Study on dynamic characteristics, noise analysis and noise reduction of Manifold Block relief valve
Manifold block relief valve is an important pressure control and adjustment element in servo hydraulic system, and it is also one of the main noise sources in hydraulic system. According to the current investigation data, the biggest noise source besides the hydraulic pump is Manifold block relief valve. This noise not only directly endangers people’s emotions, health and the surrounding environment, but also affects the working performance of the hydraulic system, shortens the service life of itself or other hydraulic components, and reduces the reliability of products. Even lead to servo energy function failure. At present, many relief valve products have put forward the noise index requirements. Therefore, the vibration and noise of Manifold block relief valve are studied, the dynamic characteristics and the internal noise are analyzed
In relation, it is of great significance to find ways to reduce and eliminate noise.
The noise of Manifold Block hydraulic system is divided into mechanical noise and fluid noise. Mechanical noise is mainly caused by the vibration of mechanical parts. Fluid noise is caused by pressure and flow pulsation, cavitation and cavitation, vortex movement, sudden change of high and low pressure, fluid friction and other reasons. For the relief valve, the mechanical noise is mainly caused by the self-excited oscillation of the mass-spring system of the pilot valve or the main valve, mainly including the following two cases:
1. Self-excited vibration noise
The valve core of Manifold block relief valve is supported on the spring. When the mass of spring (including the elasticity of oil), the damping hole of relief valve and related parameters matching with the load exceed the critical value of stability, the valve core will produce continuous self-excitation vibration and abnormal noise due to the disturbance of other parts. The vibration is related to the shape and size of the pilot valve and the main valve of the relief valve, and the machining accuracy of the pilot valve, the main valve and the seat will also affect the occurrence of such noise. The higher the temperature of the oil, the lower the viscosity of the oil
The more likely it is to happen. General pilot valve close to the opening pressure is the most easy to vibration, and bring the corresponding vibration of the main valve.
2. Resonance noise
Resonance noise is the result of high-order harmonic resonance between the spring mass system of relief valve and the pressure pulsation of hydraulic pump and other equipment. This resonance can sometimes cause the spool to hit the seat, producing a strong noise. This paper mainly analyzes the dynamic and modal characteristics of a relief valve from the perspective of stability, especially its stability. Then the frequency spectrum of the valve noise is analyzed to find out the internal relationship between the dynamic characteristics and the noise.
Preliminary study on noise reduction
In general, according to experience, when the relief valve is found to whistle, the muffler or muffler screw can be first considered to change its natural frequency, followed by the method of reducing the volume of the front cavity of the pilot valve core. The AMESim simulation analysis shows that the gain margin of the relief valve is small. In order to improve its stability, the method of increasing the damping effect of the inlet is adopted to reduce the system stiffness, so as to try to reduce the natural frequency and noise.
Based on the dynamic stability of the relief valve and the modal analysis of the frequency characteristics, the natural frequency of the more complex relief valve model is found out, and the spectrum characteristics are studied with the noise test. The stability margin of the relief valve is improved by optimizing, and the natural frequency is reduced, so as to achieve the goal of reducing the noise. The test results show that increasing the oil inlet sleeve in the front cavity of the main valve can improve the damping effect of the inlet of the main valve and basically eliminate the frequency noise of about 1000Hz. It should be pointed out that there are many factors contributing to the noise of the relief valve, and it is not enough to analyze the stability and frequency spectrum only through simplified mathematical model, but also to fully consider the related factors of the hydraulic system. Such as the working pressure and flow of the equipment, the viscosity of the oil, cleanliness, oil temperature, the oil circuit is normal, and other factors.