CA2253169A1 - Pinion gear retainer assembly for an electric starter - Google Patents

Abstract

A pinion gear retainer assembly for an electric internal combustion engine starter having a two piece keeper and a spring retainer which interface on correspondingfrustoconical surfaces and are urged into contact by a compression spring disposed over and extending along the starter shaft and abutting the pinion gear. The cooperative engagement of the frustoconical surfaces of the keeper and spring retainer permit the easy assembly and disassembly of the pinion retainer assembly without fasteners and/or their related tools.

Description

CA 022~3169 1998-11-02 Jonathan W. Furlong PINION GEA~ ~FTA~NFR ASSFMRr Y FOR AN El FCTRIC STARTER
BACKGROUND OF THF ~VENTION
1. FieldofInvention:
The invention relates generally to electric starters for intemal combustion engines and, 5 more particularly, to a retainer assembly for the pinion gear of a starter for an internal combustion engine.

2. Background Art:
Electric starters are widely utilized for cranking internal combustion engines such as small gasoline-powered engines used in lawn and garden tractors, lawn mowers, tillers, snow 10 blowers and the like, and the concept and embo-limentc of these aulolllaLically eng~ging and ~licerlg~ging starters for internal combustion engines are well known. In a conventional starter, a colllples~ion spring biases a pinion gear, which is rotatably disposed upon the starter shaft, against a follower, which is threaded onto a helically-splined portion of the shaft, such that the gear and the follower are in clutched engagement, usually through a resilient, 15 intermediate member adhered to the pinion or the follower. Upon operation of the electric starter motor, the rapidly accelerated starter shaft rotates relative to the follower and pinion gear due to their relatively higher rotational moments of inertia. Following the helical threads of the shaft, the follower causes the pinion gear to be moved axially along the motor drive shaft against the force of a colllplession spring retained at the end of the shaft by a somewhat 20 annular retainer, and the teeth of the pinion gear inte rrn.o~h with those of a ring gear on the engine flywheel. As the follower approaches its end of travel on the shaft's helically-splined portion, an axially extending portion of the pinion gear abuts the facing surface of the retainer, increasing the clutched engagement bclwcell the pinion gear and the follower. The follower, held in axial position on the rotating shaft by the axially retained pinion gear, is 25 forced through its threaded interengagement with the shaft to rotate with the shaft, inducing the pinion gear to rotate via their clutched engagement. The rotating pinion gear, through its engagement with the teeth of the ring gear, hence rotates the engine flywheel. When the engine starts, its flywheel rotates at a speed faster than that of the starter shaft, thus unloading the pinion gear and the follower, which are forced by the spring to move axially away from CA 022~3169 1998-11-02 the ring gear, back along the starter shaft into their retracted positions. Such a conventional starter is disclosed in U.S. Patent No. 3,791,685 (~mm~n) Proper operation of the starter requires that the pinion gear be retained onto the shaft and biased toward its retracted position. Ordinarily, a retainer resembling an axial thrust bearing washer having a hole through which the starter shaft protrudes provides a fixed stop against which the pinion-biasing compression spring and, during cranking, the pinion gear itself abut. Generally, axial movement of the retainer away from the pinion gear in response to the force of the co.l.p.es~ion spring and the axial movement of the follower during cranking is prevented by an abutting snap ring disposed in an annular shaft groove, a nut threaded onto the end of the shaft, or by other means requiring fasteners and/or tools for its assembly. Previous starters employing such f~cteners for assembling the pinion gear retainer are disclosed in U.S. Patent Nos. 4,308,462 (McMillen), 4,330,713 (Greenwood) and 4,785,679 (Weber et al.). There is a need for a means of retaining the pinion gear assembly of a starter which can be easily assembled and ~ csembled without fasteners and their related tools.
Generally, the axial force of the pinion gear against the retainer during cranking is substantial, subjecting the pinion gear retainer assembly to significant stress which rnay result in failure of the retainer assembly. A pinion gear retainer assembly which can better accommodate these stresses and provide more secure retention of the pinion gear is desirable.
SUMMARY OF THE I~VE~TION
The present invention provides an easily assembled and ~lis~ssembled pinion gearretainer assembly for the electric starter of an internal combustion engine. The inventive retainer assembly further provides improved pinion gear retention capability vis-a-vis previous pinion gear retainers which assemble using f~teners such as snap rings or threaded nuts. The present invention is adapted to conventional, known starters such as described above and provides a pinion gear retainer assembly in which an annular retainer having a frustoconical inner surface is disposed over the shaft, abutting the co~ ,s~ion spring and, during cranking, an axial face of the pinion gear, and a two (2) piece keeper having a frustoconical outer surface is assembled onto the starter shaft. In one embodiment, the keeper assembly has a cylindrical inner surface with an int~rn~lly protruding ridge which is received in a mating annular groove located in the shaft's outer surface. In an alternative embodiment, .

CA 022~3169 1998-11-02 the keeper and shaft have no such ridge and groove engagement. Tncte~ the base of the keeper abuts a stop integral to the shaft. In both of these embo~1imentc the retainer's frustoconical inner surface is urged into cooperative engagement with the keeper's frustoconical outer surface by the co~ ssion spring, the retainer thereby holding the two halves of the keeper onto the shaft by the axial force of the spring which is tr~n~l~teci to a 5 radial force sandwiching the keeper components between the shaft and the retainer.
No f~ct~ner such as a snap ring or a threaded nut is required in the assembly of the inventive pinion gear retainer. Thus, the present invention provides the advantage of assembling the pinion gear retainer assembly easily and without f~ct~n~ors and their related tools. Likewise, it may be easily tii~s~mbled for repair or rebuild.
The spring biasing force acts through the retainer to hold the split keepers in place during assembly and while the starter is off. During engine cranking, increased axial loading of the retainer due to increased spring forces associated with axial pinion gear movement and the abutting engagement of the pinion gear itself col~s~ondingly increases the inwardly radial retention force exerted by the split keepers on the outer surface of the shaft, increasing 15 the capability of the keeper to ~ the axial position of the retainer. Thus, the present invention provides the additional advantage of being an improved, more reliable ret~ining mech~nl ~m .
The present invention provides a pinion gear retainer assembly for an electric internal combustion engine starter having a shaft and a pinion gear disposed thereon, the retainer 20 assembly comprising a retainer having an inner surface and disposed about the shaft, a spring disposed about the shaft and intermediate the pinion gear and the retainer, the spring exerting an axial force on the retainer and on the pinion gear, and a keeper having an outer surface and disposed about the shaft, the keeper outer surface and the retainer inner surface adapted to form a wedge-like relationship whereby the axial force exerted against the retainer is 25 tr~n~l~ted at least in part into a radial force acting upon the keeper.

BRIEF DESCRIPTION OF THF. DRAWINGS
The above mentioned and other feaLu~;s and objects ofthis invention, and the manner Of ~ ining them, will become more a~pale.lt and the invention itself will be better CA 022~3169 1998-11-02 understood by reference to the following description of embo~limenSc of the invention taken in conjunction with the acco.llp~l~ g drawings, wherein:
Fig. 1 is a partial sectional side view of a starter employing one embodiment of the pinion gear retainer assembly of the present invention.
Fig. 2 is an exploded p~.a~e~ re view of the embodiment of the pinion gear retainer 5 assembly shown in Fig. 1.
Fig. 3 is an exploded pe.sl,c, li~e view of an alternative embodiment of the pinion gear retainer assembly of the present invention.
Fig. 4 is a fra~",~ y sectional side view of the embodiment shown in Fig. 2, as assembled.
' Fig. 5 is a fr~ornent~ry sectional side view of the embodiment shown in Fig. 3, as assembled.
Fig. 6 is an axial front view of the spring retainer of the present invention.
Fig. 7 is a sectional side view of the spring retainer of Fig. 6, taken along line 7-7.
Fig. 8 is an axial front view of the keeper assembly shown in Fig. 2.
Fig. 9 is a sectional side view of the keeper of Fig. 8, taken along line 9-9.
Corresponding reference cl~acle.a indicate corresponding parts throughout the several views. Although the drawings le~l~,sellL embo~limentc of the present invention, the drawings are not necçcc~rily to scale and certain feal~es may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein 20 illustrate embodiments of the invention in ~ltern~tive forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
DETATT Fn DF~CE~TPTION OF THF ~NVENTION
The embo-liments disclosed below are not inten~ç~l to be e~h~llctive or limit the invention to the precise forms disclosed in the following detailed description. Rather, the 25 embo-limentc are chosen and described so that others skilled in the art may utilize its te~chingc Referring to the drawings and particularly to Fig. 1, it can be seen that a conventional starter 10 comprises housing 12 co~ ;nillg an electric motor comprising stator 14 and rotor 16. Shaft 20, which may be made of steel, is secured to rotor 16 and extends from housing 30 12, the extended length of the shaft including helically-splined portion 30 upon which is CA 022~3169 1998-11-02 rotatably received threaded follower 28. Follower 28 may be made from sintered powdered metal or forged steel, and includes radially-extPn~ing base 32 having a circular periphery.
Coaxially disposed upon shaft 20 is pinion gear 22 having annular rear face 24 and axially extPnc1ing annular front face 25. Pinion gear 22 may be made from sintered powdered metal, m~rhinPd from steel or all.~ninllm, or may be injection molded plastic. Adhered to rear face 5 24 is slip clutch member 26, which may be made of a resilient material such as Buna Nitrile rubber, which abuts and clutchedly engages follower base 32.
Coll~lc;ssion spring 34 extends coaxially over shaft 20 and has one end disposedwithin annular spring-receiving portion 36 of pinion gear 22, located inwardly adjacent to and coaxial with front face 25, and the other end disposed within annular spring-receiving portion 38 of annular spring retainer 40, which is disposed over shaft 20. As shown in detail at Figs.
6 and 7, retainer 40 has frustoconical inner surface 42 which transitions from major inside diameter 44 down to reduced minor inside ~ metPr 46 on its opposite axial sides. Spring receiving portion 38 is provided by an annular recess formed in retainer 40 ~dj~cent minor inside diameter 46. Axially çxtPn~ed annular retainer face 39 is disposed outwardly adjacent to and coaxial with spring receiving portion 38 such that face 39 and front face 25 of pinion gear 22 are substantially aligned and face each other. It is not necessary, however, that retainer 40 be provided with spring receiving portion 38. Altematively, spring 34 may abut a flat annular face (not shown) provided on retainer 40 adjacent minor inside ~ metpr 46 and still m~int~in proper ~lignmPnt about shaft 20. In either embodiment, let~ er 40 may be made from sintered powdered metal, forged from steel, or m~rl~inPd from hardened steel.
Referring now to Figs. 8 and 9, split keeper 48, con~icting of halves 48a and 48b which are preferably identical and may be made of sintered powdered metal or m~ inP~
steel, has a generally cylindrical inner surface 50 from which inwardly protruding annular ridge 52 çxtPntl~ Keeper 48 has frustoconical outer surface 56 angularly COll~ ipollding to inner surface 42 of retainer 40. Cylindrical surface 50 is adapted to circumferentially fit the diameter of shaft 20 and ridge 52 corresponds to annular groove 54 located in the radial surface of shaft 20 near its outer end 21. Assembled keeper 48 provides base 58 at its wider axial end and tip 60 at its opposite axial end. As i~ tp~l~ major diameter 44 of retainer 40 is somewhat smaller than the outside ~i~nnet~pr of keeper base 58, and the outside ~ rn~tPr of keeper tip 60 is somewhat smaller than the minor tii~metPr 46 of retainer 40.

CA 022~3169 1998-11-02 Assembling the pinion gear retainer assembly to starter motor 10 comprises disposing spring 34 over shaft 20 such that one end of the spring is received in portion 36 of pinion gear 22, disposing retainer 40 over shaft 20 such that the other end of spring 34 is received in portion 38, forcing retainer 40 aYially against spring 34 towards pinion gear 22, assembling keeper halves 48a and 48b over shaft 20 such that base 58 of keeper 48 is oriented towards outer end 21 of shaft 20 and, in the embo.lim~ntc of Figs. 1, 2 and 4, ridge 52 is received in annular groove 54. The spring-opposing force upon letah~el 40 is removed after keeper halves 48a and 48b have been assembled onto shaft 20 and spring 34 urges retainer 40 coaxially upon keeper 48, bringing their frustoconical surfaces into interfacing contact as shown in Fig. 4. A portion of the axial force imposed by spring 34 upon retainer 40 is imparted radially inward upon keeper halves 48a and 48b, m~inf~inin~ the stability and placement of the assembled keeper 48 to shaft 20, while another portion of the force causes keeper ridge 52 to bear axially against the side of annular shaft groove 54. Once assembled, spring 34 is m~int~ined in a somewhat colllplessed state to thereby provide retention of the pinion gear and bias same towards a retracted position. Thus, the present invention provides a pinion gear retainer assembly which may be easily assembled, and co~ve~aiely rlic~ss~mbled, without f~cten~ors An alternative embodiment of the present invention, shown in Figs. 3 and 5, has cylindrical stop 64 provided at end 21 of shaft 20 to provide an axial thrust bearing surface.
Stop 64 is preferably m~rllint-~ or coined from the end of shaft 20 but may be a separate, annular member (not shown) fastened to shaft end 21. Stop 64 has outside tii~meter 66 larger than the ~ m~t,-r of cylindrical inner surface 50 of split keeper 48 and smaller than minor diameter 46 of retainer 40 so that retainer 40 may be received th~ leove~ during assembly. In this embodiment, keeper ridge 52 and corresponding annular shaft groove 54 are elimin~te~
and keeper 48 is instead axially ~ dined by its base 58 abutting stop 64 of shaft 20. In this embodiment, retainer 40 and keeper 48 would interrelate as described above.
As illustrated, split keeper 48 comprises halves 48a and 48b, although the scope of the present invention should not be so limited. It is envisioned that keeper 48 may be comprised of more than two component pieces or of a single element. Furthermore, it is within the scope of the present invention that instead of the above-described shaft and keeper interengagement methods, shaft 20 may be adapted to provide a frustoconical outer surface CA 022~3169 1998-11-02 thereon (not shown), having its base near end 21, about which a plurality of keeper elements (not shown) are disposed such that a frustoconical keeper outer surface is formed which would engage retainer inner surface 42 in the marmer described above.
As illustrated, keeper 48 is disposed upon a reduced ~ meter portion 62 of shaft 20, which allows the outside diameter of keeper tip 60 to be flush to or slightly smaller than the diameter of shaft 20 rearwardly adjacent tip 60, thus preventing undesired interference between retainer 40 and tip 60 as retainer 40 is received onto keeper 48 during assembly.
Although the illustrated embodiment~ show such an arrangement, it is not intenfl~ that the scope of the present invention be so limited. It may be understood that the pinion gear retainer assembly of the present invention is adaptable to shafts having no such reduced diameter portion 62.
While the present invention provides a pinion gear retainer assembly which can be easily assembled and ~ cse~nbled~ it can be readily envisioned from the foregoing description and accompanying drawings that the present invention provides a pinion gear retainer assembly which is also more reliable under the higher stresses of starter operation.
During cranking, the rapidly accelerated rotation of shaft 20 relative to follower 28 and pinion gear 22 causes axial movement of follower 28 along helically-threaded portion 30 of rotating shaft 20. During cranking, keeper 48 and retainer 40 may be rotating with shaft 20. Spring 34 may or may not be rotating with shaft 20 and its ends, disposed in retainer portion 38 and pinion gear portion 36, will be in sliding and/or abutting engagement therewith. Base 32 forces pinion gear 22 axially towards shaft end 21 and ring gear 8 of engine nywLccl 6 (Fig.
1) via abutment with resilient slip clutch member 26 adhered to surface 24 of pinion gear 22.
As the axial movement of pinion gear 22 further coll~p~esses spring 34, the opposing force of the spring forces slip clutch member 26 into increasingly clutched engagement with follower base 34. As follower 28 axially travels on splined portion 30 of rotating shaft 20 the teeth of substantially non-rotation pinion gear 22 become ;-lt~ ",eched with the teeth of stationary ring gear 8. Finally, follower 28 forces face 25 of pinion gear 22 into sliding abutment with the rotating face 39 of retainer 40, halting the axial movement of both pinion gear 22 and follower 28 and increasing the clutched engagement via slip clutch member 26 disposed therebetween. Restricted in forward axial movement, follower 28 and thus slip clutch member 26 and pinion gear 22 are forced through the threaded engagement of follower 28 on CA 022~3169 1998-11-02 helical spines 30 to rotate with shaft 20. Hence pinion gear 22 rotates ring gear 8 of flywheel 6.
Upon starter operation, the axial force exerted on retainer 40 by spring 34 increases linearly with the tli~t~nce pinion gear 22 moves toward ring gear 6, co~ u.e;,sing the spring.
More significantly, an abruptly in~ ced axial force is exerted on face 39 of retainer 40 by the S abutting front face 25 of pinion gear 22 as they meet just prior to and during engine cranking.
A portion of these increased axial forces exerted on retainer 40 during starter operation are distributed normally from the retainer's inside frustoconical surface 42 to the keeper's outside frustoconical surface 56. The force exerted normally upon surface 56 of keeper 48 has an axial component and a radial component. In the embo~im~nt~ shown in Figs. 1, 2 and 4, the axial force component being transferred axially toward shaft end 21 from the annular axial edge of keeper ridge 52 to the abutting side of receiving shaft groove 54. In the embodiment shown in Figs. 3 and S, the axial force component exerted on keeper 48 is lrallsr~llcd axially from keeper base 58 to the abutting annular surface of shaft stop 64. In both shown embo~liment~ the radial force component is L~ rcllcd radially inward from keeper inner surface 50 the int.orf~ing outside surface of shaft 20, forcing split keeper halves 48a and 48b radially inward onto the outer shaft surface. Thus, the present invention provides t_at during operation of the starter keeper 48 and retainer 40 are more firmly retained in position on shaft 20, ensuring more secure pinion gear retention under the high stress retainer assembly loading encountered during starter operation than is available using prior retainer assemblies.
In all of the above-described embo-lim~ntc, the pinion gear ret~ining assembly may be protected from cont~min~tion, damage or accidental dic~cs~nnbly by cover 68, having a cylindrical wall and an approximately hçmicph.orical end portion which enclose the assembly.
Cover 68 may be a drawn metal s~ )il.g or an injection molded thermoplastic such as nylon 6/6, and may be i~lt~ ~re~ence fitted over forwardly-ext~n~ling cylindrical portion 70 of pinion gear 22.
While this invention has been described as having exemplary methods and design~,the present invention can be further modified within the spirit and scope of this disclosure.
This application is therefore inten~ed to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is int~n~ecl to cover such .. .~

departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.

Claims (23)

1. A pinion gear retainer assembly on an electric internal combustion engine starter having a shaft and a pinion gear disposed on the shaft, said retainer assembly comprising:
a retainer having an inner surface and disposed about the shaft;
a spring disposed about the shaft and intermediate the pinion gear and said retainer, said spring exerting an axial force on said retainer and on the pinion gear;
a keeper disposed about the shaft and having an outer surface, said keeper outer surface and said retainer inner surface engaging and having a wedge-like relationship whereby said axial force exerted against said retainer is translated at least in part into a radial force acting upon said keeper.

2. The pinion gear retainer assembly of Claim 1, wherein said keeper comprises aplurality of elements.

3. The pinion gear retainer assembly of Claim 2, wherein the shaft includes an outer surface about which said plurality of keeper elements are disposed and therewith engaged.

4. The pinion gear retainer assembly of Claim 3, wherein each said keeper element has a substantially rectangular cross section.

5. The pinion gear retainer assembly of Claim 3, wherein each said keeper element has a substantially arcuate cross section.

6. The pinion gear retainer assembly of Claim 1, wherein said retainer inner surface and said keeper outer surface are frustoconical.

7. The pinion gear retainer assembly of Claim 1, further comprising a stop disposed on an outer end of the shaft, said keeper abutting said stop.

8. The pinion gear retainer assembly of Claim 1, further comprising an annular groove in an outer surface of the shaft near an outer end of the shaft, said keeper having an internally protruding ridge received in said groove.

9. The pinion gear retainer assembly of Claim 1, further comprising a cover secured to the pinion gear and enclosing said retainer assembly.

10. The pinion gear retainer assembly of Claim 1, wherein said keeper comprises a pair of keeper elements, each said keeper element being generally semicircular in cross section, and wherein said keeper elements, when assembled, being frustoconical in shape.

11. The pinion gear retainer assembly of Claim 10, wherein said retainer inner surface is frustoconical.

12. A pinion gear retainer assembly on an electric internal combustion engine starter having a shaft and a pinion gear disposed on the shaft, comprising:
a retainer disposed about the shaft, said retainer having an inner surface;
a spring disposed about the shaft and intermediate the pinion gear and said retainer, said spring exerting an axial force on said retainer and on the pinion gear; and a keeper disposed over the shaft near its outer end, said keeper having an outersurface corresponding to said inner surface of said retainer, said keeper at least partially disposed within said retainer and in wedge-like engagement therewith.

13. The pinion gear retainer assembly of Claim 12, wherein said retainer inner surface and said keeper outer surface are frustoconical.

14. The pinion gear retainer assembly of Claim 12, wherein said keeper comprisesa plurality of elements.

15. The pinion gear retainer assembly of Claim 12, further comprising an annulargroove in an outer surface of the shaft near an outer end of the shaft, said keeper having an internally protruding ridge received in said groove.

16. A starter for an internal combustion engine comprising, in combination:
an electric motor having a housing, a stator, a rotor and a rotatable shaft attached to said rotor and extending from said housing;
a follower threadedly engaging said shaft;
a pinion gear disposed about said shaft and adjacent said follower; and a pinion gear retainer assembly, said retainer assembly comprising:
a retainer having an inner surface and disposed about said shaft;
a spring disposed about said shaft and intermediate said retainer and said pinion gear;
a keeper disposed about said shaft and having an outer surface;

said retainer inner surface urged by said spring onto said keeper outer surface, said keeper disposed at least partially within said retainer.

17. The starter of Claim 16, wherein said keeper comprises a plurality of elements.

18. The starter of Claim 16, wherein said retainer inner surface and said keeperouter surface are frustoconical.

19. The starter of Claim 16, wherein said shaft has an outer end, futher comprising a stop disposed on said shaft outer end, said keeper abutting said stop.

20. The starter of Claim 16, wherein said shaft has an outer surface, further comprising an annular groove located on said shaft outer surface, said keeper having an internally protruding ridge received in said groove.

21. The starter of Claim 16, further comprising a cover secured to said pinion gear and enclosing said spring, said retainer and said keeper.

22. A method for assembling a pinion gear retainer assembly for an electric starter comprising:
threading a follower onto a helically-splined portion of a starter shaft;
sliding a pinion gear having resilient slipclutch over said shaft such that saidslipclutch comes into contact with said follower;
installing a compression spring over said shaft, abutting said gear;
installing a spring retainer having a frustoconical inner surface defining a major diameter and a smaller minor diameter over said shaft such that said minor diameter faces said gear;
forcing said retainer against said spring towards said gear;
then installing a keeper having a frustoconical outer surface over said shaft such that base of said keeper faces towards the outer end of said shaft; and then releasing said force on said retainer whereby said retainer is urged by said spring onto said keeper, cooperatively engaging the said frustoconical surfaces of said retainer and said keeper.

23. The method of Claim 22, wherein said keeper installation step comprises holding a plurality of keeper elements in their assembled configuration about the shaft until said retainer inner surface is urged into contact with said keeper outer surface.