(1) Integral structure.
Compared with the split multi-way directional valve structure, it avoids the shortcomings of sealing between valve plates, easy leakage and easy deformation at the connection, so the internal leakage of the integral multi-way valve is less; The integral multi-way valve adopts precision casting, and the pressure loss and energy loss of the flow channel are less than those produced by chip machining.
(2) Two levels of safety protection.
The main safety valve is installed on the main oil circuit of P1 and P2 pumps to avoid overload of the main pump, protect the hydraulic system and realize primary protection; Boom linkage valve, bucket linkage valve and stick linkage valve are also equipped with safety valves to avoid overload of each actuator and realize secondary protection.
(3) Confluence function.
The multi-channel valve of Hitachi excavator can realize the confluence of large and small cavities of bucket hydraulic cylinder, large and small cavities of stick hydraulic cylinder and large cavities of boom hydraulic cylinder. PL and P2 pumps supply oil to one actuator at the same time, and the combination of two pumps greatly improves the working efficiency of the excavator.
(4) Regeneration function.
During the operation of the excavator, the working device is frequently released and retracted. When the boom and stick are released, the hydraulic energy is transformed into the potential energy of the working device. When they are retracted, the potential energy is transformed into hydraulic energy. In the original multi-way valve, a one-way throttle valve is often set on the oil return path of the large cavity of the boom cylinder and the small cavity of the stick cylinder to limit the overspeed decline of the working device due to its own weight. The throttling generates more heat and reduces the efficiency of the hydraulic system. The multi-channel valve sets a regeneration circuit in the return oil of the large chamber of the boom cylinder and the small chamber of the stick cylinder, which recovers the potential energy and reduces the heating of the system at the same time; The efficiency of the working device is improved and its overspeed reduction is avoided [2].
(5) Positive flow control.
Compared with negative flow control, positive flow control has good operational sensitivity. Figure 2.5 shows the schematic diagram of sampling points of positive and negative flow control systems. It can be seen from figure 2.5A) that negative flow control collects the pressure signal at the outlet of the main control valve, which means that the control of variable displacement pump always lags behind the control of the main control valve, and the negative pressure signal will be generated only when the main control valve acts, Change the displacement of the pump. Fig. 2.5B) is a schematic diagram of signal sampling points 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 displacement pump and the main control valve at the same time to complete their actions synchronously. This is the main reason for "good operational sensitivity of positive flow control compared with negative flow control". In addition, compared with negative flow control, positive flow control is more energy-saving. The generation of negative pressure signal requires a pressure of 5 ~ 6Mpa; The positive flow control system is only the return oil back pressure of about 0.5MPa, which reduces unnecessary power loss and fuel consumption.
(6) Swing priority.
During the combined action of swing and stick light load retraction, the swing valve and stick valve are connected in parallel, and the swing start load is very large. In order to give priority to ensuring the swing speed, the stick retraction return oil circuit throttling measures are adopted to increase the return oil pressure, so as to increase the pressure in the large cavity of the stick cylinder, that is, the oil inlet circuit pressure of the cylinder increases, so that the pressure oil acts on the swing valve first, Realize swing priority control.
(7) Boom, stick locked.
Both the large chamber of boom cylinder and the small chamber of stick cylinder are equipped with locking valves. When the boom valve and stick valve are in the neutral position, the boom and stick can be locked to prevent the boom and stick from falling naturally due to their own weight.
