JP7843674B2 - Flow detection device - Google Patents

Description

This disclosure relates to a flow detection device.

Patent Document 1 below discloses a flow rate anomaly detection device that detects flow rate anomalies without contact with the fluid. This flow rate anomaly detection device clamps a flexible tube connected to a roller pump between a hinged case body and a lid. 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, thereby detecting flow rate anomalies.

Japanese Patent Publication No. 2018-132364

Incidentally, when detecting the flow state of minute flow rates, the displacement of the tube is extremely small, sometimes less than 1 μm. In sensors that measure this displacement by pressing strain gauges or similar devices against the tube, as in the conventional technology described above, the signal level becomes small, and the influence of external forces and vibrations on displacement becomes relatively large. This can then act as a noise source, potentially preventing accurate detection of the tube's displacement. In other words, even if the sensor itself is high-performance and high-resolution, external disturbances can degrade the signal-to-noise ratio, making measurement difficult.

This disclosure was made in view of the above-mentioned problems, and aims to provide a fluid flow detection device that can reduce the effects of external forces and vibrations on the fluid flow path and detect changes in the shape of the fluid flow path due to changes in fluid pressure.

(1) A fluid detection device according to one aspect of the present disclosure comprises a flow path having a flow wall that expands and contracts in response to pressure changes of the fluid flowing inside; an inner layer that covers at least a portion of the periphery of the flow wall and whose volume fluctuates in accordance with the expansion and contraction of the flow wall; a pressure receiving unit having a non-permeable outer layer that is less deformable than the inner layer and surrounds the inner layer, and having a window in the outer layer through which gas from the inner layer enters and exits in accordance with the volume fluctuations of the inner layer; and a pressure sensor communicating with the window.

According to the flow detection device of this embodiment, when the flow wall of the flow path expands or contracts due to pressure changes of the fluid flowing inside, the volume of the inner layer of the pressure-receiving section that covers at least a part of the periphery of the flow wall changes, and gas enters and exits through a window provided in the non-permeable outer layer that covers the inner layer. The pressure sensor then detects the pressure change caused by the gas entering and exiting through the window. Here, since the outer layer is less deformable than the inner layer, the pressure cannot escape due to the deformation of the outer layer.
On the other hand, if the flow path is subjected to external forces or vibrations, the flow wall will not expand or contract due to these factors alone. As a result, the volume of the inner layer of the pressure-receiving section will not change, and the pressure sensor will hardly react.
Therefore, the fluid flow detection device according to this embodiment can reduce the influence of external forces and vibrations on the flow path and detect changes in the shape of the flow path due to changes in fluid pressure.

(2) In the fluid detection device according to the embodiment of (1), the pressure sensor may be an absolute pressure sensor that detects changes in absolute pressure due to the gas entering and exiting the window.

In this case, changes in the absolute pressure caused by the gas entering and exiting through the window can be used to detect changes in the shape of the flow path.

(3) In the fluid detection device according to the embodiment of (1), the pressure sensor may be a differential pressure sensor having a first sensor opening communicating with the window portion and a second sensor opening communicating with an air chamber not communicating with the window portion, and detecting the change in differential pressure between the pressure of the air chamber and the pressure due to the gas entering and leaving the window portion, with the pressure of the air chamber as the reference pressure.

In this case, the change in the shape of the flow path can be detected by the change in differential pressure caused by the gas entering and exiting through the window.

(4) In a flow detection device according to any of the embodiments of (1) to (3), the inner layer may be softer than the flow wall.

In this case, for example, when the flow wall expands, the softer inner layer begins to collapse before the flow wall completely collapses in the thickness direction due to the internal fluid pressure. This improves the responsiveness of the inner layer's volume fluctuations, allowing for sensitive detection of changes in the flow path shape due to fluid pressure changes.

(5) In a flow detection device according to any of the embodiments of (1) to (4), the inner layer may be formed of an elastic body having communicating bubbles.

In this case, the inner layer can elastically support the flow wall of the channel. Furthermore, if the flow wall expands or contracts, the inner layer can elastically deform in accordance with that expansion or contraction. In addition, the elastic deformation of the inner layer can dampen vibrations in the channel.

(6) In the flow detection device according to the embodiment of (5), the elastic body may be made of foamed resin.

In this case, the inner layer of the pressure-receiving section can be manufactured at a low cost.

(7) In any of the flow detection devices described in (1) to (6), a pressing member may be provided to press the pressure receiving section against the flow wall.

In this case, since the inner layer of the pressure-receiving section is in close contact with the flow wall, the responsiveness to volume changes in 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.

(8) In a flow detection device according to any of the embodiments of (1) to (7), the pressure receiving portion may include a cylindrical portion surrounding the flow wall, and the cylindrical portion may have a slit extending in the longitudinal direction of the flow path.

In this case, since the flow path can be inserted into the pressure-receiving section through the slit, the installation of the pressure-receiving section against the flow wall becomes easier.

(9) In a flow detection device according to any of the embodiments of (1) to (8), the periphery of the flow wall may be surrounded by a plurality of flow detection units, including the pressure receiving section and the pressure sensor.

In this case, since the flow wall is surrounded by multiple flow detection units, the volume of the inner layer of the pressure-receiving section for each flow detection unit is reduced. This improves the responsiveness to volume changes in the inner layer due to the expansion and contraction of the flow wall, allowing for sensitive detection of changes in the flow path shape due to fluid pressure changes.

In the flow detection device according to the embodiments of (10) and (9), the plurality of 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 include a signal processing circuit that adds the signals output from the pressure sensors of the first flow detection unit and the second flow detection unit to cancel out vibration noise in the flow path.

In this case, even if vibration noise from the flow path is picked up as a result of dividing the signal into multiple flow detection units, the vibration noise can be canceled out by adding the signals output from the pressure sensors of the first and second flow detection units, which are positioned opposite each other across the flow path. This allows for highly accurate detection of changes in the flow path shape due to changes in fluid pressure.

According to one aspect of the above disclosure, a fluid flow detection device can be provided that reduces the influence of external forces and vibrations on the fluid flow path and can detect changes in the shape of the fluid flow path due to changes in fluid pressure.

This is a cross-sectional view of the flow detection device according to the first embodiment. This is a cross-sectional view taken along the line II-II shown in Figure 1. This figure shows how the flow path in the flow detection device according to the first embodiment is displaced upward relative to the pressure receiving part due to external force, vibration, etc. This figure shows how the flow path in the flow detection device according to the first embodiment is displaced to the right relative to the pressure receiving part due to external force or vibration. This figure shows how the flow wall of the flow channel expands due to a pressure change of the fluid flowing inside in the flow detection device according to the first embodiment. This figure shows how the flow wall of the flow channel contracts due to a pressure change of the fluid flowing inside in the flow detection device according to the first embodiment. This figure shows an example of output waveform data from the flow detection device according to the first embodiment. This is a cross-sectional view of the flow detection device according to the second embodiment. This is a cross-sectional view of the flow detection device according to the third embodiment. This is a cross-sectional view of the flow detection device according to the fourth embodiment. This is a cross-sectional view of the flow detection device according to the fifth embodiment. This is a cross-sectional view of the flow detection device according to the sixth embodiment.

The embodiments relating to this disclosure will be described below with reference to the drawings.

(First Embodiment)
Figure 1 is a cross-sectional view of the flow detection device 1 according to the first embodiment. Figure 2 is a cross-sectional view taken along the line II-II shown in Figure 1.
As shown in Figure 1, the flow detection device 1 comprises a flow path 10, a pressure receiving unit 20, and a pressure sensor 30.

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

The flow path 10 is connected to, for example, a pulsating pump (not shown). A pulsating pump can be exemplified by a so-called roller pump, which draws in fluid stored in a water 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 wave-like manner in response to the fluid pulsation.

The pressure-receiving section 20 has an inner layer 21 that covers at least a portion (the entire circumference in the first embodiment) of the flow wall 11 and whose volume changes in accordance with the expansion and contraction of the flow wall 11, and a non-permeable outer layer 22 that covers the inner layer 21. The outer layer 22 is provided with a window 23 through which air (gas) from inside the inner layer 21 enters and exits as the volume of the inner layer 21 changes. In this embodiment, if an airtight space can be formed in the pressure-receiving section 20, the inner layer 21 may be filled with a gas other than air (e.g., nitrogen gas).

The inner layer 21 and the outer layer 22 form a cylindrical portion 20A concentric with the central axis O of the flow path 10. The inner layer 21 is formed from an elastic body having interconnected air bubbles. Examples of the elastic body forming the inner layer 21 include foamed resins such as polyurethane foam. The inner layer 21 only needs to be elastically deformable in response to the internal fluid pressure; it is particularly preferable if it is softer than the flow wall 11, as this improves the responsiveness to volume fluctuations.

Furthermore, the inner layer 21 may be a hollow space, or a fiber cushion capable of retaining air in the gaps between fibers, as long as its volume can change in accordance with the expansion and contraction of the flow wall 11. Alternatively, the inner layer 21 may be made by crushing a closed-cell material, such as a rubber sponge, with rollers to create a connected-cell structure.

The outer layer 22 covers the entire outer surface of the inner layer 21, except for the window portion 23. Specifically, as shown in Figure 2, the outer layer 22 covers the outer circumferential surface of the inner layer 21 and both end faces in the longitudinal direction of the inner layer 21. The window portion 23 is formed at an intermediate position in the longitudinal direction of the outer circumferential surface of the outer layer 22.

The outer layer 22 is, for example, a skin layer (surface layer) such as integral skin foam or coated urethane, which is softer than the inner layer 21, and is harder and almost impermeable to air. The outer layer 22 may be made of hard plastic or metal, as long as it is impermeable and maintains the external shape of the pressure-receiving section 20. Here, "impermeable" does not mean completely airtight; it is sufficient for the pressure sensor 30 to detect pressure fluctuations from the window section 23.

Returning to Figure 1, the window portion 23 is formed on a part of the outer circumferential surface of the outer layer portion 22. The surface of the inner layer portion 21, i.e., the communicating air bubble, is exposed through the window portion 23. A retaining member 24 is provided around the window portion 23 to hold the cylindrical portion 20A, which includes the inner layer portion 21 and the outer layer portion 22. The retaining member 24 airtightly encloses the window portion 23 and is connected to the sensor substrate 31 of the pressure sensor 30.

The pressure sensor 30 includes a sensor substrate 31. The sensor substrate 31 is, for example, a printed circuit board. The sensor substrate 31 has a through-hole 31a that penetrates in the thickness direction. The through-hole 31a is located inside the holding member 24 and communicates with the window portion 23. The sensor substrate 31 is also provided with an electrical connector 31b for electrical connection to an external device (not shown, for example, a personal computer or power supply).

The pressure sensor 30 has a sensor opening 30a that communicates with the window portion 23 via a through hole 31a. The pressure-sensitive portion of the pressure sensor 30 is located within the sensor opening 30a. The pressure sensor 30 can be any pressure sensor capable of detecting pressure changes due to gas entering and exiting the window portion 23; for example, resistive, capacitive, piezoelectric, optical, or MEMS (Micro Electro-Mechanical System) types can be used. In the following description, an absolute pressure sensor is used as an example of the pressure sensor 30, but a differential pressure sensor or gauge pressure sensor may also be used, as in the embodiments described later.

Next, the operation of the flow detection device 1 with the above configuration will be explained with reference to Figures 3 to 7.

Figure 3 shows how the flow path 10 is displaced upward relative to the pressure receiving section 20 due to external force, vibration, etc., in the flow detection device 1 according to the first embodiment.
As shown in Figure 3, 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 section 20, the upper part of the inner layer 21 elastically deforms and narrows, but the lower part of the inner layer 21 widens, so the overall cross-sectional area of the inner layer 21 does not change. In other words, since no volume change occurs in the inner layer 21, no air enters or leaves the window 23, and the pressure sensor 30 hardly reacts.

Figure 4 shows how the flow path 10 is displaced to the right relative to the pressure receiving section 20 due to external force or vibration in the flow detection device 1 according to the first embodiment.
As shown in Figure 4, when the central axis O1 of the flow path 10 is displaced by a distance D2 to the right of the central axis O2 of the pressure receiving section 20, the right side of the inner layer 21 elastically deforms and narrows, but the left side of the inner layer 21 widens, so the overall cross-sectional area of the inner layer 21 remains unchanged. In other words, since no volume change occurs in the inner layer 21, no air enters or exits through the window 23, and the pressure sensor 30 hardly reacts. The same applies when the flow path 10 is displaced in directions other than up, down, left, or right, such as diagonally.

Figure 5 shows how the flow wall 11 of the flow channel 10 expands due to a pressure change of the fluid flowing inside in the flow detection device 1 according to the first embodiment.
As shown in Figure 5, when the flow wall 11 of the flow path 10 expands due to a pressure change of the fluid flowing inside, the inner layer 21 is compressed, and its cross-sectional area becomes smaller. As a result, the air in the communicating bubbles of the inner layer 21 is pushed out through the window 23, and the pressure sensor 30 detects the pressure change caused by this air.

Figure 6 shows how the flow wall 11 of the flow path 10 contracts due to a pressure change of the fluid flowing inside in the flow detection device 1 according to the first embodiment.
As shown in Figure 6, when the flow wall 11 of the flow path 10 shrinks due to a pressure change of the fluid flowing inside (returning from the state shown in Figure 5 to its original state), the inner layer 21 deforms to restore its shape, and its cross-sectional area returns to its original size. As a result, air is drawn into the inner layer 21 through the window 23, and the pressure sensor 30 detects the pressure change caused by this air.

Figure 7 shows an example of output waveform data for the flow detection device 1 according to the first embodiment. In Figure 7, the vertical axis represents voltage [V] and the horizontal axis represents time [sec].
As shown in Figure 7, in the initial flow state when the pulsating pump is activated, the internal pressure of the flow path 10 changes due to the pulsating flow caused by the pulsating pump, and the flow wall 11 pulsates, so output waveform data of periodic pressure changes synchronized with the pulsation is obtained.

On the other hand, if a blockage occurs in the flow path 10 downstream of the flow detection device 1, the internal pressure of the flow path 10 will rise immediately after the blockage occurs, causing the output of the pressure sensor 30 to increase and the amplitude of the pulsation to increase. By observing the magnitude of this output waveform data, it becomes possible to estimate whether or not there is a blockage in the flow path 10 and the flow state.

As shown in Figures 3 and 4 above, the flow detection device 1 can eliminate noise caused by external forces and vibrations, thereby improving the signal-to-noise ratio (S/N ratio). This allows for high-precision detection of changes in the shape of the flow path 10 due to fluid pressure changes caused by the flow state (such as blockage) within the flow path 10. Therefore, it becomes possible to accurately detect the flow state, especially at minute flow rates.

As described above, the flow detection device 1 according to this embodiment comprises a flow path 10 having a flow wall 11 that expands and contracts in response to pressure changes of the fluid flowing inside; an inner layer 21 that covers at least a portion of the periphery of the flow wall 11 and whose volume fluctuates in accordance with the expansion and contraction of the flow wall 11; and a pressure receiving unit 20 having a non-permeable outer layer 22 that is less deformable than the inner layer 21 and surrounds the inner layer 21, with a window 23 provided in the outer layer 22 through which air from inside the inner layer 21 enters and exits in accordance with the volume fluctuations of the inner layer 21; and a pressure sensor 30 communicating with the window 23.

According to this flow detection device 1, when the flow wall 11 of the flow path 10 expands or contracts due to pressure changes of the fluid flowing inside, the volume of the inner layer 21 of the pressure receiving section 20, which covers at least a part of the periphery of the flow wall 11, changes, and air enters and exits through the window 23 provided in the non-permeable outer layer 22 that covers the inner layer 21. The pressure sensor 30 then detects the pressure change caused by the air entering and exiting through the window 23. Here, since the outer layer 22 is less prone to deformation than the inner layer 21, the pressure cannot escape due to the deformation of the outer layer 22.
On the other hand, if the flow path 10 is subjected to external force or vibration, the flow wall 11 will not expand or contract by itself, so the volume of the inner layer 21 of the pressure receiving section 20 will not change, and the pressure sensor 30 will hardly react.
Therefore, the fluid detection device 1 according to this embodiment can reduce the influence of external forces and vibrations on the flow path 10 and detect changes in the shape of the flow path 10 due to changes in fluid pressure.

Furthermore, in the flow detection device 1 of this embodiment, the pressure sensor 30 is an absolute pressure sensor that detects changes in absolute pressure due to air entering and exiting the window 23. With this configuration, changes in the absolute pressure due to gas entering and exiting the window 23 can be used to detect changes in the shape of the flow path 10.

Furthermore, in the flow detection device 1 of this embodiment, the inner layer 21 is softer than the flow wall 11. With this configuration, for example, as shown in Figure 5 above, when the flow wall 11 expands, the softer inner layer 21 begins to collapse before the flow wall 11 is completely collapsed in the thickness direction due to the internal fluid pressure. This improves the responsiveness of the volume fluctuations of the inner layer 21, allowing for sensitive detection of changes in the shape of the flow path 10 due to fluid pressure changes.

Furthermore, in the flow detection device 1 of this embodiment, the inner layer 21 is formed of an elastic body having communicating bubbles. This configuration allows the inner layer 21 to elastically support the flow wall 11 of the flow channel 10. Also, when the flow wall 11 expands or contracts, the inner layer 21 can elastically deform in accordance with that expansion or contraction. Moreover, the elastic deformation of the inner layer 21 can dampen vibrations in the flow channel 10.

Furthermore, in the flow detection device 1 of this embodiment, the elastic body is made of foamed resin. This configuration allows for the low-cost production of the inner layer 21 of the pressure-receiving section 20.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following description, components identical or equivalent to those in the above-described embodiment will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

Figure 8 is a cross-sectional view of the flow detection device 1 according to the second embodiment.
As shown in Figure 8, the flow detection device 1 of the second embodiment includes a pressing member 50 that presses the pressure receiving section 20 against the flow wall 11. The pressing member 50 includes a pair of pressing pieces 51.

The pressing piece 51 comprises 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 substrate 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.

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 nut 53 are configured to adjust the magnitude of the pressure applied by the pair of pressing pieces 51 against the pressure receiving portion 20. Note that the pair of pressing pieces 51 may be fixed using a configuration other than the bolt 52 and nut 53. For example, the pair of pressing pieces 51 may be fixed using a locking structure with claws (such as a snap-fit).

According to the second embodiment of the above configuration, since the pressure-receiving portion 20 is provided with a pressing member 50 that presses it against the flow wall 11, the inner layer 21 of the pressure-receiving portion 20 adheres closely to the flow wall 11, improving the responsiveness of the volume change of the inner layer 21 due to the expansion and contraction of the flow wall 11, and enabling sensitive detection of changes in the shape of the flow path 10 due to changes in fluid pressure.

Furthermore, since the displacement of the outer shape of the pressure-receiving section 20 is suppressed by the pressing member 50, it becomes easier to directly detect changes in the shape of the flow path 10 (expansion and contraction) due to changes in fluid pressure in the inner layer 21. Moreover, since the tightening of the pressing member 50 can be optimized with the bolts 52 and nuts 53, variations in the inner diameter of the pressure-receiving section 20 can be absorbed. Additionally, since the pressure-receiving section 20 is not exposed, noise caused by external forces directly acting on the pressure-receiving section 20 can be avoided.

(Third Embodiment)
Next, a third embodiment of the present invention will be described. In the following description, components identical or equivalent to those in the above-described embodiments will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

Figure 9 is a cross-sectional view of the flow detection device 1 according to the third embodiment.
As shown in Figure 9, the pressure receiving section 20 of the third embodiment has a cylindrical section 20A surrounding the flow wall 11, and a slit 20B extending in the longitudinal direction of the flow path 10 that is detachable from the flow wall 11 is formed therein.

In other words, in the third embodiment, the cylindrical portion 20A of the pressure-receiving section 20 has a circumferential portion of the cylindrical portion 20A 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 a non-permeable outer layer 22. In the third embodiment, the pressure-receiving section 20, excluding the slit 20B, covers substantially the entire periphery of the flow wall 11.

Furthermore, in the third embodiment, a spacer 54 is sandwiched between a pair of pressing pieces 51. The spacer 54 has, for example, a hole through which a bolt 52 can be inserted. By changing the thickness of the spacer 54, the magnitude of the pressure applied to the pressure-receiving portion 20 by the pressing member 50 can be adjusted and fixed.

According to the third embodiment of the above configuration, the pressure-receiving section 20 includes a cylindrical section 20A surrounding the flow wall 11. The cylindrical section 20A has a slit 20B extending in the longitudinal direction of the flow path 10, which is detachable from the flow wall 11. Therefore, installation of the pressure-receiving section 20 on the flow wall 11 becomes easier. That is, because the pressure-receiving section 20 is split, it can be attached by covering the flow wall 11 from above. In other words, the effort of attaching the pressure-receiving section 20 from the end of the flow path 10 is eliminated.

Furthermore, in the third embodiment, since a spacer 54 is sandwiched between the pair of pressing pieces 51, it becomes easier to adjust the magnitude of the pressure applied to the pressure-receiving portion 20 by the pressing member 50.

(Fourth Embodiment)
Next, a fourth embodiment of the present invention will be described. In the following description, components identical or equivalent to those in the above-described embodiments will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

Figure 10 is a cross-sectional view of the flow detection device 1 according to the fourth embodiment.
As shown in Figure 10, the flow detection device 1 of the fourth embodiment includes a plurality of flow detection units 2, each including a pressure receiving unit 20 and a pressure sensor 30, and these plurality of flow detection units 2 surround the flow wall 11. In the example shown in Figure 10, the flow detection device 1 includes two flow detection units 2, but it may also include three or more flow detection units 2.

The flow detection device 1 comprises a first flow detection unit 2A and a second flow detection unit 2B, which are arranged opposite each other across the flow path 10. The first flow detection unit 2A and the second flow detection unit 2B each include a semi-circular pressure receiving section 20, a pressure sensor 30, and a coupling 55 that constitutes the aforementioned pressing member 50.

The semicircular pressure-receiving sections 20 are positioned opposite each other across the flow path 10 and cover at least a portion (approximately the entire circumference in the fourth embodiment) of the flow wall 11. The coupling 55 has a semicircular shape with the same or approximately the same curvature as the outer surface of the pressure-receiving section 20. The coupling 55 of the first flow detection unit 2A and the second flow detection unit 2B is fastened via bolts 52 and nuts 53 with a spacer 54 in between, allowing adjustment of the amount of pressure applied to hold down the pressure-receiving section 20.

The flow detection device 1 includes a signal processing circuit 70 that processes the signals output from the pressure sensors 30 of the first flow detection unit 2A and the second flow detection unit 2B. For example, the signal processing circuit 70 adds the signals output from the pressure sensors 30 of the first flow detection unit 2A and the second flow detection unit 2B to cancel out vibration noise in the flow path 10 (noise associated with vibrations in the flow path 10 as shown in Figures 3 and 4 above).

According to the fourth embodiment of the above configuration, as shown in Figure 10, the flow wall 11 is surrounded by a plurality of flow detection units 2, including a pressure receiving section 20 and a pressure sensor 30. By surrounding the flow wall 11 with multiple flow detection units 2 in this way, the volume of the inner layer 21 of the pressure receiving section 20 per flow detection unit 2 can be reduced. This improves the responsiveness of the volume fluctuations of the inner layer 21 due to the expansion and contraction of the flow wall 11, allowing for sensitive detection of changes in the shape of the flow path 10 due to changes in fluid pressure.

Furthermore, the multiple flow detection units 2 include a first flow detection unit 2A and a second flow detection unit 2B, which are positioned opposite each other across the flow path 10. The unit includes a signal processing circuit 70 that adds the signals output from the pressure sensors 30 of the first flow detection unit 2A and the second flow detection unit 2B to cancel out vibration noise in the flow path 10. With this configuration, even if vibration noise from the flow path 10 is picked up as a result of dividing the system into multiple flow detection units 2, the vibration noise can be canceled out by adding the signals output from the pressure sensors 30 of the first flow detection unit 2A and the second flow detection unit 2B, which are positioned opposite each other across the flow path 10. This allows for highly accurate detection of changes in the shape of the flow path 10 due to changes in fluid pressure.

(Fifth Embodiment)
Next, a fifth embodiment of the present invention will be described. In the following description, components identical or equivalent to those in the above-described embodiments will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

Figure 11 is a cross-sectional view of the flow detection device 1 according to the fifth embodiment.
As shown in Figure 11, the flow detection device 1 of the fifth embodiment is equipped with a differential pressure sensor 30 that detects the differential pressure with respect to a reference pressure.

The pressure sensor 30 comprises a second sensor opening 30b for detecting a reference pressure and a cavity housing 35 surrounding the second sensor opening 30b. The second pressure-sensitive element of the pressure sensor 30 is located within the second sensor opening 30b. In this case, the sensor opening 30a communicating with the aforementioned window 23 may be referred to as the "first sensor opening." Furthermore, the pressure-sensitive element within the sensor opening 30a may be referred to as the "first pressure-sensitive element."

The cavity housing 35 is formed in a bottomed cylindrical shape, and its internal space is connected to the second sensor opening 30b of the pressure sensor 30. The cavity housing 35 forms a first air chamber 30A, which serves as the reference pressure for the pressure sensor 30. The first air chamber 30A is preferably an airtight chamber. The pressure sensor 30 detects the differential pressure between the first air chamber 30A and the second air chamber 30B. The second air chamber 30B refers to the space inside the retaining member 24, the through hole 31a, and the sensor opening 30a, which communicates with the window portion 23.

According to the fifth embodiment of the above configuration, the pressure sensor 30 has a sensor opening 30a (first sensor opening) communicating with the window portion 23, and a second sensor opening communicating with the first air chamber 30A (air chamber) which is not communicating with the window portion 23. The pressure in the first air chamber 30A is used as the reference pressure, and the differential pressure sensor detects changes in the pressure difference between this reference pressure and the pressure caused by the air entering and exiting the window portion 23. With this configuration, changes in the shape of the flow path 10 can be detected by changes in the differential pressure caused by the gas entering and exiting the window portion 23.

(Sixth Embodiment)
Next, a sixth embodiment of the present invention will be described. In the following description, components identical or equivalent to those in the above-described embodiments will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

Figure 12 is a cross-sectional view of the flow detection device 1 according to the sixth embodiment.
As shown in Figure 12, the flow detection device 1 of the sixth embodiment is equipped with a gauge pressure sensor as the pressure sensor 30 for detecting gauge pressure.

The pressure sensor 30 is equipped with a second sensor opening 30b for detecting atmospheric pressure. In other words, in the sixth embodiment, the cavity housing 35 described above is not connected to the second sensor opening 30b, and the first air chamber 30A is open to the atmosphere. For example, if the flow detection device 1 is placed in a space with little influence from the outside air, the cavity housing 35 may be omitted.

According to the sixth embodiment of the above configuration, the pressure sensor 30 detects pressure changes due to air entering and exiting the window 23 using gauge pressure. This allows detection of changes in the shape of the flow path 10 due to fluid pressure changes. Since atmospheric pressure is affected by fluctuations and elevation differences, an absolute pressure sensor as exemplified in the first to fourth embodiments or a differential pressure sensor as exemplified in the fifth embodiment is preferred for highly sensitive detection of changes in the shape of the flow path 10.

While preferred embodiments of this disclosure have been described and explained above, it should be understood that these are illustrative examples of the disclosure and should not be considered limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of this disclosure. Therefore, this disclosure should not be considered limited by the foregoing description, but rather limited by the claims.

1...Flow detection device 2...Flow detection unit 2A...First flow detection unit 2B...Second flow detection unit 10...Flow path 11...Flow wall 20...Pressure receiving section 20A...Cylindrical section 20B...Slit 21...Inner layer section 22...Outer layer section 23...Window section 30...Pressure sensor 30A...First air chamber (air chamber)
30B...Second air chamber 30a...Sensor opening (first sensor opening)
30b...Second sensor opening 35...Cavity housing 50...Pressing member 70...Signal processing circuit

Claims (10)

A flow channel having a flow wall that expands and contracts due to pressure changes of the fluid flowing inside,
A pressure receiving section having an inner layer that covers at least a portion of the periphery of the flow wall and whose volume changes in accordance with the expansion and contraction of the flow wall, and a non-permeable outer layer that is less deformable than the inner layer and surrounds the inner layer, and the outer layer is provided with a window through which gas in the inner layer enters and exits as the volume of the inner layer changes,
A flow detection device characterized by comprising a pressure sensor communicating with the aforementioned window portion. The flow detection device according to claim 1, characterized in that the pressure sensor is an absolute pressure sensor that detects changes in absolute pressure due to the gas entering and exiting the window. The flow detection device according to claim 1, characterized in that the pressure sensor has a first sensor opening communicating with the window portion and a second sensor opening communicating with an air chamber not communicating with the window portion, and is a differential pressure sensor that uses the pressure in the air chamber as a reference pressure and detects changes in the differential pressure between that and the pressure due to the gas entering and leaving the window portion. The flow detection device according to claim 1, characterized in that the inner layer is softer than the flow wall. The flow detection device according to any one of claims 1 to 4, characterized in that the inner layer is formed of an elastic body having interconnected air bubbles. The flow detection device according to claim 5, characterized in that the elastic body is a foamed resin. The flow detection device according to any one of claims 1 to 4, characterized in that it comprises a pressing member that presses the pressure-receiving portion against the flow wall. The pressure receiving section includes a cylindrical portion that surrounds the flow wall,
The flow detection device according to any one of claims 1 to 4, characterized in that a slit extending in the longitudinal direction of the flow path is formed in the cylindrical portion. The flow detection device according to any one of claims 1 to 4, characterized in that the periphery of the flow wall is surrounded by a plurality of flow detection units, including the pressure receiving section and the pressure sensor. The plurality of flow detection units include a first flow detection unit and a second flow detection unit arranged opposite each other across the flow path,
The flow detection device according to claim 9, further comprising a signal processing circuit that adds the signals output from the pressure sensors of the first flow detection unit and the second flow detection unit and cancels out vibration noise in the flow path.