Method of and system for computing fuel injection amount for internal combustion engine

Claim 1

In an internal combustion engine, the engine having a cylinder, a throttle valve and an injector: an airflow meter disposed in a suction system of the engine, said airflow meter outputting a signal indicative of an intake air flow; a throttle sensor disposed in said suction system of the engine, said throttle sensor outputting a signal indicative of an opening degree of the throttle valve; a crank angle sensor arranged to output a signal from which an engine speed is calculated; and a microcomputer based control unit connected to said airflow meter, said throttle sensor and said crank angle sensor, said control unit computing a fuel injection amount in accordance with said signal indicative of said intake air flow, said control unit comprising: surging smoothing means for smoothing a parameter for a computation of said fuel injection amount in accordance with a smoothing degree set in response to operating conditions of the engine and decreasing said smoothing degree in a transient state and increasing said smoothing degree in a fully open state at least; phase adjustment means for correcting said parameter as smoothed so as to correct a time lag produced from a measuring position of said intake air flow of said airflow meter to a position of the cylinder; prefetched correction means for correcting said parameter as smoothed in accordance with a variation of said intake air flow calculated from said opening degree of the throttle valve and said engine speed; first determination means for determining whether a variation of said parameter as corrected by said surging smoothing means is positive or negative; second determination means for determining that said parameter as corrected by said surging smoothing means, said phase adjustment means and said prefetched correction means is greater than said parameter as corrected by said surging smoothing means; switching restriction means for carrying out a switching of said smoothing degree of said surging smoothing means when said first determination means provide a result that said variation of said parameter as corrected by said surging smoothing means is negative and said second determination means provide a result that said parameter as corrected by said surging smoothing means, said phase adjustment means and said prefetched correction means is greater than said parameter as corrected by said surging smoothing means during a process of passage from said transient state to said fully open state; and injection control means for controlling a fuel injection of the injector into the cylinder.

Claim 4

A method of operating an internal combustion engine, the engine being provided with a cylinder, an injector, an airflow meter for measuring an intake air flow, a throttle sensor for sensing an opening degree of a throttle valve and a crank angle sensor for obtaining an engine speed, the method comprising the steps of: smoothing a parameter for a computation of a fuel injection amount in accordance with a smoothing degree set in response to operating conditions of the engine and decreasing said smoothing degree in a transient state and increasing said smoothing degree in a fully open state at least; correcting said parameter as smoothed so as to correct a time lag produced from a measuring position of the intake air flow of the airflow meter to a position of the cylinder; correcting said parameter as smoothed in accordance with a variation of the intake air flow calculated from the opening degree of the throttle valve and the engine speed; determining whether a variation of said parameter as corrected at said smoothing step is positive or negative; determining that said parameter as corrected at said smoothing step and said two correcting steps is greater than said parameter as corrected at said smoothing step; carrying out a switching of said smoothing degree at said smoothing step when said positive/negative determining step provides a result that said variation of said parameter as corrected at said smoothing step is negative and said greater determining step provides a result that said parameter as corrected at said smoothing step and said two correcting steps is greater than said parameter as corrected at said smoothing step during a process of passage from said transient state to said fully open state; and controlling a fuel injection of the injector into the cylinder.

Claim 5

A method of operating an internal combustion engine, the engine being provided with a cylinder, an injector, an airflow meter for measuring an intake air flow, a throttle sensor for sensing an opening degree of a throttle valve and a crank angle sensor for obtaining an engine speed, the method comprising the steps of: smoothing a parameter for a computation of a fuel injection amount in accordance with a smoothing degree set in response to operating conditions of the engine and decreasing said smoothing degree in a transient state and increasing said smoothing degree in a fully open state at least; correcting said parameter as smoothed so as to correct a time lag produced from a measuring position of the intake air flow of the airflow meter to a position of the cylinder; correcting said parameter as smoothed in accordance with a variation of the intake air flow calculated from the opening degree of the throttle valve and the engine speed; determining whether a variation of said parameter as corrected at said smoothing step is positive or negative; determining that said parameter as corrected at said smoothing step and said two correcting steps is greater than said parameter as corrected at said smoothing step; carrying out a switching of said smoothing degree at said smoothing step when said positive/negative determining step provides a result that said variation of said parameter as corrected at said smoothing step is negative and said greater determining step provides a result that said parameter as corrected at said smoothing step and said two correcting steps is greater than said parameter as corrected at said smoothing step during a process of passage from said transient state to said fully open state; and controlling a fuel injection of the injector into the cylinder.