HARNESS-BATTER 6U0909 - Caterpillar

Illustration 1 g01013593
Air starting system (typical example)
(1) Relay valve
(2) Hose
(3) Starting motor solenoid
(4) Hose
(5) Air starting motor
Illustration 2 g01192361
Air starting motor
(6) Air inlet
(7) Vanes
(8) Rotor
(9) Pinion
(10) Reduction gears
(11) Piston
(12) Piston spring When the main supply of pressurized air is ON, pressurized air is provided to relay valve (1). The main supply of pressurized air is blocked by the relay valve. The relay valve allows some control air pressure to flow through hose (2) from the bottom of the relay valve to another valve that is connected to starting motor solenoid (3).When the normally closed starting motor solenoid is activated for start-up, the solenoid opens the connected valve. The valve allows the control air pressure to flow behind piston (11) inside air starting motor (5).The control air pressure pushes the piston. The piston compresses piston spring (12) and the piston moves the drive shaft for pinion (9) outward in order to engage the pinion with the flywheel ring gear. The starting motor does not crank the engine yet.After the pinion is engaged with the flywheel ring gear, a port in the starting motor is opened in order to allow the control air pressure to flow through hose (4) to the top of relay valve (1). The relay valve opens in order to allow the main supply of pressurized air to flow through the starting motor's air inlet (6).The pressurized air causes vanes (7) and rotor (8) to rotate. The rotor uses reduction gears (10) to rotate the drive shaft for the pinion and the pinion rotates the flywheel in order to crank the engine.When the engine starts to run, the flywheel will begin to rotate faster than the pinion. The design of the drive shaft for the pinion allows the pinion to move away from the flywheel. This prevents damage to the air starting motor, to the pinion, and to the flywheel ring gear.When the engine control senses the crank terminate speed, starting motor solenoid (3) is de-energized. The solenoid closes the attached valve and the control air pressure is removed from piston (11). Piston spring (12) retracts the piston, the drive shaft, and pinion (9).The retraction of piston (11) closes the passage for the control air pressure to relay valve (1). The relay valve closes in order to shut off the main supply of pressurized air to the starting motor.