JPH109916A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute the entirety of an ultrasonic flowmeter having a flow interrupting function compactly by arranging a flow control valve in the form of a straight tube on the upstream side of a flow measuring section. SOLUTION: A first ultrasonic oscillator 7 is disposed on one side of a flow measuring section 6 while a second ultrasonic oscillator 8 is disposed on the other side of the flow measuring section 6. A flow control valve 11 comprising a fixed opening plate 9 and a sliding opening plate 10 are arranged in the form of a straight tube on the upstream side of a flow measuring section 6 and a straightening 27 is interposed between the flow control valve 11 and the flow measuring section 6. When a seismic sensor 25 senses an abnormal vibration due to earthquake or the like, a control section 26 operates to drive a solenoid 13 thus closing the opening plate 10. Consequently, the flow from the direction of an arrow (a) is blocked. The entire channel can be constituted into a straight tube by combining the flow measuring section 6 and the control valve 11 and the entirety of flowmeter can be made compact. Furthermore, the length can be shortened in the flow direction by driving the control valve 11 with a solenoid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flow meter having a flow blocking function.

[0002]

2. Description of the Related Art FIG.
As shown in FIG. 2, an ultrasonic flow rate measuring unit 3 is provided in an oblique direction between a gas inlet flow path 1 and an outlet flow path 2, and pressure is adjusted between the inlet flow path 1 and the ultrasonic flow rate measuring unit 3. In some cases, a vessel 4 and a shutoff valve 5 were arranged.

[0003]

However, in this case, a compact structure cannot be obtained due to the structure of the shut-off valve 5 and the overall arrangement thereof.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a flow control valve and a flow measuring unit arranged in a straight tube so as to make the whole compact.

[0005]

According to an ultrasonic flowmeter of the present invention, a first ultrasonic vibrator and a second ultrasonic vibrator disposed in a flow measuring section having a rectangular cross section are provided. A flow rate calculation unit that calculates a flow rate based on a signal from a child,
A flow control valve arranged in a straight tube on the upstream side of the flow measurement unit, a drive unit of the flow control valve, a control unit of the drive unit, and a rectification unit disposed between the flow control valve and the flow measurement unit. It has.

According to the present invention, flow measurement and flow cutoff control can be performed with a compact configuration.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to achieve the above object, the present invention provides a flow measuring section having a rectangular cross section, first and second ultrasonic vibrators arranged in the flow measuring section, A flow calculation unit that calculates the flow rate based on the signal from the, a flow control valve disposed in a straight tube upstream of the flow measurement unit, a drive unit of the flow control valve, and a control unit of the drive unit , And a rectifying unit disposed between the flow control valve and the flow measuring unit.

Also, a flow rate measuring section having a rectangular cross section, first and second ultrasonic vibrators arranged in the flow rate measuring section, and a flow rate calculating section for calculating a flow rate based on a signal from the vibrator. And a flow control valve arranged on the upstream side of the flow rate measurement unit, comprising a fixed opening plate, a sliding opening plate, and a pressing member that increases the adhesion between the sliding opening plate and the fixed opening plate, It is configured to include a drive solenoid of the flow control valve, a control unit of the drive solenoid, and a rectification unit disposed between the flow control valve and the flow measurement unit.

Also, a flow measuring unit having a rectangular cross section, first and second ultrasonic vibrators arranged in the flow measuring unit, and a flow calculating unit for calculating a flow based on a signal from the vibrator. A fixed opening plate, a sliding opening plate, a pressing member for increasing the adhesion between the sliding opening plate and the fixed opening plate, and a pressing member disposed on the upstream side of the flow rate measuring section; A flow control valve formed of a sliding member disposed between the opening plate, a drive solenoid of the flow control valve, a control unit of the drive solenoid, and a flow control valve disposed between the flow control valve and the flow measurement unit The rectifying unit is configured to include the rectifying unit.

Also, a flow rate measuring section having a rectangular cross section, first and second ultrasonic vibrators arranged in the flow rate measuring section, and a flow rate calculating section for calculating a flow rate based on a signal from the vibrator. And a fixed aperture plate disposed upstream of the flow rate measurement unit and disposed with a first permanent magnet, a sliding aperture plate disposed with a second permanent magnet, the sliding aperture plate and the fixed aperture plate A flow control valve composed of a pressing member for increasing the adhesion of the flow control valve, a drive solenoid of the flow control valve, a control unit of the drive solenoid, and a rectifier disposed between the flow control valve and the flow measurement unit. It is constituted so that it consists of a part.

Also, a flow measuring unit having a rectangular cross section, first and second ultrasonic vibrators arranged in the flow measuring unit, and a flow calculating unit for calculating a flow based on a signal from the vibrator. And a flow control valve arranged on the upstream side of the flow rate measurement unit, comprising a fixed opening plate, a sliding opening plate, and a pressing member that increases the adhesion between the sliding opening plate and the fixed opening plate, It is configured to include a drive motor for the flow control valve, a control unit for the drive motor, and a rectification unit disposed between the flow control valve and the flow measurement unit.

A flow measuring section having a rectangular cross section; first and second ultrasonic vibrators arranged in the flow measuring section; and a flow calculating section for calculating a flow rate based on a signal from the vibrator And a flow control valve disposed in a straight tube downstream of the flow measurement unit, a driving unit of the flow control valve, and a control unit of the driving unit.

[0013] Also, a flow rate measuring section having a rectangular cross section, first and second ultrasonic vibrators arranged outside the flow path of the flow rate measuring section, and a flow rate calculated based on a signal from the vibrator. And a flow control valve disposed in a straight tube downstream of the flow measurement unit, a drive unit for the flow control valve, and a control unit for the drive unit.

According to the present invention, the flow rate measurement and the cutoff control can be performed in a compact configuration by the above configuration.

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 6 denotes a flow rate measuring unit;
Is a first ultrasonic vibrator arranged on one side of the flow measuring unit 6, and 8 is a second ultrasonic vibrator arranged on the other side of the flow measuring unit 6.

Reference numeral 9 denotes a fixed opening plate, and reference numeral 10 denotes a sliding opening plate.
Is configured. A spring (pressing member) 12 presses the sliding opening plate 10 against the fixed opening plate 9. 13 is a solenoid (drive unit), 14 is a plunger, 15 is a coil, and 16 is a permanent magnet. The plunger 14 has an integral structure with the spring receiver 17 and the shaft 18. 19 is a yoke and 20 is a spring. The shaft 18 is fixed to the sliding opening plate 10. Reference numeral 21 denotes an O-ring for preventing fluid leakage inside and outside when the shaft 18 slides. 22 is a lead wire of the coil 15. Reference numeral 23 denotes a recess for accommodating the fixed opening plate 9 and the sliding opening plate 10. 24 is a pipeline, 25
Is a seismic sensor attached to the conduit 24, and 26 is a control unit of the solenoid 13. Reference numeral 27 denotes a rectifying unit, which is composed of, for example, a strainer, a mesh, or the like. 28 is a flow rate calculation unit. Further, the flow control valve 11, the rectifying unit 27, and the flow measuring unit 6 are arranged in a straight tube.

In FIG. 2, (a) shows the fixed opening plate 9, and 29a, 29b, 29c and 29d are the openings. (B) shows the sliding opening plate 10, 30a, 30b, 30c and 30d are openings, and 31a, 31b, 31c and 31d are closing parts.

FIG. 3 shows a cross section taken along the line AA 'of FIG. Reference numeral 32 denotes a fixing portion of the spring 12, and FIG. 4 shows a cross section taken along line BB 'of FIG.

FIG. 5 is a control block diagram of the flow rate calculator 28. In FIG. 5, reference numeral 33 denotes a flow rate calculating unit that receives signals from the first ultrasonic vibrator 7 and the second ultrasonic vibrator 8 and calculates a flow rate. 34 is a start signal generator, 35 is a transmitter, 36 is a receiver, and 37 is a switcher. The transmission section 35 is composed of a trigger signal generation section 38 and an oscillation section 39. The receiving unit 36 includes an amplifying unit 40 for a received signal and a comparing unit 41 for comparing with a reference value.
42 is a repetition unit, 43 is a clock unit, and 44 is a calculation unit.

Next, the operation will be described. At the time of a normal measurement operation, the flow control valve 11 is configured such that the openings 30a, 30b, 30c and 30d of the sliding opening plate 10
Openings 29a, 29b, 29c and 29 of fixed aperture plate 9
It is in the same state as d.

At this time, the flow flowing from the direction of arrow a in FIG. 1 passes through the flow control valve 11 and is rectified by the rectification unit 27 into a flow suitable for measurement, and then flows through the flow measurement unit 6. It flows out as indicated by an arrow b toward a measurement object (not shown).

In such a state, the start signal generator 34
When a signal comes in from, the trigger signal generator 38 operates and the signal is sent to the switching unit 37 by the oscillator 39. The switching unit 37 is configured such that the transmission unit 35 is initially connected to the first ultrasonic vibrator 7.
The receiving section 36 is set to be connected to the second ultrasonic transducer 8. Therefore, an ultrasonic signal is emitted from the first ultrasonic transducer 7 into the flow rate measuring section 6 by the trigger signal.

This signal is received by the second ultrasonic transducer 8, amplified by the amplifier 40, and compared with the reference signal by the comparator 41. After this process is performed the number of times set by the repetition unit 42, a signal is sent to the timer unit 43. The timer 43 measures the elapsed time (T1) from the generation of the trigger signal to the signal transmitted at this time. On the other hand, when the predetermined number of repetitions is completed, a signal is sent from the repetition unit 42 to the switching unit 37, and the transmission unit 35 is connected to the second ultrasonic vibrator 8, and the reception unit 36 is connected to the first ultrasonic vibration Connect to child 7. At the same time, a drive signal to the trigger signal generator 38 is sent again.

Thus, the same operation as described above is performed in the direction opposite to the flow, and the elapsed time (T2) is measured.
Based on the elapsed times T1 and T2 measured in this manner, the flow rate is calculated by the calculation unit 44 by the following calculation formula. First, the flow velocity v is obtained by the following equation.

V = (L / 2 cos θ) ((1 / T1) −
(1 / T2)) Here, θ is the angle between the flow and the ultrasonic wave propagation path, and L is the length of the flow measurement unit.

Next, the flow rate Q is calculated by adding the flow rate
Is multiplied by the cross-sectional area s of. Q = kvs Here, k is a correction coefficient for converting the measured flow velocity v into the average flow velocity in the measurement cross section. In the above description, T
The measurement of 1 and T2 was repeatedly performed, but may be performed once when accurate measurement is performed.

Next, when the seismic sensor 25 in the piping section 24 detects any abnormality, for example, abnormal vibration due to an earthquake, the control section 26 of the solenoid 13 operates and the solenoid 13
Drive. As a result, as shown in FIG. 6, the sliding opening plate 10 has the closing portions 31a, 31b, 31c of the sliding opening plate 10.
And 31d are openings 29a, 29b, 2 of the fixed opening plate 9.
9c and 29d are closed. Thereby, in FIG. 1, the flow flowing in from the direction of the arrow a is closed by the flow control valve 11.

As described above, the flow control valve 11 formed by the fixed opening plate 9 and the sliding opening plate 10 is combined with the rectangular flow measuring unit 6, and the rectifying unit is disposed therebetween, whereby the entire flow is measured. The flow path can be configured as if it were a straight tube, and the entire flow meter can be made compact. Also, by making the flow control valve a sliding type and being driven by a solenoid,
The length in the flow direction can be reduced, and a more compact flowmeter can be configured.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 7, reference numeral 45 denotes a sliding member. Note that the other parts are the same as those in the first embodiment, and are therefore denoted by the same reference numerals.

Next, the operation will be described. In this example,
This is the same as the first embodiment except that the sliding member 45 operates by being arranged between the sliding opening plate 10 and the spring 12.
According to this embodiment, by disposing the sliding member 45 between the sliding opening plate 10 and the spring 12, friction during sliding of the sliding opening plate 10 is reduced, and the operation reliability of the flow control valve 11 is improved. Performance can be improved.

(Embodiment 3) Next, a third embodiment will be described with reference to FIG. In FIG. 8A, the fixed aperture plate 9 has permanent magnets 46a, 46b, 46c, 46d and 4 on both sides of the apertures 29a, 29b, 29c, and 29d.
7a, 47b, 47c and 47d. Also,
In FIG. 8B, the sliding opening plate 10 has a closing portion 31a,
Permanent magnets 48a, 4b on both sides of 31b, 31c and 31d
8b, 48c and 48d and 49a, 49b, 49c
And 49d. Except for the above, all are the same as in the first embodiment, and a description thereof will be omitted.

Next, the operation will be described with reference to FIGS.
In the state shown in FIG. 1, the permanent magnet 4
6a, 46b, 46c and 46d and 47a, 47
b, 47c and 47d and the permanent magnet 4 of the sliding aperture plate 10
8a, 48b, 48c and 48d and 49a, 49
The positions are shifted from b, 49c and 49d. Next, FIG.
As shown in FIG. 7, when the sliding opening plate 10 is lowered, the permanent magnets 46a, 46b, 46c and 46d and 47a, 47b, 47c and 47d of the fixed opening plate 9 and the sliding opening plate 1
0, the positions of the permanent magnets 48a, 48b, 48c and 48d and 49a, 49b, 49c and 49d coincide,
The sliding opening plate 10 is in close contact with the fixed opening plate 9. Thereby, the closing performance of the flow control valve 11 is further ensured.

(Embodiment 4) Next, a fourth embodiment will be described with reference to FIG. In FIG. 9, reference numeral 50 denotes a drive motor. 51 is a coil and 52 is a rotor formed of a permanent magnet. 53 is an upper shaft and 54 is a lower shaft. Both the upper shaft 53 and the lower shaft 54 are formed in a screw shape. The lower shaft 54 is rotatably attached to the sliding opening plate 10. Reference numerals 55 and 56 denote threaded ball bearings, which make the upper shaft 53 and the lower shaft 54 movable by rotation of the upper shaft 53 and the lower shaft 54. 5
7 is a casing. 58 is a lead wire of the drive motor 50, and 59 is a control unit of the drive motor 50. Except for the above, all are the same as in the first embodiment, and a description thereof will be omitted.

Next, the operation will be described. Now, when the seismic sensor 25 in the pipe section 24 detects any abnormality, for example, abnormal vibration due to an earthquake, the control section 59 operates and the drive motor 5
Drive 0. As a result, the sliding opening plate 10 is in a state similar to that of FIG. 6, and the closing portions 31a, 31
b, 31c, 31d are the openings 29a, 2
9b, 29c and 29d are closed. Thus, the arrow a
The flow flowing from the direction is closed by the flow control valve 11. According to this embodiment, the flow control valve is driven by a motor,
By adopting the sliding structure, the length in the flow direction can be reduced, and a more compact flowmeter can be created.

(Embodiment 5) Next, a fifth embodiment will be described with reference to FIG. In FIG. 10, reference numeral 60 denotes a flow measurement unit, 61 denotes a first ultrasonic vibrator arranged on one side of the flow measurement unit 60, and 62 denotes a flow measurement unit 60.
Is a second ultrasonic transducer disposed on the other side of the second ultrasonic transducer. 6
Reference numeral 3 denotes a fixed opening plate, and 64 denotes a sliding opening plate. The fixed opening plate 63 and the sliding opening plate 64 constitute a flow control valve 65. 66 is a spring (pressing member) for pressing the sliding opening plate 64 against the fixed opening plate 63. 67 is a solenoid (drive unit), 68 is a plunger, 69 is a coil, and 70 is a permanent magnet. Plunger 68 is spring receiver 7
1. It has an integral structure with the shaft 72. 73 is a yoke and 74 is a spring. The shaft 72 is a sliding opening plate 64
It is fixed to. Reference numeral 75 denotes an O-ring for preventing leakage of the measurement fluid when the shaft 72 slides. 76 is a lead wire of the coil 69. 77 is a fixed opening plate 63, a sliding opening plate 64
Is a recess for accommodating therein. Reference numeral 78 denotes a sensor attached to the pipe 79, and reference numeral 80 denotes a control unit of the solenoid 67.
81 is a flow rate calculation unit. As described above, the flow control valve 6
5. The flow measuring units 60 are arranged in a straight tube. In addition,
The flow of signal processing is the same as in FIG.

Next, the operation will be described. During the normal measurement operation, the openings 30a, 30b, 30
c and 30d are the openings 29a, 29 of the fixed opening plate 63.
b, 29c and 29d. At this time, the flow that flows in the direction of arrow a in FIG. 10 passes through the flow rate measuring unit 60 and then flows out through the flow rate control valve 65 toward the target (not shown) as indicated by arrow b. The signal processing is the same as in the first embodiment.

Next, when the seismic sensor 78 in the piping section 79 detects any abnormality, the control section 80 operates to drive the solenoid 67. As a result, the sliding opening plate 64 moves upward, and the closing portions 31a, 31b, 3
1c and 31d are openings 29a, 29 of the fixed opening plate 9.
b, 29c and 29d are closed. As a result, FIG.
, The flow flowing from the direction of arrow a is the flow control valve 6
Closed at 5. By arranging the flow control valve 65 on the downstream side of the flow measuring unit 60 in this way, an ultrasonic flow meter with a shut-off function can be configured without the need for a rectifying unit, so that a more compact configuration is achieved. Is what you can do.

(Embodiment 6) Next, a sixth embodiment will be described with reference to FIG. In FIG. 11, reference numeral 82 denotes a flow measuring unit, 83 denotes a first ultrasonic vibrator disposed on one side of the flow measuring unit 82, and 84 denotes a first ultrasonic vibrator disposed on the other side of the flow measuring unit 82. This is the second ultrasonic transducer. In this case, the ultrasonic transducers 83 and 84 are mounted outside the pipe 85. Incidentally, reference numerals 86 and 87 denote acoustic matching layers, and the other parts are the same as those in the sixth embodiment, and are indicated by the same reference numerals.

Next, the operation will be described. In this case, the operation is the same as that of the sixth embodiment except that the ultrasonic vibrators 83 and 84 are mounted outside the pipe 85.

In this embodiment, by arranging the ultrasonic vibrators 83 and 84 outside the tube, the airtightness of the measuring section can be ensured, and the reliability of the flow interruption can be increased. Moreover, since the flow is not disturbed by the arrangement of the vibrator, the measurement accuracy can be improved.

The signal processing in the present invention can be realized by software using a microcomputer such as a one-chip microcomputer.

[0043]

As described above, according to the present invention, the following effects can be obtained.

(1) By arranging the rectifying section between the rectangular flow rate measuring section and the flow rate control valve, the entire flow path configuration can be configured as a straight tube, and the entire flow meter can be made compact. be able to.

(2) The flow control valve is driven by a solenoid,
By making the valve a sliding type structure with a fixed opening plate and a sliding opening plate, the length in the flow direction can be shortened, and a more compact flowmeter can be made.

(3) By disposing the sliding member between the pressing portion of the flow control valve and the sliding opening plate, the operation reliability of the flow control valve can be improved.

(4) A strong closing force can be obtained by disposing permanent magnets on the fixed opening plate and the sliding opening plate of the flow control valve.

(5) Since the flow control valve is driven by a motor and has a sliding structure, the length in the flow direction can be shortened, and a more compact flow meter can be manufactured.

(6) By arranging the flow control valve on the downstream side of the flow measuring section, the influence of the flow control valve on the flow is reduced, and the flow measurement accuracy can be improved.

(7) By arranging the ultrasonic vibrator outside the tube, the reliability when cutting off the flow can be improved.

[Brief description of the drawings]

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

FIG. 2A is an elevation view of a fixed opening plate of a flow control valve in the flow meter. FIG. 2B is an elevation view of a sliding opening plate in the flow meter.

FIG. 3 is a sectional view taken along line A-A ′ of FIG. 1 in the flow meter.

FIG. 4 is a sectional view of the flow meter taken along line B-B ′ of FIG. 1;

FIG. 5 is a control block diagram of a flow rate calculation unit in the flow meter.

FIG. 6 is a vertical sectional view showing different operation states of the flow control valve in the flow meter.

FIG. 7 is a vertical sectional view of an ultrasonic flowmeter according to a second embodiment of the present invention.

FIG. 8A is an elevation view of a fixed opening plate of a flow control valve according to a third embodiment of the present invention. FIG. 8B is an elevation view of a sliding opening plate of the control valve.

FIG. 9 is a vertical sectional view of an ultrasonic flowmeter according to a fourth embodiment of the present invention.

FIG. 10 is a vertical sectional view of an ultrasonic flowmeter according to a fifth embodiment of the present invention.

FIG. 11 is a vertical sectional view of an ultrasonic flowmeter according to a sixth embodiment of the present invention.

FIG. 12 is a vertical sectional view of a conventional ultrasonic flowmeter.

[Explanation of symbols]

 Reference Signs List 6 Flow rate measuring unit 7 First ultrasonic vibrator 8 Second ultrasonic vibrator 11 Flow control valve 13 Drive unit 26 Control unit 27 Rectifying unit 28 Flow rate calculating unit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yukinori Ozaki 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A flow rate measuring section having a rectangular cross section, a first ultrasonic vibrator and a second ultrasonic vibrator arranged in the flow rate measuring section, and a signal from the ultrasonic vibrator. A flow calculation unit that calculates the flow rate, a flow control valve disposed in a straight tube upstream of the flow measurement unit, a driving unit of the flow control valve, a control unit of the driving unit, and the flow control valve. An ultrasonic flowmeter comprising a rectifier disposed between the flowmeter and the flowmeter. 2. A flow measuring unit having a rectangular cross section, a first ultrasonic vibrator and a second ultrasonic vibrator arranged in the flow measuring unit, and a signal from the ultrasonic vibrator. A flow rate calculation unit configured to calculate a flow rate, a flow rate configured by a fixed opening plate, a sliding opening plate, and a pressing member that increases the adhesion between the sliding opening plate and the fixed opening plate, which is disposed upstream of the flow rate measurement unit. An ultrasonic flowmeter comprising a control valve, a drive solenoid of the flow control valve, a control unit of the drive solenoid, and a rectification unit disposed between the flow control valve and the flow measurement unit. 3. A flow measuring section having a rectangular cross section, a first ultrasonic transducer and a second ultrasonic transducer disposed in the flow measuring section, and a signal from the ultrasonic transducer. A flow rate calculating unit for calculating a flow rate, a fixed opening plate disposed upstream of the flow rate measuring unit, a sliding opening plate, and a pressing member for increasing the adhesion between the sliding opening plate and the fixed opening plate; and the pressing member. And a flow control valve formed of a sliding member disposed between the sliding opening plate, a drive solenoid of the flow control valve, a control unit of the drive solenoid, the flow control valve and the flow measurement unit, Ultrasonic flowmeter consisting of a rectification unit located between the two. 4. A flow measuring section having a rectangular cross section, a first ultrasonic transducer and a second ultrasonic transducer disposed in the flow measuring section, and a signal from the ultrasonic transducer. A flow rate calculation unit for calculating the flow rate, a fixed aperture plate disposed on the upstream side of the flow rate measurement unit and disposed with a first permanent magnet, a sliding aperture plate disposed with a second permanent magnet, and the sliding aperture plate; A flow control valve constituted by a pressing member that increases the adhesion of the fixed opening plate, a drive solenoid of the flow control valve, a control unit of the drive solenoid, and a flow control valve and a flow measurement unit An ultrasonic flow meter consisting of a rectifying section arranged. 5. A flow measuring section having a rectangular cross section, a first ultrasonic transducer and a second ultrasonic transducer disposed in the flow measuring section, and a signal from the ultrasonic transducer. A flow rate calculation unit configured to calculate a flow rate, a flow rate configured by a fixed opening plate, a sliding opening plate, and a pressing member that increases the adhesion between the sliding opening plate and the fixed opening plate, which is disposed upstream of the flow rate measurement unit. An ultrasonic flowmeter comprising a control valve, a drive motor for the flow control valve, a control unit for the drive motor, and a rectification unit disposed between the flow control valve and the flow measurement unit. 6. A flow measuring section having a rectangular cross section, a first ultrasonic transducer and a second ultrasonic transducer disposed in the flow measuring section, and a signal from the ultrasonic transducer. An ultrasonic flowmeter comprising a flow calculating unit for calculating a flow rate, a flow control valve disposed in a straight tube downstream of the flow measuring unit, a driving unit for the flow control valve, and a control unit for the driving unit. . 7. A flow measuring unit having a rectangular cross section, a first ultrasonic vibrator and a second ultrasonic vibrator disposed outside a flow path of the flow measuring unit, A flow rate calculation unit that calculates a flow rate based on a signal, a flow rate control valve disposed in a straight tube downstream of the flow rate measurement unit, a drive unit of the flow rate control valve, and a control unit of the drive unit. Sonic flow meter.