Wheel driving unit and method of manufacturing the same

Abstract

It is an object of the invention to provide a wheel-driving unit which is small in size and weight, can facilitate its assembling operation, and can prevent generation of jarring teeth striking sounds, and a method for manufacturing the same. The circumferential-direction widths of teeth respectively constituting a male spline portion ( 47 a ) formed in the outer peripheral surface of a spline shaft ( 17 ) and a female spline portion ( 48 a ) formed in the inner peripheral surface of a spline hole ( 14 ) are varied gradually in the respective axial directions of the male and female spline portions ( 47 a ), ( 48 a ). The directions where the widths of the teeth respectively constituting the male and female spline portions ( 47 a ) , ( 48 a ) increase in the axial direction are set so as to differ from each other, whereby the spline teeth respectively constituting the male and female spline portions ( 47 a ), ( 48 a ) are engaged with each other in a wedge-like manner. A retaining ring ( 33 b ) is bridgingly interposed between the outer peripheral surface of the outer end portion of the spline shaft ( 17 ) and the inner peripheral surface of the near-to-outer-end portion of the spline hole ( 14 ) to thereby prevent the spline shaft ( 17 ) from slipping out of the spline hole ( 14 ).

What is claimed is:  
     
         1 . A wheel-driving unit comprising a wheel-supporting bearing unit and a constant velocity joint unit connected together through a retaining ring, 
 said wheel-supporting bearing unit comprising:    an outer ring including a double row of outer raceways formed in the inner peripheral surface thereof and unrotatable even when it is in use;    a hub including a flange for supporting wheels in the near-to-outer-end portion of the outer peripheral surface thereof, and a first inner raceway formed directly or through a separately disposed inner ring in the middle portion thereof, with the inner ring including a second inner raceway formed in the outer peripheral surface thereof being fitted with and fixed to the outer surface of the near-to-inner-end portion of the outer peripheral surface of said hub;    rolling elements rollably interposed between one of said outer raceways and said first inner raceway as well as between the other of said outer raceways and said second inner raceway respectively by twos or more; and,    a first spline portion formed in said hub or in a portion of the peripheral surface of a member connected to and fixed to said hub,    said constant velocity joint unit comprising a differential-side constant velocity joint and a wheel-side constant velocity joint respectively connected to the both end portions of a drive shaft, said constant velocity joint unit further comprising a drive member including, in the outer end portion thereof, a second spline portion to be spline engaged with said first spline portion and also having an inner end portion formed as an outer ring for a constant velocity joint constituting said wheel-side constant velocity joint,    said retaining ring being formed so as to have an incomplete ring shape as a whole and enlargeable and reducible in diameter; and also, in a state where said first and second spline portions are spline engaged with each other, said retaining ring being bridgingly interposable between a first engaging portion formed in said hub or in a portion of the peripheral surface of a member connected and fixed to said hub and a second engaging portion formed in a portion of the peripheral surface of the outer end portion of said drive member to thereby prevent removal of the engagement between said first and second spline portions,    wherein the circumferential-direction widths of at least part of a plurality of teeth constituting at least one of said first and second spline portions are varied gradually in the axial direction of said spline portion, whereby, as said second spline portion is inserted into said first spline portion, said teeth are able to bite into the groove portions of its mating spline portion in a wedge-like manner.    
     
     
         2 . The wheel-driving unit as set forth in  claim 1 , wherein said first and second spline portions to be engaged with each other are respectively composed of a male spline portion formed in the outer peripheral surface of a spline shaft to be incorporated into the inside diameter side and a female spline portion formed in the inner peripheral surface of a spline hole to be incorporated into the outside diameter side for spline engagement with said male spline portion; the circumferential-direction widths of a plurality of teeth constituting said male spline portion are varied almost over the entire lengths of said teeth in a direction where they increase as they go backwardly in the insertion direction of said spline shaft, and the circumferential-direction widths of a plurality of teeth constituting said female spline portion are varied almost over the entire lengths of said teeth in a direction where they decrease as they go forwardly in the insertion direction of said spline shaft, whereby, as said spline shaft is inserted into said spline hole, said plurality of teeth constituting said male and female spline portions are able to bite into the groove portions of their mating spline portions in a wedge-like manner; and, at least one of said first and second engaging portions is worked on the basis of said male or female spline portion formed in said drive member or said hub or said member connected and fixed to said hub in which said one engaging portion is to be formed.  
     
     
         3 . A method for manufacturing a wheel-driving unit, wherein, when manufacturing a wheel-driving unit as set forth in  claim 2 , in a state where a female-side gauge including a female spline portion for gauging formed in the inner peripheral surface thereof is fitted with the outer surface of said male spline portion until they are engaged together with no clearance between them, a member including said male spline portion is assembled to a working apparatus with part of said female-side gauge as a basis thereof, and, of said first and second engaging portions, an inside engaging portion to be disposed on the inside diameter side is formed in the outer peripheral surface of a portion of said member using said working apparatus.  
     
     
         4 . A method for manufacturing a wheel-driving unit, wherein, when manufacturing a wheel-driving unit as set forth in  claim 2 , in a state where a male-side gauge including a male spline portion for gauging formed in the outer peripheral surface thereof is fitted with the inner surface of said female spline portion until they are engaged together with no clearance between them, a member including said female spline portion is assembled to a working apparatus with part of said male-side gauge as a basis thereof, and, of said first and second engaging portions, an outside engaging portion to be disposed on the outside diameter side is formed in the outer peripheral surface of a portion of said member using said working apparatus.  
     
     
         5 . The wheel-driving unit as set forth in  claim 1 , wherein, of said first and second spline portions to be engaged with each other, said second spline portion is a male spline portion formed by pressing in the outer peripheral surface of said spline shaft to be incorporated onto the inside diameter side, and the circumferential-direction widths of a plurality of teeth constituting said male spline portion are varied almost over the entire lengths of said teeth in a direction where said widths increase gradually as they go backwardly in the insertion direction of said spline shaft; said first spline portion is a female spline portion formed by pressing in the inner peripheral surface of said spline hole and engageable with said male spline portion, and the circumferential-direction widths of a plurality of teeth constituting said female spline portion are varied almost over the entire lengths of said teeth in a direction where said widths decrease gradually as they go forwardly in the insertion direction of said spline shaft at the same angle as said plurality of teeth constituting said male spline portion in the opposite direction thereto; and, as said spline shaft is inserted into said spline hole, said plurality of teeth constituting said male and female spline portions are allowed to bite into the groove portions of their mating spline portions in a wedge-like manner.  
     
     
         6 . The method for manufacturing a wheel-driving unit, wherein when working a male spline portion in the outer peripheral surface of a spline shaft so as to manufacture a wheel-driving unit as set forth in  claim 5 , in a blank member for forming said spline shaft, there is formed a conical-shaped taper shaft inclined in a direction where the outside diameter thereof existing backwardly in the insertion direction of said spline shaft in the spline engagement of said male spline portion with said female spline portion is larger than the outside diameter thereof existing forwardly in said insertion direction and, after then, according to a pressing operation in which a die including in the inner peripheral surface thereof a plurality of projecting strips such as female spline teeth having their circumferential-direction widths varying in such a direction as to increase gradually as they go backwardly in said insertion direction is pushed into said taper shaft to be formed into said spline shaft, said male spline portion formed is formed in the outer peripheral surface of said taper shaft, thereby forming said spline shaft the axial-direction outside diameter of which unvary; and, when working a female spline portion in the inner peripheral surface of a spline hole, in a portion of said spline hole inner peripheral surface which is to be worked into said female spline portion, there is formed a blank hole, that is, a conical-shaped taper hole having an inside diameter existing forwardly in the insertion direction of said spline shaft in the spline engagement of said spline hole with said spline shaft larger than an inside diameter existing backwardly in said insertion direction is formed and, after then, according to a pressing operation in which a punch including in the outer peripheral surface thereof a plurality of projecting strips such as male spline teeth having their circumferential-direction widths varying in such a direction as to increase gradually as they go backwardly in said insertion direction is pushed into said blank hole which is to be formed into said spline hole, thereby forming said spline hole the axial-direction inside diameter of which unvary.  
     
     
         7 . The wheel-driving unit as set forth in  claim 5 , wherein the diameter of such portion of said spline shaft as situated backwardly of and adjacently to said male spline portion in said insertion direction is larger than the diameter of the root circles of the teeth of the complete spline portions of said male spline portion.  
     
     
         8 . The wheel-driving unit as set forth in  claim 1 , wherein, of said first and second spline portions to be engaged with each other, said second spline portion is a male spline portion formed in the outer peripheral surface of said spline shaft to be incorporated onto the inside diameter side, and the circumferential-direction widths of a plurality of teeth constituting said male spline portion are varied almost over the entire lengths of said teeth in a direction where said widths increase gradually as they go backwardly in the insertion direction of said spline shaft; said first spline portion is a female spline portion formed in the inner peripheral surface of said spline hole and engageable with said male spline portion, and the circumferential-direction widths of a plurality of teeth constituting said female spline portion are varied almost over the entire lengths of said teeth in a direction where said widths decrease gradually as they go forwardly in the insertion direction of said spline shaft at the same angle as said plurality of teeth constituting said male spline portion in the opposite direction thereto; and, as said spline shaft is inserted into said spline hole, said plurality of teeth constituting said male and female spline portions are allowed to bite into the groove portions of their respective mating spline portions in a wedge-like manner, 
 and also wherein said retaining ring to be arranged between said first and second engaging portions is formed to have a corrugated shape or a polygonal shape in the circumferential direction thereof, whereby, in a plurality of portions of the inner peripheral edge portion of said retaining ring in the circumferential direction thereof, there are formed inwardly projecting portions respectively projecting more inwardly in the diameter portion of said retaining ring than the remaining portions thereof and, in a plurality of portions of the outer peripheral edge portion of said retaining ring in the circumferential direction thereof, there are formed outwardly projecting portions respectively projecting more outwardly in the diameter portion of said retaining ring than the remaining portions thereof.    
     
     
         9 . The wheel-driving unit as set forth in  claim 8 , wherein said first engaging portion is a securing groove or a securing stepped portion formed in the near-to-outer-end portion of the inner peripheral surface of said hub, and said second engaging portion is a securing groove formed in the outer peripheral surface of the outer end portion of said spline shaft.  
     
     
         10 . The wheel-driving unit as set forth in  claim 8 , wherein said first spline portion is a male spline portion formed in the outer peripheral surface of an intermediate seat fitted with and fixed to the outer surface of the inner end portion of said hub, said intermediate seat being formed integrally with or separately from an inner ring, said second spline portion is a female spline portion formed in the inner peripheral surface of the outer end portion of a drive member formed to have a substantially cylindrical shape as a whole, said first engaging portion is an inside-diameter-side securing groove formed in the outer peripheral surface of said inner ring or said intermediate seat, and said second engaging portion is an outside-diameter-side securing groove formed in the inner peripheral surface of the outer end portion of said drive member.  
     
     
         11 . A wheel-driving unit, comprising: 
 a differential-gear-side constant velocity joint connected to the output portion of a differential gear for transmitting the rotary motion of the output portion of said differential gear while securing the constant velocity property of said rotary motion;    a wheel-side constant velocity joint;    a drive shaft with said two constant velocity joints respectively connected to the two end portions thereof; and,    a wheel-supporting bearing unit connected to said wheel-side constant velocity joint for supporting wheels on the near-to-outer-end portion thereof,    wherein at least one of the following four connecting portions, that is, a connecting portion between the output portion of said differential gear and said differential-gear-side constant velocity joint, a connecting portion between said differential-gear-side constant velocity joint and one end portion of said drive shaft, a connecting portion between the other end portion of said drive shaft and said wheel-side constant velocity joint, and a connecting portion between said differential-gear-side constant velocity joint and said wheel-supporting bearing unit, is formed by spline engaging said first and second spline portions with each other; and, the circumferential-direction both-side surfaces of at least one of first and second spline teeth respectively constituting said first and second spline portions are inclined almost over the entire length of said spline portion with respect to the direction of the center axis of a member including said spline portion in a direction where the circumferential-direction widths of said spline teeth increase as they go toward the insertion-direction backward portions in which, when said first and second spline portions are spline engaged with each other, said spline portion is engaged with its mating spline portion relatively later.