JP2002157019A - Massflow controller, regulating method of massflow controller, and storage medium with regulation program of massflow controller stored therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a massflow controller capable of omitting the waste in performance of each circuit system thereof and being improved in precision by regulating the device signal of the value of the massflow controller so as to be within its operation range, regulating method of massflow controller and a storage medium with regulation program of massflow controller stored therein. SOLUTION: This massflow controller 1 comprises a control part 5 for outputting an opening signal So so that the flow rate Q of a fluid running in a passage 2 is a flow rate shown by a flow set signal Sin, and a valve drive circuit 6 for receiving the opening signal So and outputting a value operation signal Sb for opening and closing a valve 3 provided within the passage 2. The valve drive circuit 6 outputs the valve operation signal Sb within an output range B regulated according to the characteristic of the valve 3 in conformation to the opening signal So.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow controller for measuring a mass flow rate of a fluid and controlling the fluid flow rate.
The present invention relates to a mass flow controller adjustment method and a recording medium on which a mass flow controller adjustment program is recorded.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram schematically showing a configuration of a conventional mass flow controller 21. In FIG. 7, reference numeral 22 denotes a fluid flow path, 23 denotes a valve provided in the flow path 22, 24 denotes a flow rate measurement unit provided in the same flow path 22, and 25 denotes a flow rate of the fluid flowing through the flow path 22. The control unit 26 outputs the opening signal So so as to make the flow rate indicated by the signal Sin, and the valve driving circuit 26 receives the opening signal So and outputs a valve operation signal So 'for opening and closing the valve 23. .

An AD converter 27 converts an analog signal such as a flow signal Sq measured by the flow measuring unit 24 or a flow setting signal Sin into a digital signal.
Reference numeral 8 denotes a DA converter for converting the opening signal So from a digital signal to an analog signal, and 29 denotes a storage unit provided in the control unit 25.

The control unit 25 outputs an opening signal So obtained by dividing the minimum value to the maximum value by 100 in order to adjust the opening of the valve 23 by, for example, PID control, and the DA converter 28 converts this into an analog signal. Convert. And
The valve drive circuit 26 constitutes an amplifier for adjusting the opening signal So converted into an analog signal to a voltage level suitable for operating the valve 23, and this voltage level is controlled by the control unit 2.
5 is adjusted according to the type of the valve 23 used by the adjustment signal Sa output from the control unit 5.

For example, the maximum operating voltage of the valve 23 is 15 V
, The valve drive circuit 26 sets the opening signal So to 0 to
It is converted into a 15V valve operation signal So '. On the other hand, when the maximum operation voltage of the valve 23 is 150V, the valve drive circuit 26 converts the opening signal So into a valve operation signal So 'of 0 to 150V. That is, the valve operation signal S
o ′ is proportional to the opening signal So, and the valve drive circuit 26 operates as a voltage amplification amplifier.

Further, the valve driving circuit 26 takes the operating range of the valve into consideration and amplifies the valve operating signal S which is amplified.
The size of o 'may be adjusted. In other words, even if the maximum operating voltage of the valve 23 is 15 V, if it is clear that almost all the valves 23 are fully opened while receiving the signal of the voltage 10 V, the amplification range by the valve driving circuit 26 is changed. It was sometimes set to 0-10V.

[0007]

However, the operation range of the valve from when the valve 23 starts to open until it is fully opened is the amplification range (full scale) of the valve operation signal So '.
This is problematic in that it causes a reduction in the resolution of the circuit system.

FIG. 8 shows the magnitude X of the valve operation signal So '.
FIG. 4 is a diagram illustrating a relationship between (voltage) and a flow rate of a fluid flowing through a flow path 22. In the case of the valve 23 shown in FIG. 8, the valve 23 starts to open when the valve operation signal So 'is slightly larger than about 2 V, and when the valve operation signal So' is slightly before about 3 V, the valve 23 is fully opened. I understand. Therefore, when the valve 23 having the characteristic shown in FIG. 8 is used, the actual operating range of the valve 23 is 2 to 3 V, which is extremely large compared to the amplification range (0 to 10 V) of the valve operation signal So ′. It was inevitable that it would narrow.

The narrower the operation range of the valve 23 is compared to the amplification range of the valve operation signal So ',
Control unit 25, DA converter 28, valve drive circuit 26
The ability of such a circuit system could not be fully utilized. For example, even if the control unit 25 calculates and outputs a 100-stage opening signal So, and the DA converter 28 has a resolution for converting the opening signal So into a 100-stage analog value, the characteristic shown in FIG. When the valve 23 was used, flow control could be performed only with a resolution of 10 steps or less within the operating range of the valve 23.

For this reason, the control unit 25 controls the DA
As in the case where the converter 28 is used, the opening degree signal So
A sudden change in the flow rate with respect to the change in the flow rate makes it difficult to control the flow rate. That is, unless the operation speed and the calculation accuracy of the control unit 25 are increased more than necessary, a problem such as fluctuation of the flow rate control may occur.

Therefore, it is conceivable that the amplification range by the valve drive circuit 26 is reduced and the opening signal So is set to, for example, 0 to 4 V. However, the voltage b ₁ when the valve 23 is fully opened is considered. It is inevitable that individual differences occur, and the operating range is unknown. Therefore, at the time of design, it is necessary to allow a margin in the amplification range of the valve operation signal So ′.

[0012] In addition, since the voltage a ₁ in which the valve 23 begins to open is not a 0V, valve operation signal at the time of start-up So 'was not also inevitably be a delay occurs between the until the voltage a ₁ start of opening of the valve 23 . However, the lower limit of the amplification range of the valve operation signal So ′ could not be determined due to the individual difference in the voltage a ₁ at the start of opening.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described circumstances, and has as its object to make it possible to adjust a drive signal of a valve of a mass flow controller so as to fall within an operation range thereof, and to make each circuit system of a mass flow controller possible. It is an object of the present invention to provide a mass flow controller which can reduce the performance waste and improve the accuracy, a method of adjusting the mass flow controller, and a recording medium which records an adjustment program of the mass flow controller.

[0014]

In order to achieve the above object, a mass flow controller according to the present invention comprises: a control unit for outputting an opening signal so that a flow rate of a fluid flowing through a flow path is set to a flow rate indicated by a flow rate setting signal; A mass flow controller having a valve drive circuit for receiving the opening signal and outputting a valve operation signal for opening and closing a valve provided in the flow path, wherein the valve drive circuit is adjusted according to the characteristics of the valve. The valve operating signal within the output range thus set is output in accordance with the opening signal. (Claim 1)

Therefore, by using this mass flow controller, the valve drive circuit outputs a valve operation signal in an output range corresponding to the valve characteristics in accordance with the opening signal, and the full scale of the opening signal is substantially reduced. It is possible to correspond to a fully closed to fully open valve. That is, since the output range of the valve operation signal can be optimized in almost the same state as the circuit system, finer control can be performed, and the performance cost ratio can be improved. In addition, since the resolution of each circuit system constituting the control unit is fully utilized, the circuit system does not require high resolution or advanced information processing, and the manufacturing cost of the mass flow controller can be reduced.

An input section for inputting the relationship between the valve operation signal and the flow rate, and a relation obtained by differentiating the flow rate with the magnitude of the valve operation signal are obtained. An arithmetic unit for determining a range within four times the standard deviation before and after the vertex of the logistic distribution curve as an output range of a valve operation signal adapted to valve characteristics, assuming a logistic distribution curve similar to a normal distribution having a vertex; And an output section for outputting an adjustment signal for adjusting the valve drive circuit so as to output a valve operation signal within the specified output range (claim 2). You can ask for
As a result, reliable operation and further improvement in accuracy can be achieved.

According to the method of adjusting a mass flow controller of the present invention, there is provided a control unit for outputting an opening signal so that a flow rate of a fluid flowing through a flow path is set to a flow rate indicated by a flow rate setting signal, A valve drive circuit that outputs a valve operation signal for opening and closing a valve provided in the road, a method of adjusting a mass flow controller,
The relationship between the valve operation signal and the flow rate is measured, and the minimum value and the maximum value of the valve operation signal including from the start of opening of the valve to the full opening are calculated based on the relationship, and the maximum value and the minimum value of the valve operation signal are calculated. The valve drive circuit is adjusted so as to output a valve operation signal corresponding to the opening signal, with an output range up to the value. (Claim 3)

That is, even if there is an individual difference in the characteristics of the valves, the relationship between the valve operation signal and the flow rate is measured to set the output range of the valve operation signal. Since the output is performed in response to the signal, the output range of the valve operation signal can be set according to the characteristics of each valve. Therefore, the resolution of the valve operation signal can be increased accordingly, and the reliability of the mass flow controller can be improved.

From the relationship between the valve operation signal and the flow rate, a relation obtained by differentiating the flow rate with the magnitude of the valve operation signal is obtained, and this relation is defined as a normal distribution having the inflection point of the relation between the magnitude of the valve operation signal and the flow rate at the top. A case where the minimum value and the maximum value of the valve operation signal are determined by regarding a range within four times the standard deviation before and after the vertex of the logistic distribution curve as a similar range of the logistic distribution curve as an output range of the valve operation signal. In 4), the minimum value and the maximum value of the valve operation signal can be more accurately determined by using the relationship between the valve operation signal and the flow rate represented by the following equation (1). Q = Q _MAX / [1 + exp {−β (X−α)}] Expression (1) where α, β> 0 Q: Flow rate Q _MAX : Maximum flow rate α, β: Parameter X: Magnitude of valve operation signal

The recording medium storing the adjustment program of the mass flow controller according to the present invention includes a control section for outputting an opening signal so that the flow rate of the fluid flowing through the flow path is equal to the flow rate indicated by the flow rate setting signal; A mass flow controller having a valve drive circuit that outputs a valve operation signal for opening and closing a valve provided in the flow path in response to the measurement, measuring a relationship between the valve operation signal and the flow rate in an arithmetic processing unit, Based on this relationship, the minimum value and the maximum value of the valve operation signal including from the start of opening of the valve to the full opening are calculated, and the output range is defined as the output range between the minimum value and the maximum value of the valve operation signal. Record the adjustment program of the mass flow controller to execute the adjustment operation to adjust the valve drive circuit to output the valve operation signal corresponding to the signal It is characterized in that was. (Claim 5)

That is, a minimum value and a maximum value of the valve operation signal are set by executing the adjustment program by an arithmetic processing unit mounted inside or outside the mass flow controller, and the valve operation signal corresponding to the opening signal is set. The output range can be adjusted appropriately.

The adjustment program obtains a relationship obtained by differentiating the flow rate with the magnitude of the valve operation signal from the relationship between the valve operation signal and the flow rate, and calculates the inflection point of the relationship between the magnitude of the valve operation signal and the flow rate. The minimum value and the maximum value of the valve operation signal are regarded as the output range of the valve operation signal, with a range within four times the standard deviation before and after the vertex of the logistic distribution curve being regarded as a logistic distribution curve similar to a normal distribution having a vertex. If it is what you want (Claim 6)
Thus, the output range of the valve operation signal can be obtained automatically and accurately.

[0023]

FIG. 1 is a block diagram showing an example of a mass flow controller 1 according to the present invention. The mass flow controller 1 of this embodiment includes a flow path 2 for flowing a fluid, and a valve 3 provided in the flow path 2 for controlling the flow of the fluid.
A flow measurement unit 4 provided in the flow path 2 for measuring the flow rate of the fluid; and a control unit 5 for outputting the opening signal So so that the flow rate measured by the flow measurement unit 4 becomes the set flow rate.
And a valve drive circuit 6 for converting the opening signal So into a valve operation signal Sb having electric power necessary for driving the valve 3.
And

Reference numeral 7 denotes an input section for inputting an analog flow rate setting signal Sin input from the outside, a flow rate signal Sq measured by the flow rate measuring section 4, and the valve operation signal Sb. The unit 5 controls each signal Sin, S
This is an AD converter for enabling the magnitudes of q and Sb to be input by digital signals. The flow rate setting signal S
In is not limited to being input analogly through the AD converter 7, but may be input only by a digital signal described later.

Reference numeral 8 denotes a DA converter for converting the opening signal So output from the digital signal into an analog value, and has a function of converting, for example, a digital value of 100 stages into a corresponding analog value. Although the opening degree signal So converted into the analog value is output to the outside of the mass flow controller 1, the state of the mass flow controller 1 can be monitored from the outside.
The opening signal So may be output to the outside only by a digital signal.

Reference numeral 9 denotes a computer-readable recording medium for recording programs executed by the control unit 5 in its internal processing and various data, such as a nonvolatile rewritable memory IC. It is needless to say that the present invention does not limit the type of the recording medium 9 or the point that the control unit 5 and the storage medium 9 are separately provided.

An interface 10 for exchanging information with an external device, for example, an EIA-232 standard, is connected to an external information processing apparatus 11 in this example. And
In this example, the flow rate setting signal Sin is given as a digital signal from the information processing device 11 through the interface 10 and is input to the control unit 5. On the other hand, the opening signal S
The o, the flow signal Sq, and the valve operation signal Sb are configured to be monitored and output to the information processing device 11 via the interface 10. That is, in this example, the information processing apparatus 1
1 and one mass flow controller 1.

Reference numeral 12 denotes an operation unit (for example, a CPU) provided inside the information processing apparatus 11, and reference numeral 13 denotes the operation unit 1.
A memory 14 is connected to the interface 10 for inputting the signals So, Sb, Sq, and outputting the flow rate setting signal Sin and the adjustment signal Sa described later. The interface is not limited to the EIA-232 standard, and it goes without saying that various interfaces can be used.

The valve 3 is, for example, a piezo valve composed of a diaphragm valve element shown in FIG. 7 and a valve element operation section in which piezo elements are stacked to move the valve element forward and backward. It shall be operated by a voltage signal. Therefore, the responsiveness of the change in the operation amount of the valve body to the change in the valve operation signal Sb is improved, and more accurate valve body operation is enabled.

However, making the valve 3 a piezo valve is not the gist of the present invention, and it goes without saying that the present invention is not limited to this.

The control unit 5 is, for example, a one-chip microcomputer, and has a simple arithmetic circuit (arithmetic unit) inside. Then, the external device (the information processing device 1 in this case)
1), the various signals Sin, Sq, Sb, and So are transferred, and the opening signal So output to the DA converter 8 is transmitted.
Output of the mass flow controller 1
Is controlled. Further, it has a function of receiving an adjustment signal Sa for setting an amplification factor, an offset voltage and the like of the valve drive circuit 6 from the information processing device 11 and outputting the signal to the valve drive circuit 6.

That is, the control unit 5 of this embodiment performs an operation for outputting the opening signal So in its operation unit, but obtains an output range of the valve operation signal Sb according to the characteristics of the valve 3 described later. Is configured not to be performed by the calculation unit in the control unit 5 but by the calculation unit 12 in the information processing apparatus 11. In the following description, it is assumed that the characteristics of the valve 3 of this example are the same as the characteristics of the valve 23 of the conventional mass flow controller 21 shown in FIG.

Sa is an adjustment signal generated in accordance with the characteristics of the valve 3 obtained by the calculation unit 12, and adjusts the valve drive circuit 6 so as to output a valve operation signal Sb within a predetermined output range. It is for. That is, in this example, the interfaces 10 and 14 and the control unit 5 constitute an output unit that outputs the adjustment signal Sa.

On the other hand, the valve drive circuit 6 receives the adjustment signal S
a to output a valve operation signal Sb within a voltage range adjusted in accordance with the characteristics of the valve 3 in accordance with the opening signal So. For example, as shown in FIG. Adjustment section 15.

In FIG. 2, reference numeral 16 denotes a multiplier for amplifying the opening signal So at an arbitrary amplification factor A, and 17 denotes a minimum value a of the valve operation signal Sb by adding an offset voltage Vo to the amplified opening signal So. Can be set. Therefore, when the adjustment signal Sa is input to the adjustment unit 15,
The offset voltage Vo and the amplification factor A are adjusted by the adjusting unit 15.
Is output, and a valve operation signal Sb within a predetermined output range can be output in accordance with the opening degree signal So.

The present invention does not limit the adjustment of the output range of the valve operation signal Sb by the adjustment signal Sa as shown in FIG. That is, by providing an adjusting element such as a variable resistor in place of the adjusting section 15 and changing the offset Vo and the amplification factor A, the valve driving circuit 6
Can be simplified.

FIG. 3 is a diagram showing the input-output characteristics of the valve drive circuit 6 of the present embodiment. That is, in the case of the present example, the amplification factor A is adjusted so that the offset voltage Vo is 2 V and the output range B of the valve operation signal Sb is 2 to 3 V. That is, for example, when the opening signal So is 100, the voltage is 100
Assuming mV, the amplification factor A is 10.

In this manner, the valve drive circuit 6 is adjusted so that the minimum value a of the valve operation signal Sb becomes the offset voltage Vo (2 V in this example) and the maximum value b becomes 3 V in this example, and the opening degree is adjusted. It outputs a valve operation signal Sb that changes linearly with the signal So. In this example, the output range B of the valve operation signal Sb is described as 2 to 3 V for the sake of simplicity, and indicates that the minimum value a and the maximum value b are integers. It goes without saying that it is not.

Therefore, as compared with the characteristics of the valve 3 shown in FIG. 8, the valve operation signal Sb when the opening signal So is 0 is the minimum value a slightly smaller than the voltage a _{1 at} which the valve 3 starts to open. valve operation signal Sb when opening signal so is 100 becomes the maximum value b is slightly larger than the voltage b ₁ the valve 3 is fully opened.

Various modifications are conceivable, for example, the configuration and input-output characteristics of the valve drive circuit 6 of the present invention are adjusted to have a curved input-output characteristic in accordance with the characteristics of the valve 3. . In any case, by setting the minimum value Vmin and the maximum value Vmax of the valve operation signal Sb in accordance with the characteristics of the valve 3, the full-scale of the opening degree signal So is controlled to control the actual opening / closing state of the valve 3. Can be used.

Next, a method for measuring the characteristics of the valve 3 will be described with reference to the flowchart shown in FIG. 4 and FIGS. In the following description, the measurement of the characteristics of the valve 3 is performed using the adjustment program P (FIG. 1) of the mass flow controller.
(See FIG. 3), but it goes without saying that the operator may measure the characteristics of the valve 3 according to this procedure. The adjustment program of the mass flow controller is, for example, a CD-ROM or a floppy (registered trademark).
It is supplied in a state recorded on a recording medium such as a disk or a memory chip.

FIG. 4 shows an example of a calculation method for obtaining the output range B of the valve operation signal Sb according to the characteristics of the valve 3. In this example, the adjustment of the mass flow controller executed by the information processing apparatus 11 is performed. Program P
The operation of FIG. Running this regulatory program P, the information processing apparatus, first, as shown in step S ₁ is performed to initialize the valve drive circuit 6. That is, in response to the change of the opening signal So from 0 to 100, the voltage 0
An adjustment signal Sa is output to the valve drive circuit 6 so as to output a valve operation signal Sb of 15V.

Next, the information processing device 11 writes the value obtained by dividing the opening signal So from the minimum value to the maximum value by 100 into the DA converter 8 in order from the minimum value, and writes the valve operation signal Sb and the value at that time. The value of the flow signal Sq is read and the relationship is measured. (Step S ₂ ) The relationship between the magnitude X (voltage) of the valve operation signal Sb measured at this time and the magnitude of the flow rate signal Sq (hereinafter, simply referred to as flow rate Q) is the same as that shown in FIG. .

Note that the information processing device 11 outputs the flow signal S
By reading only the value of q, the relationship between the magnitude of the output opening signal So and the flow rate Q at that time may be obtained. However, in this example, by reading the magnitude of the valve operation signal Sb via the AD converter 7, signal distortion that may be caused by the DA converter 8, the internal circuit of the valve drive circuit 6, and the like is measured at the same time. Control is performed.

Next, the flow rate Q obtained by the information processing device 11
Is differentiated by the magnitude X of the valve operation signal Sb. (Step S ₃ )

FIG. 5 is a diagram showing the relationship between the flow rate change rate dQ / dX and the magnitude X of the valve operation signal Sb when the flow rate Q is differentiated with the magnitude of the valve operation signal Sb being X.
Incidentally, the relationship between the flow rate Q and the magnitude X of the valve operation signal Sb is, as already described in detail by using the equation (1), Q = Q
_MAX / [1 + exp {-β (X-α)}], and
It becomes a logistic curve. Therefore, a curve L obtained by differentiating the flow rate Q by the magnitude X of the valve operation signal Sb is a logistic distribution curve L.
Becomes That is, the standard deviation σ of the logistic distribution curve L can be calculated. (Step S ₄ )

The logistic distribution curve L is 99.7% of the whole within 3.6 times the standard deviation σ from its center.
Is known to be included. Therefore, in this example, the magnitude X of the valve operation signal Sb at the top of the curve L is α
Then, the position of 4σ right and left from the center point α is obtained as the minimum value a and the maximum value b of the valve operation signal Sb.
(Step S ₅₎

It should be noted that the value of four times the standard deviation σ is the value of the valve.
3 Opening voltage a₁And full open voltage b₁But surely
Of the lube operation signal Sb between the minimum value a and the maximum value b.
It is a value determined in advance, but it can be calculated by the method shown in the present invention.
With this, the optimum output range B can be set very easily and accurately.
Can be specified. However, the voltage a ₁
And full open voltage b₁Is the output range B of the valve operation signal Sb.
If it deviates from the inside, take a width of at least 4 times the standard deviation σ.
You may.

Also in this case, it is desirable that the output range B of the valve operation signal Sb should be set to about 5 times or less of the standard deviation σ so that the effect of the present invention is sufficiently exhibited. Therefore, even if the output range B of the valve operation signal Sb is expanded to some extent, the opening voltage a ₁ and the fully open voltage b _{1 of} the valve 3 are not changed.
If not, it may be determined that the valve 3 is defective.

Next, the information processing device 11 is a valve drive circuit.
And outputs an adjustment signal Sa to the valve driving circuit 6.
A valve within the output range B adjusted according to the characteristics of the valve 3
The lube operation signal Sb is output in accordance with the opening signal So.
Set as follows. (Step S ₆)

Then, the opening signal So is again divided into 100 equal parts, the opening signal So is sequentially changed and output, and the change in the flow rate Q with respect to the magnitude X of the valve operation signal Sb at that time is measured. (Step S ₇₎

FIG. 6 is a diagram showing the relationship between the flow rate Q and the valve operation signal Sb or the opening signal So measured at this time. As shown in FIG. 6, by using the present invention, the valve drive circuit 6 can output the valve operation signal Sb by dividing the limited output range B from the minimum value a to the maximum value b into 100 equal parts. That is, the information processing device 11 obtains a characteristic curve of the flow rate Q with respect to the opening signal So. (Step S ₈ )

The flow rate Q corresponding to the opening degree signal So
As shown by the characteristic curve, the information processing apparatus 11 or the control unit 5 can use the almost full scale of the opening degree signal So for controlling the flow rate Q. That is, even when the resolution of the DA converter 8 mounted on the mass flow controller 1 is low, it is possible to perform the flow control with extremely high accuracy.

In the above-described example, the information processing device 11 having the operation unit 12 different from the control unit 5 is connected to measure the characteristics of the valve 3, and the adjustment signal Sa to the valve drive circuit 6 is supplied to an external device. Although the example given from the information processing apparatus 11 has been described, the present invention does not limit this configuration.
That is, if the control unit 5 has a sufficient calculation capability,
An arithmetic unit in the control unit 5 may execute the adjustment program P of the mass flow controller to set the valve drive circuit 6.

The control unit 5 controls the valve driving circuit 6
When the adjustment signal Sa is output to the external device, it is not necessary to provide the interface 10 to the external device. In this case, the mass flow controller 1 may be an analog input mass flow controller having only an input section for an analog flow rate setting signal Sin.

In addition, the interface 10 measures the characteristics of the valve 3 and sends an adjustment signal Sa to the valve drive circuit 6.
May be used only when outputting. That is, when the mass flow controller 1 is manufactured, an external information processing device 11 is connected only when the characteristics of the valve 3 are first measured and the valve drive circuit 6 is set so that appropriate control can be performed. Otherwise, the controller 5 may be configured to output the opening signal So.

Further, the output of the adjustment signal Sa to the valve drive circuit 6 may be performed not only at the time of manufacturing the mass flow controller 1 but also at predetermined intervals as maintenance. In this case, even if the characteristics of the valve 3 change with time, the opening of the valve 3 can be controlled in an optimum state at all times.

The output of the adjustment signal Sa to the valve drive circuit 6 is also performed by the existing digital mass flow controller 21 as shown in FIG. By using this, even in the existing mass flow controller 21, the output range B of the valve operation signal Sb can be set to an appropriate value.

In any of the above cases, the valve 3
Can be optimized in almost the same state with respect to the circuit system such as the DA converter 8, so that finer control is possible. Further, since the capability of the circuit system can be sufficiently utilized, the performance waste of the circuit components such as the DA converter 8 can be reduced, and the performance cost ratio can be improved.

In particular, by utilizing the characteristic that the characteristic of the valve operation becomes a logistic curve and utilizing the principle of the standard deviation effectively, the voltage at the time of opening the valve and the voltage at the time of full opening can be extremely easily. In addition, it is possible to obtain the value accurately and to facilitate the design or adjustment of the circuit system.

[0061]

As described above, according to the present invention, the valve drive circuit outputs a valve operation signal within an output range corresponding to the valve characteristics in accordance with the opening signal, thereby providing a full scale of the opening signal. Can be fully closed to fully opened and the output range of the valve operation signal can be optimized in almost the same condition for the circuit system, so that finer control is possible and the performance cost ratio is improved. Can be. In addition, since the resolution of each circuit system constituting the control unit is fully utilized, the circuit system does not require high resolution or advanced information processing, and the manufacturing cost of the mass flow controller can be reduced.

Further, the present invention utilizes the fact that the flow rate is differentiated with the magnitude of the valve operation signal to form a logistic distribution curve. Therefore, an appropriate output range of the valve operation signal can be easily obtained, and each valve can be easily obtained. Characteristic can be obtained extremely easily and accurately, whereby reliable operation and further improvement of accuracy can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a mass flow controller according to the present invention.

FIG. 2 is a block diagram showing an example of a valve drive circuit of the mass flow controller.

FIG. 3 is a diagram showing input-output characteristics of the valve drive circuit.

FIG. 4 is a diagram illustrating an example of a method of adjusting a mass flow controller by an adjustment program of the mass flow controller.

FIG. 5 is a diagram illustrating a method of adjusting the mass flow controller.

FIG. 6 is another diagram illustrating a method of adjusting the mass flow controller.

FIG. 7 is a diagram illustrating an example of a configuration of a conventional mass flow controller.

FIG. 8 is a diagram showing characteristics of a valve of the mass flow controller.

[Explanation of symbols]

1 ... mass flow controller, 2 ... flow path, 3 ... valve,
4 ... Flow measurement unit, 5 ... Control unit, 6 ... Valve drive circuit, 7
... Input unit, 13 ... Recording medium, 12 ... Calculation unit, 14,1
0,5 ... output unit, a ... minimum value of the valve operating signal, a ₁ ...
The voltage at which the valve starts to open, b: the maximum value of the valve operation signal,
b ₁ : full open voltage of valve, B: output range, L: normal distribution curve, P: adjustment program, Q: flow rate, Sa: adjustment signal, Sb: valve operation signal, So: opening signal, α: center, σ …standard deviation.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Sanzo Shimomura 11-5 Kamibahakodatemachi, Minami-ku, Kyoto-shi, Kyoto F-term in ESTEC Co., Ltd. (reference) 3J071 AA11 BB11 BB14 CC12 DD14 EE02 EE18 EE25 FF01 FF04 FF11 5H004 GA14 GB15 HA02 HB02 JB19 KA44 KA54 LA17 MA04 5H307 BB01 DD20 EE02 EE07 EE12 FF06 GG15 HH04 HH08 HH12

Claims (6)

[Claims] A control unit that outputs an opening degree signal so that a flow rate of a fluid flowing through the flow path is set to a flow rate indicated by a flow rate setting signal;
A mass flow controller having a valve drive circuit for receiving the opening signal and outputting a valve operation signal for opening and closing a valve provided in the flow path, wherein the valve drive circuit is adjusted according to the characteristics of the valve. A mass flow controller for outputting a valve operation signal within the specified output range in accordance with the opening signal. 2. An input section for inputting the relationship between the valve operation signal and the flow rate, and a relation obtained by differentiating the flow rate with the magnitude of the valve operation signal is obtained, and this relation is inflected in the relation between the magnitude of the valve operation signal and the flow rate. An arithmetic unit that regards a logistic distribution curve similar to a normal distribution having a point as an apex, and obtains a range within four times the standard deviation before and after the apex of the logistic distribution curve as an output range of a valve operation signal adapted to valve characteristics; The mass flow controller according to claim 1, further comprising: an output unit that outputs an adjustment signal for adjusting a valve drive circuit so as to output a valve operation signal within the determined output range. A controller that outputs an opening signal so that the flow rate of the fluid flowing through the flow path is set to the flow rate indicated by the flow rate setting signal;
A valve drive circuit that outputs a valve operation signal for opening and closing a valve provided in the flow path in response to the opening signal, the method for adjusting a mass flow controller, wherein the valve operation signal and the flow rate Measure the relationship, calculate the minimum and maximum values of the valve operation signal that includes from the start of valve opening to full open based on this relationship, and output the range from the minimum value to the maximum value of this valve operation signal. Adjusting a valve drive circuit so as to output a valve operation signal corresponding to the opening degree signal. 4. The relationship between the valve operation signal and the flow rate,
Find the relationship that differentiates the flow rate with the magnitude of the valve operation signal,
This relationship is regarded as a curve of a logistic distribution similar to a normal distribution having the inflection point of the relationship between the magnitude of the valve operation signal and the flow rate as a vertex, and a range within four times the standard deviation before and after the vertex of the logistic distribution curve is defined as a valve. 4. The method according to claim 3, wherein a minimum value and a maximum value of the valve operation signal are obtained as the output range of the operation signal. 5. A control unit that outputs an opening degree signal so that a flow rate of the fluid flowing through the flow path is set to a flow rate indicated by the flow rate setting signal.
A mass flow controller having a valve drive circuit that receives the opening signal and outputs a valve operation signal for opening and closing a valve provided in the flow path. Measure
Based on this relationship, the minimum value and the maximum value of the valve operation signal including from the start of opening of the valve to the full opening are calculated, and the output range is defined as the output range between the minimum value and the maximum value of the valve operation signal. A computer-readable recording medium recording an adjustment program of a mass flow controller for executing an adjustment operation for adjusting a valve drive circuit so as to output a valve operation signal corresponding to the signal. 6. The adjustment program obtains a relationship obtained by differentiating the flow rate with the magnitude of the valve operation signal from the relationship between the valve operation signal and the flow rate, and determines the relationship as an inflection of the relationship between the magnitude of the valve operation signal and the flow rate. It is regarded as a curve of a logistic distribution similar to a normal distribution having a point as a vertex, and a range within four times the standard deviation before and after the vertex of the logistic distribution curve is defined as an output range of the valve operation signal. A computer-readable recording medium for recording a program for adjusting a mass flow controller according to claim 5, which calculates a value.