Starter motor and components

Description 5520B

COMPOSITION

The starting system consists of the ignition switch operated by the key and the starter motor which is connected directly to the battery.

In addition to tried and tested starter motors which are energized in series and in series/parallel, for some time now starter motors are being developed which are energized by ceramic, ferrite type permanent magnets.

CIRCULAR SECTOR MAGNET WITH MAGNETICALLY PRE-ORIENTATED CRYSTALS

The rough components are formed into the desired shape by pressing and extrusion. Finally, after a thorough baking process, the material produces the mangets which are black in colour with a ceramic structure. The magnetizing treatment takes place during the manufacturing process.

The magnets have a circular section and replace the polar section and winding.

1 - Radial orientation

2 - Parallel orientation

STATOR-INDUCTOR

The positioning of the magnets cannot take place using strong compression or riveting, also because the magnets are fairly fragile: they are secured by flexible fastenings and springs and, in some cases, they are stuck to the casing. The casing can be compared to a simple mechanical component without wires and is fitted using two stay bolts; it is equipped with 6 magnetic poles.

1 - N-S permanent magnets

ROTOR-ARMATURE

The diagram below shows the rotor-armature assembly.

1 - Shaft

2 - Ring gear

3 - Satellite/planet gears

4 - Pinion/sun gear

5 - Armature

6 - Manifold/switch

Given that the magnetic field is created by permanent magnets, the energizing is the same in all motor operating conditions; in addition, as there are no energizing windings, there is neither an energizing current nor ohmic resistance: the total resistance depends solely on the armature circuit. The rotation speed is only affected by the current which passes through the blades and reaches the rotor depending on the voltage. Since the motor is equipped with permanent magnets, i.e. with fixed polarity, the direction of rotation depends on how the current is sent to the blades.

When the rotor rotates it transmits movement to the three satellite gears on special supports which transmit their torque to the ring gear on the output shaft where the pinion which rotates the flywheel can be found. The optimum reduction ratio 1:4.26 is 4.26 revolutions of the rotor for each revolution of the ring gear and the presence of the permanent magnets makes it possible to construct motors of equal power from a simple design which are small in size compared with motors which have windings.

STARTER MOTOR DIAM 74.5 1.1/12V

1 - Pinion with free wheel

2 - Epicyclic reduction gear

3 - Rotor permanent mangets

4 - Complete polar casing

5 - Armature or rotor

6 - Blades

7 - Manifold

8 - Manifold side support

9 - Engagment relay

10 - Lever

11 - Control side support

TECHNICAL DATA

Starter motor: AM 74.5 1.1 12V

Nominal voltage: 12V

Rated power: 1.1 kw

Pinion side rotation: clockwise

Energizing: 6 permanent magnet poles

Electro-magnetic operation with pull in and hold in winding

Reduction ratio 1:4.26

Blades 2+2

Free wheel engagement

WIRING DIAGRAM

The starter motor wiring diagram is illustrated below.

1 - Control unit on battery

2 - Starter motor

3 - Alternator

4 - Body computer

5 - Ignition switch

6 - Engine compartment control unit (CVM)

7- Control unit under dashboard (CPL)