Abstract:
A drive device includes a first member including a first shoulder, and a second member positioned in close proximity to the first member and including a second shoulder. The device also includes a coupling arrangement including a strut having a first edge for direct engagement with the first shoulder, a second edge for engagement with the second shoulder and supported for pivotal movement between engaged and overrun positions, based on relative rotation of the first and second members such that the first member drives the second member in a drive mode with the strut in the engaged position and the first and second members can overrun with respect to one another with the strut in the overrun position. The coupling arrangement also includes a cushioning member disposed between the second edge and the second shoulder for cushioning each initial engagement of the strut in the drive mode.

Description:
RELATED APPLICATION 
     The present application is a Continuation of U.S. patent application Ser. No. 10/118,041, now U.S. Pat. No. 6,896,111, entitled ONE-WAY DRIVE DEVICE WITH REDUCED ENGAGEMENT IMPACT, filed on Apr. 5, 2002, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to one-way drive devices and methods of operating such devices and, more specifically, to one-way drive devices in which the engagement impact in the transition from the overrunning mode to the locked mode is reduced. 
     One-way drive devices join two shafts in such a way that the first shaft drives the second shaft when driven in one direction, but the first shaft disconnects from the second shaft when driven in the opposite direction. An example of a one-way clutch is the type known as a MECHANICAL DIODE® (hereafter referred to as MD) manufactured under license given by Epilogics, Inc. The MD achieves this one-way drive behavior using a high resolution, planar ratchet mechanism. Such a device is disclosed, for instance, in U.S. Pat. No. 5,070,978 issued to Paul B. Pires (hereafter referred to as the Pires patent and incorporated herein by reference). 
     Turning now to the drawings, wherein like components are indicated by like reference numbers throughout the various figures, attention is immediately directed to  FIGS. 1A and 1B , which illustrate the major components of a typical MD of the type disclosed in the Pires patent.  FIG. 1A  illustrates one face of a pocket plate  10  of an MD mechanism. Pocket plate  10  includes a plurality of indentations  12  for coupling out or in of torque to or from an external shaft (not shown). Pocket plate  10  also includes a plurality of pockets  14 , which are configured for housing a plurality of struts  16  therein. Each strut  16  also includes a pair of ears  17  along one edge. Ears  17  are designed to cooperate with a pair of strut locating shoulders  18  of pocket  14  such that strut  16  remains within pocket  14  during the operation of the MD. Another component of a typical MD mechanism is a notch plate  20 , illustrated in  FIG. 1B , which includes a plurality of notches  22  on one face. When notch plate  20  is positioned in a face-to-face relationship with pocket plate  10  of  FIG. 1A , notches  22  are designed cooperate with struts  16  such that one of struts  16  engages one of notches  22  to transfer torque therebetween. It should be noted that torque can be transferred from pocket plate  10  to notch plate  20  via one of struts  16  such that pocket plate  10  drives notch plate  20  or, just as readily, torque can be transferred from notch plate  20  to pocket plate  10  via one of struts  16  such that notch plate  20  drives pocket plate  20 . 
     The details of the operation of the typical MD is further illustrated in  FIGS. 2A and 2B , which illustrate partial cross-sectional views of the MD with pocket plate  10  and notch plate  20  arranged in face-to-face relationship. As can be seen in  FIGS. 2A and 2B , pocket  14  of pocket plate  10  includes a well  32 , which is configured to accommodate a bias spring  32 . Bias spring  32  is configured to bias a first edge  34  of strut  16  toward notch plate  20 . A second edge  36  of strut  16  is designed such that, as first edge  34  rotates toward notch plate  20 , second edge  36  rotates into pocket  14  such that second edge  36  engages a load bearing surface  38  of pocket  14 . Each of notches  22  of notch plate  20  includes a slanted surface  40  and a shoulder  42 . 
     The MD in driving mode is shown in  FIG. 2A . As can be seen in  FIG. 2A , shoulder  42  is configured to cooperate with first edge  34  of strut  16  such that when, for example, notch plate  20  rotates in a driving direction as indicated by arrow  50 A, first edge  34  of strut  16  is biased into engagement with shoulder  42 . Consequently, torque is transferred from shoulder  42  through first edge  34  and second edge  36  of strut  16  to pocket plate  10  through load bearing surface  38  such that pocket plate  10  is driven in a driven direction indicated by an arrow  52 . The direct imposing of strut  16  between notch plate  20  and pocket plate  10  forms a very strong connection between the two plates, thus allowing the transfer of large torques and loads therebetween. 
     In contrast, the MD in overrunning mode is shown in  FIG. 2B . In this case, notch plate  20  rotates in an overrunning direction as indicated by an arrow  50 B. Slanted surface  40  of each notch  22  serves to rotate strut  16  toward pocket plate  10  and thus out of engagement with shoulder  42 . As a result, notch plate  20  no longer drives pocket plate  10  and the two plates are rotationally disconnected. In other words, in the overrunning mode, pocket plate  10  and notch plate  20  each moves freely with respect to the other plate. Also, ears  17  on strut  16  cooperate with strut locating shoulders to keep strut  16  substantially within pocket  14  during overrunning mode. 
     Continuing to refer to  FIGS. 2A and 2B  in conjunction with  FIGS. 1A and 1B , one possible problem with the MD type of one-way drive device is a noise or abrupt shock caused during the transition from the overrunning mode to the drive mode. There are thought to be two reasons for the shock or noise present during this operating mode change. The first reason is the positive, surface to surface contact of the strut and plates when in the drive mode, as shown in  FIG. 2A . That is, the impact of first edge  34  of strut  16  hitting shoulder  42  of notch plate  20  can result in a noise or shock. A second reason is the angular distance between engagement opportunities (i.e., the angular distance between the opportunities for one of the struts in the pocket plate to engage a shoulder of one of the notches in the notch plate) afforded by the MD design. As most readily seen in  FIGS. 1A and 1B , this angular distance can vary from as little as 1- or 2-degrees to as much as 10- to 20-degrees depending on the number and position of struts/pockets and the number of notches used in a specific clutch arrangement. Regardless of this angular distance, the actual reversal of driving direction in the transition from the overrunning mode to the drive mode, if the transition occurs in a random fashion, can occur anywhere within the space between engagement opportunities. On those occasions when the reversal occurs just before an engagement opportunity, i.e., just before a strut is able to engage a shoulder in a notch, the notch plate accelerates in the drive direction from the instant of reversal until the strut becomes fully seated in the previously encountered notch. That is, the notch plate accelerates in the drive direction until the instant of engagement such that, when engagement does occur, the notch plate must be decelerated almost instantaneously to match the speed of the pocket plate or the pocket plate must be almost instantaneously accelerated to match the speed of the notch plate. This very rapid change in speed occurring at the instant of engagement can, under some conditions, be perceived as an audible click or perturbation of the motion of the shafts attached to the MD. This occasional click occurring at the instant of engagement can be especially objectionable when one of the plates of the MD is attached to a stationary drive line element, such as an automotive transmission case. 
     The present invention provides one-way drive devices which are intended to reduce or eliminate the foregoing problems in a heretofore unseen way and which provides still further advantages. 
     SUMMARY OF THE INVENTION 
     As will be described in more detail hereinafter, there is disclosed herein a one-way drive device designed in accordance with one aspect of the present invention and including a first, drive member rotatable about an axis in both a drive direction and an opposite, overrun direction. The one-way drive device also includes a second, driven member rotatable about the axis in at least a driven direction. The one-way drive device further includes a coupling arrangement including at least one strut cooperating with the first and second members such that the first member is able to drive the second member in the driven direction by causing the strut to initially engage and remain engaged between the first and second members during the time the first member drives the second member. In addition, the coupling arrangement includes a cushioning arrangement for cushioning the initial engagement of the strut between the first and second members. 
     In another aspect of the invention, an associated method of operating a one-way drive device, as described above, is disclosed. The method includes the steps of providing a first, drive member rotatable about an axis in both a drive direction and an opposite, overrun direction and providing a second, driven member rotatable about the axis in at least a driven direction. The method further includes the step of driving the second member in the driven direction using the first member by causing a strut to initially engage and remain engaged between the first and second members during the time the first member drives the second member. The method also includes the step of cushioning the initial engagement of the strut between the first and second members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be understood by reference to the following detailed description taken in conjunction with the drawings briefly described below. 
         FIG. 1A  is a diagrammatic illustration of a pocket plate, which is a part of a Pires-type MD mechanism. 
         FIG. 1B  is a diagrammatic illustration of a notch plate, which is another part of a Pires-type MD mechanism. 
         FIG. 2A  is a partial, enlarged cross-sectional view of a Pires-type MD mechanism, shown here to illustrate details of the Pires-type MD mechanism in driving mode. 
         FIG. 2B  is a partial, enlarged cross-sectional view of a Pires-type MD mechanism, shown here to illustrate details of the Pires-type MD mechanism in overrunning mode. 
         FIG. 3  is a partial, enlarged cross-sectional view of a first embodiment of a pocket plate for a one-way drive device, shown here to illustrate details of a strut cushioning mechanism designed in accordance with the present invention. 
         FIG. 4A  is a partial, enlarged cross-sectional view of the first embodiment of a one-way drive device including the strut cushioning mechanism of the present invention, shown here to illustrate the details of the MD mechanism in driving mode in partial engagement. 
         FIG. 4B  is a partial, enlarged cross-sectional view of the first embodiment of the one-way drive device including the strut cushioning mechanism of the present invention, shown here to illustrate the details of the MD mechanism in driving mode in full engagement. 
         FIG. 5A  is a diagrammatic illustration of a pocket plate for a one-way drive device, shown here to illustrate an arrangement of struts with an alternative strut cushioning mechanism of the present invention. 
         FIG. 5B  is a partial, diagrammatic illustration of a second embodiment of a pocket plate for a one-way drive device, shown here to illustrate details of the alternative strut cushioning mechanism designed in accordance with the present invention. 
         FIG. 5C  is a partial, cross-sectional view of the second embodiment of the pocket plate for a one-way drive device, shown here to illustrate the strut biasing effect of the alternative strut cushioning mechanism of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the described embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. 
     Attention is directed to  FIG. 3 , in which a pocket plate  110  and strut configuration of the one-way drive device of the present invention is described. As will be described in detail immediately hereinafter, the present invention is a modification of the aforedescribed MD for reducing the engagement impact of the strut, which engagement impact can cause an audible or sensible perturbation in the one-way drive device operation. Like pocket plate  10  of  FIGS. 1A ,  2 A and  2 B, pocket plate  110  includes strut  16  with first edge  34 , which is biased toward potential engagement with a notch plate (not shown) by bias spring  32  housed in well  30 . Pocket plate  110  also includes an extended pocket  114  for accommodating a cushioning spring  115  between second edge  36  of strut  16  and a load bearing surface  138  of extended pocket  114 . When the one-way drive device of the present invention is in the overrunning mode, cushioning spring  115  keeps second edge  36  of strut  16  in a position as far from load bearing surface  138  as allowed by the spring force and the pocket design. In practical designs, the distance between second edge  36  and load bearing surface  138  is, for example, a distance of a few tenths of a millimeter to a few millimeters. Furthermore, extended pocket  114  includes an additional spring pocket  140 , which is designed to accommodate cushioning spring  115  therein as cushioning spring  115  is compressed. That is, as cushioning spring  115  is compressed by a load applied to strut  16 , cushioning spring  115  is compressed into spring pocket  140  such that at least a portion of second edge  36  of strut  16  comes in direct contact with load bearing surface  138 . The operation of the strut configuration with the cushioning spring will be described in further detail immediately hereinafter. 
     Turning now to  FIGS. 4A and 4B , the operation of pocket plate  110  of the present invention in one embodiment of the one-way drive device in the transition from overrunning mode to the drive mode is described.  FIG. 4A  illustrates a partial cross-sectional view of a one-way drive device  150 A including pocket plate  110  immediately after first edge  34  of strut  16  has come into initial engagement with shoulder  42  of notch plate  20 . As shown in  FIG. 4A , notch plate  20  is moving in the drive direction as indicated by arrow  50 A. Cushioning spring  115  serves to cushion the initial engagement such that second edge  36  of strut  16  does not engage load bearing surface  138  right away. In this way, there is created a brief period of time during which the load transferred through strut  16  to pocket plate  110  is gradually increased as cushioning spring  115  is compressed, rather than an abrupt, almost instantaneous application of load from notch plate  20  to the pocket plate  110 . That is, as cushioning spring  115  is compressed due to the torque transferred from notch plate  20 , second edge  36  of strut  16  moves toward load bearing surface  138  until cushioning spring  115  is completely compressed. Furthermore, as cushioning spring  115  is compressed, cushioning spring  115  is accommodated into spring pocket  140  such that at least a portion of second edge  36  directly engages load bearing surface  138 , as shown in  FIG. 4B . When at least a portion of second edge  36  engages load bearing surface  138  with cushioning spring  115  being completely compressed (and thus tucked away into spring pocket  140 ), as illustrated in  FIG. 4B , the load from notch plate  20  is transferred through strut  16  to pocket plate  110  and pocket plate  110  moves in the driven direction of arrow  52 . This gradual increase in load over the period of time required for the cushioning spring to become fully compressed such that first edge  34  is engaged in shoulder  42  simultaneously with second edge  36  being engaged with load bearing surface  138  greatly reduces or eliminates entirely the noise and abruptness of the initial engagement present in previous one-way drive devices. 
     Attention is now directed to  FIGS. 5A–5C , which illustrate an alternative strut and cushioning spring arrangement of the present invention. An alternative pocket plate  210  is shown in  FIG. 5A . Pocket plate  210  includes a plurality of indentations  212  for coupling out (or in) of torque to an external shaft (not shown). Alternatively, splines such as those commonly known in the prior art, can be used for the same purpose. Pocket plate  210  further includes a coupling face  213 , which will face a notch plate (not shown) in the same manner as the aforedescribed one-way drive devices and includes a plurality of pockets  214 . Each one of pockets  214  is configured to accommodate a cushioning spring  215  and a shaped strut  216 . Pockets  214  are arranged around pocket plate  210  so as to be compatible with a notch plate, such as notch plate  20  shown in  FIG. 1B , in a one-way drive device configuration. Cushioning spring  215  in this embodiment is a leaf spring such that, under full load, the compressed spring lays flat between the strut and the pocket such that the load is evenly transferred through the strut to the pocket plate without the need for a spring pocket, as will be described in detail immediately hereinafter. 
     Details of one of pockets  214  are illustrated in  FIG. 5B . As can be seen in  FIG. 5B , strut  216  includes a first edge  234 , which is configured to engage, for example, shoulder  42  of notch plate  20  of  FIG. 1B . Strut  216  further includes a second edge  236 , which is designed to indirectly engage a load bearing surface  238  of pocket  214  through cushioning spring  215  when cushioning spring  215  is completely compressed. As earlier noted, cushioning spring  215  is a leaf spring designed to lie flat against load bearing surface  238  of pocket  214  when compressed such that, when strut  216  is engaged between the notch plate and the pocket plate, the load is evenly transferred through the strut between the notch plate and the pocket plate. That is, the use of the leaf spring as cushioning spring  215  eliminates the need for a spring pocket because the leaf spring itself flattens into a good load bearing surface when a load is applied. Strut  216  also includes a pair of ears  240  along second edge  236 . Ears  240  are designed to cooperate with cushioning spring  215  and a pair of strut locating shoulders  242  of pocket  214  such that cushioning spring  215  pushes ears  240  against strut locating shoulders  242 . A spring pocket may alternatively be included in the design of pocket  214  or strut  216 , if so desired, although is not considered to be necessary when a leaf spring is used as the cushioning spring. 
     Referring to  FIG. 5C  in conjunction with  FIG. 5B , further details of the relationship between the cushioning spring, strut and strut locating shoulders are described. Second edge  236  of strut  216  is designed such that the second edge is cut at an obtuse angle with respect to a top surface  244  of strut  216 . Therefore, the spring force from cushioning spring  215  is applied to the lower portion of strut  216 , as shown in  FIG. 5C . Similarly, ears  240  are shaped such that strut locating shoulders  242  contact the upper portion of ears  240  when the spring force of cushioning spring  215  pushes strut  216  to the right, as shown in  FIG. 5C . As a result, the combined forces from cushioning spring  215  and strut locating shoulders  242  create a moment on the strut to rotate first edge  234  of the strut to rotate toward engagement with a notch plate (or upward in  FIG. 5C ). In this way, cushioning spring  215  can serve to cushion the initial engagement of the strut with a notch plate as well as bias the strut toward engagement with the notch plate, thus eliminating the need for a separate, bias spring as required in previous embodiments of the one-way drive device. The elimination of the bias spring is significant because of a reduction in the number of parts required as well a simplification in the pocket design. 
     Although each of the aforedescribed embodiments have been illustrated with various components having particular respective orientations, it should be understood that the present invention may take on a variety of specific configurations with the various components being located in a wide variety of positions and mutual orientations and still remain within the spirit and scope of the present invention. Furthermore, suitable equivalents may be used in place of or in addition to the various components, the function and use of such substitute or additional components being held to be familiar to those skilled in the art and are therefore regarded as falling within the scope of the present invention. For example, rather than the notch plate driving the pocket plate, as illustrated in  FIGS. 4A and 4B , the pocket plate can be used to drive the notch plate, in which case the cushioning spring will still act to cushion the initial engagement of the strut. Also, in the embodiment illustrated in  FIGS. 3 ,  4 A and  4 B, the spring pocket for accommodating the cushioning spring can be formed in the strut itself rather than in the strut pocket. In addition, the spring constant and initial load of the cushioning spring can be adjusted to accommodate the anticipated drive loads and distances between engagement opportunities of a particular pocket plate and notch plate configuration. It is anticipated, however, that the spring constant and initial load need not be precisely determined because the load carrying ability of the one-way drive device is not altered by the addition of the cushioning spring and, potentially, a slight modification of the strut surfaces. Therefore, any value of spring properties which sufficiently reduce the clicking noise or engagement abruptness are considered acceptable in the present application. Also, the exact positioning and configuration of the cushioning spring can be modified from the configurations shown in  FIGS. 3–5B  as long as the cushioning configuration accomplishes the desired goal of cushioning the initial engagement of the strut with the notch plate. For example, a ferrous or non-ferrous metal spring, a polymer spring, a piece of rubber material, a liquid or a gas can be used instead of the aforedescribed coil or leaf spring, and the cushioning arrangement can be positioned elsewhere in the one-way drive device, such as in the notches of the notch plate rather than in the pockets of the pocket plate. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.