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

Abstract

To prevent an unnatural behavior of a calculated flow to be outputted from a fluid controller.SOLUTION: A fluid controller includes an actual flow calculation unit 24 that calculates a flow on the basis of measurement pressures of an upstream pressure sensor 21 and a downstream pressure sensor 23 respectively, and a flow output unit 4 that outputs the flow calculated by the actual flow calculation unit 24. When it is decided that a fluid control valve 1 is closed, the flow output unit 4 exerts a zero output feature or a feature of outputting a zero value irrespective of the calculated flow. The fluid controller further includes a switching unit 5 that switches implementation and suspension of the zero output feature to be exerted by the flow output unit 4. When the fluid control valve 1 is open and a difference P1-P2 obtained by subtracting the measurement pressure P2 of the downstream pressure sensor 23 from the measurement pressure P1 of the upstream pressure sensor 21 is larger than a predetermined suspension threshold Th2, the switching unit 5 suspends the zero output feature so that the calculated flow can be outputted from the flow output unit 4.SELECTED DRAWING: Figure 9

Description

[Technical Field]

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

[0002] As shown in Patent Document 1, a conventional fluid control device is a so-called differential pressure type mass flow controller that is configured to output a zero value regardless of the calculated flow rate calculated based on the differential pressure when the fluid control valve is closed.

[0003] In such a configuration, the timing at which the output is returned from zero to the calculated flow rate may be when the fluid control valve switches from a closed state to an open state.

[0004] However, simply switching the output from zero to the calculated flow rate at this timing may result in unnatural output behavior, such as the flow rate becoming negative immediately after switching, as shown in FIG.

[0005] One of the reasons for the unnatural behavior of the output is, for example, when a large flow rate flows through a flow path connected downstream of the mass flow controller, causing part of the fluid to flow back into the mass flow controller.

[0006] Furthermore, even if the fluid control valve is in the closed state, pressure changes occur in the downstream stages due to the flow in and out of the fluid control valve, so one factor that can be cited as causing the calculated flow rate in the closed state to vary from zero depending on the set flow rate and pressure conditions immediately before the valve is closed, or the waiting time in the closed state (see Figure 7). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2018-18351 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above problems, and its main object is to suppress unnatural behavior of the calculated flow rate output from a fluid control device. [Means for solving the problem]

[0009] The fluid control device of the present invention has a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor provided on a flow path, and is equipped with an actual flow rate calculation unit that calculates a flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, and a flow rate output unit that outputs the calculated flow rate calculated by the actual flow rate calculation unit, and is configured so that the flow rate output unit performs a zero output function, which is a function of outputting a zero value regardless of the calculated flow rate when it is determined that the fluid control valve is in a closed state. In addition, in the above-mentioned configuration, this fluid control device further includes a switching unit that switches between executing and stopping the zero output function by the flow rate output unit, and is characterized in that when the fluid control valve is in an open state and the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than a predetermined stop threshold, the switching unit stops the zero output function and causes the flow rate output unit to output the calculated flow rate.

[0010] With such a fluid control device, the conditions for stopping the zero output function include not only that the fluid control valve be in an open state, but also that the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor be greater than a predetermined stop threshold.Therefore, it is possible to prevent a negative value from being output immediately after the zero output function is stopped and the output is switched from a zero value to a calculated flow rate. This provides a zero output function that outputs a zero value regardless of the calculated flow rate when the fluid control valve is closed, while preventing unnatural behavior when switching the output from a zero value to the calculated flow rate.

[0011] Here, the execution conditions for executing zero output will be considered. For example, in the event of an abnormality such as a failure of the outflow or pressure sensor of the fluid control valve, the calculated flow rate may become an abnormal value that is significantly different from zero even though the fluid control valve is in a closed state. In such a case, if a zero value were output simply on the condition that the fluid control valve is closed, the above-mentioned abnormal values ​​would be hidden (not output) by the zero value, making it difficult to detect various abnormalities, etc. Therefore, it is preferable that the switching unit executes the zero output function and outputs a zero value to the flow rate output unit when the fluid control valve is in a closed state and the absolute difference between the measured pressure of the upstream pressure sensor and the measured pressure of the downstream pressure sensor is smaller than a predetermined execution threshold. With this configuration, even if the fluid control valve is closed, if the absolute difference between the measured pressure of the upstream pressure sensor and the measured pressure of the downstream pressure sensor is greater than a predetermined execution threshold, the zero output function will not be executed, so the above-mentioned abnormal value can be output, and various abnormalities can be quickly detected.

[0012] Preferably, the execution threshold is at least greater than the stop threshold. In this way, it is possible to provide the zero output function while still outputting the abnormal value described above.

[0013] As described above, the fluid control device according to the present invention can prevent a negative value from being output immediately after the output is switched from a zero value to a calculated flow rate. However, in the event of an abnormality, such as a pressure sensor failure, a large value (abnormal value) may be calculated as the calculated flow rate even though the fluid control valve is closed. In such a case, if a zero value continues to be output, the zero value will hide the abnormal value (it will not be output), which may also delay the detection of the abnormality. Therefore, it is preferable that the switching unit stops the zero output function and causes the flow rate output unit to output the calculated flow rate when either the following first or second stop condition is satisfied. (1st stop condition) When the fluid control valve is in an open state and the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than the stop threshold value. (Second stop condition) When the absolute difference between the pressure measured by the upstream pressure sensor and the pressure measured by the downstream pressure sensor is greater than a predetermined upper limit value that is greater than the stop threshold value. With this configuration, even when the second stop condition is satisfied, the zero output function is stopped, so that an abnormal value can be output and various abnormalities can be quickly detected.

[0014] In order to prevent unnatural behavior while outputting the abnormal negative value described above, it is preferable that the upper limit value is at least greater than the stop threshold value.

[0015] Furthermore, the fluid control system according to the present invention is characterized in that the above-described fluid control device is arranged in some or all of a plurality of branch flow paths connected to a main flow path and arranged in parallel. Such a fluid control system can achieve the same effects as the above-mentioned fluid control device.

[0016] Furthermore, the program for a fluid control device according to the present invention is a program used in a fluid control device in which a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on a flow path, and causes a computer to function as an actual flow rate calculation unit that calculates a flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, and a flow rate output unit that outputs the calculated flow rate calculated by the actual flow rate calculation unit, and the flow rate output unit is configured to perform a zero output function that outputs a zero value regardless of the calculated flow rate when it is determined that the fluid control valve is closed, and further causes the computer to function as a switching unit that switches between executing and stopping the zero output function by the flow rate output unit, and is characterized in that when the fluid control valve is open and the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than a predetermined stop threshold, the switching unit stops the zero output function and causes the flow rate output unit to output the calculated flow rate.

[0017] In addition, 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, and a downstream pressure sensor are provided on a flow path, and includes an actual flow rate calculation step of calculating a flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, and a flow rate output step of outputting the calculated flow rate calculated by the actual flow rate calculation unit, and if it is determined in the flow rate output step that the fluid control valve is closed, a zero value is output regardless of the calculated flow rate, and the method further includes a switching step of switching between executing and stopping the output of the zero value in the flow rate output step, and is characterized in that in the switching step, if the fluid control valve is open and the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than a predetermined stop threshold, the calculated flow rate is output in the flow rate output step.

[0018] According to such a program for a fluid control device and a fluid control method, it is possible to achieve the same effects as those of the above-described fluid control device.

[0019] Incidentally, as described in the Background Art section, immediately after the fluid control valve switches from the closed state to the open state, for example, a large flow rate may be flowing through the flow path connected to the downstream side of the mass flow controller, and a negative flow rate may be output due to a part of the fluid flowing back into the mass flow controller.

[0020] Therefore, one object of the present invention is to prevent a negative flow rate from being output and to suppress unnatural behavior of the output.

[0021] That is, another aspect of the fluid control device according to the present invention is characterized in that a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on a flow path, and the device comprises an actual flow rate calculation unit that calculates a flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, and a flow rate output unit that outputs the calculated flow rate calculated by the actual flow rate calculation unit, and the flow rate output unit exhibits a negative burst cut function, which is a function that outputs a zero value regardless of the calculated flow rate when the fluid control valve is in an open state and the flow rate calculated by the actual flow rate calculation unit is a negative flow rate.

[0022] With a fluid control device configured in this manner, when the flow rate calculated by the actual flow rate calculation unit is a negative flow rate, the flow rate output unit exhibits a negative burst cut function by outputting a zero value, thereby suppressing unnatural behavior of the output.

[0023] Factors that can cause a negative flow rate to be calculated include not only the backflow to the mass flow controller as described above, but also, for example, a malfunction of a fluid control valve or an abnormality in a sensor. If the abnormal value output due to such a malfunction or abnormality is hidden by a zero value, it becomes difficult to detect the malfunction or abnormality. Therefore, it is preferable that the negative burst cut function be stopped when the time that has elapsed since the fluid control valve was opened exceeds a predetermined set time. In this case, if the set time is set longer than the time it would take for the backflow to the mass flow controller to subside, the negative burst cut function will stop if a negative flow rate continues to be calculated even after this set time has been exceeded, allowing the above-mentioned failure or abnormality to be detected quickly.

[0024] In the above-described configuration, it is preferable that the set time be changeable in order to allow the set time to be set flexibly.

[0025] Since there are cases where a negative flow rate is desired to be output depending on the user or process, it is preferable that the flow rate output section be configured to be selectable as to whether or not to exercise the negative burst cut function.

[0026] In addition, the program for a fluid control device according to the present invention is used in a fluid control device in which a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on a flow path, and causes a computer to function as an actual flow rate calculation unit that calculates a flow rate based on the measured pressures of the upstream pressure sensor and the downstream pressure sensor, and a flow rate output unit that outputs the calculated flow rate calculated by the actual flow rate calculation unit, and is characterized in that the flow rate output unit performs a negative burst cut function, which is a function that outputs a zero value regardless of the calculated flow rate when the fluid control valve is in an open state and the flow rate calculated by the actual flow rate calculation unit is a negative flow rate.

[0027] Furthermore, the fluid control method according to the present invention is a method using a fluid control device in which a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on a flow path, and comprises an actual flow rate calculation step of calculating a flow rate based on the pressures measured by the upstream pressure sensor and the downstream pressure sensor, and a flow rate output step of outputting the calculated flow rate calculated by the actual flow rate calculation unit, wherein in the flow rate output step, when the fluid control valve is in an open state and the flow rate calculated by the actual flow rate calculation unit is a negative flow rate, the method is characterized in that a negative burst cut function is exerted, which is a function of outputting a zero value regardless of the calculated flow rate.

[0028] According to such a program for a fluid control device and a fluid control method, it is possible to achieve the same effects as those of the above-described fluid control device. [Effects of the Invention]

[0029] According to the present invention as described above, it is possible to suppress unnatural behavior of the calculated flow rate output from the fluid control device. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic diagram showing the configuration of a fluid control system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the fluid control device of the embodiment. [Figure 3] FIG. 2 is a functional block diagram showing functions of a control unit of the embodiment. [Figure 4] 4 is a flowchart showing the operation of a control unit of the embodiment. [Figure 5] 4 is a graph showing an output of the fluid control device of the embodiment. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a fluid control device according to another embodiment. [Figure 7] 10 is a graph illustrating unnatural behavior of the output flow rate that occurs in a conventional configuration. [Figure 8] FIG. 4 is a schematic diagram showing the configuration of a fluid control device according to a second embodiment. [Figure 9]FIG. 10 is a functional block diagram showing functions of a control unit according to a second embodiment. [Figure 10] 10 is a flowchart showing the operation of a control unit according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] [First embodiment] A fluid control device according to a first embodiment of the present invention will be described below with reference to the drawings.

[0032] <Device configuration> The fluid control device 100 of this embodiment is used in, for example, a semiconductor manufacturing process, and as shown in FIG. 1, constitutes a fluid control system 200 that controls the flow rate of a fluid supplied to a process chamber CH.

[0033] In this fluid control system 200, the above-mentioned fluid control device 100 is disposed in some or all of a plurality of flow paths L2 (hereinafter also referred to as branch flow paths L2) provided in parallel, and the downstream of these plurality of branch flow paths L2 is connected to a main flow path L1 that communicates with, for example, a process chamber CH. Note that the main flow path L1 is a flow path that can suddenly become higher in pressure than the inside of the fluid control device 100. In addition, shutoff valves V1, V2 are provided on the upstream and downstream sides of the fluid control device 100 in the branch flow paths L2, respectively.

[0034] 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 this order from the upstream side, and a control unit C that controls the fluid control valve 1 is packaged together with these fluid devices 21 to 23. 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 21 to 23 described above are attached to this block B, so that these fluid devices 21 to 23 are arranged on the internal flow path L3. Note that the fluid control device 100 may further include a pressure sensor upstream of the fluid control valve 1.

[0035] 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, and as shown in FIG. 2, by executing a program for a fluid control device stored in the memory, it performs the functions of at least the actual flow rate calculation unit 24 and the valve control unit 3.

[0036] The actual flow rate calculation unit 24 calculates the flow rate of the fluid flowing through the internal flow path L3 from the measured pressure P1 measured by the upstream pressure sensor 21 and the measured pressure P2 measured by 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 actual flow rate calculation unit 24 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.

[0037] The valve control unit 3 performs flow rate feedback control of the opening of the fluid control valve 1 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.

[0038] Here, the control unit C of this embodiment includes a flow rate output unit 4 that outputs the calculated flow rate to, for example, a display D, as shown in FIG.

[0039] In such a configuration, for example, when the valve control section 3 receives a full-close command and closes the fluid control valve 1, the output from the flow rate output section 4 is generally considered to be a zero value.

[0040] However, due to various factors, such as an outflow from the fluid control valve 1 or a backflow from the main flow path L1 to the branch flow path L2, a difference may occur between the measured pressure P1 of the upstream pressure sensor 21 and the measured pressure P2 of the downstream pressure sensor 23, even though the fluid control valve 1 is in a closed state. When this happens, a flow rate corresponding to this difference is calculated by the actual flow rate calculation unit 24, and a calculated flow rate different from zero may be output by the flow rate output unit 4, even though there is no problem in using the fluid control device 100.

[0041] Therefore, the flow rate output unit 4 of this embodiment is configured to perform a zero output function, which outputs a zero value regardless of the calculated flow rate when it is determined that the fluid control valve 1 is in a closed state.

[0042] Here, "outputting a zero value" means indicating that there is substantially no fluid flow, and specific examples include outputting the number "0" in the area showing the flow rate on display D, or outputting a straight line indicating that the flow rate is zero in a graph showing the change in flow rate over time. However, the present invention is not limited to the above-mentioned examples, as long as it indicates that there is substantially no fluid flow rate.

[0043] 2, the above-described valve control unit 3 is configured to control the fluid control valve 1 based on a full-close command that forcibly closes the fluid control valve 1 or a set flow rate that is set as a target value for the calculated flow rate. That is, when the valve control unit 3 receives a full-close command or receives a zero value as the set flow rate, the valve control unit 3 attempts to close the fluid control valve 1.

[0044] In consideration of such operation of the valve control unit 3, the flow rate output unit 4 is configured to output a zero value regardless of the calculated flow rate when the valve control unit 3 receives a full close command or when the valve control unit 3 receives a zero value as the set flow rate, at least in response to that event. Note that the timing at which the flow rate output unit 4 outputs the zero value may be immediately after the valve control unit 3 receives a full close command or immediately after receiving a zero value as the set flow rate, or may be after a predetermined condition is satisfied, such as after a predetermined time has elapsed since the valve control unit 3 received the full close command or the zero value as the set flow rate.

[0045] In this configuration in which the flow rate output unit 4 performs the zero output function, the control unit C of this embodiment further includes a switching unit 5 that switches between executing and stopping the zero output function by the flow rate output unit 4, as shown in FIG. 3.

[0046] The switching unit 5 is configured to execute the zero output function when a predetermined execution condition is met, and to stop the zero output function when a predetermined stop condition is met.

[0047] The operation of the switching unit 5 will be described below with reference to the flowchart of FIG.

[0048] First, a description will be given of the operation when the switching unit 5 executes the zero output function. When the fluid control device 100 is powered on, the zero output function is stopped (S0).

[0049] The execution conditions include at least the fluid control valve 1 being in a closed state. Here, in the event of an abnormality such as a malfunction of the outflow or pressure sensors 21 and 23 of the fluid control valve 1, the calculated flow rate may become an abnormal value that is significantly different from zero even though the fluid control valve 1 is in a closed state. In such a case, if a zero value is output simply based on the condition that the fluid control valve 1 is closed, the abnormal value of the calculated flow rate described above will be hidden (not output) by the zero value, making it difficult to detect the abnormality described above.

[0050] Therefore, in this embodiment, the execution conditions are set such that the fluid control valve 1 is in a closed state and the absolute difference |P1-P2| between the measured pressure P1 of the upstream pressure sensor 21 and the measured pressure P2 of the downstream pressure sensor 23 is smaller than a predetermined execution threshold value Th1.

[0051] This execution threshold value Th1 is stored in advance in a switching threshold value storage unit 6 set in a predetermined area of ​​the memory (see FIG. 3). The execution threshold value Th1 is set to a value that is at least larger than a stop threshold value Th2, which will be described later, and specifically, is set to a value that does not appear as an absolute difference |P1-P2| under normal circumstances when the fluid control valve 1 is in a closed state.

[0052] Based on this execution condition, the switching unit 5 determines whether the fluid control valve 1 is in a closed state and whether the absolute difference |P1-P2| between the pressure P1 measured by the upstream pressure sensor 21 and the pressure P2 measured by the downstream pressure sensor 23 is smaller than a predetermined execution threshold Th1, i.e., whether the execution condition is satisfied (S1). Regarding the determination of whether the fluid control valve 1 is in a closed state, the switching unit 5 determines that the fluid control valve 1 is in a closed state if the valve control unit 3 has received a full-close command or if the valve control unit 3 has received a zero value as the set flow rate; otherwise, it determines that the fluid control valve 1 is in an open state. Furthermore, this determination in S1 may be a step that is executed after the valve control unit 3 has received a full-close command or after the valve control unit 3 has received a zero value as the set flow rate, or it may be a step that is executed immediately after S0, regardless of the reception of the full-close command or the zero value.

[0053] Then, if the execution condition is met in S1, the switching unit 5 executes the zero output function and causes the flow rate output unit 4 to output a zero value (S2). On the other hand, if the execution condition is not met in S1, the switching unit 5 causes the flow rate output unit 4 to output the calculated flow rate without executing the zero output function, that is, while keeping the zero output function stopped (S0).

[0054] After the switching unit 5 executes the zero output function in S2, the process moves to determining whether or not the stop condition described below is satisfied.

[0055] In this embodiment, the stop condition (hereinafter also referred to as the first stop condition) is set such that the fluid control valve 1 is in an open state (in other words, the fluid control valve 1 is not in a closed state) and the difference P1-P2 obtained by subtracting the measured pressure P2 of the downstream pressure sensor 23 from the measured pressure P1 of the upstream pressure sensor 21 is greater than a predetermined stop threshold Th2. Note that the stop threshold Th2 is a value at least equal to or greater than 0, but is preferably a positive value greater than 0.

[0056] However, in the event of an abnormality, such as a failure of the pressure sensors 21 and 23, a large value (abnormal value) may be calculated as the calculated flow rate even though the fluid control valve 1 is in the closed state. In such a case, if the first stop condition described above is satisfied and a zero value continues to be output, the large abnormal value will be hidden (not output) by this zero value, which may delay the detection of the abnormality.

[0057] Therefore, in this embodiment, the stop condition (hereinafter also referred to as the second stop condition) is set to be that the absolute difference |P1-P2| between the measured pressure P1 of the upstream pressure sensor 21 and the measured pressure P2 of the downstream pressure sensor 23 is greater than a predetermined upper limit value Th3, and the switching unit 5 stops the zero output function when either the first stop condition or the second stop condition is satisfied.

[0058] This upper limit value Th3 is stored in advance in the switching threshold value storage unit 6 (see FIG. 2). The upper limit value Th3 is set to a value greater than at least the stop threshold value Th2 described above, and specifically, is set to a value greater than or equal to a value that does not appear as the absolute difference |P1-P2| under normal circumstances when the fluid control valve 1 is in the closed state. Note that the upper limit value Th3 may be greater than or equal to the execution threshold value Th1 described above, or may be less than or equal to the execution threshold value Th1.

[0059] Based on these stop conditions, the switching unit 5 determines whether the fluid control valve 1 is in the open state and whether the difference P1-P2 obtained by subtracting the measured pressure P2 of the downstream pressure sensor 23 from the measured pressure P1 of the upstream pressure sensor 21 is greater than a predetermined stop threshold Th2, i.e., whether a first stop condition is satisfied (S3), and also determines whether the absolute difference |P1-P2| between the measured pressure P1 of the upstream pressure sensor 21 and the measured pressure P2 of the downstream pressure sensor 23 is greater than a predetermined upper limit value Th3, i.e., whether a second stop condition is satisfied (S4). Note that the determination in S3 may be a step that is executed after the valve control unit 3 receives a value greater than zero as the set flow rate, or may be a step to which the process proceeds immediately after S2, regardless of the reception of this set flow rate.

[0060] Then, in S3 and S4, if either the first stop condition or the second stop condition is satisfied, the switching unit 5 stops the zero output function and causes the flow rate output unit 4 to output the calculated flow rate (S0). On the other hand, if neither the first nor the second stop condition is satisfied in S3 and S4, the switching unit 5 causes the flow rate output unit 4 to output a zero value without stopping the zero output function, i.e., while maintaining the execution of the zero output function (S2).

[0061] After the switching unit 5 stops the zero output function in S5, the process returns to S1 and moves to determining whether the execution condition is met.

[0062] <Effects of the first embodiment> According to the fluid control device 100 configured in this manner, the conditions for stopping the zero output function include not only that the fluid control valve 1 be in an open state, but also that the difference P1-P2 obtained by subtracting the measured pressure P2 of the downstream pressure sensor 23 from the measured pressure P1 of the upstream pressure sensor 21 be greater than a predetermined stop threshold Th2. This makes it possible to prevent a negative value from being output immediately after the zero output function is stopped and the output is switched from a zero value to a calculated flow rate. This makes it possible to prevent unnatural behavior when switching the output flow rate from a zero value to a calculated flow rate in a fluid control device 100 configured to output a zero value regardless of the calculated flow rate when the fluid control valve 1 is closed, as shown in FIG. 5.

[0063] Furthermore, the conditions for executing the zero output function include not only that the fluid control valve 1 be in the closed state, but also that the absolute difference |P1-P2| between the measured pressure P1 of the upstream pressure sensor 21 and the measured pressure P2 of the downstream pressure sensor 23 be smaller than a predetermined execution threshold Th1. Therefore, even if the fluid control valve 1 is in the closed state, if the absolute difference |P1-P2| between the measured pressure P1 of the upstream pressure sensor 21 and the measured pressure P2 of the downstream pressure sensor 23 is larger than the predetermined execution threshold Th1, the zero output function will not be executed, and abnormal values ​​due to various factors can be output without being hidden, making it possible to quickly detect various abnormalities, etc.

[0064] Furthermore, since the execution threshold value Th1 is set to a value greater than or equal to a value that does not appear as the absolute difference |P1-P2| under normal circumstances when the fluid control valve 1 is in a closed state, the effect of the zero output function can be ensured, and if an abnormal value occurs, the abnormal value can be output without being hidden.

[0065] Furthermore, even if the switching unit 5 satisfies the second stop condition, the zero output function is stopped, so that if a large negative value is calculated, the negative value can be output without being hidden, and various abnormalities can be quickly detected.

[0066] In addition, since the upper limit value Th3 included in the second stop condition is greater than at least the stop threshold value Th2, it is possible to output an abnormal negative value while preventing unnatural behavior.

[0067] <Modification of the First Embodiment> The present invention is not limited to the first embodiment.

[0068] For example, in the first embodiment, the execution threshold Th1 is described as being greater than the stop threshold Th2, but the execution threshold Th1 and the stop threshold Th2 may be equal to each other.

[0069] Furthermore, the functions of the actual flow rate calculation unit 24, the valve control unit 3, the flow rate output unit 4, the switching unit 5, and the switching threshold value storage unit 6 do not necessarily have to be performed by one CPU, and some of these functions may be performed by different CPUs.

[0070] In the first embodiment, the fluid control device 100 is configured to include one fluid control valve 1. However, as shown in FIG. 6, the fluid control device 100 may further include a second fluid control valve 1′ provided downstream of the downstream pressure sensor 23, in addition to the fluid control valve 1 of the above embodiment. In this case, the phrase "the fluid control valve is in a closed state" in the claims means that either or both of the fluid control valve 1 and the second fluid control valve 1' are in a closed state, and the phrase "the fluid control valve is in an open state" means that both the fluid control valve 1 and the second fluid control valve 1' are in an open state. As shown in FIG. 6, the fluid control device 100 may further include a pressure sensor 20 provided upstream of the fluid control valve 1.

[0071] [Second embodiment] Next, a fluid control device according to a second embodiment of the present invention will be described with reference to the drawings.

[0072] <Device configuration> The fluid control device 100 of this embodiment, like the first embodiment, is used, for example, in a semiconductor manufacturing process, and multiple fluid control devices 100 form a fluid control system 200 in which the flow rate of a fluid supplied to a process chamber is controlled.

[0073] Compared to the device configuration of the first embodiment, each fluid control device 100 differs in that, in addition to the upstream pressure sensor 21 and the downstream pressure sensor 23, it further includes a third pressure sensor 20 provided upstream of the fluid control valve 1, as shown in FIG. 8.

[0074] Furthermore, in this fluid control device 100, the function of the control unit C is different from that of the first embodiment, and therefore the control unit C will be described in detail below.

[0075] As shown in FIG. 9, this control section C is common to the first embodiment in that it functions as an actual flow rate calculation section 24, a valve control section 3, and a flow rate output section 4.

[0076] The flow rate output unit 4 of this embodiment is configured to perform a negative burst cut function, which is a function of outputting a zero value regardless of the calculated flow rate when the fluid control valve 1 is in an open state and the flow rate calculated by the actual flow rate calculation unit 24 is a negative flow rate. In the second embodiment, the flow rate output section 4 may or may not have the zero output function of the first embodiment.

[0077] Furthermore, "outputting a zero value" means, as in the first embodiment, indicating that there is substantially no fluid flow, and specific examples include outputting the number "0" in the area showing the flow rate on display D, or outputting a straight line indicating that the flow rate is zero in a graph showing the change in flow rate over time. However, the present invention is not limited to the above-mentioned embodiments as long as it indicates that there is substantially no fluid flow rate.

[0078] Furthermore, as shown in FIG. 9, the control unit C of this embodiment includes a switching unit 5 that switches between execution and stop of the negative burst cut function by the flow rate output unit 4.

[0079] More specifically, the switching unit 5 stops the negative burst cut function when the time that has elapsed since the fluid control valve 1 was opened exceeds a predetermined set time. When the negative burst cut function is stopped, the flow output unit 4 may output the calculated flow rate of the actual flow rate calculation unit 24, or may output a warning indicating that an abnormality has occurred instead of or in addition to the calculated flow rate.

[0080] The above set times can be changed by the user or the manufacturer. Here, the upper limit of the set time is set to approximately the time from when backflow of fluid into the fluid control device 100 occurs until the backflow is expected to subside, for example, 60,000 msec. On the other hand, the lower limit of the set time is set to 0 msec here. This allows the negative burst cut function to be forcibly stopped by changing the set time to 0 msec. In other words, in this embodiment, it is possible to select whether or not to enable the flow rate output unit 4 to perform the negative burst cut function, and it is possible to output the negative flow rate calculated by the actual flow rate calculation unit 24 as necessary.

[0081] Next, the operation of the control unit C of this embodiment will be described with reference to the flowchart of FIG.

[0082] First, when a set flow rate greater than zero or a full-open command is input to the control unit C, the valve control unit 3 changes the fluid control valve 1 from a closed state to an open state (T1).

[0083] Next, the flow rate output unit 4 determines whether or not the time that has elapsed since the fluid control valve 1 was opened exceeds a predetermined set time (T2).

[0084] At T2, if the elapsed time exceeds the set time, the switching unit 5 stops the negative burst cut function, and the flow rate output unit 4 outputs the flow rate calculated by the actual flow rate calculation unit 24 (T3).

[0085] On the other hand, if the elapsed time does not exceed the set time at T2, the flow rate output unit 4 determines whether the flow rate calculated by the actual flow rate calculation unit 24 is a negative flow rate (T4).

[0086] At T4, if the calculated flow rate is zero or a positive flow rate, the flow rate output unit 4 outputs the calculated flow rate to a display or the like (T5).

[0087] On the other hand, if the calculated flow rate is a negative flow rate at T4, the flow rate output unit 4 performs a negative burst cut function and outputs a zero value to a display or the like regardless of the calculated flow rate (T6).

[0088] After the calculated flow rate is output at T5 and after a zero value is output at T6, the process returns to T2 and the operations from T2 to T5 are repeated. As a result, the negative burst cut function is exerted until the elapsed time exceeds the set time, so that whenever the calculated flow rate becomes a negative flow rate, a zero value is output. On the other hand, if a negative flow rate continues to be calculated until the set time is exceeded, the negative burst cut function is stopped at the timing when the elapsed time exceeds the set time, and a negative flow rate is output.

[0089] <Effects of the second embodiment> According to the fluid control device 100 configured in this manner, when the flow rate calculated by the actual flow rate calculation unit 24 is a negative flow rate, the flow rate output unit 4 exhibits a negative burst cut function by outputting a zero value, thereby suppressing unnatural behavior of the output.

[0090] Furthermore, if the actual flow rate calculation unit 24 continues to calculate a negative flow rate for a predetermined set time, the negative burst cut function is stopped, so that a negative flow rate calculated due to an abnormality, such as a failure of the fluid control valve 1, can be output, and such an abnormality can be detected quickly.

[0091] <Modification of the second embodiment> As in the first embodiment, the fluid control device 100 according to the present invention does not necessarily have to include the third pressure sensor 20, as long as it includes the upstream pressure sensor 21 and the downstream pressure sensor 22.

[0092] Furthermore, the switching unit 5 may be configured to stop the negative burst cut function when the flow rate calculated by the actual flow rate calculation unit 24 falls below a preset lower limit value. In this way, if the calculated flow rate is extremely small due to various abnormalities, the abnormality can be detected quickly.

[0093] Furthermore, as shown in FIG. 6, the fluid control device 100 may further include a second fluid control valve 1′ provided downstream of the downstream pressure sensor 23, in addition to the fluid control valve 1 of the second embodiment. In this case, the phrase "the fluid control valve is in an open state" in the claims refers to the case where both the fluid control valve 1 and the second fluid control valve 1' are in an open state. As shown in FIG. 6, the fluid control device 100 may further include a pressure sensor 20 provided upstream of the fluid control valve 1.

[0094] In addition, the fluid control device 100 of the above embodiment was configured to stop the negative burst cut function when the elapsed time since the fluid control valve was opened exceeds a predetermined time, but it may also be configured to execute the negative burst cut function even after the elapsed time exceeds the predetermined time. In this case, in order to quickly detect abnormalities, the negative burst cut function may be stopped if the actual flow rate calculation unit 4 continues to calculate a negative flow rate for a predetermined set time.

[0095] [Other embodiments]

[0096] In each of the above embodiments, the fluid control system 200 is provided with a plurality of fluid control devices 100, but the fluid control system may also be provided with a single fluid control device 100.

[0097] Additionally, in each of the above embodiments, the fluid control device 100 has been described as being used in a semiconductor manufacturing process, but the fluid control device 100 according to the present invention can be used in various systems other than semiconductor manufacturing processes.

[0098] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0099] 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 section 2. Flow sensor 3 Valve control section 4...Flow rate output section 5. Switching section 6. Switching threshold storage section

Claims

1. a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on the flow path; an actual flow rate calculation unit that calculates a flow rate based on the pressures measured by the upstream pressure sensor and the downstream pressure sensor; a flow rate output unit that outputs the calculated flow rate calculated by the actual flow rate calculation unit, In a fluid control device configured such that the flow rate output unit performs a zero output function, which is a function of outputting a zero value regardless of the calculated flow rate when it is determined that the fluid control valve is in a closed state, a switching unit that switches between execution and stop of the zero output function by the flow rate output unit, A fluid control device characterized in that, when the switching unit determines that the fluid control valve is in an open state and that the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than a predetermined stop threshold, the switching unit stops the zero output function and causes the flow output unit to output the calculated flow rate.

2. 2. The fluid control device according to claim 1, wherein the switching unit executes the zero output function and causes the flow rate output unit to output a zero value when the switching unit determines that the fluid control valve is in a closed state and that an absolute difference between the measured pressure of the upstream pressure sensor and the measured pressure of the downstream pressure sensor is smaller than a predetermined execution threshold.

3. The fluid control device of claim 2 , wherein the run threshold is at least greater than the stop threshold.

4. 4. The fluid control device according to claim 1, wherein the switching unit stops the zero output function and causes the flow rate output unit to output the calculated flow rate when it determines that either a first stop condition or a second stop condition below is satisfied. (First stop condition) When the fluid control valve is in an open state and the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than the stop threshold value. (Second stop condition) When the absolute difference between the pressure measured by the upstream pressure sensor and the pressure measured by the downstream pressure sensor is greater than a predetermined upper limit value that is greater than the stop threshold value.

5. A fluid control system, characterized in that the fluid control device according to any one of claims 1 to 4 is disposed in some or all of a plurality of branch flow paths connected to a main flow path and arranged in parallel.

6. A program used in a fluid control device in which a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on a flow path, an actual flow rate calculation unit that calculates a flow rate based on the pressures measured by the upstream pressure sensor and the downstream pressure sensor; a computer to function as a flow rate output unit that outputs the calculated flow rate calculated by the actual flow rate calculation unit; The flow rate output unit is configured to perform a zero output function, which is a function of outputting a zero value regardless of the calculated flow rate when it is determined that the fluid control valve is in a closed state, The computer further functions as a switching unit that switches between execution and stop of the zero output function by the flow rate output unit, A program for a fluid control device, characterized in that when the switching unit determines that the fluid control valve is in an open state and that the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than a predetermined stop threshold, the program stops the zero output function and causes the flow rate output unit to output the calculated flow rate.

7. A fluid control method using a fluid control device in which a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor are provided on a flow path, an actual flow rate calculation step of calculating a flow rate based on the pressures measured by the upstream pressure sensor and the downstream pressure sensor; a flow rate output step of outputting the calculated flow rate calculated in the actual flow rate calculation step, In the flow rate output step, when it is determined that the fluid control valve is in a closed state, a zero value is output regardless of the calculated flow rate, a switching step of switching between execution and stop of output of the zero value by the flow rate output step, A fluid control method characterized in that, in the switching step, if it is determined that the fluid control valve is in an open state and that the difference obtained by subtracting the measured pressure of the downstream pressure sensor from the measured pressure of the upstream pressure sensor is greater than a predetermined stop threshold, the calculated flow rate is output in the flow rate output step.

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