JPH11271113A - Ultrasonic vortex flowmeter - Google Patents

Abstract

(57) [Summary] In an ultrasonic vortex flowmeter, the ultrasonic beam width is made smaller than 1/2 of the pitch of the Karman vortex without increasing the size of the piezoelectric element, thereby improving the flow rate measurement accuracy. A vortex generator (5) is provided in a pipe (4), and piezoelectric elements (6a, 7a) are mounted in mounting holes (8, 9) in a pipe wall of a housing (3) with a Karman vortex K generation region (E) interposed therebetween. The acoustic bonding material is formed by projecting the joint 19 from the diaphragm 7b at the bottom of the mounting hole 9 on the receiving side.
It is joined to the receiving surface of the piezoelectric element 7b via 12. For the transmission beam width T of the ultrasonic transmitter 6, since the width W ₁ of the joint 19 it is possible to limit the ultrasonic beam width R ₁ which is received by the piezoelectric element 7a of the receiving side, the joint 19 Width W ₁
Is reduced, the beam width R _{1 of the} ultrasonic wave can be reduced to _one of the pitch P of the Karman vortex without reducing the size of the piezoelectric element 7a.
/ 2. As a result, an ultrasonic wave modulated by a single Karman vortex can be received, and the measurement accuracy of the flow rate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vortex flowmeter for measuring a flow rate of a fluid to be measured in a pipe based on a generation cycle of Karman vortices.

[0002]

2. Description of the Related Art An example of a conventional ultrasonic vortex flowmeter is described below.
This will be described with reference to FIGS. As shown in FIG. 5, the ultrasonic vortex flowmeter 1 includes a vortex generator 5 traversing a pipe 4 in a housing 3 connected to a pipe 2 through which a fluid to be measured (the flow direction is indicated by a thick arrow) flows. Is provided. A pair of ultrasonic transceivers 6 and 7 are provided on the tube wall of the housing 3 with a pair of ultrasonic transceivers 6 and 7 sandwiching a generation region E of a Karman vortex K generated downstream of the vortex generator 5 by the flow of the fluid to be measured. It is mounted so as to be orthogonal.

In the ultrasonic transmitters / receivers 6, 7, the piezoelectric elements 6a, 7a are inserted into mounting holes 8, 9 provided on the outer peripheral portion of the housing 3, respectively, and screwed, welded, or bonded to the housing 3. An acoustic bonding agent 12 such as an adhesive or grease is applied to the tube walls forming the diaphragms 6b and 7b by being pressed through an elastic body 11 such as silicon rubber by a lid member 10 fixed by the
Are fixedly bonded (joined) via

[0006] As shown in FIG. 6, the schematic configuration of the flow rate measuring circuit of the ultrasonic eddy flow meter 1 is as follows.
(Piezoelectric element 6a) and the phase comparison circuit 14, and the ultrasonic receiver 7 (piezoelectric element 7a) is connected to the phase comparison circuit 14 via the amplification circuit 15;
Are connected to the conversion circuit 16. In the figure, reference numeral 17 denotes a power supply circuit.

Next, the operation of the ultrasonic vortex flowmeter 1 will be described.

The piezoelectric element 6a of the ultrasonic transmitter 6 vibrates by an electric signal from the transmission circuit 13, and oscillates ultrasonic waves into the fluid to be measured in the pipe 4 via the acoustic bonding agent 12 and the diaphragm 6b. . The ultrasonic wave propagates through the fluid to be measured in the pipe 4 and is modulated by the Karman vortex K generated downstream of the vortex generator 5 by the flow of the fluid to be measured. And is received by the piezoelectric element 7a via the interface and converted into an electric signal.

[0007] The electric signal is amplified by the amplifier circuit 12 and input to the phase comparison circuit 14. The phase comparison circuit 14 compares the phase of the signal including the modulation by the Karman vortex K from the ultrasonic receiver 7 with the phase of the original signal from the oscillation circuit 13 and detects the modulation by the Karman vortex K to detect the Kalman vortex. Vortex K
Is output as a modulated signal having a frequency equal to the generation cycle of Since the frequency of the modulation signal is proportional to the flow rate of the fluid to be measured, the conversion circuit 16 processes this modulation signal and outputs a pulse signal representing the flow rate of the fluid to be measured. The measured flow rate of the fluid to be measured can be obtained by processing this pulse signal by various arithmetic and control circuits (not shown).

In the ultrasonic vortex flowmeter in which the generation frequency of the Karman vortex is detected using ultrasonic waves as described above, the ultrasonic waves oscillated from the ultrasonic transmitter 6 have a predetermined transmission beam width T. A predetermined beam that propagates through the fluid to be measured in the pipe line 4 with the directivity (ultrasonic transmission area) and is received by the ultrasonic receiving surface (ultrasonic receiving area) of the piezoelectric element 7b of the ultrasonic receiver 7 Received in the range of width _R0 . At this time, within the range of the beam width R _{0 of the} ultrasonic wave oscillated by the ultrasonic transmitter 6 and received by the ultrasonic receiver 7 (the width of the overlapping portion between the ultrasonic transmission region and the ultrasonic reception region). If a plurality of Karman vortices K are present at the same time, the modulation signal will not represent the modulation by the single Karman vortex K, and the accuracy of the modulation signal, that is, the flow rate measurement accuracy will be reduced.

When the beam width R _{0 of the} ultrasonic wave is equal to the pitch P of the Karman vortex K (the head of the n-th Karman vortex formed in the same direction and n
+1 is the distance between the head of the Karman vortex and the vortex generator 5
And generally, P / 2 = (1 / 0.5
6) d or P / 2 = approximately 1.6d to 1.8d)
When the ratio is larger than / 2 (R ₀ > P / 2), a plurality of Karman vortices K exist within the range of the beam width R ₀ , and the Karman vortex street has vortices in the forward and reverse directions arranged alternately. Adjacent Karman vortices act so as to cancel out modulation of ultrasonic waves (ultrasonic waves in the range of the beam width _R0 ) received by the entire piezoelectric element 7a. For this reason, the modulation by the Karman vortex K does not clearly appear in alternation, and the time-series Karman vortex cannot be detected, so that the accuracy of the flow rate measurement decreases. On the other hand, by making the beam width R ₀ smaller than の of the pitch P of the Karman vortex and receiving an ultrasonic wave modulated in one direction by a single Karman vortex K, a continuous alternating A modulation signal that clearly indicates the change can be detected, and the measurement accuracy of the flow rate can be improved.

Next, the beam width of the ultrasonic wave and the phase comparison circuit
The relationship with the 14 output waveforms will be described with reference to FIG. 7 (A), (B) and (C) show the pipe diameter D = 6.0 mm, the vortex generator width d = 1.4 mm, and the distance from the front end of the vortex generator to the center of the piezoelectric element of the ultrasonic transceiver. L = 2.8mm, measured fluid flow rate
2.0 l / min, and the width W of the piezoelectric element of the ultrasonic transceiver is W = 3.0 mm in (A), W = 2.0 mm in (B), and W = 1.0 mm in (C). 3 shows an actual output waveform from the phase comparison circuit 14.

FIG. 7 shows that the smaller the beam width of the ultrasonic wave, that is, the width W of the piezoelectric element of the ultrasonic transmitter / receiver, the smaller the (A), (B),
In the order of (C), the output waveform of the phase comparison circuit 14 is stabilized, and the width W of the piezoelectric element of the ultrasonic transceiver is set to 1 of the pitch P of the Karman vortex.
(C) when W = 1.0 mm, which is smaller than / 2, that is, P / 2 = (1 / 0.56) d = 2.1 mm, shows that the output waveform is the most stable.

[0012]

In order to measure a very small flow rate using the above-mentioned conventional ultrasonic vortex flowmeter 1, the flow velocity (Reynolds number) of the fluid to be measured is increased to the Karman vortex generation region. It is necessary to generate a stable Karman vortex, and therefore, it is necessary to set the diameter D of the pipe 4 of the housing 3 to be sufficiently small. Therefore, when the diameter D of the conduit 4 is reduced, the width d of the vortex generator 5 is also reduced.
Since the pitch P of the Karman vortex determined by the vortex becomes smaller, it is necessary to sufficiently reduce the beam width of the ultrasonic wave in order to measure the flow rate stably.

However, when trying to reduce the size of the piezoelectric elements 6a, 7a of the ultrasonic transceivers 6, 7, the piezoelectric elements 6a, 7a
It becomes difficult to ensure the performance stability of 7a, and the production and assembling workability is reduced, and the production cost is increased. In addition, piezoelectric elements of various dimensions according to the measured flow rate
It is necessary to prepare 6a and 7a, which causes an increase in the manufacturing cost of the ultrasonic vortex flowmeter.

The present invention has been made in view of the above points, and has been made without reducing the size of the ultrasonic transceiver.
It is an object of the present invention to provide an ultrasonic vortex flowmeter capable of reducing an ultrasonic beam width.

[0015]

According to a first aspect of the present invention, a vortex generator is provided in a pipe through which a fluid to be measured flows, and a piezoelectric element and an acoustic bonding agent are attached to the piezoelectric element. A pair of ultrasonic transmitter / receiver composed of a diaphragm joined together is disposed so as to sandwich the generation region of the Karman vortex generated by the vortex generator in the conduit, and is detected by the ultrasonic transmitter / receiver. In the ultrasonic vortex flowmeter that measures the flow rate of the fluid to be measured based on the generation cycle of the Karman vortex, the acoustic bonding agent between the piezoelectric element and the diaphragm in at least one of the pair of ultrasonic transceivers. The width of the joint portion in the flow direction of the fluid to be measured is smaller than the width of the piezoelectric element in the flow direction of the fluid to be measured.

According to this structure, at least one of the ultrasonic transmission area and the ultrasonic reception area is compared with the case where the entire surface of the piezoelectric element of the ultrasonic transceiver is bonded to the diaphragm by the acoustic bonding agent. Of the measured fluid in the flow direction is reduced.

According to a second aspect of the present invention, in the configuration of the first aspect, the width of the vibration plate in the flow direction of the fluid to be measured at the joint of the vibration plate and the piezoelectric element by the acoustic bonding agent is set to be smaller than that of the vortex generator. The width in a direction orthogonal to each of the flow direction of the fluid to be measured and the axial direction of the vortex generator is not more than 1 / 0.56 times.

With this configuration, the width of at least one of the ultrasonic transmission region and the ultrasonic reception region of the pair of ultrasonic transceivers in the flow direction of the measured fluid is equal to the pitch of the Karman vortex (in the same direction). Generation interval of Karman vortex
, Ie, less than the width where only a single Karman vortex exists.

According to a third aspect of the present invention, a vortex generator is provided in a conduit through which a fluid to be measured flows, and a pair of ultrasonic transceivers having a piezoelectric element is used to generate a Karman vortex generated by the vortex generator in the conduit. An ultrasonic vortex flowmeter arranged to sandwich a generation area and measuring a flow rate of the fluid to be measured based on a generation cycle of the Karman vortex detected by the ultrasonic transceiver, wherein the pair of ultrasonic transceivers Of the ultrasonic transmission area of the ultrasonic transmitter and the ultrasonic reception area of the ultrasonic receiver, the width in the flow direction of the fluid to be measured of the overlapping portion in the generation region of the Karman vortex, the ultrasonic transceiver of The pair of ultrasonic transceivers are offset from each other so as to be smaller than the width of the ultrasonic receiving surface of one of the piezoelectric elements.

With this configuration, the width of the overlapping portion of the ultrasonic transmission region and the ultrasonic reception region in the flow direction of the fluid to be measured is smaller than that in the case where the pair of ultrasonic transceivers are arranged opposite to each other. Becomes smaller.

The "offset arrangement" mentioned in claim 3 means that a pair of ultrasonic transceivers do not face each other so as to sandwich the center of the pipeline, or the flow of the fluid to be measured from the vortex generator. The arrangement is such that the distances in the directions are not equal.

According to a fourth aspect of the present invention, in the configuration of the third aspect, the ultrasonic receiving surfaces of the piezoelectric elements of the pair of ultrasonic transceivers face the central axis of the conduit respectively, and It is characterized by being arranged offset in the flow direction of the fluid to be measured.

[0023] With this configuration, the ultrasonic transmission region and the ultrasonic transmission region can be formed without forming a stagnation portion in the conduit as compared with a case where a pair of ultrasonic transceivers are arranged opposite to each other. The width of the overlapping portion with the sound wave receiving area in the flow direction of the fluid to be measured is reduced.

It should be noted that the phrase “disposed in the direction opposite to the pipe line and in the flow direction of the fluid to be measured” in claim 4 means:
The pair of ultrasonic transceivers should be arranged so that the surfaces facing each other are parallel and face the center of the conduit, and the distances in the flow direction of the fluid to be measured from the vortex generator are not equal. It is.

According to a fifth aspect of the present invention, in the configuration of the third or fourth aspect, the ultrasonic transmission area of the ultrasonic transmitter and the ultrasonic reception area of the ultrasonic receiver among the pair of ultrasonic transceivers. And the width of the overlapping portion in the generation region of the Karman vortex in the flow direction of the fluid to be measured is in a direction orthogonal to the flow direction of the fluid to be measured of the vortex generator and the axial direction of the vortex generator. The width is set to be 1 / 0.56 times or less of the width.

With this configuration, the width of the overlapped portion of the ultrasonic wave transmission region and the ultrasonic wave reception region in the flow direction of the fluid to be measured is equal to the pitch of the Karman vortex (the generation interval of the Karman vortex in the same direction). １ ／, that is, less than the width where only a single Karman vortex exists.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description,
4 and 5 are denoted by the same reference numerals, and only different portions will be described in detail.

A first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, in the ultrasonic vortex flowmeter 18 according to the first embodiment, the piezoelectric element 7a of the ultrasonic receiver 7 is provided at the center of the bottom (diaphragm 7b) of the mounting hole 9 of the piezoelectric element 7a. The joint 19 smaller than the ultrasonic receiving surface is projected,
This bonding part 19 is an acoustic bonding agent on the ultrasonic receiving surface of the piezoelectric element 7a.
12 are joined through. The joining portion 19 forms an acoustic transmission path for transmitting the ultrasonic wave that has propagated through the fluid in the conduit 4 and has reached the receiving diaphragm 7b to the ultrasonic receiving surface of the piezoelectric element 7a.

The joint 19 has a width W based on the pitch P of Karman vortices determined by the width d of the vortex generator 5.
₁ (dimension along the flow direction of the fluid to be measured) is set to be smaller than 1/2 of the vortex pitch P (W ₁ <P /
2), the relationship between the width d of the vortex generator 5 and the vortex pitch P (generally, P / 2 = (1 / 0.56) d or P / 2 = 1.6d or more)
Based on the order of 1.8 d), for example, and W ₁ <1.6d~1.8d the width d of the vortex generator 5, preferably W ₁ ≦ ₍₁ / 0.56)
It is good to be d. The joint 19 is arranged at a position where an ultrasonic wave modulated by one of the Karman vortices K generated downstream of the vortex generator 5 is received.

A retainer 20 having a recess having a fitting size into which the piezoelectric element 7a is fitted is fitted to the back of the piezoelectric element 7a. The outer peripheral portion of the retainer 20 has a fitting dimension fitted into the mounting hole 9, and the parallelism of the piezoelectric element 7 a to the conduit 4 is ensured by the retainer 20. Then, the retainer is pressed through an elastic body 11 such as silicon rubber by a cover member 10 fixed to the housing 3 by screwing, welding, bonding, or the like, so that the piezoelectric element 7 a It is closely attached to 19 and fixed.

The operation of the first embodiment configured as described above will now be described.

As shown in FIG. 4, the ultrasonic transmitter 6
The ultrasonic wave oscillated from the piezoelectric element 6a propagates through the fluid to be measured with a directivity (spread) having a predetermined transmission beam width T, is modulated by the Karman vortex K, and is vibrated on the receiving side.
To reach. Then, the sound is received by the piezoelectric element 7a via the acoustic transmission path formed by the joint 19 and the acoustic bonding agent 12. At this time, a space S is formed between the ultrasonic wave receiving surface of the piezoelectric element 7a and the diaphragm 7b by the joint 19,
Can limit the transmission path of the ultrasonic signals to the width W ₁ of the joint 19, thereby, the width W of less than 1/2 junction 19 of the pitch P of the Karman vortex beam width R ₁ of the piezoelectric element 7a Can be limited to _one .

As a result, the ultrasonic wave modulated by the single Karman vortex K can be received by the piezoelectric element 7a of the ultrasonic receiver 7, and the output of the phase comparison circuit 14 as shown in FIG. A stable output waveform similar to the waveform can be obtained, and the measurement accuracy of the flow rate can be improved.

In order to measure the minute flow rate, the width d of the vortex generator 5 becomes smaller as the diameter of the conduit 4 becomes smaller, and even if the pitch P of the Karman vortex becomes smaller, the width of the vortex generator 5 becomes smaller. joint according to the vortex pitch P determined by d
By sufficiently small set 19 width of, without reducing the size of the dimension or the piezoelectric element 7a ultrasonic receivers 7, it is possible to obtain a beam width R ₁ of desired ultrasound, single Karman vortex Receiving the ultrasonic waves which have been continuously subjected to the modulation by the above, the measurement accuracy of the flow rate can be improved. At this time,
The piezoelectric element 7a of the ultrasonic receiver 7, because the parallelism with respect to the pipe 4 by the retainer 20 is securely supported in a state of being reserved, even unstable attachment state to reduce the width W ₁ of the joint 19 Never be.

Thus, the piezoelectric element 7a of the ultrasonic receiver 7
Performance stability can be easily ensured, and the reduction in manufacturing and assembling workability due to miniaturization can be prevented, and the increase in manufacturing cost can be prevented. Further, it is not necessary to manufacture the piezoelectric elements of each dimension according to the measured flow rate, so that the ultrasonic receiver can be shared, and the manufacturing cost can be reduced.

[0036] The shape and dimensions of the joint portion 19 can be set variously depending on the beam width R ₁ of desired ultrasound. Further, in the above embodiment, the joint 19 is formed integrally with the tube wall of the housing 3, but these may be attached as separate members.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

As shown in FIG. 2, in the ultrasonic vortex flowmeter 21 according to the second embodiment, the mounting hole 22 of the piezoelectric element 7a of the ultrasonic receiver 7 has an The ultrasonic wave transmitter 6 is disposed at a position downstream of the mounting hole 8 of the piezoelectric element 6a by a distance A and has a directivity (spread) of a predetermined transmission beam width T oscillated from the ultrasonic wave transmitter 6. Beam width in the Karman vortex generation region E where the ultrasonic transmission region overlaps with the reception region that is the propagation region of ultrasonic waves that can be received on the ultrasonic reception surface of the piezoelectric element 7a of the ultrasonic receiver 7
R ₂ is smaller than 小 さ く of the vortex pitch P. Then, one of the Karman vortex K generated on the downstream of the vortex generator 5 is entered into the beam width R ₂ (see area F ₁ in FIG. 2), ultrasonic wave modulated by this single Karman vortex K Is received by the piezoelectric element 7a of the ultrasonic receiver 7.

Here, the reception beam width R ₂ is a vortex pitch P determined by the width d of the vortex generator 5 (generally, P / 2 = 1.
In consideration of 6d to 1.8d), R ₂ <1.6d to 1.8d, and preferably R <(1 / 0.56) d.

The operation of the second embodiment configured as described above will now be described.

As shown in FIG. 4, the ultrasonic transmitter 6
The ultrasonic wave transmitted from the piezoelectric element 6a propagates through the fluid to be measured with a directivity (spread) of a predetermined transmission beam width T, is modulated by the Karman vortex K, and is vibrated on the receiving side.
And is received by the piezoelectric element 7a via the diaphragm 7b and the acoustic bonding agent 12. At this time, since the ultrasonic transmitter 6 and the ultrasonic receiver 7 are offset by the distance A and the beam width R ₂ is smaller than の of the vortex pitch P, the modulation by the single Karman vortex K is performed. Can be received by the ultrasonic receiver 7 continuously, and the measurement accuracy of the flow rate can be improved.

Further, by offsetting the ultrasonic transmitters / receivers 6, 7, the propagation distance of the ultrasonic wave in the fluid to be measured becomes longer than the diameter D of the pipe 4, so that the amount of phase modulation by the Karman vortex K is reduced. It becomes larger, and the measurement sensitivity can be increased.

FIG. 3 shows a pipe diameter D = 6.0 mm, a vortex generator width d = 1.4 mm, a distance L ₁ = 1.57 mm from the front end of the vortex generator to the center of the ultrasonic transmitter, and an ultrasonic receiver. Distance to center L ₂
5 shows an actual output waveform of the phase comparison circuit when the ultrasonic transmitter / receiver width W = 2.0 mm and the measured fluid flow rate 2.0 l / min. At this time, when R ₂ = 1.0 mm, (1 / 0.56) d
= Smaller than 2.50 mm. FIG. 3 shows that a stable output waveform can be obtained.

In order to measure the minute flow rate, even if the width d of the vortex generator becomes smaller as the diameter of the conduit 4 becomes smaller and the pitch P of the Karman vortex becomes smaller, the vortex generator d becomes smaller.
By adjusting the offset distance A between the ultrasonic transceivers 6 and 7 according to the vortex pitch P determined by the above, the desired ultrasonic beam width R ₂ can be obtained without reducing the size of the ultrasonic receiver 7. Can be obtained, and a stable signal can be received to improve the measurement accuracy of the flow rate.

Thus, the piezoelectric element 7a of the ultrasonic receiver 7
Performance stability can be easily ensured, and the reduction in manufacturing and assembling workability due to miniaturization can be prevented, and the increase in manufacturing cost can be prevented. Further, it is not necessary to manufacture the piezoelectric elements of each dimension according to the measured flow rate, so that the ultrasonic receiver can be shared, and the manufacturing cost can be reduced.

As a modification of the second embodiment,
As shown in FIG. 4, the positions of the ultrasonic transmitters / receivers 6 and 7 in the flow direction of the fluid to be measured are not offset, and the mounting angles thereof are offset so that they do not face each other. and less than half the beam width of the vortex pitch P of the Karman vortex K, can receive the ultrasonic waves being modulated by a single Karman vortex in the area F _2. However, in this case, a concave portion 23 that causes stagnation is formed in the pipeline 4.

[0047]

As described above in detail, according to the ultrasonic eddy flow meter according to the first aspect, at least one of the pair of ultrasonic transceivers is joined to the piezoelectric element and the diaphragm by the acoustic bonding agent. By making the width of the measured fluid in the flow direction smaller than the width of the piezoelectric element in the flow direction of the measured fluid, the entire surface of the piezoelectric element of the ultrasonic transceiver is joined to the diaphragm by the acoustic bonding agent. The width of at least one of the ultrasonic transmission region and the ultrasonic reception region in the flow direction of the fluid to be measured can be smaller than that in the case of the above. Therefore, even if the diameter of the conduit is reduced, the beam width of the ultrasonic wave can be reduced without reducing the size of the piezoelectric element. Can be prevented, and an increase in manufacturing cost can be prevented. Further, it is not necessary to manufacture the piezoelectric elements of each dimension according to the measured flow rate, so that the ultrasonic receiver can be shared, and the manufacturing cost can be reduced.

According to the ultrasonic vortex flow meter according to the second aspect,
In the configuration according to claim 1, the width of the portion of the diaphragm to be joined to the piezoelectric element by the acoustic joining agent in the flow direction of the fluid to be measured is set to be different in the flow direction of the fluid to be measured and the axial direction of the vortex generator. The width in the flow direction of at least one of the ultrasonic transmission region and the ultrasonic reception region of the pair of ultrasonic transceivers in the flow direction of It is の of the vortex pitch (the generation interval of Karman vortices in the same direction), that is, less than the width in which only a single Karman vortex exists. Therefore, even if the diameter of the conduit is reduced, it is possible to receive the ultrasonic waves continuously modulated by only a single Karman vortex without reducing the size of the piezoelectric element, thereby improving the flow rate measurement accuracy.

According to the ultrasonic vortex flowmeter according to the third aspect,
The width in the flow direction of the fluid to be measured of the overlapping portion in the Karman vortex generation region between the ultrasonic transmission region of the ultrasonic transmitter and the ultrasonic reception region of the ultrasonic receiver of the pair of ultrasonic transceivers, The pair of ultrasonic transceivers are offset from each other so as to be smaller than the width of the ultrasonic receiving surface of one of the piezoelectric elements of the transceiver, so that the pair of ultrasonic transceivers face each other. The width of the overlapping portion between the ultrasonic transmission region and the ultrasonic reception region in the flow direction of the fluid to be measured is smaller than that in the case of the arrangement. Therefore, even if the diameter of the conduit is reduced, the beam width of the ultrasonic wave can be reduced without reducing the size of the piezoelectric element. Can be prevented, and an increase in manufacturing cost can be prevented. Further, it is not necessary to manufacture the piezoelectric elements of each dimension according to the measured flow rate, so that the ultrasonic receiver can be shared, and the manufacturing cost can be reduced.

According to the ultrasonic vortex flowmeter according to the fourth aspect,
In the configuration according to claim 3, the ultrasonic receiving surfaces of the piezoelectric elements of the pair of ultrasonic transceivers are disposed so as to face each other with respect to the central axis of the pipeline and are offset in the flow direction of the fluid to be measured. Without forming a portion that stagnates the flow in the pipeline, the fluid to be measured in the overlapping portion of the ultrasonic transmission region and the ultrasonic reception region is compared with a case where a pair of ultrasonic transceivers are arranged opposite to each other. The width in the flow direction is reduced. Therefore, in addition to the effect of the third aspect, the measurement accuracy of the flow rate can be improved without disturbing the generation of the Karman vortex.

According to the ultrasonic vortex flow meter according to the fifth aspect,
5. A fluid to be measured in an overlapping portion in a Karman vortex generation region between an ultrasonic transmission region of an ultrasonic transmitter and an ultrasonic reception region of an ultrasonic receiver among a pair of ultrasonic transceivers according to claim 3 or 4. The width of the vortex generator in the flow direction is set to be 1 / 0.56 times or less the width of the vortex generator in the direction perpendicular to the flow direction of the fluid to be measured and the vortex generator axial direction, respectively. The width in the flow direction of the fluid to be measured at the overlapping portion between the region and the ultrasonic receiving region is の of the pitch of the Karman vortex (the generation interval of the Karman vortex in the same direction), that is, only a single Karman vortex exists. It becomes less than the width to do. Therefore, even if the diameter of the conduit is reduced, it is possible to receive the ultrasonic waves continuously modulated by only a single Karman vortex without reducing the size of the piezoelectric element, thereby improving the flow rate measurement accuracy.

[Brief description of the drawings]

FIG. 1 is a horizontal and vertical sectional view of an ultrasonic vortex flowmeter according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an ultrasonic vortex flowmeter according to a second embodiment of the present invention.

FIG. 3 is a graph showing an output waveform of a phase comparison circuit of the device of FIG. 2;

FIG. 4 is a horizontal and vertical sectional view of an ultrasonic vortex flowmeter according to a modification of the second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional ultrasonic vortex flowmeter.

FIG. 6 is a block diagram showing a schematic configuration of a flow measurement circuit of the ultrasonic vortex flowmeter.

FIG. 7 is a graph showing a relationship between a reception beam width of an ultrasonic signal of an ultrasonic vortex flowmeter and an output waveform of a phase comparison circuit.

[Explanation of symbols]

4 Pipeline 5 Vortex generator 6 Ultrasonic transmitter 7 Ultrasonic receiver 6a, 7a Piezoelectric element 6b, 7b Vibration plate 18,21 Ultrasonic vortex flow meter 19 Joint A offset d Vortex generator width E Karman vortex Generation area K Karman vortex P Karman vortex pitch R ₁ , R ₂ Beam width

Claims (5)

[Claims] A vortex generator is provided in a conduit through which a fluid to be measured flows, and a pair of ultrasonic transceivers each including a piezoelectric element and a vibration plate bonded to the piezoelectric element by an acoustic bonding agent are provided in the conduit. An ultrasonic wave that is disposed so as to sandwich a generation region of the Karman vortex generated by the vortex generator, and that measures a flow rate of the fluid to be measured based on a generation period of the Karman vortex detected by the ultrasonic transceiver; In the vortex flowmeter, the width of at least one of the pair of ultrasonic transceivers in the flow direction of the fluid to be measured at a joining portion of the piezoelectric element and the vibration plate with the acoustic bonding agent is set to the width of the piezoelectric element. An ultrasonic vortex flowmeter characterized in that the width is smaller than the width of the fluid to be measured in the flow direction. 2. A width of a portion of the diaphragm to be joined with the piezoelectric element by an acoustic bonding agent in a flow direction of the fluid to be measured is determined by a flow direction of the fluid to be measured of the vortex generator and an axis of the vortex generator. 1 / 0.56 of the width in the direction perpendicular to each direction
2. The ultrasonic vortex flowmeter according to claim 1, wherein the number is not more than twice. 3. A vortex generator is provided in a conduit through which a fluid to be measured flows, and a pair of ultrasonic transceivers having a piezoelectric element are sandwiched between a generation region of Karman vortices generated by the vortex generator in the conduit. An ultrasonic vortex flowmeter configured to measure a flow rate of the fluid to be measured based on a generation cycle of the Karman vortex detected by the ultrasonic transmitter / receiver; The width in the flow direction of the fluid to be measured of an overlapping portion in the generation region of the Karman vortex between the ultrasonic transmission region of the device and the ultrasonic reception region of the ultrasonic receiver is one of the ultrasonic transceivers. An ultrasonic vortex flowmeter, wherein the pair of ultrasonic transceivers are offset from each other so as to be smaller than the width of the ultrasonic receiving surface of the piezoelectric element. 4. An ultrasonic receiving surface of the piezoelectric element of the pair of ultrasonic transceivers is disposed so as to face the central axis of the conduit and to be offset in the flow direction of the fluid to be measured. The ultrasonic vortex flowmeter according to claim 3, wherein 5. The measurement target fluid of an overlapping portion in the Karman vortex generation region between the ultrasonic transmission region of the ultrasonic transmitter and the ultrasonic reception region of the ultrasonic receiver among the pair of ultrasonic transceivers. The width in the flow direction is set to be 1 / 0.56 times or less the width of the vortex generator in a direction perpendicular to the flow direction of the fluid to be measured and the vortex generator axial direction. The ultrasonic vortex flowmeter according to claim 3 or 4, wherein