Since the vibration and noise of the hydraulic system are inevitable, and in recent years, with the development of hydraulic technology in the direction of high speed, high pressure and high power, the noise of the hydraulic system has become increasingly serious, and has become a factor hindering the further development of hydraulic technology. If it exceeds 70dB, it will become noise, which makes people feel extremely uncomfortable, and even makes people restless. As pollution, noise has been paid more and more attention by people. Therefore, it has positive and far-reaching significance to study and analyze the mechanism of hydraulic noise and vibration, thereby reducing and reducing vibration and noise, and improving the performance of hydraulic system.

Mechanical noise is caused by contact, impact and vibration between parts.

① Unbalance of the rotating body

In the hydraulic system, the electric motor, hydraulic pump and hydraulic motor all rotate at high speed. If their rotating parts are unbalanced, periodic unbalanced force will be generated, causing bending vibration of the rotating shaft, resulting in noise. This vibration is transmitted to When the fuel tank and pipeline make a loud noise, in order to control this noise, the rotor should be subjected to a precise dynamic balance experiment, and attention should be paid to avoid the resonance area as much as possible.

② Motor noise

Motor noise mainly refers to mechanical noise, ventilation noise and electromagnetic noise. Mechanical noise includes low frequency noise caused by rotor imbalance, high frequency noise caused by defective bearings and improper installation, and noise caused by resonance between the motor bracket and the motor. The control method is that the bearing should be properly matched with the motor housing and the motor shaft, the interference should not be too large or too small, the holes on the two ends of the motor should be coaxial, and the bearing should be well lubricated.

③Coupling causes noise

The coupling is the connecting mechanism between the hydraulic pump and the electric motor. If the electric motor and the hydraulic pump are not coaxial so that the coupling is skewed, vibration and noise will be generated. Therefore, during installation, the two should be kept to a minimum.

In hydraulic systems, fluid noise accounts for a considerable proportion. This noise is caused by fluid flow rates, sudden changes in pressure, and cavitation.

① Fluid noise of hydraulic pump

The fluid noise of the hydraulic pump is mainly caused by the periodic change of the pressure and flow of the pump and the cavitation phenomenon. In the oil suction and oil pressure cycle of the hydraulic pump, periodic pressure and flow changes are generated, forming pressure pulsation, which causes hydraulic vibration and spreads to the entire system through the outlet. At the same time, the pipes and valves of the hydraulic circuit reflect the pressure of the hydraulic pump, causing fluctuations in the circuit, causing the pump to resonate and make noise; on the other hand, about 5% of the air is dissolved in the hydraulic system (referring to the open circuit). When the pressure in the system is lower than the air separation pressure for some reason, the gas dissolved in the oil is quickly separated in large quantities to form bubbles. These bubbles are crushed when they encounter high pressure, resulting in a strong hydraulic shock. . For the former control method, the gear module should be as small as possible, the number of teeth should be as large as possible, the shape and size of the unloaded groove should be reasonable, and the number of plungers of the plunger pump should be an odd number, preferably 7 to 9. The upper triangular grooves are symmetrically opened on the inlet and outlet oil distribution plates to prevent oil trapping of the plunger pump.

In order to reduce noise, it is necessary to conduct an actual investigation of the noise source, measure and analyze the sound pressure level of the hydraulic system, and conduct frequency analysis, so as to grasp the size and frequency characteristics of the noise source, and take corresponding measures, which are listed as follows:

① Use low-noise motors; and use elastic couplings to reduce vibration and noise caused by this link;

② Anti-vibration rubber pads should be installed on the installation surfaces of motors, hydraulic pumps and hydraulic valves;

③ Try to use hydraulic manifolds instead of pipes to reduce vibration;

④ Use accumulator and rubber hose to reduce the vibration caused by pressure pulsation, the accumulator can absorb noise below 10 Hz, and high-frequency noise, using hydraulic hose is very effective;

⑤ Use a sound-proof cover with sound-absorbing material to cover the hydraulic pump to effectively reduce noise;

⑥ A venting device shall be provided in the system.