JP2000028443A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a simple electrode film constitution by making a common electrode film to commonly act on an electrode film for producing vibration and an electrode film for detecting vibration and, at the same time, to enable a pressure sensor to simultaneously detect both an applied pressure and external vibrations by constituting the sensor in such a way that the sensor can obtain signals against external vibrations. SOLUTION: When a pressure is applied upon one planar vibrating body in which an electrode film 12 for generating vibration, an electrode film 14 for detecting vibration, and a common electrode film 14 are integrated, a pressure sensor detects the vibrational characteristic of the vibration body at a prescribed frequency between the electrode films 12 and 14. Therefore, the level of the pressure can be detected with a simple electrode film constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A conventional pressure detector of this type is as follows.

[0003] First, IEEE Transaction on Electron Dev
Ices, vol. ED-26, No. 5, p815 to p817, 1979 (hereinafter referred to as Conventional Example 1) proposed a bimorph-type pressure detector as shown in FIG. As shown in the figure, the electrodes 1b, 1c and 2b, 2b are provided on both sides of the piezoelectric films 1a and 2a.
The two band-shaped piezoelectric films 1 and 2 provided with c are attached to each other, one end of which is supported in a cantilever shape by a support portion 3, and a voltage is applied to the piezoelectric film 1 from a transmitting portion 4 to vibrate,
The output by the vibration was taken out from the piezoelectric film 2. With this configuration, when the object 5 comes into contact with the piezoelectric film 2, the contact of the object is detected based on a change in the output signal of the piezoelectric film 2. FIG. 8 shows the contact position L of the object 5 and the frequency f of the applied voltage of the transmitting unit 4 at this time.
The relationship between the output signal V of the piezoelectric film 2 and the contact position L is shown using It is apparent from the figure that the contact position L is detected by selecting an appropriate frequency f and monitoring the output signal V.

Japanese Patent Application Laid-Open No. Hei 8-62068 (hereinafter referred to as Conventional Example 2) discloses a pressure detecting device for detecting distribution of fine peaks and valleys such as fingerprints. As shown in FIG. 9, a plurality of scanning electrodes 6a and 6b are formed in a matrix on the front and back surfaces of a piezoelectric film 6, and an insulating protective film 7, an insulating film 8, and a high-frequency vibrator 9 are laminated thereon. . When an object comes into contact with the insulating protective film 7 according to the above configuration, the undulations of the object due to peaks and valleys are received at a number of pressure detection points of the piezoelectric sensor, and the peaks are scanned by the matrix-shaped scanning electrodes 6a and 6b. And the valley distribution was detected. As an example, FIG. 10 shows how the distribution of the peaks and valleys of the fingerprint is detected when the finger 10 touches the insulating protection film 7.

[0005]

However, the pressure detecting device of the prior art 1 can detect the presence or absence and the contact position of the object 5 on the piezoelectric film 2 based on the characteristics as shown in FIG. There is a problem that the pressure level due to the contact of the object 5 cannot be detected. Also,
Due to the cantilever type structure, there has been a problem that when an object repeatedly comes into contact, settling occurs on the piezoelectric film and the detection sensitivity is reduced.

Further, in the pressure detecting device of the conventional example 2, although there is no problem of durability due to the above-mentioned cantilever type structure, it is possible to detect at many pressure detecting points of the piezoelectric sensor, for example, as shown in FIG. It is merely a matter of whether the peak of the fingerprint pattern or the valley of the fingerprint pattern hits each intersection point. That is, Conventional Example 2 is for detecting the presence or absence of contact of an object at each point, and has a problem that the pressure level of the object cannot be detected at each point.

Further, it has been desired to simultaneously detect pressure and vibration in various applications, but both references have the problem that they cannot meet this kind of demand.

[0008]

In order to solve the above-mentioned problems, the present invention provides a vibration generating electrode film provided at one end of a surface of a planar vibrator, and a vibration generating electrode film separated from the vibration generating electrode film. The pressure sensor includes a vibration detection electrode film provided on the other end of the surface and a common electrode film provided on another surface of the planar vibrator.

According to the invention, when a pressure is applied to the planar vibrating body at a predetermined frequency, the vibration characteristics of the planar vibrating body, which change in accordance with the pressure, are determined by the vibration detecting electrode film and the common electrode film. Since the detection is performed between the pressure levels, the pressure level can be detected with a simple configuration.

[0010]

According to a first aspect of the present invention, there is provided a pressure sensor comprising: a vibration generating electrode film provided at one end of a surface of a planar vibrating body; And a common electrode film provided on the other surface of the planar vibrating body.

[0011] When a pressure is applied to the planar vibrating body vibrating at a predetermined frequency, the vibration characteristics of the planar vibrating body, which changes according to the pressure, are determined by using a vibration detecting electrode film and a common electrode. Since the detection is performed between the membranes, the pressure level can be detected with a simple configuration.

In the pressure detecting device according to a second aspect of the present invention, the vibration generating electrode film, the vibration detecting electrode film, and the common electrode film are provided separately from the ends of the planar vibrator.

Then, an alternating voltage is applied between the vibration-generating electrode film and the common electrode film to vibrate the planar vibrator at a predetermined frequency. Detection is performed between the detection electrode film and the common electrode film. At this time, the distance between the vibration-generating electrode film and the common electrode film and the distance between the vibration-detecting electrode film and the common electrode film can be increased as necessary, so that an AC voltage can be stably applied.

A pressure sensor according to a third aspect of the present invention comprises:
A plurality of lead wire connecting extensions are arranged on the side surface of the planar vibrator, and on the surface of each of the lead wire connecting extensions,
A conductive film connected to the vibration generation electrode film, the vibration detection electrode film, and the common electrode film is formed.

The lead wire is an electrode film for vibration generation,
Not directly connected to the vibration detection electrode film and the common electrode film,
Since the connection is made to each of the lead wire connection terminals, the vibration of the planar vibrator can be stabilized.

A pressure sensor according to a fourth aspect of the present invention comprises:
A conductive film is formed on either one surface or the other surface of the lead wire connecting extension.

Since there is no conductive film facing the lead wire connecting terminal portion, no power is consumed in the lead wire connecting terminal portion, and the lead wire connection is facilitated.

A pressure sensor according to a fourth aspect of the present invention comprises:
The conductive film formed on the surface of the lead wire connecting extension is made of the same material as the vibration generation electrode film and the vibration detection electrode film.

Since the conductive film and these electrode films can be formed simultaneously in the same step, the forming steps can be simplified.

[0020]

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

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

Reference numeral 11 denotes a planar vibrator using a polymer piezoelectric material. An electrode film 12 for vibration generation is formed at one end of the surface, and is separated from the electrode film 12 for vibration generation and the other end on the same surface. Then, the vibration detection electrode film 13 is formed. On the other surface of the polymer piezoelectric body 11, a common electrode film 14 is formed including a surface facing the vibration generation electrode film 12 and the vibration detection electrode film 13. As the polymer piezoelectric body 11, a film of a polymer piezoelectric material such as polyvinylidene fluoride is used. Further, as the vibration generation electrode film 12, the vibration detection electrode film 13, and the common electrode film 14, for example, an Ag electrode film made of Ag particles and an organic binder, an evaporated Al electrode film, a sputtered Ni electrode film, or the like is used.

Next, the operation and operation will be described. When applying an AC signal V ₀ between the common electrode film 14 and the vibration generating electrode film 12, polymeric piezoelectric members 11a sandwiched between the both vibrate.

The vibration passes through the vibration-generating electrode film 12 and the portion of the polymer piezoelectric body 11b where the vibration detecting electrode film 13 is not formed (hereinafter, simply referred to as a separation portion 11b), and then passes through the vibration detecting electrode film. Propagation to the piezoelectric polymer 11c sandwiched between the common electrode film 13 and the common electrode film 14 causes the entire piezoelectric polymer 11 to vibrate with certain characteristics. Then, a piezoelectric electromotive force V ₁ is generated between the vibration detection electrode film 13 and the common electrode film 14 according to the vibration.

At this time, as shown in FIG. 1, when a pressure W is applied to the vibration generating electrode film 12 by a heavy object or the like, as described in detail later, the piezoelectric electromotive force V ₁ corresponding to the pressure is applied. Is generated between the vibration detection electrode film 13 and the common electrode film 14. Incidentally, the separation unit 11b, also be a pressure is applied to the vibration detecting electrode film 13, piezoelectric electromotive force V ₁ corresponding to the pressure is generated between the common electrode film 14 and the vibration detecting electrode film 13.

FIG. 2 shows that the AC signal V ₀ (frequency f ₁ ) and the piezoelectric electromotive force in a frequency region where the signal of the piezoelectric electromotive force V ₁ decreases when pressure is applied to the planar vibrator 11. it is a characteristic diagram showing the V ₁ of the signal waveform. The vertical axis in the figure V ₀ and V _1, the horizontal axis represents the time t.

When no pressure is applied to the planar vibrator including the electrode films 12 and 13 (t <t ₁ ), V is synchronized with V _0.
1 is output. Further, a phase difference _L01 occurs due to the propagation of vibration from the vibration generation electrode film 12 side to the vibration detection electrode film 13. Next, at time t ₁ , when a certain object is mounted on the vibration generating electrode film 12 or a pressure W is applied by the pressure of the surrounding gas or liquid, the pressure is applied to the vibration generating electrode film 12 side. vibration of the planar vibrating body 11a is inhibited amplitude V ₁ was decreased to D ₁ from D _01. It should be noted, changes phase from L ₀₁ to L _1. The degree of these changes depends on the planar vibrator 11, the vibration generation electrode film 12, the vibration detection electrode film 1, and the like.
3 depends on the vibration characteristics and shape. The vibration characteristics of these members may be optimized depending on the application. The change in the vibration characteristics when the pressure is applied as described above is electrically detected between the vibration detection electrode film 13 and the common electrode film 14.

As is clear from the description of FIG. 2, since the pressure W and the piezoelectric electromotive force D show a fixed relationship, the pressure W can be calculated with high accuracy using this relationship. Further, as is apparent from the above operation, the pressure device of the present invention can detect the pressure level with a simple configuration. In particular, the common electrode film 1
4 has a simple electrode film configuration because it acts on both the vibration generation electrode film 12 and the vibration detection electrode film 13 in common.

The vibration-generating electrode film 12, the vibration-detecting electrode film 13, and the common electrode film 14 are integrated on one polymer piezoelectric body 11, and the polymer piezoelectric body 11a is flexible. For example, when detecting the pressure of a contacting object, there is a degree of freedom of attachment such that the object can be attached along the object, and the thickness can be reduced.

Further, the frequency f1 is applied to the polymer piezoelectric body 11.
When an external vibration having a frequency different from that of the vibration is applied, an electromotive force corresponding to the vibration is applied to the vibration detecting electrode film 13 and the common electrode film 1.
Obviously what happens between the four. Therefore, by filtering the signal obtained between the vibration detection electrode film 13 and the common electrode film 14, the pressure signal and the vibration signal can be separated.
Obviously, both can be detected simultaneously.

(Embodiment 2) FIG. 3 is a plan view of a pressure sensor according to Embodiment 2 of the present invention. FIG. 4 is a cross-sectional view taken along a line AA ′ in FIG. In the pressure sensor according to the present embodiment, the vibration generation electrode film 12 and the vibration detection electrode film 1 are used.
3 and the common electrode film 14 are formed at a distance L from the end 11E of the planar vibrator 11, respectively.

An AC signal V ₀ is applied between the vibration-generating electrode film 12 and the common electrode film 14 to vibrate the planar vibrator 11 at a predetermined frequency. Characteristics are detected between the vibration detection electrode film 13 and the common electrode film 14. AC signal V ₀ is, usually, is a (10~100) V. The thickness of the polymer piezoelectric body 11 is usually (10
１００100) μm. As shown in FIG. 1, when the vibration generation electrode film 12, the vibration detection electrode film 13, and the common electrode film 14 are formed without being separated from the end 11 E of the planar vibration body 11, respectively, the vibration generation electrode The distance between the film 12 and the common electrode film 14 and the distance between the vibration detection electrode film 13 and the common electrode film 14 are approximately equal to the thickness of the piezoelectric polymer 11. At such a small distance, (10 to 10
0) The electric field strength when V is applied may be 104 V / cm or more. Such a high electric field is not preferable because it causes surface leakage. In this embodiment, the distance between the vibration generation electrode film 12 and the common electrode film 14 and the distance between the vibration detection electrode film 13 and the common electrode film 14 can be increased as necessary, so that the AC signal can be stably obtained. Can be applied.

(Embodiment 3) FIG. 5 is a plan view of a pressure sensor according to Embodiment 3 of the present invention. In the pressure sensor according to the third embodiment, a plurality of extension portions 15 for connecting lead wires are arranged on the side surface of the planar vibrating body 11, and the surface of each of the extension portions 15 for connecting lead wires is provided with a vibration generation electrode film 12. Are formed, a conductive film 13a connected to the vibration detection electrode film 13, and a conductive film 14a connected to the common electrode film 14.

As described above, when an AC signal V ₀ is applied between the vibration generating electrode film 12 and the common electrode film 14, the polymer piezoelectric body 11a sandwiched between the two vibrates. This vibration passes through the polymer piezoelectric body 11b (hereinafter simply referred to as a separation portion 11b) on which the vibration generation electrode film 12 and the vibration detection electrode film 13 are not formed, and then the vibration detection electrode film 13 and the common electrode film. The piezoelectric polymer 11c propagates to the polymer piezoelectric body 11c sandwiched between 14, and vibrates with certain characteristics. The overall vibration of the polymer piezoelectric body 11 depends on the piezoelectric properties and shape of the polymer piezoelectric body 11, and also on the density and shape of the vibration generation electrode film 12, the vibration detection electrode film 13, and the common electrode film 14. Depends on it.

However, in order to induce this vibration or detect a signal, the lead wire is connected to each of the electrode films 12, 13,
14 must be connected. When a lead wire is directly connected to each of the electrode films 12, 13, and 14, for example, when a Cu wire having a diameter of about 0.1 is connected by solder or conductive paste, the weight of the connection portion includes the connection portion. Since it is larger than that of the peripheral piezoelectric polymer 11 and the electrode films 12, 13 and 14 by one digit or more, the piezoelectric polymer 1
One of the overall vibrations is disturbed, which is undesirable.

In the pressure sensor of this embodiment, the planar vibrator 1
A plurality of lead wire connecting extensions 15 are arranged on one side surface, and a conductive film 12 connected to the vibration generating electrode film 12 is provided on the surface of each of the lead wire connecting extensions 15.
a, conductive film 13a connected to vibration detection electrode film 13
In addition, a conductive film 14a connected to the common electrode film 14 is formed. The lead wire connecting extension 15 is constituted by the planar vibrator 11 itself, and further comprises the conductive films 12a, 13a.
Since a and 14a can be formed by the same forming method as the vibration generation electrode film 12, the vibration detection electrode film 13, and the common electrode film 14,
These weights are almost the same as those of the planar vibrator 11 and the like. Therefore, the influence on the overall vibration of the polymer piezoelectric body 11 forming the lead wire connecting extension 15 can be ignored. The lead wire is connected to the tip of the conductive film 12a, 13a, 14a formed on the surface of the lead wire connecting extension 15.
Since the entire vibration of the polymer piezoelectric body 11 is not transmitted to the distal end of the lead wire connecting extension 15, the connection of the lead wire does not affect the overall vibration of the polymer piezoelectric body 11.

The conductive films 12a, 13a, 14a
May be made of a different material from the above-described conductive films 12, 13, and 14, but is preferably made of the same material. This is because the conductive films 12a, 13a, and 14a can be formed at the same time when the conductive films 12, 13, and 14 are formed, so that the formation process can be simplified.

Further, a plurality of lead wire connecting extension portions 15
On either one surface or the other, respectively
Preferably, conductive films 12a, 13a, and 14a are formed.
Good. FIG. 6 is a sectional view taken along a straight line BB 'in FIG.
(A). The part C in the figure shows the polymer piezoelectric body 11,
D part and D 'part form a part of the lead wire connecting extension part 15.
Show. On one surface of the lead wire connecting extension portion 15 of the D portion
A conductive film 14a is formed and connected to the common electrode film 14.
ing. Also, one of the lead wire connecting extension portions 15 in the D 'portion
A conductive film 12a is formed on one surface and an electrode for vibration generation
It is connected to the membrane 12. On the other hand, as shown in FIG.
To one surface of one lead connecting extension 15.
The conductive film 14a is formed, and the conductive film 12a is formed on the other surface.
It is not preferable to achieve this. Extension part 1 for lead wire connection
5 has conductive films 12a and 14a formed on both surfaces.
Thus, an alternating current is applied between the vibration generation electrode film 12 and the common electrode film 14.
Signal V ₀Is applied, this lead wire connecting extension 1
5 also consumes power. However, power consumption in this part
The cost does not contribute to the vibration of the entire polymer piezoelectric body 11
Therefore, it is preferable that there is no power consumption. Also, the conductive film 1
2a and the conductive film 14a are very close to each other,
The connection work of the lead wire becomes difficult.

The structure shown in FIGS. 6A and 6B is different from the structure shown in FIGS. 6A and 6B in that the conductive films 12a and 13
Since the a and a are formed, the above-described disadvantage can be solved.

Although the pressure W is applied to the vibration-generating electrode film 12 in the above embodiment, the pressure W may be applied to the separation portion 11b or the vibration-detecting electrode film 13, or one of them may be placed. It may be placed in more than one place.

[0041]

As described above, according to the pressure sensor according to the first aspect of the present invention, the common electrode film acts in common on the vibration generating electrode film and the vibration detecting electrode film, so that it is simple. The electrode structure can be obtained in various ways. Further, since a signal is obtained for external vibration, both pressure and external vibration can be detected simultaneously.

Further, according to the pressure detecting sensor of the second aspect of the present invention, the distance between the vibration generating electrode film and the common electrode film and the distance between the vibration detecting electrode film and the common electrode film can be changed as required. The AC signal can be stably applied.

According to the pressure sensor according to the third aspect of the present invention, since the lead wire is connected by the lead wire connecting extension and is not directly connected to each electrode film, stable vibration can be obtained.

According to the pressure sensor of the fourth aspect of the present invention, the conductive film is formed on one of the one surface and the other surface of the lead wire connecting extension, and the lead wire connecting terminal is provided. Since there is no conductive film facing the part,
There is no power consumption at the lead wire connection terminal portion, and the lead wire connection is facilitated.

According to the pressure sensor according to the fifth aspect of the present invention, the conductive film formed on the surface of the extended portion for connecting the lead wire includes the electrode film for vibration generation, the electrode film for vibration detection, and the common electrode film. Since the conductive film and these electrode films can be formed simultaneously in the same process, the forming process can be simplified.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram of an AC signal applied between a vibration generation electrode film and a common electrode film of the sensor and an output signal obtained between the vibration detection electrode film and the common electrode film.

FIG. 3 is a plan view of a pressure sensor according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along a line AA ′ shown in FIG. 3;

FIG. 5 is a plan view of a pressure sensor according to a third embodiment of the present invention.

6A is a cross-sectional view taken along a straight line BB ′ shown in FIG. 5. FIG. 6B is a cross-sectional view showing an unfavorable example taken along a straight line BB ′ shown in FIG.

FIG. 7 is a block diagram of a conventional pressure detecting device.

FIG. 8 is a characteristic diagram showing a relationship among a contact position L of an object, a frequency f of a voltage applied to an oscillation unit, and an output signal V of a piezoelectric film in the pressure detection device.

FIG. 9 is an external view showing a configuration of a conventional pressure detecting device.

FIG. 10 is a schematic diagram showing a state when the insulating protective film is touched with a finger in the pressure detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Polymer piezoelectric substance 12 Electrode film for vibration generation 13 Electrode film for vibration detection 14 Common electrode film

 ──────────────────────────────────────────────────の Continuing on the front page (72) Katsuhiko Yamamoto, Inventor 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Terms (reference) 2F055 AA40 BB20 CC02 CC53 DD11 EE23 FF43 GG01

Claims (5)

[Claims] 1. A vibration generating electrode film provided at one end of one surface of a planar vibrator, and a vibration detecting electrode film provided at the other end of the surface separately from the vibration generating electrode film. And a common electrode film provided on another surface of the planar vibrator. 2. The pressure sensor according to claim 1, wherein the vibration-generating electrode film, the vibration-detecting electrode film, and the common electrode film are provided separately from ends of the planar vibrator. 3. A plurality of extension portions for connecting lead wires are arranged on a side surface of the planar vibrator, and a vibration generation electrode film, a vibration detection electrode film, and a common electrode are provided on the surface of each of the lead wire connection extension portions. 3. The pressure sensor according to claim 2, wherein a conductive film connected to each of the electrode films is formed. 4. The pressure sensor according to claim 3, wherein a conductive film is formed on one of the one surface and the other surface of the lead wire connecting extension. 5. The pressure sensor according to claim 3, wherein the conductive film formed on the surface of the lead wire connecting extension is made of the same material as the vibration generating electrode film and the vibration detecting electrode film.