US20100216676A1

US20100216676A1 - Lubricating oil composition

Info

Publication number: US20100216676A1
Application number: US12/680,906
Authority: US
Inventors: Toshihiko Ichihashi; Mitsugu Kudo; Toshiki Ikeda
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 2007-11-16
Filing date: 2008-10-29
Publication date: 2010-08-26
Also published as: JP5280668B2; CN101861378A; WO2009063752A1; JP2009120760A

Abstract

A lubricating oil composition includes: a lubricating base oil; and an imide compound, an amide compound and an aliphatic amine compound mixed with the lubricating base oil. A content of the imide compound is 300 to 1000 ppm by mass of the total amount of the composition in terms of nitrogen. A content of the amide compound is 380 to 1300 ppm by mass of the total amount of the composition in terms of nitrogen. A content of the aliphatic amine compound is 35 to 360 ppm by mass of the total amount of the composition in terms of nitrogen.

Description

TECHNICAL FIELD

The present invention relates to a lubricant oil composition used for an automatic transmission such as a multistage transmission and a continuously variable transmission.

BACKGROUND ART

A lubricating oil composition used for an automatic transmission such as a multistage transmission and a continuously variable transmission is required to have a high power (torque) transmission volume. Accordingly, various lubricating oil compositions for an automatic transmission that can favorably transmit power with a large power transmission volume have been known (see, for instance, Patent Documents 1 and 2).
A lubricating oil composition disclosed in Patent Document 1 is a mixture of a sulfur extreme pressure agent, a phosphorous extreme pressure agent and an alkali earth metal detergent with a lubricating base oil so that the lubricating oil composition exhibits an excellent wear resistance and extreme-pressure property, maintains a high friction coefficient for a long period and transmits a large volume of torque.
A lubricating oil composition disclosed in Patent Document 2 is a mixture of an effective amount of bisimide succinate having a predetermined structure with a lubricating base oil for enhancing a power transmission volume and improving anti-shudder property.
Patent Document 1: JP-A-9-100487
Patent Document 2: JP-A-9-202890

DISCLOSURE OF THE INVENTION

Problems to Be Solved by the Invention

In addition to a high coefficient of static friction (μs) as an index of transmission torque at engagement of the clutch, it is also required as a clutch friction property for an automatic transmission that a “ratio (μo/μd) of a friction coefficient to a coefficient of kinetic friction just before stopping,” which is an index allowing for smooth transmission by preventing transmission shock (shudder), is sufficiently small, e.g., 1.05 or less. On the other hand, new automobiles in the market, which have a variety of types by domestic and foreign manufacturers, have a variety of materials and mechanisms for a clutch used therein. The clutch further exhibits a variety of degree of aging deterioration.
However, the lubricating oil compositions disclosed in Patent Documents 1 and 2 have not provided a sufficient clutch friction property yet.
An object of the present invention is to provide a lubricating oil composition balancing both of a high transmission torque at engagement of the clutch and a high transmission-shock prevention in an automatic transmission such as a multistage transmission and a continuously variable transmission.

Means for Solving the Problems

In order to solve the above-mentioned problems, according to an aspect of the invention, there is provided a lubricating oil composition described below.
[1] A lubricating oil composition including: a lubricating base oil; and an imide compound, an amide compound and an aliphatic amine compound mixed with the lubricating base oil, in which a content of the imide compound is 300 to 1000 ppm by mass of a total amount of the composition in terms of nitrogen; a content of the amide compound is 380 to 1300 ppm by mass of the total amount of the composition in terms of nitrogen; and a content of the aliphatic amine compound is 35 to 360 ppm by mass of the total amount of the composition in terms of nitrogen.
[2] The lubricating oil composition according to the above aspect of the invention, in which the contents of the imide compound, the amide compound and the aliphatic amine compound amount to 1000 to 2000 ppm by mass of the total amount of the composition in terms of nitrogen.
[3] The lubricating oil composition according to the above aspect of the invention, in which the imide compound is a succinimide compound.
[4] The lubricating oil composition according to the above aspect of the invention, in which the lubricating oil composition is used for a multistage transmission or a continuously variable transmission.
[5] The lubricating oil composition according to the above aspect of the invention, in which the continuously variable transmission is a belt-type continuously variable transmission equipped with a metallic belt.
According to the lubricating oil composition of the aspect of the invention, since the predetermined amounts of three specified organic nitrogen compounds (the imide compound, the amide compound and the aliphatic amine compound) are mixed with the base oil, the coefficient of static friction (μs) is high, resulting in a high transmission torque. Further, when used for an automatic transmission such as a multistage transmission and a continuously variable transmission, the lubricating oil composition of the aspect of the invention exhibits an excellent anti-shock transmission property (anti-shudder property) without decreasing transmission torque. Particularly, the lubricating oil composition of the aspect of the invention is preferably used for a belt-type continuously variable transmission equipped with a metallic belt.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred exemplary embodiment for implementing the invention will be described below.

[Arrangement of Lubricating Oil Composition]

A lubricating oil composition of an aspect of the invention is provided by mixing at least an imide compound, amide compound and aliphatic amine compound with a lubricating base oil. The invention will be described below in detail.

(Lubricating Base Oil)

As the lubricating base oil, at least one of a mineral oil and a synthetic oil may be used alone or in a combination of two types or more, or a combination of the mineral oil and the synthetic oil may be used.
Such mineral oil and synthetic oil are not particularly limited, but any mineral oil and synthetic oil are applicable as long as they are generally usable as a base oil for a transmission. Particularly, the lubricating base oil preferably has a kinematic viscosity of 1 mm²/s to 50 mm²/s, more preferably 2 mm²/s to 15 mm²/s at 100 degrees C. When the kinematic viscosity is too high, a low temperature viscosity may be deteriorated. When the kinematic viscosity is too low, wear at a sliding portion such as a gear bearing and a clutch in the continuously variable transmission may be increased. Accordingly, the lubricating base oil preferably has the kinematic viscosity of 1 mm²/s to 50 mm²/s, more preferably 2 mm²/s to 15 mm²/s at 100 degrees C.
A pour point, which is an index of a low temperature fluidity of the lubricating base oil, is not limited, but is preferably minus 10 degrees C. or lower, particularly minus 15 degrees C. or lower.
The lubricating base oil is not particularly limited, but preferably has a saturated hydrocarbon component of 90 mass % or more, a sulfur component of 0.03 mass % or less and a viscosity index of 100 or more. When the saturated hydrocarbon component is less than 90 mass %, degraded products may be increased. Moreover, when the sulfur component is more than 0.03 mass %, degraded products may be increased. Further, when the viscosity index is less than 100, wear at a high temperature may be increased. Consequently, the mineral oil and synthetic oil having the saturated hydrocarbon component of 90 mass % or more, the sulfur component of 0.03 mass % or less and the viscosity index of 100 or more may be preferably used.
Examples of the mineral oil include a paraffinic mineral oil, an intermediate base mineral oil and a naphthenic mineral oil. Specifically, the mineral oil is exemplified by a light neutral oil, a medium neutral oil, a heavy neutral oil, bright stock and the like that are produced by solvent purification or hydrogenation purification.
Examples of the synthetic oil include poly-α-olefins, α-olefin copolymers, polybutene, alkyl benzene, polyol esters, diacid esters, polyoxyalkylene glycol, polyoxyalkylene glycol esters, polyoxyalkylene glycol ethers, hindered esters, silicone oil and the like. Polyolefins and polyol esters are particularly preferable.

(Imide Compound)

As the imide compound mixed in the lubricating oil composition of the aspect of the invention, a succinimide is preferable in terms of an increase in μ ratio and consequent excellent anti-shudder property. Particularly, the succinimide preferably has an alkyl group or an alkenyl group of a number average molecular weight of 500 to 3000 in a side chain. Various succinimides can be listed as the above succimide, examples of which include a succinimide having a polybutenyl group and a succinimide having a polyisobutenyl group. The polybutenyl group means polymerized mixture of 1-butene and isobutene, polymerized highly-pure isobutene or a hydrogenerated polyisobutenyl group. The succinimide may be so-called mono-type alkenylsuccinimide or alkylsuccinimide, or so-called bis-type alkenylsuccinimide or alkylsuccinimide.
Succinimides having a side chain may be manufactured by any conventional methods. In order to manufacture polybutenyl succinimide, for instance, polybutene or chlorinated polybutene having a number average molecular weight of approximately 500 to 3,000 is reacted with maleic anhydride at approximately 100 to 200 degrees C. to form polybutenyl succinic acid, and the obtained polybutenyl succinic acid is reacted with polyamine.
Examples of polyamine are diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine and the like.
The alkyl or alkenyl-succinimide may be an alkylphenol derivative or a sulfurized alkylphenol derivative in which the alkyl or alkenyl-succinimide is fused with an aromatic compound such as alkylphenol or sulfurized alkylphenol by Mannich condensation. The alkyl group of the alkylphenol typically has 3 to 30 carbon atoms.
The succinimide, which has in the side chain an alkyl or alkenyl group having a number average molecular weight of 500 to 3,000, unfavorably exhibits deteriorated dispersibility into the base oil when the number average molecular weight of the side chain is less than 500. On the other hand, when the number average molecular weight of the side chain is more than 3000, the handleability in preparing the lubricating oil composition is deteriorated. Moreover, when the composition having an excessively increased viscosity is applied to, for instance, a wet clutch, a friction property of the composition may be deteriorated.
The above succinimide is also preferably boron-modified in use. For instance, in order to manufacture boronated polybutenyl succinimide, an organic solvent such as alcohols, hexane or xylene is added with polyamine, polybutenyl succinic acid (anhydride) and a boron compound such as boracic acid, and is subsequently heated under suitable conditions. Besides boracic acid, examples of the boron compound include boric anhydride, boron halogenide, borate ester, amide borate, boric oxide and the like. Among the above, boracic acid is particularly preferable.
The boron-modified succinimide can increase a coefficient of kinetic friction because of its bulky structure when mixed in the composition, thereby preferably providing increased transmission torque.
When the boron-modified succinimide is mixed in the composition, a boron content is preferably 50 to 3,000 ppm by mass of a total amount of the composition, more preferably 50 to 2,500 ppm by mass. When the boron content is 50 ppm by mass or more, heat resistance of the prepared lubricating oil composition is enhanced. When the boron content is 3,000 ppm by mass or less, it is preferable that hydrolysis of boron portions can be restrained and manufacturing cost can also be reduced.
A nitrogen content derived from the imide compound mixed in the lubricating oil composition of the aspect of the invention is necessarily 300 to 1000 ppm by mass of the total amount of the composition, preferably 400 to 800 ppm by mass._nWhen the nitrogen content derived from the imide compound is less than 300 ppm by mass, the prepared lubricating oil composition provides insufficient transmission torque. When the nitrogen content derived from the imide compound is more than 1000 ppm by mass, the prepared lubricating oil composition exhibits large transmission shock. Moreover, when the mineral oil is used as the base oil, solubility of the composition is deteriorated.

(Amide Compound)

An amide compound mixed in the lubricating oil composition of the aspect of the invention is exemplified by fatty acid amide obtained by fusing a fatty acid to an amine (including ammonia).
The fatty acid is preferably a saturated/unsaturated or linear/branched fatty acid having 8 to 30 carbon atoms. In addition, the fatty acid may be a monobasic acid or polybasic acid. Specifically, examples of the fatty acid include caprylic acid, pelargonic acid, capric acid, lauric acid (lauryl acid), isolauric acid, myristic acid, isomyristic acid, pentadecyl acid, palmitic acid, palmitoyl acid, margaric acid, stearic acid, isostearic acid, oleic acid, vaccenic acid, linoleic acid, malonic acid, succinic acid, sebacic acid and the like.
Examples of the amine include: ammonia; alkyl amines (an alkyl group may be linear or branched) such as monomethylamine, monoethylamine, monopropylamine, monobutylamine, monopentylamine, monohexylamine, monoheptylamine, monooctylamine, dimethylamine, methylethylamine, diethylamine, methylpropylamine, ethylpropylamine, dipropylamine, methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine and dioctylamine; alkanol amines (an alkanol group may be linear or branched) such as monomethanolamine, monoethanolamine, monopropanolamine, monobutanolamine, monopentanolamine, monohexanolamine, monoheptanolamine, monooctanolamine, monononanolamine, dimethanolamine, methanolethanolamine, diethanolamine, methanolpropanolamine, ethanolpropanolamine, dipropanolamine, methanolbutanolamine, ethanolbutanolamine, propanolbutanolamine, dibutanolamine, dipentanolamine, dihexanolamine, diheptanolamine and diooctanolamine; and a mixture thereof.
Further, besides the above monoamines, a so-called polyamine having a plurality of amino groups in a molecule is suitable as the amine. Examples of the polyamine include diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine and the like.
Suitable examples of the amide compound obtained by fusing the fatty acid to the amine as described above include: a polyamide obtained by fusing isostearic acid to polyamines such as triamine, tetraamine and pentamine; a polyamide obtained by fusing oleic acid to a polyamine; and a polyamide obtained by fusing lauric acid to a polyamine.
A nitrogen content derived from the amide compound mixed in the lubricating oil composition of the aspect of the invention is necessarily 380 to 1300 ppm by mass of the total amount of the composition, preferably 500 to 1000 ppm by mass. When the nitrogen content derived from the amide compound is less than 380 ppm by mass, the prepared lubricating oil composition exhibits insufficient anti-shock transmission property. When the nitrogen content derived from the amide compound is more than 1300 ppm by mass, the prepared lubricating oil composition is deficient in transmission torque.

(Aliphatic Amine Compound)

Among aliphatic amine compounds used for producing the above amide compounds, an aliphatic amine compound mixed in the lubricating oil composition of the aspect of the invention preferably has a relatively high molecular weight. Specifically, examples of the aliphatic amine compound include oleylamine, stearylamine and isostearylamine.
Moreover, the aliphatic amine compound may not be used singularly, but preferably used in a form such as a mixed fatty acid amine and beef tallow propylenediamine.
A nitrogen content derived from the aliphatic amine compound mixed in the lubricating oil composition of the aspect of the invention is necessarily 35 to 360 ppm by mass of the total amount of the composition, preferably 100 to 300 ppm by mass. When the nitrogen content derived from the aliphatic amine compound is less than 35 ppm by mass, the prepared lubricating oil composition exhibits insufficient initial anti-shock transmission property. When the nitrogen content derived from the aliphatic amine compound is more than 360 ppm by mass, the prepared lubricating oil composition is deficient in transmission torque and exhibits unfavorable durability due to sludge generation.
In the lubricating oil composition of the aspect of the invention, the contents of the imide compound, amide compound and aliphatic amine compound described above preferably amount to 1000 to 2000 ppm by mass of the total amount of the composition in terms of nitrogen, more preferably 1100 to 1900 ppm by mass.
In other words, when the contents of the three components are within the above-described range, transmission torque and anti-shock transmission property, which are wet clutch performance generally in a trade-off relation, can be more fully satisfied

(Other Additives)

The lubricating oil composition of the aspect of the invention may be added with an additive as long as an object of the invention to reliably provide less transmission shock and high transmission torque is achieved.
Examples of the additive include an antioxidant, a metal deactivator, an antifoaming agent, a viscosity index improver, a pour point depressant, a surfactant, a coloring agent and the like.
Examples of the antioxidant include an amine antioxidant, a phenolic antioxidant, a sulfuric antioxidant and the like.
Examples of the amine antioxidant include: monoalkyldiphenylamines such as monooctyldiphenylamine and monononyldiphenylamine; dialkyldiphenylamines such as 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine, 4,4′-dihexyldiphenylamine, 4,4′-diheptyldiphenylamine, 4,4′-dioctyldiphenylamine and 4,4′-dinonyldiphenylamine; polyalkyldiphenylamines such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine and tetranonyldiphenylamine; and naphthylamines such as α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine and nonylphenyl-α-naphthylamine. Particularly, the amine antioxidant preferably has an alkyl group of 4 to 24 carbon atoms, more preferably 6 to 18 carbon atoms. One of the above amine antioxidants may be used alone or a combination of two or more thereof may be used.
Examples of the phenolic antioxidant include 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4,4′-methylene-bis(2,6-di-t-butylphenol), 4,4′-butylidene-bis(3-methyl-6-t-butylphenol), 2,2′-methylene-bis(4-ethyl-6-t-butylphenol), 2,2′-methylene-bis(4-methyl-6-t-butylphenol), 4,4′-isopropylidene-bisphenol, 2,4-dimethyl-6-t-butylphenol, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzil)benzene, 2,6-di-t-butyl-4-ethylphenol and the like.
Examples of the sulfuric antioxidant include, dialkylthiodipropionate, a derivative of dialkyldithio-carbamic acid (except a metal salt), bis(3,5-di-t-butyl-4-hydroxybenzil)sulfide, mercaptobenzothiazole, a reactant of phosphorus pentasulfide and olefin, dicetyl sulfide and the like.
One of the above various antioxidants may be used alone or a combination of two or more thereof may be used. Particularly, the amine antioxidant, phenolic antioxidant or zinc alkyldithiophosphate are preferably used. A content of such an antioxidant is preferably in a range from 0.05 to 3 mass % of the total amount of the composition.
The metal deactivator is exemplified by benzotriazole and thiadiazole, which may be used alone or in a combination of two or more. A content of such a metal deactivator is preferably in a range from 0.01 to 5 mass % of the total amount of the composition.
Examples of the antifoaming agent include a silicone compound and an ester compound, which may be used alone or in a combination of two or more. A content of such an antifoaming agent is preferably in a range from 0.05 to 5 mass % of the total amount of the composition.
Examples of the viscosity index improver include polymethacrylate, an olefin copolymer such as an ethylene-propylene copolymer, a dispersed olefin copolymer, a styrene copolymer such as a hydrogenated styrene-diene copolymer, which may be used alone or in a combination of two or more thereof. A content of such a viscosity index improver is preferably in a range from 0.01 to 10 mass % of the total amount of the composition.
The pour point depressant may be exemplified by polymethacrylate. A content of such a pour point depressant is preferably in a range from 0.01 to 10 mass % of the total amount of the composition.
The surfactant may be exemplified by polyoxyethylene alkylphenyl ether. A content of such a surfactant is preferably in a range from 0.01 to 10 mass % of the total amount of the composition.
The lubricating oil composition of the above aspect of the invention can be used for various automatic transmissions such as a multistage transmission, a chain type continuously variable transmission equipped with a chain, a belt-type continuously variable transmission equipped with a metallic belt or a traction-drive type continuously variable transmission equipped with a traction-drive.

EXAMPLES

The invention will be described in more detail below with reference to examples and comparatives.
The invention should not be construed as limited to what is described in the examples and the like.

Examples 1 to 9 and Comparatives 1 to 6

Lubricating oil compositions as shown in Tables 1 and 2 were prepared. The prepared lubricating oil compositions were evaluated on coefficient of kinetic friction (μd) and coefficient of static friction (μo) when being dynamic and coefficient of static friction (μs) when being static with use of SAE No. 2 friction testing machine under the following experimental conditions (based on JASOM348-2002). Specifically, the evaluation was carried out with a cellulose clutch material used for a practical transmission under the conditions of surface pressure being 0.2 to 0.3 N/mm², oil temperature being 100 degrees C., dynamic rotation speed being 3000 rpm and static rotation speed being 0.7 rpm.
Under the above experimental conditions, μd and μs at 3000 cycles were measured and μ ratio (μo/μd) was obtained. When μs is more than 0.1, transmission torque is practically high enough. When μ ratio is 1 or less, anti-shock transmission property is excellent.
The results are shown in Table 1 and Table 2. Components used are respectively shown below.
(1) Lubricating base oil: Paraffinic base oil having a pour point of minus 30 degrees C., a kinematic viscosity at 100 degrees C. of 3.5 mm²/s and % C_Abeing 0.1 mass % or less

(2) Additive:

(2-1) Component A: Imide Compound

- A1: Polybutenyl succinimide
- (polybutenyl group: 950 molecular weight (Mw); Nitrogen content in the compound: 1.5 mass %)
- A2: Boron-containing polybutenyl succinimide
- (polybutenyl group: 2200 molecular weight (Mw); Nitrogen content in the compound: 0.5 mass %)
- A3: Polybutenyl succinimide
- (polybutenyl group: 280 molecular weight (Mw); Nitrogen content in the compound: 5 mass %)

(2-2) Component B: Amide Compound

- B1: Polyamide obtained by fusing isostearic acid to tetraethylenepentamine (Nitrogen content in the compound: 5 mass %)
- B2: Polyamide obtained by fusing oleic acid to diethylenepentamine (Nitrogen content in the compound: 3 mass %)
- B3: Polyamide obtained by fusing lauric acid to hexaethylenepentamine (Nitrogen content in the compound: 8 mass %)

(2-3) Component C: Aliphatic Amine Compound

- C1: Oleylamine (Nitrogen content in the compound: 5 mass %)
- C2: Mixed fatty acid amine (Nitrogen content in the compound: 3 mass %)
- C3: Beef tallow propylenediamine (Nitrogen content in the compound: 8 mass %)

(2-4) Component D: Antioxidant

- D1: Alkyldiphenylamine (Nitrogen content in the compound: 4.8 mass %)

TABLE 1

		Example 1	Example 2	Example 3	Example 4	Example 5

Lubricating oil	Lubricating base oil	remainder	remainder	remainder	remainder	remainder

composition	Additive	Component	A1	540	—	—	540	540
	(ppm by	A (Imide)	A2	—	300	—	—	—
	mass)		A3	—	—	950	—	—
		Component B	B1	650	650	650	—	—
		(Amide)	B2	—	—	—	380	—
			B3	—	—	—	—	1300
		Component C	C1	170	170	170	170	—
		(Aliphatic	C2	—	—	—	—	35
		amine)	C3	—	—	—	—	—

A + B + C (Total)	1360	1120	1770	1090	1875
Component D	140	—	—	—	—
(antioxidant)

Evaluation result	SAENo2	μs	0.122	0.105	0.135	0.115	0.110
		μ0/μd	0.94	0.88	0.99	0.94	0.96

		Example 6	Example 7	Example 8	Example 9

Lubricating oil	Lubricating base oil	remainder	remainder	remainder	remainder

composition	Additive	Component	A1	540	—	540	—
	(ppm by	A (Imide)	A2	—	—	—	—
	mass)		A3	—	950	—	950
		Component B	B1	650	—	—	650
		(Amide)	B2	—	380	350	—
			B3	—	—	—	—
		Component C	C1	—	—	170	170
		(Aliphatic	C2	35	—	—	—
		amine)	C3	—	360	—	—

A + B + C (Total)	1225	1690	1060	1770
Component D	—	—	—	140
(antioxidant)

Evaluation result	SAENo2	μs	0.120	0.103	0.101	0.150
		μ0/μd	0.96	0.90	0.88	0.99

TABLE 2

Compar-	Compar-	Compar-	Compar-	Compar-	Compar-
ative 1	ative 2	ative 3	ative 4	ative 5	ative 6

Lubricating oil

Lubricating base oil

remainder

composition	Additive	Component	A1	—	280	540	—	—	—
	(ppm by	A (Imide)	A2	180	—	—	—	200	—
	mass)		A3	—	—	—	1500	—	1050
		Component	B1	—	—	650	—	—	—
		B (Amide)	B2	—	280	—	380	—	380
			B3	1300	—	—	—	1600	—
		Component	C1	—	—	—	170	—	—
		C (Aliphatic	C2	—	—	—	—	35	—
		amine)	C3	360	360	—	—	—	450

A + B + C (Total)	1840	920	1190	2050	1835	1880
Component D	—	—	—	—	—	—
(antioxidant)

Evaluation	SAENo2	μs	0.05	0.08	0.09	0.15	0.09	0.08
result		μ0/μd	0.82	0.85	1.03	1.30	0.92	0.88

[Evaluation Results]

As is understood from Examples 1 to 9 of Table 1, in each of the lubricating oil compositions of the aspect of the invention, μs is 0.1 or more (i.e., transmission torque is large) and μ ratio (μo/μd) is small at 1 or less (i.e., anti-shock transmission property is excellent).
On the other hand, as is understood from Table 2, in Comparative 1, is extremely small since the content of the imide compound is low although the contents of the amide compounds and the aliphatic amine compounds are sufficient. Consequently, transmission torque becomes quite deficient. In Comparative 2, μs is not sufficient since the imide compound and the amide compound each are less contained although the content of the aliphatic amine compound is sufficient. Consequently, transmission torque becomes deficient. In Comparative 3, the aliphatic amine compound is not contained, so that μ ratio is large and anti-shock transmission property is poor. In Comparative 4, since the imide compound is excessively contained, μ ratio is large and anti-shock transmission property is considerably poor although μs is large. In Comparative 5, the content of the imide compound is excessively small and the content of the amide compound is excessively large, so that μs is slightly low at 0.09 although μ ratio is 1 or less. Consequently, transmission torque becomes deficient. In Comparative 6, the contents of the imide compound and the amide compound are excessively large, so that μs is slightly low at 0.08 although μ ratio is 1 or less. Consequently, transmission torque becomes deficient.

INDUSTRIAL APPLICABILITY

The invention is applicable as a lubricating oil composition for an automatic transmission used for a multistage transmission and a continuously variable transmission of a metallic belt type, a chain type, a traction drive type and the like.

Claims

1. A lubricating oil composition comprising: a lubricating base oil; and an imide compound, an amide compound and an aliphatic amine compound mixed with the lubricating base oil, wherein

a nitrogen content of the imide compound is 300 to 1000 ppm by mass of a total amount of the composition;

a nitrogen content of the amide compound is 380 to 1300 ppm by mass of the total amount of the composition; and

a nitrogen content of the aliphatic amine compound is 35 to 360 ppm by mass of the total amount of the composition.

2. The lubricating oil composition according to claim 1, wherein

the contents of the imide compound, the amide compound and the aliphatic amine compound amount to 1000 to 2000 ppm by mass of the total amount of the composition in terms of nitrogen.

3. The lubricating oil composition according to claim 1, wherein the imide compound is a succinimide compound.

4. The lubricating oil composition according to claim 1, wherein a multistage transmission or a continuously variable transmission comprises the lubricating oil composition.

5. The lubricating oil composition according to claim 4, wherein the continuously variable transmission is a belt-type continuously variable transmission equipped with a metallic belt.