JP2018136842A - Maintenance judgment index estimation device, flow control device, and maintenance judgment index estimation method - Google Patents

Abstract

Kind Code: A1 An index for determining whether maintenance is necessary for a flow control device and its related equipment is estimated during operation of the device. A maintenance determination index estimating device acquires a valve opening when a fluid flow rate is maintained at a predetermined target flow rate during a flow rate control in which a fluid flow rate is controlled using a valve. At the time of this acquisition, based on the opening degree acquisition unit 3, the function that approximates the relationship between the valve opening degree and the flow rate of the fluid, and the valve opening degree acquired by the valve opening degree acquisition unit 3, It is provided with a flow rate upper limit estimator 4 for estimating a flow rate upper limit value assuming that the opening reaches the upper limit as a maintenance determination index of the flow rate control device. [Selection] Fig. 3

Description

  The present invention relates to a technique for estimating a determination index as to whether maintenance is necessary for a flow rate control device such as a mass flow controller and related equipment such as a filter.

  A semiconductor manufacturing apparatus or the like employs a flow rate control device such as a mass flow controller as shown in FIG. 6 in order to introduce a material gas or the like into a vacuum chamber at a constant flow rate (see Patent Document 1). In FIG. 6, 100 is a main body block, 101 is a sensor package, 102 is a head portion of the sensor package 101, 103 is a fluid sensor mounted on the head portion 102, 104 is a valve, and 105 is formed inside the main body block 100. A flow path 106 is an opening on the inlet side of the flow path 105, and 107 is an opening on the outlet side of the flow path 105.

  The fluid flows into the flow path 105 from the opening 106, passes through the valve 104, and is discharged from the opening 107. The fluid sensor 103 measures the flow rate of the fluid flowing through the flow path 105. A control circuit (not shown) of the mass flow controller drives the valve 104 so that the fluid flow rate measured by the fluid sensor 103 matches the set value.

  If the flow control of the material gas is continuously performed by such a mass flow controller, the mass flow controller itself or related equipment such as a filter provided in the flow path of the material gas is contaminated due to the influence of components contained in the material gas. A problem may occur due to the adhesion.

  In view of this, there has been proposed a device for operating and calibrating the valve opening so that a flow rate error and a pressure error only occur within an allowable accuracy range in the entire measurement range of the fluid sensor built in the mass flow controller (Patent Document). 2). However, although the diagnostic mechanism disclosed in Patent Document 2 can diagnose whether the error between the measured value of the fluid sensor and the actual flow rate is an acceptable level with accuracy, However, it is necessary to maintain the valve provided on the flow path in a fully closed state or to change the valve from a fully closed state to an open state, which makes it difficult to make a diagnosis during operation of the apparatus. It was. When the mass flow controller is provided in, for example, a semiconductor manufacturing apparatus, it is difficult to stop the entire semiconductor manufacturing apparatus in order to diagnose the mass flow controller.

  Further, in the diagnosis mechanism disclosed in Patent Document 2, when the mass flow controller is diagnosed at the operation stop timing of the semiconductor manufacturing apparatus, the valve is opened after the fluid flows into the flow path of the mass flow controller during the operation stop. There is a problem that it is necessary to change to the fully closed state, and it takes time and effort for the diagnosis work. In a semiconductor manufacturing apparatus or the like, if it becomes possible to determine the necessity of maintenance during the operation of the apparatus, it becomes easier to manage the operation, and therefore improvement is required.

JP 2008-039588 A Japanese Patent No. 5931668

  The present invention was made in order to solve the above problems, and a maintenance determination index estimation device capable of estimating a determination index as to whether maintenance is necessary for a flow rate control device and related equipment during operation of the device, An object of the present invention is to provide a flow rate control device and a maintenance judgment index estimation method.

The maintenance judgment index estimation device according to the present invention acquires the opening degree of the valve when the flow rate of the fluid is maintained at a predetermined target flow rate during flow rate control for controlling the flow rate of the fluid using the valve. Based on a valve opening degree obtaining unit configured as described above, a function approximating the relationship between the opening degree of the valve and the flow rate of the fluid, and the opening degree of the valve obtained by the valve opening degree obtaining unit. A flow rate upper limit estimation unit configured to estimate a flow rate upper limit value when the opening degree of the valve has reached an upper limit at the time of acquisition as a maintenance determination index of the flow rate control device. It is a feature.
Further, in one configuration example of the maintenance determination index estimation device of the present invention, the flow rate upper limit estimation unit sets the upper limit of the valve opening corresponding to the flow rate upper limit value to 100%. .

Further, in one configuration example of the maintenance determination index estimation device of the present invention, the function is defined by at least a term relating to the valve opening and a gain which is a numerical value multiplied by the term, and the flow rate upper limit estimation. The flow rate upper limit value based on a mathematical expression obtained from the function when the gain is assumed to decrease with time and the valve opening obtained by the valve opening obtaining unit. It is characterized by estimating.
Further, in one configuration example of the maintenance judgment index estimation device of the present invention, the function is a function that approximates a nonlinear relationship between the opening degree of the valve and the flow rate of the fluid, and a term related to the opening degree of the valve It is expressed by an exponential function.
Further, in one configuration example of the maintenance judgment index estimation device of the present invention, the function is a function that approximates a nonlinear relationship between the opening degree of the valve and the flow rate of the fluid, and a term related to the opening degree of the valve It is represented by a fraction function.

Further, in one configuration example of the maintenance determination index estimation device according to the present invention, the flow rate upper limit estimation unit is configured to estimate the flow rate upper limit value and the valve opening degree acquired by the valve opening degree acquisition unit at the present time. A gain calculation unit that calculates the current gain based on the target flow rate, and a flow rate upper limit calculation unit that calculates the flow rate upper limit value based on the gain calculated by the gain calculation unit. It is characterized by.
In addition, one configuration example of the maintenance judgment index estimation device of the present invention further includes an estimation result output unit that numerically displays the flow rate upper limit value estimated by the flow rate upper limit estimation unit.
Further, one configuration example of the maintenance judgment index estimation device of the present invention further includes an estimation result output unit that issues an alarm when the flow rate upper limit value estimated by the flow rate upper limit estimation unit is less than a predetermined threshold value. It is characterized by comprising.

  Further, the flow rate control device of the present invention is preliminarily defined as a flow rate measurement unit that measures a flow rate of fluid flowing through the flow channel, a valve provided in the flow channel, and the flow rate measured by the flow rate measurement unit. A flow rate control unit that operates the valve so as to match a target flow rate, and a maintenance determination index estimation device; and the valve opening degree acquisition unit of the maintenance determination index estimation device is provided in the flow path The opening degree of the valve is acquired.

  Further, the maintenance judgment index estimation method of the present invention provides the valve opening degree when the fluid flow rate is maintained at a predetermined target flow rate during the flow rate control for controlling the fluid flow rate using the valve. Based on the first step to be acquired, a function that approximates the relationship between the opening of the valve and the flow rate of the fluid, and the opening of the valve acquired by the first step. And a second step of estimating the upper limit value of the flow rate when it is assumed that the opening degree of the valve has reached the upper limit as a maintenance judgment index of the flow rate control device.

  ADVANTAGE OF THE INVENTION According to this invention, the judgment parameter | index (flow volume upper limit) whether a maintenance is required about a flow control apparatus and its related apparatus can be estimated during operation | movement of an apparatus. As a result, it becomes easier for an operator to perform operation management of a semiconductor manufacturing apparatus provided with a flow rate control device. Further, according to the present invention, it is possible to greatly reduce the labor required for determining whether maintenance is necessary.

It is a figure which shows one example of the relationship between the opening degree of the valve provided in the mass flow controller, and the flow volume of the fluid. It is a figure which shows the other example of the relationship between the opening degree of the valve provided in the mass flow controller, and the flow volume of the fluid. It is a block diagram which shows the structure of the flow control apparatus which concerns on the Example of this invention. It is a flowchart explaining the flow control operation | movement of the flow control apparatus which concerns on the Example of this invention. It is a flowchart explaining the maintenance judgment parameter | index estimation operation | movement of the flow control apparatus concerning the Example of this invention. It is sectional drawing of a massflow controller.

[Principle of the Invention]
The use of a mass flow controller is to stably maintain a fluid flow rate at a target flow rate that is predetermined in many cases. Therefore, assuming such an application, the influence of filter clogging and the like can be estimated under highly reliable detection conditions. Specifically, a state where the target flow rate is stably maintained is detected, and a valve opening instruction signal under the condition is acquired.

  Considering the case where the filter installed upstream of the mass flow controller is clogged, the flow rate that can be reached with the valve opening saturated at 100% is the upper limit of the controllable flow rate at that time. In other words, it is efficient to determine whether to perform maintenance by estimating the upper limit value. Therefore, the inventor acquires highly reliable valve opening information based on the use conditions specific to the mass flow controller, and estimates the upper limit value of the flow rate estimated from the information (for example, the estimated flow rate when the valve opening degree is 100%). We thought that it was appropriate to use as an indicator for determining whether maintenance is necessary.

[Example]
Embodiments of the present invention will be described below with reference to the drawings. Patent Document 2 shows that when the opening degree of a valve provided in the mass flow controller is linearly changed with time, the flow volume of the fluid flowing through the flow path is smaller as the opening degree is higher. . As described above, the valve opening MV and the flow rate PV are in a non-linear relationship, and it is known that the change amount of the flow rate PV decreases with respect to the change amount of the opening degree MV toward the higher opening side. An outline of the characteristics of such a mass flow controller is shown in FIG. In the example of FIG. 1, the flow rate PV is normalized to a value of 0 to 100%. The characteristic shown in FIG. 1 is a non-linear convergence phenomenon, and can be expressed by the following exponential function.
PV = K {1.0-exp (-MV / A)} (1)

Thus, the function approximating the relationship between the valve opening MV and the flow rate PV is a constant term (1.0), a term relating to the valve opening MV, and a gain K which is a numerical value multiplied by each of these terms. And is defined by A in Equation (1) is a coefficient that gives a nonlinear convergence state. A curve cur1 in FIG. 1 shows an initial characteristic of the mass flow controller. On the basis of the supply pressure that can be grasped in advance, the valve opening MV = 100% and the flow rate PV becomes a maximum value of 100%, and the curve cur1 is expressed by the following equation in accordance with a general image of nonlinearity. It can be expressed by an exponential function of various coefficient values.
PV = 104.0 {1.0-exp (-MV / 30.0)} (2)

  In equation (2), K = 104.0 and A = 30.0 are examples of these numerical values. In the clogging phenomenon of the filter provided in the flow path, it can be estimated that the non-linearity which is the characteristic of the valve of the mass flow controller located downstream of the filter does not change, so the coefficient A can be regarded as constant. . Therefore, it is assumed that only the gain K decreases due to a filter clogging phenomenon or the like.

  In determining whether maintenance of the mass flow controller and related equipment of the mass flow controller is necessary, although it is estimated that several factors affect the operation time of the mass flow controller, it is roughly proportional to the operation time, In other words, it is reasonable to assume that the gain K decreases at a constant and moderate pace so that there is no sudden deterioration.

Here, it is assumed that the predetermined target flow rate PVx is PVx = 60.0%. That is, the most standard numerical value given as the flow rate setting value SP of the mass flow controller is SPx = 60.0%. Assuming that the initial valve opening of the mass flow controller for setting the flow rate of the fluid to PVx = 60.0% is MV1, MV1 = 25.8% according to the curve cur1. Since the coefficient A = 30.0 of the non-linear characteristic is known in advance, the gain K1 in the initial state can be calculated backward as follows based on PVx = 60.0% and MV1 = 25.8%. In this initial state, the flow rate (flow rate upper limit PVh) at the valve opening degree of 100% is PVh = 100% as described above.
K1 = PVx / {1.0-exp (-MV1 / A)}
= 60.0 / {1.0-exp (-25.8 / 30.0)} = 104.0
... (3)

  Next, it is assumed that the valve opening degree MV for maintaining the target flow rate PVx when the operation time of the mass flow controller has passed to such an extent that the filter is clogged is acquired. At this time, the target flow rate PVx may be different from the initial target flow rate PVx. Here, the target flow rate PVx = 40.0%. For example, it is assumed that MV2 = 16.2% is detected as the valve opening degree MV for maintaining the target flow rate PVx = 40.0% when 72 hours have elapsed from the start of operation. This value is such that the pressure at the point of flow into the mass flow controller decreases due to the filter clogging phenomenon, and the valve opening MV for maintaining the target flow rate PVx = 40.0% must be MV2 = 16.2%. It means no longer.

The gain K2 at the time when 72 hours have elapsed from the start of operation can be back-calculated as follows based on PVx = 40.0% and MV2 = 16.2%.
K2 = PVx / {1.0-exp (-MV2 / A)}
= 40.0 / {1.0-exp (-16.2 / 30.0)} = 96.0
... (4)

Therefore, it is estimated that the gain K decreased from the initial state K1 = 104.0 to K2 = 96.0 by a numerical value of 8.0 in 72 hours. In this case, the characteristics of the mass flow controller are as shown by the curve cur2 in FIG. In this cur2 state, the flow rate (flow rate upper limit PVh) at a valve opening degree of 100% can be calculated as follows.
PVh = 96.0 {1.0-exp (-100.0 / 30.0)} = 96.6
... (5)

  Thus, PVh = 96.6% is the upper limit value of the controllable flow rate in the state of cur2, and it can be determined that the state is not so serious. That is, it becomes a judgment index that the maintenance of the mass flow controller is not yet required.

Since it is assumed that the gain K decreases at a constant pace roughly in proportion to the operation time of the mass flow controller, when about 72 hours have passed since the cur2 state, the gain K is probably further decreased by about 8.0. Thus, it can be estimated that the characteristics of the mass flow controller are as shown by the curve cur3 (K3 = 88.0) in FIG. In the state of cur3, the flow rate (flow rate upper limit PVh) at a valve opening degree of 100% can be calculated as follows. However, this is limited to the case where the gain K decreases at a constant pace.
PVh = 88.0 {1.0-exp (-100.0 / 30.0)} = 84.9
... (6)

  Once the above is organized, it becomes as follows. In the initial state (cur1), PVh = 100.0% can be estimated from the results of PVx = 60.0% and MV1 = 25.8%. In a state 72 hours after the start of operation (cur2), PVh = 96.6% can be estimated from the results of PVx = 40.0% and MV2 = 16.2%. Furthermore, in the state after 72 hours (cur3), it can be estimated that PVh = 84.9%.

Next, it is assumed that the valve opening MV for maintaining the target flow rate PVx is acquired when a further time elapses. At this time, the target flow rate PVx is set to 30.0%, and it is assumed that MV4 = 19.8% is detected as the valve opening degree MV for maintaining the target flow rate PVx = 30.0%. In this case, based on PVx = 30.0% and MV4 = 19.8%, the gain K4 can be calculated backward as in the following equation.
K4 = PVx / {1.0-exp (-MV4 / A)}
= 30.0 / {1.0-exp (-19.8 / 30.0)} = 62.0
... (7)

In this case, the characteristics of the mass flow controller are as shown by the curve cur4 in FIG. In the state of cur4, the flow rate (flow rate upper limit PVh) at a valve opening degree of 100% can be calculated as follows.
PVh = 62.0 {1.0-exp (-100.0 / 30.0)} = 59.8
... (8)

  Thus, PVh = 59.8% is the upper limit value of the controllable flow rate in the state of cur4. As past results, there is a case where the target flow rate PVx is set to PVx = 60.0%. Since PVh = 59.8% is lower than the past target flow rate PVx, it can be determined that the state is serious. That is, it becomes a judgment index that the maintenance of the mass flow controller is necessary.

  From the above, the procedures for obtaining the judgment index for the necessity of maintenance of the mass flow controller and related equipment can be organized as shown in (I) and (II) below. According to the present embodiment, even when it seems that there is a margin in the valve opening by controlling with a low flow rate and a low opening (an opening where the valve opening is sufficiently away from the upper limit), it is reasonable. A judgment index can be obtained.

(I) The valve opening degree MV for maintaining the fluid flow rate at an arbitrary target flow rate PVx can be acquired. A gain K is calculated based on the valve opening MV. However, the nonlinearity coefficient A is defined in advance.
K = PVx / {1.0-exp (-MV / A)} (9)

(II) The flow rate when the valve opening degree MV reaches an upper limit of 100% is calculated as a controllable flow rate upper limit value PVh, and whether or not the flow rate upper limit value PVh requires maintenance of the mass flow controller and related devices. It is a judgment index.
PVh = K {1.0-exp (-100.0 / A)} (10)

As long as the function can approximate the non-linearity of FIG. 1, a method other than the exponential function can be applied. For example, in the case of the following fractional function, the nonlinearity between the valve opening and the flow rate can be described with only four arithmetic operations.
PV = K [{− A / (MV + B)} + C]
= 1.0 [{-3130.0 / (MV + 25.0)} + 125.2]
(11)
K = PVx / [{− A / (MV + B)} + C] (12)
PVh = K [{− A / (100.0 + B)} + C] (13)

  Similar to Equation (1), the function of Equation (11) is defined by a constant term (C = 15.2), a term relating to the valve opening MV, and a gain K multiplied by each of these terms. . According to the equations (11) to (13), the characteristics of the mass flow controller can be represented in FIG. 2 similar to FIG. The gain K1 in the state of the curve cur1 in FIG. 2 is 1.0, the gain K2 in the state of the curve cur2 is 0.923, the gain K3 in the state of the curve cur3 is 0.846, and the gain K4 in the state of the curve cur4 is 0.596. It is. That is, as in the example of FIG. 1, the gain K decreases at a constant pace in proportion to the operating time.

  Next, the configuration of the flow control device (mass flow controller) of this embodiment will be described. As shown in FIG. 3, the flow rate control device of the present embodiment is configured so that the flow rate measurement unit 1 that measures the flow rate of the fluid flowing through the flow path matches the flow rate measured by the flow rate measurement unit 1 and the target flow rate PVx. A valve opening degree obtaining unit 3 for obtaining a valve opening degree MV when the flow rate of the fluid is maintained at a predetermined target flow rate PVx during the flow rate control, and a valve opening degree. A flow rate upper limit estimation unit 4 that estimates a flow rate upper limit PVh as a maintenance determination index when it is assumed that the valve opening has reached an upper limit (for example, 100%) at the time of obtaining the degree MV; And an estimation result output unit 5 that outputs information on the estimation result.

Next, the operation of the flow control device of this embodiment will be described with reference to FIGS. FIG. 4 is a flowchart for explaining the flow rate control operation, and FIG. 5 is a flowchart for explaining the maintenance judgment index estimation operation.
The flow rate measuring unit 1 continuously measures the flow rate of the fluid flowing through the flow channel (the flow channel 105 in FIG. 6) (step S100 in FIG. 4). The flow rate measuring unit 1 corresponds to the fluid sensor 103 of FIG. 6 and has a well-known configuration provided in the mass flow controller.

The flow rate control unit 2 continuously operates the valve (the valve 104 in FIG. 6) so that the flow rate of the fluid measured by the flow rate measurement unit 1 coincides with the target flow rate PVx set by the operator, for example (step in FIG. 4). S101). The flow rate control unit 2 is also a known configuration provided in the mass flow controller.
Thus, for example, until the operation of the apparatus is instructed by the operator (YES in step S102 in FIG. 4), the processes in steps S100 and S101 are repeatedly executed at predetermined intervals (for example, 50 msec.).

  On the other hand, the valve opening degree obtaining unit 3 obtains the valve opening degree MV (target maintenance valve opening degree) when the fluid flow rate is maintained at the target flow rate PVx (step S200 in FIG. 5). Specifically, the valve opening degree acquisition unit 3 is in the case where the absolute value of the deviation between the flow rate measured by the flow rate measurement unit 1 and the target flow rate PVx is within a specified value in a period from a certain time before to the present time. Determines that the fluid flow rate is maintained at the target flow rate PVx, and obtains the current valve opening MV. The value of the fixed time t is set in the valve opening degree acquisition unit 3 as a specified value.

  The valve opening itself may be detected. However, in terms of mounting, the exact valve opening is not detected, but a signal output from the flow control unit 2 to the valve (for example, a valve opening instruction signal or a valve drive) Current) is obtained, and the valve opening may be determined based on this signal.

  Next, the flow rate upper limit estimation unit 4 reaches the upper limit (for example, 100%) at the time of acquisition based on the valve opening MV (target maintenance valve opening) acquired by the valve opening acquisition unit 3. The flow rate upper limit PVh in the case of assuming that the flow rate is assumed is estimated as a judgment index called a controllable flow rate. As shown in FIG. 3, the flow rate upper limit estimation unit 4 includes a gain calculation unit 40 that calculates the gain K and a flow rate upper limit calculation unit 41 that calculates the flow rate upper limit PVh.

  The gain calculation unit 40 of the flow rate upper limit estimation unit 4 calculates the current gain K for which the flow rate upper limit value PVh is to be calculated, using Expression (9) (step S201 in FIG. 5). The coefficient A in Expression (9) is set in the flow rate upper limit estimation unit 4 as a specified value. In order to grasp the coefficient A, for example, a flow rate test of the flow rate control device may be performed in advance to check the value of the coefficient A.

  Then, the flow rate upper limit calculation unit 41 of the flow rate upper limit estimation unit 4 calculates the flow rate upper limit value PVh by the equation (10) based on the gain K calculated by the gain calculation unit 40 (step S202 in FIG. 5). Above, the process of the flow volume upper limit estimation part 4 is complete | finished.

  The estimation result output unit 5 outputs the estimation result of the flow rate upper limit estimation unit 4 (step S203 in FIG. 5). As an output method of the estimation result, there are, for example, numerical display of the flow rate upper limit PVh, alarm output based on the flow rate upper limit PVh, transmission of the estimation result information to the outside, and the like. In the case of an alarm output, when the flow rate upper limit PVh becomes less than a predetermined threshold value (for example, less than 60%), an LED for notifying an alarm may be turned on.

  The valve opening degree acquisition unit 3, the flow rate upper limit estimation unit 4, and the estimation result output unit 5 perform predetermined processes of steps S200 to S203 until, for example, an operator finishes the operation of the apparatus (YES in step S204 in FIG. 5). It is repeatedly executed every period ΔT (for example, 24 hours).

  As described above, in this embodiment, the determination index (flow rate upper limit PVh) for whether or not maintenance is necessary for the flow rate control device and related equipment (such as a filter provided in the flow path) is estimated during operation of the device. be able to. Since the operator can determine whether or not a serious situation requiring maintenance has been reached based on the estimation result of the flow rate control device, the operation management of the semiconductor manufacturing device or the like can be easily performed. In addition, in this embodiment, the operation of flowing the fluid into the flow path of the mass flow controller during the operation stop of the semiconductor manufacturing apparatus becomes unnecessary, so that the labor required for determining whether or not the maintenance is necessary can be greatly reduced. Can do.

If the valve opening degree obtaining unit 3 determines that the fluid flow rate is not maintained at the target flow rate PVx, the valve opening degree MV cannot be obtained. In this case, the flow rate upper limit PVh cannot be calculated. It will be.
Further, the present embodiment can be applied even when the target flow rate PVx is changed in the middle. However, the valve opening degree acquisition unit 3 determines whether or not the fluid flow rate is maintained at the target flow rate PVx. During the period of <ΔT), the target flow rate PVx needs to be maintained at the same value. When the target flow rate PVx is changed during the fixed time t, the valve opening MV cannot be acquired.

  Further, the flow rate upper limit estimation unit 4 may calculate the gain K and the flow rate upper limit PVh using the equations (12) and (13) instead of the equations (9) and (10). The coefficients A, B, and C in the equations (12) and (13) are set in the flow rate upper limit estimation unit 4 as specified values. In order to grasp the coefficients A, B, and C, for example, a flow rate test of the flow rate control device may be performed in advance.

  Further, in this embodiment, all the configurations shown in FIG. 3 are provided in the flow rate control device (mass flow controller), but the present invention is not limited to this. The valve opening degree acquisition unit 3, the flow rate upper limit estimation unit 4 and the estimation result output unit 5 are provided in a host device (for example, a programmable logic controller PLC) as a maintenance judgment index estimation device, and the flow rate measurement unit 1 and the flow rate control unit 2 are provided. You may make it use in combination with the common microflow controller containing.

  The flow rate control apparatus described in the present embodiment can be realized by a computer having a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. Similarly, the maintenance determination index estimation device including the valve opening degree acquisition unit 3, the flow rate upper limit estimation unit 4, and the estimation result output unit 5 can be realized by a computer and a program. The CPU of each device executes the processing described in the present embodiment in accordance with a program stored in each storage device. Thereby, the maintenance judgment index estimation method of the present embodiment can be realized.

  The present invention can be applied to a technique for managing a flow control device and related equipment.

  DESCRIPTION OF SYMBOLS 1 ... Flow measurement part, 2 ... Flow control part, 3 ... Valve opening degree acquisition part, 4 ... Flow volume upper limit estimation part, 5 ... Estimation result output part, 40 ... Gain calculation part, 41 ... Flow rate upper limit calculation part

Claims (10)

A valve opening degree acquisition unit configured to acquire the opening degree of the valve when the flow rate of the fluid is maintained at a predetermined target flow rate during flow rate control for controlling the flow rate of the fluid using a valve. When,
Based on the function that approximates the relationship between the opening of the valve and the flow rate of the fluid, and the opening of the valve acquired by the valve opening acquisition unit, the opening of the valve at the time of acquisition is A maintenance determination index estimation device comprising: a flow rate upper limit estimation unit configured to estimate a flow rate upper limit value when it is assumed that the upper limit has been reached as a maintenance determination index of the flow control device. In the maintenance judgment index estimation device according to claim 1,
The flow rate upper limit estimation unit sets the upper limit of the valve opening corresponding to the flow rate upper limit value to 100%, and the maintenance determination index estimation device. In the maintenance judgment index estimation device according to claim 1 or 2,
The function is defined by at least a term relating to the opening of the valve and a gain which is a numerical value multiplied by the term,
The flow rate upper limit estimator is based on the mathematical formula obtained from the function when the gain is assumed to decrease with time, and the valve opening obtained by the valve opening obtaining unit, A maintenance judgment index estimation device for estimating a flow rate upper limit value. In the maintenance judgment index estimation device according to claim 3,
The function is a function that approximates a non-linear relationship between the opening degree of the valve and the flow rate of the fluid, and a term relating to the opening degree of the valve is represented by an exponential function. . In the maintenance judgment index estimation device according to claim 3,
The function is a function that approximates a non-linear relationship between the opening degree of the valve and the flow rate of the fluid, and a term relating to the opening degree of the valve is expressed by a fractional function. . In the maintenance judgment index estimation device according to any one of claims 3 to 5,
The flow rate upper limit estimator is
A gain calculation unit for calculating the current gain based on the valve opening and the target flow rate acquired by the valve opening acquisition unit at the current time to estimate the flow rate upper limit;
A maintenance determination index estimation device comprising: a flow rate upper limit calculation unit that calculates the flow rate upper limit value based on the gain calculated by the gain calculation unit. In the maintenance judgment index estimation device according to any one of claims 1 to 6,
The maintenance judgment index estimation device further comprising an estimation result output unit that numerically displays the flow rate upper limit value estimated by the flow rate upper limit estimation unit. In the maintenance judgment index estimation device according to any one of claims 1 to 6,
A maintenance judgment index estimation device further comprising an estimation result output unit that issues an alarm when a flow rate upper limit estimated by the flow rate upper limit estimation unit becomes less than a predetermined threshold value. A flow rate measurement unit for measuring the flow rate of the fluid flowing through the flow path;
A valve provided in the flow path;
A flow rate control unit that operates the valve so that the flow rate measured by the flow rate measurement unit matches a predetermined target flow rate; and
The maintenance judgment index estimation device according to any one of claims 1 to 8,
The valve opening degree obtaining unit of the maintenance judgment index estimating device obtains an opening degree of the valve provided in the flow path. A first step of acquiring an opening of the valve when the flow rate of the fluid is maintained at a predetermined target flow rate during flow rate control for controlling the flow rate of the fluid using a valve;
Based on a function that approximates the relationship between the opening of the valve and the flow rate of the fluid, and the opening of the valve acquired by the first step, the opening of the valve is at the upper limit at the time of acquisition. And a second step of estimating a flow rate upper limit value as a maintenance determination index of the flow rate control device.