Microphone unit

Abstract

To provide a microphone unit with a small size and a low cost, which corresponds to a maximum level IPX9K of an on-vehicle IP(K) test.SOLUTION: A microphone unit comprises: a cylindrical case in which an upper surface and a lower surface are opened; a metal waterproof film having a thickness of 0.01 mm or more and 0.05 mm or less, a hardness of 100HV or more, a bearing force of 70 N / mm2 or more, a tension strength of 350 N / mm2 or more, and fixed to a lower surface of the case so as to block an open part of the lower surface of the case; a substrate arranged within the case; a microphone mounted on the substrate; and a sealing member that seals the open part of the upper surface of the case.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a microphone unit.

Background Art

[0002] As a conventional example of a microphone having a waterproof mechanism, there is Patent Document 1. The microphone of Patent Document 1 includes a diaphragm, a housing processed into a hemispherical, parabolic, or conical shape inside, an acoustic transducer that converts sound pressure into an electrical signal, and a wiring that transmits the electrical signal from the acoustic transducer to the outside. The sound pressure input surface of the acoustic transducer is arranged at the bottom surface portion of the hemispherical, parabolic, or conical surface inside the housing, and the diaphragm, the housing, and the housing and the wiring have a waterproof mechanism that prevents water from entering.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Many of the conventional waterproof mechanisms did not have the performance to withstand the water resistance test at the highest level IPX9K (ISO20653, JISD5020) in the in-vehicle IP(K) test. Also, no method for realizing a microphone that satisfies such performance in a small size and at a low cost has been known.

[0005] Therefore, an object of the present invention is to provide a microphone unit that is compatible with the highest level IPX9K of the in-vehicle IP(K) test and is small-sized and low-cost.

Means for Solving the Problems

[0006] The microphone unit of the present invention comprises a cylindrical case with open top and bottom surfaces, and a material with a thickness of 0.01 mm to 0.05 mm, a hardness of 100 HV or more, and a yield strength of 70 N / mm². 2 The above tensile strength is 350 N / mm². 2 The above includes a metal waterproof membrane fixed to the bottom surface of the case so as to close the opening on the bottom surface of the case, a circuit board disposed inside the case, a microphone mounted on the circuit board, and a sealing member that seals the opening on the top surface of the case. [Effects of the Invention]

[0007] According to the present invention, a compact and low-cost microphone unit can be realized that complies with the highest level of IPX9K in automotive IP(K) testing. [Brief explanation of the drawing]

[0008] [Figure 1] Plan view of the microphone unit of Example 1 and Modification 1. [Figure 2] A cross-sectional view of the microphone unit of Example 1, based on the projection direction indicated by the 2-2 cutting line and arrow in Figure 1. [Figure 3] Bottom view of the circuit board. [Figure 4] A cross-sectional view of the microphone unit of Modification 1, based on the projection direction indicated by the 2-2 cutting line and arrow in Figure 1. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below. Components having the same function will be given the same number, and redundant explanations will be omitted. [Examples]

[0010] The structure of the microphone unit of Embodiment 1 will be described below with reference to Figures 1 and 2. As shown in Figure 2, the microphone unit 1 of this embodiment includes a cylindrical case 11 with openings on the top and bottom, a metal waterproof membrane 12 fixed to the bottom surface of the case 11 so as to close the opening on the bottom surface of the case 11, a conductive material spacer 13 sandwiched between a substrate 14 and the waterproof membrane 12, a substrate 14 placed inside the case 11, a microphone 15 mounted on the substrate 14, and a sealing member 16 that seals the opening on the top surface of the case 11. Holes 145 are formed in the substrate 14, and holes 165 are formed in the sealing member 16. An amplification circuit, a filter circuit, and an equalizer circuit are mounted on the substrate 14 as electronic circuits for characteristic adjustment. In this embodiment, a MEMS microphone is assumed, but this can be replaced with an ECM or a dynamic microphone. When using an ECM or a dynamic microphone, the heat resistance temperature will change, so it is necessary to design with this in mind.

[0011] Case 11 is made of a material that can withstand high water pressure (e.g., 10 MPa) and is compatible with the material of the vibrating membrane. For example, a stainless steel case is acceptable. The thickness of case 11 (t1 in the figure) is preferably around 0.2 mm to 3.0 mm.

[0012] The material for the waterproof membrane 12 should be one that is air-impermeable, springy, and returns to its original shape even when deformed by pressure. A thin film of a corrosion-resistant metal, such as a SUS film, is suitable. This improves water resistance and waterproofing. Similar performance can be achieved if the waterproof membrane 12 is made of a thin film of resin.

[0013] Furthermore, the waterproof membrane 12 has a thickness (t2 in the diagram) of 0.01 mm to 0.05 mm, a hardness of 100 HV or more, and a yield strength of 70 N / mm². 2 The above tensile strength is 350 N / mm². 2 By doing so, a waterproof structure that meets the highest level of the automotive IP(K) test, IPX9K, can be achieved. As an additional condition, elongation of 10% or more may be added. As a result, the microphone unit 1 of this embodiment can achieve a waterproof structure that can withstand high-pressure washing, and can therefore be used as an external microphone.

[0014] The waterproof film 12 may be fixed to the lower surface of the case 11 by spot welding or seam welding. Also, the waterproof film 12 may be joined to the lower surface of the case 11 with an adhesive or a strong double-sided adhesive tape. By firmly connecting the waterproof film 12 and the case 11, the joint will not break even under high water pressure (e.g., 10 MPa).

[0015] The distance between the substrate 14 and the waterproof film 12 is a parameter for sensitivity adjustment, and the optimal value varies depending on the structure and vibration diameter. For example, when the film thickness of the waterproof film 12 (SUS film) is 30 μm and the outer diameter is Φ14 (vibration diameter: Φ12), it is preferable that the distance between the substrate 14 and the waterproof film 12 is 0.01 mm to 0.5 mm. In this embodiment, the height of the spacer 13 (t3 in the figure) is set to 0.1 mm or more and 0.5 mm or less to provide a gap between the substrate 14 and the waterproof film 12, and the distance between the substrate 14 and the waterproof film 12 is set to 0.1 mm or more and 0.5 mm or less.

[0016] Also, by adjusting the distance between the substrate 14 and the waterproof film 12, a structure is formed in which the substrate 14 supports the waterproof film 12 even under high water pressure (e.g., 10 MPa), making it difficult to exceed the yield limit of the waterproof film 12 and shortening the recovery time of the waterproof film 12.

[0017] It is also possible to further reduce the size by reducing the diameter of the microphone unit 1 and making the film thickness of the waterproof film 12 thinner.

[0018] When joining the substrate 14 and the case 11, it may be joined by pressing from above with a highly elastic adhesive or a structure such as a cap. Due to the springiness of the waterproof film 12 and the fixing method of the substrate 14 (using a highly elastic adhesive), it is possible to cope with air pressure fluctuations that occur at temperatures from 105°C to -40°C.

[0019] As shown in FIG. 3, a GND pattern 147 is provided at the outer edge of the bottom surface of the substrate 14, and by contacting (connecting) the GND pattern 147 and the spacer 13 (conductive material), the case 11 and the waterproof film 12 can be used as shields, improving resistance to static electricity and electromagnetic noise.

[0020] <Modification Example 1> As shown in FIG. 4, the waterproof film 12 may be fixed by press-fitting (crimping) the waterproof film 12 together with the washer 17 into the groove 111 provided on the inner periphery of the lower end of the case 11. It can be fixed by spot welding or seam welding as in Example 1, or by crimping together with the washer 17 as in this modification example, so that it has a structure that can withstand a pressure of 10 Mpa and the water pressure underwater.

[0021] <Usage Applications of the Microphone Units of Example 1 and Modification Example 1> The microphone units of Example 1 and Modification Example 1 can be used in, for example, the following articles.

[0022] 1) Waterproof microphones, outdoor microphones, external vehicle microphones 2) Vending machines (voice recognition microphones) 3) Security cameras 4) Entrance doors (voice recognition microphones, intercoms, etc.) 5) Microphones for vehicle reverse warning buzzer control 6) Microphones for answer-back sound control for keyless unlocking / locking 7) Failure detection of heavy machinery and robots

Claims

1. A cylindrical case with openings on the top and bottom, A SUS film is fixed to the lower surface of the case so as to close the opening on the lower surface of the case, A circuit board placed inside the aforementioned case, A microphone mounted on the aforementioned circuit board, Includes a sealing member that seals the opening on the upper surface of the case, The thickness of the SUS film is 30 μm, the outer diameter of the SUS film is φ14, and the vibration diameter of the SUS film is φ12. A gap is provided between the substrate and the SUS film such that the distance between the substrate and the SUS film is 0.01 mm or more and 0.5 mm or less. Microphone unit.

2. A microphone unit according to claim 1, The substrate and the SUS film are sandwiched together, and the spacer is made of a conductive material connected to the GND of the substrate. Microphone unit.

3. A microphone unit according to claim 1 or 2, The SUS film was fixed to the lower surface of the case by spot welding. Microphone unit.

4. A microphone unit according to claim 1 or 2, The SUS film was fixed to the lower surface of the case by seam welding. Microphone unit.

5. A microphone unit according to claim 1 or 2, The SUS film was fixed in place by fitting it into a groove provided on the inner circumference of the lower end of the case. Microphone unit.

6. A microphone unit according to any one of claims 1 to 5, An amplifier circuit, a filter circuit, and an equalizer circuit were mounted on the aforementioned substrate as electronic circuits. Microphone unit.

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