GREASE COMPOSITION, MACHINE COMPONENT, AND STARTER OVERRUNNING CLUTCH
A silicone grease composition having high friction characteristics and wear characteristics is disclosed. The silicone grease composition is provided by adding a zinc salt (B) containing, at a mass ratio from 1:99 to 99:1, a zinc dialkyldithiophosphate (B1) and a zinc dialkyldithiocarbamate (B2) as an extreme-pressure additive to a silicone oil (A).
1 . A grease composition comprising:
a silicone oil (A); and
a zinc salt (B) containing, at a mass ratio from 1:99 to 99:1, a zinc dialkyldithiophosphate (B1) and a zinc dialkyldithiocarbamate (B2).
2 . The grease composition according to claim 1 , wherein a content of the zinc salt (B) is not less than 5 mass % and not greater than 30 mass % relative to the entire grease composition.
3 . The grease composition according to claim 1 , wherein the zinc salt (B) contains the zinc dialkyldithiophosphate (B1) and the zinc dialkyldithiocarbamate (B2) at a mass ratio from 2:98 to 50:50.
4 . The grease composition according to claim 1 , further comprising one or more types of thickeners (C) selected from the group consisting of lithium soaps and lithium complex soaps.
5 . The grease composition according to claim 1 , wherein a content of the silicone oil (A) is in a range of not less than 50 mass % and not greater than 95 mass % relative to the total amount of the grease composition, and the silicone oil (A) has an aromatic hydrocarbon group in a molecule.
6 . The grease composition according to claim 1 , further comprising a partial ester (D) of a polyhydric alcohol.
7 . The grease composition according to claim 1 , wherein the grease composition is a grease composition for a power transmission device.
8 . A machine component in which the grease composition according to claim 1 is enclosed.
9 . The machine component according to claim 8 , wherein the machine component is a clutch or a torque limiter mechanism.
10 . An overrunning clutch, wherein the grease composition according to claim 1 is enclosed in a clutch cam chamber formed from an outer clutch and an inner clutch.
11 . The grease composition according to claim 2 , wherein the zinc salt (B) contains the zinc dialkyldithiophosphate (B1) and the zinc dialkyldithiocarbamate (B2) at a mass ratio from 2:98 to 50:50.
12 . The grease composition according to claim 11 , further comprising one or more types of thickeners (C) selected from the group consisting of lithium soaps and lithium complex soaps.
13 . The grease composition according to claim 12 , wherein a content of the silicone oil (A) is in a range of not less than 50 mass % and not greater than 95 mass % relative to the total amount of the grease composition, and the silicone oil (A) has an aromatic hydrocarbon group in a molecule.
14 . The grease composition according to claim 13 , further comprising a partial ester (D) of a polyhydric alcohol.