Hydraulic Valves Basic Working Principle

A component used in a hydraulic drive to control liquid pressure, flow, and direction. One of the control pressure is called the pressure control valve, the control flow is called the flow control valve, controls the passage and the flow direction as the direction control valve.

Pressure control valve: according to the use of overflow valve, pressure relief valve and sequence valve. (1) relief valve: can control the hydraulic system to achieve the set pressure to maintain a constant state. A relief valve for overload protection is called a safety valve. When the system fails, the pressure rises to the limit may cause damage, the valve port will open and overflow to ensure the safety of the system. (2) pressure reducing valve: can control the branch circuit to get lower than the main circuit pressure pressure. The pressure relief valve according to its control of the pressure function is different, but also can be divided into constant pressure valve (output pressure is constant) ﹑ differential pressure reducing valve (input and output pressure difference is set) and the ratio of pressure reducing valve (Input and output pressure to maintain a certain proportion). (3) sequence valve: can make an implementation of components (such as hydraulic cylinders, hydraulic motors, etc.) after the action, and then in order to make other actuators action. The pressure generated by the pump first to promote the movement of the hydraulic cylinder 1, while the inlet valve through the sequence of action on the area A, when the hydraulic cylinder 1 is fully completed, the pressure increases, the role of the area of the upward thrust greater than the spring Value, the spool up so that the inlet and outlet port connected to the hydraulic cylinder 2 movement.

Flow control valve: the use of regulating the spool and the valve body between the throttle area and the local resistance generated by the flow to adjust, so as to control the speed of the actuator. The flow control valve is divided into five types according to its application. (1) Throttle: After adjusting the orifice area, the moving speed of the actuator with little change in load pressure and less uniformity of movement is basically maintained. (2) speed control valve: in the load pressure changes can keep the throttle valve inlet and outlet pressure for the fixed value. In this way, after the throttle area is set, regardless of how the load pressure changes, the governor can keep the flow through the throttle constant, thus stabilizing the speed of the actuator. (3) diverter valve: regardless of the size of the load, can make the same oil source of the two actuators are equal flow equal to the diversion valve or synchronous valve; get proportional flow proportional distribution valve. (4) the flow of the valve: the role of the opposite with the diversion valve, so that the flow into the flow of the proportional distribution of the valve. (5) shunt flow valve: both flow distribution valve and the two functions of the collector.

Directional control valve: according to the use of one-way valve and valve. Check valve: only allows the fluid in the pipeline in one direction, reverse that cut off. Reversing valve: change the relationship between the different pipe ﹑ ﹑ ﹑ according to the valve body in the valve body in the number of working positions divided into two, three, etc .; according to the number of channels controlled by the two links, three links, Five pass, etc .; according to the spool drive way manual, mobile, electric, hydraulic and so on. Figure 2 for the three four-way valve works. P is the oil supply port, O is the return port, and A is the output port leading to the actuator. When the spool is in the middle position, all the port cut off, the implementation of the component does not move; when the spool moved to the right position, P and A, B and O through; when the spool to the left position, P and B Pass, A and O pass. In this way, the implementation of components can be positive and reverse movement.

Hydraulic valve basic working principle: the use of spool in the valve body relative movement to control the valve opening and closing and the size of the valve port to achieve pressure, flow and direction control; and flow through the valve port and the valve port before and after the pressure difference And the valve port area, always meet the pressure flow equation.