JP2016095176A - Angular velocity sensor and electronic apparatus using the angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular velocity sensor capable of stably outputting angular velocity by reducing leakage of vibration from an angular velocity detection element.SOLUTION: The angular velocity sensor is a sensor which has an angular velocity detection element. The angular velocity detection element includes: a base part; a pair of arms extending from the base part; and a frame part connected to the pair of arms. The angular velocity detection element is driven to vibrate by means of piezoelectric effect. Piezoelectric body is not disposed at a displacement point of 90% or more of a maximum displacement point of the angular velocity detection element which is being driven to vibrate.SELECTED DRAWING: Figure 1

Description

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

Conventionally, as an angular velocity sensor, a vibration type angular velocity sensor using Coriolis force is known. For example,
When an angular velocity is applied while the weight is driven to vibrate, a Coriolis force is applied to the weight. As a result, a detection vibration corresponding to the direction of Coriolis force is generated, and the angular velocity can be detected by detecting this detection vibration as an electric signal.

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

JP 2012-237653 A

  However, it has been found that in the conventional configuration as described above, the weight does not completely oscillate horizontally, causing vibration leakage.

  When such vibration leakage occurs, there is a problem that the angular velocity output becomes unstable.

  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.

  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 angular velocity detection element includes a base, a pair of arms extending from the base, and the pair of pairs. A frame portion connected to the arm, the angular velocity detection element is driven to vibrate by a piezoelectric effect, and a piezoelectric body is not disposed at a displacement location of 90% or more of the maximum displacement location during the drive vibration of the angular velocity detection element. It is characterized by that.

  With the configuration described above, the angular velocity detection element does not have a piezoelectric body disposed at a displacement location of 90% or more of the maximum displacement location at the time of driving vibration, so that vibration in the thickness direction (unnecessary vibration) of the angular velocity detection element can be reduced. Therefore, leakage vibration from the angular velocity detection element to the outside can be reduced, and the resonance vibration of the angular velocity detection element is less likely to fluctuate due to the influence of the disturbance. Therefore, it is possible to provide an angular velocity sensor with stable angular velocity output. .

Top view of angular velocity detecting element in the first embodiment Sectional drawing of the AA 'part in FIG. Illustration of driving vibration of angular velocity detection element Side view of the same angular velocity detection element The figure explaining the drive vibration using the side view of the same angular velocity detection element Diagram of electronic device of Embodiment 2

(Embodiment 1)
Hereinafter, the angular velocity sensor of the present embodiment 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 of the present embodiment is an angular velocity sensor provided with an angular velocity detecting element 101, and the angular velocity detecting element 101 includes a base 102, a first arm 103a extending from the base, and a first arm 103a. 2 arms 103b and a frame portion 104 connected to each of the arms. Here, when the angular velocity detecting element 101 is driven and vibrated by the piezoelectric effect, and the displacement of the portion where the displacement is greatest during the driving vibration is defined as the maximum displacement, the displacement at the time of the driving vibration is defined on the angular velocity detecting element 101. However, a portion where 90% or more of the maximum displacement is not provided with the piezoelectric body.

  Hereinafter, each component will be described.

  The base 102 is a fixing member for supporting 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 in directions opposite to each other from the base 102 along the Y-axis direction in FIG.

  The frame portion 104 is disposed so as to surround the base portion 102, and is connected to one end of the first arm 103a and the second arm 103b. The pair of weight parts (the first weight part 105a and the second weight part 105b) are connected to the frame part 104, and are arranged at symmetrical positions on the X axis with the base part 102 in between. .

  Here, preferably, the base portion 102 is desirably arranged at substantially the center of the frame portion 104 so as not to cause unnecessary resonance in the angular velocity detection element 101. Further, it is desirable that the first weight portion 105a and the second weight portion 105b have a symmetrical shape with respect to the Y axis in the drawing passing through the center of the base portion 102.

  The shaded area and the plain area in FIG. 1 will be described. First, the displacement of the portion having the largest displacement on the angular velocity detection element 101 during drive vibration is defined as the maximum displacement. At this time, the shaded portion in FIG. 1 is a portion on the angular velocity detection element 101 where the displacement during driving vibration is 90% or less of the maximum displacement (hereinafter referred to as “a portion of 90% or less of the maximum displacement”). ). Similarly, the plain portion in FIG. 1 indicates a portion where the displacement during driving vibration is 90% or more of the maximum displacement (hereinafter referred to as “a portion where 90% or more of the maximum displacement”).

  2 is used to show a cross-sectional structure of the AA ′ portion in FIG. In the portion where 90% or more of the maximum displacement is reached, the piezoelectric body 108 is not disposed on the substrate 110. That is, on the angular velocity detecting element 101, the displacement during driving vibration is 90% or more of the maximum displacement. While the piezoelectric body 108 is not provided, the piezoelectric body 108 is disposed on the substrate 110 in a portion of 90% or less of the maximum displacement. As will be described later, the piezoelectric body 108 does not necessarily have to be disposed at all of the displacement locations that are 90% or less of the maximum displacement location. In order to give the piezoelectric body 108 a drive or detection function, it is necessary to provide an upper electrode 107 and a lower electrode 109 so as to sandwich the piezoelectric body 108.

  Here, by using a silicon wafer as the material of the substrate 110, the angular velocity detecting element 101 can be formed in a very small size using a fine processing technique, and the cost can be reduced by mass production. Further, by using platinum for the lower electrode 109, lead zirconate titanate for the piezoelectric body 108, and gold for the upper electrode 107, the electrode portion 106 having stable piezoelectric characteristics can be formed.

  The drive vibration of the angular velocity detection element 101 will be described with reference to FIG. 3A shows a state where two weights are open, and FIG. 3B shows a state where two weights are closed.

  The drive vibration is a movement in which the first weight portion 105a and the second weight portion 105b vibrate in the opposite directions along the X axis in the figure, and the two weights open or close. In this example, the tip portion P of the first weight portion 105a or the second weight portion 105b is the portion having the largest displacement during driving vibration. Hereinafter, the displacement of the tip portion P is referred to as “maximum displacement”. In the driving vibration of the angular velocity detecting element 101, the two weight portions and a part of the frame portion 104 are portions of 90% or more of the maximum displacement, and the remaining regions are portions of 90% or less of the maximum displacement. For this reason, the cross-sectional structure of the angular velocity detecting element 101 is as shown in FIG. 4, and no piezoelectric body is disposed at each weight portion which is 90% or more of the maximum displacement.

  The state of drive vibration is shown in FIG. FIG. 5A shows a state where two weights are open, and FIG. 5B shows a state where two weights are closed.

  In the portion of 90% or more of the maximum displacement, since there is no density gradient of the laminated structure of the piezoelectric body 108 and the substrate 110, the weight portion is more likely to vibrate horizontally in the X-axis direction during driving vibration than in the conventional configuration. Therefore, vibration (unnecessary vibration) in the Z-axis direction is suppressed, and leakage vibration leaking from the angular velocity detection element 101 to the outside can also be suppressed. In particular, it is desirable that the region where the piezoelectric body is not disposed is limited to a portion of 90% or more of the maximum displacement. This is because if the piezoelectric body 108 is removed to a portion of 90% or less of the maximum displacement, the electrode portion necessary for driving and detecting the angular velocity detecting element 101 becomes extremely small, and the efficiency of driving and detecting becomes worse. It is.

  Further, the width in the Y-axis direction of the portion where the piezoelectric body 108 is not provided (W2 in FIG. 1) from the width in the Y-axis direction (W1 in FIG. 1) of the first weight portion 105a and the second weight portion 105b. Is small. That is, the width in the Y-axis direction of the portion where the piezoelectric body 108 is not provided on the frame portion 104 is smaller than the width in the axis (axis passing through the center of the base portion 102 and passing through the pair of arms) of the pair of weight portions. .

  Next, the operation of the angular velocity detection element 101 will be described.

  The angular velocity detection element 101 is fixed to an angular velocity sensor package (not shown) via the base portion 102.

The angular velocity detecting element 101 is supplied with a driving voltage signal from an external driving circuit (not shown), and the first weight portion 105a and the second weight portion 105b are formed along the X-axis direction in FIG. Drive vibrations in opposite directions with respect to each other. At this time, when an angular velocity (Ω _Z ) around the Z axis in the drawing is applied to the angular velocity detecting element 101, the Y axis in the drawing is applied to the first weight portion 105a and the second weight portion 105b. Coriolis force (Fc) is applied in the opposite direction. As a result, a detection vibration corresponding to the direction of Coriolis force is generated in the angular velocity detection element 101, and distortion is applied to the first arm 103a and the second arm 103b. This distortion can be detected as an electrical signal by the piezoelectric effect and output as an angular velocity signal by a detection circuit (not shown) connected to the angular velocity detection element 101. That is, the Coriolis force generated due to the angular velocity during driving vibration is detected.

  Due to the above effects, the angular velocity sensor provided with the angular velocity detecting element of the present embodiment can reduce leakage vibration during driving vibration, and can suppress fluctuations in driving resonance vibration due to the influence of disturbance. Therefore, it is possible to provide an angular velocity sensor with stable angular velocity output.

(Embodiment 2)
In this embodiment, an electronic device on which the angular velocity sensor of Embodiment 1 is mounted will be described with reference to FIG.

  An electronic apparatus 170 (for example, a digital camera) in FIG. 6 includes an angular velocity sensor including the angular velocity detection element 101, a display unit 171, a processing unit 172 such as a CPU, a memory 173, and an operation unit 174. Yes.

  As shown in FIG. 1 and the like, the angular velocity sensor including the angular velocity detection element 101 processes the signals from the angular velocity detection element 101, the drive circuit 3 that drives and vibrates the angular velocity detection element 101, and the angular velocity detection element 101 to obtain an angular velocity signal. Is included. The angular velocity detecting element 101 has an excellent characteristic that leakage vibration can be reduced. Therefore, when the electronic device 170 including the angular velocity sensor including the angular velocity detection element 101 is, for example, a video camera or a digital still camera, processing such as high-precision camera shake correction can be performed. Performance is improved. The electronic device 170 may be a car navigation system, a vehicle, an aircraft, or a robot in addition to a digital camera.

  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.

101 Angular Velocity Detection Element 102 Base 103a First Arm 103b Second Arm 104 Frame 105a First Weight 105b Second Weight 107 Upper Electrode 108 Piezoelectric 109 Lower Electrode 110 Substrate 170 Electronic Device 171 Display 172 Processing Unit 173 Memory 174 Operation unit

Claims (8)

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 frame portion connected to the pair of arms;
A drive electrode for driving and vibrating the angular velocity detection element;
A detection electrode for detecting a Coriolis force generated due to an angular velocity during the driving vibration;
A piezoelectric body provided on the angular velocity detection element,
The drive electrode and the detection electrode are electrodes provided on the piezoelectric body,
On the angular velocity detection element, when the displacement of the portion where the displacement is greatest during the driving vibration is defined as the maximum displacement,
An angular velocity sensor in which the piezoelectric body is not provided in a portion where the displacement during the driving vibration is 90% or more of the maximum displacement on the angular velocity detection element. The angular velocity sensor according to claim 1, wherein the frame portion is disposed so as to surround the base portion and has a pair of weight portions. 3. The angular velocity sensor according to claim 2, wherein each of the pair of weight portions is symmetrical with respect to an axis passing through the center of the base portion and passing through the pair of arms. The angular velocity sensor according to claim 3, wherein, in the axial direction, the width of the portion on the frame portion where the piezoelectric body is not provided is smaller than the width of the pair of weight portions. The angular velocity sensor according to claim 4, wherein the pair of weight parts vibrate in opposite directions with the base interposed therebetween during the driving vibration. The angular velocity sensor according to claim 1, wherein the pair of arms extend in opposite directions from the base. The angular velocity sensor according to claim 1, further comprising a package that accommodates the angular velocity detection element. An electronic apparatus comprising the angular velocity sensor according to claim 1.

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