JPH03242556A - Piezoelectric acceleration sensor - Google Patents

Abstract

PURPOSE:To prevent noise from occurring due to a pyroelectric effect, etc. by providing a compensating piezoelectric body made of the same material and having the same thickness and the same electrode area as a film piezoelectric body for detecting acceleration in the vicinity of a detector. CONSTITUTION:A film piezoelectric body 13 and a load 14 are laminated on a seat 11 to constitute a sensor A. The load 14 functions as an intertial mass part and, with acceleration applied, generates strain on the film piezoelectric body 13. A compensating piezoelectric body 15 made of a film piezoelectric body having the same thickness and approximately the same electrode area as the film piezoelectric body 13 is adhered to a side of the film piezoelectric body 13 of the sensor A on the upper face of the seat 11, while electrodes of both piezoelectric bodies 13, 15 are wired to eliminate difference in potentials and electric charge generated between the upper and lower electrodes of both piezoelectric bodies. Thus an influence of a pyroelectric effect and common mode noise can be reduced.

Description

Detailed Description of the Invention "Industrial Applications" This invention relates to a piezoelectric acceleration sensor using a film-like piezoelectric material, and in particular to an output due to the pyroelectric effect in both the output as a voltage and the output as an electric charge. Concerning reduced fluctuations.

``Prior Art'' Piezoelectric acceleration sensors can be broadly classified by material: those that use an inorganic or ceramic piezoelectric material in the acceleration sensing portion, and those that use a polymer-based piezoelectric material.

Inorganic/ceramic sensors have advantages such as high accuracy and a wide usable temperature range, but they also have problems such as being easily destroyed by impact and difficult to miniaturize. Taking an acceleration sensor using a titanate zirconate ceramic piezoelectric material as an example, it is difficult to miniaturize the sensing part because it is molded by sintering, and the physical properties of the sensing part are brittle. It is thought that impact resistance is impaired.

On the other hand, according to published patent publications and sensors generally available on the market, polymer-based sensors are not only made of piezoelectric polymers, but also contain inorganic/ceramic piezoelectric powders dispersed in polymers. Although it uses a physical notebook, its impact resistance has been improved, but it is not necessarily small, and has problems such as a narrow frequency band, poor crosstalk, and low net output sensitivity. There is.

Incidentally, as an example of the above-mentioned acceleration sensor, the
A method disclosed in Japanese Patent No. 10258 is known.

As shown in FIG. 18, this acceleration sensor has a piezoelectric polymer vibrating membrane 1 fixed at its periphery to an annular frame 2, and a load body 3 that functions as an inertial mass on both sides of the central part of the vibrating membrane 1. The frame body 2 is fixed to a pedestal 4.

However, the acceleration sensor with this structure also has a vibrating membrane structure in which the periphery of the polymer vibrating membrane l is fixed, and due to the low elastic modulus of the polymer, it is difficult to detect acceleration in the direction perpendicular to the sensing axis G. Because of this, there is a drawback that it causes problems such as the Talostalk problem mentioned above.

As described above, the performance of the piezoelectric acceleration sensor is considered to be deeply related to the material Ij of the piezoelectric body and the structure of the sensor.

Therefore, in order to eliminate the drawbacks of the conventional sensor described above, the present inventors developed a pedestal that is rigidly attached to the object to be measured, and a membrane that is fixed at a point θ1j perpendicular to the sensing axis of this pedestal. He devised a sensor characterized by comprising a membrane-shaped piezoelectric body and a rigid load body fixed on the membrane-shaped piezoelectric body and acting as an inertial mass part.
A patent application has been filed as No. 55.

Such a sensor has the advantages of an extremely simple structure, extremely low noise output when acceleration is applied in a direction perpendicular to the sensing axis, and a wide measurable frequency range. There is.

"Problems to be Solved by the Invention" However, it was necessary to solve the following disadvantages with this new type of sensor.

In a sensor with the above structure, when a temperature change causes a partial temperature change in the piezoelectric film, the pyroelectric effect caused by this temperature distribution produces an excess electrical output, which becomes a noise output, and is It was difficult to use it in places with severe temperature changes.

Also, since the noise output due to the pyroelectric effect is on the low frequency side as a frequency component, can it be cut by using a bypass filter?
There was a disadvantage that acceleration on the low frequency side could not be measured either.

Therefore, the present inventors have proposed Japanese Patent Application No. 1-190824 and 43 as a measure to reduce noise output due to this pyroelectric effect.
A patent application has been filed in Japanese Patent Application No. 1-229807.

In these patent applications, when a bimorph element made by laminating film-like piezoelectric materials whose polarization directions are opposite to each other is incorporated into a piezoelectric material block, and when a temperature change occurs in the thickness direction of the film-like piezoelectric material, the polarization The problem of noise output due to the pyroelectric effect was solved by canceling out the extra electromotive force between the film-like piezoelectric bodies in different directions.

However, the acceleration sensor with the above structure is effective when the temperature distribution inside the piezoelectric body changes, for example, when a temperature change occurs due to heat conduction from either side of the sensing part, but when there is a sudden temperature change, such as directly under an incandescent electrolyte, In locations where temperature changes occur, there is a problem in that the output level fluctuates greatly depending on the temperature fluctuations.

Therefore, at present, it is necessary to design and manufacture a package of an acceleration sensor so that the package or the like is strongly thermally insulated so that a temperature change in the detection part occurs only by heat transfer from one direction.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a piezoelectric acceleration sensor that can reduce noise output due to the pyroelectric effect and can be used in environments with severe temperature changes. do.

"Means for Solving the Problems" In order to solve the above problems, the invention according to claim I includes a pedestal that is rigidly attached to an object to be measured, and a membrane-like structure that is fixed to the measurement surface of the pedestal and is provided with electrodes. a sensing section having a piezoelectric body and a rigid load body fixed on the membrane piezoelectric body and acting as an inertial mass section; A compensating piezoelectric body made of a film-like piezoelectric body made of the same material as the film-like piezoelectric body and having almost the same thickness as the film-like piezoelectric body is provided, and the areas of the electrodes provided on the bottom surface of the film-like piezoelectric body and the top and bottom surfaces of the compensation piezoelectric body are approximately the same. The electrodes are connected so as to cancel out the potential difference and charge generated between the upper and lower electrodes of the film-like piezoelectric body and the potential difference and charge generated between the upper and lower electrodes of the compensation piezoelectric body.

The present invention will be described in detail below.

1 and 2 show an example of the sensor of the present invention, in which a membrane piezoelectric material 13 and a load body I4 are layered on a pedestal 11 to form a sensing portion Ah.

The pedestal II forms the base of the sensor, is rigidly attached to the object to be measured, and has sufficient rigidity (made of 5 materials, for example, steel, copper-resistant, aluminum, etc. The elastic modulus of the material forming 11 is higher than that of the film-like piezoelectric material described later, and the thickness of the pedestal II (preferably several times that of the film-like piezoelectric material) is formed.The pedestal 11 in this example is formed in the shape of a rectangular parallelepiped. However, the shape of the pedestal 11 is not limited to this, and may be a plate shape, a columnar shape, or the like.

One surface (upper surface) of this pedestal 11 is a flat and smooth measurement surface. This measurement plane needs to be a vertical plane that is exactly perpendicular to the acceleration sensing axis G of this sensor.

This pedestal! On the measurement surface of I, a piezoelectric film I3 is firmly fixed to the base 11 via an adhesive layer.

The film-like piezoelectric material I3 in this example is a film-like material with a thickness of 10 to 100 μm made of a piezoelectric material, and whose thickness is sufficiently uniform and whose whole is sufficiently homogeneous. It will be done.

Examples of piezoelectric materials include polyvinylidene fluoride,
Polyvinylidene chloride, polyvinyl fluoride, polyhinyl chloride, nylons such as nylon 11 and polymetaphenylene isophthalamide, tetrafluoroethylene, trifluoroethylene, copolymers of vinyl fluoride and hnylidene fluoride, vinyl acetate In addition to polymer systems such as copolymers of vinyl propionate, vinyl benzoate, etc. and hnylidene noanide, blend polymers of polyvinylidene fluoride and polycarbonate, and pret polymers of polyvinylidene fluoride and polyvinyl fluoride, metal titanates It is made by adding and dispersing powders of high-pressure materials such as salts, metal salts of zirconate titanates, etc. to polymers.

The upper surface (front surface) and lower surface (back surface) of this film-like IE heavy body 13 are made of aluminum foil or the like for taking out the output.
Extreme adventure or setting;■S has been set. And this membranous +:, tt
Is the fixation between c+3 and pedestal 11 an Evokin type connection? Til
This is done using a hardening adhesive with l ji.

A load body 14 made of a rigid body and functioning as an inertial mass portion is integrally fixed to the film-like piezoelectric body 13 via an adhesive layer. This load body I4 is displaced in response to acceleration and causes distortion or stress in the membrane YJ (electric body 13), and its weight is related to the electrical output per unit acceleration of the sensor, so it is not particularly limited. There isn't, but
The range is such that creep does not occur in the piezoelectric film 13. The fixation of the film-like piezoelectric body I3 to the load body I4 is similar to the fixation of the pedestal 11 and the film-like piezoelectric substance 13.

On the other hand, on the upper surface of the pedestal 11, the film-like piezoelectric material 1 of the detection part A
A compensating piezoelectric material 15 made of the same material, the same thickness, and approximately the same area as the film-like piezoelectric material I3 is adhered to the side of the film-like piezoelectric material I3. The area of each electrode attached to the upper and lower surfaces of the compensating piezoelectric body 15 is approximately equal to the area of each electrode attached to the upper and lower surfaces of the compensating piezoelectric body 15.

Note that the term "the areas of the electrodes are substantially the same" means that the difference between the area of each electrode of the film-like piezoelectric material 13 and the area of each electrode of the compensation piezoelectric material I5 is within ±5%.

Here, if the area difference is ±5% or more, the charge output will be compensated when the connection is made as shown in Figure 2, and both the charge output and voltage output will be compensated when the connection is made as shown in Figure 17. This is undesirable because it can become overwhelming. Furthermore, it is preferable that the compensation piezoelectric body 15 be fixed at a position as close as possible to the detection part A, preferably within 5 m.
It is preferably within m.

FIG. 2 shows an example of a wiring structure for obtaining electrical output from the membrane piezoelectric body 13 and the compensating piezoelectric body I5. When the same temperature change and the same strain are applied, each piezoelectric body 1
Since the same charges and voltages are generated on the electrodes of 3.15, the reason is that these voltages and charges can be canceled out.

That is, in this example, since the polarization direction of the film-like piezoelectric material I3 and the polarization direction of the compensation piezoelectric material 15 are both directed upward as shown in FIG. The electrode and the electrode on the bottom side of the pressure body I5 for ura-compensation are connected with the first wiring 16, and the lead wire 17 is connected to the electrode on the top side of the membrane piezoelectric body 13.
is connected, and a lead wire 18 is connected to the electrode on the upper surface side of the compensating piezoelectric body I5, so that the output of the sensor can be taken out from the lead wire 17.18.

On the other hand, the planar shape of the piezoelectric film 13 is important for reducing crosstalk.

Crosstalk in this invention refers to the sensing axis G of the sensor.
Ratio P2/P of the output P1 when receiving acceleration in the direction and the output P when receiving acceleration in the direction perpendicular to the sensing axis G
, is expressed as .

First, the planar shape of the piezoelectric film 13 and the electrode shape must be point symmetrical with respect to the sensing axis G as the center of symmetry in a plane parallel to the measurement surface of the pedestal 11. The example shown in FIG. 1 has a rectangular shape, but there are other planar shapes that do not satisfy the above conditions, such as those shown in FIGS. 3 to 8, for example. Figure 3 is a parallelogram, Figure 4 is a circle,
5 shows an ellipse, FIG. 6 shows a regular hexagon, FIG. 7 shows a hexagon, and FIG. 8 shows a torus. In these figures, the reference numeral G indicates the sensing axis G. All of these planar shapes are point symmetrical with respect to the sensing axis G as the center of symmetry. Of course, planar shapes other than these can also be used if the above conditions are met.

Furthermore, the three-dimensional shape of the load body 14 is important for reducing crosstalk.

First, the surface of the load body 14 that is in contact with the membrane piezoelectric material 13 (hereinafter referred to as
It's called the bottom. ) is exactly perpendicular to the sensing axis G,
In addition, the planar shape of the bottom surface needs to be symmetrical about the sensing axis G as the center of symmetry. Therefore, as the shape that satisfies this condition, the shapes shown in FIGS. 3 to 8, for example, can be adopted, similar to the planar shape of the film-like piezoelectric body I3. However, in the combination of the membrane piezoelectric body 13 and the load body 14, the planar shape of the bottom surface of the load body 14 and the plane shape of the membrane piezoelectric body 13 do not necessarily have to be the same. It is sufficient that the planar shape of the load body 13 is square and the planar shape of the bottom surface of the load body 14 is circular.As will be described later, the sensing axis G may be the same.

At the same time, when the load body 14 is cross-sectioned through countless planes passing through the sensing axis G and perpendicular to the bottom surface, it is necessary that all the cross sections have line symmetry with the sensing axis G as the axis of symmetry. Figures 9 to 15 satisfy this line symmetry condition.
There is one shown in the figure.

The one shown in Figure 9 is plate-shaped, the one in Figure 10 is a note, the one in Figure 1+ is cone-shaped, the one in Figure 12 is a sphere cut out on a plane, and the one in Figure 13 is an ellipse. The one whose body is cut out on a plane, the one shown in Fig. 14 is columnar, the one with a space formed inside, and the one shown in Fig. 15 is a combination of a column and a plate. In the given figure, the symbol S indicates the bottom surface and G is the axis of symmetry that coincides with the sensing axis. The center of gravity of the load body 14 that satisfies this line symmetry condition is located on the sensing axis G.

Moreover, the load body 14 can be made of a composite material made of different materials in addition to being made of the same material as a whole, but in this case, each material is firmly attached and the whole is rigid. It is necessary for each part to have a vertical axis, and each part must not undergo different displacements when subjected to acceleration.

Under these conditions, the load body 14 having symmetry has its axis of symmetry aligned with the center of symmetry of the membrane piezoelectric body I3, in other words, the symmetry center of the membrane piezoelectric body 13 and the load are aligned on the sensing axis G. arranged so that the axis of symmetry of the body 14 coincides with the axis of symmetry of the body 14,
It is fixed.

Next, the operation of the acceleration sensor having the above configuration will be explained.

The sensor with the above configuration is used by attaching the pedestal II to the object to be measured, and when acceleration is applied in the direction of the sensing axis G, the load body 14 applies a load to the piezoelectric film 13 according to the acceleration, and this load is The membrane piezoelectric material 13 is
A difference in potential and charge is generated between the electrode on the front side and the electrode on the back side. Here, since the film-like piezoelectric material I3 is located at the acceleration detection section and the load body 14 is located at the second place, a potential difference and a load difference corresponding to the acceleration can be obtained, but the compensating piezoelectric material I5
Since there is no load on it, even if acceleration is applied, there will be no difference between the potential difference and the 71X load. Therefore, wiring 17.
18, the magnitude of acceleration can be measured by measuring the difference in potential and charge.

However, in the installation environment of the acceleration sensor, if a sudden temperature change is applied even without applying acceleration, a difference in potential and charge will occur between the electrodes of the membrane piezoelectric material 13 and the electrodes of the compensation piezoelectric material I5 due to the pyroelectric effect. occurs.

At this time, the difference in potential and charge between the film piezoelectric material 13 and the compensating piezoelectric material 15 is due to the same temperature fluctuation and charge difference, since the piezoelectric materials 13.15 are made of the same material and the electrode areas are approximately the same. The same charge difference and potential difference are generated for the same strain, and as these cancel each other out, both the difference in potential output and the difference in charge output become zero.

However, the above explanation is applicable when the piezoelectric body 13.15 is subjected to the same temperature change, so the piezoelectric body 13.15 is placed in the same space (in the same package).
Moreover, it is desirable to install them at a close distance (preferably within 5 mm). Therefore, for example, it is possible to divide an electrode of the same piezoelectric body into two parts, place a load body on one side, and not place a load body on the other side, thereby forming a compensating piezoelectric body.

In addition, since the operational outputs of both positive electric bodies 13 and 15 are used as sensor outputs, even if common mode noise output occurs due to causes such as deformation of the pedestal 11, the noise output can be reduced by canceling out those noise outputs. The value can be reduced.

On the other hand, in the sensor with the above configuration, the pedestal 11, the membrane piezoelectric body 13, and the load body 14 are simply laminated,
Since the electrode layer formed on the piezoelectric body 13 can also be formed using a general film forming process, the structure is simple and manufacturing is easy, and miniaturization is possible.

Further, the planar shape of the membrane piezoelectric material 13 is point symmetrical with respect to the sensing axis G, and the planar shape of the bottom surface of the load body I4 is point symmetrical with the sensing axis G as the center of symmetry. Since the three-dimensional shape of 14 does not extend to the hair surface passing through the sensing axis G and is line symmetrical with the sensing axis G as the axis of symmetry, crosstalk is slight.

In general, if a sensor JJ- has a direction other than its sensing axis, then according to the law of vector decomposition, □
, 5' (, 11 The component in the two directions perpendicular to the axis t5<tray and the component in the direction of the falling direction are 5) 2'. Directly to this sensing axis, the ) component acts on the center of gravity of the load body 1.1, and the bending moment about the center of gravity is
I'm going to work hard. For two reasons, the membrane piezoelectric material l3p)-,
The contractile force ljl acts on −rl<, and the tensile force acts on the rest. The compressive force and the tensile horn generate charges of opposite signs in the piezoelectric film 13, and the piezoelectric film 3,'
) So 4 or S will occur? Although there is a difference in position a, if the loads of opposite signs are equal, the total value of the potentials generated from each electrode will not vary.

Therefore, if compressive force and tensile force of equal magnitude act on the membrane piezoelectric body I3, the output fluctuation from the membrane piezoelectric body 13 becomes zero, and acceleration in directions other than the sensing axis direction is no longer detected. .

In this invention, since the shapes of the piezoelectric film 13 and the load body 14 have the above-mentioned symmetry, the piezoelectric film 13 is not affected even if acceleration is applied in a direction other than the direction of the sensing axis G. Since compressive force and tensile force of equal magnitude act on each other, there is no output fluctuation from the membrane piezoelectric material 13,
Cross daughters become extremely small. In order to reduce crosstalk in this manner, it is preferable to arrange the divided electrodes symmetrically with respect to the sensing axis G as the center of symmetry.

Furthermore, this sensor has a high measurable frequency limit and a wide measurable frequency band.

The upper limit of the measurable frequency of this type of sensor is determined by the sensor's resonant frequency.

The resonance frequency of the sensor in this invention is determined by the elastic modulus of what exists between the pedestal If and the load body 14, that is, the membrane piezoelectric material 13, the adhesive layer, and the electrode layer due to its structure. Since it is proportional to the value divided by , it should be noted.

For this reason, the membrane piezoelectric body 13, the pedestal 11 and the load body 14
In the case where an adhesive is used for fixing the adhesive layer, the elastic modulus of the adhesive layer is EA, the thickness is tA, and the elastic modulus of the piezoelectric film 13 is E.
l), when the thickness is tp, it is necessary to satisfy the relationship expressed by the following formula.

(E A / tA) / (E p / tp) ≧ 01 This formula means that the force generated on the load body 14 due to acceleration is transmitted to the membrane piezoelectric material I3 without being absorbed and relaxed by the adhesive layer. This is the condition for the value of the above formula to be 0
．． When it is less than 1, the absorption by the adhesive layer cannot be ignored, and the centripetal frequency decreases as described above, narrowing the measurable frequency band.

Note that the thickness of the adhesive layer in the above formula refers to the total thickness of all adhesive layers existing between the pedestal II and the load body 14. In addition, if the type of adhesive is different and the modulus of elasticity is different, calculate the ratio of the modulus of elasticity to the thickness of each adhesive layer,
All you have to do is add this up and substitute it into the above formula.

Therefore, the adhesive should be a hardening type such as epoxo-based, phenol-based, or anoacrylate-based and has a high elastic modulus, and rubber-based adhesives are inappropriate for live pipes. Moreover, a conductive adhesive can also be used.

In the above embodiment, a single layer piezoelectric film I3 was used, but the piezoelectric film I3 may also have a multilayer structure. Further, as shown in FIG. 16, film-like piezoelectric bodies 30.31 having different polarities are stacked with intermediate electrodes 32 interposed therebetween, and end electrodes 33 are formed on both upper and lower surfaces of the stacked film-like piezoelectric bodies 30.31. A bimorph element 35 made of one piece may be formed, and this bimorph element 35 may be used instead of the membrane piezoelectric material 13.

On the other hand, FIG. 17 shows another example of the wiring structure of the sensor of the present invention. In this example, the polarization direction of the membrane piezoelectric material 13 and the polarization direction of the compensating piezoelectric material I5 are opposite to each other. This is an example of wiring when In this example, the electrode on the bottom side of the membrane piezoelectric body 13 and the electrode on the bottom side of the compensation piezoelectric body 15 are connected by a lead wire 20, and the electrode on the top side of the membrane piezoelectric body 13 and the compensation piezoelectric body 15 are connected. The electrode on the upper surface side is connected to the lead wire 21.

In the structure of this example as well, as in the case explained in the previous example, the electric current (vertical difference and charge) generated in the membrane piezoelectric material 13 due to the pyroelectric effect and the potential difference and charge generated in the compensation piezoelectric material 15 are As a result, no extra potential fluctuations and charge fluctuations occur due to the focus 7a effect.

"Example 1" An aluminum plate with a thickness of 5 mm is used as a pedestal, and on the top surface of this, two square-shaped PVDFIEE electric films with a thickness of 100 μm, a length of 10 mm, and a diameter of II Omm are placed 2 mm apart from each other.
I glued them together with epoxy adhesive while separating them. Cu/Ni electrodes are formed on both the upper and lower surfaces of these piezoelectric films. Further, a load body made of brass made of filOg was fixed to one of the two PvDF piezoelectric films with an epoxy adhesive to construct a sensor. Note that the wiring structure shown in FIG. 2 was adopted for the structure of this sensor.

"Example 2" A sensor was constructed using the same piezoelectric film as in Example 1, and the wiring structure shown in Table 1 was adopted, and the thickness and planar dimensions of the membrane piezoelectric material and the compensation piezoelectric material were were set as shown in Table 1.

"Comparative Examples 1, 2, 3, 4j Each sensor was constructed using the same piezoelectric film as in Example 1, and the wiring structure shown in Table 1 was adopted,
The thickness and planar dimensions of the film piezoelectric material and the compensation piezoelectric material are
The settings were as shown in the table.

"Comparative Example 5" One side with a thickness of 100 μm on an aluminum plate with a thickness of 51
A 0 mm square PVDF film was fixed with an epoxy adhesive, and a 10 g load body 11 was bonded thereon to form a sensor with a structure in which output was taken out from both sides of the PVDF film.

The following measurement tests were conducted on the sensors on each side that adopted the structure described above.

(+) JtG main output output measurement test pressure output; IG via impedance conversion circuit
The basic output of each sensor was measured.

(Peak (Direct) ■Later 6: J Output The JI of the sensor per IG was measured via a charge amplifier (this output was measured).

(2) Output change test against temperature fluctuation 0) No impedance conversion circuit or sensor [1]
The sensor was installed in a pan cage made of No. 6, and when the temperature near the sensor was changed to 1°C by blowing hot air, it was measured to see which +-F fluctuations occurred in the output. (m V / °C) ■ Assemble the sensor in a nylon 6 pan cage, connect a piano amplifier, and blow hot air onto the package to see how much the output fluctuation occurs when the temperature near the sensor rises by l'C. It was measured.

(pC/'C) The above test results are shown in Table 1.

Table 1 From Table 1, it has been found that the acceleration sensor of the present invention can suppress output fluctuations in response to temperature changes.

In the comparison example, in the ζ sensor, one of the small pressure output and the small charge output should be able to cancel out the variation due to the difference in the thickness of the two piezoelectric bodies or the difference in the surface h1. Comparative example 2
(Although the output fluctuation is relatively small, it is better to use piezoelectric materials of the same thickness, even from the perspective of variations in the piezoelectric constant and insulation resistance of the piezoelectric materials.) it is obvious.

As explained above, the present invention provides, in addition to the film-like piezoelectric material for detecting acceleration, the film-like piezoelectric material made of the same material as the film-like piezoelectric material.
Now, a piezoelectric material with the same area as the ri bond is provided near the detection part, and the wires are wired so that the difference in potential and charge between the two is compensated for. Even if such a change occurs, the noise output due to the pyroelectric effect can be significantly reduced, and the accuracy of measurement of acceleration draft can be improved. Furthermore, according to the present invention, acceleration can be detected based on both the potential difference and the charge difference, which enables more accurate measurement, improves the reliability of measured values, and reduces restrictions on use. be.

In addition, since the sensor output is generated by canceling out the charges on the circular piezoelectric body due to causes other than acceleration, it is possible to reduce humon mode noise other than temperature fluctuations, such as noise output caused by deformation of the pedestal. It's effective.

Furthermore, since the sensor of the present invention has a pedestal, a piezoelectric film, and a load body stacked and fixed, the structure is simple and can be easily miniaturized. Furthermore, there are effects such as extremely little crosstalk, a wide measurable frequency band, easy design that matches the measurement purpose, and a high degree of freedom in design.

[Brief explanation of drawings]

Figures 1 and 2 show one embodiment of the present invention.
The figure is a perspective view, Figure 2 is a wiring diagram of the piezoelectric body, Figures 3 to 8 are diagrams each showing modifications of the planar shape of the membrane piezoelectric body, and Figures 9 to 15 are respectively diagrams of the load body. 16 is a sectional view showing a bimorph element, FIG. 17 is a wiring diagram of another example of the acceleration sensor of the present invention, and FIG. 18 is a sectional view showing a conventional acceleration sensor. be. A...Detection part, 11...Pedestal, I3...Membrane piezoelectric material,
14...Load body, I5...Mi compensation piezoelectric body, G...
Sensing axis, +7.18, 20.21...Leader line.

Claims (1)

[Claims] A load body consisting of a pedestal rigidly attached to an object to be measured, a membrane piezoelectric body fixed to a measurement surface of the pedestal and provided with an electrode, and a rigid body fixed on the membrane piezoelectric body and acting as an inertial mass part. a compensation piezoelectric body made of the same material as the film-like piezoelectric body and having substantially the same thickness as the film-like piezoelectric body, disposed on the side of the detection unit and close to the detection unit; The areas of the electrodes provided on both the upper and lower surfaces of the piezoelectric material and the upper and lower surfaces of the compensating piezoelectric material are formed to be almost the same, and the potential difference and charge generated between the upper and lower electrodes of the membrane piezoelectric material and the upper and lower electrodes of the compensating piezoelectric material are A piezoelectric acceleration sensor characterized in that each electrode is connected so as to cancel out the potential difference and charge generated between them.