JP7796524B2 - Fluid control device, fluid control system, program for fluid control device, and fluid control method - Google Patents

Description

The present invention relates to a fluid control device, etc.

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

In such a configuration, the timing for returning the output from zero to the calculated flow rate is thought to be when the fluid control valve switches from a closed state to an open state.

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 Figure 7.

One example of a cause of unnatural output behavior is when a large flow rate flows through the flow path connected downstream of the mass flow controller, causing some of the fluid to flow back into the mass flow controller.

In addition, even when the fluid control valve is closed, pressure changes occur downstream due to factors such as the flow in and out of the fluid control valve. This means that the calculated flow rate in the closed state can vary from zero depending on factors such as the set flow rate and pressure conditions immediately before the valve is closed, or the waiting time in the closed state (see Figure 7).

JP 2018-18351 A

The present invention was developed to solve the above problems, and its main objective is to suppress unnatural behavior of the calculated flow rate output from a fluid control device.

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.

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.

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.

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.

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.
(First stop condition)
The fluid control valve is in an open state, and the difference obtained by subtracting the pressure measured by the downstream pressure sensor from the pressure measured by the upstream pressure sensor is greater than the stop threshold (second stop condition).
When the absolute difference between the measured pressure of the upstream pressure sensor and the measured pressure of the downstream pressure sensor is even 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 met, the zero output function is stopped, so that an abnormal value can be output and various abnormalities can be quickly detected.

To prevent unnatural behavior while outputting the abnormal negative value described above, it is preferable that the upper limit value be at least greater than the stop threshold value.

Furthermore, the fluid control system according to the present invention is characterized in that the above-described fluid control device is disposed 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.

Furthermore, the fluid control device program of the present invention is a program used in a fluid control device having a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor 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 pressures measured by 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. 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. The program also causes the computer to function as a switching unit that switches between enabling and disabling the zero output function of the flow rate output unit, and is characterized in that when the fluid control valve is open and the difference obtained by subtracting the pressure measured by the downstream pressure sensor from the pressure measured by 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.

In addition, the fluid control method according to the present invention is a fluid control method using a fluid control device having a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor provided on a flow path, and includes 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. If the fluid control valve is determined to be closed in the flow rate output step, a zero value is output regardless of the calculated flow rate. The method further includes a switching step of switching between enabling and stopping output of the zero value in the flow rate output step. In the switching step, if the fluid control valve is open and the difference obtained by subtracting the pressure measured by the downstream pressure sensor from the pressure measured by the upstream pressure sensor is greater than a predetermined stop threshold, the calculated flow rate is output in the flow rate output step.

This fluid control device program and fluid control method can achieve the same effects as the fluid control device described above.

As mentioned in the background art, immediately after a fluid control valve switches from a closed state to an open state, a negative flow rate may be output due to, for example, a large flow rate flowing through a flow path connected downstream of a mass flow controller, causing some of the fluid to flow back into the mass flow controller.

Therefore, one objective of this invention is to prevent negative flow rates from being output and suppress unnatural output behavior.

In other words, another aspect of the fluid control device according to the present invention is characterized in that it includes a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor 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, 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 outputs a zero value regardless of the calculated flow rate when the fluid control valve is open and the flow rate calculated by the actual flow rate calculation unit is a negative flow rate.

With a fluid control device configured in this way, if the flow rate calculated by the actual flow rate calculation unit is negative, the flow rate output unit will exhibit a negative burst cut function, outputting a zero value, thereby suppressing unnatural output behavior.

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.

In the above-described configuration, it is preferable that the set time be changeable so that the set time can be set flexibly.

Depending on the user or process, there may be cases where a negative flow rate is desired to be output, so it is preferable that the flow rate output unit be configured to allow selection of whether or not to perform the negative burst cut function.

The program for a fluid control device according to the present invention is used in a fluid control device having a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor 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 pressures measured by 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. The program is characterized in that the flow rate output unit performs a negative burst cut function, which outputs a zero value regardless of the calculated flow rate when the fluid control valve is open and the flow rate calculated by the actual flow rate calculation unit is a negative flow rate.

Furthermore, the fluid control method according to the present invention uses a fluid control device having a fluid control valve, an upstream pressure sensor, and a downstream pressure sensor provided on a flow path, and includes an actual flow rate calculation step for 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 for outputting the calculated flow rate calculated by the actual flow rate calculation unit. The method is characterized in that, 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 exhibits a negative burst cut function, which outputs a zero value regardless of the calculated flow rate.

This fluid control device program and fluid control method can achieve the same effects as the fluid control device described above.

The present invention described above makes it possible to suppress unnatural behavior in the calculated flow rate output from the fluid control device.

1 is a schematic diagram showing the configuration of a fluid control system according to an embodiment of the present invention; FIG. 2 is a schematic diagram showing the configuration of the fluid control device of the embodiment. FIG. 2 is a functional block diagram showing functions of a control unit of the embodiment. 4 is a flowchart showing the operation of a control unit of the embodiment. 4 is a graph showing an output of the fluid control device of the embodiment. FIG. 10 is a schematic diagram showing the configuration of a fluid control device according to another embodiment. 10 is a graph illustrating unnatural behavior of the output flow rate that occurs in a conventional configuration. FIG. 5 is a schematic diagram showing the configuration of a fluid control device according to a second embodiment. FIG. 10 is a functional block diagram showing functions of a control unit according to a second embodiment. 10 is a flowchart showing the operation of a control unit according to a second embodiment.

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

<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.

In this fluid control system 200, the above-mentioned fluid control device 100 is disposed in some or all of multiple flow paths L2 (hereinafter also referred to as branch flow paths L2) arranged in parallel, 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. Note that the main flow path L1 is a flow path that can suddenly become higher in pressure than the interior of the fluid control device 100. In addition, shutoff 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.

As shown in FIG. 2, the fluid control device 100 is a differential pressure mass flow controller that includes a fluid control valve 1, an upstream pressure sensor 21, a fluid resistance element 22, and a downstream pressure sensor 23, arranged in this order from the upstream side. These fluid devices 21-23 are packaged together with a control unit C that controls the fluid control valve 1. More specifically, the mass flow controller 100 includes a block B in which an internal flow path L3 is formed. The various fluid devices 21-23 described above are attached to this block B, so that these fluid devices 21-23 are arranged on the internal flow path L3. The fluid control device 100 may also include a pressure sensor upstream of the fluid control valve 1.

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 Figure 2, performs the functions of at least the actual flow rate calculation unit 24 and the valve control unit 3 by executing a fluid control device program stored in the memory.

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 the differential pressure flow sensor 2. The calculated flow rate calculated by this actual flow rate calculation unit 24 is output to the valve control unit 3.

The valve control unit 3 performs flow feedback control of the opening of the fluid control valve 1 so as to minimize 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.

Here, as shown in Figure 3, the control unit C in this embodiment is equipped with a flow rate output unit 4 that outputs the calculated flow rate to, for example, a display D.

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

However, due to various factors, such as outflow from the fluid control valve 1 or 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 when the fluid control valve 1 is closed. When this happens, the actual flow rate calculation unit 24 calculates a flow rate corresponding to this difference, and the flow rate output unit 4 may output a calculated flow rate different from zero, even though there is no problem with using the fluid control device 100.

Therefore, the flow rate output unit 4 in 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.

Here, "outputting a zero value" means indicating that there is substantially no fluid flow. Specific examples of this include outputting the number "0" in the area of display D that indicates the flow rate, or outputting a straight line indicating that the flow rate is zero in a graph that shows the change in flow rate over time. However, this is not limited to the above-mentioned examples, as long as it indicates that there is substantially no fluid flow.

As shown in FIG. 2, the above-mentioned 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. In other words, when the valve control unit 3 receives a full-close command or a zero value as the set flow rate, it attempts to close the fluid control valve 1.

In consideration of this 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. 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 a zero value as the set flow rate.

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 performing and stopping the zero output function of the flow rate output unit 4, as shown in Figure 3.

This switching unit 5 is configured to execute the zero output function when predetermined execution conditions are met, and to stop the zero output function when predetermined stop conditions are met.

The operation of the switching unit 5 will be explained below with reference to the flowchart in Figure 4.

First, we will explain the operation when the switching unit 5 executes the zero output function. Note that when the fluid control device 100 is powered on, the zero output function is stopped (S0).

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 were output simply based on the condition that the fluid control valve 1 is closed, the abnormal value of the calculated flow rate described above would be hidden (not output) by the zero value, making it difficult to detect the abnormality described above.

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 Th1.

This execution threshold Th1 is pre-stored in the switching threshold storage unit 6, which is set in a specified area of the memory (see Figure 3). The execution threshold Th1 is set to a value greater than at least the stop threshold Th2, which will be described later; specifically, it is set to a value greater than or equal to a value that does not normally appear as the absolute difference |P1 - P2| when the fluid control valve 1 is closed.

Based on this execution condition, the switching unit 5 determines whether the fluid control valve 1 is closed and 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 smaller than a predetermined execution threshold Th1, i.e., whether the execution condition is met (S1). Regarding the determination of whether the fluid control valve 1 is closed, the switching unit 5 determines that the fluid control valve 1 is closed 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 open. Furthermore, this determination in S1 may be a step 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 to which the process proceeds immediately after S0, regardless of the reception of the full-close command or a zero value.

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 conditions are 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, i.e., while keeping the zero output function stopped (S0).

After executing the zero output function in S2, the switching unit 5 proceeds to determine whether the stop conditions described below are met.

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.

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

In this embodiment, therefore, 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 met.

This upper limit value Th3 is pre-stored in the switching threshold value storage unit 6 (see Figure 2). The upper limit value Th3 is set to a value greater than at least the stop threshold value Th2 described above; specifically, it is set to a value greater than or equal to a value that does not normally appear as the absolute difference |P1 - P2| 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.

Based on these stop conditions, the switching unit 5 determines whether the fluid control valve 1 is in an 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 the first stop condition is met (S3), and 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 Th3, i.e., whether the second stop condition is met (S4). The determination in S3 may be a step executed after the valve control unit 3 receives a set flow rate greater than zero, or it may be a step to which the process proceeds immediately after S2, regardless of the reception of this set flow rate.

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, in S3 and S4, if both the first stop condition and the second stop condition are not met, 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).

After the switching unit 5 stops the zero output function in S5, it returns to S1 and moves on to determining whether the execution conditions are met.

<Effects of 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. 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 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.

Furthermore, the conditions for executing the zero output function include not only that the fluid control valve 1 be closed, 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 closed, 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 greater than the predetermined execution threshold Th1, the zero output function will not be executed, and abnormal values caused by various factors can be output without being hidden, allowing various abnormalities to be detected quickly.

Furthermore, since the execution threshold Th1 is set to a value equal to or greater than the value that does not normally appear as the absolute difference |P1 - P2| when the fluid control valve 1 is closed, the effects of the zero output function can be ensured while, if an abnormal value occurs, the abnormal value can be output without being hidden.

In addition, even if the switching unit 5 meets the second stop condition, the zero output function is stopped. Therefore, if a large negative value is calculated, the negative value can be output without being hidden, allowing various abnormalities to be detected quickly.

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

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

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 values.

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

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 one 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 .

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

<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.

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 downstream pressure sensor 23, it further includes a third pressure sensor 20 provided upstream of the fluid control valve 1, as shown in Figure 8.

Furthermore, since the function of the control unit C in this fluid control device 100 differs from that in the first embodiment, the control unit C will be described in detail below.

As shown in Figure 9, this control unit C is similar to the first embodiment in that it functions as an actual flow rate calculation unit 24, a valve control unit 3, and a flow rate output unit 4.

Furthermore, 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.

Furthermore, "outputting a zero value" means, as in the first embodiment, indicating that there is substantially no fluid flow. Specific implementations include, for example, 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 on a graph showing the change in flow rate over time. However, implementations are not limited to those described above, as long as they indicate that there is substantially no fluid flow rate.

Furthermore, as shown in FIG. 9, the control unit C of this embodiment is equipped with a switching unit 5 that switches between executing and stopping the negative burst cut function by the flow output unit 4.

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.
In addition, 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.

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. As a result, by changing the set time to 0 msec, the negative burst cut function can be forcibly stopped. 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.

Next, the operation of the control unit C of this embodiment will be explained with reference to the flowchart in Figure 10.

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).

Next, the flow rate output unit 4 determines whether the time elapsed since the fluid control valve 1 was opened exceeds a predetermined set time (T2).

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).

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).

If the calculated flow rate is zero or a positive flow rate at T4, the flow rate output unit 4 outputs the calculated flow rate to a display or the like (T5).

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

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 activated until the elapsed time exceeds the set time, so whenever the calculated flow rate becomes negative, 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 when the elapsed time exceeds the set time, and a negative flow rate is output.

<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.

In addition, if the actual flow rate calculation unit 24 continues to calculate a negative flow rate for a specified set period of 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, allowing such an abnormality to be detected quickly.

<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 .

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.

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 .

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 period of time.

[Other embodiments]

In each of the above embodiments, a fluid control system 200 including multiple fluid control devices 100 was described, but the fluid control system may also include a single fluid control device 100.

In addition, 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.

In addition, various modifications and combinations of the embodiments may be made as long as they do not contradict the spirit of the present invention.

100...Fluid control device (mass flow controller)
DESCRIPTION OF SYMBOLS 1 Fluid control valve 21 Upstream pressure sensor 22 Fluid resistance element 23 Downstream pressure sensor L3 Internal flow path C Control unit 24 Actual flow rate calculation unit 2 Flow rate sensor 3 Valve control unit 4 Flow rate output unit 5 Switching unit 6 Switching threshold value storage unit

Claims (7)

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. 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. The fluid control device of claim 2, wherein the execution threshold is at least greater than the shutdown threshold. 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)
The fluid control valve is in an open state, and the difference obtained by subtracting the pressure measured by the downstream pressure sensor from the pressure measured by the upstream pressure sensor is greater than the stop threshold (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. 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. 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. 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.