Vibration detection device, vital sensor, and pipe inspection device

Abstract

To provide vibration detection devices of various configurations capable of suppressing a decrease in sensitivity due to an increase in a gap around a vibrating part.SOLUTION: A vibration detection device includes a vibration part 10, a support part 12 for vibratably supporting the vibration part 10, and structures 30 and 40 provided on at least one of the vibration part 10 and the support part 12. The structure 30 provided on the vibration part 10 is provided from at least a part of a peripheral edge including a vibratable free end 11a of the vibration part 10 in a direction opposite to a direction J in which the vibration part 10 warps, whereas the structure 40 provided on the support part 12 is provided from at least a part of a peripheral edge including an opposing end 20 of the support part 12 facing the free end 11a of the vibration part 10 in the direction J in which the vibration part 10 warps.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vibration detection device, a vital sensor, and a piping inspection device. [Background technology]

[0002] 2. Description of the Related Art As a vibration detection device for detecting vibration, a piezoelectric vibration detection device that detects displacement due to external vibration by utilizing the piezoelectric effect is known.

[0003] For example, Patent Document 1 (JP 2014-515214 A) proposes a piezoelectric transducer that includes a substrate and a plurality of adjacent tapered cantilever beams, each of which defines a beam base end, a beam tip end, and a beam main body portion disposed between the beam base end and the beam tip end, in order to suppress a decrease in low-frequency sensitivity due to an increase in the gap around the cantilever beam, which is the vibrating part, and is disposed so that each beam tip end extends toward a common imaginary point, and each beam is coupled to the substrate along the beam base end but not along the beam main body portion.

[0004] However, Patent Document 1 does not propose any suppression of sensitivity reduction in configurations other than the specific configuration described above, i.e., a configuration in which the tip ends of each of multiple cantilever beams (vibration parts) are arranged to extend toward a common imaginary point. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to make it possible to suppress a decrease in sensitivity that occurs with an increase in the gap around the vibrating part in vibration detection devices of various configurations. [Means for solving the problem]

[0006] The vibration detection device of the present invention comprises a vibration unit, a support unit that supports the vibration unit so that it can vibrate, and a structure provided on at least one of the vibration unit and the support unit, wherein the structure provided on the vibration unit is provided in a direction opposite to the direction in which warping of the vibration unit occurs from at least a portion of the peripheral portion including the vibrating free end of the vibration unit, and the structure provided on the support unit is provided in a direction in which warping of the vibration unit occurs from at least a portion of the peripheral portion including the opposing end of the support unit that faces the free end. [Effects of the Invention]

[0007] It is possible to provide a vibration detection device with improved sensitivity. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view of a vibration detection device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along the line A1-A1 in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along the line B1-B1 in FIG. [Figure 4] 2 is a cross-sectional view taken along the line A1-A1 in FIG. 1, illustrating the effects of the first embodiment of the present invention. FIG. [Figure 5] 2 is a cross-sectional view taken along the line B1-B1 in FIG. 1, illustrating the effects of the first embodiment of the present invention. FIG. [Figure 6] FIG. 4 is a cross-sectional view showing the configuration of a vibration detection device according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration of a vibration detection device according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view showing a state in which upward warping occurs in the third embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view showing a state in which downward warping occurs in the third embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing the configuration of a vibration detection device according to a fourth embodiment of the present invention. [Figure 11] FIG. 10 is a cross-sectional view showing the configuration of a vibration detection device according to a fifth embodiment of the present invention. [Figure 12] FIG. 10 is a plan view showing the configuration of a vibration detection device according to a sixth embodiment of the present invention. [Figure 13] 13 is a cross-sectional view taken along the line A2-A2 in FIG. 12. [Figure 14] 13 is a cross-sectional view taken along the line B2-B2 in FIG. 12. [Figure 15] FIG. 13 is a plan view showing the configuration of a vibration detection device according to a seventh embodiment of the present invention. [Figure 16] 16 is a cross-sectional view taken along the line A3-A3 in FIG. 15. [Figure 17] 16 is a cross-sectional view taken along the line B3-B3 in FIG. 15. [Figure 18] 16 is a cross-sectional view taken along the line A3-A3 in FIG. 15, illustrating the effects of the seventh embodiment of the present invention. FIG. [Figure 19] 16 is a cross-sectional view taken along the line B3-B3 in FIG. 15, illustrating the effects of the seventh embodiment of the present invention. FIG. [Figure 20] FIG. 12 is a cross-sectional view showing a configuration in which a modification similar to that in the second embodiment of the present invention is added in a seventh embodiment of the present invention. [Figure 21] FIG. 12 is a cross-sectional view showing a configuration in which a modification similar to that in the third embodiment of the present invention is added in a seventh embodiment of the present invention. [Figure 22] FIG. 11 is a cross-sectional view showing a configuration in which the same changes as in the fourth embodiment of the present invention are added in the seventh embodiment of the present invention. [Figure 23] FIG. 11 is a cross-sectional view showing a configuration in which a modification similar to that in the fifth embodiment of the present invention is added in a seventh embodiment of the present invention. [Figure 24] FIG. 13 is a plan view showing a configuration in which the same changes as in the sixth embodiment of the present invention are added in the seventh embodiment of the present invention. [Figure 25] FIG. 13 is a plan view showing the configuration of a vibration detection device according to an eighth embodiment of the present invention. [Figure 26] 26 is a cross-sectional view taken along the line A4-A4 in FIG. 25. [Figure 27]26 is a cross-sectional view taken along the line A4-A4 in FIG. 25, illustrating the effects of the eighth embodiment of the present invention. FIG. [Figure 28] 10A and 10B are diagrams illustrating modified examples of the arrangement of structures provided on the vibrating section. [Figure 29] 10A and 10B are diagrams illustrating another modified example of the arrangement of structures provided in the vibrating section. [Figure 30] 10A and 10B are diagrams illustrating modified examples of the arrangement of structures provided on the support portion. [Figure 31] 10A and 10B are diagrams showing another modified example of the arrangement of structures provided on the support portion. [Figure 32] FIG. 10 is a diagram illustrating the deflection angle of a cantilever beam. [Figure 33] FIG. 10 is a diagram illustrating an example of a model of a vibration unit. [Figure 34] FIG. 10 is a diagram illustrating another example of a model of a vibration unit. [Figure 35] FIG. 10 is a diagram showing a model in which the sensitivity of a vibration section is improved. [Figure 36] FIG. 10 is a diagram showing a model of a vibration part used in a simulation. [Figure 37] FIG. 37 is a diagram showing the results of a simulation of the amount of deflection when the same sound pressure is applied to each model in FIG. 36. [Figure 38] FIG. 10 is a diagram illustrating a model used for simulating a resonance frequency. [Figure 39] FIG. 39 is a diagram showing the simulation results of sensitivity when the same sound pressure is applied to each model in FIG. 38. [Figure 40] 10 is a diagram showing a comparison of the center of gravity positions of a rectangular vibrating part model and a vibrating part model whose width increases from the fixed end toward the tip end. FIG. [Figure 41] FIG. 10 is a diagram illustrating a model used for simulating a resonance frequency. [Figure 42] FIG. 10 is a diagram showing a simulation result of a resonance frequency. [Figure 43] FIG. 10 is a plan view showing a first modified example of a vibrating section. [Figure 44] FIG. 10 is a plan view showing a second modified example of the vibrating section. [Figure 45] It is a cross-sectional view showing a third modification of the vibrating portion. [Figure 46] It is a diagram showing a modification example of the arrangement of the strain detection unit. [Figure 47] It is a diagram showing an example in which the vibration detection device according to the present invention is applied to a vital sensor. [Figure 48] It is a diagram showing an example in which the vibration detection device according to the present invention is applied to a pipe inspection device. [Figure 49] It is a reference diagram for explaining the problem of sensitivity reduction due to an increase in the gap around the vibrating portion.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the description of the drawings, the same reference numerals are given to the same elements, and duplicate descriptions are omitted.

[0010] <Types of MEMS Microphones> First, the types of MEMS microphones, which are an example of the vibration detection device, will be described.

[0011] A MEMS microphone is a device that receives external vibrations such as sound waves by a vibrating portion and converts the displacement of the vibrating portion due to the external vibration into an electrical signal. For example, MEMS microphones for measuring audible voice are mainly used in audio equipment, household appliances, smartphones, etc. In recent years, as new applications of MEMS microphones, in addition to vital sensors that acquire vital data such as heartbeat and respiration, use in pipe inspection devices that detect pipe abnormalities has been proposed, and the demand for MEMS microphones has been increasing.

[0012] Such MEMS microphones are mainly classified into a capacitive type and a piezoelectric type from the viewpoint of the detection principle.

[0013] Capacitive MEMS microphones detect the displacement of a movable electrode by detecting the electromotive force generated by the change in capacitance between parallel plate electrodes (a movable electrode and a fixed electrode) subjected to external vibrations, and convert the external vibrations into an electrical signal. This is the most widely used type of microphone, due to its high sensitivity and low noise floor, resulting in a high signal-to-noise ratio (S / N ratio), and excellent frequency characteristics. Reducing the inter-electrode distance is advantageous for increasing device sensitivity, and in recent years, the inter-electrode distance has been reduced to approximately 1 μm. However, applications such as vital signs sensors require high sensitivity in the low-frequency band below 100 Hz. However, when attempting to achieve high sensitivity in low-frequency bands by reducing the inter-electrode distance and increasing the displacement of the vibrating part, the vibrating part comes into contact with the opposing electrode, which prevents the design of a low resonant frequency (i.e., the sensitivity at low frequencies cannot be improved). Furthermore, capacitive MEMS microphones require an input power source to charge the parallel plate electrodes by applying a constant electric field between them during detection, and the applied electric field generates an attractive force between the parallel plate electrodes, resulting in a narrow dynamic range. Furthermore, issues have been pointed out regarding capacitive MEMS microphones, such as the fact that the air resistance experienced by the movable electrode significantly affects their characteristics.

[0014] On the other hand, piezoelectric MEMS microphones detect external vibrations by converting displacements caused by external vibrations into electrical signals through the piezoelectric effect. Piezoelectric MEMS microphones can detect vibrations with a simple structure, which simplifies the device fabrication process and makes them suitable for miniaturization. Furthermore, piezoelectric MEMS microphones do not require an input power source, which simplifies the passive circuitry. Furthermore, piezoelectric MEMS microphones have a wider dynamic range than capacitive MEMS microphones. However, it has been pointed out that piezoelectric MEMS microphones have relatively poorer characteristics, such as sensitivity, noise characteristics, and S / N ratio, compared to capacitive MEMS microphones. To improve the S / N ratio, it is necessary to improve both sensitivity and noise characteristics. Therefore, MEMS microphones have been proposed that reduce noise caused by residual stress in the piezoelectric film by using a cantilever structure for the piezoelectric film.

[0015] <Issue of decreased sensitivity due to increased gap around the vibrating part> However, in piezoelectric MEMS microphones, if the vibrating part that receives external vibrations warps (curves) due to residual stress, the gap between the tip of the vibrating part and the part facing that tip increases, resulting in a decrease in low-frequency sensitivity.

[0016] For example, as shown in Figure 49, when warping occurs in the vibrating section 10 and the vibrating section 10 is curved as shown by the two-dot chain line in the figure, the tip 11a of the vibrating section 10 is farther away from the opposing end 20 of the support section 12 than in the state without warping (flat state) shown by the solid line in the figure, and the size of the gap between the tip 11a and the opposing end 20 increases from G to G'. When the gap increases in this way, the effect of air leakage increases and the low-frequency sensitivity decreases.

[0017] To address the issue of reduced sensitivity due to an increase in the gap around the vibrating part, Patent Document 1 above proposes a technology for suppressing the reduction in sensitivity by arranging the tips of multiple cantilever beams (vibrating parts) so that they extend toward a common imaginary point. However, while Patent Document 1 proposes suppression of sensitivity reduction in a specific configuration, it does not propose measures to suppress sensitivity reduction in other configurations.

[0018] Therefore, in the present invention, in vibration detection devices of various configurations, a vibration detection device as follows is proposed so that a decrease in sensitivity due to an increase in the gap around the vibrating part can be suppressed. Hereinafter, an embodiment of the vibration detection device according to the present invention will be described.

[0019] <Configuration of the first embodiment of the present invention> Fig. 1 is a plan view of a vibration detection device 1 according to a first embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line A1-A1 in Fig. 1, and Fig. 3 is a cross-sectional view taken along line B1-B1 in Fig. 1.

[0020] 1 to 3, the X direction, Y direction, and Z direction are defined for convenience as directions of three-dimensional coordinate axes of the vibration detection device 1 according to the first embodiment of the present invention. Specifically, the X direction indicates the horizontal direction when the vibration detection device 1 is viewed from above as in FIG. 1. The Y direction indicates the vertical direction perpendicular to the X direction (horizontal direction) when the vibration detection device 1 is viewed from above. The Z direction indicates the depth direction perpendicular to each of the X direction and Y direction when the vibration detection device 1 is viewed from above (for example, the vertically upward direction when the vibration detection device 1 is placed on a plane). Note that the X direction, Y direction, and Z direction in the other drawings also indicate the same directions as those in FIGS. 1 to 3, respectively.

[0021] As shown in FIG. 1, a vibration detection device 1 according to a first embodiment of the present invention includes a vibrating section 10, a supporting section 12, and structures 30 and 40 provided on the vibrating section 10 and the supporting section 12, respectively.

[0022] The vibrating section 10 is a section that vibrates in response to external vibrations such as sound waves. In this case, the vibrating section 10 is made up of a rectangular sheet-like member such as a square. On the other hand, the support section 12 is a section that supports the vibrating section 10 so that it can vibrate. In this case, the support section 12 is made up of a frame-like member such as a square with a certain width that surrounds the entire periphery of the vibrating section 10.

[0023] The vibrating section 10 has four linear sides 11a to 11d that form an outline when viewed from above. Of these sides 11a to 11d, the vibrating section 10 is connected to and supported by the support section 12 at one side 11c. That is, the side 11c that is connected to the support section 12 constitutes a fixed end that is fixed so as not to vibrate relative to the support section 12. In contrast, the three sides 11a, 11b, and 11d of the vibrating section 10 other than the fixed end (side 11c) are arranged close to the support section 12 with gaps between them, and constitute free ends that can vibrate. When the vibrating section 10 is subjected to external vibrations, the vibrating section 10 vibrates in the vertical direction in FIGS. 2 and 3, with the fixed end (side 11c) as the base point.

[0024] As shown in FIGS. 2 and 3, the vibrating section 10 according to the first embodiment of the present invention is configured with a layer structure including a strain detection section 14 and a vibrating section substrate 16.

[0025] The strain detection unit 14 has a piezoelectric film formed from a piezoelectric material. The material of the piezoelectric film is selected from materials that can be made into thin films, such as PZT (lead zirconate titanate), KNN (potassium sodium niobate), and AlN (aluminum nitride). The piezoelectric film is sandwiched between a lower electrode and an upper electrode. When strain is generated in the piezoelectric film due to external vibration, a potential difference is generated between the upper and lower electrodes. By detecting this potential difference, the strain generated by the vibration can be detected.

[0026] The vibration unit substrate 16 is a substrate made of silicon or the like. Silicon substrates have high crystallinity and vibrate flexibly without breaking. The thickness of the vibration unit substrate 16 may be any thickness that allows the vibration unit 10 to vibrate appropriately, and is, for example, on the order of several microns to several tens of microns. The vibration unit substrate 16 is formed by a semiconductor process for MEMS (Micro Electro Mechanical Systems) or the like.

[0027] The support 12 is formed of silicon or the like, similar to the vibration substrate 16. The support 12 may also be composed of multiple layers, such as an active silicon layer and a silicon oxide layer. Of the multiple layers of the support 12, any one of them may be the same silicon layer as the vibration substrate 16. The thickness of the support 12 is preferably approximately 200 to 600 microns, which allows for easy handling as a wafer in semiconductor processing. The support 12 has the mechanical strength required for the external shape of the vibration detection device 1, and is suitable for the bonding step in the semiconductor process. The back surface of the support 12 is fixed to a semiconductor package with an adhesive, and electrical connection is established by wire bonding between electrode pads on the vibration detection device 1 and electrode pads on the semiconductor package. This allows electrical signals to be extracted from the semiconductor package.

[0028] 2 and 3, one layer 25 of the multiple layers constituting the support portion 12 is formed from the same layer as the vibration portion substrate 16. Therefore, the support portion 12 has one layer 25 formed from the same layer as the vibration portion substrate 16, and a multiple-layer portion 26 made up of an active silicon layer, a silicon oxide layer, etc., provided below the one layer 25 in the Z direction.

[0029] As shown in Fig. 1, the structure 30 provided on the vibration section 10 is disposed continuously along one side 11a of the free ends (sides 11a, 11b, 11d) of the vibration section 10, which is the farthest from the fixed end (side 11c). Hereinafter, for convenience, the side 11a farthest from the fixed end (side 11c) will be referred to as the "tip". As shown in Fig. 2, the structure 30 is provided so as to protrude downward in the Z direction in Fig. 2 from the tip 11a of the vibration section 10.

[0030] On the other hand, the structure 40 provided on the support part 12 is continuously arranged at locations facing the three sides 11a, 11b, and 11d that constitute the free end of the vibration part 10. In other words, the structure 40 is continuously arranged along the opposing ends 20 of the support part 12 that face each of the sides 11a, 11b, and 11d other than the fixed end (side 11c) of the vibration part 10. Also, as shown in Figures 2 and 3, the structure 40 is arranged so as to overlap the support part 12 upward in the Z direction.

[0031] <Effects of the first embodiment of the present invention> Next, the effects of the first embodiment of the present invention will be described with reference to FIGS.

[0032] First, as shown in Figure 4, when warping (curving) occurs in the vibrating part 10 in the direction of arrow J in the cross section of line A1-A1 in Figure 1, the tip 11a of the vibrating part 10 is displaced upward in the Z direction, and the size of the gap between the tip 11a of the vibrating part 10 and the opposing end 20 of the support part 12 facing the tip 11a increases from G1 to G2.

[0033] Furthermore, in the cross section of line A1-A1 in Figure 1 shown in Figure 5, when the vibrating part 10 is displaced upward in the Z direction due to warping, the size of the gap between the free end (sides 11b, 11d) other than the tip 11a of the vibrating part 10 and the opposing end 20 of the support part 12 opposite thereto increases from G3 to G4.

[0034] Incidentally, if warping occurs in the vibrating section 10, the free ends (sides 11a, 11b, and 11d) of the vibrating section 10 are displaced in the Z direction, and therefore, when viewed from the side as in FIGS. 4 and 5, the free ends (sides 11a, 11b, and 11d) of the vibrating section 10 may no longer strictly face the support section 12. However, the opposing end 20 of the support section 12 facing the free ends (sides 11a, 11b, and 11d) of the vibrating section 10 here means a portion that faces the free ends (sides 11a, 11b, and 11d) of the vibrating section 10 when viewed in plan as in FIG. 1, even if warping occurs in the vibrating section 10. In addition, the size of the gap between the free ends (sides 11a, 11b, and 11d) of the vibrating section 10 and the opposing end 20 of the support section 12 means the shortest distance between the free ends (sides 11a, 11b, and 11d) and the opposing end 20. The same applies to the "opposing end 20" and "size of the gap" in the following description.

[0035] As described above, in the first embodiment of the present invention, when warping occurs in the vibrating section 10, the size of the gap between the free end (sides 11a, 11b, 11d) of the vibrating section 10 and the opposing end 20 of the supporting section 12 that faces it increases. However, in the first embodiment of the present invention, structures 30 and 40 are provided on the vibrating section 10 and the supporting section 12, respectively, so that the substantial increase in the gap is suppressed.

[0036] 4, in the first embodiment of the present invention, when the tip 11a of the vibrating section 10 is displaced upward in the Z direction due to warping, the structure 30 provided on the tip 11a of the vibrating section 10 approaches the structure 40 provided on the support section 12. In other words, the structure 30 provided on the vibrating section 10 is provided in the opposite direction (downward in the Z direction) from the tip 11a of the vibrating section 10 to the direction J in which warping of the vibrating section 10 occurs, so that the structure 30 approaches the structure 40 on the support section 12 when warping occurs in the vibrating section 10. For this reason, when warping occurs in the vibrating section 10, the size of the gap along the tip 11a of the vibrating section 10 decreases from the size of the gap G2 when the structures 30, 40 are not present to the size of the gap S1 between the structures 30, 40 when the structures 30, 40 are present (S1 <G2)。

[0037] Further, as shown in FIG. 5, at the free ends (sides 11b, 11d) other than the tip 11a of the vibrating portion 10, when the free ends (sides 11b, 11d) of the vibrating portion 10 are displaced upward in the Z direction due to warping, the free ends (sides 11b, 11d) of the vibrating portion 10 approach the structure 40 provided on the support portion 12. Therefore, the size of the gap along the free ends (sides 11b, 11d) decreases from the size G4 of the gap when there is no structure 40 to the size S2 of the gap between the free ends (sides 11b, 11d) and the structure 40 when there is the structure 40 (S2 < G4). That is, the structure 40 on the support portion 12 is provided from the opposing end 20 of the support portion 12 in the direction J (upward in the Z direction) in which the vibrating portion 10 warps so as to approach the free ends (sides 11b, 11d) of the vibrating portion 10 that are displaced upward when warping occurs in the vibrating portion 10.

[0038] As described above, in the first embodiment of the present invention, since the structures 30 and 40 for suppressing an increase in the gap are provided on the vibrating portion 10 and the support portion 12 respectively, even when warping occurs in the vibrating portion 10, the gap around the free ends (sides 11a, 11b, 11d) including the tip of the vibrating portion 10 can be substantially reduced. As a result, it becomes possible to suppress a decrease in sensitivity accompanying an increase in the gap.

[0039] In FIG. 4, the case where the structure 30 provided on the vibrating portion 10 approaches the structure 40 on the support portion 12 when warping occurs in the vibrating portion 10 has been described as an example. However, the structure 30 provided on the vibrating portion 10 may approach the opposing end 20 of the support portion 12 instead of the structure 40 on the support portion 12. Even in that case, since the gap is substantially reduced, it is possible to suppress a decrease in sensitivity accompanying an increase in the gap.

[0040] [Other Embodiments] Next, other embodiments of the present invention will be described. In the following description, mainly the parts different from the first embodiment of the present invention will be described, and the same parts will be omitted as appropriate.

[0041] [[ID>=19]]<Configuration of the Second Embodiment of the Present Invention>

[0042] FIG. 6 is a cross-sectional view showing the configuration of a vibration detection device 1 according to a second embodiment of the present invention.

[0043] In the second embodiment of the present invention shown in Fig. 6, the direction of warping that occurs in the vibrating section 10 differs from that in the first embodiment of the present invention. In this case, warping occurs downward in the Z direction (direction of arrow J), opposite to the first embodiment of the present invention. For this reason, the structure 30 provided on the vibrating section 10 is also provided so as to protrude upward in the Z direction from the tip 11a of the vibrating section 10. That is, in the second embodiment of the present invention, since warping occurs downward in the Z direction, the structure 30 provided on the vibrating section 10 is provided so as to protrude upward in the opposite direction to the direction in which warping occurs.

[0044] As a result, also in the second embodiment of the present invention, as shown by the solid line in Fig. 6, when warping occurs in the vibrating section 10, the structure 30 provided on the vibrating section 10 approaches the opposing end 20 of the support section 12, thereby suppressing an increase in the gap around the tip 11a of the vibrating section 10. Note that when the vibrating section 10 warps downward in the Z direction, the structure 40 does not need to be provided on the support section 12, and therefore the structure 40 is not provided on the support section 12. This allows for a reduction in manufacturing costs.

[0045] <Configuration of the third embodiment of the present invention>

[0046] FIG. 7 is a cross-sectional view showing the configuration of a vibration detection device 1 according to a third embodiment of the present invention.

[0047] As described above, in the first and second embodiments of the present invention, examples have been described in which the warping of the vibrating section 10 occurs upward in the Z direction or downward in the Z direction, but if the direction of the warping of the vibrating section 10 cannot be predicted, the structure 30 may be provided so as to protrude both upward and downward in the Z direction from the tip 11a of the vibrating section 10, as shown in Fig. 7. In other words, the structure 30 may be provided in both directions (up and down) in which the vibrating section 10 vibrates.

[0048] In this case, when warping of the vibrating part 10 occurs upward in the Z direction as shown in Fig. 8, the downwardly protruding structure 30 approaches the opposing end 20 of the support part 12 or the structure 40 on the support part 12, thereby suppressing an increase in the gap around the tip 11a of the vibrating part 10. Conversely, when warping of the vibrating part 10 occurs downward in the Z direction as shown in Fig. 9, the upwardly protruding structure 30 approaches the opposing end 20 of the support part 12, thereby suppressing an increase in the gap around the tip 11a of the vibrating part 10.

[0049] In this way, when the direction of warping cannot be predicted, by arranging the structure 30 in both directions, the structure 30 is ultimately arranged in the direction opposite to the direction J in which warping of the vibrating part 10 occurs, so that, as in the above embodiments, an increase in the gap around the tip 11a of the vibrating part 10 can be suppressed.

[0050] <Configuration of the fourth embodiment of the present invention>

[0051] FIG. 10 is a cross-sectional view showing the configuration of a vibration detection device according to a fourth embodiment of the present invention.

[0052] As shown in Figure 10, in the fourth embodiment of the present invention, the structure 30 provided on the vibrating part 10 is provided so as to gradually protrude from the tip 11a of the vibrating part 10 toward the support part 12 in the opposite direction (downward in the Z direction) to the direction J in which warping occurs.

[0053] In this way, by providing the structure 30 so that it gradually protrudes toward the support portion 12, when warping occurs in the vibrating portion 10, the structure 30 provided on the vibrating portion 10 comes even closer to the opposing end 20 of the support portion 12 or the structure 40 on the support portion 12. This further reduces the gap around the tip 11a of the vibrating portion 10, making it possible to more effectively suppress a decrease in sensitivity that would otherwise accompany an increase in the gap. Furthermore, in this case, it is also possible to improve sensitivity by reducing the gap. Note that the structure 30 is not limited to protruding gradually toward the support portion 12, and may also protrude in a stepped manner.

[0054] Generally, methods for manufacturing the vibration part 10 include photolithography and dry etching, which are used in semiconductor manufacturing. However, when these manufacturing methods are used, the processing limit (minimum dimension) of the gap between the vibration part 10 and the support part 12 is several micrometers. If a special processing method is used, it is possible to further reduce the gap size, but this increases manufacturing costs. In contrast, in the fourth embodiment of the present invention, the size of the gap can be easily reduced below the processing limit simply by providing the vibration part 10 with a structure 30 that protrudes toward the support part 12. Therefore, according to the fourth embodiment of the present invention, it is possible to improve sensitivity at low cost.

[0055] 10, the fourth embodiment of the present invention has been described taking as an example a configuration in which the structure 30 protrudes downward in the Z direction from the tip 11a of the vibrating section 10, but the configuration according to the fourth embodiment of the present invention can also be applied to a configuration in which the structure 30 protrudes upward in the Z direction from the tip 11a of the vibrating section 10. In this case, too, by providing the structure 30 so that it protrudes toward the support section 12 in the direction opposite to the direction J in which the vibrating section 10 warps (upward in the Z direction), the gap around the tip 11a of the vibrating section 10 when warping occurs can be further reduced.

[0056] <Configuration of the fifth embodiment of the present invention> FIG. 11 is a cross-sectional view showing the configuration of a vibration detection device according to a fifth embodiment of the present invention.

[0057] As shown in Figure 11, in the fifth embodiment of the present invention, a structure 40 provided on the support part 12 is provided so as to gradually protrude from the opposing end 20 of the support part 12 toward the vibration part 10 in the direction J (upward in the Z direction) in which warping of the vibration part 10 occurs.

[0058] 11, if warping occurs in the vibrating section 10, the structure 30 provided on the vibrating section 10 approaches the structure 40 on the support section 12, thereby further reducing the gap at the tip 11a of the vibrating section 10. Therefore, according to the configuration of the fifth embodiment of the present invention, it is possible to suppress a decrease in sensitivity simply and at low cost, and also to improve sensitivity. Note that the structure 40 is not limited to protruding gradually toward the vibrating section 10, and may protrude in a stepped manner.

[0059] <Configuration of the sixth embodiment of the present invention> Fig. 12 is a plan view showing the configuration of a vibration detection device according to a sixth embodiment of the present invention, Fig. 13 is a cross-sectional view taken along line A2-A2 in Fig. 12, and Fig. 14 is a cross-sectional view taken along line B2-B2 in Fig. 12.

[0060] As shown in FIG. 12, in the sixth embodiment of the present invention, the structure 30 provided on the vibration part 10 is provided around the tip 11a of the vibration part 10 and around the two corners 13a, 13b located at both ends of the tip 11a.

[0061] As shown in FIG. 12, in a cantilevered vibration unit 10 supported at one side 11c (fixed end), the amount of deflection is likely to be large at the tip 11a, which is the first side farthest from the fixed end (side 11c), and at the corners 13a and 13b located at both ends of the tip 11a. Therefore, gaps due to warping tend to be large around the tip 11a and the corners 13a and 13b. For this reason, in the sixth embodiment of the present invention, structures 30 are provided continuously around the tip 11a and each of the corners 13a and 13b of the vibration unit 10, where gaps are likely to be large. This makes it possible to effectively suppress a decrease in sensitivity due to an increase in the gap.

[0062] In addition, since the amount of deflection at the free ends (sides 11b, 11d) other than the tip 11a of the vibrating part 10 is less likely to increase compared to the tip 11a, and since the provision of the structure 30 makes it more difficult for the vibrating part 10 to vibrate, the structure 30 is not provided in any part other than the tip 11a and the periphery of the corners 13a, 13b. Also, for the same reason, in each of the above embodiments, it is preferable that the structure 30 is not provided at the free ends (sides 11b, 11d) of the vibrating part 10 other than the tip 11a.

[0063] 12 to 14, in the sixth embodiment of the present invention, the structure 40 is not provided on the support portion 12. In this way, the structure 40 may not be provided on the support portion 12, and the structure 30 may be provided only on the vibration portion 10. If a large warp occurs in the vibration portion 10, it is preferable to have the structure 40 also on the support portion 12. However, even if the structure 40 is not provided on the support portion 12, when warp occurs, the structure 30 provided on the vibration portion 10 approaches the opposite end 20 of the support portion 12, thereby making it possible to suppress an increase in the gap around the vibration portion 10. Furthermore, by configuring the support portion 12 without providing the structure 40, it is possible to reduce manufacturing costs.

[0064] <Configuration of the seventh embodiment of the present invention> Fig. 15 is a plan view showing the configuration of a vibration detection device according to a seventh embodiment of the present invention, Fig. 16 is a cross-sectional view taken along line A3-A3 in Fig. 15, and Fig. 17 is a cross-sectional view taken along line B3-B3 in Fig. 15.

[0065] 15, the seventh embodiment of the present invention is provided with four vibration parts (vibration parts 10a, 10b, 10c, and 10d). The four vibration parts 10a, 10b, 10c, and 10d are arranged point-symmetrically within the frame of the support part 12, and form a substantially square when the vibration parts 10a, 10b, 10c, and 10d are combined. Furthermore, since the four vibrating parts 10a, 10b, 10c, and 10d have the same shape, taking one vibrating part 10a as an example, the outline of vibrating part 10a when viewed from above is made up of four sides: straight side 11c which is a fixed end connected to support part 12, straight side 11d which is a free end extending from one end of the fixed end (side 11c), concave curved side 11b which is a free end extending from the other end of the fixed end (side 11c), and convex curved side 11a which is the free end farthest from the fixed end (side 11c). Furthermore, each side (11a, 11b, 11d) which constitutes the free end of vibrating part 10a is arranged so as not to come into contact with the adjacent support part 12 and other vibrating parts via a gap. Here, if the side 11a farthest from the fixed end (side 11c) of the vibrating part 10a is referred to as the "tip", the structure 30 is provided continuously along the tip 11a of the vibrating part 10a. Note that the structure 30 is not provided at locations along the free ends (sides 11b, 11d) other than the tip 11a. On the other hand, the structure 40 is provided on the support part 12 over the entire support part 12 when viewed in a plan view.

[0066] <Operation and effect of the seventh embodiment of the present invention> Next, the effects of the seventh embodiment of the present invention when warping occurs in each of the vibrating parts 10a, 10b, 10c, and 10d will be described.

[0067] As shown in Fig. 18, in the cross-section along the line A3 - A3 of Fig. 15, when a warp in the direction of arrow J occurs in the vibrating part 10a, the tip 11a of the vibrating part 10a is displaced upward in the Z direction. Therefore, the size of the gap between the tip 11a of the vibrating part 10a and the free end (side 11b) of the other vibrating part 10b facing the tip 11a increases from G5 to G6. Here, the free end (side 11b) of the other vibrating part 10b facing the tip 11a of the vibrating part 10a means a part in a positional relationship such that it faces the tip 11a of the vibrating part 10a when viewed in plan as shown in Fig. 15, regardless of the displacement of the tip 11a due to the warp. Also, the size of the gap between the tip 11a of the vibrating part 10a and the free end (side 11b) of the other vibrating part 10b facing the tip 11a means the shortest distance between the tip 11a and the free end (side 11b) of the other vibrating part 10b facing it.

[0068] Also, in the cross-section along the line A3 - A3 of Fig. 15 shown in Fig. 19, when each of the vibrating parts 10a, 10c is displaced upward in the Z direction due to the warp, the size of the gap between the free end (side 11d) of each of the vibrating parts 10a, 10c and the opposing end 20 of the supporting part 12 facing it increases from G7 to G8.

[0069] However, in the seventh embodiment of the present invention, as shown in Fig. 18, when the tip 11a of the vibrating part 10a is displaced upward in the Z direction, the structure 30 provided at the tip 11a of the vibrating part 10a approaches the free end (side 11b) of the other vibrating part 10b. Therefore, the gap around the tip 11a of the vibrating part 10a can be made into a substantially small gap S3 (S3 < G6). Also, in Fig. 19, when each of the vibrating parts 10a, 10c is displaced upward in the Z direction, the free end (side 11d) of each of the vibrating parts 10a, 10c approaches the structure 40 provided on the supporting part 12. Therefore, the gap around the free end (side 11d) of each of the vibrating parts 10a, 10c can be made into a substantially small gap S4 (S4 < G8). In other cross-sections, similar operational effects can be obtained.

[0070] In this way, in the seventh embodiment of the present invention, the structures 30 and 40 are provided on the vibrating parts 10a, 10b, 10c, and 10d and the support part 12, respectively, so that even if the vibrating parts 10a, 10b, 10c, and 10d are warped, the gaps around the free ends of the vibrating parts 10a, 10b, 10c, and 10d can be substantially reduced, thereby making it possible to suppress a decrease in sensitivity due to an increase in the gaps.

[0071] Furthermore, in the seventh embodiment of the present invention, it is also possible to add modifications similar to those in the second to sixth embodiments of the present invention.

[0072] That is, as shown in Figure 20, when the warping direction J of each vibrating part 10a (10b, 10c, 10d) is the opposite direction (downward in the Z direction) to that in the example of Figure 18, the structure 30 may be provided so as to protrude upward in the Z direction from the tip 11a of the vibrating part 10a (10b, 10c, 10d), opposite to that in Figure 18. That is, also in the seventh embodiment of the present invention, the structure 30 provided on each vibrating part 10a (10b, 10c, 10d) may be provided in the opposite direction to the direction J in which warping occurs in each vibrating part 10a (10b, 10c, 10d).

[0073] Also, as shown in Figure 21, when the direction of warping cannot be predicted, the structure 30 may be arranged to protrude from the tip 11a of each vibrating part 10a (10b, 10c, 10d) both upward and downward in the Z direction (both directions in which the vibrating part 10 vibrates).

[0074] Also, as shown in Figure 22, the structure 30 provided on each vibrating part 10a (10b, 10c, 10d) may be provided so as to protrude toward another vibrating part (for example, side 11b of vibrating part 10b in Figure 22) that faces the tip 11a of each vibrating part 10a (10b, 10c, 10d).

[0075] Furthermore, as shown in FIG. 23, the structure 40 provided on the support portion 12 may be provided so as to protrude toward the opposing vibrating portion (for example, the side 11d of each of the vibrating portions 10a and 10c in FIG. 23).

[0076] 24, the structure 30 provided on each of the vibrating parts 10a, 10b, 10c, and 10d may be provided at least around the tip 11a (first side) of the free ends (sides 11a, 11b, and 11d) of each of the vibrating parts 10a, 10b, 10c, and 10d that is farthest from the fixed end (side 11c) and around a corner 13b located at one end of the tip 11a. In the example of FIG. 24, corners 13a and 13b are provided at both ends of the tip 11a of each of the vibrating parts 10a, 10b, 10c, and 10d, respectively. In this case, the structure 30 is provided around the corner 13b that is farther from the fixed end (side 11c). This effectively prevents the gap from increasing around the tip 11a and the corner 13b, where the gap is likely to become large, and effectively prevents a decrease in sensitivity due to the increase in the gap.

[0077] Eighth embodiment of the present invention Fig. 25 is a plan view showing the configuration of a vibration detection device according to an eighth embodiment of the present invention, and Fig. 26 is a cross-sectional view taken along line A4-A4 in Fig. 25.

[0078] As shown in FIGS. 25 and 26 , in the eighth embodiment of the present invention, support members 12 are disposed between the free ends (sides 11a, 11b, and 11d) of the vibrating members 10a, 10b, 10c, and 10d, and a structure 40 is provided on the support members 12. Therefore, in this case, the support members 12 have a rectangular annular frame portion disposed so as to surround the entire four vibrating members 10a, 10b, 10c, and 10d, and curved intersecting portions disposed between the vibrating members 10a, 10b, 10c, and 10d. Furthermore, in the eighth embodiment of the present invention, the structure 40 is provided over the entire support member 12 when viewed from above. Meanwhile, the structure 30 is not provided on the vibrating members 10a, 10b, 10c, and 10d.

[0079] In this way, by providing support parts 12 between the free ends (sides 11a, 11b, 11d) of each of vibrating parts 10a, 10b, 10c, 10d and further providing structure 40 on support parts 12, it becomes possible to suppress an increase in the gap due to warping of each of vibrating parts 10a, 10b, 10c, 10d without providing structure 30 on the free ends (sides 11a, 11b, 11d) of each of vibrating parts 10a, 10b, 10c, 10d. That is, even if tip 11a of vibrating part 10a is displaced upward in the Z direction due to warping as shown in Fig. 27, tip 11a of vibrating part 10a is disposed opposite structure 40 on support part 12, so that an increase in the gap around tip 11a of vibrating part 10a can be suppressed.

[0080] Furthermore, in the eighth embodiment of the present invention, the structures 30 are not provided on the vibrating units 10a, 10b, 10c, and 10d, thereby avoiding changes in vibration characteristics that would otherwise occur if the structures 30 were provided on the vibrating units 10a, 10b, 10c, and 10d. Furthermore, omitting the structures 30 also reduces manufacturing costs. For example, if the structures 30 are formed on the vibrating units 10a, 10b, 10c, and 10d using photolithography and dry etching, the etching rate difference between the portions where the structures 30 are provided and the portions where they are not provided would be large, which would increase the difficulty of processing and the manufacturing costs. In contrast, in the eighth embodiment of the present invention, the structures 40 are provided only on the support unit 12, and the structures 30 are not provided on the vibrating units 10a, 10b, 10c, and 10d, thereby reducing manufacturing costs.

[0081] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and may be configured by appropriately combining two or more of the above embodiments. In addition, appropriate design changes are possible within the scope of the gist of the invention.

[0082] <Example of changing the placement of structures> Here, a modified example of the arrangement of the structures 30, 40 provided on the vibration section 10 and the support section 12 will be described.

[0083] In each of the embodiments of the present invention, the structure 30 provided on the vibrating part 10 (10a, 10b, 10c, 10d) is provided along the free end of the vibrating part 10. However, as shown in FIG. 28, the structure 30 may be provided so as to project from the free end of the vibrating part 10 (in this case, the tip 11a) toward the opposing support part 12. Conversely, as shown in FIG. 29, the structure 30 may be provided at a position retracted in the direction opposite to the direction in which it projects from the free end of the vibrating part 10 (in this case, the tip 11a). In any case, when the vibrating part 10 is warped, the structure 30 provided on the vibrating part 10 can approach the opposing end 20 of the support part 12 or the structure 40 on the support part 12. Therefore, it is possible to suppress a decrease in sensitivity due to an increase in the gap around the vibrating part. Accordingly, the structure 30 provided on the vibrating part 10 does not have to be provided so as to necessarily coincide with the free end of the vibrating part 10, and may be provided on at least a part of the peripheral edge including the free end and a position slightly deviated from the free end.

[0084] However, in the case of FIG. 29, if the structure 30 is provided at a position significantly retracted from the free end of the vibrating part 10, there is a concern that the gap suppression effect cannot be obtained. Therefore, in the present invention, the "peripheral edge" of the vibrating part 10 on which the structure 30 is provided means a range in which, in FIG. 29, when the size of the gap between the free end (tip 11a) of the vibrating part 10 and the opposing end 20 of the opposing support part 12 is G and the distance from the structure 30 to the free end (tip 11a) is D1, the relationship D1 < G is satisfied. By providing the structure 30 in such a range (peripheral edge), it becomes possible to suppress a decrease in sensitivity due to an increase in the gap.

[0085] Similarly, in the structure 40 provided on the support portion 12, the structure 40 is not limited to being provided so as to necessarily coincide with the opposing end 20 of the support portion 12, and may be provided on at least a part of the peripheral edge portion including the opposing end 20 of the support portion 12 and a position slightly deviated from the opposing end 20. Therefore, as shown in FIG. 30, the structure 40 may be provided so as to protrude from the opposing end 20 of the support portion 12 toward the vibrating portion 10 on the opposite side, or conversely, as shown in FIG. 31, the structure 40 may be provided at a position retracted in a direction opposite to the direction protruding from the opposing end 20 of the support portion 12.

[0086] However, in the case of FIG. 31, if the structure 40 is provided at a position greatly retracted from the opposing end 20 of the support portion 12, there is a concern that the gap suppression effect cannot be obtained. Therefore, in the present invention, the "peripheral edge portion" of the support portion 12 where the structure 40 is provided means a range in which, in FIG. 31, when the size of the gap between the free end (tip 11a) of the vibrating portion 10 and the opposing end 20 of the support portion 12 facing it is G and the distance from the structure 40 to the opposing end 20 is D2, the relationship D2 < G holds. By providing the structure 40 in such a range (peripheral edge portion), it becomes possible to suppress a decrease in sensitivity accompanying an increase in the gap.

[0087] <Sensitivity in the low frequency band> Subsequently, the sensitivity of the vibrating portion 10 will be described.

[0088] Sensitivity indicates the degree to which external vibrations can be detected. When the sensitivity is high, it becomes possible to detect weak external vibrations such as smaller sounds.

[0089] FIG. 32 is a model of the vibrating portion 10 and is a diagram for explaining the deflection angle of a cantilever beam.The broken line shown in FIG. 32 represents the vibrating portion 10 deformed by the moment M0 generated by the sound pressure P0. The angle indicated by this broken line is taken as the deflection angle θ.

[0090] Fig. 33 is a diagram showing an example of a model of the vibrating unit 10. The charge generated in the strain detecting unit 14 when external vibrations such as sound are incident is proportional to the amount of distortion of the strain detecting unit 14. The amount of distortion dz / dx (= deflection angle θ) of the strain detecting unit 14 is expressed as follows using the distance x in the direction from the tip 19 of the vibrating unit 10 in Fig. 33 toward the fixed end 18 (-X direction). Note that the tip 19 refers to the point on the outer periphery of the vibrating unit 10 that is farthest from the fixed end 18 in the direction perpendicular to the line segment direction of the fixed end 18 (X direction).

[0091]

number

[0092] Here, dz and dx are the minute changes on the X-axis and Z-axis shown in Fig. 33, respectively. M(x) is the bending moment at position x, W(x) is the width in the line segment direction of the fixed end of vibrating section 10 at position x, E is Young's modulus, I(x) is the second moment of area at position x, and t is the thickness (width in the Z-axis direction) of vibrating section 10. It is assumed that the thickness t of vibrating section 10 is constant.

[0093] Next, we will explain how to calculate the bending moment M(x) at position x when sound pressure P0 is applied to the vibrating part 10. The magnitude of the load acting on the infinitesimal length dξ is W(ξ)P0dξ. From this, the bending moment at position ξ can be expressed as W(ξ)ξP0dξ, where ξ indicates an arbitrary position in the section of distance x from the tip 19. The bending moment M(x) at distance x is the integration of W(ξ)ξP0dξ from the tip 19 (x=0) to distance x, and can be expressed as follows: Note that the direction in which sound pressure P0 is applied is parallel to the Z axis, and it is assumed that the pressure is the same in all regions on the model.

[0094]

number

[0095] The sum of the strain amount dz / dx of the strain detection unit 14 from the tip 19 (x=0) of the cantilever (vibration unit 10) to the fixed end 18 (x=L) can be expressed by the following formula.

[0096]

number

[0097] It should be noted that L is the length from the fixed end 18 to the tip 19 (reference point) of the vibration part 10 that is farthest in the direction perpendicular to the line segment direction of the fixed end 18 (X-axis direction).

[0098] Figure 34 shows another example of a model of the vibrating part 10. In this example, the vibrating part 10 is rectangular. The width of the vibrating part 10 is constant at W0. The length L of the vibrating part 10 is the same as that of the model in Figure 33. It is assumed that the areas of the model in Figure 33 and the model in Figure 34 are the same. The sum of the strain amount dz / dx of the strain detection part 14 in Figure 34 from the tip 19 (x = 0) of the cantilever beam (vibrating part 10) to the fixed end 18 (x = L) can be expressed by the following equation.

[0099]

number

[0100] 34, the deflection angle θ becomes larger for the same pressure (sound pressure P0) due to the larger distortion amount dz / dx. This improves the sensitivity of the vibration detection device 1. In other words, the sensitivity can be improved by satisfying the following equation:

[0101]

number

[0102] If Young's modulus E, thickness t, and sound pressure P0 are omitted from both sides of the above equation, the following (Equation 1) is derived.

[0103]

number

[0104] This condition can be met by designing the shape of the vibrating part 10 so that its width increases from the fixed end 18 toward the tip 19 (X direction), thereby improving sensitivity. Another method for evaluating the shape of an actually created vibrating part 10 is to use microscopic photography. By detecting the image, it is possible to quantify the area, which is the integral value of each positional information, using image processing. For example, by using a Keyence digital microscope (VHX-8000), it is possible to quantitatively calculate the area of ​​any shape, moments calculated by distance, and the like. It is also possible to calculate the center of gravity by assuming mass and density.

[0105] Fig. 35 is a diagram showing a model in which the sensitivity of vibrating unit 10 is improved. A feature of the model in Fig. 35 is that when the area of ​​vibrating unit 10 is divided in half by straight line 58 in a direction parallel to the line segment direction of fixed end 18 (Y direction) that passes through midpoint 54 of shortest line segment 52 among line segments in a direction perpendicular to the line segment direction of fixed end 18 (X direction) that connects the outer periphery of vibrating unit 10 and fixed end 18, the area on the fixed end 18 side is defined as first area 62, and the area on the tip side (opposite side from fixed end 18) is defined as second area 64. In this case, the area 64 on the tip side of vibrating unit 10 divided in half by straight line 58 is larger than area 62 on the fixed end 18 side.

[0106] Next, the shape characteristics that further enhance the sensitivity of the vibration part 10 will be explained from another perspective. The width characteristics of the vibration part 10 are shown.

[0107] When taking the midpoint 54 of the shortest line segment 52 among the line segments in the direction (X direction) perpendicular to the line segment direction of fixed end 18 connecting fixed end 18 and the outer periphery of vibrating unit 10, the width of vibrating unit 10 in the direction (Y direction) parallel to the line segment direction of fixed end 18 is maximum at a position farther from fixed end 18 than midpoint 54 in the direction (X direction) perpendicular to the line segment direction of fixed end 18. In other words, the position of maximum width 56 of vibrating unit 10 in the direction (Y direction) parallel to the line segment direction of fixed end 18 is farther from fixed end 18 than midpoint 54. This enables the sensitivity of vibration detection device 1 to be improved.

[0108] Next, the results of verifying the above effects through simulation are shown. Figure 36 shows the models used in the simulation. In Figure 36, (a) shows a model of a triangular vibration part 10, (b) shows a model of a rectangular vibration part 10, and (c) shows a model of a trapezoidal vibration part 10 whose width increases from the fixed end 18 toward the tip 19 (X direction). The areas of all the models in Figure 36 are the same.

[0109] Figure 37 shows the results of a simulation of the amount of deflection when the same sound pressure is applied to each model in Figure 36. The vertical axis represents the amount of deflection, and the horizontal axis represents the position in the X direction. It can be seen that the model in Figure 36(c) has a larger amount of deflection and higher sensitivity than the models in Figures 36(a) and 36(b).

[0110] To improve the sensitivity of the vibration detection device 1, it is necessary to increase the deflection angle at each point of the vibrating unit 10 when a uniform pressure is applied to the vibrating unit 10. Therefore, it is sufficient to increase the area from a certain point to the tip of the vibrating unit 10. A highly sensitive vibration detection device 1 can be realized by shaping the vibrating unit 10 so that its width increases continuously from the fixed end to the tip. Therefore, in the vibration detection device 1 according to the present invention, sensitivity in the low frequency band can be improved by shaping the vibrating unit 10 so that its width increases continuously from the fixed end to the tip. For example, in the configuration shown in FIG. 15, the width of each of the vibrating units 10a, 10b, 10c, and 10d increases continuously from the fixed end (side 11c) to the tip 11a, compared to the configuration shown in FIG. 1, thereby improving sensitivity in the low frequency band.

[0111] Figure 38 is a diagram illustrating models used in a simulation of the resonance frequency. In Figure 38, (a) shows a model of a triangular vibration part 10, (b) shows a model of a rectangular vibration part 10, (c) shows a model of a trapezoidal vibration part 10 whose width increases from the fixed end 18 toward the tip 19 (X direction), and (d) shows a trapezoidal model in which the length L from the tip to the fixed end is twice that of the model in (c). Note that the areas of all the models in Figure 38 are the same.

[0112] FIG. 39 shows the simulation results of the sensitivity when the same sound pressure is applied to each model in FIG. 38. Here, the relative sensitivity is shown when the sensitivity of the model in FIG. 38(a) is set to "1" (reference). From this result, it can be seen that the sensitivity of the model in FIG. 38(c) is improved compared to the models in FIG. 38(a) and FIG. 38(b). Furthermore, it can be seen that the model in FIG. 38(d), which has twice the length from the tip to the fixed end compared to the model in FIG. 38(c), has even improved sensitivity. Therefore, it can be said that sensitivity is further improved when the vibrating part 10 is made longer in the direction perpendicular to the line segment direction of the fixed end (X direction).

[0113] Next, the resonant frequency band of the vibrating unit will be described. When the resonant frequency of the vibrating unit is in the vicinity of 100 to several kHz, unlike the general sound range of several tens of kHz, this is a low frequency band, making it suitable for measuring heart rate or hydrophones used for pipe inspections. One method for realizing a vibrating unit suitable for measuring such a low frequency band is to reduce the frequency by lengthening the vibrating unit 10, as described above. However, lengthening the vibrating unit 10 not only increases the size of the vibration detection device 1, but also reduces the mechanical strength of the vibrating unit 10, thereby reducing reliability. For this reason, methods for reducing the frequency without lengthening the vibrating unit 10 have been explored.

[0114] Figure 40 is a diagram showing a comparison of the center of gravity positions of a model of a rectangular vibration section 10 and a model of a vibration section 10 whose width increases from the fixed end 18 toward the tip 19 (X direction). In the model of the rectangular vibration section 10, the center of gravity is located at point 22 in the center of L / 2. In contrast, in the model of the vibration section 10 whose width increases, the tip 19 side of the vibration section is wider than the fixed end 18, so the center of gravity is located at point 24 on the tip 19 side from the center. The mass per unit volume of each vibration section 10 is constant.

[0115] FIG. 41 is a diagram illustrating a model used for simulating the resonance frequency. In FIG. 41, W1 is the length of the fixed end 18 of the vibrating unit 10 in the line segment direction (Y direction), and W2 is the length of the tip 19 in the line segment direction (Y direction). The length of the tip 19 is W2, which is the length of the tip 19 at the position farthest from the fixed end 18 in the direction perpendicular to the line segment direction of the fixed end 18 (X direction). The area (W1 + W2)L / 2 of the vibrating unit 10 and the length L of the vibrating unit 10 were assumed to be constant, and the resonance frequency was calculated when W2 / W1 was changed. However, the end shapes other than the fixed end 18 and the tip 19 were assumed to be connected in a straight line shape without any concave or convex shape. The thickness and density of the vibrating unit 10 were also assumed to be constant.

[0116] The simulation results are shown in Figure 42. In Figure 42, the vertical axis represents the resonant frequency, and the horizontal axis represents the value of W2 / W1. When W2 / W1 = 1, this represents a model of a rectangular vibration unit 10, and indicates that the shape of the vibration unit 10 increases as the value of W2 / W1 increases, resulting in a shape in which the width of the tip of the vibration unit 10 increases. According to this simulation result, the resonant frequency decreases as W2 / W1 increases, which indicates that the resonant frequency can be reduced by widening the tip of the vibration unit 10 compared to when the vibration unit 10 is rectangular. Furthermore, as the width of the tip of the vibration unit 10 increases, the resonant frequency also decreases. This can be restated in terms of the position of the center of gravity mentioned above. It can be said that the resonant frequency can be reduced by making the distance between the center of gravity of the vibration unit 10 and the fixed end a value of L / 2 or more.

[0117] Therefore, in the vibration detection device 1 of the present invention, when the length of the fixed end 18 of the vibrating part 10 in the linear direction (Y direction) is W1 and the length of the tip in the linear direction (Y direction) is W2, by satisfying the relationship W2 / W1>1, the mass increases as one approaches the tip of the vibrating part 10, thereby decreasing the resonant frequency and improving sensitivity in the low frequency band.

[0118] [Variations in the shape of the vibrating part] Next, modified shapes of the vibrating portion according to the present invention will be described.

[0119] <First Modification> FIG. 43 is a plan view showing a first modified example of the vibrating section.

[0120] The first modification of Figure 43 is characterized in that the outer periphery of each of the four vibrating parts 10a, 10b, 10c, and 10d is formed by four straight sides 11a, 11b, 11c, and 11d, and the width of each of the vibrating parts 10a, 10b, 10c, and 10d increases continuously from the fixed end (side 11c) toward the tip 11a. In this way, the shape of the vibrating part may have an outer periphery made up of only straight sides, and the width may increase toward the tip. When the outer periphery of the vibrating part is formed only by straight sides, it has the advantage of being more resistant to manufacturing errors in the semiconductor process due to the anisotropy of silicon crystals, compared to when it includes curved sides as shown in Figure 15.

[0121] <Second Modification> FIG. 44 is a plan view showing a second modified example of the vibrating section.

[0122] The second modification of Fig. 44 is characterized in that the four vibration parts 10a, 10b, 10c, and 10d are each formed as a polygon with five or more corners. Also in this case, each of the vibration parts 10a, 10b, 10c, and 10d is formed so that its width increases continuously from the fixed end (side 11c) toward the tip 11a.

[0123] In this way, when the vibration parts 10a, 10b, 10c, and 10d are polygonal in shape with five or more corners, the degree of freedom in design can be improved compared to the square vibration part 10 shown in Figure 1. Furthermore, with the improvement in the degree of freedom in design, it becomes possible to change the design so that the pressure received by the tips of the vibration parts 10a, 10b, 10c, and 10d is increased. This makes it possible to generate a large deflection angle and improve sensitivity.

[0124] <Third Modification> FIG. 45 is a cross-sectional view showing a third modified example of the vibrating section.

[0125] In the third modified example of FIG. 45, the vibrating unit 10 is characterized by having two layers of strain detection units: a first strain detection unit 14 and a second strain detection unit 15. Each strain detection unit 14, 15 is sandwiched between a lower electrode and an upper electrode. The strain state of each strain detection unit 14, 15 can be detected from the potential generated between the upper and lower electrodes. An insulating layer is formed between each strain detection unit 14, 15, electrically isolating them. Alternatively, the lower electrode of the first strain detection unit 14 and the upper electrode of the second strain detection unit 15 may be a common electrode without an insulating layer. In this case, it is possible to detect the potential of each strain detection unit 14, 15 independently.

[0126] Furthermore, when viewed from above, the strain detection units 14 and 15 are arranged overlapping in roughly the same area. When external vibrations occur and the vibrating unit 10 vibrates, compressive or tensile strain occurs in each strain detection unit 14 and 15. Since the stresses generated in each strain detection unit 14 and 15 are of opposite signs, the potentials generated in each strain detection unit 14 and 15 are also of opposite signs. By detecting the potential difference between each strain detection unit 14 and 15, the signal is doubled. For example, if one has a potential of 5 [V] and the other has a potential of -5 [V], the difference between the two potentials is 5 [V] - (-5 [V]) = 10 [V]. If a potential occurs only in one side, the signal is noise. By calculating the signal difference and doubling the signal, the influence of electrical noise can be reduced, thereby improving sensitivity.

[0127] Therefore, in the vibration detection device 1 of the present invention, the vibration section 10 has a two-layer structure consisting of a first strain detection section 14 and a second strain detection section 15, and by subtracting the signal of the second strain detection section 15 from the signal of the first strain detection section 14, noise can be reduced, the signal can be doubled, and sensitivity can be improved.

[0128] <Example of changing the placement of the strain detector> FIG. 46 is a diagram showing a modified example of the arrangement of the distortion detector.

[0129] The arrangement of the strain detection unit 14 can be changed to various positions. For example, as shown in FIG. 46( a), the strain detection unit 14 may be arranged so as to cover the entire vibrating unit 10. Alternatively, as shown in FIG. 46( b), the strain detection unit 14 may be arranged so as to extend onto the support unit 12. Alternatively, as shown in FIG. 46( c), the strain detection unit 14 may not cover the entire vibrating unit 10, but may be arranged only on a portion of the vibrating unit 10 on the fixed end (side 11 c). Alternatively, as shown in FIG. 46( d), the strain detection unit 14 may be arranged only near the fixed end (side 11 c). When external vibration is applied to the vibration detection device 1, the amount of strain of the strain detection unit 14 increases as it approaches the fixed end (side 11 c) of the vibrating unit 10. Therefore, by arranging the strain detection unit 14 on the fixed end (side 11 c) of the vibrating unit 10, it is possible to increase sensitivity.

[0130] As described above, in the vibration detection device 1 according to the present invention, the shape of the vibrating part 10 can be appropriately modified. Furthermore, by applying the present invention to vibration detection devices having vibration parts 10 of these various shapes, it is possible to suppress a decrease in sensitivity that accompanies an increase in the gap around the vibrating part. Therefore, unlike the invention described in Patent Document 1, the vibration detection device 1 according to the present invention can suppress a decrease in sensitivity that accompanies an increase in the gap around the vibrating part in vibration detection devices of various configurations.

[0131] [Application example of the vibration detection device according to the present invention] Next, an application example of the vibration detection device according to the present invention will be described.

[0132] <Vital Sensor> FIG. 47 is a diagram showing an example in which the vibration detection device according to the present invention is applied to a vital sensor.

[0133] The vibration detection device 1 according to the present invention can be applied to a vital sensor that detects heartbeat pulse waves with little noise. A vital sensor incorporating the vibration detection device 1 has the function of converting information related to various data detected by the vibration detection device 1, such as heartbeat, heart rate (pulse rate), blood pressure, respiratory sounds, and respiratory rate, into vital data.

[0134] As shown in Figure 47, the vibration detection device 1 is attached to the ear (Figure 47(a)) or wrist (Figure 47(b)) and used as a vital sensor. Pulse wave sensors that use light to detect heartbeats are also available as devices for detecting heartbeats. However, such sensors are unable to measure waveforms with high accuracy due to noise such as ambient light or fluctuations in the state of attachment caused by body movement, and are therefore limited to applications such as pulse rate. In contrast, a piezoelectric vibration detection device 1 such as that of the present invention detects heartbeats using sound, making it possible to greatly reduce noise generation. Therefore, by using the vibration detection device 1 of the present invention as a vital sensor, it is possible to perform highly accurate analysis of frequency components from the detected pulse wave.

[0135] Furthermore, analyzing the frequency components of the pulse wave using the vibration detection device 1 according to the present invention enables highly accurate understanding of the psychological state. Furthermore, by applying machine learning to the analysis of the frequency components, it is possible to interpret information related to the heartbeat with high accuracy and estimate the psychological state from multiple angles.

[0136] Furthermore, a system for detecting the psychological state of an office worker may be mounted on a vital sensor that employs the vibration detection device 1 according to the present invention. By wearing a vital sensor that employs the vibration detection device 1 according to the present invention during work such as meetings, programming, writing emails, or one-on-one meetings with a boss, it becomes possible to read the heart rate and detect the psychological state (stress, concentration level, etc.).

[0137] Furthermore, the system for detecting a psychological state to which the vibration detection device 1 according to the present invention is applied may have a UI for visualizing changes in the psychological state such as the concentration level, stress level, etc. Specifically, by displaying in a graph or table how much the stress and concentration level change depending on the type of work, the user can intuitively understand the change.

[0138] Furthermore, a system for detecting psychological states that employs the vibration detection device 1 according to the present invention may be configured to analyze the conditions under which concentration is possible (time of day, meeting partner, work environment) by utilizing machine learning. This system's analysis can suggest the optimal work environment to the user and support effective schedule creation. In addition, if the user's concentration decreases and stress is felt, the system can sound an alarm to encourage the user to relax.

[0139] <Pipe inspection equipment> FIG. 48 is a diagram showing an example in which the vibration detecting device according to the present invention is applied to a piping inspection device.

[0140] The vibration detection device 1 according to the present invention can also be applied to a pipe inspection device that detects the location of a water leak in a pipe.

[0141] As shown in Figure 48, the vibration detection device 1 according to the present invention is installed on the surface (outer surface) of a pipe 200, and the vibration detection device 1 is used to detect vibrations transmitted to the surface of the pipe 200, thereby making it possible to detect the location of a water leak in the pipe 200. Piezoelectric sensors used to inspect pipes are available that are based on piezoelectric ceramics, but have high acoustic impedance and limited sensitivity. In contrast, the vibration detection device 1 according to the present invention can be made more sensitive, and can also be made smaller and less expensive.

[0142] 48, the vibration detection device 1 according to the present invention may be installed inside a pipe 200 and used as a hydrophone 2 that detects, as vibrations, sounds transmitted through the liquid flowing inside the pipe 200. The hydrophone 2 detects sounds transmitted through the pipe 200 from vibrations transmitted through the water, thereby suppressing vibration attenuation and enabling detection of vibration sources at greater distances compared to when vibrations are detected through air. When the vibration detection device 1 according to the present invention is used as a hydrophone 2, performance is improved by detecting low frequencies of several hundred Hz, enabling inspection over long distances, for example, up to 1 km, and making it applicable to the inspection of large-scale pipelines.

[0143] Furthermore, by installing the vibration detection device 1 according to the present invention both on the surface and inside of the pipe 200 and using it as a microphone and hydrophone, it is possible to improve detection accuracy. The microphone and hydrophone wirelessly transmit detection signals to the computing device 201, and by synchronizing the respective signals in a time series, it is possible to analyze the location of water leaks, etc.

[0144] To summarize the above-described aspects of the present invention, the present invention includes at least the following aspects.

[0145] [First aspect] The first aspect is a vibration detection device comprising a vibrating unit, a support unit that supports the vibrating unit so that it can vibrate, and a structure provided on at least one of the vibrating unit and the support unit, wherein the structure provided on the vibrating unit is provided in a direction opposite to the direction in which warping of the vibrating unit occurs from at least a portion of a peripheral portion including a vibrating free end of the vibrating unit, and the structure provided on the support unit is provided in a direction in which warping of the vibrating unit occurs from at least a portion of a peripheral portion including an opposing end of the support unit that faces the free end.

[0146] [Second aspect] In a second aspect, in the first aspect, the structure provided on the vibrating part is provided from at least a part of the peripheral edge part in both directions in which the vibrating part vibrates.

[0147] [Third aspect] In the third aspect, in the first or second aspect, the structure provided on the vibrating part is provided so as to protrude toward another vibrating part or the support part that faces the free end in the direction opposite to the direction in which the warping occurs.

[0148] [Fourth aspect] A fourth aspect is any one of the first to third aspects, wherein the structure provided on the support part is provided so as to protrude toward the side of the vibration part opposite the opposing end in the direction in which the warping occurs.

[0149] [Fifth aspect] A fifth aspect is any one of the first to fourth aspects, wherein the structure provided on the vibrating part is provided at least on a first side of the free end that is farthest from a fixed end of the vibrating part supported by the support part, and on a corner located at the end of the first side.

[0150] [Sixth aspect] A sixth aspect is any one of the first to fifth aspects, wherein the vibration unit has a plurality of vibration units, and the structure provided on the support unit is arranged between the free ends of the vibration units.

[0151] [Seventh aspect] A seventh aspect is the first aspect, wherein the structure is provided only on the vibration part.

[0152] [Eighth aspect] An eighth aspect is the first aspect, wherein the structure is provided only on the support portion.

[0153] [Ninth aspect] A ninth aspect is any one of the first to eighth aspects, wherein the vibrating section has at least one layer of strain detecting section that detects strain in the vibrating section.

[0154] [Tenth aspect] A tenth aspect is a vital sensor equipped with the vibration detection device according to any one of the first to ninth aspects.

[0155] [Eleventh aspect] An eleventh aspect is a piping inspection device equipped with the vibration detection device according to any one of the first to ninth aspects. [Explanation of symbols]

[0156] 1. Vibration detection device 10 Vibration unit 12 Support part 11a Tip (free end) 11c fixed end 14 Distortion detection section 30 Structures 40 Structures [Prior art documents] [Patent documents]

[0157] [Patent Document 1] Special Publication No. 2014-515214

Claims

1. A vibration unit; a support portion that supports the vibration portion so that the vibration portion can vibrate; a structure provided on at least one of the vibration section and the support section, the structure provided on the vibration section is provided in a direction opposite to a direction in which warping of the vibration section occurs from at least a part of a peripheral edge portion including a vibrating free end of the vibration section, A vibration detection device characterized in that the structure provided on the support portion is provided in a direction in which warping of the vibrating portion occurs from at least a portion of the peripheral portion including the opposing end of the support portion opposite the free end.

2. The vibration detection device according to claim 1 , wherein the structure provided on the vibrating part is provided from at least a part of the peripheral edge part in both directions in which the vibrating part vibrates.

3. The vibration detection device according to claim 1, wherein the structure provided on the vibrating part is arranged so as to protrude toward another vibrating part or the support part that faces the free end in a direction opposite to the direction in which the warping occurs.

4. The vibration detection device according to claim 1 , wherein the structure provided on the support portion is provided so as to protrude toward the vibrating portion facing the opposing end in the direction in which the warp occurs.

5. The vibration detection device of claim 1, wherein the structure provided on the vibrating part is provided at least on a first side of the free end that is farthest from the fixed end of the vibrating part supported by the support part, and on a corner located at the end of the first side.

6. A plurality of the vibration units are provided, The vibration detection device according to claim 1 , wherein the structure provided on the support section is disposed between the free ends of the plurality of vibrating sections.

7. The vibration detection device according to claim 1 , wherein the structure is provided only on the vibrating portion.

8. The vibration detection device according to claim 1 , wherein the structure is provided only on the support portion.

9. The vibration detection device according to claim 1 , wherein the vibrating section has at least one layer of strain detection section for detecting strain of the vibrating section.

10. A vital sensor equipped with the vibration detection device according to claim 1.

11. A piping inspection device equipped with the vibration detection device according to claim 1.

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