GB1601265A

GB1601265A - Automatic clutch

Info

Publication number: GB1601265A
Application number: GB19351/78A
Authority: GB
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1977-05-23
Filing date: 1978-05-12
Publication date: 1981-10-28
Also published as: DE2822373A1; FR2392276A1; ZA782790B; ES470025A1; CA1102722A; DE2822373C2; FR2392276B1; IT1094778B; AU523030B2; AU3613278A; JPS6328809B2; IT7823631A0; JPS53147152A

Description

(54) AUTOMATIC CLUTCH (71) We, BORG-WARNER CORPORA TION, a corporation duly organized and existing under and by virtue of the laws of the State of Delaware, United States of America, having its principal office and place of business at 200, South Michigan Avenue, Chicago, Illinois 60604, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to automatic clutches.

Such an automatic clutch is particularly, but not exclusively, applicable in vehicles having an optional four-wheel drive capability. For example, in vehicles with permanent drive arrangements to the rear wheels the clutch may be used for effecting locking engagement between each respective front drive axle and the wheel thereof for fourwheel drive operation when power is applied to the front drive axles.

The present invention provides an automatic clutch comprising first and second rotatable members, first and second clutch elements respectively rotatable with said first and second rotatable members, said first clutch element being movable between a first position out of contact with the second clutch element and a second position in which said clutch elements are coupled in either a first or a second mode in which the first or second rotatable member respectively is the driving member, said clutch elements being relatively rotatable whilst coupled to change between modes, means responsive to rotation of said first rotatable member in one direction for moving said first clutch element to said second position, means for retaining said first clutch element in said second position so long as said first rotatable member is subject to rotation in said one direction irrespective of mode, means for maintaining said first clutch element in said second position as the direction of rotation of said first rotatable member is changed from said one direction to the opposite direction, said retaining means also being effective for retaining said first clutch element in said second position so long as said first rotatable member is subject to rotation in said opposite direction irrespective of mode, and means biasing said first clutch element towards said first position.

The automatic clutch to be described will automatically engage a front drive axle and an associated wheel in response to engagement of the front wheel drive system, and will maintain engagement positively in the drive and coast modes of operation, that is respectively when the rotational speed of the axle tends to exceed that of the wheel and therefore the axle is the driving member, and when the rotational speed of the wheel tends to overrun the axle so that the wheel is the driving member. The described clutch also maintains engagement during the transition between drive and coast, and in forward and reverse operation as well as during the transition between forward and reverse, and disengages automatically upon disengagement of the front wheel drive system. 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 engaged in forward or reverse, and maintains engagement positively until the operator shifts out of four-wheel drive and reverses direction.

In order that the invention may be well understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings in which: FIGURE 1 is a sectional view showing details of an 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 drive or first mode whilst in forward gear; FIGURE 5 is a developed view similar to FIGURE 3 showing the clutch in its coast or second mode whilst in forward gear; FIGURE 6 is a developed similar to FIGURE 3 showing the clutch in its drive mode whilst in reverse gear; FIGURE 7 is a developed view similar to FIGURE 3 showing the clutch in its coast mode whilst in reverse gear; and FIGURE 8 is a schematic view showing an associated transfer case for use in conjunction with the clutch.

Referring to the drawings now in greater detail, and with particular reference to FIG URES 1, 2, and 3, there is shown a first rotatable member, driving member or shaft 10, which is one of the front axles of a fourwheel drive vehicle. Axle 10 is rotatably supported in a conventional 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 or second rotatable member 20, which is the associated front wheel hub of the 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 or second clutch element 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 closes its outer end.

Hub extension 28 defines a plurality of clutch teeth 32.

A camming device comprises an annular rotatable cam 34 which 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, An axle clutch sleeve or first clutch element 44 is splined to collar 18 for rotation therewith and sliding movement relative thereto between first and second positions.

Sleeve 44 defines a plurality of clutch teeth 46 adapted for meshing engagement with teeth 32 of hub extension 28 when sleeve 44 is in its second position. A suitable spring 48 reacts against spring retainer 14 and biases sleeve 44 inwardly to its first position such that teeth 46 normally are out of meshing engagement with teeth 32. Sleeve 44 defines a plurality of cam follower means comprising rise surfaces 50. Surfaces 50 diverge inwardly toward an inner smooth dwell surface 52.

Sleeve 44 also supports a plurality of cam stop pins 54.

Cam surfaces 36 of cam 34 and cam follower rise surfaces 50 of sleeve 44 are complementary. 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 desired 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 is retarded.

Surfaces 50 ride outwardly on surfaces 36, and sleeve 44 is moved outwardly against the biasing force of spring 48 from the position shown in FIGURE 3 to the position shown in FIGURE 4. Dwell 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 outwardly into meshing engagment with teeth 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 first or drive mode to second or coast mode, as for example when the operator lifts his foot off of the accelerator, hub 20 tends to overrun axle 10. In this condition relative rotation takes place between first and second clutch elements 44, 28 and teeth 32 shift from the position shown in FIGURE 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 modes, 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 gear, and then starts the vehicle once again, all the while remaining in fourwheel drive. Because the backlash between teeth 32 and 46 is smaller than the distance between surfaces 50 and pins 54, tooth contact is established before surfaces 50 come into contact with surfaces 36. Sufficient pressure is established between teeth 32 and 46 such that sleeve 44 is 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 surfaces 36, and four-wheel drive operation is maintained. When in reverse, the vehicle may shift between th,e 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 clutch, direct drive may be established 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 complementary sprocket 62 is secured to a front output 64 which is connected through a front propeller shaft to front axle 10. A suitable chain 66 couples sprockets 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 transferred 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 automatically.

Thus it will be seen that positive drive is established automatically in both the drive and coast modes of operation when fourwheel 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 described clutch provides a novel arrangement for clutching the front drive axles 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.

WHAT WE CLAIM IS: 1. An automatic clutch comprising first and second rotatable members, first and second clutch elements respectively rotatable with said first and second rotatable members, said first clutch element being movable between a first position out of contact with the second clutch element and a second position in which said clutch elements are coupled in either a first or a second mode in which the first or second rotatable member respectively is the driving member, said clutch elements being relatively rotatable whilst coupled to change between modes, means responsive to rotation of said first rotatable member in one direction for moving said first clutch element to said second position, means for retaining said first clutch element in said second position so long as said first rotatable member is subject to rotation in said one direction irrespective of mode, means for maintaining said first clutch element in said second position as the direction of rotation of said first rotatable member is changed from said one direction to the opposite direction, said retaining means also being effective for retaining said first clutch element in said second position so long as said first rotatable member is subject to rotation in said opposite direction irrespective of mode, and means biasing said first clutch element towards said first position.

2. A clutch as claimed in claim 1, wherein said moving means comprises a camming device having a rotatable cam, means for retarding rotation of said cam, and a cam follower rotatable with said first member and coupled with said first element.

3. A clutch as claimed in claim 2, wherein said camming device defines said retaining means.

4. A clutch as claimed in claim 2 or 3, wherein said cam has a cam surface, and said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the transmission out of a forward gear and into reverse gear, and then starts the vehicle once again, all the while remaining in fourwheel drive. Because the backlash between teeth 32 and 46 is smaller than the distance between surfaces 50 and pins 54, tooth contact is established before surfaces 50 come into contact with surfaces 36. Sufficient pressure is established between teeth 32 and 46 such that sleeve 44 is 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 surfaces 36, and four-wheel drive operation is maintained. When in reverse, the vehicle may shift between th,e 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 clutch, direct drive may be established 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 complementary sprocket 62 is secured to a front output 64 which is connected through a front propeller shaft to front axle 10. A suitable chain 66 couples sprockets 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 transferred 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 automatically. Thus it will be seen that positive drive is established automatically in both the drive and coast modes of operation when fourwheel 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 described clutch provides a novel arrangement for clutching the front drive axles 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. WHAT WE CLAIM IS:

1. An automatic clutch comprising first and second rotatable members, first and second clutch elements respectively rotatable with said first and second rotatable members, said first clutch element being movable between a first position out of contact with the second clutch element and a second position in which said clutch elements are coupled in either a first or a second mode in which the first or second rotatable member respectively is the driving member, said clutch elements being relatively rotatable whilst coupled to change between modes, means responsive to rotation of said first rotatable member in one direction for moving said first clutch element to said second position, means for retaining said first clutch element in said second position so long as said first rotatable member is subject to rotation in said one direction irrespective of mode, means for maintaining said first clutch element in said second position as the direction of rotation of said first rotatable member is changed from said one direction to the opposite direction, said retaining means also being effective for retaining said first clutch element in said second position so long as said first rotatable member is subject to rotation in said opposite direction irrespective of mode, and means biasing said first clutch element towards said first position.

cam follower has rise and dwell surfaces, said rise and cam surfaces being adapted to be in contact as said first element is moved to said second position, said dwell and cam surfaces being adapted to be in contact when said first element is in said second position, and said cam and cam follower defining means for rotating 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 mode.

5. A clutch as claimed in any of the preceding claims, wherein said first and second elements define said maintaining means.

6. A clutch as claim in claim 5, wherein said first and second elements have clutch teeth, said clutch teeth being adapted for meshing engagement in either of said modes when said first element is in said second position, said meshing engagement developing a force sufficient to overcome the force of said biasing means and thus maintain said first element in said second position as the direction of rotation of said first member is changed.

7. An automatic clutch substantially as herein described with reference to the accompanying drawings.