JP7529664B2 - Flow control device, flow measurement method, and program for flow control device - Google Patents

Description

The present invention relates to a flow control device, such as a mass flow controller.

For example, in a semiconductor manufacturing process, it is necessary to accurately supply a process gas or the like to a target such as a chamber at a predetermined set flow rate. Mass flow controllers used for such purposes include those equipped with a pressure control valve provided upstream, a flow control valve provided downstream and equipped with an aperture sensor, and various sensors that measure the temperature and pressure of the fluid in the volume between the two valves, as described in Patent Document 1, for example.

This mass flow controller uses a pressure control valve located upstream to keep the pressure of the gas within the volume constant, and then uses a flow control valve located downstream to control the flow rate of gas flowing out of the volume.

Specifically, the mass flow controller stores a map showing the relationship between the temperature and pressure of the fluid within the volume, the flow rate of the fluid passing through the flow control valve, and the aperture of the flow control valve. The mass flow controller then references the map based on the set flow rate and the measured temperature and pressure, and outputs the corresponding aperture as the set aperture. The flow control valve is also controlled so that the measured aperture measured by the aperture sensor becomes the set aperture.

However, in maps like the one above, the relationships between the parameters can change over time or due to the operating environment, and the mass flow controller may no longer output the correct flow rate. For this reason, the map must be calibrated appropriately based on some kind of reference flow rate.

In Patent Document 1, for example, a period when no process is being performed in the chamber is used to perform the following calibration operation to calibrate the map. First, the downstream flow control valve is fully closed to store gas at a predetermined pressure in the volume between the pressure control valve and the flow control valve. Then, the upstream pressure control valve is fully closed and the flow control valve is opened, and the pressure and temperature changes in the volume from that point are measured. The flow rate of gas flowing out of the volume through the flow control valve is calculated by substituting the pressure differential, which indicates the amount of change in pressure over time, and the temperature into a flow calculation formula derived from the gas state equation. The measured flow rate calculated in this way is compared with the flow rate under the corresponding conditions stored in the map, and if there is a difference of a predetermined value or more, the flow rate stored in the map is updated to the measured flow rate.

However, even if the map is updated using this calibration method, the various valve operations described above cannot be performed while flow control is actually being performed, so the valve flow rate, which is the flow rate of gas flowing out of the flow control valve, cannot be monitored. In other words, it is not possible to guarantee that the correct flow rate is actually being supplied to the chamber during the actual process.

On the other hand, if a flow sensor or the like is provided between the downstream side of the flow control valve of the mass flow controller and the chamber to actually measure the valve flow rate and thereby ensure the accuracy of the valve flow rate, the flow path resistance will increase significantly due to the fluid resistance provided for flow rate measurement. This will result in a significant decrease in response speed during transient responses, for example, and the required specifications may not be met.

JP 2015-064893 A

The present invention has been made in consideration of the above-mentioned problems, and aims to provide a flow control device that can ensure the accuracy of the valve flow rate without increasing the flow path resistance between the flow control valve and the supply target.

That is, the flow control device according to the present invention is characterized by comprising a flow control valve provided in a main flow path, a second pressure sensor provided upstream of the flow control valve, a flow controller that controls the flow control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate, a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a target to which the fluid is to be supplied, a second branch flow path that branches off from the main flow path downstream of the flow control valve, a third pressure sensor provided on the second branch flow path, and a valve flow calculation unit that calculates the flow rate of the fluid passing through the flow control valve based on at least the second pressure and the third pressure measured by the third pressure sensor.

The flow control method according to the present invention is a flow measurement method for use in a flow control device that includes a flow control valve provided in a main flow path, a second pressure sensor provided upstream of the flow control valve, and a flow controller that controls the flow control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate, and is characterized in that it includes a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a target to which the fluid is to be supplied, a second branch flow path that branches off from the main flow path downstream of the flow control valve, and a third pressure sensor provided on the second branch flow path, and calculates the flow rate of the fluid passing through the flow control valve based on at least the second pressure and the third pressure measured by the third pressure sensor.

In this way, the third pressure sensor used to calculate the valve flow rate is provided in the second branch flow path that branches off separately from the first branch flow path connected to the supply target downstream of the flow control valve, thereby preventing an increase in flow path resistance between the flow control valve and the supply target. In addition, the valve flow rate calculation unit can constantly calculate the valve flow rate, which is the flow rate of the fluid passing through the flow control valve, based on the second pressure and the third pressure, so that the valve flow rate can be constantly monitored.

In order to estimate the valve flow rate, which is the flow rate of the fluid passing through the flow control valve, and to realize flow rate feedback control, the flow controller further includes a fluid resistance provided upstream of the second pressure sensor, a first pressure sensor provided upstream of the fluid resistance, and a resistance flow rate calculation unit that calculates the flow rate of the fluid flowing through the fluid resistance based on the first pressure and the second pressure measured by the first pressure sensor, and the flow controller includes a map storage unit that stores a map showing the relationship between at least the resistance flow rate calculated by the resistance flow rate calculation unit, the second pressure, and the flow rate of the fluid passing through the flow control valve, a map reference unit that refers to the map based on the measured resistance flow rate and the second pressure, and outputs the corresponding flow rate of the fluid passing through the flow control valve as an estimated valve flow rate, and an opening control unit that controls the flow control valve so that the estimated valve flow rate becomes the set flow rate. In addition, with such a device, whether the result of controlling the flow control valve based on the estimated valve flow rate is operating correctly can be confirmed by referring to the actual valve flow rate calculated by the flow rate calculation unit.

For example, in order to further improve the response speed of the transient response in flow control or to make the flow control less susceptible to the effects of fluctuations in the supply pressure to the chamber, it is sufficient to further include a pressure control valve provided upstream of the first pressure sensor, and a pressure control unit that controls the pressure control valve so that the first pressure becomes a set pressure.

A control method for realizing flow control without using fluid resistance within a flow control device further includes an aperture sensor that measures the aperture of the flow control valve. The flow controller includes a map storage unit that stores a map showing the relationship between at least the second pressure, the aperture of the flow control valve, and the flow rate of the fluid passing through the flow control valve, a map reference unit that references the map based on the measured second pressure and the set flow rate and outputs the corresponding aperture of the flow control valve as a set aperture, and an aperture control unit that controls the flow control valve so that the measured aperture measured by the aperture sensor becomes the set aperture.

In order to implement constant pressure control in the above-mentioned control method and improve the response speed of flow control, the control method may further include a pressure control valve provided upstream of the second pressure sensor, and a pressure control unit that controls the pressure control valve so that the second pressure becomes a set pressure.

In order to ensure that the valve flow rate output from the flow control valve is an accurate value even if changes occur over time, etc., it is sufficient to further include a calibrator that updates the map based on the actual valve flow rate calculated by the valve flow rate calculation unit.

In order to use the map as is when an accidental error occurs and to update the map only when a systematic error occurs, the calibrator needs to update the map when the difference between the estimated valve flow rate and the actual measured valve flow rate is equal to or greater than a predetermined value.

A specific configuration for calculating the valve flow rate passing through the flow control valve based on the second pressure and the third pressure includes a valve flow rate calculation unit that calculates the actual valve flow rate based on the conductance of the flow control valve and the differential pressure between the second pressure and the third pressure.

For example, a configuration example for accelerating the transient response control of the flow rate of the fluid passing through the flow control valve may include a fluid resistance provided upstream of the second pressure sensor, a first pressure sensor provided upstream of the fluid resistance, a resistance flow rate calculation unit that calculates the flow rate of the fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure, and a pressure control valve provided upstream of the first pressure sensor, and the flow controller includes a valve flow rate estimation unit that estimates the flow rate passing through the flow control valve based on the resistance flow rate calculated by the resistance flow rate calculation unit and the time change amount of the first pressure measured by the first pressure sensor, and an opening control unit that controls the flow control valve so that the estimated valve flow rate estimated by the valve flow rate estimation unit becomes the set flow rate. In this case, the flow rate of the fluid passing through the flow control valve can be calculated using information on the pressure between the pressure control valve and the fluid resistance, thereby improving the control performance of the transient response.

A flow control device that includes a flow control valve provided in a main flow path, a second pressure sensor provided upstream of the flow control valve, a pressure control valve provided upstream of the second pressure sensor, and one or more temperature sensors provided in a volume formed between the pressure control valve and the flow control valve, can accurately measure the temperature of the fluid that is actually flowing, compared to a case in which a temperature sensor is provided outside the volume and indirectly measures the temperature of the fluid. As a result, it is possible to accurately calculate, for example, a flow rate by using the accurate fluid temperature.

In order to stabilize the temperature of the fluid within the volume and enable more accurate measurement of the temperature of the fluid flowing within the volume, the volume may further include a mesh member filled therein.

In order to achieve more accurate flow control than conventional methods based on the accurately measured temperature of the fluid, it is sufficient to further include a flow controller that controls the flow control valve based on at least the second pressure measured by the second pressure sensor, the temperature measured by the temperature sensor, and the set flow rate.

If the device further includes a valve flow rate calculation unit that calculates the flow rate of the fluid passing through the flow control valve based on at least the second pressure and the measured temperature measured by the temperature sensor, it is possible to accurately calculate the flow rate of the fluid passing through the flow control valve by utilizing the accurately measured temperature.

In order to enable more accurate calculation of the flow rate of the fluid passing through the flow control valve even during flow control, while preventing an increase in flow path resistance between the flow control valve and the target to which the fluid is to be supplied, the system may further include a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to the target to which the fluid is to be supplied, a second branch flow path that branches off from the main flow path downstream of the flow control valve, and a third pressure sensor provided on the second branch flow path, and the valve flow rate calculation unit is configured to calculate the flow rate of the fluid passing through the flow control valve based on at least the second pressure, the third pressure measured by the third pressure sensor, and the measured temperature.

In order to obtain the same effect as the flow control device of the present invention by updating a program used in an existing flow control device, it is sufficient to use a program for a flow control device that includes a flow control valve provided in a main flow path, a second pressure sensor provided upstream of the flow control valve, a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a fluid supply target, a second branch flow path that branches off from the main flow path downstream of the flow control valve, and a third pressure sensor provided on the second branch flow path, the program causing a computer to perform the functions of a flow controller that controls the flow control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate, and a valve flow calculation unit that calculates the flow rate of fluid passing through the flow control valve based on at least the second pressure and the third pressure measured by the third pressure sensor.

The program for the flow control device may be distributed electronically or may be recorded on a program recording medium such as a CD, DVD, HDD, or flash memory.

In this way, with the flow control device according to the present invention, the third pressure sensor is provided on the second branch flow path that is formed downstream of the flow control valve and is not connected to the target to which the fluid is supplied, so that the flow rate of the fluid passing through the flow control valve can be measured based on the output of the third pressure sensor without increasing the flow path resistance downstream of the flow control valve. As a result, it is possible to control the flow rate while actually monitoring the valve flow rate.

1 is a schematic diagram showing a configuration of a flow rate control device according to a first embodiment of the present invention; FIG. 2 is a schematic diagram showing a configuration of a flow rate controller of the flow rate control device according to the first embodiment of the present invention. FIG. 5 is a schematic diagram showing the configuration of a flow rate control device according to a second embodiment of the present invention. FIG. 6 is a schematic diagram showing a configuration of a flow rate controller of a flow rate control device according to a second embodiment of the present invention. FIG. 11 is a schematic diagram showing the configuration of a flow rate control device according to a third embodiment of the present invention. FIG. 11 is a schematic diagram showing a configuration of a flow rate controller of a flow rate control device according to a third embodiment of the present invention. FIG. 13 is a schematic diagram showing the configuration of a flow rate control device according to a fourth embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing details of the internal structure of a flow control device according to a fourth embodiment of the present invention.

DESCRIPTION OF SYMBOLS 100...Flow control device FM...Flow sensor 1...Resistance flow calculation section 2...Flow controller 21...Map memory section 22...Map reference section 23...Opening control section 24...Valve flow estimation section 25...Time change calculation section 26...Output section 3...Valve flow calculation section 4...Calibrator 5...Pressure control section ML...Main flow path DL1...First branch flow path DL2...Second branch flow path P1...First pressure sensor P2...Second pressure sensor P3...Third pressure sensor V1...Pressure control valve V2...Flow control valve R...Fluid resistance

A flow control device 100 according to a first embodiment of the present invention will be described with reference to Figure 1. The flow control device 100 of the first embodiment is used to supply a fluid gas to a chamber CN at a set flow rate, for example, in a semiconductor manufacturing process.

That is, as shown in FIG. 1, the flow control device 100 includes a fluid device consisting of a sensor and a valve provided in a flow path, and a control mechanism COM that controls the fluid device.

In order from the upstream side, the main flow path ML is provided with a supply pressure sensor P0, a pressure control valve V1, a first pressure sensor P1, a fluid resistance R, a second pressure sensor P2, and a flow control valve V2. The main flow path ML is branched into two paths downstream of the flow control valve V2: a first branch flow path DL1 connected to the chamber CN to which the fluid is supplied, and a second branch flow path DL2 not connected to the chamber CN and with its downstream end closed. In addition, a third pressure sensor P3 is provided on the second branch flow path DL2, which is a third pressure sensor that measures the pressure downstream of the flow control valve V2. Here, the fluid resistance R is, for example, a laminar flow element, and generates a differential pressure according to the gas flow rate flowing before and after it.

The supply pressure sensor P0 is used to monitor the pressure of the gas supplied from the upstream side. Note that the supply pressure sensor P0 may be omitted in cases where it is guaranteed that the supply pressure is stable.

The first pressure sensor P1 measures the first pressure, which is the pressure of gas charged in the upstream volume, which is the volume between the pressure control valve V1, which is located upstream in the flow path, and the fluid resistance R.

The second pressure sensor P2 measures the second pressure, which is the pressure of gas charged to the downstream volume, which is the volume in the flow path between the fluid resistance R and the flow control valve V2 located downstream.

In this way, the first pressure sensor P1 and the second pressure sensor P2 respectively measure the pressure in the two volumes formed by the pressure control valve V1, the fluid resistance R, and the flow control valve V2. In other words, the first pressure sensor P1 and the second pressure sensor P2 measure the pressure in the respective volumes located before and after the fluid resistance R.

In the first embodiment, the pressure control valve V1 and the flow control valve V2 are of the same type, for example, a piezoelectric valve in which a valve body is driven against a valve seat by a piezoelectric element. The pressure control valve V1 and the flow control valve V2 each change their opening according to a voltage input as an operation amount. Here, at least the flow control valve V2 is equipped with an opening sensor V2, which can measure the current opening. The opening sensor V2 can be a displacement sensor that outputs according to the movement of the valve body or a plunger or actuator connected to the valve body.

Next, the control mechanism COM will be described in detail.

The control mechanism COM is a so-called computer equipped with, for example, a CPU, memory, A/D converter, D/A converter, input/output means, etc., and performs the functions of at least the resistance flow calculation unit 1, flow controller 2, valve flow calculation unit 3, calibrator 4, and pressure control unit 5 by executing the flow control device program stored in the memory and various devices working together.

The resistance flow calculation unit 1, together with the first pressure sensor P1, the fluid resistance R, and the second pressure sensor P2, constitutes a so-called differential pressure type flow sensor FM. In other words, the resistance flow calculation unit 1 receives the first pressure measured by the first pressure sensor P1 and the second pressure measured by the second pressure sensor P2 as inputs, calculates the resistance flow rate, which is the flow rate of the fluid flowing through the fluid resistance R, and outputs it. Here, the calculation formula for the flow rate used in the resistance flow calculation unit 1 can be an existing one. The resistance flow rate calculated by the resistance flow calculation unit 1 changes continuously, but there is a certain time delay with respect to the actual flow rate passing through the flow control valve V2, which is realized by controlling the flow control valve V2.

The flow controller 2 controls the flow control valve V2 so that the valve flow rate, which is the flow rate of the fluid passing through the flow control valve V2, becomes the set flow rate based on at least the second pressure measured by the second pressure sensor P2 and the set flow rate set by the user. In the first embodiment, the flow controller 2 estimates the valve flow rate from the resistance flow rate calculated by the resistance flow rate calculation unit 1 and the second pressure measured by the second pressure sensor, and performs flow feedback control of the flow control valve V2 so that the valve flow rate becomes the set flow rate. Here, the valve flow rate is estimated by referring to a map based on the resistance flow rate and the second pressure.

Specifically, as shown in Figure 2, the flow controller 2 has a map memory unit 21, a map reference unit 22, and an opening control unit 23.

The map storage unit 21 stores a map showing the relationship between at least the resistance flow rate, the second pressure, and the valve flow rate. Such a map is created by, for example, implementing each combination of resistance flow rate and second pressure, placing a flow sensor downstream of the flow control valve V2 to perform actual measurements, and storing the relationship between each parameter in a database. The map may be in the form of a table, or may be an equation showing the relationship between each parameter.

The map reference unit 22 refers to the map stored in the map storage unit 21 based on the measured resistance flow rate and the second pressure, and outputs the corresponding valve flow rate as an estimated valve flow rate to the opening control unit 23. The valve flow rate estimated in this manner is configured to have a smaller delay with respect to the actual valve flow rate compared to the resistance flow rate.

The opening control unit 23 controls the flow control valve V2 so that the estimated valve flow rate becomes the set flow rate. In the first embodiment, the voltage applied to the flow control valve V2 is feedback controlled so that the deviation between the estimated valve flow rate and the set flow rate becomes small.

The valve flow calculation unit 3 shown in FIG. 1 calculates the flow rate of the fluid passing through the flow control valve V2 based on at least the second pressure and the third pressure measured by the third pressure sensor. Specifically, the valve flow calculation unit 3 calculates the actual valve flow rate from the conductance determined from the opening of the flow control valve V2 and the differential pressure between the second pressure and the third pressure. Here, the valve flow calculation unit 3 stores a table showing the relationship between the opening and the conductance, and outputs the actual valve flow rate using the conductance according to the opening measured by the opening sensor V21. In this way, the valve flow calculation unit 3 calculates the flow rate of the fluid passing through the flow control valve V2 based on the actual measurement value, so unlike the estimated valve flow rate, this valve flow rate is a value actually measured in real time during flow control. In addition, in this embodiment, the actual valve flow rate is used to update the map.

The calibrator 4 updates the map in the flow controller 2 based on the actual valve flow calculated by the valve flow calculation unit 3 as shown in Figures 1 and 2. Specifically, when the difference between the estimated valve flow used to control the flow control valve V2 and the actual valve flow becomes equal to or greater than a predetermined value, the valve flow corresponding to the second pressure and resistance flow at that time in the map is updated to the actual valve flow.

The pressure control unit 5 controls the pressure control valve V1 based on the set pressure set by the user and the first pressure measured by the first pressure sensor P1. Specifically, the pressure control unit 5 performs pressure feedback control of the voltage applied to the pressure control valve V1 so that the deviation between the set pressure and the first pressure is reduced.

According to the flow control device 100 of the first embodiment configured in this manner, the flow rate of the fluid passing through the flow control valve V2 can be monitored based on the second pressure and the third pressure while performing flow rate feedback control so as to achieve a set flow rate using the flow control valve V2.

In addition, the third pressure sensor P3 provided downstream of the flow control valve V2 is provided on the second branch flow path DL2 that is not connected to the chamber CN to which the fluid is supplied, so that the device provided to actually measure the valve flow rate does not increase the flow path resistance between the flow control valve V2 and the chamber CN. Therefore, the flow control device 100 of the first embodiment can maintain a high response speed while ensuring the accuracy of the valve flow rate of the fluid passing through the flow control valve V2.

A modified example of the first embodiment is described.

The map may show the relationship between resistance flow, second pressure, temperature, and valve flow to allow for the effect of fluid temperature to be taken into account.

In this case, for example, the temperature of the fluid resistance R can be measured by a temperature sensor such as a thermistor, and the map reference unit 22 can be configured to output the valve flow rate by referring to the map based on the measured temperature, second pressure, and resistance flow rate.

In addition, the conductance used in the valve flow calculation unit 3 may be set to a different value depending on the temperature measured by the temperature sensor.

Next, we will explain the second embodiment of the present invention.

As shown in Figures 3 and 4, the flow control device 100 of the second embodiment has a different configuration of the flow controller 2 from that of the first embodiment.

Specifically, the flow controller 2 is configured to calculate the estimated valve flow rate based on the amount of change in the first pressure over time, rather than by referring to a map. Therefore, whereas the second pressure was input to the flow controller 2 in the first embodiment, the first pressure is input to the flow controller 2 in the second embodiment, as shown in FIG. 3.

Specifically, the flow controller 2 is provided with a valve flow estimation unit 24 which estimates the flow rate passing through the flow control valve V2 based on the resistance flow rate calculated by the resistance flow rate calculation unit 1 instead of the map memory unit 21 and the map reference unit 22 as shown in FIG. 4 and the amount of change over time in the first pressure measured by the first pressure sensor P1.

The valve flow rate estimation unit 24 includes a time change amount calculation unit 25 that calculates, for example, a time derivative value of the first pressure as the time change amount of the first pressure and outputs a value obtained by multiplying the derivative value by a predetermined coefficient, and an output unit 26 that calculates an estimated valve flow rate based on the time change amount and the resistance flow rate from the time change amount calculation unit 25. Note that the time change amount calculation unit 25 is not limited to a unit that differentiates the first pressure, and may be a unit that performs a difference calculation for each sampling time of the first pressure sensor P1.

In addition, in the second embodiment, when the difference between the estimated valve flow rate and the actual measured valve flow rate is equal to or greater than a predetermined value, the calibrator 4 corrects the coefficient used in the time change calculation unit 25 in accordance with the difference.

The flow control device 100 of the second embodiment configured in this way can calculate the estimated valve flow rate by correcting the resistance flow rate based on the time differential value of the first pressure. In addition, since a value that takes into account the change in upstream pressure in the resistance flow rate can be output, it becomes possible to correct transient changes in the valve flow rate.

Next, the flow control device 100 relating to the third embodiment of the present invention will be described with reference to Figures 5 and 6.

The flow control device 100 of the third embodiment differs from the flow control device 100 shown in the first and second embodiments in that no fluid resistance R is provided between the pressure control valve V1 and the flow control valve V2, and the space between the pressure control valve V1 and the flow control valve V2 is configured as one large volume VL. In addition, the first pressure sensor is omitted, and only the second pressure sensor P2 is provided. In other words, the function for measuring the flow rate is omitted in this volume, and the pressure control valve V1 is also controlled based on the output of the second pressure sensor P2.

In addition, since the resistance flow rate is not measured, the configuration of the flow rate controller 2 is also different from that of the first and second embodiments, as shown in Fig. 6. That is, the flow rate controller 2 calculates a set opening corresponding to the realized valve flow rate based on the second pressure measured by the second pressure sensor P2 and the set flow rate, and controls the flow rate control valve V2 so that the deviation between the calculated set opening and the measured opening measured by the opening sensor V21 is small.

Specifically, in the flow controller 2 of the third embodiment, the map indicates the relationship between at least the second pressure, the opening of the flow control valve V2, and the flow rate of the fluid passing through the flow control valve V2. The map reference unit 22 then references the map based on the measured second pressure and measured opening, and the set flow rate set by the user, and outputs the corresponding set opening.

In addition, the opening control unit 23 controls the voltage applied to the flow control valve V2 so that the measured opening output from the opening sensor V21 provided in the flow control valve V2 becomes the set opening output from the map reference unit 22.

5, the valve flow calculation unit 3 receives the second pressure, which is the pressure on the upstream side of the flow control valve V2, the third pressure, which is the pressure on the downstream side, and the measured opening, and calculates the actual valve flow based on these values. More specifically, the valve flow calculation unit 3 calculates the actual valve flow, for example, for each control cycle, based on the differential pressure between the second pressure and the third pressure, and the conductance according to the measured opening of the flow control valve V2.

As shown in Figures 5 and 6, the calibrator 4 updates the map each time the actual valve flow rate is calculated by the valve flow rate calculation unit 3. Specifically, the calibrator 4 updates the flow rate to the actual flow rate in the set of second pressure, opening, and flow rate that is referenced to output the set opening.

With the flow control device 100 of the third embodiment configured in this manner, it is possible to estimate the valve flow rate passing through the flow control valve V2 and perform flow control without measuring the flow rate based on differential pressure using fluid resistance as in the first and second embodiments.

In addition, the valve flow rate passing through the flow control valve V2 is actually measured from the pressure before and after the flow control valve V2, and the map is updated sequentially, so that even when the flow control valve V2 is controlled as described above, the valve flow rate can be controlled essentially always based on the measured flow rate.

Therefore, unlike conventional techniques, it is possible to guarantee the flow rate even when fluid is being supplied to the chamber CN. In addition, it is possible to avoid placing devices that cause flow resistance in the main flow path ML and the second branch flow path DL2 as much as possible, so it is possible to guarantee the accuracy of the flow rate while improving, for example, the transient response characteristics.

A modified example of the third embodiment is described.

In the third embodiment, the flow control valve V2 may also be controlled directly from the measured flow rate, rather than controlling the flow control valve V2 by referring to a map. Specifically, the flow controller 2 may not include the map storage unit 21 and the map reference unit 22, and the actual valve flow rate calculated by the valve flow rate calculation unit 3 may be fed back to the opening control unit 23. In other words, the opening control unit 23 may control the voltage applied to the flow control valve V2 so as to reduce the deviation between the actual valve flow rate calculated from the second pressure measured by the second pressure sensor P2 and the third pressure measured by the third pressure sensor P3, and the set flow rate.

In addition, the flow control device 100 may further include a temperature sensor that measures the temperature of the fluid flowing through the volume VL between the pressure control valve V1 and the flow control valve V2, and the flow control may be performed based on a map that also takes this temperature into consideration. That is, the map indicates the relationship between the second pressure, the aperture, the temperature, and the flow rate, and the map reference unit 22 may output the set aperture from the measured second pressure, aperture, and temperature.

Next, a fourth embodiment of the present invention will be described with reference to Figures 7 and 8. Note that the same reference numerals will be used to designate components corresponding to those described in the third embodiment.

In the flow control device 100 of the fourth embodiment, similar to the flow control device 100 shown in the third embodiment, no fluid resistance R is provided between the pressure control valve V1 and the flow control valve V2, and the space between the pressure control valve V1 and the flow control valve V2 is configured as one large volume VL.

More specifically, between the pressure control valve V1 and the flow control valve V2, there is provided a volume VL which is a cavity formed inside, and a block body BL in which an inlet path and an outlet path for introducing and discharging gas into and from the volume VL are formed. In addition, a pressure control valve V1 is provided at a gas inlet of the block body BL, and a flow control valve V2 is provided at a gas outlet of the block body BL. As shown in Figure 8, in the volume VL formed inside the block body BL, there are provided a mesh member M which fills the entire volume VL, and a temperature sensor TS for measuring the temperature of the gas in the volume VL.

The mesh member M is selected to have a mesh number that does not substantially impede the passage of gas, while making the temperature of the gas present in the volume VL approximately uniform. By filling the volume VL with the mesh member M, the stability of the measured temperature during temperature measurement for updating the map described below is improved, and accurate values can be obtained.

The temperature sensor TS is provided so as to contact a part of the mesh member M in the volume VL. As shown in FIG. 8, the temperature sensor TS is provided in contact with the inner wall surface of the block body BL in the volume VL, or in contact with the mesh member M at a position close to the inner wall surface, so that the wiring can be easily taken out to the outside of the block body BL. The temperature sensor TS is provided in a position where it directly contacts the gas, so that a sensor having corrosion resistance is appropriately selected according to the type of gas to be flowed. In this embodiment, two temperature sensors TS are provided in the volume VL, and the average value of the measured temperatures of these temperature sensors TS is adopted as the temperature of the gas. The number of temperature sensors TS can be appropriately selected, and may be one or three or more. The temperature sensor TS may be provided in the volume VL and may directly measure the temperature of the fluid.

In the flow controller 2 of the fourth embodiment, the map indicates the relationship between at least the second pressure, the opening of the flow control valve V2, the gas temperature, and the flow rate of the gas passing through the flow control valve V2. The map reference unit 22 then references the map based on the measured second pressure, the measured opening, the measured temperature measured by the temperature sensor TS, and the set flow rate set by the user, and outputs the corresponding set opening.

In addition, the opening control unit 23 controls the voltage applied to the flow control valve V2 so that the measured opening output from the opening sensor V21 provided in the flow control valve V2 becomes the set opening output from the map reference unit 22.

The valve flow calculation unit 3 calculates the actual valve flow rate using the existing ROF method or the like based on the second pressure and the measured temperature acquired while the flow control by the opening control unit 23 is not performed and the calibration control for updating the map is performed. The ROF method can be briefly explained as follows. First, a gas of a predetermined pressure is charged into the space between the pressure control valve V1 and the flow control valve V2. Then, the flow control valve V2 is opened at a predetermined opening, causing a pressure drop in the gas in the space. The flow rate passing through the flow control valve V2 can be calculated based on the second pressure measured during this pressure drop, the measured temperature, the volume value of the space in which the gas was charged, and an equation obtained by time-differentiating the state equation of the gas. In the fourth embodiment, the mesh member M is filled in the volume VL and the temperature of the gas is uniformed, so that the temperature of the gas during the pressure drop can also be accurately measured. As a result, the valve flow calculation unit 3 can accurately calculate the actual valve flow rate.

The calibrator 4 updates the map each time an actual valve flow rate is calculated by the valve flow rate calculation unit 3. Specifically, the calibrator 4 updates the map to the actual valve flow rate with the flow rate corresponding to the set of the second pressure, opening, and temperature used when the valve flow rate calculation unit 3 calculates the actual valve flow rate.

In the flow control device 100 of the fourth embodiment configured in this manner, the mesh member M is filled in the volume VL between the pressure control valve V1 and the flow control valve V2, and a temperature sensor TS is provided in the volume VL, so that, for example, the gas temperature required when calculating the actual valve flow rate based on the gas state equation can be accurately obtained. As a result, the actual valve flow rate calculated when updating the flow rate map can be made more accurate, and the accuracy of the final flow control can be further improved.

A modified example of the fourth embodiment will be described. In the fourth embodiment, the mesh member M was filled in the volume VL, but the mesh member M may be omitted and only the temperature sensor TS may be provided in the volume VL. In the fourth embodiment, as in the third embodiment, the main flow path ML is branched into a first branch flow path DL1 connected to a fluid supply target downstream of the flow control valve V2 and a second branch flow path DL2 not connected to a fluid supply target, and a third pressure sensor P3, which is a third pressure sensor, may be provided in the second branch flow path DL2. In this way, when each branch flow path DL1, DL2, and the third pressure sensor P3 are provided, the valve flow calculation unit 3 may be configured to calculate the flow rate of the fluid passing through the flow control valve V2 based on at least the second pressure measured by the second pressure sensor P2, the third pressure measured by the third pressure sensor P3, and the measured temperature measured by the temperature sensor TS.

Other embodiments are described below.

The method of calculating the measured valve flow rate based on the second pressure and the third pressure is not limited to the calculation using conductance as shown in each embodiment. For example, a map showing the relationship between the second pressure, the third pressure, and the valve flow rate may be measured in advance and stored in a database, and the map may be referenced with the measured second pressure and third pressure to output the corresponding flow rate as the valve flow rate. Also, the calibrator may be omitted and only a valve flow rate calculation unit may be provided, and the flow control valve may be feedback-controlled with the measured valve flow rate calculated by the valve flow rate calculation unit.

In addition, parts of each embodiment may be combined or modified as long as this does not go against the spirit of the present invention.

In this way, the present invention can provide a flow control device that can ensure the accuracy of the valve flow rate without increasing the flow path resistance between the flow control valve and the supply target.

Claims (14)

A flow control valve provided in the main flow path;
A second pressure sensor provided upstream of the flow control valve;
a flow rate controller that controls the flow rate control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate;
a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a supply target of the fluid;
a second branch flow path branching from the main flow path downstream of the flow control valve;
a third pressure sensor provided on the second branch flow path;
a valve flow rate calculation unit that calculates a flow rate of a fluid passing through the flow control valve based on at least the second pressure and a third pressure measured by the third pressure sensor;
a fluid resistance provided upstream of the second pressure sensor;
a pressure control valve provided upstream of the fluid resistance ;
a pressure control unit that controls the pressure control valve so that the second pressure becomes a set pressure;
A first pressure sensor provided upstream of the fluid resistance;
a resistance flow rate calculation unit that calculates a flow rate of the fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure,
The flow rate controller,
a map storage unit that stores a map indicating a relationship between at least the resistance flow rate calculated by the resistance flow rate calculation unit, the second pressure, and a flow rate of the fluid passing through the flow control valve;
a map reference unit that references the map based on the measured resistance flow rate and the second pressure, and outputs a flow rate of the fluid passing through the corresponding flow control valve as an estimated valve flow rate;
an opening control unit that controls the flow control valve so that the estimated valve flow rate becomes the set flow rate. The flow rate control device according to claim 1 , further comprising a pressure control section that controls the pressure control valve so that the first pressure becomes a set pressure. An opening sensor for measuring an opening of the flow control valve is further provided,
The flow rate controller,
a map storage unit configured to store a map indicating a relationship between at least the second pressure, an opening degree of the flow control valve, and a flow rate of the fluid passing through the flow control valve;
a map reference unit that references the map based on the measured second pressure and the set flow rate, and outputs a corresponding opening degree of the flow control valve as a set opening degree;
2. The flow control device according to claim 1, further comprising an opening control section that controls the flow control valve so that the measured opening measured by the opening sensor becomes the set opening. A first pressure sensor provided upstream of the fluid resistance;
a resistance flow rate calculation unit that calculates a flow rate of the fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure,
4. The flow control device according to claim 1, further comprising a calibrator that updates a map indicating a relationship between at least the resistance flow rate calculated by the resistance flow rate calculation unit, the second pressure, and the flow rate of the fluid passing through the flow control valve, based on an actual valve flow rate calculated by the valve flow rate calculation unit. 5. The flow control device according to claim 4, wherein the calibrator refers to the map based on the measured resistance flow rate and the second pressure, and updates the map when a difference between an estimated valve flow rate, which is the flow rate of fluid passing through the corresponding flow control valve, and the actual measured valve flow rate is equal to or greater than a predetermined value. 6. The flow control device according to claim 1, wherein the valve flow calculation unit calculates an actual valve flow rate calculated by the valve flow calculation unit based on the conductance of the flow control valve and the differential pressure between the second pressure and the third pressure. A flow control valve provided in the main flow path;
A second pressure sensor provided upstream of the flow control valve;
a flow rate controller that controls the flow rate control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate;
a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a supply target of the fluid;
a second branch flow path branching from the main flow path downstream of the flow control valve;
a third pressure sensor provided on the second branch flow path;
a valve flow rate calculation unit that calculates a flow rate of a fluid passing through the flow control valve based on at least the second pressure and a third pressure measured by the third pressure sensor;
a fluid resistance provided upstream of the second pressure sensor or a volume formed in place of the fluid resistance;
a pressure control valve provided upstream of the fluid resistance or the volume;
a pressure control unit that controls the pressure control valve so that the second pressure becomes a set pressure;
a fluid resistance provided upstream of the second pressure sensor;
A first pressure sensor provided upstream of the fluid resistance;
a resistance flow rate calculation unit that calculates a flow rate of the fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure;
a pressure control valve provided upstream of the first pressure sensor,
The flow rate controller,
a valve flow rate estimating unit that estimates a flow rate passing through the flow control valve based on the resistance flow rate calculated by the resistance flow rate calculating unit and the amount of change over time of the first pressure measured by the first pressure sensor;
an opening control unit that controls the flow control valve so that the estimated valve flow rate estimated by the valve flow rate estimating unit becomes the set flow rate. A flow control valve provided in the main flow path;
A second pressure sensor provided upstream of the flow control valve;
a pressure control valve provided upstream of the second pressure sensor;
one or more temperature sensors disposed within a volume defined between the pressure control valve and the flow control valve;
A flow rate control device comprising: a mesh member filled in the volume. 9. The flow control device according to claim 8 , further comprising a flow controller that controls the flow control valve based on at least the second pressure measured by the second pressure sensor, the temperature measured by the temperature sensor, and a set flow rate. The flow control device according to claim 8 or 9, further comprising a valve flow rate calculation unit that calculates a flow rate of a fluid passing through the flow control valve based on at least a second pressure measured by the second pressure sensor and a measured temperature measured by the temperature sensor. a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a supply target of the fluid;
a second branch flow path branching from the main flow path downstream of the flow control valve;
A third pressure sensor provided on the second branch flow path,
The flow control device according to claim 10, wherein the valve flow calculation unit is configured to calculate the flow rate of the fluid passing through the flow control valve based on at least the second pressure, the third pressure measured by the third pressure sensor, and the measured temperature. A flow rate measurement method for use in a flow control device including a flow rate control valve provided in a main flow path, a second pressure sensor provided upstream of the flow rate control valve, and a flow rate controller that controls the flow rate control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate, comprising:
a first branch flow path which branches off from the main flow path downstream of the flow control valve and is connected to a target to which a fluid is to be supplied; a second branch flow path which branches off from the main flow path downstream of the flow control valve; a third pressure sensor provided on the second branch flow path; a fluid resistor provided upstream of the second pressure sensor; a pressure control valve provided upstream of the fluid resistor ; and a first pressure sensor provided upstream of the fluid resistor,
Calculating a flow rate of the fluid passing through the flow control valve based on at least the second pressure and a third pressure measured by the third pressure sensor;
controlling the pressure control valve so that the second pressure becomes a set pressure;
Calculating a flow rate of the fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure;
storing a map showing a relationship between at least the calculated resistance flow, the second pressure, and a flow rate of the fluid passing through the flow control valve;
referring to the map based on the measured resistance flow rate and the second pressure, and outputting the flow rate of the fluid passing through the corresponding flow control valve as an estimated valve flow rate;
A flow rate measuring method, comprising controlling the flow rate control valve so that the estimated valve flow rate becomes the set flow rate . a first branch flow path branching from the main flow path downstream of the flow control valve and connected to a target to which a fluid is to be supplied; a second branch flow path branching from the main flow path downstream of the flow control valve; a third pressure sensor provided on the second branch flow path; a fluid resistor provided upstream of the second pressure sensor; a pressure control valve provided upstream of the fluid resistor ; and a first pressure sensor provided upstream of the fluid resistor ,
a function as a flow rate controller that controls the flow rate control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate;
a function as a valve flow rate calculation unit that calculates a flow rate of a fluid passing through the flow control valve based on at least the second pressure and a third pressure measured by the third pressure sensor;
a function as a pressure control unit that controls the pressure control valve so that the second pressure becomes a set pressure;
a resistance flow rate calculation unit that calculates a flow rate of a fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure;
The function of the flow rate controller is to
a function as a map storage unit that stores a map showing a relationship between at least the resistance flow rate calculated by the resistance flow rate calculation unit, the second pressure, and the flow rate of the fluid passing through the flow control valve; and
a function of a map reference unit that refers to the map based on the measured resistance flow rate and the second pressure, and outputs the flow rate of the fluid passing through the corresponding flow control valve as an estimated valve flow rate;
and a function as an opening control unit that controls the flow control valve so that the estimated valve flow rate becomes the set flow rate . A flow control valve provided in the main flow path;
A second pressure sensor provided upstream of the flow control valve;
a flow rate controller that controls the flow rate control valve based on at least a second pressure measured by the second pressure sensor and a set flow rate;
a first branch flow path that branches off from the main flow path downstream of the flow control valve and is connected to a supply target of the fluid;
a second branch flow path branching from the main flow path downstream of the flow control valve;
a third pressure sensor provided on the second branch flow path;
a valve flow rate calculation unit that calculates a flow rate of a fluid passing through the flow control valve based on at least the second pressure and a third pressure measured by the third pressure sensor;
a volume in which the second pressure sensor is provided and which is formed in place of a fluid resistance;
a pressure control valve provided upstream of the volume;
a pressure control unit that controls the pressure control valve so that the second pressure becomes a set pressure.

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