JPH08145691A - Piezoelectric oscillation gyro - Google Patents

Abstract

PURPOSE: To obtain a piezoelectric oscillation gyro having good characteristics by leading out the electrode of a piezoelectric element conveniently without causing any trouble in the operation thereof. CONSTITUTION: A plurality of electrodes 14B, 14C are formed on the surface of a piezoelectric 14A mounted on each side of a rectangular prism oscillator 12. These electrodes 14B, 14C are used for different purposes, e.g. as common electrode and drive electrode. When a drive signal is applied between the electrodes 14B, 14C, the piezoelectric 14A causes the oscillator 12 to oscillate. Since the common potential is taken out on the surface of the piezoelectric 14, the common potential is not required for the oscillator 12 and an insulator can be employed as an oscillator as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrating gyro using a piezoelectric material used in, for example, an automobile navigation system, and more specifically, a piezoelectric vibrating device having a piezoelectric element for vibrating a vibrating body. Regarding gyro.

[0002]

BACKGROUND ART A vibration gyro utilizes a mechanical phenomenon that a Coriolis force is generated perpendicularly to the vibration direction when an angular velocity is applied to a vibration body. A piezoelectric vibration gyro uses a piezoelectric element for vibration and detection. Is. Various types are already known, and they are applied to navigation systems of automobiles and camera shake adjustment of video cameras.

As an example, the one disclosed in Japanese Patent Laid-Open No. 2-266214 will be described. In FIG. 8, a piezoelectric vibrating gyro 900 is mainly composed of a vibrating body 902 made of an elinvar alloy and having a regular triangular prism shape. Piezoelectric elements 904, 906, and 908 are bonded to the central portions of the three side surfaces by an adhesive. Has been done. The piezoelectric element 904 has electrodes 90 on both main surfaces (front and back) of the piezoelectric ceramic 904.
4B and 904C are formed. The same applies to the other piezoelectric elements 906 and 908.

Electrode 908B of piezoelectric element 908 for feedback
Is connected to the input side of the oscillation circuit 910, and the output side of the oscillation circuit 910 is connected to the electrodes 904B and 906B on the input side of the piezoelectric elements 904 and 906 for excitation through fixed resistors 912 and 914, respectively. It is connected. Further, the electrodes 904B of the piezoelectric elements 904 and 906 for excitation,
906B is connected to the detection terminals 916 and 918, respectively. These detection terminals 916 and 918 are connected to the differential detection circuit 920, respectively, so that the potential difference between the detection terminals 916 and 918 is detected. Further, the vibrating body 902 is connected to the ground, which also serves as a common potential of the oscillation circuit 910 and the differential amplification circuit 920.

The oscillation circuit 910 allows the piezoelectric element 90 to
When a driving voltage is applied between the piezoelectric elements 904 and 906 and the piezoelectric element 908, the piezoelectric ceramics 904A, 906A and 908A
The piezoelectric effect causes the vibrating body 902 to flexurally vibrate in the vertical direction in FIG. In this state, when the piezoelectric vibrating gyro 900 rotates about the longitudinal direction of the vibrating body 902 (direction perpendicular to the paper surface of the drawing) as an axis, the piezoelectric vibrating gyro 900 rotates in the Coriolis direction (left and right direction of the drawing) orthogonal to the exciting direction according to the angular velocity of rotation. Coriolis power works. Therefore, the vibration direction of the vibrating body 902 deviates from the vertical direction when there is no rotation.

Then, the impedance of the piezoelectric elements 904 and 906 changes according to the rotational angular velocity of the piezoelectric vibrating gyro 900, and the potential corresponding to this change appears at the detection terminals 916 and 918. Differential detection circuit 920
Then, the potential difference between the detection terminals 916 and 918 is detected. This potential difference corresponds to a change in impedance of the piezoelectric elements 904 and 906, that is, a shift in the vibration direction based on the Coriolis force, and as a result, the rotational angular velocity of the vibration gyro 900 can be known from the output of the differential detection circuit 920. .

[0007]

By the way, in the piezoelectric vibrating gyro having the above structure, the piezoelectric elements 904 and 90 are used.
It is necessary to pull out the electrodes 904C, 906C, and 908C of 6,908, but it is difficult because they are on the back surface side of the piezoelectric element. Therefore, in the background art described above, the vibrating body 90 is used.
By using a metal as 2 and setting it to a common potential, the electrodes 904C to 908C of the piezoelectric elements 904 to 908 are drawn out. However, when a metal is used as the vibrating body 902, the influence of the external magnetic field becomes large.

In order to avoid this, for example, if an insulating material is used as the vibrating body 902, then the surface of the vibrating body needs to be plated. The present invention has been made in view of the above points, and an object thereof is to provide a piezoelectric vibrating gyro having good characteristics by easily performing electrode extraction of a piezoelectric element without disturbing the operation of a vibrator or a piezoelectric element. And

[0009]

According to the present invention, the same surface of the piezoelectric body provided for vibrating the vibrating body for detecting the angular velocity, for example, one of the front and back surfaces or the inner surface, A plurality of electrodes are divided and formed at intervals. The electrode extraction from the piezoelectric element is easily performed from the divided electrodes. The external lead-out land portion of each electrode is preferably provided at a vibration node of the vibrating body. Since the land portion does not vibrate, the connection between the lead wire and the electrode can be maintained well.

When the number of the electrodes is two, the land portion of one electrode is arranged at the position of one vibration node of the vibrating body, and the land portion of the other electrode is arranged at the position of the other vibration node of the vibrating body. To be done. Thereby, the electrode arrangement with respect to the vibrating body is balanced, and good vibration is possible. The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS While there may be many embodiments of the piezoelectric vibrating gyro of the present invention, a suitable number of embodiments will now be shown and described in detail.

<Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. In Figure 1 (A),
The external appearance of the piezoelectric vibration gyro of Example 1 is shown. A vertical end face viewed in the direction of the arrow along the line # 1- # 1 in the figure is shown in FIG. 7B, and a horizontal end face viewed in the direction of the arrow along the line # 2- # 2 is shown. It is shown in FIG.

In these figures, a piezoelectric vibration gyro 1
0 is configured around the vibrating body 12. Vibrating body 12
Is formed into a regular quadrangular prism by an insulating material such as resin. Piezoelectric elements 14, 16, 18, and 20 are formed on the side surfaces of the vibrating body 12, respectively. FIG.
Only the piezoelectric elements 14 and 18 among them are shown in (A).

Of these, the piezoelectric element 14 is a piezoelectric body 14A made of a piezoelectric material such as a piezoelectric ceramic.
The electrodes 14B and 14C are formed on one of the planes. The other flat surface of the piezoelectric body 14A is bonded to the side surface of the vibrating body 12 with an adhesive or the like. The electrodes 14B and 14C are arranged in a comb shape such that the teeth are alternately arranged in the lateral direction (direction orthogonal to the longitudinal direction) of the vibrating body 12. The polarization of the piezoelectric body 14A is caused by the electrodes 14B, 1
It is performed by applying a voltage for polarization during 4C. The same applies to the other piezoelectric elements 16, 18, 20.

Regarding the shape of the electrode of each piezoelectric element, the following points are considered. In FIG. 3 showing a part of the electrodes 14B and 14C in an enlarged scale, it is assumed that a voltage is applied so that the piezoelectric body 14A extends in the direction of arrow F1. At this time, focusing on the top of the electrode 14B, the piezoelectric body 14A extends in the direction of the arrow F2. In other words, the arrow F
The piezoelectric body 14A contracts in three directions. This arrow F3
The contraction in the direction cancels the expansion in the arrow F1 direction. In the electrode configuration of the piezoelectric element, such inconvenience should be avoided.

That is, the interval m in the direction in which desired compression / expansion is desired is made narrower than the interval n in the direction orthogonal thereto.
That is, m <n, and preferably 2m ≦ n.
In this embodiment, the interval in the arrow F1 direction corresponds to m, and the interval in the arrow F2 direction corresponds to n. In the piezoelectric vibrating gyro 10 as described above, for example, the node points (points that serve as vibration nodes) of the vibrating body 12 are fixed to appropriate support wires by soldering or the like. Then, each leg of the support wire is erected oscillatingly by standing on a printed circuit board or the like.

Next, an example of the drive detection circuit will be described with reference to FIG. In the figure, the electrodes 14B and 16 of the piezoelectric elements 14 and 16 located on the upper and lower surfaces of the vibrating body 12, respectively.
B is connected to the oscillation circuit 22. On the other hand, the vibrating body 1
Electrodes 18 of piezoelectric elements 18 and 20 located on the left and right sides of 2
B and 20B are connected to the differential input side of the differential amplifier circuit 24. Furthermore, the output side of the differential amplifier circuit 24 is connected to a synchronous detection circuit 26, and this synchronous detection circuit 26 is connected to a ripple filter 28.

Further, the other electrodes 14C to 20C of the piezoelectric elements 14 to 20 are all grounded, which are the oscillation circuit 22, the differential amplifier circuit 24, and the synchronous detection circuit 2.
6, It is also the common potential of the ripple filter 28.

Next, the operation of this embodiment will be described. By the oscillator circuit 22, the electrodes 14B, 1 of the piezoelectric elements 14, 16 are
When a drive voltage is applied to 6B, the piezoelectric bodies 14A, 16A
Will expand and contract. The piezoelectric bodies 14A and 16A
Has the opposite effect: one stretches and the other shrinks. For this reason, the vibrating body 12 comes to undergo flexural vibration excited in the vertical direction of the drawing. In this state, since there is no difference in impedance between the left and right piezoelectric elements 18 and 20, there is no difference in their potentials.

However, when the piezoelectric vibrating gyro 10 rotates about the longitudinal direction of the vibrating body 12 (the direction perpendicular to the plane of the drawing), the Coriolis direction (left-right direction in the same drawing) orthogonal to the exciting direction is generated according to the angular velocity of rotation. ) Coriolis force works. Therefore, the vibration direction of the vibrating body 12 deviates from the vertical direction when there is no rotation. Then, the impedances of the piezoelectric elements 18 and 20 change according to the rotational angular velocity of the piezoelectric vibration gyro 10, and the potential corresponding to this change appears on the input side of the differential amplifier circuit 24. Differential amplifier circuit 24
Then, the potential difference between them is detected.

This potential difference corresponds to a change in the impedance of the piezoelectric elements 18 and 20, that is, a shift in the vibration direction based on the Coriolis force, and as a result, the rotational angular velocity of the piezoelectric vibration gyro 10 is output by the output of the differential amplifier circuit 24. I can know. The detection signal is synchronously detected by the synchronous detection circuit 26 in the oscillation cycle of the oscillation circuit 22, that is, the vibration cycle of the vibrating body 12, and the ripple component is further removed by the ripple filter 28 to obtain the direct current component. By measuring this DC output, the rotational angular velocity applied to the piezoelectric vibration gyro 10 can be measured.

By the way, as described above, according to this embodiment, the electrodes of the piezoelectric elements 14 to 20 are all formed on the surface thereof. Therefore, the electrode can be easily pulled out from the surface of the piezoelectric element. Further, it is not necessary to use a metallic vibrating body 12 or to plate the surface thereof. Therefore, the influence of the external magnetic field can be significantly reduced, and an insulating material can be used as the vibrating body, so that the range of material selection can be widened.

In this embodiment, as shown in FIG. 1A, it is assumed that the positions FA and FB where the lead wires are connected to the electrodes 14A and 14C of the piezoelectric element 14 are the nodes of the vibrating body 12. It is convenient because the soldering point does not move. The same applies to the other piezoelectric elements 16 to 20.

<Embodiment 2> Next, Embodiment 2 will be described with reference to FIGS. The second embodiment is various examples of electrode shapes. In FIG. 4, only the electrode shape of the piezoelectric element on any one surface is shown. First,
The embodiment shown in FIG. 4 (A) is the simplest and basic example, in which two electrodes 32 and 34 are formed on the piezoelectric body 30 at appropriate intervals. As described above, basically, two electrodes having an appropriate shape may be arranged at intervals.

In the embodiment shown in FIGS. 3B and 3C, the electrodes 36 and 38 are formed so as to be comb-shaped in the longitudinal direction of the vibrating body 12. In the figure (B), lands 36A and 38A for drawing out lead wires are provided at the positions of the nodes on the left and right of the vibrating body 12, respectively. Both 38A are located at one node.

In the embodiment shown in FIG. 3D, electrodes 42 and 44 are formed separately in an outer rectangular electrode 40. The electrodes 42 and 44 are made of a soft metal such as gold. It is connected by a lead wire 46. Piezoelectric body 30
The polarization is applied by applying a polarization voltage between the electrode 40 and the electrodes 42 and 44 connected by the lead wire 46.

In addition, in the electrode shape of the first embodiment, the land arrangement as shown in FIG. 4C may be adopted. However, in order to excite the vibrating body 12 favorably, it is preferable that the electrodes are arranged symmetrically.

Even in the land arrangement as shown in FIG. 4C, any two lands of the four piezoelectric elements are positioned at one node and the lands of the other two piezoelectric elements are set at the other. It may be possible to make a balance by setting it as the position of the node. In the example developed and shown in FIG. 5A, the lands of the piezoelectric elements 48A and 48C are located on the node FA side of the vibrating body 12, and the lands of the piezoelectric elements 48B and 48D are located on the node FB side. . In the example of FIG.
The lands of the piezoelectric elements 48A and 48B are located on the node FA side of No. 2, and the lands of the piezoelectric elements 48C and 48D are located on the node FB side. In the same figure (A), lead wires are drawn to the oscillation circuit 22 and the differential amplifier circuit 24 shown in FIG.
Since the land positions for connection are aligned, it is more convenient than the one shown in FIG.

<Third Embodiment> Next, a third embodiment will be described with reference to FIG. Various types of piezoelectric vibrating gyros are known, and the present invention can be applied to any type. Among them, the one in which the present invention is applied to a ring-shaped vibrating body is the present embodiment. Here is an example.

In the embodiment shown in FIG. 3A, piezoelectric elements 54, 56 and 58 are formed on the upper surface 52 of a ring-shaped vibrating body 50. Electrodes 54B and 54C are respectively formed in a comb shape on the piezoelectric body 54A of the piezoelectric element 54. The same applies to the piezoelectric elements 56 and 58. The piezoelectric elements 54 and 56 are for driving and detecting, and correspond to the piezoelectric elements 904 and 906 in FIG. The piezoelectric element 58 is for feedback and corresponds to the piezoelectric element 908 in FIG. Same figure (B)
In the embodiment shown in (1), the piezoelectric element 54, 56, 58 (only 58 is shown) is provided on the side surface 62 of the vibrating body 60. It should be noted that as the shape of the electrodes in these embodiments, any one of the above embodiments may be applied.

<Fourth Embodiment> Next, a fourth embodiment will be described with reference to FIG. This embodiment relates to the arrangement of electrodes and piezoelectric bodies. In the embodiment described above, the electrodes are formed on the surface of the piezoelectric body, but in the embodiment of FIG. 7A, the electrodes 72 and 74 are formed on the piezoelectric body 70.
A piezoelectric body 76 is further formed thereon. That is, the electrodes 72 and 74 are sandwiched between the piezoelectric bodies 70 and 76. The land portion of the electrode is exposed because the lead wire is pulled out.

In the embodiment shown in FIG. 3B, the electrodes 80 and 82 are formed on the surface of the piezoelectric body 78, but the land portions thereof are formed on the vibrating body 12. In the embodiment shown in FIG. 6C, electrodes 84 and 86 are formed on the vibrating body 12, and the vibrating body 88 is formed on the electrodes 84 and 86. The shape and the land arrangement of each electrode may be any of those in the above-mentioned embodiments.

<Other Embodiments> The present invention can be variously modified based on the above disclosure, and includes, for example, the following. (1) In the above-described embodiment, the piezoelectric element is provided mainly on the quadrangular prism vibrating body, but the vibrating body may have various shapes such as a triangular prism, a cylinder, an octagonal prism, and a cylinder. Further, the number of piezoelectric elements formed on the vibrating body may be appropriately set as necessary. The electrode shape is also the same, such as triangle, circle,
Various shapes such as an ellipse, a staircase shape, and a wave shape may be used. (2) The drive detection circuit can also have various design changes, such as the configuration shown in FIG.

[0034]

As described above, the present invention has the following effects. (1) Since the electrodes for the piezoelectric body are divided and formed at intervals, the electrodes can be easily drawn out. As a result, it is not necessary to form the vibrating body of metal so as to have a common potential, so that the influence of the magnetic field is reduced. Further, when the vibrating body is made of a resin material, there is no need to apply a common potential to the surface of the vibrating body by plating or the like, so that the number of manufacturing steps can be reduced. (2) Since the land part for drawing out the electrode to the outside is located at the node of the vibrating body, the connecting part does not vibrate and good coupling can be maintained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a lateral end surface and a drive detection circuit according to the first embodiment.

FIG. 3 is a diagram showing a relationship between an electrode shape and expansion / contraction of a piezoelectric body in Example 1.

FIG. 4 is a diagram showing an electrode shape of a piezoelectric element in Example 2.

FIG. 5 is a diagram showing an example of land arrangement in electrodes of a piezoelectric element.

FIG. 6 is a diagram showing an embodiment of a ring-type piezoelectric vibrating gyro.

FIG. 7 is a diagram showing an arrangement example of a piezoelectric body and electrodes.

FIG. 8 is a diagram showing an example of a conventional piezoelectric vibration gyro and its drive detection circuit.

[Explanation of symbols]

10, 50, 60 ... Piezoelectric vibrating gyro 12, 52, 62 ... Vibrating body 14, 16, 18, 20, 48A, 48B, 48C, 4
8D, 54, 56, 58 ... Piezoelectric element 14A, 16A, 18A, 20A, 30, 54A, 56
A, 58A, 70, 76, 78, 88 ... Piezoelectric body 14B, 16B, 18B, 20B, 14C, 16C, 1
8C, 20C, 32, 34, 36, 38, 40, 42,
44, 54B, 54C, 56B, 56C, 58B, 58
C, 72, 74, 80, 82, 84, 86 ... Electrode 22 ... Oscillation circuit 24 ... Differential amplification circuit 26 ... Synchronous detection circuit 28 ... Ripple filter 36A, 38A ... Land portion 46 ... Lead wire FA, FB ... Vibration section

Claims (3)

[Claims] 1. A vibrating body for detecting an angular velocity; a piezoelectric body provided on the vibrating body for vibrating the vibrating body;
A piezoelectric vibrating gyro having a plurality of electrodes formed on the same surface of the piezoelectric body at intervals. 2. The piezoelectric vibrating gyro according to claim 1, wherein the external lead-out land portion of the electrode is provided at a vibration node of the vibrating body. 3. The electrode is divided into a first electrode and a second electrode, and a land portion of the first electrode is a position of a first vibration node of the vibrating body, and a land portion of the second electrode. The piezoelectric vibrating gyro according to claim 2, wherein is the position of the second vibration node of the vibrating body.