(1) Integral structure.
Compared with the split-type multi-way directional valve structure, it avoids the shortcomings of the need to seal between the valve pieces, easy leakage, and easy deformation of the connection, so the internal multi-way valve has less internal leakage; and the integrated multi-way valve Using precision casting, the flow channel produces less pressure loss and less energy loss than the split-machined flow channel [20].
(2) Two-level security protection.
The main safety valve is installed on the main oil path of the P1 and P2 pumps to avoid overload of the main pump, protect the hydraulic system, and achieve first-level protection; the boom joint valve, bucket joint valve, and stick joint valve are also equipped with safety valves , To avoid overloading of each implementing agency, to achieve secondary protection.
(3) Confluence function.
The Hitachi excavator multi-way valve can realize the combination of large and small bucket hydraulic cylinders, large arm hydraulic cylinders, small cavity and boom hydraulic cylinders. Pl and P2 pumps simultaneously supply oil to an actuator, and the combination of double pumps greatly improves the working efficiency of the excavator.
(4) Regeneration function.
The working device is frequently released and retracted during the operation of the excavator. When the boom and arm are released, the hydraulic energy is converted into the potential energy of the working device. When they are retracted, the potential energy is converted into hydraulic energy. In the original multi-way valve, a one-way throttle valve was often installed in the large cavity of the boom cylinder and the small cavity of the arm cylinder to limit the overspeed drop of the working device due to its own weight. The efficiency of the hydraulic system is reduced. The multi-way valve is provided with a regeneration circuit in the large chamber of the boom cylinder and the small chamber of the stick cylinder to recover the potential energy while reducing the system heating; improving the efficiency of the working device and avoiding its overspeed decline 2].
(5) Positive flow control.
Compared with the negative flow control, the positive flow control has good operation sensitivity. Figure 2.5 is a schematic diagram of the sampling points of the positive and negative flow control systems. From Figure 2.5a), it can be seen that the negative flow control collects the pressure at the outlet of the main control valve. Signal, which means that the control of the variable pump has been lagging behind the control of the main control valve. Only when the main control valve is activated will a negative pressure signal be generated to change the displacement of the pump. Figure 2.5b) is a schematic diagram of the signal sampling point of the positive flow control system. It can be seen that the positive flow control system collects the pilot secondary pressure of the main control valve, and the signal is sent to the variable pump and the main
Control valve, so that the two actions are completed synchronously. This is the main reason why "positive flow control is more sensitive to operation than negative flow control." In addition, compared to negative flow control, positive flow control is more energy efficient. The generation of negative pressure signal requires a pressure of 5-6MPa; while the positive flow control system is only a back pressure of about 0.5MPa, which reduces unnecessary power loss and reduces fuel consumption.
(6) Rotation priority.
In the compound action of swing and stick light recovery, the swing valve and the stick valve are connected in parallel, and the load of the swing start is large. In order to ensure the speed of the swing, the measure of throttle return to the oil return path is adopted to increase the oil return pressure. The pressure in the large cavity of the stick cylinder is increased, that is, the pressure in the oil inlet of the cylinder is increased, so that the pressure oil preferentially acts on the rotary valve, and the rotary priority control is realized.
(7) The boom and stick are locked.
The large cavity of the boom cylinder and the small cavity of the arm cylinder are equipped with locking valves. When the boom valve and the stick valve are in the neutral position, the boom and the stick can be locked to prevent the boom and the stick from causing natural weight. Down 20.
