Method and system for controlling fuel to be supplied from fuel pump to engine

Claim 1

A controller for controlling fuel supplied by a fuel pump driven by a fuel pump motor to a fuel injection valve of an engine, comprising: (a) a plurality of sensors for detecting engine operating conditions and for generating sensor signals corresponding thereto; (b) an input unit responsive to the sensor signals for providing digital output signals corresponding thereto; (c) a microcomputer connected to said input unit for receiving said digital output signals, said microcomputer being operable to calculate a basic fuel injection time period during which said fuel injection valve injects fuel into the engine and a basic motor-drive duty cycle for driving the fuel pump motor to supply fuel from the fuel pump to the fuel injection valve in accordance with the digital output signals; (d) an injector drive unit connected to said microcomputer for outputting a pulse signal to the fuel injection valve, said pulse signal having a pulse width corresponding to the basic fuel injection time period calculated by said microcomputer; and (e) a pump drive unit connected to said microcomputer for outputting a pulse signal to said fuel pump motor having a duty cycle corresponding to the basic motor-drive duty cycle calculated by said microcomputer; wherein said basic fuel injection time period and said basic motor drive duty cycle correspond such that the amount of fuel pumped from the fuel pump matches the amount of fuel injected by the injector; and wherein said microcomputer generates clock pulses and said pump drive unit comprises: (1) a first counter for counting the number of said clock pulses inputted thereto; (2) a first register connected to said microcomputer for storing a first data calculated by said microcomputer, said first data being representative of the period of said pulse signal from the pump drive unit; (3) a first comparator for comparing the number of clock pulses counted by said first counter with the first data stored in said first register and for outputting a set signal when the counted number is equal to the first data stored in said first register; (4) a second counter for counting the number of clock pulses inputted thereto; (5) a second register connected to said microcomputer for storing the basic motor-drive duty cycle calculated by said microcomputer; (6) a second comparator connected to said second counter and second register for comparing the number of clock pulses of said second counter with the basic motor-drive duty cycle stored in said second register and for outputting a reset signal when the counted number of clock pulses reaches the basic motor-drive duty cycle stored in said second register; (7) a flip flop for outputting said pulse signal of said pump drive unit, the flip flop output being set to a first level when said first comparator outputs the set signal thereto and being reset to a second level when said second comparator outputs the reset signal thereto; and (8) an AND circuit for outputting the clock pulses to said second counter only while the flip-flop output is at said first level.