US3458019A - Starter engaging mechanism - Google Patents

Description

' July 29, 1969 FANT ET 3358919 STARTER ENGAGING MECHANISM Filed Feb. 6. 1968' 1 2 Sheets-Sheet 1 so no TO STARTER M OTOR FIG. 2

DENNEN J. BUNGER WARWICK FANT INVENTORS July 29, 1969 FANT ET 3,458,019

STARTER ENGAGING MECHANISM Filed Feb. 6. 1968 2 Sheets-Sheet 2 DENNEN J. BUNGER WARWICK FANT INVENTORS United States Patent US. Cl. 19242 Claims ABSTRACT OF THE nrscLosURE A starter engaging mechanism wherein the driving and driven jaws are engaged at rest. The driving jaw advances upon a helical spline under screw-jack action, retarding the driven jaw which has been extended under spring pressure. When the driven engine starts, centrifugal weights lock the driven jaw in its retarded position and the driving jaw retracts under spring bias when the starter is turned off. The driven jaw will remain in the retarded position until engine speed drops sufiiciently below locking speed to allow the centrifugal weights to unlock. At this time, it will again be extended into engagement with the driving jaw.

Brief summary of invention In starting an engine, the start speed is usually well below the normal operating speed so that it becomes desirable to separate the starting motor from the main engine once the main engine has started. This is necessary to reduce power losses from the main engine, prevent the starter motor from wearing due to extended periods of rotation at speeds above that for which the starter motor was designed and to reduce the wear due to ratcheting on the driving and driven jaws of those starter mechanisms equipped with overrunning clutches.

Since the spaced-apart relationship of the starter jaws is necessary when the starter motor is turned off after the main engine has been started, one logical approach was to maintain the spaced-apart relationship at all times when the starter motor is turned off, and to then use the energy developed during the first few moments of engine start to advance the driving jaw of the starter mechanism into engagement with the driven jaw.

Prior art starter engaging mechanisms which have employed the sequence of disengaged, advanced into engagement, engaged during start up, and disengaged, have suffered from any one of a series of problems and difficulties. These have ranged from impositive advance, torque losses and bounce experienced by inertia and friction advance to high cost and complexity of design in the pneumatic advance systems.

On the other hand, those systems which have started with the driving and driven jaws in contact,-such as shown in US. Patent 3,319,755, issued to J. J. Digby, have required large rotational diameters and/or massive separating means to achieve and maintain the jaw separating function. This system has the obvious drawbacks of extreme size of weights and radius of rotation and associated costs of manufacture, and in some applications, these drawbacks are prohibitive. It is, therefore, anobject of this invention to provide a starter engaging mechanism having an initial position with the starter jaws in contact but in which separation is achieved wthout the use of massive separating weights, but 2 rather, by employing those forces already present and available in the starter engaging mechanisms which start with the torque transmitting jaws in a spaced-apart relationship.

It is an object of this invention to provide a starterengaging mechanism in which the driving and driven jaws maintain a spaced-apart relationship during engine runice ning and are, therefore, not subject to to excessive wear and damage. It is also an object of this invention to pro vide a starter-engaging mechanism wherein the limitations imposed by the present methods of advancing the driving jaw into engagement with the driven jaw are overcome. It is a further object of this invention to provide a starter wherein the starter jaws are engaged at all times except when the engine has been started and is running.

Other and further objects and advantages of this invention will be apparent to those skilled in the art from the description and claims which follow and from the appended drawings.

Brief description of drawings FIGURE 1 shows, in partial section, one embodiment of the starter-engaging mechanism of this invention in the at-rest position, that is, with both starter motor and engine at rest.

FIGURE 2 shows, in partial section, the starter-engaging mechanism in the start position.

FIGURE 3 shows, in partial section, the starter-engaging mechanism in the separated position with the starter motor at rest and the engine running.

FIGURE 4 shows a second embodiment of the starterengaging mechanism according to this invention.

FIGURE 5 shows a cross section, along line 55, of the mechanism shown in FIGURE 4.

Detailed description Referring now to the drawings and, in particular, FIG- URE l, the numeral '10 indicates a starter-engaging mechanism, according to the teachings of the present invention, for coupling a starter motor to an engine to be started in which both starter and engine are initially at rest. A driving jaw carrier 12, having helical splines 14, is connected to the output shaft 13 of a starter motor, not shown, having helical splines 15, in the usual fashion. A driving jaw 16 is coupled to the carrier 12 by axiallyextending straight splines 18 and 19 and is urged away from the starter motor by spring 20 acting between the jaw 16 and an internal shoulder of the driving jaw carrier 12. This spring is ordinarily functional only to facilitate overrun, but is also provided as a driving jaw cushion in the event re-start is necessary at a time when the engine already has some rotational velocity and the starter jaws are separated. In both cases, its function is wellknown and need not be further discussed. The driving jaw 16 is connected to the driven jaw 22 by axially-extending, circumferentially-spaced overrunning teeth 24 on the driving jaw 16 and mating teeth 26 on the driven jaw 22. These teeth permit the driving jaw 16 to transmit torque to the driven jaw 22, but inhibit the transmission of torque in the reverse direction by causing the jaws to separate due to the ramp surface of the teeth.

Driven jaw 22 is coupled to the driven jaw carrier 28 by axially-extending straight splines 30 on the jaw 22 and splines 32 on the carrier 28. As an alternative, any axially-straight coupling means, like one or more key ways or roller or ball splines, could be used. The carrier 28 is, in turn, connected by bolt 34, or any other suitable means, to the input shaft 35 of an engine to be started, not shown. The driven jaw 22 is urged away from the engine shaft by a spring 26 acting between the rear portion 23 of the jaw 22 and the rear interior wall of the carrier 28. Abutment stop 48 is also shown at the rear interior wall of the carrier 28.

The centrifugal-locking device, indicated generally by 38, is pivotally connected to a ring element 40, rigidly contained within the driven jaw 22, and is shown in the radially-inward position. Bias spring 42 acts between the ring element 40 and the arm 41 of the centrifugal-locking device 38 to bias the locking device toward the unlocked position. The end of the centrifugal-locking device 38, opposite the arm 4'1, is the weight member 44.

FIGURE 2 shows the starter-engaging mechanism, in partial section, in the operating condition with the engine to be started running and the starter motor not yet turned off. For clarity, only those component parts being here discussed are numbered. The driving jaw carrier 12 and the driving jaw 16 have advanced (i.e. moved rightward in the drawing) because of the screw-jack action of the helical splines 14 and 15 and the jaws 16 and 22 are still engaged. Because the driven jaw carrier 28 is axially stationary, the driven jaw 22 has been forced back into its recessed position and has abutted stop 48, thereby terminating the axial travel. Since the engine has started and is accelerating toward its normal operating speed, the centrifugal-locking device 38 has operated and weight 44 has pivoted, due to centrifugal force, into the locked-out position behind the splines 32 on the driven jaw carrier 28. The driving jaw carrier .12 has advanced against the spring bias of spring 46 which is attached to a stationary portion of the frame of the starter motor or the like.

FIGURE 3 shows the starter jaws 16 and 22 in the spaced-apart relationship necessary for the engine to run. The locking device 38 is preventing the driven jaw 22 from executing axial movement away from the engine which the spring 36 is urging the jaw 22 to execute. The starter motor has been turned off and the spring 46 has withdrawn the driving jaw 16 from engagement with the driven jaw 22. The running clearance which has been established between the starter jaws is, of course, equal to the amount of rightward travel of the driven jaw 22.

Referring now to FIGURE 4, a second embodiment of this invention is shown in section wherein the component parts having the same functional purpose as those shown in FIGURES l, 2 and 3 have the same numbers but are in the 100 series. The starter engaging mechanism, shown generally by 110, has a one-piece driving jaw element 112 having helical splines 114 on one end, adapted to engage mating splines on a shaft 113, shown by broken lines, of a starter motor, not shown, and circumferential dentil teeth 124 on the other end. Spring 146 places a bias on the driving jaw element .112, tending to hold it in its extreme leftward position. The dentil teeth 124, on the driving jaw element 112, engage mating teeth 126 on the driven jaw 122. The driven jaw 122 is slidably retained by driven jaw carrier 128 so that there can be limited relative axial motion between the driven jaw 122 and driven jaw carrier 128, but not relative rotation therebetween. The driven jaw 122 may be retained by the driven jaw carrier 128 by means of axial splines, as shown here, or by one or more keyways or by roller or ball splines. The driven jaw carrier 128 is connected to the input shaft 135 of an engine, not shown, by any suitable means. Springs 136 serve to bias the driven jaw towards its extreme axially-leftward position. Centrifugal-locking device 138, comprised of a series of weight members 144 interconnected by leaf springs, shown in FIGURE as number 142, is shown with the springs urging the weight members 144 toward their radially-inward position. Seal 150 serves as a lubricant seal and also provides a small friction force to assist, in the conventional manner, in starter jaw advance in the event that a restart is desired and necessary, while the starter jaws are in a spaced-apart condition; i.e. after the engine has been started and the starter motor brought to rest.

In this configuration, the springs 146 are attached to the shaft 113 and rotate with the shaft but remain axially stationary. It should also be noted that the stop 148 is located on the end of shaft 113 and is a discontinuity in the threaded portion of the shaft 113. By placing the stop 148 on the end of the shaft 113, axial thrust loading of the shaft 135 of the engine to be started is kept to a 4 Referring now to FIGURE 5, the weight members 144 are shown slidingly retained on the rear of the driven jaw 122 by dual pins which allow slight radial movement. Leaf springs 142 are shown which urge the weight members radially inward.

Operation Using the starter-engaging mechanism depicted in FIGURES 1, 2 and 3 and starting with the starter motor and engine at rest, as in FIGURE 1, the starter motor is initially turned on. As the output shaft of the starter motor begins to rotate, the driving jaw carrier 12 and driving jaw 16 attempt to rotate along with the output shaft. However, the contact between the driving and driven jaws imposes the torque load of the engine upon the driving jaw carrier 12 and retards its rotation. The output shaft of the motor is now rotating relative to the driving jaw carrier 12 and because of the helical spline connection between the starter motor output shaft and driving jaw carrier, the driving jaw carrier axially advances on the shaft. The torque load of the engine provides very positive advance without reliance on friction, inertia or other impositive advance techniques.

As soon as the driven jaw 22 reaches the stop 48 on the driven jaw carrier 28, it ceases its axial travel, causing the driving jaw to cease its axial advance and to begin to rotate with the output shaft, causing the engine to begin to rotate. At this point, the driven jaw has been recessed to its extreme rightward position as shown in FIGURE 2, but the locking device has not yet operated due to the bias spring 42. At some point after the enine has caught and begun to accelerate, the locking device rotates due to the centrifugal force operating on the weight member 44in opposition to the spring 42. As shown in FIGURE 2, the weight member will then have moved radially outward into a position directly behind the axial splines 32 of the driven jaw carrier 28. Since the engine will now be rotating at a higher rotational velocity than the starter motor, overrun will occur, and spring 20 will allow the driving jaw to move axially leftward to provide overrun tooth clearance as the teeth 24 and 26 cam apart.

As soon as the starter motor is turned off, the spring 46 will draw the driving jaw axially leftward. Depending on requirements and spring strength, spring 46 may be a light anti-drift spring or it may provide the major retraction force to retract the driving jaw carrier when the starter motor is switched off. With the screw-jack forec removed by the overrunning of the starter jaws, the only forces acting on the carrier are the slight inertia of its own mass, the spring force, and the frictional force of seal 50. These forces will result in a resultant force causing the axially leftward motion of the carrier. If a false start should occur or should the engine cease running for some reason, the starter motor may be turned back on, and the frictional force provided by the seal along the inertia of the jaw and jaw carrier will serve to advance the carrier and jaw in order to engage the starter jaws and initiate a restart. As the engine decelerates, the locking device will disengage at some speed below the lockup speed due to the friction force between the weight member and splines, and the return spring will urge the driven jaw forward. By selecting springs 36 and 42 of proper spring constants, the locking device disengagement speed can be as low as may be desirable to reduce jaw ratcheting after engine shut-off.

Two clearly defined start conditions exist, first with the jaws in contact and second with the jaws separated. In the first condition, engine speed is either zero or very close to zero, and there .are no impact loads. In the second, the engine is running at some speed above the locking device disengagement speed, and a restart is being initiated. In this situation, impact loads will be encountered, but the relative rotation between the jaws will be low, thereby minimizing impact loads to the point that they are completely tolerable.

If restart is not necessary, the situation shown in FIG- URE 3 will prevail, and the driven jaw and its carrier will rotate at engine speed without making contact with the driving jaw which has come to rest .at its axially-leftward position. Seal 50 will then be necessary only as a lubricant seal.

We claim:

1. A starter engaging mechanism for coupling a starter motor having an output shaft to an engine to be started having an input shaft comprising:

driving jaw means coupled to said output shaft by a first connection means for rotation therewith;

driven jaw means in normally-abutting contact and in axial alignment with said driving jaw means;

said first connection means operative upon initial rotation of said output shaft to cause said driving jaw means to advance from a first position to a second position while forcing said driven jaw means from .a first position to a second position;

a driven jaw carrier fixedly connected to said input shaft and coupled to said driven jaw means by a second connection means; and

locking means connected to one of said driven jaw means and said driven jaw carrier, and operative upon rotation to lock said driven jaw means in its second position.

2. The starter engaging mechanism as claimed in claim 1 wherein:

said first connection means comprise a pair of mated helical threads operative upon mutual relative rotation of said output shaft and said driving jaw means to cause axial translation of said driving jaw means with respect to said output shaft.

3. The starter engaging mechanism as claimed in claim 1 including further:

first resilient means operative to bias said driven jaw means into said first position; and

second resilient means operative to bias said locking means in the unlocked position. v 4. The starter engaging mechanism as claimed in claim 2 wherein:

carrier.

5. The starter engaging mechanism as claimed in claim 2 wherein:

said second connection means is operative to allow relative axial motion but prevents relative rotational motion.

References Cited UNITED STATES PATENTS Jones 746 Miller 746 Miller 746 Sabatini 192-114XR Poliseo 19246 Giometti 19246 XR Digby 192-42 XR CARLTON R. CROYLE, Primary Examiner ALLAN D. HERRMANN, Assistant Examiner US. Cl X.R.

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