Flow Detection Device

Abstract

To provide a flow detector that can reduce the influence of an external force and vibration on a channel and highly accurately detect a change in shape of the channel in association with a change in pressure of fluid.SOLUTION: A flow detector 1 comprises: a channel 10 that has a flow wall 11 swelling and contracting according to a change in pressure of fluid flowing inside the channel; a pressure receiving part 20 that has an inner layer part 21 covering at least part of the periphery of the flow wall 11 and changing its volume according to the swelling and contracting of the flow wall 11 and a non-air permeable outer layer part 22 surrounding the inner layer part 21, and is provided, in the outer layer part 22, with a window part 23 through which gas inside the inner layer part 21 comes in and goes out in association with the change in volume of the inner layer part 21; and a pressure detection part 30 that has a cantilever 32 bent and deformed by the gas coming in and going out through the window part 23.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to flow sensing devices. [Background technology]

[0002] The following Patent Document 1 discloses a flow abnormality detection device that detects flow abnormalities without contacting the fluid. This flow abnormality detection device clamps a flexible tube connected to a roller pump between a case body and a lid that are connected by a hinge. A strain gauge is provided in the case body, and by pressing the strain gauge against the outer surface of the tube, the pressure received from the tube is measured and a flow abnormality is detected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-132364 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when detecting the flow state of a minute flow rate, the displacement of the tube is very small, for example, in some cases less than 1 μm. In a sensor that measures the displacement by pressing a strain gauge or the like against the tube, as in the above-mentioned conventional technology, the signal level becomes small and the influence of the displacement due to external forces and vibrations becomes relatively large. This may become a noise source, making it difficult to detect the displacement of the tube with high accuracy. In other words, even if the sensor itself has high performance and high resolution, there is a problem that the signal-to-noise ratio deteriorates due to disturbances, making measurement difficult.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a flow detection device that reduces the effects of external forces, vibrations, etc. on a flow path and can detect changes in the shape of a flow path due to changes in fluid pressure with high accuracy. [Means for solving the problem]

[0006] (1) A flow detection device according to one embodiment of the present disclosure comprises a flow path having a flow wall that expands and contracts due to pressure changes of a fluid flowing therethrough, an inner layer that covers at least a portion of the periphery of the flow wall and whose volume changes in response to the expansion and contraction of the flow wall, and an air-impermeable outer layer that surrounds the inner layer, the outer layer having a window through which gas within the inner layer can enter and exit as the volume of the inner layer changes, and a pressure detection unit having a cantilever that flexes and deforms due to the gas entering and exiting through the window.

[0007] In the flow detection device according to this aspect, when the flow wall of the flow path expands and contracts due to a pressure change of the fluid flowing inside, the volume of the inner layer of the pressure-receiving part that covers at least a part of the periphery of the flow wall changes, and gas flows in and out through a window provided in the gas-impermeable outer layer that covers the inner layer. The cantilever is then flexed and deformed by the gas flowing in and out through the window. Even if the amount of gas flowing in and out through the window is very small, the cantilever flexes and deforms in response to the gas pressure with high sensitivity, and therefore the flow state of the fluid can be detected with high sensitivity. On the other hand, when the flow channel is subjected to an external force from the outside or is vibrating, the flow wall does not expand or contract by itself, so the volume of the inner layer of the pressure-receiving part does not change and the cantilever hardly reacts. Therefore, the flow detection device according to this embodiment can reduce the effects of external forces, vibrations, etc. on the flow path, and can detect changes in the shape of the flow path associated with changes in fluid pressure with high accuracy.

[0008] (2) In the flow detection device of aspect (1), the inner layer portion may be formed of an elastic body having interconnected cells.

[0009] In this case, the inner layer can elastically support the flow wall of the flow path. Also, when the flow wall expands or contracts, the inner layer can elastically deform in response to the expansion or contraction. Furthermore, the elastic deformation of the inner layer can damp vibrations of the flow path.

[0010] (3) In the flow detection device of aspect (2), the elastic body may be polyurethane foam.

[0011] In this case, the inner layer of the pressure-receiving part can be produced at low cost.

[0012] (4) In the flow detection device according to any one of (1) to (3), the inner layer portion may be softer than the flow wall.

[0013] In this case, for example, when the flow wall expands, the inner layer, which is softer than the flow wall, begins to collapse before the flow wall is completely crushed in the thickness direction by the internal pressure of the fluid, improving the responsiveness of the inner layer to volume fluctuations and enabling sensitive detection of changes in the shape of the flow path accompanying changes in fluid pressure.

[0014] (5) In the flow detection device according to any one of (1) to (4), the pressure detection unit may include a cavity housing that forms a differential pressure chamber that communicates with the window portion across the cantilever.

[0015] In this case, the cantilever is less susceptible to the effects of the outside air, so that changes in the shape of the flow path accompanying changes in fluid pressure can be detected with high accuracy.

[0016] (6) In the flow detection device according to any one of (1) to (5), a pressing member may be provided that presses the pressure-receiving portion against the flow wall.

[0017] In this case, the inner layer of the pressure-receiving part is in close contact with the flow wall, so that the response to the volume fluctuation of the inner layer due to the expansion and contraction of the flow wall is improved, and changes in the shape of the flow path due to changes in fluid pressure can be detected with high sensitivity.

[0018] (7) In the flow detection device of any one of aspects (1) to (6), the pressure-receiving portion may have a cylindrical portion surrounding the flow wall, and a slit extending in the longitudinal direction of the flow path may be formed in the cylindrical portion.

[0019] In this case, the flow path can be inserted into the pressure-receiving portion through the slit, which makes it easy to install the pressure-receiving portion on the flow wall.

[0020] (8) In the flow detection device according to any one of (1) to (7), the flow wall may be surrounded by a plurality of flow detection units, each including the pressure receiving portion and the pressure detecting portion.

[0021] In this case, since the flow wall is surrounded by multiple flow detection units, the volume of the inner layer of the pressure receiving part per flow detection unit can be reduced, improving the responsiveness of the inner layer to the volume fluctuations caused by the expansion and contraction of the flow wall, and enabling the sensitive detection of changes in the shape of the flow path caused by changes in the fluid pressure.

[0022] In the flow detection device of aspects (9) and (8), the multiple flow detection units may include a first flow detection unit and a second flow detection unit arranged opposite each other across the flow path, and may be equipped with a signal processing circuit that adds signals output from the pressure detection sections of the first flow detection unit and the second flow detection unit and cancels vibration noise of the flow path.

[0023] In this case, even if vibration noise from the flow path is picked up as a result of dividing the flow detection units into multiple units, the vibration noise from the flow path can be offset by adding the signals output from the pressure detection units of the first flow detection unit and the second flow detection unit arranged opposite each other across the flow path, and changes in the shape of the flow path due to changes in fluid pressure can be detected with high accuracy. Effect of the Invention

[0024] According to one aspect of the present disclosure, it is possible to provide a flow detection device that can reduce the influence of external forces, vibrations, and the like on a flow path and detect changes in the shape of the flow path associated with changes in fluid pressure with high accuracy. [Brief description of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of a flow detection device according to a first embodiment. FIG. [Diagram 2] 2 is a cross-sectional view taken along line II-II of FIG. 1. [Diagram 3] FIG. 2 is a plan view showing an example of the configuration of a cantilever according to the first embodiment. [Figure 4] 2 is a circuit diagram showing an example of the configuration of an analog circuit unit according to the first embodiment. FIG. [Diagram 5] 4 is a diagram showing a state in which a flow path is displaced upward relative to a pressure-receiving part due to an external force, vibration, or the like in the flow detection device according to the first embodiment. FIG. [Figure 6] 4 is a diagram showing a state in which a flow path in the flow detection device according to the first embodiment is displaced to the right relative to a pressure-receiving part due to an external force, vibration, or the like. FIG. [Figure 7] 4A and 4B are diagrams showing a state in which a flow wall of a flow channel in the flow detection device according to the first embodiment is expanded due to a pressure change of a fluid flowing inside. [Figure 8] 5A and 5B are diagrams showing a state in which a flow wall of a flow channel in the flow detection device according to the first embodiment is contracted due to a pressure change of a fluid flowing inside. [Figure 9] FIG. 4 is a diagram showing an example of output waveform data of the flow detection device according to the first embodiment. [Figure 10] FIG. 11 is a cross-sectional view of a flow detection device according to a second embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a flow detection device according to a third embodiment. [Figure 12] FIG. 11 is a cross-sectional view showing the configuration of a flow detection device according to a fourth embodiment. [Figure 13] FIG. 13 is a configuration diagram showing a first example of a signal processing circuit according to a fourth embodiment. [Figure 14] FIG. 13 is a configuration diagram showing a second example of a signal processing circuit according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0027] (First embodiment) Fig. 1 is a cross-sectional view of a flow detection device 1 according to a first embodiment. Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1. As shown in FIG. 1, the flow detection device 1 includes a flow path 10, a pressure receiving section 20, and a pressure detection section 30.

[0028] The flow path 10 has a flow wall 11 that expands and contracts due to pressure changes of the fluid flowing therethrough. The flow path 10 of this embodiment is a so-called liquid delivery tube that has at least flexibility and elasticity, and is formed long with a constant inner diameter (cross-sectional area). Depending on the type and application of the fluid, the flow wall 11 may be subjected to various treatments such as oxidation treatment as necessary, and various properties such as heat resistance and transparency may be added.

[0029] The flow path 10 is connected to, for example, a pulsating pump (not shown). The pulsating pump can be, for example, a so-called roller pump that sucks in the fluid stored in a water supply tank and discharges it while pulsating at a known reference frequency. Since the flow path 10 has at least flexibility and elasticity, the flow wall 11 expands and contracts in a wavy manner in response to the pulsation of the fluid.

[0030] The pressure-receiving section 20 has an inner layer section 21 that covers at least a portion of the periphery of the flow wall 11 (the entire periphery in the first embodiment) and whose volume changes according to the expansion and contraction of the flow wall 11, and an air-impermeable outer layer section 22 that covers the inner layer section 21. The outer layer section 22 is provided with a window section 23 through which air (gas) enters and exits within the inner layer section 21 as the volume of the inner layer section 21 changes. Note that, as in this embodiment, when the pressure detection section 30 has a cavity housing 35 and can form an airtight space, the inner layer section 21 may be filled with a gas other than air (for example, nitrogen gas, etc.).

[0031] The inner layer portion 21 and the outer layer portion 22 form a tubular portion 20A concentric with the central axis O of the flow path 10. The inner layer portion 21 is formed of an elastic body having interconnected cells. An example of the elastic body forming the inner layer portion 21 is polyurethane foam. This inner layer portion 21 only needs to be able to elastically deform in response to the internal pressure of the fluid, and it is particularly preferable for the inner layer portion 21 to be softer than the flow wall 11, as this enhances the responsiveness to volumetric fluctuations.

[0032] The inner layer portion 21 may be a space (hollow) or may be a fiber cushion capable of holding air in gaps between fibers, so long as the volume of the inner layer portion 21 can change in response to the expansion and contraction of the flow wall 11. The inner layer portion 21 may be formed by compressing closed cells such as rubber sponge with a roller or the like to form interconnected cells.

[0033] The outer layer portion 22 covers the entire outer surface of the inner layer portion 21 except for the window portion 23. Specifically, as shown in Fig. 2, the outer layer portion 22 covers the outer peripheral surface of the inner layer portion 21 and both longitudinal end faces of the inner layer portion 21. The window portion 23 is formed at a central position in the longitudinal direction of the outer peripheral surface of the outer layer portion 22.

[0034] The outer layer 22 is, for example, a skin layer (surface layer) of integral skin foam or coated urethane, in which the inner layer 21 is soft, and is harder than the inner layer 21 and has almost no breathability. The outer layer 22 may be made of hard plastic or metal, etc., as long as it is breathable and can maintain the outer shape of the pressure-receiving part 20. The "breathable" mentioned here does not have to be completely airtight, but may be such that the pressure detection part 30 can detect pressure fluctuations from the window part 23.

[0035] Returning to Fig. 1, the window portion 23 is formed in a part of the outer peripheral surface of the outer layer portion 22. The surface of the inner layer portion 21, i.e., the interconnected air bubbles, are exposed from the window portion 23. A holding member 24 that holds the tubular portion 20A including the inner layer portion 21 and the outer layer portion 22 is provided around the window portion 23. The holding member 24 airtightly surrounds the window portion 23 and is connected to the sensor substrate 31 of the pressure detection portion 30.

[0036] The pressure detection unit 30 includes a sensor substrate 31, a cantilever 32, an analog circuit unit 33, a digital processing unit , and a cavity housing . The sensor board 31 is, for example, a printed circuit board. A through hole 31a penetrating the sensor board 31 in the thickness direction is formed in the sensor board 31. The through hole 31a is disposed inside the holding member 24 and communicates with the window portion 23.

[0037] The cavity housing 35 is formed in a cylindrical shape with a bottom, and is connected to the surface of the sensor substrate 31 opposite to the surface to which the holding member 24 is connected so as to surround the through-hole 31a. The cantilever 32 is disposed inside the cavity housing 35. The cantilever 32 is attached to the open end of a cylindrical lever support part 36 connected to the inside of the cavity housing 35 so as to surround the through-hole 31a.

[0038] The cavity housing 35 is partitioned into a first air chamber 30A and a second air chamber 30B across the cantilever 32. The first air chamber 30A and the second air chamber 30B communicate with each other via a communication hole 42 provided in the cantilever 32. The window portion 23 of the pressure receiving portion 20 and the through hole 31a of the sensor substrate 31 communicate with the second air chamber 30B. The first air chamber 30A is a differential pressure chamber (airtight chamber) that communicates with the second air chamber 30B across the cantilever 32.

[0039] FIG. 3 is a plan view showing an example of the configuration of the cantilever 32 according to the first embodiment. The cantilever 32 is formed on a semiconductor substrate 40, such as an SOI substrate. Gaps G1 and G2 are provided in the semiconductor substrate 40, and a lever body 41 and a lever support portion 43 of the cantilever 32 are formed therein. The gaps G1 and G2 serve as a communication hole 42 that communicates between the first air chamber 30A and the second air chamber 30B.

[0040] The lever body 41 is supported in a cantilever manner with its base end 41b connected to the lever support part 43 and its tip end 41a being a free end. The lever body 41 is in the form of a plate extending in one direction from the base end 41b to the tip end 41a, and is flexed and deformed in response to the pressure difference between the first air chamber 30A and the second air chamber 30B of the cavity housing 35.

[0041] Gap G1 is a groove formed between the semiconductor substrate 40 and the outer periphery of the lever body 41, and having a U-shape in plan view that penetrates the semiconductor substrate 40 in the thickness direction. Gap G2 is a groove formed in the base end portion 41b of the lever body 41, and having a U-shape in plan view that penetrates the lever body 41 in the thickness direction. Gap G2 is disposed in the center of the base end portion 41b of the lever body 41 in the width direction of the lever body 41.

[0042] The two lever support parts 43 are arranged side by side in the width direction of the lever body 41 with a gap G2 therebetween, and connect the lever body 41 to the semiconductor substrate 40 and support the lever body 41 in a cantilever state. The support widths of the two lever support parts 43 in the width direction of the lever body 41 are made equal. Therefore, when the lever body 41 is bent and deformed, the stress per unit area acting on one lever support part 43 is equal to the stress per unit area acting on the other lever support part 43.

[0043] A doped layer 44 (impurity semiconductor layer) which is a piezoresistor (resistance element) is formed on the semiconductor substrate 40 so as to include the lever body 41. This doped layer 44 is formed by doping a dopant (impurity) such as phosphorus by various methods such as ion implantation and diffusion. Of the doped layer 44, the portion where the lever body 41 is formed (including the portion formed on the lever support portion 43) functions as a resistor R1 (differential pressure detection resistor Rsen1).

[0044] The resistance value of the resistor R1 changes according to the amount of deflection of the lever support portion 43. Although not shown, an electrode made of a conductive material (e.g., Au (gold) or the like) having a lower electrical resistivity than the doped layer 44 is formed on the upper surface of the doped layer 44. This electrode functions as a first end and a second end of the resistor R1 (differential pressure detection resistor Rsen1).

[0045] Returning to Fig. 1, the analog circuit unit 33 is a circuit that performs analog processing to detect a displacement corresponding to the bending deformation of the lever body 41. This analog circuit unit 33 is an AFE (analog front end). The analog circuit unit 33 is disposed inside the cavity housing 35, i.e., in the first air chamber 30A.

[0046] FIG. 4 is a circuit diagram showing an example of the configuration of the analog circuit unit 33 according to the first embodiment. 4, the analog circuit unit 33 includes a Wheatstone bridge circuit 61 and a differential amplifier circuit 62. The Wheatstone bridge circuit 61 includes a resistor R1 (differential pressure detection resistor Rsen1) that the cantilever 32 has, a resistor R2, a resistor R3, and a resistor R4.

[0047] The resistor R1 (differential pressure detection resistor Rsen1) has a first end connected to the reference voltage circuit Vref and a second end connected to a node N1, and the resistance changes according to the differential pressure between the first air chamber 30A and the second air chamber 30B. The resistor R1 is, for example, a piezoresistor (doped layer 44). The resistor R2 has a first end connected to the node N1 and a second end connected to the power supply GND.

[0048] The resistor R3 has a first end connected to the reference voltage circuit Vref and a second end connected to the node N2. The resistor R4 has a first end connected to the node N2 and a second end connected to the power supply GND. The resistor R1 is configured within the cantilever 32, and the resistors R3 and R4 are external resistors provided outside the cantilever 32.

[0049] Resistor R2 (reference resistor Rref1) is, for example, a resistor formed so as to have the same temperature characteristics as resistor R1, and may be configured inside cantilever 32, or may be provided externally in the vicinity of cantilever 32. By matching the temperature characteristics of resistors R1 and R2, analog circuit section 33 can reduce the effect of temperature fluctuations on the detection results.

[0050] The differential amplifier circuit 62 is, for example, an instrumentation amplifier, which amplifies the potential difference between node N1 and node N2 and outputs it as an output signal. This potential difference has a value according to the change in resistance value of the piezoresistor, that is, a value based on the displacement of the cantilever 32. The differential amplifier circuit 62 has an inverting input terminal (- terminal) connected to node N1 and a non-inverting input terminal (+ terminal) connected to node N2.

[0051] 1, the digital processing unit 34 is, for example, a digital processing circuit such as a microcontroller, and converts output waveform data corresponding to the differential pressure detected by the analog circuit unit 33 into pressure fluctuation information. The digital processing unit 34 is, for example, mounted (placed) on the sensor board 31, and is placed outside the cavity housing 35.

[0052] Next, the operation of the flow detection device 1 having the above configuration will be described with reference to FIGS.

[0053] FIG. 5 is a diagram showing a state in which the flow channel 10 in the flow detection device 1 according to the first embodiment is displaced upward with respect to the pressure-receiving portion 20 due to an external force, vibration, or the like. 5, when the central axis O1 of the flow path 10 is displaced upward by a distance D1 relative to the central axis O2 of the pressure-receiving part 20, the upper side of the inner layer part 21 elastically deforms and narrows, but the lower side of the inner layer part 21 widens, so that the overall cross-sectional area of ​​the inner layer part 21 does not change. In other words, since no volumetric fluctuation occurs in the inner layer part 21, air does not enter or exit through the window part 23, and the cantilever 32 hardly reacts.

[0054] FIG. 6 is a diagram showing a state in which the flow channel 10 in the flow detection device 1 according to the first embodiment is displaced to the right with respect to the pressure-receiving portion 20 due to an external force, vibration, or the like. 6, when the central axis O1 of the flow path 10 is displaced a distance D2 to the right relative to the central axis O2 of the pressure-receiving part 20, the right side of the inner layer part 21 elastically deforms and narrows, but the left side of the inner layer part 21 widens, so that the overall cross-sectional area of ​​the inner layer part 21 does not change. In other words, since no volume fluctuation occurs in the inner layer part 21, air does not enter or exit through the window part 23, and the cantilever 32 hardly reacts. The same applies when the flow path 10 is displaced in a diagonal direction other than up, down, left, or right.

[0055] FIG. 7 is a diagram showing a state in which the flow wall 11 of the flow channel 10 in the flow detection device 1 according to the first embodiment is expanded due to a pressure change of the fluid flowing therethrough. 7, when the flow wall 11 of the flow channel 10 expands due to a pressure change of the fluid flowing inside, the inner layer portion 21 is compressed and its cross-sectional area decreases. Then, the air in the interconnected bubbles of the inner layer portion 21 is pushed out from the window portion 23, and the cantilever 32 is bent and deformed.

[0056] That is, when the flow wall 11 of the flow channel 10 expands and the inner layer 21 of the pressure-receiving part 20 is compressed, reducing the cross-sectional area, air is pushed out from the window part 23, and the pressure in the second air chamber 30B increases. Then, the cantilever 32 detects the pressure difference between the first air chamber 30A and the second air chamber 30B, and the change in shape of the flow channel 10 due to the increase in the internal pressure of the flow channel 10 can be detected.

[0057] FIG. 8 is a diagram showing a state in which the flow wall 11 of the flow channel 10 in the flow detection device 1 according to the first embodiment is contracted due to a pressure change of the fluid flowing therethrough. As shown in Fig. 8, when the flow wall 11 of the flow path 10 shrinks due to a pressure change of the fluid flowing inside (when it returns to its original state from the state shown in Fig. 7), the inner layer portion 21 is deformed to restore its original cross-sectional area. Then, air is taken into the inner layer portion 21 from the window portion 23, the pressure difference between the first air chamber 30A and the second air chamber 30B is alleviated, and the cantilever 32 is deformed to restore its original shape.

[0058] Fig. 9 is a diagram showing an example of output waveform data of the flow detection device 1 according to the first embodiment. In Fig. 9, the vertical axis represents voltage [V], and the horizontal axis represents time [sec]. As shown in FIG. 9, in the initial flow state when the pulsating pump is operating, the internal pressure of the flow path 10 changes due to the pulsating flow caused by the pulsating pump, causing the flow wall 11 to pulsate, and output waveform data of periodic pressure changes synchronized with the pulsation is obtained.

[0059] On the other hand, if a blockage occurs in the flow channel 10 downstream of the flow detection device 1, the internal pressure of the flow channel 10 rises immediately after the blockage occurs, and the pulsation output waveform data also increases. By observing the magnitude of this output waveform data, it becomes possible to estimate the presence or absence of a blockage in the flow channel 10 and the flow state.

[0060] 5 and 6, the flow detection device 1 can eliminate noise due to external forces and vibrations, improving the signal-to-noise ratio and enabling highly accurate detection of changes in the shape of the flow channel 10 associated with changes in fluid pressure due to flow conditions (such as clogging) in the flow channel 10. This makes it possible to accurately detect flow conditions, particularly at very small flow rates.

[0061] As described above, the flow detection device 1 of this embodiment comprises a flow path 10 having a flow wall 11 that expands and contracts due to pressure changes of the fluid flowing therethrough, a pressure-receiving section 20 having an inner layer section 21 that covers at least a portion of the periphery of the flow wall 11 and whose volume changes according to the expansion and contraction of the flow wall 11, and an outer layer section 22 that is non-breathable and surrounds the inner layer section 21, and in which a window section 23 is provided in the outer layer section 22 through which air within the inner layer section 21 enters and exits as the volume of the inner layer section 21 changes, and a pressure detection section 30 having a cantilever 32 that flexes and deforms due to air entering and exiting through the window section 23.

[0062] According to this flow detection device 1, when the flow wall 11 of the flow path 10 expands and contracts due to pressure changes of the fluid flowing therein, the volume of the inner layer 21 of the pressure-receiving part 20 covering at least a part of the periphery of the flow wall 11 changes, and air flows in and out through the window 23 provided in the air-impermeable outer layer 22 covering the inner layer 21. The air flowing in and out through the window 23 causes the cantilever 32 to flex and deform. Even if the amount of air flowing in and out through the window 23 is minute, the cantilever 32 flexes and deforms in response to the air pressure with high sensitivity, and therefore the flow state of the fluid can be detected with high sensitivity. On the other hand, when the flow channel 10 is subjected to an external force from the outside or is vibrating, the flow wall 11 does not expand or contract by itself, so the volume of the inner layer portion 21 of the pressure-receiving portion 20 does not change and the cantilever 32 hardly reacts. Therefore, the flow detection device 1 according to this embodiment can reduce the influence of external force, vibration, etc. on the flow channel 10, and can detect changes in the shape of the flow channel 10 associated with changes in fluid pressure with high accuracy.

[0063] Moreover, in the flow detection device 1 of this embodiment, the inner layer portion 21 is formed of an elastic body having interconnected bubbles. With this configuration, the inner layer portion 21 can elastically support the flow wall 11 of the flow path 10. Furthermore, when the flow wall 11 expands or contracts, the inner layer portion 21 can elastically deform in response to the expansion or contraction. Furthermore, the elastic deformation of the inner layer portion 21 can damp vibrations of the flow path 10.

[0064] In the flow detection device 1 of the present embodiment, the elastic body is polyurethane foam. With this configuration, the inner layer portion 21 of the pressure-receiving part 20 can be produced at low cost.

[0065] In the flow detection device 1 of this embodiment, the inner layer portion 21 is softer than the flow wall 11. With this configuration, for example, as shown in Fig. 7 described above, when the flow wall 11 expands, the inner layer portion 21, which is softer than the flow wall 11, begins to collapse before the flow wall 11 is completely collapsed in the thickness direction by the internal pressure of the fluid, so that the responsiveness of the inner layer portion 21 to the volumetric fluctuation is improved, and the change in shape of the flow channel 10 accompanying the change in pressure of the fluid can be detected with good sensitivity.

[0066] 1, in the flow detection device 1 of this embodiment, the pressure detection unit 30 includes a cavity housing 35 that forms a first air chamber 30A serving as a differential pressure chamber that communicates with the window portion 23 across the cantilever 32. With this configuration, the cantilever 32 is less susceptible to the effects of outside air, so that changes in the shape of the flow path 10 due to changes in the pressure of the fluid can be detected with high accuracy.

[0067] Second embodiment Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent configurations as those in the above-described embodiment are given the same reference numerals, and the description thereof will be simplified or omitted.

[0068] FIG. 10 is a cross-sectional configuration diagram of a flow detection device 1 according to the second embodiment. 10, the flow detection device 1 of the second embodiment includes a pressing member 50 that presses the pressure-receiving portion 20 against the flow wall 11. The pressing member 50 includes a pair of pressing pieces 51.

[0069] The pressing piece 51 includes a fixed portion 51a, a movable portion 51b, a hinge 51c, and a fastened portion 51d. The fixed portion 51a is fixed to the sensor board 31 on the outside of the holding member 24. The movable portion 51b is connected to the upper end of the fixed portion 51a via the hinge 51c. The movable portion 51b has an arc shape with the same or approximately the same curvature as the outer circumferential surface of the pressure receiving portion 20.

[0070] The fastened portion 51d is provided at the upper end of the movable portion 51b, and is fastened to the fastened portion 51d of the other pressing piece 51 via a bolt 52 and a nut 53. The bolt 52 and the nut 53 are configured to adjust the magnitude of pressure with which the pair of pressing pieces 51 press the pressure receiving portion 20.

[0071] According to the second embodiment having the above configuration, a pressing member 50 is provided for pressing the pressure-receiving portion 20 against the flow wall 11, so that the inner layer portion 21 of the pressure-receiving portion 20 adheres closely to the flow wall 11, improving the responsiveness of the volumetric fluctuation of the inner layer portion 21 accompanying the expansion and contraction of the flow wall 11, and enabling the sensitive detection of changes in the shape of the flow path 10 accompanying changes in fluid pressure.

[0072] In addition, because the deformation of the outer shape of the pressure-receiving part 20 is suppressed by the pressing member 50, it becomes easier to directly detect the change in shape (expansion / contraction) of the flow passage 10 accompanying the change in fluid pressure in the inner layer part 21. Furthermore, because the tightening condition of the pressing member 50 can be optimized by the bolts 52 and nuts 53, it is possible to absorb the variation in the inner diameter of the pressure-receiving part 20. Furthermore, because the pressure-receiving part 20 is not exposed, it is possible to avoid noise due to external forces acting directly on the pressure-receiving part 20.

[0073] Third embodiment Next, a third embodiment of the present invention will be described. In the following description, the same or equivalent configurations as those in the above-described embodiment are given the same reference numerals, and the description thereof will be simplified or omitted.

[0074] FIG. 11 is a cross-sectional configuration diagram of a flow detection device 1 according to the third embodiment. As shown in FIG. 11, the pressure-receiving portion 20 of the third embodiment has a tubular portion 20A surrounding the flow wall 11, and a slit 20B extending in the longitudinal direction of the flow path 10 and detachable from the flow wall 11 is formed in the tubular portion 20A.

[0075] That is, a part of the circumferential direction of the cylindrical portion 20A of the pressure-receiving portion 20 of the third embodiment is split from end to end along the longitudinal direction of the flow path 10. The inner wall surface of the slit 20B is covered with an air-impermeable outer layer portion 22. The pressure-receiving portion 20 of the third embodiment covers almost the entire periphery of the flow wall 11 except for the slit 20B.

[0076] In the third embodiment, a spacer 54 is sandwiched between the pair of pressing pieces 51. The spacer 54 is formed with a hole through which the bolt 52 can be inserted, for example, and the thickness of the spacer 54 can be changed to adjust and fix the magnitude of pressure applied by the pressing member 50 to the pressure-receiving portion 20.

[0077] According to the third embodiment having the above configuration, the pressure-receiving part 20 includes a cylindrical part 20A surrounding the flow wall 11, and the cylindrical part 20A is formed with a slit 20B extending in the longitudinal direction of the flow path 10 and detachable from the flow wall 11, so that the pressure-receiving part 20 can be easily installed on the flow wall 11. That is, since the pressure-receiving part 20 is split, the pressure-receiving part 20 can be attached by covering the flow wall 11 from above. That is, the effort of attaching the pressure-receiving part 20 from the end of the flow path 10 is eliminated.

[0078] In the third embodiment, since the spacer 54 is sandwiched between the pair of pressing pieces 51, it becomes easier to adjust the amount of pressure applied to the pressure-receiving portion 20 by the pressing member 50.

[0079] (Fourth embodiment) Next, a fourth embodiment of the present invention will be described. In the following description, the same or equivalent configurations as those in the above-described embodiment are given the same reference numerals, and the description thereof will be simplified or omitted.

[0080] FIG. 12 is a cross-sectional configuration diagram of a flow detection device 1 according to the fourth embodiment. 12, the flow detection device 1 of the fourth embodiment includes a plurality of flow detection units 2, each including a pressure receiving section 20 and a pressure detection section 30, and these flow detection units 2 surround the flow wall 11. In the example shown in FIG. 12, the flow detection device 1 includes two flow detection units 2, but may include three or more flow detection units 2.

[0081] The flow detection device 1 includes a first flow detection unit 2A and a second flow detection unit 2B disposed opposite each other across a flow path 10. Each of the first flow detection unit 2A and the second flow detection unit 2B includes a semicircular arc-shaped pressure receiving portion 20, a pressure detection portion 30, and a coupling 55 that constitutes the pressing member 50 described above.

[0082] The semicircular pressure receiving parts 20 are disposed opposite each other across the flow path 10, and cover at least a portion of the periphery of the flow wall 11 (almost the entire periphery in the fourth embodiment). The coupling 55 has a semicircular shape with the same or nearly the same curvature as the outer circumferential surface of the pressure receiving part 20. The couplings 55 of the first flow detection unit 2A and the second flow detection unit 2B are fastened via a bolt 52 and a nut 53 with a spacer 54 in between, so that the magnitude of the pressure pressing down on the pressure receiving part 20 can be adjusted.

[0083] The flow detection device 1 includes a signal processing circuit 70 that processes signals output from the pressure detection sections 30 of the first flow detection unit 2A and the second flow detection unit 2B.

[0084] FIG. 13 is a configuration diagram showing a first example of a signal processing circuit 70 according to the fourth embodiment. As shown in FIG. 13, the resistance R1 of the cantilever 32 of the first flow detection unit 2A and the resistance R4 of the cantilever 32 of the second flow detection unit 2B may be incorporated into the same Wheatstone bridge circuit 61.

[0085] The resistor R1 has a first end connected to the reference voltage circuit Vref and a second end connected to the node N1. The resistor R1 is a variable piezoresistor (doped layer 44) of the cantilever 32 of the first flow detection unit 2A. The resistor R2 has a first end connected to the node N1 and a second end connected to the power supply GND.

[0086] The resistor R3 has a first end connected to the reference voltage circuit Vref and a second end connected to the node N2. The resistor R4 has a first end connected to the node N2 and a second end connected to the power supply GND. The resistor R4 is a variable piezoresistor (doped layer 44) of the cantilever 32 of the second flow detection unit 2B.

[0087] The differential amplifier circuit 62 amplifies the potential difference between the node N1 and the node N2 and outputs it as an output signal. This potential difference has a value according to the change in the resistance value of the piezoresistor, that is, a value based on the displacement of the cantilever 32. The differential amplifier circuit 62 has an inverting input terminal (- terminal) connected to the node N1 and a non-inverting input terminal (+ terminal) connected to the node N2.

[0088] FIG. 14 is a configuration diagram showing a second example of the signal processing circuit 70 according to the fourth embodiment. 14, the signals output from the pressure detection sections 30 of the first flow detection unit 2A and the second flow detection unit 2B may be added by an adder circuit 71 to cancel out the vibration noise of the flow path 10. In the example shown in FIG.

[0089] 14, each of the first flow detection unit 2A and the second flow detection unit 2B includes a Wheatstone bridge circuit 61 and a differential amplifier circuit 62. The differential amplifier circuit 62 is configured to adjust the gain so that the sensor sensitivity of the first flow detection unit 2A and the second flow detection unit 2B is the same. For example, when vibration noise of the flow path 10 is detected, the gain may be adjusted so that the vibration noise is minimized.

[0090] According to the fourth embodiment having the above configuration, as shown in Fig. 12, the flow wall 11 is surrounded by a plurality of flow detection units 2, each including a pressure receiving portion 20 and a pressure detection portion 30. By surrounding the flow wall 11 with a plurality of flow detection units 2 in this manner, the volume of the inner layer portion 21 of the pressure receiving portion 20 per flow detection unit 2 can be reduced. This improves the responsiveness of the volume fluctuation of the inner layer portion 21 accompanying the expansion and contraction of the flow wall 11, and enables the shape change of the flow passage 10 accompanying the pressure change of the fluid to be detected with good sensitivity.

[0091] The multiple flow detection units 2 may include a first flow detection unit 2A and a second flow detection unit 2B arranged opposite to each other across the flow path 10, and may include a signal processing circuit 70 that adds up signals output from the pressure detection units 30 of the first flow detection unit 2A and the second flow detection unit 2B to cancel vibration noise of the flow path 10, as shown in Fig. 14. With this configuration, even if vibration noise of the flow path 10 is picked up as a result of dividing the flow detection units 2 into multiple units, the vibration noise of the flow path 10 can be canceled out by adding up signals output from the pressure detection units 30 of the first flow detection unit 2A and the second flow detection unit 2B arranged opposite to each other across the flow path 10, and changes in the shape of the flow path 10 associated with changes in fluid pressure can be detected with high accuracy.

[0092] Although the preferred embodiments of the present disclosure have been described and illustrated above, it should be understood that they are illustrative of the present disclosure and should not be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present disclosure. Thus, the present disclosure should not be considered as limited by the foregoing description, but rather by the scope of the claims.

[0093] For example, in the above embodiment, the change in the resistance value of the cantilever 32 is detected using the Wheatstone bridge circuit 61, but the present invention is not limited to this case. As long as the change in the resistance value of the cantilever 32 can be detected, the detection circuit may be configured in any way. In addition, in the above embodiment, a configuration in which the pressure detection unit 30 has a cavity housing 35 is exemplified, but for example, if the flow detection device 1 is placed in a space that is hardly affected by outside air, the cavity housing 35 may not be necessary. [Explanation of symbols]

[0094] 1...Flow detection device 2...Flow detection unit 2A…First flow detection unit 2B: Second flow detection unit 10...Flow path 11…Flowing wall 20…Pressure receiving part 20A…Cylindrical part 20B…Slit 21…Inner layer 22…Outer layer part 23…Window section 30...Pressure detection section 30A…First air chamber (differential pressure chamber) 30B…Second air chamber 32…Cantilever 35…Cavity housing 50...Pressing member 70...Signal processing circuit

Claims

1. a flow path having a flow wall that expands and contracts due to a pressure change of a fluid flowing therethrough; a pressure receiving section having an inner layer section which covers at least a part of the periphery of the flow wall and whose volume varies in accordance with the expansion and contraction of the flow wall, and an air-impermeable outer layer section which surrounds the inner layer section, and in which a window section is provided in the outer layer section through which gas in the inner layer section can enter and exit in accordance with the volume variation of the inner layer section; and a pressure detecting section having a cantilever which is flexibly deformed by the gas entering and exiting through the window section, A flow detection device characterized in that the inner layer portion is formed of an elastic body having interconnected cells.

2. 2. The flow detection device according to claim 1, wherein the elastic body is polyurethane foam.

3. 3. The flow detection device according to claim 1, wherein the inner layer portion is softer than the flow wall.

4. 4. The flow detection device according to claim 1, wherein the pressure detection unit includes a cavity housing that defines a differential pressure chamber that communicates with the window portion across the cantilever.

5. 5. The flow detection device according to claim 1, further comprising a pressing member that presses the pressure receiving portion against the flow wall.

6. The pressure-receiving portion includes a cylindrical portion surrounding the flow wall, 6. The flow detection device according to claim 1, wherein the cylindrical portion is formed with a slit extending in a longitudinal direction of the flow channel.

7. 7. The flow detection device according to claim 1, wherein the flow wall is surrounded by a plurality of flow detection units, each including the pressure receiving portion and the pressure detecting portion.

8. The plurality of flow detection units include a first flow detection unit and a second flow detection unit that are disposed opposite each other across the flow path, The flow detection device according to claim 7, further comprising a signal processing circuit that adds up signals output from the pressure detection portions of the first flow detection unit and the second flow detection unit to cancel vibration noise in the flow path.

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