Structure and working principle

The automatic pressure switching valve is mainly composed of an adjusting screw plug, an adjusting spring, a control valve core and a valve body.

Connect the low-pressure test instrument to the P1 port of the valve, the high-pressure instrument to the P2 port, and the pressure oil source to the P port.

When the switching valve is working, the control valve core 4 is simultaneously subjected to the hydraulic pressure F1 acting on the A1 surface due to the pressure oil entering the valve chamber, the hydraulic pressures F2 and F3 acting on the A2 surface and the A3 surface, and the spring force Ft generated by the spring compression.

Since once the structural dimensions of the switching valve are determined, F1, F2 and F3 are only proportional to the hydraulic oil working pressure p, these three forces can be simplified into one force Fy.

Fy＝C.p

Where C is constant

Spring force:

　　Ft＝K.Δx

The equilibrium equation of K-spring stiffness force can be written as:

Fy－Ft＝0

Therefore, a relationship between pressure p and spring deformation Δx can be established:

Δx＝A.p

Where A is a constant related only to the structure size and spring stiffness of the automatic pressure switching valve.

From this formula, it can be seen that the displacement of the control valve core Δx is directly proportional to the working pressure p of the oil entering the valve cavity. That is to say, when the system pressure reaches a certain level (the switching pressure set by the adjustment spring), Δx is also large enough, and the control valve core moves to cover the P1 port, cutting off the oil supplied from P1 to the outside, thus protecting the low-pressure pressure gauge. The maximum displacement of the control valve core can be limited, and the relationship between the control valve core and the P1 port is positive covering to prevent the control valve core from excessive displacement.