JP4634270B2 - An anemometer using a surface acoustic wave device, its element, and a method for measuring the velocity - Google Patents

Description

  The present invention relates to a flowmeter using a surface acoustic wave element, for example, a small-sized flowmeter that has durability and can detect changes in pressure and density.

  An anemometer based on the general atmosphere is used to measure the velocity of gas flow. This is a kind of anemometer. On the other hand, a flow meter is, for example, a mass flow meter that measures how much mass of gas is flowing in a predetermined cross section in a certain time. Flowmeters and velocimeters measure the total amount flowing from a certain point, with liquid meters generally measuring liquids whose density does not change significantly, whereas flowmeters are localized or their distribution. As for the point which shows the movement speed of the substance as. Assuming a constant cross section through which the fluid flows, the value obtained by integrating the product of the velocity and density crossing in the normal direction of the cross section over the cross section is the flow rate.

  For example, when the base material closes the pipe cross section inside the pipe, the actual speed of the fluid flowing on the base surface increases, but this speed is perpendicular to the cross section of the pipe cross section of the part where the base material inside the pipe is not plugged. Although the value is different from the average value of the flow velocity of the fluid, it changes according to the change in the flow velocity or flow rate of the fluid flowing in the pipe.

  The present invention can also be used for flow rate measurement, and does not distinguish whether the measurement target is a flow rate or whether the flow rate is a measurement target. It shall be called. Any method may be used as long as the degree of flow is measured by utilizing the outflow of the heat amount of the base material as the fluid moves in the space where the base material is disposed.

  Furthermore, even if the actual flow rate is constant, the present invention detects the change in the amount of heat that loses the change even if the density of the surrounding fluid changes or fluids with different thermal conductivities flow. Also in this case, as long as the flow state of the fluid is detected by the heat outflow rate from the base material, it is not excluded.

  When the pressure changes and the density changes, the flow meter naturally indicates a different flow rate, but the flow rate shows the same value if the moving speed of the medium is the same. When a gas is handled, a density distribution is generated spatially depending on the momentum of the gas, so that it is necessary to measure the flow velocity distribution.

  That is, it is desired to measure the density and flow of the fluid independently when controlling or measuring the flow of the fluid.

Regarding the flow velocity, a hot-wire anemometer or the like has been conventionally known (for example, see Patent Document 1). In view of this, it has been considered to use such an anemometer to determine the flow velocity of hydrogen gas or the like in the pipe.
JP 2000-266773 A

  In recent years, a microfluidic chip has been studied as a process using a very small amount of liquid material, and studies have been made to make a complicated process small. A process using a small amount of gaseous material has also been developed. In a very small amount of gas analyzer or odor analysis, the flow rate of a very small amount of gas is controlled using a piston or a rotary pump, but it is difficult to downsize the device for measuring the flow rate.

  In addition, in the measurement of flow velocity (flow rate), miniaturization has been achieved by incorporating a very small heater and a very small temperature measurement mechanism using micromachine technology, but it is more robust and durable. A system is needed.

However, the mass flow rate of hydrogen gas or the like cannot be obtained only with the conventional anemometer (velocimeter) as described above. That is, the mass flow rate of the gas in the pipe is
Mass flow rate = (Density x Cross-sectional area) x Flow velocity (1)
It is calculated based on the following formula. Density is approximately proportional to pressure.

  Under such circumstances, when trying to measure and control the flow of fluid (especially gas), any two of density, flow velocity, and flow rate must be measured. In addition to the size of the flow meter itself, a pressure gauge or the like for determining the density (pressure) is also required. As a result, there arises a problem that the entire measuring apparatus becomes large.

  When the entire measuring device becomes large, it may not be used as a measuring device for piping mounted on an automobile or the like. For example, when considering mounting a fuel cell as the power of an automobile, a pipe having a diameter of 5 mm or less is required. Therefore, the sensor part that directly measures hydrogen gas or the like in the measuring device is required to have a diameter of 5 mm or less. In this regard, in the conventional anemometer, the sensor portion has a size of about 1 cm or more, and it is difficult to install it on the pipe.

  Further, a flow meter that measures the flow rate of hydrogen gas or the like is required to have durability. That is, if hydrogen gas is leaking and an accurate flow rate value cannot be measured, an explosion cannot be predicted and it is extremely dangerous. In this regard, the sensor part of the conventional anemometer is made of wire and is fragile.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a small-sized current meter having durability.

  The present invention takes the following means in order to solve the above problems.

The invention corresponding to claim 1 is a flowmeter that uses a surface acoustic wave element to obtain a flow velocity of a fluid flowing therearound, and the surface acoustic wave element is a circle capable of propagating by making multiple rounds of surface acoustic waves. A three-dimensional substrate having an annular propagation surface; heating means formed on the surface of the three-dimensional substrate for heating the substrate based on a heating control signal from the anemometer body; and an excitation control signal from the anemometer body And a detecting means for detecting the surface acoustic wave that circulates around the propagation surface and outputting a detection signal. A heating control means connected to the surface wave element to send and control a heating control signal to the heating means so as to heat the base material, and an elastic surface on the propagation surface of the base material heated by the heating means To the excitation means to excite the wave Excitation control means for sending and controlling an initiation control signal, acquisition means for acquiring temperature information from the rotation speed or phase information obtained from the detection signal of the surface acoustic wave output from the detection means, and data of the detection signal Temperature measurement means for measuring the temperature of the propagation surface, and flow rate calculation means for calculating the flow rate of the substance based on the temperature information and the heating amount obtained by the temperature measurement means, and the flow rate The meter body is used in the pipe where the fluid flows, and it is possible to measure the density or pressure of the fluid according to the measurement of the amount of attenuation accompanying the circulation of the surface acoustic wave that circulates around the surface of the three-dimensional substrate. An anemometer.

According to a second aspect of the present invention, there is provided a surface acoustic wave device used in the anemometer according to the first aspect, wherein the heating means is a base material by thermally absorbing energy associated with the circulation of the surface acoustic wave on the propagation surface. It is a velocimeter using the surface acoustic wave element characterized by heating.

According to a third aspect of the present invention, in the surface acoustic wave device used in the anemometer according to the first or second aspect, the three-dimensional base material includes a cavity having the propagation surface on the inner surface. Is a velocity meter using a surface acoustic wave element characterized by

The invention corresponding to claim 4 is the surface acoustic wave device used for the anemometer according to any one of claims 1 to 3 , wherein the annular propagation surface of the three-dimensional substrate has a spherical shape. This is a flowmeter using a surface acoustic wave element.

The invention corresponding to claim 5 is the surface acoustic wave device used in the anemometer according to any one of claims 1 to 4 , wherein the three-dimensional substrate is made of a piezoelectric material, and the excitation means Is a surface acoustic wave element comprising interdigital electrodes formed on the piezoelectric material.

The invention corresponding to claim 6 includes a three-dimensional substrate having an annular and spherical propagation surface capable of propagating a surface acoustic wave by multiple wrapping, and heating means for heating the substrate based on a heating control signal. A surface acoustic wave device comprising: excitation means for exciting a surface acoustic wave on the propagation surface based on an excitation control signal; and detection means for detecting a surface acoustic wave that circulates the propagation surface and outputting a detection signal. A heating control step of sending and controlling a heating control signal to the heating means so as to heat the three-dimensional base material, and a propagation surface of the base material heated by the heating means, An excitation control step for sending and controlling an excitation control signal to the excitation means so as to excite the surface acoustic wave, and temperature information from the revolving speed or phase information obtained from the detection signal of the surface acoustic wave output by the detection means A flow rate calculation for calculating the flow rate of the substance based on the acquisition step to be acquired, the temperature measurement step of the propagation surface based on the data of the detection signal, the temperature information obtained by the temperature measurement step, and the heating amount A flow velocity measurement comprising: a step; and a step of measuring the density or pressure of the fluid in accordance with the measurement of the amount of attenuation accompanying the circulation of the surface acoustic wave that circulates around the surface of the three-dimensional substrate in a pipe through which the fluid flows Is the method.

<Terminology>
Here, in the present invention, the wave described as “surface acoustic wave” is a boundary wave, a corridor wave, a surface wave that circulates the inner shell, a surface acoustic wave, a leaky surface acoustic wave, a pseudo surface acoustic wave, a pseudo leak It includes all surface acoustic waves that propagate by concentrating energy on a spherical surface, such as surface acoustic waves.

  For example, when the base material closes the pipe cross section inside the pipe, the actual speed of the fluid flowing on the base surface increases, but this speed is perpendicular to the cross section of the pipe cross section of the part where the base material inside the pipe is not plugged. Although the value is different from the average value of the flow velocity of the fluid, it changes according to the change in the flow velocity or flow rate of the fluid flowing in the pipe.

  The present invention can also be used for flow rate measurement, and does not distinguish whether the measurement target is a flow velocity or whether the flow rate is a measurement target. I will call it. Any method may be used as long as the degree of flow is measured by utilizing the outflow of the heat amount of the base material as the fluid moves in the space where the base material is disposed.

Furthermore, even if the actual flow rate is constant, the present invention detects the change in the amount of heat that loses the change even if the density of the surrounding fluid changes or fluids with different thermal conductivities flow. Also in this case, as long as the flow state of the fluid is detected by the heat outflow rate from the base material, it is not excluded.

<Action>
Therefore, the present invention has the following effects by taking the above-described means.

According to the inventions according to claims 1 and 6 , a flowmeter using a surface acoustic wave element, the heating control means for controlling the substrate to be heated to a set temperature, and the heated substrate Based on the excitation control means for controlling the surface of the propagation wave to excite the surface acoustic wave, the acquisition means for acquiring the circular velocity or phase information obtained from the detection signal of the surface acoustic wave, and the phase data of the detection signal, A temperature measuring means for measuring the temperature of the propagation surface, and a flow velocity calculating means for calculating the flow velocity of the substance based on the temperature information and the heating amount , the anemometer body is used in the pipe through which the fluid flows, Detection from a single surface acoustic wave device with a configuration that enables measurement of fluid density or pressure according to the measurement of attenuation associated with the surface acoustic wave that circulates around the surface of a three-dimensional substrate. Based on signal data Flow rate of material of the inner can be calculated. That is, since the flow velocity and pressure are calculated by a single surface acoustic wave element, a small-sized anemometer can be realized. Moreover, since the flow velocity and pressure are measured by the surface acoustic wave element, it has durability compared to an anemometer using a wire.

  Moreover, since the temperature calculation means calculates the temperature from the propagation velocity (circumferential velocity) of the surface acoustic wave propagating on the propagation surface, the temperature can be obtained with high accuracy. That is, since the change amount of the propagation speed of the surface acoustic wave can be calculated in the ppm unit, the change amount can be calculated in the ppm unit even in the temperature measurement.

Further, the invention according to claim 1, 6, similar the pipe body flows, according to the measurement of the attenuation with the surface of the three-dimensional substrate in the circumferential surface acoustic wave multi-turn, the fluid density or pressure Since the measurement is performed, the flow velocity can be measured with high accuracy.

According to the second aspect of the invention, in addition to the operation corresponding to the first aspect, as the heating means of the surface acoustic wave element, the substrate is overheated by circulating the surface acoustic wave around the propagation surface. It is not necessary to install a heater or the like on the element, and the apparatus can be simplified.

According to the third aspect of the invention, in addition to the actions corresponding to the first and second aspects, the substrate of the surface acoustic wave element includes the cavity having the propagation surface on the inner surface, so that the progress of the substance is not hindered. The flow rate in the pipe can be measured.

According to the fourth aspect of the present invention, in addition to the actions corresponding to the first to third aspects, the surface of the surface acoustic wave element has a spherical shape. Can be excited. Therefore, the flow rate can be measured along the traveling direction of the substance in the pipe.

According to the fifth aspect of the present invention, in addition to the actions corresponding to the first to fourth aspects, the substrate of the surface acoustic wave element is made of quartz crystal, which is a piezoelectric crystal. Therefore, the surface acoustic wave element can be simplified.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the flowmeter which can also measure the small pressure or density which has durability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
(1-1. Configuration)
FIG. 1 and FIG. 2 are schematic views showing the configuration of a velocity meter 20 using the surface acoustic wave element 10 according to the first embodiment of the present invention.

  Here, the velocity meter 20 using the surface acoustic wave element 10 is used for measuring the flow velocity of the substance 6 in the pipe 5.

  The pipe 5 is a gas supply pipe having a diameter of about 5 mm. The diameter of the crystal sphere of the spherical surface acoustic wave element is 1 mm, and its frequency is about 150 MHz. The number of interdigital electrodes is 10, and the line width and space are about 5 micrometers. The overlapping width of the electrodes is 0.12 mm. In FIG. 1, the size of the crystal sphere is drawn relatively large with respect to the diameter of the pipe, and the pattern is omitted. In addition, as the piping 5, the supply pipe | tube etc. of a vacuum gas process apparatus are mentioned, for example. In addition, although it is set as the gas supply pipe | tube here, not only gas but a liquid supply pipe | tube may be sufficient.

  The substance 6 is a gas such as air or hydrogen gas. Various other gases can also be mentioned. Moreover, it is not necessarily limited to gas but may be liquid.

  The surface acoustic wave element 10 is formed by forming a heater 12 and an interdigital electrode 13 on the surface of a substrate 11. The surface acoustic wave element 10 is fixed in the pipe 5 by the installation table 14.

The base material 11 has a propagation surface 11S through which surface acoustic waves can propagate in multiple turns. Specifically, crystal, langasite (La ₃ Ga ₅ SiO ₁₄ ) and their families, crystal spheres made of piezoelectric crystals such as LiNbO 3 · LiTaO 3, and the like can be used. Note that the size of the crystal sphere is preferably about 1 mm to 3 mm, but if it is too large, the heat capacity of the crystal sphere increases and the responsiveness deteriorates.

  In the propagation surface 11S, the propagation velocity (also referred to as the circular velocity) of the surface acoustic wave has temperature dependence. For example, when a crystal sphere is used as the surface acoustic wave base material 11, the propagation speed changes with respect to the temperature at a change rate of about 25 ppm / ° C. in the surface acoustic wave circulation path called a Z-axis cylinder. When LiNbO3 is used, it has a temperature dependency of 52 ppm / ° C. Based on the temperature dependence of the propagation surface 11S, the temperature of the propagation surface can be accurately measured from a change in propagation speed to two decimal places or less.

  The heater 12 heats the base material 11. Specifically, the heater power source 12S receives a heating control signal from the flow meter 20 (control unit 22). And based on this heating control signal, the temperature of the heater 12 is controlled and the base material 11 is heated. Various materials can be used for the heater 12. Nichrome wire material or platinum may be used. The film forming method may be vapor deposition or spuck. It can also be easily created by a plating method. Patterning can also be created using photolithography technology, and various printing methods can be employed. Moreover, in order to heat the base material 11 as uniformly as possible, it is desirable to route the platinum fine wire pattern over a wide area.

  As the heater for heating in the present embodiment, those having the following specifications can be used on both sides of the Z-axis cylinder path.

  A gold film is formed on a sputter of a slight chromium layer for improving adhesion to have a line width of 5 micrometers, a total length of 2570 micrometers, and a thickness of 1 to 1.5 micrometers. The resistance value is about 10 ohms. The patterning uses a lift-off method.

  The interdigital electrode 13 excites a surface acoustic wave on the propagation surface 11S. Specifically, the high frequency signal source 13S receives an excitation control signal from the flow meter 20 (control unit 22). A surface acoustic wave (SAW) is excited on the propagation surface 11S by applying a burst signal to the interdigital electrode 13 based on the excitation control signal. The excited surface acoustic wave goes around the propagation surface 11S. Therefore, the interdigital electrode 13 can propagate a surface acoustic wave over a substantially long distance in a limited region. In this way, by causing the surface acoustic wave to propagate for a long distance, the circulation speed can be measured with high accuracy, and a sensor based on the speed change can be configured.

  Further, the interdigital electrode 13 has a role of exciting the surface acoustic wave, and can detect the surface acoustic wave after the surface acoustic wave circulates around the propagation surface 11S. The detected surface acoustic wave is output to the flow meter 20 (acquisition unit 24) as a detection signal. The burst signal input from the high-frequency signal 13S and the detection signal output to the flow meter 20 (acquisition unit 24) are performed via the circulator 15.

  In this embodiment, the excitation means and the detection means are made up of one interdigital electrode.

  The installation base 14 fixes the surface acoustic wave element 10 to the pipe 5. Further, the surface acoustic wave element 10 and the main body of the flow meter 20 are electrically connected via the installation table 14. As a result, signals can be exchanged between the surface acoustic wave element 10 and the main body of the flow meter 20.

  The flow meter 20 includes a storage unit 21, an input unit 22, a control unit 23, an acquisition unit 24, a temperature calculation unit 25, a released heat amount calculation unit 26, a pressure calculation unit 27, and a flow velocity calculation unit 28.

  The storage unit 21 stores “table 1” in which the propagation speed of the surface acoustic wave propagating on the propagation surface 11S is associated with the temperature of the propagation surface 11S. “Table 2” in which the flow velocity of the substance 6 in the pipe 5 is associated with the attenuation rate of the temperature of the propagation surface 11S is stored. “Table 3” in which the pressure of the substance 6 in the pipe 5 is associated with the attenuation rate of the intensity of the reference signal is stored. Further, the storage unit 21 stores information such as a cross-sectional area of the pipe 5. The reference signal data and information stored in the table are input by the input unit 22.

  The input unit 22 inputs information such as the set temperature of the heater 12 and the timing of inputting a high frequency signal to the interdigital electrode 13. The input information is sent to the control unit 23. In addition, before using the flow meter 20, reference phase and intensity data and the like are input via the input unit 22, and these pieces of information are sent to the storage unit 21.

  The control unit 23 is electrically connected to the surface acoustic wave element 10 and controls the heater 12 to have a set temperature. Specifically, a heating control signal is sent to the heater power supply 12S to control the heater 12 so that the heater 12 has a set temperature input by the input unit 22.

  The high frequency signal source 13S sends an excitation control signal and adjusts the timing of inputting the high frequency signal.

  The acquisition unit 24 acquires phase and intensity data of a detection signal of the surface acoustic wave every time a surface acoustic wave is detected by the interdigital electrode 13. The acquired detection signal phase data is sent to the temperature calculation unit 25, and the detection signal intensity data is sent to the pressure calculation unit 27.

  The temperature calculation unit 25 calculates the temperature of the propagation surface 11S based on the data or calculation formula stored in the storage unit for the phase data of the detection signal. At this time, the phase data of the detection signal is received from the acquisition unit 24, and the calculated temperature data of the propagation surface 11 </ b> S is sent to the released heat amount calculation unit 26.

  The temperature calculation method is as follows. Here, it demonstrates using FIG.

  In order to calculate the temperature, first, a burst signal is input to the interdigital electrode 13, and a surface acoustic wave is excited on the propagation surface 11S so as to make multiple turns. Thereafter, the detection signal L1 is acquired (FIG. 3A). Next, the phase difference ΔP between the phase of the detection signal L1 after the multiple rounds and the phase at the temperature T stored in the table 1 of the storage unit 21 is calculated (FIG. 3B). The phase difference ΔP is multiplied by the period of the burst signal from the high-frequency signal source 13S to determine the propagation velocity change amount ΔV. Then, the rate of change is obtained by dividing the change ΔV in the propagation velocity by the propagation time from the excitation of the surface acoustic wave until the phase is measured, and further divided by the proportionality constant representing the temperature dependence to obtain the temperature change. The quantity ΔT is determined. By adding this temperature change amount ΔT to the temperature T, the temperature T + ΔT of the propagation surface 11S can be obtained. In this case, a sufficient dynamic range is ensured by phase unwrapping even when there is a phase change of 2π or more by referring to the phase change of the signal at the time when the number of laps is small after applying the burst signal. However, since the phase difference is calculated, the temperature can be calculated with high accuracy.

  Further, in this description, phase measurement is measured by the phase of the signal at the designated number of rounds, and these phase changes are equivalent to the measurement of the round speed of the surface acoustic wave. On the other hand, the circumferential velocity of the surface acoustic wave is, for example, when an excitation signal having a long duration is applied to the interdigital electrode when excitation is performed at a frequency such that the time for one round is an integral multiple of one cycle of the circulating surface acoustic wave. When applied, the surface acoustic wave on the circulation path of the surface acoustic wave element is in a resonance state, and produces a very large output. Such a frequency is inversely proportional to the circumferential velocity of the surface acoustic wave. Therefore, instead of measuring the phase at a specific time and measuring the change thereof, the present invention does not exclude the change of the peripheral speed by obtaining the resonance frequency and the temperature measurement.

  The pressure calculation unit 27 calculates the pressure of the propagation surface 11S based on the intensity data of the detection signal and the reference intensity data stored in the storage unit. At this time, the intensity data of the detection signal is received from the acquisition unit 24, and the calculated pressure data of the propagation surface 11S is sent to the flow velocity calculation unit 28.

  The amount of attenuation of the surface acoustic wave energy is affected by the ambient pressure. When the ambient pressure is large, the Rayleigh wave LW propagating on the surface of the sphere leaks energy to the periphery as shown in FIG. On the other hand, the magnitude of the signal attenuation and the pressure value associated with the circulation of the surface acoustic wave are stored in the storage unit 21 in the form of Table 3, so that the pressure is uniquely determined from the signal intensity attenuation. be able to. Here, as shown in FIG. 7, the detection signal is curve-fitted (attenuation curves D1 and D2 in FIG. 7) to calculate the attenuation rate α, and the pressure is obtained from the attenuation rate. Here, C is an arbitrary constant. The attenuation rate does not always need to follow this equation, and it is only necessary to be able to measure the degree of weakening with the lap, and for example, it may be obtained as a ratio of the intensity between signals of different laps.

  The flow velocity calculation unit 28 obtains the flow velocity of the substance 6 in the pipe 5 based on the temperature data of the propagation surface 11S, the data of the pressure calculation unit, the data of the table 2 stored in the storage unit 21, and the initial temperature of the fluid. Is.

  Generally, when heat flows out (releases) from a solid surface to a gas, if the density of the gas is large, more heat is carried away. Therefore, the speed measured by the thermal type anemometer does not correspond one-to-one with the speed at which the surrounding fluid actually flows.

  Further, when the pressure (density) changes, the amount of heat outflow changes more variously due to the difference in fluid flow distribution (for example, laminar flow or turbulent flow). Therefore, when the flow rate is measured from the heat outflow amount, or even if the heat outflow amount is proportional to the product of density × flow velocity to some extent, the accuracy is limited. To accurately measure and measure the flow velocity and flow rate with respect to changes in pressure (density), measure the pressure (density) at the same time, and heat outflow (outflow velocity) for each pressure. And storing a correlation table between the flow velocity and the flow rate. Thus, the ability to measure both the pressure (density) and the amount of heat outflow has the effect of improving accuracy in either flow rate measurement or mass flow rate measurement in process management.

  Here, a method for obtaining the flow velocity from the temperature will be described.

  As a method for obtaining the flow velocity from the temperature, for example, a thermal anemometer can be cited. In this thermal anemometer, heat equal to the amount of heat dissipated by the cooling action of the wind is supplied to the wind speed element. As a result, the amount of heat dissipated and the amount of heat supplied are in an equilibrium state, and the temperature of the wind speed element is kept constant. At this time, since the supplied heat amount corresponds to the wind speed, the wind speed can be measured by measuring the supplied heat amount. As shown in FIG. 4, the specific configuration of the thermal anemometer is such that a bridge is formed with respect to an anemometer W1 made of platinum wire. In this case, the amount of heat supplied can be measured by measuring the change in resistance of the wind speed element W1 with the indicator as the change in voltage of the resistance W2.

  Further, the heating element is controlled so as to generate (consume) a certain amount of heat (electric power), and the loss of heat accompanying the flow of the surrounding fluid can be measured by the temperature drop curve or the equilibrium temperature. There is a one-to-one correspondence between the temperature and flow rate at which equilibrium is reached.

  Various methods can be adopted for this embodiment as well as the conventional anemometer, but the fact that the increase in the flow velocity affects the increase in the outflow of heat from the element is the same, and is known. Either of the above methods can be employed. In the flow meter according to the present embodiment, the flow rate of the substance 6 is measured from the temperature decay rate.

  The simplest way to measure the flow velocity is as follows. First, when the heater 12 is heated at time t0, as shown in FIG. 5, the temperature (the difference from the fluid temperature) increases with time. Next, heating is stopped at time t1. Thereafter, the temperature is measured every time t2, t3, t4. Thereby, the attenuation rate can be obtained by curve fitting the attenuation curve C (C1, C2 in the figure) of the temperature T with respect to the time t. When the pressure or density of the fluid is constant, the attenuation rate value and the flow velocity value have a one-to-one correspondence, so data is stored in advance in the form of a table (corresponding to table 2 in this embodiment). Can be kept. Therefore, by referring to the table 2, the flow velocity of the substance 6 can be measured from the temperature decay rate of the heater 12.

  The flow rate calculation unit 28 calculates the flow rate of the substance 6 in the pipe 5. Specifically, the flow rate is determined by the heat release heat amount speed amount calculated by the heat release amount calculation unit 26 from the information of the temperature calculation unit 25 and the initial temperature of the fluid stored in the storage unit and the pressure calculated by the pressure calculation unit 27. It is possible to more accurately detect the initial fluid condition.

  When the fluid is a gas, if the pressure (density) is small, the rate of heat release increases substantially in proportion to the density of the fluid even at the same flow rate. Therefore, it is desirable to measure the pressure (density) at the same time. It is. A table can be prepared that associates different heat release levels with flow rates according to pressure.

  On the other hand, if the pressure is constant, the pressure is not used as a variable, but according to the amount of heat released (such as the aforementioned α value) and the temperature of the fluid (the temperature before heating or the temperature of the fluid measured upstream). The flow velocity can be obtained. The flow rate flowing through the pipe can be determined according to the shape and cross section of the pipe.

(1-2. Operation)
Next, the operation of the flow meter 20 according to the present embodiment will be described using the flowchart of FIG.

  First, before performing measurement using the flow meter 20, data is initially set in the storage unit 21 via the input unit 22 (S1). For example, the fluid temperature, the cross-sectional area of the pipe 5, the temperature of the heater 12, the burst signal input timing, the temperature measurement time, and the like are set.

  It is obvious that the above-described temperature measurement of the fluid in the initial setting can be measured by the phase of the surface acoustic wave that circulates and the resonance frequency. In order to measure the temperature of the fluid, it is desirable to install a separate thermometer on the fluid river, and by providing a separate spherical surface acoustic wave element (which may not include a heater) It is preferable to measure the temperature of the fluid.

  After the initial setting, the heater power source 12S is controlled to heat the heater 12 (S2). Thereby, the temperature of the heater 12 rises proportionally with time. When the temperature of the heater 12 reaches the set temperature, the heater power source 12S stops heating (S3).

  Subsequently, a burst signal is input to the interdigital electrode 13 from the high frequency signal source 13S. Thereby, the surface acoustic wave is excited and goes around the propagation surface 11S. At this time, each time the surface acoustic wave circulates around the propagation surface 11S, a detection signal is output through the interdigital electrode 13. The output detection signals are sequentially acquired by the acquisition unit 24 (S4).

  The acquired phase data of the detection signal is sent to the temperature calculation unit 25. Then, based on the transmitted phase data, the temperature change of the propagation surface 11S is calculated by the temperature calculation unit 25 by obtaining the change in the circulation speed (S5).

  The detection signal data is acquired until the temperatures for all the measurement times input by the input unit 21 are calculated (S6-No).

  On the other hand, when the acquisition of the detection signal data is completed, the elemental surface temperature attenuation rate α previously obtained from the original temperature before the fluid is heated and the circular velocity of the surface acoustic wave is obtained by the emitted heat quantity calculation unit 26. (S6-Yes, S7). Specifically, when the heater power supply 12S is turned off, the temperature of the propagation surface 11S decreases as shown in FIG. At this time, if a substance flows around the propagation surface 11S, the temperature of the heater cools according to the flow velocity of the object. If the flow rate is fast, it is cooled in a short time as shown by the decay curve C1, and if the flow rate is slow, it takes a long time to cool as shown by the decay curve C2. Thus, the flow rate of the surrounding substance is obtained from the difference in time until the temperature cools.

  Further, the pressure is calculated by the pressure calculation unit 27 based on the waveform of the detection signal at the time when the heating is stopped (S8).

  And the flow rate is calculated | required from the pressure and discharge | release heat amount which were calculated | required by the pressure calculation part 27, and the mass flow rate of the substance 6 is calculated from information, such as a pipe cross section (S9).

(1-3. Effect)
As described above, the flow meter 20 using the surface acoustic wave element 10 according to the present embodiment stores the pressure in the material 6 and the propagation surface 11S in the pipe 5 and the attenuation rate of the intensity in association with each other. A control unit 23 that controls the substrate 11 to be heated to a set temperature, an acquisition unit 24 that acquires phase and intensity data of the detection signal of the surface acoustic wave, and a change in the phase data of the detection signal Therefore, the temperature calculation unit 25 calculates the temperature of the propagation surface 11S, and the pressure calculation unit 27 calculates the pressure of the propagation surface 11S based on the intensity of the detection signal or the attenuation constant thereof.

  That is, in the present embodiment, the heating heater 12 and the interdigital electrode 13 are formed on the surface of the same base material 11, thereby measuring the temperature, measuring the pressure, and the amount of heat to be heated. A mechanism for observing the temperature change is configured in a single surface acoustic wave element 10. As described above, since the flow velocity and pressure are measured by the single surface acoustic wave element 10, it is possible to realize the velocimeter 20 capable of measuring a small pressure or density without having a complicated mechanism. Can do.

  In addition, since a crystal sphere of quartz or the like is used for the base material 11 of the surface acoustic wave element 10, it has durability compared to an anemometer or the like using a wire. In this respect, since the heater 12 is directly formed on the surface of a crystal sphere or the like of a crystal, unlike a conventional anemometer or the like, there is no linear heater, so it is clear that the measuring device is not easily destroyed. Since the quartz crystal is a piezoelectric crystal, it is not necessary to form a piezoelectric film or the like for forming the propagation surface 11S, and the surface acoustic wave element 10 can be simplified. For such a thermal velocimeter that requires heating, this structure that does not need to worry about peeling of the piezoelectric film is extremely useful and preferable.

  In the present embodiment, the temperature calculation unit 25 calculates the temperature from the propagation velocity of the surface acoustic wave propagating on the propagation surface 11S, so that the temperature can be obtained with high accuracy. That is, since the change amount of the propagation velocity of the surface acoustic wave can be calculated in ppm, the change amount can be calculated with an accuracy of 0.01 degrees even in the temperature measurement. Therefore, highly accurate temperature measurement can be performed.

  Moreover, since the base material 11 of the surface acoustic wave element 10 according to the present embodiment is spherical, it accompanies the movement of the substance 6 in the pipe 5.

  In addition, it is good also as a structure which heats the base material 11 by making the propagation surface 11S circulate around a propagation surface 11S instead of heating the base material 11 using the heater 12. FIG. With such a configuration, the apparatus can be simplified.

  When measuring the temperature using the output of the spherical surface acoustic wave element, the circulation speed of the surface acoustic wave is determined by the influence of the temperature dependence (particularly the volume expansion coefficient) on all the circulation paths. . Therefore, it is possible to measure an average temperature instead of a temperature at a specific location.

  Further, in the case of a spherical surface acoustic wave device using a crystal sphere, for example, when the pressure is reduced from 1 atm to 0 atm, the decrease in Rayleigh wave phase velocity is 30 ppm or less. On the other hand, the temperature changes by 25 ppm per 1 ° C. as described above. From this, when the change in pressure is smaller than the predetermined change, it is possible to measure the temperature from the change in phase (= change in the circulation speed or change in the resonance frequency) and measure the pressure from the intensity.

(Example)
Here, examples related to the present embodiment will be described.

  In this example, the surface acoustic wave element 10 was used to measure changes in flow velocity (flow rate) and temperature in a 6 mm diameter pipe.

  First, a voltage of 1 V was applied to the heater 12, a current of about 95 mA flowed, and an equilibrium state was reached at a temperature of about 100 ° C. The temperature was measured by applying a burst signal and changing the propagation speed of the surface acoustic wave.

  The propagation speed is measured by measuring the waveform at the 51st lap with the air (fluid) temperature at 30 ° C., and obtaining the temporal movement (delay time) of the position of the same waveform to determine the change in the lap speed at 0.2 L / min. When the temperature change was monitored while repeating ON and OFF from 2 to 2 L / min, the graph shown in FIG. 9 could be obtained.

  It can be seen that as the flow rate increases, the temperature change at which the equilibrium state is reached is accurately measured. FIG. 10 is a graph in which the temperature at which the equilibrium state is reached is converted into a temperature drop value from the rotation speed change rate and is graphed.

  From this graph, it was shown that the flow rate (flow velocity) can be measured from the temperature value at which equilibrium is reached. In this experiment, since the pressure is constant at atmospheric pressure with respect to the flow rate flowing through the piping, it is not necessary to measure the pressure and can be easily measured, and the flow rate can be measured with high accuracy according to the temperature measurement accuracy. Is possible. Regarding the flow velocity, the flow velocity can be obtained by dividing the previously obtained flow rate by the pipe diameter.

  Next, FIG. 11 shows the temperature drop with respect to the flow rate performed in the same manner as in FIG. 10 when the same experimental apparatus was put in the pressure chamber and reduced to 0.8 atmosphere and 0.6 atmosphere. The pressure measurement was performed in advance using a correlation table (FIG. 12) between the change in the intensity (voltage) of the signal of 150 laps and the pressure (atmospheric pressure). The characteristic is that when the pressure decreases, the density of air decreases and the strength value associated with the surface acoustic wave wrap decreases. If the intensity before attenuation is known or constant, the attenuation constant α can be easily obtained by measuring the intensity at an arbitrary number of laps (delay time).

  It can be seen that the amount of temperature decrease accompanying the flow rate UP decreases as the pressure decreases. In general, since more molecules take heat away from the element surface in proportion to the pressure, it is shown that more accurate flow rate (flow velocity) measurement is possible by performing pressure measurement. The flow rate on the horizontal axis in FIGS. 9, 10, and 11 is a volume flow rate defined by the volume in each gas pressure state.

  Thus, it is possible to prepare correspondence curves (tables) between different temperature drops and flow rates with respect to pressure.

  In this embodiment, the heater control unit is controlled to perform constant overheating, but the control unit is controlled to maintain a constant temperature based on the temperature data from the temperature calculation unit, The amount of heat lost to the fluid of the element can also be obtained by measuring the power (heat amount) for overheating input at the input unit. Even if such a method of measuring the flow velocity with electric power necessary to maintain the element at a constant temperature is adopted, the advantage of using the spherical surface acoustic wave element and the pressure measurement described above are possible. There is no.

  Since the amount of heat flowing out of the element is approximately proportional to the pressure (density) and the flow velocity, the gas density can be calculated by measuring the pressure by the above-described method of measuring the intensity (decay rate), and the measured heat It is obvious that the flow rate can be measured from the amount of lost water.

<Second Embodiment>
FIG. 13 is a schematic diagram showing a configuration of a surface acoustic wave element 10X according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the part same as the already demonstrated part, and the overlapping description is abbreviate | omitted. In addition, the following description is also omitted in the following embodiments.

  In this embodiment, LiNbO3 is used for the base material 11X. Unlike quartz, LiNbO3 has a plurality of surface acoustic wave propagation surfaces 11S.

Although three propagation surfaces 11S are shown in FIG. 13, one of the three can be used for intensity measurement (pressure measurement) and the other can be used for temperature measurement. In the figure, the heater pattern for heating is omitted. It is desirable that the heater pattern does not intersect the path as much as possible, but it can be formed to the extent that it does not interfere with the measurement of the rotational speed for temperature measurement and the pressure measurement by any of these paths. is there. In this way, if the temperature is measured by forming multiple paths on the surface of the crystal sphere, it is possible to measure the average temperature of the element even when the flow direction of the fluid changes, and to measure the flow velocity (flow rate) accurately. Has the advantage of

<Third Embodiment>
FIG. 14 is a schematic diagram showing a configuration of a surface acoustic wave element 10Y according to the third embodiment of the present invention.

  In the present embodiment, a surface acoustic wave element is not installed in the pipe 5, but a base material 11Y having a spherical cavity (hollow) is provided in the pipe 5, and the interdigital electrode 13 is formed on the wall surface. ing. That is, since the structure has a cavity having the propagation surface 11S on the inner surface, the flow rate can be measured without obstructing the progress of the substance 6 in the pipe 5. This example is a method of heating by elastic waves, and the heater is also an interdigital electrode.

<Type of heater used in the present invention>
In addition, in the propagation path of the surface acoustic wave, the surface acoustic wave energy is thermally absorbed, and in some cases, the surface acoustic wave energy is efficiently absorbed to generate heat, such as an organic film, and the surface It is possible to play the role of a heater by inputting a signal that is much longer than the burst signal as shown in FIG. 3 as a high-frequency signal for exciting the wave. The heat generation of the propagation surface due to the energy of the surface acoustic wave is well known and will not be further described here, but in the embodiment described, it is only used for temperature measurement or pressure measurement (density measurement). Since large electrical energy is input to the electrode, the interdigital electrode is likely to be deteriorated or evaporated. As a countermeasure, the load can be reduced by increasing the number of repetitions of the interdigital electrode pattern and exciting the surface acoustic wave in a large area.

  Furthermore, the interdigital electrode for exciting and detecting the surface acoustic wave for measurement of temperature and pressure and the interdigital electrode as a heater for the heating may be formed separately. In particular, by forming on the same path, it is possible to heat the same path as the temperature measurement path, and to measure the calorific value flowing out with higher accuracy and to expect a high-speed response.

  Thus, in the present invention, the method of heating the substrate is not limited to resistance heating alone. In some cases, it is obvious that an infrared absorbing film such as a resin thin film formed on the surface of the substrate by introducing infrared into the surface acoustic wave path can be used as a heating element.

<Others>
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine a component suitably in different embodiment.

It is a schematic diagram which shows the structure of the velocity meter 20 using the surface acoustic wave element 10 which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the velocimeter 20 using the surface acoustic wave element which concerns on 1st Embodiment. It is a figure for demonstrating the calculation method of the temperature of the propagation surface 11S which concerns on 1st Embodiment. It is a schematic diagram which shows the example of a structure of a thermal-type anemometer. It is a figure for demonstrating the calculation method of the flow velocity of the substance 6 which concerns on 1st Embodiment. It is a figure for demonstrating the relationship between the leak of the energy of a Rayleigh wave, and a pressure. It is a figure for demonstrating the calculation method of the pressure which concerns on 1st Embodiment. It is a flowchart for demonstrating operation | movement of the anemometer 20 which concerns on 1st Embodiment. It is the figure which showed the change when changing the flow volume of the change rate of the circulation speed measured using the surface acoustic wave signal of the 50th rotation relevant to the 1st Example. It is the figure which showed the temperature fall when changing the flow volume relevant to the 1st Example. It is the figure which measured the fall temperature with respect to the flow volume used for the 1st Example, changing the pressure. It is the figure which showed the correlation with the pressure of the amplitude value of the signal of the 150th turn of the spherical surface acoustic wave element used for the 1st Example. It is a schematic diagram which shows the structure of the surface acoustic wave element 10X concerning the 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the surface acoustic wave element 10Y which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

      5 ... Piping, 6 ... Substance, 10.10X.10Y ... Surface acoustic wave element, 11.11X.11Y ... Base material, 11S ... Propagation surface, 11P ... Diffraction pattern, 12 ... Heater, 12S ... Heater power supply, 13 ... Electrode, 13S ... high frequency signal source, 14 ... installation base, 15 ... circulator, 20 ... current meter, 21 ... storage unit, 22 ... input unit, 23 ... control unit, 24 ... acquisition unit, 25 ... temperature calculation unit, 26 ... calorific value calculation part, 27 ... pressure calculation part, 28 ... flow velocity calculation part, W1 ... wind speed element.

Claims (6)

An anemometer that uses a surface acoustic wave element to determine the flow velocity of the fluid flowing around it,
The surface acoustic wave element is
A three-dimensional base material having an annular propagation surface capable of propagating a surface acoustic wave through multiple laps;
Based on the heating control signal from the anemometer body formed on the surface, heating means for heating the substrate,
Excitation means for exciting a surface acoustic wave on the propagation surface based on an excitation control signal from the anemometer body;
Detecting means for detecting the surface acoustic wave that circulates around the propagation surface and outputting a detection signal;
The anemometer body is
Heating control means connected to the surface acoustic wave element to send and control a heating control signal to the heating means to heat the substrate;
Excitation control means for sending and controlling an excitation control signal to the excitation means so as to excite surface acoustic waves on the propagation surface of the substrate heated by the heating means;
An acquisition means for acquiring temperature information from the rotational speed or phase information obtained from the detection signal of the surface acoustic wave output by the detection means;
Temperature measuring means for measuring the temperature of the propagation surface based on the data of the detection signal;
A flow rate calculating means for calculating a flow rate of the substance based on the temperature information and the heating amount obtained by the temperature measuring means ,
The anemometer body is used in a pipe through which a fluid flows, and measures the density or pressure of the fluid in accordance with the measurement of the amount of attenuation associated with the circulation of the surface acoustic wave that circulates around the surface of the three-dimensional substrate. An anemometer characterized in that it was made possible . In the surface acoustic wave device used for the anemometer according to claim 1 ,
The said heating means heats a base material by the thermal absorption of the energy accompanying the circumference | surroundings of a surface acoustic wave on the said propagation surface, The velocimeter using the surface acoustic wave element characterized by the above-mentioned. In the surface acoustic wave device used for the anemometer according to claim 1 or 2 ,
The three-dimensional base material includes a cavity having the propagation surface on an inner surface thereof, and a velocimeter using a surface acoustic wave element. In the surface acoustic wave element used for the anemometer according to any one of claims 1 to 3 ,
An annular propagation surface of the three-dimensional substrate has a spherical shape, and a velocimeter using a surface acoustic wave element. In the surface acoustic wave element used for the anemometer according to any one of claims 1 to 4 ,
The three-dimensional substrate is made of a piezoelectric material,
2. The surface acoustic wave device according to claim 1, wherein the excitation means comprises a comb-like electrode formed on the piezoelectric material. A three-dimensional base material having an annular and spherical propagation surface capable of propagating by making multiple rounds of surface acoustic waves; heating means for heating the base material based on a heating control signal; and an excitation control signal on the propagation surface A flow velocity measuring method using a surface acoustic wave element comprising: excitation means for exciting a surface acoustic wave based on the detection means; and detection means for detecting a surface acoustic wave that circulates around the propagation surface and outputting a detection signal,
A heating control step of sending and controlling a heating control signal to the heating means so as to heat the three-dimensional substrate;
An excitation control step of sending and controlling an excitation control signal to the excitation means so as to excite a surface acoustic wave on the propagation surface of the substrate heated by the heating means;
An acquisition step of acquiring temperature information from the rotational speed or phase information obtained from the detection signal of the surface acoustic wave output by the detection means;
Based on the data of the detection signal, the temperature measurement step of the propagation surface,
A flow rate calculating step for calculating a flow rate of the substance based on the temperature information and the heating amount obtained by the temperature measuring step ;
A step of measuring the density or pressure of the fluid according to the measurement of the amount of attenuation accompanying the circulation of the surface acoustic wave that circulates around the surface of the three-dimensional substrate in the pipe through which the fluid flows. A flow velocity measurement method characterized by

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