JP2013024678A - Vibration gyro element, gyro sensor and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate or reduce influence due to mechanical vibration leakage of driving vibration arms and to enhance detection accuracy and sensitivity in a two-sided tuning-fork type vibration gyro element.SOLUTION: A vibration gyro element 11 comprises individual pairs of driving vibration arms 13a and 13b and detecting vibration arms 14a and 14b that extend in directions opposite to each other from a supporting portion 12. The pair of driving vibration arms 13a and 13b vibrate in a flexural manner in an XY in-plane direction at resonance frequency fin a driving mode. In a detecting mode, the driving vibration arms 13a and 13b vibrate in the flexural manner in a Z-axis direction with a phase opposite to an application direction of Coriolis force by the Coriolis force due to rotation thereof about a Y-axis and the pair of detecting vibration arms 14a and 14b vibrate in the flexural manner in the Z-axis direction with a phase opposite to the phase of the driving vibration arms 13a and 13b. The detecting vibration arms 14a and 14b are set to vibrate in the flexural manner in the XY in-plane direction at resonance frequency f<f, and the resonance frequency fis set to reduce a difference |S1-S2| between detected signal values S1 and S2 output from each of the detecting vibration arms 14a and 14b in the driving mode.

Description

  The present invention relates to a vibration gyro element using a bending vibration piece, a gyro sensor using the vibration gyro element, and an electronic apparatus.

  Conventionally, in electronic devices such as watches, home appliances, various information / communication devices and OA devices, a piezoelectric vibrator as a clock source of an electronic circuit, a piezoelectric device such as an oscillator mounted with a piezoelectric vibrating piece and an IC chip, and a real-time clock module. The device is widely used. Also, physical quantities such as angular velocity, angular acceleration, acceleration, and force are detected in various electronic devices such as digital still cameras, video cameras, navigation devices, body posture detection devices, pointing devices, game controllers, mobile phones, and head mounted displays. Therefore, a sensor such as a piezoelectric vibration gyro using a bending vibration piece is widely used.

  For example, there is known a double-side tuning fork-type bending vibration piece including a pair of drive vibration arms extending in parallel from the base to one side and a pair of detection vibration arms extending in parallel to the opposite side. (For example, see Patent Documents 1 and 2). FIG. 10 schematically shows a typical example of a vibration gyro element and a detection circuit made of a conventional double-side tuning fork type bending vibration piece. In the figure, a vibrating gyro element 1 includes a pair of driving vibrating arms 3a and 3b extending in parallel to one side from a central support portion 2 and a pair of driving vibrating arms 3a and 3b extending in parallel to the opposite side. It has detection vibrating arms 4a and 4b.

  When a predetermined AC voltage is applied to the driving electrodes formed on the surfaces of the driving vibrating arms 3a and 3b, the driving vibrating arms 3a and 3b bend and vibrate in opposite directions within the same XY plane as the main surface. When the vibrating gyro element 1 rotates around the Y axis in the longitudinal direction in this driving mode, the vibrating arms for driving are opposite to each other in the Z-axis direction perpendicular to the main surface by the action of Coriolis force according to the angular velocity. The detection vibrating arms 4a and 4b bend and vibrate in the opposite directions in the Z-axis direction.

  At this time, the rotation of the vibration gyro element 1 and its angular velocity are obtained by taking out the potential difference generated between the detection electrodes formed on the surface of each of the detection vibrating arms by the detection circuit 5. The detection circuit 5 includes, for example, a current-voltage conversion circuit including charge amplifiers 6a and 6b, a differential amplifier circuit including a differential amplifier 7, a synchronous detection circuit including a high-pass filter 8, and an AC amplifier 9. The differential amplifier circuit amplifies and outputs a difference between detection signals input from the detection electrodes through corresponding current-voltage conversion circuits.

  As a similar double-side tuning fork type, there is known an angular velocity sensor having a pair of first and second vibrating pieces each extending vertically from a connecting piece and a supporting piece extending vertically from the connecting piece. (For example, refer to Patent Document 3). In order to improve the detection accuracy of the angular velocity, this angular velocity sensor is designed so that leakage vibration occurs in the same direction as the Coriolis force in one vibrating piece and leakage vibration occurs in the opposite direction to the Coriolis force in the other vibrating piece. By determining the drive vibration frequency and the detected vibration frequency, the electric signal due to the leakage vibration cancels out.

  Further, an angular velocity detection device including a double-side tuning fork type piezoelectric vibration gyro provided with an electrode structure that enables highly accurate angular velocity detection has been proposed (for example, see Patent Document 3). This piezoelectric vibration gyro is generated when electric charges concentrate on the first and second corners of a cross section when a vibrating arm with a rectangular cross section made of a piezoelectric crystal material such as quartz vibrates in the Z-axis direction with Coriolis force. Focusing on this, the first and second electrodes are provided so as to cover the corners.

JP 2002-340559 A JP 2007-93400 A JP-A-9-329444 JP 9-311041 A

  As described above, a vibration gyro element having a pair of detection vibrating arms differentially amplifies detection signals output from the respective detection vibrating arms, thereby eliminating unnecessary noise and the like contained in the same level. The signal component can be effectively removed. However, when unnecessary signal components included in the detection signals of the respective vibrating arms for detection are unbalanced, they cannot be sufficiently removed, so that the detection accuracy may be reduced.

  In general, a vibrating gyro element is formed by photo-etching a wafer of piezoelectric single crystal material such as quartz to process a desired outer shape, and patterning an electrode film on the surface. However, since the piezoelectric single crystal material has etching anisotropy, the cross section of the vibrating arm processed by wet etching is not an ideal rectangle but an asymmetric shape on the left and right. In addition, if there is a deviation in the alignment of the photomask during the outer shape processing, the cross-section of the vibrating arm may become asymmetric in the thickness direction. As a result, mechanical vibration leakage may occur from the drive detection arm in the drive mode, and a detection signal may be output from the detection vibration arm even though the vibration gyro element is not rotating.

  Moreover, there is a possibility that the vibrations of each pair of vibration arms are unbalanced on the left and right. As a result of such unbalanced vibration, there is a risk that an unbalanced signal component unnecessary for the detection signal from each detection vibrating arm may be included. Such an unbalanced unnecessary signal component cannot be effectively removed when differential amplification is performed in the detection circuit, which may reduce detection accuracy.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a vibration tuning gyro element of a double-side tuning fork type that detects each detection vibrating arm caused by mechanical vibration leakage from the driving detection arm. The object is to eliminate detection signal imbalance and improve detection accuracy and sensitivity.

In order to achieve the above object, the vibrating gyro element of the present invention is
A support part;
A pair of drive vibrating arms extending side by side from the support;
A pair of detection vibrating arms extending side by side on the opposite side of the driving vibration arm from the support portion;
The pair of vibrating arms for driving is a driving mode in which the bending vibration at a predetermined resonance frequency f _d in opposite directions in the plane direction along its front and back faces,
Due to the Coriolis force acting by the rotation around the extending direction of the vibrating arm, the pair of driving vibrating arms are opposite to each other in the out-of-plane direction intersecting the front and back main surfaces and opposite to the direction of action of the Coriolis force. A detection mode in which the pair of detection vibrating arms bend and vibrate in opposite directions to each other in the out-of-plane direction and in the opposite phase to the driving vibration arm,
The pair of detection vibrating arms are set so as to bend and vibrate at a predetermined resonance frequency f _h lower than the resonance frequency f _d of the driving vibration arm in opposite directions in the in-plane direction. The resonance frequency f _h is set so as to reduce the difference | S1−S2 | between the value S1 of the detection signal output from the vibration arm for detection and the value S2 of the detection signal output from the other vibration arm for detection. It is characterized by.

  As will be described later, the inventors of the present application detect each detection arm by utilizing the resonance frequency when the vibrating arm for detection is flexibly vibrated in the same in-plane direction as the drive mode, that is, in the in-plane mode. It has been found that unnecessary signal components included in the unbalance in the detection signal from the vibrating arm for use can be effectively removed or greatly reduced. The present invention has been made based on such knowledge.

Since the difference | S1−S2 | of the detection signal values output from the detection vibrating arms is the difference in mechanical vibration leakage of the driving vibrating arms acting unbalanced on the detection vibrating arms. and a resonant frequency f _d of the driving vibration arms and the resonance frequency f _h of the vibrating arms for detection and f _{h <f d,} and | by the setting the resonance frequency f _h as small, | S1-S2 The influence of the mechanical vibration leakage of the driving vibrating arm on the detection sensitivity and / or accuracy of the vibrating gyro element can be substantially eliminated or greatly reduced.

The vibrating gyro element of the present invention is
A support part;
A pair of drive vibrating arms extending side by side from the support;
A pair of detection vibrating arms extending side by side on the opposite side of the driving vibration arm from the support portion;
The pair of vibrating arms for driving is a driving mode in which the bending vibration at a predetermined resonance frequency f _d in opposite directions in the plane direction along its front and back faces,
Due to the Coriolis force acting by the rotation around the extending direction of the vibrating arm, the pair of driving vibrating arms are opposite to each other in the out-of-plane direction intersecting the front and back main surfaces and opposite to the direction of action of the Coriolis force. A detection mode in which the pair of detection vibrating arms bend and vibrate in opposite directions to each other in the out-of-plane direction and in the opposite phase to the driving vibration arm,
The pair of detection vibrating arms are set to bend and vibrate at a predetermined resonance frequency f _h in opposite directions in the in-plane direction, and the resonance frequency f _h is
f _h <f _d and | (f _h −f _d ) / f _d | ≧ 0.3
It is characterized by satisfying.

By setting the resonance frequencies f _h and f _d in this way, the difference | S 1 −S 2 | between the detection signal values from the detection vibrating arms, that is, the drive acting on the detection vibrating arms in an unbalanced manner. Since the difference in mechanical vibration leakage of the vibration arm for use can be reduced, the detection sensitivity and / or accuracy of the vibration gyro element can be improved.

In one embodiment, the resonance frequency f _h satisfies | (f _h −f _d ) / f _d | ≧ 0.4, so that the mechanical vibration leakage of the drive vibrating arm causes each detection vibrating arm to The imbalance of the effect on the detection signal can be eliminated, and the detection sensitivity and / or accuracy of the vibration gyro element can be further improved.

  In another embodiment, by setting the length Lb of the support portion with respect to the length Ld of the driving vibrating arm to be in a range of Lb / Ld ≧ 2, the mechanical vibration leakage of the driving vibrating arm can be detected by each detecting vibrating arm. The influence on the detection signal can be reduced, and the detection sensitivity and / or accuracy of the vibration gyro element can be further improved.

  In yet another embodiment, the influence of the mechanical vibration leakage of the driving vibrating arm is further reduced by setting the length Lb of the support portion to the length Ld of the driving vibrating arm within the range of Lb / Ld ≧ 3. can do.

  According to another aspect of the present invention, a gyro sensor with high detection sensitivity and / or accuracy is provided by including the above-described vibrating gyro element of the present invention.

  Further, according to another aspect of the present invention, there is provided a high-performance and high-precision electronic device including a sensor device such as a gyro sensor having high detection sensitivity and / or accuracy by including the above-described vibration gyro element of the present invention. Provided.

The top view which shows the vibration mode in the vibration gyro element by the Example of this invention, and its drive mode. FIG. 4A is a diagram illustrating a vibration mode in the detection mode of the vibration gyro element of FIG. 1, and FIG. 4B is an explanatory diagram illustrating a vibration mode in the in-plane direction of the vibration arm for detection. The circuit diagram which shows the typical example of the detection circuit connected to the vibration gyro element of FIG. The diagram which shows the difference of the vibration leak signal of each detection vibrating arm in a drive mode regarding the difference between the resonance frequency of 50 kHz of a drive vibrating arm and the resonance frequency of the detection vibrating arm in in-plane mode. The diagram which shows the change rate of the difference of the vibration leak signal of each vibration arm for a drive in the drive mode regarding the ratio of the difference with the resonance frequency of the vibration arm for a detection in the in-plane mode with respect to the resonance frequency of 50 kHz of the vibration arm for a drive. The diagram which shows the change rate of the difference of the vibration leak signal of each vibration arm for a drive in the drive mode regarding the ratio of the difference with the resonance frequency of the vibration arm for a detection in the in-plane mode with respect to the resonance frequency of 100 kHz of the vibration arm for a drive. The diagram which shows the difference of the vibration leak signal of each detection vibration arm in a drive mode regarding ratio Lb / Ld of the length of a drive vibration arm and the length of a support part in the resonance frequency of 50 kHz of a drive vibration arm. The diagram which shows the difference of the vibration leak signal of each vibration arm for a drive mode regarding ratio Lb / Ld of the length of the vibration arm for a drive, and the length of a support part in the resonance frequency of 100 kHz of the vibration arm for a drive. (A) is a plan view showing a metal mask formed on a quartz wafer in the manufacturing process of the vibrating gyro element of FIG. 1, and (B) is an enlarged sectional view taken along the line IX-IX. Schematic which shows the structure of the conventional vibration gyro element and a detection circuit.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same or similar reference numerals.

  FIG. 1 schematically shows a vibrating gyro element 11 according to a first embodiment of the present invention used for an angular velocity sensor, for example. The vibration gyro element 11 is composed of a double-side tuning fork-type bending vibration piece, a substantially rectangular support portion 12 at the center, and a pair of drive vibration arms 13a and 13b extending in parallel from one side of the support portion. And a pair of detection vibrating arms 14a and 14b extending in parallel in parallel to the opposite side. Each of the vibrating arms is provided with a weight portion 15a, 15b, 16a, 16b at the tip so that the vibration frequency can be stabilized by suppressing the generation of the higher-order vibration mode even if the length thereof is shortened. . Tapered portions 17a, 17b, 18a, and 18b having narrow widths are formed on the left and right sides of the connecting portions of the drive vibrating arms and the support portions 12 and the weight portions 15a and 15b toward the vibrating arms. . Similarly, tapered portions 19a, 19b, 20a, and 20b having narrow widths are formed on the left and right sides of the coupling portions of the detection vibrating arms, the support portion 12, and the weight portions 16a and 16b toward the vibrating arms. Has been.

  On the surface of the drive vibrating arms 13a and 13b, in order to cause the drive vibrating arms to bend and vibrate in an in-plane direction along the front and back main surfaces in the drive mode, for example, in an XY plane parallel to the main surfaces. (Not shown) is formed. In order to detect a potential difference generated on the surface of the detection vibrating arms 14a and 14b when the detection vibrating arm intersects with the front and back main surfaces in the detection mode, for example, when it bends and vibrates in the Z-axis direction perpendicular to the main surface. In addition, a detection electrode (not shown) is formed. When a predetermined AC voltage is applied to the drive electrode in the drive mode, the drive vibrating arms 13a and 13b bend and vibrate in the reverse direction in the in-plane direction, that is, in the direction of approaching and separating from each other, as shown by arrows in FIG. .

  When the vibrating gyro element 11 rotates around the Y axis in the longitudinal direction in this state, the driving vibrating arms 13a and 13b are driven in an out-of-plane direction perpendicular to the main surface, that is, Z, by the action of Coriolis force generated according to the angular velocity. Bend and vibrate in opposite directions in the axial direction. As shown in FIG. 2A, the vibration directions of the drive vibrating arms are in reverse phase with respect to the Coriolis force acting directions 21a and 21b. Resonating with the vibration in the Z-axis direction, the vibrating arms for detection 14a and 14b bend and vibrate in the detection mode and in the same direction opposite to each other in the Z-axis direction. At this time, the vibration direction of each of the detection vibrating arms has a phase opposite to that of the driving vibrating arms 13a and 13b.

  In this detection mode, the rotation of the vibrating gyro element 11 and its angular velocity are obtained by taking out the potential difference generated between the detection electrodes of the detection vibrating arms 14a and 14b. FIG. 3 shows an example of a detection circuit that is connected to the vibration gyro element 11 and forms a part of the gyro sensor. The detection circuit 22 includes charge amplifiers 23a and 23b, a differential amplifier 24, a high pass filter 25, and an AC amplifier 26. Each detection electrode is actually connected to the detection circuit 22 via a connection electrode (not shown) drawn on the support portion 12 of the vibrating gyro element 11.

  The differential amplifier 24 amplifies and outputs a difference between detection signals input from the detection electrodes via the corresponding charge amplifiers 23a and 23b. Thereby, ideally, unnecessary signal components such as noise generated in the same degree in each of the detection vibrating arms 14a and 14b can be effectively removed from the detection signal, and high detection accuracy can be obtained. However, if unnecessary signal components are included in the detection signals from the detection vibrating arms 14a and 14b in the imbalance, they cannot be effectively removed, and the detection accuracy may be reduced.

According to the present invention, the vibrating arms for detection 14a and 14b are independently bent and vibrated in opposite directions in the same in-plane direction as in the drive mode as shown in FIG. 2B, not in the Z-axis direction of the detection mode. In other words, by using the resonance frequency of the in-plane mode, unnecessary signal components included in the imbalance in the detection signals from the respective detection vibrating arms are effectively removed or greatly reduced. The resonance frequency f _h of the in-plane mode of the detection vibrating arms 14a and 14b is set as described below in relation to the resonance frequency f _d of the driving mode of the driving vibrating arms 13a and 13b.

First, the resonance frequency f _h of the in-plane mode of the detection vibrating arm is set so as to always satisfy f _h <f _d with respect to the resonance frequency f _d of the driving mode of the driving vibration arm. Wherein the resonant frequency f _d of the driving mode of the driving vibration arms and 50kHz constant, the vibrating gyro element 11 of Figure 1 designed generally varied between ± 50kHz resonance frequency f _h of the detection vibration arms, drive The detection signals output from the detection vibrating arms 14a and 14b when the driving vibrating arms 13a and 13b were vibrated in the mode were measured. The detection signal in this drive mode is a vibration leakage signal due to mechanical vibration leakage in which the vibration of the driving vibration arm propagates through the support portion 12 to cause each detection vibration arm to vibrate in the Z-axis direction.

Table 1 below shows the measurement results. In the table, the left column is the difference Δf _h = f _h −f _d between the resonance frequency f _h of the detection vibrating arm and the resonance frequency f _d of the driving vibration arm in the in-plane mode. The right column represents the difference between the vibration leakage signal S1 of one detection vibrating arm 14a and the vibration leakage signal S2 of the other detection vibrating arm 14b as a voltage value mV _p1-p2 . From the table, it can be seen that the difference in the vibration leakage signal is relatively large in the range of f _h > f _d and increases with the frequency difference, and can be reduced only in the range of f _h <f _d .

FIG. 4 shows the vibration output from each detection vibrating arm in the drive mode with respect to the frequency difference Δf _h = f _h −f _{d in the in} -plane mode in the range of f _h <f _d. The difference | S1-S2 | of the leak signal is shown in ppm. From the figure, it can be seen that when the frequency difference Δf _h becomes smaller than −15 kHz, the difference between the vibration leakage signals starts to decrease rapidly. When the frequency exceeds −20 kHz, the difference in the vibration leakage signal is reduced to an extent that the influence on the detection signal is substantially eliminated or extremely small. Therefore, in this embodiment, the detection vibrating arm is designed so that the resonance frequency f _h in the in-plane mode is smaller than −20 kHz with respect to the resonance frequency f _d = 50 kHz of the driving vibrating arm. The influence of the mechanical vibration leakage of the driving vibrating arm on the detection sensitivity and / or accuracy can be substantially eliminated or greatly reduced.

5, the vibrating gyro element 11 of the same resonance frequency _f d = 50 kHz, the difference in vibration leakage signal about the resonance frequency _{f h} of the detection vibration arms | indicates the rate of change | S1-S2. In the figure, the horizontal axis represents the ratio of the frequency difference Δf _h = f _h −f _{d in} the in-plane mode to the resonance frequency f _d of the driving vibrating arm, F _c = (f _h −f _d ) / f _d. (%). The vertical axis indicates the ratio of vibration leak signal difference m = | S1-S2 | relative to the difference | S1−S2 | (ppm) of vibration leak signal when F _c = 1% as a reference value m _{0 r} = m / m ₀ is expressed as a vibration leakage change rate.

As can be seen from the above description and Table 1 and FIG. 4, since the difference m ₀ of vibration leakage when F _c = 1% is considerably large, the smaller the vibration leakage change rate is, the smaller the difference m of vibration leakage signals is. It is preferable for improving sensitivity and accuracy. From the figure, when the resonance frequency of both vibrating arms in the in-plane mode is f _h <f _d and the ratio of frequency differences is F _c ≦ −50%, the vibration leakage change rate is 0.8 or less. It turns out that it becomes small. Furthermore, when the frequency difference ratio F _c ≦ −75%, the vibration leakage change rate can be reduced to 0.6 or less, and when F _c ≦ −84%, the vibration leakage change rate can be reduced to 0.5 or less. it can. Since f _d = 50 kHz, F _c = −50%, −75%, and −84% correspond to Δf _h = −25 kHz, −37.5 kHz, and −42 kHz, respectively.

6, for the same vibrating gyro element 11 and the resonance frequency _f d = 100kHz, the difference in vibration leakage signal about the resonance frequency _{f h} of the detection vibration arms | indicates the rate of change | S1-S2. In the figure, the horizontal and vertical axes are the same as those in FIG. From the figure, when the resonance frequency of both the vibrating arms in the in-plane mode is f _h <f _d and the ratio of the frequency difference is F _c ≦ −30%, the vibration leakage change rate is as small as 0.9 or less. I understand that Further, when the frequency difference ratio F _c ≦ −60%, the vibration leakage change rate can be reduced to 0.8 or less, and when F _c ≦ −70%, the vibration leakage change rate can be reduced to 0.7 or less. it can. Since f _d = 100 kHz, F _c = −30%, −60%, and −70% correspond to Δf _h = −30 kHz, −60 kHz, and −70 kHz, respectively.

  Further, the dimensional ratio of the length Lb of the support portion 12 to the length Ld of the driving vibrating arms 13a and 13b along the longitudinal direction of the vibrating gyro element 11, that is, the Y-axis direction is detected from the driving vibrating arm in the driving mode. It is known that the vibration leakage to the vibrating arms 14a and 14b can be affected. Here, the length Ld of the vibration arm for driving is the length Ld of the vibration arm for driving, as shown in FIG. 1, from the total length of the vibration arm, the weight portions 15a, 15b and the taper portions 17a, 17b, The length of the portion that directly determines the resonance frequency, excluding the lengths 18a and 18b, is used.

Therefore, the difference | S1-S2 | (ppm) of the vibration leakage signal related to the dimensional ratio Lb / Ld between the length of the driving vibrating arm and the length of the support portion was measured by simulation. FIG. 7 shows a simulation result when the resonance frequency f _d of the driving vibrating arm is 50 kHz. As can be seen from the figure, by increasing the length Lb of the support portion 12 to about 1.6 times or more the length Ld of the driving vibrating arm, the difference in the vibration leakage signal affects the detection signal. Has been substantially eliminated or reduced to a very small extent.

FIG. 8 shows a simulation result when the resonance frequency f _d of the driving vibrating arm is 100 kHz. From this figure, the difference in the vibration leakage signal can be detected by increasing the length Lb of the support portion 12 to about twice or more, preferably about 2.4 times or more the length Ld of the driving vibrating arm. It can be seen that the effect on the signal has been substantially eliminated or reduced to a very small extent.

  In general, the vibrating gyro element as in the present embodiment can be manufactured from, for example, a quartz wafer using a processing method using photoetching. However, since a single crystal piezoelectric material such as quartz has an anisotropic etching anisotropy, the cross-section of the vibrating arm is not an ideal rectangle but an asymmetric shape on the left and right. Further, in the outer shape processing of the bending vibration piece, if there is a deviation in the alignment of the photomask, the cross section of the vibrating arm may become asymmetric in the thickness direction. As a result, there is a possibility that the vibrations of each pair of vibration arms are unbalanced on the left and right. Furthermore, such unbalanced vibrations are detected because unnecessary signal components are included in the detection signals from the detection vibrating arms and cannot be effectively removed when they are differentially amplified in the detection circuit. There is a risk of reducing accuracy.

  The vibrating gyro element 11 of the present embodiment can be manufactured with high accuracy from a quartz wafer by using the following processing method. First, a metal film having a two-layer structure in which, for example, Au is laminated on Cr is formed on the entire front and back surfaces of a quartz wafer, and a photoresist is applied thereon, and this is exposed and developed to form the outer shape of the vibrating gyro element 1. A corresponding resist pattern is formed. The metal film exposed from the resist pattern is wet-etched to form metal patterns on both the front and back surfaces of the crystal wafer.

  9A and 9B show the metal patterns 32 formed on both the front and back surfaces of the crystal wafer 31 in this way. In the same figure, the imaginary lines 33a and 33b are the left and right sides excluding the weight portions 15a to 16a and 15b to 16b and the tapered portions 17a to 20a and 17b to 20b from the driving vibrating arms 13a and 13b of the vibrating gyro element 1. Represents. The metal pattern 32 is formed so that the portions corresponding to the left and right sides 33a and 33b of the drive vibrating arms 13a and 13b are slightly wider outside the desired position.

  Next, as shown in FIG. 9B, the laser beam 34 is irradiated from either one of the front surface and the back surface of the crystal wafer 31 to correspond to the left and right sides 33a and 33b of the driving vibrating arms 13a and 13b. Only the part is ablated. Since the laser light is transmitted through the transparent and thin quartz wafer 31, the metal patterns 32 and 32 on both the front and back surfaces of the wafer can be processed accurately at the same time and substantially without causing any misalignment.

  In particular, the distance Dd between the left and right drive vibrating arms 13a and 13b is preferably matched with the spot diameter RL of the laser beam 34 as shown in FIG. Accordingly, the portions corresponding to the both sides of the metal patterns 32 and 32 on both sides of the front and back surfaces can be obtained by scanning the laser beam 34 once in one direction along the adjacent sides 33a and 33b of the driving vibration arm. It can be processed at the same time.

  Next, the crystal wafer is wet-etched using the metal pattern processed in this way as a mask to form an element piece having the outer shape of the vibrating gyro element 11. An electrode film is deposited on the surface of the obtained element piece, and is patterned using a photoetching technique to form the drive electrode, the detection electrode, wirings drawn from these electrodes, and the like.

  According to the present embodiment, the front and back alignment of the portions corresponding to the left and right sides 33a and 33b of the driving vibrating arms of the metal patterns 32 and 32 on both sides can be more accurately aligned in this way. Therefore, the drive vibrating arms 13a and 13b can be processed into a cross-sectional shape closer to a desired rectangular shape. In addition, since only specific portions of the metal patterns 32, 32 on both the front and back surfaces are processed with laser light, the processing time is greatly reduced as compared to the case where the entire metal pattern is processed with laser light as a whole process. In addition, the processing cost can be reduced. In the above embodiment, only the driving vibrating arms 13a and 13b are processed by laser light irradiation, but the detecting vibrating arms 14a and 14b can be processed in the same manner.

  The present invention is not limited to the above embodiments, and can be implemented with various modifications or changes within the technical scope thereof. For example, the present invention can be similarly applied to a vibrating gyro element having a structure other than the double-side tuning fork type described above. In addition to the quartz crystal, the vibrating gyro element of the present invention may be formed from a piezoelectric single crystal such as lithium tantalate or lithium niobate, a piezoelectric material such as piezoelectric ceramics such as lead zirconate titanate, or a silicon semiconductor material. it can. Furthermore, the vibrating gyro element of the present invention is not limited to the piezoelectric driving type using the piezoelectric element as described above, but the electrostatic driving type using electrostatic attraction, the magnetic driving type using electromagnetic force (Lorentz force), and the alternating current. Various driving systems such as a system driven by a Coulomb force by applying a voltage can be employed.

  Furthermore, the present invention can be applied to a gyro sensor by mounting the vibration gyro element on an appropriate package or the like. Furthermore, by mounting this gyro sensor, it can be widely applied to electronic devices such as a digital still camera, a video camera, a navigation device, a vehicle body posture detection device, a pointing device, a game controller, a mobile phone, and a head mounted display.

DESCRIPTION OF SYMBOLS 1,11 ... Vibration gyro element 2,12 ... Support part, 3a, 3b, 13a, 13b ... Drive vibration arm, 4a, 4b, 14a, 14b ... Detection vibration arm, 5, 22 ... Detection circuit, 6a, 6b, 23a, 23b ... charge amplifier, 7, 24 ... differential amplifier, 8, 25 ... high-pass filter, 9, 26 ... AC amplifier, 15a, 15b, 16a, 16b ... weight, 17a-20a, 17b-20b ... Tapered portion, 31 ... quartz wafer, 32 ... metal pattern, 33a, 33b ... imaginary line, side, 34 ... laser beam.

Claims (7)

A support part;
A pair of drive vibrating arms extending side by side from the support;
A pair of detection vibrating arms extending side by side on the opposite side of the driving vibrating arm from the support portion,
The pair of vibrating arms for driving is a driving mode in which the bending vibration at a predetermined resonance frequency f _d in opposite directions in the plane direction along its front and back faces,
By the Coriolis force acting by rotation around the extending direction of the vibrating arm, the pair of driving vibrating arms are opposite to each other in the out-of-plane direction intersecting the front and back main surfaces, and the direction of action of the Coriolis force A detection mode in which the pair of detection vibrating arms bend and vibrate in reverse phase, and the pair of detection vibrating arms bend in opposite directions to the out-of-plane direction and in reverse phase with the driving vibrating arm;
The pair of detection vibrating arms are set so as to bend and vibrate at a predetermined resonance frequency f _h lower than the resonance frequency f _d of the driving vibrating arm in directions opposite to each other in the in-plane direction. The resonance frequency is set so as to reduce the difference | S1−S2 | between the value S1 of the detection signal output from one of the detection vibrating arms and the value S2 of the detection signal output from the other detection vibrating arm. vibrating gyro element characterized by setting the f _h. A support part;
A pair of drive vibrating arms extending side by side from the support;
A pair of detection vibrating arms extending side by side on the opposite side of the driving vibrating arm from the support portion,
The pair of vibrating arms for driving is a driving mode in which the bending vibration at a predetermined resonance frequency f _d in opposite directions in the plane direction along its front and back faces,
By the Coriolis force acting by rotation around the extending direction of the vibrating arm, the pair of driving vibrating arms are opposite to each other in the out-of-plane direction intersecting the front and back main surfaces, and the direction of action of the Coriolis force A detection mode in which the pair of detection vibrating arms bend and vibrate in reverse phase, and the pair of detection vibrating arms bend in opposite directions to the out-of-plane direction and in reverse phase with the driving vibrating arm;
The pair of detection vibrating arms are set to flexurally vibrate at a predetermined resonance frequency f _h in directions opposite to each other in the in-plane direction, and the resonance frequency f _h is
f _h <f _d and | (f _h −f _d ) / f _d | ≧ 0.3
A vibrating gyro element characterized by satisfying 3. The vibrating gyro element according to claim 2, wherein the resonance frequency f _h satisfies | (f _h −f _d ) / f _d | ≧ 0.4.   4. The vibrating gyro element according to claim 2, wherein a length Lb of the support portion with respect to a length Ld of the driving vibrating arm is set in a range of Lb / Ld ≧ 2.   5. The vibrating gyro element according to claim 4, wherein a length Lb of the support portion with respect to a length Ld of the driving vibrating arm is set in a range of Lb / Ld ≧ 3.   A gyro sensor comprising the vibrating gyro element according to claim 1.   An electronic device comprising the vibrating gyro element according to claim 1.

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