Abstract:
A starter motor for an internal combustion engine having an integral one-way roller clutch and epicycle gear train unit is provided. The integrated unit includes an integrated gear support/clutch barrel which, on one side, houses the roller and spring elements of the clutch and, on the other side, supports the planetary gears of the epicycle gear assembly. The invention is of simple construction and provides reduced overall starter motor dimension while demonstrating improved noise, vibration and harshness characteristics.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to starter motors used to crank internal combustion engines. More particularly, the present invention relates to a starter motor which integrates the epicycle gear train and the one-way roller clutch into an axially compact unit. 
     Internal combustion engines conventionally use electric starter motors for cranking. Electric starter motors became popular in the late 1900&#39;s and early 1910&#39;s and incorporated a one-way clutch fitted to the end of the armature shaft of the starter. The one-way clutch is used during engine cranking to transmit torque and motion from the electrical motor to the output shaft and pinion and to the ring gear on the engine crankshaft. By only operating in a single direction, the clutch prevents the electric motor from being rotated too fast when driven by the engine after it has been successfully started. Typically the one-way clutch is in the form of a roller clutch that provides extra protection when a large load is transmitted from the engine to the starter by any means. The motor armature shaft is connected directly with the output shaft via the one-way clutch. 
     As engine size and cylinder compression increased with advances in engine technology, an epicycle or planetary gear train was added to the starter motor arrangement to increase torque. According to known design, the epicycle gear train is separate from the one-way roller clutch assembly. By having two separate assemblies the overall length of the starter is inherently long, thus creating engine compartment packaging problems. In addition, the greater length of the starter, which is a direct result of the arrangement of the two separate assemblies, results in vibration and fatigue failures. 
     SUMMARY OF THE INVENTION 
     The present invention provides an integral one-way roller clutch and epicycle gear train unit that overcomes the problems and limitations of known starter motors. Briefly, the integrated unit includes an integrated gear support/clutch barrel which, on one side, houses the roller and spring elements of the clutch and, on the other side, supports the planetary gears of the epicycle gear assembly. 
     This configuration offers several advantages over known starter motors. The integrated unit of the present invention provides for a shorter starter motor size, thus allowing for a superior packaging arrangement in the engine compartment. The present invention also is simpler than known starter motors in that it has fewer parts, thus saving material cost and reducing the tolerance stack-up from the normal variation of parts. In addition, the starter motor of the present invention demonstrates improved noise, vibration and harshness characteristics. 
     Further scope of applicability of the present invention will become apparent from the following detailed description, claims, and drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which: 
         FIG. 1  is a longitudinal sectional view of a portion of a starter motor illustrating the epicycle gear train and the one-way roller clutch as being two separate assemblies as is known in the art; 
         FIG. 2  is a longitudinal sectional view of the starter motor of the present invention illustrated in the disengaged position; 
         FIG. 3  is an exploded perspective view of certain elements of the starter motor illustrated in  FIG. 2  which illustrates the relationship of the integral epicycle gear train and one-way roller clutch; and 
         FIG. 4  is a longitudinal sectional view of the starter motor of the present invention similar to the view of  FIG. 2  but illustrating the motor in the engaged position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment of the present invention provides an example of the present invention. The embodiment discussed herein is merely exemplary in nature and is not intended to limit the scope of the invention in any manner. Rather, the description of the preferred embodiment serves to enable a person of ordinary skill in the relevant art to make and use the present invention. 
       FIG. 1  illustrates a longitudinal sectional view of a portion of a known starter motor, generally illustrated as  10 . The starter motor  10  illustrates the epicycle gear train and the one-way roller clutch as being two separate assemblies as is known in the art. The starter motor  10  includes a motor housing  12  having a known configuration. Internally the starter motor  10  includes an armature shaft, the end of which is shown as shaft drive end  14 , and an output shaft  16 . The drive end  14  has a sun gear  18  formed thereon. The drive end  14  terminates at a bearing surface  20 . 
     The output shaft  16  includes an end  22 . Defined within the end  22  of the output shaft  16  is a bearing pocket  24 . A sleeve bearing  26  is disposed within the bearing pocket  24 . A thrust ball  28  is also fitted within the pocket  24 . The bearing journal surface  20  is rotatably mounted within the sleeve bearing  26 . 
     A plurality of planetary gear shafts are fitted to the end  22  of the output shaft  16 , of which a single planetary gear shaft  30  is illustrated according to the sectional view of  FIG. 1 . A like plurality of planetary gears are rotatably mounted on the planetary gear shafts, of which planetary gears  32 ,  32 ′ are illustrated with the planetary gear  32 ′ being fitted to the planetary gear shaft  30 . The planetary gears are operatively mounted within a stationary gear  34  which is fixedly mounted within the starter motor housing  12 . The operation of the sun, planetary, and stationary gears is known in the art. 
     A one-way clutch assembly, generally illustrated as  36 , is illustrated relative to the epicycle gear train. The one-way clutch assembly  36  includes a clutch barrel  38  and a carrier shaft  40 . A clutch roller cavity  42  is defined between the inner wall of the clutch barrel  38  and the outer wall of the carrier shaft  40 . Within the clutch roller cavity  42  are disposed a plurality of clutch rollers, of which one, clutch roller  44 , is illustrated, and a like plurality of springs (not illustrated). The rollers are movable between a slipping position and a working position depending on the relative rotational speeds of the clutch barrel  38  and the carrier shaft  40  as is known in the art. The biasing action of the springs acts to maneuver the rollers to their locked (working) positions, as is also known in the art. 
     As may be seen by reference to  FIG. 1 , the epicycle gear train and the one-way clutch assembly are spaced apart according to known configurations. The present invention, described hereinafter and illustrated in  FIGS. 2 through 4 , overcomes the disadvantages of this traditional arrangement by providing an integrated epicycle gear train/one-way clutch assembly. 
       FIG. 2  is a longitudinal sectional view of a starter motor, generally illustrated as  100 , according to the present invention. The starter motor  100  is shown in its disengaged position in this figure. 
     The starter motor  100  includes a housing  102 . The housing  102  is comprised of a motor cover  104  removably attached to a starter housing  106 . The motor cover  104  includes a closed end  108 . Internally, the starter motor  100  includes a motor portion, generally illustrated as  110 , an epicycle gear train/one-way roller clutch assembly, generally illustrated as  112 , and a solenoid assembly, generally illustrated as  114 . 
     The motor portion  110  includes an armature  116  having an armature shaft  118  which itself includes a first end  120  and a second end  122 . The first end  120  of the armature shaft  118  is rotatably mounted within a sleeve bearing  124  that is mounted in the closed end  108  of the motor cover  104 . The motor portion  110  further includes armature windings  126  and a commutator  128  formed on the armature shaft  118  as is known in the art. The motor portion  110  also includes a plurality of magnets  130  fixed to the inner wall of the motor cover  104  and brush assemblies  132 ,  132 ′ mounted to a support plate  134 . The support plate  134  is fixedly mounted to the inner wall of the motor cover  104 . 
     The second end  122  of the armature shaft  118  terminates in and is thus part of the epicycle gear train/one-way roller clutch assembly  112 . The assembly  112  includes an integrated gear support/clutch barrel  136  having a gear side  138  and a clutch side  140 . A plurality of planetary gear shafts are fitted to the gear side  138  of the integrated gear support/clutch barrel  136 , of which a single planetary gear shaft  142  is illustrated according to the sectional view of  FIG. 2 . Similarly,  FIG. 3 , which shows an exploded perspective view of the operative epicycle gear train/one-way roller clutch assembly  112  including the integrated gear support/clutch barrel  136 , illustrates additional planetary gear shafts  142 ′,  142 ″. 
     A like plurality of planetary gears are rotatably mounted on the planetary gear shafts, of which planetary gears  144 ,  144 ′ are illustrated in  FIG. 2  with the planetary gear  144 ′ being fitted to the planetary gear shaft  142 . The planetary gears  144 ,  144 ′ are also seen in  FIG. 3 , which shows an additional planetary gear  144 ″. The planetary gears are operatively mounted within a stationary gear  146  which is fixedly mounted within the starter motor housing  102 . The integrated gear support/clutch barrel  136  is operatively mated to the stationary gear  146  by a support ring  147 . The support ring  147  is fixedly attached to the stationary gear  146 . A support wall  149  is partially defined in the starter housing  106  against which the support ring  147  partially rests. The clutch barrel  136  is freely rotatable within the support ring  147 . 
     The second end  122  of the armature shaft includes a sun gear  148  and a bearing surface  150  that is rotatably mounted within a sleeve bearing  152  that is fixedly and centrally mounted within an aperture defined in the end of the integrated gear support/clutch barrel  136 . A thrust ball  151  is also fitted within the aperture defined in the end of the integrated gear support/clutch barrel  136 . The operation of the sun, planetary, and stationary gears is consistent with known operation. 
     The epicycle gear train/one-way roller clutch assembly  112  further includes an output shaft  154 . The output shaft  154  includes a race  156 . A clutch roller housing  158  is defined between the inner wall of the clutch barrel  136  and the race  156 . Within the clutch roller housing  158  is disposed a plurality of clutch rollers, of which two clutch rollers  160 ,  160 ′ are shown in  FIG. 3 . A like number of springs are provided for biasing the clutch rollers into their locked or working positions as is known in the art. Some of the springs are shown generally in  FIG. 2 , while a pair of springs  162 ,  162 ′ are more clearly seen in  FIG. 3 . 
     The output shaft  154 , which is also part of the clutch assembly  112 , includes a series of parallel external helical splines  164  which are cut into the shaft  154 . The helical splines  164  are seen sectionally in  FIG. 2  and perspectively in  FIG. 3 . The helical splines  164  mesh with a like number of internal helical splines  166  formed in the inner wall of an input end  168  of a carrier shaft  170 , shown sectionally in  FIG. 2 . The carrier shaft  170  also includes an output end  172  which is mated via splines to a pinion gear  174  which is selectively matable with the ring gear of the internal combustion engine crankshaft (not shown) as will be described below. The output end  172  of the carrier shaft  170  is rotatably mounted within the clutch housing  106  by a bearing assembly  175 . 
     The solenoid assembly  114  is of the open frame or “D” frame configuration. The assembly  114  includes a solenoid plunger  176  which selectively reciprocates with and lends support to the carrier shaft  170  in a known manner. A solenoid coil and bobbin assembly  178  is mounted in a coil frame  180 . The frame  180  is fixedly mounted within the starter housing  106 . 
     The solenoid assembly  114  is shown in  FIG. 2  in its open position wherein the motor  100  is disengaged and is in its resting configuration. In this position no power is directed to the motor  100 . 
       FIG. 4  illustrates the motor  100  in its engaged position in which the solenoid coil  178  has been energized via the ignition/starter switch (not shown), thus causing the solenoid plunger  176  to be drawn into the solenoid coil  178  against the force of a return spring  177 . This position effects operative engagement of the pinion gear  174  with the ring gear (not shown). Engagement of the pinion gear  174  with the ring gear is assisted by a meshing spring  182  which is pre-loaded and provides a high pushing force to engage the pinion gear  174  with the ring gear. Electrical power is also sent to the motor portion  110 , thus effecting rotation of the armature shaft  118 . The shaft  118  drives the integrated gear support/clutch barrel  136  via the sun gear  148  and the planetary gears  144 . The integrated gear support/barrel  136  drives the race  156  because of the friction that results between the integrated gear support/clutch barrel  136 , the clutch rollers  160 ,  160 ′ . . . , and the race  156 . The output shaft  154  effects rotation of the pinion gear  174  via the carrier shaft  170 . 
     Once the engine starts running, the revolutions of the race  156  exceed the revolutions of the integrated gear support/clutch barrel  136 , and the rollers  160 ,  160 ′ . . . are returned to their pre-engagement positions as is known in the art. This causes the epicycle gear train/one-way roller clutch assembly  112  to slip, thus leading to the breaking of the connection between the pinion gear  174  and the armature shaft  118 . By breaking this rotational connection the armature shaft  118  is prevented from being rotated too fast, thus avoiding being damaged. The pinion gear  174  remains meshed with the ring gear as long as the solenoid coil  178  is energized. The solenoid plunger  176 , the carrier shaft  170 , and the pinion gear  174  are all returned to their initial positions by the return spring  177  once the solenoid coil  178  is de-energized. 
     The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.