JP2004045439A - Ultrasonic transducer and ultrasonic flowmeter using the same - Google Patents

Abstract

To improve the measurement accuracy of an ultrasonic flowmeter using an ultrasonic transducer capable of transmitting and receiving an ultrasonic pulse having a short reverberation.
A case (7) is provided with a bent portion (11) to increase rigidity, thereby making it difficult to vibrate. As a result, it is possible to obtain an ultrasonic transducer 6 capable of transmitting and receiving an ultrasonic pulse having a short reverberation, and by using the ultrasonic transducer 6, it is possible to improve the measurement accuracy of the ultrasonic flowmeter.
[Selection diagram] Fig. 1

Description

The present invention relates to an ultrasonic vibrator for measuring a flow rate and a flow velocity of a gas or a liquid by ultrasonic waves and an ultrasonic flowmeter using the same.

FIGS. 18 and 19 show an ultrasonic transducer conventionally used for this type of ultrasonic flowmeter. As shown in FIG. 18, a piezoelectric ceramic 1 is brazed to a metal diaphragm 2, and the metal diaphragm 2 is welded to a metal housing 3 (for example, see Patent Document 1). Further, a pot-shaped matching layer 5 made of epoxy resin and fine glass spheres is commonly used as a case containing the piezoelectric ceramic 4 (for example, see Patent Document 2).
JP-A-4-309817 Japanese Patent Publication No. 6-500389

However, in the above-described conventional configuration, if a material made of epoxy resin and fine glass spheres is used as the case, the case is less likely to vibrate and the reverberation is reduced. However, since such a material generally has microporosity, the fluid to be measured infiltrates into the case, and depending on the components of the fluid to be measured, there is a problem that the electrodes of the piezoelectric body are corroded and the characteristics are deteriorated. Was.

で は The present invention solves the above-mentioned problems, and aims to realize a highly reliable ultrasonic transducer and improve the measurement accuracy of an ultrasonic flowmeter.

In order to solve the above problems, the present invention provides an ultrasonic vibrator having a ceiling portion, a side wall portion, and an opening, a cylindrical case having an opening, a piezoelectric body fixed to an inner wall surface of the ceiling portion, and the case. And a sealing body for closing the opening of the case, wherein the inside of the case sealed by the sealing body is replaced with nitrogen or an inert gas.

According to the above invention, deterioration of characteristics due to corrosion of the electrodes and the like of the piezoelectric body can be prevented, so that the reliability of the ultrasonic vibrator can be improved.

As is apparent from the above description, according to the ultrasonic transducer of the present invention and the flow meter using the same, according to the present invention, a ceiling-shaped cylindrical case having a ceiling, a side wall, and an opening, and an inner wall surface of the ceiling And a sealing body that closes an opening of the case, and an inert gas is sealed inside the case sealed by the sealing body. Therefore, deterioration of characteristics due to corrosion can be prevented, so that a highly reliable ultrasonic vibrator and ultrasonic flowmeter can be obtained.

According to the first aspect of the present invention, there is provided an ultrasonic vibrator having a ceiling-shaped cylindrical case having a ceiling, a side wall, and an opening, a piezoelectric body fixed to an inner wall surface of the ceiling, and an opening of the case. A sealing member for closing the portion, and the inside of the case sealed by the sealing member is replaced with nitrogen or an inert gas, so that deterioration of characteristics due to corrosion of the electrodes and the like of the piezoelectric body can be prevented. Thus, a highly reliable ultrasonic transducer can be obtained.

An ultrasonic flowmeter according to a second aspect of the present invention is an ultrasonic flowmeter including a flow path through which a flammable fluid to be measured flows, and an ultrasonic vibrator provided in the flow path and transmitting and receiving an ultrasonic signal. Further, the ultrasonic vibrator has a ceiling-shaped cylindrical case having a ceiling, a side wall, and an opening, a piezoelectric body fixed to an inner wall surface of the ceiling, and a sealing member for closing the opening of the case. The case is provided with a stopper, and the inside of the case sealed by the sealing member is replaced with nitrogen or an inert gas, so that deterioration of characteristics due to corrosion of the electrodes and the like of the piezoelectric body can be prevented. A high ultrasonic transducer and ultrasonic flow meter are obtained.

An ultrasonic transducer according to a third aspect of the present invention includes a flow path through which a flammable fluid to be measured flows, and a pair of ultrasonic vibrators provided in the flow path and transmitting and receiving an ultrasonic signal. An ultrasonic flowmeter that measures the flow rate by measuring the ultrasonic propagation time between transducers, wherein the ultrasonic transducer has a ceiling-shaped cylindrical case having a top part, a side wall part, and an opening part, A piezoelectric body fixed to an inner wall surface of the top portion, an acoustic matching layer provided on an outer wall surface of the top portion, and a sealing member closing an opening of the case, and sealed by the sealing member. In addition, since the inside of the case is replaced with nitrogen or an inert gas to prevent deterioration of characteristics of the electrodes of the piezoelectric body due to corrosion, a highly reliable ultrasonic vibrator and ultrasonic flowmeter can be obtained.

According to the ultrasonic vibrator of the fourth aspect of the present invention, since the piezoelectric body and the case are bonded and fixed, deterioration due to long-term use of the adhesive layer can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, components denoted by the same reference numerals are the same components, and a detailed description thereof will be omitted.

(Example 1)
FIG. 1 is an external view of an ultrasonic transducer according to a first embodiment of the present invention. FIG. 2 is a sectional view of the ultrasonic transducer shown in FIG. FIG. 3 is an external view of a piezoelectric body used in the ultrasonic transducer of FIG. In FIG. 1, 6 is an ultrasonic transducer, 7 is a case, 8 is a top part of the case 7, 9 is an acoustic matching layer fixed to an outer wall surface of the top part 8, 10 is a side wall part of the case 7, and 11 is a side wall. A bent portion 12 fixed to the portion 10 is a support portion for fixing the case 7. In FIG. 2, reference numeral 13 denotes a piezoelectric body disposed on the inner wall surface of the ceiling portion 8, 14 denotes a terminal plate fixed to the support portion 12, 15a and 15b denote terminals provided on the terminal plate 14, and 16 denotes a terminal 15a and a terminal. An insulating portion for insulating 15b and a lead wire 17 for electrically connecting the piezoelectric body 13 and the terminal 15a are provided. In FIG. 3, reference numeral 18 denotes an electrode of the piezoelectric body 13 and 19 denotes a groove provided in the piezoelectric body 13.

の 一 One example of a method for producing the ultrasonic transducer configured as described above will be described with reference to FIGS. Assuming that the ultrasonic vibrator 6 is used in LP gas or natural gas, a material made of stainless steel for the case 7 and a mixture of epoxy resin and hollow glass spheres for the acoustic matching layer 9 is selected. In consideration of mass productivity, the forming method of the case 7 is not a cutting but a forming such as drawing. The thickness of the stainless steel should be about 0.1 to 0.5 mm and about one-tenth or less of the wavelength because of the ease of forming the case 7, the structural strength, and the sensitivity of the ultrasonic vibrator 6. select. Next, since the piezoelectric body 13 is bonded and fixed to the ceiling portion 8 made of stainless steel, vibration in the spreading direction is inhibited. In order to increase the sensitivity of the ultrasonic vibrator 6, it is more advantageous to use the thickness longitudinal vibration in the main mode rather than the spread vibration. However, the main mode of vibration of the piezoelectric body 13 is determined by the shape thereof, and the allowable range for the shape and use frequency of the piezoelectric body 13 is narrow. Therefore, a structure in which two grooves 19 are provided in the rectangular parallelepiped piezoelectric body 13 as shown in FIG. 3 was selected. The provision of the groove 19 allows the thickness mode of the piezoelectric body 13 having a width of 20 mm, a height of 8 mm and a thickness of 22 mm to be 4 mm and a thickness vibration mode of about 400 KHz. However, the number, depth, and direction of the grooves 19 are determined based on the shape of the piezoelectric body 13, the influence of the unnecessary mode, and the ease of handling.

First, a cylindrical case 7 having a disk-shaped top portion 8 having a diameter of about 13 mm is formed from a stainless steel plate having a thickness of 0.2 mm. At this time, one bent portion 11 concentric with the top portion 8 is formed on the side wall portion 10 at the same time. Next, a disc-shaped acoustic matching layer 9 having a diameter of 12.5 mm is fixed to the outer wall surface of the top portion 8 and the piezoelectric body 13 is fixed to the inner wall surface by using an epoxy adhesive. At this time, by bonding and fixing the electrode 18 and the top part 8 divided by the groove 19 via a thin adhesive layer of 10 μm or less, electrical conduction between the divided electrode 18 and the top part 8 can also be obtained. The lead wire 17 is soldered to the electrode of the piezoelectric body 13 not shown and the terminal a, respectively. Finally, a terminal plate 14 made of a stainless steel plate having a diameter of about 16 mm and a thickness of about 0.8 mm is fixed to the support portion 12 by electric welding, and sealing and electric conduction are simultaneously performed. The piezoelectric body 13 uses the case 7 as a ground and is covered with the case 7 and the terminal plate 14, so that the effect of noise can be reduced. Further, when the inside of the case 7 is replaced with dry nitrogen or an inert gas, the deterioration of the electrodes of the piezoelectric body 13 and the adhesive layer between the piezoelectric body 13 and the case 7 due to long-term use can be prevented.

(4) A method for manufacturing an ultrasonic flowmeter using the ultrasonic vibrator prepared as described above will be described with reference to FIGS. The material constituting the flow rate measuring unit 23 was an aluminum alloy die cast assuming a household gas meter for measuring the flow rate of LP gas or natural gas. The upper plate portion 36 is screwed onto the end surfaces of the side wall portions 24 and 25 via a sealing material 35 made of, for example, cork material, so that the flow path measuring section 23 having a rectangular channel cross section 37 is formed. The ultrasonic vibrators 27 and 28 are fixed to vibrator mounting holes 29 and 30 provided obliquely on the side walls 24 and 25 so that the transmitting and receiving surfaces face each other via sealing materials 31 and 32 made of, for example, O-rings.

The operation of the ultrasonic flowmeter using the flow rate measuring unit 23 configured as described above will be described. Let L be the distance connecting the centers of the ultrasonic transducers 27 and 28, and let θ be the angle between this straight line and the longitudinal direction of the flow path 26, which is the direction of flow. The sound speed of the LP gas in a windless state is C, and the flow velocity of the LP gas in the flow path 26 is V. The ultrasonic waves transmitted from the ultrasonic transducer 27 arranged on the upstream side of the flow measuring unit 23 obliquely cross the flow path 26 and are received by the ultrasonic transducer 28 arranged on the downstream side.

伝 搬 The propagation time t1 at this time is

で示される。次に送信・受信する超音波振動子を切り替え、超音波振動子２８から超音波を送信し、超音波振動子２７で受信する。このときの伝搬時間ｔ２は、

Indicated by Next, the ultrasonic transducer to be transmitted / received is switched, an ultrasonic wave is transmitted from the ultrasonic transducer 28, and the ultrasonic transducer 27 receives the ultrasonic wave. The propagation time t2 at this time is

で示される。ｔ１とｔ２の式からＬＰガスの音速Ｃを消去すると、

Indicated by Eliminating the sound velocity C of LP gas from the equations of t1 and t2,

の式が得られる。Ｌとθが既知ならば、計測回路３３にてｔ１とｔ２を測定すれば流速Ｖが求められる。この流速Ｖから流量Ｑは、断面３７の面積をＳ、補正係数をＫとすれば、流量演算回路３４で、
　Ｑ＝ＫＳＶ
を演算し、流量を求めることができる。

Is obtained. If L and θ are known, the flow velocity V can be obtained by measuring t1 and t2 in the measurement circuit 33. From the flow velocity V, the flow rate Q can be calculated by the flow rate calculation circuit 34 if the area of the cross section 37 is S and the correction coefficient is K.
Q = KSV
To calculate the flow rate.

で は In the ultrasonic flowmeter, it is important to measure the times t1 and t2 with high accuracy for high-accuracy flow measurement. Therefore, the influence of the vibration of the case 7 on the measurement will be considered. On the transmission side, the vibration of the piezoelectric body 13 generated by the drive signal is not only emitted as an ultrasonic pulse to the LP gas through the acoustic matching layer 9 but also causes the case 7 to vibrate. On the receiving side, the case 7 is vibrated at the same time as the received ultrasonic pulse is converted into an electric signal by the piezoelectric body 13. Here, if the case 7 vibrates, the vibration can hardly be attenuated in the case 7, so that a long reverberation of the piezoelectric body 13 is observed on both the transmitting side and the receiving side. The reverberation on the transmission side becomes electrical noise to the measurement circuit 33, which degrades the S / N of the received ultrasonic pulse and causes a reduction in measurement accuracy. Also, the reverberation on the receiving side is combined with the received ultrasonic pulse, so that it affects the amplitude and phase and causes an error in the measurement of the times t1 and t2. In the present embodiment, since the rigidity of the side wall 10 is increased by the bent portion 11 of the case 7, the side wall 10 is less likely to vibrate. Therefore, the vibration of the case 7 can be suppressed, and the reverberation of the ultrasonic vibrator 6 can be reduced. Therefore, the measurement accuracy of the ultrasonic flowmeter can be improved.

As described above, according to the present embodiment, the thickness longitudinal vibration can be used as the main mode by providing two grooves in the rectangular parallelepiped piezoelectric body 13. In addition, by bonding and fixing the piezoelectric body 13 and the top part 8 with an epoxy-based adhesive of 10 μm or less, it is possible to conduct simultaneously with the adhesive strength. In addition, by bonding and fixing the electrode 18 divided by the groove 19 of the piezoelectric body 13 to the top portion 8, the connection of the divided electrode 18 becomes easy, and the divided piezoelectric body 13 bends in the horizontal direction. Vibration can be prevented. Since the piezoelectric body 13 is shielded by the stainless steel case 7 and the terminal plate 14, the influence of external noise can be reduced.

In the first embodiment, one bent portion 11 is provided. However, two or more bent portions 11 may be provided, and a structure in which a beat 38 is provided on the side wall portion 10 as shown in FIG. Further, although the top portion 8 has a disk shape, it may have an elliptical diameter.

(Example 2)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 7 is a top view of the ultrasonic vibrator 39, and FIG. 8 is a side view of the ultrasonic vibrator 39. 8 is a top part, 9 is an acoustic matching layer, 10 is a side wall part, 12 is a support part, 14 is a terminal plate, 15 is a terminal, and the above is the same as the structure of FIG. 1 and 2 is that the side wall portion 10 is provided with eight convex portions in the axial direction.

An example of a method for producing the ultrasonic transducer configured as described above will be described with reference to FIGS. Assuming that the ultrasonic vibrator 39 is used in LP gas or natural gas, a material made of stainless steel for the case 7 and a mixture of epoxy resin and hollow glass spheres for the acoustic matching layer 9 is selected. In consideration of mass productivity, the forming method of the case 7 is not a cutting but a forming such as drawing.

First, a cylindrical case 7 having a disk-shaped top portion 8 having a diameter of about 13 mm is formed from a stainless steel plate having a thickness of 0.2 mm. At this time, eight convex portions 40 are formed in the side wall portion 10 in the axial direction, and when viewed from above, the side wall portion 10 looks like a petal. Next, a disk-shaped acoustic matching layer 9 having a diameter of 12.5 mm is bonded and fixed to the outer wall surface of the top section 8 using an epoxy-based adhesive. The method of manufacturing the ultrasonic vibrator 39, the method of manufacturing the ultrasonic flowmeter, and the operation principle thereafter are the same as those in the first embodiment, and thus description thereof is omitted.

(4) The higher the rigidity of the side wall portion 10 is, the harder the case 7 is to vibrate, so that reverberation can be suppressed. In order to increase the rigidity of the case 7 made of a thin metal plate, a convex portion or a concave portion may be provided, and the molding process can be facilitated. In this embodiment, by providing eight convex portions 40 in the axial direction of the side wall portion 10, rigidity can be increased and reverberation of the ultrasonic transducer 39 can be reduced.

In the second embodiment, eight convex portions 40 are provided on the side wall portion 10. However, any number of one or more convex portions may be used. Further, as shown in FIG. 9, a concave portion 41 may be provided in the side wall portion 10 to form a crown, or a convex portion and a concave portion may be combined.

(Example 3)
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 10 is an external view of the ultrasonic vibrator 42. Reference numeral 7 denotes a case, 10 denotes a side wall portion, and 12 denotes a support portion. The above is the same as the configuration in FIG. The difference from the configuration of FIG. 1 is that the top 43 is rectangular, the acoustic matching layer 44 is a rectangular parallelepiped, and the bent portion 45 is provided in the axial direction of the side wall 10.

An example of a method for producing the ultrasonic transducer configured as described above will be described with reference to FIG. Assuming that the ultrasonic vibrator 42 is used in LP gas or natural gas, the case 7 is made of stainless steel, and the acoustic matching layer 44 is made of a material made of a mixture of epoxy resin and hollow glass spheres. In consideration of mass productivity, the forming method of the case 7 is not a cutting but a forming such as drawing.

(1) First, a case 7 having a square-topped square shape having a square top portion 43 with a side of 9 mm is molded from a stainless steel plate having a thickness of 0.2 mm. At this time, the bent portion 45 is formed on the side wall portion 10 so that the side wall portion 10 becomes substantially a square pillar. Next, a rectangular parallelepiped acoustic matching layer 44 having a square surface of 8 mm on a side is bonded and fixed to the top part 43 using an epoxy adhesive. The method of manufacturing the ultrasonic transducer 42, the method of manufacturing the ultrasonic flowmeter, and the operation principle thereafter are the same as those in the first embodiment, and thus description thereof is omitted.

(4) The higher the rigidity of the side wall portion 10 is, the harder the case 7 is to vibrate, so that reverberation can be suppressed. Here, in order to increase the rigidity of the case 7 made of a thin metal plate, the side wall may be formed in a polygonal column shape, and it is easy to mold the side wall 10 into a polygon. In the present embodiment, by forming the side wall portion 10 as a square pole, rigidity can be increased and reverberation of the ultrasonic transducer 42 can be reduced.

In the third embodiment, the top part 43 is a square and the side wall part 10 is a square pole, but may be a polygon other than a square. Further, although the support portion 12 has a disk shape, the support portion 12 may have a square shape similarly to the top plate 8, or may have another polygonal shape.

(Example 4)
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 11 is a sectional view of the ultrasonic vibrator 46, and FIG. 12 is a top view of the ultrasonic vibrator 46. 7 is a case, 8 is a top, 9 is an acoustic matching layer, 10 is a side wall, 12 is a support, 13 is a piezoelectric body, 14 is a terminal plate, 15a and 15b are terminals, and 16 is a terminal 15a and a terminal 15b are insulated. Insulating portions 17 are lead wires for electrically connecting the piezoelectric body 13 and the terminals 15a, and have the same configuration as that of FIG. The configuration shown in FIG. 1 is different from the configuration in that convex portions 47 a to 47 d are provided at four positions on an outer peripheral portion 49 of the top portion 8, and a gap portion 48 is provided between the convex portion 47 and the acoustic matching layer 9.

An example of a method for producing the ultrasonic transducer 46 configured as described above will be described with reference to FIGS. Assuming that the ultrasonic vibrator 46 is used in LP gas or natural gas, a material made of stainless steel for the case 7 and a mixture of epoxy resin and hollow glass spheres for the acoustic matching layer 9 is selected. In consideration of mass productivity, the forming method of the case 7 is not a cutting but a forming such as drawing. First, a cylindrical case 7 having a disk-shaped top portion 8 having a diameter of about 15 mm is formed from a stainless steel plate having a thickness of 0.2 mm. At this time, on the outer peripheral portion 49 of the top portion 8, convex portions 47 a to 47 d having a height smaller than the thickness of the acoustic matching layer 9 and about 0.8 mm are formed concentrically. Next, a disc-shaped acoustic matching layer 9 having a diameter of 12.5 mm is bonded and fixed on the outer wall surface of the top portion 8 inside the convex portions 47a to 47d using an epoxy-based adhesive. At this time, a gap 48 is formed between the acoustic matching layer 9 and the protrusions 47a to 47d. The method of manufacturing the ultrasonic transducer 46, the method of manufacturing the ultrasonic flow meter, and the operation principle thereafter are the same as those in the first embodiment, and thus description thereof is omitted.

(4) When the rigidity of the outer peripheral portion 49 of the ceiling portion 8 is increased, the vibration is less likely to be transmitted to the side wall portion 10 and the case 7 is less likely to vibrate. Therefore, reverberation of the ultrasonic transducer 46 can be suppressed. Here, in order to increase the rigidity of the case 7 made of a thin metal plate, a convex portion or a concave portion may be provided on the outer peripheral portion 49, and it is easy to mold the convex portion or the convex portion on the outer peripheral portion 49. is there. In this embodiment, by providing four convex portions 47a to 47d on the outer peripheral portion 49, the rigidity of the case 7 can be increased and the reverberation of the ultrasonic transducer 39 can be reduced.

In the fourth embodiment, four convex portions 47 are provided on the outer peripheral portion 49. However, any number of one or more convex portions may be provided, and the convex portions 50 may be provided in an annular shape as shown in FIG. Further, although the convex portion is provided on the outer peripheral portion 49, a plurality of concave portions 51 or an annular concave portion 51 may be provided as shown in FIG. Although the gap 48 is provided between the acoustic matching layer 9 and the projection 47, the gap 48 may be filled with an epoxy-based adhesive in order to increase the adhesive strength of the acoustic matching layer 9; An elastic body such as silicon rubber may be filled to stop the attenuation of the vibration of the matching layer 9.

(Example 5)
Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 15 is a cross-sectional view of the ultrasonic transducer 52. 7 is a case, 8 is a top, 9 is an acoustic matching layer, 10 is a side wall, 12 is a support, 13 is a piezoelectric body, 14 is a terminal plate, 15a and 15b are terminals, and 16 is a terminal 15a and a terminal 15b are insulated. Insulating portions 17 are lead wires for electrically connecting the piezoelectric body 13 and the terminals 15a, and have the same configuration as that of FIG. 1 in that a thin portion 54 is provided on the outer peripheral portion 53 of the top portion 8.

An example of a method for producing the ultrasonic transducer 52 configured as described above will be described with reference to FIG. Assuming that the ultrasonic vibrator 52 is used in LP gas or natural gas, stainless steel is used for the case 7 and a material made of a mixture of epoxy resin and hollow glass spheres is selected for the acoustic matching layer 9. In consideration of mass productivity, the forming method of the case 7 is not a cutting but a forming such as drawing.

First, a cylindrical case 7 having a disk-shaped top portion 8 having a diameter of about 14 mm is formed from a stainless steel plate having a thickness of 0.3 mm. At this time, one thin portion 54 having a thickness of about 0.1 mm, which is concentric with the top portion 8, is formed on the outer peripheral portion 53 of the inner wall surface and the outer wall surface of the top portion 8. Next, a disc-shaped acoustic matching layer 9 having a diameter of 12.5 mm is adhered and fixed to the outer wall surface of the top portion 8 inside the thin portion 54 using an epoxy adhesive. The piezoelectric body 13 is bonded and fixed to the inner wall surface of the top section 8 with an epoxy adhesive. The method of manufacturing the ultrasonic transducer 46, the method of manufacturing the ultrasonic flow meter, and the operation principle thereafter are the same as those in the first embodiment, and thus description thereof is omitted.

In order to suppress the vibration of the case 7, there is a method of easily vibrating the ceiling portion 8 in addition to increasing the rigidity of the case 7. This is made possible by weakening the vibrational connection between the top section 8 and the side wall section 10. Therefore, the thin portion 54 makes it easy for the inside of the thin portion 54 of the top portion 8 to vibrate, and makes it difficult for the vibration to be transmitted to the outside. For this reason, the case 7 does not easily vibrate, and the reverberation of the ultrasonic transducer 52 can be suppressed.

In the fifth embodiment, the thin portion 54 is provided on the inner wall surface and the outer wall surface of the outer peripheral portion 54. However, only the inner wall surface or the outer wall surface may be provided. In addition, although one concentric thin portion 54 is provided, two or more concentric thin portions may be provided, and the concentric thin portions 54 may not be continuous in an annular shape.

(Example 6)
Hereinafter, a sixth embodiment of the present invention will be described with reference to the drawings.

FIG. 16 is a cross-sectional view of the ultrasonic vibrator 55, and FIG. 17 is a cross-sectional view of an ultrasonic vibrator mounting portion of the flow measuring unit 23 of the ultrasonic flowmeter. 7 is a case, 8 is a top portion, 9 is an acoustic matching layer, 10 is a side wall portion, 11 is a bent portion, 12 is a support portion, 13 is a piezoelectric body, 15a and 15b are terminals, and 16 is an insulating terminal 15a and a terminal 15b. Insulating portions 17 are lead wires for electrically connecting the piezoelectric body 13 and the terminals 15a, and have the same configuration as that of FIG. The difference from the configuration in FIG. 1 is that the diameter of the terminal plate 56 is larger than the support portion 12 and that a seal portion 57 is provided on the outer periphery of the terminal plate 56. The method for producing the ultrasonic transducer 55 having the above-described structure, the method for producing the ultrasonic flowmeter, and the operating principle are the same as those in the first embodiment, and a description thereof will be omitted.

(4) A method of attaching the ultrasonic transducer 55 to the flow measuring unit 23 will be described. The ultrasonic transducer 55 is inserted into the transducer mounting hole 29 provided in the side wall part 24. The terminal plate 56 of the ultrasonic transducer 55 has a thickness of 1 mm and a diameter of 20 mm. The terminal plate 56 is configured to be 4 mm larger than the support portion 12 with a diameter of 16 mm, and a seal portion 57 is provided in this portion. A seal member 57 made of an O-ring is interposed between the seal portion 57 and a flow path seal surface 58 provided on the side wall portion 24. Next, the terminal plate 56 is fixed by applying pressure from the back surface with a donut-shaped fixing body and a screw (not shown).

In the ultrasonic transducer 55, when the support portion 12 and the terminal plate 56 are electrically welded, the surface of the support portion 12 may have irregularities. If the surface of the support portion 12 has irregularities, it is conceivable that even if the seal material 59 is used, it is not possible to prevent gas from leaking from the vibrator mounting hole 29. In the present embodiment, by using the terminal plate 56 having a larger outer dimension than the support portion 12, it is possible to have a smooth seal portion 57 on the outer periphery of the terminal plate 56 which is not affected by electric welding. Therefore, the safety of the ultrasonic flowmeter against gas leakage can be improved.

In the sixth embodiment, the terminal plate 56 and the seal portion 59 have the same thickness. However, the terminal plate 56 and the seal portion 59 do not have to have the same thickness. It may be thick. Further, although the terminal plate 56 has a disk shape, the terminal portion 56 may be configured by bending the seal portion 59. Although the diameter of the terminal plate 56 is larger than that of the support portion 12, the diameter of the support portion 12 may be larger than that of the terminal plate 56, and the support portion 12 may be provided with a seal portion.

In the first to sixth embodiments, the piezoelectric body 13 is a piezoelectric ceramic, the frequency is 400 KHz, the shape is a rectangular parallelepiped having a length of 8 mm, a width of 8 mm, and a thickness of 4 mm, and two grooves are provided. Instead, the material, frequency, shape, dimensions, and number of grooves can be changed as appropriate, and for example, thickness vibration of a thin disk, or thickness vibration of a cylinder or prism can be used. Although the material of the flow rate measuring unit 23 is an aluminum alloy die-cast, the present invention is not limited to the above conditions, and the material can be appropriately changed depending on the fluid to be measured. Further, the cross section 37 of the flow path is rectangular, and the ultrasonic transducers 27, 28, and 55 are arranged obliquely with respect to the flow path 26. However, the present invention is not limited to the above conditions. The flow path shape may be cylindrical, or the ultrasonic vibrator may be arranged in parallel to the flow. Although the seal members 31, 32, and 59 are O-rings, the present invention is not limited to the above conditions, and the material and shape can be appropriately changed as long as the flammable fluid to be measured can be sealed.

(4) Although the fluid to be measured is LP gas or natural gas, other gases or liquids such as liquefied natural gas, petroleum, and kerosene may be used. A household gas meter is assumed as the ultrasonic flow meter, but other ultrasonic flow meters or ultrasonic flow meters may be used, and a flow meter for controlling the flow rate of gas in a water heater, or a flow meter for air or fuel in an automobile. I do not care. Although the case 7 and the terminal plates 14 and 56 are made of stainless steel, the present invention is not limited to the above conditions, and the materials can be appropriately changed. Further, although the support portion 12 is provided on the end face of the side wall portion, it may be provided in other places. The matching layers 9 and 44 use only one layer of a material made of epoxy resin and micro glass spheres, but there is no need to provide one or more layers of a material having a shape suitable for the fluid to be measured or depending on the fluid to be measured. There is also. Moreover, you may implement combining the structure of several Example. Although the ultrasonic transducer is used for the ultrasonic flow meter, it may be used as an ultrasonic sensor such as a distance sensor. Although the space surrounded by the case 7 and the terminal plate 14 is replaced by dry nitrogen or an inert gas, the space may be evacuated or air.

明 ら か As is clear from the above description, the following effects can be obtained by the ultrasonic vibrator according to the embodiment of the present invention and the flow meter using the same.

The first ultrasonic vibrator according to the embodiment of the present invention includes a 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 an outer portion of the top portion. An acoustic matching layer provided on the wall surface, and a support provided on the outer wall of the side wall portion, and the case has a vibration-proof structure to prevent the vibration of the piezoelectric body from propagating to the case. It is possible to transmit and receive short ultrasonic pulses and obtain an ultrasonic transducer capable of measuring high S / N with reduced influence of noise due to reverberation.

The second ultrasonic vibrator according to the embodiment of the present invention has a shape in which the rigidity of the side wall portion is increased, so that the vibration of the piezoelectric body is prevented from propagating to the side wall portion, and transmission / reception of the ultrasonic pulse having a short reverberation is achieved. This makes it possible to obtain an ultrasonic transducer capable of measuring high S / N with reduced influence of noise due to reverberation.

In the third ultrasonic vibrator according to the embodiment of the present invention, since the side wall is provided with a bent portion concentric with the top, the rigidity of the side wall is increased, and the vibration of the piezoelectric body is prevented from propagating to the side wall. As a result, it is possible to transmit and receive an ultrasonic pulse having a short reverberation, and to obtain an ultrasonic transducer capable of measuring a high S / N with reduced influence of noise due to the reverberation.

Since the fourth ultrasonic vibrator in the embodiment of the present invention has a plurality of convex portions or concave portions in the axial direction of the side wall portion, the rigidity of the side wall portion increases, and the vibration of the piezoelectric body can propagate to the side wall portion. An ultrasonic vibrator that is prevented from transmitting and receiving ultrasonic pulses with a short reverberation and that can measure high S / N with reduced influence of noise due to reverberation can be obtained.

In the fifth ultrasonic transducer according to the embodiment of the present invention, since the side wall portion is formed in a polygonal cylindrical shape, the rigidity of the side wall portion is increased, and the vibration of the piezoelectric body is prevented from propagating to the side wall portion. It is possible to transmit and receive short ultrasonic pulses and obtain an ultrasonic transducer capable of measuring high S / N with reduced influence of noise due to reverberation.

Since the sixth ultrasonic vibrator according to the embodiment of the present invention has the convex portion or the concave portion on the outer peripheral portion of the top portion, the rigidity of the outer peripheral portion of the top portion increases, and the vibration of the piezoelectric body propagates to the side wall portion. Thus, it is possible to transmit and receive an ultrasonic pulse having a short reverberation, and to obtain an ultrasonic transducer capable of measuring high S / N with reduced influence of noise due to reverberation.

In the seventh ultrasonic transducer according to the embodiment of the present invention, since the thin portion is provided on the outer peripheral portion of the top portion, the portion of the top portion to which the piezoelectric body is fixed easily vibrates, and the vibration of the piezoelectric body is transmitted to the side wall portion. Since propagation is prevented, an ultrasonic pulse having a short reverberation can be transmitted and received, and an ultrasonic transducer capable of measuring high S / N with reduced influence of noise due to reverberation can be obtained.

An ultrasonic flowmeter according to an embodiment of the present invention includes a flow measurement unit through which a fluid to be measured flows, and a pair of first to seventh ultrasonic transducers provided in the flow measurement unit and configured to transmit and receive ultrasonic waves. And a measuring circuit for measuring the propagation time between the ultrasonic transducers and a flow rate calculating means for calculating a flow rate based on a signal from the measuring circuit, so that the influence of noise due to reverberation can be reduced. And an ultrasonic flowmeter having high measurement accuracy of the flow rate and the flow velocity of the fluid to be measured can be obtained.

The ultrasonic flowmeter according to the embodiment of the present invention includes the ultrasonic vibrator having the seal portion on the terminal plate fixed to the support portion, so that the fluid to be measured can be prevented from leaking from the flow measurement portion to the outside, A highly reliable ultrasonic flowmeter can be obtained.

As described above, the ultrasonic vibrator according to the present invention and the ultrasonic flowmeter using the same can be applied to the measurement of the flow rate and the flow velocity of a gas or a liquid by ultrasonic waves.

1 is an external view of an ultrasonic transducer according to a first embodiment of the present invention. Cross section of the same ultrasonic transducer External view of piezoelectric body used in the ultrasonic transducer Configuration diagram including a partial cross-sectional view of the ultrasonic flow meter used for the ultrasonic transducer Cross-sectional view taken along line aa ′ of the flow meter Sectional view of a modified example of the ultrasonic transducer Top view of ultrasonic transducer according to Embodiment 2 of the present invention Side view of the same ultrasonic transducer External view of a modified example of the ultrasonic transducer External view of an ultrasonic vibrator according to a third embodiment of the present invention Sectional view of an ultrasonic transducer according to a fourth embodiment of the present invention. Top view of the same ultrasonic transducer Top view of a modified example of the ultrasonic transducer Sectional view of a modified example of the ultrasonic transducer Sectional view of an ultrasonic transducer according to a fifth embodiment of the present invention. Sectional view of an ultrasonic transducer according to a sixth embodiment of the present invention. Sectional view of the ultrasonic transducer mounting part of the flow measuring unit of the ultrasonic flow meter Cross section of conventional ultrasonic transducer for ultrasonic flow meter Sectional view of another conventional ultrasonic transducer for ultrasonic flowmeter

Explanation of reference numerals

Reference Signs List 6 ultrasonic vibrator 7 case 8 top part 9 acoustic matching layer 10 side wall part 11 bent part 12 support part 13 piezoelectric body 27, 28 ultrasonic vibrator 23 flow measuring part 33 measuring circuit 34 flow calculating means 40, 47 convex part 41 , 51 concave portion 54 thin portion 57 seal portion

Claims (4)

A sealed case comprising: a topped cylindrical case having a top, a side wall, and an opening; a piezoelectric body fixed to an inner wall surface of the top; and a sealing body for closing the opening of the case. An ultrasonic vibrator configured by replacing the inside of the case sealed with nitrogen or an inert gas. An ultrasonic flowmeter comprising a flow path through which a flammable fluid to be measured flows, and an ultrasonic vibrator provided in the flow path for transmitting and receiving an ultrasonic signal, wherein the ultrasonic vibrator has a ceiling and a side wall. A cylindrical case having a portion and an opening, a piezoelectric body fixed to an inner wall surface of the top portion, an acoustic matching layer provided on an outer wall surface of the top portion, and closing an opening of the case An ultrasonic flowmeter comprising a sealing body, wherein the inside of the case sealed by the sealing body is replaced with nitrogen or an inert gas. A flow path through which the flammable fluid to be measured flows, and a pair of ultrasonic vibrators provided in the flow path for transmitting and receiving ultrasonic signals, and measuring an ultrasonic propagation time between the ultrasonic vibrators to determine a flow rate; An ultrasonic flowmeter for measuring, wherein the ultrasonic vibrator is a cylindrical case having a ceiling, a side wall, and an opening, a piezoelectric body fixed to an inner wall surface of the ceiling, and An acoustic matching layer provided on an outer wall surface of a top portion, and a sealing body for closing an opening of the case, wherein the inside of the case sealed by the sealing body is replaced with nitrogen or an inert gas. Sound flow meter. The ultrasonic vibrator according to claim 1, wherein the piezoelectric body and the case are adhered and fixed.

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