(11) Case drain outlet (12) Closed circuit loop line. (13) Closed circuit
loop line. (14) Servo pressure port.
High pressure oil enters the motor through closed circuit loop
line (12). Oil flows through port plate (5) to piston (3) in
cylinder block (1). The force of the oil pushes the piston
against swashplate (9). The piston reacts by trying to reach
maximum outward stroke. Since the swashplate is at an angle,
the piston will start to move along the swashplate. This
movement causes the cylinder, and output shaft (10), to rotate.
As the cylinder and output shaft continue to rotate, the piston
moves around the angled swashplate and piston stroke starts
to decrease. Oil is forced through the opposite side of port
plate (5) to low pressure closed circuit loop line (13).
Closed circuit loop line (13) is called a low
pressure loop line, and closed circuit loop line
(12) is called a high pressure loop line. Moving
the pump swashplate over-center in the opposite
direction causes a change in the direction of flow
in the pump and motor closed circuit loop
(FORWARD or REVERSE operation). Closed
circuit loop line (13) becomes high pressure and
closed circuit loop line (12) becomes low
pressure. A change in the direction of flow in the
closed loop circuit will cause a change in motor
direction of rotation.
Charge pressure on the low pressure side of the closed circuit
loop is routed through the motor flush valve to the motor case.
Oil from the motor flush valve enters the motor case through
the drain line. Oil circulated through the motor case serves to
cool and flush the motor.
Axle Motor Servo Control.
(4) Servo piston assembly. (9) Swashplate. (15) Spring. (16) Pin.
(17) Servo pressure port. (18) End cap.
The motor uses servo piston assembly (4) to change the
operating angle of swashplate (9). The assembly is controlled
by the pump charge pressure through the speed shift control
valve. The speed shift switch is located on the main console.
The piston is connected to the swashplate by pin (16). Servo
pressure port (17) is located in end cap (18). When the speed
shift switch is in the HIGH position, the control valve opens.
Charge oil pressure at the servo pressure port acts on the
piston and overcomes the force of spring (15). The piston
moves and causes the swashplate to rotate. In this position
the swashplate is at the minimum angle. At minimum angle,
the motor pistons have minimum stroke (displacement) and
can produce high speeds.
When the switch is in the LOW position, the control valve
closes and oil pressure to the servo pressure pod is open to
tank. Spring (15) pushes piston assembly (4) and causes
swashplate (9) to rotate. The spring holds the piston and
swashplate at the maximum angle. At maximum angle, the
motor pistons have maximum stroke (displacement) and can
produce low speeds.