Abstract:
A constant velocity joint structure including an inner joint member, a retaining ring, and a shaft which are configured to prevent the shaft from being withdrawn from the inner joint member when a pulling force is applied to one side of the shaft is disclosed. A retaining ring groove is disposed at an opposite side of the shaft. In a preferred embodiment, the retaining groove has at least two points which contact an inner surface of the retaining ring when the pulling force is applied to prevent the retaining ring from contracting in a radial direction, thereby preventing the shaft from being withdrawn from the inner joint member.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   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 equipment. 
   2. Description of the Related Art 
   In conventional constant velocity joints for a driving system or the like of automobiles, an inner joint member and a shaft are engaged detachably, and a structure for preventing the shaft from coming off is employed for reduction of the maintenance man-hours for replacement of boots or the like. In this structure, a groove is formed at an end face of the shaft, a retaining ring is provided in 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 corner is provided on the contacting face to interfere with the retaining ring when the shaft is pulled out, and disengagement is performed by radially contracting the retaining ring by a component force of the interference force with the retaining ring (see Japanese Unexamined Patent Publication No. 08-68426, Japanese Utility Model Publication No. 64-5124). 
   There is a demand for a structure for connecting a shaft and an inner joint member so that they cannot be disassembled once built. 
   A structure according to Japanese Unexamined Patent Publication No. 08-68426 is such that a retaining ring is provided at a non-end face side of a shaft and a groove for inserting a tool for contracting a retaining ring is provided at an end face of an inner joint member, thereby allowing assembly and disassembly. However, this mechanism requires much time and forming the tool engagement groove on the inner joint member is expensive. 
   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 in a sidewall for effecting two types of configurations where one allows a shaft to be pulled out and the other does not. 
   SUMMARY OF THE INVENTION 
   Considering the aforementioned problems, the present invention provides a structure adapted to bring about two functions without increasing the number of 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. The present invention provides a structure for preventing a shaft of constant velocity joint from coming off. The structure comprises an inner joint member 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 the retaining ring groove that can be elastically expanded and contracted. In the invention, since 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 usually be pulled out when a pulling force is applied to the shaft. The structure of the invention comprises at least two contacting points in a sidewall of the retaining ring groove, which is located at a side of the shaft opposite to the side at which the pulling force is applied shaft. 
   The contacting points prevent the retaining ring from contracting when a force is applied to the shaft in a pulling out direction because the 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. 
   The present invention further comprises a step part on one side of the retaining ring groove that is opposite to the side of the shaft to which the pulling force is applied. The step part has a depth less than the thickness of the retaining ring. 
   The shaft and the inner joint member are coupled with a spline section. The shaft cannot be pulled out because the retaining ring and its groove are located outside the spline section of the inner joint member and the retaining ring is sandwiched between the at least two contacting points of the groove and the slope part of the insertion hole, thereby preventing inward movement of the ring. 
   As the shaft is inserted into and coupled with the insertion hole of the inner joint member through the spline section, the retaining ring groove is located in the range of a slope part formed in the spline section of the inner joint member which faces toward the retaining ring groove wall of the shaft. 
   With this configuration, even when a force is applied to one side of the shaft in a pulling out direction, the slope part formed in the spline section of the inner joint member, and the at least two contacting faces formed on a side wall of the retaining ring groove located at the opposite side of the shaft, 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. 
   With the present invention, when a force is applied to the shaft in a pulling out direction, a 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. Thus, a structure for preventing disassembly of the inner joint member and the shaft can be produced simply. 
   Accordingly, it is possible to produce a structure which allows disassembly and a structure that prevents disassembly based on the structure of a side wall of a retaining ring groove formed on a shaft without employing a particular inner joint member and a particular retaining ring. Therefore, shared use of parts is made possible, thereby reducing the man-hours required for parts control. 
   In order to allow disassembly of an inner joint member and a shaft, with the at least two contacting faces on a side wall of a retaining ring groove of a shaft, and the 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 are not provided. Thus, when a force is applied to the shaft in a pulling out direction, the diameter of the retaining ring is contracted, the retaining ring is moved in the insertion hole, and the retaining ring does not prevent disassembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary sectional view of a constant velocity joint showing embodiment of the present invention. 
       FIG. 2  is an enlarged view of part A in  FIG. 1 . 
       FIG. 3  is a perspective view of retaining ring shown in  FIG. 1 . 
       FIG. 4  is a sectional view showing a shaft pulled out state corresponding to  FIG. 2 . 
       FIG. 5  is a sectional view showing a retaining ring corresponding to  FIG. 2  in sandwiched state. 
       FIG. 6  is a sectional view showing a first embodiment of a retaining ring groove illustrated in  FIG. 2 . 
       FIG. 7  is a sectional view showing a second embodiment of a retaining ring groove illustrated in  FIG. 2 . 
       FIG. 8  is a sectional view showing a retaining ring groove illustrated in  FIG. 2  in a different position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1  to  FIG. 8 , the embodiments of the present invention will be explained. For convenience of explanation, “front edge side” denotes the left side in the drawings and “anti-front edge side” denotes the right side in the drawings. 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 as an inner ring. 
   As shown in  FIG. 1 , the 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 is not limited to the fixed type constant velocity joint  1 , and may be a sliding movement type constant velocity joint such as a double-offset type, a cross-groove type, a tripod type, or the like. The inner joint member in the double-offset type and the cross-groove type are also referred to as the inner ring, while the inner joint member in the tripod type is referred to as a trunnion. 
   A curved guide groove  7  is formed on a spherical inside diameter surface of the outer ring  2  in a circumferential direction at regular intervals. A curved guide groove  8  is formed on a spherical outside diameter surface of the inner joint member  3  in a 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 . 
   As shown in  FIG. 2 , an insertion hole  9  for engagement with the shaft  6  is formed on the inner joint member  3  in an axial direction. A spline  10  is formed on an inner circumferential surface of insertion hole  9 . When the spine  10  is engaged with a spline  11  formed on the shaft  6 , the inner joint member  3  and the shaft  6  are transmittably coupled. The distance L 3  corresponds to the distance between the inner radial limit of shaft spine  11  and the inner radial limit of joint member spine  10 . 
   The front edge side of the shaft  6  of the insertion hole  9  is subjected to diameter expansion processing as shown in  FIG. 2 , and a hole  12  having diameter larger than the insertion hole  9  is formed. The hole  12  is continuous with a tapered, terminal part  10   a  of the spline  10  via a slope surface  12   a.    
   A retaining ring groove  13  having a ring shape is formed at a 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 greater 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 ). With this configuration, when the shaft  6  is inserted into the insertion hole  9  of the inner joint member  3  from right to left, as shown in  FIG. 4 , it is possible to cause the retaining ring  14  to contract to a diameter less than a minor diameter of the spline  10  of the inner joint member  3 . 
   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. 
   On a wall  13   a  at a front edge side of the retaining ring groove  13  (side wall at the side of the shaft opposite to the side to which the pulling force is applied) 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 a corner  13   c . This step part  13   d  has a depth L 4  in radial direction of the shaft  6 , and a width W 2  in axial direction, both of which are smaller than wire diameter L 2  of the retaining ring  14  (L 2 &gt;L 4 , L 2 &gt;W 2 ). The step part  13   d  has a radial direction dimension L 4  that is smaller than wire diameter L 2  of the retaining ring  13 , and an axial direction dimension W 2  that is smaller than the same. 
   An inner surface of the retaining ring  14  (a center side surface since the retaining ring  14  is being formed in a ring-shape), is designated by arrow  14   a  in  FIG. 3 . The inner surface  14   a  is a half circle for a ring having a circular cross section, and includes the boundary between the lower surface and the upper surface of the retaining ring. 
   When L 2 ≦L 3 , since the retaining ring  14  is accommodated within the step part  13   d , the function for preventing the shaft from coming off is lost. Further, as shown in  FIG. 2 , the retaining ring  14  does not interfere with the inner diameter of the inner joint member spline  10 . Besides, when L 2 ≦W 2 , the 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. 
   As for attachment of the shaft  6  to the inner joint member  3 , the shaft  6  is inserted into the insertion hole  9  while the retaining ring  14  is disposed in the retaining ring groove  13  and diameter contracted. On this occasion, the retaining ring  14  moves in a sliding state while making elastic contact with the spline  10  of the insertion hole  9  (arrow A direction in  FIG. 4 ). 
   When the 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 the anti-front edge side of the insertion hole  9  makes contact with a part  6   a  of the shaft  6 , and further insertion is prevented. Alternatively, a retaining ring may be mounted separately to regulate the length of the shaft  6  inserted, in which case the retaining ring makes contact with the anti-front edge side of the insertion hole  9 , thereby preventing further insertion. 
   At the point of time when insertion of the shaft  6  into the insertion hole  9  is ceased, the retaining ring  14  is no longer in contact with spline  10 , and positioned at the hole  12 , which has a larger diameter. Therefore, the diameter is expanded elasticity. When the diameter of the retaining ring  14  is expanded, an outer circumferential 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 becomes attached to the inner joint member  3 . 
   At this state, the retaining ring  14  is not expanded completely and is positioned within an engagement range of the splines  10  and  11 , while making contact with the peripheral wall of the hole  12  and the tapered part  10   a.    
   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 horizontally from the position illustrated  FIG. 2  to the position illustrated in  FIG. 5  (this means movement in a direction of disengagement of splines  10  and  11 ). At this moment, a surface positioned at the 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 . At the same time, the 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 the terminal part 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. 
   The retaining ring  14  contacts the perpendicular wall  13   b  at the boundary between its inner surface  14   a  and its upper surface  14   b . The lower surface  14   a  of the retaining ring contacts the corner  13   c  at a lower left circular arc surface, i.e. the quarter area corresponding to the area from the six o&#39;clock position to the nine o&#39;clock position in  FIG. 5 . 
   The perpendicular wall  13   b  formed at the 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 the terminal part 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. 
   When a pulling force is applied to the shaft, the perpendicular wall  13   b , 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   b  and the corner  13   c . Thus, the retaining ring  14  cannot be entered in the retaining ring groove  13  and locked. As a result, the shaft  6  cannot be pulled out. 
   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 by the tapered part  10   a  and slope surface  12   a  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 . 
   As mentioned above, the step part  13   d  is obvious since 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 non-removable, thereby reducing the man-hours required for parts control. 
   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 by contracting the retaining ring and inserting the same into the insertion hole of the inner joint member  3 . 
   Also, the 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 formed by the perpendicular wall  13   b  and the corner  13   e  shown in  FIG. 6 , or by the perpendicular wall  13   b  and the circular arc surface  13   f  shown in  FIG. 7  can also provide at least two contacting parts. Although the step part  13   d  has been explained based on two contacting parts, it is possible to increase the number of contacting parts depending on the profile of step part. 
   Furthermore, the hole 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 hole  15  is provided in the middle of the spline  10 . This hole  15  and the retaining ring  14  are disposed opposedly so that a part of the retaining ring  14  can be introduced into the hole  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 an anti-front side of the hole  15 . If a wall  15   a  is tilted so that the open side of the hole is widened in similar fashion as the slope surface  12   a  being continuous with the tapered part  10   a  of the spline  10 , as the operations attained by the structure illustrated in  FIG. 2  are also obtained.