First, the working principle of the pilot valve
The pilot valve is composed of an electromagnet for a wet valve, a valve core, a transmission plunger, a valve sleeve, a thimble rod, a steel ball, a steel ball seat, a return spring and the like. The valve core and the valve body are threadedly connected. One end of the driving plunger is connected to the electromagnet armature, and the other end is against the steel ball. Therefore, no matter the thrust of the upper electromagnet or the force of the lower spring, the two steel balls and the thimble rod are in a linked relationship. There is a circular control cavity between the two ends of the thimble rod and the valve core, and they are respectively connected with the radial holes on the valve core. This is a two-position three-way two-ball normally closed solenoid valve. When the solenoid is de-energized, the pressure oil entering from the P cavity directly acts on the ball seat of the pilot valve, and the elastic force of the return spring also acts on the ball seat in the same direction, so that the lower valve port of the pilot valve is closed and the upper valve port is opened. Therefore, the pressure oil passage and the control oil passage A are blocked, and the control oil passage and the oil return passage T are opened. In this case, the control oil circuit is in an unloading state; when the electromagnet is energized, the transmission plunger pushes the upper steel ball to move downward, the upper valve port is closed, and the lower valve port is opened. Therefore, the passage of the control oil passage and the return oil passage is blocked, and at the same time, the pressure oil passage and the control oil passage are opened. The pressure oil enters the oblique hole of the valve body through the control volume of the pilot valve, so that the control oil circuit is in a working state.
Second, the characteristics of the pilot valve
(1) A pilot control liquid bridge is formed with the fixed liquid resistance, and the main valve or the secondary valve or the variable lever is controlled according to the input signal.
(2) The flow of the first-stage pilot valve is generally only about 1 liter / minute and 3 liters / minute. The flow of the second-stage pilot valve must be determined according to actual needs.
(3) The input signals are relatively small.
(4) Can accept a variety of input methods, such as manual, electric, hydraulic, pneumatic, mechanical cam, electrical ratio, etc.
(5) In the case of variable pump control, a variety of pilot valves form a modular structure, and a variety of functions are convenient to choose from.
(6) The pilot valve itself is often a small size control valve, mostly a pressure control valve.
