Solenoid

Solenoid




The Solenoid performs the following functions:
- Pull the pinion to engage the flywheel
- Hold the pinion engaged with the flywheel during starting rotation.
- Complete the electrical circuit from the battery to the brushes of the starter.
- Cause the pinion to retract from the flywheel

Two windings are used to pull and hold the pin ion engaged to the flywheel.

Pull-In Winding - The stronger of the two windings, used to pull the pinion into engagement. This winding is released when the starter circuit is completed

Hold-In Winding - Used to help the pull-in winding move the pinion initially, then holds the pinion engaged to the flywheel.

Signal 50 is received at the solenoid, energizing both windings. The windings cause the armature to be drawn into the coils, pressing on a spring, causing the moving contacts to close. The pull-in winding is released, the starter begins to turn. When signal 50 is released, the power is lost to the hold-in winding, spring pressure forces the armature out Of the coil, the moving contacts are opened and the pinion returns to the rest position.

Workshop Hint
The starter motor does not begin to spin until after the pinion is engaged in the flywheel.
This aids in the meshing of the pinion and flywheel

Workshop Hint

Battery voltage is critical.
The combination of the pull-in winding and the hold- in winding may have sufficient power to engage the pinion. When the moving contacts are completed and the increased load of the starter motor is added to the system. low voltage will cause the hold-in winding to release the pinion. If signal 50 is still pre-sent the pull-in winding will again assist in pulling the pinion into engagement and the cycle starts over again. This gives the "clicking" noise from the starter.

Pinion Drive

The Pinion Drive gear is attached to the roller-type overrunning clutch which is splined via a helical shaft to the starter armature. At rest the spring pressure in the overrunning clutch wedge rollers between the pinion shaff and the clutch hub race. This locks the pinion to the clutch. During start-up the clutch and pinion rotate as one.

As the engine speed exceeds starter speed, the pinion pushes the rollers, against the spring pressure, into a wider area. This movement of the rollers allow the pinion to turn independently of the starter armature, not causing the armature to overspeed. When the solenoid windings are released the clutch assembly is pulled away from the flywheel through spring pressure.

Phases of Starter Operation