ROLLER ASSEM. 8H3936 - Caterpillar

Illustration 1 g06036333
(1) Starter motors
Illustration 2 g03380048
Hydraulic starting motor
(2) Hydraulic motor
(3) Pinion
Illustration 3 g03380645
Hydraulic starting system diagram (typical example)
(4) Reservoir.
(5) Low-pressure filter
(6) Hand pump
(7) Control valve
(8) Hydraulic starter
(9) Soft engage valve
(10) Accumulator
(11) High-pressure filter
(12) Recharging pumpHydraulic starting motors (8) are used to turn the engine flywheel fast enough to get the engine started. When the engine is running, hydraulic pump (12) pushes oil through filter (11) into accumulator (10). Accumulator (10) is a thick wall cylinder. The accumulator has a piston which is free to move axially in the cylinder. A charge of nitrogen gas is sealed in one end of the cylinder by the piston. The other end of the cylinder is connected to hydraulic pump (12) and hydraulic starting motors (8). The oil from hydraulic pump (12) pushes the piston which puts more compression on the nitrogen gas in the cylinder. When the oil pressure gets to 20700 kPa (3000 psi), accumulator (10) has a full charge. This point the piston is approximately in the middle of the cylinder.When control valve (7) is activated, the oil is pushed from accumulator (10) by the nitrogen gas. The oil flows through hydraulic starting motors (8), the compression of the fluid is changed to mechanical energy for turning the engine flywheel.
Illustration 4 g03380681
Hydraulic Starting Motor
(13) Rotor
(14) Pistons
(15) Thrust bearing
(16) Starter pinion
(A) Oil inlet
(B) Oil outletThe hydraulic starting motor is an axial piston hydraulic motor. The lever for the starter control valve pushes starter pinion (16) into engagement with the engine flywheel. At the same time the control valve opens the way for high-pressure oil to get into the hydraulic starting motor.When the high-pressure oil goes into the hydraulic starter motor, the oil goes behind a series of pistons (14) in a rotor (13). The rotor (13) is a cylinder which is connected by splines to the drive shaft for starter pinion (16). When pistons (14) are under the force of the oil, the piston moves until the piston is against the thrust bearing (15). The thrust bearing is at an angle to the axis of rotor (13). This action makes pistons (14) slide around thrust bearing (15). As the piston slides, the piston turns rotor (13) which connects through the drive shaft and starter pinion (16) to the engine flywheel. The pressure of the oil makes pinion (16) turn fast. In turn the engine flywheel fast enough for quick starting.