Fluid control devices

Abstract

The present invention provides a fluid impedance component, which can enjoy the advantages brought by using ceramics to form an impedance flow path, and can be reasonably assembled to the flow path through which the fluid flows. The fluid impedance component (R) includes: a flow path forming member (10) made of ceramic, having one or more impedance flow paths (10a); and a metal covering member (20) covering the outer peripheral surface of the flow path forming member (10).

Description

Technical Field

[0001] The invention relates to a fluid impedance component and a fluid control device comprising the fluid impedance component. Background Art

[0002] The so-called fluid impedance component has a flow path that becomes an impedance when the fluid flows (hereinafter also referred to as an impedance flow path). For example, the fluid flow rate can be measured based on the upstream and downstream pressures when the fluid flows in the fluid impedance component.

[0003] However, for example, in a material gas flow control device used in semiconductor manufacturing, the fluid impedance element used therein requires an extremely fine element for flow control accuracy, and sometimes a impedance flow path with a thickness of several tens of μm is required.

[0004] Therefore, for example, in Patent Document 1, a metallic slit plate having a thickness of several tens of μm and a plurality of slits formed radially is sandwiched between a pair of covering plates, thereby forming a resistance flow path with the slit portions.

[0005] While this type of fluid impedance component can make the impedance flow path finer, the slit plate, which is several tens of micrometers thick, will slightly flex when held between the covering plates. Consequently, slight variations in the force applied when the slit plate is held between the covering plates can cause variations in impedance characteristics, making it difficult to stably manufacture a fluid impedance component with uniform impedance characteristics.

[0006] In contrast, as disclosed in Patent Document 2, a fluid impedance component made of ceramic can be processed with high dimensional accuracy, and thus a fluid impedance component having uniform impedance characteristics can be stably manufactured.

[0007] However, when attempting to fit a ceramic fluid impedance component of comparable diameter into a very narrow flow path of several millimeters in diameter without a gap, such as when controlling a low-flow fluid, the fluid impedance component may break or become damaged, making it difficult to assemble into the fluid control device.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-257004

[0011] Patent Document 2: Japanese Utility Model Application Laid-Open No. 59-77027 Summary of the Invention

[0012] Therefore, the present invention aims to solve the above problems at one stroke, and its main subject is to enable the fluid impedance component to be rationally assembled in the flow path through which the fluid flows, while enjoying the advantages of forming the impedance flow path using ceramics.

[0013] Specifically, the fluid impedance assembly of the present invention is characterized by comprising: a ceramic flow path forming member having one or more impedance flow paths; and a metal covering member covering the outer peripheral surface of the flow path forming member.

[0014] If a fluid impedance assembly is constructed in this manner, since the flow path forming member is made of ceramic, it can be processed with high dimensional accuracy, thereby stably producing fluid impedance assemblies with uniform impedance characteristics. Specifically, for example, by cutting a long strip of ceramic with an internal impedance flow path into equal lengths and using each of the obtained pieces as a flow path forming member, several fluid impedance assemblies with uniform impedance characteristics can be produced. Moreover, since the flow path forming member is made of ceramic, it can be assembled into the flow path through which the fluid flows without crushing the impedance flow path, and thus has advantages such as low thermal expansion coefficient, high corrosion resistance, and low price compared to metal. In addition, since the impedance characteristics can be changed by changing the number of impedance flow paths, it can also be used, for example, for ultra-low flow measurement. Moreover, since the impedance flow path can be processed into a circular tubular shape, the flow of the fluid becomes ideal, thereby simplifying various simulations.

[0015] In this way, while enjoying the various advantages brought by using ceramics to form the impedance flow path, the metal covering member covers the outer peripheral surface of the flow path forming member. Therefore, when the fluid impedance component is embedded in the flow path through which the fluid flows, the metal covering member acts as a buffer between the wall surface forming the flow path and the flow path forming member, thereby allowing it to be reasonably arranged in the flow path without damaging the fluid impedance component.

[0016] Preferably, the flow channel forming member is columnar, the covering member is cylindrical, and the flow channel forming member is fitted into the covering member with a fitting tolerance.

[0017] According to this structure, the flow channel forming member and the covering member can be constructed with a fitting tolerance, thereby facilitating assembly of the fluid impedance module.

[0018] In order to more reliably prevent damage to the flow channel forming member, it is preferable that the entire outer peripheral surface of the flow channel forming member is covered with the covering member.

[0019] In order to enable measurement of low flow rates, the aspect ratio, which is the ratio of the length dimension to the diameter dimension of the resistive flow path, is preferably 200 or greater.

[0020] In addition, the fluid control device of the present invention is characterized in that it includes: the fluid impedance component mentioned above, which is arranged in the internal flow path through which the fluid flows; an upstream pressure sensor and a downstream pressure sensor, which are arranged on the upstream side and downstream side of the fluid impedance component in the internal flow path; and a flow regulating valve, which is arranged in the internal flow path.

[0021] Furthermore, another fluid control device of the present invention is characterized in that it includes: the fluid impedance component mentioned above, which is arranged in the internal flow path where the fluid flows; a sensor flow path, connecting the upstream side and the downstream side of the internal flow path; an upstream side resistance component and a downstream side resistance component, which are arranged in the sensor flow path; and a flow control valve, which is arranged in the internal flow path.

[0022] The differential pressure type fluid control device or thermal type fluid control device configured in this manner includes the fluid impedance component described above, and thus can achieve the same operational effects as the fluid impedance component of the present invention.

[0023] As a more specific structure, the following structure can be listed, which includes: a flow calculation circuit that calculates the flow rate of the fluid flowing in the internal flow path; and a control circuit that controls the flow control valve in such a way that the measured flow rate calculated by the flow calculation circuit becomes a predetermined target flow rate.

[0024] As an example of the arrangement of the fluid impedance element, a plurality of the fluid impedance elements having different impedance values ​​are provided in series or in parallel.

[0025] As a more specific structure, the following structure can be listed: a first pressure sensor, a second pressure sensor and a third pressure sensor are arranged in the internal flow path, the first fluid impedance component is arranged between the first pressure sensor and the second pressure sensor, and the second fluid impedance component is arranged between the second pressure sensor and the third pressure sensor, and also includes a diagnostic circuit, which compares the first flow rate with the second flow rate to diagnose whether an adverse condition occurs, the first flow rate is a flow rate calculated based on the impedance value of the first fluid impedance component, the detection value of the first pressure sensor and the detection value of the second pressure sensor, and the second flow rate is a flow rate calculated based on the impedance value of the second fluid impedance component, the detection value of the second pressure sensor and the detection value of the third pressure sensor.

[0026] With this structure, it is possible to diagnose whether a malfunction has occurred in the fluid control device through the diagnostic circuit.

[0027] However, when the flow rate is low, the fluid discharge performance from the fluid resistance component is poor during descent, resulting in a decrease in responsiveness.

[0028] Therefore, in order to solve the above problem, it is preferable that the first fluid impedance component is provided between the upstream pressure sensor and the downstream pressure sensor, and the second fluid impedance component is provided in parallel with the first fluid impedance component.

[0029] With this structure, the fluid can be forcibly exhausted via the second fluid resistance element, thereby ensuring the flow rate. Thus, the descent can be completed in about 3 seconds instead of about 30 seconds.

[0030] Another configuration of the fluid impedance element is to provide a plurality of fluid impedance elements having equal impedance values ​​in series.

[0031] As a more specific structure, a structure in which the plurality of fluid impedance elements are provided between the upstream pressure sensor and the downstream pressure sensor can be cited.

[0032] With this configuration, the impedance between the upstream pressure sensor and the downstream pressure sensor can be made high, thereby enabling measurement of low flow rates.

[0033] According to the present invention thus constituted, various advantages of the flow path forming member being made of ceramics can be enjoyed while enabling rational assembly to the flow path. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a fluid circuit diagram of a fluid control device in one embodiment of the present invention.

[0035] Figure 2 It is a cross-sectional view showing the internal structure of the fluid control device according to the embodiment.

[0036] Figure 3 It is a schematic diagram showing the structure of the fluid impedance module of the embodiment.

[0037] Figure 4 This is a fluid circuit diagram of a fluid control device in another embodiment.

[0038] Figure 5 Schematic diagram showing the arrangement of a fluid impedance component in another embodiment.

[0039] Figure 6 This is a fluid circuit diagram of a fluid control device in another embodiment.

[0040] Description of Reference Numerals

[0041] 100···Fluid control device

[0042] L···Internal flow path

[0043] Pa···Upstream pressure sensor

[0044] Pb···Downstream pressure sensor

[0045] R···Fluid impedance components

[0046] 10a···Internal flow path

[0047] 10···Flow path forming member

[0048] 20···Covered components DETAILED DESCRIPTION

[0049] Hereinafter, one embodiment of the fluid impedance component of the present invention will be described with reference to the drawings.

[0050] The fluid impedance module of the present embodiment is one of the components of a fluid control device that controls the mass flow rate of a material gas or the like used in, for example, semiconductor manufacturing.

[0051] Specifically, if Figure 1 Fluid circuit diagram, Figure 2 As shown in the internal structure of FIG, the fluid control device 100 includes: an internal flow path L, in which a fluid as a controlled object flows; a flow control valve V, which is provided in the internal flow path L; a flow measurement mechanism X, which is provided on the downstream side of the flow control valve V and measures the flow rate of the fluid flowing in the internal flow path L; and a control circuit C1 ( Figure 2 (not shown), the flow rate regulating valve V is controlled so that the flow rate measured by the flow rate measuring mechanism X becomes a predetermined target flow rate.

[0052] The flow rate measuring mechanism X is of a differential pressure type and includes: an upstream pressure sensor Pa provided on the upstream side of the internal flow path L; a downstream pressure sensor Pb provided on the downstream side of the upstream pressure sensor Pa; a fluid impedance element R provided between the upstream pressure sensor Pa and the downstream pressure sensor Pb in the internal flow path L to generate a pressure difference; and a flow rate calculation circuit C2 ( Figure 2 (not shown), the flow rate of the fluid flowing in the internal flow path L is calculated based on the pressure measurement values ​​measured by the upstream pressure sensor Pa and the downstream pressure sensor Pb and the impedance value of the fluid impedance element R.

[0053] In this embodiment, the fluid impedance element R is characteristic and will be described in detail below.

[0054] like Figure 3 As shown, the fluid impedance element R provides impedance when the fluid flows, and specifically includes a ceramic flow path forming member 10 having a flow path 10 a (hereinafter also referred to as impedance flow path 10 a ) providing impedance.

[0055] The flow path-forming member 10 is formed of a ceramic such as quartz, alumina, zirconia, or silicon nitride. Specifically, it has a cylindrical shape and has one to several hundred impedance flow paths 10a formed along the axial direction. The flow path-forming member 10 herein has an outer diameter (outer diameter) of approximately several millimeters (e.g., 1.5 mm) and a length (axial dimension) of several to several dozen millimeters (e.g., 7 mm). These dimensions may be varied as appropriate.

[0056] The impedance flow path 10a extends axially through the flow path-forming member 10 and is a linear path with a circular cross-section. Examples of such paths include a resistance flow path formed on the tubular axis of the flow path-forming member 10 or a plurality of resistance flow paths regularly arranged around the tubular axis. The impedance flow path 10a herein has an inner diameter (inner diameter) of less than 1 mm and approximately several tens of μm (e.g., 30 μm), and a length (axial dimension) of approximately several to several tens of mm (e.g., 7 mm), similar to that of the flow path-forming member 10. However, these dimensions may be varied as appropriate.

[0057] In this embodiment, the aspect ratio of the length dimension of the resistance flow path 10a to the diameter dimension is greater than 200, more preferably greater than 300. The impedance value of the fluid impedance component R is determined based on the aspect ratio or the number of the resistance flow paths 10a.

[0058] Moreover, if Figure 3 As shown, the fluid impedance module R of this embodiment further includes a metal covering member 20 that covers the outer peripheral surface of the flow channel forming member 10 .

[0059] To describe in more detail, the covering member 20 is made of a metal such as stainless steel or a nickel alloy, the hardness of which is at least lower than that of ceramics. Here, the length dimension (dimension along the axial direction) of the covering member 20 is approximately the same as the length dimension (dimension along the axial direction) of the flow path forming member 10, so that the entire outer peripheral surface of the flow path forming member 10 is covered by the covering member 20.

[0060] The covering member 20 of this embodiment is formed into a cylindrical shape by machining or drawing a metal columnar member using, for example, a drill, and has an inner diameter within a predetermined fitting tolerance relative to the outer diameter of the flow path forming member 10. Thus, the covering member 20 is externally fitted to the flow path forming member 10 by, for example, an interference fit, a clearance fit, or an intermediate fit.

[0061] The covering member 20 is interposed between the wall surface forming the internal flow path L and the outer peripheral surface of the flow path forming member 10 (see FIG. Figure 2), and functions as a buffer when the fluid impedance component R is inserted into the internal flow path L.

[0062] To explain more specifically, the internal flow path L in this embodiment is formed by drilling a hole through a block B, for mounting the aforementioned flow control valve V, upstream pressure sensor Pa, and downstream pressure sensor Pb, using a drill or the like. The fluid impedance assembly R is disposed in the portion of the internal flow path L that connects the upstream pressure sensor Pa and the downstream pressure sensor Pb. Furthermore, when the fluid impedance assembly R is inserted into this portion of the internal flow path L, the deformation of the covering member 20 cushions the impact (stress) applied to the flow path-forming member 10.

[0063] According to the fluid impedance assembly R of this embodiment, constructed in this manner, since the flow path-forming member 10 is made of ceramic, it can be processed with high dimensional accuracy, enabling the stable production of fluid impedance assemblies R with uniform impedance characteristics. Specifically, by cutting a long strip (e.g., 1 meter) of ceramic, with an internal impedance flow path 10a, into pieces of uniform length (e.g., a few millimeters), each piece being used as a flow path-forming member 10, it is possible to produce multiple fluid impedance assemblies R with uniform impedance characteristics. On the other hand, by varying the cut length, fluid impedance assemblies with various impedance characteristics can be easily produced, facilitating various model designs, for example. Furthermore, since the flow path-forming member 10 is made of ceramic, it can be inserted into the internal flow path L without crushing the impedance flow path 10a. Furthermore, compared to metal components, it has advantages such as a low thermal expansion coefficient, high corrosion resistance, and low cost. Furthermore, since the impedance characteristics can be varied by changing the number of impedance flow paths 10a, it can also be used for ultra-low flow measurement, for example. Furthermore, since the resistance flow path 10a can be processed into a circular tubular shape, the flow of the fluid becomes an ideal flow, and various simulations can be simplified.

[0064] In this way, while enjoying the various advantages brought by using ceramics to form the impedance flow path 10a, the metal covering member 20 covers the outer peripheral surface of the flow path forming member 10. Therefore, when the fluid impedance component R is embedded in the internal flow path L, the metal covering member 20 acts as a buffer between the wall surface forming the internal flow path L and the flow path forming member 10, so that it can be reasonably arranged in the internal flow path L without damaging the fluid impedance component R.

[0065] Furthermore, when the fluid impedance assembly R is arranged in the internal flow path L, the covering member 20 is slightly crushed (deformed) between the wall surface of the internal flow path L and the outer peripheral surface of the flow path forming member 10 , so that the fluid impedance assembly R can be fixed in the internal flow path L.

[0066] Furthermore, during the manufacture or handling of the fluid impedance module R, the flow channel forming member 10 is covered with the covering member 20 , thereby reducing the risk of contamination or damage to the flow channel forming member 10 .

[0067] Furthermore, since the entire outer peripheral surface of the flow path forming member 10 is covered by the covering member 20 , damage to the flow path forming member 10 that may occur when the fluid resistance module R is inserted into the internal flow path L can be more reliably prevented.

[0068] Furthermore, since the inner diameter of the covering member 20 is within a predetermined fitting tolerance relative to the outer diameter of the flow path forming member 10 , the flow path forming member 10 and the covering member 20 can be constructed within the fitting tolerance, thereby facilitating assembly of the fluid impedance assembly R.

[0069] Furthermore, since the aspect ratio, which is the ratio of the length dimension to the diameter dimension of the resistance flow path 10 a , is 200 or greater, it is possible to measure an ultra-low flow rate.

[0070] Furthermore, if the fluid impedance component is formed by sandwiching a slit plate with a covering plate as previously described (in the background art), there is also the problem of needing to form a separate configuration space that matches the shape of the fluid impedance component in the middle of the internal flow path L. However, in the case of the fluid impedance component R of this embodiment, it can be reasonably arranged in the internal flow path L, so there is no need to form such a dedicated space.

[0071] In addition, the present invention is not limited to the above-described embodiment.

[0072] For example, the fluid control device 100 includes a single fluid impedance component R in the embodiment described above, but may also include a plurality of fluid impedance components R. Figure 4 As shown, it includes multiple fluid impedance components R.

[0073] As an example, the following can be cited: Figure 4 (A) shows a configuration in which a plurality of fluid resistance elements R are arranged in series.

[0074] Specifically, three or more pressure sensors (hereinafter referred to as the first pressure sensor P1 to the third pressure sensor P3) are arranged in the internal flow path L, a first fluid impedance component R(A) is arranged between the first pressure sensor P1 and the second pressure sensor P2, and a second fluid impedance component R(B) is arranged between the second pressure sensor P2 and the third pressure sensor P3.

[0075] In the above configuration, the fluid control device 100 preferably includes a diagnostic circuit (not shown) that diagnoses whether a malfunction has occurred in the fluid control device 100 by comparing a first flow rate calculated based on the impedance value of the first fluid impedance element R(A), the detection value of the first pressure sensor P1, and the detection value of the second pressure sensor P2 with a second flow rate calculated based on the impedance value of the second fluid impedance element R(B), the detection value of the second pressure sensor P2, and the detection value of the third pressure sensor P3. Specific embodiments of the diagnostic circuit include one in which a malfunction is diagnosed when the difference between the first and second flow rates exceeds a predetermined threshold.

[0076] In addition, through Figure 4 As shown in (B), a plurality of fluid impedance components R are provided in series between the upstream pressure sensor Pa and the downstream pressure sensor Pb, so that the impedance between the upstream pressure sensor Pa and the downstream pressure sensor Pb is high, thereby enabling low flow rate measurement.

[0077] As another example, we can cite Figure 4 (C) shows a configuration in which a plurality of fluid resistance components R are arranged in parallel with each other.

[0078] Specifically, a first fluid impedance component R(A) is provided between the upstream pressure sensor Pa and the downstream pressure sensor Pb, and a second fluid impedance component R(B) is provided in the discharge flow path Z branching from the upstream or downstream of the first fluid impedance component R(A).

[0079] According to this structure, a predetermined amount of fluid is discharged from the discharge flow path, thereby ensuring the flow rate flowing into the fluid control device 100. Therefore, the response speed can be improved when the control flow rate is low. Specifically, when the flow rate is low, the responsiveness is reduced due to the poor discharge performance of the fluid relative to the fluid impedance component R during the descent. However, by Figure 4 As shown in FIG (C), the first fluid resistance element R(A) and the second fluid resistance element R(B) are arranged in parallel, and the fluid can be forcibly exhausted through the second fluid resistance element R(B). This ensures the flow rate, so that the descent can be completed in about 3 seconds instead of about 30 seconds.

[0080] In addition, when the fluid control device 100 includes a plurality of fluid impedance components R as described above, these fluid impedance components R may have different impedances or may have the same impedance.

[0081] In addition, the fluid impedance element R is provided in the internal flow path L communicating with the upstream pressure sensor Pa and the downstream pressure sensor Pb in the above embodiment, but it may also be provided as follows. Figure 5 As shown, it is built into the upstream pressure sensor Pa or the downstream pressure sensor Pb. Specifically, the fluid resistance element R may be provided in the flow path L1 for guiding the fluid to the diaphragm D which is a component of the pressure sensor.

[0082] Furthermore, in the embodiment, the flow path forming member 10 is embedded in the cylindrical covering member 20, but for example, the metal covering member 20 can also be rolled on the outer peripheral surface of the flow path forming member 10, or the metal covering member 20 can be set on the outer peripheral surface of the flow path forming member 10 through surface treatment such as vapor deposition.

[0083] Furthermore, the flow path forming member 10 is cylindrical in the above embodiment. However, if the cross section of the flow path is triangular, quadrilateral, or polygonal, the flow path forming member 10 may also be a columnar shape having a triangular, quadrilateral, or polygonal cross section corresponding to these shapes. In this case, the covering member 20 may also be a cylindrical shape having a triangular, quadrilateral, or polygonal cross section corresponding to the cross-sectional shape of the flow path.

[0084] As the fluid control device 100 , another device unit such as a flow meter (flow rate measuring device) that does not have the flow rate regulating valve V may be used.

[0085] In the above embodiment, the fluid resistance element R is used to constitute the pressure type fluid control device 100, but it may also be used as follows. Figure 6 As shown, a thermal fluid control device 100 is configured with a thermal flow sensor provided in an internal flow path L. Specifically, the flow measurement mechanism X in this case includes: a fluid resistance element R provided in the internal flow path L; a sensor flow path Lb connecting the upstream and downstream sides of the internal flow path L; an upstream resistor element T1 and a downstream resistor element T2 provided in the sensor flow path Lb; and a flow calculation circuit C2 that calculates the fluid flow rate based on the values ​​output from these resistor elements T1 and T2.

[0086] In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

[0087] Industrial Applicability

[0088] According to the present invention, while enjoying the advantages of using ceramics to form a resistance flow path, the fluid resistance component can be rationally assembled to the flow path through which the fluid flows.

Claims

1. A fluid control device comprising: internal flow path for fluid flow; a fluid impedance component, embedded and fixed in the internal flow path; as well as An upstream pressure sensor and a downstream pressure sensor are provided on the upstream side and downstream side of the fluid impedance component in the internal flow path. The fluid control device is characterized in that: The fluid impedance component has: a ceramic flow path forming member having one or more resistive flow paths; and The metal covering member covers the outer peripheral surface of the flow channel forming member and has a lower hardness than the ceramic.

2. The fluid control device according to claim 1, wherein: The flow path forming member is cylindrical, The covering member has a cylindrical shape, and the flow path forming member is fitted into the covering member with a fitting tolerance.

3. The fluid control device according to claim 1, wherein: The entire outer peripheral surface of the flow channel forming member is covered by the covering member.

4. The fluid control device according to claim 1, wherein: The aspect ratio, which is a ratio of a length dimension to a diameter dimension of the impedance flow path, is 200 or greater.

5. The fluid control device according to claim 1, wherein: It also includes a flow regulating valve, which is arranged in the internal flow path.

6. The fluid control device according to claim 5, characterized in that: include: a flow calculation circuit for calculating the flow rate of the fluid flowing in the internal flow path; as well as The control circuit controls the flow rate regulating valve so that the measured flow rate calculated by the flow rate calculation circuit becomes a predetermined target flow rate.

7. The fluid control device according to claim 1, wherein: A plurality of the fluid impedance components having different impedance values ​​are arranged in series or in parallel.

8. The fluid control device according to claim 7, characterized in that: A first pressure sensor, a second pressure sensor, and a third pressure sensor are provided in the internal flow path. The first fluid impedance component is disposed between the first pressure sensor and the second pressure sensor, The second fluid impedance component is disposed between the second pressure sensor and the third pressure sensor, The fluid control device also includes a diagnostic circuit, which compares a first flow rate with a second flow rate to diagnose whether an adverse condition occurs, the first flow rate is calculated based on the impedance value of the first fluid impedance component, the detection value of the first pressure sensor, and the detection value of the second pressure sensor, and the second flow rate is calculated based on the impedance value of the second fluid impedance component, the detection value of the second pressure sensor, and the detection value of the third pressure sensor.

9. The fluid control device according to claim 7, characterized in that: The first fluid impedance component is disposed between the upstream pressure sensor and the downstream pressure sensor. The second fluid impedance component is arranged in parallel with the first fluid impedance component.

10. The fluid control device according to claim 1, wherein: A plurality of the fluid impedance components having mutually equal impedance values ​​are provided in series.

11. The fluid control device according to claim 10, wherein: The plurality of fluid impedance components are disposed between the upstream pressure sensor and the downstream pressure sensor.

12. A fluid control device comprising: internal flow path for fluid flow; a fluid impedance component, embedded and fixed in the internal flow path; a sensor flow path connecting an upstream side and a downstream side of the internal flow path; The upstream side resistor component and the downstream side resistor component are arranged in the sensor flow path, The fluid control device is characterized in that: The fluid impedance component has: a ceramic flow path forming member having one or more resistive flow paths; and The metal covering member covers the outer peripheral surface of the flow channel forming member and has a lower hardness than the ceramic.

13. The fluid control device according to claim 12, wherein: The flow path forming member is cylindrical, The covering member has a cylindrical shape, and the flow path forming member is fitted into the covering member with a fitting tolerance.

14. The fluid control device according to claim 12, wherein: The entire outer peripheral surface of the flow channel forming member is covered by the covering member.

15. The fluid control device according to claim 12, wherein: The aspect ratio, which is a ratio of a length dimension to a diameter dimension of the impedance flow path, is 200 or greater.

16. The fluid control device according to claim 12, wherein: It also includes a flow regulating valve, which is arranged in the internal flow path.

17. The fluid control device according to claim 16, wherein: include: a flow calculation circuit for calculating the flow rate of the fluid flowing in the internal flow path; as well as The control circuit controls the flow rate regulating valve so that the measured flow rate calculated by the flow rate calculation circuit becomes a predetermined target flow rate.

18. The fluid control device according to claim 12, wherein: A plurality of the fluid impedance components having different impedance values ​​are arranged in series or in parallel.

19. The fluid control device according to claim 12, wherein: A plurality of the fluid impedance components having mutually equal impedance values ​​are provided in series.

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