The starter solenoid is a crucial component of the car starter, serving to maintain the engine and prevent engine damage caused by the starter reversing.

The operation principle of the starter one-way clutch is that once the starter is powered on, the drive gear engages with the flywheel's gear ring. Under the spring's action, the bearing pushes the drive gear to tightly mesh with the flywheel gear ring, thereby completing the starting process. If the starter is reversed, the one-way clutch acts as a restraint, preventing the drive gear from disengaging from the flywheel gear ring, thereby protecting the engine.

The starter solenoid is primarily composed of three main parts: the housing, ball bearings, and torsion spring.

The housing is the external packaging of the unidirectional valve, which can be fixed onto the engine. The ball is the core part inside the unidirectional valve, capable of being freely flipped. The torsion spring serves to connect the housing and the ball.

Moreover, depending on the type of starter, the one-way clutch may also include additional components such as driving gears and matching shafts.