AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

gears engage and when the engine kicks back due to ignition. When the engine starts
and runs on its own power, the ring gear drives the pinion at a higher speed than does
the starter. This action causes the pinion to turn in the opposite direction on the
threaded sleeve and automatically disengages from the ring gear. This prevents the
engine from driving the starter.
The OVERRUNNING CLUTCH (fig. 2-39) provides positive meshing and demeshing
of the starter motor pinion gear and the ring gear. The starting motor armature shaft
drives the shell and sleeve assembly of the clutch. The rotor assembly is connected to
the pinion gear which meshes with the engine ring gear. Spring-loaded steel rollers are
located in tapered notches between the shell and the rotor. The springs and plungers
hold the rollers in position in the tapered notches. When the armature shaft turns, the
rollers are jammed between the notched surfaces, forcing the inner and outer members
of the assembly to rotate as a unit and crank the engine.
Figure 2-38.- Starting motor with a Bendix drive.
Figure 2-39.- Typical overrunning clutch.
After the engine is started, the ring gear rotates faster than the pinion gear, thus
tending to work the rollers back against the plungers, and thereby causing an
overrunning action. This action prevents excessive speed of the starting motor. When
the starting motor is released, the collar and spring assembly pulls the pinion out of
mesh with the ring gear.
AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 45/ 101