Abstract:
A pressure regulator valve assembly for an automatic transmission that provides continuous hydraulic fluid flow into the torque converter charge circuit in all operating modes to prevent torque converter overheating is disclosed. The present pressure regulator valve assembly includes a valve piston subassembly having an encapsulated internal check valve in fluid communication with the line pressure circuit, which diverts hydraulic fluid to the torque converter charge circuit responsive to a lower fluid pressure (i.e. 2-5 psi range) than is normally required to fill the torque converter. When the vehicle engine is shut off, the internal check valve also prevents hydraulic fluid from draining back through the pressure regulator valve to maintain an adequate fluid level in the torque converter. In addition, an internal balance boost circuit has been added to the valve piston subassembly to assist the balance circuit in counteracting electronic pressure control (EPC) solenoid pressure.

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. 60/361,402 filed Mar. 5, 2002, entitled Pressure Regulator Valve. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to automatic transmission systems and, more particularly, to an improved Pressure Regulator Valve Assembly for Ford E40D transmissions. 
     Automatic transmission systems of the prior art have a hydraulic circuit subsystem 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 so-called spool valves 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”). It will be understood that in describing hydraulic fluid circuits, ATF usually changes names when it passes through an orifice or control valve in a specific circuit. 
     Pumps in automatic transmission systems are generally positive displacement pumps driven by the engine of the vehicle wherein the transmission is installed. A positive displacement pump is one, which has the same output per revolution regardless of pump speed or pressure already developed in the system. Thus, it is necessary to regulate ATF pressure so it does not get too high or too low and damage other components. 
     A basic pressure regulator employs a piston and a spring that compresses at a specific pressure to allow some ATF to flow back to the pump reservoir or sump bypassing the hydraulic circuits and reducing pressure. By using a pressure regulator with a spring calibrated to a pressure lower than the pump&#39;s output, constant pressure can be maintained in the system during operation. 
     Vehicles with Ford E40D transmissions often have service complaints of the torque converter overheating and high line pressure, which is attributable, in part, to the design of the original equipment manufacture (hereinafter “OEM”) Main Regulator Valve. When in the Park gear range and at low speeds, the Ford E40D Main Regulator Valve is designed to feed adequate ATF to the torque converter and transmission cooler circuits. However, at higher speeds and/or under high EPC solenoid pressure, ATF flow to the torque converter charge circuit and cooler circuits can be shut down by the Main Regulator Valve resulting in torque converter overheating. 
     Another contributing factor to the torque converter overheating problem is that the OEM balance circuit for the Main Regulator Valve does not provide sufficient ATF flow to properly counteract EPC solenoid pressure, which tends to keep the Main Regulator Valve in the high line position restricting ATF feed to the torque converter and cooler circuits. 
     There are several known prior art patents that are available in the field and their discussion follows. One example is U.S. Pat. No. 4,271,939 to Iwanga et al., which discloses a hydraulic control system for a torque converter for ensuring release of the lock-up condition of the torque converter. This is accomplished by providing a flow restrictor in the hydraulic working fluid supply passage for the torque converter to make the flow resistance of the passage equal to or larger than the flow resistance of the hydraulic working fluid supply passage for the lock-up control chamber. In this control system a first or feed passageway communicates with a source of pressurized fluid and with a torque converter chamber, a second or discharge passageway communicates with the torque converter chamber and a third passageway communicates with a lock-up control or clutch chamber of the lockup clutch. A lockup control valve communicates with the same source of pressurized fluid and with the third passageway. The first passageway is provided with the flow restrictor. With the provision of the flow restrictor, the disengagement of the lockup clutch will be assured upon pressurization of the third passageway. 
     Another example is U.S. Pat. No. 4,618,036 to Ideta, which discloses a hydraulic control system for the lockup clutch of a torque converter wherein release of a lockup clutch is ensured even when the discharge flow rate of the pump is low. This control system comprises a pump driven by an engine to discharge fluid, a torque converter having a lockup clutch with a lockup clutch piston movable to a clutch released position when fluid pressure within a lockup release chamber is higher than fluid pressure within a working chamber in the torque converter cavity, a line pressure regulator valve and an orifice, which provides a restricted flow communication between the torque converter and the pump even when line pressure generated by the line pressure regulator valve is lower than a predetermined value. 
     The Ideta (&#39;036) patent utilizes cutouts  20  formed on the land  32   d  of the first spool  32  (FIG. 1) on the line pressure regulator valve to permit a sufficient flow of hydraulic fluid via oil conduit  62  to torque converter  10  at low speed operation to ensure the release of the lockup clutch. 
     The present invention provides a Pressure Regulator Valve Assembly having advantages over the prior art. The present invention is a replacement Pressure Regulator Valve Assembly for maintaining a continuous flow of hydraulic fluid to the torque converter in all operating modes of an automatic transmission such as the Ford E40D and other similar transmissions to prevent torque converter overheating. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present Pressure Regulator Valve Assembly includes a valve piston subassembly having an encapsulated internal check valve in fluid communication with the line pressure circuit, which diverts ATF to the torque converter charge circuit responsive to a lower fluid pressure (i.e. 2-5 psi) than is required to fill the torque converter under normal operating conditions. Thus, at high pressure conditions and during torque converter release an adequate ATF level is maintained in the torque converter to prevent overheating. 
     When the vehicle engine is shut off the internal check valve also prevents ATF from draining back through the Pressure Regulator Valve to the sump to maintain an adequate ATF level in the torque converter at engine startup. In addition, a Balance Boost fluid circuit has been added to the present Pressure Regulator Valve to assist the OEM Balance circuit in counteracting the electronic pressure control (EPC) solenoid pressure. 
     The present Pressure Regulator Valve is a direct replacement for the OEM Main Regulator Valve that is standard equipment on Ford E40D transmission, which will be referred to throughout this specification. 
     There has thus been outlined, rather broadly, the important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. 
     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 schematic drawing of the pump body of the Ford E40D transmission showing the location of the Main Regulator Valve and labeled Prior Art; 
     FIG. 2 is a cross-sectional view of the Ford E40D pressure regulator valve shown in an open position within the valve body and labeled Prior Art; 
     FIG. 3 is a cross-sectional view of the Pressure Regulator Valve of the present invention showing the components thereof; 
     FIG. 4A is a cross-sectional view of the present Pressure Regulator Valve shown in the low line pressure position within the valve body; and 
     FIG. 4B is a cross-sectional view of the present Pressure Regulator Valve shown in the high line pressure position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Prior to describing the present invention in detail it may be beneficial to review the function of the Main Regulator Valve within the hydraulic system of the Ford E40D automatic transmission. Referring to FIG. 1 there is shown a schematic view of a portion of the hydraulic system of the aforementioned Ford E40D transmission wherein a Main Regulator Valve, indicated generally at  200 , is illustrated in the Park gear range. The Main Regulator Valve  200  is located in the pump body, indicated generally at  205 , of the transmission and regulates line pressure in relation to vehicle operating conditions. 
     More particularly, in the Ford E40D transmission the Powertrain Control Module (not shown) controls line pressure via the Electronic Pressure Control (EPC) solenoid, indicated generally at  210 . ATF under pressure in the EPC circuit as at  214  primarily controls the position of the Main Regulator Valve  200 . 
     The position of the Main Regulator Valve  200  is also controlled by fluid under pressure in the Reverse circuit as at  220 . ATF flow within the Reverse circuit provides a boost in line pressure when the transmission operates in the Reverse gear range and in Manual 1 st  gear. 
     The Main Regulator Valve  200  also controls the flow of ATF from the pump  205  into the suction circuit as at  215  to the sump  216 . If more fluid from the pump  205  enters the suction circuit  215 , pressure in the line circuit as at  212  is lower. If less fluid from the pump  205  enters the suction circuit  215 , pressure in the line circuit  212  is higher. ATF in the line circuit  217  supplies the other hydraulic circuits as at  222 . 
     As shown in FIG. 2 the OEM Main Regulator Valve  200  comprises a spool type valve including an elongated cylindrical piston  230  having a plurality of concentric diameters or spools, a compression spring  232 , and a spring seat  233  arranged coaxially within the pump body  205  shown in partial section. The Main Regulator Valve  200  functions in combination with the OEM Reverse Boost Valve, indicated generally at  240 , which includes a valve piston  242  disposed within a valve sleeve  244 . 
     In operation the force of the spring  232  acting on the piston  230  keeps the Main Regulator Valve  200  and Reverse Boost Valve  240  substantially closed (i.e. shifted to the right) at idle and low engine speeds. As engine speed increases, fluid pressure from the electronic pressure control (EPC) circuit  214  acts directly on the reverse boost valve  240 , stroking the piston  242  against the force of spring  232  which, in turn, strokes the valve piston  230  to generate increased line pressure as illustrated in FIG.  2 . It will be noted that in the OEM design ATF flow to the torque converter/cooler charge circuit  217  is blocked when the valve piston  230  is in the high line pressure position (FIG.  2 ). 
     This shut down of ATF flow to the torque converter/cooler charge circuit  217  in the high pressure position is compounded by the fact that the OEM balance circuit as at  219  delivers insufficient ATF flow to properly counteract EPC circuit  214  pressure. This results in delayed ATF feed to the torque converter/cooler circuit  217  and retention of high line pressure after a return to low demand conditions. These design characteristics combine to cause torque converter overheating problems in the Ford E40D transmission, which are well known in the transmission service industry. 
     Thus, the present invention has been developed to provide an improved Pressure Regulator Valve Assembly to correct these problems, which will now be described. Referring now to FIG. 3 there is shown therein an improved Pressure Regulator Valve Assembly in accordance with the present invention, indicated generally at  10 , which is a direct replacement for the OEM Main Regulator Valve  200 . 
     As shown in FIG. 3 the Pressure Regulator Valve Assembly  10  is comprised of a piston body  15  having control lands  36 - 38  and a snout member  20 , which are mechanically attached in end-to-end relation by mating threads as at  12  encapsulating an internal check valve, indicated generally at  50 . The internal check valve  50  functions to provide a continuous flow of ATF to the cooler/converter charge circuits  217  in all operating modes as explained hereinafter in further detail. 
     The check valve  50  is comprised of a check ball  52 , which is captured within valve chamber  16  and disposed in opening/closing relation to a fluid passage  14  formed in the piston body  15 . A compression spring  54  is arranged within a recess  22  formed in the snout member  20  to spring bias the check ball  52  to the closed position as shown in FIG.  3 . The valve chamber  16  is in fluid communication with the line pressure circuit  213  (FIG. 4B) via fluid passage  14  and orifice  17 . A plurality of ATF feed holes  23  extend radially from the valve chamber  16  and feed into groove  25 , which is in fluid communication with the torque converter/cooler circuit  217  (FIGS.  4 A and  4 B). 
     The present Pressure Regulator Valve Assembly  10  also provides structures comprising fluid balancing means including, but not limited to, the following structures. The piston body  15  includes an internal Balance Boost circuit, indicated generally at  30 , as shown in FIG. 3, which is comprised of a fluid passage  32  of a predetermined diameter formed along the longitudinal axis -A- at the distal end (i.e. left end in FIG. 3) of the piston body  15  in fluid communication with the preexisting balance circuit  219  (FIG.  4 A). The passage  32  is also positioned in fluid communication with regulated line pressure as at  221  via orifice  27 . Thus, the present Balance Boost circuit  30  provides for the ingress of Regulated Line Pressure, which acts in conjunction with the fluid pressure in the preexisting Balance circuit  219  to counterbalance EPC circuit pressure  214  facilitating the return stroke of the Pressure Regulator Valve  10  to the low pressure position as hereinafter explained. 
     Still referring to FIG. 4A the present Pressure Regulator Valve  10  is shown installed in the valve body  205  in direct replacement of the OEM Main Regulator Valve  200 . FIG. 4A represents the Pressure Regulator Valve  10  at the low pressure position (i.e. low EPC solenoid fluid pressure). It will be noted that in this low demand position regulated line pressure as at  221  enters the Balance Boost circuit  30  (shown by directional arrows  33 ) to assist the OEM Balance circuit as at  219  in the return stroke of the valve piston. In this position the port to the torque converter/cooler circuit  217  and connecting lubrication circuit  222  (FIG. 1) is open to permit ATF flow therein. Thus, the check ball  52  is held in the closed position by spring  54  as shown in FIG.  4 A. 
     FIG. 4B represents the Pressure Regulator Valve  10  at high engine speed and high EPC solenoid fluid pressure. It will be seen that in this high demand position EPC fluid pressure  214  strokes the Reverse Boost Valve  240  against the pressure of spring  232  which, in turn, strokes the piston body  15  closing the torque converter/cooler circuit  217  and the sump circuit  215 . 
     In the present Pressure Regulator Valve Assembly  10  increased fluid pressure within line circuit  213  enters the orifice  17  and the check ball  52  is unseated against the pressure of spring  54  (FIG. 3) to permit the flow of ATF via feed holes  23  into the torque converter/cooler circuit  217 . The spring  54  is calibrated to allow the check ball  52  to open in the range of 2 to 5 pounds per square inch (psi) and to permit full flow at 10 psi. In this manner a continuous flow of ATF is provided to the torque converter/cooler circuit  217  in all operating modes of the Ford E40D transmission and the torque converter overheating problem is substantially eliminated. 
     When the engine is turned off the present Pressure Regulator Valve Assembly  10  returns to the position shown in FIG.  4 A and the internal check ball  52  is spring-biased to the closed position by spring  54 , which prevents ATF within the converter/cooler charge circuit as at  217  from draining back through the present Valve Assembly  10  to the sump. 
     Thus, it can be seen that the present Pressure Regulator Valve Assembly  10  is a direct replacement for the OEM Ford E40D Main Regulator Valve  200 , which includes an internal check valve  50  that provides increased ATF flow into the cooler/converter charge circuit  217  during high pressure operating modes. After sufficient line pressure is built up, the internal check valve  50  is opened and line pressure is diverted to the torque converter/cooler circuit  217 . When the engine is shut off the present internal check valve  50  closes to prevents ATF from draining back through the present Valve Assembly  10  substantially reducing converter drain back. 
     The present Pressure Regulator Valve Assembly  10  also provides an internal Balance Boost circuit  30  within the piston body  15 , which diverts regulated line pressure to the preexisting Balance circuit  219  to assist in shifting the valve instantaneously from the high pressure position (FIG. 4B) to the low pressure position (FIG.  4 A). 
     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 Pressure Regulator 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.