Digital control device for a fuel injection system of an internal combustion engine

Claim 1

A digital control device of an internal combustion engine for controlling at least one solenoid of the fuel injection valves in accordance with the amount of air introduced into said engine and with the rotational speed of said engine, said digital control device comprising: a first pulse generating means for generating pulse signals having a frequency which is proportional to the rotational speed of said engine, said first pulse generating means having an output terminal; a bistable circuit connected to the output terminal of said first pulse generating means and triggered by said pulse signals provided from said first pulse generating means, said bistable circuit having an output terminal; a second pulse generating means for generating pulse signals having a frequency which is proportional to the amount of air introduced into said engine, said second pulse generating means having an output terminal and directly converting the resistance value corresponding to the amount of air introduced into the engine into the frequency value of the pulse signals, said second pulse generating means comprising a variable resistor and a pulse generator comprising an RC generator having a feed back circuit to which the variable resistor is connected; a first switching element having a first input terminal connected to the output terminal of said second pulse generating means and having a second input terminal connected to the output terminal of said bistable circuit, said first switching element being actuated by pulse signals provided from said bistable circuit and having an output terminal; a binary counter having an input terminal connected to the output terminal of said first switching element for counting the number of pulse signals passing through said first switching element during one operation period of said first switching element, said binary counter having an output terminal; a second switching element having a first input terminal connected to the output terminal of the binary counter for receiving binary output signals therefrom, a second input terminal, and an output terminal; a monostable circuit having an input terminal which is also connected to the output terminal of the bistable circuit and an output terminal which is connected to the second input terminal of the second switching element, said monostable circuit being triggered by the trailing edge of each of the pulse signals from the bistable circuit and supplying pulse signals of a certain duration to the second input terminal of the second switching element to close it during those times; and a digital computer comprising an input terminal connected to the output terminal of the second switching element for receiving the binary output signals of said binary counter, an output terminal for providing control signals so as to control at least one of said solenoids of said fuel injection valves, an arithmetic unit for multiplying the values of input signals which are responsive to said output signals of said binary counter with information corresponding to the operating characteristics of said engine, and a storage unit for storing said information.