Abstract:
A transmission includes an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque-transmitting devices. A hydraulic fluid control circuit is provided for controlling the operation of the plurality of torque-transmitting devices. The hydraulic fluid control circuit receives pressurized hydraulic fluid from an off-axis hydraulic fluid pump and has a plurality of fluid passages disposed in the transmission house, input member and other coupling members.

Description:
FIELD 
       [0001]    The present invention relates generally to multiple speed transmissions using hydraulic torque-transmitting devices and more particularly to hydraulic torque-transmitting devices having a return spring. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    A typical multi-speed automatic transmission uses a combination of torque transmitting devices, such as clutches, dog clutches/synchronizers, or brakes, to achieve a plurality of forward and reverse gear or speed ratios. Selection of speed ratios is typically accomplished by a microprocessor transmission control module that employs various vehicle parameters, for example vehicle speed, and various driver input signals, for example accelerator pedal position, to select the appropriate speed ratios. The transmission then actuates or engages a combination of the toque transmitting devices to provide the desired speed ratios. 
         [0004]    The torque-transmitting devices can use various actuating techniques and mechanisms for transferring torque from one rotating member to another. One type of torque-transmitting device uses a plurality of rotating plates and a hydraulically actuated piston. The hydraulically actuated piston is moved to an engaged position by application of a hydraulic force on the piston. However, the hydraulically actuated piston requires a regulating force to retract the piston from the engaged position. The regulating force may be provided in various manners, for example, a separate hydraulic circuit may provide another hydraulic force on the piston in order to provide the regulating force. However, hydraulic circuits may increase the size and weight of the transmission. In other applications a mechanical spring may be used to apply the regulating force to the piston. However, in previous designs the mechanical spring assembly limits the overall compact size of a transmission as typically a plurality of torque-transmitting devices are employed in each transmission. Accordingly, there is room in the art for an improved torque-transmitting device that includes a piston actuating assembly that reduces the size of the torque-transmitting device. 
       SUMMARY 
       [0005]    In one aspect of the present disclosure a torque-transmitting mechanism is provided for transmitting torque from one interconnecting member to another interconnecting member. The torque-transmitting mechanism includes a housing, a piston, a plurality of coil springs, a spring retainer, a first retainer ring and a plurality of friction plates. The housing is connectable to the first member and includes a piston chamber including an outer wall, an inner wall radially inboard the outer wall and a ring retainer groove disposed in the outer wall. The piston is disposed in the piston chamber of the housing and includes a base portion and an apply portion. The apply portion is a plurality of projections extended from the base portion. The plurality of coil springs each include a first and a second end, wherein the first end is in contact with the base portion of the piston. The spring retainer has a retainer surface, a plurality of projections and a plurality of slots. Each of the plurality of projections retain the second end of each of the plurality of springs and the plurality of slots are formed to receive the plurality of projections of the apply portion of the piston. The first ring retainer has an outer portion that is disposed in the groove of the outer wall of the piston chamber and an inner portion in contact with the surface of the spring retainer. A plurality of reaction plates is disposed in the housing with the reaction plates are rotatably engaged to the housing. A plurality of friction plates rotatably is engaged to the second member. The piston is actuatable to force the reaction plates against the friction plates to transmit torque from the first member to the second member. 
         [0006]    In one example of the present disclosure, the apply portion of the piston is partially corrugated. 
         [0007]    In another example of the present disclosure, the apply portion of the piston includes a strengthening rib. 
         [0008]    In yet another example of the present disclosure, the slots of the spring retainer include a narrow end and a guide tab disposed at the narrow end. 
         [0009]    In yet another example of the present disclosure, the piston further comprises an inner and outer seal disposed on the base portion. The inner seal is compressed between the piston and the inner wall of the piston chamber and the outer seal is compressed between the piston and the outer wall of the piston chamber. 
         [0010]    In yet another example of the present disclosure, the piston actuating assembly further includes a cushion plate. The housing further includes a splined portion having a ring retainer groove. The plurality of reaction plates and cushion plate are disposed in the splined portion of the housing. 
         [0011]    In yet another example of the present disclosure, the torque-transmitting mechanism further includes a backing plate and a second ring retainer. The backing plate is disposed axially adjacent to the plurality of friction plates. The second ring retainer has an outer portion that is disposed in the groove of the splined portion of the housing and an inner portion in contact with the backing plate. 
         [0012]    Further objects, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
    
     
       DRAWINGS 
         [0013]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way; 
           [0014]      FIG. 1  is a cross-section of a transmission having a torque-transmitting mechanism including an actuating assembly in accordance with an embodiment of the present invention; 
           [0015]      FIG. 2  is a perspective and exploded view of a torque-transmitting mechanism in accordance with an embodiment of the present invention; and 
           [0016]      FIG. 3  is a perspective view of an actuation assembly in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0018]    Referring to the drawings, wherein like reference numbers refer to like components, in  FIG. 1  a cross-sectional view of a transmission  10  and a torque-transmitting device  20  is shown. Some reference numbers are better viewed in  FIG. 2  which illustrates an exploded perspective view in accordance with an embodiment of the present invention. The torque-transmitting mechanism  20  is configured to transmit torque from a first interconnecting member  24  to a second interconnecting member  25  of the transmission  10 . In one embodiment of the present invention, the interconnecting members  24 ,  25  are members connecting rotating transmission components to the torque-transmitting device, however, the description also contemplates that the interconnecting members are members of a planetary gear set, shafts or a portion of the transmission housing. 
         [0019]    The torque-transmitting mechanism  20  includes a housing  22 , an actuating assembly  32 , and a set of plates  38 . The housing  22  is connectable to the first interconnecting member  24  and includes a piston chamber portion  26  and a splined portion  30 . The piston chamber portion  26  is defined by an outer wall  26 A, an inner wall  26 B and a back wall  26 C. The inner wall  26 B is formed radially inward from the outer wall  26 A and the back wall  26 C is adjacent each of the inner and outer walls  26 A-B. The splined portion  30 , better viewed in  FIG. 2 , extends from the outer wall  26 A of the piston chamber portion  26 . The splined portion  30  has a splined inner surface  30 A designed to engage the set of plates  38 . 
         [0020]    The actuating assembly  32  is disposed predominantly in the piston chamber portion  26  of the housing  22 . The actuating assembly  32  includes a piston  42 , a spring retainer  44  and a plurality of coil springs  54 . For example, the plurality of coil springs  54  are disposed between the spring retainer  44  and the piston  42 . The coil springs  54  have a first end  54 A in contact with the piston  42  and second end  54 B in contact with the spring retainer  44 . The spring retainer  44  is grounded to the housing  22  to prevent relative axial movement between the spring retainer  44  and the housing  22 . The outer wall  26 C of the housing includes a groove  22 A. The actuating assembly  32  is restricted from moving axially by a ring retainer  34  disposed in the groove  22 A. The piston  42  is disposed in the piston chamber portion  26  of the housing  22 . The piston  42  has an outer and inner seal  46 ,  48  that contact the outer and inner wall  26 C,  26 B of the piston chamber portion  26 , respectively. The piston  42  and seals  46 ,  48  enclose the piston chamber portion  26  and establish a leak-resistant seal required for selective hydraulic pressurization of the piston chamber portion  26 . 
         [0021]    The set of plates  38 , better viewed in  FIG. 2 , have alternatively stacked reaction plates  38 A, friction plates  38 B and a cushion plate  38 C. The outer diameter splined reaction plates  38 A engage with the splines  30 A of the splined portion  30  and the inner diameter splined friction plates  38 B engage with a splined portion  25 A of the second interconnecting member  25 . 
         [0022]    The piston  42  is aligned to contact cushion plate  38 C of the set of friction plates  38 . Upon pressurization of the piston chamber portion  26 , the hydraulic pressure acts on the piston  42  moving the piston  42  axially toward the cushion plate  38 C and thus transferring the pressure to the set of plates  38 . A backing plate  50  is retained in the splined portion  20  of the housing  22  by a ring retainer  51  that is disposed partially in a groove  51 A, better viewed in  FIG. 2 , in the splined portion  30 . The backing plate  50  constrains the plates  38  from moving axially. The plates  38  are compressed together creating friction to restrict relative movement between the reaction plates  38 A and the friction plates  38 B and as a result, between the first and second interconnecting members  24 ,  25 . 
         [0023]    Referring now to  FIG. 3 , a perspective view of the actuating assembly  32  is illustrated and will now be described. The actuating assembly  32  includes the piston  42 , a spring retainer  52  and a plurality of coil springs  54 . The piston  42  further includes a base portion  56  and an apply portion  58 . The base portion  56  contacts each of the outer and inner walls  26 A,  26 B of the piston chamber portion  26  (shown in  FIG. 1 ) forming a pressurized hydraulic seal. The apply portion  58  of the piston includes a plurality of projections  64  that lengthen selected portions of the base portion  56  of the piston  42 . In the example provided, the projections  64  are equally spaced around the perimeter of the piston  42 . Additionally, corrugations  66  are formed in the projections  64  to provide additional strength and rigidity although other methods, such as ribs (not shown) may be utilized to achieve such an effect. 
         [0024]    The spring retainer  52  includes an inner portion  68  and an outer portion  70  that are connected by a plurality of connective portions  72 . The connective portions  72  are disposed at equal distances along the perimeter between the inner and outer portions  68 ,  70 . A plurality of slots  74  are formed by an outer edge  68 A of the inner portion  68 , an inner edge  70 A of the outer portion  70 , and the side edges  72 A of each adjacent connective portion  72 . The slots  74  provide clearance for the projections  64  of the piston  42  to pass through the spring retainer  52 . A tab  78  is formed at each of the side edges  72 A of the connective portions  72 . The tabs  78  include a corner radius  78 A and an inner surface  78 B to help guide the projections  64  through the slots  68  of the spring retainer  52 . 
         [0025]    The inner portion  68  of the spring retainer  52  includes a rim  80  and a plurality of spring indentations  82 . The rim  80  is formed along the inner edge  68 B of the inner portion  68  and at least partially encloses the plurality of springs  54 . The spring indentations  82  each include a spherical raised portion  82 A. The spring indentations  82  have a same or slightly smaller diameter than the inner diameter of the springs  54 . The springs  54  are disposed between the piston  42  and the spring retainer  52  so that the raised portion  82 A of the spring indentations  82  pass at least partially through the inside diameter of the springs  54 . The piston  44 , rim  80  and plurality of spring indentations  82  cooperate to retain the springs  54 . The springs  54  are oriented so that the compressed forces of the springs  54  act to oppose the piston  42  and the spring retainer  52 . The combined force of the springs  54  offsets the force applied to the piston  42  as the hydraulic pressure in the piston chamber portion  26  is relieved. 
         [0026]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.