Method of manufacturing resin boots for constant velocity universal joint and resin boots for constant velocity universal joint

Abstract

A large thickness portion molding space which forms a large thickness portion and a small thickness portion molding space which forms a small thickness portion form a secondary molding space connecting in the circumferential direction between an outer periphery of a core positioned in a large diameter side end portion of a resin bellows and an inner surface of the large diameter side end portion. A molten material for secondary molding is injected into the each small thickness portion molding space, and the molten material is charged in the secondary molding space. The molten material charged in the secondary molding space is cured, whereby the large thickness portion and the small thickness portion are welded and integrated in the inner surface of the large diameter side end portion.

1 . A method of manufacturing resin boots for constant velocity universal joint in which an inner surface of a large diameter side end portion is provided with large thickness portions and small thickness portions thinner than the large thickness portions in its diametrical direction, comprising: 
 a step of preparing resin bellows primarily molded into entirely an approximately conical shape and the resin bellows including an approximately conical bellows-shaped portion with its inner hollow part, a small diameter end portion communicated with an inner space of the bellows-shaped portion and arranged at one end, and the large diameter side end portion communicated with the inner space of the bellows-shaped portion and arranged at the other end;    a secondary molding step in which the large thickness portions arranged in a circumferential direction in approximately equal space and the small thickness portions arranged between the large thickness portions are welded and integrated in the inner surface of the large diameter side end portion of the resin bellows;    the secondary molding step including:    a first step of holding the resin bellows in a mold and forming a secondary molding space in which large thickness molding spaces for molding the large thickness portions and small thickness molding spaces for molding the small thickness portions are communicated to each other in their circumferential direction between an outer peripheral surface of a core mold positioned in the large diameter side end portion of the resin bellows and an inner surface of the large diameter side end portion;    a second step of injecting molten material for secondary molding from pin gates arranged in an approximately center in the circumferential direction of the each small thickness molding spaces into each of the small thickness portion molding spaces and for charging the molten material into the secondary molding space; and    a third step in which the molten material charged in the secondary molding space is cured, and the large thickness portions and the small thickness portions are welded and integrated in the inner surface of the large diameter side end portion.    
   
   
       2 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein the second step injects the molten material from the end surface sides of the small thickness portions into each of the small thickness portion molding spaces.  
   
   
       3 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein the second step injects the molten material into each of the small thickness portion molding spaces approximately at the same time.  
   
   
       4 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein the first step includes fitting an outer circumference of the core mold into an inner surface of a boundary between the large diameter side end portions of the resin bellows and the end portion of the bellows-shaped portion.  
   
   
       5 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein the inner surfaces of the large diameter side end portions of the resin bellows primarily molded are formed with at least one or more of convex portions and recess portions lying in a circumferential direction of the inner surfaces.  
   
   
       6 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein, in the second step, an orientation θ of the pin gates is set to 0°≦θ≦90° in respect to the inner surface of the large diameter side end portion and at the same time when a distance between the inner surface of the large diameter side end portion and the center of the pin gate is set to t, and a diametrical distance of the injection side end portion of the secondary molding space is set to a, the molten material is brought into slidable contact with the inner surface of the large diameter side end portion with the position of the injection gate being set to 0≦t≦2a/3.  
   
   
       7 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein, in the first step, the secondary molding spaces are formed near the large diameter side end portions rather than a boundary portion between the large diameter side end portions of the resin bellows and the end portions of the bellows-shaped portion.  
   
   
       8 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 1 , wherein further comprising: a step of inserting and arranging one or two pins while being spaced apart in the large thickness molding spaces before the second step; and one or two holes are formed in the large thickness portion.  
   
   
       9 . A resin boot for constant velocity universal joint in which an inner surface of a large diameter side end portion is provided with large thickness portions and small thickness portions thinner than the large thickness portions in its diametrical direction, comprising: 
 the resin bellows primarily molded into entirely an approximately conical shape and the resin bellows including an approximately conical bellows-shaped portion with its inner hollow part, a small diameter end portion communicated with an inner space of the bellows-shaped portion and arranged at one end, and the large diameter side end portion communicated with the inner space of the bellows-shaped portion and arranged at the other end;    the large thickness portions arranged in a circumferential direction in approximately equal space in the inner surface of the large diameter side end portion of the resin bellows; and    the small thickness portions arranged between the large thickness portions in the inner surface of the large diameter side end portion of the resin bellows,    wherein the large thickness portions and the small thickness portions are welded and integrated in the inner surface of the large diameter side end portion by curing the molten material injected from an approximately center in the circumferential direction of the each small thickness portion.    
   
   
       10 . The resin boots for constant velocity universal joint, which is manufactured by the manufacturing method according to  claim 1 .  
   
   
       11 . A method of manufacturing resin boots for constant velocity universal joint in which an outer surface of a large diameter side end portion is provided with large thickness portions and small thickness portions thinner than the large thickness portions in its diametrical direction, comprising: 
 a step of preparing resin bellows of entirely approximately conical shape and with the large diameter side end portion being primarily molded into entirely an approximately similar shape to that of an outer peripheral surface of an outer case of the constant velocity universal joint and the resin bellows including an approximately conical bellows-shaped portion with its inner hollow part, a small diameter end portion communicated with an inner space of the bellows-shaped portion and arranged at one end, and the large diameter side end portion communicated with the inner space of the bellows-shaped portion and arranged at the other end, and    a secondary molding step in which the large thickness portions arranged in a circumferential direction in approximately equal space and the small thickness portions arranged between the large thickness portions are welded and integrated in the outer surface of the large diameter side end portion of the resin bellows;    the secondary molding step including;    a first step of holding the resin bellows in a mold and forming a secondary molding space in which large thickness molding spaces for molding the large thickness portions and small thickness molding spaces for molding the small thickness portions are communicated to each other in their circumferential direction between an inner peripheral surface of a core mold positioned outside the large diameter side end portion of the resin bellows and an outer surface of the large diameter side end portion;    a second step of injecting molten material for secondary molding from pin gates arranged in an approximately center in the circumferential direction of the each small thickness molding spaces into each of the small thickness portion molding spaces and for charging the molten material into the secondary molding space and;    a third step in which the molten material charged in the secondary molding space is cured, and the large thickness portions and the small thickness portions are welded and integrated in the outer surface of the large diameter side end portion.    
   
   
       12 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 11 , wherein the second step injects the molten material from the end surface sides of the small thickness portions into each of the small thickness portion molding spaces.  
   
   
       13 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 11 , wherein the second step injects the molten material into each of the small thickness portion molding spaces approximately at the same time.  
   
   
       14 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 11 , wherein, in the second step, an orientation θ of the pin gates is set to 0°≦θ≦90° in respect to the outer surface of the large diameter side end portion and at the same time when a distance between the outer surface of the large diameter side end portion and the center of the pin gate is set to t, and a diametrical distance of the injection side end portion of the secondary molding space is set to a, the molten material is brought into slidable contact with the outer surface of the large diameter side end portion with the position of the injection gate being set to 0≦t≦2a/3.  
   
   
       15 . The method of manufacturing resin boots for constant velocity universal joint according to  claim 11 , further comprising: a step of inserting and arranging one or two pins while being spaced apart in the large thickness molding spaces before the second step; and one or two holes are formed in the large thickness portion.  
   
   
       16 . A resin boot for constant velocity universal joint in which an outer surface of a large diameter side end portion is provided with large thickness portions and small thickness portions thinner than the large thickness portions in its diametrical direction, comprising: 
 the resin bellows of entirely approximately conical shape and with the large diameter side end portion being primarily molded into entirely an approximately similar shape to that of an outer peripheral surface of an outer case of the constant velocity universal joint and the resin bellows including an approximately conical bellows-shaped portion with its inner hollow part, a small diameter end portion communicated with an inner space of the bellows-shaped portion and arranged at one end, and the large diameter side end portion communicated with the inner space of the bellows-shaped portion and arranged at the other end, and    the large thickness portions arranged in a circumferential direction in approximately equal space in the outer surface of the large diameter side end portion of the resin bellows; and    the small thickness portions arranged between the large thickness portions in the outer surface of the large diameter side end portion of the resin bellows,    wherein the large thickness portions and the small thickness portions are welded and integrated in the outer surface of the large diameter side end portion by curing the molten material injected from an approximately center in the circumferential direction of the each small thickness portion.    
   
   
       17 . The resin boots for constant velocity universal joint, which is manufactured by the manufacturing method according to  claim 11.