Coaxial (Sliding Gear) Starter Motor

Similar to the axial starter motor, the coaxial starter motor moves the pinion into engagement under reduced power and when it is fully meshed only then full power is applied. The main difference lies in the method of sliding the pinion into mesh with the ring gear. Instead of the whole armature assembly moving axially, in this type a solenoid mounted coaxially with the shaft in a housing moves only the pinion for engagement.

The main details of the circuit of a coaxial starting motor are shown in Fig. 15.30. The main terminal is connected directly to the battery and the terminal marked ‘sol’ is connected to the battery through the drivers starter switch. When this switch is operated, the two-stage solenoid is energized, which moves the pinion into mesh and also closes the first set of contacts, the second set is kept open by trip lever. During this period, a resistor limits the current to the main field, so the armature rotates slowly. Just before reaching the fully meshed position between the pinion and ring gear, a lever trips the second set of contacts. This action by-passes the resistor, and supplies full current to the main field so that the motor produces its maximum torque.


Fig. 15.31. Actions of coaxial starter.
A. At rest position. B. Cranking position.
C. Engaging position. D. Over-speed position.

The actions of one type of Lucas CAV motor are presented in Fig. 15.31. This design uses four steel balls, which lock the pinion sleeve to the shaft to avoid premature rejection of the pinion during spasmodically firing of the engine. When the engine starts and operates on it own, over-speeding of the motor is prevented by the centrifugal action of a set of steel balls placed adjacent to the locking balls. When a pre-set speed is reached, the centrifugal force on the balls moves the locking collar outward and allows the pinion to disengage. A return spring positioned at the flywheel end of the armature shaft helps pinion disengagement and holds the pinion clear of the flywheel during running of the engine.

In Bosch sliding-gear motors the main solenoid is installed at the opposite end of the motor to the pinion. This solenoid holds the pinion in full engagement position until the driver releases the starter switch. Drive from the armature to the pinion is transmitted by a multi-disc clutch. This clutch limits the torque to be transmitted and hence prevents over speeding of the motor by releasing the plates and slipping when the engine is started. Some motors have a shunt field winding, which limits the no-load speed and others use a brake winding that comes into action when the driver releases the starter switch.




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Heavy Vehicle Starter Motors

An engine with a capacity of more than 3 L requires a large starting motor, specifically for a compression-ignition (CI) engine. CI engines must be cranked at a speed of at least 100 rpm to initiate combustion. Due to a very high compression ratio in CI engines, the maximum torque required is greater than a petrol engine.

The high pressure in the cylinder accelerates the piston rapidly during its downward movement. This causes considerable variation of both the rotation­al speed and the resisting torque loading on the starter motor.

To achieve high starting power heavy vehicles normally use a 24 V system. For a given electrical power requirement, the doubling of the voltage compared with a 12 V systems, reduces the current by half. Without the extra 12 volts, the current load on the battery and starter circuit becomes exceptionally high, especially on a cold morning in winter. Another problem associated with large engines is the requirement of high torque to overcome breakaway and inertia of the heavy parts. It also needs a strong drive system and the pinion of this system must be fully meshed with the ring gear before the motor is fully powered. Two types of motor and drive system in use are axial (sliding armature), and coaxial (sliding gear).

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Global Automotive Starter Motor and Alternator Market

Global Automotive Starter Motor and Alternator Market: Overview

The research study analyzes the automotive starter motor and alternator market on global basis and provides estimates in terms of revenue (USD million) from 2015 to 2024. It describes the market dynamics affecting the industry and analyzes their impact through the forecast period. Moreover, it highlights the significant opportunities for market growth in the next eight years.

A starter motor in an automobile is one of the most vital components. It is an electric motor, which ignites the engine to start. It comprise of direct current electric motor and a starter solenoid. The starter motor is powered by the battery of the car and to turn over the engine, it requires very high electric current, which comes from the battery. On the other hand, automotive alternators are components in automobiles, which charges the battery and powers the electrical systems when the engine is running.

Global Automotive Starter Motor and Alternator Market: Regional Outlook

Asia Pacific, Middle East and Africa, and Latin America are key markets for the future and are expected to provide huge opportunities to the global automotive Cummins starter motor and alternator manufacturers because of the growth in the automotive sector and increasing demand for passenger vehicles in the regions. Moreover, in the past five years, there has been an increasing production of vehicles globally because of the rising demand and usage of passenger vehicles. This in turn is driving the demand and growth of starter motors and alternators used in the production of automobiles.

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