CDM816D WHEEL LOADER
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Fig. 3-5 Schematic Diagram of Hydraulic Steering System
(i) Working principle of steering system
The pressure oil from oil pump first flows into the pilot valve which distributes oil flow to steering gear
preferentially no matter how high or low the load, pressure and steering wheel speed are, or whether
the engine is idling or running at high speed, so as to ensure sufficient oil supply for steering and
stable and reliable steering actions. When the engine is running at high speed or not steering or
steering slowly, the pilot valve will supply the remaining oil to the working device hydraulic system.
The one-way valve installed on the full hydraulic steering gear inlet pipe is used to prevent the oil in
steering cylinder from flowing back into the flow amplifying steering gear, resulting in steering kickback.
When turning the steering wheel right, the oil flows into the small chamber of steering cylinder through
steering gear to make the loader turn right; on the contrary, when turning the steering wheel left, the oil
flows into the large chamber of steering cylinder through the steering gear to make the loader turn left.
If the system pressure exceeds 16 MPa when a wheel encounters an obstacle or the wheels are
turned to limit positions, the safety valve in pilot valve will be opened to unload and the oil returns into
the oil tank to prevent the system against overload.
(ii) Structures & performances of main components
(1) YXL-F160L-N7 pilot valve
Nominal pressure: 16MPa
Nominal flow: 160L/ min
Working principle:
When the steering gear is set at neutral position, the oil from pilot valve partly flows to LS port through
the orifice in the steering gear and acts on one side of pilot valve core, and partly flows through the
control port in the pilot valve core and acts on the other side (PP port). The pressure at pilot valve PP
port shall be greater than that at LS port and the elastic force of the spring, under the action of the
pressure at PP port, only a small amount of oil flows into the steering gear through CF port and the
remaining oil from the steering pump flows into the working device hydraulic system through EF
port.
When the steering gear moves away from the neutral position, the pressure at LS port increases and
the pilot valve core moves toward PP port under the action of elastic force, so as to supply the oil from
steering pump to the steering gear and meet the steering requirements.
(2) BZZ5-315 steering gear
Nominal pressure: 14MPa
Theoretical output: 315ml / r
Working principle:
When the steering gear does not work, the oil from it flows to the oil inlet of steering gear valve body
through the pilot valve, and the oil partly flows to the rear of the valve core through the thermal balance
port between the valve core and valve sleeve and then to the oil return hole of the steering gear
through the hole in the valve core and finally to the oil return tank. The remaining oil flows to the ring
移至
P48
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