Abstract:
An overrunning coupling assembly and a method of controlling the engagement of planar first and second members are provided wherein two sets of opposed engaging struts are applied with one motion of a single control plate or member. The planar first and second members have inside surfaces extending generally normal to a first axis. The assembly includes free-floating, forward keys and free-floating, reverse keys opposed to the forward keys. The forward and reverse keys are movable between a notch-engaging, engaged position and a disengaged position in which the second member is permitted to free-wheel relative to the first member. The planar control member is disposed between the first and second surfaces and is controllably rotatable about the first axis between first and second angular positions relative to the first member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to overrunning coupling assemblies and methods for controlling the engagement of planar members.  
         [0003]     2. Background Art  
         [0004]     Overrunning coupling assemblies may be used for transferring torque from a driving member to a driven member in a variety of structural environments. This permits the transfer of torque from a driving member to a driven member while permitting freewheeling motion of the driving member relative to the driven member when torque is interrupted. Such couplings often comprise an outer race concentrically disposed with respect to an inner race, the outer race having cammed surfaces that define a pocket in which coupling rollers are assembled.  
         [0005]     A driving member is connected to one race, and a driven member is connected to the other race. During torque transfer from the driving member to the driven member, the rollers become locked with a camming action against the cam surfaces, thereby establishing a positive driving connection between the driving member and the driven member. When the torque is interrupted, the driven member may freewheel relative to the driving member as the rollers become unlocked from their respective cam surfaces.  
         [0006]     Another common overrunning coupling includes inner and outer races wherein one race is connected to a driving member and the other race is connected to the driven member. Overrunning coupling sprags are disposed between the inner cylindrical surface of the outer race and the outer cylindrical surface of the inner race so that the sprags lock the races together as torque is delivered to the driven member. The sprags become unlocked with respect to the inner and outer race surfaces when torque transfer is interrupted.  
         [0007]     U.S. Pat. No. 5,927,455 discloses a bi-directional overrunning pawl-type clutch having a driving member mounted for power rotation, a driven member mounted for rotation adjacent the driving member, with each of the driving and driven members having pawl engaging shoulders, and a plurality of rigid pawls interposed between the driving and driven members. A control element is mounted for shifting movement between the driving and driven members to control the position of the pawls which are yieldably biased toward positions of engagement extending between the driving and driven members to produce driving engagement therebetween. The control element is shiftable to various positions to permit driving and overrunning in one direction or driving and overrunning in the opposite direction dependent upon the direction of rotation of the driving member.  
         [0008]     U.S. Pat. No. 6,244,965 discloses a planar overrunning coupling for transfer of torque from a driving member to a driven member in one direction and which permits freewheeling motion between the members upon a torque reversal. The coupling includes coupling plates situated in close proximity with a strut retainer plate disposed between them. One plate is connected to the driving member and the other plate is connected to the driven member. Each plate has strut recesses. A series of struts is located in the recesses of one plate so that each strut may be pivoted, thereby allowing the struts to engage the companion recesses in the other coupling plate. The retainer has angularly spaced apertures that register with the struts to permit pivotal movement of the struts when the retainer plate is in one rotary position. The retainer plate, when it is in a second rotary position, prevents pivotal motion of the struts, thereby permitting freewheeling relative motion of the coupling plates.  
         [0009]     U.S. Pat. No. 6,116,394 discloses an overrunning coupling assembly including a notch plate and an annular coupling pocket plate positioned in face-to-face relationship with respect to each other along a common axis. The pocket plate includes strut pockets disposed at angularly spaced positions about the axis. The notch plate includes notch recesses at angularly spaced positions about the common axis and positioned in juxtaposed relationship with respect to the strut pockets. The notch plate includes an inner circumferential rail at a radially inward side of the notch recesses and an outer circumferential rail at a radially outward side of the notch recesses. Torque-transmitting struts are positioned in the strut pockets. Each strut has first and second ears at one edge thereof for enabling pivotal motion of the struts about an ear axis intersecting the ears. The opposite edge of each strut is engageable with one of the notch recesses whereby one-way torque transfer may occur between the plates. Each opposite edge has first and second corners. Each strut pocket is sufficiently enlarged to allow pivotal movement of each strut about a strut axis which is parallel with the common axis, thereby enabling one of the first and second corners to be selectively supported by one of the inner and outer circumferential rails to prevent the struts from slapping against the notch recesses as the notch plate and pocket plate are respectively counterrotated.  
         [0010]     U.S. Pat. No. 5,964,331 discloses a one-way clutch comprising a pocket plate and a notch plate situated in a juxtaposed adjacent relationship. One-way clutches of this kind are sometimes referred to as planar clutches because the adjacent juxtaposed surfaces are situated in radial planes with respect to the axis of the clutch.  
         [0011]     For purposes of this disclosure, the term coupling should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms coupling, clutch and brake may be used interchangeably.  
         [0012]     A pocket plate may be provided with angularly disposed recesses or pockets about the axis of a one-way clutch. The pockets are formed in the planar surface of the pocket plate. Each pocket receives a torque transmitting strut, one end of which engages an anchor point in a pocket of the pocket plate. An opposite edge of the strut, which may hereafter be referred to as an active edge, is movable from a position within the pocket to a position in which the active edge extends outwardly from the planar surface of the pocket plate. The struts may be biased away from the pocket plate by individual springs.  
         [0013]     A notch plate may be formed with a plurality of recesses or notches located approximately on the radius of the pockets of the pocket plate. The notches are formed in the planar surface of the notch plate.  
         [0014]     Another example of an overrunning planar clutch is disclosed in U.S. Pat. No. 5,597,057.  
         [0015]     Other U.S. patents related to the present invention include: 5,070,978; 5,449,057; 5,806,643; 5,871,071; 5,918,715; 5,979,627; 6,065,576; 6,125,980; 6,129,190; 6,186,299; 6,193,038; 6,386,349; 6,481,551; 6,505,721; 6,571,926; and 6,854,577.  
         [0016]     It is often desirable to have opposed engaging struts in a selectable or controllable clutch or coupling assembly so that torque can be transferred in both directions about an axis. It is also desirable to have an overrunning or free-wheeling capability in such clutches or assemblies. One way to control such sets of opposed struts or keys is to provide two slide or control plates. However, two slide plates add cost and complexity to the selectable clutch. In addition, such plates are more difficult to control external to the clutch.  
       SUMMARY OF THE INVENTION  
       [0017]     An object of the present invention is to provide an overrunning coupling assembly and method for controlling the engagement of planar members wherein a single control plate or member is provided to reduce the above-noted cost, complexity and control concerns.  
         [0018]     In carrying out the above object and other objects of the present invention, an overrunning coupling assembly is provided. The assembly includes a planar first member having an inside first surface. The first member has at least one recess formed in the first surface. The assembly further includes a planar second member rotatable about a first axis having an inside second surface extending generally normal to the first axis and disposed closely adjacent to the first surface. The second surface has at least one notch formed there. The assembly includes at least one free-floating, forward key and at least one free-floating, reverse key opposed to the at least one forward key. The keys are received and retained in the at least one recess but not physically secured to the first member. The forward and reverse keys are movable between a notch-engaging, engaged position and a disengaged position in which the first and second members are permitted to free-wheel relative to each other. A first set of biasing members are carried by the first member and urge the forward and reverse keys toward the second surface. A single planar control member is disposed between the first and second surfaces and is controllably rotatable about the first axis between first and second angular positions relative to the first member. The control member has at least one aperture which extends completely therethrough to allow the forward and reverse keys to extend therethrough to the notch-engaging, engaged position in the first angular position of the control member. The control member maintains the forward and reverse keys in the disengaged position in the second angular position of the control member.  
         [0019]     The at least one recess may be sufficiently enlarged to allow pivotal movement of one of the keys about a key axis which is substantially parallel to the first axis. The assembly may further include at least one biasing member carried by the first member to urge the one of the keys to pivot about the key axis during rotation of the control member.  
         [0020]     One forward key and one reverse key may be received and retained in the same recess.  
         [0021]     One forward key and one reverse key may extend through the same aperture in the control member in the notch-engaging, engaged position.  
         [0022]     A plurality of adjacent notches may be formed in the second surface, and one forward key and one reverse key may engage adjacent notches in the second surface in the engaged position.  
         [0023]     At least one of the keys is trapezoidal in cross section to facilitate movement of the at least one key out of its engaged position.  
         [0024]     Further in carrying out the above object and other objects of the present invention, an overrunning coupling assembly is provided. The assembly includes a planar first member having an inside first surface. The first member has at least one recess formed in the first surface. A planar second member is rotatable about a first axis and has an inside second surface extending generally normal to the first axis and disposed closely adjacent to the first surface. The second surface has at least one notch formed therein. The assembly includes at least one free-floating, forward key and at least one free-floating, reverse key opposed to the at least one forward key. The keys are received and retained in the at least one recess but not physically secured to the first member. The forward and reverse keys are movable between a notch-engaging, engaged position and a disengaged position in which the first and second members are permitted to free-wheel relative to each other. A first set of biasing members are carried by the first member and urge the forward and reverse keys toward the second surface. A single planar control member is disposed between the first and second surfaces and is controllably rotatable about the first axis between first and second angular positions relative to the first member. The control member has at least one aperture which extends completely therethrough to allow the forward and reverse keys to extend therethrough to the notch-engaging, engaged position in the first angular position of the control member. The control member maintains the forward and reverse keys in the disengaged position in the second angular position of the control member. At least one biasing member is carried by the first member and urges one of the keys to pivot about a key axis which is substantially parallel to the first axis during rotation of the control member.  
         [0025]     One forward key and one reverse key may be received and retained in the same recess.  
         [0026]     One forward key and one reverse key may extend through the same aperture in the control member in the notch-engaging, engaged position.  
         [0027]     A plurality of adjacent notches may be formed in the second surface, and one forward key and one reverse key may engage adjacent notches in the second surface in the engaged position.  
         [0028]     At least one of the keys is trapezoidal in cross section to facilitate movement of the at least one key out of its engaged position.  
         [0029]     Still further in carrying out the above object and other objects of the present invention, a method of controlling engagement of planar first and second members is provided. The first member has an inside first surface. The first member has at least one recess formed in the first surface. The planar second member is rotatable about a first axis and has an inside second surface extending generally normal to the first axis and disposed closely adjacent to the first surface. The second surface has at least one notch formed therein. The method includes providing at least one free-floating, forward key and at least one free-floating, reverse key opposed to the at least one forward key. The keys are received and retained in the at least one recess but not physically secured to the first member. The method further includes urging the forward and reverse keys toward the second surface. The method includes providing a single planar control member between the first and second surfaces and which is rotatable about the first axis relative to the first member. The control member has at least one aperture which extends completely therethrough. The method further includes rotating the control member relative to the first member about the first axis. The at least one aperture allows the keys to extend therethrough and engage the at least one notch in the second member in a first angular position of the control member. The control member maintains the keys in a disengaged position in a second angular position of the control member in which the first and second members are positioned to free-wheel relative to each other.  
         [0030]     The method may further include rotating one of the keys to pivot about a key axis which is substantially parallel to the first axis to permit free-wheeling of the first and second members.  
         [0031]     The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]      FIG. 1  is an exploded, perspective view of an overrunning coupling or clutch assembly constructed in accordance with one embodiment of the present invention;  
         [0033]      FIG. 2  is a top plan view of the assembly of  FIG. 1 ;  
         [0034]      FIG. 3  is a sectional view taken along lines  3 - 3  of  FIG. 2 ;  
         [0035]      FIG. 4  is a sectional view taken along lines  4 - 4  of  FIG. 3 ;  
         [0036]      FIG. 5  is a perspective view of a notch plate of the assembly of  FIG. 1 ;  
         [0037]      FIG. 6  is a schematic, top plan view, partially broken away, illustrating a forward strut, a control plate and a pocket plate of another embodiment of the assembly (without the corresponding reverse strut for purposes of simplicity) wherein the assembly is in a locked position; and  
         [0038]      FIG. 7  is a view similar to the view of  FIG. 6  wherein the assembly is in an overrun position.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]      FIG. 1  shows a pocket plate, generally indicated at  10 , of a planar or overrunning coupling or clutch assembly, generally indicated at  12 , constructed in accordance with one embodiment of the present invention. A driving coupling or notch plate, generally indicated at  14 , is nested within the pocket plate  10 . The driving notch plate  14  is to be drivably connected to a torque input shaft (not shown). This driving connection is established by internal splines  16  formed on the driving notch plate  14 , which drivably engage external splines on the input shaft.  
         [0040]     The pocket plate  10  is provided with external splines  18 .  
         [0041]     An actuator (not shown) may be drivably connected to a slide or control plate, generally indicated at  20 , via a slide plate fork  22 , which is secured to a tab  23  of the control member or plate  20 , thereby causing the control plate  20  to be adjusted angularly with respect to the axis of the input shaft (which corresponds to a first axis  24  about which the plates  14  and  20  are rotatable, as shown in  FIG. 3 ). The control plate  20  is disposed between the plates  10  and  14  for limited angular rotation relative to the plates  10  and  14 .  
         [0042]     The plate  14  can free-wheel in both angular directions about the axis  24  relative to the plate  10 . The bi-directional free-wheeling motion is achieved in an operating mode when the actuator adjusts the angular position of the control plate  20  relative to the pocket plate  10  (via the fork  22 ) about the axis  24  to a position (i.e., overrun or disengaged position), as shown in  FIG. 7 .  FIG. 6  illustrates an angular position (i.e., locked or engaged position) of the control plate  20  relative to the pocket plate  10 .  
         [0043]      FIG. 1  illustrates the clutch or coupling assembly  12  in an exploded view. The driving notch plate  14  has an inside surface  26  with one or more notches  28  formed therein and separated by common walls  29 , as shown in  FIG. 5 . The notch plate  14  is adapted to be received in the pocket plate  10 .  
         [0044]     The pocket plate  10  has an inside surface  30  with one or more elongated recesses  32  formed therein. Located intermediate the inside surfaces  26  and  30  of the plate  14  and the plate  10 , respectively, is the control plate  20 .  
         [0045]     There are preferably twelve struts or keys received and retained in the six recesses  32  in pocket plate  10 . Six of the keys are forward keys  34  for transferring torque in a forward direction about the axis  24  and six of the keys are reverse keys  36  opposed to their respective forward keys  34  for transferring torque in a reverse direction about the axis  24 . Each of the struts or keys  34  and  36  includes a planar substantially rectangular portion  38  and  40 , respectively, and a pair of ears  42  and  44 , respectively. Each recess  32  preferably receives and retains one forward key  34  and one reverse key  36 , which opposes its respective forward key  34  as best shown in  FIG. 4 .  
         [0046]     As best shown in  FIG. 4 , the struts  34  and  36  are trapezoidal in cross section. In other words, the face free edges of the struts  34  and  36  are angled (i.e. are not parallel) to improve the ability of the plates  10  and  14  to disengage.  
         [0047]     A reverse key such as the reverse key  36  is not shown in  FIGS. 6 and 7  for purposes of simplicity. However, it is to be understood that a reverse key  36  is preferably disposed in each recess  32  which also receives and retains a forward key  34 .  
         [0048]     As seen in  FIG. 4 , pivotal edges (i.e., the edges of the keys about which they rotate within the recesses  32 ) of the struts  34  and  36  are located at opposite ends of the recess  32 . Similarly, the pivotal edges for the other struts  34  and  36  are located at opposite ends of their respective recesses  32 .  
         [0049]     The control plate  20  is provided with six elongated apertures  46 . These are equally spaced and arranged angularly about the axis  24 . When the control plate  20  is appropriately positioned angularly for torque transfer in either direction about the axis  24 , one aperture  46  will be disposed directly over each recess  32  (i.e., see  FIGS. 3 and 4 ;  FIG. 6  shows only a portion of the recess  32 , a portion of the aperture  46  and the forward key  34  but not its corresponding reverse key  36  for purposes of simplicity).  
         [0050]     The apertures  46  and the notches  28  are sized so that the portions  38  and  40  of the keys  34  and  36 , respectively, can enter adjacent notches  28  in the notch plate  14  and engage edges of the notches  28  to establish a locking action between the keys  34  and  36  and the plate  14  that will permit torque transfer in both directions between the plate  14  and the plate  10 .  
         [0051]     If the control plate  20  is rotated to different angular positions, as shown in  FIG. 7 , both struts  34  and  36  in each recess  32  rotate downwardly into their recess  32  and will be at least partially covered by the control plate  20  and prevented from moving pivotally upward about their respective pivotal edges. (As described hereinbelow, the forward key  34  also rotates about a key axis which is substantially parallel to the axis  24  during such control plate  20  rotation.) When the control plate  20  is thus positioned, the plate  14  can free-wheel, in either direction about the axis  24  with respect to the plate  10 .  
         [0052]     The forward keys  34  may be covered by the control plate  20  and/or the notch plate  14 . The keys  34  may rotate outwardly while being partially held by the notch plate  14 . In other words, the control plate  20  may move before the torque is released on the forward keys  34 . As the control plate  20  is rotated to an angular position as shown in  FIG. 7 , the forward keys  34  do not all necessarily rotate outward immediately. If the forward struts  34  are loaded at time of control plate movement, the struts  34  will remain locked. Once the assembly begins forward over run movement, the struts  34  will be forced down by the notch plate  14  and rotated into final over run position by the springs  66 .  
         [0053]     Although any suitable strut spring can be used with the invention,  FIGS. 1, 3  and  4  show strut coil springs  48  used in this embodiment of the invention. One spring  48  is located under each of the struts  34  and  36  within recesses  50  formed in the recesses  32 .  
         [0054]      FIG. 1  also shows elongated portions  52  and  54  of the recesses  32  that receive the ear portions  44  and  42 , respectively, of the struts  36  and  34 , respectively. The portions  52  and  54  of the recesses  32  are sized so that the ear portions  44  and  42 , respectively, at the pivotal edge of each of the struts  36  and  34 , respectively, can be secured therein.  
         [0055]     When the notch plate  14  is received within the pocket plate  10  with the control plate  20  therebetween, the plates  10  and  14  are held axially fast by retainer ring or snap-ring  56 . The snap-ring  56  is received and retained in an external groove  58  formed in the notch plate  14 , the groove  58  being seen in  FIG. 3 . When assembled, the control plate  20  is located within an annular groove  60  formed in the pocket plate  10 . As seen in  FIG. 1 , the control plate  20  is provided with angularly spaced, outer peripheral bent flanges  62  which extend into an outer peripheral groove  64  formed in the inside surface or face  30  of the plate  10 . The control plate  20  thus can slide angularly about the axis  24  of the assembly  12 .  
         [0056]     Coil springs, one of which is shown at  66  in  FIGS. 6 and 7 , are disposed in the groove  64  between the flanges  62  and the larger one of the ears  42  of the forward keys  34 . Upon movement of the control plate  20  in a clockwise direction from the locked position of  FIG. 6 , the flanges  62  urge their respective springs into contact with the larger one of the ears  42  of the key  34  and thereby compress the coil springs  66  to rotate the key  34  about an axis substantially parallel to the axis  24 . The keys  34  are rotated within the recesses  32  until they reach the overrun position of  FIG. 7 . Inner flanges  68  which extend from the apertures  46  in the control plate  20  help to control rotation of the keys  34  within their respective recesses  32  during rotation from overrun to the lock-up position.  
         [0057]     In general and with reference to  FIGS. 6 and 7 , for overrun, the slide plate  20  rotates clockwise, lays down the reverse struts  36  (not shown in  FIGS. 6 and 7 ) and the springs  66  contact the ears  42  of the forward struts  34 . The forward struts  34  rotates outwardly and the clutch assembly  12  overruns.  
         [0058]     For lockup, the slide plate  20  rotates counterclockwise, the springs  66  releases tension and the forward struts rotate  34  into lock-up position urged by the inner flanges  68 . The reverse struts  36  flip up and the assembly  12  is locked.  
         [0059]     The configuration of the notch and pocket plates  14  and  10 , respectively, of the assembly  12  reduce parasitic overrun drag. This happens due to the inability of the assembly  12  to hold any significant amount of oil over and above boundary lubrication.  
         [0060]     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.