JP2005326310A - Vibration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration sensor capable of preventing sensitivity for detecting vibration from being lowered, and having improved shock resistance. <P>SOLUTION: This vibration sensor is equipped with a fixed electrode 4, and a diaphragm 3 wherein the surface facing to the fixed electrode 4 functions as a vibrating electrode and a weight 1 is provided on the surface on the opposite side of the vibrating electrode. In the sensor, the weight 1 is displaced in the direction orthogonal to the surface of the diaphragm 3, and a vibration detection signal is outputted based on the change of a capacitance between the fixed electrode 4 and the diaphragm 3. The weight 1 is formed circularly, and the sensor is also equipped with a regulation member 2 in contact with the weight 1, for regulating displacement of the weight 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a fixed electrode and a vibration plate having a surface facing the fixed electrode functioning as a vibration electrode, and a weight provided on a surface opposite to the vibration electrode, and orthogonal to the surface of the vibration plate. The present invention relates to a vibration sensor that outputs a vibration detection signal based on a change in electrostatic capacitance between the fixed electrode and the diaphragm.

  An electrostatic capacitance detection type, that is, an electret condenser microphone (hereinafter referred to as “ECM”) type vibration sensor is widely used in various applications including a microphone and a pedometer. For example, Patent Document 1 discloses a technique of an ear microphone that detects bone conduction vibration. In this document, in order to satisfactorily detect a minute vibration called bone conduction vibration, a weight (weight) is attached to the movable electrode (corresponding to a diaphragm), and the mass of the movable electrode is substantially increased. A method for increasing the sensitivity by increasing the amplitude is shown. In addition, in order to improve the followability to high-frequency vibration, a method for improving the frequency characteristics by making the movable electrode into a piece with one end fixed or providing an annual ring-like slit is shown.

  Further, in Patent Document 2, in order to satisfactorily detect vibration in a low frequency (frequency) region such as when walking, a weight is applied to an impact applying means and a movable electrode that vibrates due to the impact applied by the impact applying means. The structure which provides is shown. That is, the vibration applying means transmits the vibration at a low frequency to the movable electrode, and the movable electrode is configured so as to have a higher natural vibration than the detected frequency, so that the vibration in the low frequency region such as when walking is satisfactorily performed. To be able to detect.

JP-A-59-79700 (FIGS. 2 to 3, FIG. 6, top of pages 1 and 2 and bottom left of page 3) Japanese Patent Laid-Open No. 10-9944 (FIG. 1, paragraphs 0006 to 0019)

  By adopting the configuration as described above, it is possible to increase the inertial force and increase the sensitivity of the sensor. However, when the inertial force increases and the amplitude increases, the impact resistance during dropping is impaired. That is, there is a high possibility that the diaphragm is damaged or deformed by an impact. As a countermeasure, there is a method of providing a regulating member to regulate excessive displacement of the weight. In this case, unless the gap between the weight and the regulating member is narrowed, the regulating effect cannot be obtained sufficiently, and the diaphragm is allowed to be damaged or deformed. However, if the gap is made too narrow, the required amplitude is also restricted, so this gap needs to be provided with high accuracy. For this reason, accuracy is required for assembling. As a result, the assembling property is deteriorated, and there is a problem that the performance variation of the product becomes large due to an assembling error.

  Further, the vibration sensor has been miniaturized, and as the sensor size is reduced, the gap is also reduced. If it does so, the escape route of the air which exists between a weight and a control board will also become narrow, and this air will act so that vibration of a weight may be resisted. This is called air damping, and the smaller the sensor, the greater the effect of this air damping on the amplitude of the weight (diaphragm).

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vibration sensor with improved impact resistance while preventing the sensitivity of vibration detection from being lowered.

  The characteristic configuration of the vibration sensor according to the present invention for achieving the above object is that a fixed electrode and a surface facing the fixed electrode function as a vibration electrode, and a weight is provided on the surface opposite to the vibration electrode. The weight is displaced in a direction perpendicular to the surface of the diaphragm, and a vibration detection signal is output based on a change in capacitance between the fixed electrode and the diaphragm. In addition, the weight is formed in an annular shape, and a regulating member that regulates the amount of displacement of the weight in contact with the weight is provided.

  According to this characteristic configuration, since the weight is formed in an annular shape, for example, compared with a case where the weight is formed in a columnar shape, the weight having the same mass and the weight spreading in the radial direction of the vibration sensor or the vibration plate is used as the vibration plate. Can be attached. Then, it is possible to make contact with the regulating member that regulates the amount of displacement of the weight on the outer side in the radial direction, and when the annular weight is displaced with excessive oscillation about the diameter, the displacement is further reduced. It can regulate suitably. For example, when the weight is provided in an annular shape, the length to the outside in the radial direction of the weight is constant. Therefore, even if the diaphragm is displaced with excessive oscillation in any direction, the excessive displacement can be regulated in the same manner. As a result, the load applied to the diaphragm is reduced, and damage and deformation of the diaphragm can be prevented.

  Moreover, the said structure WHEREIN: It is preferable in the said control member being a control board which has a hole in the center.

  When the vibration sensor is downsized, the problem of air damping becomes obvious as described above. However, the weight is annular, and the center of the regulating plate that regulates the displacement of the weight is configured to have a hole. Then, this air damping problem can be reduced. For example, if the restricting member is configured without a hole, the air between the restricting member and the weight is caused by the gap between the restricting member and the weight, and the weight and the vibration sensor case on the outside in the radial direction. It is necessary to move between and between the spaces. However, if a hole is provided in the restriction plate as the restriction member, air can move through the hole in the restriction plate. At this time, if the weight is not annular, the weight is displaced so as to block the hole of the restricting plate, so that a portion where the air flow between the weight and the restricting plate is hindered occurs. However, when the weight is configured in an annular shape, the hole in the center of the weight is opposed to the hole in the center of the weight and the hole in the center of the weight and the hole in the restriction plate. The air flow is unhindered. As a result, the problem that the amplitude of the diaphragm is limited by air damping can be reduced.

  In addition, the diaphragm is provided with a slit, and a vibration part located at a central part and provided with the weight, a fixing part located at a peripheral part and fixing the diaphragm, the vibration part and the fixing part It is preferable to be divided and formed into an elastic support portion that connects the two.

  When the diaphragm is formed as described above, since the elastic support portion has a spring structure, sufficient amplitude can be obtained and sensitivity can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of a vibration sensor according to the present invention, and FIG. 2 is a cross-sectional view of the vibration sensor shown in FIG. As shown in FIGS. 1 and 2, the vibration sensor according to one embodiment of the present invention includes a fixed electrode 4 in which an electret layer 6 is formed on the inner surface of a housing 5, and a surface facing the fixed electrode 4 as a vibration electrode. And a vibration plate 3 having a weight 1 provided on the surface opposite to the vibration electrode. The weight 1 is displaced in a direction perpendicular to the surface of the vibration plate 3, and the fixed electrode 4 and the vibration plate 3 A vibration detection signal is output based on a change in capacitance between the first and second weights. The weight 1 is formed in an annular shape, and the weight plate 1 is in contact with the weight 1 to restrict the displacement of the weight (a restriction member). ) 2.

  The fixed electrode 4 is provided at the bottom of a cylindrical housing 5 having an electret layer 6 formed on the inner surface and one end opened. A ring-shaped resin spacer 7 and the diaphragm 3 are attached to the bottom, and a predetermined interval of the capacitor portion for detecting a change in capacitance is provided by the thickness of the spacer 7. A weight 1 is attached to the diaphragm 3, a regulating ring 8 capable of regulating displacement of the weight 1 in the surface direction of the diaphragm 3 (hereinafter, “lateral direction”), and a direction orthogonal to the surface of the diaphragm 3 (hereinafter, The regulating plate 2 capable of regulating the displacement of the weight 1 in the “vertical direction”) and the gate ring 9 are sequentially stacked. Then, the structure is such that the vibration sensor is assembled by covering the substrate 10 on which the output circuit of the vibration detection signal is mounted and fastening it to the housing 5. In this structure, the diaphragm 3 is fixedly supported by being sandwiched between a spacer 7 and a regulating ring 8. Moreover, the housing 5, the regulation ring 8, and the gate ring 9 are made of metal. The regulating ring 8 also serves as a raising ring for forming an interval for obtaining a sufficient amplitude for the weight 1 that is displaced in a direction orthogonal to the surface of the diaphragm 3.

  For the diaphragm 3, stainless steel, tungsten, 42 alloy, Ti-Cu, Be-Cu, or SK material can be used. In particular, when a hard material such as Ti—Cu, Be—Cu, or SK material is used in consideration of resistance to drop impact, there is no need to consider excessive displacement in the lateral direction. Will be solely responsible for the function of the raised ring.

  FIG. 3 is a diagram showing an example of dividing and forming the diaphragm of the vibration sensor according to the present invention. As shown in FIG. 3, the diaphragm 3 is provided with slits 11, a vibration part 33 provided at the center and provided with the weight 1, and a fixing part 31 located at the periphery and fixing the diaphragm 3. The elastic support portion 32 that connects the vibration portion 33 and the fixed portion 31 is divided. Further, the weight 1 is formed in an annular shape with a hole 13 in the middle in the vibrating portion 33 of the diaphragm 3. By forming the weight 1 in an annular shape in this way, the weight 1 can be attached wider in the radial direction of the diaphragm 3 with the same weight 1 as compared with the case where the weight 1 is formed in a columnar shape, for example. As a result, as shown in FIG. 4A, when the weight 1 is displaced with excessive oscillation about the diameter of the diaphragm 3, it comes into contact with the regulating plate 2 on the outer side of the diameter. That is, the vibration plate 3 comes into contact with the regulating plate 2 in a state where the shake in the surface direction is a smaller angle. As a result, the swing about the diameter of the weight 1 can be effectively suppressed, the excessive displacement of the weight 1 can be preferably suppressed, and the breakage and deformation of the diaphragm 3 can be prevented.

  An example of the weight regulating action by the regulating member of the vibration sensor according to the present invention is shown in FIG. As described above, in this example, since the annular weight 1 is provided, the shape is larger in the radial direction than the cylindrical weight 1, for example. Therefore, it is possible to contact the regulating plate 2 that regulates the amount of displacement of the weight 1 on the outer side in the radial direction, and when the weight 1 is displaced with excessive oscillation about the diameter, the displacement is more suitably performed. Can be regulated. That is, when the weight 1 is excessively swung, an angle A (see FIG. 4A) formed by a part of the weight 1 coming into contact with the restriction plate 2 is an excessive swing of the cylindrical weight 1. When the movement occurs, the angle is smaller than an angle B (see FIG. 4B) formed by a part of the weight 1 contacting the restriction plate 2. As a result, the load on the diaphragm 3, particularly the elastic support portion 32 is reduced, and the diaphragm 3 can be prevented from being damaged or deformed. For example, when the weight is provided in an annular shape, the length to the outside in the radial direction of the weight is constant. Therefore, even if the diaphragm is displaced with excessive swinging in any direction, it is preferable because the excessive displacement can be similarly controlled.

Further, since the weight 1 has an annular shape having a hole 13 in the center, and the restriction member that contacts the weight 1 and restricts the amount of displacement of the weight 1 is the restriction plate 2 having the hole 12 in the center, the weight 1 When displaced in the vertical direction, air existing between the regulating plate 2 and the weight 1 can smoothly move through the holes 13 and 12. An example of the air flow between the regulating member and the weight of the vibration sensor according to the present invention is shown in FIG. FIG.5 (b) is an example at the time of forming the weight 1 in the column shape. In this case, since the weight 1 is not annular, even if the hole 12 is provided in the central portion of the regulating plate 2, it is displaced so as to close the hole 12 by the columnar weight 1. As a result, the air flow becomes worse as indicated by the arrows in the figure. Air damping due to the displacement of the weight 1 affects the amplitude of the diaphragm 3.
However, as shown in FIG. 5 (a), when the weight 1 is formed in an annular shape, the hole 13 of the annular weight 1 is opposed to the hole 12 portion of the restricting plate 2. Can flow through the hole 13 of the weight 1 and the hole 12 of the restricting plate 2, and the air flow is not hindered. That is, air smoothly flows through the hole 13 of the weight 1 and the hole 12 of the restriction plate 2 as shown by the arrows in the drawing. As a result, the influence of air damping due to the displacement of the weight 1 on the amplitude of the diaphragm 3 is reduced.

  When the size of the vibration sensor is reduced, the gap between the weight 1 and the restriction plate 2 is also reduced accordingly, and the influence of air damping on the amplitude of the vibration plate 3 is increased. By configuring as described above, This problem of air damping can be improved satisfactorily.

  FIG. 3 includes an outer track positioned on the fixed portion 31 side, an inner track positioned on the vibrating portion 33 side, and a substantially S-shaped connecting track connecting the outer track and the inner track. The shape slit 11 was illustrated. And by this slit 11, the elastic support part 32 of the diaphragm 3 has one end part 32a that is a boundary part with the fixed part 31 and the other end part 32b that is a boundary part with the vibration part 33, and this It will be formed in the beam-like body which consists of the center part 32c located between both ends and narrower than this both ends.

  The amplitude of the diaphragm 3, that is, the amplitude of the vibrating portion 33 is given by the elasticity of the central portion 32 c of the elastic support portion 32 of the beam-like body. Therefore, in order to obtain a large amount of this elastic effect, the elastic support portion is preferably formed to be elongated. However, since the end portions 32a and 32b of the elastic support portion 32, which is a boundary portion between the elastic support portion 32 and the fixed portion 31 or the vibration portion 33, serve as fulcrums of the elastic support portion 32 that is elastically moved, a certain degree of strength. It is preferable to be formed so as to be able to hold. This is to make it difficult to cause breakage such as cracks due to vibration and deformation due to torsion. Therefore, the diaphragm 3 has a slit shape such that both end portions 32a and 32b of the elastic support portion 32 are formed thicker than the central portion 32c, so that the diaphragm 3 can obtain a lot of elastic effects and increase the strength. Good amplitude can be obtained over a long period of time.

  Further, the diaphragm 3 is not limited to the shape shown in FIG. 3, but may be formed in another shape. That is, the slit 11 that divides and forms the diaphragm 3 into the fixing portion 31, the elastic support portion 32, and the vibrating portion 33 is formed continuously from the fixing portion 31 toward the vibrating portion 33, and the adjacent slits 11 are fixed. Since the part 31 side and the vibration part 33 side are provided at equal intervals along the circumferential direction so as to overlap with each other in the radial direction, a plurality of elastic support portions 32 may be formed at equal intervals in the circumferential direction. It can also be formed.

  As shown in FIG. 6, the slit 11 may be formed along a spiral trajectory from the fixed portion 31 side toward the center of the vibrating portion 33. In the spiral track, the curvature of the track becomes larger (the radius of curvature is smaller) toward the center, and the curvature becomes smaller (the radius of curvature is larger) toward the periphery. That is, the slit 11 along the spiral trajectory is formed such that the end portion on the vibrating portion 33 side enters the center side and the end portion on the fixed portion 31 side extends to the peripheral portion. Therefore, the end portion 32b or the fixed portion 31 on the vibrating portion 33 side of each elastic support portion 32 formed between the end portion on the vibrating portion 33 side or the end portion on the fixed portion 31 side of each slit formed between the adjacent slits. The side end portion 32 a is formed to have a wider width than the central portion 32 c of each elastic support portion 32. Further, in this case, since the slit 11 is formed by a series of curved orbits, the force that resists distortion against an impact in the surface direction of the diaphragm 3 is further increased. For this reason, sufficient amplitude can be obtained and sensitivity can be improved, and even when an impact is applied, a structure that is resistant to breakage and deformation can be obtained.

  Moreover, the example of the shape (shape of the elastic support part 32) of another slit 11 is shown. The slit 11 provided in the diaphragm 3 shown in FIG. 7 is a saddle type with an outer track positioned on the fixed portion 31 side, an inner track positioned on the vibrating portion 33 side, and the outer track and the inner track in a radial track. And a connecting track connected to the. If comprised in this way, since an outer track and an inner track are connected in a saddle shape with a track in the radial direction, for example, the outer track and the inner track can be formed by arcs having different diameters. The shape of the slit can be easily designed, and the elasticity and strength of the formed elastic support portion can be easily calculated.

  As described above, according to the embodiment as described above, it is possible to provide a vibration sensor in which the sensitivity for detecting vibration is not lowered and the impact resistance is improved.

The perspective view which shows an example of the vibration sensor which concerns on this invention Sectional view of the vibration sensor shown in FIG. The figure which shows the 1st example which divides and forms the diaphragm of the vibration sensor which concerns on this invention. The figure which shows an example of the control effect | action of the weight by the control member of the vibration sensor which concerns on this invention The figure which shows an example of the flow of the air between the control member of the vibration sensor which concerns on this invention, and a weight. The figure which shows the 2nd example which divides and forms the diaphragm of the vibration sensor which concerns on this invention. The figure which shows the 3rd example which divides and forms the diaphragm of the vibration sensor which concerns on this invention.

Explanation of symbols

1 Weight 2 Regulating plate
3 Diaphragm 4 Fixed electrode

Claims (3)

A fixed electrode, and a surface facing the fixed electrode functions as a vibration electrode, and a vibration plate provided with a weight on a surface opposite to the vibration electrode,
The weight is displaced in a direction perpendicular to the surface of the diaphragm;
A vibration sensor that outputs a vibration detection signal based on a change in capacitance between the fixed electrode and the diaphragm,
And forming the weight in an annular shape,
A vibration sensor comprising a regulating member that contacts the weight and regulates a displacement amount of the weight.   The vibration sensor according to claim 1, wherein the restriction member is a restriction plate having a hole in the center. The diaphragm is provided with a slit,
It is divided into a vibration part located in the central part and provided with the weight, a fixing part located in the peripheral part and fixing the diaphragm, and an elastic support part connecting the vibration part and the fixing part. The vibration sensor according to claim 1 or 2.

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