U.S. patent application number 11/123986 was filed with the patent office on 2005-12-01 for lubricant composition for automobile driving system.
Invention is credited to Ichikawa, Akihiko, Kato, Tomohiro, Narihiko, Yoshimura, Saito, Koji, Yamamori, Kazuo, Yamamoto, Yoshikazu, Yoneda, Tetsuzo.
Application Number | 20050267002 11/123986 |
Document ID | / |
Family ID | 35169913 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050267002 |
Kind Code |
A1 |
Kato, Tomohiro ; et
al. |
December 1, 2005 |
Lubricant composition for automobile driving system
Abstract
A lubricant composition having a 40.degree. C. dynamic viscosity
of 40 mm.sup.2/s or less that has wear resistance equal to or
better than a lubricant having a 40.degree. C. dynamic viscosity of
76 mm.sup.2/s is achieved by providing a base oil with a zinc
dithiophosphate and alkaline earth metal salt in an amount to
provide a ratio of elemental zinc to alkaline earth metal in the
oil in the range of 0.2 to 1.0.
Inventors: |
Kato, Tomohiro; (Hannou-shi,
JP) ; Narihiko, Yoshimura; (Kawagoe-shi, JP) ;
Yamamori, Kazuo; (Nagoya-shi, JP) ; Saito, Koji;
(Toyota-shi, JP) ; Yoneda, Tetsuzo; (Toyota-shi,
JP) ; Yamamoto, Yoshikazu; (Okazaki-shi, JP) ;
Ichikawa, Akihiko; (Toyota-shi, JP) |
Correspondence
Address: |
EXXONMOBIL RESEARCH AND ENGINEERING COMPANY
P.O. BOX 900
1545 ROUTE 22 EAST
ANNANDALE
NJ
08801-0900
US
|
Family ID: |
35169913 |
Appl. No.: |
11/123986 |
Filed: |
May 6, 2005 |
Current U.S.
Class: |
508/372 ;
508/378 |
Current CPC
Class: |
C10M 2223/045 20130101;
C10N 2030/06 20130101; C10M 2207/262 20130101; C10M 2207/027
20130101; C10M 2207/028 20130101; C10M 2207/144 20130101; C10N
2030/02 20130101; C10M 2219/044 20130101; C10M 2219/046 20130101;
C10N 2010/04 20130101; C10M 163/00 20130101 |
Class at
Publication: |
508/372 ;
508/378 |
International
Class: |
C10M 141/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2004 |
JP |
2004-163106 |
Claims
What is claimed is:
1. A lubricant composition for a manual speed-change gear
comprising: a base oil; additives comprising at least one alkaline
earth metal salt and a zinc dithiophosphate, the amount of alkaline
earth metal element based on the total weight of lubricant
composition being 0.1 wt % or more, the elemental ratio of zinc to
alkaline earth metal from the additive being in the range of 0.2 to
1.0; and wherein the dynamic viscosity at 40.degree. C. of the
lubricant is 40 mm.sup.2/s or less.
2. The lubricant composition of claim 1 wherein the amount of
alkaline earth metal is from about 0.15 wt % to about 0.6 wt %.
3. The lubricant composition of claim 1 wherein the dynamic
viscosity at 40.degree. C. is 30 mm.sup.2/s or less.
4. The lubricant composition of claim 1 wherein the alkaline earth
metal salt is selected from the group consisting of sulfonates,
salicylates and phenolates.
5. The lubricant composition of claim 1 wherein the alkaline earth
metal salt is a metal sulfonate.
6. The lubricant composition of claim 4 wherein the metal sulfonate
is magnesium sulfonate.
7. The lubricant composition of claims 1 and 6 wherein the ratio of
zinc to alkaline earth metal is 0.3 to 0.8.
8. In the method of increasing the wear resistance of manual
speed-change gears by lubricating the gears, the improvement
comprising: lubricating the gears with a lubricant composition
having a dynamic viscosity at 40.degree. C. of 40 mm.sup.2/s or
less and containing an additive comprising an alkaline earth metal
salt and a zinc dialkylthiophosphate, the amount of alkaline earth
metal element in the lubricant being 0.1 wt % or more based on the
total weight of the lubricant; and the elemental ratio of zinc to
alkaline earth metal is from 0.2 to 1.0.
9. The improvement of claim 8 wherein: the alkaline earth metal
salt is selected from the group consisting of sulfonates,
salicylates and phenolates; the amount of alkaline earth metal is
from 0.15 wt % to 0.6 wt %; and the elemental ratio of zinc to
alkalinic earth metal is from 0.3 to 0.8.
10. The improvement of claim 9 wherein the alkaline earth metal
salt is magnesium sulfonate.
Description
[0001] This application claims the benefit of Japanese Patent
Application 2004-163106 filed Jun. 1, 2004 (Patent Applicants:
Tonen General Sekiyu K.K. and Toyota Motor Corporation).
FIELD OF THE INVENTION
[0002] The present invention pertains to a lubricant composition
for an automobile driving system. More specifically, the present
invention pertains to a lubricant composition for automobile gears,
especially for a manual speed-change gear.
BACKGROUND OF THE INVENTION
[0003] In recent years, as a measure for preventing global warming,
various schemes for protecting the environment have been proposed.
One said scheme calls for development of an environmentally
friendly lubricant. An environmentally friendly lubricant for use
in automobiles, is required to have an excellent effect in
improving gas mileage to reduce the amount of carbon dioxide
exhaust from internal combustion engines. In order to increase the
mileage with the lubricant, two methods have been under study, that
is, a method for reducing friction in the sliding parts and a
method for reducing the viscosity of the lubricant.
[0004] Concerning reducing friction, it has been proposed that, in
order to increase the effect of the gear lubricant used in the
power transmission system for increasing the mileage, a gear
lubricant composition prepared using molybdenum dithiophosphate or
another friction-reducing agent is used (see Japanese Kokoku Patent
Application No. Hei 6[1994]-33390). In another method, a
combination of a prescribed polymethacrylate-based viscosity index
increasing agent and a molybdenum-based friction-reducing agent is
used to obtain a lubricant composition that can maintain a low
friction coefficient even after oxidation degradation (see Japanese
Patent No. 2906024).
[0005] However, for the manual speed-change gear of an automobile,
friction between metal parts is exploited to form a synchronization
device incorporated within it. In order to realize smooth operation
of the synchronization device, lowering of the friction coefficient
is undesirable because if only the viscosity is reduced, the oil
film becomes thinner, and wear is facilitated. Aluminum parts
adopted for reducing the weight of the driving system device are
especially more prone to wear than are steel parts, and they are
more easily affected by a reduced viscosity. In practice, almost
all commercially available lubricants for manual speed-change gear
of automobiles have a dynamic viscosity at 40.degree. C.
(hereinafter referred to as "40.degree. C. dynamic viscosity")
higher than 40 mm.sup.2/s, and a lower-viscosity manual
speed-change gear lubricant has not been used in practical
application.
[0006] On such background, there is a high demand for development
of a lubricant composition for a manual speed-change gear that
exploits technology for increasing mileage by lowering the
viscosity of the lubricant.
DISCLOSURE OF THE INVENTION
[0007] The objective of the present invention is to solve the
aforementioned problems relating to the prior art for improving
mileage by providing a type of lubricant composition for automobile
gears, especially a lubricant composition for a manual speed-change
gear, characterized by the fact that the mileage can be improved by
lowering the viscosity of the lubricant and, at the same time, the
durability of wear resistance can be maintained.
SUMMARY OF THE INVENTION
[0008] In order to solve the aforementioned problems, the present
inventors have performed extensive research. As a result of this
research, it was found that when an alkaline earth metal salt and
zinc dithiophosphate are mixed at a prescribed ratio, it is
possible to obtain a lubricant composition that has a 40.degree. C.
dynamic viscosity of 40 mm.sup.2/s or lower, and, at the same time,
that has excellent wear resistance for steel parts and, especially,
for aluminum parts, equal to or better than the wear resistance of
a conventional commercially available lubricant with a 40.degree.
C. dynamic viscosity of 76 mm.sup.2/s. The present invention was
achieved based on this finding.
[0009] That is, the present invention provides a lubricant
composition for a manual speed-change gear characterized by the
following facts: the lubricant composition for a manual
speed-change gear contains a base oil, and the following components
added into said base oil: (a) at least one alkaline earth metal
salt selected from the group of alkaline earth metal salts of
sulfonate, salicylate, and phenolate, and (b) zinc
dithiophosphate;
[0010] the dynamic viscosity at 40.degree. C. of said lubricant
composition is 40 mm.sup.2/s or lower;
[0011] the content of said alkaline earth metal salt relative to
the total weight of said lubricant composition corresponds to a
content of the alkaline earth metal element in the oil of 0.1 wt %
or more;
[0012] and the ratio of the quantity of elemental zinc in the oil
to the quantity of elemental alkaline earth metal in the oil is 0.2
to 1; and
[0013] where the quantity of elemental zinc in the oil is derived
from said zinc dithiophosphate, and the quantity of alkaline earth
metal element in the oil is derived from said organic acid alkaline
earth metal salt.
DETAILED DESCRIPTION OF INVENTION
[0014] As explained above, according to the present invention, by
adding an organic acid alkaline earth metal salt, especially
magnesium sulfonate, in a prescribed quantity in a base oil with a
low viscosity, and by mixing said organic acid alkaline earth metal
salt and zinc dithiophosphate at a prescribed ratio, it is possible
to obtain a type of lubricant for a manual speed-change gear that
can display significant wear resistance for not only steel parts
but also aluminum sliding parts, and that has an excellent effect
in increasing mileage.
[0015] As explained above, the present invention provides a
lubricant composition for automobile gears, especially a lubricant
composition for a manual speed-change gear, characterized by the
fact that it is composed of a low-viscosity base oil as well as an
organic acid alkaline earth metal salt and zinc dithiophosphate in
a prescribed ratio. The preferable embodiments are the following
(1)-(6):
[0016] (1) The aforementioned lubricant composition for a manual
speed-change gear preferably is characterized by the fact that the
dynamic viscosity at 40.degree. C. of said lubricant composition is
30 mm.sup.2/s or lower.
[0017] (2) The aforementioned lubricant composition for a manual
speed-change gear preferably is characterized by the fact that said
alkaline earth metal salt is an alkaline earth metal salt of
sulfonate.
[0018] (3) The aforementioned lubricant composition for a manual
speed-change gear preferably is characterized by the fact that said
alkaline earth metal salt of sulfonate is magnesium sulfonate.
[0019] (4) The aforementioned lubricant composition for a manual
speed-change gear preferably is characterized by the fact that the
total base value of said alkaline earth metal salt is 200 mgKOH/g
or higher.
[0020] (5) A lubricant composition for a manual speed-change gear
preferably is characterized by the following facts:
[0021] it contains a base oil as well as magnesium sulfonate and
zinc dithiophosphate added into said base oil;
[0022] the dynamic viscosity at 40.degree. C. of the lubricant
composition is 30 mm.sup.2/s or lower;
[0023] the content of said organic acid alkaline earth metal salt
relative to the total weight of said lubricant composition
corresponds to a content of the alkaline earth metal element in the
oil of 0.1 wt % or more;
[0024] and the ratio of the quantity of element zinc in the oil to
the quantity of alkaline earth metal element in the oil is form 0.3
to 0.8 and where, the quantity of elemental zinc in the oil is
derived from said zinc dithiophosphate, and the quantity of
alkaline earth metal element in the oil is derived from said
organic acid alkaline earth metal salt.
[0025] (6) A lubricant composition for a manual speed-change gear
preferably is characterized by the following facts: it contains a
base oil as well as the following components added into said base
oil:
[0026] (a) at least one acid alkaline earth metal salt selected
from the group of alkaline earth metal salts of sulfonate,
salicylate, and phenolate, and
[0027] (b) zinc dithiophosphate;
[0028] the dynamic viscosity at 40.degree. C. of the lubricant
composition is 40 mm.sup.2/s or lower;
[0029] the content of said organic acid alkaline earth metal salt
relative to the total weight of said lubricant composition
corresponds to a content of the alkaline earth metal element in the
oil of 0.1 wt % or more;
[0030] and the ratio of the quantity of element zinc in the oil to
the quantity of alkaline earth metal element in the oil is from 0.2
to 1.0 and where, the quantity of elemental zinc in the oil is
derived from said zinc dithiophosphate, and the quantity of
alkaline earth metal element in the oil is derived from said
organic acid alkaline earth metal salt.
[0031] In the following, explanation will be provided for the
structural components of the lubricant composition for a manual
speed-change gear in the present invention. The lubricant
composition for a manual speed-change gear contains a base oil as
well as an organic acid alkaline earth metal salt, zinc
dithiophosphate, and other additives for a speed-change gear that
maintain the extreme-pressure performance, etc., added to the base
oil.
[0032] The base oil as a structural component of the lubricant
composition for a manual speed-change gear may be a conventional
base oil for a lubricant or another usable type, and there is no
special limitation on the type. More specifically, examples include
mineral oil base oils, GTL (gas to liquid)-based base oil,
synthetic oil-based base oil, as well as mixed base oils.
[0033] Examples of mineral oil base oils include solvent refined
mineral oils or hydrogenation treated oils and other mineral oils
prepared by treatment of a lubricant distillation fraction obtained
by reduced pressure distillation of residual oil from an ambient
pressure distillation device for paraffin-based,
intermediate-based, or naphthene-based feed oil by means of solvent
refinement, hydrogenation decomposition, hydrogenating treatment,
hydrogenating refinement, solvent dewaxing, contact dewaxing, white
clay treatment or another refinement method, mineral oil prepared
by treatment in said refinement process of de-bitumen oil prepared
by solvent de-bitumen treatment of reduced pressure distillation
residual oil, mineral oil obtained by isomerizing a wax component,
as well as mixed oils thereof. In said solvent refinement, phenol,
furfural, N-methyl-2-pyrrolidone, or another aromatic extracting
solvent is used. Also, examples of solvents for solvent dewaxing
include liquefied propane, MEK (methyl ethyl ketone)/toluene, and
the like. On the other hand, in contact dewaxing, for example, a
shape-selecting zeolite or the like may be used as the dewaxing
solvent.
[0034] Examples of refined base oil substrates prepared in the
above include different types of light neutral oils, middle neutral
oils, heavy neutral oils, bright stock, etc., having different
viscosity levels. One may blend said substrates appropriately to
prepare the mineral oil-type base oil.
[0035] Examples of GTL-type base oils include the lubricant
fraction separated from liquid product obtained from natural gas or
another raw material using a GTL process, the lubricant fraction
obtained by means of hydrogenation decomposition of generated wax,
etc. In addition, one may also use the lubricant fraction separated
from liquid oil generated in an ATL (asphalt to liquid) process
using asphalt or another heavy residual oil component as the raw
material.
[0036] On the other hand, as a synthetic oil base oil, one may
select from the following group of compounds to obtain an
appropriate viscosity property for the lubricant composition for a
manual speed-change gear: a poly(.alpha.-olefin) (such as
poly(1-hexene), poly(1-octene), poly(1-decene), and their
mixtures); polybutene; an ethylene-alkylene copolymer; an alkyl
benzene (such as dodecylbenzene, tetradecylbenzene,
di(2-ethylhexyl)benzene, dinonylbenzene, etc.); a polyphenyl (such
as biphenyl, alkylated polyphenyl, etc.); an alkylated
diphenylether, an alkylated diphenyl sulfide, and their
derivatives; esters formed from dibasic acids (such as phthalic
acid, succinic acid, alkyl succinic acid, alkenyl succinic acid,
maleic acid, azelaic acid, suberic acid, sebatic acid, fumaric
acid, adipic acid, linoleic acid dimer, etc.) and various alcohols
(such as butyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol,
dodecyl alcohol, ethylene glycol, diethylene glycol monoether,
propylene glycol, etc.); esters formed from C5-18 monocarboxylic
acids and polyols (such as neopentyl glycol, trimethylol propane,
pentaerythritol, dipentaerythritol, tripentaerythritol, and the
like); as well as a polyoxyalkylene glycol, a polyoxyalkylene
glycol ester, a polyoxyalkylene glycol ether, a phosphate, etc.
[0037] As explained above, the base oil of the lubricant
composition for a manual speed-change gear in the present invention
is prepared by selecting one of said various types of base oil
substrates, either alone or as a mixture of several, such that the
40.degree. C. dynamic viscosity of the lubricant composition is 40
mm.sup.2/s or lower, or preferably 30 mm.sup.2/s or lower. The base
oil has the desired viscosity and other properties required for a
lubricant. Consequently, the viscosity of the base oil should be
appropriate to provide a lubricant composition of the present
invention. The viscosity depends on the composition of the
additives, etc., and can be selected preferably from those having a
40.degree. C. dynamic viscosity in the range of 25-40
mm.sup.2/s.
[0038] The organic acid alkaline earth metal salt is selected from
the group of alkaline earth metal salts of sulfonate, phenolate and
salicylate.
[0039] The alkaline earth metal sulfonate is an alkaline earth
metal salt of a petroleum sulfonic acid, long-chain alkylbenzene
sulfonic acid, and alkyl napththalene sulfonic acid. It is a
component of the composition for a manual speed-change gear of the
present invention. A typical example is represented by formula (1):
1
[0040] In the formula, M represents an alkaline earth metal, such
as magnesium, calcium, or barium. Among them, magnesium is
especially preferred. R.sup.1 and R.sup.2 are C1-30 hydrocarbon
groups, which may be identical or different from each other. At
least one of the hydrocarbon groups should be a C6 or higher alkyl
group. Examples of preferable hydrocarbon groups include C1-18
straight chain or branched alkyl groups; C2-18 straight chain or
branched alkenyl groups; C6-30 cycloalkyl groups; C6-18 aryl
groups, etc. The aryl groups are optionally substituted with C1-12
alkyl groups or C2-12 alkenyl groups. Especially preferable
hydrocarbon groups include C6-18 straight-chain or branched alkyl
groups.
[0041] For the sulfonate in the lubricant composition for a manual
speed-change gear of the present invention, perbasic salts are
preferred. However, it is also possible to use a normal salt or
basic salt. A perbasic salt has excess hydroxide or carbonate
dispersed in colloidal form in the sulfonate. It is preferred that
the total base value be 200 mgKOH/g or higher.
[0042] The quantity of alkaline earth metal sulfonate should be
appropriate so that the alkaline earth metal quantity in the oil
with respect to the total weight of the composition is 0.1 wt % or
more, or preferably in the range of 0.15-0.6 wt %, or more
preferably in the range of 0.15-0.3 wt %.
[0043] As the alkaline earth metal sulfonate, magnesium sulfonate
is especially preferred. In the low-viscosity state, when it is
used together with zinc dithiophosphate, excellent wear resistance
can be displayed in a manual speed-change gear having sliding
aluminum parts.
[0044] The alkaline earth metal phenolate includes an alkaline
earth metal salt of alkyl phenol sulfide represented by formula
(2): 2
[0045] In the formula, R.sup.1, R.sup.2, R.sup.3 and R.sup.4
represent C1-30 hydrocarbon groups, which may be identical or
different from each other. At least one of the hydrocarbon groups
should be a C6 or higher alkyl group. Examples of preferable
hydrocarbon groups include C1-18 straight-chain or branched alkyl
groups; C2-18 straight-chain or branched alkenyl groups; C6-30
cycloalkyl groups; C6-18 aryl groups, etc. The aryl groups are
optionally substituted with C1-12 alkyl groups or C2-12 alkenyl
groups. Especially preferred hydrocarbon groups include C6-18
straight-chain or branched alkyl groups. x is an integer in the
range of 1-3. M represents magnesium, calcium, or barium. Among
them, magnesium is especially preferred.
[0046] A perbasic salt of phenolate is obtained by dispersing a
hydroxide or carbonate in colloidal form in phenolate, just as with
sulfonate. The total base value is preferably 200 mgKOH/g or
larger. However, one may also use a normal salt or basic salt.
[0047] The quantity of alkaline earth metal phenolate with respect
to the base oil should be appropriate to correspond to a quantity
of alkaline earth metal element in the oil with respect to the
total weight of the composition of 0.1 wt % or more, or preferably
in the range of 0.15-0.6 wt %.
[0048] The alkaline earth metal salicylate is represented by a
compound represented by formula (3): 3
[0049] where, M represents an alkaline earth metal, such as
magnesium, calcium, or barium. Among them, magnesium is especially
preferred. R.sup.1 and R.sup.2 represent C1-30 hydrocarbon groups,
which may be identical or different from each other. At least one
of the hydrocarbon groups should be a C6 or higher alkyl group.
Examples of preferable hydrocarbon groups include C1-8
straight-chain or branched alkyl groups; C2-18 straight-chain or
branched alkenyl groups; C6-30 cycloalkyl groups; C6-18 aryl
groups, etc. The aryl groups are optionally substituted with C1-12
alkyl groups or C2-12 alkenyl groups. Especially preferable
hydrocarbon groups include C6-18 straight-chain or branched alkyl
groups.
[0050] For the lubricant composition for a manual speed-change gear
of the present invention, perbasic salicylate is preferred.
However, one may also use normal salt or basic salt. A perbasic
salt is prepared by dispersing carbonate in colloidal form in
salicylate.
[0051] The quantity of alkaline earth metal salicylate with respect
to the base oil should be appropriate to correspond to a quantity
of the alkaline earth metal in the oil with respect to the total
weight of the composition of 0.1 wt % or more, or preferably in the
range of 0.15-0.6 wt %.
[0052] As explained above, the structural components of the
lubricant composition for a manual speed-change gear of the present
invention include said alkaline earth metal sulfonate, phenolate
and salicylate. Among them, especially, the alkaline earth metal
salt of sulfonate is preferred. More specifically, magnesium
sulfonate is preferred.
[0053] In the following, explanation will be provided for zinc
dithiophosphate as a structural component of the lubricant
composition for a manual speed-change gear of the present
invention.
[0054] An example of zinc dithiophosphate is a compound represented
by following formula (4): 4
[0055] In formula (4), R.sub.1 and R.sub.2 represent C1-20
hydrocarbon groups, which may be identical or different from each
other. Examples of hydrocarbon groups include C1-20 alkyl groups;
C2-20 alkenyl groups; C6-20 cyclohexyl groups, aryl groups, alkyl
aryl groups, aryl alkyl groups, etc. Specific examples include a
methyl group, ethyl group, propyl group, butyl group, pentyl group,
hexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl
group, decyl group, undecyl group, dodecyl group, tridecyl group,
tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl
group, octadecyl group, stearyl group, oleyl group, butylphenyl
group, nonylphenyl group, etc., as well as branched alkyl groups
thereof, etc. Preferable hydrocarbon groups are C3-18 alkyl groups.
Examples of alkyl groups include primary and secondary alkyl
groups. More specifically, it is preferred that compounds having
the following groups be used: isopropyl group, isobutyl group,
secondary butyl group, pentyl group, hexyl group, 4-methyl-2-pentyl
group, octyl group, 2-ethylhexyl group, nonyl group, decyl group,
as well as dodecyl group, tridecyl group, tetradecyl group,
hexadecyl group, octadecyl group, and other alkyl groups.
[0056] Typical examples of zinc dithiophosphate include zinc
diisopropyl dithiophosphate, zinc diisobutyl dithiophosphate, zinc
di-secondary butyl thiophosphate, zinc di(n-pentyl)
dithiophosphate, zinc di(n-hexyl) dithiophosphate, zinc
di(4-methyl-2-pentyl) dithiophosphate, zinc di(n-octyl)
dithiophosphate, zinc di(2-ethylhexyl) dithiophosphate, zinc
di(n-nonyl) dithiophosphate, zinc di(n-decyl) dithiophosphate, zinc
di(n-dodecyl) dithiophosphate, zinc di(n-tridecyl) dithiophosphate,
zinc di(n-tetradecyl) dithiophosphate, zinc di(n-hexadecyl)
dithiophosphate, zinc di(n-octadecyl) dithiophosphate, etc.
According to the present invention, for the lubricant composition
for a manual speed-change gear, zinc dithiophosphate containing
primary and secondary alkyl groups is preferred. For example, one
may blend a zinc dithiophosphate having primary alkyl groups as the
main component and a zinc dithiophosphate having secondary alkyl
groups as the main component appropriately to adjust the
proportions of the primary and secondary alkyl groups.
[0057] The quantity of said zinc dithiophosphate in the lubricant
composition should be appropriate corresponding to an elemental
zinc quantity in the oil in the range of 0.05-0.5 wt %, or
preferably in the range of 0.1-0.2 wt %.
[0058] For the lubricant composition for a manual speed-change gear
of the present invention, the quantity of said organic acid
alkaline earth metal salt should be appropriate corresponding to an
alkaline earth metal element quantity in the oil of 0.1 wt % or
more; and the quantity of said zinc dithiophosphate should be
appropriate corresponding to an elemental zinc quantity in the oil
in the range of 0.05-0.5 wt %. Also, the ratio of the quantity of
element zinc in the oil to the quantity of alkaline earth metal
element in the oil is from 0.21 and where, the quantity of
elemental zinc in the oil is derived from said zinc
dithiophosphate, and the quantity of alkaline earth metal element
in the oil is derived from said organic acid alkaline earth metal
salt.
[0059] Especially, the preferred ratio of the quantity of elemental
zinc in the oil to the quantity of alkaline earth metal element in
the oil is from 0.3 to 0.8.
[0060] For the lubricant composition for a manual speed-change gear
of the present invention, if the ratio of the quantity of elemental
zinc in the oil to the quantity of alkaline earth metal element in
the oil is over 1, the wear resistance decreases. On the other
hand, if said ratio is less than 0.2, the wear resistance is
worsened, and this is undesired.
[0061] In the following, explanation will be provided for other
additives in the composition as needed, in addition to the
aforementioned necessary additives.
[0062] An extreme-pressure agent is added in the lubricant
composition for a manual speed-change gear of the present invention
to maintain the extreme-pressure performance. In addition, as
needed, one may add other additives appropriately, such as an
ash-free dispersing agent, friction-adjusting agent, dissolving
agent, rubber-expansion agent, fluid point lowering agent, and
oxidation inhibitor. Also, other additives may be added as
needed.
[0063] Examples of extreme pressure agents that may be added
include an olefin polysulfide, sulfurized oils and fats, dialkyl
polysulfide, and other sulfur-based compounds; alkyl and allyl
phosphate, alkyl and allyl phosphite, amine phosphate, and other
phosphorus-based compounds; paraffin chloride, and other
chlorine-based compounds. They may be used either alone or as a
mixture of several. Also, a combination of a sulfur based
composition and a phosphorus based composition may be used. For
example, a combination of an olefin sulfide and an alkyl phosphate
may be used. The quantity is usually in the range of 0.05-3 wt
%.
[0064] Examples of ash-free dispersing agents that may be used
include polybutenyl succinic acid imide-based compounds,
polybutenyl succinic acid amide-based compounds, benzyl amine-based
compounds, succinic ester-based compounds, succinic
ester-acid-based compounds, etc., usually added in a quantity in
the range of 0.05-7 wt %.
[0065] Examples of friction-adjusting agents include organic
molybdenum-based compounds, fatty acids, higher alcohols, fatty
acid esters, oils and fats, amines, polyamide, sulfide ester,
phosphates, acidic phosphates, phosphites, phosphate amine salts,
etc. They are usually added in a quantity of 0.05-5 wt %.
[0066] Examples of defoaming agents that may be added include a
dimethyl polysiloxane, polyacrylate, etc. They may be added
appropriately in a small quantity.
[0067] Examples of fluid point decreasing agents that may be added
include an ethylene-vinyl acetate copolymer, condensate of
chlorinated paraffin and naphthalene, condensate of chlorinated
paraffin and phenol, polymethacrylate, polyalkyl styrene, etc.
Usually, the quantity is in the range of 0.1-10 wt %.
[0068] Examples of oxidation inhibitors that may be used include an
alkylated diphenylamine, phenyl-.alpha.-naphthylamine,
alkylated-.alpha.-naphthylamine, and other amine-based oxidation
inhibitors, 2,6-ditertiary butylphenol, 4,4'-methylene
bis(2,6-ditertiary butylphenol), and other phenolic oxidation
inhibitors, as well as zinc dithiophosphate, etc. The quantity is
usually in the range of 0.05-5 wt %.
EXAMPLES
[0069] In the following, explanation will be provided more
specifically for examples of the present invention and comparative
examples. However, the present invention is not limited to the
examples.
[0070] A quantitative evaluation was performed using the following
measurement methods. Also, the types of base oils and additives
used in the examples are listed below.
METHOD FOR EVALUATION OF WEAR RESISTANCE
[0071] For each oil sample, the friction width formed on a block of
the following listed material and under the following conditions
was measured using a LFW-1 tester (ASTM D2714).
[0072] Test ring: S-10 (FALEX Test Ring H60)
[0073] Block: Aluminum sliding member
[0074] Test conditions:
[0075] Load: 5N
[0076] Velocity: 2 m/s
[0077] Temperature: 100.degree. C.
[0078] Time: 1 hour
[0079] Base Oil
[0080] Refined mineral oil: 40.degree. C. dynamic viscosity of
25-26 mm.sup.2/s
[0081] Additives
[0082] Zinc dithiophosphate (ZnDTP): Mixture having
primary/secondary alkyl groups.
[0083] Magnesium sulfonate: Perbasic salt with total base value of
400 mgKOH/g.
[0084] Extreme-pressure agent, etc.: Sulfur-phosphorus-based
package containing sulfur-based and phosphorus-based
extreme-pressure agents, as well as an ash-free dispersing agent,
friction-adjusting agent, defoaming agent, etc.
Example 1
[0085] With said refined mineral oil as the base oil, magnesium
sulfonate was added at a quantity corresponding to a content of
elemental Mg in the oil of 0.15 wt %, and zinc dithiophosphate was
added in a quantity corresponding to a content of elemental Zn in
the oil of 0.1 wt %, with the ratio of the quantity of elemental Zn
in the oil to the quantity of elemental Mg in the oil adjusted to
0.67. In addition, as other additives, the sulfur-phosphorus based
(S--P) package was added in a quantity of 7.1 wt %, forming oil
sample A with a 40.degree. C. dynamic viscosity of 30
mm.sup.2/s.
[0086] For oil sample A, the friction width measured using the
aforementioned wear-resistance evaluation method was found to be
0.74 mm.
Example 2
[0087] Oil sample B with a 40.degree. C. dynamic viscosity of 30
mm.sup.2/s was prepared in the same way as in Example 1, except
that the magnesium sulfonate was added in a quantity corresponding
to a quantity of elemental Mg in the oil of 0.3 wt %, and the zinc
dithiophosphate was added in a quantity corresponding to a quantity
of elemental Zn in the oil of 0.2 wt %, with the ratio of elemental
Zn to elemental Mg in the oil being 0.67.
[0088] For oil sample B, the friction width measured using the
aforementioned wear-resistance evaluation method was found to be
0.80 mm.
Example 3
[0089] Oil sample C with a 40.degree. C. dynamic viscosity of 30
mm.sup.2/s was prepared in the same way as in Application Example
1, except that the magnesium sulfonate was added in a quantity
corresponding to a quantity of elemental Mg in the oil of 0.3 wt %,
and the zinc dithiophosphate was added in a quantity corresponding
to a quantity of elemental Zn in the oil of 0.1 wt %, with the
ratio of elemental Zn to elemental Mg in the oil being 0.33.
[0090] For oil sample C, the friction width measured using the
aforementioned wear-resistance evaluation method was found to be
0.80 mm.
Comparative Example 1-1
[0091] A commercially available oil for a manual speed-change gear
with a 40.degree. C. dynamic viscosity of 76 mm.sup.2/s (with the
ratio of elemental Zn to elemental Ca in the oil being 5.00) was
used in said wear-resistance evaluation test, and the results
indicated a friction width of 0.83 mm.
Comparative Example 1-2
[0092] A low-viscosity refined mineral oil was used to prepare oil
sample (a) with a 40.degree. C. dynamic viscosity of 30 mm.sup.2/s.
The ratio of the quantity of elemental Zn in the oil to the
quantity of elemental Ca in the oil was the same as that of the
commercially available oil used in Comparative Example 1-1, that
is, 5.00. The friction width of oil sample (a) measured using the
wear-resistance evaluation method was found to be 1.05 mm.
Comparative Examples 2-1 through 2-6
[0093] With said refined mineral oil used as the base oil,
magnesium sulfonate and zinc dithiophosphate were added in the
quantities listed in Table 1, and, as other additives, an
S--P-based package corresponding to GL-4 was added in a quantity of
7.1 wt % to obtain oil samples (b)-(g).
[0094] For samples A-C as well as the commercially available oil
and oil samples (a)-(g), the properties as well as the wear
resistance determined using said wear-resistance evaluation method
are listed in Table 1.
[0095] From the results of the friction width listed in Table 1,
significant effects can be displayed for the oil samples prepared
with a low 40.degree. C. dynamic viscosity of 30 mm.sup.2/s,
corresponding to an excellent effect in increasing the mileage,
with the quantity of elemental Mg in the oil at a prescribed value,
and with the ratio of the quantity of elemental Zn in the oil to
the quantity of elemental Mg in the oil in the prescribed range of
0.2-1. Example 1 was compared with Comparative Examples 2 and 3
with the same quantity of elemental Mg. In Example 1, the ratio of
the quantity of elemental Zn in the oil to the quantity of
elemental Mg in the oil is 0.67, that is, within the aforementioned
prescribed range. On the other hand, in Comparative Examples 2 and
3, the ratio of the quantity of elemental Zn in the oil to the
quantity of elemental Mg in the oil is 1.33, that is, outside the
aforementioned range, and the wear resistance is much worse.
[0096] The lubricant composition for a manual speed-change gear of
the present invention with the aforementioned constitution can be
used not only as a lubricant for an automobile driving system
consisting of a manual transmission (MT), but also for a manual
transmission axle (MTX) in transfer, a differential (Dif.), etc.
Consequently, it can be used as a common lubricant for said MT, MTX
and differential for FF cars, etc.
1 TABLE 1 Invention Example Comparative Example 1 2 3 1-1
1-2.sup.(2) 2-1 2-2 2-3 2-4 2-5 2-6 Oil Sample A B C .sup.(1) a b c
d e f g Quantity of elemental Mg in the oil 0.15 0.30 0.30
0.016.sup.(3) 0.016.sup.(3) 0.15 0 0.15 0 0.30 0 (derived from Mg
sulfonate) wt % Quantity of elemental Zn in the oil 0.10 0.20 0.10
0.08 0.08 0 0.10 0.20 0 0 0.20 (derived from ZnDTP) wt % Quantity
of elemental Zn in the 0.67 0.67 0.33 5.00 5.00 -- -- 1.33 -- -- --
oil/quantity of elemental Mg in the oil Dynamic viscosity 30 30 30
76 30 30 30 30 30 30 30 Friction width 0.74 0.81 0.80 0.83 1.05
1.00 1.00 0.85 1.03 0.85 0.88 Notes: .sup.(1)Commercially available
oil for a manual speed-change gear .sup.(2)Oil sample prepared
using a low-viscosity base oil .sup.(3)Quantity of elemental Ca
(derived from Ca sulfonate)
[0097] The lubricant composition for a manual speed-change gear of
the present invention contributes to protection of the environment
since it is an environmentally friendly lubricant by realizing low
viscosity. Also, it can be used as a high-quality lubricant for an
automobile driving system, such as a manual transmission, manual
transmission axle, etc. Consequently, it greatly contributes to the
petroleum and automobile industries with regard to manufacture and
application.
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