JP5397171B2 - Vibration type angular velocity sensor - Google Patents

Description

  The present invention relates to a vibration type angular velocity sensor using MEMS (Micro Electro Mechanical System).

  Conventionally, with respect to an angular velocity sensor, a method is known in which angular velocities around a plurality of axes are switched in turn in order to detect angular velocities around the angular axes in a time-sharing manner (for example, Patent Documents 1 and 3). There is also known a gyroscope having means for removing unnecessary vibration in a state where angular velocity is not applied using a signal having a phase opposite to that of a signal indicating the detected vibration (for example, Patent Document 2).

JP 2006-317462 A Japanese Patent Laid-Open No. 8-122080 JP-A-6-300568

In the method of detecting angular velocities around multiple axes in a time-sharing manner, in order to accurately detect the Coriolis force around the axis corresponding to the excitation direction after switching, the vibration in the excitation direction before switching is stabilized. Need to be. Therefore, it is desirable to be able to quickly attenuate the vibration in the excitation direction before switching.
An object of the present invention is to quickly attenuate vibration in an excitation direction before switching when switching the excitation direction in an angular velocity sensor of a time-division drive system.

(1) vibrating angular velocity sensor for achieving the above object, a flexible portion, and a support portion for supporting the flexible portion, a weight portion coupled to the flexible portion for movement with said flexible portion, vibration and excitation means for vibrating the weight section immediately interlinked plurality of driving direction, and detecting means for detecting the vibration of the weight section in the detection direction corresponding to the Coriolis force, the weight part in the driving direction before switching Generated based on signals related to the vibration of the weight part before switching during the switching period from the end of the application of the driving signal to be applied until the driving signal to vibrate the weight part in a different excitation direction is applied. And a stabilization control means for applying the determined stabilization signal to the excitation means .
According to the present invention, the vibration in the excitation direction before switching can be attenuated faster than in the case where static vibration is not applied. By quickly attenuating vibration in the excitation direction, the time-division operating frequency can be increased.

(2) In the vibrating angular velocity sensor for achieving the above object, the electrostatic constant control means, a signal obtained by inverting the phase of the signal that has been marked pressurized to said exciting means before switching, is applied to the excitation means May be.
In this case, a static signal can be generated and applied with a low-cost circuit configuration.

(3) In the vibration type angular velocity sensor for achieving the above object, the static control means may apply a signal obtained by inverting the phase of the detection signal detected by the detection means to the excitation means. .
Based on the detection signal indicating the vibration of the weight portion detected by the detection means, a signal having the opposite phase (the same amplitude and frequency) is applied to the excitation means , so that the vibration of the weight portion can be surely attenuated. it can.

(4) In the vibration type angular velocity sensor for achieving the above object, the static control means has the same amplitude as the detection signal detected by the detection means, and is applied by the excitation means before switching. A signal whose phase is inverted from that of the drive signal may be applied to the excitation means .
The amplitude of the vibration detected by the detecting means, and the phase of the weight portion is compared with the case where no static definite vibration is applied by giving the vibration of the opposite phase of the excitation vibration given by the driving means as a static definite vibration. It is possible to quickly attenuate the vibration in the excitation direction before switching.

(5) In the vibration type angular velocity sensor for achieving the above object, the static control means simulates a static signal for vibration in the excitation direction before switching, using an equivalent circuit of the excitation means and the detection means. Then, a static signal obtained by the simulation may be applied to the excitation means .
In this case, it is possible to apply to the excitation means a static definite signal that is obtained by simulation and is effective for attenuating vibration in the excitation direction before switching. As a result, the vibration of the weight portion can be attenuated faster than in the case where the static signal is not applied.

(1A) is a top view of the vibration type angular velocity sensor according to the first embodiment, and (1B) and (1C) are sectional views. (2A) is a block diagram of the vibration type angular velocity sensor according to the first embodiment, and (2B) is a diagram for explaining a signal applied to a piezoelectric element. (3A) is a block diagram of a vibration type angular velocity sensor according to the second embodiment, and (3B) is a diagram for explaining a signal applied to a piezoelectric element. (4A) is a block diagram of a vibration type angular velocity sensor according to the third embodiment, (4B) is a diagram for explaining a signal applied to a piezoelectric element, and (4C) is a circuit diagram showing an equivalent circuit.

  Hereinafter, embodiments of the present invention will be described in the following order with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.

1. First Embodiment FIG. 1 shows a first embodiment of a vibration type angular velocity sensor according to the present invention. For convenience of description, orthogonal xyz axes are defined as shown in FIG. The vibration type angular velocity sensor 1 is configured as a MEMS and is a laminated structure made of a semiconductor device material such as single crystal silicon, silicon oxide, platinum, or PZT (lead zirconate titanate). The vibration type angular velocity sensor 1 is accommodated in a package (not shown). The vibration type angular velocity sensor 1 includes a die 1a and a driving piezoelectric element 13 on which a support portion 10, a weight portion 15, beam portions 12a, 12b, 12c, and 12d, a driving piezoelectric element 13, a detecting piezoelectric element 14, and the like are formed. And a drive detection circuit (to be described later) connected to the detection piezoelectric element 14. The drive detection circuit may be formed on the die 1a, may be formed on another die accommodated in one package together with the die 1a, or one or more accommodated in a package different from the package of the die 1a. It may be formed on the die.

  The interfaces of the layers constituting the die 1a are indicated by broken lines in FIGS. 1B and 1C. The base layer 100 is made of, for example, single crystal silicon having a thickness of 625 μm. The base layer 100 is a thick layer that protrudes from the other layers. The base layer 100 constitutes most of the support portion 10 and the weight portion 15. The beam portions 12 a, 12 b, 12 c, and 12 d are composed of a spring layer 104 and an insulating layer 106. The spring layer 104 and the insulating layer 106 also constitute the upper layer portion of the support portion 10 and the weight portion 15, and are continuous over the support portion 10, the beam portions 12 a, 12 b, 12 c, 12 d, and the weight portion 15. Thereby, the support part 10, beam part 12a, 12b, 12c, 12d, and the weight part 15 are connected integrally. The spring layer 104 is made of, for example, single crystal silicon having a thickness of 10 μm. The insulating layer 106 is made of, for example, silicon oxide having a thickness of 0.5 μm. Between the base layer 100 and the spring layer 104, a stopper layer 102 that functions as an etching stopper at the time of manufacture is formed. The stopper layer 102 is made of silicon oxide having a thickness of 1 μm, for example. The driving piezoelectric element 13, the detecting piezoelectric element 14, and a wiring element (not shown) such as a conductive wire and a bonding pad are composed of a piezoelectric layer 110 and electrode layers 108 and 112 sandwiching the piezoelectric layer 110 from both sides. The electrode layers 108 and 112 are made of, for example, platinum having a thickness of 0.1 μm. The piezoelectric layer 110 is made of PZT having a thickness of 3 μm, for example.

  The support portion 10 has a rectangular frame shape. Since the support portion 10 is fixed to the package sufficiently thicker than the beam portions 12a, 12b, 12c, and 12d, it substantially behaves as a rigid body. The support portion 10 may have any shape as long as it forms a space in which the beam portions 12a, 12b, 12c, 12d and the weight portion 15 are accommodated and behaves substantially as a rigid body.

  Each of the four beam portions 12a, 12b, 12c, and 12d having flexibility has one end coupled to the support portion 10 and the other end coupled to the weight portion 15. That is, the four beam portions 12 a, 12 b, 12 c, and 12 d support the weight portion 15 inside the support portion 10. The four beam portions 12a, 12b, 12c, and 12d are arranged in a cross shape inside the support portion 10 and aligned in parallel with the xy plane. The pair of beam portions 12a and 12c is aligned in the y-axis direction and extends in the y-axis direction. The pair of beam portions 12b and 12d is aligned in the x-axis direction and extends in the x-axis direction. Since the four beam portions 12a, 12b, 12c, and 12d do not include the thick base layer 100 that protrudes from the plurality of layers constituting the weight portion 15 and the support portion 10, the four beam portions 12a, 12b, 12c, and 12d And a flat plate shape that is sufficiently thin in the z direction. Therefore, each of the four beam portions 12 a, 12 b, 12 c, and 12 d behaves as an elastic beam having one end fixed to the support portion 10 and the other end displaced with respect to the support portion 10. When the flat beam portions 12a, 12b, 12c, and 12d are bent in the z-axis direction, the weight portion 15 can vibrate in the x-, y-, and z-axis directions with respect to the support portion 10.

  The weight portion 15 has a form in which a central portion coupled to the four beam portions 12a, 12b, 12c, and 12d and four peripheral portions protruding from the central portion between the adjacent beam portions 12 are coupled. Since the weight portion 15 includes the thick base layer 100 that protrudes among the plurality of layers constituting the support portion 10, the weight portion 15 behaves as a rigid body that moves three-dimensionally with respect to the support portion 10. The central portion has the same laminated structure as the support portion 10 including the layers constituting the beam portion 12, and the peripheral portion does not include the layers constituting the beam portion 12. Since the beam portion 12 is coupled to the end portion in the z-axis direction of the weight portion 15 that is thicker than the beam portion 12 in the z-axis direction, the center of gravity of the weight portion 15 is separated from the plane including the beam portion 12 in the z-axis direction. ing. Therefore, when an inertial force in the x-axis direction or the y-axis direction acts on the weight portion 15, the motion of the center of gravity of the weight portion 15 becomes a motion accompanied by rotation around the x-axis or the y-axis. The vibration in the x-axis direction of the center of gravity of the weight portion 15 is accompanied by the bending vibration of the beam portions 12b and 12d. The vibration in the y-axis direction of the center of gravity of the weight portion 15 is accompanied by the bending vibration of the beam portions 12a and 12c. The vibration in the z-axis direction of the center of gravity of the weight portion 15 is accompanied by the bending vibration of the beam portions 12a, 12b, 12c, and 12d.

  Driving piezoelectric elements 13a, 13b, 13c, and 13d are provided as excitation portions in the vicinity of the boundaries between the beam portions 12a, 12b, 12c, and 12d and the support portions 10 on the respective surfaces. Excitation of the weight portion 15 in the y-axis direction is performed by applying excitation signals having opposite polarities to the driving piezoelectric elements 13a and 13c aligned in the y-axis direction. That is, the driving piezoelectric elements 13a and 13c function as a y-axis excitation unit. Excitation in the z-axis direction of the weight portion 15 is performed by applying excitation signals having the same polarity to the driving piezoelectric elements 13b and 13d aligned in the x-axis direction. That is, the driving piezoelectric elements 13b and 13d function as a z-axis excitation unit.

  Detecting piezoelectric elements 14a, 14b, 14c, and 14d are provided as detecting means in the vicinity of the boundary with the weight portion 15 on the surface of each beam portion 12. When the center of gravity of the weight portion 15 is displaced in the x-axis direction with respect to the support portion 10, one of the regions in the vicinity of the boundary between the surfaces of the beam portions 12b and 12d aligned in the x-axis direction and the support portion 10 extends. Shrinks. Therefore, the pair of detection piezoelectric elements 14b and 14d provided in the vicinity of the boundary between the beam portions 12b and 12d and the support portion 10 detects the vibration in the x-axis direction of the weight portion 15 relative to the support portion x. Functions as an axis detector. When the center of gravity of the weight portion 15 is displaced in the y-axis direction with respect to the support portion 10, one of the regions in the vicinity of the boundary with the support portion 10 on the surfaces of the beam portions 12a and 12c aligned in the y-axis direction extends. Shrinks. Therefore, the pair of detection piezoelectric elements 14a and 14c provided near the boundary between the beam portions 12a and 12c and the support portion 10 detects the vibration of the weight portion 15 relative to the support portion 10 in the y-axis direction. Functions as an axis detector.

  When the die 1a rotates around the x-axis, a Coriolis force parallel to the y-axis acts on the center of gravity of the weight portion 15 traveling in the z-axis direction. When the weight portion 15 vibrates in the z-axis direction, the Coriolis force parallel to the y-axis accompanying the rotation around the x-axis also vibrates, so that when the die 1a rotates around the x-axis, the center of gravity of the weight portion 15 becomes the z-axis. It vibrates parallel to the y-axis at the same frequency as the reference vibration. That is, the angular velocity around the x axis is derived based on the vibration in the y axis direction of the center of gravity of the weight portion 15.

  When the die 1a rotates around the y-axis, a Coriolis force parallel to the x-axis acts on the center of gravity of the weight portion 15 that advances in the z-axis direction. When the weight portion 15 vibrates in the z-axis direction, the Coriolis force parallel to the x-axis accompanying the rotation around the y-axis also vibrates, so that when the die 1a rotates around the y-axis, the center of gravity of the weight portion 15 becomes the z-axis. Vibrates parallel to the x-axis at the same frequency as the reference vibration. That is, the angular velocity around the y-axis is derived based on the vibration in the x-axis direction of the center of gravity of the weight portion 15.

  When the die 1a rotates around the z-axis, a Coriolis force parallel to the x-axis acts on the center of gravity of the weight portion 15 traveling in the y-axis direction. When the weight portion 15 vibrates in the y-axis direction, the Coriolis force parallel to the x-axis accompanying the rotation around the z-axis also vibrates. Therefore, when the die 1a rotates around the z-axis, the center of gravity of the weight portion 15 becomes the y-axis. Vibrates parallel to the x-axis at the same frequency as the reference vibration. That is, the angular velocity around the z axis is derived based on the vibration in the x axis direction of the center of gravity of the weight portion 15.

  FIG. 2A is a block diagram showing a circuit configuration of the vibration type angular velocity sensor 1. FIG. 2B is a diagram illustrating the timing and phase of signals applied to the driving piezoelectric elements 13a, 13b, 13c, and 13d (the wave number of the signal applied to the driving piezoelectric elements during the excitation period or the inversion period is It is illustrative and not limited to this). The drive signal generation circuit 21, the time division control circuit 23, and the inverting circuit 22 are part of the drive detection circuit described above. The vibrating portion 24 includes a driving piezoelectric element 13 and a detecting piezoelectric element 14 formed on the beam portions 12a, 12b, 12c, and 12d. The drive signal generation circuit 21 is a circuit that generates excitation signals Dy1, Dy2, Dz1, and Dz2 to be applied to the drive piezoelectric elements 13a, 13b, 13c, and 13d. The excitation signals Dy1, Dy2, Dz1, and Dz2 output from the drive signal generation circuit 21 are output in the y-axis direction and in the z-axis direction based on the timing generated by the time division control circuit 23. And are applied to the driving piezoelectric element. The excitation signals Dy1 and Dy2 applied to the driving piezoelectric elements 13a and 13c vibrate the center of gravity of the weight part 15 in the y-axis direction in which the beam parts 12a and 12c provided with the driving piezoelectric elements 13a and 13c are aligned. It is a signal to make. Excitation signals Dy1 and Dy2 vibrate at the same frequency and amplitude, and are out of phase with each other by π. Excitation signals Dz1 and Dz2 applied to the driving piezoelectric elements 13b and 13d are signals that vibrate the center of gravity of the weight portion 15 in the z-axis direction. The excitation signals Dz1 and Dz2 have the same frequency, amplitude, and phase.

  Based on the signals output from the detection piezoelectric elements 14a and 14c aligned in the y-axis direction, signals representing the vibration in the y-axis direction of the center of gravity of the weight portion 15 are obtained. Specifically, as described above, when the center of gravity of the weight portion 15 is displaced in the y-axis direction with respect to the support portion 10, the support portions 10 on the surfaces of the beam portions 12a and 12c aligned in the y-axis direction Since one of the regions in the vicinity of the boundary extends and the other contracts, the polarities of the signals output from the detection piezoelectric elements 14a and 14c provided on the surfaces of the beam portions 12a and 12c are opposite to each other. Therefore, a signal y representing the vibration of the center of gravity of the weight portion 15 in the y-axis direction can be obtained by taking the difference between the signals output from the detecting piezoelectric elements 14a and 14c.

  Based on the signals output from the detection piezoelectric elements 14b and 14d aligned in the x-axis direction, a signal representing the vibration in the x-axis direction of the center of gravity of the weight portion 15 is obtained. Specifically, as described above, when the center of gravity of the weight portion 15 is displaced in the x-axis direction with respect to the support portion 10, the support portions 10 on the surfaces of the beam portions 12b and 12d aligned in the x-axis direction Since one of the regions in the vicinity of the boundary extends and the other contracts, the polarities of signals output from the detecting piezoelectric elements 14b and 14d provided on the surfaces of the beam portions 12b and 12d are opposite to each other. Therefore, a signal x representing the vibration of the center of gravity of the weight portion 15 in the x-axis direction is obtained by taking the difference between these signals.

  When the center of gravity of the weight portion 15 is displaced in the z-axis direction with respect to the support portion 10, the region near the boundary with the support portion 10 on the surfaces of the beam portions 12b and 12d aligned in the x-axis direction is the other when one extends. When one of them extends and the other contracts, the other also contracts, so that the polarities of the signals output from the detecting piezoelectric elements 14b and 14d provided on the surfaces of the beam portions 12b and 12d are the same. Therefore, a signal z representing the vibration of the center of gravity of the weight portion 15 in the z-axis direction is obtained by taking the sum of the signals output from the detection piezoelectric elements 14b and 14d.

  The drive signal generation circuit 21 generates excitation signals Dy1 and Dy2 for vibrating the weight portion 15 in the y-axis direction and excitation signals Dz1 and Dz2 for vibrating the weight portion 15 in the z-axis direction. The output is time-divided according to the generation timing a1. In the y-axis excitation period in which the excitation signals Dy1 and Dy2 for vibrating the weight portion 15 in the y-axis direction are applied, the signal y is treated as a signal representing the reference vibration in the y-axis direction of the center of gravity of the weight portion 15; The signal x is treated as a signal representing the Coriolis force acting with the angular velocity around the z-axis with respect to the reference vibration in the y-axis direction. In the z-axis excitation period in which the excitation signals Dz1 and Dz2 for vibrating the weight portion 15 in the z-axis direction are applied, the signal z is treated as a signal representing the reference vibration in the z-axis direction of the center of gravity of the weight portion 15, The signal x is treated as a signal representing the Coriolis force generated with the angular velocity around the y-axis with respect to the reference vibration in the z-axis direction, and generated with the angular velocity around the x-axis with respect to the reference vibration in the z-axis direction. The signal y is treated as a signal representing Coriolis force.

In the present embodiment, a signal for stabilizing the excitation vibration before switching is applied during the switching period between the y-axis excitation period and the z-axis excitation period. Specifically, based on the timing a2 generated by the time division control circuit 23, a signal obtained by inverting the phase of the excitation signal by the inverting circuit 22 is applied to the driving piezoelectric element. As a result, a signal whose phase is inverted with the same amplitude and frequency as the excitation can be applied to the driving piezoelectric element 13, and the vibration due to the excitation signal applied until immediately before the switching period can be settled. However, the application of the above-described antiphase signal is not applied until immediately before the start of the next axial excitation period, but the application is finished with a predetermined time left until the start of the next axial excitation period. That is, a period for which natural damping is left from the end of application of a signal for causing static vibration to the application of a signal for excitation in the next axial direction is provided.
According to the present embodiment, a static signal can be generated and applied at low cost.

2. Second Embodiment FIG. 3A is a block diagram showing a circuit configuration of a vibration type angular velocity sensor according to a second embodiment. FIG. 3B is a diagram illustrating the timing and phase of signals applied to the driving piezoelectric elements 13a, 13b, 13c, and 13d. Since the mechanical configuration of the vibration type angular velocity sensor is the same as that of the first embodiment, the description thereof is omitted.

  In this embodiment, before switching the excitation direction, a static signal generated based on the signals detected by the detecting piezoelectric elements 14a, 14b, 14c, 14d is applied to the driving piezoelectric elements 13a, 13b, 13c, 13d. To do. Specifically, the feedback control circuit 25 statically determines a signal for applying a vibration having the same amplitude and frequency as the vibration detected by the signals detected by the detection piezoelectric elements 14a, 14b, 14c, and 14d, but having the phase reversed. A signal is generated and applied to the driving piezoelectric elements 13a, 13b, 13c, and 13d. Note that no excitation signal is output from the drive signal generation circuit 21 during the period in which the static control signal is applied by the feedback control circuit 25. As described above, in the present embodiment, by adding the static signal generated based on the amplitude, frequency, and phase of the detection signal indicating the vibration detected by the detection piezoelectric element 14 to the drive piezoelectric element 13, The vibration can be reliably damped.

  As another embodiment, the feedback control circuit 25 is a vibration having the same amplitude as the vibration detected by the detecting piezoelectric element 14, and the phase of the vibration is reversed from that of the vibration applied by the driving piezoelectric element 13 immediately before. A signal for causing such vibration may be applied to the driving piezoelectric element 13. That is, only the amplitude may be fed back, and a signal whose phase is opposite to the phase of the vibration applied to the driving piezoelectric element 13 just before may be applied as a static signal. In this case, as in the first embodiment, a period for leaving natural attenuation is provided between the end of application of the static signal and the application of the signal for axial excitation after switching. It may be.

3. Third Embodiment FIG. 4A is a block diagram showing a circuit configuration of a vibration type angular velocity sensor according to a third embodiment. FIG. 4B is a diagram illustrating the timing and phase of signals applied to the driving piezoelectric elements 13a, 13b, 13c, and 13d. Since the mechanical configuration is the same as that of the first embodiment, description thereof is omitted. In the present embodiment, an effective static stabilization signal for damping vibration in the excitation direction before switching is simulated using an equivalent circuit of the vibration section, and the optimal static stabilization signal obtained by the simulation is It is generated by the constant signal generation circuit 26 and applied to the driving piezoelectric element 13. Note that the excitation signal is not output from the drive signal generation circuit 21 during the period in which the stabilization signal is applied by the stabilization signal generation circuit 26. FIG. 4C shows an equivalent circuit of the drive unit, the vibration unit, and the detection unit. According to the present embodiment, an effective stabilization signal can be derived by simulation, so that the vibration before switching can be reliably stabilized.

4). Other Embodiments The technical scope of the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention. For example, the materials, dimensions, and shapes shown in the above embodiment are merely examples.

  1: vibration type angular velocity sensor, 1a: die, 10: support part, 12 (12a, 12b, 12c, 12d): beam part, 13 (13a, 13b, 13c, 13d): driving piezoelectric element, 14 (14a, 14b, 14c, 14d): detection piezoelectric element, 15: weight part, 21: drive signal generation circuit, 22: inversion circuit, 23: time division control circuit, 24: vibration part, 25: feedback control circuit, 100: base layer , 102: stopper layer, 104: spring layer, 106: insulating layer, 108: electrode layer, 110: piezoelectric layer, 112: electrode layer.

Claims (6)

A flexible part;
A support part for supporting the flexible part;
A weight portion coupled to the flexible portion and moving together with the flexible portion;
Excitation means for vibrating the weight portion in a plurality of orthogonal excitation directions;
Detection means for detecting the vibration of the weight portion in the detection direction corresponding to the Coriolis force;
The weight before switching during the switching period from the end of application of the drive signal for vibrating the weight in the excitation direction before switching to the application of the drive signal for vibrating the weight in another excitation direction before switching. A static signal generated based on a signal related to the vibration of the part is applied to the excitation means leaving a predetermined time until the switching period ends, and the vibration of the weight part is naturally attenuated after the static signal is applied. A static control means for causing
A vibration type angular velocity sensor comprising:

Wherein the settling control means, a signal obtained by inverting the phase of the signal that has been marked pressurized to said exciting means before switching, it is applied to the excitation means,
The vibration type angular velocity sensor according to claim 1. The static control means applies a signal obtained by inverting the phase of the detection signal detected by the detection means to the excitation means .
The vibration type angular velocity sensor according to claim 1. Wherein the settling control means applies a same amplitude detection signal and detected by said detecting means, a signal drive signal and the phase which has been applied to the excitation means before switching is inverted, the driving means To
The vibration type angular velocity sensor according to claim 1. The static control means uses an equivalent circuit of the excitation means and the detection means to simulate a static signal for vibration in the excitation direction before switching, and to obtain a static signal obtained by the simulation. Applying to the excitation means ;
The vibration type angular velocity sensor according to claim 1.   The excitation means and the detection means are piezoelectric elements.
  The vibration type angular velocity sensor according to any one of claims 1 to 5.

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