RU2245532C2 - Electronic device for determining compression in cylinders of internal combustion engine - Google Patents

Abstract

FIELD: testing of engines.

SUBSTANCE: device comprises capacitive electronic marker of cylinder number and pulse multiplying device, which multiplies signals proportional to the current consumed by the starter and voltage drop at the terminals of the storage battery when the engine is actuated with the starter. The curve obtained at the output of the device is directly proportional to the curve of variation of compression throughout the cylinders of the engine. The first input of the pulse multiplying device is connected with the output of shunting resistance (current sensor) through a differential amplifier and voltage divider. The second input is connected with the voltage divider. The shunting resistance is connected with the wire which connects the positive terminal of the storage battery with the starter. The output of the pulse multiplying device is connected with the first input of the adder through the RC-circuit and voltage follower . The second input is connected with the output of the electronic marker of cylinder number.

EFFECT: enhanced accuracy of measuring compression.

Description

The invention relates to measuring technique and equipment for the diagnosis of internal combustion engines.

A device is known for determining compression (compression pressure) [Electrical meters for diagnosing machines and mechanisms. R.S. Ermolov, R.A. Ivashov, V.K. Kolesnik, G.D. Morozov. - L .: Energy. Leningrad Branch, 1979. 128 pp., P.114] on the change in the current consumed by the starter at the time of engine scrolling. The device allows you to determine the average value and the unevenness of the compression pressure over the engine cylinders. The device consists of a shunt connected between the battery and the machine body, an amplifier, average and amplitude detectors connected to the output of the signal amplifier taken from the shunt, a differential amplifier that sets the difference between the signals at the output of the amplitude and average detectors, two voltage comparators for comparison signal with a predetermined signal from the unit settings. The second comparator is designed to determine the unevenness of the compression pressure relative to the maximum value. The device also includes a signal delay unit, which is necessary to block the operation of the device until the engine enters a stable mode of scrolling by the starter.

The disadvantages of this device are the high complexity and low accuracy of determining compression.

Of the known technical solutions, the closest to the invention in technical essence is a device for determining compression (compression pressure) by changing the voltage at the terminals of the battery when the engine is cranking with a starter [Electrical meters for diagnosing machines and mechanisms. R.S. Ermolov, R.A. Ivashov, V.K. Kolesnik, G.D. Morozov. - L .: Energy. Leningrad branch, 1979. 128 p., P.111].

The device contains an AC amplifier connected directly to the terminals of the battery and emitting an alternating voltage component that occurs due to uneven loading when the engine is cranking with a starter. The double amplitude detector records the value of the voltage drop change on the internal resistance of the battery in the sequence determined by the order of the cylinders in the engine. An analog-to-digital converter is connected to the output of the double amplitude detector, which converts the analog signal into digital information, which is transmitted and stored in memory elements with indicators at the output. The device also includes a circuit for extracting an oscillation corresponding to the compression pressure in a particular cylinder from a pulsating voltage. The circuit includes: a cycle and reference signal marker, a shift register with the number of cells equal to the number of cylinders, and pulse shapers.

The device operates as follows.

When the starter scrolls the engine, the electronic amplifier emits an alternating voltage component that occurs due to uneven loading when the starter scrolls the engine. The alternating voltage from the amplifier is fed to a double amplitude detector, which records the value of the complete change of each voltage wave in a sequence determined by the order of operation of the cylinders of the internal combustion engine. The voltage from the detector is fed to the input of an analog-to-digital converter and then stored in digital form in the memory registers, and also displayed on indicators connected to the memory registers. As a cycle marker, a capacitive or inductive converter is used, connected to the high voltage wire of one of the cylinders, and for a reference signal marker, a similar converter is installed on the common distributor wire. At a signal from the reference signal marker, the ADC driver and converter are started. At the same time, a cell in the register for storing the result corresponding to the number of the cylinder under study is cocked, and a pulse shaper is launched at the output of this cell. It generates a pulse whose duration is equal to the measurement time of the analog-to-digital converter. On the trailing edge of this pulse, the memory element of the cylinder under study opens and the value of the complete change in the voltage fluctuation, internal compression in this cylinder is fixed. After a time interval longer than the ADC memory interval, the imaging-detector from this moment is prepared to fix the amplitude of the next wave of voltage fluctuations.

The main disadvantage of this device is as follows. Compression in the above device is determined by monitoring the voltage drop on the internal resistance of the battery. Moreover, the smaller the voltage drop across the internal resistance, the greater the compression. This is due to the fact that with an increase in compression at the time of compression, the opposing moment on the shaft of the starter motor increases. It is known that the moment on the DC motor shaft is proportional not to a linear dependence on the current, but to a quadratic dependence on the current or voltage at the motor armature. In this regard, the error in determining the compression in this device is relatively high. In addition, the internal resistance of the battery is a nonlinear quantity that depends on the chemical processes in the battery (temperature, electrolyte density, state of the plates, etc.), which introduces an additional error.

The objective of the present invention is to increase the accuracy of determining compression in the engine cylinders by measuring the active power consumed by the starter at the time of engine scrolling when the high-voltage wires are disconnected from the spark plugs.

This object is achieved by the fact that the composition of the invention, which contains a capacitive electronic cylinder number marker, includes a pulse multiplying device that multiplies signals proportional to the current consumed by the starter and the voltage drop at the battery terminals when the engine starts to scroll. The curve obtained at the output of the device is directly proportional to the curve of the change in compression pressure in all engine cylinders. The first input of the pulse multiplying device is connected to the output of the shunt resistance (current sensor) through a differential amplifier and a voltage divider, and the second input is connected to a voltage divider. The shunt resistance is connected to the standard wire connecting the positive terminal of the battery with the starter. The output of the pulse multiplying device through an RC circuit and a voltage follower is connected to the first input of the adder, the second input of which is connected to the output of the electronic cylinder number marker.

As a result of a comparative analysis carried out on scientific and scientific-technical means of information containing information about analogues of this facility (Omsk Central Scientific and Technical Institute), no analogue was identified, characterized by features identical to all the essential features of the proposed technical solution, and the closest in technical essence is the above a device for determining compression (compression pressure) by changing the voltage at the terminals of the battery when the engine is cranking with a starter.

Achieving a higher technical result when using new features of a technical solution allows us to conclude that the claimed technical solution meets the requirement of "inventive step".

The invention is illustrated by the accompanying drawings, where in Fig.1 shows a structural diagram of a device; figure 2 shows a schematic diagram of a device for determining compression; figure 3 shows the timing diagrams of the operation of the device.

The block diagram of an electronic device for determining compression in the cylinders of the engine is presented in figure 1. It includes a battery 1, a current sensor 2 (shunt resistance R3), a starter 3, a gasoline internal combustion engine 4, a calculator of power consumed by a starter 5, an ignition system 6, an electronic cylinder number marker 7, a signal adder 8 (voltage adder DA3 ) recording device 9.

As a current sensor 2, a shunt resistance R3 is used, connected between the battery and the car starter. To determine the compression, disconnect the high-voltage wires from the spark plugs. An electronic marker of cylinder number 7 is connected to the high-voltage wire of the first cylinder, consisting of a differentiating RC circuit (C2, R9) connected to the input of the voltage follower on the operational amplifier DA4.

The high-voltage isolation capacitor C2 is a twisted pair of two high-voltage wires, insulated with a dielectric, about 5-7 cm long, which corresponds to a capacitance of about 10 pF.

Figure 2 shows a schematic diagram of the inclusion of an electronic device for determining compression in the cylinders of the engine.

An electronic device for determining compression includes: a voltage divider included in the starter power circuit, consisting of resistors R1, R2; shunt resistance R3 connected between the negative terminal of the battery and the car body; the shunt resistance leads are connected to the input of the operational amplifier DA1, the output of which is connected to the input of the voltage divider on the resistors R4, R5, the output of which is connected to the first input of the multiplying device, the second input of which is connected to the output of the voltage divider R1, R2; the output of the multiplier through the RC circuit R6, C1 is connected to the input of the voltage follower made on the operational amplifier DA2, the output of which through R7 is connected to the first input of the adder made on the operational amplifier DA3, to the second input of which is through R8 and the voltage follower on the operational amplifier DA4 connected differentiating RC-circuit C2, R9.

An electronic device for determining compression in the cylinders of a gasoline engine works as follows.

When the ignition switch and starter switch contacts are locked, the locking relay, the retractor and holding windings of the traction relay are connected to the battery 1. The traction relay anchor is attracted to the core of the electromagnet and, using the rod and the lever of the drive mechanism, engages the starter gear 3 in engagement with the ring gear of the engine flywheel 4 .

At the end of the armature stroke, the power contact plate closes the power contacts, and the starter motor (starter) 3, receiving power from the battery 1, rotates the crankshaft of the engine. When the high-voltage wires are disconnected from the spark plugs, the engine scrolls with the starter 3 without ignition of the working fluid, and the greater the compression pressure (compression) in the cylinder, the greater the moment the starter must create to overcome compression and, therefore, the greater the power the starter must consume.

The voltage removed from the voltage divider at the resistances R1, R2, proportional to the voltage drop at the internal resistance of the battery 1, at the time of cranking the engine with starter 3, is fed to the input of the multiplying device PU, which is part of the power calculator consumed by the starter 5. The second input of the PU voltage is supplied from the shunt resistance R3, which is proportional to the current consumption of the starter at the time of engine scrolling, through the differential amplifier DA1, which amplifies the voltage difference, Mykh at its input and a voltage divider R4, R5 to changes in signal amplitude. A signal proportional to the product of two input signals and characterizing the active power consumed by the starter when the engine is cranking is taken from the output of the multiplying device PU. From the PU output, the voltage through the voltage follower goes to the first input of the DA3 voltage adder. The second input of the adder receives a signal from the electronic marker of cylinder number 7, which includes an RC circuit and a DA4 repeater and is connected to a high-voltage wire connecting the voltage distributor and the candle of the first cylinder. From the output of the adder 8, a signal showing compression in the cylinders is fed to the input of a recording device for recording and analyzing the state of wear.

Timing diagrams of the operation of the device are shown in figure 3, where: u _article (t) is the voltage drop across the internal resistance of the battery at the time of the engine cranking by the starter; i _st - current consumed by the starter at the time of engine cranking; u _sv1 - voltage pulse coming from the voltage distributor to the high-voltage wire of the first cylinder, which allows to determine the sequence of engine operation; u _o - voltage at the input of the recording device, proportional to the power consumed by the starter at the time of scrolling, which allows to determine the change in compression in each of the cylinders of a gasoline internal combustion engine.

We show that the compression in the engine cylinders is proportional to the electric power consumed by the starter at the time of engine cranking.

The useful torque M on the shaft of the electric motor (starter) is determined by the following expression:

where P is the active electric power consumed by the DC motor;

n _a is the rotation frequency of the armature.

Given the fact that the definition of compression in the engine cylinders occurs at a steady state operating mode of the starter, i.e. anchor rotation frequency n _a = const, the formula will take the form:

where u _I (t) is the instantaneous voltage drop across the starter when the engine is cranking with the starter;

i _I (t) is the instantaneous value of the current consumed by the starter at the time of scrolling.

Useful torque M on the motor shaft is determined by the expression:

where M _SJ - the moment of compression;

M _IN - moment of inertia;

M _TR - moment of friction.

It should be noted that in the steady state M _IN becomes equal to zero, and m _TP can be considered the same for each cylinder, therefore, from the useful torque M on the motor shaft (starter), defined by expression (3), it is possible to determine the current value of compression in the engine cylinders . If compression in any cylinder decreases, this will lead to a decrease in power consumption in the corresponding compression cycle.

Claims (1)

An electronic device for determining compression in the cylinders of a gasoline internal combustion engine, comprising a capacitive electronic cylinder number marker, characterized in that the device includes a pulse multiplying device, the first input of which is connected to the output of the shunt resistance (current sensor) through a differential amplifier and a voltage divider, and the second input is connected to a voltage divider connected to a standard wire connecting the positive terminal of the battery with Intermediate location, the output pulse of a multiplying device through a RC-circuit and a voltage follower connected to the first input of the adder, a second input coupled to an output of the electronic timer cylinder number.

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