JP2009074996A - Piezoelectric vibration gyro - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost and compact piezoelectric vibration gyro needing no large space, capable of detecting angular velocities of two axes by using one vibrator which can be driven by one drive signal. <P>SOLUTION: The two-axis detection type vibrator 1 comprises: four sets of tuning forks composed of arms 2a, 2b, 2c, 2d, 2e, 2f, 2g and 2h; a base 4 positioned at the center; a coupling part for coupling the base with these tuning forks; a frame 5 disposed around the base 4; and beams 3a, 3b, 3c and 3d for connecting the base 4 and the frame 5. These are formed integrally by applying a penetration process using a sandblasting method to a flat plate made of silicon. The four sets of tuning forks are coupled with the base 4 in a radial cross-joint shape through the coupling part 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sensor for detecting acceleration, which is built in a navigation system device of an automobile or an attitude control device of an electric appliance, and more particularly to a gyroscope used in a system for detecting camera shake such as a camera-integrated VTR and a digital camera. The present invention relates to a piezoelectric vibration gyro using a tuning fork type piezoelectric vibrator.

  Piezoelectric vibratory gyros belong to a gyroscope that utilizes a dynamic phenomenon in which, when an angular velocity of rotation is given to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibration direction. In two directions orthogonal to each other, in a piezoelectric vibrator that allows one to vibrate as an excitation unit and the other as a detection unit to detect an output voltage, the two vibration surfaces intersect with the excitation unit vibrated. When the piezoelectric vibrator itself is rotated about the axis parallel to the line as a central axis, the above-mentioned Coriolis force causes a force to act in a direction perpendicular to the vibration direction of the excitation unit, thereby exciting the detection unit. . Since the magnitude of the vibration excited by the detector is proportional to the rotational angular velocity, the magnitude of the rotational angular velocity can be obtained from the magnitude of the output voltage generated by the piezoelectric phenomenon of the detector. The vibration of the excitation unit is called drive vibration, and the vibration of the detection unit is called detection vibration.

  Piezoelectric vibration gyros are particularly used in camera shake correction devices because they are small and inexpensive to manufacture. Camera shake correction devices generally require detection of angular velocities in the pitch direction and yaw direction, and conventionally, two single-axis detection type piezoelectric vibration gyros have been used. In recent years, the development of two-axis detection type gyros has been actively promoted in order to meet the needs for further miniaturization and price reduction.

  Two-axis detection type gyros include a method using two vibrators for detecting a uniaxial angular velocity and a method for detecting a biaxial angular velocity using a single vibrator. In either case, the drive detection circuit for two-axis detection can be formed on the same substrate, or it can be formed as a one-chip integrated circuit, and the number of packages containing the vibrator and circuit can be reduced to one. Compared to the case where two gyros are used, there is an advantage that the size and price can be reduced.

  Furthermore, when comparing a method that uses two vibrators that detect angular velocity of one axis and a method that detects angular velocity of two axes with one vibrator, it detects angular velocity of two axes with one vibrator. In this method, since the vibrator can be driven by one oscillation circuit, the drive detection circuit can be configured simply. In addition, the shape of the vibrator can be reduced because the base for connecting the arms of the vibrator can be commonly used at one place.

  Here, from the viewpoint of the shape and mounting area of the vibrator, the kind of the vibrator is roughly divided into two types, a sound piece and a tuning fork. In the case of a sound piece, it is necessary to support and fix it with a vibration node so as not to inhibit the vibration. However, when dealing with vibrations in two or more directions such as a drive vibration and a detection vibration like a vibration gyro, the vibration node is There is no perfect node on the surface of the vibrator because it exists inside. That is, the support and fixation influences vibration more or less. Therefore, in order to reduce the influence as much as possible, it is general to support and fix the vicinity of the vibration node with an elastic body such as a spring material. Therefore, when using the resonator of a sound piece as a vibration gyro, the space for the support member needs to be much larger than the space of the vibrator, and the problem of fixing the support of the sound piece resonator is a miniaturization of the gyro sensor. It has become an obstacle to do.

  On the other hand, in the case of a tuning fork, in-plane vibration, which is vibration in the tuning fork plane, is confined to the arm, which is a component of the tuning fork, so that the base to which the arm is connected becomes a vibration node in a wide range. Thus, it can be easily supported and fixed without requiring a special support member. However, the in-plane vibration and the out-of-plane vibration in the vertical direction are vibration modes that can exist only when the base is supported and fixed, and the support and fixing state of the base greatly affects the vibration. In general, in order to stabilize out-of-plane vibration, it is preferable that the support and fixing be completely fixed, and it is necessary to fix the vibration part with a sufficiently large mass with respect to the vibration moment of the vibration part. When a tuning fork vibrator is used as a vibrating gyroscope, a large fixing weight necessary for supporting and fixing the vibrator is an obstacle to miniaturizing the vibrating gyroscope.

  FIG. 7 is a perspective view showing the structure of a conventional vibrator. As shown in FIG. 7, the arms 64a and 64b and the arms 64c and 64d are integrally connected so that the base 63 of the tuning fork vibrator becomes a common base, and each of the tuning fork 61 and the tuning fork 62 has its own resonance. Driving at a frequency realizes two-axis detection (see, for example, Patent Document 1).

JP-A-6-294654

  However, the above-described conventional technology requires two driving circuit sections and a simple tuning fork structure, so a large fixing weight is required to stabilize the out-of-plane vibration to be detected. Therefore, there is a problem that the size cannot be reduced and the manufacturing cost increases with the increase in the size of the fixing weight.

  The present invention has been made in view of the above-described problems, and enables a two-axis angular velocity to be detected by one vibrator that can be driven by one drive signal, and does not require a large space. An object of the present invention is to provide a piezoelectric vibration gyro.

  The present invention includes a vibrator in which a tuning fork comprising an arm set in which two arms are connected at one end is connected to a base, and four sets of the tuning forks are arranged in a single plane and in a cross-radiation manner, The two arms in the tuning fork are bent and oscillated in a direction perpendicular to the single plane with opposite phases, respectively, and a pair of tuning forks arranged opposite to each other in a cross-radiating state causes the arms to have opposite phases. And a driving means for bending and vibrating in a direction perpendicular to the single plane, and a detecting means for detecting vibrations in two directions perpendicular to the vibration obtained by the driving means. It is a piezoelectric vibration gyro.

  In the vibrator according to the present invention, the four sets of tuning forks may be connected to the base by a connecting portion extending in a single plane and in a cross radial shape from the base, and the base, the connecting portion, and the tuning fork. Is a piezoelectric vibration gyro characterized by being integrally formed.

  Further, according to the present invention, the vibrator is connected to a frame disposed around the base by a beam extending from the base, and the frame and the beam are in the single plane. The piezoelectric vibration gyro is formed integrally with a base, and the base is supported and fixed to the frame by connecting the base and the frame at at least two locations.

  According to the present invention, since the angular velocity of two axes can be detected by one vibrator and the vibrator can be driven by one oscillation circuit, the drive detection circuit has a simple configuration. Furthermore, a drive detection circuit for two-axis detection can be formed on the same substrate, or can be formed as a one-chip integrated circuit. Further, the number of packages for storing the vibrators and circuits can be reduced to one. In addition, in the vibrator, since the base for connecting the tuning fork composed of the arm set can be shared by one, the shape of the vibrator itself can be reduced.

  In addition, the vibration energy of the drive of the vibrator and the two detected vibrations is confined in the arm and the base, and the vibration does not leak to the frame surrounding the outer periphery. Therefore, the frame can be easily supported and fixed without using an elastic body such as a spring material, and the fixing weight for supporting and fixing the frame does not require a particularly large mass. I do not care. From the above, according to the present invention, it is possible to provide a piezoelectric vibration gyro which is significantly smaller and thinner than conventional ones and has stable characteristics.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a top view showing a vibrator structure according to an embodiment of the present invention. This vibrator is composed of a plurality of arms 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, a base 4, a plurality of connecting portions 6, a frame 5, and a plurality of beams 3a, 3b, 3c, 3d. The In addition, although not shown, a piezoelectric film or an electrode for driving and detecting is formed on the upper surface or the rear surface of the vibrator in this figure. Here, the upper surface of the vibrator is called a main surface. A vibration gyro that realizes two-axis detection is configured by driving vibration in a direction perpendicular to the main surface of the vibrator.

  The vibrator 1 includes a base 4 located in the center, a tuning fork that is an arm set including two arms (2a and 2b), and a tuning fork that is an arm set including two arms (2c and 2d). The tuning fork, which is an arm set composed of two arms (2e and 2f), and the tuning fork, which is an arm set composed of two arms (2g and 2h), are crossed with respect to the base 4. The base 4 is connected by a radially extending connecting portion 6 and is connected by a frame 5 arranged around and the beams 3a, 3b, 3c, 3d, which are on the same plane. Is formed. These vibrators 1 are integrated by subjecting a flat plate made of silicon, lithium niobate, or the like having a thickness of about 0.05 to 0.3 mm to penetration processing by a sandblast method, a dry etching method, a wet etching method, or a laser method. Formed. The arms 2a, 2b, 2c, 2d, 2e, 2f, 2g and 2h have a width of about 0.05 to 0.3 mm.

  Since the detection sensitivity of the vibration gyro is inversely proportional to the frequency, an extension part having a load mass is provided at the tip of the arms 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, and the arms 2a, 2b, 2c , 2d, 2e, 2f, 2g, and 2h, the resonance frequency is lowered. As a result, in the present embodiment, the outer shape of the frame 5 is as small as about 2 to 5 mm, but the sensitivity is high. Here, one end of each of the beams 3 a, 3 b, 3 c, 3 d is connected to a corner of the rectangular base portion 4, and the other end is connected to a corner on the inner peripheral side of the rectangular annular frame 5. Therefore, the base 4 is held by the frame 5 via the beams 3a, 3b, 3c, 3d. In consideration of impact resistance from the outside, variation in penetration processing accuracy during manufacturing, fatigue resistance, etc., a sharp corner portion in the connection portion of the vibrator 1 with, for example, the frame 5 and the beams 3a, 3b, 3c, 3d. Is preferably rounded or C-cut. Although the case where the base 4 and the frame 5 are connected by four beams has been described here, the number of beams may be two or more, that is, the base 4 and the frame 5 may be supported and fixed at least at two locations.

  There are two major options for the material of the vibrator. First, in the first embodiment, it is possible to select a vibrator in which silicon or the like is used as a vibrating body and a piezoelectric film including a piezoelectric thin film and electrodes is formed on the main surface of the arm. Next, in the second embodiment, it is possible to select a vibrator in which electrodes are formed on the main surface of the arm or the like using quartz, lithium niobate, lithium tantalate, or the like that is a piezoelectric single crystal as the vibrator. it can.

  FIG. 5 is a cross-sectional view of the arm. FIG. 5A is an explanatory diagram in the case where the piezoelectric film is formed in two portions on the arm main surface, and FIG. 5B is a piezoelectric film on the arm main surface. It is explanatory drawing when is formed in one place. In the first embodiment, as shown in FIGS. 5A and 5B, the piezoelectric film is formed in two places or one place. By supplying a drive signal to the piezoelectric film of the arm having a piezoelectric film formed on one of the arms having the piezoelectric film formed on the main surface of the arm, out-of-plane vibration can be excited on the tuning fork. When the vibration of one tuning fork is excited, the details of the vibration mode and the like will be described later, but the tuning fork located on the opposite side of the cross also starts to vibrate via the base 4. In order to receive a signal from a detection vibration described later, the main of at least one arm of the tuning fork to which the arm to which the drive signal is supplied belongs and the two tuning forks located on the opposite side of the cross via the base 4 is used. Two piezoelectric films may be formed on the surface. For all the remaining arms, one piezoelectric film may be formed on the main surface of the arm.

  Here, the arms 2a, 2b, 2c, and 2d of the vibrator 1 include two parallel upper electrodes 11a, piezoelectric ceramics 12a, and lower electrodes 13a on the main surface of the arm 17 shown in FIG. And a piezoelectric film composed of an upper electrode 11b, a piezoelectric ceramic 12b, and a lower electrode 13b. The arms 2e, 2f, 2g, and 2h of the vibrator 1 have arms shown in FIG. An example in which a piezoelectric film composed of the upper electrode 14, the piezoelectric ceramic 15, and the lower electrode 16 is formed on the entire surface of the main surface 17 will be described. As described above, for example, when two piezoelectric films parallel to the arms 2a, 2b, 2c, and 2d are formed and when one piezoelectric film is formed on the entire surfaces of the arms 2e, 2f, 2g, and 2h. As other examples, the combination of the arm 2a, 2b, 2g, 2h and the arm 2c, 2d, 2e, 2f, or the arm 2a, 2e, 2c, 2g and the arm 2b, 2f, 2d, 2h In the case of the above, the combination of the case of the arms 2a and 2c and the case of the arms 2b, 2d, 2e, 2f, 2g and 2h, etc., or a combination in which these combinations are reversed may be used. The polarization direction is preferably the thickness direction P of the piezoelectric film, as shown in FIGS. 5 (a) and 5 (b).

  Each piezoelectric film is suitably formed before this step (that is, before being formed into a shape as an arm) when a silicon flat plate is subjected to a penetration process by a sandblast method or the like. The piezoelectric film is formed on the main surface of the arms 2a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h or on the back surface thereof, and the lower surface of platinum, gold, silver, copper, or the like using titanium, chromium, nickel, or the like in advance. After the electrodes 13a, 13b, and 16 are formed by sputtering, PZT (Pb · Zr · Ti) -based piezoelectric ceramics 12a, 12b, and 15 are formed thereon by sputtering to a thickness of about 0.1 to 2 μm. Upper electrodes 11a, 11b, and 14 such as platinum, gold, silver, and copper are formed by sputtering on a base using titanium, chromium, nickel, or the like. That is, the piezoelectric film has a three-layer structure. The piezoelectric ceramic film can be formed by sputtering, sol-gel method, hydrothermal synthesis method, aerosol deposition method, heat treatment after printing, or the like. The piezoelectric film may be formed on either the main surface or the back surface thereof. However, since the piezoelectric film can be formed at the same time in manufacturing, it is formed on one surface without changing for each arm. However, the number of manufacturing processes can be reduced.

  Further, the lower electrode and the upper electrode of the piezoelectric film pass through the arms 4a, 2b, 2c, 2d, 2e, 2f, 2g, and 2h, pass through the surface of the base 4 and the beams 3a, 3b, 3c, and 3d to the frame 5 Routed (not shown). The frame 5 is provided with pads (not shown) for connecting to the respective electrodes routed from the arms 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h.

  Next, the operation of the vibrator 1 according to the first embodiment will be described as a vibrating gyroscope. FIG. 6 is a circuit block diagram of the vibration gyro according to the embodiment of the present invention. As shown in FIG. 6, the circuit includes a self-excited oscillation circuit, a phase shift circuit, a current detection circuit, a differential circuit, a synchronous detection circuit, an addition circuit, an LPF (low-pass filter) circuit, and the like. Further, in order to reduce the size of the piezoelectric vibration gyro, the pads connected to the respective electrodes routed on the frame 5 of the vibrator 1 of the present invention are made of conductive adhesive such as epoxy or silicon. It is preferable that the vibrator 1 is supported and fixed to the substrate by directly electrically and mechanically connecting to a pad connected to each terminal of the circuit substrate. In addition to the connection using an adhesive, this connection method may be a connection using solder or wire bonding. Here, in the case of the vibrator 1 of the present invention, the vibration energy can be confined inside the frame body 5, so that the vibration energy is not transmitted to the frame body 5, and a silicon adhesive having a relatively high damping coefficient is contacted. Even if it is made, high mechanical quality factor Qm value can be maintained.

In the first embodiment, as shown in FIGS. 5A and 5B, the piezoelectric film is formed in two places or one place.
As connection of drive vibration mode described later,
The upper electrodes 14 of the arms 2e and 2h are connected to the terminal 51,
The upper electrodes 14 of the arms 2 f and 2 g are connected to the terminal 52.
The lower electrodes 16 of the arms 2e, 2f, 2g, and 2h are used as reference electrodes.

In addition, as a detection vibration mode connection described later,
The upper electrode 11a of the arm 2d is connected to the terminal 53,
The upper electrode 11b of the arm 2d is connected to the terminal 54,
The upper electrode 11a of the arm 2c is connected to the terminal 55,
The upper electrode 11b of the arm 2c is connected to the terminal 56,
The upper electrode 11a of the arm 2b is connected to the terminal 57,
The upper electrode 11b of the arm 2b is connected to the terminal 58,
The upper electrode 11a of the arm 2a is connected to the terminal 59,
The upper electrode 11b of the arm 2a is connected to the terminal 60,
The lower electrode 13a and the lower electrode 13b of each of the arms 2a, 2b, 2c, 2d are used as reference electrodes.

  FIG. 2 is a perspective view showing a drive vibration mode according to the embodiment of the present invention. The frequency of the drive signal is set near the resonance frequency of the drive vibration mode so that the operation of FIG. 2 showing the drive vibration mode of the vibrator 1 can be performed. Note that the magnitude of the vibration of the arm shown in FIG. 2 is exaggerated for easy understanding.

  The initial out-of-plane vibration caused by the signal generated when the circuit is turned on is sent from the terminal 51 connected to the upper electrode 14 of each of the arms 2e and 2h, so that the arms of the arms 2e and 2h. The pair starts with out-of-plane vibration. The circuit is configured so that a drive signal of about 0.2 to 3 Vpp (volts) is supplied from the self-excited oscillation circuit connected to the terminal 51. Further, an inverted signal having a phase difference of 180 ° from the signal supplied to the terminal 51 is supplied from the self-excited oscillation circuit to the terminal 52 via the phase shift circuit, and the vibrations of the arms 2f and 2g connected to the terminal 52 are caused. Occur.

  Since the arms 2e and 2f in the tuning fork have a 180 ° shift in the phase relationship between the expansion and contraction of the formed piezoelectric film, the direction perpendicular to the main surface of the vibrator 1 and opposite to each other as shown in FIG. It will vibrate at. Similarly, the arms 2g and 2h in the tuning fork also vibrate in a direction perpendicular to the main surface of the vibrator 1 and in mutually opposite phases. Since the arms 2e and 2f are connected by the connecting portion 6, as a result, the tuning fork (arms 2e and 2f) vibrates so as to be twisted with respect to the main surface of the vibrator 1. The same applies to other tuning forks (arms 2g and 2h), other tuning forks (arms 2a and 2b), and other tuning forks (arms 2c and 2d). If a signal having a resonance frequency in the drive vibration mode as shown in FIG. 2 is supplied, the vibrations of the tuning forks (arms 2e, 2f) and tuning forks (arms 2g, 2h) are located on the opposite side of the cross via the base 4. The tuning fork (arms 2a, 2b) and the tuning fork (arms 2e, 2f) connected to the base 4 and the tuning fork connected to the base 4 are transmitted to the tuning fork (arms 2a, 2b) and tuning fork (arms 2c, 2d). (Arms 2c, 2d) and the tuning fork (arms 2g, 2h) as a whole are twisted.

  Further, the vibration of the excited tuning fork (arms 2a, 2b) is transmitted again to the tuning fork (arms 2e, 2f) located on the opposite side of the cross via the base 4, so that the tuning fork (arm 2a) connected to the base 4 is also transmitted. , 2b) and the tuning fork (arms 2e and 2f) and the tuning fork (arms 2c and 2d) and the tuning fork (arms 2g and 2h) connected to the base 4 are further twisted. It is possible to greatly excite the vibration in the drive vibration mode as shown in FIG. At that time, a current signal having a resonance frequency of an isotopic amplitude due to this out-of-plane vibration is obtained from the upper electrode 11a of the arm 2a connected to the terminal 59 and the upper electrode 11b of the arm 2a connected to the terminal 60. As will be described later, when in-plane vibration occurs, current signals having the same phase and amplitude are obtained. These signals are respectively transmitted to terminals 59 and 60 in FIG. 6 and converted into voltage via a current detection circuit, and then the in-plane vibration component is removed by the addition circuit, and only the out-of-plane vibration component is output. At the same time as being connected to the self-excited oscillation circuit, it is used as a reference signal for synchronous detection via a phase shift circuit. As a result, stable self-excited oscillation is realized.

  FIG. 3 is a perspective view showing the detection vibration mode 1 according to the embodiment of the present invention. FIG. 4 is a perspective view showing the detection vibration mode 2 according to the embodiment of the present invention. 3 and 4, like FIG. 2, the magnitude of arm vibration is exaggerated for easy understanding.

  When the angular velocity about the axis parallel to the arms 2c, 2d, 2g, 2h is applied in a state where the drive vibration of the vibrator 1 is excited, that is, in the state where the four sets of tuning forks vibrate out of plane, That is, when the vibrator 1 rotates around the central axis, the vibration mode in FIG. 3 (hereinafter referred to as detection vibration mode 1) is newly excited, and the axis parallel to the arms 2a, 2b, 2e, 2f is centered. When an angular velocity as an axis is added, the vibration mode in FIG. 4 (hereinafter referred to as detection vibration mode 2) is newly excited. Both the detection vibration mode 1 and the detection vibration mode 2 are in-plane vibrations in the main surface of the vibrator 1, and vibrations in which the arm of the tuning fork opens in a V shape with respect to the tuning fork or contracts in an inverted V shape. It is. Since both the detection vibration mode 1 and the detection vibration mode 2 are actually mixed with vibrations in the drive vibration mode, it is necessary to separate the signals in order to know the magnitude of the angular velocity. When the detection vibration mode occurs, for example, in each of the upper electrodes 11a and 11b of the arms 2a and 2b and the arms 2c and 2d, one is extended and the other is contracted. Therefore, current signals having the same phase and amplitude are obtained from the two upper electrodes 11a and 11b. In addition, since a current signal having the same homologous amplitude is obtained from the upper electrodes 11a and 11b with respect to the drive vibration, if the difference between the signals from the upper electrodes 11a and 11b is taken, the drive vibration component having the same phase can be removed and detected. Only vibration mode 1 or detection vibration mode 2 can be extracted.

The current generated from the upper electrode 11a of the arm 2a connected to the terminal 59 and the upper electrode 11b of the arm 2b connected to the terminal 58, and the upper electrode 11b of the arm 2a connected to the terminal 60 and the terminal 57 were connected. The current generated from the upper electrode 11a of the arm 2b is
It is converted into voltage via the current detection circuit, the mutual voltage signal is differentially amplified by the differential circuit, and is synchronously detected by the synchronous detection circuit with the aforementioned reference signal to reduce noise, and rectified through the LPF circuit. Is done. As a result, an output B proportional to the angular velocity added about the axis parallel to the arms 2a, 2b, 2e, 2f is obtained. This output B is proportional to the angular velocity applied around the axis parallel to the arms 2a, 2b, 2e, 2f.

Similarly,
The current generated from the upper electrode 11a of the arm 2c connected to the terminal 55 and the upper electrode 11b of the arm 2d connected to the terminal 54, and the upper electrode 11b of the arm 2c connected to the terminal 56 and the terminal 53 The current generated from the upper electrode 11a of the arm 2d is
It is converted into voltage via the current detection circuit, the mutual voltage signal is differentially amplified by the differential circuit, and is synchronously detected by the synchronous detection circuit with the above-mentioned reference signal to reduce noise, and rectified through the LPF circuit. Is done. As a result, an output A proportional to the angular velocity added about the axis parallel to the arms 2c, 2d, 2g, 2h is obtained. This output A is proportional to the angular velocity applied around the axis parallel to the arms 2c, 2d, 2g, 2h. With the above configuration, the angular velocities of two axes parallel to the main surface of the vibrator 1 can be detected as the output A and the output B.

  Although the first embodiment has been described as the material of the vibrator so far, next, with respect to the second embodiment, an electrode is formed on the main surface of the arm using lithium niobate as a representative example of the material of the arm. Different points will be described with respect to the vibrator.

  FIG. 5 is a cross-sectional view of the arm. FIG. 5C is an explanatory diagram in the case where the electrode is divided into three parts on the main surface of the arm. FIG. It is explanatory drawing at the time of being divided and formed. In the second embodiment, out of the surface vibration can be excited on the tuning fork by supplying a drive signal to the electrode of the arm having two electrodes formed on the arm main surface. . When the vibration of one tuning fork is excited, the tuning fork located on the opposite side of the cross via the base 4 also starts to vibrate. In order to receive a signal from the detected vibration, the main surface of at least one arm of the tuning fork to which the drive signal is supplied and the two tuning forks located on the opposite side of the cross via the base portion 4 is provided. Three electrodes may be formed. For all remaining arms, two electrodes may be formed on the main surface of the arm.

  Here, the arms 2a, 2b, 2c, and 2d of the vibrator 1 are formed with three parallel electrodes 18, 19, and 20 on the main surface of the arm 23 shown in FIG. In the arm 2e, 2f, 2g, and 2h of the child 1, an example in which two parallel electrodes 21 and 22 are formed on the main surface of the arm 23 shown in FIG. The polarization direction can be varied by using a polarization inversion technique such as taking the cut angle of the crystal and applying temperature and voltage, but in the direction from the electrode 21 to the electrode 22 and the electrode 18. , 20 to the electrode 19 will be described as an example.

  When penetrating a lithium niobate flat plate by the sandblasting method, before this penetrating process, the main surfaces of the arms 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h are formed on the main surfaces of FIGS. As in d), electrodes 18, 19, and 20 such as platinum, gold, silver, and copper are formed in a thickness of about 0.1 to 2 [mu] m by sputtering or the like on a base using titanium, chromium, nickel, or the like in advance. .

The crystal orientation of lithium niobate is perpendicular to both the thickness direction of FIG. 5 (c) and the longitudinal direction of the arms 2a, 2b, 2c, and 2d, using the crystal orientation of the X axis 135 ° rotation Y. It is good to. As a result, regarding the arms 2e, 2f, 2g, and 2h, the direction of the X-axis 45 ° rotation Y is perpendicular to the thickness direction and the longitudinal direction of the arms 2e, 2f, 2g, and 2h. Incidentally, the coupling coefficient k ′ _{23 in} the direction of the X-axis 135 ° rotation Y is 0.5, which is very efficient, but the coupling coefficient k ′ _{23 in} the direction of the X-axis 45 ° rotation Y that is perpendicular thereto is also 0. 3 has sufficient efficiency to detect the angular velocity. Similarly, when other piezoelectric single crystals are used, it is preferable to use a crystal orientation in which an electromechanical coupling coefficient relating to displacement in a direction perpendicular to the applied electric field is relatively large.

  Although not particularly shown, the electrodes 18, 19, 20, 21, and 22 are routed to the frame 5 through the base 4 and the surfaces of the beams 3a, 3b, 3c, and 3d. Connected to the pad. The connection to the circuit board is the same as in the first embodiment.

  Next, the operation of the vibrator 1 according to the second embodiment described above as a vibrating gyroscope will be described. The circuit configuration is as shown in FIG.

In the second embodiment, as shown in FIGS. 5C and 5D, the electrodes are formed at three or two locations.
As drive vibration mode connection,
The electrode 21 of the arm 2e is connected to the terminal 51,
The electrode 21 of the arm 2f is connected to the terminal 52,
The electrode 21 of the arm 2g is connected to the terminal 52,
The electrode 21 of the arm 2h is connected to the terminal 51,
The electrodes 22 of the arms 2e, 2f, 2g, 2h are used as reference electrodes.

In addition, as connection of detection vibration mode,
The electrode 18 of the arm 2d is connected to the terminal 53,
The electrode 20 of the arm 2d is connected to the terminal 54,
The electrode 18 of the arm 2c is connected to the terminal 55,
The electrode 20 of the arm 2c is connected to the terminal 56,
The electrode 18 of the arm 2b is connected to the terminal 57,
The electrode 20 of the arm 2b is connected to the terminal 58,
The electrode 18 of the arm 2a is connected to the terminal 59,
The electrode 20 of the arm 2 a is connected to the terminal 60.
The electrodes 19 of the arms 2a, 2b, 2c, 2d are used as reference electrodes.

  The initial out-of-plane vibration caused by the signal generated when the circuit is turned on is sent from the terminal 21 connected to the electrode 21 of the arm 2e and the electrode 21 of the arm 2h, so that the arms 2e and 2h It begins with the arm set causing out-of-plane vibrations. The circuit is configured so that a drive signal of about 0.2 to 3 Vpp (volts) is supplied from the self-excited oscillation circuit connected to the terminal 51. Further, an inverted signal having a phase difference of 180 ° from the signal supplied to the terminal 51 is supplied from the self-excited oscillation circuit to the terminal 52 via the phase shift circuit, and the vibrations of the arms 2f and 2g connected to the terminal 52 are caused. Occur.

  The arms 2e and 2f in the tuning fork have a 180 ° shift in the phase relationship between the extension and contraction of the crystal between the electrodes, so that the arms 2e and 2f are in a direction perpendicular to the main surface of the vibrator 1 and opposite in phase as shown in FIG. It comes to vibrate. Similarly, the arms 2g and 2h in the tuning fork also vibrate in a direction perpendicular to the main surface of the vibrator 1 and in mutually opposite phases. Since the arms 2e and 2f are connected by the connecting portion 6, as a result, the tuning fork (arms 2e and 2f) vibrates so as to be twisted with respect to the main surface of the vibrator 1. The same applies to other tuning forks (arms 2g and 2h), other tuning forks (arms 2a and 2b), and other tuning forks (arms 2c and 2d). If a signal having a resonance frequency in the drive vibration mode as shown in FIG. 2 is supplied, the vibrations of the tuning forks (arms 2e, 2f) and tuning forks (arms 2g, 2h) are located on the opposite side of the cross via the base 4. The tuning fork (arms 2a, 2b) and the tuning fork (arms 2e, 2f) connected to the base 4 and the tuning fork connected to the base 4 are transmitted to the tuning fork (arms 2a, 2b) and tuning fork (arms 2c, 2d). (Arms 2c, 2d) and the tuning fork (arms 2g, 2h) as a whole are twisted.

  Further, the vibration of the excited tuning fork (arms 2a, 2b) is transmitted again to the tuning fork (arms 2e, 2f) located on the opposite side of the cross via the base 4, so that the tuning fork (arm 2a) connected to the base 4 is also transmitted. , 2b) and the tuning fork (arms 2e and 2f) and the tuning fork (arms 2c and 2d) and the tuning fork (arms 2g and 2h) connected to the base 4 are further twisted. It is possible to greatly excite the vibration in the drive vibration mode as shown in FIG. At that time, a current signal having a resonance frequency of the same homologous amplitude due to the out-of-plane vibration is obtained from the electrode 18 of the arm 2 a connected to the terminal 59 and the electrode 20 of the arm 2 a connected to the terminal 60. When in-plane vibration occurs, current signals having the same phase and amplitude are obtained. These signals are respectively transmitted to terminals 59 and 60 in FIG. 6 and converted into voltage via a current detection circuit, and then the in-plane vibration component is removed by the addition circuit, and only the out-of-plane vibration component is output. At the same time as being connected to the self-excited oscillation circuit, it is used as a reference signal for synchronous detection via a phase shift circuit. As a result, stable self-excited oscillation is realized.

  When the angular velocity about the axis parallel to the arms 2c, 2d, 2g, 2h is applied in a state where the drive vibration of the vibrator 1 is excited, that is, in the state where the four sets of tuning forks vibrate out of plane, That is, when the vibrator 1 rotates around the central axis, the detection vibration mode 1 in FIG. 3 is newly excited, and an angular velocity about the axis parallel to the arms 2a, 2b, 2e, 2f is applied. The detection vibration mode 2 in FIG. 4 is newly excited. Both the detection vibration mode 1 and the detection vibration mode 2 are in-plane vibrations in the main surface of the vibrator 1, and vibrations in which the tuning fork arm opens in a V shape with respect to the tuning fork or contracts in an inverted V shape. It is. Since both the detection vibration mode 1 and the detection vibration mode 2 are actually mixed with vibrations in the drive vibration mode, it is necessary to separate the signals in order to know the magnitude of the angular velocity. When the detection vibration mode occurs, for example, in the crystals between the electrodes 18 and 19 and the electrodes 19 and 20 of each of the arms 2a and 2b and the arms 2c and 2d, one is extended and the other is contracted. Therefore, a current signal having opposite phase and same amplitude is obtained from the electrode 18 and the electrode 20. Since a current signal having the same homologous amplitude is obtained from the electrode 18 and the electrode 20 for the drive vibration, the drive vibration component can be removed by taking the difference between the signals of the electrode 18 and the electrode 20, and the detection vibration mode 1 or Only the detected vibration mode 2 can be extracted.

The current generated from the electrode 18 of the arm 2a connected to the terminal 59 and the electrode 20 of the arm 2b connected to the terminal 58, and the current of the electrode 2 of the arm 2a connected to the terminal 60 and the arm 2b connected to the terminal 57 The current generated from the electrode 18 is
The voltage is converted into a voltage via a current detection circuit, the mutual voltage signals are differentially amplified by a differential circuit, and are synchronously detected by a synchronous detection circuit using the above-mentioned reference signal in order to reduce noise. A signal output is obtained. As a result, an output B proportional to the angular velocity added about the axis parallel to the arms 2a, 2b, 2e, 2f is obtained.

Similarly,
The current generated from the electrode 18 of the arm 2 c connected to the terminal 55 and the electrode 20 of the arm 2 d connected to the terminal 54, the electrode 20 of the arm 2 c connected to the terminal 56 and the arm 2 d connected to the terminal 53. The current generated from the electrode 18 is
The voltage is converted into a voltage via a current detection circuit, the mutual voltage signals are differentially amplified by a differential circuit, and are synchronously detected by a synchronous detection circuit using the above-mentioned reference signal in order to reduce noise. A signal output is obtained. As a result, an output A proportional to the angular velocity added about the axis parallel to the arms 2c, 2d, 2g, 2h is obtained.

  Using a flat plate made of lithium niobate having a thickness of 0.2 mm, the vibrator is provided with an arm having a width of 0.2 mm, a base portion located in the center, a connecting portion connecting the arm and the base portion, and a periphery of the base portion. The arranged frame body and the beam connecting the base and the frame body were integrally formed by performing a penetration process by a sandblast method. The frame body was 3 mm in length and width, and a gold electrode having chromium as a base was formed on the main surface of the arm in advance by sputtering, and then a desired electrode pattern was formed using a photolin technique.

  The impedance characteristics at the resonance of the manufactured vibrator were measured, and the mechanical quality factor Qm was obtained from the formula (1) based on the following formula.

  Qm = 2π × L × fr / R (1)

  The measurement results are shown in Table 1 below.

  In any of the drive vibration mode, the detection vibration mode 1, and the detection vibration mode 2, the Qm exceeded 10,000 in the air, and a high value was measured. This is because the vibrations of a plurality of arms cancel each other's moment force, and the vibration energy is confined to the inner side of the frame body 5 so that it is not transmitted to the frame body 5. This is evidence that a high Qm value can be maintained despite contact.

  As described above, a 3-4 mm square vibrator can be housed in a package as a vibration gyro, and a product size of 4-5 mm square can be reduced. At the same time, the conventional single-axis detection type vibration gyro In comparison, a highly sensitive piezoelectric vibration gyro with high sensitivity was obtained.

  The preferred embodiments of the piezoelectric vibration gyro according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

FIG. 6 is a top view illustrating a vibrator structure according to an embodiment of the invention. The perspective view showing the drive vibration mode which concerns on embodiment of this invention. The perspective view showing the detection vibration mode 1 which concerns on embodiment of this invention. The perspective view showing the detection vibration mode 2 which concerns on embodiment of this invention. Sectional drawing of an arm. Fig.5 (a) is explanatory drawing at the time of forming a piezoelectric film in two places on the arm main surface. FIG. 5B is an explanatory diagram in the case where the piezoelectric film is formed at one place on the arm main surface. FIG.5 (c) is explanatory drawing when an electrode is divided and formed in three places on the arm main surface. FIG.5 (d) is explanatory drawing in case an electrode is divided and formed in the arm main surface at two places. 1 is a circuit block diagram of a vibration gyro according to an embodiment of the present invention. The perspective view which shows the structure of the conventional vibrator | oscillator.

Explanation of symbols

1 Vibrators 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 64a, 64b, 64c, 64d, 17, 23 Arms 3a, 3b, 3c, 3d Beams 4, 63 Base 5 Frame body 6 Connecting portion 11a , 11b, 14 Upper electrodes 12a, 12b, 15 Piezoelectric ceramics 13a, 13b, 16 Lower electrodes 18, 19, 20, 21, 22 Electrodes 51, 52, 53, 54, 55, 56, 57, 58, 59, 60 Terminals 61, 62 Tuning fork 67 Installation electrode

Claims (3)

  A tuning fork formed by connecting two arms on one end side is connected to the base, and four sets of the tuning forks have vibrators arranged on a single plane and in a cross-radiating manner, and the two arms in the tuning fork Are bent and oscillated in a direction perpendicular to the single plane in opposite phases, and a pair of the tuning forks arranged opposite to each other in a cross-radiation state are arranged so that the arms are in opposite phases. A piezoelectric vibration gyro comprising drive means for bending vibration in a vertical direction with respect to each other and detection means for detecting vibrations in two directions perpendicular to the vibration obtained by the drive means.   In the vibrator, the four sets of the tuning forks are connected to the base by a connecting portion extending in a single plane and in a cross shape from the base, and the base, the connecting portion, and the tuning fork are integrally formed. The piezoelectric vibration gyro according to claim 1, wherein   The vibrator is connected to a frame disposed around the base by a beam extending from the base, and the frame and the beam are formed integrally with the base on the single plane. 3. The piezoelectric vibration gyro according to claim 1, wherein the base and the frame are connected to each other at least at two locations, so that the base is supported and fixed to the frame.

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