Bionic leaf vein film metamaterial engine nacelle cover acoustic insulation

Abstract

The present application relates to vehicle NVH sound insulation technology, disclose a kind of bionic vein film metamaterial sound insulation pad for the inner surface of engine hood cover.The pad includes a plurality of sound insulation modules and a bearing matrix, and at least two sound insulation subzones are divided in the pad surface.Each sound insulation module includes a clamping frame, a tensioned film, a bionic vein inspired swing arm skeleton coupled to the film, and a plurality of oscillators;The swing arm skeleton forms nodes, and at least two oscillators are located at different nodes, different radial positions and different masses or positions, so that a single module generates two or more staggered anti-resonance sound insulation peaks at low frequency.Different subzones use different parameter combinations to further stagger the peak frequency and form a multi-peak coverage, thereby improving the low-frequency sound insulation of the engine compartment under the conditions of thinness and curved assembly.The clamping frame preferably clamps the film with a pressing frame and a supporting frame, and a pre-tightening structure is provided to adjust and lock the pre-tightening force to reduce peak frequency drift;Transition connection zones can be provided between adjacent modules.

Description

Technical Field

[0001] This invention relates to the field of vehicle noise, vibration and acoustic comfort (NVH) technology, and more particularly to a low-frequency sound insulation pad for the inner surface of an engine hood, and more specifically to an engine hood sound insulation pad based on the anti-resonance mechanism of a tensioned film and employing a biomimetic leaf vein-inspired swing arm frame and multi-vibrator coupling structure. Background Technology

[0002] Engine hood sound insulation cotton / sound insulation pads typically employ a composite structure of porous sound-absorbing materials such as fibers, foams, and non-woven fabrics, along with a skin layer, damping layer, or foil layer. This type of structure is effective against mid-to-high frequency noise, but its effectiveness in controlling low-frequency noise in engine compartments is often limited by constraints in thickness, surface density, installation space, and weight. Simply increasing the thickness or surface density will lead to increased weight, installation difficulties, and increased costs.

[0003] Thin-film acoustic structures can utilize the coupling of a tensioned membrane with an additional vibrator to generate a transmission loss peak (anti-resonance sound insulation peak) at low frequencies, thereby achieving enhanced sound insulation with a relatively small thickness. However, existing structures mostly employ regular frames and single mass blocks (or a few mass blocks), often relying on multi-layer stacking or simple juxtaposition of units with different parameters to achieve multi-peak coverage. Furthermore, under conditions of curved surface assembly of the engine hood and exposure to heat, oil mist, and vibration, the long-term stability of the membrane tension boundary and the control of peak frequency drift become engineering challenges.

[0004] Therefore, there is a need for an engine hood sound insulation pad that can maintain tension boundary stability under curved surface assembly constraints, form controllable multi-state anti-resonance multi-peaks within a single module, and achieve multi-peak coverage through in-plane partitioning. Summary of the Invention

[0005] The purpose of this invention is to provide a biomimetic leaf vein film metamaterial engine hood sound insulation liner to solve the problems of limited improvement in low-frequency sound insulation under the constraints of thickness, weight and temperature resistance, insufficient film boundary stability under curved surface assembly and difficulty in achieving multi-peak coverage in the existing technology.

[0006] To achieve the above objectives, the present invention provides an engine hood sound insulation pad, the sound insulation pad comprising a supporting substrate and a plurality of sound insulation modules, and divided into at least two sound insulation zones within its surface.

[0007] Each sound insulation module includes a peripheral clamping frame, a tensioning membrane, a biomimetic leaf vein-inspired swing arm skeleton, and multiple vibrators. "Peripheral" refers to the direction along the periphery of the membrane's outer boundary, which can be square, rectangular, or other polygonal, and is not limited to a circular boundary. The swing arm skeleton includes at least one main swing arm and several swing arm units connected to the main swing arm. Each swing arm unit is a straight line segment or a broken line segment, and optionally a multi-level branch structure, thus forming multiple nodes. Multiple vibrators are positioned at different nodes and / or different radial positions, with at least two vibrators differing in mass and / or installation position, thereby creating two or more staggered anti-resonance sound insulation peaks within a single sound insulation module.

[0008] Different combinations of parameters (film preload, film thickness, number / size / angle of the swing arm / number of branches, vibrator mass and vibrator installation position, etc.) are used in different sound insulation zones to further stagger the anti-resonance sound insulation peak frequencies of different zones and achieve multi-peak coverage.

[0009] Furthermore, the peripheral clamping frame adopts a structure in which the pressure frame and the support frame clamp the film, and a pre-tightening structure is set to form a repeatable film pre-tightening boundary; the sound insulation module can be a replaceable module; a transition connection area can be set between adjacent sound insulation modules to improve the compatibility of curved surface assembly and reduce stress concentration.

[0010] Sound insulation zones can be determined based on the structural and acoustic characteristics of the inner surface of the engine hood. The structural characteristics include at least one of the following: distribution of reinforcing ribs, distribution of fixing points, and curvature variation zones. The acoustic characteristics include at least one of the following: distribution of sound pressure hotspots or distribution of order peaks of the target low-frequency noise. The peak-frequency difference of the first anti-resonance sound insulation peak between adjacent sound insulation zones can be set to be no less than 30Hz, or no less than 5% of the lower peak frequency in adjacent sound insulation zones, to reduce peak frequency overlap between zones and improve the repeatability of in-plane multi-peak coverage.

[0011] Compared with the prior art, the present invention has at least the following beneficial effects:

[0012] (1) By coupling the swing arm skeleton inspired by bionic leaf veins with different nodes and positions of multiple oscillators, a multi-state anti-resonance multi-peak is formed within a single module, reducing the dependence on multi-layer superposition;

[0013] (2) By using different parameter combinations in the in-plane partitioning, the peak frequencies are staggered to achieve multi-peak coverage and improve the sound insulation efficiency of the target low-frequency band;

[0014] (3) By using the peripheral clamping frame to maintain the membrane tension boundary, the preload change and peak frequency drift caused by curved surface assembly and working conditions are reduced, thereby improving durability and consistency;

[0015] (4) Improve low-frequency sound insulation of engine hood and enhance cockpit comfort under the constraints of thinness and lightness. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the installation position of the engine hood and the sound insulation pad of the present invention;

[0017] Figure 2 A schematic diagram of the in-plane partitioning layout of the sound insulation pad;

[0018] Figure 3 This is a structural breakdown diagram of the sound insulation module;

[0019] Figure 4 A schematic diagram of the transitional structure of the biomimetic leaf vein network swing arm skeleton;

[0020] Figure 5 A schematic diagram of the arrangement of the swing arm and vibrator in the sound insulation module after topology optimization based on the biomimetic leaf vein-inspired structure.

[0021] Figure 6 This is a schematic diagram of the cross-sectional structure of the surrounding clamping frame;

[0022] Figure 7 This is a schematic diagram of the transition connection area between adjacent sound insulation modules;

[0023] Figure 8 This is a schematic diagram comparing the experimental and simulation results of the sound insulation module after topology optimization.

[0024] Figure 9 This is a schematic diagram illustrating the effect of different film thicknesses on sound transmission loss.

[0025] Figure 10 This is a schematic diagram illustrating the effect of different swing arm thicknesses on sound transmission loss.

[0026] Figure Labels

[0027] 1 Engine hood; 2 Sound insulation pad; 20 Load-bearing base; 21 First zone; 22 Second zone; 30 Sound insulation module; 31 Peripheral clamping frame; 311 Pressure frame; 312 Support frame; 313 Pre-tightening structure; 40 Membrane; 50 Bionic leaf vein-inspired swing arm skeleton; 51 Main swing arm; 52 Swing arm unit (can be a branch swing arm); 53 Node; 60 Vibrator; 61 Long vibrator; 62 Short vibrator; 70 Transition connection area; 80 Anti-oil mist protective layer. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings. It should be understood that equivalent substitutions in structural form, size, and materials without departing from the spirit of the present invention shall fall within the scope of protection of the present invention.

[0029] Overall structure and installation

[0030] like Figure 1As shown, a sound-insulating pad 2 is provided on the inner surface of the engine hood 1.

[0031] like Figure 2 As shown, the sound insulation pad 2 includes a supporting base 20 and sound insulation modules 30. The sound insulation modules 30 can be replaceable modules, preferably installed on the supporting base 20 in a detachable manner; the detachable manner includes, but is not limited to, snap-fit ​​connection, screw connection, or a combination of the above, to facilitate maintenance, replacement, and zone tuning. The shape of the supporting base 20 matches the inner surface of the engine hood 1, and mounting holes or fixing points can be provided to adapt to the hood structure. The sound insulation pad 2 is divided into at least two sound insulation zones within its surface, such as a first zone 21 and a second zone 22. The sound insulation modules 30 in the first zone 21 and the second zone 22 use different parameter combinations to stagger the anti-resonance sound insulation peak frequencies of each zone, thereby forming multi-peak coverage of low-frequency noise in the engine compartment.

[0032] The sound pressure hotspot area can be obtained by measuring the sound pressure on the inner surface of the engine hood within the target frequency band using a whole vehicle or test bench, or by acoustic simulation. The boundary of the sound pressure hotspot area can be determined by the contour lines of the sound pressure level in the target frequency band. Preferably, the contour line corresponding to a certain percentage threshold of the sound pressure level reaching its peak value is used as the boundary to determine the range and boundary location of the sound insulation zone.

[0033] Sound insulation module structure

[0034] like Figure 3 As shown, the sound insulation module 30 includes a peripheral clamping frame 31, a tensioning membrane 40, a biomimetic leaf vein swing arm skeleton 50, and multiple vibrators 60.

[0035] like Figure 4 As shown, the transition structure of the swing arm frame 50 includes a main swing arm 51 and several swing arm units 52, and forms a node 53 at the intersection of the swing arms; Figure 4 This is used to illustrate the "biomimetic-inspired structural generation approach" and does not require the final sound insulation module to adopt the exact same branch form.

[0036] like Figure 5 As shown, Figure 4 The biomimetic-inspired structure shown is used to obtain a structural arrangement for the sound insulation module through topology optimization: multiple vibrators 60 are set at different nodes 53 and / or different swing arm positions; at least two vibrators differ in mass and / or installation position, and may be located at different radial distances to form two or more staggered anti-resonance sound insulation peaks. The vibrator 60 may include a long vibrator 61 and a short vibrator 62, which differ in length, mass and / or installation radius to achieve peak frequency and peak spacing adjustment.

[0037] Tensioning boundary and pretensioning structure

[0038] like Figure 6As shown, the peripheral clamping frame 31 includes a pressure frame 311 and a support frame 312, with the diaphragm 40 clamped between the pressure frame 311 and the support frame 312. A pre-tightening structure 313 is provided between the pressure frame 311 and the support frame 312. The pre-tightening structure 313 can be a screw clamping structure, a wedge-shaped pressure ring structure, or a distributed clamping component, used to adjust and lock the pre-tightening force of the diaphragm 40, so that the diaphragm 40 remains in a taut state after assembly and forms repeatable boundary conditions, thereby reducing peak frequency drift caused by curved surface assembly and changes in operating conditions.

[0039] In this invention, the peripheral clamping frame 31 may include an outer contour dimension and an inner window dimension: the outer contour dimension is used to match the installation space of the supporting substrate 20, and the inner window dimension is used to define the effective vibration area of ​​the film 40. The film boundary clamping length (clamping coverage width) is the clamping coverage width w of the pressure frame 311 and the support frame 312 on the film 40, where w is 1mm to 10mm. Taking a square sound insulation module as an example, when the side length of the film blank is L, the side length of its effective vibration area can be (L−2w), and the side length of the inner window can be the same as or approximately the same as the side length of the effective vibration area; thus, while satisfying the clamping length w, it ensures that the film 40 forms a stable and repeatable peripheral clamping boundary condition.

[0040] The characteristic dimensions of the swing arm frame are used to characterize the density and equivalent stiffness of the swing arm frame. The characteristic dimensions can be characterized by at least one or a combination of the swing arm length, swing arm width, swing arm thickness, polygonal angle, and distance between adjacent nodes. The number of oscillators 60 can be 2 to 18, and the oscillators 60 can be set at different nodes 53 to form different modal coupling conditions.

[0041] Partition transition and protective layer

[0042] like Figure 7 As shown, a transition connection zone 70 can be set between adjacent sound insulation modules. The transition connection zone 70 includes flexible splicing pieces and an elastic buffer structure to adapt to changes in the curvature of the hatch and reduce stress concentration at the boundary of the partition. The sound insulation pad 2 may also include an anti-oil mist protective layer 80, which is bonded to the supporting substrate 20 for environmental protection; the anti-oil mist protective layer 80 does not serve as the dominant structure for forming the anti-resonance sound insulation peak.

[0043] For ease of reproduction, this embodiment provides a set of manufacturable and tunable parameters: Thin film 40: square, 50mm long, 50mm wide, and 0.2mm thick; material is polyimide (PI); peripheral clamping frame 31: 50mm × 50mm in shape, 2mm thick; swing arm frame 50: swing arm length 12mm, width 2mm, and thickness 4mm (adjustable within the range of 2mm to 6mm); wherein, the "length / width" of the thin film 40 refers to the external dimensions of the thin film blank; the effective vibration area of ​​the thin film 40 is jointly defined by the inner window size of the peripheral clamping frame 31 and the clamping length w. When the clamping length w is 1mm to 10mm, the effective vibration area size can be (50−2w)mm × (50−2w)mm accordingly. The material is steel; the swing arm unit can be a straight segment or a broken segment, and optionally has two or more branches; the vibrator 60 can be of two types: long and short, with the long vibrator being 10mm long and the short vibrator being 5mm long and 2mm wide; the vibrator thickness is 1mm (adjustable within the range of 1mm to 3mm); the vibrator 60 can be arranged to extend along the in-plane direction of the membrane 40 (i.e., the angle between the extension direction of the vibrator and the out-of-plane normal direction of the membrane is approximately 90°), to form in-plane coupling and facilitate the arrangement of different vibrators at different installation radii. The installation radii of the two types of vibrators from the center can be approximately 8mm and approximately 13mm, respectively, to form different equivalent masses and different coupling positions; the material is steel. The preload force (preload stress) of the membrane 40 can be 1MPa to 3MPa, and can be repeatedly adjusted and locked through the preload structure 313.

[0044] The aforementioned anti-resonance sound insulation peak frequency position, peak transmission loss, and sound insulation bandwidth can be obtained through impedance tube transmission loss testing or finite element / acoustic simulation. When combining experiments and simulations, the parameter variation trend can be determined first through simulation, and then the key peak frequency can be calibrated through sample testing to improve the consistency and repeatability of engineering applications.

[0045] The structure of this invention can form an anti-resonance sound insulation peak in the target low-frequency range (100Hz~1000Hz). The following is a set of regular results that can be used for zone tuning:

[0046] When the preload of the membrane increases from 1 MPa to 3 MPa, the frequency of the first sound insulation peak can be increased from about 460 Hz to about 560 Hz, and the sound transmission loss at the peak can be increased from about 57 dB to about 62 dB, and the sound insulation bandwidth can be increased from about 730 Hz to about 800 Hz.

[0047] When the film thickness increases from 0.1 mm to 0.3 mm, the frequency of the first sound insulation peak can be increased from about 310 Hz to about 710 Hz, the transmission loss at the peak can be increased from about 54 dB to about 61 dB, and the sound insulation bandwidth can be increased from about 470 Hz to about 1090 Hz.

[0048] When the thickness of the swing arm increases from 2mm to 6mm, the frequency of the first sound insulation peak can be reduced from about 610Hz to about 390Hz, the transmission loss at the peak can be changed from about 55dB to about 60dB, and the sound insulation bandwidth is about 710Hz to 770Hz.

[0049] When the thickness of the vibrator increases from 1 mm to 3 mm, the frequency of the first sound insulation peak can change from about 460 Hz to about 600 Hz, the transmission loss at the peak can change from about 57 dB to about 60 dB, and the sound insulation bandwidth is about 730 Hz to 910 Hz.

[0050] Accordingly, different parameter combinations can be used for different sound insulation zones to stagger the peak frequencies and cover the target low-frequency noise spectrum peaks; and since the peripheral clamping frame 31 can lock the pre-tightening boundary of the film, it can reduce the impact of assembly and working conditions on peak frequency drift.

[0051] The determination of sound insulation zones can be based on at least one or a combination of the distribution of reinforcing ribs, fixed points, curvature change areas, and sound pressure hotspots / order peaks of the target low-frequency noise on the inner surface of the engine hood, so that different zones cover different target frequency sets or frequency bands respectively.

[0052] The peak-to-peak frequency difference of the first anti-resonance sound insulation peak between adjacent sound insulation zones can be set to no less than 30Hz, or no less than 5% of the lower peak frequency, in order to reduce the decrease in coverage efficiency caused by peak frequency overlap.

[0053] The thin film can be square, with a side length that can be selected in the range of 30mm to 80mm, in order to balance the array arrangement and the target peak frequency range.

Claims

1. A biomimetic leaf vein film metamaterial sound insulation pad for the inner surface of an engine hood, comprising a supporting substrate and a plurality of sound insulation modules disposed on the supporting substrate, wherein the sound insulation pad is divided into at least two sound insulation zones in its surface. Its features are: Each sound insulation module includes a peripheral clamping frame, a membrane fixed to the peripheral clamping frame and in a tensioned state, a swing arm frame located on one side of the membrane and coupled to the vibration of the membrane, and a plurality of vibrators disposed on the swing arm frame. The swing arm frame is an asymmetrical structure, including at least one main swing arm and several multi-level branch swing arm units connected to the main swing arm. The swing arm units are straight segments or broken segments and form multiple nodes that are not uniformly distributed. The multiple oscillators include at least two oscillators, which are set at different nodes and / or different swing arm positions and are different in mass and / or position, causing the sound insulation module to produce modal symmetry breaking and local impedance mismatch, forming two or more staggered anti-resonance sound insulation peaks in the 100Hz~1000Hz Goal low frequency band. The sound insulation modules in different sound insulation zones adopt different parameter combinations. The parameter combinations include at least one of the following: film preload, film thickness, swing arm geometric parameters, oscillator mass and oscillator position, so that the anti-resonance sound insulation peak frequencies of different sound insulation zones are staggered to form multi-peak coverage. The peripheral clamping frame includes a pressure frame and a support frame. The film is clamped between the pressure frame and the support frame, and a pre-tightening structure is provided between the pressure frame and the support frame to adjust and rigidly lock the pre-tightening force of the film to form a repeatable tension boundary condition, so that the pre-tightening force of the film is maintained within a preset gradient range, thereby reducing peak frequency drift caused by assembly and operating condition changes and maintaining the peak frequency difference between different sound insulation zones; and the peak frequency difference of the first anti-resonance sound insulation peak of adjacent sound insulation zones is not less than 30Hz, or not less than 5% of the lower peak frequency in adjacent sound insulation zones; the film is a polyimide film, a PET film, or a composite film thereof.

2. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: A transition connection area is provided between adjacent sound insulation modules. The transition connection area includes a flexible splicing piece and an elastic buffer structure. The stiffness of the flexible splicing piece is less than that of the surrounding clamping frame. It is used to absorb the stress caused by the curvature change of the inner surface of the engine hood without damaging the rigid tension boundary of the sound insulation module.

3. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The sound insulation module is a replaceable sound insulation module, which is fixed to the supporting substrate by snap-fit ​​connection, screw connection or a combination of the above methods.

4. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The pre-tightening structure is a screw clamping structure, a wedge-shaped clamping ring structure, or a distributed clamping component.

5. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The swing arm unit has a branch structure of 2 levels or more.

6. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The oscillator includes a long oscillator and a short oscillator, which differ in length, mass and / or installation radius.

7. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 6, characterized in that: The oscillator extends in the in-plane direction of the thin film, and the angle between the extension direction of the oscillator and the out-of-plane normal direction of the thin film is 80° to 100°.

8. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The sound insulation pad also includes an oil mist protection layer, which is bonded to the surface of the supporting substrate, and the oil mist protection layer is not the dominant structure forming the anti-resonance sound insulation peak.

9. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The sound insulation zones are determined based on the structural and acoustic characteristics of the inner surface of the engine hood. The structural characteristics include at least one of the following: distribution of reinforcing ribs, distribution of fixing points, and curvature variation zones. The acoustic characteristics include at least one of the following: sound pressure hotspot regions and order peak regions.

10. The biomimetic leaf vein film metamaterial sound insulation pad as described in claim 1, characterized in that: The peripheral clamping frame has a clamping coverage width of 1mm to 10mm for the film; the film is a square film with a side length of 30mm to 80mm; the preload of the film is 1MPa to 3MPa.

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