JP4911690B2 - Vibrating gyro vibrator - Google Patents

Description

  The present invention relates to a gyroscope for detecting an angular velocity, and more particularly to a vibrator for a vibration gyro suitable for an automobile navigation system, attitude control, or a camera shake correction device for a camera-integrated VTR.

  A gyroscope is an angular velocity sensor that utilizes a dynamic phenomenon that when an angular velocity is applied to an object having velocity, a Coriolis force is generated in the object itself in a direction perpendicular to the velocity direction. The gyroscope is an electrical signal that excites mechanical vibrations as drive vibrations, and mechanical vibrations having a component orthogonal to the drive vibrations caused by the Coriolis force as detection vibrations. It is a sensor to detect at.

  When the gyroscope gives an angular velocity of rotation around an axis parallel to the intersection line of the drive vibration surface and the detection vibration surface with the drive vibration excited in advance, the detection vibration is generated by the Coriolis force. , Detected as an output voltage. Since the detected output voltage is proportional to the magnitude and angular velocity of the drive vibration, the magnitude of the angular speed can be obtained from the magnitude of the output voltage in a state where the magnitude of the drive vibration is constant. Among gyroscopes, a gyroscope that uses a vibrator such as a piezoelectric element having a piezoelectric effect is called a vibrating gyroscope.

  Since the vibration gyro is small and can be manufactured at low cost, it is particularly used in a camera shake correction device for a camera. A camera shake correction device generally requires two-axis angular velocity detection in the pitch direction and yaw direction applied to the camera body. Therefore, two uniaxial detection type vibration gyros are used to detect biaxial angular velocity. However, when two uniaxial detection type vibration gyros are used, there is a problem that interference noise occurs.

  When the resonance frequencies of the vibrators used for the two vibratory gyros are close to each other, interference noise having a frequency component that is the difference between the resonance frequencies of the two vibrators is generated in the output signal, and the vibration gyroscope S / N ratio is deteriorated. To solve this problem, measures are taken such as making the resonance frequency of the vibrators sufficiently different by making the shapes of the vibrators different from each other and attenuating interference noise with a low-pass filter.

  In order to meet the needs for downsizing and cost reduction, a two-axis detection type vibration gyro capable of detecting a two-axis angular velocity with one vibration gyro has been proposed. However, this two-axis detection type gyro also has the above-mentioned problem of interference noise and requires countermeasures.

  FIG. 1 is a cross-sectional view of a vibrating gyroscope according to Conventional Example 1. A conventional vibration gyro 80 shown in FIG. 1 has two vibration gyro vibrators 81 and 82 supported in a cantilever shape by a base 84 provided inside a housing 83. The vibrators 81 and 82 for the vibration gyro are each driven to detect the biaxial angular velocity. The two vibratory gyro vibrators 81 and 82 are processed so as to have the same resonance frequency, and are driven by an AC voltage having the same frequency. Since the frequency of the drive vibration of the two vibratory gyro vibrators 81 and 82 is the same, the generation of interference noise is reduced. Such a vibration gyro is disclosed in Patent Document 1.

  FIG. 2 is a perspective view of a vibrator for a vibrating gyroscope according to a second conventional example. The conventional vibratory gyro vibrator 90 shown in FIG. 2 has a vibrator 91 integrated with a piezoelectric body 92 and an electrode 93 and has a common driving vibration mode, so that it is not affected by machining accuracy and temperature characteristics, and can be driven. The resonance frequency of the vibration mode of the vibration is made to coincide so that the detection sensitivity of the two axes to be detected does not vary, and one drive circuit is used. Such a vibrator for a vibratory gyro is disclosed in Patent Document 2.

  FIG. 3 is a cross-sectional view of a vibrator for a vibrating gyroscope according to Conventional Example 3. A conventional vibratory gyroscope 70 shown in FIG. 3 is provided with a drive electrode 73, detection electrodes 75, 77, and reference electrodes 74, 76, 78 on the outer periphery of a columnar vibrator 71. This vibratory gyroscope 70 inputs a drive signal to the drive electrode 73 to excite the drive vibration in the fx direction, and detects the vibration detected in the fy direction orthogonal to the drive vibration by the detection electrodes 75 and 77. A child. By flattening the side surface 72 on which the drive electrode 73 is formed, symmetry between the drive electrode 73, the detection electrodes 75 and 77, and the reference electrodes 74, 76, and 78 is improved, and detection accuracy is improved. This is a vibrator for a vibration gyro in which a vibration direction is fixed in a desired direction by giving a difference sufficiently larger than an error due to processing in a driving vibration direction and a detection vibration direction. Such a vibrator for a vibratory gyro is disclosed in Patent Document 3.

Japanese Patent Laid-Open No. 7-190783 Japanese Patent No. 3206551 Japanese Patent No. 3511142

  In the vibration gyro of the conventional example 1 shown in FIG. 1, in order to make the detection sensitivities of the two axes to be detected equal, depending on the vibration sharpness Qm value of the vibrators, two vibrators 81 for vibration gyro, It is necessary to make the shape and size of 82 equal to match the resonance frequency. Processing such as frequency adjustment takes time and effort, and there is a problem that it lacks mass productivity.

  The vibrator 2 for vibratory gyro shown in FIG. 2 has a configuration in which the drive vibration mode at the resonance frequency and the two detection vibration modes are matched with each other, but the direction of the detection vibration mode is the machining accuracy. Therefore, when the angular velocity is applied to one axis, it is not desired to detect vibration, and the other detected vibration is also excited. As a result, the sensitivity of the other axis is high and the accuracy is poor. There is a problem of becoming.

  This problem will be described using a simple model. FIG. 4 is an explanatory diagram of the vibration mode of the vibrator for the vibration gyro according to the conventional example 2. 4A is an explanatory diagram in the X-axis direction, FIG. 4B is an explanatory diagram in the Z-axis direction, and FIG. 4C is an explanatory diagram in the Y-axis direction. The vibrator for a vibrating gyroscope of Conventional Example 2 is represented by a cube 31 as a simple model. The coordinate 11 indicates the coordinate axes with respect to the cube 31 by X, Y, and Z.

  In FIG. 4A, the direction of the drive vibration mode in the X-axis direction is indicated by a solid line arrow. This vibration mode has a resonance frequency determined by the thickness of the cube 31 in the X-axis direction. In FIG. 4B, the detected vibration mode in the Z-axis direction orthogonal to the vibration mode shown in FIG. This vibration mode has a resonance frequency determined by the thickness of the cube 31 in the Z-axis direction. Further, in FIG. 4C, the detected vibration mode in the Y-axis direction orthogonal to both the vibration modes shown in FIGS. 4A and 4B is indicated by a solid line arrow. This vibration mode has a resonance frequency determined by the thickness of the cube 31 in the Y-axis direction.

  The biaxial detection type vibratory gyro vibrator handles these three vibration modes. Here, FIG. 4A is a drive vibration mode. The detected vibration mode when the angular velocity around the Y axis is applied is shown in FIG. 4B, and the detected vibration mode when the angular velocity around the Z axis is applied is shown in FIG. 4C. Since the vibrator for vibrating gyroscope of Conventional Example 2 is represented by a cube 31 as a simple model, all the resonance frequencies are equal. However, when the fabrication is actually attempted, a complete cube cannot be obtained due to errors such as processing accuracy. The three vibration modes cannot be vibrated in the desired directions because the directions are slightly shifted as indicated by the dotted arrows.

  In the state where the drive vibration mode is shifted in the direction indicated by the dotted arrow in this way, vibration is generated in the Z-axis direction and the Y-axis direction even though no angular velocity is applied, resulting in a null voltage. Detected. Also, if the detected vibration mode in the Z-axis direction is deviated and the detected vibration mode in the Y-axis direction is included at the same time, it will cause the occurrence of other-axis sensitivity and the accuracy will deteriorate. That is the problem.

  In the vibrator for gyroscope of the conventional example 3 shown in FIG. 3, the side surface 72 on which the drive electrode 73 is formed is flattened to improve the symmetry of the vibration direction and to fix the vibration direction in a desired direction. However, the problem of the vibrator for the vibration gyro will be further described using a simple model.

  FIG. 5 is an explanatory diagram of the vibration mode of the vibrator for a vibration gyro according to the conventional example 3. 5A is an explanatory diagram in the X-axis direction, FIG. 5B is an explanatory diagram in the Z-axis direction, and FIG. 5C is an explanatory diagram in the Y-axis direction. The vibrator for a vibrating gyroscope of Conventional Example 3 is represented by a rectangular parallelepiped 41 as a simple model. The coordinate 11 indicates the coordinate axes with respect to the rectangular parallelepiped 41 by X, Y, and Z. Since the rectangular parallelepiped 41 is expressed as a model whose thickness in the X-axis direction is thicker than the thickness in other directions, compared with the cubic model in FIG. 4, the resonance frequency of the driving vibration mode in the X-axis direction, There is a difference between the resonance frequency of the detected vibration mode in the Y-axis direction or the Z-axis direction.

  Therefore, although the detection sensitivity is low, a slight machining error does not cause a shift in the direction of the drive vibration indicated by the solid line arrow in FIG. Therefore, when no angular velocity is applied, there is no vibration in the Z-axis direction and the Y-axis direction, that is, no null voltage is generated. However, since the thicknesses in the Z-axis direction and the Y-axis direction are equal and the resonance frequencies are almost equal, it is difficult to vibrate the detected vibration in a desired direction even with a minute processing error. Therefore, as indicated by the dotted arrows in FIG. 5B and FIG. 5C, there is a problem in that the detected vibration mode is deviated in direction and the other-axis sensitivity is generated.

  In order to solve the above problems, it is conceivable to make a difference in the frequency in the vibration mode in each of the X-axis, Y-axis, and Z-axis directions. FIG. 6 is an explanatory diagram of the vibration mode of the vibrator for a vibration gyro according to the conventional type. 6A is an explanatory diagram in the X-axis direction, FIG. 6B is an explanatory diagram in the Z-axis direction, and FIG. 6C is an explanatory diagram in the Y-axis direction. In FIG. 6, the rectangular parallelepiped 51 is modeled by reducing the thickness in the Y-axis direction of the rectangular parallelepiped used as the simplified model of the vibrator for gyroscope of the conventional example 3 shown in FIG.

  When the resonance frequency in the Y-axis direction is further lowered, the frequency in the vibration modes in the X-axis, Y-axis, and Z-axis directions can be made different, and all vibration modes can be used even if minute machining errors occur. Can be fixed in a desired direction. Therefore, a gyro that does not generate the null voltage and the other-axis sensitivity as described above can be obtained. However, compared with the resonance frequency of the detection vibration mode in the Z-axis direction, it is difficult to obtain sufficient sensitivity because the resonance frequency of the drive vibration mode and the resonance frequency of the detection vibration mode in the Y-axis direction are too far apart. There is a problem.

  Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art. Specifically, the present invention provides a small and low-priced vibratory gyro vibrator for a two-axis detection type that can generate a null voltage and other axis sensitivities, has little sensitivity variation, and can be configured with a single drive circuit. This is the issue.

  The present invention employs the following means in order to solve the above problems. That is, according to the present invention, in a vibrator for a vibration gyro that detects angular velocities in two axial directions, the resonance frequencies of one drive vibration and two detection vibrations are different from each other. The gist is to set the resonance frequency in the middle.

According to the present invention, a plate-like body, a frame body, a beam portion having both ends supported by the frame body, one or more first arm portions formed to intersect the beam portion, One or more second arm parts formed extending from the first arm part, a third arm part supported by the second arm part, and supported by the third arm part The frame body, the beam portion, the first arm portion, the second arm portion, the third arm portion, and the additional mass portion are flush with each other. A vibrator for a vibrating gyroscope that is arranged in a line and is arranged so that each of the additional mass portions is line-symmetric with respect to each of the beam portion and the first arm portion, and detects angular velocities in two axial directions. The first vibration mode serving as drive vibration and the second vibration mode serving as detection vibration And the third vibration mode, the resonance frequency of the second vibration mode is lower than the resonance frequency of the third vibration mode, and the resonance frequency of the first vibration mode is equal to that of the second vibration mode. A vibrator for a vibration gyro characterized by being higher than the resonance frequency and lower than the resonance frequency of the third vibration mode is obtained.

  The vibrator for a vibration gyro according to the present invention has a first vibration mode, a second vibration mode, and a third vibration mode, wherein the first vibration mode is a drive vibration, and the second vibration mode and the second vibration mode are the same. 3 vibration mode is detected vibration. At this time, when the resonance frequency of the first vibration mode is expressed as fx, the resonance frequency of the second vibration mode is expressed as fy, and the resonance frequency of the third vibration mode is expressed as fz, the relation of fy <fx <fz is established. Like that. That is, by setting the resonance frequency of the first vibration mode, which is the drive vibration, to a resonance frequency between the resonance frequency of the second vibration mode and the resonance frequency of the third vibration mode, which are the two detection vibrations, A vibrator for a vibration gyro with little occurrence of null voltage or other axis sensitivity and little variation in sensitivity can be obtained. In the second vibration mode and the third vibration mode, “second” and “third” are used to distinguish two detection vibration modes, and “second”. May be read as “third” and “third” may be read as “second”.

  According to the invention, there is obtained a vibrator for a vibration gyro characterized in that the first vibration mode, the second vibration mode, and the third vibration mode have vibration directions orthogonal to each other. . In the present invention, by detecting the first vibration mode, the second vibration mode, and the third vibration mode to be orthogonal to each other, the detection accuracy of two orthogonal rotational angular velocities is improved.

  Here, the vibration mode of the vibrator for piezoelectric vibration gyro according to the present invention will be described with reference to the drawings.

  FIG. 7 is an explanatory diagram of a vibration mode of the vibrator for piezoelectric vibration gyro according to the present invention. 7A is an explanatory diagram in the X-axis direction, FIG. 7B is an explanatory diagram in the Z-axis direction, and FIG. 7C is an explanatory diagram in the Y-axis direction. FIG. 7 shows a piezoelectric vibration gyro vibrator according to the present invention modeled as a rectangular parallelepiped 61. The coordinate 11 indicates the coordinate axes with respect to the rectangular parallelepiped 61 by X, Y, and Z. The rectangular parallelepiped 61 has a relationship of thickness in the Y direction> thickness in the X direction> thickness in the Z direction. If the vibration in the X direction is the drive vibration, each vibration in the Y-axis direction and the Z-axis direction is the detection vibration, the resonance frequency of the drive vibration is fx, and the resonance frequencies of the detection vibration are fy and fz, respectively, fy <fx <fz Since the three resonance frequencies are different from each other, the directions of the three vibration modes can be fixed in a desired direction without being affected by a machining error. That is, null voltage and other-axis sensitivity can be suppressed.

  In addition, the relationship of fy <fx <fz shown in FIG. 7 indicates that the resonance frequency of the drive vibration and the resonance frequency of the detection vibration mode in the Y direction are different from the resonance frequency of the detection vibration in the Z direction shown in FIG. Unlike the relationship of passing too much, | fx−fy | = | fx−fz | can be used to equalize the resonance frequency difference between the drive vibration and the two detected vibrations. Each sensitivity variation can be reduced. Furthermore, since the drive vibration mode in the two-axis detection is the same, it is possible to operate with one drive circuit.

Further, according to the present invention, the frame body, the beam portion, the first arm portion, the second arm portion, the third arm portion, and the additional mass portion are arranged in the same plane, The beam portion, the first arm portion, the second arm portion, the third arm portion, and the additional mass portion are disposed inside the frame body, and the beam portion is a central portion of the frame body. It will be Mashimashi equidistant extending from said first arm portion, Mashimashi center as perpendicular and equidistant extension of the beam part, prior to pressurizing parts by weight with SL are arranged four or more, the first In the vibration mode, the adjacent additional mass portions vibrate outwardly in the same plane with opposite phases, and the second vibration mode and the third vibration mode are both the first vibration mode and the first vibration mode. Vibration gai characterized in that vibration directions are orthogonal and vibration directions are orthogonal to each other Use the vibrator is obtained.

  Further, according to the present invention, the third arm portion is a shape bent in a U shape in the middle of the connecting portion with the additional mass portion and the connecting portion with the second arm portion. Thus, a vibrator for a vibrating gyroscope can be obtained. In the present invention, since an appropriate frequency can be designed in each mode of the vibrator, sensitivity is improved.

  Further, according to the present invention, electrodes are formed on both surfaces of the plate-like body, a drive electrode portion is formed on one surface, and a detection electrode portion is formed on the other surface. A vibrator for a vibration gyro is obtained.

According to the present invention, the first vibration mode is configured such that the third arm portion extends in a strip shape along a portion of the third arm portion that is formed substantially parallel to the first arm portion. Excited by at least two electrodes formed on the arm portion of
The second vibration mode is substantially parallel to the first arm portion on the surface of the third arm portion opposite to the surface on which the electrode for exciting the first vibration mode is formed. Detected by at least two electrodes formed to include a strip-shaped electrode portion,
The third vibration mode is along the first arm portion on the surface of the first arm portion opposite to the surface on which the electrode for exciting the first vibration mode is formed. A vibrator for a vibrating gyroscope characterized in that it is detected by at least two electrodes formed so as to extend in a band shape.

  The vibrator for a vibrating gyroscope according to the present invention comprises a plate-like body, for example, a through hole is provided in a flat plate, and a frame, a beam portion, a first arm portion, and a second arm are provided on the same plane of the flat plate. Part, a third arm part, and an additional mass part. The frame supports both ends of the beam portion, and the beam portion supports the first arm at the center of the beam portion. The first arm unit supports the second arm unit at the end of the first arm unit, and the second arm unit supports one end of the third arm unit at the end of the second arm unit. The other end of the third arm unit is configured to support the additional mass unit so that the additional mass unit can vibrate.

  The frame is preferably circular, oval, or rectangular, but the outer shape is not particularly limited. The beam part is preferably in the form of a straight belt, but is not limited to a straight line as long as it has symmetry, and may have a plurality of symmetry with respect to the center point without passing through the center point. The first arm portion preferably has a straight belt shape and is preferably orthogonal to the beam portion, but is not limited to a straight line as long as it has symmetry.

  Further, the first arm portion may be a plurality having the symmetry with respect to the center point without passing through the center point. It is desirable that the second arm portion has a straight belt shape and is orthogonal to the beam portion. However, the second arm portion is not limited to being linear or orthogonal as long as it has symmetry. Further, the second arm portion is preferably an end portion of the first arm portion, but is not limited to the end portion as long as it has a symmetry other than the central portion. The additional mass portion is preferably circular, elliptical, or rectangular, but is not limited thereto. The above structure can be formed by making a groove penetrating a single plate.

  In addition, by inputting an electric signal to the electric electrode input drive electrode unit included in the first arm unit, the additional mass unit is vibrated, and the vibration detection detection electrode unit included in the second arm unit By detecting the output signal, the rotational angular velocity of the two axes can be detected.

  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.

  Further, the additional mass portion arranged with good symmetry vibrates in a drive mode with good symmetry. Therefore, the vibration in the drive mode is difficult to leak to the outside, and the vibration and displacement in the drive mode existing in the frame body are small.

  The vibrator for a vibrating gyroscope of the present invention has a planar structure, and can be easily formed by increasing the productivity by punching a square piezoelectric plate or piezoelectric single crystal plate. Furthermore, a vibrator for a vibration gyro having a high S / N ratio can be provided by using a high binding material such as lithium niobate. The plate-like body may not be a single material but may have a laminated structure in which the same or different materials are stacked in the thickness direction.

  The vibrator for a vibrating gyroscope according to the present invention has a plate shape made of a piezoelectric material, and includes a frame, a beam portion supported at both ends of the frame, and one or more formed to intersect the beam portion. One or more second arm portions formed extending from the arm portion, one or more third arm portions formed extending from the second arm portion, and the third arm portion And an electrode for driving and detecting is formed on the surface of the structure.

  In the present invention, the adjacent additional mass portions are in the first vibration mode in which the additional mass portions vibrate in the outward direction of the same plane in mutually opposite phases, the first vibration mode and the vibration direction are orthogonal, and the vibration directions are orthogonal to each other. The vibration to be performed is defined as the second vibration mode and the third vibration mode. Furthermore, when the resonance frequency of the first vibration mode is expressed as fx, the resonance frequency of the second vibration mode is expressed as fy, and the resonance frequency of the third vibration mode is expressed as fz, fy <fx <fz or fy> fx> The relationship is fz. The resonance frequency can be adjusted by changing the length of the third arm portion.

  As described above, according to the present invention, by setting the resonance frequency of the vibration mode serving as the drive vibration to the resonance frequency between the second vibration mode and the third vibration mode, which are the two detection vibrations, It is possible to provide a small and low-priced vibrator for a vibratory gyroscope of a two-axis detection type that can be configured with a single drive circuit with little generation of voltage and other-axis sensitivity and little variation in sensitivity.

  The vibrator for a vibration gyro according to the present invention has a first vibration mode, a second vibration mode, and a third vibration mode, wherein the first vibration mode is a drive vibration, and the second vibration mode and the second vibration mode are the same. 3 vibration mode is detected vibration. Further, when the resonance frequency of the first vibration mode is expressed as fx, the resonance frequency of the second vibration mode is expressed as fy, and the resonance frequency of the third vibration mode is expressed as fz, fy <fx <fz or fy> fx. > Fz relationship. Furthermore, it is desirable that the vibration directions of the first vibration mode, the second vibration mode, and the third vibration mode are orthogonal to each other.

  Hereinafter, embodiments of a vibrator for a detection type vibration gyro according to the present invention will be described in detail with reference to the drawings.

  FIG. 8 is a plan view of the vibrator 10 for vibratory gyroscope according to the embodiment of the present invention. By forming a through-groove 2 having a width of about 0.2 mm in a flat plate 1 having a rectangular shape of 2.8 mm in length and 4.3 mm in width and made of a piezoelectric single crystal of lithium niobate and having a thickness of 0.2 mm, In the same plane of the single piezoelectric single crystal plate, the frame 3, the beam part 4 in the central part longitudinal direction, the first arm part 5 in the lateral direction in the central part, and two first parts at both ends of the first arm part 5. A total of four additional mass portions 7a, 7b, 7c, 7d were formed on both ends of the second arm portion 6a, 6b and the second arm portion via the third arm portions 12a, 12b, 12c, 12d, respectively.

The third arm portion was formed in a U shape between the second arm portion and the additional mass portion. In this example,
(1) The third arm portion is formed by extending a substantially parallel arm from the second arm end portion to the first arm portion,
(2) An arm substantially parallel to the beam portion 4 extends from the end thereof, and
(3) Further, an arm substantially parallel to the first arm portion is formed to extend,
(4) An additional mass portion is formed at the end portion.
The third arm part is not limited to the shape, and the third arm part may extend at an angle with respect to the first arm and the beam part 4; You may provide R in a corner part.

  In this embodiment, the shape is symmetrical with respect to the center line 8 of the beam portion 4, and the shape is also symmetrical with respect to the center line 9 of the first arm portion 5. Drive electrode portions 13a and 13b and reference potential electrode portions 14a and 14b are formed on the surface of the first arm portion 5, and detection electrode portions 15a, 15b and 15c are formed on the surface of the second arm portions 6a and 6b. 15d and reference potential electrode portions 14c, 14d, 14e, 14f, 14g, and 14h. In each of the electrode portions, electrodes were formed of gold with chromium as a base.

  Here, the operation principle of the vibration gyro element according to the embodiment described above will be described. FIG. 9 is an explanatory diagram of the vibration mode of the vibrator for the vibration gyro according to the present embodiment. 9A is an explanatory diagram in the X-axis direction, FIG. 9B is an explanatory diagram in the Z-axis direction, and FIG. 9C is an explanatory diagram in the Y-axis direction.

  9A, the additional mass portions 7a, 7b, 7c, and 7d vibrate in the X-axis direction. In that case, the additional mass parts adjacent to each other vibrate in opposite phases. 9B, the additional mass portions 7a, 7b, 7c, and 7d vibrate in the Z-axis direction within the same plane. At this time, the additional mass parts adjacent to each other vibrate in opposite phases. In the vibration in the Y-axis direction shown in FIG. 9C, the additional mass portions 7a, 7b, 7c, and 7d vibrate in the Y-axis direction in the same plane. At this time, the additional mass parts adjacent to each other vibrate in opposite phases. In FIG. 9, in order to schematically explain the vibration mode, the displacement of the additional mass portions 7a, 7b, 7c, and 7d is displayed exaggerated to be larger than actual.

  For example, when a rotational angular velocity is applied around the Z-axis in a state where vibration in the X-axis direction is excited as drive vibration, vibration in the Y-axis direction is generated due to the influence of Coriolis forces acting on the four additional mass portions. Similarly, when a rotational angular velocity is applied around the Y axis in a state where vibration in the X axis direction is excited as drive vibration, vibration in the Z axis direction is generated. At this time, if the vibration velocity in the X-axis direction is constant, the amplitude of the vibration in the Y-axis direction and the vibration generated in the Z-axis direction is proportional to the applied rotational angular velocity. If taken out, it functions as a rotational angular velocity sensor. That is, the detection electrode unit formed on the second arm unit is excited by vibration in the X-axis direction by inputting an electric signal to the drive electrode units 13a and 13b formed on the first arm unit shown in FIG. By detecting charges generated in 15a, 15b, 15c, and 15d, vibrations in the Y-axis direction and the Z-axis direction can be detected.

  In this embodiment, by adjusting the dimensions of the third arm portions 12a, 12b, 12c, and 12d, the resonance frequency fx of vibration in the X-axis direction is 29 kHz, and the resonance frequency fy of vibration in the Y-axis direction is 30.5 kHz. The resonance frequency fz of the vibration in the Z-axis direction was adjusted to 27.5 kHz. The piezoelectric single crystal plate of lithium niobate can be processed by ultrasonic machining, sandblasting, laser machining, etc., or wet etching or dry etching. Is previously known to have a processing error of 0.5% at 3σ. Therefore, in order to give each vibration mode a difference in resonance frequency sufficiently larger than the machining error, the difference between the resonance frequency of vibration in the X-axis direction and the resonance frequency of vibration in the Y-axis direction and the Z-axis direction is 1.5 kHz. did.

FIG. 10 is a graph showing the relationship between the sensitivity and the resonance frequency of the vibrator for a vibration gyro according to the present embodiment. The graph of FIG. 10 uses the resonance frequency fx of the vibration in the X-axis direction that is the first vibration mode that is the drive vibration and the resonance frequency fy of the vibration in the Y-axis direction that is the second vibration mode that is the detection vibration. The value A calculated by equation (1) is shown on the horizontal axis, and the detection sensitivity when the detection sensitivity when A = 0 is 1 is shown on the vertical axis.
A = (fy−fx) / fx × 100 (%) (1)

  The value A represents the difference between the resonance frequency fx of the first vibration mode and the resonance frequency fy of the second vibration mode as a ratio to the resonance frequency fx of the first vibration mode. It can be understood from the graph of FIG. 10 that the detection sensitivity is maximized when the value of A is near 0, that is, when the resonance frequency fx of the first vibration mode is equal to the resonance frequency fy of the second vibration mode. That is, if the resonance frequency fx of the vibration mode and the resonance frequency fy of the second vibration mode are slightly different, the sensitivity decreases rapidly. If the vibration gyro vibrator is processed with a processing accuracy of 0.5%, the resonance frequency fx of the first vibration mode and the resonance frequency fy of the second vibration mode depend on the processed dimensions. The difference is also 0.5%. This means that while the maximum sensitivity is 1, the minimum sensitivity is 0.08, and the sensitivity variation is very large, resulting in a vibrator for a vibrating gyroscope.

  On the other hand, the vibrator for the vibration gyro according to the present embodiment is designed so that the difference between the resonance frequency fx of the vibration mode and the resonance frequency fy of the second vibration mode is A = 5.0%, so that the machining dimension is 0.5%. Even if there is a variation, the sensitivity varies between A = 4.5% and A = 5.5% as shown in the graph of FIG. 10, so the detection sensitivity is about 0.010 to 0.008, A vibrator for a vibrating gyroscope with very small variations in sensitivity can be obtained. The resonance frequency fx of the first vibration mode and the resonance frequency fy of the second vibration mode are related to the resonance frequency fx of the first vibration mode and the third vibration which is another detected vibration. The same applies to the relationship between the mode and the resonance frequency fz. In this case, the magnitude relationship between fx and fz is fx> fz.

  Thus, the value A may be set to 5%, but the relationship between the resonance frequency fx of the first vibration mode, the resonance frequency fy of the second vibration mode, and the resonance frequency fz of the third vibration mode. Fy <fx <fz and 1.02 × fx ≦ fz, fy ≦ 0.98 × fx, or fy> fx> fz and 1.02 × fx ≦ fy, fz ≦ 0.98 × fx is preferable. However, (fy−fx) / fx and (fx−fz) / fx when fy <fx <fz, or (fz−fx) / fx and (fx−fy) when fy> fx> fz. Since the detection sensitivity decreases as the value of / fx increases, each value is set in consideration of the performance of the amplifier circuit, the S / N ratio, and the like. It is preferable that Further, it is more preferable that | fx−fy | = | fx−fz |.

  The vibration gyro element according to this embodiment has a null voltage and detection sensitivity variation of about ± 11%, and is necessary for the hand shake correction gyro by fine adjustment on the circuit side without mechanical adjustment of the vibrator. It was confirmed that the specifications were fully satisfied. In addition, it was confirmed that the other-axis sensitivity was 1% or less, which was also a practical level. The evaluation was performed by operating with one driving circuit so that a stable driving vibration was obtained using an AGC circuit (auto gain control circuit). Further, in order to further stabilize the vibration of the vibrator, the vibrator was hermetically sealed in a dry nitrogen atmosphere containing no humidity. The detection electrode portions 15a, 15b, 15c, and 15d generate charges due to the vibration in the Y-axis direction and the vibration in the Z-axis direction. Can be detected.

  In this embodiment, a flat plate made of a piezoelectric single crystal of lithium niobate having a thickness of 0.2 mm and a thickness direction of the plate having an X direction is selected, and as shown in a plan view in FIG. The vibrator was manufactured so that the direction from the lower end 8a to the upper end 8b was + 140Y. The vibrator has a rectangular shape with a length of 2.8 mm and a width of 4.3 mm, and a through-groove 2 having a width of about 0.2 mm is formed, so that the frame 3 is formed in the same plane of one piezoelectric single crystal plate. And a beam part 4 in the longitudinal direction of the central part, a first arm part 5 in the lateral direction of the central part, two second arm parts 6a, 6b at both ends of the first arm part 5, and a second arm part. A total of four additional mass portions 7a, 7b, 7c, and 7d were formed on both ends of each of these through the U-shaped third arm portions 12a, 12b, 12c, and 12d.

  The optimum electrode configuration when this crystal orientation is selected is shown in FIGS. That is, FIG. 12 is a plan view of electrodes that excite the first mode, and FIG. 13 is a plan view of electrodes that detect the second mode and the third mode. The plate-like vibrator of the present embodiment has electrodes formed on both surfaces, and FIG. 12 shows one surface on which the drive electrode portions 23a, 23b, 23c, and 23d are formed, and the detection electrode portion 24a, The other surface on which 24b, 24c, 24d, 25a and 25b are formed is shown in FIG. In addition, there is a method of applying or generating an AC voltage to the drive or detection electrode unit using the reference potential electrode unit for the actual drive electrode unit and detection electrode unit, but in this embodiment, the reference potential electrode unit is used. Regardless of whether or not they are present, the names of the drive electrode portion and the detection electrode portion are collectively used. Also in the first embodiment, it is needless to say that a method of applying or generating AC voltages whose phases are reversed without using the reference potential electrode portion is possible.

  The first mode is excited by inputting an electric signal to the drive electrode portions 23a, 23b, 23c, and 23d formed on the third arm portion shown in FIG. 12, and the third arm portion shown in FIG. By detecting the charges generated in the detection electrode portions 24a, 24b, 24c, and 24d formed in the second detection mode, the second mode can be detected, and the detection electrode portions 25a formed in the first arm portion shown in FIG. By detecting the charge generated in 25b, the vibration in the third mode can be detected. In each of the electrode portions, electrodes were formed of gold with chromium as a base.

  The arrangement of the electrode portions is determined by analyzing the distribution of charges generated on the surfaces of the first arm portion and the third arm portion in each vibration mode. 14 to 16 are schematic diagrams showing the distribution of electric charges. 14 to 16, “+” and “−” indicate the polarities of the generated charges, and the ellipse indicates the approximate range thereof. This charge distribution shows various distributions depending on the orientation of the selected crystal. FIG. 14 is a schematic diagram showing the distribution of charges in the first mode. For example, in the third arm portion 12c, + and − charges appear at the edge of the arm portion. When the additional mass portion 7c is displaced in the front direction of the paper, the third arm portion 12c connected to the second arm portion 6b is displaced to the back of the paper surface. From the respective charge distributions, the additional mass portions 7c and 7b and the additional mass portions 7a and 7d are displaced in opposite phases. FIG. 15 is a schematic diagram showing the charge distribution in the second mode. For example, in the third arm portions 12c-1 and 12c-2, charges having the same sign are generated at the edges, and the charge is reversed at the central portion of the arm. Electric charge is generated. Within the plane of the paper, the third arm portion 12c-1 and the third arm portion 12c-2 can detect electric charges when a mode in which they are displaced in opposite phases occurs. FIG. 16 is a schematic diagram showing the distribution of charges in the third mode. In the first arm portions 5a and 5b, charges having the same sign are generated at the edges of the arms, and reverse charges are generated in the central portion. . Within the plane of the drawing, the first arms 5a and 5b generate the same charge, and therefore can detect the charge when a mode that shifts to the same phase occurs.

  By the way, the electrode parts shown in FIGS. 12 and 13 are for concisely expressing the electrode parts for generating or detecting the charge distribution shown in FIGS. 14 to 16, and these electrodes are formed on an actual crystal substrate. It goes without saying that the wiring part connected to the part is omitted. For example, among the four strip-shaped electrodes formed on the drive electrode portion 23a in FIG. 12, the same charge generation polarity shown in FIG. 14 is short-circuited to form two terminals, that is, on the U-shaped arm. The points that connect the outside and the inside of the are omitted. Further, the wiring pattern with the electrode portion is also omitted. In addition, although the sensitivity is lowered, priority is given to the simplicity of the structure, and an electrode arrangement that does not use some of the generated charges is also possible. Then, the number of electrodes decreases, but at least two electrodes are required for each of the first to third arms in order to cope with positive and negative charges.

  In the above embodiment, a lithium niobate piezoelectric single crystal plate is used. However, a useful vibrating gyroscope can be constituted by lithium tantalate, quartz, langasite, zinc oxide, PZT, piezoelectric thin film, and the like. . Furthermore, the above embodiment is a vibrator for a vibration gyro using piezoelectricity or a vibration gyro, but a part or all of the drive and detection methods are a transducer using electromagnetic induction or electrostatic force, or You may replace with the displacement detection by the capacitance change between electrodes.

  As described above, according to the present invention, the resonance frequency of the vibration mode serving as the drive vibration is set to the resonance frequency between the second vibration mode and the third vibration mode, which are the two detection vibrations, so that the null A small and low-priced two-axis detection type vibratory gyro vibrator that can be configured with a single drive circuit with little occurrence of voltage and other-axis sensitivity and little variation in sensitivity can be obtained.

  The vibrator for a vibration gyro according to the present invention can be used as a gyroscope for detecting an angular velocity, as well as for a navigation system of an automobile, attitude control, or a camera shake correction device for a camera-integrated VTR.

Sectional drawing of the vibration gyro of the prior art example 1. FIG. FIG. 10 is a perspective view of a vibrator for a vibrating gyroscope according to Conventional Example 2. Sectional drawing of the vibrator for vibratory gyros of the prior art example 3. FIG. Explanatory drawing of the vibration mode of the vibrator for vibratory gyros of the conventional example 2. FIG. FIG. 4A is an explanatory diagram in the X-axis direction. FIG. 4B is an explanatory diagram in the Z-axis direction. FIG. 4C is an explanatory diagram in the Y-axis direction. Explanatory drawing of the vibration mode of the vibrator | oscillator for vibration gyros of the prior art example 3. FIG. FIG. 5A is an explanatory diagram in the X-axis direction. FIG. 5B is an explanatory diagram in the Z-axis direction. FIG. 5C is an explanatory diagram in the Y-axis direction. Explanatory drawing of the vibration mode of the vibrator | oscillator for piezoelectric vibration gyros which concerns on the conventional type. FIG. 6A is an explanatory diagram in the X-axis direction. FIG. 6B is an explanatory diagram in the Z-axis direction. FIG. 6C is an explanatory diagram in the Y-axis direction. Explanatory drawing of the vibration mode of the vibrator | oscillator for piezoelectric vibration gyroscopes which concerns on this invention. FIG. 7A is an explanatory diagram in the X-axis direction. FIG. 7B is an explanatory diagram in the Z-axis direction. FIG. 7C is an explanatory diagram in the Y-axis direction. 1 is a plan view of a vibrator for a vibrating gyroscope according to Embodiment 1. FIG. FIG. 9A is an explanatory diagram in the X-axis direction, FIG. 9B is an explanatory diagram in the Z-axis direction, and FIG. 9C is Y Explanatory drawing of an axial direction. 5 is a graph showing the relationship between the sensitivity of the vibrator for a vibration gyro according to the first embodiment and the resonance frequency. FIG. 6 is a plan view showing an outer shape of a vibrator for a vibrating gyroscope according to a second embodiment. FIG. 10 is a plan view of an electrode for exciting the first mode in the second embodiment. The top view of the electrode which detects the 2nd mode and 3rd mode in Example 2. FIG. FIG. 6 is a schematic diagram illustrating a charge distribution in a first mode according to the second embodiment. FIG. 6 is a schematic diagram showing a charge distribution in the second mode of Example 2. FIG. 6 is a schematic diagram showing a charge distribution in a third mode of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flat plate 2 Through-groove 3 Frame 4 Beam part 5, 5a, 5b 1st arm part 6a, 6b 2nd arm part 7a, 7b, 7c, 7d Additional mass part 8, 9 Centerline
8a Lower end 8b Upper end 10, 70, 81, 82, 90 Vibrating gyro vibrator 11 Coordinates 12a, 12b, 12c, 12d, 12c-1, 12c-2 Third arm portions 13a, 13b (in the first mode) Drive electrode portions 14a, 14b (first mode) reference potential electrode portions 14c, 14d, 14e, 14f, 14g, 14h (second and third mode) reference potential electrode portions 15a, 15b, 15c, 15d (second mode) Detection electrode portions 23a, 23b, 23c, 23d (in the first mode) Drive electrode portions 24a, 24b, 24c, 24d (in the second mode) Detection electrode portions 25a (in the second mode) 25b Detection electrode portion 31 (in the third mode) Cube 41, 51, 61 Rectangular body 71, 91 Vibrator 72 Side surface 73 Drive electrode 74, 76, 78 Reference electrode 75, 77 Detection electrode 80 Vibrating gyro 83 Housing 84 Base 92 Piezoelectric body 93 Electrode

Claims (6)

A plate-like body, a frame body, a beam part supported at both ends by the frame body, one or more first arm parts formed to intersect the beam part, and the first arm part One or more second arm portions that extend and form, a third arm portion that is supported by the second arm portion, and one or more that are supported by the third arm portion consists of a additional mass portion, the frame and the beam portion and the first arm portion and said second arm portion and said third arm portion and the additional mass portions are disposed in the same plane, the Each of the additional mass sections is arranged so as to be line-symmetric with respect to each of the beam section and the first arm section, and is a vibrator for a vibrating gyroscope that detects angular velocities in two axial directions. The first vibration mode to be, the second vibration mode to be detected vibration, and the third vibration mode. The resonance frequency of the second vibration mode is lower than the resonance frequency of the third vibration mode, the resonance frequency of the first vibration mode is higher than the resonance frequency of the second vibration mode and A vibrator for a vibration gyro, which has a resonance frequency lower than that of the third vibration mode.   2. The vibrator for a vibration gyro according to claim 1, wherein the first vibration mode, the second vibration mode, and the third vibration mode have mutually orthogonal vibration directions. The beam portion, the first arm portion, the second arm portion, the third arm portion, and the additional mass portion are disposed inside the frame body, and the beam portion is a central portion of the frame body. It will be Mashimashi equidistant extending from said first arm portion, Mashimashi center as perpendicular and equidistant extension of the beam part, prior to pressurizing parts by weight with SL are arranged four or more, the first In the vibration mode, the adjacent additional mass portions vibrate outwardly in the same plane with opposite phases, and the second vibration mode and the third vibration mode are both the first vibration mode and the first vibration mode. 3. The vibrator for a vibration gyro according to claim 2, wherein the vibration directions are orthogonal and the vibration directions are orthogonal to each other.   The said 3rd arm part is a shape bent in the shape of a U-shape in the middle of the connection part with the said additional mass part, and the connection part with a 2nd arm part, The 3rd aspect is characterized by the above-mentioned. Vibrating gyro vibrator.   5. An electrode is formed on both surfaces of the plate-like body, a driving electrode portion is formed on one surface, and a detection electrode portion is formed on the other surface. A vibrator for a vibrating gyroscope according to any one of the above. There are at least two first vibration modes on the third arm portion so as to extend in a strip shape along a portion of the third arm portion that is formed substantially parallel to the first arm portion. Excited by the electrode formed above,
The second vibration mode is substantially parallel to the first arm portion on the surface of the third arm portion opposite to the surface on which the electrode for exciting the first vibration mode is formed. Detected by at least two electrodes formed to include a strip-shaped electrode portion,
The third vibration mode is along the first arm portion on the surface of the first arm portion opposite to the surface on which the electrode for exciting the first vibration mode is formed. 6. The vibrator for a vibrating gyroscope according to claim 5, wherein the vibrator is detected by at least two electrodes formed so as to extend in a strip shape.

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