Abstract:
A clutching device includes an outer race, an inner race, a plurality of rollers and an actuator plate. The outer and inner races have axial ridges to define opposed outer and inner race pockets. The rollers are positioned in the outer and inner race pockets. The clutching device further includes an axial projection coupled for rotation with one of the inner and outer race. An actuator plate is coupled for rotation with one of the inner and outer race and axially moveable between a first position wherein the actuator plate engages the axial projection and a second position wherein the actuator plate does not engage the axial projection.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Patent Application 60/625,217 filed Nov. 5, 2004, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND  
       [0002]     The present invention relates to clutches. More particularly, the present invention relates to a slipper clutch and means for selectively actuating the slipper clutch.  
         [0003]     A slipper clutch can replace a parallel combination of a one-way clutch and mode selecting plate clutch assembly in an automatic transmission, eliminating the frictional drag of the plate clutch. Mode control of such a clutch in the prior art has employed radial features on the clutch races engaging with slots in a cylindrical control element. Supporting the cylindrical control element requires additional parts being used or results in difficult assembly, since the control element requires a supporting diameter that is greater than the shaft diameter.  
       SUMMARY  
       [0004]     The present invention provides a clutching device comprising an outer race, an inner race, a plurality of rollers and an actuator plate. The outer race has a radially inward surface having a plurality of axial ridges to define outer race pockets and the inner race has a radially outward surface having a plurality of axial ridges to define inner race pockets opposed to the outer race pockets. The rollers are positioned between the outer and inner races in the outer and inner race pockets. The clutching device further includes an axial projection coupled for rotation with one of the inner and outer race. An actuator plate is coupled for rotation with one of the inner and outer race and axially moveable between a first position wherein the actuator plate engages the axial projection and a second position wherein the actuator plate does not engage the axial projection. The present invention allows for radial support of the control element at smaller diameters and minimizes the space required for actuation.  
         [0005]     In one embodiment, the outer race includes an outer race axial tab having a first axial length and the inner race includes an inner race axial tab having a second axial length different from the first axial length. The actuator plate is axially moveable between a first position wherein the actuator plate engages both the outer and inner axial tabs and a second position wherein the actuator plate engages only one of the outer and inner axial tabs. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a sectional view of a clutching assembly that is a first embodiment of the present invention.  
         [0007]      FIG. 2  is a sectional view taken along the line  2 - 2  in  FIG. 1 .  
         [0008]      FIG. 3  is an elevation view of the actuator plate and inner and outer race tabs along the line  3 - 3  in  FIG. 1 .  
         [0009]      FIG. 4  is a sectional view of a clutching assembly that is a second embodiment of the present invention.  
         [0010]      FIG. 5  is a sectional view of a clutching assembly that is a third embodiment of the present invention.  
         [0011]      FIG. 6  is a radially inward view taken along the line  6 - 6  in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION  
       [0012]     The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, “top”, “bottom”, “right”, “left”, “front”, “frontward”, “forward”, “back”, “rear” and “rearward”, is used in the following description for relative descriptive clarity only and is not intended to be limiting.  
         [0013]     Referring to  FIGS. 1-3 , a selectable mode clutch  10  that is a first embodiment of the present invention is shown. The clutch  10  generally comprises an outer ring  12 , an inner ring  14 , an outer race  16 , an inner race  18 , rollers  20 , an actuator plate  22 , a spring  24 , and actuator pins  26 . The outer race  16  is press fit into the outer ring  12 , which is fixed to a non-rotating housing via a spline  2 . The inner race  18  is slip fit to the inner ring  14  and is cut axially to make it a non-continuous ring, as indicated at  19  in  FIG. 2 . Alternatively, the inner race  18  can be interference fitted to the inner ring  14  to provide a small amount of drag to allow the clutch to engage. A shaft  4  is rotationally fixed to the inner ring  14 . Both the inner and outer race  18 ,  16  have axial ridges  23  that form pockets  25  into which rollers  20  are placed. The side faces of these ridges  23  can contact the roller  20  at angles that tend to wedge the roller  20  against these faces. Both the outer and inner races  16 ,  18  have shoulders  11 ,  13  and  15 ,  17 , respectively, at each end of the rollers  20  to contain the rollers  20  axially.  
         [0014]     Both the outer and inner races  16 ,  18  have projections or tabs  28 ,  30  extending axially away from the rollers  20 . One of the tabs  28  has an axial length greater than the other tab  30 . While the illustrated embodiment shows the outer race tab  28  having a greater length, it is also contemplated that the inner race tab  30  could have the greater length. Referring to  FIG. 3 , the actuator plate  22  has a radial slot  27  configured to receive the tabs  28 ,  30 . The actuator plate  22  is axially moveable between a first position, as shown in  FIG. 1 , and a second position in which the actuator plate  22  moves in the direction of arrow W in  FIG. 1 . In the first position, both tabs  28 ,  30  are within the actuator plate slot  22  and are engaged by the actuator plate  22 . The actuator plate  22  maintains the outer and inner races  16 ,  18  in rotational alignment such that the pockets  25  remain rotationally aligned, thereby preventing wedging of the rollers  20  as friction of the inner ring  14  rotating against the inner race  18  creates a torque on the inner race  18 . The actuator plate  22  is preferably maintained in the first position by the force of the spring  24 . While a spring  24  is described, other biasing means, for example, a resilient ring may also be utilized.  
         [0015]     When an external force is applied to the actuator pins  26 , the actuator plate  22  moves in the direction of arrow W to the second position, compressing the spring  24 . Since the inner race tab  30  is shorter than the outer race tab  28 , the actuator plate  22  disengages the inner race tab  30 . The outer race tab  28  remains within the actuator plate slot  27 . Since the outer race tab  28  is engaged by the actuator plate  22  and the inner race tab  30  is not, the inner race  18  is free to rotate with the frictional torque created by the inner ring  14  rotating against the inner race  18 . Rotation of the inner race  18  relative to the outer race  16  causes the rollers  20  to engage the side faces of the ridges  23  such that the rollers  20  wedge causing the inner race  18  to contract the space  19  and engage the inner ring  14 , thereby carrying torque. When the force is removed from the actuator pins  26 , the return spring  24  attempts to return the actuator plate  22  to the first position. However, the relative rotation of the inner race  18  causes the inner race tab  30  to rotationally misalign with the actuator plate slot  27  such that the actuator plate  22  will be blocked by the inner race tab  30  unless the outer and inner race  16 ,  18  are rotationally neutral. At the moment of rotational alignment of the outer and inner races  16 ,  18 , the actuator plate  22  will move in the direction opposite that of arrow W with the force of the spring  24 , deactivating the clutch  10 .  
         [0016]     Referring to  FIG. 3 , outer and inner tabs  28  and  30  have the same circumferential width such that when the actuator plate  22  is in the first position, the tabs  28  and  30  are both engaged in the same manner. Alternatively, the first position of the actuator plate  22  can provide a one-way clutch function if the inner race tab  30  is reduced in circumferential width such that the inner race  18  has freedom of rotational movement to allow lock in one direction but is blocked from rotation and thus locking in the opposite direction of rotation.  
         [0017]     Referring to  FIG. 4 , a selectable mode clutch  10 ′ that is an alternate embodiment of the present invention is shown. The clutch  10 ′ is substantially the same as that in the previous embodiment and includes an outer ring  12 , an inner ring  14 , an outer race  16 , an inner race  18 , rollers  20 , an actuator plate  22  and a spring  24 . The outer and inner races  16 ,  18  include axial tabs  28 ,  30  configured to be received in a radial slot  27  of the actuator plate  22 . In the present embodiment, instead of actuator pins, an annular electric coil  40  is fitted into the stationary housing  3 . The electric coil  40  is a distance A from the actuator plate  22  and the actuator plate has travel B. When the coil  40  is de-energized and the actuator plate  22  is in the illustrated first position, both tabs  28 ,  30  are received in the slot  27  and engaged by the actuator plate  22 . When the coil  40  is energized, the actuator plate  22  moves in the direction of arrow X such that a small operating gap between the coil and actuator plate occurs (A minus B), avoiding drag. The tab  30  is no longer engaged by the actuator plate  22  and the clutch  10 ′ operates in the manner described with respect to the first embodiment.  
         [0018]     With this device, power can be switched from one rotating element to another. This device can be applied to create an ‘on-demand’ four wheel drive system. This system comprises a front axle and rear axle. The clutch  10 ′ of  FIG. 4  is inserted into the driveline of one of the two axles. The axle whose torque is interrupted by the clutch  10 ′ is driven with a higher numerical drive reduction ratio than the other axle. When a significant speed difference across the clutch device is sensed, indicating wheel slip, the coil  40  is activated, causing torque to be transmitted though the clutch and into the secondary axle. After triggering the clutch, the coil  40  is immediately de-energized so that when traction is regained, the ratio difference will cause a torque reversal through the clutch  10 ′, causing the clutch  10 ′ to disengage.  
         [0019]     Referring to  FIGS. 5 and 6 , a selectable mode clutch  10 ″ that is another alternate embodiment of the invention is shown. The clutch  10 ″ is substantially the same as in the previous embodiments and includes an outer ring  12 , an inner ring  14 , an outer race  16 , an inner race  18 , rollers  20  and an actuator plate  22 . The outer and inner races  16 ,  18  include axial tabs  28 ,  30 ′ configured to be received in a radial slot  27  of the actuator plate  22 . In the present embodiment, the inner race tab  30 ′ has two circumferential widths, a narrow portion  31  and a wider portion  33 , as shown in  FIG. 6 , and the actuator plate  22  is moveable between three positions. In the center position shown in  FIGS. 5 and 6 , both tabs  28  and  30 ′ are within the actuator plate slot  27 , with the actuator plate  22  aligned with the narrow portion  31  of the tab  30 ′. As such, freedom of relative rotation is allowed in one direction thus creating a one-way clutch function. Preferably, the actuator plate  22  is biased to the center position by two springs  32 ,  34 , or other biasing means. The springs  32 ,  34  are preferably such that spring  32  is a high rate spring and spring  34  is a low rate spring.  
         [0020]     The actuator plate  22  is moveable in the direction of arrow Y to a position where the actuator plate slot  27  is free of the inner race tab  30 ′ but not the outer race tab  28 , similar to the second position in the previous embodiments. In the present embodiment, the actuator plate  22  is moved in the direction Y by energizing an electric coil  40 . The actuator plate  22  is also moveable in the direction Z to a position where the actuator slot  27  is aligned with the outer tab  28  and the wider portion  33  of the inner tab  30 ′ such that the actuator plate  22  rotationally aligns the outer and inner races  16 ,  18  to prevent lock in both directions, similar to the first position in the previous embodiments. In the present embodiment, the actuator plate  22  is moved in the direction Z by energizing an electric coil  42 .  
         [0021]     The ‘on-demand’ four wheel drive system previously described with respect to  FIG. 4  is similar when using this clutch  10 ″ embodiment except that the one way clutch function provides automatic ‘on-demand’ torque to the auxiliary axle in forward driving without speed sensors. When the main axle slips, the speed difference across the clutch  10 ″ is reversed, causing it to lock. In good traction conditions, the axle drive ratio difference keeps the clutch  10 ″ from locking. For engine braking in forward drive, the actuator plate is moved in the direction of arrow Y. To prevent locking in reverse drive, the actuator plate is moved in the direction of arrow Z.  
         [0022]     While the present invention has been described in use with specific clutching applications, the clutches of the present invention can be utilized in various systems and applications.  
         [0023]     Additionally, while in the illustrated embodiments the tabs  28 ,  30  are integrally formed with the races  16 ,  18 , those skilled in the art will understand that the tabs  28 ,  30  could be separate components directly attached to the races, or could take other forms and configurations of axial projections that are coupled for rotation with the races  16 ,  18  in other manners.