Application of Relief Valve in Hydraulic System
(1) Pressure regulating overflow. In a hydraulic system that uses a quantitative pump to supply oil, the overflow valve is usually connected in parallel at the outlet of the hydraulic pump, and a throttle valve or a speed control valve is set on its oil inlet or return path to allow a part of the pump oil to enter the hydraulic cylinder to work , and the excess oil must flow back to the oil tank through the relief valve, and the relief valve is in a normally open state under its set pressure. Adjusting the compression force of the spring also adjusts the working pressure of the system. Therefore, in this case, the role of the relief valve is to regulate the relief. As shown in Figure 1(a).
(2) Security protection. When the hydraulic system uses a variable pump to supply oil, there is no excess oil in the system that needs to overflow, and its working pressure is determined by the load. At this time, the overflow valve connected in parallel with the pump needs to be opened only when it is overloaded, so as to ensure the safety of the system. Therefore, the overflow valve in this system is also called a safety valve, which is normally closed, as shown in Figure 1(b).
(3) Unload the pump. As shown in Figure 1(c), the pilot-operated relief valve plays the role of pressure regulation and relief for the pump. When the electromagnet of the two-position two-way valve is energized, the external control port of the overflow valve is connected with the fuel tank. At this time, because the main valve spring is very soft, the main valve core can be lifted quickly when the inlet pressure is very low, so as to unload the pump and reduce energy consumption. At this time, the pump is close to no-load operation, and the power consumption is very small, that is, it is in an unloaded state. The two-position two-way valve used in this unloading method can be a valve with a small diameter. Since this unloading method is often used in practice, the overflow valve and the electromagnetic reversing valve connected in series to the external control port of the valve are often combined into one component, which is called an electromagnetic overflow valve.
(4) Remote pressure regulation. When the external control port (remote control port) of the pilot relief valve is connected with the relief valve (or remote pressure regulating valve) with lower pressure regulation, the oil pressure in the upper chamber of the main valve core only needs to reach the adjustment pressure of the low pressure valve. , the main spool can be lifted to overflow (its pilot overflow valve no longer plays the role of pressure regulation), that is, to realize remote pressure regulation. As shown in Figure 1(d), when the electromagnet of the solenoid valve is energized, the right position of the solenoid valve works, and the external control oil port of the pilot relief valve is connected with the low-pressure pressure regulating valve to realize remote pressure regulation.
(5) Used as a back pressure valve. The overflow valve connected to the oil return line of the hydraulic cylinder can generate resistance to the oil return, that is, form a back pressure, and use the back pressure to improve the movement stability of the actuator.
