ENGINE AR 4P8980 - Caterpillar

Illustration 1 g02735326
Piston motor 1 shown. Piston motor 2 has flushing valve block attached opposite of proportional solenoid.
(1) Drive shaft
(2) Motor case
(3) Port
(4) Retainer
(5) Piston
(6) Minimum displacement screw
(7) Head
(8) Proportional solenoid
(9) Control lens
(10) Spring
(11) Barrel
(12) Pivot pin The piston motors convert hydraulic power into mechanical power. The piston motors are mounted to the transmission. The piston motors are infinitely variable and controlled by proportional solenoid valves (8) in the head.The following components rotate within the piston motor:
Drive shaft (1)
Retainer (4)
Pistons (5)
Barrel (11)The following components do not rotate with the piston motor:
Motor case (2)
Head (7)
Control lens (9)Spring (10) pushes barrel (11) against control lens (9). Pressure from spring (10) creates a high-pressure seal between barrel (11) and control lens (9) and between control lens (9) and head (7).Control lens (9) has two oil control slots. One control slot is for the high-pressure loop. The other control slot is for the low-pressure loop.When the high-pressure oil is at the high-pressure loop port, oil from the port flows to the control slot in control lens (9). Oil in the control slot flows into the cylinders of barrel (11) that are over the control slot.The spherical piston heads are held in the sockets in the drive shaft (1) by retainer (4). Seven pistons (5) are held by barrel (11). Barrel (11) rotates around pivot pin (12) which is at an angle to the axis of drive shaft (1). The seven pistons move in and out of the cylinders as pressure oil enters the cylinders and pressure oil leaves the cylinders. This movement forces the pistons, the barrel, and the drive shaft to rotate.While the pistons, the barrel and the drive shaft continue to rotate, piston (5) reaches the fully retracted position. At the same time, the cylinder begins to overlap the control slot in control lens (9) on the low-pressure side of the loop. The piston starts to move back into barrel (11). As piston (5) moves back into barrel (11), piston (5) pushes oil out of the cylinder. The oil is pushed through the control slot to the low-pressure side of the loop.The motor bearings receive oil for lubrication and for cooling from the charge pump. The oil flows from the charge pump through port (3) to the motor bearings. The internal components other than the bearings, get lubrication oil from normal leakage from pistons (5) and from barrel (11).