U.S. patent application number 12/779504 was filed with the patent office on 2010-11-25 for fan control apparatus and fan control method.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Hiroyuki Furuya, Kazuhiro Nitta, Atsushi Yamaguchi.
Application Number | 20100296945 12/779504 |
Document ID | / |
Family ID | 43027667 |
Filed Date | 2010-11-25 |
United States Patent
Application |
20100296945 |
Kind Code |
A1 |
Nitta; Kazuhiro ; et
al. |
November 25, 2010 |
FAN CONTROL APPARATUS AND FAN CONTROL METHOD
Abstract
A fan controlling apparatus for controlling a plurality of fans
which are tandemly arranged in ventilation direction of a chamber
to control a temperature of a hot generating object placed in the
chamber, the apparatus includes a memory for storing data of the
rotational speed each of fans in relation to the temperature of the
heat generating object, and a controller for controlling the
rotational speed of each of the fans respectively in dependence on
the temperature of the heat generating object in reference to the
data stored in the memory.
Inventors: |
Nitta; Kazuhiro; (Kawasaki,
JP) ; Yamaguchi; Atsushi; (Kawasaki, JP) ;
Furuya; Hiroyuki; (Kawasaki, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
43027667 |
Appl. No.: |
12/779504 |
Filed: |
May 13, 2010 |
Current U.S.
Class: |
417/2 |
Current CPC
Class: |
G06F 1/206 20130101;
H05K 7/20836 20130101 |
Class at
Publication: |
417/2 |
International
Class: |
F04D 27/00 20060101
F04D027/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2009 |
JP |
2009-123500 |
Claims
1. A fan controlling apparatus for controlling a plurality of fans
which are tandemly arranged in ventilation direction of a chamber
to control a temperature of a hot generating object placed in the
chamber, comprising: a memory for storing data of the rotational
speed each of fans in relation to the temperature of the heat
generating object; and a controller for controlling the rotational
speed of each of the fans respectively in dependence on the
temperature of the heat generating object in reference to the data
stored in the memory.
2. The fan controlling apparatus according to claim 1, wherein the
controller controls the rotational speed of each of the fans so
that the difference of an actual rotational speed of each of the
fans lower than predetermined value.
3. The fan controlling apparatus according to claim 1, wherein the
data that the memory stored are control parameters of each of the
fans with respect to a plurality of the temperatures.
4. The fan controlling apparatus according to claim 3, wherein the
control parameters are respectively values of pulse width in
accordance with the pulse width control of each fan, and the
parameters are respectively parameters corresponding to pulse width
inputs to each of the fans.
5. The fan controlling apparatus according to claim 1, wherein the
controller controls the rotational speed of each of the fans so
that the difference of an actual rotational speed of each of the
fans lower than 10 percents.
6. A fan controlling method for controlling a plurality of fans
which are tandemly arranged in ventilation direction of a chamber
to control a temperature of a hot generating object placed in the
chamber, comprising: detecting the temperature of a hot generating
object; and controlling the rotational speed of each of the fans
respectively in dependence on the temperature detected in reference
to data stored in the memory, the memory storing the data of the
rotational speed each of fans in relation to the temperature of the
heat generating object.
7. The fan controlling method according to claim 6, wherein the
controlling controls the rotational speed of each of the fans so
that the difference of an actual rotational speed of each of the
fans lower than predetermined value.
8. The fan controlling method according to claim 6, wherein the
data that the memory stored are control parameters of each of the
fans with respect to a plurality of the temperatures.
9. The fan controlling method according to claim 8, wherein the
control parameters are respectively values of pulse width in
accordance with the pulse width control of each fan, and the
parameters are respectively parameters corresponding to pulse width
inputs to each of the fans.
10. The fan controlling method according to claim 6, wherein the
controlling controls the rotational speed of each of the fans so
that the difference of an actual rotational speed of each of the
fans lower than 10 percents.
11. A computer-readable recording medium storing a computer program
controlling a plurality of fans which are tandemly arranged in
ventilation direction of a chamber to control a temperature of a
hot generating object placed in the chamber, the program being
designed to make a computer perform the steps of: detecting the
temperature of a hot generating object; and controlling the
rotational speed of each of the fans respectively in dependence on
the temperature detected in reference to data stored in the memory,
the memory storing the data of the rotational speed each of fans in
relation to the temperature of the heat generating object.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority of the prior Japanese Patent Application No. 2009-123500,
filed on May 21, 2009, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] The embodiments discussed herein are relates to a fan
control apparatus and a fan control method.
BACKGROUND
[0003] In existing electronic equipment such as a server device, a
PC (Personal Computer) and others, in some cases, fans that send
air into equipment concerned to radiate heat in the equipment to
the outside in order to avoid temperature rising in the equipment
with heat generated from a processor or the like are mounted on the
equipment.
[0004] In a fan, noise (whirring sounds) is generated owing to
formation of air eddies in the vicinity of blades. Noise generated
from a fan is increased with increasing an air flow rate at which
the fan blows off air. Therefore, if it is intended to increase the
number of revolutions (hereinafter, referred to as the revolution
number) of the fan to increase the air flow rate, the noise will be
increased accordingly. Specifically, it is known that noise from a
fan is proportional to the fifth or sixth power of the number of
axial rotations of the fan.
[0005] Recently, such a situation has been more and more frequently
observed that electronic equipment is installed not only in a
specific place such as a computer room but also in a general office
and hence consciousness of noise reduction is now being raised.
Therefore, how the noise generated from a fan is reduced is one of
important problems to be solved.
[0006] As a method of reducing noise generated from a fan, a method
of monitoring the temperature of a heating element and the
environmental temperature around the heating element and changing
the revolution number of the fan concerned in accordance with the
temperatures so monitored to control the noise from the fan so as
not to increase more than needed is known. The revolution number of
the fan is controlled by modulating the pulse width (the PWM value)
of a voltage or PWM (Pulse Width Modulation) signal to control
energy to be supplied to the motor of the fan.
[0007] On the hand, nowadays, in some cases, a space for an air
passage in equipment is reduced with size and thickness reduction
of the electronic equipment and such a case in which only a small
fan is allowed to be installed is now being more frequently
observed. In addition, a heating value of electronic equipment is
more and more increased every year as processing speed and
performance of electronic equipment get higher. Thus, such a
countermeasure is taken that a plurality of fans is superposed on
one another in a multi-stage form so as to sufficiently cool the
inside of electronic equipment even when installation of only
small-sized fans is allowed.
[0008] In this connection, an example in which a plurality of fans
is superposed on one another in a multi-stage form is illustrated
in FIG. 26. FIG. 26 illustrates an example of electronic equipment
in which two fans are disposed in series.
[0009] As illustrated in FIG. 26, two fans 321a and 321b are
installed in series in an air passage 310 of electronic equipment
300. The electronic equipment 300 includes a fan power source
section 330 and a control section 340. The fan power source section
330 is a power source for supplying power to motors not illustrated
which are built in the fans 321a and 321b. The control section 340
controls amounts of energy supplied to the fans 321a and 321b on
the basis of temperatures of heating elements 350a and 350b
detected using temperature sensors 341a and 341b and an
environmental temperature detected using a temperature sensor 341c.
Next, a specific configuration of the control section 340 will be
illustrated. FIG. 27 is a block diagram illustrating a
configuration of the existing control section 340.
[0010] As illustrated in FIG. 27, the control section 340 includes
the temperature sensors 341a to 341c, temperature check sections
342a and 342b, revolution number detecting sections 343a and 343b,
a revolution number error check section 344 and a pulse generator
345. The control section 340 also includes a RAM (Random Access
Memory) 346, a ROM (Read Only Memory) 347 and a processor 348.
[0011] The temperature sensors 341a and 341b are attached to the
heating elements 350a and 350b in the electronic equipment 300 to
detect the temperatures of the heating elements 350a and 350b. The
temperature sensor 341c is installed outside of the electronic
equipment 300 to detect the environmental temperature around the
fan 321a. The temperature check sections 342a and 342b check to see
to which extent the temperatures of the heating elements 350a and
350b detected using the temperature sensors 341a and 341b vary from
a target temperature and notify the processor 348 of results of
check in the form of predetermined variables.
[0012] The revolution number detecting sections 343a and 343b
detect the revolution numbers of the fans 321a and 321b. The
revolution number check section 344 checks to see whether the fans
321a and 321b normally rotate on the basis of the revolution
numbers of the fans 321a and 321b detected using the revolution
number detecting sections 343a and 343b and notifies the processor
348 of a result of check. The pulse generator 345 inputs pulses for
controlling the revolution numbers of the fans 321a and 321b into
the fans 321a and 321b in pulse widths in accordance with an
instruction from the processor 348.
[0013] The ROM 347 stores therein a table indicating predetermined
variables corresponding to temperatures of the heating elements
350a and 350b and PWM values of pulses to be input into the heating
elements 350a and 350b in one-to-one correspondence and a table
indicating environmental temperatures and the PWM values in
one-to-one correspondence. The processor 348 determines the pulse
widths of pulses to be output to the fans 321a and 321b on the
basis of the predetermined variables sent from the temperature
check sections 342a and 342b and the environmental temperature
detected using the temperature sensor 341c. A specific example
thereof is as illustrated in FIG. 27. FIG. 28 is a flowchart
illustrating an example of procedures of processing executed using
the existing processor 348.
[0014] As illustrated in FIG. 28, first, the processor 348 performs
temperature measurement (step S001). That is, the processor 348
acquires predetermined variables corresponding to the temperatures
of the heating elements 350a and 350b detected using the
temperature sensors 341a and 341b from the temperature check
sections 342a and 342b. The processor 348 also acquires the
environmental temperature detected using the temperature sensor
341c.
[0015] Next, the processor 348 instructs the pulse generator 345 to
modulate the pulse widths on the basis of results of measurement of
the environmental temperature and the temperatures of the heating
elements 350a and 350b (step S002). Specifically, first, the
processor 348 determines PWM values corresponding to the
predetermined variables acquired from the temperature check
sections 342a and 342b or the environmental temperature acquired
from the temperature sensor 341c on the basis of the tables stored
in the ROM 347. Then, the processor 348 instructs the pulse
generator 345 to modulate widths of pulses to be input into the
fans 321a and 321b to have the PWM values so determined (step
S002).
[0016] The pulse generator 345 then inputs pulses whose widths have
been modulated to have the PWM values as instructed from the
processor 348. As a result, the revolution numbers of the fans 321a
and 321b are changed to the revolution numbers conforming to the
environmental temperature and the temperatures of the heating
elements 350a and 350b. As described above, the existing processor
348 determines the pulse widths on the basis of the environmental
temperature and the temperatures of the heating elements 350a and
350b. Incidentally, the existing control section 340 detects the
revolution numbers of the fans 321a and 321b using the revolution
number detecting sections 343a and 343b to check on errors in the
revolution numbers. Specifically, the processor 348 sends an error
notification that the fans 321a and 321b are now in stopped states
to the electronic equipment 300 on the basis of results of
revolution number error check acquired from the revolution number
error check section 344.
[0017] Incidentally, hitherto, the control section 340 has
controlled the fans 321a and 321b in the same manner. In the
following, the fan 321a which is situated on the side of taking air
into the equipment from the outside will be referred to as a
front-stage fan 321a and the fan 321b which is situated on the side
of sending the air into the electronic equipment 300 will be
referred to as a rear-stage fan 321b.
[0018] The processor 348 determines a pulse width of a pulse which
is commonly input into the front-stage fan 321a and the rear-stage
fan 321b at step S002 in FIG. 28 and notifies the pulse generator
345 of the pulse width. As a result, hitherto, energy of the same
amount has been usually supplied from the pulse generator 345 to
the front-stage fan 321a and the rear-stage fan 321b as illustrated
in FIG. 29.
[0019] However, in the case that the fans 321a and 321b are
superposed on each other in a multi-stage form, the work amount
with which the rear-stage fan 321b blows off air is reduced
influenced by an air current generated from the front-stage fan
321a. Therefore, if the amount of energy supplied to the
front-stage fan 321a is the same as that supplied to the rear-stage
fan 321b, the rear-stage fan 321b will run idle and hence the
revolution number of the rear-stage fan 321b will be increased.
Noise is generated greatly influenced by the operation of the fan
of the largest revolution number and hence an increase in
revolution number of the rear-stage fan 321b will be a major factor
to cause an increase in noise.
[0020] In this connection, a technique for, example, making the
revolution number of the front-stage fan 321a different from that
of the rear-stage fan 321b is known. Specifically, in the above
mentioned technique, the pulse width of a pulse input into the
rear-stage fan 321b is controlled to become shorter than that of a
pulse input into the front-stage fan 321a. In the above mentioned
case, if the revolution number of the rear-stage fan 321b is
reduced, an air flow rate (needed air flow rate) needed to cool
heating elements may not be possibly obtained. Therefore, it may
become needed to increase the revolution number of the front-stage
fan 321a more than that needed when the energy of the same amount
is applied to each of the fans 321a and 321b. An example of the
above mentioned technique is disclosed, for example, in Japanese
Laid-open Patent Publication No. 2004-179186.
[0021] However, in the above mentioned known technique, the
revolution number of the front-stage fan 321a is simply increased
with no consideration of the system impedance characteristic of the
electronic equipment 300, so that the noise may be rather increased
as compared with a case in which the energy of the same amount is
applied to each of the fans 321a and 321b. The system impedance
characteristic is a pressure loss determined from a density at
which components constituting the electronic equipment 300 are
packaged and the shape of an air passage therein and is a
characteristic intrinsic to the electronic equipment 300
concerned.
[0022] That is, the noise generated from the fans 321a and 321b
varies depending on the characteristics and the shapes of these
fans 321a and 321b and also depending on the configuration of the
electronic equipment 300 concerned on which the fans 321a and 321b
are mounted and locations of the fans 321a and 321b in the
electronic equipment 300 concerned. Therefore, if the revolution
number of the front-stage fan 321a is simply increased, the noise
generated from the front-stage fan 321a may be possibly increased
more than the noise generated from the rear-stage fan 321b when the
energy of the same amount is applied to each of the fans 321a and
321b depending on the locations of the fans.
SUMMARY
[0023] According to an aspect of the embodiments, a fan controlling
apparatus for controlling a plurality of fans which are tandemly
arranged in ventilation direction of a chamber to control a
temperature of a hot generating object placed in the chamber, the
apparatus includes a memory for storing data of the rotational
speed each of fans in relation to the temperature of the heat
generating object, and, a controller for controlling the rotational
speed of each of the fans respectively in dependence on the
temperature of the heat generating object in reference to the data
stored in the memory.
[0024] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims. It is to be understood that both the
foregoing general description and the following detailed
description are exemplary and explanatory and are not restrictive
of the invention, as claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 is a block diagram illustrating a configuration of a
fan control device according to an embodiment 1;
[0026] FIG. 2 is a diagram illustrating a configuration of
electronic equipment according to an embodiment 2;
[0027] FIG. 3 is a block diagram illustrating a configuration of a
fan control device according to the embodiment 2;
[0028] FIG. 4 is a block diagram illustrating specific
configurations of a processor and a ROM according to the embodiment
2;
[0029] FIG. 5 is a diagram illustrating an example of an equipment
state management table;
[0030] FIG. 6 is a diagram illustrating information stored in a
control data storage section according to the embodiment 2;
[0031] FIG. 7A is a diagram illustrating an example of a
heating-element-temperature-based PWM value determination
table;
[0032] FIG. 7B is a diagram illustrating an example of an
environmental-temperature-based PWM value determination table;
[0033] FIG. 8 is a diagram explaining a difference between energy
supplied to a front-stage fan and energy supplied to a rear-stage
fan;
[0034] FIG. 9 is a diagram illustrating a specific configuration of
a database preparing section according to the embodiment 2;
[0035] FIG. 10 is a flowchart illustrating an example of procedures
of preparing the heating-element-temperature-based PWM value
determination table and the environmental-temperature-based PWM
value determination table;
[0036] FIG. 11 is a flowchart illustrating an example of procedures
of processing executed using the processor according to the
embodiment 2;
[0037] FIG. 12 is a diagram illustrating effects brought about by
the embodiment 2;
[0038] FIG. 13 is a diagram illustrating examples of measurement
conditions involving experiments for validation;
[0039] FIG. 14A is a diagram illustrating data indicative of a
result of measurement of the front-stage revolution number, the
rear-stage revolution number and the device noise performed under a
measurement condition A;
[0040] FIG. 14B is a diagram illustrating data indicative of a
result of measurement of the front-stage revolution number, the
rear-stage revolution number and the consumption power performed
under the measurement condition A;
[0041] FIG. 14C is a diagram illustrating data indicative of a
result of analysis of frequencies of the device noise performed
under the measurement condition A;
[0042] FIG. 15A is a diagram illustrating a result of measurement
performed under a condition A-1;
[0043] FIG. 15B is a diagram illustrating a result of measurement
performed under a condition A-2;
[0044] FIG. 15C is a diagram illustrating a result of measurement
performed under a condition A-3;
[0045] FIG. 16A is a diagram illustrating data indicative of a
result of measurement of the front-stage average revolution number,
the rear-stage average revolution number and the device noise
performed under conditions B-1 and B-2;
[0046] FIG. 16B is a diagram illustrating data indicative of a
result of measurement of the front-stage average revolution number,
the rear-stage average revolution number and the consumption power
performed under the conditions B-1 and B-2;
[0047] FIG. 16C is a diagram illustrating data indicative of a
result of analysis of frequencies of the device noise performed
under the conditions B1 and B2;
[0048] FIG. 17A is a diagram illustrating a result of measurement
performed under the condition B-1;
[0049] FIG. 17B is a diagram illustrating a result of measurement
performed under the condition B-2;
[0050] FIG. 18A is a diagram illustrating data indicative of a
result of measurement of the front-stage average revolution number,
the rear-stage average revolution number and the device noise
performed under conditions B-3 and B-4;
[0051] FIG. 18B is a diagram illustrating data indicative of a
result of measurement of the front-stage average revolution number,
the rear-stage average revolution number and the consumption power
performed under the conditions B-3 and B-4;
[0052] FIG. 18C is a diagram illustrating data indicative of a
result of analysis of frequencies of the device noise performed
under the conditions B3 and B4;
[0053] FIG. 19A is a diagram illustrating a result of measurement
performed under the condition B-3;
[0054] FIG. 19B is a diagram illustrating a result of measurement
performed under the condition B-4;
[0055] FIG. 20 is a functional block diagram illustrating an
example of a computer for executing a fan control program;
[0056] FIG. 21 is a block diagram illustrating a configuration of a
fan control device according to an embodiment 3;
[0057] FIG. 22 is a block diagram illustrating specific
configurations of a processor and a ROM according to the embodiment
3;
[0058] FIG. 23 is a diagram illustrating information stored in a
control data storage section according to the embodiment 3;
[0059] FIG. 24 is a diagram illustrating an example of a rear-stage
PWN value change table;
[0060] FIG. 25 is a flowchart illustrating an example of procedures
of processing executed using the processor according to the
embodiment 3;
[0061] FIG. 26 is a diagram illustrating an example of electronic
equipment in which two fans are disposed in series;
[0062] FIG. 27 is a block diagram illustrating a configuration of
an existing control section;
[0063] FIG. 28 is a flowchart illustrating an example of procedures
of processing executed using an existing processor; and
[0064] FIG. 29 is a diagram illustrating that the amount of energy
supplied to a front-stage fan is the same as that supplied to a
rear-stage fan.
DESCRIPTION OF EMBODIMENTS
[0065] Next, preferred embodiments of a fan control device, a fan
control method and a fan control program disclosed in the present
application will be described in detail with reference to the
accompanying drawings.
Embodiment 1
[0066] A fan control device according to an embodiment 1 will be
described. The fan control device according to the embodiment 1 is
a control device that controls operational conditions of a
plurality of fans disposed in series relative to an air passage
formed in equipment.
[0067] The plurality of fans blow off air to heating elements
disposed in the equipment to forcibly air-cool the heating
elements. The fan control device controls the revolution number of
each of the plurality of fans. FIG. 1 is a block diagram
illustrating a configuration of the fan control device according to
the embodiment 1.
[0068] As illustrated in FIG. 1, a fan control device 500 according
to the embodiment 1 includes a temperature detecting section 510
and a control section 520. The temperature detecting section 510
detects the temperature of each heating element. The control
section 520 then controls the revolution numbers of the fans such
that an air flow rate needed for cooling the heating elements is
obtained in a state that the revolution numbers of the fans
coincide with each other on the basis of the temperatures of the
heating elements detected using the temperature detecting section
510.
[0069] Specifically, the control section 520 according to the
embodiment 1 controls the revolution numbers of the fans such that
the needed air flow rate (the cooling air flow rate) needed to cool
the heating elements obtained from the temperatures of the heating
elements, the pipeline resistance in the equipment and the total
static pressure-air flow rate characteristic of the fans in a state
in which a difference in revolution number between the fans is in a
predetermined tolerance is acquired and the difference in
revolution number between the fans is set in the predetermined
tolerance. By controlling the revolution number of each fan in the
above mentioned manner, the respective fans rotate in a state in
which the difference in revolution number between the fans is
maintained in the predetermined tolerance, that is, rotate in a
state in which the revolution numbers of the respective fans
coincide with each other in the predetermined tolerance to send air
to the heating elements at a needed air flow rate determined in
accordance with the current temperature of each heating
element.
[0070] As described above, the fan control device 500 according to
the embodiment 1 controls so as to maintain the difference in
revolution number between the fans in the predetermined tolerance,
desirably, so as to control the revolution numbers of the fans to
coincide with each other. Therefore, such a situation may be
avoided that the total noise generated from the fans is increased
owing to surplus noise generated from a fan of the largest
revolution number.
[0071] The needed air flow rate attained according to the
embodiment 1 is obtained by taking the temperatures of the heating
elements, the pipeline resistance in the equipment and the total
static pressure-air flow rate characteristic of the fans obtained
in a state in which the difference in revolution number between the
fans is maintained in the predetermined tolerance into
consideration. Therefore, according to the embodiment 1, the air
flow rate suited to cool the heating elements may be obtained in a
state in which the difference in revolution number between the fans
is maintained in the predetermined tolerance regardless of the
configuration of the equipment and the locations of the fans in the
equipment.
[0072] Therefore, according to the embodiment 1, it may be possible
to reduce the noise generated from the plurality of fans while
obtaining the air flow rate needed for cooling the heating elements
in the equipment using the plurality of fans.
Embodiment 2
[0073] Next, a fan control device according to an embodiment 2 will
be described. The fan control device according to the embodiment 2
is configured to control the revolution numbers of two fans
installed in electronic equipment such as a rack-mounted type
server device, a general PC and others. First, a configuration of
electronic equipment in which the fan control device according to
the embodiment 2 is installed will be described. FIG. 2 is a
diagram illustrating a configuration of the electronic equipment
according to the embodiment 2.
[0074] As illustrated in FIG. 2, electronic equipment 50 according
to the embodiment 2 includes two fans 3a, 3b and heating elements
52a and 52b such as processors installed in an air passage 51
formed in the electronic equipment 50.
[0075] The fans 3a and 3b are axial fans of the same shape and
characteristic. The fans 3a and 3b are disposed in series relative
to the air passage 51 and generate air currents flowing from the
fan 3a toward the fan 3b to forcibly air-cool the heating elements
52a and 52b disposed downstream of the air currents. In the
following, of the fans 3a and 3b, the fan 3a for sucking air from
the outside of the electronic equipment 50 will be referred to as a
front-stage fan and the fan 3b for distributing the air which has
been sucked using the front-stage fan 3a into the electronic
equipment 50 will be referred to as a rear-stage fan.
[0076] The electronic equipment 50 also includes a fan control
device 1 and a fan power source section 2 installed outside of the
air passage 51. The fan power source section 2 is a power source
for supplying power to motors not shown which are built in the fans
3a and 3b. That is, when the power is supplied from the fan power
source section 2, the motors of the fans 3a and 3b rotate and
blades attached to the motors rotate in cooperation with the
rotation of the motors, and hence the fans 3a and 3b generate air
currents flowing toward the heating elements 52a and 52b.
[0077] The fan control device 1 detects the temperatures of the
heating elements 52a and 52b and the temperature (the environmental
temperature) outside of the electronic equipment 50 using
temperature sensors 11a to 11c. The fan control device 1 then
controls the revolution numbers of the fans 3a and 3b so as to
obtain an air flow rate needed for cooling the heating elements 52a
and 52b in a state in which the difference in revolution number
between the fans 3a and 3b is maintained in the predetermined
tolerance on the basis of the temperatures detected using the
temperature sensors 11a to 11c. Next, a specific configuration of
the fan control device 1 described above will be illustrated. FIG.
3 is a block diagram illustrating a configuration of the fan
control device according to the embodiment 2.
[0078] As illustrated in FIG. 3, the fan control device 1 includes
the temperature sensors 11a to 11c, temperature check sections 12a
and 12b, revolution number detecting sections 13a and 13b, a
revolution number error check section 14 and pulse generators 15a
and 15b. The fan control device 1 also includes a RAM 16, a ROM 17
and a processor 18.
[0079] The temperature sensors 11a and 11b are attached to the
heating elements 52a and 52b and detect the temperatures of the
heating elements 52a and 52b. The temperature sensor 11C is
disposed outside of the electronic equipment 50 and detects the
environmental temperature around the front-stage fan 3a. The
temperature sensors 12a and 12b check to see to which extent the
temperatures of the heating elements 52a and 52b detected using the
temperature sensors 11a and 11b are varied from a target
temperature and notify the processor 18 of results of check in the
form of predetermined variables.
[0080] The revolution number detecting sections 13a and 13b are,
for example, pulse counters and respectively detect the revolution
numbers of the fans 3a and 3b. The revolution number error check
section 14 checks to see whether the fans 3a and 3b normally rotate
on the basis of the revolution numbers of the fans 3a and 3b
detected using the revolution number detecting sections 13a and 13b
and notifies the processor 18 of a result of check.
[0081] The pulse generators 15a and 15b input pulses used to
control the revolution numbers of the fans 3a and 3b in pulse
widths (PWM values) as instructed from the processor 18 into the
fans 3a and 3b. Specifically, the pulse generator 15a inputs a
pulse of a PWM value as instructed from the processor 18 into the
front-stage fan 3a. The pulse generator 15b inputs a pulse of a PWM
value as instructed from the processor 18 into the rear-stage fan
3b. As a result, the fans 3a and 3b rotate with the revolution
numbers conforming to the pulse widths of the pulses input from the
pulse generators 15a and 15b.
[0082] The ROM 17 stores therein various pieces of data needed for
processing executed using the processor 18. The processor 18
determines PWM values of pulses to be input into the front-stage
fan 3a and the rear-stage fan 3b on the basis of the temperatures
detected using the temperature sensors 11a to 11c. Next, specific
configurations of the processor 18 and the ROM 17 according to the
embodiment 2 will be described. FIG. 4 is a block diagram
illustrating the specific configurations of the processor 18 and
the ROM 17 according to the embodiment 2.
[0083] As illustrated in FIG. 4, the ROM 17 includes an equipment
state storage section 171 and a control data storage section 172.
The equipment state storage section 171 stores an equipment state
management table. The equipment state management table is a table
used to specify the system impedance (the pipeline resistance)
corresponding to the current configuration of the electronic
equipment 50. FIG. 5 illustrates an example of the equipment state
management table 61.
[0084] As illustrated in FIG. 5, in equipment state management
table 61, system impedances and one equipment state specification
flag are stored such that the flag corresponds to one of the
impedances. In the example illustrated in the drawing, the
impedance is a pressure loss determined from a density rate at
which the respective components of the electronic equipment 50 are
packaged and the shape of an air passage in the equipment. In the
equipment state management table 61 according to the embodiment 2,
a plurality of impedances measured by changing the configuration of
the electronic equipment 50 are stored and the equipment state
specification flag is set for a system impedance corresponding to
the current configuration of the electronic equipment 50.
[0085] For example, in the equipment state management table 61
illustrated in FIG. 5, system impedances A to C respectively
measured by changing the configuration of the electronic equipment
50 are stored and the electronic state specification flag is set
for the system impedance A. That is, the equipment state management
table 61 illustrated in FIG. 5 indicates that the system impedance
corresponding to the current configuration of the electronic
equipment 50 is "A". In the case that the configuration of the
electronic equipment has been changed, the equipment state
management table 61 is manually updated by a user of the electronic
equipment 50. Owing to the above mentioned operation, even when the
configuration of the electronic equipment 50 has been changed, the
system impedance corresponding to a fresh configuration of the
electronic equipment 50 may be specified.
[0086] The control data storage section 172 stores a
heating-element-temperature-based PWM value determination table and
an environmental-temperature-based PWM value determination table.
The heating-element-temperature-based PWM value determination table
is a table used to specify PWM values of pulses to be input into
the fans 3a and 3b on the basis of the temperatures of the heating
elements 52a and 52b. The environmental-temperature-based PWM value
determination table is a table used to specify PWM values of pulses
to be input into the fans 3a and 3b on the basis of the
environmental temperature. Next, these pieces of information stored
in the control data storage section 172 will be specifically
described. FIG. 6 is a diagram for explaining information stored in
the control data storage section 172 according to the embodiment
2.
[0087] As illustrated in FIG. 6, the control data storage section
172 stores heating-element-temperature-based PWM value
determination tables 71a to 71c and environmental-temperature-based
PWM value determination tables 72a to 72c in one-to-one
correspondence with the plurality of system impedances A to C.
Specifically, the control data storage section 172 stores the
heating-element-temperature-based PWM value determination table 71a
and the environmental-temperature-based PWM value determination
table 72a corresponding to the system impedance A. The control data
storage section 172 also stores the
heating-element-temperature-based PWM value determination table 71b
and the environmental-temperature-based PWM value determination
table 72b corresponding to the system impedance B. The control data
storage section 172 further stores the
heating-element-temperature-based PWM value determination table 71c
and the environmental-temperature-based PWM value determination
table 72c corresponding to the system impedance C.
[0088] FIG. 7A illustrates an example of the
heating-element-temperature-based PWM value determination table
71a. As illustrated in FIG. 7A, in the
heating-element-temperature-based PWM value determination table
71a, heating element temperatures, common revolution numbers,
front-stage PWM values and rear-stage PWM values are stored in
one-to-one correspondence. For example, as illustrated in FIG. 7A,
in the heating-element-temperature-based PWM value determination
table 71a, the common revolution number "aaa", the front-stage PWM
value "Nfa" and the rear-stage PWM value "Nra" are stored
corresponding to the heating element temperature "A". The heating
element temperatures are stored in the form of predetermined
variables output from the temperature check sections 12a and 12b in
accordance with the temperatures of the heating elements 52a and
52b.
[0089] The common revolution number (min.sup.-1) is a revolution
number commonly set for the fans 3a and 3b in the case that an air
flow rate needed for cooling the heating elements 52a and 52b is
obtained in a state in which a difference in revolution number
between the fans 3a and 3b is maintained in a predetermined
tolerance. In the example illustrated in FIG. 7A, the needed air
flow rate stored in the heating-element-temperature-based PWM value
determination tables 71a to 71c is an air flow rate determined in
accordance with temperatures of the heating elements 52a and 52b, a
system impedance in the electronic equipment 50 and a total PQ
characteristic (a static pressure-air flow rate characteristic) of
the fans 3a and 3b obtained in a state in which the difference in
revolution number between the fans 3a and 3b is maintained in the
predetermined tolerance. Incidentally, the system impedance, the PQ
characteristic and the common revolution number are obtained from
thermal hydraulic simulation and measurement performed on the basis
of measurement of temperatures of the heating elements 52a and 52b.
Details thereof will be described later.
[0090] In this embodiment, the "predetermined tolerance" is a range
in which the difference in revolution number between the
front-stage fan 3a and the rear-stage fan 3b is less than 10%. That
is, ideally, the noise generated from these fans 3a and 3b may be
minimized by controlling the revolution number of the front-stage
fan 3a to coincide with that of the rear-stage fan 3b. However,
even in the case that the revolution number of the front-stage fan
3a is slightly different from that of the rear-stage fan 3b, any
problem will not cause as long as an error in noise caused by the
slight difference of the revolution number of the front-stage fan
from that of the rear-stag fan is so small that it is not
recognized with human's ears. In the case that the difference in
revolution number between the front-stage fan 3a and the rear-stage
fan 3b is 10%, the noise generated from these fans 3a and 3b is
larger than the noise generated when the revolution numbers of the
front-stage blower 3a and the rear-stage blower 3b are controlled
to coincide with each other by about 3 dB. Basically, it is said
that the error of 3 dB is not recognized with human's ears.
Therefore, in this embodiment, the "predetermined tolerance" is
defined as a range in which the difference in revolution number
between the front-stage fan 3a and the rear-stage fan 3b is less
than 10%.
[0091] However, some persons may recognize the error of 3 dB with
their ears, so that, more preferably, the difference in revolution
number between the front-stage blower 3a and the rear-stage blower
3b is set to be less than 5%. With the difference in revolution
number between the front-stage fan 3a and the rear-stage fan 3b of
less than 5%, the noise generated from the front-stage fan 3a and
the rear-stage fan 3b becomes larger than the noise generated when
the revolution numbers of the front-stage fan 3a and the rear-stage
fan 3b are controlled to coincide with each other by about 1 dB. As
described above, a noise reduction effect which is equivalent to
that attained when the revolution numbers of the front-stage fan 3a
and the rear-stage fan 3b are controlled to coincide with each
other may be more obtained by setting the "predetermined tolerance"
to a range in which the difference in revolution number between the
front-stage fan 3a and the rear-stage fan 3b is less than 5%.
[0092] The front-stage PWM value (s) is a PWM value of a pulse to
be input into the front-stage fan 3a in order to rotate the
front-stage fan 3a with a common revolution number. The rear-stage
PWM value (s) is a PWM value of a pulse to be input into the
rear-stage fan 3b in order to rotate the rear-stage fan 3b with the
common revolution number. That is, for example, when the heating
element temperature is "A", the pulse of the front-stage PWM value
"Nfa" is input into the front-stage fan 3a and the pulse of the
rear-stage PWM value "Nra" corresponding to the front-stage PWM
value "Nfa" is input into the rear-stage fan 3b, thereby rotating
the fans 3a and 3b with the common revolution number "aaa". These
front-stage and rear-stage PWM values may be obtained from
measurement performed in advance.
[0093] FIG. 7B illustrates an example of the
environmental-temperature-based PWM value determination table 72a.
As illustrated in FIG. 7B, environmental temperatures, common
revolution numbers, front-stage PWM values and rear-stage PWM
values are stored in the environmental-temperature-based PWM value
determination table 72a in one-to-one correspondence. For example,
as illustrated in FIG. 7B, the common revolution number "fff", the
front-stage PWM value "Nff" and the rear-stage PWM value "Nrf" are
stored in the environmental-temperature-based PWM value
determination table 72a corresponding to the heating element
temperature "F". In the example illustrated in the drawing, the
environmental temperature is a temperature detected using the
temperature sensor 11c.
[0094] The common revolution number is a revolution number which is
commonly set for the fans 3a and 3b in order to obtain an air flow
rate needed to cool the heating elements 52a and 52b in a state in
which the difference in revolution number between the fans 3a and
3b is maintained in the predetermined tolerance as in the case in
the heating-element-temperature-based PWM value determination
tables 71a to 71c. In the example illustrated in the drawing, the
needed air flow rate stored in the environmental-temperature-based
PWM value determination tables 72a to 72c is an air flow rate which
is obtained in accordance with an environmental temperature, a
system impedance in the electronic equipment 50 and a total PQ
characteristic of the fans 3a and 3b obtained when a difference in
revolution number between the fans 3a and 3b is in the
predetermined tolerance.
[0095] The front-stage PWM value and the rear-stage PWM value are
PWM values of pulses to be input into the front-stage fan 3a and
the rear-stage fan 3b in order to rotate the front-stage fan 3a and
the rear-stage fan 3b with a common revolution number as in the
case in the heating-element-based PWM value determination tables
71a to 71c. That is, for example, with the heating element
temperature "G", the pulse of the front-stage PWM value "Nfg" is
input into the front-stage fan 3a and the pulse of the rear-stage
PWM value "Nrg" corresponding to the front-stage PWM value "Nfg" is
input into the rear-stage fan 3b to rotate the fans 3a and 3b with
the common revolution number "ggg".
[0096] As described above, the control data storage section 172
corresponds to control data storage means and stores input values
of pulses to be input into the fans 3a and 3b per temperature in
order to obtain the air flow rate needed to cool the heating
elements in a state in which the difference in revolution number
between the fans 3a and 3b is maintained in the predetermined
tolerance. In addition, the control data storage section 172
corresponds to control data storage means and stores input values
of pulses to be input into the front-stage fan 3a and the
rear-stage fan 3b per system impedance.
[0097] As illustrated in FIG. 4, the processor 18 includes an error
processing section 181, a temperature information acquiring section
182, an input value determining section 183 and database preparing
section 184.
[0098] The error processing section 181 executes an error notifying
process on the basis of information acquired from the revolution
number error check section 14. The error processing section 181
acquires a result of check indicating that the front-stage fan 3a
or the rear-stage fan 3b is now in a stopped state from the
revolution number error check section 14. The error processing
section 181 then sends an error notification that the fan 3a or 3b
is in the stopped state to the electronic equipment 50 on the basis
of the result of check acquired. As a result, an error message that
the fan 3a or 3b is now in the stopped state is displayed on a
display not illustrated of the electronic equipment 50.
[0099] The temperature information acquiring section 182 acquires
predetermined variables corresponding to temperatures of the
heating elements 52a and 52b from the temperature check sections
12a and 12b as data indicative of the heating element temperatures.
The temperature information acquiring section 182 also acquires the
environmental temperature from the temperature sensor 12c. As
described above, the temperature sensors 11a and 11b, the
temperature check sections 12a and 12b and the temperature
information acquiring section 182 functions as an example of
temperature detecting means for detecting the temperatures of the
heating elements 52a and 52b installed in the electronic equipment
50. The temperature sensor 11c and the temperature information
acquiring section 182 also function as an example of temperature
detecting means for detecting the temperature outside of the
electronic equipment 50.
[0100] The input value determining section 183 specifies a system
impedance corresponding to the current configuration of the
electronic equipment 50 with reference to data stored in the
equipment state storage section 171. In addition, the input value
determining section 183 acquires the respective PWM values of
pulses to be input into the fans 3a and 3b from the control data
storage section 172 on the basis of the specified system impedance
and the heating element temperatures or the environmental
temperature acquired from the temperature information acquiring
section 182.
[0101] Specifically, the input value determining section 183
acquires a front-stage PWM value and a rear-stage PWM value
corresponding to a combination of the specified system impedance
with temperature information of the heating elements 52a and 52b
acquired from the temperature information acquiring section 182
from the heating-element-temperature-based PWM value determination
tables 71a to 71c. In addition, the input value determining section
183 acquires a front-stage PWM value and a rear-stage PWM value
corresponding to a combination of the specified system impedance
with environmental temperature information acquired from the
temperature information acquiring section 182 from the
environmental-temperature-based PWM value determination tables 72a
to 72c.
[0102] For example, in the case that the specified system impedance
is "A" and the heating element temperature acquired from the
temperature information acquiring section 182 is "C", the input
value determining section 183 acquires the front-stage PWM value
"Nfc" and the rear-stage PWM value "Nrc" from the
heating-element-temperature-based PWM value determination table 71a
as illustrated in FIG. 7A.
[0103] The input value determining section 183 then instructs the
pulse generator 15a to input the pulse of the acquired front-stage
PWM value into the front-stage blower 3a and instructs the pulse
generator 15b to input the pulse of the acquired rear-stage PWM
value into the rear-stage blower 3b. In response to the
instructions, the pulse generators 15a and 15b respectively input
the pulses of the front-stage PWM value and rear-stage PWM value as
instructed from the input value determining section 183 into the
front-stage fan 3a and the rear-stage fan 3b. As a result, the
front-stage fan 3a rotates with the revolution number conforming to
the front-stage PWM value of the pulse input from the pulse
generator 15a and the rear-stage fan 3b rotates with the revolution
number conforming to the rear-stage PWM value of the pulse input
from the pulse generator 15b.
[0104] Incidentally, as described above, the front-stage PWM value
and the rear-stage PWM value are PWM values of pulses to be input
into the fans 3a and 3b in order to obtain the needed air flow rate
in a state in which the difference in revolution number between the
fans 3a and 3b is maintained in the predetermined tolerance.
Therefore, the difference in revolution number between the fans 3a
and 3b is set in the predetermined tolerance by inputting pulses of
the above mentioned front-stage and rear-stage PWM values into the
respective fans 3a and 3b and air is fed into the equipment at the
needed air flow rate conforming to the temperatures of the heating
elements 52a and 52b.
[0105] As described above, in the fan control device 1 according to
this embodiment, since the difference in revolution number between
the fans 3a and 3b is maintained in the predetermined tolerance,
that is, the revolution numbers of the fans 3a and 3b are
controlled to coincide with each other in the predetermined
tolerance, such a situation may be avoided that surplus noise is
generated from a fan of the largest revolution number to increase
the total noise from the fans 3a and 3b.
[0106] In addition, the needed air flow rate according to this
embodiment is determined by taking the temperatures of the heating
elements 52a and 52b, the system impedance within the electronic
equipment 50 and the total PQ characteristic of the fans 3a and 3b
obtained when the difference in revolution number between the fans
3a and 3b is maintained in the predetermined tolerance into
consideration. Therefore, according to this embodiment, the air
flow rate suitable for cooling the heating elements 52a and 52b may
be obtained in a state in which the revolution numbers of the fans
3a and 3b are controlled to coincide with each other in the
predetermined tolerance regardless of the configuration of the
electronic equipment 50 concerned and the locations of the fans 3a
and 3b in the electronic equipment 50.
[0107] Incidentally, the input value determining section 183
determines different PWM values for the front-stage fan 3a and the
rear-stage fan 3b and inputs pulses of the determined PWM values
into the fans 3a and 3b via the pulse generators 15a and 15b. That
is, as illustrated the graph 1001 in FIG. 8, different amounts of
energy 1010 are supplied to the front-stage fan 3a and the
rear-stage fan 3b. Specifically, the work amount of the rear-stage
fan 3b is reduced influenced by the air currents generated from the
front-stage fan 3a, so that the amount of energy supplied to the
rear-stage fan 3b becomes smaller than that supplied to the
front-stage fan 3a in the case that the revolution numbers of the
fans 3a and 3b are controlled to coincide with each other.
[0108] In addition, in the case that the common revolution number
obtained on the basis of the environmental temperature is larger
than the common revolution number obtained on the basis of the
heating element temperatures, the input value determining section
183 controls the revolutions numbers of the fans 3a and 3b by using
the environmental-temperature-based PWM values. Specifically, the
input value determining section 183 acquires common revolution
numbers corresponding to the environmental temperature and the
heating element temperatures acquired from the temperature
information acquiring section respectively from the
environmental-temperature-based PWM determination tables 72a to 72c
and the heating-element-temperature-based PWM value determination
tables 71a to 71c. The input value determining section 183 then
compares a common revolution number obtained from the environmental
temperature with a common revolution number obtained from the
heating element temperatures, and in the case that the common
revolution number obtained from the environmental temperature is
larger than that obtained from the heating element temperatures,
acquires the front-stage PWM value and the rear-stage PWM value
corresponding to the environmental temperature concerned from the
environmental-temperature-based PWM value determination tables 72a
to 72c. As described above, the revolution numbers of the fans 3a
and 3b are controlled on the basis of one of the environmental
temperature and the heating element temperatures which will
influence the heating elements 52a and 52b more greatly than
another, so that the heating elements 52a and 52b may be maintained
at more appropriate temperatures.
[0109] As described above, the input value determining section 183
and the equipment state storage section 171 function as an example
of equipment state acquiring means for acquiring information on the
system impedance within the electronic equipment 50. In addition,
the input value determining section 183 and the pulse generators
15a and 15b function as an example of control means for controlling
the revolution number of each fan on the basis of the temperature
information acquired using the temperature information acquiring
section 182 such that the air flow rate of air for cooling the
heating elements 52a and 52b which is determined in accordance with
the temperatures of the heating elements 52a and 52b, the system
impedance within the electronic equipment 50 and the total static
pressure-air flow rate characteristic of the fans 3a and 3b
attained when the difference in revolution number between the fans
3a and 3b is maintained in the predetermined tolerance may be
obtained and the difference in revolution number between the fans
3a and 3b may be set in the predetermined tolerance.
[0110] The database preparing section 184 executes various
calculating processes in order to prepare the
heating-element-temperature-based PWM value determination tables
71a to 781c and the environmental-temperature-based PWM value
determination tables 72a to 72c before the fan control device is
incorporated into the electronic equipment 50. Next, a specific
configuration of the database preparing section 184 will be
described. FIG. 9 is a block diagram illustrating a specific
configuration of the database preparing section according to the
embodiment 2.
[0111] As illustrated in FIG. 9, the database preparing section 184
includes a measured (already measured) system impedance information
storage section 81, an equipment configuration information storage
section 82, a system impedance information storage section 83, a
temperature information storage section 84 and a temperature
standard value information storage section 85. The database
preparing section 184 also includes a needed air flow rate
information storage section 86, a measured (already measured) PQ
characteristic information storage section 87, a PQ characteristic
information and revolution number information storage section 88
and a PWM value information storage section 89. The database
preparing section 184 further includes a system impedance
calculating section 91, a needed air flow rate calculating section
92, a fan PQ performance calculating section 93 and a fan PWM value
calculating section 94.
[0112] The measured system impedance information storage section 81
stores measured system impedances of the electronic equipment 50.
For example, the measured system impedance information storage
section 81 stores system impedances corresponding to full
configurations and popular configurations of the electronic
equipment 50. The equipment configuration information storage
section 82 stores a plurality of patterns of configurations of the
electronic equipment 50. For example, the equipment configuration
information storage section 82 stores information on the number of
CPUs and the number of power sources which are built into the
electronic equipment 50 per configuration of the electronic
equipment 50. The system impedance information storage section 83
stores system impedances which are calculated per configuration of
the electronic equipment 50 using the system impedance calculating
section 91.
[0113] The temperature information storage section 84 stores the
environmental temperature and the temperatures of the heating
elements 5a and 52b. For example, the temperature information
storage section 84 stores the temperatures of the CPUs and memories
built into the electronic equipment as the temperatures of the
heating element 52a and 52b. The temperature standard value
information storage section 85 stores standard values of
temperatures of the heating elements 52a and 52b. The needed air
flow rate information storage section 86 stores the needed air flow
rates calculated using the needed air flow rate calculating section
92.
[0114] The measured PQ characteristic information storage section
87 stores the information on the maximum and minimum revolution
numbers of the fans 3a and 3b. The PQ characteristic information
and revolution number information storage section 88 stores the
total PQ characteristic of the fans 3a and 3b and the common
revolution numbers of the fans 3a and 3b calculated using the fan
PQ performance calculating section 93. The PWM value information
storage section 89 stores the front-stage PWM values and rear-stage
PWM values calculated using the fan PWM value calculating section
94.
[0115] The system impedance calculating section 91 calculates each
system impedance of each configuration of the electronic equipment
50 on the basis of the information on the measured system
impedances stored in the measured system impedance information
storage section 81 and the information on the configurations of the
electronic equipment 50 stored in the equipment configuration
information storage section 82. The needed air flow rate
calculating section 92 calculates the needed air flow rates on the
basis of the temperatures stored in the temperature information
storage section 84 and the temperature standard values stored in
the temperature standard value information storage section 85.
[0116] The fan PQ performance calculating section 93 calculates the
total PQ characteristic of the fans 3a and 3b and the common
revolution numbers of the fans 3a and 3b. The calculation is
performed on the basis of information on the system impedances
stored in the system impedance information storage section 83, the
needed air flow rates stored in the needed air flow rate
information storage section 86 and the maximum and minimum
revolution numbers of the fans 3a and 3b stored in the measured PQ
characteristic information storage section 87. The fan PWM value
calculating section 94 calculates the front-stage PWM values and
rear-stage PWM values. The calculation is performed on the basis of
information on the maximum and minimum revolution numbers of the
fans 3a and 3b stored in the measured PQ characteristic information
storage section 87 and the total PQ characteristic of the fans 3a
and 3b and the common revolution numbers of the fans 3a and 3b
stored in the PQ characteristic information and revolution number
information storage section 88.
[0117] Next, procedures of preparing the
heating-element-temperature-based PWM value determination tables
71a to 71c and the environmental-temperature-based PWM value
determination tables 72a to 72c will be described. FIG. 10 is a
flowchart illustrating an example of procedures of preparing the
heating-element-temperature-based PWM value determination tables
71a to 71c and the environmental-temperature-based PWM value
determination tables 72a to 72c.
[0118] As illustrated in FIG. 10, as work to be previously
performed in preparation of the heating-element-temperature-based
PWM value determination tables 71a to 71c and the
environmental-temperature-based PWM value determination tables 72a
to 72c, first, measurement and simulation are performed (step
S101). Specifically, system impedances corresponding to the full
and popular configurations of the electronic equipment, and maximum
and minimum revolution numbers, air flow rates, static pressures
and noise levels of the fans 3a and 3b are obtained by the
measurement and simulation.
[0119] Next, various calculations are performed on the basis of the
information obtained at step S101 using the database preparing
section 184 (step S102). Specifically, each system impedance of
each equipment configuration and each needed air flow rate, each
common revolution number, each front-stage PWM value and each
rear-stage PWM value at each temperature are calculated (step
102).
[0120] Then, each system impedance calculated for each equipment
configuration and each needed air flow rate, each common revolution
number, each front-stage PWM value and each rear-stage PWM value
which are calculated at each of the environmental temperature and
the heating element temperatures are arranged in the form of
databases and stored in the ROM 17 (step S103). Owing to the above
mentioned operations, the heating-element-temperature-based PWM
value determination tables 71a to 71c and the
environmental-temperature-based PWM value determination tables 72a
to 72c are stored in the ROM 17. The fan control device 1 is then
incorporated into the electronic equipment 50 in a state in which
the heating-element-temperature-based PWM value determination
tables 71a to 71c and the environmental-temperature-based PWM value
determination tables 72a to 72c are stored in the ROM 17.
[0121] Next, specific operations of the processor 18 according to
this embodiment will be described. FIG. 11 is a flowchart
illustrating an example of procedures of processing executed using
the processor according to the embodiment 2. Incidentally, only a
procedure involving revolution number control of the front-stage
fan 3a and the rear-stage fan 3b of the procedures of processing
executed using the processor 18 is illustrated in FIG. 11.
[0122] As illustrated in FIG. 11, first, the input value
determining section 183 acquires an equipment state (step S201).
Specifically, the input value determining section 183 specifies a
system impedance to which an equipment state specification flag is
set as the system impedance corresponding to the current
configuration of the electronic equipment 50 with reference to data
stored in the equipment state storage section 171.
[0123] Next, the input value determining section 183 selects a
database corresponding to the specified system impedance (step
S202). Specifically, the input value determining section 183
selects one heating-element-temperature-based PWM value
determination table from within the
heating-element-temperature-based PWM value determination tables
71a to 71c and one environmental-temperature-based PWM value
determination table from within the environmental-temperature-based
PWM value determination tables 72a to 72c.
[0124] Next, the processor 18 executes temperature measurement
(step S203). Specifically, the temperature information acquiring
section 182 acquires predetermined variables corresponding to
temperatures of the heating elements 52a and 52b from the
temperature check sections 12a and 12b as heating element
temperatures and acquires an environmental temperature from the
temperature sensor 12c. The temperature information acquiring
section 182 then notifies the input value determining section 183
of the acquired heating element and environmental temperatures.
[0125] Next, the input value determining section 183 selects a
common revolution number corresponding to the heating element
temperatures acquired at step S203 with reference to the
heating-element-temperature-based PWM determination table (step
S204). The input value determining section 183 also selects a
common revolution number corresponding to the environmental
temperature acquired at step S203 with reference to the
environmental-temperature-based PWM value determination table (step
S205).
[0126] Next, the input value determining section 183 judges whether
the heating-element-temperature-based common revolution number is
larger than the environmental-temperature-based common revolution
number (step S206). In the above mentioned process, in the case
that it has been judged that the common revolution number obtained
from the heating element temperature is larger than the common
revolution number obtained from the environmental temperature (Yes
at step S206), the input value determining section 183 determines
the PWM values of pulses to be input into the fans 3a and 3b using
the heating-element-temperature-based PWM value determination table
71.
[0127] Specifically, the input value determining section 183
determines the front-stage PWM value corresponding to the common
revolution number selected at step S204 with reference to the
heating-element-temperature-based PWM value determination table 71
(step S207). The input value determining section 183 then
determines the rear-stage PWM value corresponding to the
front-stage PWM value with reference to the
heating-element-temperature-based PWM value determination table 71
(step S208). For example, in the case that the current system
impedance of the electronic equipment 50 is "A" and the heating
element temperature acquired using the temperature information
acquiring section 182 is "C", the input value determining section
183 selects the common revolution number "ccc" with reference to
the heating-element-temperature-based PWM value determination table
71a illustrated in FIG. 7A. Then, the input value determining
section 183 determines the front-stage PWM value "Nfc" and the
rear-stage PWM value "Nrc" corresponding to the common revolution
number "ccc" as the PWM values of the pulses to be input into the
fans 3a and 3b.
[0128] On the other hand, at step S204, it has been judged that the
heating-element-temperature-based common revolution number is not
larger than the environmental-temperature-based common revolution
number (No at step S206); the input value determining section 183
determines the PWM values of pulses to be input into the fans 3a
and 3b by using the heating-element-temperature-based PWM value
determination table 71.
[0129] Specifically, the input value determining section 183
determines a front-stage PWM value corresponding to the common
revolution number selected at step S205 with reference to the
environmental-temperature-based PWM value determination table 72
(step S209). The input value determining section 183 determines a
rear-stage PWM value corresponding to the front-stage PWM value
with reference to the heating-element-temperature-based PWM value
determination table 71 (step S210). For example, in the case that
the current system impedance of the electronic equipment 50 is "A"
and the environmental temperature acquired using the temperature
information acquiring section 182 is "G", the input value
determining section 183 selects the common revolution number "ggg"
with reference to the environmental-temperature-based PWM value
determination table 72a as illustrated in FIG. 7B. The input value
determining section 183 then determines the front-stage PWM value
"Nfg" and the rear-stage PWM value "Nrg" corresponding to the
common revolution number "ggg" as the PWM values of pulses to be
input into the fans 3a and 3b.
[0130] At the completion of execution of the process at step S208
or step S210, the input value determining section 183 instructs to
rotate the fans (step S211). That is, the input value determining
section 183 instructs the pulse generators 15a and 15b to input
pulses of the front-stage and rear-stage PWM values determined at
steps S207 and S208 or at steps S209 and S210 respectively into the
front-stage fan 3a and the rear-stage fan 3b. In response to the
instruction, the pulse generator 15a inputs the pulse of the above
front-stage PWM value into the front-stage fan 3a as instructed
from the input value determining section 183. Likewise, the pulse
generator 15b inputs the pulse of the above rear-stage PWM value
into the rear-stage fan 3b as instructed from the input value
determining section 183. As a result, the front-stage fan 3a and
the rear-stage fan 3b rotate with the revolution numbers
corresponding to the front-stage PWM value and the rear-state PWM
value which have been input from the pulse generators 15a and
15b.
[0131] Incidentally, as described above, the front-stage PWM value
and the rear-stage PWM value are PWM values of pulses to be input
into the fans 3a and 3b in order to obtain the needed air flow rate
in a state in which the difference in revolution number between the
fans 3a and 3b is maintained in the predetermined tolerance.
Therefore, the fans 3a and 3b rotate in a state in which the
revolution numbers of the fans coincide with each other in the
predetermined tolerance by inputting the pulses of the above
front-stage and rear-stage PWM values respectively into the fans 3a
and 3b and air is fed into the heating elements 52a and 52b at the
needed air flow rates conforming to the temperatures of the heating
elements 52a and 52b.
[0132] FIG. 12 is a diagram illustrating an effect of the
embodiment. In FIG. 12, a left part is a graph indicative of
changes in static pressure, revolution number and noise relative to
a change in air flow rate obtained when the PWM values of the
pulses applied to the front-stage fan 3a and the rear-stage fan 3b
are made the same as each other at a predetermined temperature.
[0133] As illustrated in the graph, in the case that pulses of the
same PWM value have been applied to the fans 3a and 3b, if it is
intended to obtain a needed air flow rate 3003 at which the total
aerodynamic performance 3001 of the fans 3a and 3b intersects the
system impedance 3002, the revolution number of the rear-stage fan
3b (the rear-stage revolution number 3004B) will become larger than
the revolution number of the front-stage fan 3a (the front-stage
revolution number 3004A). The reason therefore lies in the fact
that the work amount with which the rear-stage fan 3b blows off air
is reduced under the influence of the air currents generated from
the front-stage fan 3a to increase the revolution number of the
rear-stage fan 3b. The noise 3005 is also increased with increasing
the revolution number of the rear-stage fan 3b.
[0134] On the other hand, in FIG. 12, a right part is a graph
indicative of changes in static pressure, revolution number and
noise relative to a change in air flow rate obtained in the case
that the fan control device 1 according to this embodiment has
controlled such that the difference in revolution number (4004A,
4004B) between the front-stage fan 3a and the rear-stage fan 3b is
maintained in the predetermined tolerance at a predetermined
temperature. As illustrated in this graph, according to this
embodiment, it may become possible to obtain the needed air flow
rate 4003 at which the system impedance 4002 within the electronic
equipment 50 intersects the total aerodynamic characteristic 4001
(the PQ characteristic) of the fans 3a and 3b when the difference
in revolution number between the fans 3a and 3b is maintained in
the predetermined tolerance in a state in which the difference in
revolution number between the fans is set in the predetermined
tolerance at the predetermined temperature.
[0135] Therefore, according to this embodiment, such a situation
may be avoided that the revolution number of any one of the fans
becomes larger than that of another fan to generate surplus noise.
In addition, according to this embodiment, the air flow rate suited
to cool the heating elements 52a and 52b may be obtained in a state
in which the difference in revolution number between the fans 3a
and 3b is maintained in the predetermined tolerance regardless of
the configuration of the electronic equipment 50 and the locations
of the fans 3a and 3b within the electronic equipment 3a and
3b.
[0136] Next, results of experiments performed to validate that the
noise generated from the plurality of fans 3a and 3b is reduced by
using the fan control device 1 according to this embodiment will be
described. Respective measurement conditions 3010 are illustrated
in FIG. 13. FIG. 13 illustrates measurement conditions of the
experiments for validation. As illustrated in FIG. 13, a case in
which two fans of the same type are disposed in series is assumed
to be a measurement condition A and a case in which two fans of the
same type are disposed in series and four fans of the same type are
disposed in parallel is assumed to be a measurement condition
B.
[0137] Under the measurement condition A, experiments were
performed under three conditions of conditions A-1 to A-3.
Specifically, under the condition A-1, voltages of the same amount
were supplied to the front-stage and rear-stage fans. Under the
condition A-2, the same air flow rate as that under the condition
A-1 was set and voltages were controlled such that the ratio of the
front-stage fan revolution number to the rear-stage fan revolution
number is 1:1. The condition A-2 corresponds to a condition under
which the same control as that performed using the fan control
device 1 according to this embodiment is performed. Under the
condition A-3, the same air flow rate at that under the condition
A-1 was set and voltages were controlled such that the ratio of the
front-stage fan revolution number to the rear-stage fan revolution
number is 1:0.9.
[0138] In addition, as illustrated in FIG. 13, under the
measurement condition B, experiments were performed under four
conditions of conditions B-1, B-2, B-3 and B-4. Specifically, under
the condition B-1, voltages of the same amount were supplied to the
front-stage and rear-stage fans. Under the condition B-2, the same
air flow rate as that under the condition B-1 was set and voltages
were controlled such that the ratio of the front-stage fan
evolution number to the rear-stage fan revolution number is 1:1.
The condition B-2 corresponds to a condition under which the same
control as that performed using the fan control device 1 according
to this embodiment is performed.
[0139] Under the condition B-3, voltages of the same amount which
is different from that of the voltages supplied under the condition
B-1 were supplied to the front-stage and rear-stage fans. Under the
condition B-4, the same air flow rate as that under the condition
B-3 was set and voltages were controlled such that the ratio of the
front-stage fan revolution number to the rear-stage fan revolution
number is 1:1. The condition B-4 corresponds to a condition under
which the same control as that performed using the fan control
device 1 according to this embodiment is performed.
[0140] First, results of measurements performed under the
measurement condition A will be described. FIG. 14A illustrates
data indicative of the result of measurement of the front-stage fan
revolution number 5001A, the rear-stage fan revolution number 5001B
and the device noise 5002 performed under the measurement condition
A. FIG. 14B illustrates data indicative of the result of
measurement of the front-stage fan revolution number 6001A, the
rear-stage fan revolution number 6001B and the consumption power
6002 performed under the measurement condition A. FIG. 14C
illustrates data indicative of the result of frequency analysis of
the device noise performed under the measurement condition A. FIG.
15A is a diagram 3020A illustrating a result of measurement
performed under the condition A-1, FIG. 15B is a diagram 3020B
illustrating a result of measurement performed under the condition
A-2 and FIG. 15C is a diagram 3020C illustrating a result of
measurement performed under the condition A-3.
[0141] As illustrated in FIGS. 14A and 15A, under the condition
A-1, the front-stage revolution number 5001A was 12257 min.sup.-1
and the rear-stage revolution number 5001B was 13523 min.sup.-1,
indicating that in the case that voltages of the same amount have
been supplied to the front-stage and rear-stage fans, the
rear-stage fan revolution number 5001B is increased influenced by
air currents generated from the front-stage fan. As illustrated in
FIGS. 14A and 15C, under the condition A-3, the front-stage
revolution number was 13643 min.sup.-1 and the rear-stage
revolution number was 12277 min.sup.-1, indicating that the
front-stage fan revolution number measured under the condition A-3
is larger than the rear-stage fan revolution number measured under
the condition A-1. On the other hand, as illustrated in FIGS. 14B
and 15B, under the condition A-2, the front-stage revolution number
was 12615 min.sup.-1 and the rear-stage revolution number was 12555
min.sup.-1, indicating that these revolution numbers are smaller
than the rear-stage revolution number measured under the condition
A-1 and the front-stage revolution number measured under the
condition A-3.
[0142] In addition, as illustrated in FIG. 14A and FIGS. 15A to
15C, the device noise 5002 measured under the condition A-1 was
55.5 dB (A), the device noise 5002 measured under the condition A-2
was 53.4 dB(A) and the device noise 5002 measured under the
condition A-3 was 56 dB(A). That is, the device noise was the
lowest when measured under the condition A-2 corresponding to a
control system of the fan control device 1 according to this
embodiment and was reduced from the value measured under the
condition A-1 by about 2 dB(A). On the other hand, the highest
device noise 5002 was measured under the condition A-3. It is
thought that the reason therefore lies in the fact that the
front-stage revolution number 5001A measured under the condition
A-3 exhibited the highest value of the values measured under the
respective conditions A-1 to A-3.
[0143] As described above, the noise generated from each fan may be
reduced by controlling so as to attain a needed air flow rate in a
state in which the revolution numbers of the front-stage and
rear-stage fans (5001A, 5001B) are controlled to coincide with each
other in the predetermined tolerance as in the case with the fan
control device 1 according to this embodiment. Incidentally, the
device noise 5002 under each of the conditions A-1 to A-3 is of a
value calculated on the basis of the result of analysis of the
frequency of the device noise illustrated in FIG. 14C.
[0144] In addition, as illustrated in FIG. 14B and FIGS. 15A to
15C, the total consumption power 5003 of the front-stage and
rear-stage fans was 7.20 W under the condition A-1, was 6.78 W
under the condition A-2 and was 7.65 W under the condition A-3.
That is, as in the case of the device noise 5002 the total
consumption power 5003 was also the lowest when measured under the
condition A-2 corresponding to that of the control system of the
fan control device 1 according this embodiment and was reduced from
the value measured under the condition A-1 by about 6%. As
described above, the consumption power 5003 of each fan may be
reduced by controlling so as to attain the needed air flow rate in
a state in which the revolution numbers of the front-stage and
rear-stage fans (5001A, 5001B) are controlled to coincide with each
other in the predetermined tolerance as in the case with the fan
control device 1 according to this embodiment.
[0145] Next, results of measurements performed under the
measurement condition B will be described. First, the results of
measurements performed under the conditions B-1 and B-2 will be
described. FIG. 16A illustrates data indicative of the result of
measurement of the front-stage average revolution number 7001A, the
rear-stage average revolution number 7002A and the device noise
7003 performed under the conditions B-1 and B-2. FIG. 16B
illustrates data indicative of the result of measurement of the
front-stage average revolution number 7001A, the rear-stage average
revolution number 7001B and the consumption power 7003 performed
under the conditions B-1 and B-2. FIG. 16C illustrates data
indicative of the result of frequency analysis of the device noise
7002 performed under the conditions B-1 and B-2. FIG. 17A is a
diagram 3030 illustrating the result of measurement performed under
the condition B-1 and FIG. 17B is a diagram 3040 illustrating the
result of measurement performed under the condition B-2. In the
examples illustrated in the drawings, the front-stage average
revolution number 7001A is the average value of revolution numbers
of four front-stage fans and the rear-stage average revolution
number 7001B is the average value of revolution numbers of four
rear-stage fans.
[0146] As illustrated in FIGS. 16A and 17A, the front-stage average
revolution number 7001A was 14488 min.sup.-1 and the rear-stage
average revolution number 7001B was 15548 min.sup.-1 under the
condition B-1. These values indicate that in the case that the
voltages of the same amount have been supplied to the front-stage
fan and the rear-stage fan as in the case under the condition A-1,
the revolution number of the rear-stage fan 7001B is increased
influenced by the air currents generated from the front-stage fan.
On the other hand, as illustrated in FIGS. 16A and 17B, the
front-stage average revolution number 7001A was 14825 min.sup.-1
and the rear-stage average revolution number 7001B was 14859
min.sup.-1 under the condition B-2. These revolution numbers 7001A,
7001B are smaller than the rear-stage average revolution number
measured under the condition B-1.
[0147] As illustrated in FIG. 16A and FIGS. 17A and 17B, the device
noise 7002 under the condition B-1 was 62.6 dB(A) and the device
noise 7002 under the condition B-2 was 61.6 dB(A). That is, as in
the case under the measurement condition A, the device noise 7002
measured under the condition B-2 which is the same as that of the
fan control device 1 according to this embodiment was lower than
that measured under the condition B-1 and was reduced from the
value measured under the condition B-1 by about 1 db(A).
[0148] As described above, even when the front-stage fans and the
rear-stage fans are disposed in series and in parallel, an effect
equivalent to that attained when the front-stage fan and the
rear-stage fan are disposed only in series is obtained.
Incidentally, the values of the device noise illustrated in FIG.
16A were calculated on the basis of the result of analysis of the
frequency of the device noise 7002 illustrated in FIG. 16C.
[0149] In addition, as illustrated in FIG. 16B and FIGS. 17A and
17B, the total consumption power 7003 of the front-stage and
rear-stage fans was 43.08 W under the condition B-1 and was 41.83 W
under the condition B-2. That is, the total consumption power 7003
was the lowest when measured under the condition B-2 corresponding
to that of the fan control device 1 according to this embodiment
and was reduced from the value measured under the condition B-1 by
about 3%.
[0150] Next, results of measurements performed under the conditions
B-3 and B-4 will be described. FIG. 18A illustrates data indicative
of the result of measurement of the front-stage average revolution
number 8001A, the rear-stage average revolution number 8001B and
the device noise 8002 performed under the conditions B-3 and B-4,
FIG. 18B illustrates data indicative of the result of measurement
of the front-stage average revolution number 8001A, the rear-stage
average revolution number 8001B and the consumption power 8003
performed under the conditions 18-3 and 18-4 and FIG. 18C
illustrates data indicative of the result of analysis of the
frequency of the device noise 8002 performed under the conditions
B-3 and B-4. FIG. 19A is a diagram 3050 illustrating the result of
measurement performed under the condition B-3 and FIG. 19B is a
diagram 3060 illustrating the result of measurement performed under
the condition B-3.
[0151] As illustrated in FIGS. 18A and 19A, under the condition
B-3, the front-stage average revolution number 8001A was 12576
min.sup.-1 and the rear-stage average revolution number was 13354
min.sup.-1. This result is the same as those attained under the
conditions A-1 and B-1. On the other hand, as illustrated in FIGS.
18A and 19B, under the condition B-4, the front-stage average
revolution number was 12826 min.sup.-1 and the rear-stage average
revolution number 8001B was 12809 min.sup.-1. That is, these values
are smaller than the value of the rear-stage average revolution
number 8001B measured under the condition B-3.
[0152] As illustrated in FIG. 18A and FIGS. 19A and 19B, the device
noise 8002 under the condition B-3 was 58.7 db(A) and the device
noise 8002 under the condition B-4 was 57.7 dB(A). That is, the
device noise 8002 measured under the condition B-4 which is the
same as that of the fan control device 1 according to this
embodiment was lower than that measured under the condition B-3 and
was reduced from the value measured under the condition B-3 by
about 1 db(A) as in the case in the relation between the conditions
B-1 and B-2.
[0153] As described above, it has been found that even when the air
flow rates of air generated from each front-stage fan and each
rear-stage fan are varied, the same result may be obtained by
changing the amount of voltages applied in the case that the
front-stage fans and the rear-stage fans are disposed in series and
in parallel. Incidentally, the values of the device noise
illustrated in FIG. 18A are calculated on the basis of the result
of analysis of the frequency of the device noise illustrated in
FIG. 18C.
[0154] As illustrated in FIG. 18B and FIGS. 19A and 19B, the total
consumption power 8003 of the front-stage and rear-stage fans was
27.80 W under the condition B-3 and was 26.87 W under the condition
B-4. That is, the total consumption power 8003 was also the lowest
when measured under the condition B-4 which is the same as that of
the fan control device 1 according to this embodiment as in the
case in the relation between the conditions B-1 and B-2 and was
reduced from the value measured under the condition B-3 by about
3%.
[0155] As described above, according to the embodiment 2, the air
flow rate of air cooling the heating elements 52a and 52b which is
determined from the temperatures of the heating elements 52a and
52b, the system impedance within the electronic equipment 50 and
the total PQ characteristic of the fans 3a and 3b attained in a
state in which the difference in revolution number between the fans
3a and 3b is maintained in the predetermined tolerance is obtained.
In addition, the revolution number of each of the fans 3a and 3b is
controlled on the basis of the temperatures of the heating elements
and the environmental temperature such that the difference in
revolution number between the fans 3a and 3b is set in the
predetermined tolerance. That is, in the embodiment 2, the
revolution number of each of the fans 3a and 3b is controlled on
the basis of the heating element temperatures and the environmental
temperature such that the needed air flow rate which is needed for
cooling the heating elements 52a and 52b and is determined from the
temperatures of the heating elements 52a and 52b, the system
impedance within the electronic equipment 50 and the total PQ
characteristic of the fans 3a and 3b obtained in a state in which
the revolution numbers of the fans 3a and 3b are controlled to
coincide with each other in the predetermined tolerance may be
obtained in a state in which the revolution numbers of the fans 3a
and 3b coincide with each other in the predetermined tolerance.
[0156] That is, according to this embodiment, such a situation that
the total noise generated from the fans 3a and 3b owing to the
surplus noise generated from the fan of the largest revolution
number may be avoided by maintaining the difference in revolution
number between the fans 3a and 3b in the predetermined tolerance.
In addition, in this embodiment, the needed air flow rate may be
obtained by taking the temperatures of the heating elements 52a and
52b, the system impedance within the electronic equipment 50 and
the total PQ characteristic of the fans 3a and 3b obtained in a
state in which the difference in evolution number between the fans
3a and 3b is in the predetermined tolerance into consideration.
Therefore, according to this embodiment, the air flow rate suited
to cool the heating elements 52a and 52b may be obtained in a state
in which the difference in revolution number between the fans 3a
and 3b is maintained in the predetermined tolerance regardless of
the configuration of the electronic equipment 50 concerned and the
locations of the respective fans 3a and 3b within the electronic
equipment 50.
[0157] As described above, according to this embodiment, the noise
generated from the plurality of fans 3a and 3b may be reduced while
attaining the air flow rate needed for cooling the heating elements
52A and 52B within the electronic equipment 50 using the plurality
of fans 3a and 3b.
[0158] In addition, according to this embodiment, the revolution
number of the rear-stage fan 3b is reduced more remarkably than
that attained when the energy of the same amount is supplied to the
both fans 3a and 3b and hence the service life of the rear-stage
fan 3b may be increased. Further, according to this embodiment,
addition of components is not needed and hence the above mentioned
effects may be realized at a cost equivalent to an ever attained
cost.
[0159] Incidentally, a fan control program is stored in the ROM 17
of the fan control device 1 and functions as mentioned above are
implemented by executing this fan control program using the
processor 18. Next, an example of a computer for executing the fan
control program will be illustrated. FIG. 20 is a functional block
diagram illustrating a computer for executing the fan control
program.
[0160] As illustrated in FIG. 20, a computer 600 serving as the fan
control device 1 includes an HDD 610, a RAM 620, a ROM 630, a CPU
60 and a bus 650 for connecting these elements with one another.
The ROM 630 corresponds to the ROM 17 illustrated in FIG. 2 and
stores in advance the fan control program. The fan control program
includes a temperature detection program 631 and a control program
632.
[0161] Then, the CPU 640 reads the temperature detection program
631 and the control program 632 out of the ROM 630 and executes
these programs. As a result of execution of these programs, the
programs 631 and 632 come to function respectively as a temperature
detection process 641 and a control process 642. As described
above, the CPU 640 corresponds to the processor 18 in FIG. 2.
[0162] The ROM 630 includes the equipment state storage section 171
and the control data storage section 172 and stores the equipment
state management table 61, the heating-element-temperature-based
PWM value determination tables 71a to 71c and the
environmental-temperature-based PWM value determination tables 72a
to 72c in these storage sections. The CPU 640 reads these tables
stored in the ROM 630 and stores these tables in the RAM 620 such
that the processes 641 and 642 execute various processes utilizing
the data stored in the RAM 620.
Embodiment 3
[0163] Although, in the above mentioned embodiment 2, the evolution
numbers of the fans 3a and 3b detected using the revolution number
detecting sections 13a and 13b are used only for revolution number
error check, the revolution numbers of the fans 3a and 3b may be
utilized as feedback information used to set the difference in
revolution number between the fans 3a and 3b in the predetermined
tolerance. Next, an embodiment involving a case as mentioned above
will be described. FIG. 21 is a block diagram illustrating a
configuration of a fan control device according to an embodiment 3.
Incidentally, the same numerals are assigned to parts having the
same configurations as those previously described and description
thereof will be omitted.
[0164] As illustrated in FIG. 21, in a fan control device 1'
according to this embodiment, a processor 18' acquires information
on the revolution numbers of the fans 3a and 3b from the revolution
number detecting sections 13a and 13b. Next, specific
configurations of the processor 18' and a ROM 17' according to this
embodiment will be described herein below. FIG. 22 is a block
diagram illustrating specific configurations of the processor 18'
and the ROM 17' according to the embodiment 3.
[0165] As illustrated in FIG. 22, the processor 18' according to
this embodiment includes the error processing section 181, the
temperature information acquiring section 182, an input value
determining section 183', the database preparing section 184 and a
revolution number information acquiring section 185. The revolution
number information acquiring section 185 acquires information on
the revolution numbers of the front-stage fan 3a and the rear-stage
fan 3b respectively from the revolution number detecting sections
13a and 13b. As described above, the revolution number information
acquiring section 185 and the revolution number detecting section
13a function as an example of front-stage revolution number
detecting means for detecting the revolution number of the
front-stage fan 3a and the revolution number information acquiring
section 185 and the revolution number detecting section 13a
functions as an example of rear-stage revolution number detecting
means for detecting the revolution number of the rear-stage fan
3b.
[0166] The input value detecting section 183' then performs
feedback control on the revolution number of the rear-stage fan 3b
on the basis of information acquired from the revolution number
information acquiring section 185. Specifically, in the case that a
difference in revolution number between the front-stage fan 3a and
the rear-stage fan 3b is out of a predetermined tolerance, the
input value determining section 183' changes the revolution number
of the rear-stage fan such that the difference in revolution number
between the front-stage fan 3a and the rear-stage fan 3b is set in
the predetermined tolerance. Processing as mentioned above is
executed with reference to a rear-stage PWM value change table
stored in a control data storage section 172'.
[0167] The control data storage section 172' according to this
embodiment stores a PWM value for the rear-stage fan 3b obtained
when a difference in evolution number between the front-stage fan
3a and the rear-stage fan 3 is reduced to have a value in the
predetermined tolerance per revolution number. Next, information
stored in the control data storage section 172' will be described.
FIG. 23 is a diagram illustrating information stored in the control
data storage section according to the embodiment 3.
[0168] As illustrated in FIG. 23, rear-stage PWM value change
tables 73a to 73c corresponding to the system impedances A to C are
stored in the control data storage section 172' according to this
embodiment in addition to the heating-element-temperature-based PWM
value determination tables 71a to 71c and the
environmental-temperature-based PWM value determination tables 72a
to 72c. FIG. 24 illustrates an example of the rear-stage PWM change
table 73a.
[0169] As illustrated in FIG. 24, in the rear-stage OWM value
change table 73a, each front-stage revolution number indicative of
the revolution number of each front-stag fan 3a is stored
corresponding to each rear-stage PWM value. For example, in the
rear-stage PWM value change table 73a, the front-stage revolution
number "jjj" is stored corresponding to the rear-stage PWM value
"Nrj".
[0170] The rear-stage PWM value stored in the rear-stage PWM value
change table 3a is a PWM value needed to control the revolution
number of the rear-stage fan 3b to have a difference relative to
the evolution number of the front-stage fan 3a in a predetermined
tolerance. That is, for example, in the case that the revolution
number "kkk" of the front-stage fan 3a has been acquired from the
revolution number information acquiring section 185, the input
value determining section 183' determines the rear-stage PWM value
"Nrk" corresponding to the acquired revolution number with
reference to the rear-stage PWM value change table 73a. The input
value determining section 183' then inputs the pulse of the
determined rear-stage PWM value "Nrk" into the rear-stage fan 3b
via the pulse generator 15b. Owing to the above mentioned
operations, even when the revolution number of the front-stage fan
3a differs from the revolution number of the rear-stage fan 3b, the
fan control device 1' will be capable of performing correction such
that the difference in revolution number between these fans is set
in the predetermined tolerance.
[0171] Next, specific operations of the processor 18' according to
this embodiment will be described. FIG. 25 is a flowchart
illustrating an example of processing executed using the processor
18' according to the embodiment 3. Incidentally, in FIG. 25, in
procedures of processing executed using the processor 18', only a
procedure of processing involving control of the revolution numbers
of the front-stage and rear-stage fans 3a and 3b will be described.
Processes executed at steps S301 to S311 in FIG. 25 are the same as
the processes executed at steps S201 to S211 in FIG. 11 and hence
description thereof will be omitted.
[0172] As illustrated in FIG. 25, after an instruction to rotate
the fans 3a and 3b has been given at step S311, the input value
determining section 183' measures the revolution numbers of the
fans (step S312). Specifically, the input value determining section
183' acquires information on the revolution numbers of the
front-stage and rear-stage fans 3a and 3b from the revolution
number information acquiring section 185.
[0173] Next, the input value determining section 183' judges
whether a difference in revolution number between the front-stage
and rear-stage fans is in a predetermined tolerance (step S313). In
the case that it has been judged that the difference in revolution
number between the fans is in the predetermined tolerance in
execution of the above mentioned process (Yes at step S313), the
input value determining section 183' shifts the process to step
S312.
[0174] On the other hand, in the case that the difference in
revolution number between the fans is not in the predetermined
tolerance (No at step S313). The input value determining section
183' changes the rear-stage PWM value (step S314). Specifically,
the input value determining section 183' determines, on the basis
of information on the revolution number of the front-stage fan 3a
acquired from the revolution number acquiring section 185, the
rear-state PWM value corresponding to the acquired revolution
number of the front-stage fan 3a with reference to the rear-stage
PWM value change table. The input value determining section 183'
then gives an instruction to rotate the fans (step S315).
Specifically, the input value determining section 183' instructs
the pulse generator 15b to input the pulse of the rear-stage PWM
value which has been determined at step S312 into the rear-stage
fan 3b. Owing to the above mentioned operation, the pulse of the
rear-stag PWM value conforming to the revolution number of the
front-stage fan 3a is input into the rear-stage fan 3b and the
revolution numbers of the front-stage fan 3a and the rear-stage fan
3b come into coincidence with each other in the predetermined
tolerance.
[0175] As described above, in the embodiment 3, in the case that
the difference in revolution number between the front-stage fan 3a
and the rear-stage fan 3b is out of the predetermined tolerance,
the revolution number of the rear-stage fan is changed such that
the difference in revolution numbers between the fans is set in the
predetermined tolerance. Owing to the above mentioned operation, it
may become possible to more set the difference in revolution number
between the front-stage fan 3a and the rear-stage fan 3b in the
predetermined tolerance.
[0176] Although several embodiments haven been described in detail
with reference to the accompanying drawings, these embodiments are
merely examples and the embodiments may be modified in other forms
which are altered and improved in a variety of ways on the basis of
skills of persons in the art including the embodying aspects as
described above.
[0177] For example, although in the above mentioned embodiments,
the database preparing section 184 is used only in the case that
heating-element-temperature-based PWM value determination tables
71a to 71b and the environmental-temperature-based PWM value
determination tables 72a to 72c are prepared, the revolution
numbers of the fans 3a and 3b may be controlled using the database
preparing section 184.
[0178] Specifically, first, the database preparing section 184
acquires the temperatures of the heating elements or the
environmental temperature from the temperature information
acquiring section 182. Then, the database preparing section 184
calculates a front-stage PWM value and a rear-stage PWM value of
pulses to be input into the respective fans 3a and 3b in the case
that an air flow rate needed for cooling the heating elements 52a
and 52b is obtained in a state in which a difference in revolution
number between the fans 3a and 3b is in a predetermined tolerance
on the basis of the acquired temperature(s). Then, the database
preparing section 184 notifies the input value determining section
183 (or the input value determining section 183') of the calculated
front-stage PWM value and rear-stage PWM value.
[0179] All examples and conditional language recited herein are
intended for pedagogical purposes to aid the reader in
understanding the invention and the concepts contributed by the
inventor to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions, nor does the organization of such examples in the
specification relate to a showing of the superiority and
inferiority of the invention. Although the embodiments of the
present invention have been described in detail, it should be
understood that the various changes, substitutions, and alterations
could be made hereto without departing from the spirit and scope of
the invention.
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