Design

Design

Exploded view of the starter motor




The starter motor consists of:
1. Drive cover
2. Gear wheel
3. Solenoid magnet
4. Battery terminal
5. Rear end and bearing
6. Carbon brush holder and carbon brushes
7. Commutator
8. Armature
9. Permanent magnet
10. Armature housing
11. Planetary train
12. Lever with free rotating clutch
13. Engagement unit for the pinion.

Note! The starter motor of the V8 engine is equipped with field windings instead of permanent magnets. The field windings are electrically connected in series with the carbon brushes.




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

Control 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 control solenoid consists of the following components:
1. Moving steel cores. Moved by pull-in winding in the control 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. Disconnect 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 control solenoid is supplied
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. 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 with the fixed switches
10. Return spring. Resets the control solenoid components to the rest position when the starter motor relay is disconnected.

Freewheel




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 engine cannot drive the starter motor because the pinion turns in the rollers.
The freewheel clutch is attached to the armature shaft by spiral splines, which facilitate engagement and disengagement of the starter motor pinion / 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 rotation 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