U.S. patent application number 12/145398 was filed with the patent office on 2008-10-16 for vehicle rooftop engine cooling system.
This patent application is currently assigned to ISE CORPORATION. Invention is credited to Juergen Schulte, Kevin Thomas Stone.
Application Number | 20080251039 12/145398 |
Document ID | / |
Family ID | 46322183 |
Filed Date | 2008-10-16 |
United States Patent
Application |
20080251039 |
Kind Code |
A1 |
Stone; Kevin Thomas ; et
al. |
October 16, 2008 |
Vehicle Rooftop Engine Cooling System
Abstract
A method of using an engine cooling system with a bus includes
providing a horizontal rooftop engine cooling system including a
radiator unit through which coolant fluid flows for removing heat
from the radiator unit, a fan to assist in removing heat from the
radiator unit, and a continuously variable power drive and speed
control system for controlling power to and the speed of the fan;
horizontally locating the rooftop engine cooling system on a
rooftop of the bus; interconnecting the radiator unit of the
rooftop engine cooling system to a passage of an engine of the bus
to allow coolant to flow between the engine and the rooftop cooling
system to cool the engine; and controlling power to and the speed
of the fan with the continuously variable power drive and speed
control system using pulse width modulation.
Inventors: |
Stone; Kevin Thomas; (San
Diego, CA) ; Schulte; Juergen; (San Diego,
CA) |
Correspondence
Address: |
PROCOPIO, CORY, HARGREAVES & SAVITCH LLP
530 B STREET, SUITE 2100
SAN DIEGO
CA
92101
US
|
Assignee: |
ISE CORPORATION
Poway
CA
|
Family ID: |
46322183 |
Appl. No.: |
12/145398 |
Filed: |
June 24, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11169184 |
Jun 28, 2005 |
|
|
|
12145398 |
|
|
|
|
10339735 |
Jan 8, 2003 |
6910529 |
|
|
11169184 |
|
|
|
|
Current U.S.
Class: |
123/41.48 ;
180/68.4 |
Current CPC
Class: |
B60K 11/04 20130101;
F28F 9/001 20130101; F01P 2011/063 20130101; F28D 1/04 20130101;
F01P 7/08 20130101; F01P 2005/025 20130101; F01P 3/18 20130101 |
Class at
Publication: |
123/41.48 ;
180/68.4 |
International
Class: |
F01P 7/14 20060101
F01P007/14 |
Claims
1. A method of using an engine cooling system with a bus including
a rooftop and an engine in an engine compartment for propelling the
bus, the engine including a passage for allowing coolant to flow
there through for cooling the engine, the method comprising:
providing a horizontal rooftop engine cooling system including a
radiator unit through which coolant fluid flows for removing heat
from the radiator unit, a fan to assist in removing heat from the
radiator unit, and a continuously variable power drive and speed
control system for controlling power to and the speed of the fan;
horizontally locating the rooftop engine cooling system on the
rooftop of the bus; interconnecting the radiator unit of the
rooftop engine cooling system to the passage of the engine to allow
coolant to flow between the engine and the rooftop cooling system
to cool the engine; controlling power to and the speed of the fan
with the continuously variable power drive and speed control system
using pulse width modulation.
2. The method of claim 1, wherein the continuously variable power
drive and speed control system includes a temperature sensor to
determine coolant temperature, a controller to determine minimum
desired fan speed, and a switching controller to vary voltage to
the fan, and the method further includes measuring temperature of
the coolant in the radiator unit with the temperature sensor,
determining the appropriate fan speed for removing heat from the
radiator unit based on the temperature sensed, controlling the
switching controller to vary the voltage to the fan for controlling
the fan speed.
3. The method of claim 2, wherein controlling the switching
controller includes controlling the switching controller with a
pulse width modulated waveform.
4. The method of claim 1, wherein the rooftop of the bus includes
an area, and the rooftop engine cooling system includes a footprint
area that is at least 70% of the area of the rooftop of the
bus.
5. The method of claim 1, wherein the rooftop of the bus includes
an area, and the rooftop engine cooling system includes a footprint
area that is at least 80% of the area of the rooftop of the
bus.
6. The method of claim 1, wherein the rooftop of the bus includes
an area, and the rooftop engine cooling system includes a footprint
area that is at least 90% of the area of the rooftop of the
bus.
7. The method of claim 1, wherein the radiator unit is
longitudinally oriented with respect to the bus.
8. The method of claim 1, wherein the rooftop engine cooling system
is used to cool a charge air cooler of the bus.
9. The method of claim 1, wherein the rooftop engine cooling system
is used to cool a motor of the bus.
10. The method of claim 1, wherein the rooftop engine cooling
system is used to cool an inverter drive controller of the bus.
11. The method of claim 1, wherein the rooftop engine cooling
system is used to a bus electric drive element.
12. A method of using an engine cooling system with a bus including
a rooftop and an engine in an engine compartment for propelling the
bus, the engine including a passage for allowing coolant to flow
there through for cooling the engine, the method comprising:
providing a horizontal rooftop engine cooling system including a
radiator unit through which coolant fluid flows for removing heat
from the radiator unit; horizontally locating the rooftop engine
cooling system on the rooftop of the bus; interconnecting the
radiator unit of the rooftop engine cooling system to the passage
of the engine to allow coolant to flow between the engine and the
rooftop cooling system to cool the engine, wherein the rooftop of
the bus includes an area, and the rooftop engine cooling system
includes a footprint area that is at least 70% of the area of the
rooftop of the bus.
13. The method of claim 12, wherein the rooftop engine cooling
system includes a footprint area that is at least 80% of the area
of the rooftop of the bus.
14. The method of claim 12, wherein the rooftop engine cooling
system includes a footprint area that is at least 90% of the area
of the rooftop of the bus.
15. The method of claim 12, wherein the radiator unit is
longitudinally oriented with respect to the bus.
16. The method of claim 12, wherein the rooftop engine cooling
system is used to cool a charge air cooler of the bus.
17. The method of claim 12, wherein the rooftop engine cooling
system is used to cool a motor of the bus.
18. The method of claim 12, wherein the rooftop engine cooling
system is used to cool an inverter drive controller of the bus.
19. The method of claim 12, wherein the rooftop engine cooling
system is used to a bus electric drive element.
20. A method of using an engine cooling system with a bus including
a rooftop and an engine in an engine compartment for propelling the
bus, the engine including a passage for allowing coolant to flow
there through for cooling the engine, the method comprising:
providing a horizontal rooftop engine cooling system including a
radiator unit through which coolant fluid flows for removing heat
from the radiator unit; horizontally locating the rooftop engine
cooling system on the rooftop of the bus; interconnecting the
radiator unit of the rooftop engine cooling system to the passage
of the engine to allow coolant to flow between the engine and the
rooftop cooling system to cool the engine; interconnecting the
radiator unit of the rooftop engine cooling system to a non-engine
component of the bus to allow coolant to flow there between to cool
the bus component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/169,184 filed Jun. 28, 2005, which is a continuation-in-part
application of U.S. application Ser. No. 10/339,735, filed on Jan.
8, 2003, which issued as U.S. Pat. No. 6,910,529 on Jun. 28, 2005.
All of the above applications are incorporated by reference as
though set forth in full.
FIELD OF THE INVENTION
[0002] The field of the invention relates, in general, to systems
and methods for cooling motor vehicle engines, and, in particular,
to systems and methods for cooling motor vehicle engines and other
vehicular components of buses.
BACKGROUND OF THE INVENTION
[0003] Some type of radiator or heat exchanger is normally required
to remove heat from an internal combustion engine. For most
applications, the power required to turn the fan that moves air
through the radiator has been obtained through some mechanical,
hydraulic, or belt-driven connection to the engine crankshaft.
[0004] A conventional radiator includes an intake tank, a core made
up of a plurality of finned tubes, and an exit tank connected by
hoses. The radiator may be used to cool the means of propulsion
(e.g., gas engine, diesel engine, fuel cell engine) in the motor
vehicle. The radiator may be filled with a coolant to radiate
superfluous heat from the engine into the air by means of
conduction and convection. Fans, which may be powered by the
vehicle engine or electrically powered, propel ambient air near the
surface of the road through the radiator core to accelerate the
cooling process. The radiator is typically placed in a vertical
orientation in close proximity to the vehicle engine in a tight,
confined engine compartment. The fan draws the air through the
radiator core area and directs it around the confined engine
compartment. The ambient air passing through the radiator is heated
and passes over the engine, tightly enclosed within the engine
compartment. The air then is forced downward, under the vehicle.
The location of the radiator often makes it difficult to perform
maintenance on the engine. In some cases, the radiator shroud or
the complete radiator must be removed to perform certain tasks.
[0005] Large vehicles such as buses, motor homes, and delivery vans
have limited frontal access to the engine compartment that is often
partially or completely blocked by the radiator of the vehicle.
This can make maintenance on the engine or other engine compartment
components very difficult. Standard bus radiator installations are
close to the street level, typically on the street side of the bus.
This low mounting location increases the dirt and debris collected
by the radiator, and, hence, increases the number of times the
radiator needs to be cleaned and checked, and decreases the
cleaning intervals. Radiator cleaning requirements stipulate that
the radiator be cleaned in the opposite direction of the airflow.
Therefore, most radiators need to be cleaned from the inside of the
engine compartment. This may require partial disassembly of the
radiator shroud to effectively clean the radiator, increasing the
time and complexity of the radiator cleaning process.
SUMMARY OF THE INVENTION
[0006] Accordingly, an aspect of the invention relates to a new and
unique vehicle rooftop engine cooling system that improves the
efficiency of present engine cooling systems used on buses. The
engine cooling system includes one or more radiator units that are
preferably horizontally oriented on the rooftop of a bus.
Interconnected tubing connects the engine in the engine compartment
to the one or more radiator units on the rooftop of a vehicle.
[0007] Horizontally orienting the one or more radiator units on the
rooftop of a vehicle reduces the power load of the radiator fans on
the internal combustion engine and/or battery. The horizontal
rooftop engine cooling system may include electrically driven,
thermostatically controlled fans to assist in cooling the rooftop
engine cooling system. The large surface area of the roof top of
the bus significantly reduces the fan power requirement by more
than a factor of ten compared to a standard radiator in an engine
compartment. Standard bus radiators/intercoolers consume up to 50
HP of engine power to drive the radiator cooling fan alone. The
electrically driven radiator fans used with the horizontal rooftop
engine cooling system consume less than 3 HP of engine power for
equivalent cooling. The larger surface area of the roof top reduces
the required airspeed through the radiator units and the required
air pressure drop across the radiator units, thus, increasing the
cooling system efficiency of the radiator units.
[0008] The horizontal rooftop engine cooling system also allows for
natural convection air current to rise through the radiator units
in an unconfined area. With the radiator unconfined on the rooftop
of the vehicle, and with less demanding size limitations, the heat
may be dissipated in a natural upward direction, minimizing the use
of the electrically driven, thermostatically controlled fans.
Consequently, the load of the electrically driven, thermostatically
controlled fans is far less than that of fans of a standard
radiator located in the engine compartment of a vehicle or even
hydraulically powered fans mounted vertically on the rooftop.
[0009] A further benefit of locating the cooling system
horizontally on the rooftop of the vehicle is that some of the
cleanest and coolest air is available at the altitude of the
rooftop, reducing the number of times the radiator needs to be
serviced and increasing the duration between radiator cleanings.
Because radiator cleaning requirements stipulate that the radiator
be cleaned in the opposite direction of the airflow, the cooling
system can be cleaned by simply spraying water through the fan
orifices and shroud openings from outside of the cooling system.
This type of cleaning would occur each time the bus passes through
a normal bus wash cycle without any component disassembly. This is
much simpler and less time-consuming than cleaning a radiator from
the inside of the engine compartment, which may require partial
disassembly of the radiator shroud to effectively clean the
radiator.
[0010] Another aspect of the invention involves a method of using
an engine cooling system with a bus including a rooftop and an
engine in an engine compartment for propelling the bus, the engine
including a passage for allowing coolant to flow there through for
cooling the engine. The method includes providing a horizontal
rooftop engine cooling system including a radiator unit through
which coolant fluid flows for removing heat from the radiator unit,
a fan to assist in removing heat from the radiator unit, and a
continuously variable power drive and speed control system for
controlling power to and the speed of the fan; horizontally
locating the rooftop engine cooling system on the rooftop of the
bus; interconnecting the radiator unit of the rooftop engine
cooling system to the passage of the engine to allow coolant to
flow between the engine and the rooftop cooling system to cool the
engine; and controlling power to and the speed of the fan with the
continuously variable power drive and speed control system using
pulse width modulation.
[0011] A further aspect of the invention involves a method of using
an engine cooling system with a bus including a rooftop and an
engine in an engine compartment for propelling the bus, the engine
including a passage for allowing coolant to flow there through for
cooling the engine. The method includes providing a horizontal
rooftop engine cooling system including a radiator unit through
which coolant fluid flows for removing heat from the radiator unit;
horizontally locating the rooftop engine cooling system on the
rooftop of the bus; and interconnecting the radiator unit of the
rooftop engine cooling system to the passage of the engine to allow
coolant to flow between the engine and the rooftop cooling system
to cool the engine, wherein the rooftop of the bus includes an
area, and the rooftop engine cooling system includes a footprint
area that is at least 70% of the area of the rooftop of the
bus.
[0012] A still further aspect of the invention involves a method of
using an engine cooling system with a bus including a rooftop and
an engine in an engine compartment for propelling the bus, the
engine including a passage for allowing coolant to flow there
through for cooling the engine. The method includes providing a
horizontal rooftop engine cooling system including a radiator unit
through which coolant fluid flows for removing heat from the
radiator unit; horizontally locating the rooftop engine cooling
system on the rooftop of the bus; interconnecting the radiator unit
of the rooftop engine cooling system to the passage of the engine
to allow coolant to flow between the engine and the rooftop cooling
system to cool the engine; and interconnecting the radiator unit of
the rooftop engine cooling system to a non-engine component to
allow coolant to flow there between to cool the bus component. In a
preferred implementation of the above aspect of the invention, the
non-engine component is at least one of a generator, motor,
inverter drive controller, bus electric drive element, and charge
air cooler.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying drawings, which are incorporated in and
form a part of this specification, illustrate embodiments of the
invention and together with the description, serve to explain the
principles of this invention.
[0014] FIG. 1 depicts a perspective view of an embodiment of a
horizontal rooftop engine cooling system with two radiator units,
fan mounting shrouds, and an optional overflow tank all mounted
perpendicular to the direction of vehicle travel. Alternatively,
the cooling system may be mounted parallel to the direction of
vehicle travel.
[0015] FIG. 2 is a top plan view of the horizontal rooftop engine
cooling system illustrated in FIG. 1 with the optional overflow
tank and portions of a fan mounting shroud broken away to reveal a
radiator intake tank, a radiator core, and an exit tank.
[0016] FIG. 3 is a cross-sectional view of the horizontal rooftop
engine cooling system of FIG. 1 taken along lines 3-3 of FIG. 1 and
shows a radiator of one of the radiator units in a horizontal
position.
[0017] FIG. 4 is block diagram of an embodiment of a continuously
variable power drive and speed control system for the rooftop fans
of the rooftop engine cooling system.
[0018] FIG. 5 is a top plan view of another embodiment of a rooftop
engine cooling system where the rooftop engine cooling system
includes a footprint area that occupies substantially all of the
area of the rooftop of the bus.
[0019] FIG. 6 is a block diagram of an embodiment of a rooftop
cooling system that cools one or more of a generator, motor(s),
inverter drive controller(s), charge air cooler, bus electric drive
element(s), and other electrical component(s) of the bus requiring
cooling.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] With reference to FIG. 1, an embodiment of a horizontal
rooftop engine cooling system 10 will be described. The horizontal
rooftop engine cooling system 10 is preferably implemented on a
rooftop 11 of a bus; however, it should be fully understood that
the rooftop engine cooling system 10 may be applied to the rooftop
of any vehicle propelled by a propulsion system requiring cooling.
Further, the rooftop engine cooling system 10 may be incorporated
into new vehicles or may be a retrofitted onto existing
vehicles.
[0021] The rooftop engine cooling system 10 may include one or more
horizontal radiator units 12 and an optional overflow tank 14
located on the rooftop 11 of a vehicle 16. Each horizontal radiator
unit 12 may include one or more types of shrouds 18 having one or
more fan orifices 20 and one or more respective electrically
driven, thermostatically controlled fans 22 housed over a radiator
24.
[0022] The type of shroud 18 can be for fan mounting, aerodynamic
air-flow, or ornamental. A fan mounting shroud provides structure
for the mounting placement and proper spacing of the one or more
fans 22 from the radiator 24 and has one or more fan orifices 20 to
obtain a more uniform air flow for removing heat from the radiator
24. A fan mounting shroud is typically used with all automotive
radiator installations. An aerodynamic shroud has a surface design
that ducts and directs the air flow across a moving vehicle to
provide or assist the cooling air flow through the radiator 24. An
ornamental shroud is used to cover the cooling system installation
for aesthetic appearance and/or safety protection against
inadvertent fan blade contact. The electrically driven,
thermostatically controlled fans 22 may be electrically connected
to one or more power sources of the vehicle 16 through wiring. Any
of the shrouds 18 may be attached to a horizontal mounting frame
25, which is mounted to the rooftop 11 of the vehicle 16.
[0023] The configuration of the horizontal radiator units 12, and
the number of fan orifices 20 and fans 22 may vary depending upon
such factors as the configuration of the rooftop 11 of the vehicle
16, the size of the fans 22, and the cooling requirements of the
vehicle engine. Although the one or more elongated radiator units
12 of the cooling system 10 are shown mounted perpendicular to the
direction of vehicle travel, in an alternative preferred
embodiment, the one or more elongated radiator units 12 of the
cooling system 10 are mounted parallel to the direction of vehicle
travel.
[0024] The radiators 24 may be interconnected by tubing 26. The
tubing may interconnected to provide either complete flow or
partial flow with bypass through each radiator. A partial flow with
bypass is typically used in the art as a method for eliminating
trapped air from within the liquid coolant tanks and passages. Each
radiator 24 may have a conventional fill orifice 28 and pressure
cap 30. The optional overflow tank 14 may have a conventional fill
orifice 32 and cap 34. The overflow tank 14 may be connected to the
fill orifice 28 of one of the radiators 24 through tank connecting
tube 36.
[0025] Interconnecting tubing 35 covered by a secondary heat shield
37 may run down along a side 39 of the vehicle 16 for connecting
the rooftop engine cooling system 10 to the one or more coolant
passages of the vehicle engine in the engine compartment. In
alternative embodiments, the interconnecting tubing 35 may run
inside the vehicle 16, outside the vehicle 16, or a combination of
inside and outside the vehicle 16. In the embodiment of the rooftop
engine cooling system 10 where the system 10 is incorporated into a
new vehicle, the interconnecting tubing 35 may also be incorporated
into the vehicle design. One or more circulation pumps (not shown)
may be used to pump coolant through the rooftop engine cooling
system 10, the vehicle engine, and the interconnecting tubing.
[0026] In an alternative embodiment, an electric heater unit may be
added to the system 10 to heat the coolant to a convenient working
temperature under extreme cold weather conditions.
[0027] The one or more of the rooftop radiator units 12 may work in
combination to cool the vehicle engine or the one or more radiator
units 12 may be separate rooftop radiator units 12 that are
separately used to cool separate vehicle components requiring
cooling. For example, but not by way of limitation, a first rooftop
radiator unit 12 may be used for cooling the vehicle engine, and a
separate, second rooftop radiator unit 12 may be used to cool
another vehicle component requiring cooling (e.g., a turbo charger
intercooler, a high power electric motor drive, or an
inverter-controller of a hybrid bus).
[0028] FIG. 2 is a top plan view of the rooftop engine cooling
system 10. The two radiator units 12 are shown connected by the
interconnecting tubing 26 and connected to the optional overflow
tank 14 through tank connecting tube 36. Portions of the fan
mounting shroud 18 are shown broken away to reveal the radiator 24.
The radiator 24 may include a radiator intake tank 38, a radiator
core 40 and a radiator exit tank 42. One or more fluid level floats
(not shown) in one or more of the tanks may be used to indicate the
coolant fluid level to the vehicle instrumentation system,
including but not limited to, a gage located on a dashboard of the
vehicle 16. Also shown are the plurality of fan orifices 20 and
thermostatically controlled electric fans 22.
[0029] FIG. 3 shows that the radiator core 40 of the radiator 24
may include a plurality of fine radiator core tubes 44. A heat
shield 46 may be located between the rooftop engine cooling system
10 and the rooftop 11 of the vehicle 16.
[0030] In FIG. 3, ambient air may flow into the side of the
radiator unit 12 through air inlet(s) 48, underneath the radiator
core 40, over the radiator core 40, and up and out of the fan
orifice(s) 20 with the assistance of the fan 22.
[0031] The large surface area of the roof top 11 significantly
reduces the fan power requirement by more than a factor of ten
compared to a standard radiator in an engine compartment. Standard
bus radiators/intercoolers consume up to 50 HP of engine power to
drive the radiator cooling fan alone. The electrically driven
radiator fans 22 consume less than 3 HP for equivalent cooling. The
larger surface area of the roof top 11 causes the airspeed through
the much larger horizontally mounted radiator units 12 to be
reduced and the air pressure drop across the radiator units 12 to
be reduced, increasing the cooling system efficiency. This results
in decreasing the engine load by more than 20% (50 HP-3 HP=47 HP;
assuming 185-280 HP at full power for a standard 40 ft. bus
engine). In one preferred embodiment mounted on a model RTS NOVA
bus, the standard fan consumed 40 to 50 HP while the horizontal
rooftop cooling system required 1.5 HP at full fan power. This
approximately 30 times power reduction demonstrates the significant
benefits of the horizontal rooftop cooling system.
[0032] The horizontal rooftop engine cooling system 10 also allows
for natural convectional air current to rise through the radiator
units 12 and allows ambient air to easily flow into and through the
cooling system 10, minimizing the power burden of the fans 22.
Natural convection currents of the heated cooling fluid may also
assist the circulation pump(s) in conveying the coolant through the
rooftop engine cooling system 10. With the radiator units 12
unconfined on the rooftop 11 of the vehicle 16, and with less
demanding size limitations, the heat may be dissipated in a natural
upward direction, minimizing the use of the electrically driven,
thermostatically controlled fans 22. Consequently, the load of the
electrically driven, thermostatically controlled fans 22 is far
less than that of fans of a standard radiator located in the engine
compartment of a vehicle. This greatly improves the efficiency of
the vehicle 16.
[0033] In addition to reducing the load on the engine and/or power
sources of the vehicle 16, moving the cooling system 10 from the
engine compartment to the rooftop 11 of the vehicle improves the
airflow of ambient air into the engine compartment and over the
engine, and makes the engine compartment more accessible, reducing
maintenance and repair time.
[0034] A further benefit of locating the cooling system 10 on the
rooftop 11 of the vehicle 16 is that some of the cleanest and
coolest air is available at the altitude of the rooftop 11,
reducing the number of times the radiator needs to be serviced and
increasing the duration between radiator cleanings. Because
radiator cleaning requirements stipulate that the radiator be
cleaned in the opposite direction of the airflow, the cooling
system 10 can be cleaned by simply spraying water through the fan
orifices 20 and fans 22 of the ornamental shroud 18 from outside of
the cooling system 10 such as may occur during a normal bus wash
cycle. This is much simpler and less time-consuming than cleaning a
radiator from the inside of the engine compartment, which may
require partial disassembly of the radiator shroud to effectively
clean the radiator.
[0035] With reference to FIG. 4, an embodiment of a continuously
variable power drive and speed control system ("control system")
100 for rooftop fan(s) 22 will be described. The control system 100
includes one or more temperature sensors 110 thermally coupled to
the rooftop engine cooling system 10 to determine coolant
temperature. A controller 120, which in the embodiment shown is a
digital microcomputer, includes an algorithm to determine the
minimum desired air movement and fan speed. A switching controller
130 is controlled by the controller 120 to vary the voltage, and,
hence, vary the speed, of the fans 22.
[0036] The controller 120 receives coolant temperature information
from the temperature sensor(s) 110 and uses an algorithm in a
digital microcomputer to determine the minimum desired air movement
and fan speed. Keeping fan speed at a minimum conserves vehicle
accessory power and minimizes fan audible noise for the
environment. The control algorithm uses the coolant temperature to
determine the desired voltage square-shaped waveform (e.g., PWM
power waveform) for the desired average DC voltage and fan speed.
The fan speed is controlled by varying the voltage with the
switching controller 130. The controller 130 uses power transistors
called IGBT's to turn on and off the supply voltage in pulse width
modulation to vary the average voltage applied to the fan(s) 22. In
the embodiment shown, waveforms are used to change the average fan
voltage in 10% steps; however, in an alternative embodiment, the
pulse widths can be varied to produce continuously variable power
drive and speed control for the rooftop fans 22. The switched
controller 130 is significantly more efficient and variable than a
tapped resistor controller.
[0037] With reference to FIG. 5, another embodiment of a rooftop
engine cooling system 200 will be described. The rooftop engine
cooling system 200 includes two radiator units 12 longitudinally
oriented/aligned with the longitudinal direction of the rooftop 11
of the vehicle 16 (e.g., bus). Although two radiator units 12 are
shown, the rooftop engine cooling system 200 may include one or
more radiator units 12. Further, although the rooftop engine
cooling system 200 is shown longitudinally oriented with the
longitudinal direction of the rooftop 11, the rooftop engine
cooling system 200 may be laterally oriented (or oriented in
another direction) with respect to the rooftop 11.
[0038] In a preferred embodiment of the rooftop engine cooling
system 200, the area footprint of the rooftop engine cooling system
200 occupies at least 70% of the area of the rooftop 11 of the
vehicle 16. In a more preferred embodiment, the area footprint of
the rooftop engine cooling system 200 occupies at least 80% of the
area of the rooftop 11 of the vehicle 16. In a most preferred
embodiment, the area footprint of the rooftop engine cooling system
200 occupies at least 90% of the area of the rooftop 11 of the
vehicle 16. Providing a rooftop engine cooling system 200,
especially a longitudinally oriented rooftop engine cooling system
200, on the rooftop 11 to match the shape of the bus rooftop 11
with a larger radiator surface area minimizes the cooling air flow
and corresponding fan power required to cool the rooftop engine
cooling system 200.
[0039] The longitudinal orientation for the rooftop engine cooling
system 200 was chosen to match the shape of the bus rooftop 11. The
rooftop location on a bus offers more square area space than other
bus locations to place a liquid/air heat exchanger. Greater exposed
surface area for the liquid coolant/air interface of the rooftop
engine cooling system 200 translates to less required air flow
across the interface surface area to achieve a given level of
cooling. The limited space available in a bus engine compartment
requires high air flow volumes to achieve the required cooling. To
get higher air flows through the typical engine compartment
radiator requires an exponentially increasing level of power to
drive the fan. Also, high-flow fans in the engine compartment
create high audible noise for the surrounding environment. By using
a larger area rooftop engine cooling system 200 on the bus rooftop
11 the required air flow and, therefore, the power to drive the
fans is significantly minimized and results in a savings of 30 to
50 horsepower (and adds to the vehicle fuel economy) for a typical
bus application. Fan noise is also significantly reduced because of
lower air velocity with multiple fans. Another advantage is lower
maintenance with less debris in that location, compared to ground
level, to clog the radiator air flow. And, with variable speed
control, as described above with respect to FIG. 4, fan power is
only used when required, and audible fan noise is similarly
reduced.
[0040] With reference to FIG. 6, a rooftop cooling system similar
to those described above may be used for heat exchanger cooling of,
but not by way of limitation, one or more of the following
components (in addition to or instead of the engine): a generator
210, motor(s) 220, a charge air cooler 230, inverter drive
controller(s) 240, bus electric drive element(s) 250, and other
electrical component(s) 260. In the example of the charge air
cooler, the charge air cooler 230 receives circulated coolant from
the rooftop cooling system for cooling turbo charger air to the
engine (diesel or gasoline) intake manifold.
[0041] The vehicle rooftop engine cooling systems shown in the
drawings and described in detail herein disclose arrangements of
elements of particular construction and configuration for
illustrating preferred and alternate embodiments of structure and
method of operation of the present invention. It is to be
understood, however, that elements of different construction and
configuration and other arrangements thereof, other than those
illustrated and described may be employed for providing a rooftop
engine cooling system in accordance with the spirit of this
invention, and such changes, alternations and modifications as
would occur to those skilled in the art are considered to be within
the scope of this invention as broadly defined in the appended
claims.
* * * * *