JPH11118822A - Triaxial acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a triaxial acceleration sensor capable of suppressing a variation and dispersion in the peak value of a spontaneous polarization charge due to an error of the fixed position of a weight. SOLUTION: Detecting electrodes DX1, DX2, DY1, DY2, and DZ1 to DZ4 are formed so that they constitute an annular row of electrodes surrounding those areas opposed to a weight 5A. Also each of the detecting electrodes DX1... is formed so that a virtual line extending through a center point of a piezoelectric ceramic substrate 5 in the area opposed to the weight 5A and an middle point positioned at the middle of a pair of sides (K3, K4) of each of the detecting electrodes DX1... and the pair of sides (K3, K4) are extended in parallel with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 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 A detection electrode pattern including an X-axis direction acceleration detection electrode, a Y-axis direction acceleration detection electrode, and a Z-axis direction acceleration detection electrode is formed on one surface, and a detection electrode pattern is formed on the other surface. A polarization process is performed on the piezoelectric ceramic substrate on which the counter electrode pattern facing the electrode pattern is formed, and the X-axis and the X-axis are determined based on spontaneous polarization charges generated in the acceleration detecting electrode in each direction due to stress generated in the piezoelectric ceramic by receiving acceleration. A three-axis acceleration sensor that outputs a signal corresponding to acceleration components in the Y-axis and Z-axis directions is known. The basic principle and basic technology of this three-axis acceleration sensor are described in International Publication WO93.
/ 02342 (PCT / JP92 / 00882).

FIG. 4 shows a basic electrode pattern formed on the surface of a piezoelectric ceramic substrate 101 used in a conventional three-axis acceleration sensor developed by the applicant based on this basic technology. In this figure, X1 and X2 are X-axis direction acceleration detecting electrodes, Y1 and Y2 are Y-axis direction acceleration detecting electrodes, and Z1 to Z4 are Z-axis direction acceleration detecting electrodes. Further, a pair of X, X is an X-axis direction acceleration output electrode, a pair of Y, Y is a Y-axis direction acceleration output electrode, and Z is a Z-axis additional direction speed output electrode. And a pair of X1
0 and X10 are X-axis direction acceleration detecting electrodes X1 and X2.
And a first wiring pattern for connecting the X-axis direction acceleration output electrodes X and X, respectively.
A second wiring pattern for connecting the axial acceleration detection electrodes Y1 and Y2 and the Y-axis acceleration output electrodes Y and Y;
Z10 is a third wiring pattern for connecting the Z-axis direction acceleration detecting electrodes Z1 to Z4 and the Z-axis direction acceleration output electrodes Z. On the back surface of the piezoelectric ceramic substrate 101, a counter electrode pattern facing these electrode patterns is formed. A diaphragm is bonded to the back surface of the piezoelectric ceramic substrate 101 via an adhesive layer, and a columnar or cylindrical weight is fixed to a central portion on the back surface side of the diaphragm. Piezoelectric ceramic substrate 1
01 is a circular weight facing region 10
1A is formed. When the acceleration acts on the weight, the piezoelectric ceramic substrate is supported by the pedestal so that a stress generating region (intermediate region) 101B in which stress is generated outside the weight facing region of the piezoelectric ceramic substrate is formed. I have.

Each portion of the piezoelectric ceramic substrate 101 corresponding to the X-axis direction acceleration detecting electrodes X1 and X2 has one X-axis direction acceleration detecting electrode X1 and the other X-axis direction acceleration detecting electrode X1 when the same type of stress is generated in each portion. X-axis direction acceleration detection electrode X2
The polarization processing is performed in advance so that spontaneously polarized charges of opposite polarities appear at the time of the first and second times. A piezoelectric ceramic substrate 101 corresponding to the Y-axis direction acceleration detecting electrodes Y1 and Y2.
Are such that spontaneously polarized charges of opposite polarities appear on one Y-axis direction acceleration detecting electrode Y1 and the other Y-axis direction acceleration detecting electrode Y2 when the same type of stress is generated in each part. Has been subjected to a polarization treatment in advance. Further, each part of the piezoelectric ceramic substrate 101 corresponding to the four Z-axis direction acceleration detecting electrodes Z1 to Z4 has the same polarity to all the Z-axis direction acceleration detecting electrodes when the same type of stress is generated in each part. The polarization processing is performed in advance so that spontaneous polarization charges appear. The polarization processing is described in detail in Japanese Patent Application Laid-Open No. 8-288080, which is a prior application of the present applicant. In the triaxial acceleration sensor subjected to the polarization processing as described above, when an acceleration in each direction is applied to the weight, the largest stress is generated at the boundary between the weight facing area and the intermediate area,
The stress decreases radially outward from the boundary. That is, as the distance from the boundary part increases, the amount of stress per unit area decreases, and the spontaneous polarization charge appearing on the detection electrode decreases. Therefore, each of the detection electrodes X1... Has a length imaginary across the detection electrode X1.
Is proportional to the peak value of the spontaneously polarized charge.

In this type of three-axis acceleration sensor, the detection electrodes X1... Are usually formed so as to form a ring-shaped electrode row surrounding the weight facing region 101A. To explain using the reference numerals used for the detection electrodes X1, in the conventional three-axis acceleration sensor, each of the detection electrodes X1 is a pair of sides X20, X30 located in a direction in which the annular electrode row extends.
Is the piezoelectric ceramic substrate 1 from the center point of the counterweight region.
It is formed so as to radially expand toward the outside of 01.

[0006]

In the triaxial acceleration sensor, in order to accurately detect the acceleration, the weight is accurately adjusted with respect to the diaphragm so that the center of the piezoelectric ceramic substrate 101 and the center of the weight match. It is desired to fix in position. However, it is technically difficult to fix the weight at the correct position with respect to the diaphragm at all times, and there is a slight error in the fixed position. In a conventional three-axis acceleration sensor, a pair of sides X20,
Since X30 is formed to spread radially,
If the fixed position of the weight shifts, a virtual boundary line (hereinafter simply referred to as a boundary line) is formed at the boundary between the weight-facing region and the intermediate region.
Vary across the detection electrodes X1. For example, as shown in FIG. 5, when the fixed position of the weight shifts by the length h in the direction from the X-axis detection electrode X2 toward the detection electrode X1, the length across the boundary line changes from L1 to L2. It will be longer. Further, in this case, the length of the detection electrode other than the detection electrode X1 also varies across the boundary line. For this reason, there is a problem that the dispersion of the peak values of the spontaneous polarization charges appearing on the respective detection electrodes X1... Increases, and the detection accuracy of the acceleration decreases. When acceleration is applied in the Z-axis direction in such a state that the fixed position of the weight is shifted, a large spontaneous polarization charge appears on the detection electrode X1, and a small spontaneous polarization charge appears on the detection electrode X2. . Therefore, an incorrect acceleration is detected in the X-axis direction.

It is an object of the present invention to provide a three-axis acceleration sensor capable of reducing the variation in the peak value of spontaneous polarization charge due to an error in the fixed position of the weight.

Another object of the present invention is to provide a three-axis acceleration sensor capable of making the signal levels of acceleration signals substantially equal.

It is another object of the present invention to provide a three-axis acceleration sensor which does not require adjustment of a signal level using an amplifier or requires only a small adjustment operation.

[0010]

According to the present invention, there is provided a three-axis acceleration sensor for detecting at least one X-axis acceleration which detects X-axis direction acceleration.
Axial acceleration detection electrode, 1 for detecting Y-axis acceleration
The above-described electrodes for detecting acceleration in the Y-axis direction, one or more electrodes for detecting acceleration in the Z-axis direction for detecting acceleration in the Z-axis direction, and one or more X electrodes for detecting acceleration in the Z-axis direction.
An axial acceleration output electrode, one or more Y-axis acceleration output electrodes, one or more Z-axis acceleration output electrodes, one or more X-axis acceleration detection electrodes, and one or more X-axis acceleration output electrodes One wiring pattern, a second wiring pattern for connecting one or more Y-axis direction acceleration detection electrodes and one or more Y-axis direction acceleration output electrodes, one or more Z-axis direction acceleration detection electrodes, and one or more Z-axis An electrode pattern including a third wiring pattern connecting the direction acceleration output electrodes is formed on the front surface, and a counter electrode pattern facing at least each detection electrode is formed on the back surface, and one or more X-axis direction acceleration detection electrodes are formed. A piezoelectric ceramic substrate in which a portion between the electrode, one or more electrodes for Y-axis acceleration detection, and one or more electrodes for Z-axis acceleration detection and the counter electrode pattern is polarized;
A diaphragm in which the back surface of the piezoelectric ceramic substrate is bonded to the front surface via an adhesive layer, a columnar or cylindrical weight fixed to the diaphragm so as to protrude to the back surface side of the diaphragm, And a pedestal for supporting the outer peripheral portion of the diaphragm so as to allow displacement. The one or more electrodes for detecting acceleration in the X-axis direction, the one or more electrodes for detecting acceleration in the Y-axis direction, and the one or more electrodes for detecting acceleration in the Z-axis are opposed to a circular weight of the piezoelectric ceramic substrate facing the weight. It is formed so as to form a ring-shaped electrode array that straddles the region and the intermediate region located between the weight facing region and the outer peripheral portion and surrounds the weight facing region at intervals.

In the present invention, the X-axis direction acceleration detection electrode, the Y-axis direction acceleration detection electrode, and the Z-axis direction acceleration detection electrode are arranged such that a pair of sides located in the direction in which the annular electrode row extends are substantially parallel. Form electrodes. In other words, each detection electrode is formed such that a pair of sides located in a direction in which the detection electrodes constituting the annular electrode row are arranged are substantially parallel.

When each detecting electrode is formed as in the present invention, a boundary line crosses over a pair of parallel sides of each detecting electrode. Therefore, the fixing position of the weight is slightly shifted,
Even if the weight-facing region of the piezoelectric ceramic substrate is displaced, the length of the boundary line across each detection electrode does not change significantly. Therefore, even if the fixed position of the weight is displaced within the manufacturing error range, the fluctuation or variation of the peak value of the spontaneous polarization charge appearing on each detection electrode is small, and it is possible to suppress a decrease in acceleration detection accuracy. it can. Further, even if acceleration is applied in the Z-axis direction in a state where the fixed position of the weight is displaced, the amounts of spontaneously polarized charges appearing on the plurality of detection electrodes in the X-axis direction become substantially equal. Further, the amounts of spontaneously polarized charges appearing on the plurality of detection electrodes in the Y-axis direction are also substantially equal. Therefore, it is possible to prevent the acceleration from being erroneously detected in the X-axis direction or the Y-axis direction.

A pair of sides of the X-axis direction acceleration detecting electrode are:
The electrode for Y-axis direction acceleration detection is made substantially parallel to an imaginary line extending through the center point of the weight-facing region of the piezoelectric ceramic substrate and an intermediate point located between the pair of sides of the X-axis direction acceleration detection electrode. Are substantially parallel to an imaginary line extending through a center point of the weight-facing region of the piezoelectric ceramic substrate and an intermediate point located between the pair of sides of the Y-axis direction acceleration detecting electrode, The pair of sides of the direction acceleration detecting electrode are substantially imaginary lines extending through the center point of the weight-facing region of the piezoelectric ceramic substrate and an intermediate point located between the pair of sides of the Z-axis direction acceleration detecting electrode. Preferably, they are parallel. With this configuration, the detection electrodes can be formed symmetrically with respect to the virtual line in the left-right direction, and the acceleration occurring in each direction can be accurately detected.

In addition, a virtual boundary line between the counterweight region and the intermediate region of the piezoelectric ceramic substrate has one or more X lines.
The total value of the length traversing the electrode for detecting the acceleration in the axial direction, the total value of the length traversing the electrode for detecting the acceleration in the Y-axis direction having one or more boundaries, and the electrode for detecting the acceleration in the Z-axis direction having one or more boundary lines The total value of the traversing lengths is substantially equal to one or more X
The total value of the areas of the electrodes for detecting the axial acceleration and one or more Y
It is preferable that the total value of the area of the electrodes for detecting the acceleration in the axial direction is substantially equal to the total value of the area of the electrodes for detecting the acceleration in the Z-axis direction of one or more. With this configuration, the peak values of the spontaneous polarization charges generated from the detection electrodes can be made substantially equal, and the generation distribution state of the spontaneous polarization charges generated from the detection electrodes in each direction can be approximated. Therefore, spontaneous polarization charges appearing on the respective detection electrodes can be made more equal.

The counter electrode pattern is formed in an annular shape so as to face one or more electrodes for detecting acceleration in the X-axis direction, one or more electrodes for detecting acceleration in the Y-axis direction, and one or more electrodes for detecting acceleration in the Z-axis direction. Is preferred. In other words, it is preferable to form a counter electrode pattern so as not to directly face each output electrode and each wiring pattern. In this case, since a large capacitance does not occur between each output electrode and each wiring pattern and the counter electrode pattern, the amount of charge accumulated between each detection electrode and each output electrode (separately). From the viewpoint of (1), the amount of spontaneous polarization charge that decreases from each detection electrode to each output electrode) can be reduced.

As described above, even if the fixing position of the weight is shifted,
After configuring so that the fluctuation of the peak value of the spontaneous polarization charge appearing on each detection electrode can be reduced, the spontaneous polarization charge appearing on each detection electrode can be made more equal, or between each detection electrode and each output electrode. When the amount of charge stored in the electrodes is reduced, the signal levels of the acceleration signals output from the output electrodes can be made substantially equal. Therefore, it is possible to obtain a three-axis acceleration sensor that does not require signal level adjustment using an amplifier or requires only a small adjustment operation.

As a specific embodiment of the present invention, a pair of electrodes for detecting X-axis direction acceleration for detecting X-axis direction acceleration,
A pair of Y-axis direction acceleration detecting electrodes arranged on a line orthogonal to a line connecting the pair of X-axis direction acceleration detecting electrodes to detect Y-axis direction acceleration, a pair of X-axis direction acceleration detecting electrodes, and a pair of Y Four Zs which are arranged between two adjacent electrodes of the axial acceleration detecting electrode and detect Z-axial acceleration.
An axial acceleration detection electrode, one or more X-axis acceleration output electrodes, one or more Y-axis acceleration output electrodes, one or more Z-axis acceleration output electrodes, a pair of X-axis acceleration detection electrodes and one or more A first wiring pattern for connecting the X-axis direction acceleration output electrodes, a second wiring pattern for connecting a pair of Y-axis direction acceleration detection electrodes and one or more Y-axis direction acceleration output electrodes, and four Z-axis direction acceleration detections; An electrode pattern including a third wiring pattern for connecting the first electrode and one or more Z-axis direction acceleration output electrodes is formed on the front surface, and a counter electrode pattern facing at least each of the detection electrodes is formed on the rear surface. A piezoelectric ceramic substrate in which portions between the X-axis direction acceleration detecting electrode, the pair of Y-axis direction acceleration detecting electrodes, the four Z-axis direction acceleration detecting electrodes, and the counter electrode pattern are polarized. When the diaphragm rear surface of the piezoelectric ceramic substrate is bonded through an adhesive layer on the surface,
A pair of weights fixed to the diaphragm so as to protrude to the back side of the diaphragm, and a pedestal supporting the outer peripheral portion of the diaphragm so as to allow displacement of the weight; An electrode, a pair of Y-axis direction acceleration detecting electrodes, and four Z-axis direction acceleration detecting electrodes are provided between the circular weight facing region of the piezoelectric ceramic substrate facing the weight and the weight facing region and the outer peripheral portion. And a three-axis acceleration sensor formed so as to form a ring-shaped electrode array that straddles the intermediate region located at and surrounds the weight-facing region with an interval therebetween. A pair of sides located in a direction in which the annular electrode row of the X-axis direction acceleration detection electrode extends
The piezoelectric ceramic substrate is substantially parallel to an imaginary line extending through the center point of the weight-facing region of the piezoelectric ceramic substrate and an intermediate point located between a pair of sides of the X-axis direction acceleration detection electrode. A pair of sides located in the direction in which the annular electrode row extends extends through a center point of the weight-facing region of the piezoelectric ceramic substrate and an intermediate point located between the pair of sides of the Y-axis direction acceleration detection electrode. Almost parallel to the imaginary line, Z
A pair of sides of the axial acceleration detection electrode located in the direction in which the annular electrode row extends is located between the center point of the weight-facing region of the piezoelectric ceramic substrate and the pair of sides of the Z-axis acceleration detection electrode. It is almost parallel to an imaginary line extending through the intermediate point.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a three-axis acceleration sensor 1 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the three-axis acceleration sensor 1 mounted on a mounting member 2.

As shown in FIGS. 1 and 2, the three-axis acceleration sensor 1 comprises a sensor body 3 and a cylindrical metal base (support member) 4 for supporting an outer peripheral portion of the sensor body 3. The triaxial acceleration sensor 1 is mounted on the mounting member 2 by joining the pedestal 4 to the metal mounting member 2 with an adhesive so as to allow the displacement of the weight 7. The sensor main body 3 includes a piezoelectric ceramic substrate 5, a metal diaphragm 6 joined to the piezoelectric ceramic substrate 5, and a weight 7 joined to the metal diaphragm 6. The piezoelectric ceramic substrate 5 is a piezoelectric ceramic substrate that has been subjected to a polarization process so that a spontaneous polarization charge is generated when a stress is applied to the inside. The piezoelectric ceramic substrate 5 has a quadrangular contour. The polarization process will be described later in detail. An electrode pattern E1 is formed on one surface (front surface) of the piezoelectric ceramic substrate 5, and the other surface (back surface) of the piezoelectric ceramic substrate 5 is formed.
Is formed with a counter electrode E0.

The piezoelectric ceramic substrate 5 has a weight facing region 5A and an intermediate region 5B. Weight facing area 5A
Has a circular shape at the center of the piezoelectric ceramic substrate 1. The weight 7 is joined to the weight-facing region 5A with an epoxy-based adhesive via a counter electrode E0 and a metal diaphragm 6. The weight 7 is formed in a cylindrical shape from an aluminum alloy, a copper alloy, or an iron alloy.
The weight 7 is fixed to the metal diaphragm 6 such that an axis passing through the center of gravity passes through the center of the weight facing region 5A and is orthogonal to the surface of the piezoelectric ceramic substrate 5 in a stationary state.

The intermediate region 5B has an annular shape surrounding the weight facing region 5A, and is located between the weight facing region 5A and the outer periphery of the diaphragm 6. Middle area 5B
When an acceleration acts on the weight 7 in a direction parallel to the piezoelectric ceramic substrate 1, a point-symmetrically different state about the center of gravity of the weight 7 (the state where a tensile stress is applied,
And a state where a compressive stress is applied). When acceleration acts on the weight 7 in a direction orthogonal to the piezoelectric ceramic substrate 1, each part of the intermediate region 5B is deformed to the same state (state in which a tensile stress is applied).

Each of the electrode pattern E1 and the counter electrode E0 formed on the front and back surfaces of the piezoelectric ceramic substrate 5 is formed by screen printing using silver paste, and forms an annular electrode row of the electrode pattern E1. Detection electrodes DX1, DX2, DY1, DY2, DZ1 to DZ
Three axes (X axis, Y axis, Z axis) added to the weight 7 due to a change in spontaneous polarization charge generated between Z4 and the counter electrode E0
The acceleration in the direction is measured. Note that the X axis, Y
The axis and the Z axis are axes extending in directions orthogonal to each other, the X axis and the Y axis extend in the surface direction of the piezoelectric ceramic substrate 5, and the Z axis extends in the direction orthogonal to the surface direction of the piezoelectric ceramic substrate 5. I have. The opposing electrode E0 has an electrode pattern E1.
Detection electrodes DX1, DX2, DY1, DY2, DZ1
~ DZ4, it is formed in an annular shape,
It has a thickness of 10 μm. Piezoelectric ceramic substrate 5
Is joined to a metal diaphragm 6.
Specifically, the piezoelectric ceramic substrate 5 is bonded to the metal diaphragm 6 by the adhesive layer S in a portion where the counter electrode E0 is not formed. In a portion where the counter electrode E0 is formed, the piezoelectric ceramic substrate 5 is bonded to the metal diaphragm 6 by an adhesive via the counter electrode E0. Although not shown, the back surface of the counter electrode E0 has irregularities, and the adhesive is applied to the counter electrode E0.
And the metal electrode 6 is joined to the counter electrode E0 by entering the concave portion on the back surface of the substrate. The convex portion of the counter electrode E0 is joined to the metal diaphragm 6. Thereby, the counter electrode E0 is grounded to the mounting member 2 via the metal diaphragm 6 and the pedestal (support member) 4. Note that the grounding pattern may be provided separately, and the grounding pattern may be joined to the metal diaphragm 6 via a conductive adhesive, so that the grounding may be further ensured. The electrode pattern E1 has three electrode pattern portions in three axes (X-axis, Y-axis, and Z-axis), and has a thickness of 10 μm, like the counter electrode E0. The X-axis direction electrode pattern portion of the electrode pattern E1 includes two X-axis direction acceleration detection electrodes DX1 and DX2 and two X-axis acceleration output electrodes OX.
1 and OX2 are two pattern portions LX1 and LX, respectively.
2 is connected. In this example, a first wiring pattern is configured by the two pattern portions LX1 and LX2. The pattern portions LX1 and LX2 have connection portions made of silver paste at the ends connected to the detection electrodes DX1 and DX2.

The detection electrodes DX1 and DX2 have a substantially rectangular shape. Specifically, the detection electrode DX1 will be described in detail. The detection electrode DX1 has an arcuate curved side K extending along the outer circumference of the annular intermediate region 5B.
1, a curved side K2 extending along the inner periphery of the annular intermediate area 5B and located in the weight counter area 5A, and two straight sides extending parallel to each other between the two curved sides K1 and K2. K
3 and K4. In other words, the detection electrode DX1 is formed such that the pair of sides K3, K4 located in the direction in which the annular electrode row formed by the detection electrodes DX1, DZ1,. The pair of sides K3 and K4 pass through the center point of the weight-facing region 5A of the piezoelectric ceramic substrate 5 and an intermediate point located between the pair of sides K3 and K4 of the X-axis direction acceleration detection electrode DX1. It also extends substantially parallel to the extending virtual line (XL). As described above, the detection electrodes DX1 and DX2 are mostly formed on the surface located in the intermediate region 5B, and partially formed so as to straddle the weight facing region 5A and the intermediate region 5B. I have. Then, the detection electrodes DX1 and DX2
Are positioned on a virtual X-axis straight line XL extending on the surface of the piezoelectric ceramic substrate 5, and are symmetrically arranged so as to sandwich the weight facing region 5A therebetween.

The pair of output electrodes OX1 and OX2 have a substantially square shape. The output electrodes OX1, OX2 and the pattern portions LX1, LX2 are connected to the output electrodes OX1, OX2.
Is located on the outer peripheral portion of the piezoelectric ceramic substrate 5,
It is formed outside the intermediate region 5B.

The electrode pattern section in the Y-axis direction has a structure in which two Y-axis direction acceleration detecting electrodes DY1 and DY2 and two Y-axis acceleration output electrodes OY1 and OY2 are connected by two pattern sections LY1 and LY2, respectively. have.
In this example, a second wiring pattern is configured by the pattern portions LY1 and LY2. The pattern portions LY1,
LY2 also has a connection made of silver paste.

Electrodes DY1 and DY for detecting acceleration in the Y-axis direction
2 has a shape close to a rectangle like the X-axis direction acceleration detection electrodes DX1 and DX2. That is, each detection electrode D
The detection electrodes DY1 and DY2 are formed such that a pair of sides located in a direction in which an annular electrode row formed by X1, DZ1,... In addition, the pair of sides are imaginary lines extending through the center point of the weight facing region 5A of the piezoelectric ceramic substrate 5 and an intermediate point located between the pair of sides of the Y-axis direction acceleration detecting electrodes DY1 and DY2. YL) extend substantially in parallel. Most of the detection electrodes DY1 and DY2 are formed on the surface located in the intermediate region 5B, and partly formed so as to straddle the weight facing region 5A and the intermediate region 5B. Also, Y
The electrodes DY1 and DY2 for axial acceleration detection are a pair of X
It is positioned on a virtual Y-axis straight line YL extending horizontally to the surface of the piezoelectric ceramic substrate 5 orthogonally to a virtual X-axis straight line XL connecting the axial acceleration detection electrodes DX1 and DX2, and sandwiching the weight facing region 5A therebetween. They are arranged symmetrically. Since the virtual Y-axis straight line YL and the virtual X-axis straight line XL are orthogonal to each other, the detection electrodes DX1, DY1, DX2, and DY2 are arranged at an angular interval of 90 degrees.

The pair of output electrodes OY1 and OY2 have a substantially square shape like the output electrodes OX1 and OX2. Output electrodes OY1, OY2 and pattern parts LY1, L
Y2 is also formed outside the intermediate region 5B so that the output electrodes OY1 and OY2 are located on the outer peripheral portion of the piezoelectric ceramic substrate 5.

In the electrode pattern portion in the Z-axis direction, four Z-axis direction acceleration detecting electrodes DZ1 to DZ4 are connected to each other by a first pattern portion LZ1, and one detecting electrode DZ
3 has a structure connected to the Z-axis acceleration output electrode OZ by the second pattern portion LZ2. In the present example, a third wiring pattern is formed by the first pattern portion LZ1 and the second pattern portion LZ2. The pattern portions LZ1 and LZ2 also have connection portions made of silver paste at their ends.

Z-axis direction acceleration detecting electrodes DZ1 to DZ4
Similarly, the X-axis direction acceleration detection electrodes DX1 and DX2 have a shape close to a rectangle. That is, each detection electrode DX
The detection electrodes DZ1 to DZ4 are formed such that a pair of sides located in a direction in which the annular electrode row formed by the electrodes 1, DZ1,. Further, the pair of sides is also a virtual line extending through the center point of the weight facing region 5A of the piezoelectric ceramic substrate 5 and an intermediate point located between the pair of sides of the Z-axis direction acceleration detecting electrodes DZ1 to DZ4. They extend almost parallel. The detection electrodes DZ1 to DZ1
Z4 is mostly formed on the surface located in the intermediate region 5B, and a part of the Z4 is formed between the weight facing region 5A and the intermediate region 5B.
It is formed so as to straddle. Further, the four Z-axis direction acceleration detecting electrodes DZ1 to DZ4 are
1 and the detection electrode DY1, between the detection electrode DY1 and the detection electrode DX2, between the detection electrode DX2 and the detection electrode D.
Y2 and at the center between the detection electrode DY2 and the detection electrode DX1. Therefore,
The detection electrodes DZ1 to DZ4 are arranged at 90 degree intervals. Also, with such an arrangement, the detection electrodes DX1, DX2, DY1, DY2, DZ
1 to DZ4 constitute an annular electrode row surrounding the weight facing region 5A.

One output electrode OZ has a substantially rectangular shape. The output electrode OZ and the pattern portion LZ2 are formed outside the intermediate region 5B such that the output electrode OZ is located on the outer peripheral portion of the piezoelectric ceramic substrate 5. This output electrode OZ and each output electrode OX1, O
X2, OY1 and OY2 are connected to an arithmetic circuit (not shown), and an acceleration signal is sent from each output electrode to the arithmetic circuit. Further, the pattern portion LZ1 is formed in the weight facing region 5A.
The detection electrode DZ1 and the detection electrode D
A wiring portion LZ11 for connecting Z2 with the detection electrode DZ3;
LZ12 connecting the wiring LZ12 and the detection electrode DZ4, and the wiring LZ connecting the wiring LZ11 and the wiring LZ12
13.

Further, in this embodiment, the length l1 of the imaginary boundary line between the counterweight region 5A and the intermediate region 5B of the piezoelectric ceramic substrate 5 crosses the detection electrode DX1.
And the length l2 of the boundary line crossing the detection electrode DX2 (l1 + l2), the length l3 of the boundary line crossing the detection electrode DY1, and the length l of the boundary line crossing the detection electrode DY2.
4 and the boundary line is the detection electrode D.
The total value of the length l5 crossing Z1 and the length l6 of the boundary line crossing the detection electrode DZ2, the length l7 of the boundary line crossing the detection electrode DZ3, and the length l8 of the boundary line crossing the detection electrode DZ4 ( l5 + l6 + l7 + l8) is equal to (3.0
8 mm), the detection electrodes in each direction are formed. Further, the sum of the areas of the pair of detection electrodes DX1 and DX2, the sum of the areas of the pair of detection electrodes DY1 and DY2, and the sum of the areas of the four detection electrodes DZ1 to DZ4 are equal (4 The detection electrodes in each direction are formed so as to be 0.4 mm ² ). Therefore, when an equal amount of acceleration in the X-axis direction, Y-axis direction, or Z-axis direction is independently applied to the weight 7, the detection electrode DX1 and the detection electrode DX
2 and the detection electrode DY1
And spontaneous polarization charges generated on both the detection electrode DY2 and
The peak values of the spontaneously polarized charges generated in the detection electrodes DZ1 to DZ4 are substantially equal, and the generation distributions are also substantially equal. As a result, the amounts of spontaneously polarized charges generated from the detection electrodes in each direction can be made substantially equal.

X-axis direction acceleration detecting electrodes DX1, DX2
When the same type of stress is generated in each portion of the piezoelectric ceramic substrate 5 (when acceleration is generated only in the Y-axis direction or the Z-axis direction), the weight facing region 5A
X-axis direction acceleration detection electrode DX1 located on one side of
And X-axis direction acceleration detection electrode DX2 located on the other side
The polarization process is performed so that spontaneous polarization charges of opposite polarities appear at the time. In this example, when a tensile stress is generated in each portion of the piezoelectric ceramic substrate 5 corresponding to the X-axis direction acceleration detection electrodes DX1, DX2, a positive spontaneous polarization charge appears on the X-axis direction acceleration detection electrode DX1, The polarization processing is performed so that a negative spontaneous polarization charge appears on the X-axis direction acceleration detection electrode DX2.

The electrodes DY1 and DY1 for detecting the acceleration in the Y-axis direction are provided.
Each part of the piezoelectric ceramic substrate 5 corresponding to DY2 is also X
When the same kind of stress is generated in each part as in each part of the piezoelectric ceramic substrate 5 corresponding to the axial acceleration detecting electrodes DX1 and DX2 (when acceleration is generated only in the X-axis direction or the Z-axis direction) Polarized so that spontaneously polarized charges of opposite polarities appear on the Y-axis direction acceleration detecting electrode DY1 located on one side of the weight facing region 5A and the Y-axis direction acceleration detecting electrode DY2 located on the other side. Processing has been applied. In this example, the Y-axis direction acceleration detection electrode DY
1 and DY2, when a tensile stress is generated in each portion of the piezoelectric ceramic substrate 5, a positive spontaneous polarization charge appears on the Y-axis direction acceleration detecting electrode DY1 and a negative spontaneous polarization charge appears on the Y-axis direction acceleration detecting electrode DY2. Polarization treatment was performed so that spontaneous polarization charges appeared.

The Z-axis direction acceleration detecting electrodes DZ1 to DZ1
Each part of the piezoelectric ceramic substrate 5 corresponding to DZ4
When the same type of stress is generated in each portion (when acceleration is generated only in the Z-axis direction), the polarization process is performed so that spontaneously polarized charges of the same polarity appear in all the Z-axis direction acceleration detection electrodes DZ1 to DZ4. It has been subjected. In this example, when a tensile stress is generated in a portion of the piezoelectric ceramic substrate 5 corresponding to the Z-axis direction acceleration detecting electrodes DZ1 to DZ4, a positive spontaneous polarization charge appears on the Z-axis direction acceleration detecting electrodes DZ1 to DZ4. Was subjected to a polarization treatment. These polarization treatments were performed by applying a DC voltage to the piezoelectric ceramic substrate 5 after forming the detection electrodes DX1... And the counter electrode E0 of the electrode pattern E1.

As described above, in the three-axis acceleration sensor of the present embodiment, a pair of sides located in the direction in which the annular electrode row formed by the detection electrodes DX1, DZ1,. , Are formed. In other words, the detection electrodes DX1... Are formed such that a pair of sides on which the detection electrodes DX1. Therefore, as shown in FIG. 3, even if the fixing position of the weight is shifted by the length h10 in the direction from the X-axis detection electrode DX2 toward the detection electrode DX1, the length of the boundary line that crosses the detection electrode DX1. (L10 and L20) do not substantially change. In addition, in this case, the length of the detection electrode other than the detection electrode DX1 does not change much. Therefore, even if the fixed position of the weight is displaced within the range of manufacturing error, the fluctuation or variation of the spontaneous polarization charge peak value appearing on each of the detection electrodes DX1. it can. Further, even if acceleration is applied in the Z-axis direction in such a state that the fixed position of the weight is shifted, there is a large difference between the spontaneous polarization charge appearing on the detection electrode DX1 and the spontaneous polarization charge appearing on the detection electrode DX2. Does not occur. Therefore, it is possible to prevent the acceleration from being erroneously detected in the X-axis direction.

In the above example, the diaphragm 6
Is made of metal, but the diaphragm is not limited to metal. When the diaphragm is formed of a non-metal such as glass, the counter electrode E0 may be directly connected to an arithmetic circuit (not shown). Further, in the above example, the weight 7 and the diaphragm 6 are formed separately, but they may be formed integrally.

[0037]

According to the present invention, since each detection electrode is formed so that a pair of sides located in the direction in which the annular electrode row extends are substantially parallel, the fixed position of the weight is shifted, and Even if the weight-facing region of the ceramic substrate is displaced, the length of the boundary line across each detection electrode does not change significantly. Therefore, even if the fixed position of the weight shifts within the manufacturing error range, the fluctuation and variation in the peak value of the spontaneous polarization charge appearing on each detection electrode are small, and it is possible to suppress a decrease in the accuracy of acceleration detection. it can. Further, even if acceleration is applied in the Z-axis direction with the fixed position of the weight shifted, it is possible to prevent the acceleration from being erroneously detected in the X-axis direction and the Y-axis direction.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view of the three-axis acceleration sensor according to the embodiment of the present invention.

FIG. 3 is a partially enlarged view used to explain the operation of the three-axis acceleration sensor according to the embodiment of the present invention.

FIG. 4 is a plan view of the triaxial acceleration sensor according to the embodiment of the present invention.

FIG. 5 is a partially enlarged view used to explain a problem of a conventional three-axis acceleration sensor.

[Explanation of symbols]

 4 Pedestal 5 Piezoelectric ceramic substrate 5A Weight counter area 5B Intermediate area 6 Diaphragm 7 Weight E1 Electrode pattern E0 Counter electrode DX1, DX2 X-axis direction acceleration detection electrodes DY1, DY2 Y-axis direction acceleration detection electrodes DZ1-DZ4 Z-axis Direction acceleration detection electrodes OX1, OX2 X-axis direction acceleration output electrode OY1, OY2 Y-axis direction acceleration output electrode OZ Z-axis direction acceleration output electrode LX1, LX2 Pattern portion of first wiring pattern LY1, LY2 Second wiring pattern Pattern portion LZ1, LZ2 Pattern portion of third wiring pattern K3, K4 A pair of sides

Claims (5)

[Claims] 1. One or more X-axis acceleration detection electrodes for detecting X-axis acceleration, one or more Y-axis acceleration detection electrodes for detecting Y-axis acceleration, and one or more Z-axis acceleration detection , One or more X-axis acceleration output electrodes, one or more Y-axis acceleration output electrodes, one or more Z-axis acceleration output electrodes, and one or more of the X electrodes.
A first wiring pattern for connecting the axial acceleration detection electrode to the one or more X-axis acceleration output electrodes; connecting the one or more Y-axis acceleration detection electrodes to the one or more Y-axis acceleration output electrodes; A second wiring pattern to be formed and an electrode pattern including a third wiring pattern connecting the at least one Z-axis direction acceleration detection electrode and the at least one Z-axis direction acceleration output electrode are formed on the front surface, and on the back surface. A counter electrode pattern facing at least each of the detection electrodes is formed, the one or more X-axis direction acceleration detection electrodes, the one or more Y-axis direction acceleration detection electrodes, and the one or more Z-axis direction acceleration detection A piezoelectric ceramics substrate in which a portion between the electrode for use and the counter electrode pattern is polarized, and a die in which the back surface of the piezoelectric ceramics substrate is bonded to the front surface via an adhesive layer. A diaphragm, a columnar or cylindrical weight fixed to the diaphragm so as to protrude to the back side of the diaphragm, and a pedestal supporting an outer peripheral portion of the diaphragm so as to allow displacement of the weight. Wherein the one or more electrodes for X-axis direction acceleration detection, the one or more electrodes for Y-axis direction acceleration detection, and the one or more Z-axis direction acceleration detection electrodes face the weight. Forming a ring-shaped electrode array that straddles a circular counterweight region of the ceramic substrate and an intermediate region located between the counterweight region and the outer peripheral portion and surrounds the counterweight region at an interval from each other; A three-axis acceleration sensor formed so that the X-axis direction acceleration detection electrode, the Y-axis direction acceleration detection electrode, and the Z-axis direction acceleration detection electrode are formed by extending the annular electrode row. A three-axis acceleration sensor characterized in that a pair of sides located in different directions are formed to be substantially parallel. 2. The pair of sides of the X-axis direction acceleration detecting electrode are located between a center point of the weight facing region of the piezoelectric ceramic substrate and the pair of sides of the X-axis direction acceleration detecting electrode. The pair of sides of the Y-axis direction acceleration detecting electrode are substantially parallel to a virtual line extending through the located intermediate point, and the pair of sides of the Y-axis direction acceleration detection electrode are located at the center of the weight-facing area of the piezoelectric ceramic substrate and the Y-axis. The pair of sides of the Z-axis direction acceleration detecting electrode are substantially parallel to an imaginary line extending through an intermediate point located between the pair of sides of the axial direction acceleration detecting electrode. A center point of the weight-facing area of the ceramic substrate and an imaginary line extending through an intermediate point located between the pair of sides of the Z-axis direction acceleration detection electrode, being substantially parallel to an imaginary line. Claim 1 Three-axis acceleration sensor. 3. A total value of a length of a boundary line imaginary at a boundary between the weight-facing region and the intermediate region of the piezoelectric ceramic substrate crossing the one or more X-axis direction acceleration detecting electrodes, The total value of the length of the boundary line crossing the one or more Y-axis direction acceleration detecting electrodes is substantially equal to the total value of the length of the boundary line crossing the one or more Z-axis direction acceleration detecting electrodes. The total value of the area of the one or more electrodes for X-axis acceleration detection, the total value of the area of the one or more electrodes for Y-axis acceleration detection, and the area of the one or more electrodes for Z-axis acceleration detection. 2. The method according to claim 1, wherein the sum is substantially equal to the sum.
Or the three-axis acceleration sensor according to 2. 4. The opposing electrode pattern is opposed to the at least one X-axis direction acceleration detecting electrode, the one or more Y-axis direction acceleration detecting electrode, and the one or more Z-axis direction acceleration detecting electrode. An annular shape is formed in the ring.
Or the three-axis acceleration sensor according to 3. 5. A pair of X-axis direction acceleration detecting electrodes for detecting X-axis direction acceleration, and are disposed on a line orthogonal to a line connecting the pair of X-axis direction acceleration detecting electrodes to detect Y-axis direction acceleration. A pair of Y-axis acceleration detection electrodes, a pair of X-axis acceleration detection electrodes, and a pair of Y-axis acceleration detection electrodes disposed between two adjacent electrodes for detecting Z-axis acceleration. One Z-axis direction acceleration detection electrode, one or more X-axis direction acceleration output electrodes, one or more Y-axis direction acceleration output electrodes, one or more Z-axis direction acceleration output electrodes, and the pair of X-axis direction acceleration detection electrodes. A first wiring pattern that connects the one or more X-axis acceleration output electrodes, a second wiring pattern that connects the pair of Y-axis acceleration detection electrodes and the one or more Y-axis acceleration output electrodes, and Four Z axes An electrode pattern including a third wiring pattern for connecting a direction acceleration detection electrode and the one or more Z-axis direction acceleration output electrodes on a front surface, and a counter electrode pattern on a back surface facing at least the detection electrodes; Is formed, the pair of electrodes for detecting acceleration in the X-axis direction,
The pair of electrodes for detecting acceleration in the Y-axis direction and the four Z electrodes
A piezoelectric ceramics substrate in which a portion between the electrode for axial acceleration detection and the counter electrode pattern is polarized, a diaphragm having a front surface joined to the back surface of the piezoelectric ceramics substrate via an adhesive layer, A weight that is fixed to the diaphragm so as to protrude to the rear surface side of the diaphragm; and a pedestal that supports an outer peripheral portion of the diaphragm so as to allow displacement of the weight. A directional acceleration detecting electrode, the pair of Y-axis directional acceleration detecting electrodes, and the four Z-axis directional acceleration detecting electrodes, wherein the circular weight facing region of the piezoelectric ceramic substrate facing the weight and the weight; It is formed so as to form an annular electrode row which straddles an intermediate region located between an opposing region and the outer peripheral portion and surrounds the weight opposing region at an interval from each other. A three-axis acceleration sensor, wherein a pair of sides of the X-axis direction acceleration detection electrode located in a direction in which the annular electrode row extends are a center point of the weight-facing region of the piezoelectric ceramic substrate and the X-axis. A direction substantially parallel to an imaginary line extending through an intermediate point located between the pair of sides of the axial acceleration detection electrode, and a direction in which the annular electrode row of the Y-axis acceleration detection electrode extends A virtual line extending through a center point of the weight-facing area of the piezoelectric ceramic substrate and an intermediate point located between the pair of sides of the Y-axis direction acceleration detection electrode. A pair of sides that are substantially parallel to each other and are located in a direction in which the annular electrode row of the Z-axis direction acceleration detection electrode extends is a center point of the weight-facing region of the piezoelectric ceramic substrate and the Z-axis direction. acceleration Triaxial acceleration sensor, wherein a virtual line that extends through an intermediate point located in the middle of said pair of sides of the output electrode and are substantially parallel.