Abstract:
The present invention presents a structure for preventing a shaft of constant velocity joint from coming off which allows changing design of connection between the shaft and an inner joint member to a type for disassembly or anti-disassembly. The anti-disassembly type is realized in such a manner that a wall at an opposite side to a shaft pulling out direction of a retaining ring groove of the shaft is used as a contacting part to a retaining ring, wherein at least two points are formed on the contacting part, one of which is on a perpendicular surface and the other is a corner of the contacting part, these two points are contacted with an inner surface of the retaining ring thereby provides the anti-disassembly type for preventing the ring from being contracted in a radial direction.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a spline engagement structure for coupling an inner joint member with a shaft of constant velocity joints used in automobiles and various industrial equipments,.  
       BACKGROUND OF THE INVENTION  
       [0002]     In conventional constant velocity joints for driving system or the like of automobiles, an inner joint member and a shaft are engaged detachably while employing a structure for preventing the shaft from coming off for reduction of maintenance man-hours of replacement of boots or the like. With this structure, a groove is formed at end face of the shaft, a retaining ring is provided to this groove, and the shaft is engaged with a contacting face being formed on the inner joint member by means of elastic expansion of the retaining ring. A mechanism used here is such that a corner is provided to a contacting face that interferes with the retaining ring when the shaft is pulled out, and disengagement is performed by radially contracting the retaining ring by component force of interference force with the retaining ring (see Japanese Unexamined Patent Publication No. 08-68426, Japanese Utility Model Publication No. 64-5124).  
       SUMMARY OF THE INVENTION  
       [0003]     There is a demand for a structure for connecting a shaft and an inner joint member that they should be anti-disassembly once built and disassembly.  
         [0004]     A structure according to Japanese Unexamined Patent Publication No. 08-68426 is such that a retaining ring is provided at non-end face side of a shaft and a groove for inserting a tool for contracting a retaining ring is provided at end face of an inner joint member, thereby allowing assembly and disassembly. However, this mechanism requires much time and expenses to machine the tool engagement groove on the inner joint member.  
         [0005]     Further, Japanese Utility Model Publication No. 64-5124 discloses a structure for contracting a retaining ring thereby allowing a shaft to be pulled out. The publication, however, does not show how to manage an angle of a groove sidewall for effecting two types of configurations where the one allows a shaft to be pulled out and the other does not.  
         [0006]     Considering the aforementioned problems, the present invention presents a structure adapted to bring about two functions without increasing inside joint members, one of which prevents a shaft from coming off once the joint is assembled and the other allows a shaft to be pulled out.  
         [0007]     The present invention provides a structure for preventing a shaft of constant velocity joint from coming off where the structure comprises an inner member of constant velocity joint having an insertion hole to be engaged with a shaft, a shaft having a ring-shaped retaining ring groove, and a retaining ring located within said retaining ring groove that can be elastically expanded and contracted. In the invention, when a pulling force is applied to the shaft, as the retaining ring is disposed between a slope part formed in an insertion hole of the inner joint member and the retaining groove, the shaft cannot be pulled out usually. The structure of the invention comprises at least two contacting points in a sidewall of the retaining ring groove, which is opposite to the direction for pulling out the shaft.  
         [0008]     Those contacting portions prevent the retaining ring to be contracted when a force is applied to the shaft in a pulling out direction because said two contacting points contact the inner surface of the retaining ring thereby preventing the contracting movement of the ring. Thus the shaft cannot be pulled out.  
         [0009]     The present invention further comprises a step part on one side of the retaining ring groove that is opposite to the pulling out direction of the shaft. The step part has a depth shorter than the thickness of the retaining ring.  
         [0010]     The shaft and the inner joint member are coupled with spline section. The shaft cannot be pulled out as the retaining ring and its groove are located outside the spline section of the inner joint member and the retaining ring is sandwiched by the at least two contacting points of the groove and the slope part of the insertion hole thereby preventing inward movement of the ring.  
         [0011]     As the shaft is inserted to and coupled with the insertion hole of said inner joint member through the spline section, the retaining ring groove is located in the range of the spline section of the inner joint member so that the retaining ring groove of the inner joint member forms a slope part to the retaining ring with facing to a retaining ring groove wall of the shaft.  
         [0012]     With this configuration, even when a force is applied to the shaft in a pulling out direction, the slope part formed in the spline section of the inner joint member, at least two contacting faces formed on a side wall of the retaining ring groove at an opposite side of a shaft pulling out direction, or the step part contact with an inner surface of the retaining ring and sandwich the retaining ring thereby surely preventing movement in a radial contracting direction.  
         [0013]     With the present invention, when a force is applied to the shaft in a pulling out direction, lower surface side of the retaining ring and at least two contacting faces of the retaining ring groove, or the step part make contact, and therefore, movement of the retaining ring in a radial contracting direction is prevented, and specification with which disassembly of the inner joint member and the shaft is not possible can be produced simply.  
         [0014]     Accordingly, it is possible to produce specification with which disassembly is possible by a structure of a side wall of a retaining ring groove formed on a shaft without constituting an inner joint member and a retaining ring each as exclusive member, and specification with which disassembly is not possible, and therefore, shared use of parts is made possible thereby reducing man-hours required for parts control.  
         [0015]     In order to obtain specification which allows disassembly of an inner joint member and a shaft, with specification free from at least two contacting faces on a side wall of a retaining ring groove of a shaft, and step part, by which such a force is given to move the retaining ring in a radial contracting direction using slope part at inner joint member side as slope surface, when a force is applied to the shaft in a pulling out direction, diameter of the retaining ring is contracted, the retaining ring is moved in the insertion hole, and prevention by the retaining ring can be prevented.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a fragmentary sectional view of a constant velocity joint showing embodiment of the present invention.  
         [0017]      FIG. 2  is an enlarged view of part A in  FIG. 1 .  
         [0018]      FIG. 3  is a perspective view of retaining ring shown in  FIG. 1 .  
         [0019]      FIG. 4  is a sectional view showing a shaft pulled out state corresponding to  FIG. 2 .  
         [0020]      FIG. 5  is a sectional view showing a retaining ring corresponding to  FIG. 2  in sandwiched state.  
         [0021]      FIG. 6  is a sectional view showing one embodiment of a retaining ring groove corresponding to  FIG. 2 .  
         [0022]      FIG. 7  is a sectional view showing one embodiment of a retaining ring groove corresponding to  FIG. 2 .  
         [0023]      FIG. 8  is a sectional view showing a retaining ring groove corresponding to  FIG. 2  in different position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Referring now to  FIG. 1  to  FIG. 8 , embodiments of the present invention will be explained hereafter. For convenience of explanation, front edge side denotes left side on the drawing and anti-front edge side denotes right side on the drawing. For convenience, explanations will be given referring to a fixed type constant velocity joint as shown in  FIG. 1  in which the inner joint member is also referred to also as an inner ring.  
         [0025]     As shown in  FIG. 1 , fixed type constant velocity joint  1  comprises outer ring  2 , inner joint member  3 , torque transmission ball  4 , and cage  5  for torque transmission ball  4 . Further, shaft  6  for transmitting torque is mounted to the inner joint member  3  in an engaging manner. The constant velocity joint, not limited to the fixed type constant velocity joint  1 , may be sliding movement type constant velocity joint such as double-offset type, cross-globe type, tripod type or the like. Meanwhile, inner joint member in the double-offset type and cross-globe type are also referred to as the inner ring, while inner joint member in the tripod type are those referred to as a trunnion.  
         [0026]     With the outer ring  2 , a guide groove  7  in curved form is being formed on inside diameter surface in spherical form in circumferential direction at regular intervals. With the inner joint member  3 , a guide groove  8  in curved form is being formed on outside diameter surface in spherical form in circumferential direction at regular intervals. The torque transmission ball  4  is built into a ball track formed by the guide groove  7  of the outer ring  2  and the guide groove  8  of the inner joint member  3 .  
         [0027]     As shown in  FIG. 2 , an insertion hole  9  for engagement with the shaft  6  is formed on the inner joint member  3  in axial direction. A spline  10  is formed on inner circumference surface of insertion hole  9  and when engaged with a spline  11  formed on the shaft  6 , the inner joint member  3  and the shaft  6  are transmittably coupled.  
         [0028]     The front edge side of the shaft  6  of the insertion hole  9  is subjected to diameter expansion processing and as shown in  FIG. 2 , a hole  12  having diameter larger than the insertion hole  9  is being formed. The hole  12  is continuous with a tapered part  10   a  of termination of the spline  10  via a slope surface  12   a.    
         [0029]     A retaining ring groove  13  in ring shape is being formed at front edge side of the shaft  6 . As shown in  FIG. 2 , depth L 1  and width W 1  of this retaining ring groove  13  are made larger than wire diameter L 2  of a retaining ring  14  for preventing a breakaway of the inner joint member  3  and the shaft  6  (L 1 &gt;L 2 , W 1 &gt;L 2 ). W 1 th this configuration, when inserting the shaft  6  into the insertion hole  9  of the inner joint member  3  from right to left on  FIG. 4 , it is possible to cause diameter contraction of the retaining ring  14  less than a minor diameter of the spline  10  of the inner joint member  3 .  
         [0030]     As shown in  FIG. 3 , although the retaining ring  14  has a ring shape, it is cut in part so that it may be inserted into the retaining ring groove  13  after diameter contraction.  
         [0031]     To a wall  13   a  at front edge side of the retaining ring groove  13  (side wall at an opposite side of a shaft pulling out direction) are formed a wall  13   b  perpendicular to an axis line to which an inner surface  14   a  of the retaining ring  14  makes contact when a force is applied to the shaft  6  in a pulling out direction and an orthogonal step part  13   d  which forms an corner  13   c.  This step part  13   d  has depth L 3  in radial direction of the shaft  6  and width W 2  in axial direction both of which are designed to be smaller than wire diameter L 2  of the retaining ring  14  (L 2 &gt;L 3 , L 2 &gt;W 2 ). Namely, the step part  13   d  is being formed by radial direction dimension L 3  that is smaller than wire diameter L 2  of the retaining ring  13  and axial direction dimension W 2  that is smaller than the same.  
         [0032]     An inner surface of the retaining ring  14  denotes a center side surface since the retaining ring  14  is being formed in ring-shape, and a range shown by an arrow  14   a  in  FIG. 3  is meant. The range of this arrow  14   a  becomes a half circle for circular section case and includes a boundary between lower surface and upper surface.  
         [0033]     When L 2 ≦L 3 , as the retaining ring  14  is accommodated within the step part  13   d,  a function for preventing the shaft from coming off is lost. Besides, when L 2 ≦W 2 , width of the retaining ring  13  becomes larger and an idle space where the shaft  6  can move in right and left directions in  FIG. 2  becomes large which is not practical.  
         [0034]     As for attachment of the shaft  6  to the inner joint member  3 , the shaft  6  is inserted to the insertion hole  9  while the retaining ring  14  is disposed to the retaining ring groove  13  and the retaining ring  14  is being diameter contracted. On this occasion, the retaining ring  14  moves in sliding state while making elastic contact with the spline  10  of the insertion hole  9  (arrow A direction in  FIG. 4 ).  
         [0035]     When front edge of the shaft  6  reaches a position passing through the insertion hole  9  (virtually, a position where contact with the spline  10  is lost), an end  9   a  at anti-front edge side of the insertion hole  9  makes contact with a part  6   a  of the shaft  6  and insertion is blocked. Alternatively, a retaining ring may be mounted separately to regulate insertion length of the shaft  6  in which case the retaining ring makes contact with anti-front edge side of the insertion hole  9  thereby preventing further insertion.  
         [0036]     At the point of time when insertion of the shaft  6  into the insertion hole  9  is ceased, the retaining ring  14  is positioned at the hole  12  with larger diameter getting away from contact with the spline  10 , and therefore, diameter is expanded by elasticity. When the retaining ring  14  is diameter expanded, an outer circumference surface of the retaining ring  14  comes to contact with a peripheral wall of the hole  12  by elastic force, and therefore, the shaft  6  is brought into such that it is attached to the inner joint member  3 .  
         [0037]     At this state, the retaining ring  14  is not expanded completely and is positioned within an engagement range of the spline  10 ,  11  while making contact with the peripheral wall of the hole  12  and tapered part  10   a.    
         [0038]     Therefore, when a force (arrow B direction in  FIG. 5 ) is applied to the shaft  6  in a pulling out direction, the shaft  6  moves in parallel from  FIG. 2  state to  FIG. 5  state (this means movement in a direction of disengagement of spline  10 ,  11 ), while at this moment, a surface positioned at front edge side of the lower surface  14   a  of the retaining ring  14  makes contact with two points, the perpendicular wall  13   b  of the step part  13   d  and the corner  13   c,  and at the same time, anti-front edge side of the upper surface  14   b  of the retaining ring  14  makes contact with either the tapered part  10   a  formed at termination of the spline  10  of the inner joint member  3  or the slope part  12   a,  and the retaining ring  14  is brought into sandwiched state.  
         [0039]     A contact with the perpendicular wall  13   b  takes place at a boundary between an inner surface  14   a  and an upper surface  14   b  of the retaining ring  14 . A contact with the corner  13   c  takes place at a lower left circular arc surface, quarter area corresponding to from six o&#39;clock to nine o&#39;clock of a clock, in  FIG. 5  of the lower surface  13   a  of the retaining ring  13 .  
         [0040]     The perpendicular wall  13   b  formed at front edge side of the retaining ring groove  13  and the corner  13   c  act as a contacting face of the shaft side and the tapered part  10   a  at termination of the spline  10  or the slope part  12   a  act as a slope part of the insertion hole  9  at inner joint member  3  side.  
         [0041]     When a force is applied to the perpendicular wall  13   b  in a direction of pulling out the retaining ring  14 , an inward force is applied to the retaining ring by a slope part (tapered part  10   a  or slope part  12   a ) to urge the ring to be contracted in a direction toward the center of the shaft. However, the contraction movement of the ring is prevented by the contacting part of the retaining ring groove  13 , i.e., the perpendicular wall  13   c  and the corner  13   c.  Thus the retaining ring  14  cannot be entered in the retaining ring groove  13  as being locked. As a result, the shaft  6  cannot be pulled out.  
         [0042]     In the case where the shaft  6  needs to be removed from the inner joint member  3 , the step part  13   d  in the retaining ring groove  13  of the shaft  6  is not necessary. If the step part  13   d  is not formed and a force is applied to the shaft  6  in a pulling out direction, the retaining ring  14  is urged to be contracted by the tapered part  10   a  and slope surface  12   a  thereby entered into the retaining ring groove  13 . As a result, the shaft  6  can be removed in a direction opposite to arrow A in  FIG. 4 .  
         [0043]     As mentioned above, the step part  13   d  is obvious at a glance as the step  13  is formed in the retaining ring groove  13  of the shaft  6 . To render the shaft  6  removable, the step part  13   d  in the retaining ring groove  13  of the shaft  6  should be abolished. The appearance of the shaft provides a clear recognition if the shaft is removable or not. Further, common use of inner joint member can be accomplished in each construction where the shaft is removable or anti removable, thereby reducing man-hours required for parts control.  
         [0044]     When assembling the inner joint member  3  and the shaft  6 , no special structure for preventing the removal of the shaft is needed and the conventional way of assembling can be simply used with contracting the retaining ring and inserting the same into the insertion hole of the inner joint member  3 .  
         [0045]     Besides, profile of the step part  13   d  may not necessarily be formed by the perpendicular wall  13   b  and the corner  13   c  as shown in  FIG. 1 . For example, a profile by the perpendicular wall  13   b  and the corner  13   e  as shown in  FIG. 6  or by the perpendicular wall  13   b  and the circular arc surface  13   f  as shown in  FIG. 7  can also provide at least two contacting parts. Although this step part  13   d  has been explained based on two contacting parts in the embodiment, it is possible to increase the number of contacting parts depending on a profile of step part.  
         [0046]     Furthermore, the retaining ring groove  13  may be located anywhere within a range of the insertion hole  9  of the inner joint member  3 . For example, as shown in  FIG. 8 , a groove  15  is provided in the middle of the spline  10 , this groove  15  and the retaining ring  13  are disposed opposedly so that a part of the retaining ring  14  can be introduced into the groove  15 . In this configuration, the structure of the retaining ring groove  13  is the same as that in  FIG. 2  and a slope part of the inner joint member  3  forms a wall  15   a  at anti-front side of the groove  15 . If a wall  15   a  is tilted so that the open side of the groove is widened in similar fashion as the slope surface  12   a  being continuous with the tapered part  10   a  of the spline  10 , operational effects as attained in  FIG. 2  are also obtained.