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| Illustration 1 | g00798458 |
Schematic of the Main Hydraulic System (Supply Oil, Return Oil, and Case Drain Oil) (1) Extendable stick cylinder (2) Implement control valve (3) Grapple cylinder (4) Rotator (5) Stick cylinder (6) Boom cylinder (7) Swing cylinders (8) Gate horizontal cylinder (9) Boom tilt cylinder (10) Steering cylinders (11) Steering priority valve (12) Steering metering pump (13) Combination valve (14) Bogie control valve (15) Hydraulic oil tank (16) Hydraulic oil cooler bypass valve (17) Hydraulic oil cooler (18) Implement pump (19) Case drain filter (20) Left bogie float valve (21) Right bogie float valve (22) Left bogie cylinder (23) Right bogie cylinder (24) Return filter (A) Return oil to tank (B) Pressure oil to brake charging valve (AA) Pressure tap (BB) Pressure oil (CC) Return oil (DD) Case drain oil | |
Oil is drawn from hydraulic oil tank (15) by implement pump (18). The implement pump supplies pressurized oil to implement control valve (2), steering priority valve (11), combination valve (13), bogie control valve (14), and the brake charging valve. The implement pump is a variable displacement axial piston pump. The pump allows constant pressure control with load sensing.
Note: The pressure of the oil from the implement pump can be measured with pressure tap (AA). The pressure tap is located near the end of the implement control valve on the "PX" port.
The implement control valve controls the flow of pressure oil to steering cylinders (10), boom tilt cylinder (9), gate horizontal cylinder (8), swing cylinders (7), boom cylinder (6), stick cylinder (5), rotator (4), grapple cylinder (3), and extendable stick cylinder (1). The valve spools in the implement control valve are spring centered. The spools are in the closed centered position. No pressure oil will flow to the components, unless the valve spools are moved.
The pressure oil from the pump flows through the implement control valve to priority valve (11). The priority valve prevents oil from flowing to steering metering pump (12) when the steering wheel is not being turned.
The pressure oil that flows to combination valve (13) controls the differential lock, the parking brakes, the ladder, the oscillation lock, and the gate vertical cylinders. The oil flow to the hydraulic components is reduced in pressure by pressure reducing valves in each section of the combination valve. The oil flow is controlled by on/off solenoids.
The gate valve has a pressure line relief valve that is mounted between the pressure reducing valve and the manifold. The pressure line relief valve protects the gate vertical cylinders from high pressure conditions.
Pressure oil flows through the combination valve to bogie control valve (14). The bogie control valve controls the flow of oil to the bogie cylinders. When bogie float valves (20) and (21) are in the FLOAT position, the bogies will move in order to follow the terrain.
The implement control valve and the bogie control valve control the movement of the valve spools with pilot oil. The pilot oil for each control valve is created by a pilot valve in each control valve. The pilot valves reduce the pressure oil from the implement pump to pilot pressure. Proportional solenoids then control the flow of pilot oil to the valve spools.
Reference: Pressure oil flows to the brake charging valve through line (A). For more information on the brake system, refer to the Service Manual module for Systems Operation, RENR3027, "554 Forwarder and 574 Forwarder Power Train System".
Oil that returns from the steering metering pump, the combination valve, and the bogie control valve flows through return filter (24) to the hydraulic oil tank. Oil from the implement control valve returns to hydraulic oil cooler (17). The cooler reduces the temperature of the oil before entering the hydraulic oil tank.
When the temperature of the oil is low, the oil will not flow through the hydraulic oil cooler easily. When the pressure in the cooler exceeds the pressure setting of bypass valve (16) the oil flows directly to the tank. All return oil is then filtered by return filter (24) before entering the tank.
Some oil that flows through the implement pump leaks into the case. The oil is used to cool the pump and flush debris from the pump. The oil is filtered by case drain filter (19) before entering the tank.