U.S. patent application number 12/911219 was filed with the patent office on 2012-02-02 for automobile transmission oil composition with improved low-temperature transmission performance.
This patent application is currently assigned to KIA MOTORS CORPORATION. Invention is credited to Sung Uk Lee.
Application Number | 20120028857 12/911219 |
Document ID | / |
Family ID | 45527311 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120028857 |
Kind Code |
A1 |
Lee; Sung Uk |
February 2, 2012 |
AUTOMOBILE TRANSMISSION OIL COMPOSITION WITH IMPROVED
LOW-TEMPERATURE TRANSMISSION PERFORMANCE
Abstract
The present invention provides a manual transmission oil
composition containing a predetermined amount of polyalphaolefin
(PAO) synthetic base oil and a predetermined amount of
polyalkylmethacrylate having a number-average molecular weight of
300,000 to 400,000 as a viscosity index improver and thus having a
high viscosity even at high temperatures and a low viscosity at low
temperatures compared to other manual transmission oils having the
same viscosity grade (SAE 75W85 grade).
Inventors: |
Lee; Sung Uk; (Hwaseong,
KR) |
Assignee: |
KIA MOTORS CORPORATION
Seoul
KR
HYUNDAI MOTOR COMPANY
Seoul
KR
|
Family ID: |
45527311 |
Appl. No.: |
12/911219 |
Filed: |
October 25, 2010 |
Current U.S.
Class: |
508/175 ;
508/287; 508/465 |
Current CPC
Class: |
C10M 2219/044 20130101;
C10M 169/04 20130101; C10N 2030/08 20130101; C10M 2205/0285
20130101; C10M 2219/08 20130101; C10M 2223/04 20130101; C10N
2030/02 20130101; C10M 2219/046 20130101; C10M 2209/084 20130101;
C10M 2215/28 20130101; C10M 2223/045 20130101; C10N 2030/68
20200501; C10M 2205/0285 20130101; C10M 2205/0285 20130101; C10M
2209/084 20130101; C10N 2020/04 20130101; C10M 2209/084 20130101;
C10N 2020/04 20130101 |
Class at
Publication: |
508/175 ;
508/465; 508/287 |
International
Class: |
C10M 169/04 20060101
C10M169/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2010 |
KR |
10-2010-0074076 |
Claims
1. A manual transmission oil composition comprising: 78 to 80 wt %
of polyalphaolefin synthetic base oil; 10 to 12 wt % of
polyalkylmethacrylate having a number-average molecular weight of
300,000 to 400,000; and 8 to 12 wt % of at least one additive
selected from the group consisting of an anti-wear agent, a
metallic detergent-dispersant, a phosphate ester friction modifier,
a bis-succinimide ashless dispersant, an extreme pressure additive,
and a mixture thereof.
2. The manual transmission oil composition of claim 1, wherein the
base oil has an average kinematic viscosity of 3 to 8 cSt at
100.degree. C., a viscosity index of 130 or higher, and a pour
point of -60.degree. C.
3. The manual transmission oil composition of claim 1, wherein the
polyalkylmethacrylate comprises 60 to 80 wt% of C.sub.12 to
C.sub.15 alkyl methacrylate and 20 to 40 wt % of 2-ethyihexyl
methacrylate.
4. The manual transmission oil composition of claim 1, wherein the
anti-wear agent is zinc dithiophosphate, the metallic
detergent-dispersant is calcium sulfonate, and the extreme pressure
additive is polysulfide.
5. A manual transmission oil composition comprising: 78 to 80 wt %
of a synthetic base oil; 10 to 12 wt % of a viscosity index
improver; and 8 to 12 wt % of at least one additive selected from
the group consisting of anti-wear agents, metallic
detergent-dispersants, phosphate ester friction modifiers,
bis-succinimide ashless dispersants, extreme pressure additives,
and a mixture thereof.
6. The manual transmission oil of claim 5, wherein the synthetic
base oil has an average kinematic viscosity ranging from about 3 to
8 cSt at 100.degree. C.
7. The manual transmission oil composition of claim 5, wherein the
viscosity index improver has a number-average molecular weight of
300,000 to 400,000.
8. A manual transmission oil composition comprising: 78 to 80 wt %
polyalphaolefin synthetic base oil; 10 to 12 wt % of a viscosity
index improver having a number-average molecular weight of 300,000
to 400,000; and one or more additives selected from the group
consisting of anti-wear agents, metallic detergent-dispersants,
phosphate ester friction modifiers, bis-succinimide ashless
dispersants, and extreme pressure additives.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims under 35 U.S.C. .sctn.119(a) the
benefit of Korean Patent Application No. 10-2010-0074076 filed Jul.
30, 2010, the entire contents of which are incorporated herein by
reference.
BACKGROUND
[0002] (a) Technical Field
[0003] The present disclosure relates to an automobile transmission
oil and a method of lubricating an automobile transmission using
the oil. More particularly, it relates to a manual transmission oil
composition containing a polyalphaolefin synthetic base oil and a
viscosity modifier.
[0004] (b) Background Art
[0005] In a typical vehicle, a transmission is installed between a
clutch and a drive shaft or between a clutch and a final reduction
gear. The transmission converts the engine's output by adjusting
the speed and torque so as to drive the wheels with rotational
speeds and forces suitable for operating the vehicle. A manual
transmission changes the rotational speed and force transmitted
from the engine through a gear shaft which is in connection with
the clutch such that, according to the running conditions of the
vehicle and the manipulation of the clutch, the power is converted
and transmitted to the drive wheels, thereby providing the speed
and torque that the driver demands.
[0006] The manual transmission can be equipped with a synchronizer
to facilitate the driver's gear shift. A synchronizer is a device
for synchronizing the speed of a shift gear with the speed of a
clutch gear during gear shifting to provide smoother shifting. In
some embodiments, the synchronizer includes a synchromesh which
brings the speed of the shift gear in synchronization with the
speed of the clutch gear before engaging the gears, for example by
the inclined contact of a synchromesh and a shift gear.
[0007] Automobile transmissions, including manual transmissions,
importantly use a transmission oil, which has a main function of
lubricating the moving parts. However, as it is known, the
viscosity of oil varies with temperature change and, thus, the
viscosity of the transmission oil can vary depending on factors
such as the time of year and whether and/or how much the vehicle
has been warmed up. If the viscosity of the transmission oil is
significantly increased, such as during cold winter conditions,
synchronization achieved by friction during contact is impeded,
thereby reducing shifting performance. Further, in conditions where
the outside temperature is very low, such as -20 to -50.degree. C.,
gear shifting may even be prevented.
[0008] In attempt to deal with this problem, Korean Patent No.
298,035, Korean Patent No. 706,434, Korean Patent Publication No.
2008-0109877, etc. provides a method for reducing the viscosity of
transmission oil at low temperatures. However, the method provided
simply reduces the overall viscosity, and thus the viscosity at
high temperatures is also reduced. As a result, the durability of
the transmission is deteriorated and significant rattle noise
occurs.
[0009] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention and therefore it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY OF THE DISCLOSURE
[0010] The present invention features an automobile transmission
oil composition which is provided with a low viscosity at low
temperatures, while reducing rattle noise and maintaining excellent
transmission durability even at high temperatures. The transmission
oil composition is useful for lubricating and operating various
types of transmissions, including a manual transmission. According
to an aspect of the present invention, an automobile transmission
oil composition comprises a synthetic base oil and a viscosity
index improver. Preferably, polyalphaolefin (PAO) synthetic base
oil is used as the base oil and polyalkylmethacrylate is used as
the viscosity index improver. The combination of predetermined
amounts of a synthetic base oil and a viscosity index improver in
accordance with the present invention provides an oil having a low
viscosity at low temperatures as compared to other transmission
oils having the same viscosity grade (SAE 75W85 grade).
[0011] In an exemplary embodiment, a manual transmission oil
composition is provided which comprises about 78 to 80 wt % of
polyalphaolefin synthetic base oil, about 10 to 12 wt % of
polyalkylmethacrylate, and one or more additives. In certain
aspects, the polyalkylmethacrylate has a number-average molecular
weight of about 300,000 to 400,000. Preferably, the composition
includes about 8 to 12 wt % of one or more additives. These
additives can include any known additives commonly included in
transmission oils such as, for example, anti-wear agents, metallic
detergent-dispersants, friction modifiers (particularly phosphate
ester friction modifiers), dispersants (particularly
bis-succinimide ashless dispersants), extreme pressure additives,
and mixtures thereof.
[0012] It is understood that the term "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles, plug-in
hybrid electric vehicles, hydrogen-powered vehicles and other
alternative fuel vehicles (e.g. fuels derived from resources other
than petroleum). As referred to herein, a hybrid vehicle is a
vehicle that has two or more sources of power, for example both
gasoline-powered and electric-powered vehicles.
[0013] The above and other features of the invention are discussed
infra.
DETAILED DESCRIPTION
[0014] Hereinafter reference will now be made in detail to various
embodiments of the present invention, examples of which are
described below. While the invention will be described in
conjunction with exemplary embodiments, it will be understood that
present description is not intended to limit the invention to those
exemplary embodiments. On the contrary, the invention is intended
to cover not only the exemplary embodiments, but also various
alternatives, modifications, equivalents and other embodiments,
which may be included within the spirit and scope of the invention
as defined by the appended claims.
[0015] One aspect of the present invention provides an automobile
transmission oil composition comprising a synthetic base oil,
preferably polyalphaolefin (PAO) synthetic base oil, and a
viscosity index improver. In certain embodiments, as a viscosity
index improver, polyalkylmethacrylate is used, particularly
polyalkylmethacrylate having a number-average molecular weight
ranging from about 300,000 to 400,000. It is noted that synthetic
base oils and viscosity index improvers are known and, thus, it is
possible to use known materials rather than or in combination with
the specific synthetic base oils and viscosity index improvers
specifically described herein. Such transmission oil compositions
are able to reduce the flow resistance at low temperatures, which
beneficially improves the shifting performance at low temperatures.
The present transmission oil compositions also provide improved
transmission durability as well as enhanced performance features
(such as shear stability, friction characteristics, thermal
stability, and oxidation stability). Further, the rattle noise
which often results at high operating temperatures is reduced when
using the present compositions.
[0016] In one embodiment, a manual transmission oil composition is
provided wherein the polyalphaolefin (PAO) synthetic base oil has
an average kinematic viscosity ranging from about 3 to 8 cSt at
100.degree. C. It has been found that when the kinematic viscosity
at 100.degree. C. is less than 3 cSt, the amount of oil evaporated
during use increases under high temperature and dry conditions. It
has also been found that when the kinematic viscosity at
100.degree. C. exceeds 8 cSt, the viscosity of the oil
significantly increases, which reduces the shifting performance and
fuel efficiency at low temperatures. As such, it is preferable that
the synthetic base oil have the kinematic viscosity in the above
range so as to reduce or eliminate these problems. In some
embodiments, the polyalphaolefin (PAO) synthetic base oil further
has a viscosity index of about 130 or higher, and a pour point of
about -60.degree. C.
[0017] Moreover, The PAO synthetic base oil is generally contained
in a large amount of the transmission oil composition (i.e., more
than about 50 wt % relative to the total weight of the lubricating
oil composition). Preferably, the transmission oil composition
contains at least about 75 wt %, more preferably at least about 78
wt %, and preferably no greater than about 80 wt % PAO synthetic
base oil. In a preferred embodiment, the transmission oil
composition contains about 78 to 80 wt % PAO synthetic base oil,
The transmission oil composition further includes a viscosity index
improver. Without being bound by theory, it is believed that by
combining the synthetic base oil with a viscosity index improver in
accordance with the present invention, the viscosity of the manual
transmission oil is increased and the increase in viscosity at low
temperatures is inhibited or even prevented, which thereby improves
the viscosity index of the oil. A particularly preferred viscosity
index improver is polyalkylmethacrylate. Suitable
polyalkylmethacrylate may have at least 4 polymer chains, and in
some preferred embodiments may have 4 to 10 polymer chains. In an
exemplary embodiment, the polyalkylmethacrylate contains about 60
to 80 wt % of C.sub.12 to C15 alkyl methacrylate and about 20 to 40
wt % of 2-ethylhexyl methacrylate. Preferred polyalkylmethacrylates
are those which have a kinematic viscosity of about 650 cSt or
higher at 100.degree. C. In preferred embodiments, the transmission
oil compositions contains about 10 to 12 wt %
polyalkylmethacrylate. It has been found that when the amount of
polyalkylmethacrylate used is less than 10 wt %, the viscosity is
not adequately increased at high and low temperatures, which causes
an excessive increase in viscosity at low temperatures. It has
further been found that if the amount of polyalkylmethacrylate used
exceeds 12 wt %, the viscosity at high and low temperatures is
increased at the same time, which causes a reduction in viscosity
due to shear as time goes on, thereby reducing the durability.
[0018] In some embodiments, the automobile transmission oil
composition may further contain one or more additives which have
conventionally been used in transmission oil compositions. The
additives may make up the balance of the transmission oil based on
the amounts of PAO synthetic base oil and viscosity index improver.
For example, in some embodiments, one or more additives may be
added in an amount of about 8 to 12 wt % with respect to the total
weight of the manual transmission oil composition. Suitable
additives include, but are not limited to, anti-wear agents,
metallic detergent-dispersants, friction modifiers (particularly a
phosphate ester friction modifier), dispersants (particularly a
bis-succinimide ashless dispersant), and extreme pressure
additives. As an anti-wear agent, any anti-wear agents that are
known for inclusion in transmission oils can be used such as, for
example, zinc dithiophosphate. Likewise, as a metallic
detergent-dispersant, any materials that are known for inclusion in
transmission oils can be suitably be used, such as, for example,
calcium sulfonate. Extreme pressure additives can also be selected
from any of those materials known for inclusion in transmission
oils, such as, for example. polysulfide.
[0019] In another aspect, as discussed above, the present invention
provides a method for lubricating automobile transmissions using
the above-described lubrication oil compositions. As discussed
above, the kind and size of the transmissions are not limited and,
in certain embodiments, the transmission is a manual transmission.
The above-described lubricating oil compositions may be supplied to
the transmissions in any way known to those of skill in the
art.
[0020] Next, the present invention will be described in more detail
with reference to examples. However, the present invention is not
limited by the following examples.
Examples 1 To 3 & Comparative Examples 1 to 6
Preparation of Manual Transmission Oil Compositions
[0021] Manual transmission oil compositions were prepared by
stirring the components listed in Table 1 together at 60 to
80.degree. C.
TABLE-US-00001 TABLE 1 Classification Example Comparative Example
(Unit: wt %) 1 2 3 1 2 3 4 5 6 Synthetic base oil .sup.(1) 18.0
18.0 18.0 41.0 20.0 37.0 17.0 35.0 15.0 Synthetic base oil .sup.(2)
61.0 61.0 61.0 40.0 61.0 40.0 60.0 40.0 60.0 Viscosity index
improver .sup.(3) 11.0 11.0 11.0 9.0 9.0 13.0 13.0 15.0 15.0
Additives Dithiophosphate 1.0 1.0 2.0 1.0 1.0 2.0 1.0 1.0 2.0
Calcium sulfonate 4.0 2.0 3.0 4.0 2.0 3.0 4.0 2.0 3.0 phosphate
ester 2.0 4.0 2.0 2.0 4.0 2.0 2.0 4.0 2.0 Bis-succinimide 2.0 2.0
2.0 2.0 2.0 2.0 2.0 2.0 2.0 Polysulfide 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
.sup.(1) Chevron Phillips, PAO 4 (Kinematic viscosity at
100.degree. C. 3.8 cSt; Viscosity index 130; Pour point -69.degree.
C. .sup.(2) Chevron Phillips, PAO 6 (Kinematic viscosity at
100.degree. C. 5.9 cSt; Viscosity index 135; Pour point -61.degree.
C. .sup.(3) Lubrizol, Anglamol (Number-average molecular weight
about 350,000)
Test Example: Evaluation of Viscosity (Kinematic Viscosity And
Low-Temperature Viscosity At -40.degree. C.) And Shear
Stability
[0022] The kinematic viscosity (ASTM D 445) and low-temperature
viscosity (ASTM D 2983) of the manual transmission oil compositions
prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were
evaluated, and the results are shown in the following table 2.
[0023] The shear stability was evaluated for 48 hours according to
CEC L-45-A-99 Viscosity shear stability of transmission lubricants
(Taper Roller Bearing Rig), and the change in viscosity is shown as
percentage in the following table 2.
TABLE-US-00002 TABLE 2 Example Comparative Example Classification 1
2 3 1 2 3 4 5 6 Kinematic at 100.degree. C. 11.2 11.3 11.2 8.0 8.5
12.5 13.0 13.5 13.5 Viscosity at 40.degree. C. 51.1 49.3 49.5 39.7
42.1 59.3 61.2 68.2 69.2 Viscosity index 219 228 227 179 185 215
219 206 202 Low-tem. viscosity 11,000 10,000 10,000 10,000 10,500
15,000 18,500 28,000 30,000 (at -40.degree. C., cP) Shear stability
(%) 28 28 28 28 28 32 32 35 35
[0024] As demonstrated in Table 1, while the shear stability and
low-temperature viscosity of the oil compositions prepared in
Comparative Examples 1 and 2 are good, the kinematic, viscosity is
low, which is disadvantageous in terms of durability and rattle
noise. Moreover, while the kinematic viscosity at a high
temperature of the oil compositions prepared in Comparative
Examples 3 to 6 is high, which is advantageous in terms of
durability and rattle noise, the shear stability and low-
temperature are notably lower than those of Examples 1 to 3. The
kinematic viscosity at a high temperature of the oil compositions
prepared in Example 1 to 3 was 11.2 to 11.3, which satisfies the
requirements of transmission durability and reduced rattle noise.
Furthermore, the low-temperature viscosity of the oil compositions
prepared in Example 1 to 3 was 10,000 to 11,000, which exhibits
excellent fluidity at low temperatures. Therefore, it is expected
that the manual transmission oil compositions prepared in Examples
1 to 3 can improve the low- temperature shifting performance, and
thus it can be seen that the oil compositions of Examples 1 to 3
have excellent viscosity characteristics compared to those of
Comparative Examples 1 to 6.
[0025] As described above, the manual transmission oil composition
according to the present invention improves the durability of the
manual transmission, reduces the rattle noise, and improves the
low-temperature shifting performance.
[0026] The invention has been described in detail with reference to
preferred embodiments thereof. However, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
invention, the scope of which is defined in the appended claims and
their equivalents.
* * * * *