Electronics in auto diagnostics. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices

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Statistics show that electrical equipment accounts for about 25% of all vehicle malfunctions that occur during operation. The condition of the ignition system significantly affects the operation of the engine. Due to the wear of its elements, loosening of connections, erosion of contacts, engine start worsens, fuel consumption increases, power is lost, battery life decreases and exhaust gas toxicity increases. For example, a violation of the normal operation of a centrifugal or vacuum ignition timing controller causes an increase in fuel consumption by 6 ... 8%; one non-working candle out of four - a drop in power up to 30%; delay of the ignition moment by 5...8° against the norm reduces the effective power of the engine by 8...12%.

Special stands have been created for diagnosing electrical equipment. One of the most common is the oscilloscope device for testing engines "Elkon S-200" manufactured by VNR. Using this device, you can detect malfunctions of the primary and secondary circuits of the ignition system by evaluating the voltage oscillograms in them, measure the angle of the closed state of the breaker contacts in the range from 36 to 90 °, the ignition timing from 0 to 60 °, peak voltages in the primary circuit up to 40 In and secondary up to 40 kV, measure the engine speed up to 10000 min-I, and also evaluate the difference in power developed by the cylinders.

Structural diagram of the device "Elcon S-200" is shown in fig. 1 in the text. The investigated signals from the vehicle distributor are taken from the inductive and capacitive sensors Ul, U2.

Fig.1 (click to enlarge)

After limiting and synchronizing with the speed of the distributor shaft, the signals through the operating mode switch enter the electronic switch. The tachometer input signals and ignition timing meters also come here. The operation of the electronic switch is synchronized by the sawtooth voltage generator. As a result, on the screen of the cathode ray tube, in the intervals between the image of the analog signal, the speed and ignition timing are reproduced in the form of vertically moving marks.

When measuring the amplitude of the breakdown voltage on the spark plugs, the sawtooth voltage generator generates a sweep signal for the horizontal deflection of the beam. In addition, its functions include the control of the step signal generator, which is necessary to create bitmaps. The step signal generator generates pulses to control beam suppression when measuring the power difference of the cylinders. In this case, a bitmap image of the analog signal in the primary or secondary circuit of the ignition system appears on the screen.

After pressing the button for automatically turning off the cylinders, the oscillograms of the operation of the ignition system of each of the cylinders sequentially disappear on the screen and the engine speed changes, which can be controlled on the tachometer scale on the right side of the image. Readings that are out of range indicate malfunctions in the ignition system.

The signal from the tachometer unit is fed to the ignition timing meter (voltage-frequency converter), which, in turn, ensures the operation of the stroboscope. The voltage required for the operation of the CRT is generated by the power supply; it also performs the functions of suppressing the reverse motion of the sweep beam, receiving signals from the generator, sawtooth voltage and the electronic switch.

Recently, the production of specialized portable small-sized devices has been increasing. A typical representative of this class of devices is the so-called measuring bag "Elkon S-320" (VNR) for car diagnostics. The minimum number of connecting cables and the multifunctional inductive probe, which allows you to determine the condition of the diodes and the generator coil, greatly facilitate the measurement. Modern external design, small dimensions and weight (6 kg), ease of maintenance provide fast and accurate diagnostic tests.

Long-term business contacts connect our foreign trade organizations with the Austrian company Sime und Klein. It supplies automotive and service companies with diagnostic equipment, fast battery chargers, etc.

The latest model of the company "Microcomputer motor-tester 1212". Unlike previous models, microprocessor technology is widely used here, a digital printing device is used. The device is designed for three main modes: start-motion-cylinder analysis. The analog display shows the necessary information about the order of work performed, stored in ROM. Moreover, the language in which information is displayed on the display can be easily changed by replacing just one chip. The digital display is designed to compare the actual measured values ​​with the table values ​​stored in the storage device. If it is inconvenient for the operator to approach the dashboard, then you can switch the device to the next mode from the remote control panel.

The share of road transport in air pollution in large cities is 30 ... .40%, and most of the harmful emissions are carbon monoxide. The content of this extremely harmful substance in the exhaust gases of cars with a gasoline engine is regulated by GOST and should not exceed 1,5 ... 3,5%.

In the conditions of service stations, the content of toxic components is determined by means of gas analyzers. One of such devices is the gas analyzer "Infralit-8T" manufactured by the GDR, the device of which is shown schematically in fig. 2.

Ris.2

Infrared radiation from two heated spirals 1 (they are included in the collector circuit of a powerful power supply transistor) is directed by parabolic mirrors 2 along the comparison chamber 3 and the working chamber 4, respectively. The first is filled with nitrogen, which practically does not absorb infrared radiation. In the working chamber, through which the exhaust gases of the engine are blown, they absorb part of the spectrum components. Both chambers are closed at the ends with light filters that are transparent to IR rays. Under the influence of radiation, the air in the cavities of the receiver 7, separated by a partition 5, heats up in different ways. The pressure difference causes the baffle to sag. It is a condenser pressure sensor.

Working in conjunction with the electronic unit 6, the sensor generates a signal that is a function of the percentage of carbon monoxide. After amplification, the signal is fed to the indicator - pointer device 9, showing the content of carbon monoxide, and to the recorder 8.

It is well known that the angles of the front wheels and the pressure in the tires have a significant impact on their wear, vehicle handling and driving safety in general. Therefore, these diagnostic parameters should be checked regularly. Stand model 9820 (Sims und Klein) is designed to control the geometry of the wheels. Large alphanumeric LED indicators display information about toe and camber angles, kingpin longitudinal inclination, steering centering. The stand self-adjusts, it is controlled by a microprocessor. Unlike other similar devices that use special optics, the stand uses liquid and semiconductor sensors that respond to angular and linear displacements.

Tire wear is also affected by wheel balancing. The French company Bem Muller produces a model 5609 stand for balancing wheels without removing them from the car. A small electric motor is installed on the mobile cart, equipped with a device for spinning the wheel, which is previously raised with a jack. The oscillations of the vehicle suspension caused by the imbalance of the rotating wheel are sensed by a piezoelectric sensor. When a maximum signal is received, the strobe lamp turns on and the operator easily determines the point corresponding to the position of the unbalanced mass. After conversion, the signals coming from the sensor are displayed by a pointer, the scale of which is graduated in grams of additional weight.

Recently, the endoscope has found wide application in technology - a medical device for examining the stomach. Firm "Storts" (Germany) produces one of the varieties of light endoscope - Motoscope, designed for self-diagnosis. A powerful focused light beam is directed along a flexible light guide to the surface under study. The brightness of the lamp is controlled by a trinistor regulator. Special nozzles make it possible to observe with magnification the centers of corrosion hidden for the eye, the nature of wear of parts in closed cavities, the surface of cylinders, etc. The object under study can be photographed or displayed on an enlarged scale on the display screen.

Even from our brief review, it is clear what a strong place electronics occupies in auto diagnostics today. With the help of a microprocessor, in the near future, the machine will "diagnose" itself. Constantly polling the controlled parts of the car every few minutes according to a programmed cycle, the alarm system gives the driver processed information in ready-made phrases, for example: "fuel reserve", "oil pressure drop", "overspeed", etc. In parallel, the display shows the values ​​of the measured parameters . Sensors that convert various non-electrical signals into electrical ones will also change. Information from the sensors will come in one line, enclosing the car in a ring.

Author: A. Krymsky, Moscow; Publication: N. Bolshakov, rf.atnn.ru

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