Grease composition, machine component, and starter overrunning clutch

Abstract

A silicone grease composition is disclosed. The silicone grease composition contains a silicone oil (A) and zinc dialkyldithiocarbamate (BX) as an extreme-pressure additive. The silicone grease composition contains substantially no zinc dialkyldithiophosphate (BX). The silicone grease composition achieves high friction characteristics and wear characteristics.

1 . A grease composition comprising:
 a silicone oil (A); and   zinc dialkyldithiocarbamate (B);   wherein the grease composition comprises substantially no zinc dialkyldithiophosphate (BX).   
     
     
         2 . The grease composition according to  claim 1 , wherein a content of the zinc dialkyldithiophosphate (BX) is 0.01 mass % or less relative to the total amount of the grease composition. 
     
     
         3 . The grease composition according to  claim 1 , wherein a content of the zinc salt (B) is from 5 mass % to 30 mass % relative to the total amount of the grease composition. 
     
     
         4 . The grease composition according to  claim 1 , further comprising at least one type of thickener (C) selected from the group consisting of lithium soap and lithium complex soap. 
     
     
         5 . The grease composition according to  claim 1 , wherein a content of the silicone oil (A) is in a range of 50 mass % to 95 mass % relative to the total amount of the grease composition, and the silicone oil (A) has an aromatic hydrocarbon group per molecule. 
     
     
         6 . The grease composition according to  claim 1 , wherein the grease composition is a grease composition for a power transmission device. 
     
     
         7 . A machine component comprising the grease composition according to  claim 1 . 
     
     
         8 . The machine component according  claim 7 , wherein the machine component is a clutch or a torque limiter mechanism. 
     
     
         9 . An overrunning clutch comprising the grease composition according to  claim 1  in a clutch cam chamber formed by an outer clutch and an inner clutch. 
     
     
         10 . The grease composition according to  claim 2 , wherein a content of the zinc salt (B) is from 5 mass % to 30 mass % relative to the total amount of the grease composition. 
     
     
         11 . The grease composition according to  10 , further comprising at least one type of thickener (C) selected from the group consisting of lithium soap and lithium complex soap. 
     
     
         12 . The grease composition according to  claim 11 , wherein a content of the silicone oil (A) is in a range of 50 mass % to 95 mass % relative to the total amount of the grease composition, and the silicone oil (A) has an aromatic hydrocarbon group per molecule. 
     
     
         13 . An overrunning clutch comprising the grease composition according to  claim 12  in a clutch cam chamber formed by an outer clutch and an inner clutch.