Abstract:
A starter drive for an internal combustion engine having a clutch to provide rotary torque from a starter motor to a pinion gear connectable to a gear associated with an engine. The clutch has means for indexing the pinion gear to engage the gear associated with the engine, means for maintaining the teeth of the clutch engaged during the indexing function, means for automatically separating the clutch teeth when the engine starts and for maintaining separation of the teeth as long as the rotational speed of the pinion gear is greater than a predetermined speed. The starter drive includes two serially arranged resilient members between a driven clutch member and the sleeve on which the starter drive is slidably mounted. The housing is resiliently suspended between the two resilient members.

Description:
BACKGROUND OF THE INVENTION 
     1. FIELD OF THE INVENTION 
     The invention is related to a starter drive for internal combustion engines and in particular to a starter drive having increased impact resistance. 
     2. DESCRIPTION OF THE PRIOR ART 
     The invention is an improvement of the starter drive such as those taught by Digby in U.S. Pat. No. 3,263,509 and U.S. Pat. No. 3,714,834. These starter drives are slidably disposed on a power shaft connected to a starter motor and are axially displaced along the power shaft to engage a pinion gear with the ring gear of the engine. The starter drives taught by Digby contain an indexing mechanism which rotates the pinion gear in the event that the teeth of the pinion gear fail to mesh with the teeth of the ring gear of the engine as the starter drive is displaced. The indexing mechanism includes a spring or resilient bumper which absorbs the shock when the pinion gear abuts rather than engages the ring gear. 
     In an alternate arrangement taught by Johnson in U.S. Pat. No. 3,915,020, a bumper spring is applied between the external housing and a drive clutch member which permits the pinion gear to be indexed when it abuts rather than engages the ring gear. Johnson also provides a multi-piece external housing in which two concentric housing members are biased toward each other by an annular resilient member. This resilient member partially absorbs the force resulting from the axial displacement of the clutch and the pinion members by the bumper spring when the pinion gear is indexed into alignment with the ring gear of the engine. 
     SUMMARY OF THE INVENTION 
     The invention is a starter drive for an internal combustion engine having a power shaft rotatably connectable to a starter motor. A sleeve is slidably disposed on the power shaft and is rotatable therewith. The sleeve has an input end portion, an output end portion, and an intermediate portion. The intermediate portion has an external helical spline provided therealong. A driving clutch member circumscribes the intermediate portion of the sleeve and has internal helical splines which engage the external helical splines of the intermediate portion. A driven clutch member is slidably journaled to the output end portion of the sleeve. The driven clutch member has one end adjacent to the driving clutch member. A pinion gear is attached to the driven clutch member and is axially movable therewith into and out of engagement with a gear of an engine to be started. A cylindrical housing circumscribes the sleeve, the driving clutch member, and a portion of the driven clutch member. The housing has a closed end slidably attached to the sleeve and an open end circumscribing a portion of the driven clutch member. A cylindrically shaped retainer member is concentrically disposed within the housing. The retainer member has a first end adjacent to the open end of the housing and a radial flange provided at a second end which is opposite the first end. A first abutment is provided within the housing adjacent to the open end and a resilient annular member is compressively disposed between the radial flange of the retainer and the first abutment which produces a force biasing the retainer member in an axial direction towards the closed end of the housing. A second abutment is provided at the first end of the retainer member and is adapted for engagement with the driven clutch member to limit the displacement of the driven clutch member in an axial direction away from the driving clutch member. Resilient means are provided within the housing adjacent to the closed end for biasing the housing relative to the sleeve in a direction away from the intermediate portion. A coil spring is disposed within the housing for producing a force urging the driving clutch member towards the driven clutch member to maintain the first set of teeth provided on the driving clutch member in engagement with the second set of teeth provided on the driven clutch member and for resiliently biasing the driving and driven clutch members, as a unit, towards the second abutment. 
     A first object of the invention is a starter drive having two shock absorbers. 
     A second object of the invention is a starter drive having a shock absorber disposed between the housing and the driven clutch member. 
     Still another object of the invention is the use of a second shock absorber in the form of an annular resilient member disposed within the housing. 
     Still another object of the invention is the use of an intermediate cylindrical member between the housing and the driven clutch member and a resilient annular bumper disposed between the housing and the intermediate cylindrical member. 
     Yet another object of the invention is to have the annular bumper member compressively loaded in an axial direction maintaining contact between the intermediate cylindrical member and the driven clutch member when the pinion gear abuts rather than engages the starter gear of the engine to be started. 
     These and other objects of the invention will become more apparent from a reading of the specification in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a partial cross-sectional side view showing the details of the starter drive incorporating the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawing there is illustrated a starter drive 10 for an internal combustion engine incorporating two shock absorbers. The starter drive 10 is mounted on a power shaft 12 of a starter motor (not shown). The starter drive 10 includes an axially extending sleeve 14 rotatably connected to the power shaft 12 by mating longitudinal splines 16 as is known in the art. The longitudinal splines 16 permit the sleeve 14 to be axially displaced along the power shaft 12. An annular driving clutch member 18 is rotatably mounted on the sleeve 14 and is connected thereto by mating helical splines 20 provided on the internal surface of the driving clutch member 18 and the external surface of the sleeve 14. The mating helical splines 20 are arranged to displace the driving clutch member 18 towards a driven clutch member 22 when the power shaft 12 is rotated by the starter motor in a first direction relative to the driving clutch member 18. 
     The driven clutch member 22 is slidably journaled on the sleeve 14 by means of a first sleeve bearing 24. The sleeve 14 is slidably supported on the power shaft 12 at the end opposite the longitudinal splines 16 by a second sleeve bearing 26. A pinion gear 28 is fixedly attached to the driven clutch member 22. Preferably the pinion gear 28 is formed integrally with the driven clutch member 22, but the driven clutch member 22 and the pinion gear 28 may be separate elements fixedly attached to each other as shown. 
     The opposing adjacent faces of the driving clutch member 18 and the driven clutch member 22 are provided with complementary mutually engagable inclined torque transmitting dentil teeth as known in the art. The dentil teeth are of the sawtooth variety to produce a one way overrunning clutch connection. 
     A cylindrically shaped housing 30 having an open end 32 and a closed end 34 is slidably supported at its closed end 34 on the external surface of the sleeve 14. A first lock ring 36 is seated in an annular groove adjacent to the open end 32 of the housing 30. The first lock ring 36 retains an annular seat 38 for a first annular resilient member 40. The opposite end of the first annular resilient member 40 abuts a radial flange 42 of a cylindrically shaped intermediate retainer member 44. The annular resilient member 40 is preferably made from an elastically deformable material such as rubber and is compressively disposed between the annular seat 38 and the radial flange 42. The intermediate retainer member 44 is concentrically disposed in the open end 32 of the housing 30. 
     A second lock ring 46 is seated in an annular groove at the end of the intermediate retainer member 44 opposite the radial flange 42. The second lock ring 46 engages a radially extending peripheral lip 48 of the driven clutch member 22. The second lock ring 46 ties the axial displacement of the driven clutch member 22 to the axial displacement of the intermediate retainer member 44. 
     The sleeve 14 is provided with a radial shoulder 50 which serves as an abutment for an annular retainer 52 slidably journaled on the sleeve 14. A second annular resilient member 54 circumscribes the sleeve 14 and is compressively disposed between the annular retainer 52 and the closed end 34 of the housing 30. The annular resilient member 54 is preferably made from an elastically deformable material such as rubber. A coil spring 56 is compressively confined between the annular retainer 52 and an annular shoulder provided on the driving clutch member 18, as shown, to resiliently bias the driving clutch member 18 in a direction towards the driven clutch member 22. 
     Means for moving the starter drive 10 towards or away from the gear 58 associated with the internal combustion engine (not shown) may be a conventional solenoid, air, or hydraulic cylinder actuated lever (not shown) connected between the closed end 34 of the housing 30 and a shift collar 60 attached to the sleeve 14. 
     Means for accomplishing the automatic separation of the dentil teeth of the driving clutch member 18 and the driven clutch member 22, respectively, are arranged in an annular recess 62 of the driven clutch member 22. An annular thrust washer 64 backed by an annular cam 66 abuts a shoulder provided on the driving clutch member 18 adjacent to the driven clutch member 22. The inner surface of the annular cam 66 has a conical shape concentric with the axis of the sleeve 14. A plurality of arcuate centrifugal flyweight members 68 are disposed in the annular recess 62 adjacent to the annular cam 66. Each flyweight member 68 has an inclined surface complementary with and abutting the conically shaped inner surface of the annular cam 66. The flyweight members 68 have guide apertures located near their center of gravity which receive radially disposed guide pins 70. The guide pins 70 are received in radial bores provided in the driven clutch member 22 and secured therein. The guide pins 70 permit radial displacement of the flyweight members 68 but restrain the flyweight members from displacement in an axial or circumferential direction relative to the driven clutch member 22. 
     In operation, when it is desired to crank the engine, the starter drive 10 is shifted along the power shaft 12 by means of a positioning mechanism connected between the housing 30 and the shift collar 60 to engage the pinion gear 28 with the gear 58 associated with the engine. The starter motor then rotates the power shaft 12 which in turn rotates the pinion gear 28 through the longitudinal splines 16, sleeve 14, driving clutch member 18, and driven clutch member 22. When the engine starts, the gear 58 will rotate the pinion gear 28, the driven clutch member 22, and the driving clutch member 18 at a speed which is faster than the rotational speed of the starter motor and the sleeve 14. As a result, the driving clutch member 18 will be axially displaced by the dentil teeth and the helical splines 20 away from the driven clutch member 22 against the force of the coil spring 56. At the same time, the centrifugal forces will radially displace the flyweight members 68 which will displace the annular cam 66 to follow the axial displacement of the driving clutch member 18. The centrifugal force acting on the flyweight members 68 due to the rotation of the pinion gear 28 by the running engine is sufficient to hold the flyweight members 68 in their radially displaced position preventing the annular cam 66 and the driving clutch member 18 to return to their original position. The radially displaced flyweight members 68 and the resultant axial displacement of the annular cam 66 hold the driving clutch member 18 in a displaced position in which its dentil teeth are physically separated from the dentil teeth of the driven clutch member 22, preventing chattering and wear of the dentil teeth. 
     Once the engine is started, the starter motor is deenergized and the starter drive 10 is displaced back to its original position, as shown in the drawing in which the pinion gear 28 is disengaged from the gear 58. The rotational speed of the pinion gear 28 and the driven clutch member 22 will rapidly decrease to the point where the centrifugal forces acting on the flyweight members 68 are no longer capable of holding the annular cam 66 and the driving clutch member 18 in the displaced position. The coil spring 56 will then displace the driving clutch member 18 back into engagement with the driven clutch member 22 as shown in the drawing. The driven clutch member 22 is resiliently connected to the housing by the intermediate retainer member 44 and the first annular resilient member 40. Therefore, a portion of the shock generated when the driving clutch member 18 reengages the driven clutch member 22 is absorbed by the first annular resilient member 40, while a second portion of this shock is absorbed by the second annular resilient member 54 between the housing 30 and the sleeve 14. 
     In the event that the teeth of the pinion gear 28 are not aligned with the teeth of the gear 58 associated with the engine as the starter drive 10 is displaced along the power shaft 12, the teeth of the pinion gear 28 will abut the sides of the mating teeth of the gear 58. The initial shock of the teeth of the pinion gear 28 abutting the sides of the teeth on the gear 58 will be partially absorbed by the coil spring 56 and the second annular resilient member 54. After the initial shock, only the housing 30 and the sleeve 14 are displaced towards the gear 58 by the positioning means. 
     As the sleeve 14 is advanced, the helical splines 20 rotate the driving clutch member 18 which in turn rotates the driven clutch member 22 and the pinion gear 28 until the teeth on the pinion gear 28 become aligned with the teeth of the gear 58. When the teeth of the pinion gear 28 and the teeth of the gear 58 become aligned, the coil spring 56 and the second annular resilient member 54 urge the driving clutch member 18 and the driven clutch member 22 towards the gear 58 which displaces the pinion gear 28 into engagement with the gear 58. 
     Because the first annular resilient member 40 was compressively disposed between the housing 30 and the intermediate retainer member 44, the second lock ring 46 is held in physical contact with the peripheral lip 48 of the driven clutch member 22. The rapid axial displacement of the driving and driven clutch members 18 and 22 by the coil spring 56 is absorbed by the first annular resilient member 40 rather than resulting in a hard direct metal-to-metal contact between the peripheral lip 48 of the driven clutch member 22 and the second lock ring 46 as taught by the prior art. 
     It is to be noted that the first and second annular resilient members 40 and 54 are serially arranged between the driven clutch member 22 and the sleeve 14 with the mass of the housing 30 being suspended therebetween. This arrangement of using two serially arranged resilient members with the mass of the housing suspended therebetween has been found to be more effective in absorbing the impact shocks during engagement of the pinion gear 28 with the gear 58 associated with the engine than the use of the single resilient member as taught by the prior art. 
     It is not intended that the invention be limited to the specific structure shown in the figure and described in the specification. It is understood that those skilled in the art will be able to make changes or otherwise modify the structure of the starter drive within the scope of the invention as described above and set forth in the appended claims.