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| Illustration 1 | g00710932 |
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Rest position (1) Return spring (2) Solenoid assembly (3) Pull-in winding (4) Start terminal "S" (5) Hold-in winding (6) Battery terminal "Bat" (7) Key start switch (8) Solenoid contacts (9) Motor terminal "Mtr" (10) Shift lever assembly (11) Field winding assembly (12) Pinion drive assembly (13) Pinion gear (14) Armature assembly (15) Battery (16) Flywheel ring gear | |
A DC Series wound motor is used as the starting motor. The starting motor has a field winding assembly (11) and armature assembly (14). The excitation and armature windings are connected in series. The pinion end of the armature shaft has splines for the pinion drive assembly (12).
The solenoid assembly (2) is an integral part of the starting motor. The solenoid energizes pulling on the plunger assembly and on the shift lever assembly (10). The shift lever will then push the pinion drive assembly (12) which will engage the pinion gear (13) onto the flywheel ring gear (16). After the key start switch (7) has been released and the solenoid contacts (8) have been opened, the return spring (1) will return the plunger assembly, the pinion drive assembly, and the shift lever assembly to the rest position .
The starting motor has a two-stage mechanical pinion drive assembly (12) that protects the armature assembly (14) from an overspeed condition. The pinion drive assembly is held on the splines of the armature shaft. The pinion gear (13) is connected to the pinion drive assembly through the teeth of the overrunning clutch. The shift lever assembly (10) moves the pinion drive assembly axially in the direction of the flywheel ring gear (16).
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| Illustration 2 | g00711161 |
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Partial engagement (1) Return spring (2) Solenoid assembly (3) Pull-in winding (4) Start terminal "S" (5) Hold-in winding (6) Battery terminal "Bat" (7) Key start switch (8) Solenoid contacts (9) Motor terminal "Mtr" (10) Shift lever assembly (11) Field winding assembly (12) Pinion drive assembly (13) Pinion gear (14) Armature assembly (15) Battery (16) Flywheel ring gear (17) Brush | |
When the key start switch (7) is closed, battery current will flow in two directions. Current will flow from the battery (15) through the switch. From the switch, the current will flow through the hold-in winding to ground. The current will also flow from the switch through the following components to ground: pull-in winding (3), field winding (11), armature (14) and brushes (17). The activation of the pull-in winding (14) and the hold-in winding (12) produces a magnetic force. The magnetic force will pull the plunger (10) to the right. The plunger will pull the shift lever which will compress the return spring (1). The shift lever will push the pinion assembly along the armature shaft toward the flywheel ring gear (16).
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| Illustration 3 | g00711192 |
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Blocked engagement (1) Return spring (2) Solenoid assembly (3) Pull-in winding (4) Start terminal "S" (5) Hold-in winding (6) Battery terminal "Bat" (7) Key start switch (8) Solenoid contacts (9) Motor terminal "Mtr" (10) Shift lever assembly (11) Field winding assembly (12) Pinion drive assembly (13) Pinion gear (14) Armature assembly (15) Battery (16) Flywheel ring gear | |
The pinion gear (13) may meet a tooth of the flywheel ring gear (16) as the pinion gear tries to move forward. The other drive components will continue to be pushed forward. The helical spline of the overrunning clutch portion of the pinion drive assembly (12) rotates the pinion gear in the cranking direction. The spring of the pinion drive assembly is being compressed. The pinion tooth will slide past the tooth on the flywheel ring gear until the next gap is found. The pinion gear will then engage onto the flywheel due to the pressure that is built up in the compressed spring. At the same time, the overrunning clutch rotates in the overspeed direction.
The pinion gear may also meet a damaged ring gear tooth or a notched ring gear tooth. While the pinion drive assembly (12) is being pushed forward, the armature assembly (14) is being rotated in the opposite direction. This is due to the helical spline. The spring of the Pinion drive assembly is also becoming compressed. Due to the forces that are being applied to the drive components onto the damaged tooth, the starting motor current may not have force enough to turn the armature. The starting attempt must be stopped. When the key start switch is released, the pinion drive assembly will release the compression of the spring. This will cause the pinion gear to rotate. The pinion gear is now ready to mesh with the flywheel ring gear. The starting attempt can now be retried.
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| Illustration 4 | g00711193 |
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Full engagement (1) Return spring (2) Solenoid assembly (3) Pull-in winding (4) Start terminal "S" (5) Hold-in winding (6) Battery terminal "Bat" (7) Key start switch (8) Solenoid contacts (9) Motor terminal "Mtr" (10) Shift lever assembly (11) Field winding assembly (12) Pinion drive assembly (13) Pinion gear (14) Armature assembly (15) Battery (16) Flywheel ring gear | |
When the pinion gear (13) meshes completely with the flywheel ring gear (16), Solenoid contacts (8) close. Full battery voltage is then applied to the battery terminal "Bat" (6) and the motor terminal "Mtr" (9). Starting motor current will then energize the field winding (11) and the armature (14). The pull-in winding (3) will become de-energized. The hold-in winding (5) will still have enough force to hold in the plunger assembly until the solenoid contacts (8) are open. The starting motor starts to crank the engine with full torque.
As soon as the engine starts, the flywheel ring gear (16) turns the pinion gear (13) faster than the starting motor's normal speed. The overrunning clutch (6) breaks the mechanical connection between the two gears. The pinion gear turns on the helical spline which will compress the spring in the pinion drive assembly. The pinion gear will then be pulled from the flywheel gear. Flyweights also help to break the mechanical connection between the two gears. This process must take place in order to prevent the starting motor from being rotated at speeds higher than maximum permissible speed. When the key start switch (7) is released, the shift lever assembly and pinion drive assembly will return to the rest position. The solenoid contacts open and the starting motor turns off. The rotating armature is quickly stopped by a mechanical brake disc.