JP2000028444A - Pressure detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect pressure levels in a simple constitution by oscillating one end of plane- shaped pizoelectrics by an oscillation generating means, detecting the oscillation characteristics of the piezoelectrics which change in response to pressure when the piezoelectrics are applied with pressure by an oscillation detecting means, and computing the pressure on the basis of an output signal by a pressure computing means. SOLUTION: In an oscillation generating means 12, the part of the plane-shaped piezoelectrics 11a sandwiched by electrodes 12a and 12b is oscillated in response to an oscillation signal generated at a signal generating part 14. This oscillation is propagated to an oscillation detecting means 13 and an oscillation characteristics control means 16 via the part of the high-molecular piezoelectrics 11b to oscillate the overall plane-shaped piezoelectrics 11 with certain characteristics. A detection voltage is generated at the detecting means 13 in response to the oscillation. The oscillation of the overall piezoelectrics 11 also largely depends on the frequency of an oscillation signal. The frequency at which the detection voltage detected at the detecting means 13 first shows a local maximum is defined as the first resonance frequency. When the piezoelectrics 11 are applied with pressure or weight, the first resonance frequency is approximately determined dependently on the length L of the piezoelectrics 11 and the velocity of sound, and the distortion and stress of the piezoelectrics 11 become maximum at its center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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, electrodes 1b, 1c and 2 are provided on both sides of piezoelectric films 1a and 2a.
b, two belt-shaped piezoelectric films 1 and 2 provided with 2c 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.
4 shows the relationship between the output signal V of the piezoelectric film 2 and the contact position L, using the contact position L of the object 5 and the frequency f of the voltage applied to the transmitter 4 as parameters. 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. This is Figure 1
As shown in FIG. 4, a plurality of scanning electrodes 6a and 6b were 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 were 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. 15 shows how the distribution of peaks and valleys of a fingerprint is detected when the insulating protective film 7 is touched with the finger 10.

[0005]

However, the pressure detecting device of the first conventional example 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.

In addition, since the cantilever type structure is used, when an object repeatedly comes into contact, there is a problem that the piezoelectric film is set 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 can be detected at a number of 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, Reference 2 detects the presence or absence of contact of an object at each of the above points,
There is a problem that the pressure level of the object cannot be detected at each point.

Further, it is desired to simultaneously detect pressure and vibration in various applications, but both conventional examples have a problem that they cannot meet this kind of demand.

[0009]

In order to solve the above-mentioned problems, the present invention provides a vibration generating means provided at one end of a planar piezoelectric body, and a vibration generating means separated from the vibration generating means. A vibration detecting unit provided at an intermediate portion, a vibration characteristic controlling unit provided at the other end of the planar piezoelectric body, and a pressure calculating unit for calculating a pressure applied to the planar piezoelectric body; The one end of the planar piezoelectric body is vibrated by a generating unit, and when a pressure is applied to the planar piezoelectric body, a vibration characteristic of the planar piezoelectric body that changes according to the pressure is detected by the vibration detecting unit. A pressure detecting device for calculating the pressure by the pressure calculating means based on an output signal of the vibration detecting means.

According to the present invention, when pressure is applied to the planar piezoelectric body, the vibration detecting means calculates the vibration characteristic of the planar piezoelectric body which changes according to the pressure. Level can be detected.

[0011]

According to a first aspect of the present invention, there is provided a pressure detecting device comprising: a vibration generating means provided at one end of a planar piezoelectric body; A vibration detecting unit provided in the unit, a vibration characteristic controlling unit provided at the other end of the planar piezoelectric body, and a pressure calculating unit for calculating a pressure applied to the planar piezoelectric body; Means for vibrating the one end of the planar piezoelectric body,
When pressure is applied to the planar piezoelectric body, vibration characteristics of the planar piezoelectric body that change according to the pressure are detected by the vibration detecting unit, and the pressure is determined based on an output signal of the vibration detecting unit. It is calculated by the calculation means.

When the pressure is applied to the planar piezoelectric body, the vibration detecting means calculates the vibration characteristic of the planar piezoelectric body which changes in accordance with the pressure. can do.

According to a second aspect of the present invention, there is provided a pressure detecting device, wherein the vibration generating means is formed on one end of the planar piezoelectric body and on both surfaces thereof, and comprises vibration generating electrode films opposed to each other. It is composed of a vibration detecting electrode film formed on an intermediate portion of the planar piezoelectric body and on both surfaces thereof and facing each other.

Since both the vibration generating means and the vibration detecting means are composed of electrode films opposed to each other via the planar piezoelectric body, the vibration can be efficiently generated in the planar vibration body and the planar vibration body can be efficiently generated. Can be efficiently generated as a detection voltage.

In the pressure detecting device according to a third aspect of the present invention, the vibration characteristic control means is constituted by a part of the planar piezoelectric body.

Since a material different from the planar piezoelectric material is not used for the vibration characteristic control means, the pressure detecting device can be configured with a simple configuration. In the pressure detecting device according to a fourth aspect of the present invention, the vibration detecting means is provided with a length of the planar piezoelectric body (0.4 to 0.4).
0.6).

When the planar piezoelectric body is vibrated, the largest strain is generated at the center in the length direction, and the strain is attenuated toward both ends. Therefore, since the vibration detecting means is disposed near the center of the length of the planar piezoelectric body, a large detection voltage can be obtained.

The pressure detecting device according to claim 5 of the present invention applies pressure to the vibration characteristic control means.

Even when pressure is applied to the vibration characteristic control means, no pressure is applied to the vibration generation means and the vibration detection means, so that stable vibration can be generated and detected.

In the pressure detecting device according to claim 6 of the present invention, at least one of the amplitude of vibration and the resonance frequency is used as the vibration characteristic.

When the amplitude of the vibration is used as the vibration characteristic, the sensitivity to the applied pressure and the weight is large.
When the resonance frequency of the vibration is used, there is an advantage that it is hardly affected by the fluctuation of the detection voltage.

According to a seventh aspect of the present invention, there is provided a pressure detecting device comprising a common electrode film which functions as both a vibration generating electrode and a vibration detecting electrode on one surface of a planar piezoelectric body.

The common electrode film is used as one of the vibration generation electrode films and also as one of the vibration detection electrode films. That is, since the electrode film is common to both vibration generation and vibration detection, not only can the electrode film configuration be simplified, but also the number of lead wires can be reduced.

The pressure detecting device according to claim 8 of the present invention is provided with a plurality of vibration detecting means.

Since a plurality of detection signals can be used, highly reliable pressure detection can be performed. Claim 9 of the present invention
The pressure detecting device according to (1) applies pressure to both at least one of the plurality of vibration detecting means and the vibration characteristic control means.

Since no pressure is applied to the vibration generating means and no pressure is applied to the other vibration detecting means, stable vibration can be generated and detected. Further, since the pressure applied state can be detected by the vibration detecting means to which the pressure is applied, the detection signal obtained by the other vibration detecting means can be corrected according to the pressure applied state.

[0027] In the pressure detecting device according to claim 10 of the present invention, the electromechanical coupling coefficient of the planar piezoelectric body is maximum in the direction from the vibration generating means to the vibration detecting means.

The vibration generated by the vibration generating means is
Since the maximum value is obtained in the direction toward the vibration detecting means, a large detection signal is obtained by the vibration detecting means.

A pressure detecting device according to claim 11 of the present invention comprises a first filtering section for separating only a vibration frequency component generated by the vibration generating means from an output signal of the vibration detecting means, and an output signal of the vibration detecting means. A second filtering unit that separates components other than the vibration frequency from the above, calculates the pressure applied to the planar piezoelectric body based on the separated components, and calculates the vibration applied to the planar piezoelectric body. Detects vibration components other than frequency.

The pressure applied to the planar piezoelectric body is calculated based on the output signal of the first filtering section, and the pressure applied to the planar piezoelectric body is calculated based on the output signal of the second filtering section. Since a vibration component other than the vibration frequency is detected, pressure and vibration, that is, both static pressure and dynamic pressure can be simultaneously detected using one planar piezoelectric body.

[0031]

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

(Embodiment 1) FIG. 1 is a sectional view showing the structure of a pressure detecting device according to Embodiment 1 of the present invention. Planar piezoelectric body 11
The electrodes 12a and 12b are formed on both surfaces at one end of the.
Further, the electrodes 13a and 13b are formed at the intermediate portions on both sides of the planar piezoelectric element 11. Further, the planar piezoelectric body 11 extends from the middle portion of the planar piezoelectric body 11 to the other end. Electrode 12
a and 12b are connected to the signal generator 14 and
Pressure calculating means 15 is connected to 3a and 13b, respectively. The vibration generating means 12 includes electrodes 12a and 12b facing each other.
And a portion of the planar piezoelectric body 11a sandwiched between these electrodes.
It is composed of The vibration detecting means 13 includes electrodes 13a and 13b facing each other and a planar piezoelectric body 11c at a portion sandwiched between these electrodes. Electrode 1
The electrodes 2a and 12b and the electrodes 13a and 13b need not necessarily face each other. However, as will be described later, when an oscillation signal generated by the signal generator 14 is applied to the planar piezoelectric body 11a between the electrodes, the electrodes 12a and 12b facing each other exert a maximum electric field strength on the planar piezoelectric body 11a. The vibration can be generated in the planar piezoelectric body 11 more efficiently. Further, electrodes 13a and 13b facing each other
Can efficiently generate distortion generated in the planar piezoelectric body 11c as a detection voltage.

The planar piezoelectric body 11b separates the vibration generating means 12 and the vibration detecting means 13 from each other. Further, the vibration characteristic control means 16 is composed of a planar piezoelectric body 11d from the intermediate portion to the other end of the planar piezoelectric body 11.
However, the vibration characteristic control means 16 may be made of a material different from that of the planar piezoelectric body 11. However, in this case, since the vibration characteristic control means 16 must be continuously connected to the vibration detection means 13, the configuration becomes complicated, and a connection operation is also required. In this regard, the vibration characteristic control means 16
It is preferable to use the planar piezoelectric body 11d because it has a simpler configuration and connection work is unnecessary.

As the sheet-like piezoelectric member 11, for example, a film-like polymer piezoelectric material such as polyvinylidene fluoride (PVDF), a mixture of resin and piezoelectric ceramic powder, and a piezoelectric ceramic are used. Electrodes 12a, 12b,
13a and 13b are formed by printing and baking a silver paste, for example, but may be formed by using a copper foil or by evaporating a metal material such as aluminum.

Next, the operation and operation will be described. The vibration generating means 12 responds to the oscillating signal generated by the signal generating section 14 to produce a planar piezoelectric body 11a sandwiched between the electrodes 12a and 12b.
Parts vibrate. Here, the frequency of the oscillation signal is f ₁
And This vibration is caused by the electrodes 12a, 12b, 13a, 1
The vibration detecting means 1 passes through a portion of the polymer piezoelectric body 11b (hereinafter simply referred to as a separating means 11b) on which no 3b is formed.
3 and the vibration characteristic control means 16 to vibrate with a certain characteristic. The vibration detecting means 13 generates a piezoelectric electromotive force (detection voltage) according to the vibration. Vibration of the entire planar piezoelectric body 11 depends significantly to the frequency f ₁ of the oscillation signal. When the frequency f _{1 of the} oscillation signal is changed from a low frequency to a high frequency, the vibration detecting means 13
The frequency at which the detection voltage (the signal obtained between the electrodes 13a and 13b) detected at the first time shows a local maximum is defined as the first resonance frequency. Even at a frequency higher than the first resonance frequency, a higher-order resonance frequency is observed. Planar piezoelectric body 11
When no pressure or weight is applied to the
The resonance frequency is determined substantially depending on the length L (FIG. 1) of the planar piezoelectric body 11 and the speed of sound. At that time, the strain and stress of the planar piezoelectric body 11 are maximum at the center of the planar piezoelectric body 11. become. The vibration characteristic control means 16 is composed of only the planar piezoelectric body 11d and has no electrodes. However, as described above, the vibration characteristic can be controlled in that it governs the resonance characteristic.

When no pressure is applied to the planar piezoelectric body 11,
FIG. 2 shows an example of the relationship between the first resonance frequency and the length L of the planar piezoelectric body 11. A PVDF film (about 28 μm in thickness and about 20 mm in width) is used as the planar piezoelectric element 11, and the length of the electrode films 12 a and 12 b of the vibration generating means 12 is 20 mm (constant).
Assuming that the length of the separation part 11b is 1 mm (constant) and the length of the electrode films 13a and 13b of the vibration detecting means 13 is 3 mm (constant), the length of the vibration characteristic control means 16 is changed between (0 to 16) mm. Therefore, the length L of the planar piezoelectric body 11 is changed from (24 to 4
0) mm, the first resonance frequency was measured.
From the figure, the first resonance frequency shows a good linear relationship with 1 / L, and its slope shows 691 m / s.
It was about 1/2 of the sound speed (about 1.4 km / s). Thus, the first resonance frequency is substantially equal to the length L of the planar piezoelectric body 11.
It is clear that it depends on the sound speed.

When no pressure is applied to the planar piezoelectric body 11, the position of the vibration detecting means 13 and the effective value of the detected voltage [E
s (rms)] is shown in FIG. A PVDF film (about 28 μm in thickness, about 20 mm in width, and 40 mm in length) is used as the planar piezoelectric body 11, the length of the electrode films 12 a and 12 b of the vibration generating means 12 is 20 mm (constant), and the separation section 11 b
1 mm (constant), electrode film 13 of vibration detecting means 13
a, 13b 3 mm (constant) in length, and a second separation part 1 mm (constant) in length from the vibration detecting means 13 and 3 mm in length
By repeatedly providing (constant) second vibration detecting means, a total of five vibration detecting means are formed, and the effective voltage 2 from the signal generating unit 14 at the first resonance frequency (about 17.3 kHz).
0 V is supplied to vibrate the planar piezoelectric body 11. Each detection voltage of the five vibration detecting means was measured. Vibration generating means 12
Is the distance from the edge of the center of the electrode of the vibration detecting means to L.
e, assuming that the length of the planar piezoelectric body 11 is L (40 mm), the positions of the five vibration detecting means are indicated by Le / L. As is clear from FIG. 3, the vibration detecting means 13 is disposed near the center of the planar piezoelectric body 11 and the length L of the planar piezoelectric body 11 (from 0.4 to 0.
6), the vibration generating means 12 is provided at one end of the planar piezoelectric body 11 and the vibration characteristic controlling means 16 is provided at the other end.
Is preferably arranged. In the vicinity of the first resonance frequency, larger strains and stresses are shown than at other frequencies, and even at that frequency, the strains and stresses vary depending on the position of the planar piezoelectric body 11, become larger at the center, and become smaller toward both ends. . Therefore, the strain and stress of the planar piezoelectric body 11 increase near the center of the planar piezoelectric body 11, so that a large detection voltage can be obtained. When pressure or weight is applied to one or more of the vibration generating means 12, the vibration detecting means 13, the separating section 11b, and the vibration characteristic control means 16, a detection voltage is obtained according to each of them. It is preferable to apply pressure or weight to the characteristic control means 16. When pressure or weight is applied to the vibration generating means 12, the vibration detecting means 13, etc., the electrodes 12a, 12b, 13a, 13b
Pressure or weight is applied through the electrodes. At this time, since strain and stress are generated in the planar piezoelectric body 11,
Strain and stress are also generated at the interface between a, 12b, 13a, 13b and the planar piezoelectric body 11 in the state where pressure or weight is applied. As described above, the planar piezoelectric body 11 has the heavy electrodes 12a and 12a.
Since b and 13a and 13b are dragged to generate strain and stress, the adhesive strength between the two tends to decrease. The separating part 11b and the vibration characteristic control means 16 are constituted only by the planar piezoelectric body 11c,
Since there is no electrode, even if pressure or weight is applied, the above-described decrease in adhesive strength does not occur. Above all, the vibration characteristic control means 16 is superior to the separating portion 11b in that a large area is easily obtained, and that the three-terminal electrode configuration described later does not have an electrode.

FIG. 4 shows an example of the frequency characteristic of the detected voltage near the first resonance frequency when a weight is applied to the vibration characteristic control means 16. . PVD as the planar piezoelectric body 11
Using an F film (about 52 μm in thickness and about 40 mm in width), the length of the electrode films 12 a and 12 b of the vibration generating means 12 is 20 mm
(Constant), 2 mm (constant) length of the separation part 11b, 8 mm (constant) length of the electrode films 13a and 13b of the vibration detecting means 13,
Assuming that the length of the vibration characteristic control means 14 is 25 mm (constant),
An effective voltage of 20 V from the signal generation unit 14 to the vibration generation means 12
And the weight is added to the vibration characteristic control means 14 (0 to 11).
The same frequency characteristic was measured by applying kg. As is clear from the figure, the resonance characteristics change depending on the applied weight. That is, the first resonance frequency is about 1 when a weight of 1 kg is applied.
From 1.4 kHz, it increases as the weight increases, and the weight 11
It increased to about 13.2 kHz when kg was applied. As is clear from this, for example, if the weight is 1 kg or more, the weight can be detected by the resonance frequency. Weight detection using the resonance frequency is low in sensitivity to weight, but is excellent in that it is not affected by fluctuations in the detection voltage due to fluctuations in the signal voltage supplied from the signal generation unit 14. At this time, it is clear that a resonance frequency detecting means may be used as the vibration detecting means 13.

FIG. 5 shows a frequency f = 13.7 kHz.
FIG. 4 is a characteristic diagram in which a relationship between weight and detection voltage is plotted in a range of 1 kg or more as (constant). As is clear from the figure, weight detection can be performed with high sensitivity by the detection voltage. In this case, as is clear from FIG. 4, for example, if the weight detection range is 1 kg to 5 kg, the frequency is set to 1
By measuring around 2.6 kHz, weight can be detected with even higher sensitivity. As described above, the weight detection using the detection voltage is excellent in that the sensitivity can be selected according to a required weight range. At this time, it is clear that the amplitude detection means of the detection voltage may be used as the vibration detection means 13.

(Embodiment 2) FIG. 6 is a sectional view showing the structure of a pressure detecting device according to Embodiment 2 of the present invention. In this embodiment,
It differs from the first embodiment in the following points. That is, one of the electrodes 12a constituting the vibration generating means 12 and one electrode 13a constituting the vibration detecting means 13 shown in the first embodiment are connected on the same surface of the planar piezoelectric body 11. . The common electrode 17 connected to both functions as both an electrode constituting the vibration generating means 12 and an electrode constituting the vibration detecting means 12 in common. In this case, for example, in the first embodiment, four lead wires are required to be connected to the signal generating unit 14 and the pressure calculating means 15 from each electrode, whereas in the present embodiment, three lead wires are required. The book is excellent in that it is sufficient.

Although the above description has been made with reference to the cross-sectional view (FIG. 6), FIG. 7 shows a plan view as seen from the arrow 18 shown in FIG. The connection between one electrode 12a forming the vibration generating means 12 and one electrode 13a forming the vibration detecting means 13 on one surface of the planar piezoelectric body 11 shown in FIG. 7) may cover the entire surface of the planar piezoelectric body 11 or may be partially connected as shown in FIG. 7 (b). The position of the partial connection is also determined by the planar piezoelectric body 1.
1 may be a central part or an end part.

(Embodiment 3) FIG. 8 is a block diagram of a pressure detecting device according to Embodiment 3 of the present invention.

The difference from the first and second embodiments is that a plurality of detecting means 131 and 132 are provided. First detecting means 13
1 denotes a common electrode 17, a planar piezoelectric body 11c, and an electrode 131b.
The detection voltage generated by the first detection means 131 is input to the first pressure calculation means 151. Also, the second
The detecting means 132 includes the common electrode 17, the planar piezoelectric body 11e, and the electrode 132b, and the detection voltage generated by the second detecting means 132 is input to the second pressure calculating means 152. In addition, using only one of the pressure calculation means,
Obviously, the detection voltage generated by the first detection means 131 and the detection voltage generated by the second detection means 132 may be alternately input at appropriate time intervals.

When the entire surface of the planar piezoelectric body 11 vibrates with certain characteristics in response to the oscillation signal generated by the signal generating section 14, the vibration detecting means 131 and 132 perform different detections according to the vibration. Voltage is generated. In the present embodiment, since a plurality of detection signals can be used, for example, even if a local disconnection occurs when the detection voltage generated by the first detection unit 131 is detected, the second detection unit 1
There is an advantage that the detection voltage generated at 32 can be used. That is, there is an advantage that the reliability with respect to disconnection is high.

Further, by applying pressure or weight to both the electrode 132b of the second detection means 132 and the vibration characteristic control means 16, for example, the following advantages can be obtained.
FIG. 9 shows the effective value [E _{s1 (rms)} ] of the detection voltage generated by the first detection means 131 and the detection voltage of the detection voltage generated by the second detection means 132, starting from the time when a weight of 1 kg is applied to both of them. Change of the effective value [E _{s2 (rms)} ] with respect to the elapsed time,
FIG. 7 is a diagram showing a change in elapsed time of a ratio [E _{s1 ( rms)} / E _{s2 (rms)} ] of the two. Effective value E of detection voltage
_{s1 (rms)} and _{Es2 (rms)} changed about 13% and about 14%, respectively, after about 300 minutes. However, the ratio [E _{s1 (rms)} / E _{s2 (rms)} ] of the two was extremely stable, and showed a change of ± 1.5% or less within the same time. Therefore, by using the ratio of the two as a signal, there is obtained an advantage that time instability of the detection voltage can be eliminated.

When an oscillating signal generated by the signal generating section 14 is applied to the vibration generating means 12 to vibrate the planar piezoelectric body 11, the electric energy applied to the vibration generating means 12 is converted into vibration energy. What proportion? It is generally defined as an electromechanical coupling coefficient. The electromechanical coupling coefficient differs depending on the crystal direction of the planar piezoelectric body 11. Therefore, it is desirable to select the direction of the planar vibrating body 11 so that the electromechanical coupling coefficient becomes maximum in the direction from the vibration generating means 12 to the vibration detecting means 13. This is because the detection voltage generated by the vibration detection means 13 can be increased.

(Embodiment 4) FIG. 10 is a block diagram of a pressure detecting device according to Embodiment 4 of the present invention. The difference from the first embodiment is that the pressure calculation means 15 separates only the component of the vibration frequency generated by the vibration generation means 12 from the detection voltage of the vibration detection means 13, and the detection of the vibration detection means 13 A second filtering unit 15b for separating components other than the vibration frequency generated by the vibration generating means 12 from the voltage, and electrodes 12a, 12b, 13a, and 13b based on the separated components.
And a calculating unit 15c that calculates the pressure applied to the planar piezoelectric body 11 including the above and detects a vibration component other than the vibration frequency applied to the planar vibrating body 11.

The first filtering section 15a and the second filtering section 15b
Are band-pass filters, and the center frequencies of the transmission characteristics are f ₁ and f ₂ , respectively. The frequency of the signal generated by the signal generator 14 is f _1. The components having the same reference numerals as those in the first embodiment have the same structure, and a description thereof will be omitted.

Next, the operation and operation will be described. Here, a case where an object having a weight W is placed on the vibration characteristic control means 16 will be described. The object is applied with a vibration of frequency f ₂ from the outside, or has a vibration body of frequency f ₂ inside,
Whole object is assumed to vibrate at a frequency f _2. As in the first embodiment, the vibration generation unit 12 includes the signal generation unit 14
The planar piezoelectric body 11 vibrates according to the oscillation signal generated in the step (1). The frequency of the oscillation signal is f _1. The more the vibration of the frequency f ₂ of the vibration and the object of the frequency f ₁ by the vibration generating means 12 are combined, the electrodes 12a, 12b, 13
The entire planar vibrator 11 including a and 13b vibrates with certain characteristics. Then, according to the vibration, the vibration detecting means 1
In No. 3, a detection voltage is generated. The generated detection voltage is filtered by the first filtering unit 15a and the second filtering unit 15b based on the filtering characteristics. That, f ₁ component of the detection voltage of the first filter portion 15a in the vibration detecting means 13 is filtered, second
F ₂ components are filtered out of the detection voltage of the filter section 15b in the vibration detecting means 13.

At this time, the oscillation signal V of the signal generator 14₀,
Output V of first filtering section 15a₁Of the second filtering unit 15b
Output V_Two11 (a) and 11 (b) respectively.
Become like As shown in FIG.
State (t <t₁), V₁And V_TwoThe amplitude of it
Each D₀And 0. And time t₁The object 19 is a laminate
13 and put on V₁And V_TwoThe amplitude of D₁And D_Two
Changes to The calculating unit 15c calculates the actual weight of the object.
It is calculated in the same manner as in the first embodiment. Object frequency f _TwoShake
For example, the calculation unit 15c calculates the amplitude D_TwoLarge
The magnitude of the vibration is calculated by detecting the magnitude.

By the above operation, the pressure calculating means 15 separates only the component of the vibration frequency generated by the vibration generating means 12 from the voltage detected by the vibration detecting means 13.
a from the detected voltage of the vibration detecting means 13
And a second filtering unit 15b for separating components other than the vibration frequency generated by the second filter unit 2. The weight and pressure applied to the vibration generating means 12 are calculated based on the output signal of the first filtering unit 15a. Since the vibration component other than the vibration frequency applied to the object is detected based on the output signal of the second filtering unit 15b,
Using the planar vibrating body 11 including the electrodes 12a, 12b, 13a, and 13b, it is possible to simultaneously detect pressure and vibration, that is, both static pressure and dynamic pressure.

Also, the weight and the distortion were detected at the same time,
When the vibration generating means 12 is generating vibration, the pressure applied to the vibration generating means 12 is calculated, and when the vibration generating means 11 is not generating vibration, the pressure is generated in the vibration generating means 12 and the vibration detecting means 13. The vibration may be calculated. Similarly to the above, both the pressure and the vibration using the planar vibrator 11 including the electrodes 12a, 12b, 13a, and 13b, that is, both the static pressure and the dynamic pressure are used. Can be detected simultaneously.

[0053]

As described above, in the pressure detecting device according to the first aspect of the present invention, pressure and weight are applied to one planar vibrator in which vibration generating means, vibration detecting means and vibration characteristic controlling means are integrated. Then, since the vibration characteristic of the planar vibrating body, which changes according to the pressure and the weight, is calculated by the vibration detecting means, the pressure level can be detected with a simple configuration.

In the pressure detecting device according to the second aspect of the present invention, the vibration generating means is formed of one end of the planar piezoelectric body and both sides thereof, and comprises vibration generating electrode films opposed to each other. Since the means is formed on the intermediate portion of the planar piezoelectric body and on both surfaces thereof and is constituted by the vibration detecting electrode films facing each other, efficient vibration generation and vibration detection can be performed.

Further, in the pressure detecting device according to claim 3 of the present invention, the vibration characteristic control means is constituted by a part of the planar piezoelectric body and does not use a material different from the planar piezoelectric body.
The pressure detection device can be configured with a simple configuration.

Further, in the pressure detecting device according to the fourth aspect of the present invention, the vibration detecting means is provided with a length of (0.4) of the planar piezoelectric body.
To 0.6), a large detection voltage can be obtained. This is because, when the planar piezoelectric body is vibrated, the largest strain is generated in the central portion in the length direction, and the strain is attenuated toward both ends.

In the pressure detecting device according to the fifth aspect of the present invention, since the pressure is applied to the vibration characteristic control means, even when the pressure is applied to the vibration characteristic control means, the vibration generation means and the vibration detection means are provided. Since no pressure is applied to the pressure sensor, stable generation and detection of vibration can be performed. In addition, in the pressure detection device according to claim 6 of the present invention, at least one of vibration amplitude and resonance frequency is used as the vibration characteristic. When the amplitude of the vibration is used as the vibration characteristic, there is an advantage that the sensitivity to the applied pressure and weight is large, and when the resonance frequency of the vibration is used, there is an advantage that the detection voltage is hardly affected.

In the pressure detecting device according to claim 7 of the present invention, a common electrode film which functions as both a vibration generation electrode and a vibration detection electrode is provided on one surface of the planar piezoelectric body. Not only the structure of the electrode film can be simplified, but also the number of lead wires can be reduced.

In the pressure detecting device according to claim 8 of the present invention, since a plurality of vibration detecting means are provided,
Highly reliable pressure detection is possible.

In the pressure detecting device according to the ninth aspect of the present invention, since pressure is applied to at least one of the plurality of vibration detecting means and the vibration characteristic control means, stable vibration can be obtained. Since the pressure can be generated and detected, and the pressure applied state can be detected by the vibration detecting means to which the pressure is applied, the detection signal obtained by the other vibration detecting means can be corrected according to the pressure applied state.

In the pressure detecting device according to the tenth aspect of the present invention, the electromechanical coupling coefficient of the planar piezoelectric member is maximum in the direction from the vibration generating means to the vibration detecting means. Obtained by detection means.

Further, in the pressure detecting device according to claim 11 of the present invention, a first filtering section for separating only a vibration frequency component generated by the vibration generating means from an output signal of the vibration detecting means, A second filtering unit that separates components other than the vibration frequency from the output signal, calculates a pressure applied to the planar piezoelectric body based on the separated components, and applies the pressure to the planar piezoelectric body. Since a vibration component other than the vibration frequency is detected, pressure and vibration, that is, both static pressure and dynamic pressure can be simultaneously detected using one planar piezoelectric body.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pressure detection device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a length of a planar piezoelectric body and a first resonance frequency of the device.

FIG. 3 is a characteristic diagram showing a relationship between a position of a vibration detecting unit of the apparatus and a detected voltage.

FIG. 4 is a characteristic diagram showing a relationship between a frequency and a detection voltage of the device.

FIG. 5 is a characteristic diagram showing the relationship between the weight of the device and the detected voltage.

FIG. 6 is another configuration diagram of the pressure detection device according to the second embodiment of the present invention.

FIG. 7A is a configuration diagram of a pressure detection device having the same surface-shaped piezoelectric material on the entire surface. FIG.

FIG. 8 is a configuration diagram of a pressure detection device according to a third embodiment of the present invention.

FIG. 9 is a characteristic diagram showing a time dependency of a detection voltage generated by a first detection unit, a detection voltage generated by a second detection unit, and a ratio between the two.

FIG. 10 is another configuration diagram of the pressure detection device according to the fourth embodiment of the present invention.

[11] (a) characteristic diagram showing a filtering characteristic of the first filter section and the second filter section of a vibration waveform of a frequency f ₁ (b) the apparatus of the device

FIG. 12 is a block diagram of a conventional pressure detecting device (conventional example 1).

FIG. 13 is a characteristic diagram showing a relationship among a contact position L of an object, a frequency f of a voltage applied to a transmitter, and an output signal V of a piezoelectric film in the device.

FIG. 14 is an external view of a conventional pressure detecting device (conventional example 2).

FIG. 15 is a schematic view showing a state when the insulating protective film is touched with a finger in the device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Planar piezoelectric body 12 Vibration generating means 12a, 12b electrode 13 Vibration detecting means 13a, 13b electrode 14 Signal generating part 15 Pressure calculating means 15a First filtering part 15b Second filtering part 16 Vibration characteristic control means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuhiko Yamamoto, Inventor 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Takahiro Umeda 1006 Odaka Kadoma, Kadoma City, Osaka Matsushita Electric Industrial F Terms (reference) 2F055 AA40 BB11 CC53 CC55 DD09 DD11 EE23 FF43 GG11 GG47

Claims (11)

[Claims] A vibration generating means provided at one end of the planar piezoelectric body; a vibration detecting means provided separately from the vibration generating means at an intermediate portion of the planar piezoelectric body; Vibration characteristic control means provided at the other end of the sheet, pressure calculation means for calculating the pressure applied to the planar piezoelectric body, the vibration generating means vibrates the one end of the planar piezoelectric body, When a pressure is applied to the planar piezoelectric body, vibration characteristics of the planar piezoelectric body that change according to the pressure are detected by the vibration detecting unit, and the pressure is calculated based on an output signal of the vibration detecting unit. Pressure detecting device calculated by means. 2. A vibration generating means is formed on one end of a planar piezoelectric body and on both sides thereof, and is constituted by vibration generating electrode films opposed to each other. The vibration detecting means is provided on an intermediate portion of the planar piezoelectric body and on both sides thereof. The pressure detecting device according to claim 1, wherein the pressure detecting device is formed of vibration detection electrode films that are formed and face each other. 3. The pressure detecting device according to claim 1, wherein the vibration characteristic control means is constituted by a part of a planar piezoelectric body. 4. The method according to claim 1, wherein the vibration detecting means has a length of (0.
3. The pressure detecting device according to claim 2, wherein the pressure detecting device is arranged at a position of 4 to 0.6). 5. The pressure detecting device according to claim 3, wherein a pressure is applied to the vibration characteristic control means. 6. The pressure detecting device according to claim 1, wherein the vibration characteristic is at least one of an amplitude of vibration and a resonance frequency. 7. The pressure detecting device according to claim 1, wherein a common electrode film that functions as both a vibration generating electrode and a vibration detecting electrode is provided on one surface of the planar piezoelectric body. 8. The pressure detecting device according to claim 1, wherein a plurality of vibration detecting means are provided. 9. The pressure detecting device according to claim 8, wherein a pressure is applied to at least one of the plurality of vibration detecting means and the vibration characteristic control means. 10. The pressure detecting device according to claim 1, wherein an electromechanical coupling coefficient of the planar piezoelectric body is maximum in a direction from the vibration generating means to the vibration detecting means. 11. A first filter for separating only a vibration frequency component generated by a vibration generator from an output signal of the vibration detector, a pressure calculator comprising: a first filter for separating a frequency other than the vibration frequency from an output signal of the vibration detector; A second filtering section for separating the components, calculating the pressure applied to the planar piezoelectric body based on the separated components, and calculating the vibration components other than the vibration frequency applied to the planar vibration body. The pressure detecting device according to claim 1, wherein the pressure is detected.