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| Illustration 1 | g00487468 |
(1) Steering control (2) Hydraulic displacement control valve (3) Steering filter (4) Line to the charge circuit for the implement hydraulic system (5) Bypass valve (6) Diverter valve (7) Multifunction valve (8) Line to the charge circuit for the transmission hydraulic system (9) Charge relief valve (10) Steering motor (11) Steering pump (12) Tandem charge pump (13) Drive gear for the steering pump (14) Internal charge pump (15) Common sump (16) Regulator valve (17) Suction screen (18) Line from implement hydraulic system (19) Line for lubrication oil for the differential (BB) Oil from the small section of the tandem charge pump (EE) Charge oil (FF) Oil from the large section of the tandem charge pump (LL) Drain oil | |
The steering hydraulic system shares common sump (15) with the implement hydraulic system. Oil from both systems is filtered through 250 micron screen (17) before the oil enters the hydraulic system.
The steering hydraulic system is a high pressure closed loop system. The steering hydraulic system consists of the following main components:
- Steering pump (11)
- Steering motor (10)
- Steering control (1)
- Diverter valve (6)
- Common sump (15)
- Steering filter and bypass valve (3)
- Tandem charge pump (12)
Tandem charge pump (12) produces two separate flows from common sump (15) .
The smaller section of the tandem charge pump produces oil flow for the following components: the transmission, the transmission control valve, the brakes and the power take-off (PTO).
Note: The smaller section of the tandem charge pump is the section that is closest to the steering pump.
The large section of the tandem charge pump produces low pressure oil for the implement hydraulic system and for the steering hydraulic system. The steering oil flows through the filter and bypass valve (3) to steering pump (11) and the inlet for internal charge pump (14) .
Internal charge pump (14) provides higher pressure oil for the steering hydraulic system. The higher pressure oil protects steering pump (11) from cavitation. Also, the internal charge pump helps provide a quick steering response.
Oil flow from internal charge pump (14) is used in several places. The oil flow is routed to the steering control for use as pilot oil for hydraulic displacement control valve (2) .
In the inside of the steering pump, internal charge pump (14) provides oil flow to multifunction valve (7) in order to keep the closed loop system full of oil.
Charge oil that is not used in the circuit is relieved over a charge relief valve. The oil from the charge relief valve is directed to the pump case. Then, the oil flows through the case drain lines to the differential steering unit. The oil is used for lubrication. Finally, the oil returns to common sump (15) .
Steering control (1) regulates the pressure and the direction of the oil that is sent to steering pump (11). Hydraulic displacement control valve (2) controls the direction and the angle of the tilt of the swashplate.
Diverter valve (6) reverses the oil flow from the steering control when the machine is operated in reverse. The reverse oil flow gives the machine a conventional steering response.
Oil flow from steering pump (11) flows to steering motor (10). Steering motor (10) is a bidirectional fixed displacement motor. The steering motor converts oil flow and pressure from the steering pump into speed and torque. The speed and the torque are delivered to the differential steering unit.
Oil flow from steering pump (11) causes a clockwise rotation or a counterclockwise rotation of steering motor (10). The steering motor turns the input gear to the differential steering unit. This causes the machine to turn. The direction of the turn and the speed of the turn are controlled by the direction of the rotation and the speed of the steering motor.