Abstract:
A SOWC for use with a vehicle transmission is provided. The clutch includes outer and inner elements, also referred to as races, with the latter oriented concentrically within the former about an axis of rotation. A selection mechanism, which may be annular plates operatively connected with the side of the races and with one another, is selectively rotatable with respect to the inner and outer elements between different positions. Pivotable rocker elements are positioned between the races and are movable along cammed slots of the annular plates when the annular plates are rotated to establish a forward, a reverse, and a neutral operating mode corresponding with the different positions of the annular plates. In some embodiments, in the neutral operating mode, none of the rocker elements are in contact with the inner race.

Description:
TECHNICAL FIELD 
     The invention relates to a selectable one-way clutch. 
     BACKGROUND OF THE INVENTION 
     In a variety of mechanical devices, including the powertrains of vehicle automatic transmissions, overrunning clutches are used to produce a one-way driving connection between an input and an output race of the overrunning clutch. Specifically, the clutch is capable of transmitting torque when the rotation of one race with respect to the other is in one direction, and the clutch overruns, or freewheels, when the rotational direction of one race with respect to the other is reversed. 
     The shape and orientation of the input and output races with respect to each other may vary depending on design. Some one-way clutches have input and output races that are oriented radially concentric with respect to each other. In another design, the confronting faces of the input and output races are planar. 
     The mechanical means used to lock a one-way clutch are varied, but commonly consist of rollers, sprags, rockers, or strut types of torque transmitting elements positioned between an input and an output race. Depending on the particular type of one-way clutch and the direction of rotation, each of the races contains unique surface features that engage one or more of the torque transmitting elements. 
     The operating modes of a basic one-way clutch are a locked mode in one given direction, and a freewheel mode in the opposite direction. In this type of one-way clutch, the operating mode of the clutch is determined only by the direction of torque being applied to the input race. 
     The increased complexity of power transmitting mechanisms has led to a class of selectable one-way clutches, henceforth referred to as SOWC&#39;s. A SOWC is similar to a one-way clutch in basic operation as described above. However, as the name implies, SOWC&#39;s are capable of producing a driving connection between an input and output race in one or both rotational directions and/or are also able to freewheel in one or both rotational directions. 
     In a SOWC, a moveable selector ring or plate, henceforth to be called a selector plate, is commonly employed to restrict the free movement of one or more of the torque transmitting elements to achieve the various operating modes. For example, but not limited to the following, in a first position of a selector plate in a SOWC, the torque transmitting elements may have movement that is unrestricted by the selector plate, while in a second position of the selector plate, some or all of the elements may be either held in contact with the confronting face, or kept from contacting the confronting face. 
     SUMMARY OF THE INVENTION 
     A SOWC for use with a vehicle transmission is provided. The clutch includes outer and inner elements, also referred to as races, with the latter oriented concentrically within the former about an axis of rotation. At least one of the races is rotatable about the axis of rotation. The races each have first and second opposing sides. A selection mechanism, which may be annular plates operatively connected with the side of the races and with one another, is selectively rotatable with respect to the inner and outer elements between different positions. The annular plates have cammed slots spaced therearound. Pivotable rocker elements are positioned between the races and are movable along the cammed slots when the annular plates are rotated to establish a forward, a reverse, and a neutral operating mode corresponding with the different positions of the annular plates. Torque is transferred between the races in a first direction via at least one of the rocker elements in the forward operating mode. Torque is transferred between the races via at least one other of the rocker elements in an opposing second direction in the reverse operating mode. No torque is transferred between the races in the neutral operating mode. As used herein, torque is transferred from the inner race to the outer race whether the outer race is rotatable (i.e., the SOWC is a rotating-type clutch) or is stationary, such as a stationary housing (i.e., the selectable one-way clutch is a brake-type clutch). 
     In the neutral operating mode, the inner race is able to freewheel in both directions of rotation, and in some embodiments the cam profile of the cam slots on the annular plates is such that none of the rocker elements are in contact with the inner race in the neutral mode, eliminating rocker movement completely, and thereby increasing the durability of the SOWC and thus decreasing drag in the clutch. 
     Each rocker element may include a body portion with a first partial cylindrical surface and a second partial cylindrical surface, both of the cylindrical surfaces are concentric about a pivot axis and are of different radial sizes. The outer race is configured with recesses, grouped in pairs, referred to herein as pocket pairs, having partial cylindrical surfaces of the different radial sizes to maintain the rocker elements within the recesses. The inner race has notches and is configured to be selectively engaged by one or more of the rocker elements at one or more of the notches. 
     The design of the cam window on the selector plates enables a mode of operation where the inner race is able to freewheel in both directions. In this mode, henceforth referred to as neutral, all of the rockers are prevented from engaging the inner race. The reduction in drag afforded may reduce spin losses. Additionally, SOWCs typically have lower manufacturing costs and reduced mass in comparison with multi-plate clutches. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective illustration of a selectable one-way clutch (SOWC); 
         FIG. 2  is a schematic perspective illustration in exploded view of the SOWC of  FIG. 1 ; 
         FIG. 3  is a schematic perspective illustration of a rocker element include in the SOWC of  FIGS. 1 and 2 ; 
         FIG. 4  is a schematic perspective partially cross-sectional and fragmentary illustration of the SOWC of  FIGS. 1-2  showing the rocker element of  FIG. 3  establishing a forward operating mode; 
         FIG. 5  is a fragmentary side view illustration of the SOWC in the forward operating mode; 
         FIG. 6  is a fragmentary side view illustration of the SOWC in the forward operating mode with a front selector plate removed; 
         FIG. 7  is a fragmentary side view illustration of the SOWC in a neutral operating mode; 
         FIG. 8  is a fragmentary side view illustration of the SOWC in the neutral operating mode with the front selector plate removed; 
         FIG. 9  is a fragmentary side view illustration of the SOWC in a reverse operating mode; and 
         FIG. 10  is a fragmentary side view illustration of the SOWC in the reverse operating mode with front selector plate removed. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIG. 1 , there is shown a selectable one-way clutch or SOWC  10  having an outer race  12  and an inner race  14 . For clarity, the outer and inner races,  12  and  14  respectively, are referred to hereinafter as pocket ring  12  and notch ring  14 . The pocket ring  12  is preferably equipped with a plurality of external spline teeth  16  that are drivingly engageable or otherwise matable with spline teeth of a stationary reaction member, such as an automobile transmission case (not shown). A first selector plate  17  is rotatably affixed between the pocket ring  12  and the notch ring  14 . A second selector plate  18 , not clearly visible in  FIG. 1 , but similar in configuration and function to the first selector plate  17 , is rotatably affixed to the far side of the SOWC  10 . The notch ring  14  preferably has a plurality of equally spaced, internal teeth or splines  20  that are drivingly engageable or matable with opposing teeth or splines of a torque input device (not shown). The notch ring  14 , as shown in  FIG. 2 , also contains a plurality of preferably equally spaced rocker recesses or notches  22  formed in a radially-outer surface of the notch ring  14 , i.e., in a notch ring face  24 . The first selector plate  17  contains a selector lever  26  that is moved and held in one of three positions (to be described later) by an external force (not shown) that is, but not limited to, hydraulic, mechanical, or electromechanical in nature. 
     In  FIG. 2 , the SOWC  10  is shown in exploded view. The pocket ring  12  has a first face  28  and a second face  30  (not visible). Since all features on the second face  30  are identical to those on the first face  28 , only the features on the first face  28  will be described. A plurality of radial slots  32 , also referred to as positioning slots, is formed in the first face  28  of pocket ring  12  to provide an opening suitable for receiving a radial tab  36  on the first or second selector plate,  17  and  18  respectively. As best shown in  FIG. 4 , a stepped pin  38  extending through a hole  40  in radial tab  36  and then peened in place connects the first and second selector plates,  17  and  18 , together and also retains all the parts of the SOWC  10 . However, it should be evident to those familiar with the art that many different economical and common assembly methods could be used. At locations on the pocket ring  12  where the first and second selector plates,  17  and  18 , are joined together, a relief or positioning slot  42  of sufficient arc length is provided to permit free angular movement of the stepped pin  38 . 
     The three positions of the selector lever  26  are a forward position  44 , as shown in  FIG. 5 , a neutral position  46 , as shown in  FIG. 7 , and a reverse position  48 , as shown in  FIG. 9 . The forward position  44  is defined when stop  50  located on each side of radial tab  36  comes in contact with one side  53  of the radial slot  32 . In a similar fashion, the reverse position  48  is defined when the selector lever  26  is moved in the opposite direction and a stop  50  comes in contact with the other side  57  of radial slot  32 . The neutral position  46  is defined as a position midway between the forward position  44  and the reverse position  48 . 
     Referring to  FIG. 2 , a set of first recesses includes a plurality of equally spaced rocker pocket pairs  54  formed and positioned circumferentially around and along the internal face  55  of the pocket ring  12 . Each rocker pocket pair  54  contains one forward rocker pocket  56  and one reverse rocker pocket  58  (see  FIG. 6 ). A plurality of accordion style compression springs  60  are contained in an additional recess, also referred to as a spring pocket  62  formed with or otherwise provided adjacent to each rocker pocket,  56  and  58 . The springs  60  are each configured to exert a sufficient spring force on an opposing rocker element  64  to thereby actuate or move the rocker element  64  into engagement with the notch ring  14 , as described later herein below. While the accordion style compression springs  60  are preferred, an alternate energy storage device, such as a helical compression spring, or springs, (not shown), could also be employed in place of the accordion style compression spring  60 . However, if helical compression springs are used, the shape of the spring pocket  62  adjacent to the rocker pocket,  56  and  58 , would preferably be formed with a suitable round profile instead of a rectangular profile in order to best accommodate the shape of the compression spring. Rockers  64  that are located in forward rocker pockets  56  are henceforth referred to as forward rockers  66 , and rockers  64  that are located in reverse rocker pockets  58  are henceforth referred to as reverse rockers  68 . 
     Referring to  FIG. 2 , the first selector plate  17  is radially constrained in a counter bore  70  on the first face  28  of the pocket ring  12 . The second selector plate  18  is radially constrained in a like manner on the second face  30  of the pocket ring  12 . A first pilot bore  72  on the first selector plate  17  and a second pilot bore  74  on the second selector plate  18  engage the pilot diameters  76  on each side of notch ring  14  to maintain concentricity between the pocket ring  12  and the notch ring  14 . 
     A plurality of preferably equally sized and spaced radial cam slots  78 , each defining a cam profile  79 , are formed in the first selector plate  17  in a quantity equal to the number of rocker pocket pairs  54  formed in the pocket ring  12 . The size and number of cam slots  78  formed in the second selector plate  18  are similar to those in the first selector plate  17 . Each cam slot  78  is configured to allow axial extensions, also referred to as cam pins  80 , protruding from each side of rocker element  64  to engage a cam slot  78  on the first and second selector plates  17  and  18 , respectively. The cam slot  78  is shaped and positioned so the cam pins  80  from one forward rocker  66  located in a forward rocker pocket  56  and from one reverse rocker  68  located in a reverse rocker pocket  58  engage the same cam slot  78 . 
     Each cam slot  78  is configured to allow only the forward rockers  66  located in the forward rocker pockets  56  to contact the notch ring face  24  when the selector lever  26  is in the forward position  44 , as shown in  FIGS. 5 and 6 . Similarly, as shown in  FIGS. 9 and 10 , each cam slot  78  is configured to allow only the reverse rockers  68  located in the reverse rocker pockets  58  to contact the notch ring face  24  when the selector lever  26  is in the reverse position  48 . In the neutral position  46 , none of the rockers  64  are free to contact the notch ring face  24 . This can best be seen in  FIGS. 7 and 8 . 
     Turning again to  FIG. 4 , the SOWC  10  is shown in perspective cross-sectional view, with cross-sections taken at various locations to best view the interfitting of the rocker element  64  in notch  22 , within cam slots  78  and biased by spring  60  such that pocket ring  12  is in mating engagement with notch ring  14 . Each rocker pocket  56  and  58 , in pocket ring  12  contains a rocker element  64  that is free to rock about its own axis  82  (see  FIG. 3 ) within the rocker pocket,  56  and  58 . In the SOWC  10  as shown, two diametrically opposite rocker elements  64  simultaneously engage diametrically opposite rocker notches  22  in the notch ring  14  thereby canceling out the reaction forces generated by the engagement of rocker element  64  with the notch  22 . However, the number of rocker elements  64  that are simultaneously engaged with an adjacent rocker notch  68  can be more or less, and depends on the ratio of rocker pocket pairs  54  in the pocket ring  12  to the number of notches  22  on the notch ring  14 . 
     Turning now to  FIG. 3 , which shows the rocker element  64  in detail, the rocker element  64  includes a cylindrical body  84  formed by a smaller partially cylindrical surface  86  and a larger partially cylindrical surface  88  concentrically located about a rocker axis  82 . Correspondingly, the forward and reverse rocker pockets  56  and  58 , respectively, each contain a similar small cylindrical surface  90  and a larger cylindrical surface  92  concentrically positioned. The arc length of the cylindrical surfaces  90  and  92  in the pocket ring  12  are sufficiently longer than the arc lengths  86  and  88  on the rocker element  64  such that the rocker elements  64  can not move radially out of the respective rocker pockets  56  and  58 . The rocker elements  64  are installed in the respective rocker pockets  56  and  58  by sliding into position from either side of the pocket ring  12 . Attached to and extending from the cylindrical body  84  of the rocker element  64  is a plate or finger  94  with the base  96  preferably being thicker or wider than the free end  98 , thereby reducing bending stresses on the rocker element  64 . The inward facing surface  100  of the finger  94  that contacts the notch ring  14  is slightly convex such that the center of radius of the inward facing surface  100  is coincident with the axis of rotation of the SOWC  10  when the rocker element  64  is disengaged from the notch ring  14 , i.e., when the selector lever  26  is in the neutral position  46  (best seen in  FIG. 8 ). A spring retaining rib  102  on the finger  94  of rocker element  64  restricts movement of the end of the accordion style compression spring  60  that is in contact with the rocker element  64 . However, if helical compression springs are used, the shape of the spring retaining rib  102  would preferably be of a suitable round profile, such as a counter-bored recess or protruding pin, to best accommodate the shape of a round spring. 
     Turning now to  FIGS. 5 and 6 , the “forward locked” position is shown with notch ring  14  rotating in a counterclockwise direction as indicated by the arrow. This direction is henceforth referred to as the forward direction. A forward rocker  66  is shown fully engaged in a rocker notch  22  on the notch ring  14 . As the selector lever  26  is slidably rotated to the forward position  44 , the cam pins  80  on all of the forward rockers  66  in the forward rocker pockets  56  will be positioned over the substantially V-shaped recess portion  104  in the middle of each cam slot  78 . In this position, the forward rockers  66  are urged into contact with the notch ring face  24  by the accordion style compression springs  60  with at least one forward rocker  66  fully engaging a rocker notch  22  on the notch ring  14  thereby enabling a force to be transmitted between the pocket ring  12  and the notch ring  14 . With the selector lever  26  in the forward position  44 , and the direction of rotation of the notch ring  14  changed to a clockwise direction, henceforth referred to as the reverse direction, the forward rockers  66  are free to move away from engagement with the rocker notches  22  by pivoting about the rocker axis  82 . In this manner, the notch ring  14  is free to rotate in the reverse direction. 
     Turning now to  FIGS. 7 and 8 , a neutral position is shown, with notch ring  14  free to rotate in both directions as indicated by the double ended arrow. When the selector lever  26  is rotated to the neutral position  46 , the cam pins  80  on all the rocker elements  64  are positioned in the slotted ends  106  of the cam slots  78 . In this position, all of the forward rockers  66  and all of the reverse rockers  68  are prevented from coming in contact with the notch ring face  24 . 
     In  FIGS. 9 and 10 , the “reverse locked” position is shown with notch ring  14  rotating in a clockwise, or reverse, direction as indicated by the arrow. A reverse rocker  68  is shown fully engaged in a rocker notch  22  on the notch ring  14 . As the selector lever  26  is slidably rotated to the reverse position  48 , the cam pins  80  on all of the reverse rockers  68  in the reverse rocker pockets  58  will be positioned over the V-shaped recess portion  104  in the middle of each cam slot  78 . In this position, the reverse rockers  68  are urged into contact with the notch ring face  24  by the accordion style compression springs  60  with at least one reverse rocker  68  fully engaging a rocker notch  68  on the notch ring  14 , thereby enabling a force to be transmitted between the pocket ring  12  and the notch ring  14 . With the selector lever  26  still in the reverse position  48  and the direction of rotation of the notch ring  14  changed to the forward direction, the reverse rockers  68  are free to move away from engagement with the rocker notches  22  by pivoting about the rocker axis  82 . In this manner, the notch ring  14  is free to rotate in the forward direction. 
     The force transmitted between the pocket ring  12  and the notch ring  14  via a rocker element  64  contains both a radial and a tangential component. To minimize bearing loading, maintain concentricity between mating parts, and increase the torque capacity of the SOWC  10 , more than one equally spaced rocker element  64  may be engaged with a like number of rocker notches  22 . However, torque will be transmitted between the pocket ring  12  and the notch ring  14  even if only a single rocker element  64  engages a notch  22  on the notch ring face  24  of the notch ring  14 . 
     A series of radial oil passages  107  (see  FIGS. 1 and 2 ) in the notch ring  14  provide damping and lubrication to the rocker elements  64  as they move in and out of the rocker notches  22  in the notch ring face  24  during the freewheeling modes. The radial oil passages  107  also provide lube oil and cooling to part surfaces moving relative to each other during the freewheeling modes. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.