SU1268988A1 - Device for determining top dead centre of internal combustion engine - Google Patents

Abstract

The invention relates to the field of instrumentation and can be used in electronic devices intended for the investigation, testing and diagnostics of internal combustion engines. It expands the field of application of the device, which contains induction sensor 1, first amplifier 2, reference voltage source 3, first and second comparators

Description

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4 and 5, the first trigger 6, which forms the cascade 7, the assembly element 8 and the pulse generator 9. In addition, it contains a second amplifier 11, a third and fourth comparators 12 and 13, a second trigger 14, a low-pass filter 15, and a threshold element 16. When the engine is not running, the signal pulses at the output of sensor 1 of amplifier 2, and hence at the input of the source 3, the first inputs of the comparators 12 and 13 and the second inputs of the comparators 4 and 5 are missing. Further operation of the circuit leads to the fact that the signal pulses at the output 17 of the device are missing. After the engine is started and its speed reaches the working frequency range, two-polar signal pulses with a frequency of a signal appear at the output of the engine. Sensor I is set against the top dead center. The label can be made either in the form of a pin or in the form of a hole in the engine flywheel. The device circuit works in such a way that in both

In cases of tagging, the output of the amplifier 11 is always the first to receive a positive half-wave pulse. Further operation of the circuit causes a pulse to appear at the output 17 of the device, the front of which coincides with the zero-crossing moment of the two-polar signal of sensor 1. With the appearance of pulses at the output 17 of the device, the generator 9 stops working. Source 3 fixes the maximum value of the input signal for each pulse from the output of the forming cascade 7 arriving at its control input through the assembly element 8 and updates the value of the reference signal at its output in accordance with the maximum value of each previous its input signal pulse. As a result, the device comes to a steady state, which is not disturbed when the engine speed changes within the operating frequency range of the sensor. 1 il.

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The device relates to instrumentation engineering and can be used in electronic devices intended for the investigation, testing and diagnostics of internal combustion engines.

The aim of the invention is to expand the field of application of the device.

The drawing shows a block diagram of the device.

The device includes an induction sensor 1, the first amplifier 2, the source of the reference voltage 3, the first and second comparators 4 and 5, the first trigger 6, which forms the cascade 7, the assembly element 8 and the pulse generator 9. The output of sensor 1 is connected via serially connected first amplifier 2 and source 3 of reference voltage to the first input of the first comparator 4, the output of which is connected to the first input of the first trigger 6. The output of the latter is connected to the control input of the shaping stage 7, the input of which is connected to the output of the second comparator 5, and the output with the second input of the first trigger 6, the control input of the generator 9 and the first input of the assembly element 8. The second input of the assembly element 8 is connected to the output of the generator 9, and the output to the control input of the source 3. A zero potential is connected to the first input 10 of the comparator 5.

The amplifier 11, the third and fourth comparators 12 and 13, the second trigger 14, the low-pass filter 15 and the threshold element 16 are introduced into the device. The output of the first amplifier 2 is connected to the second inputs of the comparators 4 and 5 through the amplifier 1 and directly to the first inputs of the third and the fourth comparators 12 and 13, the second inputs of which are connected to the output of the source 3 of the reference voltage, and the outputs to the corresponding inputs of the second trigger 14. The output of the latter is connected through the serially connected low-pass filter 15 and the threshold element 16 The index of the control amplifier 11. 17 denotes the output device.

The source 3 of the reference voltage contains a series-connected peak detector 18, a dynamic storage element 19, a voltage divider 20. entrance

the control of the peak detector 18 is connected to the control input of the source 3 via the pulse shaper 21, and the control input of the dynamic storage element 19 is directly connected. The input of the peak detector 18 serves as the input of source 3, and

0 output divider 20 - its output.

The induction sensor 1, when passing a tag in the form of a metal pin or aperture on the engine flywheel, produces a two-pole signal, the moment of transition through the zero level in which corresponds to the middle of the tag. The design of such sensors is well known.

Amplifier 2 performs the functions of a buffer stage and can be implemented on a 0 operational amplifier with a negative

feedback, for example on a chip type K14UD6.

The source 3 of the reference voltage automatically generates a constant voltage, the level of which is equal to Um / Kg, where Urn is the maximum value of the signal; Cg is the division factor of the voltage divider 20.

Typically, the voltage level at the output of source 3 is set to 60-70% of the value of Um-Source 3 updates the level of the output voltage when each signal from the top dead center mark arrives at its control input.

The first to fourth comparators 4, 5, 12, and 13 are conventional single-threshold level detection devices, the output voltage of which is set at the logical "O or logical" 1 levels depending on whether the input voltage exceeds the reference voltage. Comparator 13 is different from the others in that the voltage of its threshold has a sign opposite to that of the reference voltage. The schemes of single-threshold comparators are widely known and can be performed both on operational amplifiers and with the use of integral comparators, for example, of the type K554SAZ. The first and second triggers 6 and 14 can be implemented, for example, on chips of the type K155TM2.

Forming cascade 7 at the front of a pulse at the input produces a short pulse at the output if its control input is set to the enabling level of a logic signal, and does not generate a pulse if the control input has an opposite logic signal. The forming cascade can be performed, for example, on a K155AG1 microcircuit using one of its information inputs as a control input.

Element 8 of the assembly performs the function of the logical OR and can be implemented, for example, on one of the logic elements of the K155LL1 chip.

The pulse generator 9 generates a pulse train with a natural frequency fr, which is less than the lower FH value of the working frequency range of sensor 1. The pulse arriving at the control input of the generator 9 affects its time defining the chain so that it "breaks oscillations of the generator 9. For example, performing the latter on the basis of an integral timer “The disruption of oscillations can be organized by discharging the capacitor, the time of setting the RC-epi to earth through a key, made, for example, on a transistor, for the duration of the impedance lsa for controlling S., entering it. As a result, the pulses at the output of the generator 9 are not generated if the frequency of the appearance of pulses at the control input is higher than the natural frequency fr of the pulses of the generator.

In the generator circuit can be used, for example, an integrated timer type KR1006VI1.

Amplifier 11 has different gain signs depending on the level of the logic signal at its control input. If there is a logic level at the control input, “O at the output of the amplifier

the signal is of the same polarity as the input signal, and at the level of the logical “I is a signal of the inverse polarity.

The low pass filter 15 produces a voltage at its output, the level of which is inversely proportional to the duty ratio of the pulses arriving at its input. The threshold element 16 is triggered and forms a logical "1" signal when a high voltage level is present at its input. As the threshold element 16 may

0 to be used Schmitt trigger type K155TL1.

Voltage divider 20 can be made on resistors.

The pulse shaper 21 is triggered by the cutoff of the pulse at the input and forms

the output of a pulse of duration sufficient to zero the peak detector 18. Shaper 21 can be performed, for example, on a K155A1 type microcircuit.

The device works as follows. When the engine is off pulses

 the signal at the output of sensor 1, amplifier 2, and consequently, at the input of source 3, the first inputs of comparators 12 and 13 and the second inputs of comparators 4 and 5 are missing. The generator 9 generates pulses with a certain frequency fr. The pulses from the output of the generator 9 pass through the assembly element 8 to the input of the control source 3. Each subsequent pulse sets the voltage at the source output to k, times less than the maximum signal value by

0 input for the expired period of pulses at the control input.

Since the signal voltage at the input of source 3 is constant and close to zero, a potential close to zero is established at its output and, therefore, at the first input of the comparator 4 and the second inputs of com parators 12 and 13. At the same time, comparators 4, 12, and 13 are shifted in one of the inputs so that, regardless of the noise level, the comparators do not operate. As a result, the trigger 14 can be in any of its states, and the trigger 6 is set and remains in the initial state, and the shaping stage 7 is blocked by a logic "O" signal at its control input. Thus, impulse:

5 signals at the output 17 of the device are missing.

After starting the engine and leaving it

speed limit per operating range

The frequencies of sensor 1 at the output of the latter appear bipolar signal pulses with a frequency. Let source 3 fix the amplitude of the positive half-wave of the pulse. At some point in time, source 3 fixes the maximum value of Um, of the increased signal over a time interval equal to the period of the generator pulses 9, and sets at its output the level Umi / kg, which is fed to the reference inputs of the comparators 4, 12 and 13. Later on signal at the output 17, and therefore, at the input of the generator 9, this level is updated with the frequency fr of the pulses of the generator 9. Thus, at the output of the source 3 before the appearance of the pulses at the output 17, a positive threshold level is automatically generated Ani comparators 4 and 12 equal Umi + n / g, wherein Umi + n - n maximum amplitude pulses received on the input source 3 in a time l / fr, and n ent (fn / fr). The threshold level of operation of the comparator 13, due to the design features of the latter, is different, i.e. is negative. Let the sensor 1 is installed against the TDC mark, made in the form of a pin (protrusion) on the engine flywheel. In this case, the first half-wave of a two-pole signal pulse appears first at the output of sensor 1. When this pulse reaches a positive threshold level of the comparator 12, the latter triggers, and a signal appears at its output that sets trigger 14 to one state. After passing the midpoint of the TDC mark past sensor 1, a negative half-wave pulse appears at the output of the latter. When this pulse reaches the negative threshold level of the comparator 13, the latter triggers and sets the trigger 14 to the initial zero state. In this case, a short pulse is formed at the output of trigger 14, the duration of which is equal to the time of passing TDC marks past sensor 1. Thus, a sequence of short pulses is formed at the output of trigger 14 with a frequency n following sensor 1 signals and a duty cycle equal to the ratio of the length of the flywheel to the mark length TDC Since the duty cycle of the pulses at the input of the filter 15 is large, a low voltage level is produced at its output, which is well below the threshold level of the threshold element 18 and does not trigger the latter. In this case, the output of the threshold element 18 is a logical signal "O", which is fed to the control input of the amplifier 11 and sets it to a positive gain factor, i.e. The polarity of the signal at the output of amplifier 11 repeats the polarity of the signal at the output of amplifier 2. Let sensor 1 be installed against an TDC mark made as a hole (groove) in the flywheel of the engine. In this case, the first half-wave of a two-pole pulse appears at the output of sensor 1. When this pulse reaches the negative threshold level of the compiler 13, the latter triggers and at its output a signal appears that sets the trigger 14 to the initial zero state. After passing the midpoint of the TDC point past the sensor 1, a positive half-wave pulse appears at the output of the latter. When this pulse reaches the positive threshold level of the comparator 12 after, the first one triggers and sets the trigger 14 to one state. The trigger 14 is in the unit state until the next pulse of the sensor 1 arrives, which, with the first half-wave, having negative polarity, sets the trigger 14 to the initial zero state, and the second (positive) half-wave - into the single state. Thus, at the output of the trigger 14, a sequence of pulses is formed with a duty cycle equal to the ratio of the length of the circumference of the flywheel to the difference between the lengths of the circumference of the flywheel and the TDC mark. Since the duty cycle of the pulses at the input of the filter 15 is small, a high voltage level is produced at the output of the latter, which exceeds the threshold of the threshold element 16 and triggers the latter. At the same time, at the output of the threshold element a logical signal "1" is formed, which switches amplifier 1 to the inverting mode of the input signal so that the positive half-wave of the pulse arrives first at the output of amplifier 11. Thus, when performing the TDC mark, both in the form of a hole (groove) and in the form of a pin (protrusion), the output of the amplifier 11 always receives the positive half-wave of the pulse first. This half-wave pulse triggers the comparator 4, the output of which produces a pulse equal in duration to the input signal of the threshold of the comparator 4 set by source 3. The pulse from the output of the comparator 4 sets the trigger 6 to unlock the signal from its output. stage 7. At the moment of changing the polarity of the pulse at the output of the amplifier 1 1 from positive to negative, the comparator 5 is triggered, since its threshold is set to constant zero. As a result, the forming cascade 7 is started and at its output, i.e. at the output 17 of the device, a pulse appears, the front of which coincides with the moment when the two-polar signal of sensor 1 crosses through zero. This pulse arrives at the second input of trigger 6 and makes it

Claims (1)

Claim A device for determining the top dead center of an internal combustion engine, comprising an induction sensor, a first amplifier, a reference voltage source, a first and second comparators, a first trigger forming a cascade, an assembly element and a pulse generator, the output of the induction sensor being connected through a first amplifier and a source connected in series voltage reference to the first input of the first comparator, the output of which is connected to the first input of the first trigger, the output of which is connected to the control input of the form the cascade, the input of which is connected to the output of the second comparator, and the output - to the second input of the first trigger, the control input of the pulse generator and the first input of the assembly element, the second input of which is connected to the output of the pulse generator, the output - to the control input of the reference voltage source, and on the first input of the second comparator is connected to zero potential, characterized in that, for the purpose of understanding the scope, a second amplifier, fourth comparators, a second low-pass filter and a threshold element are introduced into it, at the output of the first amplifier is connected through the second amplifier to the second inputs of the first and second comparators and directly to the first inputs of the third and fourth comparators, the second inputs of which are connected to the output of the reference voltage source, and the outputs are connected to the corresponding inputs of the second trigger, the output of which is connected through series-connected a low-pass filter and a threshold element with a control input of the second amplifier.