JP5076657B2 - Double tuning fork type vibration element and acceleration detection unit for stress sensitive sensor - Google Patents

Description

  The present invention relates to a double tuning fork type piezoelectric vibration element and an acceleration detection unit, and more particularly to a double tuning fork type piezoelectric vibration element in which a groove is formed in a vibrating arm portion to improve sensitivity and an acceleration detection unit using the same.

  Conventionally, acceleration sensors have been widely used from automobiles, airplanes, rockets to abnormal vibration monitoring devices for various plants. Above all, the pressure sensor and acceleration sensor using a double tuning fork type piezoelectric vibration element change the frequency of the double tuning fork type piezoelectric vibration element in proportion to the magnitude of applied stress, making data processing easy and measuring accuracy, Excellent measurement sensitivity, reproducibility, temperature characteristics, etc. The electrode structure of the double tuning fork type piezoelectric vibration element is disclosed in Patent Document 1. FIG. 5A is a perspective view of a double tuning fork type piezoelectric vibration element 50, that is, a piezoelectric bending vibrator having a shape in which the free ends of two tuning fork type piezoelectric vibration elements are connected to each other. The double tuning fork type piezoelectric vibrating element 50 includes a piezoelectric substrate 51 having a base 52 and two vibrating arm portions 53a and 53b, excitation electrodes 55 formed on four surfaces of the vibrating arm portions 53a and 53b, and an extraction electrode. (Lead electrode) 57.

FIG. 5B is a plan view of the double tuning fork type piezoelectric vibration element 50, and excitation electrodes 55 divided into three are formed on the respective vibrating arm portions 53a and 53b. The excitation electrode 55 is divided at a vibration node, and the excitation electrode 55 is connected to the divided excitation electrodes 55 adjacent to each other so as to apply a voltage having a reverse polarity. As shown in FIG. 5B, the excitation electrode 55 is divided at a point of 0.255 L from the ends of the base portions 52 near the center, where L is the length of the vibrating arm portion 53 a (53 b). FIG. 5C is a cross-sectional view taken along the line AA of FIG. 5B, and shows a method for connecting the excitation electrodes 55 formed on the front and back surfaces and both side surfaces of the vibrating arm portions 53a and 53b. It is. The opposing excitation electrodes 55 of the vibrating arm portions 53a and 53b are connected to each other, and electrodes having the same polarity are connected to form two terminals. When the excitation electrodes 55 are connected in this way, voltages having opposite polarities are applied to the corresponding excitation electrodes 55 of the vibrating arm portions 53 a and 53 b, and the longitudinal axis of the double tuning fork type piezoelectric vibrating element 50 is Symmetric bending vibrations can be excited on both sides.
In recent years, tuning fork-type piezoelectric vibrators having grooves on the front and back surfaces of both vibrating arms have been put into practical use.
JP 60-39911 A

However, Patent Document 1 merely discloses an electrode structure of a double tuning fork type piezoelectric vibration element. When the size of the double tuning fork type piezoelectric vibration element is reduced, the excitation efficiency deteriorates, the effective resistance of the vibrator, that is, the CI value increases, and the design of the oscillation circuit becomes extremely difficult when used in the acceleration detection unit. there were.
The present invention has been made to solve the above problems, and it is an object of the present invention to provide a double tuning fork type piezoelectric vibration element having excellent excitation efficiency and an acceleration detection unit using the same.

To achieve the above object, the double-ended vibration element for stress-sensitive sensor of the present invention, both end portions
A pair of parallel vibrating arms in which the frequency of flexural vibration changes according to the change in stress applied between them ,
The base part integrally joined to each of the end parts in the longitudinal direction of each of the vibrating arm parts, the vibration
A plurality of grooves arranged along the longitudinal direction on at least one of the front and back surfaces of the arm, and
And an excitation electrode formed in each of the plurality of grooves .
When the double tuning fork type piezoelectric vibration element is configured as described above, the excitation efficiency is high, that is, the effective resistance of the double tuning fork type piezoelectric vibration element is reduced. There is an advantage that an acceleration detection unit with excellent accuracy and sensitivity can be configured.

Moreover , the double tuning fork type vibration element for a stress sensitive sensor according to the present invention is provided between the adjacent grooves.
It is characterized by the presence of bending vibration nodes.
When the double tuning fork type piezoelectric vibration element is configured as described above, the excitation efficiency is high, that is, the effective resistance of the double tuning fork type piezoelectric vibration element is reduced. There is an advantage that an acceleration detection unit with excellent accuracy and sensitivity can be configured.

The double-ended vibration element for stress-sensitive sensor of the present invention, either each end of the vibrating arms of the respective
When the first vibration is divided into the first, second, and third vibration region in order toward the other end, the first vibration
The moving portion, the second vibrating portion, and the third vibrating portion have the plurality of groove portions on the front and back surfaces, respectively.
And the excitation electrode, and other excitation electrodes on both side surfaces thereof, in front of the first vibrating section
The excitation electrode on the back surface of the front surface, the other excitation electrode of the second vibration part, and the table of the third vibration part
The excitation electrode on the back surface is conductive, the other excitation electrode of the first vibration part, the second vibration
The excitation electrodes on the front and back surfaces of the part and the other excitation electrodes of the third vibration part are conductive,
The excitation electrode on the front and back surfaces of the first vibration part and the other vibration arm part of the first vibration arm part
The other excitation electrode of the first vibrating part is electrically connected, and the first vibration of one of the vibrating arm parts is provided.
The other excitation electrode of the moving part and the excitation electrode of the front and back surfaces of the first vibrating part of the other vibrating part
And is conductive .
When the double tuning fork type piezoelectric vibration element is configured as described above, the excitation efficiency is good, that is, the effective resistance of the double tuning fork type piezoelectric vibration element is reduced. For example, when used in an acceleration detection unit, the structure of the oscillation circuit is easy, and the acceleration circuit There is an advantage that an acceleration detection unit with excellent accuracy and sensitivity can be configured.

A fixed member, the fixed member supporting lifting by Tei Ru movable member, the fixed member and the and connects the movable member, position of the movable member based on the position of the fixing member with the change in acceleration
A beam having flexibility so that the device is displaced, and the vibrating arm according to the displacement of the fixing member
Is supported at both ends the stress applied to the parts is through a fixed member and a movable member so as to change
A double-ended tuning fork vibration element of the present invention which are, an acceleration sensing unit which includes a.
When the acceleration detection unit is configured as described above, the configuration of the oscillation circuit is easy, and an acceleration detection unit having excellent acceleration accuracy and sensitivity can be configured.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing a configuration of a double tuning fork type crystal vibrating element 1 according to a first embodiment of the present invention. In the double tuning fork type crystal resonator element 1, one end of each of a pair of rectangular parallelepiped elongated vibrating arms 7 and 8 is joined to one base 6a, and the other end is connected to the other base 6b. 2 is a double tuning fork type piezoelectric vibration element including a piezoelectric substrate 5 bonded to each other and excitation electrodes formed on four surfaces of the respective vibrating arm portions 7 and 8.
The vibrating arm portions 7 and 8 are formed symmetrically with respect to the center axis of the double tuning fork type piezoelectric vibrating element with the gap 9 interposed therebetween, and the first vibrating portions 7a and 8a, the second vibrating portions 7b and 8b, and the third vibrating portion, respectively. It is comprised from the vibration parts 7c and 8c. The first vibrating parts 7a and 8a and the third vibrating parts 7c and 8c have substantially the same length, and the second vibrating parts 7b and 8b are formed longer than the first vibrating parts 7a and 8a.
The first, second, and third groove portions 11a, 11b, and 11c are provided on at least one of the front and back surfaces of the first, second, and third vibrating portions 7a, 7b, and 7c of the vibrating arm portion 7, respectively. It is formed across the bridging portions 13a and 13b. Similarly, the first, second, and third groove portions 12a, 12b, and 12b, respectively, are provided on at least one of the front and back surfaces of the first, second, and third vibrating portions 8a, 8b, and 8c of the vibrating arm portion 8. 12c is formed across the bridging portions 14a and 14b.

In the first embodiment shown in FIG. 1, an example in which grooves are formed on the front and back surfaces of the vibrating arm portions 7 and 8 is shown. For example, the first groove portions formed on the front and back surfaces of the first vibrating portion 7a of the vibrating arm portion 7 are both indicated as 11a. The first, second, and third grooves 11a, 11b, 11c, 12a, 12b, and 12c of the vibrating arm portions 7 and 8 are respectively deposited on the first, second, and third grooves by means of vacuum deposition or sputtering. Excitation electrodes 20a, 20b, 20c, 22a, 22b and 22c are formed. In the case of the excitation electrode, the same symbols are attached to the front and back electrodes.
On both side surfaces of the first, second and third vibrating portions 7a, 7b and 7c of the vibrating arm portion 7, fourth, fifth and sixth excitation electrodes 21a are formed by means of vacuum deposition or sputtering, respectively. , 21b, 21c are formed. The fourth, fifth, and sixth excitation electrodes 21a, 21b, and 21c are insulated by electrodeless portions. Similarly, fourth, fifth, and sixth excitation electrodes 23a, 23b, and 23c are formed on both side surfaces of the first, second, and third vibrating portions 8a, 8b, and 8c of the vibrating arm portion 8, respectively. .

FIG. 2 is a diagram for explaining the excitation electrodes formed on the vibrating arm portions 7 and 8, and the first, second and third vibrating portions 7a, 7b and 7c of the vibrating arm portion 7, and the vibrating arm portions. 8 is a cross-sectional view showing excitation electrodes formed on eight first, second, and third vibrating portions 8a, 8b, and 8c. FIG. In order to indicate the polarity of each excitation electrode, it is displayed using diagonal lines and dots.
On the left side of FIG. 2, the first, second, and third excitation electrodes 20a, 20b, and 20c formed in the first, second, and third grooves 11a, 11b, and 11c on the front and back surfaces of the vibrating arm portion 7 are illustrated. And fourth, fifth and sixth excitation electrodes 21a, 21b and 21c formed on both side surfaces of the first, second and third vibrating portions 7a, 7b and 7c. In the case of the excitation electrode as well, the same reference numerals are given to the front and back surfaces or both side surfaces facing each other in the same manner as the groove.
Further, on the right side of FIG. 2, the first, second, and third excitation electrodes 22a, 22b, and 22c formed in the grooves 12a, 12b, and 12c on the front and back sides of the vibrating arm portion 8 and the vibrating portions 8a, 8b, and 8c are formed. The fourth, fifth and sixth excitation electrodes 23a, 23b and 23c formed on both side surfaces are shown.

FIG. 2 shows the configuration of the excitation electrodes of the vibrating portions 7a, 7b, 7c, 8a, 8b, and 8c of the vibrating arm portions 7 and 8, and also shows the electric lines of force from one excitation electrode to the other excitation electrode. ing. The electric lines of force are stronger than the conventional electric lines of force shown in FIG. 5C, the electric field strength in the X-axis direction is increased, and the vibration efficiency is increased. Each excitation electrode is connected using a lead electrode (not shown) formed on the vibrating arm portions 7 and 8 by means such as vapor deposition. Exciting electrodes 20a to 20c and 22a to 22c on the front and back surfaces of the vibrating arm portions 7 and 8 and the exciting electrodes 21a to 21c and 23a to 23c on both sides are connected to each other. Next, the first excitation electrode 20 a on the front and back surfaces of the vibrating arm portion 7, the fifth excitation electrode 21 b on both side surfaces, and the third excitation electrode 20 c on the front and back surfaces were formed on the vibrating arm portion 7. Connection is made with a lead electrode (not shown). Then, the fourth excitation electrode 21a on both side surfaces of the vibrating arm portion 7, the second excitation electrode 20b on the front and back surfaces, and the sixth excitation electrode 21c on both side surfaces are connected by lead electrodes.
Similarly, the first excitation electrode 22 a on the front and back surfaces of the vibrating arm portion 8, the fifth excitation electrode 23 b on both side surfaces, and the third excitation electrode 22 c on the front and back surfaces are formed on the vibrating arm portion 8. Connection is made with a lead electrode (not shown). Then, the fourth excitation electrode 23a on both side surfaces of the vibrating arm portion 8, the second excitation electrode 22b on the front and back surfaces, the sixth excitation electrode 23c on both side surfaces, and the lead electrodes are connected. The first excitation electrodes 20a on the front and back surfaces of the vibrating arm portion 7 and the fourth excitation electrodes 23a on both side surfaces of the vibrating arm portion 8 are connected by lead electrodes, and fourth electrodes on both side surfaces of the vibrating arm portion 7 are connected. The excitation electrode 21a and the first excitation electrode 22a on the front and back surfaces of the vibrating arm portion 8 are connected by a lead electrode to constitute a two-terminal double tuning fork type piezoelectric vibration element.

As shown in FIG. 1 and FIG. 2, when the electrodes divided into three are formed on the vibrating arm portions 7 and 8 and connected as described above with the lead electrodes (not shown), the longitudinal direction of the double tuning fork type quartz vibrating element 1 Symmetrical bending vibrations are excited on both sides of the central axis.
A characteristic of the double tuning fork type crystal resonator element of the first embodiment is that three groove portions are formed on the front and back surfaces of each vibrating arm portion of the double tuning fork type crystal resonator element, and excitation electrodes are formed in the groove portions. As a result, the electric field in the X-axis direction is strengthened, and as a result, flexural vibration is effectively excited, and the effective resistance of the double tuning fork type crystal vibrating element is reduced. If such a miniaturized double tuning fork type crystal vibrating element is used in a force detection unit or acceleration detection unit, the unit can be downsized, the design of the oscillation circuit is easy, and a unit with high detection sensitivity is constructed. There is an effect that can be done.

FIG. 3 is a perspective view showing a configuration of a double tuning fork type crystal vibrating element according to the second embodiment.
In the double tuning fork type crystal resonator element of the first embodiment, three groove portions are formed on the front and back surfaces of each vibrating arm portion, and excitation electrodes are formed in the groove portions. The double tuning fork type crystal resonator element according to the embodiment is characterized in that one groove portion is formed on each of the front and back surfaces of each vibrating arm.
That is, in the double tuning fork type crystal vibrating element 2, one end of each of two parallel vibrating arm portions 7 and 8 having a thin prismatic shape is joined to one base portion 6a, and each of the vibrating arm portions 7 and 8 is connected to the other. This is a double tuning fork type piezoelectric vibration element including a piezoelectric substrate 5 having its end portion bonded to the other base portion 6b and excitation electrodes formed on the four surfaces of the respective vibrating arm portions 7 and 8.
The vibrating arm portions 7 and 8 are formed symmetrically with the gap 9 interposed therebetween, and are composed of first vibrating portions 7a and 8a, second vibrating portions 7b and 8b, and third vibrating portions 7c and 8c, respectively. The lengths of the first vibrating parts 7a, 8a and the third vibrating parts 7c, 8c are substantially equal, and the second vibrating parts 7b, 8b are longer than the first vibrating parts 7a, 8a. Has been.

Groove portions 11 and 12 are formed on at least one of the front and back surfaces of the vibrating arm portions 7 and 8, respectively. First, second, and third excitation electrodes 20a, 20b, and 20c are formed on the front and back surfaces of the first, second, and third vibrating portions 7a, 7b, and 7c of the vibrating arm portion 7, and the vibrating portion The fourth, fifth and sixth excitation electrodes 21a, 21b and 21c are formed on both side surfaces of 7a, 7b and 7c. Similarly, first, second, and third excitation electrodes 22a, 22b, 22c are formed on the front and back surfaces of the first, second, and third vibrating portions 8a, 8b, 8c of the vibrating arm portion 8, and Fourth, fifth, and sixth excitation electrodes 23a, 23b, and 23c are formed on both side surfaces of the vibrating portions 8a, 8b, and 8c. In the example of FIG. 3, the example which formed the groove parts 11 and 12 in the front and back of each vibration arm part 7 and 8 is shown in figure, respectively. The groove portions 11 and 12 (not shown) on the back surface are also denoted by the same reference numerals as those on the front surface, and the front and back surfaces and both side surfaces are also denoted by the same reference numerals in the case of excitation electrodes.
Configurations of excitation electrodes formed on the grooves 11 and 12 in the first, second and third vibrating portions 7a, 7b, 7c, 8a, 8b and 8c of the vibrating arm portions 7 and 8 and excitation electrodes on both sides. Is as shown in FIG. First, second and third excitation electrodes 20a to 20c and 22a to 22c on the front and back surfaces of the vibrating arm portions 7 and 8, and fourth, fifth and sixth excitation electrodes 21a to 21c and 23a on both side surfaces. ˜23c, the excitation electrodes facing each other are connected by extraction electrodes (lead electrodes) (not shown) formed on the respective vibrating arm portions 7 and 8.

Next, the first excitation electrode 20 a on the front and back surfaces of the vibrating arm portion 7, the fifth excitation electrode 21 b on both side surfaces, and the third excitation electrode 20 c on the front and back surfaces were formed on the vibrating arm portion 7. Connection is made with a lead electrode (not shown). Then, the fourth excitation electrode 21a on both side surfaces of the vibrating arm portion 7, the second excitation electrode 20b on the front and back surfaces, the sixth excitation electrode 21c on both side surfaces, and the lead electrodes are connected.
Similarly, the first excitation electrode 22 a on the front and back surfaces of the vibrating arm portion 8, the fifth excitation electrode 23 b on both side surfaces, and the third excitation electrode 22 c on the front and back surfaces are formed on the vibrating arm portion 8. Connection is made with a lead electrode (not shown). Then, the fourth excitation electrode 23a on both side surfaces of the vibrating arm portion 8, the second excitation electrode 22b on the front and back surfaces, the sixth excitation electrode 23c on both side surfaces, and the lead electrodes are connected. Next, the first excitation electrode 20a on the front and back surfaces of the vibrating arm portion 7 and the fourth excitation electrode 23a on both side surfaces of the vibrating arm portion 8 are connected by lead electrodes, and the both side surfaces of the vibrating arm portion 7 are connected. The fourth excitation electrode 21a and the first excitation electrode 22a on the front and back surfaces of the vibrating arm portion 8 are connected by a lead electrode to constitute a two-terminal double tuning fork type piezoelectric vibration element.
As described above, in the double tuning fork type crystal resonator element according to the second embodiment, one groove portion is formed on each of the front and back surfaces of each vibrating arm of the double tuning fork type crystal resonator element, and an excitation electrode is formed on the groove portion. As a result, the electric field in the X-axis direction is strengthened. As a result, flexural vibration is effectively excited, and the effective resistance of the double tuning fork type crystal vibrating element is reduced. When used in the force detection unit or the acceleration detection unit as in the first embodiment, there is an effect that the oscillation circuit becomes easy and a unit with high detection sensitivity can be configured.

FIG. 4 is a perspective view showing the configuration of the acceleration detection unit of the present embodiment, a fixed member 30 that is not displaced by application of acceleration, and a movable member 35 that is supported by the fixed member 30 in a state of being movable in the direction of acceleration application. The flexible beam 40 for connecting the fixed member 30 and the movable member 35, and the above-mentioned double tuning fork type vibration element 1 having the fixed ends at both ends supported by the fixed member 30 and the movable member 35, respectively. I have. When acceleration in the X-axis direction (shown at the lower left end in FIG. 1) is applied to the acceleration detection unit 3, the beam 40 is stretched / compressed stress (acceleration × mass) to the double tuning fork type vibration element 1 via the movable member 35. ) Is configured to displace the movable member 35 in the acceleration application direction (X axis). The fixed member 30, the movable member 35, and the beam 40 are integrally formed by machining a metal material such as brass, aluminum, phosphor bronze, or the like.
If the double tuning fork type crystal resonator element of the first and second embodiments is used for the acceleration detection unit 3, there is an effect that a unit with high detection sensitivity can be configured.

It is the perspective view which showed the structure of the double tuning fork type piezoelectric vibration element of 1st Embodiment. It is sectional drawing which shows the electrode structure of each vibration part in each vibration arm part. It is the perspective view which showed the structure of the double tuning fork type piezoelectric vibration element of 2nd Embodiment. It is a perspective view which shows the structure of an acceleration detection unit. It is explanatory drawing of the conventional double tuning fork type piezoelectric vibration element, (a) is a perspective view, (b) is a top view which shows electrode arrangement | positioning, (c) is sectional drawing which shows arrangement | positioning of an electrode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 Twin tuning fork type piezoelectric vibration element, 3 Acceleration detection unit, 5 Piezoelectric substrate, 6a, 6b Base part, 7, 8 Vibration arm part, 7a, 7b, 7c, 8a, 8b, 8c Vibration part, 9 Cavity part, 11 11a, 11b, 11c, 12, 12a, 12b, 12c Groove part, 13a, 13b, 14a, 14b Bridge part, 20a, 20b, 20c, 21a, 21b, 21c, 22a, 22b, 22c, 23a, 23b, 23c Excitation electrode, 30 fixed member, 35 movable member, 40 beams

Claims (2)

The frequency of flexural vibration changes according to a change in stress applied between the one end and the other end, and the first vibrating portion and the second vibrating portion in order from the one end side to the other end side. , A third vibrating portion, a bottomed first groove portion that is on the front and back sides of the first vibrating portion and extends from the one end side toward the other end side,
A bottomed second groove portion which is adjacent to the first groove portion on the front and back sides of the second vibration portion and extends from the one end side toward the other end side;
And a third groove portion that is adjacent to the second groove portion on the front and back sides of the third vibrating portion and extends from the one end side toward the other end side,
Furthermore, between the first groove portion and the second groove portion, and between the second groove portion and the third groove portion, a place serving as a node of the bending vibration is included and the first groove portion Projecting from the bottom surface and the bottom surface of the second groove,
A first oscillation arm and the second oscillation arm parallel,
A base portion integrally joined to each of the end portions in the longitudinal direction of each vibrating arm portion, and
In the first groove portion, both side surfaces of the second vibrating portion and the third groove portion, a first excitation electrode which is electrically connected to each other, both side surfaces of the first vibrating portion, the second A second excitation electrode that is electrically connected to each other in the groove portion and on both side surfaces of the third portion, and the first excitation electrode and the second excitation electrode that are provided in the first vibrating arm portion. The second excitation electrode provided in the vibrating arm portion is electrically connected, and the second excitation electrode provided in the first vibrating arm portion and the first vibrating arm portion are provided in the first vibrating arm portion. A double tuning fork type vibration element for a stress sensitive sensor , wherein the excitation electrode is electrically connected . A fixed member, a movable member supported by the fixed member, and the fixed member and the movable member are connected to each other, and the position of the movable member is determined based on the position of the fixed member with a change in acceleration. Both ends of the beam are supported by the fixed member and the movable member so that the stress applied to the vibrating arm portion is changed with the displacement of the fixed member and the beam having flexibility so as to be displaced. An acceleration detection unit comprising: a double tuning fork type vibration element for a stress sensitive sensor according to claim 1 .

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