Introduction
“From a little spark may burst a flame” by Dante Alighieri, Rightly said that a
spark is required to start a flame and in automobile since there is a conversion
of chemical energy (i.e. air-fuel mixture) into mechanical energy i.e. (crankshaft
rotation) spark is essential which is responsible for the combustion, but from
where does this spark comes? How does the timing of spark and prepared air-
fuel mixture is managed? Let’s just dig it out.
In internal combustion engine, combustion is a continuous cycle and occurs
thousands time in a minute so a effective and accurate source of ignition is
required. The idea of spark ignition came from a toy electric pistol that used
electric spark to ignite a mixture of hydrogen and air to shoot a cork.
Electronic ignition system is the type of ignition system that uses electronic
circuit, usually by transistors controlled by sensors to generate electric pulses
which in turn generate better spark that can even burn the lean mixture and
provide better economy and lower emission.
Why Electronic Ignition System?
Various types of ignition systems were used lately that are
1. Glow plug ignition system,
2. Magneto ignition system
3. Electric coil or Battery ignition system,
But all these systems have their own limitations that are:
Glow plug ignition system is the oldest of all and is obsolete because of its
many limitations-
Glow plug ignition system has a problem of causing uncontrolled combustion
due to the use of electrode as a ignition source, which is solved later after the
introduction of Magneto ignition system in which electrodes are replaced by
spark plug. Unlike magneto ignition, Glow plug produces high exhaust emission
due to the incomplete combustion.
Magneto ignition system: It is the system introduce to overcome the
limitations of old ignition systems, but it has its own limitations-
It depends on the engine speed, so shows starting problem due to low speed at
the starting of the engine, which is later solved with the introduction of Battery
coil ignition system in which battery becomes the energy source for the system.
Expensive than electric coil ignition system.
Wear and tear is more than battery coil ignition because of greater number of
mechanical moving parts than battery coil system.
Can cause misfire due to leakage.
Electric coil ignition or Battery ignition system – System is the latest of all
above and is being used from long time due to its better efficiency and accuracy
but it also shows some limitations-
Less efficient with the high speed engines
High maintenance required due to mechanical and electrical wear of the contact
breaker points
So, Since in the modern automobile new technologies are introduced and it is
found that use of sensors and electronic component gives more effective and
accurate outputs than that of mechanical components so the use of sensors with
electronic controlled unit becomes essential to fulfill the needs of modern high
power and high speed automobiles or hyper series of automobiles, so to fulfill
the need for high performance, high mileage and greater reliability has led to the
development of Electronic ignition system.
Main Components
1. Battery
It is the powerhouse of the ignition system as it supplies the necessary energy to
the ignition system, same as battery coil ignition system.
2. Ignition Switch
it is the switch used in ignition system which governs the ON and OFF of the
system, same as the battery coil ignition system.
3. Ignition Control Module or Control Unit of Ignition System
It is the brain or programmed instruction given to the ignition system which
monitors and control the timing and intensity of the spark automatically. It is the
device that receives voltage signals from the armature and set the primary coil
to ON and OFF, it can be placed separately outside the distributor or can be
place in electronic control unit box of the vehicle.
4. Armature
Contact breaker points of battery ignition system is replaced by an armature
which consists of a armature with teeth (the rotating part), vacuum advance and
a pickup coil(to catch the voltage signals). Electronic module receives the
voltage signals from the armature in order to make and break the circuit, which
in turn sets the timing of the distributor to accurately distribute current to the
spark plugs.
5. Ignition Coil
Same as the battery ignition coil system ignition coil is used in electronic
ignition system to produce high voltage to the spark plug.
6. Ignition Distributor
As the name indicates it is the device use to distribute the current to the spark
plugs of the multi cylinder engine.
7. Spark Plug
Spark plug is used to generate spark inside the cylinder.
Working of Electronic Ignition System
To understand the working of the electronic ignition system let’s consider above
figure in which all the components mentioned above are connected in their
working order.
When the driver switch ON the ignition switch in order to start a vehicle the
current starts flowing from the battery through the ignition switch to the coil
primary winding, which in turn starts the armature pickup coil to receives and
send the voltage signals from the armature to the ignition module.
When the tooth of the rotating armature comes in front of the pickup coil as
shown in the fig the voltage signal from pickup coil is sent to the electronic
module which in turn senses the signal and stops the current to flow from
primary coil.
When the tooth of the rotating armature goes away from the pickup coil, the
change in voltage signal is sent by pickup coil to the ignition module and a
timing circuit inside ignition module turns ON the current flow.
A magnetic field is generated in the ignition coil due to this continuous make
and break of the circuit which induced an EMF in secondary winding which
increases the voltage upto 50000 Volts.
This high voltage is then sent to distributor, which has the rotating rotor and
distributor points which is set according to the ignition timing.
When the rotor comes in front of any of those distributor points the jumping of
voltage through the air gap from the rotor to the distributor point takes place
which is then sent to the adjacent spark plug terminal through the high tension
cable and a voltage difference is generated between the central electrode and
ground electrode which is responsible for generating a spark at the tip of the
spark plug and finally the combustion takes place.
Application
Electronic ignition system is used in modern and hyper cars like Audi A4,
Mahindra XUV-500, etc. and bikes like KTM Duke 390cc, Ducati super sports
etc. to meet the high reliability and performance need .
It is also used in aircrafts engine due to its better reliability and less
maintenance
WORKING OF CONVENTIONAL
IGNITION SYSTEM
An automotive ignition system is divided into two electrical circuits -- the
primary and secondary circuits.
1. The primary circuit carries low voltage. This circuit operates only on battery
current and is controlled by the breaker points and the ignition switch. When
the ignition key is turned on, a low voltage current from the battery flows
through the primary windings of the ignition coil, through the breaker points
and back to the battery. This current flow causes a magnetic field to form
around the coil.
2. The secondary circuit consists of the secondary windings in the coil, the high
tension lead between the distributor and the coil (commonly called the coil
wire) on external coil distributors, the distributor cap, the distributor rotor, the
spark plug leads and the spark plugs. As the engine rotates, the distributor
shaft cam turns until the high point on the cam causes the breaker points to
separate suddenly. Instantaneously, when the points open (separate) current
flow stops through the primary windings of the ignition coil. This causes the
magnetic field to collapse around the coil. The condenser absorbs the energy
and prevents arcing between the points each time they open. This condenser
also aids in the rapid collapse of the magnetic field.
3. The line of flux in the magnetic field cut through the secondary windings of
the ignition coil, creating a high voltage - high enough to jump the gaps
between the rotor and the distributor cap terminals, and the electrodes at the
base of the spark plug. Assuming that the engine is properly timed, the spark
reaches the air-fuel mixture in the cylinder and combustion begins.
4. As the distributor continues to rotate, electrical contact between the rotor and
distributor cap terminal is broken, stopping the secondary flow. At the same
time, breaker points close to complete the primary circuit, allowing primary
current to flow. This primary current will again create a magnetic field and
the cycle is repeated for the next cylinder in the firing order.
