Control system for compression ignition internal combustion engine

Abstract

A compression ignition internal combustion engine includes injectors, each of which injects fuel into a corresponding cylinder. An ECU determines target ignition timing based on engine operational information and adjusts fuel injection start timing and a fuel injection quantity of each injector based on the target ignition timing. The engine further includes an air/fuel ratio sensor, which senses an oxygen concentration of exhaust gas. The ECU corrects the target ignition timing based on the oxygen concentration, which is sensed with the air/fuel ratio sensor, with reference to a predefined relationship between the oxygen concentration and ignition timing for achieving a generally equal constant torque of the engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a diagram showing an entire structure of an engine control system according to an embodiment of the present invention;

FIG. 2 is a diagram showing combustion modes with reference to an engine operational range;

FIG. 3 is a diagram showing a relationship between an exhaust gas oxygen concentration and ignition timing for achieving a generally equal constant shaft torque according to the embodiment;

FIG. 4A is a flowchart showing an operational procedure of a fuel injection control operation according to the embodiment;

FIG. 4B is a flowchart showing an operational procedure of an air system control operation according to the embodiment;

FIG. 5A is a diagram showing changes in fuel injection timing, ignition timing, an exhaust gas oxygen concentration, a shaft torque and an injection quantity with time in an exemplary case where the fuel injection control operation of FIG. 4A is not applied;

FIG. 5B is a diagram similar to FIG. 5A but showing a case where the fuel injection control operation of FIG. 4A is applied; and

FIG. 6A and 6B are diagrams showing a way of correcting fuel injection timing according to a previously proposed technique.

Claims

1. A control system for a compression ignition internal combustion engine that has a fuel injection valve, which injects fuel into a corresponding cylinder of the engine, the control system comprising: a control means for determining target ignition timing based on operational information of the engine and for adjusting a fuel injection mode at the fuel injection valve according to the target ignition timing;an oxygen information obtaining means for obtaining oxygen information of exhaust gas, which is exhausted from the cylinder of the engine; anda correcting means for correcting the target ignition timing based on the oxygen information, which is obtained by the oxygen information obtaining means, with reference to predefined constant torque characteristic data, which indicates a relationship between the oxygen information and ignition timing for achieving a generally equal constant torque.

2. The control system according to claim 1, wherein: the oxygen information obtaining mean includes an oxygen concentration sensor, which senses an oxygen concentration of the exhaust gas as the oxygen information; andthe correcting means corrects the target ignition timing based on the oxygen concentration of the exhaust gas, which is sensed with the oxygen concentration sensor.

3. The control system according to claim 1, wherein: the constant torque characteristic data is preset for each of a plurality of combustion modes, each of which is preset according to an operational state of the engine; andwhen a combustion mode of the engine is changed from one of the plurality of combustion modes to another one of the plurality of combustion modes, the correcting means corrects the target ignition timing based on the corresponding constant torque characteristic data, which is preset for the another one of the plurality of combustion modes.

4. The control system according to claim 3, wherein the plurality of combustion modes includes a premixed combustion and a conventional combustion.

5. The control system according to claim 1, further comprising a pressure sensor, which senses one of an intake air pressure and an exhaust gas pressure, wherein the correcting means corrects the target ignition timing based on the one of the intake air pressure and the exhaust gas pressure, which is sensed with the pressure sensor, in addition to the oxygen information.

6. The control system according to claim 1, further comprising an ignition timing sensor that senses ignition timing of the cylinder, wherein the control means adjusts the fuel injection mode at the fuel injection valve in such a manner that the sensed ignition timing, which is sensed with the ignition timing sensor, coincides with the target ignition timing.