Ignition system for car Samara. Free Technical Library article

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Ignition system for car Samara

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Quite frequent failures of the electronic switch 36.3734 in the ignition system reduce the operational reliability of VAZ-2108, VAZ-2109 vehicles. To improve the process of ignition of the combustible mixture in the engine of these vehicles, the spark gap in the glow plugs has been increased and the high-voltage output voltage developed by the ignition system has been increased. Due to impulse surges in the circuit of the primary winding of the ignition coil, reaching 400 V, there are cases of damage to the output transistor key of the switch. In addition, it turns out to be a faulty chip. As a result, the repair of the switch becomes inaccessible for many motorists.

The device described below is designed to replace a failed 36.3734 switch. It can work in conjunction with a contactless sensor-distributor installed on the engine of these vehicles. In this case, the gap of the glow plugs should be reduced, which will reduce the load on the insulation of the plugs, high-voltage conductors, and the distributor. The decrease in the spark gap is compensated by an increase in the energy and duration of the spark discharge, and the gap breaks through twice during one sparking cycle.

The device is based on the block described in [1], in which the circuit of the source of triggering pulses is changed and elements are introduced that ensure the operation of the block from the contactless sensor 40.3706. To check the operability of the sensor, block and glow plugs, as well as to facilitate the adjustment, a sensor simulator has been introduced. Anti-theft blocking circuit is provided.

The ignition unit consists of a single vibrator (VT1, VT2), a current amplifier (VT3), an output key (VT4) and a bit key (VS1). Connector XI connects the unit to the vehicle's on-board network, ignition coil T2 and sensor (not shown in the diagram). The designation of contacts and conductors is the same as that of the replaced ignition system [2]. SA1 - anti-theft switch.

When the key is turned to the "Ignition on" position, power is supplied to the unit from the on-board network through pin 4 of connector X1. The voltage to the contactless sensor is supplied through the filter-stabilizer R4C1VD1. In the source of triggering pulses, made according to the single vibrator circuit, the transistor VT1 is open, and VT2 is closed. The time-setting capacitor C 4 is charged through resistors R8, R9 and the emitter junction of the transistor VT1 to a voltage limited by the zener diode VD3. If the resistance of the output circuit of the sensor is high, then the capacitor C1 of the one-shot start circuit is charged through resistors R3-R1 to the voltage across the capacitor CXNUMX.

At the moment of sparking, the output resistance of the sensor decreases sharply, so the capacitor C2 is discharged along the circuit: resistor R1 - normally closed contacts of the SB6 button - pin 3 of the connector - sensor - pin 3 - resistor RXNUMX.

(click to enlarge)

A negative pulse from the resistor R3 is fed to the emitter junction of the transistor VT1 through the diode VD2 and closes it, and the transistor VT2 opens. Capacitor C4 is recharged through diode VD4 and resistors R10, R5, R6. Thus, the single vibrator generates a positive pulse with a duration of 2,3 ... 2,5 ms. The operation of this node is described in detail in [1].

By changing the resistance of the R5R6 circuit, it is possible to regulate the duration of the one-shot pulse and, accordingly, the time of energy accumulation in the ignition coil T2 over a wide range. Resistor R10 limits the current in the discharge circuit of the timing capacitor C4. The introduction of resistor R9 reduces the duration of the pulse generated by the single vibrator at a high sparking frequency. This leads to a limitation of the maximum current consumed by the device at a level of about 5 A (in terms of other characteristics, the block is similar to that described in [1]).

In the event that the sensor is in a state in which its output resistance is low, the unit generates a spark each time the SB1 button is pressed and each time it is released.

Closing the contacts of the anti-theft switch SA1 will cause the zener diode VD3 to be shunted by the VD5R11 circuit. In this case, the duration of the pulse generated by the single vibrator will decrease to 0,8 ms, which will cause a sharp decrease in the spark energy and a violation of the engine start.

The lower the resistance of the resistor R11, the weaker the spark.

The device is best assembled in a case from a faulty switch 36.3734, which already contains the X1 connector. If a case of a different design is chosen, then to connect the device, it is necessary to use the ShR plug connector, and the conductors from pins 1 and 4 must have a cross section of at least 1,5 mm² and minimum length. To improve cooling, the VD10 diode and the VT4 transistor are attached to the device case (the diode is through a mica gasket). A simulator of the sensor-button SB1 is also installed on the case.

Capacitor C1 in the block - K53-1A; C2, SZ, C5-K10-7B; C4-K73-9 or K73-17; C7 - K52-1. Resistor R5 - SPZ-6a. Zener diode VD1 can be replaced with any other with a stabilization voltage of 12 ... 14 V, VD3-on KS168A. Diodes KD522A can be replaced by KD521, D223, D220 with any letter index. Button SB1 - KM1-1, switch SA1-MT1-1 or any other.

The winding characteristics of the isolating transformer T1 are specified in [1]. The device is not critical to the parameters of the magnetic circuit and the number of turns of this transformer. It can be replaced with a factory-made pulse transformer, for example, I-58, I-48, MIT-3, MIT-9. The transformer windings must be connected strictly according to the scheme.

Ignition coil T2 - B114 with any letter index, previously converted as described in [1].

The adjustment is carried out with single triggering pulses from the button SB1, as described in [1]. It should be remembered that with an increase in the sparking frequency, the average voltage across the storage capacitor C6 decreases, and the maximum remains close to 100 V - this is not a sign of a device malfunction.

Since the duration of the spark discharge reaches 4,8 ms, for a more complete transfer of energy to the spark plugs and to reduce the burning of the distribution plate on the ignition distributor slider, it is necessary to lengthen its working end. How to do this can be found in [4]. The converted slider works fine in the original ignition system.

The B114 ignition coil used in the device has a high resistance of the secondary winding (about 20 kOhm), so the interference suppression resistor on the slider can be eliminated by closing it with a wire jumper with a diameter of 0,25 ... 0,4 mm.

The recommended spark gap in spark plugs is 0,5 ... 0,6 mm.

Literature

1. Bespalov V. Block of electronic ignition. - Radio, 1987, No. 1, p. 25-27.

2. Cheplanov V., Pustelnikov O. Ignition system VAZ-2108: malfunctions and their elimination. - Behind the wheel, 1987, No. 6, p. 28, 29.

3. Bespalov V. Our consultation. - Radio, 1987, No. 8, p. 62.

4. Sinelnikov A. X. Electronics in the car, - M .: Radio and communication, 1985; With. 32.

Author: V. Bespalov, Kemerovo; Publication: cxem.net

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