U.S. patent application number 11/294691 was filed with the patent office on 2006-06-08 for electric fan system for vehicle.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Takahiro Iwasaki, Shinichi Oda.
Application Number | 20060120903 11/294691 |
Document ID | / |
Family ID | 36500368 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060120903 |
Kind Code |
A1 |
Iwasaki; Takahiro ; et
al. |
June 8, 2006 |
Electric fan system for vehicle
Abstract
An electric fan system for a vehicle including two electric fans
(10, 20) arranged in parallel in a vehicle width direction so as to
blow cooling air to a radiator (100) and a condenser (110), wherein
the electric fans are driven by a brushless motor (12) and a brush
motor (22), a first drive voltage V1 for driving the brushless
motor is set so as to increase in accordance with an increase of a
water temperature (Tw) of the radiator or a coolant pressure (Pc)
of the condenser, and simultaneously a second drive voltage V2 for
driving the brush motor is set so as to increase monotonously as a
value lower than the first drive voltage, whereby the two electric
fans can operate simultaneously at all times, unevenness of the
distribution of the flow rate can be reduced, and the drive voltage
of the brush motor is reduced, so the lifetime can be extended and,
further, provision is made of an electronic control unit (40a) for
preferentially operating the electric fan (10) driven by the
brushless motor over the electric fan (20) driven by the brush
motor based on the temperature of the engine cooling water and the
electric fan (10) driven by the brushless motor is designed to cool
by cooling air other vehicle-mounted parts besides the radiator
(100) and the condenser (110), specifically for example the ECU box
(410).
Inventors: |
Iwasaki; Takahiro;
(Okazaki-city, JP) ; Oda; Shinichi; (Okazaki-city,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
36500368 |
Appl. No.: |
11/294691 |
Filed: |
December 5, 2005 |
Current U.S.
Class: |
417/423.1 ;
417/32 |
Current CPC
Class: |
F01P 2025/04 20130101;
Y02B 30/70 20130101; F01P 2005/046 20130101; F04D 27/004 20130101;
F01P 2025/46 20130101; F01P 2005/025 20130101; F01P 2060/14
20130101; F01P 7/048 20130101 |
Class at
Publication: |
417/423.1 ;
417/032 |
International
Class: |
F04B 49/10 20060101
F04B049/10; F04B 17/00 20060101 F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2004 |
JP |
2004-352743 |
Dec 27, 2004 |
JP |
2004-376269 |
Claims
1. An electric fan system for a vehicle which circulates cooling
air to a heat exchange unit provided with a radiator for cooling
cooling water circulating inside a water-cooled engine for vehicle
operation and a condenser for cooling a coolant circulating inside
a refrigeration cycle apparatus, the system comprising: a brushless
motor driven by a first drive voltage, a first electric fan
circulating cooling air to the heat exchange unit by the brushless
motor, a brush motor driven by a second drive voltage, a second
electric fan circulating cooling air to the heat exchange unit by
the brush motor, and a control device supplying the brushless motor
with the first drive voltage so that the first drive voltage
monotonously increases up to a first maximum drive voltage in
accordance with a rise in temperature of the cooling water and for
supplying the brush motor with the second drive voltage so that the
second drive voltage monotonously increases up to a second maximum
drive voltage in accordance with a rise in temperature of the
cooling water and becomes a voltage lower than the first drive
voltage based on the detection output from a temperature sensor for
detecting the temperature of the cooling water.
2. An electric fan system for a vehicle as set forth in claim 1,
wherein when the temperature of the cooling water is a temperature
of a temperature threshold value or more, the first and second
maximum drive voltages are set to become constant values.
3. An electric fan system for a vehicle which circulates cooling
air to a heat exchange unit provided with a radiator for cooling
cooling water circulating inside a water-cooled engine for vehicle
operation and a condenser for cooling a coolant circulating inside
a refrigeration cycle apparatus, the system comprising: a brushless
motor driven by a first drive voltage, a first electric fan
circulating cooling air to the heat exchange unit by the brushless
motor, a brush motor driven by a second drive voltage, a second
electric fan for circulating cooling air to the heat exchange unit
by the brush motor, and a control device for supplying the
brushless motor with the first drive voltage so that the first
drive voltage monotonously increases up to a first maximum drive
voltage in accordance with a rise in pressure of the coolant and
for supplying the brush motor with the second drive voltage so that
the second drive voltage monotonously increases up to a second
maximum drive voltage in accordance with a rise in pressure of the
coolant and becomes a voltage lower than the first drive voltage
based on the detection output from a pressure sensor for detecting
the pressure of the coolant in the condenser.
4. An electric fan system for a vehicle as set forth in claim 3,
wherein when the pressure of the coolant is a pressure of a
pressure threshold value or more, the first and second maximum
drive voltages are set to become constant values.
5. An electric fan system for a vehicle as set forth in claim 1,
wherein both the first and second electric fans are axial flow fans
and the fan diameters are substantially equal.
6. An electric fan system for a vehicle which circulates cooling
air to a heat exchange unit provided with a radiator for cooling
cooling water circulating inside a water-cooled engine for vehicle
operation and a condenser for cooling a coolant circulating inside
a refrigeration cycle apparatus, the system comprising: a first
electric fan circulating cooling air to the radiator and condenser
by operation of a brushless motor, a second electric fan for
circulating cooling air to the radiator and condenser by a brush
motor, and a control means for operating the first electric fan
preferentially over the second electric fan based on a state of
either the cooling water and the coolant, the first electric fan
being designed to cool other vehicle-mounted parts than the
radiator and condenser by cooling air.
7. An electric fan system for a vehicle as set forth in claim 6,
wherein the control means determines the flow rate of cooling air
by the first electric fan based on both the state of one of the
cooling water and the coolant and the temperature of the other
vehicle-mounted parts.
8. An electric fan system for a vehicle as set forth in claim 6,
wherein the first electric fan is designed to blow air toward
locations different from the locations where the other
vehicle-mounted parts are arranged.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is based upon and claims priorities of
Japanese Patent Application No. 2004-352743, filed in the Japan
Patent Office on Dec. 6, 2004, and Japanese Patent Application No.
2004-376269, filed in the Japan Patent Office on Dec. 27, 2004, the
contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electric fan system for
a vehicle which uses an electric fan to generate cooling air.
[0004] 2. Description of the Related Art
[0005] In the past, as an electric fan system for a vehicle, there
has been one which used an electric fan to circulate cooling air to
a radiator for cooling engine cooling water and a condenser for
vehicle air-conditioning so as cool the radiator and condenser.
[0006] In general, in a taxi, bus, or other vehicle with a high
frequency of use of the electric fan, a sufficient fan capacity,
rectification of the distribution of air blown to the radiator,
extension of the lifetime of the electric motor, and reduction of
the cost are demanded.
[0007] For example, when applying this electric fan system for a
vehicle to a taxi, bus, or other vehicle with a high frequency of
use of the electric fan, an electric motor with a large rated
capacity has been employed as the electric motor of the electric
fan and this electric motor has been operated by a power lower than
the rated capacity so as to keep the deterioration of the electric
motor itself to a minimum and extend the lifetime of the electric
motor.
[0008] However, in this case, by employing an electric motor with a
large rated capacity, there is a possibility of inviting not only
an increase in cost, but also an increase in weight.
[0009] Further, in an electric motor for an electric fan, it is
known to employ a brushless motor so as to extend the lifetime of
the electric motor, but when the dimension of the radiator in the
vehicle width direction (left-right direction of vehicle) is larger
than the dimension of the rotor of the electric fan in the vehicle
width direction, with just a single electric fan, the distribution
of air blown to the radiator would deteriorate and parts of the
radiator where cooling air is not blown would end up arising
thereby inviting a drop in the cooling efficiency of the radiator
and in turn deterioration of the fuel economy.
[0010] As opposed to this, by employing two or more electric fans
using brushless motors, it would become possible to rectify the
distribution of blown air to the radiator and send sufficient
cooling air to the radiator, but the control circuit for
controlling the brushless motors would become complicated in
configuration and a further increase in cost would be invited.
[0011] Therefore, the assignees proposed in a prior Japanese Patent
Application No. 2003-273458 an electric fan system for a vehicle
designed to keep down the increase in cost and extend the lifetime.
The invention of this prior application provides a first electric
fan for circulating cooling air to the radiator and condenser by a
brushless motor and a second electric fan for circulating cooling
air by a brush motor. For example, when it is judged that the
temperature of the cooling water circulating through the radiator
is less than a predetermined value, just the first electric fan is
operated, while when it is judged that the temperature of the
cooling water is the predetermined value or more, both the first
and second electric fans are operated.
[0012] In this electric fan, when the temperature of the cooling
water becomes higher than a first threshold value, only the first
electric fan is operated. When the temperature of the cooling water
exceeds a second threshold value higher than the first threshold
value (>first threshold value), the first and second electric
fans are both operated. Therefore, the first electric fan is
operated preferentially compared with the second electric fan.
Accordingly, wear of the second electric fan, that is, wear of the
brush motor, is suppressed and the lifetime is extended.
[0013] That is, if the temperature of the cooling water does not
become the predetermined value or more, the second electric fan
does not operate thereby reducing the operating rate of the brush
motor and reducing the wear of the brush motor, that is, extending
the lifetime of the brush motor. Therefore, by jointly employing a
brushless motor free from problems in terms of motor lifetime and a
brush motor extended in lifetime, it is possible to reduce the
total cost of the electric fan system for a vehicle and extend its
lifetime.
[0014] However, in the invention of the prior application, when the
temperature of the cooling water is less than the predetermined
temperature, the brush motor stops operating, but during this time
the distribution of the flow rate in the vehicle width direction of
the radiator becomes uneven. In the end a large power is required
for obtaining the same performance (heat dissipation) with just the
first electric fan. Further, at the parts usually blown upon by the
stopped second electric fan, hot air sneaks around (flows back)
from the high temperature, high pressure engine side to the vehicle
front direction (radiator front side), the temperature in front of
the heat exchanger rises, and the cooling performance and
air-conditioning performance drop.
[0015] Further, in the engine compartments of recent vehicles,
aside from the radiator and condenser, the electronic control unit,
headlamps, rubber engine mounts, and other parts mounted in the
vehicle also have to be cooled. In the above electric fan system
for a vehicle using a brushless motor and brush motor, however, no
consideration was given to cooling these other vehicle-mounted
parts.
SUMMARY OF THE INVENTION
[0016] A first object of the present invention is to provide an
electric fan system for a vehicle enabling an extension of the
lifetime while reducing the unevenness of the distribution of the
flow rate.
[0017] A second object of the present invention is to provide an
electric fan system for a vehicle designed to enable cooling of not
only the radiator and condenser, but also other vehicle-mounted
parts while extending the lifetime.
[0018] To achieve the first object, according to a first aspect of
the present invention, there is provided an electric fan system for
a vehicle which circulates cooling air to a heat exchange unit
provided with a radiator for cooling cooling water circulating
inside a water-cooled engine for vehicle operation and a condenser
for cooling a coolant circulating inside a refrigeration cycle
apparatus, the system provided with a brushless motor driven by a
first drive voltage, a first electric fan for circulating cooling
air to the heat exchange unit by the brushless motor, a brush motor
driven by a second drive voltage, a second electric fan for
circulating cooling air to the heat exchange unit by the brush
motor, and a control device for supplying the brushless motor with
the first drive voltage so that the first drive voltage
monotonously increases up to a first maximum drive voltage in
accordance with a rise in temperature of the cooling water and for
supplying the brush motor with the second drive voltage so that the
second drive voltage monotonously increases up to a second maximum
drive voltage in accordance with a rise in temperature of the
cooling water and becomes a voltage lower than the first drive
voltage based on the detection output from a temperature sensor for
detecting the temperature of the cooling water.
[0019] According to the first aspect, the drive voltage of the
brushless motor constituted by the first drive voltage is made to
monotonously increase in accordance with a rise in temperature of
the cooling water and the drive voltage of the brush motor
constituted by the second drive voltage is made a voltage lower
than the first drive voltage and is made to monotonously increase
in accordance with a rise in temperature of the cooling water.
Therefore, when the first electric fan of the brushless motor is
operating, the second electric fan of the brush motor does not stop
and is also simultaneously operating, so hot air sneaking its way
to the parts meant to be blown on of the second electric fan in the
heat exchange unit is avoided and therefore the unevenness of the
distribution of the flow rate can be reduced and the cooling
efficiency of the heat exchange unit can be raised.
[0020] Further, in the process of increasing the drive voltage
along with a rise in the temperature of the cooling water, since
the drive voltage of the brush motor constituted by the second
drive voltage is set lower than the drive voltage of the brushless
motor constituted by the first drive voltage, the lifetime of the
brush motor can be extended and the lifetime of the electric fan
system can be prolonged.
[0021] Note that according to a second aspect of the present
invention, when the temperature of the cooling water is a
temperature of a temperature threshold value or more, the first and
second maximum drive voltages may be set to become constant
values.
[0022] According to a third aspect of the present invention,
instead of the rise in the temperature of the cooling water of the
first aspect of the invention, the first and second drive voltages
are made to monotonously increase in accordance with the rise of
the pressure of the coolant. Therefore, in the same way as the
first aspect of the invention, the drive voltage of the brushless
motor constituted by the first drive voltage is made to
monotonously increase in accordance with a rise in the coolant
pressure and the drive voltage of the brush motor constituted by
the second drive voltage is made a voltage lower than the first
drive voltage and is made to monotonously increase in accordance
with a rise in the coolant pressure. Therefore, when the first
electric fan of the brushless motor is operating, the second
electric fan of the brush motor also simultaneously operates
without stopping, so hot air sneaking its way to the parts meant to
be blown on of the second electric fan in the heat exchange unit is
avoided and therefore the unevenness of the distribution of the
flow rate can be reduced and the cooling efficiency of the heat
exchange unit can be raised.
[0023] Further, in the process of increasing the drive voltage
along with a rise in the coolant pressure, since the drive voltage
of the brush motor constituted by the second drive voltage is set
lower than the drive voltage of the brushless motor constituted by
the first drive voltage, the lifetime of the brush motor can be
extended and the lifetime of the electric fan system can be
prolonged.
[0024] According to a fourth aspect of the present invention, when
the pressure of the coolant is a pressure of a pressure threshold
value or more, the first and second maximum drive voltages can be
set to become constant values.
[0025] According to a fifth aspect of the present invention, both
the first and second electric fans are axial flow fans. By making
the fan diameters substantially equal, it is possible to make the
distribution of the flow rate to the entire surface of the heat
exchange unit uniform and possible to raise the cooling efficiency
of the heat exchange unit.
[0026] To achieve the second object, according to a sixth aspect of
the present invention, there is provided an electric fan system for
a vehicle which circulates cooling air to a heat exchange unit
provided with a radiator for cooling cooling water circulating
inside a water-cooled engine for vehicle operation and a condenser
for cooling a coolant circulating inside a refrigeration cycle
apparatus, the system provided with a first electric fan for
circulating cooling air to the radiator and condenser by operation
of a brushless motor, a second electric fan for circulating cooling
air to the radiator and condenser by a brush motor, and a control
means for operating the first electric fan preferentially over the
second electric fan based on a state of either the cooling water
and the coolant, the first electric fan being designed to cool
other vehicle-mounted parts than the radiator and condenser by
cooling air.
[0027] According to the sixth aspect of the present invention,
since the first electric fan is operated preferentially over the
second electric fan, the wear of the second electric fan, that is,
the wear of the brush motor, can be suppressed. Further, since the
first electric fan is designed to cool other vehicle-mounted parts
besides the radiator and condenser by cooling air, the lifetime is
extended and other vehicle-mounted parts can also be cooled.
[0028] Here, according to a seventh aspect of the present
invention, there is provided the electric fan system for a vehicle
as set forth in the sixth aspect of the invention wherein the
control means determines the flow rate of cooling air by the first
electric fan based on both the state of one of the cooling water
and the coolant and the temperature of the other vehicle-mounted
parts, so the other vehicle-mounted parts, radiator, and condenser
can be suitably cooled.
[0029] According to an eighth aspect of the present invention, the
first electric fan is designed to blow air toward locations
different from the locations where the other vehicle-mounted parts
are arranged.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] These and other objects and features of the present
invention will become clearer from the following description of the
preferred embodiments given with reference to the attached
drawings, wherein:
[0031] FIG. 1 is a schematic view of the electric fan system for a
vehicle according to an embodiment of the present invention;
[0032] FIG. 2 is a view of the arrangement of a radiator and a
condenser according to the electric fan system for a vehicle of
FIG. 1;
[0033] FIG. 3 is a schematic view of the electrical system of the
electric fan system for a vehicle of FIG. 1;
[0034] FIG. 4 is a view of the electrical system of an electric fan
drive circuit of the electric fan system for a vehicle of FIG.
1;
[0035] FIG. 5 is a flow chart of a fan control routine;
[0036] FIG. 6 is a graph of a control characteristic with respect
to a water temperature of a brushless motor of a first electric
fan;
[0037] FIG. 7 is a graph of a control characteristic with respect
to a coolant pressure of a brushless motor of a first electric
fan;
[0038] FIG. 8 is a graph of a control characteristic of a brush
motor of a second electric fan;
[0039] FIG. 9 is a graph of a control characteristic of a brush
motor of another embodiment;
[0040] FIG. 10 is a schematic view of the configuration of an
electric fan system for a vehicle of another embodiment of the
present invention;
[0041] FIG. 11 is a schematic view of the electrical system of the
electric fan system for a vehicle of FIG. 10;
[0042] FIG. 12 is a flow chart of the control processing by an
electronic control unit of FIG. 11;
[0043] FIG. 13 is a graph for determining a flow rate of an
electric fan by an electronic control unit of FIG. 11;
[0044] FIG. 14 is a graph for determining a flow rate of an
electric fan by an electronic control unit of FIG. 11;
[0045] FIG. 15 is a graph for determining a flow rate of an
electric fan by an electronic control unit of FIG. 11;
[0046] FIG. 16 is a schematic view of the configuration of an
electric fan system for a vehicle according to a modification of
the present invention; and
[0047] FIG. 17 is a graph for determining the flow rate of an
electric fan in the modification shown in FIG. 16.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] Below, preferred embodiments of the present invention will
be explained with reference to the drawings. Throughout the
drawings, the same reference numerals indicate the same
objects.
First Embodiment
[0049] FIG. 1 to FIG. 4 show the configuration of an electric fan
system for a vehicle according to a first embodiment of the present
invention. FIG. 1 and FIG. 2 are schematic views of the
configuration of the electric fan system for a vehicle.
[0050] The electric fan system for a vehicle is provided inside an
engine compartment of the vehicle, as shown in FIG. 1, with first
and second electric fans 10 and 20 comprised of axial flow fans.
The first electric fan 10 is comprised of a rotor 11 and a
brushless motor 12 for driving rotation of the rotor 11, while the
second electric fan 20 is comprised of a rotor 21 and a brush motor
(DC motor) 22 for driving rotation of the rotor 21.
[0051] The first and second electric fans 10 and 20 function to
circulate cooling air to the radiator 100 and the condenser 110
forming the heat exchange unit so as to cool the radiator 100 and
the condenser 110.
[0052] Further, the radiator 100 and the condenser 110 are arranged
in the engine compartment in the front-rear direction of the
vehicle. The radiator 100 cools the cooling water circulating
inside a water-cooled engine for driving the vehicle (engine
cooling water). The condenser 110 is one component of the vehicle
air-conditioning system for air-conditioning of the inside of the
vehicle compartment in a refrigeration cycle (refrigeration cycle
system) and cools the coolant circulating through the inside of the
vehicle air-conditioning system.
[0053] Note that the fan diameters of the rotors 11 and 21 of the
first and second electric fans 10 and 20 are set to be
substantially equal to each other. Due to this, it is possible to
achieve a uniform flow rate of the cooling air (reduce the
unevenness) over the entire surface of the heat exchange unit and
possible to improve the cooling efficiency in the heat exchange
unit.
[0054] Next, the schematic electrical system of the electric fan
system for a vehicle of the present embodiment will be explained
using FIG. 3 and FIG. 4. FIG. 3 is a block diagram showing the
schematic electrical system of the electric fan system for a
vehicle, while FIG. 4 is a block diagram showing details of the
electric fan drive circuit in FIG. 3.
[0055] The electric fan system for a vehicle, as shown in FIG. 3,
is comprised of an electric fan drive circuit 30 and an engine
electronic control unit (E/G-ECU) 40. The electric fan drive
circuit 30, as shown in FIG. 4, is comprised of a control unit 31,
a brushless motor driver 32, and a brush motor driver 33.
[0056] The control unit 31 is comprised of a brushless motor
control unit 31a, a power logic generation circuit 31b, and a brush
motor control unit 31c.
[0057] Here, the brushless motor control unit 31a detects the
actual position of a rotor 12b of the brushless motor 12 based on
detection output from a magnetic pole sensor 13 in the brushless
motor 12. Note that the actual position of the rotor 12b detected
will be referred to below as the detected position of the rotor
12b.
[0058] The magnetic pole sensor 13 is comprised of three Hall
elements. The magnetic pole sensor 13 is arranged around the rotor
12b in the brushless motor 12 and detects changes in the magnetic
field accompanying rotation of the rotor 12b. Further, the rotor
12b is comprised of a permanent magnet and makes the rotor 11 turn
by its rotation.
[0059] The brushless motor control unit 31a detects the target
speed of the brushless motor 12 as a control instruction value
(brushless motor control instruction value I.sub.1) based on a duty
ratio Ds of a pulse signal sent from the engine electronic control
unit 40.
[0060] Further, the power logic generation circuit 31b drives a
brushless motor driver 32 based on the detected position of the
rotor 12b so as to make the actual speed of the brushless motor 12
approach the target speed.
[0061] The brushless motor driver 32 is a known inverter circuit
which is supplied with power from a DC power supply Ba and controls
the three-phase AC power supplied to a stator coil 12a of the
brushless motor 12 and is comprised of six field effect transistors
U+, V+, W+, U-, V-, and W- used to form a three-phase full wave
bridge circuit.
[0062] Note that the brushless motor control instruction value
I.sub.1 is set by the later explained control characteristic graphs
(FIG. 6 and FIG. 7). Due to the control instruction value, the
brushless motor 12 is given a first drive voltage V1 as an average
value and rotates by a predetermined target speed in accordance
with the first drive voltage V1.
[0063] The brush motor control unit 31c controls the brush motor
driver 32 by pulse width modulation (PWM) in accordance with a
control signal output from the engine electronic control unit 40 so
as to give a predetermined target speed (brush motor control
instruction value I.sub.2) based on a later explained control
characteristic graph (FIG. 8 or FIG. 9).
[0064] The brush motor driver 33 is comprised of a single field
effect transistor which is supplied with power from a DC power
supply Ba and controls the power to the brush motor 22. Due to
this, the brush motor 22 is supplied with the second drive voltage
V2 as an average value and operates by a predetermined target speed
in accordance with the second drive voltage V2.
[0065] The engine electronic control unit 40 is comprised of a
microcomputer, a memory, etc. and controls the first and second
electric fans 10 and 20 through the electric fan drive circuit 30
based on the detection output of a water sensor 41 for detecting
the temperature of the cooling water of an engine (not shown) and
the detection output of a pressure sensor 42 for detecting the
pressure of the coolant (coolant pressure) flowing through the
condenser 110. The water temperature sensor 41 detects the water
temperature of the cooling water flowing out from the radiator 100
and returning to the water-cooled engine.
[0066] Next, the operation of this embodiment will be explained
using FIG. 5 to FIG. 8. FIG. 5 is a flow chart showing a fan
control routine of the engine electronic control unit 40. The
engine electronic control unit 40 runs a computer program stored in
the memory in accordance with the flow chart shown in FIG. 5. This
computer program is repeatedly run every predetermined time
(control period).
[0067] First, at step S100, the temperature of the cooling water
(hereinafter referred to as the water temperature Tw) is read from
the water temperature sensor 41 and the coolant pressure Pc is read
from the pressure sensor 42.
[0068] Next, at step S110, first and second duty ratios D1 and D2
of a pulse signal for controlling the first electric fan 10 and a
third duty ratio D3 of a pulse signal for controlling the second
electric fan 20 are determined based on the water temperature Tw,
the coolant pressure Pc, and the control characteristic graphs of
FIG. 6, FIG. 7, and FIG. 8 stored in advance in the memory.
[0069] Specifically, as the first duty ratio D1, as shown in FIG.
6, a value is selected set so as to monotonously increase from a
duty ratio corresponding to the minimum speed Nf0 as the water
temperature Tw becomes larger in the period from the temperature T1
to the temperature T2 (for example, 105.degree. C.>T1). Due to
this, a first drive voltage V1 is supplied to the brushless motor
12. Further, when the water temperature Tw is the temperature
threshold value T2 or more, the first duty ratio D1 is set to a
constant duty ratio corresponding to the fan speed NF2(1) and the
constant value first maximum drive voltage VM1 is supplied to the
brushless motor 12 in accordance with this.
[0070] Further, as the second duty ratio D2, as shown in FIG. 7, a
value is selected set so as to monotonously increase from a duty
ratio corresponding to the minimum speed Nf0 as the coolant
pressure Pc becomes larger in the period from the pressure P1 to
the pressure P2 (>P1). Due to this, a first drive voltage V1 is
supplied to the brushless motor 12. Further, when the coolant
pressure Pc is the pressure threshold value P2 or more, the first
duty ratio D1 is set to a constant duty ratio corresponding to the
fan speed number of rotations of the fan per second NF2(1) and,
accompanied by this, the constant value first maximum drive voltage
VM1 is supplied to the brushless motor 12. Hereinafter, the fan
speed means the number of rotations of the fan.
[0071] In this way, the first and second duty ratios D1 and D2 are
values showing the speed of the brushless motor 12. This
corresponds to the speed of the first electric fan 10, that is, the
flow rate. Note that the minimum speed Nf0 may also be zero
(stopped) or a finite value.
[0072] FIG. 8 is a graph of the control characteristic of the brush
motor 22 and also shows the control characteristic graphs of the
brushless motor 12 of FIG. 6 and FIG. 7.
[0073] As shown in FIG. 8, the third duty ratio D3 is is selected
as a value which monotonously increases along with the rise of the
water temperature Tw in the period from the temperature T1 to the
temperature T2 (>T1). Due to this, the second drive voltage V2
is supplied to the brush motor 22. Further, when the water
temperature Tw is the temperature threshold value T2 or more, the
third duty ratio D3 is set to a constant duty ratio and a constant
value constituted by the second maximum drive voltage VM2 is
supplied to the brush motor 22 in accordance with this.
[0074] Alternatively, the third duty ratio D3 (corresponding to the
second drive voltage V2) is set so as to monotonously increase
along with the rise of the coolant pressure Pc as shown in FIG. 8
and so as to become a constant duty ratio (corresponding to the
second maximum drive voltage VM2) when the coolant pressure Pc is
the pressure threshold value Pc or more.
[0075] Note that the third duty ratio D3 is a value indicating the
speed of the brush motor 22. This corresponds to the speed, that
is, flow rate, of the second electric fan 20.
[0076] Further, as shown in FIG. 8, the second drive voltage V2 and
second maximum drive voltage VM2 supplied to the brush motor 22 are
set so as to become lower than the first drive voltage V1 and the
first maximum drive voltage VM1 supplied to the brushless motor 12.
Due to this, it is possible to suppress hot air sneaking to the
locations blown upon by the second electric fan 20 and to extend
the lifetime of the brush motor 22.
[0077] Next, at step S120, the larger of the first and second duty
ratios D1 and D2 determined from the water temperature Tw and the
coolant pressure Pc is selected and used as the duty ratio Ds.
[0078] Further, at step S130, a pulse signal of this selected duty
ratio Ds is output to the brushless motor control unit 31a of the
control unit 31 of the electric fan drive circuit 30.
[0079] Here, the brushless motor control unit 31a detects the
target speed based on the duty ratio Ds of the pulse signal,
detects the detected position of the rotor 12b based on the
detection output from the magnetic pole sensor 13, generates a
drive signal including the detected position of the rotor 12b and
the target speed, and outputs this to the power logic generation
circuit 31b.
[0080] Along with this, the power logic generation circuit 31b
individually switches the transistors U+, V+, W+, U-, V-, and W-
forming the brushless motor driver 33 based on the drive signal
from the brushless motor control unit 31a so as to make the actual
speed of the brushless motor 12 approach the target speed.
[0081] Further, these transistors U+, V+, W+, U-, V-, and W- supply
three-phase AC power to the stator coil 12a by the individual
switching. Further, among the transistors U+, V+, W+, U-, V-, and
W-, the low potential side transistors U-, V-, and W- are
controlled by PWM based on the control of the power logic
generation circuit 31b.
[0082] Along with this, by control of the three-phase AC power
supplied to the stator coil 12a, the speed of the rotor 12b and in
turn the speed of the rotor 11 is controlled. Due to this, the
speed of the rotor 11 is controlled based on the duty ratio Ds of
the pulse signal.
[0083] That is, the first electric fan 10 can be made to send
cooling air of the flow rate determined in accordance with the
detection signals Tw and Pc to the radiator 100 and the condenser
110.
[0084] Further, at step S140, a pulse signal of the third duty
ratio D3 determined above is output to the brush motor control unit
31c of the control unit 31 of the electric fan drive circuit
30.
[0085] Along with this, the brush motor control unit 31c controls
the brush motor driver 33 so that the brush motor driver 33 drives
the brush motor 22 to the target speed by the drive voltage V2
corresponding to the third duty ratio D3 of the pulse signal.
[0086] In this case, the second electric fan 20 can be made to send
cooling air of the flow rate determined in accordance with the
detection signal Tw (or Pc) to the radiator 100 and the condenser
110.
[0087] Due to this, the second electric fan 20 can send cooling air
to the radiator 100 and the condenser 110 along with the first
electric fan 10.
[0088] Below, the actions and effects of this embodiment will be
explained.
[0089] According to this embodiment, while the first electric fan
10 is operating, the second electric fan 20 is also operating
without stopping, so in the operating region of the second electric
fan 20, unevenness of the distribution of the flow rate caused by
hot air sneaking in to the front of the vehicle is suppressed. Due
to this, it is possible to suppress a drop in the cooling
efficiency in the heat exchange unit (radiator 100 and condenser
110).
[0090] Simultaneously, since the drive voltage V2 of the brush
motor 22 of the second electric fan 20 is controlled to be smaller
than drive voltage V1 of the brushless motor 12 of the first
electric fan 10 at all times, it is possible to extend the lifetime
of the brush motor 22 and possible to extend the lifetime of the
electric fan system.
Modifications of First Embodiment
[0091] In the above embodiment, the second drive voltage V2
supplied to the brush motor 22 driving the second electric fan 20
was set so as to linearly increase in accordance with the increase
in the water temperature Tw (or coolant pressure Pc) up to the
temperature threshold value T2 (or pressure threshold value P2),
but the invention is not limited to this. For example, as shown in
FIG. 9, it is also possible to make the second drive voltage V2
increase stepwise in accordance with the increase in the water
temperature Tw or coolant pressure Pc under condition of being
lower than the first drive voltage V1.
[0092] In the above embodiment, the example was explained of
setting the second drive voltage V2 supplied to the brush motor 22
driving the second electric fan 20 based on the water temperature
Tw or coolant pressure Pc, but the invention is not limited to
this. That is, in the same way as the method of determining the
control instruction value of the brushless motor 12 constituted by
the duty ratio Ds, it is also possible to make the larger of the
third duty ratio D3(T) set in accordance with the water temperature
Tw and the third duty ratio D3(P) set in accordance with the
coolant pressure Pc in FIG. 8 the third duty ratio D3 and control
the brush motor 22 based on this selected third duty ratio D3.
[0093] In the above embodiment, the example was explained of
controlling the brushless motor 12 and the brush motor 22 driving
the first and second electric fans 10 and 20 based on the water
temperature Tw and/or the coolant pressure Pc, but the invention is
not limited to this. It is also possible to control these in
accordance with the engine speed, vehicle speed detected by a
vehicle speed sensor 43 etc. Alternatively, it is also possible to
control the motors 12 and 22 in accordance with the rates of change
of the water temperature Tw and coolant pressure Pc.
Second Embodiment
[0094] FIG. 10 shows the configuration of an electric fan system
for a vehicle according to a second embodiment of the present
invention. FIG. 10 is a view showing the partial configuration in
the engine compartment of a vehicle.
[0095] The electric fan system for a vehicle is provided with, as
shown in FIG. 10, electric fans 10 and 20. The electric fans 10 and
10 are arranged inside the engine compartment in the front-rear
direction at the front side of a water-cooled engine 300. The
electric fan 10 is the same as that shown in FIG. 1 and is
comprised of a rotor and a brushless motor for driving rotation of
the rotor, while the electric fan 20 is comprised of a rotor and a
brush motor for driving rotation of the rotor.
[0096] On the other hand, at the front side of the electric fans 10
and 20, a radiator 100 and a condenser 110 are arranged in parallel
in the front-rear direction. The electric fans 10 and 20 function
to send cooling air to the radiator 100 and the condenser 110 to
cool the radiator 100 and the condenser 110.
[0097] Here, the radiator 100 is a heat exchanger for cooling the
cooling water circulating inside the water-cooled engine 300. The
condenser 110 is one component of the vehicle air-conditioning
system for air-conditioning of the inside of the vehicle
compartment in a refrigeration cycle (refrigeration cycle system)
and cools the coolant circulating through the inside of the vehicle
air-conditioning system.
[0098] At the left side of the water-cooled engine in the engine
compartment, an electronic control unit (ECU) box 410 is arranged.
This ECU box 410 holds an electronic control unit 40 (FIG. 11) for
controlling the engine.
[0099] Next, the schematic electrical system of the electric fan
system for a vehicle of the present embodiment will be explained
using FIG. 11. FIG. 11 is a block diagram showing the schematic
electrical system of the electric fan system for a vehicle.
[0100] The electric fan system for a vehicle, as shown in FIG. 11,
is comprised of an engine electronic control unit (E/G-ECU) 40a.
The electronic control unit 40a is comprised of a microcomputer, a
memory, peripheral circuits, etc. and controls the electric
actuators of the water-cooled engine 300. Further, the electronic
control unit 40a controls the electric fans 10 and 20 based on the
detection output of a temperature sensor 60 for detecting the
temperature of the cooling water of the engine. The temperature
sensor 60 detects the temperature of the cooling water near the
cooling water outlet of the radiator 100 or near the cooling water
outlet of the engine 300.
[0101] Here, in the present embodiment, when using the electronic
control unit 40a to control the electric fans 10 and 20, in
addition to the temperature sensor 60, the detection output of a
temperature sensor 61 for detecting the surface temperature of an
ECU box 410 as the part temperature is used.
[0102] Further, the electric fan system for a vehicle is provided
with an electric fan drive circuit 30a. This electric fan drive
circuit 30a is comprised of a control unit 31a, a brushless motor
driver 32a, and a brush motor driver 33a. The control unit 31a
controls the brushless motor driver 32a and the brush motor driver
33a based on control instruction values instructed from the
electronic control unit 40a.
[0103] The brush motor driver 33a is supplied with power from the
DC power supply Ba and gives voltage to the electric fan 20 to
control its speed. Specifically, the brush motor driver 33a adjusts
the value of the voltage given to the brush motor 22 of the
electric fan 20 so as to adjust the speed of the brush motor 22 and
in turn the flow rate of the electric fan 20. That brush motor 22
is comprised of a known electric DC motor.
[0104] On the other hand, the brushless motor driver 33a is
provided with a known inverter circuit serving as a three-phase
full wave bridge circuit supplied with power from the DC power
supply Ba and generating three-phase AC power for supply to the
brushless motor 12 and a control circuit controlling this inverter
circuit by PWN and outputting a three-phase AC power to be supplied
to the brushless motor 12 from the inverter circuit to the
brushless motor 12. The brushless motor 12 is comprised of a
three-phase synchronous device motor.
[0105] Next, the operation of this embodiment will be explained
using FIG. 12 and FIG. 13. FIG. 12 is a flow chart of the
processing for fan control by the electronic control unit 40a. The
electronic control unit 40a runs a computer program stored in
advance in accordance with the flow chart shown in FIG. 12.
[0106] First, the temperature of the cooling water (water
temperature) is read from the temperature sensor 60 and the surface
temperature of the ECU box 410 is read as the part temperature from
the temperature sensor 61. Further, it is judged if the temperature
of the cooling water (water temperature) is the threshold value Tw
or more (step S121).
[0107] Here, when the temperature of the cooling water (water
temperature) is less than a threshold value Tw (temperature of
cooling water.ltoreq.Tw), it is judged NO. That is, it is judged
that it is not necessary for the electric fan 10 to cool the
radiator 100 and the condenser 110.
[0108] Further, it is judged if the part temperature constituted by
the surface temperature of the ECU box 410 is a threshold value Ta
or more (step S122). When the part temperature is the threshold
value Ta or more (part temperature.gtoreq.Ta), it is judged YES.
That is, it is judged that it is necessary for the electric fan 10
to cool the ECU box 410, that is, the electronic control unit 40a
itself.
[0109] In this case, in the following way, the fan speed (that is,
flow rate) required for cooling the ECU box 410 by the electric fan
10 based on the control pattern A stored in advance in the memory
is calculated as a control instruction value. Here, the control
pattern A, as shown in FIG. 13, is a characteristic graph having an
abscissa showing the part temperature and the ordinate showing the
fan speed where the fan speed and the part temperature are
specified one-to-one.
[0110] Here, in the control pattern A, when the part temperature is
within the intermediate temperature range, the fan speed becomes
higher the higher the part temperature. Further, when the part
temperature is less than the intermediate temperature range, the
fan speed becomes the constant value of zero. That is, the electric
fan 10 enters the OFF state. On the other hand, when the part
temperature is above the intermediate temperature range, the fan
speed becomes a constant value.
[0111] Further, the fan speed corresponding to the detected
temperature read from the temperature sensor 61 (part temperature)
is determined based on this control pattern A and the thus
determined fan speed is output as the duty ratio of the control
pulse signal to the control unit 31a of the electric fan drive
circuit 30a.
[0112] On the other hand, the control unit 31a drives the brushless
motor driver 32a based on the duty ratio of the control pulse
signal, so the brushless motor driver 32a supplies three-phase AC
power corresponding to the duty ratio to the brushless motor 12 of
the electric fan 10.
[0113] Here, the three-phase AC power becomes larger as the duty
ratio becomes larger, while the three-phase AC power becomes
smaller as the duty ratio becomes smaller. Therefore, the speed of
the brushless motor 12 becomes higher as the duty ratio becomes
larger, and the speed of the brushless motor 12 becomes lower as
the duty ratio becomes smaller.
[0114] Since the speed of the brushless motor 12 is controlled in
this way, the fan speed of the electric fan 10 is controlled in
accordance with the part temperature.
[0115] On the other hand, the electric fan 10 is arranged at the
right side in the engine compartment and the rotor of the electric
fan 10 turns clockwise, so the air blown by the rotor flows to the
right side of the engine 300 as shown by the arrows Y1 in FIG. 10.
Therefore, the air pressure in the space at the right side of the
engine 300 becomes higher and relative to this the air pressure in
the space at the left side of the engine 300 (that is, around the
ECU box 410) becomes lower.
[0116] Therefore, outside air flows into the left side space from
the front of the vehicle as shown by the arrow Y2. Here, the ECU
box 410 (that is, the electronic control unit 40a) is arranged in
the left side space, so the ECU box 410 is cooled by the outside
air flowing in from the front of the vehicle.
[0117] After this, the routine proceeds to step S129, wherein the
operating state of the electric fan 20 is decided based on the
control pattern C. This control pattern C, as shown in FIG. 14, is
a characteristic graph having an abscissa showing the cooling water
temperature and the ordinate showing the operating state of the
electric fan 20 where the operating state of the electric fan 20
and the cooling water temperature are specified one-to-one.
[0118] Specifically, in the control pattern C, to avoid control
hunting of the operating state of the electric fan 20, hysteresis
is set between the cooling water temperature and the operating
state. When the cooling water temperature becomes higher than the
temperature Ty, the electric fan 20 enters the ON state. On the
other hand, when the cooling water temperature becomes lower than
the temperature Tx (<Ty), the electric fan 20 enters the OFF
state.
[0119] Based on this control pattern C, the operating state of the
electric fan 20 corresponding to the cooling water temperature read
from the temperature sensor 60 is determined and the thus decided
operating state is output as the duty ratio of the control pulse
signal to the control unit 31a of the electric fan drive circuit
30a.
[0120] Here, when deciding on the ON state as the operating state,
the duty ratio dn is determined, while when deciding on the OFF
state as the operating state, the duty ratio df (not equal to dn)
is determined.
[0121] On the other hand, the control unit 31a drives the brush
motor driver 33a based on the duty ratio of the control pulse
signal, so the brush motor driver 32a controls the brush motor 22
of the electric fan 20 so as to correspond to that duty ratio.
[0122] Here, in the case of the duty ratio dn, the brush motor
driver 33a supplies a constant voltage to the brush motor 22, so
the brush motor 22 operates at a constant speed. Therefore, the
electric fan 20 operates by a constant fan speed, so the radiator
100 and the condenser 110 are cooled by the air blown from the
electric fan 20.
[0123] On the other hand, in the case of the duty ratio df, the
brush motor driver 32a stops the supply of voltage to the brush
motor 22, so the electric fan 20 stops the fan operation.
[0124] Further, when the temperature of the cooling water (water
temperature) is the threshold value Tw or more at the above step
S121 (temperature of cooling water>Tw), it is judged YES. That
is, it is judged that it is necessary for the electric fan 10 to
cool the radiator 100 and the condenser 110.
[0125] Next, the routine proceeds to step S125, where the fan speed
(that is, flow rate) required for cooling the radiator 100 and the
condenser 110 by the electric fan 10 based on the control pattern B
stored in advance in the memory is calculated as a control
instruction value. Here, the control pattern B, as shown in FIG.
14, is a characteristic graph having an abscissa showing the
cooling water temperature and the ordinate showing the fan speed
where the fan speed and the cooling water temperature are specified
one-to-one.
[0126] Here, in the control pattern B, when the cooling water
temperature is within the intermediate temperature range, the fan
speed becomes higher the higher the cooling water temperature.
Further, when the cooling water temperature is less than the
intermediate temperature range, the fan speed becomes the constant
value of zero. That is, the electric fan 10 enters the OFF state.
On the other hand, when the cooling water temperature is above the
intermediate temperature range, the fan speed becomes a constant
value.
[0127] Further, the fan speed corresponding to the detected
temperature read from the temperature sensor 60 (cooling water
temperature) (hereinafter referred to as the "fan speed Kb") is
determined based on this control pattern B.
[0128] Next, it is judged if the part temperature (surface
temperature of ECU box 410) is the threshold value Ta or more (step
S126). Further, when the part temperature is less than the
threshold value Ta (part temperature<Ta), it is judged NO. That
is, it is judged that there is no need for the electric fan 10 to
cool the ECU box 410, that is, the electronic control unit 40a
itself.
[0129] In this case, as explained above, the fan speed Kb
determined based on the control pattern B is output as the duty
ratio of the control pulse signal to the control unit 31a of the
electric fan drive circuit 30a.
[0130] Therefore, the control unit 31b drives the brushless motor
driver 32a based on the duty ratio Kb of the control pulse signal,
so the brushless motor driver 32a supplies three-phase AC power
corresponding to the duty ratio to the brushless motor 12 of the
electric fan 10.
[0131] Here, the speed of the brushless motor 12 is controlled so
as to correspond to the duty ratio Kb, so the fan speed of the
electric fan is controlled in accordance with the cooling water
temperature. Further, the air from the electric fan 10 cools the
radiator 100 and the condenser 110.
[0132] Here, explaining the relationship between the control
patterns B and C, in the control pattern B, when the cooling water
temperature is higher than the temperature TSB, the brushless motor
12 enters the ON state, while when the cooling water temperature is
lower than the temperature TSB, the brushless motor 12 enters the
OFF state.
[0133] On the other hand, in the control pattern C, when the
cooling water temperature becomes higher than the temperature Ty,
the electric fan 20 enters the ON state, while when the cooling
water temperature becomes lower than the temperature Tx, the
electric fan 20 enters the OFF state.
[0134] Further, since the temperatures Tx and Ty are set higher
than the temperature TSB, in the low cooling water temperature
region, only the electric fan 10 operates. When the cooling water
temperature reaches the high temperature region, both the electric
fans 10 and 20 operate. Due to this, the frequency of operation of
the electric fan 10 becomes higher than the frequency of operation
of the electric fan 20. That is, the electric fan 10 is operated
preferentially over the electric fan 20.
[0135] Note that when the part temperature is the threshold value
Ta or more at the above step S126 (part temperature.gtoreq.Ta), it
is judged YES. That is, it is judged that it is necessary to use
the electric fan 10 to cool the ECU box 410, that is, the
electronic control unit 40 itself.
[0136] In this case, in the same way as the processing for control
of the above step S130, the fan speed of the electric fan 10
(hereinafter referred to as the "fan speed Ka") is determined based
on the control pattern A and the part temperature (step S127).
Further, the higher of the fan speeds Ka and Kb is selected and the
selected fan speed Kc is output as the duty ratio of the control
pulse signal to the control unit 51 of the power fan drive circuit
50.
[0137] Therefore, the control unit 31a drives the brushless motor
driver 32a based on the duty ratio Kc of the control pulse signal,
so the brushless motor driver 32a supplies three-phase AC powr
corresponding to the duty ratio to the brushless motor 12 of the
electric fan 10.
[0138] Here, since the speed of the brushless motor 12 is
controlled so as to correspond to the duty ratio Kc, the fan speed
of the electric fan 10 is controlled in accordance with the cooling
water temperature and the part temperature. The air blown by the
electric fan 10 cools all of the radiator 100, condenser 110, and
ECU box 410 (electronic control unit 40a).
[0139] After this, the routine proceeds to step S129, where
processing is performed to control the brush motor 22. Note that at
step S122, when the part temperature is less than a threshold value
Ta (part temperature<Ta), it is judged NO, the operation of the
electric fan 10 is prohibited, and the routine proceeds to step
S129.
[0140] Below the actions and effects of this embodiment will be
explained. That is, the electric fan system for a vehicle of this
embodiment circulates cooling air to a radiator 100 for cooling
cooling water circulating inside a water-cooled engine 300 for
vehicle operation and a condenser 110 for cooling a coolant
circulating inside a vehicle air-conditioning system. It is
provided with an electric fan 10 for circulating cooling air to the
radiator 100 and condenser 110 by operation of a brushless motor
12, an electric fan 20 for circulating cooling air to the radiator
100 and condenser 110 by a brush motor 22, and an electronic
control unit 40a for operating the electric fan 10 preferentially
over the electric fan 20 based on the temperature of the engine
cooling water, wherein the electric fan 10 is designed to cool the
ECU box 410 (that is, the electronic control unit 40a) in addition
to the radiator 100 and the condenser 110.
[0141] According to the present embodiment, since the electric fan
10 is operated preferentially over the electric fan 20, the wear of
the electric fan 20, that is, the wear of the brush motor 22, can
be suppressed. Further, the electric fan 10 is made to also use
cooling air to cool the ECU box 410 as one of the "other
vehicle-mounted parts" besides the radiator 100 and the condenser
110. Therefore, it is possible to cool the ECU box 410 (other
vehicle-mounted part) while extending the lifetime.
[0142] Here, the electronic control unit 40a determines the fan
speed (flow rate) of the electric fan 10 based on the surface
temperature of the ECU box 410 and the temperature of the engine
cooling water, so the radiator 100, condenser 110, and ECU box 410
(that is, the electronic control unit 40a) can be suitably
cooled.
[0143] Further, in the embodiment, rubber engine mounts 310 are
arranged at the four corners of the water-cooled engine between the
water-cooled engine 300 and chassis. The rubber engine mounts 310
function to suppress transmission of vibration of the water-cooled
engine to the chassis.
[0144] Here, when the rubber engine mounts 310 become high in
temperature, they deteriorate in characteristics, so cooling is
required, but since the air blown from the electric fan 10 flows as
shown by the arrows Y1 in FIG. 11, the rubber engine mounts 310 at
the right side are cooled by the cooling air from the electric fan
10.
Modifications of Second Embodiment
[0145] In the above embodiment, the example was explained of using
the temperature of the cooling water of the engine 300 when
controlling the electric fans 10 and 20, but the invention is not
limited to this. The coolant temperature or the coolant pressure
may also be used. Further, any of the cooling water temperature,
coolant temperature, and coolant pressure may be used in
combination.
[0146] In the above embodiment, the example was explained of not
causing the air blown from the electric fan 10 to directly strike
the ECU box 410, but to lower the air pressure around the ECU box
410 and cool the ECU box 410 by the outside air flowing in from the
sides of the vehicle, but instead of this it is also possible to
make the air blown from the electric fan 10 directly strike the ECU
box 410 so as to cool the ECU box 410.
[0147] In the above embodiment, the example was explained of
employing the ECU box 410 as one of the "other vehicle-mounted
parts", detecting the surface temperature of the ECU box 410, and
using the detected temperature to control the speed of the electric
fan 10, but instead of this it is also possible to employ the
headlamps or rubber engine mounts 310 as the "other vehicle-mounted
part", detect the temperature of the same, and use the detected
temperature to control the speed of the electric fan 10.
[0148] For example, when cooling the headlamps 200 (specifically,
the headlamps using light emitting diodes), as shown in FIG. 16, it
is also possible to employ ducts D1 and D2 for blowing air from the
electric fan 10 to the headlamps 200.
[0149] In the above embodiment, the example was explained of the
electric fan 20 entering the ON state when the temperature of the
cooling water becomes higher than the temperature Ty and the
electric fan 20 entering the OFF state when the temperature of the
cooling water becomes lower than the temperature Tx in accordance
with the control pattern C, but the invention is not limited to
this. Even if the temperature of the cooling water becomes lower
than the temperature Ta, so long as to an extent where no wear of
the brush motor 22 occurs, it is possible to operate the electric
fan 20.
[0150] In the above embodiment, the example was explained of
determining one of the ON state and OFF state of the operating
states of the electric fan 20 based on the temperature of the
cooling water, but the invention is not limited to this. It is also
possible to make the fan speed of the electric fan 20 gradually
rise along with the rise in temperature of the cooling water and
make the fan speed of the electric fan 20 gradually fall along with
the fall in temperature of the cooling water.
[0151] In this case, the relationship between the control patterns
B and C becomes as shown in FIG. 17. That is, compared with the
control pattern B, the inclination of the control pattern C is
smaller. If the power supplied to the brush motor 22 is set lower
than the power supplied to the brushless motor 12, the frequency of
operation of the brushless motor 12 becomes higher compared with
the frequency of operation of the brush motor 22.
[0152] That is, the brushless motor 12 is operated preferentially
over the brush motor 22. Therefore, compared with the electrical
wear of the brushless motor 12, the electric wear of the brush
motor 22 can be reduced. Along with this, it is possible to
suppress electrical wear of the electric fan 20 compared with the
electric fan 10, so the lifetime can be extended.
[0153] In the second embodiment, the example was explained where
the electric fan 10 (brushless motor 12) was arranged at the right
side and the electric fan 20 (brush motor 22) was arranged at the
left side, but the invention is not limited to this. It is also
possible to arrange the electric fan 10 (brushless motor 12) at the
left side and arrange the electric fan 20 (brush motor 22) at the
right side.
[0154] Further, in working the invention, the fan rotational
directions of the electric fans 10 and 20 may be freely set.
Further, the other vehicle-mounted parts (for example, the ECU box
410) which have to be cooled may also be freely arranged.
[0155] Explaining the correspondence between the second embodiment
and the claims, the electronic control unit 40a corresponds to the
control means.
[0156] While the invention has been described with reference to
specific embodiments chosen for purpose of illustration, it should
be apparent that numerous modifications could be made thereto by
those skilled in the art without departing from the basic concept
and scope of the invention.
* * * * *