JPH0449690Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application The present invention relates to a flow rate control device, and particularly to a valve device for automatically correcting the flow rate control range of a fluid to be treated, and for detecting abnormalities occurring in a valve device and a flow path for controlling the flow rate. The present invention relates to a flow rate control device configured to allow detection.

2. Description of the Related Art In general, a flow rate control device measures the flow rate of a fluid flowing through a flow path using a flow rate measurement section such as a thermal mass flowmeter, and receives a flow rate measurement signal from the flow rate measurement section.
The flow rate is controlled by comparing the flow rate with a setting signal and varying the valve opening of the valve device so that the difference becomes zero. The above-mentioned valve device displaces the valve body by the driving force of an electromagnetic solenoid, for example,
The valve body is pressed against the valve seat to close the valve, and the valve body is assembled with a packing that comes into contact with the valve seat when the valve is closed.

Problems that the invention aims to solve: However, when using the above flow rate control device for a long time, the packing on the valve body gradually deforms and the valve opening position at maximum flow rate and the valve opening position at the beginning of flow shift, making it difficult to accurately control the flow rate. There is a problem that it becomes difficult to control well. Further, as the fluid passes through the flow path of the flow control device, foreign matter in the fluid may accumulate in the middle of the flow path or adhere to the throttle in the flow path. As described above, if the packing of the valve device is deformed or foreign matter occurs in the flow path, it becomes difficult to accurately control the flow rate even if the valve device is driven. However, conventional flow rate control devices are not equipped with any means for detecting abnormalities in the valve devices as described above, so there is a problem in that abnormalities in the valve devices, etc. cannot be discovered until the flow rate cannot be controlled. There is.

Therefore, an object of the present invention is to provide a flow rate control device that solves the above problems.

Means and Effects for Solving Problems The present invention uses the above flow rate control device to store the current value of the electromagnetic solenoid when the valve device opens and fluid starts to flow as an offset current, and to store the current value of the electromagnetic solenoid when the valve device opens and fluid starts flowing, and The device is equipped with means for storing current values and monitoring the current values based on the offset current and the maximum flow rate current, thereby automatically correcting the flow rate control range and detecting the occurrence of an abnormality.

Embodiment FIG. 1 shows an embodiment of the flow rate control device according to the present invention. In FIG. 1, a flow path 2 of a flow rate control device 1 is provided with an electromagnetic solenoid driven valve device 3. The flow path 2 on the upstream side of the valve device 3 is the sensor flow path 4
and a bypass flow path 5. A throttle 6 is provided in the bypass flow path 5, and the sensor flow path 4
branches from the bypass flow path 5 on the upstream side of the throttle 6 and connects to the bypass flow path 5 on the downstream side of the throttle 6. Note that the throttle 6 is made up of a plurality of thin tubes, functions as a throttle, and makes the flow of the fluid to be laminar.

Due to the pressure loss when the to-be-side fluid passes through the restrictor 6 while flowing through the flow path 2, the to-be-side fluid is divided into the sensor flow path 4 and the bypass flow path 5 at a constant dividing ratio.
Therefore, the total flow rate of the fluid flowing through the flow path 2 can be determined by measuring the flow rate of the sensor flow path 4.

The sensor flow path 4 is formed by a sensor pipe 7 made of a thin, thin-walled pipe. A pair of self-heating resistors 9a, 9 forming a thermal mass flowmeter as the flow rate measuring section 8 are disposed on the outer periphery of the sensor pipe 6.
b is wound. A pair of self-heating resistors 9
a and 9b are connected to a pair of resistors (not shown) in the detection circuit 10 to form a bridge circuit. When measuring the flow rate, the self-heating resistors 9a and 9b are supplied with current and heated.

Since the self-heating resistors 9a and 9b are deprived of heat according to the flow rate of the fluid flowing in the sensor flow path 4, the heat is removed between the upstream self-heating resistor 9a and the downstream self-heating resistor 9b. A temperature difference occurs. Therefore, due to the temperature difference, the self-heating resistors 9a and 9b
The resistance value changes, the current value changes, and the bridge circuit balance is disrupted. As a result, the detection circuit 10 outputs a voltage proportional to the flow rate as a flow rate measurement signal.

The signal output from the detection circuit 10 is sent to the amplifier circuit 1.
1 and supplied to the control circuit 12. Also,
A setting signal S for setting the flow rate is input to the control circuit 12 in advance. The control circuit 12 is the amplifier circuit 1
The flow measurement signal q from 1 is compared with the setting signal S, and the deviation between the two is output. Valve drive circuit 13
is input with the deviation signal from the control circuit 12,
The current value to the electromagnetic solenoid 14 is varied according to the deviation.

The electromagnetic solenoid 14 that drives the valve device 3 is supplied with a current according to the deviation from the valve drive circuit 13 to vary the valve opening degree of the valve device 3. Also, the control circuit 1
The current from the valve drive circuit 13 is input to the valve drive circuit 2.

The control circuit 12 has means for monitoring the drive current of the electromagnetic solenoid 14, and stores the current value when the valve device 3 opens and fluid begins to flow as an offset current If. Further, the control circuit 12 stores the current value when the fluid has the maximum flow rate as the maximum drive current Im. The valve drive circuit 13 is supplied with a signal that is a combination of the deviation signal and the offset current If signal. The electromagnetic solenoid 14 is driven by a drive current having a current value based on a signal that is a combination of the deviation signal and the offset current If signal, and controls the valve opening degree of the valve device 3.

Therefore, even if the offset current If when the fluid starts to flow changes due to changes in the packing etc. over time,
The control circuit 12 stores the current value and automatically corrects the drive current supplied to the electromagnetic solenoid 14.
That is, the control circuit 12 sets the control current range between the offset current value and the maximum drive current value using the offset current If as a reference. Therefore, the control circuit 12
Flow rate control can be performed with higher accuracy than when the current of the electromagnetic solenoid 14 is controlled within the control range from zero to the maximum drive current value. That is, since the number of bits (resolution) handled as data by the control circuit 12 is determined, the narrower the control range, the more finely divided the current value can be controlled, thereby increasing the accuracy of flow rate control.

For example, when an abnormality occurs in the valve device 3 or the like as described later, the control circuit 12 has means for detecting the occurrence of the abnormality and outputting a signal indicating the abnormality by monitoring the drive current value of the electromagnetic solenoid 14. . An abnormality indicator 15 is connected to the control circuit 12 . When the abnormality indicator 15 receives a signal indicating the occurrence of an abnormality, it displays the details of the abnormality that has occurred in the flow rate control device 1, or issues an alarm to inform the operator.

FIG. 2 shows the internal structure of the valve device 3. In FIG. 2, an electromagnetic solenoid 14 is assembled to the upper part of the main body 3a of the valve device 3. Electromagnetic solenoid 14
is formed by inserting a plunger 14b into an annular coil portion 14a. A valve body 16 is screwed onto the lower end of the plunger 14b.

Further, a disc-shaped leaf spring 17 having a slit is interposed between the lower end of the plunger 14b and the valve body 16.

The peripheral edge of the leaf spring 17 is connected to the stepped portion _3a1 of the main body 3a,
It is held between a contact member 18 whose upper surface is brought into contact with the electromagnetic solenoid 14. Therefore, the valve body 16
The biasing force of the leaf spring 17 acts in the valve closing direction, and when the valve is opened, the plunger 14b is attracted by the electromagnetic force of the coil portion 14a and moves upward against the biasing force of the leaf spring 17. Reference numeral 25 denotes an O-ring that provides a fluid-tight seal between the contact member 18 and the main body 3a.

The main body 3a of the valve device 3 is provided with an inlet 19 that communicates with the flow path 2 and an outlet 21 that communicates with a downstream piping 20. A valve seat member 22 having a valve seat 22a on the upper surface is screwed into the flow path between the inlet 19 and the outlet 21 and facing the valve body 16.

Further, a flat gasket 23 is buried in the recessed portion of the lower surface of the valve body 16, and when the valve is closed, the gasket 23 is pressed against the valve seat surface 22a by the biasing force of the leaf spring 17, thereby closing the flow path. Note that an O-ring 24 is interposed between the valve seat member 22 and the mounting surface of the main body 3a to provide a liquid-tight seal.

Here, the processing executed by the control circuit 12 will be explained with reference to FIGS. 3 and 4.

When the control circuit 12 opens the valve device 3 and starts flow rate control, it executes the process shown in FIG. 3.

First, when an electric current is supplied to the electromagnetic solenoid 14 to move the plunger 14b upward, the valve body 16 is separated from the valve seat surface 22a and the valve is opened. When fluid begins to flow during the valve opening operation, the driving current value of the electromagnetic solenoid 14 at that time is set and stored as an offset current If (step S1).

Next, it is determined whether an abnormality has occurred by checking whether the current value of the offset current If is greater than zero (step S2). That is, in the valve device 3, when the valve is closed, the valve body 16 is pressed against the valve seat surface 2 by the urging force of the plate spring 17.
2a, the valve seat surface 22a bites into the elastic packing 23. Therefore, although the gasket 23 is elastically deformed when the valve is closed, its restoring force weakens over time. Therefore, after long-term use, the portion of the packing 23 that comes into contact with the valve seat surface 22a gradually deforms.

As shown in FIG. 4, for example, if the initial flow rate control characteristics are plotted, the flow rate control characteristics will change as shown in the diagram as the gasket 23 deforms. Therefore, the offset current If when the fluid starts to flow gradually decreases as the packing 23 deforms.

However, when the offset current If becomes zero, it is no longer possible to close the valve device 3, so when If=0 in step S2, it is determined that an abnormality has occurred in the valve device 3 (step S2).
S3). Therefore, the abnormality indicator 15 displays that an abnormality has occurred in the valve device 3 to notify the operator. Therefore, the worker does not control the flow rate while there is an abnormality, but instead inspects and removes the abnormality.

If If > 0 in step S2, it is determined that the flow rate control characteristics of the valve device 3 are normal. When the valve device 3 is normal as described above, the drive current value (maximum drive current value Im) of the electromagnetic solenoid 14 when the fluid flows at the maximum flow rate is set and stored (step S4).

Next, a setting signal S for a desired flow rate is inputted by an external setting operation (step S5).

A flow rate measurement signal from the flow rate measurement unit 8 is input,
The flow rate is measured and calculated based on this signal (step S6).

Here, the setting signal s and the flow rate measurement signal q are compared to find the deviation thereof (step S7). step
In S7, when the flow rate measurement signal q is not equal to the setting signal s (s≠q), a signal corresponding to the difference between the flow rate measurement signal q and the setting signal s and an offset current signal are
If is supplied to the valve drive circuit 13, and a drive current is input to the electromagnetic solenoid 14. Therefore, the plunger 14b of the electromagnetic solenoid 14 is displaced in accordance with the drive current, and the valve opening of the valve device 3 is varied to control the flow rate to the set flow rate (step S8).

Note that, in step S8, flow rate control is performed within the range of the offset current value If stored in step S1 and the maximum drive current value Im stored in step S4.
In other words, in the case of the diagram shown in Fig. 4, control is performed within a control range a from If to Im. This control range a can be divided into fine units determined by the number of bits (resolution) treated as data, and the flow rate can be determined with high precision. control. Further, when the gasket 23 of the valve device 3 is deformed, the flow rate control characteristic is set to the control range b shown in the diagram in FIG. 4, for example, and the flow rate is controlled within this range. Therefore, even if the valve opening position of the valve device 3 changes over time, the flow rate control characteristics are automatically corrected in response to the change and the flow rate is controlled with high precision.

Also, after the operation of step S8, the flow rate measurement signal q
Steps S6 to S8 until becomes equal to the setting signal s.
Repeat the process. Next, in step S7,
When s=q, the valve opening degree is maintained, and in step S9 it is determined whether the drive current I of the electromagnetic solenoid 14 is smaller than the maximum drive current Im. That is, foreign matter may accumulate in the flow path 2 or the aperture 6 may
The cross-sectional area of the flow path may become narrow due to blockage caused by foreign matter, such as when foreign matter adheres to the channel. In this case, the maximum drive current of the electromagnetic solenoid 14 becomes larger than the current value Im stored in step S4.

Therefore, in step S9, the maximum drive current I is
<Im, and detect that there is no clogging of the flow path. Also, step
When the drive current I becomes large and I>Im in S9, it is determined that an abnormality has occurred in the flow path, and the abnormality indicator 15 indicates the occurrence of the abnormality.

The operator knows from the display on the abnormality indicator 15 that an abnormality has occurred in the flow path 2, and promptly removes the abnormality. Note that the above process ends when the power is turned off.

In this way, by monitoring the drive current of the electromagnetic solenoid 14, the control range can be automatically corrected according to changes in the offset current value If of the electromagnetic solenoid 14, and the flow rate can be controlled with high precision. The occurrence of an abnormality in the flow path 2 can be detected and displayed.

In addition, although the said Example demonstrated using the thermal type mass flowmeter as a flow measurement part, it is needless to say that it is not limited to this.

Effects of the Invention As described above, the flow control device according to the present invention can automatically correct the flow control range based on the change in offset current when fluid starts flowing by monitoring the current value of the electromagnetic solenoid. By setting the flow rate control range between the offset current value and the maximum drive current value, the control range can be narrowed, the current value can be divided more finely, and the flow rate can be controlled with high precision. In addition, based on the offset current value and maximum drive current value, it is possible to detect, for example, an abnormality in a valve device or a clogging in a flow path, so that the abnormality can be detected immediately without having to control the flow rate while the abnormality occurs. It has features such as being able to deal with the problem in a way that removes it.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an embodiment of the flow rate control device according to the present invention, Fig. 2 is a longitudinal sectional view of the valve device, and Fig. 3 is a longitudinal sectional view of the valve device.
The figure is a flowchart for explaining the processing executed by the control circuit, and FIG. 4 is a diagram showing flow rate control characteristics. DESCRIPTION OF SYMBOLS 1... Flow rate control device, 2... Flow path, 3... Valve device, 4... Sensor flow path, 8, 9... Self-heating resistor, 12... Control circuit, 13... Valve drive circuit, 14 ...Electromagnetic solenoid, 15 ... Abnormality indicator, 16 ... Valve body, 17 ... Leaf spring, 23 ... Packing.

Claims (1)

[Scope of utility model registration request] a flow rate measuring section that measures the mass flow rate of the measured fluid flowing in the flow path; a control circuit that compares the flow rate measurement signal from the flow rate measuring section with a preset setting signal; In a flow control device having an electromagnetic solenoid that is driven based on a deviation and a valve device that varies the valve opening degree by driving the electromagnetic solenoid, the current of the electromagnetic solenoid when the valve device opens and fluid starts flowing. A flow rate control device comprising means for storing a value as an offset current, further storing a current value of the electromagnetic solenoid at the time of maximum flow rate, and monitoring the current value based on the offset current and the maximum flow rate current.