Sound detection device

Abstract

To provide a sound detection device capable of suppressing a decrease in detection accuracy of a sound pressure or output accuracy from a sound sensor by having a substrate structure that is less likely to deform with respect to a pressing force or a temperature change.SOLUTION: A sound detection device 100 includes: a device housing 10; a sound propagation path 20; a substrate 40; and a sound sensor 50. A substrate mounting part 17 on which the substrate 40 is mounted with a plate thickness direction of the substrate 40 as a mounting direction is provided at an end part of a sound propagation path 20 on an apparatus casing inner side. A mounting part 15 recessed in the mounting direction is formed in the substrate mounting part 17. The mounting part 15 is provided with an elastic member 60. The substrate 40 is mounted on the substrate mounting part 17 via an elastic member 60. The device housing 10 is provided with at least a pair of spaced-apart fixing parts 16 for fixing the substrate 40, and a pitch L between one fixing part 16 and the other fixing part 16 is 11.0 times or less a plate thickness dimension t1 of the substrate 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, a sound detection device has been known that includes a device housing, a cover, a vent, 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 surface 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 an extension of the sound propagation path provided in the device housing so as to measure only the desired sound pressure and prevent a decrease in accuracy due to pickup of ambient noise. [Prior art documents] [Patent documents]

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

[0004] However, in conventional sound detection devices, a shield plate is attached tightly to the substrate to prevent the intrusion of electromagnetic noise from the external environment, and this shield plate abuts against an O-ring to support the pressing force, but if the shield plate is omitted in an environment where the influence of electromagnetic noise is small or absent, the substrate will be subjected to pressing force from the O-ring, which may cause the substrate to deform, resulting in a decrease in detection accuracy and output accuracy from the sound sensor.In addition, due to differences in the linear expansion coefficients of the substrate, shield plate, and device housing, changes in the ambient temperature may also cause the substrate to deform, potentially resulting in a decrease in detection and output accuracy.

[0005] The present invention aims to provide a sound detection device that has a substrate structure that is resistant to deformation due to pressure or temperature changes, thereby preventing a decrease in the accuracy of sound pressure detection and the accuracy of output from a sound sensor. [Means for solving the problem]

[0006] In order to solve the above problems, the sound detection device of the present invention is a sound detection device comprising: a device housing; a sound propagation path that communicates between the inside and outside of the device housing and propagates sound from outside; a substrate provided on the inside side of the device housing of the sound propagation path; and a sound sensor that is provided inside the device housing and detects external sound, wherein a substrate mounting portion is provided at an end of the sound propagation path on the inside side of the device housing, on which the substrate is mounted, with the thickness direction of the substrate being the mounting direction, and a mounting portion that is recessed in the mounting direction is formed in the substrate mounting portion, and an elastic member that abuts against the substrate in the thickness direction is installed in the mounting portion, and the substrate is mounted on the substrate mounting portion via the elastic member, and the device housing is provided with at least a pair of spaced-apart fixing portions that fix the substrate, and the distance between one of the fixing portions and the other of the fixing portions is 11.0 times or less the thickness dimension of the substrate.

[0007] In this case, the elastic member is formed in a ring shape having a predetermined width, and the mounting portion is provided with a convex portion that protrudes toward the substrate mounting portion in the mounting direction within an area not exceeding the substrate mounting portion, and it is preferable that the convex portion has a width dimension smaller than the width dimension of the elastic member and abuts against the surface of the elastic member on one side in the mounting direction over the entire circumference.

[0008] Preferably, the elastic member has a deformation margin that allows deformation in the placement direction, and the dimension in the placement direction from the top of the convex portion to the bottom of the attachment portion is equal to or greater than the deformation margin.

[0009] Furthermore, it is preferable that the dimension in the placement direction from the substrate placement portion to the top of the convex portion is set to be equal to or less than the dimension in the placement direction of the elastic member installed in the attachment portion.

[0010] Furthermore, it is preferable that the sound propagation path is provided inside a cylindrical wall portion that communicates with the inside and outside of the device housing, the substrate mounting portion is formed by a flat end surface of the cylindrical wall portion on the inside side of the device housing, the fixing portion is provided near the outside of the end of the sound propagation path on the inside side of the device housing, and the end surface and the fixing portion are located on the same plane. [Effects of the Invention]

[0011] According to the present invention, a sound detection device can be obtained that has a substrate structure that is resistant to deformation due to pressure or temperature changes, and that can suppress deterioration in the detection accuracy of sound pressure and the output accuracy from the sound sensor. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a sound detection device according to an embodiment of the present invention. [Figure 2] 2A is a front view of the device housing of the sound detection device, and FIG. 2B is a cross-sectional view taken along line AA in FIG. 2A. [Figure 3] 2(A) is a cross-sectional view taken along line BB in FIG. [Figure 4] (A) is a partial enlarged view of the sound detection device before the substrate is fixed, and (B) is a partial enlarged view of the sound detection device after the substrate is fixed. [Figure 5] FIG. [Figure 6] FIG. 2A is an exploded perspective view of the sound detection device, and FIG. 2B is a perspective view of the sound detection device from the rear side with a substrate attached to the device housing. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to Figs. 1 to 6. Fig. 1 is a cross-sectional view of a sound detection device 100 according to one embodiment of the present invention. Fig. 2(A) is a front view of a device housing 10 of the sound detection device 100, and Fig. 2(B) is a cross-sectional view taken along line AA in Fig. 2(A). Fig. 3 is a cross-sectional view taken along line BB in Fig. 2(A).

[0014] In the drawings, arrows X, Y, and Z indicate directions perpendicular to one another. In this embodiment, the direction from one side of the device housing 10 to the other side is indicated by arrow X, and arrow X is referred to as the "left-right direction X." The left side of the left-right direction X is referred to as the "left side X1," and the right side is referred to as the "right side X2." The direction perpendicular to the left-right direction X of the device housing 10 is indicated by arrow Y, and arrow Y is referred to as the "front-rear direction Y." The front side of the front-rear direction Y is referred to as the "front side Y1," and the rear side is referred to as the "rear side Y2." The direction perpendicular to the left-right direction X and the front-rear direction Y is indicated by arrow Z, and is referred to as the "upper-lower direction Z." The upper side of the up-down direction Z is referred to as the "upper side Z1," and the lower side is referred to as the "lower side Z2."

[0015] The sound detection device 100 according to this embodiment is placed near a sound source (e.g., a speaker, etc.) and is used to detect whether the sound source is functioning normally. The sound detection device 100 is used to detect, for example, warning sounds at railroad crossings and guidance sounds at pedestrian crossings. As shown in FIG. 1 , the sound detection device 100 includes a box-shaped device housing 10, a sound propagation path 20 that propagates sound from the outside, a vent portion 30 provided on the exterior side of the sound propagation path 20, a substrate 40 provided on the interior side of the sound propagation path 20, a sound sensor 50 provided on the substrate 40, an elastic member 60 abutting against the substrate 40 in the thickness direction, and a cover 70 that closes an opening provided in the device housing 10 to form a housing internal space 10c1.

[0016] The device housing 10 accommodates the components of the sound detection device 100 to ensure waterproofing and protection from the external environment. As shown in FIG. 2 , a female thread 10a, a groove 10b, and an opening 10c are formed in the wall on the rear side Y2 of the device housing 10. The female thread 10a is a portion into which a bolt 11 is fastened when fixing the cover 70 to the device housing 10, and is formed at each corner of the wall on the rear side Y2 of the device housing 10. The groove 10b is a groove for arranging a sealing member 12 such as an O-ring, and is formed in a circular shape when viewed from the back of the device housing 10. The opening 10c is formed in a substantially circular shape along the inner edge of the groove 10b, located inward from the inner edge of the groove 10b, and opens to communicate between the inside and outside of the device housing 10. The opening 10c is configured to be closed by the cover 70, which will be described later. When the cover 70 is closed, a housing internal space 10c1 is formed inside the opening 10c. As shown in FIG. 1, a draw-out port 10d that opens in the vertical direction Z is formed in the wall portion of the lower side Z2 of the device housing 10, and a cable 13 for outputting a sound pressure signal is attached to this draw-out port 10d via an attachment member 13a.

[0017] A cylindrical wall portion 14 is formed on the wall portion on the front side Y1 of the device housing 10, rising toward the rear side Y2 and penetrating in the front-rear direction Y. A substrate placement portion 17 is formed on the end portion of the cylindrical wall portion 14 on the rear side Y2 (the end portion on the interior side of the device housing 10) for placing a substrate 40 in the front-rear direction Y (plate thickness direction, placement direction). A mounting portion 15 is formed on the inner periphery of the substrate placement portion 17 at the end portion on the rear side Y2 of the cylindrical wall portion 14 for placing an elastic member 60 on the front side Y1 side (placement direction) of the substrate placement portion 17. As shown in FIG. 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 smaller than the outer diameter of the elastic member 60 (described later) to prevent the elastic member 60 from falling off. The outer diameter of the mounting portion 15 is set larger than the outer diameter of the elastic member 60 to prevent the elastic member 60 from riding up.

[0018] The mounting portion 15 has a step recessed from the substrate placement portion 17 toward the front side Y1. That is, the mounting portion 15 is recessed toward the front side Y1 (placing direction). The mounting portion 15 has a protrusion 15a on the rear side Y2 (the substrate placement portion 17 side in the placing direction) that protrudes within a range not exceeding the substrate placement portion 17. Therefore, the periphery of the protrusion 15a is relatively recessed toward the front side Y1, and this portion forms a recess 15b. As shown in FIG. 2(A), the protrusion 15a and the recess 15b are formed in a circular shape when viewed from the rear of the device housing 10. As shown in FIG. 4(A), the width dimension s1 of the protrusion 15a is set smaller than the width dimension s2 of the elastic member 60, and the top of the protrusion 15a abuts the entire periphery against the middle portion of the width direction of the front side Y1 surface (the surface on one side in the placing direction) of the elastic member 60. The recess 15b is a portion that allows a portion of the deformed elastic member 60 to escape when the elastic member 60 deforms, and its depth, i.e., the dimension from the top of the protrusion 15a to the bottom of the recess 15b, is set to be equal to or greater than the deformation allowance s4 of the elastic member 60 shown in Fig. 4(B). Also, the dimension s3 from the substrate mounting portion 17 to the top of the protrusion 15a (also referred to as the dimension in the mounting direction, height difference, or component dimension) is set to be equal to or less than the thickness t2 of the elastic member 60 (the dimension in the mounting direction of the elastic member 60 installed in the mounting portion 15).

[0019] As shown in FIG. 2A , a pair of connecting plates 14a are formed at the end of the rear surface side Y2 of the cylindrical wall 14 (the tip of the opening of the sound propagation path 20 on the device housing 10 interior side), i.e., at both ends of the mounting portion 15 in the left-right direction X. The connecting plates 14a each extend in the left-right direction X and are connected to a wall portion on the rear surface side Y2 of the device housing 10. Each connecting plate 14a is formed with a fixing portion 16 for fixing the board 40 to the device housing 10. That is, the device housing 10 is provided with at least a pair of spaced-apart fixing portions 16 for fixing the board 40. The fixing portions 16 are formed on the plate surface of the rear surface side Y2 of the connecting plate 14a at positions closer to the cylindrical wall 14. That is, the fixing portions 16 are provided radially outward near the tip of the opening of the sound propagation path 20 on the device housing 10 interior side. The fixing portion 16 is configured with a female screw for fastening a screw 16a (see FIGS. 6(A) and 6(B)) when fixing the substrate 40 to the device housing 10.

[0020] The amount of deformation of the substrate 40, the amount of deformation of the elastic member 60, and the reaction force due to excessive deformation of the elastic member 60 are affected by factors such as the amount of tightening (i.e., tightening torque) when the screws 16a are tightened to the fixing portions 16 and differences in the linear expansion coefficients of the device housing 10 and the substrate 40 due to temperature changes. Therefore, it is preferable to adjust the pitch L (separation distance, see FIGS. 2A and 5) between one fixing portion 16 and the other fixing portion 16 so that it is relatively small with respect to the thickness t1 (see FIG. 1) of the substrate 40. In other words, it is preferable to increase the thickness t1 of the substrate 40 in the front-rear direction Y relative to the pitch L. That is, the smaller the ratio L / t of the pitch L of the fixing portions 16 to the thickness t1 of the substrate 40, the smaller the amount of deformation of the substrate 40 can be. Specifically, when L=19 mm, the amount of deformation of 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 this embodiment, the pitch L between one fixing portion 16 and the other fixing portion 16 is set to 11.0 times or less the thickness dimension t1 of substrate 40, and preferably to 8.0 times or less the thickness dimension t1.

[0021] In this embodiment, the fixing portion 16 is configured with a pair of female screws as described above. However, other than female screws, the fixing portion 16 may be configured to fix the device housing 10 and the substrate 40 by hooking with a claw extending from the device housing 10 side or the substrate 40 side. Alternatively, the fixing portion 16 may be configured by hooking with a claw or by a combination of a screw and a claw. Furthermore, an adhesive may be applied to the end surface of the rear side Y2 of the cylindrical wall portion 14 around the entire circumference of the opening, and the portion where the adhesive is applied may be configured as the fixing portion 16. Alternatively, the substrate 40 may be fixed to the device housing 10 by adhering an adhesive sheet, double-sided tape, or the like. In this embodiment, a pair of fixing portions 16 is provided. However, more than one pair of fixing portions 16 may be provided to support the substrate 40 at three points. In this embodiment, it is preferable that the substrate mounting portion 17, the fixing portion 16, and the connecting plate portion 14a are on the same plane. By adopting such a configuration, it is possible to prevent the substrate 40 from being deformed from its initial state due to an undesired stress being applied to the substrate 40 when the substrate 40 is fixed.

[0022] As shown in FIG. 1 , an internal thread 14b is formed on the inner wall surface of the cylindrical wall portion 14. The internal thread 14b is adapted to engage with an external thread 31a formed on the outer wall surface of a vent body 31 (described later) of the vent portion 30. The inside of the cylindrical wall portion 14 defines a linear space extending in the front-rear direction Y. This space communicates with the inside and outside of the device housing 10 and constitutes a sound propagation path 20 through which sound from the outside propagates. That is, the cylindrical wall portion 14 surrounds the periphery of the sound propagation path 20. The distal end of the cylindrical wall portion 14 on the rear side Y2 constitutes the distal end of the opening of the sound propagation path on the inside side of the device housing 10. In this embodiment, the cylindrical wall portion 14 surrounds the periphery of the sound propagation path 20. However, for example, it is also possible to thicken the wall on the front side Y1 of the device housing 10 and form a through-hole penetrating the thick wall in the front-rear direction Y, thereby using the through-hole as the sound propagation path 20 and omit the cylindrical wall portion 14. In this case, the above-mentioned substrate mounting portion 17 and mounting portion 15 are formed at the end of the rear side Y2 of the thick wall portion, and a fixing portion 16 is provided near the radially outer side of the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10.

[0023] 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 member that covers the sound propagation path 20 and is waterproof, dustproof, and breathable. The vent section 30 includes a cylindrical vent body 31 and a columnar cap section 32 that protrudes radially outward from the end of the vent body 31 on the front side Y1. A male thread 31a is formed on the outer peripheral surface of the vent body 31. The inside of the vent body 31 forms the sound propagation path 20, similar to the cylindrical wall section 14 of the device housing 10.

[0024] The cap portion 32 is formed with a plurality of first through holes 32a in the circumferential direction, each penetrating radially toward the center and communicating with the inside and outside, and a second through hole 32b formed in the center, communicating each of the first through holes 32a with the space inside the vent body 31 and penetrating in the front-to-rear direction Y. When attaching the vent portion 30 to the device housing 10, a sealing press ring 33 is attached to the end of the outer peripheral wall of the vent body 31 on the front side Y1, and the male screw 31a is tightened into the female screw 14b on the inside of the cylindrical wall portion 14, thereby fixing the vent portion 30 to the device housing 10.

[0025] The substrate 40 is attached to the substrate placement portion 17 via an annular elastic member 60 that contacts the substrate 40 in the front-rear direction Y (thickness direction) and closes the leading end of the opening of the sound propagation path 20 toward the interior of the device housing 10. As shown in FIG. 5 , the substrate 40 is formed in an octagonal plate shape 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. A through-hole 40a that communicates with the sound propagation path 20 and allows sound waves to pass through is formed at the center of the substrate 40 in the front-rear direction Y (thickness direction). At least one minute vent hole 40b is provided on an upper side Z1 of the through-hole 40a, connecting the sound propagation path 20 to the housing internal space 10c1. The vent hole 40b is a hole for equalizing the pressure between the sound propagation path 20 and the housing internal space 10c1 and has a humidity control function. The hole diameter of a through hole in a typical electronic circuit board is set to 0.8 to 1.0 mm to correspond to the wire diameter of the lead wire of an electronic component. However, in this embodiment, with a typical hole diameter, the sound that has propagated through the sound propagation path 20 cannot be picked up by the sound sensor 50, resulting in a decrease in sensor output and an error. Therefore, the hole diameter of the ventilation hole 40b is set to about 0.3 mm.

[0026] A connector 41 is provided on the upper side Z1 of the substrate 40, and a signal line 13b of the cable 13 is connected to the connector 41. A pair of screw holes 40c are formed at both ends of the substrate 40 in the left-right direction X, penetrating the substrate 40 in the front-rear direction Y (thickness direction). The screw holes 40c are holes through which screws 16a are fastened to the fixing portions 16. When attaching the substrate 40 to the device housing 10, as shown in FIGS. 6(A) and 6(B), the substrate 40 is positioned so that the central axis of the screw holes 40c is coaxial with the central axis of the fixing portions 16, and the substrate 40 is fastened and fixed by the screws 16a. The sound sensor 50 is disposed on the rear surface Y2 (mounting surface) of the substrate 40 so as to close the rear end Y2 of the through hole 40a. The sound sensor 50 may be, for example, a capacitive MEMS acoustic sensor chip. The MEMS acoustic sensor chip is a small acoustic sensor formed on a semiconductor substrate using MEMS (micro electro-mechanical system) technology.

[0027] The elastic member 60 is a member interposed between the substrate 40 and the mounting portion 15 when the substrate 40 is attached to the device housing 10. The elastic member 60 is made of butyl rubber and has a circular (annular) shape in a plan view, with a deformation margin s4 in the front-rear direction Y (thickness direction) so as to absorb the pressing force on the substrate 40 in the front-rear direction Y. The width dimension s2 of the elastic member 60 is set to be larger than the dimension in the front-rear direction Y, thereby forming a rectangular flat plate-like cross section as shown in FIG. 4(A). As shown in FIGS. 4(A) and 4(B), the elastic member 60 is arranged between the substrate 40 and the periphery of the opening on the back side Y2 (inside the device housing 10) of the sound propagation path 20. When the substrate 40 is attached to the mounting portion 15, the elastic member 60 is pressed toward the front side Y1 and deformed. At this time, the elastic member 60 closes the gap between the mounting portion 15 and the substrate 40. That is, the elastic member 60 is arranged to close the inside of the sound propagation path 20. In this manner, when the substrate 40 is placed so as to abut against the substrate placing portion 17, by setting the dimension s3 from the substrate placing portion 17 to the top of the convex portion 15a, it is possible to fix the substrate 40 so that the amount of compression of the elastic member 60 is constant. With this configuration, sound leakage from the sound propagation path 20 to the housing internal space 10c1 is prevented, and a decrease in sensor output caused by input attenuation to the sound sensor 50 due to the sound leakage and an output error of the sound sensor caused by sound diffraction due to the sound leakage are prevented.

[0028] The elastic member 60 is not limited to butyl rubber, and may be made of silicone packing, high-density urethane foam, or the like. In the present embodiment, the elastic member 60 is fixed to the device housing 10 while sandwiched between the mounting portion 15 and the substrate 40. However, the elastic member 60 may be fixed to the device housing 10 by, for example, applying an adhesive to one side of the elastic member 60, or by attaching an adhesive sheet or double-sided tape. The elastic member 60 may be made of a flat, annular packing as in the present embodiment, or may be made of a caulking material such as silicone. While the elastic member 60 has an annular (ring-shaped) shape in a plan view, the shape is not limited to an annular shape in a plan view, as long as the shape is based on the planar shape of the rear-side Y2 opening of the sound propagation path 20. In other words, as long as the shape of the cover abuts against the end of the rear side Y2 opening of the sound propagation path 20 around the entire circumference and abuts against the substrate 40, thereby sealing the rear side Y2 opening of the sound propagation path 20 around the entire circumference, the effect of preventing sound leakage from the sound propagation path 20 can be maintained.

[0029] Furthermore, the cross-sectional shape of the elastic member 60 may be formed in a circular shape instead of a flat plate shape as in this embodiment. When the cross-sectional shape of the elastic member 60 is formed in a flat plate shape, the contact area between the elastic member 60 and the substrate 40 can be increased, thereby increasing the reaction force when the substrate 40 is pressed against the front side Y1, 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 formed in a circular shape, the contact area between the elastic member 60 and the substrate 40 can be reduced, thereby reducing the reaction force when the substrate 40 is pressed against the front side Y1, and the risk of deformation of the substrate 40 can be reduced.

[0030] The cover 70 is a lid member that closes the opening 10c of the device housing 10. The cover 70 is a plate-like 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 space 10c1 of the housing is formed on the back side Y2 of the substrate 40 (the side opposite the sound propagation path 20). The cover 70 is not limited to a plate-like member, and may be, for example, a screw-type lid that can be screwed to the opening 10c, like the vent portion 30 described above. The cover 70 may also have a cylindrical portion that is inserted into the opening 10c and fitted with an engaging claw, and a flange portion that protrudes toward the back side Y2, and the flange portion can be sealed with the seal member 12.

[0031] The sound detection device 100 according to this embodiment is assembled in the following manner. First, as shown in FIG. 1, with the retaining ring 33 attached to the vent portion 30, the male screw 31a is fastened to 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 FIG. 6(A), the elastic member 60 is placed on the rear side Y2 of the device housing 10, and as shown in FIG. 1, the front side Y1 surface of the elastic member 60 is brought close to the rear side Y2 surface of the convex portion 15a of the mounting portion 15 until it abuts against that surface. At this time, the top of the convex portion 15a is brought into contact with the center of the width of the elastic member 60. Next, the substrate 40 is placed on the rear side Y2 of the device housing 10, and as shown in FIG. 1, the front side Y1 surface of the substrate 40 is brought close to the rear side Y2 surface of the elastic member 60 until it abuts against that surface. The substrate 40 is fixed to the device housing 10 by aligning the central axis of the screw hole 40c of the substrate 40 with the central axis of the fixing portion 16 and tightening the screw 16a into the fixing portion 16. At this time, as shown in FIG. 4(B), the front side Y1 surface of the substrate 40 abuts against the surface of the substrate mounting portion 17 and also abuts against the rear side Y2 surface of the elastic member 60, pressing the elastic member 60 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 manner, the elastic member 60 fills the gap between the mounting portion 15 and the substrate 40.

[0032] In this embodiment, when the substrate 40 is fixed to the device housing 10, the elastic member 60 is compressed to bring the front side Y1 of the substrate 40 into contact with the rear side Y2 of the substrate mounting portion 17. However, the front side Y1 of the substrate 40 does not have to be in contact with the rear side Y2 of the substrate mounting portion 17. That is, as long as the front side Y1 of the substrate 40 is in close contact with the elastic member 60, a gap may be formed between the substrate 40 and the substrate mounting portion 17. For this reason, the elastic member 60 does not necessarily have to be deformed. Even if the deformation allowance s4 of the elastic member 60 is 0, that is, even if the elastic member 60 is in contact with the mounting portion 15 and the substrate 40 without being compressed, a gap may be formed between the substrate 40 and the substrate mounting portion 17. Therefore, during design, it is sufficient to adjust the height of the convex portion 15a, the thickness of the elastic member 60, or the tightening amount of the screw 16a so that a gap does not occur between the elastic member 60 and the substrate 40. Then, after the substrate 40 is fixed to the device housing 10, the signal line 13b is connected to the connector portion 41 of the substrate 40, and then the opening 10c is closed with the cover 70. In this way, the sound detection device 100 is completed.

[0033] According to this embodiment, the sound detection device 100 is a sound detection device 100 comprising: 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 outside; a substrate 40 provided on the back side Y2 (the end on the internal side 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 a housing internal space 10c1, wherein the device housing 10 is provided with at least a pair of spaced-apart fixing portions 16 that fix the substrate 40, and the pitch L (separation distance) between one fixing portion 16 and the other fixing portion 16 is 11.0 times or less the plate thickness dimension t1 of the substrate 40.

[0034] According to the present invention, by setting the pitch L between the pair of fixing portions to 11.0 times or less the thickness dimension t1 of the substrate 40, the thickness of the substrate 40 is made thicker relative to the pitch L of the fixing portions 16, thereby improving the rigidity of the substrate 40. Therefore, deformation of the substrate 40 can be suppressed compared to a conventional configuration in which the substrate 40 is subjected to a pressing force from an O-ring when a shield plate is omitted. Furthermore, by making the thickness of the substrate 40 thicker relative to the pitch L of the fixing portions 16, deformation of the substrate 40 due to differences in the linear expansion coefficients of the substrate 40 and the device housing 10 when the ambient temperature changes can be suppressed. Therefore, by having a substrate 40 structure that is less likely to deform due to pressing forces and temperature changes, it is possible to obtain a sound detection device 100 that can suppress deterioration in the sound pressure detection accuracy and the output accuracy from the sound sensor 50.

[0035] Furthermore, in this embodiment, the substrate 40 is attached to the device housing 10 via an annular elastic member 60 that abuts against the substrate 40 in the front-rear direction Y. Therefore, the substrate 40 can be attached to the device housing 10 via the annular elastic member 60 that abuts against the substrate 40 in the plate thickness direction, which prevents gaps from occurring at the attachment portion due to close contact between the substrate 40 and the device housing 10, suppresses sound leakage from the attachment portion within the sound propagation path 20, and suppresses a decrease in sensor output. Furthermore, the pressing force applied when attaching the substrate 40 to the device housing 10 can be absorbed by the elastic member 60, so that the pressing force applied to the substrate 40 can be reduced and deformation of the substrate 40 can be suppressed compared to a configuration that does not use the elastic member 60.

[0036] Furthermore, by making the protrusion 15a, which has a width dimension s1 smaller than the width dimension s2 of the elastic member 60, contact the middle portion of the elastic member 60 in the width direction, it is possible to reduce the contact area between the device housing 10 and the elastic member 60 compared to a configuration in which the protrusion 15a is not provided. This makes it possible to reduce the range in which a reaction force is generated when the elastic member 60 is pressed by the device housing 10, thereby reducing the effect of the reaction force on the board 40 and preventing deformation of the board 40.

[0037] Furthermore, because the dimension s3 from the substrate placement portion 17 to the top of the protrusion 15a is set to be equal to or less than the thickness t2 of the elastic member 60, the compression amount of the elastic member 60 pressed against the protrusion 15a is determined by the dimension s3 (component dimension) from the substrate placement portion 17 to the top of the protrusion 15a, ensuring a constant compression amount regardless of the mounting state. At this time, a recess 15b is formed adjacent to the protrusion 15a, allowing a portion of the pressed elastic member 60 to escape into the recess 15b. This reduces the impact on the substrate 40 of the reaction force when the elastic member 60 is pressed by the device housing 10. This reduces deformation of the substrate 40 due to the reaction force when the elastic member 60 is pressed by the device housing 10.

[0038] Furthermore, by providing the fixing portions 16 near the radially outer side of the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10, 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. This allows the thickness dimension t1 of the substrate 40 to be relatively large with respect to the pitch L, thereby improving the rigidity of the substrate 40. Furthermore, the thickness of the substrate 40 that satisfies the relationship between the pitch L and the thickness dimension t1 of the substrate 40 can be made thinner compared to a configuration in which the pitch L is large, and this prevents the sound detection device 100 from becoming larger.

[0039] Furthermore, a minute ventilation hole 40b that connects the sound propagation path 20 to the housing internal space 10c1 is provided in the substrate 40 that closes the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10, so that the air pressure in the sound propagation path 20 and the air pressure in the housing internal space 10c1 become equal, preventing condensation from occurring in the housing internal space 10c1.

[0040] Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and design changes and the like that do not deviate from the gist of the present invention are also included in the present invention. In this embodiment, a pair of connecting plates 14a are formed at the end of the rear side Y2 of the cylindrical wall portion 14, i.e., at both ends of the mounting portion 15 in the left-right direction X, and each connecting plate portion 14a is formed with a fixing portion 16 that is an internal thread for fixing the circuit board 40 to the device housing 10. However, the type and arrangement of the fixing portions are not limited to this. For example, the end surface of the rear side Y2 of the cylindrical wall portion 14 and the surface of the front side Y1 of the circuit board 40 may be bonded with an adhesive, and this adhesive portion may serve as the fixing portion.

[0041] Alternatively, the surface on the front side Y1 of the elastic member 60 may be bonded to the end of the back side Y2 of the cylindrical wall portion 14, and the surface on the back side Y2 of the elastic member 60 may be bonded to the surface on the front side Y1 of the substrate 40 with an adhesive, with this bonded portion serving as the fixing portion. In this case, the inner diameter dimension of the elastic member 60 is the separation dimension L (pitch L in this embodiment), but as described above, the outer dimension of the mounting portion 15 is set larger than the outer diameter dimension of the elastic member 60 so that the elastic member 60 does not ride up. Therefore, the inner diameter dimension of the elastic member 60, i.e., the separation dimension L, can be made smaller than when the 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 portions 16 in this embodiment is L=19 mm, the ratio L / t is 11.8 at t=1.6 mm and 5.9 at t=3.2 mm, whereas if the inner diameter of the elastic member 60 is the separation dimension L, if L=12 mm, the ratio L / t can be 7.5 at t=1.6 mm and 3.7 at t=3.2 mm. This allows the thickness dimension t1 of the substrate 40 to be even larger relative to the separation dimension L. [Explanation of symbols]

[0042] t1 Plate thickness L Pitch (separation distance) 100 Sound detection device 10. Device housing 16 Fixed part 17 Substrate placement section 20 Sound propagation path 30 Vent section 40 boards 50 Sound Sensor 60 Elastic member 70 Cover

Claims

1. A sound detection device comprising: a device housing; a sound propagation path that communicates between the inside and outside of the device housing and propagates sound from outside; a substrate that is provided on the inside side of the sound propagation path of the device housing; and a sound sensor that is provided inside the device housing and detects external sound, a substrate placement portion on which the substrate is placed with the thickness direction of the substrate as a placement direction is provided at an end portion of the sound propagation path on the inside side of the device housing; a mounting portion recessed in the substrate placement direction is formed in the substrate placement portion, an elastic member that abuts against the substrate in the thickness direction is provided in the mounting portion; the substrate is placed on the substrate placement portion via the elastic member, the device housing is provided with at least a pair of spaced-apart fixing portions that fix the substrate, and the distance between one of the fixing portions and the other of the fixing portions is 11.0 times or less the thickness dimension of the substrate.

2. The elastic member is formed in a ring shape having a predetermined width, the mounting portion is provided with a convex portion that protrudes toward the substrate placement portion in the placement direction within a range not exceeding the substrate placement portion, 2. The sound detection device according to claim 1, wherein the protrusion has a width smaller than a width of the elastic member and abuts on the surface of the elastic member on one side in the installation direction over the entire periphery.

3. the elastic member has a deformation margin that allows deformation in the mounting direction, 3. The noise detection device according to claim 2, wherein the dimension in the placement direction from the top of the convex portion to the bottom of the attachment portion is equal to or greater than the deformation allowance.

4. 4. The noise detection device according to claim 2, wherein a dimension in the placement direction from the substrate placement portion to the top of the convex portion is set to be equal to or less than a dimension in the placement direction of the elastic member installed in the mounting portion.

5. the sound propagation path is provided inside a cylindrical wall portion that communicates with the inside and outside of the device housing, the substrate placement portion is configured by a flat end surface of the cylindrical wall portion on the inside side of the device housing, the fixing portion is provided near the outside of an end portion of the sound propagation path on the inside side of the device housing, 4. The noise detection device according to claim 1, wherein the end surface and the fixing portion are located on the same plane.

6. the sound propagation path is provided inside a cylindrical wall portion that communicates with the inside and outside of the device housing, the substrate placement portion is configured by a flat end surface of the cylindrical wall portion on the inside side of the device housing, the fixing portion is provided near the outside of an end portion of the sound propagation path on the inside side of the device housing, The sound detection device according to claim 4 , wherein the end surface and the fixing portion are located on the same plane.

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