JP2005207523A - Flow control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow control device capable of effectively restraining extraordinary generation of heat of a solenoid even though inflow or outflow of fluid is disturbed. <P>SOLUTION: The device is provided with a solenoid type valve mechanism which regulates a flow rate of fluid flowing through a predefined flow passage by adjusting valve opening in accordance with a carried current of a proportional solenoid and a flow sensor which detects a flow rate of fluid flowing through the flow passage. The device is also provided with a first control means which adjusts valve opening of the valve mechanism in accordance with the set flow rate value or in accordance with a difference between setting flow rate value and flow rate detected via the flow sensor and a second control means which throttles the valve opening to the predefined value instead of the first control means when the flow rate detected via the flow sensor keeps below the predefined value for a constant time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flow rate control device that controls a flow rate of a fluid flowing through a predetermined flow path using a solenoid type valve mechanism.

In various industrial processes, process processing is often performed while supplying a predetermined fluid (for example, process gas) at a predetermined flow rate. For such fluid supply amount (flow rate) control, a valve mechanism using a proportional solenoid is exclusively used. This type of valve mechanism varies the valve opening according to the energization current of the proportional solenoid, thereby adjusting the flow rate of the fluid flowing through a predetermined flow path, and is also referred to as a proportional solenoid valve. In addition, the flow rate control device using this valve mechanism (proportional solenoid valve) detects the flow rate of the fluid flowing through the flow path with a flow rate sensor provided in the flow path, while the difference between the detected flow rate and the set flow rate. The valve opening degree of the valve mechanism is varied in accordance with (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2001-227657

  By the way, when the proportional solenoid, particularly the solenoid portion thereof, is miniaturized in order to miniaturize the above-described flow rate control device, it is generally necessary to increase the energization current in order to maintain the same driving force. Then, it cannot be denied that the amount of heat generated by the solenoid increases as the energization current increases. Incidentally, since the heat generated by the solenoid is normally transferred to the fluid flowing through the flow rate control device (proportional solenoid) and released to the outside, the proportional solenoid does not generate heat abnormally.

  However, even though the fluid flow rate is controlled by the proportional solenoid, if the main flow plug of the fluid supply source is closed or the fluid to be supplied disappears (so-called gas shortage), the fluid does not flow. Not only does heat dissipation through the fluid disappear, but the proportional solenoid is automatically set to the fully open state in accordance with the comparison result with the flow rate setting value by the flow rate control, and a large drive current flows. If the proportional solenoid is fully opened, the proportional solenoid may break down due to abnormal heat generation. Further, the heat generated by the solenoid is transmitted to the flow rate sensor provided in the flow path through the flow path body, which may adversely affect the measurement characteristics of the flow rate sensor. Therefore, it is necessary to suppress abnormal heat generation of the proportional solenoid.

  The present invention has been made in consideration of such circumstances, and its purpose is to effectively suppress the abnormal heat generation of the solenoid even when the fluid flow is obstructed for some reason. To provide a flow control device.

In order to achieve the above-described object, the flow rate control device according to the present invention includes:
<a> a solenoid-type valve mechanism that is provided in a predetermined flow path and adjusts the flow rate of the fluid flowing through the flow path by changing the valve opening according to the energization current of the proportional solenoid;
<b> a flow sensor for detecting the flow rate of the fluid flowing through the flow path;
<c> Control means for adjusting the valve opening degree of the valve mechanism in accordance with the designated valve opening degree or according to the difference between the set flow rate value and the flow rate detected through the flow rate sensor (first In particular, the heat generation of the solenoid-type valve mechanism becomes a problem when the fluid flow is interrupted by any cause, and the fluid flow is blocked. Focusing on the fact that the detected state can be detected via the flow sensor,
<d> means for narrowing the valve opening to a predetermined value instead of the control means (first control means) when the flow rate detected via the flow sensor falls below a predetermined value for a predetermined time (first 2 control means) is provided.

  That is, the present invention includes a solenoid-type valve mechanism and a flow sensor, and according to a specified valve opening or according to a difference between a set flow rate value and a flow rate detected through the flow sensor. Focusing on the fact that the flow rate control device that controls the flow rate of the fluid flowing through the valve mechanism by varying the valve opening degree of the valve mechanism detects the flow rate by the flow rate sensor, If the flow rate is lower than the predetermined value despite being controlled to the set value, it is determined that the flow of fluid is hindered for some reason, and the valve opening of the valve mechanism is increased. It is characterized by forcibly narrowing down to a predetermined value, thereby suppressing heat generation of the solenoid type valve mechanism.

  Incidentally, when the flow rate is lower than the predetermined value even though the flow rate is being made constant under the feedback control, the valve opening of the valve mechanism is set to the fully open state under the feedback control. Therefore, it is desirable that the second control means is configured to operate by detecting that the valve opening degree controlled by the first control means is fully open over a certain period of time.

  Further, in the second control means, when the time during which the valve opening is further reduced to the predetermined value described above continues for a predetermined time, it is determined that the abnormal state is continuing and the valve opening is set. It is desirable to have a function of fully closing.

  According to the flow control device configured as described above, if the flow rate continues to be lower than the predetermined value even though the valve mechanism is controlled to set the flow rate to the set value, some abnormality occurs. The valve opening of the solenoid-type valve mechanism is narrowed down to a predetermined value, effectively preventing abnormal heat generation of the valve mechanism even in situations where heat dissipation due to fluid flow cannot be expected. can do. As a result, failure of the solenoid type valve mechanism due to abnormal heat generation, deterioration of measurement characteristics of the flow rate sensor, and the like can be simplified and effectively prevented. In addition, the solenoid-type valve mechanism is not fully opened over a long period of time even though no fluid is flowing, so that the amount of drive current can be suppressed to a small extent, which greatly contributes to power saving.

  Furthermore, as described above, since the valve opening degree of the solenoid type valve mechanism is merely narrowed to a predetermined value, the flow of the fluid through the valve mechanism resumes when the abnormal factor is removed. As a result, the resumption of fluid flow can be quickly detected via the flow sensor, so that the flow rate stabilization control by the drive control of the valve mechanism based on the fluid flow rate can be resumed quickly. It becomes.

Hereinafter, a flow control device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a flow control device according to this embodiment, and 10 is a flow channel body in which a flow channel having a predetermined shape is formed. The flow channel body 10 is generally provided with a round hole-shaped upstream flow channel 11 drilled from one end side to a predetermined depth, and a round hole-shaped downstream flow channel 12 drilled from the other end side. And a block body in which communication holes 13 and 14 communicating with the bottoms of the flow paths 11 and 12 are opened on the side of the flow path body 10 (upper side in the drawing).

  A solenoid type valve mechanism 20 is attached to the communication holes 13 and 14 of the flow path body 10. The solenoid-type valve mechanism 20 includes a valve body 23 at the tip of a thrust shaft 22 that is driven forward and backward by a solenoid 21, and a clearance (valve opening degree) between the valve seat 24 facing the valve body 23 and the valve body 23. ). In particular, the valve mechanism 20 has a shape in which the valve body 23 with respect to the valve seat 24 is flattened, and functions as a shut-off valve that blocks the flow path by closing the valve seat 24 with the valve body 23. have. The solenoid 21 is energized and the valve body 23 is pulled away from the valve seat 24, whereby the valve opening degree (the gap between the valve body 23 and the valve seat 24) is varied to proportionally control the fluid flow rate. It has become something that has.

  Further, here, the outer side of the valve body 23 in the valve mechanism 20 is connected to the upstream flow path 11 through the communication hole 13, and the inner side (the valve seat 24 side) of the valve body 23 is connected to the downstream side through the communication hole 14. By connecting to the side channel 12, a so-called flow-to-close type valve that controls the flow rate of the fluid flowing from the outside to the inside of the valve is realized. The fluid (gas) introduced into the upstream flow path 11 of the flow path body 10 is guided to the downstream flow path 12 through the valve mechanism 20 having such a structure.

  A plurality of rectifying wire meshes (rectifying bodies) 15 are fitted in the inlet portion of the upstream flow path 11 in the flow path body 10 so as to overlap each other. These rectifying metal meshes 15 play a role of rectifying the fluid (gas) introduced into the upstream flow path 11 so that the fluid (gas) smoothly flows along the flow path. In addition, a flow rate sensor 30 is provided on the downstream wall surface of the rectifying wire mesh 15 in the upstream flow path 11, and the upstream flow path 11 is connected to the upstream flow path 11 via the flow path body 10. The flow rate of the flowing fluid is detected. Incidentally, the flow rate sensor 30 has a structure in which a pair of temperature sensors are provided with a heating element sandwiched in the direction of fluid flow, and a change in temperature distribution due to the flow velocity (flow rate) of the fluid is detected by the pair of temperature sensors. It consists of a thermal flow sensor that detects the mass flow rate.

  As described above, the solenoid-type valve mechanism 20 is attached to the flow path block 10 in which a predetermined flow path is formed, and the main body of the flow rate control device incorporating the flow rate sensor 30 is mainly composed of a microprocessor (CPU) 41. The operation is controlled by the control unit 40. The microprocessor 41 inputs switch information instructed from a setting / display unit 42 as a man-machine interface via a switch input circuit 43, and sets a flow rate setting value and other operating conditions. The microprocessor 41 basically inputs the output (flow rate) of the flow rate sensor 30 via the sensor signal processing circuit 44, and controls the operation of the proportional valve drive circuit 45 in accordance with the flow rate, thereby controlling the solenoid. 21 changes the energizing current, thereby controlling the operation of the valve mechanism 20, specifically the valve opening degree.

  The microprocessor 41 receives an operation switching request such as forcibly fully closing or fully opening the valve mechanism 20 via the external contact input circuit 46. The flow rate setting value for the above-described flow rate control can be input as voltage information via the analog setting input circuit 47 without passing through the setting / display unit 42 described above. Further, the microprocessor 41 has a function of communicating information with a main control circuit (not shown) via a communication interface 48 and a function of storing predetermined information using a memory 49 such as an EEPROM. Further, the microprocessor 41 appropriately displays information such as the flow rate obtained from the flow rate sensor 30 by its operation on the setting / display unit 42 via the display output circuit 50 and also via the control flow rate output circuit 51. The information is output, and information such as an abnormality alarm is output via the event / alarm output circuit 51.

Basically, in the flow rate control device configured as described above, the present invention is characterized in that the control function of the microprocessor 41 is detected by the flow rate sensor 30 as shown in FIG. A PID calculation unit (first operation) for comparing the flow rate Q of the fluid (gas) with the set flow rate value SP described above and obtaining the drive current I for the solenoid 21 for adjusting the valve opening degree of the valve mechanism 20 according to the difference. 1 control means) 60. Further, the microprocessor 41 compares the drive current I obtained by the PID calculation unit 60 with a preset current limit value I ₂ to detect the fully open state of the valve mechanism 20, and the flow sensor 30. The comparison unit 62 detects the state in which the flow rate Q detected in step 1 is compared with a predetermined flow rate threshold value Q _L and the flow rate is less than the flow rate threshold value Q _L. Further, the microprocessor 41 receives the outputs of the comparison units 61 and 62, and sets the duration of the state in which the valve mechanism 20 is fully open and the flow rate Q is less than the flow rate range value Q _L to the first and The second timer units 63 and 64 have a function of measuring time.

Incidentally, the first timer unit 63 outputs a time over signal when the valve mechanism 20 is fully open and the duration of the state where the flow rate Q is less than the flow rate range value Q _L continues for, for example, 5 minutes. In addition, the second timer unit 64 is used when the valve mechanism 20 is in a fully open state and the duration of the state where the flow rate Q is less than the flow rate range value Q _L continues for, for example, 30 minutes. A time over signal is output.

The output control unit 65 determines the valve opening degree of the valve mechanism 20 from the output of the PID calculation unit 60, and from the output of the comparison unit 61 and the outputs of the first and second timer units 63 and 64. A decrease in the flow rate of the fluid and its duration are determined, and the operation of the selector 66 is controlled based on these determination results. The output control section 65 in particular, the PID operator if 61 is the drive current I obtained does not reach the current limit value I _2, the comparison unit 61 is that the clogging valve mechanism 20 is not fully opened state Is determined, the output (drive current I) of the PID calculation unit 60 is directly output as a valve opening control value for the proportional valve drive circuit 45 via the selector 66. The valve opening degree of the valve mechanism 20 is feedback-controlled according to the flow rate Q by the output (drive current I) of the PID calculation unit 60, and basically the fluid flow rate Q via the flow rate control device is kept constant. Be drunk.

In contrast, when the drive current I has reached the current limit value I ₂ and the comparison unit 61 determines that the valve mechanism 20 is fully open, the output control unit 65 first determines the comparison unit 65. from the output of 62 determines whether the flow rate Q is less than the flow rate range value Q _L. Then, the output of the first timer unit 63 is monitored. And by the time-over signal from the first timer section 63, for example, when the valve mechanism 20 has been shown that the flow rate Q for over 5 minutes a condition below the flow threshold Q _L, the output control section 65 switches the selector 66 and selects a preset current value I ₁ instead of the drive current I obtained by the PID calculation unit 60 described above, and outputs the selected current value I ₁ to the proportional valve drive circuit 45. Is set to a state where the valve is slightly opened from the fully closed state (second control means). Further, when the time-over signal from the second timer unit 64 indicates that the flow rate Q of the valve mechanism 20 is below the flow rate threshold value Q _L for 30 minutes or more, for example, output control The section 65 selects the preset current value I ₀ (= 0) instead of the current value I ₁ described above, and switches the operation of the selector 66 so as to output it to the proportional valve drive circuit 45, thereby The valve mechanism 20 is forcibly set to a fully closed state.

In other words, the output control unit 65 first determines whether or not the valve mechanism 20 is fully opened as shown in FIG. 3 as an example of the control procedure [step S1]. It is determined whether or not Q is equal to or less than a predetermined flow rate Q _L [step S2]. When these conditions are satisfied, it is determined whether or not the duration is t ₁ (for example, 5 minutes) or more [Step S3], and further, the duration is t ₂ (for example, 30 minutes) or more. [Step S4]. And according to these conditions, or to control the operation of the valve mechanism 20 with the output of the PID calculation section 60 described above (the drive current I) [step S5], or preset current value valves with I ₁ or mechanism 20 is set to slightly open state [step S6], and more selectively performs control to set the valve mechanism 20 to the fully closed state [step S7] by using the current value I _0.

Thus, according to such control, as shown in the operation timing in FIG. 4, when the flow rate Q of the fluid flowing through the flow rate control device decreases for some reason, the flow rate decrease is compensated for by a predetermined amount. The drive current I of the solenoid 42 is increased to ensure the set flow rate, and the valve mechanism 20 is automatically set to the fully open state. At this time, the drive current I of the solenoid 42 is limited to the maximum limit value I ₂ . When the flow rate Q of the fluid flowing through the flow rate control device does not increase in spite of such control, the valve mechanism 20 is kept fully open under the above-described PID control. If it is confirmed that the flow rate Q measured in this state is lower than the flow rate range value Q _L for a predetermined time t ₁ , the current for driving the solenoid 42 is reduced to the predetermined value I ₁ . Then, by narrowing the valve opening of the valve mechanism 20 to a predetermined value, while maintaining a state in which a fluid (gas) can flow slightly, heat generation in the solenoid 42 is suppressed, and at the same time wasteful power consumption is reduced.

Further, after the valve opening degree of the valve mechanism 20 is narrowed as described above, when the state where the flow rate Q of the fluid is lower than the flow rate range value Q _L continues for a time t ₂ or more, It is determined that the flow is not expected to be restored, and the current for driving the solenoid 42 is reduced to a predetermined value I ₀ (= 0). Then, by setting the valve mechanism 20 to a fully closed state, heat generation of the solenoid 42 is suppressed, and unnecessary power consumption in the solenoid 24 is eliminated. As a result, for example, when all of the fluid source housed and supplied in the cylinder is consumed and the flow of the fluid through the flow rate control device is lost, under the above-mentioned PID control as the flow rate decreases. The valve mechanism 20 is not controlled to be fully opened for a long time. Therefore, when the fluid flow is lost, a situation in which the solenoid 42 generates heat abnormally due to the drive current I ₂ that fully opens the valve mechanism 20 is effectively prevented. Therefore, the valve mechanism 20 does not cause a problem that the heat is generated by the heat generation, and the power consumption can be sufficiently reduced. Further, since there is no abnormal heat generation of the valve mechanism 20, the heat is not transmitted to the flow path sensor 30 via the flow path block 10, and the measurement accuracy of the flow path sensor 30 is not deteriorated, so that stable operation is guaranteed. It becomes possible to do.

If the flow of the fluid to the flow control device is resumed before the time t ₂ described above with the valve opening degree of the valve mechanism 20 reduced as described above, the operation timing is shown in FIG. Since the fluid flow rate Q exceeds the flow rate range value Q _L , the above-described narrowing of the valve mechanism 20 is released. As a result, the current value I corresponding to the difference between the flow rate Q obtained by the PID control unit 60 and the flow rate set value SP is supplied to the solenoid 21 via the selector 66. The feedback control is resumed. As a result, the flow control by the flow controller returns to the normal state. At this time, the heat generated by the energizing current of the solenoid 21 is dissipated to the outside while being absorbed by the fluid flowing through the valve mechanism 20, so that abnormal heat generation of the valve mechanism 20 is effectively suppressed.

  Here, the valve mechanism 20 described above will be described. The valve mechanism 20 has a flow to close method as shown in FIG. 6A and a flow as shown in FIG.・ Some models have a flow to open method. As described above, the flow-to-close type valve mechanism 20 is of a type that allows fluid to flow from the outside to the inside of the valve, and moves the valve body 23 in a direction against the pressure applied from the fluid supply side. And configured to increase the flow rate. The flow-to-open type valve mechanism 20 is of a type that allows fluid to flow from the inside to the outside of the valve. The valve body 23 is moved in the direction of pressure applied from the fluid supply side to increase the flow rate. Configured to let

Further, the solenoid type valve mechanism 20 having this kind of shut-off function is such that the valve opening is varied by the drive current of the solenoid 21, and the flow rate Q with respect to the increase or decrease of the drive current I is shown in FIG. ) And a hysteresis characteristic as shown in FIG. Moreover, the hysteresis characteristic changes depending on the differential pressure between the outside and inside of the valve. Specifically, in the flow-to-close type valve mechanism 20, the pressure on the fluid supply side acts so as to hold down the valve body 23, so that the flow rate Q exceeds a predetermined flow rate threshold value Q _L. The drive current I ₁ may be smaller as the differential pressure applied to the valve mechanism 20 is smaller. In the flow-to-open method of the valve mechanism 20 with respect to this, the pressure of the fluid supply side acts to expand pushing the valve element 23, since the flow rate Q is to exceed a predetermined flow rate threshold value Q _L The drive current I ₁ may be smaller as the differential pressure applied to the valve mechanism 20 is larger.

On the other hand, in the state where the valve opening degree of the valve mechanism 20 is reduced and the heat generation amount is suppressed as described above, in order to detect the resumption of fluid flow and quickly return the valve mechanism 20 to normal operation, It is desirable that the fluid starts to flow through the valve mechanism 20 with a small differential pressure applied to the valve mechanism 20. Thus while suppressing as much as possible reduce the driving current I ₁ for such flow Q as described above exceeds the flow threshold value Q _L, the normal operation of the valve mechanism 20 by detecting the flow rate of the fluid exceeds the above flow threshold value Q _L In order to start, it is desirable that the drive current I _{1 be} in the range shown in FIGS. 6B and 7B. Further, as is clear from the comparison of the current / flow rate characteristics shown in the figure, the drive current I _{1 is} greater when the flow-to-close type valve mechanism 20 is used than when the flow-to-open type valve mechanism 20 is used. Can be set to be low, which is advantageous.

Incidentally, when the flow-to-close type valve mechanism 20 is used, the drive current I ₁ for exceeding the flow rate threshold value Q _L increases as the differential pressure applied to the valve mechanism 20 increases. Therefore, when a high differential pressure is applied to the valve mechanism 20 when fluid flow is resumed, the differential pressure acts in the direction of closing the valve body 21 in a state where the drive current I ₁ is kept constant, so that the valve mechanism 20. There is a possibility that the flow rate Q flowing through the flow rate becomes lower than the flow rate threshold value Q _L. However, in actuality, the differential pressure applied to the valve mechanism 20 does not increase rapidly due to the piping capacity in the piping system in which the flow rate control device is incorporated, and thus changes gradually. As illustrated in FIG. fluid flowing at a rate exceeding the threshold value Q _L. Therefore, when the flow rate temporarily exceeds the flow rate threshold value Q _L , this is detected and immediately the supply of the drive current I ₁ is canceled, and the difference between the flow rate Q from the PID control unit 60 and the flow rate set value SP. If the current I corresponding to is supplied, the flow control device can be returned to normal operation.

Therefore, as described above, when the flow rate Q of the fluid falls below the flow rate threshold value Q _L for a predetermined time, the drive current I of the valve mechanism 20 is kept low as described above to suppress the heat generation and wasteful power consumption. However, the flow rate control device can be quickly returned to normal operation when the fluid resumes flow after exceeding the flow rate threshold value Q _L.
The present invention is not limited to the embodiment described above. For example, the above-described flow rate threshold value Q _L may be determined according to the flow rate of the fluid to be controlled, and the valve mechanism 20 also applies to the drive current I ₁ that causes the flow rate Q to exceed the flow rate threshold value Q _L. What is necessary is just to determine according to the specification etc. Although the flow control device that automatically controls the flow rate Q has been described as an example here, it is needless to say that the form of feedback control is not limited to PID control.

The present invention can be similarly applied to an apparatus that manually sets the flow rate Q by feedforward control of the valve opening. That is, when the flow rate Q is less than the predetermined flow rate threshold value Q _L regardless of the valve opening degree being set to full open by manual operation, the valve opening amount is reduced to the predetermined value as described above. Anyway. In addition, various modifications can be made without departing from the scope of the present invention.

1 is a schematic configuration diagram of a flow control device according to an embodiment of the present invention. The figure which shows the structural example of the control circuit with respect to a valve mechanism. The figure which shows the example of the control processing procedure with respect to a valve mechanism. The timing diagram which shows the flow volume suppression and interruption | blocking operation | movement of a valve mechanism. The timing diagram which shows the flow volume suppression of a valve mechanism, and its return operation | movement. The figure which shows the valve mechanism of a flow-to-close system, and its operation characteristic. The figure which shows the valve mechanism of a flow-to-open system, and its operation characteristic. The figure which shows the relationship between the flow volume added to a valve mechanism at the time of a fluid flow start, and differential pressure | voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow path block 20 Valve mechanism 30 Flow rate sensor 40 Control part 41 Microprocessor

Claims (3)

A solenoid-type valve mechanism that is provided in a predetermined flow path and adjusts the flow rate of the fluid flowing through the flow path by changing the valve opening according to the energization current of the proportional solenoid;
A flow rate sensor for detecting a flow rate of the fluid flowing through the flow path;
First control means for adjusting the valve opening of the valve mechanism according to a specified valve opening or according to a difference between a set flow rate value and a flow rate detected via the flow sensor;
A second control means for reducing the valve opening to a predetermined value instead of the first control means when the flow rate detected via the flow sensor falls below a predetermined value for a predetermined time; A flow control device characterized by.   2. The flow rate control device according to claim 1, wherein the second control unit operates by detecting that the valve opening degree controlled by the first control unit is fully open over a predetermined time.   The said 2nd control means is provided with the function which makes the said valve opening fully closed when the time which narrowed down the said valve opening to predetermined value continued over predetermined time. 2. The flow control device according to 2.

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