Study*-010-Solenoid Valve

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1.1 Solenoid valve 1, Basic diagrams of solenoid valves: From left to right and from top to bottom, they are as follows – Direct-acting types: 2/2 way, 2/3 way normally open, 2/3 way normally closed; Pilot-operated types: 2/2 way, 2/3 way normally open, 2/3 way normally closed, 2/5 way with single control, 2/5 way with dual control; 3/5 way with central seal, 3/5 way with central drain, 3/5 way with medium pressure. The “number of positions” refers to the number of operating states that the valve has; it can be determined by counting the squares representing the valve body in the diagram (with arrows or T-shaped lines inside). And the “several crossings” referred to later represent the number of points on one of the squares (the points where it intersects with the arrow lines and T-lines); that number is what constitutes the “several crossings”. The meanings of graphic symbols are generally as follows: 1. Boxes are used to indicate the operating position of the valve, with the number of boxes indicating the number of \"positions\"; 2. Arrows inside the boxes indicate that the oil path is connected, but the direction of the arrows does not necessarily reflect the actual direction of fluid flow; 3. The symbols \"┻\" or \"┳\" inside the boxes indicate that the corresponding path is closed; 4. The number of connections outside the box indicates the number of \"paths\"; 5. Generally, the inlet for oil/gas supply connecting the valve to the system’s oil/gas supply path is denoted by the letter P, while the outlet for oil/gas return connecting the valve to the system’s oil/gas return path is denoted by t (sometimes o). The oil/gas ports connecting the valve to the actuator are denoted by letters such as A and B. Sometimes, the letter l is used on graphic symbols to indicate the oil leakage port. 6. Important: Analysis of the normal position of solenoid valves – Directional control valves have two or more operating positions, one of which is the normal position, that is, the position when the valve spool is not under any acting force. I feel the description here is inaccurate; theoretically, the valve core is subject to three forces: the elastic force of the spring, the magnetic force of the electromagnetic coil, and the air pressure from the pilot valve ； Under normal conditions, if the spring returns to its original position, the valve spool is not subjected to any elastic force. Moreover, the electromagnetic coil is not powered under normal conditions, so there is no electromagnetic force either. Without this electromagnetic force, if the pilot valve does not open, the pressure from the air supply cannot act on the valve spool, and the valve spool is thus not affected by the air supply pressure ； Thus, it is said here that the position of the valve core when no operating force is applied is its normal state. If the spring in this normal state has not fully returned to its original position, then the valve core should still be under the influence of the spring’s force; however, this is not important, as the elastic force always acts to return the valve core to its normal position. If the spring fails, the valve core is likely to fail to return to its proper position, resulting in leakage in the normal operating state. In the graphic symbols, 【Median】 represents the 【normal position of the three-way valve】. A two-position valve that uses spring return has the path state [within the box adjacent to the spring] as its [normal position]. When drawing a system diagram, the oil/gas lines should generally be connected to the normal position of the directional control valve. Automatic control instruments