JP2011085395A - Unit and device for detecting force - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a unit and device for detecting force which is adapted to miniaturization and whose force detection sensitivity is not deteriorated by the miniaturization. <P>SOLUTION: The unit for detecting force includes: first and second frames 3, 4 including a sheet shape having flexibility in the thickness direction; first and second beams 5, 15 connecting facing sides of the first and second frames 3, 4 and subjected to thickness-shear vibration by an electric field in the thickness direction; and upper electrodes 10a, 11a, 20a, 21a and lower electrodes 10b, 11b, 20b, 21b formed on upper and lower surfaces of the first and second beams 5, 15 except the central regions of the first and second beams 5, 15. The first and second beams 5, 15 have a structure connecting each side of the first and second frames 3, 4 along the extension direction of the first and second beams 5, 15 and are constituted so that bending vibration is excited by the thickness-shear vibration generated when a drive signal is applied to the upper and lower electrodes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a force detection unit and a force detection device, and in particular, excites thickness shear vibration by two pairs of upper and lower electrodes sandwiching a piezoelectric beam and excites two pairs of thickness shear vibrations with a phase difference of 180 degrees from each other. The present invention relates to a force detection unit using bending vibration and a force detection device configured using the force detection unit.

Conventionally, force detection units and force detection devices are widely used from automobiles, airplanes, rockets to monitoring abnormal vibrations of various plants. Patent Document 1 discloses an acceleration detection unit using a double tuning fork type piezoelectric vibrator as a stress sensitive element, and an acceleration sensor.
FIG. 6 is a perspective view showing the configuration of the acceleration detection unit 71, and the Z-axis direction is the acceleration detection axis direction. The acceleration detection unit 71 includes an outer frame member 75 and a double tuning fork type piezoelectric vibration element 80 having a stress sensitive part and two fixed end parts 80a and 80b sandwiching the stress sensitive part. The outer frame member 75 is configured by joining the ends of two rectangular and long rectangular columnar members 75a and 75b and two short square columnar members 75c and 75d. Outer frame member 75
And the piezoelectric substrate of the double tuning fork type piezoelectric vibration element 80 are integrally formed of the same piezoelectric material, and the piezoelectric substrate is thinner than the outer frame member 75 and has one surface of the outer frame member 75. Are formed in parallel.
Two opposing ends 80a, 80b of the double tuning fork type piezoelectric vibration element 80 are joined to one opposing short side member 75c, 75d of the outer frame member 75, respectively, and the other opposing long side of the outer frame member 75 is joined. Grooves 77a and 77b are formed in the members 75a and 75b, respectively. Groove 77a, 77
The member 75d side from b is a fixed end, and the member 75c side from the groove portions 77a and 77b is a free end (movable end). For example, the fixed end side is fixed to a base (not shown) at the black spot in the figure, and the free end side is Z
When an acceleration G in the axial direction (vertical direction in the figure) is applied, it is formed so as to be flexible from substantially the center part of the groove parts 77a and 77b.

As shown in FIG. 6, when the acceleration G in the Z-axis direction is applied to the free end side, the grooves 77a, 77b
However, as a result, a compression or expansion stress acts on the double tuning fork type piezoelectric vibration element 80 connected to the member 75c. When stress acts on the double tuning fork type piezoelectric vibration element 80, the resonance frequency of the double tuning fork type piezoelectric vibration element 80 changes. Since the frequency change amount of the double tuning fork type piezoelectric vibration element 80 is proportional to the applied stress, it is disclosed that the applied stress (acceleration × mass), that is, acceleration can be measured from the frequency change amount.

JP 2008-309731 A

There is a strong demand for miniaturization of acceleration sensors, force detection devices, and the like. However, when a conventional acceleration detection unit (force detection unit), for example, the acceleration detection unit disclosed in Patent Document 1, is reduced in size, it is necessary to reduce the size of the tuning fork type piezoelectric vibration element. When the tuning fork type piezoelectric vibration element is downsized, there is a problem that the stress detection sensitivity is lowered.
The stress sensitivity of the tuning fork type piezoelectric vibration element is inversely proportional to the cube of the width of the vibrating arm and proportional to the square of the length. That is, if the length of the vibrating arm is shortened, the sensitivity decreases. Further, if the width of the vibrating arm is reduced to increase the stress sensitivity, it becomes difficult to form the excitation electrode and the extraction electrode. Further, when the width of the vibrating arm is reduced, the thermoelastic loss is increased, and there is a problem that the Q value of the tuning fork type piezoelectric vibrating element is deteriorated.
The present invention has been made to solve the above-described problems, and provides a force detection unit and a force detection device that have good force detection sensitivity and are suitable for downsizing.

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 In order to realize a force detection unit with good force detection sensitivity and suitable for downsizing, the force detection unit according to the present invention is a thin plate-like first and second plate having flexibility in the thickness direction. A first frame and a second beam, which are coupled to the opposing sides of the first frame body and the first frame body, and vibrate due to slip strain due to an electric field in the thickness direction, and the first and second beams The upper and lower electrodes formed on the upper and lower surfaces of the first and second beams, avoiding the central region, and the first and second frames along the extending direction of the first and second beams Connecting each side of the body, the first and second beams are
The present invention is characterized in that bending vibration is excited by vibration due to slip distortion generated when a drive signal is applied to the upper electrode and the lower electrode.

Bending vibration is excited in each of the first and second beams by using two thickness shear vibrations having different phases that are excited in the first and second beams. Since the resonance frequency of the bending vibration of the beam is changed by the force applied to the first and second beams, the frequency change is used for force detection. Therefore, compared with the tuning fork type piezoelectric vibration element, there is an effect that the electrode can be easily formed even if the size is reduced, and the detection sensitivity can be maintained. Moreover, there is an effect that the force detection sensitivity can be doubled by differentially operating the first and second beams excited by bending vibration. Further, the differential operation has an effect of reducing unnecessary vibrations picked up by the first and second beams, for example, vibrations in the other axis direction.

Application Example 2 In the force detection unit, the bottom surface of the first beam is flush with the bottom surface of the first frame, and the top surface of the second beam is flush with the top surface of the second frame. The force detection unit according to Application Example 1, wherein the force detection unit is located above.

The force detection unit forms the first beam below the center line in the thickness direction of the first frame,
Since the second beam is formed above the center line in the thickness direction of the second frame, the first beam and the second beam are applied when a force in the thickness direction is applied to the force detection unit. The stress generated in the beam is
One is elongation stress and the other is compression stress. That is, the resonance frequencies of the first beam and the second beam change in opposite directions. That is, since the first beam and the second beam can be differentially operated, the force detection sensitivity is doubled, and unnecessary vibration generated in the first and second beams, for example, vibration in the other axis direction is reduced. There is an effect that can be.

Application Example 3 Further, in the force detection unit, the first and second frame bodies are the first and second frames.
The force detection unit according to the first application example, wherein a groove is provided on at least one of the upper and lower surfaces of the member parallel to the beam.

By forming groove portions in the members of the first and second frame members parallel to the first and second beams, the first and second frame members are applied from the groove portions by applying a force in the thickness direction. It becomes possible to be configured to bend easily, it becomes possible to detect a small force, and there is an effect that the detection range of the force is expanded.

Application Example 4 In addition, the force detection unit includes the first and second beams on both sides of the first and second beams.
And a counter beam extending from the opposing sides of the second frame body in parallel with the first and second beams, respectively, and extending toward the center of each of the first and second frame bodies, The force detection unit according to Application Example 1, wherein the counter beam is displaced so as to cancel the displacement due to the bending vibration of the first and second beams.

By disposing the counter beam parallel to the first and second beams on both sides of the first and second beams, respectively, the displacement of the first and second beams due to the bending vibration is canceled out.
Since the counter beam is displaced, vibration leakage of the first and second beams can be reduced. As a result, there is an effect that the Q value of the first and second beams can be increased and the detection accuracy of the force detection unit can be increased.

Application Example 5 A force detection device according to the present invention detects a frequency change of the bending vibration or thickness shear vibration of the force detection unit according to any one of Application Examples 1 to 4 and the first and second beams. And a detecting unit.

If the force detection unit according to any one of the application examples 1 to 4 is used, the bending vibrations of the first and second beams are differentially operated, and the frequency change is detected by the detection unit, thereby detecting sensitivity. There is an effect that it is possible to construct a force detection device in which the power is doubled. In addition, it is possible to reduce the leakage of bending vibrations of the first and second beams, to have excellent detection sensitivity, to suppress other axis sensitivity, and to configure a force detection device with a wide detection range.

The structure of the force detection unit 1 which concerns on this invention is shown, (a) is a top view, (b) is sectional drawing in PP, (c), (d) is a top view of the frames 3 and 4. FIG. (A), (b), (c) is sectional drawing in Q1-Q1, Q2-Q2, Q3-Q3 of Fig.1 (a), respectively. The principal part expanded sectional view explaining the vibration mode of a 1st beam (or 2nd beam). (A), (b) is sectional drawing which shows a mode that the force detection unit 1 deform | transforms with the applied force F. FIG. Sectional drawing which shows the structure of the force detection apparatus of this invention. The perspective view which shows the structure of the conventional acceleration detection unit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a force detection unit 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 PP. 1 (c) and 1 (d) are divided into two parts in order to understand the structure of the piezoelectric substrate 2, and the first and second beams 5, 15 and the counter beams 6, 7, 16, 16, 1
In the plan view in which 7 is omitted, they are referred to as frames 3 and 4 respectively. However, the first and second beams 5, 15
The broken lines 5 and 15 are shown to show the mounting positions of
In the force detection unit 1, slip distortion occurs due to the thin plate-like first and second frame bodies 3 and 4 having flexibility in the thickness direction, in the Y-axis direction in FIG. 1A, and the electric field in the thickness direction. For example, the first and second beams 5 and 15 that vibrate in thickness-shear vibration are provided, and the first and second frames 3 and 4 have first and second members 3b and 3d, which will be described later, as constituent elements. The beam 5 is connected, and the second beam 15 is connected between the member 4b and the member 4d. Further, on both sides of the first beam 5, counter beams 6, 7 extending from the opposing members 3 b, 3 d of the first frame 3 to the central region of the frame 3 in parallel with the first beam 5 are provided. . Similarly, the opposing members 4 of the second frame 4 on both sides of the second beam 15.
counter beams 16 extending from b, 4d to the central region of the frame 4 in parallel with the second beam 15, respectively.
, 17.

The first frame 3 is composed of four members 3a, 3b, 3c, and 3d having the same thickness (Y-axis direction) as shown in the plan view of FIG. 1 (c), and one end of the member 3a. And one end of the member 3b, the other end of the member 3b and one end of the member 3c are joined, and the other end of the member 3c and one end of the member 3d are joined together. The other end of the member 3d and the other end of the member 3a are joined to form a hollow flat frame 3.
Similarly, as shown in the plan view of FIG. 1 (d), the second frame body 4 is 4 having the same thickness (Y-axis direction).
It consists of the members 4a, 4b, 4c, 4d, and joins one end of the member 4a and one end of the member 4b, and connects the other end of the member 4b and one end of the member 4c. The other end of the member 4c and one end of the member 4d are joined, the other end of the member 4d and the other end of the member 4a are joined, and a hollow flat frame 4 Is configured.
A thin groove portion 30 is formed on at least one of the upper and lower surfaces of the central portions of the members 3a and 3c and the members 4a and 4c of the first and second frame bodies 3 and 4, and the groove portion in the thickness direction (Y-axis direction). The structure is more flexible than 30.
In addition, although it was set as the structure which joined several members as the 1st frame 3 and the 2nd frame 4, the structure by which several members were integrally formed may be sufficient.

The first beam 5 and the counter beams 6 and 7 have substantially the same thickness (in the Y-axis direction) and are formed thinner than the thickness of the first frame 3. The bottom surfaces of the first beam 5 and the counter beams 6 and 7 and the bottom surface of the first frame 4 are configured to be on the same plane.
Further, the second beam 15 and the counter beams 16 and 17 have substantially the same thickness, and are formed thinner than the thickness of the second frame 4. The upper surfaces of the second beam 15 and the counter beams 16, 17;
The upper surface of the frame 4 is configured to be on the same plane.
The outer side surface of the member 3c of the first frame 3 and the outer side surface of the member 4a of the second frame 4 are combined,
The first and second frames 3 and 4 are integrated together to form the piezoelectric substrate 2.
That is, the first beam 5 and the counter beams 6 and 7 are in the thickness direction (Y-axis direction) of the piezoelectric substrate 2.
The second beam 15 and the counter beams 16 and 17 are formed above the center line in the thickness direction (Y-axis direction) of the piezoelectric substrate 2.

As shown in FIG. 1A, FIG. 2A, and FIG. 2B, the upper electrodes 10a and 11a are formed on the upper surface of the first beam 5, avoiding the central region of the first and second beams 5 and 15. On the upper surface of the second beam 15, the upper electrode 2
0a and 21b are formed. Lower electrodes 10b and 11b are formed on the lower surface of the first beam 5, and lower electrodes 20b and 21b are formed on the lower surface of the second beam 15.
Furthermore, extraction electrodes 10c, 11c and 20c, 21c extend from the upper electrodes 10a, 11a and 20a, 21a of the first and second beams 5, 15 and are pad electrodes (formed at the ends of the force detection unit 1). (Not shown). Similarly, the lower electrodes 10b, 11b and 20
Lead electrodes 10d, 11d and 20d, 21d extend from b and 21b and are connected to pad electrodes (not shown) formed at the ends of the force detection unit 1.
The extraction electrodes 10c, 11c, 10d, and 11d of the frame 3 shown in FIG. 1A and the extraction electrodes 20c, 21c, 20d, and 21d of the frame 4 are examples, and there are various extraction methods. In short, if the members 3b, 4b side (free end side) of the first and second frame bodies 3, 4 are flexed in the Y-axis direction, they are pulled out to the fixed end side (members 3d, 4d side) of the force detection unit 1. It is desirable to provide a pad electrode for the electrode.

The piezoelectric substrate 2 of the force detection unit 1 has been described as having the first frame 3 and the second frame 4 integrally joined together, but actually the piezoelectric substrate is made of a material using a photolithography technique and an etching technique. A method of processing the first frame body 3 and the second frame body 4 on one piezoelectric substrate is desirable. Examples of the piezoelectric substrate include crystal, lithium tantalate, lithium niobate, and langasite. When a quartz substrate is used, there are an AT-cut quartz substrate (AT plate), a BT-cut quartz substrate (BT plate), a Y-cut quartz substrate (Y plate; a substrate perpendicular to the crystal axis Y of quartz), and the like.
If an AT plate, a BT plate, or a Y plate is used, slip distortion is generated by applying a voltage in the thickness direction, and thickness shear vibration can be easily excited.

The example shown in FIGS. 1 and 2 is an example in which a flat crystal substrate 2 is processed, and the etching rate varies depending on the crystal axis direction of the crystal. Therefore, as shown in FIGS. Rather than being perpendicular to the substrate surface, inclined surfaces 3′a, 3′b, 3′c, 3′d, 4′a, 4′b, 4′c and 4′d are formed.
Since the first beam 5, the counter beams 6 and 7, and the openings 8 a and 8 b are etched from the upper surface of the piezoelectric substrate 2, the first beam 5 and the counter beams 6 and 7 are the bottom of the piezoelectric substrate 2. Formed.
On the other hand, the second beam 15, the counter beams 16, 17 and the openings 18a, 18b are etched from the lower surface of the piezoelectric substrate 2, so that the second beam 15, the counter beams 16, 1
7 is formed on the upper surface of the piezoelectric substrate 2.

FIG. 3 is an enlarged cross-sectional view of a main part for explaining the vibration state of the first beam 5, wherein the upper electrode 10 a and the lower electrode 11 b are connected and the extraction electrode is connected so as to connect the upper electrode 11 a and the lower electrode 10 b. Is connected. That is, when an excitation voltage is applied to the electrodes 10a and 10b, the electric field in the left region in the figure of the first beam 5 and the electric field in the right region in the figure can be made different from each other. By being different by 180 degrees, it is possible to excite thickness shear vibrations by slip strains having different phases. Due to this thickness-shear vibration, at a certain moment, a displacement as shown by a wavy line in FIG. 3 occurs inside the first beam 5, and a displacement toward the center direction occurs at the upper part of the first beam 5, Displacement occurs in the lower part of the beam 5 toward both ends. Further, at a certain moment, the upper part of the first beam 5 is displaced toward both ends, and the lower part of the first beam 5 is displaced toward the center.
Due to this displacement, bending vibration in the Y-axis direction indicated by the solid line is excited in the first beam 5. That is, it is possible to drive the bending vibration to the first beam 5 by applying a voltage to the upper electrodes 10a and 11a and the lower electrodes 10b and 11b formed on the first beam 5.
Since the same applies to the second beam 15, the description thereof is omitted.
The first and second beams 5 and 15 have a low frequency bending vibration depending on the dimensions (length, width, etc.) of the beams 5 and 15 and a high frequency proportional to the reciprocal of the thickness of the beams 5 and 15. Thickness shear vibration is excited simultaneously. Since the bending vibration and the thickness shear vibration have a large frequency, a driving oscillator is prepared separately from each other. The frequency change of the bending vibration is used for force detection, and the frequency of the highly stable thickness-slip vibration is used for temperature detection of the force detection unit 1 using the frequency-temperature characteristics, and the temperature correction of the resonance frequency of the bending vibration is performed. Can be used.

The operation when the force detection unit 1 of the present invention is connected and fixed to the base 40 via the conductive adhesive 35 will be described with reference to FIG. 4 (a) and 4 (b) show Q1-Q1 in FIG. 1 (a).
And is a sectional view taken along line Q2-Q2.
When the force F is applied to the force detection unit 1 in the −Y-axis direction or the force Y in the + Y-axis direction, the first and second beams 5 and 15 are grooved 30 as shown in FIGS. It will bend more in the -Y-axis direction. At this time, compressive stress is applied to the first beam 5 positioned below the center line L in the thickness direction of the piezoelectric substrate 2, and the frequency of bending vibration of the first beam 5 decreases. On the other hand, a tensile (extension) stress is applied to the second beam 15 located above the center line L in the thickness direction of the piezoelectric substrate 2, and the bending vibration frequency of the second beam 15 increases.
When the force F is applied to the force detection unit 1 in the + Y-axis direction or the acceleration α is applied to the -Y-axis direction, the first and second beams 5 and 15 are bent from the groove 30 in the + Y-axis direction. Tensile (elongation) stress is applied to one beam 5, the bending vibration frequency of the first beam 5 is increased, and compressive stress is applied to the second beam 15, and the bending vibration frequency of the second beam 15 is decreased. .

By making the voltages applied to the electrodes 10a and 10b and the electrodes 11a and 11b have opposite phases, bending vibration is excited in the first and second beams 5 and 15. When an extension (tensile) stress or a compressive stress is applied to a beam that undergoes bending vibration, the resonance frequency of the beam changes, and the resonance frequency increases with an extension (tensile) stress and decreases with a compression stress. The amount of change in the resonance frequency of the beam is substantially proportional to the applied stress. However, when the detection accuracy of the force detection unit 1 is expected, the force applied to the beam and the frequency change of the bending vibration of the beam The correspondence table may be stored in a storage device and used.
By applying force F or acceleration α in the Y-axis direction of the force detection axis direction, the frequency change of the bending vibration of the first beam 5 and the frequency change of the bending vibration of the second beam 15 change in opposite directions. That is, the first and second beams 5 and 15 can be differentially operated. The advantage of the differential operation is that the frequency sensitivity, that is, the force detection sensitivity is doubled as is well known. Also, the first and second beams 5
By taking the difference between the resonance frequencies of 15 and 15, it is possible to reduce unnecessary vibration, for example, the sensitivity in the direction of the other axis.

In the force detection unit 1 shown in FIG. 1, the first beam is formed from the members 3 b and 3 d of the frame 3 on the same plane as the first beam 5 on both sides of the joint between the both ends of the first beam 5 and the frame 3. Counter beams 6 and 7 extending in the central portion in parallel to the central portion 5 are formed. Similarly, on both sides of the connecting portion between the both ends of the second beam 15 and the frame body 4, on the same plane as the second beam 15, the members 4 b and 4 d of the frame body 4 are parallel to the second beam 15 and centered. Extending counter beams 16 and 17 are formed, respectively.
The counter beams 6, 7, 16, and 17 are cantilever beams, and the first and second beams 5 and 15 are respectively.
It is formed symmetrically with respect to the center line of the width.
The functions of the counter beams 6, 7, 16 and 17 are that when the first and second beams 5 and 15 are displaced in the Y-axis direction, the counter beams 6, 17, 16 and 17 are displaced in the opposite direction to the propagation of vibrations to the frame body. It suppresses and works to reduce vibration leakage of the first and second beams 5 and 15.

Bending vibration is excited in each of the first and second beams 5 and 15 by using two thickness shear vibrations having different phases excited in the first and second beams 5 and 15 shown in FIG. 1st and 2nd
Since the resonance frequency of the bending vibration of the beam is changed by the force applied to the beams 5 and 15, the frequency change is used for force detection. Compared to a conventional tuning fork type piezoelectric vibration element, it is easy to form an electrode even if it is downsized, and there is an effect that the detection sensitivity can be maintained. In addition, there is an effect that force detection sensitivity can be doubled by differentially operating the first beam and the second beams 5 and 15 excited by bending vibration. In addition, the differential operation can reduce unnecessary vibrations picked up by the first and second beams 5 and 15, for example, vibrations in the other axis direction.
Further, the force detection unit 1 forms the first beam 5 below the center line in the thickness direction of the first frame 3, and the second beam 15 above the center line in the thickness direction of the second frame 4. Since a force in the thickness direction is applied to the force detection unit 1, one of the stresses generated in the first beam 5 and the second beam 15 is an extension stress and the other is a compression stress. . That is, the resonance frequencies of the first beam and the second beam change in opposite directions. That is, since the first beam 5 and the second beam 15 can be differentially operated, the force detection sensitivity is doubled, and unnecessary vibrations generated in the first and second beams 5 and 15, for example, vibrations in the other axis direction are reduced. There is an effect that it can be reduced.

By forming the groove portions 30 in the members of the first and second frames 3 and 4 parallel to the first and second beams 5 and 15, the first and second frames 3 and 4 are in the thickness direction. By applying this force, it can be configured to bend more easily than the groove portion, so that a small force can be detected, and the force detection range is widened.
Further, by arranging the counter beams 6, 7, 16, and 17 in parallel with the first and second beams 5 and 15 on both sides of the first and second beams 5 and 15, the first and second beams 5 and 15 are arranged. Since the counter beams 6, 7 and 16, 17 are displaced so as to cancel the displacement caused by the bending vibration of the first and second beams 15, vibration leakage of the first and second beams 5, 15 can be reduced. As a result, the first and second
There is an effect that the Q value of the beams 5 and 15 can be increased and the detection accuracy of the force detection unit can be increased.

FIG. 5 is an example of a cross-sectional view of the force detection device 50 of the present invention. The force detection device 50 includes a force detection unit 1 illustrated in FIG. 1, a detection unit 55 that detects a change in frequency of bending vibration or thickness shear vibration of the first and second beams 5 and 15 of the force detection unit 1, and And a package 51 that accommodates the force detection unit 1 and the detection unit 55.
The detection unit 55 includes an IC or the like that includes an oscillation circuit for exciting the first and second beams 5 and 15 and an arithmetic circuit that performs arithmetic processing on the output frequency of the oscillation circuit. The package 51 includes a package main body 51a and a lid member 51b, and external connection terminals 52 are formed on the outer bottom portion of the package main body 51a. A pedestal 53 for mounting the force detection unit 1 via, for example, a conductive adhesive 53 is provided inside the package body 51a. Detection unit 5
5 is connected to an internal electrode formed inside the package package body 51a. The internal electrode and the external connection terminal 52 are electrically connected.
If the force detection unit 1 according to any one of the application examples 1 to 4 is used, the bending vibrations of the first and second beams are differentially operated, and the frequency change is detected by the detection unit. There is an effect that a force detection device with doubled sensitivity can be configured.
In addition, it is possible to reduce the leakage of bending vibrations of the first and second beams, to have excellent detection sensitivity, to suppress other axis sensitivity, and to configure a force detection device with a wide detection range.

DESCRIPTION OF SYMBOLS 1 ... Force detection unit, 2 piezoelectric substrate, 3 ... 1st frame, 3a, 3b, 3c, 3d ... member, 3 '
a, 3'b, 3'c, 3'd, 4'a, 4'b, 4'c, 4'd ... inclined surface, 4 ... second frame, 4a, 4b, 4c, 4d ... member, 5 ... 1st beam, 6, 7, 16, 17 ... Counter beam, 8a, 8b, 18a, 18b opening, 10a, 11a, 20a, 21b ... Upper electrode, 1
0b, 11b, 20b, 21b ... lower electrode, 10c, 10d, 11c, 11d, 20c,
20d, 21c, 21d ... extraction electrode, 15 ... second beam, 30 ... groove, 35 ... conductive adhesive,
40 ... Base, 50 ... Force detection device, 51 ... Package, 51a ... Package body, 51b ...
Lid member, 52 ... external connection terminal, 53 ... pedestal, 55 ... detector

Claims (5)

Thin plate-like first and second frames having flexibility in the thickness direction;
First and second beams that connect opposite sides of the first and second frame bodies and vibrate due to slip strain by an electric field in the thickness direction;
An upper electrode and a lower electrode formed on the upper and lower surfaces of the first and second beams, avoiding a central region of the first and second beams;
With
Combining each side of the first and second frame bodies along the extending direction of the first and second beams;
The force detection unit characterized in that the first and second beams are configured to bend and vibrate due to vibration caused by slip strain generated when a drive signal is applied to the upper electrode and the lower electrode. . The bottom surface of the first beam is flush with the bottom surface of the first frame;
The upper surface of the second beam is flush with the upper surface of the second frame.
The force detection unit described in 1. 2. The force detection unit according to claim 1, wherein the first and second frame bodies have a groove on at least one of upper and lower surfaces of a member parallel to the first and second beams. On both sides of each of the first and second beams, each of the first and second frames is parallel to the first and second beams from the opposite sides of the first and second frames, respectively. Having a counter beam extending towards the center of each,
2. The force detection unit according to claim 1, wherein the counter beam is displaced so as to cancel the displacement caused by the bending vibration of the first and second beams. A force detection unit according to any one of claims 1 to 4,
A detection unit for detecting a change in frequency of bending vibration or thickness shear vibration of the first and second beams;
A force detection device comprising:

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