Abstract:
A constant velocity joint assembly comprises outer and inner joint members having engaging contact surfaces which support the joint for articulation about a common center point. The joint members have ball grooves which diverge inwardly of the joint and whose inner and outer ball groove surfaces are axially offset with respect to the center point for urging the balls axially inwardly. A ball retainer is provided within the outer joint member. The ball retainer is spring-biased into engagement with an end of the inner joint member and pivots about the center point of the joint to engage and hold the balls within the ball grooves, maintaining them in a common plane.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to constant velocity universal joints. 
     2. Related Art 
     Constant velocity joints are used to transmit torque through an angle while maintaining constant velocity ratio between a driving and driven shaft member of the joint at all angles. A typical constant velocity joint includes an outer joint member formed with a part-spherical inner surface and a series of ball grooves, an inner joint member formed with a part-spherical outer surface and a series of complimenting ball grooves aligned with the grooves of the outer joint member, a plurality of torque-transmitting balls received in the aligned grooves, and a ball cage disposed between the inner and outer joint members and having part-spherical surfaces in contact with those of the inner and outer joint members for articulation of the joint and capture of the balls within the grooves. 
     The package size of a constant velocity joint is dependent in part on the angle to be achieved in the stack-up dimensions of the component parts, namely the inner joint part, the outer joint part and the intervening ball cage. Reducing the thickness of any one or more of these components may impair the strength or integrity of the joint, and thus there is a limit as to how small the conventional constant velocity joint can be made without detracting from its strength or reducing its degree of articulation. 
     U.S. Pat. Nos. 5,201,107 and 5,230,659 disclose constant velocity joints in which the conventional cage has been eliminated and the balls held in the grooves by a retainer within the outer joint member. Both joints are of rather complex construction, requiring special machining and component parts as well as special installation techniques to assemble the parts. The ball retainer of U.S. Pat. No. 5,201,107 is pivotally supported by the outer joint member along a line of curvature corresponding to that of the contact surfaces between the inner and outer joint members, which lends to a rather large package size in both the radial and axial directions. 
     It is an object of the present invention to provide a simple, efficient, compact constant velocity joint. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     A constant velocity joint assembly constructed according to the invention comprises an outer joint member and an inner joint member disposed at least partially within the outer joint member. The outer and inner joint members have abutting contact surfaces supporting the joint members for relative pivotal movement about a fixed center point of the joint members. The outer and inner joint members have a plurality of circumferentially spaced ball grooves formed in the contact surfaces and diverging toward one end of the outer joint member. A plurality of torque-transmitting balls are disposed in the ball grooves. A ball retainer is disposed within the outer joint member and has an inner seat portion and a ball-engaging portion engaging the balls. The inner joint member has an end portion engaging the inner seat portion of the ball retainer and supporting the ball retainer for relative pivotal movement about a pivot point common with the fixed center point of the outer and inner joint members. 
     The invention has the advantage of simplifying the construction and assembly of fixed-center constant velocity joints. The ball retainer is constructed and supported in such manner as to provide an overall compact constant velocity joint in length and in diameter compare to known prior art constant velocity joints with and without the usual ball cage. 
     The invention has the further advantage of providing an inner joint member which is solid throughout in the vicinity of the center of the joint and which directly supports the ball retainer during pivotal movement, providing strength and integrity to the joint under load. 
    
    
     THE DRAWINGS 
     These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein: 
     FIG. 1 is a fragmentary sectional view of a joint assembly constructed according to a presently preferred embodiment of the invention; 
     FIG. 2 is a view like FIG. 1 but showing the joint at an angle; 
     FIG. 3 is an enlarged fragmentary sectional view of the joint of FIG. 1; 
     FIG. 4 is a cross-sectional view taken generally along lines  4 — 4  of FIG. 1; and 
     FIG. 5 is a view like FIG. 4 but of an alternative joint construction. 
    
    
     DETAILED DESCRIPTION 
     A constant velocity joint assembly constructed according to a presently preferred embodiment of the invention is shown generally at  10  in FIGS. 1 and 2 and comprises an outer joint member  12 , an inner joint member  14 , a plurality of torque-transmitting balls  16  and a ball retainer  18 . 
     The outer joint member  12  comprises an outer joint housing  20  that is generally cup-shaped having an open end  22  and an axially opposite closed end  24 . A shaft  26  extends from the closed end  24  along an axis  28  of the outer joint member  12 . The housing may comprise a separate structure from the shaft  26  joined thereto such as by welding, bolting, screw threads, pinning, etc. to facilitate installation of the inner joint member  14  within the outer joint member  12 . 
     The inner joint member  14  is disposed at least partially within the outer joint member  12 . The inner joint member  14  comprises an enlarged joint head or joint portion  30  carried at one end of a shaft  32  of the inner joint member  14  extending along an axis  34  of the inner joint member  14 . The joint head  30  is received within the outer joint housing  20 . The outer joint housing  20  and joint head  30  present mutual contact surfaces  36 , 38  which are configured to directly engage one another and to support the outer and inner joint members  12 , 14  for articulated or pivotal movement about a fixed center point  40  of the joint assembly  10 , enabling the joint members  12 , 14  to pivot in all directions about the center point  40 . The contact surfaces  36 , 38  are preferably, but not necessarily, part-spherical. As best shown in FIGS. 1 and 2, the contact surface  36  of the outer joint member  12  is part-spherical adjacent the open end  22  and transitions into a linear section  42  parallel to the axis  28  of the outer joint member  12  adjacent the closed end  24  at a point in a plane P perpendicular to the axis  28  and passing through the joint center  40 . 
     The contact surface  38  on the inner joint member  14  is preferably part-spherical and slightly smaller in diameter than the diameter of the linear section  42 . The contact surface  36  adjacent the open end  22  terminates at the open end  22  in a diameter slightly smaller than the diameter of the contact surface  38  so as to secure the inner joint member  14  against removal from the outer joint member  12  axially away from the closed end  24 . 
     The outer and inner joint members  12 , 14  are formed with a plurality of circumferentially spaced ball grooves  44  which extend into the contact surfaces  36 , 38  and diverge toward the closed end  24  of the outer joint member  12 . The ball grooves  44  are each formed by opposing ball groove surfaces formed in the outer and inner joint members  12 , 14 . As best shown in FIG. 1, the ball groove surface  46  of the outer joint member  12  has a center of curvature B which is offset axially from the center point  40  of the joint assembly  10  by a fixed axial distance along the axis  28 . The ball groove surface  48  of the inner joint member  14  is spaced radially inwardly from the outer ball groove surface  46  and has a center of curvature A spaced axially from the center point  40  by a distance equal to the spacing of the center point B but on the axially opposite side of the center point  40  along the axis  34 . This offset relationship of the inner and outer ball groove centers in relation to the center point  40  and inward divergent relationship of the ball groove surfaces  46 , 48  tends to push the balls  16  toward the closed end  24  of the outer joint member  12 . The balls  16  are held in place in the ball grooves  44  by the ball retainer  18 , supporting the balls  16  in a common ball plane C which passes through the center point  40  at all joint angles, as illustrated in FIGS. 1 and 2. 
     The ball retainer  18  includes a central body portion  50  having an inner seat portion  52  engaging an end portion  54  of the inner joint member  14  for supporting the ball retainer  18  for pivotal movement relative to the outer and inner joint members  12 , 14  about a pivot point common with the center point  40  of the joint assembly  10 . The inner seat portion  52  is concave in curvature and has a center of curvature at the center point  40 . The end portion  54  is preferably in the form of a part-spherical protrusion extending axially beyond the ball groove surfaces  48  and has a center of curvature at the center point  40 . As best shown in FIGS. 1 and 2, the inner joint member  14  is solid in section at the center point  40  and through to the end portion  54  for strength and durability. The inner seat portion  52  is spaced closer to the fixed center point  40  than are the contact surfaces  36 ,  38  of the outer and inner joint members  12 ,  14 , respectively. 
     The central body  50  of the ball retainer  18  has an outer convex surface  56  having a center of curvature at the center point  40 , but spaced further from the center point  40  than that of the inner seat portion  52  while still being spaced closer to the center point  40  than are the contact surfaces  36 ,  38  of the outer  12  and inner  14  point members. The outer convex surface  56  engages a concave retainer seat  58  supported by the outer joint member  12 . The concave retainer seat  58  preferably comprises a part-spherical recess in the ball retainer  18  having a center of curvature in common with the center point  40  of the joint  10 . The concave retainer seat  58  is movable axially relative to the outer joint member  12  along the axis  28 . The concave retainer seat  58  is formed on the end of a plunger  60  which is received in an axial bore  62  of the outer joint member  12  along the axis  28 . A spring  64  is disposed in the bore  62  and acts on the plunger  60  to urge the plunger  60  constantly toward the center point  40  along the axis  28 . Such constant force acts to bias the concave retainer seat  58  constantly against the outer convex surface  56  of the ball retainer  18 , and further to bias the inner seat portion  52  constantly against the end portion  54  of the inner joint member  14  at all joint angles. 
     The ball retainer  18  includes a plurality of fingers extending radially outwardly of the central body portion  50  and aligned radially with the ball grooves  44 . The number of fingers  66  corresponds to the number of ball grooves  44 . The fingers  66  extend upwardly into each ball groove  44  and terminate at ends  68  which contact the balls  16 . The fingers  66  are constantly biased axially toward the open end  22  of the outer joint member  12 , and thus constantly urge the balls  16  axially toward the open end  22 , thereby holding the balls  16  within their respective ball grooves  44  through all angles of the joint. The fingers  66  are formed as one piece with the central body  50  and are elastically resilient to maintain the constant bias force on the balls  16 . The central body  50  and fingers  66  may be formed of metal or plastics material, such as a metal stamping, having a plurality of radial spring arms serving as the fingers  66 . The plunger  60  may likewise be fabricated of metal or plastics material. 
     The shaft  32  of the inner joint member  14  has an outer diameter surface adjacent an enlarged joint portion of the inner joint member  14  in which the ball groove surfaces  48  are formed. The ball groove surfaces  48  extend inwardly of the enlarged joint portion  30  beyond the outer diameter surface of the shaft  32 . 
     No portion of the ball retainer  18  extends beyond the center point  40  axially outwardly of the outer joint member  12 . 
     FIG. 4 is a cross-sectional view of the joint of FIGS. 1 and 2 taken along the ball center plane C. It will be seen that there are an even number of balls, namely six shown. FIG. 5 shows an alternative embodiment of the joint assembly in which there are an odd number of balls  16  and ball grooves  44 ′, namely three shown. The same reference numerals are used in FIG. 5 to designate like features, but are primed. The invention thus contemplates odd and even numbers of balls of any multiple, with a minimum of three balls being required, and the maximum being determined by the space available and the required strength of the joint. A range of 3-8 balls is preferred. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. The invention is defined by the claims.