JP2006349439A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily attach a ultrasonic vibrator to a laid pipe, in an ultrasonic flowmeter which has the same method as one with annular ultrasonic vibrator. <P>SOLUTION: Two ultrasonic transmitter/receiver are placed with a distance so as to contact the pipe of the flow path of fluid to be measured. These are mutually functioned as ultrasonic transmitter and ultrasonic receiver, and the ultrasonic flowmeter calculates flow velocity from an upstream ultrasonic transmission time and a down stream ultrasonic transmission time. Each of the ultrasonic transmitter/receiver is constituted of two semicircular ultrasonic vibrators. A tightening mechanism for surrounding the pipe and fixing the two semicircular ultrasonic vibrators is provided. The two semicircular ultrasonic vibrators fixed at each length position of the pipe vibrate with the same phase, and are electrically connected so as to output with the same phase as the vibration of the measuring pipe. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, two ultrasonic transmitters / receivers are provided in a measurement tube for flowing a fluid to be measured at a distance from the flow. One of the two ultrasonic transmitters / receivers is an ultrasonic transmitter and the other is an ultrasonic wave. The present invention relates to a so-called propagation time difference type ultrasonic flowmeter which operates as a receiver and calculates a flow velocity by measuring a downstream ultrasonic wave propagation time and an upstream ultrasonic wave propagation time.

  The ultrasonic flowmeter does not require any mechanism inside the pipe, so there is no pressure loss associated with the measurement, and it has excellent features such as that both forward and reverse flows can be measured from zero flow velocity. In principle, an ultrasonic flowmeter has a propagation time difference method and a Doppler method, but a propagation time difference method with good accuracy is generally used. As a general form of the propagation time difference type ultrasonic flowmeter, an ultrasonic transducer attached to a plastic wedge so that the ultrasonic wave is obliquely incident on the pipe body is obliquely formed on the outer surface of the pipe body. The two ultrasonic transducers are mutually operated as an ultrasonic transmitter / receiver. Accordingly, the flow velocity can be calculated by measuring the ultrasonic propagation time in the downstream direction and the ultrasonic propagation time in the upstream direction.

  In the method of driving ultrasonic waves obliquely with respect to the pipe body from the ultrasonic vibrator as described above, the diameter of the pipe body is large enough to attach such an ultrasonic vibrator or wedge. In addition, when the tube is thinned, the measurement interval becomes very short, and sufficient measurement accuracy cannot be obtained. Also, for the purpose of ensuring sufficient spacing between the upstream and downstream ultrasonic transducers, a method of bending the pipe at a right angle and driving ultrasonic waves from the outer surface of the right angle portion in the axial direction of the pipe body is widely performed. If the thickness of the tube becomes thinner, the cross-sectional area of the tube body becomes very small compared to the vibration area of the ultrasonic transducer, and sufficient ultrasonic energy cannot be injected into the fluid in the tube.

Therefore, a method of using an annular ultrasonic transducer as disclosed in Japanese Patent Laid-Open No. 8-86675 has been devised to enable measurement of the flow rate in a thin tube. In this method, two ultrasonic transducers such as annular piezoelectric bodies are provided at a distance so as to come into contact with a straight tube. Since the annular ultrasonic transducer can be fitted on the outer surface of the measuring tube, flow measurement using ultrasonic waves can be applied even to a thin tube. Moreover, since the ultrasonic wave propagates through the entire cross section of the tube, this method is not easily affected by the flow velocity distribution such as turbulent flow and laminar flow. There is an advantage that can be obtained. Furthermore, since the distance between the pair of ultrasonic transducers arranged upstream and downstream can be made sufficiently long, there is an advantage that the measurement sensitivity can be increased by increasing the difference in the propagation time in the upstream direction and the downstream direction.
JP-A-8-86675

  By the way, in the case of an ultrasonic flowmeter using an annular ultrasonic transducer as described above, it is necessary to provide a measurement tube through the ultrasonic transducer, but it is in close contact so that vibration is transmitted from the transducer to the measurement tube. It is difficult to install in the state. Therefore, an apparatus in which two ultrasonic transducers are attached to a measurement tube in advance is provided, and it is generally performed by connecting both ends of the measurement tube to a pipeline with a joint. For this reason, it was difficult to measure the flow rate using the existing pipeline as it is. However, for example, a tube for injecting a medicine in the medical field has a problem that it becomes difficult to maintain a sterilized state when another tube is connected. In view of the above, the present invention provides an ultrasonic flowmeter of the same type as that of the above-described annular ultrasonic transducer, which can easily attach the ultrasonic transducer to an existing pipe line. The purpose is to do.

  The present invention solves the above-described problem, and provides two ultrasonic transmitters / receivers at a distance so as to come into contact with a pipe body of a fluid to be measured. One is an ultrasonic transmitter, the other is an ultrasonic receiver, and the other is an ultrasonic transmitter as the ultrasonic transmitter / receiver on the upstream side of the measured fluid. In the ultrasonic flowmeter for calculating the flow velocity by the ultrasonic propagation time in the upstream direction when the ultrasonic transmitter / receiver on the downstream side is an ultrasonic transmitter, each of the ultrasonic transmitter / receiver has two semicircular Each of the fastening mechanisms is composed of a sound wave oscillator, and is provided with a fastening mechanism for fixing the two semicircular ultrasonic vibrators around the tube body, and is fixed to each length position of the tube body. The semicircular ultrasonic transducers vibrate in the same phase. It is an ultrasonic flowmeter according to claim in which relative vibration of the measuring tube are electrically connected to the output of the same phase.

  In the present invention, two ultrasonic transmitters / receivers are provided at a distance so as to be in contact with the pipe body of the flow path of the fluid to be measured, one of the two ultrasonic transmitters / receivers being an ultrasonic transmitter and the other Are mutually operated as an ultrasonic receiver and the ultrasonic transmitter / receiver on the upstream side of the fluid to be measured is used as an ultrasonic transmitter, and the ultrasonic transmitter / receiver on the downstream side of the fluid to be measured In the ultrasonic flowmeter for calculating the flow velocity by the ultrasonic propagation time in the upstream direction when the ultrasonic transmitter is used as the ultrasonic transmitter, each of the ultrasonic transmitters / receivers is constituted by two semicircular ultrasonic transducers, A fastening mechanism is provided for fixing two semicircular ultrasonic transducers with a distance in the longitudinal direction of the tubular body in a state of surrounding the tubular body, and at each length position of the tubular body. Two fixed semicircular ultrasonic transducers vibrate in the same phase, It is an ultrasonic flowmeter according to claim in which relative vibration of the measuring tube are electrically connected to the output of the same phase.

  Further, in each of the ultrasonic flowmeters described above, the two semicircular ultrasonic transducers fixed at the respective length positions of the tubular body are not in contact with each other.

  According to the ultrasonic flowmeter of the present invention, by attaching an ultrasonic vibrator to an existing pipe line, an operation equivalent to that of an ultrasonic flowmeter in which an annular ultrasonic vibrator is attached in advance to a dedicated measurement pipe is performed. Can be made. Therefore, in a small-diameter pipe that is particularly suitable for use of an annular ultrasonic transducer, the flow rate can be measured with the existing pipe without connecting a measuring pipe dedicated to the ultrasonic flowmeter.

  FIG. 1 is a conceptual diagram of an ultrasonic flowmeter according to the present invention. The main part is two ultrasonic transmitters / receivers provided at a distance so as to be in contact with the tube 1 of the flow path of the fluid to be measured. 2 and 3 and a control unit for inputting measurement data and calculating a flow rate or flow rate. The ultrasonic transmitters / receivers 2 and 3 use special forms different from the conventional ones in the present invention, and will be described in detail later. In the control unit, two ultrasonic transmitters / receivers 2 and 3 are alternately connected to the electric pulse excitation unit 9 and the signal amplifier 10 via a two-circuit interlocking type changeover switch 7. In the figure, 8 is a changeover switch control unit, and 11 is a measurement / calculation unit. The measurement / calculation unit 11 sends an operation command to the changeover switch control unit 8 and the electric pulse excitation unit 9 and inputs a signal from the signal amplifier 10 to input the downstream ultrasonic wave propagation time, the upstream ultrasonic wave propagation time, and the ultrasonic wave. The flow rate is output from measurement data such as the period or frequency of the propagation waveform.

When two ultrasonic transmitters / receivers are operated as one ultrasonic transmitter and the other as an ultrasonic receiver as described above, and the ultrasonic transmitter / receiver upstream of the fluid to be measured is used as the ultrasonic transmitter The flow velocity is calculated from the downstream ultrasonic propagation time and the upstream ultrasonic propagation time when the ultrasonic transmitter / receiver downstream of the fluid to be measured is an ultrasonic transmitter. That is, when the velocity of sound in the fluid is c, the flow velocity of the fluid is V, the distance between the two ultrasonic transceivers is L, the ultrasonic propagation time in the downstream direction is T ₁ , and the ultrasonic propagation time in the upstream direction is T ₂ , T ₁ = L / (c + V) and T ₂ = L / (c−V). When the difference between the propagation time in the upstream direction and the downstream direction is ΔT, the average propagation time in the upstream direction and the downstream direction is T ₀ , and these equations are arranged considering c >> V, V = ΔT · L / (2T ₀ ² ), and the flow velocity V can be obtained without specially knowing the speed of sound c in the fluid. However, in practice, such a mathematical formula is established only when there is no influence of the measuring tube. Since the ultrasonic propagation velocity in the tube is affected by the vibration of the measurement tube, a method for correcting the accurate flow rate based on the sound velocity data has been proposed, but the details are not related to the present invention. Does not say.

  The ultrasonic flowmeter of the present invention is characterized by the form of an ultrasonic transmitter / receiver. FIG. 2 is a front view of the ultrasonic transmitter / receiver of the present invention, and FIG. 3 is a cross-sectional view parallel to the tube. Two ultrasonic transmitters / receivers 2 and 3 are provided at intervals along the tube 1 which is a fluid flow path. Of course, the pipe body itself is indispensable for the flow rate measurement, but an existing pipe may be used, and the ultrasonic flowmeter itself of the present invention is not necessarily prepared. The two ultrasonic transmitters / receivers 2 and 3 have the same configuration, but each includes two semicircular ultrasonic transducers 21 and 22 and 31 and 32. These two semicircular ultrasonic transducers are attached so as to surround the tube so as to form a ring shape when the flow rate is measured. The inner diameter of the semicircular ultrasonic transducer coincides with the outer diameter of the tube, and is attached in close contact with the tube.

  As a material of the above ultrasonic vibrator, for example, a piezoelectric vibrator in which an electrode is provided on a piezoelectric body such as PZT (zircon / lead titanate) can be used. In particular, a semi-circular shape with electrodes provided on both sides perpendicular to the axis of the circle is suitable. The surface in contact with the body can be vibrated. If there is a gap between the inner surface of the transducer and the tube, it will be filled and closely attached to the tube, so a semi-circular ferrule such as plastic of appropriate thickness will be attached when installing the ultrasonic transducer. May be sandwiched between them.

  As described above, the fastening mechanisms 4 and 5 are provided as means for fixing the two semicircular ultrasonic transducers 21, 22, 31, and 32 to the tubular body so as to form an annular shape. . Since both of the fastening mechanisms have the same configuration, the fastening mechanism 4 on the side shown in FIG. 2 will be described. Semicircular vibrators surrounding the outer circumferences of the respective semicircular ultrasonic vibrators 21 and 22. The holders 41 and 42 and two screws 43 and 44 for fastening the flange portions provided at both ends of the vibrator holders to each other are provided. In addition, it is preferable to fix each ultrasonic vibrator, for example, 21 and each vibrator holder, for example, 41 beforehand in a predetermined position by means of adhesion or the like in order to quickly attach and detach the pipe body.

  Thus, an ultrasonic transmitter / receiver composed of two semicircular ultrasonic transducers is provided at intervals in a pipeline, and these are mutually operated as an ultrasonic transmitter and an ultrasonic receiver so The flow rate is measured by measuring the sound propagation time. The principle of flow measurement itself is the same as that using a conventional annular ultrasonic transducer, but if such semicircular ultrasonic transducers are combined and arranged in an annular shape, an annular ultrasonic transducer will inevitably occur. It does not operate in the same way as a sound wave vibrator. That is, even if two semicircular ultrasonic transducers attached in an annular shape are brought into contact with each other, they do not vibrate mechanically as a unit. Therefore, as shown in FIG. It is better to arrange with twelve. Because it is difficult to make two semicircular ultrasonic transducers in close contact with each other and accurately contact each other, priority is given to close contact with the tube important for propagation to ultrasonic waves. Because it should be.

  Since the two semicircular ultrasonic transducers attached in an annular shape as described above do not vibrate mechanically as one body, it is necessary to match the phases of the respective vibrations. For this reason, the two semicircular ultrasonic transducers fixed at the respective positions of the tube body vibrate in the same phase and are electrically output so as to output the same phase with respect to the vibration of the measuring tube. Connecting. Specifically, as shown in FIG. 1, each of the two semicircular ultrasonic transducers 21, 22, 31, and 32 that are attached in an annular shape are opposed to each other at a right angle to the axis of the circle. The electrodes on the same side of the electrodes provided on one surface may be connected in parallel. It is also possible to connect in series in the direction in which the outputs of the same phase are added.

  In addition, in the two semicircular ultrasonic transducers attached so as to form an annular shape, the phase of the output waveform of the two ultrasonic transducers is shifted if there is a shift in the length direction of the tubular body. . However, if the ultrasonic wave wavelength (= sound speed / frequency) in the fluid in the pipe line is 1 mm or more, there is no problem even if the accuracy of the ultrasonic transducer mounting position is the level of accuracy in a general mechanical device. Therefore, the outputs of the two ultrasonic transducers connected in parallel do not cancel each other due to a large phase shift.

  FIG. 4 is a cross-sectional view of the ultrasonic flowmeter of the present invention parallel to the tube of another embodiment different from the above. The front view is the same as FIG. In the case of FIG. 4, two semicircular ultrasonic transducers 21, 22, 31, and 32 are provided at a distance in the length direction of the tube body while surrounding the tube body 1. Is the same. On the other hand, the fastening mechanism is different, and all ultrasonic transducers are attached to the tube body by one fastening mechanism. For this reason, the fastening mechanism includes two bowl-shaped vibrator holders 61 and 62 having a semicircular cross section and a plurality of screws (not shown) that mutually hold the flange portions. The ultrasonic vibrators 21 and 31 are attached in advance in the vicinity of both ends in the length direction of one vibrator holder 61, and similarly, the ultrasonic vibrators 22 and 32 are attached to the other vibrator holder 62. Pre-installed. Therefore, since the interval in the tube length direction of the ultrasonic transducer can be made constant at all times, the apparatus can be easily adjusted when the flow meter is attached to the tube.

  The present invention is not limited to the above-described ones, and can be appropriately modified within the scope of the technical idea. For example, the fastening mechanism is not limited to the above-described structure. For example, the fastening mechanism may be clamped with a clamp instead of being screwed. Also, instead of the bowl-shaped vibrator holders 61 and 62 having a semicircular cross section shown in FIG. 4, vibrator holders 41, 42, 51 and 52 having a short length as shown in FIG. A similar function can be obtained even in a structure in which a plurality of parallel bars are connected to each other.

Conceptual diagram of the ultrasonic flowmeter of the present invention Front view of the ultrasonic transceiver of the present invention Sectional view parallel to the tube of the ultrasonic transceiver of FIG. Sectional drawing parallel to the tubular body of the ultrasonic transceiver of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tubular body 2, 3 Ultrasonic transmitter / receiver 4, 5 Fastening mechanism 7 Changeover switch 8 Changeover switch control part 9 Electric pulse excitation part 10 Signal amplifier 11 Measurement / calculation part 12 Gap 21, 22, 31, 32 Ultrasonic transducer 41 , 42 Vibrator holder 43, 44 Screw 61, 62 Vibrator holder

Claims (3)

Two ultrasonic transmitters / receivers are provided at a distance so as to be in contact with the pipe body of the flow path of the fluid to be measured, one of the two ultrasonic transmitters / receivers being an ultrasonic transmitter and the other being an ultrasonic receiver. When the ultrasonic transmitter / receiver upstream of the fluid to be measured is used as the ultrasonic transmitter, the ultrasonic propagation time in the downstream direction and the ultrasonic transmitter / receiver downstream of the fluid to be measured are In the ultrasonic flowmeter for calculating the flow velocity based on the ultrasonic propagation time in the upstream direction, each of the ultrasonic transceivers is composed of two semicircular ultrasonic transducers, and each of the two half A fastening mechanism for fixing the circular ultrasonic transducer around the tube is provided, and the two semicircular ultrasonic transducers fixed at the respective length positions of the tube are in phase. Output in the same phase with respect to the vibration of the measuring tube. Ultrasonic flow meter, characterized by being urchin electrically connected. Two ultrasonic transmitters / receivers are provided at a distance so as to be in contact with the pipe body of the flow path of the fluid to be measured, one of the two ultrasonic transmitters / receivers being an ultrasonic transmitter and the other being an ultrasonic receiver. When the ultrasonic transmitter / receiver upstream of the fluid to be measured is used as the ultrasonic transmitter, the ultrasonic propagation time in the downstream direction and the ultrasonic transmitter / receiver downstream of the fluid to be measured are In the ultrasonic flowmeter for calculating the flow velocity based on the ultrasonic propagation time in the upstream direction, each of the ultrasonic transceivers is composed of two semicircular ultrasonic transducers, and each of the two half A fastening mechanism is provided for fixing the circular ultrasonic transducer with a distance in the length direction of the tubular body in a state of surrounding the tubular body, and two pieces are fixed at respective length positions of the tubular body. The semicircular ultrasonic transducers vibrate in the same phase and the measurement tube Ultrasonic flow meter, characterized in that it is electrically connected to the output of the same phase against. The ultrasonic flowmeter according to claim 1 or 2, wherein the two semicircular ultrasonic transducers fixed at respective length positions of the tubular body are not in contact with each other.

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