Starter system
Engine cannot generate the first combustion to start without the external power. The starter motor helps to start the engine by rotating the crankshaft via the ring gear.
The starter is required to generate the very high torque from the limited battery power and must be compact and light as well.
In order to start the engine, the crankshaft has to rotate faster than the minimum cranking seed. The minimum cranking speed required to start the engine depends on the engine’s construction and operating conditions.
Starter circuit |
B | Starter motor |
C | SP 210/body |
D | K9 start coil relay |
E | Ignition switch |
F | Electronic control unit (ECU) |
G | Battery |
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Components of starter
Planetary reduction gear starter is used in the vehicle and it consists of the following components:
1) Magnetic switch |
B1 | Main contact |
B2 | Plunger |
B3 | Return spring |
B4 | Plunger shaft |
B5 | Pull in coil |
B6 | Hold in coil |
B7 | Drive spring |
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Magnetic switch operates as a main switch for the current flowing to the motor and controls the pinion gear (push out / pull in).
The pull-in coil has a thicker wire wind up and greater magnetomotive force than that of hold-in coil.
Vehicle starter motors are typically provided with a drive unit and a solenoid, with a shift lever connecting the solenoid to the drive unit. When a solenoid coil is energized a solenoid plunger extends, thereby actuating the shift lever and engaging a starter pinion gear with flywheel of the engine. Vehicle starter motors that utilize a self-start engagement system must provide a substantial amount of current prior to actual crank. Begin rotation of the starter pinion gear and to cause the pinion gear to engage with the flywheel.
The IMS is basically a small solenoid that mounts on the starter to power. The solenoid switch terminal and to reduce the current load on the ignition wiring on the vehicle.
2) Armature and ball bearing |
C1 | Ball bearing |
C2 | Armature coil |
C3 | Armature core |
C4 | Commutator |
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The armature generates a motor revolving force, and the ball bearing supports the high speed revolution of the armature.
3) Yoke sub-assembly |
D1 | Yoke |
D2 | Pole core |
D3 | Field coil |
D4 | Brush |
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The yoke sub-assembly works as an outer case of the field coil, the pole core and a passage for the magnetic force lines. Also work to produce the magnetic field required for the motor to operate. The field coil is connected in series to the coil of the armature.
4) Brush and brush holder |
E1 | Brush |
E2 | Brush spring |
E3 | Body earth |
E4 | Brush holder |
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The brushes pressed against the armature commutator by the brush springs, helps the current to flow from coil to the armature in fixed direction. The copper carbon prepared brush has excellent conductivity and abrasion resistance characteristics. By pressing brush, the brush springs presses again and again on the excessive revolution of the armature and stop armature revolution just after the starter stops.
5) Planetary reduction gear |
F1 | Drive gear |
F2 | Idler gear |
F3 | Clutch gear |
F4 | Ball bearing |
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The planetary reduction gear helps to increase the torque by transmitting the revolving force of the motor to the pinion gear.
The Planetary reduction gear which has built-in overrunning clutch also helps in reducing the revolution of the motor.
6) Overrunning clutch |
G1 | Spline shaft |
G2 | Clutch roller |
G3 | Return spring |
G4 | Clutch gear |
G5 | Pinion shaft |
G6 | Pinion gear |
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The overrunning clutch helps to transmit the motor revolution to the engine through the pinion gear.
This is a one-way type with rollers to help prevent the starter breakage by its high-speed revolution from the engine start.
7) Pinion gear and helical spline |
H1 | Spline shaft |
H2 | Pinion gear |
H3 | Ring gear |
H4 | Pinion shaft |
H5 | Helical spline |
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The pinion gear and the ring gear helps to transmit the revolving force of the starter to the engine in secure manner. The pinion gear has chamfered which is used for excellent engagement. The helical spline converts revolving force of the motor to drive force pinion and supports the engagement the disengagement of the pinion gear as well.