U.S. patent application number 14/414897 was filed with the patent office on 2015-05-21 for lubricating oil composition for continuously variable transmission.
This patent application is currently assigned to JX NIPPON OIL & ENERGY CORPORATION. The applicant listed for this patent is JX Nippon Oil & Energy Corporation. Invention is credited to Noriko Ayame, Takahiro Fukumizu, Jyunichi Nishinosono, Masashi Ogawa, Yasushi Onumata, Minoru Yamashita.
Application Number | 20150141305 14/414897 |
Document ID | / |
Family ID | 49948801 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150141305 |
Kind Code |
A1 |
Onumata; Yasushi ; et
al. |
May 21, 2015 |
LUBRICATING OIL COMPOSITION FOR CONTINUOUSLY VARIABLE
TRANSMISSION
Abstract
A lubricating oil composition for a continuously variable
transmission has low viscosity to exhibit fuel savings, higher
metal-to-metal friction coefficient to ensure high power
transmission, wet clutch friction characteristics and anti-shudder
properties required for transmissions, and low traction coefficient
to achieve fuel savings. The composition contains a base oil
adjusted so the product (EC.times.V40) of the mass % (ECmass %) of
saturated cyclic component based on the total base oil and the
40.degree. C. kinematic viscosity (V40 mm.sup.2/s) is 500 or less
and the 100.degree. C. kinematic viscosity is 3.6 to 4.1
mm.sup.2/s, (B) a phosphorus compound, (C) a calcium salicylate
and/or a calcium sulfonate, (D) a boron-modified ashless dispersant
in an amount of 0.001 to 0.008 mass % as boron, and (E) a friction
modifier, each in a specific amount, the lubricating oil
composition having a 100.degree. C. kinematic viscosity of 5.2 to
5.6 mm.sup.2/s and a viscosity index of 165 or greater.
Inventors: |
Onumata; Yasushi; (Tokyo,
JP) ; Ayame; Noriko; (Tokyo, JP) ; Fukumizu;
Takahiro; (Toyota-shi, JP) ; Yamashita; Minoru;
(Toyota-shi, JP) ; Ogawa; Masashi; (Toyota-shi,
JP) ; Nishinosono; Jyunichi; (Toyota-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JX Nippon Oil & Energy Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
JX NIPPON OIL & ENERGY
CORPORATION
Tokyo
JP
|
Family ID: |
49948801 |
Appl. No.: |
14/414897 |
Filed: |
July 16, 2013 |
PCT Filed: |
July 16, 2013 |
PCT NO: |
PCT/JP2013/069266 |
371 Date: |
January 15, 2015 |
Current U.S.
Class: |
508/192 ;
508/287 |
Current CPC
Class: |
C10N 2030/02 20130101;
C10N 2030/45 20200501; C10N 2060/14 20130101; C10N 2030/68
20200501; C10M 141/10 20130101; C10M 169/045 20130101; C10M
2219/046 20130101; C10N 2020/02 20130101; C10N 2040/045 20200501;
C10M 2215/08 20130101; C10M 2207/281 20130101; C10N 2030/42
20200501; C10N 2030/06 20130101; C10M 2207/262 20130101; C10N
2030/54 20200501; C10N 2030/76 20200501; C10M 2203/1065 20130101;
C10N 2020/019 20200501; C10M 2219/046 20130101; C10N 2010/04
20130101; C10M 2207/262 20130101; C10N 2010/04 20130101; C10M
2219/046 20130101; C10N 2010/04 20130101; C10M 2207/262 20130101;
C10N 2010/04 20130101 |
Class at
Publication: |
508/192 ;
508/287 |
International
Class: |
C10M 141/10 20060101
C10M141/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 20, 2012 |
JP |
2012-161270 |
Claims
1. A lubricating oil composition for a continuously variable
transmission, comprising a base oil having been adjusted so that
the product (EC.times.V40) of the mass percent (EC (mass %)) of a
saturated cyclic component on the total base oil mass basis and the
40.degree. C. kinematic viscosity (V40 (mm.sup.2/s)) is 500 or less
and the 100.degree. C. kinematic viscosity is from 3.6 to 4.1
mm.sup.2/s, (B) a phosphorus compound in an amount of 0.01 to 0.03
percent by mass as phosphorus, (C) a calcium salicylate and/or a
calcium sulfonate in an amount of 0.03 to 0.05 percent by mass as
calcium, the elemental ratio (P/Ca) of phosphorus and calcium in
the lubricating oil composition being from 0.3 to 0.7, (D) a
boron-modified ashless dispersant in an amount of 0.001 to 0.008
percent by mass as boron, and (E) a friction modifier in an amount
of 0.01 to 2 percent by mass on the total composition mass basis,
the lubricating oil composition having a 100.degree. C. kinematic
viscosity of 5.2 to 5.6 mm.sup.2/s and a viscosity index of 165 or
greater.
2. The lubricating oil composition for a continuously variable
transmission according to claim 1 wherein Component (E) is a fatty
acid ester-based friction modifier and/or a fatty acid amide-based
friction modifier.
Description
TECHNICAL FIELD
[0001] The present invention relates to lubricating oil
compositions for continuously variable transmissions, more
specifically to the lubricating oil compositions with enhanced fuel
saving properties, suitable for metal belt type continuously
variable transmissions of automobiles.
BACKGROUND ART
[0002] Recently, energy saving in automobiles and construction or
agricultural machinery, i.e., fuel saving has become an urgent need
in order to deal with environmental issues such as reduction in
carbon dioxide emissions, and systems such as engines,
transmissions, final reduction gears, compressors, or hydraulic
power units have been strongly demanded to contribute to energy
saving.
[0003] As one of means for saving fuel by transmissions, the use of
continuously variable transmissions has been growingly expanding.
This is for maximizing the fuel economy by driving an internal
combustion engine under the most efficient driving conditions.
[0004] Furthermore, continuously variable transmissions have become
highly efficient by reducing the size and weight thereof.
Accompanied with this high efficiency, the lubricating oil used in
the transmissions have been required to have fuel saving
properties. For this requirement, a measure has been generally
taken, wherein the lubricating oil is further lowered in viscosity
or suppressed from being increased in viscosity at low temperatures
so as to reduce the stir and frictional resistances in the torque
converter, wet clutch, gear bearing mechanism and oil pump.
[0005] However, since the lubricating oil used in continuously
variable transmissions is also used as a medium for a hydraulic
control system, excess reduction of the viscosity causes some
defects such as poor lubricity by wear or seizure due to
insufficient oil film thickness, and failure of generation of
sufficient hydraulic pressure caused by oil leakage from the
control valves or oil pumps. High molecular weight additives, i.e.,
viscosity index improver is usually added to the base oil to
suppress the viscosity from increasing particularly at low
temperatures. However, even though the oil retain a proper
viscosity when it is fresh, addition of the high molecular weight
additive causes a problem that the additive cannot retain a proper
viscosity because it is subjected to shear and is reduced in
viscosity as the lubricating oil is used.
[0006] Conventionally, an automatic transmission oil has been
provided, which is low in viscosity as the whole composition to
enhance fuel efficiency but is increased in the base oil viscosity
to retain properties such as shear stability, lubricating oil life
and the like and also increased in high temperature high shear
(HTHS) viscosity to enhance oil film retaining properties and to
provide the composition with excellent anti-wear properties,
anti-pitching properties, shear stability and low temperature
viscosity characteristics (see, for example, Patent Literature 1
below). However, the oil has been unable to meet the recent further
fuel saving demand.
CITATION LIST
Patent Literature
[0007] Patent Literature 1: Japanese Patent Application Laid-Open
Publication No. 2009-096925
SUMMARY OF INVENTION
Technical Problem
[0008] The present invention has been achieved in view of the
above-described current situation and has an object to provide a
lubricating oil composition for continuously variable transmissions
having a viscosity that is low enough to exhibit fuel saving
properties but maintaining the viscosity required for a lubricating
oil composition through the period of use in a system and also a
higher metal-to-metal friction coefficient to ensure a high power
transmitting capacity and providing a wet clutch friction
characteristics and anti-shudder properties required for a
transmission as well as having a low traction coefficient to
achieve further improved fuel saving properties.
Solution to Problem
[0009] As the results of extensive studies carried out to achieve
the above object, the present invention has been accomplished on
the basis of the finding that the object was able to be achieved by
a lubricating oil composition comprising a selected combination of
a specific base oil and specific additives.
[0010] That is, the present invention relates to a lubricating oil
composition for a continuously variable transmission, comprising a
base oil having been adjusted so that the product (EC.times.V40) of
the mass percent (EC (mass %)) of a saturated cyclic component on
the total base oil mass basis and the 40.degree. C. kinematic
viscosity (V40 (mm.sup.2/s)) is 500 or less and the 100.degree. C.
kinematic viscosity is from 3.6 to 4.1 mm.sup.2/s, (B) a phosphorus
compound in an amount of 0.01 to 0.03 percent by mass as
phosphorus, (C) a calcium salicylate and/or a calcium sulfonate in
an amount of 0.03 to 0.05 percent by mass as calcium, the elemental
ratio (P/Ca) of phosphorus and calcium in the lubricating oil
composition being from 0.3 to 0.7, (D) a boron-modified ashless
dispersant in an amount of 0.001 to 0.008 percent by mass as boron,
and (E) a friction modifier in an amount of 0.01 to 2 percent by
mass on the total composition mass basis, the lubricating oil
composition having a 100.degree. C. kinematic viscosity of 5.2 to
5.6 mm.sup.2/s and a viscosity index of 165 or greater.
Advantageous Effect of Invention
[0011] The continuously variable transmission lubricating oil
composition of the present invention has a viscosity that is low
enough to exhibit fuel saving properties but maintaining the
viscosity required for a lubricating oil composition through the
period of use in a system and a higher metal-to-metal friction
coefficient to ensure a high power transmitting capacity and
provides wet clutch friction characteristics and anti-shudder
properties required for a transmission as well as having a low
traction coefficient to achieve further improved fuel saving
properties.
DESCRIPTION OF EMBODIMENTS
[0012] The present invention will be described below.
[0013] The base oil used in the present invention is a base oil
having been adjusted so that the product (EC.times.V40) of the mass
percent (EC (mass %)) of a saturated cyclic component on the basis
of the total base oil mass and the 40.degree. C. kinematic
viscosity (V40 (mm.sup.2/)) is 500 or less and the 100.degree. C.
kinematic viscosity is from 3.6 to 4.1 mm.sup.2/s and may be a
mineral lubricating base oil, a synthetic lubricating base oil or a
mixture thereof.
[0014] Examples of the mineral lubricating base oil which may be
used in the present invention include paraffinic or naphthenic
mineral base oils which can be produced by subjecting a lubricating
oil fraction produced by atmospheric- or vacuum-distillation of a
crude oil, to any one of or any suitable combination of refining
processes selected from solvent deasphalting, solvent extraction,
hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining,
sulfuric acid treatment, and clay treatment; n-paraffins; and
iso-paraffins. These base oils may be used alone or in combination
at an arbitrary ratio.
[0015] Examples of preferred mineral lubricating base oils include
the following base oils:
[0016] (1) a distillate oil produced by atmospheric distillation of
a paraffin base crude oil and/or a mixed base crude oil;
[0017] (2) a whole vacuum gas oil (WVGO) produced by vacuum
distillation of the topped crude of a paraffin base crude oil
and/or a mixed base crude oil;
[0018] (3) a wax produced by a lubricating oil dewaxing process
and/or a Fischer-Tropsch wax produced by a GTL process;
[0019] (4) an oil produced by mild-hydrocracking (MHC) one or more
oils selected from oils of (1) to (3) above;
[0020] (5) a mixed oil of two or more oils selected from (1) to (4)
above;
[0021] (6) a deasphalted oil (DAO) produced by deasphalting an oil
of (1), (2) (3), (4) or (5);
[0022] (7) an oil produced by mild-hydrocracking (MHC) an oil of
(6); and
[0023] (8) a lubricating oil produced by subjecting a mixed oil of
two or more oils selected from (1) to (7) used as a feed stock
and/or a lubricating oil fraction recovered therefrom to a normal
refining process and further recovering a lubricating oil fraction
from the refined product.
[0024] No particular limitation is imposed on the normal refining
process used herein. Therefore, there may be used any refining
process having been conventionally used upon production of a
lubricating base oil. Examples of the normal refining process
include (a) hydro-refining processes such as hydrocracking and
hydrofinishing, (b) solvent refining such as furfural extraction,
(c) dewaxing such as solvent dewaxing and catalytic dewaxing, (d)
clay refining with acidic clay or active clay and (e) chemical
(acid or alkali) refining such as sulfuric acid treatment and
sodium hydroxide treatment. In the present invention, any one or
more of these refining processes may be used in any combination and
order.
[0025] The mineral lubricating base oil used in the present
invention is particularly preferably a base oil produced by further
subjecting a base oil selected from (1) to (8) described above to
the following treatments.
[0026] That is, preferred are a hydrocracked mineral oil and/or
wax-isomerized isoparaffinic base oil produced by hydrocracking or
wax-isomerizing a base oil selected from (1) to (8) described above
as it is or a lubricating fraction recovered therefrom and
subjecting the resulting product as it is or a lubricating fraction
recovered therefrom to dewaxing such as solvent dewaxing or
catalytic dewaxing, followed by solvent refining or followed by
solvent refining and then dewaxing such as solvent dewaxing or
catalytic dewaxing.
[0027] Examples of synthetic lubricating base oils which may be
used in the present invention include poly-.alpha.-olefins and
hydrogenated compounds thereof; isobutene oligomers and
hydrogenated compounds thereof; isoparaffins; alkylbenzenes;
alkylnaphthalenes; diesters such as ditridecyl glutarate,
di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate and
di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane
caprylate, trimethylolpropane pelargonate, pentaerythritol
2-ethylhexanoate and pentaerythritol pelargonate; polyoxyalkylene
glycols; dialkyldiphenyl ethers; and polyphenyl ethers.
[0028] Preferred synthetic lubricating base oils are
poly-.alpha.-olefins. Typical examples of poly-.alpha.-olefins
include oligomers or cooligomers of .alpha.-olefins having 2 to 32,
preferably 6 to 16 carbon atoms, such as 1-octene oligomer,
1-decene oligomer, ethylene-propylene cooligomer, and hydrogenated
compounds thereof.
[0029] Component (A), i.e., the lubricating base oil used in the
present invention has a 100.degree. C. kinematic viscosity of 3.6
to 4.1 mm.sup.2/s, preferably 3.8 mm.sup.2/s or higher, and 4.0
mm.sup.2/s or lower. The use of a lubricating base oil with a
100.degree. C. kinematic viscosity of 4.1 mm.sup.2/s or lower
renders it possible to produce a lubricating oil composition having
a smaller frictional resistance at lubricating sites because of its
small fluid resistance. The use of a lubricating base oil with a
100.degree. C. kinematic viscosity of 3.6 mm.sup.2/s or higher
renders it possible to produce a lubricating oil composition which
is sufficient in oil film formation and thus more excellent in
lubricity and less in evaporation loss of the base oil under
elevated temperature conditions.
[0030] One of the factors achieving the effect for improving the
fuel saving properties of the present invention is a reduction in
the traction coefficient. One major factor affecting the traction
coefficient is the saturated cyclic component of abase oil. More
the saturated cyclic component, more the traction coefficient is
likely to be high. Another major factor is the base oil
viscosity.
[0031] A lower base oil viscosity is more advantageous in fuel
saving properties, but if a base oil has a too low viscosity, it
causes various adverse effects and thus the base oil is desired to
have a viscosity within the above-described range. Therefore, since
the traction coefficient is largely influenced by the viscosity and
saturated cyclic component of the base oil, the lubricating base
oil used in the present invention has a product (EC.times.V40) of
the mass percent (EC (mass %)) of a saturated cyclic component on
the basis of the total base oil mass and the 40.degree. C.
kinematic viscosity (V40 (mm.sup.2/s)) of necessarily 500 or less,
preferably 470 or less, more preferably 450 or less, particularly
preferably 400 or less, most preferably 350 or less so as to
decrease the traction coefficient.
[0032] The saturated cyclic component is the value measured in
accordance with ASTM D2786 test method, and the unit is converted
to be percent by mass.
[0033] No particular limitation is imposed on the viscosity index
of the lubricating base oil used in the present invention, which
is, however, preferably 100 or greater, more preferably 110 or
greater, particularly preferably 130 or greater, most preferably
135 or greater and preferably 160 or less. The use of a lubricating
base oil having a viscosity index of greater than 100 renders it
possible to produce a composition exhibiting excellent viscosity
characteristics from low temperatures to high temperatures and
having a low traction coefficient. The use of a lubricating base
oil having a viscosity index of greater than 160 would deteriorate
the viscosity characteristics at low temperatures.
[0034] No particular limitation is imposed on the sulfur content of
the lubricating base oil used in the present invention, which is,
however, preferably 100 ppm by mass or less, more preferably 10 ppm
by mass or less, particularly preferably 1 ppm by mass or less.
Reduction of the sulfur content of Component (A) renders it
possible to produce a composition having a more excellent oxidation
stability.
[0035] Component (A), i.e., lubricating base oil used in the
present invention is particularly preferably (A1) a base oil
produced by hydrocracking and catalytic dewaxing a feedstock
containing 50 percent by mass or more of wax alone or a mixture of
base oil (A1) and (A2) a hydrocracked and catalytically dewaxed
base oil.
[0036] The wax content of the feedstock used to produce base oil
(A1) produced by hydrocracking and catalytic dewaxing a feedstock
containing 50 percent by mass or more of wax is preferably 60
percent by mass or more, particularly preferably 80 percent by mass
or more.
[0037] A mixture of (A1) the base oil and (A2) the base oil
contains (A1) the base oil in an amount of preferably 20 percent by
mass or more, more preferably 40 percent by mass or more,
particularly preferably 70 percent by mass or more, most preferably
90 percent by mass or more on the basis of the total base oil mass.
A mixture containing 20 percent by mass or more of (A1) the base
oil renders it possible to produce a composition having a viscosity
index of 175 or greater and exhibiting excellent fuel saving
properties because the traction coefficient can be also
reduced.
[0038] This is because when branches having the same carbon number
in the molecular structures constituting base oils are compared,
base oil (A1) is longer in methylene chain than base oil (A2) and
thus has properties that it has a higher viscosity index and reduce
the traction coefficient. The properties are superior to those of
the above-described poly-.alpha.-olefin synthetic oil.
[0039] Component (A), i.e., lubricating base oil used in the
lubricating oil composition of the present invention is a
lubricating base oil adjusted to have a 100.degree. C. kinematic
viscosity of from 3.6 to 4.1 mm.sup.2/s and is preferably one or a
mixture of two or more types selected from the (Aa) and (Ab)
below:
[0040] (Aa) a mineral base oil having a 100.degree. C. kinematic
viscosity of 1.5 to lower than 3.5 mm.sup.2/s, preferably 1.9 to
3.2 mm.sup.2/s, more preferably 2.2 to 2.9 mm.sup.2/s; and
[0041] (Ab) a mineral base oil having a 100.degree. C. kinematic
viscosity of 3.5 to lower than 7 mm.sup.2/s, preferably 3.6 to 4.5
mm.sup.2/s.
[0042] It will be understood that base oils (Aa) and (Ab) are any
of base oils (A1) or (A2).
[0043] The use of a mixture of base oils having different
viscosities can enhance the viscosity index of the resulting
composition despite of the same viscosity and thus can improve fuel
saving properties.
[0044] The lubricating oil composition of the present invention
contains a phosphorus compound as Component (B).
[0045] No particular limitation is imposed on the phosphorus
compound if it contains phosphorus per molecule, which may be, for
example, phosphoric acid monoesters, phosphoric acid diesters,
phosphoric acid triesters, phosphorus acid monoesters, phosphorus
acid diesters, phosphorus acid triesters, thiophosphoric acid
monoesters, thiophosphoric acid diesters, thiophosphoric acid
triesters, thiophosphorus acid monoesters, thiophosphorus acid
diesters, thiophosphorus acid triesters, all having a hydrocarbon
group of 1 to 30 carbon atoms, salts of these esters and amines or
alkanol amines or metal salts such as zinc salt of these
esters.
[0046] Examples of the hydrocarbon group having 1 to 30 carbon
atoms include alkyl, cycloalkyl, alkenyl, alkyl-substituted
cycloalkyl, aryl, alkyl-substituted aryl and arylalkyl groups. One
or more type of the groups may be contained in the compound. These
hydrocarbon groups may be those containing sulfur in the main
chain.
[0047] In the present invention, the phosphorus compound is
preferably a phosphorus acid ester or phosphoric acid ester, having
an alkyl group of 4 to 20 carbon atoms or an (alkyl) aryl group of
6 to 12 carbon atoms.
[0048] Alternatively, the phosphorus compound is more preferably
one or a mixture of two or more types selected from phosphorus acid
esters having an alkyl group of 4 to 20 carbon atoms and phosphorus
acid esters having an (alkyl)aryl group of 6 to 12 carbon
atoms.
[0049] Furthermore, the phosphorus compound is more preferably a
phosphorus acid ester having an (alkyl)aryl group of 6 or 7 carbon
atoms such as phenylphosphite and/or a phosphorus acid ester having
an alkyl group of 4 to 8 carbon atoms. Among these
phosphorus-containing additives, dibutylphosphite is most
preferable.
[0050] The alkyl group may be straight-chain but is more preferably
branched. This is because alkyl groups of fewer carbon atoms or
branched result in higher metal-to-metal friction coefficient.
[0051] Component (B), i.e., phosphorus compound used in the present
invention is preferably (B-1) a phosphorus compound represented by
formula (1):
##STR00001##
[0052] In formula (1), X.sup.1, X.sup.2 and X.sup.3 are each
independently oxygen or sulfur, and R.sup.20, R.sup.21 and R.sup.22
are each independently hydrogen, a hydrocarbon group having 1 to 30
carbon atoms or a hydrocarbon group having 3 to 30 carbon atoms
containing at least one sulfur.
[0053] In formula (1), preferably X.sup.1, X.sup.2 and X.sup.3 are
all oxygen. At least one of R.sup.20, R.sup.21 and R.sup.22 is
preferably hydrogen. At least one of R.sup.20, R.sup.21 and
R.sup.22 is hydrogen, one or both of the others is preferably a
straight-chain hydrocarbon group containing sulfur in the main
chain. Particularly preferably, one of R.sup.20, R.sup.21 and
R.sup.22 is hydrogen and both of the others are a straight-chain
hydrocarbon group containing sulfur in the main chain. Whereby,
anti-wear properties and metal-to-metal friction coefficient can be
enhanced.
[0054] The straight-chain hydrocarbon groups containing sulfur in
the main chain are preferably those of different carbon number.
[0055] The straight-chain hydrocarbon group containing sulfur in
the main chain is a group represented by the following formula:
(CH.sub.2).sub.n--S--C.sub.mH.sub.2m+1
[0056] In the case where one of R.sup.20, R.sup.21 and R.sup.22 is
hydrogen and both of the others are straight-chain hydrocarbon
groups containing sulfur in the main chain, the carbon number n of
the alkylene group between oxygen bonding to phosphorus and sulfur
contained in the main chain of the hydrocarbon group is preferably
4 or fewer, more preferably 2 or fewer. The carbon number m of at
least one of the alkyl groups bonding to sulfur in the main chain
of the hydrocarbon group is preferably 8 or more, more preferably
10 or more. The other is preferably 4 or fewer, more preferably 2
or fewer. The alkyl group having 4 or fewer carbon atoms is most
preferably an alkyl group whose hydrogen at a terminal is
substituted by a hydroxyl group. Whereby, anti-wear properties and
metal-to-metal friction coefficient can be further enhanced.
[0057] In the case where all of R.sup.20, R.sup.21 and R.sup.22 are
straight-chain hydrocarbon groups containing sulfur in the main
chain, the carbon number n of the alkylene group between oxygen
bonding to phosphorus and sulfur contained in the main chain of the
hydrocarbon group is preferably 4 or fewer, more preferably 2 or
fewer. The carbon number m of the alkyl groups bonding to sulfur in
the main chain of the hydrocarbon group is preferably 8 or more,
more preferably 10 or more. Whereby, anti-wear properties and
metal-to-metal friction coefficient can be further enhanced.
[0058] Component (B), i.e., phosphorus compound of the lubricating
oil composition of the present invention may be a mixture further
containing (B-2) a phosphorus compound represented by formula
(2):
##STR00002##
[0059] In formula (2), R.sup.23, R.sup.24 and R.sup.25 are each
independently hydrogen or a hydrocarbon group having 3 to 30 carbon
atoms.
[0060] When Component (B-1) and Component (B-2) are mixed, the
ratio (B-2)/(B-1) of Component (B-2) and Component (B-1) on the
phosphorus basis is preferably from 0 to 2, more preferably from 0
to 0.5. Whereby anti-wear properties and metal fatigue durability
can be further enhanced.
[0061] The lower limit content of Component (B), i.e., phosphorus
compound of the lubricating oil composition of the present
invention is 0.01 percent by mass, preferably 0.015 percent by mass
as phosphorus on the total composition mass basis while the upper
limit content is 0.03 percent by mass, preferably 0.025 percent by
mass. The content of Component (B) set to the above-described range
renders it possible to produce a lubricating oil composition having
excellent torque capacity and shifting properties and also
excellent anti-shudder properties.
[0062] The lubricating oil composition of the present invention
contains a calcium salicylate and/or a calcium sulfonate as
Component (C).
[0063] No particular limitation is imposed on the structure of the
calcium salicylate, which may be a calcium salt of salicylic acid
having one or two alkyl group having 1 to 30 carbon atoms.
[0064] In the present invention, the calcium salicylate is
preferably an alkylsalicylic acid calcium salt and/or an
(overbased) basic salt thereof, wherein the component ratio of the
monoalkylsalicylic acid calcium salt is from 85 to 100 percent by
mole, the component ratio of the dialkylsalicylic acid calcium salt
is from 0 to 15 percent by mole and the component ratio of the
3-alkylsalicylic acid calcium salt is from 40 to 100 percent by
mole with the objective of further enhancing anti-shudder
durability.
[0065] Examples of the alkyl group of the alkylsalicylic acid
calcium salt include alkyl groups having 10 to 40, preferably 10 to
19 or 20 to 30, more preferably 14 to 18 or 20 to 26, particularly
preferably 14 to 18 carbon atoms. These alkyl groups may be
straight-chain or branched and primary and secondary alkyl
groups.
[0066] The calcium salicylate may be a basic salt produced by
heating an alkali metal or a neutral salt of calcium, together with
an excess amount of a calcium salt in the presence of water or an
overbased salt produced by reacting such a neutral salt with a base
such as a hydroxide of calcium in the presence of carbonic acid
gas, boric acid or borate.
[0067] Component (C) of the lubricating oil composition of the
present invention may be a calcium sulfonate, the structure of
which no particular limitation is imposed on.
[0068] The calcium sulfonate is, for example, preferably a calcium
salt of an alkyl aromatic sulfonic acid produced by sulfonating an
alkyl aromatic compound having a molecular weight of 100 to 1500,
preferably 200 to 700.
[0069] Alternative examples of the calcium sulfonate include
neutral alkaline earth metal sulfonates produced by reacting the
above-mentioned alkyl aromatic sulfonic acid directly with an oxide
or hydroxide of calcium or produced by once converting the alkyl
aromatic sulfonic acid to an alkali metal salt such as a sodium
salt or a potassium salt and then substituting the alkali metal
salt with a calcium salt; but also basic calcium sulfonates
produced by heating such neutral calcium sulfonates and an excess
amount of an calcium salt or a calcium base in the presence of
water; and carbonate overbased calcium sulfonates and borate
overbased calcium sulfonates produced by reacting such neutral
metal sulfonates with a base of calcium in the presence of carbonic
acid gas and/or boric acid or borate.
[0070] In the present invention, the above-described neutral
calcium sulfonates, basic calcium sulfonates, overbased calcium
sulfonates and mixtures thereof may be used.
[0071] The base number of Component (C), i.e., calcium salicylate
and/or calcium sulfonate used in the present invention is optional
and usually from 0 to 500 mgKOH/g. However, it is preferred to use
a calcium salicylate or a calcium sulfonate with a base number of
100 to 450 mgKOH/g, preferably of 200 to 400 mgKOH/g because it is
excellent in an effect to enhance torque capacity. The term "base
number" used herein denotes a base number measured by the
perchloric acid potentiometric titration method in accordance with
JIS K2501.
[0072] The content of Component (C) of the lubricating oil
composition of the present invention is from 0.03 to 0.05 percent
by mass, preferably from 0.035 percent by mass or more, more
preferably 0.04 percent by mass or more and preferably 0.045
percent by mass or less as calcium on the total composition mass
basis. The content of Component (C) within these ranges renders it
possible to produce a lubricating oil composition which is
excellent in torque capacity, shifting characteristics and
anti-shudder properties.
[0073] In the lubricating oil composition of the present invention,
the ratio (P/Ca) of the phosphorus content of Component (B) and the
calcium content of Component (C) in the lubricating oil composition
is from 0.3 to 0.7, preferably from 0.4 to 0.6, particularly
preferably from 0.45 to 0.55. The content of Component (C) within
these ranges renders it possible to produce a lubricating oil
composition which is excellent in torque capacity, shifting
characteristics and anti-shudder properties.
[0074] The lubricating oil composition of the present invention
contains a boron-modified ashless dispersant as Component (D).
[0075] The ashless dispersant used in the present invention may be
any ashless dispersant that is used in lubricating oil. Examples of
the ashless dispersant include nitrogen-containing compounds having
in per molecule at least one straight-chain or branched alkyl or
alkenyl group having 40 to 400 and derivatives thereof and modified
products of alkenylsuccinicimides. Any one or more type selected
from these ashless dispersants may be blended in the lubricating
oil composition of the present invention.
[0076] The carbon number of the alkyl or alkenyl group of the
ashless dispersant is preferably 40 to 400, more preferably 60 to
350. If the carbon number of the alkyl or alkenyl group is fewer
than 40, the ashless dispersant would tend to be degraded in
solubility in the lubricating base oil. Whereas, if the carbon
number of the alkyl or alkenyl group is more than 400, the
resulting lubricating oil composition would be degraded in
low-temperature fluidity. The alkyl or alkenyl group may be
straight-chain or branched but is preferably a branched alkyl or
alkenyl group derived from oligomers of olefins such as propylene,
1-butene or isobutylene or a cooligomer of ethylene and
propylene.
[0077] Specific examples of the ashless dispersant include the
following compounds, one or more of which may be used:
[0078] (I) succinimides having in their molecules at least one
alkyl or alkenyl group having 40 to 400 carbon atoms and
derivatives thereof;
[0079] (II) benzylamines having in their molecules at least one
alkyl or alkenyl group having 40 to 400 carbon atoms and
derivatives thereof; and
[0080] (III) polyamines having in their molecules at least one
alkyl or alkenyl group having 40 to 400 carbon atoms and
derivatives thereof.
[0081] Specific examples of (I) succinimides include compounds
represented by formulas (3) and (4):
##STR00003##
[0082] In formula (3), R.sup.1 is an alkyl or alkenyl group having
40 to 400, preferably 60 to 350, and b is an integer of 1 to 5,
preferably 2 to 4
##STR00004##
[0083] In formula (4), R.sup.2 and R.sup.3 are each independently
an alkyl or alkenyl group having 40 to 400, preferably 60 to 350
carbon atoms, and particularly preferably a polybutenyl group, and
b is an integer of 0 to 4, preferably 1 to 3.
[0084] Succinimides include mono-type succinimides wherein a
succinic anhydride is added to one end of a polyamine, as
represented by formula (3) and bis-type succinimides wherein a
succinic anhydride is added to both ends of a polyamine, as
represented by formula (4). The lubricating oil composition may
contain either type of the succinimides or a mixture thereof.
[0085] No particular limitation is imposed on the method for
producing the succinimide. For example, method may be used, wherein
an alkyl or alkenyl succinimide produced by reacting a compound
having an alkyl or alkenyl group having 40 to 400 carbon atoms with
maleic anhydride at a temperature of 100 to 200.degree. C. is
reacted with a polyamine. Examples of the polyamine include
diethylene triamine, triethylene tetramine, tetraethylene
pentamine, and pentaethylene hexamine.
[0086] Specific examples of (II) benzylamines include compounds
represented by formula (5):
##STR00005##
[0087] In formula (5), R.sup.4 is an alkyl or alkenyl group having
40 to 400, preferably 60 to 350 and c is an integer of 1 to 5,
preferably 2 to 4.
[0088] No particular limitation is imposed on the method for
producing the benzylamines. They may be produced by reacting a
polyolefin such as a propylene oligomer, polybutene, or
ethylene-.alpha.-olefin copolymer with a phenol so as to produce an
alkylphenol and then subjecting the alkylphenol to Mannich reaction
with formaldehyde and a polyamine such as diethylenetriamine,
triethylenetetramine, tetraethylenepentamine, or
pentaethylenehexamine.
[0089] Specific examples of (III) polyamines include compounds
represented by formula (6):
R.sup.5--NH--(CH.sub.2CH.sub.2NH).sub.d--H (6)
[0090] In formula (6), R.sup.5 is an alkyl or alkenyl group having
40 to 400, preferably 60 to 350 and d is an integer of 1 to 5,
preferably 2 to 4.
[0091] No particular limitation is imposed on the method for
producing the polyamines. For example, the polyamines may be
produced by chlorinating a polyolefin such as a propylene oligomer,
polybutene, or ethylene-.alpha.-olefin copolymer and reacting the
chlorinated polyolefin with ammonia or a polyamine such as
ethylenediamine, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, and pentaethylenehexamine.
[0092] In the present invention, a so-called boron-modified ashless
dispersant produced by allowing the above-described ashless
dispersant to react with boric acid to neutralize the whole or part
of the remaining amino and/or imino groups is used as Component
(D). This boron-modified ashless dispersant is excellent in heat
resistance and anti-oxidation properties and thus is effective to
enhance the oxidation stability and corrosion-prevention properties
of the lubricating oil composition for a continuously variable
transmission of the present invention.
[0093] The above-described boron-modified compound is generally
produced by allowing succinimide to react with boric acid to
neutralize the whole or part of the remaining amino and/or imino
groups. Examples of a method of producing a boron-modified
succinimide are those disclosed in Japanese Patent Publication Nos.
42-8013 and 42-8014 and Japanese Laid-Open Patent Publication Nos.
51-52381 and 51-130408. More specifically, a boron-modified
succinimide may be produced by mixing polyamine and
polybutenylsuccinic acid (anhydride) with a boron compound such as
boric acid, a boric acid ester, or a borate in a solvent including
alcohols, organic solvent such as hexane or xylene, or a light
fraction lubricating base oil and by heating the mixture under
appropriate conditions.
[0094] No particular limitation is imposed on the boron content of
the boron-containing ashless dispersant such as a boron-containing
succinimide used in the present invention, which is, however,
usually from 0.1 to 3 percent by mass, preferably 0.3 percent by
mass or more, more preferably 2 percent by mass or less, more
preferably 1.7 percent by mass or less, particularly preferably 1.5
percent by mass or less. The boron-containing ashless dispersant is
preferably a boron-containing succinimide, particularly desirously
a boron-containing bis-type succinimide, with a boron content
within the above-described range. If the boron content is more than
3 percent by mass, concerns about stability are arisen.
[0095] No particular limitation is imposed on the boron/nitrogen
mass ratio (B/N ratio) of the boron-containing ashless dispersant
such as the above-described boron-containing succinimide, which is
usually from 0.05 to 5, preferably 0.2 or greater and preferably 2
or less, more preferably 1.5 or less, more preferably 1.0 or less,
particularly preferably 0.9 or less. The boron-containing ashless
dispersant is preferably a boron-containing succinimide with a B/N
ratio within this range, particularly desirously a boron-containing
bis-type succinimide. If the B/N ratio exceeds 5, concerns about
stability are arisen.
[0096] The content of Component (D), i.e., boron-modified ashless
dispersant of the lubricating oil composition of the present
invention is 0.001 percent by mass or more, preferably 0.003
percent by mass more and 0.008 percent by mass or less, preferably
0.006 percent by mass or less as boron on the basis of the total
mass of the composition.
[0097] If the boron content of the composition exceeds 0.008
percent by mass, the friction characteristics of a wet friction
clutch would be degraded. If the boron content is less than 0.001
percent by mass, the resulting composition has no effect in
enhancing the oxidation stability or corrosion prevention
properties that is one of the properties of a continuously variable
transmission lubricating oil composition.
[0098] The lubricating oil composition of the present invention
contains Component (E) as a friction modifier.
[0099] The friction modifier is preferably a fatty acid ester-based
friction modifier and/or a fatty acid amide-based friction
modifier.
[0100] The fatty acid that is a raw material of a fatty acid
ester-based compound or a fatty acid amide-based compound blended
as the friction modifier preferably has a straight-chain structure,
and the hydrocarbon group thereof may be an alkyl or alkenyl group.
The carbon number is from 10 to 30, preferably 12 or more, more
preferably 16 or more and preferably 26 or fewer, more preferably
24 or fewer. If the carbon number is fewer than 10, the friction
modifier would be less effective. If the carbon number exceeds 30,
the resulting composition would be deteriorated in low temperature
viscosity characteristics.
[0101] The alcohol that is a raw material of an fatty acid
ester-based compound blended as the friction modifier may be a
monohydric alcohol or a polyhydric alcohol but is preferably a
polyhydric alcohol. The polyhydric alcohols may be those of usually
dihydric to decahydric, preferably dihydric to hexahydric. Specific
examples of the polyhydric alcohols of dihydric to decahydric
include dihydric alcohols such as ethylene glycol, diethylene
glycol, polyethylene glycol (trimer to pentadecamer of ethylene
glycol), propylene glycol, dipropylene glycol, polypropylene glycol
(trimer to pentadecamer of propylene glycol), 1,3-propanedioil,
1,2-propanediol, 1,3-butanediol, 1,4-butanediol,
2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol,
1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol,
and neopentyl glycol; polyhydric alcohols such as glycerin,
polyglycerin (dimer to octamer thereof, such as diglycerin,
triglycerin, and tetraglycerin), trimethylolalkanes
(trimethylolethane, trimethylolpropane, trimethylolbutane) and
dimers to octamers thereof, pentaerythritol and dimers to tetramers
thereof, 1,2,4-butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetriol,
1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol-glycerin
condensate, adonitol, arabitol, xylitol, and mannitol; saccharide
such as xylose, arabinose, ribose, rhamnose, glucose, fructose,
galactose, mannose, sorbose, cellobiose, maltose, isomaltose,
trehalose, and sucrose; and mixtures thereof. Among these
polyhydric alcohols, preferable examples include those of dihydric
to hexahydric, such as ethylene glycol, diethylene glycol,
polyethylene glycol (trimer to decamer of ethylene glycol),
propylene glycol, dipropylene glycol, polypropylene glycol (trimer
to decamer of propylene glycol), 1,3-propanedioil,
2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl
glycol, glycerin, diglycerin, triglycerin, trimethylolalkanes
(trimethylolethane, trimethylolpropane, trimethylolbutane) and
dimers to tetramers thereof, pentaerythritol, dipentaerythritol,
1,2,4-butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetriol,
1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol-glycerin
condensate, adonitol, arabitol, xylitol, and mannitol, and mixtures
thereof. More preferable examples include ethylene glycol,
propylene glycol, neopentyl glycol, glycerin, trimethylolethane,
trimethylolpropane, and mixtures thereof. Among these alchils,
glycerin is particularly preferable.
[0102] The amine that is a raw material of a fatty acid amide
compound blended as a friction modifier may be ammonia, primary
amine, a secondary amine but is preferably ammonia or a primary
amine. Examples of the specific structure of the primary amine
include diamines such as monoalkylamines, monoalkanolamines,
aromatic amines, ethylenediamines and the like. Among these
compounds, particularly preferred is ammonia.
[0103] Specific examples of (E) the fatty acid ester-based friction
modifier used in the present invention include esters produced by
reacting fatty acid selected from lauric acid, myristic acid,
palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic
acid, linolenic acid, eicosanoic acid, behenic acid, and lignoceric
acid or mixtures thereof with alcohols selected from ethylene
glycol, propylene glycol, neopentyl glycol, glycerin,
trimethylolethane and trimethylolpropane or mixtures thereof. The
structure of the ester may be a full ester wherein all of the
hydroxyl groups in a polyhydric alcohol are esterified or a partial
ester wherein a part of the hydroxyl groups remains unesterified.
Particularly preferred is a partial ester of the above-described
fatty acid having 16 to 20 carbon atoms and glycerin.
[0104] Specific examples of (E) the fatty acid amide-based friction
modifier used in the present invention include amides produced by
reacting fatty acid selected from lauric acid, myristic acid,
palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic
acid, linolenic acid, eicosanoic acid, behenic acid, and lignoceric
acid or mixtures thereof with ammonia, methylamine, ethylamine,
ethanolamine, aniline, ethylenediamine or a mixture thereof. The
structure of the amide may be a primary amide, a secondary amide or
a tertiary amide but is preferably a primary amide or a secondary
amide. Particularly preferred is a primary amide of the
above-described fatty acid having 16 to 20 carbon atoms and
ammonia.
[0105] The use of a fatty acid ester-based compound and/or a fatty
acid amide-based friction modifierthe as a friction modifier in the
lubricating oil composition of the present invention can ensure
anti-shudder properties without decreasing the metal-to-metal
friction coefficient.
[0106] The content of Component (E) is from 0.01 to 2 percent by
mass, preferably from 0.05 percent by mass or more and preferably
1.0 percent by mass or less, more preferably 0.5 percent by mass or
less, more preferably 0.2 percent by mass or less on the total
composition mass basis. If the content is less than 0.01 percent by
mass, the friction modifier cannot exhibit its effect. If the
content exceeds 2 percent by mass, low temperature solubility is
concerned.
[0107] The lubricating oil composition of the present invention
contains preferably a viscosity index improver as Component
(F).
[0108] The viscosity index improver used in the lubricating oil
composition of the present invention is preferably a
poly(meth)acrylate-based additive substantially containing a
structural unit derived from a monomer represented by formula (7)
below:
##STR00006##
[0109] In formula (7), R.sup.1 is hydrogen or methyl, preferably
methyl, and R.sup.2 is a hydrocarbon group having 1 to 30 carbon
atoms.
[0110] Specific examples of the hydrocarbon group having 1 to 30
carbon atoms include alkyl groups having 1 to 30 carbon atoms, such
as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,
sec-butyl, tert-butyl, straight-chain or branched pentyl,
straight-chain or branched hexyl, straight-chain or branched
heptyl, straight-chain or branched octyl, straight-chain or
branched nonyl, straight-chain or branched decyl, straight-chain or
branched undecyl, straight-chain or branched dodecyl,
straight-chain or branched tridecyl, straight-chain or branched
tetradecyl, straight-chain or branched pentadecyl, straight-chain
or branched hexadecyl, straight-chain or branched heptadecyl,
straight-chain or branched octadecyl, straight-chain or branched
nonadecyl, straight-chain or branched eicosyl, straight-chain or
branched heneicosyl, straight-chain or branched docosyl,
straight-chain or branched tricosyl, and straight-chain or branched
tetracosyl groups.
[0111] In addition to a structural unit derived from a monomer
represented by formula (7), Component (F), i.e.,
poly(meth)acrylate-based additive used in the present invention may
contain a structural unit derived from a monomer represented by
formula (8) or (9) below.
##STR00007##
[0112] In formula (8), R.sup.3 is hydrogen or methyl, R.sup.4 is an
alkylene group having 1 to 30 carbon atoms, E.sup.1 is an amine
residue or heterocyclic residue having 1 or 2 nitrogen atoms and 0
to 2 oxygen atoms, and a is an integer of 0 or 1.
##STR00008##
[0113] In formula (9), R.sup.5 is hydrogen or methyl, and E.sup.2
is an amine residue or heterocyclic residue having 1 or 2 nitrogen
atoms and 0 to 2 oxygen atoms.
[0114] Specific examples of the groups represented by E.sup.1 and
E.sup.2 include dimethylamino, diethylamino, dipropylamino,
dibutylamino, anilino, toluidino, xylidino, acetylamino,
benzoilamino, morpholino, pyrrolyl, pyrrolino, pyridyl,
methylpyridyl, pyrolidinyl, piperidinyl, quinonyl, pyrrolidonyl,
pyrrolidono, imidazolino and pyrazino groups.
[0115] Preferred examples include dimethylaminomethyl methacrylate,
diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate,
diethylaminoethyl methacrylate, 2-methyl-5-vinyl pyridine,
morpholinomethyl methacrylate, morpholinoethyl methacrylate,
N-vinyl pyrrolidone and mixtures thereof.
[0116] Specific examples of the viscosity index improver (Component
(F)) include copolymers of monomers (Fa) to (Fd) represented by
formula (7) and polar group-containing monomers (Fe) represented by
formula (8) and/or (9) used if necessary:
[0117] (Fa) a (meth)acrylate wherein R.sup.2 is an alkyl group
having 1 to 4 carbon atoms;
[0118] (Fb) a (meth)acrylate wherein R.sup.2 is an alkyl group
having 5 to 10 carbon atoms;
[0119] (Fc) (meth)acrylates wherein R.sup.2 is an alkyl group of 12
to 18 carbon atoms;
[0120] (Fd) (meth)acrylate wherein R.sup.2 is an alkyl group of 20
or more carbon atoms; and
[0121] (Fe) polar group-containing monomers.
[0122] The structural ratio of the monomers in Component (F) used
in the present invention is preferably the following ratio on the
basis of the total amount of the monomers constituting the
poly(meth)acrylate:
[0123] Component (Fa): preferably 10 to 60 percent by mass, more
preferably 20 to 50 percent by mass;
[0124] Component (Fb): preferably 0 to 50 percent by mass, more
preferably 0 to 20 percent by mass;
[0125] Component (Fc): preferably 10 to 60 percent by mass, more
preferably 20 to 40 percent by mass;
[0126] Component (Fd): preferably 1 to 20 percent by mass, more
preferably 5 to 10 percent by mass,
[0127] Component (Fe): preferably 0 to 20 percent by mass, more
preferably 0 to 10 percent by mass, particularly preferably 0
percent by mass.
[0128] With this formulation, Component (F) can achieve both low
temperature viscosity characteristics and a fatigue life extending
effect for the resulting composition.
[0129] No particular limitation is imposed on the method for
producing the above-described poly(meth)acrylate. For example, it
can be easily produced by radical-solution polymerization of a
mixture of monomers (Fa) to (Fe) in the presence of a
polymerization initiator such as benzoyl peroxide.
[0130] The weight-average molecular weight of Component (F), i.e.,
poly(meth)acrylate-based additive is 60,000 or less, preferably
50,000 or less, more preferably 40,000 or less and 5,000 or
greater, preferably 10,000 or greater, more preferably 20,000 or
greater. If Component (F) has a weight-average molecular weight of
more than 60,000, the resulting composition would be too low in
shear stability and cannot retain the viscosity as required for the
lubricating oil composition. If Component (F) has a weight-average
molecular weight of smaller than 5,000, it would be less effective
in enhancing the viscosity index and thus would deteriorate the
fuel saving properties.
[0131] Component (F), i.e., poly(meth)acrylate-based additive used
in the lubricating oil composition of the present invention is
blended in such an amount that the 100.degree. C. kinematic
viscosity and viscosity index of the lubricating oil composition
are from 5.2 to 5.6 mm.sup.2/s and 165 or greater,
respectively.
[0132] More specifically, the blend amount is 15 percent by mass or
less, preferably 10 percent by mass or less, more preferably 6
percent by mass or less and 2 percent by mass or more, preferably 3
percent by mass or more, more preferably 4 percent by mass or more
on the basis of the total mass of the composition. If Component (F)
is blended in an amount of more than 15 percent by mass, the
viscosity reduction caused by shear would be too large. If
Component (F) is blended in an amount of less than 2 percent by
mass, a sufficient composition viscosity cannot be ensured.
[0133] The 100.degree. C. kinematic viscosity and viscosity index
of the lubricating oil composition of the present invention are
necessarily from 5.2 to 5.6 mm.sup.2/s and 165 or greater,
respectively.
[0134] If the composition has a 100.degree. C. kinematic viscosity
of lower than 5.2, it causes a deterioration in extreme pressure
properties or a decrease in fatigue life of bearings and thus
possibly degrade the reliability of the system wherein the
composition is used. If the composition has a 100.degree. C.
kinematic viscosity of higher than 5.6 mm.sup.2/s or a viscosity
index of less than 165, it would be less effective in fuel
saving.
[0135] The lubricating oil composition of the present invention has
a viscosity reduction rate of preferably 8% or less at 100.degree.
C. 20 hours after a sonic shear stability test. The sonic shear
stability test referred herein is determined by a method prescribed
in JASO M 347.
[0136] As described above, the lubricating oil composition of the
present invention is also used as a medium for a hydraulic system,
and if reduced in viscosity causes the system to have problems such
as failure to produce sufficient pressure, due to leakage of the
oil from the oil pump or control valve. Thus, the lubricating oil
to be used until the working life of a system ends needs to
maintain the viscosity as required for this purpose.
[0137] The lubricating oil composition of the present invention
needs to maintain a sufficient viscosity even if applied with
repetitive shear force. What is meant by that the lubricating oil
composition of the present invention has a viscosity reduction rate
of 8% or less at 100.degree. C. 20 hours after a sonic shear
stability test is the value to ensure that the composition has such
a viscosity.
[0138] On the hand, the viscosity reduction rate can be reduced by
blending a less amount of the viscosity index improver and on the
other hand, the composition would be less effective in fuel saving.
Therefore, the viscosity reduction rate range of the lubricating
oil composition of the present invention is preferably 2% or
greater and 8% or less, more preferably 3.5% or greater and 7% or
less.
[0139] The lubricating oil composition of the present invention has
preferably a traction coefficient of 0.02 or less at 40.degree. C.,
an average speed of 3.0 m/s, a slip ratio of 10%, and a contact
pressure of 0.4 GPa.
[0140] This traction coefficient is measured with a steel ball
disk. While a disk with a radius of 13 cm is rotated at 286.7 rpm,
a load of 20 N is applied on a ball with a radius of 1.27 cm placed
on a position 10 cm apart radially from the center of the disk to
measure the rotation torque applied to the ball at 40.degree. C.,
an average speed of 3.0 m/s, a slip ratio of 10%, and a contact
pressure of 0.4 GPa.
[0141] This condition does not reach what is called the complete
elastohydrodynamic lubrication condition and thus is still in an
intermediate region between the fluid lubrication condition and the
elastohydrodynamic lubrication condition. Conventionally, the
traction coefficient of a lubricating oil composition is measured
at a high contact pressure, specifically a contact pressure of
greater than 1 GPa, and a composition with a higher oil film
formability, i.e., traction coefficient under such a high contact
pressure condition is likely to form an oil film and has been
evaluated as having an excellent lubricity under sever
conditions.
[0142] However, the condition of measuring the traction coefficient
in the present invention is that for measuring it under an
intermediate surface pressure condition that is 0.4 GPa as
described above and thus can be regarded as a typical condition for
parts where the traction coefficient is involved with the
resistance to lubrication among the parts of a machine to be
lubricated except for ball bearings or roller bearings. Therefore,
reduction of the traction coefficient under the above-described
conditions reduces the resistance relating to the traction
coefficient under lubricating conditions in a machine. That is,
since the traction coefficient at 40.degree. C., an average speed
of 3.0 m/s, a slip ratio of 10% and a contact pressure of 0.4 GPa
is set to 0.02 or less, the composition of the present invention
can secure a fuel saving effect.
[0143] Under these conditions, the traction coefficient is 0.02 or
less and is better as it is low, but as described above, is
preferably 0.005 or greater to secure the lubricity for ball
bearings or roller bearings under a higher contact pressure
condition.
[0144] The lubricating oil composition of the present invention is
required to be high in metal-to-metal friction coefficient as a
continuously variable transmission lubricating oil composition.
This is because if the metal-to-metal friction coefficient between
the belt and pulleys of a metal belt type continuously variable
transmissions is higher, the same torque can be transmitted even
though the applied pressure is low, that is a high torque can be
transmitted with a low hydraulic pressure.
[0145] The metal-to-metal friction characteristics between the belt
and pulleys of a metal belt type continuously variable transmission
is evaluated using Falex Block-on-Ring Test Machine. Specific
conditions are as follows.
[0146] (Test Conditions)
[0147] ring: Falex S-10 Test Ring (EAE 4620Steel)
[0148] block: Falex H-60 Test Block
[0149] oil temperature: 80.degree. C.
[0150] applied load: 445N
[0151] slipping speed: 0.1 m/s
[0152] Under the foregoing conditions, the metal-to-metal friction
coefficient is preferably 0.115 or greater, more preferably 0.118
or greater, most preferably 0.12 or greater and 0.14 or less. If
the composition has a metal-to-metal friction coefficient of less
than 0.115, it cannot exhibit the fuel saving properties intended
by the present invention. If the composition has a metal-to-metal
friction coefficient of greater than 0.14, the composition is
unlikely to satisfy the anti-shudder properties. Furthermore, it
increases the friction at bearings and thus would be adversely
deteriorated in fuel saving properties.
[0153] The friction characteristics at the shifting clutch of a
metal belt type continuously variable transmission is evaluated
using SAE No. 2 test apparatus. As the friction characteristics
after a lapse of 5000 cycles in an evaluation in accordance with
JASO M348: 2002 using SD-1777X as a friction plate, the static
friction coefficient (pt) is 0.13 or greater and 0.16 or less, and
the .mu.0/.mu.d is preferably 0.9 or greater and 1.05 or less. If
the static friction coefficient is less than 0.13, slipping at the
shifting clutch would be concerned. If the static friction
coefficient exceeds 0.16, the composition is unlikely to satisfy
the anti-shudder properties. If the .mu.0/.mu.d exceeds 1.05,
generation of shock at shifting would be concerned. If the
.mu.0/.mu.d is less than 0.9, the composition is unlikely to ensure
the static friction coefficient.
[0154] The anti-shudder properties at the lock-up clutch of a metal
belt type continuously variable transmission is evaluated using a
low velocity friction apparatus (LVFA) in accordance with JASO
M349: 2010. In this evaluation, the d.mu./dv at 0.3 m/s is
preferably positive gradient. If the d.mu./dv is negative gradient,
shudder could be generated.
[0155] If necessary, the lubricating oil composition of the present
invention may be blended with various additives other than those
described above, such as viscosity index improvers, extreme
pressure additives, dispersants, metallic detergents,
anti-oxidants, corrosion inhibitors, rust inhibitors, demulsifiers,
metal deactivators, pour point depressants, seal swelling agents,
anti-foaming agents, and dyes, alone or in combination in order to
further enhance the properties of the composition or impart the
composition with properties required for a lubricating oil.
[0156] Examples of the viscosity index improvers include those
other than Component (F) that are the above-described
poly(meth)acrylates, such as non-dispersant or dispersant type
ethylene-.alpha.-olefin copolymers and hydrogenated compounds
thereof; polyisobutylene and hydrogenated compounds thereof;
styrene-diene hydrogenated copolymers; styrene-maleic anhydride
ester copolymers; polyalkylstyrenes; and copolymers of
(meth)acrylate monomers represented by formula (7) and unsaturated
monomers such as ethylene/propylene/styrene/maleic anhydride.
[0157] When the lubricating oil composition of the present
invention is blended with a viscosity index improver (excluding
Component (F)), no particular limitation is imposed on the content
thereof if the resulting composition meets the requirements
regarding the 100.degree. C. kinematic viscosity and viscosity
index. The content is usually from 0.1 to 15 percent by mass,
preferably 0.5 to 5 percent by mass on the total composition mass
basis.
[0158] Although the viscosity index of the lubricating oil
composition is 165 or greater, it is preferably 175 or greater,
more preferably 180 or greater, most preferably 190 or greater in
view of the fuel saving effect.
[0159] As the extreme pressure additive other than Component (B)
that is a phosphorus compound, the composition may be blended with
at least one type of sulfur extreme pressure additive selected from
sulfurized fats and oils, sulfurized olefins, dihydrocarbyl
polysulfides, dithiocarbamates, thiaziazoles, and
benzothiazoles.
[0160] As the dispersant other than Component (D) that is a
boron-modified ashless dispersant, the composition may be blended
with an ashless dispersant such as succinimide, benzylamine,
polyamines, each having a hydrocarbon group having 40 to 400 carbon
atoms or an acid- or sulfur-modified compound.
[0161] In the present invention, any one or more type of compound
selected from these dispersants may be contained in any amount but
usually in an amount of 0.01 to 20 percent by mass, preferably 0.1
to 10 percent by mass on the basis of the total mass of the
composition. If the content exceeds 20 percent by mass, the
resulting lubricating oil composition would be extremely degraded
in low temperature fluidity.
[0162] Examples of the metallic detergent other than Component (C)
that is calcium salicylate and/or calcium sulfonate include
metallic detergents such as alkaline earth metal sulfonates,
alkaline earth metal phenates and alkaline earth metal
salicylates.
[0163] In the present invention, any one or more type of compound
selected from these metallic detergents may be contained in any
amount but usually in an amount of 0.01 to 10 percent by mass,
preferably 0.1 to 5 percent by mass on the basis of the total mass
of the composition.
[0164] The anti-oxidant may be any anti-oxidant that has been
usually used in lubricating oil, such as phenol- or amine-based
compounds.
[0165] Specific examples of the anti-oxidant include alkylphenols
such as 2-6-di-tert-butyl-4-methylphenol; bisphenols such as
methylene-4,4-bisphenol (2,6-di-tert-butyl-4-methylphenol);
naphthylamines such as phenyl-.alpha.-naphthylamine;
dialkyldiphenylamines; zinc dialkyldithiophosphates such as zinc
di-2-ethylhexyldithiophosphate; and esters of
(3,5-di-tert-butyl-4-hydroxyphenyl) fatty acid (propionic acid)
with a monohydric or polyhydric alcohol such as methanol,
octadecanol, 1,6-hexanediol, neopentyl glycol, thiodiethylene
glycol, triethylene glycol and pentaerythritol.
[0166] Any one or more of compounds selected from these compounds
may be contained in any amount, which is, however, usually from
0.01 to 5 percent by mass, preferably 0.1 to 3 percent by mass on
the total composition mass basis.
[0167] Examples of the corrosion inhibitor include benzotriazole-,
tolyltriazole-, thiadiazole-, and imidazole-types compounds.
[0168] Examples of the rust inhibitor include petroleum sulfonates,
alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl
succinic acid esters, and polyhydric alcohol esters.
[0169] Examples of the demulsifier include polyalkylene
glycol-based non-ionic surfactants such as polyoxyethylenealkyl
ethers, polyoxyethylenealkylphenyl ethers, and
polyoxyethylenealkylnaphthyl ethers.
[0170] Examples of the metal deactivator include imidazolines,
pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles,
benzotriazoles and derivatives thereof,
1,3,4-thiadiazolepolysulfide,
1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate,
2-(alkyldithio)benzoimidazole, and
.beta.-(o-carboxybenzylthio)propionitrile.
[0171] The anti-foaming agent may be any compounds that have been
usually used as anti-foaming agents for lubricating oil. Examples
of such compounds include silicones such as dimethylsilicone and
fluorosilicone. Any one or more of compounds selected from these
compounds may be contained in any amount.
[0172] The seal swelling agent may be any compound that has been
usually used as a seal swelling agent for lubricating oils.
Examples of such a seal swelling agents include ester-, sulfur- and
aromatic-based seal swelling agents.
[0173] The dye may be any compound that has been usually used and
may be blended in any amount. The amount is usually from 0.001 to
1.0 percent by mass on the total composition mass basis.
[0174] When these additives are blended with the lubricating oil
composition of the present invention, the corrosion inhibitor, rust
inhibitor, and anti-foaming agent are each contained in an amount
of 0.005 to 5 percent by mass, the metal deactivator is contained
in an amount of 0.005 to 2 percent by mass, the seal swelling agent
is contained in an amount of 0.01 to 5 percent by mass, and the
anti-foaming agent is contained in an amount of 0.0005 to 1 percent
by mass, all on the total composition mass basis.
[0175] The lubricating oil composition of the present invention can
be used in various applications such as lubricating oils for manual
transmissions, automatic transmissions, continuously variable
transmissions, final reduction gears and engine of automobiles and
those for agricultural machines and construction machines. The
lubricating oil composition is most suitably used for continuously
variable transmissions. This is because the properties of the
present invention are most effectively utilized in a continuously
variable transmission having many parts to be subjected to shear
and high contact pressure.
EXAMPLES
[0176] Hereinafter, the present invention will be described in more
detail by way of the following examples and comparative examples,
which should not be construed as limiting the scope of the
invention.
Examples 1 to 4, Comparative Examples 1 to 3
[0177] Table 1 sets forth the results of viscosity temperature
characteristics, EC.times.V40, viscosity reduction rate by shear
test (JASO sonic method, 20 hours) and traction coefficient
measurements of lubricating oil compositions (Examples 1 to 4) of
the present invention and those for comparison (Comparative
Examples 1 to 3).
Examples 5 to 12, Comparative Examples 4 to 10
[0178] Table 2 sets forth the results of metal-to-metal friction
coefficient, shifting clutch characteristics (static friction
coefficient, .mu.0/.mu.d) and anti-shudder properties measurements
of lubricating oil compositions of the present invention (Examples
5 to 12) and those for comparison (Comparative Examples 4 to
10).
TABLE-US-00001 TABLE 1 Example Example Example Example Comparative
Comparative Comparative 1 2 3 4 Example 1 Example 2 Example 3 Base
oil total base oil mass basis Base oil 1 inmass % 95 50 25 25 70
Base oil 2 inmass % 40 60 71 85 100 Base oil 3 inmass % 5 10 15 4
15 30 Mixed base oil kinematic viscosity mm.sup.2/s 15.5 15.8 15.4
17.1 16.3 18.4 13.0 (40.degree. C.) (V40) (100.degree. C.)
mm.sup.2/s 3.8 3.8 3.7 4.0 3.8 4.2 3.3 viscosity index 141 136 130
135 128 133 129 saturated cyclic structure analysis ALKANES
(0-Rings) 80.5 73.6 68.9 72.9 66.1 71.6 68.4 1-Ring 12.5 14.6 15.9
14.9 16.8 15.5 15.6 2-Ring 5.8 8.3 9.9 8.7 10.9 9.4 9.5 3-Ring 0.7
2.7 4.0 3.0 4.8 3.4 3.9 4-Ring or more 0.4 0.9 1.4 0.4 1.4 0.1 2.6
total of saturated cyclic % 19.5 26.4 31.1 27.1 33.9 28.4 31.6
components (EC) saturated cyclic 302 417 478 462 552 523 410
component .times. kinematic viscosity (40.degree. C.) (EC .times.
V40) Additives total composition mass basis viscosity index
improver mass % 4.2 4.2 4.2 3.0 4.2 2.4 6.6 other additives mass %
10 10 10 10 10 10 10 Evaluation results kinematic viscosity
(40.degree. C.) mm.sup.2/s 22.2 22.7 23.0 23.5 24.2 24.7 21.7
kinematic viscosity (100.degree. C.) mm.sup.2/s 5.4 5.4 5.4 5.4 5.4
5.4 5.4 viscosity index 194 187 183 177 168 162 202 Shear test
(JASO sonic method, 20 h) kinematic viscosity after shear
(100.degree. C.) mm.sup.2/s 5.1 5.1 5.1 5.2 5.1 5.2 4.9 viscosity
reduction rate % 6 6 6 4 6 3 10 traction coefficient 0.011 0.015
0.017 0.017 0.024 0.021 0.014 Base oil 1: wax-hydroisomerized base
oil (100.degree. C. kinematic viscosity: 3.9 mm.sup.2/s, total of
saturated cyclic components: 17.1 mass %) Base oil 2: hydrorefined
base oil (100.degree. C. kinematic viscosity: 4.2 mm.sup.2/s, total
of saturated cyclic components: 28.4 mass %) Base oil 3:
hydrorefined base oil (100.degree. C. kinematic viscosity: 2.5
mm.sup.2/s, total of saturated cyclic components: 65.3 mass %)
viscosity index improver: non-dispersant type polymethacrylate (Mw
30,000, main side chain hydrocarbon group is C16 to C22) other
additives: phosphorus acid ester-based antiwear agent (phosphorus
amount (composition basis): 200 ppm by mass), overbased Ca
salicylate (Ca amount (composition basis): 400 ppm by mass),
non-boronated succinimide (bis-type, amount (composition basis):
2.5 mass %) boronated succinimide (bis-type, amount (composition
basis): 1.5 mass %, B amount (composition basis): 50 ppm by mass),
anti-oxidant (amine-based, phenol-based) friction modifier (fatty
acid ester compound (partial ester produced from glycerin and fatty
acid having 16 to 20 carbon atoms), amount (composition basis): 0.1
mass %), oil seal swelling agents, silicone-based anti-foaming
agents and the like are contained
TABLE-US-00002 TABLE 2 Example Example Example Example Example
Example 5 6 7 8 9 10 Base oil total base oil mass basis Base oil 1
inmass % 50 50 50 50 50 50 Base oil 2 inmass % 40 40 40 40 40 40
Base oil 3 inmass % 10 10 10 10 10 10 Additives total composition
mass basis B-1 (B) phosphorus-containing P amount massppm 200 200
200 250 200 200 additive C-1 (C) Ca detergent 1 Ca amount massppm
400 200 400 300 450 C-2 (C) Ca detergent 2 Ca amount massppm 200
400 D-1 (D) non-boronated mass % 2.5 2.5 2.5 2.5 2.5 2.5
succinimide D-2 (E) boronated succinimide mass % 1.5 1.5 1.5 1.5
1.5 1.5 E-1 Friction modifier 1 mass % 0.1 0.1 0.1 0.1 0.1 0.1 E-2
Friction modifier 2 mass % Y-1 other additives mass % 9 9 9 9 9 9 P
amount/Ca amount elemental ratio 0.50 0.50 0.50 0.63 0.67 0.44 B
amount massppm 50 50 50 50 50 50 Evaluation results metal-to-metal
friction coefficient (LFW-1) 0.120 0.120 0.121 0.118 0.118 0.119
shifting clutch characteristics (SAE No. 2 test) static friction
coefficient (.mu.t) 0.135 0.135 0.136 0.139 0.143 0.132 .mu.0/.mu.d
1.00 1.00 1.00 1.02 1.03 0.99 anti-shudder properties (LVFA)
d.mu./dv (0.3 m/s) positive positive positive positive positive
positive gradient gradient gradient gradient gradient gradient
Example Example Comparative Comparative Comparative 11 12 Example 4
Example 5 Example 6 Base oil total base oil mass basis Base oil 1
inmass % 50 50 50 50 50 Base oil 2 inmass % 40 40 40 40 40 Base oil
3 inmass % 10 10 10 10 10 Additives total composition mass basis
B-1 (B) phosphorus-containing P amount massppm 150 200 300 100 400
additive C-1 (C) Ca detergent 1 Ca amount massppm 400 400 300 400
400 C-2 (C) Ca detergent 2 Ca amount massppm D-1 (D) non-boronated
mass % 2.5 2.5 2.5 2.5 2.5 succinimide D-2 (E) boronated
succinimide mass % 1.5 1.5 1.5 1.5 1.5 E-1 Friction modifier 1 mass
% 0.1 0.1 0.1 0.1 E-2 Friction modifier 2 mass % 0.1 Y-1 other
additives mass % 9 9 9 9 9 P amount/Ca amount elemental ratio 0.38
0.50 1.00 0.25 1.00 B amount massppm 50 50 50 50 50 Evaluation
results metal-to-metal friction coefficient (LFW-1) 0.121 0.120
0.118 0.123 0.112 shifting clutch characteristics (SAE No. 2 test)
static friction coefficient (.mu.t) 0.132 0.134 0.146 0.125 0.149
.mu.0/.mu.d 1.00 0.99 1.08 0.97 1.07 anti-shudder properties (LVFA)
d.mu./dv (0.3 m/s) positive positive positive positive positive
gradient gradient gradient gradient gradient Comparative
Comparative Comparative Comparative Example 7 Example 8 Example 9
Example 10 Base oil total base oil mass basis Base oil 1 inmass %
50 50 50 50 Base oil 2 inmass % 40 40 40 40 Base oil 3 inmass % 10
10 10 10 Additives total composition mass basis B-1 (B)
phosphorus-containing P amount massppm 200 200 200 200 additive C-1
(C) Ca detergent 1 Ca amount massppm 200 600 400 400 C-2 (C) Ca
detergent 2 Ca amount massppm D-1 (D) non-boronated mass % 2.5 2.5
0.4 2.5 succinimide D-2 (E) boronated succinimide mass % 1.5 1.5
3.6 1.5 E-1 Friction modifier 1 mass % 0.1 0.1 0.1 E-2 Friction
modifier 2 mass % Y-1 other additives mass % 9 9 9 9 P amount/Ca
amount elemental ratio 1.00 0.33 0.50 0.50 B amount massppm 50 50
120 50 Evaluation results metal-to-metal friction coefficient
(LFW-1) 0.121 0.117 0.120 0.123 shifting clutch characteristics
(SAE No. 2 test) static friction coefficient (.mu.t) 0.147 0.120
0.136 0.136 .mu.0/.mu.d 1.08 0.95 1.06 1.00 anti-shudder properties
(LVFA) d.mu./dv (0.3 m/s) positive positive positive negative
gradient gradient gradient gradient Base oil 1: wax-hydrogenated
isomerized base oil (100.degree. C. kinematic viscosity: 3.9
mm.sup.2/s, total of saturated cyclic components: 17.1 mass %) Base
oil 2: hydrorefined base oil (100.degree. C. kinematic viscosity:
4.2 mm.sup.2/s, total of saturated cyclic components: 28.4 mass %)
Base oil 3: hydrorefined base oil (100.degree. C. kinematic
viscosity: 2.5 mm.sup.2/s, total of saturated cyclic component:
65.3 mass %) phosphorus-containing additive: phosphorus acid ester
Ca detergent 1: overbased Ca salicylate (TEN 300) Ca detergent 2:
overbased Ca sulfonate (TEN 300) Friction modifier.1: (fatty acid
ester compound (partial ester produced from glycerin and fatty acid
having 16 to 20 carbon atoms) Friction modifier 2: fatty acid amide
compound (primary amide produced from ammonia and fatty acid having
16 to 20 carbon atoms) other additives non-dispersant type
polymethacrylate (Mw 30,000), anti-oxidant (amine-based,
phenol-based), oil seal swelling agent, silicone-based anti-foaming
agent and the like are contained
[0179] As set forth in Tables 1 and 2, the lubricating oil
compositions of the present invention retain a high metal-to-metal
friction coefficient, is excellent in shifting clutch
characteristics and anti-shudder properties and can achieve a
further improvement in fuel saving properties due to the low
traction coefficient.
INDUSTRIAL APPLICABILITY
[0180] The lubricating oil composition of the present invention is
excellent in fuel saving properties and suitably used for not only
continuously variable transmissions but also for manual
transmissions, automatic transmissions and final reduction
gears.
* * * * *