Noise pollution is a kind of environmental pollution, water pollution, air pollution, solid pollution is the world's most important environmental problems. In physics, noise is the sound produced when the attack body makes irregular vibration, which is transmitted to the human ear through air or other elastic media. Physiologically speaking, any sound that interferes with normal rest, study and work, as well as the sound that interferes with the sound that people want to hear, is noise. The hearing frequency ranges from 20Hz to 20,000 hz. Noise can make people anxious, reduce work efficiency, harm people's physical and psychological well-being, countries pay more and more attention to the control of noise. Micro water pump is a common part of instruments, widely used in scientific research, medical treatment. Scientific research, medical units on noise control request more stringent. For example, China's hospital management standards require operating room noise not higher than 38dB. And medical instruments are the main noise source in the operating room, some ventilators, absorbers noise as high as more than 70 dB. Reducing noise pollution in operating room is the necessity of modern medicine. Micro pump is also almost all laboratory will have common equipment. With the increasing attention of customers on the noise of pumps, reducing the noise of humble pumps has become an important direction of efforts of consumer manufacturers.
Estrangement pump is a kind of micro water pump, it is the application of motor drive film reciprocating motion vacuum, so as to inhale and pressure out of the fluid. High efficiency of micro pump; The motion mechanism is completely isolated from the delivery medium and pollution-free to the medium; Non-dynamic seal, no leakage; Good firmness; Small size, light weight; Not afraid of idling; No need for smooth care; Low noise itself. Micro vacuum pump in pumping use, without irrigation pump, immediately after the start of water drainage, both pumping and pumping, no water is not afraid of dry turn. Many advantages of micro pump make it widely used in the instrument industry.
From the source, the noise of micro water pump is mainly divided into: fluid power noise, mechanical noise of mechanical moving parts and motor noise three parts.
Fluid power noise is caused by the continuous pulse of fluid pressure generated when the micro pump is working, which arouses the noise radiated from the vibration signal of pump body, valve and pipe. By aijiakang company researchers measured, fluid power noise is the most important noise of micro pump. The hydrodynamic noise of micro pump belongs to low and middle frequency noise. Micro vacuum air pump suction, the inlet valve is open, the outlet valve is closed, the air is sucked into the pump chamber, the inlet and the valve chamber produce violent pressure shake, the pressure shake of the gas in the way of sound waves from the inlet radiation out, constitute the intake noise. Inlet noise is a broadband continuous spectrum, and its fundamental frequency can be calculated by the formula F =2n/60 (n is the speed per minute). In addition to the fundamental frequency, there are high frequency harmonics, but the high frequency harmonics sound level is lower than the fundamental frequency. The higher the speed, the greater the vacuum, the greater the flow, the greater the intake noise. When exhaust, the inlet valve is closed, the outlet valve is opened, the air shrinks, and the airflow rapidly flows through the outlet to produce sound waves that constitute exhaust port noise. Exhaust noise is also a wide band continuum spectrum. The higher the speed, the greater the pressure, the greater the flow, the greater the noise of the exhaust port. The noise from the air inlet and exhaust port after connecting the long plastic pipe will drop. The cause of noise of micro vacuum pump is complicated. Due to the periodic fluctuation of the pressure in the pump chamber, a large number of eddy currents are generated in the water unstable activities, and the rapid change of the pressure of the water flow on the film, the pump chamber and the valve and the friction between the water flow and the pump body produce noise. Especially when the water temperature is high and the vacuum degree of the pump is low, the pressure in the pump cavity of the suction stroke may be lower than the saturated steam pressure of the water at the temperature, and the water will vaporize and produce a large number of bubbles, forming a very complex two-phase flow. When the pump is compressed, under the action of higher pressure, the bubble is rapidly disillusioned, so that the water around the bubble rushes to the center of the bubble at a great speed, resulting in high frequency and high impact water strike, which strikes the internal parts of the pump from time to time. Pump vibration and noise, this phenomenon is called cavitation. Cavitation occurs on the solid boundary, which is the result of the impact force produced by the rapid disillusionment of cavitation in the high pressure region. Cavitation damage is greater, will damage parts, reduce efficiency, and produce vibration and noise. The noise produced by the micro vacuum pump belongs to low frequency noise. Fluid power noise is determined by the working principle of vacuum pump, and the improved pump body design can play a role in noise reduction, but the effect of active noise reduction is still far from people's expectation.
Mechanical noise is not the main source of micro pump noise, it is produced in the pump internal membrane vibration, bearing friction, eccentric movement of crankshaft and connecting rod, one-way valve impact. This kind of noise has randomness and presents broadband characteristics. In terms of active noise reduction, material selection, design, parts processing accuracy, balance and other aspects should be improved.
Motor is also the main noise source of micro pump, motor noise generally has three categories: one, electromagnetic noise, two, mechanical noise, three, aerodynamic noise. Electromagnetic noise is mainly caused by the magnetostriction and vibration caused by the radial electromagnetic force of the motor which changes periodically or the unbalanced magnetic pull force. Electromagnetic noise is also related to the vibration characteristics of stator and rotor. When the excitation force and the natural frequency resonance, even a small electromagnetic force will produce a large noise. In order to reduce electromagnetic noise, sinusoidal winding should be used as far as possible to reduce harmonic components; Selection of appropriate air gap magnetic density; Choose appropriate groove fit; Rotor chute; Stator and rotor magnetic circuit symmetrical and average, tight stacking; Should pay attention to the roundness and coaxiality of fixed and rotor; Be careful to avoid their resonant frequencies. In order to prevent the electromagnetic force from resonating with the housing, appropriate elastic structure can be used. Mechanical noise is the most important part of motor noise, derived from bearing noise, rotor imbalance and assembly eccentricity. Carbon brushes also vibrate and cause noise. In order to reduce mechanical noise, sealed bearings should be used to avoid debris entering. Bearing ball, inner ring, outer ring machining must meet the design requirements, there should be strict demagnetization cleaning process. Smooth grease must be cleaned. The mating of bearing outer ring and bearing room, inner ring and shaft should not be too tight. In order to eliminate the axial clearance of the rotor, appropriate pressure must be applied to the bearing. Low noise bearings should be selected for motors with particularly severe noise requirements. When the load is not too large, oil-bearing sliding bearings can be used, and the noise of rolling bearings of the same size can sometimes be about 10dB lower. Adequate bearing oil can effectively reduce noise. The machining accuracy of the rotor must reach the design requirements. The rotor with high speed must adjust dynamic equalization. Brushless motor can be used to eliminate brush noise. Aerodynamic noise is caused by the cooling fan attached to the motor. The thicker the motor iron shell, the smaller the amplitude, can absorb vibration energy, shielding sound transmission. Through the experiment, if the thickness of iron shell is not much, the improvement of dB is not obvious.
Domestic micro pump industry leader SCKOOCOM pump for many years micro pump development experience, relying on the technical strength of national level aerodynamic research institutions and universities, from time to time to optimize the pump body structure design, selection of high-quality information, strict control of processing accuracy in the manufacturing process, reduce the gap, effectively reduce the noise of the micro pump. Especially the latest development of short-lived life, adjustable voltage, micro pump, a pressure regulating vacuum pump, pump (extraction cheer amphibious) voltage regulator, pumps (pump suction amphibious) types, the first adopts the advanced imported brushless motor, not only have a short-lived life, no noise interference and can secure bento regulate traffic, can output speed response signal, and eliminate the brush noise. High quality imported brushless motor noise is significantly lower than the original motor. The brushless motor micro pump is equipped with a flexible vibration absorber which can be rotated to isolate the vibration of the pump body and facilitate the user's device. "SCKOOCOM" company also designed special muffler for micro pump, using advanced multiple muffler principle, small pressure loss, good noise reduction effect. In the pump inlet and outlet device special muffler is better. When the user uses the micro pump, the noise of the whole system is also related to all the components on the gas road. The noise can be effectively reduced when the flow velocity in the pipe is low. The use of "SCKOOCOM" speed regulating pump can be sensitively adjusted according to demand pump speed and flow, reduce noise. Also can be installed in the pipeline buffer tank, eliminate the pipeline pressure and flow pulsation, reduce pipeline vibration, reduce system noise. The exhaust port or exhaust port of the miniature air pump is connected to a longer pipe, and the method of bending and coiling the inner diameter of the experiment can change the size and frequency of the noise. In addition to reducing the intensity of the noise, the frequency of changing it can also make the noise sound less uncomfortable. In practice, the user's pipeline system is different, and the best noise reduction effect can be achieved only by the overall debugging of the gas path system.