Regulating Transmission Fluid and Engine Coolant Temperatures in a Motor Vehicle

Abstract

A system for controlling the temperature of a transmission fluid includes a first heat exchanger communicating with a source of engine coolant for transferring heat between the engine coolant and the transmission fluid and including a first outlet through which transmission fluid exits the first heat exchanger, a second heat exchanger through which air may flow for transferring heat between the transmission fluid and the air and including a second inlet through which transmission fluid enters the second heat exchanger, and second outlet through which transmission fluid exits the second heat exchanger, and a first bypass valve for alternately opening and closing the second inlet and the second outlet when a temperature of transmission fluid exiting the first outlet is greater than a first reference temperature, and for bypassing the second heat exchanger when the temperature of transmission fluid exiting the first outlet is less than the second reference temperature.

1 . In a motor vehicle having an internal combustion engine and automatic transmission, a system for regulating the temperature of transmission fluid and engine coolant comprising:
 a source of engine coolant;   a source of transmission fluid;   a first heat exchanger communicating with the source of engine coolant, including a first inlet through which transmission fluid enters the first heat exchanger from the source of transmission fluid, and a first outlet through which transmission fluid exits the first heat exchanger, for transferring heat between the engine coolant and the transmission fluid;   a second heat exchanger through which air may flow, including a second inlet through which transmission fluid enters the second heat exchanger, and second outlet through which transmission fluid exits the second heat exchanger, for transferring heat between the transmission fluid and the air;   a first bypass valve for opening communication through the second inlet and the second outlet when a temperature of transmission fluid exiting the first outlet is greater than a first reference temperature, and for closing communication through the second inlet and the second outlet when the temperature of transmission fluid exiting the first outlet is less than the second reference temperature.   
   
   
       2 . The system of  claim 1  wherein the first heat exchanger and the first bypass valve are connected to the transmission. 
   
   
       3 . The system of  claim 1  further comprising:
 a third heat exchanger communicating with the source of engine coolant; and   a second bypass valve for opening communication between the engine coolant in the third heat exchanger and the engine coolant in the first heat exchanger when a temperature of engine coolant entering the second bypass valve is greater than a third reference temperature, and closing communication between the engine coolant in the third heat exchanger and the engine coolant in the first heat exchanger when the temperature of said engine coolant entering the second bypass valve is less than the third reference temperature.   
   
   
       4 . The system of  claim 1  wherein the first heat exchanger, the first bypass valve and the second bypass valve are connected to the transmission. 
   
   
       5 . The system of  claim 1  wherein the third heat exchanger further comprises a heater core for transferring heat from the engine coolant to air in a passenger compartment of the vehicle. 
   
   
       6 . The system of  claim 1  wherein the third heat exchanger further comprises a radiator for transferring heat from the engine coolant to ambient air. 
   
   
       7 . The system of  claim 1  wherein the third heat exchanger further comprises:
 a heater core for transferring heat from the engine coolant to air in a passenger compartment of the vehicle; and   a radiator communicating with the heater core, for transferring heat from the engine coolant to ambient air.   
   
   
       8 . The system of  claim 1  further comprising a connection between the first outlet and the source of transmission fluid. 
   
   
       9 . The system of  claim 1  wherein the first bypass valve further includes a connection between the first outlet and the source of transmission fluid. 
   
   
       10 . A method for regulating the temperature of transmission fluid and engine coolant in a motor vehicle having a source of engine coolant and a source of transmission fluid, the method comprising the steps of:
 providing a first heat exchanger communicating with the source of engine coolant and including a first inlet through which transmission fluid enters the first heat exchanger from the source of transmission fluid and a first outlet through which transmission fluid exits the first heat exchanger;   using the first heat exchanger to transfer heat between the engine coolant and the transmission fluid;   providing a second heat exchanger that includes a second inlet through which transmission fluid enters the second heat exchanger, and second outlet through which transmission fluid exits the second heat exchanger;   using the second heat exchanger to transfer heat between the transmission fluid and ambient air;   opening communication through the second inlet and the second outlet when a temperature of transmission fluid exiting the first outlet is greater than a first reference temperature; and   closing communication through the second inlet and the second outlet when the temperature of transmission fluid exiting the first outlet is less than the first reference temperature.   
   
   
       11 . The method of  claim 10  further comprising the steps of:
 providing a third heat exchanger communicating with the source of engine coolant;   opening communication between the engine coolant in the third heat exchanger and the engine coolant in the first heat exchanger when a temperature of engine coolant exiting the third heat exchanger is greater than a third reference temperature; and   closing communication between the engine coolant in the third heat exchanger and the engine coolant in the first heat exchanger when the temperature of engine coolant exiting the third heat exchanger is less than the third reference temperature.