JP3326298B2 - Exhaust control device in draft chamber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device in a draft chamber, which keeps the velocity of air flowing into an opening of a processing chamber constant.

[0002]

2. Description of the Related Art In a draft chamber, a certain standard is set for the speed of an opening by a law so as to prevent harmful gas from flowing out of a processing chamber or a worker to inhale harmful gas by mistake. . In this regard, it is considered that a control wind speed sensor should be provided in the opening and the exhaust means should be adjusted so that the value measured by the control wind speed sensor becomes the same as the target value. Providing a wind speed sensor not only hinders work, but also makes it difficult to perform accurate control because the wind speed and direction are disturbed by the operation of the worker.In addition, scattered chemicals adhere to the control wind speed sensor, and There is a disadvantage that it becomes impossible to measure accurately.

Conventionally, attention has been paid to the fact that there is a fixed relationship between the wind speed at the opening of the processing chamber and the wind speed at the location on the inner surface, and a control wind speed sensor is provided on the inner surface of the processing chamber. By adjusting the displacement so that the value measured by the control wind speed sensor becomes the same as the target value, the wind speed at the opening is kept constant. As shown in FIG. 6, the wind speed sensor is incorporated in the bridge circuit as resistors R3 and R4 so that the resistors R3 and R4 made of platinum or thermistor are heated to a predetermined temperature. The current is added so that the temperature of the resistors R3 and R4 becomes constant when the resistors R3 and R4 are cooled by the wind, and the intensity of the current at that time is taken out as the wind speed. Things. In other words, it is configured to detect the wind speed as the intensity (or voltage) of the current.

[0004]

However, while this control wind speed sensor has been used, the resistor R3
R4 may deteriorate over time or become dirty due to chemicals or smoke scattered in the processing chamber, so that the accuracy of the control wind speed sensor decreases, and the opening of the opening calculated based on the control wind speed sensor is reduced. The wind speed will deviate from the actual wind speed.

Conventionally, the wind speed at the opening is regularly measured using a calibration sensor whose accuracy is guaranteed by a public organization, and the wind speed measured by the calibration sensor and the wind speed calculated from the control wind speed sensor are conventionally measured. Based on the difference between this and the new relational expression is input to the control unit,
This task was troublesome. An object of the present invention is to make it possible to easily perform calibration work due to deterioration of control wind speed sensor due to aging and dirt and deterioration of accuracy.

[0006]

In order to achieve this object, the present invention relates to a main body having a processing chamber having a front opening, an exhaust duct communicating with the processing chamber, and an exhaust rate for controlling an exhaust rate from the exhaust duct. Adjusting means, a control wind speed sensor is provided at an appropriate position on the inner surface of the processing chamber, and based on an output signal from the control wind speed sensor, the exhaust air volume is adjusted so that the wind speed of the opening coincides with a target value. In a draft chamber configured to control the adjusting means, based on an output signal from a calibration sensor temporarily provided in the opening, an accurate wind speed in the opening and detection from the control wind speed sensor were detected. A controller is provided which calculates the difference between the wind speed of the opening and the target, and automatically resets the relationship between the output signal from the control wind speed sensor and the target value based on the difference. It was.

[0007]

In this configuration, when a calibration sensor whose accuracy is guaranteed by receiving a guarantee from a public organization or the like is installed in the opening, and this calibration sensor and the control device are connected by a cord, The output signal from the calibration sensor is input to the controller, and the difference between the accurate wind speed of the opening measured by the calibration sensor and the wind speed measured by the control wind sensor is calculated, and the control wind speed is calculated based on the difference. The new relationship between the sensor measured value and the target value will be automatically reset, thereby maintaining the wind speed at the opening at the target value based on the accuracy of the control wind speed sensor at that time. .

As described above, according to the present invention, when the accuracy of the control wind speed sensor is deteriorated due to aging or dirt, the calibration is performed so that the wind speed of the opening becomes the target value under the accuracy. An extremely simple operation of simply installing a calibration sensor in the opening and connecting with a cord has the effect of being extremely easy and accurate.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway front view of the draft chamber 1,
2 is a sectional view taken along the line II-II of FIG. 1, and FIG.
a-IIIa sectional view, FIG. 3 (b) is III b-III in FIG.
4 is a front view showing a state in which a number of draft chambers 1 are installed, and FIG. 5 is a block diagram showing a control circuit in principle.

The draft chamber 1 has a main body 2 having a processing chamber 3 having a front opening, and a front door 4 for closing the front of the processing chamber 3 is mounted on the front of the main body 2 so as to be vertically adjustable. I have. The front door 4 is formed of a transparent plate such as acrylic resin or glass, and can be held at an arbitrary height manually or electrically. A partition plate 5 is provided inside the main body 2 so as to provide an interval between the back plate and the top plate, and a suction hole 6 is formed in an appropriate portion of the partition plate 5. The main body 2 does not necessarily need to be provided with the partition plate 5.

A branch duct 7 communicating with the inside of the main body 2 is protruded from the upper surface of the main body 2 and connected to a main duct 8. A damper 9 is rotatably mounted inside the branch duct 7 as an example of an air volume adjusting means, and a motor 10 for rotating the damper 9 is mounted outside the branch duct 7. As shown in FIG. 4, a suction fan 11 is provided at one end of the main duct 8, and exhaust of a number of draft chambers 1 is performed by one suction fan 11.
To do it.

A control wind speed sensor 12 based on the principle described above with reference to FIG. 6 is provided on the left inner side surface of the main body 2. At the right end of the front door 4, a rack rod 13 penetrating below the processing chamber 3 is provided to protrude downward, and an opening of the front door 4 is provided near the rack rod 13 on the right side surface of the main body 2. A potentiometer 14 for measuring the degree (height) H is attached.

The potentiometer 14 has a structure similar to that described in, for example, FIG. 3 of Japanese Patent Publication No. 2-20040, and includes a pinion (not shown) that meshes with the rack rod 13. By converting the rotation of the pinion into a value of electric resistance, the height H (opening) of the front door 4 is detected as an electric signal. Body 2
Among them, a control panel 16 is provided below the processing chamber 3, and a control unit 17 having a memory, an arithmetic circuit, and the like is provided inside the control panel 16. The control wind speed sensor 12, the motor 10 for damper adjustment, and the potentiometer 14 are connected to a circuit of the control unit 17. The control unit 17
Need not necessarily be provided on the main body 2 and may be provided on other parts of the room.

As shown in FIG. 1, a proper value of the displacement varies depending on the work content. Therefore, as shown in FIG. Is provided. When the suction fan 11 is driven, the air in the processing chamber 3 is exhausted through the main duct 8 and the branch duct 7, and accordingly,
Air outside the draft chamber 1 is sucked from the opening 15. In this case, if the average wind speed at the opening 15 (center value of the wind speed) is V _FR and the wind speed at the control wind speed sensor 12 is V _SI , if the height H of the opening 15 is constant, V _FR There is a certain relationship between _FR and V _SI "V _FR = F
Since (V _SI ) = aV _SI ^ex ”is established, this relational expression is stored in a memory (a, e, and x are constants determined by the shape, volume, and the like of the processing chamber 3).

When the height H of the opening 15 changes,
Wind speed V _SI and average wind speed V at the control wind speed sensor 12
The relationship with _FR also changes. The distribution of the wind speed at the opening 15 also changes according to the height H of the front door 4, and the average wind speed V _FR
The height position at which occurs also changes. Therefore, in advance, by previously measuring the average wind speed V _FR of the height H of the opening 15 various varied, the relationship between the height H of the opening 15 and the average wind speed V _FR "V _FR = G (H) ”And store it in memory.

A switch 25 is inserted in the circuit from the potentiometer 14, and the switch 25 is turned on in a normal use state. Next, control in a normal use state will be described with reference to FIG. First, after turning on the power, the operator selects the legally-designated wind speed with the changeover switch 18 according to the work content, and then starts the experiment work. Then, the output signal from the control wind speed sensor 12 is amplified and input to the first comparison operation circuit 20, and the difference between the output signal from the control wind speed sensor 12 and the set value is calculated. An output signal from the first comparison operation circuit 20 is input to a damper drive circuit 21, and the damper drive circuit 21
By rotating the motor 10 based on the output from the motor, the damper 9 rotates, and the wind velocity V _BD sucked from the branch duct 7 is adjusted.

When the damper 9 rotates and the suction wind speed V _BD changes, the wind speed V _SI at the control wind speed sensor 12 changes, and the output signal from the control wind speed sensor 12 changes. The same operation as described above is repeated, and when it becomes the same as the target value, the rotation of the damper 9 stops. That is, a feedback circuit is constituted as a whole. Therefore, when the wind velocity V _MD changes in the main duct 8, to the output signal changes from the control air velocity sensor 12 suction amount is changed from the branch duct 7, the same effect as above is repeated,
The output signal from the control wind speed sensor 12 is automatically adjusted so as to be equal to the target set value.

On the other hand, the output signal from the potentiometer 14 is amplified and input to the second comparison / calculation circuit 22, where the difference from the reference value is calculated, and the output signal is passed through the correction circuit 23 to the damper drive circuit. 21 is input to it than the rotation of the damper 9 is corrected, thereby, in accordance with the change of the height H of the opening 15, V _FR are corrected so that the target setpoint.

That is, control is performed so as to satisfy the relationship of V _FR = F (V _SI ) + G (H). When the damper 9 is rotated by a signal from the potentiometer 14, the flow velocity in the processing chamber 3 changes and the output signal from the control wind speed sensor 12 changes. Therefore, the signal from the correction circuit 23 is input to the first comparison operation circuit 20 so that the signal is not affected by the correction based on the potentiometer 14.

As described above, even if the control by the control wind speed sensor 12 becomes incomplete due to the change in the height H of the opening 15, the exhaust gas is exhausted by -9 times based on the height H of the opening 15. By correcting the moving angle, the average wind speed _VFR at the opening 15 can be maintained at a legal value, so that a safe operation can be performed regardless of the opening degree of the front door 4. In addition, you may set so that the minimum wind speed among the wind speeds in each part of the opening part 15 may become a target value.

Next, the calibration (correction) in the case where the accuracy of the control wind speed sensor 12 is deteriorated due to aging or dirt will be described. In the calibration, as shown in FIG.
With the height of the opening 15 as a standard state, a calibration sensor 25 whose accuracy is guaranteed by a public organization is set at the standard position of the opening 15, and the output terminal of the calibration sensor 26 is connected to the controller of the controller 17. 27. When the calibration sensor 25 is connected, the switch 25 of the circuit for correcting the height H of the front door 5 is OFF.

By changing the opening degree of the damper 9, the wind speed of the opening 15 can be adjusted to an appropriate range (for example, 0.3
１．０1.0 m / sec), and the output signal from the calibration sensor 26 is input to the controller 27, where the accurate wind speed of the opening 15 measured based on the output signal from the calibration sensor 26. And the difference between the wind speed at the inner surface of the processing chamber 3 measured by the control wind speed sensor 12 and
The difference is rewritten in the memory of the first comparison operation circuit 20. In other words, the target value of the wind speed at the wind speed V _FI an opening 15 which is measured by controlling the wind speed sensor 12 (set value)
The relational expression with V _FR is calculated every time calibration is performed, V _FR = F ₁ (V _SI ),
V _FR = F ₂ (V _SI )... V _FR = F _n (V _SI ) automatically shifts in accordance with the accuracy of the control wind speed sensor 12, whereby the control wind speed Calibration due to deterioration or contamination of the sensor 12 can be easily performed without any trouble.

The controller 27 may be formed separately from the draft chamber 1 so that the controller 27 is connected to the controller 17 of the draft chamber 1 only during calibration. Also, many draft chambers 1
Is installed, the calibration of each draft chamber 1 may be performed simultaneously by one controller 27.

The exhaust control means is not limited to rotating the damper 9 by the motor 10 as in the embodiment,
It is needless to say that another form may be adopted, such as providing a suction fan for controlling the output. Further, the position at which the control wind speed sensor is provided is not limited to the side surface of the processing chamber, and may be provided at a portion other than the opening, such as the back surface of the processing chamber.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a draft chamber.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3A is a sectional view taken along the line IIIa-IIIa in FIG. 1;
FIG. 3B is a sectional view taken along line IIIb-IIIb in FIG. 1.

FIG. 4 is a front view of a state where a number of draft chambers are installed.

FIG. 5 is a block diagram of a control circuit.

FIG. 6 is a circuit diagram showing the principle of a control wind speed sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Draft chamber 2 Main body 3 Processing room 4 Front door 7 Branch duct 9 Damper 11 Suction fan 12 Control wind speed sensor 14 Potentiometer 15 Opening 17 Control part 26 Calibration sensor

Continuation of the front page (56) References JP-A-7-190431 (JP, A) JP-A-59-70913 (JP, A) JP-A-2-139080 (JP, U) JP-A-5-51442 (JP) , U) JitsuHiraku Akira 62-105447 (JP, U) real public Akira 47-36855 (JP, Y1) US Patent 4741257 (US, a) (58 ) investigated the field (Int.Cl. ^7, DB name) B01L 1/00-1/04 F24F 7/06

Claims (1)

(57) [Claims] A main body having a processing chamber with a front opening, an exhaust duct communicating with the processing chamber, and an exhaust amount adjusting means for controlling an exhaust amount from the exhaust duct; A control wind speed sensor is provided, and based on an output signal from the control wind speed sensor,
In a draft chamber configured to control the displacement control means so that the wind speed of the opening coincides with a target value, based on an output signal from a calibration sensor temporarily provided in the opening, The difference between the accurate wind speed of the opening and the wind speed of the opening detected from the control wind speed sensor is calculated, and based on the difference, the relationship between the output signal from the control wind speed sensor and the target value is automatically calculated. An exhaust control device for a draft chamber, comprising a controller that resets the exhaust gas control to a new setting.