JP2009042240A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized acceleration sensor of high detection sensitivity. <P>SOLUTION: This acceleration sensor 1 is a vibratory body 10 having a base part 20 fixed on a base and a beam-shaped vibration arm 21 extended out of the base part 20 and bendingly vibrating in a planar direction at a prescribed resonance frequency. The vibration arm 21 includes: vibration arm parts 23 and 24 separated from each other by a through hole 22 bored therethrough at its width direction middle part, vertically to its thickness direction, and in its longitudinal direction; an additional mass part 25 together connecting end parts of the arm parts 23 and 24 separated from each other; and excitation electrodes 31 to 34 provided as excitation means on the arm parts 23 and 24. The vibration arm 21 is supported by a pseudo both-end fixation structure or a single-end fixation structure, having the base part 20 and the mass part 25, and used for detecting a change in the resonance frequency of the vibratory body 10 owing to an inertia effect of the mass part 25 when acceleration is given thereto. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an acceleration sensor that detects that the resonance frequency of a vibrating body changes when acceleration is applied.

2. Description of the Related Art Conventionally, a bending spring, a resonator, and silicon having a vibrating mass suspended on a frame, acceleration is detected based on a change in the frequency of the resonator, and the bending spring, the frame, and the vibrating mass have a structure of a silicon plate. There is known an acceleration sensor created by conversion (see, for example, Patent Document 1).

A cantilever having one end fixed on the substrate of the silicon wafer and the other having a deformable free end; a piezoelectric element film formed on the surface of the cantilever; and metal electrodes formed on both front and back surfaces of the piezoelectric element film; There is known an acceleration sensor including a piezoelectric vibrator composed of a weight fixed to a free end of a cantilever (see, for example, Patent Document 2).

In addition, a plate-shaped vibrating body, a piezoelectric element formed to face both surfaces of the vibrating body, and a supporting means for supporting one end of the vibrating body, a hole is formed near one end of the vibrating body, The vibrating body vibrates in the length direction (that is, longitudinal vibration). An acceleration sensor is also known in which a vibrating body and a piezoelectric element bend due to acceleration in the vibration direction of the vibrating body, and a voltage generated in the piezoelectric element due to this bending is detected (for example, see Patent Document 3).

Furthermore, an inertial body that can be moved by acceleration, a support beam that supports the inertial body and deforms when the inertial body moves, and a resonator that is installed on the support beam, the resonator detects the excitation unit and the vibration state. It consists of a receiving part and a propagation part that propagates vibration from the excitation part to the receiving part, and when acceleration is applied,
An acceleration sensor that measures the applied acceleration by detecting changes in the vibration state of the resonator caused by the deformation of the resonator corresponding to the deformation of the support beam from the input signal to the excitation unit and the output signal to the reception unit Is known (see, for example, Patent Document 4).

JP-A-6-43179 (page 3, FIG. 1) JP-A-2-248865 (second and third pages, FIGS. 3 and 9) JP-A-8-146033 (page 3, FIGS. 1 and 2) Japanese Patent Laid-Open No. 7-191052 (pages 1, 2 and 1)

In Patent Document 1 described above, the amount of change in the frequency of the resonator that occurs when the flexure spring is deflected by applying acceleration is detected. In addition, a vibrating mass is added to increase detection sensitivity. Also in Patent Document 2, the detection sensitivity is increased by adding a weight to the tip of the cantilever. And since these vibration masses and weights are provided in the direction in which acceleration is applied, it is considered that the energy required to vibrate the vibrating body increases and the impact resistance decreases.
In addition, there is a problem that it is difficult to reduce the size of the acceleration sensor.

In Patent Document 3, longitudinal vibration of a vibrating body is used. In the case of longitudinal vibration, the amount of change in frequency is extremely small compared to bending vibration, and it is difficult to increase detection sensitivity. In addition, there is a problem that the support structure of the vibrating body is complicated and vibration leakage is likely to occur.

Furthermore, since a hole is provided in the vicinity of one end portion of the vibrating body and stress concentration tends to occur at the peripheral portion of the hole, there is a problem that impact resistance is reduced.

Further, the acceleration sensor according to Patent Document 4 has a structure in which deformation generated in the support beam is detected by a resonator bonded to the support beam. The support beam and the resonator are made of different materials and have different coefficients of thermal expansion. Therefore, a difference in deformation of the support beam or the resonator due to a temperature change occurs, which is output as a frequency change, resulting in poor temperature characteristics. It has a problem.

In addition, since the support beam and the resonator are joined, there is a problem that a force propagation loss due to acceleration occurs at the joint, and it is difficult to ensure long-term reliability at the joint.

In addition, accurate acceleration detection requires the position accuracy of the resonator relative to the support beam, but the support beam and the resonator are separate members, which makes it difficult to achieve position accuracy, increasing manufacturing costs, and reducing the size. It is predicted that it will be difficult.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1] An acceleration sensor according to this application example includes a base portion fixed to a base and a beam-like vibrating arm extending from the base portion and bending-vibrating in a plane direction at a predetermined resonance frequency. The vibrating arm is divided by a through-hole that is formed in the center in the width direction perpendicular to the thickness direction and in the longitudinal direction, and the distal end portion of the divided vibrating arm portion And an excitation means provided on the vibrating arm, and the vibrating arm is supported by the base and the additional mass in a pseudo double-end fixed structure or a single-end fixed structure, and an acceleration is provided. A change in the resonance frequency of the vibrating body due to the inertial effect of the additional mass when added is detected.

The pseudo-both-end fixed structure is, for example, that the base of the vibrating body is a fixed end and the tip of the vibrating arm (the portion corresponding to the additional mass) is a free end, but the tip is not large because the additional mass is large. It means a fixed structure that hardly vibrates.

According to this application example, when the acceleration is applied, the resonance effect of the vibrating body is changed by the expansion and contraction stress (tensile stress and compressive stress) generated in the vibrating arm due to the inertial effect of the additional mass part. Thus, the acceleration is detected. Specifically, when a tensile stress is generated in the vibrating arm, the resonance frequency is high, and when a compressive stress is generated in the vibrating arm, the resonance frequency is low. Since this vibrating body is a flexural vibration of a one-end fixed structure, the amount of change in the resonance frequency due to the application of acceleration becomes larger than the longitudinal vibration of the prior art described above, and an acceleration sensor with high detection sensitivity can be realized.

In addition, since the through-hole is provided in the longitudinal direction of the vibrating arm, the cross-sectional area of the vibrating arm is reduced, and the electric field efficiency is high because the distance between the excitation electrodes provided on the side surfaces is small, resulting in low current consumption. be able to.

Further, the vibrating arm is divided into two vibrating arm portions having a small cross-sectional area by the through hole. Therefore, the expansion and contraction stress generated in the bent portion when acceleration is applied increases, and the amount of change in the resonance frequency increases, so that the detection sensitivity can be increased.

Furthermore, since the acceleration sensor according to this application example has a structure that detects a change in the resonance frequency due to the stretching stress generated in the vibrating arm, when the vibrating body is packaged, the length of the vibrating arm in the longitudinal direction due to the acceleration is extremely low. It is sufficient if there is a space in a range where the vibrating arm is flexibly vibrated, and the size can be reduced.

In addition, since the acceleration sensor according to this application example has the base portion and the vibrating arm integrally formed, the support beam and the resonator according to the above-described prior art (Patent Document 4) are configured separately and joined. In addition, the deformation difference of the support beam or the resonator due to the temperature change caused by the difference in thermal expansion coefficient is not output as a frequency change, and an acceleration sensor with good temperature characteristics can be realized.

In addition, since there is no joint compared to the structure in which the support beam and the resonator are joined as in the prior art, there is no loss of force propagation caused by acceleration at the joint, and long-term reliability is achieved. There is an effect that it can be secured.
Furthermore, since the base portion and the vibrating arm are integrally formed in the same plane, there is no projecting portion in the thickness direction, and a reduction in thickness can be realized.

Application Example 2 In the acceleration sensor according to the application example, the base, the vibrating arm,
Two sets of vibrating bodies including the additional mass portion are provided, and the two sets of additional mass portions are common additional mass portions, and two sets of the additional mass portions are symmetrical with respect to the center of gravity of the common additional mass portion. It is preferable that the vibrating bodies are connected linearly.

According to such a structure, a structure having a pair of vibrating bodies facing each other with the additional mass portion interposed therebetween is configured. At this time, each of the vibrating arms facing each other has a sufficiently large mass, so that a vibrating body having a high-order bending vibration mode having an opposite phase to each other and having a good vibration balance can be formed. . That is, a high Q value is obtained.

Further, when acceleration is applied, compressive stress is generated in one vibrating arm portion of adjacent vibrating arm portions, and tensile stress is generated in the other vibrating arm portion. In the case of such a structure, there is an effect that the influence of the frequency temperature characteristic can be canceled by taking the difference between the resonance frequencies of both vibrators.

Application Example 3 The acceleration sensor according to this application example includes a base fixed to a base and a plurality of beam-like vibrations extending in parallel from the base and bending-vibrated in a plane direction at a predetermined resonance frequency. Arms,
Each of the plurality of vibrating arms has at least one through-hole formed perpendicularly to the vibration direction and in the longitudinal direction at the center in the width direction of each of the plurality of vibrating arms, and tip portions of the plurality of vibrating arms. An additional mass part to be connected, excitation electrodes provided on both side surfaces of each of the plurality of vibrating arms and the inner side surface of the through hole, and the inertial effect of the additional mass part when acceleration is applied It is characterized by detecting a change in the resonance frequency of the vibrating body.

In the acceleration sensor configured as described above, through holes are provided in a plurality of vibrating arms having tip portions connected by additional mass portions. Therefore, since the cross-sectional area of the vibrating arm is reduced and the displacement amount of the vibrating arm when acceleration is applied can be increased, the detection sensitivity can be increased.
Furthermore, since the excitation electrodes are provided on both side surfaces of the vibrating arm and the inner side surface of the through hole, the distance between the excitation electrodes is shortened and the electric field efficiency is increased. This has the effect of reducing power consumption.

Application Example 4 In the acceleration sensor according to Application Example 3, it is preferable that the through hole is provided in the vicinity of a connection portion between at least the plurality of vibrating arms and the base portion.

The vicinity of the connecting portion between the vibrating arm and the base is a position where the distortion is the largest in bending vibration. Therefore, by providing a through hole at a position where such distortion is large and providing excitation electrodes on both side surfaces of the vibrating arm and the inner side surface of the through hole, the distance between the excitation electrodes is shortened, and the electric field efficiency can be increased. Low power consumption can be realized.

[Application Example 5] The acceleration sensor according to Application Example 3, wherein the through hole has a plurality of vibrating arms in the vicinity of a connection part with the base, a connection part with the additional mass part, and a longitudinal direction. The central part,
It is preferable to be established in

In this way, the electric field efficiency can be further improved by providing the position where the distortion is greatest in the bending vibration, the through hole in the center part and the tip part of the vibrating arm, and providing the excitation electrode.
Low power consumption can be realized.

[Application Example 6] The acceleration sensor according to Application Example 3, wherein two sets of vibration bodies each including the base portion, the plurality of vibrating arms in which the through holes are opened, and the additional mass portion are provided, It is preferable that two sets of the additional mass portions are common additional mass portions, and the two sets of the vibrating bodies are linearly connected so as to be point-symmetric with respect to the position of the center of gravity of the common additional mass portion.

In this way, a vibrating body having a both-ends fixed structure having a vibrating body composed of a pair of curved vibrating arms facing each other with the additional mass portion interposed therebetween is configured. At this time, the vibrating arms facing each other can form a vibrating body having an antiphase high-order bending vibration mode and a good vibration balance. That is, a high Q value is obtained.

Application Example 7 In the acceleration sensor according to the application example described above, it is preferable that the vibrator is made of quartz.

The material of the vibrating body is not particularly limited as long as it is a piezoelectric material, but if it is made of quartz, it has good frequency-temperature characteristics, and can be easily formed integrally by photolithography technology, including through-holes. Can be formed with high accuracy.

[Application 8] In the acceleration sensor according to the application example described above, it is preferable that the vibrating body is made of a constant elastic material, and a piezoelectric element film is formed on a side surface of the vibrating arm.

The constant elastic material includes, for example, nickel, iron, chromium, titanium, or an elimba or an iron-nickel alloy thereof.
As described above, the use of a constant elastic material as the vibrator increases the structural strength and has an effect of being able to cope with detection of a strong acceleration region.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show an acceleration sensor according to Embodiment 1, FIG. 6 shows Embodiment 2, FIG. 7 shows Embodiment 3, FIG. 8 shows Embodiment 4, FIG. 9 shows Embodiment 5, and FIG. FIG. 11 shows the seventh embodiment.
Is shown.
Note that the drawings referred to in the following description are schematic views in which the vertical and horizontal scales of members or portions are different from actual ones for convenience of illustration.
(Embodiment 1)

FIG. 1 shows an example of an acceleration sensor according to the first embodiment, where (a) is a front view and (b) is (a
It is sectional drawing which shows the HH cut surface of FIG. In FIG. 1 (a), the acceleration sensor 1 has a base (
The vibrating body 10 includes a base 20 that is fixed to the base 20 and a beam-like vibrating arm 21 that extends from an end face of the base 20 and flexurally vibrates in a plane direction at a predetermined resonance frequency.

The vibrating body 10 is made of a piezoelectric material. As a piezoelectric material, lead titanate (P
bTiO ₃ ), lead zirconate titanate (PZT (registered trademark)), zinc oxide (ZnO), quartz, and the like can be used. In this embodiment, however, the quartz has excellent frequency-temperature characteristics and a high Q value. The case where is used will be described as an example.

The vibrating body 10 is a Z plate developed on the XY plane, and is configured by extending a simple beam-like vibrating arm 21 from the center of one side of the base 20 in the Y-axis direction. The base 20 is a fixing part for fixing the vibrating body 10 to a base of a package (not shown). The central portion of the vibrating arm 21 in the width direction (X-axis direction) is perpendicular to the vibrating direction of the vibrating arm 21, that is, penetrates in the thickness direction (Z-axis direction) and extends in the longitudinal direction (Y-axis direction). A through-hole 22 is opened along.

An additional mass portion 25 is formed at the tip (free end) of the vibrating arm 21. Additional mass part 2
In this embodiment, the plane size is set so that the mass is equal to or larger than the base 20 in this embodiment. Further, one end portion of the through hole 22 reaches the connecting portion with the base portion 20, and the other end portion reaches the connecting portion with the additional mass portion 25.
In addition, the magnitude | size of the additional mass part 25 can be set to arbitrary magnitude | sizes in the range used as the pseudo | simulation both-ends fixing structure mentioned above.

The vibrating arm 21 is divided into a vibrating arm portion 23 and a vibrating arm portion 24 by a through-hole 22, and the distal end portion is connected by an additional mass portion 25. The vibrating arm portions 23, 24 are center axes P of the vibrating arm 21.
Is symmetrical. Excitation electrodes are formed on the side surfaces of the vibrating arm portions 23 and 24, respectively.

Next, the configuration of the excitation electrode as the excitation means will be described with reference to FIG. An excitation electrode 31 is formed on the outer side surface 23a of the vibrating arm 23, and an excitation electrode 33 is formed on the inner side surface 23b. An excitation electrode 32 is formed on the outer surface 24a of the vibrating arm 24, and an excitation electrode 34 is formed on the inner surface 24b. Excitation electrodes 31-34 are formed in the whole range of the side surface of through-hole 22 in the Y-axis direction. The excitation electrodes 31 to 34 also serve as detection electrodes.

The excitation electrodes 31 and 32 are electrodes having the same potential, and the excitation electrodes 33 and 34 are excitation electrodes 31 and 32.
Are electrodes having different potentials, and although not shown, each extends to the surface of the base 20,
It is connected to an oscillation circuit and a detection circuit (not shown).

When excitation signals having opposite potentials are input to the excitation electrodes 31 and 32 and the excitation electrodes 33 and 34 from the oscillation circuit, the resonating arm 21 will perform primary bending vibration with the vicinity of the connecting portion with the base 20 as a vibration node. Then, since the additional mass part 25 is large, it resonates by secondary bending vibration as shown in FIG.

That is, when an excitation signal is input to the vibrating arm 21, the tip of the additional mass portion 25 tries to vibrate in the direction of arrow C, but there is a large additional mass portion 25, so that the amount of movement is very small and vibration occurs. The arm 21 exhibits a secondary bending vibration as indicated by a two-dot chain line C ′.

Similarly, when the tip of the additional mass portion 25 tries to vibrate in the direction of the arrow B, the additional mass portion 25 exists, so that the amount of movement is very small, and the vibrating arm 21 is indicated by a broken line B ′. Such secondary bending vibration occurs.

Therefore, although such a vibrating body 10 has a one-end fixed structure in which the base portion is a fixed portion, by making the additional mass portion 25 equal to or larger than the base portion 20, It can be said that a pseudo-both-end fixing structure is formed between the two. Therefore, the vibrating arm 21 becomes a higher-order flexural vibration mode having vibration nodes in the vicinity of the connecting portion between the vibrating arm 21 and the base portion 20 and in the vicinity of the connecting portion between the vibrating arm 21 and the additional mass portion 25. .

Next, acceleration detection will be described.
In FIG. 1A, when acceleration + Ay in the + Y-axis direction is applied when the vibrating arm 21 is subjected to secondary bending vibration at a predetermined resonance frequency in the X-axis direction, A compressive stress is generated in the connecting portion and the bent portion due to the inertia effect of the additional mass portion 25. When compressive stress is generated, the resonance frequency changes in the direction of lowering. Further, when the acceleration −Ay is applied in the −Y-axis direction, tensile stress is generated in the connecting portion and the bent portion of the vibrating arm 21 with the base portion 20. When a tensile stress is generated, the resonance frequency changes in a higher direction.

This change in resonance frequency can be detected by a detection circuit, and the detected resonance frequency can be converted into a voltage by a conversion circuit (not shown) and detected as an acceleration.
The resonance frequency may be regarded as the phase velocity, and the change value of the phase velocity may be differentiated with respect to time by a differentiation circuit to obtain acceleration.

Therefore, according to the first embodiment described above, the resonance of the vibrating body 10 due to the expansion and contraction stress (tensile stress and compression stress) generated in the vibrating arm 21 due to the inertial effect of the additional mass portion 25 when acceleration is applied. The acceleration is detected by utilizing the change in frequency. Specifically, when a tensile stress is generated in the vibrating arm 21, the resonance frequency increases, and the vibrating arm 21
When compressive stress is generated, the resonance frequency is lowered. Therefore, according to the vibrating body 10, the amount of change in the resonance frequency due to the application of acceleration is larger than the longitudinal vibration of the conventional technology described above, and an acceleration sensor with high detection sensitivity can be realized.

Further, by providing the through-hole 22 in the longitudinal direction of the vibrating arm 21, the vibrating arm portions 23, 2 are provided.
Since the sectional area of 4 is reduced and the distance between the excitation electrodes provided on the side surfaces is reduced, the electric field efficiency is high, and as a result, the current consumption can be kept low.

The vibrating arm 21 is divided into two vibrating arm portions 23 and 24 having a small cross-sectional area by the through hole 22. Therefore, the expansion and contraction stress generated in the bent portion when acceleration is applied increases, and the amount of change in the resonance frequency increases, so that the detection sensitivity can be increased.

Further, by making the additional mass portion 25 sufficiently large with respect to the vibrating arm, the moving amount of the tip portion of the vibrating arm 21 is extremely small. Therefore, the vibrating arm 21 is in a higher-order bending vibration mode because the pseudo both-ends fixing structure is configured between the additional mass portion 25 and the base portion 20. In such a higher-order bending vibration mode, an acceleration sensor with good detection sensitivity can be realized.

Furthermore, the acceleration sensor 1 according to the present embodiment has a structure that detects a change in resonance frequency due to stretching stress generated in the vibrating arm 21. Therefore, by providing the additional mass portion 25 having a large mass, the detection sensitivity can be increased because the tensile stress or the compressive stress generated in the bent portion when acceleration is applied is increased.

In addition, the magnitude | size of the additional mass part 25 can be set to arbitrary magnitude | sizes in the range used as the pseudo | simulated both-ends support structure mentioned above. When the vibrating body 10 is packaged, expansion and contraction in the length direction of the vibrating arm 21 due to acceleration is very small, and it is sufficient if there is a space in a range where the vibrating arm 21 performs flexural vibration, and the size can be reduced.

In addition, since the base 20 and the vibrating arm 21 are integrally formed, each of the heat beams as in the structure in which the supporting beam and the resonator according to the above-described prior art (Patent Document 4) are configured separately and joined. An acceleration sensor with good temperature characteristics can be realized without the deformation difference of the support beam or the resonator due to the temperature change caused by different expansion coefficients being output as a frequency change.

In addition, since there is no joint compared to the structure in which the support beam and the resonator are joined as in the prior art, there is no loss of force propagation caused by acceleration at the joint, and long-term reliability is achieved. There is an effect that it can be secured.
Furthermore, since the vibrating body 10 is made of quartz and the base 20 and the vibrating arm 21 are integrally formed in the same plane, the frequency temperature characteristic is good, and the through hole 22 and the through hole 22 are integrally formed by photolithography. It is easy and easy to manufacture and can be formed with high accuracy. Further, there is no protrusion in the thickness direction, and a reduction in thickness can be realized.

In addition, although Embodiment 1 mentioned above illustrates the pseudo | simulation both-ends fixing structure, it is applicable also to the vibrating body of a one-end fixing structure.
(Modification 1)

Next, an acceleration sensor according to Modification 1 of Embodiment 1 will be described with reference to the drawings. Modification 1 is characterized in that the vibrating body has a one-end fixed structure and performs primary bending vibration.
FIG. 2 is a perspective view showing the configuration of the acceleration sensor according to the first modification. In FIG. 2, the vibrating body 10 as an acceleration sensor has the same shape as that of the first embodiment (see FIG. 1) except for the additional mass portion 25. The additional mass portion 25 is provided on an extension of the vibrating arm 21, and the vibrating arm 21 is divided into vibrating arm portions 23 and 24 by through holes 22.

Excitation electrodes 31 to 34 shown in FIG. 1 are provided on the side surfaces of the vibrating arm portions 23 and 24. When excitation signals having opposite potentials are input from the oscillation circuit to the excitation electrodes 31 and 32 and the excitation electrodes 33 and 34, the resonating arm 21 performs primary bending vibration with the vicinity of the connecting portion with the base 20 as a vibration node. (Indicated by arrow A).

The acceleration is detected in the same manner as in the first embodiment. In other words, when acceleration + Ay in the + Y-axis direction is applied while the vibrating arm 21 is performing primary bending vibration at a predetermined resonance frequency in the X-axis direction, the connecting portion and the bending portion of the vibrating arm 21 with the base portion 20 are applied. , A compressive stress is generated due to the inertial effect of the additional mass portion 25. When compressive stress is generated, the resonance frequency changes in the direction of lowering. Further, when the acceleration −Ay is applied in the −Y-axis direction, tensile stress is generated in the connecting portion and the bent portion of the vibrating arm 21 with the base portion 20. When a tensile stress is generated, the resonance frequency changes in a higher direction. This change in resonance frequency can be detected by a detection circuit, and the detected resonance frequency can be converted into a voltage by a conversion circuit (not shown) and detected as an acceleration.

It has been confirmed by simulation and experiment that the amount of frequency fluctuation due to acceleration varies by changing the ratio of the length L2 of the through hole 22 to the total length L1 of the vibrating arm.
FIG. 3 is a graph showing the relationship between the ratio of the length L2 of the through hole to the total length L1 of the vibrating arm and the amount of frequency fluctuation. As shown in FIG. 3, the amount of frequency fluctuation with respect to acceleration (m / s ² ) (
ppm / (m / s ² ) is the ratio of the length L2 of the through hole 22 to the total length L1 of the vibrating arm (L2
/ L1 (expressed in%)).

From this graph, when L2 / L1 is 0 (when there is no through hole 22), the frequency fluctuation amount is 0.
. 1 ppm / (m / s ² ), indicating that acceleration can be detected even when there is no through hole 22. However, when the frequency fluctuation amount is 0.1 ppm / (m / s ² ), the detection sensitivity is low, which is not preferable for practical use.

As L2 / L1 increases, the amount of frequency fluctuation increases and shows a maximum value in the vicinity of 80%. And when L2 / L1 is in the range of ± 20% centering on 80%, the frequency fluctuation amount is about 1p.
The detection sensitivity is pm / (m / s ² ) or higher, which is a practically preferable level.

According to the first modification, the same effect as that of the first embodiment described above can be obtained even when the vibrating body 10 has a one-end fixed structure and a primary bending vibration structure.
(Modification 2)

Next, an acceleration sensor according to Modification 2 of Embodiment 1 will be described with reference to the drawings.
The modification 2 is characterized in that a large additional mass part that performs primary bending vibration is provided at the free end of the vibrating arm. Therefore, the description will focus on the differences from the first embodiment (see FIG. 1). Common parts are denoted by the same reference numerals as those in the first embodiment.
FIG. 4 is a front view showing a vibrating body according to this modification. In FIG. 4, the vibrating body 10 has a beam-like vibrating arm 21 extending vertically from the center of one side of the base 20 in the Y-axis direction. Vibration arm 2
1 in the center in the width direction (X-axis direction), penetrates in the thickness direction (Z-axis direction), and extends in the longitudinal direction (Y
A through hole 22 is formed along the axial direction.

The through-hole 22 is formed at the same position and size as in the first embodiment (see FIG. 1), and the relationship between the length of the through-hole 22 and the total length of the vibrating arm 21 including the additional mass portion 25 is also generally the embodiment. It is based on 1. An additional mass portion 25 is formed at the tip (free end) of the vibrating arm 21. The additional mass unit 25 is set to be larger than the first modification (see FIG. 2) and smaller than the first embodiment (see FIG. 1). Therefore, the vibrating arm 21 performs primary bending vibration with the vicinity of the connecting portion with the base 20 as a vibration node.

By providing the additional mass portion 25 as described above to the vibrating arm 21, the tensile stress or the compressive stress generated in the bent portion when acceleration is applied becomes larger than that in the first modification due to the increase in the mass of the vibrating arm 21. , Detection sensitivity can be increased.
(Modification 3)

Next, an acceleration sensor according to Modification 3 of Embodiment 1 will be described with reference to the drawings.
The modified example 3 is characterized in that a plurality of vibrating arms are provided in contrast to the single vibrating arm provided in the first embodiment. Here, a structure including two vibrating arms will be described as an example.
5A and 5B show a vibrating body according to the third modification, in which FIG. 5A is a front view and FIG. 5B is a cross-sectional view showing a JJ section of FIG. 5A and 5B, the vibrating body 50 as an acceleration sensor
The two vibrating arms 54 and 58 are extended from one side of the base 51 vertically and in parallel. That is, the vibrating body 50 is a tuning fork type vibrating body.

In the vibrating arms 54 and 58, through holes 55 and 59 are formed in the center in the width direction, respectively.
The shapes of the vibrating arms 54 and 58 and the through holes 55 and 59 correspond to the vibrating arm 21 and the through hole 22 of the above-described first embodiment (see FIG. 1). By providing the through holes 55 and 59, the vibrating arm 54 is divided into the vibrating arm portions 56 and 57, and the vibrating arm 58 is divided into the vibrating arm portions 60 and 57.
It is divided into 61. The vibrating arm portions 56 and 57 are connected at their distal ends with an additional mass portion 54a, and the vibrating arm portions 60 and 61 are connected at their distal ends with an additional mass portion 58a.

As shown in FIG. 5B, excitation electrodes are formed on the side surfaces of the vibrating arm portions 56, 57, 60, and 61, respectively. Specifically, an excitation electrode 71 is provided on the outer side surface 56a of the vibrating arm portion 56, and an excitation electrode 72 is provided on the inner side surface 56b. On the other hand, an excitation electrode 73 is formed on the outer surface 57a of the vibrating arm 57, and an excitation electrode 74 is formed on the inner surface 57b. Further, an excitation electrode 77 is provided on the outer side surface 60 a of the vibrating arm 60, an excitation electrode 78 is provided on the inner side surface 60 b, and the outer side surface 6 of the vibrating arm unit 61.
An excitation electrode 75 is formed on 1a, and an excitation electrode 76 is formed on the inner side surface 61b.

The excitation electrodes 71, 73, 76, 78 are an electrode group having the same potential, and the excitation electrodes 72, 74, 75, 77.
Is an electrode group of the same potential, the excitation electrodes 71, 73, 76, 78 and the excitation electrodes 72, 74, 75.
, 77 are inputted with excitation signals having opposite potentials. With this configuration, the vibrating arm 54,
58 performs primary bending vibrations so that the phases are opposite to each other in the directions of arrows B and C, that is, in the X-axis direction.

The base 51 is connected to the vibrating arms 54 and 58 by the connecting portion 52, and a vibration node exists in this region. A constricted portion 53 is formed between the connecting portion 52 and the base portion 51. Constriction part 5
3 is provided to prevent the vibrations of the vibrating arms 54 and 58 from being transmitted to the fixed portion.

Such a structure is a tuning fork type vibrating body, and the tuning fork type vibrating body has structural symmetry, and when vibrating, the vibrating arms 54 and 58 vibrate in mutually opposite phases, so that vibration leakage is small and vibration efficiency is low. There is an advantage of high.

Further, since the through-holes 55 and 59 are provided in the vibrating arms 54 and 58, respectively, the cross-sectional area of the vibrating arms 54 and 58 is reduced, so that the generated expansion / contraction stress is increased. Therefore, even in the shape having a plurality of vibrating arms, the contraction stress and the tensile stress due to acceleration are increased, and the amount of change in resonance frequency is large, so that high detection sensitivity can be obtained.
In the present embodiment, a structure including two vibrating arms is illustrated, but three or more may be used. In the case of three, the center vibrating arm can be used for detection.
(Embodiment 2)

Next, the acceleration sensor according to the second embodiment will be described with reference to the drawings. Embodiment 2
Is characterized in that it has a double-end fixing structure, whereas the first embodiment and the modification described above have a pseudo double-end fixing structure or a single-end fixing structure.
FIG. 6 is a front view showing the acceleration sensor according to the second embodiment. In FIG. 6, the acceleration sensor 40 is configured by connecting two sets of vibrating bodies 10 and 11 in a straight line at a common additional mass portion 25.

As shown in FIG. 6, the right side of the gravity center G of the acceleration sensor 40 is the vibrating body 10 including the base 20, the vibrating arm 21, and the additional mass unit 25, and the left side is the base 45, the vibrating arm 41, and the additional mass unit. The vibrating body 11 is composed of 25. The resonating arm 21 has resonating arm portions 23 and 24 divided by a through-hole 22, and excitation electrodes as shown in FIG.

On the other hand, the resonating arm 41 has resonating arm portions 43 and 44 divided by a through hole 42, and each is provided with an excitation electrode as shown in FIG. Therefore, the additional mass unit 25 is a common additional mass unit for the vibrating body 10 and the vibrating body 11. The acceleration sensor 40 has a point-symmetric shape with respect to the center of gravity position G, and two bases of the vibrator 10 and the vibrator 11 are linearly connected at the common additional mass part 25, and the base 20 and the base It is a both-ends fixing structure having 45 as a fixing part. Further, the additional mass portion 25 has a planar size that is equal to or larger than the base portions 20 and 45.

Here, when an excitation signal having a reverse potential, a reverse phase, and the same frequency is input to each of the vibrating arms 21 and 41, the additional mass portion 25 has a sufficiently large mass. It is slight. Accordingly, the resonating arm 21 has a connecting portion between the resonating arm 21 and the base portion 20 and a vibration node in the vicinity of the connecting portion between the resonating arm 21 and the additional mass portion 25, and the direction of the arrow D ′ or the arrow E
'Secondary bending vibration in the direction. The resonating arm 41 has a connecting portion between the resonating arm 41 and the base portion 45 and a vibration node in the vicinity of the connecting portion between the resonating arm 41 and the additional mass portion 25. Of bending vibration.

According to the structure of the second embodiment described above, the acceleration sensor 40 has a both-ends fixed structure having the vibrating bodies 10 and 11 that are opposed to each other with the additional mass portion 25 interposed therebetween. At this time, the respective vibrating arms 21 and 4
1 has an antiphase high-order bending vibration mode and constitutes a vibrating body having a good vibration balance. That is, a high Q value is obtained.

Further, when acceleration in the Y-axis direction is applied to the opposing vibrating arms 21 and 41, contraction stress is generated on one side, and tensile stress is generated on the other vibrating arm. In the case of such a structure, there is an effect that the influence of the frequency temperature characteristic can be canceled by taking the difference between the resonance frequencies of both vibrators.
(Embodiment 3)

Next, an acceleration sensor according to Embodiment 3 will be described with reference to the drawings. Embodiment 3
Is characterized in that a constant elastic material is used in contrast to the use of quartz as the vibrator in the first and second embodiments. Although the same concept as the shapes of the first and second embodiments can be applied to the shape of the vibrating body of the present embodiment, here, the same shape as that of the first embodiment (see FIG. 1) will be described as an example.
FIG. 7: shows the vibrating body which concerns on Embodiment 3, (a) is a front view, (b) is sectional drawing which shows the KK cut surface of (a). 7A and 7B, the vibrating body 80 is configured by extending a vibrating arm 82 from one side of a base 81 in the vertical direction. The base part 81 is a fixing part for fixing the vibrating body 80 to a base of a package (not shown). In the center of the vibrating arm 82 in the width direction,
A through hole 83 penetrating in the thickness direction and long in the longitudinal direction is formed.

The vibrating body 80 is made of a constant elastic material such as nickel, iron, chromium, titanium, or an alloy thereof such as Elinba or an iron-nickel alloy, and is selected according to a desired resonance frequency and size.

The vibrating arm 82 is divided into vibrating arm portions 84 and 85 by providing a through hole 83.
The tip ends of the vibrating arm portions 84 and 85 are connected by an additional mass portion 82a. And the vibrating arm 8
Piezoelectric element films 86 and 87 are formed on the outer side surfaces of the four and 85, respectively. FIG. 7 (b)
As shown in FIG. 4, the piezoelectric element film 86 has an upper electrode 88a and a lower electrode 88 on both the front and back surfaces.
b is formed. An insulating film (not shown) is formed between the lower electrode 88 b and the outer side surface of the vibrating arm portion 84.

On the other hand, an upper electrode 89a and a lower electrode 89b are formed on the front and back surfaces of the piezoelectric element film 87, respectively. In addition, an insulating film (not shown) is formed between the lower electrode 89 b and the outer side surface of the vibrating arm portion 85.

When an excitation signal having a reverse potential is input to each of the piezoelectric element films 86 and 87, the vibrating arm 82 performs a secondary bending vibration similar to that in the first embodiment, and continues a stable vibration at a predetermined resonance frequency. To do.
As materials for the piezoelectric element films 86 and 87, lead titanate (PbTiO ₃ ), lead zirconate titanate (PZT (registered trademark)), zinc oxide (ZnO), or the like can be used.

Therefore, according to the above-described third embodiment, the structural strength is increased by using the constant elastic material for the vibrating body 80 and the cross-sectional area of the vibrating arm portions 84 and 85 is reduced. However, there is an effect that it can cope with detection of a strong acceleration region.
(Embodiment 4)

Next, an acceleration sensor according to Embodiment 4 will be described with reference to the drawings. Embodiment 4
Is characterized in that a through hole is provided in each of the plurality of vibrating arms. In the present embodiment, a case where there are two vibrating arms will be described as an example.
8A and 8B show the acceleration sensor according to the present embodiment, where FIG. 8A is a front view and FIG. 8B is a partial front view showing an enlarged configuration of the excitation electrode. In FIG. 8A, a vibrating body 100 as an acceleration sensor includes vibrating arms 105 and 11 divided by a through hole 101 from one side of a base portion 102.
2 are extended in parallel to each other, and the tip portions thereof are one-end fixing structures connected by an additional mass portion 113.

In addition, the vibrating arm 105 is provided with the through-hole 106 so that the vibrating arm portions 107 and 108 are opened.
And the vibrating arm 112 is formed by opening the through-hole 109 so that the vibrating arm portions 110 and 1
11 is formed. Note that the lengths of the through holes 106 and 109 are substantially equal to the lengths of the vibrating arms 105 and 112. The vibrating arm 105 and the vibrating arm 112 are symmetrical with respect to the central axis P.

The base portion 102 includes a connecting portion 104 with the vibrating arms 105 and 112 and a constricted portion 103.
Also in the additional mass portion 113, the connecting portion 115 with the vibrating arms 105 and 112 and the constricted portion 114.
And is configured. As shown in FIG. 8B, excitation electrodes are formed on both side surfaces of the vibrating arms 105 and 112 and inner side surfaces of the through holes 106 and 109, respectively.

As shown in FIG. 8B, each excitation electrode has an excitation electrode 120 on the outer side surface of the vibrating arm 110.
Excitation electrodes 121 and 122 are provided on the inner side surface of the through hole 109, excitation electrodes 123 and 124 are provided on the inner side surface of the through hole 101, excitation electrodes 125 and 126 are provided on the inner side surface of the through hole 106, and vibration An excitation electrode 127 is provided on the outer side surface of the arm portion 107.

The excitation electrodes 120 to 123 and the excitation electrodes 124 to 127 are configured to be symmetrical with respect to the central axis P. And excitation electrode 120,122,125,127.
Is a first electrode group having the same potential, and the excitation electrodes 121, 123, 124, and 126 are second electrode groups having the same potential.

Here, by applying a reverse-phase potential to the first electrode group and the second electrode group, the vibrating arm 105
The vibrating arm 112 performs primary bending vibration having a vibration node at the connecting portion of the base portion 102.

When an acceleration in the axial direction is applied to the acceleration sensor, a change in the resonance frequency is caused by the expansion and contraction stress generated in the vibrating arms 105 and 112, and the change in the resonance frequency is detected as an acceleration.
In addition, the arrangement of the excitation electrode with respect to the through holes 106 and 109 in the present embodiment is such that the vibrating arm 1
It is possible to set various values for 05 and 112 to perform primary bending vibration.

For example, all or part of the excitation electrodes 120 to 127 may be connected to the base 1 of the vibrating arms 105 and 112.
It can be biased in the direction of 02. In the primary bending vibration, the portion where the distortion caused by the vibration is large is in the vicinity of the connecting portion between the vibrating arms 105 and 112 and the base portion 102 (the connecting portion 104). Good.

Similarly, the shape of the through holes 106 and 109 in this embodiment, the opening position, and the arrangement of the excitation electrodes associated therewith can be set in various ways.
(Embodiment 5)

Next, an acceleration sensor according to Embodiment 5 will be described with reference to the drawings. The present embodiment is characterized in that the through holes are arranged so as to be biased toward the base portion. Therefore, the fourth embodiment (
The description will focus on the parts different from FIG.
9A and 9B show a vibrating body according to the fifth embodiment, where FIG. 9A is a front view and FIG. 9B is a partial front view showing an enlarged configuration of an excitation electrode. In FIG. 9A, through-holes 151 and 153 are formed in the vibrating arms 105 and 112, respectively. The through holes 151 and 153 are opened to be biased toward the base portion 102 and are provided in a range from the connecting portion 104 to the substantially central portion of the length of the vibrating arms 105 and 112.

Note that the through holes 151 and 153 are provided in a range where the distortion generated when the vibrating arms 105 and 112 undergo primary bending vibration is large.

As shown in FIG. 9B, the excitation electrodes are provided on the outer side surfaces of the vibrating arms 105 and 112 and the inner side surfaces of the through holes 101, 151, and 153. Excitation electrodes 123 and 124 are provided on the inner side surface of the through hole 101, and excitation electrodes 137 and 138 are provided on the inner side surface of the through hole 153.
Excitation electrodes 141 and 142 are provided on the inner side surface of 1. Further, the excitation electrodes 124 and 127 on both side surfaces of the vibrating arm 105 are generally in the length range of the vibrating arm 105, and the excitation electrodes 120 and 123 on both side surfaces of the vibrating arm 112 are generally in the length range of the vibrating arm 112. .

These excitation electrodes 120, 123, 137, 138 and excitation electrodes 124, 127, 14
1 and 142 are configured to be symmetrical with respect to the central axis P. The excitation electrodes 120, 138, 141, 127 are a first electrode group having the same potential, and the excitation electrodes 137, 1
Reference numerals 23, 124 and 142 denote a second electrode group having the same potential.

Here, by applying a reverse-phase potential to the first electrode group and the second electrode group, the vibrating arm 105
The vibrating arm 112 performs primary bending vibration having a vibration node at the connecting portion of the base portion 102.

When an acceleration in the axial direction is applied to the acceleration sensor, a change in the resonance frequency is caused by the expansion and contraction stress generated in the vibrating arms 105 and 112, and the change in the resonance frequency is detected as an acceleration.

The arrangement of the excitation electrodes described above is an example, and the excitation electrodes 120, 123, 124, 1
27 may be provided to have the same length as the excitation electrodes 137, 138, 141, 142.
(Embodiment 6)

Next, an acceleration sensor according to Embodiment 6 will be described with reference to the drawings. Embodiment 6
Is characterized in that a plurality of through holes are formed in each vibrating arm. Therefore, it demonstrates centering on a different part from Embodiment 4 (refer FIG. 8). In addition, common parts are denoted by the same reference numerals.
10A and 10B show an acceleration sensor according to the sixth embodiment, where FIG. 10A is a front view and FIG. 10B is a partial front view showing an enlarged configuration of excitation electrodes. In FIG. 10A, the vibrating arm 105 has through holes 150, 155 and 151, and the vibrating arm 112 has through holes 152, 156 and 153.

The through holes 150 and 152 are provided in the vicinity of the additional mass portions 113 of the vibrating arms 105 and 112, respectively. Specifically, the through holes 150 and 152 extend from the additional mass portion 113 to the vibrating arm 10.
5,112 in the range of approximately 30% of the entire length in the longitudinal direction. Also, the through holes 151 and 15
3 is provided in the vicinity of the base 102. The through holes 151 and 153 are provided in a range of approximately 30% of the entire length in the longitudinal direction of the vibrating arms 105 and 112 from the base 102. Furthermore, through holes 155 and 156 are provided in the longitudinal center of the vibrating arms 105 and 112, and the through holes 15
Reference numerals 5 and 156 denote the vibrating arms 105 and 112 with the center in the longitudinal direction of the vibrating arms 105 and 112 as the center.
In the range within 60% of the total length in the longitudinal direction.

The through holes 151 and 153 are provided at positions where the distortion generated when the vibrating arms 105 and 112 undergo primary bending vibration is the largest, and the through holes 155 and 156 and the through holes 150 and 152 are positions where the distortion gradually decreases. It is. The outer side surfaces of the vibrating arms 105 and 112 and the through hole 150
Excitation electrodes are provided on the inner side surfaces of ˜153, 155, and 156, respectively.

As shown in FIG. 10B, the excitation electrode 127 is provided on the outer side surface of the vibrating arm 105. Further, excitation electrodes 125 and 126 are provided on the inner side surface of the through hole 150, excitation electrodes 141 and 142 are provided on the inner side surface of the through hole 151, and excitation electrodes 133 and 134 are provided on the inner side surface of the through hole 155.
Is provided. Excitation electrodes 123 and 124 are provided on the inner side surface of the through hole 101, excitation electrodes 121 and 122 are provided on the through hole 152, and excitation electrodes 129 and 13 are provided on the inner side surface of the through hole 156.
0, excitation electrodes 137 and 138 are provided on the inner side surface of the through hole 153. An excitation electrode 120 is provided on the outer side surface of the vibrating arm 112. These excitation electrodes have a central axis P
Is symmetric.

The excitation electrodes 120, 123, 124, 127 are a first electrode group having the same potential, and the excitation electrodes 121, 122, 129, 130, 137, 138, 125, 126, 133, 13
Reference numerals 4, 141, 142 denote second electrode groups having the same potential.

Here, by applying a reverse-phase potential to the first electrode group and the second electrode group, the vibrating arm 105
The vibrating arm 112 performs primary bending vibration having a vibration node at the connecting portion 104 of the base portion 102.

When an acceleration in the axial direction is applied to the acceleration sensor, a change in the resonance frequency is caused by the expansion and contraction stress generated in the vibrating arms 105 and 112, and the change in the resonance frequency is detected as an acceleration.

In addition, the structure of the excitation electrode in Embodiment 6 mentioned above is an example, For example, excitation electrode 120,123,124,127 is the through-hole 150,151,152,153,155,155.
It is good also as a structure divided | segmented so that each of 156 might be opposed.

As described above, in the fourth embodiment, the through holes 151 and 153 are provided over the entire longitudinal direction of the vibrating arms 105 and 112, and in the fifth embodiment, the through holes 106 and 109 are provided in the vicinity of the base portion 102. In the sixth embodiment, through-holes 155 and 156 are further provided in the longitudinal center portions of the vibrating arms 105 and 112. Accordingly, the base 102 (the connecting portion 10
4) Since the through-holes are provided at the position where the distortion generated in the primary bending vibration having the vibration node in the vicinity is large and the position where the distortion occurs although it is smaller than that, the vibrating arms 105 and 11 are provided.
The cross-sectional area of the deforming position 2 becomes smaller and the generated stress becomes larger. Further, since the displacement amount of the vibrating arms 105 and 112 when acceleration is applied can be increased, the amount of change in the resonance frequency is increased, and the detection sensitivity can be increased.

In addition, the distance between the excitation electrodes is further reduced as compared with the first to third embodiments, and the electric field efficiency is increased. This has the effect of reducing power consumption.
(Embodiment 7)

Next, an acceleration sensor according to Embodiment 7 will be described with reference to the drawings. Embodiment 7
Is characterized in that the acceleration sensor (vibrating body) according to Embodiments 4 to 6 described above has a one-end fixing structure, but has a two-end fixing structure.
FIG. 11 is a front view showing an acceleration sensor according to the seventh embodiment. In FIG. 11, the acceleration sensor 200 is configured such that two sets are connected in a straight line at an additional mass portion 113 where the vibrating bodies 100 and 180 are common.

As shown in FIG. 11, the right side of the center of gravity position G of the acceleration sensor 200 is a vibrating body 100 composed of vibrating arms 105 and 112 and an additional mass portion 113 divided by a base portion 102 and a through hole 101. The left side is the vibrating arm 1 divided by the base 160 and the through-hole 163.
The vibrating body 180 includes 64 and 165 and the additional mass portion 113. Vibrating arm 105,
Reference numeral 112 is formed by being divided by the through hole 101. The vibrating arm 105 has a through hole 106, and the vibrating arm 112 has a through hole 109.
On the other hand, a through hole 166 is formed in the vibrating arm 164, and a through hole 168 is formed in the vibrating arm 165.

The base portion 102 is provided with a connecting portion 104 to which the vibrating arms 105 and 112 are connected and a constricted portion 103. In the additional mass part 113 to which the vibrating arms 105 and 112 are connected,
A connecting portion 115 and a constricted portion 114 are provided.

On the other hand, in the vibrating body 180, the base portion 160 is provided with a connecting portion 162 to which the vibrating arms 164 and 165 are connected, and a constricted portion 161. The additional mass portion 113 to which the vibrating arms 164 and 165 are connected is provided with a connecting portion 118 and a constricted portion 119.

The additional mass portion 113 is a common additional mass portion for the vibrating body 100 and the vibrating body 180 and has a mass that is equal to or larger than that of the base portions 102 and 160 and has a planar shape. The acceleration sensor 200 is point-symmetric with respect to the gravity center position G. Therefore, the acceleration sensor 200 includes the vibrating body 100 and the vibrating body 18 having the same shape as the vibrating body 100 in the common additional mass unit 113.
This is a double-end fixing structure in which 0 is linearly connected and the base 102 and the base 160 are fixed to the base. Each of the vibrating bodies 100 and 180 is the same as that in the fourth embodiment described above (see FIG. 8).
And the excitation electrode.

Here, if the excitation signals having the reverse potential, the reverse phase, and the same frequency are input to the vibrating arms 105 and 112 and the vibrating arms 164 and 165, respectively, as in the fourth embodiment, the additional mass unit 113 has a sufficiently large mass. Therefore, the vibrating arms 105 and 112 and the vibrating arms 164 are hardly displaced.
, 165 are the base part 102 (connecting part 104), 160 (connecting part 162) and the additional mass part 1
This is a secondary bending vibration in which the vicinity of the connecting portion to the vibration 13 is a vibration node.

Therefore, according to the seventh embodiment described above, the vibrating bodies 10 that face each other with the additional mass portion 113 interposed therebetween.
Both ends are fixed structure having 0,180. At this time, the vibrating arms 105 and 112 and the vibrating arm 164
, 165 constitutes a vibrating body having an antiphase secondary bending vibration mode and a good vibration balance. That is, a high Q value is obtained.

In addition, when the acceleration in the Y-axis direction is applied to the opposing vibrating arms 105 and 112 and the vibrating arms 164 and 165, contraction stress is generated on one side, and tensile stress is generated on the other vibrating arm.
In the case of such a structure, there is an effect that the influence of the frequency temperature characteristic can be canceled by taking the difference between the resonance frequencies of both vibrators.

In addition, the through hole in the configuration of the present embodiment may be configured to be biased toward the base 102 as in the above-described fifth embodiment (see FIG. 9), or as in the sixth embodiment (see FIG. 10). In addition, a plurality of vibrating arms 105 and 112 may be provided.

An example of the acceleration sensor which concerns on Embodiment 1 is shown, (a) is a front view, (b) is sectional drawing which shows the HH cut surface of (a). FIG. 6 is a perspective view illustrating a configuration of an acceleration sensor according to a first modification of the first embodiment. The graph which shows about the relationship between the ratio of the length L2 of the through-hole with respect to the total length L1 of a vibrating arm, and the amount of frequency fluctuations. FIG. 6 is a front view showing an acceleration sensor according to a second modification of the first embodiment. The acceleration sensor which concerns on the modification 3 of Embodiment 1 is shown, (a) is a front view, (b) is sectional drawing which shows the JJ cut surface of (a). FIG. 6 is a front view showing an acceleration sensor according to a second embodiment. The acceleration sensor which concerns on Embodiment 3 is shown, (a) is a front view, (b) is sectional drawing which shows the KK cut surface of (a). The acceleration sensor which concerns on Embodiment 4 is shown, (a) is a front view, (b) is a partial front view which expands and shows the structure of an excitation electrode. The vibrating body which concerns on Embodiment 5 is shown, (a) is a front view, (b) is a partial front view which expands and shows the structure of an excitation electrode. The acceleration sensor which concerns on Embodiment 6 is shown, (a) is a front view, (b) is a partial front view which expands and shows the structure of an excitation electrode. FIG. 10 is a front view showing an acceleration sensor according to a seventh embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Acceleration sensor, 10 ... Vibrating body, 20 ... Base part, 21 ... Vibrating arm, 22 ... Through-hole, 23,
24 ... vibrating arm part, 25 ... additional mass part, 31-34 ... excitation electrode as excitation means.

Claims (8)

A vibrating body comprising: a base fixed to a base; and a beam-like vibrating arm extending from the base and bending-vibrating in a plane direction at a predetermined resonance frequency,
The vibrating arm is connected to a vibrating arm portion divided by a through-hole opened in the longitudinal direction in the width direction at a center portion in the width direction and an additional mass connecting the tip portion of the divided vibrating arm portion. And an excitation means provided on the vibrating arm portion,
The vibrating arm is supported by the base and the additional mass portion in a pseudo-both fixed structure or a one-end fixed structure,
An acceleration sensor for detecting a change in resonance frequency of the vibrating body due to an inertial effect of the additional mass portion when acceleration is applied. The acceleration sensor according to claim 1,
Two sets of vibrating bodies comprising the base, the vibrating arm, and the additional mass portion are provided,
Two sets of the additional mass portions are common additional mass portions, and the two sets of the vibrating bodies are linearly connected so as to be point-symmetric with respect to the center of gravity of the common additional mass portion. Acceleration sensor. A vibrating body comprising a base fixed to a base and a plurality of beam-like vibrating arms extending in parallel from the base and bending-vibrating in a plane direction at a predetermined resonance frequency,
At least one through-hole formed in the longitudinal direction perpendicular to the vibration direction in the widthwise center of each of the plurality of vibrating arms;
An additional mass portion that connects the tip portions of the plurality of vibrating arms;
Exciting electrodes provided on both side surfaces of each of the plurality of vibrating arms and the inner side surface of the through hole,
An acceleration sensor for detecting a change in resonance frequency of the vibrating body due to an inertial effect of the additional mass portion when acceleration is applied. The acceleration sensor according to claim 3,
The acceleration sensor, wherein the through hole is provided in the vicinity of a connecting portion between at least a plurality of the vibrating arms and the base. The acceleration sensor according to claim 3,
The acceleration sensor according to claim 1, wherein the through-hole is formed in a plurality of the vibrating arms in the vicinity of a connection portion with the base portion, in the vicinity of a connection portion with the additional mass portion, and in a central portion in the longitudinal direction. The acceleration sensor according to claim 3,
Two sets of vibrating bodies each including the base, the plurality of vibrating arms having the through-holes, and the additional mass portion are provided,
Two sets of the additional mass portions are common additional mass portions, and the two sets of the vibrating bodies are linearly connected so as to be point-symmetric with respect to the center of gravity of the common additional mass portion. Acceleration sensor. The acceleration sensor according to any one of claims 1 to 6,
An acceleration sensor, wherein the vibrating body is made of quartz. The acceleration sensor according to any one of claims 1 to 6,
An acceleration sensor, wherein the vibrating body is made of a constant elastic material, and a piezoelectric element film is formed on a side surface of the vibrating arm.

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