JP2000074938A - Piezoelectric three-axis acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-axis acceleration sensor without any need for using a signal amplification circuit. SOLUTION: Electrodes DX1 and DX2 for detecting X-axis acceleration and electrodes DY1 and DY2 for detecting Y-axis acceleration are constituted of charge generation parts X21 and Y11 for generating a spontaneous polarization charge and load parts X22 and Y12 that become a load for the charge generation parts X21 and Y11. As a result, by reducing the output level of an acceleration signal that is outputted from the electrodes DX1 and DX2 for detecting X-axis acceleration and the electrodes DY1 and DY2 for detecting Y-axis acceleration, the level of an X-axis acceleration detection signal that is obtained from each electrode for detection and the levels of a Y-axis acceleration detection signal and a Z-axis acceleration detection signal are set essentially equally when an acceleration with the same size operates on a weight 3 in the directions of X, Y, and Z axes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric type three-axis acceleration sensor for detecting three-axis accelerations in mutually orthogonal X-axis, Y-axis and Z-axis directions using piezoelectric ceramics. .

[0002]

2. Description of the Related Art FIG. 3 shows a basic electrode pattern formed on the surface of a piezoelectric ceramic substrate 101 used in a conventional piezoelectric type triaxial acceleration sensor. As shown in this figure,
On one surface of the piezoelectric ceramic substrate 101, a detection electrode pattern E101 is formed. The detection electrode pattern E101 includes an X-axis direction electrode pattern in which X-axis acceleration detection electrodes X1 and X2 and X-axis output electrodes X3 and X4 are connected in series by connection lines X5 and X6, respectively, and a Y-axis acceleration detection electrode pattern. The Y-axis direction electrode pattern in which the electrodes Y1, Y2 and the Y-axis output electrodes Y3, Y4 are connected in series by connection lines Y5, Y6, respectively, and the Z-axis acceleration detection electrodes Z1 to Z1 connected to each other by a connection line Z6. Z4 and Z-axis output electrode Z5
And the Z-axis direction electrode pattern connected by the connection line Z7. As shown in the schematic diagrams of FIGS. 4A and 4B, a counter electrode pattern E10 facing the acceleration detection electrodes X1.
2 is formed. Also, the piezoelectric ceramic substrate 10
A diaphragm 102 is bonded to the back surface of the diaphragm 1 via an adhesive layer, and a columnar or cylindrical weight 103 is fixed to a central portion on the back surface side of the diaphragm.
As shown in FIG. 3, a portion of the piezoelectric ceramic substrate 101 facing the weight 103 has a circular weight facing region 101A.
Is formed. When the acceleration acts on the weight 103, the weight facing region 1 of the piezoelectric ceramic substrate 101 is moved.
The piezoelectric ceramic substrate 101 is supported by the pedestal 104 such that a stress generating region (intermediate region) 101B in which stress is generated is formed outside 01A.

Each part of the piezoelectric ceramic substrate 101 corresponding to the X-axis acceleration detecting electrodes X1 and X2 has one X-axis acceleration detecting electrode X1 and the other X-axis acceleration detecting element when the same kind of stress is generated in each part. The polarization processing is performed in advance so that spontaneous polarization charges of opposite polarities appear on the acceleration detection electrode X2. Also, when the same type of stress is applied to each part of the piezoelectric ceramic substrate 101 corresponding to the Y-axis acceleration detection electrodes Y1 and Y2, one Y-axis acceleration detection electrode Y1 and the other Y-axis acceleration The polarization processing is performed in advance so that spontaneous polarization charges of opposite polarities appear on the detection electrode Y2. Further, each part of the piezoelectric ceramic substrate 101 corresponding to the four Z-axis acceleration detecting electrodes Z1 to Z4 has spontaneous polarization of the same polarity applied to all the Z-axis acceleration detecting electrodes when the same type of stress is generated in each part. A polarization process has been performed in advance so that charges appear.

In the conventional piezoelectric type triaxial acceleration sensor, the acceleration detecting electrodes X1, X2, Y1, Y2, and Z1 to Z4 form a weight facing region 101A on a surface of the piezoelectric ceramic substrate 101 corresponding to the stress generating region 101B. It is formed so as to form an annular row. Then, as shown in FIG. 4A, when an acceleration A1 in the X-axis direction acts on the weight 103, the piezoelectric ceramic substrate 101 is deformed point-symmetrically about the center of gravity of the weight 103. In this case, a compressive stress is generated at the X-axis acceleration detecting electrode X1 and X
Tensile stress is generated at the axial acceleration detection electrode X2, and spontaneous polarization charges (positive in this case) having the same polarity appear on both the detection electrodes X1 and X2. X-axis output electrode X3
A current based on these same-polarity spontaneous polarization charges flows from X4. Similarly, when acceleration in the Y-axis direction is applied,
A current based on the charge obtained by adding the spontaneous polarization charges of the same polarity flows out from the shaft output electrodes Y3 and Y4.

On the other hand, as shown in FIG.
When the acceleration A2 in the Z-axis direction acts on the weight 103, a tensile stress is generated inside the portion of the piezoelectric ceramic substrate 101 on which the Z-axis acceleration detecting electrodes Z1, Z3,. Since the portions of the piezoelectric ceramic substrate corresponding to the Z-axis acceleration detecting electrodes Z1, Z3,... Are all polarized to the same polarity, all the Z-axis acceleration detecting electrodes Z1, Z3,. .. Appear in this case, and the charges appearing on the Z-axis acceleration detecting electrodes Z1, Z3,... Are added and output as a current signal or a voltage signal from the Z-axis output electrode Z5. In this way, the triaxial acceleration is detected by the current value or the voltage value output from each of the output electrodes X3, X4, Y3, Y4, and Z5. However, in this type of piezoelectric triaxial acceleration sensor, when acceleration in the X-axis direction or the Y-axis direction acts on the weight 103 as shown in FIG. Stress tends to concentrate on the portion of the piezoelectric ceramic substrate 101 where the X2 or Y-axis acceleration detecting electrodes Y1 and Y2 are formed. On the other hand, FIG.
As shown in the figure, the acceleration of the same magnitude in the Z-axis direction
3, the Z-axis acceleration detecting electrode Z1
Are hardly concentrated on the portion of the piezoelectric ceramic substrate 101 where... Are formed. Therefore, when detecting accelerations of the same magnitude, only the Z-axis acceleration signal (voltage or current) of the X-, Y-, and Z-axis acceleration signals obtained from the piezoelectric three-axis acceleration sensor is the other two. It is smaller than the acceleration signal. Therefore, conventionally, a signal amplifying circuit is provided in the sensor to match the magnitudes of the X-axis, Y-axis, and Z-axis acceleration signals.

[0006]

However, if a signal amplification circuit is provided in the sensor, the production of the piezoelectric triaxial acceleration sensor becomes complicated, and the miniaturization of the piezoelectric triaxial acceleration sensor is hindered. there were.

An object of the present invention is to provide a piezoelectric three-axis acceleration sensor that does not require the use of a signal amplification circuit.

Another object of the present invention is to provide a piezoelectric three-axis acceleration sensor which does not need to change the degree of amplification according to the acceleration signal in each direction even if an amplifier circuit is used, thereby simplifying the configuration and design of the amplifier circuit. Is to provide.

[0009]

SUMMARY OF THE INVENTION A piezoelectric three-axis acceleration sensor to which the present invention is applied detects three-axis accelerations in the X-axis direction, the Y-axis direction, and the Z-axis direction which are orthogonal to each other. A pair of electrodes for X-axis acceleration detection, a pair of electrodes for Y-axis acceleration detection and a plurality of electrodes for Z-axis acceleration detection on the front surface, and one or more counter electrodes facing each detection electrode on the back surface. A piezoelectric ceramic substrate having, a diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate, and a weight provided at the center of the back surface of the diaphragm,
A base supporting the diaphragm so that a portion of the piezoelectric ceramic substrate around the weight is bent when acceleration is applied to the weight. The pair of X-axis acceleration detecting electrodes are arranged side by side in the X-axis direction with a weight therebetween, and the portions of the piezoelectric ceramic substrate corresponding to the pair of X-axis acceleration detecting electrodes are respectively polarized to opposite polarities. I have. The pair of Y-axis acceleration detecting electrodes are arranged side by side in the Y-axis direction with a weight therebetween, and the portions of the piezoelectric ceramic substrate corresponding to the pair of Y-axis acceleration detecting electrodes are respectively polarized in opposite polarities. I have. Further, the plurality of Z-axis acceleration detecting electrodes are arranged with a weight therebetween, and the portions of the piezoelectric ceramic substrate corresponding to the one or more pairs of Z-axis acceleration detecting electrodes are respectively polarized to the same polarity. The X-axis acceleration detecting electrode, the Y-axis acceleration detecting electrode, and the Z-axis acceleration detecting electrode generate an X-axis acceleration detecting signal by spontaneous polarization charges generated by bending of a portion of the piezoelectric ceramic substrate caused by displacement of the weight. They are arranged so that a Y-axis acceleration detection signal and a Z-axis acceleration detection signal can be obtained. In the present invention, when accelerations of the same magnitude act on the weight in the X-axis direction, the Y-axis direction, and the Z-axis direction, an X-axis acceleration detection signal, a Y-axis acceleration detection signal, The shapes and arrangement positions of the X-axis acceleration detection electrode, the Y-axis acceleration detection electrode, and the Z-axis acceleration detection electrode are determined so that the levels of the Z-axis acceleration detection signals are substantially equal.

According to the present invention, the X-axis acceleration detecting electrode, Y
If the shape and arrangement position of the electrode for axis acceleration detection and the electrode for Z axis acceleration detection are determined, using one diaphragm,
It is possible to obtain a piezoelectric three-axis acceleration sensor that can match the output levels of acceleration signals without using a signal amplification circuit. Further, since the signal levels of the X-axis acceleration signal, the Y-axis acceleration signal, and the Z-axis acceleration signal can be made the same, even if an amplifier circuit is used, it is not necessary to change the degree of amplification according to the acceleration signal in each direction. Is simpler in structure and design.

The diaphragm, the weight, the base and the additional weight are preferably formed integrally. In this way, unlike the conventional acceleration detecting device in which each member is joined by an adhesive, the weight, the additional weight, and the base can be securely connected to the diaphragm. Further, since the weight and the additional weight are integrally formed with the diaphragm, the mounting position of the weight with respect to the diaphragm and the additional weight can be made constant, and a decrease in the measurement accuracy of the acceleration detection device can be suppressed. Also,
The number of parts of the acceleration detection device is reduced, and the manufacture of the acceleration detection device is facilitated.

The present invention is also applied to a piezoelectric type triaxial acceleration sensor in which a weight is directly joined to the center of the back surface of a piezoelectric ceramic substrate without using a diaphragm, and the piezoelectric ceramic substrate is directly supported by a base. can do. In this case, the piezoelectric ceramic substrate is directly bent by the displacement of the weight. Therefore, since the stress due to the displacement of the weight caused by the acceleration acting on the weight is directly generated in the piezoelectric ceramic substrate, the measurement accuracy or sensitivity of the piezoelectric acceleration sensor can be increased. Also, since there is no need to use a diaphragm, the number of parts can be reduced.

According to the present invention, the X-axis acceleration detecting electrode, Y
Various methods can be adopted to determine the shapes and the positions of the electrodes for detecting the axial acceleration and the electrodes for detecting the Z-axis acceleration. For example, an X-axis acceleration detection electrode and a Y-axis acceleration detection electrode are used to generate a spontaneously polarized electric charge.
What is necessary is just to comprise so that it may have a load part which becomes a load with respect to this charge generation part. In this way, a part of the spontaneous polarization charges generated in the X-axis acceleration detection electrode and the Y-axis acceleration detection electrode can be consumed by the load of each electrode. Therefore, the output level of the acceleration signal output from the X-axis acceleration detection electrode and the Y-axis acceleration detection electrode can be reduced to be the same as the output level of the acceleration signal output from the Z-axis acceleration detection electrode. In this case, the load portion may be configured to be located outside the charge generation portion and extend in a direction away from the weight. Further, an X-axis direction acceleration detection electrode and a Y-axis direction acceleration detection electrode are formed on a stress generating region located outside a weight facing region facing the weight of the piezoelectric ceramic substrate, and the weight facing region is formed with a stress. An electrode for acceleration detection in the Z-axis direction may be formed above the counterweight region and the stress generation region so as to straddle a virtual boundary line at the boundary with the generation region. Normally, when the acceleration in each direction is applied to the weight, the largest stress is generated at the boundary between the weight facing region and the stress generating region, and the radially outward (outside of the stress generating region) is separated from the boundary. The stress decreases in accordance with Therefore, if the X-axis acceleration detecting electrode and the Y-axis acceleration detecting electrode are arranged as described above, when the same magnitude of acceleration acts on the weight in each direction, the weight is arranged so as to straddle the boundary line. The amount of spontaneously polarized charges generated in the X-axis acceleration detection electrode and the Y-axis acceleration detection electrode is smaller than that in the first embodiment. As a result, the output level of the acceleration signal output from the X-axis acceleration detection electrode and the output level of the acceleration signal output from the Y-axis acceleration detection electrode can be matched with the output level of the acceleration signal output from the Z-axis acceleration detection electrode.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic plan view of a piezoelectric triaxial acceleration sensor according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line BB of FIG. 1A. As shown in both figures, the piezoelectric triaxial acceleration sensor includes a diaphragm 1, a weight 3, a base 5, an acceleration detecting element 7,
And In the figure, the thickness of each part of the acceleration detecting element 7 is exaggerated for easy understanding.

The diaphragm 1, the weight 3, and the base 5 are integrally formed of a metal material made of brass. Diaphragm 1 has a disk shape and has a thickness of 0.1 mm. The weight 3 has a columnar shape, and is provided at the center of the rear surface of the diaphragm 1 so that the extension of the axis passes through the center of the diaphragm 1. The base 5 has a cylindrical shape surrounding the weight 3, and the diaphragm 1 around the weight 3 when acceleration acts on the weight 3.
The diaphragm 1 is supported so as to bend at the portion. When the base 5 is joined to the mounting member 9, the piezoelectric triaxial acceleration sensor is fixed to the mounting member 9. In this example, a cylindrical metal material made of brass was prepared, and the cylindrical metal material was subjected to cutting to integrally form the diaphragm 1, the weight 3, and the base 5.

The acceleration detecting element 7 has a structure in which an electrode pattern E1 for detecting triaxial acceleration is formed on the front surface of a piezoelectric ceramic substrate 7a, and a counter electrode pattern E2 is formed on the back surface. The back surface of the piezoelectric ceramic substrate 7a and the counter electrode pattern E2 are joined to the surface of the diaphragm 1 with an epoxy-based adhesive, and the acceleration detecting element 7 is attached to the diaphragm 1.

The piezoelectric ceramic substrate 7a has a rectangular plate shape, and a portion corresponding to the acceleration detection electrodes DX1 is subjected to a polarization process so that spontaneous polarization charges are generated when stress is applied to the inside. . The polarization process will be described later in detail. Further, the piezoelectric ceramic substrate 7a
It has a weight facing region 11A, a stress generating region 11B, and a base facing region 11C. The weight facing region 11 </ b> A has a circular shape at the center of the piezoelectric ceramic substrate 1. The weight 3 is located in a portion corresponding to the weight facing region 11A.

The stress generating region 11B has an inner peripheral stress generating region 11B1 and an outer peripheral stress generating region 11B2. The inner peripheral side stress generation region 11B1 is
It has an annular shape surrounding A. When an acceleration acts on the weight 3 in a direction parallel to the piezoelectric ceramic substrate 7a, the inner peripheral stress generation region 11B1 is different in a point-symmetrical manner with respect to the center of gravity of the weight 3 (tensile stress is applied). And a state in which compressive stress is applied). When an acceleration acts on the weight 3 in a direction orthogonal to the piezoelectric ceramic substrate 7a, each part of the inner peripheral side stress generating region 11B1 is deformed to the same state. The outer peripheral stress generating area 11B2 has an annular shape surrounding the inner peripheral stress generating area 11B1. This outer peripheral side stress generation region 11B
2, when an acceleration acts on the weight 3 in a direction orthogonal to the piezoelectric ceramic substrate 1,
Deforms to a state different from B1.

The base facing region 11C has an annular shape surrounding the outer peripheral side stress generating region 11B2. The base 5 is located at a portion corresponding to the base facing region 11C.

The detection electrode pattern E1 and the counter electrode pattern E2 formed on the front and back surfaces of the piezoelectric ceramic substrate 7a are both formed by screen printing. The counter electrode pattern E2 is the acceleration detection electrodes DX1, DX2, D of the detection electrode pattern E1 described later.
Y1, DY2, DZ1 and DZ4 are formed at portions opposed to each other. When the diaphragm 1 is deformed based on the acceleration acting on the weight 3, the spontaneous polarization charge generated between the acceleration detecting electrode DX1 of the detecting electrode pattern E1 and the counter electrode pattern E2 changes, and the triaxial (X axis, Y
The acceleration in the (axis, Z-axis) direction is measured as a change in current or voltage. The X axis, the Y axis, and the Z axis are axes extending in directions orthogonal to each other, the X axis extends in the direction of the virtual straight line XL, the Y axis extends in the direction of the virtual straight line YL, and the Z axis. Extends in a direction perpendicular to the surface direction of the piezoelectric ceramic substrate 7a. The configuration of such a piezoelectric type triaxial acceleration sensor using piezoelectric ceramics is disclosed in a plurality of publications such as US Pat. No. 5,365,799.

The detection electrode pattern E1 is composed of an X-axis electrode pattern 13, a Y-axis electrode pattern 15, and a Z-axis electrode pattern 17.
And The X-axis electrode pattern 13 has a structure in which a pair of X-axis acceleration detection electrodes DX1, DX2 and an X-axis output electrode OX are connected by connection lines L1, L2. The X-axis acceleration detecting electrodes DX1 and DX2 are formed to a thickness of 10 μm by screen printing using a silver paste, and are arranged side by side with the weight 3 in the virtual straight line XL direction. Also, the electrode DX for X-axis acceleration detection
1 and DX2 are mostly inner peripheral side stress generating regions 11B1
The edge portion along the inner periphery of the inner peripheral side stress generating region 11B1 enters the counterweight region 11A. The structure of the X-axis acceleration detecting electrode DX2 will be described in more detail with reference to DX2 in FIG. 1. The X-axis acceleration detecting electrode DX2 includes a charge generating portion X21 that generates spontaneously polarized charges, and a charge generating portion X21. A load portion X22 serving as a load is provided for the portion X21. The charge generation portion X21 is formed by a virtual boundary line K at the boundary between the weight facing region 11A and the inner peripheral side stress generation region 11B1.
The load portion X22 is a portion including the upper portion and located outside the charge generation portion X21 and extending in a direction away from the weight 3. Part of the spontaneous polarization charge generated in the charge generation portion X21 is consumed in the load portion X22. Then, when an acceleration of a certain magnitude acts in the Z-axis direction, a combined signal (Z) obtained from the Z-axis acceleration detecting electrodes DZ1 to DZ4.
The level of the X-axis acceleration detection signal) is substantially the same as the level of the composite signal (X-axis acceleration detection signal) obtained from the X-axis acceleration detection electrodes DX1 and DX2 when an acceleration of the same magnitude acts in the X-axis direction. The size and shape of the load portion X22 are designed so as to be substantially equal.

The X-axis output electrode OX has a substantially rectangular shape, and is formed so as to be located on the outer peripheral edge of the piezoelectric ceramic substrate 7a outside the base facing region 11C. The Y-axis electrode pattern 15 includes a pair of Y-axis acceleration detection electrodes DY1 and DY2 and a Y-axis output electrode OY connected to a connection line L3.
To L5. The Y-axis acceleration detecting electrodes DY1 and DY2 are formed to a thickness of 10 μm by screen printing using a silver paste.
They are arranged side by side in the imaginary straight line YL direction with the weight 3 therebetween. The Y-axis acceleration detecting electrodes DY1 and DY2 also have the same shape as the X-axis acceleration detecting electrodes DX1 and DX2, and are formed so that most of them are located on the surface corresponding to the inner peripheral side stress generating region 11B1. The edge portion along the inner periphery of the inner peripheral side stress generation region 11B1 enters the counterweight region 11A. The configuration of the Y-axis acceleration detecting electrode will be described more specifically with reference to DY1 in FIG. 1. The Y-axis acceleration detecting electrode DY1 also generates spontaneous polarization charges similarly to the X-axis acceleration detecting electrode DX2. And a load portion Y12 acting as a load on the charge generation portion Y11. When an acceleration of a certain magnitude acts in the Z-axis direction, the Z-axis acceleration detecting electrode DZ
When the level of the combined signal (Z-axis acceleration detection signal) obtained from 1 to DZ4 is equal to the acceleration applied in the Y-axis direction, the Y-axis acceleration detection electrodes DY1, DY2
The size and shape of the load portion Y12 are designed so as to be substantially equal to the level of the combined signal (Y-axis acceleration detection signal) obtained from. Accordingly, when accelerations of the same magnitude act on the weight 3 in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, the synthesized X-axis acceleration detection signal obtained from each detection electrode, The levels of the acceleration detection signal and the Z-axis acceleration detection signal become substantially equal.

The Y-axis output electrode OY also has a substantially rectangular shape like the X-axis output electrode OX, and has a base facing region 11C.
Are formed alongside the X-axis output electrode OX so as to be located at the outer peripheral edge of the piezoelectric ceramic substrate 7a outside the piezoelectric ceramic substrate 7a.

The Z-axis electrode pattern 17 includes a Z-axis acceleration detection electrode DZ1, a Z-axis acceleration detection electrode DZ2, a Z-axis acceleration detection electrode DZ3, and a Z-axis acceleration detection electrode DZ4, Z
The shaft output electrodes OZ have a structure in which they are connected in series in this order by connection lines L6 to L9. The four Z-axis acceleration detecting electrodes DZ1 to DZ4 are formed to a thickness of 10 μm by screen printing using a silver paste, and have a shape close to a rectangle. Most of the Z-axis acceleration detecting electrodes DZ1 to DZ4
It is formed so as to be located on a surface corresponding to the inner peripheral portion of B1, and an edge portion along the inner periphery of the inner peripheral side stress generating region 11B1 enters the counterweight region 11A. Also Z
The electrodes DZ1 to DZ4 for detecting the axis acceleration are disposed between the electrode DX2 for detecting the X-axis acceleration and the electrode DY1 for detecting the Y-axis acceleration.
Axis acceleration detection electrode DY1 and X-axis acceleration detection electrode DX
1, between the X-axis acceleration detecting electrode DX1 and the Y-axis acceleration detecting electrode DY2, and between the Y-axis acceleration detecting electrode DY2 and the X-axis acceleration detecting electrode DX2. ing. Therefore, the Z-axis acceleration detecting electrodes DZ1 to DZ4 are arranged at intervals of 90 degrees.

The Z-axis output electrode OZ also has a substantially rectangular shape similarly to the X-axis output electrode OX.
Are formed side by side with the X-axis output electrode OX and the Y-axis output electrode OY so as to be located on the outer peripheral edge of the piezoelectric ceramic substrate 7a on the outside.

The connection line L of each axis electrode pattern
3, L4, L5, L7 and the piezoelectric ceramic substrate 7a, a low dielectric constant layer LE1 is formed, and connection lines L2, L9
A low dielectric constant layer LE between the substrate and the piezoelectric ceramic substrate 7a.
2 are formed. The low dielectric constant layers LE1 and LE2 are formed using glass, a thermosetting resin such as epoxy, or the like having a relative dielectric constant sufficiently smaller than that of the piezoelectric ceramic substrate 7a. These low dielectric layers LE1 and LE2 reduce the capacitance between each connection line L3... And the counter electrode pattern E2, and the spontaneous polarization charges generated in the acceleration detection electrodes DX1. Plays a role in preventing accumulation in the

Each portion of the piezoelectric ceramic substrate 7a corresponding to the X-axis acceleration detecting electrodes DX1 and DX2 has an X-position which is located on one side when the same type of stress is generated in each portion.
The polarization processing is performed so that spontaneous polarization charges of opposite polarities appear on the axial acceleration detecting electrode DX1 and the X-axis acceleration detecting electrode DX2 located on the other side, respectively. In this example, when a tensile stress is generated in each portion of the piezoelectric ceramic substrate 7a corresponding to the X-axis acceleration detection electrodes DX1 and DX2, a positive spontaneous polarization charge appears on the X-axis acceleration detection electrode DX1, and The polarization processing is performed so that a negative spontaneous polarization charge appears on the acceleration detection electrode DX2.

Further, the Y-axis acceleration detecting electrodes DY1, DY
Each of the portions of the piezoelectric ceramic substrate 7a corresponding to the electrode 2 is also one side when the same type of stress is generated in each portion, similarly to the portions of the piezoelectric ceramic substrate 7a corresponding to the X-axis acceleration detecting electrodes DX1 and DX2. Are polarized so that spontaneously polarized charges of opposite polarities appear on the Y-axis acceleration detecting electrode DY1 located on the other side and the Y-axis acceleration detecting electrode DY2 located on the other side. In this example, when a tensile stress is generated in each portion of the piezoelectric ceramic substrate 7a corresponding to the Y-axis acceleration detection electrodes DY1 and DY2, the Y
The polarization processing was performed so that a positive spontaneous polarization charge appeared on the axis acceleration detection electrode DY1 and a negative spontaneous polarization charge appeared on the Y-axis acceleration detection electrode DY2.

Also, the Z-axis acceleration detecting electrodes DZ1 to DZ
Each of the portions of the piezoelectric ceramic substrate 7a corresponding to No. 4 is subjected to a polarization process so that spontaneous polarization charges of the same polarity appear on all the Z-axis acceleration detecting electrodes DZ1 to DZ4 when the same type of stress is generated in each portion. It has been subjected. In this example,
When a tensile stress is generated in the portion of the piezoelectric ceramic substrate 5 corresponding to the Z-axis acceleration detecting electrodes DZ1 to DZ4, Z
Polarization processing was performed so that positive spontaneous polarization charges appeared on the axial acceleration detection electrodes DZ1 to DZ4. In this example, the X-axis acceleration detecting electrodes DX1 and DX2, the Y-axis acceleration detecting electrodes DY1 and DY2, and the Z-axis acceleration detecting electrodes DZ1 to DZ.
4 and the low dielectric constant layers LE1 and LE2 are formed by screen printing, and the connection lines L1 to L9 are formed by screen printing with silver paste to form the detection electrode pattern E1.
Was formed. In addition, the polarization process is performed for each acceleration detection electrode DX.
1, a DC voltage was applied to the piezoelectric ceramic substrate 7a at a stage before forming the connection lines L1 to L9 after forming the low dielectric layers LE1 and LE2 and the counter electrode pattern E2.

In this embodiment, the diaphragm 1, the weight 3, and the base 5 are integrally formed. However, each member may be formed by another member. Also, as shown in FIG. 2, without using a diaphragm, a weight is directly joined to the center of the back surface of the piezoelectric ceramic substrate, and a piezoelectric type triaxial acceleration sensor that directly supports the piezoelectric ceramic substrate with a base is provided. Needless to say, the electrode arrangement structure of this example may be adopted.

FIG. 2A is a schematic plan view of a piezoelectric three-axis acceleration sensor according to another embodiment of the present invention.
FIG. 2B is a sectional view taken along line BB of FIG. The piezoelectric three-axis acceleration sensor according to the present embodiment includes a weight, a base, X
The configuration of the electrode for detecting the axial acceleration and the electrode for detecting the Y-axis acceleration are different from those of the piezoelectric three-axis acceleration sensor shown in FIG. In the piezoelectric triaxial acceleration sensor according to the present embodiment, the weight 23 and the base 25 are directly joined to the piezoelectric ceramic substrate 7a without using a diaphragm. More specifically, the weight 23 has a columnar shape and is made of metal such as brass. The center line is directly joined to the center of the back surface of the piezoelectric ceramic substrate 7a by an appropriate adhesive such as an epoxy adhesive so that the extension of the center line passes through the center of the piezoelectric ceramic substrate 7a. The base 5 has a cylindrical shape and is made of synthetic resin or metal. The base 5 is directly bonded to the piezoelectric ceramic substrate 7a by an adhesive so as to allow displacement of the weight 3 while being fixed to the mounting member 9 such as a case.

The X-axis direction acceleration detecting electrodes DX1 'and DX2' and the Y-axis direction acceleration detecting electrodes DY1 'and DY2' of this piezoelectric three-axis acceleration sensor do not enter the weight-facing area 11A. , Inner peripheral side stress generating region 11
It is formed only on B1. On the other hand, the Z-axis direction acceleration detecting electrodes DZ1 to DZ4 are imagined at the boundary between the weight facing region 11A and the inner peripheral side stress generating region 11B1 similarly to the piezoelectric triaxial acceleration sensor shown in FIG. It is formed on the weight facing region 11A and the inner peripheral side stress generating region 11B1 so as to straddle the boundary line K. Normally, when the acceleration in each direction is applied to the weight 3, the largest stress is generated at the boundary K, and the stress increases as the distance from the boundary K to the outside in the radial direction (outside the inner circumferential side stress generation region 11B1). Decrease. In this example, according to this rule, when accelerations of the same magnitude act on the weight 3 in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, the combined X-axis acceleration obtained from each detection electrode The levels of the detection signal, the Y-axis acceleration detection signal, and the Z-axis acceleration detection signal are set so that X levels are substantially equal.
The positions of the axial acceleration detection electrodes DX1 'and DX2' and the Y-axis acceleration detection electrodes DY1 'and DY2' were determined.

Although the present embodiment is applied to a piezoelectric three-axis acceleration sensor that does not use a diaphragm, the electrode arrangement structure of the present embodiment can be applied to a piezoelectric three-axis acceleration sensor that uses a diaphragm as in the example of FIG. Of course.

[0034]

According to the present invention, it is possible to obtain a piezoelectric type three-axis acceleration sensor that can match the output level of an acceleration signal using one diaphragm without using a signal amplification circuit. Further, since the signal levels of the X-axis acceleration signal, the Y-axis acceleration signal, and the Z-axis acceleration signal can be made the same, even if an amplifier circuit is used, it is not necessary to change the degree of amplification according to the acceleration signal in each direction. The circuit configuration and design are simplified.

[Brief description of the drawings]

FIG. 1A is a schematic plan view of a piezoelectric three-axis acceleration sensor according to one embodiment of the present invention, and FIG.
It is a BB sectional view taken on the line of (A).

FIG. 2A is a schematic plan view of a piezoelectric three-axis acceleration sensor according to another embodiment of the present invention, and FIG.
It is a BB sectional view taken on the line of (A).

FIG. 3 is a view showing a basic electrode pattern formed on the surface of a piezoelectric ceramic substrate used in a conventional piezoelectric three-axis acceleration sensor.

FIG. 4 (A) shows a conventional piezoelectric three-axis acceleration sensor when the acceleration in the X-axis direction acts on an additional weight;
It is a figure used for explaining the spontaneous polarization charge of the electrode for axial acceleration detection, (B) explains the spontaneous polarization charge of the electrode for Z-axis acceleration detection when acceleration in the Z-axis direction acts on an additional weight. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Diaphragm 3 Weight 5 Base 7 Acceleration detecting element 7a Piezoelectric ceramic substrate E1 Detecting electrode pattern E2 Opposing electrode pattern DX1, DX2, DX1 ', DX2' X-axis acceleration detecting electrodes DY1, DY2, DY1 ', DY2' Y-axis Electrode for acceleration detection DZ1 to DZ4 Z-axis acceleration detection electrode

Claims (6)

[Claims] 1. A pair of X-axis acceleration detection electrodes, a pair of Y-axis acceleration detection electrodes, and a plurality of Y-axis acceleration detection electrodes for respectively detecting three-axis accelerations in the X-axis direction, the Y-axis direction, and the Z-axis direction orthogonal to each other. A piezoelectric ceramic substrate having a Z-axis acceleration detecting electrode on its front surface and having at least one counter electrode on its back surface facing each of the detecting electrodes, and the back surface of the piezoelectric ceramic substrate bonded to the front surface A diaphragm, a weight provided at the center of the back surface of the diaphragm, and the diaphragm such that when the acceleration acts on the weight, a portion of the piezoelectric ceramic substrate around the weight is bent. A pair of X-axis acceleration detecting electrodes are arranged side by side in the X-axis direction with the weight interposed therebetween, and correspond to the pair of X-axis acceleration detecting electrodes. The portions of the piezoelectric ceramic substrate are polarized in opposite polarities, and the pair of Y-axis acceleration detecting electrodes are arranged side by side in the Y-axis direction with the weight therebetween, and the pair of Y-axis acceleration detecting electrodes The portions of the piezoelectric ceramic substrate corresponding to the electrodes are respectively polarized in opposite polarities, and the plurality of Z-axis acceleration detecting electrodes are arranged with the weight therebetween, and correspond to the pair of or more Z-axis acceleration detecting electrodes. The portions of the piezoelectric ceramics substrate are polarized to have the same polarity, and the X-axis acceleration detecting electrode, the Y-axis acceleration detecting electrode, and the Z-axis acceleration detecting electrode are formed by the piezoelectric ceramics generated by displacement of the weight. An X-axis acceleration detection signal, a Y-axis acceleration detection signal, and a Z-axis acceleration detection signal are obtained by spontaneous polarization charges generated by bending of the portion of the substrate. In the piezoelectric type three-axis acceleration sensor arranged and arranged, the shape and arrangement position of the X-axis acceleration detection electrode, the Y-axis acceleration detection electrode, and the Z-axis acceleration detection electrode are as follows:
An X-axis acceleration detection signal obtained from each of the detection electrodes when acceleration of the same magnitude acts on the weight in the X-axis direction, the Y-axis direction, and the Z-axis direction;
A piezoelectric three-axis acceleration sensor, wherein the levels of the Y-axis acceleration detection signal and the Z-axis acceleration detection signal are determined to be substantially equal. 2. The piezoelectric three-axis acceleration sensor according to claim 1, wherein the diaphragm, the weight, and the base are integrally formed. 3. A pair of X-axis acceleration detecting electrodes, a pair of Y-axis acceleration detecting electrodes, and a plurality of X-axis acceleration detecting electrodes for detecting three-axis accelerations in the X-axis direction, the Y-axis direction, and the Z-axis direction which are orthogonal to each other. A piezoelectric ceramic substrate having a Z-axis acceleration detection electrode on the front surface and having at least one counter electrode on the back surface facing each of the detection electrodes; and a piezoelectric ceramic substrate provided at the center of the back surface of the piezoelectric ceramic substrate. A weight, and a base that supports the piezoelectric ceramic substrate so that a portion of the piezoelectric ceramic substrate around the weight is bent when the acceleration acts on the weight. A pair of X-axis acceleration detecting electrodes are arranged side by side in the X-axis direction with the weight interposed therebetween, and portions of the piezoelectric ceramic substrate corresponding to the pair of X-axis acceleration detecting electrodes are separated into opposite polarities. The pair of Y-axis acceleration detection electrodes are arranged side by side in the Y-axis direction with the weight therebetween, and the portions of the piezoelectric ceramic substrate corresponding to the pair of Y-axis acceleration detection electrodes are respectively The plurality of Z-axis acceleration detection electrodes are polarized with opposite polarities, and the plurality of Z-axis acceleration detection electrodes are disposed with the weight therebetween, and the portions of the piezoelectric ceramic substrate corresponding to the pair of or more Z-axis acceleration detection electrodes have the same polarity, respectively. The electrode for X-axis acceleration detection, the electrode for Y-axis acceleration detection, and the electrode for Z-axis acceleration detection are spontaneously polarized charges generated by bending of the portion of the piezoelectric ceramic substrate caused by displacement of the weight. Wherein the piezoelectric type three-axis acceleration sensor is arranged so as to obtain an X-axis acceleration detection signal, a Y-axis acceleration detection signal, and a Z-axis acceleration detection signal. The X-axis acceleration detection electrode, the Y-axis acceleration detection electrode, and the Z-axis acceleration detection electrode have the following shapes and arrangement positions:
An X-axis acceleration detection signal obtained from each of the detection electrodes when acceleration of the same magnitude acts on the weight in the X-axis direction, the Y-axis direction, and the Z-axis direction;
A piezoelectric three-axis acceleration sensor, wherein the levels of the Y-axis acceleration detection signal and the Z-axis acceleration detection signal are determined to be substantially equal. 4. The X-axis acceleration detecting electrode and the Y-axis acceleration detecting electrode have a charge generating portion for generating the spontaneously polarized charge and a load portion serving as a load on the charge generating portion. 4. The method according to claim 1, wherein
3. The piezoelectric three-axis acceleration sensor according to 1. 5. The piezoelectric triaxial acceleration sensor according to claim 4, wherein the load portion is located outside the charge generation portion and extends in a direction away from the weight. 6. The X-axis direction acceleration detection electrode and the Y-axis direction acceleration detection electrode are formed on a stress generating region located outside a weight facing region of the piezoelectric ceramic substrate facing the weight. The Z-axis direction acceleration detection electrode is formed on the weight opposing region and the stress generating region so as to straddle a boundary line imagined at a boundary between the weight opposing region and the stress generating region. The piezoelectric type three-axis acceleration sensor according to claim 1 or 3, wherein: