Starting apparatus

A starting apparatus includes a drive motor and a reduction gear having a planetary gear for starting an engine by the drive motor via the reduction gear. An internal gear of the reduction gear includes a locking projection projecting in an axial direction. A rotation restricting member is formed with a guide groove in which the locking projection is loosely received and guided in a circumferential direction. A shock absorbing member is held in the guide groove in a state of being elastically in close contact with the locking projection in the circumferential direction. Thus, shock load to the internal gear is alleviated from the start.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No. 2002-125979 filed on Apr. 26, 2002, No. 2002-363019 filed on Dec. 13, 2002 and No. 2002-363023 filed on Dec. 13, 2002, the disclosure of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a starting apparatus used to start an engine. More specifically, the present invention relates to a starting apparatus having a reduction gear with a planetary gear.

BACKGROUND OF THE INVENTION

An internal combustion engine (hereinafter, simply referred to as “engine”) needs to be driven by a starting apparatus (hereinafter, pertinently referred to as “starter”) in starting the engine. As the starting apparatus, there are a gear type starter, a belt type starter and the like all of which are common in that an electric motor constitutes a drive source.

In starting the engine, comparatively large torque is required although depending on a kind and a displacement thereof. Therefore, when the engine is cranked directly by the motor, the physical configuration of the motor naturally becomes large. Hence, in a recent starting apparatus requesting light-weighted compact formation, high torque necessary for starting is achieved by interposing a reduction gear between the motor and the engine to thereby increase a speed reducing ratio.

Although there are various reduction gears, a planetary gear-type reduction gear, which compactly achieves a large speed reducing ratio, is frequently used. In the planetary-type reduction gear, a driving force inputted from the motor to a sun gear of the reduction gear is outputted from a carrier supporting planetary gears with high torque. In this case, rotation of an internal gear, which meshes with the planetary gears, in the circumferential direction is restricted to achieve a predetermined speed reducing ratio. That is, a large reaction force (torque) produced in accordance with the output needs to be received by the internal gear. Therefore, rotation of the internal gear in the circumferential direction needs to be constrained.

Meanwhile, according to the engine, torque necessary for rotation is rapidly varied by strokes of intake, compression and the like and an engine rotation speed is also pulsated. The motor of the starter cannot well follow such a load variation or the like and therefore, impact load is applied between the internal gear and a rotation restricting portion thereof. Further, the reaction force applied to the internal gear is not constant. As a result, unpleasant sound is likely to be caused in starting the engine due to vibration or the like of the internal gear by simply constraining the internal gear.

When the internal gear is rigidly restricted here, it is required to reinforce the internal gear or the restricting portion to be able to withstand the shock load, which hampers light-weighted compact formation of the starter. Hence, in order to alleviate the shock load applied to the internal gear and the like, a shock absorbing member including an elastic body made of such as rubber is provided between the internal gear and the rotation restricting portion. These are proposed in, for example, JP-Y2-2-31581, JP-Y2-2-31583, JP-B2-4-40549 (U.S. Pat. No. 4,561,316), and JP-A-5-52166 (U.S. Pat. No. 5,323,663).

For example, according to JP-Y2-2-31581, JP-Y2-2-31588 and JP-B2-4-40549, the shock absorbing member is for example provided on an outer peripheral side of an internal gear. However, an outer diameter of a reduction gear is increased thereby and compact formation of a starter is not achieved.

According to JP-A-5-52166, a projection extending from a side face of an internal gear in an axial direction is held by a shock absorbing member (elastic body) and therefore, in this case, a starter is not enlarged in an outer diameter direction. However, the projection of the internal gear is not held elastically by the shock absorbing member from the start. Therefore, shock load is not necessarily alleviated sufficiently from start of operation thereof. Particularly, in the case in which the internal gear and the like are made of synthetic resin in view of light-weighted and low coast formation or the like, when shock load is insufficiently alleviated, reliability of the internal gear and therefore, the starter can be lessened.

Further, in JP-A-5-52166, a friction plate is separately pressed to a pivoting plate engaged with the internal gear and the internal gear is constricted by friction force produced therebetween. Therefore, the structure of the starting apparatus is complicated.

Also, the shock absorbing member used in JP-A-5-52166 is rubber in a shape of a rectangular parallelepiped and an area thereof in contact with an inner wall of a containing portion thereof is large. Therefore, compression operability of the shock absorbing member is poor and the shock absorbing member is likely to easily wear.

Further, the shock absorbing member only receives reaction force in the circumferential direction of the internal gear. There is not a specific disclosure with regard to supporting the internal gear in an axial direction. In addition, the internal gear is not provided with a detent and therefore, the internal gear continues rotating little by little while the exerted reaction force is large. As a result, efficiency of transmitting driving force of the motor is likely to be lessened.

SUMMARY OF THE INVENTION

The present invention has been carried out in view of such a situation and it is an object of the present invention to provide a starting apparatus capable of alleviating shock load applied in accordance with a variation in engine load from the start and achieving compact formation.

It is another object of the present invention to provide a starting apparatus capable of resolving unpleasant sound in starting.

It is further another object of the present invention to provide a comparatively simple and efficient starting apparatus with improvements of durability of a shock absorbing member and reliability.

According an aspect of the present invention, a starting apparatus includes a drive motor and a reduction gear. The reduction gear includes a sun gear rotated by receiving an input from the drive motor, an internal gear arranged concentrically around the sun gear, a rotation restricting member for restricting free rotation of the internal gear, a shock absorbing member interposed between the internal gear and the rotation restricting member. A carrier rotatably supports a planetary gear meshing with the sun gear and the internal gear and outputs an input of the sun gear by reducing a speed thereof. A driving force from the drive motor is transmitted to an engine via the reduction gear, thereby starting the engine.

The internal gear includes a locking projection projecting from a side face thereof along a rotation axis of the reduction gear. The locking projection is loosely received in a guide groove formed on the rotation restricting member, and guided therein in a circumferential direction. The shock absorbing member is held in the guide groove in a state of being elastically in close contact with circumferential side faces of the locking projection.

According to the starting apparatus, the locking projection projects in the axial direction from the side face of the internal gear. Therefore, an outer diameter of the reduction gear is not enlarged.

The locking projection can be moved in the guide groove of the rotation restricting member in a certain range in accordance with a direction of reaction force or impact load applied to the internal gear from the planetary gear. In this case, the locking projection is elastically supported by the shock absorbing member in the guide groove from both of the sides in the circumferential direction, irrespective of whether reaction force is applied to the internal gear. Thus, the internal gear is in a state of being elastically held from start of operating reaction force. Even when the reaction force or the shock load is released, also the other side face of the locking projection in the circumferential direction is elastically supported by the shock absorbing member. Therefore, it is less likely that rapid load will be operated to the internal gear.

Accordingly, large shock load to the internal gear is suppressed. Reliability of the starter is ensured even when the internal gear is made of synthetic resin. Further, by alleviating the shock load, unpleasant sound generated in starting the engine is also decreased. Although the shock absorbing member includes a spring or the like, an elastic body comprising rubber or the like is general therefore in consideration of cost, shock absorbing function or the like.

According to another aspect of the present invention, a starting apparatus includes a drive motor and a reduction gear. The drive motor starts to rotate an engine via the reduction gear. The reduction gear includes a sun gear rotated by receiving an input from the drive motor, an internal gear arranged concentrically with the sun gear on an outer peripheral side of the sun gear, a planetary gear meshing with the sun gear and the internal gear, a carrier rotatably supporting the planetary gear and outputting an input of the sun gear by reducing a speed thereof. The reduction gear further includes a rotation constraining unit for constraining rotation of the internal gear arranged movable in a circumferential direction.

The rotation constraining unit includes a movable locking portion integrated movable with the internal gear in the circumferential direction, an unmovable locking portion arranged in a state opposing to the movable locking portion in the circumferential direction and unmovable in the circumferential direction, and a shock absorbing member including an elastic block portion. The elastic block portion is elastically held at least between the movable locking portion and the unmovable locking portion. The elastic block portion elastically receives a reaction force applied to the internal gear when the drive motor starts to rotate the engine via the reduction gear.

According to the starting apparatus, the internal gear is restricted from rotating at least in one direction by the rotation constraining unit including the movable locking portion, the unmovable locking portion and the shock absorbing member.

In starting the engine, the internal gear receives a reaction force in a direction opposite to an output of the carrier. The reaction force is received by the unmovable locking portion from the movable locking portion integrally moved with the internal gear via the elastic block portion of the shock absorbing member. Thus, the internal gear is restricted from rotating in the direction of the reaction force.

The reaction force is gradually elastically received by the unmovable locking portion. Therefore, it is less likely that shock load will be applied to respective portions and unpleasant sound will be caused by direct contact of locking members. Further, the shock absorbing member also works as a vibration isolating member and therefore, can absorb vibration and sound generated at the reduction gear or a surrounding thereof. In this way, the reduction gear can reduce vibration, unpleasant sound generated in operating the starting apparatus although the reduction gear is provided with a comparatively simple structure.

DETAILED DESCRIPTION OF EMBODIMENTS

The first embodiment of the present invention will be described hereinafter with reference toFIGS. 1 through 3.

FIG. 1shows a gear-type starter (hereinafter, simply referred to as a starter)1. The starter1mainly includes a reduction gear10, a motor80and a magnet switch90. Although not illustrated in details, an output of the motor80is transmitted to an output shaft that is formed with a helical spline on its outer peripheral face via the reduction gear10.

An overrunning clutch (one way clutch) and a pinion gear are arranged on the helical spline. (See,FIG. 7) In starting, the overrunning clutch and the pinion gear are pushed in an axially forward direction (to a left side ofFIG. 1) by lever operation of the magnet switch90. Further, the pinion gear is temporarily brought in mesh with a ring gear attached to a crankshaft of the engine to thereby crank the engine. When the engine has been started, the pinion gear of the starter1is idly rotated by the overrunning clutch to thereby prevent excessive rotation of the motor80.

The reduction gear10has a sun gear11, three planetary gears12, a carrier13, an internal gear14, a shock absorbing member15, and a gear housing (rotation restricting member)18. The sun gear11is formed on or spline-fitted to a motor main shaft811that extends from a rotor81of the motor80. The three planetary gears12are arranged at a surrounding of the sun gear11. The planetary gears12mesh with the sun gear11. The carrier13rotatably and revolvably supports the planetary gears12via a roller bearing122and a pin123. The internal gear14is arranged on outer peripheral sides of the planetary gears12. The internal gear14has internal teeth and meshes with the planetary gears12. The gear housing18covers the outer periphery and an axially front end (left side ofFIG. 1) of the internal gear14. The shock absorbing member15is interposed between the internal gear14and the gear housing18.

The gear housing18is fixed to a motor housing88that surrounds the motor80at an axially front end of the motor housing88. A cover plate19is provided between the gear housing18and the motor housing88to partition therebetween. The cover plate19is in contact with a rear end face of the internal gear14to thereby also restrict the internal gear14in the axial direction. Further, the internal gear14is made of thermosetting resin.

Next, an explanation will be given of the internal gear14, the shock absorbing member15and the gear housing18which are characteristic portions of the embodiment with reference toFIG. 2.

The internal gear14has four locking projections143. The locking projections143projects from an axial front surface of the internal gear14at a slightly inner peripheral side. The locking projections143are arranged at equal intervals in a circumferential direction of the internal gear14. Inner and outer peripheral faces of the locking projection143include circular arc faces. Circumferential faces of the locking projection143lie substantially perpendicular to the circumference of the gear.

The shock absorbing member15is a ring-shaped rubber member. The shock absorbing member15includes locking recessed portions156at an axial rear end face and fixed recessed portions155at an axial front end face. Rubber blocks (elastic blocks) disposed on both sides of the locking recessed portion156constitute a first elastic block portion151and a second elastic block portion152. A portion connecting the first elastic block portion151and the second elastic block portion152on a side opposite to the fixed recessed portion155constitutes a bridging portion153. Further, a small semispherical elastic projection154protrudes from a center of a bottom face of the locking recessed portion156in an axially rear direction. Further, the shock absorbing member15is made of oil resistant rubber (for example, NBR) that is not easily deteriorated even when grease or the like is adhered thereto. The shock absorbing member15is formed by integral molding of rubber.

The gear housing18is a substantially cylindrical member and provided with a through hole183to support an output shaft of the carrier13via a sleeve bearing132(FIG. 1) at a center thereof. Guide grooves181having bottomed circular arc shapes are arranged in a ring-like shape at equal intervals in the circumferential direction to surround an outer periphery of the through hole183. Further, the guide grooves181are partitioned with ribs185extending in a radial direction.

The respective members are integrated as follows. First, the shock absorbing member15is press-fitted to the guide grooves181of the gear housing18. At this time, the first elastic block portion151and the second elastic block portion152opposing each other by interposing the locking recessed portion156are fitted in the same guide groove181.

Further, the fixed recessed portion155is fitted to the rib185of the gear housing18. In this condition, there is no clearance or play between the gear housing18and the shock absorbing member15in the circumferential direction. Further, the locking projection143of the internal gear14is press-fitted to the locking recessed portion156of the shock absorbing member15.

Therefore, circumferential faces of the first elastic block portion151and the second elastic block portion152that are opposed through the locking recessed portion156are in a state of being elastically in close contact with the circumferential faces of the locking projection143. That is, the locking projection143is in a state of being previously pressed by the first elastic block portion151and the second elastic block portion152.

Accordingly, the shock absorbing member15absorbs shock load applied to the internal gear14gradually from start of displacement thereof in the circumferential direction. The behavior is shown inFIG. 3by a solid line X.FIG. 3conceptually shows a relationship between rotational displacement of the internal gear and shock absorbing function of the shock absorbing member. A dotted line Y shows a case in which a shock absorbing member is not in close contact with the locking projection and a clearance (δ) is present between the shock absorbing member and a wall face of a guide groove as in the prior art. In the case of the dotted line Y, shock load is absorbed after an internal gear is displaced by an amount of the clearance. Further, the absorption is considerably rapid by an amount of retarding to absorb shock load. Therefore, it is known that according to the conventional shock absorbing structure, absorption and reduction of the shock load applied to the internal gear are insufficient.

According to the embodiment, the locking projection143extending from the front face of the internal gear14in the axial direction and therefore, the reduction gear10is not enlarged in the outer diameter direction.

Also, the locking projections143can move in the guide grooves181of the rotation restricting member18in a certain range in accordance with a direction of reaction force or impact load applied to the internal gear14from the planetary gears12. The locking projections143are elastically supported at the circumferential faces by the shock absorbing member15, which is held in the guide grooves181, in the circumferential direction, irrespective of whether reaction force is applied to the internal gear14. That is, the internal gear14is elastically held from start of operating reaction force.

Further, even when the reaction force or the shock load is released, the circumferential faces of the locking projections143are elastically supported by the shock absorbing member15. Therefore, it is less likely that the load will be rapidly applied to the internal gear14. In this way, the internal gear14is restrained from large shock load more than that of the prior art. The internal gear14is firmly protected. As a result, reliability of the starter1is ensured even when the internal gear14is made of synthetic resin. Further, by the alleviation of the shock load, unpleasant sound generated in starting the engine is decreased.

Meanwhile, although the shock absorbing member15includes a spring or the like, an elastic body including rubber or the like is general therefore in consideration of cost, shock absorbing function or the like.

Although an explanation has been given of shock absorbing operation when force is applied to the internal gear14in the circumferential direction, in consideration of various vibrations applied to the internal gear14, integration tolerance and the like, it is preferable that the internal gear14is elastically held also in the axial direction. Here, the shock absorbing member15has the semispherical elastic projections154projecting in the axial direction. Therefore, the axial end faces of the locking projections143are elastically held by the elastic projections154.

Next, the second embodiment will be described with reference toFIG. 4.

In the second embodiment, a shock absorbing member25has a shape different from the shape of the shock absorbing member15of the first embodiment. Shock load applied to the internal gear14is absorbed by four independent shock absorbing members25each having the same shape.

Each of the shock absorbing member25includes a first elastic block portion251, a second elastic block portion252and a bridging portion253for bridging the first elastic portion251and the second elastic portion252. An elastic projection254is formed on the bridging portion253to elastically contact with an axially front end face of the internal gear14. The shock absorbing member25is formed by integral molding of rubber.

The shock absorbing member25is fixed to the gear housing18such that a fixed recessed portion255formed between the first elastic block portion251and the second elastic block portion252, that is, on a front side of the bridging portion253is press-fitted to the rib185partitioning the guide grooves181. Therefore, the first elastic block portion251and the second elastic block portion252of one of the block absorbing members25are respectively held in contiguous ones of the guide grooves181. Further, the locking projection143of the internal gear14is press-fitted between the first elastic block portion251of one shock absorbing member25and the second elastic block portion252of the different shock absorbing member25.

Reaction force or shock load applied to the internal gear14is received and absorbed mainly by the first elastic block portion251having a larger rubber volume. At this time, a circumferential face of the first elastic block portion251on a side of the bridging portion253is supported by the rib185, that is, supported by an inner wall of the guide groove181.

Therefore, even when the first elastic block portion251is considerably contracted, the bridging portion253is hardly effected by that contraction. That is, different from the case of the shock absorbing member15, the bridging portion253is not stretched by the contraction of the first elastic block portion251. Accordingly, the elastic projection254stably, presses the front end face of the internal gear14in the axial direction.

In the second embodiment, the first and the second elastic block portions251,252are filled in the guide grooves181. Therefore, the locking projections143are held in a state of being elastically in contact with the shock absorbing member25.

In a case that there are a plurality of partitioned guide grooves, a large number of steps are required for fitting the elastic members piece by piece. Also, a number of parts is increased. However, the plurality of guide grooves181is arranged at equal intervals in the circumferential direction. Also, the shock absorbing member25is formed such that the first elastic block portion251and the second elastic block portion252, which are respectively fitted in contiguous guide grooves181, are connected by the bridging portion253to span the one guide groove181. Accordingly, the number of parts is reduced. Further, the first elastic block portion251and the second elastic block portion252can be fitted in the guide grooves181in one motion.

Further, the elastic projection254is provided at the bridging portion253to elastically contact with the front end face of the internal gear14. Since the shock absorbing members25are separate in the circumferential direction, influence by the contraction of the first elastic block portion251or the second elastic block portion252is hardly effected on the bridging portion253due to restriction by the inner wall of the guide groove181. That is, the elastic projection254is not moved in the circumferential direction by being dragged by contraction of the elastic block portions251,252. Thus, the elastic projection254can stably urge the internal gear14in the axial direction. Accordingly, uneven wear or the like of the internal gear14can be effectively restrained. Thus, reliability of the starter1increases.

Next, the third embodiment will be described with reference toFIG. 5. In the third embodiment, the shock absorbing member35includes a first elastic block portion351, a second elastic block portion352and a bridging portion353, similar to the shock absorbing member25of the second embodiment. However, the first elastic block portion351is significantly different from the first elastic block portion251of the shock absorbing member25in that a central portion of the first elastic block portion351is slenderly constricted. That is, the first elastic block portion351includes end portions351aand351band a constricted portion351c.

The end portions351ais a portion being in contact with the circumferential face of the locking projection143of the internal gear14. Further, the end portions351aand351bare fitted in the guide groove181in a state that the inner and outer peripheral walls of the end portions351a,351bare loosely in contact with inner walls of the guide groove181. That is, the end portions351a,351bare held in the guide groove181in a loosely press-fitted state. Meanwhile, the constricted portion351cis not in contact with either of inner walls of the guide groove181and an air gap is formed therebetween.

Further, when reaction force or impact load is operated to the internal gear14and the first elastic block portion351is pressed, the constricted portion351cthat has small deformation resistance (low rigidity) mainly starts contracting and expanding in the outer peripheral direction. At this time, since the air gap is present between the constricted portion351cand the inner wall of the guide groove181, considerable deformation function is manifested by the constricted portion351c. Thus, the shock absorbing member35provided shock absorbing function larger than that of the shock absorbing member25.

Further,FIG. 5shows a case in which width of the bridging portion353is expanded in the radial direction more than the bridging portion253of the shock absorbing member25.

When the guide groove181is excessively filled with the elastic block, deformation resistance of the elastic block portion351is rapidly increased and block absorbing function by the elastic block portion251is reduced. Hence, in order to ensure the deformation resistance of the elastic block portion351in a certain range, a volume of the elastic block portion351is increased when deformed may be devised to escape.

In the third embodiment, the central portion351cof the first elastic block portion351is narrower than the end portions351a,351b. Thus, the first elastic block portion351is contractable in the circumferential direction. Further, the clearance is formed between the first elastic block portion351and the walls of the guide groove181. Therefore, the first elastic block portion351can be stably deformed by an amount of the clearance.

Further, the end portions351a,351bof the first elastic block portion351, which are elastically in contact with the end face of the locking projection143, are conversely thickened and therefore, the first elastic block portion351can firmly receive reaction force or shock load applied to the internal gear14. It is preferable that the circumferential end face of the end portion351aand the circumferential end face of the locking projection143which are in contact with each other, have the same size.

Next, the fourth embodiment will be described with reference toFIG. 5. By devising the shape of the first elastic block portion351, the deformation resistance is restrained to be low to provide the shock absorbing member35excellent in shock absorbing function. However, there is a limit therein, for example, when shock load larger than anticipated is abruptly operated, the first elastic block portion351is expanded in an outer diameter direction in accordance with contraction in the circumferential direction and also the outer peripheral face of the constricted portion351cis brought into close contact with the inner wall of the guide groove181. Then, abruptly, the deformation resistance of the first elastic block portion351increases. As a result, shock absorbing performance by the shock absorbing member35decreases.

Hence, in order to ensure the shock absorbing function by the shock absorbing member even when shock load or the like larger than anticipated is applied, it is preferable to make a volume of the guide groove181variable.FIG. 6shows such a structure.

In the fourth embodiment, the internal gear14and the shock absorbing member25are similar to those of the second embodiment. Although the shock absorbing member25is illustrated inFIG. 6, the shock absorbing member15may be used in place thereof, further, when the shock absorbing member35is used, more excellent shock absorbing function is achieved.

The fourth embodiment is characterized in a structure of a gear housing4. The gear housing4includes a circular disc48, a Belleville spring47, and a case46. The circular disk48is formed with guide grooves481penetrated in a circular arc shape uniformly at four locations. The belleville spring47is arranged on an axially front side of the circular disk48. The case46has a bottomed cylindrical shape. The case46surrounds the circular disk48and the belleville spring47and has a through hole463at a center thereof.

When the respective members are arranged as shown byFIG. 6and integrated, the belleville spring47forms a bottom portion of the guide grooves481. When load is applied in the axial direction, the belleville spring47is flexed in a direction of the load to expand a volume of the guide groove481.

Specifically, when the first elastic block portion251of the shock absorbing member25is pressed by the locking projection143of the internal gear14to contract in the circumferential direction, the first elastic block portion251is expanded to an outer side, thereby pressing the belleville spring47.

When the pressing force exceeds predetermined load, the belleville spring47is flexed and the volume of the guide groove481is expanded. As a result, the first elastic block portion251contracted in the circumferential direction is produced with an allowance of further expanding to the other side.

In this way, stable shock absorbing function by the shock absorbing member25is ensured without rapidly increasing the deformation resistance of the first elastic block portion251. Further, a clearance for bending the belleville spring47is naturally ensured between the belleville spring47and a bottom portion of the case46. A wave washer or the like may substitute for the belleville spring47. Further, although not illustrated in the drawings, a stopper is provided between an outer peripheral side of the internal gear14and the gear housing4,18. Thereby, an allowed revolution amount of the internal gear10is finally restricted.

In this way, the volume of the guide grooves481can be changed in accordance with contraction of the first elastic block portion251without devising the shape of the first elastic block portion251. Naturally, the volume of the guide grooves481can be changed also by making an inner wall thereof movable other than the bottom portion. However, in order to change the volume of the guide groove481without increasing an outer diameter of the reduction gear, a request for compact formation of the starter is complied with, further, the change of the volume of the guide groove481can be realized by a comparatively simple mechanism by making the bottom portion movable in the axial direction.

Accordingly, not only the starting apparatus1is compact but also shock load or the like applied to the internal gear14of the reduction gear10is more firmly absorbed and reliability of the internal gear14and therefore, the starting apparatus1can be promoted.

Next, the fifth embodiment will be described with reference toFIGS. 7 through 13B.

As shown inFIG. 7, the internal gear649is formed on an inner cylindrical wall of a cylindrical resin member64. The cylindrical resin member64meshes with the planetary gears12through the internal gear649. A containing case68(case) is provided on the front side (left side ofFIG. 7) of the cylindrical resin member64, in place of the gear housing4,18. A shock absorbing member65is interposed between the cylindrical resin member64and the containing case68.

The cover plate19is provided at a rear end face of the cylindrical resin member64, similar to the first embodiment. Thus, the cover plates19closes a front portion of the motor housing88of the motor80and restricting the cylindrical resin member64from moving backward in the axial direction.

The cylindrical resin member64, the shock absorbing member65and the containing case68are included in a rotation constraining unit which is characterizing portion of the fifth embodiment.

As shown inFIG. 8, the cylindrical resin member64has substantially a cylindrical shape having a ring-shaped bottom face. The cylindrical resin member64is integrally molded by thermoplastic resin. Also the internal gear649is integrally molded on the inner cylindrical wall of the cylindrical portion disposed on the rear side (right side ofFIG. 8) of the cylindrical resin member64.

The ring shape bottom face of the cylindrical resin member64is disposed on a front side of the cylindrical resin member64. The bottom face is provided with three pairs of movable locking projections641and movable contact projections642projecting in the axially forward direction. The movable locking projections641and the movable contact projections642are radially and uniformly arranged. A wall thickness of the movable contact projection642is thicker than a wall thickness of the movable locking projection641to be able to stably receive large reaction force.

Further, the cylindrical resin member64is provided with an inner ring-like projection645and an outer ring-like projection646projecting slightly to the front side from an inner peripheral edge and an outer peripheral edge of the bottom face. Further, main movable recessed portions643and sub movable recessed portions644, which are slightly recessed, are alternately formed by the inner ring-like projection645, the outer ring-like projection646, the movable locking projections641, and the movable contact projections642.

Further, a ratio of lengths in the circumferential direction of the main movable recessed portion643and the sub movable recessed portion644can be easily adjusted at where the movable locking projection641is arranged between the contiguous movable contact projections642.

As shown inFIG. 9, the shock absorbing member65includes a main elastic block portion651, a sub elastic block portion652and a bridging portion653bridging the main elastic block portion651and the sub elastic block portion652. The shock absorbing member65is integrally molded by an oil resistant synthetic resin (NBR or the like). Here, the oil resistant synthetic resin is used such that the rubber is not deteriorated even when grease used for reducing abrasive resistance is adhered to the rubber, the function of the shock absorbing member65is maintained for a long period of time.

The main elastic block portion651is in the form of a fan-shaped block and a surrounding of substantially a central portion thereof is constricted, that is, is narrow. Further, semispherical elastic projections654are provided at an outer peripheral end of the main elastic block portion651on both axial front and rear faces to make contact with the containing case68.

Although the sub elastic block portion652is in the form of a fan-shaped block, its circumferential length is considerably shorter than that of the main elastic block portion651. In this embodiment, the ratio of circumferential lengths of the main elastic block portion651and the sub elastic block portion652is set to about 5:1. The bridging portion653connects ends of the main elastic block portion651and the sub elastic block portion652in a strip-like shape.

As shown inFIG. 10, the containing case68has substantially a circular disk shape. The containing case68is formed by pertinently machining an aluminum alloy cast product. Although a front side (left side ofFIG. 10) of the containing case68is formed substantially in a shape of a planar plate, a rear side (right side) thereof is provided with three pairs of unmovable locking projections681and unmovable contact projections682projected to a rear side in the axial direction. The unmovable locking projections681and unmovable contact projections682are radially and uniformly arranged. A wall thickness of the unmovable contact projection682is thicker than a wall thickness of the unmovable locking projection681to be able to stably receive large reaction force.

Further, the containing case68is provided with an inner ring-like projection685and an outer ring-like projection686projecting to the rear side from an inner peripheral side and an outer peripheral side on the rear side of the containing case68. Further, main unmovable recessed portions683and sub unmovable recessed portions684, which are recessed, are alternately formed by the inner ring-like projection685, the outer ring-like projection686, the unmovable locking projections681, and the unmovable contact projections682.

Further, a ratio of circumferential lengths of the main unmovable recessed portion683and the sub unmovable recessed portion684can be easily adjusted by to which portion the unmovable locking projection681is arranged between the contiguous unmovable contact projections682.

The containing case68is provided with a locking piece689on an outer peripheral edge thereof. Although not illustrated, the locking piece689is engaged with a housing of the starter1to constrain such that the containing case68is not rotated in the circumferential direction.

Next, an explanation will be given of integration of the cylindrical resin member64, the shock absorbing member65and the containing case68with reference toFIGS. 11 and 12.FIG. 11shows a disassembled arrangement view of the three members andFIG. 12shows a state of integrating the shock absorbing member65to the cylindrical resin member64.

AlthoughFIG. 12shows the state of integrating the shock absorbing member65to the cylindrical resin member64for convenience of explanation, actually, after integrating the shock absorbing member65to the containing case68, the cylindrical resin member64is integrated thereto. An explanation will be given as follows in view thereof.

First, the shock absorbing member65is integrated to the containing case68. At this time, the shock absorbing member65is integrated to the containing case68such that the shock absorbing member65is fitted between the unmovable locking projection681and the unmovable contact projection682of the containing case68.

Further, the shock absorbing member65is integrated to the cylindrical resin member64such that the movable locking projection641formed at the cylindrical resin member64is pushed in between the main elastic block portion651and the sub elastic block portion652of the shock absorbing member65.

Thereby, the main elastic block portion651and the sub elastic block portion652are in a state of elastically holding the movable locking projection641therebetween. This integration of the shock absorbing member65and the cylindrical resin member64is performed at three locations along the circumferential direction.

Thus, the unmovable locking projection681is in a state of being substantially interposed between the movable contact projection642of the cylindrical resin member64and the main elastic block portion651of the shock absorbing member65. Meanwhile, the unmovable contact projection682is in a state of elastically interposing the sub elastic block portion652of the shock absorbing member65between the unmovable contact projection682and the movable locking projection641of the cylindrical resin member64.

Further, the inner ring-like projection645and the outer ring-like projection646of the cylindrical resin member64and the inner ring-like projection685and the outer ring-like projection686of the containing case68are formed to respectively correspond to each other. A substantially hermetically sealed inner space is formed between the cylindrical resin member64and the containing case68. Three shock absorbing members65are contained in the inner space.

In this condition, the cylindrical resin member64is in a state of being elastically supported in the axial direction (thrust direction) relative to the containing case68by the elastic projections654provided on both face sides of the end portions of the main elastic block portions651of the shock absorbing member65. The elastic projection654has the semispherical shape and makes point contact with the wall face.

Therefore, pivoting of the cylindrical resin member64relative to the containing case68is hardly hampered, and wear or deterioration of the elastic projection654is inconsiderable. Further, since the cylindrical resin member64is supported by the shock absorbing members65at the three locations uniformly disposed in the circumferential direction, the cylindrical resin member64is maintained stably. Therefore, transmission loss of the driving force of the internal gear649caused by an inclination or the like thereof, wear or the like thereof can be sufficiently restrained and reduced.

Next, operation of the cylindrical resin member64, the shock absorbing member65and the containing case68before and after starting the engine by the starter1will be described with reference toFIGS. 13A and 13B.FIGS. 13A and 13Bare views respectively developing planarly behaviors before and after operating the starter1.

As is apparent also fromFIG. 13A, before starting the starter1, the shock absorbing member65is fitted in a space (main unmovable recessed portion683) formed by the unmovable locking projection681and the unmovable contact projection682of the containing case68and the movable locking projection641of the cylindrical resin member64. Further, the movable contact projection642of the cylindrical resin member64is loosely located in a space (sub unmovable recessed portion684) between the unmovable locking projection681and another one of the unmovable contact projection682contiguous thereto.

Further, before operating the starter1, the shock absorbing member65is not substantially compressed except a pre-compression amount in attaching the shock absorbing member65. Also, the movable contact projection642is disposed at a position separated from the unmovable contact projection682, that is, adjacent to the unmovable locking projection681.

Meanwhile, when the starter1starts operation, the cylindrical resin member64receives the reaction force from the internal gear649in a direction denoted by an arrow A1inFIG. 13B. By the reaction force, the movable locking projection641compresses the main elastic block portion651of the shock absorbing member65in the direction A1of the reaction force.

In this embodiment, before starting the starter1, the movable locking projection641and the main elastic block portion651are held in a state of being elastically in close contact with each other. Therefore, the reaction force applied to the cylindrical resin member64is gradually absorbed from the start by the main elastic block portion651via the movable locking projection641. Accordingly, it is less likely that shock load or the like will be applied rapidly thereto.

Further, when the main elastic block portion651is compressed, the main unmovable recessed portion683achieves a function of a guide groove and the shock absorbing member65and the movable locking projection641are respectively guided thereby. Further, the sub unmovable recessed portion684achieves a function of a guide groove and the movable contact projection642is guided thereby.

When the reaction force is further increased and a compressed amount of the main elastic block portion651by the movable locking projection641reaches a vicinity of a limit (for example, compressed amount of 30%), the movable contact projection642rotated integrally with the movable locking projection641is brought into contact with the unmovable contact projection682of the fixed containing case68as in the state shown inFIG. 13B.

Then, thereafter, the cylindrical resin portion64cannot be rotated in the direction A1of the reaction force. Thus, the compressed amount of the main elastic block portion651is restricted from exceeding the limit compressed amount (maximum compressed amount) by the movable locking projection641.

Further, when the reaction force applied to the cylindrical resin member64is released after starting the engine, the shock absorbing member65and the cylindrical resin member64return from the state shown inFIG. 13Bto the state shown inFIG. 13A. At this time, the movable locking projection641is reversely moved, that is, returned toward another unmovable contact projection182(to a bottom side ofFIGS. 13A and 13B). However, inherently, the operated force is weak and the sub elastic block portion152is present between the movable locking projection641and the unmovable contact projection182. Therefore, shock load or the like is hardly applied to respective portions at this time. Accordingly, it is less likely that unpleasant sound or the like will occur at the surrounding.

In the starter1, the cylindrical resin member64of the reduction gear10is restricted from rotating at least in one direction by the rotation restricting means including the movable locking portion641, the unmovable locking portion681, and the shock absorbing member65.

Further, the shock absorbing member65serves as vibration isolating member and therefore, can absorb vibration or sound generated at the reduction gear10or a surrounding thereof. In this way, the reduction gear10of the invention can sufficiently reduce vibration, unpleasant sound or the like generated in operating the starting apparatus although the reduction gear10is provided with a comparatively simple structure.

Meanwhile, the shock absorbing member65has an elastic projected portion654projecting from at least one side of the main elastic block portion651in the axial direction. The elastic projected portion654elastically holds the internal gear in the axial direction. That is, the elastic projected portion654serves as a thrust bearing of the cylindrical resin member64. Further, vibration, deflection or the like of the internal gear10is restrained and therefore, a stable output at reduced speed is provided without bringing about wear or the like of the internal gear649.

Further, the elastic projected portion654is projected from the axial end face of the main elastic block portion651and therefore, an area thereof in contact with a sliding wall disposed on the side in the axial direction of the shock absorbing member65is very small. Therefore, as compared with the case in which an axial side face of the elastic block portion is totally brought into slide contact with a wall face or the like of a case containing the elastic block portion, movement of the main elastic block portion651in compressing operation becomes very smooth. In addition thereto, since the elastic projected portion654is mainly slide contact with the sliding wall face or the like. Therefore, wear or deterioration of the first elastic block portion651and the like is reduced. Accordingly, reliability of the shock absorbing member65can be increased.

In consideration of various vibrations applied to the internal gear649, integration tolerance and the like, it is preferable that the cylindrical resin member64is elastically held also in the axial direction. The shock absorbing member65has the elastic projected portions654projecting in the axial direction. Further, the elastic projected portions654are on the side of the unmovable locking projections681. Therefore, the elastic projected portions654are not dragged when the movable locking portions641slide. Accordingly, the elastic projected portions654achieve stable holding function.

Further, since the elastic projected portions654have semispherical shapes and make point contact with an abrasive face, abrasion resistance is reduced. Therefore, the cylindrical resin member64is smoothly moved. Further, since the sliding area is small, wear and damage of the shock absorbing member65is decreased.

Further, by providing the elastic projected portions654on the first elastic block portion651, rigidity of the first elastic block portion651at a vicinity thereof increases. With this, unexpected deformation of the elastic block portion651, which is compressed in operating the starter1, can be restrained and therefore, reliability of the shock absorbing member65is further increased.

Further, the rotation constraining unit includes the movable contact portion642and the unmovable contact portion682. The movable contact portion642is arranged at a predetermined interval from the movable locking portion641and integrally pivoted with the movable locking portion641. The unmovable contact portion682extends in the axial direction to be opposed to the movable contact portion642, faces the movable contact portion642in the circumferential direction. The unmovable contact portion682is arranged in a state of being unmovable in the circumferential direction.

Thus, a compressed amount of the elastic block portion651by the movable locking portion641and the unmovable locking portion681can be restricted by bringing the movable contact portion642and the unmovable contact portion682into contact with each other.

In this structure, even when the large reaction force is applied to the internal gear649, rotation of the cylindrical resin member64is restricted to a range until bringing the movable contact portion642into contact with the unmovable contact portion682. Therefore, also a compressed amount of the elastic block portion651by the movable locking portion641and the unmovable locking portion681is restricted within a predetermined range. Thereby, destruction, damage, early fatigue or the like of the shock absorbing member65by an excessively large compressed amount can be decreased beforehand. Thus, reliability of the shock absorbing member65and therefore, reliability of the starter1is increased.

Further, even when large reaction force is applied to the internal gear649, the movable contact portion642and the unmovable contact portion682are operated as a detent. Therefore, rotation of the internal gear64is restricted. Accordingly, an input from the drive motor80is efficiently speed reduced and outputted from the carrier13.

Since the movable locking portion641and the unmovable locking portion681are elastically held by the elastic block portion651, load is elastically and gradually applied to the movable locking portion641from the start of operation of the starter1. Further, also when the elastic block portion651returns after starting the engine, force is gradually exerted to the movable locking portion641.

Here, a state in which the elastic block portion651is elastically held between the movable locking portion641and the unmovable locking portion681is achieved by integrating the shock absorbing member65between the movable locking portion641and the unmovable locking portion681in a state that the shock absorbing member65is slightly compressed. In this way, the highly reliable and highly efficient starter1restraining unpleasant sound or the like is provided.

Further, the compressed amount (maximum compressed amount) allowed to the elastic block portion651can be easily set to change by adjusting an interval between the movable contact portion642and the unmovable contact portion682. Thus, the reduction gear10has flexibility in designing.

As the shock absorbing member65, a spring, synthetic resin, synthetic rubber or the like can be used. The elastic rubber block including synthetic rubber as in the embodiment has a degree of freedom of the shape. Thus, the elastic rubber is preferable in view of function, reliability, cost, integration performance or the like. Particularly, when the elastic block portion includes synthetic rubber, it is preferable that the movable contact portion642and the unmovable contact portion682are arranged such that a maximum compression rate thereof falls in a range of 10% through 30%.

A general allowable maximum compression rate of synthetic resin is normally set to be around 20% in consideration of durability thereof. In the case that the elastic block portion is used in a short period of time in starting the engine, even if the compression rate exceeds 20%, the reliability may not be deteriorated for a long period of time. However, when the compression rate exceeds 30%, the elastic block portion may be destructed or damaged.

Hence, in the embodiment, the compression rate is confined in 30%. Further, an upper limit of the compression rate can be easily restricted by the movable contact portion642and the unmovable contact portion682. A lower limit of the compression rate is set to 10% for effectively utilizing elasticity of the elastic block portion.

An explanation has mainly been given of the case of compressing the main elastic block portion651by the movable locking portion641. However, a direction of force applied to the movable locking portion641is changed before and after starting the engine. Therefore, the movable locking portion641and therefore, the internal gear64can be rotated in a direction opposite to the direction of the reaction force.

Here, the shock absorbing member65includes the main elastic block portion651and the sub elastic block portion652elastically held between the movable locking portion641and the unmovable contact portion682and the bridging portion653connecting the main elastic block portion651and the sub elastic block portion652to span the movable locking portion641. Also, the ratio of the circumferential length of the main elastic block portion651as compared with that of the sub elastic block portion652is in a range of 4 through 6.

Thereby, the movable locking portion641is elastically held by the sub elastic block portion652even on the side opposite to the main elastic block portion651. As a result, the movable locking portion641and therefore, the internal cylindrical resin member649are held in a state of being elastically held in both rotational directions thereof. Therefore, the movable locking portion641is in a state of being held further stably. Accordingly, unpleasant sound and vibrations reduce in the reduction gear10. Further, since the main elastic block portion651and the sub elastic block portion652are connected by the bridging portion653. Therefore, the shock absorbing member65is easily integrated. Further, it facilitates part control.

Here, the ratio of the circumferential length of the main elastic block portion651with respect to that of the sub elastic block portion652is made in the range of 4 through 6 because the force applied in a direction of compressing the main elastic block portion651, that is, reaction force in starting, is larger than the force applied in a direction of compressing the sub elastic block portion652, that is, the force opposite to reaction force.

In a case that the ratio of the circumferential length is less than 4, it is difficult to ensure durability of the main elastic block portion651. Further, in a case that the ratio of the circumferential length exceeds 6, it is difficult to achieve compact formation. Here, the ratio of the circumferential length may be compared by lengths of center circle arcs of the main elastic block portion651and the sub elastic block portion652.

The substantially center portion in the circumferential direction of the elastic block portion (main elastic block portion)651is constricted narrower than the end portion thereof. Therefore, the main elastic block portion651is compressible in the circumferential direction. Also, a deformation resistance is reduced at least at the constricted central portion. When the main elastic block portion651is compressed, the constricted portion is expanded to the surrounding.

Because a change of shape accompanied by the compression is brought about the constricted portion, elasticity of the elastic block portion is effectively utilized. Thus, the shock absorbing member65provides large shock absorbing function. Further, the main elastic block portion651is not constricted at an end portion thereof. Therefore, the main elastic block portion651is stably held at the end portions thereof by the movable locking portion641and the unmovable locking portion681.

In the embodiment, a mode, a number or the like of the shock absorbing member65is not particularly limited. However, in order to achieve compact formation of the starter1and stable operation of the internal gear649, it is preferable to arrange the shock absorbing members65respectively uniformly at three locations or more in the circumferential direction. Hence, it is preferable that three pairs or more of the movable locking portions641and the movable contact portions642and the unmovable locking portions681and the unmovable contact portions682are respectively arranged uniformly in the circumferential direction. Similarly, it is preferable that three or more pairs of the movable contact portions642and the unmovable contact portions682are arranged uniformly in the circumferential direction.

Thereby, inclination or deviation of the internal gear64in starting can be restrained and the smooth operation of the starting apparatus is ensured. Further, also reaction force in starting can be received by a plurality of the elastic block portions651. Therefore, the shock absorbing member65can be downsized and stable shock absorbing function can be achieved.

The movable locking portion641and the movable contact portion642are integrally molded in the cylindrical resin member64having the bottom. Also, the internal gear649is formed in the inner cylindrical wall of the resin member649. By integrating those members, part control or integration is facilitated. Further, even when the cylindrical resin member64has a complicated shape, it can be comparatively easily be provided at low cost by integral molding of resin.

Further, shock due to the reaction force applied to the internal gear649and the movable locking portion641can be sufficiently absorbed by the shock absorbing member65. Therefore, even when the members are integrally molded by resin, the members are not destructed or damaged and are excellent in wear resistance and highly reliable.

Although the movable locking portions641and the movable contact portions642are rotated integrally with an internal gear649, it is not always necessary that those members are integrated. For example, there may be established a locking relationship in which the movable locking portion641and the movable contact portion642of the internal gear are constituted by separate members and the both members are integrally rotated.

In this way, the starter1receives the reaction force, which is caused in operating the starter1, by the shock absorbing member65while alleviating the reaction force. Further, the starter1reduces damage or the like of the shock absorbing member65and is still and highly reliable. Further, sufficient reliability is ensured even when the internal gear649made of resin is used.

In this description, “unmovable” state referring to the unmovable locking portion or the unmovable contact portion signifies that the portion is not substantially pivoted. It is, not used against play or vibrations. Further, the starter1is not limited to the gear type starter but may be other type of starter. Further, “circumferential direction” and “axial direction” are defined relative to a rotation center axis of the reduction gear10.

The present invention should not be limited to the disclosed embodiments, but may be implemented in other ways without departing from the spirit of the invention.