JPH0868635A - Piezoelectric vibration angular speedometer and its manufacture - Google Patents

Abstract

PURPOSE: To mass-produce and miniaturize a vibrator by a method wherein two piezoelectric or electrostrictive ceramic plates in which electrode patterns have been formed on both faces and whose size is identical are bonded and this assembly is cut by a precision cutter. CONSTITUTION: Rectangular papallelepipeds composed of piezoelectric members 1, 2 in which electrodes have been formed on two opposite side faces are bonded in such a way that the electrodes are matched. In the piezoelectric member 1 which is used for detection, the electrode 3 on the surface of a vibrator is divided into two parts so as to be symmetric with respect to the central axis of the vibrator. In the piezoelectric member 2 which is used for driving, the electrodes on both faces are formed as whole-face electrodes. Both piezoelectric members 1, 2 are polarization-treated in the direction of the electrodes, and they are cut in such a way that a cross section which is perpendicular to a vibration direction becomes a square. In order to manufacture a piezoelectric-vibration angular speedometer, for example, two plates composed of piezoelectric members in which mercury electrodes have been formed on both faces and which have been polarization-treated are bonded by an adhesive, a photoresist film is placed on the surface of the electrode on one side, and a resist pattern which corresponds to the electrode is formed by an aligner. It is used as a protective mask, the mercury electrode which has been exposed is removed, the central part of the remaining electrode is cut, and the vibrator which has two-split electrodes is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrating angular velocity meter, and more particularly to a piezoelectric vibrating angular velocity meter that is small and can be mass-produced at low cost.

[0002]

2. Description of the Related Art Conventionally, two main types of vibration angular velocimeters are GE type and Watson type piezoelectric vibrating angular velocimeters which utilize positive and negative piezoelectric effects. In both types, when natural vibration is excited in the vibrator and rotation occurs around the vibrator axis, Coriolis force is generated in a direction perpendicular to both directions. This force is expressed by the following equation. Fc = 2 m [V · Ω] (1) where Fc is the Coriolis force, m is the mass of the vibrator, v is the vibration speed of the vibrator, and Ω is the rotational angular velocity.

In the GE type piezoelectric vibrating angular velocity meter, as shown in FIG. 6, a piezoelectric ceramic plate (10) is adhered to a rod-shaped vibrator (9) made of metal, thereby driving the metal vibrator and simultaneously driving the vibrator. The Coriolis force generated in the direction perpendicular to the driving direction due to the rotation of is detected. The mode of vibration used is unrestrained lateral vibration, which is usually fixed to the substrate at the node of vibration. In the Watson-type piezoelectric vibrating angular velocity meter, as shown in FIG. 7, four piezoelectric ceramic bimorphs (11, 12) are formed in a stacked tuning fork shape so that two of them are orthogonal to each other, and the driving bimorph excites the entire tuning fork. The Coriolis force generated with the rotation of the element is detected by the detection bimorph.

A GE which has a particularly simple structure and is suitable for downsizing
As the piezoelectric vibrating angular velocity meter of the type, recently, one using a triangular prism-shaped metal vibrator, one using a cylindrical piezoelectric ceramics as a vibrator, and the like have been developed. When using a metal oscillator, a piezoelectric ceramic plate is bonded to the oscillator. When a piezoelectric ceramic vibrator is used, electrodes are formed on the side surfaces of the cylinder, and then polarization processing is performed.

[0005]

However, these vibration angular velocimeters have problems in inexpensively manufacturing the vibrator and miniaturizing the vibrator. That is, when the process of joining the piezoelectric ceramic plate to the metal vibrator is included,
Since it becomes necessary to bond the piezoelectric ceramic plate to the side surface of each vibrator, a great amount of time is required for this process, which is an obstacle to mass production. Further, in this process, the smaller the size of the vibrator, the worse the workability. Also,
Even when forming electrodes on the side surface of a cylindrical piezoelectric ceramic, it is necessary to form electrodes on each vibrator using a roll type printing machine, etc., and then individually perform polarization processing. Not suitable for conversion. The object of the present invention is to solve this problem.

[0006]

The present invention focuses on the fact that if a two-dimensionally structured electrode is formed on a ceramic plate made of a piezoelectric or electrostrictive material, a large number of small vibrators can be manufactured at one time. A bimorph vibrator having a quadrangular prism-shaped first member made of a piezoelectric or electrostrictive material and a quadrangular prism shaped second member made of a piezoelectric or electrostrictive material; and a first member and a second member. The present invention has provided a piezoelectric vibrating angular velocity meter having an internal electrode formed between a member and an external electrode formed on a side surface of the first member and the second member facing the internal electrodes.

[0007]

By joining two piezoelectric or electrostrictive ceramics plates of the same size with electrode patterns formed on both sides and then cutting them, a large amount of bimorph type vibrators can be manufactured at one time. Further, by forming an electrode pattern by reactive etching and cutting the bonded ceramics plate by a precision cutting machine, an extremely small bimorph type vibrator can be produced with good reproducibility.

By using a bimorph-shaped internal electrode as a ground and applying a voltage between this and the external electrode of the driving piezoelectric or electrostrictive member, a so-called piezoelectric lateral effect is utilized to generate unrestrained basic vibration in the bimorph oscillator. To excite. Therefore, vibration occurs in a direction perpendicular to the electrode surface, and when rotation occurs around the axis of the vibrator, the vibrator bends in the electrode surface due to Coriolis force. The bending caused by the Coriolis force is detected by the detecting piezoelectric or electrostrictive member.

In the above structure, a piezoelectric signal associated with the driving of the vibrator is also generated in the Coriolis force detection electrode, so that the Coriolis force detection actually requires a large load on the electric system. Therefore, the external electrode of the detection piezoelectric or electrostrictive member is divided into two parts with the center line in the vibrator axial direction as a reference.
The signals generated at the two electrodes have the same frequency and opposite phases with respect to the Coriolis force, and the ones caused by the drive have the same phase. Therefore, if the differential voltage between the two is taken, it is almost due to the Coriolis force. Only the signal can be obtained.

If the resonator cross section is square and the resonance frequencies in the Coriolis force direction and the driving direction can be matched, the vibrator can be driven near the resonance frequency with a simple oscillation circuit by feeding back the output from the detection electrode. Therefore, the vibration based on the Coriolis force is also in a resonance state, and the detection sensitivity is improved. In order to eliminate complicated procedures for resonance frequency adjustment, the resonator cross section is made rectangular to intentionally shift the resonance frequencies in both directions, and the drive is a bimorph drive in which a large amplitude can be obtained without resonance. The frequency of the AC voltage for this driving is the resonance frequency of the fundamental vibration in the Coriolis force direction. Also, when performing bimorph drive, if driven at a frequency higher than the fundamental resonance frequency, stable vibration cannot be obtained due to coupling with the higher order mode, etc.
The cross section of the vibrator is a rectangle whose electrode surface direction is short.

As a method of fixing the vibrator, it is the simplest and desirable to support and fix it at the node points of the unconstrained fundamental vibration.

[0012]

Example 1 The present invention will be described in more detail with reference to the following examples. FIG. 1 is a basic configuration of an example of a vibration angular velocity meter based on the present invention. Rectangular parallelepipeds (1 and 2) made of a piezoelectric material and having electrodes formed on two opposite side surfaces are joined together with their electrode surfaces aligned with each other. In the piezoelectric member (1) for detection, the electrode (3) on the upper surface of the vibrator is divided into two symmetrically with respect to the central axis of the vibrator. In the piezoelectric member (2) for driving, both electrodes on both sides are full-scale electrodes. Both piezoelectric members are polarized in the electrode direction. The cross section of the oscillator perpendicular to the oscillator axis direction is substantially square in order to match the resonance frequencies in the driving direction and the Coriolis force direction.

FIG. 2 shows the operating principle of the piezoelectric vibration angular velocity meter shown in FIG. The oscillator vibrates under unrestrained conditions, and the center and end of the oscillator have velocities in opposite directions at the boundary of the node (4) of vibration (2-1). At this time, when rotation occurs around the oscillator axis, the speed directions are opposite,
Coriolis force is generated in the opposite direction with the contact point of vibration as the boundary (2
-2). This force causes the vibrator to bend in the direction of the electrode surface (2-3). Driving vibration (2
-Piezoelectric signal due to 1) and deformation due to Coriolis force (2
A piezoelectric signal due to (3) is simultaneously generated. Of this,
The piezoelectric signals caused by the Coriolis force are almost opposite in phase between the two electrodes. This means that, for example, in the deformed state shown in FIGS. 2-3, compressive stress acts on the electrode 3-a side and tensile stress acts on the electrode 3-b side, and the sign of the stress is always between the two electrodes. Because it is different. On the other hand, since the piezoelectric signals due to driving are almost the same between both electrodes, if differential signals are taken from both electrodes, it is possible to obtain almost only the piezoelectric signals due to the Coriolis force.

FIG. 3 shows an example of a vibrator supporting method for realizing the unconstrained vibration condition of the vibrator shown in FIG. The portion corresponding to the node of vibration is fixed to the support base (5) using a silicone adhesive. Further, as a simple fixing method, it is possible to embed the entire vibrator in an adhesive having a relatively low elastic constant. FIG. 4 shows an example of a manufacturing process of the piezoelectric vibration angular velocity meter shown in FIG. Silver plates (6) are formed on both sides, and two plates (7) made of a piezoelectric material that have already been polarized in the electrode direction are bonded with an epoxy adhesive (4-1). In order to maintain high alignment accuracy in the post process, the shape of the periphery of the bonding plate is adjusted with a dicing saw (4-2). A photoresist film (8) is placed on the surface of one electrode, and a resist pattern corresponding to the electrode pattern of equal width and equal spacing is formed by an exposure device (4-3). Using this resist as a protective mask, the silver electrode exposed by reactive ion etching is removed (4-4). After that, the resist is peeled off (4-5), and the center portion of the remaining rod-shaped silver electrode is cut with a dicing saw to manufacture a vibrator having two-divided electrodes symmetrical with respect to the vibrator central axis (4). -6). According to such a process, a large number of small-sized bimorph type piezoelectric vibrating gyroscopes can be manufactured from a set of piezoelectric plates.

[0015]

[Embodiment 2] FIG. 5 shows the basic construction of another example of the vibration angular velocity meter according to the present invention. The mechanism is basically the same as that of the example shown in FIG. Regarding the shape of the cross section of the vibrator, the side in the electrode direction is shorter than the side in the direction perpendicular to this. Drive,
The detection principle is basically the same as that described with reference to FIG. However, the unrestricted vibration fundamental resonance frequency in the drive direction represented by V in the figure and in the Coriolis direction represented by F _C in the figure is
Since the thickness in the Coriolis force direction is thin, the resonance frequency in this direction becomes lower than the resonance frequency in the driving direction. The external electrode of the driving piezoelectric member is also divided into two, like the external electrode for detection.

When an AC voltage near the unrestricted vibration fundamental resonance frequency in the Coriolis force direction is applied to the driving piezoelectric member (2) through the driving electrode, vibration is excited in the direction indicated by V. The vibration generated at this time does not resonate because the frequency of the applied alternating current is lower than the vibration fundamental resonance frequency in the driving direction, but since it has a bimorph structure, a sufficiently large amplitude can be given if an appropriate voltage is applied. . The driving external electrode is divided into two parts with respect to the central axis of the vibrator in order to maintain the balance of vibration and prevent the vibration due to driving from coupling in the Coriolis force direction.

When rotation occurs around the axis of the vibrator, Coriolis force is generated, but since the frequency of the AC voltage used for driving is the vibration fundamental resonance frequency in the Coriolis force direction, resonance occurs once bending occurs due to Coriolis force. A state is obtained, and an amplitude that is a quality factor times (several tens to several thousand times) the vibration of the static amplitude obtained by the piezoelectric strain is obtained.

The Coriolis signal is detected by the divided electrodes, and the detection principle is the same as that shown in the first embodiment.

[0019]

As described above, according to the present invention, it is possible to provide a large-scale, inexpensive and small vibration angular velocity meter.

[Brief description of drawings]

FIG. 1 is an example of a piezoelectric vibrating angular velocity meter according to the present invention.

FIG. 2 illustrates the operation of the piezoelectric vibration angular velocity meter of FIG. 2-1 is a diagram for showing vibration due to driving from the side face, and 2-1 and 2-2 are diagrams for showing Coriolis force from the electrode face and deformation accompanying it.

FIG. 3 is an example of a method of fixing the vibrator shown in FIG.

FIG. 4 is an example of a method of manufacturing the piezoelectric vibration angular velocity meter shown in FIG.

FIG. 5 is another example of the piezoelectric vibration gyro according to the present invention.

FIG. 6 is a conceptual diagram of a conventional piezoelectric vibration angular velocity meter.

FIG. 7 is a conceptual diagram of a conventional piezoelectric vibration angular velocity meter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detection piezoelectric member 2 Driving piezoelectric member 3 Detection electrode 4 Vibration nodal point 5 Support stand 6 Silver electrode 7 Piezoelectric member plate 8 Photoresist 9 Metal vibrator 10 Piezoelectric ceramic plate 11 Driving piezoelectric bimorph 12 Detection piezoelectric bimorph

Claims (6)

[Claims] 1. A vibrator comprising a quadrangular prism-shaped first member made of a piezoelectric or electrostrictive material and a quadrangular prism shaped second member made of a piezoelectric or electrostrictive material, and a first member and a second member. A piezoelectric vibrating angular velocity meter having an internal electrode formed between the internal electrode of the first member and the second electrode, and an external electrode formed on a side surface of the first member and the second member facing the internal electrodes of the first member and the second member. A piezoelectric vibrating angular velocity meter characterized by vibrating an oscillator by an internal electrode and detecting the generated Coriolis force. 2. The piezoelectric vibrating angular velocity meter according to claim 1, wherein one of the first member and the second member is a driving means for exciting a vibrator, and the other one detects a Coriolis force generated. A piezoelectric vibrating angular velocity meter, which is a detecting means for 3. The piezoelectric vibration angular velocity meter according to claim 2, wherein the external electrode of the first or second member, which is the detection means, is divided into two and the differential voltage between them is detected. Vibration angular velocity meter. 4. The piezoelectric vibration angular velocity meter according to claim 3, wherein the cross section of the vibrator perpendicular to the vibrator axis is square. 5. The piezoelectric vibrating angular velocity meter according to claim 3, wherein the cross section of the vibrator perpendicular to the vibrator axis is a rectangle whose sides in the electrode direction are shorter than the sides in the direction perpendicular thereto. A vibrating gyro. 6. A first plate-like member made of a piezoelectric or electrostrictive material, having a pattern of internal electrodes formed on one surface and a pattern of external electrodes formed on the surface opposite to the internal plate, and an internal plate formed on one surface. Forming a pattern of electrodes and joining a second plate-shaped member made of a piezoelectric or electrostrictive material having a pattern of external electrodes on the surface opposite to the pattern on the surface on which the internal electrodes are formed, and then cutting. A method of manufacturing a plurality of piezoelectric vibrating angular velocimeters, comprising: