Patent Publication Number: US-2023135948-A1

Title: Drop-in signal accumulator piston kit and method for replacing an original equipment signal accumulator piston

Description:
CROSS-REFERENCE TO RELATED APPLICATION DATA 
     This application is a continuation-in-part of U.S. patent application Ser. No. 17/527,946, filed Nov. 16, 2021, titled DROP-IN SIGNAL ACCUMULATOR PISTON KIT AND METHOD FOR REPLACING AN ORIGINAL EQUIPMENT SIGNAL ACCUMULATOR PISTON, which claims the benefit of and priority to Provisional U.S. patent application Ser. No. 63/115,924, filed Nov. 19, 2020, titled DROP-IN SIGNAL ACCUMULATOR PISTON KIT AND METHOD FOR REPLACING AN ORIGINAL EQUIPMENT SIGNAL ACCUMULATOR PISTON, the disclosures of which are incorporated herein in their entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to a replacement kit for signal accumulator pistons in control solenoid valves in a vehicle transmission, and more particularly to a drop-in kit for replacement signal accumulator pistons in original equipment (OE) control solenoid valve bodies. 
     Control solenoids in a vehicle transmission supply control fluid for the proper operation, e.g., shifting, of the vehicle transmission. Proper operation is accomplished by controlling the pressure in and through solenoid valves that control the actuation (engagement and disengagement) of clutches in the transmission. Signal accumulators dampen or smooth out the signal fluid pressure applied from each control solenoid before the fluid flows to a control valve, thus providing for smoother operation of the transmission. 
     Wear in the signal accumulator piston bores in the control valve body results in loss of the variable force solenoid (VFS) signal pressure. Pressure loss results in poor shift control (soft shifts), no converter apply, hydraulic-related converter warning codes, and burnt clutches. 
     Known ways in which to address signal loss due to low or loss of fluid line pressure resulting from wear in piston bore in the control valve body include replacing the control valve body or boring out (e.g., machining or reaming) the bore and installing an oversized piston. Both of these solutions are costly and time consuming solutions. 
     Accordingly, there is a need for an assembly or kit for replacing the signal accumulator pistons in an OE control solenoid valve body. Desirably, such an assembly can be installed in the OE control solenoid valve body without modification of the valve body. More desirably still such an assembly restores hydraulic control, maintaining proper fluid line pressure control. 
     SUMMARY 
     In one aspect of the present disclosure a drop-in signal accumulator piston assembly replaces an original equipment (OE) signal accumulator piston in a vehicle transmission hydraulic circuit. The OE signal accumulator piston is positioned in a bore in a valve body having a fluid port. 
     The drop-in signal accumulator piston assembly includes a cylindrical sleeve having open first and second ends and a piston positioned in the sleeve. The piston is cup-shaped, having an open end and a closed end. 
     A spring is positioned in part in the open end of the piston and in part extending beyond an end of the piston. The sleeve is positioned in the valve body bore, with the piston and the spring positioned in the sleeve, and the sleeve, the piston, and the spring are enclosed within the valve body bore. 
     In an embodiment, the piston includes a plurality of circumferential recesses in an outer wall thereof. The sleeve includes a receiving region for receiving a seal. The seal is positioned between the sleeve and the valve body bore. In some embodiments the receiving region is a circumferential recess; in some embodiments the receiving region is a chamfered end wall in the sleeve; and in some embodiments the receiving region is a stepped region in the sleeve. 
     In embodiments, an end of the spring abuts an inner end wall of the piston and an opposite end of the spring abuts an inner wall of the valve body. In embodiments, the sleeve has a first wall thickness and a second wall thickness greater than the first wall thickness, and the circumferential recess is in a portion of the sleeve at the second wall thickness. 
     In embodiments, the assembly further includes a plug positioned in the valve body bore adjacent the sleeve. The plug can be positioned in the valve body bore adjacent the sleeve, to enclose the sleeve, the piston, and the spring in the valve body bore. The plug can include a receiving region for receiving a seal, which seal is positioned between the plug and the valve body bore. The receiving region can be a circumferential recess in the plug. 
     In embodiments, the plug includes an axial through hole. An end of the spring can abut an inner end wall of the piston and an opposite end of the spring can abut the plug. 
     In another aspect, a method for replacing an original equipment (OE) signal accumulator piston in a vehicle transmission hydraulic circuit, the OE signal accumulator piston positioned in a bore in a valve body having a fluid port is disclosed. 
     The method includes removing the OE signal accumulator piston from the bore, installing a cylindrical sleeve having open first and second ends in the bore, positioning a piston in the sleeve, and positioning a spring in part in the piston and in part extending beyond the piston. The sleeve, the piston, and the spring are enclosed within the valve body bore, and a head of the piston is positioned in facing relationship to the fluid port. 
     In methods the piston includes a plurality of circumferential recesses in an outer wall thereof, and in methods the sleeve includes a circumferential recess, and further includes a seal positioned in the recess. 
     The method may include a sleeve having a first wall thickness and a second wall thickness greater than the first wall thickness, such that the circumferential recess is in a portion of the sleeve at the second wall thickness. 
     In still another aspect, a drop-in signal accumulator piston assembly replaces an original equipment (OE) signal accumulator piston in a vehicle transmission hydraulic circuit, in which the OE signal accumulator piston is positioned in a bore in a valve body having an open end and a fluid port. 
     The drop-in signal accumulator piston assembly includes a cylindrical sleeve having open first and second ends, one of the first and second open ends having a reduced diameter region relative to an outer wall of the sleeve, a piston positioned in the sleeve, a spring positioned in part in the piston and in part extending beyond and end of the piston and a seal positioned at the reduced diameter region. 
     The sleeve is positioned in the valve body bore, with the seal, the piston, and the spring, such that the seal is positioned between side and bottom walls of the valve body bore and wherein the seal provides a seal between the valve body bore and the sleeve. 
     In embodiments, the reduced diameter region is a chamfer formed in the sleeve. In embodiments, the reduced diameter region is an inwardly stepped region formed in the sleeve. And in embodiments, the reduced diameter region defines a circumferential recess and wherein the seal is positioned in the circumferential recess. 
     Further understanding of the present disclosure can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       An embodiment of a vehicle transmission is disclosed as an example and is not limited by the figures of the accompanying drawings, in which like references may indicate similar elements and in which: 
         FIGS.  1 A and  1 B  are illustrations of an example of a control solenoid valve body for a vehicle transmission, in which  FIG.  1 A  illustrates the valve body with a cover in place, and  FIG.  1 B  illustrates the valve body with the cover removed; 
         FIG.  2    is an illustration of an embodiment of the replacement accumulator piston kit; 
         FIG.  3    illustrates various components of the kit; 
         FIG.  4    is an illustration of a portion of a hydraulic control circuit for a vehicle transmission; 
         FIGS.  5  and  6    are illustrations of a standard test set up for testing the accumulator; 
         FIGS.  7  and  8    are graphical representations of a comparison of control line signal pressure versus time in an accumulator with the OE piston and in an accumulator with the present drop-in accumulator piston; 
         FIGS.  9 A and  9 B  are illustrations of another embodiment of the replacement accumulator piston kit  FIG.  9 A  showing a front view of the replacement accumulator piston kit in cross-section and  FIG.  9 B  showing a perspective view in cross-section; 
         FIGS.  10 A and  10 B  are illustrations of still another embodiment of the replacement accumulator piston kit  FIG.  10 A  showing the showing a front view of the replacement accumulator piston kit in cross-section and  FIG.  10 B  showing a perspective view in cross-section; 
         FIGS.  11 A and  11 B  illustrate yet another embodiment of the replacement accumulator piston kit shown in a sectional perspective view,  FIG.  11 B  showing the kit in place in the valve body and illustrating a mating portion of the valve body and a separator plate; and 
         FIGS.  12 A and  12 B  illustrate still another embodiment of a replacement accumulator piston kit shown in sectional front and perspective views. 
     
    
    
     DETAILED DESCRIPTION 
     While the present disclosure is susceptible of embodiments in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification and is not intended to limit the disclosure to the specific embodiment illustrated. 
     Referring briefly first to  FIG.  1   , there is shown a portion of a control valve body B that houses a hydraulic circuit C for a vehicle transmission. Now referring to  FIG.  4   , the circuit C includes, among other things, a torque converter clutch (TCC) control solenoid valve assembly V 1 , a converter control valve assembly V 2 , and a lube flow regulator valve V 3 . A signal accumulator  1  is illustrated associated with the TCC control solenoid valve assembly V 1 . The components are housing within the control valve body B. It will be appreciated that signal accumulators  1  are associated with other components within the hydraulic circuit C including, for example, various control circuits for forward and reverse clutch operation. 
       FIG.  2    illustrates an embodiment of the replacement accumulator piston assembly  10  installed in the OE valve bore  12 . The assembly  10  includes a sleeve  14  positioned in the OE valve bore  12 , a piston  16  positioned in the sleeve  14 , and a spring  18  (see  FIG.  3   ) positioned in part in the piston  16  and in part extending beyond the piston  16 . In an embodiment, the sleeve  14  has a cylindrical shape with open ends  20 ,  22 . The piston  16  can have a cup-shaped body  30 , having a cylindrical wall  24  with one open end  26  and one closed end  28 . The spring  18  can be positioned in the piston open end  26  and reside, at least in part, in the piston body  30 . The piston  16  is positioned in the sleeve  14  with the piston closed end  28  proximal the valve body port  32  which provides fluid flow into the accumulator bore  12 . In an embodiment, an outer wall  34  of the piston  16  has one or more circumferential grooves or recesses  36 . In embodiments, the spring  18  abuts an inner end wall  38  of the piston  16 . 
     A plug  40  is positioned to close the bore  12  and a seal  42 , such as an  0 -ring is positioned in a circumferential recess  44  in the plug  40  to seal the accumulator piston assembly  10  in the valve bore  12 . A through-hole  46  can be formed in the plug  40  to, for example, allow for readily removing the plug  40  to facilitate removal of the piston  16 , spring  18  and/or sleeve  14 . The through-hole  46  can be threaded so that a bolt  48  or other threaded tool/element can be threaded into the through-hole  46  for ease of removing the plug  40 . The plug  40  is at an end of the valve bore  12  opposite the fluid port  32 . The through-hole  46  can also serve as a blow by exhaust for fluid that leaks by the piston  16 . 
     The sleeve  14  is sized to fit into the OE valve bore  12  without modification (e.g., tooling or reaming) of the bore  12 . In this configuration, the replacement accumulator piston assembly  10  can readily replace the OE accumulator piston, without modification to the valve body B. The sleeve  14  is fit in the valve bore  12  with a tight tolerance. A locking compound (not shown) may be used to secure or maintain the sleeve  14  in the bore  12 . 
     For purposes of the following description regarding  FIGS.  9 A,  9 B,  10 A and  10 B , it should be noted that these figures are inverted (upside down) relative to the assembly  10  illustrated in  FIG.  2   .  FIGS.  9 A and  9 B  illustrate another embodiment of a replacement accumulator piston assembly  210  installed in the OE valve bore  212 . The assembly  210  includes a sleeve  214  positioned in the OE valve bore  212 , a piston  216  positioned in the sleeve  214 , and a spring  218  positioned in part in the piston  216  and in part extending beyond the piston  216 . 
     In an embodiment, the sleeve  214  has a cylindrical shape with open ends  220 ,  222 , and the piston  216  has a cup-shaped body  230 , having a cylindrical wall  224  with one open end  226  and one closed end  228 . The spring  218  can be positioned in the piston open end  226  and reside, at least in part, in the piston body  230 . The piston  216  is positioned in the sleeve  214  with the piston closed end  228  proximal the valve body port  232  which provides fluid flow into the accumulator bore  212 . In an embodiment, an outer wall  234  of the piston  216  has one or more circumferential grooves or recesses  236 . In embodiments, the spring  218  abuts an inner end wall  238  of the piston  216 . 
     The valve bore  212  includes an end wall  248  having a through-hole  246  formed therein. The through-hole  246  serves as a blow by exhaust for fluid that leaks by the piston  216 . The sleeve  214  includes an inwardly beveled (or angled) end wall or chamfer  238  at the sleeve open end  220 . A seal, such as the illustrated O-ring seal  242  is positioned in a capture region  239  defined in the valve bore  212  by the valve bore end wall  248  and side wall  250 , and the sleeve chamfered end wall  238 . The capture region  239  can have a reduced diameter relative to the sleeve  214  outer wall. The seal  242  seals the accumulator piston assembly  210  in the valve bore  212  and prevents leakage from the valve bore  212  and the leakage of any fluid that may be present between the sleeve  214  and the piston side wall  224 . In the illustrated assembly, the portion of the spring  218  that extends beyond the open end of the piston  226  extends through sleeve open end  220  and contacts the valve bore end wall  248 . 
     As with the previously disclosed embodiment, the sleeve  214  is sized to fit into the OE valve bore  212  without modification (e.g., tooling or reaming) of the bore  212 . In this configuration, the replacement accumulator piston assembly  210  can readily replace the OE accumulator piston, without modification to the valve body. The sleeve  214  is fit in the valve bore  212  with a tight tolerance. A locking compound (not shown) may be used to secure or maintain the sleeve  214  in the bore  212 . 
     It is envisioned that this configuration may be desirable due to the small size of this part (e.g., the piston  216 ) in that a conventional O-ring groove around the diameter may be difficult in execution. The chamfered sleeve bottom end  238  compresses the O-ring  242  against the bottom corner (i.e., the bottom wall  248  and side wall  250 ) of the valve bore  212 . This requires less space for the seal  242 , which allows for greater space for the spring  218  and piston  216  function. In addition, the O-ring  242  compressed against the valve bore end or bottom wall  248  prevents pressure loss between the sleeve  214  and the valve bore  212  which in turn directs the pressure onto the piston  216 . 
       FIGS.  10 A and  10 B  illustrate yet another embodiment of a replacement accumulator piston assembly  310  installed in the OE valve bore  312 . The assembly  310  includes a sleeve  314  positioned in the OE valve bore  312 , a piston  316  positioned in the sleeve  314 , and a spring  318  positioned in part in the piston  316  and in part extending beyond the piston  316 . 
     In an embodiment, the sleeve  314  has a cylindrical shape with open ends  320 ,  322 , and the piston  316  has a cup-shaped body  330 , having a cylindrical wall  324  with one open end  326  and one closed end  328 . The spring  318  can be positioned in the piston open end  326  and reside, at least in part, in the piston body  330 . The piston  316  is positioned in the sleeve  314  with the piston closed end  328  proximal the valve body port  332  which provides fluid flow into the accumulator bore  312 . In an embodiment, an outer wall  334  of the piston  316  has one or more circumferential grooves or recesses  336 . In embodiments, the spring  318  abuts an inner end wall  338  of the piston  316 . 
     The valve bore  312  includes an end wall  348  having a through-hole  346  formed therein. The through-hole  346  serves as a blow by exhaust for fluid that leaks by the piston  316 . The sleeve  314  includes an inwardly stepped end wall  338  at the sleeve open end  320 . The inwardly stepped end wall  338  provides a region or seat  352  for a seal  342 , such as the illustrated  0 -ring seal that is positioned and captured in a capture region  339  defined in the valve bore  312  by the valve bore side wall  350 , valve bore end wall  348  and the sleeve stepped end wall  338 . The capture region  339  can have a reduced diameter relative to the sleeve  314  outer wall. The seal  342  seals the accumulator piston assembly  310  in the valve bore  312  and prevents leakage from the valve bore  312  and the leakage of any fluid that may be present between the sleeve  314  and the piston side wall  324 . In the illustrated assembly, the portion of the spring  318  that extends beyond the open end of the piston  326  extends through sleeve open end  320  and contacts the valve bore end wall  348 . 
     As with the previously disclosed embodiment, the sleeve  314  is sized to fit into the OE valve bore  312  without modification (e.g., tooling or reaming) of the bore  312 . In this configuration, the replacement accumulator piston assembly  310  can readily replace the OE accumulator piston, without modification to the valve body. The sleeve  314  is fit in the valve bore  312  with a tight tolerance. A locking compound (not shown) may be used to secure or maintain the sleeve  314  in the bore  312 . 
       FIG.  11    illustrates still another embodiment of a replacement accumulator piston assembly  410  installed in the OE valve bore  412 . The assembly  410  includes a sleeve  414  positioned in the OE valve bore  412 , a piston  416  positioned in the sleeve  414 , and a spring  418  positioned in part in the piston  416  and in part extending beyond the piston  416 . 
     In embodiments, the sleeve  414  has a cylindrical shape with open ends  420 ,  422 , and the piston  416  has a cup-shaped body  430 , having a cylindrical wall  424  with one open end  426  and one closed end  428 . The spring  418  can be positioned in the piston open end  426  and reside, at least in part, in the piston body  430 . The piston  416  is positioned in the sleeve  414  with the piston closed end  428  proximal the valve body port (illustrated generally at  432 ) which provides fluid flow into the accumulator bore  412  (illustrated generally by the arrow at  456 ). In an embodiment, an outer wall  434  of the piston  416  has one or more circumferential grooves or recesses  436 . In embodiments, the spring  418  abuts an inner end wall  437  of the piston  416 . 
     The valve bore  412  includes an end wall  448  that has a through-hole  433  formed therein that serves as a blow by exhaust for fluid (illustrated generally at  458 ) that leaks by the piston  416 . The sleeve  414  includes an inwardly angled inner end wall  438  at the sleeve open end  420 . An outer wall  440  of the sleeve  414  includes a circumferential groove  442  for receipt of an O-ring (not shown) to provide a seal between the sleeve  414  and the valve bore  412 . The seal seals the accumulator piston assembly  410  in the valve bore  412  and prevents leakage from the valve bore  412  and the leakage of any fluid that may be present between the sleeve  414  and the piston side wall  424 . In the illustrated assembly, the portion of the spring  418  that extends beyond the open end of the piston  426  extends through sleeve open end  420  and contacts the valve bore end wall  448 . 
     As with the previously disclosed embodiments, the sleeve  414  is sized to fit into the OE valve bore  412  without modification of the bore  412 , and the replacement accumulator piston assembly  410  can readily replace the OE accumulator piston, without modification to the valve body. The sleeve  414  is fit in the valve bore  412  with a tight tolerance. A separator plate  450  is positioned on the portion of the valve body  452  in which the sleeve  414 , piston  416  and spring  418  are installed and a mating portion  454  of the valve body is positioned on the separator plate  450 . The separator plate and mating valve body portions can be used with all previously described embodiments. A locking compound (not shown) may be used to secure or maintain the sleeve  414  in the bore  412 . 
       FIGS.  12 A and  12 B  illustrate yet another embodiment of a replacement accumulator piston assembly  510  installed in the OE valve bore  512 .  FIGS.  12 A and  12 B  differ only in that a lower region of the sleeve  514  in  FIG.  12 A  is shorter than a lower portion of the sleeve  514  in FIG,  12 B. The assembly  510  includes the sleeve  514  positioned in the OE valve bore  512 , a piston  516  positioned in the sleeve  514 , and a spring  518  positioned in part in the piston  516  and in part extending beyond the piston  516 . 
     In embodiments, the sleeve  514  has a cylindrical shape with open ends  520 ,  522 , and the piston  516  has a cup-shaped body  530 , having a cylindrical wall  524  with one open end  526  and one closed end  528 . The spring  518  can be positioned in the piston open end  526  and reside, at least in part, in the piston body  530 . The piston  516  is positioned in the sleeve  514  with the piston closed end  528  proximal the valve body port  532  (see,  FIG.  12 B ) which provides fluid flow into the accumulator bore  512 . 
     In embodiments, an outer wall  534  of the piston  516  has one or more circumferential grooves or recesses  536 . In embodiments, the spring  518  abuts an inner end wall  538  of the piston  516 . 
     The valve bore  512  includes an end wall  548  that can have a through-hole  533  formed therein to serve as a blow by exhaust for fluid that leaks by the piston  516 . An outer wall  540  of the sleeve  514  includes a circumferential groove  542  for receipt of an  0 -ring (not shown) to provide a seal between the sleeve  514  and the valve bore  512 . The seal seals the accumulator piston assembly  510  in the valve bore  512  and prevents leakage from the valve bore  512  and the leakage of any fluid that may be present between the sleeve  514  and the piston side wall  524 . In the illustrated assembly, the portion of the spring  518  that extends beyond the open end of the piston  526  extends through sleeve open end  520  and contacts the valve bore end wall  548 . 
     As with the previously disclosed embodiments, the sleeve  514  is sized to fit into the OE valve bore  512  without modification of the bore  512 , and the replacement accumulator piston assembly  510  can readily replace the OE accumulator piston, without modification to the valve body. The sleeve  514  is fit in the valve bore  512  with a tight tolerance. A locking compound (not shown) may be used to secure or maintain the sleeve  514  in the bore  512 . The piston  516  includes a projection or stop  550  on an outer surface  552  of the piston closed end  528 . The stop prevents the piston  516  from topping out (or bottoming out) so as to close off the valve body port  532 . 
     It is anticipated that this configuration may be desirable due to the small size of this part in that a conventional O-ring groove formed in the entirety of the sleeve, around the diameter of the sleeve, may be difficult in execution. The stepped sleeve bottom end wall  338  compresses the O-ring  342  against the bottom corner (i.e., the bottom wall  350  and side wall  348 ) of the valve bore  312 . This requires less space for the seal  342 , which allows for greater space for the spring  318  and piston  316  function. In addition, the O-ring  342  compressed against the valve bore bottom wall  350  prevents pressure loss between the sleeve  314  and the valve bore  312  which in turn directs the pressure onto the piston  316 . 
     Tests were conducted to determine whether the smaller diameter replacement piston  16  (and thus smaller volume of the accumulator) has an adverse effect on the function of the accumulator and the hydraulic circuit compared to an accumulator with an OE piston. 
     Referring now to  FIGS.  5  and  6   , a test set  102  up was constructed in which an acrylic plate  104  was installed on the back side of a control valve body B. Taps  108  were made in the plate  104  for solenoid feed  110  and solenoid output  112 , and solenoid output was connected to the accumulator. Passages were drilled for fluid flow connections  114  from the solenoid to the control valve and signal accumulator piston. A dial indicator (not shown) was installed to monitor the piston stroke via a pin inserted into the spring pocket (i.e., piston open end). This was done for the accumulator with the OE piston and the present drop-in accumulator piston assembly  10 . 
       FIGS.  7  and  8    illustrate graphically a comparison of the control line signal pressure versus time with an accumulator with the OE piston and the present drop-in accumulator piston. In  FIG.  7    the pump pressure (pressure supplied to the solenoid in psi) is shown on the y-axis and time (in milliseconds) is shown on the x-axis. Curve  7 - 1  (C 7 - 1 ) is the solenoid feed/pump pressure in cycling of the normally high solenoid (with a normally high solenoid, the solenoid is electrically actuated and the fluid flow through the solenoid valve decreases with increasing electrical current, conversely with a normally low solenoid, the solenoid is electrically actuated and there is fluid flow through the solenoid valve that increases with increased electrical current). The solenoid was cycled five times. 
     In  FIG.  7   , Curve  7 - 2  (C 7 - 2 ) shows the solenoid/feed pump pressure flowing to the solenoid. Curve  7 - 1  (C 7 - 1 ) shows the flow response/solenoid output pressure as the solenoid is actuated between solenoid duty 0% and solenoid duty at 60%. When the solenoid duty drops to zero (0), the pressure in the system increases (solenoid output increases). The pressure in the system with the OE piston and the present drop-in piston overlap one another in Curve  7 - 1  (C 7 - 1 ), and as such it appears as one curve. This shows that the OE accumulator piston and the present drop-in accumulator piston function equally. 
       FIG.  8    is a repetition of the test results in  FIG.  7   , with Curve  8 - 1  showing solenoid feed/pump pressure to the normally high solenoid (C 8 - 1 ) and Curve  8 - 2  (C 8 - 2 ) showing the solenoid output pressure. Again, the solenoid output pressure with the OE piston and the present drop-in piston overlap one another in Curve  8 - 2  (C 8 - 2 ), and as such it appears as one curve, and again, this shows that the OE accumulator piston and the present drop-in accumulator piston function equally. 
     Table 1, below shows a comparison of the OE piston stroke to the present drop-in signal accumulator piston stroke at various solenoid duty percentages which correspond to solenoid output pressure (in psi) during the same tests captured in  FIG.  8   . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Comparison of OE and Drop-in Piston 
               
               
                 Stroke at Various Solenoid Duties 
               
            
           
           
               
               
               
               
            
               
                 Solenoid 
                 Solenoid 
                   
                   
               
               
                 duty % 
                 output (psi) 
                 OE piston stroke 
                 Drop-in piston stroke 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 60 
                 0 
                 0 
                 0 
               
               
                   48.9 
                 5 
                 0.02 
                 0.015 
               
               
                 44 
                 24 
                 0.032 
                 0.035 
               
               
                   36.9 
                 55 
                 0.051 
                 0.055 
               
               
                 29 
                 88 
                 0.072 
                 0.075 
               
               
                      0 n1   
                 125 
                 0.093 
                 0.095 
               
               
                   
               
               
                 Note: 
               
               
                   n1 —at 0% duty cycle the pistons bottom out in the bore. 
               
            
           
         
       
     
     As can be seen from Table 1, the stroke for the accumulator drop-in piston and the stroke for the accumulator with the OE piston are essentially equal. As such, in viewing the system pressure test results and the piston stroke test results, it can be seen that the present accumulator drop-in piston functions as well as the OE accumulator piston. 
     A method to correct and/or reduce the wear of an OE control valve body B accumulator piston bore  12  includes removing the OE accumulator piston and spring from the accumulator piston bore  12 . The method further includes installing a sleeve  14  in the bore  12 , and installing a replacement piston  16  having a cup-shaped body  30  with an open end  26  and a closed end  28  in the sleeve  14 . The piston  16  is installed with the open end  26  facing out and the closed end  28  proximal the valve body port  32  into the accumulator bore  12 . 
     A spring  18  is positioned in the piston open end  26  and resides, at least in part, in the piston body  30  and in part extends out of the piston body  30 . In methods the piston  16  has one or more circumferential grooves or recesses  36  in an outer wall  34  of the piston  16 . 
     A plug  40  is installed in the accumulator piston bore  12  to enclose the sleeve  14 , piston  16  and spring  18  in the bore  12 . A seal  42  can be positioned in a circumferential groove or recess  44  in the plug  40 . In methods, the plug  40  has an opening, such as a central through-hole  46 . The through-hole  46  can be threaded so that a threaded member, such as a threaded tool or bolt  48  can be used to install and/or remove the plug  40 . In methods, the through-hole  46  can be used as a vent or blow by exhaust for fluid that leaks the piston  16 . 
     It is anticipated that a hard-coat anodized aluminum piston can be used to reduce and/or prevent premature wear. It is also anticipated that the annular groove(s) in the piston will reduce and/or prevent premature wear. It is further anticipated that O-rings located on the sleeve, between the sleeve and the valve body bore provide a positive seal to prevent critical pressure leakage. It is still further anticipated that mating/specifically specified springs can re-establish OE dampening action 
     It will be recognized by those skilled in the art that there are numerous vehicle transmissions for which the present drop-in accumulator assembly can be used. In particular, it has been identified that the present drop-in accumulator assembly functions well for certain General Motors transmissions, namely the GM 8L90 and the GM 8L45 transmissions. It is anticipated that the present drop-in accumulator assembly will function well in those transmission control valve that utilize piston-type accumulators to dampen or smooth out the signal fluid pressure in hydraulic systems. 
     It will be appreciated that the present accumulator drop-in piston restores hydraulic control, maintaining proper fluid line pressure control through an assembly that can be installed in the OE control solenoid valve body. Advantageously, the present drop-in piston accomplishes this without modification of the control valve body, and has been shown to function as well as the larger OE piston and without loss of control signal pressure control. 
     In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. All patents and published applications referred to herein are incorporated by reference in their entirety, whether or not specifically done so within the text of this disclosure. 
     It will also be appreciated by those skilled in the art that any relative directional terms such as side(s), upper, lower, top, bottom, rearward, inboard, forward, outboard and the like may be for explanatory purposes only and may not be intended to limit the scope of the disclosure. It will further be appreciated that features from any one disclosed embodiment may be used in any other disclosed embodiment. 
     From the foregoing it will be observed that numerous modifications and variations can be made without departing from the true spirit and scope of the novel concepts of the present disclosure. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred.