JPH09178642A - Vibration controller sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent or decrease the unnecessary vibration of a sensor element excited by bending vibration without obstructing the bending vibration of a piezoelectric element and a vibrating part. SOLUTION: This sensor has a substrate 10 having a vibrating part 12, a piezoelectric element 20 having a piezoelectric film 22 and a pair of electrodes 24a and 24b and a vibration preventing layer 30, which covers at least a part of the substrate. The vibration preventing layer 30 can have plates 32 and 34 and a bonding layer 36 for fixing the plates and the substrate. A hole 38 can be formed in the vibration preventing layer 30 so as not to cover the piezoelectric element 20. In the battery having a pair of first electrodes 42a and 42b and a porous body 44, the above described sensor is provided in the interior of the porous body 44, and the porous body or the first electrodes act as a vibration preventing layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor element having a piezoelectric element, and an object thereof is to prevent vibration that causes noise.

[0002]

2. Description of the Related Art A sensor element having a vibrator such as a piezoelectric element is used for measuring the viscosity of a fluid. For example, Japanese Patent Laid-Open Nos. 1-311250 and 2-213.
In Japanese Patent No. 743 and Japanese Patent Laid-Open No. 3-189540, a piezoelectric element, particularly a crystal oscillator, is brought into contact with a fluid, and the viscosity is measured by a change in resonance frequency or loss resistance at that time.
Further, in JP-A-3-148040, the viscosity is measured by vibrating a bimorph oscillator in a fluid at a predetermined frequency and detecting the impedance at that time.

Further, in Japanese Patent Application No. 7-112128, a piezoelectric film made of ceramic and a vibrating part are vibrated, and the loss coefficient, electric resistance, reactance, etc. of the piezoelectric film are changed,
Measure the viscosity. Since the piezoelectric film or the vibrating part contacts the fluid, the amplitude of the piezoelectric film and the vibrating part becomes small when the viscosity of the fluid is large, and the amplitude of the piezoelectric film and the vibrating part becomes large when the viscosity of the fluid is small. Become. When a voltage is applied to the piezoelectric film, a current corresponding to the amplitude or the like is detected. On the other hand, when the viscosity of the fluid has a correlation with the density of the fluid or the concentration of the component in the fluid, the density and the concentration of the fluid can also be detected. For example, in an aqueous sulfuric acid solution, the viscosity and the density have a certain correlation, and the viscosity and the concentration of sulfuric acid also have a certain correlation.

[0004]

All of these methods are for vibrating a vibrator to detect some physical property correlated with the viscosity of a fluid. However, the vibration of the vibrator causes the vibration of the sensor element itself, resulting in noise, which may interfere with the detection of such physical properties. For example, when detecting an electric signal such as a current with a pair of electrodes, noise caused by vibration of the sensor element itself is superimposed on the electric signal to be detected, which makes it difficult to detect the electric signal to be originally detected. was there. Especially,
When the piezoelectric element is fixed to the vibrating portion of the ceramic substrate, the mass of the ceramic substrate itself may be about 10 to 100 times that of the vibrating portion and the piezoelectric element, and it seems that the vibration of the ceramic substrate itself cannot be ignored. . Therefore, the present inventor repeated trial and error to prevent unnecessary vibration of the sensor element excited by the vibration without disturbing the vibration of the piezoelectric element and the vibration part, and as a result, the sensor is provided by providing the vibration prevention layer. The present invention has been completed by finding that vibration of the element can be prevented or reduced.

[0005]

That is, according to the present invention,
A piezoelectric element having a base having a vibrating portion, a piezoelectric film fixed to one surface of the vibrating portion and having a piezoelectric film and a pair of electrodes sandwiching the piezoelectric film, and a vibration prevention layer covering at least a part of the base. There is provided a sensor element having: Here, it is preferable that the vibration of the vibrating portion is a bending motion in the vibrating portion thinly formed on the base body. According to the present invention, it is preferable that the vibration prevention layer has a film made of a synthetic resin. Further, the vibration prevention layer may include a plate made of metal, ceramics, or synthetic resin, and an adhesive layer for fixing the plate and the base. Further, it is preferable that holes are formed in the vibration prevention layer so as not to cover the piezoelectric element. Furthermore, it is preferable that the substrate has a protective cover that covers the piezoelectric element, and that the vibration prevention layer covers at least a part of the protective cover.

Further, it is preferable that a space in which fluid can be guided is formed in the base body on a side opposite to the piezoelectric element with respect to the vibrating portion. Furthermore, it is preferable that a hole communicating with the void of the base is formed in the vibration prevention layer. Further, it is preferable that an introduction hole communicating with the void is formed in the base body, and the base body has a protrusion portion outside the void and near the introduction hole. The piezoelectric element has a lead wire connected to the electrode of the piezoelectric element and fixed to the base body or the vibration prevention layer, and the vibration prevention layer has at least an end portion of the lead wire on the base body side, It is preferable to coat the end of the base on the lead wire side.

Further, according to the present invention, in a battery having a pair of first electrodes and a porous body sandwiched by the first electrodes, the sensor element is provided inside the porous body, and There is provided a battery, characterized in that the body or the first electrode acts as the anti-vibration layer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows a sensor element 1 of the present invention.
It is an explanatory sectional view of 0. Further, FIG. 2 is a developed view of a part of the sensor element 10 of FIG. The sensor element is the base body 10.
And a piezoelectric element 20 fixed to the vibrating portion 12 of the base body 10. The substrate 10 is preferably formed of ceramics, and preferably has a laminated structure in which two or more ceramic sheets are laminated and integrated. Substrate 10
Has a structure in which the sheets 10a, 10b, and 10c are integrally laminated. The shape of the substrate is not particularly limited and may be appropriately selected depending on the application. The substrate preferably has a plate shape, but may have a rod shape or a pipe shape.

A cavity 14 is formed in the base 10 so that the vibrating portion 12 is thin. The vibrating portion 12 has a pair of surfaces 12s and 12t, and one surface 12s has
The piezoelectric element 20 is fixed. The other surface 12t on the opposite side of the vibrating portion 12 provides a void 14 inside the base 10. The base body 10 communicates with the void 14 to allow the fluid to flow into the void 14.
Introducing holes 16a and 16b are formed for introduction into the.
The shape of the void 14 is not limited. However, the introduction hole is not an essential requirement as long as the fluid can be introduced into the void. For example, a concave portion is formed in the base body 10, and the vibrating portion 12
The other surface may have a concave shape. Further, when the introduction hole is provided, the introduction hole may be one or two or more as long as the fluid can be introduced into the void. When there are two or more introduction holes, the shape of each introduction hole may be the same or different.
Since the shape is suitable for vibration, the vibrating portion 12 is preferably in the shape of a plate. In this case, the thickness of the plate is 1 to 100 μm.
m is preferable, 3 to 50 μm is more preferable, and 5 to 20 μm is still more preferable. Thickness is 100μ
This is because when it is larger than m, the sensitivity is lowered, and when the thickness is smaller than 1 μm, the mechanical strength is lowered.

The piezoelectric element 20 has a piezoelectric film 22 and a pair of electrodes 24 a and 24 b sandwiching the piezoelectric film 22. When a voltage is applied to the piezoelectric film 22 through the pair of electrodes 24a and 24b, dielectric polarization occurs, and the piezoelectric element 20 flexurally vibrates together with the vibrating portion 12 in the thickness direction of the piezoelectric film 22 and the vibrating portion 12. The thickness of the piezoelectric film is preferably 1 to 100 μm, more preferably 5 to 50 μm, even more preferably 5 to 30 μm. This is because when the thickness is larger than 100 μm, the sensitivity is lowered, and when the thickness is smaller than 1 μm, it is difficult to secure the reliability.

The piezoelectric film may be dense or porous, and when it is porous, the porosity is preferably 40% or less. Further, the piezoelectric film 22 may have a single layer or a laminated structure of two or more layers. When the laminated structure has two or more layers, each layer may be provided laterally or may be provided upright. The electrode has an appropriate thickness depending on the application, but preferably has a thickness of 0.1 to 50 μm.

In FIG. 1, the anti-vibration layer 30 is the film 3
2, 34 and an adhesive layer 36. By fixing the vibration prevention layer 30 to the substrate 10, the mass of the entire sensor element is increased, and unnecessary vibration other than bending vibration of the vibrating portion 12 and the piezoelectric element 20 is prevented or reduced. It is considered that this unnecessary vibration is generated in the substrate 10 and the like and is excited by the bending vibration. Further, when the anti-vibration layer 30 has a soft synthetic resin, rubber, epoxy resin that acts as an adhesive, or the like, these absorb the vibration,
Damps vibration. In FIG. 1, the vibration prevention layer 30 is provided with a hole 37 communicating with the introduction holes 16a and 16b.
Further, a hole 38 is formed so as not to cover the piezoelectric element 20. This is because when the vibration prevention layer 30 covers the piezoelectric element 20, the bending vibration of the piezoelectric element 20 and the vibrating portion 12 may be hindered. However, in FIG. 1, the hole 38 allows the piezoelectric element 20 and the vibrating portion 12 to perform bending vibration. It should be noted that this bending vibration does not spread to the entire sensor element due to the vibration prevention layer 30 as described above. The films 32 and 34 may be made of a synthetic resin such as polyethylene, polypropylene, polyester, polyvinyl chloride, polyamide, or polypropylene.

The adhesive layer is not always an essential requirement.
For example, the antivibration layer may be fixed to the substrate 10 by a so-called resin mold in which a solution or a melt of a synthetic resin is applied to the element and then cured. Further, the base body and the vibration prevention layer may be fixed with a fastener such as a bolt or a screw. Furthermore, when a ceramic plate is used instead of the film and the base body is made of ceramic, the ceramic plate and the ceramic base body can be integrally formed. When the substrate 10 has a substantially plate shape extending in the plane direction, the area of the vibration-proof layer 30 is preferably 1 time or more, and more preferably 1.5 times or more the area of the substrate. It is more preferable that the amount is 2 times or more. This is because the larger the vibration prevention layer 30 is, the more the vibration of the substrate can be reduced.

FIG. 2 shows an exploded perspective view of the sensor element in a state where the vibration prevention layer is not covered. Four ceramic green sheets 22, 10a, 10b and 10
It can be integrated by laminating c and sintering. That is, the piezoelectric element 20 is also preferably formed integrally with the base body 10. In the sensor element of the present invention,
Electric power or the like is supplied to the piezoelectric element to vibrate the piezoelectric element and the vibrating portion, and vibrates the fluid that contacts the vibrating portion. Then, the piezoelectric film of the piezoelectric element converts this vibration into an electric signal, and outputs this electric signal via the electrodes sandwiching the piezoelectric film. For example,
A voltage is applied to the piezoelectric element 20, and the piezoelectric element 20 and the vibrating portion 12 are flexibly vibrated while being in contact with the fluid or in the fluid. Then, by detecting a current through the electrodes 24a and 24b of the piezoelectric element 20, values such as impedance, phase, resistance, reactance, admittance, conductance, susceptance, inductance, capacitance, loss coefficient of the piezoelectric element, and the like, Information about the value of the frequency (resonance frequency) corresponding to the value is obtained. Since such information has a correlation with characteristics such as viscosity of the fluid, the characteristics of the fluid can be detected.

As shown in FIGS. 3 and 4, instead of the films 32 and 34 of FIG. 1, a plate made of metal, ceramics or synthetic resin may be fixed to the substrate 10 and the piezoelectric element by an adhesive layer 36. . Even in this case, the plate increases the mass of the entire sensor element, which makes it difficult for the sensor element itself to vibrate. Further, vibration may be absorbed by the adhesive layer 36. The metal, ceramics, and synthetic resin are not particularly limited as long as they have sufficient strength to hold the sensor element. Examples of the metal include steel, carbon steel, alloy steel and the like. Examples of ceramics include stabilized or partially stabilized zirconia, silicon nitride, and aluminum oxide. 3 and 4, the element body shown in FIGS. 1 and 2 (having the base body 10 and the piezoelectric element 20) may be used, or the element body shown in FIGS. 5 and 6 may be used. .

In FIGS. 5 and 6, the base body 10 is the cover 1.
7 and a protrusion 18. However, in FIG. 6, the vibration prevention layer is omitted. In FIG. 5, the cover 17 has a lid member 17a and a frame 17b, and the piezoelectric element 20 covers the cover 17a.
Covered with. When the surface 17s of the cover 17 is covered with the vibration preventing layer, the vibration preventing layer can prevent or reduce the vibration of the substrate 10 itself without affecting the vibration itself of the piezoelectric element 20 and the vibrating portion 12. . Further, when measuring the viscosity of a strong acid such as sulfuric acid or a strong alkali such as an aqueous sodium hydroxide solution, the piezoelectric element can be further separated from these liquids by the cover 17. 5 and 6
In the above, the protrusion 18 is formed to form a space where the fluid can stay outside the introduction holes 16a and 16b. FIG.
Also, in FIG. 6, the protrusion 18 forms a recess 19 communicating with the introduction holes 16a and 16b. However, it is not necessary that the protruding portion 18 continuously surround the periphery of the base body 10, and only a part of the protruding portion 18 may protrude. In addition, the height of the protrusion need not be constant.

In FIGS. 5 and 6, the lead wires 26 a, 26
b is connected to the electrodes 24a and 24b of the piezoelectric element 20, respectively. The lead wires 26a and 26b are connected to leads covering the surface of the base 10 via a connection, and the leads are connected to the electrodes 24a and 24b. Lead wire 26
a and 26b are fixed to the base body 10 by connection. The vibration prevention layers 32, 34 and 36 are connected to the lead wires 26a and 26.
The end of the base 10 on the side of the base 10 and the end 10d of the base 10 on the side of the lead wires 26a and 26b are covered. In FIG. 5, the anti-vibration layers 32, 34, 36 not only prevent unnecessary vibration of the base body 10 and the like, but also lead wires 26a, 26b.
To protect the lead wires 26a, 26b from breaking easily from the connection or the like.

FIG. 7 shows an exploded perspective view of the sensor element of FIG. However, the adhesive layer is omitted. Further, the lead wires 26a and 26b are fixed on the other side of the base 10 as compared with FIG. Further, the base body 10 of FIG. 7 corresponds to the base body 10 on which the protrusions 18 are already formed. here,
A ceramic sheet having the same shape as the frame 17b may be used to form the protrusions on the base 10. The frame is
There is no limitation as long as it has a shape capable of supporting the lid member 17a.
In FIG. 7, the frame 17b has four sides so as to surround the piezoelectric element 20. However, the frame may have a shape in which any one of these sides is missing. This is because, even with such a shape, the frame can support the lid member 17a and can prevent the vibration prevention layer from coming into contact with the piezoelectric element 20.

The frame is preferably an electrically insulating material. This is to prevent a short circuit with the lead covering the surface of the base 10. As the frame, for example, a punched body in a plate state such as ceramics or organic resin is used. In the case of an organic resin, it may be a film. Further, the frame may be composed of an adhesive, a paste, or the like applied to the surface of the base body 10. When the cover 17 and the protrusion 18 are made of ceramics, they may be sintered and integrated with the base 10. Alternatively, the cover 17 and the protrusion 18 are
Regardless of these materials, the cover 17 and the protrusions may be fixed to the base 10 by an adhesive layer made of synthetic resin such as epoxy resin or glass. However, the piezoelectric element 20
When the surface of the frame is fixed to the surface 12s of the vibrating portion 12 by fixing, that is, when no adhesive or the like is interposed between the piezoelectric element 20 and the vibrating portion 12, the frame and the base 10 are made of epoxy resin or the like. It is preferable to use an adhesive layer made of synthetic resin, glass or the like for bonding. In the case of using the adhesive layer, it goes without saying that the adhesive layer needs to have resistance to the fluid because the adhesive layer comes into contact with the fluid detected by the sensor element. Further, since the base body, the cover and the like come into contact with the fluid to be measured, the materials of the base body, the cover and the like are required to have resistance to the fluid.

The electrodes 24 a and 24 b of the piezoelectric element 20 are
The leads are connected to the leads covering the surface of the substrate 10, and the leads and the lead wires 26a and 26b are connected by the connection on the surface of the substrate 10. That is, the electrodes 24a and 24b are connected to the lead wires 26a and 26b, respectively. The connection between the lead and the lead wire is made through a conductive member such as solder or a conductive paste, or by mechanical contact between the lead wire 26a, 26b and the lead. The lead wires 26a and 26b may be wires covered with an organic resin, or may be metal layers sandwiched by insulating films. Alternatively, the leads may be connected to each other by a connection via another electric conductive member.

In FIG. 8, the battery 40 includes a pair of electrodes 42.
a and 42b, and a porous body 44 sandwiched between them. Each of the electrodes 42a and 42b has a plate shape. The pores of the porous body 44 may be filled with an electrolytic solution such as sulfuric acid. A void 46 is formed in the porous body 44 to embed an element body 48 having a piezoelectric element and a base body. The element body 48 may be the one shown in FIG. 1 or the one shown in FIG.

In FIG. 8, the porous body 46 acts as a vibration preventing layer of the element body 48. Therefore, the element body does not require the vibration prevention layer 30 such as a plate member or a film. However, the element body may be covered with a vibration prevention layer. The void 46 of the porous body 44 may be formed so as to conform to the shape of the element body 48, and the element body 48 may be fixed by being fitted into the void 46. On the other hand, the element body 48 may be fixed to the space 46 of the porous body 44 with an adhesive such as an epoxy resin.

In FIGS. 9 and 10, the base body 10 has a protrusion 18 that forms a void 19. In FIG. 9, the side of the substrate 10 where the void 19 is present is in contact with the porous body 44, and the surface of the substrate 10 opposite to the void 19 is the electrode 4
Touch 2a. On the other hand, in FIG.
9 is in contact with the electrode 42a, and the surface of the substrate 10 opposite to the void 19 is in contact with the porous body 44. 9 and 10, the extending direction of the substantially plate-shaped substrate 10 is arranged substantially parallel to the extending directions of the electrodes 42a and 42b. However, the electrodes 42a, 42
It may be arranged so as to intersect the direction in which b extends.

In FIG. 11, the porous body 44 is provided with a cavity 4 so as to communicate with the introduction holes 16 a and 16 b of the element body 48.
7 are formed. Due to the space 47, the introduction hole 16a,
A fluid such as an electrolytic solution can easily flow into 16b. When the element main body 48 is incorporated into the porous body 44, an electrolyte solution or a liquid which can be mixed with the electrolyte solution and which may be mixed is sealed in advance inside the cavity 19 of the element body 48. Is preferred. As a result, the electrolytic solution in the pores of the porous body 44 can be easily replaced with the electrolytic solution or liquid in the void 19.

The materials and materials of each element will be described below. The vibrating portion 12 is preferably made of an electrically insulating material. This is because the electrode that covers at least a part of the vibrating portion 12 is conductive. The vibrating portion 12 may be a highly heat resistant metal, and the metal surface may be coated with a ceramic such as glass. However, the vibrating portion 12 is preferably made of ceramics. Examples of ceramics forming the vibrating portion include stabilized zirconium oxide, aluminum oxide, magnesium oxide, mullite,
Aluminum nitride, silicon nitride, glass or the like can be used. Stabilized zirconium oxide is preferable because of its high mechanical strength, high toughness, and low chemical reactivity with the piezoelectric film and electrodes even when the vibrating part is thin.

Stabilized zirconium oxide includes stabilized zirconia and partially stabilized zirconia.
Stabilized zirconium oxide does not cause a phase transition because it has a crystal structure such as cubic crystal. On the other hand, zirconium oxide undergoes a phase transition between a monoclinic system and a tetragonal system at around 1000 ° C., and cracks may occur during this phase transition. Stabilized zirconium oxide includes calcium oxide, magnesium oxide, yttrium oxide, scandium oxide,
1 to 30 mol% of a stabilizer such as ytterbium oxide, cerium oxide, or an oxide of a rare earth metal is contained. The stabilizer preferably contains yttrium oxide in order to increase the mechanical strength of the vibrating portion. At this time, yttrium oxide is preferably contained in an amount of 1.5 to 6 mol%, more preferably 2 to 4 mol%. Further, the main crystal phase is tetragonal, mixed phase of tetragonal and cubic, mixed phase of cubic and monoclinic, mixed phase of tetragonal and monoclinic, or cubic, tetragonal and monoclinic. May be a mixed phase. Among them,
From the viewpoint of mechanical strength, toughness and durability, it is preferable that the main crystal phase is tetragonal or a mixed phase of tetragonal and cubic.

The ceramics forming the vibrating section 12 are
It preferably contains 0.5 to 5% by weight of silicon oxide, and more preferably 1 to 3% by weight of silicon oxide. This is because when the piezoelectric element 20 is formed by heat treatment, silicon oxide can avoid an excessive reaction between the vibrating portion 12 and the piezoelectric element 20 and obtain good piezoelectric characteristics. When the vibrating portion 12 is made of ceramics, a large number of crystal grains form the vibrating portion, but the average grain size of the crystal grains is 0.05 to 2 in order to increase the mechanical strength of the vibrating portion.
The thickness is preferably μm, more preferably 0.1 to 1 μm.

For the piezoelectric film, piezoelectric ceramics can be preferably used, but electrostrictive ceramics or ferroelectric ceramics may be used. The material may or may not require a polarization treatment. Ceramics used for the piezoelectric film are, for example, lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead antimony stannate, lead titanate, lead manganese tungstate, cobalt niobate. Examples of the ceramic include lead, barium titanate, and the like, or a component containing a combination of any of these. It goes without saying that these compounds may be the main components that account for 50% by weight or more. Ceramics containing lead zirconate are preferably used. In addition to the above-mentioned ceramics, lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, oxides such as manganese, or any combination thereof, or any other compound, ceramics appropriately added. You may use. For example, it is preferable to use ceramics containing lead magnesium niobate, lead zirconate, and lead titanate as main components, and further containing lanthanum and strontium.

The electrode 24a is preferably solid at room temperature and made of a conductive metal. For example,
A single metal or an alloy containing aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, lead and the like can be mentioned. . It goes without saying that these elements may be contained in any combination. Further, an electrode material containing a platinum group metal such as platinum, rhodium or palladium, or an alloy containing these platinum group metals and having an alloy such as silver-platinum or platinum-palladium as a main component is preferably used. Also copper,
Silver and gold are more preferable because they are durable.

The electrode 24b is preferably made of a simple substance or an alloy containing a high melting point metal such as platinum, ruthenium, rhodium, palladium, iridium, titanium, chromium, molybdenum, tantalum, tungsten, nickel and cobalt. It goes without saying that these refractory metals may be contained in any combination. Further, an electrode material containing a platinum group metal such as platinum, rhodium or palladium, or an alloy containing these platinum group metals and having an alloy such as silver-platinum or platinum-palladium as a main component is preferably used. This is because the electrode 24b may be exposed to a high temperature during the heat treatment of the piezoelectric film, and is therefore preferably a metal that can withstand a high-temperature oxidizing atmosphere. Further, with these refractory metals, alumina, zirconium oxide, silicon oxide,
It may be a cermet containing a ceramic such as glass.

Next, a method of manufacturing the element body of the sensor element of the present invention will be described. The base body can be integrated by stacking a molding layer, which is a green sheet or a green tape, by thermocompression bonding and then sintering. For example, in the substrate 10 of FIG. 1, three layers of green sheets or green tapes are laminated, but a through hole having a predetermined shape may be provided in advance in the second layer before lamination so as to be a void. In addition, forming a molding layer by pressure molding using a molding die, casting molding, injection molding, etc., cutting, grinding processing, laser processing,
A void or the like may be provided by mechanical processing such as punching by pressing. The molding layers do not have to have the same thickness as each other, but it is preferable that the molding layers have the same degree of shrinkage due to sintering. Further, the green sheet or green tape before sintering may be formed into a shape corresponding to the void, or may be machined after sintering.

A method of forming the piezoelectric element 20 on the vibrating portion 12 will be described. A piezoelectric body is molded by a press molding method using a die or a tape molding method using a slurry raw material, and the piezoelectric body before sintering is laminated on the vibrating portion of the substrate before sintering by thermocompression bonding, There is a method of simultaneously sintering and forming a substrate and a piezoelectric body. In this case, the electrodes need to be formed on the substrate or the piezoelectric body in advance by a film forming method described later. The sintering temperature of the piezoelectric film is appropriately determined depending on the material constituting the piezoelectric film, but is generally 800 ° C to 14 ° C.
The temperature is 00 ° C, preferably 1000 ° C to 1400 ° C. In this case, in order to control the composition of the piezoelectric film, it is preferable to perform sintering in the presence of an evaporation source of the piezoelectric film material.

On the other hand, in the film forming method, the piezoelectric element 20 is formed by laminating the electrode 24 b, the piezoelectric film 22, and the electrode 24 a on the vibrating portion 12 in this order. Known film forming methods, for example, thick film method such as screen printing, coating method such as dipping, ion beam, sputtering, vacuum deposition,
A thin film method such as ion plating, chemical vapor deposition (CVD), and plating is appropriately used, but is not limited thereto. Of these, the screen printing method is preferable because it allows stable production. The electrodes 24b and the leads can be simultaneously printed and applied by screen printing. Further, the piezoelectric film 22 is preferably
It is formed by screen printing, dipping, coating, etc. These methods can form a film on a substrate by using a paste or slurry containing ceramic particles made of a material of a piezoelectric film as a main component, and excellent piezoelectric characteristics can be obtained. In addition, when the piezoelectric film is formed by the film forming method as described above, the piezoelectric element and the vibrating portion can be integrally bonded without using an adhesive, so that the reliability and reproducibility are excellent, and further, the integration is improved. It is particularly preferable because it is easily converted into. Moreover, the shape of such a film may form an appropriate pattern. The pattern may be formed by a screen printing method, a photolithography method or the like, and a mechanical processing method such as a laser processing method, slicing or ultrasonic processing is used,
Unnecessary portions may be removed to form a pattern.

Further, the shapes of the piezoelectric film and the electrodes to be formed are not limited at all, and any shape may be adopted depending on the application. For example, it may be a polygon such as a triangle or a quadrangle, a curved shape such as a circle, an ellipse, or a ring, a comb shape, a lattice shape, or a special shape in which these are combined. Further, the piezoelectric element 20 does not need to be provided on the entire surface of the vibrating portion 12, but is preferably provided on a portion where the strain generated by vibration is the largest. The respective films (22, 24a, 24b) thus formed on the substrate may be subjected to heat treatment every time each film is formed so as to be integrated with the substrate, or After forming the films, the films may be heat-treated simultaneously to integrally bond the films to the substrate. Note that when electrodes are formed by a thin film method, heat treatment is not necessarily required to integrate these electrodes.

[0035]

According to the sensor element of the present invention, the vibration prevention layer can prevent or reduce unnecessary vibration of the sensor element excited by this vibration without disturbing the vibration of the piezoelectric element and the vibration part. When the sensor element outputs an electric signal, noise due to unnecessary vibration is reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view of a sensor element of the present invention,
It is a XX 'cross section of FIG.

FIG. 2 is an exploded perspective view of an example of an element body.

FIG. 3 is a front explanatory view of an embodiment of the sensor element of the present invention.

FIG. 4 is a side sectional view of the embodiment of FIG.

FIG. 5 is a cross-sectional explanatory view of another embodiment of the sensor element of the present invention.

FIG. 6 is a front view of the embodiment of FIG.

FIG. 7 is an exploded perspective view of the embodiment of FIG.

FIG. 8 is an explanatory cross-sectional view of one embodiment of the battery of the present invention.

FIG. 9 is a cross sectional view showing another embodiment of the battery of the present invention.

FIG. 10 is a cross sectional view showing another embodiment of the battery of the present invention.

FIG. 11 is a cross sectional view showing another embodiment of the battery of the present invention.

[Explanation of symbols]

10 ... Sensor element, 10a ... End of sensor element, 10
b ... end of sensor element, 12 ... vibrating section, 12s, 12
t ... surface of vibrating part, 14 ... void, 16a, 16b ...
Introduction hole, 17 ... Protective cover, 17a ... Lid member, 17b
... Frame, 18 ... hole, 20 ... piezoelectric element, 22 ... piezoelectric film,
24a, 24b ... Electrodes, 26a, 26b ... Lead wires,
30 ... Anti-vibration layer, 32, 34 ... Film or plate, 3
6 ... Adhesive layer, 37 ... Hole, 38 ... Hole, 40 ... Battery, 4
2a, 42b ... electrode, 44 ... porous body, 46 ... void,
48: Element body

Claims (10)

[Claims] 1. A piezoelectric element having a vibrating portion, a piezoelectric element fixed to one surface of the vibrating portion and having a piezoelectric film and a pair of electrodes sandwiching the piezoelectric film, and at least a part of the substrate. A vibration-proof layer covering the sensor element. 2. The sensor element according to claim 1, wherein the anti-vibration layer has a film made of synthetic resin. 3. The anti-vibration layer has a plate made of metal, ceramics or synthetic resin, and an adhesive layer for fixing the plate and the base.
The sensor element according to 1. 4. The sensor element according to claim 1, 2 or 3, wherein a hole is formed in the vibration prevention layer so as not to cover the piezoelectric element. 5. The substrate has a protective cover that covers the piezoelectric element, and the vibration-preventing layer covers at least a part of the protective cover.
The sensor element according to 2 or 3. 6. The base body according to claim 1, wherein a space into which a fluid can be introduced is formed in the base body on a side opposite to the piezoelectric element with respect to the vibrating portion. Sensor element. 7. The sensor element according to claim 6, wherein the vibration preventing layer has a hole communicating with the void of the base body. 8. An introduction hole communicating with the void is formed in the substrate, and the substrate has a projection portion outside the void and near the introduction hole. Item 6. The sensor element according to Item 6 or 7. 9. A lead wire connected to the electrode of the piezoelectric element and fixed to the base body or the vibration prevention layer, wherein the vibration prevention layer is at least on the base body side of the lead wire. The sensor element according to claim 1, wherein an end portion and an end portion of the base body on the lead wire side are covered. 10. A battery having a pair of first electrodes and a porous body sandwiched between the first electrodes, wherein
The sensor element according to 9 is provided inside the porous body,
A battery, wherein the porous body or the first electrode acts as the vibration prevention layer.