US2481250A - Engine starting apparatus - Google Patents

Description

W 9 M49 P. SCHNEEDER ET AL 2,481,250

ENGINE STARTING APPARATUS 2 Sheets-Sheet 1 Filed May 20, 1948 Lia igmv Q f N? Swat & 14%

Filed May 20, 1948 P. L. SCHNEIDER ET AL.

ENGINE STARTING APPARATUS 2 Sheets-Sheet 2 Patented Sept. 6, 1949 ENGINE STARTING APPARATUS Paul L. Schneider and Dennis W. Nighbert, Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application May 20, 1948, Serial No. 28,198

Claims.

This invention relates to engine startin apparatus of the type in which the operation of the electric motor causes a pinion driven thereby to be moved axially into mesh with the flywheel gear of the engine to be started and in which the pinion is automatically demeshed from the gear when the engine becomes self-operative and tends to drive the pinion faster than it can be driven by the engine starting motor.

An object of the present invention is to provide an engine starter drive of the type referred to which effects the meshing of the pinion with the engine gear although the pinion teeth may abut the ends of the gear teeth. In order to accomplish this object, the disclosed embodiment of the present invention includes a spring through which motion is transmitted axially to the pinion so that, in the event of abutment of the pinion teeth with the flywheel gear teeth, the pinion teeth can slip on the gear teeth while the pinion is being rotated by the motor into meshing registration with the gear.

Further objects and advantages of the present invention will be apparent from the following 'des-cription, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a longitudinal sectional view of a portion of the housing and electric starting motor supported thereby together with aside elevation partly in longitudinal section of an engine starter drive embodyin the present invention.

Fig. 2 is a sideview of the engine starter drive looking in the direction of arrow 2 of Fig. 1.

Figs. 3 and 4 are sectional views taken, respectively, on lines 3--3 and 4-4 of Fig. 1.

Fig. 5 is a side view of part II shown in Fig. 2 at the left end of the starter drive.

Fig. 6 is a view in the direction of arrow '6 of Fig. 5.

Fig. 7 is partly a fragmentary view in the direction of arrow 1 of Fig. 6 and partly a sectional view on line 1-4 of Fig. 6.

Fig. 8 is a view in the direction of arrow 8 of Fig. 7, the part in section being taken on line 83 of Fig. 7.

Fig. 9 is a view partly in the direction of arrow 9 of Fig. 8 and partly a'sectiona'l view on line 99 of Fig. 8.

Fig. 10 is a view of part 51 shown in Fig. 2.

Fig. 11 is a view in the direction of arrow H of Fig. 10. I

Fig. 12 is a sectional view on line 12-12 of Fig. 11.

Fig. 13 is a sectional View on the line IS-I3 of Fig. 4, showing parts BI and .83.

Fig. 14 is an end view of a spring 61.

Fig. 15 is a view in the direction of arrow 15 of Fig. 14.

Fig. 16 is a side view partly insection of part M.

Figs. 17 and 18 are views in the direction of arrows 1"! and I8 respectively, of Fig. 16..

Referring to Fig. 1, a housing 30 adapted to be attached to the housing of an engine flywheel gear supports a motor field frame 3| whose left end, not shown, supports a bearing for an armature shaft 32 journalled also in a bearing 33 .provided by frame The shaft 32 supports an armature 34 rotating between field pole pieces 35 surrounded by field coils (not shown).

The engine starter drive All comprises a screw 4! shown in detail in Figs. 16-18. Screw 41 comprises a sleeve 62 provided externally with triplethread helical splines 43 which are segments of a triple-thread screw. Sleeve 42 provides a wide flange dd having holes 45 diametrically opposite for receiving a pin at (Fig. 1 passin diametrically through the shaft 3 2. The flange M has a groove 61. The threaded portion '48 of screw 4-! receives a nut 5c retainable by a lock washer 49 which retains, in assembly with screw 41, a nut 51 provided internally with triple-thread helical splines 53 adapted to cooperate with the helical threads is of the screw M. Nut5l provides a hole 52 (Fig.2) for receiving end portion 5230i 2. spring 6! which, as shown in Fig. 1, is located betweenthe nut 5i and the screw flange 44 and has an end portion 63 received in the groove M of said flange dd, said portion 63 having a right angle bend 54 extending across the left face of the flange M. Nut 5! has a stop lu 54 adapted to engage with a stop lug M of a ring H which fits around the flange d4 of the screw 4! :andhas holes .12 for receiving the ends of pin "45, said pin being retained by a split wire snap ring 13 received by groove ltin the ring H. To'retain the snap ring I3, it is provided with an inwardly extending .portion 13a (Fig. 2) received by ahole 16 in ring H (Figs. 7 and 8). Nut 5! provides stepped cylindrical surfaces 55, 56 and 51 and a plane annular surface 53 and an annular groove 59.

The assembly (Fig. 13) comprises a ring 51 having notches 82 for receiving the teeth of the pinion lot. Ring BI is brazed to a sleeve 83 having an internal flange B4 and an internal cylindrical surface 85 which is adapted to fit closely around the surface 55 of nut 5|. Sleeve 83 hasa cylindrical surface 86 of the 'same diameter as surface'iit of nut 51 and the cylindrical surface 81 of the same diameter as the surface 51 of nut 5|. As shown in Fig. 1, the sleeve 83 and the nut 5| are surrounded by a clutch spring 98 having its end turns ground to provide plane surfaces perpendicular to the axis of the spring adapted to contact plane surface 58 of part 5| and plane surface 88 of part 8|, respectively. Spring 98 is confined between surfaces 58 and 88, the distance between these surfaces with registers 55 and 85 in engagement being slightly greater than the overall length of spring 98 and the parts are retained by a sleeve 92 surrounding the spring 98 and the ring 8|, the right end being shaped at 9| to conform to the rounded edge of the ring 8|, and the left edge of the sleeve 92 being crimped at 93 into the groove 59 of the nut 5|. Normally the spring 98 frictionally engages the nut 5| at the surface 51 and the sleeve 83 at the surface 81.

The pinion I88 has a hub extension I8| which fits within the internal flange 84 of the sleeve 83 and is surrounded by a spring I82 located between the left ends of the pinion teeth and the flange 84. The pinion is retained in assembly by a split wire snap ring I83 which snaps into a groove in the hub extension WI and is engaged by the flange 84. When the starting motor is connected with a current source, its shaft 32 accelerates rapidly in a clockwise direction as viewed in the direction of arrow I85 (Fig. 1), thereby causing the nut 5| to move toward the right and to move the pinion [88 into engagement with the flywheel gear I86. When the pinion I88 is in fully meshed position I88, the nut 5| will have moved against the stop washer 49. Since the nut 5| cannot move further into the right, the screw 4| and the nut 5| rotate together as a unit. For the moment, the portion of spring 98 engaging surface 8'! of sleeve 83 can be considered fixed since ring 8| connects sleeve 83 with pinion I88. Therefore, since the left end of spring 98 frictionally engages surface 51 of the rotating nut 5|, the spring 99 wraps itself about the surfaces 56 and 86 of the nut 5| and sleeve 83 respectively, thereby effectively transmitting torque from the screw to the pinion I88 and causing the pinion to turn and drive the engine gear I86.

When the engine becomes self-operative, it tends to drive the pinion I88 faster than it can be driven by the starting motor and the pinion is automatically demeshed and returns to the normal position with the stop lug 54 of the nut 5| abutting the stop lug 14 of the ring 'II. The return of the pinion to normal position is assisted by the spring 6|, the turns of which had been deflected axially and torsionally during movement of the pinion into mesh with the flywheel gear.

Motion of the nut 5| is transmitted axially to the pinion through the spring I82. If the ends of the pinion teeth should abut the ends of the gear teeth, spring I82 is deflected as nut 5| continues moving right. Since spring I82 is relatively light because it has several turns of relatively small wire, it may be considerably compressed before the pressure applied by the pinion teeth to the gear teeth increases to a value such that the clutch spring 98 begins to wrap itself about the nut 5| and sleeve 83 and a torque is transmitted to the pinion suficient to cause it to turn into meshing registration with the gear. It

the running friction is slightly less than the static friction. Should the pinion teeth rub against a slight irregularity of the gear teeth, the pinion is free to move left, so that it can slide over the irregularity because the pressure applied to the pinion is a yielding pressure. Entrance of the pinion teeth into, the spaces between the gear teeth is facilitated by chamfering the pinion teeth as shown in Figs. 2 and 4. When meshing registration is efiected, the spring I82 is released to move the pinion quickly into substantially complete engagement with the gear. If the nut 5| had engaged the stop washer 49 when meshing registration had been effected, the spring I82 would have moved the pinion into complete meshing engagement with the gear. Thereafter the clutch spring 98 transmits to the pinion the torque required for it to rotate the gear.

Since the pressure which the pinion teeth can exert against the flywheel gear teeth in case of abutment is limited to the pressure applied by spring I82, the apparatus can be used successfully with a flywheel gear I86 having no chamfered teeth or teeth chamfered on both sides as indicated at I86a and I86b in Fig. 1. If a corner of a pinion tooth should engage a surface I86a of a gear tooth, abutment can be cleared by rotation of the pinion because the limited pressure applied by spring I82 would allow the pinion to be cammed left to clear the surface I86a and the pinion tooth and to slide on the end surface of the gear tooth and then to allow the pinion tooth chamfer to slide on the gear tooth chamfer I861).

The internal diameter of spring 98 is normally greater than the diameter of surfaces 58 and B6 of parts 5| and 83, respectively, and is less than the diameter of surfaces 51 and 81 of these parts. Hence, the spring 98 is expanded to fit over surfaces 51 and 81. The so-called interference fit between spring 98 and surfaces 51 and 8'! must be such as to cause the spring 98 to wrap itself about the surfaces 56 and 86 but not so great as to prevent slippage. Some slippage should be present to cushion the shock incidental to starting the cranking operation. The clutch should slip a little to absorb the kinetic energy stored in the rotating motor armature and thus reduce the shock and noise which occur when the pinion engages. For a brief interval after the pinion engages, during which the gear starts moving, an abnormally high torque produced by the kinetic energy stored in the rotating armature is applied and the clutch slips. As this kinetic energy is dissipated the torque decreases to the normal torque produced by the startin motor and the clutch slippage decreases to zero under normal cranking conditions. The clutch must be capable of transmitting the full normal torque developed by the starting motor without slipping.

When the drive disengages and stop lugs 54 and I4 meet, considerable kinetic energy is stored in the parts which are rotating with respect to the screw 4|. If this energy were all absorbed instantaneously when the stop lugs meet, undesirably high stresses and some rebound would result. In this design some of the kinetic energy stored in spring 98, tubular case 92, assembly 88, and pinion I 88 is dissipated by the slipping of the spring clutch 98 when torque in a clockwise direction is applied to'it.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form,

' it is to be understood that other forms might be,

adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An engine starter comprising an electric motor having a shaft, a screw supported by the shaft and driven thereby, a pinion supported by the shaft for axial movement into mesh with the gear of an engine to be started; a nut threadedly engaging the screw, a sleeve which is moved axially by the nut and which has axial st motion connection with the pinion and which has a 1ongitudinal spline connection with the pinion, a spring for transmitting motion from the sleeve to the pinion in a direction to move the pinion toward the gear, a clutch spring having its end turns normally in frictional engagement with the nut and sleeve and which wraps itself about the nut and sleeve in response to a rotative movement of the nut relative to the sleeve in the engine starting direction of rotary movement of the pinion, and an abutment provided by the screw for engagement by the nut whereby the screw and nut rotate together as a unit to rotate the pinion through the clutch spring while the pinion is fully meshed with the engine gear.

2. An engine starter according to claim 1 in which the connection between the sleeve and the pinion is provided by a ring attached to the sleeve and having internal longitudinal splines engaging the teeth of the pinion.

3. An engine starter according to claim 1 in which the nut abuts the sleeve whereby motion is transmitted axially in the pinion meshin direction from the nut to the sleeve, and in which motion is transmitted axially in the opposite direction by a tubular case enclosing the clutch spring and retaining the clutch spring, nut and sleeve in assembly.

4. An engine starter according to claim 1 in which the spring which transmits motion from the sleeve to the pinion surrounds a hub extension of the pinion which extends through an internal annular flange of the sleeve which flange engages a split-Wire snap ring received by an annular groove provided by the hub extension of the pinion.

5. .An engine starter according to claim 1 in which the screw provides a stop lug for receiving a stop lug provided by the nut, and in which a torsion and tension spring connecting the nut and screw yieldingly maintains engagement of the stop lugs.

PAUL L. SCHNEIDER. DENNIS W. NIGHBERT.

No references cited.

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