U.S. patent application number 11/722816 was filed with the patent office on 2010-02-04 for fan filter unit.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Masafumi Matsui.
Application Number | 20100028164 11/722816 |
Document ID | / |
Family ID | 36916516 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100028164 |
Kind Code |
A1 |
Matsui; Masafumi |
February 4, 2010 |
FAN FILTER UNIT
Abstract
A fan filter unit includes a plurality of fan motors, a
plurality of detectors, a total controller, and a filter. Each of
the fan motors includes a fan and a motor. The total controller
performs a feedback control to the respective fan motors so that
the detected rotating speeds are identical with a set rotating
speed, based on rotating speeds detected by the detectors. When one
detected rotating speed value by any of the detectors is smaller
than the other detected rotating speed value by the other detector,
the total controller performs a tuning control of rotating speed so
that a rotating speed of the other fan motor is adjusted to the
slower rotating speed of the fan motor.
Inventors: |
Matsui; Masafumi; (Aichi,
JP) |
Correspondence
Address: |
RATNERPRESTIA
P.O. BOX 980
VALLEY FORGE
PA
19482
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Osaka
JP
|
Family ID: |
36916516 |
Appl. No.: |
11/722816 |
Filed: |
February 17, 2006 |
PCT Filed: |
February 17, 2006 |
PCT NO: |
PCT/JP2006/302799 |
371 Date: |
June 26, 2007 |
Current U.S.
Class: |
417/2 |
Current CPC
Class: |
Y02B 30/70 20130101;
F04D 27/004 20130101; Y02A 50/20 20180101; F04D 25/166 20130101;
F24F 11/77 20180101; F24F 11/0001 20130101; F24F 8/108
20210101 |
Class at
Publication: |
417/2 |
International
Class: |
F04D 27/00 20060101
F04D027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2005 |
JP |
2005-043712 |
Claims
1. A fan filter unit comprising: a first fan motor having a first
fan and a first motor; a first detector configured to detect a
rotating speed of the first motor; a second fan motor having a
second fan and a second motor; a second detector configured to
detect a rotating speed of the second motor; a filter configured to
clean air blown from the first fan and the second fan; and a total
controller configured to perform a feedback control so that a
rotating speed of the first fan motor is identical with a set
rotating speed based on the rotating speed detected by the first
detector, to perform a feedback control so that a rotating speed of
the second fan motor is identical with the set rotating speed based
on a rotating speed detected by the second detector, to perform a
tuning control of rotating speed so that the rotating speed of the
second fan motor is reduced to the rotating speed detected by the
first detector when the rotating speed detected by the first
detector is slower than the rotating speed detected by the second
detector by at least a predetermined value, to perform a tuning
control of rotating speed so that the rotating speed of the first
fan motor is reduced to the rotating speed detected by the second
detector when the rotating speed detected by the second detector is
slower than the rotating speed detected by the first detector by at
least a predetermined value.
2. The fan filter unit according to claim 1, wherein the total
controller includes: a first rotation controller configured to
perform a feedback control so that the rotating speed of the first
fan motor is identical with a set rotating speed based on the
rotating speed detected by the first detector; a second rotation
controller configured to perform a feedback control so that the
rotating speed of the second fan motor is identical with the set
rotating speed based on the rotating speed detected by the second
detector; a first comparator configured to compare the rotating
speed detected by the first detector with the set rotating speed
and to transmit a comparison result to the first rotation
controller; a second comparator configured to compare the rotating
speed detected by the second detector with the set rotating speed,
and to transmit a comparison result to the second rotation
controller; a third comparator configured to calculate a difference
between the rotating speed detected by the first detector and the
rotating speed detected by the second detector; and a rotating
speed tuning controller configured to perform a tuning control so
that the rotating speed of a faster fan motor among the first fan
motor and the second fan motor is reduced via one of the first and
second rotation controllers when a calculation result of the third
comparator is at least the predetermined value, upon receiving the
calculation result of the third comparator.
3. The fan filter unit according to claim 1, wherein the total
controller is configured to delay a start of the tuning control of
rotating speed by a predetermined time.
4. The fan filter unit according to claim 3, wherein the
predetermined time is set a time required for a preparatory
operation during which the rotation speeds detected by the first
detector and the second detector are stabilized, just after one of
the start of the operation of the fan filter unit and a change of
the set rotation speed for the fan motors.
5. The fan filter unit according to claim 1, wherein the total
controller is configured to perform a retry control so that the
rotating speeds of the first fan motor and the second fan motor are
adjusted to the set rotating speed when the tuning control of
rotating speed is performed for a predetermined time.
6. The fan filter unit according to claim 5, wherein the total
controller is configured to stop the fan motors when the retry
control is repeated a predetermined times within a predetermined
period of time.
7. The fan filter unit according to claim 1, wherein the total
controller is configured to stop the first fan motor and the second
fan motor when any of a difference between the set rotating speed
and the rotating speed detected by the first detector, and a
difference between the set rotating speed and the rotating speed
detected by the second detector is larger than a predetermined
value.
8. The fan filter unit according to claim 1, wherein the total
controller is configured to stop the first fan motor and the second
fan motor when a difference between the set rotating speed and the
rotating speed detected by the first detector and a difference
between the set rotating speed and the rotating speed detected by
the second detector are larger than a predetermined value,
respectively.
Description
[0001] THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCT
INTERNATIONAL PATENT APPLICATION NO. PCT/JP2006/302799.
TECHNICAL FIELD
[0002] The present invention relates to a fan filter unit used in a
clean room requiring a clean space for manufacturing
semiconductors, liquid crystal or plasma display panels for
example.
BACKGROUND ART
[0003] A fan filter unit is required to have a thin thickness, an
opening having a wide area for blowing clean air, and a capability
to supply uniform and sufficient air volume. To realize these
demands, a plurality of fan motors have been used. The use of a
plurality of fan motors, however, may cause a whining sound.
[0004] A technique for suppressing the whining sound is disclosed
by Japanese Patent Unexamined Publication No. 2004-205095 for
example. This technique controls the rotation numbers per a unit
time (hereinafter referred to as rotating speed) of a plurality of
fan motors, accurately.
[0005] In a conventional control for suppressing the whining sound
in a filter unit having a plurality of fan motors, the rotating
speed of a second fan motor is adjusted to the rotating speed of a
first fan motor and then the rotating speed of a third fan motor is
adjusted to the rotating speed of the second fan motor. However,
this adjustment of motor rotating speeds may be prevented from
being achieved when variation in capabilities of a plurality of
motors causes a later motor to have a capability inferior to that
of a former motor.
SUMMARY OF THE INVENTION
[0006] The present invention solves the conventional disadvantage
as described above. It is an objective of the present invention to
provide a fan filter unit that can cope with the variation in
capabilities of motors of a fan filter unit to suppress the whining
sound. The fan filter unit of the present invention has a plurality
of fan motors, a plurality of detectors, a total controller, and a
filter. Each of the fan motors includes a fan and a motor. Each of
the detectors detect a rotating speed of each of the motors. The
total controller subjects, based on rotating speeds detected by the
detectors, the respective fan motors to a feedback control by which
the detected rotating speeds are identical with a set rotating
speed. When a rotating speed value detected by any of the detectors
is smaller than a rotating speed value detected by the other
detector, the total controller performs a tuning control of the
rotating speeds so that the rotating speed of the other fan motor
is adjusted to the slower rotating speed of the fan motor.
According to the present invention, in a fan filter unit having a
plurality of fan motors, the rotating speed of the respective fan
motors including variation in the motor capability can be
identical. Even when the rotating speeds of the fan motors change
due to variation in air pressure in a place holding the fan motors,
the fan filter unit can allow the rotating speeds to be identical
so as to suppress the whining sound.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic diagram illustrating a fan filter unit
according to a first exemplary embodiment of the present
invention.
[0008] FIG. 2 is a block circuit diagram illustrating the fan
filter unit shown in FIG. 1.
[0009] FIG. 3 is a block circuit diagram illustrating a fan filter
unit according to a second exemplary embodiment of the present
invention.
[0010] FIG. 4 is a block circuit diagram illustrating a fan filter
unit according to a third exemplary embodiment of the present
invention.
[0011] FIG. 5 is a block circuit diagram illustrating a fan filter
unit according to a fourth exemplary embodiment of the present
invention.
[0012] FIG. 6 is a block circuit diagram illustrating a fan filter
unit according to a fifth exemplary embodiment of the present
invention.
[0013] FIG. 7 is a block circuit diagram illustrating a fan filter
unit according to a sixth exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0014] Hereinafter, embodiments of the present invention will be
described with reference to the drawings. It is noted that the same
components in the respective embodiments as those of the antecedent
embodiment(s) may be denoted with the same reference numerals and
may not be described further. The present invention is not limited
to these embodiments.
First Exemplary Embodiment
[0015] FIG. 1 illustrates a schematic structure of a fan filter
unit according to a first exemplary embodiment of the present
invention. FIG. 1 is a front view in which the filter is partially
cut out. FIG. 2 is a block circuit diagram thereof. This fan filter
unit has first fan motor 5A, second fan motor 5B, and filter 6. Fan
motor 5A is composed of first fan 2A, first motor 3A, and first
motor driver 4A. Fan motor 5B is composed of second fan 2B, second
motor 3B, and second motor driver 4B. Filter 6 cleans air blown by
fans 2A and 2B. Filter 6 has glass fibers, for example, and
captures micron-order fine particles with a high efficiency. More
specifically, filter 6 traps fine particles of 0.3 .mu.m with a
trapping efficiency of 99.97% or more. Filter 6 is provided at the
blowing side or suction side of fans 2A and 2B.
[0016] Fan filter unit has: total controller 7 (hereinafter
referred to as controller 7) configure to control fan motors 5A and
5B; first detector 9A configured to detect a rotating speed of
motor 3A; and second detector 9B configured to detect a rotating
speed of motor 3B. Controller 7 has: rotating speed setting section
8 configured to set rotating speeds of fan motors 5A and 5B; first
rotation controller 10A (hereinafter referred to as controller 10A)
configured to receive a rotating speed detected by detector 9A to
control the rotation of fan motor 5A; and second rotation
controller 10B (hereinafter referred to as controller 10B)
configured to receive a rotating speed detected by detector 9B to
control the rotation of fan motor 5B. Controller 7 also has; first
comparator 30A; second comparator 30B; third comparator 31; and
rotating speed tuning controller 11 (hereinafter referred to as
controller 11). Comparator 30A compares a rotating speed set by
rotating speed setting section 8 with the rotating speed detected
by detector 9A to transmit the result to controller 10A. Comparator
30B compares the rotating speed set by rotating speed setting
section 8 with the rotating speed detected by detector 9B to
transmit the result to controller 10B. Comparator 31 compares the
rotating speed detected by detector 9A with the rotating speed
detected by detector 9B to calculate how much the slower rotating
speed is slower than the faster rotating speed to transmit the
result represented by r/min. to controller 11. In other words,
comparator 31 calculates a difference between the rotating speed
detected by detector 9A and that detected by detector 9B. When the
result by comparator 31 is equal to or higher than a predetermined
value, controller 11 subjects fan motors 5A and 5B to a tuning
control via one of controllers 10A and 10B so that the faster
rotating speed of those of fan motors 5A and 5B is reduced.
[0017] Motors 3A and 3B are electronic control-type brushless
motors, for example. Motor drivers 4A and 4B are composed of a
microcomputer and software or an exclusive circuit, respectively.
It is noted that motors 3A and 3B also may be motors based on a
system other than the above one and motor drivers 4A and 4B also
may be composed of circuits configured to control power applied to
motors 3A and 3B.
[0018] Each part of controller 7 is composed of a microcomputer and
software or an exclusive circuit. These parts may be provided
integrally or may be provided separately.
[0019] Detectors 9A and 9B are composed of, for example, magnets
rotated by motors 3A and 3B, magnetic detection elements configured
to detect changes in the magnetism, and circuits configured to
calculate rotating speeds based on the changes in the magnetism.
Alternatively, detectors 9A and 9B also may be composed by, for
example, circular disks having reflection sections rotated by
motors 3A and 3B, optical elements configured to detect the
brightness thereof, and circuits configured to calculate rotating
speeds based on the changes in the brightness. As described above,
detectors 9A and 9B can be configured based on a magnetic method,
an optical method or the like. Each of detectors 9A and 9B
generates clock vibration by a crystal oscillator to calculate a
rotation number of motors 3A or 3B per a unit time based on this
vibration. The structure as described above provides accurate
detection of the rotation speeds of motors 3A and 3B.
[0020] In the above structure, a rotating speed of 2000 r/min set
by rotating speed setting section 8 is given to motors 3A and 3B.
Then, a feedback control is performed so that the respective
detected rotating speeds of motors 3A and 3B reach the set rotating
speed. Specifically, comparators 30A and 30B compare the rotating
speeds detected by detectors 9A and 9B with the rotating speed set
by rotating speed setting section 8, respectively, to send the
result to controllers 10A and 10B. Based on the results by
comparators 30A and 30B, controllers 10A and 10B control motor
drivers 4A and 4B so that motors 3A and 3B can have rotating speeds
closer to the set rotating speed, respectively.
[0021] Even the feedback control as described above may cause fan
motors 5A and 5B to have different rotating speeds due to variation
in the capability between fan motors 5A and 5B or a change in an
air pressure in a place holding fan motors 5A and 5B. When the
difference in the rotating speeds is 10 r/min or more for example,
whining sound is caused.
[0022] In this case, controller 11 controls controller 10B based on
the calculation result of comparator 31 so that the higher
detection rotating speed of fan motor 5B is adjusted to the lower
detection rotating speed of fan motor 5A. Specifically, controllers
10A and 10B prioritizes the control from controller 11 over the
results from comparators 30A and 30B. As a result, whining sound is
suppressed from being caused without being influenced by variation
in the capability between fan motors 5A and 5B or a change in an
air pressure in a place holding fan motors 5A and 5B.
[0023] It is noted that conditions causing whining sound change
depending on the rotation speeds, sizes of fan motors 5A and 5B, or
the shapes of fans 2A and 2B. Thus, a threshold value of a
difference between the rotating speeds at which a tuning control of
rotating speeds is started is preferably determined on a
case-by-case basis.
[0024] As described above, based on the rotating speed detected by
detector 9A, controller 7 provides a feedback control by which the
rotating speed of fan motor 5A is identical with the set rotating
speed. Similarly, based on the rotating speed detected by detector
9B, controller 7 also provides a feedback control by which the
rotating speed of fan motor 5B is identical with the set rotating
speed. Furthermore, when the rotating speed detected by detector 9A
is slower than the rotating speed detected by detector 9B by an
amount equal to or larger than a predetermined value, controller 7
performs a tuning control to the rotating speed so that the
rotating speed of fan motor 5B is reduced to the rotating speed
detected by detector 9A. When the rotating speed detected by
detector 9B is slower than the rotating speed detected by detector
9A by an amount equal to or larger than a predetermined value,
controller 7 also performs a tuning control to the rotating speed
so that the rotating speed of fan motor 5A is reduced to the
rotating speed detected by detector 9B.
[0025] It is noted that, although a case where two fan motors are
provided is described above, the above system also can be applied
to a case where three or more fan motors are provided. In such a
case, a control may be provided by which rotating speeds of fan
motors are adjusted to the lowest rotating speed of a fan
motor.
Second Exemplary Embodiment
[0026] FIG. 3 is a block circuit diagram illustrating a fan filter
unit according to a second exemplary embodiment of the present
invention. This exemplary embodiment has the same structure as that
of the first exemplary embodiment except for that total controller
73 is structured so that stabilizer 16 is provided between
comparator 31 and rotation speed tuning controller 11 (hereinafter
referred to as controller 11).
[0027] Stabilizer 16 is designed to prevent controller 11 from
functioning until a preparatory operation performed for a
predetermined time is completed. Stabilizer 16 prevents controller
11 from functioning in a time zone in which detected rotating
speeds of fan motors 5A and 5B are unstable e.g., at a time just
after the start of the operation of fan motors 5A and 5B or in a
case where the rotating speeds change instantaneously. Stabilizer
16 is also composed by a microcomputer, for example.
[0028] Specifically, when a set rotating speed is 2000 r/min. for
example, and detected rotating speed of fan motors 5A and 5B are
different from each other in an amount equal to or higher than +10
r/min, stabilizer 16 prevents controller 11 from functioning for a
predetermined time. In other words, stabilizer 16 delays the start
of a tuning control of the rotating speed by a predetermined time.
Specifically, when a difference in the detected rotating speeds of
fan motors 5A and 5B is equal to or larger than .+-.10 r/min,
controller 11 does not function for a predetermined time.
[0029] The predetermined time is set to 30 seconds for a timing
just after the start of the operation by power activation and is
set to 10 seconds for a case where a set rotating speed is changed
or a case where a sudden change in loads to motors 5A and 5B causes
a change in the detected rotating speeds, for example. Each of
these set times correspond to a preparatory operation time. This
can avoid an excessive response of the tuning control of the
rotating speed in a state in which fan motors 5A and 5B have
unstable rotating speeds.
[0030] As described above, total controller 73 delays the start of
a tuning control of the rotating speed by a predetermined time.
This prevents controller 11 from functioning in a time zone in
which the detected rotating speeds of fan motors 5A and 5B are
unstable.
Third Exemplary Embodiment
[0031] FIG. 4 is a block circuit diagram illustrating a fan filter
unit according to a third exemplary embodiment of the present
invention. This exemplary embodiment has the same structure as that
of the first exemplary embodiment except for that total controller
74 includes retry section 19. Retry section 19 is also composed of
a microcomputer, for example.
[0032] Retry section 19 has a retry function to try to provide a
control by which the rotation speeds of fans 2A and 2B are adjusted
to a rotating speed set by rotating speed setting section 8, when
rotating speed tuning controller 11 (hereinafter referred to as
controller 11) continuously performs a tuning control of rotating
speed for a predetermined time.
[0033] When fan motors 5A and 5B are stopped during an important
process in a clean room using the fan filter unit, the process may
have a remarkably-deteriorated productivity. If fan motors 5A and
5B are operated with a low rotating speed, an expected air volume
provided by a set rotating speed is not supplied. It is thus
desirable that such a continuous operation of fan motors 5A and 5B
is avoided during such an important process.
[0034] Retry section 19 measures a time during which a tuning
control of rotating speed is continued. When a tuning control of
the rotating speed is continued for 10 minutes, for example, due to
variation in the capability between fan motors 5A and 5B, for
example, retry section 19 tries to control fan motors 5A and 5B
with an initial set rotating speed via rotation controllers 10A and
10B (hereinafter referred to as controllers 10A and 10B).
Specifically, an instruction by retry section 19 is prioritized
over the control by controller 11. As described above, total
controller 74 performs a retry control by which the rotating speeds
of motors 5A and 5B are adjusted to a set rotating speed when a
tuning control of rotating speed continues for a predetermined
time. This prevents a situation where fan motors 5A and 5B are
continuously operated with a low rotating speed while a tuning
control of rotating speed prevents an expected air volume provided
by a set rotating speed. Fan motors 5A and 5B can thus fully use
the capabilities thereof. Then, fan motors 5A and 5B are operated
again with a rotating speed as much as close to the set rotating
speed.
[0035] A predetermined time measured by retry section 19 depends on
an inner volume of a clean room or the like attached with the fan
motor unit or a required air volume.
[0036] It is noted that, even when the retry control cannot prevent
a difference in the rotating speeds of fan motors 6A and 5B equal
to or larger than a predetermined value of rotating speed, the
rotating speeds are preferably subjected to a tuning control again.
Thus, a retry control is not continuously performed. Once retry
section 19 instructs controllers 10A and 10B to perform a retry
control, a time during which a tuning control of rotating speed is
performed, which is measured by retry section 19, is reset. Then, a
normal control as in the first exemplary embodiment is returned.
The control as described above is preferred.
Fourth Exemplary Embodiment
[0037] FIG. 5 is a block circuit diagram illustrating a fan filter
unit according to a fourth exemplary embodiment of the present
invention. This exemplary embodiment has the same structure as that
of the third exemplary embodiment except for that total controller
75 includes retry counter 20 and operation stop section 18. Retry
counter 20 and operation stop section 18 are also composed of a
microcomputer, for example. It is noted that operation stop section
18 also may be configured to stop the power supply to motors 3A and
3B, instead of stopping fan motors 5A and 5B via rotation
controllers 10A and 10B. In other words, operation stop section 18
also may be configured by a relay.
[0038] When retry counter 20 detects that the retry function by
retry section 19 is repeatedly performed a predetermined times
within a predetermined period of time, retry counter 20 skips a
tuning control of rotating speed to automatically stop fan motors
5A and 5B via operation stop section 18. Specifically, an
instruction by operation stop section 18 is prioritized over that
by retry section 19. As described above, when a retry control is
repeated a predetermined times within a predetermined period of
time, total controller 75 stops fan motors 5A and 5B.
[0039] Retry counter 20 counts how many times a retry function is
performed within one hour, for example. When the counted number
exceeds five, for example, retry counter 20 determines an abnormal
use. Such status is caused, for example, when an abnormal pressure
is caused in a place where the fan filter unit is placed, when the
fan filter unit is used in an abnormal use, for example, when a
foreign matter such as rope winds around fan motors 5A and 5B, or
when filter 6 has abnormality. When the number of a retry function
performed within a predetermined period of time is equal to or more
than a predetermined value, retry counter 20 outputs a signal to
operation stop section 18. Upon receiving this signal, operation
stop section 18 automatically stops fan motors 5A and 5B. In this
manner, an abnormal use of fan motors 5A and 5B is automatically
prevented.
[0040] It is appropriate that the predetermined period of time
within which retry counter 20 measures how many times retry section
19 has instructed a retry function is about one hour to two hours.
This control intends to detect abnormality as described above and
thus determination within a short time is preferred. When an
abnormality is caused, a retry function is continuously performed.
Thus, a threshold value for outputting a signal to operation stop
section 18 may be about 3 to 5.
Fifth Exemplary Embodiment
[0041] FIG. 6 is a block circuit diagram illustrating a fan filter
unit according to a fifth exemplary embodiment of the present
invention. This exemplary embodiment has the same structure as that
of the first exemplary embodiment except for that total controller
76 includes third comparator 21 having a different function from
that of comparator 31 and operation stop section 18. Comparator 21
is also composed of a microcomputer, for example.
[0042] Comparator 21 has the same function as that of comparator 31
to compare the rotating speed detected by detector 9A with the
rotating speed detected by detector 9B to transmit the result to
rotating speed tuning controller 11 (hereinafter referred to as
controller 11). Comparator 21 also compares a set rotating speed
set by rotating speed setting section 8 with the rotating speeds
detected by detectors 9A and 9B. Then, comparator 21 determines
whether or not a difference between the set rotating speed and any
of the rotating speeds detected by detectors 9A and 9B is larger
than a rotation difference limit corresponding to 25%, for example,
of the set rotating speed. When comparator 21 detects that the
difference is larger than the rotation difference limit, comparator
21 skips a tuning control of rotating speed via operation stop
section 18 to automatically stop fan motors 5A and 5C. As described
above, an instruction by operation stop section 18 is prioritized
over that by controller 11.
[0043] As described above, comparator 21 compares the rotating
speeds detected by detectors 9A and 9B with the set rotating speed
set by rotating speed setting section 8 to detect a difference in
the rotating speeds.
[0044] There may be a case as shown in FIG. 6 in which fan motor 5C
completely different from fan motor 5B is provided when fan motors
5B and 5C are arranged. When fan motor 5C is used in a wrong manner
as described above, comparator 21 detects that fan motor 5C has a
rotating speed significantly different from that of fan motor 5B,
and is able to determine that fan motor 5B and fan motor 5C are
arranged in a wrong manner. For example, comparator 21 detects that
a difference between a set rotating speed of 2000 r/min. and
detected rotating speeds is 500 r/min. or more. In such a case,
comparator 21 outputs a signal to operation stop section 18. Upon
receiving this signal, operation stop section 18 automatically
stops fan motors 5A and 5C. In this manner, an abnormal use of fan
motor 5C is automatically avoided.
[0045] Alternatively, fan motors 5A and 5B are also stopped when
motors 5A and 5B are correctly provided and filter 6 is locally
clogged to prevent one of fan motors 5A and 5B from correctly
operating.
[0046] It is noted that, when fan motor 5B having the same function
as that of fan motor 5A is placed instead of fan motor 5C, a
criterion value used by comparator 21 is set so as to prevent
operation stop section 18 from operating.
[0047] As described above, when a difference between a set rotating
speed and a rotating speed detected by detector 9A or detector 9B
is larger than a predetermined value, total controller 76 stops the
fan motors. This prevents one fan motor from being wrongly used or
operating in an abnormal condition.
Sixth Exemplary Embodiment
[0048] FIG. 7 is a block circuit diagram illustrating a fan filter
unit according to a sixth exemplary embodiment of the present
invention. This exemplary embodiment has the same structure as that
of the first exemplary embodiment except for that total controller
77 includes third comparator 22 and operation stop section 18.
Third comparator 22 is used instead of comparator 31 and has a
different function. Comparator 22 is also composed of a
microcomputer or the like.
[0049] Comparator 22 has the same function as that of comparator 31
to compare a rotating speed detected by detector 9A with a rotating
speed detected by detector 9B to transmit the result to rotating
speed tuning controller 11 (hereinafter referred to as controller
11). Comparator 22 also compares rotating speeds detected by
detectors 9A and 9B with a set rotating speed set by rotating speed
setting section 8. When a difference between the rotating speeds
detected by detectors 9A and 9B and the set rotating speed is equal
to or larger than a predetermined value, comparator 22 stops fan
motors 5C and 5D via operation stop section 18.
[0050] Fan motors 5C and 5D here are different from fan motors 5A
and 5B having a required capability that should be attached. In
such a case, fan motors 5C and 5D cannot be rotated with the
required rotating speed. Specifically, the detected rotating speeds
in this case do not identical with the set rotating speed just
after the start of the operation in spite of that the set rotating
speed is set to be equal to or lower than a predetermined rotating
speed determined within a range of capabilities of the fan motors
that should be attached. In such a case, comparator 22 compares
rotating speeds detected by detectors 9A and 9B with the set
rotating speed set by rotating speed setting section 8 to detect a
wrong use of fan motors 5C and 5D. Then, comparator 22 skips a
tuning control of the rotating speed to allow operation stop
section 18 to automatically stop fan motors 5C and 5D.
[0051] Assume a case where rotating speed setting section 8 is used
to set a set rotating speed of 1800 r/min. that is within a range
of 1000 to 2000 r/min as a range of capabilities of rotating speeds
of fan motors 5A and 5B. In this case, fan motors 5A and 5B have a
sufficient capability and can be subjected to a feedback control.
However, fan motors 5C and 5D arranged in a wrong manner prevent
the rotating speed detected by detectors 9A and 9B from being
within a range of .+-.10 r/min within the set rotating speed, for
example. In such a case, comparator 22 determines an abnormal use
in which fan motors 5C and 5D having capabilities totally different
from those of fan motors 5A and 5B are wrongly used. Then,
comparator 22 outputs a signal to operation stop section 18. Upon
receiving this signal, operation stop section 18 automatically
stops fan motors 5C and 5D. In this manner, an abnormal use of fan
motors 5C and 5D is automatically avoided.
[0052] It is noted that, when fan motors 5A and 5B are provided
instead of fan motors 5C and 5D, a criterion value used by
comparator 22 is set so as to prevent operation stop section 18
from operating.
[0053] Fan motors may have unstable rotating speeds just after the
start of the operation as described in the second exemplary
embodiment. Thus, as in the function of stabilizer 16 of the second
exemplary embodiment, operation stop section 18 is preferably
suppressed from operating for a predetermined time.
[0054] As described above, total controller 77 stops the fan motors
when a difference between a set rotating speed and rotating speeds
detected by detectors 9A and 9B is larger than a predetermined
value.
[0055] It is noted that the respective structures unique to the
second exemplary embodiment to the sixth exemplary embodiment may
be combined so long as they are incompatible to each other. Such a
combination is covered by the scope of the present invention. For
example, the structure of the second exemplary embodiment may be
combined with the structures of the third to sixth exemplary
embodiments.
INDUSTRIAL APPLICABILITY
[0056] According to the present invention, in a room including a
clean room holding therein a plurality of fans having similar
rotating speeds, a tuning control of rotating speed can be used to
suppress whining sound by the fans. Thus, the invention can be used
for an application for making not only a work environment but also
a living environment more comfortable.
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