Prevention and improvement of vibration and noise

1. improve the installation of hydraulic devices

(1) correct installation of hydraulic pump, installation of hydraulic pump and motor, attention should be paid to the coaxial error control within 0.02mm, and the use of flexible couplings. The swing part must be balanced. If the pump and motor are mounted on the fuel tank cover, the pump motor and the tank cover shall be provided with shock proof rubber pads and sound-absorbing materials. If possible, pump suction height and filter density should be minimized.

(2) install the piping correctly

1) better anti vibration measures are connected by hoses at both ends of the hard tube. The pipe should be as short as possible, and it is necessary to set enough vibration isolation support points for the long pipe to ensure that the pipeline has enough rigidity to prevent the pipe from resonance.

2) the pipe and pump, valve, intermediary flange and so on the position is correct, the connection seal is good, in order to avoid to suck back the oil pipeline, mixes the human air to produce the noise and the vibration.

3) the bending angle of the pipe should be less than 300, and the radius of curvature should be five times larger than the diameter of the pipe.

2. improve the structure of the hydraulic system

(1) using low noise hydraulic components, old hydraulic pump noise, can be replaced by a new hydraulic pump. The vibration and noise of piston pump and gear pump is larger than the vane pump vane pump, but not so high rated pressure piston pump, vane pump rated pressure has greatly improved, up to 20MPa, with a blade pump to replace the piston pump is a way to reduce noise and vibration.

(2) reduce the number of hydraulic pumps, children hydraulic pumps less, less vibration source, noise will be reduced. The old hydraulic system uses a number of hydraulic pumps to regulate the flow and pressure of the system. The new hydraulic system uses proportional valves to adjust the system pressure and flow, which can reduce the number of hydraulic pumps.

(3) the serious noise caused by the pressure pulsation of the accumulator hydraulic system is set up in the system, and the pressure pulsation can be eliminated by parallel accumulator in the system. The accumulator has little capacity, but requires little inertia and quick response. The accumulator has a frequency of less than a few tens of Hertz, and is more effective for absorbing low-frequency pressure pulsation.

The hydraulic system of a wave maker is shown in Figure 3-2, which is a long pipe hydraulic system. During the debugging process, the system pipe had a strong vibration and noise, and then a small energy accumulator (below 6.3L) was installed on the noise return pipeline, which significantly reduced the noise. This is because the servo valve switch back to the oil pipeline, the valve back to the oil pipeline to produce a large value of pressure fluctuations, the pressure change rate of dP/dt is also considerable, which caused vibration and noise. An accumulator is installed here to effectively absorb the pressure pulsation, thereby reducing vibration and reducing noise.

(4) vibration absorber and filter are set up in the system. For high frequency vibration and noise, the vibration absorber and filter can be eliminated by setting vibration absorber and filter. There are many types of vibration absorber: Figure 3-3 is a high frequency vibration adjustable vibrator. A spiral groove is inserted inside the cylindrical housing 1 to screw the tube with the outer thread 2. Turn the pipe 2 so that it moves along the axis of the housing. The pulsation of the liquid through the side hole left tube and shell Jinren muffler. The two fluids are assembled at the right end of the shell with a certain vibration phase difference so as to suppress vibration and noise. By rotating the pipe 2, the vibration frequency that needs to be eliminated can be adjusted. Fig. 3-4 is a micro perforated hydraulic vibration absorber. The vibration absorber is composed of a shell 1, a micro perforation 2 and an end cover 3. A micro perforated sound absorption structure is composed of a micro perforated tube and a cavity behind the tube. The processing of holes can be carried out as shown in figure 3-4A or B. The size of the cavity can control the peak frequency.

The hydraulic filter is the liquid volume, liquid sense, liquid resistance unit or their combination in the pipeline, which is used to attenuate the pulsation amplitude, and usually connect them in series, parallel or series parallel to the hydraulic system. The basic form of the filter is shown in figure 3-5.

In practical work, the use of vibration absorber and filter to eliminate vibration and noise is a simple and effective method.

3., the correct choice and use of oil

(1) the choice of oil, such as the choice of viscosity is too high, the hydraulic pump suction resistance will increase, prone to noise. It requires the selection of moderate viscosity and oil foam dissipation good, it has a large investment, but its long service life of the hydraulic pump and control element damage small, from the overall economic point of view, than the cheap oil. In view of antiwear hydraulic oil pour point is usually -25 degrees, when the environment temperature is not lower than -15 DEG C, recommended the use of antiwear hydraulic oil.

(2) to prevent oil pollution, pollution to a certain extent, will filter the oil tank screen, so that the oil pump suction difficult, back oil is not smooth, resulting in noise and vibration. The pollution of the oil can also cause the valve core of the control element to block or block the damping hole, and also cause noise. The solution: cleaning the tank regularly injected when the oil filter or screen made of double funnel, the oil into the tank, the tank between the area and the oil back to oil filter with separated; the lower part of a partition, the oil back to oil in the precipitation of impurities after back to oil can no longer stay in the flow of oil zone.

4. prevent hydraulic impact

(1) the sudden impact of the pressure drop on the valve port is prevented by the sudden closure of the valve. The following measures can be taken to solve the problem:

L) slow down the closing speed of the reversing valve, i.e. increase the commutation time t. If the actuator braking reversing time is t>0.2s, the impact pressure can be greatly reduced. In the hydraulic system, the reversing valve with adjustable reversing time can be adopted;

2) increase the diameter, reduce the flow rate of V0, which can reduce the pressure to reduce the impact of Delta V, Delta P, the pipeline flow restriction below 4.5m/s;

3) shorten the length, avoid unnecessary bends, or the soft camp also effective;

4) slow down the flow of liquid before the spool closes completely.

(2) when a moving part is suddenly braked, decelerated or stopped. A hydraulic shock, such as a hydraulic cylinder, that prevents a moving part from being suddenly braked, decelerated, or stopped:

1) set up a small safety valve of fast response and high sensitivity in the entrance and exit of the hydraulic cylinder (straight moving type), adjust the pressure in the middle and low pressure system, for the maximum working pressure of 105%~115%; in high pressure system, for the maximum working pressure of 125%. This prevents the impact pressure from exceeding the above adjustment.

2) in the hydraulic cylinder at the end of the use of deceleration valve, due to slow closure of the oil circuit and to ease the hydraulic impact.

3) limit the speed of moving parts. Moving parts generally do not exceed 10m/min.

4) a buffer device (such as a one-way throttle valve) is arranged at the lower part of the hydraulic cylinder to control the speed of oil discharge at the end of the hydraulic cylinder, so that when the hydraulic cylinder moves to the end of the cylinder, the utility model is stable and has no impact.

5) in the hydraulic cylinder return oil control circuit, the balance valve and back pressure valve are set up to control the impact of the rapid decline or horizontal movement, and appropriately adjust the back pressure.

6) use the rubber hose to absorb the hydraulic impact energy, and set the accumulator to absorb the shock pressure in the pipeline position which is easy to produce hydraulic shock.

7) adopt the hydraulic reversing valve with damping, and adjust the big damping, that is to turn off the one-way throttle valve at both ends.

8) may reduce the lubrication pressure suitably.

9) cylinder hydraulic hole with the gap (gap seal) is too large or the seal is damaged, and the working pressure and adjustment is large, easy to produce shock, the approach taken is to replace the piston or piston seal and appropriate to reduce the working pressure.