Tripod type constant velocity joint and grease for the joint

Abstract

In order to reduce vibration and improve durability at a low cost through the reduction of induced thrust, such a grease is used that has SRV friction coefficient μ h under a contact pressure of 2176 MPa in a range from 0.060 to 0.080 and decreasing rate of SRV friction coefficient μ 1 under a contact pressure of 3954 MPa with respect to the friction coefficient μ h , namely (μ h −μ 1 )/μ h ×100%, in a range from 40 to 60%. The outer joint member 1 is filled with this grease.

What is claimed is:  
     
         1 . A grease for a tripod type constant velocity joint having SRV friction coefficient μ h  under a contact pressure of 2176 MPa in a range from 0.060 to 0.080 and decreasing rate of SRV friction coefficient μ 1  under a contact pressure of 3954 MPa with respect to the friction coefficient μ h  in a range from 40 to 60%, the decreasing rate being represented by the following formula (1): 
       (μ h −μ 1 )/μ h ×100(%)  (1). 
     
     
         2 . A grease for a tripod type constant velocity joint according to  claim 1 , wherein said grease shows a wear amount of 10 mg or lower in Fafnir friction oxidation test.  
     
     
         3 . A grease for s tripod type constant velocity joint according to  claim 1 , wherein 0.3 to 1.5 wt % of molybdenum disulfide is added thereto.  
     
     
         4 . A tripod type constant velocity joint comprising an outer joint member having track grooves formed in the axial direction at equal intervals on an inner circumference thereof and having roller guide surfaces extending in the axial direction on both sides of each track groove, a tripod member having trunnions projecting in the radial direction and disposed at equal intervals along the circumference, rollers mounted rotatably on the respective trunnions and a grease filled the inside of the joint, the rollers being guided on the respective roller guide surfaces of the track grooves, wherein the grease has SRV friction coefficient μ h  under a contact pressure of 2176 MPa in a range from 0.060 to 0.080 and decreasing rate of SRV friction coefficient μ 1  under a contact pressure of 3954 MPa with respect to the friction coefficient μ h  in a range from 40 to 60%, said decreasing rate being represented by the following formula (1): 
       (μ h −μ 1 )/μ h ×100(%)  (1). 
     
     
         5 . A tripod type constant velocity joint according to  claim 4 , wherein the grease shows a wear amount of 10 mg or lower in Fafnir friction oxidation test.  
     
     
         6 . A tripod type constant velocity joint according to  claim 4 , wherein 0.3 to 1.5 wt % of molybdenum disulfide is added to said grease.  
     
     
         7 . A tripod type constant velocity joint according to one of claims  4  through  6 , wherein the inner circumference surface of the outer joint member is subjected to shot peening treatment.