Internal combustion engine with variable speed coolant pump

Abstract

An internal combustion engine has a variable speed coolant pump which is operated at a variable duty-cycle at lower coolant temperatures, while transitioning to a predetermined fixed speed during a final warmup period of operation, and finally to a select-speed operation at one of a selected number of steady state operating speeds selected as a function of at least engine load.

1 . An internal combustion engine, comprising:
 an engine housing having a plurality of coolant passages;   a heat exchanger for rejecting heat from coolant circulated from said engine housing; and   a variable speed coolant pump for circulating coolant from said engine housing to said heat exchanger, with said coolant pump operating according to a predetermined, variable duty cycle at lower coolant temperatures, and with the pump operating at a selected one of a plurality of predetermined fixed speeds, as a function of at least engine speed and engine load, once the engine has attained a higher, stable operating temperature.   
   
   
       2 . An internal combustion engine according to  claim 1 , wherein the operating speed of said pump is additionally a function of engine coolant temperature. 
   
   
       3 . An internal combustion engine according to  claim 1 , wherein said pump is operated at a predetermined fixed speed if heat is requested from a passenger cabin heater furnished with coolant by said pump. 
   
   
       4 . An internal combustion engine according to  claim 1 , wherein said pump is driven by a motor. 
   
   
       5 . An internal combustion engine according to  claim 4 , wherein said pump is driven by an electric motor. 
   
   
       6 . An internal combustion engine according to  claim 4 , wherein said pump is driven by a fluid motor. 
   
   
       7 . An internal combustion engine according to  claim 1 , wherein said pump is shut of when the engine is turned off, unless heat is requested from a passenger cabin heater furnished with coolant by said pump. 
   
   
       8 . An internal combustion engine according to  claim 1 , wherein operation of said pump at said variable duty cycle is at a fixed speed. 
   
   
       9 . An internal combustion engine according to  claim 1 , further comprising a controller for operating said pump. 
   
   
       10 . A method for operating a variable speed coolant pump for circulating liquid coolant through a housing of an internal combustion engine, as well as through a heat exchanger, comprising:
 duty-cycle operation of the pump initially at a variable duty cycle selected as a function of at least a temperature of the engine; and   select-speed operation of the pump at a selected one of a plurality of predetermined fixed speeds, with said speed being selected as a function of at least engine speed and engine load, once the engine has attained a stable operating temperature.   
   
   
       11 . A method according to  claim 10 , further comprising operating the pump during final warmup at a single predetermined fixed speed between said duty-cycle operation and said select-speed operation. 
   
   
       12 . A method according to  claim 10 , wherein said duty-cycle operation comprises a first period of operation at a shorter duty cycle, while the coolant temperature is below a first threshold, and a second period of operation, at a longer duty cycle, while the coolant is between said first threshold and a second, higher threshold. 
   
   
       13 . A method according to  claim 12 , wherein operation at said longer duty cycle is followed by operation of the pump during a third time period at a single predetermined fixed speed during final warmup at temperatures between said second threshold and a third threshold which is higher than the second threshold. 
   
   
       14 . A method according to  claim 13 , wherein said select-speed operation is initiated at coolant temperatures above said third threshold. 
   
   
       15 . A method according to  claim 10 , wherein said duty-cycle operation comprises a first period of operation at a shorter duty cycle in the range of 10%-20%, while the coolant temperature is below a first threshold, and a second period of operation, at a longer duty cycle, in the range of 40%-60%, while the coolant is between said first threshold and a second, higher threshold. 
   
   
       16 . A method according to  claim 10 , wherein said duty-cycle operation comprises a first period of operation at a shorter duty cycle, while the coolant temperature is below a first threshold, and a second period of operation, at a longer duty cycle, while the coolant is between said first threshold and a second, higher threshold, with said duty-cycle operation occurring at a fixed pump speed. 
   
   
       17 . A hybrid vehicle, comprising:
 an internal combustion engine;   an energy storage device incorporated in a regenerative braking system; and   a cooling system for said engine, with said cooling system comprising:
 an engine housing having a plurality of coolant passages; 
 a heat exchanger for rejecting heat from coolant circulated from said engine housing; and 
 a variable speed coolant pump for circulating coolant from said engine housing to said heat exchanger, with said coolant pump operating according to a predetermined, variable duty cycle at lower coolant temperatures, and with the pump operating at a selected one of a plurality of predetermined fixed speeds, as a function of at least engine speed and engine load, once the engine has attained a stable operating temperature. 
   
   
   
       18 . A hybrid vehicle according to  claim 17 , wherein said pump is operated at a predetermined fixed speed if heat is requested from a passenger cabin heater furnished with coolant by said pump. 
   
   
       19 . A hybrid vehicle according to  claim 17 , further comprising a controller, connected with said engine and said energy storage device, for operating said pump, as a function of engine speed, engine temperature, and engine load. 
   
   
       20 . A hybrid vehicle according to  claim 17 , further comprising a controller, connected with said engine and said energy storage device, for operating said pump, as a function of engine speed, engine temperature, and engine operating condition.