Motor aerodynamic active noise reduction structure and system

Abstract

The invention discloses a motor aerodynamic active noise reduction structure, which comprises a motor body provided with an end cover and fan blades, the end cover and the fan blades adopt a hummingbird wing imitating curved surface structure, the outer edge of the end cover adopts a tapered spiral curved surface, the curvature radius is gradually changed from 10 mm to 5 mm along the axial direction, and the gradient change rate is 0.5 mm / 10 degrees. A micro-groove array is arranged on the surface of the end cover, the depth of the micro-groove array is 0.2 mm, the distance between the micro-groove array and the end cover is 1 mm, airflow separation is delayed through the boundary layer adsorption effect, the front edges of the fan blades are of a sawtooth structure and are non-uniformly distributed in the spanwise direction, and the density of the fan blades is increased along with increase of the blade tip speed. The design is reasonable, the bionics principle and the intelligent control technology are deeply fused, and the frequency band limitation and the dynamic response bottleneck of a traditional motor noise reduction system are broken through through the synergistic effect of noise reduction optimization and noise cancellation. Experimental data show that under the working condition of 4000 rpm, the system can enable the aerodynamic noise of the motor to be reduced from 78 dB (A) to 56 dB (A), and the matching requirements of precision equipment are met.

Description

Technical Field

[0001] The present invention relates to the technical field of motor noise reduction, and in particular to a motor aerodynamic active noise reduction structure and system. Background Art

[0002] Motor aerodynamic noise is the aerodynamic noise generated by the interaction between airflow and components when the motor is running. It is a broadband noise (wide frequency range) and is commonly found in equipment such as fans, compressors, and electric vehicle drive motors.

[0003] The aerodynamic noise during motor operation mainly comes from the following two aspects: 1. Airflow separation and turbulent noise: When the high-speed rotating fan blades interact with the surrounding air, the airflow separates at the leading and trailing edges of the blades, forming turbulent vortices and generating broadband noise (100Hz-10kHz). Especially under high-speed operating conditions of the motor, the airflow separation phenomenon is aggravated, resulting in a significant increase in noise energy. 2. Howling caused by uneven air gap: The slight unevenness of the air gap between the rotor and stator of the motor will cause local airflow pressure fluctuations (usually the frequency is an integer multiple of the fundamental frequency, such as 1kHz-5kHz), forming a narrowband howling noise. This type of noise not only affects acoustic comfort, but may also aggravate mechanical vibrations and reduce motor life.

[0004] Existing noise reduction technologies have limitations. For example, they typically use traditional mufflers and sound-absorbing materials for noise reduction, which have limited effectiveness against low- and mid-frequency noise and increase size and weight. Using acoustic interference noise reduction, for example, requires complex algorithms and high-power hardware, resulting in high costs and difficulty suppressing broadband noise. Furthermore, static air gap designs often fail to adapt to the dynamic thermal deformation and mechanical vibration of the motor, resulting in deterioration in air gap uniformity with operating conditions and unstable noise control. To address these issues, we have designed a motor aerodynamic active noise reduction structure and system. Summary of the Invention

[0005] This invention aims to address the challenges of the existing technology by proposing a motor aerodynamic active noise reduction structure and system. This system deeply integrates bionic principles with intelligent control technology. By combining "noise reduction optimization" with "noise cancellation," it overcomes the frequency band limitations and dynamic response bottlenecks of traditional motor noise reduction systems. Experimental data shows that at 4000 rpm, the system can reduce motor aerodynamic noise from 78dB(A) to 56dB(A), meeting the requirements for precision equipment.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A motor aerodynamic active noise reduction structure and system includes a motor body provided with an end cover and fan blades. The end cover and fan blades adopt a hummingbird wing-like curved surface structure. The outer edge of the end cover adopts a tapered spiral curved surface, and the curvature radius gradually changes from 10 mm to 5 mm along the axial direction, with a gradient change rate of 0.5 mm / 10°. The surface of the end cover is provided with a micro-groove array with a depth of 0.2 mm and a spacing of 1 mm, and the boundary layer adsorption effect is used to delay airflow separation. The leading edge of the fan blade adopts a serrated structure with non-uniform distribution along the span direction, and the density increases with increasing tip speed. The annular array of air outlets of the motor body is provided with a detachable Helmholtz resonance cavity silencer.

[0008] Preferably, the leading edge of the fan blade adopts a fractal sawtooth structure with a sawtooth height of 0.5 mm, a base width of 2 mm, and a tooth tip angle of 30° to suppress high-frequency vortex shedding.

[0009] Preferably, the cavity of the Helmholtz resonance cavity muffler adopts a honeycomb aluminum composite sound absorption layer with a thickness of 3 mm and a porosity of 85% to enhance broadband sound absorption.

[0010] Preferably, the single cavity volume V of the Helmholtz resonance cavity silencer is 8 cm 3 , using a magnetic quick-release interface.

[0011] An electric motor aerodynamic active noise reduction system includes an active noise reduction structure, an intelligent air gap adjustment module, and an active noise suppression module. The active noise reduction structure includes an end cap, fan blades, and a Helmholtz resonant cavity muffler. The intelligent air gap adjustment module includes an air gap pressure monitoring array, an air gap dynamic adjustment mechanism, and an air gap optimization algorithm module. The active noise suppression module includes a sensor array, a control unit, an actuator array, an acoustic field reconstruction module, an antiphase acoustic wave generation module, and an adaptive control algorithm module.

[0012] Preferably, the air gap pressure monitoring array is integrated at the rotor shaft end, and includes a plurality of micro MEMS pressure sensors and non-contact displacement sensors arranged in a circular array. The sampling frequency of the micro MEMS pressure sensor is 50 kHz, and the non-contact displacement sensor is installed on the stator side with a resolution of 0.001 mm, and detects the rotor eccentricity in real time. The air gap dynamic adjustment mechanism includes an air gap adjustment gasket, and the air gap adjustment gasket is installed in a circular array at the stator end with a stroke of 0-0.5 mm and a repeatability accuracy of ±0.01 mm. It is driven by a servo motor through a harmonic reducer to adjust the uniformity of the air gap width. The air gap optimization algorithm module controls the air gap uniformity to σ≤0.05 mm based on the gradient descent method of LMS adaptive filtering.

[0013] Preferably, the surface of the air gap adjustment gasket is coated with a silicon carbide-graphene composite coating with a thickness of 50 μm to suppress the generation of local eddy currents.

[0014] Preferably, the sensor array is a microphone, the control unit is an algorithm processor, and the actuator array is a speaker array.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. In this application, a bionic spiral guide shell is adopted, that is, the motor end cover and the fan adopt a hummingbird wing curved surface structure with a curvature radius R = 5-10mm gradient, combined with a serrated design of the leading edge of the fan blade, with a serration height of 0.5mm and a spacing of 2mm, which reduces the airflow separation noise by 6-8dB; a detachable Helmholtz resonance cavity silencer is set at the air outlet, and the resonance frequency covers 500-3000Hz to further attenuate the aerodynamic noise.

[0017] 2. In this application, an intelligent air gap adjustment system is adopted, and a micro pressure sensor is installed at the end of the rotor shaft to monitor the air gap airflow pressure in real time. The adjustable air gap gasket is driven by a servo motor with an accuracy of ±0.01mm, dynamically optimizing the air gap uniformity with a deviation of ≤1%, thereby suppressing the aerodynamic whistling caused by uneven air gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a motor aerodynamic active noise reduction structure proposed by the present invention;

[0019] Figure 2 This is a schematic diagram of the connection between the fan blades and the serrated structure;

[0020] Figure 3 This is a schematic diagram of the connection between the end cover and the Helmholtz resonance cavity muffler.

[0021] In the figure: 1. end cover; 101. micro-groove array; 2. fan blade; 201. serrated structure; 3. motor body; 4. Helmholtz resonance cavity muffler. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0023] Reference Figure 1-Figure 3A motor aerodynamic active noise reduction structure includes a motor body 3 with an end cap 1 and fan blades 2. The end cap 1 and fan blades 2 are biomimetic in design, imitating the curved surface structure of a hummingbird wing. The outer edge of the end cap 1 adopts a tapered spiral surface, with the curvature radius gradually changing from 10mm to 5mm along the axial direction, with a gradient change rate of 0.5mm / 10°. The surface of the end cap 1 is provided with a microgroove array 101, with a depth of 0.2mm and a spacing of 1mm. This structure utilizes the boundary layer adsorption effect to delay airflow separation. The noise reduction mechanism of this structure is as follows: the gradual curvature guides the airflow to spirally diffuse from the center of the end cap 1 to the edge, reducing the local flow velocity gradient and reducing airflow shear noise. The microgroove array 101 suppresses turbulent bursts through secondary flow, and has been measured to reduce vortex shedding noise by 6-8dB(A).

[0024] The leading edge of fan blade 2 features a serration structure 201, which is non-uniformly distributed along the span. Its density increases with increasing tip speed. This fractal serration structure 201, with a 0.5mm height, a 2mm base width, and a 30° tip angle, suppresses high-frequency vortex shedding. This structure's noise reduction mechanism is as follows: the serrations break up large-scale vortices into smaller ones, shifting the noise spectrum toward higher frequencies (avoiding the human ear's sensitive frequency band) while also reducing the sound pressure level at the pass-through frequency (BPF) of fan blade 2. Experimental results show that noise levels above 1kHz can be reduced by 4-6dB.

[0025] The air outlet of the motor body 3 is provided with a detachable Helmholtz resonance cavity muffler 4 array in a ring shape. The cavity of the Helmholtz resonance cavity muffler 4 adopts a honeycomb aluminum composite sound absorption layer with a thickness of 3mm and a porosity of 85%, which enhances broadband sound absorption. The single cavity volume of the Helmholtz resonance cavity muffler 4 is V = 8cm 3 The Helmholtz resonant cavity muffler 4 provides targeted noise reduction, targeting the fundamental frequency noise of the fan blades 2 (e.g., blade pass frequency (BPF) = fan speed × number of blades) by absorbing energy through the resonant cavity, attenuating the corresponding frequency band noise by 5-8dB(A).

[0026] The Helmholtz resonant cavity muffler 4 consists of a resonant neck tube, a resonant cavity, and a sound-absorbing lining. The resonant neck tube has a diameter d = 8-12 mm (acoustic impedance matching section), a resonant cavity volume V = 0.5-2 L (frequency tuning cavity), and a sound-absorbing lining made of a 50 mm thick gradient porous material (porosity 70%-90%).

[0027] The Helmholtz resonance cavity silencer 4 is provided with a rotatable neck tube adjuster and an adaptive valve, which can achieve frequency ±15% adjustment by changing the effective length of the neck tube (stroke ±5mm) and automatically switch the cavity combination mode according to the feedback signal of the microphone array.

[0028] The Helmholtz resonance cavity silencer 4 adopts a spring clip + sealing ring design, which is easy to disassemble and assemble. The inner wall of the cavity is sprayed with a nano-hydrophobic coating (contact angle > 150°), and an integrated piezoelectric film sensor is used to detect the thickness loss of the lining.

[0029] The present invention also proposes an active noise reduction system for electric motor aerodynamics, comprising an active noise reduction structure, an intelligent air gap adjustment module, and an active noise suppression module. The active noise reduction structure comprises an end cap 1, fan blades 2, and a Helmholtz resonant cavity muffler 4. The intelligent air gap adjustment module comprises an air gap pressure monitoring array, an air gap dynamic adjustment mechanism, and an air gap optimization algorithm module. The active noise suppression module comprises a sensor array, a control unit, and an actuator array. Furthermore, the system comprises an acoustic field reconstruction module, an antiphase acoustic wave generation module, and an adaptive control algorithm module.

[0030] The air gap pressure monitoring array is integrated into the rotor shaft end and includes multiple micro-MEMS pressure sensors and non-contact displacement sensors arranged in a circular array. The micro-MEMS pressure sensor is embedded in the rotor shaft end, with a range of 0-10kPa, a sampling rate of 10kHz, and 8 measuring points evenly distributed around the circumference. It synchronously collects air gap pressure pulsation signals. The micro-MEMS pressure sensor has a sampling frequency of 50kHz. The non-contact displacement sensor is installed on the stator side with a resolution of 0.001mm, which detects rotor eccentricity in real time. Micro pressure sensor: Integrated into the rotor shaft end, the micro-MEMS pressure sensor monitors the airflow pressure fluctuations in the air gap in real time (with an accuracy of 0.1Pa), identifying pressure mutations caused by uneven air gaps, such as the high-speed jet noise generated when the air gap on one side is too small.

[0031] The dynamic air gap adjustment mechanism includes air gap adjustment pads coated with a 50μm-thick silicon carbide-graphene composite coating to suppress local eddy current generation. A circular array of these pads is mounted on the stator end, offering a travel range of 0-0.5mm and a repeatability of ±0.01mm. Driven by a servo motor through a harmonic reducer, they adjust the uniformity of the air gap width. The air gap optimization algorithm, based on the gradient descent method of LMS adaptive filtering, maintains air gap uniformity within a range of σ ≤ 0.05mm. A closed-loop control system dynamically adjusts the air gap pad thickness based on sensor data, with a response time of less than 50ms. Air gap non-uniformity is corrected to a control deviation of less than 0.02mm, suppressing aerodynamic whistles caused by air gap vortex shedding.

[0032] The sensor array is a microphone, the control unit is an algorithm processor, and the actuator array is a speaker array. The microphone array is used to capture environmental noise, distinguish electromagnetic noise (low frequency) from aerodynamic noise (medium and high frequency), and can pick up residual noise to optimize the compensation signal (closed-loop control). The multi-microphone array can improve the accuracy of noise positioning and reduce blind spots. The algorithm processor is an ANC chip, which runs an adaptive filtering algorithm (such as the minimum mean square error algorithm LMS) in real time and dynamically adjusts the compensation signal parameters. It supports multi-band noise reduction (such as independent processing of low frequencies below 100Hz and medium frequencies 100-500Hz).

[0033] The speaker needs to have a wide-band response (especially in the low frequency band) and low distortion (THD < 1%) to avoid noise generated by the compensation signal itself.

[0034] The present invention can be explained through the following operation mode:

[0035] In the present invention, the motor aerodynamic active noise reduction structure and system mainly include the following steps when working:

[0036] S1. Noise source identification:

[0037] The rotation of fan blade 2 generates broadband aerodynamic noise (mainly caused by airflow separation and blade load pulsation);

[0038] Uneven air gap causes narrowband whistling noise (generated by periodic airflow impacting the stator teeth).

[0039] S2. Bionic active noise reduction structure noise reduction:

[0040] The curved end cover 1 guides the airflow to flow closely, reduces the vortex separation intensity at the trailing edge of the fan blade 2, and reduces broadband noise by 3-5dB(A);

[0041] The serrated leading edge increases the main frequency of eddy current shedding noise from 500Hz to above 800Hz, avoiding the sensitive frequency band of the human ear (200-500Hz).

[0042] S3. Directional noise elimination in Helmholtz resonant cavity:

[0043] For the fan fundamental frequency noise (such as blade passing frequency BPF = fan speed × number of blades), the Helmholtz resonance cavity muffler 4 absorbs energy through resonance, attenuating the corresponding frequency band noise by 5-8dB(A).

[0044] S4. Intelligent air gap active control:

[0045] The pressure sensor monitors air gap pressure fluctuations in real time, detecting air gap unevenness. When abnormal pulsation is detected (e.g., fluctuation amplitude > 10Pa), real-time feedback control is initiated to generate a gasket adjustment amount. The servo motor drives the gasket to adjust the air gap, suppressing high-frequency whistling caused by air gap unevenness, reducing noise in this frequency band by 10-15dB(A). A multi-microphone array improves noise localization accuracy. The algorithm processor runs an adaptive filtering algorithm in real time, dynamically adjusting compensation signal parameters, and the speaker generates acoustic interference for compensation.

[0046] The hybrid control strategy is:

[0047] Low frequency band (<1kHz): air gap adjustment + Helmholtz resonance cavity muffler 4 resonance absorption;

[0048] Mid-frequency band (1-3kHz): Bionic airflow guidance + active noise reduction of end cover 1 and fan blade 2;

[0049] High frequency band (>3kHz): leading edge sawtooth + acoustic wave interference.

[0050] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A motor aerodynamic active noise reduction structure, comprising a motor body 3 provided with an end cover 1 and fan blades 2, characterized in that: The end cover 1 and the fan blade 2 adopt a hummingbird wing curved surface structure. The outer edge of the end cover 1 adopts a tapered spiral surface, and the curvature radius gradually changes from 10 mm to 5 mm along the axial direction, with a gradient change rate of 0.5 mm / 10°. A micro-groove array 101 is provided on the surface of the end cover 1, with a depth of 0.2 mm and a spacing of 1 mm, and the boundary layer adsorption effect is used to delay airflow separation. The leading edge of the fan blade 2 adopts a serrated structure 201, which is unevenly distributed along the span direction, and the density increases with increasing tip speed. The air outlet ring array of the motor body 3 is provided with a detachable Helmholtz resonance cavity muffler 4.

2. The motor aerodynamic active noise reduction structure according to claim 1, characterized in that: The leading edge of the fan blade 2 adopts a fractal sawtooth structure 201 with a sawtooth height of 0.5 mm, a base width of 2 mm, and a tooth tip angle of 30° to suppress high-frequency vortex shedding.

3. The motor aerodynamic active noise reduction structure according to claim 1, characterized in that: The cavity of the Helmholtz resonance cavity muffler 4 adopts a honeycomb aluminum composite sound absorption layer with a thickness of 3 mm and a porosity of 85%, which enhances broadband sound absorption.

4. The motor aerodynamic active noise reduction structure according to claim 1, characterized in that: The Helmholtz resonance cavity muffler 4 has a single cavity volume V=8 cm 3 , using a magnetic quick-release interface.

5. A motor aerodynamic active noise reduction system, using the motor aerodynamic active noise reduction structure according to any one of claims 1 to 4, characterized in that: It includes an active noise reduction structure body, an intelligent air gap adjustment module and an active noise suppression module. The active noise reduction structure body includes an end cover 1, fan blades 2 and a Helmholtz resonance cavity muffler 4. The intelligent air gap adjustment module includes an air gap pressure monitoring array, an air gap dynamic adjustment mechanism and an air gap optimization algorithm module. The active noise suppression module includes a sensor array, a control unit and an actuator array.

6. The motor aerodynamic active noise reduction system according to claim 5, characterized in that: The air gap pressure monitoring array is integrated into the rotor shaft end and includes multiple micro-MEMS pressure sensors and non-contact displacement sensors arranged in a ring array. The micro-MEMS pressure sensor has a sampling frequency of 50kHz. The non-contact displacement sensor is installed on the stator side with a resolution of 0.001mm and detects the rotor eccentricity in real time. The air gap dynamic adjustment mechanism includes air gap adjustment gaskets. The air gap adjustment gaskets are installed in a ring array at the stator end, have a stroke of 0-0.5mm, and a repeatability accuracy of ±0.01mm. They are driven by a servo motor through a harmonic reducer to adjust the uniformity of the air gap width. The air gap optimization algorithm module controls the air gap uniformity to σ≤0.05mm based on the gradient descent method of LMS adaptive filtering.

7. The motor aerodynamic active noise reduction system according to claim 6, characterized in that: The surface of the air gap adjustment gasket is coated with a silicon carbide-graphene composite coating with a thickness of 50 μm to suppress the generation of local eddy currents.

8. The motor aerodynamic active noise reduction system according to claim 5, characterized in that: The sensor array is a microphone, the control unit is an algorithm processor, and the actuator array is a speaker array.

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