Abstract:
Vehicle oil, particularly transmission hydraulic fluid, is cooled by circulating the oil from the working component to a heat exchanger submerged in the fuel tank.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The invention relates to cooling of vehicle working fluids such as transmission fluid.  
         [0003]     2. Description of the Problem  
         [0004]     The oils used for vehicle hydraulic systems, such as drive train components, and for vehicle engines break down when subjected to sustained overheating. Oil coolers are frequently required for heavy duty vehicles to keep oil temperature within limits. Such cooling systems are known for power steering and transmission hydraulic fluid circuits as well as for engine oil systems. Oil coolers of various types have typically relied on direct air cooling, typically accomplished by positioning an oil cooler in line with an engine coolant radiator. However, air cooling is not the most effective method, and positioning an oil radiator directly behind the engine coolant radiator detracts from the performance of the engine radiator and adds heat to air entering the engine compartment. It is also known to use engine coolant to cool transmission fluid, though this arrangement adds to the load on the engine cooling system. Both of these solutions add the overarching problem of removing heat from the engine compartment.  
       SUMMARY OF THE INVENTION  
       [0005]     According to the invention there is provided an oil cooling system. The oil cooling system utilizes a side mounted truck fuel tank in which a heat exchanger is installed. The heat exchanger is located low in the fuel tank to remain submerged in the liquid fuel. Oil is circulated through the heat exchanger from an inlet to the heat exchanger to an outlet. The oil circulates from a vehicle component, such as the transmission, and is returned to the component from the outlet from the heat exchanger. Hoses or other conduits serve to deliver fluid to and from the heat exchanger.  
         [0006]     Additional effects, features and advantages will be apparent in the written description that follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0008]      FIG. 1  is a side elevation of a truck equipped with a side mounted saddle tank.  
         [0009]      FIG. 2  is a perspective view of the relative positions of a vehicle transmission and the saddle tank.  
         [0010]      FIG. 3  is a cut open of a saddle with a heat exchanger installed in the bottom thereof. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]     Referring now to the figures and in particular to  FIG. 1 , a truck  14  equipped with a fuel tank  20  adapted for transmission fluid cooling is illustrated. Truck  14  is equipped with wheels  12  and a diesel engine (not shown) located in an engine compartment  18 . Fuel tanks  20  are saddle type, mounted along the sides of the vehicle where they are attached to vehicle side frame rails  22 . Fuel tanks  20  are cylindrical, mounted partially extending into the vehicle slipstream and outside the heat reservoir associated with engine compartment  18 .  
         [0012]     Referring now to  FIG. 2 , connection of a vehicle transmission housing  24  to the left side fuel tank  20  is illustrated. Transmission housing  24  is located between frame rails  22  directly behind the diesel engine for connection to the engine crankshaft. In this location the transmission housing  24  is exposed to heat transfer from the engine compartment. An engine crankcase  26  installed directly below the diesel engine and directly forward from the transmission housing  24  is also shown. The transmission within transmission housing  24  utilizes an oil or transmission fluid as a working fluid. In operation the transmission fluid is exposed to substantial heating during circulation through the transmission. To allow cooling of the oil the oil circulation circuit includes an outlet hose  28  and a return hose  30  from and to the transmission housing  24  for transfer of transmission fluid to and from a heat exchanger  36 . The present invention provides that the heat exchanger  36  be installed submerged in fuel in one of side mounted fuel tanks  20 . Outlet hose  28  is illustrated connected to the front face of fuel tank  20  and return hose  30  is connected to the trailing face of fuel tank  20  for delivering transmission fluid to and taking it from the heat exchanger. Fuel tank  30  is equipped with a fuel vent  32 .  
         [0013]     Referring to  FIG. 3 , a cutaway section view of the bottom of fuel tank  30 , taken along section lines  3  in  FIG. 2  is illustrated. Heat exchanger  36  is positioned in the bottom portion of fuel tank  30  where it remains submerged in fuel  40  even when only a fraction of the tanks capacity is taken up by fuel. Heat exchanger  36  extends from front wall  31  to back wall  33 , connecting at its ends to the outlet hose  28  and return hose  30 , respectively. Heat exchanger  36  may be a straight through pipe, or it may be serpentine in shape, as shown, to promote the transfer of heat. Heat exchanger  36  is preferably made of a good heat conducting material, such as copper. Heat is thereby transmitted to the fuel  40  and from the fuel through tank walls  34  to the ambient atmosphere. A fuel level sensor  38  is preferably included in the tank for provided indication of fuel levels approaching the upper edge of the heat exchanger  36 . This is useful in preventing so much fuel being drained from the tank  20  so as to expose the heat exchanger  36  and compromising heat transfer. Circulation of fuel  40  within the tank  20  promotes transfer of heat to the tank wall  34  where it is radiated to the environment.  
         [0014]     Because of the advantages of using a liquid over air to remove heat from transmission fluid, the heat exchange mechanism can be made simple, and radiating vanes may not be necessary.  
         [0015]     While the invention is shown in only two of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.