Abstract:
Disclosed herein is a starter motor clutch. The clutch includes, a shell, a wedgable component support member operably positioned adjacent the shell, and at least one wedgable component positioned between the shell and the wedgable component support member. The at least one wedgable component is displaceable into engagement with the shell to lock the shell into synchronous movement with the wedgable component support member upon initial rotational movement of the wedgable component support member in either direction relative to the shell while allowing asynchronous movement of the shell relative to the wedgable component support member.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional application, 60/833,451, filed Jul. 26, 2006, the entire contents of which are incorporated herein by reference. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    Starter motors typically have an armature, gear system, clutch and pinion in a stacked axial alignment along a major axis of the machine. Such an arrangement limits how short the machine can be along the major axis. With the continuing desire for increased cabin volume in modern automobiles any decrease in size of the components in the engine compartment is well received. As such, a decrease in the major axis of the starter motor would also be well received. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    Disclosed herein is a starter motor clutch. The clutch includes, a shell, a wedgable component support member operably positioned adjacent the shell, and at least one wedgable component positioned between the shell and the wedgable component support member. The at least one wedgable component is displaceable into engagement with the shell to lock the shell into synchronous movement with the wedgable component support member upon initial rotational movement of the wedgable component support member in either direction relative to the shell while allowing asynchronous movement of the shell relative to the wedgable component support member. 
         [0004]    Further disclosed herein is a starter motor. The starter motor includes, a housing, an armature within the housing, a pinion within the housing drivable by the armature, and a clutch within the housing in operational communication with the armature and the pinion. The clutch includes, a shell, a wedgable component support member operably positioned adjacent with the shell, and at least one wedgable component positioned between the shell and the wedgable component support member. The at least one wedgable component is displaceable into engagement with the shell to lock the shell into synchronous movement with the wedgable component support member upon initial rotational movement of the wedgable component support member in either direction relative to the shell while allowing asynchronous movement of the shell relative to the wedgable component support member. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0006]      FIG. 1  depicts a sectioned view of the starter motor disclosed herein; 
           [0007]      FIG. 2  depicts a cross sectional view of the starter motor of  FIG. 1  taken at arrows  2 - 2 ; 
           [0008]      FIG. 3  depicts a partially sectioned perspective view of the clutch disclosed herein shown in assembly with a gear system, shaft and pinion; 
           [0009]      FIG. 4  depicts a perspective view of the shell of the clutch disclosed herein; 
           [0010]      FIG. 5  depicts a cross sectional perspective view of the shield shown in assembly in  FIG. 3 ; 
           [0011]      FIG. 6  depicts a perspective view of the shaft of  FIG. 1 ; and 
           [0012]      FIG. 7  depicts a perspective view of the pinion of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0014]    Referring to  FIG. 1 , a starter motor  10  disclosed herein is illustrated in cross section. The starter motor  10  includes among other things, a housing  12 , a solenoid  14 , an armature  18 , a gear system  22 , a clutch  26 , a shaft  30  and a pinion  34 . The armature  18  provides rotational energy to the pinion  34  through the gear system  22 , the clutch  26  and the shaft  30 . This rotational energy is used to start an engine, such as an internal combustion engine of an automobile (not shown), for example. To do so the solenoid  14  is electrically energized causing a lever  38  to move the pinion  34  axially along the shaft  30  until external gear teeth  42  on the pinion engage with gear teeth (not shown) on a flywheel of the engine. Once the engine starts, the rotational velocity of the engine quickly overtakes the rotational velocity of the pinion  34 . When this happens, the clutch  26  disengages the pinion  34  from the armature  18  to prevent damage to the starter motor  10  as will be described in greater detail below. Once the engine is started electrical energy to the solenoid  14  is removed and a return spring  46  within the solenoid  14  returns the solenoid  14  and the pinion  34 , through the lever  38 , to its original position along the shaft  30 . 
         [0015]    With reference to  FIGS. 2 and 3 , the gear system  22  and clutch  26  will be described in detail. In this embodiment the gear system  22  is a planetary gear system although other embodiments could use other mechanisms for rotational reduction such as harmonic drives and cyclo reductors, for example. A sun gear  50  is connected to the output of the armature  18  and rotationally drives one or more planet gears  54 . All three of the planet gears  54  are attached to a flange  60  of the shaft  30 . As such, rotation of the planet gears  54  around the sun gear  50  results in rotation of the shaft  30 . The planet gears  54 , however, may not revolve around the sun gear  50  if a ring gear  64  engaged with the three planet gears  54  is allowed to rotate. In this situation, the sun gear  50  will cause the planet gears  54  to rotate about their individual axis thereby driving the ring gear  64  to rotate while the flange  60  and shaft  30  remain stationary. Thus, rotational coupling of the armature  18  with the shaft  30  is controllable by controlling the rotational freedom of the ring gear  64 . 
         [0016]    Rotational control of the ring gear  64  is accomplished, in this embodiment, with the clutch  26 . The clutch  26  includes a shell  68  with a plurality of pockets  72  having a biasing member disclosed herein as spring  76  and a wedgable component referred to hereinafter as roll  80  positioned therewithin, and a wedgable component support member, which in this embodiment is represented as the ring gear  64 . It should be noted that although in this embodiment the wedgable member is roll  80  with a cylindrical shape alternate embodiments could use wedgable members with non-cylindrical shapes such as elliptical or polygonal, for example. The shell  68  has relatively thin walls  82  made from a process such as stamping, for example, for shells made of metal. The springs  76  and rolls  80  are oriented within the pockets  72  so that the springs  76  all bias the rolls  80  in the same circumferential direction, which is clockwise as viewed in  FIG. 2 . The pockets  72  have a pentagon shape with the two radially outermost surfaces  84  having an arcuate shape as well. Each of the pockets  72  is symmetrical about a radial line extending from an axis of the shell  68  through a point where the outermost surfaces  84  meet. An annular distance  88  between the outermost surfaces  84  and an outer radial surface  92  of the ring gear  64  is greatest where the two outermost surfaces  84  meet and decreases at distances further from where the two outermost surfaces  84  meet. The annular distance  88  is sized to be larger than the diameter of the rolls  80  at its greatest point and smaller than the diameter of the rolls  80  at its smallest point. Thus, when the rolls  80  are positioned toward the center of the pockets  72  the rolls  80  are free to rotate and, consequently, the ring gear  64  is free to rotate within the shell  68 . This condition occurs when the ring gear  64  is rotated in a counterclockwise direction relative to the shell  68  in the view of  FIG. 2 . The rolls  80  in this instance are being forced toward the springs  76  and toward the center of the pockets  72  where the annular distance  88  is greatest. When there is no relative motion between the ring gear  64  and the shell  68  the rolls  80  are partially wedged between the outer radial surface  92  and the shell  68  due to the springs  76  bias against the rolls  80  in that direction. With any clockwise rotation of the ring gear  64  relative to the shell  68 , therefore, the rolls  80  become even further wedged between the ring gear  64  and the shell  68  thereby prevents any additional relative rotation therebetween. 
         [0017]    The embodiment disclosed herein has the pockets  72  formed in the shell  68  that is radially outwardly of the outer radial surface  92 . Alternate embodiments, however, could have pockets receptive of the springs  76  and the rolls  80  formed on a radially outwardly facing surface that interface with a cylindrical shaped radially inwardly facing surface of the shell, for example. 
         [0018]    By fixing the shell  68  to the housing  12  in the foregoing structure a clockwise rotation of the sun gear  50  will cause the planet gears  54 , the flange  60 , the shaft  30  and the pinion  34  to all rotate clockwise as well. The rotational velocity of the above listed components is less than that of the sun gear  50  due to the reducing action of the gear system  22 . The pinion  34  will cause the engine flywheel to rotate in the direction in which the pinion  34  is driving it until the engine starts. Once started the engine rotates the flywheel faster than the pinion  34  can drive it, and as such the flywheel begins driving the pinion  34 . This driving action of the pinion  34  is communicated back to the planet gears  54  through the shaft  30  and the flange  60 . The resultant torque on the ring gear  64  from this flywheel driven speed is in a counterclockwise direction thereby dislodging the rolls  80  from their wedged orientation and allowing the ring gear  64  to freely rotate relative to the shell  68 . It should also be understood that the pockets  72  disclosed herein, being symmetrical, allow for full reversal in direction of operation of the clutch  26  by simply reversing the relative positions of the springs  76  and the rolls  80  within the pockets  72 . Thus changing the direction of bias on the rolls  80  provided by the springs  76 . As such, the starter motor  10  can be made to operate in either direction with no additional parts, design work or tool fabrication thereby saving costs for a producer. 
         [0019]    The ring gear  64 , in addition to having the outer radial surface  92 , has a radially extending portion  96 . The radially extending portion  96  axially retains the springs  76  and the rolls  80  in the pockets  72 . 
         [0020]    The relative positioning of the clutch  26  and the gear system  22  described in the structure above allows a major axis of the machine to be shorter than is possible with conventional starter motor structures. Specifically, the major axis through the armature  18 , gear system  22 , clutch  26 , shaft  30  and pinion  34  may be shorter due to the clutch  26  being positioned radially outwardly of the gear system  22 . Since the clutch  26  is in axial alignment with the gear system  22  and is not axially displaced from the gear system  22  the presence of the clutch  26  adds substantially no additional axial length to the major axis of the starter motor  10 . 
         [0021]    Referring to  FIG. 4  since, as described above, the shell  68  may be fixed to the housing  12 , the housing  12  can be used to structurally support the shell  68 . For example, the shell  12  may be deep draw stamped from a thin metal such that the shape of the pockets  72  is easily observable on an outer surface thereof. Such a thin walled component, though easily manufactured, may not be rigid enough to prevent deformation due to the force of the rolls  80  wedging within the pockets  72 . The housing  12 , however, with thick walls  96  that may be cast aluminum, for example, can support the thin walled shell  68  and prevent such deformations. The walls  96  can be cast in details to complement the convoluted configuration of the outer surface of the shell  68 . In addition to preventing deformation of the shell  68  the support of the shell  68  by the housing  12  may also attenuate noise due to impact of the rolls  80  against the shell  68  due to rapid changes in rotational velocity caused by the flywheel as the engine starts. 
         [0022]    Referring to  FIG. 5 , by positioning the clutch  68  radially outwardly of the ring gear  64  a shield  100  can be implemented that serves several purposes. First, the shield  100  acts as a dust seal to prevent brush and commutator wear debris from reaching the gear system  22 . Secondly, the shield  100  retains grease in the pockets  72  to maintain lubrication to the rolls  80  and the springs  76  while also maintaining the springs  76  and roll  80  in proper axial alignment within the pockets  72 . The shield  100 , in this embodiment, includes an axially extending through hole  104  in an annular wall  108  having a radially extending flange  112  and an annular ring portion  116 . The shield  100  may be retained to the clutch  26  and gear system  22  through an interference fit of the annular ring portion  116  with a complementary annular portion  120  ( FIGS. 3 and 4 ) of the shell  68 . The shield  100  may be made of a thin stamped metal, for example, to allow elastic flexibility to facilitate the interference fit with the shell  68 . Such an interference fit may sealably attach the shield  100  to the shell  68  while holding the annular wall  108  in close proximity to an axial face  124  ( FIG. 3 ) of the ring gear  64  thereby creating a seal between the ring gear  64  and the shield  100  in accommodation of their relative rotational movements. As such, the two fore mentioned seals may retain grease within the pockets  72  for the life of the starter motor  10 . 
         [0023]    In this embodiment, a diameter of the hole  104  is sized to accommodate the sun gear  50  therethrough, thereby creating a moving dust seal by the small annular clearance between the hole  104  and the sun gear  50 . Centrifugal forces will act on dust particles that surround the armature  18  due to rotation thereof. Such centrifugal forces will urge the dust particles radially outwardly thereby discouraging axial movement of the dust particles through the hole  104 . The shield may additionally provide bearing support to the armature  18 . To do so a bearing (not shown) could be fixedly attached to the shield  100  at the hole  104  that operationally engages with the armature  18 . 
         [0024]    Referring to  FIGS. 6 and 7 , the shaft  30  and pinion  34  are illustrated in detail. The shaft  30 , as mentioned above, has the flange  60  that interfaces with the planet gears  54  by axles (not shown) that are fixedly attached to the flange  60  by, for example, threadable engagement into threaded holes  128 . Further along the shaft  30  is gear  132 . Although in this embodiment the gear  132  is helical alternate embodiments could have a non-helical gear. The pinion  34  has an internal gear  136  integrated on an inner diameter thereof. The internal gear  136  has a complementary helical angle to that of the gear  132  and as such engages with the gear  132 . The engagement of the gears  132 ,  136  is such that the pinion  34  is axially movable relative to the shaft  30 . Axial movement of the pinion  34  relative to the shaft  30  is controlled by the solenoid  14  through the lever  38  ( FIG. 1 ) as described above. 
         [0025]    The starter motor  10  disclosed herein, by having the internal gear  136  integrated directly onto the pinion  34 , has fewer components than a typical starter motor in which a pinion is not rotationally fixed directly with a shaft but instead is coupled to a clutch, or other component, that is rotationally fixed to a shaft. The internal gear  136  is one the features of the disclosed starter motor  10  that allows the major axis, described above, to be shorter than that of conventional starter motors. This is due, in part, to the removal of the axial length required of an internal gear that is integrated into a clutch, or other component, that is axially stacked along the major axis of the machine. 
         [0026]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.