PLATE 2G3986 - Caterpillar

Illustration 1 g02413516
Schematic of the hydraulic fan motor
(1) Fan motor inlet
(2) Hydraulic fan motor
(3) Fan motor outlet
(4) Check valve
(5) Case drain
Illustration 2 g02413517
Piston motor (Hydraulic fan)
(1) Inlet
(2) Hydraulic motor
(3) Outlet
(4) Makeup valve Pressurized oil from the hydraulic fan pump flows to the hydraulic fan motor through fan motor inlet (1). The high-pressure oil causes piston movement within the rotator. The pistons cause the rotator and the motor shaft to rotate. The oil exits hydraulic fan motor (2) through fan motor outlet (3).
Illustration 3 g02413577
Section View of the Piston Motor
(5) Outlet passage
(6) Rotator
(7) Spring
(8) Piston
(9) Case drain
(10) Valve plate
(11) Inlet passage
(12) Shoe
(13) Swashplate
(14) Drive shaft High-pressure oil enters the hydraulic motor through fan motor inlet (1). The high-pressure oil flows from inlet (1) through the port in valve plate (10). The high-pressure oil flows through inlet passage (11). The high-pressure oil initiates a force against the piston (8). The force against piston (8) pushes the piston out of rotator (6). The pistons that are pushing out of rotator (6) will push shoe (12) against swashplate (13). The force of the pistons causes the shoes to slide on swashplate (13). The shoes will follow the path of least resistance and slide toward the greater angle. The movement of the shoes will initiate the rotation of rotator (6). As rotator (6) turns, spring (7) holds rotator (6) against valve plate (10). As the rotator turns, the oil will be held between the piston and the rotator.As the shoes follow the decreasing angle of swashplate (13), the piston starts to move back into the rotator. When rotator (6) rotates over outlet passage (5), the oil will be pushed out of the rotator. The low-pressure oil will flow out of the motor through the port in valve plate (10) to fan motor outlet (3).Oil that has leaked within the pump cavity will flow out of the motor through case drain (9). The case drain allows oil that is for lubricating the components to return to the hydraulic tank.The amount of torque that is developed by the motor will depend on the following conditions: force of the piston, piston circle radius and the angle of the swashplate.
Illustration 4 g02413578
(4) Check valve The piston motor is equipped with a makeup valve. The makeup valve allows oil exiting the motor to return to the inlet during a reduction of flow from the pump or a complete shutdown. If the pressure at outlet line (3) is higher than the pressure in inlet line (1), oil will open check valve (4). The oil will flow through check valve (4) and back to inlet (1). The makeup valve eliminates cavitation of the fan motor (3) during reduced oil flow. The return oil from hydraulic fan motor (2) is used as makeup oil to prevent a vacuum condition in inlet (1). This condition happens when the fan slows and/or the fan stops. When the hydraulic fan pump slows down, the supply of oil to fan motor (2) is reduced. Motor (2) continues rotating because