Magnetic Switch

Magnetic Switch

The magnetic switch (Also referred to as a Solenoid) consists of a hold-in coil, Pull-in coil, A return Spring, A plunger and other components. It is activated by the magnetic forces generated in the coils and carries out the following two functions:

• It pushes the pinion gear so that it meshes with the ring gear.

• It serves as a main switch or relay, Allowing heavy current to pass from the battery to the starter motor.  

Field Coils

Field Coils

The electrical current from the magnetic switch flows through the field coils, Which generate the magnetic field required to rotate the armature.

Brushes

Carbon Brush

The brushes, pressed against the segments of the armature commutator by the brush springs, Allow the current to pass from the field coils to the armature.

NOTE

Weakened brush springs or worn brushes may lead to insufficient electrical contact 
between the brushes and the segments of the commutator. The resulting excessive 

electrical resistance at the contact points will reduce the supply of current to 

the motor, Impeding torque build-up.

Armature

 
The armature, The revolving component of the motor, Consists of the armature core, Armature coils, Commutator, etc. It revolves as a result of the interaction between the magnetic fields generated by the armature coils and the field coils.

Starter Clutch

Starter Clutch

The starter motor must crank the engine until the engine fires and starts to run on its own. Once the engine has started, However, It would force the starter motor to rotate at a much higher speed than that for which it is designed, Which would damage the starter motor. The starter clutch is a one-way clutch which protects the starter motor from this. Although the construction of the starter clutch used for the conventional type starter motor is somewhat different from that used for the reduction type starter motor, The principle and operation of each is essentially the same.
Although the construction of the starter clutch used for the conventional type starter motor is somewhat different from that used for the reduction type starter motor, The principle and operation of each is essentially the same.

Starter Clutch During Cranking

Starter Clutch During Cranking

 The rotating armature tries to force the clutch housing to which it is splined, To rotate faster than the inner race, Which is combined with the pinion gear. The clutch rollers are therefore forced to roll toward the narrower sections between the clutch housing and inner race until they jam between the clutch housing and the inner race. As a result, The rollers transfer the rotational movement of the clutch housing to the inner race and thence to the pinion gear.

Starter Clutch after Engine is Started

Once the engine has started, Its torque tries to force the inner race to rotate faster than the clutch housing. The clutch rollers therefore roll against the springs towards the wider sections inside the housing. As a result, The clutch housing and the inner race disengage to prevent the starter clutch from transmitting the engine torque from the pinion gear to the starter motor.