JP2002135894A - Ultrasonic sensor and electronic device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which is waterproof, moisture-proof, and airtight and improves the sensitivity and reverberation characteristics. SOLUTION: One principal face 101 of an acoustic matching layer 10 has an edge part 61 fixed to the upper end face of a cylindrical case 50, and the other principal face 102 of the acoustic matching layer 10 is covered with a first waterproof material 30, and a side face 103 of the acoustic matching layer 10 is covered with a second waterproof material 40, and the second waterproof material 40 is joined to the first waterproof material 30 without a gap in a vicinity 61 of the edge part of the other principal face 102 of the acoustic matching layer 10 and is joined to a case 50 without a gap on a side face 63 of the case 50. Consequently, the first very thin waterproof material can be easily provided on the other principal face of the acoustic matching layer to realize efficient work and cost reduction. Since a node of the acoustic matching layer can be bound by highly rigid waterproof materials, the ultrasonic sensor having satisfactory sensitivity and reverberation characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ultrasonic sensor and an electronic device using the same, for example, an ultrasonic sensor for measuring a gas flow rate by transmitting and receiving ultrasonic waves, and an electronic device using the same.

[0002]

2. Description of the Related Art Generally, in a high frequency type ultrasonic sensor, an ultrasonic sensor in which a vibrating surface of a vibrator is joined to one principal surface of an acoustic matching layer and an ultrasonic wave is transmitted / received from the other principal surface of the acoustic matching layer is often used. Are known. It is known that an ultrasonic sensor having such a configuration can transmit and receive ultrasonic waves efficiently by setting the acoustic impedance of the acoustic matching layer to a value between the impedance of air and the impedance of the vibrator. I have.

It is known that in an ultrasonic sensor, in order to transmit and receive ultrasonic waves with high sensitivity, it is only necessary to lower the density of the acoustic matching layer. However, when the density of the acoustic matching layer is reduced, many voids are generated inside the acoustic matching layer, and the acoustic matching layer does not have waterproofness and moisture resistance. Since the ultrasonic sensor is sometimes used in a humid environment, when the acoustic matching layer is reduced in density, it is necessary to cover the acoustic matching layer with a waterproof and moisture-resistant coating.

In an ultrasonic sensor for measuring the flow rate of a flammable fluid such as gas, it is necessary to ensure the airtightness of the piezoelectric element so that sparks generated from the piezoelectric element do not ignite the fluid. In this case, it is necessary to cover the acoustic matching layer with an airtight coating.

FIG. 6 shows a conventional ultrasonic sensor. FIG.
The ultrasonic sensor 9a includes a disk-shaped piezoelectric body 20 as a vibrator, a columnar acoustic matching layer 10, a cylindrical case 50, and a metal cap 70. In the ultrasonic sensor 9a, one main surface 101 of the acoustic matching layer 10
Of the piezoelectric body 20 is fixed to the vibrating surface of the piezoelectric body 20, and the edge 6
1 is fixed to the upper end surface of the case 50. Metal cap 7
Numeral 0 is provided so as to cover the acoustic matching layer 10, and the vicinity of the end on the opening side is fixed to the side surface 63 near the upper end of the case 50.

[0006] In the ultrasonic sensor 9a having such a configuration, the acoustic matching layer 10 is formed on the edge 6 of the one main surface 101 thereof.
Only the neighborhood of 1 is restricted. Then, the acoustic matching layer 10
Is one main surface 1
01 vibrate so that the vicinity of the edge 61 becomes the node N1.

In the ultrasonic sensor 9a having such a configuration, even when the acoustic matching layer 10 has a low density, since the acoustic matching layer 10 is covered with the metal cap 70, waterproofness, moisture resistance, The airtightness can be improved.

FIG. 7 shows another conventional ultrasonic sensor.
7, the same or equivalent parts as those of the ultrasonic sensor 9a shown in FIG. 6 are denoted by the same reference numerals, and the description will be omitted.

In FIG. 7, the ultrasonic sensor 9b has a disk-shaped piezoelectric body 20, a columnar acoustic matching layer 10, a case 52, and an extremely thin resin 71. The acoustic matching layer 10 of the ultrasonic sensor 9b has
And the other main surface 102 is covered with the resin 71. The case 52 and the resin 71 are joined without any gap.

In the ultrasonic sensor 9b having such a configuration, the side surface 103 of the acoustic matching layer 10
Is bound by The acoustic matching layer 10 oscillates by the vibration propagated from the piezoelectric body 20 such that the entire side surface 103 of the acoustic matching layer 10 becomes the node N3.

In the ultrasonic sensor 9b having such a configuration, even when the acoustic matching layer 10 is reduced in density, the acoustic matching layer is covered with the resin 71 and the case 52, so that the ultrasonic sensor 9b has waterproofness and moisture resistance. Performance can be improved.

[0012]

In the conventional ultrasonic sensor 9a shown in FIG. 6, since the acoustic matching layer 10 is covered by the case 50, the ultrasonic sensor 9a has a waterproof property and a moisture resistance property.
The airtightness can be improved.

However, the acoustic matching layer 1 of the ultrasonic sensor 9a
In the case where the thickness of the metal cap 70 is not sufficiently small in the vicinity of the other main surface 102 of 0, vibration on the other main surface 102 of the acoustic matching layer 10 is hindered, and the sensitivity as an ultrasonic sensor decreases, There is a problem that reverberation characteristics deteriorate.

The metal cap 70 is formed by metal drawing, and the acoustic matching layer 1 is formed by metal drawing.
It is extremely difficult to work to a thickness that does not hinder the vibration of zero, and there is a problem that work efficiency and cost cannot be reduced. In addition to the metal drawing process, the cap can be formed by resin injection molding. However, it is extremely difficult to process the acoustic matching layer 10 to a thickness that does not hinder the vibration by the resin injection molding. There is a problem that efficiency and cost reduction cannot be achieved.

Although not shown, the metal cap 7
Instead of 0, the other main surface 102 and the side surface 103 of the acoustic matching layer 10 may be hardened after a resin or the like is applied without leaving any gap, thereby improving the waterproofness and moisture resistance of the ultrasonic sensor. However, in this method, the resin is
It is necessary to apply a sufficiently thick resin in consideration of soaking into the resin. Therefore, in the vicinity of the other main surface 102 of the acoustic matching layer 10, the thickness of the resin is increased, the vibration of the acoustic matching layer 10 is hindered, and the sensitivity as an ultrasonic sensor is reduced, and the reverberation characteristics are deteriorated.

The conventional ultrasonic sensor 9 shown in FIG.
In b, since the resin 71 is extremely thin, the vibration of the acoustic matching layer 10 is not hindered by the resin 71.

However, since the entire side surface 103 of the acoustic matching layer 10 is constrained, free vibration of the acoustic matching layer 10 is hindered, which lowers the sensitivity as an ultrasonic sensor and deteriorates reverberation characteristics. There is.

Accordingly, the present invention provides an ultrasonic sensor which has waterproofness, moisture resistance, and airtightness, can improve sensitivity and reverberation characteristics, and can achieve work efficiency and cost reduction. With the goal.

Another object of the present invention is to provide an electronic device which can achieve high precision and low cost.

[0020]

In order to achieve the above object, an ultrasonic sensor according to the present invention has a vibrating surface of a vibrator fixed to a central portion of one main surface, and transmits and receives ultrasonic waves from the other main surface. An ultrasonic sensor having an acoustic matching layer formed as described above, wherein only the vicinity of an edge of one main surface and the other main surface of the acoustic matching layer is restricted.

Further, the ultrasonic sensor according to the present invention is an ultrasonic sensor having an acoustic matching layer to which a vibrating surface of a vibrator is fixed near a central portion of one main surface and an ultrasonic wave is transmitted and received from the other main surface. An edge of one main surface of the acoustic matching layer is fixed to an upper end surface of a cylindrical case, and the other main surface of the acoustic matching layer is closely bonded to a first waterproof material, and a side surface of the acoustic matching layer is provided. Is covered with a second waterproof material, and an upper end of the second waterproof material is tightly joined to the first waterproof material near an edge of the other main surface of the acoustic matching layer, and the second waterproof material is The lower end of the material is closely joined to the case on the side surface of the case.

Further, in the ultrasonic sensor according to the present invention, the first waterproof material has a small rigidity so as not to hinder the vibration of the other main surface of the acoustic matching layer, and the second waterproof material is The acoustic matching layer has a rigidity large enough to restrain the node on the other main surface.

Further, the ultrasonic sensor according to the present invention is characterized in that the second waterproof material has higher rigidity than the first waterproof material.

Further, the ultrasonic sensor according to the present invention is characterized in that the acoustic matching layer has an airtight and waterproof structure by the first waterproof material, the second waterproof material, and the case.

The ultrasonic sensor according to the present invention is characterized in that the first waterproof material has a thickness of 30 μm or less.

The electronic device according to the present invention includes the ultrasonic sensor, a driving circuit for vibrating the vibrator, and a detection circuit for detecting an output generated from the vibrator. .

With this configuration, the ultrasonic sensor of the present invention can achieve waterproofness, moisture resistance, and airtightness even when the acoustic matching layer has a low density, and has good sensitivity and reverberation characteristics. Can be

Further, in the ultrasonic sensor according to the present invention, it is easy to provide an extremely thin first waterproof material on the other main surface of the acoustic matching layer, so that work efficiency and cost can be reduced. .

Further, the electronic device of the present invention has good sensitivity,
Since an ultrasonic sensor that can facilitate the operation process is used, high accuracy and low cost can be achieved.

[0030]

FIG. 1 is a perspective view of an embodiment of an ultrasonic sensor according to the present invention, and FIG. 2 is a sectional view taken along the line 1x-1x. 1 and 2, the ultrasonic sensor 9 shown in FIG.
The same reference numerals are given to the same or equivalent parts as those of a, and the description is omitted.

1 and 2, an ultrasonic sensor 1 includes a columnar acoustic matching layer 10, a disc-shaped piezoelectric body 20 as a vibrator, and a first waterproof material 30 formed in a disc shape. And a second waterproof member 40 formed in a cylindrical shape, and a cylindrical case 50. One main surface 101 of the acoustic matching layer 10 is
1 is fixed to the upper end surface of the case 50. The other main surface 102 of the acoustic matching layer 10 is tightly joined to the first waterproof material 30, and the side surface 103 of the acoustic matching layer 10 is
0, but not joined. Second waterproof material 4
0 is located on the other main surface 102 of the acoustic matching layer 10.
In the vicinity 62 of the edge of the first waterproof material 30, the inner surface of the lower end of the second waterproof material 40 is closely attached to the case 50 at the side surface 63 of the case 50. The first waterproof material 30 is made of PET resin, has a thickness of 30 μm, and has a small rigidity so that the vibration of the other main surface 102 of the acoustic matching layer 10 is not hindered. The second waterproof material 40 is made of PET resin, has a thickness of 60 μm, and has sufficiently high rigidity. Since the edge of the other main surface 102 of the acoustic matching layer 10 is connected to the second waterproof material 40 via the first waterproof material 30, the vicinity of the edge of the other main surface 102 of the acoustic matching layer 10 is Is restrained. Therefore, when a force for displacing the acoustic matching layer 10 is given by the vibration of the piezoelectric body 20, the force for displacing the acoustic matching layer 10 is canceled in the vicinity of the edge of the other main surface 102 of the acoustic matching layer 10. The force acts on the piezoelectric body 20
A non-displaced node N2 is generated by the vibration of the node N2. here,
The first waterproof material 30 and the second waterproof material 40 can be made of the same material or different materials, respectively.
When the first waterproofing material 30 and the second waterproofing material 40 are made of the same material, “the thickness of the second waterproofing material 40 /
It is preferable that the "thickness of the first waterproof material 30" is 2 or more.

The ultrasonic sensor 1 of the present invention having such a configuration
Are one main surface 101 and the other main surface 10 of the acoustic matching layer 10.
2 is constrained only near the edge, and that portion is
1, N2, and the other parts are not restricted, so that the sensitivity and the reverberation characteristics can be improved.

The ultrasonic sensor 1 has a first waterproof material 3
Since the thickness of 0 is 30 μm or less, the vibration of the acoustic matching layer 10 is hardly hindered.

The ultrasonic sensor 1 has an acoustic matching layer 10
Is covered with the first waterproof material 30 and the second waterproof material 40, so that even when the acoustic matching layer 10 has a low density, the waterproofness, moisture resistance, and airtightness can be improved. In addition,
In order to further ensure airtightness, it is desirable that the first waterproof material 30 and the second waterproof material 40 be made of metal.

Also, since the ultrasonic sensor 1 is provided with a waterproof material separately on the other main surface 102 and the side surface 103 and then joined, high-precision mechanical processing such as injection molding of a metal cap is performed. It is unnecessary, and the very thin first waterproof material 30 can be easily provided on the other main surface 102. Therefore, work efficiency and cost can be reduced.

The ultrasonic sensor 1 has a first waterproof material 3
Since the 0 and the second waterproof material 40 are separately provided and then joined, the rigidity of the first waterproof material 30 / the rigidity of the second waterproof material 40 can be set to a desired value.

The acoustic matching layer 10 and the first waterproof material 30
, The first waterproofing material 30 and the second waterproofing material 40, and the second waterproofing material 40 and the case 50
It can be realized by means such as adhesion, welding, and welding.

By providing a gap between the side surface 103 of the acoustic matching layer 10 and the second waterproof member 40, the side surface 1
03 may not be affected by the second waterproof material 40 at all. However, the side surface 103 and the second waterproof material 4
Even if no gap is provided between the second waterproof member 40 and the second waterproof material 40, the second waterproof material 40 may come into contact with the side surface 103 of the acoustic matching layer 10 but is not positively joined. The vibration of 103 is hardly hindered.

Although not shown, a backing material made of a high-density and soft substance may be provided on the surface of the vibrator 20 opposite to the surface fixed to the acoustic matching layer 10. In this case, rubber or the like can be used as the backing material. The ultrasonic sensor 1 of the present invention using the backing material suppresses the vibration of the vibrator 20 and
By damping the Q of the mechanical resonance of the above, an ultrasonic sensor having a good rise characteristic can be configured.

It is needless to say that the ultrasonic sensor 1 of the present invention is not limited to a sensor for transmitting and receiving ultrasonic waves, but may be a sensor for transmitting or receiving only ultrasonic waves.

Next, FIGS. 3 and 4 show sectional views of another embodiment of the ultrasonic sensor of the present invention. 3 and 4, the same or equivalent parts as those of the ultrasonic sensor 1 shown in FIG.

First, in FIG. 3A, in the ultrasonic sensor 1a of the present invention, the upper end surface of the second waterproof material 40 is located near the edge 62 of the other main surface 102 of the acoustic matching layer 10 in the first direction. Only the part which is joined to the waterproof material 30 without any gap is different from the ultrasonic sensor 1 shown in FIG.

In FIG. 3B, in the ultrasonic sensor 1b of the present invention, in the vicinity 62 of the edge of the other main surface 102 of the acoustic matching layer 10, the first waterproof material 30 is Only the part that goes around to the outer side surface of the upper end of the second waterproof material 40 at that position without gaps is shown in FIG.
Is different from the ultrasonic sensor 1 shown in FIG.

In FIG. 3C, in the ultrasonic sensor 1c of the present invention, in the vicinity 62 of the edge of the other main surface 102 of the acoustic matching layer 10, the upper end of the second waterproof member 40 is the first waterproof member. The ultrasonic sensor 1 shown in FIG. 1 is different from the ultrasonic sensor 1 shown in FIG. 1 only in that the part goes around to the upper surface of the member 30 and is joined to the first waterproof member 30 without any gap at that position.

In FIG. 4A, the ultrasonic sensor 1d of the present invention has a case 51 instead of the case 50 of the ultrasonic sensor 1 shown in FIG. The case 51 is provided with a flange 51a on an end surface opposite to the end surface on which the acoustic matching layer 10 is provided. And the second waterproof material 4
0 extends to the flange 51a, and at this position, a portion which is tightly joined to the case 51 is different from the ultrasonic sensor 1 shown in FIG.

In FIG. 4B, the ultrasonic sensor 1e includes an end face 50a opposite to the end face on which the acoustic matching layer 10 is provided, with the second waterproof material 40 covering the entire case 50 without any gap. 1 is different from the ultrasonic sensor 1 shown in FIG.

The ultrasonic sensor 1 having such a configuration
a, 1b, 1c, 1d, and 1e also have the same operation and effect as the ultrasonic sensor 1 of the present invention.

Next, FIG. 5 shows an embodiment of an electronic device using the ultrasonic sensor of the present invention. FIG. 5 is a block diagram showing one embodiment of a flow meter which is an electronic device of the present invention.

In FIG. 5, the flow meter 8 of the present invention comprises a pipe 81, the ultrasonic sensors 1, 1 'of the present invention, and a switching circuit 8
2, a transmission circuit 83, a reception circuit 84, a propagation time measurement circuit 85, and a flow rate calculation circuit 86. A flammable fluid such as gas flows through the pipe 81 of the flow meter 8. The ultrasonic sensor 1 and the ultrasonic sensor 1 ′ are arranged on the upstream side of the pipe 81 so that they face each other, and the ultrasonic sensor 1 ′ is arranged on the downstream side of the pipe 81. The ultrasonic sensor 1 and the ultrasonic sensor 1 '
The switching circuit 82 is connected to the transmission circuit 83
And the receiving circuit 84. The receiving circuit 84 is connected to the propagation time measuring circuit 85,
Is connected to the flow rate calculation circuit 86. Then, the switching circuit 82 connects the ultrasonic sensor 1 to the transmission circuit 83 and connects the ultrasonic sensor 1 ′ to the receiving circuit 84, and connects the ultrasonic sensor 1 to the receiving circuit 84. ′
Is connected to the transmission circuit 83 at predetermined time intervals. Here, the signal output from the transmission circuit 83 is output from one of the ultrasonic sensors 1 and 1 ′, passes through the fluid, is input to the other, and is input to the reception circuit 84. The propagation time measuring circuit 85 processes the signal input to the receiving circuit 84, measures the propagation time required for the signal to propagate through the pipe 81, and outputs the measured time to the flow rate calculating circuit 86. The flow rate calculation circuit 86 calculates the flow rate of the fluid and the flow rate of the fluid from the difference between the propagation time when the signal is output from the ultrasonic sensor 1 and the propagation time when the signal is output from the ultrasonic sensor 1 ′. And outputs the flow value to the outside.

The flow meter 8 of the present invention having such a configuration
Since the ultrasonic sensors 1, 1 'are airtightly sealed by the first waterproof member 30, the second waterproof member 40, and the case 50, it is ensured that the spark generated from the piezoelectric body 20 ignites the fluid. Can be prevented.

Since the flow meter 8 of the present invention uses the waterproof and moisture-resistant ultrasonic sensors 1 and 1 ', the flow rate of a liquid or a fluid containing moisture can be measured.

The flow meter 8 of the present invention has good sensitivity,
Since an ultrasonic sensor that can facilitate the operation process is used, high accuracy and low cost can be achieved.

Although the electronic device using the ultrasonic sensor of the present invention has been described using the flow meter 8, the electronic device of the present invention is not limited to such a flow meter.

[0054]

According to the ultrasonic sensor of the present invention, only the vicinity of the edges of the one main surface and the other main surface of the acoustic matching layer is restrained, the portions become nodes N1 and N2, and the other portions are not restrained. With the configuration, sensitivity and reverberation characteristics can be improved.

Further, in the ultrasonic sensor according to the present invention, since the acoustic matching layer is covered with the first waterproof material and the second waterproof material, even when the acoustic matching layer has a low density, it has waterproofness and moisture resistance. And airtightness can be improved.

Further, in the ultrasonic sensor of the present invention, since the first waterproof material and the second waterproof material are separately provided and then joined, an extremely thin first waterproof material is formed on the other side of the acoustic matching layer. It can be easily provided on the main surface, so that work efficiency and cost can be reduced.

Also, since the electronic device of the present invention uses an ultrasonic sensor having waterproofness, moisture resistance and airtightness, it is necessary to measure the flow rate of a fluid containing moisture or a flammable fluid. Can be.

The electronic device of the present invention has good sensitivity,
Since an ultrasonic sensor that can facilitate the operation process is used, high accuracy and low cost can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an ultrasonic sensor according to the present invention.

FIG. 2 is a 1x-1x sectional view of the ultrasonic sensor of FIG.

FIG. 3 is a sectional view showing another embodiment of the ultrasonic sensor of the present invention.

FIG. 4 is a sectional view showing still another embodiment of the ultrasonic sensor of the present invention.

FIG. 5 is a block diagram showing one embodiment of the electronic device of the present invention.

FIG. 6 is a sectional view showing a conventional ultrasonic sensor.

FIG. 7 is a sectional view showing another conventional ultrasonic sensor.

[Explanation of symbols]

1, 1 ', 1a, 1b, 1c, 1d, 1e: Ultrasonic sensor 8: Electronic device 10: Acoustic matching layer 20: Vibrator 30: First waterproof material 40: Second waterproof material 50: Case N1, N2 ... node

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04R 1/44 330 G01S 7/52 A

Claims (7)

[Claims] 1. An ultrasonic sensor having an acoustic matching layer to which a vibrating surface of a vibrator is fixed near a central portion of one main surface and an ultrasonic wave transmitted and received from the other main surface, wherein one of the acoustic matching layers is provided. An ultrasonic sensor, wherein only the vicinity of the edge of the main surface and the other main surface is restricted. 2. An ultrasonic sensor having an acoustic matching layer to which a vibrating surface of a vibrator is fixed near a central portion of one main surface and an ultrasonic wave transmitted and received from the other main surface, wherein one of the acoustic matching layers is provided. The main surface has an edge fixed to the upper end surface of the cylindrical case, the other main surface of the acoustic matching layer is closely bonded to a first waterproof material, and the side surface of the acoustic matching layer is covered with a second waterproof material. The upper end of the second waterproof material is tightly joined to the first waterproof material in the vicinity of the edge of the other main surface of the acoustic matching layer, and the lower end of the second waterproof material is a side surface of the case. 2. The ultrasonic sensor according to claim 1, wherein the ultrasonic sensor is in close contact with the case. 3. The first waterproof material has a small rigidity so as not to hinder the vibration of the other main surface of the acoustic matching layer, and the second waterproof material has a rigidity on the other main surface of the acoustic matching layer. The ultrasonic sensor according to claim 2, wherein the ultrasonic sensor has a rigidity large enough to restrain the node. 4. The ultrasonic sensor according to claim 3, wherein the second waterproof material has higher rigidity than the first waterproof material. 5. The acoustic matching layer according to claim 2, wherein the first waterproof material, the second waterproof material, and the case have an airtight and waterproof structure. 2. The ultrasonic sensor according to claim 1. 6. The ultrasonic sensor according to claim 2, wherein the first waterproof material has a thickness of 30 μm or less. 7. An ultrasonic sensor according to claim 1, comprising: a drive circuit for vibrating the vibrator; and a detection circuit for detecting an output generated from the vibrator. Electronic device characterized by.