US2996924A

US2996924A - Starter gearing for internal combustion engines

Info

Publication number: US2996924A
Application number: US852879A
Authority: US
Inventors: John J Sabatini
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1959-11-13
Filing date: 1959-11-13
Publication date: 1961-08-22
Anticipated expiration: 1978-08-22

Description

Aug. 22, 1961 J. .1. sABATlNl 2,996,924

STARTER GEARING FOR INTERNAL COMEUSTION ENGINES Filed Nov. 13, 1959 2 Sheets-Sheet 1 ENTOR.

` 9 g WITNESS: 3

Aug. 22, 1961 J. J. sABATlNl 2,995,924

` STARTER GEARING FOR INTERNAL COMBUSTION ENGINES Filed Nov. 13, 1959 2 Sheets-Sheet 2 @515%9 5% 515g 39 55 g1 52 46 .af/61? 36 Q7 l lll" 'mijl aZ/w WITNESS.' BY im. m-

AT HNE Y nited States Patent ce Patented Aug. 22, 1961 2,996,924 STARTER GEARING FOR INTERNAL COMBUSTION ENGINES John J. Sabatini, Horseheads, N.Y., assgnor to The Bendix Corporation, a corporation of Delaware Filed Nov. 13, 1959, Ser. No. 852,879 11 Claims. (Cl. 74-7) The present invention relates to starter gearing for internal combustion engines and more particularly to the type of gearing which is automatically meshed and demeshed. More specifically the invention relates to a type of starter gearing in which sequentially centrifugally actuated latch means are incorporated for sequentially opposing and limiting the operation of an overrunning clutch and preventing the demesh of the gearing until the engine is reliably self-operative.

In the development of drives of this particular character the problem of pumping has become quite serious. When the engine is rotated to a point just beyond its peak compression, or if an engine misre occurs, there is an inherent tendency for the engine to momentarily drive a portion of the starter gearing at a faster rotational rate than that of the starting motor armature. This ternporary assumption of the propelling duties by the engine momentarily releases the starting motor from any load thereby allowing its armature to accelerate and incidentally causing separations between the teeth of the overrunning clutch members and between the screw shaft and the abutment member.

It has been found that if the reduction of the backlash and lost motion associated with the described separations can be eliminated or held to the absolute mechanical minimum, there will be a considerable reduction of the peak-torque requirement placed on the starting motor upon its resumption of the driving duties.

Reduction of the described separations has also been found to have the added effect of all but eliminating the noise of impact, which noise is a highly undesirable thumping or knocking associated with the taking up of the backlash and lostV motion. Elimination of the separations causes the engine, when temporarily assuming the propelling duties, to drive the starting motor armature as well as the entire starter drive assembly. This temporary driving of the starting motor by the engine generally does not exceed the free-running armature speed and consequently it is not detrimental to the starting motor, or if it should exceed the free-running speed of the starting motor it is of such a short duration as not to b e harmful.

The use of sequentially operating centrifugal latch means provided in the control nut member and screw shaft have been found to attain the desired objects. The screw shaft is provided with notch means which are engaged by detent means in the control nut at various positions in the axial travel of the control nut. The initial detent-notch engagement effectively locks up the overrunning clutch and additionally eliminates or lessens the axial separation between the screw shaft and abutment member. This initial detent-notch engagement is maintained until the engine drives the pinion at a rst predetermined speed somewhat under the free-running armature speed whereupon the detent is urged radially outwardly due to centrifugal force thus allowing the control nut to axially traverse the screw shaft in a direction tending to demesh the pinion. The second sequence of detent-notch engagement then becomes operative and again effectively limits the axial travel of the control nut. The second detent-notch engagement is so positioned as to allow the normal operation of the overrunning clutch permitting the pinion and associated parts to overrun the starting motor armature. When a true engine start has been effected and the pinion rotated at a second predetermined speed centrifugal force will again cause the detent to disengage from the notch thereby allowing the control nut to axiallytraverse the screw shaft causing the starter gearing to completely demesh.

It is an object of the present invention to provide a novel engine starter drive of the automatically meshing and demeshing type which is eficient and reliable in operation and simple and relatively economical in construction.

It is a primary object to provide sequentially operating means for effectively and automatically controlling the demeshing functions of starter gearing.

It is `an object to provide centrifugal latch means'which will maintain the starter gearing overruning clutch members inoperative during a predetermined starting interval.

It is another object to provide centrifugal latch means which will maintain the starter gearing in mesh with a gear of an engine to be started but allow an overrunning clutch member to function with-in a predetermined range of overrunning speeds.

It is still another object to provide centrifugal latch means which will release as soon as the engine and the drive pinion have attained a predetermined rotational speed which speed indicates a true engine start and allows the demesh of the starter gearing.

It is a further object to provide latch means which substantially eliminate all but the initial impact noise associated with starter drive engagement.

IIt is a still further object to provide means whereby the peak-torque requirements placed on the starter n10-tor armature when its kinetic energy is transferred to the engine flywheel after a false or Vabortive engine start are considerably reduced.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing which illustrates two complete examples of the physical embodiments of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. l is a longitudinal sectional view, partly broken away, of a preferred embodiment of the invention'showing the parts in a normal or idle position;

FIG. 2 is `a view similar to FIG 1 showing the parts in a cranking position;

FIG. 3 is a view similar to FIG. l, showing the position of the parts when the engine has momentarily as-v sumed propelling duties due to a misfire;

FIG. 4 is a view similar to FIG. l showing the parts in an overrunning position;

FIG. 5 is a section taken of line 5-5 of FIG. 4;

FIG. 6 is a fragmentary longitudinal sectional view illustrating a second embodiment of the invention; and

FIG. 7 is a sectional view of the embodiment illustrated in FIG. 6 showing the detent means engaging the deepest notch of the stepped recess.

In FIG. l there is illustrated a power shaft 11 on which a hollow sleeve 12 is rigidly mounted by any suitable manner as by means of a cross-pin 13. A hollow screw shaft 14 is slidably journalled on the sleeve 12 and. has threaded thereon a control nut 16 which is connected by a barrel member 17 to a pinion 18 slidably journalled on the power shaft 11 for movement into and out of mesh with an engine gear 19.

Means for transmitting rotation from the sleeve 12 to the screw shaft 14 is provided comprising a driving clutch member 21 splined on said sleeve as indicated at 22, and having teeth 23 cooperating with similar teeth 24 on Vthe end `of the screw shaft. An abutment ring 26, retained on the endof the sleeve 12 by a lock ring 27 serves'td substantially on the plane delne the meshed position of the pinion 18 by -limiting the travel of the control nut 16, a thrust washer 28 being preferably interposed between the screw shaft and the abutment ring. -A light spring 29 locked between the abutment ring 26 and the .thrust washer 28 serves to normally hold the overrunning

clutch teeth

23, 24 in engagement.

Cushioning means is provided for resisting axial movement of the screw shaft 14 and the clutch member 21 responsive to the screw-jack action of said screw shaft and control nut V16 after the meshing movement of the control nut is arrested'by the abutment ring 26. The cushioning means is in the form of a hollow cylinder 31 of elastically deformable material such as rubber locked between a thrust washer 32 seated on the driving clutch member 21 against a shoulder 33 and an annular pressure plate 34 seated on the end of the sleeve 12 against a flange 36.

The cushioning element 31 is heldin the assembled position under initial compression by a sleeve member 37 surrounding the cushioning element and having

terminal flanges

38 and 39 limiting axial expansion thereof. The sleeve 37 also prevents outward radial expansion of the cushioning element 31 whereby axial compression thereof deforms it radially inward as is illustrated in FIG. 2.

Latch means on the control nut and screw shaft sequentially and centrifugally operate to progressively control the degree of demesh of the pinion as well as to oppose and limit the operation of the overrunning clutch members.

'Ihe control nut 16 is formed with an integral flange 41 having cylindrical `passages 42 providing

radial openings

43 and 44. Detent means 46 and 46a are mounted in the passages 42 for radial movement therein while engaging portions of the screw shaft 1.14. A calibrated spring 47 normally yieldably holds the detent means in engagement with the screw shaft.

The detent means comprise, in addition to the spring 47, a substantially cup-shaped housing 48 consisting of a bottom face 49 and an integral cylindrical side Wall 51 with the spring 47 being seated within the cup-shaped housing 48 and extending radially outward to compressively abut an integral projection 52 of a sleeve member 53. The sleeve memberadditionally consists of a flat annular `body 54 secured by any convenient method to one side of the control mit ange 41.

Notch means are formed on the periphery of the screw shaft in position to receive the

detent means

46 and 46a as the pinion and its yassociated parts approach the meshed position. The detent-notch engagement sequentially prevents the complete demeshing of the pinion until the rotation of the pinion and associated parts exceeds predetermined speeds and additionally opposes and limits the operation of the overrunning clutch. These notch means comprise peripheral axially spaced recesses 56 and v57 best illustrated in FIGURES 3 and 4.

In operation starting with the parts in the position illustrated in FIG. 1, rotation ofthe power shaft 11 in the direction of the arrow (a) causes `the clutch member 21 and the screw shaft 14 to rotate and ythereby threadedly traverse the control nut 16fpartially by reason of its inertia until it directly engages the Ythrust washer 28 and indirectly engages the abutment ring 26, thfus defining the meshed position of the pinion 18 as shown in FIG 2. The screw-jack action of the screw shaft and control nut then thrust the clutch member 21 backwards, compressing the cushioning element 31, illustrated in FIG. 2, to provide a yieldable driving connection for the initial cranking operation.

During the cranking operation premature demeshing of the pinion responsive to sporadic explosions or false starts of the engine is prevented by the sequential engagement of the

detent means

46 and 46a with the notch means 56 and 57 of the screw shaft. The sporadic explosions or misres of the engine tend to cause the pinion and associated parts to overrun the power shaft 11 and cause an axial separation to occur between the

teeth

23 and 24 of the clutch members. This separation of the clutch parts just after the cranking operation has been initiated tends to produce ahighly undesirable knocking or thumping sound. To eliminate this undesirable condition the detent means 46 will engage the notch 56 of thescrew shaft as illustrated in FIG. 3 and in so doing will oppose longitudinal movement of the screw shaft away from the clutch member, causing the

clutch teeth

23, 24 to be locked and the overrunning clutch function to be completely eliminated. This locking up of the clutch causes the pinion to momentarily drive the power shaft. The free running speed of the lpower shaft in most modern installations is approximately 5,000 to 9,000 r.p.m. and it has been found that this initial driving of the power shaft by the pinion due to clutch lock-up will occur at speeds considerably under 5,000 r.p.m. and not be harmful to the starting motor. The detent means 46 will move out of the notch 56 at a first predetermined speed, generally, about 2,000 r.p.m. a speed normally greater than that generated by abortive starts but considerably under a true starting speed, so as to permit the control nut to thread itself back on the screw shaft 14 towards the idle position. However, the second detent means 46a then engages the notch 57 of the screw shaft thereby permitting the pinion and screw shaft to overrun the driving clutch member but maintaining the starter drive in a position to again assume cranking duties in the event of a false start. Sufficient longitudinal movement of the screw shaft which permits the teeth 24 of the screw shaft 14 to disengage the teeth 23 of the clutch member 21 is provided for by the compression of the spring 29. This engagement of the detent 46a with the notch S7 allows the pinion and associated parts to overrun at speeds in excess of the free-running speed of the power shaft 11. When the engine becomes reliably self-operative and rotates the pinion '18 and the control nut 16 above a second predetermined speed the detent means 46a by centrifugal force moves out of the notch 57 to permit the control nut to thread itself back on the screw shaft 14 toward the position illustrated in FIG.1.

In FIG. 6 of the drawing there is illustrated latch means comprising a second embodiment of the invention and showing a screw shaft 14' having formed therein astepshaped peripheral recess 58 providing

different depth notches

59, 61. The control nut flange 41 is also provided with a passage 42 and an enclosing sleeve member 53. Detent means 62 is slidably journalled in the passage 42 and comprises a cup-shaped housing 48 having a bottom base 49 and a substantially cylindrical side wall 51. Composite yielding means 63 `are housed within the cup-shaped housing 48 and consists of a first spring 64 centrally disposed within the housing 48', and a second spring 66 also disposed within the housing 48 and encompassing the first spring 64.

When the detent means 62 engages notch 61, as illustrated in FIG. 7, the overrunning clutch will be maintained inoperative. In this position it will be noted that the spring 66 while radially projecting above the cylindrical side walls 51' does not abut the sleeve projection 52 whereas the spring 64 compressively engages this projection. When the first predetermined rotational speed is reached centrifugal force will urge the detent means 62 outward and compress the spring 64 allowing the detent means to withdraw from the notch 61. The radial movement of the detent will then be limited by the additional compressive abutment of spring 66 causing the detent 62 to engage the shallower depth notch 59. The engagement of the detent in notch S9 allows the overrunning clutch -to become operative but limits the demeshing action of the pinion and its associated parts. At a second predetermined rotational speed, indicative of-a true start, the composite force of springs 64, 66 will be overcome by centrifugal force and the detent 62 will be withdrawn from the step-recess 58 so as to permit the control nut to thread itself back on the screw shaft 14 towards an idle position comparable to that illustrated in FIG. 1.

Although two forms of the invention have been shown and described in detail it will be understood that changes may be made in the form and arrangement of the parts without departing from the spirit of the invention.

I claim:

l. In an engine starter drive a power shaft, a sleeve fixedly mounted on said shaft, a screw shaft slidably journalled on said sleeve, a pinion slidably journalled on said shaft for movement into and out of mesh with a gear of an engine to be started, a control nut threaded on the screw shaft, means connecting the control nut and pinion for axially and rotatably actuating the pinion, an abutment member on said sleeve limiting axial movement in the meshing direction of said screw shaft and said control nut, means for actuating said screw shaft from said sleeve including a driving clutch member splined on said sleeve having an overrunning clutch connection with said screw shaft, yielding means resisting axial movement in the demeshing direction of said driving clutch member, latch means in the control nut and in the screw shaft operatively engaged during pinion mesh sequentially cooperating to progressively control the overrunning clutch connection and the degree of demesh of said pinion.

2. An engine starter drive as set forth in claim 1 in which the latch means includes notch means formed in the screw shaft, and sequentially operating yielding detent means supported in the control nut, said detent means engaging said screw shaft notch means during pinion mesh whereby the longitudinal movement of said screw shaft away from said clutch member is sequentially opposed and limited, said detent means being centrifugally releasable at predetermined rotational speeds.

3. An engine starter drive as set forth in claim 1 in which said latch means comprise: peripherally spaced recesses formed in the screw shaft, yielding detent means mounted in the control nut adapted to provide the sequential engagement with said recesses when the pinion is in its meshed position.

4. An engine starter drive as set forth in claim 3 in which the control nut comprises an integral radial flange housing a plurality of slidably axially aligned detent means, said detent means each being centrifugally releasable at various predetermined rotational speeds.

5. An engine starter drive as set forth in claim 1 in which the latch means comprise: a plurality of separate peripheral recesses axially spaced on the screw shaft; yielding detent means mounted in the control nut adapted for sequential radial movement, said detents including spring means normally urging said detents into engagement with said screw shaft and into engagement with said recesses during pinion mesh whereby the detents sequentially oppose and limit the longitudinal movement of said shaft away from the clutch member while the pinion is in its meshed position.

6. An engine starter drive as set forth in claim 5 in which the yielding detents are sequentially centrifugally releasable.

7. An engine starter drive as set forth in claim 1 in which said latch means comprises: a stepped peripheral recess formed in the screw shaft, a yielding detent mounted in the control nut positioned therein to sequentially engage the steps of the recess when the pinion is in its meshed position.

8. An engine starter drive as set forth in claim 7 in which the control nut includes a ange member having radially opening passages formed therein, a sleeve member having a at annular body adjacent one side of said ange and an integral projection angularly disposed relative to the annular body covering one of said passage openings, the yielding detent means being slidably mounted in said passages and comprising a cup-shaped body having a bottom face and a cylindrical side wall, the bottom face adapted to engage portions of the screw shaft through the other of said radial openings, composite yielding means contained within said cup-shaped housing yieldably resisting radial movement of the detent means, said yielding means comprising a irst spring member centrally disposed within said cup-shaped housing and yieldingly abutting the bottom face and the sleeve member, a second spring member disposed within said cupshaped housing and encompassing said rst spring, said second spring having a substantially high coecient of resistance to pressure and having an assembled radial height less than that of said first spring.

9. An engine starter drive as set forth in claim 8 in which said rst spring assembled height exceeds that of said second spring by an amount substantially equal to the height of a step of said peripheral recess.

10. In an engine starter drive a power shaft, a sleeve ixedly mounted on said shaft, a screw shaft slidably journalled on said sleeve, a pinion slidably journalled on said shaft for movement into and out of mesh with a gear of an engine to be started, a control nut threaded on the screw shaft, means connecting the control nut and pinion for axially and rotatably actuating the pinion, an abutment member on said sleeve limiting axial movement in the meshing direction of said screw shaft and said control nut, means for actuating said screw shaft from said sleeve including a driving clutch member splined on said sleeve having an overrunning clutch connection with said screw shaft, yielding means resisting axial movement in the demeshing direction of said driving clutch member, said screw shaft having a pair of peripheral axially spaced notch means formed therein, said control nut having a pair of axially aligned yielding detents mounted therein, one of said detents positioned to enter one of said notch means when the pinion is moved into mesh with said gear thereby preventing the longitudinal movement of said screw shaft away from said clutch member and preventing the operation of the overrunning clutch connection, said one detent being centrifugally releasable at a rst predetermined rotational speed whereby said control nut is allowed movement in a demeshing direction, said other detent being positioned to sequentially enter said other notch means thereby allowing the operation of said overrunning clutch connection but opposing further demeshing movement of said control nut, said other detent being centrifugally releasable at a second predetermined rotational speed thereby allowing the pinion to move out of mesh with said gear.

11. In an engine starter drive a power shaft, a sleeve fixedly mounted on said shaft, a screw shaft slidably journalled on said sleeve, a pinion slidably journalled on said shaft for movement into and out of mesh with a gear of an engine to be started, a control nut threaded on the screw shaft, means connecting the control nut and pinion for axially and rotatably actuating the pinion, an abutment member on said sleeve limiting axial movement in the meshing direction of said screw shaft and said control nut, means for actuating said screw shaft from said sleeve including a driving clutch member splined on said sleeve having an overrunning clutch connection with said screw shaft, yielding means resisting axial movement in the demeshing direction of said driving clutch member, said screw shaft having a stepped peripheral recess defining a plurality of varying depth notch means, said control nut having a detent mounted therein positioned to enter one of said notch means when the pinion is moved into mesh with said gear thereby preventing the longitudinal movement of the screw shaft away from said clutch member and preventing the operation of the overrunning clutch, composite yielding means within said detents for yieldably resisting radial movement of said detent, said yielding means comprising a rst spring member having a predetermined coeicient of resistance to pressure and a second spring member 7 8 having a substantially higher coefficient; and in which rotational speed to overcome said second spring member said detent is centrfugally actuated at a rst predeterthereby allowing the ,pinion tomove out of mesh with said -mined rotational speed to overcome said rst spring gea; member whereby said control nut is allowed movement in a demeshng direction, said detent subsequently engaging 5 References Cited in the le 0f this patent other of 'said notch means thereby allowing the operation of said overrunnng clutch connection and opposing fur- UNITED STATES PATENTS ther demeshing movement of said control'nut, said detent 2,704,939 Mendenhall `1 Mar- 29, 1955 being centrifugally actuated at a second predetermined 2,863,320 Mendenhall Dec. 9, 1958