Abstract:
The present disclosure relates to a piston-actuated clutch assembly for a transmission. Interconnecting members are integrated into a pressure plate of the clutch assembly. The interlocking members are configured to selectively interlock the piston and the pressure plate. The location of the interlocking members reduces wear on the piston and other transmission components.

Description:
TECHNICAL FIELD 
       [0001]    The present inventions relate to a clutch assembly for an automobile transmission, more specifically, to a piston-pressure plate connection in the clutch assembly. 
       BACKGROUND 
       [0002]    Conventional automobile transmissions include various clutch assemblies that enable the transmission to power the wheels at different speeds. Clutch assemblies are typically hydraulically actuated using some sort of apply piston. In past arrangements pistons have included pins that connect the piston with a backing plate of the clutch assembly. These pins interface with the backing plate carrying the force or load of engagement when applied. Concentrated over a relatively small surface area, these forces can cause unwanted wear on the piston and pins. 
         [0003]    Additionally in certain sections of the transmission—typically near the output shaft of the transmission—the apply pistons can neighbor other transmission components such as speed sensors and park pawls. Accordingly, it can be desirable to restrict the rotational range of movement of the piston in order to ensure that the piston does not disrupt other transmission components when applying the clutch. Very high forces can develop when the piston is directly tied to the transmission case. These forces can cause unwanted wear and brinelling on the piston and neighboring transmission components. 
         [0004]    Therefore, it is desirable to have a clutch assembly for a transmission that includes interconnecting members that produce less wear on the piston and other transmission components. It is also desirable to provide a method of manufacturing the clutch assembly that is cost efficient. 
       SUMMARY 
       [0005]    The present inventions may address one or more of the above-mentioned issues. Other features and/or advantages may become apparent from the description which follows. 
         [0006]    Certain embodiments of the present inventions provide a piston-actuated clutch assembly for a transmission, including: a clutch pack having a plurality of friction plates; a pressure plate at one end of the clutch pack; and interconnecting members integrated into the pressure plate, configured to selectively interlock the piston and the pressure plate. The piston is configured to actuate the clutch pack. 
         [0007]    Other exemplary embodiments of the present inventions include a vehicle transmission, having: a housing; a hydraulically actuable clutch pack having a plurality of friction plates configured to selectively engage a planetary gear set; a pressure plate at one end of the clutch pack; and interconnecting members integrated into the pressure plate, configured to selectively interlock the piston and the pressure plate. 
         [0008]    Another exemplary embodiment of the present inventions includes a method of manufacturing a clutch assembly for a transmission with reduced wear. The method includes: forming a piston; forming at least one receiving member in the piston; forming a pressure plate configured to selectively engage the piston; and forming an interconnecting member attached to the pressure plate and matable with the receiving member. 
         [0009]    One advantage of some of the techniques discussed in the present disclosure is that they reduce wear in the transmission. There is less force in the apply piston and less wear on the piston and neighboring transmission components. 
         [0010]    Another advantage of the present teachings is that they provide an inexpensive method of manufacturing a transmission with clutch assembly having reduced wear and greater durability. 
         [0011]    In the following description, certain aspects and embodiments will become evident. It should be understood that the inventions, in their broadest sense, could be practiced without having one or more features of these aspects and embodiments. It should be understood that these aspects and embodiments are merely exemplary and explanatory and are not restrictive of the inventions. 
         [0012]    The inventions will be explained in greater detail below by way of example with reference to the figures, in which the same references numbers are used in the figures for identical or essentially identical elements. The above features and advantages and other features and advantages of the present inventions are readily apparent from the following detailed description of the best modes for carrying out the inventions when taken in connection with the accompanying drawings. In the figures: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a partial cross-sectional view of a vehicle transmission with a clutch assembly according to an exemplary embodiment of the present inventions. 
           [0014]      FIG. 2  is a perspective view of the clutch assembly of  FIG. 1 . 
           [0015]      FIG. 3  is a perspective view of the pressure plate and interconnecting members of  FIG. 2 . 
           [0016]      FIG. 4  is a perspective view of the piston of  FIG. 2 . 
           [0017]      FIG. 5  illustrates a method of manufacturing a transmission according to another exemplary embodiment of the present inventions. 
       
    
    
       [0018]    Although the following detailed description makes reference to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly. 
       DETAILED DESCRIPTION 
       [0019]    Referring to the drawings,  FIGS. 1-5 , wherein like characters represent the same or corresponding parts throughout the several views there is shown various transmission clutch assemblies. The clutch assemblies include a pressure plate that is engaged by a hydraulic apply piston. There are any number of interconnecting members formed in the pressure plate between the plate and piston to selectively interlock the piston and pressure plate. The placement and configuration of the interconnecting members yields greater durability and less wear on the piston and other transmission components. 
         [0020]    Referring now to  FIG. 1 , there is shown therein a partial cross-sectional view of an automobile transmission  10 . This cross-section shows the rear section of the transmission  10  or the section closest an output shaft  20  of the transmission. The shown transmission  10  is a six speed transmission. An exemplary piston-actuated clutch assembly  30  shown in  FIG. 1  is configured to selectively engage a planetary gear set  40 . The shown gear set  40  and clutch pack  50  enables the transmission  10  to operate in neutral, a first speed and reverse. In this manner the clutch assembly  30  is sometimes referred to as a low-reverse clutch assembly. 
         [0021]    Clutch assembly  30 , as shown in  FIG. 1 , includes a hydraulically actuable clutch pack  50  having five clutch or friction plates  60  that selectively engage the ring or carrier gear  70  of the planetary gear set. A pressure plate  80  is located at one end of the clutch pack  50 . The pressure plate  80  has a series of splines  90  on an outer surface; pressure plate  80  is splined to and engages a transmission housing  100 . The splines  90  engage the transmission housing  100  and substantially prevent the pressure plate  80  from rotating. Pressure plate  80  is configured to move axially, transferring pressure to the friction plates  60  and enabling friction plates to engage the gear set  40 . Pressure plate  80  is actuated by an apply piston  110 . Pressure plate  80  includes several interconnecting members  120  attached to the pressure plate. Interconnecting members  120  are configured to engage the apply piston  110  and interlock the piston and pressure plate  80  when so engaged. Each interconnecting member  120  includes a chamfered edge. In the shown embodiment, interconnecting members  120  are rectangular and are integrally formed with the pressure plate  80 . 
         [0022]    Piston  110  is configured to apply pressure to the pressure plate  80  and actuate clutch pack  50 . Piston  110  includes receiving members  130  that are matable with interconnecting members  120 . In the illustrated embodiment of  FIG. 1 , receiving members  130  are slots or perforations at one end of the piston  110 . Piston  110  also includes an alignment member  140  on an outer surface. Alignment member  140  assists in positioning piston  110 , with respect to the transmission housing  100  during assembly. Alignment member  140  further partially prevents piston  110  from tilting with respect to the transmission housing  100 . Alignment member  140  includes a chamfered edge. In the shown embodiment, alignment member  140  is integrally formed with the piston  110 . 
         [0023]    With reference to  FIG. 1 , piston  110  is journaled onto a hub  170  of the transmission  10 . The output shaft  20  includes a ring gear  150  that is at least partially journaled onto an intermediate shaft  160  of the transmission. The transmission housing  100  includes hub  170  that is journaled onto the output shaft  20 . Bearings  180 ,  190  are fitted between the transmission hub  170  and the output shaft  20 . A cylinder  200  is in the transmission housing  100  between piston  110  and ring gear  150 . Piston  110  is nested inside cylinder  200 . Cylinder  200  includes a number of seals  210  to control fluid distribution between the piston  110  and cylinder. When the piston  110  is actuated fluid fills between cylinder  200  and piston to axially move piston toward pressure plate  80 . 
         [0024]    A set of annularly arranged coil springs  220  are fixed to the cylinder  200  and positioned against the piston  110 . Springs  220  bias piston  110  toward cylinder  200 . At rest, piston  110  is forced towards cylinder  200 . When actuated the pressure applied by fluid travelling between the piston  110  and cylinder  200  must be greater than the force applied by the coil springs  220  and seal drag to actuate the clutch pack  50 . 
         [0025]    The bottom half of the transmission  10 , illustrated in  FIG. 1 , shows the clutch assembly  30  in the off or inactive position. Piston  110  is not engaged with pressure plate  80  as shown at  230 . A park lock mechanism  240  for the transmission  10  is located at the bottom of the transmission. The park lock mechanism  240  includes a park pawl  250  and a park gear  260 . Due to the rearward position of clutch assembly  30 , piston  110  is configured to accommodate transmission components located near the output shaft  20 . The park lock mechanism  240  includes the park pawl  250  that engages the park gear  260  that is nested inside of piston  110 . Park gear  260  is fixed to ring gear  150  of the output shaft  20 . When the park pawl  250  engages gear  260  the output shaft  20  is substantially prevented from rotating. Piston  110  includes an orifice  270  through which park pawl  250  can fit. The orifice  270  is sufficiently large so that minor rotations of piston  110  do not cause the piston to touch or disrupt the park pawl  250 . 
         [0026]    In  FIG. 1 , there is also shown a speed sensing apparatus  280  for the transmission. Speed sensing apparatus  280  includes an arm  290  that has a sensor (not shown) mounted at and end of the arm. The sensor monitors the rotational speed of the output shaft  20  at ring gear  150 . Piston  110  includes an orifice  300  through which the arm  290  of the speed sensing apparatus can fit. In the illustrated embodiment, piston  110  is therefore substantially prevented from rotating to accommodate the speed sensing apparatus  280  and the park lock mechanism  240 . 
         [0027]    Referring now to  FIGS. 2-4  a piston-actuated clutch assembly  400  is shown removed from a vehicle transmission housing. Specifically with reference to  FIG. 2  there is shown therein a perspective view of a clutch assembly  400 . The clutch assembly  400  is rotated 90 degrees clockwise from the operating position. Clutch assembly  400  includes a hydraulically actuable clutch pack  410 , pressure plate  420  and piston  430 . Clutch pack  410  includes several friction plates  440 . Juxtaposed between each friction plate  440  are pressure plates  450 . Pressure plates  450  have splines  460  on the outer surfaces of each plate. At the end of the clutch pack  410  is the pressure plate  420 . Pressure plate  420  is thicker than plates  450 . Pressure plate  420  also has a series of splines  460  on the outer surface. Pressure plate  420  is configured to engage piston  430 . 
         [0028]    As shown in  FIG. 3 , formed in the pressure plate  420  are three interconnecting members  470 . Interconnecting members  470  interlock piston  430  and pressure plate  420 . Members  470  prevent piston  430  from substantially rotating with respect to the transmission housing. Members  470  also properly align piston  430  with pressure plate  420  during engagement. In the shown embodiment, interconnecting members  470  are rectangular lugs. Interconnecting members  470  are chamfered on all five surfaces of the lug. The face of the lug  470  is chamfered with respect to the side surfaces; each side surface is respectively chamfered as well. The radius of chamfer can be, e.g., 30 degrees. Lugs  470  extend axially along one end of the pressure plate  420 . Interconnecting members  470  are formed integrally with the pressure plate  420 . In this embodiment, interconnecting members  470  are formed of powdered metal processes with the pressure plate. In other embodiments interconnecting members  470  are welded onto the face of pressure plate. Interconnecting members  470  are configured of a sufficient cross-sectional area to sustain forces from the piston  430 . Since these interconnecting members  470  are formed on the pressure plate  420  and interconnect the piston to the housing  100  through the pressure plate, as opposed to directly connecting the piston  430  to the housing  100 , the members undergo much less force during torque reversals. 
         [0029]    Referring now to  FIG. 4 , there is shown therein a perspective view of the piston  430 . Piston  430  includes three receiving members  480  that are matable with the interconnecting members  470  of the pressure plate  420  (as shown in  FIG. 3 ). Receiving members  480  are axial slots located at the end of the piston. Slots  480  are designed to fit interconnecting members  470  therein. Slots  480  are longer than the interconnecting members  470  so that piston  430  does not necessarily engage interconnecting members  470  at surface  490  of piston. This allows a path for lube oil to exit the piston when the piston is applied. Slots  480  are also of a rectangular configuration. In one embodiment, slots  480  include chamfered or beveled edges to facilitate the interaction between interconnecting members and piston. 
         [0030]    Also shown in  FIG. 4  are several orifices  500  (or holes) in the body of the piston. These holes  500  can be used to accommodate non-rotating transmission components such as the park pawl  250  and speed sensor apparatus  280 , as shown in  FIG. 1 . Piston  430  further includes protrusions  510  on the outer surface. Protrusions  510  act as alignment members or features for the piston. Alignment member  510  assists in positioning the piston  430  in the transmission housing during assembly. Alignment member  510  can also prevent the piston from tilting with respect to the housing. Piston  430  includes an orifice  520  at the other end to enable the output shaft to fit therethrough. 
         [0031]    Referring now to  FIG. 5 , there is shown therein a method of manufacturing a transmission with reduced wear  600 . The steps of the method include forming a piston  610 . Piston can be formed using any number of forming techniques such as, e.g., die casting, machining, and extrusion. The next step is forming at least one receiving member in the piston  620 . Receiving slot can be rectangular or any other shape. Forming a pressure plate configured to selectively engage the piston is also included in the method  630 . Pressure plate can be formed using any number of forming techniques such as, e.g., die casting, machining, and extrusion. Also the method includes forming an interconnecting member attached to the pressure plate and matable with the receiving member  640 . Interconnecting member can be rectangular or of any other shape that is compatible or matable with the receiving member. Interconnecting member can be formed using any number of forming techniques such as, e.g., die casting, machining, and extrusion. In one embodiment, the method includes forming a chamfer on an edge of the interconnecting member. Chamfer can be, for example, machined into the interconnecting member post casting or chamfer can be included in the mold cavity for the pressure plate. 
         [0032]    In the shown embodiments the transmission housing, pressure plate, interconnecting members and piston are composed of an aluminum alloy. These components are formed via powder-metal processes, die casted and these components can also be machined, if needed. Any one of these components can be composed of other materials including, e.g., steel or titanium alloys. 
         [0033]    Though the illustrated embodiments relate to clutch assemblies that selectively engage a pressure plate and piston, it should be appreciated that the disclosed interconnecting members and receiving members can be used for selective engagement of any number of transmission components. Moreover, interconnecting members and receiving members can be of any number of shapes including, circular and triangular configurations. 
         [0034]    For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the written description or claims are approximations that can vary depending upon the desired properties sought to be obtained by the present inventions. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
         [0035]    It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural referents unless expressly and unequivocally limited to one referent. Thus, for example, reference to “an interconnecting member” includes two or more different interconnecting members. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items. 
         [0036]    It will be apparent to those skilled in the art that various modifications and variations can be made to the methodologies of the present disclosure without departing from the scope of its teachings. Other embodiments of the inventions will be apparent to those skilled in the art from consideration of the specification and practice of the teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only. 
         [0037]    While the best modes for carrying out the inventions have been described in detail, those familiar with the art to which these inventions relate will recognize various alternative designs and embodiments for practicing the inventions within the scope of the appended claims.