KIT-SHIM 4575578 - Caterpillar

Solenoid (5) - Cross Sectional View
(4) Plunger. (19) Windings. (20) Contacts. (21) Return spring.Solenoid (5) contains windings (19), plunger (4), and solenoid contacts (21). When the key switch and start relay are closed, pull-in and hold-in windings (19) are energized which moves plunger (4) and connecting shift lever (2) to the left. When solenoid contacts (20) close, full battery current is sent to the motor and the engine begins to crank.Starting Motor Operation
General Operation
The starting motor is a series wound D.C. motor. It has an integral solenoid and drive clutch. The function of the starting motor is to rotate the engine fast enough to produce combustion. This is accomplished by converting the electrical energy stored in the battery into rotational energy which drives the engine ring gear.When the key switch is activated, electricity from the electrical system causes:The solenoid to move the pinion drive assembly toward the flywheel ring gear of the engine.The pinion to rotate slowly.When the pinion has meshed with the ring gear, full battery power is applied to the motor. This is a shunt coil engagement starting motor.When the engine begins to run, the overrunning clutch section of the pinion drive prevents damage to the armature caused by excessive speeds. This is done by breaking the mechanical connection between the pinion and the armature. The pinion stays meshed with the ring gear until the key switch is released. A return spring returns the pinion drive to its rest position.Component Operation
Solenoid
The solenoid performs two functions:* It slides the pinion gear into mesh with the engine ring gear.* It makes an electrical connection between the battery and the starting motor.The result of the functions is the rotation of the starting motor and then the engine. Both of the functions are described in the Starting Operation section.Pinion Drive
Pinion Drive
(8) Overrunning clutch. (9) Pinion. (22) Rollers. (23) Outer shell. (24) Inner shell.The pinion drive contains pinion (9) and overrunning clutch (8). Overrunning clutch (8) performs two functions:* Conveying of torque from the armature to pinion (9).* Protecting the motor during engine overrun. Torque Conveying
Overrunning Clutch (8) - During Cranking
(9) Pinion. (22) Rollers. (23) Outer shell. (24) Inner shell. (25) Springs. (26) Armature shaft.The overrunning clutch (8) passes armature torque to pinion (9), which then passes the torque to the engine ring gear. As shown in the illustration, rollers (22) are wedged between outer shell (23) and inner shell (24). This provides a mechanical connection between the armature and pinion (9). Splines on armature shaft (26) connect the armature to outer shell (23). Motor Protection
Overrunning Clutch (8) - During Engine Overrun
(9) Pinion. (22) Rollers. (23) Outer shell. (24) Inner shell. (25) Springs. (26) Armature shaft.The clutch disengages armature shaft (26) from pinion (9) during engine overrun. Engine overrun occurs when the engine starts and begins to rotate faster than the starting motor. At these high rotational speeds, the armature bars and commutator segments tend to lift away from the shaft and could burst. This high speed continues until the operator