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| Illustration 1 | g00704074 |
Hydraulic schematic (1) Swing motor (2) Left travel brake valve (3) Large travel motor (left) (4) Small travel motor (left) (5) Right travel brake valve (6) Large travel motor (right) (7) Small travel motor (right) (8) Grapple cylinders (9) Boom cylinders (10) Stick cylinder (11) Boom lowering control valves (12) Stick lowering control valves (13) Bleeder valve (14) Grapple control valve (15) Swivel (16) Pressure switch (implement or swing) (17) Pressure switch (travel) (18) Stick drift reduction valve (19) Main control valve (20) Grapple rotate motor (21) Main relief valve (22) Grapple rotate control valve (23) Pressure switch (boom raise) (24) Generator motor (25) Case drain filter (generator) (26) Pilot control valve (travel) (27) Pilot control valve (swing or stick) (28) Solenoid valve (fine control) (29) Solenoid valve (travel speed) (30) Solenoid valve (swing priority mode) (31) Proportional reducing valve (32) Pilot oil manifold (33) Pilot control valve (boom) (34) Hydraulic activation control valve (35) Accumulator (36) Upper pump (37) Automatic travel speed change valve (38) Lower pump (39) Drain filter (40) Oil cooler (41) Bypass check valve (42) Return filter (43) Hydraulic tank (44) Pilot filter (45) Grapple rotate pump (46) Pilot pump (47) Generator pump | |
Pump Pressure
Introduction
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| Illustration 2 | g00668268 |
Pump compartment (36) Upper pump (38) Lower pump | |
This machine is driven and controlled by the following systems.
- The main hydraulic system supplies oil to the cylinders and motors of the machine.
- The pilot hydraulic system supplies oil to the control circuits.
- The electronic control system controls the output from the engine and the pump.
The main hydraulic system oil is supplied by upper pump (36) and lower pump (38). Pumps (36) and (38) are variable displacement piston pumps. Pumps (36) and (38) are identical in performance. Upper pump (36) is directly connected to the engine by a flexible coupling. Pumps (36) and (38) are mechanically connected in parallel through gears.
Gear type pilot pump (46) supplies oil to the pilot hydraulic system. Gear type pilot pump (46) is directly connected to lower pump (38) by a gear. All engine output is used to drive these three pumps.
Each of the main pumps delivers approximately 240 L/min (63.4 US gpm) of hydraulic oil at no load. The pilot pump delivers approximately 36.5 L/min (9.6 US gpm) of hydraulic oil at no load. When a load is placed on the machine, the hydraulic oil is forced into the main hydraulic circuit.
When the load increases, the main pumps increase the delivery pressure and the pumps decrease the flow rate. The hydraulic horsepower remains constant even though the oil pressure and the flow rates change. The hydraulic horsepower is approximately identical to the engine horsepower.
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| Illustration 3 | g00668265 |
Main control valve compartment (21) Main relief valve (48) Right control valve body (49) Left control valve body | |
The oil from upper pump (36) flows into right valve body (48). The oil from lower pump (38) flows into left valve body (49). Main control valve (19) is made up of right valve body (48) and left valve body (49) .
When no work is being performed, pump oil flows through main control valve (19) and into hydraulic tank (43). The main control valve sends a negative flow control signal to each main pump in order to destroke the pump to the minimum output flow.
If an operation is being performed, main control valve (19) directs pump oil to the respective cylinders (boom, grapple, and stick) and/or motors (swing and travel). Main control valve (19) contains numerous valve stems, passages, check valves, and orifices in order to carry out a single operation or a combined operation. The working pressure of the main hydraulic system is restricted by main relief valve (21). The main relief valve is set for a maximum oil pressure of 34300 kPa (4975 psi) during travel and implement operation. The relief pressure for the swing system is 24000 kPa (3500 psi). This pressure is controlled by relief valves in the swing motor.
Pilot Hydraulic System
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| Illustration 4 | g00668263 |
Cab (50) Monitor panel (51) Control lever (stick and swing) (52) Control lever (boom and bucket) (53) Travel pedal (left) (54) Travel pedal (right) (55) Engine speed dial | |
The pilot pump delivers a constant flow of oil pressure to the pilot circuit. The operating pilot pressure increases to the pilot relief valve setting of 4100 kPa (595 psi).
The pilot circuit performs the following functions:
- The pilot circuit operates main control valve (19). When control levers (51) and (52) or pedals (53) and (54) are operated, pilot oil flows to main control valve (19) through pilot control valves (26), (27), and (33). The pilot oil pressure shifts the stems in main control valve (19) in order to send the main pump oil to the required circuits. The circuits include cylinder (10), cylinders (8), cylinders (9), motor (1), motor (3), motor (4), motor (6), and motor (7) .
- The pilot circuit controls the output of pumps (36) and (38). Proportional reducing valve (31) receives an electronic signal. Proportional reducing valve (31) uses the pilot system oil to develop a hydraulic signal pressure. The hydraulic signal pressure flows to the regulators in pumps (36) and (38). The regulators control the output flow of pumps (36) and (38) .
- The pilot circuit activates the Automatic Engine Speed Control (AEC) system. This causes functions to automatically reduce the engine speed when no hydraulic operation is called for.
- The pilot circuit develops a pilot signal pressure in the pilot circuit in order to release the swing motor parking brake.
- The pilot circuit operates the straight travel control valve. This maintains straight travel during the operation of an implement.
- The pilot circuit controls the operation of the valves that can be used during a loading operation or a trenching operation.
Note: For details of the pilot control system, refer to Systems Operation, "Gear Pump (Pilot)".
Electronic Control System
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| Illustration 5 | g00668264 |
Controller compartment (56) Controller | |
The electronic control system controls the outputs from the engine and the pumps through controller (56). Controller (56) senses the position of the governor lever which is selected by engine speed dial (55). Controller (56) senses the power mode position which is selected by the power mode switch. The power mode switch is located on monitor panel (50). The controller processes the information. The controller sends a pressure signal to the pump. The pump supplies the optimum output that matches the machine loading and the engine speed.
The electronic control system has the following four major functions.
- When a large load is placed on the machine, the system allows the pumps to destroke. The system utilizes the maximum horsepower from the engine.
- The load of the machine controls the output of the pumps. The output is based on two power modes and three work modes. The machine operates at optimum efficiency which helps to reduce fuel consumption.
- When there is a very small load condition or no load condition, the system automatically decreases the engine speed. This improves the fuel consumption and this reduces the noise level.
- The system causes the activation of solenoid valve (28), solenoid valve (29), and solenoid valve (30). The activation of solenoid valve (29) changes the travel speed.
Note: For details of the electronic control system, refer to Electrical Control System, SENR9291.