Figure 2 (a) shows the offload circuit using three four-wire electromagnetic swap valves, with a medium function of m. The back-to-back system is a high-pressure high-flow system, with a larger pressure shock when switching to the valve. In addition to m, the median of the three valves is type h and type k. Such circuits are generally used for hydraulic systems with low pressure (less than 2. 5 mpa), small flow (less than 40 l/min), and are a simple and effective method of offloading。
For high-pressure, high-flow hydraulic systems, when the export pressure of the pump is changed from high to almost zero pressure, or from zero pressure quickly to high pressure, a hydraulic shock is inevitable when switching to the valve. The hydraulic shock was also forced to increase because of the rapid switch to the electromagnetic valve without buffer time。
Three four electromagnetics to the valve
Change three electromagnetic valves to electron valves
Figure 2 (b)
The transition time from the liquid to the fluid valve in the valves has been time-modifiable and the shift to a buffer period has led to a change in the pressure of the pump's exports rising or falling, increasing the smoothness of the switch and thus avoiding a clear pressure shock。
The function of a one-way valve in the circuit is to keep a pressure value (0. 2-0. 3mpa) for pump discharges for control of the circuit。
The above analysis applies mainly to the machine-bed hydraulic system, which does not allow hydraulic shocks, and any small impact affects the processing accuracy of the parts。
For engineering mechanical hydraulic systems, which are generally high-pressure, high-flow systems, the valves are more m-type, so why not have hydraulic shocks? This is due to the fact that, in the hydraulic system of engineering machinery, the switch valves are generally manual and the buffer when switching to the switch valves is performed by the operator. The valve switch to the valve is also a throttle, and the manipulator, when manipulating the handle, should gradually open or close the valve to avoid a hydraulic shock。
Hydraulic pumps should be offloaded by the working body of the hydraulic system during the interval between the cessation of work and the operation of the payload, or even if the hydraulic pump is operating under almost zero pressure. This reduces power consumption, reduces system heat and prolongs the useful life of hydraulic pumps. Hydraulic systems with a general power greater than 3 kw shall have offload function。
