Abstract:
An automotive car and truck transmission clutch module friction plate and a method of manufacture thereof is provided wherein the friction plate is fabricated from a polymeric material, which is less expensive and lighter than comparable steel friction plates.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/705,581, filed Aug. 4, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the present invention is that of friction plates. More particularly the present invention relates to friction plates used in wet friction clutch modules in automotive transmissions for car and truck vehicles.  
       BACKGROUND OF THE INVENTION  
       [0003]     Currently, most if not all friction plates used in automotive transmissions are fabricated from steel stampings. Steel as a commodity has most recently experienced a high demand that has highly escalated its cost. To meet various environmental, economic, and national defense concerns, there has been an increased demand for fuel efficiency in automotive vehicles. Accordingly, there is a desire to achieve weight and cost savings in vehicle components.  
       SUMMARY OF THE INVENTION  
       [0004]     To make manifest the above noted desires, a revelation of the present invention is brought forth. In a preferred embodiment, the present invention provides a friction plate and a method of manufacture thereof wherein the friction plate is fabricated from a polymeric material, which is less expensive and lighter than comparable steel friction plates.  
         [0005]     Other features of the invention will become more apparent to those skilled in the art as the invention is further revealed in the accompanying drawings and detailed description of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIGS. 1 and 1 A are front elevational views of preferred embodiment friction plates of the present invention.  
         [0007]      FIG. 2  is a side elevational view of a core plate utilized in the friction plate shown in  FIG. 1 .  
         [0008]      FIG. 3  is an enlargement of the core plate shown in  FIG. 2  and is a partial sectional view of a friction disc shown in  FIG. 1 .  
         [0009]      FIGS. 4A-4C  are partial side elevational views of a portion of a friction pack module utilizing various embodiments of friction plates of the present invention.  
         [0010]      FIG. 5  is a view similar to  FIG. 1  of an alternative preferred embodiment friction plate of the present invention.  
         [0011]      FIG. 6  is an enlarged partial sectional view showing an interface between a core plate and a backing. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]     A friction plate  7  is provided in  FIG. 1 . The friction plate  7  has an annular core plate  10 . Preferably, the core plate  10  is fabricated from a polymeric material. A preferred material is a semi-crystalline thermo plastic such as nylon or other suitable plastic. The core plate material may be reinforced with glass fibers or other materials for added strength and/or heat capacity. Thermoset plastic material may also be used.  
         [0013]     The core plate  10  has an integral reduced thickness rim portion  14 . The core plate  10  may be fabricated from a sheet material or may be injection, compression, or extrusion molded. Typical core plates  10  have a thickness ranging from 0.76-1.20 mm with an outer diameter of 75 to 225 mm depending upon the application. Core plates outside of this size range may also be considered for this plastic design.  
         [0014]     The inner diameter of the typical core plate has a series of radially inward facing spline teeth  16  ( FIG. 1A ). Some core plate applications will have radially outward facing spline teeth instead of inward facing spline teeth. The spline teeth  16  provide a torsional interface for the friction plate  7  with a rotating member (not shown). Further, some applications may not have any spline teeth at all.  
         [0015]     Connected with the rim  14  is a friction facing  18 . The friction facing may be on both sides of the core plate, or only on one side. The friction facing  18  is typically a cellulosic fiber base friction material, although other friction materials such as sintered metals, ceramics, or foam may also be used. As shown, the friction facing  18  is a paper fiber based friction material. The friction facing may be a continuous ring or may be fabricated from individual arcuate segments arranged radially. The preferred number of segments is 3-5. The segmenting of the facing  18  provides significant savings in friction material cost. The individual arcuate segments  22  have interlocking tab  24  and slot  26  end portions. Another segmented facing design provides for independent or non-interlocking facing segment arcs and can provide an oil flow path between facing segments. The friction base facing  18  can be connected with the rim  14  by adhesives or by other means as described herein.  
         [0016]     In other embodiments the facing (full ring or segments) is first placed in open halves of an injection mold. The mold halves are closed. In a preferred application, the mold is then pressurized to hold the facing in position against a surface of the mold half. In an alternate application, the facing may be held by fixtures and or by a vacuum. Under relatively high temperatures and pressure, the molten material of the core plate  10  then injected between the mold halves. As the plastic material solidifies and forms the core plate geometry, the fibers  108  of the facing  18  are partially encapsulated by the material  112  of the core plate  10 , creating a boundary layer  110  and a mechanical bond between facing and core plate. To facilitate the connection of the core plate material to the facing, the facing can have a polymeric backing or be impregnated with a polymeric saturate. In either case, the polymeric backing or saturate should have a melting temperature within 22.2 degrees C. (40 degrees F.) of the material of the core plate.  
         [0017]     In another embodiment, the friction facing  18  is welded on. The friction facing  18  can be welded by vibration welding, spin welding, or ultrasonic welding or staking or other suitable technique. The friction facing  18  can have a polymeric backing to aid in its attachment by welding. In another embodiment, the friction facing  18  can be impregnated with a polymeric material to facilitate the welding operation. Both the polymeric saturate and backing should have melting temperatures as previously mentioned.  
         [0018]     In another embodiment the facing  18  is connected with the rim  14  by hot platen bonding. This process can be achieved in several ways. First, this process utilizes heated platens to transfer heat through facings to achieve localized surface melting of core plate, which when under pressure, allows for a bond between the facing and core plate, as the core plate plastic cools. The heat can be applied to the facings seated on both sides of the core plate or the heat can be applied to one facing only and join both facings to the core plate rim. Second, a bonding process may use plastic core plates pre-heated to achieve localized surface melting, and then transferred into a bond press where facing is positioned to core plate, and the bond is achieved under pressure. Additionally adhesive materials may be added to either facing or core plate to facilitate and/or improve bonding in all the aforementioned bonding processes.  
         [0019]     Referring to  FIG. 4A , a partial view of a clutch pack module  27  is provided having two separate plates  34 . When the separator plates  34  engage with the friction plate facings, the separator plates  34  are separated by a first distance  36 . The thickness of the spline teeth  16  is greater than the thickness of the rim  14 , but equal to the final design thickness  36  of the finished friction plate, to provide more strength to the spline teeth  16 . Referring to  FIG. 4B  a clutch module  40  having a friction plate  47  has spline teeth  46  that have a thickness less than the first distance  36 . Referring to  FIG. 4C  a clutch module  50  has a friction plate  57  having spline teeth  56  that are greater width than the first distance  36 .  
         [0020]     Referring to  FIG. 5 a  friction plate  67  is provided wherein the friction facing  71  have a plurality of radially extending oil grooves  74 . The oil grooves  74  can be formed on the facing  71  before connection with the core plate. In another embodiment, the oil grooves  74  can be cut after connection of the friction facing  71  with the underlying core plate. The cut oil grooves  74  can also extend into the core plate.  
         [0021]     In another embodiment, the oil grooves  74  can be formed in the facing  71  and optionally in the core plate in an injection molding operation. A mold cavity will be machined with a rib to impart a slightly oversize oil groove to compensate for any spring back in the material. In another embodiment, the oil grooves  74  can be formed ultrasonically in the facing  71  and underlying core plate when the facing is ultrasonically welded to the core plate  10 .  
         [0022]     In another embodiment, the oil grooves can be formed in alternative geometries, such as single direction parallel, double direction parallel (criss-crossed), non-standard linear or non-linear pattern. Oil grooves may extend fully through facing, allowing a through oil passage, or may terminate short of outer diameter to create a dead-end groove.  
         [0023]     In another embodiment, the oil grooves may be formed through the use of the plastic injection molding process (insert loading as described previously in this document), whereas the individual, non-connected arcuate segments are positioned with a defined gap between segments into mold, with the molding process forming the core plate and achieving the required bond between friction material and core plate.  
         [0024]     While preferred embodiments of the present invention have been disclosed, it is to be understood it has been described by way of example only, and various modifications can be made without departing from the spirit and scope of the invention as it is encompassed in the following claims.