Sound detection device

Abstract

To obtain a sound detection device that suppresses deterioration in sound pressure detection accuracy and output precision from the sound sensor by having a substrate structure resistant to deformation under pressure and temperature changes.SOLUTION: A sound detection device 100 comprises a device housing 10 with a cylindrical internal space 10c1, a sound sensor 50 positioned within internal space 10c1 to detect external sounds, and a substrate 40 on which the sound sensor 50 is mounted. The substrate 40 is positioned within internal space 10c1 with its substrate plane oriented perpendicular to the axis of internal space 10c1. At least a portion of substrate 40 is cut away to avoid interference with other components within internal space 10c1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sound detection device. [Background Art]

[0002] Conventionally, there is known a sound detection device including a device housing, a cover, a vent portion, a substrate, and a sound sensor (see, for example, Patent Document 1). In the sound detection device described in Patent Document 1, the substrate is fixed to the inner peripheral end face of the opening of the device housing via a shield plate and an O-ring. The sound sensor is attached in close contact with the substrate on the extension line of a sound propagation path provided in the device housing, so as to measure only a desired sound pressure and suppress a decrease in accuracy caused by picking up ambient noise. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2020-113874 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, in the conventional sound detection device, in order to prevent intrusion of electromagnetic noise from the external environment, the shield plate is brought into close contact with the substrate, and the shield plate abuts against the O-ring to support the pressing force. If the shield plate is omitted in an environment where the influence of electromagnetic noise is absent or small, the substrate receives the pressing force from the O-ring, and deformation of the substrate may cause a decrease in detection accuracy and output accuracy from the sound sensor. Further, due to the difference in linear expansion coefficients among the substrate, the shield plate and the device housing, even when the ambient temperature changes, deformation of the substrate similarly occurs, which may cause a decrease in detection and output accuracy.

[0005] An object of the present invention is to provide a sound detection device that has a substrate structure that is not easily deformed by pressing force or temperature change, and thus can suppress a decrease in sound pressure detection accuracy and output accuracy from a sound sensor. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides a sound detection device comprising: a device housing having a cylindrical internal space; a sound sensor disposed in the internal space for detecting external sounds; and a substrate on which the sound sensor is mounted, wherein the substrate is disposed in the internal space in a orientation in which the substrate plane is perpendicular to the axis of the internal space, and at least a portion of the substrate but A notch is cut out to avoid interference with other components in the aforementioned internal space. As a result, the edges of the substrate are in a non-contact state with the inner wall of the device housing around their entire circumference. It is characterized by the following:

[0007] In this case, it is preferable that the shape of the substrate is a polygonal shape in which, in a plan view, the corners that constitute a rectangle are missing the corners that interfere with the other components.

[0008] Furthermore, the shape of the substrate is preferably an octagon in which, in a plan view, the corners that make up a rectangle are each missing opposite corners. [Effects of the Invention]

[0009] According to the present invention, a sound detection device can be obtained that has a substrate structure that is resistant to deformation under pressure and temperature changes, thereby suppressing a decrease in the accuracy of sound pressure detection and the accuracy of output from the sound sensor. [Brief explanation of the drawing]

[0010] [Figure 1] A cross-sectional view of a sound detection device according to one embodiment of the present invention. [Figure 2] (A) is a front view of the housing of the sound detection device, and (B) is a cross-sectional view of (A) taken along line AA. [Figure 3] Figure 2(A) is a cross-sectional view taken along the line BB. [Figure 4] (A) is a magnified view of the sound detection device before the circuit board is fixed, and (B) is a magnified view of the sound detection device after the circuit board is fixed. [Figure 5] A front view of the mounting surface of the aforementioned substrate. [Figure 6] (A) is an exploded perspective view of the sound detection device, and (B) is a perspective view of the sound detection device from the rear, with the circuit board attached to the device housing. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to Figures 1 to 6. Figure 1 is a cross-sectional view of a sound detection device 100 according to one embodiment of the present invention. Figure 2(A) is a front view of the device housing 10 of the sound detection device 100, and Figure 2(B) is a cross-sectional view taken along line AA in Figure 2(A). Figure 3 is a cross-sectional view taken along line BB in Figure 2(A).

[0012] In the drawings, arrows X, Y, and Z represent directions that are perpendicular to each other. In this embodiment, arrow X indicates the direction from one side of the device housing 10 to the other side, and is denoted as "left-right direction X". The left side of the left-right direction X is denoted as "left side X1", and the right side as "right side X2". Arrow Y indicates the direction perpendicular to the left-right direction X of the device housing 10, and is denoted as "front-back direction Y". The front side of the front-back direction Y is denoted as "front side Y1", and the rear side as "rear side Y2". Arrow Z indicates the direction perpendicular to both the left-right direction X and the front-back direction Y, and is denoted as "up-down direction Z". The upper side of the up-down direction Z is denoted as "up side Z1", and the lower side as "down side Z2".

[0013] The sound detection device 100 according to this embodiment is placed near a sound source (for example, a speaker, etc.) and used to detect whether or not the sound source is functioning normally. The sound detection device 100 is used, for example, to detect warning sounds at railroad crossings or guidance voices at pedestrian crossings. As shown in Figure 1, the sound detection device 100 comprises a box-shaped device housing 10, a sound propagation path 20 for transmitting sound from the outside, a vent 30 provided on the outside of the sound propagation path 20, a substrate 40 provided on the inside of the sound propagation path 20, a sound sensor 50 provided on the substrate 40, an elastic member 60 that abuts in the thickness direction of the substrate 40, and a cover 70 that closes an opening provided in the device housing 10 to form an internal space 10c1 of the housing.

[0014] The device housing 10 houses the components that make up the sound detection device 100 in order to ensure waterproofing and protection from the external environment. As shown in Figure 2, the rear wall Y2 of the device housing 10 has female threads 10a, grooves 10b, and openings 10c. The female threads 10a are the parts into which bolts 11 are tightened when fixing the cover 70 to the device housing 10, and are formed at the four corners of the rear wall Y2 of the device housing 10. The grooves 10b are grooves for arranging sealing members 12 such as O-rings, and are formed in a circular shape when viewed from the rear of the device housing 10. The openings 10c are formed in a substantially circular shape along the inner edge of the grooves 10b, in the part inside the inner edge of the grooves 10b, and open to communicate with the inside and outside of the device housing 10. These openings 10c are closed by the cover 70, which will be described later, and when closed by the cover 70, an internal housing space 10c1 is formed inside the openings 10c. As shown in Figure 1, an outlet 10d that opens in the vertical direction Z is formed in the lower wall Z2 of the device housing 10, and a cable 13 for outputting a sound pressure signal is attached to this outlet 10d via a mounting member 13a.

[0015] A cylindrical wall portion 14 is formed on the front wall Y1 of the device housing 10, rising to the rear Y2 and penetrating in the front-to-back direction Y. A substrate mounting portion 17 is formed at the rear end Y2 of the cylindrical wall portion 14 (the end on the inside side of the device housing 10) for mounting the substrate 40 in the front-to-back direction Y (plate thickness direction, mounting direction). Furthermore, a mounting portion 15 is formed on the inner circumference side of the substrate mounting portion 17 at the rear end Y2 of the cylindrical wall portion 14 for mounting the elastic member 60 on the front Y1 side (mounting direction) of the substrate mounting portion 17. As shown in Figure 2(A), the mounting portion 15 is formed in a circular shape when viewed from the rear of the device housing 10. The inner diameter of the mounting portion 15 is set to be smaller than the outer diameter of the elastic member 60 so that the elastic member 60, which will be described later, does not fall off. Also, the outer diameter of the mounting portion 15 is set to be larger than the outer diameter of the elastic member 60 so that the elastic member 60 does not ride up on it.

[0016] The mounting portion 15 has a stepped portion that is recessed one step in the front direction Y1 from the substrate mounting portion 17. That is, the mounting portion 15 is recessed in the front direction Y1 (mounting direction). The mounting portion 15 is provided with a protrusion 15a on the rear side Y2 (mounting direction substrate mounting portion 17 side) that protrudes within a range that does not exceed the substrate mounting portion 17. Therefore, the area around the protrusion 15a is relatively recessed in the front direction Y1, and this portion constitutes a recess 15b. As shown in Figure 2(A), the protrusion 15a and recess 15b are formed in a circular shape when viewed from the rear of the device housing 10. As shown in Figure 4(A), the width dimension s1 of the protrusion 15a is set to be smaller than the width dimension s2 of the elastic member 60, and the top of this protrusion 15a abuts over the entire circumference of the middle part in the width direction of the front side Y1 surface (one side in the mounting direction) of the elastic member 60. The recess 15b is a portion that allows a part of the deformed elastic member 60 to escape when the elastic member 60 deforms. Its depth, i.e., the dimension from the top of the convex portion 15a to the bottom of the recess 15b, is set to be greater than or equal to the deformation allowance s4 of the elastic member 60 shown in Figure 4(B). Furthermore, the dimension s3 from the substrate mounting portion 17 to the top of the convex portion 15a (also called the dimension in the mounting direction, height difference, or component dimension) is set to be less than or equal to the thickness t2 of the elastic member 60 (the dimension in the mounting direction of the elastic member 60 installed on the mounting portion 15).

[0017] At the end on the rear side Y2 of the cylindrical wall portion 14 (the distal end of the opening on the inner side of the device housing 10 of the sound propagation path 20), that is, at both ends in the left-right direction X of the mounting portion 15, as shown in FIG. 2(A), a pair of connecting plate portions 14a each extending in the left-right direction X and connected to the wall portion on the rear side Y2 of the device housing 10 are formed. Each connecting plate portion 14a is formed with a fixing portion 16 for fixing the substrate 40 to the device housing 10 respectively. That is, the device housing 10 is provided with at least a pair of spaced apart fixing portions 16 for fixing the substrate 40. The fixing portion 16 is formed at a position close to the cylindrical wall portion 14 on the plate surface on the rear side Y2 of the connecting plate portion 14a. That is, the fixing portion 16 is provided near the radially outer side of the distal end of the opening on the inner side of the device housing 10 of the sound propagation path 20. The fixing portion 16 is configured as a female screw for tightening a screw 16a (see FIGS. 6(A) and (B)) when fixing the substrate 40 to the device housing 10.

[0018] The amount of deformation of the substrate 40, the amount of deformation of the elastic member 60, and the reaction force caused by excessive deformation of the elastic member 60 are affected by reasons including the tightening amount (that is, the tightening torque) when tightening the substrate 40 to the fixing portion 16 with the screw 16a and the difference in linear expansion coefficients between the device housing 10 and the substrate 40 due to temperature changes. Therefore, it is preferable to adjust the pitch L (the separation distance, see FIG. 2(A) and FIG. 5) between one fixing portion 16 and the other fixing portion 16 to be relatively small with respect to the plate thickness dimension t1 (see FIG. 1) of the substrate 40. In other words, it is preferable to make the plate thickness dimension t1 of the substrate 40 in the front-rear direction Y relatively large with respect to the pitch L. That is, the smaller the ratio L / t of the pitch L of the fixing portions 16 to the plate thickness dimension t1 of the substrate 40 is, the smaller the deformation amount of the substrate 40 can be. Specifically, when L=19 mm, the deformation amount of the substrate 40 can be made smaller when t=3.2 mm and the ratio L / t is 5.9 than when t=1.6 mm and the ratio L / t is 11.8. Therefore, in the present embodiment, the pitch L between one fixing portion 16 and the other fixing portion 16 is set to 11.0 times or less of the plate thickness dimension t1 of the substrate 40, and preferably set to 8.0 times or less of the plate thickness dimension t1.

[0019] In this embodiment, the fixing portion 16 is formed of a pair of female threads as described above. However, instead of female threads, the fixing portion 16 may be configured to fix the device housing 10 and the substrate 40 by being hooked by claws extending from the device housing 10 side or the substrate 40 side. The fixing portion 16 may also be configured by hooking with claws, or using a combination of screws and claws. Furthermore, an adhesive may be applied to the end face of the back side Y2 of the cylindrical wall portion 14 over the entire circumference of the opening, and the portion to which this adhesive is applied may be used as the fixing portion 16; alternatively, the substrate 40 may be fixed to the device housing 10 by attaching an adhesive sheet, a double-sided tape, or the like. In addition, in this embodiment, a pair of fixing portions 16 is provided; however, two or more fixing portions 16 may be provided to support the substrate 40 at three points, for example. In this embodiment, it is preferable that the substrate placement portion 17, the fixing portion 16, and the connecting plate portion 14a are located on the same plane. With this configuration, when the substrate 40 is fixed, it is possible to prevent undesirable stress from being applied to the substrate 40 and the substrate 40 from being deformed from the initial state.

[0020] On the inner wall surface of the cylindrical wall portion 14, as shown in FIG. 1, a female thread 14b that screws together with a male thread 31a formed on the outer wall surface of a vent body 31, which will be described later of the vent portion 30, is formed. The inner side of the cylindrical wall portion 14 forms a linear space extending in the front-rear direction Y, and this space constitutes a sound propagation path 20 that communicates with the inside and outside of the device housing 10 and propagates sound from the outside. That is, the cylindrical wall portion 14 surrounds the periphery of the sound propagation path 20. Further, the tip end on the back side Y2 of the cylindrical wall portion 14 constitutes the tip end of the opening on the inner side of the device housing 10 of the sound propagation path. In this embodiment, the cylindrical wall portion 14 is configured to surround the periphery of the sound propagation path 20. However, for example, by making the wall portion on the front side Y1 of the device housing 10 thick and forming a through hole penetrating in the front-rear direction Y in the thick wall portion, the through hole can be used as the sound propagation path 20, and the cylindrical wall portion 14 can be omitted. In this case, the above-described substrate placement portion 17 and mounting portion 15 may be formed at the end portion on the back side Y2 of the thick wall portion, and the fixing portion 16 may be provided near the radially outer side of the tip end of the opening on the inner side of the device housing 10 of the sound propagation path 20.

[0021] The vent section 30 is provided on the front side Y1 (outside the device housing 10) of the sound propagation path 20. The vent section 30 is a component that covers the sound propagation path 20 and has waterproof, dustproof, and breathable properties. The vent section 30 comprises a cylindrical vent body 31 and a cylindrical cap section 32 that protrudes radially outward from the end of the front side Y1 of the vent body 31. A male screw 31a is formed on the outer circumferential surface of the vent body 31. The inside of the vent body 31 is configured to form the sound propagation path 20 in the same way as the cylindrical wall section 14 of the device housing 10.

[0022] The cap portion 32 has multiple first through holes 32a formed in the circumferential direction, each extending radially toward the center and communicating with the inside and outside, and a second through hole 32b formed in the center, connecting each first through hole 32a to the space inside the vent body 31 and extending in the front-to-back direction Y. When attaching the vent portion 30 to the device housing 10, the vent portion 30 is fixed to the device housing 10 by attaching a sealing retaining ring 33 to the front side Y1 end of the outer peripheral wall of the vent body 31 and then tightening the male screw 31a into the female screw 14b inside the cylindrical wall portion 14.

[0023] The substrate 40 is attached to the substrate mounting section 17 via an annular elastic member 60 that abuts the substrate 40 in the front-rear direction Y (thickness direction), and is provided to close the front end of the opening on the inside side of the device housing 10 of the sound propagation path 20. As shown in Figure 5, the substrate 40 is formed in the shape of an octagonal plate when viewed from the front. The substrate 40 is a printed circuit board on which a sound sensor 50 for detecting sound pressure and an IC chip (not shown) for signal reading are mounted. At the center of the substrate 40, a through hole 40a is formed in the front-rear direction Y (thickness direction) that communicates with the sound propagation path 20 and allows sound waves to pass through. Above the through hole 40a Z1, at least one minute ventilation hole 40b is provided that communicates the sound propagation path 20 with the internal space 10c1 of the housing. The ventilation hole 40b is a hole for equalizing the pressure between the sound propagation path 20 and the internal space 10c1 of the housing, and has a humidity control function. While the diameter of through-holes in typical electronic circuit boards is set to 0.8 to 1.0 mm to accommodate the wire diameter of the lead wires of electronic components, in this embodiment, with a typical hole diameter, the sound transmitted through the sound propagation path 20 cannot be fully picked up by the sound sensor 50, resulting in a decrease in sensor output and causing errors. Therefore, the diameter of the ventilation hole 40b is set to approximately 0.3 mm.

[0024] A connector section 41 is installed on the upper Z1 portion of the circuit board 40, and the signal line 13b of the cable 13 is connected to this connector section 41. A pair of screw holes 40c are formed through both ends of the circuit board 40 in the left-right direction X, penetrating in the front-back direction Y (plate thickness direction). These screw holes 40c are for screws 16a that are tightened into the fixing part 16. When attaching the circuit board 40 to the device housing 10, as shown in Figures 6(A) and 6(B), the circuit board 40 is positioned so that the central axis of these screw holes 40c is coaxial with the central axis of the fixing part 16, and then it is tightened and fixed with screws 16a. The sound sensor 50 is positioned on the back side Y2 of the circuit board 40 so as to close the end of the back side Y2 of the through hole 40a. For example, a capacitive type MEMS acoustic sensor chip is used for the sound sensor 50. A MEMS acoustic sensor chip is a small acoustic sensor formed on a semiconductor substrate using MEMS (micro electro-mechanical system) technology.

[0025] The elastic member 60 is an interposed member between the substrate 40 and the mounting part 15 when the substrate 40 is attached to the device housing 10. It is made of butyl rubber with a deformation allowance s4 in the front-to-back direction Y (plate thickness direction) to absorb the pressing force on the substrate 40 in the front-to-back direction Y, and is formed in an annular shape in plan view. The width dimension s2 of the elastic member 60 is set to be larger than the dimension in the front-to-back direction Y, so that the cross-sectional shape is formed in the shape of a rectangular flat plate, as shown in Figure 4(A). As shown in Figures 4(A) and (B), this elastic member 60 is positioned between the perimeter of the opening on the rear side Y2 (inside the device housing 10) of the sound propagation path 20 and the substrate 40. When the substrate 40 is attached to the mounting part 15, the elastic member 60 is pressed against the front side Y1 and deforms. At this time, the elastic member 60 closes the gap between the mounting part 15 and the substrate 40. In other words, the elastic member 60 is provided to close the inside of the sound propagation path 20. In this mounting configuration, where the substrate 40 is in contact with the substrate mounting portion 17, the substrate 40 can be fixed in such a way that the compression amount of the elastic member 60 remains constant by setting the dimension s3 from the substrate mounting portion 17 to the top of the protrusion 15a. This configuration prevents sound leakage from the sound propagation path 20 into the internal space 10c1 of the housing, thereby preventing a decrease in sensor output due to attenuation of input to the sound sensor 50 caused by the sound leakage, and preventing output errors of the sound sensor due to sound diffraction caused by the sound leakage.

[0026] The elastic member 60 is not limited to butyl rubber; it may also be made of silicone packing, high-density foamed urethane, or the like. In this embodiment, the elastic member 60 is fixed to the device housing 10 by being sandwiched between the mounting part 15 and the substrate 40, but the elastic member 60 may also be fixed to the device housing 10 by, for example, applying adhesive to one side of the elastic member 60, or by attaching an adhesive sheet or double-sided tape. The elastic member 60 may also be made of a flat, annular shape, as in this embodiment, or it may be made using a sealant such as silicone. The elastic member 60 is annular in plan view, but this is not limited to an annular shape in plan view, as long as the shape is based on the planar shape of the Y2 opening on the back side of the sound propagation path 20. In other words, if the shape is such that it abuts against the end of the Y2 opening on the back side of the sound propagation path 20 over its entire circumference, and also abuts against the substrate 40, and can seal the Y2 opening on the back side of the sound propagation path 20 over its entire circumference, the effect of preventing sound leakage from the sound propagation path 20 can be maintained.

[0027] Furthermore, the cross-sectional shape of the elastic member 60 may be circular instead of flat as in this embodiment. When the cross-sectional shape of the elastic member 60 is flat, the contact area between the elastic member 60 and the substrate 40 can be increased, so the reaction force when the substrate 40 is pressed against the front side Y1 can be increased, and the state in which the substrate 40 is in contact with the elastic member 60 can be stably maintained. On the other hand, when the cross-sectional shape of the elastic member 60 is circular, the contact area between the elastic member 60 and the substrate 40 can be reduced, so the reaction force when the substrate 40 is pressed against the front side Y1 can be reduced, and the risk of deformation of the substrate 40 can be reduced.

[0028] The cover 70 is a lid member that closes the opening 10c of the device housing 10. This cover 70 is a plate-shaped member with an outer edge that follows the outer edge of the opening 10c of the device housing 10. When the cover 70 is fixed to the device housing 10, the opening 10c is closed and an internal housing space 10c1 is formed on the rear side Y2 of the substrate 40 (opposite the sound propagation path 20). Note that the cover 70 is not limited to a plate-shaped member, but may also be a screw-in type lid that can be screw-fixed to the opening 10c, for example, as the vent portion 30 described above. Furthermore, the cover 70 may have a cylindrical portion that is inserted into the opening 10c and fitted by engaging claws, and a flange portion that protrudes on the rear side Y2, and the flange portion may be sealed by the sealing member 12.

[0029] The sound detection device 100 according to this embodiment is assembled by the following procedure. First, as shown in Figure 1, with the retaining ring 33 attached to the vent portion 30, the male screw 31a is tightened into the female screw 14b of the cylindrical wall portion 14 to attach the vent portion 30 to the device housing 10. The cable 13 is then attached to the outlet 10d of the device housing 10 via the mounting member 13a. Next, as shown in Figure 6(A), the elastic member 60 is placed on the rear side Y2 of the device housing 10, and as shown in Figure 1, the front side Y1 of the elastic member 60 is brought close to the rear side Y2 of the convex portion 15a of the mounting portion 15 and brought into contact with that surface. At this time, the top of the convex portion 15a is brought into contact with the center of the elastic member 60 in the width direction. Next, the substrate 40 is placed on the rear side Y2 of the device housing 10, and as shown in Figure 1, the front side Y1 of the substrate 40 is brought close to the rear side Y2 of the elastic member 60 and brought into contact with that surface. Then, the central axis of the screw holes 40c in the substrate 40 and the central axis of the fixing part 16 are made coaxial, and the screws 16a are tightened into the fixing part 16 to fix the substrate 40 to the device housing 10. At this time, as shown in Figure 4(B), the front side Y1 of the substrate 40 is in contact with the surface of the substrate mounting part 17, and the back side Y2 of the elastic member 60 is in contact with the elastic member 60 and is pressed toward the front side Y1. The elastic member 60 is crushed and deformed by being pressed by the substrate 40. When the substrate 40 is fixed to the device housing 10 in this state, the elastic member 60 closes the gap between the mounting part 15 and the substrate 40.

[0030] In this embodiment, when fixing the substrate 40 to the device housing 10, the elastic member 60 is compressed to bring the front surface Y1 of the substrate 40 into contact with the rear surface Y2 of the substrate mounting portion 17. However, the front surface Y1 of the substrate 40 does not necessarily have to be in contact with the rear surface Y2 of the substrate mounting portion 17. That is, as long as the front surface Y1 of the substrate 40 is in close contact with the elastic member 60, a gap may exist between the substrate 40 and the substrate mounting portion 17. Therefore, it is not always necessary to deform the elastic member 60, and even if the deformation allowance s4 of the elastic member 60 is 0, i.e., it is in contact with the mounting portion 15 and the substrate 40 without compression, a gap may exist between the substrate 40 and the substrate mounting portion 17. Therefore, when designing, the height of the protrusion 15a and the thickness of the elastic member 60, or the tightening amount of the screw 16a should be adjusted so that no gap occurs between the elastic member 60 and the substrate 40. Then, after fixing the circuit board 40 to the device housing 10, the signal line 13b is connected to the connector portion 41 of the circuit board 40, and then the opening 10c is closed with the cover 70. In this way, the sound detection device 100 is completed.

[0031] According to this embodiment, the sound detection device 100 comprises a device housing 10, a sound propagation path 20 that communicates with the inside and outside of the device housing 10 and propagates sound from the outside, a substrate 40 provided on the rear side Y2 (inside end of the device housing 10) of the sound propagation path 20, a sound sensor 50 provided on the substrate 40, and a cover 70 that closes the opening of the device housing 10 and forms an internal space 10c1 of the housing, wherein the device housing 10 is provided with at least one pair of spaced-apart fixing parts 16 for fixing the substrate 40, and the pitch L (spaced distance) between one fixing part 16 and the other fixing part 16 is 11.0 times or less the thickness dimension t1 of the substrate 40.

[0032] According to this invention, by setting the pitch L between the pair of fixed parts to 11.0 times or less the thickness dimension t1 of the substrate 40, the thickness of the substrate 40 can be made relatively thicker than the pitch L of the fixed parts 16, thereby improving the rigidity of the substrate 40. Therefore, compared to the conventional configuration in which the substrate 40 receives pressing force from the O-ring when the shield plate is omitted, deformation of the substrate 40 can be suppressed. Furthermore, by making the thickness of the substrate 40 relatively thicker than the pitch L of the fixed parts 16, deformation of the substrate 40 due to the difference in the coefficient of linear expansion between the substrate 40 and the device housing 10 when the ambient temperature changes can be suppressed. Thus, by having a substrate 40 structure that is resistant to deformation due to pressing force and temperature changes, a sound detection device 100 can be obtained that can suppress a decrease in the sound pressure detection accuracy and the output accuracy from the sound sensor 50.

[0033] Furthermore, in this embodiment, the substrate 40 is attached to the device housing 10 via an annular elastic member 60 that abuts the substrate 40 in the front-rear direction Y. Therefore, since the substrate 40 can be attached to the device housing 10 via an annular elastic member 60 that abuts the substrate 40 in the thickness direction, the substrate 40 and the device housing 10 are in close contact, preventing gaps from forming at the attachment point, suppressing sound leakage from the sound propagation path 20 through that point, and suppressing a decrease in sensor output. In addition, since the pressing force when attaching the substrate 40 to the device housing 10 can be absorbed by the elastic member 60, the pressing force generated on the substrate 40 can be reduced and deformation of the substrate 40 can be suppressed compared to a configuration without an elastic member 60.

[0034] Furthermore, by positioning the protrusion 15a, which has a width dimension s1 smaller than the width dimension s2 of the elastic member 60, to abut the middle portion in the width direction of the elastic member 60, the contact area between the device housing 10 and the elastic member 60 can be reduced compared to a configuration without the protrusion 15a. As a result, the range over which the reaction force is generated when the elastic member 60 is pressed by the device housing 10 can be reduced, thereby reducing the impact of this reaction force on the substrate 40 and suppressing deformation of the substrate 40.

[0035] Furthermore, since the dimension s3 from the substrate mounting portion 17 to the top of the protrusion 15a is set to be less than or equal to the thickness t2 of the elastic member 60, the amount of compression of the elastic member 60 pressed by the protrusion 15a is determined by the dimension s3 (part dimension) from the substrate mounting portion 17 to the top of the protrusion 15a, so a constant amount of compression can be ensured regardless of the mounting state. At this time, a recess 15b adjacent to the protrusion 15a is formed, so a part of the pressed elastic member 60 can escape into the recess 15b. Therefore, the influence on the substrate 40 due to the reaction force when the elastic member 60 is pressed from the device housing 10 can be reduced. Consequently, deformation of the substrate 40 due to the reaction force when the elastic member 60 is pressed from the device housing 10 can be suppressed.

[0036] Furthermore, since the fixing portion 16 is provided near the radially outer end of the tip of the opening on the inside side of the device housing 10 of the sound propagation path 20, each fixing portion 16 can be brought as close as possible to the center of the substrate 40, and the pitch L of the pair of fixing portions 16 can be reduced. As a result, the plate thickness dimension t1 of the substrate 40 can be made relatively larger with respect to the pitch L, and the rigidity of the substrate 40 can be improved. In addition, the plate thickness of the substrate 40 required to satisfy the above-mentioned relationship between the pitch L and the plate thickness dimension t1 of the substrate 40 can be made thinner compared to a configuration with a large pitch L, and the size of the sound detection device 100 can be suppressed.

[0037] Furthermore, since the substrate 40 that seals the tip of the opening on the inside side of the device housing 10 of the sound propagation path 20 is provided with a minute ventilation hole 40b that connects the sound propagation path 20 and the internal space 10c1 of the housing, the air pressure in the sound propagation path 20 and the air pressure in the internal space 10c1 of the housing become equal, and condensation can be prevented from occurring in the internal space 10c1 of the housing.

[0038] Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design changes and the like that do not depart from the gist of the present invention are also included in the present invention. In this embodiment, a pair of connecting plate portions 14a are formed at the end of the rear side Y2 of the cylindrical wall portion 14, that is, at both ends in the left-right direction X of the mounting portion 15, and fixing portions 16, which are female screws for fixing the substrate 40 to the device housing 10, are formed on each connecting plate portion 14a. However, the type and arrangement of the fixing portions are not limited thereto. For example, the end face of the rear side Y2 of the cylindrical wall portion 14 and the front side Y1 of the substrate 40 may be bonded together with an adhesive, and this bonded portion may be used as the fixing portion.

[0039] Alternatively, the front surface Y1 of the elastic member 60 may be bonded to the rear end Y2 of the cylindrical wall portion 14, and the rear surface Y2 of the elastic member 60 may be bonded to the front surface Y1 of the substrate 40 with adhesive, and this bonded portion may be used as a fixing portion. In this case, the inner diameter of the elastic member 60 becomes the separation dimension L (pitch L in this embodiment), but as described above, the outer dimensions of the mounting portion 15 are set to be larger than the outer diameter of the elastic member 60 so that the elastic member 60 does not ride up on it, so the inner diameter of the elastic member 60, i.e., the separation dimension L, can be made smaller than when a fixing portion 16 is formed on the connecting plate portion 14a extending in the left-right direction X of the mounting portion 15 as in this embodiment. Specifically, if the pitch L of the fixing portion 16 in this embodiment is L=19mm, the ratio L / t is 11.8 at t=1.6mm and 5.9 at t=3.2mm. In contrast, if the inner diameter dimension of the elastic member 60 is set to the separation dimension L, then if L=12mm, the ratio L / t can be set to 7.5 at t=1.6mm and 3.7 at t=3.2mm. Therefore, the plate thickness dimension t1 of the substrate 40 can be made relatively larger with respect to the separation dimension L. [Explanation of Symbols]

[0040] t1 Plate thickness dimension L Pitch (distance between spaces) 100-sound detection device 10. Device housing 16 Fixed part 17. Substrate mounting section 20 Sound propagation paths 30 Vent section 40 circuit boards 50 Tone Sensor 60 Elastic members 70 Cover

Claims

1. A device housing having a cylindrical internal space, The aforementioned internal space is equipped with a sound sensor that detects external sounds, A sound detection device comprising a circuit board on which the sound sensor is mounted, The substrate is arranged in the internal space in a orientation such that the substrate plane is perpendicular to the axis of the internal space. A sound detection device characterized in that at least a portion of the substrate is missing to avoid interference with other components in the internal space, so that the edges of the substrate are in a non-contact state with the inner wall of the device housing around their entire circumference.

2. The shape of the substrate is such that, in a plan view, the corners that form a rectangle interfere with the other components. The sound detection device according to claim 1, characterized in that it has a polygonal shape with a missing corner.

3. The shape of the substrate is such that, in a plan view, the corners that form a rectangle are missing from each of the opposing corners. The sound detection device according to claim 1 or 2, characterized in that the digits are octagonal in shape.

Images