Fluid control device, fluid control system, program for fluid control device, and fluid control method

Abstract

In order to suppress a flow rate that is unexpectedly output, and quickly stabilize the output flow rate, provided is a fluid control device 100 which is provided with a fluid control valve 1, an upstream pressure sensor 21, a fluid resistance element 22, and a downstream pressure sensor 23 are disposed in this order from the upstream side, the fluid control device comprising: an actual flow rate calculation unit 24 which calculates the flow rate on the basis of the pressures measured by the upstream pressure sensor 21 and the downstream pressure sensor 22; a delayed flow rate calculation unit 4 which calculates a delayed flow rate by causing a response delay in the calculated flow rate calculated by the actual flow rate calculation unit 24; and a flow rate output unit 5 which compares an absolute difference between the predetermined reference value and the calculated flow rate and an absolute difference between the reference value and the delayed flow rate, and outputs the calculated flow rate or the delayed flow rate with the smaller absolute difference.

Description

Technical Field

[0001] The present invention relates to a fluid control device and the like.

Background Art

[0002] As a conventional fluid control device, as shown in Patent Document 1, there is a differential pressure type mass flow controller in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side.

[0003] Here, for example, in a semiconductor manufacturing system, consider a configuration in which the above-described mass flow controller is arranged in at least one of a plurality of flow paths provided in parallel, and the downstream of these flow paths is connected to a process flow path connected to a process chamber, for example.

[0004] In such a system, when a large flow rate flows through the process flow path with the fluid control valve closed, fluid may flow backward from the process flow path to the mass flow controller. Then, the measured pressure by the downstream pressure sensor increases, and the measured pressure by the upstream pressure sensor increases with a time difference due to the fluid resistance element. As a result, a difference occurs in the measured pressures of the upstream pressure sensor and the downstream pressure sensor, so that an unexpected flow rate corresponding to the pressure difference is output as a measured value even though the fluid control valve is closed.

[0005] Thus, the following are also cited as factors causing the flow rate to be unexpectedly output. In other words, in the system described above, a shut-off valve is provided downstream of the mass flow controller. When the shut-off valve is opened from a state where both the shut-off valve and the fluid control valve are closed, the fluid remaining inside the mass flow controller flows out into the process flow path. As a result, the pressure measured by the downstream pressure sensor decreases, and after a time lag caused by the fluid resistance element, the pressure measured by the upstream pressure sensor also decreases. Consequently, a difference arises between the pressures measured by the upstream and downstream pressure sensors, and even though the fluid control valve is closed, a flow rate corresponding to this pressure difference is output. Furthermore, such problems can occur not only in semiconductor manufacturing systems but also in various fluid control systems.

[0006] Therefore, as a method to suppress unexpectedly output flow rates, one could consider, for example, using a low-pass filter to introduce a first-order lag into the output flow rate.

[0007] However, in this case, although the output flow rate can be reduced, a time delay is introduced into the output flow rate, leading to another problem: a longer time is required for the flow rate to stabilize. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-102807 [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the present invention was made to solve the above-mentioned problems, and its main objective is to quickly stabilize the output flow rate while suppressing unexpectedly output flow rates. [Means for solving the problem]

[0010] In other words, the fluid control device according to the present invention is a fluid control device in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side, and is characterized by comprising: an actual flow rate calculation unit that calculates a flow rate based on the measured pressure of the upstream pressure sensor and the downstream pressure sensor; a delayed flow rate calculation unit that calculates a delayed flow rate by generating a response delay to the calculated flow rate calculated by the actual flow rate calculation unit; and a flow rate output unit that compares the absolute difference between a predetermined reference value and the calculated flow rate, and the absolute difference between the reference value and the delayed flow rate, and outputs the calculated flow rate or the delayed flow rate whichever of the two absolute differences is smaller.

[0011] With this type of fluid control device, the flow rate output unit outputs the flow rate that has the smaller absolute difference from the reference value between the calculated flow rate and the delayed flow rate. Therefore, when an unexpected flow rate is output (hereinafter, this phenomenon will also be called a burst), initially, the delayed flow rate, which is closer to the reference value than the calculated flow rate, is output. Subsequently, since the calculated flow rate stabilizes more quickly, at a certain point the calculated flow rate will overtake the delayed flow rate and approach the reference value, and from that point onward, the quickly stabilizing calculated flow rate will be output. Thus, according to the fluid control device of the present invention, at the beginning of a burst, a delayed flow rate closer to the reference value than the calculated flow rate is output, and from a certain point in time when the absolute difference with the reference value is reversed, a quickly stable calculated flow rate is output. This makes it possible to quickly stabilize the output flow rate while suppressing unexpectedly output flow rates.

[0012] Incidentally, when the fluid control valve is closed, the calculated flow rate output (i.e., the output value) should be zero, and at first glance, it seems that setting the aforementioned reference value to zero would suffice. However, the output value when the fluid control valve is closed may fluctuate slightly over time. As shown in Figure 9, if the output value when the fluid control valve is closed shifts to a value less than zero, and the reference value remains set to zero, the calculated flow rate will be closer to zero than the lagging flow rate at the beginning of the burst. As a result, the calculated flow rate will be output, and the waveform of the output flow rate (solid line in Figure 9) will become distorted. Therefore, it is preferable to further include a reference value update unit that updates the reference value at predetermined time intervals. With this configuration, the reference value can be continuously set to an appropriate value, and the correct waveform can be output.

[0013] Preferably, the reference value update unit samples the calculated flow rates over a predetermined period of time, and when the absolute difference between these calculated flow rates and the reference value falls below the update threshold over the predetermined period of time, it updates one of the sampled calculated flow rates as the new reference value. With this configuration, the stable output value at any given time while the fluid control valve is closed can be used as the reference value for updating.

[0014] For example, immediately after closing a shut-off valve or fluid control valve located upstream of a fluid control device, the calculated flow rate may not stabilize immediately. If a reference value is set or updated during this transient state, there is a risk that the calculated flow rate output during this unstable state may be set as the reference value. Therefore, it is preferable to further include a stability state determination unit that determines that the calculated flow rate is in a stable state when the absolute difference between the calculated flow rate and the reference value falls below a stable state threshold for a predetermined period of time, and that sampling of the calculated flow rate by the reference value update unit is started after the stability state determination unit has determined that the flow rate is in a stable state. With this configuration, sampling of the calculated flow rate by the reference value update unit will not start until the calculated flow rate stabilizes, preventing the calculated flow rate in an unstable state from being set as the reference value.

[0015] As mentioned above, the calculated flow rate is unstable immediately after closing the fluid control valve, so it is preferable that the flow rate output unit does not perform its function at this point. On the other hand, immediately after opening the fluid control valve, there is a risk that the fluid remaining inside may flow back upstream, causing an unexpected negative flow rate to be output. Therefore, it is preferable to keep the flow output unit functioning to suppress this burst. Therefore, it is preferable to further provide a switching unit in the flow rate output unit that switches whether or not to allow the comparison of the absolute difference to be performed. With this configuration, the flow rate output unit's function can be enabled or disabled at the appropriate time.

[0016] It is preferable that the switching unit activates the function of the flow rate output unit when the fluid control valve is in a closed state and the absolute difference between the calculated flow rate and the reference value falls below the effective judgment threshold. With this configuration, the function of the flow output unit can be activated immediately after the fluid control valve is closed, once the calculated flow rate has stabilized.

[0017] It is preferable that the switching unit disables the function of the flow rate output unit when the fluid control valve is in the open state and the value obtained by subtracting the measured pressure of the downstream pressure from the measured pressure of the upstream pressure sensor exceeds the invalid judgment threshold. With this configuration, the function of the flow output unit can be disabled immediately after opening the fluid control valve, once the risk of bursting due to backflow of residual fluid inside has been eliminated. In other words, the bursting due to backflow mentioned above can be suppressed.

[0018] The extent to which a user tries to suppress a burst may differ depending on whether the burst appears on the positive side or the negative side. In order to meet such a demand, it is preferable that the time constant of the response delay generated by the delay flow rate calculation unit is different between the case where the fluid flows from the upstream side to the downstream side in the fluid resistance element and the case where the fluid flows in the opposite direction.

[0019] Further, the fluid control system according to the present invention is characterized in that it is connected to the main flow path and the above-described fluid control device is arranged in part or all of a plurality of branch flow paths provided in parallel. In such a fluid control system, the same operational effects as those of the above-described fluid control device can be obtained.

[0020] Further, the program for the fluid control device according to the present invention is a program used for a fluid control device in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side, and based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, a real flow rate calculation unit that calculates the flow rate, a delay flow rate calculation unit that generates a response delay in the calculated flow rate calculated by the real flow rate calculation unit and calculates the delayed flow rate, and a function as a flow rate output unit that compares the absolute difference between a predetermined reference value and the calculated flow rate and the absolute difference between the reference value and the delayed flow rate, and outputs the calculated flow rate or the delayed flow rate with the smaller absolute difference is caused to be exhibited by a computer.

[0021] Furthermore, the fluid control method according to the present invention is a fluid control method using a fluid control device in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side, and includes a real flow rate calculation step of calculating the flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, a delay flow rate calculation step of generating a response delay in the calculated flow rate calculated by the real flow rate calculation step and calculating the delayed flow rate, and a step of comparing the absolute difference between a predetermined reference value and the calculated flow rate and the absolute difference between the reference value and the delayed flow rate, and outputting the calculated flow rate or the delayed flow rate with the smaller absolute difference.

[0022] Such a fluid control program and fluid control method can achieve the same effects as the fluid control device described above. [Effects of the Invention]

[0023] According to the present invention described above, it is possible to quickly stabilize the output flow rate while suppressing unexpectedly output flow rates. [Brief explanation of the drawing]

[0024] [Figure 1] A schematic diagram showing the configuration of a fluid control system related to one embodiment of the present invention. [Figure 2] A schematic diagram showing the configuration of the fluid control device according to the same embodiment. [Figure 3] A graph showing unexpectedly output flow rates (bursts). [Figure 4] A functional block diagram showing the functions of the control unit in the same embodiment. [Figure 5] A graph showing the delayed flow rate calculated by the delayed flow rate calculation unit of the same embodiment. [Figure 6] A graph showing the flow rate output by the flow rate output unit of the same embodiment. [Figure 7] A flowchart showing the operation of the stable state determination unit and the reference value update unit of the same embodiment. [Figure 8] A flowchart illustrating the operation of the switching unit in the same embodiment. [Figure 9] A graph showing the possible flow rates when the baseline value is left at zero. [Modes for carrying out the invention]

[0025] A fluid control device according to one embodiment of the present invention will be described below with reference to the drawings.

[0026] <Device configuration> The fluid control device 100 of this embodiment is used, for example, in a semiconductor manufacturing process, and as shown in Figure 1, it constructs a fluid control system 200 that controls the flow rate of fluid supplied to the process chamber CH.

[0027] This fluid control system 200 has the above-described fluid control device 100 positioned in some or all of the multiple parallel flow paths L2 (hereinafter also referred to as branch flow paths L2), and the downstream ends of these multiple branch flow paths L2 are connected to a main flow path L1 that communicates with, for example, a process chamber CH. The main flow path L1 is a flow path that can suddenly become more high pressure than the inside of the fluid control device 100. In addition, shut-off valves V1 and V2 are provided on the upstream and downstream sides of the fluid control device 100 in the branch flow paths L2, respectively.

[0028] As shown in Figure 2, the fluid control device 100 is a differential pressure type mass flow controller in which a fluid control valve 1, an upstream pressure sensor 21, a fluid resistance element 22, and a downstream pressure sensor 23 are arranged in that order from the upstream side. A control unit C that controls the fluid control valve 1 is packaged together with these fluid devices. More specifically, the mass flow controller 100 includes a block B in which an internal flow path L3 is formed, and the various fluid devices described above are attached to this block B, and a fluid at a lower pressure than the main flow path L1 flows through this internal flow path L3. In addition, the fluid control device 100 may also have a pressure sensor provided upstream of the fluid control valve 1.

[0029] The control unit C is a so-called computer equipped with a CPU, memory, A / D converter, D / A converter, and various input / output devices. As shown in Figure 2, it performs functions as at least the actual flow rate calculation unit 24 and the valve control unit 3 when the fluid control device program stored in memory is executed.

[0030] The actual flow rate calculation unit 24 calculates the flow rate of the fluid flowing through the internal flow path L3 from the measured pressures measured by the upstream pressure sensor 21 and the downstream pressure sensor 23. In other words, the upstream pressure sensor 21, the fluid resistance element 22, the downstream pressure sensor 23, and the flow rate calculation unit constitute a differential pressure type flow sensor 2. The calculated flow rate calculated by this actual flow rate calculation unit 24 is output to the valve control unit 3 as the measured flow rate.

[0031] The valve control unit 3 controls the opening degree of the fluid control valve 1 using flow rate feedback control so that the deviation between the set flow rate set by the user and the calculated flow rate calculated by the actual flow rate calculation unit 24 becomes small.

[0032] Here, when the fluid control valve 1 described above is closed and the shut-off valve V2 located downstream is open, if a large flow rate flows through the main flow path L1, fluid may flow back from the main flow path L1 to the mass flow controller 100 via the branch flow path L2. When this happens, the pressure measured by the downstream pressure sensor 23 increases, and after a time difference caused by the fluid resistance element 22, the pressure measured by the upstream pressure sensor 21 also increases.

[0033] As a result, a difference occurs in the measured pressure between the upstream pressure sensor 21 and the downstream pressure sensor 23. Therefore, as shown in the upper part of Figure 3, even though the fluid control valve 1 is closed, a calculated flow rate corresponding to this pressure difference is output (hereinafter, this phenomenon will also be called a burst). In this case, the burst appears on the negative side.

[0034] On the other hand, as shown in the lower part of Figure 3, bursts can also occur on the positive side, and one of the reasons for this is as follows:

[0035] When the fluid control valve 1 is closed and the shut-off valve V2 located downstream of the mass flow controller 100 is also closed, opening the shut-off valve V2 causes the fluid remaining in the internal flow path L3 and branch flow paths L2 of the mass flow controller 100 to flow into the main flow path L1. As a result, the pressure measured by the downstream pressure sensor 23 decreases, and after a time difference caused by the fluid resistance element 22, the pressure measured by the upstream pressure sensor 21 also decreases.

[0036] As a result, a difference occurs in the measured pressures of the upstream pressure sensor 21 and the downstream pressure sensor 23. Therefore, as shown in the lower part of Figure 3, even though the fluid control valve 1 is closed, a calculated flow rate corresponding to that pressure difference is output.

[0037] Therefore, in order to suppress the burst described above, the control unit C of this embodiment is further equipped with a function as a delayed flow rate calculation unit 4, which calculates a delayed flow rate that generates a response delay in the calculated flow rate, as shown in Figure 4.

[0038] This delayed flow rate calculation unit 4 is configured using a low-pass filter and calculates a delayed flow rate that has a first-order delay in the calculated flow rate. The low-pass filter may be an analog low-pass filter configured using resistive and capacitive elements, or it may be a digital low-pass filter created by a program.

[0039] In this embodiment, the time constant is set to a different value depending on whether the fluid flows from upstream to downstream through the fluid resistance element 22 or in the opposite direction. That is, the time constant is set to a different value depending on whether the calculated flow rate bursts to the negative side or to the positive side. In other words, the response delay time constant is set to a different value depending on whether the measured pressure of the upstream pressure sensor 21 is greater than the measured pressure of the downstream pressure sensor 23. Specifically, the time constant when the calculated flow rate is positive is set to be larger than the time constant when the calculated flow rate is negative. However, the time constant when the calculated flow rate is positive may be set to be smaller than the time constant when the calculated flow rate is negative, or they may be set to the same value.

[0040] In this way, by introducing a response delay to the calculated flow rate, bursts are suppressed, as shown by the solid line in Figure 5. Although Figure 5 shows the suppression of positive bursts, negative bursts can be suppressed in the same way. However, on the other hand, the time it takes for the delayed flow rate calculated by the delayed flow rate calculation unit 4 to stabilize back to the original flow rate before the burst (zero in Figure 5) is longer than the time it takes for the delayed flow rate to stabilize back to the original flow rate (zero in Figure 5).

[0041] Therefore, as shown in Figure 4, the control unit C of this embodiment is further equipped with the function of a flow rate output unit 5 that compares the absolute difference between a predetermined reference value and the calculated flow rate, and the absolute difference between the reference value and the delayed flow rate, and outputs the calculated flow rate or the delayed flow rate whichever has the smaller absolute difference. That is, as shown in Figure 4, this flow rate output unit 5 has the function of a determination unit 51 that determines the flow rate to be output by comparing the absolute difference between the reference value and the calculated flow rate and the absolute difference between the reference value and the delayed flow rate.

[0042] More specifically, the flow rate output unit 5 outputs the flow rate flowing through the flow sensor 2, i.e., the calculated flow rate described above, to a display D or the like during a steady state in a semiconductor manufacturing process. For example, it is configured to output the flow rate in real time on a graph where time is set on the horizontal axis and flow rate on the vertical axis. The flow rate output unit 5 may also be configured to transmit the calculated flow rate as numerical information to the user via a communication unit (not shown).

[0043] Furthermore, when predetermined conditions are met, the flow rate output unit 5 is configured to output the flow rate that is closer to the reference value among the calculated flow rate and the delayed flow rate, as shown by the solid line in Figure 6. Hereafter, this function of the flow rate output unit 5 will be referred to as the burst cut function.

[0044] In Figure 6, an example is shown where the reference value is set to zero. However, the control unit C in this embodiment includes functions as a stable state determination unit 6 and a reference value update unit 7 for updating the aforementioned reference value. Furthermore, the control unit C of this embodiment also includes a switching unit 8 that enables (ON) or disables (OFF) the burst cut function according to predetermined conditions.

[0045] First, the functions and operations for updating the reference values ​​will be explained with reference to the flowchart in Figure 7.

[0046] For example, when the product is shipped from the factory, if no fluid is flowing through the flow sensor 2, the output value displayed as the calculated flow rate should be zero. As shown in Figure 6, by setting the reference value to zero, the burst cut function of the flow output unit 5 can be effectively utilized.

[0047] However, the output value when the fluid control valve 1 is closed may fluctuate slightly over time. As shown in Figure 9, if the output value when the fluid control valve 1 is closed shifts to a negative value, and the reference value remains set to zero, the calculated flow rate will be closer to zero than the delayed flow rate at the beginning of a burst. As a result, the calculated flow rate will be output, causing the waveform of the output flow rate (solid line in Figure 9) to become distorted, and the burst cut function will not be able to be effectively performed.

[0048] Therefore, the control unit C in this embodiment is configured to sequentially update the reference value as described above. However, if, for example, fluid control valve 1 is switched from an open state to a closed state, the calculated flow rate will not stabilize immediately after fluid control valve 1 is closed, and it is undesirable for the reference value to be updated during that transient state.

[0049] In view of this, as shown in Figure 7, the stability determination unit 6 first determines whether the fluid control valve 1 is closed and whether the absolute difference between the calculated flow rate and the reference value is below a predetermined stability threshold Th1 for a first predetermined time T1 (S11). If it is below the threshold, it determines that the calculated flow rate is in a stable state (S12).

[0050] In this embodiment, for example, the initial reference value, such as at the time of factory shipment, is set to zero, and the first predetermined time T1 is set to, for example, several tens of seconds. That is, the stability determination unit 6 of this embodiment determines that the calculated flow rate is in a stable state when the absolute difference between the calculated flow rate and zero falls below a predetermined stability threshold Th1 for, for example, several tens of seconds. If the absolute difference between the calculated flow rate and the reference value does not fall below the predetermined stability threshold Th1 for the predetermined time, the determination in S11 is repeated.

[0051] Next, after it is determined that the calculated flow rate is in a stable state, the reference value is updated by the reference value update unit 7. More specifically, the reference value update unit 7 starts sampling the calculated flow rate over a second predetermined time T2 after the stable state determination unit 6 determines that the calculated flow rate is in a stable state (S13). The reference value update unit 7 then determines whether the fluid control valve 1 is closed and whether the absolute difference between the calculated flow rate sampled in S13 and the reference value is below the update threshold Th2 over the second predetermined time T2 (S14). If it is below the threshold, it updates one of the sampled calculated flow rates as the new reference value (S15). The first predetermined time T1 and the second predetermined time T2 may be the same or different.

[0052] The reference value update unit 7 in this embodiment is configured to update the latest (most recent) calculated flow rate among the sampled calculated flow rates as the new reference value. Alternatively, the reference value update unit 7 may update the average value of the sampled calculated flow rates as the new reference value, or it may update the lowest calculated flow rate among the sampled calculated flow rates as the new reference value.

[0053] Subsequently, the sampling in S13 and the judgment in S14 by the reference value update unit 7 are repeated.

[0054] In this embodiment, the reference value updated by the reference value update unit 7 is temporarily stored in a reference value storage unit 71 formed in a predetermined area of ​​the memory, as shown in Figure 4. The reference value stored in this reference value storage unit 71 is output to the determination unit 51 of the flow rate output unit 5 and used by the flow rate output unit 5 to determine whether to perform the burst cut function.

[0055] In S14, if the absolute difference between the sampled calculated flow rate and the reference value does not fall below the update threshold Th2 over the second predetermined time T2, that is, if the absolute difference between at least one of the sampled calculated flow rates and the reference value becomes equal to or greater than the update threshold Th2, the reference value stored in the reference value storage unit 71 at that time is not updated, and the process returns to the determination in S11 by the stable state determination unit 6.

[0056] With the above configuration, the stable output value at any given time when the fluid control valve 1 is closed can be updated as a reference value, and the reference value can be continuously set to an appropriate value, thereby enabling the burst cut function to be effectively utilized. Furthermore, sampling of the calculated flow rate by the reference value update unit 7 is not started until the calculated flow rate stabilizes, preventing the calculated flow rate in an unstable state from being set as the reference value.

[0057] Next, the functions and operations for enabling (ON) or disabling (OFF) the burst cut function will be explained with reference to the flowchart in Figure 8.

[0058] As mentioned above, the calculated flow rate is unstable immediately after closing the fluid control valve 1, so it is preferable that the flow rate output unit 5 does not perform its function at this point. On the other hand, immediately after opening the fluid control valve 1, there is a risk that the fluid remaining inside may flow back upstream, causing an unexpected negative flow rate to be output. Therefore, it is preferable to keep the flow rate output unit 5 functioning to suppress this burst.

[0059] Therefore, in this embodiment, the control unit C is configured such that the switching unit 8 enables or disables the burst cut function by the flow rate output unit 5 based on predetermined conditions (effective conditions and ineffective conditions described later). In other words, this switching unit 8 switches whether or not to allow the determination unit 51 of the flow rate output unit 5 to compare absolute differences.

[0060] More specifically, the switching unit 8 determines whether the fluid control valve 1 is in the closed state and whether the absolute difference between the calculated flow rate and the reference value is below the effective judgment threshold Th3 (hereinafter also referred to as the effective condition) (S21). If this effective condition is met, the burst cut function by the flow rate output unit 5 is activated (S22). In other words, if this effective condition is met, the flow rate output unit 5 outputs the flow rate that is closer to the reference value among the calculated flow rate and the delayed flow rate. The effective judgment threshold Th3 is stored in advance in the threshold storage unit 81 set in a predetermined area of ​​the memory, as shown in Figure 4. With this configuration, immediately after closing the fluid control valve 1, the function of the flow rate output unit 5 can be activated after the calculated flow rate has stabilized.

[0061] Subsequently, the switching unit 8 determines whether the fluid control valve 1 is in the open state and whether the value obtained by subtracting the measured pressure P2 of the downstream pressure from the measured pressure P1 of the upstream pressure sensor 21 exceeds the invalidation judgment threshold Th4 (hereinafter also referred to as the invalidation condition) (S23). If this invalidation condition is met, the burst cut function by the flow rate output unit 5 is disabled (S24). That is, if this invalidation condition is met, the flow rate output unit 5 outputs the calculated flow rate without outputting a delayed flow rate. The invalidation judgment threshold Th4 is stored in advance in the threshold storage unit 81, as shown in Figure 4. With this configuration, immediately after opening the fluid control valve 1, the function of the flow output unit 5 can be disabled after the risk of bursting due to backflow of residual fluid inside has been eliminated. In other words, such bursts can be suppressed.

[0062] Thereafter, the switching unit 8 repeats the operations S21 to S24.

[0063] <Effects of this embodiment> With the fluid control device 100 configured in this way, the flow rate output unit 5 outputs the flow rate that has a smaller absolute difference from the reference value between the calculated flow rate and the delayed flow rate. For example, if an unexpected flow rate is output due to backflow into the fluid control device 100, the delayed flow rate, which is closer to the reference value than the calculated flow rate, will be output initially. Subsequently, since the calculated flow rate stabilizes more quickly, at a certain point the calculated flow rate will overtake the delayed flow rate and approach the reference value, and from that point onward, the quickly stabilizing calculated flow rate will be output.

[0064] Thus, according to the fluid control device 100 of the present invention, at the beginning of a burst, it outputs a delayed flow rate that is closer to the reference value than the calculated flow rate, and from a certain point in time when the absolute difference with the reference value reverses, it outputs a calculated flow rate that stabilizes quickly. This makes it possible to quickly stabilize the output flow rate while suppressing unexpectedly output flow rates.

[0065] <Other Embodiments> For example, in the above embodiment, the delayed flow rate calculation unit 4 was configured to generate a first-order delay in the calculated flow rate, but it may also generate a second-order delay in the calculated flow rate.

[0066] Furthermore, while the switching unit 8 in the above embodiment activated the burst cut function when the fluid control valve 1 was in a closed state and the absolute difference between the calculated flow rate and the reference value fell below the effective judgment threshold Th3, the switching unit 8 may also activate the burst cut function when the fluid control valve 1 was in a closed state and a predetermined time had elapsed since it had been in the closed state.

[0067] Furthermore, in the above embodiment, the switching unit 8 disabled the burst cut function when the fluid control valve 1 was in the open state and the value obtained by subtracting the measured pressure P2 of the downstream pressure from the measured pressure P1 of the upstream pressure sensor 21 exceeded the invalid judgment threshold Th4. However, the switching unit 8 may also disable the burst cut function when the fluid control valve 1 is in the open state and a predetermined time has elapsed since it became open.

[0068] In addition, although the fluid control device 100 was described in the above embodiment as being used in a semiconductor manufacturing process, the fluid control device 100 according to the present invention can be used in various systems other than semiconductor manufacturing processes.

[0069] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention. [Industrial applicability]

[0070] According to the present invention, it is possible to quickly stabilize the output flow rate while suppressing unexpectedly output flow rates. [Explanation of Symbols]

[0071] 100... Fluid control device (mass flow controller) 1. Fluid control valve 21 ···Upstream pressure sensor 22 ··· Fluid resistance element 23 ···Downstream pressure sensor L3 ···Internal flow path C...control section 24 ···Actual flow rate calculation unit 2 ···Flow Sensor 3. Valve control unit 4. Delayed flow rate calculation unit 5...Flow rate output section 51...judgment section 6. Stability determination unit 7 ···Reference value update section 8 ···Switching section

Claims

1. A fluid control device is provided in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side. An actual flow rate calculation unit that calculates the flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, A delayed flow rate calculation unit calculates a delayed flow rate by generating a response delay in the calculated flow rate calculated by the actual flow rate calculation unit, A fluid control device comprising a flow rate output unit that compares the absolute difference between a reference value, which is a value indicating the calculated flow rate when the fluid control valve is closed, and the calculated flow rate, with the absolute difference between the reference value and the delayed flow rate, and outputs the calculated flow rate or the delayed flow rate whichever of the two absolute differences is smaller.

2. The fluid control device according to claim 1, further comprising a reference value update unit that updates the reference value at predetermined time intervals.

3. The fluid control device according to claim 2, wherein the reference value update unit samples the calculated flow rates over a predetermined period of time, and updates one of the sampled calculated flow rates as the new reference value if the absolute difference between these calculated flow rates and the reference value falls below an update threshold over the predetermined period of time.

4. The system further includes a stability state determination unit that determines that the calculated flow rate is in a stable state when the absolute difference between the calculated flow rate and the reference value falls below a stability state threshold for a predetermined period of time. The fluid control device according to claim 3, wherein, after the stable state determination unit determines that a stable state has been reached, the reference value update unit starts sampling of the calculated flow rate.

5. The fluid control device according to any one of claims 1 to 4, further comprising a switching unit for switching whether or not to allow the flow rate output unit to perform the comparison of the absolute difference.

6. The fluid control device according to claim 5, wherein the switching unit enables the function of the flow rate output unit when the fluid control valve is in a closed state and the absolute difference between the calculated flow rate and the reference value falls below an effective judgment threshold.

7. The fluid control device according to claim 5 or 6, wherein the switching unit disables the function of the flow rate output unit when the fluid control valve is in the open state and the value obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor exceeds an invalid judgment threshold.

8. The fluid control device according to any one of claims 1 to 7, wherein the time constant of the response delay generated by the delayed flow rate calculation unit is different for the case in which fluid flows from upstream to downstream through the fluid resistance element and for the case in which fluid flows in the opposite direction.

9. A fluid control system characterized in that a fluid control device according to any one of claims 1 to 8 is arranged in some or all of a plurality of branch channels connected to a main channel and arranged in parallel.

10. A program used in a fluid control device in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side, An actual flow rate calculation unit that calculates the flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, A delayed flow rate calculation unit calculates a delayed flow rate by generating a response delay in the calculated flow rate calculated by the actual flow rate calculation unit, A fluid control device program characterized by causing a computer to function as a flow rate output unit, which outputs the calculated flow rate or the delayed flow rate, by comparing the absolute difference between a reference value, which is a value indicating the calculated flow rate when the fluid control valve is closed, and the absolute difference between the reference value and the delayed flow rate.

11. A fluid control method using a fluid control device in which a fluid control valve, an upstream pressure sensor, a fluid resistance element, and a downstream pressure sensor are arranged in this order from the upstream side, A step of calculating the actual flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, A delayed flow rate calculation step, which involves generating a response delay in the calculated flow rate calculated in the actual flow rate calculation step and calculating a delayed flow rate, A fluid control method comprising the steps of: comparing the absolute difference between a reference value, which is a value indicating the calculated flow rate when the fluid control valve is closed, and the calculated flow rate, with the absolute difference between the reference value and the delayed flow rate, and outputting the calculated flow rate or the delayed flow rate whichever of the two absolute differences is smaller.

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