JP2007316037A - Angular velocity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost angular velocity sensor which can be easily produced by MEMS process, and can made primary vibrations change into the outside of the same plane as a ring part. <P>SOLUTION: The ring part 11 and a drive electrode 3 are arranged within substantially the same plane, and a voltage applied to the drive electrode 3 is set the voltage value, based on the proper frequency of the ring part 11, then the ring part 11 is vibrated in three dimensions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an angular velocity sensor including a semiconductor substrate on which a vibrator having a ring portion whose vibration state changes according to an angular velocity of a detection target.

  In recent years, as an angular velocity sensor aiming at cost reduction and miniaturization, using MEMS (Micro Electro Mechanical System) technology that realizes miniaturization of various mechanical elements by applying technology in the semiconductor manufacturing process etc. An angular velocity sensor for forming a vibrator on a silicon wafer has been developed (for example, Patent Document 1).

  FIG. 6 is a partial side sectional view of the vicinity of the vibrator in Patent Document 1. In the angular velocity sensor of Patent Document 1, a vibrator having a ring part 110 is connected to a support body 120 at the center of the ring part 110 by a beam part (not shown) and supported on the support body layer 20. . Then, a drive voltage is applied between the drive electrode 40 provided in the vicinity of the ring part 110 and the ring part 110, and a predetermined vibration state (primary vibration) is created by the electrostatic force, while depending on the angular velocity of the detection target. The vibration state is changed by the Coriolis force, and this changed vibration state (secondary vibration) is detected from the secondary vibration detection electrode 30 provided in the vicinity of the ring portion 110, so that the angular velocity of the detection target can be calculated. Has been.

Here, in Patent Document 1, the primary vibration is displaced out of the same plane as the ring part 110 (three-dimensionally displaced) so that the angular velocities about the two axes can be detected simultaneously. ). For this reason, Patent Document 1 adopts a three-dimensional structure in which the drive electrode 40 is formed on the support layer 20 below the ring portion 110.
WO99 / 47891 pamphlet

  However, according to the above configuration, it is necessary to add a process for manufacturing the drive electrode 40 and to use an expensive substrate material such as an SOI wafer, and it is good at manufacturing a two-dimensional layout mechanism. There is a problem that it is difficult to apply to the system and a large cost reduction cannot be expected.

  The present invention has been made in view of the prior art, and the primary vibration can be changed out of the same plane as the ring portion by the main mechanism laid out two-dimensionally, and can be easily and inexpensively manufactured by the MEMS process. An object of the present invention is to provide an angular velocity sensor capable of

  An angular velocity sensor according to the present invention is an angular velocity sensor including a semiconductor substrate on which a vibrator having a ring portion whose vibration state changes according to an angular velocity of a detection target is formed, and electrostatically drives the vibrator. And a secondary vibration detection electrode for detecting the capacitance changed between the vibrator and the vibrator by the secondary vibration based on the primary vibration. The detection electrode is disposed on substantially the same plane as the ring portion, and by applying an alternating voltage based on a frequency unique to the ring portion to the drive electrode, the ring portion is vibrated three-dimensionally as primary vibration, An angular velocity is detected by detecting a change in the distance between the ring portion and the secondary vibration detection electrode in a plane from the secondary vibration detection electrode as a change in the capacitance. Than is.

  According to the angular velocity sensor having the above configuration, the vibrator having the ring portion is formed on the semiconductor substrate. This ring portion changes its vibration state according to the angular velocity of the detection target.

  In order to detect the change in the vibration state, the drive electrode and the secondary vibration detection electrode are disposed on substantially the same plane as the ring portion. First, the ring electrode is electrostatically driven by the drive electrode to generate primary vibration. When an angular velocity is generated in a predetermined axial direction in the detection target in a state where primary vibration has occurred, Coriolis force is generated and secondary vibration is excited. On the other hand, using the secondary vibration detection electrode, in order to detect the secondary vibration, which is a vibration state changed according to the angular velocity of the detection target, the capacitance changed between the vibrator and the secondary vibration detection electrode is changed. To detect. Thus, the angular velocity of the detection target is detected (can be calculated) based on the detected capacitance change. Since the secondary vibration is a component that vibrates in substantially the same plane as the ring portion, the vibration is detected by detecting the change in the distance between the ring portion and the secondary vibration detection electrode in the plane from the secondary vibration detection electrode. A change in capacitance due to a change in state can be detected.

  Here, in order to vibrate the primary vibration of the ring part three-dimensionally (displace it out of the same plane as the ring part), the inventor determines the frequency applied to the drive electrode based on the frequency unique to the ring part. It was found that the ring part can be vibrated three-dimensionally by resonance due to the AC voltage even when the ring part and the drive electrode are arranged in substantially the same plane. .

  Theoretically, the force vector in the direction perpendicular to the plane that excites the vibration in the three-dimensional direction is not generated in the ring portion and the drive electrode that are configured completely on the same plane. However, devices that are actually manufactured generate forces in the vertical direction due to processing errors that exist, and vibrations start. Once vibration is started, the driving electrode and the ring face are displaced from each other, so that a sufficient driving force can be obtained.

  Therefore, it is possible to change the primary vibration out of the same plane as the ring part after arranging the ring part, the drive electrode and the secondary vibration detection electrode, which are the components for detecting the change of the vibration state, in substantially the same plane. it can. In addition, by forming the angular velocity sensor capable of three-dimensional vibration in two dimensions, the MEMS process can be easily applied in the production of the angular velocity sensor, and can be produced at a lower cost.

  In addition, it is preferable that the frequency of the alternating voltage used for a drive is set to 2 times or more of the natural frequency of the primary vibration of a ring part.

  When the ring portion and the drive electrode are arranged on the same plane, a change in the distance (or the facing area) between the ring portion and the drive electrode occurs for two cycles during one cycle of the primary vibration of the ring portion. Furthermore, since the electrostatic attractive force acting between the ring part and the drive electrode functions as an elastic action, when a voltage is applied, the natural frequency of the ring part shifts to a higher level. Therefore, resonance is more likely to occur when the drive voltage is set to be twice or more the natural frequency. Furthermore, the change in elastic constant due to electrostatic attraction is non-linear (changes depending on the amount of displacement), and vibration may become unstable at a frequency lower than the resonance peak frequency. It is preferable to set the frequency side.

  Preferably, either the drive electrode or the secondary vibration detection electrode is provided inside the ring part, and the other of the drive electrode or the secondary vibration detection electrode is provided outside the ring part.

  In this case, the drive electrode is provided inside the ring portion, and the secondary vibration detection electrode is provided outside the ring portion. Alternatively, the drive electrode is provided outside the ring portion, and the secondary vibration detection electrode is provided inside the ring portion.

  Therefore, since the drive electrode and the secondary vibration detection electrode are provided in the same plane as the ring portion and on both sides of the ring portion, the electrodes can be arranged efficiently in space. In addition, by disposing the drive electrode and the secondary vibration detection electrode separately on the inner side or the outer side of the ring portion, it is possible to make it difficult to cause capacitive coupling (crosstalk) between the electrodes. Therefore, a more stable primary vibration can be generated in the drive electrode, and a secondary vibration can be detected with higher sensitivity and accuracy in the secondary vibration detection electrode.

  More preferably, the drive electrode is configured to be provided in the vicinity of a position where the amount of displacement in the direction perpendicular to the plane in the primary vibration of the ring portion is maximum.

  In this case, when primary vibration is generated by the voltage applied to the drive electrode, the amount of displacement in the direction perpendicular to the plane of the ring portion due to the primary vibration is maximized in the ring portion located in the vicinity of the drive electrode.

  As described above, since the displacement amount in the three-dimensional direction of the ring portion is maximized in the vicinity of the drive electrode, the primary vibration in the ring portion can be generated more efficiently.

  More preferably, the secondary vibration detection electrode is configured to be provided in the vicinity of a position where the amount of displacement in the direction parallel to the plane in the secondary vibration of the ring portion is maximum.

  In this case, when the vibration state changes according to the angular velocity of the detection target and secondary vibration occurs, the secondary vibration is detected at a position where the amount of displacement of the ring portion in the direction parallel to the plane including the ring portion is maximum. Electrodes are pre-arranged.

  Therefore, since the displacement amount of the ring part in the direction parallel to the plane including the ring part is maximized in the vicinity of the secondary vibration detection electrode, the secondary vibration in the ring part can be detected with higher sensitivity.

  More preferably, it is configured to include a primary vibration detection electrode that detects primary vibration caused by the drive electrode.

  In this case, the primary vibration detection electrode detects the primary vibration (change in capacitance between the vibrator and the primary vibration detection electrode) generated in the ring portion by the drive electrode.

  Here, the vibration of the ring portion may change the natural frequency of the vibration due to a change in the surrounding environment such as temperature, or may change the amplitude value of the vibration due to a change in the viscosity of the vibrator atmosphere. Therefore, in order to stabilize the primary vibration of the ring portion, it is necessary to change the voltage applied to the drive electrode in accordance with the change in the natural frequency and the change in the amplitude. Therefore, by detecting the primary vibration generated in the ring part by the primary vibration detection electrode, it becomes possible to apply feedback to the drive electrode, and the primary vibration in the ring part regardless of changes in the surrounding environment such as temperature. Can be generated more stably.

  More preferably, a vibration suppression electrode that applies an electrostatic attraction to the vibrator so as to cancel a change in capacitance detected from the secondary vibration detection electrode is provided, and a voltage applied to the vibration suppression electrode is applied to the secondary vibration detection electrode. The angular velocity is detected by detecting instead of the capacitance change of vibration.

  In this case, based on the electrostatic capacitance detected from the secondary vibration detection electrode by the secondary vibration of the ring portion, a predetermined voltage is applied to the vibration suppression electrode so as to generate a vibration that cancels this change. Then, the angular velocity is detected by detecting the voltage applied to the vibration suppression electrode instead of the capacitance change of the secondary vibration.

  Here, when the secondary vibration is generated in the ring portion, a Coriolis force different from that generated between the secondary vibration and the primary vibration between the angular velocity of the detection target may be generated. Such another Coriolis force is preferably not generated because it can be a disturbance of secondary vibration detection. Therefore, by applying a predetermined voltage to the vibration suppression electrode, the generation of the secondary vibration is canceled, and the voltage applied to the vibration suppression electrode for canceling is detected instead of the capacitance change of the secondary vibration. In other words, by canceling the Coriolis force generated by the primary vibration using the electrostatic attraction acting on the vibration suppression electrode, the magnitude of the Coriolis force (extensive angular velocity) that excites the secondary vibration without actually generating the secondary vibration. ) Can be detected. Therefore, the angular velocity can be detected with higher accuracy while eliminating the occurrence of disturbance.

  More preferably, the vibrator has a plurality of beam portions, one end of which is supported at the center of the ring portion and the other end connected to the ring portion, and the beam portion is a mode of a vibration mode in the primary vibration of the vibrator. The number of orders is twice as many as the order, and the drive electrodes are provided approximately in the middle of adjacent beam portions and inside or outside the ring portion.

  In this case, the vibrator is supported at one end on the center side of the ring portion of the beam portion, and the other end is connected to the ring portion. The beam portion is provided with a number (4, 6,..., 2n) which is twice the mode order (2, 3,..., N) of the vibration mode (cos 2θ, cos 3θ,... Cosn θ mode) in the primary vibration of the vibrator. The drive electrode is provided substantially in the middle of the beam portion and inside or outside the ring portion.

  Here, in the primary vibration that vibrates out of the plane of the ring portion, the position where the amount of displacement in the direction perpendicular to the plane of the ring portion is the maximum is twice the mode order of the vibration mode in the primary vibration, It occurs at equal intervals in the circumferential direction. On the other hand, the positions where the amount of displacement in the direction perpendicular to the plane of the ring portion is the same as this number are generated at equal intervals in the circumferential direction of the ring portion. Further, the position where the displacement amount is maximum and the position where the displacement amount is minimum occur alternately at equal intervals in the circumferential direction of the ring portion.

  Therefore, the number of beams (and drive electrodes) is twice the mode order of the vibration mode, and the drive electrode is provided at the approximate center of the adjacent beam portions, so that the displacement of the drive electrode due to the primary vibration is maximized. It becomes possible to arrange at the position, and it becomes possible to arrange the beam portion at the position where the amount of displacement due to the primary vibration is minimized. By disposing the drive electrode at a position where the displacement due to the primary vibration is maximized, the primary vibration due to the drive electrode can be further stabilized, and the beam portion is disposed at a position where the displacement due to the primary vibration is minimized. As a result, the deformation (twist) of the beam portion can be reduced to improve the durability of the vibrator, and the influence on the primary vibration due to the presence of the beam portion can be minimized.

  Preferably, the secondary vibration detection electrode detects a secondary vibration caused by an angular velocity acting around the axis of the first axis for each of the first axis and the second axis orthogonal to each other in the plane. A secondary vibration detection electrode and a second-axis secondary vibration detection electrode for detecting secondary vibration due to an angular velocity acting around the second axis are configured.

  In this case, the first axis secondary vibration detection electrode detects a change in capacitance due to the angular velocity acting around the predetermined first axis in the detection target, and the second axis secondary vibration detection electrode detects in the detection target. A change in capacitance due to the angular velocity acting around the second axis orthogonal to the first axis is detected.

  Therefore, angular velocities acting around two orthogonal axes in the detection target can be detected simultaneously.

  More preferably, the number of drive electrodes is twice as many as the mode order of the vibration mode in the primary vibration of the vibrator, and each of the first-axis secondary vibration detection electrode and the second-axis secondary vibration detection electrode is a vibrator. The number of vibration modes in the secondary vibration is twice as many as the mode order.

  In this case, the number of drive electrodes is twice as many as the mode order of the vibration mode in the primary vibration of the vibrator, and each of the first-axis secondary vibration detection electrode and the second-axis secondary vibration detection electrode is the second of the vibrator. Two times the mode order of the vibration mode in the secondary vibration is provided.

  Here, in the primary vibration that vibrates out of the plane of the ring portion, the position where the amount of displacement in the direction perpendicular to the plane of the ring portion is the maximum is twice the mode order of the vibration mode in the primary vibration, It occurs at equal intervals in the circumferential direction. Similarly, in the secondary vibration that vibrates in the plane of the ring portion, each of the secondary vibration due to the angular velocity acting around the axis of the first axis and the secondary vibration due to the angular velocity acting around the axis of the second axis, The position where the amount of displacement in the direction parallel to the plane of the ring portion is maximized is twice as many as the mode order of the vibration mode in the secondary vibration and is equally spaced in the circumferential direction of the ring portion.

  Therefore, by setting the drive electrode to twice the mode order of the vibration mode of the primary vibration, it becomes possible to place the drive electrode at all positions where the amount of displacement due to the primary vibration is maximum in the ring part. The primary vibration caused by the electrode can be generated more efficiently. In addition, by setting each secondary vibration detection electrode for the first axis and the second axis to be twice the mode order of the vibration mode of the secondary vibration, all the displacement amount due to the secondary vibration in the ring part is maximized. Since the first-axis and second-axis secondary vibration detection electrodes can be respectively disposed at the positions, it is possible to detect the change in electrostatic capacitance of the secondary vibration with higher sensitivity and higher accuracy.

  More preferably, a first-axis vibration suppression electrode that applies an electrostatic attraction to the vibrator so as to cancel a change in capacitance detected from the first-axis secondary vibration detection electrode, and a second-axis secondary vibration detection A second-axis vibration suppression electrode that applies an electrostatic attractive force to the vibrator so as to cancel a change in capacitance detected from the electrode, and the first-axis vibration suppression electrode and the second-axis vibration suppression electrode are respectively provided. The angular velocity of each axis is detected based on the applied voltage.

  In this case, each of the secondary vibrations related to the first axis and the second axis was detected from the first axis and the second axis secondary vibration detection electrode by the first axis and the second axis vibration suppression electrode. An electrostatic attraction is applied to the vibrator so as to cancel the change in capacitance.

  By applying a predetermined independent AC voltage to each of the first axis and the second axis vibration suppression electrode, the generation of secondary vibrations acting around the first axis and the second axis is canceled. At the same time, the voltage applied to the vibration suppression electrode for canceling out is detected as the magnitude of the generated Coriolis force instead of the capacitance change of the secondary vibration, whereby the angular velocity of each axis is detected. Therefore, it is possible to detect the angular velocities about two orthogonal axes with higher accuracy while eliminating the occurrence of disturbance.

  More preferably, half of the drive electrodes are used as primary vibration detection electrodes, and half of the first-axis secondary vibration detection electrode and the second-axis secondary vibration detection electrode are used as first-axis vibration suppression electrodes and It is configured to be used as a second axis vibration suppression electrode.

  In this case, the respective electrodes are arranged in a position where the effects of the respective electrodes can be maximized. Therefore, each electrode can be arranged effectively without interfering with the effect of each electrode.

  Moreover, it is preferable that a DC voltage can be applied to the ring portion.

  In this case, a DC voltage is applied to the ring part. When an AC voltage is applied by a drive electrode while a DC voltage is applied to the ring portion to electrostatically drive the ring portion, a large electrostatic force can be generated even with a small AC voltage. Here, if the AC voltage applied to the drive electrode is large, a crosstalk phenomenon in which the drive electrode and the secondary vibration detection electrode side are electrically integrated by electrostatic induction is likely to occur, causing noise. This hinders high-precision detection. Therefore, by applying a DC voltage to the ring portion, it is possible to detect secondary vibration with higher accuracy while generating an effective electrostatic force with a small AC voltage.

  According to the angular velocity sensor of the present invention, the ring part, the drive electrode, and the secondary vibration detection electrode, which are the components for detecting the change in the vibration state, are arranged in substantially the same plane, and then the primary vibration is the ring part. It can be changed out of the same plane. In addition, by forming the angular velocity sensor capable of three-dimensional vibration in two dimensions, the MEMS process can be easily applied in the production of the angular velocity sensor, and can be produced at a lower cost.

  Hereinafter, a preferred embodiment of an angular velocity sensor according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view of an angular velocity sensor according to the first embodiment of the present invention. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along the line AA in FIG. In this embodiment, the out-of-plane cos 2θ mode is adopted as the vibration mode of the primary vibration of the vibrator, and the state change of the vibrator in the in-plane cos 3θ mode, which is one of the corresponding vibration modes of the secondary vibration, is detected. However, other out-of-plane vibration modes can be employed as appropriate.

  As shown in FIG. 1, the angular velocity sensor according to the present invention is an angular velocity sensor including a semiconductor substrate 2 on which a vibrator 1 having a ring portion 11 in which a vibration state changes according to an angular velocity of a detection target, A secondary vibration that detects a change in capacitance between the drive electrode 3 that generates a primary vibration by electrostatically driving the vibrator 1 and a secondary vibration based on the primary vibration and the vibrator 1. The drive electrode 3 and the secondary vibration detection electrode 4 are arranged on substantially the same plane as the ring portion 11, and an AC voltage based on the frequency unique to the ring portion 11 is applied to the drive electrode 3. When applied, the ring portion 11 is vibrated three-dimensionally as a primary vibration, and a change in the distance between the ring portion 11 and the secondary vibration detection electrode 4 in the plane is detected as a change in the electrostatic capacitance. It is characterized in detecting the angular velocity by detecting the pole 4.

  According to the angular velocity sensor having the above configuration, the vibrator 1 having the ring portion 11 is formed on the semiconductor substrate 2. The vibration state of the ring unit 11 changes according to the angular velocity of the detection target.

  In order to detect the change in the vibration state, the drive electrode 3 and the secondary vibration detection electrode 4 are disposed on substantially the same plane as the ring portion 11. First, the ring 11 is electrostatically driven by the drive electrode 3 to generate primary vibration. When an angular velocity is generated in a predetermined axial direction in the detection target in a state where primary vibration has occurred, Coriolis force is generated and secondary vibration is excited. On the other hand, the static vibration changed between the vibrator 1 and the secondary vibration detection electrode 4 in order to detect the secondary vibration, which is a vibration state changed according to the angular velocity of the detection object, using the secondary vibration detection electrode 4. Detect capacitance. In this way, the angular velocity of the detection target is detected (can be calculated) from the detected capacitance change. Since the secondary vibration is a component that vibrates in substantially the same plane as the ring portion 11, a change in the distance between the ring portion 11 and the secondary vibration detection electrode 4 in the plane is detected from the secondary vibration detection electrode 4. Thus, a change in capacitance due to a change in vibration state can be detected.

  Here, in order to vibrate the primary vibration of the ring part 11 three-dimensionally (displace it out of the same plane as the ring part 11), the inventor uses MEMS (Micro Electro Mechanical Systems) technology to apply to the drive electrode 3. By setting the voltage to be applied to a voltage value based on the frequency unique to the ring part 11, the ring part 11 is three-dimensionally arranged even when the ring part 11 and the drive electrode 3 are arranged in substantially the same plane. It was found that it can be vibrated.

  Theoretically, in the ring portion 11 and the drive electrode 3 that are configured completely on the same plane, a force vector in a direction perpendicular to the plane that excites vibration in the three-dimensional direction is not generated. However, devices that are actually manufactured generate forces in the vertical direction due to processing errors that exist, and vibrations start. Once the vibration is started, the driving electrode and the 3-ring portion 11 are displaced from each other so that a sufficient driving force can be obtained.

  Therefore, after arranging the ring part 11, the drive electrode 3 and the secondary vibration detection electrode 4 which are the components for detecting the change of the vibration state in substantially the same plane, the primary vibration is out of the same plane as the ring part 11. Can be changed. In addition, since the main configuration mechanism is two-dimensionally arranged, it can be easily manufactured by the MEMS process, and an inexpensive angular velocity sensor can be provided. Hereinafter, each configuration will be described in more detail.

  In the present embodiment, as shown in FIG. 1B, a semiconductor substrate 2 made of silicon or the like on which a vibrator 1 and each electrode are formed by a MEMS technique is attached on a glass substrate 5 by anodic bonding. . Although not shown, the vibrator 1 may be sealed at a low pressure by attaching a similar glass substrate to the upper surface of the semiconductor substrate 2.

  The vibrator 1 is formed by etching the semiconductor substrate 2 using the MEMS technology. The vibrator 1 includes a plurality of beam portions 13 having one end supported on the glass substrate 5 by the support portion 12 at the center of the ring portion 11 and the other end connected to the ring portion 11. The number of modes of the vibration mode cos 2θ in the primary vibration of the vibrator 1 is twice as many as the mode order n = 2, that is, four are provided at equal intervals. That is, the connection points between the beam portion 13 and the ring portion 11 are provided 45 ° apart from each other in the circumferential direction of the ring portion 11. Manufacturing the ring part 11, the support part 12, and the beam part 13, which are constituent elements of the vibrator 1, from the same material, the manufacturing cost can be kept low, the introduction of MEMS technology is easy, and the fine structure However, it can be manufactured with high accuracy and ease. In addition, in order not to disturb the swing of the ring portion 11 and the beam portion 13 that can swing with the ring portion 11, the ring portion 11 and the beam portion 13 are below (if there is a glass substrate above, the upper side ) Is not provided in contact with the glass substrate 5, and a concave portion (notch portion) 51 by sandblasting is provided in a corresponding portion of the surface of the glass substrate 5.

  As shown in FIG. 1A, the drive electrode 3 is configured so that the drive electrodes 3 are provided at regular intervals inside the ring portion 11 in the middle of the adjacent beam portions 13 in a stationary state. . That is, in the present embodiment, the drive electrodes 3 are also provided on the inner side along the circumferential direction of the ring portion 11, that is, four times the number of mode orders n = 2 of the vibration mode cos 2θ in the primary vibration of the vibrator 1. It has been. Since the drive electrode 3 is manufactured by etching the same semiconductor substrate 2 simultaneously with the ring portion 11, the drive electrode 3 is provided in the same plane as the vibrator 1 formed on the semiconductor substrate 2. The same applies to other electrodes described later.

  FIG. 2 is a diagram showing a vibration mode in the angular velocity sensor of FIG. 2A is a yz plan view and an xy plan view showing an out-of-plane cos 2θ mode which is a primary vibration, and FIG. 2B is a secondary vibration when an angular velocity around the x axis is generated. FIG. 2C is an xy plan view showing a certain in-plane cos 3θ mode, and FIG. 2C is an xy plan view showing an in-plane cos 3θ mode that is a secondary vibration when an angular velocity around the y axis is generated. The broken line portion indicates the ring portion 11 in a stationary state, and the thick line portion indicates the ring portion 11 in each vibration state.

  As shown in FIG. 2A, in the primary vibration that vibrates out of the plane of the ring portion 11, the position where the displacement amount in the direction perpendicular to the plane of the ring portion 11 is the maximum is the mode of the vibration mode cos2θ in the primary vibration. The number of occurrences is twice the number of orders 2, that is, four each in the circumferential direction of the ring portion 11 at regular intervals (45 ° intervals). In FIG. 2A, there are two maximum displacement points Pd on the x-axis and y-axis, respectively. On the other hand, the positions where the amount of displacement in the direction perpendicular to the plane of the ring portion 11 is minimized occur at equal intervals in the circumferential direction of the ring portion 11. Further, the position where the displacement amount is maximum and the position where the displacement amount is minimum occur alternately at equal intervals in the circumferential direction of the ring portion (the position where the displacement amount is maximum in FIG. 2A is y = 2 points each on ± x).

  Accordingly, the number of the beam portions 13 and the number of the drive electrodes 3 are set to be twice the mode order 2 of the vibration mode cos 2θ, and the drive electrodes 3 are provided at the approximate center of the adjacent beam portions 13. Can be disposed at a position where the amount of displacement due to the primary vibration is maximized, and the beam portion 13 can be disposed at a position where the amount of displacement due to the primary vibration is minimized. By disposing the drive electrode 3 at a position where the amount of displacement due to the primary vibration is maximized, the primary vibration due to the drive electrode 3 can be excited more efficiently and the amount of displacement due to the primary vibration can be minimized. By disposing at the position, the deformation of the beam portion 13 can be reduced, the durability of the vibrator 1 can be improved, and the influence on the primary vibration due to the presence of the beam portion 13 can be minimized. .

  On the other hand, the secondary vibration detection electrode 4 is provided outside the ring portion 11. That is, in the present embodiment, the drive electrode 3 is provided inside the ring portion 11, and the secondary vibration detection electrode 4 is provided outside the ring portion 11.

  Therefore, since the drive electrode 3 and the secondary vibration detection electrode 4 are provided on both sides of the ring part 11 in the same plane as the ring part 11, the electrodes can be arranged with high space efficiency. In addition, by arranging the drive electrode 3 and the secondary vibration detection electrode 4 separately on the inside or the outside of the ring portion 11, the drive electrode 3 can generate a more stable primary vibration, and the secondary vibration. The detection electrode 4 can detect the secondary vibration with higher sensitivity and higher accuracy. The drive electrode 3 may be provided outside the ring portion 11 and the secondary vibration detection electrode 4 may be provided inside the ring portion 11.

  Here, in FIG. 2A, when the angular velocity Ωx acting around the x axis is generated and when the angular velocity Ωy acting around the y axis is generated, the acting Coriolis force is different. As shown in b) and FIG. 2C, the secondary vibrations are both in the xy plane, but their vibration directions are different and independent.

  Therefore, in the present embodiment, the secondary vibration detection electrode 4 has an angular velocity Ωx acting around the x-axis about each of the x-axis that is the first axis orthogonal to the plane and the y-axis that is the second axis in the plane. X-axis secondary vibration detection electrode (first-axis secondary vibration detection electrode) 41 for detecting secondary vibration due to, and y-axis secondary vibration detection for detecting secondary vibration due to angular velocity Ωy acting around the y-axis axis And an electrode (second axis secondary vibration detection electrode) 42.

  In this case, the x-axis secondary vibration detection electrode 41 detects a change in capacitance due to the angular velocity Ωx acting around the x-axis in the detection target as shown in FIG. 42 detects a change in capacitance due to the angular velocity Ωy acting around the y-axis orthogonal to the x-axis in the detection target.

  Therefore, the angular velocities Ωx and Ωy acting around two orthogonal axes in the detection target can be detected simultaneously.

  Further, each of the x-axis secondary vibration detection electrode 41 and the y-axis secondary vibration detection electrode 42 is provided twice as many as the mode order 3 of the vibration mode cos3θ in the secondary vibration of the vibrator 1, that is, six. Each of the x-axis and y-axis secondary vibration detection electrodes 41 and 42 is provided in the vicinity of a position where the amount of displacement in the direction parallel to the plane in the secondary vibration of the ring portion is maximum. Composed.

  Here, in the secondary vibration that oscillates in the plane of the ring portion 11, each of the secondary vibration caused by the angular velocity Ωx acting around the x axis and the secondary vibration caused by the angular velocity Ωy acting around the y axis, respectively. The positions where the amount of displacement in the direction parallel to the plane is maximum occur twice as many as the mode order 3 of the vibration mode cos3θ in the secondary vibration, that is, six at regular intervals in the circumferential direction of the ring portion 11.

  More specifically, when an angular velocity Ωx around the x-axis occurs in the primary vibration of FIG. 2A, as shown in FIG. 2B, two points on the y-axis and the two points The maximum displacement point Px exists at a position spaced apart by 60 ° in the circumferential direction of the ring portion 11. Similarly, in the primary vibration of FIG. 2A, when an angular velocity Ωy about the y-axis occurs, as shown in FIG. 2C, two points on the x-axis and the two points from the two points The maximum displacement points Py exist at positions spaced apart at 60 ° intervals in the circumferential direction. Therefore, in the present embodiment, the x-axis secondary vibration detection electrode 41 is disposed on the radially outer side of the displacement point Px, and the y-axis secondary vibration detection electrode 42 is disposed on the radially outer side of the displacement point Py.

  As described above, the secondary vibration detection electrodes 41 and 42 with respect to the x-axis and the y-axis are respectively set to twice the mode order 3 of the vibration mode cos3θ of the secondary vibration, whereby the ring portion 11 is displaced by the secondary vibration. Since the x-axis and y-axis secondary vibration detection electrodes 41 and 42 can be arranged at all the positions (displacement points) Px and Py where the amount is maximum, respectively, the capacitance change of the secondary vibration can be further reduced. It can be detected with high sensitivity and high accuracy.

  FIG. 3 is a wiring diagram of the angular velocity sensor of FIG. In FIG. 3, the wiring for the x-axis secondary vibration detection electrode 41 is omitted for easy understanding, but can be realized in the same manner as the wiring for the y-axis secondary vibration detection electrode 42.

  First, an AC power supply 7 for applying a drive voltage for primary vibration is connected between the drive electrode 3 and the ring portion 11. A detection amplifier 8 is connected to the (y-axis) secondary vibration detection electrode 4 (42). On the other hand, a DC power source 6 is connected to the ring portion 11 of the vibrator 1 via a support 12 and a beam portion 13, and a DC voltage is applied to the ring portion 11. As a result, the vibrator 1 side is at a higher potential than the secondary vibration detection side grounded by the detection amplifier 8 by a DC voltage.

  In this state, a voltage is applied from the AC power supply 7 to the drive electrode 3 to cause primary vibration. In this state, when the vibration state changes according to the angular velocity of the detection target and secondary vibration as shown in FIG. 2C occurs, the distance between the ring portion 11 and the secondary vibration detection electrode 4 is displaced. To do. Accordingly, the capacitance C changes. The change in capacitance C (dC / dt) is proportional to the detected current value (I = dQ / dt) (dQ / dt = VdC / dt V is the difference between the vibrator 1 and the secondary vibration detection electrode 4. Potential difference). Therefore, the detection amplifier 8 converts the alternating current value flowing through the secondary vibration detection electrode 4 into an alternating voltage value and outputs it.

  In the present embodiment, the secondary vibration detection electrodes 4 are provided at all six positions of the maximum displacement point Py of the secondary vibration. However, as shown in FIG. Since the phases are opposite to each other, also in the wiring, as shown in FIG. 3, the electrodes having the same phase in the detected secondary vibration are connected to the same detection amplifier 8. Here, two detection amplifiers 8 are provided for the y-axis secondary vibration detection electrode 41 (four in total including the x-axis system), and the y-axis secondary vibration detection electrode 42 (or the x-axis secondary vibration detection electrode). 41) adjacent y-axis secondary vibration detection electrodes 42 (or x-axis secondary vibration detection electrodes 41) are connected to different detection amplifiers 8. Therefore, in-phase detection currents detected from the respective secondary vibration detection electrodes 4 are added by the respective detection amplifiers 8 and then converted into AC voltages. Here, the AC voltage output from one detection amplifier 8 and the AC voltage output from the other detection amplifier 8 are inverted in phase. Therefore, by inverting any one of the outputs by the inverting circuit 9 and adding, all the capacitance changes detected from all the secondary vibration detection electrodes 4 can be effectively added. Thereby, the detection sensitivity in the secondary vibration detection electrode 4 can be made high, and highly accurate and stable detection can be performed.

  Here, applying a DC voltage to the ring portion 11 has an advantage that not only can it be used for current detection in the detection amplifier 8, but also a large electrostatic force can be generated even with a small AC voltage. Here, if the AC voltage applied to the drive electrode 3 is large, the crosstalk phenomenon that the drive electrode 3 and the secondary vibration detection electrode 4 side are electrically integrated by electrostatic induction is likely to occur, and the cause of the noise Thus, high-precision detection is hindered. Therefore, by applying a DC voltage to the ring portion, it is possible to detect secondary vibration with higher accuracy while generating an effective electrostatic force with a small AC voltage.

  In addition, it is preferable that the frequency of the alternating voltage used for a drive is set to 2 times or more of the natural frequency of the primary vibration of the ring part 11.

  When the ring part 11 and the drive electrode 3 are arranged on the same plane, the change in the distance (or the facing area) between the ring part 11 and the drive electrode 3 is 2 periods during one period of the primary vibration of the ring part 11. Occurs for minutes. Furthermore, since the electrostatic attractive force acting between the ring part 11 and the drive electrode 3 also functions as an elastic action, when a voltage is applied, the natural frequency of the ring part 11 shifts to a higher level. Therefore, resonance is more likely to occur when the drive voltage 3 is set to be twice or more the natural frequency. Furthermore, the change in elastic constant due to electrostatic attraction is non-linear (changes depending on the amount of displacement), and vibration may become unstable at a frequency lower than the resonance peak frequency. It is preferable to set the frequency side.

  The secondary vibration detection electrode 4 also detects a change in capacitance due to the primary vibration, but the change in capacitance due to the primary vibration is caused by the secondary vibration detection electrode 4 and the ring portion 11 being installed on the same plane. Therefore, the vibration is generated at a frequency twice the vibration frequency of the primary vibration and the vibration frequency of the secondary vibration. Therefore, by using a low-pass filter or the like, it is possible to easily separate and extract only the signal due to the secondary vibration.

  Subsequently, a second embodiment of the present invention will be described. FIG. 4 is a plan view showing an angular velocity sensor according to the second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The wiring diagram also conforms to the first embodiment.

  This embodiment differs from the first embodiment in that half of the drive electrodes 3 in the first embodiment are used as the primary vibration detection electrode 31 for detecting the primary vibration by the drive electrode 3 and the x-axis secondary vibration detection. Of the electrode 41 and the y-axis secondary vibration detection electrode 42, half of each of the electrodes 41 and the y-axis secondary vibration detection electrode 42 applies an electrostatic attractive force to the vibrator 1 so as to cancel the change in capacitance detected from the x-axis secondary vibration detection electrode 41. Y-axis vibration suppression that applies electrostatic attraction to the vibrator 1 so as to cancel the change in capacitance detected from the axial vibration suppression electrode (first axis vibration suppression electrode) 411 and the y-axis secondary vibration detection electrode 42 Each electrode is configured to be used as an electrode (second axis vibration suppression electrode) 421.

  The primary vibration detection electrode 31 is an electrode that detects primary vibration generated by the drive electrode 3. The detection method is the same as that of the secondary vibration detection electrode 4. Therefore, as described for the drive electrode 3, it is preferable that the drive electrode 3 be disposed at any one of the displacement points (displacement point Pd in FIG. 2A) where the displacement due to the primary vibration becomes maximum. In the present embodiment, the primary vibration detection electrode 31 is disposed on the x axis and the drive electrode 3 is disposed on the y axis so that the two drive electrodes 3 face each other and the two primary vibration detection electrodes 31 face each other. Is done.

  The vibration suppression electrodes 411 and 421 are electrodes that electrostatically drive the vibrator 1 so as to cancel the change in electrostatic capacitance detected from the secondary vibration detection electrodes 41 and 42. The method of electrostatic driving is the same as that of the driving electrode 3. Therefore, as described for the secondary vibration detection electrodes 41 and 42, the displacement point at which the displacement due to the secondary vibration becomes maximum (the angular velocity Ωx around the x axis is about the displacement points Px and y around the y axis in FIG. 2B). The angular velocity Ωy is preferably arranged at any one of the displacement points Py) in FIG. In this embodiment, each of the x-axis secondary vibration detection electrode 41 and the y-axis secondary vibration detection electrode 42 is connected to one of the detection amplifiers 8 used in the first embodiment. One set of 41 (three for each of the x-axis and y-axis) is used as the vibration suppression electrodes 411 and 421.

  Thus, by arranging all the electrodes equally, each electrode of the drive electrode 3, the primary vibration detection electrode 31, the secondary vibration detection electrode 4 (41, 42), and the vibration suppression electrodes 411, 421 can be changed. Arranged in a position that maximizes the electrode effect. Therefore, each electrode can be arranged effectively without interfering with the effect of each electrode.

  Here, by providing the primary vibration detection electrode 31, primary vibration (change in electrostatic capacitance between the vibrator 1 and the primary vibration detection electrode 31) generated in the ring portion 11 by the drive electrode 3 is detected.

  The vibration of the ring portion 11 may change its natural frequency due to changes in the surrounding environment such as temperature. Therefore, in order to stabilize the primary vibration of the ring portion 11, it is necessary to change the AC voltage applied to the drive electrode 3 in accordance with the change in the natural frequency. Therefore, it is possible to apply feedback to the drive electrode 3 by detecting the primary vibration generated in the ring portion 11 by the primary vibration detection electrode 31, and the ring portion regardless of changes in the surrounding environment such as temperature. 11 can be generated more stably.

  Further, vibration suppression electrodes 411 and 421 are provided so that an electrostatic attraction force that cancels this change is applied based on the electrostatic capacitance detected from the secondary vibration detection electrodes 41 and 42 by the secondary vibration of the ring portion 11. A predetermined alternating voltage is applied to the vibration suppression electrodes 411 and 421. And the angular velocity of each axis | shaft is detected by detecting instead of the electrostatic capacitance change of a secondary vibration as a magnitude | size of the Coriolis force which the alternating voltage applied to the vibration suppression electrodes 411 and 421 generate | occur | produced.

  Here, when a secondary vibration is generated in the ring portion 11, a Coriolis force different from that generated between the secondary vibration and the primary vibration between the angular velocity of the detection target may be generated. Such another Coriolis force is preferably not generated because it can be a disturbance of secondary vibration detection. Therefore, by applying a predetermined independent AC voltage to each of the vibration suppression electrodes 411 and 421, the occurrence of secondary vibrations acting around the x-axis and the y-axis is canceled and vibration suppression for canceling the vibration is performed. The AC voltage applied to the electrodes 411 and 421 is detected as the magnitude of the Coriolis force that generates the secondary vibration. Therefore, it is possible to detect the angular velocities about two orthogonal axes with higher accuracy while eliminating the occurrence of disturbance.

  The embodiment according to the present invention has been described above, but the present invention is not limited to the above embodiment, and various improvements, changes, and modifications can be made without departing from the spirit of the present invention. In particular, the size, number and arrangement of each electrode and the selection of the vibration mode of the primary vibration and the corresponding secondary vibration (either n−1 or n + 1 for the mode order n (n ≧ 2) of the out-of-plane primary vibration) Can be selected as appropriate according to the detection target, detection environment, and the like.

  Further, in the present embodiment, the configuration in which the ring portion 11 is supported via the beam portion 13 by the support portion 12 inside the ring portion 11 has been described, but is not limited thereto, and is supported outside the ring portion 11. It is good also as a structure by which a ring part 11 is supported from an outer side by providing a part and connecting the said support part and ring part by a beam part.

  In the present embodiment, the configuration in which the beam portion 13 is provided twice the mode order 2 of the vibration mode cos 2θ has been described. However, the present invention is not limited to this. The end portions on the 12 side are all attached at positions facing the drive electrode 3, and the end portions on the ring portion 11 side are attached so that one end is located on both sides of the drive electrode 3. FIG. 5 is a schematic view showing a modification of the angular velocity sensor of FIG. FIG. 5 differs only in that a pair of two beam portions 13 'are attached instead of the beam portion 13 of FIG. As a result, regardless of whether clockwise or counterclockwise Coriolis force is generated, the stress applied to the beam portion 13 ′ and thus the ring portion 11 does not change depending on the rotation direction, and the angular velocity is detected with higher accuracy. be able to.

It is the schematic of the angular velocity sensor in 1st Embodiment which concerns on this invention. It is a figure which shows the vibration aspect in the angular velocity sensor of FIG. It is a wiring diagram of the angular velocity sensor of FIG. It is a top view which shows the angular velocity sensor in 2nd Embodiment which concerns on this invention. It is the schematic which shows the modification of the angular velocity sensor of FIG. 10 is a partial side cross-sectional view in the vicinity of a vibrator in Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrator 2 Semiconductor substrate 3 Drive electrode 4 Secondary vibration detection electrode 11 Ring part 13 Beam part 31 Primary vibration detection electrode 41 X-axis secondary vibration detection electrode (1st axis secondary vibration detection electrode)
42 y-axis secondary vibration detection electrode (second-axis secondary vibration detection electrode)
Pd, Px, Py Maximum displacement point

Claims (12)

An angular velocity sensor including a semiconductor substrate on which a vibrator having a ring portion whose vibration state changes according to an angular velocity of a detection target is formed,
A drive electrode for generating primary vibration by electrostatically driving the vibrator;
A secondary vibration detection electrode for detecting a capacitance changed between the vibrator and the secondary vibration based on the primary vibration;
The drive electrode and the secondary vibration detection electrode are disposed on substantially the same plane as the ring portion,
By applying an alternating voltage based on the natural frequency of the ring part to the drive electrode, the ring part is vibrated three-dimensionally as primary vibration, and the distance between the ring part and the secondary vibration detection electrode in the plane is An angular velocity sensor that detects an angular velocity by detecting a change from the secondary vibration detection electrode as a change in capacitance.   The drive electrode or the secondary vibration detection electrode is provided inside the ring portion, and the other of the drive electrode or the secondary vibration detection electrode is provided outside the ring portion. Angular velocity sensor.   3. The angular velocity sensor according to claim 1, wherein the drive electrode is provided in a vicinity of a position where a displacement amount in a direction perpendicular to the plane in the primary vibration of the ring portion is maximized. 4.   The angular velocity according to any one of claims 1 to 3, wherein the secondary vibration detection electrode is provided in the vicinity of a position where a displacement amount in a direction parallel to the plane in the secondary vibration of the ring portion is maximized. Sensor.   The angular velocity sensor according to any one of claims 1 to 4, further comprising a primary vibration detection electrode that detects primary vibration caused by the drive electrode. Comprising a vibration suppression electrode that applies an electrostatic attraction to the vibrator so as to cancel the change in capacitance detected from the secondary vibration detection electrode;
The angular velocity sensor according to claim 1, wherein an angular velocity is detected by detecting a voltage applied to a vibration suppressing electrode instead of a change in capacitance of the secondary vibration. The vibrator has a plurality of beam portions in which one end is supported at the center of the ring portion and the other end is connected to the ring portion,
The number of beam portions is twice the mode order of the vibration mode in the primary vibration of the vibrator,
The angular velocity sensor according to any one of claims 1 to 6, wherein a drive electrode is provided substantially in the middle of adjacent beam portions and inside or outside the ring portion.   The secondary vibration detection electrode includes a first axis secondary vibration detection electrode for detecting secondary vibration due to an angular velocity acting around the axis of the first axis for each of the first axis and the second axis orthogonal to each other in the plane. The angular velocity sensor according to claim 1, further comprising a second-axis secondary vibration detection electrode that detects secondary vibration caused by an angular velocity acting about the axis of the second axis. The number of drive electrodes is twice as many as the mode order of the vibration mode in the primary vibration of the vibrator,
9. The number of each of the first-axis secondary vibration detection electrode and the second-axis secondary vibration detection electrode is twice as many as the mode order of the vibration mode in the secondary vibration of the vibrator. Angular velocity sensor. A first axis vibration suppression electrode that applies an electrostatic attraction to the vibrator so as to cancel the change in capacitance detected from the first axis secondary vibration detection electrode;
A second-axis vibration suppression electrode that exerts an electrostatic attraction on the vibrator so as to cancel the change in capacitance detected from the second-axis secondary vibration detection electrode;
The angular velocity sensor according to claim 9, wherein an angular velocity of each axis is detected based on a voltage applied to each of the first axis vibration suppression electrode and the second axis vibration suppression electrode.   Half of the drive electrodes are used as primary vibration detection electrodes, and half of the first-axis secondary vibration detection electrodes and second-axis secondary vibration detection electrodes are respectively used as first-axis vibration suppression electrodes and second-axis vibrations. The angular velocity sensor according to claim 10, wherein each angular velocity sensor is used as a suppression electrode. The angular velocity sensor according to claim 1, wherein a DC voltage can be applied to the ring portion.

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