Abstract:
A valve actuating mechanism for a transmission/engine fluid cooler bypass valve of the type in which a responsive element expands to urge a valve member against a valve seat and thereby causes transmission fluid to flow through an oil fluid cooler. A cast valve housing is utilized which is interposed between the cooler and the oil source. The valve actuating mechanism is designed to allow fluid to pass through the valve once the fluid has reached an elevated pressure level.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part application of U.S. patent application Ser. No. 10/330,695 filed on Dec. 27, 2002 now U.S. Pat No. 6,719,208, which is a continuation-in-part application of U.S. patent application Ser. No. 09/945,037 filed on Aug. 31, 2001, now U.S. Pat. No. 6,499,666. The disclosure of the above applications is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to oil cooler bypass valves, and more particularly to a bypass valve which is coup able to an oil source which is thermally responsive to changes in oil temperatures. 
   BACKGROUND OF THE INVENTION 
   Oil cooler bypass valves are used in conjunction with engines, transmissions, power steering systems, and hydraulic systems. They are designed to provide a flow path by which oil passing to the valve from the oil source is returned without passing through a heat exchanger during warm-up periods. 
   Typical transmission bypass valves have several connecting joints and complicated return features which increases costs and the likelihood of failures caused by leaks. In most prior art systems, the valve member is an integral part of a thermally responsive element which expands to cause the valve member to engage the valve seat. Once seated such a valve member is susceptible to at least two malfunctions. It is impossible to unseat the valve member to relieve excessive system pressures which may occur if the valve ports are improperly connected to the cooler or in the event the oil line is damaged or blocked or the cooler itself has become inoperable. Secondly, the components of the bypass valve are often damaged when the thermally responsive element continues to expand, which sometimes occurs when the cooler is overloaded and the oil heats excessively. Such damage can include cracking of the valve member mounting, or internal failure of the valve components. In either case the bypass valve is unfit for further service. 
   SUMMARY OF THE INVENTION 
   According to the present invention, an oil/fluid cooler bypass valve is provided for use in conjunction with a cooling system of the type which includes a manifold type valve housing having a valve chamber communicating with an oil/fluid supply, fluid return, cooler supply, and cooler return lines. A valve member having a cooling position for directing fluid from the fluid supply line to the cooler supply line for circulation through a cooler, and then from the cooler return line to the oil return line. The valve has a warm-up position for directing oil from the oil supply line back to the oil return line, thus bypassing the heat exchanger. 
   The valve actuation mechanism of the present invention is operative to move the valve member between its warm-up and cooling positions and comprises an element responsive to changes in temperature or pressure of the fluid prior to entry to the cooler. The responsive element is integral with the valve member. The valve member is enclosed with a manifold which is fastened directly to the oil containing body. In one embodiment of the invention, the manifold is directly seated against the oil containing body. 
   In another embodiment of the present invention, the valve body has a pair of integral input and output ports. Machined into the cavity about the ports are a pair of notches configured to accept O-ring seals. These O-ring seals function to seal the ports when they are bolted directly onto the oil containing body. 
   In another embodiment of the present invention, an insertable valve element is disclosed. The valve element has a component which is responsive to changes in temperatures. The thermal component has a first valve bearing surface which mates upon a first valve seat within the valve body and a second bearing element which seals a second valve seat. Disposed between the first valve seat and an annular flange on the thermal element is a first spring which functions to bias the first bearing surface against the first valve seat at temperatures above a pre-determined level. A second bi-pass spring is disposed between the thermal element and the mounting member. The mounting member is used to fixably couple the valve element within the valve body. 
   In yet another embodiment of the present invention, the valve element having a sliding valve component is disclosed. The sliding valve component has an axial through bore which mates to an outer surface of a thermal element. The sliding valve member further has a through passage which regulates the flow of oil through the valve. 
   Other objects and features of the invention will become apparent from consideration of the following description taken in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a first embodiment of the present invention; 
       FIG. 2  is an exploded side view of the bypass valve of  FIG. 1 ; 
       FIG. 3  is a top view of an assembled bypass valve in its closed position; 
       FIG. 4  is a side view of the valve housing of the present invention; 
       FIG. 5  is a top view of the valve assembly is an open warm-up position; 
       FIG. 6  is a top view of the valve assembly of valve  1  in its bypass position; 
       FIGS. 7 and 7   a  are an exploded view of the valve elements of a second embodiment of the present invention; 
       FIG. 8  is a view of an assembled valve assembly using the valve elements according to the second embodiment of the present invention in their open position; 
       FIG. 9  is a top view of a valve assembly utilizing the valve elements according to the second embodiment of the present invention in its closed position; 
       FIGS. 10 and 10   a  are exploded views of the valve elements according to a third embodiment of the present invention; 
       FIG. 11  is a top view of a valve utilizing the valve elements according to the third embodiment of the present invention in its opened position; 
       FIG. 12  is a top view of a valve in its closed position utilizing the valve elements of the third embodiment of the present invention; 
       FIG. 13  is a top view of a valve utilizing the valve elements of the third embodiment of the present invention in its bypass mode. 
       FIGS. 14 and 15  depict perspective views of another embodiment of the present invention; 
       FIGS. 16-18  depict cross-sectional views of the bypass valve depicted in  FIG. 15 ; 
       FIGS. 19-21  depict cross-sectional views of another embodiment according to the teachings of the present invention; 
       FIGS. 22 and 23  depict a perspective view of another bypass valve according to the teachings of the present invention; 
       FIGS. 24-26  depict cross-sectional views of the bypass valve depicted in FIG.  23 . 
       FIGS. 27  depict a perspective view of another bypass valve according to the teachings of the present invention; and 
       FIGS. 28-30  depict cross-sectional views of the bypass valve depicted in FIG.  27 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIGS. 1-6 , there is illustrated a fluid cooler bypass valve  18  which can be connected to a transmission, engine or power steering fluid pump. The valve  18  is primarily formed by a housing  20  and valve element  22 . The housing  20  defines a heat exchanger bore  24  having an input port  26  and a heat exchanger output port  28 . The housing further defines a fluid return bore  30  having a return input port  32  and a return output port  34 . Disposed between the heat exchanger bore  24  and the return bore  30  is a bypass passage  36 . The bypass passage  36  is configured to accept the valve element  22 . The bypass passage  36  has a first portion  38  having a first diameter and a second portion  40  having a second diameter which is greater than the first diameter. A threaded portion  42  facilitates the coupling of the valve element  22  to the housing  20 . 
   The first portion  38  is fluidly coupled to heat exchanger bore  24  through a first valve seat  44 . Disposed between the first portion  38  and the second portion  40  is a second valve seat  46 . After assembly, the bypass valve  18  is bolted through the mounting bore  48  to the body of the oil supplying unit (not shown). Both the input port  26  and the return output port  34  are directly fastened to output ports of the oil supplying unit (not shown). Each port  26  and  34  have a port flange  52  which facilitates the coupling of the housing  20  to the output and input ports oil supply. Disposed on the mounting surface  47  of the housing  20  is a pair of annular grooves  59  about the ports  26  and  34 . These annular grooves  59  accept gaskets  50  which fluidly seal the ports  26  and  34 . 
   The valve element  22  according to the first embodiment of the present invention includes a generally cylindrical thermal element  54 . The thermal element  54  is constructed of a central member  56  and an exterior star flange  58 . The star flange  58  axially and radially supports the position of the thermal element  54 . The thermal element  54  further has a first valve bearing element  60  at the thermal element&#39;s distal end  61 . The first valve bearing element  60  interacts with the first valve seat  44  in the housing  20 . Disposed between the first valve bearing element  60  and the star flange  58  is a spring which generally biases the valve element  22  in its closed position. 
   The valve element  22  further has a second spring  64  disposed between the star flange  58  and an interior bearing surface  66  of a mounting member  68 . The mounting member  68  is constructed of a base portion  70  having a hex cap  72 . The base portion  70  defines a bore  74  with the interior bearing surface  66 . 
   As previously indicated in the description of the prior art, the purpose of the bypass valve  18  is to receive heated fluid from a transmission or engine by means of input port  26  and to return the fluid through return output port  34  before the fluid is passed through a heat exchanger during warm-up periods such as when the oil temperature is at a temperature of 160° F., or less. When the oil fluid temperature exceeds 160° F., at least a portion of the oil is directed by the valve  18  to the cooler (not shown) by means of the heat exchanger bore  24  through heat exchanger output port  28 . The cooled oil passes from the cooler (not shown) by means of return input port  32  to the valve  18  and back to the oil source by means of return output port  34 . At temperatures above 180° F., essentially all of the oil is routed through the cooler (not shown). It should be understood that these temperatures are merely exemplary and are not critical to the operating limits. 
     FIG. 3  depicts a top view of the valve assembly  18  according to the first embodiment of the present invention. Shown is the valve element  22  in its closed position. As can be seen, the first valve bearing element  60  is positioned so that the first valve seat  44  is closed. In this configuration, fluid will flow in through the input port, through the heat exchanger bore  24  and to the heat exchanger through heat exchanger output port  28 . After cooling, the fluid will flow into the bypass valve through return input port  32  and to the oil source by return output port  34 . The first and second springs  62  and  64  function to bias the valve in this position. 
   As can be seen in  FIG. 5 , when the thermal element  54  is lower than a temperature of approximately 180° F., the thermal element retracts the first valve bearing element  60  away from the first valve seat  44 . Fluid is then allowed to pass through the notches in the star flange  58 , along side the thermal element  54 , through the bypass passage  36 , and into the return bore  30 . As previously mentioned, heat exchangers can plug, causing a malfunction in the cooling system. Rather than prevent flow of the engine oil, thus causing permanent damage to the engine, the valve assembly  18  of the present invention has an integral bypass function. As best can be seen in  FIG. 6 , upon the plugging of the oil cooler (not shown), the pressure and temperature of the fluid within heat exchanger bore  24  increases substantially. This increased pressure causes the second spring  64  to be compressed, thus allowing passage of fluid from the heat exchanger bore  24  through bypass passage  36  into return bore  30 . This bypass feature forms a rapid warm-up system which contains a safety relief in the event of a catastrophic failure of any of the cooling system components. 
     FIG. 7  represents an exploded view of a valve element  76  according to a second embodiment of the present invention. Shown is a mounting member  78  having a base  80  and a hexagonal endcap  82 . The mounting member  78  further has an axially disposed engagement member  84 . Engaged to the bearing surface  85  of the engagement member  84  is the thermal unit  86 . The thermal unit is generally cylindrical having an annular flange  88  disposed on its outer surface  90 . Further disposed about the outer surface  90  is a first helical spring  92 . The thermal unit is slid into a through bore  94  of a sliding valve element  96 . 
   The sliding valve element  96  is generally cylindrical having an exterior surface  98  having a first diameter. Disposed on the distal end  97  of the sliding valve member  96  is an annular ring  100  which has a diameter greater than the first radius of the exterior surface  98 . The annular ring  100  functions to couple to interior surface  101  of bypass passage  36 . 
     FIG. 7   a  depicts a thermal unit  86  in its engaged position. When the thermal unit  86  reaches a predetermined temperature, for example 180° F., it deploys a first piston member  102 . Deployment of piston  102  functions to move the thermal unit  86  within the bypass passage  36  with respect to the outer elements of valve element  76 . 
     FIG. 8  depicts the valve element  76  shown in  FIG. 7  assembled into valve housing  104 . Mounting member  78  functions to sealably enclose the elements of valve element  76  within bypass passage  36 . As can be seen, the exterior surface  90  of thermal unit  86  is disposed within the first helical spring  92 . A portion of the first helical spring  92  is disposed within a first portion  103  of through bore  94 . First helical spring  92  is coupled against annular flange  88  of the thermal unit  86 . As can be seen, when the thermal unit  86  is below about 180° F., a flow passage  108  is opened in the slot  106 . As shown, fluid is allowed flow from input port  26  through the bypass passage  36  through output port  32 . 
   When the thermal unit  86  reaches a temperature of about 180° F., the first piston  102  is deployed and engages against a surface of engagement member  84 . This forces the body of thermal unit  86  further into the through bore  94  closing off the flow passage  108 . Although a slot  106  is shown, flow passage  108  can take the form of a hole formed through the exterior surface  98  of the sliding valve element  96  into the through bore  94 . Once the temperature of the oil drops below about 180° F., the piston  102  compresses first helical spring  92  and forces the thermal member toward the mounting member  78  re-opening flow passage  108 . This again allows fluid to flow from input port  26  to output port  32  through bypass passage  36 . 
     FIG. 10  discloses an exploded view of a valve assembly  105  according to the third embodiment of the present invention. The third embodiment has the sliding valve element  96 , intermediate first helical spring  92 , and thermal element  86 . Additionally, the valve assembly  105  of the third embodiment has an intermediate bearing member  110 . The intermediate bearing member  110  has a cylindrical portion  112  which allows it to couple to a second helical spring  114 . The second helical spring  114  is mounted within the base portion  70  of the mounting member  78 .  FIG. 10   a  depicts the thermal unit having a deployed piston member  102  as is also shown in  FIG. 7   a.    
   Generally, with reference to  FIGS. 11-13 , shown is valve assembly  105  according to the third embodiment of the present invention. Depicted in  FIG. 11  is the valve assembly  105  shown in its open position. Depicted is the sliding valve member  96  disposed about the exterior surface  90  of thermal member  86 . Disposed between the thermal member  86  and the sliding valve member  96  is a first helical spring  92 . The first helical spring functions to bias the thermal member  86  into a generally opened position allowing fluid to flow through the bypass passage  36  through flow passage  108 . Intermediate bearing member  110  and a second helical spring  114  are configured to allow the proper relationship of these components. 
   Upon reaching an elevated temperature such as 180° F., piston member  102  is deployed from thermal unit  86 . In doing so, thermal unit  86  is forced further into through bore  94  compressing first helical spring  92 , and thus closing flow passage  108 . The closing of port  108  is similar to that shown in embodiment two. 
   Should a situation occur when there is a malfunction of the cooling system, such as a blockage, a second helical spring  114  compresses under the pressure of the heated oil to allow fluid to flow around annular flange  100  of the sliding base member  96 . It should be noted that typically, when there is a blockage in the cooling system, the temperature of the fluid to be cooled quickly rises. This causes the piston  102  of thermal element  86  to be extended, normally closing off the flow of fluid through bypass passage  36 . By providing a thermal, as well as pressure bypass system, overall cooling system safety can be ensured. 
   Referring now to  FIGS. 14-18 , there is illustrated a fluid cooler bypass valve  118  which can be connected to a transmission, engine or power steering fluid pump. The valve  118  is primarily formed by a valve body  120  and valve element  122 . The valve body  120  defines a heat exchanger bore  124  having an input port  126  and a heat exchanger output port  128 . The valve body  120  further defines a fluid return bore  130  having a return input port  132  and a return output port  134 . Disposed between the heat exchanger bore  124  and the return bore  130  is a bypass passage  136 . The bypass passage  136  is configured to accept the valve element  122 . The bypass passage  136  has a first portion  138  having a first diameter and a second portion  140  having a second diameter which is greater than the first diameter. A threaded portion  142  facilitates the coupling of the valve element  122  to the valve body  120 . 
   The first portion  138  is fluidly coupled to heat exchanger bore  124  through a first valve seat  144 . After assembly, the bypass valve  118  is bolted to the valve body  120  of the oil supplying unit (not shown). Both the input port  126  and the return output port  134  are directly fastened to output ports of the oil supplying unit (not shown). Each port  126  and  134  have couplings  152  which facilitate the coupling of the valve body  120  to the output and input ports oil supply. 
   The valve element  122  according to the first embodiment of the present invention includes a generally cylindrical thermal element  154 . The thermal element  154  is constructed of a central member  156  and an exterior star washer  158 . The star washer  158  axially and radially supports the position of the thermal element  154 . Coupled to the thermal element  154  is a first valve bearing element  160  at the thermal element&#39;s distal end  161 . The first valve bearing element  160  interacts with the first valve seat  144  in the valve body  120 . Disposed between a radial flange on the first valve bearing element  160  and the first valve seat  144  is a spring which generally biases the first bearing element  160  in its opened position. 
   The first bearing element  160  further has an elastic member  164  disposed between the thermal element  154  and an interior bearing surface  166  of a mounting member  168 . The mounting member  168  is constructed of a base portion  170  having a hex cap  172 . The base portion  170  defines a bore  174  with the interior bearing surface  166 . The elastic member  164  functions to allow proper tolerance stackup during assembly of the valve, but can also function as compressible oil pressure override should the system pressure get too high. 
   As previously indicated in the description of the prior art, the purpose of the bypass valve  118  is to receive heated fluid from a transmission or engine by means of input port  126  and to return the fluid through return output port  134  before the fluid is passed through a heat exchanger during warm-up periods such as when the oil temperature is at a temperature of 160° F., or less. When the oil fluid temperature exceeds 160° F., at least a portion of the oil is directed by the valve  118  to the cooler (not shown) by means of the heat exchanger bore  124  through heat exchanger output port  128 . The cooled oil passes from the cooler (not shown) by means of return input port  132  to the valve  118  and back to the oil source by means of return output port  134 . At temperatures above 180° F., essentially all of the oil is routed through the cooler (not shown). It should be understood that these temperatures are merely exemplary and are not critical to the operating limits. 
     FIGS. 16-18  depict side views of the valve assembly  118 . Shown is the valve element  122  in its closed position. As can be seen, the first valve bearing element  160  is positioned so that the first valve seat  144  is closed. In this configuration, fluid will flow in through the input port, through the heat exchanger bore  124  and to the heat exchanger through heat exchanger output port  128 . After cooling, the fluid will flow into the bypass valve through return input port  132  and to the oil source by return output port  134 . The spring  162  functions to bias the valve in this position. 
   As can be seen in  FIG. 18 , when the thermal element  154  is a temperature less than approximately 180°, the thermal element retracts the first valve bearing element  160  away from the first valve seat  144 . Fluid is then allowed to pass through the notches in the star flange  158 , along side the thermal element  154 , through the bypass passage  136 , and into the return bore  130 . Alternatively, the input and outputs can be exchanged. In this instance, as previously mentioned, heat exchangers can plug, causing a malfunction in the cooling system. Rather than prevent flow of the engine oil, thus causing permanent damage to the engine, the valve assembly  118  of the present invention has an integral bypass function. Upon the plugging of the oil cooler (not shown), the pressure and temperature of the fluid within heat exchanger bore  124  increases substantially. Optionally, this increased pressure causes the elastic element  164  to be compressed, thus allowing passage of fluid from the heat exchanger bore  124  through bypass passage  136  into return bore  130 . This bypass feature forms a rapid warm-up system which contains a safety relief in the event of a catastrophic failure of any of the cooling system components. 
     FIGS. 19-21  represent a cross-sectional view of a valve  176  according to another embodiment of the present invention. Shown is a mounting member  178  having a base  180  and a hexagonal endcap  182 . The mounting member  178  further has an axially disposed engagement member  184 . Engaged to the bearing surface  185  of the engagement member  184  is a first helical spring  192  and a thermal unit  186 . The thermal unit  186  is generally cylindrical having an annular flange  188  which forms a metering surface  189  disposed on its outer surface  190 . The thermal unit  186  is slid into a through bore  194  of a sliding valve element  196 . 
     FIG. 19  depicts a thermal unit  186  in its bypass position. When the thermal unit  186  reaches a predetermined temperature, for example 180° F., it deploys a first piston member  202 . Deployment of piston  202  functions to move the thermal unit  186  within the bypass passage  136  with respect to the outer elements of valve element  176 . 
     FIG. 20  depicts the valve element  176  shown in  FIG. 19  assembled into valve housing  204 . Mounting member  178  functions to sealably enclose the valve element  176  within bypass passage  136 . As can be seen, the metering surface  189  of thermal unit  186  is disposed adjacent the input port. The metering surface  189  defines a bevel  191  which prevents a total closure of the input port, which has a cross-sectional area larger than the area of the metering surface. Thus, the metering surface partially obscures the input port. First helical spring  192  is coupled against annular flange  188  of the thermal unit  186 . As can be seen, when the thermal unit  186  is above about 180° F., oil flows past the bevel  191  of metering surface  189  into the cooler. As shown, fluid is allowed flow from input port  126  through the cooler and through output port  132 . 
   When the thermal unit  186  reaches a temperature above about 180° F., the first piston  202  is fully deployed and engages against a surface of engagement member  184 . This forces the body of thermal unit  186  further into the through bore  194  closing off the flow passage  208 . Once the temperature of the oil drops below about 180° F., the piston  202  is compressed by first helical spring  192  and forces the thermal member  186  to reopen flow passage  208 . 
     FIG. 21  depicts an optional bypass notch  185 . Should the head exchanger plug, pressure increases force the compression of the helical spring  192 . The pressurized oil will then pass the bevel  191  on the metering surface  189  and travel through the flow passage  208 . 
     FIG. 22  discloses an exploded view of a valve assembly  205  according to another embodiment of the present invention. The valve assembly has the sliding valve element  196 , intermediate first helical spring  192 , and thermal element  186 . Additionally, the valve assembly  205  of the third embodiment has a pair of star washers  210 . The star washers  210  are coupled into the valve body  220  by a snap ring  214 . The snap ring  214  is mounted within a groove defined in the flow passage  208 . 
   The valve body  220  is cylindrical and has a first portion  222  which has a threaded outer surface  224  and a second portion  225  which has a diameter smaller than the first portion  222 . The threaded outer surface  224  is configured to be mated with a threaded bore  226  defined in a transmission case  228 . Fluidly coupled to the bore  226  is at least one oil cooler supply line  230 . The second portion  225  is configured to be positioned adjacent to the fluid supply lines  230  to allow oil to fill the cavity formed between the second portion  225  and the bore  226  of transmission case  228 . 
   Defined within the second portion  225  is at least one orifice  232  for bringing oil into the bypass valve assembly  205 . The orifice  232  fluidly couples the cavity  231  to a flow passage  234  defined within the valve body  220 . Defined on a distal end  236  of the valve body  220  is a bypass orifice  238  which returns oil back to the transmission. The bypass orifice  238  defines a valve seat  240  which mates with the valve element  196 . 
   As best seen in  FIG. 25 , when the temperature of the oil is above about 180° F., the thermal element  186  actuates a piston  102 , forcing the valve element  196  into the valve seat  240 . This allows the coolant to pass through the flow passage  234  to a heat exchanger (not shown). Oil flowing through the heat exchanger returns to the transmission case at a location remote from the valve body. It should be noted that the flow passage  234  defines a coupling  246  at a proximal end  248  of the body  220  for fluidly coupling the valve body  220  to the heat exchanger. 
   As best seen in  FIG. 26 , when the temperature is below about 160° F., the thermal element  196  retracts its piston, which moves the sliding valve element  196  away from the valve seat  240 . Oil then bypasses the heat exchanger and immediately returns to the transmission case  228  via the bypass orifice  238 . 
     FIG. 27  discloses an exploded view of a valve assembly  256  according to another embodiment of the present invention. The valve assembly has the sliding valve element  258 , first and second intermediate helical springs  260  and  262 , thermal element  186  and valve seal  265 . Additionally, the valve assembly  256  has a valve body  264  which is configured to encase the afore mentioned components. A snap ring  266 , which functions as a valve seal stop, is mounted within a groove  268  defined on the sliding valve element  258 . 
   The valve body  264  is cylindrical and is configured to be disposed within an aperture  270  formed within a structure  272 . In this regard, the valve body  264  has outer surface  274  is configured to be frictionally engaged with the interior surface  276  of the aperture  270 . A notch  275  formed on the outer surface  274  which is configured to hold an O-ring  277  that fluidly seals and couples the valve body outer surface  274  within the aperture  270 . Additionally the valve body  264  defined a through bore  278 . Fluidly coupled to the bore  278  is at least one oil cooler supply line  230  which is fluidly coupled to an oil cooler (not shown). The valve body  264  is configured to be positioned adjacent to the fluid supply lines  230  to allow oil to bypass the oil cooler and flow through the valve assembly  256  to the fluid return  280 . 
   Defined within a first portion  281  of the valve body  264  is at least one orifice  282  for bringing oil into the bypass valve assembly  256 . The orifice  282  fluidly couples the oil cooler supply line  230  to a flow passage  284  defined within the valve body  264 . Defined on the outer surface  274  of distal end  286  of the valve body  264  is a bypass orifices or slots  288  which fluidly couples the flow passage  284  to a cavity  290  formed by the outer surface  274  of the valve body  264  and the aperture  270 . The cavity  290  is fluidly coupled to the fluid return line through slots  292  defined in the outer surface of the valve body  264 . Although slots are shown, it is envisioned that a star washer can be used to retain the valve body and allow the flow of the bypass oil. As further described below, the bypass orifice  282  defines an outer spring bearing surface  283  and a valve seat  294  which mates with the valve element  262 . 
   As best seen in  FIG. 28 , the thermal element  186  is fixably coupled to an interior surface of the through passage valve body  264 . The thermal element  186  has an exterior cylindrical bearing surface  300  which is used to slidably support an interior bearing surface  302  defined in the sliding valve element  258 . As previously described, the thermal element  186  has an actuatable piston which actuates or retracts as the temperature of the thermal element increases or decreases. This actuatable piston is configured to apply force onto an interior surface of the sliding valve element  258 . 
   The sliding valve element  258  has a first outer bearing surface  304  which is configured to engage a first end of the second intermediate spring  262 . The sliding valve element  250  further has a second exterior bearing surface  306  which is configured to engage a first end  308  of the second intermediate spring. Disposed adjacent to the second exterior bearing surface  300  is a cylindrical valve element bearing surface  310 . The cylindrical valve element bearing surface  310  slidably supports the valve seal  265  and regulates the movement of the valve seal  265  toward and away from the valve seat  294 . The valve seal  265  is biased by the second intermediate spring toward the snap ring  266 . The snap ring  266  functions to regulate the movement of the valve element  264  along the cylindrical valve element bearing surface  310 . The first spring is annularly disposed about a portion of the sliding valve element  258 . The first spring is configured to bias the sliding valve element  258  away from the bearing seat  294 . 
   When the temperature is below about 160° F., the thermal element  186  retracts its piston, which allows the sliding valve element  262  away from the valve seat  294 . Oil then bypasses the heat exchanger by passing through the flow passage  284  and though the cavity  290  formed by the outer surface  274  of the valve body  264  and the aperture  270 . The bypass fluid then pass through the slots  292  defined in the outer surface of the valve body  264  the and immediately returns to the transmission case  228  via the return line  280 . 
   As best seen in  FIG. 29 , when the temperature of the oil is above about 180° F., the thermal element  186  actuates a piston, forcing the sliding valve element  258  and seal  265  into the valve seat  294 . As shown, the snap ring  266  is positioned within the orifice  282  in such a way to allow the engagement of the valve element with the valve seat. This allows the coolant to pass the bypass passage and flow through a heat exchanger (not shown). Oil flowing through the heat exchanger returns to the transmission case at a location remote from the valve body. It should be noted that the flow passage  234  defines a coupling  246  at a proximal end  248  of the body  220  for fluidly coupling the valve body  220  to the heat exchanger. 
   As best seen in  FIG. 30 , when the temperature of the oil is above about 180° F. and the pressure is above a predetermined level from an oil cooler blockage, the valve seal  265  is forced by the increased oil pressure away from the valve seat  294 . The valve element slides along valve element bearing surface away from the snap ring. This allows the oil to pass through the bypass valve and to bypass the heat exchanger (not shown). Oil flowing through the bypass valve  256  returns to the transmission case. It should be noted that the flow passage  234  defines a coupling  246  at a proximal end  248  of the body  220  for fluidly coupling the valve body  220  to the heat exchanger. 
   The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention.