Flow Detection Device

Abstract

To provide a flow detection device with which it is possible to reduce noise due to the vibration of a passage and detect the state of a flow, even at a minute flow rate, in the passage with good accuracy.SOLUTION: A flow detection device 1 comprises: a passage 10 having an outer wall 11 which is displaced by a pressure change of a fluid flowing in the inside; a pressure detection unit 2 having a pressure reception unit 30 for receiving pressure due to the displacement of the outer wall 11; and a passage fixing unit 3 provided to the pressure detection unit 2 upstream and / or downstream of the passage 10. The passage fixing unit 3 includes an inside fixing unit 60 for fixing the passage 10 at a position separated from the pressure detection unit 2 and an outside fixing unit 70 for fixing the passage 10 at a position separated even farther from the pressure detection unit 2 than the inside fixing unit 60.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 below discloses a transducer for detecting pressure changes in a pipe that detects pressure changes in the pipe by detecting deformation of the pipe and converting the pressure changes in the pipe into an electrical signal. This transducer uses a piezoelectric element with a bimorph structure as the measuring element, and this piezoelectric element has a structure in which an intermediate layer is provided between two piezoelectric bodies, and is configured so that the piezoelectric element is pressed against the pipe surface by a holding material. The holding material has elasticity such that both ends of the piezoelectric element along the circumferential direction of the pipe springly contact the outer surface of the pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. Hei 2-203230 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 pipe is very small, sometimes less than 1 μm. In sensors that measure displacement by pressing a piezoelectric element against the pipe, as in the above-mentioned conventional technology, the signal level is small, and when the flow path vibrates due to external forces or wind, the effect of the displacement becomes relatively large. This can become a source of noise, making it difficult to accurately detect the pipe displacement. In other words, even if the sensor itself has high performance and high resolution, there is a problem in 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 noise caused by vibration of the flow path and can accurately detect the flow state within the flow path even at minute flow rates. [Means for solving the problem]

[0006] (1) A flow detection device according to one aspect of the present disclosure comprises a flow path having an outer wall that is displaced by pressure changes in a fluid flowing therethrough, a pressure detection unit having a pressure-receiving part that receives pressure in accordance with the displacement of the outer wall, and a flow path fixing part provided on at least one of the upstream and downstream sides of the flow path relative to the pressure detection unit, wherein the flow path fixing part comprises an inner fixing part that fixes the flow path at a position spaced apart from the pressure detection unit, and an outer fixing part that fixes the flow path at a position even further apart from the pressure detection unit than the inner fixing part.

[0007] According to the flow detection device of this embodiment, when the flow path vibrates, the flow path fixing portion, which fixes the flow path on at least one of the upstream and downstream sides of the flow path relative to the pressure detection portion, suppresses the propagation of flow path vibrations to the pressure detection portion. This flow path fixing portion has an outer fixing portion positioned away from the pressure detection portion and an inner fixing portion positioned close to the pressure detection portion, with the outer fixing portion filtering out large vibrations and the inner fixing portion filtering out remaining small vibrations. In other words, since flow path vibrations may be propagated even when the flow path is fixed at one point, the flow path fixing portion of this embodiment fixes the flow path at at least two points, the outer fixing portion and the inner fixing portion. Fixing the flow path at at least two points in this manner reduces noise caused by flow path vibrations, enabling accurate detection of the flow state within the flow path even at minute flow rates.

[0008] (2) In the flow detection device of aspect (1), the inner fixing portion may fix the flow path so as to press the outer wall against the pressure receiving portion of the pressure detection portion.

[0009] In this case, the outer wall of the flow path is pressed against the pressure receiving portion of the pressure detecting portion, so that the pressure receiving portion can detect the displacement of the outer wall with high sensitivity.

[0010] (3) In the flow detection device of aspect (2), the center line of the flow path in the inner fixed part may be located closer to the pressure receiving part than the center line of the flow path in the pressure detection part.

[0011] In this case, the flow path is pulled toward the pressure-receiving part by the inner fixing part, and the tension of the flow path presses the outer wall against the pressure-receiving part, allowing the pressure-receiving part to sensitively detect the displacement of the outer wall.

[0012] (4) In the flow detection device according to any one of (1) to (3), the inner fixing portion may have a greater pressing force against the outer wall than the outer fixing portion.

[0013] In this case, the flow path is loosely fixed by the outer fixing part, which removes large vibrations in the flow path, while the inner fixing part removes remaining small vibrations, and the inner fixing part firmly fixes the flow path near the pressure detection part. In this way, by loosely fixing the flow path by the outer fixing part, it is possible to suppress the effect on the flow in the flow path at the outer fixing part, where the flow path hits hard due to vibrations. Furthermore, by firmly fixing the flow path by the inner fixing part, it is possible to reliably suppress vibrations in the flow path near the pressure detection part, and it is possible to detect the displacement of the flow path due to changes in fluid pressure with high accuracy.

[0014] (5) In the flow detection device according to any one of (1) to (4), the flow path fixing portion may include an elastic body that presses against the outer wall.

[0015] In this case, the flow path can be elastically supported by the flow path fixing portion, so the flow path does not need to be fixed tightly, and damage or clogging of the flow path can be suppressed. In addition, the elastic deformation of the elastic body can damp vibration of the flow path.

[0016] (6) In the flow detection device according to the aspect (5), the elastic body of the inner fixing part may have a higher hardness than the elastic body of the outer fixing part.

[0017] In this case, by selecting the hardness of the elastic member, it is possible to easily make the force pressing the outer wall at the inner fixing part greater than that at the outer fixing part, thereby loosely fixing the flow path with the outer fixing part, eliminating rough flow path vibrations at the outer fixing part, and firmly fixing the flow path near the pressure detection part by eliminating remaining small vibrations at the inner fixing part.

[0018] (7) In the flow detection device of any one of aspects (1) to (6), the first distance from the pressure detection unit to the inner fixed part and the second distance from the inner fixed part to the outer fixed part may be different from each other.

[0019] In this case, since the first distance from the pressure detection unit to the inner fixed part and the second distance from the inner fixed part to the outer fixed part do not match, vibrations such as standing waves in the flow path can be easily suppressed.

[0020] (8) In the flow detection device of any of the aspects (1) to (7), the first gap formed between the pressure detection unit and the inner fixed part may be narrower than the second gap formed between the inner fixed part and the outer fixed part.

[0021] In this case, the outer fixing part, which removes vibrations from the flow path, is positioned farther away from the inner fixing part, which firmly fixes the flow path near the pressure detection part, making it difficult for vibrations from the flow path to be transmitted to the pressure detection part.

[0022] (9) In the flow detection device according to any one of the aspects (1) to (8), the contact surface of the flow path fixing portion that contacts the outer wall may be formed in an arc or V-shape.

[0023] In this case, the flow path fixing portion can stably fix the outer wall of the flow path, which increases the effect of suppressing vibration of the flow path.

[0024] (10) The flow detection device according to any one of (1) to (9) above may further include an upper plate and a bottom plate disposed on either side of the flow path, the pressure detection unit, and the flow path fixing unit.

[0025] In this case, the upper plate and the bottom plate facilitate the fixing and positioning of the flow path, the pressure detection unit, and the flow path fixing unit.

[0026] (11) In the flow detection device of the aspect (10), the upper plate may have a window portion at least in a portion facing the pressure receiving portion of the pressure detection portion across the flow path.

[0027] In this case, by providing a window in the upper plate facing the pressure receiving part of the pressure detection part across the flow path, it becomes possible to check the relative positions of the pressure receiving part and the flow path, and whether there are any air bubbles in the flow path above the pressure receiving part. In other words, it becomes possible to determine whether the false pressure detection is due to misalignment of the flow path or air bubbles in the flow path, or whether the pressure detection part itself is malfunctioning.

[0028] (12) In the flow detection device according to the aspect (10) or (11), the upper plate may be made of a transparent material.

[0029] In this case, since the upper plate is made of a transparent material, the range over which the flow path can be observed is widened, and it is also possible to check for the presence of air bubbles in the flow path on the upstream and downstream sides of the pressure receiving portion.

[0030] (13) In the flow detection device according to the aspect (11), the upper plate may be provided with a reference line that passes through the center of the pressure receiving portion of the pressure detection portion in a plan view.

[0031] In this case, by providing a reference line centered on the pressure receiving part of the pressure detection part on the transparent upper plate, it is possible to check whether there is any excess load due to misalignment of the flow path.

[0032] (14) In the flow detection device according to any one of (10) to (13), at least the opposing surfaces of the upper plate and the bottom plate may be formed in an arc shape.

[0033] In this case, the opposing surfaces of the upper plate and the bottom plate are tubular like the flow passages, so that the dead space at least on the opposing surfaces is reduced, allowing the overall device to be made smaller.

[0034] (15) In the flow detection device according to any one of (10) to (14), at least one of the upper plate and the bottom plate may be formed integrally with the flow path fixing portion.

[0035] In this case, by providing at least one of the upper plate and the bottom plate with the function of a flow path fixing portion, it is possible to reduce the number of parts and make the device smaller. [Effects of the Invention]

[0036] According to one aspect of the present disclosure, it is possible to provide a flow detection device that can reduce noise caused by external forces or vibrations on a flow channel and can accurately detect the flow state in the flow channel even at a minute flow rate. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a plan view of a flow detection device according to a first embodiment. [Figure 2] FIG. 1 is a front view of a flow detection device according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 2 is a plan view showing an example of the configuration of the cantilever according to the first embodiment. [Figure 5] FIG. 2 is a circuit diagram showing an example of the configuration of an analog circuit unit according to the first embodiment. [Figure 6] FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 2. [Figure 8] 5A and 5B are schematic diagrams for explaining the vibration suppressing effect of the flow path by the flow path fixing portion according to the first embodiment. [Figure 9]FIG. 3 is a diagram showing an example of output waveform data of the flow detection device according to the first embodiment. [Figure 10] FIG. 10 is a front view of a flow detection device according to a second embodiment. [Figure 11] 10 is a schematic diagram showing the positional relationship between a pressure detection unit, an inner fixed unit, and an outer fixed unit 70 of a flow detection device according to a third embodiment. FIG. [Figure 12] FIG. 10 is a plan view of a flow detection device according to a fourth embodiment. [Figure 13] 13 is a cross-sectional view taken along the line XIII-XIII in FIG. 12. [Figure 14] 14 is a cross-sectional view taken along the line XIV-XIV in FIG. 13. [Figure 15] 14 is a cross-sectional view taken along the line XV-XV of FIG. 13. [Figure 16] FIG. 10 is a longitudinal sectional view of a flow detection device according to a fifth embodiment. [Figure 17] FIG. 17 is a cross-sectional view taken along the line XVII-XVII shown in FIG. 16. [Figure 18] FIG. 10 is a longitudinal sectional view of a flow detection device according to a sixth embodiment. [Figure 19] 19 is a cross-sectional view taken along the line XIX-XIX of FIG. 18. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0039] (First embodiment) Fig. 1 is a plan view of the flow detection device 1 according to the first embodiment, and Fig. 2 is a front view of the flow detection device 1 according to the first embodiment. 1 and 2, the flow detection device 1 includes a pressure detection unit 2 that detects the pressure inside a flow path 10, and a flow path fixing unit 3 that fixes the flow path 10 on at least one of the upstream and downstream sides (both in this embodiment) of the pressure detection unit 2. In the following description, the left side of the paper in FIGS. 1 and 2 will be referred to as the upstream side of the flow path 10, and the right side of the paper will be referred to as the downstream side of the flow path 10. The pressure detection unit 2 and the flow path fixing unit 3 are attached to a bottom plate 4.

[0040] 3 is a cross-sectional view taken along the line III-III of FIG. 2. FIG. The flow channel 10 has an outer wall 11 that is displaced by pressure changes of the fluid flowing therethrough. The flow channel 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). Note that, depending on the type of fluid, application, etc., various treatments such as oxidation treatment may be performed on the outer wall 11 as necessary, and various properties such as heat resistance and transparency may be added.

[0041] The flow path 10 is connected to, for example, a pulsating pump (not shown). The pulsating pump can be a so-called roller pump that sucks in 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 outer wall 11 expands and contracts (displaces) in a wavy manner in response to the pulsation of the fluid.

[0042] The pressure detection unit 2 includes a flow path holding unit 20 and a pressure receiving unit 30. The flow path holding portion 20 includes a cylindrical portion 21 that surrounds the outer wall 11, and a fixing portion 22 that fixes the cylindrical portion 21 to the pressure-receiving portion 30. A slit 23 extending in the longitudinal direction of the flow path 10 is formed in the cylindrical portion 21. That is, a portion of the cylindrical portion 21 in the circumferential direction is split from end to end along the longitudinal direction of the flow path 10.

[0043] An engagement claw 24 is provided on one side of the slit 23 of the cylindrical portion 21. A knob portion 24a is formed on the engagement claw 24. An engagement protrusion 25 with which the engagement claw 24 can be engaged is formed on the other side of the slit 23 of the cylindrical portion 21. When the engagement of the engagement claw 24 with the engagement protrusion 25 is released, the slit 23 of the cylindrical portion 21 can be widened, and the flow path 10 can be inserted into the flow path holding portion 20 through the slit 23.

[0044] A communication hole 26 is formed in the cylindrical portion 21 at a position circumferentially different from the slit 23. The communication hole 26 penetrates the fixed portion 22 and connects the inside of the cylindrical portion 21 to the pressure-receiving chamber 30A of the pressure-receiving portion 30. A first elastic body 27 is provided on the inner wall surface of the cylindrical portion 21 on the side opposite to the communication hole 26. The first elastic body 27 is, for example, polyurethane foam, and elastically deforms in response to the expansion and contraction of the outer wall 11.

[0045] An airtight second elastic body 28 is provided around the opening of the communication hole 26 on the inner wall surface of the cylindrical portion 21. The second elastic body 28 is in close contact with the outer wall 11 and airtightly surrounds the periphery of the communication hole 26. An example of the second elastic body 28 is a gel body. The fixing portion 22 is formed in a flat plate shape, and its lower surface is airtightly connected to the sensor substrate 31 of the pressure receiving portion 30 via a connecting member 29. The connecting member 29 is, for example, double-sided tape or adhesive.

[0046] The pressure receiving section 30 includes a sensor substrate 31, a cantilever 32, an analog circuit section 33, a digital processing section , and a cavity housing . The sensor substrate 31 is, for example, a printed circuit board. A through hole 31a that penetrates the sensor substrate 31 in the thickness direction is formed in the sensor substrate 31. The through hole 31a communicates with the communication hole 26 of the flow path holding portion 20.

[0047] 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 fixed portion 22 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 portion 36 that is connected inside the cavity housing 35 so as to surround the through-hole 31a.

[0048] The cavity housing 35 is partitioned into a pressure receiving chamber 30A and a differential pressure chamber 30B with the cantilever 32 sandwiched therebetween. The pressure receiving chamber 30A and the differential pressure chamber 30B communicate with each other via a communication hole 42 provided in the cantilever 32. The communication hole 26 of the flow path holding unit 20 and the through-hole 31a of the sensor substrate 31 communicate with the pressure receiving chamber 30A. The differential pressure chamber 30B is an airtight chamber that communicates with the pressure receiving chamber 30A with the cantilever 32 sandwiched therebetween.

[0049] According to this configuration, when the outer wall 11 of the flow channel 10 expands due to a change in pressure of the fluid flowing therein, the first elastic body 27 and the second elastic body 28 are compressed, and the pressure in the pressure-receiving chamber 30A communicating with the communication hole 26 increases. As a result, the cantilever 32 detects the pressure difference between the pressure-receiving chamber 30A and the differential pressure chamber 30B by deflection deformation, and it is possible to detect a change in the shape of the flow channel 10 due to an increase in the internal pressure of the flow channel 10.

[0050] FIG. 4 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 form a communication hole 42 that communicates between the pressure-receiving chamber 30A and the differential pressure chamber 30B.

[0051] The lever body 41 is cantilevered with its base end 41b connected to the lever support part 43 and its tip end 41a serving as a free end. The lever body 41 is plate-shaped and extends in one direction from the base end 41b to the tip end 41a, and is flexibly deformed in response to the pressure difference between the pressure-receiving chamber 30A and the differential pressure chamber 30B in the cavity housing 35.

[0052] Gap G1 is a groove that is C-shaped in plan view and that penetrates the semiconductor substrate 40 in the thickness direction, formed between the semiconductor substrate 40 and the outer periphery of the lever body 41. Gap G2 is a groove that is C-shaped in plan view and that penetrates the lever body 41 in the thickness direction, formed in the base end 41b of the lever body 41. Gap G2 is located in the center of the base end 41b of the lever body 41 in the width direction of the lever body 41.

[0053] Two lever support portions 43 are arranged side by side in the width direction of the lever body 41 with a gap G2 between them, connecting the lever body 41 and the semiconductor substrate 40 and supporting the lever body 41 in a cantilevered state. The support widths of the two lever support portions 43 in the width direction of the lever body 41 are the same. Therefore, when the lever body 41 is bent and deformed, the stress per unit area acting on one lever support portion 43 is the same as the stress per unit area acting on the other lever support portion 43.

[0054] 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 main body 41. This doped layer 44 is formed by doping a dopant (impurity) such as phosphorus by various methods such as ion implantation or diffusion. Of the doped layer 44, the portion where the lever main body 41 is formed (including the portion formed on the lever support portion 43) functions as a resistor R1 (differential pressure detection resistor Rsen1).

[0055] The resistance value of resistor R1 changes depending on the amount of deflection of lever support portion 43. Although not shown, an electrode made of a conductive material (e.g., Au (gold)) having a lower electrical resistivity than doped layer 44 is formed on the upper surface of doped layer 44. This electrode functions as a first end and a second end of resistor R1 (differential pressure detection resistor Rsen1).

[0056] 3, the analog circuit unit 33 is a circuit that performs analog processing to detect displacement corresponding to the flexural 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 differential pressure chamber 30B.

[0057] FIG. 5 is a circuit diagram showing an example of the configuration of the analog circuit unit 33 according to the first embodiment. 5, the analog circuit unit 33 includes a Wheatstone bridge circuit 51 and a differential amplifier circuit 52. The Wheatstone bridge circuit 51 includes a resistor R1 (differential pressure detection resistor Rsen1) that the cantilever 32 has, a resistor R2, a resistor R3, and a resistor R4.

[0058] 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 its resistance changes depending on the differential pressure between the pressure receiving chamber 30A and the differential pressure 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.

[0059] Resistor R3 has a first end connected to reference voltage circuit Vref and a second end connected to node N2. Resistor R4 has a first end connected to node N2 and a second end connected to power supply GND. Resistor R1 is configured within cantilever 32, while resistors R3 and R4 are external resistors provided outside cantilever 32.

[0060] 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 provided externally near cantilever 32. By matching the temperature characteristics of resistors R1 and R2, analog circuit section 33 can reduce the influence of temperature fluctuations on the detection results.

[0061] The differential amplifier circuit 52 is, for example, an instrumentation amplifier, which amplifies the potential difference between the node N1 and the node N2 and outputs the amplified potential difference as an output signal. This potential difference has a value corresponding to the change in the resistance value of the piezoresistor, i.e., a value based on the displacement of the cantilever 32. The differential amplifier circuit 52 has an inverting input terminal (- terminal) connected to the node N1 and a non-inverting input terminal (+ terminal) connected to the node N2.

[0062] 3 is 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 mounted (placed) on the sensor substrate 31, for example, and is placed outside the cavity housing 35.

[0063] 1 and 2 , the flow path fixing unit 3 includes an inner fixing unit 60 that fixes the flow path 10 at a position spaced apart from the pressure detection unit 2, and an outer fixing unit 70 that fixes the flow path 10 at a position further away from the pressure detection unit 2 than the inner fixing unit 60. Note that the flow path fixing unit 3 may include fixing units that fix the flow path 10 at multiple locations in addition to the inner fixing unit 60 and the outer fixing unit 70. That is, it is sufficient for the flow path fixing unit 3 to fix the flow path 10 at at least two locations, the outer fixing unit 70 and the inner fixing unit 60. Furthermore, the flow path fixing unit 3 in this embodiment is provided on both the upstream side and the downstream side of the pressure detection unit 2, but may be provided on only one of the upstream side and the downstream side of the pressure detection unit 2 if the direction of propagation of vibration in the flow path 10 is known in advance.

[0064] 6 is a cross-sectional view taken along the line VI-VI shown in FIG. As shown in Figure 6, the outer fixed portion 70 comprises a first outer clamping piece 71 fixed to the bottom plate 4 and a second outer clamping piece 72 that clamps the flow path 10 between the first outer clamping piece 71 and the second outer clamping piece 72.

[0065] The first outer clamping piece 71 has a first contact surface 71a that contacts the outer wall 11 of the flow channel 10. The first contact surface 71a is formed in a V shape when viewed from the longitudinal direction of the flow channel 10. The first contact surface 71a contacts the circumferential surface of the outer wall 11 at least at two points.

[0066] The second outer clamping piece 72 has a second contact surface 72a that contacts the outer wall 11 of the flow channel 10, at a position opposite to the first contact surface 71a across the flow channel 10. The second contact surface 72a is formed in an arc shape when viewed in the longitudinal direction of the flow channel 10. The second contact surface 72a is in close contact with the circumferential surface of the outer wall 11.

[0067] At least one of the first outer clamping piece 71 and the second outer clamping piece 72 is formed from an elastic body so as not to hinder the expansion and contraction of the outer wall 11. Examples of the elastic body include urethane foam. Note that the outer fixing part 70 may be configured such that only the portion forming the first contact surface 71a or the second contact surface 72a is elastic, and the elastic body is supported by a rigid body.

[0068] 7 is a cross-sectional view taken along the line VII-VII shown in FIG. As shown in Figure 7, the inner fixed portion 60 includes a first inner clamping piece 61 fixed to the bottom plate 4 and a second inner clamping piece 62 that clamps the flow path 10 between the first inner clamping piece 61 and the second inner clamping piece 62.

[0069] The first inner clamping piece 61 has a first contact surface 61a that comes into contact with the outer wall 11 of the flow channel 10. The first contact surface 61a is formed in an arc shape when viewed from the longitudinal direction of the flow channel 10. The first contact surface 61a is in close contact with the circumferential surface of the outer wall 11.

[0070] The second inner clamping piece 62 has a second contact surface 62a that contacts the outer wall 11 of the flow channel 10, at a position opposite to the first contact surface 61a across the flow channel 10. The second contact surface 62a is formed in an arc shape when viewed in the longitudinal direction of the flow channel 10. The second contact surface 62a is in close contact with the circumferential surface of the outer wall 11.

[0071] At least one of the first inner clamping piece 61 and the second inner clamping piece 62 is formed from an elastic body so as not to hinder the expansion and contraction of the outer wall 11. Examples of the elastic body include urethane foam. Note that the inner fixing part 60 may be configured such that only the portion forming the first contact surface 61a or the second contact surface 62a is elastic, and the elastic body is supported by a rigid body.

[0072] The inner fixing part 60 has a larger contact area with the outer wall 11 than the outer fixing part 70, and exerts a larger pressing force on the outer wall 11 than the outer fixing part 70. Even if the contact area of ​​the inner fixing part 60 with the outer wall 11 is the same as that of the outer fixing part 70 (or the contact surface shape is the same), if the elastic body of the inner fixing part 60 has a higher hardness than the elastic body of the outer fixing part 70, the force of the inner fixing part 60 pressing on the outer wall 11 can be larger than that of the outer fixing part 70. Of course, the inner fixing part 60 may have a larger contact area with the outer wall 11 than the outer fixing part 70 and may include an elastic body that has a higher hardness than the elastic body of the outer fixing part 70.

[0073] Next, the positional relationship between the inner fixed portion 60 and the outer fixed portion 70 will be described. As shown in FIG. 1 , a first distance D1 from the pressure detection unit 2 to the inner fixed portion 60 and a second distance D2 from the inner fixed portion 60 to the outer fixed portion 70 are different from each other. The first distance D1 is determined based on the longitudinal center position of the flow path 10 in the flow path holding portion 20 of the pressure detection unit 2 and the longitudinal center position of the flow path 10 in the inner fixed portion 60. The second distance D2 is determined based on the longitudinal center position of the flow path 10 in the inner fixed portion 60 and the longitudinal center position of the flow path 10 in the outer fixed portion 70. In this embodiment, the first distance D1 is longer than the second distance D2.

[0074] Furthermore, the first gap S1 formed between the pressure detection unit 2 and the inner fixed part 60 is wider than the second gap S2 formed between the inner fixed part 60 and the outer fixed part 70. The first gap S1 defines the length of the space from the flow path holding part 20 of the pressure detection unit 2 to the inner fixed part 60 where the flow path 10 is not fixed and is left free. The second gap S2 defines the length of the space from the inner fixed part 60 to the outer fixed part 70 where the flow path 10 is not fixed and is left free.

[0075] 2, the center line O1 of the flow path 10 in the inner fixed part 60 is located closer to the pressure-receiving part 30 (lower) than the center line O of the flow path 10 in the pressure detection part 2. In other words, the inner fixed part 60 fixes the flow path 10 so as to press the outer wall 11 against the pressure-receiving part 30 of the pressure detection part 2. The center line O2 of the flow path 10 in the outer fixed part 70 is located closer to the pressure-receiving part 30 (lower) than the center line O of the flow path 10 in the pressure detection part 2 and above the center line O1 of the flow path 10 in the inner fixed part 60, but may be located above the center line O of the flow path 10 in the pressure detection part 2 or may be located below the center line O1 of the flow path 10 in the inner fixed part 60.

[0076] Next, the vibration suppression effect of the flow path 10 by the flow path fixing portion 3 configured as described above will be described.

[0077] FIG. 8 is a schematic diagram for explaining the vibration suppressing action of the flow path 10 by the flow path fixing part 3 according to the first embodiment. As shown in FIG. 8 , the flow path fixing unit 3 has an outer fixing unit 70 disposed away from the pressure detection unit 2 and an inner fixing unit 60 disposed near the pressure detection unit 2. When the flow path 10 vibrates, the outer fixing unit 70 removes large vibrations at a position away from the pressure detection unit 2, and the inner fixing unit 60 removes small vibrations that remain near the pressure detection unit 2. That is, even if the flow path 10 is fixed at one location (for example, only the outer fixing unit 70), vibrations of the flow path 10 may propagate as shown by the dotted line in FIG. 8 . Therefore, the flow path fixing unit 3 fixes the flow path 10 at at least two locations, the outer fixing unit 70 and the inner fixing unit 60. Fixing the flow path 10 at at least two locations in this way reduces noise caused by vibrations of the flow path 10, enabling accurate detection of the flow state within the flow path 10 even at very small flow rates.

[0078] 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 Figure 9, 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, causing the outer wall 11 to pulsate, and output waveform data showing periodic pressure changes synchronized with the pulsation is obtained.

[0079] 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 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 whether the flow path 10 is clogged or not and the flow state.

[0080] As described above, the flow detection device 1 according to this embodiment comprises a flow path 10 having an outer wall 11 that displaces (expands and contracts) in response to pressure changes in the fluid flowing therethrough, a pressure detection unit 2 having a pressure-receiving unit 30 that receives pressure in response to displacement of the outer wall 11, and a flow path fixing unit 3 provided on at least one of the upstream and downstream sides of the flow path 10 relative to the pressure detection unit 2, the flow path fixing unit 3 comprising an inner fixing unit 60 that fixes the flow path 10 at a position spaced apart from the pressure detection unit 2, and an outer fixing unit 70 that fixes the flow path 10 at a position further apart from the pressure detection unit 2 than the inner fixing unit 60. This configuration reduces noise due to vibration of the flow path 10, making it possible to accurately detect the flow state within the flow path 10 even at minute flow rates.

[0081] 2, in the flow detection device 1 of this embodiment, the inner fixing part 60 fixes the flow path 10 so as to press the outer wall 11 against the pressure receiving part 30 of the pressure detection part 2. With this configuration, the outer wall 11 of the flow path 10 is pressed strongly against the pressure receiving part 30 of the pressure detection part 2, so that the pressure receiving part 30 can sensitively detect the displacement of the outer wall 11.

[0082] Furthermore, in the flow detection device 1 of this embodiment, the center line O1 of the flow path 10 in the inner fixing part 60 is located closer to the pressure receiving part 30 than the center line O of the flow path 10 in the pressure detection part 2. With this configuration, the flow path 10 is pulled toward the pressure receiving part 30 by the inner fixing part 60, and the tension of the flow path 10 can press the outer wall 11 against the pressure receiving part 30. This allows the pressure receiving part 30 to sensitively detect the displacement of the outer wall 11.

[0083] Furthermore, in the flow detection device 1 of this embodiment, the inner fixing portion 60 exerts a greater pressing force on the outer wall 11 than the outer fixing portion 70. With this configuration, the outer fixing portion 70 loosely fixes the flow path 10, eliminating large vibrations of the flow path 10 while eliminating remaining small vibrations at the inner fixing portion 60, and the inner fixing portion 60 firmly fixes the flow path 10 near the pressure detection unit 2. In this way, by loosely fixing the flow path 10 at the outer fixing portion 70, the influence of the outer fixing portion 70, which is hit by the flow path 10 strongly due to vibrations, on the flow within the flow path 10 can be suppressed. Furthermore, by firmly fixing the flow path 10 at the inner fixing portion 60, vibrations of the flow path 10 near the pressure detection unit 2 can be reliably suppressed, enabling displacement of the flow path 10 due to changes in fluid pressure to be detected with high accuracy.

[0084] Furthermore, in the flow detection device 1 of this embodiment, the flow path fixing part 3 includes an elastic body that presses against the outer wall 11. With this configuration, the flow path 10 can be elastically supported by the flow path fixing part 3, so that the flow path 10 does not need to be strongly fixed, and damage or clogging of the flow path 10 can be suppressed. Furthermore, the elastic deformation of the elastic body can damp vibrations of the flow path 10.

[0085] Furthermore, in the flow detection device 1 of this embodiment, the elastic body of the inner fixing part 60 has a higher hardness than the elastic body of the outer fixing part 70. With this configuration, by selecting the hardness of the elastic member, it is possible to easily make the force with which the inner fixing part 60 presses against the outer wall 11 greater than that of the outer fixing part 70. As a result, the outer fixing part 70 loosely fixes the flow path 10, which eliminates rough vibrations of the flow path 10, and the inner fixing part 60 eliminates any remaining small vibrations, making it possible to firmly fix the flow path 10 in the vicinity of the pressure detection unit 2.

[0086] Furthermore, in the flow detection device 1 of this embodiment, the first distance D1 from the pressure detection unit 2 to the inner fixed part 60 and the second distance D2 from the inner fixed part 60 to the outer fixed part 70 are different from each other. With this configuration, the first distance D1 from the pressure detection unit 2 to the inner fixed part 60 and the second distance D2 from the inner fixed part 60 to the outer fixed part 70 do not match, making it easier to suppress vibrations such as standing waves in the flow path 10.

[0087] Furthermore, in the flow detection device 1 of this embodiment, the first gap S1 formed between the pressure detection unit 2 and the inner fixed part 60 is wider than the second gap S2 formed between the inner fixed part 60 and the outer fixed part 70. This configuration makes it easier to ensure a working space near the pressure detection unit 2, and makes it easier to insert the flow path 10 into the flow path holding part 20, for example.

[0088] In the flow detection device 1 of this embodiment, the contact surface of the flow path fixing part 3 that contacts the outer wall 11 is formed in an arc or V-shape, as shown in Figures 6 and 7. With this configuration, the flow path fixing part 3 can stably fix the outer wall 11 of the flow path 10, thereby increasing the effect of suppressing vibration of the flow path 10.

[0089] (Second embodiment) Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0090] FIG. 10 is a front view of the flow detection device 1 according to the second embodiment. As shown in FIG. 10, in the flow detection device 1 of the second embodiment, the second inner clamping piece 62 of the inner fixed part 60 and the second outer clamping piece 72 of the outer fixed part 70 are attached to the upper plate 5.

[0091] The upper plate 5 has approximately the same size as the bottom plate 4. By attaching the second inner clamping piece 62 of the inner fixing part 60 and the second outer clamping piece 72 of the outer fixing part 70 to the upper plate 5 in this manner, the fixing operations of the flow path 10 in the inner fixing part 60 and the outer fixing part 70 can be performed simultaneously.

[0092] 10, the flow path holding portion 20 of the pressure detection unit 2 is the lower half, and a pressing piece 80 that presses the flow path 10 against the lower half of the flow path holding portion 20 is attached to the upper plate 5. With this configuration, the work of fixing the flow path 10 in the pressure detection unit 2 can also be performed at the same time.

[0093] As described above, the flow detection device 1 of the second embodiment includes the upper plate 5 and the bottom plate 4, which are arranged on either side of the flow path 10, the pressure detection unit 2, and the flow path fixing unit 3. With this configuration, the upper plate 5 and the bottom plate 4 make it easy to fix and position the flow path 10, the pressure detection unit 2, and the flow path fixing unit 3.

[0094] Furthermore, in the flow detection device 1 of the second embodiment, the first gap S1 formed between the pressure detection unit 2 and the inner fixed part 60 is narrower than the second gap S2 formed between the inner fixed part 60 and the outer fixed part 70. With this configuration, the inner fixed part 60 strongly fixes the flow path 10 near the pressure detection unit 2, while the outer fixed part 70, which removes vibrations of the flow path 10 on the front side, is positioned farther away, making it difficult for vibrations of the flow path 10 to propagate to the pressure detection unit 2.

[0095] (Third embodiment) Next, a third embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0096] FIG. 11 is a schematic diagram showing the positional relationship between the pressure detection unit 2, the inner fixed unit 60, and the outer fixed unit 70 of the flow detection device 1 according to the third embodiment. As shown in FIG. 11, in the flow detection device 1 of the third embodiment, the first distance D1 from the pressure detection unit 2 to the inner fixed part 60 is the same as the second distance D2 from the inner fixed part 60 to the outer fixed part 70.

[0097] According to this configuration, even if vibrations of the flow path 10 occur like standing waves with nodes at the outer fixed part 70 and the inner fixed part 60, as shown in Figure 11, the pressure detection part 2 will similarly become nodes of vibration, so even if the flow path fixing part 3 cannot completely prevent the propagation of vibrations of the flow path 10, it is possible to reduce noise in the pressure detection part 2.

[0098] (Fourth embodiment) Next, a fourth embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiments will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0099] Fig. 12 is a plan view of the flow detection device 1 according to the fourth embodiment. Fig. 13 is a cross-sectional view taken along the line XIII-XIII in Fig. 12. Fig. 14 is a cross-sectional view taken along the line XIV-XIV in Fig. 13. Fig. 15 is a cross-sectional view taken along the line XV-XV in Fig. 13. As shown in FIG. 12, in the flow detection device 1 of the fourth embodiment, the upper plate 5 is provided with a window portion 90.

[0100] The window portion 90 is formed in a portion of the upper plate 5 that faces the pressure receiving portion 30 of the pressure detection unit 2 across the flow path 10. The window portion 90 is formed as a rectangular through-hole that penetrates the upper plate 5 in the thickness direction. Note that the window portion 90 is not limited to the portion of the upper plate 5 that faces the pressure receiving portion 30 of the pressure detection unit 2 across the flow path 10. For example, the window portion 90 may be formed between the inner fixing portion 60 and the outer fixing portion 70 so that deflection of the flow path 10 between them can be confirmed. Note that, as will be described later, if the upper plate 5 is made of a transparent material, the window portion 90 does not have to be formed as a through-hole. Also, if the upper plate 5 is made of a non-transparent material, the window portion 90 may be formed as a through-hole, or a transparent material may be fitted into the through-hole.

[0101] The upper plate 5 of the fourth embodiment is formed from a transparent material. The upper plate 5 is formed from a transparent material, for example, a highly transparent resin material such as acrylic resin, or glass. The upper plate 5 is provided with a reference line 91 passing through the center of the pressure receiving portion 30 of the pressure detection unit 2 in the plan view shown in FIG. 12. The reference line 91 is formed by drawing a dotted line with, for example, a marker pen. Note that the type and method of forming the reference line 91 are not limited as long as it serves as a reference line for the arrangement of the flow path 10.

[0102] As shown in Fig. 13, the second inner clamping piece 62 of the inner fixing part 60 and the second outer clamping piece 72 of the outer fixing part 70 are attached to the upper plate 5. In addition, the first inner clamping piece 61 of the inner fixing part 60 and the first outer clamping piece 71 of the outer fixing part 70 are attached to the bottom plate 4. Note that, as shown in Fig. 14, the bottom plate 4 is formed from a non-transparent material.

[0103] As shown in Fig. 13, an accommodating groove 4a that accommodates a part of the pressure detection unit 2 is formed on the upper surface of the bottom plate 4 of the fourth embodiment. As shown in Fig. 15, the accommodating groove 4a accommodates the cavity housing 35 of the pressure receiving unit 30. In addition, the sensor substrate 31 of the pressure receiving unit 30 is placed and fixed on the periphery of the opening of the accommodating groove 4a.

[0104] Furthermore, in the fourth embodiment, in order to check the flow path 10 through the window portion 90, the above-described flow path holding portion 20 (see FIG. 3) is not provided, and the outer wall 11 of the flow path 10 is pressed directly against a third elastic body 38 that covers the through-hole 31a of the sensor substrate 31. The third elastic body 38 has elasticity that allows it to elastically deform in response to displacement of the outer wall 11. The third elastic body 38 is preferably formed from a material that is softer than the outer wall 11 and a gel or the like that has sealing properties that allow it to hermetically seal the through-hole 31a.

[0105] 12, the upper plate 5 is provided with a window 90 at least in a portion facing the pressure receiving portion 30 of the pressure detection unit 2 across the flow path 10. With this configuration, by providing the window 90 in the upper plate 5, it is possible to check the positional relationship between the pressure receiving portion 30 and the flow path 10 and the presence or absence of air bubbles in the flow path 10 above the pressure receiving portion 30. In other words, it is possible to determine whether erroneous pressure detection is due to misalignment of the flow path 10 or air bubbles in the flow path 10, or whether the pressure detection unit 2 itself is malfunctioning.

[0106] In the fourth embodiment, the upper plate 5 is made of a transparent material. With this configuration, the upper plate 5 is made of a transparent material, so that the range in which the flow path 10 can be viewed is widened, and it is also possible to check whether there are any bubbles in the flow path 10 on the upstream and downstream sides of the pressure-receiving portion 30.

[0107] Furthermore, in the fourth embodiment, the upper plate 5 is provided with a reference line 91 that passes through the center of the pressure receiving portion 30 of the pressure detecting portion 2 in a plan view. With this configuration, it is possible to check whether there is any extra load due to misalignment of the flow path 10 based on the reference line 91 that is centered on the pressure receiving portion 30 of the pressure detecting portion 2.

[0108] (Fifth embodiment) Next, a fifth embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiments will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0109] Fig. 16 is a vertical cross-sectional view of the flow detection device 1 according to the fifth embodiment. Fig. 17 is a cross-sectional view taken along the line XVII-XVII shown in Fig. 16. As shown in Fig. 17, in the flow detection device 1 of the fifth embodiment, the upper plate 5 and the bottom plate 4 are formed in an arc shape. Note that, as shown in Fig. 16, also in the fifth embodiment, a window portion 90 is provided in the upper plate 5.

[0110] 17, the opposing surfaces of the upper plate 5 and the bottom plate 4 are formed in an arc shape, and the outer shape of the inner fixed part 60 (similar to the outer fixed part 70) is also formed in a cylindrical shape corresponding to this. Incidentally, in the fifth embodiment, the sensor substrate 31 of the pressure detection part 2 is placed and fixed on the flat parts 4b at both ends of the arc of the bottom plate 4.

[0111] The non-facing surfaces (outer surfaces) of the upper plate 5 and the bottom plate 4 may be block-shaped to facilitate installation on an installation surface (not shown). However, if the upper plate 5 and the bottom plate 4 are installed in a suspended manner or the like to float above the installation surface due to the miniaturization of the flow detection device 1, the non-facing surfaces (outer surfaces) of the upper plate 5 and the bottom plate 4 may also be formed in an arc shape as shown in Fig. 17.

[0112] As described above, according to the fifth embodiment, at least the opposing surfaces of the upper plate 5 and the bottom plate 4 are formed in an arc shape. With this configuration, the opposing surfaces of the upper plate 5 and the bottom plate 4 are tubular like the flow path 10, so that the dead space at least on the opposing surfaces is reduced, allowing the overall device to be made more compact. Furthermore, by also making the non-opposing surfaces of the upper plate 5 and the bottom plate 4 arc-shaped, the dead space in the overall device is reduced, allowing the overall device to be made even more compact.

[0113] (Sixth embodiment) Next, a sixth embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiments will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

[0114] Fig. 18 is a vertical cross-sectional view of the flow detection device 1 according to the sixth embodiment. Fig. 19 is a cross-sectional view taken along the line XIX-XIX shown in Fig. 18. 18, in the flow detection device 1 of the sixth embodiment, at least one of the upper plate 5 and the bottom plate 4 is formed integrally with the flow path fixing part 3. Also in the sixth embodiment, a window part 90 is provided in the upper plate 5.

[0115] As shown in Fig. 18, the bottom plate 4 is formed integrally with the first inner clamping piece 61 of the inner fixing part 60. The bottom plate 4 is formed from a material with high hardness, just like the first inner clamping piece 61. The upper plate 5 has the same function as the second inner clamping piece 62 of the inner fixing part 60, and is formed from a material with high hardness, just like the second inner clamping piece 62. In the example shown in Fig. 18, the flow path 10 is directly fixed on the lower surface of the upper plate 5, but it is also possible to provide a convex portion on the lower surface of the upper plate 5 and fix the flow path 10 by the convex portion.

[0116] A first outer clamping piece 71 (elastic body) of the outer fixing part 70, which has a lower hardness than the inner fixing part 60, is attached to the upper surface of the bottom plate 4. A clamping piece mounting part 5a that is recessed upward is formed in the portion of the underside of the upper plate 5 facing the first outer clamping piece 71. A second outer clamping piece 72 (elastic body) of the outer fixing part 70, which has a lower hardness than the inner fixing part 60, is attached to the clamping piece mounting part 5a by fitting or the like. This makes it possible to reduce the thickness of the second outer clamping piece 72 in the gap between the upper plate 5 and the bottom plate 4, and to directly fix the flow path 10 to the underside of the upper plate 5 in the portion facing the first inner clamping piece 61.

[0117] As described above, according to the sixth embodiment, at least one of the upper plate 5 and the bottom plate 4 is integrally formed with the flow path fixing portion 3. With this configuration, by providing the function of the flow path fixing portion 3 to at least one of the upper plate 5 and the bottom plate 4, it is possible to reduce the number of parts and make the device more compact. Note that not only the inner fixing portion 60 but also the outer fixing portion 70 may be integrally formed with at least one of the upper plate 5 and the bottom plate 4 by, for example, two-color molding.

[0118] While preferred embodiments of the present disclosure have been described and illustrated above, it should be understood that these 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. Accordingly, the present disclosure should not be deemed limited by the foregoing description, but rather by the scope of the claims.

[0119] For example, in the above embodiment, the Wheatstone bridge circuit 51 is used to detect the change in the resistance value of the cantilever 32, but the present invention is not limited to this. 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. Furthermore, in the above embodiment, a configuration in which the pressure receiving portion 30 is provided with 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. Furthermore, the pressure receiving portion 30 of the pressure detecting portion 2 is not limited to a differential pressure sensor equipped with the cantilever 32, but may be a sensor such as a strain gauge pressed against the outer wall 11 or a piezoelectric element. Furthermore, the flow path fixing part 3 may have three or more fixing parts including at least the inner fixing part 60 and the outer fixing part 70. Moreover, as long as the inner fixing part 60 and the outer fixing part 70 are separated, they may be in contact with each other. Furthermore, the configurations of the upstream flow path fixing part 3 and the downstream flow path fixing part 3 do not have to be symmetrical with respect to the pressure detection part 2. For example, the first distance D1 may be different between the upstream flow path fixing part 3 and the downstream flow path fixing part 3. Furthermore, for example, the second distance D2 may be different between the upstream flow path fixing part 3 and the downstream flow path fixing part 3. [Explanation of symbols]

[0120] 1...Flow detection device 2...Pressure detection unit 3...Flow path fixing part 4...Bottom plate 5...Upper plate 10...Flow path 11...Exterior wall 30...Pressure receiving part 60…Inner fixed part 61...First inner clamping piece 61a...1st contact surface 62…Second inner clamping piece 62a…Second contact surface 70...Outer fixing part 71...First outer clamping piece 71a...1st contact surface 72…Second outer clamping piece 72a…Second contact surface 90...Window section 91...Baseline D1: First distance D2…Second distance O…center line O1…center line O2…center line S1: First gap S2: Second gap

Claims

1. a flow path having an outer wall that is displaced by a pressure change of a fluid flowing therethrough; a pressure detection unit having a pressure receiving part that receives pressure in accordance with the displacement of the outer wall; a flow path fixing portion provided on at least one of the upstream side and the downstream side of the flow path with respect to the pressure detection portion, The flow path fixing portion is an inner fixing portion that fixes the flow path at a position spaced apart from the pressure detection portion; an outer fixing portion that fixes the flow path at a position that is further away from the pressure detection portion than the inner fixing portion, A flow detection device, characterized in that the inner fixing portion fixes the flow path so as to press the outer wall against the pressure receiving portion of the pressure detection portion.

2. The flow detection device according to claim 1 , wherein a center line of the flow passage in the inner fixed portion is located closer to the pressure receiving portion than a center line of the flow passage in the pressure detection portion.

3. 3. The flow detection device according to claim 1, wherein the inner fixing portion exerts a greater pressing force on the outer wall than the outer fixing portion.

4. 4. The flow detection device according to claim 1, wherein the flow path fixing portion includes an elastic body that presses against the outer wall.

5. The flow detection device according to claim 4, wherein the elastic body of the inner fixing part has a higher hardness than the elastic body of the outer fixing part.

6. A flow detection device as described in any one of claims 1 to 5, characterized in that a first distance from the pressure detection unit to the inner fixed unit and a second distance from the inner fixed unit to the outer fixed unit are different from each other.

7. A flow detection device described in any one of claims 1 to 6, characterized in that a first gap formed between the pressure detection unit and the inner fixed unit is narrower than a second gap formed between the inner fixed unit and the outer fixed unit.

8. 8. The flow detection device according to claim 1, wherein a contact surface of the flow path fixing portion that contacts the outer wall is formed in an arc or V-shape.

9. 9. The flow detection device according to claim 1, further comprising an upper plate and a bottom plate arranged to sandwich the flow path, the pressure detection unit, and the flow path fixing unit.

10. A flow path having an outer wall that is displaced by a pressure change of a fluid flowing therethrough; a pressure detection unit having a pressure receiving part that receives pressure in accordance with the displacement of the outer wall; a flow path fixing portion provided on at least one of the upstream side and the downstream side of the flow path with respect to the pressure detection portion, The flow path fixing portion is an inner fixing portion that fixes the flow path at a position spaced apart from the pressure detection portion; an outer fixing portion that fixes the flow path at a position that is further away from the pressure detection portion than the inner fixing portion, A flow detection device comprising an upper plate and a bottom plate arranged to sandwich the flow path, the pressure detection unit, and the flow path fixing unit.

11. 11. The flow detection device according to claim 9, wherein the upper plate has a window portion at least in a portion facing the pressure receiving portion of the pressure detection portion across the flow path.

12. 12. The flow detection device according to claim 9, wherein the upper plate is made of a transparent material.

13. The flow detection device according to claim 12, wherein the upper plate is provided with a reference line that passes through the center of the pressure receiving portion of the pressure detection portion in a plan view.

14. 14. The flow detection device according to claim 9, wherein at least the opposing surfaces of the upper plate and the bottom plate are formed in an arc shape.

15. The flow detection device according to any one of claims 9 to 14, wherein at least one of the upper plate and the bottom plate is formed integrally with the flow path fixing portion.

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