CA1102722A

CA1102722A - Automatic locking clutch

Info

Publication number: CA1102722A
Application number: CA302,899A
Authority: CA
Inventors: Mark J. Fogelberg
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1977-05-23
Filing date: 1978-05-09
Publication date: 1981-06-09
Also published as: ES470025A1; IT7823631A0; FR2392276A1; DE2822373A1; FR2392276B1; AU3613278A; DE2822373C2; JPS53147152A; GB1601265A; JPS6328809B2; AU523030B2; ZA782790B; IT1094778B

Abstract

ABSTRACT

A clutch for engaging a driving member with a driven member automatically upon application of torque to rotate the driving member, in either direction, for maintaining engagement in either the drive or coast mode of operation and during the transition between drive and coast, for maintaining engagement in either forward or reverse operation and during the transition between forward and reverse, and for disengaging automatically upon interruption of the torque and slight rotation of the driving member in the opposite direction.

Description

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This invention relates generally to clutches. More particularly, it relates to a clutch for use in effecting locking engagement between a front drive axle and a front wheel of a four-wheel drive vehicle in response to the application of power to the front drive axle. The clutch automatically effects disengagement upon cessation of the application of power to the front drive axle, together with a direction reversal thereof.
Heretofore, various clutching mechanisms have been used for engaging a front drive axle with its associated wheels in a four-wheel drive vehicle. One such mechanism normally is disengaged to allow the wheels to rotate independently of the front drive system. This requires that the operator lock each clutch manually to engage the front drive axle and wheels, and to unlock them manually to disengage.
Another such mechanism provides an overrunning clutch which engages automatically when power is applied to the front drive axle and when operation is in the drive mode.
However, such an overrunning clutch disengages automatically upon operation in the coast mode. In other words, the overrunning clutch engages when the rotational speed of the axle tends to exceed the rotational speed of the wheel, but disengages when t~e rotational speed of the wheel tends to overrun that of the axle. Such overrunning clutches generally provide some means by which the operator may override manually to insure locking engagement between the axle and wheels.
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Yet another such mechanism provides a clutch which operates in response to the application of torque to the front drive axle to move pins into slots so as to engage the axle with its associated wheels, Although a Dechanism of this type will effect engagement in either the drive or coast mode of operation, there is the possibility tha~ the pins will slip out of the slots during movement between drive and coast, in which case the clutch would disengage and then re-engage automatically. At normal operating speeds such disengagement and re-engagement could cause severe shocks to the clutch components and, indeed, to the entire front drive line. This would result in a dangerous and possibly destructive condition. Further, in a Lloat condition wherein the axle is rotating but no torque is transferred between the axle and wheels, an inadvertent tendency for movement between the drive and coast modes of operation could develop. This could cause the clutch to disengage and then re-engage, and establish the same dan-gerous condition.
There remains a need in the art for a clutch which will automatically engage a front drive axle and an associated wheel in response to engagement of the front wheel drive system, which will maintain engagement positively in the drive and coast modes of operation as well as during the transition between drive and coast, which will maintain engagement positively in forward and reverse operation as well as during the transition between forward and revPrse, and which will disengage automatically upon disengagement of the front wheel drive system.

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A primary object of this invention is to provide an improved automatic clutch which will meet the need noted above. The invention is directed to an improved clutch for automatically effecting engagement between dxiving and driven members in response to rotation of the driving member.
According to the present invention there is provided an automatic clutch in~luding first and second rotatable members ana first and second clutch elements respectively rotatable with the first and second elements, the first element being movable relative to the first member between first and second positions, the first and second elements bei~g relatively rotata~le between engagement in drive and coast modes when the first element is in the -second position. Means is provided for biasing the first element for movement toward the first position. Means is responsive to rotation of the first member in one direction for moving the first element to the first position and means is provided for retaining the first element in the second position so long as the first member is subject to rotation in the one direction irrespective of the relative rotation ~-of the first and second elements between engagement in the drive and coast modes. Means is provided for maintaining the first element in the second position as the direction of rotation of the first member is changed from the one ~` direction to the opposite direction. The retaining means also is effective for retaining the first element in the second position so long as the first member is subject to rotation in the opposite direction irrespective of the relative rotation of the first and second elements between engagement in the drive and coast modes.
The clutch maintains positive engagement between the -members so long as the driving member rotates, and disengages , .

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automatically when rotation of the driving member is reversed.
The clutch of the present invention is adapted for use in four-wheel drive vehicles where it is desirable to provide automatic engagement of the front wheels when the operator engages the front wheel drive system. The clutch is operative when the vehicle is engagea in forward or reverse, and maintains engagement positively until the operator shifts out of four-wheel drive and reverses direction.
In the accompanying drawings:
FIGURE 1 is a sectional view showing details of the improved automatic locking clutch;
FIGURE 2 is a sectional view taken along the line 2-2 of FIGURE 1 showing additional details of the clutch;
FIGURE 3 is a developed view taken along the line 3-3 of FIGURE 1 showing the clutch in its disengaged position;
FIGURE 4 is a developed view similar to FIGURE 3 showing the clutch in its forward drive position;
FIGURE 5 is a developed view similar to FIGURE 3 showing the clutch in its forward coast position;
FIGURE 6 is a developed view similar to FIGURE 3 showing the clutch in its reverse drive position;
FIGURE 7 is a developed view similar to FIGURE 3 showing the clutch in its reverse coast position; and FIGURE 8 is a schematic view showing an associated transfer case for use in conjunction with the clutch.
While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and herein will be described in detail a preferred embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, and is not intended to limit the invention to this embodiment.

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Referring to the drawings now in greater detail, and with particular reference to FIGURES 1, 2, and 3, thPre is shown a driving member or shaft 10, which in one preferred form of the invention is the front axle of a four-wheel drive vehicle. A~le 10 is rotatably supported in a con-ventional manner within an axle housing 12. Axle 10 extends outwardly beyond the spindle of housing 12, and a spring retainer 14 is secured to the outer end thereof by a bolt 16 or the like. A collar 18 is secured to axle 10 for rotation therewith, and is oriented between the spindle of housing 12 and spring retainer 14.
A driven member 20, which in one preferred form of the invention is ~he front wheel hub of a four-wheel drive vehicle, is supported by a conventional bearing, not shown, for rotation about housing 12. Lock nuts 22 and 24 secure this bearing in the usual manner. However, lock nut 24 defines a smooth annular surface 26.
A hub extension sleeve 28 is secured to wheel hub 20 for rotation therewith. Hub extension 28 extends outwardly beyond spring retainer 14 and bolt 16, and a suitable cap 30 close~ its outer end. Hub extension 28 defines a plurality of clutch teeth 32.
An annular cam 34 is spaced from the spindle of housing 12 and from collar 18 so as to be rotatable relative thereto.
Cam 34 defines outwardly converging cam surfaces 36. A
pin 38 is secured to cam 34 and extends inwardly therefrom.
A drag ring 40 in frictional contact with surface 26 of lock nut 24, is engaged by pin 38. Cam 34 also defines a plurality of outwardly extending fingers 42.

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An axle clutch sleeve 44 is splined to collar 18 for rotation therewith and sliding movement rela~ive thereto.
Sleeve 44 defines a plurality of clutch teeth 46 adap~ed for meshing engagement with teeth 32 of hub extension 28.
A suitable spring 48 reacts against spring retainer 14 and biases sleeve 44 inwardly such that teeth 46 normally are out of meshing engagement with teeth 32. Sleeve 44 defines a plurality of cam follower means comprising surfaces 50.
Surfaces 50 diverge inwardly toward an inner smooth surface 52. Sleeve 44 also supports a plurality of cam stop pins 54.
Cam surfaces 36 of cam 34 and cam follower surfaces 50 of sleeve 44 are complimentary. With sleeve 44 in the position shown in FIGURE 1, surfaces 36 and 50 are in the position shown in FIGURE 3. Teeth 32 and 46 are out of mesh, and wheel hub 20 rotates freely about stationary axle 10 with the associated vehicle in two-wheel drive.
When the operator desires to establish four-wheel drive, he directs power to axle 10. Collar 18 and sleeve 44 rotate with axle 10. The force developed by the frictional contact of drag ring 40 with lock nut 24 is sufficient such that rotation of cam 34 i~ retarded. Surfaces 50 ride outwardly on surfaceQ 36, and sleeve 44 is moved outwardly against the biasing force of spring 4~ from the position shown in FIGURE 3 to the position shown in FIGURE 4. Surface 52 rides along the outwardmost point of surfaces 36 until pins 54 abutt fingers 42, whereupon cam 34 is rotated with sleeve 44.
Teeth 46 are moved outwardl~ into meshing engagement with ~77059-WG
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~eeth 32, and a positive driving engagement is established between axle 10 and wheel hub 20. Teeth 32 and 46 are constructed such that the backlash therebetween is smaller than the distance between the inner end of each cam follower surface 50 and an adjacent pin 54 along surface 52.
When the vehicle shifts from drive to coast, as for example when the operator lifts his foot off of the accelerator, hub 20 tends to overrun axle 10. In this condition teeth 32 shift from the position shown in FIGU~E 4 to the position shown in FIGURE 5. In effect, an engine braking condition is established. Pins 54 continue to abutt fingers 42, and sleeve 44 continues to rotate cam 34 and drag ring 40 relative to lock nut 24. The vehicle may shift back and forth between drive and coast, but teeth 32 and 46 will remain in meshing engagement, thus ensuring that four-wheel drive operation is maintained.
When the operator desires to move the vehicle in reverse, he stops the vehicle, shifts the transmission out of a forward gear and into reverse gear7 and then starts the vehicle once again, all the while remaining in four-wheel drive. Because the backlash between teeth 32 and 46 is smaller than the distance between surfaces 50 and pins 54, tooth contact i5 established before surfaces 50 come into contact with surfaces 36. Sufficient pressure is established between teeth 32 and 46 such that sleeve 44 i~ held against the biasing force of spring 48 as it moves from the position shown in FIGURE 4, for example, to the position shown in FIGURE 6. Cam follower surfaces 50 do not ride down cam ~77059-WG

surfaces 36, and four-wheel drive operation is maintained.
When in reverse, the vehicle may shift between the drive mode shown in FIGURE 6 and the coast mode shown in FIGURE
7 while remaining positively engaged for four-wheel drive operation.
An important advantage of the arrangement disclosed herein is that a positive drive condition is maintained in both the drive and the coast modes, either in forward or reverse. This positive drive is established automatically, thereby eliminating any need for manually locking the wheel hubs.
When the operator desires to establish two-wheel drive, he stops the vehicle, discontinues the transfer of power to axle 10, and moves the vehicle in the reverse direction sufficiently to align surfaces 36 and 50. Spring 48 biases sleeve 44 inwardly to the position shown in FIGURES 1 and 3.
The operator may then proceed in either direction in two-wheel drive.
In one preferred form of the invention, direct drive may be e~tablished from an engine to a rear drive axle, with offset drive being established to a front drive axle. As shown in FIGURE 8, one example of such an arrangement includes a transfer case having an input 56 adapted to receive power from the transmission of a four-wheel drive vehicle~ A rear output 58 is connected directly to input 56, and is connected through a rear propeller shaft to the rear axle. A sprocket 60 is journaled for rotation relative to input 56, and a complimentary sprocket 62 is secured to a ' , ~77059-WG
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front output 64 which is connected through a front propeller shaft to front axle 1~. A suitable chain ~6 couples sproc~ets 60 and 62 for power transfer therebetween. A clutch 68 is controllable by the vehicle operator through a suitable actuating mechanism 70. In one position, clutch 68 disengages sprocket 60 from input 56 such that power is transferred from input 56 to output 58, but not to output 64. Two-wheel drive is established. In another position, clutch 68 engages sprocket 60 with input 56 such that power is trans-ferred from input 56 to both outputs 58 and 64. With clutch 68 engaged and power transferred to output 64, front axle 10 will rotate and four-wheel drive will be established auto-matically.
Thus it will be seen that positive drive is established automatically in both the drive and coast modes of operation when four-wheel drive is engaged. The automatic feature eliminates any necessity for manual lock-up in order to insure positive drive. The automatic feature maintains four-wheel drive in either the drive or coast modes, and during the transition between drive and coast. Similarly, four-wheel drive is maintained in either forward or reverse gears, and during the shift between forward and reverse.
It should be apparent that although the invention provides a novel arrangement for clutching the front drive axle and its associated wheels in a four-wheel drive vehicle, it is readily available for use in any environment where automatic clutching between driving and driven members is desired.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An automatic clutch comprising first and second rotatable members, first and second clutch elements respectively rotatable with said first and second members, said first element being movable relative to said first member between first and second positions, said first and second elements being relatively rotatable between engagement in drive and coast modes when said first element is in said second position, and means biasing said first element for movement toward said first position; characterized by means responsive to rotation of said first member in one direction for moving said first element to said second position, means for retaining said first element in said second position so long as said first member is subject to rotation in said one direction irrespective of said relative rotation of said first and second elements between engagement in said drive and coast modes, and means for maintaining said first element in said second position as the direction of rotation of said first member is changed from said one direction to the opposite direction, said retaining means also being effective for retaining said first element in said second position so long as said first member is subject to rotation in said opposite direction irrespective of said relative rotation of said first and second elements between engagement in said drive and coast modes.

2. The invention of Claim 1, further characterized by said moving means including a rotatable cam, means tending to retard rotation of said cam, and a rotatable cam follower coupled with said first element, said cam and cam follower defining said retaining means, and said first and second elements defining said maintaining means.

3. The invention of Claim 2, further characterized by said cam having a cam surface, and said cam follower having rise and dwell surfaces, said rise and cam surfaces being in contact when said first element is in said first position, said dwell and cam surfaces moving into contact as said first element is moved to said second position, and said cam and cam follower defining means for rotation of said cam with said cam follower to retain said dwell and cam surfaces in contact when said first element is in said second position irrespective of said relative rotation of said first and second elements between engagement in said drive and coast modes.

4. The invention of Claim 3, further characterized by said first and second elements having clutch teeth adapted for meshing engagement in said drive and coast modes, said meshing engagement developing a force sufficient to overcome the force of said biasing means and maintain said first element in said second position with said rise and cam surfaces out of contact as the direction of rotation of said first member is changed.

5. The invention of Claim 4, further characterized by said clutch teeth having a predetermined backlash, said cam having a finger, and said cam follower having a pair of pins spaced from said rise surface by a distance greater than said backlash, one of said pins engaging said finger to rotate said cam with said cam follower upon rotation of said first member in one direction, and the other of said pins engaging said finger to rotate said cam with said cam follower upon rotation of said first member in the opposite direction.