JP2000298045A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a stability of a zero point by a temperature change by constituting an ultrasonic vibrator to reduce effects of the temperature change to measured results in a state without a flow. SOLUTION: A driving circuit 5 drives an ultrasonic vibrator 2 under the control of a control part 10 and a timer 8 starts measuring a time. An ultrasonic pulse propagating in a flow rate measurement part 1 is received by an ultrasonic vibrator 3 and, a reception detection circuit 7 sends a reception detection signal to the control part 10. After the process is repeated N times, a propagation time t1 is operated from a measured time of the timer 8. Thereafter, a switching circuit 6 switches to make the ultrasonic vibrator 3 transmit the pulse, and a propagation time t2 is obtained. A flow rate is calculated from a flow velocity operated from the propagation times t1 and t2 and, an area of the flow rate measurement part 1. At this time, a zero point varies depending on a temperature due to an effect of an unnecessary vibration mode in a state without a flow. Therefore, the ultrasonic vibrators are constituted to make different resonance frequencies of the unnecessary vibration mode of a piezoelectric body and a case. An effect of a temperature change is thus reduced and the zero point is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter for measuring the flow rate and flow rate of a gas or liquid using ultrasonic waves.

[0002]

2. Description of the Related Art A conventional ultrasonic flowmeter of this type is known, for example, from Japanese Patent Application Laid-Open No. Hei 9-133561, and includes a temperature (T0) of a non-measured fluid in a standard state and a temperature of a non-measured fluid in a used state. From the information (Tsv), T0 / Tsv was used as a correction coefficient to increase the flow rate measurement accuracy.

[0003]

However, in the above-mentioned conventional ultrasonic flowmeter, if the measurement result in a state where there is no flow (hereinafter referred to as a zero point) becomes a value other than 0 due to a temperature change, the operation compensation temperature range It is difficult to set the whole to 0 only by the correction coefficient, and there is a problem that the stability of the zero point due to a temperature change cannot be obtained.

An object of the present invention is to solve the above-mentioned problems, and to improve the stability of a zero point due to a temperature change by using an ultrasonic vibrator.

[0005]

In order to solve the above-mentioned problems, the present invention is configured so that the unnecessary vibration mode of the piezoelectric body and the resonance frequency of the case are different from each other.

According to the above invention, the resonance between the piezoelectric body and the case can be prevented, and the influence of unnecessary vibration on the ultrasonic pulse transmitted and received by the pair of ultrasonic transducers can be reduced. Therefore, the stability of the zero point due to the temperature change can be improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic flowmeter according to a first embodiment of the present invention comprises a flow rate measuring section through which a fluid to be measured flows, and a pair of ultrasonic transducers provided in the flow rate measuring section for transmitting and receiving ultrasonic waves. A drive circuit that drives one ultrasonic transducer, a reception detection circuit that is connected to the other ultrasonic transducer and detects an ultrasonic pulse, a timer that measures the propagation time of the ultrasonic pulse, and the drive circuit A control unit for controlling a timer, and a calculation unit for calculating a flow rate from the output of the timer by calculation, comprising a pair of ultrasonic transducers so as to reduce the influence of a temperature change on the measurement result when there is no flow. Therefore, the stability of the zero point due to the temperature change can be improved.

According to the ultrasonic flowmeter of the second embodiment of the present invention, in the ultrasonic flowmeter of the first embodiment, the pair of ultrasonic vibrators are configured to reduce the influence of the unnecessary vibration mode.
The stability of the zero point due to a temperature change can be improved.

An ultrasonic flowmeter according to a third aspect of the present invention is the ultrasonic flowmeter according to the second aspect, wherein the pair of ultrasonic vibrators are a piezoelectric body and a piezoelectric body which mutually convert an electric signal and mechanical vibration. A case is provided on the outside of the body, and the resonance frequency of the unnecessary vibration mode of the piezoelectric body and the resonance frequency of the case are configured to be different, so the influence of the unnecessary vibration mode can be reduced and the stability of the zero point due to temperature change is improved. Can be done.

An ultrasonic flowmeter according to a fourth aspect of the present invention is the ultrasonic flowmeter according to the second aspect, wherein the pair of ultrasonic vibrators are a piezoelectric body and a piezoelectric body which mutually convert an electric signal and mechanical vibration. A case is provided on the outside of the body, and the frequency of the unnecessary vibration mode of the piezoelectric body is configured to be higher than the frequency used, so the influence of the unnecessary vibration mode can be reduced and the stability of the zero point due to temperature change can be improved. it can.

An ultrasonic flowmeter according to a fifth aspect of the present invention is the ultrasonic flowmeter according to the second aspect, wherein the pair of ultrasonic vibrators comprises a piezoelectric body and a piezoelectric body which mutually convert an electric signal and mechanical vibration. Since the case is provided outside the body, and the case is provided with the vibration damper to inhibit the vibration of the case, the influence of the unnecessary vibration mode can be reduced and the stability of the zero point due to the temperature change can be improved.

An ultrasonic flowmeter according to a sixth aspect of the present invention is the ultrasonic flowmeter according to the fifth aspect, wherein the vibration damping body is made of a rigid body, so that the mass of the case is increased to prevent unnecessary vibration, thereby reducing unnecessary vibration. The influence of the vibration mode can be reduced, and the stability of the zero point due to the temperature change can be improved.

An ultrasonic flowmeter according to a seventh aspect of the present invention is the ultrasonic flowmeter according to the fifth aspect, wherein the vibration damper is made of an elastic body, so that unnecessary vibration of the case is lost by the elastic body, The influence of the mode can be reduced, and the stability of the zero point due to the temperature change can be improved.

An ultrasonic flowmeter according to an eighth aspect of the present invention is the ultrasonic flowmeter according to the second aspect, wherein the pair of ultrasonic vibrators are a piezoelectric body and a piezoelectric body which mutually convert an electric signal and mechanical vibration. Since the case is provided outside the body, and the case is provided with a bent portion on the side wall so as to inhibit unnecessary vibration, the influence of the unnecessary vibration mode can be reduced and the stability of the zero point due to a temperature change can be improved.

According to the ultrasonic flowmeter of the ninth embodiment of the present invention, since the bending portion is provided so that the direction of the piezoelectric body can be recognized in the ultrasonic flowmeter of the eighth embodiment, the direction of the piezoelectric body can be recognized. And it becomes easy to attach to the ultrasonic flowmeter.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the components denoted by the same reference numerals are the same, and the detailed description is omitted.

FIG. 1 is a block diagram showing an ultrasonic flowmeter according to a first embodiment of the present invention. In FIG. 1, 1
Is a flow rate measuring unit through which the fluid to be measured flows, 2 and 3 are ultrasonic vibrators arranged obliquely to the flow direction of the flow measuring unit 1, and 4 is a frequency used by the ultrasonic vibrators 2 and 3. An oscillation circuit for transmitting, 5 is a drive circuit connected to the oscillation circuit 4 for driving the ultrasonic vibrators 2 and 3, 6 is a switching circuit for switching the ultrasonic vibrator for transmission and reception, and 7 is a reception detection circuit for detecting an ultrasonic pulse. , 8 is a timer for measuring the propagation time of the ultrasonic pulse, 9 is a calculation unit for calculating the flow rate from the output of the timer 8, and 10 is a control unit for outputting a control signal to the drive circuit 5 and the timer 8.

First, the operation and operation will be described. For example, the non-measuring fluid is air, and the operating frequency of the ultrasonic vibrators 2 and 3 is selected to be about 500 kHz. The oscillation circuit 4 is composed of, for example, a capacitor and a resistor, and transmits a square wave of about 500 kHz.
The driving circuit 7 can output a driving signal composed of burst signals of three square waves in order to drive the ultrasonic transducer 2 from the signal of the oscillation circuit 4. In order to improve the resolution of the measured flow rate, for example, a sing-around method is used for the measuring means.

The control section 10 outputs a transmission start signal to the drive circuit 5 and at the same time causes the timer 8 to start measuring time. Upon receiving the transmission start signal, the drive circuit 5 drives the ultrasonic transducer 2 and transmits an ultrasonic pulse. The transmitted ultrasonic pulse propagates in the flow measurement 1 and is received by the ultrasonic transducer 3. The received ultrasonic pulse is converted into an electric signal by the ultrasonic transducer 3 and output to the reception detection circuit 7. The reception detection circuit 7 determines the reception timing of the reception signal, and outputs the reception detection signal to the control unit 10. Upon receiving the reception detection signal, the control unit 10 receives a delay time t set in advance.
After the elapse of d, a transmission start signal is output to the drive circuit 5 again, and 2
Perform the second measurement. After repeating this operation N times, the timer 8 is stopped. The calculation unit 10 calculates the propagation time t1 by dividing the time measured by the timer 8 by the number of measurements N and subtracting the delay time td.

Subsequently, the switching unit 6 switches the ultrasonic transducers connected to the driving circuit 5 and the receiving circuit 7, and again the control unit 1
At 0, a transmission start signal is output to the drive circuit 5, and at the same time,
The timer 8 starts time measurement. Contrary to the measurement of the propagation time t1, the ultrasonic pulse is transmitted by the ultrasonic vibrator 3 and the measurement received by the ultrasonic vibrator 2 is repeated N times, and the arithmetic unit 9 calculates the propagation time t2.

Here, the ultrasonic oscillator 2 and the ultrasonic oscillator 3
L is the distance connecting the centers of the air, C is the sound speed in the absence of air,
Assuming that the flow velocity in the flow rate measuring unit 1 is V, and the angle between the direction of the flow of the non-measurement fluid and the line connecting the centers of the ultrasonic transducers 2 and 3 is θ, the propagation times t1 and t2 are t1 = L / (C + Vcosθ) (1) t2 = L / (C−Vcosθ) (2) (1) When the sound velocity C is eliminated from the equation (2) and the flow velocity V is obtained, the following equation is obtained: V = L / 2 cos θ (1 / t1-1 / t2) (3) Since L and θ are known, the flow velocity V can be obtained by measuring t1 and t2. The flow velocity V and the flow rate measurement unit 1
If the area of S is S and the correction coefficient is K, the flow rate Q can be calculated by Q = KSV (4).

Next, the influence of the unnecessary vibration mode on the flow rate measurement in a state where there is no flow will be considered. Generally, in the sing-around method, the reverberation time of the ultrasonic pulse transmitted from the ultrasonic transducer 2 and the ultrasonic transducer 3 which receives the ultrasonic pulse
If the vibration time is longer than the propagation time t1, these vibrations are affected in the time measurement. Therefore, assuming that these vibrations contain frequency components other than the used frequency,
Calculate zero point variation with temperature. The frequency to be used is f1, the frequency of the unnecessary vibration is f2, f1 and f2 are continuous sine waves, and the amplitude of the unnecessary vibration is A to simplify the calculation. Note that there is a frequency shift in f2, and the frequency difference is df2. Also, because there is no air flow,
Assuming that the temperature is T, the propagation time Pt between the ultrasonic transducers
Is expressed as Pt = L / (331 + 0.6 · T) (5)

Here, the case of transmission by the ultrasonic vibrator 2 is as follows: R1 = sins2π · f1 · (t−Pt)｝ + Asin (2π · f2 · t) (6) The case of transmission by the ultrasonic vibrator 3 Let R2 = sin {2π · f1 · (t−Pt)} + Asin ｛2π · (f2 + df2) · t｝ (7) R when temperature T is changed according to equations (6) and (7)
The times t1 and t2 at which the first and R2 cross zero at the fifth time are obtained, and the flow rate is calculated using the equation (3). f1 at 500kH
Assuming that z and f2 are 200 kHz and A is -60 dB, FIGS. 2 to 4 show calculation results when df2 is 0 kHz, 1 kHz, and 5 kHz.

As shown in FIG. 2, when there is no deviation in f2,
There is no change in the zero point due to temperature. On the other hand, df2 is 1
In FIGS. 3 and 4, which are kHz and 5 kHz, the zero point periodically fluctuates depending on the temperature. Also, depending on the size of df2,
There is a change in amplitude. From the above calculation results, it can be estimated that the zero point periodically fluctuates depending on the temperature under the influence of the unnecessary vibration mode.

Therefore, the configuration and operating frequency of the ultrasonic vibrator,
The relationship between the unnecessary vibration frequencies is shown. FIG. 5 shows an example of the configuration of the ultrasonic vibrator 11, and FIGS. 6 and 7 show a piezoelectric body used for the ultrasonic vibrator 11. The ultrasonic transducer 11 includes a piezoelectric body 12, a case 13, a matching layer 14, and a back cover 15. Case 13
Is formed using a stainless steel having a thickness of 0.2 mm so as to have a depth of about 3 mm. When a vibration analysis of a shape in which only the case back 15 is attached to the case 13 is performed by using the finite element method, a resonance mode exists at about 200 kHz. The piezoelectric body 12 used for the ultrasonic vibrator 11 is a square having one side of the electrode surface of about 8 mm and a height of about 2.7 mm. Since the piezoelectric body 12 having this shape cannot longitudinally vibrate, the piezoelectric body 16 is provided with three vertical grooves 17 as shown in FIG. 6 and the piezoelectric body 18 is provided with three vertical and horizontal grooves 19 as shown in FIG. A configuration is possible. FIGS. 8 and 9 show impedance characteristics of the piezoelectric bodies 16 and 18 having these configurations. In the impedance characteristic of FIG. 8, resonance of an unnecessary vibration mode is observed at around 200 kHz. On the other hand, in the impedance characteristic of FIG. 9, resonance of an unnecessary vibration mode near 200 kHz is hardly observed.

FIGS. 10 and 11 show the results of an experiment in which an ultrasonic vibrator using the piezoelectric bodies 16 and 18 was constructed and the change of the zero point due to a temperature change was measured. In FIG. 10, the zero point shows a periodic fluctuation due to a temperature change. On the other hand, in FIG. 11, no periodic phenomenon is observed in the fluctuation of the zero point due to the temperature change.

From the above results, when the resonance frequency of the unnecessary vibration mode of the piezoelectric body 12 and the resonance frequency of the case 13 are close to each other, the zero point periodically fluctuates due to a temperature change.
When the piezoelectric body 12 is configured such that the resonance frequency of the unnecessary vibration mode and the resonance frequency of the case 13 are different from each other, it is understood that the zero point is stabilized without depending on the temperature change.

In the first embodiment, the sing-around method is used for the flow rate measurement. However, the present invention is not limited to the above conditions, and even a single measurement, a periodic measurement is performed N times and the average value is measured. May be used. Although the non-measurement fluid is air, it may be a gas other than air, such as LP gas or city gas, or a liquid such as water or gasoline.

Although a pair of ultrasonic transducers are disposed so as to be obliquely opposed to the flow, they may be disposed in parallel to the flow, and the reflection on the inner wall surface of the flow rate measuring unit is used. It may be arranged at such a position. The operating frequency of the ultrasonic vibrator is 500 kHz, and the frequency of unnecessary vibration is 2
Although it was set to 00 kHz, it is not limited to the above conditions,
The frequency used is generally in the range of about 10 kHz to 1 MHz for gas and about 100 kHz to 10 MHz for liquid. The electrode surface of the piezoelectric body is a square of 8 mm on a side and 2.7 mm in height.
However, a rectangular parallelepiped other than the above dimensions, a thin disk, a column, or a polygonal column may be used.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 12 shows the second embodiment.
3 is a sectional view of the ultrasonic transducer of FIG. 20 is an ultrasonic transducer,
Reference numeral 22 denotes a case, 23 denotes a matching layer, and 24 denotes a back cover. The above is the same as the configuration shown in FIG. 5 in that the piezoelectric body 12 has a columnar shape. The principle of operation is the same as that of the first embodiment, and a description thereof will be omitted.

For example, nine cylindrical piezoelectric members 21 having a diameter of 1.5 mm and a height of 2.7 mm, and a matching layer 23 are adhesively fixed to the top of the case 22, and the back lid 24 is electrically welded to the case 22. I do. In the piezoelectric body 21, the resonance frequency of the spread vibration exists at a higher frequency than the resonance frequency of the longitudinal vibration. For this reason, if the spread vibration is regarded as unnecessary vibration, the resonance frequency of the unnecessary vibration mode of the piezoelectric body 21 and the resonance frequency of the case 22 are different from each other. The zero point is stable regardless of.

In the second embodiment, the vertical vibration of the columnar piezoelectric body is used. However, the vertical vibration of the polygonal columnar piezoelectric body or the spread vibration of a thin circular plate may be used. In addition, although nine piezoelectric bodies 21 are provided, the required number may be used and any number of one or more may be used.

Embodiment 3 Hereinafter, Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 13 shows the third embodiment.
3 is a sectional view of the ultrasonic transducer of FIG. 25 is an ultrasonic transducer,
26 is a piezoelectric body, 27 is a case, 29 is a matching layer, and 30 is a back cover. The above is the same as the configuration of FIG. 5 is different from the configuration of FIG.
Is provided. The principle of operation is the same as that of the first embodiment, and a description thereof will be omitted.

For example, a vibration damper 27 made of a stainless steel ring having a thickness of 0.3 mm and a width of 2.5 mm is bonded and fixed to the inner wall side surface of the case 28. Since the characteristics of the piezoelectric body 26 deteriorate when the piezoelectric body 26 comes into contact with the vibration damper 28, the piezoelectric body 26 and the vibration damper 27 are configured so as not to contact with each other. The ultrasonic transducer 25 is configured by attaching the matching layer 23 and the back cover 30. Piezoelectric body 26
The resonance frequency of the unnecessary vibration mode is about 2 as shown in FIG.
00 kHz. In the case 28, since the vibration damping body 27 is bonded, the mass increases, and the resonance frequency shifts to a lower frequency side than 200 kHz. Further, since the rigidity is improved, it is difficult to vibrate.

In an experiment in which the change of the zero point due to the temperature change was measured by the ultrasonic flowmeter using the ultrasonic vibrator 25 having the above-described structure, a result almost equal to that of the first embodiment shown in FIG. 11 was obtained.
As described above, even if the piezoelectric body 26 has the unnecessary vibration mode of 200 kHz, the vibration damper 27 made of a rigid body is provided in the case 28 so that the resonance frequency is different from the frequency of the unnecessary vibration mode of the piezoelectric body 26. For example, it is understood that the zero point is stabilized irrespective of the temperature change. Further, since the vibration damping body 27 is contained in the case 28, it hardly comes into direct contact with the non-measuring fluid, so that corrosion by the non-measuring fluid can be prevented, and the long-term reliability can be improved.

In the third embodiment, the damping body 27 has a thickness of 0.1 mm.
Although a stainless steel ring having a width of 3 mm and a width of 2.5 mm is used, the dimensions, material, and shape may be changed, and a plurality of bars or plates may be used. In addition, the vibration damping body 27 is bonded and fixed to the inner wall side surface of the case 28, but may be fixed by means other than bonding.
It may be provided on the side surface of the outer wall.

Embodiment 4 Hereinafter, Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 14 shows the fourth embodiment.
3 is a sectional view of the ultrasonic transducer of FIG. 31 is an ultrasonic transducer,
Reference numeral 32 denotes a piezoelectric body, reference numeral 34 denotes a case, reference numeral 35 denotes a matching layer, reference numeral 36 denotes a back cover. The above is the same as the configuration shown in FIG. 5 is different from the configuration in FIG.
Is provided. The principle of operation is the same as that of the first embodiment, and a description thereof will be omitted.

For example, polyimide having a thickness of 50 μm and 25
A Kapton tape made of a silicon-based adhesive of μm is used as the vibration damper 33. Since the hardness of the silicone-based adhesive hardly changes even at a low temperature, it can be used as an elastic body in a wide temperature range. In addition, polyimide has a function of increasing the mass of the damping body 33 and increasing the damping effect. The piezoelectric body 32 and the matching layer 35 are bonded to the case 34,
6 is electrically welded, and a Kapton tape is wound around the outer wall side surface of the case 34 several times to form the vibration damping body 33. It was confirmed that the resonance at around 200 kHz of the ultrasonic vibrator 31 was slightly weakened by providing the vibration damper 33. This is probably because the vibration damper 33, which is an elastic body, absorbed and lost the vibration energy of the case 34 and reduced the mechanical Q.

In an experiment in which the change of the zero point due to the temperature change was measured by the ultrasonic flowmeter using the ultrasonic vibrator 31 having the above configuration, a result almost equal to that of FIG. 11 of the first embodiment was obtained.
As described above, even if the piezoelectric body 32 and the case 34 have an unnecessary vibration mode of 200 kHz, if the vibration suppressor 33 made of an elastic body is provided in the case 34 to weaken the resonance of the ultrasonic vibrator 31, temperature change may occur. It can be seen that the zero point is stable without depending on it. Further, since the vibration damper 33 is very thin, the stability of the zero point can be improved without making the ultrasonic transducer 31 too large.

In the fourth embodiment, the vibration damper 33 is made of a Kapton tape made of polyimide and a silicone-based adhesive.
3, a tape other than Kapton tape may be used. A cylindrical or ring-shaped rubber molded product may be fitted on the outer or inner wall of the case 33, or a rubber may be formed on the outer or inner wall of the case 34. Alternatively, it may be configured by applying a damping paint or the like.

(Embodiment 5) Hereinafter, Embodiment 5 of the present invention will be described with reference to the drawings. FIG. 15 shows the fifth embodiment.
3 is a sectional view of the ultrasonic transducer of FIG. 37 is an ultrasonic transducer,
Reference numeral 38 denotes a piezoelectric body, 39 denotes a case, 41 denotes a matching layer, and 42 denotes a back cover. The above is the same as the configuration shown in FIG. The difference from the configuration of FIG. 5 is that a bent portion 40 concentric with the top portion is provided on the side wall of the case 39 to increase the rigidity of the case 39. The principle of operation is the same as that of the first embodiment, and a description thereof will be omitted.

The stainless steel plate having a thickness of 0.2 mm
Is molded. At this time, a bent portion 40 concentric with the ceiling portion 43 is simultaneously formed on the side wall. The piezoelectric body 38 is adhered and fixed to the inner wall side of the top part 43 and the matching layer 41 is adhered and fixed to the outer wall side, and the back cover 42 is electrically welded to assemble the ultrasonic vibrator 37. Although the case 39 has substantially the same configuration as the case 13 of the first embodiment, the rigidity is increased due to the provision of the bent portion 40, and the side wall portion is less likely to vibrate. The resonance frequency of the case 39 shifts to a higher frequency side than 200 kHz, and is different from the frequency of the unnecessary vibration mode of the piezoelectric body 38. Thus, the piezoelectric body 38
Even if an unnecessary vibration mode of 00 kHz exists, the bent portion 4
0 to increase the rigidity of the case 39, the case 3
A stable zero point that does not depend on temperature changes can be easily obtained without attaching a component such as a vibration damper to 9 or changing its size.

In the fifth embodiment, the bent portion 40 is
3 and the bent portion 40 is formed as a concentric circle.
For example, a plurality of beads 43 may be provided as shown in FIG. 16, or a bent portion 44 may be provided in the vertical direction as shown in FIG. When the piezoelectric body is, for example, a square, if the top part 45 is formed into a shape similar to a square as shown in FIG. 18, the direction of the piezoelectric body contained in the case can be understood, and Mounting becomes easy. If the piezoelectric body is a polygon other than a square,
It goes without saying that at least the shape of the top portion may be changed according to the shape of the piezoelectric body.

In the first, third to fifth embodiments, the case is made of stainless steel. However, any material that can be used in the non-measuring fluid may be used. Although the thickness of the case is 0.2 mm, it may be thicker or thinner than this thickness, and it is not necessary to make the thickness of the entire case the same. Also, the operating frequency of the piezoelectric body was 500 kHz, and the unnecessary vibration frequency was 200 kHz.
It goes without saying that the used frequency and the unnecessary vibration frequency change depending on the shape and vibration mode of the piezoelectric body used.

[0045]

As is apparent from the above description, the following effects can be obtained according to the ultrasonic flowmeter of the present invention.

The first ultrasonic flow meter includes a flow measuring unit through which a fluid to be measured flows, a pair of ultrasonic transducers provided in the flow measuring unit for transmitting and receiving ultrasonic waves, and one of the ultrasonic transducers. A drive circuit for driving, a reception detection circuit connected to the other ultrasonic transducer and detecting an ultrasonic pulse, a timer for measuring the propagation time of the ultrasonic pulse, and a control unit for controlling the drive circuit and the timer, Equipped with a calculation unit that calculates the flow rate from the output of the timer by calculation, and a pair of ultrasonic vibrators are configured to reduce the effect of temperature change on the measurement result when there is no flow, so the zero point is stabilized by temperature change It is possible to obtain an ultrasonic flowmeter having high performance.

In the second ultrasonic flow meter, the pair of ultrasonic vibrators are configured so that the influence of the unnecessary vibration mode is reduced, so that an ultrasonic flow meter having high stability of the zero point due to a temperature change can be obtained. .

In the third ultrasonic flowmeter, the pair of ultrasonic transducers includes a piezoelectric body for converting an electric signal and mechanical vibration to each other, and a case outside the piezoelectric body. Since the configuration is such that the frequency and the resonance frequency of the case are different from each other, it is possible to reduce the influence of the unnecessary vibration mode and obtain an ultrasonic flowmeter with high stability of the zero point due to a temperature change.

The fourth ultrasonic flowmeter has a pair of ultrasonic vibrators each including a piezoelectric body for converting an electric signal and mechanical vibration to each other and a case outside the piezoelectric body, and a frequency of an unnecessary vibration mode of the piezoelectric body. Is configured to be higher in frequency than the frequency used, the influence of the unnecessary vibration mode can be reduced, and an ultrasonic flowmeter having high stability of the zero point due to a temperature change can be obtained.

In the fifth ultrasonic flowmeter, the pair of ultrasonic transducers includes a piezoelectric body for converting an electric signal and mechanical vibration to each other, and a case outside the piezoelectric body. Since the vibration damping member is provided in the apparatus, the influence of the unnecessary vibration mode can be reduced, and an ultrasonic flowmeter having a high zero point stability due to a temperature change can be obtained.

The ultrasonic flowmeter according to the sixth embodiment of the present invention is different from the ultrasonic flowmeter according to the fifth embodiment in that the vibration damper is made of a rigid body, so that the mass of the case is increased to prevent unnecessary vibration and to reduce unnecessary vibration. The influence of the mode can be reduced, and an ultrasonic flowmeter having high stability of a zero point due to a temperature change can be obtained.

In the seventh ultrasonic flowmeter, since the vibration damper is made of an elastic body, unnecessary vibration of the case can be lost by the elastic body to reduce the influence of the unnecessary vibration mode, and the zero point stability due to temperature change is high. An ultrasonic flow meter can be obtained.

In the eighth ultrasonic flowmeter, the pair of ultrasonic transducers has a piezoelectric body for converting electric signals and mechanical vibrations mutually and a case outside the piezoelectric body, and the case inhibits unnecessary vibrations. Since the bent portion is provided on the side wall as described above, the influence of the unnecessary vibration mode can be reduced, and an ultrasonic flowmeter having high stability of the zero point due to the temperature change can be obtained.

In the ninth ultrasonic flowmeter, since the bent portion is provided so that the direction of the piezoelectric body can be recognized, the direction of the piezoelectric body can be recognized, and an ultrasonic flowmeter that can be easily assembled can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an ultrasonic flow meter according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram calculated for the flow meter when the frequency difference df2 is 0 kHz.

FIG. 3 is a characteristic diagram calculated when the frequency difference df2 is 1 kHz in the same flowmeter.

FIG. 4 is a characteristic diagram calculated in a case where a frequency difference df2 is 5 kHz in the same flowmeter.

FIG. 5 is a sectional view of an ultrasonic transducer in the flow meter.

FIG. 6 is a sectional view of an ultrasonic transducer in the flow meter.

FIG. 7 is an external perspective view of a piezoelectric body (length and width grooves) in the flow meter.

FIG. 8 is an impedance characteristic diagram of a piezoelectric body (vertical groove) in the flow meter.

FIG. 9 is an impedance characteristic diagram of a piezoelectric body (length and width grooves) in the flow meter.

FIG. 10 is a characteristic diagram measured by using a piezoelectric material in a vertical groove in the flow meter.

FIG. 11 is a characteristic diagram of the flow meter measured using piezoelectric bodies in vertical and horizontal grooves.

FIG. 12 is a sectional view of an ultrasonic vibrator according to a second embodiment of the present invention.

FIG. 13 is a sectional view of an ultrasonic transducer according to a third embodiment of the present invention.

FIG. 14 is a sectional view of an ultrasonic transducer according to a fourth embodiment of the present invention.

FIG. 15 is a sectional view of an ultrasonic transducer according to a fifth embodiment of the present invention.

FIG. 16 is a sectional view of Modification Example 1 of the ultrasonic transducer.

FIG. 17 is a side view of a modified example 2 of the ultrasonic transducer.

FIG. 18 is an external view of Modification 3 of the ultrasonic transducer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow rate measurement part 2, 3, 20, 25, 31, 37 Ultrasonic vibrator 5 Drive circuit 7 Reception detection circuit 8 Timer 9 Calculation part 10 Control part 12, 21, 26, 32, 38 Piezoelectric body 13, 22, 28 , 34, 39 Case 27, 33 Damper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04R 1/44 330 H04R 1/44 330D 3/00 330 3/00 330 17/00 330 17/00 330Y ( 72) Inventor Masahiko Hashimoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshiharu Sato 1006 Odaka Kadoma, Kadoma City Osaka Pref. Matsushita Electric Industrial Co., Ltd.F-term (reference) 2F035 DA05 DA14 DA16 DA19 5D019 AA11 BB08 BB12 BB17 EE04 FF02 GG01 5D107 AA10 AA14 CC01 CC10 CC12 CC13 CD02 CD08 FF02 FF07

Claims (9)

[Claims] 1. A flow rate measuring unit through which a fluid to be measured flows, a pair of ultrasonic transducers provided in the flow measuring unit for transmitting and receiving ultrasonic waves, a driving circuit for driving one ultrasonic transducer, and the other. A reception detection circuit connected to the ultrasonic transducer for detecting an ultrasonic pulse, a timer for measuring a propagation time of the ultrasonic pulse, a control unit for controlling the driving circuit and the timer, and an output of the timer An ultrasonic flowmeter, comprising: a calculation unit for further calculating a flow rate, wherein the pair of ultrasonic vibrators are configured to reduce an influence of a temperature change on a measurement result in a state where there is no flow. 2. The ultrasonic flowmeter according to claim 1, wherein the pair of ultrasonic vibrators are configured to reduce the influence of an unnecessary vibration mode. 3. A pair of ultrasonic vibrators each include a piezoelectric body for mutually converting an electric signal and mechanical vibration and a case outside the piezoelectric body, and a resonance frequency of an unnecessary vibration mode of the piezoelectric body and a case frequency of the case. 3. The ultrasonic flow meter according to claim 2, wherein the resonance frequencies are different. 4. A pair of ultrasonic vibrators include a piezoelectric body for mutually converting an electric signal and mechanical vibration and a case outside the piezoelectric body, and a frequency of an unnecessary vibration mode of the piezoelectric body is higher than a frequency used. 3. The ultrasonic flowmeter according to claim 2, wherein the ultrasonic flowmeter is configured to have a high frequency. 5. A pair of ultrasonic vibrators each include a piezoelectric body for mutually converting an electric signal and mechanical vibration and a case outside the piezoelectric body, and a vibration damper is provided on the case so as to inhibit the vibration of the case. The ultrasonic flowmeter according to claim 2, further comprising: 6. The ultrasonic flowmeter according to claim 5, wherein the vibration damper is made of a rigid body. 7. The ultrasonic flowmeter according to claim 5, wherein the vibration damper is made of an elastic material. 8. A pair of ultrasonic transducers comprising: a piezoelectric body for mutually converting an electric signal and mechanical vibration; and a case having a side wall outside the piezoelectric body, wherein a bent portion is provided on the side wall. Item 7. An ultrasonic flowmeter according to Item 2. 9. The ultrasonic flowmeter according to claim 8, wherein the bent portion is provided so that the direction of the piezoelectric body can be recognized.