Overseam belt presser foot empty seam noise analysis method

Abstract

The invention discloses an overseam belt presser foot gap noise analysis method which comprises the following steps: step 1, establishing a rigid body dynamic model of a presser foot mechanism and a tooth feeding structure, extracting a contact force value and a change rule in an impact process between parts, and determining a noise contribution part; 2, the finite element mesh of the noise contribution part is flexible through a modal synthesis method and replaced into a rigid body dynamic model of a presser foot mechanism and a tooth feeding structure, a rigid-flexible coupling model is built, displacement, speed response and surface vibration radiation noise ERP of the noise contribution part in the movement process are obtained, and the ERP is calculated; and vibration response area distribution of the noise contribution part is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of sewing machine noise reduction analysis, and particularly relates to a method for analyzing the noise of an overlock tape presser foot gap. Background Art

[0002] In the modern garment manufacturing industry, overlock sewing machines, as key equipment, are widely used in the edge sewing and hemming processes of various garments. Their efficient and stable performance has greatly improved the efficiency and quality of garment production. However, the noise generated by overlock sewing machines during the open-sewing process with the presser foot has caused significant problems for companies and garment factories, and has long been a pressing issue for the industry. The overlock presser foot open-sewing noise is primarily caused by high-frequency vibration and collisions of mechanical components when no load is applied. When the sewing machine is in the open-sewing mode, the presser foot comes into direct contact with components such as the feed dog and needle plate. Without the damping effect of the fabric, friction between moving parts increases, leading to resonance and impact noise. In the past five years, some companies have proposed solutions through patent portfolio development. For example, Zhejiang Duma Sewing Machine uses a spherical structure design to simplify the drive chain to reduce noise. Zhejiang Zhongbang Electromechanical has developed presser foot slow-down control technology to reduce collision impact. Qixing Technology has introduced a stepper motor drive system for digital presser foot control.

[0003] In existing technologies: The current industry analysis of gap noise is still at the qualitative observation stage:

[0004] 1. Subjective evaluation relies on manual effort: The amplitude of the presser foot's vibration is observed using a high-speed camera (1000fps) (with an error of ±0.08mm) and combined with subjective human scoring (on a 1-10 scale). This cannot accurately match the time-domain and frequency-domain characteristics of the noise signal.

[0005] 2. Single scenario isolated analysis: This analysis only focuses on the single operating condition of "no-load static start" or "constant speed gap", and does not focus on the resonance differences when switching between different tooth heights (three gears) and different tooth running trajectories;

[0006] However, there is a lack of technical means to analyze and find the real source of noise and the source of key parts of noise after mixing, resulting in the inability to overcome and improve it in a targeted manner and effectively reduce noise. The result is often blind vibration reduction of all components, which is costly and ineffective. Summary of the Invention

[0007] The present invention aims to provide a method for analyzing the void gap noise of the presser foot of an overlock tape. By using simulation analysis, a finite element model and a dynamic model of the presser foot mechanism module of an overlock sewing machine are constructed. By means of professional noise detection equipment, the presser foot noise is collected and analyzed, the noise contribution spectrum characteristics are identified, and the void gap noise of the overlock tape is searched and confirmed from the source of the noise generation mechanism, thereby providing an effective noise reduction implementation plan. The invention relates to the technical field of noise control and performance optimization of intelligent manufacturing equipment for clothing, and specifically is a method for accurately controlling the void gap noise of the presser foot of an overlock sewing machine that integrates multi-physical field coupling simulation, dynamic characteristic analysis and spectrum characteristic identification. The method is suitable for sound source localization, mechanism analysis and noise reduction scheme design in the void gap noise of the presser foot of a high-speed overlock sewing machine.

[0008] The present application provides a method for analyzing the gap noise of a seam tape presser foot, comprising the following steps:

[0009] Step 1: Establish a rigid body dynamics model of the presser foot mechanism and the tooth feeding structure, extract the contact force value and change law during the collision between the parts, and determine the noise contributing parts;

[0010] In the second step, the finite element mesh of the noise-contributing parts is made flexible through the modal synthesis method and replaced into the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure. A rigid-flexible coupling model is built to obtain the displacement, velocity response and surface vibration radiation noise ERP of the noise-contributing parts during the movement process, and obtain the vibration response area distribution of the noise-contributing parts.

[0011] A technical solution provided by this application also has the following technical features:

[0012] Preferably, in one embodiment of the present application, in step three, a noise testing device is used to collect the presser foot gap noise of the physical device of the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure, analyze the noise spectrum diagram, and determine the frequency band distribution of the collision noise contribution.

[0013] Preferably, in one embodiment of the present application, in step four, a damping material composite structure is matched to the noise reduction improvement target area of ​​the noise-contributing parts, and the noise reduction result is confirmed through simulation and testing.

[0014] Preferably, in one embodiment of the present application, in step one, contact characteristics are established between two parts that will cyclically generate contact and collision during operation, so as to simulate the collision between the parts in actual operation.

[0015] Preferably, in one embodiment of the present application, in step one, the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure is run, and the kinematic force analysis and comparison in different modes are obtained under different sewing requirements to obtain the maximum contact force corresponding to different sewing requirements, and the maximum contact force is the corresponding noise contributing part.

[0016] Preferably, in one embodiment of the present application, in step 2, a finite element model of the noise-contributing part is established, the noise-contributing part is made flexible, and is introduced into a rigid body dynamics model of the presser foot mechanism and the tooth feeding structure to obtain the stress distribution of the noise-contributing part in the working state, and obtain the impact force area distribution of the noise-contributing part at different times;

[0017] After setting the corresponding parameters, the modal synthesis method is used to convert the finite element model of the noise-contributing parts into a modal neutral model, which is then imported into the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure to replace the noise-contributing parts of the pure rigid body, thus obtaining the rigid-flexible coupling dynamic model of the noise-contributing parts.

[0018] Preferably, in an embodiment of the present application, in step three, the target contribution frequency band of the impact noise is locked.

[0019] Preferably, in one embodiment of the present application, in step four, for the noise contributing parts, damping materials are matched and combined according to the distribution of vibration response areas and are set in the target vibration area of ​​the noise contributing parts.

[0020] Preferably, in one embodiment of the present application, in step three, the target contribution frequency band of the presser foot impact noise is 600-2000 Hz.

[0021] Preferably, in one embodiment of the present application, in step 2, the rigid-flexible coupling dynamic model is the Hertz model in the rigid body-flexible body contact mechanics model; in the modeling state of the rigid-flexible coupling dynamic model, no penetration occurs in the initial contact state between the noise-contributing parts and the parts colliding with them; when establishing the contact of the rigid-flexible coupling model, the maximum penetration value is in the range of less than or equal to 0.3.

[0022] Preferably, in one embodiment of the present application, in step 2, a rigid-flexible coupling dynamic model is run to obtain the stress distribution of the noise-contributing parts during operation and when colliding with the parts colliding with them, and to obtain the vibration displacement response and vibration velocity response of the noise-contributing parts, as well as the surface vibration sound radiation ERP cloud map, to determine the vibration response area distribution of the noise-contributing parts.

[0023] Preferably, in one embodiment of the present application, in step one, the parts of the rigid body dynamics model include a handwheel, a main shaft, a tooth lifting slider, a main differential tooth rack, a main differential tooth, a main feed connecting rod, a main feed crank, a differential crank, a differential slider assembly, a feed step shaft, a differential feed connecting rod, a cloth feed assembly, a lower knife seat, a needle plate pad, a needle plate, a presser foot assembly, a presser foot arm, a presser foot shaft, and a pressure rod assembly.

[0024] Preferably, in one embodiment of the present application, in step one, the contact force value and change pattern during the collision between the presser foot and the needle plate and teeth are extracted.

[0025] Preferably, in one embodiment of the present application, in step one, material parameters are assigned to the parts included in the rigid body dynamics model, and the material parameters include: Young's modulus E, Poisson's ratio V and material density P.

[0026] Preferably, in one embodiment of the present application, the connection relationship between the parts included in the rigid body dynamics model is achieved by adding kinematic pairs.

[0027] Preferably, in one embodiment of the present application, in step one, contact characteristics are established between the presser foot and the teeth; contact characteristics are established between the presser foot and the needle plate; the values ​​required for modeling are determined according to the geometric matching relationship and material properties of the two contacting parts; and contacts are established between the presser foot bottom plate plane and the needle plate upper plane, and between the presser foot bottom plate plane and the main differential teeth.

[0028] Preferably, in one embodiment of the present application, in step one, a rigid body dynamics model of the presser foot mechanism and the tooth feeding structure is run to obtain the contact force between the impact parts.

[0029] Preferably, in one embodiment of the present application, in step one, a rigid body dynamics model of the presser foot mechanism and the tooth feeding structure is run to obtain the contact force between the presser foot bottom plate plane and the needle plate and the teeth.

[0030] Preferably, in one embodiment of the present application, in step 2, the contact collision force between the noise-contributing part and the part colliding with it is obtained through the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure, which is used to establish a finite element model of the noise-contributing part.

[0031] Preferably, in one embodiment of the present application, in step 2, in the modeling state of the rigid-flexible coupling dynamic model, no penetration occurs in the initial contact state between the presser foot sole surface and the teeth and needle plate; when establishing the contact of the rigid-flexible coupling model, the maximum penetration value is in the range of less than or equal to 0.3.

[0032] Preferably, in one embodiment of the present application, in step two, a rigid-flexible coupling dynamic model of the noise-contributing parts is run to obtain the stress distribution of the presser foot sole when it collides with the needle plate and the teeth during work, and the vibration displacement response and vibration velocity response of the surface of the presser foot sole are obtained, as well as the surface vibration sound radiation ERP cloud map, and the front end area of ​​the presser foot sole is obtained as the target vibration area according to the vibration response distribution.

[0033] Preferably, in one embodiment of the present application, in step 4, for broadband noise, a composite structure of at least two damping materials is arranged in a target vibration region of the noise-contributing component.

[0034] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention.

[0035] 1. This application proposes a method for analyzing the gap noise of the presser foot of the overlock tape, and provides a method for finding the noise source, especially the key areas of the key parts where the noise is generated, so that it can be accurately improved. It also provides a method for how to effectively reduce and verify the noise;

[0036] 2. This application provides the analysis and parameter setting method steps of the contact characteristics between the presser foot and the needle plate and teeth;

[0037] 3. The noise analysis method in the analysis process of this application is suitable for a variety of existing sewing equipment, and can be used for noise reduction analysis, and improve the target area, accurately locate the noise source, eliminate or reduce the vibration response of the target area, and achieve noise reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0039] Figure 1 Schematic diagram of a flow chart of a method for analyzing gap noise of a presser foot of an overlock tape according to the present invention;

[0040] Figure 2 The dynamic model of the presser foot assembly and feeding mechanism of the overlock sewing machine is constructed for the present invention Figure 1 ;

[0041] Figure 3 The dynamic model of the presser foot assembly and feeding mechanism of the overlock sewing machine is constructed for the present invention Figure 2 ;

[0042] Figure 4 Schematic diagram of contact force between the presser foot and the needle plate in a method for analyzing gap noise of an overlock tape presser foot according to the present invention;

[0043] Figure 5 Schematic diagram of contact force between the presser foot and teeth in a method for analyzing gap noise of a seam-seaming tape presser foot according to the present invention;

[0044] Figure 6 A cloud diagram showing the maximum stress value of a presser foot in one operating cycle of a method for analyzing gap noise of a presser foot of an overlock tape according to the present invention;

[0045] Figure 7 A surface displacement cloud diagram of a presser foot sole plate in a method for analyzing gap noise of a seam-seaming tape presser foot according to the present invention;

[0046] Figure 8 A vibration response curve of a point on the surface of the presser foot sole plate of a method for analyzing gap noise of an overlock tape presser foot according to the present invention;

[0047] Figure 9 The present invention provides an analysis of the ERP of the presser foot sole plate surface in a method for analyzing the gap noise of a seam-seaming tape presser foot;

[0048] Figure 10 A noise spectrum comparison diagram of a method for analyzing the gap noise of a seam-seaming tape presser foot in the present invention under the conditions of gaps between the presser foot and the no-load state;

[0049] Figure 11 A presser foot assembly for analyzing gap noise of a presser foot of an overlock tape according to the present invention;

[0050] Figure 12 A presser foot bottom plate mechanism of a method for analyzing gap noise of a presser foot of an overlock tape according to the present invention;

[0051] Components in the picture:

[0052] 1. Handwheel

[0053] 2. Spindle

[0054] 3. Main differential gear rack

[0055] 4. Eccentric shaft

[0056] 5. Differential slider assembly

[0057] 6. Differential crank

[0058] 7. Fabric feeding assembly

[0059] 8. Lower knife seat

[0060] 9. Needle plate pad

[0061] 10. Needle plate

[0062] 11. Presser foot assembly

[0063] 12. Pressure rod assembly

[0064] 13. Presser foot arm

[0065] 14. Presser foot shaft

[0066] 15. Differential teeth

[0067] 16. Main delivery teeth

[0068] 17. Tooth lifting slider

[0069] 18. Main feeding connecting rod

[0070] 19. Main feed crank

[0071] 11-1. Presser foot

[0072] 11-2. Wire pressing plate

[0073] 11-3. Presser foot plate

[0074] 11-4. Presser foot claw

[0075] 11-5. Auxiliary presser foot. DETAILED DESCRIPTION

[0076] The following further describes the specific embodiments of the present application in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present application and are not intended to limit the present invention.

[0077] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0078] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0079] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0080] like Figure 1 A method for analyzing the gap noise of a seam tape presser foot comprises the following steps:

[0081] First, build the rigid body dynamics model of the presser foot mechanism and tooth feeding structure, such as Figure 2 、 3 As shown, it includes a handwheel 1, a main shaft 2, a main differential tooth frame 3, an eccentric shaft 4, a differential slider assembly 5, a differential crank 6, a cloth feed assembly 7, a lower knife seat 8, a needle plate spacer 9, a needle plate 10, a presser foot assembly 11, a presser bar assembly 12, a presser foot arm 13, a presser foot shaft 14, differential teeth 15, a main feed tooth 16, a tooth lifting slider 17, a main feed connecting rod 18, a main feed crank 19, and supporting components;

[0082] Assign material parameters to each part. The material parameters of the parts generally include Young's modulus E (describing the stiffness of the material), Poisson's ratio V (describing the degree of lateral contraction or expansion of the material when stretched or compressed) and material density P (describing the unit volume mass of the material).

[0083] The connection between parts is defined by adding kinematic pairs, primarily revolute pairs, cylindrical pairs, planar pairs, translation pairs, and fixed pairs. Accordingly, a typical kinematic mechanism also requires setting certain contact characteristics and external force loading. In the model presented here, the focus is on the noise generation mechanism when the presser foot is in a gap. The presser foot and teeth, as well as the presser foot and needle plate, will cyclically contact and collide during operation, so contact characteristics need to be established between them. This contact setting simulates actual collisions between parts during operation.

[0084] The Penalty Method is selected in combination with the Coulomb friction model to calculate the contact force, also known as the spring-damper model to simulate the contact force, and the contact process is regarded as the action of a virtual spring and damper. The elastic force simulates the restoring force generated by the deformation of the contact object (similar to Hooke's law); the damping force simulates the energy dissipation during the contact process (such as frictional heat generated during collision); the friction force is based on the Coulomb friction law, considering the static friction and kinetic friction stages.

[0085] Contact types also include point-to-surface contact: using discrete points to approximate the contact surface and calculate the penetration depth between the point and the surface; surface-to-surface contact: discretizing the contact surface into a grid (such as triangular elements) and calculating the penetration and contact force distribution between the elements;

[0086] The contact force Fcontact consists of two parts: normal force and tangential friction force;

[0087] The expression is:

[0088] Fcontact=Fn·n+Ft·t

[0089] n: contact surface normal unit vector;

[0090] t: tangential unit vector of the contact surface (direction opposite to relative sliding or trend).

[0091] According to the parameters required in the above calculation formula, when actually modeling, the appropriate values ​​are determined according to the geometric matching relationship and material properties of the two contacting parts. The needle plate, teeth, and presser foot bottom plate are all made of 20Cr. When setting the contact characteristics, the contact characteristics between steel and steel are selected, and the stiffness coefficient is set to 100000, the damping coefficient is set to 10, the dynamic friction coefficient is set to 0.2, the stiffness index is set to 1.5, the rebound damping coefficient is set to 0.25, and the maximum step size factor is set to 10. Contact is established between the presser foot bottom plate plane and the needle plate plane, and between the presser foot bottom plate plane and the main differential teeth.

[0092] The presser arm assembly contains a compression spring that applies force to the presser foot arm, ensuring that the presser foot is always in a state of pressing the fabric tightly when sewing. In dynamic modeling, a spring force is applied, and the spring stiffness coefficient, damping coefficient, and initial length of the spring are set. The software automatically detects the real-time change in the distance between the marking points at both ends of the spring force and calculates the spring force according to Hooke's law.

[0093] F=-k·x

[0094] F: elastic force exerted on the spring;

[0095] k: spring coefficient, reflecting the rigidity of the spring;

[0096] x: the deformation of the spring, i.e. the extension or compression (the initial length of the spring minus the actual distance between the two marking points of the spring during movement);

[0097] Minus sign (-): Indicates that the direction of the elastic force is opposite to the direction of the deformation (the direction of the spring's restoring force always points to the equilibrium position).

[0098] By adding a rotary drive to the main shaft and running the dynamic model of the presser foot mechanism, the contact forces between the presser foot base plane and the needle plate and the teeth can be obtained in the result file, such as Figure 4 、 5 As shown in the figure. The resulting curve shows that the contact force between the presser foot and the teeth is affected by the tooth shape and movement of the teeth, resulting in an irregular and relatively large impact force. The needle plate, which is fixed to the lower cutter block via a needle plate spacer, has a large contact surface between the presser foot and the needle plate, resulting in a relatively regular, periodic contact force. The analyzed overlock sewing machine has three adjustable tooth trajectory settings. The main differences between these settings are changes in tooth height and inclination, corresponding to thin, medium-heavy, and thick material sewing, respectively. A comparative kinematic force analysis under these three modes preliminarily determined that in the thin material sewing mode, the contact force between the presser foot and the needle plate is smaller than that between the presser foot and the teeth, with the primary noise contribution being the impact sound between the teeth and the presser foot. In the medium-heavy and thick material sewing modes, the contact force between the presser foot and the needle plate is greater, with the primary noise contribution being the sound of the presser foot striking the needle plate.

[0099] Figure 4 is the contact force between the presser foot and the needle plate, Figure 5 It is the contact force between the presser foot and the teeth.

[0100] Using a rigid-body dynamics model of the presser foot structure, we determined the contact and collision forces between the presser foot and the needle plate, and between the presser foot and the teeth. Further analysis established a finite element model of the presser foot base, making it flexible and incorporating it into the aforementioned dynamics model. This model determined the stress distribution of the presser foot during operation and identified the primary impact stress areas at different times. In this model, the presser foot base measures approximately 17mm by 50mm in length and width. Its 2D mesh size is set to 0.5mm triangular elements, and its 3D mesh type is a tetrahedral mesh. 20Cr material parameters are assigned, and rigid elements are established to define the interface points connecting the presser foot base finite element body and the presser foot frame.

[0101] After setting various parameters, the modal synthesis method is used to convert the finite element file of the presser foot sole into a modal neutral file, which is then imported into the rigid body dynamics model of the presser foot mechanism to replace the above-mentioned pure rigid body presser foot sole, thereby obtaining the rigid-flexible coupling dynamics model of the presser foot mechanism. The advantage of using the modal synthesis method is that the elastic deformation of the flexible body is decomposed into a series of modes, and the amount of calculation is reduced through modal coordinates. In addition, there is a finite element flexible body (FE-Flex), which is directly imported into the finite element mesh and is suitable for complex geometry and local stress analysis. Which flexible body modeling method to use needs to be determined based on the specific analysis conditions, taking into account both the accuracy of the results and the rationality of resources. In the rigid-flexible coupling dynamics model, we focus on the stress distribution area and changes of the presser foot sole, and select the modal synthesis method. The flexible body dynamics equation is mainly based on the Lagrange equation, and the motion of the flexible body is expressed as:

[0102] Mq¨+Cq˙+Kq=F+Fcontact

[0103] q: generalized coordinate vector (including rigid body position / attitude and elastic modal coordinates)

[0104] M: mass matrix

[0105] C: damping matrix;

[0106] K: Stiffness matrix

[0107] F: external force (such as gravity, driving force);

[0108] Fcontact: contact force

[0109] The most commonly used rigid-flexible contact mechanics model is an extension of the Hertz-Mindlin model, where Fn = kn·δp + cn·δ˙ (δ>0). The key is the value of δ, which is the depth of penetration of the flexible body node into the rigid body surface (calculated by the contact detection algorithm).

[0110] When building a rigid-flexible coupling dynamic model, the initial contact state between the presser foot sole and the teeth and needle plate must ensure that no penetration occurs.

[0111] When establishing contact for a rigid-flexible coupling model, set the Maximum Penetration value to within 0.3.

[0112] By running the rigid-flexible coupling dynamic model, the stress distribution of the presser foot sole when it collides with the needle plate and teeth during operation is obtained, and the vibration displacement response and vibration velocity response of the presser foot sole surface are obtained.

[0113] Figure 6 This is the maximum stress cloud diagram of the presser foot during one operating cycle, and the maximum stress is 134.3 MPa;

[0114] Figure 7 This is the displacement cloud diagram caused by the collision and knocking of the presser foot sole during operation;

[0115] Figure 8 It is the speed response curve of the presser foot at a point in operation.

[0116] Sound power is proportional to the square of the vibration velocity. The greater the speed response, the more sound energy is radiated per unit time and the stronger the sound.

[0117] Therefore, at the same frequency, the greater the velocity response, the greater the sound intensity and the louder the sound. For areas with large velocity response, it is necessary to design and add damping materials to reduce their vibration response.

[0118] After the presser foot sole is made flexible, surface vibration sound radiation (ERP) is a very useful method for analyzing vibration sound. The vibrating surface is used as the sound source, and its normal velocity directly determines the sound radiation intensity.

[0119] According to acoustic theory, the normal velocity distribution vn(r, t) of the vibrating surface and the radiated sound pressure p(r, t) satisfy the Rayleigh Integral relationship:

[0120]

[0121] Where ρ0 is the medium density, ω is the angular frequency, k is the wave number, and S is the vibrating surface area.

[0122] Figure 9 It is the surface vibration acoustic radiation ERP cloud diagram of the presser foot sole, which shows that during operation, the vibration response of the front end of the presser foot sole is the most obvious.

[0123] Theoretically, the mechanism by which parts produce sound during collisions is the conversion of mechanical energy into acoustic energy. This involves the coupling of multiple physical fields, including solid vibration, acoustic radiation, and energy transfer, encompassing multiple links: contact mechanics, structural vibration, and acoustic radiation. The core mechanisms include elastic modal excitation: the collision force drives the structure to vibrate at its natural frequency; nonlinear effects: contact / friction nonlinearities introduce harmonic components; energy transfer: vibration energy is converted into acoustic energy through damping dissipation and acoustic radiation; and environmental coupling: acoustic propagation and reflection in the medium further modulate the acoustic characteristics. In engineering, noise suppression can be achieved through modal frequency avoidance, increased damping, and optimized contact interfaces. Through the above finite element and dynamic analyses of the presser foot mechanism, the impact force magnitude and stress distribution characteristics of the presser foot during operation were identified. The main noise contributors to the three-speed adjustable gear were compared, and feasible noise reduction solutions were identified. Simultaneously, professional noise testing equipment was used to collect the overall noise of the presser foot when it was not in the gap. Through narrowband spectrum analysis, 1 / 3 octave band analysis, and colormap analysis, the primary frequency contribution to the presser foot impact noise was determined to be between 600-2000Hz.

[0124] Specifically, in one embodiment of the present application, Figure 10 The noise spectrum comparison chart of the machine with the presser foot in the gap and in the no-load state verifies that the impact noise has the characteristics of a wide bandwidth and rich high-frequency components, and the amplitude and duration of the structural vibration directly determine the noise intensity. High-frequency vibrations are more easily absorbed by damping materials because the friction between molecules is more intense at high frequencies. The function of the damping material is to absorb this energy during the vibration transmission process, reducing the amplitude and duration of the vibration, thereby reducing the noise. Therefore, damping materials are more effective in this regard. Different damping materials have different effects on vibrations of different frequencies. For wide-band noise, a composite structure of multiple damping materials can be used to better cover noise reduction in various frequency bands. The core parameter for measuring the energy dissipation capacity of a material is the loss factor of the damping material. The larger the η, the more efficient the energy conversion into heat energy. Wide-temperature viscoelastic polymer damping materials with an η of 0.5 or above are selected.

[0125] Specifically, in one embodiment of the present application, according to the analysis results, a reasonable presser foot structure is designed, a multi-layer damping composite material is matched, and the damping peak frequency bands of different materials are superimposed to achieve broadband noise reduction; wherein the presser foot component structure is as follows Figure 11 As shown, the detailed structure of the presser foot bottom plate is as follows Figure 12As shown. The main material of the presser foot bottom plate is 20CrMo, and its tail end is the area in direct contact with the main feed teeth and auxiliary teeth. During the entire movement process, the front half of the main feed teeth and the back half of the differential teeth are in contact with the presser foot the most. Secondly, the main feed teeth are the first to contact the presser foot, so the presser foot and the main feed teeth are more worn. A composite material filling area Ⅰ11-3-1 is designed here, and the filling depth is 1.5mm; the tail end of the presser foot bottom plate is connected to the wire pressing plate 11-2 through the threaded hole Ⅰ11-3-2, and the area next to it is the bending needle avoidance groove 11-3-4; the U-shaped groove 11-3-3 is the joint between the presser foot and the presser foot frame to ensure that the presser foot bottom plate is in a state of flexible rotation during work; the composite material filling area Ⅱ11-3-5 is designed The front area where the presser foot plate contacts the differential teeth is designed, and this is where stress on the presser foot plate is most concentrated during operation. The filling depth is 1.5mm. The presser foot claw 11-4 is secured to the presser foot plate 11-3 via threaded hole II 11-3-6, and the auxiliary presser foot 11-5 is secured to the presser foot plate 11-3 via threaded hole III 11-3-7. The front end of the presser foot plate features an arcuate surface to guide the fabric through smoothly and reduce resistance during sewing. Composite material filling area III 11-3-8 is designed, with a filling depth of 1.5mm. The presser foot plate includes three composite material filling areas, cleverly designed at the front, middle, and back of the plate. This effectively reduces the noise caused by high-frequency vibrations that occur when the presser foot periodically collides with the needle plate and teeth during operation.

[0126] The present invention uses professional simulation analysis methods to build a finite element model and a dynamic model of the presser foot mechanism module of the overlock sewing machine, obtains the contact force of the presser foot colliding with the needle plate and the contact force of the presser foot colliding with the teeth during operation, and determines the main noise contribution mechanism of the machine under three different tooth trajectory modes; further, the presser foot sole is made flexible, so as to understand the rigidity of the presser foot sole and determine whether resonance occurs in the presser foot sole during operation, resulting in energy surge and increased noise value; and according to the vibration response of the presser foot surface during operation, a damping embedded structure scheme for the presser foot sole is formulated;

[0127] At the same time, professional noise detection equipment is used to collect and analyze presser foot noise, identify the noise contribution spectrum characteristics, and lock the broadband spectrum of the presser foot impact noise to 600-2000Hz. In this way, a presser foot with a composite structure of multiple damping materials with better vibration absorption effect that matches this frequency range is designed.

[0128] In summary, this invention aims to locate the noise source of sewing equipment and identify the key response areas of noise source components. Through analysis and location, it identifies target areas for improvement. Furthermore, by targeting frequency bands and matching composite noise-reducing damping materials, it achieves precise and efficient noise reduction. This invention uses simulation technology to deeply analyze the overlock seam noise from the perspective of noise generation, identifying the main noise-contributing components and the noise-contributing frequency bands. This allows for the design of a more reasonable and effective presser foot noise reduction solution.

[0129] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for analyzing the noise of the seam opening of the presser foot of a seam tape, characterized in that: The steps include: Step 1: Establish a rigid body dynamics model of the presser foot mechanism and the tooth feeding structure, extract the contact force value and change law during the collision between the parts, and determine the noise contributing parts; In the second step, the finite element mesh of the noise-contributing parts is made flexible through the modal synthesis method and replaced into the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure. A rigid-flexible coupling model is built to obtain the displacement, velocity response and surface vibration radiation noise ERP of the noise-contributing parts during the movement process, and obtain the vibration response area distribution of the noise-contributing parts.

2. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 1, wherein: Step 3: Use noise testing equipment to collect the presser foot gap noise of the physical device of the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure, analyze the noise spectrum, and determine the frequency band distribution of the collision noise contribution.

3. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 2, wherein: Step 4: For the noise reduction improvement target area of ​​the noise-contributing parts, match the damping material composite structure and confirm the noise reduction results through simulation and testing.

4. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 1, wherein: In step 1, contact characteristics are established between two parts that will cyclically generate contact and collision during operation to simulate the collision between parts in actual operation; In step 1, the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure is run to obtain a kinematic force analysis and comparison under different modes under different sewing requirements, and the maximum contact force corresponding to different sewing requirements is obtained. The maximum contact force is the corresponding noise contributing part.

5. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 4, characterized in that: In step 2, a finite element model of the noise-contributing part is established, and the noise-contributing part is made flexible and incorporated into the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure to obtain the stress distribution of the noise-contributing part in the working state and the distribution of the impact force area of ​​the noise-contributing part at different times; After setting the corresponding parameters, the modal synthesis method is used to convert the finite element model of the noise-contributing parts into a modal neutral model, which is then imported into the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure to replace the noise-contributing parts of the pure rigid body, thus obtaining the rigid-flexible coupling dynamic model of the noise-contributing parts.

6. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 3, characterized in that: In step 3, the target contribution frequency band of the impact noise is locked; In step 4, for the noise contributing parts, damping materials are matched and combined according to the distribution of vibration response areas and set in the target vibration area of ​​the noise contributing parts.

7. A method for analyzing seam noise caused by a presser foot of a seam tape according to claim 6, characterized in that: In step 3, the target contribution frequency band of the presser foot impact noise is 600-2000 Hz.

8. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 5, characterized in that: In step 2, the rigid-flexible coupling dynamic model is the Hertz model in the rigid-flexible body contact mechanics model; in the modeling state of the rigid-flexible coupling dynamic model, the initial contact state between the noise contributing part and the part colliding with it does not penetrate; When establishing contact for a rigid-flexible coupling model, the maximum penetration value is within the range of less than or equal to 0.3; In step 2, the rigid-flexible coupling dynamic model is run to obtain the stress distribution of the noise-contributing parts during operation and when they collide with the parts that collide with them. The vibration displacement response and vibration velocity response of the noise-contributing parts, as well as the surface vibration sound radiation ERP cloud map, are obtained to determine the vibration response area distribution of the noise-contributing parts.

9. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 4, characterized in that: In step 1, the parts of the rigid body dynamics model include the handwheel, the main shaft, the tooth lifting slider, the main differential tooth frame, the main differential tooth, the main feed connecting rod, the main feed crank, the differential crank, the differential slider assembly, the feeding shaft, the differential feed connecting rod, the cloth feeding assembly, the lower knife seat, the needle plate pad, the needle plate, the presser foot assembly, the presser foot arm, the presser foot shaft, and the press rod assembly; In step 1, the contact force value and its changing pattern during the impact between the presser foot and the needle plate and teeth are extracted; In step 1, material parameters are assigned to the parts included in the rigid body dynamics model. The material parameters include: Young's modulus E, Poisson's ratio V and material density P; The connection relationship between the parts included in the rigid body dynamics model is realized by adding kinematic pairs; In step 1, the contact characteristics between the presser foot and the teeth are established; the contact characteristics between the presser foot and the needle plate are established; the values ​​required for modeling are determined according to the geometric matching relationship and material properties of the two contacting parts; the contact between the presser foot bottom plate plane and the needle plate plane, and the presser foot bottom plate plane and the main differential teeth are established respectively; In step 1, the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure is run to obtain the contact forces between the presser foot bottom plate plane and the needle plate and the teeth; In step 2, in the modeling state of the rigid-flexible coupling dynamic model, no penetration occurs in the initial contact state between the presser foot sole surface and the teeth and needle plate; when establishing the contact of the rigid-flexible coupling model, the maximum penetration value range is less than or equal to 0.

3.

10. The method for analyzing the gap noise of the presser foot of the overlock tape according to claim 5, characterized in that: In step 1, the rigid body dynamics model of the presser foot mechanism and the tooth feed structure is run to obtain the contact force between the impacting parts; In step 2, the contact collision force between the noise-contributing part and the part that collides with it is obtained through the rigid body dynamics model of the presser foot mechanism and the tooth feeding structure, and is used to establish a finite element model of the noise-contributing part; In step 2, the rigid-flexible coupling dynamic model of the noise-contributing parts is run to obtain the stress distribution of the presser foot sole when it collides with the needle plate and teeth during operation, and the vibration displacement response and vibration velocity response of the presser foot sole surface, as well as the surface vibration sound radiation ERP cloud map, are obtained. According to the vibration response distribution, the front end area of ​​the presser foot sole is obtained as the target vibration area.

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