Hydraulic valves


The main function of a hydraulic valve is to control the pressure, flow, and direction of the liquid in the hydraulic system. Specifically, hydraulic valves play the following key roles in the hydraulic system:

1. Pressure control: pressure control valves, such as relief valves, pressure reducing valves, sequential valves, etc., can maintain or regulate the pressure in the system. For example, a relief valve is used to set the maximum pressure of the system, and when the system pressure exceeds the set value, the relief valve opens to allow excess oil to flow back to the tank, thus protecting the system from excessive pressure.

2. Flow control: flow control valves, such as throttle valves, speed control valves, etc., can regulate the flow of liquid in the system. By controlling the flow rate, speed control of hydraulic actuators (e.g. cylinders, motors) can be realized. For example, installing a throttle valve at the inlet of the cylinder can change the flow rate of oil entering the cylinder by adjusting the opening of the throttle valve, thereby controlling the speed of movement of the cylinder.

3. Direction control: Directional control valves, such as check valves, reversing valves, etc., can control the flow direction of liquids in the system. For example, by changing the position of the spool, the reversing valve can realize the switching of the oil circuit, so that the liquid flows to different actuators, so as to realize the reversing movement of the actuators.


In addition, hydraulic valves can also be used with sensors, controllers and other devices to achieve more complex control functions, such as synchronous control, position control, speed control, etc. By selecting and combining hydraulic valves, it is possible to build a hydraulic system that meets a variety of needs.


Hydraulic valves achieve the function of pressure control through their internal spools and control devices. Specifically, the pressure control function of the hydraulic valve can be achieved in the following ways:

1. Balance between spring force and liquid pressure: There is usually a spring inside the pressure valve (such as the relief valve), which interacts with the liquid pressure. When the system pressure rises, the liquid pressure acts on the spool in an attempt to push the spool open. At the same time, the spring exerts a reverse force in an attempt to push the spool back into place. When these two forces are balanced, the spool remains in a stable position, thus controlling the pressure of the system.

2. Manual adjustment: For some hydraulic valves, the position of the spool can be adjusted by manual knob or rod. This can change the pressure setpoint of the system by changing the preload of the spring or adjusting the gap between the spool and the seat.

3. Automatic adjustment: In more complex hydraulic systems, self-regulating pressure control valves may be used. These valves are usually equipped with pressure sensors and controllers. The pressure sensor monitors the pressure of the system in real time and transmits the pressure signal to the controller. The controller automatically controls the pressure of the system by adjusting the position of the spool through electrical or hydraulic signals according to the preset pressure range and adjustment algorithm.

4. Feedback control: In some advanced hydraulic systems, feedback control will also be used to achieve more accurate pressure control. The feedback control system reduces the difference between the actual pressure and the set pressure and adjusts the position of the spool accordingly. This method of control allows for faster and more accurate pressure regulation.


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