Patent Abstract:
A controllable selectable one-way clutch is provided for use within a hybrid transmission. The clutch comprises an outer and inner race, and a first and second selector plate. A transmission motor controller synchronizes the speeds of the races to facilitate application and release of the clutch, and a transmission controller communicates a signal to the clutch for re-positioning of the plates to apply and release the clutch. The clutch has three operational modes, including freewheeling and holding torque in one direction or both directions. A method is also provided for applying a selectable one-way clutch in a vehicle having a hybrid transmission with a motor controller and a transmission controller, including synchronizing the clutch speed using the motor controller, detecting the direction of the race speed difference, communicating the race speed difference to the transmission controller, and selecting between the clutch operational modes in response to the detected speed difference.

Full Description:
TECHNICAL FIELD 
     The present invention relates generally to the control of a selectable one-way clutch, and in particular to a selectable one-way clutch having three operational modes for use within a hybrid transmission having a motor controller and a transmission controller, wherein clutch speed synchronization is controlled by the motor controller and clutch actuation and release are controlled by the transmission controller. 
     BACKGROUND OF THE INVENTION 
     In a vehicle having a gasoline/electric hybrid transmission, the vehicle may be powered alternately by a gasoline-powered internal combustion engine or an electric motor to thereby optimize fuel efficiency while reducing vehicle emissions. Hybrid vehicles achieve their relatively high fuel efficiency in large part by alternating between the gasoline-powered engine and the electric motor when one power source is better suited than the other for a specific vehicle operating condition. For example, a gasoline-powered engine is known to be more efficient than an electric motor during periods of constant or relatively non-variable vehicle speed, such as while cruising at a sustained rate of speed, while an electric motor is generally better suited than a gasoline engine for use when the vehicle power requirements are highly variable, such as during starting or stopping of the vehicle. 
     Vehicles having either conventional internal combustion or hybrid gasoline/electric transmissions typically utilize a torque-transmitting device known as a friction clutch or clutch pack for smoothly engaging or coupling two rotating bodies or shafts to transmit torque therebetween. Likewise, the same clutch pack is used to subsequently disengage the coupled shafts to interrupt the power transfer and permit, for example, a smooth shifting between the various gears of a planetary gear set and/or decoupling of one or more motor/generators. Hybrid vehicles in particular generally shift gears in a more controlled and synchronous manner relative to conventional gas engines, due in part to the unique configuration and integrated hybrid motor and transmission controls. However, even within the more synchronous shifting mechanism of a hybrid transmission, conventional clutch packs tend to require a higher hydraulic pump pressure to quickly and fully actuate the conventional clutch-apply mechanism, which may in turn lead to higher losses within the hydraulic circuit and/or spin losses at or along the clutch plate interface. 
     SUMMARY OF THE INVENTION 
     Accordingly, a hybrid gasoline/electric transmission having a motor controller and a transmission controller is provided comprising a controllable three-mode, selectable one-way clutch with an outer race, an inner race, a pair of actuators, and two selector plates that are slidingly engageable within the outer race, the transmission controller being configured to select between the three operating modes and the motor controller being configured to synchronize the clutch speed to facilitate mode selection. 
     In one aspect of the invention, the three operational modes comprise freewheeling in two clutch rotational directions, torque holding in one rotational direction, and torque holding in two rotational directions. 
     In another aspect of the invention, a method is provided for controlling a selectable one-way clutch within a hybrid transmission having a motor controller and a transmission controller. The method includes detecting the speed difference across the selectable one-way clutch using a speed sensor, communicating the detected speed difference from the speed sensor to the transmission controller, synchronizing the clutch speed using the motor controller, and selecting between one of three clutch operational modes in response to a speed difference signal from the transmission controller. 
     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. 1A  is a schematic plan view of a controllable, selectable one-way clutch having three operational modes according to the invention; 
         FIG. 1B  is a schematic plan view of an outer race and dual-selector plates of a controllable, selectable one-way clutch according to the invention; 
         FIG. 1C  is a schematic plan view of an inner race of a controllable, selectable one-way clutch according to the invention; 
         FIG. 2A  is a table describing three clutch operational modes according to the invention; 
         FIG. 2B  is a schematic fragmentary cross sectional side view of an outer and inner race of a controllable, selectable one-way clutch having two selector plates showing a first operational mode according to the invention; 
         FIG. 2C  is a schematic fragmentary cross sectional side view of an outer and inner race of a controllable, selectable one-way clutch having two selector plates showing a second operational mode according to the invention; 
         FIG. 2D  is a schematic fragmentary cross sectional view of an outer and inner race of a controllable, selectable one-way clutch having two selector plates showing a third operational mode according to the invention; 
         FIG. 3A  is a graphical illustration of differential clutch speed versus three clutch operating modes during application of a selectable one-way clutch according to the invention; 
         FIG. 3B  is a graphical illustration of differential clutch speed versus three clutch operating modes during release of a controllable, selectable one-way clutch according to the invention; 
         FIG. 4A  is a lever diagram of a representative hybrid transmission having a controllable, selectable one-way clutch in “released” mode; and 
         FIG. 4B  is a lever diagram of a representative hybrid transmission having a controllable, selectable one-way clutch in “applied” mode. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, there is shown in  FIG. 1A  a portion of a hybrid transmission  10  having a controllable, selectable one-way clutch  18 , hereinafter referred to as clutch  18 . Clutch  18  is preferably a mechanical diode-type selectable one-way clutch, but may also take the form of, for example, a sprag clutch, roller clutch, or other selectable one-way clutch. Clutch  18  has mating concentric inner and outer races  20 ,  22 , respectively. As shown in  FIG. 1C , inner race  20  has an outer wall  39 , a plurality of angled wells  36  as will be described later hereinbelow, and a plurality of radially-inward projecting teeth or splines  24  that are configured to engage or mate with slots or grooves of a rotatable body, such as a drive or crank shaft (not shown). Likewise, as shown in  FIG. 1A , outer race  22  has an outer wall  35  having a plurality of outwardly-projecting teeth or splines  26  that are configured to mate with slots or grooves of a preferably stationary or grounded clutch hub (not shown). 
     Hybrid transmission  10  has a speed sensor  11 , a motor controller  16 , and a transmission controller  14 . Speed sensor  11  is preferably an input/output-type speed sensor of the type known in the art, and is configured to deliver a speed sensor signal to the transmission controller  14 . The motor controller  16  is configured to control the operation of at least one and preferably two motor/generators  82 ,  84 , labeled M/G 1 and M/G 2, respectively, as well as to synchronize the rotational speeds of the inner and outer races  20 ,  22 , as described later herein. The transmission controller  14  is configured to control the operation and/or functionality of the non-motor components of the hybrid transmission  10 , and is configured to receive a signal from the speed sensor  11  for actuation (i.e. apply and release) of the clutch  18 . A first and second projection or arm  12 A and  12 B are each operatively and respectively connected to a first and second selector plate  50 ,  52  of the clutch  18 , with each selector plate  50 ,  52  shown in more detail in  FIG. 1B . 
       FIG. 1B , which is a plan view depicting clutch  18  with inner race  20  removed to show the internal detail of clutch  18 , shows the outer race  22  with a preferably continuous circumferential groove  56  that is sized and shaped to guide or direct selector plates  50 ,  52 , each of which are at least partially slidably moveable or repositionable within the groove  56 . Selector plates  50 ,  52  each have a plurality of preferably identical and equally spaced openings or windows  51 . Also, a plurality of substantially identical strut wells or pockets  32 A,  32 B are arranged around the outer wall  35  of outer race  22 , preferably with approximately equal spacing within each set of pockets. Pockets  32 A and  32 B are substantially identical, preferably differing only in orientation to facilitate actuation of clutch  18 . Specifically, each of pockets  32 A are preferably oriented in one direction, while each of pockets  32 B are preferably oriented approximately 180° opposite the orientation of pockets  32 A. 
     Additionally, each of the pockets  32 A,  32 B are configured and sized to receive a mating strut  34 A,  34 B, with each strut  34 A,  34 B being configured and/or shaped to engage and/or disengage with an angled well  36  (see  FIG. 1C ) or similar recess within the inner race  20  as required to respectively allow rotation of the inner race  20  in either one or both directions, as well as to lock or hold torque in both directions. First and second arms  12 A,  12 B are operatively attached to the first and second selector plates  50 ,  52 , respectively, providing a projection on which a force external to the outer race  22  may be exerted or directed for moving the selector plates  50 ,  52  to bring the windows  51  into engagement with the struts  34 A,  34 B, alternately depressing and releasing the struts  34 A,  34 B as needed. When actuated by arms  12 A,  12 B, respectively, the selector plates  50 ,  52  each slide or move along the circumferential groove  56  of outer race  22 , with each of the arms  12 A,  12 B protruding through an opening or slot  55  in outer wall  35 . The first arm  12 A is actuated by a first actuator  42 . Likewise, the second selector plate is actuated by a second actuator  43 , with the motion of the arms  12 A,  12 B represented by the arrows in  FIG. 1B . The actuators  42 ,  43  are controlled by the transmission controller  14  and are preferably slide valves of the type known in the art. However, those skilled in the art will recognize that any mechanism suitable for repositioning first and second selector plates  50 ,  52  respectively, along or within circumferential groove  56  may be used, such as, for example, a piston or motor. 
     Turning to the table of  FIG. 2A , three operational modes are shown for clutch  18  (see  FIGS. 1A-C ), with each clutch operational mode defining the direction of torque holding within the clutch  18 . In Mode  1  the clutch  18  is allowed to “freewheel”, i.e. torque is not held in either rotational direction, and permitting for example inner race  20  to rotate or spin unimpeded within a stationary outer race  22 . In Mode  2 , torque is locked or held in one rotational direction. For example, inner race  20  would be permitted to freewheel or rotate unimpeded in a clockwise direction, and lock or be held from rotating in the counter-clockwise direction. Finally, in Mode  3  the clutch  18  is locked, i.e. torque is held in both rotational directions. Each of the three operational modes described generally above as applied to clutch  18  are shown in detail in the fragmentary cross-sectional side views of  FIGS. 2B ,  2 C, and  2 D, respectively. 
     In each of  FIGS. 2B ,  2 C, and  2 D, wells  32 A,  32 B are shown with a substantially vertical locking surface  40  and a sloped surface  41 . Vertical locking surface  40  is configured and/or shaped to oppose a strut  34 A,  34 B to thereby prevent rotation in one direction when Modes  2  or  3  are selected (see  FIG. 2A ), while sloped surface  41  is configured and/or shaped to allow a strut  34 A,  34 B to be depressed into a mating pocket  32 A,  32 B as required and thereby permits relative rotation of the races  20 ,  22  in at least one direction, i.e. Modes  1  or  2  (see  FIG. 2A ). As shown in  FIGS. 2B ,  2 C, and  2 D, outer race  22  is grounded to the transmission case  70  and inner race  20  is rotating, inner race  20  being connected to motor/generator  84 , which is in communication with the motor controller  16 . Motor controller  16 , as previously described, is configured to synchronize the rotational speeds of the inner and outer races  20 ,  22  to facilitate actuation of the clutch  18 . However, in the event outer race  22  is not grounded and therefore is also rotating, the motor/generator  82  would be likewise connected to the outer race  22  and in communication with motor controller  16 , as shown by the dotted line connection. 
     In  FIG. 2B , representing Mode  1  or “freewheeling”, first and second selection plates  50 ,  52  are positioned by actuators  42 ,  43 , respectively, in response to a control signal from the transmission controller  14 . When repositioned as shown, first and second selector plates  50 ,  52  depress each of the required number of struts  34 A,  34 B into a respective mating well  32 A,  32 B, with each strut  34 A,  34 B compressing a biasing spring  37  to thereby allow inner race  20  to freely rotate or freewheel in either rotational direction, as represented by arrows  1  and  2 . Likewise, in  FIG. 2C , representing Mode  2  or torque-holding in a single direction, the first selector plate  50  is positioned in response to a signal from the transmission controller  14 . Biasing springs  37  return any depressed strut  34 A to its initial position, thus engaging the strut  34 A with a vertical locking surface  40 . Torque is held in one direction by preventing the inner race  20  from rotating in the direction of arrow  1  due to the obstructing presence of the strut  34 A. The second selector plate  52  continues to depress strut  34 B, allowing inner race  20  to continue to freely rotate in the direction of arrow  2 . Finally, in  FIG. 2D  both first and second selector plates  50 ,  52  are repositioned to allow biasing springs  37  to uncompress and return struts  34 A,  34 B to their initial, non-depressed state, thereby locking the inner race  20  in both rotational directions (arrows  1  and  2 ). While a single strut  34 A,  34 B is shown in  FIGS. 2B ,  2 C, and  2 D for illustrative simplicity, for optimal control and performance of clutch  18 , a plurality of struts  34 A,  34 B is preferred, such as shown in  FIG. 1B . 
     Turning to  FIG. 3A , a curve is shown plotting differential clutch speed (Δ S ) versus the three clutch operating modes (see  FIG. 2A ) during application of clutch  18  (see  FIGS. 1A ,  1 B, and  1 C). The three operational modes are arranged sequentially along the X axis, while the Y axis describes the speed differential Δ S  as measured across the disparately rotating inner and outer races  20 ,  22  (see  FIGS. 1A ,  1 B, and  1 C). According to the invention, each of the three operational modes, i.e. Mode  1 , Mode  2 , and Mode  3 , are selected from according to a measured or otherwise determined speed differential Δ S  determined by speed sensor  11  (see  FIG. 1A ), with Δ S  also having a positive or negative rotational direction value defined by the relative rotational direction of the inner and outer races  20 ,  22 . 
     As shown in  FIG. 3A , while in Mode  1 , i.e. “freewheeling”, to apply the clutch  18  the motor controller  16  (see  FIGS. 2A ,  2 B, and  2 C) cycles or synchronizes the outer and inner races  20 ,  22  of the clutch  18  so that Δ S  approaches approximately zero revolution per minute, as represented by point  61 . The signal communicated at point  61  precipitates a change from Mode  1  to Mode  2  when the speed sensor  11  detects that the direction of Δ S  reaches a non-negative quantity, i.e. at point  64 , at which point the transmission controller  14  signals the clutch  18  to change to Mode  2  and thereby hold torque in one rotational direction. Because of the time delay in making the physical shift by actuation of the required selector plates  50 ,  52  (see  FIG. 2C ), a slight time lag Δt occurs before Mode  2  is fully realized at point  65 . While the direction of Δ S  is positive, the clutch  18  continues freewheeling. While in Mode  2 , when the direction of Δ S  turns negative, i.e. at point  68 , the clutch  18  locks. When the speed sensor  11  detects zero differential clutch speed and zero speed change, the transmission controller  14  signals the clutch  18  to change to Mode  3  so that rotational motion is prevented in both directions, as shown in  FIG. 2D , thereby freeing or releasing the motor/generators  82 ,  84  (see  FIG. 1A ) to change speeds as necessary. Because of the time delay in making the physical shift by actuation of the required selector plates  50 ,  52  (see  FIG. 2D ), a slight time lag Δt occurs before Mode  3  is fully realized at point  69 . 
     Turning to  FIG. 3B , a similar speed curve is shown describing the release of the clutch  18 , beginning with dual-directional torque holding or Mode  3 . To initiate the release of the clutch  18 , the transmission controller  14  (see  FIGS. 1A and 1B ) commands or signals a mode change from Mode  3  to Mode  2  at point  71 . Prior to a mode change to Mode  2 , the motor controller  16  commands or signals the motor to load the clutch  18  in the direction opposite that of the impending clutch release, then in Mode  2  the motor controller  16  unloads the clutch  18  so that the clutch  18  may be easily released (i.e. the struts  34 B may be more easily disengaged in  FIG. 2C ) in the opposite direction. When the speed sensor  11  (see  FIG. 1A ) detects that the quantity Δ S  is positive, the transmission controller  14  changes the operating mode to “freewheel in both directions”, i.e. Mode  1 , which is the initial state of  FIG. 3A  as previously described hereinabove. The actuation cycle then repeats as previously described hereinabove for  FIG. 3A . 
     Turning now to  FIG. 4A , a lever diagram is shown for a representative hybrid transmission  110  having a selectable one-way clutch  180  as previously described herewithin for clutch  18 , the clutch  180  shown in a released or unapplied state (i.e. Mode  1 ). The hybrid transmission  110  has a first and second motor/generator,  182 ,  184 , respectively, an engine  186 , and a first and second planetary gear set  190 ,  192 , respectively. The first and second motor/generators  182  and  184  are controlled by a motor controller  16  (see FIGS.  1 A and  2 A-D) as previously described hereinabove. First planetary gear set  190  comprises a carrier (node C 1 ), a ring gear (node R 1 ), and a sun gear (node S 1 ). Likewise, second planetary gear set  192  comprises a carrier (node C 2 ), a ring gear (node R 2 ), and a sun gear (node S 2 ). A second clutch  181 , which may allow for different gear connections, is shown in an applied state. First motor/generator  182  is operatively connected to carrier C 1  of first planetary gear set  190 , which is in turn connected to the sun gear S 2  of the secondary planetary gear set  192 . Second motor/generator  184  is connected to the sun gear S 1 , which is in turn connected to the ring gear R 2  through the second applied clutch  181 . Engine  186  is connected to the ring gear R 1 , while the carrier C 2  is connected to the clutch output  198 . Clutch  180  of the present invention is shown in the disengaged or unapplied state. 
     Dotted lines  200 ,  201 ,  202  and  204 ,  205 , and  206  represent various speed ratios in the unapplied mode, i.e. a range of speed ratios determined by motor/generator  182 . When clutch  180  is applied as previously described hereinabove, motor/generator  182  cycles or synchronizes the speed across clutch  180  to approximately zero rpm to provide a single fixed speed ratio, as represented by dotted lines  207  and  208 . As shown in  FIG. 4B , torque is held in both directions, i.e. clutch  180  is fully applied. While the hybrid transmission  110  shown in  FIGS. 4A and 4B  is one example, those skilled in the art will recognize that various other hybrid transmission configurations and designs would be operable within the scope of the invention. 
     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.

Technology Classification (CPC): 1