Method for controlling exhaust gas heat recovery systems in vehicles

Abstract

A method of operating an exhaust gas heat recovery (EGHR) system in a vehicle including an engine, a transmission, and an EGHR heat exchanger is provided. The method includes monitoring an engine water temperature and may include monitoring a transmission oil temperature and an ambient air temperature. The method includes comparing the monitored engine water temperature to one or more calibrated engine temperatures. Based upon the monitored temperatures and comparison to the calibrated temperatures, the method controls a two-way valve. The two-way valve is configured to be set to one of an engine position and a transmission position. The engine position allows heat-exchange communication between the EGHR heat exchanger and the engine, and the transmission position allows heat-exchange communication between the EGHR heat exchanger, the transmission, and the engine.

1 . A method of operating an exhaust gas heat recovery (EGHR) system in a vehicle including an engine, a transmission, and an EGHR heat exchanger, the method comprising:
 controlling a two-way valve, wherein the two-way valve is configured to be set to one of an engine position and a transmission position, wherein the engine position allows heat-exchange communication between the EGHR heat exchanger and the engine and the transmission position allows heat-exchange communication between the EGHR heat exchanger, the transmission, and the engine;   monitoring an engine water temperature;   comparing the monitored engine water temperature to a calibrated first engine temperature; and   if the monitored engine water temperature is below the calibrated first engine temperature, setting the two-way valve to the engine position.   
     
     
         2 . The method of  claim 1 , further comprising:
 monitoring a transmission oil temperature;   comparing the monitored transmission oil temperature to a calibrated first transmission temperature; and   if the monitored transmission oil temperature is below the calibrated first transmission temperature and the monitored engine water temperature is below the calibrated first engine temperature, setting the two-way valve to the transmission position.   
     
     
         3 . The method of  claim 2 , further comprising:
 monitoring an ambient air temperature;   comparing the monitored ambient air temperature to a calibrated hot ambient temperature;   if the monitored ambient air temperature is greater than the calibrated hot ambient temperature, comparing the monitored engine water temperature to a calibrated extreme engine temperature; and   if the monitored engine water temperature is less than the calibrated extreme engine temperature, setting the two-way valve to the engine position.   
     
     
         4 . The method of  claim 3 , wherein the vehicle further includes a transmission radiator, and further comprising:
 if the monitored engine water temperature is greater than the calibrated extreme engine temperature, comparing the monitored transmission oil temperature to a calibrated extreme transmission temperature; and   if the monitored transmission oil temperature is below the calibrated extreme transmission temperature, setting the two-way valve to the transmission position, such that the transmission radiator is in heat-exchange communication with the engine.   
     
     
         5 . The method of  claim 4 , further comprising:
 if the monitored engine water temperature is greater than the calibrated extreme engine temperature and the monitored transmission oil temperature is greater than the calibrated extreme transmission temperature, setting the two-way valve to the engine position, such that the transmission radiator is not in heat-exchange communication with the engine.   
     
     
         6 . The method of  claim 5 , further comprising:
 comparing the monitored ambient air temperature to one of a calibrated cold ambient temperature, a calibrated mild ambient temperature, and the calibrated hot ambient temperature;   if the monitored ambient air temperature is below the calibrated cold ambient temperature, comparing the monitored engine water temperature to a calibrated second engine temperature, wherein the calibrated second engine temperature is greater than the calibrated first engine temperature; and   if the monitored engine water temperature is below the calibrated second engine temperature, setting the two-way valve to the engine position.   
     
     
         7 . The method of  claim 6 , further comprising:
 monitoring for an auto-stop mode, wherein the auto-stop mode occurs when the engine is not producing positive torque;   if the engine is in the auto-stop mode and if the monitored ambient air temperature is below the calibrated cold ambient temperature, comparing the monitored transmission oil temperature to a calibrated second transmission temperature, wherein the calibrated second transmission temperature is less than the calibrated first transmission temperature; and   if the monitored transmission oil temperature is below the calibrated second transmission temperature, setting the two-way valve to the transmission position.   
     
     
         8 . The method of  claim 7 , wherein the calibrated hot ambient temperature is seventeen degrees Celsius. 
     
     
         9 . The method of  claim 8 , wherein the calibrated cold ambient temperature is eight degrees Celsius. 
     
     
         10 . A method of operating an exhaust gas heat recovery (EGHR) system in a vehicle including an engine, a transmission, a transmission radiator, and an EGHR heat exchanger, the method comprising:
 controlling a two-way valve, wherein the two-way valve is configured to be set to one of an engine position and a transmission position, wherein the engine position allows heat-exchange communication between the EGHR heat exchanger and the engine and the transmission position allows heat-exchange communication between the EGHR heat exchanger, the transmission, and the engine;   monitoring an engine water temperature;   monitoring a transmission oil temperature;   monitoring an ambient air temperature; and   comparing the monitored ambient air temperature to a calibrated hot ambient temperature, and:
 if the monitored ambient air temperature is greater than the calibrated hot ambient temperature, comparing the monitored engine water temperature to a calibrated extreme engine temperature, 
 if the monitored engine water temperature is less than the calibrated extreme engine temperature, setting the two-way valve to the engine position, 
 if the monitored engine water temperature is greater than the calibrated extreme engine temperature, comparing the monitored transmission oil temperature to a calibrated extreme transmission temperature, and 
 if the monitored transmission oil temperature is below the calibrated extreme transmission temperature, setting the two-way valve to the transmission position, such that the transmission radiator is in heat-exchange communication with the engine. 
   
     
     
         11 . The method of  claim 10 , further comprising:
 if the monitored engine water temperature is greater than the calibrated extreme engine temperature and the monitored transmission oil temperature is greater than the calibrated extreme transmission temperature, setting the two-way valve to the engine position, such that the transmission radiator is not in heat-exchange communication with the engine.   
     
     
         12 . The method of  claim 11 , further comprising:
 comparing the monitored ambient air temperature to one of a calibrated cold ambient temperature, a calibrated mild ambient temperature, and the calibrated hot ambient temperature;   if the monitored ambient air temperature is below the calibrated cold ambient temperature, comparing the monitored engine water temperature to a calibrated second engine temperature, wherein the calibrated second engine temperature is greater than the calibrated first engine temperature; and   if the monitored engine water temperature is below the calibrated second engine temperature, setting the two-way valve to the engine position.   
     
     
         13 . The method of  claim 12 , further comprising:
 monitoring for an auto-stop mode, wherein the auto-stop mode occurs when the engine is not producing positive torque;   if the engine is in the auto-stop mode and if the monitored ambient air temperature is below the calibrated cold ambient temperature, comparing the monitored transmission oil temperature to a calibrated second transmission temperature, wherein the calibrated second transmission temperature is less than the calibrated first transmission temperature; and   if the monitored transmission oil temperature is below the calibrated second transmission temperature, setting the two-way valve to the transmission position.