Patent Application
20120295530
The present invention relates to a backflow prevention apparatus of a clean room applied to a dust-free room or a germ-free room of a semiconductor manufacturing plant, a FPD (Fiat Panel Display) manufacturing plant, a precision machine plant, a pharmaceutical manufacturing plant, or the like.
Conventionally, there is a total down-flow system as shown in
In a semiconductor manufacturing plant or a FPD manufacturing plant, in accordance with high integration of devices, environmental conditions such as a cleaning level, a temperature, or humidity are required to be controlled at higher level. Further, due to tougher price competition of a semiconductor or a FPD in recent years, construction cost of the clean room, that is, initial cost, and running cost of the clean room itself are required to be reduced. Thus, there are attempts to reduce the installment number of clean air blowoff devices such the FFUs.
In the clean room 262, in general, a number of manufacturing devices 265 provided only with FFUs or fans are installed, and the air taken in by the manufacturing devices is often exhausted to the external air or directly exhausted to the underfloor chamber 263, so that an air amount in the clean room 262 is decreased. Therefore, in a case where the installment number of the clean air blowoff devices such as the FFUs 217 installed in the ceiling 264 of the clean room is reduced, a point where pressure in the clean room 262 is lower than pressure of the underfloor chamber 263 is generated, so that a backflow from the underfloor chamber 263 into the clean room 262 is generated.
When the backflow from the underfloor chamber 263 into the clean room 262 is generated, an air flow in the vertically downward direction in the clean room 262 is largely disturbed so as to cause deterioration of the cleaning level. Further, in general, a pump, a chemicals tank, pipes, and the like are arranged in the underfloor chamber 263. Thus, grit and dust accumulated and attached on surfaces of these auxiliary facilities fly together with the backflow air and flow into the clean room 262, so that contamination remarkably progresses. Such a contamination problem due to the backflow is an important problem that is more unavoidable as saving facilities and energy of the clean room 262 is more facilitated to come close to a limit design.
There is a conventional technique that a sensor for detecting the flow direction or velocity of the air is arranged at a position in the vicinity of a floor, and a control means for adjusting a flow rate of the clean air blown off from the FFUs 217 installed in the ceiling of the clean room in accordance with a detected value of the sensor is provided.
This control means is a differential pressure gauge for indirectly detecting the flow direction or the velocity of the air by detecting differential pressure of upper and lower spaces taking the floor as a border by the sensor installed in the vicinity of the floor of the clean room. The control means adjusts the flow rate of the clean air blown off from the FFUs 217 installed in the ceiling 264 of the clean room in such a manner that the differential pressure detected by the differential pressure gauge is within a fixed range, so that an effect of reducing the installment number of the clean air blowoff devices such the FFUs 217 installed in the ceiling 264 of the clean room without generating the backflow from the underfloor chamber is clearly described (for example, refer to Japanese Unexamined Patent Publication No. 2004-218919).
However, with the above conventional configuration, although the problem of the backflow from the underfloor chamber into the clean room can be suppressed, the following problem still remains. That is, the backflow is generated due to equipment or a device accompanied by exhaust, and especially due to shortage of the air in the clean room. The FFUs installed in the ceiling are placed at positions distant from a point where the air is in short in the clean room. Thus, the air is spread and there is a need for supplying a flow rate which is much higher than an actual shortage flow rate in the clean room from the FFUs. Therefore, the flow rate of the FFUs installed in the ceiling cannot be reduced, and as a result, energy cost is increased to a large extent.
The present invention is in consideration with the above conventional problem, and an object thereof is to provide a backflow prevention apparatus of a clean room capable of solving a negative pressure point in the clean room so as to prevent a backflow from underfloor of the clean room.
In order to achieve the above object, the present invention is formed as follows.
According to an aspect of the present invention, there is provided a backflow prevention apparatus of a clean room in which a flow of clean air blown off from a ceiling surface flows in down-flow toward an underfloor chamber partitioned by an air-permeable floor, comprising:
a casing having an intake section having an intake port that suctions air of the underfloor chamber of the clean room and a blowoff section having a blowoff port that blows off the air into the clean room;
a fan that suctions the air of the underfloor chamber from the intake port and blows off the air from the blowoff port into the clean room;
plate shape blowoff angle adjusting fins that adjusts a direction of an air flow blown off from the blowoff port in a height direction;
plate shape radial air blowing fins extending in a radial manner from an apparatus center at the blowoff port, the radial air blowing fins being parallel to each other in the height direction; and
a control device that controls drive of the fan so as to supply a shortage flow rate in the clean room from the underfloor chamber into the clean room.
As described above, according to the backflow prevention apparatus of the clean room of the .present invention, the shortage flow rate in the clean room can be supplied and supplemented from the underfloor chamber into the clean room. Thus, without generating the backflow from the underfloor chamber, an energy-saving clean design in which the number of circulation is reduced can be provided.
These and other aspects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which:
Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The backflow prevention apparatus 10 of this clean room is formed by a casing 11 of the backflow prevention apparatus 10, a blowoff port 12 installed on a side surface of the casing 11 at a position on the upper side of the grating floor 61 of the clean room 62, a FFU (fan filter unit) 13 installed at a position away from the blowoff port 12 on the lower side of the grating floor 61 in the casing 11, and an intake port 14 arranged on a bottom surface of the casing 11 on the lower side of the FFU 13.
The blowoff port 12 of the backflow prevention apparatus 10 is preferably placed at a point not really high from a floor surface of the grating floor 61. In a case where a position of the blowoff port 12 is higher than the floor surface of the grating floor 61, the blowoff port becomes distant from the floor surface of the grating floor 61 on which a backflow is generated in the clean room 62. Thus, the blown-off air is spread, and a backflow prevention effect described later is reduced. As one example, as shown in
It should be noted that in a case where a filter is provided in the blowoff port 12 as another configuration of the backflow prevention apparatus 10, the FFU 13 may be formed only by a fan (air blower) without a filter. By installing a FFU in the blowoff port 12, no FFU 13 is arranged but only the intake port 14 may be arranged on the lower side of the casing 11 in the backflow prevention apparatus 10.
An optimal filter of the FFU 13 is adopted in accordance with a cleaning level required for the clean room 62. A fan capable of satisfying a required blowoff amount is selected and adopted.
The blowoff port 12 preferably has a structure that the air blown off from the blowoff port 12 is in the horizontal direction or obliquely downward. In a case where the air is blown off upward or obliquely upward from the blowoff port 12, an upstream flow taking in the surrounding air is generated, and accordingly, there is a possibility that the air of the underfloor chamber 63 is also taken up. Therefore, there is a possibility that the backflow is induced from the underfloor chamber 63 of the clean room 62.
The air of the underfloor chamber 63 is taken in from the intake port 14 installed in a lower part (bottom part) of the backflow prevention apparatus 10. A cleaning level of the air is increased to a cleaning level required in the clean room 62 by the FFU 13. The air is fed to the blowoff port 12 toward an upper part in the backflow prevention apparatus 10 by a fan of the FFU 13, and blown off into the clean room 62 from the blowoff port 12 whose height is positioned on the upper side of the grating floor 61 of the clean room 62, so that the shortage air in the clean room 62 is supplied.
As an operation method of the fan of the FFU 13, by operating the fan only when the backflow is generated from the underfloor chamber 63 of the clean room 62 and stopping the operation of the fan in a case where the backflow is not generated, an operation method of saving energy of the backflow prevention apparatus 10 itself can be used. In order to realize this operation, differential pressure gauges 16 for detecting differential pressure of upper and lower spaces taking the grating floor 61 as a border are installed. Detected values of the differential pressure gauges 16 are inputted to a control device 90, and the control device 90 controls to turn ON/OFF the fan of the FFU 13 based on the detected values of the differential pressure gauges 16 for realizing the above operation. As one example, the following control can be thought: when the control device 90 determines that the detected values of the differential pressure gauges 16 exceed a threshold value, the fan of the FFU 13 is turned ON so that the backflow is not generated, and when the control device 90 determines that the detected values of the differential pressure gauges 16 are a threshold value or less, the fan of the FFU 13 is turned OFF so that the backflow is not generated.
The backflow is generated because a facility 65 in the clean room 62 is exhausting. Thus, information on an operation situation of the facility 65 is inputted to the control device 90, and in accordance with the operation situation of the facility 65, the fan of the FFU 13 can be controlled and turned ON/OFF under the control of the control device 90.
A structure and a blowoff method of the backflow prevention apparatus 10 and the blowoff port 12 will be described with reference to
As shown in
As shown in
As shown in
Due to such a structure, width of the blowoff port 12 is determined by the angle θ.
Plate shape blowoff angle adjusting fins 19 for adjusting a blowoff angle in the height direction are similarly installed in the blowoff port 12.
An angle of the blowoff angle adjusting fins 19 is adjusted only to the horizontal direction and the downward direction. This is because in a case where the air blown off from the blowoff port 12 is upward, an upstream flow taking in the surrounding air is generated, and the backflow from the underfloor chamber 63 is caused. With such a configuration, the air is blown off from the blowoff port 12 by the blowoff angle adjusting fins 19 by an angle toward the lower side of the horizontal direction. The reference numeral 102 denotes streamlines indicating the blowoff direction from the blowoff port 12 in the height direction.
A shortage flow rate in the clean room 62 is equal to a backflow flow rate. Thus, not the backflow flow rate from the grating floor 61 of the clean room 62 but the shortage flow rate in the clean room 62 is calculated by an arithmetic portion 90b provided in the control device 90 separately from a control main body portion 90a. Detected information from the differential pressure gauges 16 and the like and information from the facility 65 and the like are inputted to the control main body portion 90a. When the detected information from the differential pressure gauges 16 and the like are inputted from the control main body portion 90a to the arithmetic portion 90b, the arithmetic portion 90b performs predetermined arithmetic operation. Based on an arithmetic result of the arithmetic portion 90b, the control main body portion 90a controls drive of the fan 13.
An area in which the backflow 15 is generated is A (m2), and a flow velocity at a point of the backflow determined from the detected information of a flow velocimeter or the differential pressure gauges 16 is Vi (m/s), and the backflow flow rate is Q. Then,
[Expression 1]
Q=A×∫Vi dx dy (1)
By using this expression, the arithmetic portion 90b can calculate the backflow flow rate Q. Here, x, y are x-coordinate and y-coordinate of orthogonal coordinates in a plane of
This calculated value is an actual shortage flow rate in the clean room 62.
The backflow area, the flow velocity thereof, or the differential pressure of the upper and lower spaces of the grating floor 61 can be grasped by measuring at the respective points by one or a plurality or flow velocimeters or differential pressure gauges 16.
A blowoff flow rate Qout from the blowoff port 12 of the backflow prevention apparatus 10 is required to be controlled to an appropriate amount. In a case where the blowoff flow rate Qout is too little relative to the shortage flow rate in the clean room 62, backflow prevention serving as the original object cannot be achieved, and the backflow 15 from the underfloor chamber 63 cannot be completely suppressed. In a case where the blowoff flow rate Qout is excessive relative to the appropriate amount, as shown by an arrow 101 of
At this time, the appropriate amount of the blowoff flow rate Qout preferably maintains a relationship of
[Expression 2]
1.20×Q≦Qout≦3.47×Q (2).
This relational expression was obtained by a result of thermo-fluid analysis of a relationship between an optimal value of the blowoff flow rate Qout of the backflow prevention apparatus 10 installed in the clean room 62 and the area of the backflow from the floor 61 in the clean room 62 in a configuration of
The backflow prevention apparatus 10 is installed in the clean room 62 in which the backflow 15 of 7.49 m3/min is generated in
As a result of the analysis, by making the blowoff flow rate 9 m3/min or more, the backflow 15 from the grating floor 61 was capable of being prevented. Conversely, in a case where the blowoff flow rate was 26 m3/min or more, the backflow 15 was newly generated from the underfloor chamber 63. That is, it was found that the blowoff flow rate is required to be a flow rate which is 1.20 times or more and 3.47 times or less more than the original backflow flow rate (7.49 m3/min). As a result, the above expression (2) was obtained.
The width direction of the blowoff from the blowoff port 12 of the backflow prevention apparatus 10 will be described with reference to
As shown in
With such a configuration, the width of the blowoff of the blowoff port 12 and the range capable of covering the backflow 15 (the range of the backflow 15) are determined by the angle θ′. Therefore, when the angles are θ′=θ, the width of the air blown off from the blowoff port 12 of the backflow prevention apparatus 10 just matches with the backflow range (the range of the backflow 15).
Due to such a configuration, when a case where the backflow prevention apparatus 10 is installed at a distance close to the backflow 15 is compared with a case where the backflow prevention apparatus is installed at a distance distant from the backflow 15, it is found that the angle θ is increased in the backflow prevention apparatus 10 being installed at a distance close to the backflow 15, and thus, the blowoff width of the blowoff port 12 is increased. However, the blowoff flow rate of the backflow prevention apparatus 10 is the same between a case where the backflow prevention apparatus 10 is installed at a close place to the backflow 15 and a case where the backflow prevention apparatus 10 is installed at a distant place from the backflow 15. Thus, the flow velocity is necessarily more slowed down in a case where the backflow prevention apparatus 10 is installed at a close place (when the blowoff flow velocity is V and the blowoff area is D, the blowoff flow velocity V is defined by a relational expression V=Q/D, and since Q is constant, the flow velocity V is in an inversely proportional relationship with the blowoff area D).
The blowoff width from the blowoff port 12 of the backflow prevention apparatus 10 is required to be optimal width. The blowoff width can be defined by the angle θ′ as described above. Therefore, from the relational expression θ′/θ, an optimal blowoff angle preferably maintains a relationship of
[Expression 3]
0.9≦(θ′/θ)≦1.2 (3)
This relational expression was obtained by a result of thereto-fluid analysis of a relationship between the blowoff angle θ′ from the blowoff port 12 of the backflow prevention apparatus 10 and the backflow area by using the thermo-fluid analysis software (STREAM manufactured by Software Cradle Co., Ltd.). In the analysis model of this time, a value of θ defined the embodiment is 33°.
From the result of the proper blowoff amount described above, the thermo-fluid analysis was respectively performed to Model 1 in which the flow rate from the blowoff port 12 from the backflow prevention apparatus 10 is minimum (blowoff flow rate: 9 m3/min) and Model 2 in which the flow rate from the blowoff port 12 is maximum (blowoff flow rate: 26 m3/min).
As a result of the analysis, in a case of Model 1 in which the blowoff flow rate is the minimum flow rate of 9 m3/min, it was found that when the value of θ′/θ is 0.9 or more and 1.2 or less, the backflow can be prevented.
In a case of Model 2 in which the blowoff flow rate is the maximum flow rate of 26 m3/min, it was found that when the value of θ/θ is 0.7 or more and 1.6 or less, the backflow can be prevented. The more the blowoff flow rate is, the more easily generation of the backflow is prevented. Thus, such an analysis result is obtained.
From the result of this time, it was found that the optimal value of the blowoff angle from the blowoff port 12 of the backflow prevention apparatus 10 is required to satisfy a range of
[Expression 4]
0.9≦(θ′/θ)≦1.2 (4)
which is the strictest condition of this time.
As described above, the blowoff flow rate of the backflow prevention apparatus 10 can be grasped by measuring the area and the flow velocity at the point or the differential pressure of the upper and lower spaces of the grating floor 61. However, due to an environmental change in the clean room 62 or a production situation, the blowoff flow rate might be sometimes momentarily changed. Therefore, the plurality of sensors (the flow velocimeters or the differential pressure gauges) 16 for measuring the flow velocity or the differential pressure of the upper and lower spaces of the grating floor 61 is installed in the range in which the backflow 15 is generated. The backflow area is calculated from the range of the sensors the flow velocimeters or the differential pressure gauges) 16 indicating the backflow 15, and the backflow flow rate is calculated by the arithmetic portion 90b from the flow velocity measured by the sensors or the flow velocity calculated from the differential pressure by the arithmetic portion 90b. Based on the backflow flow rate, the control device 90 controls the flow rate of the FFU 13 of the backflow prevention apparatus 10. By providing such a mechanism, the backflow area or the backflow flow velocity which is momentarily changed can be treated.
As described above, with the clean room 62 according to the embodiment, by directly supplying the shortage flow rate from the underfloor chamber 63 to a region where the air is in short in the clean room 62, FFUs 17 in the ceiling of the clean room can be further reduced, and by realizing the further energy-saving clean room 62 in comparison to the conventional example, an effect of the present invention is obtained.
It should be noted that by appropriately combining an arbitrary embodiment or modification example among the above various embodiments or modification examples, effects possessed by the embodiments and the modification examples can be obtained.
With the backflow prevention apparatus of the clean room of the present invention, the prevention of the backflow of the contaminated air from the underfloor chamber into the clean room can be realized. Thus, the present invention is useful not only for the energy-saving clean room by reduction of the number of circulation due to reduction of the FFUs of the clean room or the like but also for use of design of a general clean room accompanied by a number of apparatus exhaust.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-111498 | May 2011 | JP | national |
