It is ignited by a spark that is formed between the electrodes of the spark plug.
To form a spark, a voltage of at least 12-16 kV is required.
The generation of high voltage current, as well as its distribution among the engine cylinders, is carried out by battery ignition devices. The battery ignition system includes a low voltage current source, an ignition coil, a distributor breaker, spark plugs, a capacitor, high and low voltage wires, and an ignition switch.

Battery ignition system includes a high voltage circuit and a low voltage circuit. The low voltage circuit is powered by a battery or a generator. In addition to current sources, this circuit includes in series the ignition switch, a breaker, and the primary winding of the ignition coil with an additional resistor. All these elements are connected to each other by low voltage wires. The high voltage circuit includes: the secondary winding of the ignition coil, high voltage wires, spark plugs, and the distributor.
The formation of a high voltage current occurs in the ignition coil. It is based on the principle of self-induction. When the ignition is turned on and the breaker contacts are closed, electric current from the generator or from the battery is supplied to the primary winding of the ignition coil, as a result of which an electromagnetic field appears around it. When the breaker contacts open, the current in the primary winding disappears, and the magnetic flux around it also disappears. The vanishing magnetic flux crosses the turns of the primary and secondary windings of the ignition coil, as a result of which an EMF arises in each of them. Due to the large number of turns of the secondary winding connected in series, the total voltage at its ends reaches 20-24 kV.

From the ignition coil, high voltage current flows through the high voltage wires and distributor to the spark plugs. As a result, an electric discharge is formed between the electrodes of the spark plugs, which ignites the working mixture in the combustion chambers.
The self-induction EMF in the primary winding of the ignition coil reaches 200-300 V. Due to this, the disappearance of the magnetic flux slows down and a spark appears between the breaker contacts. In order to prevent a spark from occurring between the contacts of the breaker, a capacitor is installed parallel to the contacts.

Ignition coil, converting low voltage current into high voltage current consists of:
1) core;
2) the primary winding, which includes 250-400 turns of insulated copper wire with a diameter of 0.8 mm;
3) secondary winding, which includes 19-25 thousand turns of insulated wire with a diameter of 0.1 mm;
4) cardboard tube;
5) iron case with magnetic cores;
6) carbolite cover;
7) terminals and additional resistor.

Secondary winding of the ignition coil is located under the primary winding and is separated from it by a layer of insulating material. The ends of the primary winding are brought out to the terminals of the carbolite cover.
The ignition coil core is made of separate strips of transformer steel insulated from each other. This design reduces the formation of eddy currents. The lower end of the core is installed in a porcelain insulator. The internal cavities of the transformation coil are filled with transformer oil.

Additional ignition coil resistor consists of a spiral, ceramic sockets and two tires. The resistance of the additional resistor ranges from 0.7 to 20 Ohms. One end of the resistor is connected to the VK terminal using a bus, and the other end is connected to the VKV terminal.
At low engine speeds, the breaker contacts remain closed for a long time. As a result of this, the current in the primary circuit increases, the resistor begins to heat up, and a small electric current flows into the ignition coil, thereby protecting the coil from overheating.
In order to constantly induce a high voltage current in the secondary winding of the ignition coil, it is necessary to periodically open the primary circuit of the battery ignition system. A breaker is used for this. In addition, the high voltage generated by the ignition coil must be distributed among the engine cylinders according to the order of their operation; this function is performed by the distributor. For more convenient maintenance, as well as to simplify the design of the ignition system, the distributor and the breaker are combined into one device - the breaker-distributor.

Breaker installed on the car engine and driven by the camshaft. A thin layer of tungsten is fused onto the breaker contacts. The breaker consists of:
1) drive shaft;
2) housing;
3) movable and fixed disks;
4) centrifugal and vacuum advance regulators;
5) octane corrector;
6) cam with protrusions.

The number of lobes on the cam is equal to the number of engine cylinders. The cam is connected to the drive roller through a centrifugal regulator. A capacitor is connected in parallel to the contacts of the breaker, which prevents sparking at the contacts and also leads to the rapid disappearance of current in the primary circuit. Due to this, the voltage in the secondary circuit increases significantly. The capacitor consists of varnished paper on which a layer of zinc and tin is applied. This paper is rolled into a roll and serves as the lining of the capacitor. Flexible conductors are soldered to the ends of the roll. The roll is wrapped in cable paper and soaked in oil. The capacitor is mounted on a movable disk or externally on the breaker body.
The capacitance of the capacitor is 0.17-0.2 µF. Metallized paper capacitors can self-heal during dielectric breakdown by filling the hole with oil.

In addition, the operation of the battery ignition system is greatly influenced by the gap between the breaker contacts. Normal operation of the battery ignition system is possible with a gap between the breaker contacts ranging from 0.35 to 0.45 mm.
If the gap is large, the time the capacitor is closed will decrease, and the current in the primary winding of the ignition coil will not have time to increase to the required value. As a result, the EMF of the secondary circuit will not be high enough. In addition, if the gap is large and the crankshaft speed is high, interruptions in engine operation will occur.

With a small gap, strong sparking occurs between the contacts of the breaker, and as a result, interruptions occur in all modes of engine operation. The gap between the breaker contacts is adjusted by moving the plate with the fixed contact post.
The distributor is installed on the breaker body and consists of a rotor and a cover. The rotor is made of carbolite and has the shape of a mushroom. A contact plate is mounted on top of the rotor. The rotor is mounted on the cam lobe. The distributor cap is also made of carbolite. On the outer part of the rotor cover there are slots along the circumference according to the number of cylinders. Wires are inserted into the sockets and connected to the spark plugs. In addition, there is a central socket in the distributor cover, which is intended for fastening the high voltage wire from the ignition coil. Inside the distributor, opposite each socket, there are side contacts. In the center of the inside of the distributor there is a carbon contact with a spring, which is designed to connect the central seat to the rotor plate.

The cover is secured to the rotor body using two spring latches. The rotor, rotating together with the cam, connects the central contact in turn with all the side planes, while the high voltage circuit is closed, and the electric current flows into the spark plugs of those cylinders where the working mixture should be ignited at the moment.

Spark plug consists of a central electrode with an insulator, as well as a steel housing in which it is mounted. The spark plug body has a threaded upper part, thanks to which the spark plug is screwed into a threaded hole in the cylinder head of a car engine. There is one side electrode at the bottom of the housing. In the upper part, the spark plug body has turnkey edges. The central electrode with an insulator is rolled into the spark plug body. On the top of the central electrode there is a tip for attaching a high voltage wire.
For normal operation of the spark plug, the temperature of the lower part of the insulator must be in the range from 500 to 600 ° C. At this temperature, the carbon burns out and the spark plug is cleaned. Excessive heating of the spark plug leads to the destruction of the insulator, and as a result of hypothermia, engine oil and carbon deposits accumulate on the spark plugs.

General provisions.

The contact or classic battery ignition system (Figure 75) consists of an ignition switch, an ignition coil, an additional resistor, a distributor breaker, spark plugs, high voltage and low voltage wires.

The operating principle of the ignition system is as follows:

When the ignition switch is turned off and the breaker contacts are closed, the current from the battery passes through the primary winding of the ignition coil and creates an electromagnetic field in it.

When the crankshaft is turned, the claw clutch of the breaker opens the contacts. The current in the circuit is interrupted. The magnetic field, disappearing, crosses the turns of the secondary winding. A high voltage pulse is induced in it, which is supplied by the distributor to the spark plugs.

Contact ignition systems can be installed on UAZ-469, GAZ-66, ZIL-131, Ural-375 vehicles.

Fig.75. Schematic diagram of the contact ignition system

Construction of contact ignition system devices.

Ignition coil.

Serves to convert low voltage to high voltage. It consists of a core, primary and secondary windings, a magnetic core, an insulator, a cover with terminal clamps and a housing, in accordance with Figure 76.

The coil is an autotransformer, on the iron core of which a secondary winding is wound, and on top of it is a primary winding. The secondary winding is wound with PEL wire with a diameter of 0.06 to 0.1 mm with a number of turns from 18,000 to 43,000. The primary winding is wound with a wire of diameter 0.57-0.77 with a number of turns from 185 to 530.

The core with windings is placed in a sealed steel casing and secured in it with an insulator and a lid. All empty spaces in the coil housing are filled with transformer oil, which improves the insulation of the windings and heat dissipation from them to the housing.

Fig.76. Ignition coils:

a) Unshielded with b) shielded (B102-B).

additional resistor (B13)

The ignition coils of military vehicles differ from each other in winding data, the number of output terminals and the presence of shielding.

Additional resistor.

An additional resistor serves to ensure normal thermal conditions of the ignition coil. It installs coil mounting brackets between the legs (B13) or is performed separately (B5A, B102B).

The additional resistor consists of an insulator body on which constantan or nickel wire is wound, and output terminals, in accordance with Figure 77.

Fig.77. Additional resistor

When the engine is started by the starter, the voltage at the battery terminals is reduced so that this does not cause a decrease in the current in the primary circuit, an additional resistor is shunted by the contacts of the starter enable relay or the starter traction relay. In addition, at increased engine crankshaft speeds, selecting the resistor value together with the inductance of the primary winding of the ignition coil ensures the value of U2 › U (breakdown) throughout the entire range of rotation speeds.

Ignition distributor.

It consists of the following mechanisms: a chopper with a capacitor, a high-voltage distributor, centrifugal and vacuum ignition timing regulators and an octane corrector, in accordance with Figure 78.

In the housing, two bronze bushings rotate the drive shaft of the breaker cam clutch, the distributor rotor and the centrifugal ignition timing regulator.

The breaker serves to close and open the primary circuit of the ignition system in accordance with Figure 79.

Consists of a plate with a fixed contact, a lever with a movable contact and a leaf spring, a jaw clutch and one or two discs.

Fig.78. Design of the ignition distributor-distributor P102:

1 – cam clutch; 2 - rotor; 3 – contact corner; 4 - cover;

Fig.79. Breaker with vacuum regulator and octane corrector:

1 - cam clutch; 2 - eccentric screw; 3 - plate with movable contact; 4 - lever with a moving contact and a leaf spring; 5 - locking screw; 6 - movable disk; 7 - vacuum regulator cover; 8 - adjusting washers; 9 - sealing gasket; 10 - fitting; 11 - tube; 12 - spring; 13 - diaphragm; 14 - regulator body; 15 - traction; 16 - screw; 17 - axis; 18 - wire

The fixed contact plate is mounted on the axis of the movable contact lever and can be rotated by an eccentric, changing the gap between the contacts.

The plate is secured to the disk with a locking screw. The disk is secured with screws to the case. If the distributor has a vacuum ignition timing regulator, then the contacts are installed on a movable disk, which is placed on a ball bearing of a stationary disk fixed in the housing. The breaker contacts are tungsten.

The jaw clutch is installed on the axis of the distributor shaft. The rotation of the roller is transmitted to it through the weights of the centrifugal ignition timing regulator. The clutch opens the contacts with its edges; the contacts are closed under the action of the leaf spring of the lever with a movable contact.

Fig.80. Capacitor:

1 - clamp; 2 - wire; 3 - washer; 4 - wire; 5 - washer; 6 - end of the plates; 7 - roll of covers; 8 - conductor; 9 - cable paper; 10 - body; 11 - varnished; 12 - thin layer of zinc or tin

The capacitor (Figure 80) is connected in parallel to the contacts. It reduces arcing between contacts and increases the speed of magnetic flux measurement.

The distributor serves to supply high voltage to the spark plug electrodes in accordance with the operating order of the engine cylinders.

It consists of a cover with a contact carbon and a rotor with a current difference plate. The rotor is mounted on the breaker claw coupling.

Sealed distributors (P102) have forced ventilation of the internal cavity of the housing with discharge of spark discharge products into the carburetor suction pipe, in accordance with Figure 81.

Fig.81. Distributor ventilation diagram:

1.5 - hoses; 2.4 - tubes; 3 - carburetor suction pipe;

6 - distributor housing

In protected distributors (P13), ventilation is carried out through holes in the housing due to the air pressure created by the slider when the roller rotates.

The vacuum ignition timing regulator is used to change the ignition timing depending on the load on the engine.

It consists of a body, a diaphragm, a spring, a fitting and a rod, in accordance with Figure 79. The regulator body is divided by a diaphragm into two cavities, one of which is connected by a tube to the carburetor under-throttle space, and the other to the atmosphere. The diaphragm is connected by a rod to the movable disc of the breaker; on the other hand, a spring rests against it, counteracting the vacuum in the carburetor. Adjusting washers are installed under the spring on the fitting side.

When operating at low loads, the vacuum in the mixing chamber is large, and it is transferred to the diaphragm. The diaphragm bends, compresses the spring and, through a rod, turns the movable disk with contacts against the direction of rotation of the roller, the advance angle increases.

As the load increases, the vacuum in the mixing chamber drops and the spring, through a rod, turns the disk in the direction of rotation of the roller, reducing the ignition timing.

The vacuum regulator provides a change in ignition timing from 0 to 13˚ according to the angle of rotation of the distributor shaft. The centrifugal timing regulator is used to change the ignition timing depending on the crankshaft speed.

It consists of two weights and two springs, in accordance with Figure 82. The weights are installed on the axes of the roller flange, and with their fingers they enter the cutouts of the drive plate of the cam clutch.

The centrifugal governor comes into operation at 400 rpm. In this case, the weights diverge under the action of centrifugal forces, stretching the springs.

The fingers of the weights, moving along the rectangular cutouts of the drive plate, rotate the claw coupling and the distributor rotor in the direction of rotation of the roller. At the same time, the advance angle increases. As the rotation speed of the distributor shaft decreases, the springs are compressed and, through weights, turn the cam clutch in the opposite direction, reducing the ignition timing.

The centrifugal regulator provides a change in the ignition timing in the range from 0 to 20˚.

Fig.82. Centrifugal ignition timing regulator:

1 - cam clutch; 2 - drive plate; 3 - weight; 4 - finger;

5 - spring; 6 - roller; 7 - traverse; 8 - weight axis; 9 - weight

The octane corrector serves to change the initial ignition timing angle depending on the type of fuel used and operating conditions and ensures rotation of the distributor housing.

The octane corrector provides an angle change within ±12°.

Spark plug.

Serve to ignite the working mixture in the engine cylinders.

The spark plug, in accordance with Figure 83, consists of a body with a side electrode, an insulator, a central electrode, a contact device and sealing parts.

The insulator is made of uralite, borocorundum, synoxal or hilumin.

The central electrode in the insulator is sealed with thermal cement or glass sealant based on silicon or copper.

The material of the central electrode is nickel-manganese alloy or chromium-titanium steel. Markings are made on the cylindrical part of the candle.

Fig.83.Spark plugs:

1 - wire tip; 2 - rod; 3 - insulator; 4.12 - body; 5 - central electrode; 6.10 - side electrode; 7.11 - sealing ring; 8 - washer; 9 - conductive sealant; 13 - screen; 14 - suppressive resistor; 15.17 - ceramic bushing; 16 - high voltage wire; 18 - rubber bushing; 19 - nut; 20 - bushing; 21 - wire screen

Let's look at an example of marking spark plugs M8T, A11N, A17DV.

The letters M and A indicate thread M-18x1.5; A-14x1.25; numbers 8,11 and 17 - the value of the heat number. The letters N and D are the length of the threaded part of the spark plug body; H-11mm; D-19mm; the letter B indicates that the lower cone of the insulator protrudes beyond the spark plug body; letter T - the central electrode is sealed with thermal cement.

If there are no letters N and D in the spark plug marking, then such a spark plug has a threaded part length of 12 mm; if there is no letter T, the central electrode in the insulator is sealed with glass sealant; if there is no letter B, the insulator does not protrude beyond the spark plugs.

Ignition and starter switch.

Serves to turn on and off the primary circuit of the ignition system, starter, instrumentation and other circuits.

Consists of a housing, a locking device, in accordance with Figure 84.

It has 4 terminals AM, KZ and ST, PR, connected respectively to an ammeter, ignition coil of the starter relay, and receiver.

Figure 84 shows a diagram of the terminal connections for different positions of the ignition key.

Fig.84. Ignition switch

Action of contact ignition system.

Let us consider the operation of the ignition system according to the diagram in accordance with Figure 85.

When the ignition is turned on and the breaker contacts are closed, a low voltage current will flow in the primary circuit.

Current path: battery positive terminal - ammeter - ignition switch - additional resistor - radio interference filter - ignition coil primary winding - distributor low voltage terminal - closed contacts - housing - battery negative terminal.

Electromagnetic energy accumulates in the ignition coil. When the crankshaft is rotated by the starting handle, the contacts open under the action of the claw clutch.

The circuit of the primary winding is interrupted and a self-induction emf of about 300 volts is induced in it. In the secondary winding, a mutual induction emf of up to 20 thousand volts or more is induced.

Fig.85. Contact ignition system diagram

High voltage circuit: secondary winding - central socket of the distributor cover - contact angle - current difference plate of the runner - side electrode of the cover - central electrode of the spark plug - side electrode of the spark plug - housing - negative terminal of the battery and then along the low voltage circuit section to the secondary winding.

The self-induction emf of the primary winding charges the capacitor. During the open state of the contacts, the capacitor is discharged through the primary winding, accelerating the disappearance of the magnetic flux and increasing the duration of the spark discharge between the spark plug electrodes.

When the engine is started by the starter, the contact disk of the ST130 starter traction relay short-circuits an additional resistor.

During engine operation at medium and high crankshaft speeds, the primary circuit is powered by the generator set.

As the load on the engine changes, the vacuum ignition timing regulator comes into operation, acting on the breaker contacts. With a change in the crankshaft rotation speed, the centrifugal ignition timing regulator comes into operation, acting on the breaker cam clutch. Thus, when the vacuum regulator operates together, the engine ignition timing is determined by the algebraic summation of the values ​​of these angles and the setting ignition timing.

To stop the engine, turn off the ignition. In this case, the primary circuit is interrupted.

Ignition coil. The ignition coil serves to convert low voltage current into high voltage current. It is an electrical autotransformer with an open magnetic circuit. The design of all coils is almost the same, the differences are only in the winding data, methods of connecting the secondary winding, design features of individual components and parts, as well as in the material for filling the internal cavities.

On vehicles with a contact ignition system, oil-filled coils B102-B or B13 are installed. The filling improves the insulation of the windings and ensures heat dissipation. Transformer oil is used as a filler.

Ignition coil B13 (Fig. 12.2) consists of a core 15 made up of individual plates of electrical steel, insulated with each other by scale to reduce eddy currents generated by pulsating magnetic field. An insulating tube is put on the core, on which a secondary winding 13 is wound. A primary winding coil 12 is placed on top of the secondary winding, the ends of which are placed in insulating tubes 6 and connected one to terminal 4, and the other to the “VK” terminal. The secondary winding 13 is connected at one end to the end of the primary winding 12, and at the other to the output terminal 1 through conductor 9 and spring 3, which is pressed against the brass insert 19. The primary winding usually has 250-400 turns, and the secondary - 19-26 thousand. turns. To enhance the magnetic flux penetrating the secondary winding, a ring magnetic core 10 is installed on top of the windings.

All parts of the coil are placed in a stamped steel housing 8 and isolated from it by an insulator 14.

An additional resistor-variator 16 (SE 102), which is a spiral of soft steel wire and placed in a ceramic insulator 17 mounted on a bracket 7, is connected in series with the primary winding of the coil. The ends of the additional resistor are connected by buses 18 to the terminals "VK" and "VK- B". The variator prevents a decrease in voltage in the secondary winding when the engine is running at high crankshaft speeds, and also facilitates starting the engine with a starter.

Shielded ignition coils have a metal casing mounted on the cover

Fig. 12.2. Ignition coil

At a low engine speed, the breaker contacts are closed for a sufficiently long time and the current in the primary circuit increases to its maximum value. At the same time, the variator spiral heats up, which increases the resistance of the circuit. This limits the current in the primary circuit, and, consequently, the heating of the coil.

As the crankshaft rotation speed increases, the time the contacts are closed decreases and the current strength in the primary circuit does not have time to increase to the maximum. At the same time, the heating of the variator spiral decreases, its resistance drops and the current passing through the primary winding does not decrease so significantly. Due to this, the voltage induced in the secondary winding remains high enough and ensures uninterrupted operation of the motor.

When starting the engine with the starter, the voltage at the battery terminals is greatly reduced. At the same time, the starter solenoid relay short-circuits the additional resistor 18 (Fig. 12.1) and thereby compensates for the voltage drop at the ends of the primary winding. As a result, a voltage is induced in the secondary winding of the ignition coil, ensuring reliable engine starting.

The ignition coil is a non-separable unit and cannot be repaired during operation.

Breaker-distributor. This device interrupts the low-voltage current circuit at the required moment and distributes the high-voltage current among the spark plugs in accordance with the operating order of the cylinders, and also adjusts the ignition timing depending on the crankshaft speed and engine load. The breaker-distributor consists of a low-voltage current breaker, a high-voltage distributor, centrifugal and vacuum ignition timing regulators, an octane corrector and a housing. Depending on the number of engine cylinders, distributors are made with four, six or eight sparks, and depending on the direction of working rotation - left and right rotation

Rice. 12.3. Breaker-distributor

a-general device; b-top view without cover and rotor; e-mode operation of the vacuum regulator; g-octane corrector; d-centrifugal regulator

The design and principle of operation of the breaker-distributor is best viewed on a contact-type device (Fig. 12.3).

Two copper-graphite bushings 31 are pressed into the housing 25, serving as a bearing for the drive shaft 29 of the cam clutch 8 of the breaker, the distributor rotor 10 and the centrifugal regulator. The roller 29 receives rotation from the lubrication pump drive shaft.

The breaker is mounted on a movable disk 4, which is mounted on a ball bearing 2, pressed into the hole of a fixed disk 3 attached to the housing 25. Disks 4 and 3 are connected to each other by a flexible copper wire 5 to increase the reliability of the connection of the movable disk to ground.

The movable contact 18 on the textolite block 17 is installed on an axis fixed to the movable disk 4 and is isolated from ground. Under the action of the leaf spring 16, the movable contact of the breaker is pressed against the stationary 19, fixed to the bracket and connected to ground. The contacts are made of tungsten. The bracket together with the fixed contact can be turned by screw 37 (Fig. 12.3.6) of the eccentric, with the help of which the gap between the contacts is adjusted (0.35 - 0.45). The gap is checked with a flat feeler gauge and adjusted at maximum contact separation. After adjustment, the gap is fixed with locking screw 38.

Movable contact 18 (Fig. 12.3, a) through spring 16 and wire 5 is connected to insulated terminal 7 of the housing, to which the low voltage wire from the ignition coil is connected.

To lubricate the edges of the jaw coupling 8 and the upper end of the roller, there are felt wicks 9 and 6, and for lubricating the bushings there is a 31-cap oiler 28.

A capacitor 34 is connected parallel to the contacts. One of its plates is connected to ground, and the other to terminal 7 of the breaker-distributor.

Capacitor(Fig. 12.4) consists of a body 7, in which a roll 4 is placed, consisting of two plates 9 of tin and zinc, applied in a thin layer to sheets of paper 8. The layer of metals is not applied across the entire width of the paper. Solder is sprayed onto the ends of roll 4, to which flexible wires 2 and 5 are soldered. Roll 4 is wrapped in cable paper 6. Conductor 5 is passed through holes in housing 7 and soldered to it. Conductor 2 from another plate is soldered to a brass terminal in textolite washer 1. Washers 1 and 3 ensure the tightness of the housing. The free space in the housing is filled with transformer oil.

Rice. 12.4. Capacitor:

a-device; b-plating of the capacitor; c-symbol

The capacitance of the capacitor should be in the range of 0.17-0.25 microfarads. With a smaller capacitance, sparking at the breaker contacts increases, which leads to their burning; with a larger capacitance, the voltage in the secondary winding of the ignition coil decreases.

High voltage current distributor consists of a rotor Yu (Fig. 12.3, c) and a cover 11, reinforced with spring latches 15 on the body 25. A brass spacer plate is attached to the carbolite rotor 10. The rotor is mounted on the upper part of the cam clutch 8, which has a flat (cut) for the correct relative position of the rotor and the cam protrusions.

The correct position of the cover relative to the body is ensured by a pin on the body that fits into the groove of the cover.

The lid contains central 14 and lateral 12 electrodes made of brass. A spring is inserted into the hole of the central electrode from below, pressing the carbon contact 13 to the rotor spacer plate.

It takes several thousandths of a second to burn the working mixture. Therefore, the mixture is ignited before the piston reaches TDC. with some advance.

The angle by which the crankshaft crank does not reach TDC. when the working mixture is ignited in the combustion chamber, it is called the ignition timing angle, which for different engines ranges from 28° to 45°. Its value depends on the crankshaft speed, load, type of fuel used and other factors.

The ignition timing angle changes automatically depending on the engine operating mode. It is initially installed manually.

Centrifugal regulator! ignition timing lator changes the ignition timing depending on the engine speed.

A plate 27 is pressed onto the corrugated part of the roller 29 (Fig. 12.3, a, d), on which weights 26 of the centrifugal ignition timing regulator are installed on the axles. Cam clutch 8 has a number of faces equal to the number of engine cylinders, and can be rotated relative to the axis of the roller 29 at a certain angle. The coupling is fastened to cross-beam 1 with screw 30.

As the rotation speed of the roller 29 increases, the weights 26 of the regulator diverge under the action of centrifugal forces, overcoming the resistance of the springs 32. The pins of the weights rotate the traverse 1 and the cam clutch 8 in the direction of rotation of the breaker-distributor shaft. The cam protrusions approach the moving contact earlier and open the breaker contacts, which increases the ignition timing. When the engine crankshaft speed decreases, the ignition timing decreases, because due to the decrease in centrifugal forces, the weights converge under the action of spring 32.

Vacuum ignition timing regulator changes the ignition angle depending on the engine load.

The vacuum regulator attached to the body 25 of the breaker consists of a chamber 20, a diaphragm 24 with a rod 21 and a spring 23. The operation of the vacuum regulator is shown in Fig. 12.3, c.

As the engine load decreases, the vacuum behind the closed throttle valve increases and is transmitted through a tube connected to fitting 22 to the vacuum regulator. Under the influence of vacuum, diaphragm 24, overcoming the resistance of spring 23, bends to the right. The rod 21 turns the movable disk 4 against the direction of rotation of the distributor roller 29. The cam protrusions approach the moving contact earlier and open the breaker contacts, which increases the ignition timing. As the engine load increases, the vacuum behind the opening throttle valve and in the vacuum regulator drops, spring 23 bends diaphragm 24 to the left, and rod 21 turns disk 4 in the direction of rotation of roller 29. The breaker contacts open later, which reduces the ignition timing.

When the engine is forced to switch to fuel with a higher or lower octane number, the ignition timing is adjusted using an octane corrector. To operate the engine on fuel with a lower octane number, the ignition timing is reduced, and to operate on fuel with a higher octane number, it is increased.

The octane corrector is located at the bottom of the body 25 (Fig. 12.3, a.d) of the breaker and consists of the lower 35, middle 33 and upper 39 plates. The middle plate 33 has an oval hole for a screw 36 securing it to the bottom plate 35, and a bracket 45 with an adjusting screw 43. The bottom plate 35 has a scale and a bracket 41 for holding the adjusting nuts 42 and 44 in bracket 45. The top plate 39 is attached to the body 25 of the breaker, and with a screw 40 to the middle plate 33.

The ignition timing is changed by rotating the distributor-chopper housing using octane-corrector nuts 42 and 44 and checked using a scale and arrow.

The actual ignition timing angle is the sum of the initial setting angle and the angles set by the octane corrector, centrifugal and vacuum regulators.

Changing the gap in the breaker contacts leads to a decrease or increase in the ignition timing. Therefore, before setting the ignition timing on the engine, it is necessary to first check and, if necessary, adjust the gap between the contacts.

The breaker-distributor described above has one significant drawback, as does the entire contact ignition system, namely the inevitable burning of the breaker contacts. As a result, the starting properties of the engine deteriorate, the voltage of the secondary winding decreases, and, consequently, the spark energy.

The contactless ignition system, which will be discussed below, does not have these shortcomings.

Sweeping candle(Fig. 12.5, a) creates a spark discharge that ignites the working mixture compressed in the engine cylinders. It consists (Fig. 12.5,6) of a steel body 4 with a thread and a side electrode 6. An insulator 3 with a central electrode 5, a contact device and sealing parts are rolled into the body. Insulators have high mechanical strength and insulation resistance at high temperatures. The spark plug electrodes and the knurled central rod are made of nickel-manganese or chromium-nickel steel. The knurling ensures a strong connection with the conductive glass sealant. The gap between spark plug electrodes 5 and 6 is 0.6 - 0.8 mm. During engine operation, the gap increases by an average of 0.015 mm per 1 thousand km of vehicle mileage. A sealing metal washer 8 is installed between the housing and the insulator 3, which ensures the tightness of the connection. The sealed fastening of the spark plug in the block head is ensured by a metal-asbestos sealing ring 9 made of soft metal.

Rice. 12.5.Spark plug

a - general view; b - candle in section; c - shielded candle; 1 - contact nut; 2 - rod; 3 - insulator; 4 and 19 - buildings; 5 - central electrode; 6 and 21 - side electrodes; 7 - sealant; 8 - washer; 9 - sealing ring; 10 - wire shielding; 11 - bushing; 12 - union nut; 13 - rubber bushing; 14 - high voltage wire; 15 - contact device; 16 - ceramic bushing; 17- suppressive resistor; 18 - screen; 20 - ring

Spark plugs operate under very difficult conditions, being exposed to high voltage (up to 25 kV), high gas pressure (up to 4 MPa) and temperature changes from 40 to 2500 ° C.

To ensure uninterrupted operation of the spark plug, the lower part of the thermal cone of the insulator must have a temperature in the range of 500-600 ° C. At this temperature, carbon deposits deposited on the thermal cone of the insulator burns out, i.e. The spark plug self-cleans. With less heat, the electrodes of the spark plug will become covered with soot. In this case, the candle will work intermittently.

If the temperature of the insulator and the central electrode is too high (more than 800°C), glow ignition occurs when the working mixture ignites from contact with the heated cone of the insulator and the central electrode until a spark appears between the electrodes of the spark plug. As a result, the working mixture ignites too early.

A characteristic of the thermal properties of a candle is the glow number, which is determined in a special installation for the occurrence of glow ignition.

Non-separable design spark plugs produced by the domestic industry are designed for specific types of cars and are marked accordingly. The symbol of the candle contains the designation of the thread on the body (A-metric thread 14x1.25 or M-metric thread 18x1.5), heat number 8, 11, 14, 17, 20, 23 or 26, designation of the length of the threaded part of the body (H- 11mm, D-19mm), designation of the protrusion of the thermal cone of the insulator beyond the end of the body B, designation of sealing at the connection of the insulator - the central electrode with thermal cement -T.

The length of the threaded part of the body (12 mm), the absence of protrusion of the thermal cone of the insulator beyond the end of the body and the sealing of the insulator-central electrode connection with a sealant other than thermal cement are not indicated.

The shielded spark plug kit (Fig. 12.5c) includes a rubber sealing sleeve 13 that seals the wire entry into the spark plug, a ceramic insulating sleeve 16 of the screen, a copper sealing ring 20 and a ceramic liner with a built-in suppression resistor 17. This resistor is designed to reduce the level of radio interference by the system ignition and reducing burnout of spark plug electrodes.

Contact of the wire with the electrode is carried out using contact devices of the KU-20A type. The connection is made as follows. The rubber sealing sleeve 13 of the spark plug is put on the end of the high voltage wire 14 coming out of the shielded hose 10, and then the wire is inserted into the contact device. The wire core, exposed to a length of 8 mm, is inserted into the hole of the sleeve, flared in the bottom of the ceramic cup of the contact device 15, and fluffs out so that the contact device is clamped on the wire. Spark plugs of this type (SN-307) are installed on ZIL-131 vehicles.

Ignition switch. This device is designed to turn on and off ignition devices and connect control and measuring instruments, windshield wiper and heater motors, a radio receiver and a starter switch relay (at the moment of starting) to a power source. The switch and lock itself are placed in the switch body, cast from a zinc alloy. On the plastic cover of the switch there are terminals “AM” (ammeter), “KZ” (ignition coil), “ST” (starter) and “PR” (receiver). Using the key, the lock contact group can occupy four positions: 0 - all off; When the key is turned clockwise to a fixed position 1, the ignition and receiver are turned on, as well as instrumentation. To start the engine, you must turn the key clockwise to the “P” position - the starter switch relay and ignition devices are connected to the current source. When turning on the receiver while parked, you must turn the ignition key counterclockwise to the fixed position.

Sparking between the spark plug electrodes, the rotor and distributor cap electrodes, breaker contacts, as well as in other electrical equipment causes high-frequency electromagnetic oscillations that interfere with radio and television reception. The most severe interference is caused by the ignition system. To eliminate interference use:

Inclusion of suppressive resistances in high voltage wires;

Shielding of the electrical equipment system;

Blocking sparking contacts with high-capacity capacitors;

The use of special radio interference filter devices.

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Introduction

In the first engines (for example, the Daimler engine, as well as the so-called semi-diesel), the mixture of fuel and air was ignited at the end of the compression stroke from a red-hot glow head - a chamber communicating with the combustion chamber (synonym - glow tube). Before starting, the glow head had to be heated with a blowtorch, then its temperature was maintained by the combustion of fuel while the engine was running. Currently, glow engines used in various models (aircraft, car, ship models) operate on this principle. Glow ignition in this case benefits from its simplicity and unsurpassed compactness.

Diesel engines also do not have an ignition system; the fuel ignites at the end of the compression stroke from the highly heated air in the cylinders.

Compression carburetor engines do not require an ignition system; the air-fuel mixture is ignited by compression. These engines are also used in modeling.

But the spark ignition system has really taken root on gasoline engines, that is, a system whose distinctive feature is the ignition of the mixture by an electric discharge breaking through the air gap between the electrodes of the spark plug.

There are currently three ignition systems: magneto ignition, battery ignition using a car battery, and batteryless ignition using a motorcycle alternator.

We can distinguish: circuits without the use of radio-electronic components (“classical”) and electronic.

My thesis examines the classic contact ignition system.

The contact ignition system is the oldest type of ignition system. Currently, this system is used on some models of domestic cars (the so-called “classics”). The creation of high voltage and its distribution among the cylinders in this system occurs using contacts.

1. Contact ignition system design

1.1 Purpose of the contact ignition system

The ignition system is a set of all instruments and devices that provide the appearance of an electric spark that ignites the air-fuel mixture in the cylinders of an internal combustion engine at the right moment. This system is part of the overall electrical system. The ignition system serves to ignite the working mixture in the engine cylinders at strictly defined moments. Ignition of the mixture can be carried out by a battery ignition system or from a magneto. The vehicles studied use a battery ignition system. Based on the method of interrupting the primary circuit current, battery ignition systems are divided into contact, contact-transistor and contactless transistor. Until 1960, cars were mainly equipped with a contact ignition system. Currently, transistor ignition systems are increasingly used, especially on eight-cylinder engines.

1.2 Operating principle of the contact ignition system

Ignition system

The ignition system is used only in gasoline and gas engines. With its help, the air-fuel mixture entering the engine cylinders is ignited at a strictly defined point in time. Ignition of the mixture inside the cylinder occurs when a spark forms between the electrodes of the spark plug when a current of 18,000-20,000 V is supplied to it.

There are three types of ignition systems:

· contact,

· contactless and

· microprocessor.

The contact system is not used on modern cars. However, it was previously widespread. Let's give it its due, since it served faithfully for many years, and consider its fundamental structure. The operating principle is based on the law of electromagnetic induction. From the battery, when the ignition is on and the breaker contacts are closed, a low voltage current passes through the primary winding of the ignition coil, forming a magnetic field around it. Opening the contacts of the breaker leads to the disappearance of the current in the primary winding and the magnetic field around it. The disappearing magnetic field induces a high voltage (about 20-25 kilovolts) in the secondary winding. The distributor alternately supplies high voltage current to high-voltage wires and spark plugs, between the electrodes of which a spark charge jumps, and the air-fuel mixture in the engine cylinders ignites.

The disappearing magnetic field crosses not only the turns of the secondary, but also the primary winding, as a result of which a self-induction current of about 250-300 volts appears in it. This leads to sparking and burnt contacts, in addition, the interruption of current in the primary winding slows down, which leads to a decrease in voltage in the secondary winding. Therefore, a capacitor (usually with a capacity of 0.25 μF) is connected in parallel with the contacts of the breaker.

An additional resistance (or an additional resistor) is connected in series with the primary winding of the ignition coil. At low speeds, the breaker contacts are in the closed state most of the time and a current flows through the winding, more than sufficient to saturate the magnet wire. Excess current heats up the coil unnecessarily. When the engine starts, the additional resistance is shunted by the contacts of the starter relay, thereby increasing the energy of the electric spark at the spark plug. Operating principle of the contact ignition system

When the breaker contact is closed, low voltage current flows through the primary winding of the ignition coil. When the contacts open, a high voltage current is induced in the secondary winding of the ignition coil. Via high-voltage wires, high-voltage current is supplied to the distributor cap, from which it is distributed to the corresponding spark plugs with a certain ignition timing.

As the engine crankshaft speed increases, the distributor chopper shaft speed increases. The weights of the centrifugal ignition timing regulator diverge under the influence of centrifugal force, moving the movable plate with the breaker cams. The breaker contacts open earlier, thereby increasing the ignition timing. When the engine crankshaft speed decreases, the ignition timing decreases.

A further development of the contact ignition system is the contact-transistor ignition system. In the circuit of the primary winding of the ignition coil, a transistor switch is used, controlled by the breaker contacts. In this system, due to the use of a transistor switch, the current in the primary winding circuit is reduced, thereby increasing the service life of the breaker contacts.

Scheme 1.2.1

1. The ignition key is turned, which allows low voltage battery current to flow to the primary winding of the ignition coil.

2. When current appears on the primary winding, a magnetic field appears.

3. The breaker contacts open due to cranking of the engine, which is initially driven by the starter.

4. The low voltage current and the magnetic field, which induces a high voltage current on the secondary winding, disappears.

5. The generated high voltage current flows to the central terminal of the ignition coil, and from there to the distributor cap.

6. The distributor distributes current to each spark plug.

7. The current that appears on the spark plug forms a spark discharge between the electrodes, which ignites the fuel-air mixture.

The self-induction current appears not only on the secondary, but also on the primary winding, which leads to burnt contacts and sparking. Another influence is interruption of the current in the primary winding, which reduces the voltage in the secondary. To reduce the effect, a capacitor connected in parallel to the breaker contacts is used

Scheme 1.2.2 of the classic contact ignition system:

1 -- battery; 2, 3 -- ignition switch contacts; 4 -- additional resistor; 5 -- ignition coil; 6 -- breaker; 7, 8 -- movable and fixed contacts of the breaker; 9 -- cam; 10 -- distributor; 11 -- rotor (runner); 12 -- fixed electrode; 13 -- spark plugs; 14 -- capacitor.

1.3 Contact ignition system devices

ignition system engine

The design features of contact ignition system devices are as follows.

The contact ignition system consists of the following elements: power supply, ignition switch, low voltage mechanical circuit breaker, ignition coil, high voltage mechanical distributor, centrifugal ignition timing regulator, vacuum ignition timing regulator, spark plugs and high voltage wires.

The mechanical breaker is designed to open the low voltage circuit (the primary winding circuit of the ignition coil). When the contacts open, a high voltage is induced in the secondary circuit of the ignition coil. To protect the contacts from burning, a capacitor is connected in parallel to the contacts.

The ignition coil serves to convert low voltage current into high voltage current. The coil has two windings - low and high voltage.

The mechanical distributor ensures the distribution of high voltage current across the engine cylinder spark plugs. The distributor consists of a rotor (commonly called a “runner”) and a cover. The cover has central and side contacts. The central contact is supplied with high voltage from the ignition coil. Via the side contacts, high voltage is transmitted to the corresponding spark plugs.

The chopper and distributor are structurally combined in one housing and are driven by the engine crankshaft. This device has the general name of a breaker-distributor (the common name is “distributor”).

The centrifugal ignition timing regulator is used to change the ignition timing depending on the engine crankshaft speed. Structurally, the centrifugal regulator consists of two weights. The weights act on the movable plate on which the breaker cams are located.

The ignition timing is the angle of rotation of the engine crankshaft at which high voltage current is supplied to the spark plugs. In order for the fuel-air mixture to burn completely and efficiently, ignition is carried out in advance, i.e. until the piston reaches top dead center.

The ignition timing is set by adjusting the position of the distributor-distributor in the engine.

The vacuum ignition timing regulator provides a change in the ignition timing depending on the engine load. The load on the engine is determined by the degree of throttle opening (gas pedal position). The vacuum regulator is connected to the cavity behind the throttle valve and, depending on the degree of vacuum in the cavity, changes the ignition timing.

The high voltage wires carry high voltage current from the ignition coil to the distributor and from the distributor to the spark plugs.

The spark plug is designed to ignite the fuel-air mixture by generating a spark discharge.

1.3.1 Contact ignition system devices

1.3.2 Diagram of ignition elements on a Moskvich (AZLK) 2140 car

Description of ignition system elements

1 Drive coupling.

2 Cam plate.

3 Oiler spring.

4 Oil can.

5 Capacitor.

6 Distributor housing.

7 Low voltage terminal.

8 Cam.

9 Distributor cap.

10 Runner.

11 Slider contact plate

12 Contact carbon spring.

13 Contact angle.

14 Cam oil seal.

15 Spring for securing the distributor cap.

16 Centrifugal regulator spring.

17 Centrifugal regulator weight.

18 Bearing.

19 Distributor roller with plate.

20 Filz cam.

21 Fixed breaker plate.

22 Vacuum regulator rod.

23 Vacuum regulator.

24 Movable breaker plate.

25 Fixed contact.

26 Screw securing the contact post.

27 Contact stand.

28 Breaker lever.

29 High voltage wire.

30 Rubber cap.

31 Linen core.

32 Insulation.

33 Conductive conductor.

34 Wire lug.

35 Vacuum regulator diaphragm.

36 Vacuum regulator spring.

37 Spark plug body.

38 Contact terminal.

39 Spring bracket.

40 Side electrode.

41 Central electrode.

42 Heat sink washer.

43 Gasket.

44 Spark plug body.

45 Insulator.

46 Glass sealant.

47 Contact rod.

1.4 Technical characteristics of the ignition system Moskvich 2140

Rated supply voltage - 12±0.2V

Allowable voltage changes - from -7.8 to +18.2 V

Voltage amplitude developed in the primary short-circuit circuit - ± 500 V

Average current consumption, no more than - 2.5 A

Current consumption at 600 ±60 rpm of the distributor shaft - 0.4 A

Current consumption at 4000 ±400 rpm of the distributor shaft - 4.5 A

Current consumption through breaker contacts, no more than - 0.3 A

2. T.O. and repair of contact ignition system

2.1 Organization of a car repair mechanic’s workplace

The main workplace of a car mechanic outside of the posts and lines of maintenance and repair is a post equipped with a mechanic's workbench, on which components and devices removed from the car are disassembled and assembled and fitting and other work is performed.

The workbench cover is covered with thin sheet (roofing) steel, which protects it from damage and makes it easier to keep clean.

When starting work, a car mechanic must prepare all the tools and devices necessary to complete it and correctly position them on the workbench.

An important role is played by maintaining tools and devices in good condition and following the rules for using them. For ease of work, the vice must be mounted on the workbench at a certain height, depending on the height of the worker. The vice is installed correctly if the hand of the worker, resting his elbow on the jaws of the vice, touches the chin with the ends of his fingers.

Hammers must be firmly mounted on handles made of hardwood.

The end of the working part of chisels and crossbars must be sharpened well at a certain angle. From the upper end of the chisel, the crosspiece, as well as the bit and drift, the formed burrs should be removed, which, flying off when the hammer hits, can cause injury.

Wooden file handles must be reinforced with metal rings that protect the handles from splitting and allow them to be placed more tightly on the file shanks.

When preparing a hacksaw for work, you should correctly (the hacksaw teeth should be directed forward) install the blade into the hacksaw machine and tighten the thumb well so that the blade does not bend when cutting.

When performing work directly at the car, the car mechanic's workplace is a maintenance or repair station.

Both when performing work on a workbench and directly at the car, its organization is important.

Before starting work, a car mechanic must receive an order to perform it. The work order indicates what work needs to be done, the time limit and the price. The spare parts or materials required to complete the work are issued from the warehouse.

If the car mechanic himself needs to make a new part, he is given a drawing or a sample of the part. Having received a task (order) for work, a car mechanic must first of all prepare the tools, devices and materials necessary to complete the task, and correctly arrange them on the workbench or near the car.

Each tool must be placed in a specific place so that any item can be taken immediately, without making unnecessary movements and without spending extra time searching for it. It is advisable to train yourself to pick up an instrument without looking.

Tools that are taken with the left hand are placed on the left, and those that are taken with the right hand are placed-- on right. Everything that is used more often is placed closer to you. Items not related to the work being performed are removed from the workbench.

Job responsibilities

An auto electrician must:

1.Come to work 10 minutes before the start of the working day, change into clean overalls, and prepare the workplace for work.

2. Carry out electrical equipment repairs and vehicle diagnostics, according to the instructions received from the shift foreman:

Carry out diagnostics of electrical equipment using an existing computer to diagnose the generator and engine;

If necessary, disassemble and reassemble electrical equipment to repair the starter;

Place the car on a lift to identify and eliminate chassis faults;

If necessary, disassemble and repair vehicle components to perform gearbox repairs;

Diagnose mechanical engine faults, disassemble and repair the engine;

Hand over the finished car to a replacement technician.

3. Carry out a full list of ordered work on the car.

4. In all cases of relationships with clients, act technologically, observing the established standards for the relationship between auto center employees and clients.

5. Prevent the emergence of conflict issues with clients of the auto center, trying in all cases to satisfy the requirements of clients and maintain their friendly attitude towards the auto center.

6.Ensure proper safety of vehicles accepted for service.

7. Monitor the working condition of tools and equipment; use them correctly.

8. If faults are detected that affect the safe operation of the vehicle, bring this information to the acceptance technician and the client.

9. Observe safety precautions, fire safety rules, industrial sanitation standards.

10. Treat the issued protective clothing with care.

11.Ensure quality of work and rhythm.

2.2 Tools and devices used in the maintenance and repair of the contact ignition system

To work with automotive wiring, you need high-quality auto electrician tools and instruments for testing and diagnosing electrical equipment and batteries.

A measuring probe is a tool for measuring very small distances using the contact method, which is a set of thin metal plates of various thicknesses with a size printed on them (plate thickness). The plates of the set are inserted into the gap until the next thickest plate no longer fits into the gap being measured.

Flat measuring probes

Flat measuring probes are used to control gaps between planes.

The probe looks like a plate of a certain thickness.

Measuring probes are manufactured with a thickness of 0.02 to 1 mm.

Measuring probes are produced in the form of sets of measuring plates of different thicknesses in one holder.

Probes can be used separately or in various combinations.

Technical characteristics of flat measuring probes:

Fig 2.2.2 Electrical probe for checking electrical circuits on a car, for 6-12 and 24 V.

With test tip, protective cap, alligator clip cable.

Length 120 mm

Fig 2.2.3 Pliers

Fig 2.2.4 Combination wrenches

Fig 2.2.5 Screwdriver set

How effectively and safely a screwdriver works every day depends primarily on the quality of the tool. Not only the use of high-quality materials, but also the shape of the tool itself is of particular importance to ensure that the hand always has a strong grip on the tool.

Fig 2.2.6 Auto electrician set 226 items

1 - Pliers for stripping wires and crimping terminals 5 functions. 225mm (TCP-10353)

1 - Phillips screwdriver VDE PH1 x 80 mm

1 - Slotted screwdriver VDE SL0.8 x 4.0 x 80 mm

1 - Probe 6-12-24V

1 - Fuse puller

1 - Brush for battery terminals

Fuse set - 5A, 7.5A, 10A, 15A, 20A, 25A, 30A

Fuse set 6.35*32 mm (glass) - 5A, 10A, 15A

Euro fuse set - 8A, 10A, 16A

1 - Electrical tape 19 mm x 9 m

1 - Wire 1.25 mm² x 1.5 m

Set of terminals (fork, ring, bayonet)

Set of heat-shrinkable connecting sleeves

Set of heat shrink sleeves - W10 x 50mm, W5 x 50mm, W3 x 50mm

Set of plastic clamps - 2.5 x 100 mm, 2.5 x 160 mm, 3.6 x 200 mm

9 - Car lamps

1 - Wire with alligator clips

Quantity per box: 12 pcs; Net weight: 1.11 kg; Gross weight: 1.9 kg; Volume: 0.005 m

Fig 2.2.7 Multitestor

2.3 List of work performed in the scope of daily maintenance (ETO), TO-1, TO-2 for the contact ignition system

Maintenance of ignition system elements (distributor breaker, coil, switch and spark plugs) is carried out during each regular vehicle maintenance-2 with in-depth diagnostics of the technical condition.

In progress daily maintenance and maintenance-1 check the serviceability of the ignition switch, the reliability of electrical contacts, the condition of high-voltage wires and their insulation, and the fastening of all ignition devices. It is necessary to systematically lubricate the drive roller bearings, parts of the centrifugal ignition timing regulator, the axis of the moving contact and cam clutch, and the felt cam wick.

In the contact ignition system, burning and electrical erosion of the breaker contacts occurs, which increases the resistance in the primary circle of the induction coil and reduces the angle of the closed state of the contacts. To eliminate these shortcomings, you should promptly clean them from carbon deposits and dirt and adjust the gap between them.

During operation, it is necessary to keep high-voltage parts of the ignition system clean and prevent moisture, dust and dirt from getting on them, which can lead to partial shunting and loss of current, breakdown of high-voltage parts or surface overlap.

Spark plugs are unscrewed during TO-2 with a special key, after cleaning the socket with compressed air, and check for cracks and carbon deposits on the insulator. The gap between the electrodes is checked with a round feeler gauge and adjusted by bending the side electrode.

It is prohibited to burn out spark plugs, as this will cause microcracks to appear on the insulator, which will lead to deterioration in performance and failure of spark spark plugs.

During maintenance, you should check whether the wires that connect to the terminals of the ignition coil, additional resistance and transistor switch are mixed up, which can lead to damage to the latter

2.4 Possible malfunctions of the ignition system

2.5 Setting the ignition timing

Fig. 2.5.1 Distributor (with removed runner and cover) of engine mod. 331 and 3317

Fig. 2.5.2 Installation duplicate marks on the flywheel and clutch housing of the engine mod. 331 and 3317

Installation of ignition on engines mod. 331 and 3317 are produced when the new car has a mileage of 1.5 thousand km. and subsequently every 15 thousand km.

For engines mod. 331 and 3317 ignition distributors 47.3706 are installed.

Checking the condition of the working surface of the breaker contacts, cleaning them, and lubricating the distributor are carried out similarly to the ignition distributor of an engine mod. 2106 every 15 thousand km of vehicle mileage. Additionally, it is necessary to lubricate the cam bushing by first removing the rotor and the felt washer under it.

Adjusting the gap between the breaker contacts

1. Rotate the distributor shaft so that the gap between the contacts becomes maximum.

2. Loosen screws 3 (Fig. Distributor (with removed slider and cover) of engine mod. 331 and 3317) securing contact post 8.

3. Insert a screwdriver into groove 9 and, moving closer (or removing) contact post 8 to (from) contact(s) on breaker lever 1, set the gap between the contacts to 0.45 ± 0.05 mm.

4. After completing the adjustment, tighten screws 3.

Setting the ignition timing with the following options:

A) The distributor was not removed from the engine

1. Remove the distributor cap.

2. Rotating the crankshaft, bring the current carrying plate of the runner to the low-voltage terminal of the distributor (to the high-voltage terminal to the spark plug of the first cylinder on the distributor cover).

3. Continuing to slowly rotate the crankshaft, align mark 3 on the crankshaft pulley with the alignment pin 1 on the lower cover of the timing sprockets (duplicate mark 3 (Fig. Installation duplicate marks on the flywheel and clutch housing of the engine mod. 331 and 3317) on the flywheel should coincide with mounting lug 2 on the clutch housing). In this case, the piston of the first cylinder will be in the compression stroke, and the ignition timing will be 10° (before TDC).

4. Connect a test lamp to the low voltage terminal of the distributor 5 (see Fig. Distributor (with the slider and cover removed) (you can use any car lamp) and to ground and turn on the ignition. Turn the distributor body counterclockwise until the breaker contacts close (the lamp will go out).

5. Press the slider clockwise with your finger and slowly turn the distributor body in the same direction until the warning light comes on.

6. Check the accuracy of setting the breaker contacts to open by pressing the cam clockwise and at the same time lightly pressing the lever against it with your finger. In this case, the control lamp will either go out or the glow of its filament will decrease.

7. Tighten nut 6 securing the distributor shank to the drive housing.

8. Place the plastic cover on the distributor and secure it with two spring latches.

9. Insert the high-voltage wires coming from the spark plugs in accordance with the order of operation of the engine cylinders and taking into account the direction of rotation of the distributor rotor. Install the tip of the high-voltage wire from the spark plug of the first cylinder in the terminal socket of the distributor cover, located above the low-voltage terminal in the housing.

10. Insert the high-voltage wire coming from the ignition coil into the central socket of the cover until it stops.

B) The distributor was removed from the engine, the crankshaft was turned

1. Unscrew the spark plug of the first cylinder, close the spark plug hole in the cylinder head with a plug made of crumpled paper and rotate the crankshaft until this plug is pushed out, thus determining the beginning of the compression stroke in the first cylinder.

2. Remove the distributor cap.

3. Rotating the distributor shaft, bring the current-carrying plate of the runner to the low-voltage terminal.

4. Insert the distributor shank into the distributor drive housing on the engine.

5. Rotate the distributor shaft by the slider until the floating clutch pins align with the shaft groove in the distributor drive housing and engage them. It should be taken into account that the spikes of the floating clutch of the distributor roller and the counter groove in the drive are shifted to the side relative to the axis of symmetry. Therefore, it will not be possible to install the distributor without first turning the slider with the current carrying plate towards the low-voltage terminal. Next, the ignition installation is carried out in accordance with paragraphs 3-10.

Direction of rotation of the rotor of the ignition distributor 47.3706 engines mod. 331 and 3317 counterclockwise.

The operating order of engine cylinders is 1-3-4-2.

To install an earlier ignition, the ignition distributor housing must be turned clockwise, and a later one - counterclockwise

Conclusion

The purpose of this thesis is to study the technology of repairing the ignition system.

The thesis consists of an explanatory note and a stand with installed devices of the contact ignition system.

In the explanatory note of the diploma project, the main part discusses:

General description of the ignition system design;

Designs of repair and diagnostic devices are proposed.

The special part of the thesis examines:

A stand with devices connected to low and high voltage electrical circuits;

The main devices intended for repairing the ignition system are considered.

The topic of this thesis is very relevant and has broad practical and theoretical significance.

The diploma uses modern methods of studying, analyzing and systematizing the material.

Consequently, the goals set for the thesis have been achieved.

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Operating principle of a contact (classical) ignition system

Contact (classical) ignition system

The classic battery ignition system with a single coil and a multi-spark mechanical distributor was used in the domestic automotive industry until the end of the 20th century. The main advantage of this system is its simplicity, provided by the dual function of the distributor mechanism: interrupting the DC circuit to generate high voltage and synchronously distributing high voltage to the engine cylinders.

The schematic diagram of the classic ignition system consists of the following elements (Fig. 6.4):

· source of electricity – battery (generator) 7;

· ignition coil (induction coil) 5, which converts low voltage into high voltage (there is a transformer connection between the primary and secondary windings);

· breaker 17 containing lever 6 with pad 7 of
PCB rotating around the axis, breaker contacts 8, cam 16, having a number of faces equal to the number of cylinders. The fixed contact of the breaker is connected to ground; the movable contact is fixed at the end of the lever. If the pad does not touch the cam, the contacts are closed under the action of the spring. When the pad touches the edge of the cam, the contacts open. The breaker controls the opening and closing of contacts and the timing of the spark;

· primary circuit capacitor 18, connected in parallel to contacts 8, which is an integral element of the oscillatory circuit in the primary circuit after the contacts are opened;

· distributor 14, including slider 12, cover
10, on which fixed side electrodes 11 are located
(the number of which is equal to the number of engine cylinders) and stationary
the central electrode, which is connected via a high-voltage wire to the ignition coil. The side electrodes are connected through high-voltage wires to the corresponding spark plugs. High voltage is supplied to slider 12 through the central electrode using a sliding carbon contact. The slider has an electrode 13, which is separated by an air gap from the side electrodes 11. The distributor slider 12 and the breaker cam 16 are located on the same shaft, which is driven by a gear transmission from the engine camshaft at a frequency half the crankshaft speed. The chopper and distributor are located in one apparatus called the ignition distributor;

15 spark plugs, the number of which is equal to the number of cylinders
engine;

· ignition switch 2;

additional resistor 3 (R ext), which reduces thermal
losses in the ignition coil (when starting the engine, R ext is shunted by switch 4 simultaneously with the starter turning on.) The additional resistor is made of nichrome or constantan wire, which is wound on a ceramic insulator.

Rice. 6.4. Schematic diagram of a classic ignition system

The operating principle of the classic battery ignition system is as follows. When cam 16 rotates, contacts 8 alternately close and open. After the contacts are closed (in the case of a closed switch 2), a current flows through the primary winding of the ignition coil 5 (Fig. 6.4), increasing from zero to a certain value during the time the contacts are in the closed state. At low rotation speeds of the shaft 9 of the distributor 14, the current can increase to a value determined by the voltage of the battery (generator) and the resistance of the primary circuit (steady-state current). The flow of primary current causes the formation of a magnetic flux and the accumulation of electromagnetic energy in the windings of the ignition coil.

After the breaker contacts open, a self-induction emf is induced in the primary winding of the coil, which prevents the current from decreasing. This self-induction EMF induces an EMF (secondary voltage) in the secondary winding of the ignition coil. According to the law of induction, the greater the secondary voltage, the greater the rate of change of the magnetic flux created by the current of the primary winding, the greater the primary current at the moment of rupture, and the greater the number of turns in the secondary winding compared to the primary winding (the coil is a voltage transformer).

As a result of the transient process, a high voltage will arise in the secondary winding, reaching 15...20 kV. The self-induction EMF in the primary winding of the ignition coil reaches 200...400 V. In the absence of capacitor 18, the self-induction EMF causes the formation of a strong spark of an arc nature between the breaker contacts when they open. In the presence of capacitor 18, sparking is reduced, since the self-induction emf creates a current that charges the capacitor. In the next period of time, the capacitor is discharged through the primary winding of the coil and the battery. Thus, capacitor 18 practically eliminates arcing in the breaker, ensuring longevity of contacts and inducing high EMF in the secondary winding.

The secondary voltage is supplied to the distributor runner, and then through the electrodes in the cover and high-voltage wires to the spark plugs of the corresponding cylinders.

Rice. 6.5. Timing diagrams of primary circuit current and secondary voltage

Thus, the workflow of any battery ignition system that uses an induction coil to produce high voltage can be divided into three stages:

Stage 1. Closing the breaker contacts. At this stage it happens
connecting the primary winding of the ignition coil (accumulator) to
source of electricity. The stage is characterized by an increase in the primary current and, as a consequence, the accumulation of electromagnetic energy in the magnetic field of the coil.

Stage 2. Opening the breaker contacts. The electrical source is disconnected from the ignition coil. The primary current decreases rapidly, causing the stored electromagnetic energy to be converted into high voltage energy (EMF) in the secondary winding.

Stage 3. Breakdown of the spark gap of the spark plug. Under working conditions
At a certain voltage value, spark breakdown occurs
spark plug interval followed by the discharge process.

At the first stage, the secondary circuit has virtually no effect on the process of increasing the primary current. Currents and voltages in the secondary circuit are insignificant at a relatively low rate of increase in the primary current. The secondary circuit can be considered open. Primary capacitor C1 is short-circuited by contacts TO. The equivalent circuit for this operating stage is shown in Fig. 6.6.

The process of primary current growth according to Kirchhoff’s second law is described by the differential equation

where is the voltage of the primary power source (battery or generator); – inductance of the primary winding; – current in the primary circuit; – resistance of the primary circuit.

Rice. 6.6. Replacement diagram of the classic ignition system after closing the contacts of the breakers ( TO– breaker contacts, M– mutual induction)

The solution to this equation is the expression

Or , (6.2)

where is the time constant of the primary circuit ().

At the second stage, the contacts open. The breaking current depends on the time the contacts are in the closed state:

where – depends on the engine crankshaft speed, number of cylinders, cam profile (i.e. the ratio between the angle of the closed and open state of the contacts); – time constant of the primary circuit.

The contact opening frequency for a four-stroke engine is determined by the formula

. (6.4) Time of the complete period of operation of the breaker

where is the time of the open state of the contacts.

Stored electromagnetic energy in the primary winding of the ignition coil

The equivalent circuit for this operating stage is shown in Fig. 6.7.

Rice. 6.7. Simplified equivalent circuit of the classic ignition system after opening the breaker contacts

According to this scheme, we have two magnetically coupled circuits, each of which contains a capacitance ( C 1– primary circuit capacitor; C 2– distributed capacitance of the secondary circuit), inductance ( L 1, L 2– inductance of the primary and secondary windings of the ignition coil, respectively), equivalent active resistance ( R 1, R 2– total active resistance of the primary and secondary circuits, respectively). Shunt resistance is included in the secondary circuit R w and loss resistance R n, taking into account, respectively, current leakage on the spark plug and magnetic losses.

At the moment the breaker contacts open, the electromagnetic energy stored in the coil is converted into the energy of the electric field of the capacitors C 1 And C 2 and heat is partially converted. The value of the maximum secondary voltage can be obtained from the electrical balance equation in the circuits of the primary and secondary circuits, neglecting losses in them:

where , are the maximum values ​​of the primary and secondary voltages, respectively.

Because ,

However, this expression does not take into account energy losses in the resistance of the soot shunting the spark gap of the spark plug, magnetic losses in the steel, electrical losses in the spark gap of the distributor and in the arc at the breaker contacts. These losses lead to a decrease in the secondary voltage. In practice, to take into account losses in circuits, the attenuation coefficient is introduced as a multiplier, expressing a decrease in the maximum voltage due to energy losses:

where – the attenuation coefficient is 0.75…0.85 for contact ignition systems.

To ignite the working mixture electrically, it is necessary to create an electrical discharge between the electrodes of the spark plug, which are located in the combustion chamber. The flow of an electric discharge in a gas gap can be represented by a current-voltage characteristic (Fig. 6.8).

Plot Oab corresponds to a non-independent category. The voltage increases, the current remains practically unchanged and is negligibly small in strength. With a further increase in voltage, the speed of movement of ions towards the electrodes increases. At initial voltage U n, impact ionization begins, i.e. such a discharge that, once generated, does not require exposure to an external ionizer to maintain it. If the field is uniform, then the ionization process immediately develops into a breakdown of the gas gap. If the field is uneven, then first a local breakdown of the gas occurs near the electrodes in places with the highest electric field strength, which has reached a critical value. This type of discharge is called corona and corresponds to the stable part of the current-voltage characteristic bс. With a further increase in voltage, the corona captures new areas of the interelectrode space until breakdown occurs (point With) when a spark jumps between the electrodes. This occurs when the voltage reaches the breakdown voltage value U etc.

A leaking spark creates a highly heated and ionized channel between the electrodes. The temperature in the discharge channel with a radius of 0.2...0.6 mm exceeds 10,000 K.

The channel resistance depends on the strength of the current flowing through it. The further course of the process depends on the parameters of the gas gap in the energy source circuit. Possible or glow discharge (section de), when the currents are small, or an arc discharge (section tp), when the currents are high due to the high power of the current source and low circuit resistance. Both of these discharges are independent and correspond to stable sections of the current-voltage characteristic. A glow discharge is characterized by currents of 10 -5 ... 10 -1 A and a practically constant discharge voltage. An arc discharge is characterized by high currents at relatively low voltages on the electrodes.

The breakdown voltage is below the maximum secondary voltage developed by the ignition system, and therefore, as soon as the increasing voltage reaches the value, a spark discharge occurs in the spark plug and the oscillatory process ends (Fig. 6.5 and 6.9).

Electrical discharge has two components; capacitive and inductive. The capacitive component of a spark discharge is a discharge of energy accumulated in the secondary circuit due to its capacitance C 2. A capacitive discharge is characterized by a sharp drop in voltage and sharp surges of currents, reaching tens of amperes in strength (Fig. 6.9). Despite the insignificant energy of a capacitive spark (), the power developed by the spark, due to the short duration (high speed) of the process, can reach tens and even hundreds of kilowatts. The capacitive spark has a bright bluish color and is accompanied by a specific crackling sound.

High-frequency oscillations (10 6 ... 10 7 Hz) and high capacitive discharge current cause strong radio interference and erosion of the spark plug electrodes. To reduce erosion of the spark plug electrodes (and in unshielded systems, to reduce radio interference), noise-suppressing resistors are included in the secondary circuit (distributor cap, slider, spark plug tips, wires).

Since the spark discharge occurs before the secondary voltage reaches its maximum value, namely at voltage , only a small part of the magnetic energy accumulated in the ignition coil core is consumed by the capacitive discharge.

The remaining part of the energy is released in the form of an inductive discharge. Under the conditions inherent in the operation of distributors and arresters, and with the usual parameters of the ignition coils, an inductive discharge always occurs on the stable part of the current-voltage characteristic corresponding to the glow discharge. The inductive discharge current is 20...40 mA. The voltage between the spark plug electrodes drops significantly to 220...330 V.

Rice. 6.9. Change in spark discharge voltage and current: A And b– respectively, the capacitive and inductive phases of the discharge; – time of the inductive component of the discharge; – amplitude value of the current in the inductive phase of the discharge; – voltage of the inductive phase of the discharge

The duration of the inductive component of the discharge is 2...3 orders of magnitude higher than the capacitive one and reaches 1...1.5 ms depending on the type of ignition coil, the gap between the spark plug electrodes and the engine operating mode (breakdown voltage). The spark is a pale violet-yellow color. This part of the discharge is called the spark tail.

During the inductive discharge, energy is released in the spark gap of the spark plug, which can be determined analytically:

In practice, an approximate formula for calculating the energy of a spark discharge is widely used:

Calculations and experiments show that at low engine speeds the energy of the inductive discharge W ir= 15...20 mJ for conventional classic automotive ignition systems.

Maximum secondary voltage developed by the ignition system U 2 m.

Analytical expressions for the secondary voltage (6.8) and (6.9) show that the value U 2 m depends on the strength of the break current I r and, therefore, determined by the operating mode and type of engine ( n And z), breaker operation ( t z or τ z), parameters of the primary circuit ( L 1, R 1, C 1, UGB, and also depends on the parameters of the secondary circuit and external load ( C 2, , carbon layer resistance R w on the spark plug insulator bridging the spark plug air gap).

Addiction U 2 m on the shaft speed and the number of engine cylinders.

The time of the closed state of the contacts is determined by the expression

where is the angle of the closed state of the contacts; – distributor shaft rotation speed.

From expression (6.12) it is clear that as the roller rotation speed increases, the time decreases and the breaking current (6.3) becomes smaller. A decrease in rupture current entails a decrease in voltage U 2 m. Increasing the number of engine cylinders, all other conditions being equal and parameters of the ignition system, also reduces the time the contacts are closed and reduces the secondary U 2 m .

In Fig. 6.7 shows the characteristics of the maximum secondary voltage depending on the engine speed and the number of engine cylinders. The characteristics are of a monotonic decreasing nature, and the law of decrease is strictly determined by the parameters of the primary circuit () and the angle of the closed state of the contacts.

Voltage reduction U 2 m at low rotation speeds it is associated with arcing at the breaker contacts.

An increase in the breaking current can be achieved by increasing the angle of the closed state of the contacts, which is achieved by appropriate profiling of the cam. However, for mechanical reasons, it is practically impossible to increase the time of the closed state of the breaker contacts to more than 60...65% of the time of the full period ( = 0.60...0.65). Some foreign engines use two independent circuits with two breakers and a coil operating on one distributor. In this case, the relative closedness can reach 0.85.

Rice. 6.7. Typical performance characteristics of a conventional ignition system for four- and six-cylinder engines

The primary current and the rate of its increase depend on the time constant of the primary circuit (Fig. 6.8). The lower this indicator, the faster the current increases to a steady value. The rate of rise of current from the expression is inversely proportional to the inductance L 1:

and at . (6.13)

However, reducing the inductance is advisable only to a certain value, below which the supply of electromagnetic energy, which determines the secondary voltage, begins to decrease.

With a constant inductance of the primary circuit, the breaking current increases with decreasing resistance R 1 since the steady-state value of the current increases. For different resistance values ​​of the primary circuit, the rate of current rise at the initial moment is the same, i.e.

However, the lower the resistance R 1, the higher the current curve goes (Fig. 6.9).

Rice. 6.8. Primary current rise curves for different values ​​of primary circuit inductance ().

Rice. 6.9. Primary current rise curves for different values ​​of primary circuit resistance

Thus, to increase the maximum secondary voltage, it is necessary to reduce the resistance of the primary circuit. However, excessive reduction R 1 leads to an increase in the steady-state current, which impairs the performance of the contacts at low speeds and leads to overheating of the coil.

Addiction U 2 m from the capacity of the primary capacitor C 1.

From expression (6.8) it is clear that with a decrease in the capacitance of the capacitor C1, the secondary voltage should increase, and at C1 = 0 it reaches its maximum value. This type of change in U2m is possible only at large values ​​of C1. In the range of small capacitances, as they decrease, the secondary voltage also decreases. This phenomenon is explained by the fact that with a small capacity, arcing on the contacts is not eliminated, causing significant energy losses. The nature of the dependence of the secondary voltage on the capacitance of the primary circuit capacitor (Fig. 6.10) shows that there is an optimal value C 1, determined by the arc extinction conditions on the contacts. On practice C 1 choose within 0.15...0.35 µF.

Rice. 6.10. Dependence of the secondary voltage on the capacitance of the capacitor in the primary circuit

Addiction U 2 m from secondary tank C 2.

The value of the maximum secondary voltage also depends on the capacitance of the secondary wires, the capacitance of the spark plug, the own capacitance of the secondary winding of the ignition coil and practically cannot be less than 40...75 pF. In case of shielding of the ignition system, the capacitance of the secondary circuit increases to 150 pF. Consequently, shielding used to significantly reduce radio interference significantly reduces the value of the secondary voltage.

Addiction U 2 m from shunt resistance R w .

During engine operation, the spark plug insulator is often covered with carbon deposits, which creates a conductive bridge between the spark plug electrodes. This conductive carbon layer can be represented as a resistor R w, bridging the air gap. Due to availability R w The secondary voltage that increases after opening the contacts creates a current in the secondary circuit, called leakage current, which, circulating in the secondary circuit until the spark gap breaks down, causes a voltage drop in the secondary winding and a decrease in the voltage supplied to the spark plug.

With low shunt resistance, the leakage current increases and the secondary voltage can drop to a value of lower breakdown voltage, i.e., a spark will not occur (Fig. 6.11).

Addiction U 2 m on the transformation ratio.

If there are no leaks, the voltage U 2 m other things being equal, it increases with increasing coil transformation ratio, tending to its limit:

With an infinitely large soot resistance, all electromagnetic energy is transformed into electrostatic energy in the secondary circuit. However, if ≠ ∞, then each value of the shunt resistance corresponds to an optimal transformation ratio at which the secondary circuit voltage is maximum (Fig. 6.11). The optimal ratio for existing ignition systems with a primary winding inductance of 6.5...9.5 mH is = 55...95.

Rice. 6.11. Dependence of secondary voltage on the transformation ratio of the ignition coil.