JP3652346B2 - Flow sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow sensor that measures a flow velocity of a fluid such as a wind speed of a gas, and more particularly to a flow sensor that can detect a flow direction and a minute flow velocity and has excellent durability.
[0002]
[Prior art]
Conventionally, sensors such as a hot wire type, a windmill type, or an ultrasonic type have been widely used as flow sensors for measuring the wind velocity of gas.
[0003]
Japanese Patent Application Laid-Open No. 7-27781 discloses a flow sensor using a strain gauge that can detect a wind direction and can detect a sudden change in fluid flow. Such a sensor is composed of a rod-like member that is distorted by the force of the fluid to be measured and a plurality of strain gauges arranged around the rod-like member, and by detecting the bending of the rod-like member, It is intended to detect the flow velocity and the like. In this sensor, the strain of the rod-shaped member can be accurately, reliably, and quickly detected by the strain gauge, so that a sudden change in the flow of the fluid to be measured can also be measured.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-27781
[Problems to be solved by the invention]
However, the conventional flow sensors described above have the following drawbacks. First, in the hot wire type flow sensor, the sensitivity is not so good and the wind direction cannot be detected. In addition, it has the disadvantage of high power consumption. In addition, it is essentially difficult to ensure the explosion resistance required for detecting the flow rate of combustible gas.
[0006]
In addition, in the wind turbine type flow sensor, a bearing portion that receives the rotation of the wind turbine is necessary, and generation of particles cannot be avoided due to the presence of such a sliding portion. Therefore, there is a drawback that it cannot be used in a clean room where dust generation is strictly prohibited. Further, the ultrasonic sensor has a drawback that the apparatus becomes large and the cost is high.
[0007]
On the other hand, in the flow sensor using the strain gauge described above, it is difficult to maintain long-term stability due to a change with time, such as a change in resistance of the strain gauge and a deterioration of adhesion of the strain gauge to the rod-shaped member. In addition, since it is necessary to directly contact the strain gauge with the rod-shaped member, the electrical wiring portion cannot be separated from the movable portion, and the wiring is troublesome. In addition, the strain gauge and the electrical wiring portion are connected to the fluid to be measured. It is exposed to the inside, and there is a problem in durability depending on the fluid to be measured.
[0008]
Accordingly, an object of the present invention is a flow sensor for measuring the flow velocity of a fluid, such as the wind velocity of a gas, capable of detecting the flow direction and a minute flow velocity, having low power consumption, excellent durability, and It is to provide a dust-free flow sensor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a flow sensor according to one aspect of the present invention includes a fluid receiving portion that is displaced by the flow velocity of a fluid to be measured, a conductive portion that is displaced together with the fluid receiving portion, and the conductive portion. It has a displacement detection part fixed to the position which opposes, and detecting the displacement of the said electroconductive part. Therefore, according to the present invention, the displacement of the fluid receiving portion, that is, the flow velocity of the fluid to be measured is detected based on the change in the eddy current of the conductive portion accompanying the displacement of the fluid receiving portion. While being possible, the direction of the flow can also be detected.
[0010]
In order to achieve the above object, a flow sensor according to another aspect of the present invention is a flow sensor for measuring a flow velocity of a fluid, the fluid receiving portion being displaced by receiving the flow of the fluid, and the fluid receiving portion. A conductive portion having conductivity that is displaced together, a support portion that supports the fluid receiving portion, and a displacement detection portion that is fixed at a position facing the conductive portion and detects the displacement of the conductive portion. It is characterized by.
[0011]
Furthermore, in the above-mentioned invention, a preferable aspect thereof is characterized in that the fluid receiving portion and the conductive portion are integrated with a metal plate.
[0012]
In another aspect of the present invention, the conductive portion is a metal foil or a metal plate provided in the fluid receiving portion.
[0013]
Furthermore, in the above invention, a preferred aspect is characterized in that the displacement of the fluid receiving portion is caused by bending of the fluid receiving portion itself.
[0014]
Furthermore, in the above invention, another aspect is characterized in that the displacement of the fluid receiving portion is caused by expansion and contraction of an elastic structure of the support portion.
[0015]
Furthermore, in the above invention, another aspect is that the support portion supports one end of the fluid receiving portion, and the position of the conductive portion is more than the position where the fluid flow is received in the fluid receiving portion. It is in a position far from the supported one end. Thereby, measurement sensitivity can be raised.
[0016]
Furthermore, in the above invention, a preferred aspect is characterized in that the displacement detection unit is configured by a coil.
[0017]
In the above-mentioned invention, a preferable aspect further includes a detection signal based on displacement and temperature of the conductive portion, which is detected by applying a predetermined high-frequency signal to a predetermined circuit including the coil, and the application And a separation unit that separates the detection signal into a component based on the displacement of the conductive portion and a component based on the temperature of the conductive portion based on the high-frequency signal.
[0018]
Furthermore, in the above-mentioned invention, another aspect is characterized in that the displacement detection unit is constituted by a capacitor.
[0019]
Furthermore, in the above-described invention, a preferred aspect is characterized in that a position where the displacement detection unit is fixed is a position that does not contact the fluid. Thereby, since the displacement detection part and electronic circuit part which are comprised with a coil etc. do not exist in to-be-measured fluid, it is excellent also in durability.
[0020]
Further objects and features of the present invention will become apparent from the embodiments of the invention described below.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.
[0022]
FIG. 1 is a configuration diagram according to a first embodiment of a flow sensor to which the present invention is applied. FIG. 1 shows a wind speed detection portion including the main features of the present invention, and the processing circuit after detection is shown in FIG. 1A is a cross-sectional view viewed from a direction perpendicular to the flow direction of the measurement gas, and FIG. 1B is a front view viewed from the flow direction of the measurement gas. ing.
[0023]
As shown in FIG. 1, the flow sensor 1 according to the first embodiment includes a wind receiving plate (fluid receiving portion) 2, a conductive portion 3, a wind receiving plate support portion 4, and a coil (displacement detecting portion) 5. And the coil fixing part 6 and the like. As shown in the figure, the flow sensor 1 is installed so as to be inserted into a pipe 9 through which the gas 10 to be measured flows, and the flow of the gas 10 to be measured flowing into the flow sensor 1 through the sensing window 7. The coil 5 detects that the wind receiving plate 2 is displaced, and measures the wind speed of the measurement target gas 10.
[0024]
The wind receiving plate (fluid receiving portion) 2 of the flow sensor 1 is a thin rectangular plate as shown in FIGS. 1A and 1B, and one end thereof (in the case of FIG. 1) The upper end is fixed by the wind receiving plate support 4. Moreover, the said wind receiving plate 2 is comprised with the material which has elasticity, such as a metal and resin.
[0025]
Next, the conductive portion 3 is a metal foil or metal plate provided on both surfaces of the wind receiving plate 2 and is displaced together with the wind receiving plate 2 by the flow of the measurement target gas 10. An eddy current is generated in the conductive portion 3 by a magnetic field generated by a coil 5 described later, and displacement due to the wind speed of the measurement target gas 10 can be electrically detected. The conductive portion 3 may be made of a conductive material, not a metal foil. For example, when the wind receiving plate 2 is a metal plate, the conductive portion 3 is further added. There is no need to do this, and the metal plate has both the wind receiving plate 2 and the conductive portion 3.
[0026]
Next, the wind receiving plate support portion 4 is a portion that supports one end of the wind receiving plate 2 described above, and a pipe through which the measured gas 10 flows through one end of the wind receiving plate 2 via a coil fixing portion 6 to be described later. Fix to 9.
[0027]
The coil (displacement detection unit) 5 is a part that converts the displacement of the conductive unit 3 into an electrical signal. As shown in FIG. 1, a coil fixing unit 6 (described later) at a position facing the conductive unit 3. Is attached outside (before and after the flow direction of the measurement target gas 10). A high frequency signal is applied to the coil 5 from a later-described oscillator 21 via the wiring 8, and based on the change in impedance due to the displacement of the conductive portion 3, the displacement of the conductive portion 3, that is, the measurement target gas 10. Wind speed is detected.
[0028]
Further, the coil fixing portion 6 is a portion that hits the outer wall of the flow sensor 1 and surrounds the wind receiving plate 2 and the conductive portion 3 and is fixed to the pipe 9 of the measured gas 10 as shown in FIG. Installed. As a result, the coil 5 attached to the coil fixing portion 6 is fixed to the pipe 9, and accordingly, when the wind receiving plate 2 is not displaced, that is, when there is no wind speed of the measured gas 10. The conductive portion 3 and the coil 5 are kept at a certain distance.
[0029]
Moreover, the coil fixing | fixed part 6 located in the exterior of the piping 9 becomes a sealed structure with which four directions were covered with the wall (a side wall is not shown), and the to-be-measured gas 10 in the piping 9 leaks outside. There is no. Accordingly, the coil 5 attached to the outside of the coil fixing portion 6 does not touch the measurement target gas 10. As described above, the coil fixing portion 6 has a function of keeping the distance between the conductive portion 3 and the coil 5 and a function of isolating the electronic circuit portion of the sensor from the measured gas 10.
[0030]
Further, as shown in FIG. 1, a sensing window 7 is provided below the coil fixing portion 6, and the measurement target gas 10 flows from the opening to displace the wind receiving plate 2.
[0031]
Next, the principle of wind speed measurement by this flow sensor 1 will be described. FIG. 2 is a diagram for explaining the principle of wind speed measurement. FIG. 2 schematically shows the positional relationship between the wind receiving plate 2 and the coil 5. FIG. 2A shows a state in which the wind receiving plate 2 is not displaced, that is, the wind speed of the gas 10 to be measured. 2B shows a state where the wind receiving plate 2 is displaced by the flow of the measurement target gas 10. FIG.
[0032]
As described with reference to FIG. 1, in the present flow sensor 1, the coil 5 is arranged at a certain distance from the conductive portion 3, and the coil 5 and the conductive portion 3 are so-called mutual inductive coupling. A circuit is formed. In such a circuit, it is known that the impedance is determined by the resistance and inductance of the coil 5 and the conductive portion 3 and the distance between them.
[0033]
Therefore, in the case shown in (a) of FIG. 2 and the case shown in (b), the distance (L1 and L2 in FIG. 2) between the coil 5 and the wind receiving plate 2 (that is, the conductive portion 3) is different. The impedance is also different. Therefore, the displacement of the wind receiving plate 2 causes a change in impedance, and the wind speed of the measurement target gas 10 that is the basis of the displacement of the wind receiving plate 2 is detected by the change in the electrical signal based on the change in the impedance. Is possible.
[0034]
Next, the processing circuit portion after the coil 5 of the flow sensor 1 will be described. FIG. 3 is a diagram showing the configuration of the processing circuit portion. 3A is a configuration diagram of the processing circuit portion, and FIG. 3B is a diagram for explaining separation detection described later.
[0035]
As shown in FIG. 3A, the processing circuit portion includes a power supply unit 11, a detection unit 20, and a separation unit 30. The power supply unit 11 is a part that supplies power to necessary portions of the detection unit 20 and the separation unit 30. Moreover, the detection part 20 is a part which detects the electrical signal accompanying the change of the said impedance in the coil 5 part.
[0036]
The impedance of the coil 5 and the conductive portion 3 described above varies depending on the displacement of the wind receiving plate 2, that is, the wind speed of the measurement target gas 10 as described above, and depends on the temperature of the wind receiving plate 2 (conductive portion 3). Is also known to change. Accordingly, the electrical signals accompanying the change in impedance detected by the detection unit 20 include those caused by the wind speed (wind velocity component) and those caused by the temperature of the wind receiving plate 2 (conductive portion 3) (temperature component). Both of them are included, and it is necessary to separate them in order to measure the wind speed.
[0037]
The separation unit 30 shown in FIG. 3A is a part that separates and detects the wind speed component and the temperature component. Hereinafter, the contents of the processing performed by the detection unit 20 and the separation unit 30 will be sequentially described.
[0038]
First, a high frequency signal is applied from the oscillator 21 to the bridge circuit composed of the two coils 5 and the two resistors R shown in FIG. Next, as shown in FIG. 3A, the output from the bridge circuit is input to the differential amplifier 22. The differential amplifier 22 is adjusted so that the output is minimized when the wind speed of the gas to be measured 10 is zero and the wind receiving plate 2 (conductive portion 3) is at the reference temperature.
[0039]
Next, as shown in FIG. 3A, the output of the differential amplifier 22 and the output from the oscillator 21 are input to the separation unit 30. First, the output of the differential amplifier 22 is output from the oscillator 21. A component (Y component) having a phase different from the component in phase with the waveform (X component) by 90 °, for example, is extracted. Specifically, the X component is extracted by the multiplier 32a and the low-pass filter 33a, and the Y component is extracted by the 90 ° phase shifter 31, the multiplier 32b, and the low-pass filter 33b. Thereby, the magnitude and phase of the detection signal are detected.
[0040]
The extracted X and Y components are then input to the separation detection circuit 34, where the detected electrical signal, ie, the output from the differential amplifier 22, is separated into the wind speed component and the temperature component. Detected. The separation detection processing principle will be described with reference to the diagram shown in FIG.
[0041]
The X component and Y component input to the separation detection circuit 34 are plotted on a two-dimensional plane composed of the X component and the Y component, and the output from the differential amplifier 22 is, for example, shown in FIG. It is expressed as detected value a.
[0042]
In general, it is known that the impedance change due to the change in the distance between the primary circuit and the secondary circuit of the coupling circuit and the impedance change due to the temperature can be separated because the direction of the change is different. (Refer to Japan Nondestructive Inspection Association "eddy current testing III", published by Japan Nondestructive Inspection Association, September 1, 1990, P. 43-44) In the sensor 1, the direction on the XY plane of the output of the differential amplifier 22 caused only by the change in the distance between the primary circuit and the secondary circuit, that is, the displacement (wind speed) of the wind receiving plate 2 (see FIG. 3 (b) direction of the wind velocity component axis A) and the direction of the output of the differential amplifier 22 due to temperature only on the XY plane (temperature component axis B shown in FIG. 3B). Will be different).
[0043]
These directions can be determined in advance based on the specifications of each flow sensor 1. Therefore, in the example shown in FIG. 3B, the wind speed component axis A and the temperature component axis B are predetermined.
[0044]
The separation detection circuit 34 determines the components in the direction of the wind speed component axis A (the wind speed component B shown in FIG. 3B) and the temperature component axis B from the detected values a plotted on the XY plane. Each direction component (temperature component C shown in FIG. 3B) is obtained, and the obtained wind speed component B and temperature component C are output.
[0045]
Thereby, the separation detection of the wind speed component and the temperature component described above is completed, and the wind speed value is obtained from the detected wind speed component.
[0046]
As described above, the flow sensor 1 according to the first embodiment converts the displacement of the wind receiving plate 2 into an electrical signal and measures the wind speed of the gas 10 to be measured. Since it appears in the electrical signal, it is possible to measure even in the case of a light wind, and if the displacement direction of the wind receiving plate 2 is different, the detected electrical signal is also different, so that the wind direction can be detected. Furthermore, since the coil 5 and the electronic circuit part are not in the atmosphere of the gas to be measured 10, there is no problem such as corrosion due to the gas to be measured 10, and the durability is excellent. Moreover, since there is no sliding part, generation | occurrence | production of a particle can be prevented and power consumption is also small. Furthermore, since the separation unit 30 can separate and detect the wind speed component and the temperature component, measurement errors due to temperature can be eliminated, and accurate wind speed measurement can be performed.
[0047]
Next, a second embodiment of the flow sensor to which the present invention is applied will be described. FIG. 4 is a configuration diagram according to the second embodiment. As in FIG. 1, FIG. 4 shows only the wind speed detection portion, and shows a cross section viewed from a direction perpendicular to the direction of the flow of the gas to be measured.
[0048]
As shown in FIG. 4, the flow sensor 41 according to the second embodiment is different from the flow sensor 1 according to the first embodiment only in how the wind receiving plate is displaced. The part has the same configuration and function. Therefore, only the differences will be described below.
[0049]
In the present flow sensor 41, as shown in FIG. 4, the wind receiving plate support portions 44 are provided above and below the wind receiving plate 42, and each has a spring (elastic structure) 441 that supports the wind receiving plate 42. . The wind receiving plate 42 is attached to the spring 441 on both sides at the upper and lower portions, and is installed to be displaceable in the flow direction of the measurement target gas 400 (in the direction of the arrow in FIG. 4).
[0050]
Therefore, when the gas 400 to be measured flows in from the sensing window 47 of the coil fixing portion 46 and hits the wind receiving plate 42, the wind receiving plate 42 is pushed by the force, and the right portion of the spring 441 is compressed. 42 is displaced to the right. As a result, the distance between the coil 45 and the conductive portion 43 changes, and as in the case of the flow sensor 1 according to the first embodiment, the change can be taken out as an electrical signal to measure the wind speed. it can.
[0051]
In the flow sensor 1 according to the first embodiment, when the wind speed of the gas to be measured 10 disappears, the wind receiving plate 2 returns to the original position due to the elasticity of the wind receiving plate 2 itself. In 41, when the wind speed is lost, the wind receiving plate 42 returns to the original position by the elastic force of the spring 441. Accordingly, an inelastic material can be used as the wind receiving plate 42. In the present embodiment, a spring is used as the elastic structure, but other elastic bodies such as rubber may be used instead of the spring.
[0052]
Next, a third embodiment of the flow sensor to which the present invention is applied will be described. FIG. 5 is a diagram showing the configuration of the flow sensor according to the third embodiment. FIG. 5A shows a cross section viewed from a direction perpendicular to the flow direction of the gas to be measured, and FIG. 5B shows the effect of the flow sensor according to this embodiment. The figure is shown.
[0053]
As shown in FIG. 5, the flow sensor 51 according to the third embodiment is different from the flow sensor 1 according to the first embodiment only in how the wind receiving plate is displaced. The part has the same configuration and function. Therefore, only the differences will be described below.
[0054]
In the present flow sensor 51, as shown in FIG. 5, a wind receiving plate support 54 is provided below the wind receiving plate 52, and the wind receiving plate 52 is supported and fixed at the lower end thereof. A sensing window 57 is provided so that the wind receiving plate 52 receives the flow of the measurement target gas 500 at a position between the wind receiving plate support portion 54 and the conductive portion 53.
[0055]
In the flow sensor 51 having such a configuration, when the wind receiving plate 52 receives the flow of the measurement target gas 500, it is displaced as shown in FIG. Therefore, the displacement (L4 in FIG. 5B) at the position of the conductive portion 53 (displacement detection position) is the displacement (the wind receiving position) at the position where the wind receiving plate 52 receives the wind (the wind receiving position in FIG. 5). It becomes larger than L3) in b). Thus, in this flow sensor 51, since the displacement to detect is amplified, the sensitivity of measurement can be raised rather than the case of the flow sensor 1 which concerns on 1st embodiment.
[0056]
Next, a fourth embodiment of a flow sensor to which the present invention is applied will be described. FIG. 6 is a diagram for explaining the principle of the flow sensor according to the fourth embodiment. The flow sensor 61 according to the fourth embodiment is a coil (5, 45, 55) which is a displacement detection unit of the flow sensor (1, 41, 51) according to the first to third embodiments described above. ) Is replaced with a capacitor 65.
[0057]
As shown in FIG. 6, an electric field 600 is formed around the capacitor 65, but if there is a conductive portion 63 in the electric field 600, the electric field 600 is affected by its presence. Here, when the wind receiving plate (2, 42, 52) receives wind and is displaced, the conductive portion 63 attached to the wind receiving plate (2, 42, 52) is also displaced in the direction of the arrow in FIG. 6, thereby changing the electric field 600. . The capacitance of the capacitor 65 changes due to the change in the electric field 600. Therefore, by detecting the change in the capacitance of the capacitor 65, the displacement of the conductive portion 63, that is, the wind speed can be detected.
[0058]
In the flow sensor 61 according to the present embodiment, since the capacitor 65 is used instead of the coil as described above, it is not affected by the temperature. Therefore, the temperature component as described in the first embodiment is not affected. There is no need to perform a separation process.
[0059]
The flow sensor according to the first to fourth embodiments described above has two conductive parts and two displacement detection parts (coils or capacitors) corresponding to the two conductive parts. You may make it comprise in a part and one displacement detection part corresponding to it.
[0060]
In the above embodiment, the flow sensor for measuring the wind speed of the gas is exemplified. However, the present invention is not limited to the measurement of the wind speed of the gas. The present invention can also be applied to the measurement of the flow rate of fluids other than gases, such as the flow rate of solids such as the above, or the flow rate of solid-gas two-phase flow.
[0061]
The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.
[0062]
【The invention's effect】
As described above, according to the present invention, since the displacement of the fluid receiving portion is converted into an electric signal and the flow velocity is measured, measurement is possible even in the case of a micro flow, and the direction of the flow can also be detected. Furthermore, the flow sensor according to the present invention is excellent in durability without problems such as corrosion due to the fluid to be measured because the coil and the electronic circuit portion are not in the fluid to be measured. Moreover, since there is no sliding part, generation | occurrence | production of a particle can be prevented and power consumption is also small.
[Brief description of the drawings]
FIG. 1 is a configuration diagram according to a first embodiment of a flow sensor to which the present invention is applied.
FIG. 2 is a diagram for explaining the principle of wind speed measurement by the flow sensor 1;
3 is a diagram showing a configuration of a processing circuit portion after a coil 5 of the flow sensor 1 and the like. FIG.
FIG. 4 is a configuration diagram according to a second embodiment of a flow sensor to which the present invention is applied.
FIG. 5 is a diagram showing a configuration of a flow sensor according to a third embodiment.
FIG. 6 is a diagram for explaining the principle of a flow sensor according to a fourth embodiment.
[Explanation of symbols]
1 Flow sensor 2 Wind receiving plate (fluid receiving part)
3 Conductive part 4 Wind receiving plate support part 5 Coil (displacement detection part)
6 Coil fixing part 7 Sensing window 8 Wiring 9 Pipe 10 Gas to be measured 11 Power supply part 20 Detection part 21 Oscillator 22 Differential amplifier 30 Separation part 31 90 ° phase shifter 32a, 32b Multiplier 33a, 33b Low pass filter 34 Separation detection circuit 41 Flow sensor 42 Wind receiving plate 43 Conductive portion 44 Wind receiving plate support portion 45 Coil 46 Coil fixing portion 47 Sensing window 49 Piping 51 Flow sensor 52 Wind receiving plate 53 Conductive portion 54 Wind receiving plate support portion 55 Coil 56 Coil fixing portion 57 Sensing window 59 Piping 61 Flow sensor 63 Conductive part 65 Capacitor 400 Gas to be measured 441 Spring (elastic structure)
500 Gas to be measured 600 Electric field

Claims (3)

A flow sensor for measuring the flow velocity of a fluid,
A fluid receiving portion that is displaced in response to the flow of the fluid;
A conductive portion having conductivity that is displaced together with the fluid receiving portion;
A support portion for supporting the fluid receiving portion;
A displacement detection unit configured by a coil, which is fixed at a position facing the conductive unit and detects a displacement of the conductive unit;
The detected by applying a predetermined high frequency signal to a predetermined circuit including the coil, a detection signal based on the displacement and the temperature of the conductive portion, based on the high frequency signal the application, the detection signal, the A flow sensor comprising: a separation unit that separates into a component based on a displacement of the conductive portion and a component based on a temperature of the conductive portion based on a phase of a high-frequency signal . A flow sensor for measuring the flow velocity of a fluid,
A fluid receiving portion that is displaced in response to the flow of the fluid;
A conductive portion having conductivity that is displaced together with the fluid receiving portion;
A support portion for supporting the fluid receiving portion;
A displacement detection unit that is fixed at a position facing the conductive unit and detects a displacement of the conductive unit;
The flow sensor, wherein the displacement detection unit is configured by a capacitor different from the fluid receiving unit. In claim 1 or claim 2 ,
The position where the displacement detector is fixed is a position that does not contact the fluid.

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