How to reduce noise in the production process of rotary vane vacuum pump
The noise of the rotary vane vacuum pump usually refers to the noise level measured under the ultimate vacuum when the temperature of the pump is stable.
It includes the noise of the pump itself and the noise of the motor. For users, it is also concerned with the noise of the starting stage when the pump temperature is not stable, the noise of running under different inlet pressures, and the noise when the gas ballast is working. therefore. There are many influencing factors to consider.
As far as the parts of the sound are concerned, the noise of the pump has the following possible aspects:
(1) The impact of the rotary vane on the cylinder body, 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 sheet on the valve seat and support;
(3) Echoes and bubble bursts in the box;
(4) Bearing noise;
(5) Noise caused by a large amount of gas and oil impacting the oil baffle;
(6) Others. Such as the noise caused by the transmission, the fan noise of the air-cooled pump, etc.
(7) Motor noise, which is a crucial factor.
The design and treatment plan suggestions are described as follows:
1. The impact of the rotary vane on the cylinder wall.
If the design, manufacture or use of materials are improper, the rotary vane will not slide smoothly, or due to the existence of exhaust dead space, the incompressible oil will cause the rotary vane head to not always run close to the cylinder wall, which will cause the rotary vane to move against the cylinder wall. Bump sound. Therefore, it is advisable to adopt a structure in which a circular arc surface separates the intake and exhaust ports. Eliminate dead space with exhaust diverters. 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 70l/s, considering the actual thickness of the rotary vane, it is recommended to take 7 ~ 1mm, and the larger value for the large pump. too close, due to turning
The existence of the sub-rotary vane groove is in contact with the head of the rotary vane only by a narrow strip. When the rotary vane turns to the tangential position, once the sealing effect is not good, it will affect the pumping speed and even the ultimate pressure of the pump. It can be seen that this structure cannot completely eliminate the exhaust dead space, which limits the level of noise reduction.
It should be pointed out that excessive clearance between the vane and the groove will reduce the performance. Therefore, it is necessary to ensure a reasonable tolerance fit and shape and position tolerance value, pay attention to the thermal expansion of the rotary vane, avoid the burring of the rotary vane and the groove, pay attention to the cold oil viscosity of the oil, and design enough spring force of the rotary vane. , the additional eccentric value of the rotor center should not be too large. Otherwise, when the rotary vane passes through two arcs, it will tend to detach from the cylinder wall at the intersection point, which will cause impact noise instead. Generally, the small pump is 0.20~0.25mm, and the large pump can be appropriately enlarged.
The sound of the pressure oil in the exhaust dead space and the pressure oil in the residual volume. When the pump reaches the limit pressure, the two pressure oils will shoot into the vacuum chamber at high speed when connected to the vacuum chamber, and collide with the rotor and the cylinder wall to make a sound.
The size and location of the two volumes are related to noise.
2. The impact noise of the valve sheet on the valve seat and supporting parts
The amount of inhaled gas is large, the amount of circulating oil in the pump is large, the noise of the valve plate is greater, the valve jumps high, the area of the valve is large, the noise of the valve plate is also large, and the material of the valve plate also has a certain influence. The noise of rubber valve plate should be better than that of steel plate or laminate. To this end, it is necessary to control the oil intake, and the valve plate should be closed in time and tightly. Pay attention to the selection and structure of the valve.
3. When the volume of echo and bubble bursting sound in the box increases, this noise will increase. Therefore, the noise will increase significantly when the gas ballast is turned on or when the atmosphere is opened. If the amount of gas ballast is adjustable, the amount of gas ballast can be adjusted reasonably.
4. The noise made when a large amount of gas and oil is discharged when it hits parts such as the oil baffle. If the rigidity of the parts is insufficient, or the parts are not fastened, vibration and collision will occur, which will increase the noise. Therefore, the oil baffle should not only have sufficient rigidity and be fastened, but also use the method of clamping rubber to avoid collision noise caused by vibration and improve the oil blocking effect when it needs to be in contact with other parts (such as the fuel tank).
It includes the noise of the pump itself and the noise of the motor. For users, it is also concerned with the noise of the starting stage when the pump temperature is not stable, the noise of running under different inlet pressures, and the noise when the gas ballast is working. therefore. There are many influencing factors to consider.
As far as the parts of the sound are concerned, the noise of the pump has the following possible aspects:
(1) The impact of the rotary vane on the cylinder body, 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 sheet on the valve seat and support;
(3) Echoes and bubble bursts in the box;
(4) Bearing noise;
(5) Noise caused by a large amount of gas and oil impacting the oil baffle;
(6) Others. Such as the noise caused by the transmission, the fan noise of the air-cooled pump, etc.
(7) Motor noise, which is a crucial factor.
The design and treatment plan suggestions are described as follows:
1. The impact of the rotary vane on the cylinder wall.
If the design, manufacture or use of materials are improper, the rotary vane will not slide smoothly, or due to the existence of exhaust dead space, the incompressible oil will cause the rotary vane head to not always run close to the cylinder wall, which will cause the rotary vane to move against the cylinder wall. Bump sound. Therefore, it is advisable to adopt a structure in which a circular arc surface separates the intake and exhaust ports. Eliminate dead space with exhaust diverters. 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 70l/s, considering the actual thickness of the rotary vane, it is recommended to take 7 ~ 1mm, and the larger value for the large pump. too close, due to turning
The existence of the sub-rotary vane groove is in contact with the head of the rotary vane only by a narrow strip. When the rotary vane turns to the tangential position, once the sealing effect is not good, it will affect the pumping speed and even the ultimate pressure of the pump. It can be seen that this structure cannot completely eliminate the exhaust dead space, which limits the level of noise reduction.
It should be pointed out that excessive clearance between the vane and the groove will reduce the performance. Therefore, it is necessary to ensure a reasonable tolerance fit and shape and position tolerance value, pay attention to the thermal expansion of the rotary vane, avoid the burring of the rotary vane and the groove, pay attention to the cold oil viscosity of the oil, and design enough spring force of the rotary vane. , the additional eccentric value of the rotor center should not be too large. Otherwise, when the rotary vane passes through two arcs, it will tend to detach from the cylinder wall at the intersection point, which will cause impact noise instead. Generally, the small pump is 0.20~0.25mm, and the large pump can be appropriately enlarged.
The sound of the pressure oil in the exhaust dead space and the pressure oil in the residual volume. When the pump reaches the limit pressure, the two pressure oils will shoot into the vacuum chamber at high speed when connected to the vacuum chamber, and collide with the rotor and the cylinder wall to make a sound.
The size and location of the two volumes are related to noise.
2. The impact noise of the valve sheet on the valve seat and supporting parts
The amount of inhaled gas is large, the amount of circulating oil in the pump is large, the noise of the valve plate is greater, the valve jumps high, the area of the valve is large, the noise of the valve plate is also large, and the material of the valve plate also has a certain influence. The noise of rubber valve plate should be better than that of steel plate or laminate. To this end, it is necessary to control the oil intake, and the valve plate should be closed in time and tightly. Pay attention to the selection and structure of the valve.
3. When the volume of echo and bubble bursting sound in the box increases, this noise will increase. Therefore, the noise will increase significantly when the gas ballast is turned on or when the atmosphere is opened. If the amount of gas ballast is adjustable, the amount of gas ballast can be adjusted reasonably.
4. The noise made when a large amount of gas and oil is discharged when it hits parts such as the oil baffle. If the rigidity of the parts is insufficient, or the parts are not fastened, vibration and collision will occur, which will increase the noise. Therefore, the oil baffle should not only have sufficient rigidity and be fastened, but also use the method of clamping rubber to avoid collision noise caused by vibration and improve the oil blocking effect when it needs to be in contact with other parts (such as the fuel tank).