Abstract:
An assembly for an automatic transmission includes a casing, a carrier of a planetary gear set, a hydraulically actuated brake that driveably connects the carrier and the casing mutually when the brake is engaged in reverse drive and disconnects the carrier from the casing when the brake is disengaged in forward drive, and an overrunning clutch including an outer race driveably connected to the casing, an inner race driveably connected to the carrier, and multiple rockers carried on the inner race that pivot toward engagement with the cam surfaces, contact of the clutch with the casing providing a reaction to a force tending to engage the brake.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates in general to a clutch that produces a drive connection between components when their relative rotation is in one direction, and overruns when relative rotation is in the opposite direction. In particular, the invention pertains to using such clutches to provide a reaction to a force that actuates a friction clutch. 
         [0003]    2. Description of the Prior Art 
         [0004]    Conventional one-way clutches for producing a one-way drive connection between inner and outer races of the clutch include sprags or rollers for releasably driveably connecting the races and the components of a mechanical assembly connected to the races. Such clutches are commonly used in the powertrain or driveline of an automotive vehicle. One-way clutches perform satisfactorily in many cases, but certain applications, such as those in which large magnitudes of torque are transmitted by the clutch, or those that provide only a small space for the clutch, require one-way clutches other than conventional sprag-type or roller-type clutch to meet desire requirements. 
         [0005]    Conventional one-way clutch assemblies have at least one sprag or roller, which driveably locks two notched or pocketed races together mutually in one rotary direction and allows the races to rotate freely in the other direction. Rocker and sprag type one-way clutch assemblies can increase the torque capacity for a given package size compared to those of a roller-type clutch, but they are generally limited in torque transmitting capacity by the magnitude of the contact or bearing stresses caused by contact of the rockers or sprags with the races. 
         [0006]    Conventional one-way clutches develop relatively large magnitudes of hoop stress in the races when torque is transmitted through the clutch; therefore, the races of conventional one-way clutches are formed of bearing grade steel in order to withstand the operating hoop stress. Because the clutches develop relative low operating hoop stresses in service, those clutch can be formed of powdered metal. Clutches formed for powdered metal potentially can be produced at relative low cost compared to the cost to form and produce a conventional clutch of high grade steel, provided extensive machining is avoided. 
         [0007]    A need exits for a low cost, reliable one-way clutch that produces low operating bearing stresses, is able to be formed readily from powdered metal, and can react the actuating force produced in a hydraulically actuated friction brake. The clutch should occupy little space, minimize in-service noise, and require little or no machining. Preferably, the desired clutch should include features that facilitate its assembly in a drive system. 
       SUMMARY OF THE INVENTION 
       [0008]    An assembly for an automatic transmission includes a casing, a carrier of a planetary gear set, a hydraulically actuated brake that driveably connects the carrier and the casing mutually when the brake is engaged in reverse drive and disconnects the carrier from the casing when the brake is disengaged in forward drive, and an overrunning clutch including an outer race driveably connected to the casing, an inner race driveably connected to the carrier, and multiple rockers carried on the inner race that pivot toward engagement with the cam surfaces, contact of the clutch with the casing providing a reaction to a force tending to engage the brake. 
         [0009]    The outer race of the overrunning clutch  20  always floats while the clutch is overrunning when the transmission produces forward drive, so that the outer race can find its centerline. The clutch resists or reacts the actuating force transmitted by a piston of the reverse brake to the friction discs and plates  90  of the reverse brake. It is acceptable that clutch  20  react the pressure force applied to the reverse brake because in reverse drive, the clutch is not overrunning, there is no relative movement between its inner and outer races, and no wear is produced between races. 
         [0010]    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 
         [0011]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0012]      FIG. 1  is an end view of a one-way clutch showing rockers located in an inner race and engaged with notches in an outer race; and 
           [0013]      FIG. 2  is a cross sectional view showing the clutch of  FIG. 1  located axially between two hydraulically actuated friction brakes. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring now to the drawings, there is illustrated in  FIG. 1  a one-way clutch assembly  20 , which includes an inner race or rocker plate  22 , an outer race or cam plate  24 , and a plurality of rockers  26 , each rocker being located in a pocket  28  formed in the inner race  22  and angularly spaced mutually about a central axis  30 . The inner periphery of the outer race  24  is formed with a plurality of cams or notches  32  angularly spaced mutually about axis  30 . There are twelve rockers  26  and pockets  28  and thirty-six notches  32  in the clutch illustrated in  FIG. 1 . 
         [0015]    When the inner race  22  rotates clockwise faster than the outer race  24 , each rocker  26  pivots counterclockwise in its pocket  28  away from engagement with the notches  32  due to contact of the rockers with the inner surface of the outer race. This allows the inner race  22  to rotate freely, i.e., to overrun clockwise about axis  30  relative to the outer race  24 . When the inner race  22  attempts to rotate counterclockwise relative to the outer race  24 , the inner race and outer race are engaged or driveably connected mutually by engagement of the rockers  26  with the notches  32 . 
         [0016]    When the clutch  20  is engaged, each engaged rocker  26  transmits a force F between the inner and outer races  22 ,  24  due to surface  27  of the rocker contacting the radially directed surface  36  of the engaged notch  32  and the rocker contacting the inner surface  34  of the pocket  28 . 
         [0017]    A recess  40 , located at each pocket  28 , contains a spring, such as a helical coiled compression spring  42  or an accordion compression spring  44 , for urging each rocker to pivot in its pocket toward engagement with the notches. 
         [0018]    When clutch  20  overruns, a force P 2  is applied to each rocker  26  as it passes over the crest  46  of the radial surfaces  36  of each notches  32 . Torque about center  30  produced by force F is reacted by a force P 1  where rocker contacts the inner surface  34  of the pocket  28 . 
         [0019]    The outer surface of the outer race  24  is formed with spline teeth  54 , by which race  24  can be driveably connected to a transmission casing. The inner surface of the inner race  22  is formed with spline teeth  56 , by which race  22  can be driveably connected to a component of a transmission. 
         [0020]      FIG. 2  illustrates a one-way or overrunning clutch  20  located in a transmission case  60  between a hydraulically actuated forward brake  62  and a hydraulically actuated reverse brake  64 . When the transmission produces forward drive, brake  62  is engaged and brake  64  is disengaged. When the transmission produces reverse drive, brake  64  is engaged and brake  62  is disengaged. 
         [0021]    The forward brake  62  includes friction discs  66 , splined at their inner radial surface to a drum  67 ; plates  70 , splined at their outer radial surface to casing  60 , each plate  70  alternating with a disc  66 ; a pressure plate  72 , splined at its outer radial surface to casing  60 ; a snap ring  74  secured to the casing  70  against displacement along an axis  76  and located adjacent pressure plate  72 ; a piston  78  that moves along axis  30  in response to hydraulic pressure in the cylinder  80 , in which piston  78  is located; and a Belleville spring  82 , fitted in a recess adjacent a snap ring  84  that is secured to casing  70  and contacting the piston  78 . When cylinder  80  is pressurized, piston  78  moves leftward and forces the friction discs  66  and plates  70  into mutual frictional contact against pressure plate  72 . Spring  82  returns piston  78  to the disengaged position shown in  FIG. 2 , when pressure in the cylinder  80  is vented. 
         [0022]    The reverse brake  64  includes friction discs  86 , splined at their inner radial surface to an extension  88  that projects from the inner race  22  of clutch  20 ; plates  90 , splined at their outer radial surface to casing  60 , each plate  90  alternating with a disc  86 ; a pressure plate  92 , splined at its outer radial surface to casing  60 ; a snap ring  94  secured to the casing  70  against displacement along axis  30  and located adjacent a plate  90 ; a piston  98  that moves along axis  30  in response to hydraulic pressure in a servo cylinder, in which piston  98  is located; and a Belleville spring  100 , fitted in a recess adjacent a snap ring  102  that is secured to casing  70  and contacts the piston  98 . When the servo cylinder is pressurized, piston  98  moves rightward and forces the friction discs  86  and plates  90  into mutual frictional contact. The force of piston  98  is transmitted by the friction discs  86 , plates  90 , and the outer race  24  of one-way clutch  20 , and snap ring  74  to casing  60 . Spring  100  returns piston  98  to the disengaged position shown in  FIG. 2 , when pressure in the servo cylinder is vented. 
         [0023]    Snap ring  94  does not participate in transmitting to casing  60  the force of piston  98  that causes engagement of reverse brake  64 . Snap ring  94  prevents one-way clutch  20  from transmitting to reverse brake  64  an axial thrust force from carrier  110  when brake  64  is disengaged. 
         [0024]    The outer race  24  of clutch  20  is connected by spline teeth  54  to casing  60 , and the extension  88  of the inner race  22  is driveably connected by spline teeth  56  to spline teeth on the carrier  110  of a planetary gear set that includes a ring gear  112 . Each pocket containing a rocker  26  is closed by an end plate  114 . A snap ring  116  is secured to outer race  24  and is located adjacent the end plate  114 . The end face  118  of the outer race  24  is located for contact with either a friction plate  86  or a disc  90 , whichever is adjacent face  118 . 
         [0025]    Pressure plate  72  and snap ring  74  transmit to casing  60  the reaction to the pressure force applied by piston  78  to the discs  66  and plates  70 . 
         [0026]    The outer race  24  of reverse clutch  20  always floats while clutch  20  is overrunning when the transmission produces forward drive, so that race  24  can find its centerline. Reverse clutch  20  contacts snap ring  74 , which is secured to casing  60 . Therefore, clutch  20  resists and reacts the actuating force transmitted by piston  98  to the friction discs  86  and plates  90  of reverse brake  64 . It is acceptable that clutch  20  reacts the pressure force applied to reverse brake  64  because in reverse drive, clutch  20  is not overrunning, there is no relative movement between inner race  22  and outer race  24 , and no wear is produced between races  22 ,  24 . 
         [0027]    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.