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| Illustration 1 | g06186609 |
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Engine Compartment (1) Propel pump | |
The machine is equipped with single propel pump (1). The propel pump is located in the front of the engine compartment. The engine compartment cover provides access to this component.
Propel pump (1) is a variable-displacement, axial-piston pump. The propel pump is driven by the engine flywheel. The propel pump provides flow to the closed-circuit, hydrostatic-drive system.
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| Illustration 2 | g06187693 |
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Propel Pump (2) Seat switch solenoid (3) Neutral switch (4) Servo input lever (5) Forward combination valve (6) Pressure tap"MB" (7) Park brake solenoid (8) Pressure tap"MA" (9) Reverse combination valve | |
A mechanical linkage connects servo input lever (4) to the propel lever. The servo input lever controls a directional control valve inside the propel pump. The direction control valve controls the position of the pump servo. The swashplate in this pump is bi-directional.
The direction control valve also operates neutral switch (3). Neutral switch (3) ensures that the machine cannot be started when the propel lever is out of the NEUTRAL position. This switch also ensures that the parking brake cannot be released while the propel lever is out of the NEUTRAL position.
The steering pump supplies charge oil to the hydrostatic drive system. Charge oil is also used to release the parking brakes. A charge relief valve in the propel pump limits the pressure in the charge circuit to 2500 kPa (363 psi).
Note: This pressure is internal to the pump and is not measured at the pressure tap on the hydraulic filter.
The pump housing contains two combination valves. Forward combination valve (5) is on the top face of the pump. Reverse combination valve (9) is on the bottom face of the pump. The combination valves act as high-pressure relief valves, makeup valves, and bypass valves. The high-pressure relief function of the combination valves limits maximum system pressure in the forward circuit and the reverse circuit to 35000 kPa (5076 psi).
Note: This specification is for a differential pressure. Measuring pressure external to the pump will provide a measure of the relief valve setting added to the charge pressure.
The machine is equipped with two seat switches. The seat switches control seat switch solenoid (2). When the seat switch solenoid is energized, a passage is open between the two sides of the servo piston in the propel pump. In this case, the propel pump will not produce flow, regardless of the position of the propel lever. When the seat switch solenoid is not energized, the two sides of the pump servo piston are isolated. In this case, the propel lever can be used to cause the machine to move.
Park brake solenoid (7) controls the parking brake. When this solenoid is not energized, the parking brakes are engaged. When the solenoid is energized, the parking brakes are disengaged.
Pressure in the reverse side of the propel circuit can be measured at pressure tap"MA" (8). Pressure in the forward side of the propel circuit can be measured at pressure tap"MB" (6).
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| Illustration 3 | g06187695 |
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Propel Pump (10) Flushing valve | |
Flushing valve (10) is incorporated on the propel pump. The flushing valve is used to flush heated hydraulic oil from the propel circuit. The flushing valve consists of a flushing spool and a relief valve.
High-pressure circuit oil and low-pressure circuit oil act against either side of the flushing spool. The higher pressure oil moves the spool, allowing the lower pressure oil to flow across the spool. This oil acts on a relief valve. When the relief valve is open, oil flows to the pump case drain and is then directed to the oil cooler.