Flat diaphragm earphone with magnetic field constraint structure and manufacturing method

Abstract

The invention relates to the technical field of electro-acoustic conversion, particularly provides a panel diaphragm earphone with a magnetic field constraint structure and a manufacturing method, and is used for solving the technical bottlenecks of low magnetic field utilization rate, serious edge attenuation and high eddy current loss of a traditional panel earphone. A magnetic conductive alloy component with a square C-shaped section is arranged on the side, away from a vibrating diaphragm, of a permanent magnet, a substrate part of the magnetic conductive alloy component covers more than 40% of the area of the back side of the magnet, a side wing part wraps the side edge of the magnet according to a gradient rule, and the effective magnetic flux density is improved and the edge magnetic field uniformity deviation is smaller than or equal to 8% by restraining escape magnetic flux and guiding the direction of the vibrating diaphragm; the magnetic conductive alloy is a nickel-iron-molybdenum soft magnetic material and is subjected to cold crucible suspension smelting, nanometer groove etching and pulsed high-intensity magnetic field treatment, the frequency response linearity and long-term reliability are remarkably improved through the scheme, and the magnetic conductive alloy is suitable for high-end audio equipment.

Description

Technical Field

[0001] The present invention relates to the field of planar diaphragm earphones, and in particular to a planar diaphragm earphone with a magnetic field confinement structure and a manufacturing method thereof. Background Art

[0002] Planar diaphragm headphones are becoming a key choice for high-end audio equipment due to their advantages, such as uniform diaphragm force and low distortion. Their core sound generation principle relies on the vibration of conductive wires etched into the diaphragm in an orthogonal magnetic field, driven by the Lorentz force. Traditional designs employ an array of permanent magnets (typically neodymium iron boron) symmetrically distributed on either side of the diaphragm, creating a driving magnetic field across a magnetic gap. However, this structure has inherent drawbacks: magnetic flux lines at the edges of the magnets tend to diffuse into non-active areas, reducing the magnetic field strength acting on the diaphragm. Furthermore, the spatial distribution of the magnetic field is not uniform, which in turn affects the consistency of the force applied to the diaphragm.

[0003] The magnetic flux on the side of the permanent magnet away from the diaphragm (accounting for over 40% of the total) does not participate in the driving action, resulting in insufficient effective magnetic flux density in the diaphragm area (typically less than 0.5 T). Increasing the magnet volume or magnetic energy product can enhance the magnetic field, but it will significantly increase the weight of the headphones (>500 g) and cause wearing comfort issues.

[0004] While existing magnetic conductive structures (such as planar soft magnetic patches) can partially confine the magnetic field, their large coverage area (>90%) creates an inefficient magnetic circuit. Experiments have shown that the magnetic flux density at the edge of the diaphragm is 25%-40% lower than at the center, causing nonlinear distortion in the frequency response (THD>1%@1kHz).

[0005] The industry has tried solutions such as localized magnetic conductive sheets and segmented magnets, but none of these have solved the problem of synergistic optimization of magnetic field gradient control, lightweight, high-strength bonding, and ultra-high permeability material preparation. Therefore, there is an urgent need to develop an innovative magnetic field confinement structure that can achieve a uniform increase in magnetic flux density across the diaphragm area without significantly increasing weight and cost. Summary of the Invention

[0006] To solve the above problems, the present invention provides a planar diaphragm earphone with a magnetic field confinement structure, comprising an earphone housing and a planar diaphragm unit, wherein the planar diaphragm unit comprises a diaphragm, a bracket, a magnet assembly, and a magnetic alloy, and is characterized in that:

[0007] The magnet group includes at least one group of permanent magnets, and the permanent magnets are symmetrically arranged on both sides of the diaphragm;

[0008] The magnetic alloy is arranged on the side of the permanent magnet away from the diaphragm and only covers a portion of the surface of the permanent magnet;

[0009] The magnetic conductive alloy is used to guide the magnetic field away from the diaphragm side to the side close to the diaphragm away from the diaphragm, thereby enhancing the magnetic flux density acting on the diaphragm.

[0010] The magnetic alloy is a soft magnetic alloy component with a square C-shaped cross section, including an integrally formed base plate portion 202a and a wing portion 202b;

[0011] The substrate portion 202a covers more than 40% of the surface area of ​​the permanent magnet away from the diaphragm and has a thickness of 0.2 mm to 0.4 mm;

[0012] The side wing portions 202b are bent vertically from both sides of the base portion 202a, covering more than 30% of the height of the adjacent two sides of the permanent magnet;

[0013] The square C-shaped structure is used to constrain the magnetic flux of the permanent magnet away from the diaphragm side and guide it toward the diaphragm.

[0014] The base portion 202a or the side wing portion 202b of the magnetic alloy is provided with a mechanical anchoring protrusion extending toward the permanent magnet; the protrusion is one of a trapezoidal, rectangular column, or dovetail shape, with a height of 0.1 mm to 0.3 mm, and a bottom diameter / width accounting for 5% to 10% of the base portion coverage area;

[0015] The protrusions are embedded in the prefabricated micropores or adhesive layer on the surface of the permanent magnet, so that the shear peeling resistance of the magnetic alloy is ≥ 15N / cm; a rounded transition is formed between the root of the protrusion and the magnetic alloy substrate.

[0016] The wing portion 202b of the magnetic alloy has a gradient extension structure, and its height H changes along a direction parallel to the diaphragm plane and satisfies:

[0017] For the permanent magnet closest to the diaphragm center in the permanent magnet array, the height of its magnetic alloy side wings accounts for 30% of the total height of the permanent magnet side; for the permanent magnet farthest from the diaphragm center, the height of its magnetic alloy side wings accounts for 100% of the total height of the permanent magnet side;

[0018] The height ratio of the flanks of the remaining magnetic alloys increases linearly with the distance from the center, satisfying:

[0019] ,

[0020] Where dX is the normalized distance from the permanent magnet to the center of the diaphragm, and 0≤dX≤1, k=70%, when the distance to the center of the diaphragm is closest, dX=0, and when the distance to the center of the diaphragm is farthest, dX=1.

[0021] The material of the magnetic alloy is a nickel-iron based soft magnetic alloy, and its composition in atomic percentage is as follows:

[0022] Nickel Ni: 79.5% - 80.5%,

[0023] Iron: 19.2% - 20.0%,

[0024] Molybdenum: 0.3% - 0.5%,

[0025] Manganese Mn: ≤0.05%,

[0026] Silicon + Carbon Si + C: ≤0.05%,

[0027] And satisfy:

[0028] Initial magnetic permeability μ i ≥ 100,000, @ 0.002 T, 1 kHz;

[0029] Saturation flux density B sat ≥ 0.78 T;

[0030] Coercive force H c ≤ 0.5 A / m;

[0031] Grain size ≤ 5 μm.

[0032] The preparation method of the magnetic conductive alloy includes the following inventive steps:

[0033] S1: In an argon-hydrogen mixed atmosphere, the nickel, iron and molybdenum raw materials are melted using the cold crucible suspension melting technology and the cooling rate is controlled. , forming an amorphous mother ingot; an axial-rotating composite magnetic field is applied during the smelting process: the axial static magnetic field intensity is 0.8-1.2T, the rotating alternating magnetic field frequency is 50-100 Hz, and the peak magnetic induction intensity is 0.3-0.5T;

[0034] S2: The amorphous mother ingot is warm rolled at 450-480℃ to a thickness of 2.0 mm, with the axial deviation between the rolling direction and the magnetic field-induced 〈100〉 texture being ≤5°. After each rolling pass, laser pulse annealing is performed: wavelength 1064 nm, pulse width 10 ns, energy density 5-8 J / cm², repetition rate 20 kHz;

[0035] S3: Reactive ion beam etching is performed on the surface of the rolled thin strip;

[0036] Etching gas: Mixed gas, volume ratio 4:1, ion energy: 500-800 eV, etching depth: 0.5-1.0 μm, forming a trench array with a period of 200-300 nm and a depth-to-width ratio of 1:3;

[0037] S4: Perform three-step gradient treatment in a segmented hydrogen annealing furnace:

[0038]

[0039] S5: Apply a pulsed strong magnetic field at 10°C below the Curie temperature Tc, with a pulse width of 100 ms, a peak intensity of 6-8 T, and a direction parallel to the rolling texture axis.

[0040] The permanent magnet is a rectangular neodymium iron boron magnet, and its magnetization direction is perpendicular to the diaphragm plane;

[0041] The coverage area of ​​the magnetic conductive alloy on the permanent magnet is asymmetrically distributed.

[0042] The surface of the magnetic alloy structure is provided with an anti-eddy current coating, the coating material is a nickel-chromium alloy or nickel-phosphorus alloy , with a thickness of 1-10 μm, used to suppress eddy current losses under alternating magnetic fields.

[0043] A method for manufacturing a planar diaphragm earphone with a magnetic field confinement structure, for manufacturing the planar diaphragm earphone, specifically comprising:

[0044] Step 1: Punch the soft magnetic alloy strip into a square C-shaped component, comprising a base portion 202a and wing portions 202b; the base portion thickness is controlled to be 0.3 mm ± 0.02 mm, and the wing portions are pre-cut according to a gradient rule;

[0045] Step 2: Coat the surface of the permanent magnet away from the diaphragm with an epoxy resin layer; press the base portion 202a of the magnetic alloy onto the surface of the permanent magnet so that the mechanical anchoring protrusions 202c are embedded in the adhesive layer; and cure at 80°C for 1 hour to form a composite magnet unit with a shear resistance of ≥15 N / cm.

[0046] Step 3: Use brackets to symmetrically install the composite magnet units on both sides of the diaphragm so that all the magnetic alloys are located away from the diaphragm. Use a Gauss meter to check the magnetic field uniformity in the diaphragm area and adjust the permanent magnet spacing so that the deviation is ≤5%.

[0047] Step 4: Suspend the diaphragm between the symmetrical permanent magnets, connect the diaphragm wires to the bracket circuit, close the earphone housing, and complete the acoustic test.

[0048] The step one further comprises:

[0049] A high resistivity alloy coating is provided on the surface of the magnetic conductive alloy, and the coating meets the following conditions:

[0050] Nichrome or nickel-phosphorus alloy , resistivity , thickness 0.5μm - 2.0μm, suppresses eddy current loss of magnetic alloy under alternating magnetic field.

[0051] This invention solves the fundamental defects of the magnetic circuit system of planar diaphragm headphones through the collaborative innovation of magnetic field confinement structure, gradient magnetic conductivity design and high-performance alloy, and has the following beneficial effects:

[0052] The square C-shaped magnetic alloy redirects the ineffective magnetic flux from the permanent magnet away from the diaphragm side to the diaphragm area, increasing the diaphragm driving magnetic field strength from the traditional design of <0.5 T to 0.65-0.78 T, significantly enhancing the sound energy conversion efficiency.

[0053] The gradient extension structure of the side wings dynamically adjusts the covering height according to the position of the magnet, compensates for the edge flux loss, ensures that the deviation of the magnetic field uniformity across the diaphragm is ≤5%, and improves the linearity of the frequency response curve.

[0054] Resistivity of nickel-chromium / nickel-phosphorus high-resistance coating Combined with the soft magnetic alloy nano-groove array, the eddy current loss under the 10kHz alternating magnetic field is reduced from >15% of the traditional solution to 2.1-2.8%, significantly improving the high-frequency resolution. The synergistic effect of the magnetic alloy saturation flux density Bsat ≥ 0.78 T and the ultra-high magnetic permeability μi ≥ 100,000 makes the invalid flux recovery rate > 90%, and the driving force per unit magnet volume is 1.4 times that of the traditional design.

[0055] The mechanical anchoring protrusions are embedded in the permanent magnet micropores / glue layer to form a local interlocking structure. The shear peeling resistance of the magnetic alloy is ≥15 N / cm. The 20kHz high-frequency vibration test showed no displacement, demonstrating a 300% improvement in magnetic circuit stability. The magnetic alloy substrate is only 0.2-0.4mm thick, and combined with an asymmetric cover design, it reduces weight by 30% at the same magnetic field strength, breaking through the wearability bottleneck of high-end planar headphones.

[0056] Cold crucible levitation melting combined with pulsed magnetic field treatment reduces nickel-iron alloy grain size to ≤3 μm, coercivity Hc ≤0.3 A / m, and hysteresis loss to one-fifth of that of conventional processes. Reactive ion etching of trench arrays enhances coating adhesion, and three-step gradient annealing eliminates internal stress, resulting in a magnetic component yield exceeding 98% and a 25% reduction in manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0058] Attachment Figure 1 This is a schematic diagram of the appearance of the earphone of the present invention;

[0059] Attachment Figure 2 This is a schematic structural diagram of the earphone diaphragm unit of the present invention;

[0060] Attachment Figure 3 Schematic diagram of the structure of the permanent magnet and the magnetic alloy of the present invention;

[0061] Attachment Figure 4 Schematic diagram of the shape of the magnetic conductive alloy of the present invention;

[0062] Attachment Figure 5 Schematic diagram of magnetic field distribution of the magnet of the present invention;

[0063] Attachment Figure 6 Schematic diagram of the height change of the flank portion of the magnet and the magnetic conductive alloy of the present invention. DETAILED DESCRIPTION

[0064] Example 1:

[0065] See also Figures 1 to 6 The present invention provides a planar diaphragm earphone with a magnetic field confinement structure, comprising an earphone housing 100 and a planar diaphragm unit 200, wherein the planar diaphragm unit 200 comprises a diaphragm 204, a bracket 203, a magnet group 201, and a magnetic conductive alloy 202, and is characterized in that:

[0066] The magnet group 201 includes at least one group of permanent magnets, which are symmetrically arranged on both sides of the diaphragm 204;

[0067] The magnetic alloy 202 is arranged on the side of the permanent magnet away from the diaphragm 204 and only covers a portion of the surface of the permanent magnet;

[0068] The magnetic conductive alloy is used to guide the magnetic field away from the diaphragm side to the side close to the diaphragm away from the diaphragm, thereby enhancing the magnetic flux density acting on the diaphragm 204.

[0069] The magnetic alloy 202 is a soft magnetic alloy component with a square C-shaped cross section, including an integrally formed base plate portion 202a and a wing portion 202b;

[0070] The substrate portion 202a covers more than 40% of the surface area of ​​the permanent magnet away from the diaphragm 204 and has a thickness of 0.2 mm to 0.4 mm;

[0071] The side wing portions 202b are bent vertically from both sides of the base portion 202a, covering more than 30% of the height of the adjacent two sides of the permanent magnet;

[0072] The square C-shaped structure is used to constrain the magnetic flux of the permanent magnet away from the diaphragm side and guide it toward the diaphragm.

[0073] The base portion 202a or the side portion 202b of the magnetic alloy 202 is provided with a mechanical anchoring protrusion extending toward the permanent magnet; the protrusion is one of a trapezoidal, rectangular column, or dovetail shape, with a height of 0.1 mm to 0.3 mm, and a bottom diameter / width accounting for 5% to 10% of the base portion coverage area;

[0074] The protrusions are embedded in the prefabricated micropores or adhesive layer on the surface of the permanent magnet, so that the shear peeling resistance of the magnetic alloy 202 is ≥15 N / cm; a rounded transition is formed between the root of the protrusion and the magnetic alloy substrate.

[0075] The wing portion 202b of the magnetic alloy 202 is a gradient extension structure, and its height H changes along a direction parallel to the plane of the diaphragm 204 and satisfies:

[0076] For the permanent magnet closest to the diaphragm center in the permanent magnet array, the height of the wing portion of the magnetic alloy 202 accounts for 30% of the total height of the permanent magnet side surface; for the permanent magnet farthest from the diaphragm center, the height of the wing portion of the magnetic alloy 202 accounts for 100% of the total height of the permanent magnet side surface;

[0077] The height ratio of the flanks of the remaining magnetic alloys 202 increases linearly with the distance from the center, satisfying:

[0078] ,

[0079] Where dX is the normalized distance from the permanent magnet to the center of the diaphragm, and 0≤dX≤1, k=70%, when the distance to the center of the diaphragm is closest, dX=0, and when the distance to the center of the diaphragm is farthest, dX=1.

[0080] The material of the magnetic alloy 202 is a nickel-iron based soft magnetic alloy, and its composition in atomic percentage is as follows:

[0081] Nickel Ni: 79.5% - 80.5%,

[0082] Iron: 19.2% - 20.0%,

[0083] Molybdenum: 0.3% - 0.5%,

[0084] Manganese Mn: ≤0.05%,

[0085] Silicon + Carbon Si + C: ≤0.05%,

[0086] And satisfy:

[0087] Initial magnetic permeability μ i ≥ 100,000, @ 0.002 T, 1 kHz;

[0088] Saturation flux density B sat≥ 0.78 T;

[0089] Coercive force H c ≤ 0.5 A / m;

[0090] Grain size ≤ 5 μm.

[0091] The preparation method of the magnetic conductive alloy includes the following inventive steps:

[0092] S1: In an argon-hydrogen mixed atmosphere, the nickel, iron and molybdenum raw materials are melted using the cold crucible suspension melting technology and the cooling rate is controlled. , forming an amorphous mother ingot; an axial-rotating composite magnetic field is applied during the smelting process: the axial static magnetic field intensity is 0.8-1.2T, the rotating alternating magnetic field frequency is 50-100 Hz, and the peak magnetic induction intensity is 0.3-0.5T;

[0093] S2: The amorphous mother ingot is warm rolled at 450-480℃ to a thickness of 2.0 mm, with the axial deviation between the rolling direction and the magnetic field-induced 〈100〉 texture being ≤5°. After each rolling pass, laser pulse annealing is performed: wavelength 1064 nm, pulse width 10 ns, energy density 5-8 J / cm², repetition rate 20 kHz;

[0094] S3: Reactive ion beam etching is performed on the surface of the rolled thin strip;

[0095] Etching gas: Mixed gas, volume ratio 4:1, ion energy: 500-800 eV, etching depth: 0.5-1.0 μm, forming a trench array with a period of 200-300 nm and a depth-to-width ratio of 1:3;

[0096] S4: Perform three-step gradient treatment in a segmented hydrogen annealing furnace:

[0097]

[0098] S5: Apply a pulsed strong magnetic field at 10°C below the Curie temperature Tc, with a pulse width of 100 ms, a peak intensity of 6-8 T, and a direction parallel to the rolling texture axis.

[0099] The permanent magnet is a rectangular neodymium iron boron magnet, and its magnetization direction is perpendicular to the diaphragm plane;

[0100] The coverage area of ​​the magnetic conductive alloy on the permanent magnet is asymmetrically distributed.

[0101] The surface of the magnetic alloy structure is provided with an anti-eddy current coating, the coating material is a nickel-chromium alloy or nickel-phosphorus alloy , with a thickness of 1-10 μm, used to suppress eddy current losses under alternating magnetic fields.

[0102] Example 2:

[0103] A method for manufacturing a planar diaphragm earphone with a magnetic field confinement structure, for manufacturing the planar diaphragm earphone, specifically comprising:

[0104] Step 1: Punch the soft magnetic alloy strip into a square C-shaped component, comprising a base portion 202a and wing portions 202b; the base portion thickness is controlled to be 0.3 mm ± 0.02 mm, and the wing portions are pre-cut according to a gradient rule;

[0105] Step 2: Coat the surface of the permanent magnet 201 away from the diaphragm with an epoxy resin layer; press the base portion 202a of the magnetic alloy 202 onto the surface of the permanent magnet so that the mechanical anchoring protrusions 202c are embedded in the adhesive layer; and cure at 80°C for 1 hour to form a composite magnet unit with a shear resistance of ≥15 N / cm.

[0106] Step 3: Use brackets to symmetrically install the composite magnet units on both sides of the diaphragm so that all the magnetic alloys are located away from the diaphragm. Use a Gauss meter to check the magnetic field uniformity in the diaphragm area and adjust the permanent magnet spacing so that the deviation is ≤5%.

[0107] Step 4: suspend the diaphragm 204 between the symmetrical permanent magnets, connect the diaphragm wire to the bracket circuit, close the earphone housing, and complete the acoustic test.

[0108] The step one further comprises:

[0109] A high resistivity alloy coating 209 is provided on the surface of the magnetic conductive alloy 202. The coating meets the following conditions:

[0110] Nichrome or nickel-phosphorus alloy , resistivity , thickness 0.5μm - 2.0μm, suppresses eddy current loss of magnetic alloy under alternating magnetic field.

[0111] Example 3: Gradient magnetic conductivity verification and alloy performance analysis

[0112] (1) Magnetic field optimization effect of flank height gradient change

[0113] Three magnetic conductive structures were compared through finite element electromagnetic simulation (Ansys Maxwell) and physical prototype testing:

[0114]

[0115] Mechanism of action:

[0116] Near-center magnet (30% higher on the wing): reduces the "over-constraint" of the magnetic alloy on the edge magnetic field, avoids saturation of the central magnetic field (the hysteresis loss increases sharply when the center Bsat of the traditional solution is greater than 0.8 T), releases part of the magnetic flux to the middle of the diaphragm, and improves the driving force of the central area.

[0117] Far-center magnet (flank height 100%): completely wraps around the sides of the magnet, suppressing edge magnetic flux leakage, directing the stray magnetic flux back to the diaphragm, and compensating for the distance attenuation effect (the magnetic field attenuates by approximately 15% for every 1 cm increase in the magnet's distance from the diaphragm center).

[0118] Test conditions: NdFeB N52 magnet array, diaphragm diameter 80mm, drive voltage 2Vrms@1kHz.

[0119] Example 4: Preparation process analysis

[0120] Step S1: Cold crucible suspension melting

[0121] Argon-hydrogen mixture : Hydrogen reduces oxygen impurities to <10ppm to avoid FeO inclusion;

[0122] Axial-rotating composite magnetic field: Axial static magnetic field (1.0T) induces the prototype of <100> texture, and rotating alternating field (0.4T@80Hz) breaks up dendrites, with an amorphization rate of 99%;

[0123] Step S2: Warm rolling + laser annealing

[0124] 450℃ warm rolling: processing below the recrystallization temperature to retain the high defect density of the amorphous mother ingot;

[0125] Laser pulse annealing (7J / cm²): Instantaneous heating of the micro-area to 1200°C → excitation of nanocrystalline nuclei (size 50-80nm), cooling at a rate of 10^8 K / s to inhibit grain growth;

[0126] Step S3: Reactive Ion Etching

[0127] Etching: Etching Fe / Ni to form volatile chlorides, Physical bombardment enhances anisotropy;

[0128] Nano-groove array (aspect ratio 1:3): Increases the coating contact area by 300% and improves NiCr coating adhesion (reaching ASTM 5B grade);

[0129] Step S4: three-stage hydrogen annealing;

[0130] Eliminate rolling stress, dislocation density from down to ;

[0131] The grains are equiaxed and the grain size is uniform (3.2 ± 0.5 μm);

[0132] The magnetic domains are oriented, with 90% of the domains oriented along the <100> axis;

[0133] Step S5: Pulsed high magnetic field treatment

[0134] 10℃ below the Curie point (Tc≈480℃): Apply a strong axial magnetic field (7T) in the active magnetic state;

[0135] Pulse width 100ms: sufficient to drive magnetic domain reversal but avoid Joule heat accumulation (temperature rise <5°C);

[0136] Effect: The magnetic domain wall energy barrier is reduced by 70%, and the coercive force Hc is reduced from 0.5A / m to 0.28A / m.

[0137] Performance comparison experiment (alloy of the present invention vs. commercial 1J85):

[0138]

[0139] Test standards: μi (IEC 60404-15), Bsat (ASTM A912), eddy current loss (IEC 60404-13).

[0140] Thus far, the description of the above-described embodiments has been provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. The individual elements or features of a particular embodiment are generally not limited to the particular embodiment, but when applicable, they can be interchanged and used for selected embodiments even if not specifically shown or described. In many aspects, the same elements or features can also be changed. Such changes are not considered to depart from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

[0141] Example embodiments are provided so that the present disclosure will be thorough and will fully convey the scope to those skilled in the art. In order to thoroughly understand the embodiments of the present disclosure, numerous details are set forth, such as examples of specific parts, devices, and methods. It will be apparent to those skilled in the art that specific details need not be used, and the example embodiments may be implemented in many different forms, and neither should be construed as limiting the scope of the present disclosure. In certain example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0142] Here, professional vocabulary is used only for the purpose of describing specific example embodiments and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a" and "the" used herein may be intended to include the plural forms as well. The terms "including" and "having" are inclusive and therefore specify the presence of the claimed features, wholes, steps, operations, elements and / or components, but do not exclude the presence or additional presence of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof. Unless the order of execution is explicitly indicated, the method steps, processes and operations described herein are not to be interpreted as necessarily needing to be performed in the specific order discussed and shown. It should also be understood that additional or optional steps may be adopted.

Claims

1. A flat diaphragm earphone with a magnetic field confinement structure, comprising an earphone housing (100) and a flat diaphragm unit (200), wherein the flat diaphragm unit (200) comprises a diaphragm (204), a bracket (203), a magnet group (201) and a magnetic conductive alloy (202), characterized in that: The magnet group (201) includes at least one group of permanent magnets, and the permanent magnets are symmetrically arranged on both sides of the diaphragm (204); The magnetic conductive alloy (202) is arranged on a side of the permanent magnet away from the diaphragm (204) and only covers a portion of the surface of the permanent magnet; The magnetic conductive alloy is used to guide the magnetic field away from the diaphragm side to the side close to the diaphragm away from the diaphragm, thereby enhancing the magnetic flux density acting on the diaphragm (204).

2. The planar diaphragm earphone according to claim 1, wherein: The magnetic conductive alloy (202) is a soft magnetic alloy component with a square C-shaped cross section, comprising an integrally formed base plate portion (202a) and a wing portion (202b); The substrate portion (202a) covers more than 40% of the surface area of ​​the permanent magnet away from the diaphragm (204) and has a thickness of 0.2 mm to 0.4 mm; The wing portions (202b) are vertically bent from both sides of the base portion (202a) to cover more than 30% of the height of the adjacent two sides of the permanent magnet; The square C-shaped structure is used to constrain the magnetic flux of the permanent magnet away from the diaphragm side and guide it toward the diaphragm.

3. The planar diaphragm earphone according to claim 2, wherein: The base plate portion (202a) or the side wing portion (202b) of the magnetic conductive alloy (202) is provided with a mechanical anchoring protrusion extending in the direction of the permanent magnet; the protrusion is one of a trapezoidal, rectangular column or swallowtail shape, with a height of 0.1 mm to 0.3 mm, and a bottom diameter / width accounting for 5% to 10% of the coverage area of ​​the base plate portion; The protrusions are embedded in the prefabricated micropores or adhesive layer on the surface of the permanent magnet, so that the shear peeling resistance of the magnetic alloy (202) is ≥15 N / cm; a rounded transition is formed between the root of the protrusion and the magnetic alloy substrate.

4. The planar diaphragm earphone according to claim 3, wherein: The wing portion (202b) of the magnetic conductive alloy (202) is a gradient extension structure, the height H of which changes along a direction parallel to the plane of the diaphragm (204), and satisfies: For the permanent magnet closest to the center of the diaphragm in the permanent magnet array, the height of the flank portion of the magnetic alloy (202) accounts for 30% of the total height of the permanent magnet side surface; for the permanent magnet farthest from the center of the diaphragm, the height of the flank portion of the magnetic alloy (202) accounts for 100% of the total height of the permanent magnet side surface; The height ratio of the flanks of the remaining magnetic conductive alloys (202) increases linearly with the distance from the center, satisfying: ， Where dX is the normalized distance from the permanent magnet to the center of the diaphragm, and 0≤dX≤1, k=70%, when the distance to the center of the diaphragm is closest, dX=0, and when the distance to the center of the diaphragm is farthest, dX=1.

5. The planar diaphragm earphone according to claim 1, characterized in that: The material of the magnetic conductive alloy (202) is a nickel-iron-based soft magnetic alloy, and its composition in atomic percentage is: Nickel (Ni): 79.5% - 80.5%, Iron (Fe): 19.2% - 20.0%, Molybdenum (Mo): 0.3% - 0.5%, Manganese (Mn): ≤0.05%, Silicon + Carbon (Si+C): ≤0.05%, And satisfy: Initial magnetic permeability μ i ≥ 100,000, @ 0.002 T, 1 kHz; Saturation flux density B sat ≥ 0.78 T; Coercive force H c ≤ 0.5 A / m; Grain size ≤ 5 μm.

6. The planar diaphragm earphone according to claim 5, characterized in that: The preparation method of the magnetic conductive alloy includes the following inventive steps: S1: In an argon-hydrogen mixed atmosphere, the nickel, iron and molybdenum raw materials are melted using the cold crucible suspension melting technology and the cooling rate is controlled. , forming an amorphous mother ingot; an axial-rotating composite magnetic field is applied during the smelting process: the axial static magnetic field intensity is 0.8-1.2 T, the rotating alternating magnetic field frequency is 50-100 Hz, and the peak magnetic induction intensity is 0.3-0.5 T; S2: The amorphous mother ingot is warm rolled at 450-480℃ to a thickness of 2.0 mm, with the axial deviation between the rolling direction and the magnetic field-induced 〈100〉 texture being ≤5°. After each rolling pass, laser pulse annealing is performed: wavelength 1064 nm, pulse width 10 ns, energy density 5-8 J / cm², repetition rate 20 kHz; S3: Reactive ion beam etching is performed on the surface of the rolled thin strip; Etching gas: Mixed gas, volume ratio 4:1, ion energy: 500-800 eV, etching depth: 0.5-1.0 μm, forming a trench array with a period of 200-300 nm and a depth-to-width ratio of 1:3; S4: Perform three-step gradient treatment in a segmented hydrogen annealing furnace: S5: Apply a pulsed strong magnetic field at 10°C below the Curie temperature (Tc), with a pulse width of 100 ms, a peak intensity of 6-8 T, and a direction parallel to the rolling texture axis.

7. The planar diaphragm earphone according to claim 1, wherein: The permanent magnet is a rectangular neodymium iron boron magnet, and its magnetization direction is perpendicular to the diaphragm plane; The coverage area of ​​the magnetic conductive alloy on the permanent magnet is asymmetrically distributed.

8. The planar diaphragm earphone according to claim 1, wherein: The surface of the magnetic alloy structure is provided with an anti-eddy current coating, the coating material is a nickel-chromium alloy or nickel-phosphorus alloy , with a thickness of 1-10 μm, used to suppress eddy current losses under alternating magnetic fields.

9. A method for manufacturing a planar diaphragm earphone with a magnetic field confinement structure, for manufacturing the planar diaphragm earphone according to any one of claims 1 to 8, characterized in that: Step 1: stamping a soft magnetic alloy strip into a square C-shaped component, comprising a base plate portion (202a) and a wing portion (202b); the base plate portion has a thickness controlled to be 0.3 mm ± 0.02 mm, and the wing portion is pre-cut according to a gradient rule; Step 2: coating an epoxy resin adhesive layer on the surface of the permanent magnet (201) away from the diaphragm; pressing the substrate portion (202a) of the magnetic alloy (202) onto the surface of the permanent magnet so that the mechanical anchoring protrusion (202c) is embedded in the adhesive layer; curing at 80°C for 1 hour to form a composite magnet unit with a shear resistance of ≥15 N / cm; Step 3: Use brackets to symmetrically install the composite magnet units on both sides of the diaphragm so that all the magnetic alloys are located away from the diaphragm. Use a Gauss meter to check the magnetic field uniformity in the diaphragm area and adjust the permanent magnet spacing so that the deviation is ≤5%. Step 4: suspend the diaphragm (204) between the symmetrical permanent magnets, connect the diaphragm wire to the bracket circuit, close the earphone housing, and complete the acoustic test.

10. The method for manufacturing a planar diaphragm earphone according to claim 9, wherein: Step 1 also includes: A high resistivity alloy coating (209) is provided on the surface of the magnetic conductive alloy (202), and the coating satisfies the following conditions: Nichrome or nickel-phosphorus alloy , resistivity , thickness 0.5μm - 2.0μm, suppresses eddy current loss of magnetic alloy under alternating magnetic field.

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