Small Displacement Change Operation
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| Illustration 1 | g01109281 |
Travel motor (partial diagram) (1) Displacement change valve (2) Piston (3) Spring (4) Piston chamber (5) Swashplate (6) Passage (7) Passage (8) Port (supply oil or return oil) (9) Shuttle valve (10) Port (supply oil or return oil) (11) Passage (12) Pilot line (pilot system oil pressure) (13) Passage (14) Spring | |
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| Illustration 2 | g01109329 |
Small displacement change operation (1) Displacement change valve (2) Piston (3) Spring (4) Piston chamber (5) Swashplate (6) Passage (7) Passage (8) Port (supply oil or return oil) (9) Shuttle valve (10) Port (supply oil or return oil) (11) Passage (12) Pilot line (pilot system oil pressure) (13) Passage (14) Spring | |
When the travel speed control switch on the control panel is pushed and the rabbit appears on the display, the machine is in HIGH SPEED MODE. In this condition, an input signal from the travel speed control switch is sent to the engine and pump controller. The pressure sensor for the pump delivery also provides an input signal to the engine and pump controller. When the travel load is light and when the pump delivery pressure is below a certain level, the output signal from the pressure sensor for the pump delivery is below a certain level. When the pump delivery pressure is below a certain level, the engine and pump controller de-energizes the travel speed solenoid. When the travel speed solenoid is de-energized, pilot system oil stops flow into pilot line (12) of displacement change valve (1). Displacement change valve (1) moves to the left with the force of spring (14). Oil flows from passage (10) of the travel motor through shuttle valve (9). The main pump oil is blocked by displacement change valve (1). Spring (3) moves piston (2) away from swashplate (5). As a result, the angle of swashplate (1) is decreased and the motor displacement is decreased.
Large Displacement Change Operation
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| Illustration 3 | g01109341 |
Large displacement change operation (1) Displacement change valve (2) Piston (3) Spring (4) Piston chamber (5) Swashplate (6) Passage (7) Passage (8) Port (supply oil or return oil) (9) Shuttle valve (10) Port (supply oil or return oil) (11) Passage (12) Pilot line (pilot system oil pressure) (13) Passage (14) Spring | |
When the angle of swashplate (5) in the travel motor increases, the displacement of the travel motor increases. The angle of swashplate (5) in the travel motor will increase and the travel speed will decrease during the following two conditions.
- The angle of swashplate (5) in the travel motor will increase and the travel speed will decrease when an increase in pump pressure occurs.
When the machine is in HIGH SPEED MODE and the pump delivery pressure increases above a certain level, the engine and pump controller energizes the travel speed solenoid. When the travel speed solenoid is energized, pilot system oil flow into pilot line (12) of displacement change valve (1). Displacement change valve (1) moves to the right against the force of spring (14). Main pump oil flows from passage (10) of the travel motor through shuttle valve (9). The main pump oil then flows through displacement change valve (1) into piston chamber (4). The oil in piston chamber (4) moves piston (2) against swashplate (5). The angle of swashplate (5) increases. The oil in piston chamber (4) flows through passage (6) and passage (8). Passage (8) flows to the hydraulic tank. As the angle of swashplate (5) increases, the displacement of the travel motor increases and the travel speed decreases.
- The angle of swashplate (5) in the travel motor will increase and the travel speed will decrease when the travel speed control switch is pushed in order to obtain LOW SPEED MODE.
When the travel speed control switch on the control panel is pushed and the tortoise appears on the display, the machine is in LOW SPEED MODE. In this condition, an input signal from the travel speed control switch is sent to the engine and pump controller. The engine and pump controller energizes the travel speed solenoid. The angle of swashplate (5) increases and the displacement of the travel motor increases. The travel speed decreases.