JP2000352567A - Piezoelectric accelerometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric accelerometer whose measuring accuracy is high. SOLUTION: An electrode EP1, for pyroelectric-effect detection, which is not connected electrically to an electrode pattern for acceleration detection is formed on a stress nongenerating region 8C2 in which a stress is not generated substantially when an acceleration acts on the plumb hob of a piezoelectric ceramic substrate 7a. A counter electrode, for pyroelectric-effect detection, which faces the electrode EP1 for pyroelectric-effect detection is formed on the rear of the piezoelectric ceramic substrate 7a. A part which is situated between the electrode EP1, for pyroelectric-effect detection, on the piezoelectric ceramic substrate 7a and the counter electrode for pyroelectric-effect detection is polarization-treated. On the basis of an electric charge which is generated across the electrode EP1 for pyroelectric-effect detection and the counter electrode for pyroelectric-effect detection, a signal change portion generated by a pyroelectric effect is found. The signal change portion is subtracted from an acceleration detection signal, and the acceleration detection signal is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration using piezoelectric ceramics.

[0002]

2. Description of the Related Art A piezoelectric ceramic substrate having an electrode pattern for acceleration detection formed on one surface and a counter electrode pattern opposite to the electrode pattern for acceleration detection formed on the other surface is subjected to polarization processing to receive acceleration. 2. Description of the Related Art There is known a piezoelectric acceleration sensor that outputs an acceleration detection signal corresponding to an acceleration component in each direction based on spontaneous polarization charges generated in an acceleration detection electrode in each direction due to stress generated in a piezoelectric ceramic substrate. The basic principle and basic technology of this acceleration sensor are described in International Publication WO93 / 02342 (PCT / JP9).
2/00882).

[0003] As a result of research by the inventor, in such a piezoelectric acceleration sensor, in addition to spontaneous polarization charges generated by stress generated in the piezoelectric ceramic substrate due to acceleration, a temperature difference applied to the piezoelectric ceramic substrate causes a so-called so-called piezoelectric acceleration sensor. It has been found that spontaneous polarization charges are generated due to the pyroelectric effect. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 10-132845 (Japanese Patent Application No. 8-288080), a piezoelectric acceleration sensor in which a temperature correction electrode is formed on a piezoelectric ceramic substrate has been proposed. This temperature correction electrode is electrically connected to the acceleration detection electrode. Then, a portion of the piezoelectric ceramic substrate corresponding to the temperature correction electrode is subjected to polarization processing in a polarity opposite to that of the portion of the piezoelectric ceramic substrate corresponding to the acceleration detecting electrode. By doing so, the charge due to the temperature difference appearing at the acceleration detection electrode and the charge due to the temperature difference appearing at the temperature correction electrode cancel each other out, and the spontaneously polarized charges generated by the so-called pyroelectric effect are complementarily removed.

[0004]

However, in such a conventional piezoelectric acceleration sensor, since the acceleration detecting electrode and the temperature correction electrode are electrically connected, it is the same as when a capacitor is connected in parallel. In the state, the electric charge appearing on the acceleration detecting electrode at the time of detecting the acceleration flows to the temperature correcting electrode, and the output of the acceleration detecting signal decreases. Further, when there are a plurality of electrodes for acceleration detection, it is necessary to form the temperature correction electrodes corresponding to each of the electrodes for acceleration detection, and there is a problem that the formation pattern of the temperature correction electrodes becomes complicated. In the conventional piezoelectric acceleration sensor, the size and position of the temperature correction electrode were determined by repeating tests or experiments, but the amount of spontaneous polarization charge actually generated by the pyroelectric effect per unit area is unknown. Therefore, there is a certain limit in removing spontaneous polarization charges generated by the pyroelectric effect.

An object of the present invention is to provide a piezoelectric acceleration sensor capable of eliminating the influence of a pyroelectric effect without lowering the output of an acceleration detection signal.

Another object of the present invention is to provide a piezoelectric acceleration sensor capable of eliminating the influence of the pyroelectric effect without forming a complicated electrode pattern.

Another object of the present invention is to provide a piezoelectric acceleration sensor which can remove the influence of the pyroelectric effect to the maximum.

Another object of the present invention is to provide a piezoelectric acceleration sensor capable of measuring the amount of spontaneous polarization charge per unit area actually generated by the pyroelectric effect.

Another object of the present invention is to provide a method for correcting an acceleration detection signal which can obtain an acceleration detection signal with high measurement accuracy.

[0010]

According to the present invention, an acceleration detection electrode pattern is formed on a front surface, and a counter electrode pattern facing the acceleration detection electrode pattern is formed on a back surface. It is an object of the present invention to provide a piezoelectric acceleration sensor including a piezoelectric ceramic substrate in which a portion between the counter electrode pattern and the piezoelectric ceramic substrate is polarized. According to the present invention, a pyroelectric effect detecting electrode that is not electrically connected to the acceleration detecting electrode pattern is provided in a region of the piezoelectric ceramic substrate where stress is not substantially generated, and a pyroelectric effect detecting electrode is interposed between the piezoelectric ceramic substrate and the piezoelectric ceramic substrate. A pyroelectric effect detecting counter electrode facing the electrode is formed, and a polarization process is performed on a portion of the piezoelectric ceramic substrate located between the pyroelectric effect detecting electrode and the pyroelectric effect detecting counter electrode. By doing so, only spontaneous polarization charges due to the pyroelectric effect generated due to the temperature difference applied to the piezoelectric ceramic substrate appear between the pyroelectric effect detecting counter electrode and the pyroelectric effect detecting counter electrode. Therefore, a signal variation generated due to the pyroelectric effect is obtained based on the spontaneous polarization charge due to the pyroelectric effect, and the signal variation is subtracted from the acceleration detection signal output from the acceleration detection electrode pattern. Thus, a more accurate acceleration detection signal excluding the influence of the pyroelectric effect can be obtained.

Particularly, in the piezoelectric acceleration sensor of the present invention, unlike the conventional piezoelectric acceleration sensor, the acceleration detecting electrode and the pyroelectric effect detecting electrode are not electrically connected to each other. The problem that the appearing electric charge flows to the pyroelectric effect detection electrode and the output of the acceleration detection signal decreases can be solved. In addition, the pyroelectric effect detecting electrode may be formed at least at one location, and the formation pattern can be simplified. In addition, since the amount of spontaneous polarization charge due to the pyroelectric effect actually generated per unit area can be accurately obtained, the spontaneous polarization charge generated at each acceleration detecting electrode due to the pyroelectric effect can be almost certainly grasped. , Which can be removed.

The piezoelectric acceleration sensor of the present invention can be applied to various types of piezoelectric acceleration sensors. For example, the present invention can be applied to a one-handed piezoelectric acceleration sensor that supports a piezoelectric ceramic substrate with one hand and vibrates the piezoelectric ceramic substrate with its own weight. Further, the piezoelectric ceramic substrate further includes a diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate, and a weight fixed to the diaphragm so as to protrude to the back surface side of the diaphragm. The present invention is also applicable to a weight-type piezoelectric acceleration sensor that generates stress on a substrate.

More specifically, the weight type piezoelectric acceleration sensor has a base for supporting the outer peripheral portion of the diaphragm so as to allow displacement of the weight, and the piezoelectric ceramic substrate faces the weight. A weight facing region, a base facing region facing the base, and an intermediate region located between the weight facing region and the base facing region. And
In the intermediate region, an electrode pattern for acceleration detection is formed surrounding the weight facing region, and a stress generating region where stress is generated when acceleration acts on the weight, and a stress generating region between the stress generating region and the base facing region. As a result, a stress-free area in which stress is not substantially generated when acceleration acts on the weight appears. The non-stress-generating region does not face the weight and the base, and is a place where the heat capacity of both members is not substantially affected and no stress is generated. Therefore, if the pyroelectric effect detection electrode and the pyroelectric effect detection counter electrode are formed so as to face both surfaces of the stress non-generating region, the amount of spontaneous polarization charges generated by the pyroelectric effect per unit area is generated. Can be accurately grasped, so that the influence of the pyroelectric effect can be eliminated to the maximum.

According to the method of the present invention for correcting the acceleration detection signal output from the acceleration detection electrode pattern of the piezoelectric acceleration sensor, the electric charge generated between the pyroelectric effect detection electrode and the pyroelectric effect detection counter electrode is corrected. Then, the influence of the pyroelectric effect is removed by subtracting the signal fluctuation from the acceleration detection signal based on the signal fluctuation caused by the pyroelectric effect.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a piezoelectric acceleration sensor according to an embodiment of the present invention applied to a piezoelectric triaxial acceleration sensor using a weight. As shown in the figure, this piezoelectric triaxial acceleration sensor is fixed on a surface of the diaphragm 1, a weight 3, a base 5, and a surface opposite to the surface on which the weight 3 of the diaphragm 1 is mounted. Sensor element 7
And In the figure, the thickness of the main part of the sensor element 7 is exaggerated for easy understanding. These members are accommodated in a frame-shaped insulating resin case 9. Then, the output electrodes OX, O of the sensor element 7 are attached to the resin molding 21 in the insulating resin case 9.
Two terminal units 11, 11 to which three terminal fittings 25... Connected to Y, OZ and the electrodes OE1 to OE3 are fixed, respectively, are fitted. A metal lid member 6 is attached to the upper opening of the case 9.

The diaphragm 1, the weight 3 and the base 5
As shown in FIG. 1, FIG. 2 (A) and FIG. 2 (B), a single unit 1 integrally formed of a metal material made of brass.
It is configured as 0. FIG. 2A is a bottom view of the single unit 10, and FIG.
FIG. 4 is a cross-sectional view taken along line B. Diaphragm 1 has a disk shape and has a thickness of about 0.1 mm. Weight 3
Has a cylindrical shape, and is integrated with the diaphragm 1 so that an extension of the center line passes through the center of the diaphragm 1. The base 5 has a cylindrical shape and supports the outer peripheral portion of the diaphragm 1. Further, a V-shaped groove 5a that is continuous in the circumferential direction is formed on the outer peripheral portion of the base 5. In the present embodiment, a cylindrical metal material made of brass is prepared, and a cutting process is performed on the cylindrical metal material so as to cut out the weight 3 to form an annular cavity C, and the outer peripheral portion is formed. The V-shaped groove 5a was formed by cutting, and the single unit 10 was integrally formed.

In this example, a piezoelectric ceramic substrate 7a is used as the sensor element 7 as shown in the plan views of FIGS.
An electrode pattern E1 for acceleration detection for triaxial acceleration detection is formed on the front surface of the piezoelectric element, and an annular counter electrode pattern E0 facing the main part of the electrode pattern E1 for acceleration detection is formed on the back surface. An axis sensor element is used. The back surface of the piezoelectric ceramic substrate 7a and the counter electrode pattern E0 are joined to the surface of the diaphragm 1 with an epoxy-based adhesive, and the sensor element 7 is mounted on the diaphragm 1. The surface of the counter electrode pattern E0 on the side of the diaphragm 1 has irregularities, and an adhesive is filled between the concave part of the irregularities and the diaphragm 1 so that the convex part comes into contact with the diaphragm 1. Is
It is joined to the diaphragm 1. Therefore, the opposing electrode pattern E0 is electrically connected to the base 5 via the diaphragm 1. Piezoelectric ceramic substrate 7
“a” has a quadrangular contour shape, and a polarization treatment is applied to a portion corresponding to the electrode so that a spontaneous polarization charge is generated when a stress is applied to the inside. The polarization process will be described later in detail.

As shown in FIG. 3, the piezoelectric ceramic substrate 7a has a weight facing region 8A, a base facing region 8B, and an intermediate region 8C located between the weight facing region 8A and the base facing region 8B. are doing. The weight 3 is located at a portion corresponding to the weight opposing region 8A, and the base opposing region 8
The base 5 is located at a portion corresponding to B. The intermediate region 8C is a stress generating region 8C1 surrounding the weight facing region 8A.
And a stress non-generating region 8C2 located between the stress generating region 8C1 and the base facing region 8B.
The stress generating area 8C1 is an area in which the weight 3 is deformed when an acceleration is applied to generate an internal stress, and the acceleration detecting electrode EX of the acceleration detecting electrode pattern E1 is formed on the surface side.
1 to EZ4 are formed. This stress generating area 8C1
When an acceleration acts on the weight 3 in a direction (X-axis direction or Y-axis direction) parallel to the substrate surface of the piezoelectric ceramic substrate 7a, different states (pulling (A state where a stress is applied and a state where a compressive stress is applied). When acceleration acts on the weight 3 in a direction (Z-axis direction) perpendicular to the substrate surface of the piezoelectric ceramic substrate 7a, each part of the stress generating region 8C1 is deformed to the same state. The stress non-generating region 8C2 is a region where substantially no stress is generated even when an acceleration is applied to the weight 3, or a region where only a very small stress is generated even if a stress is generated. In FIG. 3, 8D
Is a boundary line (neutral line) between the stress generating region 8C1 and the stress non-generating region 8C2.

The acceleration detecting electrode pattern E1 and the counter electrode pattern E0 formed on the front and back surfaces of the piezoelectric ceramic substrate 7a are both formed by screen printing using a glass-silver paste. When the diaphragm 1 is deformed based on the acceleration acting on the weight 3, the piezoelectric ceramic substrate 7a bends, and the spontaneous polarization charge generated between the acceleration detection electrode pattern E1 and the counter electrode pattern E0 changes. Axis (X axis, Y axis)
The acceleration in the (axis, Z-axis) direction is measured as a change in current or voltage. The X axis, Y axis, and Z axis here are axes extending in directions orthogonal to each other. The X-axis extends in the direction of the X-axis virtual line XL, and the Y-axis is the Y-axis virtual line YL.
And the Z axis is the piezoelectric ceramic substrate 7a
Extend in a direction perpendicular to the plane direction of the.

The electrode pattern E1 for acceleration detection includes an X-axis direction detecting electrode pattern 13 and a Y-axis direction detecting electrode pattern 15.
And a Z-axis direction detection electrode pattern 17. The X-axis direction detection electrode pattern 13 has a structure in which a pair of X-axis direction acceleration detection electrodes EX1 and EX2 and an X-axis output electrode OX are connected in series by connection lines L1 and L2.
The pair of X-axis direction acceleration detection electrodes EX1 and EX2 are a pair of Y-axis direction acceleration detection electrodes EY1 and EY2 of the Y-axis direction detection electrode pattern 15 and the Z-axis direction acceleration of the Z-axis direction detection electrode pattern 17, which will be described later. Detection electrodes EZ1
Together with EZ4, an annular row surrounding the weight facing region 8A is formed. The electrodes EX1 and EX2 of the pair of X-axis direction acceleration detection electrodes are line-symmetric with respect to the X-axis direction virtual line XL, and have a weight-facing region 8A and a stress generation region 8C.
It has a shape close to a rectangle that straddles 1. The X-axis output electrode OX has a substantially square shape, and is formed so as to be located at the outer peripheral edge of the base facing region 8B.

Electrode pattern 15 for detecting acceleration in the Y-axis direction
Has a structure in which two Y-axis direction acceleration detecting electrodes EY1 and EY2 and a Y-axis output electrode OY are connected in series by connection lines L3 to L5. Each of the acceleration detection electrodes EY1 and EY2 of the pair of Y-axis direction acceleration detection electrodes has the same shape as the X-axis direction acceleration detection electrodes EX1 and EX2, and corresponds to the Y-axis direction virtual line YL. It is symmetrical and has a shape close to a rectangle straddling the weight facing region 8A and the stress generating region 8C1. Y-axis virtual line YL
And the X-axis direction virtual line XL are orthogonal to each other, so that the X-axis direction acceleration detection electrode EX1, the Y-axis direction acceleration detection electrode EY1, the X-axis direction acceleration detection electrode EX2, and the Y-axis direction acceleration detection electrode EY2 are Each of them is arranged at an interval of 90 degrees. The Y-axis output electrode OY has a substantially square shape similarly to the X-axis output electrode OX, and is formed alongside the X-axis output electrode OX so as to be located at the outer peripheral edge of the base facing region 8B.

Electrode pattern 17 for detecting acceleration in the Z-axis direction
Are Z-axis direction acceleration detecting electrode EZ1, Z-axis direction acceleration detecting electrode EZ2, Z-axis direction acceleration detecting electrode EZ3.
Z-axis direction acceleration detection electrode EZ4, Z-axis output electrode OZ
Have a structure in which they are connected in series in this order by connection lines L6 to L9. The four Z-axis direction acceleration detecting electrodes EZ1 to EZ4 have a shape close to a rectangle.
The Z-axis direction acceleration detecting electrodes EZ1 to EZ4 are also formed so as to straddle the weight facing region 8A and the stress generating region 8C1, similarly to the X-axis direction acceleration detecting electrodes EX1 and EX2. The Z-axis direction acceleration detecting electrodes EZ1 to EZ4 are
Between the X-axis direction acceleration detection electrode EX2 and the Y-axis direction acceleration detection electrode EY1, the Y-axis direction acceleration detection electrode EY1
Between the X-axis direction acceleration detecting electrode EX1 and the X-axis direction acceleration detecting electrode EX1 and the Y-axis direction acceleration detecting electrode EY.
2 and at the center between the Y-axis direction acceleration detection electrode EY2 and the X-axis direction acceleration detection electrode EX2. Therefore, the Z-axis direction acceleration detecting electrodes EZ1 to EZ4 are arranged at intervals of 90 degrees. Z-axis output electrode OZ is also X-axis output electrode O
It has a substantially square shape like X, and the X-axis output electrode OX is located at the outer peripheral edge of the base facing region 8B.
And the Y-axis output electrode OY.

X-axis direction acceleration detecting electrodes EX1, EX2
Is located on one side of the weight opposing area 8A when the same type of stress is generated in each part of the piezoelectric ceramic substrate 7a by applying acceleration in the Z-axis direction to the weight 3 at each part. The polarization processing is performed so that spontaneous polarization charges of opposite polarities appear on the acceleration detection electrode EX1 and the acceleration detection electrode EX2 located on the other side.

The Y-axis direction acceleration detecting electrodes EY1,
Similarly to the respective portions of the piezoelectric ceramic substrate 7a corresponding to the X-axis direction acceleration detection electrodes EX1 and EX2, the weight 3 has a Z portion on the piezoelectric ceramic substrate 7a corresponding to the EY2.
When the same type of stress is generated in each part by the acceleration in the axial direction, the Y-axis direction acceleration detection electrode EY1 located on one side of the weight facing region 8A and the Y-axis direction located on the other side Polarization processing is performed so that spontaneous polarization charges of opposite polarities appear on the acceleration detection electrode EY2.

The Z-axis direction acceleration detecting electrodes EZ1 to EZ1
Each part of the piezoelectric ceramic substrate 7a corresponding to the EZ4 is provided with all the Z-axis direction acceleration detecting electrodes EZ1 to EZ4 when the same type of stress is generated in the respective parts by the acceleration in the Z-axis direction acting on the weight 3. Has been subjected to a polarization treatment so that spontaneous polarization charges of the same polarity appear in FIG.

In this embodiment, the acceleration detection electrodes EX1 to EX1
EZ4 and the counter electrode pattern E0 were screen-printed using a glass-silver paste, and then baked to 5 μm.
After the formation, the piezoelectric ceramic substrate 7a was polarized by applying a DC voltage between the opposing electrodes. Then, the connection lines L1 to L9 are screen-printed with a silver paste, and the electrode patterns E1 for acceleration detection are printed.
Was formed.

FIG. 3 is a sectional view taken along the line IV-IV of FIG.
As shown in FIG. 7, a part of the surface of the non-stress generating region 8C2 of the piezoelectric ceramic substrate 7a is provided with a pyroelectric effect detecting electrode E.
P1 is formed. The pyroelectric effect detection electrode EP1 is formed in a substantially rectangular shape using a glass-silver paste similarly to the acceleration detection electrodes EX1 to EZ4, and is not electrically connected to the acceleration detection electrodes EX1 to EZ4. Is formed. In this example, the pyroelectric effect detection electrode EP
1 is located outside the Z-axis direction acceleration detection electrode EZ1. The pyroelectric effect detection electrode EP1 is connected to the connection line L1.
0 is connected to the electrode OE3. Electrodes OE1 to OE
E3 is formed on the base facing region 8B along the side facing the side of the piezoelectric ceramic substrate 7a where the output electrodes OX, OY, OZ are arranged. Further, on the back surface of the piezoelectric ceramic substrate 7a, a counter electrode EP0 for detecting a pyroelectric effect which is opposed to the electrode EP1 for detecting a pyroelectric effect is formed.
The portion of the piezoelectric ceramic substrate 7a located between the pyroelectric effect detection electrode EP1 and the pyroelectric effect detection counter electrode EP0 is also subjected to polarization processing. This polarization treatment was performed by applying a DC voltage to the piezoelectric ceramic substrate 7a after the formation of the pyroelectric effect detection electrode EP1 and the pyroelectric effect detection counter electrode EP0. The spontaneous polarization charge due to the pyroelectric effect generated by the temperature difference applied to the piezoelectric ceramic substrate 7a also appears between the pyroelectric effect detecting counter electrode EP1 and the pyroelectric effect detecting counter electrode EP0. Therefore, a signal variation caused by the pyroelectric effect is obtained based on the electric charge generated between the two electrodes, and the Z-axis direction acceleration detecting electrodes EZ1 to EZ4 are obtained.
By subtracting this signal variation from the acceleration detection signal output from the piezoelectric acceleration sensor, the effect of the pyroelectric effect can be removed from the Z-axis direction acceleration detection electrodes EZ1 to EZ4 of the piezoelectric acceleration sensor.
When obtaining the signal fluctuation, the total area S of the Z-axis direction acceleration detection electrodes EZ1 to EZ4 and the total area S ′ of the acceleration detection electrodes from which the acceleration detection signals to be corrected are output.
Since it is known in advance, the signal variation may be obtained in consideration of the area ratio S '/ S. Assuming that the spontaneous polarization charge generated at the electrode EP1 by the pyroelectric effect is Q, the spontaneous polarization charge Q 'generated at the Z-axis direction acceleration detecting electrodes EZ1 to EZ4 by the pyroelectric effect is Q' = k · Q · It can be expressed as S '/ S. Here, k is a coefficient obtained by a test and is determined by the material of each part and the position and shape of the electrode.

In this example, the X-axis direction acceleration detecting electrodes EX1 and EX2 and the Y-axis direction acceleration detecting electrode EY
The spontaneous polarization charge due to the pyroelectric effect generated in 1, EY2 is
Since the charges are canceled by charges of different polarities generated by each pair of electrodes, there is no need to perform temperature correction of the acceleration detection signal.

The ground electrode OE1 is connected to the counter electrode pattern E0 via a through-hole conductive portion penetrating the piezoelectric ceramic substrate 7a and a connection line (not shown). The ground electrode OE2 is connected to the pyroelectric effect detecting counter electrode EP0 via a through-hole conductive portion penetrating the piezoelectric ceramic substrate 7a and a connection line (not shown).

In this embodiment, an example in which the present invention is applied to a three-axis acceleration sensor is shown. However, a two-axis acceleration sensor for detecting acceleration in two axes or a one-axis acceleration sensor for detecting acceleration in one axis is also used. Of course, the present invention can be applied.

In the above example, the pyroelectric effect detecting electrode E
Although P1 is formed on the stress-free area 8C2 of the intermediate area 8C, it goes without saying that the pyroelectric effect detecting electrode EP1 may be arranged on the base facing area 8B or the weight facing area 8A. However, in this case, the value of the coefficient k may be appropriately changed in consideration of the heat capacity of the base or the weight.

Further, in the above example, an example is shown in which the present invention is applied to a weight type piezoelectric acceleration sensor which generates stress on a piezoelectric ceramic substrate by acceleration acting on the weight. Also, the present invention can be applied to a piezoelectric acceleration sensor having another structure such as a one-handed piezoelectric acceleration sensor that vibrates the piezoelectric ceramic substrate 107 by its own weight. In FIG. 5, E is an acceleration detection electrode, and EP is a pyroelectric effect detection electrode. Note that EP is formed in a region where stress is not substantially generated even when the substrate 107 vibrates. Incidentally, in the substrate having the illustrated shape, substantially no stress is generated in a region 33% from the front end of the substrate.

[0033]

According to the present invention, spontaneous polarization due to the pyroelectric effect generated between the pyroelectric effect detecting counter electrode and the pyroelectric effect detecting counter electrode due to the temperature difference applied to the piezoelectric ceramics. An electric charge appears. The signal fluctuation caused by the pyroelectric effect can be obtained based on the spontaneous polarization charge, and the signal fluctuation is subtracted from the acceleration detection signal output from the acceleration detection electrode pattern to obtain the pyroelectric effect. A more accurate acceleration detection signal excluding the effect of the effect can be obtained.

In particular, in the piezoelectric acceleration sensor according to the present invention, unlike the conventional piezoelectric acceleration sensor, the acceleration detection electrode and the pyroelectric effect detection electrode are not electrically connected, so that the output of the acceleration detection signal is obtained. Can be solved. In addition, at least one pyroelectric effect detection electrode may be formed, and the electrode pattern does not become complicated. In addition, since the amount of spontaneous polarization charges due to the pyroelectric effect generated per unit area can be obtained almost accurately, spontaneous polarization charges generated at each acceleration detection electrode due to the pyroelectric effect can be almost certainly removed. it can.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an acceleration sensor according to an embodiment of the present invention applied to a three-axis acceleration sensor.

FIG. 2A is a bottom view of a single unit used for the acceleration sensor according to the embodiment of the present invention, and FIG.
It is a BB sectional view taken on the line of (A).

FIG. 3 is a plan view of a sensor element used in the acceleration sensor according to the embodiment of the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

FIG. 5 is a plan view of an acceleration sensor according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diaphragm 3 Weight 5 Base 7a Piezoelectric ceramic substrate 8A Weight facing area 8B Base facing area 8C Intermediate area 8C1 Stress generation area 8C2 Stress non-generation area 9 Insulating resin case E1 Acceleration detection electrode pattern E0 Counter electrode pattern EP1 Pyroelectric Effect detection electrode EP0 Counter electrode for pyroelectric effect detection

Claims (4)

[Claims] 1. An acceleration detection electrode pattern is formed on a front surface, and a counter electrode pattern facing the acceleration detection electrode pattern is formed on a back surface, between the acceleration detection electrode pattern and the counter electrode pattern. A piezoelectric acceleration sensor comprising a piezoelectric ceramic substrate having a portion subjected to polarization processing, wherein a focus not electrically connected to the acceleration detection electrode pattern is provided in a region of the piezoelectric ceramic substrate where stress is not substantially generated. An electrode for detecting an electrostatic effect, and an opposing electrode for detecting a pyroelectric effect that is opposed to the electrode for detecting a pyroelectric effect with the piezoelectric ceramic substrate interposed therebetween; and the electrode for detecting a pyroelectric effect of the piezoelectric ceramic substrate is formed. A portion located between the first electrode and the pyroelectric effect detecting counter electrode is polarized. 2. An acceleration detection electrode pattern is formed on a front surface, and a counter electrode pattern facing the acceleration detection electrode pattern is formed on a back surface, and between the acceleration detection electrode pattern and the counter electrode pattern. A piezoelectric ceramics substrate having a polarized portion, a diaphragm having a front surface joined to the back surface of the piezoelectric ceramics substrate, and a weight fixed to the diaphragm so as to protrude toward the back surface side of the diaphragm. A piezoelectric acceleration sensor comprising: a pyroelectric effect detecting electrode that is not electrically connected to the acceleration detecting electrode pattern in a region of the piezoelectric ceramic substrate where stress is not substantially generated; and the piezoelectric ceramic substrate. A pyroelectric effect detection counter electrode facing the pyroelectric effect detection electrode is formed therebetween, and Piezoelectric acceleration sensor portion located between the pyroelectric effect detection electrode and the pyroelectric effect detection counter electrode mix substrate is characterized in that it is polarized. 3. An electrode pattern for acceleration detection is formed on a front surface, and a counter electrode pattern facing the electrode pattern for acceleration detection is formed on a back surface, between the electrode pattern for acceleration detection and the counter electrode pattern. A piezoelectric ceramics substrate having a portion of which is polarized, a diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate, and a weight fixed to the diaphragm so as to protrude toward the back surface side of the diaphragm; A base for supporting an outer peripheral portion of the diaphragm so as to allow displacement of the weight, wherein the piezoelectric ceramic substrate has a weight facing region facing the weight, and a base facing region facing the base. When,
An intermediate region located between the weight-facing region and the base-facing region, wherein the acceleration detection electrode pattern is formed in the intermediate region and surrounds the weight-facing region, and acceleration is applied to the weight. A stress-generating region in which stress is generated when acting, and a stress-non-generating region which is located between the stress-generating region and the base facing region and in which stress is not substantially generated when acceleration acts on the weight. Wherein the pyroelectric effect detecting electrode formed on the surface of the stress-free area of the piezoelectric ceramic substrate and not electrically connected to the acceleration detecting electrode pattern; and the piezoelectric ceramic A counter electrode for detecting the pyroelectric effect formed on the back surface of the substrate and facing the electrode for detecting the pyroelectric effect, the electrode for detecting the pyroelectric effect of the piezoelectric ceramic substrate; Piezoelectric acceleration sensor, wherein a portion located between the pyroelectric effect detection counter electrode are polarized. 4. A method for correcting an acceleration detection signal output from an acceleration detection electrode pattern of the piezoelectric acceleration sensor according to claim 1, 2, or 3, wherein the pyroelectric effect detection electrode and the pyroelectric A method for correcting an acceleration detection signal, comprising: obtaining a signal variation caused by a pyroelectric effect based on an electric charge generated between the counter electrode for effect detection; and subtracting the signal variation from the acceleration detection signal.