MOTOR GP-PSTN 3516344 - Caterpillar

Illustration 1 g01274998
(1) Main input port
(2) Charge oil line
(3) Shuttle spool
(4) Flushing Valve
(5) Relief valve
(6) Case drain
(7) Speed sensor for the piston motor
(8) Swashplate
(9) Control piston
(10) Main input port
(11) Signal oil
(12) Valve spool All wheel drive piston motors (AWD piston motors) are a variable displacement axial piston motor. Motor displacement is controlled by the AWD ECM in order to provide optimum speed and optimum torque for all conditions. Up to gear 4F or gear 3R, the motor is typically at maximum displacement. Above gear 4F or gear 3R, the motor operates at a lower displacement that is determined by the AWD ECM. When the ratio of the front motor speed to the engine speed is below 75 percent, the front motor is operating at maximum displacement. In this range below 75 percent, the front motor ratio is controlled by the pump swashplate angle only. When the ratio of the front motor speed to the engine speed is above 75 percent, the pump is operating at maximum displacement. In this range above 75 percent, the front motor ratio is controlled by reducing the angle of the motor swashplate only.Five lines are connected to each motor:
Two high-pressure lines to main ports (1) and (10)
Signal oil (11)
One case drain line (6)
One charge pressure line (2)Oil is supplied to the AWD motors by the AWD piston pumps. The direction of the motor rotation is controlled by the oil flow direction from the piston pumps. Motor displacement is regulated by valve spool (12). Valve spool (12) is controlled by the proportional solenoids that are located in the AWD control valve and by the spring.During low speed operations in the forward direction, the valve spool (12) is being held in position (B) by the spring. Charge oil is allowed to flow to the left side of control piston (9). The charge oil keeps control piston (9) to the right at the maximum displacement.During high speed operations, signal oil (11) from the AWD valve will cause valve spool (12) to shift. Valve spool (12) will shift to a position that is balanced by the force of the spring. The control piston (9) follows the position of valve spool (12). If valve spool (12) shifts to the right, position (A) is selected. The shift of valve spool (12) provides oil flow that moves control piston (9) to the right until control piston (9) is aligned with valve spool (12). The shift of control piston (9) causes a decrease in the displacement of the motor. If spool (12) shifts to the left, position (B) is selected. The shift of valve spool (12) provides oil flow that moves control piston (9) to the left until control piston (9) is aligned with valve spool (12). The shift of control piston (9) causes an increase in the displacement of the motor.In the forward direction, high-pressure oil flows to main input port (10). The high-pressure oil acts on the end of shuttle spool (3). The high-pressure oil shifts the shuttle spool to