Flow calculation device and flow calculation method

Abstract

The invention provides a flow calculation device and a flow calculation method. The flow rate calculation device includes: a specific flow path and a bypass flow path provided to divert and divert a fluid from a main flow path; the first flow resistance element is arranged in the specific flow channel; the second flow resistance element is arranged in the bypass flow channel; a container disposed on the downstream side of the first flow resistance element in the specific flow path; a pressure sensor for detecting the pressure in the container; and a flow rate calculation unit. The flow rate calculation unit calculates the flow rate of the first shunt fluid shunted to the specific flow path on the basis of the change in the pressure in the container, and calculates the flow rate of the fluid flowing through the main flow path on the basis of the calculated flow rate of the first shunt fluid and a shunt ratio determined from the first flow resistance element and the second flow resistance element.

Description

Technical Field

[0001] The invention relates to a flow calculation device and a flow calculation method. Background Art

[0002] In the past, the RoR (Rate of Rise) method was known as a method for measuring the flow rate of a fluid. The RoR method is a method of causing a fluid (e.g., gas) to flow from a test body (e.g., a flow control device) into a vacuum-evacuated container, and using the state equation of the fluid to calculate the flow rate based on the pressure rise rate in the container. For example, Patent Document 1 discloses a device for verifying the flow rate of a fluid using the RoR method.

[0003] Patent Document 1: International Publication No. 2018 / 111725

[0004] However, when the RoR method is used, if the flow rate of the fluid to be verified increases, a large (large-capacity) container must be prepared, which increases the size of the entire device. Summary of the invention

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a flow rate calculation device and a flow rate calculation method that can calculate the flow rate of a fluid without increasing the size of the entire device even when the flow rate of the fluid is large.

[0006] A flow calculation device according to one aspect of the present invention calculates the flow rate of a fluid flowing in a main flow channel, and comprises: a specific flow channel and a bypass flow channel, which are arranged to branch from the main flow channel and divert the fluid; a first flow resistance element, which is arranged in the specific flow channel; a second flow resistance element, which is arranged in the bypass flow channel; a container, which is arranged on the downstream side of the first flow resistance element in the specific flow channel; a pressure sensor, which detects the pressure in the container; and a flow calculation unit, which calculates the flow rate of the first branch fluid diverted to the specific flow channel based on the change in the pressure in the container, and calculates the flow rate of the fluid flowing in the main flow channel based on the calculated flow rate of the first branch fluid and the diversion ratio determined according to the first flow resistance element and the second flow resistance element.

[0007] Another aspect of the present invention provides a flow calculation method comprising: a process for calculating the flow rate of a first branch fluid flowing in a main channel based on a change in pressure in a container disposed on a downstream side of a first flow resistance element in the specific channel when the fluid flowing in the main channel is branched into a specific channel and a bypass channel branched from the main channel; and a process for calculating the flow rate of the fluid flowing in the main channel based on the calculated flow rate of the first branch fluid and a diversion ratio determined according to the first flow resistance element and a second flow resistance element disposed in the bypass channel.

[0008] According to the present invention, even when the flow rate of the fluid is large, the flow rate of the fluid can be calculated while avoiding an increase in the size of the entire device. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is an explanatory diagram showing a schematic configuration of a flow rate calculation device according to one embodiment of the present invention. Figure 2 It is a perspective view showing a structural example of a pressure loss element. Figure 3 It is an exploded perspective view showing another structural example of the pressure loss element. Figure 4 It is a block diagram showing the detailed structure of the control operation device. Figure 5 This is a flowchart showing the flow of each step of the flow rate calculation method. Figure 6 It is an explanatory diagram showing another structure of the flow rate calculation device. Figure 7 It is an explanatory diagram showing still another structure of the above-mentioned flow rate calculation device. DETAILED DESCRIPTION

[0010] In the following description, for any structural element of the flow rate calculation device, the side where the fluid flows in is also referred to as the upstream side or the primary side, and for the above structural element, the side where the fluid flows out is also referred to as the downstream side or the secondary side.

[0011] [1. Structure of flow rate calculation device] Figure 1 1 is an explanatory diagram showing a schematic structure of a flow rate calculation device 1 of the present embodiment. The flow rate calculation device 1 calculates the flow rate of the fluid F flowing out of the flow control device 100 and flowing in the main flow channel L0 by the method described later. Moreover, the flow rate calculation device 1 diagnoses the flow control device 100 based on the calculated flow rate and the set flow rate of the fluid F flowing out of the flow control device 100, and performs correction as needed. As the above-mentioned fluid F, for example, a material gas used in a semiconductor manufacturing process can be assumed.

[0012] The flow control device 100 is a device that flows the fluid F into the main channel L0 and is a device under test of the flow calculation apparatus 1. The flow control device 100 is, for example, a mass flow controller that controls the flow rate of the fluid F, but is not limited to this example.

[0013] The flow calculation device 1 has a specific flow channel L1 and a bypass flow channel L2. The specific flow channel L1 and the bypass flow channel L2 are arranged to branch from the main flow channel L0. The fluid F flowing out from the flow control device 100 and flowing through the main flow channel L0 is branched to the specific flow channel L1 and the bypass flow channel L2. In addition, in this specification, "diversion" means that the fluid flows separately. Hereinafter, the fluid diverted from the main flow channel L0 to the specific flow channel L1 is also referred to as the first branch fluid F1, and the fluid diverted from the main flow channel L0 to the bypass flow channel L2 is also referred to as the second branch fluid F2. That is, after the fluid F is divided into the first branch fluid F1 and the second branch fluid F2 at the branching point between the specific flow channel L1 and the bypass flow channel L2, it flows in the specific flow channel L1 and the bypass flow channel L2 respectively.

[0014] The specific flow channel L1 and the bypass flow channel L2 merge on the downstream side of the container TA described later arranged in the specific flow channel L1, and are connected to the merging line L3. The merging line L3 is connected to the pump PU. Therefore, the bypass flow channel L2 is provided to bypass the container TA of the specific flow channel L1 between the main flow channel L0 and the merging line L3.

[0015] The flow rate calculation device 1 further includes a first flow resistance element RE1 and a second flow resistance element RE2. The first flow resistance element RE1 is provided in the specific flow path L1, and the second flow resistance element RE2 is provided in the bypass flow path L2.

[0016] The first flow resistance element RE1 and the second flow resistance element RE2 are formed by, for example, a pressure loss element PL (see Figure 2 ) is formed. The pressure loss element PL refers to an element that causes pressure loss (energy loss) in the fluid. Since the first flow resistance element RE1 is provided in the specific flow channel L1, the first branch fluid F1 flowing in the specific flow channel L1 causes pressure loss. Since the second flow resistance element RE2 is provided in the bypass flow channel L2, the second branch fluid F2 flowing in the bypass flow channel L2 causes pressure loss.

[0017] For example, if flow resistance is generated, pressure loss is generated in the fluid. If pressure loss is generated in the fluid, for example, under the same pressure conditions, the flow rate of the fluid decreases. Therefore, the pressure loss element PL functions as an element that limits the flow rate, that is, as a flow resistance element, and the flow resistance element becomes a resistance element when the fluid flows. Hereinafter, the pressure loss element PL constituting the first flow resistance element RE1 is also referred to as the first pressure loss element PL1, and the pressure loss element PL constituting the second flow resistance element RE2 is also referred to as the second pressure loss element PL2.

[0018] Figure 2 1 is a perspective view showing a configuration example of the pressure loss element PL. The pressure loss element PL is configured to include a flow path forming member 10 and a covering member 20. The covering member 20 may be provided as required.

[0019] The flow channel forming component 10 is formed of ceramics such as quartz, alumina, zirconia or silicon nitride, and is molded into a cylindrical shape. The flow channel forming component 10 has at least one flow channel 10a (hereinafter also referred to as resistance flow channel 10a) which serves as a resistance member. The resistance flow channel 10a penetrates the flow channel forming component 10 in the axial direction and is formed into a circular cross-section. In the case where a covering component 20 is provided, the covering component 20 is made of a metal such as stainless steel or a nickel alloy having a hardness at least lower than that of ceramics. Such a pressure loss element PL is a restrictor made of at least ceramics, and in this sense, it is also called a ceramic restrictor.

[0020] The flow resistance of the pressure loss element PL is determined based on the aspect ratio and the number of resistance flow channels 10a. In addition, the above-mentioned aspect ratio refers to the ratio of the axial length dimension to the radial dimension of the resistance flow channel 10a. Therefore, when the aspect ratio of the resistance flow channel 10a is fixed, the flow resistance of the pressure loss element PL can be easily adjusted by changing the number of resistance flow channels 10a. Therefore, by changing the number of resistance flow channels 10a, the flow rate of the fluid flowing in the pressure loss element PL can be easily adjusted.

[0021] Furthermore, a flow resistance element (flow restrictor) used in a differential pressure type flow control device (mass flow controller) can also be appropriately used as the pressure loss element PL. Figure 3 It is an exploded perspective view showing a schematic structure of a flow restrictor as another structural example of the pressure loss element PL.

[0022] The flow restrictor is an element that generates a pressure difference (differential pressure) between two pressure sensors provided in the mass flow controller. As shown in the figure, the flow restrictor has a structure in which circular cutout plates 31 and circular cutout cover plates 32 are alternately stacked. The cutout plates 31 and the cutout cover plates 32 are formed of metal such as stainless steel (Steel Use Stainless). That is, the flow restrictor is a restrictor formed of metal.

[0023] The cutout plate 31 has a first through hole 31a that passes through the center in the thickness direction, and a plurality of cutouts 31b that are formed radially from the center. The cutout cover plate 32 has a second through hole 32a that passes through the center in the thickness direction. The outer diameter of the cutout cover plate 32 is smaller than the outer diameter of the cutout plate 31, and the inner diameter of the cutout cover plate 32 is larger than the inner diameter of the cutout plate 31.

[0024] By stacking the cutout plate 31 and the cutout cover plate 32, the inner end of the cutout 31b becomes the start end of the resistance flow channel, and the outer end of the cutout 31b becomes the end of the resistance flow channel. In addition, a through hole that penetrates along the stacking direction is formed in the central part of the flow restrictor by using the first through hole 31a of the cutout plate 31 and the second through hole 32a of the cutout cover plate 32. The through hole serves as a fluid introduction portion.

[0025] The number of the resistance flow paths can be changed by changing the number of stacked sheets of the cutout plates 31 and the cutout cover plates 32. Therefore, as in the case of the ceramic restrictor, the flow rate of the fluid flowing in the flow restrictor can be easily adjusted by changing the number of stacked sheets.

[0026] The pressure loss element PL is not limited to the ceramic restrictor and flow restrictor described above, but any element that can cause pressure loss in the fluid and restrict the flow rate of the fluid can be used. In this regard, even an element such as a throttle (orifice) can be used as the pressure loss element PL.

[0027] like Figure 1 As shown, the flow rate calculation device 1 further includes: a main channel pressure sensor P1, a container TA, a specific channel pressure sensor P2, a temperature sensor T, a bypass channel pressure sensor P3, a control valve CV, a first opening and closing valve V1, and a second opening and closing valve V2.

[0028] The main channel pressure sensor P1 (main channel pressure detection unit) measures the pressure of the fluid flowing in the main channel L0. The container TA is a tank arranged on the downstream side of the first flow resistance element RE1 in the specific channel L1. The first branch fluid F1 flowing in the specific channel L1 flows into the container TA. The specific channel pressure sensor P2 detects the pressure in the container TA. The temperature sensor T detects the gas temperature in the container TA. In addition, if the gas temperature in the container TA is equal to the temperature of the outer wall surface or the inner wall surface of the container TA, the temperature sensor T can also detect the temperature of the outer wall surface or the inner wall surface of the container TA.

[0029] The bypass flow path pressure sensor P3 is arranged on the downstream side of the second flow resistance element RE2 in the bypass flow path L2, and measures the pressure of the second branch path fluid F2 flowing through the second flow resistance element RE2. A control valve CV is provided to control the flow rate of the second branch path fluid F2 flowing in the bypass flow path L2 through the second flow resistance element RE2. The control valve CV is composed of, for example, an electromagnetic proportional valve, but may also be composed of other valves (flow control valves).

[0030] The first opening and closing valve V1 is located on the downstream side of the container TA in the specific flow channel L1, and opens and closes the flow channel. The second opening and closing valve V2 is located on the downstream side of the second flow resistance element RE2 in the bypass flow channel L2, especially on the downstream side of the control valve CV, and opens and closes the flow channel. The first opening and closing valve V1 and the second opening and closing valve V2 are composed of, for example, air valves, but may also be composed of other valves.

[0031] The flow rate calculation device 1 further includes a control calculation device COM. The control calculation device COM is composed of, for example, a computer having a central processing unit (CPU). The control calculation device COM performs various calculations based on detection signals output from each measuring device (main channel pressure sensor P1, specific channel pressure sensor P2, temperature sensor T, bypass channel pressure sensor P3) provided in the flow rate calculation device 1, and controls valves (control valve CV, first opening and closing valve V1, second opening and closing valve V2) provided in the flow rate calculation device 1.

[0032] Figure 4 COM is a block diagram showing the detailed structure of the control computing device COM. The control computing device COM includes a control unit 50 and a storage unit 60. In addition, the control computing device COM also includes an input unit (such as a keyboard, a mouse, a touch panel), a display unit (such as a liquid crystal display device), and a communication unit (such as a connector, an adapter). Since the input unit and the like are not essential structures in this embodiment, they are not described in detail. Figure 4 Illustration of the input unit etc. is omitted.

[0033] The control unit 50 includes a main control unit 51, a flow rate calculation unit 52, and an equipment diagnosis unit 53. The main control unit 51 controls the operation of each unit of the control calculation device COM and outputs a control signal for controlling the valve of the flow rate calculation device 1.

[0034] The flow rate calculation unit 52 calculates the flow rate of the fluid F flowing in the main channel L0 based on the detection signals output from the above-mentioned measuring devices of the flow rate calculation device 1. Specifically, the flow rate calculation unit 52 includes a specific channel measuring unit 52a, a bypass channel control unit 52b, a flow split ratio calculation unit 52c, and a main channel calculation unit 52d.

[0035] The specific flow channel measuring unit 52a measures the flow rate of the first branch fluid F1 branched to the specific flow channel L1 using the RoR method. The bypass flow channel control unit 52b controls the control valve CV arranged in the bypass flow channel L2. The branch ratio calculation unit 52c calculates the branch ratio, which is obtained based on the ratio of the flow rate of the first branch fluid F1 branched from the main flow channel L0 to the specific flow channel L1 and the flow rate of the second branch fluid F2 branched from the main flow channel L0 to the bypass flow channel L2. The main flow channel calculation unit 52d calculates the flow rate of the fluid F flowing in the main flow channel L0 using the flow rate of the first branch fluid F1 and the above-mentioned branch ratio. In addition, the details of the calculation method of the above-mentioned flow rate will be described later.

[0036] The device diagnosis unit 53 diagnoses the flow control device 100 that discharges the fluid F to the main flow channel L0. The flow control device 100 may be unable to control the flow rate according to the set flow rate due to aging, blockage of the flow channel, or some failure. Therefore, the device diagnosis unit 53 regularly diagnoses whether the flow control device 100 can control the flow rate according to the set flow rate based on the flow rate calculated by the flow calculation unit 52.

[0037] The storage unit 60 is a memory that stores the operation program of the control unit 50, and stores various information (detected measurement values) contained in the detection signals output from the above-mentioned measuring devices of the flow calculation device 1, information related to the first flow resistance element RE1 and the second flow resistance element RE2 (for example, information on the number of resistance flow channels), etc. Such a storage unit 60 can be composed of, for example, a hard disk, an SSD (solid state drive), an optical disk, a magnetic disk, or a non-volatile memory.

[0038] In addition, if Figure 1 As shown, the flow calculation device 1 is further provided with a main channel thermometer T0. The main channel thermometer T0 measures the temperature of the fluid F flowing in the main channel L0. The main channel thermometer T0 is provided in order to obtain the temperature information required for the calculation of the RoR method when correcting the flow rate of the fluid F flowing in the main channel L0. In addition, the correction of the above-mentioned flow rate will be explained in "5. Supplementary Explanation" described later. In addition, when correcting the above-mentioned flow rate, although strictly speaking, the information of the temperature and pressure on the upstream side of the first flow resistance element RE1 in the specific flow channel L1 and the temperature and pressure on the upstream side of the second flow resistance element RE2 in the bypass flow channel L2 is required, they can be replaced by the detection value (pressure Pr1) of the main channel pressure sensor P1 and the detection value of the main channel thermometer T0.

[0039] 〔2. About flow calculation method〕 Figure 5 Flow chart showing the flow of each step of the flow calculation method according to the present embodiment. Figure 1 to Figure 5, the flow calculation method of this embodiment is described. In addition, the following describes an example in which a flow restrictor is used as the first flow resistance element RE1 and the second flow resistance element RE2. In addition, when a ceramic restrictor is used as the first flow resistance element RE1 and the second flow resistance element RE2, the flow calculation method shown below can also be applied.

[0040] (S1: Vacuuming process) First, open both the first on-off valve V1 and the second on-off valve V2, drive the pump PU, and evacuate until the inside of the container TA reaches the set pressure. At this time, the outflow of the fluid F from the flow control device 100 to the main channel L0 is stopped in advance, but the evacuation can also be performed while the fluid F flows out. In addition, the inside of the container TA does not need to be a strict vacuum. That is, the above-mentioned set pressure can be a pressure of a degree that can be used to calculate the pressure rise rate by the RoR method described later.

[0041] (S2: Fluid supply process) Next, the fluid F with the set flow rate Q0 is made to flow out from the flow control device 100 to the main flow channel L0. Since the first opening and closing valve V1 and the second opening and closing valve V2 are opened, the above-mentioned fluid F is divided into the specific flow channel L1 and the bypass flow channel L2. After the flow rate of the first branch fluid F1 is stabilized, the first opening and closing valve V1 is closed. In addition, the second opening and closing valve V2 remains open.

[0042] (S3: CV control process) By closing the first on-off valve V1 in S2, the first branch fluid F1 flows into the container TA. As a result, the pressure in the container TA rises. At this time, the flow calculation unit 52 (particularly the bypass flow path control unit 52b) controls the control valve CV so that the pressure Pr3 on the downstream side of the second flow resistance element RE2 measured by the bypass flow path pressure sensor P3 is consistent with or close to the pressure Pr2 in the container TA detected by the specific flow path pressure sensor P2.

[0043] By the above control, the relationship between the pressure on the primary side and the pressure on the secondary side of the flow resistance element becomes the same or nearly the same in the specific flow passage L1 and the bypass flow passage L2. Therefore, the flow split ratio S can be easily expressed by the ratio of the number of resistance flow passages constituting the first flow resistance element RE1 to the number of resistance flow passages constituting the second flow resistance element RE2.

[0044] In addition, the above-mentioned flow split ratio S refers to the relative flow rate (S) of the first branch path fluid F1 branched to the specific flow channel L1 when the flow rate of the fluid F flowing in the main flow channel L0 is taken as 1 (reference). That is, since the flow rate of the second branch path fluid F2 branched to the bypass flow channel L2 is (1-S), the flow split ratio S is represented by S=S / {S+(1-S)}.

[0045] For example, when the aspect ratio of the resistance flow path is fixed and the ratio of the number of resistance flow paths constituting the first flow resistance element RE1 to the number of resistance flow paths constituting the second flow resistance element RE2 is 1:10, the ratio of the flow rate flowing in the first flow resistance element RE1 to the flow rate flowing in the second flow resistance element RE2 is 1:10. Therefore, the flow split ratio S is S=1 / (1+10). The flow rate calculation unit 52 (particularly the flow split ratio calculation unit 52c) calculates the flow split ratio S based on information pre-stored in the storage unit 60 (here, information on the number of resistance flow paths constituting the first flow resistance element RE1 and the number of resistance flow paths constituting the second flow resistance element RE2). In addition, in order to reduce the error of the flow split ratio caused by the manufacturing error of the flow resistance element, it is preferable to actually flow the fluid and find the actual flow split ratio in advance, and correct the theoretical flow split ratio determined based on the number of resistance flow paths in advance.

[0046] (S4: Flow rate calculation step of the first branch fluid) Next, the flow rate calculation unit 52 (particularly the specific flow channel measurement unit 52a) calculates the flow rate Q1 of the first branch fluid F1 branched to the specific flow channel L1 based on the RoR method, that is, based on the pressure change in the container TA. For example, it is assumed that the pressure in the container TA rises by ΔP (Pa) during the time Δt (sec). In this case, the flow rate calculation unit 52 can calculate the flow rate Q1 based on the following formula (A) by the RoR method. Q1=(ΔP / Δt)×(V / RT)×C…(A) In formula (A), V represents the volume (L) of the container TA, T represents the temperature of the gas in the container TA detected by the temperature sensor, or the temperature (K) of the outer wall or inner wall of the container TA, R represents the gas constant, and C represents the correction coefficient. By multiplying by the correction coefficient C, conversion to mass flow rate or volume flow rate, change of reference temperature, etc. can be performed. In addition, the correction coefficient C also includes the compressibility factor as a physical property parameter.

[0047] (S5: Step of calculating the fluid flow rate in the main channel) Next, the flow rate calculation unit 52 (particularly the main channel calculation unit 52d) calculates the flow rate Q of the fluid F flowing in the main channel L0 based on the calculated flow rate Q1 of the first branch fluid calculated in S4 and the above-mentioned flow division ratio S determined by the first flow resistance element RE1 and the second flow resistance element RE2. Specifically, the flow rate calculation unit 52 can calculate the flow rate Q based on the following formula (B). Q=Q1 / S…(B)

[0048] (S6: Diagnostic process of flow control equipment) Finally, the device diagnosis unit 53 diagnoses the flow control device 100 based on the set flow rate Q0 when the flow control device 100 flows out the fluid F and the flow rate Q of the fluid F flowing in the main channel L0 calculated by the flow calculation unit 52. For example, when there is a difference of a predetermined value or more between the set flow rate Q0 and the actual flow rate Q, the device diagnosis unit 53 can determine that the flow control device 100 has deteriorated over time, the flow channel is clogged, or some kind of failure has occurred. In this case, the device diagnosis unit 53 outputs a control signal for correcting the outflow flow rate to the flow control device 100, so that the flow control device 100 can operate appropriately.

[0049] As described above, the flow rate calculation unit 52 calculates the flow rate Q of the fluid F flowing in the main channel L0 based on the calculated flow rate Q1 of the first branch fluid F1 and the flow splitting ratio S (S4, S5). Thus, even when the flow rate of the fluid F is large, the flow rate Q of the fluid F can be calculated using a container TA of a size that allows a portion of the fluid F (the first branch fluid F1) to flow in. Therefore, when calculating the flow rate Q, it is not necessary to prepare a large-capacity container TA. As a result, the flow rate Q of the fluid F flowing in the main channel L0 can be calculated without increasing the size of the entire device.

[0050] In particular, the flow rate calculation unit 52 calculates the flow rate Q (S5) based on the above-mentioned formula (B). Even when the flow rate Q is large, the flow rate Q can be reliably calculated by using the formula (B) that defines the relationship between the flow rate Q1, the diversion ratio S, and the flow rate Q, without increasing the size of the container TA.

[0051] Furthermore, since the flow rate calculation unit 52 controls the control valve CV as shown in S3, the split ratio S can be easily set according to the ratio of the number of resistance flow channels. Furthermore, by adjusting the number of resistance flow channels, the split ratio S can be easily adjusted.

[0052] The first flow resistance element RE1 and the second flow resistance element RE2 are respectively pressure loss elements PL. Thus, flow resistance elements such as ceramic restrictors and throttles can be used as pressure loss elements PL. In addition, flow restrictors used in differential pressure mass flow controllers can also be used as pressure loss elements PL.

[0053] However, it is preferred that the first flow resistance element RE1 and the second flow resistance element RE2 are composed of the same type of element. For example, it is preferred that both the first flow resistance element RE1 and the second flow resistance element RE2 are composed of ceramic restrictors. Alternatively, it is preferred that both the first flow resistance element RE1 and the second flow resistance element RE2 are composed of flow restrictors. In this case, even if the pressure on the downstream side of the flow resistance element changes, the pressure loss (energy loss) generated by the shunt fluid can be made the same in the specific flow channel L1 and the bypass flow channel L2. Thereby, the risk of the diversion ratio S changing due to the change in the pressure on the downstream side of the flow resistance element can be reduced. As a result, the calculation of the flow rate Q of the main channel L0 using the diversion ratio S can be performed with stable accuracy.

[0054] [3. Other structures of flow rate calculation device] Figure 6 It is an explanatory diagram showing another configuration of the flow rate calculation device 1 . Figure 6 The flow calculation device 1 is in addition to Figure 1 The control valve CV is located in the position of the pressure control device UR, and Figure 1 The pressure control device UR has a built-in pressure gauge P4 and Figure 1 In such a pressure control device UR, the flow rate of the fluid (the pressure of the fluid flowing in the flow path) can be controlled by controlling the control valve CV based on the detection value of the pressure gauge P4.

[0055] Even if Figure 6 The structure can also be realized with Figure 5 That is, the flow rate calculation unit 52 controls the control valve CV of the pressure control device UR so that the pressure Pr3 on the downstream side of the second flow resistance element RE2 can be made consistent with or close to the pressure Pr2 in the container TA detected by the specific flow path pressure sensor P2. As a result, the same effect as described above of easily adjusting the flow split ratio S can be obtained. In addition, it can be considered that the pressure detection value of the pressure gauge P4 built into the pressure control device UR is equal to the pressure Pr3.

[0056] In addition, Figure 6In the structure, the pressure is adjusted in such a way that the pressure Pr3 on the downstream side of the second flow resistance element RE2 is consistent with or close to the pressure Pr2 in the container TA detected by the specific flow channel pressure sensor P2 by controlling the control valve CV of the pressure control device UR. However, a table or a relational expression may be pre-set, which pre-acquires the relationship between the flow rate and the pressure between the main flow channel pressure sensor P1 and the specific flow channel pressure sensor P2 in each branch flow channel, and between the main flow channel pressure sensor P1 and the bypass flow channel pressure sensor P3. In this case, instead of controlling the control valve CV as described above (even if there is no control valve CV), the difference in the pressure value of the branch flow channel can be corrected to achieve the same purpose.

[0057] [4. Other structures of flow rate calculation device] Figure 7 It is an explanatory diagram showing still another configuration of the flow rate calculation device 1 . Figure 7 The flow rate calculation device 1 is similar to the flow rate calculation device 1 except that the critical nozzle is used as the first flow resistance element RE1 and the second flow resistance element RE2, and the bypass flow channel pressure sensor P3 and the control valve CV are deleted. Figure 1 The flow calculation method is the same as the flow calculation device 1. In addition, the flow calculation method is the same as the flow calculation device 1 except that the step S3 is deleted. Figure 5 The method shown is the same.

[0058] The first flow resistance element RE1 is composed of the first critical nozzle CN1. The second flow resistance element RE2 is composed of the second critical nozzle CN2. The first critical nozzle CN1 and the second critical nozzle CN2 may have completely the same characteristics (shape, size, minimum diameter), or different characteristics.

[0059] The critical nozzle has the following properties: if the pressure reduction on the secondary side is promoted, and the flow velocity of the fluid flowing through the throttle section (throat) of the critical nozzle reaches the speed of sound (critical state), then no matter how the pressure on the downstream side of the nozzle drops, the flow velocity of the fluid passing through the throat will not exceed the speed of sound, and the flow velocity is fixed at the speed of sound. Therefore, if a critical nozzle is used, then in the critical state (under critical conditions), the flow rate of the fluid passing through the critical nozzle has nothing to do with the pressure on the secondary side of the critical nozzle, but is determined only by the pressure on the primary side. That is, in Figure 7 In the example in , the flow rate of the fluid passing through the critical nozzle is determined by the pressure Pr1 of the main channel pressure sensor P1. Specifically, in the critical state, the flow rate of the fluid passing through the critical nozzle is calculated by the following mathematical formula 1.

[0060] [Mathematical formula 1]

[0061] In equation 1, qt is the theoretical value of the mass flow rate of the fluid (kg / s), and At is the cross-sectional area of ​​the throat of the critical nozzle (m 2 ), Cc is the critical constant, Ps is the stagnation pressure (Pa), Na is the molar mass of the fluid (kg / mol), Ru is the universal gas constant (J / Kmol), and Ts is the stagnation temperature (K). Assuming the specific heat ratio is κ, the critical constant Cc is expressed by the following mathematical formula 2.

[0062] [Mathematical formula 2]

[0063] When the mass flow rate indicating the actual flow rate of the fluid is qm (kg / s), the outflow coefficient Cd is expressed by the following mathematical formula 3.

[0064] [Mathematical formula 3]

[0065] Therefore, by measuring the stagnation pressure Ps by the main channel pressure sensor P1, the other parameters are taken as known, and the theoretical value qt of the mass flow rate is calculated according to Mathematical Formulas 1 and 2, and the theoretical value qt is multiplied by the outflow coefficient Cd of Mathematical Formula 3, thereby the actual flow rate (mass flow rate qm) of the critical nozzle can be calculated.

[0066] On the other hand, the parameters other than Ps (stagnation pressure) in the above-mentioned mathematical formula 1 are composed of the inherent values ​​of the critical nozzle and the physical parameters of the fluid (gas). Therefore, in the process of making various gases flow, if Ps is the same, even if the flow rate itself flowing through each critical nozzle is unknown, the ratio of the flow rate flowing through each critical nozzle is known. Therefore, when using a critical nozzle, the diversion ratio S can be calculated using the above-mentioned flow ratio. For example, if the flow ratio of the fluid flowing through the first critical nozzle CN1 and the fluid flowing through the second critical nozzle CN2 is m:n, the diversion ratio S is represented by S=m / (m+n).

[0067] Therefore, when the first flow resistance element RE1 is composed of the first critical nozzle CN1 and the second flow resistance element RE2 is composed of the second critical nozzle CN2, it is not necessary to perform a flow splitting ratio S in order to obtain the flow splitting ratio S. Figure 5 That is, even without performing control to make the pressure on the downstream side of the second flow resistance element RE2 coincide with the pressure in the container TA, the flow split ratio S can be obtained. Therefore, it is no longer necessary to provide the bypass flow passage pressure sensor P3 and the control valve CV in the bypass flow passage L2 in order to obtain the flow split ratio S. As a result, the flow split ratio S can be obtained. Figure 1 The flow rate Q of the fluid F is calculated with a simpler structure and a simpler method.

[0068] [5. Additional explanation] exist Figure 1 In the structure shown in the figure, if the first on-off valve V1 on the downstream side of the container TA is closed, the pressure Pr2 in the container TA rises. Along with this, it can be considered that the pressure Pr1 detected by the main flow channel pressure sensor P1 on the upstream side also rises. By adding the flow rate Q calculated with the pressure rise in the specific flow channel L1 to the flow rate ΔQ calculated with the pressure rise in the main flow channel L0 on the upstream side, the flow rate Q' (=Q+ΔQ) of the flow control device 100 can be calculated with higher accuracy. In addition, the above-mentioned flow rate ΔQ can be expressed by the volume of the flow channel connecting the flow control device 100 and the two flow resistance elements (the first flow resistance element RE1 and the second flow resistance element RE2). The above-mentioned volume can be obtained by making P=Pr1 in the above-mentioned formula (A) and calculating V.

[0069] [6. Procedure] The control operation device COM of the flow calculation device 1 of the present embodiment can be composed of a computer with an action program (application software) installed. By reading and executing the above program by a computer (for example, the control unit 50), each part of the control unit 50 (main control unit 51, flow calculation unit 52, device diagnosis unit 53) can be operated to perform the above-mentioned processing (each process). Such a program is obtained by downloading from the outside through a network and stored in a memory (storage unit 60). The above program can also be stored in a computer-readable storage medium such as a CD-ROM (Compact Disk-Read Only Memory), and the above program is read from the storage medium and stored in the above memory. That is, the flow calculation program of the present embodiment is a program for causing a computer to execute the above-mentioned various processes of the flow calculation method of the present embodiment. In addition, the storage medium of the present embodiment is a computer-readable storage medium storing the above-mentioned flow calculation program.

[0070] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and the present invention can be implemented with expansion or modification within the scope not departing from the gist of the invention. Industrial Applicability

[0071] The present invention can be applied to a system for inspecting or diagnosing a flow control device such as a mass flow controller, for example. Description of Reference Numerals

[0072] 1Flow calculation device 52 Flow calculation unit 53 Equipment Diagnosis Department 100 flow control devices CN1 first critical nozzle CN2 second critical nozzle CV Control Valve F Fluid F1 first branch fluid F2 Second branch fluid L0 main channel L1 specific flow channel L2 bypass flow channel P1 Main channel pressure sensor (main channel pressure detection unit) P2 pressure sensor for specific flow path P3 bypass flow channel pressure sensor PL Pressure Loss Components PL1 first pressure loss element PL2 Second pressure loss element RE1 first flow resistance element RE2 Second flow resistance element TA container UR pressure control device.

Claims

1. A flow rate calculation device for calculating the flow rate of a fluid flowing in a main flow channel, characterized in that: include: A specific flow channel and a bypass flow channel are configured to branch off from the main flow channel to divert the fluid; A first flow resistance element is disposed in the specific flow channel; A second flow resistance element is disposed in the bypass flow channel; a container, arranged on a downstream side of the first flow resistance element in the specific flow channel; A pressure sensor for detecting the pressure in the container; as well as A flow calculation unit calculates the flow rate of the first branch fluid diverted to the specific flow channel based on the change in the pressure in the container, and calculates the flow rate of the fluid flowing in the main flow channel based on the calculated flow rate of the first branch fluid and the diversion ratio determined according to the first flow resistance element and the second flow resistance element.

2. The flow rate calculation device according to claim 1, characterized in that: When the pressure sensor is used as a pressure sensor for a specific flow path, The flow calculation device also includes: a bypass flow channel pressure sensor disposed on the downstream side of the second flow resistance element in the bypass flow channel; and a control valve for controlling the flow rate of the second branch fluid flowing in the bypass flow channel via the second flow resistance element, The flow rate calculation unit controls the control valve so that the pressure on the downstream side of the second flow resistance element measured by the bypass flow path pressure sensor is consistent with or close to the pressure in the container detected by the specific flow path pressure sensor.

3. The flow rate calculation device according to claim 2, characterized in that: It also includes a pressure control device, wherein the pressure control device has the control valve and the pressure gauge built in. The flow rate calculation unit controls the control valve of the pressure control device.

4. The flow rate calculation device according to claim 2 or 3, characterized in that: The first flow resistance element is a pressure loss element that causes pressure loss of the first branch fluid, and the second flow resistance element is a pressure loss element that causes pressure loss of the second branch fluid.

5. The flow rate calculation device according to claim 4, characterized in that: The pressure loss elements constituting the first flow resistance element and the second flow resistance element are restrictors formed of ceramics.

6. The flow rate calculation device according to claim 4, characterized in that: The pressure loss elements constituting the first flow resistance element and the second flow resistance element are restrictors formed of metal.

7. The flow rate calculation device according to claim 1, characterized in that: The first flow resistance element and the second flow resistance element are critical nozzles.

8. The flow rate calculation device according to claim 7, characterized in that: It also includes a main channel pressure detection unit disposed in the main channel, The flow calculation unit calculates the diversion ratio based on the ratio of the flow rates of the fluids flowing through the critical nozzles that constitute the first flow resistance element and the second flow resistance element, calculated using the pressure detected by the main channel pressure detection unit, under the critical condition that the flow rate of each fluid flowing in the critical nozzles that constitute the first flow resistance element and the second flow resistance element becomes the speed of sound.

9. The flow rate calculation device according to any one of claims 1 to 8, characterized in that: It also includes a device diagnosis unit, which diagnoses a flow control device that flows the fluid into the main channel. The device diagnosis unit diagnoses the flow control device based on a set flow rate when the flow control device discharges the fluid and a flow rate of the fluid flowing in the main flow channel calculated by the flow rate calculation unit.

10. The flow rate calculation device according to any one of claims 1 to 9, characterized in that: The flow rate calculation unit sets the flow ratio to S, sets the calculated flow rate of the first branched fluid to Q1, and calculates the flow rate Q of the fluid flowing in the main channel by calculating Q=Q1 / S.

11. A flow calculation method, characterized in that: have: When the fluid flowing in the main flow channel is branched into the specific flow channel and the bypass flow channel branched from the main flow channel, a flow rate of the first branched flow channel fluid flowing in the specific flow channel is calculated based on the change in pressure in the container disposed on the downstream side of the first flow resistance element in the specific flow channel; and A step of calculating a flow rate of the fluid flowing in the main channel based on the calculated flow rate of the first branched fluid and a branching ratio determined by the first flow resistance element and a second flow resistance element provided in the bypass channel.

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