JPS6320921Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an air flow rate control device for a clean room. In conventional clean room air flow rate control devices, the air flow rate was simply controlled based on the instantaneous value of the number of dust particles. However, depending on the working conditions indoors, the amount of dust generated may suddenly increase or decrease, making it impossible to keep up with the changes in the instantaneous value, resulting in the number of dust particles reaching a dangerous value, or the control system becoming unstable. There were some deficiencies such as. In order to solve this problem, this invention predicts the time until the number of dust particles reaches a dangerous value, and controls the amount of air blown into the clean room based on this predicted time.

To explain the figures, FIG. 1 is a system diagram of a clean room air conditioner using this invention.

The air supplied from the air conditioner 1 passes through an air supply duct 2, a pressure chamber 3 at the top of the clean room, and a high performance filter 4 to reach a clean room 5. From here, the air passes through the return air port 6 and the return air duct 7 and returns to the air conditioner. 8 is an outside air intake duct.

This invention provides a control device for such clean room air conditioning equipment that variably controls the amount of air blown depending on the fluctuation tendency of the number of dust particles in the clean room.

That is, as shown in FIG. 1, a dust measuring device 9 is placed in the clean room, and the number of dust particles is measured at regular time intervals using the dust measuring device 9, and the values are inputted to the control device 10. The control device 10 predicts the time when the number of dust particles reaches a dangerous value using the method described in FIG. Output. The airflow rate regulator 11 controls the airflow rate to match a set value by operating the controller 13 while monitoring the airflow rate using the airflow rate measuring device 12.

The operating device 13 is a flow restricting mechanism or resistance, and when operated, the discharge pressure of the blower 18 changes. It is detected by the pressure measuring device 14 and inputted to the pressure regulator 15. The pressure regulator compares the value with a predetermined discharge pressure set value, and outputs an output corresponding to the deviation to the rotation speed control device 16,
Thereby, the rotational speed of the electric motor 17 is controlled, thereby controlling the amount of air blown.

FIG. 2 shows a method in which the control device 10 predicts the time at which the number of dust particles reaches a critical value from the measured value of the number of dust particles. The horizontal axis of the figure is time t, the vertical axis is the number of dust N,
P ₀ , P ₁ ...P _o is a measurement point at each time. Let tn be the current time, P _o be the measurement point, Nn be the number of dust particles, and let tn _-1 , P _{o -1} , and Nn _-1 be the display at the measurement time one time before the current time, respectively. Also, let Nx be the lower limit value, that is, the dangerous value, at which the number of dust particles in the indoor unit air should not be increased any further. At this time, the time ΔT required for the number of dust particles to reach the dangerous value Nx from the current value Nn is predicted using the following equation.

ΔT＝Nx−Nn／Nn−Nn _-1 ×(tn−tn _-1 ) …(1) Or, if tn−tn ₋₁ = Δt, ΔT＝Nx−Nn／Nn−Nn ₋₁・Δt …(2 ) As can be seen from Figure 2, this equation is equivalent to P _o-1 and
Connect P _o with a straight line and find the point P _x at which the critical value is reached on the extension. On the other hand, if we use more data such as P _o-2 and P _o-3 ,
ΔT can be calculated by approximating the time-series change in the number of dust particles up to the present with a curve.

After predicting the arrival time ΔT in this way, the control device 10 outputs the air blowing amount setting value to the air blowing amount controller 11 based on the prediction. ΔT at this time
FIG. 3 shows an example of the relationship between V and the air blowing volume setting output V.

That is, between Cd in the figure, when the predicted arrival time ΔT is greater than a certain value ΔT ₂ , the blowing volume setting output V is fixed to the minimum value Vmin. Conversely, between a and b in the figure, when ΔT is smaller than a certain value ΔT ₁ , V becomes the maximum value Vmax. bc is a region where ΔT and V change proportionally. In addition to this kind of proportional operation,
It is also possible to provide an integral characteristic or a differential characteristic to the arithmetic function that determines the output V using ΔT. Although not shown in the figure, when Nn＜Nn _-1 , ΔT
When becomes negative, V is set to the minimum value Vmin.

Note that the configuration of the air supply amount control system from the control device 10 to the rotation speed control device 16 may be changed as follows.

(1) The control device 10 may directly control the air flow rate control operation device 13. In that case, the air flow regulator 11
Then, the air flow measuring device 12 becomes unnecessary.

(2) The output of the control device 10 may be applied to the rotation speed control device 16. In that case, the air flow regulator 1
1. The air flow measuring device 12, the operating device 13, the pressure measuring device 14, and the pressure regulator 15 are no longer necessary.

(3) Furthermore, the control device 10 may be provided with the function of the rotation speed control device 16, and the rotation speed of the electric motor 17 may be directly controlled by the control device 10. In that case, the air flow rate regulator 11, the air flow rate measuring device 12, the operating device 13, the pressure measuring device 14, the pressure regulator 15, and the rotation speed control device 16 become unnecessary.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a clean room air conditioner using a control device based on this invention, Figure 2 is a diagram showing a method for predicting the time required for the number of dust to reach a dangerous value, and Figure 3 is a diagram showing a method for predicting the time required for the number of dust to reach a dangerous value. FIG. 3 is a diagram showing a method for calculating an air volume setting output. Explanation of symbols, 1...Air conditioner, 2...Air supply duct, 3...Pressure chamber, 4...High performance filter, 5...Clean room, 6...Return air port, 7...
...Return air duct, 8...Outside air intake duct, 9...Dust measuring device, 10...Control device, 11...Air blow rate regulator, 12...Air blow rate measuring device, 13...Air blow rate control operation 14...Pressure measuring device, 15...Pressure regulator, 16...Rotation speed control device, 17...Electric motor, 18...Blower.

Claims (1)

[Scope of utility model registration request] An airflow control device for a clean room, characterized in that it measures the number of dust particles in the clean room, predicts the time required for the dust number to reach a dangerous value based on the change in that value over time, and controls the amount of air blown into the clean room based on that predicted time.