JP7359631B2 - flow control device - Google Patents

Description

The present invention relates to a flow rate control device that controls the flow rate of fluid such as air volume.

For example, in chemical experiments, substances that require careful handling may be used. For this reason, local exhaust devices such as draft chambers are used to prevent the diffusion of substances used in experiments. As this type of local exhaust device, there is a draft chamber that is equipped with a sash that can be opened and closed vertically or horizontally, and that controls the amount (flow rate) of air exhausted as the sash is opened and closed.

In the draft chamber described above, the local exhaust duct is provided with a venturi valve as a local exhaust valve. This Venturi valve changes the air volume within the local exhaust valve by varying the position of the valve stem using an actuator and moving the position of the valve plug.

In the draft chamber air volume control described above, the exhaust air volume to maintain the wind speed at the opening surface of the sash (surface wind speed) at a constant speed is determined according to the open/closed state of the sash, and the venturi valve is adjusted to achieve the determined exhaust air volume. control the position of the valve stem. In such control of the position of the valve stem, the position of the valve stem is measured using a potentiometer. The position of the valve stem is controlled so that the position of the valve stem measured using the potentiometer corresponds to the determined exhaust air volume.

JP2015-052336A

In the flow rate control described above, it has been confirmed that the position of the valve stem (the degree of opening of the valve) exceeds the target position and causes a phenomenon of repeated opening and closing (hunting phenomenon). In order to suppress this hunting phenomenon, a technique of providing a so-called dead zone has been proposed. However, if the hunting phenomenon occurs near the target position, it may not be easy to provide a dead zone due to, for example, control accuracy.

The present invention has been made to solve the above problems, and an object of the present invention is to suppress hunting of a valve whose opening degree is measured by a potentiometer.

The flow rate control device according to the present invention includes a valve that adjusts the flow rate of fluid flowing through piping, an actuator that changes the opening degree of the valve, a resistor, and an actuator that is in sliding contact with the resistor and is linked to the opening degree of the valve. a potentiometer equipped with a slider that changes the position on the resistor, an opening measuring section configured to measure the opening of the valve from the resistance value of the potentiometer, and an opening measured by the opening measuring section. Depending on the relationship with the set standard, the opening control section configured to control the operation of the actuator to control the opening of the valve and the operating state of the potentiometer are in the adjusted state. The valve includes a determining unit configured to determine whether the valve is in the adjusted state, and an adjusting unit configured to operate an actuator to open and close the valve within a predetermined range when the determining unit determines that the valve is in the adjusted state.

In one configuration example of the flow rate control device, the operation measuring unit is configured to measure the number of times the resistance value of the potentiometer remains in a stopped state without changing; It is set to the operating state, and it is determined whether the number of times of the stopped state has reached the specified number of times for the adjusted state.

In one configuration example of the flow rate control device described above, the operation measuring unit is configured to measure the operating time of the potentiometer, and the determining unit sets the operating time measured by the operating measuring unit to the operating state, and the operating time is adjusted. It is determined whether the specified time as a state has arrived.

In one configuration example of the flow rate control device, the determination unit sets the resistance value of the potentiometer to an operating state, and determines whether the resistance value of the potentiometer has reached an abnormal value set as an adjustment state.

In one configuration example of the flow rate control device, the adjustment unit operates the actuator to open and close the valve within a predetermined range, centering on a set location.

In one configuration example of the flow rate control device, the adjustment unit operates the actuator to open and close the valve between a maximum opening degree and a minimum opening degree.

In one configuration example of the flow rate control device, the adjustment unit operates the actuator to open and close the valve three or more times.

In one configuration example of the above-mentioned flow rate control device, the potentiometer includes a rotary shaft rotatably supported in conjunction with opening and closing of the valve, a resistor formed in an annular shape around the rotary shaft, and a resistor supported by the rotary shaft. A slider is provided which makes sliding contact with the resistor.

As described above, according to the present invention, when the determining unit determines that the valve is in the adjusted state, the adjusting unit operates the actuator to open and close the valve within a predetermined range, so that the opening of the valve is measured by the potentiometer. hunting can be suppressed.

FIG. 1 is a configuration diagram showing the configuration of a flow rate control device according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing the configuration of a venturi valve. FIG. 3A is an explanatory diagram for explaining hunting. FIG. 3B is an explanatory diagram for explaining hunting. FIG. 3C is an explanatory diagram for explaining hunting. FIG. 3D is an explanatory diagram for explaining hunting. FIG. 4 is a configuration diagram showing a part of the hardware configuration of the flow rate control device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow rate control device according to an embodiment of the present invention will be described below with reference to FIG. This flow control device includes a valve 101, an actuator 102, a potentiometer 103, an opening measuring section 104, an opening controlling section 105, a determining section 106, an adjusting section 107, and an operation measuring section 108.

Valve 101 regulates the flow rate of fluid flowing through the piping. Actuator 102 changes the opening degree of valve 101. The potentiometer 103 includes a resistor and a slider that slides into contact with the resistor and changes its position on the resistor in conjunction with the opening degree of the valve 101. The opening measuring section 104 measures the opening of the valve 101 from the resistance value of the potentiometer 103.

Here, the valve 101 is, for example, a venturi valve as shown in FIG. As shown in FIG. 2, the venturi valve includes a venturi pipe 201 as piping, a valve shaft 202 disposed at the position of the pipe shaft of the venturi pipe 201, and a valve stopper 203 fixed to the valve shaft 202. Furthermore, one end of a lever 204 that is rotatable about a fulcrum is connected to one end of the valve shaft 202, and the actuator 102 is connected to the other end of the lever 204.

The actuator 102 displaces the valve shaft 202 in the flow path direction of the Venturi tube 201 via the lever 204 . A potentiometer 103 is provided at the fulcrum of the lever 204. The potentiometer 103 in this case includes a rotary shaft that is rotatably supported in conjunction with the rotation of the lever 204, a resistor formed in an annular shape around the rotary shaft, and a resistor that is supported by the rotary shaft and resists. and a slider that makes sliding contact with the body. The opening measuring section 104 measures the opening from the position of the valve shaft 202 determined from the resistance value of the potentiometer 103.

Further, the valve stopper 203 has a built-in spring 205. In a venturi valve, when the lever 204 moves the valve shaft 202 to narrow the flow path between the venturi pipe 201 and the valve stopper 203, the resistance of the flow path increases and the amount of fluid (air) passing through is reduced. On the other hand, when the valve shaft 202 is moved by the lever 204 and the flow path between the Venturi tube 201 and the valve stopper 203 is widened, the resistance of the flow path is reduced and the amount of air passing through is increased.

In addition, by moving the position of the valve plug 203 due to the difference between the pressure difference before and after the venturi pipe 201 and the spring force of the spring 205, the amount of air passing through the venturi valve is constant with respect to the sliding position of the valve shaft 202. maintained within the range. That is, due to the valve plug 203 (pressure independent mechanism) integrated with the spring 205, when the static pressure is low, the force applied to the valve plug 203 is reduced, the internal spring 205 is expanded, and as the static pressure increases, When the force applied to the valve plug 203 increases, the spring 205 contracts, the valve shaft 202 moves, and the valve plug 203 moves toward the center, thereby maintaining the air volume.

Note that the valve 101 is not limited to the above-mentioned venturi valve, but can be any of various valves whose opening degree is changed by an actuator. Valve 101 can be, for example, a rotary valve such as a ball valve. As is well known, a rotary valve includes a valve body, an inflow passage, an outflow passage, a valve body, and a valve shaft for rotating the valve body from outside the valve body. Further, the valve body includes a through passage. By rotating the valve shaft around the axis and rotating the valve body using an actuator, the relationship between the inlet flow path, the outflow flow path, and the through flow path is changed, thereby changing the opening degree of the rotary valve. I can do it.

For example, by rotating the valve stem around its axis and rotating the valve body from a fully open state where the pipe axis of the through flow path and the pipe axes of the inflow and outflow channels coincide, the flow of fluid passing through can be adjusted. The amount of decreases. In the case of such a rotary valve, the potentiometer may be provided on the valve shaft so that the rotary shaft of the potentiometer rotates in conjunction with the valve shaft of the rotary valve. In this case, the opening measuring section 104 can measure the opening of the rotary valve from the rotational position of the valve shaft determined from the resistance value of the potentiometer 103.

The opening control section 105 controls the opening of the valve 101 by controlling the operation of the actuator 102 based on the relationship between the opening measured by the opening measuring section 104 and a set standard. The determining unit 106 determines whether the operating state of the potentiometer 103 has reached the set adjustment state. When the determining unit 106 determines that the adjustment state is established, the adjusting unit 107 operates the actuator 102 to open and close the valve 101 within a predetermined range.

For example, the adjustment unit 107 operates the actuator 102 to open and close the valve 101 within a predetermined range around a set location. Further, the adjustment unit 107 operates the actuator 102 to open and close the valve 101 between the maximum opening degree and the minimum opening degree.

The operation measurement unit 108 measures the number of times the potentiometer 103 is in a stopped state where the resistance value does not change. In this case, the determining unit 106 determines whether the number of stopped states measured by the operation measuring unit 108 is the operating state, and whether the number of stopped states has reached a prescribed number of times as an adjustment state.

Further, the operation measurement unit 108 can also be configured to measure the operation time of the potentiometer 103. In this case, the determining unit 106 sets the operating time measured by the operating measuring unit 108 to the operating state, and determines whether the operating time has reached the specified time as the adjusted state.

Further, the determining unit 106 can also set the resistance value of the potentiometer 103 to an operating state and determine whether the resistance value of the potentiometer 103 has reached an abnormal value set as an adjusted state. In this case, the operation measuring section 108 is not necessary.

As described above, according to the present embodiment, when the determining unit 106 determines that the adjustment state is established, the adjusting unit 107 operates the actuator 102 to open and close the valve 101 within a predetermined range. Hunting of the valve 101 whose opening degree is measured can now be suppressed.

Here, hunting of a valve whose opening degree is measured by a potentiometer will be explained. For example, in a fume hood, the opening and closing of the sash is often used in certain conditions. For this reason, even in the potentiometer used to measure the valve stem position as described above, the slider 132 of the potentiometer 103 is often placed at a specific location 151 of the resistor 131, as shown in FIG. 3A. do.

A detailed investigation of the condition of the potentiometer under the usage conditions described above revealed that abrasion powder, grease, etc. accumulated at a specific location 151 of the resistor 131, and a convexity due to the accumulation (accumulation) of these particles was found, as shown in FIG. 3B. It was confirmed that a portion 111 was formed. At this location of the convex portion 111, the contact between the resistor 131 and the slider 132 becomes poor, making it impossible to obtain an accurate signal from the potentiometer 103.

As described above, if an accurate signal is not obtained from the potentiometer 103, the position of the valve stem measured using the potentiometer 103 will be incorrect. In such a state, the valve stem is moved in order to eliminate the difference between the position and the position corresponding to the determined exhaust air volume. When the valve stem is moved, the slider 132 moves from the convex portion 111, and when the resistor 131 and the slider 132 come into contact (FIG. 3C), the correct position of the valve stem is measured. However, this position does not correspond to the determined exhaust air volume.

Therefore, the valve stem is further moved in the opposite direction in order to eliminate the difference from the position corresponding to the determined exhaust air volume. Due to this movement, the slider 132 moves again to the location of the convex portion 111, causing contact failure again, and the above-described operation is repeated, resulting in hunting. When hunting occurs, the actuator 102 is worn out, the resistor 131 and the slider 132 are worn out, and the product life is shortened.

As a result of intensive studies by the inventors in order to eliminate the hunting phenomenon that occurs as described above, as shown in FIG. It has been found that when the slider 132 is moved back and forth on the slider 131, the convex portion 111 is crushed, and as shown in FIG. 3D, a residual portion 112 with a residue remains is formed, which eliminates the problem of poor contact. It has been confirmed that in this state, an accurate signal can be obtained from the potentiometer 103.

When the actuator 102 is operated to open and close the valve 101, the slider 132 performs the above-mentioned reciprocating movement accordingly. Therefore, hunting can be prevented by operating the actuator 102 to open and close the valve 101 within a predetermined range using the adjustment unit 107. Here, it has been confirmed that hunting is eliminated if the slider 132 performs the above-mentioned reciprocating motion three or more times. Therefore, it is desirable that the adjustment unit 107 operate the actuator 102 so as to open and close the valve 101 three or more times.

Here, the accumulation of grease and the like at the specific locations described above occurs as the potentiometer 103 operates. Therefore, the relationship between the operating state of the potentiometer 103 and the occurrence of hunting should be observed in advance, and the adjustment state in the determination unit 106 should be determined based on the operating state of the potentiometer 103 when hunting occurs. I can do it.

For example, during operation of the flow control device, the slider of the potentiometer 103 repeatedly stops and moves. The number of times this stopped state can be used as the above-mentioned operating state. When the slider is stopped, the resistance value of the potentiometer 103 does not change, and the number of times the slider is in this stopped state is measured by the operation measurement unit 108, and the slider can be set as an operating state. In this case, the determination unit 106 may be set with a previously measured number of stops at which hunting occurs as a prescribed number of times.

Further, the operating time of the potentiometer 103 can also be set to the operating state. In this case, the operating time at which hunting occurs, which is measured in advance, may be set in the determination unit 106 as a specified time.

Further, as described above, if a convex portion is formed due to accumulation of grease or the like, the contact between the resistor 131 and the slider 132 becomes poor, and the resistance value of the potentiometer 103 becomes an abnormal value. Therefore, the above abnormal value can be set in the determination unit 106.

In addition, as shown in FIG. A computer device includes a main storage device 301, a main storage device 302, an external storage device 303, a network connection device 304, etc., and a CPU 301 operates (executes the program) according to a program developed in the main storage device 302. It is also possible to implement each of the functions described above. The above program is a program for realizing on a computer the functions shown in the embodiments described above. Network connection device 304 connects to network 305 . Also, each function can be distributed among multiple computer devices.

Furthermore, the opening measurement section 104, the opening control section 105, the judgment section 106, the adjustment section 107, and the operation measurement section 108 in the embodiment described above are programmable logic devices (PLDs) such as FPGAs (field-programmable gate arrays). It is also possible to configure it using a programmable logic device (Programmable Logic Device). For example, a logic element of an FPGA can be made to function by providing each of a storage section, an opening measurement section 104, an opening control section 105, a judgment section 106, an adjustment section 107, and an operation measurement section 108 as circuits. Each of the memory circuit, opening degree measurement circuit, opening degree control circuit, determination circuit, adjustment circuit, and operation measurement circuit can be written in the FPGA by connecting a predetermined writing device. Further, each of the above circuits written in the FPGA can be confirmed by a writing device connected to the FPGA.

As described above, according to the present invention, when the determining unit determines that the valve is in the adjusted state, the adjusting unit operates the actuator to open and close the valve within a predetermined range, so that the opening degree is measured by the potentiometer. Valve hunting can be suppressed.

It should be noted that the present invention is not limited to the embodiments described above, and many modifications and combinations can be made within the technical idea of the present invention by those having ordinary knowledge in this field. That is clear.

DESCRIPTION OF SYMBOLS 101... Valve, 102... Actuator, 103... Potentiometer, 104... Opening degree measurement part, 105... Opening degree control part, 106... Judgment part, 107... Adjustment part, 108... Operation measurement part.

Claims (8)

a valve that adjusts the flow rate of fluid flowing through the piping;
an actuator that changes the opening degree of the valve;
a potentiometer comprising a resistor and a slider that is in sliding contact with the resistor and changes its position on the resistor in conjunction with the opening degree of the valve;
an opening measuring section configured to measure the opening of the valve from the resistance value of the potentiometer;
an opening control section configured to control the opening of the valve by controlling the operation of the actuator based on the relationship between the opening measured by the opening measurement section and a set standard;
a determination unit configured to determine whether the operating state of the potentiometer has reached a set adjustment state;
and an adjusting section configured to operate the actuator to open and close the valve within a predetermined range when the determining section determines that the adjustment state is reached. The flow rate control device according to claim 1,
comprising an operation measuring unit configured to measure the number of times the potentiometer is in a stopped state where the resistance value does not change;
The determination unit is characterized in that the number of times the stopped state measured by the operation measuring unit is set as the operating state, and determines whether the number of times the stopped state has reached a prescribed number of times as the adjusted state. Flow control device. The flow rate control device according to claim 1,
comprising an operation measuring section configured to measure the operating time of the potentiometer,
The flow rate control device is characterized in that the determining unit determines whether or not the operating time measured by the operating measuring unit is the operating state, and the operating time has reached a specified time as the adjusted state. The flow rate control device according to claim 1,
The flow control device is characterized in that the determination unit sets the resistance value of the potentiometer to the operating state and determines whether the resistance value of the potentiometer has reached an abnormal value set as the adjustment state. The flow rate control device according to any one of claims 1 to 4,
The flow rate control device is characterized in that the adjustment unit operates the actuator to open and close the valve within a predetermined range centered on a set location. The flow rate control device according to any one of claims 1 to 4,
The flow control device is characterized in that the adjustment unit operates the actuator to open and close the valve between a maximum opening degree and a minimum opening degree. The flow rate control device according to any one of claims 1 to 6,
The flow control device is characterized in that the adjustment unit operates the actuator to open and close the valve three or more times. The flow rate control device according to any one of claims 1 to 7,
The potentiometer includes a rotary shaft rotatably supported in conjunction with opening and closing of the valve, a resistor formed in an annular shape around the rotary shaft, and a resistor supported by the rotary shaft. A flow rate control device comprising the slider in sliding contact.

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