US2706414A - Engine starter gearing - Google Patents

Description

April 19, 1955 J. J. sABATlNl 2,706,414

ENGIE STARTER GEARING A BY y M f WITNESS: W AT oRNEY United States Patent O ENGINE STARTER GEARIN G John I. Sabatini, Elmira, N. Y., assignor to Bendix Aviation Corporation, a corporation of Delaware Application February 24, 1954, Serial No. 412,300 6 Claims. (Cl. 74-7) The present invention relates to engine starter gearing, and more particularly to a drive of the type which engages and disengages automatically as a function of the relative speeds of the starting motor and the engine to be started.

The evolution of the prevailing types of automotive internal combustion engines from a heavy slow 'speed low power four cylinder unit to a light, high speed, high power multi-cylinder unit has radically changed the conditions and requirements of the applicable starting systems.

The early types of engines required heavy flywheels to store up kinetic energy to carry the engine over the widely separated compression points, and as a consequence, the acceleration of the crank shaft by the power impulses was correspondingly low. The starting motors at that time were comparatively large and heavy, with low stall torque, and the batteries used were not welladapted to withstand heavy current drains for substantial periods.l

All these factors tended to enhance the advantages or the automatically engaging types of drive which stored up kinetic energy in the rotating parts of the motor and drive prior to the meshing of the gears, whereby the engine was cranked from a flying start to -break the static friction of the engine and assist in rotating it past the rst compression point.

Under present conditions with light engine parts, low viscosity oils, high gear reductions and small motors with ample electrical torque and very high acceleration, the storage of kinetic energy in the drive prior to mesh is of little importance. In fact it may at times becomea disadvantage in that it necessitates design of the yielding driving connection to absorb this energy by means of an increase in size and cost over what would'suflice to transmit only the electrical torque of the starting in otor.

It is an object of the present invention to provide a novel engine starter type in which the storage of kinetic energy in the rotating parts prior to mesh is markedly reduced as compared to present commercial types of drive. n

It is another object to provide such a device in which ample room for the yielding driving connection is p rovided without increasing the overall length of the drive.

It is a further object of the invention to provide such a device in which the polar moment of inertia of the parts is comparatively high, thereby securing reliable cold weather meshing characteristics with threaded connections having higher than the conventional lead angles.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. l is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in idle position;

Fig. 2 is a similar view showing the parts in the positions assumed at the completion of the first stage in the meshing operation; and

Fig. 3 is a similar view showing position.

In Fig. shaft 1 having a sleeve means of a cross pin 3.

the parts in cranking l of the drawing there is illustrated a power 2 rigidly mounted thereon as by The sleeve 2 has a driving clutch teeth 4 formed thereon, and a hollow screw shaft 5 which is slidably journalled on the sleeve 2 has clutch teeth 6 formed on one end thereof in position to cooperate with the teeth 4 of sleeve 2 to provide an overrunning clutch conection to the screw shaft.

A stop ring 7 is located on the free end of the sleeve 2 drive of the automatically engaging Patented Apr. 19, s

iCC

by means of a split lock ring 8, and a spring washer 9 located between the stop ring 7 and the adjacent end of the screw shaft 5 serves to normally maintain the overrunning clutch teeth 4, 6 in engagement.

A control nut 11 is threaded on the screw shaft 5, its normal or idle position being defined by the ends or heels 12 of the threads of the screw shaft, and its travel away from this position being limited by the stop ring 7 on the sleeve 2, preferably with the inter position of a thrust washer 13.

A pinion 14 is slidably journalled on the power shaft 1 for movement into and out of mesh with a gear 15 of the engine to be started. A barrel member 16 is splined at one end to the pinion 14 as indicated at 17, the pinion being retained in the barrel by means of a flange 18 formed thereon or rigidly attached thereto. The opposite end of the barrel 16 is journalled on a cylindrical extension 19 of the control nut 11, and is internally threaded to cooperate with corresponding threads 21 formed on the extension 19 of the control nut for a portion only of its length.

An outer barrel 22 is non-rotatably mounted at one end as indicated at 23 on a flange 24 of the control nut and at its free end has an annular slotted anchor plate 25 rigidly mounted therein as indicated at 26, and bearing ori the inner barrel 16. Barrel 16 has a flange 27 formed thereon provided with an anchoring slot and a torsion and compression spring 28 is located within the outer barrel 22 and formed with outturned ends 29 and 31 received in the slots of aiige 27 and anchor plate 25 respectively, thereby forming a yielding driving connection between the control nut 11 and the inner barrel 16. The interior of the outer barrel 22 is provided with a shoulder 32 in position to be engaged by the flange 27 of the inner barrel 16 to thereby limit the meshing movement of the inner barrel with respect to the control nut 11.

The screw shaft 5 is provided with a notch 33, and a latch member 34 is mounted in the flange 24 of the control nut for radial movement, and is yieldingly pressed into engagement with the screw shaft by a spring 36, the notch 33 being so located as to receive the latch 34 when the control nut approaches the end of its meshing movement on the screw shaft 5, whereby demeshing movement of the control nut is resisted until the latch is withdrawn by centrifugal force.

A mesh enforcing spring 37 is located on the power shaft 1 within the inner barrel 16, bearing at one end against the flange 18 of the pinion and at its other end against a cup shaped thimble 38 the rim of which bears against the end of the extension 19 of the control nut.

In operation, starting with the parts in the positions illustrated in Fig. 1, rotation of the power shaft in the direction of the arrow is transmitted through the overrunning clutch 4, 6 to the screw shaft S whereby the control nut 11 is traversed to the right, pushing ahead of it the pinion 14 and inner barrel 16 by means of the mesh enforcing spring 37. This movement continues until the control nut is arrested by the stop ring 7, at which time the pinion 14 has entered into initial meshing relation with the engine gear 15 as shown in Fig. 2. 1n view of the short distance of movement required to reach this position, and the comparatively high pitch of the threads of the screw shaft 5 made possible by the abnormally high polar moment of inertia of the barrel and spring assembly, only a small angle of rotation of the power shaft is required so that very little kinetic energy has been stored in the rotating parts up to this time.

The control nut 11 is now compelled to rotate with the screw shaft 5, and since the pinion 14 is prevented from rotation by its engagement with the engine gear 15, further rotation of the power shaft 1 causes the inner barrel member 16 to be traversed to the right on the control nut, this movement causing both compression and torsion of the drive spring 28. The pinion 14 is thus moved into fully meshed position as shown iii Fig. 3 this position being defined by the engagement of the ange 27 of the inner barrel against the shoulder 32 of the outer barrel. Preferably the exterior threads 21 on the control nut 11 terminate at such a point that the inner barrel 16 runs off the ends of said threads just prior to the engagement of flange 27 with the shoulder 32 whereby -less on the control nut 11, but the pinion the cranking energy is yieldably transmitted to the pinion 14 through torsion of the drive spring 28. It will be appreciated that since, during the nal meshing movement of the pinion, the starting motor is being progressively loaded by the winding up of the spring 28, the motor will not vbe permitted to accelerate to a high rotational speed, and very little kinetic energy will be stored up, so that the arresting of the meshing movement and the iilitiztion of cranking take place without substantial S OC When the engine lires, the acceleration of the pinion permits the inner barrel 16 to thread itself back more or 14 is not permitted to become entirely demeshed from the engine gear since the control nut is prevented from moving back on the screw shaft 5 by the latch 34, rotation of the drive parts at higher speed than the starting motor being permitted by the overrunning clutch 4, 6.

When the engine is reliably self-operative the consequent high speed of the drive parts causes the latch 34 to be withdrawn by centrifugal force whereby the parts are permitted to return to idle position where they are maintained by engagement of the latch 34 with an inclined shoulder 39 on the screw shaft 5.

Although but one form of the invention has been shown and described in detail it will be understood that changes may be made in the design 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 driving clutch sleeve xed thereon, a hollow screw shaft and driven clutch member slidably journalled on said sleeve, means yieldably holding the clutch surfaces of the screw shaft and sleeve in contact, an externally and internally threaded control nut on said screw shaft, an abutment on said sleeve limiting the longitudinal movement of the control nut, a pinion slidably journalled on the power shaft for movement into and out of mesh with a gear of the engine to be started, a barrel member non-rotatably connected at one end to the pinion and threaded on the control nut, and a yielding driving connection between the control nut and barrel.

2. An engine starter drive as set forth in claim 1 in which the yielding driving connection between the control nut and barrel includes a torsion and compression spring non-rotatably connected at its ends to said nut and barrel, and yieldably resisting meshing movement of the barrel relative to the control nut.

3. An engine starter drive as set forth in claim 2 in which the barrel is arranged to run oi the ends of the threads of the control nut to thereby limit the compression of the spring.

4. An engine starter as set forth in claim 3 including further a ange on the barrel, and an abutment on the control nut in position to engage the ange and limit the longitudinal movement of the barrel.

An engine starter drive as set forth in claim 1 in which the pinion is splined to the barrel member, and including further means including a compression spring Liormlally holding the pinion in extended relation to the arre.

6. An engine starter as set forth in claim 5 in which the screw shaft is provided with a notch, and including further a centrifugal detent carried by the control nut in position to enter the notch when the control nut engages the abutment on the clutch sleeve, and resist demeshing movement of the control nut until released by centrifugal force.

No references cited.

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