Abstract:
A selectable one-way clutch (SOWC) assembly uses hydraulic-actuation to select operating modes within a rotating housing. Two races of the SOWC assembly can rotate at disparate speeds, i.e., one race is not grounded prior to actuation. The SOWC assembly has a pair of races keyed to different housings and hubs. The housing and hub can be attached to different elements of a gear train, for example, which can be rotating during the various gear states. A hydraulic actuator or multiple actuators can be keyed to the housing, with axial motion of the actuator or actuators selecting a state or operating mode of the SOWC assembly. The actuator has axially-extending tabs that engage radially-extending fingers of the selector plate, thus rotating the selector plate in different directions when applied or released. Multiple actuators can be used in conjunction with multiple selector plates to provide additional SOWC operating modes.

Description:
TECHNICAL FIELD 
     The present invention relates generally to an automotive powertrain, and in particular to a powertrain having a selectable one-way clutch (SOWC) assembly for selecting between different operating states or modes. 
     BACKGROUND OF THE INVENTION 
     In various mechanical devices, and particularly within a transmission of an automotive powertrain, specialized overrunning clutches or one-way clutches are used to produce a one-way driving connection between input and output members of the transmission. A one-way clutch typically has a pair of plates or races, and is capable of selectively transmitting torque between the races when the rotation of one race with respect to the other is in one direction, with the clutch “overrunning” or freewheeling when the rotational direction is reversed. 
     The relative shape and/or orientation of the races may vary depending on the particular design of the one-way clutch. The mechanical means used to lock a typical one-way clutch are varied, but commonly consist of torque-transfer elements such as diodes, rollers, sprags, rockers, prawls, or struts that are positioned between the races. Depending on the particular type or style of one-way clutch and the direction of rotation, each race may include unique features such as wells or notches suitable for engaging one or more of the torque-transfer elements in order to selectively enable various clutch operating states or modes. 
     In a basic one-way clutch, the operating mode is determined by the direction of the torque being applied to an input race of the clutch. A selectable one-way clutch or a SOWC potentially provides additional utility relative to the conventional one-way clutch, with a SOWC being capable of producing a driving connection between the input and output races in one or both rotational directions. A SOWC can also freewheel in one or both rotational directions as needed. One of the two races of a conventional SOWC can be indexed or grounded to a stationary member, such as a transmission case or center support. However, the grounding of one race prevents such a SOWC from being used in applications where both races are allowed to rotate. 
     SUMMARY OF THE INVENTION 
     Accordingly, a SOWC assembly uses hydraulic-actuation to select a state or operating mode within a rotating housing. Unlike conventional SOWC designs, both races of the SOWC assembly can rotate at disparate speeds, i.e., one race is not grounded prior to actuation. Within the scope of the invention, the SOWC assembly has a pair of races keyed or splined to different housings and hubs. The housing and the hub can be attached to different elements of a gear train, for example, which can be rotating during the various gear states. A hydraulic actuator or actuators can be keyed or splined to the housing, with axial motion of the actuator or actuators selecting a state or operating mode of the SOWC assembly. 
     The SOWC assembly includes at least one rotatable selector plate positioned between the races, and having a plurality of radially-extending fingers. One or more actuators are splined to the housing and have a plurality of tabs each extending axially from the actuator toward the selector plate or plates. The tabs engage the fingers when the actuator is applied in a first axial direction, such that a rotation of the actuator or actuators moves the fingers from a first position to a second position to thereby rotate the selector plate or plates, and to thereby select one of the plurality of SOWC operating modes. 
     In one embodiment, the tabs each define an angled slot, with each finger continuously engaged with a different angled slot to move therewithin in response to a relative rotation between the selector plate and actuator. The selector plate can include a first and a second rotatable selector plate that are each selectively and independently moveable using different actuators to thereby establish at least three operating modes. 
     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 schematic illustration of a powertrain having a selectable one way clutch (SOWC) assembly in accordance with the invention; 
         FIG. 2  is a schematic perspective side view of the SOWC assembly shown in  FIG. 1 ; 
         FIG. 3  is a schematic exploded view of the SOWC assembly of  FIG. 2 ; and 
         FIG. 4  is a schematic perspective side view of a portion of the SOWC assembly of  FIGS. 2 and 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the Figures, wherein like reference numerals refer to like or similar components throughout the several figures, and beginning with  FIG. 1 , a powertrain  10  includes an engine (E)  15 , a hydraulic pump (P)  14 , and a transmission (T)  18 . The engine  15  can be configured as a gasoline, diesel, or alternate fuel internal combustion engine of the type known in the art. In place of the engine  15 , or in conjunction therewith, an energy storage device such as a battery or battery pack can be used to supply energy to the transmission  18 . 
     The transmission  18  includes a selectable one-way clutch (SOWC) assembly  20  and a plurality of rotary elements  17 A,  17 B, for example individual gear elements of one of more planetary gear sets (not shown), rotatable shafts, or other rotating transmission power transmitting member. The SOWC assembly  20  is operable for selectively establishing, transitioning, or shifting between different operating states or modes as set forth below, with the particular operating mode determined by an electronic control unit or controller (C)  12  in conjunction with an overall powertrain control algorithm or methodology. The controller  12  is in electrical communication with the pump  14  and any associated flow directional control valves, flow and/or pressure regulators, etc. (not shown) to provide precise fluid control within the powertrain  10 . 
     The controller  12  can be configured as a distributed or central control module having such control modules and capabilities as might be necessary to operate the transmission  18  in the desired manner. For simplicity, the controller  12  is represented as a single device, although separate controllers may also be used within the scope of the invention depending on the number of additional functions which the controller  12  is intended to support or provide. The controller  12  can be configured as a general purpose digital computer generally comprising a microprocessor or central processing unit, read only memory (ROM), random access memory (RAM), electrically-programmable read only memory (EPROM), high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry, and input/output circuitry and devices (I/O), as well as appropriate signal conditioning and buffer circuitry. Each set of algorithms resident in the controller  12  can be stored in ROM and executed to provide the respective functions of each resident controller. 
     The transmission  18  can be either selectively or directly connected to the engine  15  via a first rotatable member  22 , and is configured to transmit torque from the engine  15  through the element  17 A, the SOWC assembly  20 , and the element  17 B to a second rotatable member  23 . The second rotatable member  23  ultimately rotates a set of road wheels  13  to thereby propel any vehicle using the powertrain  10 . As will be understood by those of ordinary skill in the art, any SOWC assembly, including the SOWC assembly  20  set forth herein, is designed to selectively hold torque in either, both, or neither rotational direction as needed to thereby establish or transition between different SOWC operating modes. In this manner the functionality of the transmission  18  can be optimized. 
     Referring to  FIG. 2 , the SOWC assembly  20  of  FIG. 1  is shown in partial schematic side view with respect to an axis of rotation or centerline  11  of the SOWC assembly  20 . The SOWC assembly  20  includes a rotatable outer drum or housing  24 , a rotatable inner hub  26 , a rotatable first plate or race  28 , and a rotatable second plate or race  30 . The first race  28  is connected to the housing  24  via a set of mating splines  29 , while the second race  30  is connected to the hub  26  via another set of mating splines  31 . The SOWC assembly  20  also includes at least one rotatable selector plate  32  positioned between the first and second races  28  and  30 , respectively. 
     A rotation of the selector plate  32  transitions or shifts the SOWC assembly  20  between a plurality of different SOWC operating states or modes. Directional toque transfer or holding can be provided in either direction across the SOWC assembly  20  as needed in order to establish such mode. Such torque transfer or holding can be achieved by selectively covering and uncovering different torque-transfer elements, e.g., diodes, struts, rollers, sprags, pawls, etc., thus allowing the torque-transfer elements to block or unblock rotation of one, both, or neither of the races  28  and/or  30  of the SOWC assembly  20  as needed, as determined by the controller  12 . See for example the exemplary torque-transfer element  70  of  FIG. 4 . 
     To selectively actuate the SOWC assembly  20 , a hydraulic actuator  40  is configured according to one embodiment as an annular, hydraulically-actuated piston mechanism. In this particular embodiment, the hydraulic actuator  40 , which can be splined to the housing  24  as described below with reference to  FIGS. 3 and 4  to rotate in conjunction therewith, can be selectively moved in the direction of arrow A in response to an admission of pressurized fluid (arrow F) from the pump  14  of  FIG. 1 , with the fluid (arrow F) flowing through a fluid channel  42  and into an apply chamber  46 . When pressurized fluid is discontinued by the controller  12  of  FIG. 1 , a return device  45  such as a spring cage or other suitable return mechanism reacts against a stationary balance piston or reaction plate  44  to move the hydraulic actuator  40  back in the direction of arrow R. 
     Within the scope of the invention, a plurality of axially-extending prongs, projections, or actuator tabs  48  are operatively connected to or formed integrally with the hydraulic actuator  40 , while a plurality of radially-extending pawls or fingers  36  are operatively connected to or formed integrally with a selector plate or plates  32 . That is, the tabs  48  are adapted to continuously engage a different one of the fingers  36 , with the rotation of the hydraulic actuator  40  when applied in the direction of arrow A or released in the direction of arrow R alternately moving the fingers  36  between a pair of positions in a discrete slot  72  (see  FIG. 4 ). Movement of the fingers  36  within the discrete slot  72  of  FIG. 4  exerts a force on the selector plate or plates  32  that is sufficient for rotating the selector plate  32 , an action which selectively covers and uncovers different torque-transfer elements  70  (see  FIG. 4 ) to thereby transition between the different available SOWC operating modes. 
     Still referring to  FIG. 2 , in another embodiment the SOWC assembly  20  includes an additional hydraulic actuator  50  that is positioned axially-outward of the hydraulic actuator  40  described above. As with the hydraulic actuator  40 , the hydraulic actuator  50  is biased by a return device  55 , which reacts against a balance piston or reaction plate  54 . Admission of pressurized fluid (arrow F) through a fluid channel  52  and into an apply chamber  56  moves the hydraulic actuator  50  in the direction of arrow A to thereby apply the hydraulic actuator  40 , while the return device  55  moves the hydraulic actuator  50  in the direction of arrow R to release the hydraulic actuator  50 . 
     Similar to the configuration described above for the hydraulic actuator  40 , a plurality of axially-extending prongs, projections, or actuator tabs  58  are operatively connected to or formed integrally with the hydraulic actuator  50 . The tabs  58  are engageable with the fingers  36  of the selector plate or plates  32 , i.e., with some predetermined number of the fingers  36  engaged with the tabs  58  of the hydraulic actuator  50  and the remainder of the fingers  36  engaged with the tabs  48  of the hydraulic actuator  40 , as described above. Also within the scope of the invention, and as described below with reference to  FIGS. 3 and 4 , the selector plate  32  can be alternately configured as two independently-rotatable selector plates  32 A and  32 B, with each of the selector plates  32 A and  32 B of  FIGS. 3 and 4  being separately rotatable using a respective or corresponding one of the hydraulic actuators  40  and  50 . In this manner, additional operating modes are potentially enabled in the SOWC assembly  20 . 
     For example, the SOWC  20  can have two, three, or four states or operating modes. If only two operating modes are desired, only one actuation device is required, i.e., the hydraulic actuator  40  or  50 . Such a two-mode device would have two sets of torque-transfer elements  70  (see  FIG. 4 ), with one set functioning as a traditional or conventional one-way clutch and another set which can be selectively deactivated using the selector plate  32 . Therefore, a two-mode SOWC device would be able to carry torque in both rotational directions simultaneously, or in one direction only while overrunning in the other rotational direction. Likewise, a three-mode or four-mode SOWC device can include two sets of torque-transfer elements  70  (see  FIG. 4 ), both sets being controlled by separately or independently controlled selector plates  32 A,  32 B as shown in  FIGS. 3 and 4 . With independently-acting selector plates  32 A,  32 B, the SOWC assembly  20  of  FIG. 2  can carry torque in both rotational directions, either rotational direction, or overrun in both rotational directions. 
     Referring to  FIG. 3 , an exploded view is provided of the SOWC assembly  20  of  FIG. 2 . As noted above, the SOWC assembly  20  includes the housing  24 , the first race  28 , and the second race  30 , as well as one or both of the hydraulic actuators  40  and  50 . The selector plate  32  can be alternately configured as a single selector plate for two-mode operation as set forth above, or as a set of independently-moveable selector plates  32 A,  32 B. The housing  24  has splines  33  that are engageable or mateable with the splines  29  of the first race  28 , such that the housing  24  and first race  28  rotate in unison, while the second race  30  is connected to the hub  26  (see  FIG. 2 ) via the splines  31 , thereby rotating in conjunction with the hub  26 . 
     The tabs  48 ,  58  of the respective hydraulic actuators  40 ,  50  are axially-projecting, i.e., the tabs  48 ,  58  extend in a direction substantially parallel to the centerline  11  of the SOWC assembly  20 . In one embodiment, each tab  48 ,  58  defines an angled slot  74 , with each of the fingers  36  of the selector plate  32  or plates  32 A,  32 B continuously engaged with a different one of the angled slots  74 . Each finger  36  moves within a corresponding angled slot  74  during rotation of the hydraulic actuator  40  and/or  50 , during either an application or a release thereof. 
     The first race  28  can be configured with the discrete slots  72  each having a pair of end positions  80 ,  82 , with a number of discrete slots  72  equal to the number of fingers  36  of the selector plate  32  or plates  32 A,  32 B. Each adjacent pair of splines  29  of the first race  28  define a surface or groove  84  in which the tabs  48  can be positioned, thus effectively splining the hydraulic actuators  40 ,  50  to the first race  28  and the housing  24 . Therefore, rotation of each of the hydraulic actuators  40 ,  50  can occur at a different rate than that of the second race  30 . 
     Fingers  36  engaged with the tabs  48 ,  58  will therefore alternately move between the positions  80 ,  82  of the discrete slot  72  in the circumference of the first race  28  depending on the relative rotation of the races  28 ,  30 . Torque-transfer elements  70  (see  FIG. 4 ) disposed between the selector plate  32  and the second race  30  can be selectively covered or uncovered thereby as the selector plate  32  or plates  32 A,  32 B are rotated by the interaction or engagement of the tabs  48 ,  58  and the fingers  36 . That is, rotation of the selector plate  32  or plates  32 A,  32 B can cover some number of the torque-transfer elements  70  of  FIG. 4 , depressing them into holes, notches, or wells (not shown) formed or otherwise provided in a surface  75  of the second race  30 . 
     The same torque-transfer elements  70  can also be selectively uncovered, wherein a spring device (not shown) or other suitable biasing mechanism allows the torque-transfer elements  70  to at least partially enter a corresponding cavity (not shown) in a facing surface  76  of the first race  28 . In this manner torque is held across the SOWC assembly  20  as needed, with the range of torque holding capability or number of different SOWC operating states or modes depending on the number of selector plates  32  and hydraulic actuators  40 ,  50  used, as well as the orientation and spacing of the torque-transfer elements  70 , as will be understood by those of ordinary skill in the art. 
     Referring to  FIG. 4 , the SOWC assembly  20  of  FIGS. 2 and 3  is shown with the first race  28  removed for clarity. In the embodiment of  FIG. 4 , the selector plates  32 A,  32 B are used in conjunction with hydraulic actuators  40  and  50 , with only the hydraulic actuator  40  being visible from the perspective of  FIG. 4 . Each selector plate  32 A,  32 B has one or more windows  60  defined by adjacent blocking portions  61 , such that rotation of the selector plates  32 A,  32 B selectively covers and uncovers a predetermined number of torque-transfer elements  70 . 
     While only one torque-transfer element  70  is shown in  FIG. 4  for simplicity, those of ordinary skill in the art will recognize that the actual number of torque-transfer elements  70  used in conjunction with the SOWC assembly  20 , as well as spacing thereof, is dependent upon system design, backlash considerations, desired operating modes, etc. Generally, there will be one torque-transfer element  70  for each window  60 . Likewise, for clarity the surface  75  of the second race  30  is shown without holes or wells for holding the torque-transfer elements  70 , with such detail understood as being present within the scope of the invention and the understanding of the art of selectable one-way clutches. 
     Still referring to  FIG. 4 , and in particular the area generally indicated by the arrow C, each tab  48  can be configured to define an angled slot  74 . The angled slot  74  can be shaped, sized, or otherwise configured to engage the fingers  36  of the selector plate  32  as described above. In one embodiment, the angled slot  74  can include a first slot portion  78  and a second slot portion  79 . In the embodiment shown in  FIG. 4 , the second slot portion  79  is aligned in a substantially parallel manner with respect to the centerline  11  of the SOWC assembly  20 , with the second slot portion  79  intersecting the first slot portion  78  at a predetermined angle (θ). That is, the tab  48  has a distal end or outer wall  90 , with the second slot portion  79  intersecting the outer wall in an orthogonal manner. The predetermined angle (θ) can be selected as needed to provide a smooth engagement between each finger  36  and a mating angled slot  74 . For example, a threshold range of approximately 30 to 50 degrees can be used according to one exemplary embodiment, although other ranges or angular values can also be used within the scope of the invention to provide the desired movement of the fingers  36  within a corresponding discrete slot  72  (see  FIG. 3 ). 
     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.