JP2015081771A - Angular velocity sensor and electronic apparatus using angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular velocity sensor capable of outputting an angular velocity at standstill and stable angular velocity sensitivity while reducing vibration leakage from an angular velocity detection element.SOLUTION: An angular velocity detection element 101 includes: a base part 102; a pair of arms 103a and 103b each extending from the base part 102; a first frame 104 connected to the pair of arms 103a and 103b; and a second frame 106 connected to the first frame 104 via two connection parts 105a and 105b. The pair arms 103a and 103b and the two connection parts 105a and 105b are disposed on an identical shaft.

Description

  The present invention relates to an angular velocity sensor used in various electronic devices.

  Conventionally, as an angular velocity sensor, a vibration angular velocity sensor using Coriolis force is known. In recent years, there has been proposed a technique that can detect angular velocities around a plurality of axes with a single detection element, particularly using a MEMS (Micro Electro Mechanical Systems) technique.

  Hereinafter, an example of a conventional angular velocity sensor will be described with reference to the drawings.

  FIG. 11 is a top view of a detection element used in a conventional angular velocity sensor.

  In FIG. 11, the conventional angular velocity detecting element 201 includes two arms 202, two support portions 203 that support the arms 202, two support fixing portions 204, each support portion 203, and each support fixing portion 204. Two detection units 205 to be connected. Here, the angular velocity detection element 201 is fixed to an angular velocity sensor package (not shown) via the support fixing portion 204.

  The operation of the angular velocity detection element 201 will be described with reference to FIG.

  A driving signal is given to the angular velocity detecting element 201 from a driving circuit (not shown), and as shown in FIG. 12A, the two arms 202 are mutually connected along the X-axis direction in the drawing by the piezoelectric effect or the like, for example. Drives and vibrates in the opposite direction. At this time, when an angular velocity is applied about the Y axis or the Z axis orthogonal to the X axis, a Coriolis force acts in a direction perpendicular to the driving vibration direction in a plane perpendicular to the angular velocity rotation axis. For example, when an angular velocity is applied around the Y axis, a Coriolis force acts in the Z-axis direction in the drawing as shown in FIG. 12B, and when an angular velocity is applied around the Z-axis, as shown in FIG. Coriolis force acts in the Y-axis direction in the figure. As a result, detection vibration corresponding to the direction of each Coriolis force is generated in the detection element, and distortion is applied to the arm or the detection unit. This distortion can be detected as an electrical signal by the piezoelectric effect, for example, and output as an angular velocity signal by a connected detection circuit (not shown).

  For example, Patent Literature 1 is known as prior literature information related to the invention of this application.

Japanese Patent No. 3783697

  However, in the above-described conventional configuration, when the detection vibration occurs, the distortion generated in the arm 202 and the detection unit 205 is transmitted to the support fixing unit 204 and detected from the angular velocity detection element 201 to the outside through the support fixing unit 204. Vibration is likely to leak. For this reason, when used as an angular velocity sensor, there is a problem that the detected vibration is easily affected by disturbance, and the angular velocity output and the angular velocity sensitivity at the time of stationary are not stable.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to provide an angular velocity sensor that reduces vibration leakage from the angular velocity detection element and has a stable angular velocity output and angular velocity sensitivity at rest.

  In order to achieve the above object, an angular velocity sensor according to the present invention is an angular velocity sensor including an angular velocity detection element, and the detection element includes a base, a pair of arms extending from the base, and the pair of arms. A first frame part connected to the first frame part and a second frame part connected to the first frame part via two connection parts, the pair of arms and the two connection parts, It shall be the composition arranged on the same axis.

  With the above configuration, even if a detection vibration occurs in the angular velocity detection element, the first frame portion and the second frame portion can vibrate so as to cancel each other. Vibration leakage from the base can be suppressed. Therefore, the detection vibration is not easily affected by the influence of disturbance, and it is possible to provide an angular velocity sensor with stable angular velocity output and angular velocity sensitivity at rest.

The top view of the angular velocity detection element in Embodiment 1 of this invention Example of arrangement of drive electrode and monitor electrode of the detection element Sectional drawing of the A-A 'part of the same detection element Explanatory drawing of drive vibration of the detection element Explanatory drawing of detection vibration of the same detection element An example of arrangement of detection electrodes of the same detection element Top view of another example of the detection element Top view of still another example of the detection element Diagram showing an angular velocity sensor equipped with the same angular velocity detection element A figure showing an electronic device equipped with the same angular velocity sensor Top view of conventional angular velocity detector The figure explaining operation | movement of the conventional angular velocity detection element

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a top view of an angular velocity detecting element provided in the angular velocity sensor according to the present embodiment.

  In FIG. 1, the angular velocity sensor according to the present embodiment includes an angular velocity detection element 101, and the angular velocity detection element 101 includes a pair of a base 102, a first arm 103 a extending from the base 102, and a second arm 103 b. The first frame portion 104 connected to the first arm 103a and the second arm 103b, and the first frame portion 104 via the first connection portion 105a and the second connection portion 105b. A first frame 103a, a second arm 103b, a first connection portion 105a, and a second connection portion 105b on the same axis (one point in FIG. 1). The configuration is arranged on the chain line L).

  Hereinafter, each component will be described.

  The base 102 is a fixing member that supports the angular velocity detection element 101. The angular velocity detecting element 101 is fixed to a package (not shown) using an adhesive or the like. The first arm 103a and the second arm 103b extend from the base 102 in the positive and negative directions, respectively, along the Y-axis direction in the drawing. More specifically, the first arm 103 a and the second arm 103 b extend from the side surface of the base 102.

  The first frame portion 104 is disposed so as to surround the base portion 102, and is connected to the other ends of the first arm 103a and the second arm 103b. More specifically, the side surface of the other end of each of the first arm 103 a and the second arm 103 b and the side surface of the first frame portion 104 are connected.

  The second frame portion 106 is arranged outside the first frame portion 104 and is connected to the first frame portion 104 via the first connection portion 105a and the second connection portion 105b. Here, the first arm 103a, the second arm 103b, the first connecting portion 105a, and the second connecting portion 105b are arranged on the same axis (Y-axis direction in the drawing). In other words, it can be said that the first connection portion 105a and the second connection portion 105b are arranged to face each other with the base portion 102 interposed therebetween.

  Here, preferably, the base portion 102 is preferably disposed at substantially the center of the first frame portion 104 and the second frame portion 106 so as not to cause unnecessary resonance during drive vibration. In FIG. 1, the first frame portion 104 and the second frame portion 106 are rectangular, but there is no problem even if they are circular frames.

  The angular velocity detection element 101 may be formed using a piezoelectric material such as quartz, or may be formed using a non-piezoelectric material such as silicon. In particular, by using a silicon wafer, it can be formed in a very small size using a microfabrication technique, and the cost can be reduced by mass production.

  A more detailed structure and operation of the angular velocity detection element 101 will be described.

  FIG. 2 is a diagram showing an example of the arrangement of drive electrodes and monitor electrodes of the angular velocity detecting element 101 of the angular velocity sensor in the present embodiment.

  In FIG. 2, the drive electrodes 110 a to 110 d are arranged on the second frame portion 106. In addition, the monitor electrodes 115 a to 115 d are arranged on the second frame portion 106. That is, the drive electrodes 110a to 110d and the monitor electrodes 115a to 115d are provided on the same frame portion (here, the second frame portion 106). Thus, by providing on the same frame part, the signal of drive vibration can be detected efficiently.

  Incidentally, as shown in FIG. 2, it is preferable to provide monitor electrodes 115 a to 115 d on the second frame portion 106. With this configuration, it is possible to efficiently detect only the resonance of the drive vibration with the monitor electrode as compared with other resonances.

  FIG. 3 is a cross-sectional view taken along the line A-A ′ of FIG. 2. The common electrode 109, the piezoelectric body 107, and the drive electrodes 110 a to 110 d are stacked on the second frame portion 106.

  First, the operation during driving vibration will be described with reference to FIG. The angular velocity detection element 101 can be driven to vibrate by the inverse piezoelectric effect by applying an AC voltage to the drive electrodes 110a to 110d with the common electrode 109 as the ground. At this time, when an AC voltage having an opposite phase is applied to each of the drive electrodes 110a and 110d and the drive electrodes 110b and 110c, the second frame 106 is moved to the left and right with respect to the Y axis passing through the base 102 in FIG. It can be vibrated substantially symmetrically. Since the moments generated by the drive vibration cancel each other in the left-right direction, it is difficult for the moments to be transmitted to the base portion 102. Therefore, vibration leakage during drive vibration outside the angular velocity detecting element 101 can be suppressed.

  In this embodiment, the drive electrode is provided only on the second frame portion 106, but may be provided on both the first frame portion 104 and the second frame portion 106. A drive electrode may be provided only on the first frame portion 104. Here, when the drive electrode is provided only on the first frame portion 104, the monitor electrodes 115 a to 115 d are preferably provided on the first frame portion 104. With this configuration, it is possible to efficiently detect only the resonance of the drive vibration with the monitor electrode as compared with other resonances.

  The operation when the angular velocity is applied will be described with reference to FIG.

  When an angular velocity is applied around the Y axis in FIG. 5A, as shown in FIG. 5A, the second frame portion 106 that vibrates in the X axis direction is shown in FIG. Coriolis force acts in the Z-axis direction in FIG. 5B, and detection vibrations (arrows A1 to A4 in FIG. 5A) are excited.

  Here, since the second frame 106 is driven to vibrate in directions opposite to each other with respect to the Y axis passing through the base 102, the detected vibration vibrates so as to rotate with respect to the Y axis passing through the base 102 ( Arrow A3, A4). At this time, the first frame 104 connected to the second frame 106 vibrates in the directions opposite to each other around the Y axis (arrows A1 and A2) with respect to the vibration direction of the second frame 106. This is because the arms 103a and 103b and the connecting portions 105a and 105b are arranged on the same axis (the one-dot chain line L in FIG. 1), so that the first frame portion 104 and the second frame portion 106 Can vibrate in directions opposite to each other. As a result, the first frame portion 104 and the second frame portion 106 generate rotational moments in opposite directions, so that vibration (arrows) cancels the detected vibration transmitted to the first arm 103a and the second arm 103b. A3, A4). For this reason, vibration leakage due to detected vibration from the base 102 to the outside of the angular velocity detecting element 101 can be suppressed.

  When an angular velocity is applied around the Z-axis in FIG. 5B, as shown in FIG. 5B, the second frame portion 106 that vibrates in the X-axis direction, as shown in FIG. ), Coriolis force acts in the Y-axis direction, and detection vibrations (arrows A5 to A8) are excited.

  Here, since the second frame 106 is driven to vibrate in directions opposite to each other with respect to the Y axis passing through the base 102, the detected vibration vibrates so as to rotate with respect to the Z axis passing through the base 102 ( Arrows A4 and A5). At this time, the first frame portion 104 connected to the second frame portion 106 vibrates in the direction opposite to the vibration direction of the second frame portion 106 around the Z axis. This is because the arms 103a and 103b and the connecting portions 105a and 105b are arranged on the same axis (the one-dot chain line L in FIG. 1), so that the first frame portion 104 and the second frame portion 106 Can vibrate in directions opposite to each other. As a result, the first frame portion 104 and the second frame portion 106 generate rotational moments in opposite directions, and thus operate so as to cancel the detected vibration transmitted to the first arm 103a and the second arm 103b. For this reason, similarly to when an angular velocity is applied around the Y axis, vibration leakage due to detected vibration from the base 102 to the outside of the angular velocity detecting element 101 can be suppressed.

  When the angular velocities around the Y axis and the Z axis are applied, the first frame portion 104 and the second frame portion 106 are distorted by the detection vibration, so that the detection electrode is connected to the first frame portion 104 or the second frame portion. If it is arranged on 106, the angular velocity can be detected as a charge signal by the piezoelectric effect.

  Due to the above effects, the angular velocity sensor including the angular velocity detection element of the present invention can suppress vibration leakage due to the detection vibration, and the detection vibration is hardly affected by the influence of the disturbance. Therefore, it is possible to provide an angular velocity sensor with stable angular velocity output and angular velocity sensitivity when stationary.

  FIG. 6 is a diagram illustrating an example of the arrangement of the detection electrodes of the angular velocity detection element 101.

  As shown in FIG. 6, the drive electrodes 110 a to 110 d are preferably provided on the second frame portion 106 and the detection electrodes 111 a to 111 j are preferably provided on the first frame portion 104. With this configuration, only the second frame portion 106 is driven to vibrate, and the first frame portion 104 is designed not to be driven to vibrate, thereby eliminating unnecessary vibration derived from the driving vibration generated in the detection electrode when no angular velocity is applied. The signal can be suppressed, and the noise of the angular velocity output when stationary can be reduced.

  By the way, the same effect can be obtained by providing the detection electrode on the second frame portion 106 and the drive electrode on the first frame portion 104. However, the drive amplitude is greater when the drive electrode is provided on the second frame portion 106 and the second frame portion 106 is driven to vibrate than when the second frame portion 106 drives and vibrates the first frame portion 104. Since it can be increased, the angular velocity sensitivity can be increased more by providing the drive electrode on the second frame portion 106.

  As shown in FIG. 6, it is desirable to provide a plurality of detection electrodes 111 a to 111 j on the first frame portion 104. Although there is no problem even if the number of detection electrodes is one, noise of the same phase component can be removed by differential detection using a plurality of detection electrodes as a pair, so that a lower noise angular velocity sensor can be realized.

  More specifically, the detection electrodes 111a and 111b arranged substantially symmetrically with respect to the Y axis passing through the base portion 102 are used as angular velocity detection electrodes around the Y axis, and differential detection is performed by using both electrodes as a pair. As can be seen, angular velocity detection can be realized with low noise. Similarly, the detection electrodes 111c to 111f and 111g to 111j arranged substantially symmetrically with respect to the X-axis and the Y-axis passing through the base 102 are used as angular velocity detection electrodes around the Z-axis, and both electrodes are used as a pair. By detecting, angular velocity detection can be realized with low noise as described above.

  FIG. 7 is a top view showing another example of the angular velocity detecting element 101 in the present embodiment.

  The difference in this example is that the first weight part 121 is connected to the first frame part 104 and the second weight part 122 is connected to the second frame part 106. Since the mass of the vibrating body can be increased by connecting the second weight portion 122 to the second frame portion 106 that is drivingly vibrated, a larger Coriolis force acts when the angular velocity is applied, and the sensitivity is increased. There is a great effect.

  Further, in the case of the detection vibration as shown in FIG. 5, the size of the second frame portion 106 arranged on the outside is larger than the size of the first frame portion 104 arranged on the inside. The rotational moment due to vibration increases. In order to suppress vibration leaking from the base 102 to the outside, it is desirable that the rotational moments caused by the detected vibrations of the first frame portion 104 and the second frame portion 106 be adjusted to the same extent in the opposite direction as much as possible. For this reason, by connecting the first weight part 121 having an appropriate mass to the first frame part, the rotational moment due to the detected vibration can be adjusted, and the detected vibration leakage can be further reduced. At this time, it is desirable that the first weight portion 121 and the second weight portion 122 are provided in pairs so as to be symmetrical with respect to the Y axis passing through the base portion 102 as shown in the drawing. As a result, it is possible to maintain the effect of canceling the left and right moments generated during drive vibration. In addition, it is desirable to provide the first weight 121 on the inside of the first frame 104 and the second weight 122 on the outside of the second frame 106. As a result, the weight portion can be provided while the size difference between the first frame portion 104 and the second frame portion 106 is reduced, so that the rotational moment due to the detected vibration can be balanced with a smaller weight. Therefore, the angular velocity detection element 101 can be downsized.

  In this example, the first weight part 121 and the second weight part 122 are connected at the same time, but the above-described effects can be obtained even if they are connected independently. Further, when the first weight 121 and the second weight 122 are connected at the same time, when the mass of the first weight 121 is larger than the mass of the second weight 122, the first weight Since the rotational moments due to the detected vibrations of the frame portion 104 and the second frame portion 106 can be adjusted to the same extent, it is possible to effectively suppress the detection vibration leakage.

  FIG. 8 is a top view showing still another example of the angular velocity detecting element 101 in the present embodiment.

  The difference in this example is that the frame width W1 of the first frame portion 104 is thicker than the frame width W2 of the second frame portion 106. Similar to the example in FIG. 7, by increasing the frame width W <b> 1 of the first frame portion 104, the rotational moment due to the detected vibration can be adjusted to the same level as the second frame portion 106. At this time, the first weight portion 121 or the second weight portion 122 can be added to further adjust the rotational moment due to the detected vibration. Here, as the frame width W1 and the frame width W2, the average frame width of the entire frame portion can be used instead of the width of a specific portion of the first frame portion 104 and the second frame portion 106, respectively.

  Hereinafter, the configuration and operation of the angular velocity sensor 1 including the angular velocity detection element 101 will be described.

  FIG. 9 is a diagram showing an example of the configuration of the angular velocity sensor 1 of the present invention.

  The drive circuit 3 in FIG. 9 oscillates and drives the angular velocity detection element 101 by an oscillation loop.

  The angular velocity sensor 1 includes an angular velocity detection element 101, a drive circuit 3 for oscillating and driving the angular velocity detection element 101 with a drive signal, and a detection signal (charge) generated in the angular velocity detection element 101 due to an inertial force applied from the outside. And a detection circuit 4 for processing.

  The detection circuit 4 includes an I / V conversion amplifier 5 (hereinafter, detection amplifier 5), a detector 6, and a low-pass filter 7 (LPF 7).

  An I / V conversion amplifier 8 (hereinafter referred to as an input amplifier 8) provided in the first stage of the drive circuit 3 is an integral type current / voltage conversion amplifier having an operational amplifier, a feedback resistor Rf, and a feedback capacitor Cf and having a low-pass filter characteristic. . The input amplifier 8 is one of the constituent elements of the oscillation loop, and converts the monitor signals (charges) from the monitor electrodes 115a to 115d into voltage signals. In addition, a phase shifter 9 that rotates the voltage signal by 90 ° and outputs the phase signal to the detection circuit 4 and an automatic gain adjustment circuit unit 10 (automatically adjusting the gain of the oscillation loop in accordance with the voltage signal) Hereinafter, the AGC circuit unit 10) is included. The AGC circuit unit 10 automatically adjusts the gain so that the loop gain of the oscillation loop becomes 1 in a steady oscillation state. A V / V conversion amplifier 12 (hereinafter referred to as an output amplifier 12) provided at the subsequent stage of the drive circuit 3 outputs a drive signal obtained by amplifying a signal from the AGC circuit unit 10 to the angular velocity detection element 101.

  An angular velocity detection element 101 is connected to the drive circuit 3. In FIG. 9, D1 is a monitor terminal for outputting a monitor signal from the angular velocity detection element 101, and D2 is a drive terminal for giving a drive signal to the angular velocity detection element 101. S is a detection terminal for outputting a detection signal from the angular velocity detection element 101.

  Next, the configuration and operation of the detection circuit 4 will be described. During normal operation, drive vibration in a predetermined direction is generated in the angular velocity detection element 101 by the oscillation loop including the drive circuit 3. Here, the drive vibration frequency is assumed to be fd. When a rotational inertia force (Coriolis force) is applied to the angular velocity detection element 101 in this state, a detection vibration due to the Coriolis force occurs in a direction orthogonal to the drive vibration due to the rotation, and a detection signal (charge) is generated from the detection terminal S. The generated detection signal is input to a detection amplifier 5 provided at the first stage of the detection circuit 4.

  However, an unnecessary signal (a component of driving vibration) is superimposed on the detection signal. In order to remove this unnecessary component, the detector 6 synchronously detects the detection signal with the reference signal for synchronous detection from the drive circuit 3. The synchronous detection reference signal is output from a phase shifter 9 that gives a predetermined phase rotation to the output signal from the input amplifier 8 of the drive circuit 3.

  In a situation where a constant angular velocity is applied to the angular velocity detecting element 101, the signal synchronously detected by the detector 6 includes a component caused by Coriolis force and a component caused by an unnecessary signal.

  The low-pass filter 7 removes components caused by unnecessary signals and outputs a desired angular velocity signal (DC).

(Second Embodiment)
In the present embodiment, an electronic device equipped with the angular velocity sensor 1 of the present invention will be described.

  FIG. 10 is a diagram showing a configuration example of an electronic device equipped with the angular velocity sensor 1 of the present invention.

  An electronic device 70 (for example, a digital camera) in FIG. 10 includes the angular velocity sensor 1, a display unit 71, a processing unit 72 such as a CPU, a memory 73, and an operation unit 74.

  The angular velocity sensor 1 includes an angular velocity detection element 101, a drive circuit 3, and a detection circuit 4, as shown in FIG. The angular velocity sensor 1 has an excellent characteristic that leakage vibration can be reduced. Therefore, the electronic device 70 incorporating the angular velocity sensor 1 of the present invention can perform high-precision camera shake correction and the like when the electronic device 70 is, for example, a video camera or a digital still camera.

  Thus, the performance of the electronic device 70 is improved by the present invention. In addition to the digital camera, the electronic device 70 may be a car navigation system, a vehicle, an aircraft, or a robot.

  The angular velocity sensor according to the present invention can provide an angular velocity sensor having a stable angular velocity output and angular velocity sensitivity at rest, and can be applied from camera shake correction use to vehicle control use.

DESCRIPTION OF SYMBOLS 1 Angular velocity sensor 3 Drive circuit 4 Detection circuit 5 I / V conversion amplifier (detection amplifier)
6 Detector 7 Low-pass filter (LPF)
8 I / V conversion amplifier (input amplifier)
9 Phase shifter 10 Automatic gain adjustment circuit (AGC circuit)
DESCRIPTION OF SYMBOLS 12 Output amplifier 70 Electronic device 71 Display part 72 Processing part 73 Memory 74 Operation part 101 Angular velocity detection element 102 Base part 103a 1st arm 103b 2nd arm 104 1st frame part 105a 1st connection part 105b 2nd connection Part 106 Second frame part 107 Piezoelectric body 109 Common electrode 110a to 110d Drive electrode 111a to 111j Detection electrode 115a to 115d Monitor electrode 121 First weight part 122 Second weight part

Claims (13)

An angular velocity sensor including an angular velocity detection element,
The angular velocity detecting element is
The base,
A pair of arms extending from the base;
A first frame connected to the pair of arms;
A second frame part connected to the first frame part via two connection parts,
An angular velocity sensor in which the pair of arms and the two connecting portions are arranged on the same axis. A drive electrode is provided on the second frame portion,
A detection electrode is provided in the first frame portion,
The angular velocity sensor according to claim 1. A drive electrode is provided on the first frame,
A detection electrode is provided in the second frame portion,
The angular velocity sensor according to claim 1. A first weight portion is connected to the first frame portion,
The angular velocity sensor according to claim 1. The first weight portion is disposed inside the first frame portion,
The angular velocity sensor according to claim 4. A second weight portion is connected to the second frame portion,
The angular velocity sensor according to claim 1. The second weight portion is disposed outside the second frame portion,
The angular velocity sensor according to claim 6. A first weight portion is connected to the first frame portion;
A second weight portion is connected to the second frame portion;
The mass of the first weight part is larger than the mass of the second weight part,
The angular velocity sensor according to claim 1. The frame width of the first frame portion is
It is thicker than the frame width of the second frame part,
The angular velocity sensor according to claim 1. The angular velocity sensor according to claim 2, wherein a monitor electrode is provided on the second frame portion. The angular velocity sensor according to claim 3, wherein a monitor electrode is provided on the first frame portion. The angular velocity sensor according to claim 1, wherein the two connection portions are arranged at positions facing each other with the base portion interposed therebetween. The electronic device provided with the angular velocity sensor in any one of Claims 1 thru | or 12.

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