Fluid control device, fluid control valve control method, fluid control method and fluid control program

Abstract

To reduce a damage to a valve seat or a valve body when a valve is fully closed.SOLUTION: A fluid control device includes: a fluid control valve 2 that changes a distance of a valve seat 21 and that of a valve body 22 in accordance with a value of a drive signal; and a control mechanism CTL that outputs the drive signal so as to control the fluid control valve 2. The control mechanism CTL outputs, when the fluid control valve 2 is fully closed, the drive signal for tentatively suspending the fluid control valve 2 before it becomes the fully closed state to the fluid control valve 2, and then outputs the drive signal for making the fluid control valve 2 fully closed to the fluid control valve 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a fluid control device, a control method for a fluid control valve, a fluid control method, and a fluid control program. [Background technology]

[0002] For example, in semiconductor manufacturing processes, fluid control devices are used to control the flow rate of material gases, etc. This fluid control device has a fluid control valve in which the distance between the valve seat surface and the valve body changes depending on the value of a drive signal, and a control mechanism that outputs a drive signal to control the fluid control valve.

[0003] However, when a fluid control valve is switched from an open state to a fully closed state, the valve seat surface and the valve disc collide, and the impact can damage the valve seat surface or the surface (seating surface) of the valve disc. Damage to the valve seat surface or the seating surface can cause leakage when the valve is in the fully closed state.

[0004] Furthermore, depending on the application of the fluid control device, the fluid control valve may be switched from an open state to a fully closed state in a short period of time, or may alternate between the open state and the fully closed state at a predetermined interval. Improving the response speed in these cases increases overshoot and reduces damping. This can cause the valve disc to bite into the valve seat surface due to vibrations from the overshoot or transient response, making the valve seat surface or the seating surface susceptible to damage.

[0005] Here, it is possible to reduce the movement speed of the valve disc after the distance between the valve seat surface and the valve disc reaches a predetermined distance, as shown in Patent Document 1. However, since the valve disc continues to approach the valve seat surface even after the movement speed is reduced, there is a risk that the valve disc will come into contact with the valve seat surface due to overshoot or vibration due to transient response that occurs the moment the movement speed is reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-206387 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and its main object is to reduce damage to the valve seat surface or valve body when the valve is fully closed. [Means for solving the problem]

[0008] That is, the fluid control device according to the present invention comprises a fluid control valve in which the distance between the valve seat surface and the valve body changes depending on the value of a drive signal, and a control mechanism that outputs the drive signal to control the fluid control valve, and when the fluid control valve is to be fully closed, the control mechanism outputs a drive signal to the fluid control valve to cause it to pause before reaching the fully closed state, and then outputs a drive signal to the fluid control valve to bring it to the fully closed state.

[0009] According to this fluid control device, when the fluid control valve is fully closed, it is temporarily stopped before being fully closed, so that the impact on the valve seat surface and the valve disc can be reduced compared to when the valve is fully closed all at once, and also the bite caused by overshoot and transient response vibration can be reduced, thereby reducing damage to the valve seat surface or the valve disc.

[0010] Furthermore, when the fluid control valve is to be fully closed, the control mechanism may output a drive signal to the fluid control valve to temporarily stop the gap between the valve seat surface and the valve body at a predetermined distance before the fluid control valve is fully closed, and then output a drive signal to the fluid control valve to bring the valve to the fully closed state. With this configuration, the valve seat surface and the valve body are temporarily stopped when a predetermined distance is reached, thereby reducing the risk of the valve body coming into contact with the valve seat surface due to overshoot or transient response vibrations compared to control that reduces the movement speed of the valve body.

[0011] In order to reduce the risk of the valve disc coming into contact with the valve seat surface due to an overshoot when the valve is switched from a state where the valve seat surface and the valve disc are at a predetermined distance (a state where the valve is temporarily stopped) to a fully closed state, it is desirable that the predetermined distance be a distance that prevents the valve disc from coming into contact with the valve seat surface due to an overshoot that occurs when the fluid control valve is temporarily stopped at the predetermined distance.

[0012] In order to reduce the impact on the valve seat surface and the valve body when the valve is fully closed, it is desirable that the control mechanism output a drive signal to the fluid control valve to bring the valve into the fully closed state after the specified distance has been reached and the vibration due to the transient response has converged to a specified value or less.

[0013] The valve element may have a seating surface that seats on the valve seat surface and is formed of a resin layer. In this configuration, it is preferable that, when fully closing the fluid control valve, the control mechanism outputs a drive signal to the fluid control valve to temporarily suspend the fluid control valve in a state where the valve seat surface and the seating surface are in contact or close proximity to each other before the fluid control valve is fully closed, and then outputs a drive signal to the fluid control valve to fully close the fluid control valve so that the valve seat surface further bites into the seating surface. With this configuration, the valve seat surface and the seating surface are temporarily stopped in a state of contact or close proximity before the valve is fully closed, and then the valve seat surface is further embedded into the seating surface to enter the fully closed state, thereby improving the response speed of the fully closing operation.

[0014] It is desirable that the control mechanism performs pulse control in which the fluid control valve alternates between an open state and a fully closed state. With this configuration, even if the pulse control causes repeated collisions between the valve seat surface and the valve body periodically, when switching from the open state to the fully closed state, the valve is temporarily stopped at a predetermined distance as described above, thereby reducing damage to the valve seat surface or the valve body.

[0015] In order to reduce overshoot and transient response vibration when the valve seat surface and the valve element are spaced a predetermined distance apart (temporarily stopped) and then shifted to the fully closed state, it is desirable that the predetermined distance be 30% or less of the stroke from the fully open state to the fully closed state.

[0016] When the fluid control valve is to be fully closed, the control mechanism preferably outputs a step-like drive signal for temporarily stopping the fluid control valve to the fluid control valve. With this configuration, it is possible to shorten the time it takes to temporarily stop the valve from an open state, such as a fully open state, and therefore to switch from the open state to the fully closed state in a short time while reducing damage to the valve seat surface or the valve body.

[0017] When the control mechanism is to fully close the fluid control valve, it is desirable that the control mechanism outputs a step-like drive signal to the fluid control valve to bring the fluid control valve to the fully closed state after the temporary stop. This configuration shortens the time it takes for the valve seat surface and the valve disc to be temporarily stopped at a predetermined distance before the valve is fully closed, thereby reducing damage to the valve seat surface or the valve disc and enabling the valve to be switched from the open state to the fully closed state in a short time.

[0018] Furthermore, a control method for a fluid control valve according to the present invention is a control method for a fluid control valve in which the distance between a valve seat surface and a valve body changes depending on the value of a drive signal, and controls the fluid control valve by outputting the drive signal to the fluid control valve, and is characterized in that, when the fluid control valve is to be fully closed, a drive signal for temporarily stopping the fluid control valve before it reaches a fully closed state is output to the fluid control valve, and thereafter a drive signal for bringing the fluid control valve to a fully closed state is output to the fluid control valve.

[0019] Furthermore, a fluid control method according to the present invention is a fluid control method for controlling a fluid control valve in which a distance between a valve seat surface and a valve element changes depending on the value of a drive signal by outputting the drive signal to the fluid control valve, wherein, when fully closing the fluid control valve, a drive signal for temporarily stopping the fluid control valve before it reaches a fully closed state is output to the fluid control valve, and thereafter a drive signal for bringing the fluid control valve to a fully closed state is output to the fluid control valve.

[0020] Furthermore, the fluid control program according to the present invention is a fluid control program that controls a fluid control valve in which the distance between the valve seat surface and the valve body changes depending on the value of a drive signal by outputting the drive signal to the fluid control valve, and is characterized in that when the fluid control valve is to be fully closed, the program has a function of outputting a drive signal to the fluid control valve to cause it to pause before reaching a fully closed state, and then outputting a drive signal to the fluid control valve to bring it to a fully closed state.

[0021] The fluid control program may be distributed electronically or may be recorded on a program recording medium such as a CD, DVD, or flash memory. [Effects of the Invention]

[0022] According to the present invention configured in this way, damage to the valve seat surface or the valve body when the valve is fully closed can be reduced. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram showing the configuration of a fluid control device according to an embodiment of the present invention; [Figure 2] FIG. 3 is a diagram showing a driving signal according to the embodiment; [Figure 3] 4 is an enlarged view showing a drive signal for bringing the valve into a fully closed state in the embodiment; FIG. [Figure 4] FIG. 10 is a diagram showing a driving signal (sloping) of a modified embodiment. [Figure 5] FIG. 10 is a diagram showing a drive signal (multi-stage stop) of a modified embodiment. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a fluid control device according to a modified embodiment. [Figure 7] 10A is a diagram showing various states of the valve seat surface and the valve body according to a modified embodiment, and FIG. 10B is a diagram showing a drive signal. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of a fluid control device according to the present invention will be described below with reference to the drawings. Note that, for ease of understanding, all of the drawings shown below are drawn in a schematic manner with appropriate omissions or exaggerations. Identical components are designated by the same reference numerals, and their description will be omitted where appropriate.

[0025] The fluid control device 100 according to this embodiment controls the flow rate of a material gas or the like in, for example, a semiconductor manufacturing process. For example, the fluid control device 100 controls the flow rate of a material gas (precursor) supplied to a thin film formation process such as atomic layer deposition (ALD).

[0026] Specifically, the fluid control device 100 is a so-called mass flow controller, and as shown in FIG. 1, it includes a roughly rectangular parallelepiped flow path block B in which an internal flow path R is formed, a fluid control valve 2 attached to the flow path block B, a flow sensor 3 that measures the flow rate of the fluid flowing through the internal flow path R, and a control mechanism CTL that controls the opening degree of the fluid control valve 2 based on the output of the flow sensor 3.

[0027] The fluid control valve 2 includes a valve seat surface 21, a valve element 22 that moves toward and away from the valve seat surface 21, and an actuator 23 that drives the valve element 22. This fluid control valve 2 controls the flow rate by changing the distance between the valve seat surface 21 and the valve element 22 in accordance with the value of a drive signal output from a control mechanism CTL.

[0028] Specifically, the fluid control valve 2 is of a so-called normally closed type, and when the actuator 23 is not driven (when a drive voltage, which is a drive signal, is not applied), the valve element 22 is in a fully closed state in which it contacts the valve seat surface 21. The valve element 22 is biased in the closing direction by an elastic body such as a leaf spring.

[0029] When the actuator 23 is driven (when a drive voltage is applied), the fluid control valve 2 is in an open state in which the valve element 22 is separated from the valve seat surface 21. The piezoelectric actuator 23 adjusts the distance (opening) between the valve seat surface 21 and the valve element 22, thereby controlling the flow rate of the fluid.

[0030] The flow rate sensor 3 is a pressure type provided upstream or downstream of the fluid control valve 2. The flow rate sensor of this embodiment is provided downstream of the fluid control valve 2. This flow rate sensor 3 includes a first pressure sensor 31 and a second pressure sensor 32 provided upstream and downstream of a laminar flow element 33, respectively, and a flow rate calculation unit 34 that calculates the flow rate based on the outputs of the first pressure sensor 31 and the second pressure sensor 32. The first pressure sensor 31 and the second pressure sensor 32 are attached in a row together with the fluid control valve 2 in the flow path block B. Furthermore, although the flow rate calculation unit 34 of this embodiment is configured using the calculation function of the control mechanism CTL, it may be provided separately from the control mechanism CTL.

[0031] The control mechanism CTL is a computer having a CPU, internal memory, input / output interface, AD converter, communication means, etc. The control mechanism CTL functions as a valve control unit 4 described below by the CPU and peripheral devices working together in accordance with a fluid control program stored in the internal memory.

[0032] The valve control unit 4 outputs a drive voltage, which is a drive signal, to the actuator 23 to control the fluid control valve 2 .

[0033] The valve control unit 4 of this embodiment performs pulse control to repeat an open state, such as a fully open state, and a fully closed state of the fluid control valve 2 based on an opening / closing pattern set by the user, for example. As shown in FIG. 2, the valve control unit 4 outputs a drive signal to the actuator 23, which repeats a predetermined opening signal (ON signal) and a fully closed signal (OFF signal) at a predetermined cycle. The predetermined opening signal is determined based on a set flow rate. When the fluid control valve 2 is set to an open state, the valve control unit 4 performs feedback control based on the deviation between the measured flow rate measured by the flow rate sensor 3 and the set flow rate.

[0034] When the fluid control valve 2 is fully closed, the valve control unit 4 controls the valve so as to reduce the impact applied to the valve seat surface 21 and the valve element 22.

[0035] Specifically, when the fluid control valve 2 is to be fully closed, the valve control unit 4 outputs to the fluid control valve 2 a drive signal that reduces the impact applied to the valve seat surface 21 and the valve element 22.

[0036] In detail, when the fluid control valve 2 is to be fully closed, the valve control unit 4 outputs a drive signal to the fluid control valve 2 to temporarily stop the gap between the valve seat surface 21 and the valve element 22 at a predetermined distance L1 before the fluid control valve 2 is fully closed, and then outputs a drive signal to achieve the fully closed state to the fluid control valve 2. In other words, as shown in Fig. 3, when the fluid control valve 2 is to be fully closed, the drive signal temporarily stops the movement of the valve element 22 when the gap between the valve seat surface 21 and the valve element 22 is the predetermined distance L1, and then achieves the fully closed state after the temporary stop.

[0037] Here, the predetermined distance L1 for temporary suspension is, for example, a distance of 30% or less of the stroke amount from the open state to the fully closed state. Specifically, the predetermined distance L1 is a distance at which the valve element 22 does not come into contact with the valve seat surface 21 due to an overshoot that occurs when the fluid control valve 2 is temporarily suspended at the predetermined distance L1. Note that the predetermined distance L1 may be variable depending on the opening degree in the open state.

[0038] Furthermore, after the vibration of the valve element 22 due to the transient response has converged to or below a predetermined value in a state where the valve has traveled the predetermined distance L1 (a state where the valve is temporarily stopped), the valve control unit 4 outputs a drive signal to the fluid control valve 2 to switch to the fully closed state. In other words, the temporary stop time is the time until the vibration of the valve element 22 due to the transient response has converged to or below a predetermined value. By switching to the fully closed state after the vibration of the valve element 22 due to the transient response has converged to or below a predetermined value in this way, it is possible to reduce the impact applied to the valve seat surface 21 and the valve element 22 when the valve is switched to the fully closed state.

[0039] At this time, when a predetermined convergence time has elapsed during which the vibration of the valve element 22 due to the transient response converges to a predetermined value or less, the valve control unit 4 may output a drive signal for fully closing the fluid control valve 2. This convergence time can be obtained by analyzing the fluid control valve 2 in advance.

[0040] Furthermore, in the case where the fluid control valve 2 is configured to have a position sensor (not shown) that detects the position of the valve body 22, the valve control unit 4 may output a drive signal to the fluid control valve 2 to bring it into a fully closed state when it detects, based on the position detected by the position sensor, that the vibration due to the transient response has converged to a predetermined value or less.

[0041] Furthermore, when fully closing the fluid control valve 2, the valve control unit 4 outputs a step-like drive signal to the fluid control valve 2 to move the distance between the valve seat surface 21 and the valve element 22 to a predetermined distance L1 from the open state. Furthermore, when fully closing the fluid control valve 2, the valve control unit 4 outputs a step-like drive signal to the fluid control valve 2 to move the fluid control valve 2 to the fully closed state after the distance has reached the predetermined distance L1 (after temporarily stopping).

[0042] <Effects of this embodiment> According to the fluid control device 100 of this embodiment configured as described above, when the fluid control valve 2 is fully closed, it is temporarily stopped when the distance between the valve seat surface 21 and the valve element 22 is the predetermined distance L1, and then the fluid control valve 2 is fully closed. Therefore, compared to when the fluid control valve 2 is fully closed all at once, it is possible to reduce the impact on the valve seat surface 21 and the valve element 22 and also reduce the bite caused by overshoot and vibration of the transient response. As a result, it is possible to reduce damage to the valve seat surface 21 or the valve element 22.

[0043] Furthermore, the valve control unit 4 outputs a step-like drive signal to the fluid control valve 2 as a drive signal for setting the predetermined distance L1 from the open state, thereby shortening the time required for the distance between the valve seat surface 21 and the valve element 22 to reach the predetermined distance L1 from an open state such as a fully open state. Therefore, it is possible to switch from the open state to the fully closed state in a short time while reducing damage to the valve seat surface 21 or the valve element 22.

[0044] Furthermore, since the valve control unit 4 outputs a step-like drive signal to the fluid control valve 2 as a drive signal for bringing the valve into the fully closed state after temporarily stopping at the predetermined distance L1, it is possible to shorten the time until the valve seat surface 21 and the valve element 22 reach the fully closed state after temporarily stopping at the predetermined distance L1. Therefore, it is possible to switch from the open state to the fully closed state in a short time while reducing damage to the valve seat surface 21 or the valve element 22.

[0045] <Other embodiments> For example, although the drive signal in the above embodiment has a step shape before and after a pause, it may have a slope shape before or after a pause as shown in Fig. 4. The slope before and after a pause may have the same gradient or may be different from each other.

[0046] When the valve control unit 4 fully closes the fluid control valve 2, it was configured to stop once at a predetermined distance L1. However, as shown in FIG. 5, it may be configured to set a plurality of predetermined distances (for example, L1, L2 (<L1)) and stop a plurality of times. Note that the stop time at each of the plurality of distances may be the same or different from each other.

[0047] The valve control unit 4 of the above embodiment controls the fluid control valve 2 by pulse control, but it may perform control other than pulse control.

[0048] The fluid control valve 2 of the above embodiment is of a normally closed type, but it may be of a normally open type. In this case, in a state where the actuator 23 is not driven (a state where a drive voltage, which is a drive signal, is not applied), the valve body 22 is in a fully open state separated from the valve seat surface 21.

[0049] The flow rate sensor of the above embodiment is of a pressure type, but it may be of a thermal type.

[0050] Further, the fluid control device 100 of the above embodiment has a flow rate sensor 3 and controls the fluid control valve 2 based on the measured flow rate of the flow rate sensor 3. However, as shown in FIG. 6, it may be configured without a flow rate sensor. In this case, the valve control unit 4 controls the fluid control valve 2 by a drive signal based on, for example, an opening / closing pattern set by the user (for example, a repetition of an open state such as a fully open state and a closed state). In this case, when the valve control unit 4 fully closes the fluid control valve 2, the movement of the valve body 22 is temporarily stopped when the distance between the valve seat surface 21 and the valve body 22 reaches a predetermined distance L1, and then it is brought into a fully closed state after the temporary stop.

[0051] Furthermore, if the fluid control valve 2 has a position sensor (not shown) that detects the position of the valve element 22, the fluid control valve 2 may be configured to detect a predetermined open state such as a fully open state and a fully closed state using the position sensor. The valve control unit 4 may then be configured to control the fluid control valve 2 based on the position detected by the position sensor. In this case, when the fluid control valve 2 is to be fully closed, the valve control unit 4 detects, using the position sensor, that the distance between the valve seat surface 21 and the valve element 22 has reached a predetermined distance L1, and temporarily suspends the movement of the valve element 22 when the distance between the valve seat surface 21 and the valve element 22 has reached the predetermined distance L1, and then switches the fluid control valve 2 to the fully closed state after the temporary suspension.

[0052] 7, the valve element 22 may have a seating surface 22x that seats on the valve seat surface 21 and that is formed by a resin layer 221. In this case, the control mechanism CTL may be configured to, when fully closing the fluid control valve 2, output a drive signal to the fluid control valve 2 for temporarily stopping the fluid control valve 2 in a state where the valve seat surface 21 and the seating surface 22x are in contact with or close to each other before the fluid control valve 2 is fully closed, and then output a drive signal to the fluid control valve 2 for achieving a fully closed state where the valve seat surface 21 bites into the seating surface 22x.

[0053] Here, the state in which the valve seat surface 21 and the seating surface 22x are in contact or close proximity before the fully closed state is a so-called soft close state, which is a state in which, for example, the minimum value of the gas flow rate of N2 gas or the like is 0.0009 [SLM]. Also, the fully closed state is a so-called hard close state in which the valve seat surface 21 is pressed into the seating surface 22x, which is a state in which, for example, the leak amount is 10 in a helium leak test. -8~-10 [Pa·m 3 / sec].

[0054] With this configuration, before the valve is fully closed, the valve seat surface 21 and the seating surface 22x are temporarily stopped in a state of contact or proximity, and then the valve is fully closed with the valve seat surface 21 further digging into the seating surface 22x, thereby improving the response speed of the fully closed operation. Also, if the resin layer 221, which is the seating surface 22x of the valve element 22, becomes recessed with use and causes leakage, the usable period of the valve element 22 can be extended by adjusting (for example, lowering the voltage) the drive signal for achieving the fully closed state.

[0055] 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]

[0056] 100 Fluid control device 2. Fluid control valve 21 Valve seat surface 22 Valve body CTL...control mechanism

Claims

1. a fluid control valve in which the distance between a valve seat surface and a valve element changes in response to a drive signal; a control mechanism that outputs the drive signal to control the fluid control valve; The control mechanism outputs a drive signal to the fluid control valve to temporarily stop the fluid control valve before it reaches the fully closed state when the fluid control valve is to be fully closed, and then outputs a drive signal to the fluid control valve to bring it to the fully closed state.

2. 2. The fluid control device according to claim 1, wherein the control mechanism outputs a drive signal to the fluid control valve to temporarily stop the valve seat surface and the valve element at a predetermined distance before the fluid control valve is fully closed, and then outputs a drive signal to the fluid control valve to fully close the valve.

3. 3. The fluid control device according to claim 2, wherein the predetermined distance is a distance at which the valve element does not come into contact with the valve seat surface due to an overshoot that occurs when the fluid control valve is temporarily stopped at the predetermined distance.

4. 4. The fluid control device according to claim 3, wherein the control mechanism outputs a drive signal to the fluid control valve to bring the valve into a fully closed state after vibrations in a transient response have converged to a predetermined value or less when the predetermined distance is reached.

5. 5. The fluid control device according to claim 2, wherein the predetermined distance is equal to or less than 30% of a stroke amount from a fully open state to a fully closed state.

6. the valve body has a seating surface that is formed of a resin layer and that seats on the valve seat surface, 2. The fluid control device according to claim 1, wherein the control mechanism outputs a drive signal to the fluid control valve to temporarily stop the fluid control valve in a state where the valve seat surface and the seating surface are in contact or close proximity to each other before the fluid control valve is fully closed, and then outputs a drive signal to the fluid control valve to fully close the fluid control valve in which the valve seat surface bites into the seating surface.

7. 7. The fluid control device according to claim 1, wherein the control mechanism performs pulse control in which the fluid control valve alternates between an open state and a fully closed state.

8. The fluid control device according to claim 1 , wherein the control mechanism outputs a step-like drive signal for temporarily stopping the fluid control valve when the fluid control valve is to be fully closed.

9. 9. The fluid control device according to claim 1, wherein when the fluid control valve is to be fully closed, the control mechanism outputs a step-like drive signal to the fluid control valve to bring the fluid control valve to the fully closed state after the temporary suspension.

10. 1. A method for controlling a fluid control valve in which a distance between a valve seat surface and a valve element changes depending on a value of a drive signal, by outputting the drive signal to the fluid control valve, A control method for a fluid control valve, comprising: when fully closing the fluid control valve, outputting a drive signal to the fluid control valve to cause the valve to temporarily stop before reaching a fully closed state; and thereafter outputting a drive signal to the fluid control valve to bring the valve to the fully closed state.

11. A fluid control method for controlling a fluid control valve in which a distance between a valve seat surface and a valve element changes depending on a value of a drive signal, by outputting the drive signal to the fluid control valve, comprising: a drive signal for temporarily stopping the fluid control valve before it reaches the fully closed state is output to the fluid control valve, and thereafter, a drive signal for bringing the fluid control valve to the fully closed state is output to the fluid control valve.

12. A fluid control program for controlling a fluid control valve in which a distance between a valve seat surface and a valve element changes in accordance with a value of a drive signal by outputting the drive signal to the fluid control valve, A fluid control program that provides a computer with a function of outputting, when fully closing the fluid control valve, a drive signal to the fluid control valve for temporarily stopping the fluid control valve before it reaches a fully closed state, and then outputting, to the fluid control valve, a drive signal to bring the fluid control valve to a fully closed state.

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