JP2006292378A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter capable of measuring a flow rate with high accuracy regardless of a temperature change. <P>SOLUTION: This flowmeter is equipped with a case 10 forming a passage 11 wherein fluid to be measured flows; a first ultrasonic vibrator 14 arranged on the upstream side inside the passage; a second ultrasonic vibrator 15 arranged oppositely to the first ultrasonic vibrator on the downstream side inside the passage; a control circuit 16 arranged outside the passage, for calculating the flow rate of the fluid to be measured flowing in the passage based on a propagation time of an ultrasonic wave transmitted/received between the first ultrasonic vibrator and the second ultrasonic vibrator; a signal wire 17 for connecting together the first ultrasonic vibrator and the second ultrasonic vibrator to the control circuit; and an insulating material 20 arranged in a hole 17 bored in the case, for holding the signal wire and securing insulation from the case. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves, and more particularly to a technique for improving measurement accuracy.

  Conventionally, a pair of ultrasonic transducers are arranged at a certain distance on the upstream side and downstream side of a fluid flow path, and ultrasonic waves are mutually transmitted between the pair of ultrasonic transducers under the control of a control circuit. To measure the fluid flow rate based on the difference between the integrated value of the ultrasonic propagation time from the upstream side to the downstream side and the integrated value of the ultrasonic propagation time from the downstream side to the upstream side. Ultrasonic flow meters are known. In such an ultrasonic flowmeter, a pair of ultrasonic transducers arranged in the flow path and a control circuit arranged outside the flow path are relayed to a hole provided in a case forming the flow path. The terminals are fitted and connected by signal lines passing through the relay terminals.

  In addition, as a technology related to the ultrasonic flow meter, the S / N of the ultrasonic transmission waveform is increased by reducing the vortex in the opening hole and promoting the attenuation of unnecessary components of the ultrasonic wave transmitted from the ultrasonic transmitter / receiver. There is known an ultrasonic flow rate measuring device capable of increasing the measurement accuracy and the upper limit value for flow rate measurement (see, for example, Patent Document 1).

  The ultrasonic flow rate measuring device includes a measurement channel through which a fluid flows, an ultrasonic transmitter / receiver provided upstream and downstream of the measurement channel, an upstream side where the ultrasonic transmitter / receiver faces the measurement channel, and An opening hole on the downstream side, an opening hole insulator formed of an electrically insulating material disposed on the inner surface of the opening hole, and an inflow suppressor are provided in the opening hole.

As a result, even in a compact storage space, the conductive distance between the ultrasonic transmitter / receiver and the flow path body forming the open hole is increased by the opening hole insulator, and the flow path body and the ultrasonic transmitter / receiver on the attachment side are increased due to a lightning strike or the like. Even when an abnormally high voltage occurs in the meantime, the withstand voltage leading to leakage can be increased, and the ultrasonic transceiver can be prevented from being damaged by the leakage current, thereby improving the reliability.
JP 2004-37468 A

  However, in the conventional ultrasonic flowmeter described above, when the leakage current changes due to the change in the insulation resistance between the signal line and the case at the relay terminal due to temperature or the like, a pair of ultrasonic transducers and a control circuit The waveform of the signal transmitted / received between is distorted and the offset voltage changes. As a result, there is a problem that the value of the measured flow rate varies.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an ultrasonic flowmeter capable of measuring a flow rate with high accuracy regardless of a temperature change.

  In order to solve the above-described problem, an ultrasonic flowmeter according to the present invention includes a case for forming a flow path through which a fluid to be measured flows, a first ultrasonic vibrator disposed on the upstream side of the flow path, A second ultrasonic transducer disposed on the downstream side of the flow channel so as to face the first ultrasonic transducer, and a first ultrasonic transducer and a second ultrasonic vibration disposed outside the flow channel. A control circuit for calculating a flow rate of a fluid to be measured flowing in a flow path based on a propagation time of ultrasonic waves transmitted to and received from a child, a first ultrasonic transducer, a second ultrasonic transducer, and a control circuit; It is characterized by comprising a signal line that connects the two and an insulating material that is disposed in a hole formed in the case and holds the signal line and ensures insulation from the case.

  According to the ultrasonic flowmeter of the present invention, the signal line is held between the signal line connecting the first ultrasonic transducer and the second ultrasonic transducer and the control circuit and the case and insulated from the case. Since the insulating material for ensuring the resistance is arranged, it is possible to suppress the leakage of the current flowing through the signal line to the case. As a result, distortion of signal waveforms transmitted and received between the first ultrasonic transducer and the second ultrasonic transducer and the control circuit can be suppressed, so that deterioration in flow rate measurement accuracy can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a side sectional view showing the structure of the ultrasonic flowmeter according to the first embodiment of the present invention. A flow path 11 through which a fluid flows is formed by the case 10 inside the ultrasonic flowmeter. The fluid supplied from the outside is introduced into the flow path 11 from the inlet 12 as shown by the arrow, passes through the flow path 11 and is discharged from the outlet 13.

  A first ultrasonic transducer 14 is disposed on the upstream side of the flow path 11. Further, a second ultrasonic transducer 15 is disposed on the downstream side of the flow path 11 so as to face the first ultrasonic transducer 14 at a predetermined distance.

A control circuit 16 is provided outside the flow path 11. The control circuit 16 is connected to the first ultrasonic transducer 14 and the second ultrasonic transducer 15 by a signal line 19 via a relay terminal 18 arranged in a hole 17 formed in the case 10. ing. The hole 17 is closed by the insulating material 20 of the relay terminal 18 so that the air flow path 11 is kept airtight. The insulating material 20 is configured to hold the signal line 19 and ensure insulation from the case 10. The insulating material 20 is made of a high-resistance material having a volume resistivity of 1 × 10 ¹⁵ (Ω-cm) or more, for example, a Teflon (registered trademark) material having a volume resistivity of 1 × 10 ¹⁸ (Ω-cm). can do. The insulating material 20 is not limited to a Teflon (registered trademark) material, and for example, a silicon material having a volume resistivity of 1 × 10 ¹⁵ (Ω-cm) can be used.

  In the above configuration, the first ultrasonic transducer 14 generates an ultrasonic wave according to the drive pulse signal sent from the control circuit 16 and transmits the ultrasonic wave toward the second ultrasonic transducer 15. Further, the first ultrasonic transducer 14 receives the ultrasonic wave from the second ultrasonic transducer 15, converts it into an electrical signal, and sends it to the control circuit 16. The second ultrasonic transducer 15 generates an ultrasonic wave according to the drive pulse signal sent from the control circuit 16 and transmits the ultrasonic wave toward the first ultrasonic transducer 14. The second ultrasonic transducer 15 receives the ultrasonic wave from the first ultrasonic transducer 14, converts it into an electrical signal, and sends it to the control circuit 16.

  The control circuit 16 includes, for example, a microcomputer, sends a drive pulse signal to the first ultrasonic transducer 14 or the second ultrasonic transducer 15 to generate an ultrasonic wave, and receives the first ultrasonic wave. Based on the received signal sent from the transducer 14 or the second ultrasonic transducer 15, the propagation time (forward propagation time) of the ultrasonic wave from the first ultrasonic transducer 14 to the second ultrasonic transducer 15, and The propagation time of ultrasonic waves (reverse propagation time) from the second ultrasonic transducer 15 to the first ultrasonic transducer 14 is calculated. Then, the flow velocity of the fluid is calculated based on the difference between the calculated forward propagation time and backward propagation time of the ultrasonic wave, and the volume flow rate is obtained by multiplying the calculated flow velocity by the cross-sectional area of the flow path 11. The obtained volume flow rate is output to the outside as the measured fluid flow rate.

  According to the ultrasonic flowmeter according to the first embodiment of the present invention configured as described above, the periphery of the relay terminal 18 disposed in the hole 17 formed in the case 10 is covered with the high-resistance insulating material 20. Therefore, even if there is a temperature change, it is possible to prevent the signal current flowing through the relay terminal 18 and the signal line 17 from leaking to the case 10.

  As a result, distortion of signal waveforms transmitted and received between the first ultrasonic transducer 14 and the second ultrasonic transducer 15 and the control circuit 16 can be suppressed, so that deterioration in flow rate measurement accuracy is prevented. it can.

  The ultrasonic flowmeter according to the second embodiment of the present invention uses a coaxial line instead of the signal line in the ultrasonic flowmeter according to the first embodiment. In the following, the same or corresponding parts as the structure of the ultrasonic flowmeter according to the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted or simplified.

  FIG. 2 is a side sectional view showing the structure of the ultrasonic flowmeter according to the second embodiment of the present invention. This ultrasonic flowmeter uses the coaxial line 21 instead of the relay terminal 18 and the signal line 19 of the ultrasonic flowmeter according to the first embodiment shown in FIG. The sound wave vibrator 15 and the control circuit 16 are connected. The coaxial line 21 is configured by covering two signal lines with an insulating material.

  Further, the periphery of the coaxial line 21 passing through the hole 17 formed in the case 10 is configured to be closed with a filler 22. Thereby, the airtightness of the flow path 11 can be maintained. As the filler 22, silicon material, Teflon (registered trademark) material, soft rubber, epoxy resin, or the like can be used.

  According to the ultrasonic flowmeter according to the second embodiment of the present invention configured as described above, the coaxial line 21 is connected to the connection between the first ultrasonic transducer 14 and the second ultrasonic transducer 15 and the control circuit 16. Since it is used, the relay terminal becomes unnecessary, and the coaxial line 21 itself is configured by covering the signal line with an insulating material, so that the insulation between the signal line and the case 10 can be maintained.

  The ultrasonic flowmeter according to the third embodiment of the present invention has a pair of ultrasonic transducers attached to a case. In the following, the same or corresponding parts as the structure of the ultrasonic flowmeter according to the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted or simplified.

  FIG. 3 is a side sectional view showing the structure of the ultrasonic flowmeter according to the third embodiment of the present invention. In this ultrasonic flow meter, the first ultrasonic transducer 14 is attached to the inner wall of the case 10 upstream of the flow path 11, and its signal terminal 30 is exposed to the outside from the outer wall of the case 10. Is guided to do. The signal terminal 30 of the first ultrasonic transducer 14 is connected to the control circuit 16 by a signal line 19 outside the flow path 11.

  The second ultrasonic transducer 15 is attached to the inner wall of the case 10 on the downstream side of the flow path 11 so as to face the first ultrasonic transducer 14, and the signal terminal 30 is connected to the case 10. It is led to be exposed to the outside from the outer wall. The signal terminal 30 of the second ultrasonic transducer 15 is connected to the control circuit 16 by a signal line 19 outside the flow path 11.

  FIGS. 4A and 4B are enlarged views showing a state where the first ultrasonic transducer 14 is attached. FIG. 4A is a plan view and FIG. 4B is a side sectional view. The first ultrasonic transducer 14 is exposed to the inside of the case 10 with an insulating O-ring 31 interposed so that the signal terminal 30 is exposed to the outside of the case 10 through the hole 23 formed in the case 10. Attached to the wall.

More specifically, the main body of the first ultrasonic transducer 14 is placed on the inner wall of the case 10 with an insulating O-ring 31 interposed therebetween, and the flange 14 a of the main body is pressed by the O-ring 32 so as to be fastened. Screwed to the case 10 by screws 33. The second ultrasonic transducer 15 is attached in the same manner. The insulating O-ring 31 can be produced by molding a Teflon (registered trademark) material or silicon material having a high resistance, for example, a volume resistivity of 1 × 10 ¹⁵ (Ω-cm) into a donut shape.

  According to the ultrasonic flowmeter of the third embodiment of the present invention configured as described above, the signal line 19 from the signal terminal 30 of the first ultrasonic transducer 14 and the second ultrasonic transducer 15 is connected to the flowmeter. Since it is connected to the control circuit 16 without wiring inside the path 11 (so as to pass through the outside of the flow path 11), the signal current flowing through the signal terminal 30 leaks to the case 10 even if the temperature changes. Can be suppressed.

  As a result, distortion of signal waveforms transmitted and received between the first ultrasonic transducer 14 and the second ultrasonic transducer 15 and the control circuit 16 can be suppressed, so that deterioration in flow rate measurement accuracy is prevented. it can.

  In the ultrasonic flowmeter according to the third embodiment, the first ultrasonic transducer 14 and the second ultrasonic transducer 15 are attached to the case 10 by screwing with an insulating O-ring 31 interposed. However, the first ultrasonic transducer 14 and the second ultrasonic transducer 15 may be configured to be attached to the case 10 using an adhesive having the same thermal expansion coefficient as that of the main body. In this case, since the insulating O-ring 31, the O-ring 32, and the retaining screw 33 are unnecessary, the ultrasonic flowmeter can be configured at low cost. Further, since it is not necessary to perform a screwing operation, the assembling operation is simplified and the manufacturing cost can be reduced.

  The ultrasonic flowmeter according to the fourth embodiment of the present invention monitors the leakage current between the signal line and the case in the ultrasonic flowmeter according to the first embodiment.

  FIG. 5 is a diagram illustrating a configuration of an ultrasonic flowmeter according to the fourth embodiment of the present invention. This ultrasonic flow meter is configured by adding a leakage current monitoring circuit 40 to the ultrasonic flow meter according to the first embodiment shown in FIG.

  The leakage current monitoring circuit 40 is connected to the case 10 and the insulating material 20 and measures a resistance value therebetween. Specifically, the leakage current monitoring circuit 40 periodically applies a voltage between the case 10 and the insulating material 20 and measures a leakage current flowing between the case 10 and the insulating material 20 when the voltage is applied. Then, the measured leakage current value is compared with a predetermined reference value, and when the leakage current value is equal to or higher than the reference value, the resistance value between the case 10 and the relay terminal 18 (signal line 19) is a predetermined value. It is assumed that the following has occurred, and this is notified to the outside.

  According to the ultrasonic flowmeter according to the fourth embodiment of the present invention configured as described above, when the resistance value between the case 10 and the insulating material 20 becomes a predetermined value or less, it is notified to the outside. It is possible to know that the insulating properties of the insulating material 20 have deteriorated due to aging, etc., and the insulating material 20 can be replaced as necessary.

  Accordingly, the distortion of the signal waveform transmitted and received between the first ultrasonic transducer 14 and the second ultrasonic transducer 15 and the control circuit 16 can always be kept normal, so that the measurement accuracy of the flow rate is deteriorated. Can be prevented.

  The present invention is applicable to an ultrasonic gas meter or the like.

It is a sectional side view which shows the structure of the ultrasonic flowmeter which concerns on Example 1 of this invention. It is a sectional side view which shows the structure of the ultrasonic flowmeter which concerns on Example 2 of this invention. It is a sectional side view which shows the structure of the ultrasonic flowmeter which concerns on Example 3 of this invention. It is a figure which expands and shows the attachment state of the 1st ultrasonic transducer | vibrator in the ultrasonic flowmeter which concerns on Example 3 of this invention. It is a figure which shows the structure of the ultrasonic flowmeter which concerns on Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Case 11 Flow path 12 Inlet 13 Outlet 14 1st ultrasonic transducer | vibrator 14a The collar part 15 The 2nd ultrasonic transducer | vibrator 16 Control circuit 17 Hole 18 Relay terminal 19 Signal line 20 Insulation material 21 Coaxial line 22 Filler material 23 Hole 30 Signal terminal 31 Insulating O-ring 32 O-ring 33 Set screw 40 Leakage current monitoring circuit

Claims (9)

A case forming a flow path through which the fluid to be measured flows;
A first ultrasonic transducer disposed on the upstream side of the flow path;
A second ultrasonic transducer disposed on the downstream side of the flow path so as to face the first ultrasonic transducer;
The flow rate of the fluid to be measured that flows in the flow path based on the propagation time of the ultrasonic wave that is arranged outside the flow path and is transmitted and received between the first ultrasonic transducer and the second ultrasonic transducer. A control circuit to calculate,
A signal line connecting between the first ultrasonic transducer and the second ultrasonic transducer and the control circuit;
An insulating material that is disposed in a hole formed in the case and holds the signal line and secures insulation from the case;
An ultrasonic flowmeter comprising:   The ultrasonic flowmeter according to claim 1, wherein the insulating material suppresses a leakage current to the case due to a temperature change.   The ultrasonic flowmeter according to claim 1, wherein the insulating material is made of a Teflon (registered trademark) material.   The ultrasonic flowmeter according to claim 1, wherein the insulating material is made of a silicon material.   The ultrasonic flowmeter according to claim 1, wherein the signal line is a coaxial line.   The ultrasonic flowmeter according to claim 5, wherein the insulating material is made of a filler that suppresses a leakage current to the case due to the temperature change. A case forming a flow path through which the fluid to be measured flows;
A first ultrasonic transducer disposed upstream of the flow path and attached to an inner wall of the case so that a first signal terminal is exposed to the outside of the flow path;
A second signal terminal is disposed on the downstream side of the flow path so as to face the first ultrasonic transducer and is attached to an inner wall of the case so as to be exposed to the outside of the flow path. 2 ultrasonic transducers,
The flow rate of the fluid to be measured that flows in the flow path based on the propagation time of the ultrasonic wave that is arranged outside the flow path and is transmitted and received between the first ultrasonic transducer and the second ultrasonic transducer. A control circuit to calculate,
A signal line that passes through the outside of the flow path and connects between the signal terminals of the first ultrasonic transducer and the second ultrasonic transducer and the control circuit;
An insulating material provided for each of the ultrasonic transducers and disposed between the ultrasonic transducer and an inner wall of the case;
An ultrasonic flowmeter comprising:   Each of the first ultrasonic transducer and the second ultrasonic transducer is attached to the inner wall of the case by screws with the insulating material interposed, or by an adhesive without interposing the insulating material. The ultrasonic flowmeter according to claim 7.   The ultrasonic flowmeter according to claim 1, further comprising a leakage current monitoring circuit that monitors a leakage current between the signal line and the case.

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