SU1527532A1 - Device for registering ic-engine piston top dead centre - Google Patents

Abstract

The invention relates to instrument making and can be used in electronic devices for engine diagnostics. The purpose of the invention is to improve the accuracy of determining the top dead center of the piston of an internal combustion engine. The device contains a pressure sensor 1, two formers 3 and 4 time intervals, a shaper 5 pulses, a valve 6 and a digital threshold element 7. New in the gauge is the introduction of a differential amplifier 8 and a voltage to frequency converter 9, the shaper 4 is provided with an additional output with reference voltage. Improving the accuracy of forming the top dead center when exposed to noise is achieved by appropriate processing of the pressure signal obtained when the fuel supply to the cylinder is turned off. First, using a differential amplifier, a part of the signal is extracted in the region of the top dead center. Then, using a voltage-to-frequency converter, the signal is integrated at a predetermined interval and level. The center of the signal area determines the top dead center mark. 1 il.

Description

The invention relates to instrumentation and asks for use in electronic devices for the diagnosis of internal combustion engines.

11, the inventive invention is an improvement in the accuracy of determining the top dead center of an engine piston inside pe-fniero combustion.

The drawing shows the structural electrical circuit of the proposed marker.

The marker contains pressure sensor 1, first amplifier 2, first 3 and second 4 time interval shapers, pulse shaper 5, K.iiaiuui I;., Ilio1 threshold element 7. I connected sensor stroke 1 through amplifier 2 J and with the signal input of the for- mator 4. The output of the imaging unit 3 is directly connected to the first control input of the valve 6 and through Φ (1mrmler1 5 to the control inputs of the digital threshold element and the imaging unit 4, the output of which is connected to the second control input of the valve 6. Last exit by It is connected to the counting input of the digital threshold element 7. The second amplifier 8 and the voltage-to-frequency converter 9 are connected to the timer marker. The OopMHpoBa rejTb 4 time interval is equipped with a dog1P; 11T output. the output of the driver 4. The output of the amplifier 8 through the converter 9 is connected with the signal input of the valve 6. The marker has an output of 10.

The synchronizer number 4 is made up of a maximum value converter 11 and a comparator 12. The signal and reference inputs of the comparator 12 (one directly cTjjeHHo, and the other through the converter 11) are connected to the signal input of the forg Schrovel 4, output of the comparator 12, the output and control input of converter 11 are connected respectively to the output, auxiliary output and control input of the driver 4.

The amplifier 2 is normalized and, when used as a sensor 1, a piezoelectric transducer can be configured as

five

0

five

0

five

0

five

the voltage amplifier circuit and the charge amplifier circuit.

Shaper 3 is a threshold device with a fixed trigger threshold and can be made in the form of a regenerative comparator.

The shaper 4 generates a pulse at its output, the duration of which is equal to the time that the input signal exceeds the level U, proportional to the maximum value of the input signal, and at the additional output the indicated level U. The fixation of the level U ,, corresponding to the current value U, occurs at the moment of arrival of the pulse to the driver control input 4.

The shaper 5, at its input, forms a short pulse of fixed duration at its input and can be made in the form of a one-shot.

Valve 6 performs the function of a three-input logic element I.

Digital threshold element 7 in each cycle captures the number of pulses received at its counting input, generates a threshold value equal to half the recorded number of pulses, and compares the current number of pulses with the threshold value. At the moment of equality, a short pulse appears at the output of the digital element, the leading edge of which corresponds to the moment of the top dead center.

Digital threshold element 7 can be implemented on the basis of a frequency divider into two and two reversible counters. With the arrival of the next signal at the control input of the digital threshold element, the counting modes of the counters change in such a way that one of them is reset to the initial zero state and summarizes, and the other subtracts the pulses correspondingly

but the frequency r f and d, where

fo is the frequency of the pulses at the counting input of the PD1FOR threshold element. As a result, if during the period of the control signals N pulses arrive, one of the counters accumulates a number N, N / 2 equal to the trigger threshold, and the other zeroes after the pulse Nf arrives at its input and generates digital thresholds at the output; th element short pulse.

The amplifier 8 is lolien according to the scheme of the differential amplifier and generates at its output a signal equal to the difference of the signals at its inputs.

Transducer 11 is made in the form of series-connected amplitude detector and memory element and pulse generator, the output of which is connected to the reset input of the amplitude detector. The control input of the memory element and the pulse generator forms the control of the yuts of the converter 11 input. At the output of the amplitude detector, a signal is generated and p Ki, where K is its transmission coefficient selected in the range of values from 0.9 to 0.95 A voltage equal to the current value of the signal Uj at the output of the amplitude detector is fixed to the control input of the converter 11 at the output of the memory element. By the cut-off pulse of the converter 11, the pulse shaper operates and resets the amplitude detector to the initial zero state.

The marker works as follows.

The signal of pressure sensor 1 through amplifier 2 enters the inputs of drivers 3 and 4. Shaper 3 is triggered when the pressure in the cylinder rises at the beginning of the compression stroke, and when the pressure drops at the end of the expansion stroke, it reverses. As a result, at each engine cycle, at the output of the imaging unit 3, a time interval is formed in the form of a rectangular pulse, the duration of which approximately corresponds to the duration of the compression and expansion cycles. The impulse from the output of the imaging unit 3 unlocks the valve 6 at the first control input. At the end of the impulse of the imaging unit 3, the valve 6 is again blocked, and the imaging unit 5 triggers and forms a short pulse arriving at the control inputs of the digital threshold element 7 and the imaging unit of the time interval. The latter fixes the maximum value and the signal at the output of amplifier 2, and at the moment of arrival of the pulse at its control input forms

threshold srabatynani U in the area of the top dead center, which also enters the additional output of the driver 4.

When the triggering threshold is reached and the next pressure signal, driver 4 triggers and forms a time interval at its output in the form of a rectangular impulse, length} by T. This impulse unlocks valve 6 at the second control input, and at the digital input of the digital threshold element 7 , pulses are output from the output of converter 9, the frequency of which is fast; ionic to the current value of the signal at the output of amplifier 8.

0 To the first input of amplifier B, a signal is received and (P) from the output of amplifier 2, to the second input - a constant noporoBbDi level U from the additional output of the driver 4. At the end of amplifier 5, a difference signal Up (P) is generated, the gain of which is chosen in order to match the amplitude of the difference and noisy signal above level U with

0 dynamic range converter 9 voltage to frequency. Pulses of frequency f (P) from the output of the converter 9 through the unlocked valve 6 begin to flow to the counting input of the digital threshold element 7. During time T, the element 7 enters

t

N ft (P) dt, lipov

about

five

number of pulses

portioned signal area Up (P) relative to the level U ,,. At the time of termination of the time interval T, the digital threshold element 7 forms the threshold Np N / 2. At the moment of arrival of the pulse from the output of the generator 5 to the control input of the digital threshold element 7, the corresponding counting nodes of the latter are reset to the initial zero state and element 7 is prepared to receive the next pulse train of the converter 9. Thus, before the next pressure signal appears, the digital threshold threshold element 7 is determined by half the area of the previous difference signal U (P) in the interval T.

When the next time interval T is formed, the digital threshold element 7 triggers at the moment N current pulses from the converter 9 arrive at its input and generates at its output a pulse whose front corresponds to the moment of the center of the pressure signal, i.e. the moment of passing the top dead center. In the presence of interference superimposed on the pressure signal, an error occurs in the formation of the top dead center mark. This error depends mainly on the displacement randomly due to the interference of the beginning and end of the measurement interval T. Suppose that due to the occurrence of interference in the initial part of the time interval T, the duration of the latter decreases by the value of iT. Let the average value of the frequency at the output of the converter 9 in the area i3 T be equal to (P) LT, and in the rest of the section T - i3T be equal to (P) -dt pulses, and the loss of pulses in the DT segment is LT - f (P) T.

Accordingly, the error f of the formation of the top dead center mark

f -, / n,

where c / 1 |. i3T / T is the error in the formation of the time interval;

n f (P)., T / f (P) iT. those. decreases by n times in comparison with the known marker, where the duration of the time interval T is measured by the number of pulses of a constant frequency.

Since the frequency f (P) dt at the beginning of the measurement range is small compared with the frequency f (P) r-iiT of the rest of the higher part of the measurement range, the error in the formation of the mark due to the instability of the time interval becomes negligible. Thus, in the proposed marker, the influence of interference on the accuracy of forming the top dead center point is practically excluded.

Shaper A time interval works as follows.

The signal from the output of amplifier 2 with amplitude and enters the signal

five

0

five

five

0

0

five

0

five

the input of the comparator 12 and through the converter 11 maximum values to the reference input of this comparator. The pulse generator 5, which is formed at the end of the expansion cycle and arrives at the control input of converter 11, generates a constant level signal Un Ki at the output of the latter, where K is the transfer coefficient, which is chosen to be 0.9-0.95. The constant level and is fed to the reference input of the comparator 12 and to the auxiliary output of the former 4. The operation of forming the level and is repeated in each engine cycle. When the signal on the compression stroke rises to the level and „the comparator 12 triggers and generates a single signal at the output. When the signal decreases at the expansion stroke to the level and the reverse triggering of the comparator 12 occurs and at its output a temporary

interval duration 1. i

Thus, the imaging unit 4 makes it possible to automatically form a time interval at the U level in the area of the top dead center.

Claims (1)

Invention Formula The top dead center mark of the internal combustion engine piston, comprising a pressure sensor, a first amplifier, a first and a second time interval formers, a pulse shaper, a valve and an IJDipper threshold element, the output of the pressure sensor being connected through the first amplifier to the inputs of the first and second time interval formers, the output of the first time interval generator is directly connected to the first control input of the valve and, through a pulse shaper, to the control inputs of the backlash element and the second time interval generator, while the valve output is connected to the counting input of a digital threshold element, characterized in that, in order to improve accuracy, a second amplifier with two inputs and a voltage to frequency converter are additionally introduced into it, and the second The time interval former is implemented in the form of a successively included maximum signal converter and a comparator, with the first and second inputs of the second amplifier being connected respectively to the output of the first The amplifier and the converter output the maximum values of the signal, and the output of the second amplifier is connected via a voltage to frequency converter with a signal input of the valve, the first input of the comparator is connected directly to the output of the first amplifier, and the second through the driver of the maximum values of the signal, while the output the comparator is connected to the second control input of the valve.