Grease composition, machine component, and starter overrunning clutch

1. A method for transmitting torque of a clutch or a torque limiter mechanism, the method comprising:

enclosing a grease composition in a lubricating part of the clutch or the torque limiter mechanism;

wherein the enclosed grease composition consists of:

(A) a silicone oil having the general formula (I): R 1 a SiO (4-a)/2 in which each R 1 is independently selected from the group consisting of monovalent hydrocarbon groups, and a is from 1.8 to 2.2;

(B) zinc dialkyldithiocarbamate having the general formula (II): [R 5 2 N—C(═S)—S] 2 —Zn in which each R 5 is a methyl group; and

(C) an organic thickener selected from the group consisting of lithium soap and lithium complex soap;

wherein a content of the silicone oil (A) is from 60 mass % to 90 mass %, a content of the zinc dialkyldithiocarbamate (B) is from 7.5 mass % to 20 mass %, and a content of the organic thickener (C) is from 2.5 mass % to 20 mass %, each relative to the total amount of the enclosed grease composition, provided the total of components (A), (B), and (C) is 100 mass % of the enclosed grease composition.

2. The method according to claim 1 , wherein the silicone oil (A) has an aromatic hydrocarbon group per molecule.

3. The method according to claim 1 , wherein the clutch is an overrunning clutch and wherein the enclosed grease composition is enclosed in a clutch cam chamber formed by an outer clutch and an inner clutch.

4. The method according to claim 1 , wherein the organic thickener (C) is lithium stearate.

5. The method according to claim 4 , wherein the silicone oil (A) is of the general formula

Me 3 SiO(Me 2 SiO) I (R 2 R 3 SiO) m SiMe 3

where Me is a methyl group, R 2 is a methyl group or a phenyl group, R 3 is a phenyl group, I is 0 or a positive integer, and m is a positive integer.

6. The method according to claim 1 , wherein the silicone oil (A) is of the general formula

Me 3 SiO(Me 2 SiO) I (R 2 R 3 SiO) m SiMe 3

where Me is a methyl group, R 2 is a methyl group or a phenyl group, R 3 is a phenyl group, I is 0 or a positive integer, and m is a positive integer.

7. The method according to claim 1 , wherein the organic thickener (C) is a lithium soap.

8. The method according to claim 1 , wherein:

(i) the content of the silicone oil (A) is from 73.74 mass % to 77.14 mass %;

(ii) the content of the zinc dialkyldithiocarbamate (B) is from 9.25 mass % to 13.25 mass %;

(iii) the content of the organic thickener (C) is from 13.01 mass % to 13.61 mass %; or

(iv) each one of (i) to (iii); and

wherein each mass % is relative to 100 mass % of the enclosed grease composition.

9. The method according to claim 1 , further comprising:

providing the grease composition prior to the enclosing step, wherein the grease composition consists of components (A), (B), and (C).

10. The method according to claim 1 , further comprising:

providing an automobile starter, the automobile starter having the clutch or torque limiter mechanism.

11. The method according to claim 10 , wherein the clutch is an overrunning clutch and wherein the enclosed grease composition is enclosed in a clutch cam chamber formed by an outer clutch and an inner clutch.

12. The method according to claim 10 , further comprising:

powering the automobile starter, thereby transmitting torque of the clutch or torque limiter mechanism via the enclosed grease composition.

13. A method for transmitting torque of a clutch or a torque limiter mechanism, the method comprising:

providing an automobile starter, the automobile starter having the clutch or torque limiter mechanism;

providing a grease composition;

enclosing the grease composition in a lubricating part of the clutch or the torque limiter mechanism of the automobile starter; and

powering the automobile starter, thereby transmitting torque of the clutch or torque limiter mechanism via the enclosed grease composition;

wherein the enclosed grease composition consists of:

(A) a silicone oil having the general formula (I): R 1 a SiO (4-a)/2 in which each R 1 is independently selected from the group consisting of monovalent hydrocarbon groups, and a is from 1.8 to 2.2;

(B) zinc dialkyldithiocarbamate having the general formula (II): [R 5 2 N—C(═S)—S] 2 —Zn in which each R 5 is a methyl group; and

(C) an organic thickener selected from the group consisting of lithium soap and lithium complex soap;

wherein a content of the silicone oil (A) is from 60 mass % to 90 mass %, a content of the zinc dialkyldithiocarbamate (B) is from 7.5 mass % to 20 mass %, and a content of the organic thickener (C) is from 2.5 mass % to 20 mass %, each relative to the total amount of the enclosed grease composition, provided the total of components (A), (B), and (C) is 100 mass % of the enclosed grease composition.

14. The method according to claim 13 , wherein the clutch is an overrunning clutch and wherein the enclosed grease composition is enclosed in a clutch cam chamber formed by an outer clutch and an inner clutch.

15. The method according to claim 13 , wherein the organic thickener (C) is lithium stearate.

16. The method according to claim 15 , wherein the silicone oil (A) is of the general formula

Me 3 SiO(Me 2 SiO) I (R 2 R 3 SiO) m SiMe 3

where Me is a methyl group, R 2 is a methyl group or a phenyl group, R 3 is a phenyl group, I is 0 or a positive integer, and m is a positive integer.

17. The method according to claim 13 , wherein:

(i) the content of the silicone oil (A) is from 73.74 mass % to 77.14 mass %;

(ii) the content of the zinc dialkyldithiocarbamate (B) is from 9.25 mass % to 13.25 mass %; and

(iii) the content of the organic thickener (C) is from 13.01 mass % to 13.61 mass %;

wherein each mass % is relative to 100 mass % of the enclosed grease composition.

18. The method according to claim 13 , consisting of the providing, enclosing, and powering steps.