Abstract:
A one-way clutch includes a first race secured against rotation and fitted with a coil, a second race supported for rotation, a coil carried by one of the races, and struts supported by one of the races, each strut driveably connecting and disconnecting the races in response to a magnetic field induced by current in the coil.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to magnetically-actuated one-way clutch, and, more particularly to a motor-generator that employs a magnetically actuated one-way clutch especially for use in a hybrid electric vehicle. 
         [0003]    2. Description of the Prior Art 
         [0004]    The powertrain of a hybrid electric vehicle (HEV) includes an electric motor-generator. This generator is used to start the vehicle when in electric motor mode and when in generator mode the electric generator produces ac electric current, which is converted to dc and stored in an electric storage battery. 
         [0005]    Under certain vehicle operating conditions, the motor is used to drive the vehicle wheels. In other operating conditions the electric generator produces ac electric current, which is converted to dc and stored in an electric storage battery. 
         [0006]    The generator&#39;s rotor exhibits unwanted rotation in some modes of operation. The rotor must be stopped from rotating in some modes of operation and must be allowed to rotate in either direction in other modes of operation. 
         [0007]    An actuator may include a member located between the locking elements of a one-way clutch (OWC) and the cams that are engaged by the locking members, thereby preventing engagement of the clutch, in one state of the actuator. When the actuator changes state, the member can move out of the way, thereby allowing the clutch to engage or lockup. An actuator of this kind requires many components and redundant actuation forces in addition to a spring force to ensure its reliability. Care must be exercised to ensure that the actuator member is much softer than the locking elements and the races of the one-way clutch. Otherwise, the control elements will wear prematurely before expiration of an acceptable service life. 
         [0008]    A need exists in the industry for a simpler, more reliable and less costly technique for controlling generator rotation. Preferably the technique would avoid need for linkages in the OWC. Preferably the device would be direct acting and avoid need for an electric solenoid to control the OWC actuator. 
       SUMMARY OF THE INVENTION 
       [0009]    A one-way clutch includes a first race secured against rotation and fitted with a coil, a second race supported for rotation, a coil carried by one of the races, and struts supported by one of the races, each strut driveably connecting and disconnecting the races in response to a magnetic field induced by current in the coil. 
         [0010]    The one-way clutch provides a simple, reliable, low-cost selectable technique for controlling rotation of the rotor of a motor-generator. The clutch can be used in multiple applications where a magnetic field can be turned on and off in order to control the presence and absence of a drive connection between inner and outer races of the clutch. 
         [0011]    The clutch avoids need for clutch linkages and an electric solenoid to control an actuator of the one-way clutch. 
         [0012]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0014]      FIG. 1  is a cross section of a motor generator that includes a one-way clutch; 
           [0015]      FIG. 2  is a cross section of the motor-generator and one-way clutch above the centerline to a larger scale than that of  FIG. 1 ; 
           [0016]      FIG. 3  is a cross section of the motor-generator and one-way clutch below the centerline to a larger scale than that of  FIG. 1 ; 
           [0017]      FIG. 4  is a perspective end view taken at plane  4 - 4  of  FIG. 1 ; 
           [0018]      FIG. 5  is a perspective end view showing a locking element engaged with a cam; 
           [0019]      FIG. 6  is a perspective end view showing a permanent magnet fitted into one of the pockets of the outer race; 
           [0020]      FIG. 7  is a perspective view of the inner race. 
           [0021]      FIG. 8  is an end view showing a locking element engaged with a cam and forces operating on the strut; 
           [0022]      FIG. 9  is an end view of an alternate embodiment of the clutch; and 
           [0023]      FIG. 10  is a perspective view of the embodiment of  FIG. 10  showing an accordion spring contacting the strut. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    Referring now to the drawings,  FIG. 1  shows a motor-generator  14  and one-way clutch  16  arranged about a central axis  18  and located within a space bounded by a front housing cover  20  secured by bolts  22  and to a housing  24 , whose position is fixed. 
         [0025]    The motor-generator  14  includes a stator  26 , secured by a series of bolts  28  to an extension of the housing  24  or another fixed member; electrically conductive wire wound in a coil  30  about axis  18 ; a rotor  32  surrounded by the stator; and a rotor shaft  34  supported for rotation about axis  18  on bearings  36 ,  38 . Each axial end of the rotor  32  is covered by an end cap  40 ,  42 . 
         [0026]    The one-way clutch  16  includes a cam plate or inner race  44 , secured by a series of bolts  46  to housing cover  20 ; a pocket plate or outer race  48 , secured by a series of bolts  50  to rotor  32 ; and struts or locking elements  56 . The inner race  44  is formed with an annular groove  52  located mid-way between its axial ends. A toroidal coil  54  of electrically conductive wire is located in groove  52 . 
         [0027]      FIG. 4  shows four struts  56  spaced angularly about axis  18 , each strut supported in a pockets  58  formed in the outer race  48 . The radial outer surface of the inner race  44  is formed with cams  60  spaced angularly about axis  18 . The outer race  48  is formed with four holes  62 , by which the outer race is connected by bolts  50  to the rotor  48 . When the struts  56  pivot in the pockets  58  toward the inner race  44 , the outer race rotates clockwise relative to the outer race  48 , and at least one strut engages a cam  60 , clutch  16  produces a drive connection between the races, thereby locking the clutch and preventing the rotor  32  from rotating relative to the stator  26  and housing  20 . When the outer race  48  rotates counterclockwise relative to the inner race  44 , each strut  56  ratchets on the cams  60 , the clutch  16  is unlocked or disengaged, and no drive connection between the races is produced. 
         [0028]      FIG. 5  shows a strut  56  engaged with a cam  60 . The coil groove  52  contains the coil  54 . When coil  54  is energized, the magnetic field produced by current in coil  54  forces the strut  56  toward the cams  60 . But when the outer race is rotating, centrifugal force urges the strut  56  radially outward away from the cams  60 . A permanent magnet  64 , preferably secured by a press fit to a surface of each pocket  58 , urges each strut  56  away from the cams  60 . The axial length of each strut  56  is sufficient to span the width of the coil groove  52 . 
         [0029]      FIG. 6  shows a permanent magnet  64  fitted into one of the pockets  58  of the outer race  48 . 
         [0030]      FIG. 7  shows the inner race  44  formed with a series of cams  60  on its outer radial surface, continuity of the cam surfaces being interrupted by the central, circular groove  52 , which contains the coil  54 . The inner race  44  is formed with four holes  66 , by which the inner race is connected by bolts  46  to the housing  20 . 
         [0031]    As  FIG. 8  illustrates, a force Fpm produced by the field of permanent magnet  64  on strut  56  is directed radially outward tending to move the strut  56  away from engagement with the cams  60 . When outer race  48  is rotating, centrifugal force acting on strut  56  urges the strut toward and into engagement with the cams  60 . When coil  54  is energized, its magnetic field induces a force Fc in the strut  56  urging the strut toward and into engagement with the cams  60 . 
         [0032]    When the strut  56  engages a cam, the strut pivots at its toe  72  such that the tip  70  of strut contacts the cam. A force between the locking face  70  and the cam  60  is reacted by contact between the strut&#39;s convex heel  74  and the mating concave surface  76  of the pocket  58 . 
         [0033]    A spring  80 , such as coiled helical compression spring or an accordion compression spring, located in a recess  82  formed in the pocket plate  48 , may be used to apply a force Fs to the heal  74  of strut  56  urging the strut toward and into engagement with the cams  60 . 
         [0034]      FIG. 9  shows an alternate embodiment in which the inner race  44 ′ is formed with pockets  100 , each pocket containing a strut  56 ′, and the groove  20 ′ that contains the coil  54 ′ is accessible from the radial inner surface of the race  44 ′. The radial outer surface of the outer race  48 ′ is formed with cams  60 ′. When the coil  54 ′ is energized, the heel  102  of strut  56 ′ is pulled radially inward toward axis  18 , strut  56 ′ pivots on the toe  104 , the locking face  70 ′ of the strut engages one of the cams  60 ′, and the clutch  16 ′ engages, thereby locking the clutch and preventing the rotor  32  from rotating relative to the stator  26  and housing  20 . In  FIG. 9 , Fs represents the force of spring  80  tending to move the strut  56 ′ away from the cams  60 ′, and Fm represents the force due to the permanent magnet  64  tending to move the strut into engagement with a cam. 
         [0035]      FIG. 10  is a perspective view of the embodiment of  FIG. 10  showing an accordion spring  80  located in the spring recess  82  and contacting the strut. The force applied by spring  80  urges strut  56 ′ out of engagement with the cams  60 ′. Either springs  80  or permanent magnets  64  can be used to produce a force on the struts  56 ′ in opposition to the force due to energizing electromagnetic coil  54 . 
         [0036]    In operation, when the coil  54 ,  54 ′ is energized with electric current while the rotor  32  and outer race  48  or rotating, the magnetic field induced by the current should be strong enough that, after the cams push the strut into the pocket, the strut is held in the pocket farthest away from the cams so that the clutch cannot lock. When the clutch must become locked, the coil is deenergized or, if necessary, is pulsed with a reversing current to degauss the system, allowing the spring  80  to push the strut into engagement with the cams  60 . 
         [0037]    Alternatively, the design of the clutch is such that the magnetic field induced by current in coil  54  causes the strut to pivot in the pocket, moving the strut into engagement with a cam, thereby locking the clutch. 
         [0038]    Preferably the races  44 ,  44 ′,  48 ,  48 ′ are made from non-magnetic magnetically permeable material, such as a suitable stainless steel or soft iron. Preferably the inner race  44 ,  44 ′ is of soft iron. The struts  56 ,  56 ′ are made preferably from a permeable material such as ferrous powder metal. 
         [0039]    Preferably for one application, the permanent magnet material is Alnico  5 , whose components include aluminum, nickel and cobalt. A commercial supplier of the permanent magnet material is Magnet Sales and Manufacturing Inc., Culver City, Calif. 90230. Preferably the windings have about 225 turns of 27 gauge copper wire. The current supplied to the windings is 1 amp. The rotor is non-magnetic. The permanent magnet material of the stator/strut is about 500 Webers. The field strength is about 5 amp-turns/meter. 
         [0040]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.