Yuken Solenoid Operated Directional Valves
These valves control the flow direction in hydraulic circuits, electrically operated with manual switches, limit switches, or pressure switches. They are the most popular for use in practical hydraulic systems. Three types of solenoids are available: for direct current (DC), for alternating current (AC), and with a rectifier. The solenoids can be grouped into wet and dry types in respect to the structure. Also, the explosion-proof type is available for special purposes. The solenoid with a rectifier consists of a DC solenoid, a rectifier, and a surge absorber; therefore, it can be used for systems operated with AC power supply. This type of the solenoid is characterized by its low noise and low hydraulic shock during the operation. In addition, it assures the non-burnout feature of the coil when the spool is stuck at the half way point of its changeover.
The solenoid operated directional valves are commercially available in the following sizes: less than 1/8, 1/8, 3/8, 1/2, 3/4, and 1 1/4. Among them, the 1/8 size is most often selected for practical hydraulic systems. Figure 4.1 shows the 1/8 solenoid operated directional valve (DSG- 01), and Table 4.4 lists the major specifications of the standard and shockless types.
Aside from the maximum working pressure, flow, tank-line back pressure, and changeover frequency, performance characteristics of the solenoid operated directional valves include power consumption. The maximum flow refers to the highest flow rate free from any abnormality caused in the valve operation (changeover), and it is determined by the spool profile and service condition (connecting port, voltage, frequency, etc.). To select appropriate valves for a hydraulic system, it is best to consult with valve specifications offered by the manufacturers.
Other performance characteristics to be considered are pressure drop and changeover time. Figures 4.2 and 4.3 show the pressure drop characteristics of the standard and shockless types, respectively. The pressure drop depends on the spool profile in the valves. Table 4.5 indicates changeover time, which varies according to the solenoid type.
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