JP2002296131A - Static and dynamic pressure detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that static pressure and dynamic pressure can not be accurately detected by an identical sensor when conventional sensors are used. SOLUTION: The static and dynamic pressure detecting sensor is composed of a fixed substrate 13 made of piezo electric material, on both surfaces of which a first electrode 11 and a second electrode 12 are formed on respectively, and a diaphragm 15 made of dielectric material, on the surface of which a third electrode 14 is formed. The second electrode 12 and the third electrode 14 are disposed so as to be opposite to each other, and the fixed substrate 13 and the diaphragm 15 are joined by a seal layer 16 disposed on the peripheral edge. The static pressure is detected on the basis of a capacitance value between the second electrode 12 and the third electrode 14, and the dynamic pressure is detected on the basis of a voltage value between the first electrode 11 and the second electrode 12. Thereby, the static pressure and the dynamic pressure are accurately detected using one sensor with simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static pressure dynamic pressure detection sensor.

[0002]

2. Description of the Related Art A conventional pressure detecting sensor of this type is generally the one described in Japanese Patent Application Laid-Open No. 57-97422. As shown in FIG. 10, this pressure detection sensor is composed of a fixed substrate 2 made of an electrically insulating material having a first electrode 1 formed on one surface, and an electrically insulating material having a second electrode 3 formed on the surface. And the fixed substrate 2 and the diaphragm 4 are joined via a sealing layer 5 so that the first electrode and the second electrode are arranged to face each other. The diaphragm 4 is deformed by the application of pressure, and the capacitance between the electrodes changes as the distance between the first and second electrodes changes, thereby detecting the applied pressure.

[0003]

However, in the conventional pressure detection, since the deflection of the diaphragm is detected, only the static pressure is detected, and the dynamic pressure cannot be detected with high accuracy.

[0004]

According to the present invention, there is provided a fixed substrate made of a piezoelectric material having a first electrode formed on one surface and a second electrode formed on the other surface. And a diaphragm made of an electrically insulating material having a third electrode formed on the surface thereof, wherein the second electrode and the third electrode are disposed so as to face each other, and the seal layer is located at a peripheral portion. This is a static pressure dynamic pressure detection sensor in which a fixed substrate and the diaphragm are joined.

According to the above invention, the static pressure is detected by the capacitance between the second electrode and the third electrode, and the dynamic pressure generates a voltage due to the piezoelectric effect of the piezoelectric material as the fixed substrate. By detecting the output voltage generated between the first electrode and the second electrode formed on both surfaces of the fixed substrate, the dynamic pressure can be easily and accurately detected.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The object of the present invention can be attained by implementing the structures described in the claims as embodiments. In the following, embodiments will be described by adding the functions and effects to the configuration described in each claim.

[0007] In order to solve the above problem, the invention according to claim 1 provides a fixed substrate made of a piezoelectric material having a first electrode formed on one surface and a second electrode formed on the other surface; A diaphragm made of an electrically insulating material having a third electrode formed on a surface thereof, wherein the fixed substrate is disposed by a seal layer located at a peripheral portion with the second electrode and the third electrode arranged so as to face each other. And a static pressure dynamic pressure detection sensor in which the diaphragm and the diaphragm are joined.

The static pressure can be detected by the capacitance between the second electrode and the third electrode, and the vibration can be detected by the voltage generated between the first and second electrodes. The static pressure and the dynamic pressure can be accurately detected by the sensor.

According to a second aspect of the present invention, there is provided a static pressure dynamic pressure detecting sensor configured to detect the capacitance between the second electrode and the third electrode by the capacitance detecting means.

By providing the capacitance detecting means, the capacitance changed by the application of the static pressure can be easily detected with a simple configuration.

According to a third aspect of the present invention, there is provided a static pressure dynamic pressure detection sensor having a configuration for detecting a dynamic pressure by providing a voltage detection means for detecting a voltage between the first electrode and the second electrode.

When a dynamic pressure is applied to the fixed substrate made of a piezoelectric material by providing the voltage detecting means,
Since a voltage is generated on the fixed substrate by the piezoelectric effect, an output voltage generated between the first electrode and the second electrode arranged on both surfaces of the fixed substrate can be easily detected.

According to a fourth aspect of the present invention, there is provided a static pressure dynamic pressure detecting sensor in which the fixed substrate is made of a solid solution of lead titanate and lead zirconate.

[0014] Since piezoelectric ceramic powder of a solid solution of lead titanate and lead zirconate is industrially used in a large amount, it is inexpensive and easily available. A pressure detection sensor can be provided.

The invention according to claim 5 is a static pressure dynamic pressure detection sensor in which at least the second electrode and the third electrode are formed by printing using a metal resinate paste.

Since the thin-film electrode can be easily formed by printing the electrode using a metal resinate paste, the effect of the electrode thickness on the distance between the second electrode and the third electrode can be reduced. Variations in the initial capacitance can be reduced.

According to a sixth aspect of the present invention, there is provided a static pressure dynamic pressure detecting sensor having a structure in which a spacer is provided on a seal layer.

By providing a spacer in the seal layer, the distance between the second electrode and the third electrode can be controlled, so that variations in the initial capacitance can be reduced.

According to a seventh aspect of the present invention, there is provided a static pressure dynamic pressure detection sensor in which a dummy electrode is formed on a surface of the diaphragm where the third electrode is not formed.

By providing the dummy electrode, the difference in thermal expansion between the third electrode and the diaphragm made of an electrically insulating material can be suppressed, and the warpage of the diaphragm can be reduced, so that the variation in the initial capacitance can be reduced.

According to an eighth aspect of the present invention, the third electrode is a static pressure dynamic pressure detecting sensor comprising a main electrode and a reference electrode.

By obtaining the capacitance ratio of each of the main electrode and the reference electrode constituting the second electrode and the third electrode as an output, the influence of the temperature characteristic can be eliminated, so that the reliability is high. The output is obtained.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a static pressure / dynamic pressure detection sensor according to Embodiment 1 of the present invention.

This static pressure / dynamic pressure detection sensor comprises a fixed substrate 13 made of a piezoelectric material having a first electrode 11 formed on one surface and a second electrode 12 formed on the other surface, and a third electrode 14. Diaphragm 1 made of an electrically insulating material formed on the surface
5 and a seal layer 16 formed on the outer peripheral edge of the second electrode 12 and the third electrode 14, and the second electrode 12 and the third electrode 13 are opposed to each other. The fixed substrate 13 and the diaphragm 15 were joined by the seal layer 16.

The first electrode 11, the second electrode 12, and the third electrode 14 were each formed of gold resinate to a thickness of 25 μm by screen printing, degreased and fired to a thickness of 0.1 μm. For this reason, the electrode thickness can be formed to be 1 μm or less, and the effect of the electrode thickness on the distance between the second electrode 12 and the third electrode 14 can be reduced. For this reason, sensor variations can be suppressed. The fixed substrate 13 made of a piezoelectric material on which the first electrode 11 and the second electrode 12 were formed was made of a piezoelectric ceramic of a solid solution of lead titanate and lead zirconate. Since this piezoelectric ceramic is used in large quantities in industry, it is inexpensive and easily available, so that a highly sensitive and inexpensive static pressure dynamic pressure detection sensor can be provided.

In this embodiment, the diaphragm 15 is made of alumina which is an electrically insulating material. Further, the fixed substrate 13 and the diaphragm 15 were bonded to each other by a seal layer 16 formed on the peripheral portion of the fixed substrate 13. In this embodiment, a glass paste having the same thermal expansion coefficient as the fixed substrate 13 and the diaphragm 15 was used as the seal layer 16.

Next, the operation of the static pressure dynamic pressure detection sensor of the present invention will be described.

When a static pressure is applied to the static pressure dynamic pressure detection sensor, the diaphragm 15 bends as shown in FIG. 2, and the distance between the second electrode 12 and the third electrode 14 decreases. The capacitance is expressed as C = εSX ⁻¹ (ε is the dielectric constant, S is the electrode area, and X is the distance between the electrodes). When the pressure P is applied, X becomes smaller, and the output capacitance increases. I do.

Therefore, the static pressure can be detected by detecting the capacitance value.

When a dynamic pressure is applied, the dynamic pressure is transmitted to the fixed substrate 13 made of a piezoelectric material, and a voltage is generated by the piezoelectric effect. By detecting the output voltage generated between the first electrode 11 and the second electrode 12 formed on both surfaces of the fixed substrate 13, the dynamic pressure can be easily and accurately detected.

FIG. 3 shows a configuration of a static pressure dynamic pressure sensor for detecting a static pressure by providing a capacitance detecting means 17 for detecting a capacitance between the second electrode 12 and the third electrode 14. The capacitance detecting means 17 detects static pressure by the capacitance between the second electrode 12 and the third electrode 14, and FIG. 4 shows the relationship between the load and the output of the capacitance detecting means 17. . From this result, it is understood that the static pressure can be easily detected by detecting the capacitance between the second electrode 12 and the third electrode 14 by the static pressure detecting means 17.

FIG. 5 shows the construction of a static pressure dynamic pressure detecting sensor provided with voltage detecting means 18 for detecting an output voltage generated between the first electrode 11 and the second electrode 12 formed on both surfaces of the fixed substrate 13. Is shown. The voltage detecting means 18 detects a voltage value at which a voltage is generated by a piezoelectric effect when a dynamic pressure is applied. In FIG. 6, the static pressure dynamic pressure detection sensor of the present invention is disposed under the futon,
The output result of the voltage detecting means 18 when a person sleeps thereon is shown. From this result, respiratory vibration, which is vibration from the human body,
It is understood that the sensitivity is high enough to detect the heartbeat vibration.

For this reason, the static pressure dynamic pressure detection sensor of the present invention
Static pressure and dynamic pressure can be accurately detected by one sensor.

(Embodiment 2) FIG. 7 is a sectional view of a static pressure / dynamic pressure detection sensor according to Embodiment 2 of the present invention.

The second embodiment differs from the first embodiment in that a spacer 19 is provided on the seal layer 16. Note that the portions denoted by the same reference numerals as those in the first embodiment have the same structure, and description thereof will be omitted.

In this embodiment, the spacer 19 is made of glass beads (Φ45 μm) having the same coefficient of thermal expansion as the seal layer 16.
m) was used. Since the distance between the electrodes between the second electrode 12 and the third electrode 14 can be controlled by the spacer 19, the fixed substrate 13 and the diaphragm 15 can be controlled.
It is possible to reduce the variation in capacitance between them. 100 static pressure dynamic pressure sensors provided with the spacers 19 and 100 static pressure dynamic pressure sensors without the spacers 19 were produced, and their initial capacities were evaluated. The standard deviation of the static pressure dynamic pressure detection sensor without the spacer 19 is about 10%, whereas the standard deviation of the static pressure dynamic pressure detection sensor with the spacer 19 is about 1.5.
%, Which could be reduced to 1/6. As a result, a highly accurate static pressure dynamic pressure detection sensor having no variation can be easily realized.

(Embodiment 3) FIG. 8 is a sectional view of a static pressure / dynamic pressure detection sensor according to Embodiment 3 of the present invention.

The third embodiment differs from the first and second embodiments in that a dummy electrode 20 is provided on the surface of the diaphragm 15 where the third electrode 14 is not provided.
Note that the portions denoted by the same reference numerals as those in the first embodiment have the same structure, and description thereof will be omitted. In this embodiment, the dummy electrode 20 is made of the same material as the third electrode 14, such as gold resinate.

The diaphragm 15 without the normal dummy electrode 20 is warped due to a difference in thermal expansion between the third electrode 14 and the diaphragm 15 itself, and the distance between the second electrode 12 and the third electrode 14 is reduced. Fluctuates. For this reason, it has been a factor of the variation of the initial capacitance. Further, the warpage greatly affects a change in temperature characteristics. However, by providing the dummy electrode 20, the difference in thermal expansion between the third electrode 14 and the diaphragm 15 can be canceled, so that the diaphragm 15
Warpage can be reduced, and variations in temperature characteristics can be reduced.

In this embodiment, 100 static pressure dynamic pressure sensors provided with the dummy electrodes 20 and 100 static pressure dynamic pressure sensors not provided with the dummy electrodes 20 were manufactured, and their initial capacitance variations were evaluated. The standard deviation of the static pressure dynamic pressure detection sensor having no dummy electrode is about 10%, whereas the standard deviation of the static pressure dynamic pressure detection sensor provided with the dummy electrode 20 is about 6%, which is reduced to 3/5. I was able to do it. Further, when the dummy electrode 20 was provided on the diaphragm 15 of the static pressure dynamic pressure detection sensor provided with the spacer 19 of the second embodiment, the standard deviation could be reduced to about 0.8%. As a result, by providing the dummy electrode 20, a highly accurate static pressure dynamic pressure detection sensor having no variation can be easily realized.

(Embodiment 4) FIG. 9A is a sectional view of a static pressure dynamic pressure detecting sensor according to Embodiment 4 of the present invention, and FIG. 9B is a top view of a third electrode. The fourth embodiment differs from the first to third embodiments in that the third electrode 14 is composed of a main electrode 21 and a reference electrode 22. In the present embodiment, the main electrode 21 and the reference electrode 22, which are the third electrodes 14, were formed by printing with gold resinate, and the reference electrode 22 was formed on the outer circumference of the main electrode 21. By using the ratio of each output as an output, the temperature characteristics of the diaphragm 15 can be canceled. That is, when only one capacitance value is output as the third electrode 14, the capacitance value between the second electrode 12 and the third electrode 14 changes due to the temperature characteristics of the diaphragm 15 itself. However, as in the present embodiment, the third electrode 14 is constituted by the main electrode 21 and the reference electrode 22, and the ratio of the main electrode 21 to the reference electrode 22 is taken as the output, whereby the temperature characteristics can be canceled. . For this reason, it is possible to obtain an accurate sensor output with a simple configuration.

[0043]

As is apparent from the above embodiment, according to the first aspect of the present invention, the static pressure is detected by the capacitance between the second electrode and the third electrode, and the first electrode is connected to the first electrode. Since the vibration can be detected by the voltage generated between the second electrodes, the static pressure and the dynamic pressure can be accurately detected by one sensor.

According to the second aspect of the present invention, by providing the capacitance detecting means, the capacitance changed by the application of the static pressure can be easily detected with a simple configuration.

According to the third aspect of the present invention, when a dynamic pressure is applied to the fixed substrate of the piezoelectric material by providing the voltage detecting means, a voltage is generated on the fixed substrate by the piezoelectric effect. An output voltage generated between the first electrode and the second electrode arranged on both surfaces of the substrate can be easily detected.

According to the fourth aspect of the present invention, since the piezoelectric ceramic powder of the solid solution of lead titanate and lead zirconate is industrially used in large quantities, it is inexpensive and easily available. Therefore, a highly sensitive and inexpensive static pressure dynamic pressure detection sensor can be provided.

According to the fifth aspect of the present invention, a thin-film electrode can be easily formed by printing and forming an electrode by using a metal resinate paste, so that the distance between the second electrode and the third electrode is reduced. , The influence of the electrode film thickness can be reduced, and the variation in the initial capacitance can be reduced.

According to the sixth aspect of the present invention, by providing a spacer in the seal layer, the distance between the second electrode and the third electrode can be controlled. Variation can be reduced.

According to the seventh aspect of the present invention, by providing the dummy electrode, the difference in thermal expansion between the third electrode and the diaphragm made of an electrically insulating material can be suppressed, and the warpage of the diaphragm can be reduced. Therefore, variation in the initial capacity can be reduced.

According to the present invention, the influence of the temperature characteristic is obtained by obtaining as output the capacitance ratio of each of the main electrode and the reference electrode constituting the second electrode and the third electrode. Can be removed, so that a highly reliable output can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a static pressure dynamic pressure detection sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the static pressure dynamic pressure detection sensor when a static pressure is applied.

FIG. 3 is a cross-sectional view of the static pressure dynamic pressure detection sensor and a configuration diagram of capacitance detection means for detecting capacitance.

FIG. 4 is a diagram showing the relationship between the load, capacitance detection means, and output.

FIG. 5 is a cross-sectional view of the static pressure dynamic pressure detection sensor and a configuration diagram of a voltage detection unit.

FIG. 6 is a diagram showing a relationship between an output of a voltage detecting means of the static pressure dynamic pressure detecting sensor and time.

FIG. 7 is a cross-sectional view of a static pressure dynamic pressure detection sensor according to a second embodiment of the present invention.

FIG. 8 is a sectional view of a static pressure dynamic pressure detection sensor according to a third embodiment of the present invention.

FIG. 9A is a sectional view of a static pressure dynamic pressure detection sensor according to a fourth embodiment of the present invention. FIG. 9B is a top view of the third electrode.

FIG. 10 is a sectional view of a conventional pressure detection sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 First electrode 12 Second electrode 13 Fixed substrate 14 Third electrode 15 Diaphragm 16 Seal layer 17 Capacitance detection means 18 Voltage detection means 19 Spacer 20 Dummy electrode 21 Main electrode 22 Reference electrode

Continuation of the front page (72) Inventor Naruhisa Kanazawa 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 2F055 AA39 BB11 BB14 CC02 DD09 DD19 EE23 EE25 FF01 FF11 GG12

Claims (8)

[Claims] 1. A fixed substrate made of a piezoelectric material having a first electrode formed on one surface and a second electrode formed on the other surface, and an electrically insulating material having a third electrode formed on the surface. A static pressure dynamic pressure detection sensor comprising a diaphragm, wherein the second electrode and the third electrode are arranged to face each other, and the fixed substrate and the diaphragm are joined by a seal layer located at a peripheral portion. 2. The static pressure dynamic pressure detection sensor according to claim 1, wherein capacitance detection means for detecting capacitance between the second electrode and the third electrode is provided to detect static pressure. . 3. The static pressure dynamic pressure detection sensor according to claim 1, wherein voltage detection means for detecting a voltage between the first electrode and the second electrode is provided to detect a dynamic pressure. 4. The static pressure dynamic pressure detection sensor according to claim 1, wherein the fixed substrate is a solid solution of lead titanate and lead zirconate. 5. The static pressure dynamic pressure detection sensor according to claim 1, wherein at least the second electrode and the third electrode are formed by printing using a metal resinate paste. 6. The static pressure / dynamic pressure detection sensor according to claim 1, wherein a spacer is provided on the seal layer. 7. The static pressure dynamic pressure detection sensor according to claim 1, wherein a dummy electrode is formed on a surface of the diaphragm where the third electrode is not formed. 8. The static pressure dynamic pressure detection sensor according to claim 1, wherein the third electrode comprises a main electrode and a reference electrode.