Abstract:
A mechanical connection includes first and second components supported for rotation, the first component formed with first spline teeth, the second component formed with second spline teeth meshing with the first spline teeth, and a damper fitted in a groove formed in one of the first and second components, including an extension secured to the damper, contacting and extending between at least some of the first and second spline teeth.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to a connection between two rotating components made by mating spline teeth formed on the components. 
         [0003]    2. Description of the Prior Art 
         [0004]    When a spline connection between rotating components transmits torque, an objectionable noise may be produced in a motor vehicle powertrain. A spline interface connects an electric traction motor&#39;s rotor shaft and a countershaft inside a transmission. In such transmissions, the motor&#39;s rotor is constrained axially and radially by a pair of bearings, and the countershaft is likewise constrained axially and radially by a pair of bearings. 
         [0005]    Since the two shafts are concentric, they also share a spline interface that transfers torque between them and acts as another radial constraint, thereby producing an over-constrained assembly wherein slight misalignments can subject the spline interface to varying loading conditions during rotation. Loading and subsequent relative movement between the splines can cause a ticking noise. 
       SUMMARY OF THE INVENTION 
       [0006]    A mechanical connection includes first and second components supported for rotation, the first component formed with first spline teeth, the second component formed with second spline teeth meshing with the first spline teeth, and a damper fitted in a groove formed in one of the first and second components, including an extension secured to the damper, contacting and extending between at least some of the first and second spline teeth. 
         [0007]    The connection relieves over-constraint in the transmission assembly at the spline interface between the shafts. 
         [0008]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0010]      FIG. 1A  is a cross sectional side view showing a rotor shaft and countershaft of a hybrid electric powertrain; 
           [0011]      FIG. 1B  is an end view of the shafts that are secured mutually at the spline connection showing the unaligned centers of the bearing pockets; 
           [0012]      FIG. 2A  is a cross sectional side view showing the rotor shaft and countershaft of  FIG. 1 ; 
           [0013]      FIG. 2B  is a side view showing external helical spline teeth formed on the countershaft; 
           [0014]      FIGS. 3A ,  3 B and  3 C illustrate an O-ring that is fitted into a recess in the countershaft near a spline interface; 
           [0015]      FIGS. 4A ,  4 B and  4 C illustrate an O-ring fitted into a recess in the countershaft; and 
           [0016]      FIGS. 5A and 5B  illustrate a ring component fitted into recesses in the countershaft. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Referring now to  FIG. 1 , a traction motor  10  of a hybrid electric powertrain includes a rotor shaft  12 , which supports the rotor  14  of the motor  10 , whose stator  16  surrounds the rotor. Rotor shaft  12  is supported by roller bearings  18 ,  20  on a bulkhead  22  in the transmission housing. 
         [0018]    A countershaft  24  is supported by roller bearings  26 ,  28  on the bulkhead  22  and a transmission housing  30 , respectively. Countershaft  24  is formed with a pinion  32 , which meshes continually with a gear  34 . Shaft  36 , which is formed with a pinion  38 , is connected by a spline to gear  34 . 
         [0019]    The motor&#39;s rotor  14  is constrained axially and radially by bearings  18 ,  20 . The countershaft  24  is likewise constrained axially and radially by bearings  26 ,  28 . 
         [0020]    Because rotor shaft  12  and countershaft  24  are substantially concentric with axis  40 , they also share a spline connection  42 , which transmits torque between them and provides radial constraint. 
         [0021]    In this arrangement, bearing  18  is fitted into a bearing pocket  43  formed in rotor shaft  12 , bearing  20  is fitted into a bearing pocket  44  formed in bulkhead  22 , bearing  26  is fitted into a bearing pocket  45  formed in bulkhead  22 , and bearing  28  is fitted into a bearing pocket  46  formed in transmission housing  30 . The center of each bearing pocket  43 - 46  is spaced radially from the center of each of the other bearing pockets. As  FIG. 1B  shows, the center of bearing pocket  46  for bearing  28  is located on axis  40 . But the center of bearing pocket  45  for bearing  26  is located at a lower elevation that that of axis  40 , and the center of the bearing pocket  44  for bearing  20  is located at a higher elevation than that of axis  40 . The center of the bearing pocket  43  for bearing  18  is located at a lower elevation than that of the center of bearing pocket  45 . 
         [0022]    Because the centers of the bearing pockets  43 - 46  are unaligned and offset radially, a radial preload is produced at the spline connection  42 , the preload eliminating relative movement between the teeth of the splines and reducing or eliminating noise emanating from the spline connection  42 . 
         [0023]    An alternate technique for producing a preloaded spline connection  42  is to replace one or more of the roller bearings  18 ,  20 ,  26 ,  28  with a tapered bearing. The tapered bearing produces a preload to the spline connection  42 , thereby minimizing or eliminating relative movement among the internal and external spline teeth at spline connection  42 . 
         [0024]    As  FIGS. 2A and 2B  illustrate, the countershaft  24  is formed with external helical spline teeth  47 , and the rotor shaft  12  is formed with internal helical spline teeth  48 , which mesh with spline teeth  47  at the spline connection. Either one of shafts  12 ,  24  can be formed with external spline teeth and the other shaft can be formed with internal spline teeth. The helix angle reduces the abrupt transmission of torque between mating spline teeth adjacent teeth. 
         [0025]    As  FIGS. 3A ,  3 B and  3 C illustrate, a damper  50  in the form of an O-ring made of relatively soft material is fitted into a recess  52  formed in the wall  54  of countershaft  24  near the spline connection  42 . Preferably damper  50  includes short, axial fingers  56 , which extend into the spline connection  42  and into contact with the internal and external spline teeth. These axial fingers  56  eliminate clearances between the spline teeth and provide damping to the spline connection  42 . 
         [0026]      FIGS. 4A ,  4 B and  4 C show a damper  60  in the form of an O-ring made of relatively soft material fitted into an annular recess or groove  62  formed in the wall  54  of countershaft  24  near the spline connection  42 . Preferably damper O-ring  60  includes long, axial fingers  66 , which extend axially into the spline connection  42 , into a radial space that otherwise would be occupied by spline teeth of the connection  42 , and into contact with the internal and external spline teeth of the spline connection  42 . These fingers  66  eliminate clearances between the spline teeth and provide damping to the spline connection  42 . 
         [0027]      FIGS. 5A and 5B  show a damper  70  in the form of an O-ring made of relatively soft material fitted into a first annular recess  72  formed in the wall  54  of countershaft  24  and a second annular recess  74  formed in the wall  54  of countershaft  24 , the recesses  72 ,  74  being located on opposite axial sides of and near the spline connection  42 . Preferably damper  70  includes axial legs  76 , which extend axially into the spline connection  42 , into a radial space that otherwise would be occupied by spline teeth of the spline connection  42 , and into contact with the internal and external spline teeth of the connection spline. These axial legs  76  connect two rings  78 ,  80 , each leg being fitted into one of the recesses  72 ,  74 . The axial legs  76  eliminate clearances between the internal and external spline teeth of the spline connection  42  and provide damping to the spline connection  42 . 
         [0028]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.