JP5608884B2 - Ultrasonic flow meter and fluid supply system - Google Patents

Description

The present invention is an ultrasonic flowmeter for measuring a flow rate of a fluid by the propagation time difference of the ultrasonic wave, in which relates to a fluid supply system using the same.

2. Description of the Related Art Conventionally, an ultrasonic flowmeter that measures the volume flow rate of a liquid using ultrasonic waves has been proposed (see, for example, Patent Document 1). As shown in FIG. 14, in the ultrasonic flowmeter 60 of Patent Document 1, a pair of ultrasonic transducers 62 and 63 are disposed so as to face each other on the upstream side and the downstream side of the pipe 61 through which the fluid W flows. And the propagation time until the ultrasonic wave emitted from one ultrasonic transducer propagates in the fluid W and reaches the other ultrasonic transducer is measured. Specifically, ultrasonic waves are propagated in the forward and reverse directions of the flow of the fluid W, and the propagation time in the forward direction and the propagation time in the reverse direction are measured. Here, assuming that the ultrasonic wave propagation distance L between the ultrasonic transducers 62 and 63, the speed of sound C in the fluid W, and the flow velocity V of the fluid W, the forward propagation time Td and the reverse propagation time Tu are: Are represented by the following equations (1) and (2), respectively.

That is, when the flow velocity V of the fluid W is increased, the propagation time Td of the ultrasonic S ₀ propagated in the forward direction is shortened, the propagation time Tu of ultrasonic S ₀ propagated in the opposite direction becomes longer (see FIG. 15 ). And the propagation time difference ΔT of the ultrasonic waves S ₀ is expressed as the following equation (3).

Here, the flow velocity V of the fluid W is negligible compared with the sound velocity C. Therefore, the above equation (3) can be expressed as the following equation (4).

Therefore, the flow velocity V can be obtained by the following equation (5).

  Further, the volume flow rate Q (= V × A) of the fluid W is obtained by multiplying the flow velocity V by the cross-sectional area A of the pipe 61.

  In the conventional ultrasonic flowmeter, when the temperature or concentration of the measurement fluid changes, the kinematic viscosity of the fluid changes with the change, and thus a measurement error of the flow rate Q occurs. As a countermeasure, a technique for correcting the flow rate based on the kinematic viscosity corresponding to the temperature change has been proposed (see, for example, Patent Document 2).

  In the correction method disclosed in Patent Document 2, the flow velocity and the sound velocity are measured by an ultrasonic flowmeter, and the temperature of the fluid is obtained using a temperature table using the sound velocity as a parameter. And kinematic viscosity is calculated | required using the kinematic viscosity table which made temperature the parameter, and the flow volume is correct | amended by the ratio according to the kinematic viscosity.

JP 2002-162269 A JP 2007-51913 A

  However, in the correction method of Patent Document 1 described above, when measuring a fluid of a type different from a predetermined measurement fluid, the table data used does not correspond to the measurement fluid, and thus an incorrect correction is made. Measurement error will increase. Further, depending on the type of fluid, there may be a maximum point P1 in the relationship between the speed of sound and temperature (see FIG. 16). In this case, since the temperature cannot be uniquely obtained from the measured sound speed, there is a problem that the measurable temperature range is limited.

The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic flowmeter capable of specifying the type of fluid and performing accurate flow rate correction according to the type of fluid. It is in . Et al is another object, said by using an ultrasonic flowmeter, it is to provide a fluid supply system that can accurately measure the flow rate of plural kinds of fluids at a low cost. Another object is to provide a fluid supply system that can accurately adjust the concentration and flow rate of a fluid at low cost by using the ultrasonic flowmeter.

In order to solve the above-mentioned problem, the invention described in the means 1 is provided in a pipe line constituting a flow path for flowing fluid, and propagates ultrasonic waves in the forward and reverse directions of the fluid flow in the pipe line. A first sensor unit for receiving the ultrasonic wave propagating in the forward direction and the ultrasonic wave propagating in the reverse direction and detecting the propagation time difference between the ultrasonic wave and the fluid flowing in the pipe line A second sensor unit for propagating the ultrasonic wave, receiving the ultrasonic wave reflected by the inner wall surface of the pipe and detecting its signal intensity and propagation time; and the ultrasonic wave detected by the first sensor unit Based on the propagation time difference, the flow rate calculation means for calculating the flow rate of the fluid flowing through the flow path, the propagation time of the ultrasonic wave detected by the first sensor unit or the second sensor unit, and the propagation distance of the ultrasonic wave based on the sound velocity calculation means for calculating the sound speed of the fluid, Based serial signal strength of the reflected wave detected by the second sensor unit and to the acoustic impedance of the material constituting the conduit, and the acoustic impedance calculating means for calculating the acoustic impedance of the fluid, the acoustic impedance calculating means is determined The density calculation means for calculating the density of the fluid based on the acoustic impedance of the fluid and the speed of sound, and the relationship among the three types of sound speed, density, and kinematic viscosity coefficient in the plurality of types of fluid for each of the plurality of types of fluid. Based on the storage means for storing the flow rate correction data defined in the above, the data, the sound velocity of the fluid calculated by the acoustic parameter calculation means, and the density of the fluid calculated by the density calculation means. a fluid specifying means for specifying the type of fluid flowing through the flow rate of said fluid before Symbol flow rate calculation unit has calculated, the fluid specifying means Laid An ultrasonic flow meter for the flow rate correction means for correcting using kinematic viscosity coefficient corresponding to the type of the fluid and further comprising a as its gist.

  Therefore, according to the invention described in means 1, the flow rate of the fluid flowing through the flow path is calculated by the flow rate calculation means based on the propagation time difference of the ultrasonic wave detected by the first sensor unit. Here, when a plurality of types of fluid flows through the flow path, the flow characteristics differ depending on the type of the fluid. In this case, the flow rate of the fluid calculated by the flow rate calculation means is a measurement value including a measurement error corresponding to the type of fluid. Therefore, in the present invention, the acoustic parameter calculation means obtains the acoustic parameter of the fluid based on the signal intensity of the reflected wave detected by the second sensor unit and the acoustic impedance of the material constituting the pipe. Further, the storage means stores data relating to acoustic parameters of a plurality of types of fluids. Then, based on the data in the storage means and the acoustic parameters calculated by the acoustic parameter calculation means, the type of fluid flowing through the pipe is specified by the fluid specifying means. Further, the flow rate of the fluid is corrected by the flow rate correction means according to the type of the fluid. In this way, even when the type of fluid flowing through the pipeline is changed, an accurate flow rate according to the type of fluid can be obtained.

The invention described in the means 2 includes the ultrasonic flowmeter according to the means 1, a plurality of fluid supply pipes to which a plurality of types of fluids are respectively supplied, and a fluid output pipe provided with the ultrasonic flowmeter. A fluid path, a plurality of fluid supply conduits and a fluid output conduit are connected, and any one of a plurality of types of fluids supplied from the fluid supply conduits is supplied to the fluid output Switching means for supplying to the pipeline, and the ultrasonic flowmeter specifies the type of fluid that is selectively supplied into the fluid output pipeline via the switching means, and determines the specified type. The gist of the fluid supply system is to correct the flow rate of the fluid accordingly.

Therefore, according to the invention described in the means 2 , a plurality of fluid supply pipes and fluid output pipes are connected to the switching means, and are supplied from each fluid supply pipe by the switching means. Any one of a plurality of types of fluids is supplied to the fluid output conduit. The type of fluid supplied into the fluid output conduit is specified by the ultrasonic flowmeter provided in the fluid output conduit, and the fluid flow rate is corrected according to the type. With this configuration, it is possible to accurately measure the flow rates of a plurality of types of fluids with a single ultrasonic flow meter without providing a flow meter for each of a plurality of fluid supply pipelines. Can be reduced.

The invention described in means 3 includes the ultrasonic flowmeter of means 1 , a fluid supply pipe provided with the ultrasonic flowmeter, a concentration adjusting means for adjusting the concentration of fluid supplied to the pipe, A flow rate adjusting means for adjusting a flow rate of the fluid supplied to the pipe line; and a control means for controlling the concentration adjusting means and the flow rate adjusting means. A gist of the fluid supply system is to obtain the flow rate of the fluid and output the concentration and flow rate to the control means.

Therefore, according to the invention described in the means 3 , the concentration of the fluid flowing through the fluid supply pipe line is obtained by the ultrasonic flowmeter, the flow rate of the fluid is obtained, and the concentration and the flow rate are output to the control means. . And based on the density | concentration and flow volume which were measured with the ultrasonic flowmeter, a density | concentration adjustment means and a flow volume adjustment means are controlled by a control means. In this way, even if a flow meter and a densitometer are not provided separately, a fluid having an appropriate concentration and flow rate can be flowed to the fluid supply conduit, and the cost of system components can be reduced. .

As described above in detail, according to the first aspect of the present invention, it is possible to provide an ultrasonic flowmeter capable of specifying the type of fluid and performing accurate flow rate correction according to the type of fluid. . A is found, according to the invention described in claim 2, wherein by using an ultrasonic flowmeter, it is possible to provide a fluid supply system which can accurately measure the flow rate of a plurality of types of fluids at low cost . In addition, according to the invention described in claim 3 , by using the ultrasonic flowmeter, it is possible to provide a fluid supply system capable of accurately adjusting the concentration and flow rate of the fluid at low cost.

The schematic block diagram which shows the fluid supply system of 1st Embodiment. Sectional drawing which shows schematic structure of the 2nd sensor part in 1st Embodiment. The block diagram which shows the electrical constitution of an ultrasonic flowmeter. The timing chart which shows the reception time and propagation time of each reflected wave. Explanatory drawing which shows the correlation function of a waveform signal. The flowchart which shows the process example for calculating the density of a fluid. The flowchart which shows the process example for calculating the flow volume of a fluid. The schematic block diagram which shows the fluid supply system of 2nd Embodiment. The graph which shows the relationship between ethanol aqueous solution density | concentration and each parameter. Sectional drawing which shows schematic structure of the 2nd sensor part in 3rd Embodiment. Sectional drawing which shows schematic structure of the 2nd sensor part in 4th Embodiment. Sectional drawing which shows schematic structure of the 2nd sensor part in another embodiment. Sectional drawing which shows schematic structure of the 1st sensor part in another embodiment. The schematic block diagram which shows the conventional ultrasonic flowmeter. The timing chart which shows the propagation time and propagation time difference of an ultrasonic wave. The graph which shows the relationship between sound speed and temperature.

[First Embodiment]
Hereinafter, a first embodiment in which the present invention is embodied in a fluid supply system will be described in detail with reference to the drawings. The fluid supply system according to the present embodiment is used, for example, as a system for supplying a plurality of types of chemical solutions (for example, chemical solutions for semiconductor cleaning) for performing various surface treatments of a silicon substrate (wafer) in a semiconductor production line. It is done.

  As shown in FIG. 1, the fluid supply system 1 includes an ultrasonic flow meter 2, a plurality of fluid supply pipes 3 to 6 to which a plurality of types of chemical liquids W <b> 1 to W <b> 4 (fluid) are respectively supplied, A fluid output conduit 7 provided with the sonic flow meter 2 and a flow path switching device 8 to which the fluid supply conduits 3 to 6 and the fluid supply conduit 7 are connected are provided.

  The flow path switching device 8 includes a switching valve 9 (switching means) and a controller 10 that drives and controls the switching valve 9, and the controller 10 operates the switching valve 9 so that each of the fluid supply pipes 3 to 3 is operated. 6, any one of the plurality of types of fluids W <b> 1 to W <b> 4 supplied from the fluid 6 is supplied to the fluid output conduit 7. In the fluid supply system 1 of the present embodiment, each of the fluids W1 to W4 is supplied in a state where the temperature is adjusted to be a constant temperature (for example, 20 ° C.).

  The ultrasonic flowmeter 2 is a first sensor unit 11 for measuring the volume flow rate of the fluid W (W1 to W4) by the ultrasonic propagation time difference method, and for measuring the acoustic impedance, density, etc. of the fluid W. The second sensor unit 12 is provided and provided in the middle of the fluid output conduit 7.

Hereinafter, a specific configuration of the ultrasonic flowmeter 2 will be described in detail.
As shown in FIG. 1, the first sensor unit 11 of the ultrasonic flowmeter 2 is fixed to a pipe 14 bent in a substantially U shape and two corner parts 14 a and 14 b of the pipe 14. And a pair of first ultrasonic transducers 15 and 16 arranged to face each other via 14 straight pipe portions 14c. The pipe 14 of the first sensor unit 11 is formed using a fluororesin (for example, Teflon (registered trademark)) having excellent chemical resistance, and the length of the straight pipe portion 14c is about 10 cm. Moreover, the cross-sectional shape of the flow path formed in this piping 14 is circular, and the aperture is about 10 mm. Thus, by making the cross-sectional shape of a flow path circular, the turbulent flow of the fluid W is prevented in the flow path, and the fluid W flows smoothly.

As shown in FIG. 2, the second sensor unit 12 includes a pipe 17 connected to the downstream side of the first sensor unit 11 and a pair arranged on the outer wall surfaces on the upstream side and the downstream side of the pipe 17. Second ultrasonic transducers 18 and 19. The piping 17 of the second sensor unit 12 is also formed using a fluorine resin (for example, Teflon (registered trademark)) having excellent chemical resistance. The cross-sectional shape of the flow path formed in the pipe 17 is a quadrangle, and the ultrasonic wave S ₀ emitted from each of the second ultrasonic transducers 18 and 19 is a pair of inner wall surfaces parallel to the direction in which the fluid W flows. It is made incident at an angle perpendicular to 17a and 17b. In the pipe 17, the interval between the inner wall surfaces 17 a and 17 b is different between the upstream side and the downstream side where the pair of second ultrasonic transducers 18 and 19 are provided. Specifically, the upstream side of the inner wall surface 17a, distance _{d 1} and 17b has a inner wall surface 17a, 17b 2 times the distance of the spacing _{d 2} of the downstream side. Moreover, the thickness of the side wall of the pipe 17 provided with the pair of second ultrasonic transducers 18 and 19 is equal on the upstream side and the downstream side.

  In the ultrasonic flowmeter 2, the control device 20 is electrically connected to the first ultrasonic transducers 15 and 16 of the first sensor unit 11 and the second ultrasonic transducers 18 and 19 of the second sensor unit 12. It is connected.

  FIG. 3 is a block diagram showing an electrical configuration of the ultrasonic flowmeter 2. As shown in FIG. 3, the control device 20 includes a CPU 21, a first signal processing circuit 22, a second signal processing circuit 23, a memory 24, an input device 25, a display device 26, and a data output circuit 27.

  The first signal processing circuit 22 includes a switching circuit 31, a pulse generation circuit 32, a reception circuit 33, a detection circuit 34, and an A / D conversion circuit 35.

  The switching circuit 31 connects the first ultrasonic transducer 15 on the upstream side of the pair of first ultrasonic transducers 15 and 16 to the pulse generation circuit 32 and receives the first ultrasonic transducer 16 on the downstream side. A first connection position to be connected to the circuit 33 and a second connection for connecting the downstream first ultrasonic transducer 16 to the pulse generation circuit 32 and connecting the upstream first ultrasonic transducer 15 to the reception circuit 33. The connection position can be switched. The connection position in the switching circuit 31 is controlled by a switching signal output from the CPU 21.

  The pulse generation circuit 32 operates in response to a control signal from the CPU 21 and outputs a driving pulse for driving the first ultrasonic transducers 15 and 16. This drive pulse is supplied to the first ultrasonic transducers 15 and 16 via the switching circuit 31. Here, for example, when the switching circuit 31 is switched to the first connection position, a drive pulse is supplied to the first ultrasonic transducer 15 on the upstream side, and the first ultrasonic transducer 15 vibrates. An ultrasonic wave having a predetermined frequency (specifically, a frequency of 1 MHz) is output. The ultrasonic wave propagates in the fluid W of the pipe 14 in the positive direction of the flow of the fluid W and is received by the first ultrasonic transducer 16 on the downstream side. Conversely, when the switching circuit 31 is switched to the second connection position, a drive pulse is supplied to the first ultrasonic transducer 16 on the downstream side, and the first ultrasonic transducer 16 vibrates. Thus, an ultrasonic wave having a predetermined frequency (specifically, a frequency of 1 MHz) is output. The ultrasonic wave propagates in the fluid W of the pipe 14 in the direction opposite to the flow of the fluid W, and is received by the first ultrasonic transducer 15 on the upstream side.

  The reception circuit 33 includes a signal amplification circuit (not shown), amplifies the ultrasonic signal received by each of the first ultrasonic transducers 15 and 16, and then outputs the amplified signal to the detection circuit 34. The detection circuit 34 includes a gate circuit (not shown), extracts an ultrasonic signal for one pulse from the received signal, and outputs it to the A / D conversion circuit 35. The A / D conversion circuit 35 A / D converts an ultrasonic signal that is an analog signal into a digital signal. The CPU 21 takes in the ultrasonic signal after this A / D conversion and temporarily stores it in the memory 24.

  The second signal processing circuit 23 includes a switching circuit 41, a pulse generation circuit 42, a reception circuit 43, a detection circuit 44, an A / D conversion circuit 45, and a timer 46.

  The switching circuit 41 includes a first switch unit 41a and a second switch unit 41b. In the first switch unit 41a, the second ultrasonic transducer 18 on the upstream side and the second ultrasonic transducer 19 on the downstream side are connected. The connection position is switched to either one, and the second switch unit 41 b switches the connection position to one of the pulse generation circuit 42 and the reception circuit 43. The connection position in the switching circuit 41 is also controlled by a switching signal output from the CPU 21.

  The pulse generation circuit 42 operates in response to a control signal from the CPU 21 and outputs a drive pulse for driving the second ultrasonic transducers 18 and 19. The drive pulse is output, for example, every 500 ms, and is alternately supplied to the second ultrasonic transducer 18 on the upstream side and the second ultrasonic transducer 19 on the downstream side via the switching circuit 41. Then, the second ultrasonic transducers 18 and 19 are vibrated by the drive pulse, whereby ultrasonic waves having a predetermined frequency (specifically, a frequency of 1 MHz) are output.

As shown in FIG. 2, the ultrasonic wave S ₀ output from each of the second ultrasonic transducers 18 and 19 propagates to the fluid W flowing through the side wall of the pipe 17. At this time, a part of the ultrasonic wave S ₀ is reflected by the boundary surface (one inner wall surface 17 a of the flow path) between the pipe 17 and the fluid W, and part of the ultrasonic wave S ₀ is propagated into the fluid W. Further, a part of the ultrasonic wave S ₀ propagated through the fluid W is reflected by the boundary surface between the fluid W and the pipe 17 (the other inner wall surface 17 b of the flow path). Here, on the upstream side, the reflected wave S ₀₁ reflected by one inner wall surface 17 a and the reflected wave S ₁₁ reflected by the other inner wall surface 17 b are received by the second ultrasonic transducer 18 and converted into an electronic signal. The Further, on the downstream side, and one of the inner wall surface 17a reflected wave S ₁₂ reflected by the reflection reflected wave S ₀₂ and the other inner wall surface 17b in is received by the second ultrasonic transducer 19 and converted into an electronic signal . The signals of these reflected waves S ₀₁ , S ₁₁ , S ₀₂ , S ₁₂ are supplied to the receiving circuit 43 via the switching circuit 41.

The reception circuit 43 includes a signal amplification circuit (not shown), amplifies the signals of the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , and S ₁₂ received by the second ultrasonic transducers 18 and 19, and then sends them to the detection circuit 44. Output. The detection circuit 44 is a circuit for detecting the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , S ₁₂ of the ultrasonic waves reflected by the inner wall surfaces 17a, 17b in the pipe 17, and is not shown in the figure. Etc. Specifically, the detection circuit 44 extracts the reflected waves _{S 01, S 11, S 02} , S 12 by the gate circuit corresponding to the signal intensity of each reflected wave _{S 01, S 11, S 02} , S 12 The voltage signal is output to the A / D conversion circuit 45. The A / D conversion circuit 45 A / D converts a voltage signal, which is an analog signal, into a digital signal, and the CPU 21 takes in the voltage signal after the A / D conversion, and each reflected wave S ₀₁ , S ₁₁ , S _02. , S ₁₂ , and stored in the memory 24. Further, the detection circuit 44 detects the timing at which the signals of the reflected waves S ₀₁ , S ₁₁ , S ₀₂ and S ₁₂ exceed a predetermined threshold voltage by the comparison circuit, and notifies the timer 46 of the detection signal.

The timer 46 measures the propagation time of the ultrasonic wave S ₀ based on the detection signal output from the detection circuit 44 and outputs data corresponding to the time. The propagation time data is stored in the memory 24 by the CPU 21.

  The CPU 21 executes a control program using the memory 24 and controls the entire apparatus in an integrated manner. The control program includes a program for calculating sound speed, density, flow rate, and the like, a program for specifying the type of fluid W, a program for displaying measurement values, and the like. The program executed by the CPU 21 may be a program stored in a storage medium such as a memory card or a program downloaded via a communication medium, and is read into the memory 24 and used at the time of execution.

  The display device 26 is a liquid crystal display, for example, and is used for displaying measured values such as sound velocity, density, and volume flow rate. The input device 25 includes various operation buttons and is used for starting / ending measurement, setting a display mode, and the like. The data output circuit 27 includes an interface for data output (for example, a port such as RS232), and an external device (for example, a computer that manages various controls in a semiconductor manufacturing line) that does not show data relating to the measured flow rate or fluid type. Output to.

  Next, a specific method for calculating the speed of sound C in the fluid W in the present embodiment will be described.

First, the second sensor unit 12, and outputs an ultrasonic wave S ₀ from the second ultrasonic transducer 18 on the upstream side. Pipe 17 for fluid W and the acoustic impedance consists fluororesin different, a pair of inner wall surfaces 17a, ultrasonic S ₀ at 17b (the boundary surface between the fluid W) reflected respectively. Then, the ultrasonic wave propagation time T1 (= t2−t1) is acquired from the reception times t1 and t2 of the reflected waves S ₀₁ and S ₁₁ (see FIG. 4). Specifically, as shown in FIG. 4, the detection signal from the detection circuit 44 is received at the reception times t1 and t2 of the reflected waves S ₀₁ and S ₁₁ (timing when the waveform signal exceeds a predetermined threshold voltage). Is output. In the timer 46, the time from the received reflected waves S ₀₁ based on the detection signal to the reflected wave S ₁₁ is received is measured, the measured value is acquired as the propagation time T1. Here, since the propagation distance of the ultrasonic wave S ₀ is twice the distance d ₁ (width of the flow path) between the inner wall surfaces 17a and 17b, the propagation distance 2d ₁ is propagated as shown in the following equation (6). By dividing by the time T1, the speed of sound C in the fluid W is obtained.

Further, the sound velocity C in the fluid W can be obtained in the same manner by using the second ultrasonic transducer 19 on the downstream side. It should be noted that in this case, the propagation distance of the ultrasonic wave becomes 2d _2.

Next, a method for calculating the flow rate of the fluid W from the difference in propagation time of the ultrasonic wave S ₀ will be described.

  In the present embodiment, first, in the pair of first ultrasonic transducers 15 and 16 of the first sensor unit 11, for example, a predetermined pattern in the order of the forward direction, the backward direction, the backward direction, and the forward direction every 250 μs. The ultrasonic waves are transmitted from one of the first ultrasonic transducers, and each ultrasonic wave propagated through the fluid W is received by the other first ultrasonic transducer. At this time, the ultrasonic signals converted into electrical signals by the first ultrasonic transducers 15 and 16 are further switched by the first signal processing circuit 22 in the switching circuit 31, the reception circuit 33, the detection circuit 34, and the A / D conversion circuit. After being converted to a digital signal through 35, it is stored in the memory 24 as an ultrasonic waveform signal. In the present embodiment, the waveform signals for four pulses acquired by transmitting and receiving the ultrasonic wave of the predetermined pattern described above are stored in the memory 24 as a data lump for obtaining the flow rate of the fluid W.

  Then, the correlation function of the waveform signal is calculated by comparing the waveform signals of the ultrasonic waves. Specifically, for example, the waveform signal of the first pulse transmitted / received first is compared with the waveform signal of the second pulse transmitted / received next, and a correlation function based on the first pulse is obtained. In addition, the waveform signal of the first pulse and the waveform signal of the third pulse are compared to obtain a correlation function based on the first pulse. Further, the waveform signal of the first pulse and the waveform signal of the fourth pulse are compared to obtain a correlation function based on the first pulse. Similarly, the second pulse waveform signal and the third pulse waveform signal are compared to obtain a correlation function based on the second pulse, and the second pulse waveform signal and the fourth pulse waveform signal are compared. To obtain a correlation function based on the second pulse. Further, the third pulse waveform signal and the fourth pulse waveform signal are compared to obtain a correlation function based on the third pulse.

  Here, when a foreign substance such as a bubble is included in the fluid W flowing through the pipe 14, the ultrasonic wave is irregularly reflected by the foreign substance, so that each received ultrasonic wave has a different waveform. In this case, the correlation value of the correlation function obtained from each waveform signal is considerably smaller than 1. On the other hand, when bubbles are not included in the fluid W, the waveforms of the ultrasonic waves are similar, and the correlation value of the correlation function is a value close to 1 (for example, 0.97). Therefore, in this embodiment, when the correlation value of the correlation function is a value close to 1 (for example, 0.9 or more), it is determined that the waveform signal is effective for measurement. Then, an ultrasonic propagation time difference is obtained based on the waveform signal determined to be valid.

  In the present embodiment, both the first pulse ultrasonic wave and the fourth pulse ultrasonic wave propagate in the fluid W in the positive direction. Therefore, as shown in FIG. 5, the correlation function f1 obtained by comparing the waveform signals of these ultrasonic waves has a temporal deviation of zero. In contrast, the ultrasonic waves of the first pulse and the ultrasonic waves of the second pulse propagate in the forward direction and the reverse direction. For this reason, the correlation function f2 obtained by comparing these ultrasonic waveform signals causes a deviation of the ultrasonic propagation time difference ΔT when compared with the correlation function f1. Therefore, in the present embodiment, the ultrasonic propagation time difference ΔT is obtained based on the time when the correlation value of the correlation function f2 becomes maximum.

  Then, the flow velocity V of the fluid W is obtained by substituting the speed of sound C in the fluid W obtained from the equation (6) and the propagation time difference ΔT into the equation (5). Further, the volume flow rate Q (= V × A) of the fluid W is obtained by multiplying the flow velocity V by the cross-sectional area A of the pipe 14.

  In addition, the flow velocity V measured by the first sensor unit 11 is a measured value at a substantially central portion of the pipe 14. In the pipe 14, the flow rate of the fluid W is disturbed, so that the flow velocity V on the side wall side is slower than the central portion. For this reason, it is necessary to correct the volume flow rate Q in consideration of the flow velocity distribution of the fluid W.

  Moreover, in the fluid supply system 1 of this Embodiment, it is the structure which supplies the fluid W in any one of several types of fluids W1-W4, and the characteristic of a flow changes according to the kind of each fluid W1-W4. . For this reason, it is comprised so that the flow volume correction | amendment according to the kind of the fluids W1-W4 may be performed with respect to the volume flow volume Q calculated based on the flow velocity V. FIG.

The flow velocity distribution (the characteristics of the flow of the fluid W) in the pipe 14 is determined by the Reynolds number Re represented by the following equation (7).

Here, V is a characteristic flow velocity, L ₁ is a characteristic length, and is a kinematic viscosity coefficient. The characteristic length L ₁ is a length determined by the shape of the pipe 14. When the flow rate of the fluid W is measured with the pipe 14 having a predetermined shape, the Reynolds number Re changes in proportion to the flow velocity V of the fluid W and inversely proportional to the kinematic viscosity coefficient. Accordingly, a difference occurs in the flow velocity distribution in the pipe 14 depending on the kinematic viscosity coefficient of the fluid W, and an error is generated accordingly and the measured value changes.

Table 1 shows data relating to the sound speed C, density ρ, and kinematic viscosity coefficient of a plurality of types of chemical solutions. Here, pure water, hydrofluoric acid, hydrochloric acid, aqueous ammonia solution, and hydrogen peroxide solution at 20 ° C. are shown as specific examples of the chemical solution.

As shown in Table 1, since the density ρ of pure water and hydrofluoric acid is 1.00 g / cm ³ , it is possible to specify whether the fluid W is pure water or hydrofluoric acid only by the density ρ. Although difficult, the fluid W can be specified by measuring the sound velocity C simultaneously. Even if the measured sound velocity C of the fluid W is 1493 m / s, it may be difficult to determine whether the fluid W is pure water or an aqueous ammonia solution due to a measurement error, but by simultaneously measuring the density ρ, The fluid W can be reliably identified.

  Therefore, in the ultrasonic flowmeter 2 of the present embodiment, the density ρ is obtained in addition to the sound velocity C of the fluid W, and the type of the fluid W flowing in the fluid output conduit 7 is determined based on the sound velocity C and the density ρ. The flow rate is corrected according to the specified type. In the present embodiment, data relating to a plurality of types of chemical solutions as shown in Table 1 is stored in advance in the memory 24 as data for performing flow rate correction.

  Hereinafter, a method for calculating the density ρ of the fluid W will be described.

In the second sensor unit 12, an ultrasonic _{S 0} emitted from the second ultrasonic transducer 18, 19, reflected at the boundary surface between a portion of the pipe 17 and the fluid W (the inner wall surface 17a, 17b) (See FIG. 2). The signal intensities of the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , and S _{12 on} the inner wall surfaces 17a and 17b have the following relationships (8) and (9).

Here, α is the attenuation constant of the fluid W, Z ₀ is the acoustic impedance of the fluororesin constituting the pipe 17, and Z _f is the acoustic impedance of the fluid W.

From these equations (8) and (9), the acoustic impedance Z _f of the fluid W can be obtained based on the signal intensity of each reflected wave S ₀₁ , S ₁₁ , S ₀₂ , S ₁₂ and the acoustic impedance Z _0. .

The density ρ of the fluid W is obtained by the following equation (10) based on the acoustic impedance _Zf and the sound velocity C.

  Further, in the ultrasonic flowmeter 2 of the present embodiment, the relationship between the measurement error of the flow rate Q measured by the first sensor unit 11 depends on the flow rate Q and the kinematic viscosity coefficient of the fluid W flowing in the pipe 14. The memory 24 stores the correction formulas and correction table data created according to the relationship. Then, the flow rate Q corresponding to the type of the fluid W is accurately measured by correcting the measurement error of the flow rate Q using the kinematic viscosity coefficient of the fluid W specified by using the sonic velocity C and the density ρ of the fluid W. Like to do.

  Next, in the present embodiment, a processing example for measuring the sound velocity C and density ρ of the fluid W will be described with reference to the flowchart of FIG. 6 is started when an operator operates a start button provided on the input device 25.

First, the CPU 21 operates the pulse generation circuit 42 of the second signal processing circuit 23 to output a drive pulse, for example, every 500 ms, and switches the connection position of the switching circuit 41 so that the upstream side in the second sensor unit 12 is switched. Drive pulses are sequentially supplied to the second ultrasonic transducer 18 and the downstream second ultrasonic transducer 19 (step 100). Thereby, the ultrasonic waves S ₀ are irradiated from the second ultrasonic transducers 18 and 19, and the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , and S ₁₂ reflected by the inner wall surfaces 17 a and 17 b of the flow path are reflected. An electric signal is extracted by the detection circuit 44. Then, the CPU 21 takes in the data converted by the A / D conversion circuit 45 and stores it in the memory 24 as data of the signal intensity of the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , S ₁₂ . At this time, the ultrasonic wave propagation time T1 is measured by the timer 46 based on the reception timing of the reflected waves S ₀₁ and S ₁₁ , and the data of the propagation time T 1 is stored in the memory 24.

Then, CPU 21 of the sound velocity calculation means, based on the propagation distance 2d ₁ and the propagation time T1 of the ultrasonic wave, it obtains the sound speed C of the fluid W (step 110). Further, the CPU 21 as the acoustic parameter calculation means, based on the signal intensity of each reflected wave S ₀₁ , S ₁₁ , S ₀₂ , S ₁₂ and the acoustic impedance Z _{0 of the} pipe 17 (fluororesin), _Zf is obtained (step 120). Further, CPU 21 calculates the density ρ of the fluid W by dividing the acoustic impedance _{Z f} of the fluid W at the speed of sound C (step 130).

  Thereafter, the CPU 21 determines whether or not to continue the density ρ measurement process (step 140). Specifically, the CPU 21 determines whether or not the end button of the input device 25 is operated. When the end button is not operated, the CPU 21 returns to the process of step 100 and performs the processes of steps 100 to 140. Again. And when the end button of the input device 25 is operated, CPU21 complete | finishes the process of FIG.

  Next, a processing example for measuring the flow rate of the fluid W in the present embodiment will be described with reference to the flowchart of FIG. The process of FIG. 7 is executed after the sound speed C and density ρ of the fluid W are measured by the process of FIG.

  First, the CPU 21 operates the pulse generation circuit 32 of the first signal processing circuit 22 to output a drive pulse every 250 μs, and switches the connection position of the switching circuit 31, so that the first ultrasonic transducer 15 on the upstream side is switched. And a drive pulse is sequentially supplied with respect to the 1st ultrasonic transducer | vibrator 16 of the downstream (step 200). Thereby, in each 1st ultrasonic transducer | vibrator 15, 16, the transmission / reception of an ultrasonic wave is performed by the predetermined pattern which becomes a forward direction, a reverse direction, a reverse direction, and the order of a forward direction. The ultrasonic signals received by the first ultrasonic transducers 15 and 16 are digitally transmitted through the switching circuit 31, the receiving circuit 33, the detection circuit 34, and the A / D conversion circuit 35 in the first signal processing circuit 22. Converted to a signal. The CPU 21 sequentially takes in the ultrasonic signals after the A / D conversion and stores them in the memory 24 as ultrasonic waveform signals. Here, the waveform signals for the four pulses of the predetermined pattern described above are stored in the memory 24.

  Thereafter, the CPU 21 reads the waveform signals of the respective ultrasonic waves, compares the waveform signals, and calculates a correlation function (step 210). Then, the CPU 21 determines whether or not the waveform signal is effective for measurement based on the correlation value of the correlation function of the waveform signal (step 220). Specifically, when the correlation value of the correlation function is a predetermined threshold value (for example, 0.9) or more, the CPU 21 determines that the waveform signal is effective for measurement, and stores the waveform signal data in the memory. Leave to 24. On the other hand, when it is smaller than the predetermined threshold, at least one of the compared waveform signals is a waveform signal that is invalid for measurement. In this case, the CPU 21 specifies a waveform signal that is invalid for measurement by using a correlation function obtained by comparison with another waveform signal, and deletes the waveform signal data from the memory 24. Then, in the four-pulse ultrasonic wave, it is determined that both the waveform signals of the first pulse and the fourth pulse in the forward direction or the waveform signals of the second pulse and the third pulse in the reverse direction are invalid waveform signals. In such a case, it is determined that there is foreign matter in the liquid, and the CPU 21 displays that fact on the display device 26 (step 230). Thereafter, the CPU 21 returns to the process of step 200 and performs transmission / reception of ultrasonic waves in a predetermined pattern again.

  On the other hand, it is determined that at least one of the waveform signals of the first pulse and the fourth pulse in the forward direction is valid, and at least one of the waveform signals of the second pulse and the third pulse in the reverse direction is determined to be valid. In this case, the CPU 21 obtains a propagation time difference ΔT between the ultrasonic wave propagated in the forward direction and the ultrasonic wave propagated in the reverse direction based on the correlation function of the waveform signal determined to be valid (step 240).

  Furthermore, the CPU 21 obtains the flow velocity V of the fluid W by performing an operation corresponding to the equation (5) using the sound velocity C of the fluid W obtained in the process of FIG. 6 and the propagation time difference ΔT obtained in step 240. Further, the volume flow rate Q of the fluid W is obtained by multiplying the flow velocity V by the cross-sectional area A of the pipe 14 (step 250).

  Further, the CPU 21 as the fluid specifying means specifies the type of the fluid W by referring to the data stored in the memory 24 based on the sound speed C and the density ρ of the fluid W obtained in the processing of FIG. (Step 260).

  Thereafter, the CPU 21 serving as the flow rate correction means reads kinematic viscosity coefficient data corresponding to the identified type of the fluid W from the memory 24 and corrects the flow rate Q using the data (step 270). Here, the correction rate is obtained using the correction curve data indicating the relationship between the correction coefficient according to the kinematic viscosity coefficient and the flow rate Q before correction calculated in step 250, and the flow rate Q before correction is determined by the correction rate. By correcting, the corrected flow rate Q is obtained.

  Thereafter, the CPU 21 displays the corrected flow rate Q on the display device 26 (step 280). At this time, in addition to the flow rate Q, information regarding the type of the specified fluid W may be displayed on the display device 26. In addition, at the time of a request from the external device, information on the corrected flow rate Q and the specified type of fluid W is transferred from the data output circuit 27 to the external device.

  Then, the CPU 21 determines whether or not to continue the flow rate Q measurement process (step 290). Specifically, the CPU 21 determines whether or not the end button of the input device 25 is operated. When the end button is not operated, the CPU 21 returns to the process of step 200 and performs the processes of step 200 to step 290. Again. Then, when the end button of the input device 25 is operated, the CPU 21 ends the process of FIG.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the fluid supply system 1 of the present embodiment, the ultrasonic flowmeter 2 determines the sonic velocity C and the density ρ of the fluid W flowing through the fluid output conduit 7. The type of the fluid W can be specified based on this. And the flow volume correction | amendment according to the kind of the specified fluid W can be performed exactly. In this way, the flow rate Q of a plurality of types of fluids W1 to W4 can be accurately measured without providing a flow meter for each of the plurality of fluid supply pipes 3 to 6, and the component cost of the system 1 Can be reduced.

  (2) In the ultrasonic flowmeter 2 of the present embodiment, the corrected flow rate Q and the type of the specified fluid W are displayed on the display device 26, so that the operating state of the liquid supply system 1 can be accurately grasped. can do.

  (3) Since the ultrasonic flowmeter 2 of the present embodiment can measure not only the flow rate Q of the fluid W but also the sound velocity C and density ρ of the fluid W, an abnormality in the production line can be detected based on these measurement information. It becomes possible to detect promptly.

(4) In the ultrasonic flowmeter 2 of the present embodiment, the correlation function of the waveform signal is calculated and acquired in a normal state in which no foreign matter is contained in the fluid W based on the correlation value of the correlation function. It can be determined whether the waveform signal is valid. Then, based on the waveform signal determined to be valid, the ultrasonic propagation time difference ΔT is obtained, and the flow rate Q of the fluid W is obtained from the propagation time difference ΔT. Thus, since the flow rate Q can be calculated using only a highly reliable waveform signal, the measurement accuracy can be sufficiently increased.
[Second Embodiment]

  Next, a second embodiment of the present invention will be described with reference to the drawings. The fluid supply system 1 of the present embodiment is a system that supplies a fluid W (for example, an ethanol aqueous solution) whose concentration and flow rate are adjusted, and is used, for example, to control the power generation efficiency of a fuel cell.

  As shown in FIG. 8, the fluid supply system 1 includes an ultrasonic flow meter 2, a fluid supply pipe 51 provided with the ultrasonic flow meter 2, and a concentration adjuster 52 (concentration adjusting means). , A supply tank 53 for supplying a fluid W having a predetermined concentration to the fluid supply pipe 51, a flow rate adjusting valve 54 (flow rate adjusting means) provided in the middle of the fluid supply pipe 51, a concentration adjuster 52, and a flow rate adjuster. And a controller 55 (control means) for controlling the valve 54. In the fluid supply system 1 of the present embodiment, the fluid W is supplied in a state where the temperature is adjusted to a constant temperature (for example, 20 ° C.).

  In the fluid supply system 1, the controller 55 controls the concentration adjuster 52 so that the concentration of the fluid W in the supply tank 53 is adjusted to a preset concentration. Then, the fluid W after the concentration adjustment is supplied from the supply tank 53 to the fluid supply pipe 51. Further, the controller 55 controls the opening degree of the flow rate adjusting valve 54 so that the flow rate of the fluid W flowing through the fluid supply conduit 51 is adjusted to a preset flow rate.

  The ultrasonic flowmeter 2 of the present embodiment has the same configuration as that of the first embodiment, and includes a first sensor unit 11 and a second sensor unit 12. In the ultrasonic flowmeter 2, the density ρ of the fluid W flowing through the fluid supply pipe 51 is obtained, and the concentration of the fluid W is obtained based on the density ρ.

Table 2 shows data on the concentration X, the speed of sound C, the density ρ, and the kinematic viscosity coefficient of the ethanol aqueous solution. FIG. 9 shows the relationship between the concentration X of the aqueous ethanol solution at 20 ° C., the sound velocity C, the density ρ, the viscosity η, and the kinematic viscosity coefficient.

  In the ultrasonic flow meter 2 of the present embodiment, data relating to the sound velocity C, density ρ, and kinematic viscosity coefficient corresponding to the concentration X of the aqueous ethanol solution is stored in the memory 24. Then, the concentration X of the fluid W is specified based on the density ρ of the fluid W obtained by the second sensor unit 12. Then, a kinematic viscosity coefficient is calculated based on the concentration X of the fluid W. Further, the ultrasonic flow meter 2 corrects the measurement error of the flow rate measured by the first sensor unit 11 using the kinematic viscosity coefficient of the fluid W. Thereby, the flow volume according to the density | concentration X of the fluid W can be measured correctly.

  Here, when the flow rate correction is performed by obtaining the kinematic viscosity coefficient of the ethanol aqueous solution only with the sonic velocity C as in the prior art, the measured sonic velocity C of the fluid W is, for example, 1500 m / s as shown in FIG. If it exists, it cannot be judged whether the density | concentration X of ethanol aqueous solution is 5% or 50%. Here, if an ethanol aqueous solution having a concentration of 50% is mistakenly determined to be a concentration of 5%, the numerical value of 1.1 cSt is used even though the actual fluid W has a fluid viscosity coefficient of about 2.28 cSt. The flow rate is corrected, and the measurement error becomes large. On the other hand, if the density ρ is calculated and the density ρ is used as in the present embodiment, the concentration X of the aqueous ethanol solution and its kinematic viscosity coefficient are uniquely determined. Can be resolved.

Further, the ultrasonic flowmeter 2 outputs the measured concentration W and flow rate Q of the fluid W to the controller 55. Then, the controller 55 controls the concentration adjuster 52 and the flow rate adjusting valve 54 based on the concentration X and the flow rate Q. When the fluid supply system 1 is configured in this manner, the concentration X and the flow rate Q of the fluid W flowing in the fluid supply pipe 51 can be accurately controlled without separately providing a flow meter and a concentration meter. The component cost of the system 1 can be reduced.
[Third Embodiment]

  Next, a third embodiment of the present invention will be described with reference to the drawings. The present embodiment is different from the first embodiment in that the configuration of the pipe 17 of the second sensor unit 12 in the ultrasonic flowmeter 2 is changed. In the ultrasonic flowmeter 2 of the present embodiment, the configuration other than the second sensor unit 12 (such as the electrical configuration of the first sensor unit 11 and the control device 20) is the same as that of the first embodiment. is there.

Specifically, as shown in FIG. 10, the pipe 17 of the second sensor unit 12 in the present embodiment is formed of pipe members 57 and 58 having different acoustic impedances on the upstream side and the downstream side. Further, the interval d ₁ (width of the flow path) between the inner wall surfaces 17a and 17b in the pipe 17 is formed equal on the upstream side and the downstream side.

In this case, if the acoustic impedance of the upstream piping member 57 is Z ₀₁ and the acoustic impedance of the downstream piping member 58 is Z ₀₂ , the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , S _12, the following equation (11), holds the relationship (12).

Then, according to the equations (11) and (12), the acoustic impedance Z of the fluid W is calculated based on the signal intensity of each reflected wave S ₀₁ , S ₁₁ , S ₀₂ , S ₁₂ and the acoustic impedances Z ₀₁ , Z _{02. f} can be obtained. Furthermore, the sound velocity C of the fluid W can be determined in the same manner as the first embodiment, it is possible to obtain the density ρ of the fluid W by its sound velocity C and the acoustic impedance Z _f.
[Fourth Embodiment]

  Next, a fourth embodiment embodying the present invention will be described. This embodiment is also different from the first embodiment in that the configuration of the pipe 17 in the second sensor unit 12 is changed. In the ultrasonic flowmeter 2 of the present embodiment, other configurations (such as the electrical configuration of the first sensor unit 11 and the control device 20) are the same as those of the first embodiment.

Specifically, as shown in FIG. 11, the pipe 17 of the second sensor unit 12 in the present embodiment is formed in a rectangular shape, and one of the second ultrasonic transducers 18 has a first outer surface. The second ultrasonic transducer 19 is disposed on the wall surface 17e (the outer wall surface on the short side in FIG. 11), and the other second ultrasonic transducer 19 is a second outer wall surface 17f (the long side in FIG. 11) orthogonal to the first outer wall surface 17e. It is arranged on the side outer wall surface. Moreover, the thickness of the side wall in which the pair of second ultrasonic transducers 18 and 19 are arranged in the pipe 17 is equal, and the flow path formed in the pipe 17 has a horizontal width d ₁ (inner wall surface 17a, 17b) is twice the vertical width d ₂ (the distance between the inner wall surfaces 17c and 17d). In addition, in the piping 17 of FIG. 11, the fluid W flows in the depth direction from the near side of the drawing.

Thus case where the second sensor unit 12, the reflected wave _S 01 reflected by the inner wall surfaces _{17a, 17b, 17c, 17d,} S 11, S 02, S 12 is the above equation (8), (9) The relationship holds. Therefore, also in this embodiment, as in the first embodiment, it is possible to obtain the acoustic impedance Z _f of the fluid W, further, it is possible to obtain the density ρ of the fluid W. In addition, unlike the first embodiment, each ultrasonic transducer 18 and 19 does not need to be shifted in the flow direction of the fluid W (upstream side or downstream direction), so that the ultrasonic flowmeter 2 can be formed compactly.

  In addition, you may change each embodiment of this invention as follows.

In the third embodiment, the upstream side and the downstream side of the pipe 17 in the second sensor unit 12 are formed by the pipe members 57 and 58 having different acoustic impedances Z ₀₁ and Z ₀₂ . As shown in FIG. 12, a part of the inner wall surface 17 b serving as an ultrasonic reflection surface may be formed by a reflection plate 59 made of a material having an acoustic impedance different from that of the pipe 17. Even when the second sensor portion 12 is formed in this way, the acoustic impedance of the fluid W flowing through the pipe 17 is based on the signal strength of the reflected waves S ₀₁ , S ₁₁ , S ₀₂ , S _{12 on} the inner wall surfaces 17a, 17b. _Zf and density ρ can be obtained.

In each of the above-described embodiments, the sound velocity C of the fluid W is obtained using the second ultrasonic transducers 18 and 19 in the second sensor unit 12 of the ultrasonic flowmeter 2, but the present invention is not limited to this. It is not a thing. For example, the sound velocity C of the fluid W may be obtained from the difference in ultrasonic propagation time using the first ultrasonic transducers 15 and 16 of the first sensor unit 11. A specific calculation method will be described. In the ultrasonic flowmeter 2, when the flow path length of the first sensor unit 11 is L, the sound velocity C of the fluid W, and the flow velocity V, the propagation time Td of the ultrasonic wave propagated in the forward direction of the flow of the fluid W is opposite. The propagation time Tu of the ultrasonic wave propagated to can be expressed by the above formulas (1) and (2). Therefore, the sound velocity C can be expressed as the following equation (13) by these equations (1) and (2).

Therefore, by measuring the propagation times Td and Tu of the ultrasonic waves propagating in the forward and reverse directions in the first sensor unit 11 and substituting the propagation times Td and Tu into the above equation (13), the calculation of the fluid W The speed of sound C can be obtained. Then, the acoustic impedance _Zf and density ρ of the fluid W can be obtained using the sound velocity C as in the above embodiments.

In the first embodiment, the type of the fluid W is specified by the density ρ and the sound speed C, but the present invention is not limited to this. It may be configured to identify the type of fluid W by using the acoustic impedance Z _f in place of the density [rho. However, in this case, data on the sound speed C, acoustic impedance Z _f , and kinematic viscosity coefficient of a plurality of types of fluid W is stored in the memory 24, and the type of the fluid W is specified using the data. Further, depending on the type of fluid W to be used, the identification may be possible only with the density ρ and the acoustic impedance Z _f , and in this case, the calculated density ρ and the acoustic impedance Z _f without using the sound velocity C. The fluid W may be specified by the above. Also in the second embodiment, be configured to determine the concentration X of the fluid W by using the acoustic impedance Z _f in place of the density ρ Well, speed of sound in addition to the density ρ and the acoustic impedance Z _f C May be used to determine the concentration X of the fluid W.

  In each of the above embodiments, the fluid supply system 1 or 1A is maintained in which the temperature is kept constant (for example, 20 ° C.). However, the present invention is not limited to this. When the temperature of the fluid W changes, a temperature sensor 56 (temperature detection means) such as a thermistor is provided in the middle of the pipe 14 of the first sensor unit 11 or the pipe 17 of the second sensor unit 12 (see FIG. 13). The temperature of the fluid W is measured simultaneously with the density ρ of the fluid W. Further, data such as density ρ and kinematic viscosity coefficient according to temperature are stored in the memory 24. Then, the data according to the temperature detected by the temperature sensor 56 is referred to, and if necessary, the density ρ and the kinematic viscosity coefficient are obtained by performing calculations such as interpolation and linear approximation. In this way, even when the temperature of the fluid W changes, the type of the fluid W can be reliably identified, and the flow rate correction according to the temperature can be performed.

  In each of the above embodiments, the pair of ultrasonic transducers 15 and 16 are arranged in the first sensor unit 11 so that the ultrasonic wave propagates in a direction parallel to the flow of the fluid W. However, the present invention is not limited to this. Is not to be done. For example, the ultrasonic transducers 15 and 16 may be provided so that ultrasonic waves propagate at a predetermined angle (for example, an angle of 45 °) with respect to the flow direction of the fluid W.

  In each of the above embodiments, the correlation function of the waveform signal is obtained and the waveform signal effective for measurement is determined based on the correlation value. However, the present invention is not limited to this. For example, when measuring a fluid W that does not include bubbles or the like, a highly reliable waveform signal can be reliably acquired, so there is no need to calculate a correlation function, and the acquired waveform signal is used as it is to determine the propagation time difference. It may be calculated.

In each of the above embodiments, the first sensor unit 11 may be omitted, and the second sensor unit 12 and the control device 20 may be embodied as an ultrasonic measuring instrument that measures the concentration X or kinematic viscosity coefficient of the fluid W. Good. In the ultrasonic measuring instrument, it is possible to determine the concentration X or kinematic viscosity coefficients using two parameters of sound velocity C and the acoustic impedance Z _f of the fluid W obtained by the second sensor unit 12 accurately.

In each of the above embodiments, the ultrasonic flowmeter 2 is used for the liquid supply system 1 of the semiconductor manufacturing line and the liquid supply system 1 of the fuel cell, but the present invention is not limited to this. For example, by using an ultrasonic flowmeter 2 in such apparatus for advancing a predetermined chemical reaction, determined acoustic impedance Z _f concentration X and fluid W components that contribute to the reaction in the fluid W, progress of the reaction Or the reaction efficiency may be grasped.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the respective embodiments described above are listed below.

  (1) The means 1 further includes temperature detecting means provided in the pipe and detecting the temperature of the fluid flowing through the pipe, and the storage means stores the acoustic parameter data according to the temperature of the fluid. And the fluid specifying means specifies the type of the fluid by referring to data corresponding to the temperature detected by the temperature detecting means.

  (2) In the technical idea (1), the flow rate correction unit corrects the flow rate of the fluid based on the type of the fluid and the temperature of the fluid.

  (3) In the means 1, the storage means stores fluid viscosity or kinematic viscosity coefficient data corresponding to the acoustic parameters for a plurality of types of fluids, and the fluid correction means specifies the flow rate correction means. An ultrasonic flowmeter, wherein a viscosity or a kinematic viscosity coefficient of the fluid is calculated based on the data corresponding to a type of fluid, and the flow rate is corrected based on the calculation result.

  (4) In the means 2, the fluid specifying means specifies the type of the fluid based on one of the acoustic parameters of the acoustic impedance and the density, or the acoustic parameter and the speed of sound. Ultrasonic flow meter.

  (5) The ultrasonic flowmeter according to (1) or (2), further comprising display means for displaying the corrected flow rate and the information of the specified fluid type.

DESCRIPTION OF SYMBOLS 1 ... Fluid supply system 2 ... Ultrasonic flowmeter 3-6, 51 ... Fluid supply line 7 ... Fluid output line 9 ... Switching valve as switching means 11 ... 1st sensor part 12 ... 2nd sensor part 14 ... Pipe constituting pipe 17 ... Pipe constituting pipe 17a, 17b, 17c, 17d ... Inner wall surface 20 ... Control device as control means 21 ... Sonic velocity calculation means, flow rate calculation means, acoustic parameter calculation means, fluid identification And CPU as flow rate correction means
DESCRIPTION OF SYMBOLS 24 ... Memory as memory | storage means 52 ... Concentration adjuster as density | concentration adjustment means 54 ... Flow rate adjustment valve as flow-rate adjustment means 55 ... Controller as control means

Claims (3)

An ultrasonic wave that is provided in a pipe that forms a flow path for flowing a fluid, propagates in the forward and reverse directions of the fluid flow in the pipe, and propagates in the opposite direction to the ultrasonic wave that propagates in the forward direction. And a first sensor unit for detecting the propagation time difference between them,
A second sensor for detecting the signal intensity and propagation time of the ultrasonic wave that is provided in the pipe, propagates the ultrasonic wave to the fluid flowing through the pipe, receives the ultrasonic wave reflected by the inner wall surface of the pipe, and And
A flow rate calculating means for calculating a flow rate of the fluid flowing through the flow path based on a propagation time difference of the ultrasonic wave detected by the first sensor unit ;
A sound velocity calculating means for obtaining a sound velocity of the fluid based on a propagation time of the ultrasonic wave detected by the first sensor unit or the second sensor unit and a propagation distance of the ultrasonic wave;
Acoustic impedance calculation means for obtaining the acoustic impedance of the fluid based on the signal intensity of the reflected wave detected by the second sensor unit and the acoustic impedance of the material constituting the pipe ;
Density calculating means for calculating the density of the fluid based on the acoustic impedance of the fluid and the speed of sound obtained by the acoustic impedance calculating means;
Storage means for storing flow rate correction data defining the relationship among the three types of fluid velocity, density and kinematic viscosity coefficient for each of the plurality of types of fluids ;
Based on the data, the sound velocity of the fluid calculated by the acoustic parameter calculation unit, and the density of the fluid calculated by the density calculation unit, a fluid identification unit that identifies the type of fluid flowing through the conduit;
Ultra before Symbol flow rate calculation means of the flow rate of the fluid is calculated, characterized in that the fluid specific means and a flow rate correction means for correcting using kinematic viscosity coefficient corresponding to the type of the identified said fluid Sonic flow meter. The ultrasonic flowmeter according to claim 1 ;
A plurality of fluid supply pipes to which a plurality of types of fluids are respectively supplied;
A fluid output conduit provided with the ultrasonic flowmeter;
The plurality of fluid supply conduits and fluid output conduits are connected, and any one of a plurality of types of fluids supplied from the fluid supply conduits is supplied to the fluid output conduit. Switching means for supplying to
The ultrasonic flowmeter is characterized by specifying a type of fluid that is selectively supplied into the fluid output conduit via the switching unit, and correcting the flow rate of the fluid according to the specified type. Fluid supply system. The ultrasonic flowmeter according to claim 1 ;
A fluid supply conduit in which the ultrasonic flowmeter is provided;
Concentration adjusting means for adjusting the concentration of the fluid supplied to the conduit;
A flow rate adjusting means for adjusting a flow rate of the fluid supplied to the conduit;
Control means for controlling the concentration adjusting means and the flow rate adjusting means,
The ultrasonic flowmeter obtains the concentration of the fluid flowing through the pipe line, obtains the flow rate of the fluid, and outputs the concentration and the flow rate to the control means.

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