JP2002162227A - Piezoelectric vibrator, piezoelectric vibration gyro using the same and manufacturing method of the piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a piezoelectric body film and perform non-adhesion by pressurization, heating and composition in the thickness direction of the outer face of a vibrator. SOLUTION: The piezoelectric body film is directly formed on the surface of the drive part 1 of the vibrator 3 and the surface of a detection part 2 by the pressurization, heating and composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric vibrator, a piezoelectric vibrating gyroscope using the same, and a method for manufacturing a piezoelectric vibrator.

[0002]

2. Description of the Related Art In recent years, piezoelectric vibrating gyroscopes have been developed with high sensitivity, small size and inexpensive products, and are widely used as general-purpose products for navigation systems for automobiles and camera shake preventing devices for video cameras. These piezoelectric vibrating gyros are
The piezoelectric element itself can be a vibrator.

[0003] However, the piezoelectric element has a disadvantage that the internal attenuation of vibration is large and the sensitivity of detecting vibration is low. Therefore, in many cases, the piezoelectric vibrating gyroscope uses a constant elastic metal having a small internal coefficient of vibration (that is, a large mechanical resonance sharpness Qm) and a small elastic temperature coefficient for the vibrator. Note that the piezoelectric vibrating gyroscope is classified into a tuning fork type and a vibrating piece type as vibration shapes. Further, it is classified into a resonance type and a non-resonance type depending on the vibration mode.

[0004]

The piezoelectric vibrating gyroscope is used not only to reduce the size of the whole device using the piezoelectric vibrating gyroscope but also to increase the resonance frequency and improve the response. Is required to be as small as possible.

In particular, in the case of a resonance type piezoelectric vibrating gyroscope, the sensitivity is improved by increasing the mechanical resonance sharpness Qm of the resonance frequency. However, this resonance frequency is high, and conversely, the sensitivity is lowered. Improvements in sensitivity and responsiveness due to miniaturization of the element have been demanded.

However, a piezoelectric vibrating gyroscope that requires high sensitivity can be realized by using a constant elastic metal for the vibrator and bonding a piezoelectric element having a large piezoelectric constant to the driving and detecting surfaces of the vibrator with an adhesive. And

For this reason, in the conventional piezoelectric vibrating gyroscope,
As the vibrator becomes smaller, the workability of the step of bonding the piezoelectric element becomes worse, and it becomes difficult to accurately attach the piezoelectric element to a predetermined position. Was.

Further, since the piezoelectric element is bonded to the upper surface or the side surface of the vibrator using a polymer adhesive such as an epoxy resin or an ultraviolet curable adhesive, the vibration of the piezoelectric element is transmitted to the vibrator or When the distortion of the transducer is transmitted to the piezoelectric element for detection, there is also a problem that these displacements cause attenuation of the vibration by the adhesive layer, thereby lowering the sensitivity.

The present invention has been made in view of the above circumstances, and by directly forming the composition of a piezoelectric element on the surface of a vibrator with a gradient, it is possible to prevent a decrease in sensitivity due to an adhesive layer and to perform bonding. It is an object of the present invention to provide a piezoelectric vibrator capable of alleviating distortion of a part, dispersing stress concentration, improving peel strength of a film, and miniaturizing a driving part or a detecting part of a minute part.

[0010]

Means for Solving the Problems In order to achieve this object, the present invention provides a vibrator made of an elastic metal,
The piezoelectric film is formed by continuously tilting the composition of the vibrator and the piezoelectric material. By forming a piezoelectric film in which the piezoelectric composition continuously and gradually changes from the composition of the vibrator on the surface of the vibrator made of the elastic metal, the plate-like piezoelectric element is formed of the elastic metal with an adhesive. Since there is no need to join the piezoelectric element to the vibrator, it is possible to eliminate vibration attenuation due to the adhesive layer when transmitting the vibration of the piezoelectric element to the vibrator or transmitting the distortion of the vibrator to the piezoelectric element.

Further, since the piezoelectric film is provided directly on the surface of the vibrator, the piezoelectric element can be easily formed even on a complicated and minute shaped surface of a small vibrator. Furthermore, a large amount of batch processing is possible in this film forming process. In addition, the thickness of the piezoelectric film can be increased.

According to another aspect of the present invention, a piezoelectric film in which the compositions of the vibrator and the piezoelectric material are continuously inclined is formed on the outer surface of the vibrator made of an elastic metal by pressurizing and heating. .

According to this method, a vibrator is put into a starting material solution which is a base of a piezoelectric body, and is heated and synthesized at a pressure of 10 atm or less and 200 ° C. or less to form a piezoelectric film directly on the surface of the vibrator. be able to. In addition, by this pressure heating synthesis,
A piezoelectric film can be easily formed on a complicated and minute surface of a small vibrator.

Further, another invention of the present invention is characterized in that the elastic metal is a constant elastic metal, and the influence of a temperature change is minimized by forming a piezoelectric film on the constant elastic metal. be able to. That is, it is possible to suppress a change in the resonance frequency of the member due to the temperature change and a change in the temperature of the vibration amplitude with respect to external energy for vibrating. Therefore, it is possible to configure a physical quantity detection device that detects vibration and angular velocity excellent in temperature-dependent characteristics.

In another aspect of the present invention, at least PbO, ZnO, Nb ₂ O ₅ , TiO ₂ , Zr
It is characterized by containing O ₂ , and a vibrator containing these components can form a strong piezoelectric film on a constant elastic metal and can eliminate the need for an adhesive. Therefore, even if the vibrator is driven with a large amplitude, it is possible to obtain a piezoelectric vibrator having excellent linear characteristics with respect to frequency and amplitude dependency.

According to another aspect of the present invention, the piezoelectric vibrator is used as a piezoelectric vibrating gyroscope. The piezoelectric vibrator applies an electric signal of a resonance frequency to a piezoelectric element on a driving surface to apply vibration and orthogonally intersects the vibration direction. Detecting the Coriolis force in the direction of movement by the piezoelectric film on the detection surface makes it possible to detect angular velocity with large amplitude drive. For this reason, it can be used as a highly sensitive piezoelectric gyro.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an in-plane drive type piezoelectric vibrating gyroscope using a vibrator 3 in which a driving unit 1 and a detecting unit 2 are separated. The vibrator 3 used a metal titanium plate as a constant elastic metal having a small elastic temperature coefficient. The vibrator 3 has a support portion 4, which has a plate-like shape, and the vibrator 3 is fixed to a pedestal or the like of the piezoelectric vibrating gyroscope at a mounting hole 5.

The driving unit 1 has an additional mass 6 at the tip of the tuning fork.
It is composed of two sets of tuning forks sandwiching the detection unit 2 from both sides. In FIG. 1, 7 is an additional mass, and 8 is an electrode.

A driving piezoelectric element is formed on the surface of the driving section 1 of the vibrator 3, and a power generating element for detection is formed on the surface of the detecting section 2. Both of these piezoelectric elements are composed of a piezoelectric film directly formed on the surface of the vibrator 3 by synthesis under pressure and heat. The piezoelectric film is formed only on the surface of the drive unit 1 and the surface of the detection unit 2 by patterning.
7 need not be provided. The starting materials for the piezoelectric film are commercially available chemical reagent grade Pb (NO ₃ ) ₂ (99.5%), ZnCl 2
₂ (99.5%), NbCl ₅ (99.5%), TiCl
₄ (99.8%), ZrOCl ₂ (99.5%), KOH
(99.5%) and the base metal titanium (99.9%)
No plate was used. Pb (NO ₃ ) ₂ and ZrOC
For l _2, an aqueous solution having a concentration of 1N was prepared. ZnCl ₂ , N
bCl ₅ was also prepared as a 1N aqueous solution and adjusted as follows. Cool the surroundings with water, put ice made of distilled water into a 1000 ml beaker, and put TiCl ₄ or NbCl _{5 in it.}
Was added dropwise little by little, and a 1N aqueous solution was prepared while cooling. The exact concentration of the aqueous solution can be determined by drying the gel precipitate of hydroxide with the addition of aqueous ammonia and then in air at 1273 ° C.
After heating to K, the weight of TiO ₂ was measured and determined. Next, a mixed aqueous solution for performing heating under pressure was prepared by weighing aqueous solutions of each composition so as to have the composition shown in (Table 1).

[0021]

[Table 1]

Next, this aqueous solution 10 was poured into the interior container 9 of the autoclave shown in FIG. The shape and size of the interior container 9 were cylindrical with an inner diameter of 28 cm, an inner height of 38 cm, and a wall thickness of 15 mm. The outer container 11 for holding the autoclave container 9 was made of stainless steel SUS304. The sample substrate 12 has a length of 25 cm and a width of 3.
It consists of a 5cm x 0.2mm thick metal titanium plate.
, And inserted into the container 9 containing the aqueous solution 10. Next, the container 9 is inserted into the container 11. FIG. 3 is a flow chart showing the state of the pressurized heating synthesis. Next, the container 11 of the autoclave was placed in an oven and heated at a temperature of 413 K for 16 hours. The pressurization is carried out in the closed container 9 to several atmospheres according to a function of the temperature. Hereinafter, the composition of the piezoelectric film is PZN
It is called TZ.

As a result, crystal nuclei of PZNTZ are generated on the titanium metal plate. At this time, the autoclave is
m. A second pressurized heating synthesis was performed to further grow the crystal nuclei formed on the metal titanium plate. The second pressurized heating synthesis was performed in substantially the same manner as the first press synthesis.

The already prepared aqueous solution 10 is put in the container 9. Subsequently, the first pressurized and heat-synthesized metal titanium plate held by the holder 13 was inserted into the container 9, and this was inserted into the container 11. Next, the container 11 is placed in an oven and heated under pressure in a state of being sealed at a temperature of 393 K for 16 hours to grow a crystal nucleus of PZNTZ on the titanium metal plate.

At this time, the autoclave was rotated at 15 rpm similarly to the first pressurized heating synthesis. When a plurality of pressurized heating syntheses were continuously performed, a sample was prepared by fixing the synthesis temperature and the KOH concentration in the oven under the conditions according to this method.

Next, an Au electrode was applied to the main surface of the driving unit 1 and the detecting unit 2 of the sample prepared as described above, thereby obtaining a vibrator of a vibrating gyroscope having a unimorph driving structure shown in FIG.

The size of the outer shape of the vibrator 3 shown in FIG.
mm × width 13.33 mm × thickness 0.2 mm. Although Ti is used as the material, it is possible to use another constant elastic metal. However, if it is other than Ti metal, better results can be obtained by coating Ti as a base.

The additional mass 6 provided in the driving section 1 is a weight section for generating a gyro function, and is utilized for adjusting the Coriolis force and the resonance frequency. The detector 2 gives an angular velocity when the gyro element is driven and detects angular velocity information. The additional mass 7 provided in the vicinity of the detection unit 2 is for adjusting the resonance frequency of the detection unit 2 and stabilizing the resonance mode.

FIG. 4 shows the relationship between the number of times of film formation and the thickness of the film. The film formation conditions were such that the composition shown in Table 2 was used at a reaction temperature of 393K.
The second and third pressurized heating synthesis was performed under the condition of −16 h. In one film formation, a thin film of about 3.5 μm was obtained, and in three times, a film thickness of about 11.5 μm was obtained. It is almost proportional to the number of film formation. It indicates that it is easy to achieve the target thickness by performing the number of film formations as necessary.

[0030]

[Table 2]

FIG. 5 shows a PZN film formed by pressure and heat synthesis.
A schematic diagram of the process of the crystal nuclei 14a and the crystal growth 14b of the TZ film is shown. In a process by pressure and heat synthesis, an aqueous solution containing zirconium, zinc, niobium, and lead ions is reacted with the metal titanium plate 14, which is an elastic body, to generate PZNTZ crystal nuclei on the surface thereof, and is further applied several times on this surface. A PZNTZ crystal is further grown on the crystal nucleus by performing pressure heating synthesis.

By performing the two pressurized heating syntheses, it is possible to form a highly practical piezoelectric film having a strong adhesive force on the metal titanium plate 14. Metallic titanium plate 1
At the interface of No. 4, a film is formed by the reaction of pressurized heating synthesis (not just adhesion of a piezoelectric film).

The weighed compositions are shown in (Table 2) and (Table 3)
, And three times of heating under pressure. The reaction temperature of the first pressurized heating synthesis (FIG. 5A) was 413K-1.
6h, second and third reaction temperature (393K in FIG. 5)
Crystals were grown at -16 h, and samples were obtained. The crystal particle diameter was about 2 μm, and the average thickness of the film was about 11.5 μm.

FIG. 6 shows the result of analyzing the distribution of the composition components in the thickness direction of the PZNTZ thin film by Auger electron spectroscopy. There is a composition distribution near the interface between the PZNTZ thin film and the titanium metal, indicating a maximum of the Pb component and a minimum of the Zr component. As the composition component, the piezoelectric film is formed by being continuously inclined. I understand.

FIG. 7 shows the state of the amplitude when the large amplitude drive is performed. (A) is a tuning fork portion composed of a vibrator of a piezoelectric gyro manufactured by pressurized heating synthesis.
The applied voltage at which the maximum amplitude of the tuning fork becomes 25 μm and 2.5 μm is determined in advance, and the input frequency and the vibration amplitude when applied are shown.

It can be seen that the vibration amplitude of the tuning fork (a) is relatively symmetric with respect to the frequencies around the resonance point of the tuning fork with the resonance point as a boundary. On the other hand, the amplitude characteristics of a tuning fork (b) formed by bonding a piezoelectric ceramic element having the same composition and having a thickness of 50 μm manufactured by the sintering method via an epoxy resin according to a conventional method are compared. The applied voltage is adjusted so that the maximum amplitude of the tuning fork (b) is the same as that of the tuning fork (a).
When the tuning fork (b) and the tuning fork (a) are compared under the same maximum amplitude condition, it can be seen that the tuning fork (a) is slightly better than the tuning fork (b), but is superior in the symmetry of the resonance frequency characteristic. .

One reason that the tuning fork (a) of the pressurized and heated synthetic film is superior in linear operation is that adhesive bonding is not used. That is, the actuator (FIG. 7 (b)) obtained through the bonding agent by bonding is a PZNTZ film (FIG. 7) obtained by pressurizing and heating synthesis on a metal titanium plate.
Compared with (a)) and the like, it can be considered that the influence of the low elastic body due to the interposition of the adhesive at the joint between the substrate and the piezoelectric body.

Therefore, when the tuning fork is vibrated at a large amplitude, the pressurized heating synthesis without using the adhesive bonding does not cause the phenomenon of lowering the resonance frequency due to the vibration amplitude of the bonding portion, and is excellent in linear operation characteristics.

As described above, according to the piezoelectric vibrating gyroscope of the present embodiment, the piezoelectric element constituted by the piezoelectric film is formed directly on the surface of the driving unit 1 and the surface of the detecting unit 2 of the vibrator 3. A decrease in sensitivity due to vibration damping of the adhesive layer can be prevented.

Further, since large-amplitude driving is possible, high sensitivity can be expected by large-amplitude. Further, since the piezoelectricity is formed by the pressurized heating synthesis method, the piezoelectric element can be easily formed on the drive surface or the detection surface of a small vibrator having a complicated and minute shape. The film thickness can be made sufficiently thick.

In the film forming process by the pressurized heating synthesis method, a large amount of batch processing is possible. By dividing the film forming process into two stages, the piezoelectric film can be firmly adhered to the surface of the vibrator 3. it can.

Further, in the present embodiment, since the vibrator 3 having a shape in which the driving unit 1 and the detecting unit 2 are separated is used, the distortion of the driving unit 1 itself due to the vibration of the driving piezoelectric element does not affect the detecting unit 2 so much. , Unnecessary noise is generated in the detection unit 2 and S / N
The ratio can be prevented from lowering.

In this embodiment, the vibrator 3 is made of an Elinvar alloy. However, another constant elastic metal may be used, and an elastic metal or an elastic material other than the constant elastic metal may be used. Further, in this embodiment, PZT is used as the piezoelectric film constituting the piezoelectric element, but any other composition may be used as long as the film has piezoelectricity.

Furthermore, in this embodiment, the vibrator 3 is of the resonating piece type. However, the vibrating element may have any shape of a quadrangular prism, a triangular prism, a cylinder or a cylinder. In addition, the present invention is not limited to the resonating piece, and can be implemented in a tuning fork type in which the vibrator is formed of an elastic metal.

In this embodiment, the tuning fork piezoelectric vibrator has been described. However, the present invention can be similarly applied to a piezoelectric vibrator used for a vibrating gyroscope. The same is true.

[0046]

As is apparent from the above description, according to the present invention, the vibration damping due to the adhesive layer between the piezoelectric vibrators is avoided by forming the film with the piezoelectric composition being continuously inclined. can do. When the film is formed with the piezoelectric composition inclined in this manner, the vibration of the piezoelectric element is efficiently propagated to the vibrator, and the strain vibration generated in the vibrator can be detected with high sensitivity by the piezoelectric element. Further, since large-amplitude driving becomes possible, high sensitivity can be expected by large-amplitude driving.

Further, since the piezoelectric element can be easily formed on the surface of a small vibrator having a complicated and minute shape, not only can the vibrator be miniaturized and the responsiveness improved,
When used as a piezoelectric vibrating gyroscope, the S / N ratio at the time of detection can be increased by making the shape such that distortion of the piezoelectric element on the drive surface does not directly affect the piezoelectric element on the detection surface.

Further, since a large number of batch processes can be performed in the piezoelectric film forming process, the quality can be easily made uniform as compared with the assembling process.

In addition, in the film formation by the pressurized heating synthesis of the present invention, it becomes easier to form a piezoelectric film having a larger film thickness than other thin film forming methods. In addition, by using the composition of PZNTZ, not only the sufficient performance as a piezoelectric element can be exhibited, but also the peeling of the piezoelectric element can be eliminated by increasing the adhesion of the piezoelectric film to the vibrator.

[Brief description of the drawings]

FIG. 1 is a perspective view of a piezoelectric vibrating gyroscope according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the structure of an autoclave.

FIG. 3 is a flow chart of pressure heating synthesis.

FIG. 4 is a diagram showing the relationship between the number of film formations and the film thickness.

FIGS. 5A and 5B are schematic diagrams of a crystal growth process, respectively.

FIG. 6 is a component distribution diagram in a thickness direction of a piezoelectric film.

FIGS. 7A and 7B are amplitude characteristic diagrams of a piezoelectric film when vibrating with a large amplitude, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive part 2 Detection part 3 Transducer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H03H 3/02 H01L 41/08 U 9/17 41/18 101D 41/22 Z

Claims (7)

[Claims] 1. A piezoelectric vibrator having a piezoelectric film in which the composition of the vibrator and the piezoelectric material is continuously inclined in the thickness direction of the outer surface of the vibrator made of an elastic metal. 2. The piezoelectric vibrator according to claim 1, wherein the elastic metal is a constant elastic metal. 3. The piezoelectric film comprises at least PbO, ZnO,
The piezoelectric vibrator according to claim 1, further comprising Nb ₂ O ₅ , TiO ₂ , or ZrO ₂ . 4. A piezoelectric vibrating gyroscope using the piezoelectric vibrator according to claim 1. 5. A piezoelectric vibrator characterized in that a piezoelectric film in which the composition of the vibrator and the piezoelectric body is continuously inclined is formed by pressurizing and heating synthesis in the thickness direction of the outer surface of the vibrator made of an elastic metal. Manufacturing method. 6. The method according to claim 5, wherein the elastic metal is a constant elastic metal. 7. The piezoelectric film comprises at least PbO, ZnO,
7. The method according to claim ₅ , further comprising Nb ₂ O ₅ , TiO ₂ , or ZrO ₂ .