Cold start strategy and system for gasoline direct injection compression ignition engine

Abstract

A method for starting a compression ignition engine having at least one cylinder with a reciprocating piston located therein, an intake valve configured to control the intake of air to an intake port of the cylinder and an exhaust valve configured to control the expulsion of gas from an exhaust port of the cylinder. The method includes the steps of: cranking the engine, conditioning intake air at the intake port of the cylinder to raise the temperature of air in the cylinder, controlling a valve timing the intake valve and/or the exhaust valve to allow the piston to compress the air within the cylinder, thereby increasing the temperature of the air within the cylinder, and injecting fuel into the cylinder when the air within the cylinder has been heated to a temperature sufficient to support compression ignition of a gasoline and air mixture within the cylinder.

We claim: 
     
         1 . A method for starting a compression ignition engine, the engine having at least one cylinder with a reciprocating piston located therein, an intake valve configured to control the intake of air to an intake port of the cylinder and an exhaust valve configured to control the expulsion of gas from an exhaust port of the cylinder; the method comprising the steps of:
 cranking the engine;   conditioning intake air provided at the intake port of the cylinder to raise the temperature of air in the cylinder;   controlling a valve timing of at least one of the intake valve and the exhaust valve to allow the piston to compress the air within the cylinder to a pressure above the pressure of the intake air provided at the intake port of the cylinder, thereby increasing the temperature of the air within the cylinder; and   injecting fuel into the cylinder when the air within the cylinder has been heated to a temperature sufficient to support compression ignition of a gasoline and air mixture within the cylinder.   
     
     
         2 . The method of  claim 1 , further comprising:
 controlling the valve timing of at least one of the intake valve and the exhaust valve such that the air in the cylinder is not additionally compressed by movement of the piston for a period of time from when cranking of the engine begins until engine speed reaches a first threshold value; and   controlling the valve timing to provide compression of the air in the cylinder after the engine speed reaches the first threshold value.   
     
     
         3 . The method of  claim 2  wherein the step of controlling the valve timing to provide compression of the air in the cylinder comprises controlling the valve timing to achieve a maximum effective compression ratio in the cylinder. 
     
     
         4 . The method of  claim 1  wherein the engine includes a supercharger configured to controllably compress intake air to the engine, the supercharger driven by the engine through a clutch, and the step of conditioning intake air provided at the intake port of the cylinder to raise the temperature of air in the cylinder comprises controlling the supercharger to compress intake air to the engine, thereby raising the temperature of the intake air. 
     
     
         5 . The method of  claim 4 , wherein the step of controlling the supercharger further comprises:
 cranking the engine with the clutch disengaged until the engine speed reaches a second threshold value; and   engaging the clutch after the engine speed reaches the second threshold value.   
     
     
         6 . The method of  claim 1 , wherein the engine additionally comprises a charge air cooler configured to transfer heat from the intake air to a coolant and a charge air cooler bypass valve configured to controllably route the intake air through the charge air cooler, the method additionally comprising controlling the charge air cooler bypass valve to control flow of the intake air through the charge air cooler so as to inhibit cooling the intake air while the engine is being started. 
     
     
         7 . The method of  claim 1 , wherein the engine additionally comprises a charge air cooler configured to transfer heat from the intake air to a coolant the method additionally comprising inhibiting coolant flow through the charge air cooler so as to inhibit cooling the intake air while the engine is being started. 
     
     
         8 . The method of  claim 1 , wherein exhaust gases from the engine are routed through an engine exhaust system, the exhaust system comprising a backpressure control means, the method further comprising controlling the backpres sure control means to increase exhaust backpres sure to a level higher than the pressure of the intake air at the intake port of the cylinder to promote rebreathing of engine exhaust after combustion is initially achieved within the cylinder. 
     
     
         9 . The method of  claim 1 , wherein the engine additionally comprises a system configured to route a coolant through the engine to transfer heat from the at least one cylinder to the coolant, the method additionally comprising controlling coolant flow through the engine so as to inhibit cooling the cylinder while the engine is being started. 
     
     
         10 . The method of  claim 1 , wherein the engine further comprises a heater configured to heat air at the intake port of the cylinder, and the step of conditioning intake air comprises controlling the heater to preheat intake air to the cylinder during a cold start event. 
     
     
         11 . The method of  claim 10 , wherein the heater is controlled so as to preheat intake air to the cylinder prior to cranking the engine during the cold start event. 
     
     
         12 . The method of  claim 10 , wherein the engine comprises a plurality of cylinders each configured with a corresponding individual heater configured to heat air at its intake port, and wherein each of the plurality of heaters is independently controllable. 
     
     
         13 . The method of  claim 12 , wherein combustion in each cylinder is monitored, and each individual heater is controlled based on the combustion in its corresponding cylinder. 
     
     
         14 . The method of  claim 13 , wherein a heater control parameter associated with combustion in the corresponding cylinder is retained in memory in a controller and used as a basis for controlling the corresponding heater in a subsequent cold start event. 
     
     
         15 . The method of  claim 10 , wherein the heater is controlled such that power is not applied to the heater during a time interval corresponding to a maximum current draw of a means used to crank the engine. 
     
     
         16 . The method of  claim 10 , wherein the heater is controlled to achieve a predetermined temperature of the air at the intake port of the cylinder. 
     
     
         17 . The method of  claim 10 , wherein the heater is configured to accept electrical power from an energy source external to a vehicle on which the engine is mounted. 
     
     
         18 . A system for starting a compression ignition engine, the engine having at least one cylinder with a reciprocating piston located therein, an intake valve configured to control the intake of air to an intake port of the cylinder and an exhaust valve configured to control the expulsion of gas from an exhaust port of the cylinder; the system comprising;
 means for cranking the engine;   means for increasing the temperature of intake air provided at the intake port of the cylinder;   valve timing means to control the opening and closing of at least one of the intake valve and the exhaust valve;   means for injecting fuel into the cylinder; and   a controller configured to control at least one actuator so as to perform a method comprising the steps of:   cranking the engine;   conditioning intake air provided at the intake port of the cylinder to raise the temperature of air in the cylinder;   controlling a valve timing of at least one of the intake valve and the exhaust valve to compress the air within the cylinder to a pressure above the pressure of the intake air provided at the intake port of the cylinder, thereby increasing the temperature of the air within the cylinder; and   injecting fuel into the cylinder when the air within the cylinder has been heated to a temperature sufficient to support compression ignition of a gasoline and air mixture within the cylinder.   
     
     
         19 . The system of  claim 18  further comprising a supercharger configured to controllably compress intake air to the engine, the supercharger driven by the engine through a clutch, and the step of conditioning intake air provided at the intake port of the cylinder to raise the temperature of air in the cylinder comprises controlling the supercharger to compress intake air to the engine, thereby raising the temperature of the intake air. 
     
     
         20 . The system of  claim 19  wherein the step of controlling the supercharger further comprises:
 cranking the engine with the clutch disengaged until the engine speed reaches a second threshold value; and 
 engaging the clutch after the engine speed reaches the second threshold value. 
 
     
     
         21 . The system of  claim 18  additionally comprising a charge air cooler configured to transfer heat from the intake air to a coolant and a charge air cooler bypass valve configured to controllably route the intake air through the charge air cooler, the method additionally comprising controlling the charge air cooler bypass valve to control flow of the intake air through the charge air cooler so as to inhibit cooling the intake air while the engine is being started. 
     
     
         22 . The system of  claim 18  additionally including an engine exhaust system, the exhaust system comprising a backpressure control means, the method further comprising controlling the backpressure control means to increase exhaust backpressure to a level higher than the pressure of the intake air at the intake port of the cylinder to promote rebreathing of engine exhaust after combustion is initially achieved within the cylinder. 
     
     
         23 . The system of  claim 18  wherein the engine additionally comprises a system configured to route a coolant through the engine to transfer heat from the at least one cylinder to the coolant, the method additionally comprising controlling coolant flow through the engine so as to inhibit cooling the cylinder while the engine is being started. 
     
     
         24 . The system of  claim 18 , wherein the engine further comprises a heater configured to heat air at the intake port of the cylinder, and the step of conditioning intake air comprises controlling the heater to preheat intake air to the cylinder during a cold start event. 
     
     
         25 . The system of  claim 24 , wherein the engine comprises a plurality of cylinders each configured with an individual heater configured to heat air at its intake port, and wherein each of the plurality of heaters is independently controllable.