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| Illustration 1 | g06131367 |
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Under Machine and Behind Hydraulic Tank (1) Axle motor (2) Planetary gear reducer (3) Axle (4) Flushing spool (5) Shift valve line | |
Axle motor (1) is located under the machine on the front side of the axle. This motor is a piston motor with two speeds. The axle motor drives axle (3) through planetary gear reducer (2). The axle is equipped with parking brakes.
The axle motor receives supply oil from and returns low pressure oil to the propulsion pump. Hydraulic oil flows through the forward and reverse circuit lines of the axle propulsion loop.
When the machine is in the high-speed range, the shift solenoid is energized. In this case, charge oil enters the propulsion motor through shift valve line (5). In the high-speed range, the propulsion motor operates at the minimum angle.
The axle motor contains a flushing valve. Flushing valve spool (4) directs oil from the low-pressure side of the axle propulsion loop to the flushing relief valve (not shown). When the pressure in the low-pressure side of the propulsion loop is greater than
The axle motor case drain line (not shown) directs oil from the axle motor case to the return manifold.
Axle motor (1) is equipped with minimum displacement limiter and a maximum displacement limiter. When the shift solenoid is not energized, the drum motor operates at maximum displacement in the working speed range. When the shift solenoid is energized, charge oil is directed into shift valve line (4). In this case, the motor operates at minimum displacement in the travel speed range.
Axle motor (1) is equipped with a speed sensor (not shown). The machine ECM uses input from this sensor and input from the drum speed sensor to calculate the actual machine speed. The machine ECM uses this input in the control logic for uncommanded movement and for propulsion system calibration.
Note: The propulsion system is controlled using open-loop logic. The machine propel calibration procedure uses the motor speed sensors to synchronize the axle and drum. From this calibration, ECM output to the pump control is determined for propulsion speed control, based on propulsion lever position and automatic speed control setting.
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| Illustration 2 | g06131372 |
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Motor Cross Section (4) Flushing spool (6) Output shaft (7) Swashplate (8) Piston (9) Barrel assembly (10) Servo piston (11) Maximum displacement limiter (12) Shuttle valve (13) Slipper pad (14) Slipper retainer (15) Minimum displacement limiter (16) Valve plate (17) Flushing relief valve | |
Axle motor (1) is an axial piston motor. The speed range of this type of motor shifts when the angle of swashplate (7) is changed. The motor can be operated against either minimum displacement limiter (15) or maximum displacement limiter (11). The motor operates at maximum displacement in the working speed range. The motor operates at minimum displacement in the travel speed range. The minimum displacement limiter or the maximum displacement limiter can be adjusted to control the minimum and maximum motor speeds.
A pressure differential between the forward port and the reverse port of the motor causes the motor to rotate. When the supply pump is not generating flow, pressure in the forward circuit and pressure in the reverse circuit is equal to charge pressure. In this case, a pressure differential does not exist, and the motor will not turn.
When the propulsion pump is generating flow, supply oil enters the motor. Supply oil is directed to the inlet port of valve plate (16). The valve plate directs oil into the piston chamber in barrel assembly (9). This pressure forces pistons (8) which are aligned with the inlet port to move out of the barrel assembly.
As pistons (8) are forced out of barrel assembly (9), the barrel assembly and pistons rotate. Since the barrel assembly is connected to output shaft (6), the output shaft also rotates.
As barrel assembly (9) rotates, pistons (8) align with the outlet port in valve plate (16). The rotation of the barrel assembly forces oil out of the piston chambers and into the low-pressure side of the hydrostatic loop. The low-pressure oil then returns to the inlet side of the hydraulic pump, which completes the hydrostatic circuit.
Oil in the high-pressure circuit acts against one side of shuttle valve (12). Oil in the low-pressure circuit acts against the other side of the shuttle valve. When the motor is operating, the shuttle valve shifts. This shift directs high-pressure oil to the shift spool in the motor.
Note: The shift spool is not shown on the above cross section.
When the propulsion system is in the low-speed condition, the shift spool blocks the high-pressure oil from shuttle valve (12). This action opens the chamber of servo piston (10) to the motor case drain. In this case, the pressure in the hydrostatic loop and the geometry of the motor cause swashplate (7) to move. The swashplate moves the servo piston, and the oil in the servo piston chamber flows into the motor case. The servo piston moves until the piston contacts maximum displacement limiter (11).
When the propulsion system is in the high-speed condition, charge oil moves the shift spool against the force of a spring. The shift spool then directs oil from the high-pressure circuit into the chamber of servo piston (10). In this case, the pressure causes the servo piston to move swashplate (7). The swashplate continues to move until the swashplate contacts minimum displacement limiter (15).
When the supply pump produces flow, oil flushes through the circuit. Oil in the high-pressure circuit causes flushing spool (4) to shift. Oil in the low-pressure circuit now flows to flushing relief valve (17).
Flushing relief valve (17) is set to open at a lower pressure than the setting of the charge relief valve in the supply pump. Therefore, during normal operating conditions the flushing relief valve opens when the supply pump is producing flow. This results in oil being flushed from the hydrostatic circuit. An orifice in the motor controls the flow rate.
Note: The orifice in the motor only allows a relatively small amount of oil from the low-pressure loop to flow into the motor case compared to the total amount of charge flow available. Therefore, even though flushing relief valve (17) opens at a pressure lower than charge pressure, because of the orifice, charge pressure only drops slightly when the machine is moving.