WORKING PRINCIPLE OF AUTOMOBILE STARTER

The control device of a car starter includes an electromagnetic switch, a starting relay, and an ignition start switch light component, among which the electromagnetic switch is made together with the starter.

1、 Electromagnetic switch

1. Structural characteristics of electromagnetic switches

The electromagnetic switch mainly consists of two parts: an electromagnetic mechanism and an electric motor switch. The electromagnet mechanism consists of a fixed iron core, a movable iron core, an attraction coil, and a holding coil. The fixed iron core is fixed and immovable, and the movable iron core can move axially in the copper sleeve. The front end of the movable iron core is fixed with a push rod, and the front end of the push rod is equipped with a switch contact plate. The rear section of the movable iron core is connected to the fork with adjusting screws and connecting pins. The copper sleeve is equipped with a reset spring on the outside, which is used to reset movable components such as the movable iron core. The arrangement position of the terminals for the electromagnetic switch wiring is shown in the figure

2. Working principle of electromagnetic switch

When the magnetic flux generated by the attraction coil and the holding coil are in the same direction when energized, their electromagnetic attraction is superimposed on each other, which can attract the movable iron core to move forward until the contact plate at the front end of the push rod connects the electric switch contact to the main circuit of the electric motor.

When the magnetic pain caused by the attraction coil and the holding coil are in the opposite direction when they are energized, their electromagnetic attraction cancels out each other. Under the action of the reset spring, movable components such as the movable iron core automatically reset, the contact plate and contact point are disconnected, and the main circuit of the motor is disconnected.

2、 Starting relay

The structural diagram of the starting relay is shown in the upper left corner of the figure, consisting of an electromagnetic mechanism and a contact assembly. The coil is connected to the ignition switch terminal and grounding terminal "E" on the housing, the fixed contact is connected to the starter terminal "S", and the movable contact is connected to the battery terminal "BAT" through the contact arm and bracket. The starting relay is a normally open contact when the coil is energized. When the coil is energized, the relay core generates electromagnetic force, causing its contacts to close, thereby connecting the attracting coil and holding coil circuits controlled by the relay.

1. Control circuit

The control circuit includes a starting relay control circuit and a starter electromagnetic switch control circuit.

The starting relay control circuit is controlled by the ignition switch, and the controlled object is the relay coil circuit. When the ignition switch is turned on and the starting gear is turned on, the current flows from the battery political circle through the starter power terminal to the ammeter, and then from the ammeter through the ignition switch, the relay coil returns to the negative pole of the battery. So the relay core generates strong electromagnetic attraction, causing the relay contacts to close and connect the control circuit of the starter electromagnetic switch.

2. Main circuit

As shown by the arrow in the figure, after the electromagnetic switch is turned on, strong electromagnetic attraction is generated by the attraction coil 3 and the holding coil 4, connecting the main circuit of the starter. The circuit is:

The positive pole of the battery → the power terminal of the starter → the electromagnetic switch → the excitation winding resistance → the armature winding resistance → the grounding → the negative pole of the battery, so the starter generates electromagnetic torque and starts the engine.