JP2008145325A - Vibration gyro - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost vibration gyro for detecting biaxial angular speeds by facilitating evaluation, mounting, or the like, having superior productivity and small output drift, obtaining stable output, and further having durability with respect to impacts from the outside. <P>SOLUTION: Additional mass parts 4a, 4b, 4c, 4d formed plarnarly are supported on beams 3a, 3b, 3c, 3d formed in the same plane, a connection part of the beams 3a, 3d is supported on one end of the beam 3e, and the connection part of the beams 3b, 3c is supported on one end of the beam 3f. Furthermore, a vibrator 1 connecting the other end of beams 3e, 3f is supported on a frame body 2 of an outer peripheral part via beams 3g, 3h, and the vibrator for a vibration gyro is made to function as an exciting part and a detection part is used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vibration gyro used as an angular velocity sensor, and more particularly to a vibration gyro suitable for a gyroscope used in a navigation system, an attitude control device of an automobile, a camera shake prevention device of a camera-integrated VTR, and the like.

  A vibrating gyroscope is an angular velocity sensor that utilizes a dynamic phenomenon in which when a rotational angular velocity is applied to an object having a velocity, a Coriolis force is generated in the object itself in a direction perpendicular to the velocity direction. The vibration gyro can excite mechanical vibration (hereinafter referred to as “driving mode”) by applying an electrical signal, and mechanical vibration in a direction orthogonal to the driving vibration (hereinafter, referred to as “driving mode”). A system in which the magnitude of “detection mode” can be electrically detected, and in a state where the drive mode is excited in advance, the line of intersection between the vibration surface in the drive mode and the vibration surface in the detection mode When a rotational angular velocity about a parallel axis is given, a detection mode is generated by the action of the aforementioned Coriolis force, and can be detected as an output voltage. Since the detected output voltage is proportional to the magnitude of the drive mode and the rotational angular velocity, the magnitude of the rotational angular velocity can be obtained from the magnitude of the output voltage when the magnitude of the drive mode is constant.

  In recent years, vibration gyros have been rapidly reduced in size and price in the same manner as other electronic components. In addition, for example, an anti-shake device or the like generally requires detection of a biaxial rotational angular velocity, and therefore, in most cases, two products that can detect a uniaxial rotational angular velocity are used. Under such circumstances, as one approach to reducing the size and cost of a vibrating gyroscope, studies have been made to enable detection of a biaxial rotational angular velocity within one product. In such a configuration, it is possible to share common parts such as a circuit and an external input / output terminal as compared with the case where a single-axis product is produced separately, thereby achieving a reduction in size and price. In addition, studies on mounting on mobile devices such as mobile phones have begun, and more shock resistance and higher stability are required than ever.

  FIG. 6 is a perspective view showing a conventional vibrating gyro element. In FIG. 6, the vibrator 111 is composed of a square plate-like vibrating body 112 made of a constant elastic metal material such as an elimba, and a piezoelectric element 113 arranged at the center of the main surface of the vibrating body 112. A plurality of divided electrodes 116 are arranged on the surface of the piezoelectric element 113. In the vibrating body 112, four vibrating bodies 111a, 111b, 111c, and 111d are formed by four notches 121, 122, 123, and 124 from the center of each side to the center point. The vibrator 111 vibrates in an axially symmetric mode with the node axis N1 and the node axis N2 as axes, and is supported and fixed near the intersection of the node axis N1 and the node axis N2. The angular velocity is detected by using a mode that vibrates in the plane of the vibrator 111, and two angular velocities perpendicular to each other in the plane can be detected. Such a vibration gyro is disclosed in Patent Document 1.

Japanese Patent No. 3206551

  However, in the above-described conventional vibratory gyro element, it is necessary to provide a support portion at the center of the vibrator so that the outer periphery of the vibrator can vibrate freely. There is a problem that the characteristics of the vibrator cannot be evaluated unless it is later.

  Also, it is difficult to mount the support at the center, and even when adjusting the frequency or balance of the vibrator, it is necessary to create a special jig and support and fix the vibrator only at the center to suspend it. Therefore, there is a problem that productivity is lowered.

  Furthermore, when supporting and fixing the vicinity of the node in the center, the area that can be supported and fixed is very small, and it is very difficult to support without disturbing the vibration. It is easily affected and the output becomes unstable. In addition, since the support is at one point, there is a problem that when an impact is applied from the outside, the impact force is concentrated on the one point and is easily broken.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art. Specifically, evaluation, mounting, etc. are easy, productivity is good, output drift is small, stable output is obtained, and robust against external impact, and biaxial angular velocity can be detected. It is an object to provide an inexpensive vibration gyro that is possible.

  The present invention employs the following means in order to solve the above problems. That is, according to the present invention, through holes are formed in a substantially rectangular flat plate, and a structure that supports an additional mass part that can vibrate with a beam is formed, so that it functions as an excitation part and a detection part, and is supported at its outer edge part. This is the gist.

  In the first aspect of the present invention, four additional mass portions 4a, 4b, 4c, and 4d formed in a plane are arranged in a clockwise direction, and four additional mass portions are formed in the same plane as the additional mass portion. One ends of the columnar beams 3a, 3b, 3c, and 3d are connected to the additional mass portions 4a, 4b, 4c, and 4d, respectively, and the other ends that are not connected to the additional mass portions of the beams 3a and 3d and the beams. The other ends of 3b and 3c that are not connected to the additional mass section are connected to each other, and one end of two columnar beams 3e and 3f formed in the same plane as the additional mass section are respectively connected to the beams 3a and 3d. And a beam having a structure in which the other ends of the beams 3e, 3f that are not connected to the beams 3a, 3b, 3c, and 3d are connected to each other. The two in-phase additional mass portions 4a and 4c and the two in-phase additional mass portions 4b and 4d vibrate in mutually opposite phases, and the additional mass portions 4a, 4b, 4c and 4d are A drive unit in a driving mode that vibrates in an out-of-plane direction perpendicular to the formed plane, and a first axis passing through a midpoint between the centroids of the additional mass portions 4a and 4b and a midpoint between the centroids of the additional mass portions 4c and 4d Detecting means for displacement due to Coriolis force generated by an angular velocity around an axis parallel to the first axis, passing through the midpoint between the centroids of the additional mass portions 4a and 4d and the midpoint between the centroids of the additional mass portions 4b and 4c. And a means for detecting displacement due to Coriolis force generated by an angular velocity around an axis parallel to a second axis orthogonal to the additional mass portions 4a, 4b, 4c, 4d and the beams 3a, 3b, 3c, 3d, 3e. 3f arrangement is the arrangement Having a substantially symmetric structure with respect to the second axis and an asymmetric structure with respect to the first axis, and for detecting angular velocity about an axis parallel to the first axis, two in-phase The first detection mode in which the beams 3a and 3c and the two in-phase beams 3b and 3d vibrate in opposite phases and bend and vibrate in the second axis direction is used, and is parallel to the second axis. For detecting the angular velocity around the axis, the two in-phase beams 3a and 3d and the two in-phase beams 3b and 3c vibrate in opposite phases and bend and vibrate in the second axial direction. 2 is a vibration gyro characterized by using two detection modes.

  In this drive mode, the additional mass portions 4a and 4c and the additional mass portions 4b and 4d vibrate in the out-of-plane direction perpendicular to the plane on which the additional mass portions are formed. This drive mode has very good symmetry and causes the beams 3e and 3f to twist, but the force is canceled at the connection between the beams 3e and 3f, and the connection becomes the node point of the drive mode.

  When an angular velocity around an axis parallel to the first axis is applied in the state where the drive mode is excited, a Coriolis force acts on the additional mass unit, and the additional mass units 4a and 4c and the additional mass units 4b and 4d. Oscillate in the second axial direction in mutually opposite phases. The first detection mode can be used to detect this vibration. In this first detection mode, the beams 3a and 3c and the beams 3b and 3d are in antiphase with each other and bend and vibrate in the second axial direction. The beams 3a and 3b and the beams 3c and 3d are vibration modes in which the tuning fork vibrates, respectively. Since it is a tuning fork vibration, the force caused by the vibrations of the beams 3a and 3d and the force caused by the vibrations of the beams 3b and 3c cancel each other at the connection portion between the beam 3e and the beam 3f, and the connection portion is a node in the first detection mode. It becomes a point.

  Similarly, when an angular velocity about an axis parallel to the second axis is applied with the drive mode excited, Coriolis force acts on the additional mass unit, and the additional mass units 4a and 4c, the additional mass unit 4b, 4d is opposite in phase and receives a force in the first axial direction. However, the beams 3a to 3d are connected to the additional mass portions 4a to 4d, respectively, and displacement in the first axial direction is limited. Therefore, each additional mass part rotates and vibrates in the second axial direction.

  Here, as described above, the vibrator has an asymmetric structure with respect to a plane passing through the first axis. Due to this asymmetry, the beams 3a and 3d and the beams 3b and 3c are bent and vibrated in the second axial direction in opposite phases. The second detection mode can be used to detect this vibration. In this second detection mode, the beams 3a and 3d and the beams 3b and 3c are in antiphase with each other and bend and vibrate in the second axial direction. The beams 3a and 3b and the beams 3c and 3d are vibration modes in which the tuning fork vibrates, respectively. Since it is a tuning fork vibration, the force caused by the vibrations of the beams 3a and 3d and the force caused by the vibrations of the beams 3b and 3c cancel each other at the connection portion between the beam 3e and the beam 3f, and the connection portion is a node in the second detection mode. It becomes a point.

  However, in order to use this second detection mode, it is indispensable to have an asymmetric structure with respect to a plane passing through the first axis. Without this asymmetry, the second detection mode described above cannot be used. If the structure is symmetrical with respect to the plane passing through the first axis, the additional mass portion does not vibrate in the second axial direction or all the additional mass portions vibrate in the second axial direction in phase. If it does not vibrate in the second axial direction, angular velocity cannot be detected. When all the additional mass parts vibrate in the second axial direction in the same phase, the beams 3a to 3d bend and vibrate in the second axial direction in the same phase as the additional mass part. In this case, since all the additional mass portions vibrate in the same direction, the position of the center of gravity of the vibrator is likely to change greatly. In the design of the vibration gyroscope, the design of the frequency of the vibrator is very important, but it is very difficult to design the structure with the connection point between the beam 3e and the beam 3f as the node point at the same time as the design of the frequency. is there.

  The invention according to claim 2 is the vibrating gyroscope according to claim 1, wherein one end of each of the two columnar beams 3g and 3h formed in the same plane as the additional mass portion is the beam 3e. It is connected to the connection part of the beam 3f and is arranged substantially symmetrically with respect to a plane passing through the second axis perpendicular to the plane on which the additional mass part is formed. The vibrating gyroscope is characterized in that a frame is formed in the same plane, the other ends of the beams 3g and 3h are connected to the frame, and the vibrator is supported via the frame.

  Since the connection portion between the beam 3e and the beam 3f is a node point in all of the drive mode and the first and second detection modes, the connection portion is connected to the transducer via the beams 3g and 3h. Even if it is connected to a frame disposed on the outer periphery, there is little propagation of vibration to the frame and the frame also becomes a node point. Therefore, the outer edge portion of the vibrator can be supported, good support characteristics can be obtained, output drift is reduced, mounting is easy, and productivity is increased. It is also possible to support the entire circumference of the outer edge of the vibrator, and even if an impact is applied, the impact force disperses, so it is strong against external impact, highly stable, and a highly reliable vibration gyro element. Can be provided. Further, in the vibrator manufacturing process, it is easy to inspect the characteristics of the vibratory gyro element even when a plurality of vibrators are simultaneously formed on the wafer and the outer edges are connected to each other. Inspection of vibration characteristics, frequency adjustment, and balance adjustment can be performed without cutting out the vibrators one by one. In addition, inspection and adjustment can be easily performed, the yield of the post-process can be improved, and the productivity becomes very high.

  Furthermore, according to the present invention, it is possible to detect biaxial angular velocities in the plane of the vibrator for a vibrating gyroscope. When used in a general digital still camera or the like, it can be mounted on the substrate as it is, so that mounting becomes easy. In addition, because it is possible to detect the rotational angular velocity of two axes with one vibrator, by sharing common parts such as circuits and external terminals, it is smaller and lower than using two single-axis products. Cost can be reduced.

  According to a third aspect of the present invention, in the vibration gyro according to the first or second aspect, the vibrator is integrally formed of a piezoelectric single crystal plate. The present invention has a planar structure, and can be easily formed by punching a rectangular piezoelectric single crystal plate, resulting in high productivity. Furthermore, by using a high-coupling material such as lithium niobate and performing drive mode excitation and detection mode detection, a vibration gyro element having a high S / N ratio can be provided.

  As described above, according to the present invention, evaluation, mounting, etc. are easy, productivity is good, output drift is small, stable output is obtained, and robust against external impacts. It is possible to provide an inexpensive vibration gyro capable of detecting the angular velocity.

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

  FIG. 3 is a top view showing a vibrator for a vibrating gyroscope according to an embodiment of the present invention. By applying holes to a quadrilateral lithium niobate piezoelectric single crystal plate having a size of 2.7 mm × 3.8 mm and a thickness of 0.25 mm, additional mass portions 4a to 4a are formed in the same plane of one piezoelectric single crystal plate. 4d is connected to the frame 2 by the beams 3a to 3h, and the vibrator 1 is formed. Beams 3a to 3d are connected to the additional mass portions 4a to 4d, respectively. However, since the beam is connected to the left end of each additional mass portion, in the present embodiment, the vibrator 1 is placed on the paper surface. On the other hand, it has a vertically symmetric and asymmetrical shape.

  Further, the detection electrode 6a and reference potential electrodes 7c and 7d are provided on the surface of the beam 3a, the detection electrode 6b and reference potential electrodes 7f and 7g are provided on the surface of the beam 3b, and the detection electrode 6c and reference potential are provided on the surface of the beam 3c. Electrodes 7f and 7h, detection electrode 6d and reference potential electrodes 7c and 7e on the surface of beam 3d, drive electrode 5a and reference potential electrode 7a on the surface of beam 3e, and drive electrode 5b on the surface of beam 3f, A reference potential electrode 7b was formed. Each electrode was formed of gold with chromium as a base.

  Here, the operation principle of the vibration gyro according to the present embodiment will be described. FIG. 1 is a diagram illustrating a vibration mode of the vibration gyro according to the present embodiment. That is, FIG. 1A, FIG. 1B, and FIG. 1C show a state before deformation when not operating, and are a perspective view, a front view, and a plan view, respectively, FIG. 1 (e) and 1 (f) show the X mode, which are a perspective view, a front view, and a plan view, respectively, and FIG. 1 (g), FIG. 1 (h), and FIG. 1 (j), FIG. 1 (k), and FIG. 1 (l) show the Z mode, respectively, and are a perspective view, a front view, and a plan view, respectively. is there.

  In the X mode shown in FIG. 1D to FIG. 1F, referring to FIG. 3 at the same time, two in-phase additional mass portions 4a and 4c and two in-phase additional mass portions 4b and 4d are provided. The additional mass part is vibrated in the X-axis direction in mutually opposite phases. This drive mode has very good symmetry and causes twisting of the beams 3e and 3f, but the force is canceled at the connection portions of the beams 3e and 3f, and as a result, the frame 2 connected to the beams 3g and 3h. There is little propagation of vibration to the frame 2, and the entire frame 2 becomes a node point.

  When an angular velocity about an axis parallel to the Y axis (first axis) is applied in the state where the X mode is excited, Coriolis force acts on the additional mass unit, and the additional mass units 4a and 4c and the additional mass unit 4b. And 4d are in opposite phases and vibrate in the Z-axis direction. For detection of this vibration, the Z mode shown in FIGS. 1 (j) to 1 (l) can be used. In this Z mode (first detection mode), the two in-phase beams 3a and 3c and the two in-phase beams 3b and 3d are in opposite phases and bend and vibrate in the Z-axis direction. The beams 3a and 3b and the beams 3c and 3d are vibration modes in which the tuning fork vibrates, respectively. Since it is a tuning fork vibration, the force caused by the vibration of the beam 3a and the beam 3d and the force caused by the vibration of the beam 3b and the beam 3c cancel each other at the connection portion between the beam 3e and the beam 3f. The propagation of vibration to the frame 2 thus made is small, and the entire frame 2 becomes a node point. At this time, if the vibration speed of the X mode is constant, the magnitude of the generated Z mode amplitude is proportional to the applied angular velocity, and if these vibrations are electrically extracted, the sensor functions as an angular velocity sensor. .

  Similarly, when an angular velocity about an axis parallel to the Z axis is applied in the state where the X mode is excited, Coriolis force acts on the additional mass unit, and the additional mass units 4a and 4c, the additional mass units 4b and 4d, Are opposite in phase and receive force in the Y-axis direction. However, the beams 3a to 3d are connected to the additional mass portions 4a to 4d, respectively, and displacement in the Y-axis direction is limited. Therefore, each additional mass part rotates and vibrates in the Z-axis direction.

  Here, as described above, the vibrator has a left-right asymmetric structure. Due to this asymmetry, the beams 3a and 3d and the beams 3b and 3c are bent and vibrated in the Z-axis direction in opposite phases. That is, by exciting the X mode, the additional mass parts 4a and 4c have a speed in the + X direction, and the additional mass parts 4b and 4d have a speed in the -X direction, the Z axis (second axis) When a Coriolis force is generated by applying an angular velocity around an axis parallel to the additional mass portions 4a and 4c, the additional mass portions 4a and 4c receive a force in the -Y direction, and the additional mass portions 4b and 4d receive a force in the + Y direction. However, in order to limit the displacement in the Y-axis direction due to the presence of the beams 3a to 3d, each additional mass portion tries to rotate around the connection portion with the beam. As a result, the additional mass portions 4a and 4d are displaced in the −Z direction, and the additional mass portions 4b and 4c are displaced in the + Z direction. Therefore, the beams 3a and 3d and the beams 3b and 3c are bent and vibrated in the Z-axis direction in opposite phases.

  The Y mode can be used to detect this vibration. In this Y mode (second detection mode), the two in-phase beams 3a and 3d and the two in-phase beams 3b and 3c are in antiphase with each other and bend and vibrate in the Z-axis direction. The beams 3a and 3b and the beams 3c and 3d are vibration modes in which the tuning fork vibrates, respectively. Since it is a tuning fork vibration, the force caused by the vibrations of the beams 3a and 3d and the force caused by the vibrations of the beams 3b and 3c cancel each other at the connection portion between the beam 3e and the beam 3f. As a result, the frame connected to the beams 3g and 3h The propagation of vibration to the body 2 is small, and the entire frame 2 becomes a node point. At this time, if the vibration velocity of the X mode is constant, the magnitude of the generated Y mode amplitude is proportional to the applied angular velocity, and functions as an angular velocity sensor if these vibrations are electrically extracted. .

  However, in order to use this Y mode, it is indispensable to have a left-right asymmetric structure. Without this asymmetry, the Y mode cannot be used. If the structure is symmetrical, the additional mass part does not vibrate in the Z-axis direction, or all the additional mass parts vibrate in the Z-axis direction in the same phase.

  The former is a case where the beam is connected to a position where the additional mass portion is divided into two equal parts in the Z-axis direction. Even when an angular velocity is applied around an axis parallel to the Z axis in the state where the X mode is excited and a force is applied in the Y axis direction, the additional mass portion does not rotate, so that it does not move in the Z axis direction.

  In the latter case, as in the case of the left-right asymmetry, when the angular velocity is applied around the axis parallel to the Z axis with the X mode excited, the additional mass units 4a and 4c and the additional mass units 4b and 4d are opposite to each other. Receives a force in the direction of the Y-axis. Further, in order to limit the displacement in the Y-axis direction due to the presence of the beams 3a to 3d, each additional mass portion tries to rotate around the connection portion with the beam. However, in the additional mass portions 4a and 4d and the additional mass portions 4b and 4c, the connection positions with the beams are reversed on the left and right. As a result, the additional mass portions 4a to 4d are displaced in phase in the Z-axis direction. Therefore, the beams 3a to 3d are flexibly oscillated in the Z-axis direction in the same phase. In this case, since all the additional mass portions vibrate in the same direction, the position of the center of gravity of the vibrator is likely to change greatly. In the design of the vibration gyroscope, the design of the frequency of the vibrator is very important, but it is very difficult to design the structure with the connection point between the beam 3e and the beam 3f as the node point at the same time as the design of the frequency. is there.

  An electrode disposed on the vibrator 1 is used for excitation and detection of the vibration. The X mode is excited by inputting an electric signal having a resonance frequency of the X mode to the drive electrodes 5a and 5b formed on the beams 3e and 3f shown in FIG. 3, and the detection electrodes 6a to 6d formed on the beams 3a to 3d are excited. By detecting the generated charges, vibrations in the Y mode and the Z mode can be detected.

  The arrangement of each electrode was determined by analyzing the distribution of charges generated on the surface of the beam in each vibration mode. FIG. 2 is a schematic diagram showing the charge distribution. 2A is a schematic diagram showing the charge distribution in the X mode, FIG. 2B is a schematic diagram showing the charge distribution in the Y mode, and FIG. 2C is the charge distribution in the Z mode. It is a schematic diagram shown. In FIG. 2, “+” and “−” indicate the polarities of the generated charges, and the ellipse indicates the range. This charge distribution varies depending on the selected material, and if it is an anisotropic material, it exhibits various distributions depending on the crystal orientation.

  FIG. 4 is a diagram showing the crystal orientation in the present embodiment. As shown in FIG. 4, the piezoelectric single crystal plate made of lithium niobate used in the present embodiment is made up of the Z ′ axis of the piezoelectric single crystal and the vibrator from the X plate cut to a thickness of 0.25 mm. It is cut out so that the angle formed with the Z-axis is 50 degrees, and the distribution of charges generated on the surface in each mode is as shown in FIG. Considering this charge distribution, as shown in FIG. 3, drive electrodes 5a and 5b for exciting X-mode vibration and reference potential electrodes 7a and 7b are arranged on the surfaces of the beams 3e and 3f, respectively.

  Similarly, Y-mode and Z-mode vibration detection electrodes 6a to 6d and reference potential electrodes 7c to 7h are disposed on the surfaces of the beams 3a to 3d. The detection electrodes 6a, 6b, 6c, and 6d generate Y-mode and Z-mode charges, but since the polarities of the generated charges are different from each other, the charge generated by the Y-mode and the Z-mode are generated by addition or a differential circuit. It is possible to distinguish from the generated charge.

  FIG. 5 is a block diagram illustrating a vibration gyro circuit according to an embodiment of the present invention. The driving means includes a current detection circuit 9e, a phase circuit 10a, and an AGC circuit 11 (auto gain control circuit), and the detection means includes current detection circuits 9a, 9b, 9c, and 9d, and addition circuits 14a and 14b. , 14c, 14d, differential circuits 13a, 13b, phase circuit 10b, synchronous detection circuits 15a, 15b, and filter circuits 16a, 16b, and a reference for setting the operation reference potential of each circuit A potential circuit 12 is included.

  In order to drive the drive electrodes 5a and 5b at the frequency of the X mode, the output of the AGC circuit 11 for keeping the drive state constant is connected to the drive electrodes 5a and 5b, and the current detection circuit 9e is connected to the reference potential electrode 7a and Connect to 7b. Due to the virtual ground effect of the current detection circuit 9e, the potentials of the reference potential electrodes 7a and 7b are fixed to the reference potential, and a drive voltage can be applied between the drive electrodes 5a and 5b and the reference potential electrodes 7a and 7b. It becomes.

  The drive current flowing in the drive electrodes 5a and 5b is detected by the current detection circuit 9e, adjusted in phase by the phase shift circuit 10a, adjusted in amplitude by the AGC circuit 11, and applied again to the drive electrodes 5a and 5b. This closed loop enables self-excited oscillation at the X-mode resonance frequency. At the same time, the output of the AGC circuit 11 passes through the phase shift circuit 10b and is input as a reference signal for the synchronous detection circuits 15a and 15b. When an angular velocity about the Z axis is applied in a state where the X mode is self-excited, vibration in the Y mode occurs. The electric charge shown in FIG. 2B is generated by the vibration of the Y mode.

  Accordingly, charges of opposite phases are generated in the detection electrodes 6a and 6d and the detection electrodes 6b and 6c. Current detection circuits 9a to 9d are connected to the detection electrodes 6a to 6d, respectively, and each signal is converted into a voltage. Current detection circuits 9a and 9d are connected to the adder circuit 14a, and current detection circuits 9b and 9c are connected to the adder circuit 14b to add together the signals of the in-phase components. Since the adder circuits 14a and 14b output signals of opposite phases, they can be amplified by the differential circuit 13a and taken out by the synchronous detection circuit 15a and the filter circuit 16a as electric signals proportional to the angular velocity around the Z axis. It becomes possible.

  Similarly, when an angular velocity about the Y axis is applied, vibration in the Z mode occurs. Charges as shown in FIG. 2C are generated by the vibration of the Z mode. Accordingly, charges of opposite phases are generated in the detection electrodes 6a and 6c and the detection electrodes 6b and 6d. Current detection circuits 9a and 9c are connected to the adder circuit 14c, and current detection circuits 9b and 9d are connected to the adder circuit 14d, and the signals of the in-phase components are added together. The adder circuits 14c and 14d output a signal having a reverse phase, so that they can be amplified by the differential circuit 13b and taken out by the synchronous detection circuit 15b and the filter circuit 16b as electric signals proportional to the angular velocity around the Y axis. It becomes possible.

  Further, the generated charge due to the Y mode is canceled by the adding circuits 14c and 14d, and the generated charge due to the Z mode is canceled by the adding circuits 14a and 14b. Therefore, the output of the filter circuit 16a is an output proportional to the angular velocity only around the Z axis, and the output of the filter circuit 16b is an output proportional to the rotational angular velocity only around the Y axis. That is, the vibration gyro according to the present embodiment functions as an angular velocity sensor capable of detecting the two-axis angular velocities of the Y axis and the Z axis.

  As described above, since the frame 2 can support the drive mode with less vibration, stable support characteristics can be obtained without inhibiting the drive mode. And a sensor output is stabilized and an output drift is also reduced. Further, since the entire circumference of the frame body 2 can be supported, even if an impact is applied to the vibrator 1, the force can be dispersed and a structure having high impact resistance is obtained. Furthermore, since it is possible to detect the rotational angular velocities of two orthogonal axes in the plane of the vibrator 1, common parts such as a drive circuit, a detection circuit, and an external terminal can be shared. In addition, since the frame body 2 can be supported and fixed, mounting is easy and productivity is increased.

  In the manufacturing process, even when a plurality of vibrating gyro elements are simultaneously formed on a piezoelectric single crystal wafer and the frame bodies 2 are joined together, it is easy to inspect the characteristics. In addition, vibration characteristics can be inspected, frequency adjustment, and balance adjustment can be performed without cutting out the vibrators one by one, which can be easily inspected and adjusted, and the yield of subsequent processes can be improved.

  In this embodiment, a lithium niobate piezoelectric single crystal plate is used. However, a useful vibrating gyroscope is constituted by lithium tantalate, quartz, langasite, zinc oxide, PZT, piezoelectric thin film, and the like. it can.

  This embodiment is a vibrating gyroscope that uses piezoelectricity, but some or all of the drive and detection methods are based on the use of electromagnetic induction, a transducer that uses electrostatic force, or displacement detection due to capacitance change between electrodes. May be replaced by

  As described above, according to the present invention, evaluation, mounting, etc. are easy, productivity is good, output drift is small, stable output is obtained, and robust against external impacts. It is possible to provide an inexpensive vibration gyro capable of detecting the angular velocity.

The figure which shows the vibration mode of the vibration gyro in one embodiment of this invention. 1 (a), 1 (b), and 1 (c) show a state before deformation when not operating, and are a perspective view, a front view, and a plan view, respectively, and FIG. 1 (d) and FIG. (E), FIG.1 (f) shows X mode, and are a perspective view, a front view, and a top view, respectively, FIG.1 (g), FIG.1 (h), FIG.1 (i) shows Y mode. FIG. 1 (j), FIG. 1 (k), and FIG. 1 (l) show a Z mode, respectively, and are a perspective view, a front view, and a plan view, respectively. The schematic diagram which shows distribution of an electric charge. 2A is a schematic diagram showing the charge distribution in the X mode, FIG. 2B is a schematic diagram showing the charge distribution in the Y mode, and FIG. 2C is the charge distribution in the Z mode. FIG. 1 is a top view showing a vibrator for a vibrating gyroscope according to an embodiment of the present invention. The figure which shows the crystal orientation in one embodiment of this invention. The block diagram which shows the circuit of the vibration gyro in one embodiment of this invention. The perspective view which shows the element for conventional vibration gyroscopes.

Explanation of symbols

1,111 Vibrator 2 Frames 3a to 3h Beams 4a to 4d Additional mass portions 5a and 5b Drive electrodes 6a to 6d Detection electrodes 7a to 7h Reference potential electrodes 9a to 9e Current detection circuits 10a and 10b Phase shift circuit 11 AGC circuit 12 Reference potential circuit 13a, 13b Differential circuit 14a, 14b, 14c, 14d Adder circuit 15a, 15b Synchronous detection circuit 16a, 16b Filter circuit 111a, 111b, 111c, 111d, 112 Vibrating body 113 Piezoelectric element 116 Electrodes 121, 122, 123 , 124 Notch N1, N2 Node axis

Claims (3)

Four additional mass portions 4a, 4b, 4c, 4d formed in a plane are arranged clockwise, and four columnar beams 3a, 3b, 3c, formed in the same plane as the additional mass portion, One end of 3d is connected to each of the additional mass portions 4a, 4b, 4c, 4d,
The other ends of the beams 3a and 3d not connected to the additional mass part and the other ends of the beams 3b and 3c not connected to the additional mass part are connected, respectively.
One end of two columnar beams 3e and 3f formed in the same plane as the additional mass part is connected to the connection part of the beams 3a and 3d and the connection part of the beams 3b and 3c, respectively.
A vibrating gyroscope using a vibrator having a structure in which the other ends of the beams 3e and 3f that are not connected to the beams 3a, 3b, 3c, and 3d are connected to each other;
A plane perpendicular to the plane in which the two in-phase additional mass portions 4a, 4c and the two in-phase additional mass portions 4b, 4d vibrate in opposite phases and form the additional mass portions 4a, 4b, 4c, 4d Drive means in a drive mode that vibrates outward;
Means for detecting displacement due to Coriolis force generated by an angular velocity about an axis parallel to the first axis passing through the midpoint between the centroids of the additional mass portions 4a and 4b and the midpoint between the centroids of the additional mass portions 4c and 4d;
Coriolis produced by an angular velocity around an axis parallel to a second axis perpendicular to the first axis passing through a midpoint between the centroids of the additional mass units 4a and 4d and a midpoint between the centroids of the additional mass units 4b and 4c. A means for detecting displacement by force,
The arrangement of the additional mass portions 4a, 4b, 4c, 4d and the beams 3a, 3b, 3c, 3d, 3e, 3f has a substantially symmetric structure with respect to the second axis in the arrangement plane, and the first Having an asymmetric structure with respect to the axis of
For detection of angular velocity around an axis parallel to the first axis, the two in-phase beams 3a and 3c and the two in-phase beams 3b and 3d vibrate in opposite phases and the second Using the first detection mode that flexes and vibrates in the axial direction,
For detection of angular velocity around an axis parallel to the second axis, the two in-phase beams 3a and 3d and the two in-phase beams 3b and 3c vibrate in mutually opposite phases and the second A vibration gyro using a second detection mode in which bending vibration is generated in an axial direction. The vibrating gyroscope according to claim 1,
One end of each of the two columnar beams 3g and 3h formed in the same plane as the additional mass portion is connected to the connection portion between the beam 3e and the beam 3f, and is perpendicular to the plane on which the additional mass portion is formed. Arranged substantially symmetrically with respect to a plane passing through the second axis,
A frame body is formed on the outer peripheral portion of the vibrator in substantially the same plane as the additional mass section, and the other ends of the beams 3g and 3h are connected to the frame body, and the vibrator is passed through the frame body. A vibrating gyroscope characterized by being supported. The vibrating gyroscope according to claim 1 or 2,
A vibratory gyro, wherein the vibrator is integrally formed of a piezoelectric single crystal plate.

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