Electric fuel injection tester

Claim 1

A system for determining the variable time duration of a repetitive phenomenon having a pulsating character and variable repetition frequency occurring in the electrical system of a motor vehicle comprising: means for receiving electrical pulses having a time duration representative of the duration of opening of the injection valves of an electronically controlled fuel injection system for a combustion engine, pulse converting and integrating means connected to the firstnamed means for converting said electrical pulses into sawtooth-shaped pulses having an amplitude which increases gradually from an initial value, the peak amplitude of said sawtooth-shaped pulses being representative of the duration of the injection valve opening being measured, circuit means connected to the output of said pulse converting and integrating means for measuring the peak amplitude value of said sawtooth-shaped pulses, said circuit means including a detection circuit for detecting and responding to the occurrence of a rapid decrease in the duration of the injection valve opening, indicating means connected to the output of said circuit means for indicating the duration of the injection valve opening as represented by the peak amplitude value of said sawtooth-shaped pulses, said detection circuit comprising diode means, an input capacitor and an output capacitor, and resistance means shunting said output capacitor, the voltage across said resistance means and output capacitor being representative of the peak value of the sAwtooth-shaped pulses and therefore of the time duration of the electrical pulses being measured and wherein said detection circuit has an R.C. time constant such that, when the time duration of the pulses with the lowest repetition frequency is being measured, the indicating means provides a stable indication, and further comprising a second peak detecting detecting circuit having having an R.C. time constant which is considerably smaller than that of the first detection circuit, means for supplying said sawtooth-shaped pulses to the second detecting circuit at the same time said pulses are supplied to the first detection circuit, a voltage comparing circuit connected to compare the outputs of said first detection means and second detecting means, and means connected to said voltage comparing circuit which is energized when the output voltage of the second detecting circuit drops below that of the first detection circuit, minus a particular threshold value, to trigger a switching circuit for connecting a low impedance into parallel with the output resistance of the first detection circuit.

Claim 2

A system for determining the variable time duration of a repetitive phenomenon having a pulsating character and variable repetition frequency occurring in the electrical system of a motor vehicle comprising: means for receiving electrical pulses having a time duration representative of the duration of opening of the injection valves of an electronically controlled fuel injection system for a combustion engine, pulse converting and integrating means connected to the firstnamed means for converting said electrical pulses into sawtooth-shaped pulses having an amplitude which increases gradually from an initial value, the peak amplitude of said sawtooth-shaped pulses being representative of the duration of the injection valve opening being measured, circuit means connected to the output of said pulse converting and integrating means for measuring the peak amplitude value of said sawtooth-shaped pulses, said circuit means including a detection circuit for detecting and responding to the occurrence of a rapid decrease in the duration of the injection valve opening, indicating means connected to the output of said circuit means for indicating the duration of the injection valve opening as represented by the peak amplitude value of said sawtooth-shaped pulses, said detection circuit comprising diode means, an input capacitor and an output capacitor, and resistance means shunting said output capacitor, the voltage across said resistance means and output capacitor being representative of the peak value of the sAwtooth-shaped pulses and therefore of the time duration of the electrical pulses being measured and wherein said detection circuit has an R.C. time constant such that, when the time duration of the pulses with the lowest repetition frequency is being measured, the indicating means provides a stable indication, and further comprising a second peak detecting detecting circuit having having an R.C. time constant which is considerably smaller than that of the first detection circuit, means for supplying said sawtooth-shaped pulses to the second detecting circuit at the same time said pulses are supplied to the first detection circuit, a voltage comparing circuit connected to compare the outputs of said first detection means and second detecting means, and means connected to said voltage comparing circuit which is energized when the output voltage of the second detecting circuit drops below that of the first detection circuit, minus a particular threshold value, to trigger a switching circuit for connecting a low impedance into parallel with the output resistance of the first detection circuit.