Fan filter device

Abstract

This invention provides a fan filter device that can determine what kind of abnormality has occurred when clogging or malfunction occurs in the fan filter device. [Solution] The device includes a differential pressure sensor 40 that acquires the atmospheric pressure value of the internal space 18 of the main body 12, and a control unit 30 that, when the atmospheric pressure value acquired by the differential pressure sensor 40 exceeds a first threshold, determines that a first abnormality has occurred due to clogging of the filter 20 if the rate of increase of the atmospheric pressure value is less than a predetermined reference rate of increase, determines that a second abnormality has occurred due to an event other than the first abnormality if the rate of increase of the atmospheric pressure value is greater than the reference rate of increase, and determines that a second abnormality has occurred when the atmospheric pressure value falls below a second threshold.

Description

Technical Field

[0006] , , , , ,

[0001] The present invention relates to a fan filter device.

Background Art

[0002] A fan filter device provided in the ceiling of a room such as a clean room for manufacturing semiconductors has a fan motor that blows external air into the room, and a filter that cleans the air blown by the fan motor and improves the cleanliness of the air inside the room. Since the manufacturing of this semiconductor does not stop, the fan filter device is also continuously operated for a long period of time.

Prior Art Documents

[0007] According to the present invention, it is possible to determine whether the filter unit is clogged or whether any other abnormal event is occurring based on changes in air pressure within the internal space of the main body of the fan filter device. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view diagram illustrating a fan filter device in one embodiment of the present invention. [Figure 2] This is a block diagram of the fan filter device. [Figure 3] This is a flowchart showing the control operation of a fan filter device. [Figure 4] This is a side view illustrating a fan filter device in a state where the filter is clogged. [Figure 5] This is a side view illustrating a fan filter device with damaged fan blades. [Modes for carrying out the invention]

[0009] A fan filter device 10 according to one embodiment of the present invention will be described with reference to Figures 1 to 5. This fan filter device 10 is installed in the ceiling portion of a cleanroom in a semiconductor factory, and takes in air from outside the cleanroom, cleans the taken-in air, and sends it into the cleanroom.

[0010] (1) Configuration of the fan filter device 10 As shown in Figure 1, the main body 12 of the fan filter device 10 is formed as a thin cube in the height direction so that it can be installed on the ceiling of a clean room, and the inside of the main body 12 forms an internal space 18 that is separated from the outside. An air intake port 14 for drawing in air is provided on the top surface of the main body 12, and an air outlet port 16 for blowing out air is provided on the bottom surface.

[0011] A motor 22 is positioned in the center of the circular intake port 14, and a fan 26 is attached to the rotating shaft 24 of this motor 22, forming a blower unit. This fan 26 has multiple blades 28.

[0012] A filter unit, which is a filter 20 (for example, a HEPA filter) for removing fine particles, is provided at the bottom of the internal space 18 of the main body 12.

[0013] A differential pressure sensor 40 is provided on the main body 12, which is a sensor unit that measures the pressure difference between the internal space 18 and the normal space outside the main body 12 that is separated from the internal space 18. This pressure value is static pressure, which is the force that wind exerts on its surroundings when it is stationary. The greater the static pressure, the further the wind can be sent.

[0014] A control unit 30, consisting of a computer or the like, is provided on the side of the internal space 18 of the main body 12. As shown in Figure 2, inside this control unit 30, there is a storage unit 32 that stores data, a clock unit 34 that measures time, and a communication unit 36 ​​that communicates with the outside.

[0015] A drive circuit 38 for controlling the motor 22 is connected to the control unit 30. If the motor 22 is a three-phase motor, this drive circuit 38 may be an inverter circuit or the like. The control unit 30 can communicate with a central control device 42 located outside the cleanroom via a communication unit 36, and can operate or stop the motor 22 based on control signals from the central control device 42.

[0016] When the fan 26 rotates at a predetermined rotational speed under the control of the control unit 30, this fan filter device 10 sucks in external air from the suction port 14, the air is purified by the filter 20, and the air is blown out from the blowout port 16 into the clean room at a preset air volume (the white arrow in FIG. 1). The differential pressure sensor 40 constantly measures the air pressure value, which is the differential pressure between the internal space 18 and the outside at this time, and stores it in the storage unit 32 together with the air pressure value and the current time measured by the clock unit 34. And this control unit 30 functions not only as a control device for operating the fan filter device 10 as described above, but also as an abnormality determination unit for determining an abnormality of the fan filter device 10 to be described later.

[0017] (2) Method for Determining Abnormality of Fan Filter Device 10 Next, a method for the control unit 30 to determine an abnormality of the fan filter device 10 as an abnormality determination unit will be described.

[0018] First, when each component of the fan filter device 10 is normal, that is, when the motor 22 and the drive circuit 38 operate normally and the filter 20 is not clogged, it is defined as a "normal state". In this normal state, the air pressure value measured by the differential pressure sensor 40 fluctuates up and down within a predetermined normal range. Hereinafter, the upper limit value of the air pressure value indicating this normal range is defined as the first threshold value, and the lower limit value is defined as the second threshold value.

[0019] Secondly, as shown in Figure 4, continuous use of the fan filter device 10 for many years can cause dust and fine particles to clog the filter 20, leading to clogging. This increases the static pressure in the internal space 18, and gradually the atmospheric pressure measured by the differential pressure sensor 40 rises to exceed the first threshold. At this time, the clogging of the filter 20 does not occur suddenly but gradually increases over time, so the rate at which the atmospheric pressure rises is almost fixed. Therefore, the limit of the rate at which the atmospheric pressure rises in the event of clogging is called the "reference rise rate," and if the rate at which the atmospheric pressure rises exceeds the reference rise rate, other abnormalities should be considered. Accordingly, if the atmospheric pressure rises below this reference rise rate, it is called the "first abnormality" as an abnormality caused by poor airflow due to clogging of the filter 20. Here, the rate at which the atmospheric pressure rises is obtained by acquiring the current atmospheric pressure from the differential pressure sensor 40 and the current time from the clock unit 34. Then, by going back in time from that moment (for example, one hour ago) and comparing it with the atmospheric pressure value stored in the memory unit 32 from one hour ago, the temporal change in atmospheric pressure (upper-air velocity) is determined.

[0020] Thirdly, we consider the case where the rate of increase in atmospheric pressure exceeds the standard rate of increase. This is not due to clogging, but rather, for example, as shown in Figure 5, a part of the fan blades 28 of the fan 26 is damaged, blocking the intake of the filter 20, preventing air from passing through and causing the atmospheric pressure to rise suddenly. An abnormality caused by such an event is judged as a "second abnormality," which is different from the first abnormality caused by clogging.

[0021] Fourth, if the output of the motor 22 decreases due to a malfunction or deterioration of the motor 22 or the drive circuit 38, and the amount of air drawn in decreases, the airflow rate will drop, and the static pressure value measured by the differential pressure sensor 40 may fall below the second threshold. If this pressure value falls below the second threshold, it is judged as a "second abnormality" due to an event such as a malfunction of the motor 22.

[0022] Fifth, if the starting pressure value when the fan filter device 10 is activated exceeds the third threshold, there is a possibility that some kind of abnormality has occurred. Therefore, the difference between this starting pressure value and the stopping pressure value when the fan filter device 10 was previously stopped is calculated, and if this difference is greater than or equal to the fourth threshold, it is determined that some kind of abnormality has occurred and judged as a "second abnormality".

[0023] (3) Procedure when it is determined that the fan filter device 10 is abnormal The process for determining that there is a malfunction in the fan filter device 10 will be explained with reference to the flowchart in Figure 3.

[0024] In step S1, the fan filter device 10 is activated, and the process proceeds to step S2.

[0025] In step S2, the control unit 30 obtains the starting pressure value from the differential pressure sensor 40 and proceeds to step S3.

[0026] In step S3, if the starting pressure value is below the third threshold, it is considered normal and the process proceeds to step S4. If it is above the third threshold, there is a possibility of some kind of abnormality, so the process proceeds to step S17.

[0027] In step S4, the control unit 30 uses the differential pressure sensor 40 to obtain the current atmospheric pressure value, stores it in the memory unit 32 along with the time being measured by the clock unit 34, and proceeds to step S5.

[0028] In step S5, if the current atmospheric pressure exceeds the first threshold, proceed to step S10 (if y); otherwise, it is considered normal and proceed to step S6 (if n).

[0029] In step S6, if the measured atmospheric pressure is below the second threshold, proceed to step S15 (if y); otherwise, proceed to step S7 (if n).

[0030] In step S7, since the current atmospheric pressure is within the normal range between the first threshold and the second threshold, the system proceeds to step S8, assuming that each component of the fan filter device 10 is functioning correctly.

[0031] In step S8, if a stop signal is received from the central control unit 42 or if the operating time has ended, the process proceeds to step S9; otherwise, the process returns to step S4.

[0032] In step S9, the control unit 30 obtains the stop pressure value from the differential pressure sensor 40 just before stopping, stores it in the memory unit 32 along with the current time, and then terminates.

[0033] Next, in step S5, if the current atmospheric pressure exceeds the first threshold, it means that the atmospheric pressure is rising, so the process proceeds to step S10.

[0034] In step S10, it is determined whether the rate of increase in the atmospheric pressure is less than the standard rate of increase. If it is less than the standard rate of increase, proceed to step S11 (if y); if it is equal to or greater than the standard rate of increase, proceed to step S13 (if n).

[0035] In step S11, since the rate of increase in atmospheric pressure is less than the standard rate of increase, it is determined that the filter 20 is becoming clogged, and this is judged as the first abnormality, so the process proceeds to step S12.

[0036] In step S12, the control unit 30 notifies the central control unit 42 that a first abnormality has occurred, namely that the filter 20 of the fan filter device 10 is clogged, and then terminates.

[0037] In step S13, since the rate of increase in atmospheric pressure is greater than or equal to the standard rate of increase, it is determined that the problem is not due to clogging of the filter 20, but rather a second abnormality, such as a broken fan blade 28 covering the filter 20, and the process proceeds to step S14.

[0038] In step S14, the control unit 30 notifies the central control unit 42 that a second abnormality has occurred and terminates the process.

[0039] In step S15, since the current atmospheric pressure value is below the second threshold, it is determined to be a second abnormality, such as a malfunction of the motor 22, and the process proceeds to step S16.

[0040] In step S16, the control unit 30 notifies the central control unit 42 that a second abnormality has occurred and terminates.

[0041] In step S3, if the starting pressure value is equal to or greater than the third threshold, in step S17, the difference between the starting pressure value and the stopping pressure value at the time of the previous stop is calculated, and it is determined whether this difference is equal to or greater than the fourth threshold. If it is less than the fourth threshold, it is considered normal and the process proceeds to step S4 (in the case of n). If it is equal to or greater than the fourth threshold, the process proceeds to step S18 (in the case of y).

[0042] In step S18, since the difference between the starting pressure value and the stopping pressure value is greater than or equal to the fourth threshold, it is determined that some kind of abnormality has occurred, and the process proceeds to step S19.

[0043] In step S19, the control unit 30 notifies the central control unit 42 that a second abnormality has occurred and terminates.

[0044] (4) Effects According to this embodiment, the differential pressure sensor 40 can determine from the atmospheric pressure value it measures whether there is a first abnormality, such as clogging of the filter 20 of the fan filter device 10, or a second abnormality, such as a malfunction in the motor 22, and can notify the central control device 42 of this.

[0045] This allows those managing the cleanroom to detect malfunctions or other issues with the fan filter device 10 before it completely stops, thereby preventing contamination within the cleanroom.

[0046] (5) Example of change The first to fourth thresholds are set in advance through test runs, as they will fluctuate depending on the air pressure changes according to the rotation speed of the fan 26 and the voltage applied to the motor 22.

[0047] Furthermore, since multiple fan filter devices 10 are installed in the cleanroom, the first to fourth threshold values ​​are changed according to the installation location and the number of installed devices.

[0048] Furthermore, although the above embodiment describes the fan filter device being installed in a clean room, it is not limited to this and can be installed in any room where air purification is required.

[0049] Although one embodiment of the invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and essence of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0050] 10...Fan filter device, 12...Main unit, 14...Intake port, 6...Outlet port, 18...Internal space, 20...Filter, 22...Motor, 24...Rotating shaft, 26...Fan, 28...Blades, 30...Control unit, 32...Memory unit, 34...Clock unit, 36...Communication unit, 38...Drive circuit, 40...Differential pressure sensor, 42...Centralized control unit

Claims

1. The main body has an internal space that connects from the intake to the outlet, A blower unit that introduces outside air into the internal space from the intake port and creates an airflow that is discharged from the outlet port, A filter unit that removes dust from the air flowing through the internal space, A sensor unit that acquires the pressure value of the internal space, An abnormality determination unit that, when the pressure value acquired by the sensor unit exceeds a first threshold, determines that a first abnormality has occurred due to clogging of the filter unit, provided that the rate of increase of the pressure value is less than a predetermined reference rate of increase, determines that a second abnormality has occurred due to an event other than the first abnormality, provided that the rate of increase of the pressure value is greater than the reference rate of increase, and determines that a second abnormality has occurred when the pressure value falls below a second threshold, A fan filter device characterized by having the following features.

2. The sensor unit has a storage unit that stores the atmospheric pressure value acquired by the sensor unit and the time information at the time of acquisition in correspondence with the atmospheric pressure value. The abnormality detection unit determines the rate of increase from the time change of past atmospheric pressure values ​​stored in the memory unit. The fan filter device according to claim 1.

3. The aforementioned abnormality detection unit is If the pressure value exceeds the third threshold immediately after the fan filter device starts operating, the current pressure value is compared with the pressure value at the time the fan filter device was last stopped. If the difference exceeds the fourth threshold, it is determined that the second abnormality has occurred. The fan filter device according to claim 1.

4. The atmospheric pressure value acquired by the sensor unit is the atmospheric pressure value of the internal space, with the atmospheric pressure of the external space outside the main body as the reference. The fan filter device according to claim 1.

5. The aforementioned pressure value is static pressure. The fan filter device according to claim 1.

6. The abnormality detection unit and the storage unit are located outside the main body. The fan filter device according to claim 2.

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