Short Answer:

The distributor is an important component of the ignition system in an internal combustion engine. Its main function is to distribute high-voltage current from the ignition coil to the correct spark plug in the proper firing order. It ensures that each cylinder receives the spark at the correct time for efficient combustion.

The distributor also helps in controlling the ignition timing and sometimes includes devices for advance and retard timing. By performing these functions, the distributor ensures smooth engine operation, better fuel economy, and reduced engine knocking.

Detailed Explanation :

Distributor Function

The distributor is a key part of the ignition system used in spark ignition (petrol) engines. Its main function is to route high-voltage current from the ignition coil to each spark plug in the correct sequence and at the correct time. The distributor ensures that every cylinder receives a spark at the right moment during its compression stroke, which is essential for proper combustion and smooth running of the engine.

In addition to distributing current, the distributor also plays an important role in controlling ignition timing, interruption of current flow, and sometimes advancing or retarding the spark depending on the engine speed and load conditions.

Main Functions of Distributor

1. Distribution of High Voltage:
   The most important function of a distributor is to distribute high-voltage current from the ignition coil to each spark plug according to the firing order. This is achieved through a rotating arm (rotor) inside the distributor, which connects the central coil terminal to the outer terminals connected to each spark plug wire.
2. Timing the Spark:
   The distributor ensures that the spark reaches each cylinder at exactly the right time — just before the piston reaches the top dead center (TDC) during the compression stroke. This timing is critical for efficient combustion and maximum power output.
3. Current Interruption:
   The distributor includes a contact breaker or electronic triggering device that opens and closes the primary circuit of the ignition coil. When the circuit is broken, a high-voltage current is induced in the secondary coil, which is then directed to the spark plug.
4. Spark Advance Mechanism:
   The distributor is equipped with centrifugal and vacuum advance mechanisms to automatically adjust the ignition timing.
   • Centrifugal Advance: Works based on engine speed.
   • Vacuum Advance: Works based on engine load.
     These adjustments ensure that combustion occurs at the right moment under different driving conditions.
5. Housing and Protection:
   The distributor also provides a housing that protects the ignition components such as the rotor, cam, and contact breaker points from dust, moisture, and mechanical damage.

Construction of Distributor

A typical distributor consists of the following parts:

• Distributor Shaft: A vertical shaft driven by the camshaft. It rotates in synchronization with the engine speed.
• Cam: Mounted on the shaft, it opens and closes the contact breaker points.
• Contact Breaker Points: A pair of electrical contacts that open and close to interrupt the primary current flow.
• Condenser (Capacitor): Connected across the contact breaker points to reduce arcing and improve efficiency.
• Rotor: A rotating arm connected to the coil’s secondary terminal, distributing high voltage to the spark plugs.
• Distributor Cap: Made of insulating material, it holds metal terminals that connect to spark plug wires.
• Advance Mechanisms: Includes both centrifugal and vacuum systems to automatically adjust spark timing.

All these parts work together to ensure that the high-voltage spark reaches each spark plug in the proper order and at the correct instant.

Working of Distributor

1. When the ignition switch is turned on, current flows through the primary winding of the ignition coil.
2. As the cam inside the distributor rotates, it opens and closes the contact breaker points.
3. Each time the points open, the magnetic field in the coil collapses, generating a high-voltage current in the secondary winding.
4. This high voltage is sent through the coil’s central wire to the rotor of the distributor.
5. The rotor rotates inside the distributor cap, touching each terminal sequentially.
6. Each terminal is connected to a spark plug through a high-tension lead wire, and the spark plug fires in the correct firing order.
7. The advance mechanisms adjust the timing automatically depending on engine speed and load.

This process continues repeatedly as the engine runs, ensuring proper ignition in every cylinder cycle.

Types of Distributors

There are mainly two types of distributors used in vehicles:

1. Breaker Point Type Distributor:
   Uses mechanical contact points and a condenser to break the circuit and generate high voltage. Common in older vehicles.
2. Electronic Distributor:
   Uses electronic sensors instead of mechanical contact points to trigger the ignition coil. It provides more accurate timing, less wear, and better performance.

Modern engines mostly use distributor-less ignition systems (DIS) controlled by an electronic control unit (ECU), which improve efficiency and reduce maintenance needs.

Importance of Distributor

The distributor plays a vital role in maintaining proper engine performance. Without accurate distribution and timing of the spark, the combustion process would be irregular, causing misfiring, vibration, loss of power, and poor fuel efficiency. It also ensures smooth acceleration, easy starting, and reduced emissions by providing consistent spark delivery.

Conclusion

The distributor is an essential part of the ignition system responsible for sending high-voltage current to each spark plug in the correct firing order and at the right time. It also manages spark timing through mechanical or vacuum advance mechanisms. Although modern systems have replaced mechanical distributors with electronic ones, the basic principle remains the same — accurate spark distribution for efficient combustion and smooth engine operation.