Lubricating oil composition
A lubricating oil composition may be superior in cooling performance, ensure electrical insulation, and have a high flash point. Such a lubricating oil composition may include a base oil (A) including an ester-based synthetic oil (A1), the content of the ester-based synthetic oil (A1) is 30% by mass to 100% by mass based on the total amount of the base oil (A), the ester-based synthetic oil (A1) is one or more of an ester (A1-1) of a monohydric alcohol and a monobasic acid and an ester (A1-2) of a monohydric alcohol and a polybasic acid, and the base oil (A) satisfies requirements (1) to (3): Requirement (1): the kinematic viscosity at 40° C. is 2.00 mm 2 /s to 4.00 mm 2 /s. Requirement (2): the specific heat at 20° C. is 1.75 kJ/(kg·K) or less. Requirement (3): the density at 20° C. is 0.850 g/cm 3 or more.
1 . A method of cooling an electric vehicle device, comprising:
applying a lubricating oil composition comprising a base oil to an electric vehicle device,
wherein the base oil comprises an ester-based synthetic oil such that the content of the ester-based synthetic oil is in a range of 30% by mass to 100% by mass based on the total amount of the base oil, the ester-based synthetic oil is at least one selected from the group consisting of a first ester of a first monohydric alcohol and a monobasic acid and a second ester of a second monohydric alcohol and a polybasic acid, the first monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, and octanol, the monobasic acid includes a fatty acid having 6 to 8 carbon atoms, the second monohydric alcohol has a carbon number of 1 to 8 and has no aromatic group, the polybasic acid includes a dibasic acid having 4 to 8 carbon atoms and having no aromatic group, and the base oil has a flash point of 105° C. or higher and 200° C. or lower according to a Cleveland open-cup method, a kinematic viscosity in a range of 2.00 mm 2 /s to 4.00 mm 2 /s at 40° C., a specific heat of 1.75 kJ/(kg·K) or less at 20° C., and a density of 0.850 g/cm 3 or more at 20° C.
2 . The method according to claim 1 , wherein the base oil has a thermal conductivity of 0.140 W/(m·K) or more at 20° C.
3 . The method of claim 1 , wherein the base oil has a volume resistivity of 0.03×10 7 Ω·m or more at 25° C.
4 . The method of claim 1 , wherein the ester-based synthetic oil is the second ester.
5 . A method of cooling an electric vehicle device, comprising:
applying a lubricating oil composition comprising a base oil to an electric vehicle device,
wherein the base oil comprises an ester-based synthetic oil such that the content of the ester-based synthetic oil is in a range of 30% by mass to 100% by mass based on the total amount of the base oil, the ester-based synthetic oil is at least one selected from the group consisting of a first ester of a first monohydric alcohol and a monobasic acid and a second ester of a second monohydric alcohol and a polybasic acid, the first monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, the monobasic acid includes a fatty acid having 6 to 8 carbon atoms, the second monohydric alcohol has a carbon number of 1 to 8 and has no aromatic group, the polybasic acid includes a dibasic acid having 4 to 8 carbon atoms and having no aromatic group, the base oil has a flash point of 105° C. or higher and 200° C. or lower according to a Cleveland open-cup method, a kinematic viscosity in a range of 2.00 mm 2 /s to 4.00 mm 2 /s at 40° C., a specific heat of 1.75 KJ/(kg·K) or less at 20° C., and a density of 0.850 g/cm 3 or more at 20° C. and the electric vehicle device is at least one selected from motors, generators, electric storage devices, converters, inverters, engines and transmissions.
6 . A cooling system for cooling an electric vehicle device, comprising:
a lubricating oil composition comprising a base oil,
wherein the base oil comprises an ester-based synthetic oil such that the content of the ester-based synthetic oil is in a range of 30% by mass to 100% by mass based on the total amount of the base oil, the ester-based synthetic oil is at least one selected from the group consisting of a first ester of a first monohydric alcohol and a monobasic acid and a second ester of a second monohydric alcohol and a polybasic acid, the first monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, and octanol, the monobasic acid includes a fatty acid having 6 to 8 carbon atoms, the second monohydric alcohol has a carbon number of 1 to 8 and has no aromatic group, the polybasic acid includes a dibasic acid having 4 to 8 carbon atoms and having no aromatic group, and the base oil has a flash point 105° C. or higher and 200° C. or lower according to a Cleveland open-cup method, a kinematic viscosity in a range of 2.00 mm 2 /s to 4.00 mm 2 /s at 40° C., a specific heat of 1.75 KJ/(kg·K) or less at 20° C., and a density of 0.850 g/cm 3 or more at 20° C.
7 . The method according to claim 1 , wherein the base oil has a relative heat transfer coefficient of 1.05 or more at 20° C.
8 . The method according to claim 1 , wherein the monobasic acid includes at least one selected from the group consisting of hexanoic acid, octanoic acid, hexenoic acid, heptanoic acid, and octenoic acid.
9 . The method according to claim 1 , wherein the second monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, butenol, pentenol, hexenol, heptenol, and octenol.
10 . The method according to claim 1 , wherein the polybasic acid includes at least one selected from the group consisting of butane-diacid, pentane-diacid, hexane-diacid, heptane-diacid, octane-diacid, butene-diacid, pentene-diacid, hexene-diacid, heptene-diacid, and octene diacid.
11 . The cooling system according to claim 6 , wherein the base oil has a thermal conductivity of 0.140 W/(m·K) or more at 20° C.
12 . The cooling system according to claim 6 , wherein the base oil has a volume resistivity of 0.03×10 7 Ω·m or more at 25° C.
13 . The cooling system according to claim 6 , wherein the ester-based synthetic oil is the second ester.
14 . The cooling system according to claim 6 , wherein the base oil has a relative heat transfer coefficient of 1.05 or more at 20° C.
15 . The cooling system according to claim 6 , wherein the monobasic acid includes at least one selected from the group consisting of hexanoic acid, octanoic acid, hexenoic acid, heptanoic acid, and octenoic acid.
16 . The cooling system according to claim 6 , wherein the second monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, butenol, pentenol, hexenol, heptenol, and octenol.
17 . The cooling system according to claim 6 , wherein the polybasic acid includes at least one selected from the group consisting of butane-diacid, pentane-diacid, hexane-diacid, heptane-diacid, octane-diacid, butene-diacid, pentene-diacid, hexene-diacid, heptene-diacid, and octene diacid.
18 . The cooling system according to claim 6 , wherein the ester-based synthetic oil is the first ester.