JP2011153836A - Acceleration sensor, and accelerometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor, along with an accelerometer, having a simple structure and high acceleration detection sensitivity, while reducing manufacturing cost. <P>SOLUTION: A piezoelectric sensor 10 includes a piezoelectric sensor element 20, first and second fixed parts 14a, 14c for fixing it on a support substrate, and a ring connection piece 12 for connecting the first and second fixed parts, respectively. The support substrate 4 includes a first substrate piece 5 for supporting the first fixed part, a second fixed piece 7 on the movable side for supporting the second fixed part, and a hinge 8. The ring connection piece 12 includes a first connection piece 12a for connecting both ends in the longitudinal direction of the piezoelectric sensor element, and a second connection piece 12b for connecting both ends in the longitudinal direction of the piezoelectric sensor element, and the first and second fixed parts project from the inside of the first connection piece and the second connection piece toward the piezoelectric sensor element, respectively. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an acceleration sensor and an accelerometer, and more particularly to an acceleration sensor and an accelerometer improved by converting the direction of a force generated by applied acceleration by 90 degrees and increasing the magnitude of the force. is there.

Conventionally, an acceleration sensor using a piezoelectric vibration element is known. An acceleration sensor using a piezoelectric vibration element is configured to detect acceleration applied to the acceleration sensor based on a resonance frequency of the piezoelectric vibration element that changes when a force in the detection axis direction acts on the piezoelectric vibration element. Yes.
Patent Document 1 discloses an accelerometer and a manufacturing method in which a double tuning fork type vibration element is connected to one diagonal of a hollow parallelogram frame and a compression force or an extension force is applied to the other diagonal. Yes.
As shown in the sectional view of FIG. 9, the accelerometer has a mass 11 that moves along the detection axis 119.
6 is configured to be coupled to the support 117 by a bent portion 118. Mass 11
The frequency of the pair of force detection crystals 121 and 122 connected between the support 6 and the support 117 varies depending on the applied force. These force detection crystals 121 and 122 are excited by frequency oscillators 123 and 124, and signals from the two oscillators are input to the adder circuit 126 to output an output signal corresponding to the difference between the two frequencies.

The accelerometer is formed by stacking five disk-shaped elements made of quartz (quartz crystal) or the like along the detection axis. That is, the accelerometer includes a central element 127 shown in FIG. 10 and a pair of transducer elements 12 shown in FIG. 11 arranged on both sides of the central element 127.
8 and a pair of lids (not shown) respectively disposed on both outer sides of the transducer elements 128. FIG. 10A is a plan view of the central element 127, and FIG.
It is sectional drawing in Q.
As shown in FIG. 10, the central element 127 includes a fixed part 134 and a movable part (seismic mass) 133 having a mass. The movable portion 33 is attached to the fixed portion 134 by a pair of bent portions 136 so as to be movable around a hinge shaft 137 extending perpendicularly to the detection axis. The movable part 133 and the fixed part 134 are arranged inside the mounting ring 139 to which the fixed part 134 is attached. The isolation ring 141 is disposed concentrically outside the mounting ring 139, and a flexible arm connects the mounting ring 139 and the isolation ring 141. The central element 127 is formed as an integral structure.

As shown in the plan view of FIG. 11, the transducer element 128 has a mounting ring 146 in which a force detection element (crystal) 147 and a coupling plate 148 are disposed.
The force detection element 147 connects a double tuning fork type piezoelectric vibration element 151 to one opposite diagonal of a quadrilateral frame 149 including four links 152, and pads 154, 1 to the other opposite diagonal.
56. One pad 154 is formed integrally with the coupling plate 148, and the other pad 156 is formed integrally with the mounting ring 146.
Each coupling plate 148 of the two transducer elements 128 is coupled to both main surfaces 138 of the movable portion 133 of the central element 127 by an adhesive, and the mounting ring 146 of the transducer element is bonded to the mounting ring 139 of the central element 127 by an adhesive. To be joined.
The accelerometer has a sealed structure with two lids formed in a circular shape with a depression on one side. The indentation faces each transducer element 128 and the periphery of the lid is joined to the mounting ring 146 of the transducer element 128 by an adhesive. Gas is put inside the accelerometer, and the two lids also function as braking plates.

Japanese Patent No. 2851566

However, the accelerometer disclosed in Patent Document 1 has one central element 127 and 2
There is a problem that the number of parts is too large because it is configured using two transducer elements 128 and two lids. Further, the central element 127 and the transducer element 128 have extremely complicated structures, and it is assumed that the manufacturing yield of these elements is low, and there is a possibility that it takes a lot of man-hours to adjust the assembled acceleration. There is a problem that the cost of the system becomes extremely expensive.
Further, since the braking gas is sealed inside the accelerometer, the transducer element 12
There was a problem that the Q value of the eighth vibration element 151 deteriorated and it was difficult to excite.
The invention has been made to solve the above problems, and has a simple structure and high acceleration detection feeling.
An object of the present invention is to provide an acceleration sensor and an accelerometer that can reduce the manufacturing cost.

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 the present invention includes a piezoelectric sensor and a support substrate having a first support surface and a second support surface that support the piezoelectric sensor, and the piezoelectric sensor is in a detection axis direction. A piezoelectric sensor element that generates an electrical signal corresponding to the applied force, and a first fixed part and a second fixed part that are respectively fixed to the first and second support surfaces to support the piezoelectric sensor element on the support substrate. A fixed portion; and an annular connecting piece for connecting the first fixed portion and the second fixed portion to the piezoelectric sensor element, respectively, and the support substrate is fixed with the first support surface. A first substrate piece on the side, a second substrate piece on the movable side provided with the second support surface juxtaposed in the surface direction of the first support surface, and the opposing of the first substrate piece and the second substrate piece Connecting the side edges to the second
A hinge portion that swings the substrate piece in the thickness direction, and the piezoelectric sensor element has an elongated configuration extending in a direction orthogonal to the detection axis direction, and the respective supports in a state facing the hinge portion. The annular connecting piece is separated from the surface, and the annular connecting piece includes a first connecting piece for connecting between both longitudinal ends of the piezoelectric sensor element via the first fixed portion, and the second fixed portion. A second connecting piece for connecting between both longitudinal ends of the piezoelectric sensor element via the first connecting element,
And the second fixed portion is an acceleration sensor characterized by having a configuration projecting from the inside of the first connection piece and the second connection piece toward the piezoelectric sensor element.

As described above, the support substrate includes the flat plate-like first substrate piece on the fixed side, the movable plate-like second substrate piece, and the hinge connecting the two. The piezoelectric sensor has a first fixed portion and a second fixed portion at one opposing portion of the annular connecting piece, and both ends of the piezoelectric sensor element are connected to the other opposing portion, and the first fixed portion and the first fixed portion are connected. Each of the two fixed portions is formed inside the annular connecting piece. Using a flat piezoelectric substrate, a photolithographic technique and an etching technique can be applied to form a support substrate and a piezoelectric sensor with good dimensional accuracy, and these can be used for mass production of small, low-cost acceleration sensors. is there. In addition, in the acceleration sensor, since the first fixed portion and the second fixed portion are formed inside the annular connecting piece, the direction of the force generated by applying the acceleration is changed by 90 degrees, and the magnitude of the force is increased. Compared with what was formed in the outer side of the cyclic | annular connection piece, it acts so that it may increase more. Therefore, it is possible to detect a small acceleration (high sensitivity), and to obtain an acceleration sensor with high detection accuracy and reproducibility.

[Application Example 2] In the acceleration sensor, the position of the center portion in the short direction of the sensor element is
The acceleration sensor according to Application Example 1, wherein the acceleration sensor is located within a width in a short direction of the hinge part.

By locating the center part in the short direction of the piezoelectric sensor element within the width in the short direction of the hinge part, variation in distortion generated in each part of the annular connecting piece is reduced and detection sensitivity of the acceleration sensor is improved. effective.

[Application Example 3] In the acceleration sensor, the position of the center portion in the short direction of the sensor element is
3. The acceleration sensor according to Application Example 1 or 2, wherein the acceleration sensor coincides with a widthwise central portion of the hinge portion.

By substantially matching the short direction center part of the piezoelectric sensor element and the short width direction center part of the hinge part, the distortion generated in each part of the annular connecting piece becomes uniform, and the sensitivity of the acceleration sensor (the same acceleration is The frequency change amount of the piezoelectric sensor element when applied is the best, and the reproducibility is improved.

Application Example 4 Further, in the acceleration sensor, the annular connecting piece viewed from a direction orthogonal to the first and second support surfaces is formed in a narrow band shape having the same width over the entire length. The acceleration sensor according to any one of Application Examples 1 to 3.

By forming each beam of the annular connecting piece in a narrow band shape having the same width, there is an effect that the transmission efficiency of the force generated by the application of acceleration is good and small acceleration can be detected with good reproducibility.

Application Example 5 In the acceleration sensor, each of the first and second connecting pieces has a substantially square shape (V
5. The acceleration sensor according to any one of application examples 1 to 4, wherein the acceleration sensor has a character shape.

By forming the first connecting piece and the second connecting piece in a substantially square shape (V shape), the direction of the force applied to the second substrate piece is changed by 90 degrees, and the amplification degree of the force is maximized. There is an effect that it can be enlarged.

[Application Example 6] The acceleration sensor according to any one of claims 1 to 4, wherein each of the first and second connecting pieces is U-shaped.

By forming the first connecting piece and the second connecting piece in a substantially U shape, the direction of the force applied to the second substrate piece is changed by 90 degrees and the magnitude of the force is increased. .

Application Example 7 In the acceleration sensor according to any one of Application Examples 1 to 4, the first and second connecting pieces are each in a semicircular shape, a semi-elliptical shape, or a semi-ellipse shape. The acceleration sensor described in 1.

When the first connecting piece and the second connecting piece are each formed into a semicircular shape, a semi-elliptical shape, or a semi-oval shape,
The direction of the force applied to the second substrate piece is changed by 90 degrees, the magnitude of the force is increased, and the strain in the first connecting piece and the second connecting piece is equalized, so that the acceleration strong against vibration, impact, etc. There is an effect that the sensor can be configured.

Application Example 8 An accelerometer according to the present invention includes the acceleration sensor according to any one of Application Examples 1 to 7,
An accelerometer comprising: an oscillation circuit that excites a piezoelectric sensor element of the acceleration sensor; a counter that counts an output frequency of the oscillation circuit; and an arithmetic circuit that processes a signal of the counter. is there.

The support substrate and the piezoelectric sensor are formed using a quartz substrate, and the acceleration sensor is configured with the piezoelectric sensor element as a double tuning fork type quartz vibrating element. When an accelerometer is constituted by the acceleration sensor and an IC having each function, the acceleration detection sensitivity is greatly improved, and an effect of realizing an excellent accelerometer such as detection accuracy, reproducibility, temperature characteristics, and aging can be realized. is there.

It is the schematic which showed the structure of the acceleration sensor 1 which concerns on this invention, (a) is a top view, (b) is sectional drawing. It is a figure explaining a double tuning fork type piezoelectric vibration element, (a) is a top view of a vibration mode, (b) is a figure showing an excitation electrode formed in a vibration arm, and a sign of an electric charge generated at a certain moment, (c) ) Is a wiring diagram of the excitation electrode. Schematic explaining the effect | action of a cyclic | annular connection piece (parallelogram beam). (A), (b), (c) is a principal part top view which shows the mutual positional relationship of a piezoelectric sensor element and a hinge part, respectively. The figure explaining the effect | action of a 2nd kind insulator. The top view of the modification of a piezoelectric sensor. The top view of the other modification of a piezoelectric sensor. The block diagram which shows the structure of the accelerometer of this invention. FIG. 6 is a schematic cross-sectional view showing a configuration of a conventional accelerometer. The structure of the center element of the conventional accelerometer is shown, (a) is a top view, (b) is sectional drawing. The top view which shows the structure of the transducer element of the conventional accelerometer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a configuration of an acceleration sensor 1 according to an embodiment of the present invention. FIG. 1 (a) is a plan view, and FIG.
) Is a cross-sectional view taken along the line Q-Q. The acceleration sensor 1 includes a piezoelectric sensor 10 and a support substrate 4 having a first support surface 5a and a second support surface 7a that support the piezoelectric sensor 10.
The piezoelectric sensor 10 includes a piezoelectric sensor element 20 that generates an electrical signal corresponding to the force applied in the direction of the detection axis 9 shown in FIG. 1B, and a first support for supporting the piezoelectric sensor element 20 on the support substrate 4. A first fixed portion 14a and a second fixed portion 14c fixed to the surface 5a and the second support surface 7a, respectively, and a first fixed portion 14a and a second fixed portion 14c with respect to the piezoelectric sensor element 20.
And annular connecting pieces (beams) 12 for connecting the two.

As shown in FIG. 1B, the support substrate 4 has a first support surface 5 for fixing the first fixed portion 14a.
a movable-side first substrate piece 5 having a and a second support surface 7a that is juxtaposed in the surface direction (lateral direction) of the first support surface 5a and supports the second fixed portion 14c. A second substrate piece 7 and a hinge portion 8 for connecting the opposing side edges of the first substrate piece 5 and the second substrate piece 7 to swing the second substrate piece in the thickness direction. . That is, the first substrate piece 5 and the second substrate piece 7 are continuously arranged along the substantially same plane direction via the hinge portion 8.
The hinge portion 8 is formed to be thinner than the thickness of the first substrate piece 5 and the second substrate piece 7 so that the second substrate piece 7 is flexible from the hinge portion 8 when acceleration is applied to the acceleration sensor 1. It is configured. The cross-sectional shape of the hinge portion 8 viewed from a direction orthogonal to the thickness direction of the support substrate 4 is a rectangular shape, a trapezoidal shape, an arc shape, or the like, and is formed in at least one of the thickness directions.
The first substrate piece 5, the second substrate piece 7 and the hinge portion 8 are integrally formed, and the first substrate piece 5
The first support surface 5a and the second support surface 7a of the second substrate piece 7 are on the same plane.

The piezoelectric sensor element 20 has an elongated configuration extending in a direction orthogonal to the direction of the detection axis 9 and is spaced from the support surfaces 5a and 7a in a state of facing the hinge portion 8. The configuration of the piezoelectric sensor element 20 will be described in detail. A pair of base portions 24a and 24b and base portions 24a and 24b.
A resonating arm (22a, 22b in the example of FIG. 1), a first support piece 26a, and a second support piece 26b extending outwardly from the bases 24a, 24b on the extension of the resonating arm, respectively. It is equipped with.
The annular connecting piece 12 includes a first fixed portion 14a, a first connecting piece 12a for connecting the longitudinal ends of the piezoelectric sensor element 20 via the first fixed portion 14a, and a second fixed portion 14c. When,
Second connecting the longitudinal ends of the piezoelectric sensor element 20 via the second fixed portion 14c.
Connecting piece 12b. Further, the annular connecting piece 12 includes a first connecting piece 14b connected to one of the first connecting piece 12a and the second connecting piece 12b, and a second connecting piece 14 connected to the other.
d. The piezoelectric sensor element 20 includes a first support piece 26a and a second support piece 26b.
Are connected to the first coupling piece 14b and the second coupling piece 14d, respectively.
In the example of FIG. 1 (a), the annular connecting piece 12 is a hollow frame-shaped parallelogram (diamond) having substantially the same length of four sides each having the first connecting piece 12a and the second connecting piece 12b as sides. is there.

The first fixed portion 14a and the second fixed portion 14c of the annular connecting piece 12 are configured to protrude toward the piezoelectric sensor element 20 from the inside of the first connecting piece 12a and the second connecting piece 12b, respectively. ing. The piezoelectric sensor element 20 and the annular connecting piece 12 are integrally formed. That is, as shown in the example of FIG. 1A, the first fixed portion 14a and the second fixed portion 1
4c has a width larger than the width of the annular connecting piece 12 in the portion formed by the width of the first connecting piece 12a and the second connecting piece 12d, and is, for example, a peninsula-shaped protrusion located inside the hollow parallelogram 1
4aa and 14cc are configured. The connecting pieces 12a1, 12a2, 12b1, 12b
In order to provide mechanical strength at the joint between the first fixed portion 14a and the second fixed portion 14b, the width of the annular connecting piece 12 is increased from the connecting pieces 12a1, 12a2, 12b1, 12b2 to a hollow parallelogram. Even when it is configured to be wide outside, the protruding length (length along the X axis) of this wide portion is substantially the same as the protruding length of the protruding portions 14aa and 14cc. There is no big problem as long as it is small enough not to reduce the difference.
Further, as also applied in the configuration shown in FIG. 7 described later, when there is a wide portion projecting outward, the wide portion and the surface of the support substrate 4 at a location facing the wide portion region, May not be fixed by the adhesive 30 described later.
The first connecting piece 12a and the second connecting piece 12b have a substantially rectangular shape (V shape), respectively, and are annular connecting pieces viewed from a direction orthogonal to the first support surface 5a and the second support surface 7a. 12 has a narrow band shape with the same width over its entire length.

The first fixed portion 14a and the second fixed portion 14c of the piezoelectric sensor 10 are fixed to the first support surface 5a and the second support surface 7a of the support substrate 4, and the second substrate piece 7 swings. Ring connecting piece 12
It is comprised so that it may be transmitted to the piezoelectric sensor element 20 via.
The first connecting piece 12a between the first fixed portion 14a and the first connecting piece 14b is connected to the connecting piece 12a1,
The first connecting piece 12a between the first fixed portion 14a and the second connecting piece 14d is referred to as a connecting piece 12a2. Similarly, the second connecting piece 12b between the second fixed portion 14c and the first coupling piece 14b is connected to the connecting piece 12b1, and the second connecting piece 12b between the second fixed portion 14c and the second connecting piece 14d. Connecting piece 1
2b2.
In the example of FIG. 1A, the connecting pieces 12a1, 12a2, 12b1, and 12b2 are all linear, and the angle θ1 formed by the connecting piece 12a1 and the connecting piece 12b1 in the first connecting piece 14b.
The angle θ2 formed by the connecting piece 12a2 and the connecting piece 12b2 in the second connecting piece 14d is an acute angle. The annular connecting piece 12 converts the direction of the force applied to the first fixed portion 14a and the second fixed portion 14c (X-axis direction) by 90 degrees (Y-axis direction), and increases the magnitude of the force to increase the piezoelectricity. It serves to add to the sensor element 20. The rate of increase in force varies depending on the angles θ1 and θ2.

The piezoelectric sensor element 20 includes a first coupling piece 14b and a second coupling piece 14d of the annular coupling piece 12.
Are connected to each other by a first support piece 26a and a second support piece 26b, respectively.
And the piezoelectric sensor 10 is formed. The piezoelectric sensor element 20 has an elongated configuration extending in a direction orthogonal to the detection axis direction 9 of the acceleration sensor 1, and the first fixed portion 14 a and the second fixed portion 14 c of the piezoelectric sensor 10 are connected to the first of the support substrate 4. 1 support surface 5a and second
When supporting / fixing to the holding surface 7a, the central portion of the piezoelectric sensor element 20 in the short direction is the support substrate 4.
The first support surface 5 along the longitudinal direction of the hinge portion 8 so as to be located within the width of the hinge portion 8 in the short direction.
a and the second support surface 7a. Preferably, the piezoelectric sensor element 2
The central portion in the short direction of 0 and the central portion in the short direction width of the hinge portion 8 are substantially matched.

For example, as shown in FIG. 1A, the piezoelectric sensor element 20 includes a pair of vibrating arms 22a and 22a.
A double tuning fork type piezoelectric vibration element including b and a pair of base portions 24a and 24b is used. A case where the piezoelectric sensor element 20 is constituted by a double tuning fork type piezoelectric vibration element will be briefly described with reference to FIG.
The double tuning fork type piezoelectric vibration element 20 includes a pair of base portions 24a and 24b as shown in FIG. 2A, and a stress made of a piezoelectric substrate having a pair of vibrating arms 22a and 22b that are connected between the base portions 24a and 24b. A sensitive portion and an excitation electrode formed on the vibration region of the piezoelectric substrate are provided. FIG.
The broken line a) is a plan view showing the vibration state of the double tuning fork type piezoelectric vibration element 20. The vibration mode of the double tuning fork type piezoelectric vibration element 20 is set to the longitudinal center axis of the pair of vibrating arms 22a and 22b.
Excitation electrodes are arranged to vibrate in mutually symmetric vibration modes. FIG. 2B shows the vibrating arm 22.
It is the top view which showed the code | symbol of the electric charge on the excitation electrode formed in a and 22b and the excitation electrode excited at a certain moment. FIG. 2C is a schematic cross-sectional view showing the connection of the excitation electrodes.

The double tuning fork type piezoelectric vibration element 20, for example, the double tuning fork type crystal vibration element has good sensitivity to the extension / compression stress, and when used as a stress sensitive element for an altimeter or a depth meter,
Since the decomposition ability is excellent, it is possible to know the altitude difference and the depth difference from a slight pressure difference.
The frequency-temperature characteristic of the double tuning fork type crystal resonator element is an upwardly convex quadratic curve, and the apex temperature depends on the rotation angle around the X axis (electric axis) of the crystal crystal. Generally, the peak temperature is room temperature (2
Set each parameter to 5 ° C.
The resonance frequency f _F when an external force F is applied to a pair of vibrating arms of a double tuning fork type crystal vibrating element is expressed by the equation (1
).
f _F = f ₀ (1- (KL ² F) / (2EI)) ^1/2 (1)
Here, f ₀ is the resonance frequency of the double tuning fork type quartz vibrating element when there is no external force, K is a constant according to the fundamental mode (= 0.0458), L is the length of the vibrating beam, E is the longitudinal elastic constant, I Is cross section 2
Next moment. Second moment I are from I = ^dw 3/12, the equation (1) is the formula (2
). Here, d is the thickness of the vibration beam, and w is the width.
f _F = f ₀ (1-S _F σ) ^1/2 (2)
However, the stress sensitivity _SF and the stress σ are each expressed by the following equations.
S _F = 12 (K / E) (L / w) ² (3)
σ = F / (2A) (4)
Here, A is the sectional area (= w · d) of the vibration beam.

From the above formula, when the force F acting on the double tuning fork type crystal resonator is negative in the compression direction and positive in the extension direction (tensile direction), the relationship between the force F and the resonance frequency f _F is that the force F is a compressive force. At resonance frequency f
_F decreases and increases with stretching (tensile) force. The stress sensitivity S _F is proportional to the square of the vibration beam L / w.
The piezoelectric sensor element 20 shown in FIG. 1 is not limited to the double tuning fork type crystal vibrator using the above-described quartz substrate, and any vibrating element may be used as long as the vibration element changes in frequency by extension / compression stress. For example, it is possible to use a vibration element in which a drive unit is bonded to a vibration body, a single beam vibration element, a thickness shear vibration element, a SAW vibration element, or the like.

The operation of the annular connecting piece 12 will be described using the schematic diagram shown in FIG. Second fixed part 1
The force (vector) fa in the −X axis direction (left side in the figure) acts on 4c, and the force (vector) fb in the + X axis direction (right side in the figure) acts on the first fixed portion 14a. To do. -Force in the X-axis direction fa
Is the force fa2 in the direction of the connecting piece 12b1 and the connecting piece 1 according to the law of parallelograms of vectors.
The force fb in the direction of 2b2 is decomposed, and the force fb in the + X-axis direction is decomposed into a force fb2 in the direction of the connecting piece 12a1 and a force fb1 in the direction of the connecting piece 12a2. The decomposed forces fa1, fa2, fb1, fb2 acting on the second fixed portion 14c and the first fixed portion 14a are applied to the first coupling piece 14b of the annular connecting piece 12 and the force fa2 in the direction of the connecting piece 12b1. The force fb2 in the direction of the connecting piece 12a1 is applied to the second connecting piece 14d by the force fa1 in the direction of the connecting piece 12b2 and the connecting piece 12.
The force fb1 in the direction of a2 is equivalent to acting.
When the forces fa2 and fb2 acting on the first coupling piece 14b are synthesized according to the parallelogram law, the force F
2 Similarly, when the forces fa1 and fb1 acting on the second coupling piece 14d are combined, a force F1 is obtained.
Forces fa and f acting on the first fixed portion 14a and the second fixed portion 14c of the annular connecting piece 12
b is equivalent to forces F2 and F1 acting on the first coupling piece 14b and the second coupling piece 14d, respectively. That is, the annular connecting piece 12 has a function of changing the direction of the force by 90 degrees and increasing the magnitude of the force.

One of the features of the present invention is that the first fixed portion 14a and the second fixed portion 14c are arranged inside the annular connecting piece 12, respectively. When acceleration is applied to the acceleration sensor 1, the second
A force F (= m × α, m is the mass of the second support piece 7) is applied to the emphasis of the substrate piece 7, and the force acts on the first fixed portion 14a and the second fixed portion 14c. The first fixed portion 14a and the second fixed portion 14c and the second fixed portion 14c are arranged in the case where the first fixed portion 14a and the second fixed portion 14c are arranged outside the annular connecting piece 12, respectively. The magnitude of the force acting on the portion 14c is different. The force acting on the first fixed portion 14a and the second fixed portion 14c is larger when the first fixed portion 14a and the second fixed portion 14c are arranged inside the annular coupling piece 12. Become. This is shown in FIG.
It is clear from the principle of the second kind insulator shown in That is, as shown in FIG. 5, the action point is placed at the center and the power point and the fulcrum are outside. The small upward force f applied to the force point becomes a large upward force nf at the point of action and can be increased.

The operation of the acceleration sensor 1 of the present invention will be described. The acceleration sensor 1 has a detection axis 9 (Z
When the acceleration α in the (axis) direction (+ Z-axis direction) is applied, the first support piece 5 of the support substrate 4 is fixed, so that the inertia force F (= m × α) is applied to the second support piece 7. This force F causes the second support piece 7 to bend from the hinge portion 8 in the −Z-axis direction. When the second support piece 7 bends in the −Z-axis direction, a force in the −X-axis direction acts on the second fixed portion 14 c fixed to the second support piece 7. On the other hand, since the first fixed portion 14a is fixed to the first substrate piece 5 that does not move, a force in the + X-axis direction is applied. That is, the force X in the -X-axis direction acts on the second fixed portion 14c, and the force f in the + X-axis direction acts on the first fixed portion 14a. When the same force f is applied to the first fixed portion 14a and the second fixed portion 14c of the annular coupling piece 12 in the opposite directions and in the X-axis direction, as described in FIG. A force F directed toward the center of the annular connecting piece 12 in the Y-axis direction acts on 14b and the second coupling piece 14d. Due to this force F, the piezoelectric sensor element 2
0 is a compressive force. When the piezoelectric sensor element 20 is, for example, a double tuning fork type piezoelectric vibration element, the frequency decreases.
When the acceleration α in the −Z-axis direction is applied to the acceleration sensor 1, the second support piece 7 is bent in the + Z-axis direction from the hinge portion 8, and an extension force (tensile force) is applied to the piezoelectric sensor element 20. When the piezoelectric sensor element 20 is a double tuning fork type piezoelectric vibration element, its frequency increases.
The direction of the acceleration α can be detected by increasing or decreasing the frequency of the piezoelectric sensor element 20, and the magnitude of the acceleration α can be detected from the amount of change in frequency.

4 (a), 4 (b), and 4 (c) are piezoelectric sensors supported and fixed to the hinge portion 8 of the support substrate 4, which is a main portion of the acceleration sensor 1, and the first substrate piece 5 and the second substrate piece 7. FIG. 10 is a main part plan view showing the mutual positional relationship with FIG. FIG. 4A is a plan view when the longitudinal center line of the piezoelectric sensor element 20 is shifted to the right in the figure from the longitudinal center line of the hinge portion 8. FIG.
) Is a plan view when the longitudinal center line of the piezoelectric sensor element 20 coincides with the longitudinal center line of the hinge portion 8. FIG. 4C is a plan view when the longitudinal center line of the piezoelectric sensor element 20 is shifted to the left in the figure from the longitudinal center line of the hinge portion 8.
The sensor sensitivity (frequency change when the same force is applied) in each of FIGS. 4A, 4B, and 4C was simulated using the finite element method. As a result, in the case of FIG. 4B, the stress is evenly applied to each of the connecting pieces 12a1, 12a2, 12b1, 12b2 of the annular connecting piece 12, and the stress is concentrated on the central part of the hinge part 8, so that the sensor sensitivity is improved. It turned out to be the largest. In the case of FIGS. 4A and 4C, the stress applied to each beam of the frame portion 12 is not uniform, and the stress applied to the hinge portion 8 is distributed toward the end from the center, and the sensor sensitivity is also reduced. There was found.
On the other hand, in Japanese Patent No. 2851566, as shown in FIG.
The hinge axis (the center line of the hinge) and the center line in the longitudinal direction of the vibrating branch (double tuning fork vibrator) are separated from each other, which is greatly different from the acceleration sensor of the present invention.

In the above, the shape of the annular connecting piece 12 is a parallelogram as a quadrangle in which corners exist at the positions of the first connecting piece 14b, the second connecting piece 14d, the first fixed portion 14a, and the second fixed portion 14c. However, the shape of the annular connecting piece 12 is not limited to this. Although there is a concern that the detection sensitivity of the acceleration sensor 1 may be somewhat lower than that of the above embodiment, the first connecting piece 12a and the second connecting piece 12b are different in length from each other and have a substantially letter shape (V Or a substantially U-shape.
That is, the first connecting piece 12a is configured to have the same length of the connecting piece 12a1 and the connecting piece 12a2, the second connecting piece 12b is configured to have the same length of the connecting piece 12b1 and the connecting piece 12b2, and The first connecting piece 12a and the second connecting piece 14b between the first connecting piece 14b and the second connecting piece 14d
The structure with a difference in length with the connection piece 12b may be sufficient.
Alternatively, the annular connecting piece 12 may be a hollow, substantially square or rectangular shape, and the connecting pieces 12a1, 12a2, 12b1, 12b2 may be bent or refracted so as to form square or rectangular corner portions.
Moreover, the 1st connection piece 12a and the 2nd connection piece 12b may be formed in semicircle shape, semi-elliptical shape, or semi-oval shape, respectively.
Even if it is the 1st connection piece 12a and the 2nd connection piece 12b of any shape above, the 2nd board piece 7
The direction of the force applied to the first connecting piece 12a is changed by 90 degrees and the magnitude of the force is increased.
In addition, since the distortion in the second connecting piece 12b becomes uniform, there is an effect that an acceleration sensor that is resistant to vibration, impact, and the like can be configured.

The acceleration sensor 1 is assembled by applying an adhesive 30, for example, low melting point glass with little residual strain, to the first fixed portion 14a and the second fixed portion 14c of the piezoelectric sensor 10, and the first fixed portion 14a and the second fixed portion 14c. 2 The fixed portion 14c is attached to the first support surface 5a and the second support surface 7a of the support substrate 4,
Adhere and fix. Alternatively, the adhesive 30 may be applied to predetermined portions of the first support surface 5 a and the second support surface 7 a of the support substrate 4, and the piezoelectric sensor 10 may be placed and fixed on the adhesive 30. The acceleration sensor 1 is configured by placing a piezoelectric substrate 10 fixed to the support substrate 4 in a sealed container (not shown) and evacuating the inside. By evacuating the inside of the acceleration sensor 1, the Q value of the piezoelectric sensor element 20 is improved and it is easy to excite with an oscillator.
In place of fixing by the bonding member with the adhesive 30, there are metal bonding using metal bumps and bonding using a wax made of a material such as a gold bell.
In order to increase the detection sensitivity of the acceleration sensor 1, there is a method of increasing the mass of the second support piece 7 to increase its mass or attaching a weight to the surface of the second support piece 7.
An example of a method of manufacturing the support substrate 4 and the piezoelectric sensor 10 is a method of manufacturing a flat piezoelectric substrate by applying a photolithography technique and etching means. Further, in the case of the piezoelectric sensor 10, an electrode, a lead electrode, a pad electrode, and the like are formed using a vapor deposition method. As a piezoelectric substrate,
There are piezoelectric substrates such as quartz, lithium tantalate, lithium niobate, and langasite. For example, when a quartz substrate (quartz wafer) is used, the photolithography technique and the etching technique have a long track record, and mass production of the piezoelectric sensor 10 with high dimensional accuracy and the support substrate 4 is easy.
If the same material is used for the support substrate 4 and the piezoelectric sensor 10, expansion due to temperature change,
Since the shrinkage can be made substantially the same, the detection accuracy, temperature characteristics, aging, etc. of the piezoelectric sensor are improved.

The acceleration sensor 1 includes a flat plate-like first substrate piece 5 on which the support substrate 4 is fixed, a movable-side flat plate-like second substrate piece 7, and a hinge portion 8 that connects both of them. A first fixed portion 14a and a second fixed portion 14c are provided at one facing portion of the annular connecting piece 12, and both ends of the piezoelectric sensor element 20 are connected to the other facing portion. In addition, each of the first fixed portion 14a and the second fixed portion 14c is formed to protrude into the annular connecting piece 12. Since it is such a structure, it is possible to form the supporting substrate 4 and the piezoelectric sensor 10 with high dimensional accuracy by using a flat piezoelectric substrate and applying a photolithography technique and an etching technique. The acceleration sensor 1 can be mass-produced. In addition, since the first fixed portion and the second fixed portion are formed inside the annular connecting piece, the acceleration sensor 1 converts the direction of the force generated by applying the acceleration by 90 degrees, It acts to increase the size more than that formed outside the annular connecting piece. Therefore, it is possible to detect a small acceleration (high sensitivity), and to obtain an acceleration sensor with high detection accuracy and reproducibility.

In addition, the acceleration sensor 1 is configured such that the variation in distortion generated in each part of the annular connecting piece 12 is reduced by positioning the center part in the short direction of the piezoelectric sensor element 20 within the width in the short direction of the hinge part 8. There is an effect that the detection sensitivity of the acceleration sensor is improved.
In addition, by making the short direction center portion of the piezoelectric sensor element 20 and the short width direction center portion of the hinge portion 8 substantially coincide with each other, the distortion generated in each portion of the annular connecting piece 12 becomes uniform, and the sensitivity of the acceleration sensor. There is an effect that the (frequency change amount of the piezoelectric sensor element when the same acceleration is applied) is the best and the reproducibility is improved.
Further, by forming each beam of the annular connecting piece 12 in a narrow band shape having the same width, there is an effect that the transmission efficiency of the force generated by the application of acceleration is good and small acceleration can be detected with good reproducibility. .

FIG. 6 is a modification of the piezoelectric sensor 10 shown in FIG. The first of the annular connecting piece 12
The shapes of the connecting piece 12a and the joining portion 12ab of the first fixed portion 14a are slightly different from those of the piezoelectric sensor 1 shown in FIG. That is, the center portion of the first connecting piece 12a is curved toward the center of the annular connecting piece 12, and the connector between the first fixed portion 14a and the first connecting piece 12a is also narrowed. The second connecting piece 12b is first with respect to the longitudinal center line of the piezoelectric sensor element 20.
It is formed symmetrically with the connecting piece 12a.
The annular connecting piece 12 is shaped in this way because the strain generated in the annular connecting piece 12 is evenly distributed when a force is applied to the first fixed portion 14a and the second fixed portion 14c. It is to make it.

FIG. 7 shows a modification of the piezoelectric sensor 10 shown in FIG. That is, the difference from the piezoelectric sensor 10 of FIG. 6 is that the lead pieces 16a and 16b are connected along the longitudinal direction of the piezoelectric sensor element 20 to the joint portion 12ab between the first connecting piece 12a and the first fixed portion 14a. This is the point. Lead electrodes (not shown) from the excitation electrodes of the piezoelectric sensor element 20 are formed on the extraction pieces 16a and 16b.
Is extended. A flexible and conductive silicon rubber or the like is applied between the lead pieces 16a and 16b and the first substrate piece 5 so as to be electrically connected to the lead electrode.
In addition, the drawer | drawing-out pieces 16a and 16b and the surface of the support substrate 4 of the location which opposes this are not fixed. That is, the extraction pieces 16a and 16b are in a cantilever state.

FIG. 8 is a block diagram showing the configuration of the accelerometer 3 of the present invention. The accelerometer 3 includes the acceleration sensor 1, an oscillation circuit 51 that excites the piezoelectric sensor element 20 of the acceleration sensor 1, a counter 53 that counts the output frequency of the oscillation circuit 51, and an operation that processes the signal of the counter 53. The accelerometer includes an IC 50 having a circuit 55 and a display unit 56.
The acceleration sensor 1 is configured by forming the support substrate 4 and the piezoelectric sensor 10 using a quartz substrate and using the piezoelectric sensor element 20 as a double tuning fork type quartz vibrating element. When an accelerometer is composed of the acceleration sensor 1 and the IC having the above functions, the acceleration detection sensitivity is greatly improved, and an excellent accelerometer such as detection accuracy, reproducibility, temperature characteristics, and aging can be realized. There is.

DESCRIPTION OF SYMBOLS 1 ... Acceleration sensor, 3 ... Accelerometer, 4 ... Support substrate, 5 ... 1st substrate piece, 5a ... 1st support surface, 7 ... 2nd substrate piece, 7a ... 2nd support surface, 8 ... Hinge part, 9 ... Detection axis, 10 ... piezoelectric sensor,
12 ... annular connecting piece, 12a ... first connecting piece, 12b ... second connecting piece, 12a1, 12a2, 1
2b1, 12b2 ... connecting piece, 12ab, 12cd ... joining portion, 14a ... first fixed portion, 14
b ... 1st coupling piece, 14c ... 2nd to-be-fixed part, 14d ... 2nd coupling piece, 16a, 16b ... Extraction piece, 20 ... Piezoelectric sensor element, 22a, 22b ... Vibrating arm, 24a, 24b ... Base part, 26a ...
1st support piece, 26b ... 2nd support piece, 30 ... Adhesive, 50 ... IC, 51 ... Oscillation circuit, 53 ...
Counter, 55 ... arithmetic circuit, 56 ... display unit

Claims (8)

A piezoelectric sensor; and a support substrate having a first support surface and a second support surface that support the piezoelectric sensor,
The piezoelectric sensor is fixed to the first and second support surfaces in order to support the piezoelectric sensor element on the support substrate and a piezoelectric sensor element that generates an electric signal according to a force applied in the detection axis direction. A first fixed part and a second fixed part, and an annular connecting piece for connecting the first fixed part and the second fixed part to the piezoelectric sensor element, respectively.
The support substrate includes a fixed first substrate piece having the first support surface, and a movable second substrate piece including the second support surface juxtaposed in the surface direction of the first support surface; A hinge portion for connecting the opposing side edges of the first substrate piece and the second substrate piece to swing the second substrate piece in the thickness direction;
With
The piezoelectric sensor element has an elongated configuration extending in a direction orthogonal to the detection axis direction,
And spaced apart from each of the support surfaces in a state of facing the hinge portion,
The annular connecting piece includes a first connecting piece for connecting between both ends in the longitudinal direction of the piezoelectric sensor element via the first fixed portion, and the piezoelectric sensor element via the second fixed portion. A second connecting piece for connecting the longitudinal ends.
The acceleration sensor according to claim 1, wherein the first and second fixed parts are configured to protrude toward the piezoelectric sensor element from the inside of the first connection piece and the second connection piece, respectively. The acceleration sensor according to claim 1, wherein a position of a center part in a short direction of the sensor element is located within a width in a short direction of the hinge part. The acceleration sensor according to claim 1 or 2, wherein a position of a center portion in a short direction of the sensor element coincides with a center portion in a short width direction of the hinge portion. 4. The annular connection piece viewed from a direction orthogonal to the first and second support surfaces has a narrow band shape having the same width over the entire length. 5. Acceleration sensor. The first and second connecting pieces are each substantially in a letter shape (V shape).
5. The acceleration sensor according to any one of 4 to 4. The acceleration sensor according to claim 1, wherein each of the first and second connecting pieces has a U shape. 5. The acceleration sensor according to claim 1, wherein each of the first and second connecting pieces has a semicircular shape, a semielliptical shape, or a semielliptical shape. The acceleration sensor according to any one of claims 1 to 7,
An IC having an oscillation circuit for exciting the piezoelectric sensor element of the acceleration sensor, a counter for counting the output frequency of the oscillation circuit, and an arithmetic circuit for processing the signal of the counter;
An accelerometer characterized by comprising:

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