Method and system for coolant temperature control in a vehicle propulsion system

Abstract

A vehicle propulsion system includes a prime mover having a coolant inlet and a coolant outlet, a coolant control valve having a valve inlet in communication with the prime mover coolant outlet, a first valve outlet, and a second valve outlet, a bypass flow path in communication with first valve outlet and the prime mover coolant inlet, a heat exchange flow path in communication with the second valve outlet and the prime mover inlet, a heat exchanger in the heat exchange flow path, a first temperature sensor in the bypass flow path for generating a first temperature signal, a second temperature sensor in the heat exchange flow path for generating a second temperature signal, and a controller for providing a coolant control valve command signal to the coolant control valve, using a normalized gain coefficient.

1 . A vehicle propulsion system, the system comprising:
 a prime mover having a coolant inlet and a coolant outlet;   a coolant control valve having a valve inlet in communication with the prime mover coolant outlet, a first valve outlet, and a second valve outlet;   a bypass flow path in communication with first valve outlet and the prime mover coolant inlet;   a heat exchange flow path in communication with the second valve outlet and the prime mover inlet;   a heat exchanger in the heat exchange flow path;   a first temperature sensor in the bypass flow path for generating a first temperature signal;   a second temperature sensor in the heat exchange flow path for generating a second temperature signal;   a third temperature sensor at the prime mover coolant inlet for generating a third temperature signal; and   a controller in communication with the first temperature sensor for receiving the first temperature signal, the second temperature sensor for receiving the second temperature signal, the third temperature sensor for receiving the third temperature signal, and the coolant control valve for providing a coolant control valve command signal to the coolant control valve, wherein the controller comprises a closed loop controller with a gain coefficient, and wherein the controller normalizes the gain coefficient, and wherein the controller is further in communication with the coolant control valve and controls the coolant control valve based upon the normalized gain coefficient.   
     
     
         2 . The system of  claim 1 , wherein the closed loop controller comprises a proportional/integral closed loop controller. 
     
     
         3 . The system of  claim 2 , wherein the gain coefficient comprises one of a proportional gain coefficient and an integral gain coefficient for the proportional/integral closed loop controller. 
     
     
         4 . The system of  claim 1 , wherein the controller normalizes the gain coefficient based upon a ratio of a predetermined difference in values between a first temperature signal and the second temperature signal and a current difference in values between a first temperature signal and the second temperature signal. 
     
     
         5 . The system of  claim 4 , wherein the predetermined difference in values between a first temperature signal and the second temperature signal correspond to a first temperature signal value and a second temperature signal value which both correspond to the gain coefficient. 
     
     
         6 . The system of  claim 1 , wherein the second temperature sensor is downstream of the heat exchanger in the heat exchange flow path. 
     
     
         7 . The system of  claim 1 , wherein the bypass flow path and the heat exchange flow path combine to form a prime mover coolant inlet flow path at the prime mover coolant inlet. 
     
     
         8 . The system of  claim 7 , wherein the third temperature sensor is positioned in the prime mover coolant inlet flow path. 
     
     
         9 . A method for controlling prime mover temperature in a vehicle propulsion system having a coolant control valve with a valve inlet in communication with a coolant outlet of the prime mover, and a first valve outlet in communication with a bypass flow path, and second valve outlet in communication with a heat exchange flow path, the heat exchange flow path including a heat exchanger, wherein the bypass flow path is in communication with first valve outlet and a prime mover coolant inlet, the method comprising:
 sensing a first temperature with a first temperature sensor in the bypass flow path;   sensing a second temperature with a second temperature sensor in the heat exchange flow path;   normalizing a gain coefficient in a closed loop controller based upon the first and second temperatures;   generating a command signal for the coolant control valve based upon the normalized gain coefficient; and   operating the coolant control valve based upon the command signal.   
     
     
         10 . The method of  claim 9 , wherein the closed loop controller comprises a proportional/integral closed loop controller. 
     
     
         11 . The method of  claim 10 , wherein the gain coefficient comprises one of a proportional gain coefficient and an integral gain coefficient for the proportional/integral closed loop controller. 
     
     
         12 . The method of  claim 9 , wherein normalizing the gain coefficient is based upon a ratio of a predetermined difference in first temperature and second temperature and a current difference in values between first temperature and second temperature. 
     
     
         13 . The method of  claim 12 , wherein the predetermined difference in first temperature and second temperature both correspond to the gain coefficient. 
     
     
         14 . The method of  claim 9 , wherein the second temperature sensor is downstream of the heat exchanger in the heat exchange flow path. 
     
     
         15 . The method of  claim 9 , wherein the bypass flow path and the heat exchange flow path combine to form a prime mover coolant inlet flow path at the prime mover coolant inlet. 
     
     
         16 . The method of  claim 15 , wherein the third temperature sensor is positioned in the prime mover coolant inlet flow path.