Abstract:
A hydraulic spool valve repair kit comprising a cylindrical valve cap and a replacement spring retainer plate and a method of use of these components for increasing the service longevity of such a hydraulic spool valve within the valve body of an automatic transmission is disclosed. The present valve cap is a cylindrical steel construction having a longitudinal bore, which is radially disposed about a terminal end of the aluminum valve piston to provide a more durable contact surface and to substantially reduce mechanical wear between the dissimilar materials of the original components. The replacement spring retainer plate, which inadvertently contacts the valve piston under some operating conditions, is reconfigured to include resilient leg members for retention of the spring retainer plate within the valve body and also provides a stable spring seat for the compression spring that actuates the spool valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/318,954 filed Sep. 14, 2001 entitled Valve Saver Kit. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to automatic transmissions and, more particularly, to a hydraulic valve repair kit and method of use, which functions to extend the useful service life of a hydraulic spool valve within the valve body of a transmission. 
     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 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”) within the fluid circuits 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. 
     Typically such a spool valve undergoes continuous reciprocating movement due to fluctuation in hydraulic line pressure, which can result in premature wear and improper shifting problems in the transmission. More particularly, the end faces of such a spool valve can be damaged by continuous striking against the interior of the valve body and other internal components such a spring retainer plate during operation resulting in jamming and failure of the hydraulic circuit requiring complete transmission overhaul. 
     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 spool valve repair kit comprising a valve cap and a replacement spring retainer plate, which are utilized in combination to repair the original equipment manufacture (hereinafter “OEM”) spool valve to increase the service longevity of such a spool valve in the valve body of an automatic transmission. The valve cap is a cylindrical construction, which is radially disposed about a terminal end of the valve piston to provide a durable contact surface for the valve piston. The spring retainer plate is also redesigned to prevent damage to the aformentioned contact surface and to provide a stable spring seat for a compression spring, which improves the accuracy of the valve&#39;s operation. 
    
    
     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 valve body of a Ford AXODE transmission illustrating an exploded view of a spool valve assembly wherein the present valve saver kit is to be utilized and being labeled Prior Art; 
     FIG. 2 is an exploded elevational view of the spool valve assembly of FIG. 1; 
     FIG. 3A is an exploded elevational view of the spool valve assembly of FIG. 2 showing the valve cap and spring retainer plate of the present valve saver kit; 
     FIG. 3B is an elevational view of the spool valve assembly of FIG. 3A showing the components of the present valve saver kit installed in their functional positions; 
     FIG. 4A is an enlarged cross-sectional view of the valve cap of the present valve saver kit; 
     FIG. 4B is a right end view of the valve cap shown in FIG. 4A; 
     FIG. 5A is a front elevational view of the spring retainer plate of the present valve saver kit showing the relative position of the installed valve cap in phantom outline; and 
     FIG. 5B is a side elevational view of the spring retainer plate shown in FIG.  5 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With further reference to the drawings there is shown therein an OEM spool valve assembly of the prior art, indicated generally at  100 , and illustrated in FIG.  1 . It will be noted that in the embodiment illustrated, two separate OEM spool valve assemblies  100 ,  200  are arranged in coaxial relation for control of separate hydraulic circuits. The prior art spool valve assemblies  100 ,  200  are shown in exploded view and removed from their functional position within a mating bore  125 , which is machined into the valve body, indicated generally at  110 , of a Ford AXODE transmission. For purposes of this application the term “spool valve” is used generically to apply to all hydraulic valves of this general type as described hereinafter in further detail. 
     As more clearly shown in FIG. 2, the spool valve assembly  100  includes a generally cylindrical piston  115  having a plurality of control lands or spools  101 ,  102 ,  103  formed thereon, which function to regulate the flow of automatic transmission fluid (hereinafter “ATF”) within the valve chamber defined by the stem portions  108  and the surrounding bore  125  (FIG.  1 ). The valve piston  115  also includes a coaxial spring guide diameter  112  of a sufficient size to support a compression spring  104  having a spring rate and operating characteristics suited to this application. The OEM valve piston  115  is fabricated from an aluminum material. 
     The OEM spring retainer plate  107  as seen in FIG. 2 is inserted into the valve body  110  to separate the valve assemblies  100 ,  200  and functions as a seating surface for the spring  104  and often as an unintended stop surface for the terminal end face  112   a  of the spring guide diameter  112 , which is known to strike the steel spring retainer plate  107  in operation causing physical damage to the terminal end face of the spring guide diameter. 
     The OEM retainer plate  107  is constructed of spring steel and is slightly bent along its length as shown, which provides a gripping effect when it is installed in a mating slot in the valve body  110  in a known manner. However, this design produces dissimilar surfaces as at  116 ,  118 , whereon the respective springs  104 ,  105  of valve assemblies  100 ,  200  are seated in operation (FIG.  1 ), which are not perpendicular to the longitudinal axis —A—of the valve assemblies  100 ,  200 . This produces slight differences in the compression and expansion of the springs  104 ,  105  which can affect performance of the valve assemblies  100 ,  200 . 
     An OEM end plug  106  and retaining clip  109  (FIG. 1) serve to retain the valve assemblies  100  and  200  in their functional positions within the bore  125  of the valve body  110 . 
     In operation ATF is delivered via hydraulic circuits formed in the valve body  110  into the valve chamber defined by the stem portions  108  of the valve piston  115  and the surrounding bore  125  and then passes into the hydraulic circuits controlled by the valve assemblies  100 ,  200 . If the fluid pressure within such hydraulic circuits exceeds the maximum limits for the Ford AXODE transmission, the ATF pressure acts against the force of the spring  104  to deflect or stroke the valve piston  115  such that the spools  101 ,  102 ,  103  close the valve. This reciprocating motion of the valve piston  115  is repeated as often as required to maintain ATF line pressure in the controlled circuits within predetermined limits for the transmission. 
     In the Ford AXODE transmission the reciprocating motion of the valve piston  115  causes repeated impacts of the end face  112   a  of the spring diameter  112  against the OEM spring retainer plate  107 . This results in premature wear and eventually causes mechanical damage and/or jamming of the spring guide diameter  112  within the slot  107   a  (FIG. 1) of the retainer plate  107  resulting in malfunction of the so-called Pull-In Control circuit and corresponding 3rd/2 nd  gear shift timing problems, which are well known deficiencies of this transmission. 
     Thus, the present invention has been developed to resolve this problem and will now be described. With reference to FIGS. 3A and 3B the present valve saver kit is comprised of a generally cylindrical valve cap, indicated generally at  10 , and a modified spring retainer plate, indicated generally at  20 . In one embodiment, among others, the valve cap  10  is fabricated of low carbon steel or other suitable material and dimensioned to a sliding fit condition with the spring guide diameter  112  of the OEM valve piston  115 . In the completed assembly valve cap  10  is disposed within the OEM spring  104  as shown in FIG.  3 B. The present spring retainer plate  20  is designed as a direct replacement for the OEM retainer plate  107 . 
     The present invention provides structures comprising wear-reducing means including, but not limited to, the following structures. As shown in FIGS. 4A and 4B the valve cap  10  is a generally cylindrical component designed to reduce frictional wear on spring guide diameter  112 . The present valve cap  10  includes a spring locating diameter  12  formed about a longitudinal bore  14 , which is dimensioned to a close-tolerance, slip fit condition with the OEM spring guide diameter  112 . The valve cap  10  also includes a flange  17  formed in perpendicular relation to spring guide diameter  12 , which functions as a seat for the OEM spring  104 . 
     Referring to FIGS. 5A and 5B there is shown therein the modified spring retainer plate  20  in accordance with the present invention. Retainer plate  20  is comprised of a body member  22  including a central slot  24  formed along the longitudinal centerline thereo, which defines a pair of opposed leg members  30 . Slot  24  imparts resiliency to leg members  30  permitting inward compression thereof during installation and providing an outward spring bias to the leg members to retain the spring retainer plate  20  within the valve body  110 . 
     The terminal ends of leg members  30  are relieved along the lateral aspects thereof as at  26  to provide adequate clearance with the sidewalls and corners of the hydraulic passage as at  113  (FIG. 1) within the valve body  110  wherein the retainer plate  20  is installed. It will be noted that the opposed front and back surfaces  16 ,  18  of the body member  22  are parallel as shown in FIG. 5B (in contrast to the curved surfaces  116 ,  118  of the OEM spring retainer plate  107 ) such that the compression springs  104 ,  105  are seated squarely in perpendicular relation thereto for optimal accuracy of the valve assemblies  100 ,  200  in operation. Semicircular notches  28  formed in the body member  22  provide grasping points for a retainer plate removal tool (not shown). 
     In practical use the present valve saver kit including the valve cap  10  and the spring retainer plate  20  are installed as shown in FIG.  3 B. The valve cap  10  is dimensioned to a slip fit condition with the OEM spring guide diameter  112  and abuts the first adjacent spool diameter  101 . Once installed as shown, it will be noted that the axial length of spring locating diameter  12  is at least equal to or slightly exceeds the axial length of the OEM spring guide diameter  112 . Thus, the end face  12   a  of the valve cap  12  makes direct contact with surface  18  of the spring retainer plate  20 . 
     Because both valve cap  12  and spring retainer plate  20  are constructed of steel material there is less mechanical wear at the interface of contact surfaces  12   a  and  18  than in the OEM design wherein dissimilar materials (i.e. aluminum valve piston  115  and steel retainer plate  107 ) are in direct mechanical contact. Further, the valve cap  10  prevents spring guide diameter  112  from becoming jammed within the central notch  24  of the present retainer plate  20 , which is a common service problem in the Ford AXODE transmission. That is, the spring locating diameter  12  of the valve cap  10  provides more cross-sectional contact area during operation than the spring guide diameter  112  and, thus, has less tendency for becoming jammed as illustrated in comparison view by phantom outlines  12 ′,  112 ′ in FIG.  5 A. 
     Thus, it can be seen that the present valve saver kit provides a simple and cost effective repair kit to increase the service longevity of a hydraulic spool valve by preventing premature wear and mechanical damage resulting from the repeated impact of an aluminum spool valve and a steel spring retainer plate being fabricated from dissimilar materials. 
     Further, the increased diameter and cross-sectional surface area of the present valve cap provides a valve piston which is less likely to become jammed within the central slot of the mating spring retainer plate causing improper 3/2 shifting and Pull-In Control circuit failure, which are deficiencies commonly associated with the Ford AXODE transmission. 
     Although the present invention has been developed to resolve a common deficiency associated with the Ford AXODE transmission, it will be appreciated by those skilled in the art that the present valve saver kit has broad application to spool valves in other automotive transmissions and the embodiments described herein are intended as merely illustrative and not restrictive in any sense. 
     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.