Method of Controlling the Temperature of Oil for Vehicle Powertrain

Abstract

A thermal management unit for a vehicle powertrain includes an integrated oil heater, a control valve, and a pressure relief valve. A remote oil cooler is connected to fluid ports of the thermal management unit. Transmission oil is received into the thermal management unit and is directed to one or both of the transmission oil heater and the transmission oil cooler. A portion of the flow of oil can be internally bypassed through the pressure relief valve to maintain the pressure of the oil below a threshold. The flow of oil is directed through the control valve after having been heated and/or cooled, and the proportions of oil being directed through the oil heater and the oil cooler are determined by the temperature of the oil in the control valve.

What is claimed is: 
     
         1 . A method of controlling the temperature of oil for a vehicle powertrain, comprising:
 receiving a flow of oil from the vehicle powertrain into a thermal management unit at a first pressure;   directing at least some of the flow of oil through at least one of a transmission oil heater and a transmission oil cooler;   receiving said at least some of the flow of oil into a control valve arranged within the thermal management unit after passing through the at least one of a transmission oil heater and a transmission oil cooler, wherein said oil is received into the control valve at a second pressure lower than the first pressure;   directing any remaining flow of oil through a bypass arranged within the thermal management unit to avoid passing that remaining flow of oil through either of the transmission oil heater and the transmission oil cooler;   measuring a temperature of oil received into the control valve; and   returning the flow of oil to the vehicle powertrain from the thermal management unit.   
     
     
         2 . The method of  claim 1 , wherein the step of directing any remaining flow of oil through the bypass includes flowing said oil through the control valve. 
     
     
         3 . The method of  claim 1 , wherein the amount of oil passing through the bypass is determined in response to a pressure differential between the first pressure and the second pressure. 
     
     
         4 . The method of  claim 1 , wherein the step of measuring a temperature of oil includes directing the entire flow of oil received into the thermal management unit over a temperature-responsive element arranged within the control valve. 
     
     
         5 . The method of  claim 1 , wherein said oil flowing through at least one of a transmission oil heater and a transmission oil cooler is recombined with said oil directed through the bypass prior to exiting the control valve. 
     
     
         6 . A method of managing oil for a vehicle powertrain, comprising:
 receiving a flow of oil from the vehicle powertrain into a thermal management unit at a first temperature below a threshold temperature;   dividing the flow of oil into a first portion and a second portion;   directing the first portion into a transmission oil heater integrated into the thermal management unit;   heating the first portion in the transmission oil heater;   recombining the first portion with the second portion, the second portion having bypassed the transmission oil heater, wherein the recombined flow is at a second temperature higher than the first temperature;   receiving the recombined flow of oil into a control valve located within the thermal management unit;   passing the recombined flow of oil over a temperature-responsive element arranged within the control valve; and   returning the recombined flow of oil to the vehicle powertrain from the thermal management unit at the second temperature.   
     
     
         7 . The method of  claim 6 , wherein the flow of oil is a first flow of oil, further comprising:
 receiving a second flow of oil from the vehicle powertrain into the thermal management unit some time after having returned the first flow of oil to the vehicle powertrain;   directing substantially all of the second flow of oil into the transmission oil heater;   heating the second flow of oil in the transmission oil heater;   receiving the second flow of oil into the valve at a temperature substantially equal to the threshold temperature;   actuating an actuator of the valve in response to passing the second flow of oil over the temperature-responsive element so that subsequent flows of oil into the thermal management unit are at least partially directed through an oil cooler associated with the vehicle powertrain.