In the four-way function of the electro-hydraulic directional valve, to achieve the median function, must rely on external forces to maintain the valve core in the middle position. The common way is to rely on the valve core both ends of the reset (on the center) spring or hydraulic oil pressure to achieve.
The most commonly used alignment of electro-hydraulic directional valve is spring alignment. In electro-hydraulic directional control valve should be installed at each end of the main valve core has the same specifications of the spring, when the electromagnetic directional valve electric, electric hydraulic valve start reversing, oil pressure, the side of the valve core to the compression side of the spring, when the electromagnetic directional valve and electricity control electro-hydraulic directional control valve main valve core movement of oil pressure is released, the main valve core under the action of spring force, back to the original position.
It is important to note that the spring-reset electro-hydraulic directional valve provides for the minimum pressure to control the pressure oil. Below this minimum control pressure, the main valve core will not complete the reversing.
Spring on the structure of simple, most of the median function of the electro-hydraulic valve are using spring on the center or reset design. But the spring-back electro-hydraulic directional valve has its limitations. Litian electro-hydraulic directional valve has its maximum flow standard. If the rated flow is exceeded, the working efficiency of the electro-hydraulic directional valve will be affected, or even the directional cannot be reversed, leading to failure. In this case, the spring alignment is often prone to problems. When the reversing action of the electro-hydraulic directional reversing valve ends and it needs to be reset to the middle position, the spring at the end position will push the valve core to reset. But if the flow through at this time is too large, it can produce enough force to offset the spring on the valve core reset. The valve core of the electro-hydraulic reversing valve remains in the original reversing state, thus causing the failure. And the use of hydraulic pressure on the valve core, it can relatively avoid this problem, so that the use of electro-hydraulic valve in excess of the rated flow is large still can complete the conversion.
However, in general, considering the service life of electro-hydraulic directional valve, temperature rise of hydraulic oil, working stability and other factors, the rated flow rate of electro-hydraulic directional valve must be greater than the actual working flow rate when selecting the type. Force field electro - hydraulic commutator valve of the median function is different, its rated flow will change.