluid has quasi-static friction greater than 0.098 and static
friction of 0.123 or greater, as measured on a ZF GK rig. In
another embodiment, the fluid has an anti-NVH characteristic having
a threshold pressure value greater in value than 0.8 N/mm.sup.2 as
measured on a ZF GK rig. In another embodiment, the fluid has an
anti-NVH characteristic which, after exposure to oxidizing
conditions, does not decrease in value below the initial value of
the anti-NVH characteristic value before the exposure as measured
on a ZF GK rig.
[0010] In one particular embodiment, the transmission fluid
composition comprises about 0.002 to about 0.5 wt % alkoxylated
amine, about 0.001 to about 0.5 wt % dihydrocarbyl phosphite, about
0.01 to about 1.0 wt % metallic detergent, about 0.01 to about 12
wt % phosphorylated succinimide, 0.005-1.0 wt % long chain tertiary
amine, and 0.01-0.7 ethoxylated alcohol. These components may be
introduced into a fluid composition predominantly comprising base
oil as an additive concentrate or composition in amount of about 3
wt % to about 20 wt %, particularly about 5 wt % to about 15 wt %,
based on the overall fluid composition. Nominally, the alkoxylated
amine and dihydrocarbyl phosphite are friction modifiers; the
metallic detergent has detergent effects; the phosphorylated
succinimide is an ashless dispersant; the long chain tertiary amine
is a surfactant/friction modifier; and the ethoxylated alcohol is a
non-ionic surfactant; however, their combination in effective
amounts also has been found to bring about the above-mentioned
improvement in anti-NVH durability of aging or aged fluids used in
the operation of a power transmission apparatus having a friction
torque transfer apparatus. These additive and fluid compositions
also have been developed for lubricating transmissions to maintain
high static and quasi-static friction properties while continuing
to suppress NVH even after the fluid composition ages.
[0011] Also described herein are methods of reducing NVH in a power
transmission apparatus having a friction torque transfer apparatus,
comprising maintaining a negative
.differential..mu./.differential.T slope during engaging, slipping
or modulating thereof, where ".mu." represents coefficient of
friction and "T" represents temperature. In one embodiment, the
reduction obtained in NVH may be achieved in the form of a
reduction of one or more of shift chatter, shudder, vibrations
and/or harshness relative to a reference fluid comprising a
commercial ATF product. Under preselected conditions, this negative
.differential..mu./.differential.T slope has been found to be
maintainable without loss of static and quasi-static friction
properties of the friction torque transfer apparatus during
engaging, slipping or modulating thereof. In one aspect,
appropriate selection of a transmission fluid formulation for
lubricating a friction torque transfer apparatus during operation
of the transmission apparatus is responsible for providing the
condition of a negative .differential..mu./.differential.T during
engaging, slipping or modulating of the friction torque transfer
apparatus.
[0012] The discovery that providing and maintaining a negative
.differential..mu./.differential.T slope during engaging, slipping
or modulating of a friction torque transfer apparatus can reduce
NVH is surprising and runs counter to the conventional theoretical
thinking in the power transmission field. The present investigators
also have discovered that merely using a transmission fluid in the
operation of a power transmission which yields a positive slope of
coefficient of friction (.mu.) versus sliding velocity (v) is
inadequate to significantly suppress and control NVH. It has
surprisingly been discovered that the transmission fluid run in the
transmission must possess a negative friction dependence on
temperature in the operation of the friction torque transfer
mechanism of the power transmission to suppress NVH in a meaningful
manner. In one embodiment, this applies to prevention of NVH (e.g.,
chatter, squawk, shudder, and/or noise) during the engagement of a
friction torque transfer mechanism, such as a shifting clutch. It
ensures a smooth shift in a clutch when plate temperature at the
friction interface is rising during engagement. Provision of
negative .differential..mu./.differential.T condition in a
transmission makes it possible to raise the overall value of the
coefficient of friction at essentially all or all sliding speeds
and at the same time prevent squawk, shudder and chatter from
occurring in the clutches. It also prevents lock-up when a limited
amount of slipping is desired, as is often the case in a torque
converter clutch or a limited slip differential clutch. The
negative .differential..mu./.differential.T condition is important
in formulating higher coefficient of friction and higher torque
capacity fluids that will still suppress NVH. The significant
improvements in torque capacity and NVH suppression may also make
it possible for transmissions which are smaller and/or operate at
lower pressure, all of which improve fuel economy. The discovered
significance of the negative .differential..mu./.differential.T
condition is not necessarily limited to any particular modality for
providing this prescribed performance condition.
[0013] The above-indicated inventive methodology of providing
improved friction durability and/or the negative
.differential..mu./.differential.T condition in a power
transmission is applicable to a friction torque transfer apparatus
in general, including, for example, a shifting clutch, a starting
clutch, a torque converter clutch, a band clutch, disk or plate
clutch, a limited slip differential clutch, and so forth. The types
of power transmission in which the inventive methodology may be
applied are not particularly limited, and include, e.g., automatic
transmissions, manual transmissions, continuously variable
transmissions, and manual automatic transmissions, and so forth.
These transmissions may be used in a variety of applications such
as automotive, marine, aerospace, industrial, and so forth. In a
particular embodiment, the inventive method is applied to a
multi-speed automatic transmission, such as a 4-speed or more
transmission. In one embodiment, it may be selected from the group
consisting of a 5-speed automatic transmission, a 6-speed automatic
transmission, and a 7-speed automatic transmission, and
particularly 6-speed automatic transmissions. The transmission
apparatus also may comprise a dual-clutch transmission or a heavy
duty automatic transmission.
[0014] As can be appreciated from these foregoing descriptions and
the descriptions and experimental studies reported infra, this
invention also provides a fluid composition for power transmissions
employing a friction torque transfer apparatus which can meet
requirements for high static and quasi-static friction while also
minimizing tendency for NVH phenomena which otherwise may arise.
The fluid compositions of the present invention are advantageously
suited for use in friction torque transfer devices requiring higher
quasi-static friction conditions, which have an increased tendency
for NVH phenomena.
[0015] The foregoing general description and the following detailed
description are exemplary and explanatory only and are intended to
provide further explanation of the present invention, as
claimed.
BRIEF DESCRIPTION OF THE FIGURES
[0016] FIG. 1 is a diagram of a power train model for clutch
engagement in accordance with an embodiment of the invention.
[0017] FIG. 2 is a graph of a unit impulse response of a 2.sup.nd
Order LTI system of a power train model according to an embodiment
of the invention.
[0018] FIG. 3 is a graph of a unit step response of a 2.sup.nd
Order LTI system of a power train model according to an embodiment
of the invention.
[0019] FIGS. 4-10 are plots of squawk pressure versus
.differential..mu./.differential.T as measured at different sliding
speeds at a pressure of 0.79N/mm.sup.2, respectively. The
respective sliding speeds at which measurements were taken were as
follows: FIG. 4 (5 rpm); FIG. 5 (10 rpm); FIG. 6 (20 rpm); FIG. 7
(50 rpm); FIG. 8 (100 rpm); FIG. 9 (200 rpm); and FIG. 10 (250
rpm).
[0020] FIG. 11 is plot of R.sup.2 (for correlation of
.differential..mu./.differential.T to squawk pressure) versus
sliding speed (v, rpm) for the tests of FIGS. 4-10 conducted at the
test pressure condition of 0.79N/mm.sup.2.
[0021] FIGS. 12-17 are plots of squawk pressure versus
.differential..mu./.differential.T as measured at different sliding
speeds at a pressure of 3.40N/mm.sup.2, respectively. The
respective sliding speeds at which measurements were taken were as
follows: FIG. 12 (5 rpm); FIG. 13 (10 rpm); FIG. 14 (20 rpm); FIG.
15 (50 rpm); FIG. 16 (100 rpm); and FIG. 17 (200 rpm).
[0022] FIGS. 18-19 show coefficient of friction .mu. results
observed for the eight test fluids at a pressure of 0.79N/mm.sup.2
and at temperatures of 40.degree. C. and 120.degree. C.,
respectively.
[0023] FIG. 20 is a plot of coefficient of
.differential..mu./.differential.T (reported as a value that has
been multiplied by the number negative one, i.e., "x-1") versus
sliding speed (v, rpm) at a pressure of 0.79N/mm.sup.2.
[0024] FIGS. 21-28 are plots of squawk pressure versus
.differential..mu./.differential.P as measured at different sliding
speeds, temperatures and pressures. For FIGS. 21-24,
.differential..mu./.differential.P was measured at 40.degree. C.
between 3.40 and 0.79N/mm.sup.2 at sliding speeds of 5, 50, 200 and
250 rpm, respectively. For FIGS. 25-28,
.differential..mu./.differential.P was measured at 120.degree. C.
between 3.40 and 0.79N/mm.sup.2 at sliding speeds of 5, 50, 200 and
250 rpm, respectively.
[0025] FIG. 29 shows plots of R.sup.2 versus sliding speed (v, rpm)
for the data reported in FIGS. 21-28, at temperatures of 40.degree.
C. and 120.degree. C., respectively.
[0026] FIG. 30 is a plot of coefficient of friction versus sliding
speed (v, rpm) for an aged test fluid formulated in accordance with
an embodiment of the present invention as compared to an aged
commercial ATF.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Vehicles meeting stringent demands of consumers require
durability and performance in all of the vehicular systems. One of
the most important systems is the power transmission system
("transmission") which transmits the power generated by the
automobile engine to the wheels. It being one of the most complex
systems in the vehicle, it is also one of the most costly to
diagnose, repair, or replace. The transmission usually includes,
inter alia, a clutch with plates, a torque converter, and a
plurality of gears to alter the torque and speed relationship of
the power delivered to the wheels by changing the gear ratio.
[0028] Discriminating consumers primarily desire ride comfort, high
performance, low maintenance (high mileage between servicing), and
extended life expectancy. However, with the advent of new
transmission technologies, old standards of performance which were
previously met with approval are now becoming more challenging and
problematic.
[0029] For instance, the advent of electronically controlled
converter clutch (ECCC) designs, as well as vehicles equipped with
a continuously variable transmission (CVT) and advances in
aerodynamic body design generally result in passenger cars with
smaller transmissions which tend to operate with higher energy
densities and higher operating temperatures. Consumers also are
keenly aware of the "feel" of the driving experience that a vehicle
offers. Unusual, abnormal or unexpected vehicular noises,
vibrations, and/or ride harshness make the driving experience less
comfortable. Consumers also want service intervals for replacing
fluids to be extended as much as possible without risking
performance or engine equipment integrity. Such changes challenge
lubricant suppliers to formulate automatic transmission fluids with
new and unique performance characteristics. Original equipment
manufacturers (OEMs) also desire automatic transmission fluids with
frictional characteristics capable of meeting the requirements of
ECCC, CVT, and other designs while retaining sufficient performance
in regard to anti-NVH, durability, antiwear, etc.
[0030] As power transmission fluids are desired which operate under
increasingly severe conditions, the fluids used to lubricate those
transmissions ideally would be formulated not only to endure higher
temperatures and pressures, but also control NVH. To reduce
equipment problems and increase the interval between transmission
fluid changes, the transmission additive packages ideally would be
formulated so that important fluid properties change as little as
possible during a service life in the face of these stresses.
[0031] A need exists for an effective way of addressing friction,
wear and durability problems associated with automatic
transmissions, such as to meet the needs of OEM automobile
designers and suppliers, for extended transmission fluid life and
durability while also improving anti-NVH control to increase
consumer satisfaction. This invention addresses these and other
needs.
[0032] In one particular non-limiting embodiment, a method is
provided for reducing noise-vibration-harshness ("NVH") in a power
transmission apparatus having a shifting clutch, comprising
maintaining a negative .differential..mu./.differential.T slope
during engagement of the shifting clutch. How this condition is
achieved in the transmission is not particularly limited. It may be
achieved via a novel approach in formulating the transmission
fluid, as described in more detail elsewhere herein.
[0033] The reduction obtained in NVH may be achieved in the form of
a reduction of one or more of shift shudder, chatter, squawk, or
similar noise, vibration and/or harshness, relative to a reference
fluid comprising a commercial ATF product. Under preselected
conditions, this negative .differential..mu./.differential.T slope
has been found to be maintainable without loss of static and
quasi-static friction properties at the shifting clutch during
engagement.
[0034] For purposes herein, "NVH" collectively refers to
noise-vibration-harshness as those terms are defined herein. "NVH
suppression" refers to a reduction in one or more of noise,
vibration, and/or harshness. Chatter, shudder and squawk all
originate from a vibration(s) within the transmission system and
generally are compound parameters comprised of noise and vibration
"Shift chatter", "chatter noise" or "chatter" for short, refers to
a NVH parameter that is generally balanced in being observed as
both noise and vibration. "Squawk" refers to an NVH parameter
predominantly observed as noise and less as vibration. "Squawk
pressure" is measured on a ZF GK test rig apparatus, which is
commercially available from the ZF Group, Friedrichshafen Germany.
The clutch designated by the test rig supplier as the "E-clutch" of
a ZF 6HP26 transmission is used in the ZF GK test rig. A test fluid
and friction elements are loaded where applicable in the ZF GK test
rig. The test rig includes an on-board computer with a
programmable, graphical user interface that permits the user to
select and input the desired test conditions under which squawk,
static friction and quasi-static friction are to be measured, and
the test results are stored by the system in retrievable formats.
The ZF-GK Rig test performed on the apparatus is a test developed
by ZF to measure slip controlled clutch opening and closing
performance characteristics. An interchangeable intermediate shaft
allows the measurement of frictional vibration that is the basis
for evaluation of NVH characteristics such as squawk of the test
fluid. The test uses a procedure supplied by ZF with the apparatus.
For purposes herein, squawk pressure, and is expressed in terms of
the threshold pressure beyond which squawk phenomena are observed.
The higher the value of this parameter the lower the probability
for the noise or vibration phenomena to occur for a given fluid.
Illustrations set forth herein may refer to squawk or "squawk
pressure", although it will be appreciated that the invention has
broader application to noise and vibration (NVH) phenomena in
general. Additionally, "Shudder" refers to an NVH parameter
predominantly observed as vibration and less as noise. Harshness"
refers to NVH phenomena that are predominantly sudden (e.g., shock,
jerk, clunk, impulse, pop, jolt, bang, etc.) and which may be
experienced by occupants as a sudden, and perhaps brief, noise or
vibration or both. "Harshness" is also used by some practitioners
to refer to the cumulative effects of noise and vibration on
occupant comfort and fatigue (thus, e.g., a driver is less
comfortable and tends to become fatigued more rapidly in a vehicle
with greater harshness). "Static friction" refers to breakaway
static coefficient of friction; values thereof described herein are
measured on a ZF GK rig. "Quasi-static friction" refers to dynamic
end-point coefficient of friction; values thereof described herein
are measured on a ZF GK test rig. In general it was found that the
noise phenomena decreases with decreasing quasi-static friction
level. Higher quasi-static friction is generally desirable for
higher torque transmission. "Operating", as used herein, includes,
but is not limited to, any functional utilization of the fluid
including transmitting power, lubricating, and wetting.
[0035] The discovery that providing and maintaining a negative
.differential..mu./.differential.T slope during engagement of the
shifting clutch can reduce NVH represents a surprising discovery in
the power transmission field. The present investigators also have
discovered that merely using a transmission fluid in the operation
of a power transmission which yields a positive slope of
coefficient of friction (.mu.) versus sliding velocity (v) is
inadequate to significantly suppress and control NVH. It has
surprisingly been discovered that the transmission fluid used in
the transmission must induce a negative friction dependence on
temperature in the engagement of the clutching mechanism of the
power transmission to suppress NVH in a meaningful manner. This
particularly applies, e.g., to prevention of shift shudder,
chatter, or squawk during the engagement of a clutch. It ensures a
smooth shift in a clutch when plate temperature at the friction
interface is rising during engagement. Provision of negative
.differential..mu./.differential.T condition in a transmission
makes it possible to raise the overall value of the coefficient of
friction at essentially all or all sliding speeds and at the same
time prevent squawk, shudder and chatter from occurring in the
clutches. The negative .differential..mu./.differential.T condition
is important in formulating higher coefficient of friction and
higher torque capacity fluids that will still suppress NVH. The
significant improvements in torque capacity and NVH suppression may
also make it possible for transmissions to be smaller and/or
operate at lower pressure, all of which improve fuel economy. The
discovered significance of the negative
.differential..mu./.differential.T condition is not necessarily
limited to any particular modality for providing this prescribed
performance condition.
[0036] As another discovery of the present invention, NVH-reduction
is obtained in a power transmission apparatus having a friction
torque transfer apparatus by maintaining a negative
.differential..mu./.differential.P slope during engaging, slipping
or modulating thereof.
[0037] More detail on the mathematical underpinnings of the above
unique approaches to modeling a transmission system is provided
below. Mathematical models of friction properties in clutches
suggest that the sign (positive or negative) of the slope of the
friction coefficient ".mu." with respect to temperature "T",
.differential..mu./.differential.T, or pressure,
.differential..mu./.differential.P, has opposite effects depending
on whether the clutch is engaging or disengaging. For example,
having a positive .differential..mu./.differential.T helps to
prevent vibrations when the clutch is releasing, but may promote
unstable vibrations when the clutch is engaging. Consequently, the
conventional wisdom in the lubricant additive industry is that the
lubricant's friction coefficient should be made independent of
temperature and pressure as much as possible.
I. Noise Phenomena Model
[0038] The present invention is based in part on a new and in-depth
understanding of the specific applications of automatic
transmission fluids to identify which characteristic is more
important so that .mu.-T and .mu.-P dependencies can be exploited
to improve the automatic transmission fluid's ability to suppress
unstable vibrations.
[0039] Multiple plate disk clutches are used extensively for
shifting gears in automatic transmissions. During a shift one or
more clutches is engaging or disengaging. In these active clutches
the automatic transmission fluid (ATF) and friction material
experience large changes in pressure, P, temperature, T, and
sliding speed, v. The coefficient of friction, .mu., of the ATF and
friction material is a function of these variables so .mu.(v,T,P)
also changes during clutch engagement. These changes in friction
coefficient can lead to NVH phenomena such as shift shudder,
chatter or squawk if the ATF properties and clutch friction
material are improperly selected.
[0040] An in-depth theoretical understanding of the cause of NVH in
shifting clutches is crucial in the development of a suitable ATF
to work with a particular friction material. A model has been
developed that identifies the relationships between ATF friction
properties and NVH phenomena such as squawk. In particular,
friction slope with respect to temperature,
.differential..mu./.differential.T, is identified as a primary
factor in squawk. During clutch engagement negative
.differential..mu./.differential.T increases the damping and
reduces the risk of self-excited vibration. Experimental data,
described below, has been collected which corroborate this model.
The effect of .differential..mu./.differential.T on clutch release
and the effects of other ATF friction properties are also
discussed.
[0041] A vehicle power train experiences a combination of torsional
and axial vibrations that affect vehicle performance and occupant
comfort. These vibrations and their effects are major contributors
to noise, vibration and harshness (NVH). Sources of NVH include
engine firing pulses, valve motion, engine vibrations (torsional
and axial), and tire-road interactions--any of which can excite
resonance in the vehicle. Vibrations from these sources are
transferred through engine mounts, transmission bearings, drive
shaft bearings, tires (via steering) and axle suspensions to the
passenger compartment by way of the vehicle frame, steering wheel
or brake pedal. For purposes herein, driveline vibrations from
clutch engagement were analyzed during a gear shift and it was
determined how the friction related properties of the ATF and
friction material affect them. The model of temperature in the
friction interface and the dependence of the coefficient of
friction (".mu.") on temperature ("T") are major enhancements to
the understanding of the effect of friction properties on the
stability (smoothness) of clutch engagement during a gear shift.
TABLE-US-00001 TABLE A Nomenclature Symbol Description A Total
friction surface area = number of friction interfaces in multiple
plate clutch .times. area of each surface c.sub.d, c.sub.t
Intrinsic damping in driveline, turbine c.sub.d* Effective damping
in driveline with changes in .mu.(v, P, T) c.sub.ps Specific heat
of steel reaction plate .differential..mu./.differential.v,
.differential..mu./.differential.P,
.differential..mu./.differential.T Partial derivatives of .mu.(v,
P, T) with respect to v, P and T I.sub.d, I.sub.t, I.sub.e
Equivalent inertias of driveline, turbine, engine k.sub.d Driveline
stiffness L Thickness of steel reaction plate (m) .mu.(v, P, T)
Coefficient of friction of ATF and friction material P(t) Pressure
applied (released) to shifting clutch to increase (decrease) torque
R Effective radius of friction bands in the clutch (constant) .rho.
Density (kg/m.sup.3) of the steel reaction plate t Time duration of
sliding contact in clutch T.sub.TC Total torque transferred by
torque converter and torque converter clutch T.sub.CL = .mu.ARP
Torque transferred by shifting clutch T Temperature of ATF and
friction material .tau. Time constant of sliding speed response:
v(t) = v.sub.0e.sup.-t/.tau. v(t) = R(.omega..sub.t(t) -
.omega..sub.d(t)) Linear sliding speed in the shifting clutch
.omega..sub.d(t), .omega..sub.e(t), .omega..sub.t(t) Driveline,
engine, and turbine rotational speeds .omega..sub.v Constant
reference speed at opposite end of clutch output shaft
[0042] The major components of an automotive power train equipped
with an automatic transmission are shown in FIG. 1. The engine
transfers power to the transmission through the torque converter
(TC) and torque converter clutch (TCC). The engine has inertia
I.sub.e and turns at speed .omega..sub.e(t). The turbine includes
the components from the torque converter (excluding components tied
to the engine) to the clutch pack involved in the shift. The
specific clutch involved in the shift is arbitrary as long as only
one clutch is engaging, as is typical. The specific values of the
model parameters depend on which gears are involved. Components
past the clutch are part of the driveline. The turbine components
have inertia I.sub.t, viscous damping c.sub.t and speed
.omega..sub.t(t), and are considered rigid (infinitely stiff)
relative to the driveline. The driveline has inertia I.sub.d,
damping c.sub.d, stiffness k.sub.d, and angular velocity
.omega..sub.d(t). The vehicle is represented as having a constant
speed during the shift. The constant speed .omega..sub.v may be
chosen to represent any point of interest, e.g., the gear end of
the clutch output shaft. The specific gears involved in the shift
and the choice of reference speed location affect how the inertias
of the driveline components are distributed, some included in
I.sub.d and some in the vehicle, and the values of the damping and
stiffness parameters, but they do not affect the friction
characteristics or fundamental dynamics of the system.
[0043] Before an up-shift occurs the turbine is connected to the
vehicle by the previous gear with a higher gear ratio, so the
turbine initially rotates at a higher speed than the representative
vehicle speed, .omega..sub.t(0)>.omega..sub.v. When the
transmission shifts to a higher gear one clutch pack disengages and
another engages, and the NVH phenomena under consideration are
caused by friction in the engaging clutch plates. The torque
transfer from the engine to the turbine is through the torque
converter (TTC), which has two parallel torque paths--the fluid
coupling between the pump and turbine impellers and the friction
torque in the torque converter clutch (TCL). The clutch torque is
controlled by pressure and the ATF friction characteristics. The
model represents that the vibrations as predominantly torsional,
although axial effects that might influence the motion can be
introduced as pressure oscillations that cause forced torsional
vibrations.
[0044] For analyzing squawk and shudder vibrations, in this study
focus is limited to the driveline. The engine and turbine motions
can become unstable, but since they are considered rigid (relative
to the flexible driveline) they are not sources of vibration.
[0045] From Newton's second law the driveline equation of motion
is: I d .times. .omega. . d = T CL - c d .function. ( .omega. d -
.omega. v ) - k d .times. .intg. 0 t .times. ( .omega. d .function.
( .tau. ) - .omega. v ) .times. .times. d .tau. ( 1 ) ##EQU1##
where the instantaneous clutch torque is: TC.sub.L=.mu.ARP(t)
(2)
[0046] The integral of the velocity difference between the two ends
of the clutch output shaft gives the total twist in the shaft. The
twist in the shaft multiplied by the shaft stiffness equals the
reaction torque of the shaft on inertia I.sub.d.
[0047] Traditional stability analysis about an equilibrium
condition is inappropriate for the unsteady (non-equilibrium)
conditions during a gear shift. However, if the velocity is
sufficiently damped the shift will not experience vibrations due to
step or ramp changes in pressure. (There can be forced vibrations
if there are pressure oscillations.) Consequently, an additional
time derivative of equation (1) is taken to transform it into a
second order differential equation in the variable .omega..sub.d,
which represents the output angular velocity of the clutch, and to
consider the effective damping of the equation.
[0048] The time derivative of .omega..sub.v is zero since it is
constant, and the derivative is the inverse of the integration, so
taking the derivative of equation (1), applying the chain rule to
T.sub.CL (=.mu.ARP) and rearranging terms yields: I.sub.d{umlaut
over (.omega.)}.sub.d+c.sub.d{dot over
(.omega.)}.sub.d+k.sub.d.omega..sub.d=k.sub.d.omega..sub.v+{dot
over (.mu.)}ARP+.mu.AR{dot over (P)} (3)
[0049] The coefficient of friction, .mu.(v,T(v),P), is a function
of sliding speed, v, pressure, P, and temperature, which also
depends on sliding speed, T=T(v). Consequently, the time derivative
of .mu. is: .mu. . = .differential. .mu. .differential. v .times. v
. + .differential. .mu. .differential. T .times. d T d v .times. v
. + .differential. .mu. .differential. P .times. P . ( 4 ) ##EQU2##
Sliding speed: v=R(.omega..sub.t-.omega..sub.d) so: {dot over
(v)}=R(.sub.t-{dot over (.omega.)}.sub.d) (5) Using equations (4)
and (5), equation (3) becomes: I d .times. .omega. d + c d *
.times. .omega. . d + k d .times. .omega. d = k d .times. .omega. v
+ AR .function. ( .mu. + P .times. .differential. .mu.
.differential. P ) .times. P . + AR 2 .times. P .function. (
.differential. .mu. .differential. v + .differential. .mu.
.differential. T .times. d T d v ) .times. .omega. . t ( 6 )
##EQU3## where the effective damping is given by c d * = c d + AR 2
.times. P .function. ( .differential. .mu. .differential. v +
.differential. .mu. .differential. T .times. d T d v ) ( 7 )
##EQU4## Instantaneous temperature variations at the friction
interface may be modeled approximately as: dT = 2 .times. .times.
.mu. .times. .times. vP .rho. .times. .times. c ps .times. L dt ( 8
) ##EQU5## and instantaneous variations in sliding speed are: dv =
v . dt .times. .times. so ( 9 ) d T d v = 2 .times. .times. .mu.
.times. .times. P .rho. .times. .times. c ps .times. L .times. v v
. ( 10 ) ##EQU6## Substituting equation (10) into (6) and (7), the
equation of motion becomes: I d .times. .omega. d + c d * .times.
.omega. . d + k d .times. .omega. d = k d .times. .omega. v + AR
.function. ( .mu. + P .times. .differential. .mu. .differential. P
) .times. P . + AR 2 .times. P .function. ( .differential. .mu.
.differential. v + .differential. .mu. .differential. T .times. 2
.times. .times. .mu. .times. .times. P .rho. .times. .times. c ps
.times. L .times. v v . ) .times. .omega. . t ( 11 ) ##EQU7## and
the effective damping is: c d * = c d + AR 2 .times. P .function. (
.differential. .mu. .differential. v + .differential. .mu.
.differential. T .times. 2 .times. .times. .mu. .times. .times. P
.rho. .times. .times. c ps .times. L v v . ) ( 12 ) ##EQU8##
[0050] Equations (11) and (12) describe the relationship between
ATF friction properties, .differential..mu./.differential.v and
.differential..mu./.differential.T, and shift quality as measured
by the output speed of the clutch.
[0051] The clutch output speed is determined by the forcing terms
on the right hand side of equation (11), by the damping coefficient
equation (12), and by the inertia (I.sub.d) and stiffness (k.sub.d)
coefficients. Equation (11) is a 2.sup.nd order differential
equation in the unknown motion variable .omega..sub.d. When the
coefficients (I.sub.d, c.sub.d*, k.sub.d) of the unknown motion
variable are all constant, the equation is referred to as "linear"
and "time-invariant" (LTI). The time-invariance refers to the
coefficients. The motion variable does vary with time. If the
coefficients are time-dependent, but do not depend on the motion
variable, the equation is still linear, but not time-invariant.
Equation (11) is both nonlinear (the damping coefficient, c.sub.d*,
depends on the unknown motion variable) and time-variant (the
damping coefficient changes with time). It is not typically
possible to find analytical solutions to nonlinear time-varying
equations; computer solutions are generally required. Nevertheless,
if the nonlinearity or time-variance is not strong, it is often
possible to approximate the solution of a nonlinear time-varying
equation with the solution of an LTI equation. Here the behavior of
2.sup.nd order LTI systems to impulse and step inputs is first
considered, then the implications of the nonlinear damping
coefficient are considered.
[0052] The "inputs" to an equation are the terms on the
right-hand-side that force the system to deviate from some
equilibrium condition. In equation (11) the final equilibrium
condition is reached when all terms with time derivatives are zero
(none of the variables are changing with time), and the clutch
output speed, .omega..sub.d, is equal to the constant reference
speed, .omega..sub.v, due to the first input k.sub.d.omega..sub.v,
which is constant. The second or middle input on the
right-hand-side of (11) is referred to here as the {dot over (P)}
input, and the right-most input is referred to as the {dot over
(.omega.)}.sub.t input.
[0053] The engagement of the clutch is controlled through the
pressure, P. If P is zero the clutch output shaft is not connected
to the turbine, and the {dot over (P)} and {dot over
(.omega.)}.sub.t inputs are zero. In a typical engagement, the
pressure is "stepped up" quickly to connect the turbine to the
clutch output shaft. This has the effect of switching the {dot over
(.omega.)}.sub.t input from zero to nonzero. If this nonzero value
remained constant it would look like a stair step and be called a
"step input." The sudden jump in P makes the {dot over (P)} input
very large for a very brief period of time, and then it returns to
zero when P reaches its constant target value. This is an "impulse
input;" a sudden hit with high amplitude but short duration.
[0054] The solution of 2.sup.nd order LTI systems (the "response"
of the system) to impulse and step inputs depends primarily on the
damping ratio, .zeta., which for equation (11) is: .zeta. = c d * 2
.times. k d .times. I d ( 13 ) ##EQU9## treating the damping
coefficient c.sub.d* as constant. A 2.sup.nd order system is
typically classified according to its damping ratio and the
corresponding free response to an initial displacement with no
force inputs on the right-hand-side:
[0055] .zeta.<0 Negative damping, unstable (response amplitude
increases with time)
[0056] .zeta.=0 Undamped, non-decaying vibrations at the natural
frequency
[0057] 0<.zeta.<1 Underdamped, decaying vibrations at the
damped natural frequency
[0058] .zeta.=1 Critically damped, minimum damping level to
suppresses vibration. With critically damped and overdamped systems
it is still possible to have vibration if the inputs create
"forced" vibration. It is also possible to get one oscillation in
the free response if the initial velocity is in the opposite
direction of the initial displacement.
[0059] .zeta.>1 Overdamped, no vibration, but slower convergence
to steady state than in the critically damped case (.zeta.=1).
[0060] If the system starts from equilibrium (a constant or steady
speed in this case), the vibration characteristic of the free
response also applies to the impulse and step responses. To
completely suppress transient vibration it is necessary for the
system to be critically damped or overdamped.
[0061] FIGS. 2 and 3 show the predicted response of a LTI 2.sup.nd
order system (clutch output speed in rad/s) to unit impulse and
unit step inputs ("unit" inputs have an amplitude of `1`) for three
different damping ratios. The parameter values used for the
simulations are: I d = 2 .times. .times. kg m 2 ##EQU10## .times. k
d = 12 .times. , .times. 700 .times. , .times. 000 .times. .times.
N m / rad .times. ( natural .times. .times. frequency = 401 .times.
.times. Hz ) c .times. d * = 1 , 008 .times. .times. N m s / rad
.times. ( .zeta. = 0.1 , underdamped ) .times. 10 .times. , .times.
080 .times. .times. N m s / rad .times. ( .zeta. = 1.0 , critically
.times. .times. damped ) .times. 15 .times. , .times. 120 .times.
.times. N m s / rad .times. ( .zeta. = 1.5 , overdamped ) .
##EQU10.2##
[0062] All of these are stable responses. The clutch output speed
converges to the desired value. Stability, however, is insufficient
to ensure a smooth shift without vibrations. To suppress vibration
for impulse and step inputs it is necessary to have a damping
coefficient that provides critical or overdamping
(.zeta..gtoreq.1): c*.sub.d.gtoreq.2 {square root over
(k.sub.dI.sub.d)} (14)
[0063] Equation (14) shows that to suppress NVH cd* in equation
(12) should be as positive as possible. NVH during a shift is
evidence that equation (14) is not satisfied, not necessarily that
the system is unstable, although it may be.
[0064] The nonlinearity and time-variation in c.sub.d* is driven
largely by v and {dot over (v)}. Once P is applied it is held
relatively constant, and the variation in .mu. is much smaller than
the variation in v and {dot over (v)}. It also is assumed that
.differential..mu./.differential.T is relatively constant. The
sliding speed during shift follows an approximately exponential
decay: v(t)=v.sub.0e.sup.-t/.tau. (15) where .tau. is the "time
constant," a measure of how quickly the sliding speed converges
from initial speed, v.sub.0, to zero.
[0065] If the sliding speed has the form given in equation (15),
then the rate of change of sliding speed is: v . .function. ( t ) =
- v 0 .tau. .times. e - t / .tau. ( 16 ) ##EQU11## and the v/{dot
over (v)} ratio in equations (11) and (12) ratio is: v .function. (
t ) v . .function. ( t ) = - .tau. ( 17 ) ##EQU12## where .tau. is
a positive constant. Equation (17) suggests that even though v and
{dot over (v)} depend on the unknown speeds .omega..sub.d and
.omega..sub.t (and their derivatives), the ratio v/{dot over (v)}
does not. In this case c.sub.d* no longer depends on the unknown
variable of motion and the equation is linear, although it may
still vary with time.
[0066] In this case equations (11) and (12) may be simplified
further to: I d .times. .omega. d + c d * .times. .omega. . d + k d
.times. .omega. d = k d .times. .omega. v + AR .function. ( .mu. +
P .times. .differential. .mu. .differential. P ) .times. P . + AR 2
.times. P .function. ( .differential. .mu. .differential. v -
.differential. .mu. .differential. T .times. 2 .times. .mu. .times.
.times. P .times. .times. .tau. .rho. .times. .times. c p .times.
.times. s .times. L ) .times. .omega. . t ( 18 ) c d * = c d + AR 2
.times. P .function. ( .differential. .mu. .differential. v -
.differential. .mu. .differential. T .times. 2 .times. .mu. .times.
.times. P .times. .times. .tau. .rho. .times. .times. c p .times.
.times. s .times. L ) ( 19 ) ##EQU13##
[0067] Equation (19) demonstrates that
.differential..mu./.differential.T must be negative to increase the
damping. All the parameters in the expression multiplying
.differential..mu./.differential.T are positive, so
.differential..mu./.differential.T is the only parameter that can
be made negative to ensure that c.sub.d* is as positive as
possible. If the magnitude of the negative
.differential..mu./.differential.T becomes too large (in absolute
value), torque capacity may become reduced. Thus, small negative
values of .differential..mu./.differential.T are particularly
desirable.
[0068] The .differential..mu./.differential.v term in equation (19)
is the .mu.-v gradient at constant temperature, which should also
be as positive as possible. The .differential..mu./.differential.T
term is the contribution of the ATF temperature dependence to the
total .mu.-v gradient, d.mu./dv. The contribution of
.differential..mu./.differential.T to the overall damping depends
on the temperature rise in the fluid, which is controlled by the
heat generation (.mu.vP), the thermal capacity of the steel
reaction plate (.rho.c.sub.psL), and the duration of the shift
(larger .tau. means a longer shift time). In general, the more
negative .differential..mu./.differential.T the greater the damping
at all sliding speeds and pressures, and consequently, the greater
NVH suppression, e.g., greater squawk resistance, that is predicted
and expected from the model.
[0069] Experimental data, described in the Examples below, confirm
this predictive model insofar as the provision of negative
.differential..mu./.differential.T condition improves squawk
performance in a transmission.
[0070] The coefficients of .differential..mu./.differential.T in
the exponential curve fits shown FIGS. 4-10, which are discussed in
more detail in the Examples section, provide an additional
validation of the temperature model in equation (8), and the
resulting damping equation (12). This coefficient represents the
degree to which the .differential..mu./.differential.T term
controls stability, and should have the same dependencies as the
parameters multiplying .differential..mu./.differential.T in
equation (12). One of those parameters is the sliding speed, v,
which was also one of the experimental parameters. Equation (12)
predicts that the damping should be approximately proportional to
v. The coefficients of .differential..mu./.differential.T from the
curve fits in the FIGS. 4-10 are plotted versus sliding speed in
FIG. 20, which shows good linear correlation as predicted. The
model also predicts that the factor multiplying
.differential..mu./.differential.T will increase with pressure.
FIG. 20 gives one data point at a higher pressure (3.4 MPa), which
shows the expected increase.
[0071] From equation (12) it is indicated that positive
.differential..mu./.differential.T is desired for smooth
disengagement since {dot over (v)} is positive when the clutch
releases. However, when the clutch releases the pressure drops and
there is no input energy (turbine torque) to cause self-excitation.
The shaft will unwind when it is no longer carrying torque, so
there is a risk of vibration due to this unwinding. There is also a
risk that for a controlled release--an effort to carefully exchange
the load between the releasing and engaging clutches--negative
.differential..mu./.differential.T may cause a faster than expected
drop in torque in the releasing clutch.
[0072] These risks will generally be much less than the risk of
engagement vibrations since energy absorbed by the clutch and the
heat generated are much greater during engagement. On
disengagement, the damping should not become negative because there
is no source of energy to create that unstable condition.
[0073] The squawk engagements are performed at constant pressure,
so it is difficult to discern how important
.differential..mu./.differential.P might be from squawk test data.
The importance of .differential..mu./.differential.P on shift
quality depends on how the transmission control unit applies the
pressure. If the pressure is stepped up suddenly then held
constant, as in the squawk test, .differential..mu./.differential.P
will not be particularly important. If the pressure is ramped up,
linearly or exponentially, then .differential..mu./.differential.P
may also be important. If pressure and sliding speed change
together in a predictable way, then, following the same analysis as
for temperature, the damping term will include
(.differential..mu./.differential.P)(dP/dv) so that equation (19)
becomes: c d * = c d + AR 2 .times. P .function. ( .differential.
.mu. .differential. v - .differential. .mu. .differential. T
.times. 2 .times. .mu. .times. .times. P .times. .times. .tau.
.rho. .times. .times. c p .times. .times. s .times. L +
.differential. .mu. .differential. P .times. d P d v ) ( 20 )
##EQU14##
[0074] Typically an increase in pressure (positive dP) causes a
decrease in sliding speed (dv negative) so that (dP/dv) is
negative. Consequently, if .differential..mu./.differential.P has
any effect, it is beneficial for it to be negative. Squawk pressure
versus .differential..mu./.differential.P was plotted and a very
slight correlation was found between increased squawk pressure
(better performance) and negative
.differential..mu./.differential.P. FIG. 20 includes a plot of some
of those coefficients. It shows that
.differential..mu./.differential.P is much less important for
squawk performance than .differential..mu./.differential.T, but
that is expected since the pressure is approximately constant.
[0075] Plots of squawk pressure versus
.differential..mu./.differential.T in FIGS. 4-10 show that there is
a general trend for .differential..mu./.differential.T to decrease
in magnitude (converge toward zero) at increasing sliding speeds.
In test fluids with negative .differential..mu./.differential.T the
value of .differential..mu./.differential.T was more negative a
lower sliding speeds and less negative at higher sliding speeds.
Consequently, .differential..mu./.differential.T is dependent on
sliding speed. This may also be interpreted as temperature
dependence since sliding speed and temperature are linearly related
(for constant P as in the squawk tests) according to the equation
(8) model.
[0076] Although not desiring to be bound to theory, it is more
likely that the reduction in .differential..mu./.differential.T
(FIGS. 4-10) is temperature dependence for at least two reasons.
First, the sliding speeds referred to in the plots are sliding
speeds from the SAE#2 test, not clutch engagement sliding speeds
from the squawk test. Consequently, the sliding speeds are really
indicating the amount of friction work and heating in the SAE #2
test. Second, the values of .differential..mu./.differential.T at
higher pressure are also reduced in magnitude. Equation (8) says
that higher pressure also creates more heat, so the pressure
dependence in .differential..mu./.differential.T from the SAE #2
data may also be temperature dependence. All the data are
consistent with the interpretation that
.differential..mu./.differential.T decreases in magnitude (becomes
less negative) as temperature increases.
[0077] The effect of .differential..mu./.differential.T decreasing
(in magnitude) with increasing temperature is that the contribution
of the .differential..mu./.differential.T term to the damping in
equation (12) decreases during engagement. However, as long as
.differential..mu./.differential.T remains negative it still
contributes to positive damping and improves the smoothness and
stability of the shift. Furthermore, since the variation in
.differential..mu./.differential.T with temperature is linear and
predictable, it is easily handled by the transmission control
module.
[0078] Accordingly, physical and mathematical models are presented
herein of the mechanical components in a transmission involved in
the shifting of a clutch. The clutch torque is modeled with a
coefficient of friction that depends on sliding speed, temperature
and pressure: .mu.=.mu.(v, T, P). A major advance in this model is
that the temperature rise in the clutch interface is modeled, which
is shown to be proportional to the product .mu.vP (heat generation
per unit area) and inversely proportional to {dot over (v)} (the
rate of change of sliding speed) and .rho.c.sub.psL (the thermal
mass or heat capacity of the steel reaction plate).
[0079] The most significant conclusion of the analysis is that it
is important for .differential..mu./.differential.T, a property of
the ATF and friction material, to be negative to ensure a smooth,
stable shift. It is shown that negative
.differential..mu./.differential.T increases the damping in the
system during engagement and that increased damping reduces the
risk of vibration. The equations of motion are solved using several
sample sets of data (for illustrative purposes; not based on actual
data) and plots show the reduction in vibration with increased
damping.
[0080] Experimental data, summarized in FIGS. 4-10 also validate
several key elements of the model. In particular, with respect to
the fluid tested, the data show a strong correlation between
improved squawk performance and more negative
.differential..mu./.differential.T. Furthermore, the curve fits of
squawk performance to .differential..mu./.differential.T show that
the contribution of .differential..mu./.differential.T to squawk
performance (increased damping) is linearly proportional to sliding
speed, which is predicted by the model. Sliding speed is the
dominant parameter controlling the heat generation and temperature
(in .mu.vP) since P is constant and the changes in .mu.are small
compared to the changes in v. The data suggest that
.differential..mu./.differential.T becomes less negative as the
temperature increases (higher P, sliding at constant higher v), so
that the contribution of .differential..mu./.differential.T to the
damping diminishes during the shift. This trend can be tolerated as
long as .differential..mu./.differential.T does not become positive
during engagement.
[0081] The model indicates that negative
.differential..mu./.differential.T has the reverse effect when the
clutch releases. It reduces the damping and increases the risk of
negative damping. When the clutch releases there is also the
likelihood of vibration arising due to unwinding of the shaft as
the torque on it is released. Both of these effects can be reduced
by allowing the pressure to drop quickly. In that case the
.differential..mu./.differential.T term in the damping expression
goes to zero, so .differential..mu./.differential.T does not
contribute to negative damping. Also, dropping the pressure takes
the shaft out of the driveline so that any transient "unwinding"
vibrations are not in the torque path of the power train. This
solution is less attractive when there is a control strategy to
gradually shift the torque transfer from the releasing to the
engaging clutch. In this case the calibration engineer needs to
determine the rate of pressure drop in the releasing clutch based
on how long the releasing clutch can remain stable.
[0082] The present invention recognizes that for shifting clutches
the engagement is the critical process, not the release or
disengagement. In the case of shifting clutch, the primary heat and
pressure increases occur when the clutch is engaging. During
disengagement the pressure and "apply" force are dropping so there
is much less heat generation. Consequently, lubricants can be
specifically formulated with negative values of and
.differential..mu./.differential.T (and
.differential..mu./.differential.P) in order to suppress noise and
vibration during engagement. This runs counter to the conventional
wisdom in the lubricant additive industry that seeks to make the
lubricant's coefficient of friction, .mu. as independent of P and T
as possible, which is based on a failure to recognize which process
(engagement or release of the clutch) is more critical.
[0083] Furthermore, since negative
.differential..mu./.differential.T make it possible to suppress
noise and vibration during clutch engagement, this technology will
also allow the formulation of lubricants with higher overall levels
of friction (.mu.), so that the torque capacity of the clutches
(and the whole transmission) in increased. Alternatively, higher
levels of friction permit transmission calibration engineers to
reduce the operating pressure in the transmission without
sacrificing the torque capacity, which improves fuel economy and
prolongs the life of lubricant and the mechanical components. Also,
higher levels of friction permit smaller transmissions to be used
without compromising torque capacity, which also improves fuel
economy, weight, and material cost.
[0084] Although illustrated herein by way of a shifting clutch, it
will be appreciated that the above-indicated inventive methodology
of providing negative .differential..mu./.differential.T, or
negative .differential..mu./.differential.P, condition in a power
transmission is applicable to friction torque transfer apparatus in
general, including, for example, a shifting clutch, a starting
clutch, a torque converter clutch, a band clutch, disk or plate
clutch, a limited slip differential clutch, and so forth. The types
of power transmission in which the inventive methodology may be
applied are not particularly limited, and include, e.g., automatic
transmissions, manual transmissions, continuously variable
transmissions, and manual automatic transmissions, and so forth. A
friction torque apparatus may also operate in different modes, such
as continuously slipping, modulating on-off, and engaging from
slipping to lock-up, These transmissions may be used in a variety
of applications such as automotive, marine, aerospace, industrial,
and so forth. In a particular embodiment, the inventive method is
applied to a multi-speed automatic transmission, such as a 4-speed
or more transmission. In one embodiment, it may be selected from
the group consisting of a 5-speed automatic transmission, a 6-speed
automatic transmission, and a 7-speed automatic transmission, and
particularly 6-speed automatic transmissions. The transmission
apparatus also may comprise a dual-clutch transmission or a heavy
duty automatic transmission.
[0085] In the instance of a shifting clutch as the friction torque
transfer apparatus, the clutch may comprise a lining material
comprising any suitable wet friction material such as paper, steel,
carbon, or elastomeric, etc. Paper friction materials for clutch
liners are commercially available. They generally are produced by
the steps of making wet paper from a fiber base material of natural
pulp fiber, organic synthetic fiber, inorganic fiber, etc. and a
filler and friction adjustor such as diatomaceous earth, gum, etc.;
impregnating the wet paper with a resin binder of a heat-curable
resin; and thermally hardening the wet paper. One observation of
the invention is that paper friction materials tend to be harder
than carbon fiber friction materials, and that variation in
pressure does not influence squawk as significantly as variation in
temperature with respect to clutches lined with paper friction
materials.
II. ATF Compositions
[0086] In one aspect, appropriate selection of a transmission fluid
formulation for lubricating a shifting clutch or other friction
torque transfer apparatus during operation of the transmission
apparatus is responsible for providing the condition of a negative
.differential..mu./.differential.T (or negative
.differential..mu./.differential.P) during engagement of the
shifting clutch. That is, additive and fluid compositions have been
developed for transmissions to provide high static and quasi-static
friction properties while minimizing NVH characteristics such as
shift noise, shudder, chatter and squawk. These compositions are
also effective at providing the same degree of NVH suppression
performance after aging of the fluid. Although the additive
composition components described below are described occasionally
with reference to a function, that function may be one of other
functions served by the same component and should not be construed
as a mandatory limiting function.
[0087] A. Additive Package I for Enhanced Anti-NVH Performance:
[0088] In one embodiment, an anti-NVH performance-improving
additive package comprises four critical components: alkoxylated
amine friction modifier, dihydrocarbylphosphite friction modifier,
metallic detergent, and phosphorylated succinimide ashless
dispersant.
[0089] Experimental studies were conducted, which are summarized in
more detail in the Examples section herein, which revealed that
these four components of an automatic transmission fluid are
primarily responsible for influencing the
.differential..mu./.differential.T (and
.differential..mu./.differential.P) values observed. In particular,
properly balanced combinations of these four particular components
have been discovered to have the unexpected combined effect of
bringing about the negative .differential..mu./.differential.T
slope condition during engaging, slipping or modulating of a
friction torque transfer apparatus of the transmission apparatus,
which condition surprisingly has been found to provide NVH
suppression without quasi-static or static friction losses of
significance. Indeed, it has been observed that providing even
relatively small negative .differential..mu./.differential.T values
yield very significant improvements in anti-NVH. Although higher
magnitude negative .differential..mu./.differential.T values also
may provide some additional incremental improvements in anti-NVH,
the most significant gains in NVH suppression generally can be
attained at relatively small negative
.differential..mu./.differential.T conditions. The respective
amounts of these four components needed to attain the negative
.differential..mu./.differential.T slope condition generally are
governed by the experimental discovery and observation that the
presence of alkoxylated amine, dihydrocarbyl phosphite, and
metallic detergent independently increase the negative value of
.differential..mu./.differential.T, i.e., make it more negative,
while a decreasing level thereof has the opposite effect on
.differential..mu./.differential.T, i.e., makes it less negative
(i.e., a negative value of smaller absolute magnitude or a
positive-value). On the other hand, increasing amounts of the
phosphorylated succinimide component make
.differential..mu./.differential.T less negative, while decreasing
amounts have the opposite effect. Levels of these four components
must be balanced with above criteria in mind to introduce a
negative .differential..mu./.differential.T condition, preferably a
small negative .differential..mu./.differential.T condition for
improving anti-NVH performance, among other things. Lesser included
combinations of these four components will not behave reliably in
the above indicated manner.
[0090] Component (A): Friction Modifier (1)
[0091] Component (A) comprises an alkoxylated amine friction
modifier which is used in the additive package and transmission
fluids of the present invention. Increasing the level of this
component in the transmission fluid has been found to make
.differential..mu./.differential.T more negative, and decreasing
its level has the opposite effect.
[0092] The alkoxylated amines which may be utilized in the practice
of this invention are preferably primary aliphatic amines that have
been ethoxylated or propoxylated. The resultant product is thus an
N,N-bis(hydroxyalkyl)-N-aliphatic amine in which the aliphatic
group is preferably an alkyl or alkenyl group containing from 10 to
22 carbon atoms, most preferably an alkyl or alkenyl group
containing from 16 to 18 carbon atoms.
N,N-bis(hydroxyethyl)-N-tallow amine is especially preferred.
Examples of suitable alkoxylated amine friction modifiers are
described, for example, in U.S. Pat. No. 4,855,074, which
descriptions are incorporated herein by reference.
[0093] The alkoxylated amine compounds of the invention should be
used at a concentration of about 0.002 wt % to about 0.5 wt %,
particularly about 0.01 wt % to about 0.25 wt %, to insure that the
finished blend contains an adequate quantity of the foregoing
ingredient although smaller amounts may be successfully employed,
depending on the relative amounts of components (B), (C) and
(D).
[0094] Component (B): Friction Modifier (2)
[0095] Dihydrocarbylphosphites are used as an additional friction
modifier in the additive package and transmission fluids of the
present invention. Increasing the level of this component in the
transmission fluid has been found to make
.differential..mu./.differential.T more negative, and decreasing
its level has the opposite effect.
[0096] As used herein "hydrocarbyl" is an alkyl, alkaryl, aralkyl,
alkenyl, cycloalkyl or cycloalkenyl group. Dihydrocarbylphosphites
usable in this invention include phosphite derivatives such as
dialkylphosphites, dicycloalkylphosphites, diallyl phosphites,
diarylphosphites, diaralkylphosphites, monoalkylmonoarylphosphites,
and the like. Illustrative compounds of this type include
dimethylphosphite, diethylphosphite, dipropyl phosphite,
dibutylphosphite, dioctylphosphite, dicyclohexylphosphite,
diphenylphosphite, dioleyl phosphite, methyl oleyl phosphate, butyl
lauryl phosphate, ethyl hexyl phosphate, napthyl oleyl phosphite,
dibenzylphosphite, phenylneopentylphosphite, diamyl phosphate,
dihexyl phosphate, diheptyl phosphate, di-2-ethylhexyl phosphate,
diisoctyl phosphate, didecyl phosphate, dilauryl phosphate,
didecenyl phosphate, didodecenyl phosphate, distearyl phosphate,
dieicosyl phosphate, dicresyl phosphate, dicyclohexenyl phosphate,
and dinonylphenyl phosphite and any combinations of the above.
Examples of suitable dihydrocarbyl phosphite friction modifiers are
described, for example, in U.S. Pat. Nos. 4,855,074, and 4,588,415,
which descriptions are incorporated herein by reference.
[0097] The dihydrocarbyl phosphite compounds of the invention
should be used at a concentration of about 0.001 wt % to about 0.5
wt %, particularly about 0.01 wt % to about 0.2 wt %, to insure
that the finished blend contains an adequate quantity of the
foregoing ingredient although smaller amounts may be successfully
employed, depending on the relative amounts of components (A), (C)
and (D).
[0098] Component (C): Metallic Detergent
[0099] A metallic detergent is included in the additive package and
transmission fluids of the present invention. Increasing the level
of this detergent component in the transmission fluid has been
found to make .differential..mu./.differential.T more negative, and
decreasing its level has the opposite effect.
[0100] A suitable metallic detergent may include an oil-soluble
neutral or overbased salt of alkali or alkaline earth metal with
one or more of the following acidic substances (or mixtures
thereof): (1) a sulfonic acid, (2) a carboxylic acid, (3) a
salicylic acid, (4) an alkyl phenol, (5) a sulfurized alkyl phenol,
and (6) an organic phosphorus acid characterized by at least one
direct carbon-to-phosphorus linkage. Such an organic phosphorus
acid may include those prepared by the treatment of an olefin
polymer (e.g., polyisobutylene having a molecular weight of about
1,000) with a phosphorizing agent such as phosphorus trichloride,
phosphorus heptasulfide, phosphorus pentasulfide, phosphorus
trichloride and sulfur, white phosphorus and a sulfur halide, or
phosphorothioic chloride.
[0101] Suitable salts may include neutral or overbased salts of
magnesium, calcium, or zinc. As a further example, suitable salts
may include magnesium sulfonate, calcium sulfonate, zinc sulfonate,
magnesium phenate, calcium phenate, and/or zinc phenate. See, e.g.,
U.S. Pat. Nos. 6,482,778 and 5,578,235, which descriptions are
incorporated herein by reference.
[0102] Oil-soluble neutral metal-containing detergents are those
detergents that contain stoichiometrically equivalent amounts of
metal in relation to the amount of cidic moieties present in the
detergent. Thus, in general the neutral detergents will have a low
basicity when compared to their overbased counterparts. The acidic
materials utilized in forming such detergents include carboxylic
acids, salicylic acids, alkylphenols, sulfonic acids, sulfurized
alkylphenols and the like.
[0103] The term "overbased" in connection with metallic detergents
is used to designate metal salts wherein the metal is present in
stoichiometrically larger amounts than the organic radical. The
commonly employed methods for preparing the overbased salts involve
heating a mineral oil solution of an acid with a stoichiometric
excess of a metal neutralizing agent such as the metal oxide,
hydroxide, carbonate, bicarbonate, or sulfide at a temperature of
about 50.degree. C., and filtering the resultant product. The use
of a "promoter" in the neutralization step to aid the incorporation
of a large excess of metal likewise is known. Examples of compounds
useful as the promoter include phenolic substances such as phenol,
naphthol, alkyl phenol, thiophenol, sulfurized alkylphenol, and
condensation products of formaldehyde with a phenolic substance;
alcohols such as methanol, 2-propanol, octanol, ethylene glycol,
stearyl alcohol, and cyclohexyl alcohol; and amines such as
aniline, phenylene diamine, phenothiazine,
phenyl-beta-naphthylamine, and dodecylamine. A particularly
effective method for preparing the basic salts comprises mixing an
acid with an excess of a basic alkaline earth metal neutralizing
agent and at least one alcohol promoter, and carbonating the
mixture at an elevated temperature such as 60.degree. C. to
200.degree. C.
[0104] Examples of suitable metal-containing detergents include,
but are not limited to, neutral and overbased salts such as a
sodium sulfonate, a sodium carboxylate, a sodium salicylate, a
sodium phenate, a sulfurized sodium phenate, a lithium sulfonate, a
lithium carboxylate, a lithium salicylate, a lithium phenate, a
sulfurized lithium phenate, a magnesium sulfonate, a magnesium
carboxylate, a magnesium salicylate, a magnesium phenate, a
sulfurized magnesium phenate, a calcium sulfonate, a calcium
carboxylate, a calcium salicylate, a calcium phenate, a sulfurized
calcium phenate, a potassium sulfonate, a potassium carboxylate, a
potassium salicylate, a potassium phenate, a sulfurized potassium
phenate, a zinc sulfonate, a zinc carboxylate, a zinc salicylate, a
zinc phenate, and a sulfurized zinc phenate. Further examples
include a lithium, sodium, potassium, calcium, and magnesium salt
of a hydrolyzed phosphosulfurized olefin having about 10 to about
2,000 carbon atoms or of a hydrolyzed phosphosulfurized alcohol
and/or an aliphatic-substituted phenolic compound having about 10
to about 2,000 carbon atoms. Even further examples include a
lithium, sodium, potassium, calcium, and magnesium salt of an
aliphatic carboxylic acid and an aliphatic substituted
cycloaliphatic carboxylic acid and many other similar alkali and
alkaline earth metal salts of oil-soluble organic acids. A mixture
of a neutral or an overbased salt of two or more different alkali
and/or alkaline earth metals can be used. Likewise, a neutral
and/or an overbased salt of mixtures of two or more different acids
can also be used.
[0105] As is well known, overbased metal detergents are generally
regarded as containing overbasing quantities of inorganic bases,
generally in the form of micro dispersions or colloidal
suspensions. Thus the term "oil-soluble" as applied to metallic
detergents is intended to include metal detergents wherein
inorganic bases are present that are not necessarily completely or
truly oil-soluble in the strict sense of the term, inasmuch as such
detergents when mixed into base oils behave much the same way as if
they were fully and totally dissolved in the oil. Collectively, the
various metallic detergents referred to herein above, are sometimes
called neutral, basic, or overbased alkali metal or alkaline earth
metal-containing organic acid salts.
[0106] Methods for the production of oil-soluble neutral and
overbased metallic detergents and alkaline earth metal-containing
detergents are well known to those skilled in the art, and
extensively reported in the patent literature. See, for example,
U.S. Pat. Nos. 4,647,387 and 4,880,550, which descriptions are
incorporated herein by reference.
[0107] The metallic detergents utilized in this invention can, if
desired, be oil-soluble boronated neutral and/or overbased alkali
of alkaline earth metal-containing detergents. Methods for
preparing boronated metallic detergents are described in, for
example, U.S. Pat. Nos. 4,965,003 and 4,965,004, which descriptions
are incorporated herein by reference.
[0108] The metallic detergent compounds of the invention should be
used at a concentration of about 0.01 wt % to about 1.0 wt %,
particularly about 0.01 wt % to about 0.7 wt %, to insure that the
finished blend contains an adequate quantity of the foregoing
ingredient although smaller amounts may be successfully employed,
depending on the relative amounts of components (A), (B) and
(D).
[0109] Component (D): Dispersant
[0110] Component (D) comprises phosphorylated succinimide ashless
dispersant which is included in the additive package and
transmission fluids of the present invention. Increasing the level
of this component in the transmission fluid makes
.differential..mu./.differential.T less negative, and decreasing
its level has the opposite effect.
[0111] Examples of suitable dispersants are described, for example,
in U.S. Pat. Nos. 6,627,584 and 4,857,214, which descriptions are
incorporated herein by reference. These dispersants are formed by
phosphorylating an ashless dispersant having basic nitrogen and/or
at least one hydroxyl group in the molecule, and preferably a
succinimide dispersant. As used herein the term "succinimide" is
meant to encompass the completed reaction product from reaction
between one or more polyamine reactants and a
hydrocarbon-substituted succinic acid or anhydride (or like
succinic acylating agent), and is intended to encompass compounds
wherein the product may have amide, amidine, and/or salt linkages
in addition to the imide linkage of the type that results from the
reaction of a primary amino group and an anhydride moiety.
[0112] The succinimide includes, for example, polyamine
succinimides in which the succinic group contains a hydrocarbyl
substituent containing at least 30 carbon atoms are described for
example in U.S. Pat. Nos. 3,172,892; 3,202,678; 3,216,936;
3,219,666; 3,254,025; 3,272,746; and 4,234,435, which descriptions
are incorporated herein by reference. Also included are alkenyl
succinimides, which may be formed by conventional methods such as
by heating an alkenyl succinic anhydride, acid, acid-ester, acid
halide, or lower alkyl ester with a polyamine containing at least
one primary amino group. The alkenyl succinic anhydride may be made
readily by heating a mixture of olefin and maleic anhydride to, for
example, about 180-220.degree. C. The olefin is preferably a
polymer or copolymer of a lower monoolefin such as ethylene,
propylene, 1-butene, isobutene and the like and mixtures thereof.
The more preferred source of alkenyl group is from polyisobutene
having a gel permeation chromotography (GPC) number average
molecular weight of up to 10,000 or higher, preferably in the range
of about 500 to about 2,500, and most preferably in the range of
about 800 to about 1,500.
[0113] Preferred procedures for phosphorylating ashless dispersants
include, for example, those described in U.S. Pat. Nos. 6,627,584,
4,857,214, and 5,198,133, which descriptions are incorporated
herein by reference.
[0114] The amount of ashless dispersant on an "active ingredient
basis" (i.e., excluding the weight of impurities, diluents and
solvents typically associated therewith) is generally within the
range of about 0.5 to about 7.5 weight percent (wt %), typically
within the range of about 0.5 to 6.5 wt %, preferably within the
range of about 0.5 to about 5.5 wt %, and most preferably within
the range of about 1.0 to about 4.5 wt %. In a preferred
embodiment, this dispersant component of the present invention is a
dispersant having a nitrogen to phosphorus mass ratio between about
3:1 and about 10:1. The ashless dispersant of a preferred
embodiment can be prepared by phosphorylating the succinimide
compound to such a degree that the resulting nitrogen to phosphorus
mass ratio in the reaction product is between about 3:1 and about
10:1. In another embodiment, a phosphorylated dispersant and a
non-phosphorylated dispersant are blended together such that the
total nitrogen to phosphorus mass ratio of the dispersant is
between about 3:1 and about 10:1.
[0115] The phosphorylated succinimide dispersant compounds of the
invention may be used at a concentration of about 0.01 wt % to
about 12 wt %, particularly about 0.01 wt % to about 10 wt %, to
insure that the finished blend contains an adequate quantity of the
foregoing ingredient although smaller amounts may be successfully
employed, depending on the relative amounts of components (A), (B)
and (C), and alternatively, larger amounts also may be used so long
as the relative amounts of components (A), (B) and (C) are
sufficient to keep .differential..mu./.differential.T negative.
[0116] Combined Use of Components (A) (B) (C) and (D)
[0117] Anti-NVH characteristics are improved for a power
transmission fluid which is formulated to predominantly contain
base oil, and a minor amount of an additive composition containing
0.002-0.5 wt % alkoxylated amine (Component (A)), 0.001-0.5 wt %
dihydrocarbyl phosphite (Component (B)), 0.01-1.0 wt % metallic
detergent (Component (C)), and 0.01-12 wt % phosphorylated
succinimide (Component (D)). Particularly, the fluid composition
may contain about 0.01-0.2 wt % Component (A); 0.01-0.7 wt %
Component (B); 0.01-10 wt % Component (C); and 0.01-10 wt %
Component (D). Components (A), (B), (C) and (D) may be introduced
into a fluid composition comprising a major amount of base oil
either as an additive concentrate, individually, etc. An additive
concentrate containing these components may be incorporated into a
finished composition at a treat rate of about 3 wt % to about 20,
particularly about 5 wt % to about 15 wt %, based on the overall
fluid composition.
[0118] The combined presence of these four components in properly
balanced proportions is necessary to achieve the negative the
.differential..mu./.differential.T slope condition associated with
achieving improved anti-NVH properties. In one embodiment, a fluid
composition containing all four Components (A)-(D) is formulated
such that the fluid composition such that the fluid composition
comprises a viscosity at 100.degree. C. of <6 cSt, a viscosity
at 40.degree. C. of <30 cSt, and a Brookfield Viscosity at
-40.degree. C. of <10,000 cP, and wherein the
.differential..mu./.differential.T slope value is determined from
coefficient of friction and temperature measurements taken on a low
speed SAE #2 Machine using a paper friction material lined clutch
plate and testing conditions of 0.79N/mm.sup.2, >50 rpm, and at
40.degree. C. and 120.degree. C. The paper friction material lining
material used in the testing machines may be a commercial product
made/supplied by Borg Warner Automotive as Borg Warner 4329. A
power transmission fluid including only one, two or three of
components (A)-(D), but not all, or not in balanced proportions,
can not predictably and reliably provide a transmission fluid
having a negative .differential..mu./.differential.T.
[0119] B. Additive Package II for Enhanced Anti-NVH Durability
Performance
[0120] Further experimental studies also were conducted, which also
are summarized in more detail in the Examples section below, which
show that six components, inclusive of the above four-discussed
Components (A)-(D) and two additional surfactant compounds,
Compounds (E) and (F) described in more detail below, of an
automatic transmission fluid, are critical to maintaining more
stable anti-NVH durability of the fluid as it ages over a service
life.
[0121] Component (E): Tertiary Fatty Amine
[0122] Component (E) comprises a tertiary fatty amine
surfactant/friction modifier which is included in the additive
package and transmission fluids of the present invention. The
co-presence of this component. and Component (F) described below,
in a composition containing Components (A)-(D) has been found to
help maintain desired friction properties as the fluid ages over a
service life.
[0123] The tertiary fatty amine may be represented by the following
formula: ##STR1## wherein R.sub.1 and R.sub.2 can independently
represent C.sub.1 to C.sub.6, and R.sub.3 may represent a C.sub.10
to C.sub.26 alkyl or alkenyl group. Preferred tertiary fatty amines
are selected with R.sub.3 representing dialkyl C.sub.16-C.sub.22
alkylamines in which the fatty alkyl chains. Suitable tertiary
fatty amines include, for example: dimethyl decylamine, dimethyl
laurylamine, dimethyl myristylamine, dimethyl cetylamine, dimethyl
stearylamine, dimethyl arachadylamine, dimethyl behenylamine,
dimethyl cocoylamine, and dimethyl tallowylamine, or combinations
thereof. In one preferred embodiment, the long chain tertiary amine
comprises dimethyl stearyl-amine(N,N-dimethyl 1-octadecamine) which
is represented by the formula
C.sub.18H.sub.37N(CH.sub.3).sub.2.
[0124] The tertiary fatty amine compounds of the invention should
be used at a concentration of 0.005 wt % to about 1.0 wt %,
particularly about 0.01 wt % to about 0.7 wt %, to insure that the
finished blend contains an adequate quantity of the foregoing
ingredient for anti-NVH durability enhancements although smaller
amounts may be successfully employed, depending on the relative
amounts of components (A)-(D), and (E).
[0125] Component (F): Alkoxylated Alcohol
[0126] Component (F) comprises an alkoxylated alcohol non-ionic
surfactant which is included in the additive package and
transmission fluids of the present invention. The level of this
component in the transmission fluid must be sufficient to maintain
friction properties as the fluid ages over a service life.
[0127] Alkoxylated alcohols which can be used in forming the
additives of this invention include, for example, oil-soluble
alkoxylated alkanols, alkoxylated cycloalkanols, alkoxylated
polyols, alkoxylated phenols, and alkoxylated heterocyclic alcohols
which contain an average of up to about 20 alkoxy groups per
molecule. The alkoxy groups can be methoxy, ethoxy, propoxy,
butoxy, or pentoxy, or combinations of two or more of these.
However ethoxy-substituted alcohols are preferred. The alkoxylated
alcohol should be a liquid at ambient temperatures in the range of
20-25.degree. C. Since the alkoxylated alcohol should be
oil-soluble, short chain alcohols preferably contain an average of
at least two alkoxy groups per molecule whereas longer chain
alcohols may contain one or more alkoxy groups per molecule. The
average number of alkoxy groups in any given alcohol can be as high
as 15 or 20 as long as the product is oil soluble and is preferably
a liquid at room temperature. Examples of alcohols that form
suitable alkoxylated alcohols include C.sub.1-24 alkanols, C.sub.10
cycloalkanols, polyols having up to about 16 carbon atoms and 2-5
hydroxyl groups, polyol ethers having up to about 16 carbon atoms
and at least one hydroxyl group, phenol, alkylphenols having up to
about 16 carbon atoms, and hydroxy-substituted heterocyclic
compounds such as tetrahydrofurfuryl alcohol and
tetrahydropyran-2-methanol.
[0128] Preferred is an alkoxylated alcohol of 8 to 16 carbon atoms
or mixture of two or more of such alcohols having an average of 1
to 10 ethoxy groups per molecule. Particularly preferred are
ethoxylated alcohols, such as an ethoxylated C.sub.10-14 alcohol
having an average of 1 to 3 ethoxy groups per molecule.
[0129] The alkoxylated alcohol compounds of the invention should be
used at a concentration of 0.01 wt % to about 0.7 wt %,
particularly about 0.01 wt % to about 0.5 wt %, to insure that the
finished blend contains an adequate quantity of the foregoing
ingredient for anti-NVH durability enhancements although smaller
amounts may be successfully employed, depending on the relative
amounts of components (A)-(E).
[0130] Combined Use of Components (A)-(F)
[0131] Anti-NVH durability characteristics are improved for a power
transmission fluid which is formulated to predominantly contain
base oil, and a minor amount of an additive composition containing
0.002-0.5 wt % alkoxylated amine (Component (A)), 0.001-0.5 wt %
dihydrocarbyl phosphite (Component (B)), 0.01-1.0 wt % metallic
detergent (Component (C)), 0.01-12 wt % phosphorylated succinimide
(Component (D)), 0.005-1.0 wt % long chain tertiary amine
(Component (E)), and 0.01-0.7 ethoxylated alcohol (Component (F)).
Particularly, the fluid composition may contain about 0.01-25 wt %
Component (A); 0.01-0.2 wt % Component (B); 0.01-0.7 wt % Component
(C); 0.01-10 wt % Component (D); 0.01-0.7 wt % Component (E); and
0.01-0.5 wt % Component (F). Components (A), (B), (C), (D), (E) and
(F) may be introduced into a fluid composition comprising a major
amount of base oil either as an additive concentrate, individually,
etc. An additive concentrate containing these components may be
incorporated into a finished composition at a treat rate of about 3
wt % to about 20, particularly about 5 wt % to about 15 wt %, based
on the overall fluid composition.
[0132] The combined presence of these six components is necessary
to achieve more stable and uniform friction interactions between
the fluid and clutch plate as the fluid ages. In one embodiment, a
fluid composition containing all six Components (A)-(F) is
formulated such that the fluid composition comprises a viscosity at
100.degree. C. of <6 cSt, a viscosity at 40.degree. C. of <30
cSt, and a Brookfield Viscosity at -40.degree. C. of <10,000 cP,
and wherein the the fluid has a variation in coefficient of
friction at testing rpm ranging from 50 to 300 of less than about
0.015 (absolute value) as determined from measurements taken on an
SAE #2 Machine using a test plate comprising a paper friction
material lined clutch plate and testing conditions ranging from
about 0.3 to about 3.4N/mm.sup.2, such as 0.79N/mm.sup.2 at
150.degree. C. for 200 hours. In another embodiment, the fluid
further has quasi-static friction greater than 0.098 and static
friction of 0.123 or greater, as measured on a ZF GK rig. In
another embodiment, the fluid has an NVH characteristic having a
threshold pressure value greater in value than 0.8N/mm.sup.2 as
measured on a ZF GK rig. In another embodiment, the fluid has an
NVH characteristic which, after exposure to oxidizing conditions,
does not decrease in value below the initial value of the NVH
characteristic value before the exposure as measured on a ZF GK
rig. In yet another embodiment, the fluid has an NVH characteristic
which, after exposure to oxidizing conditions, does not decrease to
a value below the initial value of the NVH characteristic before
exposure as measured on the ZF GK rig. The "NVH characteristic"
refers to noise phenomena, such as squawk, chatter, shudder, and/or
noise. In one non-limiting embodiment, the NVH characteristic is
squawk.
[0133] A power transmission fluid including less than all six of
components (A)-(F) can not predictably and reliably maintain such
uniform and stable friction properties at the clutch, e.g., greater
variation in the coefficient of friction parameter may be
observed.
[0134] Other Optional Additive Components
[0135] The fluids of the present embodiments may also optionally
include conventional additives of the type used in power
transmission fluid formulations and gear lubricants in addition to
the extreme pressure and antiwear performance improving
co-additives described above. Such additives include, but are not
limited to, metallic detergents, dispersants, friction modifiers,
antioxidants, viscosity index improvers, copper corrosion
inhibitors, anti-rust additives, antiwear additives, antifoamants,
pour point depressants, seal swell agents, colorants, metal
deactivators, and/or air expulsion additives. It will be
appreciated that various required and optional additives described
herein may have additional other advantageous effects in the
finished fluids.
[0136] Component (G): Supplemental Dispersants
[0137] Component (G) comprises at least one oil-soluble
supplemental dispersant. Suitable dispersants may include ashless
dispersants such as succinic dispersants, Mannich base dispersants,
and polymeric polyamine dispersants. Hydrocarbyl-substituted
succinic acylating agents are used to make hydrocarbyl-substituted
succinimides. The hydrocarbyl-substituted succinic acylating agents
include, but are not limited to, hydrocarbyl-substituted succinic
acids, hydrocarbyl-substituted succinic anhydrides, the
hydrocarbyl-substituted succinic acid halides (especially the acid
fluorides and acid chlorides), and the esters of the
hydrocarbyl-substituted succinic acids and lower alcohols (e.g.,
those containing up to 7 carbon atoms), that is,
hydrocarbyl-substituted compounds which can function as carboxylic
acylating agents.
[0138] Hydrocarbyl substituted acylating agents are made by
reacting a polyalkyl olefin or chlorinated polyalkyl olefin of
appropriate molecular weight with maleic anhydride. Similar
carboxylic reactants can be used to make the acylating agents. Such
reactants may include, but are not limited to, maleic acid, fumaric
acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride,
citraconic acid, citraconic anhydride, mesaconic acid, ethylmaleic
anhydride, dimethylmaleic anhydride, ethylmaleic acid,
dimethylmaleic acid, hexylmaleic acid, and the like, including the
corresponding acid halides and lower aliphatic esters.
[0139] The molecular weight of the olefin can vary depending upon
the intended use of the substituted succinic anhydrides. Typically,
the substituted succinic anhydrides will have a hydrocarbyl group
of from about 8 to about 500 carbon atoms. However, substituted
succinic anhydrides used to make lubricating oil dispersants will
typically have a hydrocarbyl group of about 40 to about 500 carbon
atoms. With high molecular weight substituted succinic anhydrides,
it is more accurate to refer to number average molecular weight
(Mn) since the olefins used to make these substituted succinic
anhydrides may include a mixture of different molecular weight
components resulting from the polymerization of low molecular
weight olefin monomers such as ethylene, propylene, and
isobutylene.
[0140] The mole ratio of maleic anhydride to olefin can vary
widely. It may vary, for example, from about 5:1 to about 1:5, or
for example, from about 1:1 to about 3:1. With olefins such as
polyisobutylene having a number average molecular weight of about
500 to about 7000, or as a further example, about 800 to about 3000
or higher and the ethylene-alpha-olefin copolymers, the maleic
anhydride may be used in stoichiometric excess, e.g. about 1.1 to
about 3 moles maleic anhydride per mole of olefin. The unreacted
maleic anhydride can be vaporized from the resultant reaction
mixture.
[0141] The polyalkyl or polyalkenyl substituent on the succinic
anhydrides employed herein is generally derived from polyolefins,
which are polymers or copolymers of mono-olefins, particularly
1-mono-olefins, such as ethylene, propylene, and butylene. The
mono-olefin employed may have about 2 to about 24 carbon atoms, or
as a further example, about 3 to about 12 carbon atoms. Other
suitable mono-olefins include propylene, butylene, particularly
isobutylene, 1-octene, and 1-decene. Polyolefins prepared from such
mono-olefins include polypropylene, polybutene, polyisobutene, and
the polyalphaolefins produced from 1-octene and 1-decene.
[0142] Polyalkenyl succinic anhydrides may be converted to
polyalkyl succinic anhydrides by using conventional reducing
conditions such as catalytic hydrogenation. For catalytic
hydrogenation, a suitable catalyst is palladium on carbon.
Likewise, polyalkenyl succinimides may be converted to polyalkyl
succinimides using similar reducing conditions.
[0143] In some embodiments, the ashless dispersant may include one
or more alkenyl succinimides of an amine having at least one
primary amino group capable of forming an imide group. The alkenyl
succinimides may be formed by conventional methods such as by
heating an alkenyl succinic anhydride, acid, acid-ester, acid
halide, or lower alkyl ester with an amine containing at least one
primary amino group. The alkenyl succinic anhydride may be made
readily by heating a mixture of polyolefin and maleic anhydride to
about 180.degree.-220.degree. C. The polyolefin may be a polymer or
copolymer of a lower monoolefin such as ethylene, propylene,
isobutene and the like, having a number average molecular weight in
the range of about 300 to about 3000 as determined by gel
permeation chromatography (GPC).
[0144] Amines which may be employed in forming the ashless
dispersant include any that have at least one primary amino group
which can react to form an imide group and at least one additional
primary or secondary amino group and/or at least one hydroxyl
group. A few representative examples are: N-methyl-propanediamine,
N-dodecylpropanediamine, N-aminopropyl-piperazine, ethanolamine,
N-ethanol-ethylenediamine, and the like.
[0145] Suitable amines may include polyalkylene polyamines, such as
propylene diamine, dipropylene triamine, di-(1,2-butylene)triamine,
and tetra-(1,2-propylene)pentamine. A further example includes the
polyethylene polyamines which can be depicted by the formula
H.sub.2N(CH.sub.2CH.sub.2NH).sub.nH, wherein n may be an integer
from about one to about ten. These include: ethylene diamine,
diethylene triamine (DETA), triethylene tetramine (TETA),
tetraethylene pentamine (TEPA), pentaethylene hexamine (PEHA), and
the like, including mixtures thereof in which case n is the average
value of the mixture. Such polyethylene polyamines have a primary
amine group at each end so they may form mono-alkenylsuccinimides
and bis-alkenylsuccinimides. Commercially available polyethylene
polyamine mixtures may contain minor amounts of branched species
and cyclic species such as N-aminoethyl piperazine,
N,N'-bis(aminoethyl) piperazine, N,N'-bis(piperazinyl)ethane, and
like compounds. The commercial mixtures may have approximate
overall compositions falling in the range corresponding to
diethylene triamine to tetraethylene pentamine. The molar ratio of
polyalkenyl succinic anhydride to polyalkylene polyamines may be
from about 1:1 to about 3.0:1.
[0146] In some embodiments, the ashless dispersant may include the
products of the reaction of a polyethylene polyamine, e.g.
triethylene tetramine or tetraethylene pentamine, with a
hydrocarbon substituted carboxylic acid or anhydride made by
reaction of a polyolefin, such as polyisobutene, of suitable
molecular weight, with an unsaturated polycarboxylic acid or
anhydride, e.g., maleic anhydride, maleic acid, fumaric acid, or
the like, including mixtures of two or more such substances.
[0147] Polyamines that are also suitable in preparing the
dispersants described herein include N-arylphenylenediamines, such
as N-phenylphenylenediamines, for example,
N-phenyl-1,4-phenylenediamine, N-phenyl-1,3-phenylenediamine, and
N-phenyl-1,2-phenylenediamine; aminothiazoles such as
aminothiazole, aminobenzothiazole, aminobenzothiadiazole, and
aminoalkylthiazole; aminocarbazoles; aminoindoles; aminopyrroles;
amino-indazolinones; aminomercaptotriazoles; aminoperimidines;
aminoalkyl imidazoles, such as 1-(2-aminoethyl)imidazole,
1-(3-aminopropyl) imidazole; and aminoalkyl morpholines, such as
4-(3-aminopropyl)morpholine. These polyamines are described in more
detail in U.S. Pat. Nos. 4,863,623 and 5,075,383. Such polyamines
can provide additional benefits, such as anti-wear and
antioxidancy, to the final products.
[0148] Additional polyamines useful in forming the
hydrocarbyl-substituted succinimides include polyamines having at
least one primary or secondary amino group and at least one
tertiary amino group in the molecule as taught in U.S. Pat. Nos.
5,634,951 and 5,725,612. Examples of suitable polyamines include
N,N,N'',N''-tetraalkyldialkylenetriamines (two terminal tertiary
amino groups and one central secondary amino group),
N,N,N',N''-tetraalkyltrialkylenetetramines (one terminal tertiary
amino group, two internal tertiary amino groups and one terminal
primary amino group),
N,N,N',N'',N'''-pentaalkyltrialkylenetetramines (one terminal
tertiary amino group, two internal tertiary amino groups and one
terminal secondary amino group),
tris(dialkylaminoalkyl)-aminoalkylmethanes (three terminal tertiary
amino groups and one terminal primary amino group), and like
compounds, wherein the alkyl groups are the same or different and
typically contain no more than about 12 carbon atoms each, and
which may contain from about 1 to about 4 carbon atoms each. As a
further example, these alkyl groups may be methyl and/or ethyl
groups. Polyamine reactants of this type may include
dimethylaminopropylamine (DMAPA) and N-methyl piperazine.
[0149] Hydroxyamines suitable for herein include compounds,
oligomers or polymers containing at least one primary or secondary
amine capable of reacting with the hydrocarbyl-substituted succinic
acid or anhydride. Examples of hydroxyamines suitable for use
herein include aminoethylethanolamine (AEEA),
aminopropyldiethanolamine (APDEA), ethanolamine, diethanolamine
(DEA), partially propoxylated hexamethylene diamine (for example
HMDA-2PO or HMDA-3PO), 3-amino-1,2-propanediol,
tris(hydroxymethyl)aminomethane, and 2-amino-1,3-propanediol.
[0150] The mole ratio of amine to hydrocarbyl-substituted succinic
acid or anhydride may range from about 1:1 to about 3.0:1. Another
example of a mole ratio of amine to hydrocarbyl-substituted
succinic acid or anhydride may range from about 1.5:1 to about
2.0:1.
[0151] The foregoing dispersant may also be a post-treated
dispersant made, for example, by treating the dispersant with
maleic anhydride and boric acid as described, for example, in U.S.
Pat. No. 5,789,353, or by treating the dispersant with nonylphenol,
formaldehyde and glycolic acid as described, for example, in U.S.
Pat. No. 5,137,980.
[0152] The Mannich base dispersants may be a reaction product of an
alkyl phenol, typically having a long chain alkyl substituent on
the ring, with one or more aliphatic aldehydes containing from
about 1 to about 7 carbon atoms (especially formaldehyde and
derivatives thereof), and polyamines (especially polyalkylene
polyamines). For example, a Mannich base ashless dispersants may be
formed by condensing about one molar proportion of long chain
hydrocarbon-substituted phenol with from about 1 to about 2.5 moles
of formaldehyde and from about 0.5 to about 2 moles of polyalkylene
polyamine.
[0153] Hydrocarbon sources for preparation of the Mannich polyamine
dispersants may be those derived from substantially saturated
petroleum fractions and olefin polymers, such as polymers of
mono-olefins having from about 2 to about 6 carbon atoms. The
hydrocarbon source generally contains, for example, at least about
40 carbon atoms, and as a further example, at least about 50 carbon
atoms to provide substantial oil solubility to the dispersant. The
olefin polymers having a GPC number average molecular weight
between about 600 and about 5,000 are suitable for reasons of easy
reactivity and low cost. However, polymers of higher molecular
weight can also be used. Especially suitable hydrocarbon sources
are isobutylene polymers and polymers made from a mixture of
isobutene and a raffinate I stream.
[0154] Suitable Mannich base dispersants may be Mannich base
ashless dispersants formed by condensing about one molar proportion
of long chain hydrocarbon-substituted phenol with from about 1 to
about 2.5 moles of formaldehyde and from about 0.5 to about 2 moles
of polyalkylene polyamine.
[0155] Polymeric polyamine dispersants suitable as the ashless
dispersants are polymers containing basic amine groups and oil
solubilizing groups (for example, pendant alkyl groups having at
least about 8 carbon atoms). Such materials are illustrated by
interpolymers formed from various monomers such as decyl
methacrylate, vinyl decyl ether or relatively high molecular weight
olefins, with aminoalkyl acrylates and aminoalkyl acrylamides.
Examples of polymeric polyamine dispersants are set forth, for
example, in U.S. Pat. Nos. 3,687,849 and 3,702,300. Polymeric
polyamines may include hydrocarbyl polyamines wherein the
hydrocarbyl group is composed of the polymerization product of
isobutene and a raffinate I stream as described above. PIB-amines
and PIB-polyamines may also be used.
[0156] Methods for the production of ashless dispersants as
described above are known to those skilled in the art and are
reported in the patent literature. For example, the synthesis of
various ashless dispersants of the foregoing types is described in
such patents as U.S. Pat. Nos. 5,137,980 and Re 26,433, herein
incorporated by reference.
[0157] An example of a suitable ashless dispersant is a borated
dispersant. Borated dispersants may be formed by boronating
(borating) an ashless dispersant having basic nitrogen and/or at
least one hydroxyl group in the molecule, such as a succinimide
dispersant, succinamide dispersant, succinic ester dispersant,
succinic ester-amide dispersant, Mannich base dispersant, or
hydrocarbyl amine or polyamine dispersant. Methods that can be used
for boronating the various types of ashless dispersants described
above are described, for example, in U.S. Pat. Nos. 4,455,243 and
4,652,387.
[0158] The borated dispersant may include a high molecular weight
dispersant treated with boron such that the borated dispersant
includes up to about 2 wt % of boron. As another example the
borated dispersant may include from about 0.8 wt % or less of
boron. As a further example, the borated dispersant may include
from about 0.1 to about 0.7 wt % of boron. As an even further
example, the borated dispersant may include from about 0.25 to
about 0.7 wt % of boron. As a further example, the borated
dispersant may include from about 0.35 to about 0.7 wt % of boron.
The borated dispersant may further include a mixture of borated
dispersants. As a further example, the borated dispersant may
include a nitrogen-containing dispersant and/or may be free of
phosphorus. As an additional example, the borated dispersant may
include phosphorus. The dispersant may be dissolved in oil of
suitable viscosity for ease of handling. It should be understood
that the weight percentages given here are for neat dispersant,
without any diluent oil added.
[0159] A dispersant may be further reacted with an organic acid, an
anhydride, and/or an aldehyde/phenol mixture. Such a process may
enhance compatibility with elastomer seals, for example.
[0160] A dispersant may be present in the power transmission fluid
in an amount of up to about 15 wt %. Further, the fluid composition
may include from about 0.1 wt % to about 10 wt % of the borated
dispersant. Further, the fluid composition may include from about 3
wt % to about 5 wt % of the borated dispersant. Further, the power
transmission fluid may include an amount of the borated dispersant
sufficient to provide up to 1900 parts per million (ppm) by weight
of boron in the finished fluid, such as for example, from about 50
to about 500 ppm by weight of boron in the finished fluid.
[0161] Component (H): Lubricity Antiwear and Extreme Pressure
Agents
[0162] Lubricity, antiwear and extreme pressure agents may be
included. Examples of these include sulfur sources such as
sulfurized fatty oils. "Sulfurized fatty oil" refers to sulfurized
fatty acids, sulfurized fatty esters, individually or as mixtures
thereof. Sulfurized fatty acid esters are preferred. The sulfurized
fatty oils may be animal or vegetable in origin. Suitable
sulfurized fatty oils include, for example, a sulfurized fatty acid
ester containing about 10% sulfur and a sulfurized sperm oil
containing about 10% sulfur.
[0163] In one particular embodiment, suitable sulfurized fatty oils
include sulfurized transesterified triglycerides, such as those
described in U.S. Pat. No. 4,380,499, which descriptions are
incorporated herein by reference. In one embodiment, a sulfurized
transesterified triglyceride additive has a total acid component
comprising no less than about 35 mol % saturated aliphatic acids
and no more than about 65 mol % unsaturated fatty acids, and
wherein the total acid component is further characterized as
comprising more than about 20 mol % of monounsaturated acids, less
than about 15 mol % of polyunsaturated fatty acids, more than about
20 mol % saturated aliphatic acids having 6 to 16 carbon atoms,
including more than about 10 mol % saturated aliphatic acids having
6 to 14 carbon atoms, and less than about 15 mol % saturated
aliphatic acids having 18 or more carbon atoms. Suitable sulfurized
fatty oils also include those such as those described in U.S. Pat.
No. 4,149,982, which descriptions are incorporated herein by
reference.
[0164] Other suitable sulfurized fatty oils include, for example,
sulfurized lard oils, sulfurized fatty compounds, sulfurized methyl
esters, sulfurized hydrocarbons, sulfurized oleic acid, sulfurized
fatty ester-polyalkanol amides, and sulfurized fatty olefins.
[0165] Other antiwear agents include phosphorus-containing antiwear
agents, such as those comprising an organic ester of phosphoric
acid, phosphorous acid, or an amine salt thereof.
[0166] The phosphorus-containing antiwear agent may be present in
an amount sufficient to provide about 50 to about 500 parts per
million by weight of phosphorus in the power transmission fluid. As
a further example, the phosphorus-containing antiwear agent may be
present in an amount sufficient to provide about 150 to about 300
parts per million by weight of phosphorus in the power transmission
fluid.
[0167] The fluid composition may include up to about 1.0 wt % of
the phosphorus-containing antiwear agent. As a further example, the
fluid composition may include from about 0.01 wt % to about 1.0 wt
% of the phosphorus-containing antiwear agent, particularly about
0.2 wt % to about 0.3 wt % of the phosphorus-containing antiwear
agent.
[0168] Component (I): Metal Deactivators
[0169] The formulations also may contain metal deactivators, which
include materials commonly used for that purpose in this general
class of fluids. These may comprise, for example, ashless dialkyl
thiadiazoles. Dialkyl thiadiazoles suitable for the practice of the
present invention may be of the general formula (I): ##STR2##
wherein R.sub.1 and R.sub.2 may be the same or different
hydrocarbyl groups, and x and y independently may be integers from
0 to 8. In one aspect, R.sub.1 and R.sub.2 may be the same or
different, linear, branched, or aromatic, saturated or unsaturated
hydrocarbyl group having from about 6 to about 18 carbon atoms,
particularly from about 8 to about 12 carbon atoms, and x and y
each may be 0 or 1.
[0170] An suitable dialkyl thiadiazoles includes
2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles. Examples of other
suitable dialkyl thiadiazoles include, for example,
2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles,
2-(tert-hydrocarbyldithio)-5-mercapto-1,3,4-thiadiazoles, and
bis-tert-dodecylthiothiadiazole.
[0171] Suitable dialkyl thiadiazoles also include those such as
described, for example, in U.S. Pat. Nos. 4,149,982 and 4,591,645,
and which descriptions are incorporated herein by reference.
Mixtures of dialkyl thiadiazoles of formula (I) with monoalkyl
thiadiazoles may also be used within the scope of the present
invention.
[0172] As used herein, the term "hydrocarbyl group" or
"hydrocarbyl" is used in its ordinary sense, which is well-known to
those skilled in the art. Specifically, it refers to a group having
a carbon atom directly attached to the remainder of a molecule and
having a predominantly hydrocarbon character. Examples of
hydrocarbyl groups include:
[0173] (1) hydrocarbon substituents, that is, aliphatic (e.g.,
alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)
substituents, and aromatic-, aliphatic-, and alicyclic-substituted
aromatic substituents, as well as cyclic substituents wherein the
ring is completed through another portion of the molecule (e.g.,
two substituents together form an alicyclic radical);
[0174] (2) substituted hydrocarbon substituents, that is,
substituents containing non-hydrocarbon groups which, in the
context of the description herein, do not alter the predominantly
hydrocarbon substituent (e.g., halo (especially chloro and fluoro),
hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and
sulfoxy);
[0175] (3) hetero-substituents, that is, substituents which, while
having a predominantly hydrocarbon character, in the context of
this description, contain other than carbon in a ring or chain
otherwise composed of carbon atoms. Hetero-atoms include sulfur,
oxygen, nitrogen, and encompass substituents such as pyridyl,
furyl, thienyl, and imidazolyl. In general, no more than two, or as
a further example, no more than one, non-hydrocarbon substituent
will be present for every ten carbon atoms in the hydrocarbyl
group; typically, there will be no non-hydrocarbon substituent in
the hydrocarbyl group.
[0176] The fluid composition may include up to about 2.0 wt % of
the metal deactivators.
[0177] Component (J): Supplemental Friction Modifiers
[0178] Supplemental friction modifiers optionally are used in
automatic transmission fluids to help decrease friction between
surfaces (e.g., the members of a torque converter clutch or a
shifting clutch) at low sliding speeds. The result is a
friction-vs.-velocity (.mu.-v) curve that has a positive slope,
which in turn leads to smooth clutch engagements and minimizes
"stick-slip" behavior (e.g., shudder, noise, and harsh shifts).
[0179] Friction modifiers include such compounds as aliphatic
amines or ethoxylated aliphatic amines, ether amines, alkoxylated
ether amines, aliphatic fatty acid amides, acylated amines,
aliphatic carboxylic acids, aliphatic carboxylic esters, polyol
esters, aliphatic carboxylic ester-amides, imidazolines, tertiary
amines, aliphatic phosphonates, aliphatic phosphates, aliphatic
thiophosphonates, aliphatic thiophosphates, etc., wherein the
aliphatic group usually contains one or more carbon atoms so as to
render the compound suitably oil soluble. As a further example, the
aliphatic group may contain about 8 or more carbon atoms.
[0180] One group of friction modifiers includes the N-aliphatic
hydrocarbyl-substituted diethanol amines in which the N-aliphatic
hydrocarbyl-substituent is at least one straight chain aliphatic
hydrocarbyl group free of acetylenic unsaturation and having in the
range of about 14 to about 20 carbon atoms.
[0181] An example of a suitable friction modifier system is
composed of a combination of at least one N-aliphatic
hydrocarbyl-substituted diethanol amine and at least one
N-aliphatic hydrocarbyl-substituted trimethylene diamine in which
the N-aliphatic hydrocarbyl-substituent is at least one straight
chain aliphatic hydrocarbyl group free of acetylenic unsaturation
and having in the range of about 14 to about 20 carbon atoms.
Further details concerning this friction modifier system are set
forth in U.S. Pat. Nos. 5,372,735 and 5,441,656.
[0182] Another friction modifier system is based on the combination
of (i) at least one di(hydroxyalkyl) aliphatic tertiary amine in
which the hydroxyalkyl groups, being the same or different, each
contain from about 2 to about 4 carbon atoms, and in which the
aliphatic group is an acyclic hydrocarbyl group containing from
about 10 to about 25 carbon atoms, and (ii) at least one
hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group
contains from about 2 to about 4 carbon atoms, and in which the
aliphatic group is an acyclic hydrocarbyl group containing from
about 10 to about 25 carbon atoms. For further details concerning
this friction modifier system, reference should be had to U.S. Pat.
No. 5,344,579.
[0183] Another suitable group of friction modifiers include
polyolesters, for example, glycerol monooleate (GMO), glycerol
monolaurate (GML), and the like.
[0184] Generally speaking, the fluid compositions may contain up to
about 1.25 wt %, or, as a further example, from about 0.05 to about
1 wt % of one or more friction modifiers.
[0185] Component (K): Antioxidants
[0186] In some embodiments, antioxidant compounds may be included
in the compositions. Antioxidants include phenolic antioxidants,
aromatic amine antioxidants, sulfurized phenolic antioxidants, and
organic phosphites, among others. Examples of phenolic antioxidants
include 2,6-di-tert-butylphenol, liquid mixtures of tertiary
butylated phenols, 2,6-di-tert-butyl-4-methylphenol,
4,4'-methylenebis(2,6-di-tert-butylphenol),2,2'-methylenebis(4-methyl6-te-
rt-butylphenol), mixed methylene-bridged polyalkyl phenols, and
4,4'-thiobis(2-methyl-6-tert-butylphenol).
N,N'-di-sec-butyl-phenylenediamine, 4-isopropylaminodiphenylamine,
phenyl-.alpha.-naphthyl amine, phenyl-.alpha.-naphthyl amine, and
ring-alkylated diphenylamines. Examples include the sterically
hindered tertiary butylated phenols, bisphenols and cinnamic acid
derivatives and combinations thereof. The amount of antioxidant in
the fluid compositions described herein may include up to about 5
wt % based on the total weight of the fluid formulation. It may
range particularly from about 0.01 to about 3.0 wt %, more
particularly from about 0.1 wt % to about 0.7 wt %, based on the
total weight of the fluid formulation.
[0187] Component (L): Anti-Rust Agents
[0188] Rust or corrosion inhibitors are another type of inhibitor
additive for use in embodiments of the present disclosure. Such
materials include monocarboxylic acids and polycarboxylic acids.
Examples of suitable monocarboxylic acids are octanoic acid,
decanoic acid and dodecanoic acid. Suitable polycarboxylic acids
include dimer and trimer acids such as are produced from such acids
as tall oil fatty acids, oleic acid, linoleic acid, or the like.
Another useful type of rust inhibitor may comprise alkenyl succinic
acid and alkenyl succinic anhydride corrosion inhibitors such as,
for example, tetrapropenylsuccinic acid, tetrapropenylsuccinic
anhydride, tetradecenylsuccinic acid, tetradecenylsuccinic
anhydride, hexadecenylsuccinic acid, hexadecenylsuccinic anhydride,
and the like. Also useful are the half esters of alkenyl succinic
acids having about 8 to about 24 carbon atoms in the alkenyl group
with alcohols such as the polyglycols. Other suitable rust or
corrosion inhibitors include ether amines; acid phosphates; amines;
polyethoxylated compounds such as ethoxylated amines, ethoxylated
phenols, and ethoxylated alcohols; imidazolines; aminosuccinic
acids or derivatives thereof, and the like. Materials of these
types are commercially available. Mixtures of such rust or
corrosion inhibitors can be used. The amount of corrosion inhibitor
in the fluid compositions described herein may include up to about
2.0 wt % based on the total weight of the composition. It may range
particularly from about 0.01 to about 2.0 wt %, more particularly
from about 0.01 to about 0.3 wt %, based on the total weight of the
formulation.
[0189] Component (M): Copper Corrosion Inhibitors
[0190] In some embodiments, copper corrosion inhibitors may
constitute another class of additives suitable for inclusion in the
compositions. Such compounds include thiazoles, triazoles, and
thiadiazoles. Examples of such compounds include benzotriazole,
tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole,
2-mercapto benzothiazole, 2,5-dimercapto-1,3,4-thiadiazole,
2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles,
2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles,
2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles, and
2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles. Suitable compounds
include the 1,3,4-thiadiazoles, a number of which are available as
articles of commerce, and also combinations of triazoles such as
tolyltriazole with a 1,3,5-thiadiazole such as a
2,5-bis(alkyldithio)-1,3,4-thiadiazole. Regarding dialkyl
thiadiazoles, for imparting corrosion inhibition, that additive
previously has been used in much smaller treat levels than the
levels used in the present invention to enhance extreme pressure
and antiwear properties (when used in combination with relatively
high levels of sulfurized fatty oil as indicated herein). The
1,3,4-thiadiazoles are generally synthesized from hydrazine and
carbon disulfide by known procedures. See, for example, U.S. Pat.
Nos. 3,862,798 and 3,840,549.
[0191] The amount of the corrosion inhibitor in the fluid
compositions described herein may include up to about 1.0 wt %
based on the total weight of the composition.
[0192] Component (N): Viscosity Index Improvers
[0193] Viscosity index improvers for use in the above described
fluid compositions and gear lubricant compositions may be selected
from polyisoalkylene compounds, polymethacrylate compounds, and any
conventional viscosity index improvers. An example of a suitable
polyisoalkylene compound for use as a viscosity index improver
includes polyisobutylene having a weight average molecular weight
ranging from about 700 to about 2,500. Embodiments may include a
mixture of one or more viscosity index improvers of the same or
different molecular weight.
[0194] Suitable viscosity index improvers may include
styrene-maleic esters, polyalkylmethacrylates, and olefin copolymer
viscosity index improvers. Mixtures of the foregoing products can
also be used as well as dispersant and dispersant-antioxidant
viscosity index improvers.
[0195] The fluid composition may include up to about 25 wt % based
of a viscosity index improver. It may contain viscosity index
improver in an amount ranging particularly from about 0.1 to about
25 wt %, based on the total weight of the formulation.
[0196] Component (O): Antifoam Agents
[0197] In some embodiments, a foam inhibitor may form another
component suitable for use in the compositions. Foam inhibitors may
be selected from silicones, polyacrylates, surfactants, and the
like. The amount of antifoam agent in the fluid compositions
described herein may include up to about 0.5 wt % based on the
total weight of the composition. It may range particularly from
about 0.01 to about 0.5 wt %, more particularly from about 0.01 to
about 0.1 wt %, based on the total weight of the formulation.
[0198] Component (P): Seal Swell Agents
[0199] The seal swell agent used in the transmission fluid
compositions described herein is selected from oil-soluble
diesters, oil-soluble sulfones, and mixtures thereof. Generally
speaking the most suitable diesters include the adipates, azelates,
and sebacates of C.sub.8-C.sub.13 alkanols (or mixtures thereof),
and the phthalates of C.sub.4-C.sub.13 alkanols (or mixtures
thereof). Mixtures of two or more different types of diesters
(e.g., dialkyl adipates and dialkyl azelates, etc.) can also be
used. Examples of such materials include the n-octyl, 2-ethylhexyl,
isodecyl, and tridecyl diesters of adipic acid, azelaic acid, and
sebacic acid, and the n-butyl, isobutyl, pentyl, hexyl, heptyl,
octyl, nonyl, decyl, undecyl, dodecyl, and tridecyl diesters of
phthalic acid.
[0200] Other esters which may give generally equivalent performance
are polyol esters. Suitable sulfone seal swell agents are described
in U.S. Pat. Nos. 3,974,081 and 4,029,587. Typically these products
are employed at levels in the range of up to about 30 wt %. The
amount of seal swell agent in the fluid compositions described
herein may range particularly from about 1 to about 15 wt %,
particularly from about 0.25 wt % to about 1 wt %, in the finished
fluid.
[0201] Suitable seal swell agents are the oil-soluble dialkyl
esters of (i) adipic acid, (ii) sebacic acid, or (iii) phthalic
acid. The adipates and sebacates may be used in amounts in the
range of up to about 30 wt %. These amounts may range particularly
from about 1 to about 15 wt %, more particularly from about 1.5 to
about 10 wt %, in the finished fluid. In the case of the
phthalates, the levels in the fluid may fall in the range of from
about 1.5 to about 15 wt %.
[0202] Component (Q): Dye:
[0203] A colorant may be added to the fluid to give it a detectable
character. Generally, azo class dyes are used, such as C.I. Solvent
Red 24 or C.I. Solvent Red 164, as set forth in the "Color Index"
of the American Association of textile Chemists and Colorists and
the Society of Dyers and Colourists (U.K.). For automatic
transmission fluids, Automatic Red Dye is preferred. Dye may be
present in a very minimal amount, such as up to about 400 ppm, and
particularly ranging from about 200 to about 300 ppm in the
finished fluid.
[0204] Component (R): Diluent
[0205] If the additives are provided in an additive package
concentrate, a suitable carrier diluent is added to ease blending,
solubilizing, and transporting the additive package. The diluent
oil needs to be compatible with the base oil and the additive
package. In one embodiment, the diluent is present in the
concentrate in an amount of between about 5 to about 20%, although
it can vary widely with application. Generally speaking, less
diluent is preferable as it lowers transportation costs and treat
rates.
[0206] Additives used in formulating the compositions described
herein can be blended into base oil individually or in various
sub-combinations. However, it is suitable to blend all of the
components concurrently using an additive concentrate (i.e.,
additives plus a diluent, such as a hydrocarbon solvent). The use
of an additive concentrate takes advantage of the mutual
compatibility afforded by the combination of ingredients when in
the form of an additive concentrate. Also, the use of a concentrate
reduces blending time and lessens the possibility of blending
errors.
[0207] Fluid compositions described herein may include diluent in
an amount of up to about 25 wt % based on the total weight of the
finished fluid.
[0208] Base Oil
[0209] Transmission fluids of the present invention typically (but
not necessarily always) are formulated with a major amount of a
base oil and a minor amount of the additive package which includes
the extreme-pressure/antiwear enhancing combination of sulfurized
fatty oil and dialkyl thiadiazole at the prescribed addition
levels. In one embodiment, a power transmission fluid composition
is formulated to contain a major amount of base oil and about 3 wt
% to about 20 wt %, particularly about 5 wt % to about 13 wt %, of
an additive composition containing the sulfurized fatty oil and
dialkyl thiadiazole in the respective levels prescribed herein.
[0210] Base oils suitable for use in formulating fluid compositions
according to the present disclosure may be selected from any of the
synthetic or natural oils or mixtures thereof. Natural oils include
animal oils and vegetable oils (e.g., castor oil, lard oil) as well
as mineral lubricating oils such as liquid petroleum oils and
solvent treated or acid-treated mineral lubricating oils of the
paraffinic, naphthenic or mixed paraffinic-naphthenic types. Oils
derived from coal or shale are also suitable. The base oil
typically has a viscosity of, for example, from about 2 to about 15
cSt and, as a further example, from about 2 to about 10 cSt at
100.degree. C. Further, oils derived from a gas-to-liquid process
are also suitable.
[0211] Synthetic oils include hydrocarbon oils such as polymerized
and interpolymerized olefins (e.g., polybutylenes, polypropylenes,
propylene isobutylene copolymers, etc.); polyalphaolefins such as
poly(1-hexenes), poly-(1-octenes), poly(1-decenes), etc. and
mixtures thereof, alkylbenzenes (e.g., dodecylbenzenes,
tetradecylbenzenes, di-nonylbenzenes, di-(2-ethylhexyl)benzenes,
etc.); polyphenyls (e.g., biphenyls, terphenyl, alkylated
polyphenyls, etc.); alkylated diphenyl ethers and alkylated
diphenyl sulfides and the derivatives, analogs and homologs thereof
and the like.
[0212] Alkylene oxide polymers and interpolymers and derivatives
thereof where the terminal hydroxyl groups have been modified by
esterification, etherification, etc., constitute another class of
known synthetic oils that may be used. Such oils are exemplified by
the oils prepared through polymerization of ethylene oxide or
propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene
polymers (e.g., methyl-polyisopropylene glycol ether having an
average molecular weight of about 1000, diphenyl ether of
polyethylene glycol having a molecular weight of about 500-1000,
diethyl ether of polypropylene glycol having a molecular weight of
about 1000-1500, etc.) or mono- and polycarboxylic esters thereof,
for example, the acetic acid esters, mixed C.sub.3-8 fatty acid
esters, or the C.sub.13 Oxo acid diester of tetraethylene
glycol.
[0213] Another class of synthetic oils that may be used includes
the esters of dicarboxylic acids (e.g., phthalic acid, succinic
acid, alkyl succinic acids, alkenyl succinic acids, maleic acid,
azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic
acid, linoleic acid dimer, malonic acid, alkyl malonic acids,
alkenyl malonic acids, etc.) with a variety of alcohols (e.g.,
butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene
glycol, etc.) Specific examples of these esters include dibutyl
adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl
sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl
phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl
diester of linoleic acid dimer, the complex ester formed by
reacting one mole of sebacic acid with two moles of tetraethylene
glycol and two moles of 2-ethylhexanoic acid and the like.
[0214] Esters useful as synthetic oils also include those made from
C.sub.5 to C.sub.12 monocarboxylic acids and polyols and polyol
ethers such as neopentyl glycol, trimethylol propane,
pentaerythritol, dipentaerythritol, tripentaerythritol, etc.
[0215] Hence, the base oil used which may be used to make the
transmission fluid compositions as described herein may be selected
from any of the base oils in Groups I-V as specified in the
American Petroleum Institute (API) Base Oil Interchangeability
Guidelines.
[0216] Such base oil groups are as follows (Table B):
TABLE-US-00002 TABLE B Saturates Base Oil Group.sup.1 Sulfur (wt %)
(wt %) Viscosity Index Group I >0.03 and/or <90 80 to 120
Group II .ltoreq.0.03 And .gtoreq.90 80 to 120 Group III
.ltoreq.0.03 And .gtoreq.90 .gtoreq.120 Group IV all
polyalphaolefins (PAOs) Group V all others not included in Groups
I-IV .sup.1Groups I-III are mineral oil base stocks.
[0217] As set forth above, the base oil may be a poly-alpha-olefin
(PAO). Typically, the poly-alpha-olefins are derived from monomers
having from about 4 to about 30, or from about 4 to about 20, or
from about 6 to about 16 carbon atoms. Examples of useful PAOs
include those derived from octene, decene, mixtures thereof, and
the like. PAOs may have a viscosity of from about 2 to about 15, or
from about 3 to about 12, or from about 4 to about 8 cSt at
100.degree. C. Examples of PAOs include 4 cSt at 100.degree. C.
poly-alpha-olefins, 6 cSt at 100.degree. C. poly-alpha-olefins, and
mixtures thereof. Mixtures of mineral oil with the foregoing
poly-alpha-olefins may be used.
[0218] The base oil may be an oil derived from Fischer-Tropsch
synthesized hydrocarbons. Fischer-Tropsch synthesized hydrocarbons
are made from synthesis gas containing H.sub.2 and CO using a
Fischer-Tropsch catalyst. Such hydrocarbons typically require
further processing in order to be useful as the base oil. For
example, the hydrocarbons may be hydroisomerized using processes
disclosed in U.S. Pat. No. 6,103,099 or 6,180,575; hydrocracked and
hydroisomerized using processes disclosed in U.S. Pat. No.
4,943,672 or 6,096,940; dewaxed using processes disclosed in U.S.
Pat. No. 5,882,505; or hydroisomerized and dewaxed using processes
disclosed in U.S. Pat. No. 6,013,171; 6,080,301; or 6,165,949.
[0219] Unrefined, refined and rerefined oils, either natural or
synthetic (as well as mixtures of two or more of any of these) of
the type disclosed hereinabove can be used in the base oils.
Unrefined oils are those obtained directly from a natural or
synthetic source without further purification treatment. For
example, a shale oil obtained directly from retorting operations, a
petroleum oil obtained directly from primary distillation or ester
oil obtained directly from an esterification process and used
without further treatment would be an unrefined oil. Refined oils
are similar to the unrefined oils except they have been further
treated in one or more purification steps to improve one or more
properties. Many such purification techniques are known to those
skilled in the art such as solvent extraction, secondary
distillation, acid or base extraction, filtration, percolation,
etc. Rerefined oils are obtained by processes similar to those used
to obtain refined oils applied to refined oils which have been
already used in service. Such rerefined oils are also known as
reclaimed or reprocessed oils and often are additionally processed
by techniques directed to removal of spent additives, contaminants,
and oil breakdown products.
[0220] In selecting any of the foregoing optional additives, it is
important to ensure that the selected component(s) is/are soluble
or stably dispersible in the additive package and finished ATF
composition, are compatible with the other components of the
composition, and do not interfere significantly with the
performance properties of the composition, such as the anti-NVH,
anti-NVH durability, extreme pressure, antiwear, friction,
viscosity and/or shear stability properties, needed or desired, as
applicable, in the overall finished composition.
[0221] In general, the ancillary additive components are employed
in the oils in minor amounts sufficient to improve the performance
characteristics and properties of the base fluid. The amounts will
thus vary in accordance with such factors as the viscosity
characteristics of the base fluid employed, the viscosity
characteristics desired in the finished fluid, the service
conditions for which the finished fluid is intended, and the
performance characteristics desired in the finished fluid.
[0222] However, generally speaking, and referring to Table C below,
the following general concentrations (weight percent unless
otherwise indicated) of the optional additional components in the
base fluids are illustrative: TABLE-US-00003 TABLE C Optional
Additive Component Range G 0.0-15.00 H 0.0-1.00 I 0.0-2.00 J
0.0-1.25 K 0.0-5.00 L 0.0-2.0 M 0.0-1.0 N 0.0-25.0 O 0.0-0.5 P
0.0-30.0 Q 0.0-400 ppm R 0.0-25.0 (in concentrate balance)
[0223] An exemplary, non-limiting fully formulated fluid
compositions for providing improved NVH suppression and/or anti-NVH
durability according to embodiments herein are set forth in Table D
below. Referenced components correspond to previously identified
classes of components. Key components, viz., Components (A)-(D) in
the case of NVH suppression, and Components (A)-(F) in the case of
anti-NVH durability improvements, within this formulation will be
balanced pursuant to guidance provided elsewhere herein within the
respective prescribed range amounts. TABLE-US-00004 TABLE D General
Range Amount, Preferred Range Component wt % Amount, wt % Friction
Modifier 0.002-0.25 0.002-0.25 (Component (A)) Friction Modifier
0.01-0.2 0.01-0.2 (Component (B)) Metallic Detergent 0.01-0.6
0.01-0.6 (Component (C)) Dispersant 0.01-10 0.01-10 (Component (D))
Surfactant/Friction 0-0.40 0.01-0.40 Modifier (Component (E))
Non-ionic Surfactant 0-0.5 0.01-0.5 (Component ((F) Antioxidants
0.1-0.7 0.1-0.5 Sulfur Source 0.05-1.5 0.05-1.5 Thiadiazole 0-2.0
0-2.0 Rust Inhibitors 0-0.3 0-0.2 Antifoam Agents 0-0.5 0-0.5
Diluent Oil 0-25 0-25 Basestock 60-95 60-95
[0224] It will be appreciated that the individual components
employed can be separately blended into the base fluid or can be
blended therein in various subcombinations, if desired. Ordinarily,
the particular sequence of such blending steps is not crucial.
Moreover, such components can be blended in the form of separate
solutions in a diluent. It is preferable, however, to blend the
additive components used in the form of a concentrate, as this
simplifies the blending operations, reduces the likelihood of
blending errors, and takes advantage of the compatibility and
solubility characteristics afforded by the overall concentrate.
[0225] Additive concentrates can thus be formulated to contain all
of the additive components and if desired, some of the base oil
component, in amounts proportioned to yield finished fluid blends
consistent with the concentrations described above. In most cases,
the additive concentrate will contain one or more diluents such as
light mineral oils, to facilitate handling and blending of the
concentrate. Thus concentrates containing up to about 50 wt % of
one or more diluents or solvents can be used, provided the solvents
are not present in amounts that interfere with the low and high
temperature and flash point characteristics and the performance of
the finished power transmission fluid composition. In this regard,
the additive components used pursuant to this invention may be
selected and proportioned such that an additive concentrate or
package formulated from such components will have a flash point of
about 170.degree. C. or above, using the ASTM D-92 test
procedure.
[0226] Power transmission fluids of the embodiments herein, as
formulated as described above, also generally provide enhanced
extreme pressure properties for applications where metal-to-metal
contact is made under high pressures, e.g., pressures in excess of
2 GPa. Such fluids are suitable for automatic and manual
transmissions such as step automatic transmissions, continuously
variable transmissions, automated manual transmissions, and dual
clutch transmissions. High metal-to-metal contact pressures such as
those found in automotive transmissions, for example, may cause
damage to transmission parts if a lubricant is used that does not
possess sufficient extreme pressure protection characteristics.
However, power transmission fluid compositions as described herein
also have good extreme pressure performance characteristics.
[0227] The fluid compositions of embodiments of this invention
described herein may be advantageously used in a wide variety of
applications, including, for example, in automatic transmission
fluids, manual transmission fluids, fluids used in dual clutch
transmissions, fluids used in heavy duty transmissions, fluids used
in continuously variable transmissions, and gear lubricants.
Further, the automatic transmission fluid may be suitable for use
in at least one transmission with a slipping torque converter
clutch, a lock-up torque converter clutch, a starting clutch,
electronically controlled converter clutch, and/or one or more
shifting clutches, and so forth. Such transmissions may include
four-, five-, six-, and seven-speed or more transmissions, and
continuously variable transmissions of the chain, belt, disk, or
toroidal type. The clutch used with these fluids may comprise,
e.g., the same clutch materials as described indicated above. They
also may be used in gear applications, such as industrial gear
applications and automotive gear applications. Gear-types may
include, but are not limited to, spur, spiral bevel, helical,
planetary, and hypoid. They may be used in axles, transfer cases,
and the like. Further, they may also be useful in metal working
applications.
EXAMPLES
[0228] Illustrative compositions suitable for use in the practice
of this invention are presented in the following Examples, wherein
all parts and percentages are by weight unless specified
otherwise.
Example A
Squawk Pressure Studies
[0229] Component effects of automatic transmission fluids were
evaluated in eight fluid samples, designated ATF-A through ATF-H
(see Table 1 below). The test fluids had a baseline composition
corresponding to the preferred formulation described above in Table
D with the following modifications. Six design variables,
designated I-VI, which corresponded to six of the components
identified in Table D, were applied, where "+" means the variable
was present in the highest level of the corresponding range
described in Table D and "-" indicates its absence or presence at
the lowest level of the corresponding range described in Table D
from a given sample run, with the further qualification that "+"
under Design Variable VI indicates the sulfur source was sulfurized
transesterified triglyceride while "-" indicated that it was a
sulfurized ester. Design variables I-VI corresponded to the
following six components of the baseline fluid: I: Component (D);
II: Component (B); III: Component (C); IV: Component (A); V: Rust
Inhibitors: and VI: Sulfur Source.
[0230] Friction characteristics for the matrix of fluids were
investigated on a Low Speed SAE#2 machine. Tests were conducted
with cellulose paper based friction material lined plates,
commercially obtained as BW 4329 plates from Borg Warner
Automotive. Friction was measured and recorded at 40.degree. C. and
120.degree. C. at four different pressures: 0.40, 0.79, 1.97 and
3.39N/mm.sup.2. Squawk pressure was measured on a
commercially-available ZF GK Rig using a test procedure supplied by
ZF with the apparatus. The squawk pressure results corresponding to
the various tested sample fluids are also reported in Table 1
below. TABLE-US-00005 TABLE 1 Squawk Design Variables pressure,
Fluid I II III IV V VI N/mm.sup.2 ATF-A + - + - + - 0.50 ATF-B - +
+ - - + 1.90 ATF-C + - - - - + 0.40 ATF-D + + + + + + 1.38 ATF-E -
- + + - - 2.20 ATF-F + + - + - - 1.13 ATF-G - + - - + - 1.05 ATF-H
- - - + + + 1.60
[0231] Using these fluid samples FIGS. 4-10 are plots of squawk
pressure versus .differential..mu./.differential.T as measured
sliding speeds at a pressure of 0.79N/mm.sup.2. FIG. 11 is a plot
of R.sup.2 (for correlation of .differential..mu./.differential.T
to squawk pressure) versus rpm for the test pressure condition of
0.79N/mm.sup.2. FIGS. 12-17 are plots of squawk pressure versus
.differential..mu./.differential.T as measured sliding speeds at a
pressure of 3.40N/mm.sup.2. FIGS. 18-19 show coefficient of
friction .mu. results observed for the eight test fluids at a
pressure of 0.79N/mm.sup.2 at temperatures at 40.degree. C. and
120.degree. C., respectively. Temperatures for
.differential..mu./.differential.T were bulk temperatures at given
pressure and rpm. For example, if .mu.(40.degree. C.) was 0.152 and
.mu.(120.degree. C.) was 0.148, then
.differential..mu./.differential.T equal
(0.148-0.152)/(120-40)=0.00005. Values were multiplied by 10,000
for ease of handling. FIG. 20 is a plot of coefficient of
.differential..mu./.differential.T versus sliding speed at a
pressure of 0.79N/mm.sup.2. FIGS. 21-28 are plots of squawk
pressure versus .differential..mu./.differential.P at a series of
different test conditions (viz., rpm's, temperature, pressure), as
indicated therein. FIG. 29 shows coefficient of friction .mu.
results observed for test fluids at temperatures at 40.degree. C.
and 120.degree. C., respectively.
[0232] The results indicate that squawk control improves with
negative .differential..mu./.differential.T. The results also show
that merely providing a fluid having a positive slope of .mu.-v is
insufficient to improve squawk performance. The correlation between
squawk and .differential..mu./.differential.T was only observed at
specific conditions in the low speed rig, viz., at a pressure of
0.79N/mm.sup.2 and above 50 rpm (0.27 m/s). The results also
indicate that squawk control improves with negative
.differential..mu./.differential.P, albeit perhaps not as
significantly as .differential..mu./.differential.T under the
particular testing conditions applied in these studies.
[0233] The results also show that the presence or absence of
certain individual components, viz., Components (A)-(D), in the
additive can significantly influence variation in friction level
due to change in temperature. The results indicated that four out
of the six variables strongly influence
.differential..mu./.differential.T (and
.differential..mu./.differential.P), which are Components (A)-(D)
described herein. These results indicate that levels of these four
components should balanced to introduce a small negative
.differential..mu./.differential.T condition for improved squawk
performance. In general it was found that the noise phenomena
decreases with decreasing quasi-static friction level. Higher
quasi-static friction is generally desirable for higher torque
transmission.
Example 1
Studies of Anti-NVH Durability and Squawk Performance in Aged
Fluids
[0234] A study was conducted to investigate the stability in
friction performance in a transmission environment for an age form
of a test fluid, Fluid A, which contains a composition as described
above in Table D, and representing an embodiment of the invention,
as compared to a commercial ATF. The comparison commercial ATF was
Shell 13754.4.
[0235] FIG. 30 shows the Low Speed SAE#2 friction characteristics
of Fluid A and the comparison fluid before (fresh fluid) and after
aging at 150.degree. C. for 200 hours. The results show that Fluid
A retains positive friction characteristics in contrast to the
comparison product, which shows a dramatic change in friction
levels and slope. Friction characteristics of the comparison fluid
can be expected to increase the probability for increased shift
chatter and shudder.
[0236] Noise phenomena, viz. squawk, was measured on a ZF GK test
rig in terms of the threshold pressure beyond which this phenomena
is detected. The higher the threshold pressure value, the lower the
probability for the noise phenomenon to occur for a given fluid.
Static and quasi-static frictions were measured during the squawk
test procedure.
[0237] Table 2 below reports the viscosity, friction, quasi-static
friction and squawk pressure ("Threshold Pressure") values observed
for the Fluid A representing the present invention and the
comparison commercial product. TABLE-US-00006 TABLE 2 Threshold
Pressure, N/mm.sup.2 KV100, Before After Fluid cSt BV-40, cP .mu.qs
.mu.s Aging Aging Fluid A 5.26 9350 0.111 0.126 1.15 1.15 Reference
5.30 8250 0.100 0.122 0.66 0.55
[0238] Table 2 indicates that Fluid A has a significantly higher
performance than the comparison commercial product in terms of
squawk performance. Additionally, even though the threshold
pressure at which noise is observed is nearly double that of the
comparison product, quasi-static friction is nearly 11% higher than
that of the comparison product. Also, based on measurements taken
on a ZF GK Rig at 0.79N/mm.sup.2 and 100 rpm, Fluid A had a
.differential..mu./.differential.T of -0.500 and a squawk pressure
>0.8N/mm.sup.2, while the comparison commercial product had a
.differential..mu./.differential.T value of 0.000 and a squawk
pressure of 0.75N/mm.sup.2, which is consistent with the inventive
noise phenomena model of this invention presented elsewhere herein.
Clearly, these results demonstrate that this invention describes an
additive/fluid composition that also provides enhanced anti-NVH
durability without lowering static and quasi-static friction.
[0239] It is thought that Fluid A can be adapted to provide
improved performance in diverse transmissions using torque
converter and other clutch devices. Examples include, heavy-duty
bus transmissions and dual clutch transmissions, etc.
[0240] As used throughout the specification and claims, "a" and/or
"an" may refer to one or more than one. Unless otherwise indicated,
all numbers expressing quantities of ingredients, properties such
as molecular weight, percent, ratio, reaction conditions, and so
forth used in the specification and claims are to be understood as
being modified in all instances by the term "about." Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the specification and claims are approximations that may
vary depending upon the desired properties sought to be obtained by
the present invention. At the very least, and not as an attempt to
limit the application of the doctrine of equivalents to the scope
of the claims, each numerical parameter should at least be
construed in light of the number of reported significant digits and
by applying ordinary rounding techniques. Notwithstanding that the
numerical ranges and parameters setting forth the broad scope of
the invention are approximations, the numerical values set forth in
the specific examples are reported as precisely as possible. Any
numerical value, however, inherently contains certain errors
necessarily resulting from the standard deviation found in their
respective testing measurements.
[0241] At numerous places throughout this specification, reference
has been made to a number of U.S. Patents. All such cited documents
are expressly incorporated in full into this disclosure as if fully
set forth herein.
[0242] Other embodiments of the present invention will be apparent
to those skilled in the art from consideration of the
specification, Figure and practice of the invention disclosed
herein. It is intended that the specification and examples be
considered as exemplary only, with a true scope and spirit of the
invention being indicated by the following claims.
* * * * *