Control apparatus for an engine of direct injection

A method of operating a multi-cylinder control apparatus for an engine of direct injection having means for detecting intake air flow into each of several cylinders, means for detecting the crank angle of each of said cylinders, means for compressing fuel and adjusting the pressure of fuel, means for detecting the opening of a throttle valve at each cylinder, means for determining a base fuel injection amount, based on said detected air intake flow, so as to realize the target air/fuel ratio, means for determining a base fuel injection time interval of each injector, including fuel injection start and end timings, corresponding to said determined base fuel injection amount, and means for controlling an ignition plug so as to ignite fuel at an ignition timing determined by said control apparatus, said method comprising the steps of:

• estimating in advance changes of the pressure in said cylinder, from the fuel injection start to the fuel injection end,
• calculating the difference between said estimated pressure in said cylinder and the pressure of fuel,
• calculating a supposed decreased amount of injected fuel, caused by the decrease of the difference between the pressure in said cylinders and the pressure of fuel, in a compression stroke, and
• determining an additional fuel injection time interval to said determined base fuel injection time interval to compensate said supposed decreased amount of injected fuel.

A control system for a fuel-injected multi-cylinder engine, comprising:

• an intake air flow sensor providing an air flow signal;
• crank angle sensors providing a crank angle signal for each of said cylinders;
• at least one fuel pump and at least one fuel pressure regulator which compresses and adjusts the pressure of a fuel;
• throttle sensors providing a throttle valve output signal for each of said cylinders;
• a control unit including a microprocessor programmed to perform the following:
• determine a base fuel injection amount based on the air intake flow signal so as to realize a target air/fuel ratio;
• determine a base fuel injection time interval for each fuel injector, including fuel injection start and end times, corresponding to the determined base fuel injection amount;
• controlling an ignition plug so as to ignite fuel at an ignition timing determined by said control unit;
• determining a new fuel injection time interval by correcting said determined base fuel injection time interval such that a supposed decreased amount of injected fuel caused by a decrease of the difference between the pressure in each of said cylinders and the pressure of the fuel, in proportion to an approach of a compression top dead center position, of the pressure in said cylinder, is compensated in a compression stroke.