JP2002362973A - Piezoelectric ceramic composition for piezoelectric vibratory gyroscope, and piezoelectric vibratory gyroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric ceramic composition for a piezoelectric vibratory gyroscope, which is almost free from the deterioration in piezoelectric characteristics even when the temperature of the atmosphere and various conditions of the external environment change and which has improved stability and reliability in the measurement accuracy. SOLUTION: The piezoelectric ceramic composition for the piezoelectric vibratory gyroscope contains, as a main component, a composite perovskite type oxide expressed by formula: PbZrO3 -PbTiO3 -Pb(Mn'Nb')O3 (where, α/β is >1/2 and <=1 and α+β=1), and exhibits a crystal structure being tetragonal in the operating temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrating gyroscope and a piezoelectric vibrating gyroscope for use in, for example, vehicle behavior detection and camera shake correction detection.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric vibrating gyroscope has been used for various purposes such as detecting the behavior of a vehicle or detecting camera shake correction. One example of this type of piezoelectric vibrating gyroscope is disclosed in Japanese Patent Application Laid-Open No. 9-79857.

A piezoelectric vibrating gyroscope includes a piezoelectric vibrator having a drive circuit for vibrating the piezoelectric vibrator and a detecting circuit for detecting Coriolis force generated by the vibration of the piezoelectric vibrator. In the above prior art, the piezoelectric vibrator includes lead oxide, zirconium oxide, and titanium oxide, and is configured using a piezoelectric material in which a crystal system is tetragonal within a use temperature range, whereby an atmosphere is formed. It is described that the fluctuation of the measurement error due to the temperature change is suppressed.
In _{addition, PbZrO 3 -PbTiO 3 -Pb (Mn} , Nb)
It is described that the same effect can be obtained even when a piezoelectric material made of an O ₃ -based ternary composite perovskite oxide is used.

[0004]

As the use of piezoelectric vibrating gyroscopes expands, there is a strong demand for a small measurement error and excellent reliability against not only ambient temperature changes but also any environmental changes. I have. In particular, when a sudden thermal shock is applied, the piezoelectric characteristics may be degraded by the pyroelectric charge generated by the pyroelectric effect in the piezoelectric ceramic. For this reason, the measurement accuracy of the piezoelectric vibrating gyroscope may be greatly impaired by the pyroelectric effect.

In manufacturing a sensor including a piezoelectric vibrating gyroscope, the piezoelectric vibrating gyroscope is exposed to a considerably high temperature in a mounting process such as a reflow soldering method. When exposed to such a high temperature, the piezoelectric characteristics of the piezoelectric ceramic deteriorate, and the detection error of the piezoelectric vibrating gyroscope may increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric vibrating gyroscope in which the deterioration of the piezoelectric characteristics hardly occurs even when various external environmental changes occur in addition to the change in the ambient temperature, and thus the stability of the measurement accuracy is improved. And a piezoelectric ceramic composition for the piezoelectric vibrating gyroscope.

[0007]

The piezoelectric ceramic composition for a piezoelectric vibrating gyroscope according to the present invention is a piezoelectric ceramic composition used for a piezoelectric vibrating gyroscope, and is composed of PbZrO ₃ -PbTiO _3.
-Pb (MnαNbβ) O ₃ , (However, 1/2 <α / β
.Ltoreq.1 and .alpha. +. Beta. = 1) as a main component, and has a tetragonal crystal structure in a use temperature range.

Further, the piezoelectric vibrating gyroscope according to the present invention comprises:
A piezoelectric vibrator, a drive circuit for driving the piezoelectric vibrator, and a detection circuit for detecting Coriolis force from the piezoelectric vibrator, wherein the piezoelectric vibrator is PbZrO ₃
-PbTiO ₃ -Pb (MnαNbβ) O ₃ (where 1
/ 2 <α / β ≦ 1 and α + β = 1) as a main component, and is formed using a piezoelectric ceramic composition having a tetragonal crystal structure in a use temperature range. It is characterized by the following.

In the piezoelectric ceramic composition for a piezoelectric vibrating gyroscope and the piezoelectric vibrating gyroscope according to the present invention, preferably, an acceptor element is added as a sub-component to the piezoelectric ceramic gyroscope. As the acceptor element, Cr, Ni,
Mg, Fe, Co and the like can be cited, and the addition of the acceptor element can further reduce the insulation resistance. Regarding the addition amount of the acceptor element, preferably,
With respect to 100 parts by weight of the above main component, converted to Cr ₂ O ₃ ,
It is in the range of 0.0005 to 0.6 parts by weight. 0.00
If the amount is less than 05 parts by weight, the effect of adding the acceptor element may not be sufficiently obtained. If the amount exceeds 0.6 parts by weight, the polarization treatment may be difficult.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail by describing specific embodiments of the present invention.

In this embodiment, Pb ₃ O ₄ , Z
Each powder of rO ₂ , TiO ₂ , MnCO ₃ , Nb ₂ O ₅ , and Cr ₂ O ₃ was weighed so as to have a material composition shown in Table 1 below,
The mixture was mixed with a ball mill and pulverized. The mixture thus pulverized was dehydrated, dried, and calcined at a temperature of 850 to 1000 ° C for 1 to 2 hours. 2 to 5% by weight of a binder resin is added to the obtained calcined powder, and then 8 to 32% by weight.
The mixture was mixed with a ball mill for an hour and pulverized to obtain a mixture.

The mixture thus obtained was dehydrated, dried and granulated to obtain a piezoelectric ceramic material powder. This piezoelectric ceramic material powder was supplied in an amount of 9.8 × 10 ⁷ Pa to 1.18 × 10 ⁸ Pa
Press molding under the above pressure to obtain a rectangular plate-shaped molded body having a size of about 40 × 30 × 0.7 mm.

The molded body was heated to remove the binder, and then calcined at a temperature of 1,050 to 1,250 ° C. for 1 to 4 hours to obtain a calcined body. The obtained fired body was lap-polished and edge-polished, and processed so as to have a rectangular plate shape of about 30 × 20 × 0.5 mm.

[0014] On both main surfaces of this rectangular plate-shaped fired body,
A nichrome layer, a monel layer, and an Ag layer were sequentially formed by sputtering to form a three-layer polarized electrode. Thereafter, a DC electric field of 2 to 4 kV / mm is applied for 10 to 60 minutes between the electrodes on both main surfaces in the insulating oil at 60 to 120 ° C., and dies in the air at 150 to 200 ° C. for 30 to 60 minutes. As a result, a piezoelectric ceramic element having a desired degree of polarization was obtained.

Piezoelectric ceramics having various material compositions shown in Table 1 were obtained, and their resistivity and coercive electric field were measured. The results are shown in Table 1 below.

[0016]

[Table 1]

As is clear from Table 1, the piezoelectric ceramic having the material composition of Sample No. 1 has a considerably high resistivity of 2.0 × 10 ^12, and thus has insufficient heat resistance. On the other hand, in sample No. 6 where α / β is larger than 1, the resistivity is 7.2 × 10 ⁹
, The polarization was difficult, and a desired degree of polarization could not be actually obtained.

On the other hand, in sample numbers 2 to 5, α /
Since β is greater than ２ and equal to or less than 1, the resistivity is as low as 6.3 × 10 ¹¹ or less, which indicates that pyroelectric charges are easily released when a temperature change is given. In addition, as is clear from Table 1, the resistivity is not too low, and a desired degree of polarization can be realized.

Further, when a piezoelectric vibrating gyroscope is used, a decrease in gyro sensitivity due to a thermal shock test is small, and it can be seen that the reliability as a piezoelectric vibrating gyroscope is high. Therefore, in the above composition formula, the crystal structure is tetragonal, and α /
By making the value of β greater than 1/2 and 1 or less,
It can be seen that the coercive electric field of the piezoelectric ceramic is increased, and deterioration of piezoelectric characteristics such as depolarization due to high temperature or thermal shock hardly occurs. In addition, it can be seen that pyroelectric charges are easily released because the resistance value is low, and deterioration of characteristics such as polarization reversal due to the pyroelectric effect can be prevented. Therefore, it can be seen that the resistance to changes in the ambient temperature, thermal shock during the manufacturing process and actual use is increased, and the reliability of the piezoelectric vibrating gyroscope is improved.

In the above composition formula, a part of Pb may be replaced with Sr, Ca, Ba or the like. Further, the ratio between the A site and the B site, that is, the ratio between Pb and the Pb-substitutable element and Zr, Ti, Mn, and Nb is not limited to 1: 1.

The piezoelectric vibrating gyroscope according to the present embodiment is configured such that a piezoelectric vibrator is formed by using a piezoelectric ceramic having the above specific composition. The structure of the piezoelectric vibrating gyroscope itself varies according to a conventionally known piezoelectric vibrating gyroscope. Can be configured. Hereinafter, as one embodiment of the present invention, a piezoelectric vibrating gyroscope using the above-described piezoelectric ceramic will be described in more detail while describing a manufacturing method thereof.

The two piezoelectric ceramic elements prepared as described above were adhered to each other using an epoxy-based adhesive so that their polarization directions were opposite to each other, and were adhered. On both main surfaces of this laminate, the electrodes used for the polarization were processed so as to form electrodes on both main surfaces of a piezoelectric bimorph vibrator to be described later. Next, it was cut by a dicer in a direction perpendicular to the bonding surface to obtain a bimorph vibrator of about 1 × 1 × 15 mm.

Using the bimorph vibrator obtained as described above, a piezoelectric vibrating gyroscope shown in FIGS. 1 and 2 was constructed. In FIG. 1, the piezoelectric vibrating gyroscope has the piezoelectric bimorph vibrator 1 obtained as described above. As shown in FIGS. 2A to 2C, the piezoelectric bimorph vibrator 1 has a structure in which two piezoelectric ceramic elements 2a and 2b are bonded using the above-described epoxy adhesive. The piezoelectric ceramic elements 2a and 2b are polarized in the thickness direction.
The polarization directions are opposite to each other.

On the upper surface 1a of the piezoelectric bimorph vibrator 1, detection electrodes 3a and 3b divided into two in the width direction by the above-described electrode processing are formed. Note that, on the upper surface of the piezoelectric bimorph vibrator 1, the detection electrodes 3a and 3b
It is offset in the length direction. On one end side of the detection electrode 3a, an electrode 3c is formed separately from the detection electrode 3a. The electrode 3c is provided to increase the bonding strength of a support member 4b described later. Similarly, on one end side of the detection electrode 3b, the electrode 3d is formed separately from the detection electrode 3b.

The detection electrodes 3a, 3b and the electrodes 3c,
As shown by hatching in FIG. 2A, electrodes 3e to 3e are located outside the portion where 3d is formed in the longitudinal direction.
Although electrodes 3h are formed, these electrodes 3e to 3h are not used as electrodes, but are electrode film portions remaining after the above-described electrode processing method.

On the other hand, the lower surface 1b of the piezoelectric bimorph vibrator 1
A drive electrode 5 is formed over the entire surface. Returning to FIG. 1, the piezoelectric bimorph vibrator 1 vibrates in a bending mode when driven. It is configured to be supported by supporting members 4a to 4d made of metal or the like near the node point of the bending mode. Support members 4a to 4d
Is formed by bending a metal wire. The support member 4a is joined to the detection electrode 3a and the electrode 3d, and the support member 4b is connected to the electrode 3c and the detection electrode 3b.
And is joined to. Similarly, the piezoelectric bimorph vibrator 1
On the lower surface of the driving electrode 5, the support members 4 c and 4 d
Is joined to.

The support members 4a to 4d not only mechanically hold the piezoelectric bimorph vibrator 1 near a vibration node, but also electrically connect the detection electrodes 3a, 3b or the drive electrode 5 to a detection circuit. It also performs a function.

Therefore, the support members 4a to 4d and the detection electrodes 3a, 3b or the drive electrode 5 are joined using a conductive joining material such as solder or a conductive adhesive. In this embodiment, the piezoelectric bimorph vibrator 1 is housed in the base member 7 in a state shown in FIG. 1 while being supported by the support members 4a to 4d. In addition, the support members 4a to 4d
Is fixed to the base member 7 by bonding with epoxy adhesive rectangular portion 4a ₁ ~4d ₁ formed in the base member 7, respectively. The support members 4a and 4b extend to electrodes (not shown) provided on the processing circuit board 8,
And are electrically connected. In this case, the support members 4a to 4d hold the piezoelectric bimorph vibrator 1 so as not to hinder the vibration of the piezoelectric bimorph vibrator 1. Also,
At least one of the support members 4c and 4d extends to an electrode on the processing circuit board 8 and is electrically connected.

Attachment members made of an elastic material are provided at both ends in the longitudinal direction of the base member 7 so that the base member 7 can be sandwiched between the stem 6 and the processing circuit board 8 without hindering the vibration of the piezoelectric bimorph vibrator 1. 7a and 7b are attached.

The processing circuit board 8 is disposed above the piezoelectric bimorph oscillator, drives the piezoelectric bimorph oscillator 1,
And a circuit for operating as a piezoelectric vibrating gyroscope. That is, the driving circuit 11 and the adding circuit 1 shown in FIG.
2 and the differential circuit 13 are formed on the processing circuit board 8.

The stem 6 is arranged below the piezoelectric bimorph vibrator. The stem 6 is provided with a plurality of terminals 6a to 6e, and the terminals 6a to 6e penetrate the stem 6 and penetrate through holes 8a to 8e provided in the processing circuit board 8. Are located in The terminals 6 a to 6 e are electrically connected to a circuit on the processing circuit board 8.

In the piezoelectric vibrating gyroscope, an oscillating circuit as a driving circuit 11 provided on the processing circuit board 8 is electrically connected to the driving electrode 5, and a bimorph vibration is generated by an output signal from the driving circuit 11. The child 1 bends and vibrates in the stacking direction. When a rotational angular velocity about the longitudinal direction is applied to the piezoelectric bimorph vibrator 1, a bending vibration corresponding to the rotational angular velocity is generated in a direction orthogonal to the bending vibration, and between the two detection electrodes 3 a and 3 b. A voltage difference occurs according to the rotational angular velocity. The difference between the output voltages generated at the detection electrodes 3a and 3b is obtained by the differential circuit 13, and the rotational angular velocity applied to the piezoelectric vibrating gyroscope is measured.

In the above-described embodiment, the bimorph type piezoelectric vibrator 1 in which two layers of piezoelectric ceramic elements are bonded is described as an example of the piezoelectric vibrator used in the piezoelectric vibrating gyroscope. The piezoelectric vibrating gyroscope may be constituted by a unimorph type piezoelectric vibrator instead of a bimorph type vibrator.

[0034]

According to the piezoelectric ceramic composition for a piezoelectric vibrating gyroscope of the present invention, PbZrO ₃ -PbTiO ₃ -Pb (MnαN
bβ) O ₃ , where ＜< α / β ≦ 1 and α + β
= 1), and has a tetragonal crystal structure in the operating temperature range. Therefore, as is clear from the above experimental example, the resistivity is low, and therefore the influence of the pyroelectric effect is obtained. Can be reduced. Therefore, it is possible to suppress the deterioration of the characteristics due to the change in the ambient temperature and the pyroelectric effect due to the thermal shock during the manufacturing process and during actual use.

In addition, since the piezoelectric ceramic composition has the above composition, the coercive electric field is increased, and therefore, deterioration of piezoelectric characteristics such as thermal polarization due to high temperature or thermal shock hardly occurs. Therefore, by forming the piezoelectric vibrator of the piezoelectric vibrating gyroscope using the piezoelectric vibrating gyroscope piezoelectric ceramic composition according to the present invention, a detection error due to a change in ambient temperature or the like is unlikely to occur, and the detection accuracy is excellent and the reliability is high. It is possible to provide a piezoelectric vibrating gyroscope according to the present invention which is excellent in quality.

[Brief description of the drawings]

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

FIGS. 2A to 2C are a plan view, a bottom view, and a front view for explaining a relationship between a piezoelectric bimorph vibrator and a support member in the piezoelectric vibrating gyroscope of the embodiment shown in FIG.

FIG. 3 is a schematic diagram for explaining a detection operation in the piezoelectric vibrating gyroscope of the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric bimorph vibrator 2a, 2b ... Piezoelectric ceramic layer 3a, 3b ... Detection electrode 4a-4d ... Support member 5 ... Drive electrode 6 ... Stem 7 ... Base member 8 ... Processing circuit board provided with drive circuit and detection circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/187 H01L 41/18 101D F-term (Reference) 2F105 AA02 AA08 BB04 BB09 BB14 CC06 CD02 CD06 4G031 AA11 AA12 AA14 AA16 AA19 AA32 BA10 CA01

Claims (4)

[Claims] 1. A piezoelectric ceramic composition used for a piezoelectric vibrating gyroscope, comprising: PbZrO ₃ -PbTiO ₃ -Pb (MnαNbβ)
O ₃ , (however, 1/2 <α / β ≦ 1, and α + β = 1)
A composite perovskite-type oxide represented by
A piezoelectric ceramic composition for a piezoelectric vibrating gyroscope, wherein the crystal structure is tetragonal in a use temperature range. 2. The piezoelectric ceramic composition for a piezoelectric vibrating gyroscope according to claim 1, wherein an acceptor element is added as a sub-component. 3. A piezoelectric vibrator, a driving circuit for driving the piezoelectric vibrator, and a detecting circuit for detecting Coriolis force from the piezoelectric vibrator, wherein the piezoelectric vibrator is PbZrO ₃ − PbTiO ₃ -Pb (M
nαNbβ) O ₃ , a piezoelectric ceramic having a composite perovskite-type oxide represented by (where <1/2 <α / β ≦ 1 and α + β = 1) as a main component, and having a tetragonal crystal structure in a use temperature range. A piezoelectric vibrating gyroscope, comprising a composition. 4. The piezoelectric vibrating gyroscope according to claim 3, wherein an acceptor element is added as a sub-component to the piezoelectric ceramic composition.