MAST AR 0341152 - Caterpillar

Illustration 1 g01393695
Piston Motor (Typical Illustration)
(1) Drive shaft
(2) Motor housing
(3) Port for flushing
(4) Retaining plate
(5) Piston
(6) Stop for the minimum displacement
(7) Head
(8) Control plate
(9) Stop for the maximum displacement
(10) Spring
(11) Barrel
(12) Center pin The piston motor ( hydrostatic) is a variable displacement piston motor. The motor converts hydraulic power into mechanical power through the transmission. Power is then sent to the front and rear axle.The actuator piston controls the motor displacement by changing the angle of the rotating group relative to the output shaft. As the stroke of the pistons increases, the stroke creates a higher torque and a lower speed. As the stroke of the pistons decreases, the stroke creates a lower torque and a higher speed. Control plate (8) has two 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 through the control slot in control plate (8). 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 drive shaft (1) by retaining plate (4). Seven pistons (5) are held by barrel (11). The barrel rotates around center pin (12), which is at an angle to the axis of drive shaft (1). As pressure oil enters the cylinders and pressure oil exits the cylinders, the seven pistons move in the cylinders and out of the cylinders. The movement of the cylinders rotates the pistons, the barrel, and the drive shaft.As the pistons, the barrel and the drive shaft continue to rotate, the piston reaches the top center (fully retracted position). At the same time, the cylinder begins to overlap the control slot in control plate (8) on the low-pressure side of the loop. The piston starts to move down. The down movement of the piston pushes oil out of the cylinder through the control slot to the low-pressure loop.The motor bearings receive lubrication from port (3) and cooling oil from port (3). The remaining internal components are lubricated by oil leakage from the pistons and barrel.