JP2010048643A - Acceleration detection unit and acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized acceleration detection unit which has superior acceleration detection sensitivity, accuracy, and temperature characteristics. <P>SOLUTION: The acceleration detection unit 1 includes: first and second dual tuning fork oscillating elements 10, 20; a fixed part and a movable part 30, 33; and connecting parts 17, 18, 27, 28 for connecting the fixed part and movable part 30, 33 and the base parts of the first and second dual tuning fork oscillating elements 10, 20, respectively. The first dual tuning fork oscillating element 10 includes two oscillating arms 11, 12 arranged in parallel and two base parts 14, 15 connecting both ends of the two oscillating arms 11, 12 in the extending direction, respectively, wherein the oscillating arms 11, 12 have the same extending direction and are arranged on the same plane. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an acceleration detection unit and an acceleration sensor, and in particular, an acceleration detection unit in which the function of a 90 ° phase shift portion in an acceleration processing circuit is replaced with a function of a coupling arm that connects resonators, and temperature characteristics are improved, And the acceleration sensor.

Conventionally, acceleration sensors have been widely used from automobiles, airplanes, and rockets to monitoring abnormal vibrations of various plants. Patent Document 1 discloses an acceleration sensor using two tuning fork vibrating elements.
FIG. 4 is a plan view of a conventional acceleration sensor element disclosed in Patent Document 1. In FIG.
The acceleration sensor element 60 includes first and second piezoelectric vibrating pieces 61 and 65, a package 70,
The first piezoelectric vibrating piece 61 and the second piezoelectric vibrating piece 65 are mounted in parallel in the package 70. The first piezoelectric vibrating piece 61 includes vibrating arms 62 and 63 that vibrate and vibrate.
2 and 63 extend parallel to each other from the base end portion 64. Then, the second piezoelectric vibrating piece 65
Includes vibration arms 66 and 67 that bend and vibrate. The vibration arms 66 and 67 extend from the base end portion 68 in parallel to each other. The vibrating arms 62 and 63 include excitation electrodes (not shown) that are electrically connected to the oscillation circuit.
The first piezoelectric vibrating piece 61 and the second piezoelectric vibrating piece 65 are mounted on the same plane of the bottom surface of the package 70, and the first piezoelectric vibrating piece 61 and the second piezoelectric vibrating piece 65 are mounted in opposite directions. Yes.
For example, when acceleration acts on the acceleration sensor element 60 from the right direction to the left direction as indicated by an arrow 71 in FIG. 4, the first piezoelectric vibrating piece 61 is moved from the proximal end side 64 to the distal end side of the vibrating arms 62 and 63. Inertia force (acceleration × mass) acts on the vibrating arms 62 and 63, and tensile stress acts on the vibrating arms 62 and 63. For this reason, the resonance frequency of the first piezoelectric vibrating piece 61 is biased toward the high frequency side, and the resonance frequency is (
f0 + Δf). On the other hand, in the second piezoelectric vibrating piece 65, an inertial force acts from the distal end side to the proximal end side 68 of the vibrating arms 66 and 67, and a compressive stress acts on the vibrating arms 66 and 67 to resonate. The frequency is biased toward the low frequency side, and the resonance frequency becomes (f0−Δf). That is, Δf is a value corresponding to the acceleration.

FIG. 6 is an explanatory diagram of a conventional acceleration sensor.
6 includes an oscillating unit 81, a waveform shaping unit 82, a 90 ° phase shifting unit 83, a phase shifting circuit unit 84, a waveform shaping unit 85, a multiplier 86, and a low-pass filter 87. And a differentiating circuit 88. The oscillating unit 81 includes the first piezoelectric vibrating piece 61 of the acceleration sensor element 60 and an oscillating circuit 81a. The phase shift circuit unit 84 is configured by a π-type circuit including the second piezoelectric vibrating piece 65 of the acceleration sensor element 60 and the resistors R1 and R2.
FIG. 5 shows the frequency-phase shift characteristics of the phase shift circuit unit 84. When no acceleration is applied, the frequency-shift phase characteristics indicated by the curve in FIG. When acceleration is applied, the characteristics shown in FIGS.
When the acceleration is applied by arranging the first and second piezoelectric vibrating pieces 61 and 65 in opposite directions like the acceleration sensor element 60 shown in FIG. 4, the phase change of the phase shift circuit unit 84 is Compared with the case where there is no phase change of the phase shift circuit unit 84, the phase shift angle is about twice.
The acceleration sensor multiplies the rectangular wave obtained by shaping the frequency of the oscillating unit 81 by the rectangular wave that has passed through the 90 ° phase shift unit 83 and the phase shift circuit unit 84 by the multiplier 86, and the low pass filter 87.
The voltage is converted to a voltage through a differentiating circuit 88 to obtain an acceleration.
JP 2008-107316 A

However, the first and second piezoelectric vibrating reeds 61 and 65 of the acceleration sensor element 60 disclosed in Patent Document 1 use tuning fork vibrating elements, and there is a problem that the measurement sensitivity and accuracy of acceleration are insufficient. It was.
Further, the 90 ° phase shift part 83 is composed of electronic components, and due to the temperature characteristics of the phase shift part 83,
There was a problem that the measurement accuracy of the acceleration was lowered due to the phase shift.
The present invention has been made to solve the above problems, and it is an object of the present invention to provide an acceleration detection unit with improved acceleration measurement sensitivity and accuracy, and an acceleration sensor with improved temperature characteristics.

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] Two resonating arms arranged in parallel and two bases respectively connecting both ends in the extending direction of the two resonating arms, each extending direction of the resonating arms being the same direction And two end portions arranged so as to sandwich the first and second double tuning fork vibration elements on both sides of the base, and the first and second double tuning fork vibration elements arranged on the same plane, A connecting portion that connects each of the end portions and a base portion adjacent to the end portion; and a coupling arm that connects at least one of the adjacent base portions of the first and second double tuning fork vibrating elements; An acceleration detection unit comprising:

As described above, by providing a coupling arm that couples the bases of the two double tuning fork vibrating elements,
The coupling arm functions as a 90 ° phase shift part, and the 90 ° phase shift part, which has conventionally been constituted by electronic components, can be made of the same material as the double tuning fork vibration element. Since it becomes unnecessary, the circuit is simplified and reduced in size, and the accuracy can be prevented from being deteriorated due to vibration leakage, and an acceleration detection unit having excellent temperature characteristics can be configured.

Application Example 2 One of the two end portions is a fixed portion and the other is a movable portion, and the coupling arm and a beam that does not contact the base portion are provided between the fixed portion and the movable portion. The acceleration detection unit according to the first application example, in which one of the beams is connected to the fixed portion and the other is connected to the movable portion.

By providing a beam between the fixed part and the movable part as described above, the acceleration unit becomes robust, and the extensional stress and the compressive stress applied to the two double tuning fork vibrating elements in parallel work more clearly. There is an effect.

Application Example 3 At least the acceleration detection unit according to claim 1, an oscillation circuit configured using one double tuning fork vibrating element of the acceleration detection unit, and the other double tuning fork of the acceleration detection unit A phase shift circuit configured using a vibration element; and a multiplier that multiplies the output signal of the phase shift circuit and the output signal of the oscillation circuit, and a phase shift angle of an input / output signal of the phase shift circuit It is characterized by an acceleration sensor that obtains acceleration from a value corresponding to the change in.

As described above, when the acceleration sensor is configured using the acceleration detection unit, the accuracy failure due to vibration leakage, which is a characteristic of the double tuning fork vibration element, is greatly suppressed, and the acceleration detection sensitivity, accuracy, and temperature characteristics are improved. There is an effect that the acceleration sensor can be miniaturized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic perspective view showing a configuration of an acceleration detection unit 1 according to an embodiment of the present invention. The acceleration detection unit 1 includes first and second double tuning fork vibrating elements 10 and 20, fixed and movable parts 30 and 33, fixed and movable parts 30 and 33, and the first and second double tuning forks. Connection portions 17, 18, 27, and 28 that connect the base portions of the vibration elements 10 and 20 are provided.
The first double tuning fork vibrating element (double tuning fork crystal vibrating element) 10 is composed of two vibrating arms 11 and 12 arranged in parallel with each other and both ends of the two vibrating arms 11 and 12 in the extending direction. The resonating arms 11 and 12 are arranged in the same direction and on the same plane. Excitation electrodes 11a and 12b are formed on the vibrating arms 11 and 12 on four sides in the cross-sectional direction, and the excitation electrodes 11a and 12b make the ends of the base portions 14 and 15 the vibration nodes, the vibrating arms 11,
12 is configured such that bending vibrations symmetrical to each other are excited with the central portion of 12 being the antinodes of vibration. The base portions 14 and 15 are provided to prevent leakage of vibration energy of the vibrating arms 11 and 12.
Similar to the first double tuning fork vibrating element, the second double tuning fork vibrating element (double tuning fork crystal vibrating element) 20 includes two vibrating arms 21 and 22 arranged in parallel, and the two vibrating arms. 21 and 22 and two base portions 24 and 25 respectively connecting both ends in the extending direction. The vibrating arms 21 and 22 are arranged in the same direction and on the same plane. As with the first double tuning fork vibrating element, the vibrating arms 21 and 22 are formed with excitation electrodes, and the vibration modes excited by the vibrating arms 21 and 22 are:
The bending vibrations are symmetrical with respect to each other, with the ends of the bases 24 and 25 being vibration nodes and the central portions of the vibrating arms 21 and 22 being antinodes of vibration.

The fixed portion 30 is formed in a rectangular flat plate shape, and an end portion on the left side in the drawing from the center of the fixed portion 30 is connected to the base portion 14 of the first double tuning fork vibrating element 10 via the connection portion 17. Further, an end portion on the right side in the drawing from the center of the fixed portion 30 is connected to the base portion 24 of the second double tuning fork vibrating element 20 via the connection portion 27. Terminal electrodes 11b and 12b that are electrically connected to the excitation electrodes 11a and 12a of the first double tuning fork vibrating element 10 are provided on the upper surface on the left side in the drawing from the center of the fixed portion 30. Further, terminal electrodes 21 b and 22 b that are electrically connected to the excitation electrodes 21 a and 22 a of the second double tuning fork vibrating element 20 are provided on the upper surface of the fixed portion 30 on the right side in the drawing. In addition, when using the acceleration detection unit 1, the fixing | fixed part 30 is fixed and used for housings, such as a package.
The movable portion 33 is formed in a rectangular flat plate shape, and an end portion on the left side in the drawing from the center of the movable portion 33 is connected to the base portion 15 of the first double tuning fork vibrating element 10 via the connection portion 18. Further, the end of the movable portion 33 on the right side in the figure is connected to the base portion 25 of the second double tuning fork vibrating element 20 via the connection portion 28. The movable portion 33 is configured to freely swing when an acceleration is applied.

In the example shown in FIG. 1, the bases 14 and 15 of the first double tuning fork vibrating element 10 and the bases 24 and 25 of the second double tuning fork vibrating element 20 are connected by thin coupling arms 19 and 29, respectively. . First
The coupling arms 19 and 29 connecting the bases 14, 15 and 24 and 25 of the second double tuning fork vibrating elements 10 and 20 function as a propagation path of vibration energy leaked from the bases 14, 15, 24 and 25. However, as long as at least one of the connecting arms 19 and 29 is provided, it functions as the acceleration detection unit 1 of the present invention.
For example, when the first double tuning fork vibrating element 10 is connected to the oscillation circuit and excited, most of the vibration energy of the first double tuning fork vibrating element 10 is confined between the bases 14 and 15.
It leaks slightly from the base parts 14 and 15, and the leaked vibration energy is transmitted through the coupling arms 19 and 29 and propagates to the base parts 24 and 25 of the second double tuning fork vibrating element 20. When the inherent resonance frequency of the second double tuning fork vibrating element 20 is close to the frequency of the leaked vibration energy, the second double tuning fork vibrating element 20 is excited with the leaked vibration energy, and the second double tuning fork vibration is generated. The element 20 resonates at a natural resonance frequency. The coupling degree of the first and second double tuning fork vibrating elements 10 and 20 can be adjusted by the structure of the coupling arms 19 and 29.

The substrate of the acceleration detection unit 1 shown in FIG. 1 can be formed, for example, by applying a photolithography technique to a Z-cut quartz wafer. Excitation electrodes 11a, 12a, 21a, 22
a and the terminal electrodes 11b, 12b, 21b, and 22b are formed by a method such as vapor deposition and sputtering in a vacuum after the substrate is formed.

Here, the twin tuning fork crystal resonator element will be briefly described. The double tuning fork crystal vibrating element has good sensitivity to tensile and compressive stress, and when used as a stress sensitive element for altimeters or depth gauges, it has excellent decomposition ability, so a slight pressure difference to an altitude difference , Know the difference in depth. Further, the frequency-temperature characteristic exhibited by the double tuning fork crystal resonator element is an upwardly convex quadratic curve, and each parameter is set so that the vertex temperature becomes room temperature (25 ° C.).
The resonance frequency f _F when the external force F is applied to the two vibrating arms of the double tuning fork crystal vibrating element is as follows.
f _F = f ₀ (1- (KL ² F) / (2EI)) ^1/2 (1)
Here, f ₀ is the resonance frequency of the double tuning fork crystal resonator element when there is no external force, K is a constant according to the fundamental wave mode (= 0.0458), L is the length of the vibrating arm, E is the longitudinal elastic constant, and I is the cross section 2 Next moment. Second moment I are from I = dw ^3/12, the equation (1) can be modified as follows. Here, d is the thickness of the vibrating arm, 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 respectively expressed by the following equations.
S _F = 12 (K / E) (L / w) ² (3)
σ = F / (2A) (4)
Here, A is the cross-sectional area (= w · d) of the vibrating arm. From the above, when the force F acting on the double tuning fork vibrator is negative in the compression direction and positive in the extension direction (tensile direction), the force F and the resonance frequency f _F
In the relationship, the force F is a compressive force, the resonance frequency f _F is decreased, and the extension (tensile) force is increased. The stress sensitivity S _F is proportional to the square of the L / w of the vibrating arm.
However, the stress-sensitive element 30 is not limited to a double tuning fork crystal vibration element, and any element may be used as long as it is a piezoelectric vibration element whose frequency changes due to stretching / compression stress. Also,
The relationship between the stress and the apex temperature has a characteristic that the apex temperature shifts to the low tone side when an extensional stress is applied to the double tuning fork crystal resonator element and shifts to the high temperature side when compressive stress is applied.

The operation of the acceleration detection unit 1 shown in FIG. 1 will be described. The fixed part 30 is fixed to an external member such as a package, and the movable part 33 is a swingable free end. The resonance frequencies of the first and second double tuning fork vibrating elements 10 and 20 are both set to f0. The acceleration detection axis direction is the Y-axis direction parallel to the main surface of the acceleration detection unit 1. When the acceleration k is applied in the arrow direction (+ Y-axis direction), a force F of Mk (M is the mass of the acceleration unit 1) acts in the −Y-axis direction due to the inertial force. With this force F, the first and second double tuning fork vibrating elements 10 and 20 bend in the −Y axis direction on a plane (Z plane) perpendicular to the Z axis. At this time, an elongation stress acts on the first double tuning fork vibrating element 10 and its resonance frequency f0 increases (f0 + Δf), and a compressive stress acts on the second double tuning fork vibrating element 20 and its resonance frequency f0. Decreases to (f0−Δf).
When the acceleration k is applied in the −Y axis direction, compressive stress acts on the first double tuning fork vibrating element 10, and the resonance frequency f 0 decreases (f 0 −Δf), and the second double tuning fork vibrating element 10 decreases. Tuning fork vibration element 2
Elongation stress acts on 0, and the resonance frequency f0 increases to (f0 + Δf).

FIG. 2 is a diagram showing a configuration of the acceleration sensor 5 according to the embodiment of the present invention. The acceleration sensor 5 includes an acceleration detection unit 1, an oscillation circuit 40, a waveform shaping unit 41, a resistance circuit 42, a waveform shaping unit 43, a multiplier 44, a low-pass filter 45, and a differentiation circuit 46. ing. The terminal electrodes 11b and 12b of the first double tuning fork vibrating element 10 of the acceleration detection unit 1 are connected to the oscillation circuit 40 and excited at the resonance frequency f0. Second of the acceleration detection unit 1
Terminal electrodes 21b and 22b of the double tuning fork vibrating element 20 are resistors R1 and R2 of the resistance circuit 42, respectively.
The other terminals of the resistors R1 and R2 are grounded. That means
The second double tuning fork vibrating element 20 and the resistors R1 and R2 form a π-type circuit, and a phase shift circuit P similar to the phase shift circuit unit 84 of the conventional acceleration sensor shown in FIG. 6 is configured.
A major difference from the configuration of the conventional acceleration sensor is that the function of the 90 ° phase shifter 83 shown in FIG. 6 is the same as that of the bases 14 and 15 of the first double tuning fork vibrating element 10 of the acceleration detection unit 1 and the second dual tuning fork. This is a point that is replaced by the function of the connecting arms 19 and 29 for connecting the base portions 24 and 25 of the tuning fork vibrating element 20 respectively. That is, the electronic circuit of the 90 ° phase shift portion 83 is configured using mechanical members such as the connecting arms 19 and 29. Combining a plurality of mechanical vibrators with a connector to form a functional device is a long-standing example in the field of mechanical filters.
When the terminal electrodes 11b and 12b of the fixed portion 30 of the acceleration detection unit 1 are connected to the oscillation circuit 40 and the first double tuning fork vibrating element 10 is excited, most vibration energy is confined between the base portions 14 and 15, and The resonance state is a symmetrical bending vibration mode. However, the vibration energy of the bending vibration slightly leaks to the base parts 14 and 15, and the base parts 14 and 15 and the connecting arms 19 and 29
And propagates to the bases 24 and 25 of the second double tuning fork vibrating element 20. Base 24, 25
If the frequency of the vibration energy propagated to is substantially equal to the resonance frequency of the second double tuning fork vibration element 20, the second double tuning fork vibration element 20 is excited by this leaked vibration energy, and in a bending vibration mode symmetrical to each other. Resonates.

A feature of the present invention is that when the vibration energy propagates through the coupling arms 19, 29, the coupling arms 19, 2
9 functions as a 90 ° phase shift part. Since the conventional 90 ° phase shift portion is configured by using electronic components, there is a problem in temperature characteristics. However, the coupling arms 19 and 29 are provided with the double tuning fork vibrating element 10.
, 20 is integrally formed of the same material as that of 20, and thus has an effect of greatly improving the temperature characteristics.
As described above, by providing a coupling arm that couples the bases of the two double tuning fork vibrating elements,
The coupling arm functions as a 90 ° phase shift portion, and the 90 ° phase shift portion, which has conventionally been constituted by electronic components, can be made of the same material as the double tuning fork vibrating element. Therefore, when configuring an acceleration sensor, a 90 ° phase shift portion is not required, so that the circuit is simplified and miniaturized, and the accuracy detection due to vibration leakage is prevented, and an acceleration detection unit having excellent temperature characteristics is configured. There is an effect that can be.

FIG. 2 is a diagram showing a configuration of an acceleration sensor 5 according to the present invention. The acceleration sensor 5 includes an acceleration detection unit 1, an oscillation circuit 40 that oscillates one double tuning fork vibrating element 10 of the acceleration detection unit 1, and acceleration detection. A phase shift circuit P including the other double tuning fork vibrating element 20 of the unit 1, a multiplier 44 for multiplying the output signal of the phase shift circuit P and the output signal of the oscillation circuit, a low-pass filter 45, a differentiation circuit 46, It is equipped with.
The operation of the acceleration sensor 5 shown in FIG. 2 and the conventional acceleration sensor 80 shown in FIG. 6 will be compared and described. 2 and 6, the output of the circuit portion having the same function is represented by using the same symbols A, B, C.
First, the operation of the acceleration sensor 5 when no acceleration is applied to the acceleration detection unit 1 will be described.
The oscillation circuit 40 to which the first double tuning fork vibrating element 10 is connected outputs a signal having a frequency f0 as a sine wave shown in FIG. This output signal is input to the waveform shaping unit 41, converted into a rectangular wave signal shown in FIG. 7B and input to the multiplier 44.
On the other hand, the first double tuning fork vibrating element 10 excited by the oscillation circuit 40 resonates at a frequency f0,
Most of the vibration energy at the time of resonance is confined between the base portions 14 and 15, but a small amount of vibration energy leaks to the base portions 14 and 15, and is transmitted through the coupling arms 19 and 29 to the second double tuning fork vibrating element 20. Reach the bases 24, 25. The vibration energy reaching the bases 24 and 25 is transmitted from the bases 24 and 25 to the vibrating arms 21 and 22, and the frequency (f0) of the vibration energy is set to be approximately equal to the resonance frequency (f0) of the vibrating arms 21 and 22. Therefore, the second double tuning fork vibrating element 20 resonates at the frequency f0.
At this time, the vibration energy leaking from the base portions 14 and 15 is delayed by 90 ° in the phase of the vibration frequency when propagating through the coupling arms 19 and 29. That is, as shown in FIG. 7C, the vibration energy whose phase is delayed by 90 ° is transmitted to the second double tuning fork vibrating element 20, and resonance at the frequency f0 occurs.

When the phase shift circuit P is configured by the second twin tuning fork vibrating element 20 and R1 and R2 of the resistance circuit 42,
The function is the same as that of the phase shift circuit unit 84 shown in FIG. That is, when no acceleration is applied, the resonance frequency f0 of the second double tuning fork vibrating element 20 of the phase shift circuit P is the same as the resonance frequency f0 of the first double tuning fork vibrating element 10. Therefore, the frequency-phase shift characteristic of the phase shift circuit P is shown by the curve in FIG. 5 (a), the frequency of the output signal of the phase shift circuit P is f0, and as shown in FIG. 7 (D), A phase change by the phase shift circuit P does not occur. The output signal of the phase shift circuit P is waveform-shaped by the waveform shaping unit 43, converted into a rectangular wave indicated by a solid line in FIG. 7E, and input to the multiplier 44.
The multiplier 44 is, for example, Ex. An OR (exclusive OR circuit) and a multiplier 44
When one of the output signals of the waveform shaping units 41 and 43 input to the “1” is “1” and the other is “0”, Ex. OR outputs “1”. That is, the solid line signal in FIG. This rectangular wave signal is integrated with respect to time by the low-pass filter 45 and output. When no acceleration is applied, the duty ratio of the rectangular wave output signal of the multiplier 44 is 50%, so the low-pass filter 44 outputs the average value V ₀ of the solid line rectangular wave signal in FIG. .

Next, consider a case where the acceleration k in the arrow direction (+ Y-axis direction) in FIG. Due to the acceleration k, an extension stress acts on the first double tuning fork vibrating element 10, and the resonance frequency changes from f0 to (f0 + Δf). A compressive stress acts on the second double tuning fork vibrating element 20 constituting the phase shift circuit P, and the resonance frequency changes from f0 to (f0−Δf). For this reason, the frequency-phase shift characteristic of the phase shift circuit P changes as shown by the curve (broken line) shown in FIG. Therefore, the resonance frequency (f0 + Δf) of the first double tuning fork vibrating element 10 is input to the phase shift circuit P with the phase delayed by 90 ° via the coupling arms 19 and 29. In the phase shift circuit P, the phase of the output signal is delayed by α (−α) with respect to the input signal by the acceleration k. Therefore, the waveform shaping unit 43 outputs a rectangular wave indicated by a broken line β in FIG. For this reason, the output signal of the multiplier 44 becomes a rectangular signal γ having a duty ratio larger than 50% indicated by a broken line in FIG. 7F, and the rectangular signal γ is input to the low-pass filter 45. The low-pass filter 45 obtains an average value of the input rectangular wave signal γ and outputs a voltage signal larger than V ₀ .
The differentiation circuit 46 receives the voltage output from the low-pass filter 45 and outputs a value differentiated with time. That is, a change in value corresponding to the amount of phase difference between the output signal via the coupling arms 19 and 29 and the output signal from the phase shift circuit P is output. Further, since the change in the shift amount corresponds to the acceleration at the time when the phase shift angle starts to change, the acceleration can be obtained from the output of the differentiation circuit 46.
As described above, when the acceleration sensor is configured using the acceleration detection unit of the present invention, the accuracy failure due to vibration leakage, which is a characteristic of the double tuning fork vibrating element, is greatly suppressed, and the acceleration detection sensitivity, accuracy, and temperature characteristics are improved. In addition, the acceleration sensor can be reduced in size.

FIGS. 3A and 3B are diagrams showing the configuration of the acceleration detection unit 2 of the second embodiment, where FIG. 3A is a plan view and FIG. 3B is a side view. The acceleration detection unit 2 is the same as the acceleration detection unit 1 shown in FIG.
Except for one of the connecting arms, for example, the connecting arm 29, a beam 35 connecting the fixed portion 30 and the movable portion 33.
Is provided. The beam 35 is formed in an arcuate shape and is configured not to contact the first and second double tuning fork vibrating elements 10 and 20, the coupling arm 19, and the like except for the fixed portion 30 and the movable portion 33.
By providing the beam 35, when acceleration is applied in the Y-axis direction, the first and second double fork vibrating elements 10 and 20 are more clearly subjected to elongation stress and compressive stress. Will come to do. Also in the acceleration detection unit 2, the resonance frequencies of the first and second double tuning fork vibrating elements 10, 20 are set to be substantially the same, and the coupling between the first and second double tuning fork vibrating elements 10, 20 is performed by the connecting arm 19. This is done by adjusting the shape dimensions.
The material of the beam 35 is not necessarily the same as that of the first and second double tuning fork vibrating elements 10 and 20.
By providing a beam between the fixed part and the movable part as described above, the acceleration unit becomes robust, and the extensional stress and the compressive stress applied to the two double tuning fork vibrating elements in parallel work more clearly. There is an effect.

The schematic perspective view which showed the structure of the acceleration detection unit which concerns on this invention. The figure which shows the structure of an acceleration sensor. (A) is a top view of the acceleration detection unit of a 2nd Example, (b) is a side view. The top view which shows the structure of the conventional acceleration sensor element. The figure which shows the frequency-phase shift characteristic of a transfer circuit part. The figure which shows the structure of the conventional acceleration sensor. (A)-(F) is a time chart explaining the effect | action of the conventional acceleration sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Acceleration detection unit, 5 ... Acceleration sensor, 10 ... 1st double tuning fork vibration element, 11
, 12, 21, 22 ... vibrating arms, 11a, 12a, 21a, 22a ... excitation electrodes, 11b, 1
2b, 21b, 22b ... terminal electrode, 14, 15, 24, 25 ... base, 17, 18, 27,
28 ... connection part, 19 and 29 ... coupling arm, 20 ... second double tuning fork vibrating element, 30 ... fixing part, 33
... Moving part, 35 ... Beam, 40 ... Oscillation circuit, 41, 43 ... Waveform shaping part, 42 ... Resistance circuit, 44
... Multiplier, 45 ... Low-pass filter, 46 ... Differentiation circuit

Claims (3)

Each of the resonating arms has two resonating arms that are arranged in parallel, and two bases that connect both ends in the extending direction of the two resonating arms, and the resonating arms have the same extending direction and the same direction. First and second double tuning fork vibrating elements arranged on a plane;
Two ends disposed so as to sandwich the first and second double tuning fork vibrating elements on both sides of the base;
A connecting portion for connecting each end portion and a base portion adjacent to the end portion;
A coupling arm that couples at least one of bases adjacent to each other of the first and second double tuning fork vibrating elements;
An acceleration detection unit comprising: One of the two end portions is a fixed portion, the other is a movable portion,
The coupling arm and a beam that does not contact the base are provided between the fixed portion and the movable portion, one of the beams is connected to the fixed portion, and the other is connected to the movable portion. Claim 1
The acceleration detection unit described in 1. Using at least the acceleration detection unit according to claim 1, an oscillation circuit configured using one of the double tuning fork vibration elements of the acceleration detection unit, and the other double tuning fork vibration element of the acceleration detection unit Comprising a phase shift circuit configured, and a multiplier for multiplying the output signal of the phase shift circuit and the output signal of the oscillation circuit, corresponding to a change in the phase shift angle of the input / output signal of the phase shift circuit An acceleration sensor characterized by obtaining an acceleration from a value.

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