Multistage fuel-injection internal combustion engine

1. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system capable of injecting fuel at a plurality of injection timings in one operating cycle of the engine, the plurality of injection timings comprising at least one sub-injection timing in addition to a main injection timing;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing by changing a valve lift characteristic or valve-open and valve-closure timings of at least one of an intake valve and an exhaust valve; and

a control unit configured to define at least two domains of a specified engine operating region as a first operating range and a second operating range and to set one of the injection timings to have a predetermined first relation with either one of the intake valve closure timing and the exhaust valve open timing in the first operating range and to set one of the injection timings to have a predetermined second relation with either one of the intake valve closure timing and the exhaust valve open timing in the second operating range.

2. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system capable of injecting fuel at a plurality of injection timings in one operating cycle of the engine;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing by changing a valve lift characteristic or valve-open and valve-closure timings of at least one of an intake valve and an exhaust valve;

a sensor provided to detect the valve lift characteristic or the valve-open and valve-closure timings of at least one of the intake and exhaust valves; and

a control unit being responsive to a sensor signal from the sensor, for executing cooperative control of one of the injection timings responsively to either one of the intake valve closure timing and the exhaust valve open timing.

3. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing;

a first sensor provided to detect operating conditions of the engine;

a second sensor provided to detect a valve lift characteristic or valve-open and valve-closure timings of at least one of an intake valve and an exhaust valve; and

a control unit configured to initiate cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing, when a difference between the intake valve closure timing detected by the second sensor and a desired intake valve closure timing value determined based on the engine operating conditions detected by the first sensor becomes greater than or equal to a predetermined threshold value or when a difference between the exhaust valve open timing detected by the second sensor and a desired exhaust valve open timing value determined based on the engine operating conditions detected by the first sensor becomes greater than or equal to the predetermined threshold value.

4. A multi-stage fuel injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected before the main injection, is phase-retarded responsively to a phase advance of the intake valve closure timing of the variable

valve actuation control system, in a very light load and low speed range substantially corresponding to idling.

5. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected before the main injection, is phase-retarded responsively to a phase retard of the intake valve closure timing of the variable valve actuation control system, in a light load range.

6. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected before the main injection, is phase-advanced responsively to a phase advance of the intake valve closure timing of the variable valve actuation control system, in a high load and low speed range.

7. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected before the main injection, is phase-advanced responsively to a phase retard of the intake valve closure timing of the variable valve actuation control system, in a high load and high speed range.

8. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected after the main injection, is phase-advanced responsively to a phase advance of the exhaust valve open timing of the variable valve actuation control system, in a high speed range.

9. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected after the main injection, is phase-retarded responsively to a phase retard of the exhaust valve open timing of the variable valve actuation control system, in a low speed range.

10. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected after the main injection, is phase-advanced responsively to a phase retard of the exhaust valve open timing of the variable valve actuation control system, under a condition where a catalyst temperature is excessively high.

11. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least one sub-injection in addition to main injection;

a variable valve actuation control system capable of changing intake valve closure timing or exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of sub-injection timing responsively to either one of the intake valve closure timing and the exhaust valve open timing,

wherein timing of the sub-injection, injected after the main injection, is phase-retarded responsively to a phase advance of the exhaust valve open timing of the variable valve actuation control system, during cold engine operation.

12. A multi-stage fuel-injection internal combustion engine comprising:

a fuel injection system enabling at least a first sub-injection injected before main injection and a second sub-injection injected after the main injection;

a first variable valve actuation mechanism capable of changing at least intake valve closure timing;

a second variable valve actuation mechanism capable of changing at least exhaust valve open timing; and

a control unit being responsive to operating conditions of the engine, for executing cooperative control of timing of the first sub-injection, injected before the main injection, responsively to the intake valve closure timing, and for executing cooperative control of timing of the second sub-injection, injected after the main injection, responsively to the exhaust valve open timing.

13. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the first sub-injection, injected before the main injection, is phase-retarded responsively to a phase advance of intake valve closure timing of the first variable valve actuation mechanism, in a very light load and low speed range substantially corresponding to idling.

14. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the first sub-injection, injected before the main injection, is phase-retarded responsively to a phase retard of intake valve closure timing of the first variable valve actuation mechanism, in a light load range.

15. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the first sub-injection, injected before the main injection, is phase-advanced responsively to a phase advance of intake valve closure timing of the first variable valve actuation mechanism, in a high load and low speed range.

16. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the first sub-injection, injected before the main injection, is phase-advanced responsively to a phase retard of intake valve closure timing of the first variable valve actuation mechanism, in a high load and high speed range.

17. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the second sub-injection, injected after the main injection, is phase-advanced responsively to a phase advance of exhaust valve open timing of the second variable valve actuation mechanism, in a high speed range.

18. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the second sub-injection, injected after the main injection, is phase-retarded responsively to a phase retard of exhaust valve open timing of the second variable valve actuation mechanism, in a low speed range.

19. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the second sub-injection, injected after the main injection, is phase-advanced responsively to a phase retard of exhaust valve open timing of the second variable valve actuation mechanism, under a condition where a catalyst temperature is excessively high.

20. The multi-stage fuel-injection internal combustion engine as claimed in claim 12 , wherein:

the timing of the second sub-injection, injected after the main injection, is phase-retarded responsively to a phase advance of exhaust valve open timing of the second variable valve actuation mechanism, during cold engine operation.