When you get the valve, you will find that the valve has three major components - pilot valve, valve body spool assembly, back cover assembly, as shown in Figure one. First of all, from the name to explain what is called two-position five-way pilot operated pneumatic solenoid valve. Single electric means that the valve only a pilot valve and coil assembly. Two-position means that the spool has two working positions, the spool will move left and right under the action of air pressure, without power spool stops in the position shown in Figure 2, when the spool is energized, the spool will stop in the position shown in Figure 3, so it's called two-position. Five-way means that the solenoid valve has five working holes A, B, R, P, S, which generally P for the valve inlet hole; A, B for the valve's working holes, through the connector connected to the cylinder or other pneumatic components; R, S for the valve vent, when the spool position switching to discharge the gas. Pilot valve is relative to the direct-acting solenoid valve, when the smaller power coils can not drive the spool directly to change direction, we need to increase the direct-acting solenoid valve to drive the spool movement on one or both sides of the valve body, this by increasing the direct-acting solenoid valve to realize the change of direction of the valve is called the pilot solenoid valve. Pneumatic means that the working medium is clean compressed gas. I do not know after reading the above analysis you understand what is a single electric two-position five-way pilot operated pneumatic solenoid valve?
Figure 2
After explaining the name now we come to introduce how the solenoid valve works. We do not talk about the inner workings of the pilot valve, put as a whole part, only know that when the coil is energized when it outputs thrust can move the spool of the valve is de-energized when the thrust is zero on the line.
We first say that when not energized, the spool in the reset spring and compressed air under the action of the position in Figure 2, at this time P through A, A and R disconnect, B and S through. Blue in the figure represents the working medium that is compressed air, the working medium in addition to the P to A through, from the P hole also leads to the back cover and the pilot valve, through the pilot valve to the pilot valve to provide the pilot valve with the direction of the compressed gas, through the back cover to the spool to provide power to the direction of the spool, some people will ask since there is a reset spring, why rely on the gas it? Or rely on compressed air alone? After testing to prove that, alone by the spring or compressed air is also possible, but if the design or manufacturing is not perfect, it will increase the minimum working pressure of the valve, which is equivalent to improve the conditions of use of the valve, the same environment so that it will be discarded by the customer and the market, so at present from the comprehensive cost, we are using the spring + gas reset. According to my understanding of the market many of the same type of valve working pressure range of 0.15 ~ 0.8Mpa, in fact, manufacturers in making factory testing, low pressure is generally set at 0.1Mpa or so, so that although it improves the solenoid valve manufacturing costs, but to bring convenience to customers, but also reduces the pressure on the company's after-sales.
When the pilot valve is energized, the spool under the action of the pilot valve piston to the back cover direction, this time is very short, generally 0.05 seconds must be able to switch completely, after stopping the movement, P through the B, B and S disconnect, A through the R. In this case, the A end of the air pressure and atmospheric consistency, B end of the air pressure and air inlet P consistency, the working pressure of the A and B holes to achieve switching, which is a complete commutation process. The actuators downstream of the valve such as cylinders are controlled by continuous energizing and de-energizing.
Figure 3
There are two issues to note here, the first is that in the process of spool reversal, the spool has two first closed, such as the spool has Figure 1 to Figure 2 of the transformation process, P and A closed at the same time as the B and S closed, and then the A and R pass and P and B pass; the other issue is that in order to maintain the state of the spool in the Figure 2 P and B pass and the spool, it is necessary to energize the coil all the time, and once the power is off, it automatically returns to the coil. The other problem is that in order to maintain the state of P and B and the spool in Fig. 2, the coil must be energized all the time, and once the power is cut off, it will automatically return to the P and A pass state. Design engineers must take this feature into account when designing the device, utilizing its strengths and avoiding its weaknesses.