Electrostatic induction type vibrating element

Abstract

To provide an electrostatic induction type vibration element that suppresses contact between interdigitated electrodes and that can withstand external impacts.SOLUTION: Provided is an electrostatic induction type vibration element including: a flexible member; a plurality of first interdigitated electrodes of which one end is fixed so as to be insulated from the flexible member and which stand up from the flexible member; a plurality of second interdigitated electrodes of which one end is fixed so as to be insulated from the flexible member and which stand up from the flexible member at internals relative to the first interdigitated electrodes, wherein, when the flexible member vibrates, the intervals between the other end sides of the first interdigitated electrodes and the second interdigitated electrodes fluctuate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrostatic induction type vibration element.

Background Art

[0002] Vibration elements that generate vibration by applying electrical energy or convert vibration energy into an electrical signal or electrical energy are used in the fields of microphones, ultrasonic sensors, or vibration power generation (see, for example, Patent Document 1 and Patent Document 2, etc.).

[0003] In the electrostatic induction type vibration element described in Patent Document 2, a member that maintains charging by applying a voltage to an electret, that is, a dielectric, is used for opposing comb-shaped electrodes. By changing the overlapping area of these electret surfaces, mechanical work can be converted into electrostatic energy by the electrostatic force acting between the comb-shaped electrodes, and an electromotive force can be generated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, because the electrostatic gap of the comb-shaped electrodes is set to be extremely small, there was a risk that the electrodes would stick together in the event of an external shock. Specifically, during the operation of the electrostatic induction type vibrator, external shocks could cause fluctuations in the electrostatic gap between the comb teeth, and if the balance of electrostatic attraction on the sides of the comb teeth was disrupted, the fluctuations could be amplified. Under these circumstances, pull-in could occur between the comb-shaped electrodes, and when the comb teeth came into contact, a large current would flow instantaneously between the electrodes with a potential difference, and in the worst case, the electrodes could fuse together and stick together, resulting in an irreversible state. (See Patent Document 3, etc.).

[0006] In view of these factors, the present invention aims to provide an electrostatic induction type vibrating element that suppresses contact between comb-shaped electrodes and is resistant to external shocks. [Means for solving the problem]

[0007] To solve the above problems, an electrostatic induction type vibration element according to one embodiment of the present invention is Flexible member and One end of the flexible member is fixed in an insulated state, and a plurality of first comb-shaped electrodes are erected from the flexible member, A plurality of second comb-shaped electrodes are fixed at one end in an insulated state to the flexible member, and are erected from the flexible member at a distance from the first comb-shaped electrode, An electrostatic induction type vibrating element having, When the flexible member vibrates, the distance between the first comb-shaped electrode and the other end of the second comb-shaped electrode changes. [Effects of the Invention]

[0008] This invention can provide an electrostatic induction type vibrating element that suppresses contact between comb-shaped electrodes and is resistant to external shocks. [Brief explanation of the drawing]

[0009] [Figure 1] This is a top view showing an electrostatic induction type vibration element according to the first embodiment of the present invention. [Figure 2] (a) A cross-sectional view of the electrostatic induction vibrating element in Figure 1 when it is stationary. (b) A cross-sectional view of the electrostatic induction vibrating element in Figure 1 when it is bent. [Figure 3] This is a top view showing an electrostatic induction type vibrating element according to a second embodiment of the present invention. [Figure 4] (a) A cross-sectional view of the electrostatic induction vibrating element in Figure 3 when it is stationary. (b) A cross-sectional view of the electrostatic induction vibrating element in Figure 3 when it is bent. [Figure 5] This is a rear perspective view showing an electrostatic induction type vibrating element according to a third embodiment of the present invention. [Figure 6] (a) A cross-sectional view of the electrostatic induction vibrating element in Figure 5 when it is stationary. (b) A cross-sectional view of the electrostatic induction vibrating element in Figure 5 when it is bent. [Figure 7] This is a schematic diagram of an ultrasonic transmitting and receiving device using an electrostatic induction type vibration element according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments.

[0011] <First Embodiment> Figure 1 is a top view showing an electrostatic induction type vibration element 100 according to the first embodiment of the present invention.

[0012] In a first embodiment of the present invention, the electrostatic induction type vibration element 100 is a vibration power generation element and comprises a flexible member 10, a first comb-shaped electrode 20, a second comb-shaped electrode 30, a first terminal 40, a second terminal 50, and a weight 60. The first comb-shaped electrode 20 and the second comb-shaped electrode 30 are installed in an insulated state on the flexible member 10 so as to extend alternately with a gap between them. The components of the electrostatic induction type vibration element 100 will be described in order below.

[0013] The flexible member 10 has a cantilever beam structure with one end fixed to a base (not shown), and a weight 60 is disposed at the free end of the cantilever beam structure. The flexible member 10 functions as a cantilever beam that deflects due to external vibrations. Although details will be described later, the first comb-shaped electrode 20 and the second comb-shaped electrode 30 are installed in a region between the fixed end and the free end of the flexible member 10.

[0014] In the embodiment described in FIG. 1, the flexible member 10 has a triangular shape, but is not limited thereto and may be rectangular. The flexible member 10 may be formed of a single member as long as it has flexibility, or may be formed of a plurality of members. For example, in the embodiments described in FIGS. 2(a) and 2(b), the flexible member 10 has a structure in which a SiO2 layer 10b is laminated on a SOI substrate handle layer 10a.

[0015] The first comb-shaped electrode 20 and the second comb-shaped electrode 30 are erected on the flexible member 10 so as to extend alternately at intervals. A comb-shaped electrode is an electrode in which a plurality of planar electrodes are arranged in parallel like the teeth of a comb, as shown in FIG. 1 and FIGS. (a) and 2(b). The number of teeth may be any number and is not limited to that shown in FIG. 1. When the number of teeth is minimized, the comb-shaped electrode has two teeth formed on one of the first comb-shaped electrode and the second comb-shaped electrode, and one tooth is formed on the other electrode so as to be inserted between the two teeth. Any comb-shaped electrode having such a basic configuration can constitute a vibration element having the functions described below regardless of the number of teeth.

[0016] The first comb-shaped electrode 20 and the second comb-shaped electrode 30 are installed on the flexible member 10 in an insulated state. To install them in an insulated state, for example, the surface on which the comb-shaped electrodes of the flexible member 10 are erected may be created with an insulating member. In the embodiments described in FIGS. 2(a) and 2(b), since the SiO2 layer 10b has insulating properties, each comb-shaped electrode provided so as to contact it is insulated. Also, each comb-shaped electrode may be separately created from the flexible member 10 and attached to the flexible member 10 with an insulating adhesive or the like.

[0017] At least one of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 has an electret formed near the surface of each opposing surface. As a result, at least one of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 will be charged. Therefore, when the flexible member 10 is deformed and the distance between the first comb-shaped electrode 20 and the second comb-shaped electrode 30 fluctuates, electrostatic induction occurs between the comb-shaped electrodes, and power generation can be performed.

[0018] The first comb-shaped electrode 20 and the second comb-shaped electrode 30 are installed in the region between the fixed end and the free end of the flexible member 10. Preferably, it is installed near the fixed end where the bending moment of the cantilever beam structure of the flexible member 10 is large. Thereby, when the vibration element vibrates, the comb-shaped electrode installation portion is deformed more greatly, and the variation in the distance between the comb-shaped electrodes becomes large, so that a larger amount of power can be obtained.

[0019] Also, the extending direction of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 is preferably installed in the horizontal direction (the left-right direction in FIG. 1) perpendicular to the beam central axis of the cantilever beam structure of the flexible member 10. Thereby, the distance between the comb-shaped electrodes is greatly affected by the deformation of the comb-shaped electrode installation portion, and a large variation can be obtained.

[0020] The first terminal 40 and the second terminal 50 are electrically connected to the first comb-shaped electrode 20 and the second comb-shaped electrode 30, respectively. The first terminal and the second terminal are each connected to an external circuit (not shown) to supply the electrical energy generated by the vibration of the electrostatic induction vibration element 100 to the external circuit.

[0021] The weight 60 is placed at the free end of the flexible member 10. This weight 60 increases the deformation of the flexible member 10, which increases the vibration of the electrostatic induction type vibrating element 100, and as a result, a larger output power can be obtained from the electrostatic induction type vibrating element 100.

[0022] (Regarding the operation of the vibration power generation element) As shown in Figure 2(a), when the electrostatic induction type vibrating element 100 is stationary, one end of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 are fixed in an insulated state to the flexible member 10, while the other ends of the first comb-shaped electrode 20 and the second comb-shaped electrode 30, which are the free ends, are spaced apart from each other.

[0023] Next, as shown in Figure 2(b), when the flexible member 10 bends due to vibration of a structure (not shown) to which the electrostatic induction vibration element 100 is attached, the distance between the other ends of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 changes, and power is generated. At this time, since one end of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 is fixed to the flexible member 10, contact between electrodes with a potential difference can be suppressed. Furthermore, even if the upward bending of the flexible member 10 becomes large and the comb-shaped electrodes come close enough to touch, the contact area becomes a line contact that is extremely small compared to the surface contact of the conventional technology, so fusion between electrodes, that is, sticking, can be suppressed. In addition, this line contact is not continuous, and in the next moment, as the flexible member 10 bends downward, a force is applied in the direction that separates the comb-shaped electrodes from each other, so the line contact between the electrodes is immediately resolved. As described above, the electrostatic induction type vibration element 100 of the first embodiment has a configuration that is resistant to external shocks, and therefore can overcome the problems of the conventional method.

[0024] In addition, the electrostatic induction type vibration element 100 of this embodiment may have a stopper (not shown), although this is not an essential component. The stopper is intended to prevent the deformation of the flexible member 10 from becoming so large that the comb-shaped electrodes come into contact with each other. For example, the stopper may be installed at the destination of the weight 60 to prevent excessive movement of the weight 60.

[0025] <Second Embodiment> Figure 3 is a top view showing an electrostatic induction type vibration element 200 according to a second embodiment of the present invention. The electrostatic induction type vibration element 200 according to the second embodiment differs from the electrostatic induction type vibration element 100 according to the first embodiment in that a pair of flexible members 10 extend symmetrically around a weight 60, and have a double-supported beam structure in which each end is fixed to a base (not shown). However, the other basic configurations are the same as those of the first embodiment. Here, the same components are denoted by the same reference numerals, and redundant explanations are omitted. In the case of the second embodiment, a first comb-shaped electrode 20 and a second comb-shaped electrode 30 are installed in the respective regions between the fixed ends of the pair of flexible members 10 and the weight 60. Similar to the first embodiment, it is preferable that the direction in which the first comb-shaped electrode 20 and the second comb-shaped electrode 30 extend is in the horizontal direction (left-right direction in Figure 3) perpendicular to the beam center axis of the double-supported beam structure of the flexible member 10. This allows the distance between the comb-shaped electrodes to be greatly affected by the deformation of the area where the comb-shaped electrodes are installed, resulting in significant variation.

[0026] (Regarding the operation of the vibration power generation element) In the second embodiment, as shown in Figure 4(a), when the electrostatic induction type vibrating element 200 is stationary, one end of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 are fixed insulated from the flexible member 10, while the other ends, which are the free ends of the first comb-shaped electrode 20 and the second comb-shaped electrode 30, are spaced apart from each other.

[0027] Next, as shown in Figure 4(b), when the flexible member 10 bends due to the vibration of a structure (not shown) to which the electrostatic induction vibration element 200 is attached, causing the weight 60 to move downward, the distance between the other ends of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 changes, and power is generated. At this time, as in the first embodiment, one end of the first comb-shaped electrode 20 and the second comb-shaped electrode 30 is fixed to the flexible member 10, so contact between electrodes with a potential difference can be suppressed. Therefore, even if the upward bending of the flexible member 10 becomes large and the comb-shaped electrodes come close enough to come into contact, the contact area will be a line contact that is extremely small compared to the surface contact of the conventional technology, thus suppressing fusion between electrodes, that is, sticking. In addition, since the second embodiment has a double-supported beam structure, the vertical movement of the weight 60 is restricted to a specific range, and contact between the comb-shaped electrodes due to excessive deformation of the flexible member 10 is suppressed. Based on the above, the electrostatic induction type vibration element 200 of the second embodiment has a configuration that is resistant to external shocks, and therefore can overcome the problems of the conventional method.

[0028] <Third Embodiment> Figure 5 is a rear perspective view showing an electrostatic induction type vibrating element 300 according to a third embodiment of the present invention. The electrostatic induction type vibrating element 300 according to the third embodiment differs from the electrostatic induction type vibrating element 100 according to the first embodiment in that the flexible member 10' is made of a membrane material, it does not have a weight, the arrangement of the first comb-shaped electrode 20' and the second comb-shaped electrode 30' is different, and it is used as an ultrasonic transducer, but the other basic configurations are the same as those of the first embodiment. Here, the same components are denoted by the same reference numerals, and redundant explanations are omitted.

[0029] In a third embodiment of the present invention, the electrostatic induction vibrating element 300 is an ultrasonic transducer and comprises a flexible member 10', a first comb-shaped electrode 20', a second comb-shaped electrode 30', a first terminal 40, and a second terminal 50. The components of the electrostatic induction vibrating element 300 will be described in order below.

[0030] The flexible member 10' has a membrane structure with its outer circumference fixed to a base (not shown) and is formed from a flexible membrane member. The first comb-shaped electrode 20' and the second comb-shaped electrode 30' are located inside the outer circumference, defining the opening 70. As will be described in detail later, the flexible member 10' is installed so as to cover the first comb-shaped electrode 20', the second comb-shaped electrode 30' and the opening 70, and insulated from these electrodes.

[0031] The first comb-shaped electrode 20' and the second comb-shaped electrode 30' are each installed alternately in the circumferential direction, with a radial spacing between them. The first comb-shaped electrode 20' is electrically connected to the first terminal 40, and the second comb-shaped electrode 30' is electrically connected to the second terminal 50. The first terminal 40 and the second terminal 50 are electrically connected to an external circuit (not shown). The external circuit may include an external power supply.

[0032] From here, using Figures 6(a) and (b), we will explain how the electrostatic induction type vibrating element 300, which is an ultrasonic transducer, functions as an ultrasonic receiver (sensor) (see 300R in Figure 7) and an ultrasonic generator (see 300T in Figure 7).

[0033] First, we will describe the case where the electrostatic induction type vibrating element 300 functions as an ultrasonic receiver (sensor) 300R. The comb-shaped electrodes 20' and 30' have electrets formed near the surface of their opposing faces, or a DC bias voltage is applied from an external power supply provided in an external circuit, creating a potential difference between the comb-shaped electrodes (Figure 6(a)).

[0034] Next, when the membrane-like flexible member 10' receives ultrasonic waves and vibrates, a bending moment is generated near the fixed end of the membrane, i.e., at the location where the comb-shaped electrodes are installed, causing it to deform in a direction that widens the distance between the comb-shaped electrodes, as shown in Figure 6(b). The electrostatic induction generated between the comb-shaped electrodes at that time generates an electrical signal, which is sent from the first terminal 40 and the second terminal 50 to an external circuit (not shown) connected to the electrostatic induction vibrating element 300.

[0035] Next, we will describe the case where the electrostatic induction type vibrating element 300 functions as an ultrasonic generator 300T. In the case of the ultrasonic generator 300T, the comb-shaped electrodes 20' and 30' either have electrets formed near the surface of their opposing faces, or a DC bias voltage is applied from an external power supply provided in an external circuit, creating a potential difference between the comb-shaped electrodes.

[0036] When an AC voltage is superimposed on the comb-shaped electrodes 20' and 30', which have an electric potential, vibrations (linear vibrations) occur between the comb-shaped electrodes at the same frequency as the applied voltage. As a result, the film-like flexible member 10' vibrates, generating ultrasonic waves.

[0037] (Regarding the operation of ultrasonic transceivers) Figure 7 is a schematic diagram of an ultrasonic transmitting and receiving device created by combining multiple electrostatic induction type vibration elements 300 according to the third embodiment of the present invention. The ultrasonic generator 300T generates ultrasonic waves when an AC voltage is applied between comb-shaped electrodes having a potential difference. The other ultrasonic receiver (sensor) 300R then vibrates due to the ultrasonic waves reflected after hitting an object, generating an electrical signal and enabling the detection of the presence of an object.

[0038] Thus, the electrostatic induction type vibration element 300 of the third embodiment of the present invention provides the same effects as the first embodiment (a configuration that suppresses contact between comb teeth and is resistant to external shocks). In addition, the electrostatic induction type vibration element 300 of the third embodiment can be used as both an ultrasonic generator and an ultrasonic receiver, despite having the same configuration, thus providing the effects of improved productivity and cost reduction.

[0039] According to the embodiments described above, the following effects and advantages are achieved.

[0040] (1) The electrostatic induction vibrating element comprises a flexible member, a plurality of first comb-shaped electrodes fixed at one end in an insulated state to the flexible member and erected from the flexible member, and a plurality of second comb-shaped electrodes fixed at one end in an insulated state to the flexible member and erected from the flexible member at a distance from the first comb-shaped electrodes, wherein the distance between the other ends of the first comb-shaped electrodes and the second comb-shaped electrodes fluctuates when the flexible member vibrates.

[0041] With this configuration, the electrostatic induction vibrator suppresses contact between the comb-shaped electrodes, providing an electrostatic induction vibrator that is resistant to external shocks.

[0042] (2) At least one of the first comb-shaped electrode and the second comb-shaped electrode has an electret formed near its surface.

[0043] With this configuration, at least one of the first comb-shaped electrode and the second comb-shaped electrode becomes charged. Therefore, when the flexible member deforms and the distance between the first and second comb-shaped electrodes changes, electrostatic induction occurs between the comb-shaped electrodes, enabling power generation.

[0044] (3) The flexible member has a cantilever structure with one end fixed, a weight is placed at the free end of the cantilever structure, and the first comb-shaped electrode and the second comb-shaped electrode are placed in the region between the fixed end and the free end of the flexible member.

[0045] With this configuration, the weight increases the vibration of the electrostatic induction type vibrating element, which in turn increases the deformation of the flexible member, resulting in a higher output power.

[0046] (4) The extension direction of the first comb-shaped electrode and the second comb-shaped electrode is set in a horizontal direction perpendicular to the beam central axis of the cantilever beam structure of the flexible member.

[0047] With this configuration, the distance between the comb-shaped electrodes is greatly affected by the deformation of the comb-shaped electrode placement area, allowing for large variations to be obtained.

[0048] (5) The flexible member extends symmetrically around the weight and has a cantilevered beam structure with each end fixed, and the first comb-shaped electrode and the second comb-shaped electrode are installed in the region between the fixed end of the flexible member and the weight.

[0049] With this configuration, the vertical movement of the weight is restricted to a specific range, and contact between the comb-shaped electrodes due to excessive deformation of the flexible member is suppressed.

[0050] (6) The extension direction of the first comb-shaped electrode and the second comb-shaped electrode is set in a horizontal direction perpendicular to the beam central axis of the cantilevered beam structure of the flexible member.

[0051] With this configuration, the distance between the comb-shaped electrodes is greatly affected by the deformation of the comb-shaped electrode placement area, allowing for large variations to be obtained.

[0052] (7) The flexible member is formed from a film member, the first comb-shaped electrode and the second comb-shaped electrode define an opening, and the flexible member is installed so as to cover the opening.

[0053] With this configuration, the flexible film-like member vibrates upon receiving ultrasonic waves, generating electrostatic induction between the first and second comb-shaped electrodes, producing an electrical signal, and thus functioning as an ultrasonic receiver (sensor). Conversely, by applying an AC voltage to the comb-shaped electrodes, vibrations are generated, allowing it to function as an ultrasonic generator that produces ultrasonic waves from the flexible film-like member.

[0054] (8) The ultrasonic transmitting and receiving device includes a plurality of ultrasonic transducers, wherein at least one of the ultrasonic transducers functions as an ultrasonic transmitter and at least one other ultrasonic transducer functions as an ultrasonic emitter.

[0055] With this configuration, the device can be used as both an ultrasonic generator and an ultrasonic receiver, allowing for improved productivity and cost reduction.

[0056] Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0057] Furthermore, one or more of the above-described embodiments and variations may be combined as appropriate. [Explanation of Symbols]

[0058] 10, 10' Flexible member 20, 20' First comb-shaped electrode 30, 30' Second comb-shaped electrode 40 First terminal 50 Second terminal 60 weight 70 Opening 100, 200, 300 Electrostatic Induction Type Vibration Element 300R Ultrasonic Receiver (Sensor) 300T Ultrasonic Generator

Claims

1. A flexible member that bends due to external vibrations, One end of the flexible member is fixed in an insulated state, and a plurality of first comb-shaped electrodes are erected from the flexible member, A plurality of second comb-shaped electrodes are fixed at one end in an insulated state to the flexible member, and are erected at a distance from the first comb-shaped electrode from the flexible member, An electrostatic induction type vibrating element having, When the flexible member vibrates, the distance between the first comb-shaped electrode and the other end of the second comb-shaped electrode changes. An electrostatic induction type vibrating element used as an electrostatic induction type power generation element.

2. The electrostatic induction type vibrating element according to claim 1, wherein at least one of the first comb-shaped electrode and the second comb-shaped electrode has an electret formed near its surface.

3. The electrostatic induction type vibrating element according to claim 1 or 2, wherein the flexible member has a cantilever structure with one end fixed, a weight is installed at the free end of the cantilever structure, and the first comb-shaped electrode and the second comb-shaped electrode are installed in the region between the fixed end and the free end of the cantilever structure of the flexible member.

4. The electrostatic induction type vibrating element according to claim 3, wherein the extending directions of the first comb-shaped electrode and the second comb-shaped electrode are installed in a horizontal direction perpendicular to the beam central axis of the cantilever beam structure of the flexible member.

5. The electrostatic induction type vibrating element according to claim 1 or 2, wherein the flexible members are a pair, extending symmetrically around a weight and having a double-supported beam structure with each end fixed, and the first comb-shaped electrode and the second comb-shaped electrode are installed in the respective regions between the fixed ends of the double-supported beam structure of the flexible members and the weight.

6. The electrostatic induction type vibrating element according to claim 5, wherein the extending directions of the first comb-shaped electrode and the second comb-shaped electrode are installed in a horizontal direction perpendicular to the beam central axis of the cantilevered beam structure of the flexible member.

7. The electrostatic induction type vibrating element according to claim 1 or 2, wherein the flexible member is formed from a film member, the first comb-shaped electrode and the second comb-shaped electrode define an opening, and the flexible member is installed so as to cover the opening.

8. An electrostatic induction type vibrating element according to claim 7, used as an ultrasonic transducer.

9. An ultrasonic transmitting and receiving device comprising a plurality of electrostatic induction vibrating elements as described in claim 8, wherein at least one of the electrostatic induction vibrating elements functions as an ultrasonic transmitter and at least one of the electrostatic induction vibrating elements functions as an ultrasonic oscillator.

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