JP2011247789A - Vibration gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration gyro which is low in height for reducing an error signal with respect to acceleration in an X-axial direction, and for detecting the angular speeds of a plurality of axes including a Z axis.SOLUTION: The vibration gyro for detecting angular speeds around a Y axis and a Z axis includes an oscillator having a first arm 4 configured to have a longitudinal direction in a Y axial direction, a connection part 3 connected to one end of the Y axial direction, and configured so as to be symmetrical with respect to the central axis of the first arm 4, second arms 5a and 5b connected to the both ends of the X axial direction, and configured to have a longitudinal direction in the Y axial direction, and third arms 7a and 7b configured to have a longitudinal direction in the Y axial direction. The vibration gyro is provided with: a driving means for carrying out the flexion vibration of the second arms to the X axial direction; a first detection means for detecting the flexion vibration of the first arm in the X axial direction; a third detection means for detecting the flexion vibration of the second arms in the Z axial direction; and a second detection means for detecting the flexion vibration of the third arms in the X axial direction. An error signal generated in the first detection means due to the acceleration of the X axial direction is offset by a detection signal generated in the second detection means.

Description

  The present invention relates to a vibration gyro for detecting an angular velocity used in a camera shake correction system, a navigation system, an attitude control system, and the like.

  A vibrating gyroscope is an angular velocity sensor that utilizes a dynamic phenomenon in which when an angular velocity is applied to an object having velocity, the object itself generates a Coriolis force in a direction perpendicular to the velocity direction. By applying an electrical signal using an electromechanical transducer such as a piezoelectric element, mechanical vibration, that is, driving vibration mode can be excited, and mechanical vibration in a direction orthogonal to the driving vibration mode. That is, in a system in which the magnitude of the detected vibration mode can be electrically detected, with the drive vibration mode excited in advance, the vibration direction of the drive vibration mode and the axis perpendicular to the vibration direction of the detected vibration mode are the center. When the angular velocity is given, a detection vibration mode is generated by the action of the Coriolis force described above, and is detected as an output signal. Since the detected output signal is proportional to the magnitude and angular velocity of the drive vibration mode, the magnitude of the angular velocity can be obtained from the magnitude of the output signal when the magnitude of the drive vibration mode is constant. Such a vibration gyro is currently applied as a camera shake correction or car navigation sensor for a video camera or the like.

  In general, in a vibration gyro using a simple sound piece-shaped or sound-shaped vibrator, the axis to be detected and the longitudinal direction of the vibrator must be arranged in parallel. Therefore, a reduction in the height of the vibration gyro is a problem in detecting the height axis. Patent Document 1 discloses a technique related to a vibration gyro for solving such a problem of reducing the height.

  FIG. 5 is a perspective view of a detection element of a conventional vibration gyro disclosed in FIG. The vibrator 101 is configured by a flat plate parallel to the XY plane, and is configured by joining a pair of vibrating pieces 102 a and 102 b to the base 103 and further connecting to an external fixing member 105 via a support body 106.

  In order to measure the angular velocity, first, the vibrating pieces 102a and 102b are vibrated so that their phases are opposite to each other in the X direction. When the rotational angular velocity ω acts around the Z axis in this state, forces F1 and F2 that are opposite to each other along the Y axis act on the vibrating pieces 102a and 102b due to the Coriolis force. As a result, moments M1 and M2 in the same direction act on both ends of the base 103. This moment causes bending vibration in the support 106. By detecting this bending vibration, the rotational angular velocity ω can be measured. As described above, the element constituted by the flat plate parallel to the XY plane enables detection of the angular velocity around the height direction axis (Z axis), thereby reducing the height of the vibration gyro.

JP-A-10-160477

  However, the vibration gyro according to the invention described in Patent Document 1 is configured to easily generate an error signal with respect to acceleration in the X-axis direction. That is, in the vibrating gyroscope of FIG. 5, Coriolis force generated by the angular velocity around the Z axis is detected as bending vibration in the X axis direction generated in the support 106, but the same X is also applied when acceleration is applied in the X axis direction. Since bending vibration in the axial direction occurs, it is difficult to distinguish a signal due to the angular velocity around the Z axis and a signal due to acceleration in the X axis direction from the detection signal.

  The present invention has been made in view of such problems, and an object of the present invention is to detect an angular velocity around the Z axis, reduce an error signal with respect to acceleration in the X axis direction, and An object of the present invention is to provide a highly accurate and small vibration gyro with a low profile.

  In order to solve the above problems, the vibrating gyroscope according to the present invention performs through-hole processing in the Z-axis direction on a flat plate parallel to the XY plane in a space represented by three axes X, Y, and Z orthogonal to each other. A vibrating gyroscope having a formed vibrator and capable of detecting at least an angular velocity around the Z axis, wherein the vibrator is connected at one end to a base provided on at least a part of a peripheral portion of the flat plate, A first arm having a longitudinal direction in a direction, a connecting portion connected to the other end of the first arm and having a shape symmetric with respect to a plane passing through the center of the first arm and parallel to the YZ plane; One end is connected to both ends in the X-axis direction of the connecting portion, a pair of second arms having a longitudinal direction in the Y-axis direction, and one end connected to each of the base portions, passing through the center of the first arm. In a plane parallel to the YZ plane And at least one or more pairs of third arms having a longitudinal direction in the Y-axis direction formed symmetrically, and driving means for bending and vibrating the second arm in the X-axis direction, First detecting means for detecting flexural vibration in the X-axis direction of the arm and second detecting means for detecting flexural vibration in the X-axis direction of the third arm, and the driving means includes the second detecting means. The first detection means has a detection electrode formed on the first arm, and the second detection means is on the third arm. At least part of an error signal generated in the detection of the angular velocity around the Z-axis by the first detection means by the acceleration in the X-axis direction by the detection signal by the second detection means. It is characterized by doing.

  Here, a third detection means for detecting bending vibration of the second arm in the Z-axis direction is provided, the third detection means has a detection electrode formed on the second arm, and Y The angular velocity around the axis may be detectable.

  Further, at least one or more pairs that are connected to the tip of at least one of the second arm and the third arm, and are formed symmetrically with respect to a plane that passes through the center of the first arm and is parallel to the YZ plane. The additional mass part may be provided.

  In addition, the outer shapes of the surfaces of the second arm and the connecting portion parallel to the XY plane have a rectangular shape composed of sides in the X-axis direction and the Y-axis direction, The length may be not less than 2 times and not more than 4 times the length of the side of the second arm in the X-axis direction.

  Further, the maximum displacement amount of the vibration generated in the first connecting portion by the driving unit may be 10% or less as compared with the maximum displacement amount of the bending vibration generated in the second arm by the driving unit. .

  Further, the driving means, the first detection means, and the second detection means may each have a piezoelectric thin film.

  As described above, the vibration gyro of the present invention is a vibration gyro having a vibrator in which a pair of second arms are connected symmetrically with respect to the longitudinal axis of the first arm by a connecting portion. The vibration in which the pair of second arms are displaced in the X-axis direction in opposite directions can obtain stable characteristics. The force generated by the displacement of the pair of second arms cancels out in the vicinity of the connection portion between the connecting portion and the first arm, and becomes a node point. This vibration is preferably selected as the drive vibration mode. This drive vibration mode can be excited by drive means including a drive electrode formed on the second arm.

  Further, the connecting portion is formed with the intention of electrical connection and propagation of vibration, and is not intended for excitation or detection of vibration. When the connecting portion has sufficient rigidity with respect to the first arm and the second arm, even if the driving vibration mode is excited, the displacement generated in the connecting portion is very small. The displacement of the second arm over time is almost limited in the X-axis direction. For this purpose, it is necessary that the maximum displacement amount of the vibration generated in the connecting portion is sufficiently smaller than the maximum displacement amount of the bending vibration generated in the second arm, for example, 10% or less. Such a connecting part has, for example, the outer shape of the surface parallel to the XY plane of the second arm and the connecting part as a rectangular shape composed of sides in the X-axis direction and the Y-axis direction, and the side of the connecting part in the Y-axis direction. The length is obtained by setting the length of the side of the second arm in the X-axis direction to be twice or more.

  When an angular velocity around the Y axis is applied in the state where the drive vibration mode is excited, the pair of second arms receive forces in the Z axis direction in opposite directions by the generated Coriolis force. Accordingly, the second arm is displaced in the Z-axis direction. This displacement in the Z-axis direction can be detected by third detection means including a detection electrode formed on the second arm. Thereby, it can be made to function as a vibration gyro which detects the angular velocity around the Y axis.

  Similarly, when an angular velocity around the Z-axis is applied in a state where the above-described drive vibration mode is excited, the pair of second arms receive forces in the Y-axis direction opposite to each other due to the generated Coriolis force. Therefore, the second arm is displaced in the Y-axis direction. However, since this force is a force acting in the longitudinal direction of the second arm, there is almost no deformation. Since the second arm has sufficient rigidity in the Y-axis direction as compared to the X-axis and Z-axis directions, the signal generated in the third detection means by this force is sufficiently negligible. It is.

  The displacement of the second arm in the Y-axis direction gives a moment about the Z-axis to the connecting portion. Accordingly, the first arm connected to the connecting portion is displaced in the X-axis direction. This displacement in the X-axis direction can be detected by first detection means including a detection electrode formed on the first arm. Thereby, it can be made to function as a vibration gyro which detects the angular velocity around the Z axis.

  Moreover, the error output with respect to the acceleration in the translational motion can be reduced by the third arm and the second detection means. Normally, the detection output of the vibration gyro is performed by signal processing by synchronous detection using the drive signal or the like as a reference signal, so that signal components other than the frequency of the drive vibration mode are removed, but the transducer such as a cantilever beam is removed. In the configuration of the vibration gyroscope with one element, it is difficult to separate a detection signal for acceleration and a detection signal for angular velocity, and an error output due to acceleration may not be negligible.

  When acceleration in the X-axis direction is applied to the vibrating gyroscope of the present invention, the first and second arms are simultaneously bent and displaced in the X-axis direction. Since this is a displacement in the X-axis direction, there is almost no influence on the detection of the angular velocity around the Y-axis. However, regarding the detection of the angular velocity around the Z-axis, the displacement in the X-axis direction is the same, so that a signal output due to acceleration is generated in the first detection means and becomes an error signal.

  However, in the present invention, the third arm is also bent and displaced in the X-axis direction at the same time, and this bending displacement is detected by the second detection means. Since this detection signal can have the same amplitude and opposite phase as the error signal generated in the first detection means, the detection signals from the first detection means and the second detection means are directly added, or By the predetermined signal processing using the detection signal by the second detection means, the influence of the acceleration in the X-axis direction can be removed with respect to the detection of the angular velocity around the Z-axis.

  Similarly, when an acceleration in the Y-axis direction is applied, the first arm, the second arm, and the third arm simultaneously receive a force in the Y-axis direction. However, since this force becomes a force in the arm length direction in each arm, the deformation is sufficiently small, and the influence of the error output on the detection output is small.

  Furthermore, when acceleration in the Z-axis direction is applied, the first arm, the second arm, and the third arm are simultaneously bent and displaced in the Z-axis direction. Since this is a displacement in the Z-axis direction, there is almost no influence on the detection of the angular velocity around the Z-axis.

  However, regarding the detection of the angular velocity around the Y-axis, a similar displacement occurs in the Z-axis direction, so that a signal is generated in the third detection means. However, the pair of second arms bend and displace in the Z-axis direction in the same direction when acceleration is applied in the Z-axis direction, and in opposite directions to each other when an angular velocity around the Y-axis is applied. Since it is bent and displaced in the axial direction, the influence of acceleration can be removed even with respect to detection of angular velocity around the Y axis by predetermined signal processing.

  As described above, in the present invention, since a stable driving vibration mode can be obtained, vibration with a high Q value can be expected. Furthermore, since the resonance frequency can be designed low by providing the additional mass portion at the tip of the second arm, the vibration displacement amount can be increased and the sensitivity can be increased. Similarly, if a mass addition part is provided at the tip of the third arm, the sensitivity of the second detection means can be increased. Further, the drive vibration direction can be limited to the X-axis direction, and the unnecessary drive vibration is small, so the other-axis sensitivity is small. Thus, according to the present invention, it is possible to increase the displacement with a high Q value and a low resonant frequency design, and a vibration gyro with high sensitivity and low sensitivity on other axes can be obtained. Furthermore, the second detection means for detecting the acceleration cancels the error signal due to the acceleration, and a vibration gyro capable of detecting the Y-axis and Z-axis angular velocities without being affected by the translational acceleration is obtained.

  With the above-described configuration, the present invention has the following effects. That is, the vibration gyro of the present invention can reduce an error signal with respect to the acceleration in the X-axis direction, and can detect the Z-axis or the angular velocity of the Z-axis and the Y-axis. In addition, since the connecting portion is not deformed, it is possible to limit the driving vibration direction to the X-axis direction, thereby reducing the other-axis sensitivity. Further, high sensitivity can be obtained by the drive vibration mode having a high Q value. Moreover, the error output with respect to the acceleration of translational motion is small. Thus, a highly accurate and small vibration gyro can be provided.

  That is, according to the present invention, it is possible to detect an angular velocity around the Z-axis, reduce an error signal with respect to acceleration in the X-axis direction, and provide a highly accurate and small-sized low-profile vibration gyro. it can.

The perspective view of the detection element in one Embodiment of the vibration gyroscope by this invention. Sectional drawing which shows the structure of the board | substrate of a 1st arm part of the vibrator | oscillator of the vibration gyroscope of this Embodiment, a piezoelectric thin film, and an electrode. Sectional drawing which shows the structure of the board | substrate of a 2nd arm part of the vibrator | oscillator of the vibration gyroscope of this Embodiment, a piezoelectric thin film, and an electrode. Sectional drawing which shows the structure of the board | substrate of the 3rd arm part of the vibrator | oscillator of the vibration gyroscope of this Embodiment, a piezoelectric thin film, and an electrode. The perspective view of the detection element of the conventional vibration gyroscope.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a perspective view of a detection element in an embodiment of a vibration gyro according to the present invention. FIG. 2 is a cross-sectional view showing the structure of the substrate, the piezoelectric thin film, and the electrode in the first arm portion of the vibrator of the vibrating gyroscope according to the present embodiment. FIG. 3 is a cross-sectional view showing the structure of the substrate, the piezoelectric thin film, and the electrodes in the second arm portion of the vibrator of the vibratory gyro according to the present embodiment. FIG. 4 is a cross-sectional view showing the structure of the substrate, the piezoelectric thin film, and the electrode in the third arm portion of the vibrator of the vibrating gyroscope according to the present embodiment. As shown in FIG. 1, the vibration gyro according to the present embodiment uses a detection element 1 having a vibrator formed by machining a through hole in the Z-axis direction on a flat plate parallel to the XY plane. This is a vibration gyro capable of detecting an angular velocity around an axis.

  The vibrator of the vibration gyro according to the present embodiment has a first arm 4 having one end connected to a base 2 provided in the periphery of the detection element 1 and having a longitudinal direction in the Y-axis direction. Connected to the other end, the connecting part 3 having a symmetrical shape with respect to a plane parallel to the YZ plane passing through the center of the first arm 4, and one end connected to both ends of the connecting part 3 in the X-axis direction, A pair of second arms 5a, 5b having a longitudinal direction in the direction, and a pair of third arms 7a, 7b each having one end connected to the base 2 and having a longitudinal direction in the Y-axis direction. have. Furthermore, the vibration gyro according to the present embodiment includes a driving unit that flexurally vibrates the second arms 5a and 5b in the X-axis direction, and a first detection unit that detects flexural vibrations of the first arm 4 in the X-axis direction. And third detection means for detecting bending vibration in the Z-axis direction of the second arms 5a and 5b, and second detection means for detecting bending vibration in the X-axis direction of the third arms 7a and 7b. I have. The drive means has drive electrodes formed on the second arms 5a and 5b, and the first detection means, the second detection means, and the third detection means are the first arm 4 and the second detection means, respectively. 3 and detection electrodes formed on the second arms 5a and 5b, and the maximum displacement of vibration generated in the connecting portion 3 by the driving means is determined by the driving means by the second arms 5a and 5b. Is 10% or less as compared with the maximum displacement amount of the bending vibration generated in the above.

  The vibrator is connected to the tips of the second arms 5a, 5b and the third arms 7a, 7b, passes through the center of the first arm 4, and is formed symmetrically with respect to a plane parallel to the YZ plane. Two pairs of additional mass portions 6a, 6b, 6c, and 6d are provided.

  Further, in the detection element 1 of the vibration gyro according to the present embodiment, the base 2 formed on the outer periphery of the detection element 1 is supported and fixed.

  Further, the outer shapes of the first arm 4, the second arms 5a and 5b, the third arms 7a and 7b, and the surface of the connecting portion 3 parallel to the XY plane are all in the X-axis direction and the Y-axis direction. It has a rectangular shape composed of sides, and the length of the side of the connecting portion 3 in the Y-axis direction is more than twice the length of the sides of the second arms 5a and 5b in the X-axis direction.

  Here, in the detection element 1 of the vibration gyro according to the present embodiment, a lower electrode is formed on one surface of a substrate which is a flat plate constituting the vibrator, a piezoelectric thin film is formed on the upper surface, and a plurality of electrodes are formed on the upper surface. The substrate on which the upper electrode is formed is subjected to through-hole processing to constitute a part of the vibrator, drive means, and detection means.

  FIG. 2 is a cross-sectional view showing the structure of the substrate, the piezoelectric thin film, and the electrode in the portion of the first arm 4. As shown in FIG. 2, the lower electrode 9, the piezoelectric thin film 10, and the detection electrodes 13 a and 13 b are sequentially formed on the first arm 4. When the first arm 4 is displaced in the X-axis direction, opposite directions of strain are generated in the piezoelectric thin film 10 in the vicinity of the detection electrodes 13a and 13b. Due to this distortion, electrical signals having opposite phases are generated in the detection electrodes 13a and 13b. By detecting this electrical signal with a predetermined detection circuit, the displacement of the first arm 4 in the X-axis direction can be detected.

  FIG. 3 is a cross-sectional view showing the structure of the substrate, the piezoelectric thin film, and the electrodes in the portions of the second arms 5a and 5b. As shown in FIG. 3, the lower electrode 9, the piezoelectric thin film 10, the drive electrodes 11a and 11b, and the detection electrode 12 are sequentially formed on the second arms 5a and 5b. When electrical signals having opposite phases are applied to the drive electrodes 11a and 11b, the piezoelectric thin film 10 in the vicinity of the drive electrodes 11a and 11b generates strains in opposite directions with respect to the length direction of the second arm. This strain can excite vibration in the X-axis direction of the second arms 5a and 5b.

  Further, since the drive electrodes 11a and 11b can detect the displacement of the second arms 5a and 5b in the X-axis direction, when the drive electrodes 11a and 11b or a part of the drive electrodes 11a and 11b constitute a self-excited oscillation circuit. It can also be used as a monitor electrode.

  Further, when the displacement in the Z-axis direction occurs, distortion occurs in the piezoelectric thin film 10 near the detection electrode 12. Due to this strain, an electrical signal corresponding to the strain is generated in the detection electrode 12. By detecting this electrical signal with a predetermined detection circuit, the displacement of the second arms 5a and 5b in the Z-axis direction can be detected. Similarly, an electrical signal corresponding to the strain is also generated in the detection electrodes 13a and 13b in FIG. However, since this electrical signal is a signal having the same phase at the detection electrodes 13a and 13b, the displacement in the Z-axis direction is not detected by performing subtraction signal processing.

  It should be noted that distortion occurs in the piezoelectric thin film 10 in the vicinity of the detection electrode 12 even when the second arms 5a and 5b are displaced in the X-axis direction. However, since this distortion is distributed in the opposite direction with respect to the center line in the width direction of the second arm, an electric signal is hardly generated in the detection electrode 12.

  FIG. 4 is a cross-sectional view showing the structure of the substrate, the piezoelectric thin film, and the electrodes in the third arms 7a and 7b. As shown in FIG. 4, a lower electrode 9, a piezoelectric thin film 10, and detection electrodes 14a and 14b are sequentially formed on the third arms 7a and 7b. When the third arms 7a and 7b are displaced in the X-axis direction, the piezoelectric thin films 10 near the detection electrodes 14a and 14b generate strains in opposite directions. Due to this distortion, electrical signals having opposite phases are generated in the detection electrodes 14a and 14b. By detecting this electrical signal with a predetermined detection circuit, the displacement of the third arms 7a and 7b in the X-axis direction can be detected.

  Further, when a displacement in the Z-axis direction occurs, an electrical signal corresponding to the strain is generated on the detection electrodes 14a and 14b. However, since this electric signal becomes a signal having the same phase at the detection electrodes 14a and 14b, the displacement in the Z-axis direction is not detected by performing subtraction signal processing.

  In order to operate as a vibration gyro, the drive vibration mode is excited in advance. The additional mass portions 6a and 6b are vibrated in the X-axis direction in opposite directions by the driving means described above. However, the frequency of the drive signal is desirably a frequency near the resonance frequency of the drive vibration mode.

  When an angular velocity is applied around the Y axis in a state where this drive vibration mode is excited, the additional mass portions 6a and 6b receive forces in the Z axis direction in opposite directions due to the generated Coriolis force. Accordingly, the second arms 5a and 5b are displaced in the Z-axis direction. This displacement in the Z-axis direction can be detected by the detection electrode 12 formed on the second arms 5a and 5b. Thereby, it can be made to function as a vibration gyro which detects the angular velocity around the Y axis.

  The connecting portion 3 is formed with the intention of electrical connection and propagation of vibration, and is not intended for excitation or detection of vibration. The first arm 4 and the second arms 5a and 5b have sufficient rigidity, and even when the drive vibration mode is excited, the displacement generated in the connecting portion 3 is very small. Therefore, the displacement of the second arms 5a and 5b and the additional mass portions 6a and 6b during the excitation in the drive vibration mode is substantially limited in the X-axis direction.

  The vibration in which the additional mass portions 6a and 6b are displaced in the X-axis direction symmetrically with respect to a plane that passes through the center of the first arm 4 and is parallel to the YZ plane has very stable characteristics. The force generated by the displacement of the two additional mass portions is canceled in the vicinity of the connecting portion between the connecting portion 3 and the first arm 4 and becomes a node point.

  With this stable driving vibration mode, high Q value vibration can be expected, and furthermore, the resonance frequency can be designed low by the additional mass part. The displacement can be increased by the high Q value and the low frequency design, and a highly sensitive vibration gyro is obtained. Furthermore, by limiting the displacement in the driving vibration mode to the X-axis direction, a vibration gyro having no other-axis sensitivity can be obtained.

  Similarly, when an angular velocity around the Z axis is applied, the two additional mass portions 6a and 6b receive a force in the Y axis direction due to the generated Coriolis force. The additional mass portions 6a and 6b receive forces in opposite directions. Accordingly, the second arms 5a and 5b are displaced in the Y-axis direction. However, since this force is a force acting in the longitudinal direction of the second arms 5a and 5b, there is almost no deformation. Since the second arms 5a and 5b have sufficient rigidity in the Y-axis direction as compared with the X-axis and Z-axis directions, signals generated at the detection electrodes 12 formed on them are sufficiently large. The size is negligible.

  The displacement of the second arms 5a and 5b in the Y-axis direction gives the connecting portion 3 a moment around the Z-axis. Accordingly, the first arm 4 connected to the connecting portion 3 is displaced in the X-axis direction. This displacement in the X-axis direction can be detected by the detection electrodes 13 a and 13 b formed on the first arm 4. Thereby, it can be made to function as a vibration gyro which detects the angular velocity around the Z axis.

  In the vibrating gyroscope according to the present embodiment, the third arm 7a, 7b can reduce an error output with respect to the acceleration in the translational motion.

  When an acceleration in the X-axis direction is applied, the four additional mass parts receive a force in the X-axis direction all at once. The first arm 4 and the second arms 5a and 5b are simultaneously displaced in the X direction in the same direction. However, since this is a displacement in the X-axis direction, no electrical signal is generated in the detection electrodes 12 formed on the second arms 5a and 5b, and there is almost no effect on the detection of the angular velocity around the Y-axis. There is no.

  On the other hand, regarding the detection of the angular velocity around the Z axis, the displacement is the same in the X axis direction, so that an electrical signal is generated at the detection electrodes 13 a and 13 b formed on the first arm 4. However, electrical signals are also generated in the detection electrodes 14a and 14b formed on the third arms 7a and 7b.

  Therefore, the influence of the acceleration can be removed by adjusting the magnitudes of the electrical signals of the detection electrodes 13a, 13b, 14a, and 14b generated by the acceleration in the X-axis direction in advance and performing predetermined signal processing. That is, the magnitude of the electric signal detected by the detection electrodes 13a and 13b formed on the first arm 4 caused by the acceleration in the X-axis direction and the detection electrodes 14a and 14b formed on the third arms 7a and 7b. The magnitudes of the detected electrical signals are substantially matched, and the phase is reversed. As a result, the electric signal generated by the acceleration in the X-axis direction is canceled out, and the error output is reduced.

  Similarly, when an acceleration in the Y-axis direction is applied, the four additional mass parts simultaneously receive a force in the Y-axis direction. However, since the connecting portion 3 has sufficient rigidity and the first arm 4, the second arms 5a and 5b, and the third arms 7a and 7b are longitudinal forces, the deformation is sufficiently small. Detection of angular velocities around the Y axis and around the Z axis has little effect.

  Furthermore, when acceleration in the Z-axis direction is applied, the four additional mass parts are displaced in the Z-axis direction all at once. Therefore, the first arm, the second arm, and the third arm are also displaced in the same direction in the Z-axis direction. Since this is a displacement in the Z-axis direction, there is almost no influence on the detection of the angular velocity around the Z-axis. Regarding the detection of the angular velocity around the Y-axis, the displacement is in the Z-axis direction in the same manner as when the angular velocity is applied, so that an electrical signal is generated at each detection electrode 12.

  However, when an angular velocity around the Y-axis is actually applied, the second arms 5a and 5b are displaced in the Z-axis direction in opposite directions, so that the influence of acceleration can be removed by predetermined signal processing.

  As described above, according to the present embodiment, a vibration gyro capable of detecting the angular velocities of the Y axis and the Z axis can be obtained. As described above, the driving vibration mode of the vibrator of the vibratory gyro according to the present embodiment is a vibration having very good symmetry. The force generated by the displacement of each additional mass part is canceled in the vicinity of the connection part between the connecting part and the first arm, and becomes a node point. The end of the first arm can be easily supported and fixed without impairing the vibration characteristics of the drive vibration mode. Therefore, it can be easily connected to the base 2. The base 2 formed around the detection element 1 makes it easy to form electrode pads necessary for signal input and output thereon, and it is also easy to mount and fix the portion of the base 2 on another mounting board. It is.

Next, a specific example of the vibrating gyroscope according to the present invention will be described. As shown in FIGS. 1 to 4, the detection element 1 is a silicon substrate having a thickness of 50 μm, a lower electrode 9 is formed on one surface, and a piezoelectric thin film 10 is formed on the upper surface of the PZT having a thickness of 2 μm. A thin film is formed, and the upper electrodes of the drive electrodes 11a and 11b and the detection electrodes 12, 13a, 13b, 14a, and 14b are formed on the upper surface, and through holes are formed by dry etching. The lower electrode 9 includes a silicon dioxide (SiO ₂ ) film having a thickness of 1 μm formed by oxidizing the surface of a silicon substrate, a titanium film having a thickness of 35 nm formed by sputtering, and a top surface thereof. And a platinum film having a thickness of 200 nm formed by sputtering. The upper electrode is composed of a chromium film having a thickness of 35 nm formed by sputtering on the upper surface of the PZT thin film and a gold film having a thickness of 300 nm formed by sputtering on the upper surface. Here, when the wiring electrode is formed on the PZT thin film, an insulating layer having a low dielectric constant may be formed on the PZT thin film and the wiring electrode may be formed thereon in order to reduce the capacitance.

  Further, the length of the side in the Y-axis direction of the connecting portion 3 is about 100 μm, and the length of the side in the X-axis direction of the second arms 5a and 5b is about 50 μm. The length of the second arms 5a and 5b in the Y-axis direction is about 1200 μm, the length of the third arms 7a and 7b in the Y-axis direction is about 500 μm, and the connecting portion 3 in the X-axis direction. The length is approximately 600 μm, and the shape of the additional mass portions 6a and 6b is approximately 200 μm on one side, and the shape of the additional mass portions 6c and 6d is a rectangle whose X-axis direction is approximately 100 μm and Y-axis direction is approximately 1000 μm. Shape. When the displacement distribution of the vibrator was analyzed by the finite element method analysis in the configuration of this example, the maximum displacement amount of the connecting portion was about 1% with respect to the maximum displacement amount of the second arm.

  As described above, the vibration gyro according to the present invention is configured by the flat plate parallel to the XY plane, and can detect the angular velocities of the Y axis and the Z axis. Further, since the connecting portion is not easily deformed, the driving vibration direction can be limited to the X-axis direction, and the other-axis sensitivity is small. Further, the sensitivity is high due to the drive vibration mode having a high Q value. Moreover, the error output with respect to the acceleration of translational motion is small. Furthermore, since the base portion formed in the periphery can be supported and fixed, mounting is easy and mass productivity is high. Accordingly, it is possible to provide a small vibration gyro with a low profile and high accuracy and excellent mass productivity.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and the present invention can be applied even if there is a design change without departing from the gist of the present invention. include. That is, it goes without saying that the present invention also includes various variations and modifications that would be obvious to those skilled in the art. For example, in the vibrating gyroscope according to the above-described embodiment, a silicon substrate having a piezoelectric thin film such as a PZT thin film has been exemplified. The shape, number and arrangement of drive electrodes and detection electrodes in the drive means and detection means, and the shape of each arm and each connecting part can be designed according to the purpose and application. Yes, and not limited to those illustrated. As for the method of making the connecting portion difficult to be deformed by driving vibration, the rigidity of the connecting portion is increased by making the planar shape greatly different from the shape of the second arm or by making it a shape other than a rectangle, or the resonance frequency thereof is increased. Various means are possible, such as keeping away from the frequency of the drive vibration, and further forming a film on which rigidity is increased. Further, the presence / absence and the shape of the mass adding portion installed at the tips of the second arm and the third arm can be selected depending on the sensitivity, response characteristics and shape required by the target vibration gyroscope.

DESCRIPTION OF SYMBOLS 1 Detection element 2,103 Base 3 Connection part 4 1st arm 5a, 5b 2nd arm 6a, 6b, 6c, 6d Additional mass part 7a, 7b 3rd arm 9 Lower electrode 10 Piezoelectric thin film 11a, 11b Drive electrode 12, 13a, 13b, 14a, 14b Detection electrode 101 Vibrator 102a, 102b Vibrating piece 105 Fixing member 106 Support

Claims (6)

  At least an angular velocity around the Z-axis having a vibrator formed by subjecting a flat plate parallel to the XY plane to through-hole processing in the Z-axis direction in a space represented by three axes X, Y, and Z orthogonal to each other The vibrator has a first arm having one end connected to a base provided on at least a part of a peripheral portion of the flat plate and having a longitudinal direction in the Y-axis direction, and the first gyroscope. A connecting portion having a symmetrical shape with respect to a plane parallel to the YZ plane passing through the center of the first arm, and one end connected to both ends of the connecting portion in the X-axis direction. A pair of second arms having a longitudinal direction in the Y-axis direction, and one end connected to each of the bases and formed symmetrically with respect to a plane passing through the center of the first arm and parallel to the YZ plane, Small with longitudinal direction in the axial direction A driving means for bending and vibrating the second arm in the X-axis direction, and a first arm for detecting bending vibration in the X-axis direction of the first arm. Detection means and second detection means for detecting bending vibration in the X-axis direction of the third arm, and the drive means has a drive electrode formed on the second arm, The first detection means has a detection electrode formed on the first arm, and the second detection means has a detection electrode formed on the third arm, and acceleration in the X-axis direction. Therefore, at least a part of an error signal generated in the detection of the angular velocity around the Z axis by the first detection means is canceled by the detection signal by the second detection means.   Third detection means for detecting bending vibration in the Z-axis direction of the second arm is provided, and the third detection means has a detection electrode formed on the second arm, and is arranged around the Y-axis. 2. The vibrating gyroscope according to claim 1, wherein angular velocity can be detected.   At least one pair of additions connected to the tip of at least one arm of the second arm or the third arm and formed symmetrically with respect to a plane passing through the center of the first arm and parallel to the YZ plane The vibrating gyroscope according to claim 1, further comprising a mass part.   The outer shapes of the surfaces parallel to the XY plane of the second arm and the connecting portion both have a rectangular shape composed of sides in the X-axis direction and the Y-axis direction, and the length of the side in the Y-axis direction of the connecting portion. The vibration gyro according to any one of claims 1 to 3, wherein the vibration gyro is 2 times or more and 4 times or less the length of the side of the second arm in the X-axis direction.   The maximum displacement amount of vibration generated in the first connecting portion by the driving means is 10% or less compared to the maximum displacement amount of the bending vibration generated in the second arm by the driving means. The vibration gyro according to any one of claims 1 to 4.   The vibrating gyroscope according to claim 1, wherein each of the driving unit, the first detection unit, and the second detection unit includes a piezoelectric thin film.

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