Control device and control method for direct injection engine
View Patent ↗A combustion control device and a method for a direct injection engine are disclosed wherein, when the engine is operating in the partial load range, the valve opening/closing mode of an intake valve and/or an exhaust valve is controlled so that exhaust gases remain in a combustion chamber; and control is performed such that fuel is injected from a fuel injection valve into residual exhaust gases at least once during the time period from the latter half of an exhaust stroke to the first half of an intake stroke in one combustion cycle, and that an air-fuel mixture is ignited in the latter half of a compression stroke thereafter.
1. A combustion control device for a direct injection engine, comprising:
a valve control device capable of varying the valve opening/closing mode of an intake valve and/or an exhaust valve;
valve opening/closing control means for controlling the valve opening/closing mode by the valve control device;
a fuel injection valve for injecting fuel into a cylinder; and
fuel injection control means for controlling the fuel injection mode by the fuel injection valve,
wherein said valve opening/closing control means controls said valve opening/closing mode of said intake valve and/or said exhaust valve so that exhaust gases remain in a combustion chamber for promoting the vaporization and radicalization of the fuel;
wherein said fuel injection control means performs control for injecting fuel from said fuel injection valve into the residual exhaust gases at least once during the time period from the latter half of an exhaust stroke to the first half of an intake stroke in one combustion cycle; and
wherein said valve opening/closing control means and said fuel injection control means perform the respective control operations so that the combustion of an air-fuel mixture becomes stoichiometric combustion.
2. A combustion control device according to claim 1 , wherein an ignition of an air-fuel mixture is performed in the latter half of a compression stroke.
3. A combustion control device according to claim 1 , wherein said valve opening/closing control means and said fuel injection control means perform the respective control operations when the engine is operating in a partial load range.
4. A combustion control device according to claim 1 , further comprising a three-way catalyst as a catalyst for purifying exhaust gases.
5. A combustion control device according to claim 1 , wherein, when the operation state of an engine satisfies a specified condition, said fuel injection control means performs a fuel injection by the fuel injection valve during one combustion cycle by dividing the fuel injection into a plurality of times of fuel injections.
6. A combustion control device according to claim 5 , wherein said fuel injection control means calculates a fuel injection quantity based on operating conditions of the engine, and wherein, when the calculated fuel injection quantity is no less than two times the minimum controllable quantity of the fuel injection valve, said fuel injection control means performs the fuel injection by dividing it into a plurality of times of fuel injections.
7. A combustion control device according to claim 5 , wherein, when performing fuel injection by dividing it into a plurality of times of fuel injections, said fuel injection control means performs a last time of fuel injection in the compression stroke.
8. A combustion control device according to claim 5 , wherein, when performing fuel injection by dividing it into a plurality of times of fuel injections, said fuel injection control means sets a fuel injection quantity at each time of the fuel injections to be equal.
9. A combustion control device according to claim 5 , wherein, when performing fuel injection by dividing it into a plurality of times of fuel injections, said fuel injection control means fixes a fuel injection quantity at the last time at a constant value, and varies the fuel injection quantities at other times.
10. A combustion control device according to claim 1 , wherein said valve opening/closing control means and said fuel injection control means close the exhaust valve before opening the intake valve, in order to cause exhaust gases to remain in the combustion chamber, and wherein said valve opening/closing control means and said fuel injection control means perform at least one time of fuel injection before the intake valve opens.
11. A combustion control device according to claim 1 , wherein said valve opening/closing control means closes the exhaust valve before the top dead center in the exhaust stroke.
12. A combustion control device according to claim 11 , wherein the valve opening/closing control means opens the intake valve at the crank angle position symmetrical with the crank angle position corresponding to the closing timing of the exhaust valve with respect to the top dead center in the exhaust stroke.
13. A combustion control device according to claim 1 , wherein said valve control device can vary an opening timing and a valve lift amount of the intake valve, and/or a closing timing and a valve lift amount of the exhaust valve.
14. A combustion control device according to claim 1 , wherein said valve control device simultaneously shifts an opening timing and the closing time of the intake valve and/or the exhaust valve.
15. A combustion control device according to claim 1 , wherein said valve control device fixes an opening timing and a closing timing of the exhaust valve, and wherein said valve control device simultaneously shifts an opening timing and a closing time of the intake valve.
16. A combustion control device according to claim 1 , wherein said valve control device simultaneously shifts an opening timing and a closing timing of the exhaust valve, and wherein said valve control device fixes an opening timing and a closing timing of the intake valve.