JP2012007976A - Ultrasonic velocity flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic velocity flowmeter capable of judging the attachment state of a vibration suppressing body and ultrasonic transmitter-receivers without visual observation.SOLUTION: An ultrasonic velocity flowmeter comprises; a flow channel 1 for flowing fluid from one opening end to the other opening end; first and second ultrasonic transmitter-receivers 4 abd 5 which are arranged upstream and downstream of the flow channel 1 to contact with the fluid; a clocking device 6 for measuring propagation time of ultrasonic waves between the first and second ultrasonic transmitter-receivers 4 and 5; operation means 7 for operating the flow rate of fluid to be measured based on the propagation time of ultrasonic waves obtained by the clocking device 6; and fixed state judging means 8 for judging whether the first and second ultrasonic transmitter-receivers 4 and 5 are correctly fixed to the flow channel 1 with a vibration suppressing body 3 interposed therebetween.

Description

  The present invention relates to an ultrasonic flow rate meter using an ultrasonic transducer for transmitting ultrasonic waves in a fluid (particularly gas) or receiving ultrasonic waves propagating in a fluid.

  Conventionally, as shown in FIG. 12, for example, this type of ultrasonic flow rate flow meter includes a measurement channel 40 through which a fluid to be measured flows, and a pair of ultrasonic waves that are arranged opposite to the measurement channel 40 to transmit and receive ultrasonic waves. Transmitters / receivers 41, 42, a time measuring device 43 that measures the ultrasonic propagation time between the ultrasonic transmitter / receivers 41, 42, and a calculation means 44 that calculates a flow rate based on a signal from the time measuring device 43. The ultrasonic transducers 41 and 42 are composed of a top part, a side wall part, a support part provided outside the side wall part, and a piezoelectric body fixed to the inner wall surface of the top part, The vibration suppression body 45 has a holding portion that abuts against the side wall portion, reduces vibration of the side wall portion, and holds the support portion, and is configured to be attached to the measurement flow path 40 (see, for example, Patent Document 1). .

JP 2001-159551 A

  However, in the conventional configuration, depending on the fixed state of the vibration suppressing body between the ultrasonic transducer and the flow path, the flow velocity measurement value may become unstable, or the flow measurement value may not be stable due to a change in temperature. There was a problem of stabilization.

  The present invention solves the above-mentioned conventional problems, and determines the attachment state of the vibration suppressor and the ultrasonic transducer without visually observing and stabilizes the flow velocity measurement value by avoiding the abnormal attachment state. An object of the present invention is to provide an ultrasonic flow velocity meter that enables flow velocity measurement with higher accuracy.

  In order to solve the above problems, an ultrasonic flowmeter of the present invention has open ends at both ends, a flow path for passing a fluid to be measured from one open end to the other open end, and an upstream of the flow path. And a pair of ultrasonic transmitters / receivers arranged in contact with the fluid to be measured downstream, a time measuring device for measuring an ultrasonic propagation time between the pair of ultrasonic transmitters / receivers, and the time measuring device. And a calculation means for calculating the flow rate of the fluid to be measured based on the ultrasonic propagation time, and having a vibration suppressing body, and the pair of ultrasonic transducers are interposed in the flow path via the vibration suppressing body. And holding state determining means for determining whether or not the vibration suppressing body is correctly fixed.

  As a result, it is possible to determine whether the vibration suppressor and the ultrasonic transducer are correctly fixed to the flow path before the flow measurement, and the flow measurement value is stabilized by avoiding an abnormal attachment state. Accurate flow measurement is possible.

  The ultrasonic flow velocity meter of the present invention determines the attachment state of the vibration suppressor without visual observation, and the flow velocity flow rate measurement value is stabilized by avoiding the abnormal attachment state, and is stable regardless of the temperature change. Since flow velocity flow measurement can be performed, more accurate flow velocity flow measurement can be stably performed.

Schematic of the ultrasonic flow velocity flowmeter in Embodiment 1 of the present invention Sectional drawing which shows the fixed state of the ultrasonic transducer in the embodiment Sectional drawing which shows the fixed state of the ultrasonic transducer in the embodiment The figure which shows the drive signal waveform and reception signal waveform which are transmitted to the ultrasonic transducer in the embodiment (A) Side surface sectional view of the ultrasonic flow velocity flow meter in the same embodiment, (b) Cross sectional view of the ultrasonic flow velocity flow meter in the same embodiment The figure which shows the drive signal waveform and reception signal waveform which are transmitted to the ultrasonic transducer in the embodiment The figure which shows the measurement interval of the drive signal waveform and reception signal waveform which are transmitted to the ultrasonic transducer in the embodiment Sectional drawing of the fixing state defect of the ultrasonic transducer in the embodiment Sectional drawing of the fixing state defect of the ultrasonic transducer in the embodiment The figure which shows the impedance characteristic of the ultrasonic transmitter-receiver in Embodiment 2 of this invention. Schematic diagram of ultrasonic flow velocity flowmeter in the same embodiment Schematic diagram of conventional ultrasonic flow velocity meter

  In the first aspect of the present invention, open ends are formed at both ends, and a flow path for passing the measured fluid from one open end to the other open end, and the measured fluid upstream and downstream of the flow path are in contact with the measured fluid. A pair of ultrasonic transceivers, a timing device for measuring an ultrasonic propagation time between the pair of ultrasonic transducers, and the measurement target based on the ultrasonic propagation time obtained by the timing device And a vibration suppression body, the pair of ultrasonic transducers are held in the flow path via the vibration suppression body, and the vibration suppression body is correctly By providing a fixed state determination means for determining whether the vibration is fixed, it is possible to determine whether the vibration suppressing body and the ultrasonic transducer are correctly fixed to the flow path, and avoid an abnormal attachment state. Stable flow rate flow rate measurement value And, it is more accurate velocity flow measurement.

  In a second aspect of the invention, particularly in the first aspect of the invention, the ultrasonic transducer includes a celestial cylindrical metal case, a piezoelectric body accommodated in the celestial cylindrical metal case, and the tentative cylindrical metal. An acoustic matching body disposed on the outer wall surface of the case so as to face the piezoelectric body, and a terminal plate that supports the terminal in a state in which the opening of the cylindrical metal case is closed and the terminal protrudes to the outside, A vibration suppression body attached to cover the side wall portion of the heavenly cylindrical metal case and the support portion provided on the outside of the side wall portion, and a structure attached to the flow path via the vibration suppression body; Therefore, it is possible to determine whether the vibration suppression body and the ultrasonic transducer having a more complicated shape are correctly fixed to the flow path, and the characteristic depending on the shape of the ultrasonic transducer Because there is vibration, analyze the characteristic vibration And it is possible to determine the abnormal mounted state in more detail by, by avoiding abnormal mounted state, the flow velocity flow rate measurement value is stabilized, it is more accurate velocity flow measurement.

  A third invention is characterized in that, in particular, in the first or second invention, the fixed state determining means determines whether or not the vibration suppressing body is correctly fixed based on at least a reception output of the ultrasonic transducer. Thus, when the propagation time is measured at a constant temperature and zero flow rate, since the sound speed of the fluid is known, it can be determined whether or not the opposing ultrasonic transducers are correctly opposed and fixed. .

  In a fourth aspect of the invention, particularly in the first or second aspect of the invention, the fixed state determination means determines whether or not the vibration suppression body is correctly fixed by at least a propagation time between the pair of ultrasonic transducers. Since the sound velocity value is known under the condition of constant temperature, it can be determined whether the distance between the ultrasonic transducers is correctly arranged with a predetermined distance.

  In a fifth aspect of the invention, particularly in the first or second aspect of the invention, the fixed state determination means determines whether or not the vibration suppression body is correctly fixed by at least housing propagation noise between the pair of ultrasonic transducers. The ultrasonic transducer is not in direct contact with the flow path, or the vibration suppressor holds the ultrasonic transducer correctly, and the ultrasonic transducer Since it is understood whether the generated vibration is efficiently suppressed, the fixed state can be determined.

  In a sixth aspect of the invention, particularly in the first or second aspect of the invention, the fixed state determination means determines whether or not the vibration suppression body is correctly fixed based on at least the vibration attenuation time of the ultrasonic transducer. Thus, it can be determined whether or not the vibration suppressing body is covered with the ultrasonic transducer.

  The seventh invention is characterized in that, in the sixth invention, in particular, the fixed state determination means is performed at least by a vibration attenuation time when driven at a frequency that increases the vibration of the dome-shaped cylindrical metal case. Therefore, the vibration attenuation time is mainly due to the vibration of the celestial cylindrical metal case, so that the vibration attenuation time can be evaluated in more detail by driving at a frequency that increases the vibration of the celestial cylindrical metal case. It can be easily determined whether or not the vibration suppressing body 3 is covered with the first ultrasonic transducer 4.

  In an eighth aspect of the invention, particularly in the first or second aspect of the invention, the fixed state determination means calculates a flow rate value by changing at least the measurement interval, and the variation in the flow rate value for each measurement converges to a predetermined value or less. By comparing the interval and a predetermined measurement interval to determine whether or not the vibration suppression body is correctly fixed, the vibration suppression body, the ultrasonic transducer, and the flow path Since it is possible to measure the flow rate after judging how much the fixed state affects the flow rate measurement accuracy, the measurement stability is improved.

  According to a ninth aspect of the present invention, in the eighth aspect of the invention, the measurement interval in which the flow rate value stably converges is stored, and the flow rate flow rate measurement is performed using the stored measurement interval. Since stable flow velocity flow rate measurement can be performed in a state where stability is ensured, measurement stability is improved.

  In a tenth aspect of the invention, particularly in the eighth aspect of the invention, a correlation equation between a temperature obtained from a measurement interval at which a variation in flow rate value at each measurement at a plurality of temperatures stably converges to a predetermined value or less and an optimum measurement interval is obtained. Optimized at different temperatures by memorizing and measuring flow velocity flow rate using the optimal measurement interval based on the correlation equation based on the temperature obtained from the propagation time during flow rate measurement Since measurement is performed using the measurement interval, stable flow rate and flow rate measurement can be performed regardless of temperature changes.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 shows a schematic diagram of an ultrasonic flow velocity meter according to the first embodiment of the present invention.

  In FIG. 1, the ultrasonic flow rate flow meter includes a flow path 1 through which a fluid to be measured (for example, gas and air) flows, and is disposed opposite to the flow rate measurement unit 2 and the upstream side and the downstream side of the flow rate measurement unit 2, First and second ultrasonic transducers (a pair of ultrasonic transducers) 4 and 5 fixed to the flow path 1 via the vibration suppressing body 3, and the first and second ultrasonic transducers A time measuring device 6 for measuring the ultrasonic propagation time between 4 and 5, a computing means 7 for calculating a flow rate per unit time of the fluid based on the ultrasonic propagation time obtained by the time measuring device 6; The ultrasonic transducers 4 and 5 of 2 and the vibration suppression body 3 are arranged so as to face the flow path 1 as designed, and the vibration suppression body 3 includes the flow path 1 and the ultrasonic transmission / reception element 4. 5 is provided with fixed state determination means 8 for determining whether or not it is correctly fixed as designed.

  Hereinafter, the operation of the ultrasonic flow rate flow meter will be described.

  When obtaining the flow velocity V of the fluid to be measured flowing through the flow path 1 in the ultrasonic flow velocity meter, first, the drive signal waveform adjusted so as to have a frequency near the resonance frequency of the first ultrasonic transducer 4. Is applied to the piezoelectric body, and the ultrasonic wave is radiated from the first ultrasonic transducer 4 into the fluid to be measured.

  The emitted ultrasonic wave propagates through the fluid to be measured, is received by the second ultrasonic transducer 5, and is converted into a voltage by the piezoelectric body of the second ultrasonic transducer 5.

  Next, when a drive signal waveform having a frequency near the resonance frequency of the second ultrasonic transducer 5 is applied to the piezoelectric vibrator, the piezoelectric transducer vibrates and radiates ultrasonic waves from the second ultrasonic transducer 5 into the fluid. To do. The emitted ultrasonic wave is received by the first ultrasonic transducer 4 and converted into a voltage by the piezoelectric body of the first ultrasonic transducer 4. By performing such repeated measurement, the stability of the flow velocity / flow rate measurement value is improved.

  Here, the flow velocity of the fluid flowing through the flow path 1 is V, the sound velocity of the ultrasonic wave in the fluid to be measured is C, and the angle between the fluid flow direction and the ultrasonic propagation direction is θ.

When the first ultrasonic transducer 4 is used as a transmitter and the second ultrasonic transducer 5 is used as a receiver, the ultrasonic waves emitted from the first ultrasonic transducer 4 are second. The propagation time t ₁ reaching the ultrasonic transducer 5 is
t ₁ = L / (C + v cos θ) (1)
Indicated by

Next, the propagation time t ₂ for the ultrasonic pulse emitted from the second ultrasonic transducer 5 to reach the first ultrasonic transducer 4 is:
t ₂ = L / (C−v cos θ) (2)
Indicated by

And if the sound velocity C of the fluid is eliminated from the equations (1) and (2),
V = L / 2 cos θ (1 / t ₁ −1 / t ₂ ) (3)
The following equation is obtained.

If L and θ are known, the flow velocity V can be obtained by measuring t ₁ and t ₂ with the timing device 6. If necessary, the flow rate Q can be obtained by multiplying the flow velocity V by the cross-sectional area S and the correction coefficient K of the flow rate measuring unit 2. That is, the calculating means 7 calculates Q = KSV.

  Next, the ultrasonic transducer used for the ultrasonic flow rate meter of this embodiment will be described in detail.

  Since the first and second ultrasonic transducers 4 and 5 have the same configuration, the configuration of the first ultrasonic transducer 4 will be described below, and the description of the second ultrasonic transducer 5 will be omitted. To do.

  FIGS. 2 and 3 are sectional views showing the fixed state of the first ultrasonic transducer 4. The first ultrasonic transducer 4 is fixed to the flow path 1 via the vibration suppressing body 3. Yes. The vibration suppressor 3 may have various shapes other than those shown in the figure, but in the present embodiment, FIGS. 2 and 3 will be described as representative examples, but the present invention is realized by limiting to the particularly exemplified structure. Is not to be done. The constituent material of the vibration suppressing body 3 is not particularly limited as long as it is a material exhibiting rubber elasticity, such as nitrile rubber, silicon rubber, or fluorosilicon rubber.

  The first ultrasonic transducer 4 includes a piezoelectric body 10 having electrodes facing each other, a dome-shaped cylindrical metal case 14 including a top portion 11, a side wall portion 12, and a support portion 13, and an acoustic matching body 15. And a terminal plate 18 having a first terminal 16 and a second terminal 17.

  For example, the piezoelectric body 10, the cylindrical metal case 14 and the acoustic matching body 15 are joined with an adhesive. Although it is possible to use a pressure-sensitive adhesive, the case of fixing with an adhesive is more preferable from the viewpoint of property stability. The piezoelectric body 10 is not particularly limited as long as it is a material having piezoelectric characteristics such as lead zirconate titanate and barium titanate.

  Examples of the celestial tubular metal case 14 include copper, iron, and stainless steel. The terminal board 18 includes a first terminal 16 and a second terminal 17, the first terminal and the second terminal are insulated by an insulator 19, and the rest are made of a metal material. The insulator 19 is not particularly limited, for example, an organic material such as a resin, or an inorganic material using a glass hermetic seal.

  The terminal plate 18 and the dome-shaped cylindrical metal case 14 are electrically connected to each other by a method such as welding or silver brazing at the support portion 13 and hermetically sealed. The second terminal 17 and one of the electrodes of the piezoelectric body 10 are electrically connected by a lead wire or the like, and the first terminal 16 and the other electrode of the piezoelectric body 10 are electrically connected via the above-described dome-shaped cylindrical metal case. It has a conductive configuration.

  The role of the acoustic matching body 15 is to efficiently propagate the vibration of the piezoelectric body 10 to the fluid. For this reason, since the fluid to be measured is lighter, the acoustic matching body 15 is preferably made of a material that is lighter and has a slower sound speed. Therefore, for example, a composite material in which a filler of a hollow glass filler is cured with an epoxy resin, or a composite material packaged with a resin film in a state in which a void of the ceramic porous body is held on the outermost layer surface of the ceramic porous body, etc. it can.

  Hereinafter, the operation of the first ultrasonic transducer 4 will be described. The first ultrasonic transducer 4 is a drive signal that vibrates a piezoelectric body of, for example, about 400 to 600 kHz to the electrode of the piezoelectric body 10 via the first terminal 16 and the second terminal 17 provided on the terminal plate 18. When the waveform is given, the piezoelectric body 10 vibrates, and the acoustic matching body 15 whose thickness is adjusted in advance resonates with the piezoelectric body 10, and as a result, the ultrasonic wave propagates to the fluid to be measured. The above operation is the same for the second ultrasonic transducer 5.

  In order to realize the measurement accuracy of this ultrasonic flow velocity meter as designed, the first and second ultrasonic transducers 4 and 5 need to be correctly fixed to the flow path 1. 2 and 3 show a state in which the first and second ultrasonic transducers 4 and 5 are fixed to the flow path 1 as designed. On the other hand, if the first and second ultrasonic transducers 4 and 5 are not correctly fixed to the flow path 1, the ultrasonic vibration generated in the first ultrasonic transducer 4 is not measured fluid. In addition to not efficiently propagating to the second ultrasonic transducer 5 separated from each other, the vibration suppressor 3 is not properly adhered to the ultrasonic transducer, and therefore should be suppressed by the vibration suppressor 3. The vibration is not suppressed, and the vibration of the ultrasonic transducer itself continuously vibrates for a long time, so that the vibration attenuation time becomes long, or the ultrasonic vibration that becomes the measurement noise more than usual also in the flow path 1. Will propagate. This is called casing propagation noise.

  Hereinafter, the fixed state determination means 8 in the embodiment of the present invention will be described.

  In the present embodiment, the fixed state determination means 8 visually checks whether the first and second ultrasonic transducers 4 and 5 and the vibration suppressing body 3 are normally attached to the flow path. It is a means for determining without fixing, and a fixed state is determined using a parameter that affects the mounting state as a determining means.

  In the present embodiment, the determination means is implemented by the following five parameters.

(A) Ultrasonic wave transmission / reception output (V ₁ )
(B) Ultrasonic propagation time (T ₁ )
(C) Housing propagation noise (V ₂ )
(D) Vibration damping time (T ₂ )
(E) Measurement interval (T ₃ ) and variation in flow rate and flow rate value Hereinafter, the determination method of the determination means by each parameter will be described in detail.

(A) Ultrasonic wave transmission / reception output (V ₁ )
FIG. 4 shows a drive signal waveform and a received signal waveform transmitted to the ultrasonic transducer.

For example, when the first ultrasonic transducer 4 is a transmitter and the second ultrasonic transducer 5 is a receiver, the drive signal waveform 20 is transmitted to the first ultrasonic transducer 4. The ultrasonic vibration propagated to the fluid to be measured and reached the second ultrasonic transducer 5 is converted by the piezoelectric body 10 and the propagation time T ₁ is calculated after the drive signal waveform 20 is transmitted. After that, an ultrasonic signal such as the received signal waveform 21 arrives. The magnitude V ₁ of the arrived signal is defined as an ultrasonic wave reception output. The ultrasonic reception output V ₁ is obtained when the first and second ultrasonic transducers 4 and 5 are fixed obliquely with respect to the flow path 1 or when the first and second ultrasonic transducers are used. Since it falls when the characteristics of 4 and 5 have deteriorated, the fixed state of the vibration suppression body 3 can be determined.

(B) Ultrasonic propagation time (T ₁ )
In FIG. 4, the ultrasonic wave propagation time represents the ultrasonic wave propagation time T ₁ until the reception signal waveform 21 arrives after transmission of the drive signal waveform 20 as shown in the figure. of the ultrasound transducer 4,5 is the channel 1, for example, if it is fixed at an angle, properly fixed state as compared to the ultrasonic propagation distance ultrasonic wave propagation time T ₁ to become longer Since it becomes long, the fixed state of the vibration suppression body 3 can be determined.

(C) Housing propagation noise (V ₂ )
FIG. 5A is a diagram viewed from a direction parallel to the direction in which the fluid to be measured flows, and FIG. 5B is a cross-sectional view viewed from the direction perpendicular to the direction in which the fluid to be measured flows.

  When transmitting / receiving ultrasonic waves, when the first ultrasonic transducer 4 is used as a transmitter and the second ultrasonic transducer 5 is used as a receiver, it is generated from the first ultrasonic transducer 4 As the ultrasonic wave propagates to the fluid to be measured by the ultrasonic vibration, the vibration of the ultrasonic transducer itself passes through the vibration suppressing body 3 as indicated by the solid line arrow in the figure. Propagates the interior and surface. This is called casing propagation, and is referred to as casing propagation noise because it becomes noise during flow rate measurement. This case-propagating noise is generated when the first and second ultrasonic transducers 4 and 5 are in direct contact with the flow path 1 or when the vibration suppressing body 3 is pressed more strongly than usual. Since it increases when it is fixed, the fixed state of the vibration suppression body 3 can be determined.

  Hereinafter, the case propagation noise will be illustrated and described.

  FIG. 6 shows a drive signal waveform and a received signal waveform transmitted to the ultrasonic transducer.

In FIG. 6, the ultrasonic wave is transmitted from the first ultrasonic transducer 4 by the drive signal waveform 20, and the reception signal waveform 21 (reception output V ₁ ) propagates through the propagation time T ₁ . The case propagation waveform 22 is a waveform (case propagation noise V ₂ ) with a small signal level received before the reception signal waveform 21. In general, the sound velocity of the fluid to be measured (mainly gas) is faster than the sound velocity of the resin or metal used as the housing, so the housing propagation waveform 22 is a received signal received through the fluid to be measured. Reach the waveform 21 faster. Since the housing propagation waveform 22 overlaps the reception signal waveform 21 before being attenuated, the flow characteristic value changes according to the signal level of the housing propagation waveform 22, so that the fixed state of the vibration suppressing body 3 is determined. be able to.

(D) Vibration damping time (T ₂ )
In FIG. 6, the vibration decay time T ₂ is defined as the time from when the received signal waveform 21 (received output V ₁ ) is received by the ultrasonic transducer until the received output is attenuated to a certain voltage level. For example, it is calculated as the time for the ratio of V ₃ / V ₁ = K to decay to 0.1 or less.

(E) Measurement interval (T ₃ ) and flow rate flow variation FIG. 7 shows a drive signal waveform to be transmitted to the ultrasonic transducer set on the transmission side, its transmission interval (measurement interval (T ₃ )), and the reception side. The reception signal waveform in the set ultrasonic transducer is shown.

In FIG. 7, the measurement interval T ₃ indicates the time from when the drive signal waveform 20 is transmitted until the next drive signal waveform 23 is transmitted. When the measurement interval T ₃ becomes shorter, without damping the vibration of the received signal waveform 24 the previously received, then in order overlaps the received signal waveform 25 is received, the flow velocity flow rate measurement value changes, the measurement error May occur. Thus, for example, room temperature, while no fluid flow, continue to shorten the measurement interval T ₃ from a long time, variation is large flow values for each measurement, or the measurement interval T ₃ the absolute value changes Is stored and is shorter than the predetermined normal fixed measurement interval T ₃ , the received signal is considered to be properly attenuated, so that the vibration suppressor 3 transmits and receives the first ultrasonic wave. If it is determined that the waver 4 is fixed correctly and is longer than a predetermined measurement interval, it can be determined that the waver 4 is not fixed correctly.

  Then, by combining the determination means based on these parameters (A) to (E), the first and second ultrasonic transducers 4 and 5 and the vibration suppressing body 3 are suitable for the flow path 1. Whether it is attached or not can be determined.

  Hereinafter, examples of the first and second ultrasonic transducers 4 and 5 and the vibration suppressing body 3 with respect to the flow path 1 will be described with reference to the drawings, and how to determine the attachment state will be described.

  8 and 9 show cross-sectional views of a defective fixed state of the first ultrasonic transducer 4 in the embodiment of the present invention.

FIG. 8 shows a state where the screw tightening of one of the two screws 26 and 27 for fixing the first ultrasonic transducer 4 is incomplete. In this case, the first ultrasonic transducer 4 is attached in a slightly inclined state with respect to the flow path 1, and there are a portion where the vibration suppressing body 3 is strongly compressed and a portion where it is weakly compressed. Exists. In this case, according to the determination means described above, the ultrasonic wave reception output (V ₁ ) is not opposed to each other as designed because the ultrasonic wave reception output (V ₁ ) is not inclined as designed. , Decrease and show abnormal value. Further, the ultrasonic wave propagation time (T ₁ ) shows an abnormal value because the ultrasonic wave propagation distance becomes long. Further, since there are a portion where the vibration suppressing body 3 is strongly compressed and a portion where the vibration suppressing body 3 is weakly compressed, the housing propagation noise (V ₂ ) is transmitted more strongly than usual through the vibration suppressing body 3 and abnormal. Indicates the value. In this way, the attachment state can be determined.

  The same will be described with reference to FIG.

FIG. 9 shows a state in which the vibration suppression body 3 is deformed and is not properly in contact with the side wall portion 12 of the cylindrical metal case 14 of the first ultrasonic transducer 4. In this case, since the first ultrasonic transducer 4 is fixed at an appropriate position with respect to the flow path 1, the determination means ultrasonic reception output (V ₁ ) and ultrasonic propagation time (T ₁ ) are It can be determined as an appropriate value. On the other hand, as shown in FIG. 9, the case propagation noise (V ₂ ) has a portion where the vibration suppressing body 3 is not in contact with the side wall portion 12 of the cylindrical metal case 14, and in this case, Since the function of the vibration suppression body 3 cannot be sufficiently exhibited, a housing propagation noise larger than usual is observed. Further, the vibration attenuation time (T ₂ ) has an abnormal value because the vibration attenuation body 3 that plays the role of attenuating vibration is not correctly fixed, and the vibration attenuation time becomes long. Further, the measurement interval (T ₃ ) and the flow rate value variation are similarly different from normal values and indicate abnormal values.

Here, in particular, a description will be given of a good method when the fixed state determination means 8 determines the mounting state using the vibration damping time (T ₂ ).

  The side wall 12 of the first ultrasonic transducer 4 shown in FIG. 9 vibrates at a frequency lower than the resonance frequency of the piezoelectric body 10.

  FIG. 10 shows impedance characteristics of the first ultrasonic transducer 4 in the embodiment of the present invention.

  In FIG. 10, the side wall portion 12 of the cylindrical metal case 14 is excited by the lateral vibration of the piezoelectric body 10 with respect to the piezoelectric body 10 resonance frequency 30 of the first ultrasonic transducer 4, and this vibration is Since the vibration is at a frequency lower than the frequency of the piezoelectric body 10, it is difficult to attenuate and becomes a main factor for prolonging the vibration attenuation time. Therefore, when the vibration suppression body 3 does not contact the side wall portion 12 as designed, the vibration attenuation time shows an abnormal value.

  Further, for example, even when the first ultrasonic transducer 4 and the vibration suppressing body 3 are correctly fixed to the flow path 1, when only the ultrasonic transmission / reception output in the determination unit is abnormal, the ultrasonic transmission / reception is performed. It can be determined that the waver itself has deteriorated. Summarizing the examples so far, it can be shown in Table 1. Table 1 shows the correlation between the attachment state of the ultrasonic transducer and the vibration suppressor and the determination means. The circles in Table 1 indicate the parameters determined as abnormal in the respective attachment states shown in FIGS. 8 and 9 and the determination results.

  In addition to this, although the attachment state abnormality is conceivable, whether the first and second ultrasonic transducers 4 and 5 and the vibration suppressing body 3 are correctly attached to the flow path 1 by the discrimination means described so far. It can be determined.

  As described above, in the present embodiment, the vibration suppressing body 3 is correctly fixed in the configuration in which the first and second ultrasonic transducers 4 and 5 are held in the flow path 1 via the vibration suppressing body 3. By providing the fixed state determination means 8 for determining whether the vibration suppressor and the ultrasonic transducer are correctly fixed to the flow path, it is possible to avoid an abnormal attachment state. The flow velocity measurement value is stabilized, and more accurate flow velocity flow measurement can be performed.

Specific fixed state determination means include ultrasonic transmission / reception output (V ₁ ), ultrasonic propagation time (T ₁ ), housing propagation noise (V ₂ ), vibration attenuation time (T ₂ ), and measurement interval. By combining each parameter of (T ₃ ) and flow velocity flow value variation, it is possible to determine whether the vibration suppressor and the ultrasonic transducer are correctly fixed to the flow path, and avoid abnormal mounting conditions This stabilizes the flow rate measurement value and enables more accurate flow rate measurement.

Furthermore, when the fixed state determination means determines the vibration attenuation time (T ₂ ), the vibration attenuation time is driven by driving at a frequency 31 (a frequency lower than the resonance of the piezoelectric body) that increases the vibration of the dome-shaped cylindrical metal case 14. Since the vibration attenuation time is mainly caused by the vibration of the celestial cylindrical metal case, the vibration attenuation time is evaluated in more detail by driving at a frequency that increases the vibration of the celestial cylindrical metal case. Therefore, it is possible to easily determine whether or not the vibration suppressing body 3 is covered with the first ultrasonic transducer 4.

(Embodiment 2)
Hereinafter, an ultrasonic flow rate flow meter according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 11 shows a schematic diagram of an ultrasonic flow velocity meter according to the second embodiment of the present invention.

  In FIG. 11, the ultrasonic flow rate flow meter includes a flow path 1 through which a fluid to be measured (for example, gas and air) flows, and is disposed opposite to the flow rate measuring unit 2 and the upstream side and the downstream side of the flow rate measuring unit 2. The first and second ultrasonic transducers (a pair of ultrasonic transducers) 4 and 5 fixed to the flow path 1 via the vibration suppressing body 3 and the first and second ultrasonic transducers A time measuring device 6 for measuring the ultrasonic wave propagation time between the measuring devices 4 and 5, a calculation means 7 for calculating a flow rate per unit time of the fluid based on the ultrasonic wave propagation time obtained by the time measuring device 6, The second ultrasonic transducers 4 and 5 and the vibration suppression body 3 are arranged so as to face the flow path 1 as designed, and the vibration suppression body 3 is connected to the flow path 1 and the first and second channels. Fixed state judging means 8 for judging whether or not the ultrasonic transducers 4 and 5 are correctly fixed as designed. To have.

  The fixed state determination means 8 calculates the flow value by changing the measurement interval, which is the interval at which the first and second ultrasonic transducers 4 and 5 are driven, and the variation in the flow value for each measurement is less than a predetermined value. It is determined whether the vibration suppression body 3 is correctly fixed by comparing the measurement interval when it converges to a predetermined measurement interval.

  In addition, storage means 32 is provided for storing an optimal drive interval when the variation in flow rate value for each measurement converges to a predetermined value or less.

  Therefore, the correlation equation between the temperature obtained from the measurement interval where the flow rate values converge stably at multiple temperatures and the optimum measurement interval are stored, and this correlation equation is based on the temperature estimated from the propagation time during flow rate measurement. Based on the above, it is also possible to perform flow rate flow rate measurement using an optimal measurement interval.

  Since the operation of the ultrasonic flow velocity meter and the ultrasonic transducer are the same as those in the first embodiment, a description thereof will be omitted.

  Hereinafter, a method for measuring the flow rate using the optimum measurement interval by changing the measurement interval will be described.

  The stability of the flow rate flow rate measurement is affected by the temperature of all the parameters of the fixed state determination means 8 described in the first embodiment depending on the temperature as well as the mounting state.

  Table 2 shows the temperature dependence of the characteristic values in the fluid to be measured.

At low temperature (−33.15 ° C.), the ultrasonic transmittance is higher than that at high temperature (66.85 ° C.), so the transmission / reception output (V ₁ ) of ultrasonic waves is high, and the vibration suppressor 3 is also hard. Therefore, the effect of efficiently reducing the vibration of the vibration suppressor 3 is halved compared to normal temperature (26.85 ° C.), the case propagation noise (V ₂ ) is increased, and the vibration attenuation time (T ₂ ) is long. Become. Further, since the speed of sound is slower than that of high temperature, the ultrasonic propagation time (T ₁ ) is also increased. The reverse is true at higher temperatures.

As described above, when the measurement interval (T ₃ ) is measured at a constant value, the sound velocity or the ultrasonic wave propagation efficiency varies depending on the temperature, resulting in different stability of the flow velocity and flow value. Therefore, the measurement interval where the flow rate value stably converges at multiple temperatures is stored, the correlation equation between the temperature and the optimal measurement interval is obtained and stored, and this is based on the temperature estimated from the propagation time during flow rate measurement. It is important to measure the flow velocity using the optimal measurement interval based on the correlation equation.Since the measurement interval is optimized within the operating temperature range, stable flow velocity flow measurement is possible regardless of the temperature. Will be able to do.

  As described above, in the present embodiment, the flow rate value is calculated by changing the measurement interval as the fixed state determination unit 8, the measurement interval at which the flow rate value stably converges is stored in the storage unit 32, and the stored measurement is performed. By performing the flow velocity flow rate measurement using the interval, it is possible to perform a stable flow velocity flow rate measurement while ensuring the stability of the measurement.

  In addition, a correlation equation between the temperature obtained from the measurement interval where the flow rate values stably converge due to multiple temperatures and the optimum measurement interval is stored, and the temperature obtained by calculation from the propagation time during flow rate measurement is used as the basis. By measuring the flow velocity using the optimum measurement interval at that temperature based on the correlation equation, the measurement is performed using the optimized measurement interval even at different temperatures. Measurement can be performed.

  As described above, since the ultrasonic flow rate meter according to the present invention enables stable flow rate measurement, it can be applied to uses such as a home flow meter and an industrial flow meter.

DESCRIPTION OF SYMBOLS 1 Flow path 2 Flow volume measurement part 3 Vibration suppression body 4 1st ultrasonic transducer (ultrasonic transmitter / receiver)
5 Second ultrasonic transducer (ultrasonic transceiver)
6 Timekeeping Device 7 Arithmetic Unit 8 Fixed State Judgment Unit 10 Piezoelectric Body 11 Top Part 12 Side Wall Part 13 Supporting Part 14 Covered Metal Case 15 Acoustic Matching Body 16 First Terminal 17 Second Terminal 18 Terminal Board

Claims (10)

Open ends are formed at both ends, and a flow path for passing the fluid to be measured from one open end to the other open end;
A pair of ultrasonic transceivers arranged so as to contact the fluid to be measured upstream and downstream of the flow path;
A timing device for measuring the ultrasonic propagation time between the pair of ultrasonic transducers;
Calculation means for calculating the flow rate of the fluid to be measured based on the ultrasonic propagation time obtained by the timing device;
With
A fixed state determination that includes a vibration suppression body, the pair of ultrasonic transducers are held in the flow path via the vibration suppression body, and the vibration suppression body is correctly fixed. Equipped with means,
Ultrasonic flow meter. The ultrasonic transducer is
A celestial tubular metal case,
A piezoelectric body housed in the celestial cylindrical metal case;
An acoustic matching body disposed on the outer wall surface of the tented cylindrical metal case so as to face the piezoelectric body;
A terminal plate that supports the terminal in a state of closing the opening of the celestial cylindrical metal case and protruding the terminal to the outside;
With
A vibration suppression body attached to cover the side wall portion of the heavenly cylindrical metal case and the support portion provided on the outside of the side wall portion, and a structure attached to the flow path via the vibration suppression body; did,
The ultrasonic flow velocity meter according to claim 1. The fixed state determination means determines whether or not the vibration suppression body is correctly fixed by at least the reception output of the ultrasonic transducer;
The ultrasonic flow velocity flowmeter according to claim 1 or 2. The fixed state determination means determines whether or not the vibration suppression body is correctly fixed based on at least a propagation time between the pair of ultrasonic transducers;
The ultrasonic flow velocity flowmeter according to claim 1 or 2. The fixed state determining means determines whether or not the vibration suppression body is correctly fixed by at least housing propagation noise between the pair of ultrasonic transducers;
The ultrasonic flow velocity flowmeter according to claim 1 or 2. The fixed state determining means determines whether or not the vibration suppression body is correctly fixed based on at least a vibration attenuation time of the ultrasonic transducer;
The ultrasonic flow velocity flowmeter according to claim 1 or 2. The fixed state determination means is performed at least by a vibration attenuation time when driven at a frequency that increases the vibration of the celestial cylindrical metal case,
The ultrasonic flow rate meter according to claim 6. The fixed state determination means calculates the flow rate value by changing at least the measurement interval, compares the measurement interval in which the variation in the flow rate value for each measurement converges to a predetermined value or less, and the predetermined measurement interval to compare the vibration. Determining whether the inhibitor is correctly fixed;
The ultrasonic flow velocity flowmeter according to claim 1 or 2. Storing a measurement interval at which the flow rate value stably converges, and performing flow velocity flow rate measurement using the stored measurement interval;
The ultrasonic flow rate flowmeter according to claim 8. Stores the correlation equation between the temperature obtained from the measurement interval where the variation in the flow rate value for each measurement stably converges below the specified value at multiple temperatures and the optimum measurement interval, and the temperature obtained from the propagation time during flow rate measurement Based on the above, performing flow rate flow rate measurement using an optimal measurement interval based on the correlation equation,
The ultrasonic flow rate flowmeter according to claim 8.

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