JP2000193502A - Flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flowmeter in which the S/N ratio of a received ultrasonic signal can be improved. SOLUTION: In this flowmeter, a sensor holder 11 and a lining layer 21 of a material whose coustic impedance is different are formed so as to cover the surface (inclusive of insertion holes of screws 5) of a part excluding a diaphragm part 15, in the sensor holder 11 in which an ultrasonic element 16 is placed on the diaphragm part 15. The boundary face between the sensor holder 11 and the lining layer 21 attenuates or scatters leakage ultrasonic waves, which are propagated in the sensor holder 11 and which creep to the inside of a pipe 1 so as to reduce the leakage ultrasonic waves which are propagated to the pipe 1. As a result, the S/N ratio of a received signal which is received by a reception-side ultrasonic element 16b is improved. It is possible to deal properly with the high pressure of a fluid to be measured, which requires an increase in the number of screws 5 and an increase in their size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flow meter for measuring a flow rate of a fluid such as a liquid, and more particularly to a flow meter using an ultrasonic sensor.

[0002]

2. Description of the Related Art An ultrasonic vortex flowmeter will be described as an example of a conventional flowmeter. The ultrasonic vortex flowmeter is arranged in a pipe constituting a flow path through which the fluid to be measured flows, and generates a Karman vortex on the outer peripheral side and changes a flow of the fluid synchronized with the Karman vortex in a measurement passage formed inside. A housing made of a substantially cylindrical vortex generator for generating a change in fluid flow (hereinafter, referred to as a fluid flow change) and an ultrasonic element are placed on the bottom surface, and the bottom surface is opposed to both openings of the vortex generator. A pair of bottomed cylindrical sensor holders that are fitted and attached to the tube together with the vortex generator by screws, and transmit and receive ultrasonic waves to and from the pair of ultrasonic elements via the fluid flow change generation region. In addition, there is an amplifier circuit that detects a modulation amount received by a received ultrasonic signal due to a change in fluid flow and determines an amount of fluid flowing through the tube.

[0003] O-rings are interposed between the sensor holder and the vortex generator and between the vortex generator and the pipe, respectively. (Hereinafter, referred to as a transmitting ultrasonic element), propagates through a vortex generator and a tube, and is received by a receiving one of the pair of ultrasonic elements (hereinafter, referred to as a receiving ultrasonic element). Ultrasonic waves (noise, wraparound ultrasonic waves) are suppressed, and the S / N ratio of ultrasonic waves received by the receiving-side ultrasonic element is improved.

[0004]

However, in the above-mentioned prior art, since the sensor holder is directly screwed to the tube, the ultrasonic wave goes around the receiving-side ultrasonic element via the screw. There has been a limitation in improving the S / N ratio of the received ultrasonic signal. In addition, a flow meter may measure a high-pressure fluid to be measured. In this case, it is necessary to increase the number of screws or increase the screw size in order to improve the pressure resistance of the sensor holder mounting portion. is there. When the number of screws or the size of the screw is increased, the contact area (adhesion) between the sensor holder and the pipe increases, and the leaked ultrasonic wave (noise) transmitted to the pipe is increased.
Is increased, and the S / N ratio of the received ultrasonic signal is reduced.

The present invention has been made in view of the above circumstances, and has as its object to provide a flowmeter capable of improving the S / N ratio of a received ultrasonic signal.

[0006]

According to the first aspect of the present invention,
A pipe through which a fluid to be measured flows, a transmitter that transmits ultrasonic waves into the pipe, and a receiver that receives ultrasonic waves transmitted from the transmitter, wherein the transmitter and the receiver include: Both have a sensor holder in which a flange for fixing to the pipe is formed on the opening side on the bottom side and an ultrasonic element is mounted on the inner surface of the bottom, and the cylindrical part of the sensor holder and the flange A lining layer having an acoustic impedance different from that of the sensor holder is formed on the outer peripheral surface.

According to a second aspect of the present invention, there is provided a pipe through which a fluid to be measured flows, a transmitter for transmitting ultrasonic waves into the pipe, and a receiver for receiving ultrasonic waves transmitted from the transmitter. In the flow meter, both the transmitter and the receiver have a sensor holder on which an ultrasonic element is mounted on the inner surface of the bottom, wherein a flange for fixing to the pipe is formed on the opening side on a bottomed cylindrical shape. A concentric wavy undulation is formed between a fixing portion of the sensor holder flange and the tube or a base end of the flange.

According to a third aspect of the present invention, there is provided a tube through which a fluid to be measured flows, a transmitter for transmitting ultrasonic waves into the tube, and a receiver for receiving ultrasonic waves transmitted from the transmitter. In the flow meter, both the transmitter and the receiver have a sensor holder on which an ultrasonic element is mounted on the inner surface of the bottom, wherein a flange for fixing to the pipe is formed on the opening side on a bottomed cylindrical shape. The sensor holder and the tube are made of materials having different acoustic impedances.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow meter according to a first embodiment of the present invention will be described below with reference to FIGS. In this embodiment, an ultrasonic vortex flowmeter is taken as an example of the flowmeter. FIG.
2 and FIG. 2, flat portions 2 are formed opposite to each other in a pipe 1 (flow path) through which a fluid to be measured flows. A hole 3 is formed in each of the portions where the flat portion 2 of the tube 1 is formed. A substantially cylindrical vortex generator 4 is inserted through the hole 3 and crosses the inside of the tube 1, sealed by an O-ring (not shown) or the like, and fixed to the tube 1 by screws 5. .

The vortex generator 4 is connected to the cylindrical vortex generator main body 6 having a length slightly shorter than the inner diameter of the pipe 1 and the vortex generator main body 6 with a step. A cylindrical fitting portion 7 having an inner diameter and an outer diameter larger than that of the cylindrical fitting portion 7 and fitted into the hole 3, and a vortex generator formed to project radially outward at a tip end side of the cylindrical fitting portion 7. The vortex generator flange 8 is joined to the flat portion 2. The O-ring and the like (not shown) are interposed between the cylindrical fitting portion 7 and the pipe 1 or between the vortex generator 4 and the flat portion 2.

By arranging the vortex generator main body 6 in the tube 1 as described above, Karman vortices are generated alternately at a frequency proportional to the flow velocity of the fluid to be measured downstream of the main body of the vortex generator 4. It has become. Further, the vortex generator body 6 is formed with two inlets 10 that communicate the inner hollow portion (hereinafter referred to as a measurement passage) 9 with the outer side.
A pressure difference is generated between the two inlets 10 as the Karman vortex is generated, and a flow (fluid flow change) is generated in the measurement passage 9 in synchronization with the Karman vortex. Here, the fluid flow change is synchronized with the Karman vortex, and by detecting the frequency of occurrence of the fluid flow change (and thus the frequency of occurrence of the Karman vortex), the flow velocity of the fluid to be measured and, consequently, the flow rate can be measured. . In the present embodiment, a housing is constituted by the vortex generator 4 and the tube 1.

A sensor holder 11 made of a material such as stainless steel is fitted and provided in the cylindrical fitting portion 7. The sensor holder 11 generally includes a bottomed cylindrical sensor holder main body 12 and an annular sensor holder flange 13 (flange) formed so as to protrude radially from the opening side of the sensor holder main body 12. An annular sealing member 14 such as an O-ring is interposed between the sensor holder flange 13 and the vortex generator flange 8, and the sensor holder 11
Together with the sealing member 14 and the vortex generator 4, the screw 5 is fixed to the pipe 1.

An ultrasonic element 16 made of a piezoelectric material is provided on a bottom portion (hereinafter referred to as a diaphragm) 15 of the sensor holder body 12.
Are acoustically bonded by a silicone adhesive or an epoxy resin (not shown), and one of the ultrasonic elements 16 vibrates in response to a drive signal from an oscillation circuit (not shown) via the diaphragm 15 of the sensor holder body 12. The ultrasonic wave is transmitted to the fluid to be measured in the measurement passage 9, and the ultrasonic wave is received by the other ultrasonic element 16 through the fluid flow change generation region. Hereinafter, for convenience, the one ultrasonic element 16 (upper side in FIG. 1) is appropriately replaced with the transmitting ultrasonic element 16.
a, the other ultrasonic element 16 is called a receiving-side ultrasonic element 16b. A lid 17 is attached to the opening of the sensor holder 11 by bonding, projection welding, screwing, or the like. An electrode 18 is attached to the lid 17 and hermetically sealed by a hermetic seal. Electrode 1
8 is connected to the ultrasonic element 16 by a lead wire 19 such as a PTFE wire or a urethane wire. The pair of ultrasonic elements 16 are connected to an oscillation circuit and an amplifier circuit (not shown) via electrodes 18, and the pair of ultrasonic elements 16
The transmission and reception of ultrasonic waves are performed, and the amount of modulation received by the received ultrasonic signal is detected by a change in the fluid flow to obtain the flow rate of the fluid to be measured flowing through the tube 1.

Further, the diaphragm 15 is provided on the sensor holder 11.
The acoustic impedance of the sensor holder 11 (made of stainless steel or the like) and a material different from that of the screw 5 so as to cover the surface (including the insertion hole 20 of the screw 5) of the portion other than the inner wall of the cylindrical fitting portion 7 (Z = ρc, where ρ: density of the propagation medium,
A lining layer 21 having a c: sound speed different from that of the sensor holder 11 and the screw 5 is formed. The lining layer 21
Due to the difference in acoustic impedance from the sensor holder 11 and the screw 5, the sensor holder 11 and the lining layer 2
At the boundary surface 1, the transmittance of the sound wave is extremely low.

In the ultrasonic vortex flowmeter configured as described above, when the fluid to be measured flows through the pipe 1, a Karman vortex is generated on the downstream side of the vortex generator 4, and the measurement passage is generated with the Karman vortex. 9, a fluid flow change occurs. At this time, when the ultrasonic wave is transmitted from the transmitting-side ultrasonic element 16a, propagates the fluid flow change, and is received by the receiving-side ultrasonic element 16b, the received ultrasonic wave modulates according to the generation frequency of the fluid flow change. Will receive it. Then, the amplifier circuit compares the transmission / reception signals of the transmission-side ultrasonic element 16a and the reception-side ultrasonic element 16b, detects this modulation, and measures the flow rate of the fluid to be measured flowing through the tube 1.

Here, the ultrasonic waves transmitted from the transmitting ultrasonic element 16a are transmitted through the fluid to be measured (hereinafter, referred to as main ultrasonic waves) and the ultrasonic waves transmitted through the sensor holder 11 and are transmitted through the tube 1. It proceeds by splitting into leaked ultrasonic waves that enter the interior. At this time, the surface of the sensor holder 11 excluding the diaphragm 15 and the inner wall of the cylindrical fitting portion 7 (the insertion hole 2 of the screw 5)
Lining layer 21 made of a material having a different acoustic impedance compared to the sensor holder 11 so as to cover the
Are formed, and the boundary surface between the sensor holder 11 and the lining layer 21 attenuates or scatters the leaked ultrasonic wave, thereby reducing the leaked ultrasonic wave transmitted to the pipe 1 (that is, the sensor holder 11 and the lining layer 21). The boundary surface 21 acoustically insulates the ultrasonic waves transmitted from the sensor holder 11 to the tube 1.) Therefore, the main ultrasonic wave becomes relatively larger than the leaked ultrasonic wave propagated to the receiving ultrasonic element 16b through the tube 1, and the S of the received signal received by the receiving ultrasonic element 16b becomes larger. / N ratio will be improved.

As described above, the receiving-side ultrasonic element 1
By improving the S / N ratio of the reception signal received at 6b, even when the diameter of the tube 1 is increased for large flow rate measurement and the propagation distance of the ultrasonic wave is increased, the reliability is high. I can deal with it. Further, as described above, the lining layer 21 is formed on the surface of the sensor holder 11 including the insertion hole 20 of the screw 5 (excluding the diaphragm 15 and the inner wall of the cylindrical fitting portion 7) to reduce leakage ultrasonic waves. S / N of the received signal regardless of the number and size of the screws 5 for fixing the sensor holder 11 and the vortex generator 4 to the tube 1
Since the ratio can be improved, it is possible to appropriately cope with an increase in the number of screws 5 and an increase in the pressure of the fluid to be measured, which requires an increase in size.

In the above-mentioned prior art, a gap is formed between the vortex generator and the tube, or an O-ring is interposed to reduce the leaked ultrasonic waves. Had to be separate. On the other hand, in the present embodiment, the lining layer 21 is formed on the surface of the sensor holder 11 to reduce the leakage ultrasonic waves and improve the S / N ratio of the received signal. The tube 1 may be integrally molded (obtained by a precision casting method such as a lost wax method). By integrally molding the vortex generator 4 and the tube 1 in this manner, the pressure resistance is increased as compared with the case where the vortex generator 4 and the tube 1 are separate bodies. In addition to improving reliability at high pressure, a member for joining the vortex generator 4 and the tube 1 so as to have a high pressure resistance at high pressure of the fluid to be measured is not required, thereby reducing the cost of the apparatus. be able to.

In the above-described embodiment, the case where the flow rate of the fluid to be measured is measured by utilizing the fact that the ultrasonic wave is modulated by a change in the fluid flow in the vortex generator 4 is described. The present invention (the invention according to claim 1) may be applied to an ultrasonic flowmeter that measures the flow rate of a fluid to be measured by utilizing the modulation of ultrasonic waves by Karman vortices. in this case,
There is no need to form the measurement passage 9 and the two inlets 10 in the vortex generator 4, and the configuration is simplified accordingly.

Further, the transmitter and the receiver of the present invention are not limited to the ultrasonic flowmeter using the Karman vortex or the change in fluid flow described above, but are inclined at a predetermined distance in the flow direction of the fluid to be measured. The present invention (the invention according to claim 1) is applied to an ultrasonic flowmeter that arranges a pair of ultrasonic elements in a tube 1 so as to face the tube and measures the flow rate of a fluid to be measured using the Doppler effect. Good. In this case, the vortex generator 4 is omitted, and the tube 1 forms a housing. Further, the present invention can be applied to a correlation type flow meter using an ultrasonic element.

Next, a flow meter according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, a seal member 14 is interposed between an outer peripheral end 13a of a sensor holder flange 13 of the sensor holder 11 and the vortex generator flange 8, and the sensor holder 11 and the vortex generator 4 is connected to the tube 1 by screws 5. Between the outer peripheral end 13a of the sensor holder flange 13 and the base end 13b of the sensor holder flange 13, a plurality of lines (six in FIG. 3) whose radial dimension increases from the base end 13b toward the outer peripheral end 13a. ) Are formed alternately on the upper surface and the lower surface of the sensor holder flange 13.

In the second embodiment, the annular concave portion 31 is formed between the outer peripheral end portion 13a and the base end portion 13b of the sensor holder flange 13, so that the ultrasonic wave propagation distance in the sensor holder 11 becomes longer. , The propagation path becomes complicated.
For this reason, the reflected ultrasonic wave is greatly attenuated because it is reflected by the boundary surface outside the annular concave portion 31 of the sensor holder flange 13, and the S / S of the received signal received by the receiving side ultrasonic element 16b (see FIG. 1). The N ratio will be improved. In this case, the sensor holder 1 is similar to the first embodiment described above.
1, a lining layer may be formed so as to cover the surface (including the insertion hole 20 of the screw 5) of the portion excluding the inner wall of the diaphragm portion 15 and the cylindrical fitting portion 7. By forming the lining layer in this way, in addition to the attenuation of the leaked ultrasonic wave by the annular concave portion 31, there is an attenuation occurring at the boundary with the lining layer,
The S / N ratio can be further improved. Further, by forming the lining layer 21 inside the annular concave portion 31, the adhesion between the lining layer 21 and the sensor holder 11 is improved, and the deformation and peeling of the lining layer 21 are suppressed.

Next, a flow meter according to a third embodiment of the present invention will be described with reference to FIG. The flowmeter according to the third embodiment is an ultrasonic flowmeter of a type that performs flow measurement using the above-described Doppler effect without using a vortex generator (Kalman vortex or fluid flow change), and is made of stainless steel. Tube 1
The sensor holder 11 is directly mounted on the (housing) with the screw 5 without the intervention of the vortex generator. In this case, the sensor holder 11 is formed of a resin material having a different acoustic impedance from the stainless steel tube 1 such as PPS.

In the third embodiment, the interface between the sensor holder 11 and the tube 1 having different acoustic impedances attenuates or scatters the leaked ultrasonic wave, thereby reducing the leaked ultrasonic wave transmitted to the tube 1. (That is, the sensor holder 1
The interface between the tube 1 and the tube 1 acoustically insulates the ultrasonic wave transmitted from the sensor holder 11 to the tube 1. ).
For this reason, the receiving side ultrasonic element 16b (FIG.
The main ultrasonic wave is relatively large compared to the leaked ultrasonic wave propagated to the receiving ultrasonic element 16b (see FIG. 1), and the S / N ratio of the received signal received by the receiving ultrasonic element 16b (see FIG. 1) is improved. become. In this case, even if the screw 5 is made of a material having the same acoustic impedance as that of the tube 1 or the sensor holder 11, the interface between the tube 1 and the sensor holder 11 whose acoustic impedance is different from that of the screw 5 and the screw 5. Exerts an acoustic insulation function, suppresses the propagation of leaked ultrasonic waves through the screw 5, and can make the received signal a good S / N ratio.

In the third embodiment, an ultrasonic flowmeter of a type not using a vortex generator is taken as an example. However, instead of this, an ultrasonic flowmeter of the type that measures a flow rate using a Karman vortex or a change in fluid flow is used. The present invention is applied to an ultrasonic flow meter (the invention according to claim 3).
May be applied. For example, in the first embodiment, the sensor holder 11 and the tube 1 are made of materials having different acoustic impedances, or the sensor holder 11 and the vortex generator 4 are made of materials having different acoustic impedances. Or you may. In this case, the lining layer 21 provided in the first embodiment may be omitted.

[0026]

According to the first aspect of the present invention, a lining layer having an acoustic impedance different from that of the sensor holder is formed on the outer peripheral surface of the cylindrical portion and the flange of the sensor holder, and the boundary between the sensor holder and the lining layer is formed. The surface attenuates or scatters the ultrasonic waves (leakage ultrasonic waves) that enter the inside of the tube by propagating through the sensor holder, and reduce the leaked ultrasonic waves transmitted to the tube. The S / N ratio of the received signal to be received is improved. Also, as described above, the S / N of the received signal received by the receiving ultrasonic element
By improving the ratio, even if the propagation distance of the ultrasonic wave is increased by increasing the diameter of the flow path of the housing,
We can deal with it with high reliability. Also, as described above, a lining layer is formed on the surface of the sensor holder including the screw insertion hole to reduce leakage ultrasonic waves,
Regardless of the number and size of the screws for fixing the sensor holder and the vortex generator to the pipe, the S / N ratio of the received signal can be improved, so the number of screws and the size of the screws are required to be increased. It is possible to appropriately cope with the increase in the pressure of the fluid to be measured.

According to a second aspect of the present invention, the sensor holder has a flange having a concentric corrugated undulation between a fixing portion of the flange of the sensor holder and the pipe or a base end of the flange. Since the ultrasonic wave propagation distance becomes longer and the propagation path becomes complicated, the leaked ultrasonic wave in the sensor holder is greatly attenuated, and the S / N ratio of the received signal received by the receiving ultrasonic element is improved. .

According to a third aspect of the present invention, the sensor holder and the tube are made of materials having different acoustic impedances, and the boundary surface between the sensor holder and the tube attenuates or scatters the leaked ultrasonic waves, and , The S / N ratio of the received signal received by the receiving-side ultrasonic element is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a flow meter according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an ultrasonic sensor mounting portion of the ultrasonic flow meter of FIG. 1;

FIG. 3 is a sectional view schematically showing a flow meter according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 pipe (flow path, housing) 4 vortex generator (housing) 11 sensor holder 15 diaphragm part (bottom part) 16 ultrasonic elements 16a, 16b transmitting side, receiving side ultrasonic elements 21 lining layer

Claims (3)

[Claims] 1. A flowmeter comprising: a pipe through which a fluid to be measured flows; a transmitter for transmitting ultrasonic waves into the pipe; and a receiver for receiving ultrasonic waves transmitted from the transmitter. The receiver and the receiver both have a bottomed cylindrical shape, a flange for fixing to the pipe on the opening side, and a sensor holder on which an ultrasonic element is mounted on the inner surface of the bottom, and the cylinder of the sensor holder A flowmeter, wherein a lining layer having an acoustic impedance different from that of the sensor holder is formed on an outer peripheral surface of the portion and the flange. 2. A flowmeter comprising: a pipe through which a fluid to be measured flows; a transmitter for transmitting ultrasonic waves into the pipe; and a receiver for receiving ultrasonic waves transmitted from the transmitter. Both the receiver and the receiver have a sensor holder in which a flange for fixing to the pipe is formed on the opening side and a ultrasonic element is mounted on the inner surface of the bottom, and the flange of the sensor holder is provided. The flowmeter according to any one of claims 1 to 3, wherein a concentric concave and convex portion is formed between the fixed portion of the pipe and the base end of the flange. 3. A flowmeter comprising: a pipe through which a fluid to be measured flows; a transmitter for transmitting ultrasonic waves into the pipe; and a receiver for receiving ultrasonic waves transmitted from the transmitter. Both the vessel and the receiver have a sensor holder on which an ultrasonic element is mounted on the inner surface of the bottom, wherein a flange for fixing to the pipe is formed on the opening side on the bottom side, and the sensor holder and the A flow meter, wherein the pipe and the pipe are made of materials having different acoustic impedances.