Hydraulic valve is to control and adjust the liquid pressure, flow direction and flow rate required by the hydraulic system to meet the requirements of the actuator to overcome the external load, change the direction of movement and the speed of movement, and are mainly divided into directional control valve, pressure control valve and flow control valve according to the use; According to the structure, it is divided into spool valve, ball valve and poppet valve; According to the connection method, it is divided into tube type, plate type, stacking type, and cartridge type. So should we pick the right hydraulic valve of tractor?
1. The rated pressure and rated flow of each hydraulic control valve should generally be close to its use pressure and flow. For systems with high reliability requirements, the valve should be rated much higher than its operating pressure. If the rated pressure and rated flow rate are exceeded, it is easy to cause hydraulic clamping and hydraulic force and have a negative impact on the working quality of the valve; For the sequential valves and pressure reducing valves in the system, the flow rate should not be much less than the rated flow, otherwise it is easy to produce vibration or other unstable phenomena; In the case of flow valves, attention should be paid to their minimum stable flow rate. For the system with a single piston rod hydraulic cylinder, it is necessary to pay attention to the difference in the return flow rate of the piston when it is extended and retracted: the ratio of the flow rate of the oil return without rod cavity when it is retracted and the oil return with rod cavity when it is extended, and the ratio of the effective working area of the two chambers is equal.
2. You should fully understand the instructions and requirements of the various control valves selected, so that they have the correct installation orientation in the system. For example, try to keep the check valve spool pressed vertically down on the seat to avoid jamming; The reversing spool valve should be kept in the horizontal direction of the axis as much as possible, so as to avoid the self-hanging of the valve core, electromagnet and other parts to cause reversing and resetting abnormalities; The spool of the manifold valve should be in the horizontal orientation of the axis, so as not to reduce its synchronization accuracy.
3. The structure of each valve should be reasonably selected according to the system pressure and flow rate of the system (simple or duplex?) and oil leakage method (internal leakage or external leakage?), when choosing an external leakage valve, attention should be paid to connecting the external leakage port to the oil tank separately.
4. According to the system layout and functional needs, the installation and connection methods of each valve are reasonably selected: tubular type, plate type, superimposed type, cartridge type, plate type and superimposed valve have strong versatility, the supporting valve block oil circuit is simple and clear, and the system is interchangeable and scalable; The threaded cartridge valve has a compact structure and good interchangeability (some threaded cartridge valves can also be installed superimposedly by designing the cartridge block).
5. The reversing frequency of the reversing valve cannot exceed the limit specified by the reversing time of the valve, otherwise the complete reversing process cannot be completed.
6. Because the working chamber of the armature of the wet solenoid reversing valve is directly connected with the oil return, the pressure of the oil return port T of the reversing valve cannot exceed the specified allowable value.
7. The two electromagnets of the double solenoid valve can not be energized at the same time, otherwise the coil will be heated and burned out, and the action of the two electromagnets should be interlocked when designing the electronic control system.
8. Affected by hydraulic clamping and hydraulic force, the valve above 10 bore should generally be selected hydraulic reversing valve or electro-hydraulic reversing valve, and the large flow cover cartridge valve should be selected for more than 25 bore.
9. There will be no hydraulic clamping phenomenon in the reversing process of the solenoid ball valve, it is less affected by hydraulic force, the steel ball displacement of the solenoid ball valve is small, there is no axial sealing length, the response is sensitive, the response speed is fast, and it is often used in the occasion of high pressure and high reversing frequency.
10. In order to ensure that the hydraulic check valve can be opened normally in reverse, the ratio of the opening and closing control area of the hydraulic check valve must be greater than the effective working area ratio of the rodless cavity and the rod cavity of the cylinder.
11. In the combined circuit of the hydraulic check valve and the reversing valve, the Y-type or H-type reversing valve with median function should be selected to ensure that the pressure of the control port of the hydraulic check valve can be released immediately and the check valve should be closed immediately. However, the selection of H-type median directional valve should be very cautious, because when the system flow is large, and the back pressure is too high due to other reasons such as slender oil return pipe or local blockage, the spool of the hydraulic check valve can not be reliably reset and the system malfunctions.
12. The relief valve with good pressure and flow characteristics should be selected as far as possible (the relief valve with appropriate pressure regulation range should be selected according to the system allowable, otherwise the pressure regulation deviation will increase) to improve the speed load characteristics and circuit efficiency of the actuator.
electro hydraulic valve
hydraulic valve block