JP5965139B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition suitable for an automatic transmission.

Conventionally, lubricating oils for automatic transmissions on the market generally have a kinematic viscosity at 100 ° C. in the range of 7.0 mm ² / s to 9.0 mm ² / s. On the other hand, in order to save fuel consumption of lubricating oil for automatic transmissions, it is effective to reduce the stirring resistance, and it is necessary to reduce the viscosity of the lubricating oil. Therefore, an automatic transmission oil having a kinematic viscosity at 100 ° C. of 5.0 to 6.0 mm ² / s has been proposed (see Patent Document 1). Further, a lubricating oil composition for a transmission containing a specific polymethacrylate-based additive in a specific lubricating base oil and a kinematic viscosity at 100 ° C. of 3 to 8 mm ² / s has also been proposed (Patent Document 2). reference).

JP 2004-169025 A JP 2006-117852 A

  However, low-viscosity lubricating oil has a problem in that the ability to form an oil film decreases at high temperatures and the durability of transmission parts (the seizure resistance of the gear system) decreases. Further, the low-viscosity lubricating oil is likely to cause oil leakage in the hydraulic control unit of the transmission, and there is a possibility that the shift control may be disabled. Therefore, in order to achieve both fuel saving performance and component durability, it is important to maintain the low temperature side viscosity for a long period of time and ensure the high temperature side viscosity. Even in the transmission oil disclosed in Patent Documents 1 and 2, it is not always sufficient to satisfy these performances simultaneously.

  An object of this invention is to provide the lubricating oil composition excellent in fuel-saving property, shear stability, and component durability.

In order to solve the above problems, the present invention provides the following lubricating oil composition.
(1) A base oil 1 having a 100 ° C. kinematic viscosity of 1.5 mm ² / s to 3.5 mm ² / s and a 100 ° C. kinematic viscosity of more than 3.5 mm ² / s and 100 mm ² / s or less A base oil 2, a polymethacrylate having a mass average molecular weight of 1 × 10 ⁴ or more and 4 × 10 ⁴ or less, and a sulfur compound are blended, and the kinematic viscosity at 100 ° C. is 5 mm ² / s or more and 6 mm ² / s or less. A lubricating oil composition having a viscosity index of 200 or more.
(2) In the lubricating oil composition according to the above (1), the blending amount (mass%) of the base oil 1 is A based on the total composition, and the blending quantity (mass%) of the base oil 2 is the composition. The following formula [1] is satisfied when B is defined as the total amount
0.6 ≦ A / (A + B) <1 [1]
A lubricating oil composition characterized by that.
(3) The lubricating oil composition as described in (1) or (2) above, wherein the blending amount B of the base oil 2 is 10% by mass or more.
(4) In the lubricating oil composition according to any one of (1) to (3) above,
A lubricating oil composition, wherein the blending amount of the polymethacrylate is 1% by mass or more and 16% by mass or less based on the total amount of the composition.
(5) The lubricating oil composition according to any one of (1) to (4) above, wherein the compounding amount of the sulfur compound is 0.03% by mass or more based on the total amount of the composition. A lubricating oil composition.
(6) The lubricating oil composition according to any one of (1) to (5) above, wherein the sulfur compound has a sulfur content of 20% by mass or more based on the compound. Lubricating oil composition.
(7) In the lubricating oil composition according to any one of (1) to (6) above, a cleaning dispersant, an antiwear agent, a friction modifier, a rust inhibitor, a metal deactivator A lubricating oil composition comprising at least one of antifoaming agent and antioxidant.
(8) A lubricating oil composition according to any one of (1) to (7), wherein the lubricating oil composition is for an automatic transmission.

  ADVANTAGE OF THE INVENTION According to this invention, the lubricating oil composition excellent in fuel-saving property, shear stability, and component durability can be provided. Therefore, the lubricating oil composition of the present invention is suitable for an automatic transmission.

The lubricating oil composition of the present invention (hereinafter also simply referred to as “the present composition”) has a base oil 1 having a 100 ° C. kinematic viscosity of 1.5 mm ² / s to 3.5 mm ² / s, and 100 ° C. A base oil 2 having a kinematic viscosity exceeding 3.5 mm ² / s and 100 mm ² / s or less, a polymethacrylate having a mass average molecular weight of 1 × 10 ⁴ or more and 4 × 10 ⁴ or less, and a sulfur compound are blended. And has a predetermined 100 ° C. kinematic viscosity and a predetermined viscosity index. Details will be described below.

[Base oil 1]
The base oil 1 in the composition has a kinematic viscosity at 100 ° C. of 1.5 mm ² / s to 3.5 mm ² / s, preferably 1.5 mm ² / s to 2.5 mm ² / s. . If the 100 ° C. kinematic viscosity is less than 1.5 mm ² / s, the seizure resistance may be lowered even if the viscosity of the base oil 2 described later is within a predetermined range. On the other hand, when the 100 ° C. kinematic viscosity exceeds 3.5 mm ² / s, the fuel efficiency is inferior even if the viscosity of the base oil 2 described later is within a predetermined range.
As such a base oil, a mineral oil or a synthetic oil may be used as long as the viscosity at 100 ° C. is in the above range, or a mixture thereof may be used.
There is no restriction | limiting in particular as mineral oil, Arbitrary things can be suitably selected and used from the mineral oil conventionally used as a base oil of the lubricating oil for transmissions for motor vehicles. Examples thereof include paraffin-based mineral oil, intermediate-based mineral oil, and naphthene-based mineral oil.
The synthetic oil is not particularly limited, and examples thereof include polybutene, polyolefin, polyol ester, dibasic acid ester, phosphoric acid ester, polyphenyl ether, polyglycol, alkylbenzene, and alkylnaphthalene. Examples of the polyolefin include α-olefin homopolymers and α-olefin copolymers.

[Base oil 2]
The base oil 2 in the present composition has a kinematic viscosity at 100 ° C. of more than 3.5 mm ² / s and not more than 100 mm ² / s, preferably not less than 4 mm ² / s and not more than 8 mm ² / s. If the 100 ° C. kinematic viscosity is 3.5 mm ² / s or less, the seizure resistance may decrease even if the viscosity of the base oil 1 is within a predetermined range. On the other hand, when the 100 ° C. kinematic viscosity exceeds 100 mm ² / s, the fuel efficiency is inferior even if the viscosity of the base oil 1 is within a predetermined range.
The base oil 2 can be of the same type as the mineral oil and synthetic oil used as the base oil 1 described above, except for the viscosity range.

Here, when the blending amount (mass%) of the base oil 1 is A based on the total composition, and the blending weight (mass%) of the base oil 2 is B based on the total composition, the following formula [ 1] is preferably satisfied.
0.6 ≦ A / (A + B) <1 [1]
When A / (A + B) is 0.6 or more, fuel economy is more sufficiently exhibited. Therefore, A / (A + B) is more preferably 0.65 or more. However, if the base oil 2 is not blended, the component durability is not sufficiently exhibited.
The blending amount B of the base oil 2 is preferably 5% by mass or more, more preferably 10% by mass or more based on the total amount of the composition. When the blending amount B of the base oil 2 is 5% by mass or more, the durability of the bearings and gear parts is further improved.

[Polymethacrylate]
The polymethacrylate in the present composition contributes as a viscosity index improver, but the mass average molecular weight is required to be 1 × 10 ⁴ or more and 4 × 10 ⁴ or less. When the weight average molecular weight of this polymethacrylate is less than 1 × 10 ⁴ , the effect as a viscosity index improver is not sufficient. On the other hand, when the mass average molecular weight of the polymethacrylate exceeds 4 × 10 ⁴ , the shear stability is poor.
Examples of such polymethacrylate include non-dispersed polymethacrylate and dispersed polymethacrylate. These 1 type may be used independently and may be used in combination. The blending amount of the polymethacrylate is preferably 1% by mass or more and 16% by mass or less, and more preferably 7% by mass or more and 13% by mass or less based on the total amount of the composition. When the blending amount of the polymethacrylate is 1% by mass or more, the effect of improving the viscosity index is sufficiently exhibited. Moreover, fuel consumption improves that a compounding quantity is 16 mass% or less.

[Sulfur compounds]
The sulfur compound in the present composition contributes to the durability of parts such as gears (gears). The sulfur content in the sulfur compound is preferably 20% by mass or more based on the sulfur compound from the viewpoint of improving durability.
As such a sulfur compound, for example, a thiadiazole compound is suitable.
Examples of thiadiazole compounds include 2,5-bis (n-hexyldithio) -1,3,4-thiadiazole, 2,5-bis (n-octyldithio) -1,3,4-thiadiazole, 2,5 -Bis (n-nonyldithio) -1,3,4-thiadiazole, 2,5-bis (1,1,3,3-tetramethylbutyldithio) -1,3,4-thiadiazole, 3,5-bis ( n-hexyldithio) -1,2,4-thiadiazole, 3,6-bis (n-octyldithio) -1,2,4-thiadiazole, 3,5-bis (n-nonyldithio) -1,2,4 -Thiadiazole, 3,5-bis (1,1,3,3-tetramethylbutyldithio) -1,2,4-thiadiazole, 4,5-bis (n-octyldithio) -1,2,3-thiadiazole 4,5-bis n- nonyldithio) -1,2,3-thiadiazole, and 4,5-bis (1,1,3,3-tetramethylbutyl dithio) -1,2,3-thiadiazoles such as can be a preferably exemplified.

As the sulfur compound in the present composition, in addition to the thiadiazole compound, a mono- or disulfide olefin, a dihydrocarbyl mono- or disulfide, a dithiocarbamate compound, or an ester compound having a disulfide structure is also suitable.
A suitable compounding amount of the sulfur compound is 0.03% by mass or more, preferably 0.05% by mass or more, based on the total amount of the composition. However, the blending amount is preferably 0.5% by mass or less from the viewpoint of oxidation stability.

[This composition]
This composition comprises the base oil and additives described above, and has a 100 ° C. kinematic viscosity of 5 mm ² / s to 6 mm ² / s. When the 100 ° C. kinematic viscosity is less than 5 mm ² / s, the component durability is inferior. On the other hand, when the 100 ° C. kinematic viscosity exceeds 6 mm ² / s, the fuel efficiency is poor.
Moreover, the viscosity index of this composition is 200 or more. Therefore, there is little decrease in high-temperature viscosity and excellent component durability.

  Since this composition is formed by blending the above-mentioned predetermined mixed base oil and a predetermined additive, fuel efficiency is reduced by maintaining an appropriate viscosity even after long-term shearing while maintaining an initial viscosity at a high temperature. In addition, the durability of parts can be exhibited. That is, problems such as deterioration of component durability (gear seizure of gears) due to a decrease in high-temperature viscosity and hydraulic leakage of the hydraulic control unit do not occur. Therefore, the present composition is particularly suitable as a lubricating oil for automatic transmissions.

  Various additives shown below may be blended with the present composition as long as the effects of the invention are not impaired. Specific examples include cleaning dispersants, antiwear agents, friction modifiers, and antioxidants.

As the cleaning dispersant, an ashless dispersant or a metallic cleaner can be used.
Examples of the ashless dispersant include succinimide compounds, boron imide compounds, Mannich dispersants, and acid amide compounds. These may be used individually by 1 type and may be used in combination of 2 or more type. Although the compounding quantity of an ashless type dispersing agent is not specifically limited, It is preferable that they are 0.1 mass% or more and 20 mass% or less on the composition whole quantity basis.
Examples of the metal detergent include alkali metal sulfonate, alkali metal phenate, alkali metal salicylate, alkali metal naphthenate, alkaline earth metal sulfonate, alkaline earth metal phenate, alkaline earth metal salicylate, and alkaline earth metal naphthenate. It is done. These may be used individually by 1 type and may be used in combination of 2 or more type. Although the compounding quantity of a metal type detergent is not specifically limited, It is preferable that it is 0.1 to 10 mass% on the basis of the total amount of the composition.

  Examples of the antiwear agent include sulfur compounds and phosphorus compounds. Examples of sulfur compounds include sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, dithiocarbamates, and polysulfides. Examples of the phosphorus compound include phosphites, phosphates, phosphonates, and amine salts or metal salts thereof. These may be used individually by 1 type and may be used in combination of 2 or more type. The blending amount of these antiwear agents is preferably 0.1% by mass or more and 20% by mass or less based on the total amount of the composition.

  Examples of the friction modifier include fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic amines, and aliphatic ethers. Specific examples include those having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule. For example, oleic acid and oleylamine are preferably used. These may be used individually by 1 type and may be used in combination of 2 or more type. The blending amount of the friction modifier is preferably 0.01% by mass or more and 2% by mass or less, and more preferably 0.01% by mass or more and 1% by mass or less, based on the total amount of the composition.

  Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated-α-naphthylamine, 2,6-di-t-butyl-4-methylphenol, 4,4- And phenolic antioxidants such as methylenebis (2,6-di-t-butylphenol). The blending amount of the antioxidant is preferably 0.05% by mass or more and 25% by mass or less based on the total amount of the composition.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

[Examples 1-5, Comparative Examples 1-5]
Each sample oil was prepared with the composition shown in Table 1, and kinematic viscosity (40 ° C., 100 ° C.), viscosity index, shear stability, and gear durability were measured by the methods shown below.

(Kinematic viscosity)
The measurement was performed according to JIS K2283.
[Viscosity index]
The measurement was performed according to JIS K2283.

[Shear stability]
A KRL shear test was performed in accordance with DIN 52350-6.
Specifically, using a KRL shear tester, the 100 ° C. kinematic viscosity after 96 hours from the start of shearing was measured. The practical target is 4.8 mm ² / s or more.

[Durability of gears]
An FZG gear test was performed according to ASTM D5182-97.
Specifically, the load stage with a scuffing width of 20 mm or more was obtained by raising the load stage stepwise at an oil temperature of 90 ° C. with a gear pitch on-circle speed of 8.3 m / s.

1) Mineral oil 1: Kinematic viscosity at 100 ° C. 2.2 mm ² / s, viscosity index 109
2) Mineral oil 2: Kinematic viscosity at 100 ° C. 2.8 mm ² / s, viscosity index 109
3) Mineral oil 3: 100 ° C. kinematic viscosity 4.1 mm ² / s, viscosity index 126
4) Mineral oil 4: Kinematic viscosity at 100 ° C. 6.5 mm ² / s, viscosity index 130
5) PMA1: Polymethacrylate having a mass average molecular weight of 3 × 10 ⁴ 6) PMA2: Polymethacrylate having a mass average molecular weight of 5 × 10 ⁴ 7) PMA3: Polymethacrylate having a mass average molecular weight of 1.2 × 10 ⁵ 8) Sulfur Compound: Thiadiazole-based additive 9) Other additives: Additive package for transmission (package containing detergent dispersant, anti-wear agent, friction modifier, antioxidant, etc.)

〔Evaluation results〕
As shown in Table 1, all of the sample oils of Examples 1 to 5 have a low viscosity and a high viscosity index, and are excellent in shear stability and gear durability. Therefore, it can be understood that the lubricating oil composition of the present invention exhibits excellent performance particularly for an automatic transmission.
On the other hand, since the sample oils of Comparative Examples 1 to 5 do not satisfy any of the configurations of the present invention, none of them is satisfactory in all of low viscosity, high viscosity index, shear stability, and gear durability.

Claims (8)

A base oil 1 having a 100 ° C. kinematic viscosity of 1.5 mm ² / s to 3.5 mm ² / s,
A base oil 2 having a 100 ° C. kinematic viscosity of more than 3.5 mm ² / s and not more than 100 mm ² / s;
A polymethacrylate having a mass average molecular weight of 1 × 10 ⁴ or more and 4 × 10 ⁴ or less;
Contains sulfur compounds,
The sulfur compound is 2,5-bis (n-hexyldithio) -1,3,4-thiadiazole, 2,5-bis (n-octyldithio) -1,3,4-thiadiazole, 2,5-bis. (N-nonyldithio) -1,3,4-thiadiazole, 2,5-bis (1,1,3,3-tetramethylbutyldithio) -1,3,4-thiadiazole, 3,5-bis (n- Hexyldithio) -1,2,4-thiadiazole, 3,6-bis (n-octyldithio) -1,2,4-thiadiazole, 3,5-bis (n-nonyldithio) -1,2,4-thiadiazole 3,5-bis (1,1,3,3-tetramethylbutyldithio) -1,2,4-thiadiazole, 4,5-bis (n-octyldithio) -1,2,3-thiadiazole, 4, , 5-Bis (n-nonyldithio) A 1,2,3-thiadiazole, and 4,5-bis (1,1,3,3-tetramethylbutyl dithio) -1,2,3 least one thiadiazole compound selected from thiadiazole,
The 100 ° C. kinematic viscosity is 5 mm ² / s or more and 6 mm ² / s or less, and the viscosity index is 205 or more,
When the blending amount (mass%) of the base oil 1 is A based on the total composition amount and the blending amount (mass%) of the base oil 2 is B based on the composition total amount, the following formula [1] is satisfied:
0.6 ≦ A / (A + B) ≦ 0.94 [1]
The lubricating oil composition, wherein the blending amount B of the base oil 2 is 10% by mass or more. The lubricating oil composition according to claim 1, wherein
The lubricating oil composition, wherein the amount of the sulfur compound is 0.5% by mass or less based on the total amount of the composition . The lubricating oil composition according to claim 1 or 2,
The base oil 1 and the base oil 2 are both mineral oils. In the lubricating oil composition according to any one of claims 1 to 3,
The lubricating oil composition, wherein the blending amount of the polymethacrylate is 1% by mass or more and 16% by mass or less based on the total amount of the composition. In the lubricating oil composition according to any one of claims 1 to 4,
Lubricating oil composition characterized in that the compounding amount of the sulfur compound is 0.03% by mass or more based on the total amount of the composition. In the lubricating oil composition according to any one of claims 1 to 5,
About the said sulfur compound, the sulfur content is 20 mass% or more on the said compound basis. The lubricating oil composition characterized by the above-mentioned. In the lubricating oil composition according to any one of claims 1 to 6,
Furthermore, the lubricant is characterized by comprising at least one of a cleaning dispersant, an antiwear agent, a friction modifier, a rust inhibitor, a metal deactivator, an antifoaming agent, and an antioxidant. Oil composition. The lubricating oil composition according to any one of claims 1 to 7, wherein the lubricating oil composition is for an automatic transmission.