How Engine Ignition system works, Types of Ignition systems

Automobile

Ignition system

1. To supply a spark inside the cylinder, at the end of compression stroke, to ignite the compressed charge of the air-fuel mixture.

2. Convert low tension current into high tension current. (6v to 12v in to 20,000 to 30,000v)

3. To produce spark in the multi cylinder engine at the right time as per the firing order

Types of ignition system

1. Battery coil Ignition system
2. Magneto Ignition system
3. Electronic Ignition system

Battery coil ignition system

The main parts of a battery coil
ignition system is

1. Battery
2. Ignition Coil
3. Contact breaker points
4. Condenser
5. Distributor
6. Spark plug
7. Ignition Switch

Battery

A battery is used to provide energy
for ignition. The battery is charged by the dynamo or alternator and provide electrical energy to the electrical parts in the vehicle as and when it is required.

Ignition coil

An ignition coil is made up of an
iron core surrounded by two insulated coils, namely primary winding and secondary winding. Acting as a step-up transformer.
It converts low tension current (12v) into high tension current of 20000 to 30000 volts. This high tension current enables to generate a spark across the electrodes of a spark plug.

Contact breaker points

The opening and closing of the
primary circuit are made by contact
breaker points. When the points are closed current flow in ignition coil and charge the primary circuit and when it open, discharge of primary current take place and by mutual induction, in secondary coil high tension current is induced.
Condenser A condenser is connected in parallel to the contact breaker points to prevent arching at the contact breaker points. Also, used to increase the intensity of the spark.

Distributor

The distributor is used in multi-
cylinder engine to distribute the high
tension current from the ignition coil to the individual spark plug as per the firing order.

Spark plug

A spark plug has two electrodes
which are separated with each other. When a high tension current is applied between these two electrodes,it produces spark to
ignite the air fuel mixture in the engine cylinder.

Working Principle

When the ignition switch is turned
“ON”, the current flows from the battery to the primary winding, through thencontact breaker. The flowing current induces a magnetic field in the primary winding. As the contact breaker opens, the current collapses resulting in high tension
induction in the secondary winding. This high tension generated in the secondary winding is transferred to the distributor by a cable. The distributor distributes high tension to the spark plug located in the individual cylinder as per the firing
order. A spark is generated in the spark plug to initialise the combustion of fuel and air.

Rotating Armature type Magento System

Magneto ignition system is a special
type of ignition system with its own electric generator to provide the required necessary energy for the vehicle. A magneto, when rotated by the engine, is capable of producing
a very high tension and doesn’t need a battery as a source of external energy. It is mounted on the engine and replaces all components of the coil ignition system except the spark plug. Magneto ignition system can be either rotating armature type or rotating magneto type.

Construction

Permanent magnets are stationary
and acting as the North and South poles.The armature consisting of the primary and secondary windings all rotate between the poles of a stationary magnet. Primary winding
will be made up of thick wire with less no. of turns (150 to 300 turns) and the secondary winding is made up of thin wire with more No. of turns (15000 to 25000 turns). Contact
breaker points and condenser are connected to the primary winding and spark plug is connected to the secondary winding.

Working Principle

When the armature rotates, the flow
of current is happening in primary winding and Contact breaker point in the closedncondition. The magnetic field is induced in primary winding. When the contact breaker point open, the magnetic field in the primary winding collapses and by mutual
induction principle, high tension current is induced in the secondary winding. This high tension current is applied to the spark plug and spark is produced to ignite the air-fuel mixture in the combustion chamber.

Rotating magnet type magneto ignition system

Construction

In this permanent magnet are fitted over the engine flywheel. The fixed armature will have few hundred winding (150 to 300 turns) made up of thick wire and this act as a primary winding. The secondary winding is made up of thin wire with thousands of turns (15000 to 25000 turns). Contact breaker points and condenser are connected to the primary
winding and spark plug is connected in the secondary winding.

Working

When the flywheel is rotated, the
permanent magnet will also rotate. This will make the flow of current to the primary winding and generates magnetic field. When the contact breaker points open, the magnetic field in the primary winding collapses and by mutual induction principle, high tension current is induced
in the secondary winding. This high tension current is applied to the spark plug and spark is produced to ignite the air-fuel mixture in the combustion chamber.

Electronic ignition system

The following are the important
parts of an Electronic Ignition System

1. Battery
2. Ignition Switch
3. Ignition Coil
4. Electronic Control Unit
5. Distributor
6. Spark Plug
7. Reluctor

Working

Permanent magnet and pick up
coil are placed in the distributor. The
magnetic flux from the magnet will pass through the reluctor. Hence, electricity is generated. The current will flow through the electronic control unit. ECU has the
diode and the transistor and it controls the flow of current to the primary circuit. When ECU closes the primary circuit, the primary winding charges. When ECU opens the primary circuit, the charge in the primary winding collapses and by
mutual induction, high tension current is induced in the secondary winding.nThis high tension current will reach the respective spark plug as per the firing order through a distributor. Thus, the spark is produced and the air-fuel ,mixture
is ignited.

Advantages

1. No moving parts
2. Ignition timing is controlled by
ECU, hence no need for an advance
mechanism
3. Long life for spark plug
4. Spark intensity is higher
5. Contact breaker points, condenser are eliminated

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