JP2004312226A - Manufacturing method of matching layer, ultrasonic sensor using matching layer, and fluid flow measuring device using ultrasonic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the uniformity of density distribution by uniformly filling hollow spheres without uneven distribution in a matching member formed of a mixture of a hollow sphere and bonding agent. <P>SOLUTION: A matching member generation jig 5 is arranged in a stand 3. A housing storing the hollow spheres is disposed in the matching member generation jig 5. The stand 3 is dropped and made to collide with a pedestal 10 in such a state. A packing degree of the hollow sphere is improved by vibration occurring at that time. Drop and collision are performed not once but for several times. Then, bonding agent is mixed and cured. Thus, density of the matching member becomes uniform. When the member is used for an ultrasonic sensor as the matching layer, performance can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Technical field to which the present invention pertains]
The present invention relates to a method for manufacturing a matching member, an ultrasonic sensor using the same, and an apparatus for measuring the flow of a gas or liquid fluid using the ultrasonic sensor.
[0002]
[Prior art]
Conventionally, a method of manufacturing a matching layer used for an ultrasonic sensor or the like includes, for example, as shown in FIG. 8A, a matching member 34 formed of a mixture of a hollow sphere 32 and a resin 33, and a load case formed of a cylindrical member. 35, and then, as shown in FIG. 8B, a matching layer 36 manufactured by cutting to a thickness corresponding to １ ／ wavelength of the resonance frequency of the piezoelectric body was manufactured.
[0003]
As shown in FIG. 8C, the matching layer 36 is mounted on a piezoelectric vibrator 37 to form an ultrasonic vibrator (see Patent Document 1).
[0004]
Further, as a matching member made of a mixture of a glass balloon and a resin, there has been disclosed one in which bubbles having a particle size smaller than the wavelength of ultrasonic waves generated from a piezoelectric material are mixed into the resin (see Patent Document 2).
[0005]
[Patent Document 1]
Japanese Patent Publication No. 6-101880 (Fig. 6)
[Patent Document 2]
JP-A-11-215594
[Problems to be solved by the invention]
However, in this conventional manufacturing method, when a hollow sphere is inserted, the outer wall surfaces of the hollow sphere come into contact with each other, causing friction.
[0007]
For this reason, there was a problem that the hollow spheres aggregated and the dispersion in the matching member became uneven.
[0008]
This is because when the hollow spheres have a glass composition, a predetermined amount of the hollow spheres cannot be put into the matching member due to a high friction coefficient between the hollow spheres.
[0009]
Therefore, as shown in FIG. 8 (b), the matching layer group in which the cylindrical member is cut to a predetermined thickness has a different ratio between the hollow sphere and the resin for each of the matching members. There was a problem.
[0010]
Also, it is very difficult to mix bubbles having a particle size smaller than the wavelength of the ultrasonic wave into the resin, and the size of the bubbles to be mixed cannot be controlled.
[0011]
Further, the density of the matching layer formed by mixing bubbles in the resin differs depending on the number of formed layers, and a constant acoustic impedance cannot be obtained.
[0012]
An object of the present invention is to solve the above-mentioned conventional problems, and to provide a matching layer with reduced density variation, a method for manufacturing the same, an ultrasonic sensor, and a flow measuring device equipped with the ultrasonic sensor.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned conventional problems, a hollow body is filled with a housing by vibrating the housing, and then the hollow sphere is mixed with a bonding material to surround the hollow sphere with the bonding material. With this configuration, the hollow spheres are uniformly filled in the storage body, and the density as the matching layer can be made uniform.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the embodiment of the present invention, the hollow sphere is filled with the hollow sphere by filling the hollow sphere by exciting the storage body, and then the hollow sphere is mixed with the bonding material, so that the hollow sphere is surrounded by the bonding material. Therefore, the hollow spheres are not unevenly distributed, and the density of the alignment member can be made uniform at any portion.
[0015]
As a specific vibrating means, a housing is provided on an alignment member forming jig supported by a pedestal, and the pedestal collides with a pedestal, thereby generating an impact vibration.
[0016]
Collisions will generally be made by accelerating by free fall. If the pedestal is formed of a polymer material, the vibration applied to the pedestal can be converged at one time.
[0017]
The bonding material is made of, for example, a thermosetting resin compound. After mixing the bonding material with the hollow sphere, the mixture is cured, and then cut into a predetermined length to form a matching layer.
[0018]
In addition, if a plurality of storage bodies are arranged in the alignment member forming jig, rational production can be performed. The hollow sphere contains a glass composition.
[0019]
The matching member made by the above method is used as a matching layer of the ultrasonic sensor. Specifically, it comprises a cylindrical case having a top portion and a side wall portion, and a piezoelectric body fixed to the inner wall surface of the top portion, and is aligned with the outer wall surface of the top portion via an adhesive layer. Layers are installed.
[0020]
At least one pair of the ultrasonic sensors is arranged in the flow direction of the fluid, and detects the velocity and / or the flow rate of the fluid based on the ultrasonic propagation time between the ultrasonic sensors.
[0021]
【Example】
Hereinafter, embodiments of the present description will be described with reference to the drawings.
[0022]
(Example 1)
1 to 3, four guide columns 2 erected from four corners of a rectangular base 1 support a pedestal 3 so as to be vertically movable.
[0023]
An alignment member making jig 5 having a storage body 4 is attached to the pedestal 3, and a circular storage chamber 6 is formed in the storage body 4.
[0024]
The pedestal 3 is locked at a predetermined height position of the guide column 2 via a lock device 7, and when compressed air is sent through a flexible tube 8, the lock device 7 is unlocked and falls due to its own weight or the like. I have to do it.
[0025]
The switch 9 controls the flow of the compressed air and operates the lock device 7. At the falling position of the pedestal 3, there is a pedestal 10 fixed to the base 1 and made of a polymer material.
[0026]
FIG. 2 also shows a method for manufacturing the alignment member.
[0027]
A hollow sphere 11 made of a glass hollow body is stored in the storage room 6 of the storage body 4. The hollow spheres 11 each have a particle size of 10 to 100 μm, and the average particle size is about 60 μm.
[0028]
The hollow sphere 11 made of a glass hollow body has a lower specific gravity than other fillers, has heat resistance, pressure resistance, and impact resistance, and has dimensional stability and moldability of the filler when used as a filler. Properties can be improved.
[0029]
The composition of the glass used was borosilicate glass. This glass hollow body is formed by melting raw materials such as silicon oxide, boric acid, calcium carbonate, sodium carbonate, and sodium sulfate at a high temperature of 1000 ° C. or higher to form a glass containing a large amount of sulfur, and then pulverizing the glass. This glass fine powder is dispersed and retained in a flame to foam sulfur as a foaming agent component.
[0030]
The hollow sphere 11 is put into the storage chamber 6 of the storage body 4 little by little, and each time, the pedestal 3 of the alignment member forming jig 5 to which the storage body 4 is attached is dropped to the receiving stand 10. As a result, the hollow sphere 11 is filled in the storage chamber 6 without a gap by the drop impact vibration.
[0031]
The storage chamber 6 is filled with the hollow spheres 11 by repeating this step several to several tens of times.
[0032]
Here, the hollow sphere 11 made of a glass hollow body has a high fluidity because the outer wall surface forms the coating layer of the surface modifying material, and does not stay even when the wall surface of each hollow sphere 11 contacts. Move into each other to form a close-packed state. Therefore, only the smallest void exists between the hollow spheres 11.
[0033]
As shown in FIG. 4 (a), filters 12 are installed vertically in the storage chamber 6 of the storage body 4 filled with the hollow spheres 11, and then the bonding material 13 is supplied and impregnated.
[0034]
Here, as the bonding material 13, an epoxy resin which is a thermosetting resin compound was used.
[0035]
This is because the epoxy resin has a small shape change after curing and has excellent long-term stability. Above all, the affinity with the surface of the hollow sphere 11 is high, so that the bonding force with the hollow sphere 11 is stably improved. I do.
[0036]
The epoxy resin used is a two-component curing type epoxy resin. The main agent is a bisphenol A type liquid epoxy resin, and the curing agent is tetrahydromethyl phthalic anhydride. The main agent and the curing agent were mixed at an optimum mixing ratio and used as an epoxy resin.
[0037]
However, the present invention is not particularly limited to a two-component curing type epoxy resin, and a one-component curing type epoxy resin may be used as long as the purpose is achieved.
[0038]
As shown in FIG. 4B, a suction jig 15 provided with a suction port 14 is installed to impregnate the bonding material 13.
[0039]
That is, the alignment member forming jig 5 in which the hollow sphere 11 is filled in the storage chamber 6 of the storage body 4 is set in a container 16 filled with a bonding material 13 made of epoxy resin.
[0040]
The filter 12 provided on the lower side of the storage chamber 6 is for preventing the hollow spheres 11 therein from leaking, and the filter 12 provided on the upper side does not suck the hollow spheres 11 together when the binding material 13 is sucked. That's why. Here, filter paper was used for the filter 12.
[0041]
The material is not limited as long as the above-described purpose of the filter 12 is achieved.
[0042]
Then, as shown in FIG. 4B, the binding material 13 in the container 16 is sucked from the suction port 14 of the suction jig 15. By setting the atmosphere in the low-pressure atmosphere in this way, the air bubbles in the gaps existing between the hollow spheres 11 are removed, and the bonding material 13 fills the gaps instead.
[0043]
Thereby, the adhesion between the hollow spheres 11 in the storage room 6 is improved, and the bonding material 13 is applied around the hollow spheres 11.
[0044]
When the bonding material 13 is sucked, it is desirable that the atmosphere be at a temperature at which it is not cured and at a temperature at which the viscosity becomes low.
[0045]
When an epoxy resin was used as the bonding material 13, the curing conditions were 80 ° C. × 2 hours, and 150 ° C. × 2 hours. Therefore, suction was performed at 60 ° C. lower than the gelling temperature of the epoxy resin.
[0046]
After the bonding material 13 is impregnated into the storage chamber 6 filled with the hollow spheres 11 as described above, the suction jig 16 is removed from the alignment member forming jig 2.
[0047]
Then, as shown in FIG. 4C, the housing 4 is taken out from the alignment member forming jig 5, and the bonding material 13 is cured by heating.
[0048]
The hardened mixture is cooled to room temperature and taken out of the housing 4 using a rod-shaped jig or the like as shown in FIG.
[0049]
Although only one storage room 6 of the storage body 4 shown in FIG. 4 exists, if a large number of storage rooms 6 are provided as shown in FIG. 5, a large number of alignment members can be taken out at once.
[0050]
Next, as shown in FIG. 4E, the matching member 17 is cut into a predetermined thickness by a dicing device or the like, that is, a thickness corresponding to １ ／ wavelength of the resonance frequency of the piezoelectric body, and the final matching layer 18 is cut. Form.
[0051]
Since the side wall of the alignment member 17 molded as described above is covered with the bonding material 13, it is not necessary to apply a special polymer material to the side wall surface.
[0052]
In the step of cutting the alignment member 17, it is necessary to prevent grinding dust generated at the time of cutting from adhering to the surface of the alignment layer 18 after cutting.
[0053]
This grinding dust is a simple substance or a mixture of a bonding material and a micro crack of a hollow sphere. In the state where these dusts adhere, a smooth coating layer of a polymer material cannot be formed on the surface of the matching layer. Therefore, if the dusts adhere, they must be removed.
[0054]
However, grinding water is caused to flow on the cutting surface during dicing in the cutting step, so that grinding dust generated during cutting is flown and does not adhere to the surface of the matching layer 18.
[0055]
A polymer material is printed and thermally cured on the surface of the matching layer 21 to form a coating layer. Here, the same resin material used for the binding material 13 was used as the polymer material.
[0056]
As described above, since the bonding material is coated on the side surface of the matching member 17, even if an equivalent bonding material is formed on the surface of the matching layer 18, the matching member 17 can easily fit into the side wall surface of the matching layer.
[0057]
Twenty matching layers 18 prepared by cutting the matching member made by the above-described method at a constant thickness were prepared, and their density distributions were measured. FIG. 6 shows the result. A shows an example of the present invention, and B shows a conventional product.
[0058]
In this example, the pedestal 3 was dropped from a height of 70 mm from the receiving table 10, and the hollow sphere was filled in the storage chamber of the storage body. The maximum acceleration at that time was about 20G. The material of the pedestal 10 was ABS resin.
[0059]
If the pedestal 10 is made of a metal material, the pedestal 3 will fall and come into contact with the pedestal 3 and then collide repeatedly with the pedestal 10 several times, so that the vibration of the pedestal 3 cannot be stopped immediately. For this reason, the filling state of the hollow spheres 11 that have been once most closely packed in the storage chamber 6 is shifted.
[0060]
However, a polymer material that drops the pedestal 3 from a certain height and hits the pedestal 10 while absorbing the vibration of the pedestal 3 is suitable. On the other hand, the pressure when the hollow sphere 11 was filled into the storage chamber 6 by the suction jig 15 such as a vacuum pump was about 0.097 Mpa.
[0061]
After the filled hollow spheres 11 were impregnated with the bonding material 13 in this manner, they were thermally cured to form the matching members 17.
[0062]
The thermosetting conditions are two-stage firing in which heating is performed at 150 ° C. × 2 hours after 80 ° C. × 2 hours.
[0063]
The matching member 17 was cut by a dicing apparatus to a thickness of 1.16 ± 0.01 (mm) to obtain a matching layer.
[0064]
No in the graph of FIG. 6 is the order when the pieces are taken out from the top of the alignment member in order. From FIG. 6, the density distribution of the matching layer A of the present embodiment is about 0.517 (g / cm ³ ) on average, and 3σ is 0.013.
[0065]
On the other hand, the average density of the conventional matching layer B formed by filling the glass hollow body with the vacuum pump suction is about 0.534 (g / cm ³ ), and 3σ is 0.028.
[0066]
From this, the matching layer of the matching member prepared in this embodiment can obtain a uniform density. This is because the hollow spheres filled in the storage room can be uniformly arranged in the storage room by applying acceleration higher than the frictional resistance of the surface.
[0067]
As described above, since the hollow spheres are not agglomerated with each other and are not unevenly distributed in the matching member in the matching member, the matching layer of the present embodiment has uniform density in any part of the matching member. A matching layer can be created.
[0068]
(Example 2)
FIG. 7 shows the use of the matching layer 18 obtained in the above embodiment in an ultrasonic sensor.
[0069]
The cylindrical case 20 made of a conductive material has a top portion 21, and the piezoelectric body 22 is bonded to the inner wall surface of the top portion 21, and the matching layer 18 is bonded to the outer wall surface.
[0070]
The lower open part of the cylindrical case 20 is closed by a terminal plate 24 to which one terminal 23 is connected.
[0071]
The other terminal 25 penetrates the terminal plate 24 through an electrically insulating material 26 and is connected to a conductor 27 that contacts the lower surface of the piezoelectric body 22. A plurality of longitudinal grooves 28 are formed in the piezoelectric body 22.
[0072]
When a voltage is applied to the piezoelectric body 22 from the terminals 23 and 25 via the conductor 27, the piezoelectric body 22 vibrates due to a piezoelectric phenomenon.
[0073]
5 vibrates at about 500 KHz, the vibration is transmitted from the case 20 to the matching layer 18, and the vibration of the matching layer 21 is transmitted to the gas as sound waves.
[0074]
When the matching layer formed by the conventional manufacturing method is bonded to the top of the case, a concave portion is formed on the surface of the matching layer because a cracked portion of the hollow sphere is exposed on the surface thereof.
[0075]
When bonding to the top of the case using an adhesive, a thermosetting adhesive is applied and formed on the matching layer or the surface of the case top by printing or the like, and the matching layer and the case top are bonded by heat curing. Also, the adhesive stayed in the concave portion of the matching layer surface, and the surface of the matching layer and the top surface of the case could not be bonded with uniform strength.
[0076]
In addition, since a minute air layer is formed at the bonding interface between the surface of the matching layer and the top surface of the case, the phase of the wavelength of the vibration propagated from the piezoelectric body through the case is shifted inside the matching layer. The strength of the vibration wave at the time is weakened, and the transmission / reception sensitivity as an ultrasonic sensor is reduced.
[0077]
On the other hand, since the surface of the matching layer 18 of the present embodiment is formed by coating a polymer material on the surface, the surface is uniformly adhered to the surface of the top portion 21 of the case 20, the adhesive strength is made uniform, and the surface of the matching layer Of the concave portion disappears.
[0078]
As a result, the phase of the vibration wave from the piezoelectric body 22 does not shift in the matching layer 18, so that the vibration wave can stably oscillate in the measurement fluid.
[0079]
Therefore, the transmission / reception sensitivity of the ultrasonic sensor can be maintained without lowering.
[0080]
The ultrasonic sensor is used in a fluid flow measuring device. That is, at least one pair of ultrasonic sensors are arranged on the fluid flow direction upstream side and downstream side of the flow path, the time until the ultrasonic wave transmitted from one ultrasonic sensor is received by the other ultrasonic sensor, that is, The ultrasonic propagation time is detected, and the flow velocity of the fluid can be measured.
[0081]
Also, the flow rate can be measured by calculating the cross-sectional area of the flow path based on the flow velocity and other factors.
[0082]
As described above, since the ultrasonic sensor has high performance, the flow velocity and / or the flow rate can be measured with high accuracy.
[0083]
As described above, according to the above-described embodiment, the following operation and effect can be expected.
[0084]
(1) Since the hollow spheres are not aggregated with each other and mixed with the binder material and the hollow spheres are not unevenly distributed in the matching member, a matching layer having a uniform density can be formed in any part of the matching member.
[0085]
(2) The pedestal integrated with the storage body is dropped from a predetermined height and moved downward to collide with the pedestal, so that impact vibration is applied to the hollow sphere, and the hollow sphere is densely and uniformly filled. can do.
[0086]
(3) Since the binding material is sucked in the housing and mixed with the hollow sphere, and the mixture of the hollow sphere and the binding material is cured in that state, the molding, curing, and removal of the alignment member are facilitated.
[0087]
(4) Since the pedestal is made of a polymer material, the vibration applied to the pedestal when the dropped pedestal is stopped against the pedestal can be converged at once.
[0088]
(5) Since the storage body has a storage chamber for molding a mixture of a hollow sphere and a binder, if the area of the matching member is determined in advance, for example, only the hardened matching member is cut to a required thickness. Thus, a matching layer having a required area can be obtained.
[0089]
(6) Since the hollow sphere and the binder can be mixed and then cured by heating by using the thermosetting resin compound as the binder, the matching member can be formed by being closely adhered to the surface of the hollow sphere and cured.
[0090]
(7) Since the hollow sphere contains the glass composition, a matching member can be formed by mixing with the bonding material while maintaining the hollow state, and the hollow state of the hollow sphere due to a change in the surrounding temperature of the matching layer is maintained, and the matching is performed. The layer density can be stabilized.
[0091]
(8) By using the matching member obtained by the above-mentioned manufacturing method as a matching layer of an ultrasonic sensor, the matching layer can efficiently propagate the vibration from the piezoelectric body as a sound wave into the gas, and the gap between the individual sensors can be improved. Variations in characteristics can be suppressed.
[0092]
(9) If this ultrasonic sensor is mounted on a fluid flow measuring device, the flow velocity and / or the flow rate can be measured with high accuracy.
[0093]
【The invention's effect】
As described above, according to the present invention, the filling of the hollow sphere can be performed reliably and at a high density, so that the performance of the matching member, and furthermore, the performance of the ultrasonic sensor using the matching member as the matching layer is improved. Further, the accuracy of the fluid flow measuring device equipped with the ultrasonic sensor can be remarkably improved.
[Brief description of the drawings]
1 is a front view of a matching member manufacturing apparatus according to an embodiment of the present invention when it is not operating; FIG. 2 is a front view of the matching member manufacturing apparatus when it is operating; FIG. 3 is a view of a storage body for filling hollow spheres; Top view FIG. 4 Manufacturing process diagram FIG. 5A Perspective view of a matching member making jig showing another embodiment of the present invention FIG. 6B Perspective view of the same housing FIG. 6 Density of matching layer FIG. 7 is a graph showing distribution. FIG. 7 is a cross-sectional view of an ultrasonic sensor using the matching layer of the present invention. FIG.
3 Pedestal 4 Housing 5 Matching member making jig 6 Storage room 10 Receiving pedestal 11 Hollow sphere 13 Bonding material 18 Matching layer 20 Tubular case 21 Top part 22 Piezoelectric body

Claims (13)

A method of manufacturing a matching member, wherein a hollow sphere is filled in a housing by vibrating the housing, and then the hollow sphere is mixed with a bonding material to surround the hollow sphere with the bonding material. 2. The container according to claim 1, wherein a housing is provided on the alignment member forming jig supported by the pedestal, and the storage body is vibrated through the alignment member forming jig by colliding the pedestal with a receiving table. Manufacturing method of the alignment member. 3. The method according to claim 2, wherein the collision is performed by generating acceleration by free fall. 3. The method according to claim 2, wherein the pedestal is formed of a polymer material. 3. The method for manufacturing an alignment member according to claim 2, wherein a plurality of storage bodies are arranged on the alignment member forming jig. The method according to claim 1, wherein the bonding material is a thermosetting resin compound. 7. The method for manufacturing an alignment member according to claim 1, wherein after the bonding material is mixed with the hollow sphere, the mixture is cured. The method for manufacturing an alignment member according to claim 7, wherein the mixture of the hollow sphere and the bonding material is cured and then cut into a predetermined length. The method according to claim 1, wherein the hollow sphere includes a glass composition. An ultrasonic sensor comprising, as a matching layer, a matching member made by the manufacturing method according to claim 1. The cylindrical case having a top portion and a side wall portion, a piezoelectric body fixed to an inner wall surface of the top portion, and a matching layer provided on an outer wall surface of the top portion via an adhesive layer. Ultrasonic sensor. 12. A fluid flow measuring device comprising at least one pair of ultrasonic sensors according to claim 10 or 11 arranged in a flow direction of a fluid, wherein the velocity of the fluid is detected based on an ultrasonic propagation time between the ultrasonic sensors. A fluid flow measurement device comprising: at least one pair of the ultrasonic sensors according to claim 10 or 11 arranged in a flow direction of the fluid; and measuring a flow rate based on a velocity of the fluid obtained by an ultrasonic propagation time between the ultrasonic sensors. apparatus.

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