Method and controller for supplying fuel to cylinders of multicylinder internal combustion engine

Abstract

A method and a controller for supplying a fuel to a plurality of cylinders of an internal combustion engine, in which engine operation conditions including the operating temperature of the engine are detected by various sensors attached to the engine and by using a microcomputer, and the fuel is successively supplied by being injected to the engine cylinders based on the detected engine operation conditions. The timing of fuel injection into each of the plurality of cylinders is . .shifted from an exhaust stroke period to a suction stroke period according to the operating temperature of the engine among the detected engine operation conditions.!. set in a suction stroke period at the time of the engine starting in a low temperature condition, and is shifted to an exhaust stroke period as the level of the engine temperature rises.

Description

BACKGROUND OF THE INVENTION

This invention relates to a method of supplying fuel to a plurality of cylinders of an internal combustion engine and, more particularly, to a method and a controller for supplying fuel to cylinders of a multicylinder internal combustion engine while controlling fuel injection valves provided in association with the respective cylinders.

A sequential fuel injection control system in which fuel injection valves provided in association with cylinders are sequentially controlled in synchronism with the rotation of the engine to supply fuel is known as a conventional fuel supply system for multicylinder internal combustion engines. For this sequential fuel injection control, blowing start control, i.e., control of fuel injection starting and blowing termination, i.e., control of injection termination are effected, as described, for example, on page 1004 of Jidosha Gijutsu, VOL. 39, No. 9, 1985. In this control system, however, the fuel injection rate and the injection timing are determined by the engine load determined from the intake air flow rate and the engine revolutions and so on. Ordinarily, fuel injection is effected during the exhaust stroke at each cylinder except for a transition period when the load is abruptly changed.

That is, in this conventional system, fuel injection into each cylinder of the internal combustion engine is controlled in such a manner that the required fuel injection rate is first obtained based on Qa/N which is a quotient of the intake air flow rate Qa corresponding to the engine load and the engine revolutions N, corrected with various correction coefficients, and injection is effected during the exhaust stroke at each cylinder in consideration of the injection period determined according to the fuel injection rate.

This conventional system entails a problem of an increase in the amount of total exhaust carbon compound (THC) components of exhaust gas and, hence, problems of an increase in the fuel consumption and deterioration in the operating performance at the time of starting of the engine or, more particularly, during warm-up started from a low temperature condition.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method and a controller for supplying fuel to the cylinders of a multicylinder internal combustion engine which method and controller are capable of improving the exhaust gas composition, reducing the fuel consumption and improving the operating performance at the time of starting of the engine or, more particularly, during an operation of starting and warming up the engine in a low temperature condition.

To achieve this object, according to the present invention, there is provided a method of supplying fuel to the cylinders of a multicylinder internal combustion engine, in which engine operation conditions including the operating temperature of the engine are detected and the fuel is successively supplied by being injected to each of the engine cylinders based on the detected engine operation conditions, the method comprising . .shifting.!. setting the fuel injection timing . .from the exhaust stroke period to.!. in the suction stroke period at the time of starting of the engine when the change in the engine speed is particularly large, thereby enabling the fuel to be supplied more precisely.

Claims

1. A method of supplying fuel to a plurality of cylinders of an . .intrnal.!. internal combustion engine, in which engine operation conditions including the operating temperature of the engine are detected and the fuel is successively supplied by being injected to each of the engine cylinders based on detected engine operation conditions, said method comprising the steps of:

. .shifting.!. setting the timing of fuel injection into each of the plurality of cylinders . .from an exhaust stroke period to a section stroke period according to the operating temperature of the engine among the detected engine operation conditions.!. in a suction stroke period at the time of engine starting in a low temperature condition, and shifting the timing of fuel injection to an exhaust stroke period progressively as the level of the engine temperature rises;

when the rate of the fuel supply to each cylinder is determined based on the detected engine operation conditions, determining a limit of fuel injection end . .portion.!. point; and

controlling the fuel supply so that the termination point of the fuel injection timing does not exceed the fuel injection end point limit.

2. A method of supplying a fuel to a plurality of cylinders of an internal combustion engine, according to claim 1, wherein the shifting of the fuel injection timing includes shifting the fuel injection start timing.

3. A method of supplying a fuel to a plurality of cylinders of an internal combustion engine, according to claim 1, wherein the fuel is injected so that the particle size of atomized fuel is not larger than 120 μm.

4. A controller for controlling the supply of a fuel to a plurality of cylinders of an internal combustion engine, comprising:

detection means for detecting engine operation conditions including the operating temperature of the engine;

control means for determining the rate at which the fuel is supplied to each of the plurality of engine cylinders and the fuel injection timing . .be.!. by being supplied with a signal from said detection means; and

fuel injection means for successively injecting the fuel to each of the plurality of engine cylinders by controlling valve opening based on a fuel injection control signal supplied from said control means:

wherein said control means is supplied with an engine temperature output signal from said engine condition detection means and . .shifts.!. sets the fuel injection timing . .based on.!. in a suction stroke period when the fuel injection control signal . .from an exhaust stroke period to a suction period according to.!. indicates that the engine is to be started in a low temperature condition, and shifts the fuel injection timing progressively to an exhaust stroke period as the level of the engine temperature output signal rises, and wherein said controller outputs the fuel injection control signal and a signal for determining a limit of the fuel injection end point, and controls valve opening of said fuel injection means so that the limit of the fuel injection end point is not exceeded.

5. An apparatus for supplying a fuel to a plurality of cylinders of an internal combustion engine according to claim 4, wherein the shifting of the fuel injection timing effected by said controller includes shifting the fuel injection start timing based on the fuel injection control signal.

6. An apparatus for supplying a fuel to a plurality of cylinders of an internal combustion engine according to claim 4, wherein said fuel injection means includes a fuel injector capable of injecting the fuel so that the particle size of atomized fuel is not larger than 120 μm.

7. A method of supplying fuel to a plurality of cylinders of an internal combustion engine, comprising the steps of:

detecting engine operating conditions including the operating temperature of the engine, intake air amount and engine rotation speed;

determining a fuel injection period during which fuel is to be injected to each of the cylinders based on said detected engine operating conditions;

determining a fuel injection start time relative to a reference angle of the engine crankshaft for each cylinder and based on a coefficient related to the operating temperature of the engine so that said fuel injection start time is shifted progressively from . .an exhaust.!. a suction stroke period toward . .a suction.!. an exhaust stroke period for a cylinder as the operating temperature of the engine increases;

determining a maximum limit for the end point of said fuel injection period; and

when the end point of said fuel injection period exceeds said maximum limit for a determined fuel injection period and a determined fuel injection start time for a given cylinder, shifting the fuel injection start time toward said exhaust stroke period to prevent said end point from exceeding said maximum limit.

8. A method according to claim 7, wherein, when the end point of said fuel injection period exceeds said maximum limit, shifting the fuel injection start time only to the extent that said end point exceeds said maximum limit.

9. A method according to claim 7, wherein said fuel injection start time Tinjst is determined from the following relationship:

Tinjst=3/4T_I -(1-Kr)Ti

where T_I represents the period of time for four strokes of the internal combustion engine, Ti is the fuel injection period and Kr is a coefficient which is obtained from a table on the basis of the detected operating temperature of the engine.

10. An apparatus for supplying fuel to a plurality of cylinders of an internal combustion engine, comprising:

means for detecting engine operating conditions including the operation temperature of the engine, intake air amount and engine rotation speed;

means for determining a fuel injection period during which fuel is to be injected to each of the cylinders based on said detected engine operating conditions;

means for determining a fuel injection start time relative to a reference angle of the engine crankshaft for each cylinder and based on a coefficient related to the operating temperature of the engine so that said fuel injection start time is . .shifted from an exhaust stroke period toward a suction stroke period for a cylinder as the operating temperature of the engine increases.!. set in a suction stroke period at the time of engine starting in a low temperature condition;

means for determining a maximum limit for the end point of said fuel injection period; and

means for shifting the fuel injection start time toward said exhaust stroke period to prevent said end point from exceeding said maximum limit, when the end point of said fuel injection period exceeds raid maximum limit for a determined fuel injection period and a determined fuel injection start time for a given cylinder.

11. An apparatus according to claim 10, wherein, when the end point of said fuel injection period exceeds said maximum limit, the fuel injection start time is shifted only to the extent that said end point exceeds said maximum limit.

12. An apparatus according to claim 10, wherein said fuel injection start time Tinjst is determined from the following relationship:

Tinjst=3/4T_I -(1-Kr) Ti

where T_I represents the period of time for four strokes of the internal combustion engine, Ti is the fuel injection period and Kr is a coefficient which is obtained from a table on the basis of the detected operating temperature of the engine.