Inertial sensor

Abstract

This inertial sensor comprises a disk and a plurality of electrodes. The plurality of electrodes include a drive electrode, a detection electrode, and a plurality of adjustment electrodes. Each of the plurality of electrodes has a facing surface which faces the outer peripheral surface of the disk. Each of the plurality of electrodes has a facing length that is the length of the facing surface in the circumferential direction of the disk. The facing length of each of the plurality of adjustment electrodes is smaller than the facing length of the drive electrode and the facing length of the detection electrode.

Description

Inertial Sensor

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to inertial sensors, and more particularly to capacitive inertial sensors.

[0002] The gyroscope (inertial sensor) described in Patent Document 1 includes a disk and a plurality of electrodes. The plurality of electrodes surround the disk. The plurality of electrodes includes a drive electrode, a detection electrode, and an electrostatic tuning electrode (adjustment electrode). A sinusoidal drive signal is applied to the drive electrode, and an output signal at the detection electrode is observed.

[0003] US Patent Application Publication No. 2007 / 220971

[0004] In Patent Document 1, by applying a voltage to an electrostatic tuning electrode (adjustment electrode), the shape of the disk can be adjusted to a shape suitable for detection by a detection electrode.

[0005] An inertial sensor according to one aspect of the present disclosure is a capacitance-type inertial sensor. The inertial sensor includes a disk and a plurality of electrodes. The plurality of electrodes face an outer peripheral surface of the disk at intervals. The plurality of electrodes include a drive electrode, a detection electrode, and a plurality of adjustment electrodes. A voltage for driving the disk is applied to the drive electrode. The detection electrode is an electrode for detecting changes in capacitance between the disk and the plurality of adjustment electrodes. A voltage for adjusting the shape of the disk is applied to the plurality of electrodes. Each of the plurality of electrodes has a facing surface facing the outer peripheral surface of the disk. Each of the plurality of electrodes has a facing length that is the length of the facing surface in the circumferential direction of the disk. The facing length of each of the plurality of adjustment electrodes is shorter than both the facing length of the drive electrode and the facing length of the detection electrode.

[0006] The present disclosure has the advantage that it can improve the precision of adjustment when adjusting the shape of the disk using multiple adjustment electrodes.

[0007] FIG. 1 is a plan view of an inertial sensor according to one embodiment. FIG. 2 is a side cross-sectional view of the inertial sensor. FIG. 3A is a plan view showing a disk shape of the inertial sensor in a drive vibration mode. FIG. 3B is a plan view showing a disk shape of the inertial sensor in a drive vibration mode. FIG. 4A is a plan view showing a disk shape of the inertial sensor in a detection vibration mode. FIG. 4B is a plan view showing a disk shape of the inertial sensor in a detection vibration mode. FIG. 5 is a plan view of an inertial sensor according to a first modified example. FIG. 6 is a plan view of an inertial sensor according to a second modified example.

[0008] An inertial sensor 1 according to an embodiment will be described below with reference to the drawings. However, the embodiment described below is merely one of various embodiments of the present disclosure. The embodiment described below can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each figure described in the embodiment described below is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0009] In this disclosure, "applying a voltage" to an object means applying a voltage between the object and a structure maintained at a reference potential (eg, ground).

[0010] 1 is a capacitance-type inertial sensor. The inertial sensor 1 includes a disk 2 and a plurality of electrodes 3. The plurality of electrodes 3 face an outer peripheral surface 20 of the disk 2 at intervals.

[0011] The plurality of electrodes 3 include a drive electrode 4, a detection electrode 5, and a plurality of adjustment electrodes 6. A voltage for driving the disk 2 is applied to the drive electrode 4. The detection electrode 5 is an electrode for detecting a change in capacitance between the drive electrode 4 and the disk 2. A voltage for adjusting the shape of the disk 2 is applied to the plurality of adjustment electrodes 6.

[0012] The capacitance between the disk 2 and the detection electrode 5 changes depending on the magnitude of the inertial force acting on the inertial sensor 1. The inertial sensor 1 outputs a detection signal from the detection electrode 5 that corresponds to the capacitance and that represents the magnitude of the inertial force acting on the inertial sensor 1.

[0013] The physical quantity detected by the inertial sensor 1 is acceleration or angular velocity. In either case, the basic detection principle is the same. In this embodiment, as a representative example, a case will be described in which the inertial sensor 1 is a gyro sensor that detects angular velocity.

[0014] When a voltage is applied to the adjustment electrode 6, an electrostatic force (electrostatic attraction) is generated between the adjustment electrode 6 and the disk 2. As a result, the shape of the disk 2 changes compared to when no voltage is applied to the adjustment electrode 6. The shape of the disk 2 is adjusted by adjusting the magnitude of the voltage applied to each of the multiple adjustment electrodes 6. Adjusting the shape of the disk 2 can improve the characteristics of the inertial sensor 1. For example, it is possible to improve the linearity between the angular velocity of the inertial sensor 1 and the detection signals output from the two detection electrodes 5, reduce noise in the detection signals, and improve the temperature characteristics of the inertial sensor 1.

[0015] 1 , each of the plurality of electrodes 3 has a facing surface 30 facing an outer peripheral surface 20 extending in the circumferential direction D2 of the disk 2. Each of the plurality of electrodes 3 has a facing length that is the length of the facing surface 30 in the circumferential direction D2 of the disk 2. The facing length of each of the plurality of adjustment electrodes 6 (facing lengths L7 and L8 in FIG. 1 ) is shorter than both the facing length L4 of the drive electrode 4 and the facing length L5 of the detection electrode 5.

[0016] The above configuration provides greater freedom in arranging the plurality of adjustment electrodes 6 compared to the conventional example in which the opposing lengths of the plurality of electrodes 3 are equal. In the inertial sensor 1 of this embodiment, for example, the number of adjustment electrodes 6 can be greater than in the conventional example. Also, in the inertial sensor 1 of this embodiment, for example, the number of possible positions for arranging the adjustment electrodes 6 is greater than in the conventional example.

[0017] The greater the number of adjustment electrodes 6, the more directions of force can be applied to the disk 2, which prevents the disk 2 from deforming in a particular direction, allowing for accurate control of the deformation of the disk 2.

[0018] Furthermore, the more positions for arranging the adjustment electrodes 6 there are, the more likely it is that a position suitable for accurately deforming the disk 2 into a desired shape (for example, a circle) can be selected.

[0019] Therefore, by increasing the degree of freedom in arranging multiple adjustment electrodes 6, the accuracy of adjustment can be improved when adjusting the shape of the disk 2 using multiple adjustment electrodes 6 (i.e., by applying voltage to multiple adjustment electrodes 6).

[0020] In this disclosure, when the shape of the disk 2 is mentioned, it refers to the shape of the disk 2 when no electrostatic force is applied to the disk 2, unless otherwise specified.

[0021] (Details) The inertial sensor 1 of this embodiment will be described in more detail below.

[0022] The inertial sensor 1 is formed using, for example, MEMS (Micro Electro Mechanical Systems) technology. As shown in Figures 1 and 2, the inertial sensor 1 includes a disk 2, a plurality of electrodes 3, a substrate 9, and a plurality of support members 10. Note that the substrate 9 is not shown in Figure 1.

[0023] The substrate 9 is a rigid substrate such as a glass epoxy substrate or a silicon substrate. The substrate 9 has a first surface 91 and a second surface 92. The first surface 91 is the surface on which the disk 2 and the plurality of electrodes 3 are mounted. The second surface 92 is the surface opposite to the first surface 91.

[0024] The disk 2 and the plurality of electrodes 3 each face a first surface 91 of the substrate 9. The disk 2 and the plurality of electrodes 3 are each mounted on the substrate 9 via a support member 10. That is, a corresponding support member 10 is sandwiched between the disk 2 and the substrate 9, and a corresponding support member 10 is sandwiched between each of the plurality of electrodes 3 and the substrate 9. The support members 10 are electrically insulating.

[0025] 2, one support member 10 is disposed at a position in contact with the center of the disk 2. However, the positions and number of support members 10 are not particularly limited. For example, one or more support members 10 may be disposed at positions in contact with the peripheral edge of the disk 2.

[0026] In this embodiment, the axis along the direction in which the substrate 9 and the disk 2 are aligned is defined as the Z-axis. An axis perpendicular to the Z-axis is defined as the X-axis, and an axis perpendicular to both the Z-axis and the X-axis is defined as the Y-axis. In each drawing, the arrows representing the X-axis, Y-axis, and Z-axis are merely shown for the purpose of explanation and do not have any substance. The direction parallel to the Z-axis is called the Z-axis direction.

[0027] The disk 2 is formed of a material containing, for example, single crystal silicon or polycrystalline silicon. The disk 2 is cylindrical in shape with a central axis 200A along the Z-axis direction. The disk 2 has a main surface 20A, a main surface 20B opposite the main surface 20A, and an outer circumferential surface 20 connected to the main surfaces 20A and 20B. The main surface 20B of the disk 2 faces the first surface 91 of the substrate 9. The main surfaces 20A and 20B are circular with a center 200. The outer circumferential surface 20 of the disk 2 is a cylindrical side surface. As shown in FIG. 1 , the outer edge of the disk 2 has a circular shape when viewed in the Z-axis direction.

[0028] For example, a through hole may be provided at the center 200 of the disk 2, and the disk 2 may have a ring shape when viewed in the Z-axis direction. The shape of the outer edge of the disk 2 may be substantially circular, and may be a polygon having octagons or more sides.

[0029] 1 , the plurality of electrodes 3 includes two drive electrodes 4, two detection electrodes 5, and four adjustment electrodes 6. The four adjustment electrodes 6 include two first adjustment electrodes 7 and two second adjustment electrodes 8.

[0030] Hereinafter, the two drive electrodes 4 will also be referred to as drive electrodes 4A and 4B, the two detection electrodes 5 will also be referred to as detection electrodes 5A and 5B, the two first adjustment electrodes 7 will also be referred to as first adjustment electrodes 7A and 7B, and the two second adjustment electrodes 8 will also be referred to as second adjustment electrodes 8A and 8B.

[0031] Each of the multiple electrodes 3 has a columnar shape with its central axis aligned along the Z-axis direction (the direction of the central axis 200A). In a cross section perpendicular to the Z-axis, each of the multiple electrodes 3 has an annulus sector (arch shape). When viewed from the Z-axis direction (the direction of the central axis 200A), each of the multiple electrodes 3 has an annulus sector (arch shape). An annulus sector is a figure enclosed by a first circle, a second circle concentric with the first circle and having a larger radius than the first circle, and two line segments connecting two points on the second circle to the center. The annulus sector includes a portion of the first circle (hereinafter referred to as the "inner arc"). Therefore, when viewed from the Z-axis direction, each of the multiple electrodes 3 includes an inner arc.

[0032] The radius of the first circle (inner arc) is the same for each of the multiple electrodes 3. The radius of the second circle (outer arc) is the same for each of the multiple electrodes 3. The center of the first circle coincides with the center 200 of the disk 2.

[0033] When viewed from the Z-axis direction, the inner arc of the multiple electrodes 3 is disposed facing the disk 2. The inner arc is included in the facing surface 30. The facing length of the electrode 3 (the length of the facing surface 30 in the circumferential direction D2 of the disk 2) is the length of the inner arc.

[0034] The two drive electrodes 4 have the same shape, and therefore the opposing lengths L4 of the two drive electrodes 4 are equal to each other.

[0035] The two detection electrodes 5 have the same shape, and therefore the facing lengths L5 of the two detection electrodes 5 are equal to each other.

[0036] The two first adjusting electrodes 7 have the same shape, and therefore the facing lengths L7 of the two first adjusting electrodes 7 are equal to each other.

[0037] The two second adjusting electrodes 8 have the same shape, and therefore the facing lengths L8 of the two second adjusting electrodes 8 are equal to each other.

[0038] The driving electrode 4A is disposed on the positive side of the X axis with respect to the center 200 of the disk 2. The driving electrode 4B is disposed on the negative side of the X axis with respect to the center 200. The disk 2 is disposed between the driving electrodes 4A and 4B. More specifically, the driving electrodes 4A and 4B are disposed in point symmetry with respect to the center 200.

[0039] The detection electrode 5A is disposed on the negative side of the Y axis with respect to the center 200 of the disk 2. The detection electrode 5B is disposed on the positive side of the Y axis with respect to the center 200. The disk 2 is disposed between the detection electrodes 5A and 5B. More specifically, the detection electrodes 5A and 5B are disposed in point-symmetric positions with respect to the center 200.

[0040] Each of the first adjustment electrodes 7 is disposed at a position opposite to the peak of the resonant vibration of the disk 2 .

[0041] Around the periphery of the disk 2, the first adjustment electrode 7A is disposed between the drive electrode 4A and the detection electrode 5A. Around the periphery of the disk 2, the first adjustment electrode 7B is disposed between the drive electrode 4B and the detection electrode 5B. The disk 2 is disposed between the first adjustment electrodes 7A and 7B. More specifically, the first adjustment electrodes 7A and 7B are disposed at positions that are point-symmetric with respect to the center 200 of the disk 2.

[0042] Each second adjustment electrode 8 is disposed at a position facing a node of the resonant vibration of the disk 2 (a point where the displacement is relatively small).

[0043] Around the periphery of disk 2, second adjustment electrode 8A is disposed between first adjustment electrode 7A and detection electrode 5A. Around the periphery of disk 2, second adjustment electrode 8B is disposed between first adjustment electrode 7B and detection electrode 5B. Disk 2 is disposed between second adjustment electrode 8A and second adjustment electrode 8B. More specifically, second adjustment electrodes 8A and 8B are disposed at positions point-symmetric with respect to center 200 of disk 2.

[0044] As described above, the facing lengths L7 and L8 of each of the plurality of adjustment electrodes 6 are shorter than both the facing length L4 of the drive electrode 4 and the facing length L5 of the detection electrode 5. In other words, the facing length L7 is shorter than both the facing lengths L4 and L5, and the facing length L8 is shorter than both the facing lengths L4 and L5.

[0045] The opposing lengths L4 and L5 may be equal to each other or may be different from each other.

[0046] The opposing lengths L7 and L8 may be equal to each other or may be different from each other.

[0047] The two first adjustment electrodes 7A and 7B are electrically connected, so that a common voltage is applied to the two first adjustment electrodes 7A and 7B.

[0048] The two second adjusting electrodes 8A and 8B are electrically connected to each other, so that a common voltage is applied to the two second adjusting electrodes 8A and 8B.

[0049] (Example of Operation) The disk 2 and the plurality of electrodes 3 of the inertial sensor 1 are electrically connected to a controller. The controller includes, for example, an ASIC (Application Specific Integrated Circuit). The controller continues to apply a constant DC voltage to the disk 2.

[0050] The controller also applies drive voltages to the two drive electrodes 4. The waveform of the drive voltage is, for example, a sine wave or a square wave. The controller applies drive voltages to the two drive electrodes 4 in opposite phases to each other.

[0051] The controller also acquires the detection signals output from the two detection electrodes 5. Furthermore, the controller adjusts the magnitude of the DC voltage applied to each of the plurality of adjustment electrodes 6.

[0052] When a drive voltage is applied to the two drive electrodes 4, the electrostatic force between the disk 2 and the two drive electrodes 4 causes the disk 2 to vibrate (expand and contract) periodically.

[0053] 3A and 3B show an example of a vibration mode (hereinafter referred to as a driving vibration mode) of the resonant vibration of the disk 2 when a driving voltage is applied to the two driving electrodes 4 and the inertial sensor 1 is stationary. In the driving vibration mode, the outer edge of the disk 2 repeatedly deforms in a manner that expands in the positive direction of the X axis as shown in Fig. 3A and in a manner that expands in the negative direction of the X axis as shown in Fig. 3B.

[0054] 4A and 4B show an example of a vibration mode (hereinafter referred to as a detection vibration mode) of the resonant vibration of the disk 2 caused by the Coriolis force when a drive voltage is applied to the two drive electrodes 4 and the inertial sensor 1 rotates. The rotation axis of the inertial sensor 1 passes through the center 200 of the disk 2 and is parallel to the Z axis. In the detection vibration mode, the outer edge of the disk 2 repeatedly deforms in the negative direction of the Y axis as shown in FIG. 4A and in the positive direction of the Y axis as shown in FIG. 4B.

[0055] In the driven vibration mode, there is almost no change in the distance between the disk 2 and each of the two detection electrodes 5. Ideally, in the driven vibration mode, there is no change in the distance between the disk 2 and each of the two detection electrodes 5.

[0056] On the other hand, in the detection vibration mode, the capacitance changes because the distance between the disk 2 and each of the two detection electrodes 5 changes according to the rotation speed of the inertial sensor 1. Therefore, the two detection electrodes 5 output a detection signal according to the angular velocity of the inertial sensor 1.

[0057] Each of the two first adjustment electrodes 7 is an electrode for adjusting the shape of the disk 2 to adjust the resonant frequency of the disk 2. More specifically, the controller suppresses the difference between the resonant frequency of the drive vibration mode and the resonant frequency of the detection vibration mode to be less than a predetermined value by adjusting the magnitude of the DC voltage applied to the two first adjustment electrodes 7. In other words, the controller achieves mode matching between the drive vibration mode and the detection vibration mode by adjusting the magnitude of the DC voltage applied to the two first adjustment electrodes 7.

[0058] Each of the two second adjustment electrodes 8 is an electrode for adjusting the shape of the disk 2 to reduce unwanted components in the detection signal output from the detection electrode 5. More specifically, in the detection vibration mode, the detection signal includes a real component and an unwanted component. The real component is a component that corresponds to the angular velocity of the disk 2. The unwanted component is a component of the resonant vibration in the drive vibration mode that leaks into the detection signal in the detection vibration mode. The controller reduces the unwanted components of the detection signal in the detection vibration mode by adjusting the magnitude of the DC voltage applied to the two second adjustment electrodes 8.

[0059] The controller determines the voltage to be applied to each adjustment electrode 6 by, for example, feedback control based on the detection signal.

[0060] In this embodiment, the phase difference between the real component and the unnecessary component is 90 degrees. That is, in this embodiment, the unnecessary component is an orthogonal component that is orthogonal to the real component. However, the phase difference between the real component and the unnecessary component is not limited to 90 degrees.

[0061] (Modifications) Modifications of the embodiment will be described below. The following modifications may be implemented in appropriate combination. Hereinafter, the configuration of the embodiment described above will be referred to as a basic example.

[0062] (Modification 1) An inertial sensor 1J according to Modification 1 will be described below with reference to Fig. 5. Components similar to those in the basic example are given the same reference numerals and descriptions thereof will be omitted.

[0063] While the number of second adjusting electrodes 8 in the basic example is two, the number of second adjusting electrodes 8 in the present modified example 1 is eight. That is, the inertial sensor 1J includes eight second adjusting electrodes 8. Hereinafter, the eight second adjusting electrodes 8 will also be referred to as second adjusting electrodes 8A, 8B, 8C, 8D, 8E, 8F, 8G, and 8H, respectively.

[0064] The two first adjusting electrodes 7 have the same shape, and therefore the facing lengths L7 of the two first adjusting electrodes 7 are equal to each other.

[0065] The eight second adjusting electrodes 8 have the same shape, and therefore the eight second adjusting electrodes 8 have the same facing length L8.

[0066] The facing length L8 of each second adjusting electrode 8 is shorter than the facing length L7 of each first adjusting electrode 7. This makes it possible to arrange a large number of second adjusting electrodes 8.

[0067] Next, the arrangement of each electrode will be described.

[0068] The arrangement of the two drive electrodes 4 and the two detection electrodes 5 is the same as in the basic example.

[0069] Around the periphery of the disk 2, the first adjustment electrode 7A is disposed between the drive electrode 4A and the detection electrode 5A. Around the periphery of the disk 2, the first adjustment electrode 7B is disposed between the drive electrode 4B and the detection electrode 5B. The disk 2 is disposed between the first adjustment electrodes 7A and 7B. More specifically, the first adjustment electrodes 7A and 7B are disposed at positions that are point-symmetric with respect to the center 200 of the disk 2.

[0070] The second adjustment electrode 8A is disposed around the periphery of the disk 2 between the first adjustment electrode 7A and the detection electrode 5A. The second adjustment electrode 8C is disposed around the periphery of the disk 2 between the first adjustment electrode 7A and the drive electrode 4A.

[0071] Around the periphery of the disk 2, the second adjustment electrode 8B is disposed between the first adjustment electrode 7B and the detection electrode 5B. Around the periphery of the disk 2, the second adjustment electrode 8D is disposed between the first adjustment electrode 7B and the drive electrode 4B.

[0072] Second adjustment electrodes 8E and 8G are disposed around the periphery of disk 2 between drive electrode 4A and detection electrode 5B. Second adjustment electrode 8E is adjacent to detection electrode 5B, and second adjustment electrode 8G is adjacent to drive electrode 4A.

[0073] Second adjustment electrodes 8F and 8H are disposed around the periphery of disk 2 between drive electrode 4B and detection electrode 5A. Second adjustment electrode 8F is adjacent to detection electrode 5A, and second adjustment electrode 8H is adjacent to drive electrode 4B.

[0074] The eight second adjusting electrodes 8 are in one-to-one correspondence. That is, the eight (more generally, 2N: N is a natural number) second adjusting electrodes 8 are made up of four pairs (N pairs) of second adjusting electrodes 8, and any pair of the four pairs of second adjusting electrodes 8 corresponds to any one of the four pairs of second adjusting electrodes 8. More specifically, second adjusting electrodes 8A and 8B correspond to each other, second adjusting electrodes 8C and 8D correspond to each other, second adjusting electrodes 8E and 8F correspond to each other, and second adjusting electrodes 8G and 8H correspond to each other.

[0075] The disk 2 is disposed between two corresponding second adjustment electrodes 8. More specifically, the two corresponding second adjustment electrodes 8 are disposed at positions that are point-symmetric with respect to the center 200 of the disk 2.

[0076] In this way, the even number of second adjustment electrodes 8 are one or more pairs of two second adjustment electrodes 8 that correspond to each other one-to-one. The disk 2 is disposed between the two second adjustment electrodes 8.

[0077] As in the basic example and Modification 1, it is preferable that the number of second adjustment electrodes 8 is an even number. Furthermore, as in Modification 1, it is preferable that the number of second adjustment electrodes 8 is four or more. By increasing the number of second adjustment electrodes 8, forces can be applied to the disk 2 in more directions, and therefore deformation of the disk 2 can be controlled with high precision.

[0078] (Modification 2) An inertial sensor 1K according to Modification 2 will be described below with reference to Fig. 6. The same components as those in Modification 1 will be denoted by the same reference numerals and description thereof will be omitted.

[0079] While the number of first adjusting electrodes 7 is two in Modification 1, the number of first adjusting electrodes 7 is four in Modification 2. That is, inertial sensor 1J includes four first adjusting electrodes 7. Hereinafter, the four first adjusting electrodes 7 will also be referred to as first adjusting electrodes 7A, 7B, 7C, and 7D, respectively.

[0080] The four first adjusting electrodes 7 have the same shape.

[0081] On the periphery of the disk 2, the first adjustment electrode 7C is disposed between the second adjustment electrodes 8E and 8G. On the periphery of the disk 2, the first adjustment electrode 7D is disposed between the second adjustment electrodes 8F and 8H.

[0082] The four first adjusting electrodes 7 are in one-to-one correspondence. More specifically, the first adjusting electrodes 7A and 7B correspond to each other, and the first adjusting electrodes 7C and 7D correspond to each other.

[0083] The disk 2 is disposed between two corresponding first adjustment electrodes 7. More specifically, the two corresponding first adjustment electrodes 7 are disposed at positions that are point-symmetric with respect to the center 200 of the disk 2.

[0084] In this way, the even number of first adjustment electrodes 7 are one or more pairs of two first adjustment electrodes 7 that correspond to each other one-to-one. The disk 2 is disposed between the two first adjustment electrodes 7.

[0085] As in the basic example, modified example 1, and modified example 2, the number of first adjusting electrodes 7 is preferably an even number. Furthermore, as in modified example 2, the number of first adjusting electrodes 7 is preferably four or more. By increasing the number of first adjusting electrodes 7, forces can be applied to the disk 2 in more directions, and therefore deformation of the disk 2 can be controlled with high precision.

[0086] There are more positions suitable for arranging the second adjusting electrodes 8 than for arranging the first adjusting electrodes 7. Therefore, in Modifications 1 and 2, the number of second adjusting electrodes 8 is made greater than the number of first adjusting electrodes 7. This makes it possible to improve the accuracy of adjusting the shape of the disk 2.

[0087] (Other Modifications of the Embodiment) Other modifications of the embodiment are listed below. The following modifications may be realized in appropriate combination. Furthermore, the following modifications may be realized in appropriate combination with the above-described modifications.

[0088] The number of drive electrodes 4 is not limited to two, but may be one or three or more.

[0089] The number of detection electrodes 5 is not limited to two, but may be one, or three or more.

[0090] The number of first adjusting electrodes 7 does not have to be an even number, as long as it is one or more.

[0091] The number of second adjusting electrodes 8 does not have to be an even number, as long as it is one or more.

[0092] The plurality of adjusting electrodes 6 may include only the plurality of first adjusting electrodes 7 or may include only the plurality of second adjusting electrodes 8 .

[0093] The facing lengths L4 of the plurality of driving electrodes 4 may be different from one another. In this case, the facing lengths L7 and L8 of the first adjusting electrode 7 and the second adjusting electrode 8 are shorter than the smallest facing length among the facing lengths L4 of the plurality of driving electrodes 4.

[0094] The facing lengths L5 of the multiple detection electrodes 5 may be different from one another. In this case, the facing lengths L7 and L8 of the first adjustment electrode 7 and the second adjustment electrode 8 are shorter than the smallest facing length among the facing lengths L5 of the multiple detection electrodes 5.

[0095] The facing lengths L7 of the plurality of first adjusting electrodes 7 may be different from one another, and the facing lengths L8 of the plurality of second adjusting electrodes 8 may be different from one another.

[0096] The plurality of electrodes 3 may include a ground electrode.

[0097] The detection electrode 5 is disposed opposite a portion of the disk 2 where displacement in the drive vibration mode is relatively small. Specifically, in the basic example, a line segment connecting the center of the drive electrode 4 and the center 200 of the disk 2 and a line segment connecting the center of the detection electrode 5 and the center 200 of the disk 2 intersect at an angle of 90 degrees. However, the positional relationship between the drive electrode 4 and the detection electrode 5 is not limited to this positional relationship.

[0098] The arrangement of each electrode 3 can be changed as appropriate. For example, it is not essential that the second adjustment electrode 8 be adjacent to the drive electrode 4 or the detection electrode 5. Also, for example, it is not essential that the first adjustment electrode 7 be adjacent to the second adjustment electrode 8.

[0099] 3A, 3B, 4A and 4B, the disk 2 deforms into a substantially triangular shape, although other vibration modes may also be used.

[0100] (Summary) The above-described embodiments and the like disclose the following aspects.

[0101] The inertial sensor (1; 1J; 1K) according to a first aspect is a capacitance-type inertial sensor (1; 1J; 1K). The inertial sensor (1; 1J; 1K) includes a disk (2) and a plurality of electrodes (3). The plurality of electrodes (3) face, at intervals, an outer peripheral surface (20) extending in a circumferential direction (D2) of the disk (2). The plurality of electrodes (3) include a drive electrode (4), a detection electrode (5), and a plurality of adjustment electrodes (6). A voltage for driving the disk (2) is applied to the drive electrode (4). The detection electrode (5) is an electrode for detecting changes in capacitance between the disk (2) and the plurality of adjustment electrodes (6). A voltage for adjusting the shape of the disk (2) is applied to the plurality of adjustment electrodes (6). Each of the plurality of electrodes (3) has a facing surface (30) facing the outer peripheral surface (20) of the disk (2). Each of the plurality of electrodes (3) has an opposing length that is the length of the opposing surface (30) in the circumferential direction (D2) of the disk (2). The opposing length (L7; L8) of each of the plurality of adjustment electrodes (6) is shorter than both the opposing length (L4) of the drive electrode (4) and the opposing length (L5) of the detection electrode (5).

[0102] The above configuration provides greater freedom in the arrangement of the plurality of adjustment electrodes 6 than when the opposing lengths of the plurality of electrodes 3 are equal to each other, thereby improving the accuracy of adjustment when adjusting the shape of the disk 2 using the plurality of adjustment electrodes 6.

[0103] In the inertial sensor (1; 1J; 1K) according to the second aspect, in the first aspect, the plurality of adjustment electrodes (6) include at least one first adjustment electrode (7) and at least one second adjustment electrode (8). The at least one first adjustment electrode (7) adjusts the shape of the disk (2) to adjust the resonant frequency of the disk (2). The at least one second adjustment electrode (8) adjusts the shape of the disk (2) to reduce unnecessary components of the detection signal output from the detection electrode (5).

[0104] According to the above configuration, the accuracy of adjustment when adjusting the shape of the disk (2) using multiple adjustment electrodes (6) can be improved compared to when the multiple adjustment electrodes (6) include only multiple first adjustment electrodes (7) and when the multiple adjustment electrodes (6) include only multiple second adjustment electrodes (8).

[0105] In addition, in the inertial sensor (1J; 1K) according to the third aspect, in the second aspect, the opposing length (L8) of at least one second adjustment electrode (8) is shorter than the opposing length (L7) of at least one first adjustment electrode (7).

[0106] According to the above configuration, the degree of freedom in arranging at least one second adjustment electrode (8) is further increased, thereby enhancing the effect of reducing unnecessary components in the detection signal output from the detection electrode (5).

[0107] Furthermore, the inertial sensor (1; 1J; 1K) according to a fourth aspect is the inertial sensor (1) according to the second or third aspect, and includes an even number of first adjustment electrodes (7) as at least one first adjustment electrode (7). The even number of first adjustment electrodes (7) are two first adjustment electrodes (7) that correspond to each other one-to-one in one or more pairs. In the even number of first adjustment electrodes (7), a disk (2) is disposed between the two corresponding first adjustment electrodes (7).

[0108] According to the above configuration, the accuracy of the adjustment of the resonant frequency can be improved.

[0109] In addition, in the inertial sensor (1K) according to the fifth aspect, in the fourth aspect, the number of first adjustment electrodes (7) is four or more.

[0110] According to the above configuration, the precision of adjustment of the resonant frequency can be improved compared to when the number of first adjustment electrodes (7) is two.

[0111] In addition, in the inertial sensor (1; 1J; 1K) relating to the sixth aspect, in the fourth or fifth aspect, the two corresponding first adjustment electrodes (7) are arranged in positions that are point-symmetric with respect to the center of the disk (2) as the center of symmetry.

[0112] According to the above configuration, the accuracy of the adjustment of the resonant frequency can be further improved.

[0113] Furthermore, the inertial sensor (1; 1J; 1K) according to a seventh aspect is any one of the second to sixth aspects, and includes an even number of second adjustment electrodes (8) as at least one second adjustment electrode (8). The even number of second adjustment electrodes (8) are two second adjustment electrodes (8) that correspond to each other one-to-one in one or more pairs. In the even number of second adjustment electrodes (8), a disk (2) is disposed between the two corresponding second adjustment electrodes (8).

[0114] According to the above configuration, it is possible to improve the accuracy of the process for reducing unnecessary components of the detection signal output from the detection electrode (5).

[0115] In addition, in the inertial sensor (1J; 1K) according to the eighth aspect, in the seventh aspect, the number of second adjustment electrodes (8) is four or more.

[0116] According to the above configuration, the accuracy of the process for reducing unnecessary components of the detection signal output from the detection electrode (5) can be improved compared to when the number of second adjustment electrodes (8) is two.

[0117] In addition, in the inertial sensor (1; 1J; 1K) according to the ninth aspect, in the seventh or eighth aspect, two corresponding second adjustment electrodes (8) are arranged in positions that are point-symmetric with respect to the center of the disk (2) as the center of symmetry.

[0118] According to the above configuration, it is possible to further improve the accuracy of the process for reducing unnecessary components of the detection signal output from the detection electrode (5).

[0119] Furthermore, the inertial sensor (1J; 1K) according to a tenth aspect is the inertial sensor of any one of the second to ninth aspects, and includes an even number of first adjusting electrodes (7) as at least one first adjusting electrode (7). The even number of first adjusting electrodes (7) are two first adjusting electrodes (7) that correspond to each other one-to-one in one or more pairs. In the even number of first adjusting electrodes (7), a disk (2) is disposed between the two corresponding first adjusting electrodes (7). The inertial sensor (1J; 1K) includes an even number of second adjusting electrodes (8) as at least one second adjusting electrode (8). The even number of second adjusting electrodes (8) are two second adjusting electrodes (8) that correspond to each other one-to-one in one or more pairs. In the even number of second adjusting electrodes (8), a disk (2) is disposed between the two corresponding second adjusting electrodes (8). The number of second adjusting electrodes (8) is greater than the number of first adjusting electrodes (7).

[0120] According to the above configuration, the accuracy of adjusting the shape of the disk (2) can be improved compared to when the number of second adjusting electrodes (8) is equal to or less than the number of first adjusting electrodes (7).

[0121] The configurations other than the first aspect are not essential for the inertial sensor (1; 1J; 1K) and can be omitted as appropriate.

[0122] 1, 1J, 1K Inertial sensor 2 Disk 3 Electrode 4 Drive electrode 5 Detection electrode 6 Adjustment electrode 7 First adjustment electrode 8 Second adjustment electrode 20 Outer circumferential surface 30 Opposing surface L4, L5, L7, L8 Opposing length

Claims

1. A capacitance-type inertial sensor comprising: a disk; and a plurality of electrodes facing, at a distance from, an outer peripheral surface extending in a circumferential direction of the disk, the plurality of electrodes including: a drive electrode to which a voltage for driving the disk is applied; a detection electrode for detecting a change in capacitance between the disk and the plurality of adjustment electrodes to which a voltage for adjusting a shape of the disk is applied, each of the plurality of electrodes having an opposing surface facing the outer peripheral surface of the disk and an opposing length that is the length of the opposing surface in the circumferential direction of the disk, the opposing length of each of the plurality of adjustment electrodes being shorter than both the opposing length of the drive electrode and the opposing length of the detection electrode.

2. An inertial sensor as described in claim 1, wherein the plurality of adjustment electrodes include at least one first adjustment electrode that adjusts the shape of the disk to adjust the resonant frequency of the disk, and at least one second adjustment electrode that adjusts the shape of the disk to reduce unnecessary components of the detection signal output from the detection electrode.

3. The inertial sensor according to claim 2, wherein the facing length of the at least one second adjustment electrode is shorter than the facing length of the at least one first adjustment electrode.

4. An inertial sensor as described in claim 2 or 3, comprising an even number of first adjustment electrodes as the at least one first adjustment electrode, the even number of first adjustment electrodes being two first adjustment electrodes corresponding to each other in a one-to-one relationship in one or more pairs, and the disk being disposed between the two first adjustment electrodes in the even number of first adjustment electrodes.

5. The inertial sensor according to claim 4, wherein the even number of first adjustment electrodes is four or more.

6. The inertial sensor according to claim 4, wherein the two first adjustment electrodes are arranged at positions that are point-symmetric with respect to the center of the disk.

7. An inertial sensor as described in claim 2 or 3, comprising an even number of second adjustment electrodes as the at least one second adjustment electrode, the even number of second adjustment electrodes being two second adjustment electrodes corresponding to each other in a one-to-one relationship in one or more pairs, and the disk being disposed between the two second adjustment electrodes in the even number of second adjustment electrodes.

8. The inertial sensor according to claim 7, wherein the even number of the second adjustment electrodes is four or more.

9. The inertial sensor according to claim 7, wherein the two second adjustment electrodes are arranged at positions that are point-symmetric with respect to the center of the disk.

10. An inertial sensor as described in claim 2 or 3, comprising an even number of first adjustment electrodes as the at least one first adjustment electrode, the even number of first adjustment electrodes being two first adjustment electrodes corresponding to each other in a one-to-one relationship in one or more pairs, the disk being arranged between the two first adjustment electrodes in the even number of first adjustment electrodes, the at least one second adjustment electrode comprising an even number of second adjustment electrodes, the even number of second adjustment electrodes being two second adjustment electrodes corresponding to each other in a one-to-one relationship in one or more pairs, the disk being arranged between the two second adjustment electrodes in the even number of second adjustment electrodes, and the number of the even number of second adjustment electrodes being greater than the number of the even number of first adjustment electrodes.

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