How a commonly used car starter motor works-Zhejiang Noontimes Autoparts Co., Ltd.

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How a commonly used car starter motor works

2021-12-29

The control system for an automotive starter includes an electromagnetic switch, a starter relay, and the ignition-start switch component, with the electromagnetic switch integrated directly into the starter mechanism.

1. Electromagnetic Switch

1. Structural Features of Electromagnetic Switches

The electromagnetic switch primarily consists of two main components: the electromagnet mechanism and the motor-driven switch. The electromagnet mechanism includes a stationary core, a movable core, an attracting coil, and a holding coil. The stationary core remains fixed, while the movable core can move axially within a copper sleeve. At the front end of the movable core is a pushrod, which supports a switch contact plate at its tip. The rear portion of the movable core is connected to a rocker arm via an adjusting screw and a connecting pin. Surrounding the copper sleeve is a return spring, which ensures that the movable components—including the core—automatically reset to their original positions. The arrangement of terminals for wiring the electromagnetic switch is illustrated in the figure provided.

2. How an Electromagnetic Switch Works

When the magnetic flux directions generated by energizing the attracting coil and the holding coil are aligned, their electromagnetic forces add up, pulling the movable iron core forward until the contact plate at the front end of the pushrod closes the contacts of the electric switch, thereby completing the connection to the motor's main circuit.

When the magnetic forces generated by the energized attracting coil and holding coil act in opposite directions, their electromagnetic attraction cancels each other out. Under the action of the reset spring, the movable components—including the armature—automatically return to their original position, causing the contact disc to separate from the contacts and opening the motor's main circuit.

2. Starter Relay

The structural diagram of the starter relay is shown in the upper-left portion of the figure and consists of an electromagnetic mechanism and a contact assembly. The coil is connected to the ignition switch terminal and the ground terminal "E" on the housing, while the fixed contact is linked to the starter terminal "S." Meanwhile, the movable contact is connected via a contact arm and bracket to the battery terminal "BAT." The starter relay contacts are normally open; when the coil is energized, the relay’s iron core generates an electromagnetic force that closes the contacts, thereby completing the circuit for both the relay-controlled pull-in coil and the hold-in coil.

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