Design

Design

Exploded view of the starter motor





The starter motor consists of:
1. Drive cover.
2. Gear wheel.
3. Solenoid.
4. Battery terminal.
5. Rear end and bearing.
6. Carbon brush holder and carbon brushes.
7. Commutator.
8. Armature.
9. Permanent magnet or field winding.
10. Armature housing.
11. Planetary train.
12. Lever with freewheeling clutch.
13. Pinion engaging drive.

Note! Starter motor for V8 engine and DV6 S/S is equipped with field winding instead of permanent magnets. The field windings are electrically connected in series by carbon brushes.





Starter motor terminals:
- #1 (30) From the battery positive terminal
- #2 (50) From starter motor relay
Ground terminal via transmission / cylinder block.

Principle




The starter motor is a DC motor which uses a permanent magnet. This type of motor operates following the principle that the same poles (North/North) are forced away from each other and opposite poles (North/South) are drawn to each other.

Solenoid




The control solenoid has two functions. The first is to mechanically engage the pinion in the flange/flywheel gear collar. The other is to function as a relay and to handle the greater current required to drive the starter motor when the pinion engages with the gear collar.

The solenoid consists of the following components:
1. Moving steel cores. Moved by pull-in winding in the solenoid, slides the pinion into position and moves the moving switch towards the fixed switches.
2. Pull-in winding. Pull in the moving steel core. Disconnects when the moving steel core reaches the bottom position.
3. Hold-in winding. Holds the moving steel core in position for as long as the solenoid is powered.
4. Fixed steel cores. Stop position for the moving steel core.
5. Contact spring
6. Fixed contacts. Closes when the moving switches reach the fixed switches.
7. Terminals. Two, one for the battery and one for the DC motor.
8. Moving switch. Switch which closes the fixed switches.
9. Moving shaft. Affected by the moving steel core and connects the moving switches to the fixed switches.
10. Return spring. Resets the solenoid components to the rest position when the starter motor relay is disconnected.

Freewheel clutch




Functions as a one way clutch (freewheel). The freewheel allows the starter motor to drive the car engine, but not the other way around. This prevents the starter motor from being over-revved. This is carried out by spring-loaded rollers which lock the pinion and gear together when the starter motor operates.
The car engine cannot drive the starter motor because the pinion would turn in the rollers.
The freewheel clutch is attached to the armature shaft by spiral splines, which facilitate engagement and disengagement of the carrier plate/flywheel ring gear.
The left-hand illustration displays the normal position. The starter motor, connected to the outer section drives the pinion (inner section) by means of the rollers, which then lock.
The right-hand illustration displays what happens when the starter motor remains connected when the engine is started. The pinion (inner section) cannot drive the starter motor (outer section) because the rollers disengage.

Planetary train




The planetary train is used to reduce the rotational speed of the pinion gear in relation to the speed of the armature and to increase the torque of the pinion.

The planetary train consists of:
1. Pinion shaft with splines
2. Ring gear (fixed section)
3. Planetary gear (connected to the pinion shaft)
4. Sun gear (connected to the rotor)
5. Armature
6. Commutator