JP2012202799A - Vibration gyro improved in bias stability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance detection type vibration gyro which is capable of uniquely determining resonant frequencies of drive mass bodies which drive and displace under opposite phases, and detection mass bodies which perform detection under opposite-phase displacement, respectively, and in which the detection mass bodies are prevented from being accompanied with displacement corresponding to drive displacement because of drive vibration.SOLUTION: Right and left drive mass bodies 4 and 6 are supported while being connected to one end of at least one of first support beams 8 and 10 which are configured to make rigidity in an X direction lower than rigidity in another direction, so as to be made movable in the X direction, respectively. The right and left drive mass bodies 4 and 6 are coupled mutually by a first connecting spring 12. The rigidity of the connecting spring 12 is adjusted in at least the X direction and a Y direction. The rigidity in the X direction is adjusted so that the right and left drive mass bodies 4 and 6 have an opposite-phase vibration mode, and the rigidity in the Y direction is adjusted so that right and left detection mass bodies 14 and 16 have an opposite-phase vibration mode in cooperation with a connecting spring 26.

Description

  The present invention relates to a vibratory gyro, and more particularly to a vibratory gyro manufactured by MEMS technology.

  By so-called micromachining technology developed rapidly since the 1990s, for example, a bulk silicon wafer bonded on a silicon substrate or glass substrate having an insulating film is processed by chemical etching such as wet etching or dry etching, and mechanical A technique has been established for forming a large number of sensor structures in a single process by forming a simple sensor structure. Sensors based on such micro electro mechanical system (MEMS) technology include acceleration sensors and vibration-type gyros, and are used in many fields such as automobiles, inertial navigation, digital cameras, game machines, and the like.

  Among them, the vibrating gyroscope uses Coriolis acceleration generated when a movable object that vibrates in one direction receives a rotational motion. When the oscillating movable mass accompanies a rotational motion, the movable mass receives a Coriolis force acting in a direction orthogonal to both the vibration direction and the rotation axis direction. Displace. The movable mass body is supported by a spring that enables displacement in this direction, and the value of the Coriolis force and the angular velocity that causes the Coriolis force can be detected from the displacement amount of the movable mass body. The displacement of the movable mass body is, for example, using a parallel plate capacitor or a comb-shaped capacitor having a pair of parallel plate structures or comb-tooth structures in which one is fixed and the other is movable together. It can be determined from the change in capacity.

  The following prior art documents disclose an angular velocity sensor or a vibration gyro that uses a driving motion that vibrates in opposite phases on the left and right.

  The angular velocity sensor described in Patent Document 1 is provided side by side in a first direction, and is supported by two first vibrating bodies 1a and 1b that are supported so as to be able to vibrate in a first direction from a fixed portion 4, respectively, and an expansion / contraction direction The vibration spring 2 that connects the two first vibrating bodies 1a and 1b with the same direction in the first direction, and the fixed part and the connected first vibrating bodies 1a and 1b are on the same plane and are orthogonal to the plane. A second vibrating body 7 supported by each of the two first vibrating bodies 1a and 1b so as to be able to vibrate in a second direction, and two first pieces capable of vibrating in a second direction orthogonal to the first direction. A second vibrating body 7 supported on each of the vibrating bodies 1a and 1b, a vibration generating means 9 for vibrating the two first vibrating bodies 1a and 1b in opposite directions in the first direction, and a second An angular velocity sensor provided with vibration detecting means 13 for detecting the vibration of the vibrating body 7 in the second direction. Support is disclosed.

  Patent Document 2 discloses a microelectromechanical structure having a driving mass 3 and first sensing masses 15 a and 15 a ′ and second sensing masses 15 b and 15 b ′ suspended and supported inside the driving mass 3. Has been.

  Further, Patent Document 3 discloses an angular velocity detection device having an excitation element disposed so as to be able to vibrate on the x axis and a Coriolis element disposed so as to be able to vibrate along the y axis while following the vibration of the excitation element. It is disclosed.

  Patent Document 4 includes two individual structures 100, 200, 300, 400, 500, and 600 that are movable with respect to the substrate on the design plane xy, and the two individual structures are connected to each other. A rotational speed sensor is disclosed in which the coupling structure has no vibration mode excited by linear acceleration in a direction parallel to the y direction.

  In Patent Document 5, the driving unit 100 driven in the first direction, the detection unit 101 movable in the second direction orthogonal to the first direction, and the elastic member 101b connecting the driving unit 100 and the detection unit 101 are disclosed. The upper surface of the drive unit 100 of the first unit and the upper surface of the drive unit 100 of the second unit are detected by the detection unit 101 of the first unit and the second unit. An angular velocity sensor connected by a coupled beam 104 spaced from the upper surface of the portion 101 is disclosed.

  Further, Patent Document 6 discloses a first drive vibrator and a second drive vibrator arranged substantially symmetrically with respect to a point O on the xy plane, and any one of a substantially circular shape and a substantially polygonal shape substantially symmetrical with respect to the point O. A detection vibrator that is formed in a frame shape and surrounds the first drive vibrator and the second drive vibrator, and a first drive vibration with respect to the detection vibrator so as to be substantially symmetrical with respect to the y direction passing through the point O. A first driving spring and a second driving spring that float and support the child and the second driving vibrator so as to vibrate in the x direction, respectively, and a torsional rotational vibration of the detection vibrator about the z axis passing through the point O with respect to the substrate. A plurality of detection springs floatingly supported, a coupled spring interposed between the first drive vibrator and the second drive vibrator and configured to vibrate the first drive vibrator and the second drive vibrator; Driving means for driving the first driving vibrator and the second driving vibrator in the x direction in opposite phases; An angular velocity sensor that includes a detector for detecting a torsional rotational vibration of the z-axis around which passes through the point O of the vibrator output is disclosed.

Japanese Patent Laid-Open No. 2001-21360 JP 2010-217165 A JP 2009-2834 A Japanese translation of PCT publication 2010-53447 JP 2010-60372 A JP 2001-264068 A

  In the vibrating gyroscope described in Patent Document 1, the pair of first vibrating bodies are driven so as to have opposite phases in the X direction, and the second vibrating bodies supported by each of the first vibrating bodies are provided. Operates in the Z direction by Coriolis force. Here, the first vibrating bodies vibrate in opposite phases by a common vibrating spring (connecting spring), but the second vibrating bodies do not have a connecting spring and each constitutes a single spring mass system. Therefore, it is difficult for the second vibrating body to have a common resonance frequency (dynamic response characteristic) due to variations in the manufacturing process. For this reason, the response displacement and the phase of each of the second vibrating bodies due to the Coriolis force induced on the basis of the drive frequency are also different from each other, and the differential output sensitivity of the displacement of the second vibrating body tends to decrease. In addition, when the Z-direction acceleration disturbance is taken into account as external noise, the second vibrating body does not have a common dynamic response characteristic, and thus a residue is generated in the differential output, which may cause output noise.

  In Patent Document 5, this problem is solved by providing a coupled beam that is separated from the upper surfaces of the detection unit 101 of the first unit and the detection unit 101 of the second unit, but the etched portion is filled in the manufacturing process. It is expected that the process of filling the material 504 and forming the coupled beam 104 on the material 504 will be complicated in manufacturing. Furthermore, since the coupled beam 104 is formed of a material different from that of the element forming layer 3, there is a problem that dynamic characteristics are likely to change due to a difference in dimensional change due to a temperature change.

  As another problem, in Patent Document 1, since the second vibrating body is accompanied by the same amount of X-direction displacement due to the X-direction driving displacement of the first vibrating body, the Y-direction displacement of the second vibrating body is detected. The detection capacitance between each fixed electrode and each of the second vibrating bodies varies. This is due to the influence of manufacturing process errors and fringe capacity. As a result, even when the angular velocity is not input, a so-called leak output (quadrature error) is generated as a detection signal, leading to problems such as generation of a bias output (sensor output at zero angular velocity) and a decrease in stability. In addition to the problem described in Patent Document 1, this problem is a vibration gyro of a system that detects displacement of the second vibrating body due to Coriolis force by capacitance change, such as the vibration gyro described in Patent Documents 2 and 3. This is a common problem when the detection vibrator is accompanied by a displacement equivalent to the drive displacement and has the detection fixed electrodes facing each other.

  In Patent Document 4, as a means for solving the above-described problem, a complicated structure in which the Coriolis element 520 is coupled by a plurality of spring elements is required in addition to the detection unit 530 provided in the excitation unit.

  Accordingly, the present invention can uniquely determine the resonance frequency (dynamic response) of each of the driving mass body that undergoes reverse-phase drive displacement and the detection mass body that is detected by reverse-phase displacement, and the detection mass body is driven to vibrate. Accordingly, an object of the present invention is to provide a capacitance detection type vibration gyro which is simple in structure and manufacturing and is not accompanied by a displacement corresponding to a driving displacement.

  In order to achieve the above object, the invention according to claim 1 is configured to be fixed to a support substrate by a second support beam and excited in one direction in a plane by a Coriolis force generated by an angular velocity. Each of the left and right detection mass bodies may be driven to vibrate in a direction in a plane perpendicular to the direction in which the left and right detection mass bodies are excited by applying an angular velocity having a vector orthogonal to the plane. Left and right drive mass bodies suspended from and supported by a first support beam, and the left and right drive mass bodies are elastic first so as to have a reverse phase vibration mode that vibrates in opposite phases. The first connection spring is connected to each other by a connection spring, and the first connection spring has a spring region having elasticity in the drive vibration direction of the left and right drive mass bodies and a mode in which the left and right detection mass bodies are excited in opposite phases. And has a spring region having elasticity in the detection direction orthogonal to the driving vibration direction, is formed so as to constitute the driving mass and the detection mass body and substantially coplanar to provide a vibration gyro.

  According to a second aspect of the present invention, in the vibrating gyroscope according to the first aspect, the left and right detection mass bodies are elastic in the detected vibration direction so as to have a reverse phase vibration mode in which they vibrate in opposite phases. Provided is a vibrating gyroscope that is connected to each other by two connecting springs.

  According to a third aspect of the present invention, there is provided one rotation detection mass body fixed to a support substrate by a second support beam and configured to be rotationally excited in one direction in a plane by a Coriolis force generated by an angular velocity. Left and right drive mass bodies suspended and supported by first support beams inside the rotation detection mass body so as to drive and vibrate in one direction in the plane, the left and right drive mass bodies, Provided is a vibrating gyroscope that is coupled to each other by a first coupling spring having elasticity in the direction of the driving vibration so as to have a reversed-phase vibration mode that vibrates in mutually opposite phases.

  According to a fourth aspect of the present invention, in the vibrating gyroscope according to any one of the first to third aspects, the detection mass body or the rotation detection mass body is disposed so as to be opposed to the projection, and a gas damping force and A vibrating gyroscope further comprising an adjustment electrode for adjusting a resonance frequency of the detection mass body or the rotation detection mass body.

  According to a fifth aspect of the present invention, in the vibrating gyroscope according to any one of the first to fourth aspects, the detection mass body or the rotation detection mass body has a plurality of penetrations extending in a thickness direction of the support substrate. A vibrating gyroscope having a honeycomb structure with holes is provided.

  According to the present invention, regarding the left and right drive mass bodies and detection mass bodies, not only the antiphase frequency and dynamic characteristics of the drive vibration but also the resonance frequency and dynamic characteristics of the antiphase vibration of the detection vibration can be uniquely determined. it can. Accordingly, it is effective in reducing translational acceleration noise, detection sensitivity, and unnecessary bias. In addition, it is possible to prevent the left and right detection mass bodies from being displaced by the same amount due to the drive displacement vibration, and it is possible to greatly reduce unnecessary leakage output appearing in the detection signal, and to improve bias output reduction and stability.

  By providing the adjustment electrode, the Q value of the vibration in the detection direction can be reduced and the Q value in the driving vibration direction can be improved.

  By making the detection mass body have a honeycomb structure, it is possible to reduce the mass while maintaining rigidity.

  It is possible to provide a structure capable of forming members constituting the vibration type gyro such as the drive mass body, the detection mass body, each support beam, and the coupling spring from a single semiconductor silicon substrate having no residual strain.

1 is a plan view showing a vibrating gyroscope according to a first embodiment of the present invention. It is sectional drawing which follows the II-II line of the gyro of FIG. It is sectional drawing which follows the III-III line of the gyro of FIG. It is sectional drawing which follows the IV-IV line of the gyro of FIG. It is a top view which shows the vibration-type gyro which concerns on the 2nd Embodiment of this invention. It is sectional drawing which follows the VI-VI line of the gyro of FIG. It is sectional drawing which follows the VII-VII line of the gyro of FIG.

  FIG. 1 is a plan view showing a basic structure of a vibrating gyroscope according to a first embodiment of the present invention, and FIGS. 2 to 4 are II-II line, III-III line and IV- It is sectional drawing which shows the cut surface along IV line.

  In FIG. 1, on a support substrate 2 made of an insulating material such as glass, a functional member of a vibrating gyroscope having a bilaterally symmetric structure made of a single crystal of silicon is disposed. Specifically, the rigidity in the X direction is higher than the rigidity in the other direction so that the left and right driving mass bodies 4 and 6 are movable in the in-plane direction of the substrate 2 and the driving direction (X direction) which is the left and right direction, respectively. It is connected to and supported by one end of at least one (four in the illustrated example) first support beams 8 and 10 configured to be lowered. The left and right drive mass bodies 4 and 6 are coupled to each other by a first coupling spring 12 that is an elastic coupling element.

  The other ends of the first support beams 8 and 10 that are not connected to the drive mass bodies 4 and 6 are connected to the left and right detection mass bodies 14 and 16, respectively, and each detection mass body is a surface of the substrate 2. At least one (four in the illustrated example) is configured such that the rigidity in the Y direction is lower than the rigidity in the other direction so as to be movable in the detection direction (Y direction) that is inward and up and down. The second support beams 18 and 20 are connected to and supported by one end of the second support beams 18 and 20. The other ends of the second support beams 18 and 20 are connected to left and right anchor portions 22 and 24, respectively, and the anchor portions 22 and 24 are joined to the support substrate 2. If necessary, the left and right detection mass bodies 14 and 16 are coupled to each other by a second coupling spring 26 that is at least one (two in the illustrated example) elastic coupling element. The second connecting spring 26 has elasticity in at least the detection vibration direction so that the left and right detection mass bodies 14 and 16 have a reverse phase vibration mode in which they vibrate in opposite phases.

  2-4, the left and right drive mass bodies 4 and 6, the first support beams 8 and 10, the first coupling spring 12, the left and right detection mass bodies 14 and 16, and the second support beam 18 are shown. And 20 and the second coupling spring 26 are arranged at a predetermined distance from the support substrate 2. Therefore, these components generally form a three-dimensional movable structure on the support substrate 2 although there is a difference in their rigidity.

  As shown in FIG. 1, comb-like projections 28 and 30 are provided on the right drive mass 6 side and the opposite side in the X direction of the left drive mass 4, respectively. Opposite to 28 and 30, a driving comb electrode 32 and a driving monitor comb electrode 34 are provided on the substrate 2, respectively. Similarly, comb-shaped projections 36 and 38 are provided on the left drive mass 4 side and the opposite side in the X direction of the right drive mass 6, respectively. Oppositely, a drive comb electrode 40 and a drive monitor comb electrode 42 are provided on the substrate 2, respectively. With such a configuration, a comb drive method using electrostatic force is adopted for excitation of drive vibration, and a method of monitoring a change in capacitance is adopted for detection of drive vibration.

  As shown in FIG. 1, a comb-like projection 44 on the opposite side of the right drive mass 16 in the X direction of the left detection mass 14 and a comb-teeth shape in which the comb-teeth interval is narrower than the projection 44. A protrusion 46 is provided, and a detection fixed electrode 48 and an adjustment electrode 50 are provided on the substrate 2 so as to face the protrusions 44 and 46, respectively. Similarly, on the opposite side of the left drive mass body 14 in the X direction of the right detection mass body 16, there are a comb-like projection portion 52 and a comb-like projection portion 54 having a comb-teeth interval narrower than the projection portion 52. The detection fixed electrode 56 and the adjustment electrode 58 are provided on the substrate 2 so as to face the protrusions 52 and 54, respectively. The adjustment electrodes 50 and 58 are adjustment electrodes for reducing the Q value (quality factor indicating the sharpness of resonance characteristics) of vibration in the detection direction, and the Q value can be reduced by increasing the number of electrodes. This point will be described below.

  The vibration type gyro can improve the detection sensitivity by increasing the drive vibration displacement. For this purpose, the drive voltage applied to the drive electrode is increased and the above-described Q value of the drive direction vibration is increased. There is a need. The Q value in the driving vibration direction depends on the degree of vacuum in the package containing the vibration type gyro, and the Q value increases as the degree of vacuum increases. On the other hand, the frequency characteristic of the gyro (the amplitude and phase of the detection output with respect to the angular velocity frequency) is limited by the Q value of the vibration in the detection direction (sensitivity peak near the angular velocity frequency corresponding to the difference between the drive vibration frequency and the detected vibration frequency). Therefore, a certain limitation is imposed on the upper limit of the Q value of the vibration in the detection direction. In order to raise the Q value of the drive vibration as much as possible in the degree of vacuum satisfying the limit of the Q value of the detection direction vibration, an adjustment electrode for improving the damping effect with the surrounding gas is provided.

  The adjustment electrodes 50 and 58 are configured so that a DC potential difference is applied between the detection mass bodies 14 and 16, respectively, and are also used for the purpose of adjusting the anti-phase resonance frequency described later. As shown in FIG. 1, the protrusions 46 and 54 provided in pairs with the adjustment electrodes 50 and 58 and spaced apart from each other need to have the same size of the narrow gap. Further, at least a part of the detection fixed electrodes 48 and 56 is a servo-type vibration type in order to electrically suppress the detection displacement of the detection mass bodies 14 and 16 by electrostatic force, and to improve the detection band and sensitivity of the angular velocity frequency. Used for gyros.

  The vibratory gyro configured as described above can be manufactured by applying the following micromachining process.

  First, dry etching using an RIE (reactive ion etching) apparatus or the like is performed so that a predetermined gap (see FIG. 2-4) is formed between the glass support substrate 2 and the movable member of the gyro. To apply. However, as a region that should not be dry-etched, a resist mask, for example, is formed in advance by applying a semiconductor photolithography technique or the like except for a portion where a gap is formed.

  Next, the glass support substrate and the silicon substrate are bonded by an anodic bonding method or the like. At this stage, polishing is performed from the silicon substrate side so that the silicon substrate has a predetermined thickness, and selective sputtering of a conductive metal such as Cr & Au is performed in an area required as a bonding pad, and electrode pads are formed. (Not shown).

  Further, a resist pattern shown in the plan view of FIG. 1 is formed on the surface side of the bonded silicon substrate using a photolithographic technique using a mask material such as a photoresist. Also in this case, the region that should not be etched is protected by the resist mask.

  Next, through etching is performed in the thickness direction of the silicon substrate by dry etching using an RIE apparatus or the like. The basic structure of the vibrating gyroscope can be manufactured by a simple manufacturing process to which the micromachining technology as described above is applied.

  As described above, only the silicon substrate and the glass substrate are necessary as the material constituting the gyro. By using a glass material having a linear expansion coefficient substantially the same as that of the silicon substrate, structural strain ( Thermal strain) and stress (thermal stress) are less likely to occur, and it is possible to provide a vibration gyro that is structurally stable and excellent in characteristics.

Next, the operation of the vibration type gyro will be described. For example, the absolute amount of the Coriolis force Fy in the Y-axis direction when the rotation around the Z-axis (rotational angular velocity Ωz) is applied to the detection mass body of the mass M that vibrates at the speed Vx in the X-axis direction is
Fy = 2ΩzMVx
It is represented by For this reason, in the vibrating gyroscope that detects the angular velocity by detecting the displacement of the detected mass body due to the Coriolis force Fy, it is necessary to excite the drive mass body at the velocity Vx. As a method for this, for example, a comb drive method using an electrostatic force is used.

Between the left drive mass 4 and the left driving comb electrodes 32, and between the right drive mass 6 and the right driving comb electrodes 40, is applied to the sum of the DC voltage V _DC and AC voltage V _AC, V voltage cycle equal to the driving force of the _AC is generated. On the other hand, since the left and right drive mass bodies 4 and 6 are connected to each other by an elastic connection spring 12, they have a so-called reverse-phase vibration resonance mode that approaches or separates from each other in the X direction. Accordingly, by vibrating the frequency of V _AC to match the resonant frequency of the reverse-phase vibration mode, the driving mass 4 and 6 exhibits an inverse phase vibration approaching and moving away from each other. The vibration speed Vx is detected as an electrostatic capacitance change by the monitor comb electrodes 34 and 42 through an electric circuit and used for driving vibration control.

  When the left and right drive mass bodies 4 and 6 vibrate in the anti-phase vibration in the X direction as described above, if the angular velocity Ωz acts in the direction perpendicular to the paper surface of FIG. Occurs. This Coriolis force is transmitted to the left and right detection mass bodies 14 and 16 through the first support beams 8 and 10, respectively. Here, since the left and right detection mass bodies are movably supported in the Y direction by the second support beams 18 and 20, respectively, they vibrate in the Y direction in opposite phases. As a result, the capacitance between the comb-shaped projections 44 and 52 provided on the left and right detection mass bodies and the left and right fixed electrodes 48 and 56 respectively changes, and this change in the differential capacitance is electrically detected. The angular velocity Ωz can be detected by

  Since the left and right detection mass bodies 14 and 16 are indirectly connected to each other via the driving mass body by the connecting spring 12, or are further connected to each other by the connecting spring 26, similarly to the driving mass body, Y It has vibration modes that are out of phase with respect to direction. The coupling spring 12 has its rigidity adjusted at least in the X direction and the Y direction. Specifically, the rigidity in the X direction is such that the left and right drive mass bodies 4 and 6 have a reverse phase vibration mode, and the rigidity in the Y direction. In cooperation with the connecting spring 26, the left and right detection mass bodies 14 and 16 are adjusted to have a reverse phase vibration mode. In other words, the first coupling spring 12 has a spring region having elasticity in the driving vibration direction of the left and right driving mass bodies 4 and 6 and a mode in which the left and right detection mass bodies 14 and 16 are excited in opposite phases. And a spring region having elasticity also in the detection direction orthogonal to the drive vibration direction.

  Further, as can be seen from FIGS. 2 to 4, the connecting springs 12 and 26 can be formed so as to constitute substantially the same plane as other structures such as the drive mass bodies 4 and 6 and the detection mass bodies 14 and 16. The simple micromachining manufacturing process described above can be applied. By setting the resonance frequency of the detection mass body in the antiphase vibration mode to the resonance frequency of the antiphase vibration mode of the driving mass body or a value close to the resonance frequency, the detection sensitivity of the vibration type gyro can be increased.

  The vibration type gyro according to the present invention is characterized by not only the vibration of the driving mass body but also the reversed-phase vibration mode of the detection mass body, and in particular, the dynamic characteristics (resonance frequency) of the left and right detection mass bodies during angular velocity detection. , Gain and phase) can be made uniform. This feature is effective in preventing the occurrence of errors during detection and a decrease in sensitivity in the following points.

  When the detection mass bodies 14 and 16 are not connected by the connection springs 12 or 26, the resonance frequencies in the Y direction of the left and right detection mass bodies should be matched with a high yield due to variations in silicon etching during the gyro manufacturing process. Is difficult. When the resonance frequency is different, the displacement amplitude and phase of the dynamic response to the Coriolis force in the Y direction are also different, and the signal sensitivity is lowered when differential signal processing is performed on these. Also, when acceleration disturbance is input in the Y direction, if the left and right detection mass bodies have different dynamic responsiveness in the Y direction, they are originally canceled by signal differential processing, but residues are generated and errors occur. Is output. As described above, in the present invention in which the single reversed-phase vibration mode of the left and right detection mass bodies can be applied, it is possible to prevent the occurrence of errors due to the acceleration disturbance and the decrease in sensitivity.

  On the other hand, a significant feature of the present invention related to bias stability, which is often regarded as a problem in vibration type gyros, will be described. In the above-described embodiment, unlike the conventional case, the detection mass bodies 14 and 16 are not configured to vibrate with the same amplitude due to the drive vibrations of the left and right drive mass bodies 4 and 6, so That is, leakage output can be suppressed. Conventionally, the detection mass body vibrates with the same amplitude due to the drive vibration of the drive mass body, and the detection mass body is obtained by facing the detection mass body with a relatively narrow gap. In such a case, the gap also varies due to variations in silicon etching during the manufacturing process, particularly when the structure is manufactured, and a leak output is generated due to a capacitance change due to drive displacement.

  On the other hand, in the embodiment according to the present invention, since the drive vibration and the detection vibration are separated as described above, the leakage output (quadrature error) when there is no angular velocity input can be greatly reduced. Furthermore, it is possible to suppress the bias value and its fluctuation caused by the leakage output.

  The Coriolis force generated by the angular velocity acts on the driven left and right driving mass bodies 4 and 6, and their detected displacement is determined by the inertia force and the Y direction (the first direction supporting the detected mass bodies 14 and 16. It is determined from the rigidity of the support beams 18 and 20 of 2). Here, in order to improve the displacement detection sensitivity by reducing the rigidity without changing the antiphase resonance frequency of the detection system, it is preferable that the left and right detection mass bodies 14 and 16 have as low a mass as possible. Therefore, as shown in FIG. 1, the left and right detection mass bodies 14 and 16 have a so-called honeycomb structure having a large number of through holes extending in the thickness direction (Z direction) in order to reduce the mass while maintaining the rigidity. It is configured as.

  As described above, according to the first embodiment, the single reversed-phase vibration mode of the left and right detection mass bodies can be applied, and the vibration of the drive mass body and the vibration of the detection mass body are separated. A vibrating gyroscope with excellent sensitivity and bias stability is provided.

  Next, a vibrating gyroscope according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a plan view showing the basic structure of the vibrating gyroscope according to the second embodiment, and FIGS. 6 and 7 are cross-sectional views taken along lines VI-VI and VII-VII in FIG. 5, respectively. It is sectional drawing shown.

  As shown in FIG. 5, on a support substrate 102 made of an insulating material such as glass, a functional member of a vibrating gyroscope having a bilaterally symmetric structure made of a single crystal of silicon is disposed. Specifically, the rigidity in the X direction is larger than the rigidity in the other direction so that the left and right driving mass bodies 104 and 106 are movable in the in-plane direction of the substrate 102 and the driving direction (X direction) which is the left and right direction, respectively. It is connected to and supported by one end of at least one (four in the illustrated example) first support beams 108 and 110 configured to be lowered. The left and right drive mass bodies 104 and 106 are coupled to each other by a coupling spring 112 that is an elastic coupling element.

  The other ends of the first support beams 108 and 110 not connected to the drive mass bodies 104 and 106 are connected to one rotation detection mass body 114 having a substantially disk shape, and the rotation detection mass body 114 is a substrate. Is connected to one end of at least one rotation support beam 118 (four in the illustrated example) so as to be rotatable around a predetermined center of rotation in the in-plane direction of the two, and the other end of the rotation direction support beam 118 is Each is connected to an anchor portion 122 fixedly arranged near the center of the substrate.

  6 and 7, the left and right drive mass bodies 104 and 106, the first support beams 108 and 110, the coupling spring 112, the detection mass body 114, and the second support beam 118 are separated from the support substrate 102. They are arranged at a predetermined distance. Therefore, these components generally form a three-dimensional movable structure on the support substrate 2 although there is a difference in their rigidity. Further, as can be seen from FIGS. 6 and 7, the coupling spring 112 can be formed so as to be substantially coplanar with other structures such as the driving mass bodies 104 and 106 and the detection mass body 114, as described above. A simple micromachining manufacturing process can be applied.

  As shown in FIG. 5, comb-like protrusions 128 and 130 are provided on the right driving mass body 106 side and the opposite side in the X direction of the left driving mass body 104, respectively. Opposite to 128 and 130, a driving comb electrode 132 and a driving monitor comb electrode 134 are provided on the substrate 102, respectively. Similarly, comb-shaped projections 136 and 138 are provided on the left drive mass 104 side and the opposite side in the X direction of the right drive mass 106, respectively. Oppositely, a driving comb electrode 140 and a driving monitor comb electrode 142 are provided on the substrate 102, respectively. With such a configuration, a comb drive method using electrostatic force is adopted for excitation of drive vibration, and a method of monitoring a change in capacitance is adopted for detection of drive vibration.

  A comb-like projection 144 extending radially outward of the rotation circle of the rotational vibration detector 114 is provided at the peripheral edge of the rotational vibration detector 114, and a narrow gap is provided with respect to the projection 144. The detection fixed electrode 148 and the adjustment electrode 150 are provided on the substrate 2 so as to face each other. A detection capacitor is formed between the protrusion 144 and the detection fixed electrode 148, while a DC potential difference is applied between the protrusion 144 and the adjustment fixed electrode 150. Used for adjustment purposes. In addition, at least a part of the detection fixed electrode 148 is used in the case of a servo-vibration gyro to electrically suppress the detection displacement of the rotation detection mass body 114 with an electrostatic force and improve the detection band and sensitivity of the angular velocity frequency. Used.

  The vibrating gyroscope according to the second embodiment configured as described above can be manufactured by applying the same micromachining process as that described in the first embodiment.

  Next, the operation of the vibration type gyro according to the second embodiment will be described. Note that the left and right drive mass bodies 104 and 106 are vibrated in the opposite direction in the X direction and may be the same as in the first embodiment, and thus the description thereof is omitted.

  When mass driving bodies 104 and 106 that are oscillating in reverse phase at a constant amplitude in the X-axis direction Vx are subjected to rotation around the Z axis (rotational angular velocity Ωz), both driving mass bodies have opposite-phase Coriolis forces Fy. Works. This force is transmitted to the rotation detection mass body 114 via the first support beam 108, and as a result, rotational vibration is induced in the rotation detection mass body 114. As a result, a change in capacitance occurs in the electrode pair composed of the comb-shaped protrusion 144 and the detection fixed electrode 148 facing the comb-shaped protrusion 144. Here, as shown in FIG. 6, by configuring the electrode pair so that the opposite phase capacitance change occurs in the same rotation direction, the differential capacitance change is converted into a voltage output through an electric circuit (not shown). A detection output proportional to the angular velocity Ωz can be obtained.

  A feature of the second embodiment is that, since rotational vibration is adopted as the detection structure, a vibration mode having a single resonance frequency (in this case, a rotational vibration mode) can be used as in the first embodiment. . In addition, the detection sensitivity of the vibration type gyro can be increased by setting the resonance frequency of the rotational vibration mode to be equal to or close to the resonance frequency of the antiphase vibration mode of the driving mass body. In this way, as in the first embodiment, the dynamic characteristics (resonance frequency, gain, and phase) of the detection mass body at the time of angular velocity detection are uniquely determined, and detection errors and sensitivity reduction that have conventionally occurred can be prevented. . Furthermore, for example, even when a translational acceleration disturbance parallel to the Y-axis is input, the detected vibration direction is the torsional rotation direction, so that it is structurally resistant to displacement that causes an output error, and is robust against acceleration disturbance ( Robust) is obtained.

  Also in the second embodiment, since the drive system vibration and the detection system vibration are separated, the bias stability is excellent. That is, unlike the conventional case, the rotational vibration detection mass body 114 does not vibrate with the same amplitude due to the drive vibrations of the left and right drive mass bodies 104 and 106, so that leakage output due to a change in detected capacity due to drive vibration can be suppressed. Conventionally, the detection mass body vibrates with the same amplitude due to the drive vibration of the drive mass body, and the detection mass body is obtained by facing the detection mass body with a relatively narrow gap. In such a case, the gap also varies due to variations in silicon etching during the manufacturing process, particularly when the structure is manufactured, and a leak output is generated due to a capacitance change due to drive displacement. On the other hand, in the second embodiment according to the present invention, since the drive vibration and the detection vibration are separated as described above, the leakage output (quadrature error) when there is no angular velocity input can be greatly reduced. In addition, it is also possible to suppress the bias value and its variation caused by the leak output.

  As in the first embodiment, the Coriolis force generated by the angular velocity acts on the driven left and right drive mass bodies 104 and 106, and their detected displacement includes inertial force and rotation detection mass body 114. It is determined from the rigidity of the second support beam 118 that supports. Here, in order to improve the displacement detection sensitivity by reducing the rigidity without changing the antiphase resonance frequency of the detection system, it is preferable that the rotation detection mass body 114 has as low a mass as possible. Therefore, as shown in FIG. 5, the rotation detection mass body 114 is configured as a so-called honeycomb structure having a plurality of through holes in the thickness direction (Z direction) in order to reduce the mass while maintaining its rigidity. Yes.

  As described above, according to the second embodiment, the single reversed phase vibration mode of the detection mass body can be applied, and the vibration of the drive mass body and the vibration of the detection mass body are separated. A vibrating gyroscope having excellent bias stability is provided.

2,102 Substrate 4, 6, 104, 106 Driving mass 8, 10, 108, 110 First support beam 18, 20, 118 Second support beam 12, 112 First connection spring 26 Second connection spring 14, 16, 114 Detection mass body adjustment electrode 50, 58, 150

Claims (5)

Left and right detection mass bodies fixed to a support substrate by a second support beam and configured to be excited in one direction in a plane by a Coriolis force generated by an angular velocity;
A first support is provided in each of the left and right detection mass bodies so that driving vibration can be performed in a direction in a plane perpendicular to the direction in which the left and right detection mass bodies are excited by applying an angular velocity having a vector orthogonal to the plane. Left and right drive mass bodies suspended by beams, and
The left and right driving mass bodies are connected to each other by an elastic first connecting spring so as to have anti-phase vibration modes that vibrate in mutually opposite phases,
The first coupling spring is orthogonal to the driving vibration direction so that a spring region having elasticity in the driving vibration direction of the left and right driving mass bodies and a mode in which the left and right detection mass bodies are excited in opposite phases are provided. It has a spring region having elasticity also in the detection direction, and is formed so as to constitute substantially the same plane as the drive mass body and the detection mass body.
Vibration type gyro.   2. The vibrating gyroscope according to claim 1, wherein the left and right detection mass bodies are coupled to each other by a second coupling spring having elasticity in a detection vibration direction so as to have a reverse phase vibration mode that vibrates in opposite phases. One rotation detection mass body fixed to a support substrate by a second support beam and configured to be rotationally excited in one direction in a plane by a Coriolis force generated by an angular velocity;
Left and right drive mass bodies suspended and supported by first support beams inside the rotation detection mass body so as to be able to drive and vibrate in one direction in the plane,
The left and right drive mass bodies are connected to each other by a first connection spring having elasticity in the direction of the drive vibration so as to have a reverse phase vibration mode that vibrates in opposite phases.
Vibration type gyro.   The electrode further includes an adjustment electrode that is disposed opposite to the protrusion of the detection mass body or the rotation detection mass body and adjusts a gas damping force and a resonance frequency of the detection mass body or the rotation detection mass body. The vibrating gyroscope according to any one of 1 to 3.   The vibrating gyroscope according to claim 1, wherein the detection mass body or the rotation detection mass body has a honeycomb structure including a plurality of through holes extending in a thickness direction of the support substrate.

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