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| Illustration 1 | g00932856 |
Location of the Piston Motor | |
The piston motor is mounted on the transfer gearbox for the front axle.
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| Illustration 2 | g00925677 |
(1) Control Valve (Motor Displacement) (2) Solenoid valve (3) Adjusting screw (4) Output shaft (5) Sliding valve plate (6) Barrel assembly (7) Control piston (8) Synchronizing shaft (9) Spherical rolls (10) Piston (11) Pilot bearing (12) Tapered roller bearing (13) Shuttle valve (14) Charge pressure relief valve | |
The piston motor is a variable displacement piston motor.
The piston motor is operated by high pressure oil from the piston pump.
The direction of rotation of the piston motor determines the travel direction of the machine. The speed of the piston motor determines the input speed of the drive shaft.
The minimum capacity of the motor can be limited within a standard range by adjusting the angle of the swashplate. The angle of the swashplate can be changed by adjusting screw (3) .
Oil flow through the piston motor can be in either direction. A change to the direction of oil flow changes the direction of rotation of barrel assembly (6), pistons (10), and output shaft (4) .
The piston motor is continuously variable by changing the placement of sliding valve plate (5) .
The angle between barrel assembly (6) and output shaft (4) can be adjusted between 32° and 6°.
As the angle of sliding valve plate (5) decreases, the output speed increases. When the angle of sliding valve plate (5) increases, the output speed decreases.
The position of sliding valve plate (5) regulates the speed of the piston motor at a constant flow from the piston pump.
The sliding valve plate (5) is connected to the control piston (7). Servo pressure controls the position of control piston (7).
The synchronizing shaft (8) and spherical rolls (9) ensure that the rotation of output shaft (4) and barrel assembly (5) are synchronized. The spherical heads of each piston (10) run in pilot bearings (11). The pilot bearings (11) are pressed into the output shaft (4). No other parts are used to connect the pistons (10) with output shaft (4). The output shaft (4) is supported by two taper roller bearings (12) .
Loop Flushing Function
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| Illustration 3 | g00924596 |
(13) Flushing valve (14) Charge pressure relief valve (15) End cap | |
A flushing valve (13) and charge pressure relief valve (14) provide the loop flushing function in order to purge excessive contamination in the high pressure circuit.
Oil from the low pressure side of the drive loop flows through the flushing valve (13) and the charge pressure relief valve (14). The purge flow removes any contaminants in the drive loop.
The purge flow also removes the hot oil from the drive loop. The purge flow exits the motor through the case drain line. The purge flow passes through the oil cooler before returning to the hydraulic oil tank.
The purging of the system also influences the pressure setting of charge pressure relief valve (14). If the pressure in charge pressure relief valve (14) is set high the flow in the system will be reduced. During the operation of the closed circuit, this action will allow the flow in the system to increase through the charge pressure relief valve in the pump. A lower setting in the charge pressure relief valve (14) will allow the purge flow to increase. This will result in an increase in pressure in the motor housing.
A correct combination of the setting for the pump charge pressure and the setting for the motor charge pressure should be maintained in order to ensure the proper function of the loop flushing circuit.
Control Valve (Motor Displacement)
The control valve (motor displacement) (1) regulates the control pressure of the system in the multi-functional block module for the capacity of the motor. The control valve (motor displacement) (1) depends on the high pressure in the system. If the high pressure remains below the control pressure of 18000 kPa (2611 psi), the adjusting unit is maintained in the position for minimum motor capacity. If the high pressure exceeds the pressure setting, the effect of the high pressure on the adjusting unit cause the motor capacity to increase.
An increase in the high pressure through the set pressure at the control valve (motor displacement) (1) leads to an increase in the capacity of the motor. Resulting in a increase in the motor output torque and a corresponding reduction in the speed of the output shaft (4) .
A solenoid valve (2) is also mounted on the control valve (motor displacement) (1). If 12 Volts are applied to the solenoid valve (2) the motor will remain at maximum capacity. This will allow the lower speed range of 8 km/h (5 mph) to be made possible.