The hydraulic pressure relief valve refers to the three parts of the upper small diameter cylindrical surface, the middle large diameter cylindrical surface and the lower cone surface of the main valve core. It is necessary to keep concentric with the inner hole of the valve cover, the inner hole of the valve body, and the cone surface of the valve seat. Three (or three levels) concentric. The relief valve must ensure that the three parts are concentric, making the processing more difficult; if the assembly is not good, the valve cover hole will jam the main spool if it is installed slightly, causing problems such as poor operation of the relief valve; the opening and closing characteristics are not as good as the two concentric valves . Because the overflow valve appeared earlier than the two-section concentric valve, the market occupies a large amount.
The so-called two-section concentric relief valve means that the cylindrical surface and the conical surface of the main spool must be concentric, which reduces the processing difficulty. Together with the appearance of the cartridge valve, the cartridge unit can be used with the cartridge valve, which has good versatility, exchangeability and repairability; the stability of the valve is also good.
The function of hydraulic pressure relief valve
There are two types of hydraulic pressure relief valves: direct-acting (direct-acting) and pilot-operated. The relief valve ensures that the pressure in the hydraulic system is a certain value by overflowing a part of the oil to the tank, and avoids system overload, pressure relief, Pressure limiting effect. The function of the overflow valve in the hydraulic system is: Stabilize the output pressure of the metering pump: In the hydraulic system of the quantitative pump source, the overflow valve 2 has the effect of regulating, limiting and overflowing to avoid system overload: the variable pump is used as the power source In the hydraulic system, the flow of pump 1 can generally be changed with the load, and there will be no residual flow. Only when the pressure exceeds a certain pre-set pressure, the overflow valve 2 will open the overflow, so that the system force will no longer increase. , To avoid the system pressure overload and the safety maintenance effect, the relief valve at this moment is called the safety valve to unload the pump: from the long-distance pressure regulating port of the relief valve 2 to the two-position two general closed electromagnetic directional valve 3, the electromagnet is off When the power is on, the valve 3 is in the cut-off position, the long-distance control port is closed, and the overflow valve 2 has a normal overflow effect. When the electromagnet is energized, the valve 3 is in the direction of the passage, the long-distance control port is connected with the fuel tank, the overflow valve 2 is in the unloading condition, and the long-distance pressure regulation: connect the oil inlet of the long-distance pressure regulating valve and the remote control port of the main overflow valve 2 Connection, complete long-distance pressure regulation within the set pressure range of the main relief valve, multi-stage control: use the three-position four-way solenoid valve for the remote control port of the main relief valve and two long-distance pressure regulators with different opening pressures 4 , 5 connection, can complete the high and low pressure three-stage pressure control, used for the brake of the hydraulic motor.
Operation principle of hydraulic pressure relief valve
In a hydraulic system with high pressure and large flow, when the electromagnetic relief valve is switched from a high-pressure condition with a load to an unloaded condition with a primary load, the time from power-on to power-off of the electromagnet is only a few tens of milliseconds. In a short period of time, the high pressure drops to low pressure, the energy is released sharply, and then large pressure shocks, oscillations and noise occur. Such shocks, oscillations and noises often cause serious obstacles under high pressure and large flow conditions. In order to avoid the occurrence of this situation, an electromagnetic overflow valve with a buffer valve can be used. The buffer valve can extend the time from the high pressure to the pressure relief process, so that the pressure can drop steadily, and the occurrence of shock, oscillation and noise can be avoided.
Adjust the adjusting screw, you can change the spool stroke and the tension spring pre-compression force, you can change the unloading time. When the adjusting screw is all loosened, the opening of the mouth and the tension spring pre-compression force are the smallest, and the unloading time is the longest; vice versa. The time is the shortest, and it does not have the effect of unloading the buffer at all.
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