U.S. patent application number 15/707014 was filed with the patent office on 2018-03-29 for lubricating oil composition for continuously variable transmission.
This patent application is currently assigned to JXTG NIPPON OIL & ENERGY CORPORATION. The applicant listed for this patent is JXTG NIPPON OIL & ENERGY CORPORATION. Invention is credited to Hiroyuki CHINEN, Hitoshi KOMATSUBARA, Yuji MATSUI, Shingo MATSUKI, Toshitaka NAKAMURA.
Application Number | 20180087002 15/707014 |
Document ID | / |
Family ID | 61688316 |
Filed Date | 2018-03-29 |
United States Patent
Application |
20180087002 |
Kind Code |
A1 |
KOMATSUBARA; Hitoshi ; et
al. |
March 29, 2018 |
LUBRICATING OIL COMPOSITION FOR CONTINUOUSLY VARIABLE
TRANSMISSION
Abstract
A lubricating oil composition for a continuously variable
transmission including: (A) a lubricant base oil; (B) a borate
ester compound in an amount of 25 to 500 mass ppm in terms of boron
on the basis of the total mass of the composition; (C) phosphoric
acid in an amount of 100 to 750 mass ppm in terms of phosphorus on
the basis of the total mass of the composition; (D) a
poly(meth)acrylate having a weight average molecular weight of no
more than 100,000, wherein the lubricating oil composition has a
kinematic viscosity at 40.degree. C. of no more than 25
mm.sup.2/s.
Inventors: |
KOMATSUBARA; Hitoshi;
(Tokyo, JP) ; MATSUKI; Shingo; (Tokyo, JP)
; NAKAMURA; Toshitaka; (Tokyo, JP) ; CHINEN;
Hiroyuki; (Tokyo, JP) ; MATSUI; Yuji; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JXTG NIPPON OIL & ENERGY CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
JXTG NIPPON OIL & ENERGY
CORPORATION
Tokyo
JP
|
Family ID: |
61688316 |
Appl. No.: |
15/707014 |
Filed: |
September 18, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2223/06 20130101;
C10N 2020/04 20130101; C10M 169/044 20130101; C10M 2229/02
20130101; C10M 2227/061 20130101; C10M 2215/28 20130101; C10M
2207/262 20130101; C10M 145/14 20130101; C10N 2030/56 20200501;
C10M 161/00 20130101; C10M 2209/084 20130101; C10M 125/24 20130101;
C10M 2201/085 20130101; C10M 2219/044 20130101; C10N 2030/68
20200501; C10M 2223/049 20130101; C10M 139/00 20130101; C10M 135/36
20130101; C10N 2030/06 20130101; C10M 2215/064 20130101; C10M
2219/046 20130101; C10M 2205/0285 20130101; C10N 2010/04 20130101;
C10M 2203/1025 20130101; C10M 2205/143 20130101; C10N 2040/045
20200501; C10M 2207/144 20130101; C10M 2201/087 20130101; C10M
2215/04 20130101; C10N 2030/02 20130101; C10M 2219/106 20130101;
C10M 2215/08 20130101; C10M 2215/26 20130101; C10M 2215/30
20130101; C10M 2227/06 20130101; C10M 101/025 20130101; C10M
2219/044 20130101; C10N 2010/04 20130101; C10M 2207/144 20130101;
C10N 2010/04 20130101; C10M 2219/044 20130101; C10N 2010/04
20130101; C10M 2207/144 20130101; C10N 2010/04 20130101 |
International
Class: |
C10M 169/04 20060101
C10M169/04; C10M 101/02 20060101 C10M101/02; C10M 139/00 20060101
C10M139/00; C10M 125/24 20060101 C10M125/24; C10M 145/14 20060101
C10M145/14; C10M 135/36 20060101 C10M135/36; C10M 161/00 20060101
C10M161/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2016 |
JP |
2016-188104 |
Claims
1. A lubricating oil composition for a continuously variable
transmission comprising: (A) a lubricant base oil; (B) a borate
ester compound in an amount of 25 to 500 mass ppm in terms of boron
on the basis of the total mass of the composition; (C) phosphoric
acid in an amount of 100 to 750 mass ppm in terms of phosphorus on
the basis of the total mass of the composition; (D) a
poly(meth)acrylate having a weight average molecular weight of no
more than 100,000, wherein the lubricating oil composition has a
kinematic viscosity at 40.degree. C. of no more than 25
mm.sup.2/s.
2. The lubricating oil composition for a continuously variable
transmission according to claim 1, further comprising: (E) a
thiadiazole compound in an amount of 180 to 900 mass ppm in terms
of sulfur on the basis of the total mass of the composition,
wherein a ratio (B+P)/S of a sum of a boron content B (unit: mass
ppm) in the composition derived from the component (B) and a
phosphorus content P (unit: mass ppm) in the composition to a
sulfur content S (unit: mass ppm) in the composition derived from
the component (E) is 1 to 3.
3. The lubricating oil composition for a continuously variable
transmission according to claim 1, the (A) lubricant base oil
comprising: (Al) a base oil having a kinematic viscosity at
100.degree. C. of no more than 2.8 mm.sup.2/s, a viscosity index of
no less than 110, and % C.sub.P of no less than 90, in an amount of
30 to 100 mass % on the basis of the total mass of the lubricant
base oil, the (A) lubricant base oil optionally comprising: (A2) an
API group III base oil or group IV base oil or mixture thereof,
having a kinematic viscosity at 100.degree. C. of 3 to 10
mm.sup.2/s, in an amount of no more than 70 mass % on the basis of
the total mass of the lubricant base oil; and a base oil other than
the base oils (Al) and (A2), in an amount of no more than 4 mass %
on the basis of the total mass of the lubricant base oil, wherein
the (A) lubricant base oil has a kinematic viscosity at 100.degree.
C. of no more than 3.4 mm.sup.2/s.
4. The lubricating oil composition for a continuously variable
transmission according to claim 1, wherein the component (B) is at
least one borate ester compound represented by the following
general formula (1): ##STR00008## wherein in the formula (1),
R.sup.1 is a hydrocarbyl group having a carbon number of 1 to 30;
and R.sup.2 and R.sup.3 are each independently a hydrogen atom or a
hydrocarbyl group having a carbon number of 1 to 30.
5. The lubricating oil composition for a continuously variable
transmission according to claim 2, the (A) lubricant base oil
comprising: (A1) a base oil having a kinematic viscosity at
100.degree. C. of no more than 2.8 mm.sup.2/s, a viscosity index of
no less than 110, and % C.sub.P of no less than 90, in an amount of
30 to 100 mass % on the basis of the total mass of the lubricant
base oil, the (A) lubricant base oil optionally comprising: (A2) an
API group III base oil or group IV base oil or mixture thereof,
having a kinematic viscosity at 100.degree. C. of 3 to 10
mm.sup.2/s, in an amount of no more than 70 mass % on the basis of
the total mass of the lubricant base oil; and a base oil other than
the base oils (Al) and (A2), in an amount of no more than 4 mass %
on the basis of the total mass of the lubricant base oil, wherein
the (A) lubricant base oil has a kinematic viscosity at 100.degree.
C. of no more than 3.4 mm.sup.2/s.
6. The lubricating oil composition for a continuously variable
transmission according to claim 2, wherein the component (B) is at
least one borate ester compound represented by the following
general formula (1): ##STR00009## wherein in the formula (1),
R.sup.1 is a hydrocarbyl group having a carbon number of 1 to 30;
and R.sup.2 and R.sup.3 are each independently a hydrogen atom or a
hydrocarbyl group having a carbon number of 1 to 30.
7. The lubricating oil composition for a continuously variable
transmission according to claim 3, wherein the component (B) is at
least one borate ester compound represented by the following
general formula (1): ##STR00010## wherein in the formula (1),
R.sup.1 is a hydrocarbyl group having a carbon number of 1 to 30;
and R.sup.2 and R.sup.3 are each independently a hydrogen atom or a
hydrocarbyl group having a carbon number of 1 to 30.
Description
FIELD
[0001] The present invention relates to lubricating oil
compositions for continuously variable transmissions, and more
specifically, relates to a lubricating oil composition preferable
for metal belt type continuously variable transmissions for
automobiles.
BACKGROUND
[0002] Recent years, it has been demanded that various machines
such as automobiles, construction machinery, and agricultural
machinery achieve energy efficiency, that is, low fuel consumption,
and that devices such as engines and transmissions contribute to
energy efficiency.
[0003] One means for transmissions to achieve energy efficiency is
making lubricating oil less viscous. It is considered that less
viscous lubricating oil reduces fluid resistance and drag torque
which are caused by viscosity resistance of lubricating oil, and
improves power transmission efficiency, and thus makes it possible
to improve fuel efficiency.
[0004] Another means for transmissions to achieve energy efficiency
is making transmissions smaller and lighter. Smaller and lighter
transmissions offer improvement of fuel consumption of vehicles on
which transmissions are mounted. Particularly, higher friction
coefficients between metals allow continuously variable
transmissions (for example, metal belt type continuously variable
transmissions) to be downsized. Thus, it is desirable that
lubricating oil used in continuously variable transmissions keep
high friction coefficients between metals.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: JP 2014-196396 A
[0006] Patent Literature 2: JP 4663843 B
SUMMARY
Technical Problem
[0007] Less viscous lubricating oil leads to reduced oil film
thickness on a lubricated surface. Reduced oil film thickness in a
mixed lubrication regime is considered to be advantageous in view
of increasing friction coefficients between metals. However,
reduced oil film thickness on a lubricated surface tends to lead to
worsened anti-seizure and anti-wear performance, and a shortened
fatigue life.
[0008] An object of the present invention is to provide a
lubricating oil composition for a continuously variable
transmission which achieves improved fuel efficiency and friction
coefficients between metals while the composition satisfies
anti-seizure performance, anti-wear performance, and a fatigue life
which are demanded of continuously variable transmission oil.
Solution to Problem
[0009] One embodiment of the present invention is a lubricating oil
composition for a continuously variable transmission comprising:
(A) a lubricant base oil; (B) a borate ester compound in an amount
of 25 to 500 mass ppm in terms of boron (as boron atom content) on
the basis of the total mass of the composition; (C) phosphoric acid
in an amount of 100 to 750 mass ppm in terms of phosphorus (as
phosphorus atom content) on the basis of the total mass of the
composition; (D) a poly(meth)acrylate having a weight average
molecular weight of no more than 100,000, wherein the lubricating
oil composition has a kinematic viscosity at 40.degree. C. of no
more than 25 mm.sup.2/s.
[0010] In this specification, "(meth)acrylate" means "acrylate
and/or methacrylate".
[0011] Preferably, the lubricating oil composition for a
continuously variable transmission further comprises: (E) a
thiadiazole compound in an amount of 180 to 900 mass ppm in terms
of sulfur (as sulfur atom content) on the basis of the total mass
of the composition, wherein a ratio (B+P)/S of a sum of a boron
content B (unit: mass ppm) in the composition derived from the
component (B) and a phosphorus content P (unit: mass ppm) in the
composition to a sulfur content S (unit: mass ppm) in the
composition derived from the component (E) is 1 to 3.
[0012] Preferably, in the lubricating oil composition for a
continuously variable transmission, the (A) lubricant base oil
comprises: (A1) a base oil having a kinematic viscosity at
100.degree. C. of no more than 2.8 mm.sup.2/s, a viscosity index of
no less than 110, and % C.sub.P of no less than 90, in an amount of
30 to 100 mass % on the basis of the total mass of the lubricant
base oil, the (A) lubricant base oil optionally comprises: (A2) an
API group III base oil or group IV base oil or mixture thereof,
having a kinematic viscosity at 100.degree. C. of 3 to 10
mm.sup.2/s, in an amount of no more than 70 mass % on the basis of
the total mass of the lubricant base oil; and a base oil other than
the base oils (A1) and (A2), in an amount of no more than 4 mass %
on the basis of the total mass of the lubricant base oil, wherein
the (A) lubricant base oil has a kinematic viscosity at 100.degree.
C. of no more than 3.4 mm.sup.2/s.
[0013] Preferably, in the lubricating oil composition for a
continuously variable transmission, the component (B) is at least
one borate ester compound represented by the following general
formula (1):
##STR00001##
wherein in the formula (1), R.sup.1 is a hydrocarbyl group having a
carbon number of 1 to 30; and R.sup.2 and R.sup.3 are each
independently a hydrogen atom or a hydrocarbyl group having a
carbon number of 1 to 30.
Advantageous Effects of Invention
[0014] The present invention can provide a lubricating oil
composition for a continuously variable transmission which achieves
improved fuel efficiency and friction coefficients between metals
while the composition satisfies anti-seizure performance, anti-wear
performance, and a fatigue life which are demanded of continuously
variable transmission oil.
DETAILED DESCRIPTION OF EMBODIMENTS
[0015] The present invention will be described hereinafter.
Expression "A to B" concerning numeral values A and B means "no
less than A and no more than B" unless otherwise specified. In such
expression, if a unit is added only to the numeral value B, the
same unit is applied to the numeral value A as well. A word "or"
means a logical sum unless otherwise specified.
[0016] <(A) Lubricant Base Oil>
[0017] A base oil consisting of at least one selected from mineral
base oils and synthetic base oils can be used as a lubricant base
oil in the lubricating oil composition for a continuously variable
transmission of the present invention (hereinafter may be referred
to as "continuously variable transmission oil" or "lubricating oil
composition") without any limitation.
[0018] Specific examples of mineral base oils include paraffinic or
naphthenic mineral base oils obtained through at least one of
refining processes such as solvent deasphalting, solvent
extraction, hydrocracking, hydroisomerizing, solvent dewaxing,
catalytic dewaxing, and hydrorefining on lubricant oil fractions
obtained by vacuum distillation of atmospheric residue obtained by
atmospheric distillation of crude oil, wax isomerized mineral oils,
and base oils produced by a process including isomerizing GTL WAX
(gas to liquid wax).
[0019] Hydrocracked mineral base oils, and/or wax isomerized
isoparaffinic base oils that are obtained by isomerizing raw
material containing 50 mass % or more of petroleum wax or GTL wax
(for example, Fischer-Tropsch synthetic oil) can be preferably used
as mineral base oils.
[0020] Examples of synthetic base oils include poly-.alpha.-olefins
(such as ethylene-propylene copolymer, polybutene, 1-octene
oligomer, and 1-decene oligomer) or hydrogenated products thereof;
monoesters (such as butyl stearate, and octyl laurate); diesters
(such as ditridecyl glutarate, bis(2-ethylhexyl) azipate,
diisodecyl azipate, ditridecyl azipate, and bis(2-ethylhexyl)
sebacate); polyesters (such as trimellitate esters); polyol esters
(such as trimethylolpropane caprylate, trimethylolpropane
pelargonate, pentaerythritol 2-ethylhexanoate, and pentaerythritol
pelargonate); aromatic synthetic oils (such as alkylbenzene,
alkylnaphthalene, and aromatic esters); and mixtures thereof.
[0021] Preferably, % C.sub.P of a mineral base oil is no less than
70, and more preferably no less than 80; and usually no more than
99, and preferably no more than 95. A mineral base oil having %
C.sub.P of this lower limit or above makes it possible to improve
viscosity-temperature characteristics, thermal and oxidation
stability, and friction properties. A mineral base oil having %
C.sub.P of this upper limit or below makes it possible to improve
solubility of additives.
[0022] Preferably, % C.sub.A of a mineral base oil is no more than
2, more preferably no more than 1, further preferably no more than
0.8, and especially preferably no more than 0.5. A mineral base oil
having % C.sub.A of this upper limit or below makes it possible to
improve viscosity-temperature characteristics, thermal and
oxidation stability, and fuel efficiency.
[0023] Preferably, % C.sub.N of a mineral base oil is no more than
30, and more preferably no more than 25; and preferably no less
than 1, and more preferably no less than 4. A mineral base oil
having % C.sub.N of this upper limit or below makes it possible to
improve viscosity-temperature characteristics, thermal and
oxidation stability, and friction properties. A mineral base oil
having % C.sub.N of this lower limit or above makes it possible to
improve solubility of additives.
[0024] In this specification, % C.sub.P, % C.sub.N and % C.sub.A
mean percentage of the paraffin carbon number to all the carbon
atoms, percentage of the naphthene carbon number to all the carbon
atoms, and percentage of the aromatic carbon number to all the
carbon atoms, which are obtained by the method conforming to ASTM D
3238-85 (n-d-M ring analysis), respectively. That is, the above
described preferred ranges of % C.sub.P, % C.sub.N, and % C.sub.A
are based on values obtained according to the above method. For
example, the value of % C.sub.N obtained according to the above
method can indicate more than 0 even if a mineral base oil does not
contain any naphthenes.
[0025] The kinematic viscosity of the lubricant base oil at
100.degree. C. is preferably no more than 6.0 mm.sup.2/s, more
preferably no more than 4.5 mm.sup.2/s, and especially preferably
no more than 3.4 mm.sup.2/s; and preferably no less than 2.0
mm.sup.2/s, more preferably no less than 2.5 mm.sup.2/s, and
especially preferably no less than 2.6 mm.sup.2/s. The base oil
having kinematic viscosity of this upper limit or below at
100.degree. C. leads to good low-temperature viscosity properties
of the lubricating oil composition, and makes it possible to
improve fuel efficiency. The base oil having kinematic viscosity of
this lower limit or above at 100.degree. C. leads to enough oil
film formation at a lubricating point, which makes it possible to
improve lubricity. In this specification, "kinematic viscosity at
100.degree. C." means kinematic viscosity at 100.degree. C., which
is specified by ASTM D-445.
[0026] The kinematic viscosity of the lubricant base oil at
40.degree. C. is preferably no more than 40 mm.sup.2/s, more
preferably no more than 30 mm.sup.2/s, further preferably no more
than 25 mm.sup.2/s, and especially preferably no more than 20
mm.sup.2/s; and preferably no less than 8.0 mm.sup.2/s, more
preferably no less than 8.5 mm.sup.2/s, and especially preferably
no less than 9.0 mm.sup.2/s. The lubricant base oil having
kinematic viscosity of this upper limit or below at 40.degree. C.
leads to good low-temperature viscosity properties of the
lubricating oil composition, and makes it possible to improve fuel
efficiency. The base oil having kinematic viscosity of this lower
limit or above at 40.degree. C. leads to enough oil film formation
at a lubricating point, which makes it possible to improve
lubricity. In this specification, "kinematic viscosity at
40.degree. C." means kinematic viscosity at 40.degree. C., which is
specified by ASTM D-445.
[0027] The viscosity index of the lubricant base oil is preferably
no less than 100, more preferably no less than 110, and further
preferably no less than 115.
[0028] The base oil having viscosity index of this lower limit or
above makes it possible to improve viscosity-temperature
characteristics, thermal and oxidation stability, and even
anti-wear properties. The viscosity index in this specification
means a viscosity index measured conforming to JIS K 2283-1993.
[0029] The pour point of the lubricant base oil is preferably no
more than -10.degree. C., more preferably no more than
-12.5.degree. C., further preferably no more than -15.degree. C.,
especially preferably no more than -17.5.degree. C., and most
preferably no more than -20.0.degree. C. The pour point beyond this
upper limit tends to lead to deteriorated low-temperature fluidity
of whole of the lubricating oil composition. The pour point in this
specification means a pour point measured conforming to JIS K
2269-1987.
[0030] The sulfur content in the lubricant base oil is, in view of
oxidation stability, preferably no more than 1.5 mass %, and more
preferably no more than 1.0 mass %.
[0031] The following base oil (hereinafter may be referred to as
"lubricant base oil according to this embodiment") is preferably
used as the lubricant base oil in the lubricant oil composition of
the present invention: the base oil comprising (A1) a base oil
having a kinematic viscosity at 100.degree. C. of no more than 2.8
mm.sup.2/s, a viscosity index of no less than 110, and % C.sub.P of
no less than 90, in an amount of 30 to 100 mass % on the basis of
the total mass of the lubricant base oil; and optionally comprising
(A2) an API group III base oil or group IV base oil or mixture
thereof, having a kinematic viscosity at 100.degree. C. of 3 to 10
mm.sup.2/s, in an amount of no more than 70 mass % on the basis of
the total mass of the lubricant base oil, and a base oil other than
the base oils (A1) and (A2), in an amount of no more than 4 mass %
on the basis of the total mass of the lubricant base oil; wherein
the base oil has a kinematic viscosity at 100.degree. C. of no more
than 3.4 mm.sup.2/s. Using the lubricant base oil according to this
embodiment as the lubricant base oil makes it possible to reduce
oil film thickness in a transition regime (mixed lubrication
regime) between a hydrodynamic lubrication regime and a boundary
lubrication regime, to improve friction coefficients between
metals.
[0032] The kinematic viscosity of the base oil (A1) at 100.degree.
C. is no more than 2.8 mm.sup.2/s, and preferably no more than 2.7
mm.sup.2/s; and preferably no less than 1.5 mm.sup.2/s, and more
preferably no less than 2.0 mm.sup.2/s. The base oil (A1) having
kinematic viscosity of this upper limit or below at 100.degree. C.
makes it possible to improve friction coefficients between metals.
The base oil (A1) having kinematic viscosity of this lower limit or
above at 100.degree. C. leads to enough oil film formation at
lubricating points, which makes it possible to improve
lubricity.
[0033] The kinematic viscosity of the base oil (A1) at 40.degree.
C. is preferably no more than 15 mm.sup.2/s, and more preferably no
more than 10 mm.sup.2/s; and preferably no less than 2.0
mm.sup.2/s, and more preferably no less than 5.0 mm.sup.2/s. The
base oil (A1) having kinematic viscosity of this upper limit or
below at 40.degree. C. makes it easy to improve friction
coefficients between metals. The base oil (A1) having kinematic
viscosity of this lower limit or above at 40.degree. C. leads to
enough oil film formation at a lubricating point, which makes it
possible to improve lubricity.
[0034] The viscosity index of the base oil (A1) is no less than
110. The base oil (A1) having viscosity index of 110 or more makes
it easy to improve friction coefficients between metals. The upper
limit thereof is not restricted, normally no more than 150, and
preferably no more than 135.
[0035] The base oil (A1) has % C.sub.P of no less than 90. The base
oil (A1) having % C.sub.P of 90 or more leads to good thermal and
oxidation stability. The upper limit thereof is not restricted,
normally no more than 99, and in view of solubility of additives,
preferably no more than 95.
[0036] Preferably, the base oil (A1) has % C.sub.A of no more than
1, more preferably no more than 0.8, and especially preferably no
more than 0.5. The base oil may have % C.sub.A of 0. The base oil
(A1) having % C.sub.A of this upper limit or below makes it
possible to improve viscosity-temperature characteristics, thermal
and oxidation stability, and fuel efficiency.
[0037] A mineral base oil having the above described properties can
be used as the base oil (A1) without any limitation.
[0038] The kinematic viscosity of the base oil (A2) at 100.degree.
C. is 3 to 10 mm.sup.2/s, preferably no more than 8.0 mm.sup.2/s,
more preferably no more than 6.0 mm.sup.2/s, and further preferably
no more than 4.5 mm.sup.2/s. The base oil (A2) having kinematic
viscosity of this upper limit or below at 100.degree. C. makes it
possible to improve friction coefficients between metals. The base
oil (A2) having kinematic viscosity of this lower limit or above at
100.degree. C. leads to enough oil film formation at a lubricating
point, which makes it possible to improve lubricity.
[0039] The base oil (A2) is a group III base oil or group IV base
oil in API classification, or mixture thereof, and preferably a
group III base oil. A group III base oil is a mineral base oil
having the sulfur content of 0.03 mass % or less, the saturated
content of 90 mass % or more, and a viscosity index of 120 or more.
Group IV base oils are poly-.alpha.-olefins.
[0040] The content of the base oil (A1) in the lubricant base oil
according to this embodiment is no less than 30 mass %, is
preferably no less than 35 mass %, and may be 100 mass %, on the
basis of the total mass of the lubricant base oil. In this
specification, "the content of the base oil (A1) is 100 mass % on
the basis of the total mass of the lubricant base oil" means that
the lubricant base oil consists of the base oil (A1).
[0041] The content of the base oil (A2) in the lubricant base oil
according to this embodiment is no more than 70 mass %, is
preferably no more than 65 mass %, and may be 0 mass %, on the
basis of the total mass of the lubricant base oil. In this
specification, "the content of the base oil (A2) is 0 mass %" means
that the lubricant base oil does not contain the base oil (A2).
[0042] The content of the base oil other than the base oils (A1)
and (A2) in the lubricant base oil according to this embodiment is
no more than 4 mass %, is preferably no more than 1 mass %, and may
be 0 mass %, on the basis of the total mass of the lubricant base
oil. In this specification, "the content of the base oil other than
the base oils (A1) and (A2) is 0 mass %" means that the lubricant
base oil consists of the base oil (A1) and (optionally) the base
oil (A2).
[0043] <(B) Borate Ester Compound>
[0044] The lubricating oil composition of the present invention
contains a borate ester compound (hereinafter may be referred to as
"component (B)").
[0045] At least one borate ester compound represented by the
following general formula (1) can be used as the component (B).
##STR00002##
wherein R.sup.1 is a hydrocarbyl group having a carbon number of 1
to 30; and R.sup.2 and R.sup.3 are each independently a hydrogen
atom or a hydrocarbyl group having a carbon number of 1 to 30.
[0046] Examples of the hydrocarbyl group include an alkyl group
(that may have a ring structure), an alkenyl group (that have a
double bond at any position, and may have a ring structure), an
aryl group, an alkylaryl group, an alkenylaryl group, an arylalkyl
group, and an arylalkenyl group.
[0047] Examples of the alkyl group include various linear and
branched alkyl groups. Examples of the alkyl group having a ring
structure include an alkylcycloalkyl group and a cycloalkylalkyl
group. Examples of the cycloalkyl group include cycloalkyl groups
having carbon number of 5 to 7 such as cyclopentyl group,
cyclohexyl group, and cycloheptyl group. A cycloalkyl ring may be
substituted in any position.
[0048] Examples of the alkenyl group include various linear and
branched alkenyl groups. Examples of the alkenyl group having a
ring structure include an alkylcycloalkenyl group, an
alkenylcycloalkyl group, a cycloalkenylalkyl group, and a
cycloalkenylalkenyl group. The cycloalkyl group is the same as the
above. Examples of the cycloalkenyl group include cycloalkenyl
groups having carbon number of 5 to 7 such as cyclopentenyl group,
cyclohexenyl group, and cycloheptenyl group. A cycloalkenyl ring
and a cycloalkyl ring may be substituted in any position.
[0049] Examples of the aryl group include phenyl group and naphthyl
group. An aryl group may have a hydrocarbyl substituent. In the
above described alkylaryl group, alkenylaryl group, arylalkyl
group, and arylalkenyl group, an aryl group may be substituted in
any position.
[0050] The hydrocarbyl group having a carbon number of 1 to 30 in
the above general formula (1) is preferably an alkyl or alkenyl
group, and more preferably an alkyl group. The above described
carbon number is preferably no less than 3, and more preferably no
less than 5; and preferably no more than 24, and more preferably no
more than 12. The hydrocarbyl group having a carbon number of this
lower limit or above makes it possible to improve solubility, and
friction coefficients between metals. The hydrocarbyl group having
carbon number beyond this upper limit tends to lead to decreased
friction coefficients between metals.
[0051] In the above general formula (1), preferably at least one of
R.sup.2 and R.sup.3 is a hydrogen atom, and more preferably both
R.sup.2 and R.sup.3 are hydrogen atoms. Using the component (B) of
such an embodiment makes it possible to strengthen a lubricating
film in a boundary lubrication regime, and to improve anti-seizure
performance and anti-wear performance.
[0052] One preferred example of the component (B) is a borate ester
compound represented by above general formula (1) wherein R.sup.1
is an alkyl or alkenyl group having a carbon number of 3 to 12, and
R.sup.2 and R.sup.3 are hydrogen atoms.
[0053] The content of the component (B) in the lubricating oil
composition is 25 to 500 mass ppm, preferably no more than 400 mass
ppm, and more preferably no more than 300 mass ppm, in terms of
boron (as boron atom content) on the basis of the total mass of the
composition. The content of the component (B) of this lower limit
or above makes it possible to strengthen a lubricating film in a
boundary lubrication regime, and to improve anti-seizure
performance and anti-wear performance. The content of the component
(B) of this upper limit or below makes it possible to strengthen a
lubricating film in a boundary lubrication regime, to improve
anti-seizure performance, and to lengthen a fatigue life.
[0054] <(C) Phosphoric Acid>
[0055] The lubricant oil composition of the present invention
contains phosphoric acid (hereinafter may be referred to as
"component (C)").
[0056] At least one phosphoric acid selected from orthophosphoric
acid, pyrophosphoric acid, condensed phosphoric acids, and
metaphosphoric acid can be used as the component (C).
Orthophosphoric aicd and/or metaphosphoric acid is/are preferable,
and orthophosphoric acid is especially preferable as the component
(C).
[0057] The content of the component (C) in the lubricating oil
composition is 100 to 750 mass ppm, preferably no less than 120
mass ppm, and especially preferably no less than 140 mass ppm, in
terms of phosphorus (as phosphorus atom content) on the basis of
the total mass of the composition. The content of the component (C)
of this lower limit or above makes it possible to strengthen a
lubricating film in a boundary lubrication regime, and to improve
anti-seizure performance and anti-wear performance. The content of
the component (C) of this upper limit or below makes it possible to
strengthen a lubricating film in a boundary lubrication regime, to
improve anti-seizure performance, and to lengthen a fatigue
life.
[0058] <(D) Poly(meth)acrylate>
[0059] The lubricating oil composition of the present invention
contains a poly(meth)acrylate having a weight average molecular
weight of no more than 100,000 (hereinafter may be referred to as
"component (D)"). In this specification, "(meth)acrylate" means
"acrylate and/or methacrylate".
[0060] The component (D) may be either a dispersant or
non-dispersant poly(meth)acrylate. The weight average molecular
weight of the component (D) is no more than 100,000, preferably no
more than 80,000, and more preferably no more than 60,000; and
preferably no less than 10,000, and more preferably no less than
15,000. The component (D) having a weight average molecular weight
of this upper limit or below makes it possible to improve shear
stability of the lubricating oil composition. The component (D)
having a weight average molecular weight of this lower limit or
above makes it easy to improve a viscosity index of the lubricating
oil composition.
[0061] The component (D) functions as a viscosity index improver.
The content of the component (D) in the lubricating oil composition
can be a content such that the kinematic viscosity of the
lubricating oil composition at 40.degree. C. becomes within the
range described later. Specific content of the component (D) varies
according to the weight average molecular weight of the component
(D). For example, the content may be 5 to 20 mass % on the basis of
the total mass (100 mass %) of the lubricating oil composition.
[0062] <(E) Thiadiazole Compound>
[0063] The lubricating oil composition of the present invention
preferably contains at least one thiadiazole compound (hereinafter
may be referred to as "component (E)").
[0064] Examples of the component (E) include a 1,3,4-thiadiazole
compound represented by the following general formula (2), a
1,2,4-thiadiazole compound represented by the following general
formula (3), and a 1,4,5-thiadiazole compound represented by the
following general formula (4).
##STR00003##
wherein in the general formulae (2) to (4), R.sup.4 and R.sup.5 may
be either the same or different, and each independently represent
hydrogen or a hydrocarbyl group having a carbon number of 1 to 20;
and a and b may be either the same or different, and each
independently represent an integer of 0 to 8.
[0065] A thiadiazole compound represented by any of the above
general formulae (2) to (4) and having a hydrocarbyldithio group
can be especially preferably used among the above thiadiazole
compounds.
[0066] The content of the component (E) in the lubricating oil
composition is 180 to 900 mass ppm, and preferably 300 to 900 mass
ppm, in terms of sulfur (as sulfur atom content) on the basis of
the total mass of the composition. The content of the component (E)
of this lower limit or above makes it easy to improve anti-seizure
performance, anti-wear performance, and friction coefficients
between metals, and to lengthen a fatigue life. The content of the
component (E) of this upper limit or below makes it easy to improve
anti-seizure performance, and to lengthen a fatigue life.
[0067] When the lubricating oil composition contains the component
(E), the ratio (B+P)/S of the sum of the boron content B (unit:
mass ppm) in the composition derived from the component (B) and the
total phosphorus content P (unit: mass ppm) in the composition, to
the sulfur content S (unit: mass ppm) in the composition derived
from the component (E) is preferably 1 to 3, more preferably no
less than 1.2, and further preferably no less than 1.4; and more
preferably no more than 2.7, further preferably no more than 2.4,
further more preferably no more than 2.2, especially preferably no
more than 2.0, and most preferably no more than 1.8. The ratio
(B+P)/S of this lower limit or above makes it easy to improve
anti-seizure performance, and to lengthen a fatigue life. The ratio
(B+P)/S of this upper limit or below makes it easy to improve
anti-seizure performance, anti-wear performance, and friction
coefficients between metals, and to lengthen a fatigue life.
[0068] <(F) Metallic Detergent>
[0069] In one preferred embodiment, the lubricant oil composition
may further contain a metallic detergent (hereinafter may be
referred to as "component (F)").
[0070] A known metallic detergent such as a sulfonate detergent, a
phenate detergent and a salicylate detergent can be used as the
component (F), and (a) sulfonate and/or salicylate detergent(s) can
be preferably used.
[0071] Preferred examples of a sulfonate detergent include alkaline
earth metal salts of alkyl aromatic sulfonic acids obtained by
sulfonation of alkylaromatics, and basic or overbased salts
thereof. The weight-average molecular weight of the alkylaromatics
is preferably 400 to 1500, and more preferably 700 to 1300.
[0072] Examples of alkaline earth metals include magnesium, barium,
and calcium, and magnesium and calcium are preferable. Examples of
alkyl aromatic sulfonic acids include what is called petroleum
sulfonic acids and synthetic sulfonic acids. Examples of petroleum
sulfonic acids here include sulfonated products of alkylaromatics
of lubricant oil fractions derived from mineral oils, and what is
called mahogany acid, which is a side product of white oils.
Examples of synthetic sulfonic acids include sulfonated products of
alkylbenzene having a linear or branched alkyl group, obtained by
recovering side products in a manufacturing plant of alkylbenzene,
which is raw material of detergents, or by alkylating benzene with
a polyolefin. Other examples of synthetic sulfonic acids include
sulfonated products of alkylnaphthalenes such as
dinonylnaphthalene. Sulfonating agents used when sulfonating these
alkylaromatics are not limited. For example, a fuming sulfuric acid
or a sulfuric anhydride can be used as a sulfonating agent.
[0073] Preferred examples of a phenate detergent include overbased
salts of alkaline earth metal salts of compounds having the
structure represented by the following general formula (5).
##STR00004##
[0074] In the formula (5), R.sup.6 is a C.sub.6-C.sub.21 linear or
branched, saturated or unsaturated alkyl or alkenyl group; c is a
polymerization degree, representing an integer of 1 to 10; A is a
sulfide (--S--) group or methylene (--CH.sub.2--) group; and d is
an integer of 1 to 3. R.sup.6 may be combination of at least two
different groups.
[0075] The carbon number of R.sup.6 in the formula (5) is
preferably 9 to 18, and more preferably 9 to 15. If the carbon
number of R.sup.6 is less than 6, the solubility in the base oil
might be poor. On the other hand, if the carbon number of R.sup.6
is beyond 21, it is difficult to be produced and thermal stability
might be poor.
[0076] The polymerization degree c in the formula (5) is preferably
1 to 3. The polymerization degree c within this range makes it
possible to improve thermal stability.
[0077] Preferred examples of a salicylate detergent include
alkaline earth metal salicylates, and basic or overbased salts
thereof. Preferred examples of alkaline earth metal salicylates
include compounds represented by the following general formula
(6).
##STR00005##
[0078] In the formula (6), R.sup.7 each independently represents a
C.sub.14-C.sub.30 alkyl or alkenyl group. "e" is 1 or 2, and
preferably 1. When e=2, R.sup.7 may be combination of different
groups. M is an alkaline earth metal, and preferably calcium or
magnesium.
[0079] A method for producing an alkaline earth metal salicylate is
not restricted, and a known method for producing
monoalkylsalicylates can be used. For example, an alkaline earth
metal salicylate can be obtained by: making a metal base such as an
oxide and hydroxide of an alkaline earth metal react with
monoalkylsalicylic acid obtained by alkylating a phenol as starting
material with an olefin, and then carboxylating the resultant with
carbonic acid gas or the like, monoalkylsalicylic acid obtained by
alkylating a salicylic acid as starting material with an equivalent
of the olefin, or the like; once converting the above
monoalkylsalicylic acid or the like to an alkali metal salt such as
a sodium salt and potassium salt, and then performing
transmetallation with an alkaline earth metal salt; or the
like.
[0080] The component (F) may be overbased. A method for obtaining
overbased calcium sulfonate, phenate or sulfonate is not limited.
For example, an alkaline earth metal sulfonate, phenate, or
salicylate is made to react with a base such as calcium hydroxide
and magnesium hydroxide in the presence of carbonic acid gas.
[0081] When the lubricant oil composition contains the component
(F), the content is preferably 100 to 1200 mass ppm, more
preferably no less than 200 mass ppm, and more preferably no more
than 1000 mass ppm, in terms of metal (as metal element content) on
the basis of the total mass of the composition. The content of the
component (F) within this range makes it possible to further
improve friction properties of wet clutches.
[0082] <(G) Ashless Dispersant>
[0083] In one preferred embodiment, the lubricating oil composition
may further contain an ashless dispersant (hereinafter may be
referred to as "component (G)").
[0084] For example, at least one compound selected from the
following (G-1) to (G-3) can be used as the component (G):
[0085] (G-1) succinimide having at least one alkyl or alkenyl group
in its molecule, or a derivative thereof (hereinafter may be
referred to as "component (G-1)");
[0086] (G-2) benzylamine having at least one alkyl or alkenyl group
in its molecule, or a derivative thereof (hereinafter may be
referred to as "component (G-2)"); and
[0087] (G-3) polyamine having at least one alkyl or alkenyl group
in its molecule, or a derivative thereof (hereinafter may be
referred to as "component (G-3)").
[0088] The component (G-1) can be especially preferably used as the
component (G).
[0089] Examples of succinimide having at least one alkyl or alkenyl
group in its molecule among the component (G-1) include compounds
represented by the following formula (7) or (8).
##STR00006##
[0090] In the formula (7), R.sup.8 is a C.sub.40-C.sub.400 alkyl or
alkenyl group; f represents an integer of 1 to 5, and preferably 2
to 4. The carbon number of R.sup.8 is preferably no less than 60,
and preferably no more than 350.
[0091] In the formula (8), R.sup.9 and R.sup.10 are each
independently a C.sub.40-C.sub.400 alkyl or alkenyl group, and may
be combination of different groups. R.sup.9 and R.sub.10 are
especially preferably polybutenyl groups. In addition, g represents
an integer of 0 to 4, and preferably 1 to 3. The carbon numbers of
R.sup.9 and R.sup.10 are preferably no less than 60, and preferably
no more than 350.
[0092] R.sup.8 to R.sup.10 in the formulae (7) and (8) having
carbon numbers of these lower limits or over make it possible to
obtain good solubility in the lubricant base oil. On the other
hand, R.sup.8 to R.sup.10 having carbon numbers of these upper
limits or below make it possible to improve low-temperature
fluidity of the lubricating oil composition.
[0093] The alkyl or alkenyl groups (R.sup.8 to R.sup.10) in the
formulae (7) and (8) may be linear or branched. Preferred examples
thereof include branched alkyl groups and branched alkenyl groups
derived from oligomers of olefins such as propylene, 1-butene, and
isobutene, or from co-oligomers of ethylene and propylene. Among
them, a branched alkyl or alkenyl group derived from an oligomer of
isobutene that is conventionally referred to as polyisobutylene, or
a polybutenyl group is most preferable.
[0094] A preferred number average molecular weight of the alkyl or
alkenyl group (R.sup.8 to R.sup.10) in the formulae (7) and (8) is
800 to 3500.
[0095] Succinimide having at least one alkyl or alkenyl group in
its molecule includes so-called monotype succinimide represented by
the formula (7) where succinic anhydride terminates only one end of
a polyamine chain, and so-called bistype succinimide represented by
the formula (8) where succinic anhydride terminates both ends of a
polyamine chain. The lubricating oil composition may include either
monotype or bistype succinimide, and may include both of them as a
mixture.
[0096] A method for producing succinimide having at least one alkyl
or alkenyl group in its molecule is not limited. For example, such
succinimide can be obtained by: making alkyl succinic acid or
alkenyl succinic acid obtained by making a compound having a
C.sub.40-C.sub.400 alkyl or alkenyl group react with maleic
anhydride at 100 to 200.degree. C., react with a polyamine. Here,
examples of a polyamine include diethylenetriamine,
triethylenetetramine, tetraethylenepentamine, and
pentaethylenehexamine.
[0097] Examples of benzylamine having at least one alkyl or alkenyl
group in its molecule among the component (G-2) include compounds
represented by the following formula (9).
##STR00007##
[0098] In the formula (9), R.sup.11 is a C.sub.40-C.sub.400 alkyl
or alkenyl group; and h represents an integer of 1 to 5, and
preferably 2 to 4. The carbon number of is preferably no less than
60, and preferably no more than 350.
[0099] A method for producing the component (G-2) is not limited.
Examples of such a method include: making a polyolefin such as a
propylene oligomer, polybutene, and an ethylene-.alpha.-olefin
copolymer, react with a phenol, to give an alkylphenol; and then
making formaldehyde, and a polyamine such as diethylenetriamine,
triethylenetetramine, tetraethylenepentamine, and
pentaethylenehexamine, react with the alkylphenol by Mannich
reaction.
[0100] Examples of a polyamine having at least one alkyl or alkenyl
group in its molecule among the component (G-3) include compounds
represented by the following formula (10).
R.sup.12--NH--(CH.sub.2CH.sub.2NH).sub.i--H (10)
[0101] In the formula (10), R.sup.12 is a C.sub.40-C.sub.400 alkyl
or alkenyl group; and i represents an integer of 1 to 5, and
preferably 2 to 4. The carbon number of R.sup.12 is preferably no
less than 60, and preferably no more than 350.
[0102] A method for producing the component (G-3) is not limited.
Examples of such a method include: chlorinating a polyolefin such
as a propylene oligomer, polybutene, and an ethylene-.alpha.-olefin
copolymer; and then making ammonia, or a polyamine such as
ethylenediamine, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, and pentaethylenehexamine react with the
chlorinated polyolefin.
[0103] Examples of derivatives among the components (G-1) to (G-3)
include (i) oxygen-containing organic compound-modified products
where a part or all of the residual amino groups and/or imino
groups is/are neutralized or amidated by making a C.sub.1-C.sub.30
monocarboxylic acid such as fatty acids, a C.sub.2-C.sub.30
polycarboxylic acid (such as ethanedioic acid, phthalic acid,
trimellitic acid, and pyromellitic acid), an anhydride or ester
thereof, a C.sub.2-C.sub.6 alkylene oxide, or a
hydroxy(poly)oxyalkylene carbonate react with the above described
succinimide, benzylamine or polyamine having at least one alkyl or
alkenyl group in its molecule (hereinafter referred to as "the
above described nitrogen-containing compound"); (ii) boron-modified
products where a part or all of the residual amino groups and/or
imino groups is/are neutralized or amidated by making boric acid
react with the above described nitrogen-containing compound; (iii)
phosphoric acid-modified products where a part or all of the
residual amino groups and/or imino groups is/are neutralized or
amidated by making the above described nitrogen-containing compound
react with phosphoric acid; (iv) sulfur-modified products obtained
by making a sulfur compound react with the above described
nitrogen-containing compound; and (v) modified products obtained by
at least two modifications selected from the oxygen-containing
organic compound modification, boron modification, phosphoric acid
modification, and sulfur modification, on the above described
nitrogen-containing compound in combination. Among these
derivatives (i) to (v), a boron-modified product of the (G-1)
compound is preferably used in view of making it possible to
further improve thermal stability of the lubricating oil
composition.
[0104] The molecular weight of the component (G) is not restricted,
and the weight-average molecular weight thereof is preferably 1000
to 20000.
[0105] When the lubricating oil composition contains the component
(G), the content thereof is, in terms of nitrogen on the basis of
the total mass of the lubricating oil composition, preferably 100
to 2000 mass ppm, more preferably no less than 500 mass ppm, and
more preferably no more than 1000 mass ppm. The content of the
component (G) of this lower limit or over makes it possible to
improve anti-coking performance (thermal stability) of the
lubricating oil composition. The content of the component (G) of
this upper limit or below makes it possible to further improve fuel
efficiency.
[0106] When a boron-modified product is used as the component (G),
the boron content derived from the component (G) in the lubricating
oil composition is, on the basis of the total mass of the
lubricating oil composition, preferably 50 to 500 mass ppm, more
preferably no less than 100 mass ppm, and more preferably no more
than 300 mass ppm. The boron content derived from the component (G)
of this upper limit or below makes it possible to further improve
fuel efficiency.
[0107] <(H) Phosphorus-based Anti-wear Agent>
[0108] In one preferred embodiment, the lubricating oil composition
may further contain a phosphorus-based anti-wear agent (hereinafter
may be referred to as "component (H)"). As the component (H), one
agent may be used alone or at least two agents may be used in
combination.
[0109] Examples of the component (H) include zinc
dialkyldithophosphate, phosphoric acid monoesters, phosphoric acid
diesters, phosphoric acid triesters, phosphorous acid monoesters,
phosphorous acid diesters, phosphorous acid triesters, salts of
phosphoric acid incomplete esters, salts of phosphorous acid
incomplete esters, and mixture thereof.
[0110] In the above examples, compounds other than phosphorous acid
are usually compounds having hydrocarbon groups of C.sub.2 to
C.sub.30, preferably C.sub.3 to C.sub.20. Specific examples of
these hydrocarbon groups of C.sub.2 to C.sub.30 include an alkyl
group, a cycloalkyl group, an alkyl-substituted cycloalkyl group,
an alkenyl group, an aryl group, an alkyl-substituted aryl group,
and aryl-substituted alkyl group. These alkyl groups may be either
linear or branched.
[0111] Examples of the above described salts of phosphoric acid
incomplete esters and salts of phosphorous acid incomplete esters
include salts where a part or all of the residual acidic hydrogen
is/are neutralized by making a nitrogen-containing compound such as
ammonia and amine compounds containing only a C.sub.1 to C.sub.8
hydrocarbon group or C.sub.1 to C.sub.8 hydroxy group-containing
hydrocarbon group in their molecules react with phosphoric acid
monoester, phosphoric acid diester, phosphorous acid monoester, or
phosphorous acid diester, or mixture thereof.
[0112] Phosphorous acid ester or its salt can be preferably used as
the component (H). Phosphorous acid incomplete ester or its salt is
more preferable, and phosphorous acid incomplete ester or its salt
having a hydrocarbon group having 8 or less carbon atoms is
especially preferable.
[0113] When the lubricating oil composition contains the component
(H), the content thereof is preferably 100 to 2000 mass ppm, more
preferably no less than 200 mass ppm, and more preferably no more
than 1000 mass ppm, in terms of phosphorus on the basis of the
total mass of the composition. The content of the component (H) of
this lower limit or above makes it possible to further improve
anti-wear performance and friction coefficients between metals. The
content of the component (H) of this upper limit or below makes it
possible to improve oxidation stability and compatibility with
sealing.
[0114] <(I) Friction Modifier>
[0115] In one preferred embodiment, the lubricating oil composition
may further contain a friction modifier (hereinafter may be
referred to as "component (I)"). As the component (I), one friction
modifier may be used alone or at least two friction modifiers may
be used in combination.
[0116] As the component (I), a compound used as a friction modifier
in the field of lubricant oil can be used without particular
limitation. Examples of a friction modifier include
C.sub.6-C.sub.50 compounds containing, in their molecules, at least
one heteroatom selected from an oxygen atom, a nitrogen atom and a
sulfur atom. More specifically, any ashless friction modifier such
as aliphatic amine compounds; aliphatic imide compounds; and fatty
acid esters, fatty acid amides, fatty acid hydrazides, fatty acid
metal salts, aliphatic alcohols, aliphatic ethers, and aliphatic
urea compounds, each having at least one C.sub.6-C.sub.30 linear or
branched alkyl or alkenyl group in its molecule, can be preferably
used.
[0117] Examples of aliphatic amine compounds include
C.sub.6-C.sub.30 linear or branched, preferably linear aliphatic
monoamines; C.sub.6-C.sub.30 linear or branched, preferably linear
aliphatic polyamines; and alkylene oxide adducts of these aliphatic
amines.
[0118] Examples of aliphatic imide compounds include succinimide
having a C.sub.6-C.sub.30 linear or branched alkyl or alkenyl
group; and modified products thereof by carboxylic acids, boric
acid, phosphoric acid, or sulfuric acid.
[0119] Examples of fatty acid esters include esters of
C.sub.6-C.sub.30 linear or branched, preferably linear fatty acids,
and aliphatic monoalcohols or aliphatic polyols.
[0120] Examples of fatty acid amides include amides of
C.sub.6-C.sub.30 linear or branched, preferably linear fatty acids,
and aliphatic monoamines or aliphatic polyamines, or ammonia.
[0121] Examples of fatty acid hydrazides include condensation
products of C.sub.6-C.sub.30 linear or branched, preferably linear
fatty acids, and unsubstituted or substituted aliphatic
hydrazines.
[0122] Examples of fatty acid metal salts include alkaline earth
metal salts (such as a magnesium salt and a calcium salt) and a
zinc salt of C.sub.6-C.sub.30 linear or branched, preferably linear
fatty acids.
[0123] When the lubricating oil composition contains the component
(I), the content thereof is preferably 0.01 to 2 mass %, more
preferably no less than 0.1 mass %, and further preferably no less
than 0.3 mass %; and more preferably no more than 1.0 mass %, and
further preferably no more than 0.8 mass %, on the basis of the
total mass of the lubricating oil composition. The content of the
component (I) of this lower limit or over makes it possible to
improve shudder prevention performance. The content of the
component (I) of this upper limit or below makes it possible to
further improve friction coefficients between metals.
[0124] <Other Additives>
[0125] In one embodiment, the lubricating oil composition may
further contain at least one additive selected from anti-wear
agents or extreme-pressure agents other than the component (H),
antioxidants, pour point depressants other than the component (D),
corrosion inhibitors other than the component (E), anti-rust
agents, metal deactivators other than the component (E), defoaming
agents, demulsifiers, and coloring agents.
[0126] Examples of anti-wear agents or extreme-pressure agents
other than the component (H) include sulfur-based compounds such as
disulfides, sulfurized olefins, and sulfurized oils. When the
lubricating oil composition contains an anti-wear agent or
extreme-pressure agent other than the component (H), the content
thereof is usually 0.01 to 5 mass % on the basis of the total mass
of the lubricating oil composition.
[0127] Examples of antioxidants include phenolic or amine ashless
antioxidants, and copper or molybdenum metallic antioxidants.
Specific examples of phenolic ashless antioxidants include
4,4'-methylenebis(2,6-di-tert-butylphenol), and
4,4'-bis(2,6-di-tert-butylphenol); and examples of amine ashless
antioxidants include phenyl-.alpha.-naphthylamine,
alkylphenyl-.alpha.-naphthylamine, and dialkyldiphenylamine. When
the lubricating oil composition contains an antioxidant, the
content thereof is usually 0.01 to 5 mass % on the basis of the
total mass of the lubricating oil composition.
[0128] For example, a known pour point depressant such as a
polymethacrylate polymer can be used as a pour point depressant
other than the component (D), according to properties of the
lubricant base oil to be used. When the lubricating oil composition
contains a pour point depressant, the content thereof is usually
0.05 to 1 mass % on the basis of the total mass of the lubricating
oil composition.
[0129] A known corrosion inhibitor such as a benzotriazole,
tolyltriazole, and imidazole compound can be used as a corrosion
inhibitor other than the component (E). When the lubricating oil
composition contains a corrosion inhibitor other than the component
(E), the content thereof is usually 0.005 to 5 mass % on the basis
of the total mass of the lubricating oil composition.
[0130] A known anti-rust agent such as petroleum sulfonate,
alkylbenzenesulfonate, dinonylnaphthalenesulfonate,
alkenylsuccinate esters, and polyol esters can be used as an
anti-rust agent. When the lubricating oil composition contains an
anti-rust agent, the content thereof is usually 0.005 to 5 mass %
on the basis of the total mass of the lubricating oil
composition.
[0131] A known metal deactivator such as imidazoline, pyrimidine
derivatives, mercaptobenzothiazole, benzotriazole and their
derivatives, 2-(alkyldithio)benzimidazole, and
.beta.-(o-carboxybenzylthio)propionitrile can be used as a metal
deactivator other than the component (E). When the lubricating oil
composition contains a metal deactivator other than the component
(E), the content thereof is usually 0.005 to 5 mass % on the basis
of the total mass of the lubricating oil composition.
[0132] A known anti-foaming agent such as silicones,
fluorosilicones, and fluoroalkyl ethers can be used as an
anti-foaming agent. When the lubricating oil composition contains
an anti-foaming agent, the content thereof is usually 0.0005 to
0.01 mass % on the basis of the total mass of the lubricating oil
composition.
[0133] A known demulsifier such as polyalkylene glycol-based
nonionic surfactants can be used as a demulsifier. When the
lubricating oil composition contains a demulsifier, the content
thereof is usually 0.005 to 5 mass % on the basis of the total mass
of the lubricating oil composition.
[0134] As a coloring agent, for example, a known coloring agent
such as azo compounds can be used.
[0135] <Lubricating Oil Composition>
[0136] The kinematic viscosity of the lubricating oil composition
at 40.degree. C. is no more than 25 mm.sup.2/s, and preferably no
less than 10 mm.sup.2/s, more preferably no less than 12
mm.sup.2/s, and further preferably no less than 15 mm.sup.2/s. When
the kinematic viscosity of the lubricating oil composition at
40.degree. C. is no more than 25 mm.sup.2/s, fuel efficiency can be
improved. The kinematic viscosity of the lubricating oil
composition at 40.degree. C. of this lower limit or above makes it
easy to achieve enough oil film formation at a lubricating point,
to improve anti-wear performance.
[0137] The kinematic viscosity of the lubricating oil composition
at 100.degree. C. is preferably no less than 5.0 mm.sup.2/s, and
preferably no more than 9.0 mm.sup.2/s, more preferably no more
than 8.0 mm.sup.2/s, and further preferably no more than 7.0
mm.sup.2/s. The kinematic viscosity of the lubricating oil
composition at 100.degree. C. of this lower limit or above makes it
easy to achieve enough oil film formation at a lubricating point,
to improve anti-wear performance. When the kinematic viscosity
thereof is this upper limit or below, fuel efficiency can be easily
improved.
[0138] The viscosity index of the lubricating oil composition is
preferably no less than 170. The upper limit of the viscosity index
of the lubricating oil composition is not restricted, and is
usually no more than 300. The lubricating oil composition having a
viscosity index of 170 or more makes it easy to improve fuel
efficiency.
[0139] Brookfield viscosity (hereinafter may be referred to as "BF
viscosity") of the lubricating oil composition at -40.degree. C. is
preferably no more than 8,000 mPas, and more preferably no more
than 7,000 mPas. The lubricating oil composition having BF
viscosity of no more than 8,000 mPas at -40.degree. C. makes it
possible to improve low-temperature startability.
[0140] (Use)
[0141] The lubricating oil composition of the present invention can
be preferably used as continuously variable transmission oil for
automobiles, and especially preferably used for lubrication of
metal belt type continuously variable transmissions where torque is
transmitted through a metal belt.
EXAMPLES
[0142] Hereinafter the present invention will be more specifically
described based on the examples and comparative examples. It is
noted that the present invention is not limited to these
examples.
Examples 1 to 19 and Comparative Examples 1 to 7
[0143] The lubricating oil compositions of the present invention
(examples 1 to 19) and the lubricating oil compositions for
comparison (comparative examples 1 to 7) were prepared as shown in
Tables 1 to 3. In Tables, the contents of the base oils are on the
basis of the total mass of the base oils, and the content of each
additive is on the basis of the total mass of the composition.
Details on the components were as follows.
[0144] ((A) Lubricant Base Oil)
[0145] A1-1: wax-isomerized base oil (kinematic viscosity
(40.degree. C.): 9.072 mm.sup.2/s, kinematic viscosity (100.degree.
C.): 2.621 mm.sup.2/s, viscosity index: 127, sulfur content: less
than 10 mass ppm, % C.sub.P: 91.8, % C.sub.N: 8.2, % C.sub.A:
0)
[0146] A1-2: wax-isomerized base oil (kinematic viscosity
(40.degree. C.): 9.617 mm.sup.2/s, kinematic viscosity (100.degree.
C.): 2.653 mm.sup.2/s, viscosity index: 112, sulfur content: less
than 10 mass ppm, % C.sub.P: 92.5, % C.sub.N: 7.3, % C.sub.A:
0.1)
[0147] A2-1: wax-isomerized base oil (kinematic viscosity
(40.degree. C.): 15.65 mm.sup.2/s, kinematic viscosity (100.degree.
C.): 3.883 mm.sup.2/s, viscosity index: 142, sulfur content: less
than 10 mass ppm, % C.sub.P: 92.5, % C.sub.N: 7.5, % C.sub.A:
0)
[0148] A2-2: wax-isomerized base oil (kinematic viscosity
(40.degree. C.): 18.24 mm.sup.2/s, kinematic viscosity (100.degree.
C.): 4.119 mm.sup.2/s, viscosity index: 130, sulfur content: less
than 10 mass ppm, % C.sub.P: 89.1, % C.sub.N: 10.9, % C.sub.A:
0)
[0149] ((B) Borate Ester Compound)
[0150] B-1: boric acid mono(C.sub.6-C.sub.8 alkyl)ester, B: 2.83
mass %
[0151] ((C) Phosphoric Acid)
[0152] C-1: phosphoric acid, P: 36 mass %
[0153] ((D) Poly(meth)acrylate) [0154] D-1: non-dispersant
polymethacrylate, weight average molecular weight: 20,000
[0155] D-2: non-dispersant polymethacrylate, weight average
molecular weight: 50,000
[0156] D-3: non-dispersant polymethacrylate, weight average
molecular weight: 40,000
[0157] D-4: non-dispersant polymethacrylate, weight average
molecular weight: 150,000
[0158] ((E) Thiadiazole Compound)
[0159] E-1: thiadiazole compound represented by any of the general
formulae (2) to (4) having a hydrocarbyldithio group, S: 36 mass
%
[0160] ((F) Metallic Detergent)
[0161] F-1: Ca sulfonate, Ca: 18.4 mass %
[0162] F-2: Ca salicylate, Ca: 8.1 mass %
[0163] ((G) Ashless Dispersant)
[0164] G-1: succinimide, N: 2.1 mass %
[0165] G-1: boron-containing succinimide, N: 2.3 mass %, B: 2.0
mass %
[0166] ((H) Phosphorus-based Anti-wear Agent)
[0167] H-1: di(n-butyl) phosphite, P: 15.5 mass %
[0168] H-2: diphenyl hydrogen phosphite, P: 13.2 mass %
[0169] ((I) Friction Modifier)
[0170] I-1: oleylamine
[0171] I-2: oleylamide
[0172] I-3: condensation product of a fatty acid and an aliphatic
monoamine, carbon number: 67 to 86
[0173] ((J) Other Additives)
[0174] J-1: rubber swelling agent
[0175] J-2: amine antioxidant
[0176] J-3: dimethylsilicone anti-foaming agent, kinematic
viscosity (25.degree. C.): 60,000 mm.sup.2/s
TABLE-US-00001 TABLE 1 Examples 1 2 3 4 5 (A) Base oil A1-1 mass %
(80) -- (83) -- (36) A1-2 mass % -- (85) -- (83) -- A2-1 mass %
(20) -- -- (17) (64) A2-2 mass % -- (15) (17) -- -- viscosity
characteristics of base oil kinematic viscosity (40.degree. C.)
mm.sup.2/s 10.0 10.5 10.1 10.4 12.7 kinematic viscosity
(100.degree. C.) mm.sup.2/s 2.82 2.82 2.81 2.82 3.34 viscosity
index 132 115 126 118 140 (B) Borate ester compound B-1 mass % 0.50
0.50 0.50 0.50 0.50 (content "B" in terms of boron) mass ppm 142
142 142 142 142 (C) Phosphoric acid C-1 mass % 0.10 0.10 0.10 0.10
0.10 (in terms of phosphorus) mass ppm 300 300 300 300 300 (D)
poly(meth)acrylate D-1 mass % 18.5 18.5 18.5 18.5 14.3 D-2 mass %
-- -- -- -- -- D-3 mass % -- -- -- -- -- D-4 mass % -- -- -- -- --
(E) Thiadiazole compound E-1 mass % 0.15 0.15 0.15 0.15 0.15
(content "S" in terms of sulfur) mass ppm 540 540 540 540 540 (F)
Metallic detergent F-1 mass % 0.22 0.22 0.22 0.22 0.22 F-2 mass %
-- -- -- -- -- (G) Ashless dispersant G-1 mass % 3.0 3.0 3.0 3.0
3.0 G-2 mass % 0.5 0.5 0.5 0.5 0.5 (H) Phosphorus-based Anti- wear
agent H-1 mass % 0.30 0.30 0.30 0.30 0.30 H-2 mass % -- -- -- -- --
(I) Friction modifier I-1 mass % 0.03 0.03 0.03 0.03 0.03 I-2 mass
% 0.05 0.05 0.05 0.05 0.05 I-3 mass % 0.50 0.50 0.50 0.50 0.50 (J)
Other additives Rubber swelling agent (J-1) mass % 0.6 0.6 0.6 0.6
0.6 Antioxidant (J-2) mass % 0.5 0.5 0.5 0.5 0.5 Anti-foaming agent
(J-3) mass % 0.003 0.003 0.003 0.003 0.003 Phosphorus content "P"
in mass ppm 765 765 765 765 765 composition (B + P)/S 1.7 1.7 1.7
1.7 1.7 viscosity characteristics of composition kinematic
viscosity (40.degree. C.) mm.sup.2/s 21.6 22.4 21.9 22.0 22.3
kinematic viscosity (100.degree. C.) mm.sup.2/s 5.35 5.31 5.33 5.26
5.41 viscosity index 199 184 193 185 194 BF viscosity (-40.degree.
C.) mPa s 4200 3800 4000 3850 4850 Shear stability test (reduction
% 1.8 1.7 1.7 1.8 1.4 of kinematic viscosity) EHL test (oil film
thickness) nm 50.1 50.2 50.1 50.1 53.1 High-speed four-ball test
LNSL N 618 618 618 618 618 Wear mark size mm 0.53 0.55 0.52 0.54
0.51 FALEX seizure test (load capacity) N 4359 4226 4404 4359 4493
Unisteel test (fatigue life L50) min 1435 1325 1411 1428 1568 LFW-1
test (friction coefficients 0.098 0.097 0.095 0.097 0.093 between
metals) Examples 6 7 8 9 10 (A) Base oil A1-1 (100) (80) (80) (80)
(80) A1-2 -- -- -- -- -- A2-1 -- (20) (20) (20) (20) A2-2 -- -- --
-- -- viscosity characteristics of base oil kinematic viscosity
(40.degree. C.) 9.1 10.0 10.0 10.0 10.0 kinematic viscosity
(100.degree. C.) 2.62 2.82 2.82 2.82 2.82 viscosity index 125 132
132 132 132 (B) Borate ester compound B-1 0.50 0.10 1.00 0.50 0.50
(content "B" in terms of boron) 142 28 283 142 142 (C) Phosphoric
acid C-1 0.10 0.10 0.10 0.05 0.20 (in terms of phosphorus) 300 300
300 150 600 (D) poly(meth)acrylate D-1 19.2 18.5 18.5 18.5 18.5 D-2
-- -- -- -- -- D-3 -- -- -- -- -- D-4 -- -- -- -- -- (E)
Thiadiazole compound E-1 0.15 0.15 0.15 0.15 0.15 (content "S" in
terms of sulfur) 540 540 540 540 540 (F) Metallic detergent F-1
0.22 0.22 0.22 0.22 0.22 F-2 -- -- -- -- -- (G) Ashless dispersant
G-1 3.0 3.0 3.0 3.0 3.0 G-2 0.5 0.5 0.5 0.5 0.5 (H)
Phosphorus-based Anti- wear agent H-1 0.30 0.30 0.30 0.30 0.30 H-2
-- -- -- -- -- (I) Friction modifier I-1 0.03 0.03 0.03 0.03 0.03
I-2 0.05 0.05 0.05 0.05 0.05 I-3 0.50 0.50 0.50 0.50 0.50 (J) Other
additives Rubber swelling agent (J-1) 0.6 0.6 0.6 0.6 0.6
Antioxidant (J-2) 0.5 0.5 0.5 0.5 0.5 Anti-foaming agent (J-3)
0.003 0.003 0.003 0.003 0.003 Phosphorus content "P" in 765 765 765
615 1065 composition (B + P)/S 1.7 1.5 1.9 1.4 2.2 viscosity
characteristics of composition kinematic viscosity (40.degree. C.)
21.2 21.6 22.0 21.0 21.1 kinematic viscosity (100.degree. C.) 5.23
5.34 5.42 5.24 5.26 viscosity index 195 198 199 199 199 BF
viscosity (-40.degree. C.) 3650 4020 4350 3980 4400 Shear stability
test (reduction 1.9 1.7 1.8 1.7 1.8 of kinematic viscosity) EHL
test (oil film thickness) 49.2 50.1 50.2 50.2 50.0 High-speed
four-ball test LNSL 618 618 618 618 618 Wear mark size 0.48 0.52
0.54 0.62 0.54 FALEX seizure test (load capacity) 4226 4048 4448
4003 4359 Unisteel test (fatigue life L50) 1411 1524 1395 1536 1389
LFW-1 test (friction coefficients 0.101 0.095 0.100 0.094 0.099
between metals)
TABLE-US-00002 TABLE 2 Examples 11 12 13 14 15 16 17 18 19 (A) Base
oil A1-1 mass % (80) (80) (80) (80) (80) (80) (80) (80) (80) A1-2
mass % -- -- -- -- -- -- -- -- -- A2-1 mass % (20) (20) (20) (20)
(20) (20) (20) (20) (20) A2-2 mass % -- -- -- -- -- -- -- -- --
viscosity characteristics of base oil kinematic viscosity
(40.degree. C.) mm.sup.2/s 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
10.0 kinematic viscosity (100.degree. C.) mm.sup.2/s 2.82 2.82 2.82
2.82 2.82 2.82 2.82 2.82 2.82 viscosity index 132 132 132 132 132
132 132 132 132 (B) Borate ester compound B-1 mass % 0.50 0.50 0.10
1.00 0.50 0.50 0.50 0.50 0.50 (content "B" in terms of mass ppm 142
142 28 283 142 142 142 142 142 boron) (C) Phosphoric acid C-1 mass
% 0.10 0.10 0.05 0.25 0.10 0.10 0.10 0.10 0.10 (in terms of
phosphorus) mass ppm 300 300 150 750 300 300 300 300 300 (D)
poly(meth)acrylate D-1 mass % 18.5 18.5 18.5 18.5 -- -- 18.5 18.5
18.5 D-2 mass % -- -- -- -- 6.2 -- -- -- -- D-3 mass % -- -- -- --
-- 10.5 -- -- -- D-4 mass % -- -- -- -- -- -- -- -- -- (E)
Thiadiazole compound E-1 mass % 0.10 0.25 0.10 0.25 0.15 0.15 0.15
0.15 0.15 (content "S" in terms of mass ppm 360 900 360 900 540 540
540 540 540 sulfur) (F) Metallic detergent F-1 mass % 0.22 0.22
0.22 0.22 0.22 0.22 0.22 0.22 0.11 F-2 mass % -- -- -- -- -- -- --
0.49 0.25 (G) Ashless dispersant G-1 mass % 3.0 3.0 3.0 3.0 3.0 3.0
3.0 3.0 3.0 G-2 mass % 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 (H)
Phosphorus-based Anti- wear agent H-1 mass % 0.30 0.30 0.30 0.30
0.30 0.30 -- 0.30 0.30 H-2 mass % -- -- -- -- -- -- 0.35 -- -- (I)
Friction modifier I-1 mass % 0.03 0.03 0.03 0.03 0.03 0.03 0.03
0.03 0.03 I-2 mass % 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
I-3 mass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 (J) Other
additives Rubber swelling agent (J-1) mass % 0.6 0.6 0.6 0.6 0.6
0.6 0.6 0.6 0.6 Antioxidant (J-2) mass % 0.5 0.5 0.5 0.5 0.5 0.5
0.5 0.5 0.5 Anti-foaming agent (J-3) mass % 0.003 0.003 0.003 0.003
0.003 0.003 0.003 0.003 0.003 Phosphorus content "P" in mass ppm
765 765 615 1215 765 765 762 765 765 composition (B + P)/S 2.5 1.0
1.8 1.7 1.7 1.7 1.7 1.7 1.7 viscosity characteristics of
composition kinematic viscosity (40.degree. C.) mm.sup.2/s 21.4
21.3 21.0 22.0 24.3 22.8 21.6 21.4 21.6 kinematic viscosity
(100.degree. C.) mm.sup.2/s 5.31 5.29 5.24 5.43 5.48 5.41 5.35 5.33
5.36 viscosity index 198 198 199 200 173 187 199 200 200 BF
viscosity (-40.degree. C.) mPa s 4130 4300 4100 4540 4250 4100 4200
4180 4210 Shear stability test (reduction % 1.7 1.8 1.7 1.8 2.1 2.0
1.7 1.7 1.7 of kinematic viscosity) EHL test (oil film thickness)
nm 50.1 50.1 50.1 50.2 49.8 51.2 50.1 50.2 50.1 High-speed
four-ball test LNSL N 618 785 618 618 618 618 618 618 618 Wear mark
size mm 0.65 0.52 0.63 0.56 0.61 0.51 0.52 0.59 0.57 FALEX seizure
test (load N 3959 4671 4270 4359 4404 4448 4226 4359 4448 capacity)
Unisteel test (fatigue life L50) min 1311 1458 1462 1395 1298 1485
1497 1386 1415 LFW-1 test (friction coeffi- 0.094 0.096 0.095 0.096
0.099 0.095 0.096 0.093 0.096 cients between metals)
TABLE-US-00003 TABLE 3 Comparative Examples 1 2 3 4 5 6 7 (A) Base
oil A1-1 mass % (80) (80) (80) (80) (80) (80) (80) A1-2 mass % --
-- -- -- -- -- -- A2-1 mass % (20) (20) (20) (20) (20) (20) (20)
A2-2 mass % -- -- -- -- -- -- -- viscosity characteristics of base
oil kinematic viscosity (40.degree. C.) mm.sup.2/s 10.0 10.0 10.0
10.0 10.0 10.0 10.0 kinematic viscosity (100.degree. C.) mm.sup.2/s
2.82 2.82 2.82 2.82 2.82 2.82 2.82 viscosity index 132 132 132 132
132 132 132 (B) Borate ester compound B-1 mass % 0.05 2.00 0.50
0.50 0.00 2.00 0.50 (content "B" in terms of mass ppm 14 566 142
142 0 566 142 boron) (C) Phosphoric acid C-1 mass % 0.10 0.10 0.01
0.30 0.00 0.30 0.10 (in terms of phosphorus) mass ppm 300 300 30
900 0 900 300 (D) poly(meth)acrylate D-1 mass % 18.5 18.5 18.5 18.5
18.5 18.5 -- D-2 mass % -- -- -- -- -- -- -- D-3 mass % -- -- -- --
-- -- -- D-4 mass % -- -- -- -- -- -- 4.5 (E) Thiadiazole compound
E-1 mass % 0.15 0.15 0.15 0.15 0.01 0.30 0.15 (content "S" in terms
of mass ppm 540 540 540 540 36 1080 540 sulfur) (F) Metallic
detergent F-1 mass % 0.22 0.22 0.22 0.22 0.22 0.22 0.22 F-2 mass %
-- -- -- -- -- -- -- (G) Ashless dispersant G-1 mass % 3.0 3.0 3.0
3.0 3.0 3.0 3.0 G-2 mass % 0.5 0.5 0.5 0.5 0.5 0.5 0.5 (H)
Phosphorus-based Anti- wear agent H-1 mass % 0.30 0.30 0.30 0.30
0.30 0.30 0.30 H-2 mass % -- -- -- -- -- -- -- (I) Friction
modifier I-1 mass % 0.03 0.03 0.03 0.03 0.03 0.03 0.03 I-2 mass %
0.05 0.05 0.05 0.05 0.05 0.05 0.05 I-3 mass % 0.50 0.50 0.50 0.50
0.50 0.50 0.50 (J) Other additives Rubber swelling agent (J-1) mass
% 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Antioxidant (J-2) mass % 0.5 0.5 0.5
0.5 0.5 0.5 0.5 Anti-foaming agent (J-3) mass % 0.003 0.003 0.003
0.003 0.003 0.003 0.003 Phosphorus content "P" in mass ppm 765 765
495 1365 465 1365 765 composition (B + P)/S 1.4 2.5 1.2 2.8 12.9
1.8 1.7 viscosity characteristics of composition kinematic
viscosity (40.degree. C.) mm.sup.2/s 21.4 21.6 21.3 21.4 21.1 22.1
25.9 kinematic viscosity (100.degree. C.) mm.sup.2/s 5.31 5.34 5.30
5.32 5.26 5.45 5.64 viscosity index 198 198 199 199 199 200 167 BF
viscosity (-40.degree. C.) mPa s 4220 4180 4080 4430 4000 4400 4600
Shear stability test (reduction % 1.8 1.7 1.7 1.8 1.7 1.8 10.3 of
kinematic viscosity) EHL test (oil film thickness) nm 50.2 50.2
50.1 50.3 50.1 50.1 50.1 High-speed four-ball test LNSL N 618 785
618 618 489 785 618 Wear mark size mm 0.74 0.44 0.79 0.41 0.83 0.55
0.54 FALEX seizure test (load N 3826 3648 3470 3381 3069 4092 4359
capacity) Unisteel test (fatigue life L50) min 1285 1110 1524 1098
998 1044 1358 LFW-1 test (friction coeffi- 0.093 0.099 0.095 0.097
0.087 0.097 0.095 cients between metals)
[0177] (Low-temperature Viscosity Characteristics)
[0178] For each lubricating oil composition, viscosity (BF
viscosity) at -40.degree. C. in oil temperature was measured using
a Brookfield viscometer. The results are shown in Tables 1 to 3. It
can be determined that low-temperature viscosity characteristics
are good when the BF viscosity at -40.degree. C. is no more than
8,000 mPas.
[0179] (Shear Stability Test)
[0180] For each lubricating oil composition, shear stability of the
lubricating oil composition was evaluated by a shear stability test
conforming to JPI-5S-29-88. Sample oil was irradiated with
ultrasonic waves of 10 kHz in frequency from an oscillator of 28
.mu.m in amplitude for 1 hour, and the reduction (%) of the
kinematic viscosity of the sample oil at 100.degree. C. after
irradiation of ultrasonic waves, to that before irradiation of
ultrasonic waves was calculated. The results are shown in Tables 1
to 3. It can be determined that shear stability is good when the
reduction of the kinematic viscosity in this test is no more than
2.5.
[0181] (EHL Test)
[0182] For each lubricating oil composition, oil film thickness
under an elastohydrodynamic lubrication condition was measured by
optical interferometry using EHL test instrument (EHD2 ultra thin
film measurement system manufactured by PCS Instruments). The
measurement conditions were as follows.
[0183] steel ball: Standard Ball (material: SUJ-2) manufactured by
PCS Instruments, diameter: 19.05 mm
[0184] disc: glass disc having a glass substrate, a Cr layer coated
on the surface of the glass substrate, and a silica layer coated on
the surface of the Cr layer
[0185] oil temperature: 80.degree. C.
[0186] load: 20 N
[0187] average Hertz contact pressure: 0.5 GPa
[0188] speed: 1 m/s
[0189] slide ratio: 10% The results are shown in Tables 1 to 3. It
can be determined that oil film thickness is sufficiently thin when
the oil film thickness measured in this test is no more than 55
nm.
[0190] (High-speed Four-ball Test)
[0191] For each lubricating oil composition, load capacity and
anti-wear performance of the lubricating oil composition were
evaluated by a high-speed four-ball test conforming to
JPI-5S-40-93.
[0192] (1) Last non-seizure load (LNSL) was measured at 1800 rpm in
rotation speed.
[0193] (2) the size of a wear mark after driving at 1200 rpm in
rotation speed at 392 N in load and 80.degree. C. in oil
temperature for 30 minutes was measured. The results are shown in
Tables 1 to 3. It can be determined that load capacity
(anti-seizure performance) is good when LNSL is no less than 618 N
in this test, and it can be determined that anti-wear performance
is good when the size of a wear mark is no more than 0.70 mm in
this test.
[0194] (FALEX Seizure Test)
[0195] For each lubricating oil composition, load capacity was
evaluated by a FALEX seizure test conforming to ASTM D3233. Under
the condition of oil temperature at 110.degree. C., a steel pin
that was sandwiched by two stationary steel V-shaped blocks was
rotated at 290 rpm, and the load at which seizure occurred was
measured. The results are shown in Tables 1 to 3. It can be
determined that load capacity (anti-seizure performance) is good
when the load at which seizure occurs is no less than 3900 N in
this test.
[0196] (Unisteel Test)
[0197] For each lubricating oil composition, a rolling fatigue life
of a thrust bearing was measured by a Unisteel test (IP305/79, The
Institute of Petroleum) using a Unisteel rolling fatigue testing
machine (triple-type high-temperature rolling fatigue testing
machine (TRF-1000/3-01H) manufactured by Tokyo Koki Testing Machine
Co. Ltd.). Time until either a roller or a test piece suffers
fatigue damage was measured for a test bearing made by replacing a
bearing ring in one side of a thrust needle bearing (FNTA-2542C
manufactured by NSK Ltd.) with a flat test piece (material: SUJ2),
under conditions of: 7000 N in load; 2 GPa in surface pressure;
1450 rpm in rotation speed; and 120.degree. C. in oil temperature.
It was determined that fatigue damage occurred when the vibration
acceleration of a testing portion measured by a vibration
accelerometer installed in the Unisteel rolling fatigue testing
machine reached 1.5 m/s.sup.2. The test was repeated ten times, and
then a fatigue life was calculated as the 50% life (L50: time for
the cumulative probability to be 50%) by a Weibull plot based on
the time it had taken for fatigue damage to occur in the tests. The
results are shown in Tables 1 to 3. It can be determined that a
fatigue life is good when the 50% life measured in this test is no
less than 1200 minutes.
[0198] (LFW-1 Test)
[0199] For each lubricating oil composition, friction coefficients
between metals (coefficient of dynamic friction) was measured
conforming to JASO M358-2005 (Standard Test Method for Metal on
Metal Friction Characteristics of Belt CVT Fluids, under high-load
condition) with a block-on-ring friction and wear testing machine
(LFW-1). The test conditions were as follows; block: H60, ring:
S10, load: 1112 N, slide speed: 0.5 m/s, and oil temperature:
90.degree. C. The results are shown in Tables 1 to 3. It can be
determined that friction coefficients between metals is
sufficiently high when the friction coefficients between metals
measured in this test is no less than 0.90.
[0200] (Evaluation Results)
[0201] The lubricating oil compositions of examples 1 to 19 showed
good results in low-temperature viscosity characteristics, shear
stability, oil film thickness, load capacity (anti-seizure
performance), anti-wear performance, a fatigue life, and a friction
coefficient between metals.
[0202] The lubricating oil composition of comparative example 1,
where the content of the component (B) was too low, was inferior in
anti-wear performance and anti-seizure performance.
[0203] The lubricating oil composition of comparative example 2,
where the content of the component (B) was too high, was inferior
in anti-seizure performance and a fatigue life.
[0204] The lubricating oil composition of comparative example 3,
where the content of the component (C) was too low, was inferior in
anti-wear performance and anti-seizure performance.
[0205] The lubricating oil composition of comparative example 4,
where the content of the component (C) was too high, was inferior
in anti-seizure performance and a fatigue life.
[0206] The lubricating oil composition of comparative example 5,
which did not contain the component (B) or (C), was inferior in
anti-seizure performance, anti-wear performance, a fatigue life,
and a friction coefficient between metals.
[0207] The lubricating oil composition of comparative example 6,
where the contents of the components (B) and (C) were too high, was
inferior in a fatigue life.
[0208] The lubricating oil composition of comparative example 7,
where a polymethacrylate out of the range of the component (D) was
incorporated instead of the component (D), was inferior in shear
stability.
* * * * *