Tripod type constant velocity universal joint

Abstract

The invention provides a tripod type constant velocity universal joint that can restrain generation of an excessive frictional force inside the joint because of the rotation phase angle of the inner joint member, thereby suppressing vibration and achieving higher rotation durability. The tripod type constant velocity universal joint includes an outer roller rotatably located inside the roller guide section of the outer joint member, and an inner roller spherically fitted to the trunnion of the inner joint member so as to be pivotally rotatable, and to support the outer roller permitting relative rotation and relative axial movement, so that when a torque is applied with the outer joint member and the inner joint member oriented with an operating angle θ, a facet of the outer roller inclined along with the rotation of the inner joint member is sustained by the track groove bottom portion formed in a flat plane.

1 . A tripod type constant velocity universal joint, comprising: 
 an outer joint member including three track grooves axially extending on an inner circumferential surface thereof and a pair of roller guide sections located on the respective sides of the track groove in a circumferential direction;    an inner joint member having three radially projecting trunnions;    an outer roller rotatably located inside the roller guide section of the outer joint member; and    an inner roller spherically fitted to the trunnion of the inner joint member so as to be pivotally rotatable, and to support the outer roller permitting relative rotation and relative axial movement;    wherein a bottom portion of the track groove of the outer joint member is a flat plane located close to a facet of the outer roller, so that the facet of the outer roller inclined due to rotation of the inner joint member is supported by the track groove bottom portion, when a torque is applied with the outer joint member and the inner joint member being oriented with a certain operating angle.    
   
   
       2 . The tripod type constant velocity universal joint according to  claim 1 , wherein a relief section having a smaller diameter than the inner circumferential surface of the inner roller is provided on a torque applying region of the trunnion of the inner joint member.  
   
   
       3 . The tripod type constant velocity universal joint according to  claim 2 , wherein the relief section is located in a region including a rib formed along a parting line of the forging process of the trunnion of the inner joint member.  
   
   
       4 . The tripod type constant velocity universal joint according to  claim 2 , wherein a cross-sectional shape of the relief section taken orthogonally to the trunnion includes a dual spherical portion.  
   
   
       5 . The tripod type constant velocity universal joint according to  claim 1 , wherein the outer circumferential surface of the outer roller and the roller guide section are formed so as to define therebetween a clearance δ 1  (mm) wider than 0.03/A when a torque is applied, wherein A=r 1 /R 1 ; r 1  is the generatrix curvature radius of the outer circumferential surface of the outer roller; and R 1  is the outer radius of the outer roller.  
   
   
       6 . The tripod type constant velocity universal joint according to  claim 1 , wherein a facet of the outer roller and the track groove bottom portion are formed so as to define therebetween a clearance δ 2  wider than 0.15×A, wherein A=r 1 /R 1 ; r 1  is the generatrix curvature radius of the outer circumferential surface of the outer roller; and R 1  is the outer radius of the outer roller.  
   
   
       7 . The tripod type constant velocity universal joint according to  claim 1 , further comprising: 
 a boot fitted to an outer periphery of the outer joint member at an end portion and to a shaft extended from the inner joint member at the other end portion so as to seal an inner region of the joint;    wherein the track groove bottom portion formed in a flat plane is located close to a facet of the outer roller;    the outer joint member includes a first reduced-thickness portion on an outer periphery thereof in a region corresponding to the region between the track grooves, and a second reduced-thickness portion on an outer periphery thereof in a region corresponding to the region where the track grooves are located; and    the second reduced-thickness portion is of a groove shape axially extending with respect to the outer joint member.    
   
   
       8 . The tripod type constant velocity universal joint according to  claim 7 , further comprising a first reduced-thickness portion and a second reduced-thickness portion, axially extending on an outer periphery of the outer joint member, and alternately aligned in a circumferential direction at positions equally dividing the circumference into six portions.  
   
   
       9 . The tripod type constant velocity universal joint according to  claim 8 , wherein the first reduced-thickness portion and the second reduced-thickness portion have generally the same cross-sectional shape taken orthogonally to an axial line of the outer joint member.