Fuel injection control system for an internal combustion engine

Claim 1

A fuel injection control system for an internal combustion engine with a fuel injection valve, the system including a microcomputer which calculates a value of fuel injection time duration Ti based on detected operating parameters of the engine including crank angle position, said system comprising: (a) means for generating a first injection signal to open said injection valve in response to a detected predetermined crank angle position; (b) means for producing clock pulse signals having a period Tc, said period Tc being a small fraction of the fuel injection time duration Ti; (c) a counter; (d) said microcomputer including a CPU, a data memory storage for storing data and a program memory storage for storing a control program for controlling said calculation and causing said CPU to (i) compare the calculated value Ti with a plurality of limit values to determine one of a plurality of ranges for Ti, each range having an upper limit value of Ti, (ii) generate a set value signal (OR) indicative of the calculated value of Ti, (iii) generate a clock control signal (CR) corresponding to said determined range for Ti, said clock control signal indicative of said clock period, Tc, wherein for each of said ranges of Ti, the ratio of the upper limit value of Ti to the value Tc is approximately equal to the largest count value within the capacity of said counter; (e) said clock pulse signal producing means including means responsive to said clock control signal for adjusting the period Tc of said clock pulse signals in dependence upon said clock control signal; (f) said counter connected to receive said clock pulse signals for counting same and connected to receive said set value signal (OR) for setting said counter to said set value indicative of said calculated value Ti; (g) said counter operative to start counting said clock pulse signals upon opening of said fuel injection value and generating a second injection signal when the number of counted clock pulse signals reaches said set value, and (h) means responsive to said second injection signal for closing said injection valve.

Claim 6

A method for controlling fuel injection in an internal combustion engine of the type having a fuel injection valve, a counter, and a microcomputer which calculates a value of fuel injection duration Ti based on detected operating parameters of the engine including crank angle position comprising the steps of: (a) generating a first injection signal to open said injection valve in response to a detected predetermined crank angle position; (b) producing clock pulse signals having a period Tc, said period Tc being a small fraction of the fuel injection duration Ti; (c) comparing the calculated value of Ti with a plurality of limit ranges to determine one of a plurality of ranges for Ti, each range having an upper limit value of Ti; (d) generating a set value signal (OR) indicative of the calculated value of Ti; (e) generating a clock control signal (CR) corresponding to said determined range for Ti, said clock control signal indicative of said clock period Tc, wherein for each of said ranges of Ti, the ratio of the upper limit value of Ti to the value of Tc is approximately equal to the largest count value within the capacity of said counter; (f) adjusting the period Tc of said clock pulse signals in dependence upon said clock control signal; (g) setting said counter to said set value indicating of said calculated value of Ti; (h) counting said clock pulse signals in said counter, starting synchronously with the opening of said injection valve; (i) generating a second injection signal when the clock pulse signal count at least equals said set value; and (j) closing said injection valve in response to said second injection signal.

Claim 7

A method for controlling fuel injection in an internal combustion engine of the type having a fuel injection valve, a counter, and a microcomputer which calculates a value of fuel injection duration Ti based on detected operating parameters of the engine including crank angle position comprising the steps of: (a) generating a first injection signal to open said injection valve in response to a detected predetermined crank angle position; (b) producing clock pulse signals having a period Tc, said period Tc being a small fraction of the fuel injection duration Ti; (c) comparing the calculated value of Ti with a plurality of limit ranges to determine one of a plurality of ranges for Ti, each range having an upper limit value of Ti; (d) generating a set value signal (OR) indicative of the calculated value of Ti; (e) generating a clock control signal (CR) corresponding to said determined range for Ti, said clock control signal indicative of said clock period Tc, wherein for each of said ranges of Ti, the ratio of the upper limit value of Ti to the value of Tc is approximately equal to the largest count value within the capacity of said counter; (f) adjusting the period Tc of said clock pulse signals in dependence upon said clock control signal; (g) setting said counter to said set value indicating of said calculated value of Ti; (h) counting said clock pulse signals in said counter, starting synchronously with the opening of said injection valve; (i) generating a second injection signal when the clock pulse signal count at least equals said set value; and (j) closing said injection valve in response to said second injection signal.