JP2011127945A - Piezoelectric vibration element and piezoelectric vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise angular velocity sensor including the rotation of axis within a plane of an oscillator and a small vibration leakage. <P>SOLUTION: A piezoelectric vibration element detects a rotary motion using a piezoelectric effect according to Coriolis' force generated by angular velocity. The piezoelectric vibration element includes: a beam including support sections at both the ends and vibrating in a twist vibration mode; and one or more detection arm extending orthogonal to the twist vibration center axis of the beam and detecting a rotary motion. The piezoelectric vibration element includes: a contact section of a beam side of the beam and an arm side of the detection arm; and an adjustment section including one portion of the beam side and one portion of the arm side and extending while allowing the detection arm to remain. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibration element and a piezoelectric vibrator.

  Angular velocity sensors that detect rotational angular velocities are widely used in navigation systems, attitude control systems for various devices, camera shake prevention devices for video cameras and digital cameras, and the like. In these electronic devices, piezoelectric vibration element sensors that can be miniaturized are frequently used.

  2. Description of the Related Art Conventionally, as an angular velocity sensor of a piezoelectric vibration element, a vibrator having a vibration means for driving vibration and a detection means for detecting a detection vibration generated by rotation, wherein the vibrator has a plurality of vibration systems with respect to the rotation axis Z. An angular velocity sensor that detects an angular velocity of a Z-axis rotation system that is formed so as to extend within a predetermined plane intersecting is known (see Patent Document 1).

  However, the angular velocity sensor disclosed in Patent Document 1 is a sensor that can detect a vibration component of a vertical rotation axis, that is, a Z-axis rotation system, and is set up for a device that requires a plurality of detection axes. It is necessary to mount, and it becomes a large-sized sensor device.

  Therefore, as an angular velocity sensor that detects a rotation axis parallel to the transducer surface, the detection unit connected to the drive unit that drives in the torsional vibration mode around the torsional center axis that intersects the rotation axis is torsionally rotated and rotated. There is known an angular velocity sensor that detects a lateral bending vibration of a detection unit caused by a Coriolis force due to motion and detects an angular velocity (see Patent Document 2).

JP-A-11-281372 JP 2007-212355 A

  However, even the angular velocity sensor according to Patent Document 2 described above causes vibration leakage due to the dimensional accuracy of the vibrator, so-called processing variation, because the detection arm provided at the end is vibrated in the Z direction by torsional vibration. The detection accuracy is lowered by outputting a signal not based on the angular velocity.

  Therefore, an accurate angular velocity sensor with less vibration leakage and having a rotation axis in the plane of the vibrator is provided.

  The present invention can be realized as the following forms or application examples so as to solve at least one of the above-described problems.

  [Application Example 1] The piezoelectric vibration element according to this application example is a piezoelectric vibration element that detects a rotational motion by a piezoelectric effect corresponding to a Coriolis force generated by an angular velocity, and includes support portions at both ends and vibrates in a torsional vibration mode. A beam and one or more detection arms that extend perpendicularly to the extension direction of the beam and detect a rotational motion, and at the intersection of the beam and the arm side of the detection arm, the beam And an adjustment portion extending to include a part of the side surface of the detection arm and a part of the side surface of the detection arm.

  According to this application example, bending vibration in an out-of-plane direction is applied to the detection arm extending from the beam that vibrates torsionally. In-plane vibration is generated by the Coriolis force generated by the rotational motion, that is, the angular velocity applied to the detection arm. However, since the detection arm itself is not provided with an excitation member, mechanical coupling caused by a shift in the cross-sectional shape of the detection arm caused by manufacturing capability (variation) is not generated. That is, the detection arm can accurately output angular velocity = 0 in the state where the rotational angular velocity is not applied. Therefore, more accurate angular velocity detection can be performed.

  Furthermore, by extending the adjusting portion to the base portion of the torsional vibration beam and the detection arm, it is possible to further reduce the error of the detection signal generated by the mechanical coupling.

  Application Example 2 In the above application example, a metal film is formed on the adjustment portion, and the adjustment is performed by removing a part of the metal film.

  According to the application example described above, it is possible to easily adjust by a conventional technique and apparatus such as laser irradiation, and it is possible to obtain a low-cost and highly reliable piezoelectric vibration element without requiring new equipment development.

  Application Example 3 In the application example described above, the adjustment is performed by removing a part of the base material of the piezoelectric vibration element of the adjustment unit.

  According to the application example described above, the piezoelectric vibration element can be obtained at lower cost.

  Application Example 4 In the application example described above, the piezoelectric vibration element base material is quartz.

  According to the application example described above, a small and thin piezoelectric vibration element having excellent temperature characteristics can be obtained.

  Application Example 5 A piezoelectric vibrator on which the piezoelectric vibration element according to the application example described above is mounted.

  According to the application example described above, it is possible to obtain a piezoelectric vibrator serving as an angular velocity sensor that detects rotation having a rotation axis in a thin in-plane direction.

The perspective view which shows the piezoelectric vibration element of this embodiment. The perspective view explaining operation | movement of the piezoelectric vibration element of this embodiment. The perspective view explaining operation | movement of the piezoelectric vibration element of this embodiment. The top view and partial sectional view explaining the composition of the electrode film of the piezoelectric vibration element of this embodiment. The flowchart which shows the manufacturing process of this embodiment. The schematic sectional drawing which shows the manufacturing method of this embodiment. The perspective view which shows the piezoelectric vibration element of other embodiment. The perspective view explaining operation | movement of the piezoelectric vibration element of other embodiment.

[First Embodiment]
A first embodiment according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic perspective view showing the piezoelectric vibration element of this embodiment. The piezoelectric vibration element 100 is formed of a piezoelectric material. In the present embodiment, the piezoelectric vibration element 100 formed from a quartz substrate will be described. The piezoelectric vibration element 100 is formed of a Z-cut substrate obtained by cutting out the X axis and the Y axis in a plane direction out of the X axis called the electric axis of the quartz substrate, the Y axis called the mechanical axis, and the Z axis called the optical axis. ing.

  The piezoelectric vibration element 100 includes a driving beam 10 that extends in the X-axis direction and includes support portions 21 and 22 at both ends, and a detection arm 30 that intersects the center of the driving beam 10 and extends in the Y-axis direction. Furthermore, the crossing part of the drive beam 10 and the detection arm 30 is provided with adjustment parts 41, 42, 43, 44 extending including the drive beam 10 and the side surfaces 10a, 30a of the detection arm 30. Adjustment members 51, 52, 53, 54 for finely adjusting weak vibration leakage due to mechanical coupling are provided on the flat portions of the adjustment units 41, 42, 43, 44. Although not shown, an adjustment member may be provided on the back surface of the drawing.

  The adjusting members 51, 52, 53, and 54 are made of a metal film, and are formed on the adjusting portions 41, 42, 43, and 44 by sputtering, CVD, or the like of, for example, Au, Ag, or W. Further, it is possible to perform adjustment by removing a part of the substrate constituting the adjusting portions 41, 42, 43, 44 without forming the adjusting members 51, 52, 53, 54.

  Next, based on FIG.2 and FIG.3, operation | movement of the piezoelectric vibration element 100 is demonstrated. The piezoelectric vibration element 100 is a gyro sensor element that detects an angular velocity ω that rotates about the Y axis that is the extending direction of the detection arm 30.

  The drive beam 10 is excited in a torsional vibration mode having a torsional central axis in the X-axis direction. That is, it is driven in a vibration mode in which the twisting direction A in FIG. 2 and the twisting direction B in FIG. 3 are repeated. The detection arm 30 extending across the drive beam 10 driven in the torsional vibration mode is shown in the LL ′ cross-sectional views of the detection arm 30 shown in FIGS. 2B and 3B. The tip of the detection arm 30 swings in the direction of the arrow, and substantially bends and vibrates in the Z-axis direction. It is a vibrating arm that vibrates out of plane with respect to the so-called XY plane.

  Here, when an angular velocity ω due to a rotational motion with the Y-axis direction as the rotational axis is loaded, the detection arm 30 is vibrated in the r direction shown in FIGS. 2A and 3A by the Coriolis force, a so-called surface. Internal bending vibration occurs. The in-plane vibration in the r direction in the detection arm 30 is detected, and the angular velocity ω is calculated from the obtained signal.

  As described above, the detection arm 30 does not include any means (excitation electrode) for exciting the detection arm 30 itself, and is driven by the torsional vibration of the drive beam 10. The mechanical coupling due to the deviation in the cross-sectional shape is very small. Therefore, since a signal with less noise can be obtained from the detection arm 30 with respect to the detection of the angular velocity ω, a gyro sensor with high detection accuracy can be realized.

  However, in order to realize high required performance (detection capability) even if the mechanical coupling is very slight in the above-described embodiment, it is desirable that the mechanical coupling is zero as much as possible. Therefore, the adjustment parts 41, 42, 43, 44 or the adjustment members 51, 52, 53, 54 arranged in the adjustment parts 41, 42, 43, 44 are partially removed, or detuning adjustment is performed while adding a minute mass material. In addition, the accuracy of sensor sensitivity can be increased.

  As an adjustment method, it is preferable to partially remove the adjustment members 41, 42, 43, 44 or the adjustment members 51, 52, 53, 54 arranged in the adjustment units 41, 42, 43, 44 by laser irradiation. Since the laser irradiation is easy to adjust the output, it is easy to control the removal amount of the adjusting members 41, 42, 43, 44 or the adjusting members 51, 52, 53, 54 arranged in the adjusting units 41, 42, 43, 44. And accurately.

  In the case of the present embodiment in which the piezoelectric vibration element 100 is made of quartz, adjustment members 51, 52, 53, disposed on the adjustment portions 41, 42, 43, 44 on the back side of the illustrated piezoelectric vibration element 100, In contrast, it is possible to irradiate a laser through the transparent crystal from the surface shown in FIG. Therefore, the adjustment members 51, 52, 53, and 54 disposed on the adjustment portions 41, 42, 43, and 44 provided on the front and back surfaces are adjusted and removed by laser irradiation from only one surface side of the piezoelectric vibration element 100. Therefore, the process can be reduced and the cost can be reduced.

  Next, the electrode film formed on the above-described piezoelectric vibration element 100 will be described with reference to FIG. 4 schematically showing the arrangement of the electrode film. In the schematic perspective view of the piezoelectric vibration element 100 shown in FIG. 4A, an arrow view from the arrow S direction (hereinafter referred to as the front surface) is shown in FIG. 4B and from the arrow T direction (hereinafter referred to as the back surface). FIG. 4 (c) shows an arrow view. 4B and 4C, the electrode film is hatched.

  The driving beam 10 has surface driving electrodes 61a and 62a on the front surface and back surface driving electrodes 61b and 62b on the back surface. The front surface driving electrode 61a and the rear surface driving electrode 61b are connected by a wiring 61c, and are connected to the connection electrode 61d. Further, the front surface driving electrode 62a and the rear surface driving electrode 62b are connected by a wiring 62c and are connected to the connection electrode 62d.

  The detection arm 30 has surface detection electrodes 71 a and 72 a on the front surface, back surface detection electrodes 71 b and 72 b on the back surface, and side detection electrodes 71 c and 72 c on the side surface of the detection arm 30. The front surface detection electrode 71a and the back surface detection electrode 71b are connected by a wiring 71d and connected to the connection electrode 71e. The side detection electrode 71c is connected by a wiring 71f and connected to the connection electrode 71g. The front surface detection electrode 72a and the back surface detection electrode 72b are connected by a wiring 72d and connected to the connection electrode 72e. The side detection electrode 72c is connected by a wiring 72f and connected to the connection electrode 72g.

  The wirings 71d, 71f, 72d, and 72f do not cross the front surface driving electrodes 61a and 62a, the back surface driving electrodes 61b and 62b, and the wirings 61c and 62c, so that many of them are on the side surfaces of the piezoelectric vibration element as illustrated. Provided.

  Next, a method for manufacturing an angular velocity sensor that is a piezoelectric vibrator using the piezoelectric vibration element 100 of the above-described embodiment will be described. FIG. 5 is a flowchart showing the manufacturing process of the angular velocity sensor, and FIG. 6 is a cross-sectional view showing the manufacturing method of the angular velocity sensor.

(Piezoelectric vibration element formation process)
First, the piezoelectric vibration element 100 having a planar shape shown in FIG. 6A is formed in the piezoelectric vibration element forming step (S101). The piezoelectric vibration element 100 forms an outer shape from a quartz substrate by photolithography and etching. An Au film serving as an electrode is formed on the surface of the crystal piece having the outer shape by a method such as vapor deposition, sputtering, or CDV, and the electrode film shown in FIG. 4 is formed by photolithography and etching. In addition, Cu, Ag, W, etc. are applicable as an electrode film material.

  The adjusting members 51, 52, 53, 54 may be formed of the same material as the electrode film material at the same time as the electrode film is formed on the adjusting portions 41, 42, 43, 44.

(Piezoelectric vibration element mounting process)
Next, the process proceeds to the piezoelectric vibration element mounting step (S102). As shown in FIG. 6B, the piezoelectric vibration element 100 is connected to the mounting portions 211 and 212 formed inside the package 200 on one surface of the piezoelectric vibration element 100 (not shown). The support portions 21 and 22 are placed with the electrodes facing the opening side of the package 200, and the piezoelectric vibration element 100 is fixed to the package 200 with the adhesives 221 and 222.

  Next, so-called wire bonding is performed in which the connection electrodes of the piezoelectric vibration element 100 and the electrodes 231 and 232 provided on the mounting portions 211 and 212 are electrically connected by the conductive wires 241 and 242. The electrodes 231 and 232 are connected to external connection electrodes 251 and 252 formed outside the package 200 by wiring (not shown).

(Detuning process)
Subsequently, the process proceeds to a detuning step (S103). In the detuning step (S103), the piezoelectric vibration element 100 is detuned in the mounted state. The detuning is to adjust the frequency of the drive vibration and the frequency of the detection vibration by separating them by a desired value, and the accuracy of detecting the angular velocity can be improved without being affected by the drive frequency.

  As shown in FIG. 6C, the detuning is performed by adjusting YAG from the laser device (not shown) to the adjusting members 51, 52, 53, and 54 formed of the Au film on the adjusting portions 41, 42, 43, and 44 of the piezoelectric vibration element 100. This is performed by irradiating a laser beam 300 such as a laser to remove a part of the adjustment members 51, 52, 53, and 54. The frequency of detection vibration (bending vibration and torsional vibration) in the detection arm 30 is set to be lower than a desired frequency by adding adjustment members 51, 52, 53, and 54 in advance. Here, by irradiating the laser beam and removing a part of the adjustment members 51, 52, 53, 54, the mass of the adjustment parts 41, 42, 43, 44 is reduced, and the detection vibration frequency of the detection arm 30 is reduced. Adjust in the direction of increasing. As a method for removing the adjusting members 51, 52, 53, and 54, a technique such as electron beam and reverse sputtering can be used in addition to the YAG laser.

  Further, since the piezoelectric vibration element 100 is a transparent quartz substrate, the adjustment members 51, 52, 53, 54 formed on the back surface of the piezoelectric vibration element 100, that is, the surface on the mounting portions 211, 212 side of the package 200 are arranged. In contrast, it is possible to irradiate the laser beam through the quartz substrate. Thereby, since the detuning range can be widened, productivity and yield can be improved. Note that heat treatment such as vacuum annealing may be performed before detuning. In this way, the frequency detuned in the subsequent process due to the influence of heat or the like is less likely to shift, and accurate detuning can be maintained. Although it is possible to perform detuning in the state of the piezoelectric vibration element, the frequency may be shifted in the joining of the piezoelectric vibration element and the support member, and at least after the piezoelectric vibration element and the support member are joined. It is preferable to perform detuning.

  In the above-described embodiment, the Au film is formed as the adjustment members 51, 52, 53, and 54. However, the crystal substrate of the adjustment portions 41, 42, 43, and 44 is partially removed without forming the adjustment member. It is also possible to detune with.

  Next, the process proceeds to the sealing step (S104). In the sealing step (S104), the inside of the package 200 on which the piezoelectric vibration element 100 is mounted is hermetically sealed. As shown in FIG. 6D, when the lid 400 arranged on the upper surface of the package 200 is a metal such as Kovar, the joint between the lid 400 and the package 200 is seam welded to make the inside of the package 200 an inert atmosphere or Seal hermetically in a reduced pressure atmosphere. Further, when transparent glass is used for the lid 400, a low melting point glass is disposed on the joining surface 213 of the lid 400 and the package 200, and joining is performed by melting the low melting point glass, and the inside of the package 200 is inert or reduced in pressure. Seal hermetically in an atmosphere. In this way, the angular velocity sensor 500 is completed.

  When transparent glass is used for the lid 400, the laser beam can be transmitted through the lid 400 to irradiate the adjustment members 51, 52, 53, and 54 so that the lid 400 is separated after the sealing step. It is possible to carry out the conditioning process.

[Second Embodiment]
An embodiment in which the piezoelectric vibration element includes a plurality of detection arms will be described. FIG. 7 shows a piezoelectric vibration element having two detection arms, which is formed of a Z-cut quartz substrate as in the first embodiment. The piezoelectric vibration element 600 includes driving beams 610 having support portions 621 and 622 at both ends and extending in the X-axis direction, and two detection arms 631 and 632 that are orthogonal to the driving beam 610 and extend in the Y-axis direction. ing.

  As in the first embodiment, adjustment units 641, 642, 643, 644, 645, 646, 647, and 648 are provided at the intersections of the drive beam 610 and the detection arms 631 and 632, and adjustment members 651 and 648 are provided in each adjustment unit. 652, 653, 654, 655, 656, 657, 658 are provided.

  As shown in FIG. 7, the drive beam 610 includes a first drive beam 610 a that is connected to the support portion 621, a second drive beam 610 b that is connected to the support portion 622, and a connection portion that is connected between the detection arm 631 and the detection arm 632. 610c. The operation of the piezoelectric vibration element 600 is shown in FIGS. The first driving beam 610a and the second driving beam 610b are in a different phase torsional vibration mode in which the torsional rotation directions are opposite to each other, that is, in FIG. 8A, the first driving beam 610a is in the A direction and the second driving beam 610b is in the A direction. 8 (b), the first drive beam 610a is twisted in the B direction, and the second drive beam 610b is twisted and driven in the A direction opposite to the B direction in FIGS. 8 (b) and 8 (b). Is given a torsional vibration mode in which are alternately driven.

  At this time, the connecting portion 610c is not provided with electrode wiring for driving, and is a beam that does not generate torsional vibration. In this way, the torsional vibration mode of the drive beam 610 is bending vibration in which the detection arms 631 and 632 are out of plane vibrations in opposite phases. That is, as shown in FIGS. 8A and 8B, reverse-phase vibrations in the direction of the arrow attached to the tip portions of the detection arms 631 and 632 occur.

  When an angular velocity ω having a rotation axis in the Y direction is applied to the piezoelectric vibration element 600 that is driven as described above, in-plane bending vibration is generated in the detection arms 631 and 632 by Coriolis force as in the first embodiment. The in-plane bending vibration is detected to calculate the angular velocity ω.

  At this time, when the drive beam 610 includes the two detection arms 631 and 632 as in the second embodiment, the two detection arms 631 and 632 vibrate in opposite phases, thereby causing the drive beam 610 to rotate. The torsional moment is canceled, and the rotational motion at the support portions 621 and 622 is suppressed. Therefore, it is possible to suppress the torsional vibration from being transmitted to the package through the support portions 621 and 622 fixed to the package, and to increase the sensitivity of the angular velocity sensor.

  DESCRIPTION OF SYMBOLS 10 ... Drive beam, 21, 22 ... Support part, 30 ... Detection arm, 41, 42, 43, 44 ... Adjustment part, 51, 52, 53, 54 ... Adjustment member.

Claims (5)

A piezoelectric vibration element that detects rotational movement by a piezoelectric effect according to Coriolis force generated by angular velocity,
Beams with support at both ends and vibrating in torsional vibration mode,
One or more detection arms that extend perpendicular to the direction of extension of the beam and detect rotational movement,
The crossing portion between the beam and the arm side of the detection arm includes an adjustment portion that extends to include a part of the side surface of the beam and a part of the side surface of the detection arm.
The piezoelectric vibration element characterized by the above-mentioned. A metal film is formed on the adjustment portion, and adjustment is performed by removing a part of the metal film.
The piezoelectric vibration element according to claim 1. Adjust by removing a part of the base material of the piezoelectric vibration element of the adjustment unit,
The piezoelectric vibration element according to claim 1.   4. The piezoelectric vibration element according to claim 1, wherein a base material of the piezoelectric vibration element is a crystal. 5.   A piezoelectric vibrator mounting the piezoelectric vibration element according to claim 1.

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