JP5239048B2 - Manufacturing method of piezoelectric acceleration sensor - Google Patents

Description

The present invention relates to a method for manufacturing a piezoelectric acceleration sensor.

Conventionally, various piezoelectric acceleration sensors using piezoelectric elements are known.
For example, in Patent Document 1, a piezoelectric element in which a pair of other surfaces of an element element, which is formed in a long plate shape and has a signal extraction electrode formed on one surface, is bonded to each other, and a support that supports both ends of the piezoelectric element. In the acceleration sensor, the piezoelectric element is deflected in the acceleration direction and polarized to output an electric signal, and movable support means for supporting the piezoelectric element so that both ends can be moved freely based on the deflection The acceleration sensor provided in is described.
In this acceleration sensor, the acceleration is obtained by detecting the polarization voltage due to the deformation generated by the inertial force acting on the piezoelectric element itself supported at both ends.
Patent Document 2 discloses an acceleration detection unit in which a weight is fixed to one surface of a diaphragm and a piezoelectric element is fixed to the other surface of the diaphragm, and is arranged on the piezoelectric element side of the acceleration detection unit. A piezoelectric acceleration sensor comprising a circuit board for amplifying a detection signal of an acceleration detection unit, wherein a connection electrode of the piezoelectric element and a connection terminal of the circuit board are connected, the connection electrode of the piezoelectric element and the connection terminal of the circuit board The piezoelectric acceleration sensor is described in which the connection electrodes and the connection terminals are connected to each other by a conductive contact material having elasticity.
In this piezoelectric acceleration sensor, the diaphragm is deformed by the inertial force acting on the weight, and the deformation acting on the diaphragm can be detected by the piezoelectric element fixed on the diaphragm, so that the acceleration acting on the weight can be detected. It is like that.
Japanese Patent Laid-Open No. 11-72504 Japanese Patent Laid-Open No. 2003-4760

However, the conventional piezoelectric acceleration sensor as described above has the following problems.
In the technique described in Patent Document 1, although acceleration can be detected by deformation of the long plate-like piezoelectric element itself, a simple configuration can be obtained, but since the deformation with respect to inertia force is small, the detection sensitivity is low. There is a problem. In order to increase the detection sensitivity, it is necessary to further increase the length of the piezoelectric element, which causes a problem that the sensor is increased in size.
Further, in order to detect the acceleration in the three-axis direction, it is necessary to arrange a similar configuration in the three-axis direction, so that there is a problem that the size is further increased.
Further, in the technique described in Patent Document 2, since the weight is eccentrically provided on the diaphragm, the diaphragm is deformed in accordance with the triaxial inertial force acting on the weight, and the deformation is applied to the piezoelectric element on the diaphragm. By detecting by this, the acceleration in the triaxial direction can be detected.
However, since the piezoelectric elements are entirely formed on the diaphragm, it takes time and effort to suppress variations in the characteristics of the piezoelectric elements, and the piezoelectric elements themselves are expensive, so that the manufacturing cost cannot be reduced. is there.
In addition, since the piezoelectric element is formed in a thin film on the diaphragm, there is a problem in that the piezoelectric element film is easily broken.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a piezoelectric acceleration sensor that can achieve good sensitivity and can be reduced in cost and size. And

In order to solve the above problems, in the invention according to claim 1, a beam portion in which a half or more of the cross section perpendicular to the axis is formed of a piezoelectric material, and a weight portion supported by one end side of the beam portion, A method of manufacturing a piezoelectric acceleration sensor, comprising: a support base portion that supports the other end side of the beam portion; and an electrode portion for extracting a polarization voltage generated in a piezoelectric body of the beam portion, wherein the weight portion And the support base part are arranged in alignment with each other, and formed in an outer shape viewed from the thickness direction of the beam part at a position where the beam part is formed between the weight part and the support base part. A disposing step of disposing the coated film forming body, and forming a film by colliding and adhering fine particles of the piezoelectric material on the film forming body, whereby the side surface of the weight portion and the support base are formed on the film forming body. Piezoelectric material forming process for forming the piezoelectric material bonded to the side surface of the part When, wherein the weight section and the support section is composed of separate members, in the disposing step, the weight portion and placing the support section on the film-forming material, the piezoelectric body forming step Thereafter, the method further includes a film forming body removing step of removing the film forming body and leaving only the piezoelectric body at an intermediate portion in the longitudinal direction of the beam portion .
According to this invention, since the weight portion is supported on one end side of the beam portion whose other end side is supported by the support base portion, when the acceleration is generated by the movement of the piezoelectric acceleration sensor, the weight portion acts on the weight portion. The beam part is deformed by the inertial force. Since the beam portion is formed of a piezoelectric body at a half or more of the cross section perpendicular to the axis, it is possible to detect not only the surface of the beam portion but also deformation in the cross section perpendicular to the axis of the beam portion with the piezoelectric body. And the acceleration according to the distortion of a beam part is detectable by taking out the polarization voltage which generate | occur | produces according to the distortion of a piezoelectric material from an electrode part.
In addition, since the weight portion is supported by the beam portion, it is easier to detect deformation even if the support portion is shorter than when the weight portion is supported by, for example, a diaphragm, so the support span can be shortened. Become.
In addition, since the piezoelectric body is formed in a beam shape, that is, in a one-dimensional manner, less piezoelectric material is required, and if the same amount of piezoelectric material is used, the beam has higher strength than the case where it is formed into a planar film shape. Can be configured. In addition, since the manufacturing becomes easier as compared with the case of forming into a planar film shape, even when a plurality of beam portions are provided, the piezoelectric element characteristics of each beam portion are easily made uniform.
In addition, since the piezoelectric material is formed by colliding the fine particles of the piezoelectric material to form the beam portion, for example, when the distance between the weight portion and the support base portion is short or the shape of each is complicated. However, since it can be manufactured easily, a small piezoelectric acceleration sensor can be formed.
Moreover, since it can be made to adhere in normal temperature environment, it becomes possible to use a heat-sensitive material for a support base part or a weight part.
In addition, since the intermediate portion in the length direction of the beam portion is formed only of the piezoelectric body, in the intermediate portion, the deformation of the beam portion is entirely the deformation of the piezoelectric body, so that the sensitivity can be improved.
In order to further improve the sensitivity, it is preferable that the entire beam portion is formed of a piezoelectric body.

In the invention described in claim 2, wherein the method of manufacturing a piezoelectric acceleration sensor according to claim 1, wherein the weight section and the support section is at least either side of the weight portion and the support section A protrusion formed on the film forming body, and in the piezoelectric body forming step, the piezoelectric body is formed to a thickness that covers the protrusion, so that at least the weight portion and the support base portion are formed. A method of joining the end portions of the beam portions at the projecting portions on any side surface.
According to the present invention, the end portion of the beam portion is joined to at least one of the side surface of the weight portion and the support base portion and the projection portion protruding from the side surface toward the beam portion side. Compared with the case where it joins, a joining area becomes large and the joining strength in the edge part of a beam part can be improved.

According to a third aspect of the present invention, a beam portion in which half or more of the cross section perpendicular to the axis is formed of a piezoelectric body, a weight portion supported by one end side of the beam portion, and the other end side of the beam portion are supported. And a method of manufacturing a piezoelectric acceleration sensor having an electrode portion for extracting a polarization voltage generated in the piezoelectric body of the beam portion, wherein the weight portion and the support base portion are positioned relative to each other. And arranging the film forming body formed in the outer shape viewed from the thickness direction of the beam portion at a position where the beam portion is formed between the weight portion and the support base portion. And forming a film by colliding and adhering the fine particles of the piezoelectric material on the film forming body, thereby bonding the side surface of the weight part and the side surface of the support base part on the film forming body. A piezoelectric body forming step of forming a piezoelectric body, the weight portion and the front The support base part has a shape in which a protrusion part protrudes from the side surface of at least one of the weight part and the support base part on the film forming body, and in the piezoelectric body forming step, the thickness that covers the protrusion part Further, by forming the piezoelectric body, the end portion of the beam portion is joined to the projection portion on at least one of the side surfaces of the weight portion and the support base portion.
According to this invention, since the weight portion is supported on one end side of the beam portion whose other end side is supported by the support base portion, when the acceleration is generated by the movement of the piezoelectric acceleration sensor, the weight portion acts on the weight portion. The beam part is deformed by the inertial force. Since the beam portion is formed of a piezoelectric body at a half or more of the cross section perpendicular to the axis, it is possible to detect not only the surface of the beam portion but also deformation in the cross section perpendicular to the axis of the beam portion with the piezoelectric body. And the acceleration according to the distortion of a beam part is detectable by taking out the polarization voltage which generate | occur | produces according to the distortion of a piezoelectric material from an electrode part.
In addition, since the weight portion is supported by the beam portion, it is easier to detect deformation even if the support portion is shorter than when the weight portion is supported by, for example, a diaphragm, so the support span can be shortened. Become.
In addition, since the piezoelectric body is formed in a beam shape, that is, in a one-dimensional manner, less piezoelectric material is required, and if the same amount of piezoelectric material is used, the beam has higher strength than the case where it is formed into a planar film shape. Can be configured. In addition, since the manufacturing becomes easier as compared with the case of forming into a planar film shape, even when a plurality of beam portions are provided, the piezoelectric element characteristics of each beam portion are easily made uniform.
In addition, since the piezoelectric material is formed by colliding the fine particles of the piezoelectric material to form the beam portion, for example, when the distance between the weight portion and the support base portion is short or the shape of each is complicated. However, since it can be manufactured easily, a small piezoelectric acceleration sensor can be formed.
Moreover, since it can be made to adhere in normal temperature environment, it becomes possible to use a heat-sensitive material for a support base part or a weight part.
Further, since the end portion of the beam portion is joined to at least one of the side surfaces of the weight portion and the support base portion and the protruding portion protruding from the side surface toward the beam portion side, the end portion of the beam portion is directly joined to the side surface. Compared to the case, the joining area becomes larger, and the joining strength at the end of the beam part can be improved.

According to a fourth aspect of the present invention, in the method for manufacturing a piezoelectric acceleration sensor according to any one of the first to third aspects, in the arranging step, the weight portion is formed by a plurality of the beam portions so that the center of gravity is in three axial directions. In order to support it in a movable manner, the film forming body is arranged at each of the plurality of beam portions 0.
According to this invention, since the weight portion is supported by the plurality of beam portions so that the center of gravity is movable in the three-axis direction, a piezoelectric acceleration sensor that detects acceleration in the three-axis direction can be configured.
At this time, since the weight portion is supported by a beam-like piezoelectric body having directionality in sensitivity, the piezoelectric bodies can be efficiently arranged.

According to the method for manufacturing a piezoelectric acceleration sensor of the present invention, a piezoelectric acceleration sensor can be manufactured in which a weight portion is supported by a beam portion in which a half or more of the cross section perpendicular to the axis is a piezoelectric body. Is obtained, and the cost and size can be reduced.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
A piezoelectric acceleration sensor according to an embodiment of the present invention will be described.
FIG. 1A is a schematic plan view showing a schematic configuration of a piezoelectric acceleration sensor according to an embodiment of the present invention. FIGS. 1B and 1C are an AA sectional view and a BB sectional view of FIG. 1A, respectively.

As shown in FIGS. 1A, 1B, and 1C, the schematic configuration of the piezoelectric acceleration sensor 1 of the present embodiment includes a support base 2 (support base part), a weight 3 (weight part), and a piezoelectric body. 4 (beam portion) and electrode 5 (electrode portion).
Note that a mating member such as a package or a substrate to which the piezoelectric acceleration sensor 1 is attached and wiring from the electrode 5 are not shown.

The support base 2 serves as a base of the piezoelectric acceleration sensor 1 and constitutes an attachment portion with a mating member such as a package or a substrate. And, even if it receives an inertial force due to the acceleration within the detectable range, it has such rigidity that it does not cause deformation or vibration that affects the detection of acceleration.
In the present embodiment, as an example, a metal frame having a square opening in plan view is used. In the present embodiment, the support base 2 is formed by pressing a metal plate material, and the thickness of the support base 2 is the same as the plate thickness of the original plate material and is shorter than the side length of the frame. ing.

  The weight 3 is for causing an inertial force acting on the center of gravity G according to the acceleration to act on the end of the piezoelectric body 4 to distort the piezoelectric body 4. In this embodiment, the weight 3 has the same thickness and the same material as the support base 2. And has a rectangular parallelepiped shape in plan view, and is arranged at the center of the opening of the support base 2.

The piezoelectric body 4 is formed of a piezoelectric material and constitutes a beam portion that fixes the weight 3 to the support base 2.
In the present embodiment, the piezoelectric body 4 includes four piezoelectric bodies 4A, 4B, 4C, and 4D, and one end side in the beam length direction is bonded to the side surface 3a of the weight 3 via an insulating layer (not shown). The other end side is joined to the inner side surface 2a (side surface of the support base) of the frame of the support base 2 facing the side surface 3a via an insulating layer (not shown).
In plan view, the piezoelectric bodies 4A and 4C are aligned on a straight line that overlaps the center of gravity G of the weight 3, and the piezoelectric bodies 4B and 4D are orthogonal to the straight line on which the piezoelectric bodies 4A and 4C are aligned. They are aligned on a straight line that overlaps G.

  In this embodiment, in order to take such a symmetrical arrangement in plan view, the beam length of each piezoelectric body 4 and the shape of the beam perpendicular to the axis (hereinafter simply referred to as the beam cross section) are set to be the same. Has been. However, the height dimension of the beam cross section of each piezoelectric body 4 is set to be smaller than the thickness of the support base 2 in the thickness direction of the support base 2, and the centroid and weight of the beam cross section of each piezoelectric body 4. 3 are shifted from each other in the thickness direction of the support base 2. That is, the center of gravity G of the weight 3 is decentered in the height direction of the beam section with respect to the centroid of the beam section of each piezoelectric body 4, and when inertial force acts in the horizontal direction in FIG. A moment is generated at the joint with the piezoelectric body 4.

  The material of the piezoelectric material is not particularly limited, but is preferably a material capable of forming a film by impact adhesion of fine particles. For example, lead zirconate titanate (PZT) can be suitably used.

  The electrode 5 is for taking out the polarization voltage generated by the deformation of the piezoelectric body 4. In each piezoelectric body 4, a film is formed on the surface facing the thickness direction of the support base 2 by, for example, vapor deposition or sputtering. The metal film is made of. Then, it can be connected to an acceleration detection circuit (not shown) by a wiring (not shown) insulated from the support base 2 and the weight 3.

Next, a method for manufacturing the piezoelectric acceleration sensor 1 will be described.
FIG. 2A is a process explanatory diagram in plan view for explaining a manufacturing process of the piezoelectric acceleration sensor according to the embodiment of the present invention. FIG.2 (b) is CC sectional drawing of Fig.2 (a). FIG. 3A is a process explanatory diagram in plan view for explaining a manufacturing process subsequent to the process shown in FIG. FIG.3 (b) is DD sectional drawing of Fig.3 (a). 4A, 4 </ b> B, and 4 </ b> C are cross-sectional views similar to the DD cross-section of FIG. 3A that sequentially explains the manufacturing process subsequent to the process illustrated in FIG. 3.

First, in order to form the support base 2 and the weight 3, the metal plate is pressed to form the support base 2 and the weight 3 simultaneously as shown in FIG.
Next, as shown in FIGS. 3 (a) and 3 (b), the formed support base 2 and weight 3 are placed on the piezoelectric body forming plate 6, and the respective positions are fixed via the bonding layer 7. To do.

The piezoelectric body forming plate 6 serves as a base for forming a beam shape by colliding and adhering fine particles of piezoelectric material, and the end of each piezoelectric body 4 is connected to the inner side surface 2 a of the support base 2 and the side surface 3 a of the weight 3. This is a member for fixing the support base 2 and the weight 3 in a fixed position in order to be joined to each other.
That is, the planar shape of the piezoelectric body forming plate 6 extends in the extending direction of the weight fixing portion 6a for fixing the weight 3 and each piezoelectric body 4 joined to the weight 3, as shown in FIG. It is a plate member on a lattice frame having a strip-shaped piezoelectric body forming part 6b and a support base fixing part 6c for fixing the support base 2. For this reason, the weight fixing portion 6a and the support base fixing portion 6c are open except for the four piezoelectric body forming portions 6b.
Here, the width dimension of the piezoelectric body forming portion 6 b is the same as the width dimension of the cross section perpendicular to the axis of the piezoelectric body 4, that is, the beam section width formed by the piezoelectric body 4.

  The bonding layer 7 is for fixing the support base 2 and the weight 3 on the piezoelectric material forming plate 6 during the formation of the piezoelectric material 4 as follows. By the processing, the piezoelectric body forming plate 6 can be peeled from the support base 2, the weight 3, and each piezoelectric body 4. In the present embodiment, a Cr layer that can be removed by an etching process is employed as the bonding layer 7.

Next, prior to the formation of the piezoelectric body 4, an insulating layer is formed on the inner surface 2 a and the side surface 3 a in the bonding region 8 (see FIG. 3B) where the ends of the piezoelectric body 4 are bonded. This insulating layer can be formed by an appropriate means such as vapor deposition or sputtering, for example. However, the insulating fine particles may be deposited by collision in the same manner as the piezoelectric body 4.
Note that this step can be omitted when the support 2 and the weight 3 are formed of an insulator.

Next, as shown in FIG. 4A, in the thickness direction of the support base 2, from the side opposite to where the piezoelectric body forming plate 6 is provided, toward the piezoelectric body forming portion 6b, for example, PZT Fine particles are caused to collide and the piezoelectric body 4 is deposited.
An aerosol deposition method (hereinafter abbreviated as the AD method) can be adopted as a technique for causing the PZT fine particles to adhere and collide. The AD method is a method in which a fine particle material to be formed is mixed with a gas to form an aerosol, and is sprayed through a nozzle against a film formation in an atmosphere of reduced pressure to form a film using a so-called room temperature impact solidification phenomenon ( For example, Akito, “Aerosol Deposition Method and Its Application”, Surface Chemistry, 2004, Vol. 25, No. 10, p. 635-641).
In the film formation process by the AD method, since the PZT fine particles are sprayed in a certain range and collide with the film forming body, the film formation proceeds. Therefore, the nozzle position and the film forming body are moved relative to each other to move the spraying area, and the adhesion amount The film thickness (the height of the beam cross section) can be controlled by controlling.
On the other hand, the width dimension of the beam cross section of the piezoelectric body 4 is determined by the dimensions of the piezoelectric body forming portion 6b of the piezoelectric body forming plate 6 which is a film forming body.
Further, the PZT fine particles that do not reach the inner side surface 2a, the side surface 3a, and the piezoelectric body forming portion 6b pass through the opening of the piezoelectric body forming plate 6 and do not contribute to the formation of the piezoelectric body 4.
In this way, as shown in FIG. 4 (a), the piezoelectric body 4 in which the cross section perpendicular to the axis is controlled between the piezoelectric body forming portion 6b on which the bonding layer 7 is formed, the side surface 3a, and the inner side surface 2a. Can be formed.

Next, after the piezoelectric body 4 is formed, the bonding layer 7 of the assembly as shown in FIG. 4A is etched, and the piezoelectric body forming plate 6 is peeled off (see FIG. 4B).
And as shown in FIG.4 (c), the electrode 5 is each formed in the surface of the piezoelectric material 4 which mutually opposes in the thickness direction of the support stand 2, and a wiring pattern not shown is formed as needed. .
In this way, the piezoelectric acceleration sensor 1 is manufactured.

According to the manufacturing method of the present embodiment, since the piezoelectric body 4 is formed by colliding and adhering fine particles of piezoelectric material, for example, when the distance between the side surface 3a and the inner side surface 2a is short, Even if the shape is complicated, the piezoelectric acceleration sensor 1 can be easily downsized because it can be easily manufactured.
Moreover, since it can be made to adhere in normal temperature environment, it becomes possible to use a heat-sensitive material for a support base part or a weight part.
In addition, since the piezoelectric body 4 is formed as a one-dimensional beam, it is easy to suppress variations in piezoelectric element characteristics in manufacturing compared to a case where the piezoelectric body 4 is formed as a two-dimensional film having a larger spread.

Next, the operation of the piezoelectric acceleration sensor 1 will be described.
FIGS. 5A and 5B are schematic operation explanatory views for explaining the operation of the piezoelectric acceleration sensor of the present embodiment, respectively.

For example, as shown in FIG. 5A, when acceleration occurs in the extending direction of the piezoelectric bodies 4B and 4D (hereinafter referred to as the x direction) due to the movement of the piezoelectric acceleration sensor 1, the center of gravity of the weight 3 the G, inertial force _{f x} acts. Since the support positions of the piezoelectric bodies 4B and 4D are eccentric from the center of gravity G, the counterclockwise moment shown in the figure depends on the eccentric position of the center of gravity G at the ends of the piezoelectric bodies 4B and 4D that support the weight 3. Works.
Thereby, the piezoelectric bodies 4B and 4D are deformed into an S shape in the figure, and a polarization voltage is generated according to each distortion. Voltage signals V _B and V _D corresponding to the polarization voltage are detected by the acceleration detection circuit 100 through the wiring 101 connected to each electrode 5.
In this case, the piezoelectric 4A disposed illustrated the depth direction, 4C is deformed by receiving a shear force in the plane in a counterclockwise twisting moment and x-direction by inertial force f _x, such variations Since the sensitivity of the piezoelectric element to the piezoelectric element is low, a smaller polarization voltage is generated according to each strain. The voltage signals V _A and V _C corresponding to the polarization voltage are detected by the acceleration detection circuit 100 through the wiring 101 connected to each electrode 5.
The acceleration detection circuit 100 calculates the acceleration in the x direction from these voltage signals V _A , V _B , V _C , and V _D based on the relationship between each voltage signal calibrated in advance and the acceleration, and detects it appropriately. The signal _Ax is output.

On the other hand, the piezoelectric body 4A, the extending direction of 4C (hereinafter, y referred to as direction), if the same inertial force f _y is applied to the weight 3, in the same manner, the size and deformation modes of the inertial force f _y Accordingly, voltage signals V _A , V _B , V _C , and V _D are generated, and acceleration in the y direction is calculated based on the relationship between each voltage signal calibrated in advance from these voltage signals and acceleration. The detection signal _Ay is output.

Further, for example, as shown in FIG. 5B, acceleration is applied to the piezoelectric acceleration sensor 1 in the thickness direction of the support 2, that is, in the direction orthogonal to the x direction and the y direction (hereinafter referred to as the z direction). Is generated, the inertial force f _z acts on the center of gravity G of the weight 3. For this reason, a shearing force of f _z / 4 acts on the ends of the four piezoelectric bodies 4 on the side of the weight 3 through the weight 3 in the same direction in the z direction, and according to the shearing force, each piezoelectric body 4. Are uniformly deformed in the z direction, and a polarization voltage is generated in accordance with the distortion of the deformation. The voltage signals V _A , V _B , V _C and V _D corresponding to each polarization voltage are detected by the acceleration detection circuit 100 through the wiring 101 connected to each electrode 5.
When the acceleration detection circuit 100 detects such a voltage signal component common to the piezoelectric bodies 4A, 4B, 4C, and 4D, the acceleration detection circuit 100 calculates the acceleration in the z direction based on the relationship between each voltage signal calibrated in advance and the acceleration. Calculate and output an appropriate detection signal _Az .

In the general case where the inertial force acting on the weight 3 includes directional components in the x direction, the y direction, and the z direction, the voltage signals V _A , V _B , V _C , V _D are generated according to the component ratios. The acceleration in each direction is calculated according to the ratio of the inertial force in each direction, and the detection signals A _x , A _y , and A _z are output accordingly.
Thus, according to the piezoelectric acceleration sensor 1, it is possible to detect accelerations in three axial directions orthogonal to each other based on the voltage signals V _A , V _B , V _C , and V _D.

According to the piezoelectric acceleration sensor 1 of the present embodiment, since the weight 3 is supported by the piezoelectric body 4 constituting the beam portion, even if the weight 3 is supported by, for example, a diaphragm, the support span is shorter. Deformation is easy to detect. Therefore, the support span can be shortened and further downsizing can be achieved.
Further, since the piezoelectric body 4 is formed one-dimensionally, it is possible to reduce the cost of the piezoelectric material and to reduce the cost. Further, compared to the case where the piezoelectric body 4 is formed into a planar film shape, the same cross section of the piezoelectric material can increase the height of the beam cross section, so that the piezoelectric body 4 having high strength can be configured.

Next, a piezoelectric acceleration sensor according to a first modification of the present embodiment will be described.
FIG. 6A is a schematic plan view showing a schematic configuration of a piezoelectric acceleration sensor according to a first modification of the embodiment of the present invention. 6B and 6C are an EE sectional view and an FF sectional view of FIG. 6A, respectively.

The piezoelectric acceleration sensor 10 according to the present modification includes a support base 12 (support base part), a weight 13 (weight part), and a piezoelectric body 14 instead of the support base 2, the weight 3 and the piezoelectric body 4 of the above embodiment. Prepare.
This modification is a modification regarding the shape of the joint portion between the end of the piezoelectric body 4 and the support base 2 and the weight 3 in the piezoelectric acceleration sensor 1 of the above-described embodiment. It is the same as the form. Hereinafter, a description will be given focusing on differences from the above embodiment.

The support base 12 is a frame having the same shape as the support base 2 of the above-described embodiment, and is a protrusion protruding from the inner side surface 2a to the inner peripheral side along one surface in the thickness direction where the piezoelectric body 14 is joined. 12a. The protrusion 12 a is set so that the dimension in the thickness direction occupies 1/2 or less of the beam cross section constituted by only the piezoelectric body 14, and the joining region with the piezoelectric body 14 is stepped.
The protrusion 12a may be provided at least in a range where the piezoelectric body 14 is bonded in the circumferential direction, but in the present embodiment, the protrusion 12a is provided over the entire circumference of the inner side surface 2a.

In the rectangular parallelepiped having the same shape as the weight 3 of the above embodiment, the weight 13 includes a protruding portion 13a that protrudes from the side surface 3a to the outer peripheral side along one surface in the thickness direction where the piezoelectric body 14 is joined. The protrusion 13a is set so that the dimension in the thickness direction occupies 1/2 or less of the beam cross section constituted by only the piezoelectric body 14, and the joining area with the piezoelectric body 14 is stepped.
The protrusion 13a only needs to be provided at least in a range where the piezoelectric body 14 is bonded in the circumferential direction, but in the present embodiment, the protrusion 13a is provided over the entire circumference of the side surface 3a.

The piezoelectric body 14 is formed of a piezoelectric material made of the same material as the piezoelectric body 4 of the above embodiment, and constitutes a beam portion that fixes the weight 13 to the support base 12.
In the present embodiment, the piezoelectric body 14 includes four piezoelectric bodies 14A, 14B, 14C, and 14D, and one end side in the beam length direction is the side surface 3a of the weight 13 and the protrusion 13a, and an insulating layer (not shown). The other end side is joined to the inner side surface 2a and the protrusion 12a of the frame of the support base 12 facing the side surface 3a via an insulating layer (not shown).
And the beam cross section of the beam part of this structure is made into the fixed rectangular cross section. For this reason, in the middle part of the beam, the beam cross section is composed of the piezoelectric body 14 similar to the piezoelectric body 4 of the above embodiment, and on the end side where the protrusion 12a (13a) protrudes, the beam cross section is the protrusion 12a. (13a) and the piezoelectric body 14.
Further, in the thickness direction of the support 12, the electrodes 5 and wirings (not shown) are provided on the surfaces of the piezoelectric bodies 14 facing each other in the same manner as in the above embodiment.

The piezoelectric acceleration sensor 10 having such a configuration can be manufactured in the same manner as the piezoelectric acceleration sensor 1 of the above embodiment.
The protrusions 12a and 13a can be formed, for example, by a die from a metal plate during a brazing process, but may be subjected to a secondary process as necessary in order to improve the shape accuracy.

According to the piezoelectric acceleration sensor 10 of the present modified example, the beam portion that supports the weight 13 is configured by the piezoelectric body 14 that is the same as the piezoelectric body 4 except for the end portion, and is therefore substantially the same as in the above embodiment. Provide operational effects.
In addition, since the projections 12a and 13a are provided on the inner side surface 2a and the side surface 3a, the joining portion with the piezoelectric body 14 is stepped. As a result, the bonding area increases, and the bonding strength at the end of the beam portion can be improved.

Next, a piezoelectric acceleration sensor according to a second modification of the present embodiment will be described.
FIG. 7A is a schematic plan view showing a schematic configuration of a piezoelectric acceleration sensor according to a second modification of the embodiment of the present invention. FIGS. 7B and 7C are a gg sectional view and an HH sectional view of FIG. 7A, respectively.

  The piezoelectric acceleration sensor 20 of this modification includes a support base 22 instead of the support base 2 and the weight 3 of the above embodiment. Hereinafter, a description will be given focusing on differences from the above embodiment.

As shown in FIGS. 7A, 7B, and 7C, the support base 22 includes a support base body 22c (support base portion) and a weight portion 22b corresponding to the support base 2 and the weight 3 of the above embodiment. In addition, on one surface side in the thickness direction where each piezoelectric body 4 is provided, they are connected to each other by a support base beam portion 22a having a cross shape in plan view that matches the arrangement of each piezoelectric body 4.
In the thickness direction of the support base 22, the height of the cross section perpendicular to the axis of the support base beam portion 22 a is equal to or less than the height of the cross section perpendicular to the axis of the piezoelectric body 4.
Each piezoelectric body 4 has one electrode 5 bonded to the support base beam portion 22a via an insulating layer (not shown), and both end portions are connected to the inner side surface 22d of the support base body 22c and the weight portion. It is joined between the side surface 22e of 22b.
For this reason, the axially perpendicular section of the beam portion formed between the inner side surface 22d and the side surface 22e is composed of the piezoelectric body 4 and the support base beam portion 22a, and the piezoelectric body 4 occupies 1/2 or more. In order to improve the sensitivity of the piezoelectric acceleration sensor 20, the ratio of the piezoelectric body 4 to the beam cross section is preferably as large as possible.

The piezoelectric acceleration sensor 20 having such a configuration can be manufactured by partially changing the manufacturing process of the piezoelectric acceleration sensor 1 of the above embodiment.
First, the support table 22 is formed by pressing, or by combining pressing with appropriate removal processing.
The support base 22 has substantially the same shape as the state in which the piezoelectric body forming plate 6 is joined to the support base 2 in the above embodiment, and the piezoelectric body 4 is formed without using the piezoelectric body forming plate 6. can do.
However, before the fine particles made of the piezoelectric material of the piezoelectric body 4 are impact-attached, the support beam portion 22a is subjected to insulation treatment, the electrode 5 is formed thereon, and the piezoelectric body 4 is formed. In addition, it is preferable to form a wiring when the electrode 5 is formed.
After the piezoelectric body 4 is formed, an electrode 5 and a wiring from the electrode 5 are further formed.
In this way, the piezoelectric acceleration sensor 20 is manufactured.

Here, as an example, the case where the support base 22 is formed from one metal plate has been described. However, the support base 22 forms the support base 2 and the weight 3 in the same manner as in the above embodiment. Alternatively, a thin plate member having a planar shape similar to that of the piezoelectric body forming plate 6 may be joined. For example, when the thin plate member is a metal, it can be integrated by thermocompression bonding with the support 2 and the weight 3.
Further, an insulator may be employed as the thin plate member, and may be joined and integrated with the support base 2 and the weight 3 by, for example, adhesion. In this case, since the support base body 22c is made of an insulator, when the electrode 5 is formed, the insulating treatment process of the support base beam portion 22a can be omitted.

According to the piezoelectric acceleration sensor 20 of the present modification, all the beam portions that support the weight 13 are composed of the piezoelectric body 4 and the support base beam portion 22a. The piezoelectric body 4 occupies a relative large area of 1/2 or more in the cross section perpendicular to the axis of the beam portion.
For this reason, not only the surface of the beam portion but also deformation in the cross section perpendicular to the axis of the beam portion can be detected by the piezoelectric body 4. And the acceleration according to the distortion of a beam part is detectable by taking out from the electrode 5 the polarization voltage which generate | occur | produces according to the distortion of the piezoelectric material 4. FIG.
Further, when the support base 22 is integrally formed, the number of parts can be reduced.
Further, when the piezoelectric body 4 is formed, the piezoelectric forming plate 6 is not used, and therefore, a process of peeling after the formation of the piezoelectric body 4 is not required, and thus the manufacturing process can be simplified. .

In the above description, the beam portion is described as an example in which the beam portion is composed of four lines arranged in two straight lines orthogonal to each other. However, the number and arrangement of the beam portions of the piezoelectric acceleration sensor of the present invention are not limited thereto. It is not limited.
For example, even in a configuration in which the weight portion is supported by three beam portions arranged in three directions intersecting each other at 120 °, the acceleration in the triaxial direction can be detected. Moreover, you may arrange | position four or more.
Moreover, it is good also as a structure which cantilever-supports a weight part with the two beam parts mutually orthogonally arranged.

  In the above description, the piezoelectric acceleration sensor has been described as an example of a configuration that can detect the acceleration in the three-axis direction. Good. For example, in a configuration in which one beam portion is used and the weight portion is cantilevered on a support base, acceleration in one axial direction can be detected.

  In the above description, the planar view shape of the support base of the piezoelectric acceleration sensor is a square, and the shape of each beam portion is the same. However, for example, the planar view shape of the support base is For example, an appropriate shape such as a rectangular shape or a circular shape can be adopted. And even if the length of a beam part becomes non-uniform | heterogenous according to such a shape, the detection sensitivity of each beam part can be equalized by changing the cross-sectional area of a beam part.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view showing a schematic configuration of a piezoelectric acceleration sensor according to an embodiment of the present invention, an AA sectional view, and a BB sectional view. It is process explanatory drawing of planar view explaining the manufacturing process of the piezoelectric acceleration sensor which concerns on embodiment of this invention, and its CC sectional drawing. It is process explanatory drawing of the planar view explaining the manufacturing process following the process shown in FIG. 2, and its DD sectional drawing. FIG. 4 is a cross-sectional view for sequentially explaining manufacturing steps subsequent to the steps shown in FIG. 3. It is typical operation explanatory drawing for demonstrating operation | movement of the piezoelectric acceleration sensor of this embodiment. It is the typical top view which shows schematic structure of the piezoelectric acceleration sensor which concerns on the 1st modification of embodiment of this invention, its EE sectional drawing, and FF sectional drawing. It is the typical top view which shows schematic structure of the piezoelectric acceleration sensor which concerns on the 2nd modification of embodiment of this invention, its gg sectional drawing, and HH sectional drawing.

Explanation of symbols

1, 10, 20 Piezoelectric acceleration sensor 2, 12 Support base (support base part)
2a, 22d Inner side surface (side surface of support base)
3 weight (weight)
3a, 22e Side surface (side surface of weight part)
4, 4A, 4B, 4C, 4D, 14, 14A, 14B, 14C, 14D Piezoelectric (beam)
5 Electrode (electrode part)
6 Piezoelectric forming plates 12a, 13a Protruding portion 22a Support base beam portion 22b Weight portion 22c Support base body (support base portion)
100 Acceleration detection circuit

Claims (4)

A beam portion having a cross section perpendicular to the axis formed of a piezoelectric body, a weight portion supported by one end side of the beam portion, a support base portion supporting the other end side of the beam portion, and the beam A method of manufacturing a piezoelectric acceleration sensor having an electrode portion for taking out a polarization voltage generated in a piezoelectric body of the portion,
The weight part and the support base part are arranged in alignment with each other, and the beam part is formed between the weight part and the support base part as viewed from the thickness direction of the beam part. An arrangement step of arranging a film forming body formed on the outer shape;
The piezoelectric body in a state of being bonded to the side surface of the weight portion and the side surface of the support base portion on the coating film forming body by depositing the fine particles of the piezoelectric material on the coating film forming body. Forming a piezoelectric body, and
Equipped with a,
The weight part and the support base part are each composed of separate members,
In the arrangement step,
The weight part and the support base part are arranged on the film forming body,
A film forming body removing step of removing the film forming body after the piezoelectric body forming step and leaving only the piezoelectric body at an intermediate portion in a length direction of the beam portion is further provided. A method for manufacturing a piezoelectric acceleration sensor. The weight part and the support base part have a shape in which a protruding part protrudes from the side surface of at least one of the weight part and the support base part on the film forming body,
In the piezoelectric body forming step,
By forming the piezoelectric body to a thickness that covers the protruding portion, the end portion of the beam portion is joined to the protruding portion on at least one side surface of the weight portion and the support base portion. A method for manufacturing the piezoelectric acceleration sensor according to claim 1 . A beam portion having a cross section perpendicular to the axis formed of a piezoelectric body, a weight portion supported by one end side of the beam portion, a support base portion supporting the other end side of the beam portion, and the beam A method of manufacturing a piezoelectric acceleration sensor having an electrode portion for taking out a polarization voltage generated in a piezoelectric body of the portion,
The weight part and the support base part are arranged in alignment with each other, and the beam part is formed between the weight part and the support base part as viewed from the thickness direction of the beam part. An arrangement step of arranging a film forming body formed on the outer shape;
The piezoelectric body in a state of being bonded to the side surface of the weight portion and the side surface of the support base portion on the coating film forming body by depositing the fine particles of the piezoelectric material on the coating film forming body. Forming a piezoelectric body, and
With
The weight part and the support base part have a shape in which a protruding part protrudes from the side surface of at least one of the weight part and the support base part on the film forming body,
In the piezoelectric body forming step,
By forming the piezoelectric body to a thickness that covers the protruding portion, the end portion of the beam portion is bonded to the protruding portion on at least one side surface of the weight portion and the support base portion. pressure electrodynamic acceleration method for manufacturing a sensor that. In the arrangement step,
The center of gravity is supported by the plurality of beam portions so that the center of gravity can move in three axial directions, and the film forming bodies are arranged at the positions of the plurality of beam portions, respectively. 4. A method for manufacturing a piezoelectric acceleration sensor according to any one of 3 above.

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