SU645082A1 - Tachometer for internal combustion engine - Google Patents

Description

one

The invention relates to the field of instrumentation and can be used in instruments for measuring parameters of automobile engines.

A device for measuring speed is known based on the formation of a voltage proportional to the frequency of the pulses by charging and discharging a capacitor. This device is not intended to measure the rotational speed of the motor shaft and has a complex pulse pattern.

A tachometer operating from the engine ignition system 2 is known, in which the average value of the current of the pulses generated by a single-stable multivibrator triggered by the ignition system interrupter is measured. This tachometer also has a relatively complex circuit.

A tachometer, 3, containing an integrating circuit with a capacitor, connected to the measuring device and controlled by the contacts of the engine ignition system interrupter, and a power source are also known.

The disadvantage of such a tachometer is its low noise immunity with respect to spurious signals that occur when the contacts of the chopper vibrate, and is associated with

This is an additional measurement error.

The purpose of the invention is to improve the accuracy of the device.

The goal is achieved by the fact that the tachometer is provided with a voltage level lock connected between the power source and the converting circuit and connected to the contacts of the chopper.

The voltage level clamp contains a series-connected resistor, a capacitor, and a diode connected to a power source, the capacitor being connected to the charge circuit of the integrating co-capacitor through the contacts of the chopper.

The tachometer circuit is shown in the drawing. Tachometer contains integrating circuit

1 consisting of a series-connected diode 2 and a capacitor 3, and in parallel with which a resistor 4 and a measuring device 5 are connected. A voltage level clamp 6 is connected to the input of the integrating circuit,

consisting of a series-connected resistor 7, a capacitor 8 and a diode 9, as well as a zener diode 10 connected in parallel with the contacts 11 of an engine ignition system interrupter.

Tachometer works as follows.

In the initial state, the cues are capacitor 8 per. voltage through resistor 7 and diode 9 to the level of voltage stabilization of diode 10. When starting the engine, the contacts and the breaker begin to periodically close, capacitor 8 each time is discharged through diode 2 and capacitor 3, resulting in a voltage across capacitor 3 increasing in proportion to the frequency contacts 11 ..

Vibration of co-tacts, which in a known tachometer causes the appearance of false impulses that occur at the moments of contact opening, has practically no effect on the accuracy of this device, since the circuit triggers the closure of the contacts and, if this causes their short-term opening due to vibration, the voltage across the capacitor 3 is unchanged.

Claims (3)

1. Tachometer for an internal combustion engine containing an integrating a capacitor circuit connected to the measuring instrument and controlled by the contacts of the engine ignition circuit breaker, and a power source, characterized in that it is equipped with a voltage level lock connected between the power source and the integrating circuit and connected to the circuit breaker terminals to increase accuracy . 2. A tachometer according to claim 1, characterized in that the voltage latch comprises a series-connected resistor, a capacitor and a diode connected to a power source, the capacitor being connected to the charge circuit of the integrating capacitor through the breaker contacts. Information sources, taken into account in the examination 1. For the UK of UK number 1422458, cl. G IN, publ. 1976. 2. Salomatin V. I. Non-contact measuring instruments of linear and angular velocities. M., “Energie, 1974, p. 41 3. US patent number 3956691, class. 324-15, publ. 1976.