Abstract:
A direct replacement boost valve assembly for use in combination with a pressure regulator valve within the valve body of an automatic transmission is disclosed. The boost valve assembly functions to boost line pressure during high load conditions in response to torque signal fluid pressure, which is proportional to engine torque. The present boost valve assembly is comprised of hard-anodized aluminum valve pistons, which are disposed within a wear resistant aluminum sleeve for maximum service longevity. Annular lubrication grooves formed in the valve pistons which comprise the boost valve assembly retain a lubricating film of transmission fluid to center the valve pistons within the sleeve ensuring accurate operation and reducing mechanical wear. The present valve sleeve features a fluid inlet port system, which increases the delivery of torque signal fluid pressure to the boost valve in order to restore its function to original factory boost ratios and specifications.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 60/350,083 filed Jan. 23, 2002 now abandoned, entitled Boost Valve Assembly. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates generally to the field of hydraulic circuits utilized in automatic transmission systems and, more particularly, to a replacement Boost Valve Assembly for use in a General Motors 4T65E transmission, which is utilized to boost hydraulic pressure during high load conditions. 
     Automatic transmission systems of the prior art have a hydraulic circuit sub-system which includes at least a hydraulic pump, a valve body having fluid conducting passages or circuits, input and exhaust ports formed within the fluid circuits, and a plurality of spool valves so-called because of their resemblance to sewing-thread type spools. Such valves are comprised of generally cylindrical pistons having control diameters or lands formed thereon, which alternately open and close the ports to the fluid circuits to regulate the flow and pressure of automatic transmission fluid (hereinafter “ATF”) in order to actuate different components of the transmission. It will be understood that in describing hydraulic circuits, ATF usually changes names when it passes through an orifice or control valve in a specific fluid circuit. 
     In the prior art, the Line Boost Valve is acted upon by Torque Signal (hereinafter “TS”) pressure and operates against the Reverse Boost Valve and Pressure Regulator spring force to increase line pressure during high load conditions. The Line Boost Valve is actuated in response to changes in throttle position such as during upshifts. 
     The original equipment manufacture (hereinafter “OEM”) Line Boost Valve and Reverse Boost Valve are comprised of steel valve pistons that reciprocate within an aluminum valve sleeve. The mechanical friction of these dissimilar materials causes premature wear, leakage of torque signal pressure, and results in improper upshifting and delayed engagement upon shifting into the Reverse gear range. 
     Thus, the present invention has been developed to resolve this problem and other shortcomings of the prior art. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is a direct replacement Boost Valve Assembly for use in combination with a Pressure Regulator Valve within the valve body of an automatic transmission, which functions to boost line pressure during high load conditions in response to Torque Signal fluid pressure, which is proportional to engine torque. 
     The present Boost Valve Assembly is comprised of hard-anodized aluminum valve pistons, which are disposed within a wear resistant aluminum sleeve for maximum service longevity. Annular lubrication grooves in the present Boost Valve Assembly provide a lubricating film of ATF to center the valve pistons within the sleeve to ensure accurate operation and to reduce wear. The present valve sleeve also features improved inlet ports to enhance the delivery of TS fluid pressure in order to restore the function of the OEM valve body to its original factory boost ratios and specifications. 
     Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of the present invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures, wherein: 
     FIG. 1 is a perspective view of the OEM valve body component of a General Motors  4 T65E transmission labeled Prior Art and indicating the location of the OEM Line Boost Valve and the OEM Reverse Boost Valve shown in exploded view; 
     FIG. 2 is a cross-sectional view of the OEM Line Boost Valve and the OEM Reverse Boost Valve shown in their functional positions within a section of the valve body; 
     FIG. 3 is a partial cross-sectional view of the present Boost Valve Assembly showing details of the construction thereof; 
     FIG. 4A is a longitudinal cross-section of the valve sleeve of the present invention; 
     FIG. 4B is a cross-sectional view of the present valve sleeve taken along section line  4 B— 4 B of FIG. 4A; 
     FIG. 4C is a cross-sectional view of the present valve sleeve taken along section line  4 C— 4 C of FIG. 4A; 
     FIG. 5A is a longitudinal cross-section of the present Boost Valve Assembly shown in its closed position within the valve body; and 
     FIG. 5B is a longitudinal cross-section of the present Boost Valve Assembly shown in its open position within the valve body. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Prior to describing the present invention in detail it may be beneficial to briefly review the structure and function of the prior art Line Boost Valve and Reverse Boost Valve of the General Motors (hereinafter “GM”) 4T65E transmission. With reference to the drawings there is shown therein a Line Boost Valve, indicated generally at  100 , and a Reverse Boost Valve, indicated generally at  200 , in accordance with the prior art and illustrated in FIG.  1 . The OEM Line Boost Valve  100  and the Reverse Boost Valve  200  are shown in exploded view and removed from their functional position within a mating bore as at  105 , which is machined into the valve body, indicated generally at  110 , of the GM 4T65E transmission. 
     In the prior art the Line Boost Valve  100  comprises a cylindrical valve piston  102  disposed within the valve sleeve  106 . The Reverse Boost Valve  200  comprises a generally cylindrical valve piston  104  also disposed within the same valve sleeve  106 . The valve pistons  102 ,  104  are arranged coaxially in end-to-end relation within the bore  105  and secured within the sleeve  106  by an end plug  108  captured by a retaining clip  109 . It will be understood that the Line Boost Valve  100  and the Reverse Boost Valve  200  act in conjunction with the Pressure Regulator Valve  120  including compression spring  112  and isolator spring  114  to regulate line pressure within the hydraulic circuits of the GM 4T65E transmission. 
     In operation the Line Boost Valve  100  responds to TS fluid pressure (as depicted in FIG.  2 ), which is routed from the Pressure Control Solenoid (PCS) (not shown). Torque Signal fluid pressure as at  150  is generally proportional to engine torque and strokes the Line Boost Valve  100  against the Pressure Regulator isolator spring  114  (i.e. to the left in FIG.  2 ). The isolator spring  114  then exerts the force from TS fluid pressure to the Pressure Regulator Valve  120  to increase line pressure. The Line Boost Valve  100  is also responsive to Park, Reverse, Neutral fluid pressure and to Low/ 1   st  gear fluid pressure when these gear ranges are selected to increase line pressure. 
     In the prior art Line Boost Valve  100  and Reverse Boost Valve  200  including the valve pistons  102 ,  104  are fabricated from steel material and the valve sleeve  106  is constructed of aluminum. The mechanical friction between these dissimilar materials during operation results in premature wear within the valve sleeve  106  as shown in FIG.  2 . Excessive wear between the sleeve  106  and the valve piston  104  as at area “A” allows TS pressure as at  150  to leak past the Line Boost Valve  100 . Because TS pressure is used to boost line pressure during high load conditions such as during upshifts, leakage of TS pressure results in a so-called “soft” upshift, which is especially noticeable during the shift from first to second gear in the GM 4T65E transmission. 
     Excessive wear between the sleeve  106  and valve piston  102  as at area “B” (FIG. 2) allows Park, Reverse, and Neutral pressure (hereinafter “PRN” pressure) as at  160  to leak past the Reverse Boost Valve  200 . PRN pressure is used to boost line pressure in Park, Reverse, and Neutral. When PRN pressure leakage occurs the result is delayed engagement in these gear ranges. The delayed engagement is most noticeable in the Reverse gear range. Thus, the present invention has been developed to resolve the hereinabove described problems and will now be described. 
     Referring now to FIG. 3 there is shown therein an improved Boost Valve Assembly in accordance with the present invention, indicated generally at  10 . The present Boost Valve Assembly  10  is comprised of a PRN valve piston  12 , a TS valve piston  14 , a modified valve sleeve  16 , and an end plug  18  being arranged for installation within the bore  105  as a direct OEM replacement for the Line Boost valve  100  and Reverse Boost Valve  200  of the prior art. 
     In the preferred embodiment both the PRN valve piston and the TS valve piston  12 ,  14  are constructed of ASTM 6262-T8/T9 aluminum, 6061-T6 aluminum in accordance with the American Society of Testing and Materials (ASTM) or other suitable materials for this application. Each valve piston  12 ,  14  is provided with a hard anodized coating to yield +0.0008/−0.0004 build up per surface, which significantly reduces wear and increases service longevity. 
     As shown in FIG. 3, the PRN valve piston  12  includes a spring guide diameter  20  of sufficient size to support the OEM isolator spring  114  in the position shown (FIG.  2 ). The terminal end  20   a  of spring guide diameter  20  is chamfered to avoid entanglement with isolator spring  114  during installation and to prevent abrasion damage to spring  114  during cycling. An opposite end of spring guide diameter  20  is integrally connected to the major diameter  22 , which serves as a seating surface for isolator spring  114 . In the preferred embodiment major diameter  22  includes at least one annular groove  24  formed therein to a predetermined depth. Annular groove  24  functions to distribute fluid pressure across the circumference of the major diameter  22  by filling with ATF during operation thereby preventing side loading (i.e. lateral movement) of the valve piston  12  as ATF surges into the valve chamber. Thus, the annular groove  24  effectively centers the PRN valve piston  12  within sleeve  16  substantially reducing friction and wear at area “B” within bore  105  (FIG.  2 ). 
     The major diameter  22  is integrally connected via relief groove  26  to the guide diameter  28  formed in coaxial relation thereto. Guide diameter  28  also functions to center the valve piston  12  within the sleeve  16  and provides a contact surface at the end face thereof for the TS valve piston  14 . In the preferred embodiment guide diameter  28  has been shortened relative to the OEM design to compensate for an increased overall length of the present TS valve piston  14 . 
     The TS valve piston  14  is a generally cylindrical construction, which resides in the central counterbore  32   c  of the valve sleeve  16 . TS valve piston  14  also includes a plurality of annular grooves  24  formed therein to a predetermined depth, which fill with ATF during operation to prevent side loading and to provide centering of the TS piston  14  within sleeve  16  reducing friction and wear. 
     The overall length of the TS valve piston  14  as at dimension “L” (FIG. 3) has been substantially increased in comparison to the OEM Line Boost Valve  104  to maximize the contact surface area between the TS valve piston  14  and the mating sleeve  16  to minimize any leakage potential. The increased overall length of the TS valve piston  14  also permits the maximum number of annular grooves  24 , which serve to center the piston  14  within sleeve  16  and to resist side loading as described hereinabove. 
     It can be seen that the TS piston  14  includes generally convex protuberances  14   a ,  14   b  integrally formed on the opposite end faces thereof. In general, the hemispherical protuberances  14   a ,  14   b  provide an optimal ATF reaction surface having an increased surface area, which improves the response and accuracy of the present valve assembly  10 . In addition, the protuberance  14   a  provides a contact surface for the transfer of ATF pressure from the TS valve piston  14  to the PRN valve piston  12 . The protuberance  14   b  also serves to stop the TS valve piston  14  as it comes into contact with the end plug  18  and to provide an improved reaction surface for ATF entering from the TS fluid circuit as at  150  (FIG.  2 ). 
     FIGS. 4A-4C illustrate the present valve sleeve  16  showing its structural features in further detail. The valve sleeve  16  is constructed of 4032-T651/T86 aluminum. This type of aluminum material has been selected after extensive testing and has been demonstrated to provide optimal wear characteristics when used in combination with the hard anodized finish applied to the valve pistons  12 ,  14  in accordance with MIL-A-8625, Type III, Class 2. 
     Referring to FIG. 4A sleeve  16  is comprised of a cylindrical body  30  including a central bore  32  having multiple counterbores  32   a ,  32   b ,  32   c , and  32   d  being dimensioned to receive the major diameter and guide diameter  22 ,  28  of the PRN valve piston  12 , the TS valve piston  14 , and the end plug  18  respectively. In the preferred embodiment the axial length of the counterbore  32   b  has been increased in comparison to the OEM sleeve  106  to provide enhanced support for the guide diameter  28  of PRN valve piston  12 . Sleeve  16  also includes a plurality of ATF distribution channels  42 ;  44 , and  46  formed about its circumference, which function as conduits for the delivery of ATF to the PRN fluid circuits, the Low- 1   st  fluid circuit  170 , and the Torque Signal circuit  150  respectively. Each channel  42 ,  44 , and  46  includes a plurality of fluid ports  45  formed therein at predetermined radial locations, which extend through the sleeve body  30  in fluid communication with the counterbores  32   a  and  32   c  to increase the flow of ATF during valve operation. 
     In the preferred embodiment an array of six ports  45  radially oriented at 60 degree angles to each other are formed within each channel  42 ,  44 , and  46  as shown in FIG.  4 B. In this configuration the flow of ATF is distributed via channels  42 ,  44 ,  46  to ports  45  under line pressure and enters the valve sleeve  16  about the entire circumference thereof to ensure even lubrication of the present valve pistons  12 ,  14  thereby reducing premature wear at areas “A” and “B” as described hereinabove (FIG.  2 ). 
     The sleeve body  30  also includes a retaining clip aperture  50  formed therein for the reinsertion of the OEM retaining clip  109  into the retaining clip groove  19  of the end plug  18  as most clearly shown in FIG.  4 C. In the preferred embodiment aperture  50  is constructed by machining a pair of horizontally opposed slots  50   a ,  50   b  through the sidewall of sleeve  16  as illustrated. 
     With reference to FIGS. 5A-5B, the operation of the present Boost Valve Assembly  10  will now be described. The present Boost Valve Assembly  10  is normally spring-biased to the rest position as shown in FIG. 5A by the force of the Pressure Regulator isolator spring  114 . During high load conditions such as upshifting, the Boost Valve Assembly  10  responds to TS fluid pressure as at  150  routed from the Pressure Control Solenoid (not shown). TS fluid pressure is proportional to engine torque and strokes the Boost Valve Assembly  10  against the force of the Pressure Regulator isolator spring  114  as shown in FIG.  5 B. The isolator spring  114  continues to exert the force generated by TS fluid pressure to the Pressure Regulator Valve  120  thereby increasing its output. Thus, the Pressure Regulator Valve  120  increases line pressure as throttle position and engine torque increase. When the upshift is completed and line pressure returns to normal operating levels, the Boost Valve Assembly  10  returns to the rest condition as shown by directional arrows in FIGS. 5A-5B. 
     Still referring to FIGS. 5A-5B, the PRN valve piston  12  is also acted upon by PRN fluid pressure as at  160  from the manual valve (not shown) and by Low/1 st  fluid as at  170  and moves against the isolator spring  114  to actuate the valve assembly when these gear ranges are selected. This increases line pressure in Park, Reverse, Neutral, and Manual 1 st  gear. 
     Although not specifically illustrated in the drawings, it should be understood that additional equipment and structural components will be provided as necessary and that all of the components described above are arranged and supported in an appropriate fashion to form a complete and operative Boost Valve Assembly incorporating features of the present invention. 
     Moreover, although illustrative embodiments of the invention have been described, a latitude of modification, change, and substitution is intended in the foregoing disclosure, and in certain instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of invention.