A carbon fiber-aluminum alloy composite structure with voice coil skeleton integrated with diaphragm and a manufacturing method thereof

Abstract

The application discloses a carbon fiber-aluminum alloy composite structure with integrated voice coil skeleton and diaphragm and a manufacturing method thereof. The structure comprises a carbon fiber composite diaphragm main body with an annular indentation in the center of the back and a carbon fiber-aluminum alloy composite round pipe voice coil skeleton; the skeleton and the diaphragm are integrally formed into a whole structure through gap cooperation and integrated solidification. The thickness of the aluminum foil layer is 0.1-0.3 mm, a three-dimensional heat bridge is constructed, the thermal resistance of the voice coil-diaphragm is reduced from 8.5°C / W of the traditional carbon fiber skeleton to 3.1°C / W, which is reduced by 62%, the moving mass is reduced by 31% compared with the pure aluminum skeleton, the gluing interface is eliminated, the interface peeling strength is greater than or equal to 15N / mm, and there is no delamination after 1000 times of temperature cycle. A carbon fiber-aluminum alloy composite voice coil skeleton is also disclosed as a separate component. The application is suitable for large-diameter subwoofer units.

Description

Technical Field

[0001] This invention relates to the field of electroacoustic transducer technology, and in particular to a carbon fiber-aluminum alloy composite structure integrating a voice coil skeleton and a diaphragm, and its manufacturing method, which is suitable for large-diameter (≥18 inches) subwoofer units. Background Technology

[0002] In large-diameter subwoofer units, the voice coil bobbin is a crucial component connecting the voice coil windings to the diaphragm, undertaking the triple functions of electromagnetic force transmission, heat conduction, and structural support. During operation, the voice coil generates a significant amount of heat due to resistive losses; for a 21-inch subwoofer unit, the voice coil temperature can reach over 200°C under continuous high-power input. If this heat cannot be dissipated in time, it will lead to the failure of the voice coil winding insulation, softening of the adhesive, and deformation of the bobbin, ultimately causing permanent damage to the speaker.

[0003] In the prior art, the voice coil skeleton materials mainly include the following categories: (1) Aluminum alloy skeleton: thermal conductivity is as high as 237W / m·K, with excellent heat dissipation performance, but the density is high (2700kg / m³), which increases the moving mass; and aluminum is a conductive material, which will generate eddy currents when moving in the magnetic gap, resulting in additional distortion and heat generation. (2) Kapton (polyimide) film: low density (1420kg / m³), high temperature resistance (up to 260°C), but extremely low thermal conductivity (about 0.12W / m·K), with almost no heat conduction ability. (3) Glass fiber / epoxy resin composite material: high temperature resistance (up to 300°C or more), good rigidity, but also low thermal conductivity (about 0.5-1.0W / m·K in the plane, even lower in the thickness direction), with limited thermal management ability. (4) Carbon fiber composites: high specific stiffness and high specific strength, but the thermal conductivity of carbon fiber is anisotropic—the thermal conductivity along the fiber direction is about 5-10 W / m·K, while it is only about 0.5-1.0 W / m·K perpendicular to the fiber direction (thickness direction). When the voice coil skeleton is a carbon fiber tube, after the heat is transferred from the winding to the skeleton, it needs to pass through the thickness direction of the carbon fiber layer to be conducted to the diaphragm. The thermal resistance of this path is extremely high, which causes heat to accumulate at the skeleton-winding interface.

[0004] Furthermore, in existing technologies, the voice coil frame and diaphragm are typically connected using adhesives (such as epoxy resin or cyanoacrylate). This connection method has the following problems: First, the adhesive layer has high thermal resistance, hindering heat conduction from the frame to the diaphragm; second, the adhesive layer is prone to softening at high temperatures, causing relative displacement between the frame and the diaphragm, affecting the linearity of the piston movement; third, the adhesive layer may delaminate after aging, reducing structural reliability.

[0005] Existing technology CN121865171A discloses a loudspeaker voice coil diaphragm structure, claiming that the voice coil frame and diaphragm are integrally molded, eliminating the adhesive bonding interface. However, the integral molding of this patent involves molding the diaphragm in pieces and then bonding them together—that is, first molding the diaphragm and frame separately, and then bonding them together by hot pressing or adhesive. Essentially, this is a physical combination rather than a chemical bond. The bonding interface still relies on physical contact and residual adhesive, resulting in high interfacial thermal resistance and significant long-term reliability affected by temperature cycling. Measured thermal resistance at the voice coil-diaphragm interface of this structure is approximately 6.5-8.0°C / W, which is orders of magnitude different from that of this invention.

[0006] To address the aforementioned issues, this invention proposes a carbon fiber-aluminum alloy composite structure integrating the voice coil skeleton and diaphragm, along with its manufacturing method. A three-dimensional thermal bridge is constructed using aluminum layers, allowing for rapid, simultaneous axial and radial heat transfer from the voice coil to the diaphragm, achieving integrated thermal management of the magnetic circuit, voice coil, and diaphragm. Simultaneously, integrated co-curing eliminates the adhesive interface, forming a truly integral structure through epoxy resin cross-linking and aluminum-resin chemical bonding, thus improving structural reliability and force transmission efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a carbon fiber-aluminum alloy composite structure integrating the voice coil skeleton and the diaphragm, and its manufacturing method. Through the design of the carbon fiber-aluminum alloy composite skeleton and the integrated co-curing molding structure, the thermal resistance of the voice coil-diaphragm is reduced by more than 60% without significantly increasing the moving mass, eliminating the adhesive interface, and improving the structural reliability and force transmission efficiency.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A carbon fiber-aluminum alloy composite structure integrating a voice coil skeleton and a diaphragm includes: a carbon fiber composite diaphragm body with an annular indentation at the center of its back; a voice coil skeleton, which is a carbon fiber-aluminum alloy composite cylindrical tube, including an inner carbon fiber coil and an outer aluminum foil layer; the upper end of the voice coil skeleton is mechanically connected to the annular indentation of the diaphragm body through a clearance fit, and the structure is integrally formed by co-curing; the thickness of the aluminum foil layer is 0.1-0.3 mm, and the wall thickness of the carbon fiber coil is 0.8-1.5 mm.

[0009] Furthermore, the aluminum foil layer is made of 1060 pure aluminum or 5052 aluminum alloy with a thermal conductivity ≥190W / m·K; the carbon fiber tube is made of T700S or T800S carbon fiber / epoxy resin prepreg, with the fiber direction being ±45° or [0° / 90°] layup.

[0010] Furthermore, the annular recess of the diaphragm body is an annular groove with a diameter of Φ150-155mm and a depth of 2.0-3.0mm, the outer diameter of the voice coil skeleton is Φ150-155mm, and the fitting gap between the voice coil skeleton and the annular recess is 0.02-0.20mm.

[0011] Furthermore, an annular aluminum foil gasket is provided between the upper end face of the voice coil skeleton and the diaphragm body. The thickness of the gasket is 0.05-0.15mm, the inner diameter is equal to the inner diameter of the voice coil skeleton, and the outer diameter is equal to the outer diameter of the voice coil skeleton. The gasket softens and fills the mating gap during the co-curing process, forming a continuous aluminum thermal bridge.

[0012] Furthermore, the outer surface of the voice coil skeleton is provided with a spiral microgroove, the depth of which is 0.05-0.15mm and the pitch is 1.0-2.0mm, which is used to increase the contact area between the voice coil winding and the skeleton and to embed it into the bottom layer of the winding.

[0013] Furthermore, the outer surface of the aluminum foil layer is provided with an anodized layer, the thickness of which is 5-15μm, to improve the winding insulation and surface hardness; the lower end of the voice coil skeleton is provided with a heat dissipation ring, which is an aluminum annular fin, integrally formed or welded to the aluminum foil layer of the voice coil skeleton, the outer diameter of which is 5-15mm larger than the outer diameter of the voice coil skeleton, and the gap between the outer diameter of which is ≥2mm and the inner diameter of the magnetic circuit system.

[0014] Furthermore, it also includes a voice coil winding, which is wound on the outer surface of the voice coil skeleton, and is made of copper or aluminum wire with a diameter of 0.3-0.5 mm and 2-4 layers.

[0015] The present invention also provides a method for manufacturing a carbon fiber-aluminum alloy composite structure integrating the voice coil skeleton and the diaphragm, comprising the following steps: S1: Preparation of carbon fiber tubes: The carbon fiber / epoxy resin prepreg is rolled into a round tube on a mandrel. After rolling, it is placed in a hot autoclave and cured at 120°C and 0.3MPa for 30-40 minutes to obtain a carbon fiber tube semi-finished product. S2: Composite aluminum foil layer: Aluminum foil is coated on the outer surface of the carbon fiber tube. Before coating with aluminum foil, the surface of the carbon fiber tube is sandblasted to a roughness Ra=3.2-6.3μm, and a primer is applied. The primer is a mixture of epoxy resin and aluminum powder, with aluminum powder mass fraction of 30%-50% and primer coating thickness of 0.03-0.08mm. Hot pressing is used for composite bonding. The hot pressing temperature is 80-100°C, the pressure is 0.2-0.4MPa, and the time is 10-15 minutes. S3: Anodizing treatment: After aluminum foil is laminated, the outer surface of the aluminum foil is anodized to form an aluminum oxide insulating layer with a thickness of 5-15μm; S4: Processing annular indentation: An annular indentation is integrally formed on the back center of the carbon fiber composite diaphragm body using a hot press mold; S5: Assemble the frame and diaphragm: Insert the upper end of the carbon fiber-aluminum alloy composite tube obtained in S2 into the annular groove of the diaphragm body, with a fitting gap of 0.02-0.20mm; place an annular aluminum foil gasket between the upper end face of the composite tube and the diaphragm body; S6: Integrated Co-curing Molding: The assembled components are placed in a hot press mold, heated to 120±3°C, pressurized to 0.5±0.1MPa, and kept at the temperature and pressure for 30-45 minutes, so that the aluminum foil layer and the carbon fiber layer of the diaphragm body form a chemical bond under the action of epoxy resin. At the same time, the aluminum foil gasket softens and fills the gap, forming an integrated structure. S7: Winding the voice coil: The voice coil winding is wound on the outer surface of the integrated voice coil skeleton obtained in S6. The winding is made of copper or aluminum wire with a diameter of 0.3-0.5mm and 2-4 layers.

[0016] Furthermore, the carbon fiber / epoxy resin prepreg mentioned in S1 is T700S or T800S carbon fiber / epoxy resin prepreg, with a layup pattern of ±45° or [0° / 90°], a single layer thickness of 0.2 mm, and a total wall thickness of 0.8-1.5 mm.

[0017] Further, the aluminum foil mentioned in S2 is 1060 pure aluminum or 5052 aluminum alloy with a thickness of 0.1-0.3mm; the base adhesive is a mixture of epoxy resin EPIKOTE 828 and aluminum powder (particle size 5-20μm), with the aluminum powder having a mass fraction of 30%-50%, and curing agent EPIKURE 3046 added (mass ratio of 30% of epoxy resin).

[0018] Furthermore, the electrolyte for the anodic oxidation treatment described in S3 is 15% sulfuric acid, the current density is 1.0-2.0 A / dm², the temperature is 18-25°C, and the oxidation time is 15-30 minutes.

[0019] Furthermore, the annular indentation described in S4 has dimensions of Φ150-155mm, a depth of 2.0-3.0mm, and a bottom arc transition of R3-5mm.

[0020] Furthermore, the thickness of the annular aluminum foil gasket in S5 is 0.05-0.15 mm, and the thickness of the gasket is greater than the mating gap.

[0021] Furthermore, the hot pressing mold in S6 includes an upper mold and a lower mold. The upper mold has a convex surface corresponding to the dome shape of the diaphragm body, and the lower mold has a positioning mandrel corresponding to the inner diameter of the voice coil skeleton, ensuring that the concentricity between the voice coil skeleton and the diaphragm body is ≤0.05mm during the curing process.

[0022] Furthermore, the interfacial bonding strength of the chemical bond described in S6 is verified by an interfacial peel strength test, wherein the peel strength is ≥15N / mm.

[0023] Beneficial effects 1. Significantly Reduced Thermal Resistance: A three-dimensional thermal bridge is constructed using aluminum foil layers, allowing heat from the voice coil to be rapidly conducted to the diaphragm along the axial direction of the aluminum foil layer, while simultaneously dissipating heat radially along the magnetic circuit. Measured voice coil-diaphragm thermal resistance decreased from approximately 8.5°C / W in the traditional carbon fiber frame to 3.1°C / W, a reduction of 62%. Under continuous 500W input, the steady-state temperature of the voice coil decreased from 185°C in the traditional structure to 143°C, a reduction of 23%, significantly extending the speaker's lifespan.

[0024] 2. Controllable motion quality: The aluminum foil layer is only 0.1-0.3mm thick, and the carbon fiber tube wall is 0.8-1.5mm thick. The overall frame weight is reduced by 35%-45% compared with the traditional pure aluminum frame, and increased by only 8%-12% compared with the pure carbon fiber frame, which is within an acceptable range.

[0025] 3. Elimination of Adhesive Interface: Through integrated co-curing, the voice coil skeleton and diaphragm body form a unified structure through the cross-linking reaction of epoxy resin and the chemical bonding of aluminum and resin, eliminating the need for traditional adhesive layers. This eliminates three major problems: thermal resistance of adhesive layers, softening and displacement of adhesive layers, and delamination due to aging of adhesive layers, significantly improving structural reliability. The interfacial peel strength is ≥15N / mm, far exceeding the 5-8N / mm of traditional adhesive bonding.

[0026] 4. Improved force transmission efficiency: The integrated structure allows the electromagnetic force of the voice coil to be directly transmitted to the diaphragm without the need for a rubber layer for buffering, improving force transmission efficiency by approximately 5%-8% and resulting in better transient response.

[0027] 5. Eddy current suppression: The aluminum foil layer is located on the outside of the carbon fiber tube and is partially shielded by the carbon fiber layer. The aluminum foil layer is thin and has a relatively high resistivity compared to copper, so the eddy current loss is reduced by about 40% compared to the traditional pure aluminum skeleton.

[0028] 6. Fundamental difference from existing technologies: CN121865171A's integrated molding involves molding the diaphragm in pieces and then bonding them together, which is a physical assembly with high interfacial thermal resistance (6.5-8.0°C / W). Its long-term reliability is greatly affected by temperature cycling. The integrated co-curing molding of this invention uses chemical bonding, resulting in low interfacial thermal resistance (3.1°C / W) and no delamination after 1000 temperature cycles. Comparative Example 4 (integrated structure without aluminum foil layer) has a thermal resistance of 7.9°C / W, demonstrating that the aluminum foil layer is crucial for thermal management; Comparative Example 3 (non-integrated structure with adhesive aluminum ring) has a thermal resistance of 5.4°C / W and debonded after 387 cycles, proving that the long-term reliability of the non-integrated structure is insufficient. Attached Figure Description

[0029] Figure 1 This is a half-section schematic diagram of the carbon fiber-aluminum alloy composite structure of the integrated voice coil skeleton and diaphragm of the present invention. Figure 2 for Figure 1 Enlarged cross-sectional view of the midrange coil frame (AA section), showing the composite structure of carbon fiber coil and aluminum foil layer; Figure 3 A magnified view of the fit between the annular indentation on the back of the diaphragm and the voice coil frame; Figure 4 A schematic diagram showing the unfolded spiral microgrooves on the outer surface of the voice coil frame; Figure 5 For the manufacturing process flowchart; Figure 6 This is a comparison diagram of the thermal resistance of the embodiments and comparative examples; Figure 7 The voice coil temperature-time curves for the examples and comparative examples under a continuous 500W input are shown. Figure 8 Temperature distribution cloud maps for finite element thermal simulation (with aluminum foil layer vs. without aluminum foil layer). Figure 9 Infrared thermal imaging (500W input steady state, diaphragm surface temperature distribution); Figure 10 The curves showing the relationship between different aluminum foil thicknesses and thermal resistance; Figure 11 This is a schematic diagram of the heat dissipation ring at the lower end of the voice coil frame. Figure 12 A comparison chart of the adhesion of windings with and without spiral microgrooves; Figure 13 This is a comparison chart of the interfacial peel strength of different base adhesive formulations. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] Example 1: Integrated voice coil frame-diaphragm structure for a 21-inch subwoofer This embodiment focuses on the Hermit Audio SW21-PRO 21-inch subwoofer unit, featuring a carbon fiber-aluminum alloy composite structure that integrates the voice coil frame and diaphragm. The voice coil frame has an outer diameter of Φ152mm and a height of 38mm.

[0032] Step S1: Preparation of carbon fiber tubes. T700S carbon fiber / epoxy resin prepreg (EPIKOTE 828 / EPIKURE 3046 system, single-layer thickness 0.2mm, areal density 200g / m²) was used. Four layers were wound on a Φ150mm stainless steel mandrel in a [0° / 90° / 0° / 90°] layup sequence, with a total wall thickness of 0.8mm. After winding, a PTFE release cloth and breathable felt were wrapped around the outside, and the tube was placed in an autoclave, heated to 120°C, pressurized to 0.3MPa, and held at that temperature and pressure for 35 minutes. After natural cooling to below 60°C, the tube was demolded to obtain a semi-finished carbon fiber tube. Measurements showed an inner diameter of Φ150.0mm, an outer diameter of Φ151.6mm, roundness ≤0.05mm, and straightness ≤0.1mm / 100mm.

[0033] Step S2: Composite Aluminum Foil Layer. 1060 pure aluminum foil is selected, with a thickness of 0.15 mm and a width of 40 mm (covering the height of the skeleton). The outer surface of the carbon fiber tube is sandblasted (quartz sand, 80 mesh, air pressure 0.4 MPa), achieving a roughness Ra = 4.5 μm. Primer Coating: Epoxy resin EPIKOTE 828 and aluminum powder (particle size 10 μm, purity ≥ 99.5%) are mixed at a mass ratio of 6:4. Curing agent EPIKURE 3046 (mass ratio of 30% of epoxy resin) is added, and the mixture is stirred evenly before coating to a thickness of 0.05 mm. The mechanism of action of aluminum powder in the primer: Aluminum powder particles are embedded in the micro-pits on the carbon fiber surface, forming a mechanical interlock; simultaneously, the oxide layer on the aluminum powder surface undergoes a coordination reaction with the epoxy resin, enhancing the interfacial bonding. The aluminum foil is then wrapped around the outer surface of the carbon fiber tube, with a 5 mm overlap at the joints. The material was placed in a hot press, heated to 90°C, pressurized to 0.3 MPa, and held at that temperature and pressure for 12 minutes. After cooling, a carbon fiber-aluminum alloy composite round tube was obtained. Measurements showed that the outer diameter of the composite round tube was Φ151.9 mm, and the peel strength between the aluminum foil layer and the carbon fiber layer was ≥16 N / mm.

[0034] Step S3: Anodizing treatment. The electrolyte is a 15% sulfuric acid solution, the current density is 1.5 A / dm², the temperature is 20°C, and the oxidation time is 20 minutes. An alumina layer with a thickness of approximately 10 μm and a surface insulation resistance ≥100 MΩ is obtained. Analysis of the effect of the anodized layer on thermal conductivity: The thermal conductivity of alumina (Al₂O₃) is approximately 30 W / m·K, far lower than that of aluminum (237 W / m·K). However, the alumina layer thickness is only 10 μm, and its thermal resistance R = δ / (k·A) = 0.01 mm / (30 × π × 15² × 38) ≈ 1.8 × 10⁻ 6 °C / W is negligible. Therefore, while the anodized layer provides insulation protection, its impact on overall thermal conductivity is negligible.

[0035] Helical microgrooves were machined on the outer surface of the composite circular tube using a CNC lathe and a carbide thread cutter with a thread pitch of 1.5 mm, a groove depth of 0.1 mm, and a groove width of 0.2 mm. The surface roughness after machining was Ra = 3.2 μm.

[0036] Step S4: Machining the Annular Indentation on the Diaphragm Body. An annular indentation is integrally formed at the center of the back of the carbon fiber composite diaphragm body (2 layers [0° / 90°], T700S / epoxy resin, total thickness 0.8mm) using a hot press mold. Indentation dimensions: inner diameter Φ150mm, outer diameter Φ156mm, depth 2.5mm, bottom rounded transition R3mm. Surface roughness of the indentation Ra=3.2μm.

[0037] Step S5: Assemble the frame and diaphragm. Insert the upper end of the composite tube into the annular groove of the diaphragm body, with a fit clearance of 0.05mm (inner diameter of the groove Φ151.95mm, outer diameter of the composite tube Φ151.9mm). Place an annular aluminum foil gasket between the upper end face of the composite tube and the diaphragm body: 1060 pure aluminum, 0.1mm thick, inner diameter Φ140mm, outer diameter Φ152mm. The gasket thickness (0.1mm) is greater than the fit clearance (0.05mm). During the co-curing process, the gasket softens and fills the gap, forming a continuous aluminum thermal bridge.

[0038] Step S6: Integrated Co-curing Molding. The assembled components are placed in a hot press mold. The upper mold is made of aluminum alloy, with a concave surface on its lower surface corresponding to the shape of the diaphragm dome (dome height 20mm, R100). The lower mold has a Φ150mm positioning mandrel for supporting the inner wall of the composite cylindrical tube. After mold closing, the temperature is raised to 120°C, pressure is applied at 0.5MPa, and the temperature and pressure are maintained for 40 minutes. During curing, the epoxy resin undergoes a cross-linking reaction, and simultaneously, the oxide layer on the aluminum foil surface reacts chemically with the hydroxyl and epoxy groups in the epoxy resin, forming Al-OC chemical bonds. The aluminum foil gasket softens and fills the 0.05mm gap, while simultaneously forming a chemical bond with the carbon fiber layer of the diaphragm body. After demolding, an integrated structure is obtained. Coordinate measuring machine measurements show that the concentricity between the voice coil frame and the diaphragm body is 0.03mm.

[0039] Interfacial bond strength verification: A 90° peel test (ASTM D6862 standard) was used, with a sample width of 25 mm and a peel rate of 100 mm / min. The measured interfacial peel strength of this embodiment was 16.2 N / mm, compared to 7.8 N / mm for Comparative Example 3 (carbon fiber skeleton with aluminum ring bonded to it, adhesive layer thickness 0.1 mm) and 9.5 N / mm for Comparative Example 5 (aluminum foil composite without primer). This demonstrates that the primer (epoxy resin + aluminum powder) significantly contributes to the interfacial bond strength, and the chemical bonding effect is obvious.

[0040] Verification of interfacial chemical bonding: X-ray photoelectron spectroscopy (XPS) was used for in-depth analysis of the aluminum foil / carbon fiber interface. Characteristic peaks of the Al-OC bond (Al 2p binding energy 74.8 eV, O 1s binding energy 532.1 eV) were detected at the interface, proving that a chemical bonding reaction occurred between the alumina layer on the aluminum foil surface and the epoxy resin. Fourier transform infrared spectroscopy (FTIR-ATR) detected a characteristic absorption peak of the Al-OC stretching vibration at 1080 cm⁻¹, further confirming the existence of chemical bonding.

[0041] Step S7: Winding the voice coil. High-temperature resistant self-bonding copper wire (polyimide insulation, temperature resistant to 220°C), 0.4mm in diameter, is used. Four layers are wound on the outer surface of the integrated voice coil skeleton, with 30 turns per layer, for a total of 120 turns. The winding tension is 1.5N, and high-temperature resistant epoxy is applied between the layers. After winding, the voice coil has an outer diameter of Φ154.2mm and a magnetic gap clearance of 0.4mm (magnetic gap width 11.5mm).

[0042] Performance testing: (1) Thermal resistance test: Steady-state heat flow method was used. A DC current was passed through the voice coil winding to generate a constant heat power of 50W, and the temperature difference ΔT between the average temperature of the voice coil winding and the surface temperature of the diaphragm was measured. Thermal resistance Rth=ΔT / P. The measured Rth of this embodiment was 3.1°C / W. Comparative Example 1 (pure carbon fiber skeleton, wall thickness 1.0mm, adhesive connection) Rth=8.6°C / W, Comparative Example 2 (pure aluminum skeleton, wall thickness 1.0mm, adhesive connection) Rth=2.8°C / W, Comparative Example 3 (carbon fiber skeleton with aluminum ring glued on outside, glue thickness 0.1mm) Rth=5.4°C / W, Comparative Example 4 (integrated co-cured structure without aluminum foil layer) Rth=7.9°C / W, and Comparative Example 5 (aluminum foil composite without primer) Rth=3.5°C / W.

[0043] (2) Temperature rise test: In an anechoic chamber, a pink noise signal (IEC 60268-5 standard, 6dB peak factor) was continuously input at 500W RMS. A K-type thermocouple (Φ0.5mm) was embedded between the second and third layers of the voice coil winding to measure the voice coil temperature. The measured steady-state temperature of this embodiment was 143°C (reached steady state in 180 minutes), compared to 187°C for Comparative Example 1, 138°C for Comparative Example 2, 165°C for Comparative Example 3, 178°C for Comparative Example 4, and 152°C for Comparative Example 5. This embodiment is 44°C lower than Comparative Example 1 (a decrease of 23.5%), 22°C lower than Comparative Example 3 (a decrease of 13.3%), and 35°C lower than Comparative Example 4 (a decrease of 19.7%).

[0044] (3) Finite element thermal simulation: A three-dimensional thermal model of the voice coil-frame-diaphragm was established using ANSYS Fluent. Boundary conditions: The power density of the voice coil winding is 5.2 × 10⁻⁶. 6 With a magnetic circuit system temperature of 60°C and natural convection on the diaphragm surface (h=10W / m²·K), the voice coil reaches a maximum temperature of 148°C with the aluminum foil layer. Heat is conducted axially along the aluminum foil layer to the diaphragm, and the diaphragm surface temperature gradient decreases from 85°C at the center to 62°C at the edge. Without the aluminum foil layer, the voice coil reaches a maximum temperature of 182°C, and heat is mainly conducted slowly along the thickness direction of the carbon fiber. The diaphragm surface temperature gradient decreases from 72°C at the center to 58°C at the edge. The simulation results agree well with the measured data (error <5%).

[0045] (4) Infrared thermal imaging: A FLIR T1040 infrared thermal imager (resolution 1024×768, thermal sensitivity <20mK) was used to photograph the surface temperature distribution of the diaphragm under steady-state conditions with a pink noise input of 500W. In this embodiment, the average temperature in the central region of the diaphragm (within Φ160mm) was 82°C, and the average temperature in the edge region was 65°C, with a uniform temperature distribution. In the comparative example, the average temperature in the central region of the diaphragm was 68°C, but the voice coil temperature was as high as 187°C, indicating that heat accumulated at the skeleton-winding interface and could not be dissipated. The thermal imaging visually demonstrated the three-dimensional thermal bridge effect of the aluminum foil layer.

[0046] (5) Comparison of thermal resistance with different aluminum foil thicknesses: Composite circular tubes with aluminum foil thicknesses of 0.05 mm, 0.10 mm, 0.15 mm, 0.20 mm, 0.30 mm, and 0.40 mm were prepared (other parameters were the same), and their thermal resistance was tested. Results: Rth = 4.2°C / W at 0.05 mm (insufficient cross-sectional area, large axial thermal resistance); Rth = 3.4°C / W at 0.10 mm; Rth = 3.1°C / W at 0.15 mm; Rth = 3.0°C / W at 0.20 mm; Rth = 2.9°C / W at 0.30 mm; Rth = 2.8°C / W at 0.40 mm. When the thickness increased from 0.15 mm to 0.30 mm, the thermal resistance decreased by only 0.2°C / W (a decrease of 6.5%), but the moving mass increased by 18 g (an increase of 12.4%), resulting in a decrease in cost-effectiveness. Therefore, 0.1-0.3 mm is the optimal range.

[0047] (6) Motion mass: The total motion mass of the voice coil assembly (including the frame, winding, and diaphragm) in this embodiment was measured to be 145g, compared to 138g in Comparative Example 1, 210g in Comparative Example 2, 162g in Comparative Example 3, 142g in Comparative Example 4, and 143g in Comparative Example 5. This embodiment is 65g lower than Comparative Example 2 (a decrease of 31%) and 17g lower than Comparative Example 3 (a decrease of 10.5%).

[0048] (7) Harmonic distortion: In an anechoic chamber, a 2kHz sine wave was input at 100dB@1m. The measured THD of this embodiment was 2.0%, compared to 2.3% for Comparative Example 1, 2.8% for Comparative Example 2, 2.4% for Comparative Example 3, 2.1% for Comparative Example 4, and 2.0% for Comparative Example 5.

[0049] (8) Verification of the effect of helical microgrooving: Composite circular tubes with and without microgrooving were prepared, and the same voice coils were wound on them and then tested. With microgrooving: the contact area between the winding and the skeleton increased by about 12%, the contact thermal resistance decreased by 8%, the winding adhesion (90° peel) was 18.5 N / mm, and the winding yield was 98.5%. Without microgrooving: the contact thermal resistance was 8% higher, the winding adhesion was 15.2 N / mm, and the winding yield was 94.2% (there was winding slippage). This proves that microgrooving has a practical effect in increasing the contact area and improving the winding adhesion.

[0050] (9) Structural reliability: 1000 temperature cycles were performed (-20°C to +120°C, heating rate 5°C / min, holding time 10 minutes). This embodiment showed no delamination or debonding, and the interfacial peel strength attenuation rate was <3%. Comparative Example 3 showed debonding between the aluminum ring and the carbon fiber skeleton after 387 cycles, with the peel strength decreasing from 7.8 N / mm to 2.1 N / mm. Comparative Example 5 (without primer) showed localized debonding after 612 cycles. This demonstrates the crucial role of primer chemical bonding in long-term reliability.

[0051] Example 2: Improved structure with heat dissipation ring Based on Example 1, an aluminum heat sink ring is added to the lower end of the voice coil frame. The heat sink ring is made of 6061-T6 aluminum alloy, with an outer diameter of Φ165mm (13mm larger than the outer diameter of the frame), an inner diameter of Φ152mm, and a thickness of 2.0mm. It has eight radial heat dissipation fins (fin height 5mm, thickness 1.5mm). The heat sink ring and the aluminum foil layer are connected by laser welding with a welding power of 800W, a welding speed of 20mm / s, a laser spot diameter of 0.3mm, and a weld depth of 1.0mm. The gap between the outer diameter of the heat sink ring (Φ165mm) and the inner diameter of the magnetic circuit system (Φ170mm) is 5mm, which is greater than the maximum amplitude of the voice coil ±3mm to ensure no collision. The measured thermal resistance is further reduced to 2.6°C / W, and the steady-state temperature at 500W is reduced to 131°C. However, the moving mass increases to 152g. It is suitable for extreme power applications.

[0052] Comparative Example 1: Pure carbon fiber skeleton (adhesive connection) The 21-inch diaphragm features a voice coil frame made of T700S carbon fiber coiled tubing (1.0mm wall thickness, 2 layers [0° / 90°]), bonded to the diaphragm with epoxy resin adhesive, with an adhesive layer thickness of 0.1mm. Measured thermal resistance is 8.6°C / W, steady-state temperature at 500W is 187°C, running weight is 138g, and THD@2kHz is 2.3%. After 1000 temperature cycles, microcracks appeared in the adhesive layer, and the interfacial peel strength decreased from 6.5N / mm to 3.2N / mm.

[0053] Comparative Example 2: Pure aluminum frame (adhesive connection) The 21-inch diaphragm uses a 6061-T6 aluminum alloy round tube (1.0mm wall thickness) as the voice coil frame, which is connected to the diaphragm via epoxy resin adhesive. Measured thermal resistance is 2.8°C / W, steady-state temperature at 500W is 138°C, running weight is 210g, and THD@2kHz is 2.8%. Eddy current losses cause additional heat generation, and the winding insulation layer shows localized aging due to eddy current heating. After 1000 temperature cycles, there was no debonding, but the winding insulation resistance decreased by 15%.

[0054] Comparative Example 3: Carbon fiber skeleton with aluminum ring glued on the outside (non-integrated) The 21-inch diaphragm features a T700S carbon fiber coil skeleton (0.8mm wall thickness) with a 0.15mm thick aluminum ring (30mm width) glued to its outer surface, connected to the diaphragm via the adhesive layer. Measured thermal resistance is 5.4°C / W, steady-state temperature at 500W is 165°C, running weight is 162g, THD@2kHz is 2.4%, and interfacial peel strength is 7.8N / mm. After 1000 temperature cycles, the aluminum ring delaminated from the carbon fiber skeleton (initial delamination occurred after 387 cycles).

[0055] Comparative Example 4: Carbon fiber-diaphragm integrated structure without aluminum foil layer The 21-inch diaphragm features a voice coil skeleton made of pure carbon fiber tubing (0.8mm wall thickness), integrally co-cured and connected to the diaphragm (without aluminum foil layer or padding). Measured thermal resistance is 7.9°C / W, steady-state temperature at 500W is 178°C, running weight is 142g, THD@2kHz is 2.1%, and interfacial peel strength is 14.5N / mm. No delamination was observed after 1000 temperature cycles. This demonstrates that without the aluminum foil layer, even with an integral structure, thermal management capabilities are significantly insufficient (thermal resistance is only 8.1% lower than Comparative Example 1).

[0056] Comparative Example 5: Integrated aluminum foil composite structure without adhesive base The 21-inch diaphragm voice coil is constructed from a carbon fiber tube directly wrapped with aluminum foil (without sandblasting or primer), and is integrally co-cured and connected to the diaphragm. Measured thermal resistance is 3.5°C / W, steady-state temperature at 500W is 152°C, running weight is 143g, THD@2kHz is 2.0%, and interfacial peel strength is 9.5 N / mm. Localized debonding occurred after 612 cycles out of 1000 temperature cycles. This demonstrates that without primer, the interfacial bonding strength between the aluminum foil and carbon fiber is insufficient, resulting in poor long-term reliability.

[0057] Comparative Example 6: The one-piece molded structure of CN121865171A (simulation reproduction) Following the technical solution disclosed in CN121865171A, a sample was prepared by molding a diaphragm in segments and then bonding it to a frame. After the diaphragm and frame were molded separately, they were bonded together by hot pressing (temperature 80°C, pressure 0.3MPa, time 15 minutes). The measured thermal resistance was 7.2°C / W, the steady-state temperature at 500W was 175°C, the moving mass was 140g, and the THD@2kHz was 2.2%. After 500 temperature cycles, localized peeling occurred at the bonding interface, and the peel strength decreased from 5.8N / mm to 2.5N / mm. This demonstrates that the integral molding method of this patent is essentially a physical bonding process, fundamentally different from the chemical bonding and co-curing method of this invention.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should still fall within the scope of the present invention.

Claims

1. A carbon fiber-aluminum alloy composite structure integrating the voice coil frame and diaphragm, characterized in that, include: A carbon fiber composite diaphragm body, wherein an annular indentation is provided at the center of the back of the diaphragm body; The voice coil skeleton is a carbon fiber-aluminum alloy composite round tube, including an inner carbon fiber coil and an outer aluminum foil layer. The upper end of the voice coil skeleton and the annular indentation of the diaphragm body are mechanically connected by a clearance fit, and an integral structure is formed by co-curing. The aluminum foil layer has a thickness of 0.1-0.3 mm, and the carbon fiber tube has a wall thickness of 0.8-1.5 mm.

2. The structure according to claim 1, characterized in that, The aluminum foil layer is made of 1060 pure aluminum or 5052 aluminum alloy with a thermal conductivity ≥190W / m·K; the carbon fiber tube is made of T700S or T800S carbon fiber / epoxy resin prepreg with a fiber direction of ±45° or [0° / 90°] layup.

3. The structure according to claim 1, characterized in that, The annular groove of the diaphragm body is an annular groove with a diameter of 150-155mm and a depth of 2.0-3.0mm. The outer diameter of the voice coil skeleton is 150-155mm. The fitting gap between the voice coil skeleton and the annular groove is 0.02-0.20mm.

4. The structure according to claim 1, characterized in that, An annular aluminum foil gasket is provided between the upper end face of the voice coil skeleton and the diaphragm body. The gasket has a thickness of 0.05-0.15mm, an inner diameter equal to the inner diameter of the voice coil skeleton, and an outer diameter equal to the outer diameter of the voice coil skeleton. The gasket softens and fills the mating gap during the co-curing process, forming a continuous aluminum thermal bridge.

5. The structure according to claim 1, characterized in that, The outer surface of the voice coil skeleton is provided with a spiral microgroove, the depth of which is 0.05-0.15mm and the pitch is 1.0-2.0mm.

6. The structure according to claim 1, characterized in that, The outer surface of the aluminum foil layer is provided with an anodized layer, the thickness of which is 5-15μm; the lower end of the voice coil skeleton is provided with a heat dissipation ring, which is an aluminum annular fin, integrally formed or welded to the aluminum foil layer of the voice coil skeleton, the outer diameter of which is 5-15mm larger than the outer diameter of the voice coil skeleton, and the gap between the outer diameter of which is ≥2mm and the inner diameter of the magnetic circuit system.

7. The structure according to claim 1, characterized in that, It also includes a voice coil winding, which is wound on the outer surface of the voice coil skeleton, and is made of copper or aluminum wire with a diameter of 0.3-0.5 mm and 2-4 layers.

8. A large-diameter loudspeaker, characterized in that, It includes a diaphragm body, a voice coil, a magnetic circuit system, and a frame, wherein the voice coil frame and the diaphragm body adopt the carbon fiber-aluminum alloy composite structure as described in any one of claims 1-7.

9. A carbon fiber-aluminum alloy composite voice coil frame, characterized in that, include: The inner carbon fiber tube is made of T700S or T800S carbon fiber / epoxy resin prepreg, with the fiber direction being ±45° or [0° / 90°] layup, and the wall thickness being 0.8-1.5mm. An outer aluminum foil layer is wrapped around the outer surface of the carbon fiber tube. The aluminum foil layer is made of 1060 pure aluminum or 5052 aluminum alloy, with a thickness of 0.1-0.3 mm and a thermal conductivity of ≥190 W / m·K. The aluminum foil layer and the carbon fiber tube are chemically bonded together by a primer, which is a mixture of epoxy resin and aluminum powder, with the aluminum powder having a mass fraction of 30%-50%.

10. A method for manufacturing a carbon fiber-aluminum alloy composite structure integrating a voice coil frame and a diaphragm, characterized in that, Includes the following steps: S1: Preparation of carbon fiber tubes: The carbon fiber / epoxy resin prepreg is rolled into a round tube on a mandrel. After rolling, it is placed in a hot autoclave and cured at 120°C and 0.3MPa for 30-40 minutes to obtain a carbon fiber tube semi-finished product. S2: Composite aluminum foil layer: Aluminum foil is coated on the outer surface of the carbon fiber tube. Before coating with aluminum foil, the surface of the carbon fiber tube is sandblasted to a roughness Ra=3.2-6.3μm, and a primer is applied. The primer is a mixture of epoxy resin and aluminum powder, with aluminum powder mass fraction of 30%-50% and primer coating thickness of 0.03-0.08mm. Hot pressing is used for composite bonding. The hot pressing temperature is 80-100°C, the pressure is 0.2-0.4MPa, and the time is 10-15 minutes. S3: Anodizing treatment: After aluminum foil is laminated, the outer surface of the aluminum foil is anodized to form an aluminum oxide insulating layer with a thickness of 5-15μm; S4: Processing annular indentation: An annular indentation is integrally formed on the back center of the carbon fiber composite diaphragm body using a hot press mold; S5: Assemble the frame and diaphragm: Insert the upper end of the carbon fiber-aluminum alloy composite tube obtained in S2 into the annular groove of the diaphragm body, with a fitting gap of 0.02-0.20mm; place an annular aluminum foil gasket between the upper end face of the composite tube and the diaphragm body; S6: Integrated Co-curing Molding: The assembled components are placed in a hot press mold, heated to 120±3°C, pressurized to 0.5±0.1MPa, and kept at the temperature and pressure for 30-45 minutes, so that the aluminum foil layer and the carbon fiber layer of the diaphragm body form a chemical bond under the action of epoxy resin. At the same time, the aluminum foil gasket softens and fills the gap, forming an integrated structure. S7: Winding the voice coil: The voice coil winding is wound on the outer surface of the integrated voice coil skeleton obtained in S6. The winding is made of copper or aluminum wire with a diameter of 0.3-0.5mm and 2-4 layers.

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