Lubricating oil composition

Abstract

To provide a lubricant oil composition which enables reduction of copper corrosion and improvement of flash point and low-temperature fluidity, and is suitable for use in a reduction gear and a transmission gear of an electric vehicle or a hybrid vehicle.SOLUTION: There is provided a lubricant oil composition for use in a reduction gear or a transmission gear of an electric vehicle or a hybrid vehicle. The lubricant oil composition includes base oil, and a content of an aromatic ring included in the base oil based on the mass of the base oil is 3,500 to 15,000 ppm.SELECTED DRAWING: None

Description

Technical Field

[0001] In recent years, from the perspective of environmental protection, electric vehicles or hybrid vehicles with low environmental impact during driving have become popular. For example, as electric vehicles, many electric vehicles that combine an electric motor with a speed reducer or a transmission for increasing the driving force of the electric motor are popular. In addition, many hybrid vehicles that combine an engine and a motor are also popular.

[0002] Lubricating oil needs to be applied to speed reducers and transmissions to smoothly transmit the driving force. However, in general electric motors, copper is used as a material for coils and wiring. Therefore, the lubricating oil used in the speed reducer of an electric vehicle or a hybrid vehicle is required to reduce copper corrosiveness. In particular, ordinary lubricating oil compositions have a problem of causing copper corrosion due to the inclusion of sulfur-based compounds and the like.

[0003] In Patent Document 1, a lubricating oil composition containing a base oil, a specific sulfur-containing compound, and a specific thiadiazole compound has been proposed as a lubricating oil composition with low copper corrosiveness.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0005] Here, an electric motor has a higher rotational speed compared to an engine, which was the power source of conventional automobiles, and the stirring resistance of the lubricating oil used in its transmission has a greater impact on energy consumption. Therefore, from the perspective of fuel efficiency, it is important that the lubricating oil used has a low viscosity and low-temperature fluidity. Furthermore, in the speed reducer of an electric vehicle or a hybrid vehicle, in addition to the heat generated by the sliding of each part of the speed reducer, it also undertakes the function of absorbing and cooling the heat generated from the motor, so a further increase in oil temperature is expected.

[0006] Regarding the lubricating oil composition according to Patent Document 1, although copper corrosiveness is considered, flash point and low-temperature fluidity are not considered, and sufficient performance may not be obtained as a lubricating oil composition applied to the speed reducer of an electric vehicle or a hybrid vehicle.

[0007] Therefore, an object of the present invention is to provide a lubricating oil composition capable of reducing copper corrosiveness, improving flash point and low-temperature fluidity, and suitable for the speed reducer and transmission of electric vehicles or hybrid vehicles.

Means for Solving the Problems

[0008] As a result of intensive research, the present inventors have found that the above problems can be solved by the base oil satisfying specific properties. That is, the present invention is as follows.

[0009] The present invention is a lubricating oil composition used in the speed reducer or transmission of an electric vehicle or a hybrid vehicle, the lubricating oil composition contains a base oil, the content of aromatic rings contained in the base oil based on the mass of the base oil is 3500 to 15000 ppm, and it is a lubricating oil composition characterized by this. the base oil includes a first base oil which is a Group 1 base oil and a second base oil which is a GTL base oil and / or PAO, the content of the first base oil based on the mass of the whole lubricating oil composition is 8 to 25% by mass, it is preferable that the content of the second base oil based on the mass of the whole lubricating oil composition is 60 to 90% by mass. Preferably, the copper elution amount measured according to JIS K 2513 of the lubricating oil composition is less than 10 ppm. Preferably, the pour point measured according to JIS K 2269 of the lubricating oil composition is less than -40°C. The lubricating oil composition preferably has a flash point measured according to JIS K 2265-4 of over 208°C.

Advantages of the Invention

[0010] It is possible to reduce copper corrosion, improve the flash point and improve the low-temperature fluidity, and a lubricating oil composition suitable for a reducer or a transmission of an electric vehicle or a hybrid vehicle can be provided.

[0011] Hereinafter, components, physical properties / characteristics, production methods, uses, etc. of the lubricating oil composition according to the present invention will be described.

[0012] <<<Components of the Lubricating Oil Composition>>> The lubricating oil composition includes a base oil and other components added according to desired properties.

[0013] <<Base Oil>> The content of aromatic rings contained in the base oil is 3500 to 15000 ppm, preferably 4000 to 14000 ppm, and particularly preferably 5000 to 13000 ppm based on the mass of the base oil. The content of aromatic rings can be measured based on ASTM D3238.

[0014] With the base oil having such properties, reduction of copper corrosion, improvement of the flash point, and improvement of low-temperature fluidity are achieved.

[0015] The base oil is not particularly limited as long as it satisfies the above properties, and mineral oils, synthetic oils, animal and vegetable oils, and mixed oils thereof can be appropriately used. As specific examples, base oils belonging to Group 1, Group 2, Group 3, Group 4, etc. in the API (American Petroleum Institute) base oil category may be used alone or as a mixture.

[0016] Group 1 base oils include, for example, paraffinic mineral oils obtained by appropriately combining refining means such as solvent refining, hydrorefining, and dewaxing for the lubricating oil fraction obtained by atmospheric distillation of crude oil.

[0017] Group 2 base oils include, for example, paraffinic mineral oils obtained by appropriately combining refining means such as hydrocracking and dewaxing for the lubricating oil fraction obtained by atmospheric distillation of crude oil. Group 2 base oils refined by a hydrorefining method such as the Gulf process have a total sulfur content of less than 10 ppm and an aroma content of 5% or less, and can be preferably used.

[0018] Group 3 base oils and Group 2 Plus base oils include, for example, paraffinic mineral oils produced by advanced hydrorefining for the lubricating oil fraction obtained by atmospheric distillation of crude oil, base oils refined by the ISODEWAX process that converts and dewaxes the wax generated in the dewaxing process into isoparaffin, and base oils refined by the Mobil WAX isomerization process, and can be preferably used.

[0019] Examples of synthetic oils include polyolefins, diesters of dibasic acids, triesters of trimellitic acid, polyol esters, alkylbenzenes, alkylnaphthalenes, esters, polyoxyalkylene glycols, polyoxyalkylene glycol esters, polyoxyalkylene glycol ethers, polyphenyl ethers, dialkyldiphenyl ethers, fluorine-containing compounds (perfluoropolyethers, fluorinated polyolefins, etc.), silicones, and the like. The above polyolefins include polymers of various olefins or hydrides thereof. Any olefin can be used, and examples include ethylene, propylene, butene, α-olefins having 5 or more carbon atoms, and the like. In the production of polyolefins, one of the above olefins may be used alone, or two or more thereof may be used in combination. In particular, polyolefins called poly-α-olefins (PAO) are preferred, and these are Group 4 base oils.

[0020] The oil (GTL base oil) obtained from GTL (gas to liquid) synthesized by the Fischer-Tropsch process of natural gas liquefaction technology has extremely low sulfur and aromatic contents and an extremely high paraffin composition ratio compared to mineral base oils refined from crude oil. Therefore, it has excellent oxidation stability and very low evaporation loss, and can be preferably used.

[0021] Preferably, the base oil includes a first base oil which is a Group 1 base oil and a second base oil which is a GTL base oil and / or PAO. In this case, based on the mass of the entire lubricating oil composition, the content of the first base oil is preferably 8 to 25% by mass, and the content of the second base oil (total content of GTL base oil and PAO) is preferably 60 to 90% by mass. By mixing and using such base oils, it becomes easy to adjust the content of aromatic rings in the lubricating oil composition, and the effects of the present invention can be further enhanced.

[0022] <<Other Components>> Examples of other components include known additives such as metal detergents, antiwear agents, dispersants, antifoaming agents, pour point depressants, metal deactivators, antioxidants, and viscosity index improvers.

[0023] The content of other components in the lubricating oil composition is not particularly limited, but based on the entire lubricating oil composition, it can be 1% by mass or more, 2% by mass or more, 3% by mass or more, or 5% by mass or more, etc., and can also be 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, etc.

[0024] In order to further enhance the effects of the present invention, the content of aromatic rings contained in other components is preferably 500 ppm or less, 100 ppm or less, 10 ppm or less, or 1 ppm or less based on the entire lubricating oil composition.

[0025] <<<Physical Properties / Properties of Lubricating Oil Composition>>> <<Copper Elution Amount>> The lubricating oil composition preferably has a copper elution amount (at 150 °C for 48 hours) measured according to JIS K 2513 of less than 10 ppm, more preferably 8 ppm or less, and particularly preferably 6 ppm or less. By satisfying such a range of the copper elution amount, the lubricating oil composition can be preferably applied to a speed reducer or a transmission of an electric vehicle or a hybrid vehicle. The copper elution amount can be measured by ICP emission spectrometry (high-frequency inductively coupled plasma emission spectrometry).

[0026] <<Pour Point>> The lubricating oil composition preferably has a pour point measured according to JIS K 2269 of less than -40 °C, more preferably -45 °C or lower, and particularly preferably -50 °C or lower. By satisfying such a range of the pour point, the lubricating oil composition can be preferably applied to a speed reducer or a transmission of an electric vehicle or a hybrid vehicle.

[0027] <<Flash Point>> The lubricating oil composition preferably has a flash point measured according to JIS K 2265-4 of more than 208 °C, more preferably 210 °C or higher. By satisfying such a range of the flash point, the lubricating oil composition can be preferably applied to a speed reducer or a transmission of an electric vehicle or a hybrid vehicle.

[0028] <<Kinematic Viscosity at 40 °C>> The kinematic viscosity at 40 °C of the lubricating oil composition measured according to JIS K 2283 is preferably 5 to 100 mm 2 / s, more preferably 10 to 80 mm 2 / s, and even more preferably 15 to 50 mm 2 / s.

[0029] <<Kinematic Viscosity at 100 °C>> The kinematic viscosity at 100 °C of the lubricating oil composition measured according to JIS K 2283 is preferably 1 to 30 mm 2 / s, more preferably 2 to 20 mm 2 / s, and even more preferably 3 to 10 mm 2 / s.

[0030] <<Viscosity Index>> The viscosity index (Viscosity Index; VI) of the lubricating oil composition is preferably 50 or more, more preferably 100 or more, and even more preferably 125 or more.

[0031] <<<Method for Producing Lubricating Oil Composition>>> The lubricating oil composition can be produced according to a known method, and each component can be appropriately mixed, and the mixing order is not particularly limited. The additive may be added as a packaged product in which a plurality of types are mixed.

[0032] <<<Use of Lubricating Oil Composition>>> The lubricating oil composition according to the present invention is used in a reducer or a transmission of an electric vehicle or a hybrid vehicle.

Examples

[0033] <<<Lubricating Oil Composition>>> The following raw materials were blended so as to have the blending amounts (mass%) shown in the table, and the lubricating oil compositions according to each example and each comparative example were produced.

[0034] <<Base Oil>> (Base Oil A-1) Mineral oil classified into Group II of the API base oil category with a kinematic viscosity at 40 °C of 12.4 m 2 / s and a kinematic viscosity at 100 °C of 3.1 mm 2 / s (Base Oil A-2) Mineral oil classified into Group III of the API base oil category with a kinematic viscosity at 40 °C of 19.6 m 2 / s and a kinematic viscosity at 100 °C of 4.2 mm 2 / s (Base Oil A-3) Mineral oil classified into Group III of the API base oil category with a kinematic viscosity at 40 °C of 47.2 m 2 / s and a kinematic viscosity at 100 °C of 7.7 mm 2 / s

[0035] (Base oil B-1) The kinematic viscosity at 40 °C is 9.9 m 2 / s, and the kinematic viscosity at 100 °C is 2.7 mm 2 / s, which is a Fischer-Tropsch-derived base oil (GTL) (Base oil B-2) The kinematic viscosity at 40 °C is 18.2 m 2 / s, and the kinematic viscosity at 100 °C is 4.1 mm 2 / s, which is a Fischer-Tropsch-derived base oil (GTL) (Base oil B-3) The kinematic viscosity at 40 °C is 43.7 m 2 / s, and the kinematic viscosity at 100 °C is 7.6 mm 2 / s, which is a Fischer-Tropsch-derived base oil (GTL)

[0036] (Base oil C-1) The kinematic viscosity at 40 °C is 18.6 m 2 / s, and the kinematic viscosity at 100 °C is 4.1 mm 2 / s, which is a polyalphaolefin base oil (PAO) (Base oil C-2) The kinematic viscosity at 40 °C is 48.0 m 2 / s, and the kinematic viscosity at 100 °C is 8.0 mm 2 / s, which is a polyalphaolefin base oil (PAO)

[0037] (Base oil D-1) The kinematic viscosity at 40 °C is 53.1 m 2 / s, and the kinematic viscosity at 100 °C is 7.6 mm 2 / s, which is a mineral oil classified in Group I of the API base oil category (Base oil D-2) The kinematic viscosity at 40 °C is 96.1 m 2 / s, and the kinematic viscosity at 100 °C is 11.2 mm 2 / s, which is a mineral oil classified in Group I of the API base oil category (Base oil D-3) The kinematic viscosity at 40 °C is 492.3 m 2 / s, and the kinematic viscosity at 100 °C is 32.7 mm 2 / s, which is a mineral oil classified in Group I of the API base oil category

[0038] <<Additive>> <Pour Point Depressant> · A polymethacrylate-based pour point depressant with a crystallization peak temperature of -29°C <Additive Package> · An additive package for lubricating oil for a speed reducer or transmission oil that also serves for the cooling application of the electric motor of an electric vehicle or hybrid vehicle

[0039] <<<Measurement / Evaluation>>> According to the aforementioned method, the kinematic viscosity at 40°C, kinematic viscosity at 100°C, viscosity index, pour point, flash point, and copper elution amount of the lubricating oil composition were measured. The measurement results are shown in a table.

[0040]

Table 1

[0041]

Table 2

Claims

Claim 1 A lubricating oil composition for use in a speed reducer or transmission of an electric vehicle or a hybrid vehicle, wherein the lubricating oil composition contains a base oil, the content of aromatic rings contained in the base oil based on the mass of the base oil is 3,500 to 15,000 ppm, the content of components other than the base oil based on the total mass of the lubricating oil composition is 30% by mass or less, when the lubricating oil composition contains components other than the base oil, the content of aromatic rings contained in the components other than the base oil based on the total mass of the lubricating oil composition is 500 ppm or less. A lubricating oil composition characterized by this. Claim 2 The base oil includes a first base oil that is a Group 1 base oil in the API base oil category, and a second base oil that is a GTL base oil and / or a PAO, the content of the first base oil based on the total mass of the lubricating oil composition is 8 to 25% by mass, The lubricating oil composition according to claim 1, wherein the content of the second base oil based on the total mass of the lubricating oil composition is 60 to 90% by mass. Claim 3 The lubricating oil composition according to claim 1 or 2, wherein the amount of copper elution measured according to JIS K 2513 (150 °C, 48 hours) is less than 10 ppm. Claim 4 The lubricating oil composition according to any one of claims 1 to 3, wherein the pour point measured according to JIS K 2269 is less than -40 °C. Claim 5 The lubricating oil composition according to any one of claims 1 to 4, wherein the flash point measured according to JIS K 2265-4 exceeds 208 °C.

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