How to reduce noise during the production of rotary vane vacuum pump?
The noise of a rotary vane vacuum pump usually refers to the noise level measured by the pump under extreme vacuum when the temperature is stable. It includes the noise of the pump itself and the noise of the motor. It is also concerned with the noise during the start-up phase when the pump temperature is not stable and the noise at different inlet pressures, as well as the noise during the operation of the open gas town.Therefore, consider a variety of influencing factors.
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In terms of the location of the sound, the noise of the pump has the following possible aspects
(1) the impact of the rotary vane on the cylinder, the residual volume of the pump and the sound of the pressure oil in the exhaust dead space;
(2) the impact of the exhaust valve plate on the valve seat and the support member;
(3) Echoes and bubble breaks in the box;
(4) bearing noise;
(5) Noise caused by a large amount of gas and oil impacting the oil deflector;
(6) Others. Such as noise caused by the transmission, fan noise of the air-cooled pump, etc.
(7) Motor noise, which is a crucial factor.
The recommendations for the design and treatment plan are described as follows
1. The impact of the rotary vane on the cylinder wall
If the design, manufacture or improper use of materials causes the sliding piece to slip poorly, or because of the exhaust dead space, the incompressible oil causes the rotating head to not always follow the cylinder wall, which will cause the rotating piece to the cylinder wall. The impact sounded. Therefore, it is preferable to use a circular arc surface to separate the structure of the intake and exhaust ports. Use the exhaust guide to eliminate dead space. When using the line separation structure, the distance from the exhaust end point to the tangent point should be shortened as much as possible. For the rotary vane pump below 70 l/s, considering the actual thickness of the rotary vane, it is recommended to take 7 to lomm, and the large pump takes a large value. When it is too close, due to the existence of the rotor vane groove and only one strip contact of the rotary vane head, once the rotary vane is turned to the tangent point position, the sealing effect is not good, which will affect the pumping speed and even the ultimate pressure of the pump. It can be seen that this structure does not completely eliminate the exhaust dead space, which limits the level of noise reduction.
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It should be pointed out that the gap between the rotary vane and the groove is too large to reduce the performance. Therefore, to ensure reasonable tolerance and shape tolerance values, pay attention to the thermal expansion of the rotary vane, avoid the rotation of the rotary vane and the groove, pay attention to the viscosity of the cold oil of the oil, design enough rotary vane spring force, when using the circular arc surface separation The additional eccentricity of the center of the rotor should not be too large. Otherwise, the rotating piece passes through two circular arcs, which will produce a tendency to detach from the cylinder wall at the intersection, and instead cause impact noise. Generally, the small pump can be 0.20~0.25mm, and the large pump can be appropriately increased.
The pressure oil in the exhaust dead space and the sound oil in the residual volume sound. When the pump reaches the limit pressure, the two pressure oils will be directed to the vacuum chamber at high speed when they are connected to the vacuum chamber, and the sound is struck against the rotor and the cylinder wall.
The size and position of the two volumes are related to noise.
2. Impact noise of the valve plate on the valve seat and the support member
The amount of gas inhaled is large, the amount of circulating oil of the pump is large, the noise of the valve plate is larger, the valve jumps high, the area of the valve is large, the noise of the valve piece is also large, and the material of the valve plate also has a certain influence.
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Rubber diaphragms should have better noise than steel sheets or laminates. To this end, to control the amount of oil, the valve should be closed in a timely manner, to be strict. Pay attention to the selection and structure of the valve.
3. This noise will increase when the echo and bubble burst in the tank increase.
This noise will increase significantly when the town is opened or when it is open to the atmosphere. If the gas volume is adjustable, the gas ballast can be adjusted reasonably.
4. Noise emitted by a large amount of gas and oil when impacting parts such as oil baffles.
If the part is not rigid enough or is not tightened, vibration and collision will increase the noise. Therefore, the oil baffle should not only have sufficient rigidity and tightness, but also, when it is required to contact other parts (such as the fuel tank), the rubber can be used to avoid the collision noise caused by vibration and improve the oil retaining effect.