ker88839_ch09.qxd
1/9/06
11:30 AM
Page 198
198
Figure 9-36.
Chapter Nine
Armature wave winding.
Figure 9-38.
A four-brush motor. (Delphi Automotive
Systems)
The magnetic field of the starter motor is provided by four or six small permanent magnets. These magnets are made from an alloy of iron and rare-earth materials that produces a magnetic field strong enough to operate the motor without relying on traditional current-carrying field coil windings around iron pole pieces. Removing the field circuit not only minimizes potential electrical problems, the use of permanent-magnet fields allows engineers to design a gear-reduction motor half the size and weight of a conventional wound-field motor without compromising cranking performance. See Chapter 9 of the Shop Manual for service and testing. Figure 9-37. The pinion gear meshes with the flywheel ring gear.
the motor field circuit, which in turn eliminates the potential for field wire-to-frame shorts, field coil welding, and other electrical problems. The motor has only an armature circuit. Because the smaller armature in permanent magnet starters uses reinforcement bands, it has a longer life than the armature in wound-field starter motors.
STARTER MOTOR AND DRIVE TYPES Starter motors, as shown in Figure 9-39 are direct-current (DC) motors that use a great amount of current for a short time. The starter motor circuit is a simple one containing just the
