JPS60138422A - Flow rate measuring device - Google Patents

Abstract

PURPOSE:To detect exactly a rise time of a receiving wave even in case of a medium in which a driving excess pulsating wave and the receiving wave are superposed, and to measure a flow rate with a high accuracy, by measuring an ultrasonic propagation time basing on a rise time of an ultrasonic waveform. CONSTITUTION:Envelope sampling information S1, S2 and sampling time information S3 obtained from ultrasonic transmitting and receiving circuits 1, 2 are stored successively in input control circuits 4, 5 and 6, respectively, by a control pulse signal S300. Subsequently, a calculating circuit 7 receives each sampling time information S3 from a latching circuit of the input control circuit 6, and also receives the envelope sampling information S1, S2 at each time from latching circuits of the input control circuit 4, 5, respectively. An m-order function fm is determined basing on said information, each ultrasonic propagation time T1, T2 is derived by calculating numerically the time when this m-order function fm passes through a zero point Z, and a flow velocity of a fluid and its flow rate are calculated, and outputted so as to be displayed on a display device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a flow rate measuring device that monitors respiratory flow rate over a long period of time, which is installed in, for example, a patient monitoring device.

[Technical background of the invention and problems with the background art] As a flow measurement device using ultrasonic waves, an ultrasonic propagation time difference method is known, which uses the fact that the distance between the ultrasonic propagation collars changes depending on the change in flow velocity. It is being This ultrasonic propagation time difference method has characteristics such as flow path obstruction, flow path resistance, measurement accuracy, measurement linearity, and long-term stability of measurement, which are different from other measurement methods, such as differential pressure applying Renoulli's theorem. Since it is more advanced than other methods, it has been put into practical use in many fields recently. The principle of a surveying and measuring device using this method is, as shown in Figure 1, for example, a pair of ultrasonic vibrations are placed at a certain distance apart on an axis that has a certain angle θ with respect to the flow in a pipe. Child PZ1. PZ2
are arranged facing each other, and this ultrasonic transducer PZ1. When PZ2 is driven at the same time, ultrasonic transducers PZ1. PZ2 husband? Ultrasonic reception time T1. T2 is measured, the flow 3iv is determined based on the time difference Δd--r2--rt, and the flow rate j'vdt is determined.

In this type of flow rate measurement, good measurement is possible because the attenuation of ultrasonic waves is small under normal air breathing. Large and good flow rate measurement results cannot be expected.

Generally, the vibration amplitude F when an ultrasonic wave propagates in a medium is F=F[ext) (-<a+Jβ) x ) ・
if), and the damping constant α is expressed as α=Ki2/P (2) where P is the atmospheric pressure in the gas, K@ is a constant determined by the medium, and J is the vibration frequency. That is, when breathing high concentration carbon dioxide, the medium constant K increases, and when breathing a large amount of gas, the atmospheric pressure P decreases.
In both of these cases, the attenuation of the ultrasound waves increases.

As is clear from the above equation (2), if the increase in the damping constant α is suppressed by decreasing the vibration frequency f, ultrasonic transmission
A time difference method can be applied.

On the other hand, the ultrasound propagation efficiency when ultrasound propagates through a gas such as breathing air is 1/100 compared to when ultrasound propagates through a living body and water as in a normal ultrahigh wave diagnostic device.
Becomes 0 or less. Therefore, even if a resonant type ultrasonic drive circuit is used or a non-resonant type ultrasonic drive circuit is used, it is necessary to increase the power supply voltage. In order to perform non-resonant drive at high voltage as described above, components with high breakdown voltage must be used in the ultrasonic drive circuit. Therefore, the non-resonant driving method is problematic because it does not meet the requirements of miniaturization and safety required for this type of device.

Therefore, above! By using a resonant ultrasonic drive circuit like IS and reducing the vibration frequency, high concentration carbon dioxide respiration and large flow rate Il? The flow m can be well measured even by suction.

However, this resonance drive method also has the following problems. That is, the driving voltage waveform (++ wave burst waveform, i.e., 11 pulse train) causes a resonance effect in the resonant circuit, and a pulse wave remains even after driving, making it difficult for the receiver to measure the ultrasonic transmission I11, Tl, and T2. This is the point where it becomes difficult to recognize the rising point of the wave. For example, Fig. 2(a)'
(b) and FIGS. 2(0) and 2(d) show examples of three-wave burst drive waveforms. Figure 2 (a >('b
) and Fig. 2(C) (d) are different in drive waveform width, that is, frequency, and Fig. 2(a) and Fig. 2(c) are different from PZl.
transmits, PZ2 receives; Fig. 2 (b) and Fig. 2 ((1
), PZ2 is transmission, pzi is reception, and Wl is the drive waveform.

W2 is a driving after-pulse wave, and W3 is a received waveform, which is transmitted.

, -#≦≧, bottle-r, Mml+bl-small i=m+, 8-
1 word 1-4・田1--7 As shown in Figure 2 (a) and (b), in both Figure 2 (a) and Figure 2 (b), the driving after-pulse wave occurs before the rising edge of the received waveform. Since the ultrasonic wave propagation time T1. It is possible to measure T2. However, in Figures 2(c) and 2(d), where the vibration frequency is low, the drive after-pulse wave overlaps with the rise of the waveform due to the decrease in the vibration frequency, making it difficult to accurately measure the ultrasonic propagation times T1 and T2. is not possible, and the measured flow rate cannot be said to be accurate.

Furthermore, in order to avoid the overlapping phenomenon of the driving after-pulse wave and the received waveform, it is conceivable to arrange separate ultrasonic transducers for transmission and reception. However, with this method, the area where the vibrator is placed (e.g. piping, etc.) becomes larger.
Furthermore, the number of cables between the camera element and the main body of the device increases, which impairs operability.Also, in order to prevent mutual interference between transmitting and receiving, the diameter of the ultrasonic propagation path must be increased, and piping, etc. [Objective of the Invention] The present invention was made based on the above circumstances. Its purpose is to create an ultrasonic propagation time difference type flow measurement device that can measure the flow rate of a medium with high precision even in a medium where the driving pulse wave and the received wave overlap. Our goal is to provide the following.

[Summary of the Invention] In the present invention, ultrasonic waves transmitted from the respective ultrasonic drive units disposed facing each other on axes having a certain angle with respect to the fluid flow direction or the opposite direction are transmitted to the respective ultrasonic transducers described above. received at
By measuring the ultrasonic propagation time, the
In the apparatus for measuring the amount of a, a first means for detecting at least one of positive and negative envelope waveforms of the received waveform from each of the vibrators; and a second means for detecting a rise time of at least one of the positive and negative envelope waveforms based on an approximate expression, and configured to measure the -C ultrasonic propagation time based on the rise time. The present invention is characterized in that even in a medium where the driving pulse wave and the received wave overlap, the rising time of the received wave can be accurately detected.

[Embodiment of the Invention] The flow rate measuring device of the present invention will be described below according to an embodiment shown in FIG.

In FIG. 3, 1 and 2 are opposed ultrasonic transducers PZ.
1. This is an ultrasonic transmitting/receiving circuit that drives and receives the PZ2, calculates the envelope of the received signal, and converts this envelope signal from analog to digital (hereinafter referred to as A/'D conversion).This transmitting/receiving circuit 1 In ゜2, 11.21 is a resonance type ultrasonic drive circuit, 12.22 is a connection from the drive circuit 11.21 to ultrasonic transducer PZ1.PZ2, '5-shielded wire, 13゜23 is a transducer PZI, Uke 1ε by PZ2
14.24 is the amplification circuit, and 15.25 is the amplification circuit ill! 14.24
16.26 is an A/'D conversion circuit that converts the output signal of the detection circuit 15.25 into a digital quantity.

3 is a time control circuit that outputs a predetermined control pulse;
This time control circuit 3 controls the ultrasonic drive timing for the ultrasonic transmitting/receiving circuits 1 and 2, and also provides a predetermined conversion timing to the A/D conversion circuits 16 and 26, and furthermore, the input control circuit (to be described later) 4, 5, 6>, the above A/
The output digital information of the D conversion circuit 16.26 and the time information outputted by itself are sequentially stored. In this time control circuit 3, 31 is an ultrasound imager P
32 is a timing circuit 3 for ultrasonic drive which determines the ultrasonic drive timing of ZI and PZ2 and outputs an n-wave burst signal (drive signal) S100;
1, a gate circuit drives and controls an oscillation circuit 33, which will be described later. 33 is an oscillation circuit activated by the output of the gate circuit 32 and provides sampling times for measuring the ultrasonic propagation times TI and T2. 34 is an output of the oscillation circuit 33. A shift register circuit 35 inputs the pulse train 3200 and provides control pulses 830' and O to the input control circuits 4 and 5.6, which will be described later.A shift register circuit 35 performs input control, which will be described later, by sequentially counting the output pulse train 5200 of the oscillation circuit 33. This is a counter circuit that outputs sampling time information S3 to the circuit 6.

4 is △ of one ultrasonic transmitter/receiver circuit 1, 2D conversion circuit 1G
The latch circuit 41. has the output information S1 therein.
42. . . , 41N is a human control circuit that sequentially stores the data.

5 is A in the other ultrasonic transmitting/receiving port 11i2, -'
This is an input control circuit that stores and overwrites the output information ff1s2 of the D conversion circuit 26 in the same manner as above.

Reference numeral 6 denotes an input control circuit that stores the output sampling time information S3 of the counter circuit 35 in the time control circuit 3. Note that in the above, the input control circuit 5 is the A/D conversion circuit 26.
Latch circuits 51, 52, . . . which sequentially store output information S2 of .
..., 511. The input control circuit 6 also includes a latch circuit 61 that sequentially stores the sampling time information S3.
．． 62. ....

It has 6n.

7 receives the information stored in the input control circuit 4.5.6 (each latch circuit), and based on that information calculates the rise time of the noise reception wave that appears when there is no driving after-pulse wave, Further, the timing circuit 31 is connected to the drive circuit 11.21.
The ultrasonic propagation time TI, T2 from the time when the drive starts to the rising time of the received wave is calculated, the flow velocity is calculated based on the sieving result, and the flow rate is determined by integrating the flow velocity over time. It is a cylindrical circuit.

Reference numeral 8 denotes a display device for displaying the above-mentioned 81 Korean results in a predetermined format.

Next, the operation of this embodiment constructed as described above will be explained with reference to FIG. First, the timing circuit 31 in the time control circuit 3 is activated, and the logic level three-wave burst signal 5100 shown in FIG. The gate circuit 32 that should transfer data to the circuit 1'm21 and start the oscillation circuit 33
are applied to the cellar 1 so that the output has the waveform shown in FIG. 4 (1).

After this, the oscillation circuit 33 continues to oscillate and sends the pulse signal @5100 shown in FIG. 4(C) to the shift register circuit 34 and the counter circuit 35. -h, the filtered burst signal 8100 is input to the ultrasonic transceiver circuit 1.2. In the ultrasonic transmitter/receiver circuit 1, the ultrasonic drive circuit 11 applies a pulse (drive waveform W1) shown in FIG. 4 ((1)) to the ultrasonic transducer via the shield wire 12 to generate an ultrasonic wave.

The ultrasonic waves emitted from the ultrasonic transducer PZ1 are received by the opposing ultrasonic transducer PZ2, converted into electrical signals, and then passed through the limiter circuit 23 and the amplifier circuit 24 to the fourth
The received waveform W3 is as shown in Figure (d) (W2 is a driving after-pulse wave). Next, the received waveform W3 is used to create a positive envelope mep as shown in FIG. The circuit 26 obtains envelope sampling information S1 at a time corresponding to each pulse of this output pulse train $200.

Similarly, in the ultrasonic transmitter/receiver circuit 2, the ultrasonic drive circuit 21 driven by the filtered burst signal 5100 vibrates the ultrasonic transducer PZ2 via the shield wire 22, and the ultrasonic wave generated thereby is an ultrasonic wave. It is received by the vibrator PZ1, and the received waveform is converted into an electric signal, and the limiter circuit 13, amplifier circuit 14, and detection circuit 15 (envelope e11
) and the A/D conversion circuit 16 to obtain the envelope sampling information S2.

These envelope sampling information S1.82 and the sampling time information S3 are sequentially sent to the input control circuits 4, 5.6 (to the internal latch circuit) by the control pulse signal Q3300 outputted from the register circuit 34 to shift 1. Stored. The input control circuit 6
It receives each sampling time information S3 from the latch circuits 61, 62, . . . , 61), and also receives envelope sampling information 81 at each time. S2 is input to the latch circuits 41, 42 . ..., 41) and 51.52.
....

5 Receive each from n.

Then, using the envelope sampling information S1 or S2 based on the received wave that is relatively less influenced by the C drive total pulse wave and has no drive after-pulse wave, m is used to estimate the rise time of this received wave.
Perform fitting to the next function. That is, it is desirable and most accurate for fitting to use the maximum value of the envelope sampling information S1.82 and the sum of sampling points of its load (m+1)III. The zero point of the fitted function indicates the rise time.

In the above, (m+1) pieces of sampling information 81.8
2 and their time information S3, FIG. 4(e)
Determine the ■order function fm shown by the broken line in (f), and determine this m
By numerically measuring the time when the next function fIll passes the zero point Z, T I , 'T 2 between each ultrasonic method mTeI
It is possible to put And the ultrasound propagation time T1 in the mouth
．． 72, the fluid flow velocity and further the flow rate can be calculated and displayed on the display device 8 in a predetermined format.

In the above, the fitting process to the m-th order function in the meter sieve circuit 7 will be explained with reference to FIG. 5, taking a quadratic function as an example. That is, the operation starts at step S1, and inputs sample link time information and envelope sampling information 51i-82i at step S2 using connector A, and
In step S3, the previous envelope zumbling information S1
i-s.

It is determined whether or not it is larger than S 2 i-1. If it is larger, the process returns to the connector A, and if it is smaller, the process proceeds to step S41\. In step S4, g+ of the previous one and two or three times
Three times of υ combining time information 53i-1゜53i-2,
33+-3, envelope sampling information 51i-1, 5l
i-2,31i-a, S2i-1.

52i-2 and 32i-3, respectively, and the process proceeds to step S5. In step S5, the quadratic function x = at2 + l + t
Substitute the enveloping cotton sampling information 81.82 into × of +C, substitute tl\Zambling time information S3, and obtain a.
Calculate b and c. Then, in step S6, at2+
In order to determine the sampling time closest to t of bj+C=Q, x(t) is calculated by 61 at all sample points. In step S7, t=tj is determined to minimize lx (t)l, and in step s8, 1j is defined as the ultrasonic propagation time.

The flow velocity and flow m are calculated in step S by combining the above processing and the ultrasonic propagation time of other channels, and step 81
It ends at 0.

In addition, in FIG. 3, the FR in the detection circuit 15.25
If the delay affects the measurement accuracy, the detection time 2
Based on the integral constants of 1i15 and 25, each sampling time information S3 can be corrected.

As described above, according to this embodiment, a large number of equations are derived from the positive or negative envelope of the received waveform, and the ultrasonic propagation times TI and T2 are determined by the zero point of this large number of equations. Conventionally, this type of ultrasonic propagation time difference method was difficult to
When the drive system pulse wave overlaps with the received waveform, the rise time of the received waveform can be used as a sieve, and the ultrasonic propagation time difference TI
.

It is now possible to measure T2 with the desired accuracy, for example, the flow rate under high concentration exhaled carbon dioxide breathing gas or under large flow hanging breathing.

It becomes possible to measure the flow rate.

Next, another embodiment of the present invention will be described with reference to FIG.

In the embodiment shown in FIG. 3 above, in the detection circuit 15°25,
Although the amplifier circuit 14.24 was configured to output only the envelope of the positive side, it also detected envelopes of both positive and negative polarities, and received signals from the positive and negative envelopes in each channel. The measurement accuracy can be further improved by adding Kl m to the rise time of the wave and applying a field such as an arithmetic mean. That is, FIG. 5 shows the above-mentioned embodiment, and in the figure,
Ml.

M2 is a detection circuit tv that creates an envelope on the negative side as shown in FIG. 4(f) for the ultrasonic transmitting/receiving circuits 1 and 2 shown in FIG. 3, respectively.
115. M25, and negative side envelope sampling information M
S1. A/D conversion circuit M16 for outputting MS2.
M26 is additionally configured.

Also, M4. M5 is the negative side stand $8 wire sampling information M
S1. MS2 is connected to each latch circuit M41.MS2 at the same operation timing as the input control circuit 4.5.6. M42.・
..., M411, tv151, tv152°..., this is an input control circuit that inputs to M5n.

Here, the calculation circuit 7 performs the twitch ink processing of a large number of mathematical expressions based on the negative electrode side envelope sampling information and the sieving of the zero point passing time in the operation described in the embodiment shown in FIG. Each ultrasound propagation time MT1. Install MT2. For example, by adjusting the arithmetic mean of T1, MTIT2, and MT2, it is possible to improve the measurement accuracy of the flow velocity and flow rate.

The present invention is not limited to the above-described embodiments, but may be modified and implemented without departing from the gist of the present invention.

[Effects of the Invention] As described above, the present invention has the advantage of transmitting ultrasonic waves transmitted from ultrasonic vibrating elements disposed facing each other on an axis having a certain angle with respect to the fluid flow direction or the opposite direction. In the apparatus for measuring the flow rate of the fluid by receiving the ultrasonic wave with the ultrasonic transducer and measuring the propagation time of the ultrasonic wave, a first means for detecting; and a second means for detecting a rise time of at least one of the positive and negative envelope waveforms based on an approximate expression calculated from the at least one of the positive and negative envelope waveforms. is configured to measure the propagation time of the MA sound wave based on the top rise time, so that even in a medium where the driving pulse wave and the received wave overlap, the rise time of the received wave can be accurately determined. Therefore, it is possible to provide a flow rate measuring device that can measure the flow rate with high precision.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the principle of a flow rate measuring device using an ultrasonic transmission m-direction type, and Figure 2 (a), (b), and (c).
) (d) is a waveform diagram showing the ultrasonic drive waveform and reception waveform at each channel, respectively, and FIG. 3 is according to the present invention. 7
A block diagram showing one embodiment of the itl measuring device, FIG.
a) to (f) are waveform diagrams for explaining the operation of the same embodiment, FIG. 5 is a flowchart for explaining quadratic function approximation in a crystal 1n circuit, and FIG. 6 is another embodiment of the present invention. FIG. 2 is a block diagram illustrating an example. 1.2. Ml, ~12... Ultrasonic transmitting/receiving circuit, 3...
・Time control circuit, 4.5.6. M4. M5... Input control circuit, 7... Pruritus circuit, 8... Display device, 11゜21... Resonance type ultrasonic drive circuit, 12.22... Shield wire, P Z 1 , P Z 2-ffl sound wave 1
1 child, 13°23...Limiter circuit, 14.24...
・Amplification circuit, 15.25. Ml5. ~125...Detection circuit, 16°26, Ml 6. M26... A/D conversion circuit, 31... Timing circuit, 32... Goo 1-
Circuit, 33... Oscillation circuit, 34... Shift register circuit, 35... Counter circuit, 41.42. ...,
40, 51, 52. .... 5n, 61, 62. −． 6n, M41. M42゜・
..., M4+1, M51. M52. ..., 1y15+
+...Latch circuit. Applicant's representative Patent attorney Takehiko Suzue Manabu Shiga, Director of the Japan Patent Office, 1996-244472+J4 2, Invention No. Flow Measuring Device 3, Supplementary 11th Case Related: Patented applicant (3 (17) Toshiba Corporation 4, agent 5, voluntary amendment 6 Number of inventions reduced by sleeve correction 1 Contents of 8 sleeve correction (1) The scope of claims is revised as shown in the attached sheet (2) In the specification No. 17, line 2, ``Korerigai ni'' is changed to ``Reception skill W3 has a difference of equal to one cycle between the positive side and the 9th side, so the correction for that difference is made. 2. Claims (1) Ultrasonic waves transmitted from ultrasonic vibrator arrays facing each other on an axis having a constant angular force with respect to the flow direction of the fluid or the opposite direction. The sr of the fluid is determined by receiving sound waves with each of the ultrasonic transducers and measuring the intercostal space of the ultrasound propagation.
-) d, 'lIn the measuring device, each of the above ]l1
ψ7] for detecting the envelope waveform of the dot waveform from the vilt11 child, and ft-1L calculated from the above envelope waveform.
In line with the second means of detecting the A "7." time of the envelope waveform by following the side-like equation, the above-mentioned wave propagation time is measured based on the rise time. 'l7Ii...Measurement equipment. Is the means for 121 years 2 mentioned above? 16. Envelope wave of stop from means of 141. The above positive enveloping line waveform is derived from the negative enclosing line waveform based on the edge approximation. One rise time of the negative envelope waveform! What did you do to detect it? Characterizing Claim No. Flow rate measuring device described in ( ). (3) The second means calculates the envelope line aQ J+ based on the approximation formulas obtained from the positive envelope waveform and the negative envelope waveform from the first means. ';
The N1 rising time of the negative envelope waveform and the negative envelope waveform are determined respectively (
Meteor survey 'Ak Sojima, which is mentioned in the 11th summit.

Claims (1)

[Claims] (1) The ultrasonic transducers receive the ultrasonic waves transmitted from the ultrasonic vibrating elements placed facing each other on an axis having a certain angle with respect to the fluid flow direction or the opposite direction, and In the device for measuring the flow rate of the fluid by measuring the propagation time of the sound wave, the device includes: a first means for detecting a positive or negative envelope waveform of a received waveform from each of the vibrators; a second means for detecting a rising time of the positive or negative envelope waveform based on an approximate expression derived from the waveform, and configured to measure the ultrasonic propagation time based on the rising time. A flow rate measuring device characterized by: (21) Each of the ultrasonic transducers receives the ultrasonic waves transmitted from the ultrasonic vibrating elements placed opposite to each other on an axis having a certain angle with respect to the flow direction of the fluid or the opposite direction, and The apparatus for measuring the flow rate of the fluid by measuring the propagation time includes a first means for detecting positive and negative envelope waveforms of received waveforms from each of the vibrators, and the positive and negative envelope waveforms. and a second means for detecting rise times of the positive and negative envelope waveforms based on approximate expressions calculated from the above, and configured to measure the ultrasonic propagation time based on the rise times. A flow rate measuring device featuring: