Patent Publication Number: US-2007119043-A1

Title: Thermoplastic automatic transmission hydraulic control module

Description:
BACKGROUND OF THE INVENTION  
      This invention relates generally to automatic transmission hydraulic control systems, and more particularly, to a hydraulic control module formed from a filled thermoplastic material.  
      Known automatic transmissions include planetary gear sets, a plurality of friction elements, for example, clutches and bands, that control the planetary gear sets, and a hydraulic control system to control the friction elements such as the clutches and bands. The hydraulic control system includes transmission fluid, a pump to pump the transmission fluid, and a hydraulic control module that includes a plurality of fluid passageways through which the transmission fluid flows.  
      Typically, the hydraulic control module is fabricated from a metal, for example, aluminum, usually by casting methods. The fabrication includes machining the main body of the hydraulic control module to obtain the required tolerances for any sealing surfaces and any mounting holes for any attached valves. Machining aluminum castings requires machine set-up time, machining time, and cleaning of the machined part to remove all debris. Also, aluminum castings can have porosity that can cause high scrap rates. Further, die cast tooling often requires refurbishing at about 100,000 part intervals which adds to the maintenance cost of a fabricating system.  
     BRIEF DESCRIPTION OF THE INVENTION  
      In one aspect, an automatic transmission hydraulic control module assembly is provided. The hydraulic control module includes a main body having a first side and an opposing second side. The main body includes a plurality of fluid passage cavities in the first side, and at least one bore extending from one of the fluid passage cavities through the main body and through the second side. The main body is formed from a filled thermoplastic material that includes at least one filler.  
      In another aspect, a method of fabricating an automatic transmission hydraulic control module assembly is provided. The hydraulic control module assembly includes a main body, and the method includes the steps of providing a mold having a predetermined shape of the main body, injecting a thermoplastic material into the mold to form the main body, and removing the injection molded main body from the mold. The main body has a first side and an opposing second side and includes a plurality of fluid passage cavities in the first side and at least one bore extending from one of the fluid passage cavities through the main body and through the second side. The thermoplastic material includes at least one filler. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded schematic illustration of an automatic transmission hydraulic control module assembly in accordance with an embodiment of the present invention.  
       FIG. 2  is an enlarged bottom schematic illustration of a portion of the main body of the hydraulic control module assembly shown in  FIG. 1 .  
       FIG. 3  is an enlarged bottom schematic illustration of another portion of the main body of the hydraulic control module assembly shown in  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A hydraulic control module assembly for an automatic transmission is describe below in detail. The hydraulic control module assembly includes a main body formed from a reinforced thermoplastic material and a cover plate that can be formed from either metal or a reinforced thermoplastic material. A thermoplastic main body that is optimized for injection molding processes results in lower cost due to the elimination of secondary processes such as machining that are required with a main body fabricated from metal, for example, aluminum. The thermoplastic main body typically weighs 25% to 40% less than an aluminum part. Also, the geometry of thermoplastic designs can be modified to add stiffness where required, such as ribs in high stress areas. In addition, the thermoplastic main body is inherently clean and free of debris since machining is not required to meet dimensional tolerances. Also, normal tool life for injection molded thermoplastic parts is about ten times the normal life of tools used for aluminum die-cast parts.  
      Referring to the drawings,  FIG. 1  is a top schematic illustration of an on exemplary embodiment of a automatic transmission hydraulic control module assembly  10  that includes a main body  12  and a cover plate  14 . Main body  14  includes a bottom side  16  (first side) and a top side  18  (second side). A plurality of fluid passage cavities  20  extend into bottom side  16  of main body  12 . At least one bore  22  is positioned in one of the fluid passage cavities  20  that extends through main body  12  from fluid passage cavity  20  and through top side  18 . Bore  22  provides fluid communication path between fluid passage cavity  20  and top side  18  of main body  12 . Main body  12  is formed, for example, by injection molding, from a fiber reinforced thermoplastic material.  
      Cover plate  14  is coupled to bottom side  16  to seal fluid passage cavities  20  to form fluid passages. In one embodiment, a sealing gasket  24  is positioned between cover plate  14  and bottom side  16  of main body  12 . Cover plate  14  can be fabricated from metal, for example, aluminum, or from a fiber reinforced thermoplastic material. Typically, when cover plate  14  is fabricate from metal, cover plate  14  is coupled to main body  12  with fasteners, and sealing gasket  24  is used to create a seal between cover plate  14  and bottom side  16  of main body  12 . In alternate embodiments, cover plate  14  is formed from a reinforced thermoplastic, and can be coupled to main body  12  by fasteners, vibration welding, sonic welding, laser welding, adhesive welding, and a snap fit. In another alternate embodiment, main body  12  and cover plate  14  are integrally molded together as one piece. Coupling a thermoplastic cover plate  14  to main body  12  by fasteners or a snap-fit typically necessitates the use of sealing gasket  24 . However, coupling a thermoplastic cover plate  14  to main body  12  by vibration welding, sonic welding, laser welding, and adhesive welding can eliminate sealing gasket  24 . Further, gasket  24  can be molded into a thermoplastic cover plate  14  using, for example a two shot molding process, to eliminate a component from the assembly and ensure proper placement of the gasket when using fasteners or a snap-fit coupling method.  
      Suitable thermoplastic resins for use in molding main body  12  and cover plate  14  include, but are not limited to, polyamids, for example semi-crystalline polyamids, such as, nylon 66 and nylon 6 commercially available from General Electric Company, polyphenylene sulfides, polyphthalamides, polyethyl imides, and mixtures thereof. The reinforcing fillers used to reinforce the thermoplastic resin can be in the form of particles and/or fibers. Suitable fillers for use in reinforcing the thermoplastic resins include, but are not limited to metal fibers, metalized inorganic fibers, metalized synthetic fibers, glass fibers, graphite fibers, carbon fibers, ceramic fibers, mineral fibers, basalt fibers, inorganic fibers, aramid fibers, mineral fillers, and mixtures thereof. Suitable, non-limiting, examples of mineral fillers include barytes, barium sulfate, asbestos, barite, diatomite, feldspar, gypsum, hormite, kaolin, mica, nepheline syenite, perlite, phyrophyllite, smectite, talc, vermiculite, zeolite, calcite, calcium carbonate, wollastonite, calcium metasilicate, clay, aluminum silicate, talc, magnesium aluminum silicate, hydrated alumina, hydrated aluminum oxide, silica, silicon dioxide, titanium dioxide, and mixtures thereof. In one embodiment, the thermoplastic material includes about 20% to about 80% by weight of reinforcing fillers, and in another embodiment from about 30% to about 55% by weight of reinforcing fillers.  
      In the exemplary embodiment, automatic transmission hydraulic control module assembly  10  also includes a plurality of valves  30 , for example solenoid valves, coupled to top side  20  of main body  12 . Each valves  30  is in fluid communication with one of the plurality of fluid passage cavities  20  through one of the plurality of bores  22 .  
      Referring also to  FIGS. 2 and 3 , thermoplastic main body  12 , in alternate embodiments, include one or more strengthening ribs  32  inside of fluid passage cavities  20 . Strengthening ribs  32  add stiffness to high stress areas of main body  12  for added strength.  
      While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.