Fluid measuring device including an ultrasonic probe having a wedge with an ultrasonic vibrator

A fluid measuring device in which an ultrasonic probe provided on an outer pipeline surface transmits and receives ultrasonic waves to and from fluid in a pipeline to measure characteristics of the fluid on the basis of propagation time of the ultrasonic waves, features a wedge included in the ultrasonic probe and having an ultrasonic vibrator provided on a wedge surface. The ultrasonic vibrator may be horizontal to a surface contacting the pipeline so that ultrasonic waves enter the fluid vertically. The ultrasonic vibrator may be provided on a wedge surface inclined with respect to an axial direction of the pipeline so that ultrasonic waves enter the fluid obliquely. The fluid measuring device embodiments are capable of measuring fluid characteristics, such as the type and velocity of various fluids, easily and accurately even when it is difficult to allow an ultrasonic signal to pass through the fluid in a pipeline.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid measuring device capable of measuring fluid characteristics such as the type and velocity of various fluids easily and accurately even when it is difficult to allow an ultrasonic signal to pass through the fluid in a pipeline.

2. Background of the Related Art

Gas pipeline for supplying town gas and pipelines such as water or sewage pipelines are buried under the ground. When construction works are performed in a place where pipelines are buried, these pipelines may be exposed and it may be difficult to identify the type of the exposed pipeline. In such a case, it is necessary to determine the type of the exposed pipeline by determining the type of fluid flowing through the pipeline (for example, the type of fluid such as town gas, water, or air) and to take measures appropriate for each type of pipeline.

As a conventional method of determining the type of fluid in a pipeline, a method of forming a hole in a pipeline and extracting the fluid through the hole is known. According to another method of determining the type of fluid in a pipeline, a neutron moisture meter is used. This method can determine the fluid type without breaking a pipeline. As still another method of determining the type of fluid in a pipeline, Japanese Patent Application Publication No. H11-94613 (Patent Literature 1) discloses a method of determining the fluid type based on transmission intensity of ultrasonic waves. Moreover, Japanese Patent No. 4687293 (Patent Literature 2) discloses a method of measuring a flow rate distribution of liquid in a pipeline by allowing ultrasonic waves to pass through the pipeline without breaking the pipeline.

However, the method of determining the type of a fluid in a pipeline by extracting internal fluid through a hole requires a pipeline recovery operation of blocking the hole after the type of fluid in the pipeline is determined, which incurs a considerable time and labor.

Moreover, the method of determining the type of fluid in the pipeline using a neutron moisture meter can identify the presence of water only. Thus, the type of fluid that can be identified is limited, and it is difficult to determine a sufficient number of types of fluid.

Further, the method of determining the type of fluid in the pipeline using the transmission intensity of ultrasonic waves, disclosed in Patent Literature 1 requires an ultrasonic probe to be provided in a pipeline, and as a result, a complex piping work is required.

Moreover, when the method disclosed in Patent Literature 2 is applied to gas such as town gas or air, since the transmittance of ultrasonic waves in gas is lower than that in liquid, it is difficult to obtain sufficient measurement accuracy. Further, when a pipeline is old, rusty, or corroded, or has sediments adhering thereto, which makes it difficult for ultrasonic waves to pass through, sufficiently accurate measurement is difficult to implement.

The present invention has been made in view of the above problems, and an object thereof is to provide a fluid measuring device capable of measuring fluid characteristics such as the type and velocity of various fluids easily and accurately even when it is difficult to allow an ultrasonic signal to pass through the fluid in a pipeline.

SUMMARY OF THE INVENTION

In order to solve the problems and attain the object, according to an aspect of the present invention, there is provided a fluid measuring device in which an ultrasonic probe provided on an outer pipeline surface transmits and receives ultrasonic waves to and from fluid in a pipeline to thereby measure characteristics of the fluid on the basis of a propagation time of the ultrasonic waves having propagated through the fluid, wherein the ultrasonic probe has a wedge in which an ultrasonic vibrator is provided on a wedge surface horizontal to a surface contacting the pipeline so that ultrasonic waves enter the fluid vertically, and the wedge has a vibrator surface on which the ultrasonic vibrator is provided and a pipeline contacting surface provided in contact with the outer pipeline surface horizontally to the vibrator surface, in a cross-section vertical to an axial direction of the pipeline, and a length of the pipeline contacting surface in the cross-section vertical to the axial direction is smaller than a length of the vibrator surface in the cross-section vertical to the axial direction.

In the fluid measuring device according to the above aspect of the present invention, the wedge may have a wedge side surface that connects the vibrator surface and the pipeline contacting surface in the cross-section vertical to the axial direction of the pipeline, and the wedge side surface may have an inclined surface portion that is inclined with respect to a line perpendicular to the vibrator surface and the pipeline contacting surface.

In the fluid measuring device according to the above aspect of the present invention, the ultrasonic vibrator may be a pair of ultrasonic vibrators provided on the same wedge to be adjacent in the axial direction of the pipeline.

According to another aspect of the present invention, there is provided a fluid measuring device in which a plurality of ultrasonic probes provided on an outer pipeline surface transmits and receives ultrasonic waves to and from fluid in a pipeline to thereby measure characteristics of the fluid on the basis of a propagation time of the ultrasonic waves having propagated through the fluid, measured by a time measuring unit that measures the time elapsed from transmission to reception of the ultrasonic waves, wherein the ultrasonic probe has a wedge in which an ultrasonic vibrator is provided on a wedge surface inclined with respect to an axial direction of the pipeline so that ultrasonic waves enter the fluid obliquely, and the wedge has a vibrator projection surface on which a vibrator surface having the ultrasonic vibrator provided thereon is projected and a pipeline contacting surface provided in contact with the outer pipeline surface, in a cross-section vertical to the axial direction of the pipeline, and a length of the pipeline contacting surface in the cross-section vertical to the axial direction is smaller than a horizontal length of the vibrator projection surface in the cross-section vertical to the axial direction.

In the fluid measuring device according to the above aspect of the present invention, the wedge may have a wedge side surface that connects the vibrator projection surface and the pipeline contacting surface in the cross-section vertical to the axial direction of the pipeline, and the wedge side surface may have an inclined surface portion that is inclined with respect to a line perpendicular to the pipeline contacting surface.

In the fluid measuring device according to the above aspect of the present invention, the ultrasonic waves generated by the ultrasonic vibrator may be SV-waves with respect to a plane that includes the center of the ultrasonic vibrator and the axis of the pipeline.

In the fluid measuring device according to the above aspect of the present invention, the wedge may have the inclined surface portion and the pipeline contacting surface that are separated in the cross-section vertical to the axial direction.

In the fluid measuring device according to the above aspect of the present invention, the wedge may be formed of a combination of a plurality of materials, and a portion that forms the vibrator surface and a portion that forms the pipeline contacting surface may be formed of different materials.

In the fluid measuring device according to the above aspect of the present invention, the material of the portion that forms the pipeline contacting surface may exhibit higher heat-resistance performance at high or low temperature than the material of the portion that forms the vibrator surface.

In the fluid measuring device according to the above aspect of the present invention, the cross-section of the wedge vertical to the axial direction may have a shape that is bilaterally symmetrical to a central line that passes the axis of the pipeline, and an angle θ of the inclined surface portion to the line perpendicular to the pipeline contacting surface and a value “a” obtained by dividing the length of the pipeline contacting surface in the cross-section vertical to the axial direction by the length of the vibrator surface in the cross-section vertical to the axial direction or the horizontal length of the vibrator projection surface in the cross-section vertical to the axial direction may satisfy a relation of tan 2θ/tan θ<(1+a)/(1−a).

In the fluid measuring device according to the above aspect of the present invention, the value “a” may satisfy a relation of ⅓<a<1.

In the fluid measuring device according to the above aspect of the present invention, the angle θ may satisfy a relation of 0°<θ<45°.

In the fluid measuring device according to the above aspect of the present invention, an ultrasonic absorber may be provided in contact with the outer pipeline surface and around a position in which the wedge makes contact with the outer pipeline surface.

In the fluid measuring device according to the above aspect of the present invention, the ultrasonic absorber may contain tungsten mixed in a base material thereof.

In the fluid measuring device according to the above aspect of the present invention, the ultrasonic absorber may contain magnetic substance mixed in a base material thereof and may be processed in a sheet form.

According to the present invention, one ultrasonic probe provided on the outer pipeline surface transmits and receives ultrasonic waves to and from the fluid in the pipeline. The ultrasonic probe used when measuring the characteristics of the fluid based on the propagation time of the ultrasonic waves having propagated through the fluid has the wedge in which the ultrasonic vibrator is provided on the surface horizontal to the surface contacting the pipeline so that the ultrasonic waves enter the fluid vertically. The wedge has the vibrator surface on which the ultrasonic vibrator is provided and the pipeline contacting surface provided in contact with the outer pipeline surface horizontally to the vibrator surface, in the cross-section vertical to the axial direction of the pipeline. The length of the pipeline contacting surface in the cross-section vertical to the axial direction is smaller than the length of the vibrator surface in the cross-section vertical to the axial direction. Due to such a configuration, the ultrasonic waves emitted from the ultrasonic vibrator concentrate vertically to the pipeline contacting surface and highly dense ultrasonic waves can enter the pipeline. As a result, it is possible to measure fluid characteristics such as the type and velocity of various fluids easily and accurately even when it is difficult to allow an ultrasonic signal to pass through the fluid in a pipeline.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment—Entire Configuration

FIG. 1is a schematic diagram illustrating an entire configuration of a fluid measuring device according to a first embodiment of the present invention. InFIG. 1, a fluid measuring device1determines the type of a fluid103flowing through a pipeline100, which is one of the characteristics of the fluid103.

As illustrated inFIG. 1, the fluid measuring device1includes a measuring unit10and a main body20. The measuring unit10includes an ultrasonic vibrator11and a wedge12. The ultrasonic vibrator11and the wedge12have such a structure that a contacting surface in which a lower portion of the wedge12makes contact with an outer pipeline surface101of the pipeline100is parallel to a surface in which the ultrasonic vibrator11is provided on an upper portion of the wedge12, and ultrasonic waves are vertically emitted to the contacting surface of the outer pipeline surface101so as to pass through the outer pipeline surface101. In order to obviate the presence of air or the like between the outer pipeline surface101and the lower portion of the wedge12where it is difficult for ultrasonic waves to pass through the air or the like, an ultrasonic connection medium13serving as an ultrasonic coupler is provided in the lower portion of the wedge12. The ultrasonic connection medium13is realized by purified water, alcohol, silicon, or the like. The ultrasonic connection medium13may be in the form of liquid, gel, rubber, or the like. The ultrasonic vibrator11, the wedge12, and the ultrasonic connection medium13form an ultrasonic probe14. Moreover, an ultrasonic absorber15that absorbs interference waves transmitted while experiencing multiple reflections through a thick portion of the pipeline100is disposed in the outer pipeline surface101around the ultrasonic probe14. The measuring unit10includes the ultrasonic probe14and the ultrasonic absorber15.

The main body20includes a transmitting unit21, a receiving unit22, a switch23, a time measuring unit24, a fluid type determining unit25, a storage unit26, and an input/output unit27, and these respective units are connected to a control unit28. The switch23is electrically connected to the ultrasonic vibrator11.

The transmitting unit21generates an ultrasonic transmission pulsating electrical signal for causing the ultrasonic vibrator11to generate an ultrasonic signal and outputs the same to the ultrasonic vibrator11via the switch23. The ultrasonic vibrator11generates an ultrasonic signal according to the ultrasonic transmission pulsating electrical signal. The generated ultrasonic signal passes through the pipeline100via the wedge12and enters the fluid103. The ultrasonic signal entering the fluid103is reflected from an inner pipeline surface102on a side opposite to the arrangement position of the ultrasonic probe14, makes one-round trip through the fluid103, passes through the pipeline100again, and then enters the ultrasonic vibrator11via the wedge12. The ultrasonic signal entering the ultrasonic vibrator11is converted to an ultrasonic reception pulsating electrical signal by the ultrasonic vibrator11and is output to the receiving unit22. The control unit28connects the switch23to the transmitting unit21during transmission of the ultrasonic transmission pulsating electrical signal only and connects the switch23to the receiving unit22during reception of the ultrasonic reception pulsating electrical signal after the ultrasonic transmission pulsating electrical signal is transmitted.

The time measuring unit24measures a propagation time required for the ultrasonic signal entering the pipeline100vertically to make one-round trip through the fluid103based on the transmission time (the time at which the ultrasonic signal is transmitted from the ultrasonic vibrator11) of the ultrasonic transmission pulsating electrical signal transmitted by the transmitting unit21and the reception time (the time at which the reflection waves of the ultrasonic signal are received by the ultrasonic vibrator11) of the ultrasonic reception pulsating electrical signal received by the receiving unit22.

Here, as illustrated inFIG. 2, the reflection waves of the ultrasonic signal output from the ultrasonic vibrator11come in three types Sa, Sb, and Sc. Reflection waves Sa are waves of some the ultrasonic signals emitted from the ultrasonic vibrator11, with these waves returning to the ultrasonic vibrator11after being reflected from the interface between the wedge12and the outer pipeline surface101. Reflection waves Sb are waves of some of the ultrasonic signals having passed through the interface between the wedge12and the outer pipeline surface101, with these waves returning to the ultrasonic vibrator11after being reflected from the interface between the inner pipeline surface102and the fluid103. Reflection waves Sc are waves that return to the ultrasonic vibrator11after passing through the fluid103, being reflected from the inner pipeline surface102on the opposite side, making one-round trip through the fluid103, and passing through the pipeline100and the wedge12among the ultrasonic signals having passed through the interface between the inner pipeline surface102and the fluid103.

FIG. 3is a timing chart illustrating the timings at which the ultrasonic vibrator11receives the reflection waves Sa, Sb, and Sc of the ultrasonic signal S transmitted by the ultrasonic vibrator11. As illustrated inFIG. 3, time to is the time (third time) elapsed from transmission of the ultrasonic signal S transmitted by the ultrasonic vibrator11to reception of the reflection waves Sa. Time tb is the time (first time) elapsed from transmission of the ultrasonic signal S transmitted by the ultrasonic vibrator11to reception of the reflection waves Sb. Time tc is the time (second time) elapsed from transmission of the ultrasonic signal S transmitted by the ultrasonic vibrator11to reception of the reflection waves Sc.

As described above, the time measuring unit24calculates a propagation time tf required for the ultrasonic signal entering the pipeline100vertically to make one-round trip through the fluid103according to Equation (1),
tf=tc−tb(1).
Fluid Type Determination when Inner Pipeline Diameter Di is Known—

The fluid type determining unit25calculates the velocity of sound in the fluid103by dividing twice the inner pipeline diameter Di by the propagation time tf calculated by the time measuring unit24. Here, the storage unit26stores velocity of sound-to-fluid type relation information DT1. The velocity of sound-to-fluid type relation information DT1indicates a relation between a fluid type and the velocity of sound uniquely determined by the type of a fluid. For example, when the fluid type is town gas, the town gas contains methane as its main component and the velocity of sound therein is approximately 430 m/s. Moreover, when the fluid type is water, the velocity of sound therein is approximately 1500 m/s. Moreover, when the fluid type is air, the velocity of sound therein is approximately 340 m/s. On the other hand, the inner pipeline diameter Di is a known value input from the input/output unit27. The inner pipeline diameter Di and outer pipeline diameter Do of the pipeline100buried under the ground are specified in the JIS standards and the like, and the inner pipeline diameter Di can be known upon reading the standard information written on the outer surface of the measuring target pipeline100. That is, the fluid type determining unit25calculates the velocity of sound in the fluid103by dividing twice the inner pipeline diameter Di by the propagation time tf and determines the fluid type corresponding to the calculated velocity of sound by referring to the velocity of sound-to-fluid type relation information DT1. The control unit28outputs the fluid type determined by the fluid type determining unit25from the input/output unit27.

Fluid Type Determination when Inner Pipeline Diameter Di is Unknown—

On the other hand, in old pipelines and buried pipelines, it may sometimes be difficult to read or identify pipe specification information written on the pipelines because the section showing the information is worn or buried. Moreover, some pipelines may not have the standard information. In such a case, the fluid type determining unit25estimates the inner pipeline diameter Di using the time ta (third time), the outer pipeline diameter Do, and the pipeline material. As long as the inner pipeline diameter Di can be estimated, the fluid type determining unit25can perform the fluid type determining process in a manner similarly to when the inner pipeline diameter Di is known.

The outer pipeline diameter Do can be measured by digging the ground so that about half of the pipeline100appears. Moreover, the pipeline material of the pipeline100can be determined by its appearance. The outer pipeline diameter Do and the pipeline material are input from the input/output unit27.

The fluid type determining unit25calculates the velocity of sound in the pipeline100corresponding to the input pipeline material based on pipeline material-to-velocity of sound relation information DT2stored in advance in the storage unit26. For example, the velocity of sound is approximately 6000 m/s when the pipeline material is metal such as iron or stainless steel, the velocity of sound is approximately 2300 m/s when the pipeline material is polyvinyl chloride which is plastic, and the velocity of sound is approximately 1900 m/s when the pipeline material is polyethylene which is plastic. It is easy to visually determine whether the pipeline material is metal or plastic. Thus, in the pipeline material-to-velocity of sound relation information DT2, the velocity of sound Cp is stored as 6000 m/s for the pipeline100when the pipeline material is metal, and the velocity of sound Cp is stored as 2000 m/s for the pipeline100when the pipeline material is plastic.

The fluid type determining unit25calculates the inner pipeline diameter Di using the outer pipeline diameter Do, the velocity of sound Cp in the pipeline100, the time tb, and the time ta according to Equation (2) below,
Di=Do−Cp(tb−ta)  (2).

Here, the value of Cp(tb−ta) corresponds to twice the thickness of the pipeline100.

However, since the velocity of sound Cp in the pipeline100is estimated, the value of the inner pipeline diameter Di in Equation (2) has an error. However, if the thickness of the pipeline100is estimated from the outer pipeline diameter Do, for example, when the diameter is 50 A (50 mm), the thickness of a metal pipeline ranges between 1.5 mm and 9 mm and the thickness of a plastic pipeline ranges between 2 mm and 8 mm. Thus, a thickness deviation is large and the error increases. On the other hand, in relation to a deviation in the velocity of sound Cp in the pipeline100depending on a difference in the pipeline material, it is possible to determine visually whether the pipeline material is metal or plastic. Thus, the thickness can be estimated with high accuracy by estimating the velocity of sound Cp in the pipeline100as described above. As a result, in the first embodiment, the inner pipeline diameter Di can be calculated with high accuracy.

Fluid Type Determining Process—

Here, the flow of a fluid type determining process performed by the fluid type determining unit25will be described with reference to the flowcharts illustrated inFIGS. 4 and 5. First, as illustrated inFIG. 4, the fluid type determining unit25acquires the time ta, tb, and tc from the time measuring unit24(step S101). After that, the propagation time tf is calculated according to Equation (1) (step S102). After that, an inner pipeline diameter (Di) acquiring process of acquiring the inner pipeline diameter Di input by the input/output unit27or the inner pipeline diameter Di calculated according to Equation (2) is performed (step S103).

After that, the fluid type determining unit25calculates the velocity of sound of the fluid103by dividing twice the inner pipeline diameter Di by the propagation time tf (step S104). Further, the fluid type determining unit25determines the fluid type corresponding to the calculated velocity of sound using the velocity of sound-to-fluid type relation information DT1(step S105) and outputs the fluid type from the input/output unit27(step S106). In this way, this process ends.

FIG. 5is a detailed flowchart illustrating the flow of the inner pipeline diameter (Di) acquiring process illustrated in step S103. As illustrated inFIG. 5, first, the fluid type determining unit25determines whether the inner pipeline diameter Di has been input by the input/output unit27(step S201). When the inner pipeline diameter Di has been input (step S201: Yes), the flow returns to step S103with no modification.

On the other hand, when the inner pipeline diameter Di has not been input (step S201: No), the outer pipeline diameter Do and the pipeline material input from the input/output unit27are acquired (step S202). After that, the fluid type determining unit25determines the velocity of sound Cp in the pipeline100corresponding to the acquired pipeline material based on the pipeline material-to-velocity of sound relation information DT2(step S203). After that, the fluid type determining unit25calculates the inner pipeline diameter Di using Equation (2) (step S204), and the flow returns to step S103.

Structure of Ultrasonic Probe—

FIG. 6is a diagram illustrating the structure of the ultrasonic probe14when seen from the surface vertical to the axial direction of the pipeline100. Moreover,FIG. 7is a diagram illustrating the structure of the ultrasonic probe14when seen from the surface horizontal to the axial direction of the pipeline100. As illustrated inFIGS. 6 and 7, a side surface (the surface extending in the direction vertical to the axial direction of the pipeline100) of the wedge12has an inclined surface portion30that is inclined at an angle with respect to a line perpendicular to a pipeline contacting surface Sβ. Moreover, a length L1in the cross-section, of a vibrator surface Sα of the wedge12on which the ultrasonic vibrator11is disposed is smaller than a length L2in the cross-section, of the pipeline contacting surface Sβ.

In the ultrasonic probe14, ultrasonic waves are generated on approximately the entire surface of the ultrasonic vibrator11and propagate in the direction vertical to the pipeline100. The ultrasonic waves entering the inclined surface portion30being in the propagation path are reflected and collected and finally enter the pipeline100while concentrating on the pipeline contacting surface Sβ that is narrower than the vibrator surface Sα.

Here, a wedge112of a conventional ultrasonic probe illustrated inFIG. 8does not have the inclined surface portion30. Thus, as illustrated inFIG. 8, a large part of the ultrasonic waves generated by the ultrasonic vibrator11are reflected from the space between the outer pipeline surface101which is a curved surface and the pipeline contacting surface Sβ of the wedge112, which is a flat surface, and do not enter the pipeline100. Thus, ultrasonic waves do not enter the pipeline100efficiently.

In contrast, in the first embodiment, ultrasonic waves can pass and enter the pipeline100while concentrating on the pipeline contacting surface Sβ which has a small area and makes contact with the outer pipeline surface101which is a curved surface. Thus, ultrasonic waves can enter the pipeline100efficiently. As a result, even when ultrasonic waves pass through a fluid such as gas or vapor, through which it is difficult for ultrasonic waves to pass, or even when the pipeline100is old, rusty, or corroded, or has sediments adhering thereto and it is difficult for ultrasonic waves to pass through the pipeline, since high intensity ultrasonic waves can enter the pipeline100, it is possible to measure ultrasonic waves with high accuracy in the fluid103.

In the first embodiment, since the stress applied when installing the ultrasonic probe14on the pipeline100concentrates on the narrow pipeline contacting surface Sβ, the outer pipeline surface101and the wedge12adhere further closely, and this close adhesion further improves the transmission efficiency of ultrasonic waves.

Moreover, although the inclined surface portion30is configured as a flat surface, the inclined surface portion30is not limited to a flat surface as long as the inclined surface portion30has such a shape in a side view that the pipeline contacting surface Sβ is smaller than the vibrator surface Sα.

When Transmission and Reception Ultrasonic Vibrators are Mounted on One Wedge—

Further, inFIGS. 6 and 7, although one transceiving ultrasonic vibrator11is provided on the vibrator surface Sα of one wedge12, two ultrasonic vibrators11aand11bmay be provided on the vibrator surface Sα of one wedge12as illustrated inFIG. 9. One ultrasonic vibrator11ais used as a transmission ultrasonic vibrator, and the other ultrasonic vibrator11bis used as a reception ultrasonic vibrator. In this case, the ultrasonic vibrators11aand11bare arranged to be adjacent to each other in the axial direction of the pipeline100. In general, when an electrical signal is transmitted to an ultrasonic vibrator to generate ultrasonic waves, echo noise occurs in a piezoelectric element and a circuit or between the piezoelectric element and the circuit, and it may take time until the echo noise is attenuated. When the pipeline diameter is small, for example, reception ultrasonic waves may enter the ultrasonic vibrator before the echo noise is attenuated, which disturbs measurement of the propagation time. In contrast, as illustrated inFIG. 9, when the transmission ultrasonic vibrator and the reception ultrasonic vibrator are provided separately, echo noise occurs between the transmission ultrasonic vibrator and a transmission circuit and has no influence on the reception ultrasonic vibrator and a reception circuit.

However, a piezoelectric element is generally used as the ultrasonic vibrator11. The piezoelectric element has a Curie point and the use under high temperature is limited. In contrast, in the first embodiment, an intermediate portion31is provided between the inclined surface portion30and the pipeline contacting surface Sβ so that the inclined surface portion30and the pipeline contacting surface Sβ are separated so as not to be connected directly. As a result, since the intermediate portion31has a narrow shape in relation to an intermediate portion32disposed between the inclined surface portion30and the vibrator surface Sα, it is possible to increase a heat-radiating effect. Thus, by adjusting the length of the intermediate portion31appropriately, the heat of the pipeline100is radiated to the surrounding and is rarely transmitted to the ultrasonic vibrator11. As a result, the device of the first embodiment can measure a high-temperature fluid easily. Similarly, the device can measure a low-temperature fluid easily.

Further, as illustrated inFIGS. 10 and 11, the wedge12is preferably formed of a combination of a plurality of materials. For example, a portion closer to the pipeline100may be formed as a metal member having high heat resistance since the portion is heated easily. A portion closer to the ultrasonic vibrator11may be formed as a resin material in order to improve assembling properties such as adhesion properties since the portion is cooled by heat radiation. In this way, it is possible to meet high-temperature applicability and satisfactory assembling properties. Specifically, inFIG. 10, the portion having the inclined surface portion30and the intermediate portion31are formed as a metal member32band the intermediate portion32is formed as a resin member32a. Moreover, inFIG. 11, the intermediate portion31is formed as a metal member33band the intermediate portion32and the portion having the inclined surface portion30are formed as a resin member33a.

Angle of Inclined Surface Portion—

However, there is a limit on the angle θ between the inclined surface portion30and the line perpendicular to the pipeline contacting surface Sβ. As illustrated inFIG. 12, this limitation on the angle θ will be described by way of an example in which the wedge12has a structure that is bilaterally symmetrical in a surface vertical to the axial direction of the pipeline100. Here, it is assumed that the length in the cross-section, of the vibrator surface Sα is D and the length in the cross-section, of the pipeline contacting surface Sβ is a×D. However, “a” is a value in the range of 0<a<1.

First, as illustrated inFIG. 13, when the angle θ is 45°, the ultrasonic waves reflected from the inclined surface portion30travel horizontally to the pipeline100and are reflected again from the inclined surface portion30on the opposite side and return to the ultrasonic vibrator11. In this case, it is difficult to allow ultrasonic waves to enter the pipeline100in a concentrated manner.

Thus, it is necessary to allow the ultrasonic waves reflected from the inclined surface portion30to enter the pipeline100in a concentrated manner without being reflected from the inclined surface portion30on the opposite side. It is assumed that the length of a component of the inclined surface portion30vertical to the pipeline is L, and the length of a component vertical to the pipeline100, corresponding to the distance in which the ultrasonic waves reflected from the inclined surface portion30reaches the intermediate portion31between the pipeline contacting surface Sβ and the inclined surface portion30on the opposite side is M. The condition under which the ultrasonic waves reflected from the inclined surface portion30are not reflected from the inclined surface portion30on the opposite side is expressed by Equation (3),
M>L(3).

The most strict condition that satisfies Equation (3) is obtained when ultrasonic waves are reflected from the outermost side of the inclined surface portion30(that is, the portion closest to the vibrator surface Sα), and in that case, the lengths L and M are expressed by Equations (4) and (5),
L·tan θ=(D−a·D)/2  (4),
M·tan 2θ=(D+a·D)/2  (5).

When Equations (4) and (5) are substituted into Equation (3), D is eliminated, and Equation (6) is obtained,
tan 2θ/tan θ<(1+a)/(1−a)  (6).

When a wedge shape that satisfies Equation (6) is designed, ultrasonic waves can be concentrated on the pipeline contacting surface Sβ.

When the angle θ in Equation (6) approaches “0,” since tan θ approximates to θ, the value “a” decreases and ultrasonic waves can be concentrated further. However, the value “a” is never smaller than ⅓. Thus, when the wedge12is designed, the value “a” needs to be larger than ⅓. As a result, the value “a” needs to be designed to be in the range of ⅓<a<1. Moreover, if the angle θ is 45°, since 2θ becomes 90° and tan 2θ becomes infinite, the angle θ cannot be designed to be at 45° or larger. Therefore, the angle θ needs to be designed to be in the range of 0°<θ<45°.

However, some of the ultrasonic signals entering from the contacting surface between the wedge12and the outer pipeline surface101are transmitted while experiencing multiple reflections using the inside of the pipeline100as a waveguide. For example, as illustrated inFIG. 14, interference waves transmitted through the pipeline100while experiencing multiple reflections may return to the ultrasonic vibrator11after making multiple round-trips through the pipeline100.FIG. 15is a vertical cross-sectional view of the pipeline100. As illustrated inFIG. 15, interference waves transmitted through the pipeline100may be reflected from the flange130provided at the end or the like in the axial direction of the pipeline100and may return to the ultrasonic vibrator11. InFIG. 15, an outbound ultrasonic signal is depicted by a solid line, and an incoming ultrasonic signal returning to the ultrasonic vibrator11after being reflected from the flange130is depicted by a broken line. These interference waves cause a measurement error in the time tc when the interference waves overlap the reflection waves Sc illustrated inFIG. 3on the time axis or occur near the reception time of the reflection waves Sc.

Thus, as illustrated inFIGS. 1 and 16, the ultrasonic absorber15is provided on the surface of the outer pipeline surface101near the ultrasonic probe14. A base material of the ultrasonic absorber15is formed of a substance such as rubber or clay that attenuates ultrasonic waves. As illustrated inFIG. 16, when interference waves experience multiple reflections through the pipeline100, some of the interference waves pass through the ultrasonic absorber15and disappear by being attenuated in the ultrasonic absorber15. Thus, a large part of the interference waves become extinct in the course of passing through the pipeline portion with which the ultrasonic absorber15and the outer pipeline surface101make contact. Due to this, it is possible to suppress a measurement error in the reflection waves Sc occurring due to overlap or presence of interference waves at the reception time of the reflection waves Sc. The ultrasonic absorber15is preferably disposed in the axial direction of the pipeline100as well as the circumferential direction of the pipeline100so as to surround all sides of the ultrasonic probe14. In this way, it is possible to absorb interference waves reflected from the flange130illustrated inFIG. 15.

As illustrated inFIG. 17, the ultrasonic absorber15preferably covers a range of regions corresponding to half or smaller of the circumference of the pipeline100. In this case, when the ground is dug so that about half of the pipeline100appears, it is possible to measure the outer pipeline diameter Do, install the ultrasonic absorber15, and install the measuring unit10easily.

When the pipeline100is metal, it is preferable to mix tungsten particles into the base material such as rubber or clay, of the ultrasonic absorber15to thereby increase the specific gravity to increase an interference wave absorbing effect. This is because, when the pipeline100and the ultrasonic absorber15have similar specific gravity, the proportion of the interference waves passing through the ultrasonic absorber15increases and the ultrasonic wave absorbing effect can be increased. In general, the specific gravity of rubber or clay which is the base material of the ultrasonic absorber15is approximate 1 to 2, which is far different from the specific gravity which is approximately 8, of a metal pipeline. Thus, by mixing tungsten whose specific gravity is approximately 19, the specific gravity of the ultrasonic absorber15can be made similar to that of the metal pipeline.

Further, when the pipeline100is formed of a magnetic substance such as iron or steel, it is preferable to mix a magnetic substance into the ultrasonic absorber15, process the ultrasonic absorber15in a sheet form, and magnetize the sheet to obtain a magnet sheet. When the ultrasonic absorber15is processed in a sheet form, the ultrasonic absorber15can be easily installed in the pipeline100. Moreover, when iron is used as the magnetic substance, since the iron has a specific gravity as small as 8, it is preferable to mix tungsten having a large specific gravity together.

In the first embodiment described above, an ultrasonic signal is incident vertically to the outer pipeline surface101of the pipeline100from one ultrasonic probe14, and the inclined surface portion30is provided so that the ultrasonic signal emitted from the ultrasonic vibrator11is concentrated and a highly dense ultrasonic signal enters the pipeline100. Thus, it is possible to measure fluid characteristics such as a fluid type in various types of pipelines with an easy-to-install structure without breaking the pipeline100. In particular, the ultrasonic signal can efficiently pass through the pipeline100having a curved outer surface. Thus, even when ultrasonic waves pass through a fluid such as gas or vapor, through which it is difficult for ultrasonic waves to pass, or even when the pipeline is old, rusty, or corroded, or has sediments adhering thereto and it is difficult for ultrasonic waves to pass through the pipeline, it is possible to measure ultrasonic waves with high accuracy.

Moreover, since the ultrasonic vibrator11that is vulnerable to high temperature can be separated from the pipeline100, it is possible to measure hot and cool fluid easily.

Further, since the ultrasonic absorber15can reduce interference waves returning while experiencing multiple reflections through the pipeline100, it is possible to suppress the influence of interference waves and to measure an accurate propagation time.

Second Embodiment—Entire Configuration

FIG. 18is a schematic diagram illustrating an entire configuration of a fluid measuring device according to a second embodiment of the present invention. InFIG. 18, a fluid measuring device2measures the velocity of a fluid103flowing through a pipeline100. The type of the fluid103may be determined based on the propagation time measured in the same manner as the first embodiment.

In the fluid measuring device2, a plurality of ultrasonic probes14aand14bis provided on an outer pipeline surface101of the pipeline100. Here, a pipeline contacting surface of each of wedges12aand12bcontacting the outer pipeline surface101is inclined with respect to a vibrator surface on which each of ultrasonic vibrators11aand11bis provided, and ultrasonic waves pass obliquely through the outer pipeline surface101.

The ultrasonic vibrators11aand11bare connected to switches43aand43bof a main body40, respectively. Moreover, the switches43aand43bare connected to both a transmitting unit41and a receiving unit42. InFIG. 18, the ultrasonic probe14ais disposed upstream the flow of the fluid103, and the ultrasonic probe14bis disposed downstream the flow of the fluid103. The switches43aand43bare controlled by a control unit48so that, when one ultrasonic vibrator is connected to the transmitting unit41, the other ultrasonic vibrator is connected to the receiving unit42.

The transmitting unit41transmits an ultrasonic transmission pulsating electrical signal to one ultrasonic vibrator11ato generate ultrasonic waves. The generated ultrasonic waves pass through the wedge12aand the outer pipeline surface101and enter the fluid103in the pipeline100obliquely. The ultrasonic waves entering the fluid103in the pipeline100are reflected from an inner pipeline surface102on the opposite side, make one-round trip through the fluid103obliquely, pass through the outer pipeline surface101and the wedge12b, and enter the other ultrasonic vibrator11b. The other ultrasonic vibrator11bconverts the entering ultrasonic waves to an ultrasonic reception pulsating electrical signal. Since the other ultrasonic vibrator11bis connected to the receiving unit42by the switch43b, the converted ultrasonic reception pulsating electrical signal is received by the receiving unit42.

The time measuring unit44measures the propagation time tf from transmission and reception of ultrasonic waves similarly to the first embodiment. Here, a fluid type determining unit25and an input/output unit47are provided similarly to the first embodiment. Thus, it is possible to calculate the velocity of sound in the fluid103and to determine the fluid type based on the velocity of sound. In the second embodiment, the velocity of the fluid103is measured.

In this case, by switching the switches43aand43b, the time measuring unit44measures the propagation time tu from the upstream ultrasonic vibrator11ato the downstream ultrasonic vibrator11bin relation to the flow of the fluid103and the reverse propagation time td from the downstream ultrasonic vibrator11bto the upstream ultrasonic vibrator11a. The ultrasonic wave propagation time changes depending on the carrying effect of the fluid103such that the propagation time tu decreases and the propagation time td increases. This difference in the propagation time tu and td changes depending on the velocity of fluid. The flow velocity measuring unit45measures this difference to measure the velocity of the fluid103. When the flow velocity measuring unit45calculates the velocity of sound in the fluid103using the average of the propagation time to and td, it is possible to improve the calculation accuracy.

Structure of Ultrasonic Probe—

FIG. 19is a diagram illustrating the structure of the ultrasonic probe14aaccording to the second embodiment of the present invention when seen from a surface vertical to the axial direction of the pipeline100. Moreover,FIG. 20is a diagram illustrating the structure of the ultrasonic probe14aaccording to the second embodiment of the present invention when seen from a surface horizontal to the axial direction of the pipeline100. As illustrated inFIG. 20, since a vibrator surface Sα1is inclined with respect to a pipeline contacting surface Sβ2, a vibrator projection surface Sα2which is a projection surface of the vibrator surface Sα1is illustrated inFIG. 19. Since the length L21in the cross-section, of the vibrator projection surface Sα2is smaller than the length L22in the cross-section, of the pipeline contacting surface Sβ2, it is possible to concentrate ultrasonic waves similarly to the first embodiment. An intermediate portion31ais provided between the inclined surface portion30aand the pipeline contacting surface Sβ2similarly to the first embodiment.

Modification of Ultrasonic Probe—

InFIGS. 19 and 20, an end surface of the inclined surface portion30ain the axial direction of the pipeline100is vertical to the pipeline100. However, in an ultrasonic probe54awhich is a modification, illustrated inFIGS. 21 and 22, an end surface of an inclined surface portion50ain the axial direction of the pipeline100is inclined with respect to the pipeline100.

Here,FIGS. 23 and 24are enlarged views of part C inFIG. 21and illustrate a reflection state of ultrasonic waves on the inclined surface portion50a. L-waves are longitudinal waves in which a vibrating direction of ultrasonic waves is identical to the traveling direction of ultrasonic waves. Moreover, SV-waves are one of transverse waves which, as illustrated inFIG. 25, vibrate vertically to a traveling direction A1of ultrasonic waves in a plane including an ultrasonic vibrator center C1and the axis of the pipeline100. When the ultrasonic waves generated by the ultrasonic vibrator11α are L-waves, and as illustrated inFIG. 23, the L-waves are reflected from the inclined surface portion50a, L-waves and SV-waves are generated in general. Thus, the ultrasonic wave energy is dispersed to the original L-waves and unwanted SV-waves and the original L-waves are attenuated. Due to this, in the present embodiment, the ultrasonic vibrator11agenerates SV-waves as ultrasonic waves. As a result, as illustrated inFIG. 24, the SV-waves are not dispersed on the inclined surface portion50a, and attenuation of ultrasonic waves can be reduced.

In the second embodiment, the wedge may be formed of a plurality of different materials similarly to the first embodiment. Moreover, the angle θ of the inclined surface portion may be applied by substituting the vibrator surface Sα with the vibrator projection surface Sα2. Further, the arrangement of the ultrasonic absorber15may be applied.

EXPLANATION OF REFERENCE NUMERALS