Abstract:
A constant velocity joint includes an outer member defining a plurality of outer member ball tracks and an inner member defining a plurality of inner member ball tracks. The outer member ball tracks and the inner member ball tracks cooperate to define a plurality of uniform funnels having a uniform width along a longitudinal axis, and a plurality of diverging funnels having a diverging width along the longitudinal axis. A drive ball is disposed within each of the uniform funnels and the diverging funnels. A cage is disposed between the outer member and the inner member, and defines a plurality of windows with one of the drive balls disposed within each of the windows. The diverging funnels urge the drive balls along the longitudinal axis to pre-load the cage, while the uniform funnels do not urge the drive balls along the longitudinal axis, thereby reducing the amount of heat generated between the cage and the drive balls.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The subject invention relates to a constant velocity joint, and more specifically to a fixed center constant velocity joint. 
         [0003]    2. Description of the Related Art 
         [0004]    Fixed center constant velocity joints typically comprise an outer member, which defines a spherical interior and a plurality of outer member ball tracks within the interior. The interior and the plurality of outer member ball tracks extend along a longitudinal axis. The plurality of outer member ball tracks includes a first group of outer member ball tracks and a second group of outer member ball tracks. An inner member is disposed within the interior, and defines a spherical outer surface and a plurality of inner member ball tracks extending along the longitudinal axis. The plurality of inner member ball tracks includes a first group of inner member ball tracks and a second group of inner member ball tracks. The first group of inner member ball tracks opposes the first group of outer member ball tracks, diverging from one another in a first axial direction to define a first group of funnels. The second group of inner member ball tracks opposes the second group of outer member ball tracks to define a second group of funnels. The constant velocity joint further comprises a plurality of drive balls, with one of the drive balls disposed within each of the first group of funnels and within each of the second group of funnels. A cage is disposed between the outer member and the inner member, and defines a plurality of windows. One of the drive balls is disposed within each of the windows. 
         [0005]    Typically, the first group of funnels and the second group of funnels include a diverging width, which urges the drive ball contained within each of the funnels in the direction of the diverging funnel. The first group of funnels and the second group of funnels may be arranged so that the funnels all diverge in the same direction, or may be arranged so that the first group of funnels and the second group of funnels diverge in opposing directions. U.S. Pat. No. 6,848,999 to Weckerling et al. discloses a fixed center constant velocity joint in which the first group of funnels diverge in an opposite direction from the second group of funnels, with the first group of funnels and the second group of funnels spaced radially about the longitudinal axis in an alternating relationship. 
         [0006]    The diverging configuration of the funnels urges the drive balls in the direction in which the funnel diverges. The cage acts against the drive balls to resist the movement of the drive balls. Accordingly, it is said that the drive balls steer the cage, i.e., pre-load the cage to de-lash the joint and keep the cage from rattling. However, a significant amount of heat is generated by friction caused by the interaction between the cage and the drive balls as the cage resists movement of the drive balls. 
       SUMMARY OF THE INVENTION AND ADVANTAGES 
       [0007]    The subject invention discloses a constant velocity joint. The constant velocity joint comprises an outer member, which defines an interior and a plurality of outer member ball tracks within the interior. The interior and the plurality of outer member ball tracks extend along a longitudinal axis. The plurality of outer member ball tracks includes a first group of outer member ball tracks and a second group of outer member ball tracks. An inner member is disposed within the interior. The inner member defines a plurality of inner member ball tracks, which extend along the longitudinal axis. The plurality of inner member ball tracks includes a first group of inner member ball tracks and a second group of inner member ball tracks. The first group of inner member ball tracks opposes the first group of outer member ball tracks to define a first group of funnels. The second group of inner member ball tracks opposes the second group of outer member ball tracks to define a second group of funnels. The constant velocity joint further comprises a plurality of drive balls, with one of the plurality of drive balls disposed within each of the first group of funnels and within each of the second group of funnels. A cage is disposed between the outer member and the inner member. The cage defines a plurality of windows, with one of the plurality of drive balls disposed within each of the plurality of windows. The first group of inner member ball tracks and the first group of outer member ball tracks of the first group of funnels are spaced from each other in parallel relationship relative to each other to define a uniform width between the first group of inner member ball tracks and the first group of outer member ball tracks along the longitudinal axis, thereby defining a plurality of uniform funnels. The second group of inner member ball tracks and the second group of outer member ball tracks of the second group of funnels are spaced from each other in non-parallel relationship to define a diverging width between the second group of inner member ball tracks and the second group of outer member ball tracks along the longitudinal axis, thereby defining a plurality of diverging funnels. 
         [0008]    Accordingly, the constant velocity joint of the subject invention includes the first group of funnels, which are uniform in width, i.e., non-diverging, in combination with the second group of funnels, which are diverging. Therefore, the second group of funnels urges the drive balls along the longitudinal axis to pre-load the cage, while the first group of funnels do not. Thus, the interaction between the cage and the first group of funnels generates significantly less heat, thereby reducing the overall amount of heat generated by the constant velocity joint of the subject invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0010]      FIG. 1  is an end view of a constant velocity joint; 
           [0011]      FIG. 2  is a cross section view along cut line  2 - 2  shown in  FIG. 1 ; 
           [0012]      FIG. 3  is a cross section view along cut line  3 - 3  shown in  FIG. 1 ; 
           [0013]      FIG. 4  is a cross section view along cut line  4 - 4  shown in  FIG. 1 ; 
           [0014]      FIG. 5  is a force diagram indicating the forces acting on individual drive balls of the constant velocity joint; 
           [0015]      FIG. 6  is a force diagram for a second embodiment of the constant velocity joint indicating the forces acting on the individual drive balls of the second embodiment of the constant velocity joint; and 
           [0016]      FIG. 7  is a force diagram for a third embodiment of the constant velocity joint indicating the forces acting on the individual drive balls of the third embodiment of the constant velocity joint. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a constant velocity joint is generally shown at  20 . The constant velocity joint  20  rotatably couples a drive shaft  22  to a driven shaft  24 . The constant velocity joint  20  permits relative rotation between the drive shaft  22  and the driven shaft  24  when the drive shaft  22  and the driven shaft  24  are angled relative to each other as is well known in the art. 
         [0018]    The constant velocity joint  20  includes an outer member  26 . The outer member  26  includes an attachment end  28  for coupling the outer member  26  to the drive shaft  22 . Typically, the drive shaft  22  is integrally formed with the outer member  26 . However, it should be appreciated that the drive shaft  22  may be fixedly connected to the attachment end  28  of the outer member  26  by any suitable method. 
         [0019]    The outer member  26  defines an interior  30  and a plurality of outer member ball tracks  32 ,  34  within the interior  30 . The interior  30  and the plurality of outer member ball tracks  32 ,  34  extend along a longitudinal axis L. The plurality of outer member ball tracks  32 ,  34  includes a first group of outer member ball tracks  32  and a second group of outer member ball tracks  34 . Preferably, the first group of outer member ball tracks  32  and the second group of outer member ball tracks  34  include a longitudinally curved cross section extending along the longitudinal axis L, and a semi-circular cross section extending transverse to the longitudinal axis L. The curved longitudinal cross section of each of the first group of outer member ball tracks  32  and the second group of outer member ball tracks  34  define an outer race center  36  positioned axially along the longitudinal axis L. However, it should be appreciated that the first group of outer member ball tracks  32  and the second group of outer member ball tracks  34  may include a shape other than the longitudinally curved cross section shown and described herein. 
         [0020]    An inner member  38  is disposed within the interior  30  of the outer member  26 . The inner member  38  defines an aperture  40  for receiving the driven shaft  24  therein, which extends away from the attachment end  28 . The driven shaft  24  is coupled to the inner member  38  for rotation with the inner member  38 . For example, the aperture  40  and the driven shaft  24  may include complimentary splines for engaging each other. It should be appreciated, however, that the driven shaft  24  may be coupled to the inner member  38  in some other suitable manner not described herein. 
         [0021]    The inner member  38  defines a plurality of inner member ball tracks  42 ,  44 , which extend along the longitudinal axis L. The plurality of inner member ball tracks  42 ,  44  includes a first group of inner member ball tracks  42  and a second group of inner member ball tracks  44 . Preferably, the first group of inner member ball tracks  42  and the second group of inner member ball tracks  44  include a longitudinally curved cross section extending along the longitudinal axis L, and a semi-circular cross section extending transverse to the longitudinal axis L. The longitudinal curved cross section of each of the first group of inner member ball tracks  42  and the second group of inner member ball tracks  44  define an inner race center  46  positioned axially along the longitudinal axis L. However, it should be appreciated that the first group of inner member ball tracks  42  and the second group of inner member ball tracks  44  may include a shape other than the longitudinally curved cross section shown and described herein. 
         [0022]    The constant velocity joint  20  further comprises a plurality of drive balls  48 . The plurality of drive balls  48  includes a spherical shape and transmit torque between the outer member  26  and the inner member  38 . One of the plurality of drive balls  48  is disposed within each of the first group of funnels  50  and within each of the second group of funnels  52 . Each of the drive balls  48  include a ball center  54  axially positioned along the longitudinal axis L. 
         [0023]    A cage  56  is disposed between the outer member  26  and the inner member  38 . The cage  56  defines a plurality of windows  58  with one of the plurality of drive balls  48  disposed within each of the plurality of windows  58 . The cage  56  maintains the drive balls  48  in a plane as the constant velocity joint  20  articulates to permit relative angular movement between the drive shaft  22  and the drive shaft  22 . 
         [0024]    The first group of inner member ball tracks  42  opposes the first group of outer member ball tracks  32  to define a first group of funnels  50 . The first group of inner member ball tracks  42  and the first group of outer member ball tracks  32  of the first group of funnels  50  are spaced from each other in parallel relationship relative to each other, and cooperate to define a uniform width W between the first group of inner member ball tracks  42  and the first group of outer member ball tracks  32 , along the longitudinal axis L. In other words, the first group of inner member ball tracks  42  and the first group of outer member ball tracks  32  of the first group of funnels  50  are concentric such that they do not diverge from one another. The uniform width W between the first group of inner member ball tracks  42  and the first group of outer member ball tracks  32  define a plurality of uniform funnels  50 . The plurality of uniform funnels  50  extends axially along the longitudinal axis L. The uniform funnels  50  includes each opposing pair of the inner race centers  46  and the outer race centers  36  aligned with each other and also aligned with the ball centers  54  of the drive balls  48  disposed within the uniform funnels  50 . As such, there is no offset between the inner race centers  46  and the ball centers  54 , nor between the outer race centers  36  and the ball centers  54 . 
         [0025]    The second group of inner member ball tracks  44  opposes the second group of outer member ball tracks  34  to define a second group of funnels  52 . The second group of inner member ball tracks  44  and the second group of outer member ball tracks  34  of the second group of funnels  52  are spaced from each other in non-parallel relationship to define a diverging width W between the second group of inner member ball tracks  44  and the second group of outer member ball tracks  34 , along the longitudinal axis L. In other words, the second group of inner member ball tracks  44  and the second group of outer member ball tracks  34  of the second group of funnels  52  are not concentric and diverge from one another in an axial direction along the longitudinal axis L. The diverging width W between the second group of inner member ball tracks  44  and the second group of outer member ball tracks  34  define a plurality of diverging funnels  52 . The diverging funnels  52  extend axially along the longitudinal axis L. 
         [0026]    The diverging funnels  52  include each opposing pair of the inner race centers  46  and the outer race centers  36  offset from the axial position along the longitudinal axis L of the ball centers  54  of the drive balls  48  disposed within the diverging funnels  52 , with the ball centers  54  disposed between the inner race centers  46  and the outer race centers  36  along the longitudinal axis L. 
         [0027]    The direction the drive balls  48  are urged by the diverging funnels  52  is dependent upon the direction in which the diverging funnels  52  are diverging. For example, if the diverging funnel  52  diverges toward the attachment end  28 , i.e., if the diverging funnel  52  expands with a decrease in distance relative to the attachment end  28 , then the drive balls  48  are urged in a first direction  60  parallel the longitudinal axis L toward the attachment end  28 . Alternatively, if the diverging funnel  52  diverges away form the attachment end  28 , i.e., if the diverging funnel  52  expands with an increase in distance relative to the attachment end  28 , then the drive balls  48  are urged in a second direction  62  parallel the longitudinal axis L away from the attachment end  28 . 
         [0028]    One way to control the direction of the diverging funnels  52  is the relative placement of the inner race centers  46  and the outer race centers  36  relative to the ball centers  54 . If the outer race center  36  is positioned along the longitudinal axis L farther from the attachment end  28  than the inner race center  46 , with the ball center  54  positioned therebetween, the offset between the outer race center  36  and the inner race center  46  opens the diverging funnel  52  toward the attachment end  28  and will urge the drive ball  48  in the first direction  60  toward the attachment end  28 . Alternatively, if the outer race center  36  is positioned along the longitudinal axis L nearer the attachment end  28  than the inner race center  46 , with the ball center  54  disposed therebetween, the offset between the outer race center  36  and the inner race center  46  opens the diverging funnel  52  away from the attachment end  28  and will urge the drive all in the second direction  62  away from the attachment end  28 . It should be appreciated that constant velocity joint  20  may include some other manner of diverging funnels  52  not described or shown herein. 
         [0029]    Preferably, the plurality of uniform funnels  50  and the plurality of diverging funnels  52  are arranged radially about the longitudinal axis L in alternating relationship relative to each other. Accordingly, there are an equal number of uniform funnels  50  and diverging funnels  52 . Preferably, the uniform funnels  50  include a group having four funnels and the diverging funnels  52  include a group having four funnels. However, it should be appreciated that the subject invention does not require the number of uniform funnels  50  to equal the number of diverging funnels  52 . It should also be appreciated that the number of uniform funnels  50  and the number of diverging funnels  52  may vary form that shown or described herein. 
         [0030]    Preferably, the plurality of diverging funnels  52  includes a first subset  64  and a second subset  66 . The first subset  64  of the plurality of diverging funnels  52  diverges toward the attachment end  28  in a first direction  60  along the longitudinal axis L. The second subset  66  of the plurality of diverging funnels  52  diverges away from the attachment end  28  in a second direction  62  along the longitudinal axis L. The first subset  64  of the plurality of diverging funnels  52  is equal in number to the second subset  66  of the plurality of diverging funnels  52 . Preferably, and as shown in the drawings, the first subset  64  of the plurality of diverging funnels  52  includes two funnels and the second subset  66  of the plurality of diverging funnels  52  includes two funnels. 
         [0031]    The plurality of uniform funnels  50  are arranged radially about the longitudinal axis L and equally spaced from each other with the first subset  64  of the plurality of diverging funnels  52  arranged opposite each other about the longitudinal axis L and the second subset  66  of the plurality of diverging funnels  52  arranged opposite each other about the longitudinal axis L. In other words, the diverging funnels  52  and the uniform funnels  50  alternate so that there are two pairs of uniform funnels  50  disposed radially opposite each other about the longitudinal axis L, with the first subset  64  of diverging funnels  52  disposed between the uniform funnels  50  and radially opposite each other and the second subset  66  of diverging funnels  52  disposed between the uniform funnels  50  and radially opposed to each other. Referring to FIG. __, the direction of the force applied to each of the drive balls  48  is schematically shown. 
         [0032]    In a second embodiment, all of the plurality of diverging funnels  52  diverge toward the attachment end  28  in a first direction  60  along the longitudinal axis L to urge the plurality of drive balls  48  in the first direction  60 . Referring to FIG. __, the direction of the force applied to each of the drive balls  48  of the second embodiment of the constant velocity joint  20  is schematically shown. 
         [0033]    In a third embodiment, all of the plurality of diverging funnels  52  diverge away from the attachment end  28  in a second direction  62  along the longitudinal axis L to urge the plurality of drive balls  48  in the second direction  62 . Referring to FIG. __, the direction of the force applied to each of the drive balls  48  of the third embodiment of the constant velocity joint  20  is schematically shown. 
         [0034]    The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, 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, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described