JP2001208768A - Piezoelectric triaxial acceleration sensor - Google Patents

Abstract

(57) [Problem] To provide a piezoelectric type three-axis acceleration sensor that does not need to adjust the level variation of X-axis, Y-axis, and Z-axis acceleration signals by a signal processing circuit. SOLUTION: A stress generation region 8 of X-axis connection lines L1, L2.
The parts L1a and L2a located on C are arranged so as to be located on the X-axis direction virtual line XL. The portions L4a and L4b of the Y-axis connection line L4 located on the stress generation region 8C are
It arrange | positions so that it may be located on the axial imaginary line YL. A portion L5a of the Z-axis connection line L5 located on the stress generation region 8C,
L5b, L5c, L5d are represented by X-axis virtual lines XL or Y
It arrange | positions so that it may be located on two virtual lines which become axisymmetric about the axial direction virtual line YL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A piezoelectric ceramic substrate having an electrode pattern for acceleration detection formed on one surface and a counter electrode pattern formed on the other surface is subjected to polarization processing, and subjected to acceleration to generate a stress in the piezoelectric ceramic substrate. There is known a piezoelectric type triaxial acceleration sensor that obtains an acceleration by using a stress generated in the sensor. FIG. 7 shows an acceleration detecting electrode pattern of this type of piezoelectric triaxial acceleration sensor. As shown in FIG. 7, the acceleration detection electrode pattern E101 is composed of a pair of X-axis acceleration detection electrodes X1 and X1 arranged on the X-axis virtual line XL.
X2, a Y-axis direction virtual line Y orthogonal to the X-axis direction virtual line XL
L, a pair of Y-axis acceleration detecting electrodes Y1 and Y
2 and a plurality of Z-axis acceleration detecting electrodes Z1 to Z4 for detecting accelerations in the Z-axis direction, an X-axis output electrode X3, a Y-axis output electrode Y3, and a Z-axis output electrode Z5 are connected to an X-axis connection line X.
4, X5, Y-axis connection lines Y4, Y5 and Z-axis connection line Z6
They are formed to be electrically connected to each other via Z9. In addition, a piezoelectric triaxial acceleration sensor has a diaphragm having a front surface joined to the back surface of a piezoelectric ceramic substrate, a weight provided at the center of the diaphragm, and a weight around the weight when acceleration acts on the weight. A base supporting the diaphragm so that a portion of a certain piezoelectric ceramic substrate is bent. As a result, the piezoelectric ceramic substrate has a weight facing region 101A facing the weight, a base facing region 101B facing the base, and the acceleration detecting electrodes located between the weight facing region 101A and the base facing region 101B. An annular stress generating region 1 in which X1.
01C. When an acceleration acts on the weight, the stress is generated in the stress generating region 101C to generate a stress. The acceleration detecting electrodes X1...
The acceleration detection signal based on the spontaneous polarization charge generated from the above is measured to determine the acceleration in each direction.

[0003]

In the conventional piezoelectric three-axis acceleration sensor, even if the same magnitude of acceleration is applied, an X-axis acceleration detection signal and a Y-axis acceleration detection signal output from the output electrodes X3, Y3, and Z5 are obtained. The levels of the signal and the Z-axis acceleration detection signal vary. Therefore, conventionally, a signal amplifying circuit provided for a piezoelectric type triaxial acceleration sensor has
The dispersion of the levels of the acceleration signals of the axes Y, Z and Z is adjusted. However, the X-axis, Y
By adjusting the dispersion of the levels of the axis and Z-axis acceleration signals,
Since the output of the piezoelectric three-axis acceleration sensor cannot be used as it is, there is a problem that a signal processing circuit is required.

It is an object of the present invention to provide an X
It is an object of the present invention to provide a piezoelectric three-axis acceleration sensor that does not need to adjust the level variation of the acceleration signals of the axes Y, Z, and Z axes.

Another object of the present invention is to provide a piezoelectric multi-axis acceleration sensor capable of removing so-called noise in which spontaneous polarization occurs in another axis despite acceleration acting only on a specific axis. is there.

[0006]

According to the present invention, there is provided a piezoelectric triaxial acceleration sensor which is improved by a pair of X-axis acceleration detecting electrodes arranged on an X-axis virtual line, and orthogonal to the X-axis virtual line. A pair of electrodes for Y-axis acceleration detection arranged on a virtual line in the Y-axis direction, a plurality of electrodes for Z-axis acceleration detection for detecting acceleration in the Z-axis direction, an X-axis output electrode, a Y-axis output electrode, An acceleration detection electrode pattern electrically connected to the Z-axis output electrode via an X-axis connection line, a Y-axis connection line, and a Z-axis connection line is formed on the front surface, and at least one pair of X-axis accelerations is formed on the back surface. A counter electrode pattern including a detection electrode, a pair of Y-axis acceleration detection electrodes, and a counter electrode facing a plurality of Z-axis acceleration detection electrodes is formed, and a portion between each of the acceleration detection electrodes and the counter electrode is polarized. Piezoelectric ceramic being processed The plate, the diaphragm with the back surface of the piezoelectric ceramic substrate joined to the front surface, the weight provided at the center of the diaphragm, and the portion of the piezoelectric ceramic substrate around the weight when acceleration acts on the weight A base for supporting the diaphragm so as to bend. Then, a weight facing region in which the piezoelectric ceramic substrate faces the weight, a base facing region facing the base, and an annular shape in which each acceleration detection electrode is located between the weight facing region and the base facing region. And a stress generating region. As a result of research conducted by the inventor, it has been found that the causes of signal variations are as follows. In the conventional piezoelectric triaxial acceleration sensor shown in FIG. 7, the portions of the connection lines X4.
3 and so on, depending on the position. Each of the connection lines X4... Of the acceleration detection electrode pattern has a small thickness, but hinders bending generated in the stress generating region 101C. Therefore, when the connection lines X4 are formed so as to be partially eccentrically arranged on the stress generating region 101C (when the connection lines X4 are not evenly arranged in a well-balanced manner), when the acceleration acts on the weight, the stress is reduced. Generation area 1
01C is hindered in a partially biased state by the connection lines X4. Therefore, in the conventional piezoelectric three-axis acceleration sensor, even if the same magnitude of acceleration acts, the X-axis acceleration detection signal, the Y-axis acceleration detection signal, and the Z-axis acceleration detection signal output from the output electrodes X3, Y3, and Z5. Level is varied. Therefore, in the present invention,
A portion of the X-axis connection line located on the stress generation region is arranged so as to be located on the imaginary line in the X-axis direction, and a portion of the Y-axis connection line located on the stress generation region is located on the imaginary line of the Y-axis direction. And the portion of the Z-axis connection line located on the stress generation region is located on two virtual lines that are line-symmetric with respect to the X-axis virtual line or the Y-axis virtual line. By arranging the respective connection lines in this manner, the respective connection lines are evenly arranged in a well-balanced manner on the stress generating region around the imaginary line in the X-axis direction and the imaginary line in the Y-axis direction (partially biased). Without being placed). Therefore, the bending of the stress generating region when acceleration acts on the weight also occurs in a well-balanced manner. As a result, variations in the levels of the X-axis acceleration detection signal, the Y-axis acceleration detection signal, and the Z-axis acceleration detection signal output from the output electrode are reduced, and it is necessary to adjust the level variation of each acceleration signal by a signal processing circuit. Disappears.

Further, if the deflection of the stress generating region when the acceleration acts on the weight occurs in a well-balanced manner as in the present invention, irregular distortion occurs in the stress generating region when the acceleration acts on the weight. Can be prevented. Therefore, it is possible to remove a so-called noise in which spontaneous polarization occurs in other axes despite acceleration acting only on a specific axis.

Further, if the ratio of the width of each connection line to the width of the X-axis acceleration detection electrode or the Y-axis acceleration detection electrode is reduced to 5 to 40%, the connection lines hinder the bending of the stress generating region. The phenomenon can be further reduced. Specific preferred examples of such a width dimension of each connection line include:
0.3 mm or less.

Further, in order to suppress the generation of capacitance between the connection line and the counter electrode pattern, the relative dielectric constant between the connection line and the piezoelectric ceramic substrate is smaller than that of the piezoelectric ceramic substrate. May be formed as a low dielectric constant layer. In this case, a low dielectric constant layer is formed between the portion of the X-axis connection line located on the stress generation region and the piezoelectric ceramic substrate so as to be symmetric with respect to a virtual line in the X-axis direction. It is preferable to form a low dielectric constant layer between the portion of the connection line located on the stress generating region and the piezoelectric ceramic substrate so as to be symmetric with respect to the imaginary line in the Y-axis direction. In this way, the low dielectric constant layer, like the connection line,
On the stress generation region, the imaginary lines in the X-axis direction and the imaginary line in the Y-axis direction are arranged in a well-balanced and uniform manner (arranged without partial bias). Therefore, even if acceleration acts on the weight, the bending of the stress generating region does not become partially biased due to the presence of the low dielectric constant layer. As a result, even when the low dielectric constant layer is provided, the X-axis acceleration detection signal, the Y-axis acceleration detection signal,
Variations in the level of the axial acceleration detection signal can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 4 are a front view, a plan view, a side view, and a rear view showing a piezoelectric triaxial acceleration sensor according to an embodiment of the present invention in a partially broken state. 2 and 3
As shown in FIG.
And a weight 3, a base 5, and an acceleration sensor element 7 fixed on a surface of the diaphragm 1 opposite to the surface on which the weight 3 is attached. These members are housed in an insulating resin case 9, in which a plurality of terminal fittings 11 </ b> A to 11 </ b> H are arranged and a metal cover member 13 is fitted. Have been.

[0011] The diaphragm 1, the weight 3 and the base 5
It is configured as a single unit 10 integrally formed of a metal material made of brass. The diaphragm 1 has a disk shape. The weight 3 has a columnar shape, and is arranged such that an extension of the axis thereof passes through the center of the diaphragm 1. The base 5 has a cylindrical shape and supports the outer peripheral portion of the diaphragm 1. Further, a V-shaped groove 5a that is continuous in the circumferential direction is formed on the outer peripheral portion of the base 5. The single unit 10 is used as an insert when forming the insulating resin case 9 together with the plurality of terminal fittings 11A to 11H.

As shown in the plan view of FIG. 5 and the back view of FIG. 6, the acceleration sensor element 7 has an acceleration detecting electrode pattern E for detecting triaxial acceleration on the surface of the piezoelectric ceramic substrate 7a.
1 is formed, and a counter electrode pattern E0 is formed on the back surface. The back surface of the piezoelectric ceramic substrate 7a and the counter electrode pattern E0 are joined to the surface of the diaphragm 1 by an adhesive layer made of a synthetic resin material such as epoxy. The piezoelectric ceramic substrate 7a has a substantially rectangular outline, and as shown in FIGS. 1 and 3,
A plurality of terminal fittings 11 </ b> A to 1 </ b> A are arranged on the main body portion 7 b located on the diaphragm 1 and on the insulating resin case 9 from the main body portion 7 b.
And an extension 7c extending to the vicinity of 1H. As shown in FIG. 1 and FIG. 5, the extension portion 7c located on the two opposite sides of the piezoelectric ceramic substrate 7a has four edges.
Two semicircular recesses 7d to 7g and four semicircular recesses 7h
To 7k are formed at equal intervals. The piezoelectric ceramic substrate 7a is subjected to a polarization treatment on a portion corresponding to the electrode so that a spontaneous polarization charge is generated when a stress is applied to the inside. The polarization processing will be described later. The piezoelectric ceramic substrate 7a has a weight facing region 8A, a base facing region 8B, and a stress generating region 8C located between the weight facing region 8A and the base facing region 8B. The weight 3 is located at a portion corresponding to the weight facing region 8A, and the base 5 is located at a portion corresponding to the base facing region 8B. The stress generating region 8C includes an annular first stress generating portion 8C1 surrounding the weight facing region 8A and an annular second stress generating portion 8C2 surrounding the first stress generating portion 8C1.
It is composed of When an acceleration acts on the weight 3 in a direction (X-axis direction or Y-axis direction) parallel to the substrate surface of the piezoelectric ceramic substrate 7a, the first stress generating portion 8C1 is turned around the center of gravity of the weight 3. Deforms symmetrically to different states (a state where a tensile stress is applied and a state where a compressive stress is applied). Further, when acceleration acts on the weight 3 in a direction (Z-axis direction) orthogonal to the substrate surface of the piezoelectric ceramic substrate 7a, each portion of the first stress generating portion 8C1 is deformed to the same state. The second stress generating portion 8C2 is
This is an area in which a different kind of stress from the stress applied to the stress generating portion 8C1 is extremely small.

The acceleration detection electrode pattern E1 and the counter electrode pattern E0 formed on the front and back surfaces of the piezoelectric ceramic substrate 7a are both formed by screen printing using a glass-silver paint. As shown in FIG. 5, the acceleration detection electrode pattern E1 has an X-axis direction detection electrode pattern 15, a Y-axis direction detection electrode pattern 17, and a Z-axis direction detection electrode pattern 19. The X-axis direction detecting electrode pattern 15 includes a pair of X-axis direction acceleration detecting electrodes E.
X1, EX2 and the X-axis output electrode OX are connected to the X-axis connection lines L1 to L1.
It has a structure connected in series by L3. The pair of X-axis direction acceleration detecting electrodes EX1 and EX2 are composed of a pair of Y-axis direction detecting electrode patterns EY1 and EY2 of a Y-axis direction detecting electrode pattern 17 and four Z-axis directions of a Z-axis direction detecting electrode pattern 19 described later. Direction acceleration detection electrodes EZ1
Together with EZ4, an annular row surrounding the weight facing region 8A is formed. The electrodes EX1 and EX2 of the pair of X-axis direction acceleration detection electrodes are line-symmetric with respect to the X-axis direction virtual line XL, and have a weight-facing region 8A and a stress generation region 8C.
And has a shape close to a rectangle straddling.

The width of the X-axis connection lines L1 to L3 is determined by the width of the X-axis acceleration detecting electrodes EX1 and EX2 extending in a direction perpendicular to the X-axis virtual line XL or the width of the Y-axis acceleration detecting electrodes EY1 and EY2. It is 5 to 40% of the width dimension (0.8 mm) extending in the direction orthogonal to the Y-axis direction virtual line YL. In this example, it was 0.15 mm (0.32 mm or less). Further, the stress generation region 8 of the X-axis connection lines L1 and L2
The portions L1a and L2a located on C are arranged so as to be located on the imaginary line XL in the X-axis direction.

Electrode pattern 17 for detecting acceleration in the Y-axis direction
Has a structure in which a pair of Y-axis direction acceleration detecting electrodes EY1, EY2 and a Y-axis output electrode OY are connected in series by a Y-axis connection line L4. The electrodes EY1 and EY2 of the pair of Y-axis direction acceleration detection electrodes have the same shape and dimensions as the X-axis direction acceleration detection electrodes EX1 and EX2, and are line-symmetric with respect to the Y-axis direction virtual line YL. And has a shape close to a rectangle straddling the weight facing region 8A and the stress generating region 8C.

The width of the Y-axis connection line L4 is also
X-axis acceleration detecting electrode EX in the same manner as the width dimensions of 1 to L3
1, EX2 or Y-axis acceleration detecting electrodes EY1, EY2
Is 5 to 40% of the width dimension (0.8 mm). The portions L4a and L4b of the Y-axis connection line L4 located on the stress generation region 8C are arranged so as to be located on the imaginary line YL in the Y-axis direction.

Electrode pattern 19 for detecting acceleration in the Z-axis direction
Has a structure in which four Z-axis direction acceleration detection electrodes EZ1 to EZ4 and a Z-axis output electrode OZ are connected in series in this order by a Z-axis connection line L5. Each of the Z-axis direction acceleration detection electrodes EZ1 to EZ4 has a substantially rectangular shape, and includes a pair of X-axis direction acceleration detection electrodes EX1 and EX2 and a pair of Y-axis direction acceleration detection electrodes E.
It is formed so as to straddle the weight facing region 8A and the stress generating region 8C while being arranged between the electrodes Y1 and EY2.

The width of the Z-axis connection line L5 is also
X-axis acceleration detecting electrode EX in the same manner as the width dimensions of 1 to L3
1, EX2 or Y-axis acceleration detecting electrodes EY1, EY2
Is 5 to 40% of the width dimension (0.8 mm). The portions L5a, L5b, L5c, L5d of the Z-axis connection line L5 located on the stress generation region 8C are two symmetrical with respect to the X-axis virtual line XL or the Y-axis virtual line YL. They are arranged so as to be located on a virtual line.

Portions L1a, L2a, L4a, L of connection lines L1, L2, L4, L5 located on stress generating region 8C
4b, L5a, L5b, L5c, L5d are arranged at positions as in this example, the connection lines L1.
In the above, the X axis direction virtual line XL and the Y axis direction virtual line Y
They are arranged evenly in a well-balanced manner about L (arranged without partial bias). Therefore, even if acceleration acts on the weight 3, unlike the related art, the bending of the stress generation region 8C is not hindered in a state where the stress generation region 8C is partially biased by the connection lines L1. As a result, the output electrodes OX, OY, OZ
Of the X-axis acceleration detection signal, the Y-axis acceleration detection signal, and the Z-axis acceleration detection signal, which are output from the CPU, and it is necessary to adjust the level variation of each acceleration signal by a signal amplification circuit. Disappears.

The X-axis output electrode OX, the Y-axis output electrode OY, and the Z-axis output electrode OZ are formed at three corners of the piezoelectric ceramic substrate 7a so as to surround the recesses 7d, 7h, and 7k, respectively. An earth electrode OE is formed at the remaining corner of the piezoelectric ceramic substrate 7a so as to surround the recess 7g. An extension 21 extending to the edge of the piezoelectric ceramic substrate 7a adjacent to the X-axis direction acceleration detection electrode EX1 is connected to the ground electrode OE. The ground electrode OE is connected to the piezoelectric ceramic substrate 7.
It is electrically connected to the base 5 via a conductive adhesive layer (not shown) formed on the side portion and the back surface of “a”.

In the weight facing region 8A, a part of the base facing region 8B and a part of the stress generating region 8C, low dielectric layers 27, 29 and 31 are located between the connecting lines L1 to L5 and the piezoelectric ceramic substrate 7a. It is formed in a predetermined pattern such that Each of the low dielectric layers 27 to 31 is formed by screen printing using a thermosetting resin (relative dielectric constant: 10) made of a resin (epoxy) paste having a dielectric constant sufficiently smaller than that of the piezoelectric ceramic substrate 7a. And has a thickness of 20 μm. For the low dielectric constant layer, it is preferable to use a dielectric material having a relative dielectric constant of 1/100 or less of that of the piezoelectric ceramic substrate 7a. As the dielectric substance, any substance having a relative dielectric constant sufficiently smaller than that of the piezoelectric ceramic substrate 7a may be used, and glass and a thermosetting resin can be used. The low dielectric constant layer 27 is formed in the weight fixing region 8.
In A, it is formed so as to be located between the connection lines L4 and L5 and the piezoelectric ceramic substrate 7a, and has a circular shape.

The low dielectric constant layer 29 includes a portion 29a located on one side of the base facing region 8B, and three portions 29b projecting from the portion 29a and located on the stress generating region 8C.
29c and 29d. The portion 29a is provided on one side of the base facing region 8B with the connecting lines L1, L2,
It is formed so as to be located between L3, L5 and the piezoelectric ceramic substrate 7a. The portion 29b is formed between the portion L1a of the connection line L1 located on the stress generating region 8C and the piezoelectric ceramic substrate 7a, and has a substantially rectangular shape so as to be symmetrical about the imaginary line XL in the X-axis direction. Is formed. The portion 29c is formed in the stress generating region 8 of the connection line L4.
Part L4a located on C and piezoelectric ceramic substrate 7a
, And is formed in a substantially rectangular shape so as to be line-symmetric with respect to the Y-axis direction virtual line YL. The portion 29d is formed between the portion L2a of the connection line L2 located on the stress generating region 8C and the piezoelectric ceramic substrate 7a, and has a substantially rectangular shape so as to be line-symmetric about the imaginary line XL in the X-axis direction. Is formed.

The low dielectric constant layer 31 has a portion 31a located on the other side of the base facing region 8B and a portion 31b projecting from the portion 31a and located on the stress generating region 8C. The portion 31a is connected to the connection lines L4, L5 and the piezoelectric ceramic substrate 7 on the other side of the base facing region 8B.
a. Part 31b
Is a portion L of the connection line L4 located on the stress generating region 8C.
It is formed between the piezoelectric ceramic substrate 4b and the piezoelectric ceramic substrate 7a so as to be line-symmetric about the virtual line YL in the Y-axis direction.
By forming the portions 29b, 29c, 29d, 31b of the low dielectric layers 29, 31 located on the stress generating region 8C as described above, the low dielectric layers 29, 31
In the above, the X axis direction virtual line XL and the Y axis direction virtual line Y
They are arranged evenly in a well-balanced manner about L (arranged without partial bias). Therefore, even if acceleration acts on the weight 3, the bending of the stress generating region 8C is not hindered by the low dielectric constant layers 29 and 31 in a partially biased state. As a result, it is possible to further prevent the levels of the X-axis acceleration detection signal, the Y-axis acceleration detection signal, and the Z-axis acceleration detection signal output from the output electrodes OX, OY, and OZ from being varied.

As shown in FIG. 6, the counter electrode pattern E0 formed on the back surface of the piezoelectric ceramic substrate 7a is the acceleration detection electrode EX1 of the acceleration detection electrode pattern E1.
EZ4, an annular opposing electrode E0a, an extension E0b extending from the opposing electrode E0a to the edge of the piezoelectric ceramic substrate 7a, and back electrode portions E0c to E0f formed at four corners of the piezoelectric ceramic substrate 7a. are doing. The counter electrode E0a has a shape along the contour of the electrode row formed by the acceleration detection electrodes EX1 to EZ4 so as not to face the connection lines L1 to L5 via the piezoelectric ceramic substrate 7a as much as possible.

A part of the extension E0b is opposed to the end 21a of the extension 21 of the electrode pattern E1 for acceleration detection, and is electrically connected to the end 21a of the extension 21 via the through-hole conductive part 23. It is connected. Thus, the counter electrode E0a included in the counter electrode pattern E0 is electrically connected to the ground electrode OE. Back electrode section E
0c to E0f are earth electrode OE, X-axis output electrode OX,
It faces the Z-axis output electrode OZ and the Y-axis output electrode OY, and is electrically connected to each of the facing electrodes via a connection portion extending on the side of the piezoelectric ceramic substrate 7a.

X-axis direction acceleration detecting electrodes EX1, EX2
Is located on one side of the weight opposing area 8A when the same type of stress is generated in each part of the piezoelectric ceramic substrate 7a by applying acceleration in the Z-axis direction to the weight 3 at each part. The polarization processing is performed so that spontaneous polarization charges of opposite polarities appear on the acceleration detection electrode EX1 and the acceleration detection electrode EX2 located on the other side. Also, each part of the piezoelectric ceramic substrate 7a corresponding to the Y-axis direction acceleration detecting electrodes EY1 and EY2 has a weight 3 similar to each part of the piezoelectric ceramic substrate 7a corresponding to the X-axis direction acceleration detecting electrodes EX1 and EX2. When the same type of stress is generated in each part by the acceleration in the Z-axis direction acting on the
A-axis direction acceleration detection electrode EY located on one side of A
1 and Y-axis direction acceleration detecting electrode EY located on the other side
2 are subjected to a polarization process so that spontaneous polarization charges of opposite polarities appear. The piezoelectric ceramic substrate 7a corresponding to the Z-axis direction acceleration detecting electrodes EZ1 to EZ4.
When the same type of stress is generated in each part by the acceleration in the Z-axis direction acting on the weight 3, the spontaneous polarization charges of the same polarity are applied to all the Z-axis direction acceleration detecting electrodes EZ <b> 1 to EZ <b> 4. Polarization has been applied to appear. For this reason,
When the diaphragm 1 is deformed based on the acceleration acting on the weight 3, the piezoelectric ceramic substrate 7a bends, and the spontaneous polarization charge generated between the acceleration detection electrode pattern E1 and the counter electrode pattern E0 changes. The acceleration in three axes (X-axis, Y-axis, and Z-axis) applied to is measured as a change in current or voltage.

In this embodiment, the acceleration detection electrodes EX1 to EZ
4, the extension portion 21, the output electrodes OX to OZ, and the counter electrode pattern E0 are screen-printed using a glass-silver paste and then fired to form a 5 μm-thick film. Polarization was performed on the piezoelectric ceramic substrate 7a by applying the voltage. next,
The low dielectric layers 27 to 31 were screen-printed with a resin (epoxy) paste, and then the connection lines L1 to L9 were screen-printed with a resin silver paste to form an acceleration detection electrode pattern E1.

As shown in FIGS. 1 to 3, the insulating resin case 9 has a substantially rectangular parallelepiped cylindrical shape, and communicates with the central cavity 9a and the central cavity 9a and the outside. A side cavity 9b is formed inside. 2 and 3, the central hollow portion 9a penetrates the insulating resin case 9 in the vertical direction of the paper surface, and a stepped portion is formed between the substantially cylindrical single-unit storage portion 9c and the inner peripheral surface of the insulating resin case 9. A substantially cylindrical gap portion 9e having a smaller diameter than the single unit storage portion 9c is formed so as to form the portion 9d. The single unit 10 is a base 5 of the single unit 10.
Are housed in the single-unit housing portion 9c so that the bottom surface of the member and the step portion 9d are in contact with each other. Also, inside the single-unit storage portion 9c, a protrusion 9f is formed by resin entering the V-shaped groove 5a of the base 5 of the single unit 10.
In this example, since the insulating resin case 9 is integrally formed by injection molding using the single unit 10 as an insert,
The step 9 d and the protrusion 9 f function as a stopper for the unit unit 10 from coming off the insulating resin case 9. In addition, by forming the insulating resin case 9 using the single unit 10 as an insert, a part 5b of the outer peripheral surface of the base 5 is exposed in the side cavity 9b of the insulating resin case 9. The insulating resin case 9 has a front surface 9g formed on the same side as the front surface of the diaphragm 1 and formed flush with the front surface of the diaphragm 1, and a back surface 9h located on the opposite side of the front surface 9g. I have. The extension 7c of the above-described piezoelectric ceramic substrate 7a is mounted on the front surface 9g. The back surface 9h has a plurality of terminal fittings 11 described later.
The other end portions 11f of A to 11H are made of an insulating resin case 9.
A plurality (three in this example) of spacers 9i projecting in the same direction as the direction projecting from the back surface 9h of the rear surface 9h are formed. By forming such spacers 9i, a gap can be formed by the spacers 9i between the back surface 9h of the insulating resin case 9 and the circuit board when the acceleration detecting device is mounted on the circuit board. Therefore, when the terminal fittings 11A to 11H of the acceleration detecting device are soldered to the circuit board, it is possible to prevent the flux contained in the solder from entering the inside of the acceleration detecting device through the insulating resin case 9 or the like. As shown in FIG. 2, the outer peripheral portion of the insulating resin case 9 has a side surface 9 k on which the side cavity 9 b is opened.
A substantially rectangular concave portion 9j that opens outward is formed in a lower portion of the upper surface.

Each of the plurality of terminal fittings 11A to 11H has the same substantially columnar shape as shown in FIG.
Piezoelectric ceramic substrate 7 in insulating resin case 9
It is arranged at a position corresponding to the concave portions 7d to 7k of FIG. One of the terminal fittings 11A to 11H is:
Annular flanges 11c, 11 protruding in a direction perpendicular to the longitudinal direction at one end 11a and a central part in the longitudinal direction, respectively.
d. Thereby, the area of the end face 11e of the one end 11a becomes larger than the cross-sectional area of the terminal fitting orthogonal to the longitudinal direction. In addition, a flange 11d at the center in the longitudinal direction
Functions as a stopper for the terminal fittings 11A to 11F to come off from the insulating resin case 9. In the plurality of terminal fittings 11A to 11H, the end face 11e of one end 11a is exposed on the surface 9g of the insulating resin case 9 and the other end 11
f is disposed in the insulating resin case 9 so as to protrude from the back surface of the insulating resin case 9. Multiple terminal fittings 1
Almost half (semicircle) of each end face 11e of 1A to 11H
Are exposed from the inside of the recesses 7d to 7k of the piezoelectric ceramic substrate 7a to the outside. As shown in FIGS. 1 and 3, among the plurality of terminal fittings 11 </ b> A to 11 </ b> H, four terminal fittings 11 </ b> A located at the corners of the piezoelectric ceramic substrate 7 a.
One end face 11e of each of 11D, 11E, 11H is electrically connected to electrodes OX, OY, OZ, OE formed on extension 7c of piezoelectric ceramic substrate 7a by conductive portions 25 made of a conductive adhesive. Have been. In this example, one end face 11e of each of the other four terminal fittings 11B, 11C, 11F, 11G among the plurality of terminal fittings 11A to 11H simply comes into contact with the edge of the piezoelectric ceramic substrate 7a. However, these end faces 11e may be connected to the edge of the piezoelectric ceramic substrate 7a by an adhesive. Note that these terminal fittings 11B, 11C, 11F,
11G constitutes a dummy terminal.

The cover member 13 has a substantially rectangular upper wall portion 13.
and has a box shape with a one-sided opening having four substantially rectangular side walls 13b to 13e, and is integrally formed of stainless steel. This cover member 13 is
a is located above the acceleration sensor element 7 and the side wall portion 13b
13e cover the acceleration sensor element 7 in a state fitted to the insulating resin case 9 so as to abut on the side surface of the insulating resin case 9. As shown in FIGS. 2 and 3, the side wall 9 b of the cover member 13 that contacts the side surface 9 k of the insulating resin case 9 (the side surface on which the side cavity 9 b of the insulating resin case 9 is formed) is in contact. The piece 13f and the projection 13g are integrally formed by press working. The contact piece 13f extends in the side cavity 9b of the insulating resin case 9 so that a part of the side wall 13b forms an opening 13h and rises to the base 5 side. It has an upright portion 13f1 extending in a direction orthogonal to the first portion, and a contact portion 13f2 bent in an arc shape at an end of the upright portion 13f1. The contact portion 13f2 is fitted in a fitting concave portion formed by a part of the V-shaped groove 5a of the base 5 (a portion exposed in the side cavity 9b).
3 is electrically connected to the base 5. As described above, since the ground electrode OE is electrically connected to the base 5 via the conductive adhesive layer (not shown), the cover member 13 is electrically connected to the ground electrode OE together with the base 5. It will be grounded. In particular, in this example, the contact portion 13f2 is pressed against the base 5 by the spring property of the upright portion 13f1 in a state where the cover member 13 is fitted into the insulating resin case 9, so that the cover member 13 and the cover member 13 are simultaneously attached to the cover member 13. The electrical connection with the base 5 can be completed, and the contact piece 13f between the base 5 and the cover member 13 can be completed.
The contact with is ensured.

The protrusion 13g is provided on the side wall 1 of the cover member 13.
Part 3b is bent and formed. The convex portion 13g is fitted in a concave portion 9j formed on the side surface 9k of the insulating resin case 9, and plays a role of fixing the cover member 13 to the insulating resin case 9. According to such a fixing method, since the convex portion 13g of the cover member 13 is fitted to the insulating resin case 9 with a spring property, the cover member 13 is attached to the insulating resin case 9 by attaching the cover member 13.
Can be fixed easily.

[0032]

According to the present invention, the portion of the X-axis connection line located on the stress generation region is arranged so as to be located on the imaginary line in the X-axis direction, and is located on the stress generation region of the Y-axis connection line. The two parts are arranged so as to be located on the imaginary line in the Y-axis direction, and the part located on the stress generation region of the Z-axis connection line is symmetrical about the imaginary line in the X-axis direction or the imaginary line in the Y-axis direction. Each connection line is placed so that it is located on the virtual line of
On the stress generation region, the imaginary lines in the X-axis direction and the imaginary line in the Y-axis direction are arranged in a well-balanced and uniform manner (arranged without partial bias). Therefore, the bending of the stress generating region when acceleration acts on the weight also occurs in a well-balanced manner. As a result, variations in the levels of the X-axis acceleration detection signal, the Y-axis acceleration detection signal, and the Z-axis acceleration detection signal output from the output electrode are reduced, and it is necessary to adjust the level variation of each acceleration signal by a signal processing circuit. Disappears.

Further, according to the present invention, since the bending of the stress generating region when the acceleration acts on the weight occurs in a well-balanced manner, when the acceleration acts on the weight, irregular distortion occurs in the stress generating region. Can be prevented. for that reason,
It is possible to eliminate so-called noise in which spontaneous polarization occurs in other axes despite acceleration acting only on a specific axis.

[Brief description of the drawings]

FIG. 1 is a front view showing a piezoelectric triaxial acceleration sensor according to an embodiment of the present invention in a partially broken state.

FIG. 2 is a plan view showing the piezoelectric triaxial acceleration sensor according to the embodiment of the present invention in a partially broken state.

FIG. 3 is a side view showing the piezoelectric three-axis acceleration sensor according to the embodiment of the present invention in a partially broken state.

FIG. 4 is a rear view of the piezoelectric three-axis acceleration sensor according to the embodiment of the present invention.

FIG. 5 is a plan view of an acceleration sensor element used for the piezoelectric three-axis acceleration sensor according to the embodiment of the present invention.

FIG. 6 is a back view of the acceleration sensor element used in the piezoelectric triaxial acceleration sensor according to the embodiment of the present invention.

FIG. 7 is a plan view of an acceleration sensor element used in a conventional piezoelectric triaxial acceleration sensor.

[Description of Signs] 1 Diaphragm 3 Weight 5 Base 7 Acceleration sensor element 8A Weight facing area 8B Base facing area 8C Stress generating area 27, 29, 31 Low dielectric constant layer E1 Acceleration detection electrode pattern EX1, EX2 A pair of X Axial acceleration detection electrodes EY1, EY2 A pair of Y-axis acceleration detection electrodes EZ1 to EZ4 Z-axis acceleration detection electrodes L1 to L5 Connection lines OX to OZ Output electrode E0 Counter electrode pattern E0a Counter electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masato Ando 3158 Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Inside (72) Yoshiyuki Nakamizo 3158 Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama (72) Inventor Tsutomu Sawai 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (4)

[Claims] 1. A pair of Xs arranged on an imaginary line in the X-axis direction
Axis acceleration detecting electrode, Y orthogonal to the X axis direction virtual line
A pair of Y-axis acceleration detecting electrodes arranged on the imaginary axial line, a plurality of Z-axis acceleration detecting electrodes for detecting acceleration in the Z-axis direction, an X-axis output electrode, a Y-axis output electrode, and a Z-axis; An acceleration detection electrode pattern electrically connected to the output electrode via an X-axis connection line, a Y-axis connection line, and a Z-axis connection line is formed on the front surface, and at least the pair of X-axis acceleration detection lines are formed on the back surface. And an opposing electrode pattern including an opposing electrode facing the pair of Y-axis acceleration detecting electrodes and the plurality of Z-axis acceleration detecting electrodes is formed between the respective acceleration detecting electrodes and the opposing electrode. A piezoelectric ceramic substrate having a portion subjected to polarization processing; a diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate; a weight provided at a central portion of the diaphragm; A base supporting the diaphragm so that a portion of the piezoelectric ceramic substrate around the weight is bent when the weight is applied, wherein the piezoelectric ceramic substrate has a weight facing the weight. A weight facing region, a base facing region facing the base,
A piezoelectric three-axis acceleration sensor having an annular stress generating region between the weight-facing region and the base-facing region and on which the acceleration detecting electrodes are arranged, wherein the X-axis connection A portion of the line located on the stress generation region is disposed so as to be located on the virtual line in the X-axis direction. A portion of the Y-axis connection line located on the stress generation region is located in the Y-axis direction. It is arranged so that it may be located on an imaginary line, and the portion located on the stress generation area of the Z-axis connection line is line-symmetric about the X-axis imaginary line or the Y-axis imaginary line. A piezoelectric triaxial acceleration sensor arranged to be located on two virtual lines. 2. A width dimension of the X-axis acceleration detection electrode extending in a direction orthogonal to the X-axis virtual line, and a width of the Y-axis acceleration detection electrode extending in a direction orthogonal to the Y-axis virtual line. The ratio of the width dimension of each connection line to the width dimension of the X-axis acceleration detection electrode or the Y-axis acceleration detection electrode is 5
The piezoelectric type three-axis acceleration sensor according to claim 1, wherein the ratio is from 40% to 40%. 3. A width dimension of each connection line is 0.32 mm.
The piezoelectric three-axis acceleration sensor according to claim 2, wherein 4. The piezoelectric ceramic substrate according to claim 1, wherein a portion of the X-axis connection line located on the stress generation region and the piezoelectric ceramic substrate are provided.
A low dielectric constant layer is formed so as to be line-symmetric with respect to the X-axis direction virtual line, and a portion between the Y-axis connection line located on the stress generating region and the piezoelectric ceramic substrate is provided. 3. The piezoelectric type triaxial acceleration sensor according to claim 1, wherein a low dielectric constant layer is formed so as to be line-symmetric with respect to the Y-axis direction virtual line.