Fuel injection controlling system for internal combustion engine

Claim 2

A fuel injection controlling system for internal combustion engines having a fuel control apparatus including an electromagnetic valve for controlling the amount of fuel delivered by the fuel supply for the engine comprising: first means for generating a plurality of signal currents each being independent from one another having a magnitude corresponding to a respective condition from which the quantity of fuel to be supplied to said engine is determined; second means for producing an output signal corresponding to an algebraic summation of the magnitudes of said independent signal currents; and third means responsive to said output signal produced by said second means for controlling the opening duration of said electromagnetic valve, to thereby feed the proper quantity of fuel to said engine.

Claim 3

A fuel injection controlling system according to claim 1, wherein said first means includes a first circuit means for producing independent condition signal currents corresponding to the respective conditions of the engine operation, a second circuit means for independently producing a timing signal current which varies with a lapse of time from the starting point of fuel injection and a third circuit means for resetting the value of said timing signal current to a predetermined level at each starting point of the fuel injection and said second means includes an input terminal with a low input impedance for simultaneously receiving said independent signal currents, and an output terminal for producing said output signal corresponding to said algebraic summation, and wherein said third means includes a discriminator means for comparing the output signal produced by said second means with a predetermined discriminating level and for closing said electromagnetic valve at a desired time after the initiation of fuel injection, when said output signal produced by said second means reaches said predetermined level.

Claim 4

A fuel injection controlling system according to claim 2, wherein each of said first circuit means and said second circuit means includes a circuit having an output terminal for producing a voltage corresponding to the relevant condition and a resistor connected between said output terminal of said circuit and said input terminal of said second means, said resistor having a relatively high resistance higher than said input impedance of said second means.

Claim 5

A fuel injection controlling system according to claim 3, further including means for changing the resistance values of said resistors in response to a predetermined value of the negative pressure in the manifold of the engine.

Claim 6

A fuel injection controlling system according to claim 4, further including a correction means for correcting for a discontinuity in an input signal when said resistance values are changed.

Claim 7

A fuel injection controlling system according to claim 2, wherein said discriminator means comprises a transistor, the input terminals of which are constituted by the base-emitter electrodes thereof, and a tunnel diode connected between the base-emitter electrodes of said transistor in the same polarity therewith, whereby the transistor of said discriminator means which is normally in its conducting state is rendered nonconductive at the beginning of the fuel injection and is rendered conductive when an input current reaches said predetermined level.

Claim 8

A fuel injection system according to claim 6, wherein the input terminals of said discriminator means are connected with the power source for said system through a capacitor so that a preparation current is supplied therethrough whereby said transistor in said discriminator means becomes conductive when said power source voltage is imparted thereto.

Claim 9

A fuel injection system according to claim 2, wherein said second means comprises an operation amplifier connected in series with said third means.

Claim 10

A fuel injection system accorDing to claim 8, further including respective resistors for supplying said independent condition signals produced from said first means to said operational amplifier.

Claim 11

A fuel injection controlling system according to claim 1, wherein said first means comprises a negative pressure detector, an engine temperature detector, and a circuit for detecting the rotational frequency of said engine, each detector circuit producing an independent signal corresponding to a separate engine parameter.

Claim 12

A fuel injection controlling system according to claim 10, wherein said engine temperature detector comprises a thermistor-resistor series circuit the output of which is connected to a nonlinear clamping circuit whose output is, in turn, fed to said second means, whereby a signal representative of a nonlinear temperature sensitive characteristic is provided by said first means.

Claim 13

A fuel injection controlling system according to claim 11, wherein said rotational frequency detector comprises a monostable multivibrator responsive to the interruption of primary current flowing through a firing circuit, an integrating circuit connected in series with said monostable multivibrator and a clamping circuit connected in series with said integrating circuit, whereby a signal representative of the rotational speed of said engine will be delivered to said second means.