Ducted cooling system with radial-flow fan

Abstract: A cooling system for a vehicle having a liquid-cooled engine (13) is provided. The cooling system includes a heat exchanger (12) constructed and arranged to be mounted in spaced relation with respect to the engine (13) for cooling the liquid by air directed from a front side of the heat exchanger through a rear side of the heat exchanger (12). Duct structure (14) is coupled to the rear side of the heat exchanger (12) so as to cover at least a portion of the rear side, and to receive at least a portion of air exiting the rear side of the heat exchanger. The duct structure (14) is mounted with respect to the heat exchanger (12) so that a portion of the duct structure (14) extends beyond bounds of a sidewall of the heat exchanger (12). At least one radial-flow type fan (16) is mounted in the extending portion (17) of duct structure (14) such that air flowing through the heat exchanger (12) and the duct structure (14) is pulled by the fan (16) so as to exit generally at the sidewall of the heat exchanger. A motor is operatively coupled to the fan (16) to drive the fan (16).

Description: FIELD OF THE INVENTION The present invention relates to an engine cooling system, and more particularly to an efficient engine cooling system including duct structure leading to a radial-flow type fan mounted so as to extend beyond a sidewall of a heat exchanger. BACKGROUND OF THE INVENTION Typical vehicle cooling systems include a low-profile axial fan mounted between a vehicle's liquid-cooled engine and a heat exchanger to draw air through the heat exchanger and thus provide cooling of the engine. Axial fans are advantageous since they may be positioned directly behind the radiator, be driven by the engine, and may be made compact. However, a drawback in using axial fans in engine cooling systems is that these types of fans have efficiencies generally between 40% and 60% and are a significant source of noise in the engine compartment. US 2,242,495 describes a system for drawing air through a radiator of a vehicle, using a duct leading from the radiator to a centrifugal fan. US 5,588,482 describes a duct apparatus for drawing a flow of air into a heat exchanger assembly of a vehicle and discharging the air away from the vehicle engine. Fans may be located within the duct. US 4,376,424 describes a duct structure placed behind an automotive radiator, guiding air through the radiator to a cross-flow fan at the outlet of the duct. US 2,503,667 describes a heating apparatus in which air is drawn past a heating pipe and through a predetermined channel by operation of centrifugal-flow fans. SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle cooling system to fulfill the need referred to above. The present invention provides a cooling system for a vehicle having a liquid-cooled engine. The system comprises a heat exchanger having a front side and a rear side linked by sidewalls, constructed and arranged to be mounted in spaced relation with respect to the engine for cooling liquid by air, the air being directed from the front side of the heat exchanger through to the rear side of the heat exchanger. The system also comprises a motor operatively coupled to at least one fan for drawing air through the heat exchanger; and a duct structure coupled to the rear side of the heat exchanger so as to cover at least a portion of said rear side, and to receive at least a portion of air exiting the rear side of the heat exchanger. In particular, the duct structure has at least one end portion which extends beyond the bounds of the sidewalls of the heat exchanger, disposed at an upper portion of the duct structure, the duct structure further comprising at least one exhaust passage respectively communicating downwardly away from the or each end portion adjacent a respective sidewall of the heat exchanger; and a motor-driven centrifugal-flow type fan is respectively mounted in the or each end portion, beyond the bounds of the sidewalls of the heat exchanger, whereby air flowing through the heat exchanger and said duct structure may be drawn by the or each said fan so as to exit through the or each respective exhaust passage. The duct structure may be arranged to receive air exiting the rear side of the heat exchanger in an initial direction, and to change the direction of air flow to be generally transverse to said initial direction in an upward direction towards the end portion(s). The duct structure preferably increases in size in a lateral direction from a first size at a central portion to a larger size at each of the end portions thereof. Such duct structure may taper outwardly toward said end portion(s) such that said end portion(s) has/have the widest cross-sectional area of the duct structure. The cooling system may further include vanes disposed in said duct structure for directing air toward said end portion(s). The duct structure may have a plurality of bores therein and may include an air door structure associated with each said bore, said air door structure being constructed and arranged to remain closed, closing said bores until exposed to a predetermined threshold air velocity, whereby said air door structures move to an opened condition, opening said bores. Each of said air door structures may comprise an upper portion, a lower portion and a hinge portion coupling the upper and lower portions. Each air door may be constructed and arranged to pivot about the associated hinge portion and move to a substantially horizontal opened position, opening the associated bore in the duct structure when exposed to a threshold air velocity. The motor(s) may be electric motor(s) constructed and arranged to be operated by the vehicle's electric system, or may be hydraulic motor(s). The present invention also provides a method of cooling a liquid-cooled engine of a vehicle comprising: directing air and liquid respectively through a heat exchanger mounted in spaced relation with respect to the engine thereby cooling the liquid, the air being directed from a front side of the heat exchanger through a rear side of the heat exchanger, and directing the air from the rear side of the heat exchanger into a duct structure covering at least a portion of said rear side. In particular, the method further comprises the steps of: directing the air through the duct structure into at least one end portion extending beyond the bounds of opposing sidewalls of the heat exchanger at an upper portion of the duct structure; and directing the air through the end portion(s) and into an exhaust passage of the duct structure, respectively downwardly away from the or each end portion, adjacent a respective sidewall of the heat exchanger and into the atmosphere, by operation of at least one motor-driven centrifugal-flow fan mounted in the end portion(s) of the duct structure beyond the bounds of the sidewalls of the heat exchanger. Other objects, features and characteristics of the present invention, as well as the methods of operation and functions of related elements of the structure, and the combination of the parts and economics of manufacture, will become more apparent upon consideration of the detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view, partially in section, of a ducted cooling system provided in accordance with the principles of the present invention shown mounted adjacent to a heat exchanger; FIG. 2 is a schematic side illustration of the cooling system of Fig. 1 mounted to a heat exchanger forward of an engine, shown with the fan motor removed for clarity of illustration; FIG. 3 is a rear view of the duct structure of FIG. 1, showing the air doors; and FIG. 4 is an enlarged sectional view taken along the line 4-4 in FIG. 3. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENT Referring to the drawings, a vehicle cooling system is shown generally indicated at 10, which embodies the principles of the present invention. In a typical vehicle, a heat exchanger 12 or radiator is conventionally mounted behind a grille and forward of a liquid-cooled engine 13 of the vehicle. In accordance with the invention, the heat exchanger 12 is part of the cooling system 10 which also includes duct structure 14 mounted on the discharge or rear side 15 of the heat exchanger 12. The block outline in FIG. 1 representing the heat exchanger 12 may also include an air-conditioning condenser, charge air cooler, transmission cooler or any other type of heat exchanger. In the illustrated embodiment, the duct structure 14 spans the width of the heat exchanger 12 and has end portions 17 that extend beyond the bounds of sidewalls 19 of the heat exchanger. As best shown in FIG. 2, the duct structure 14 is preferably made of plastic material and covers at least a portion of the rear side 15 of the heat exchanger 12 such that at least a portion of air exiting the heat exchanger 12 is introduced into the duct structure 14. It can be appreciated that the duct structure is sized to cover as much as, or as little of, the rear side 15 of the heat exchanger 12 as needed for the particular cooling application. The cooling system 10 also includes at least one radial fan 16 and a motor 18 operatively associated with the fan 16 to drive the fan. The fan 16 is mounted in the end or fan-mounting portion 17 of the duct structure generally near a top portion thereof, with the motor being operatively coupled to the fan 16. Thus, the fan 16 and motor 18 are generally disposed at a sidewall 19 of the heat exchanger 12. In the illustrated embodiment, a pair of radial fans 16, 16' and associated motors 18 and 18' are provided at opposing ends of the duct structure 14 and thus, at opposing sides of the heat exchanger 12. It can be appreciated that one motor may be provided to drive both of the fans 16, 16', if desired. Although one motor and one fan may be all that is required to cool a vehicle engine, the second fan 16' may be provided if more cooling capacity is required. The motors 18 and 18' are preferably electric motors operated by the vehicle's electrical system. However, other types of prime movers, such as hydraulic motors, may be used to drive the fans. As viewed from above and as shown in FIG. 1, the duct structure increases in size as it approaches the fan location for directing air flow to the fan 16. When two fans are provided, the duct structure increases gradually in size in opposite directions from a central portion, toward the fan locations. Further, vanes 20 may be provided in the duct structure to further channel air from the heat exchanger 12 to the inlets of the fans 16, as indicated by the arrows in FIG. 1. A plurality of air doors, generally indicated at 22, are provided in the duct structure 14 and are of the type disclosed in commonly assigned United States Patent Application No 08/711,703, filed on September 6, 1996. As best shown in FIGS. 3 and 4, each air door 22 has an upper portion 24, a generally central hinge portion 26 and a lower portion 28. The air doors are constructed and arranged to remain closed (i.e sealing associated bores 30) until there is a predetermined threshold air velocity (an air velocity typically corresponding to a designated velocity of the vehicle). At the threshold velocity, the upper and lower portions of each air door will pivot about the associated hinge portion 26 and move to a substantially horizontal, opened position, opening bores 30 in the duct structure 14 to reduce the static pressure drop across the system and increase the total flow rate through the system. With reference to the air flow arrows in FIG. 1 and 2, In general, air moving in an initial direction passes from a front side 21 to the rear side 15 of the heat exchanger 12 to the inlet of the duct structure 14 and then changes direction to move generally upwardly and transverse to the initial direction as it moves to the inlet of the fans 16, 16' wherein it is impelled inwardly by the blades of the fans and across the interior of the fans. The air Is then impelled outwardly by the blades and downwardly to an exhaust duct 32 located at the sidewalls 19, and away from or out of the engine compartment. Air exhaust duct 32 is located in a position to minimize air recirculation to the inlet of heat exchanger 12 and to take advantage of any low pressure region created by the vehicle aerodynamics. The exhaust duct 32 may be oriented toward any local hot spot in the engine compartment to provide localized cooling. Since the fans 16 and 16' are mounted generally at the sides of the heat exchanger 12, a fan module design of short axial length (dimension A in FIG. 1 of approximately 150 mm) for a high resistance heat exchanger is possible. The fans 16, 16' and motors 18, 18' are located in an area of the engine compartment that is not considered to be a prime location. Thus, the fans may have a diameter of about 12 inches (305 mm) and a length generally between 6-8 inches (152.4 to 203.2 mm) . The portion 17 of the duct structure that extends beyond sidewalls 19 may be modified accordingly to accommodate the particular fan size. The fans 16, 16' and motors 18, 18' are sized, however, for the particular cooling requirements of the engine 13. The location of the fans 16, 16' at the sides of the heat exchanger 12 increases flow resistance, requiring the relatively large duct structure 14. Thus, the fans are selected for high resistance operation and operate at higher efficiency. This will result in higher heat rejecting cooling systems. The location of the fans 16, 16' at the sidewalls of the heat exchanger 12 may also provide a reduction in noise. To reduce fan noise further, the duct structure 14 may be acoustically treated. With axial flow fan systems, the fan creates resistance to the air flow during vehicle high speed operation. This requires the fan motor to be energized to reduce flow resistance. With the ducted cooling system of the invention, the fan or fans are out of the flow stream and do not provide a resistance to the ram air, and the motor does not have to be energized, which results in a power savings. It can be seen that the invention provides a duct cooling system employing duct structure and an efficient, radial-flow type fan that is selected for high flow resistance and that is oriented, together with its motor, at a non-prime engine compartment location. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is understood that the invention is not limited to the disclosed embodiment, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims: A cooling system (10) for a vehicle having a liquid-cooled engine (13), the system comprising: a heat exchanger (12) having a front side (21) and a rear side (15) linked by sidewalls (19), constructed and arranged to be mounted in spaced relation with respect to the engine for cooling liquid by air, the air being directed from the front side of the heat exchanger through to the rear side of the heat exchanger; a motor (18,18') operatively coupled to at least one fan for drawing air through the heat exchanger; and a duct structure (14) coupled to the rear side of the heat exchanger so as to cover at least a portion of said rear side, and to receive at least a portion of air exiting the rear side of the heat exchanger, characterised in that : the duct structure has at least one end portion (17) which extends beyond the bounds of the sidewalls of the heat exchanger, disposed at an upper portion of the duct structure, the duct structure further comprising at least one exhaust passage (32) respectively communicating downwardly away from the or each end portion adjacent a respective sidewall of the heat exchanger; and in that a motor-driven centrifugal-flow type fan (16,16') is respectively mounted in the or each end portion, beyond the bounds of the sidewalls of the heat exchanger, whereby air flowing through the heat exchanger and said duct structure may be drawn by the or each said fan so as to exit through the or each respective exhaust passage. The cooling system according to claim 1, wherein the duct structure is arranged to receive air exiting the rear side of the heat exchanger in an initial direction, and to change the direction of air flow to be generally transverse to said initial direction in an upward direction towards the end portion(s). The cooling system according to any preceding claim, wherein said duct structure increases in size in a lateral direction from a first size at a central portion to a larger size at each of the end portions thereof. The cooling system according to claim 3, wherein said duct structure tapers outwardly toward said end portion(s) such that said end portion(s) has/have the widest cross-sectional area of the duct structure. The cooling system according to any preceding claim, further including vanes (20) disposed in said duct structure for directing air toward said end portion(s). The cooling system according to any preceding claim, wherein said duct structure has a plurality of bores (30) therein and includes an air door structure (22) associated with each said bore, said air door structure being constructed and arranged to remain closed, closing said bores until exposed to a predetermined threshold air velocity, whereby said air door structures move to an opened condition, opening said bores. The cooling system according to claim 6, wherein each of said air door structures comprises an upper portion (24), a lower portion (28) and a hinge portion (26) coupling the upper and lower portions, and the upper and lower portions of each air door are constructed and arranged to pivot about the associated hinge portion and move to a substantially horizontal opened position, opening the associated bore in the duct structure when exposed to a threshold air velocity. The cooling system according to any preceding claim, wherein said motor(s) is/are electric motor(s) constructed and arranged to be operated by the vehicle's electric system. The cooling system according to any of claims 1-7, wherein said motor(s) is/are hydraulic motor(s). A method of cooling a liquid-cooled engine of a vehicle comprising: directing air and liquid respectively through a heat exchanger (12) mounted in spaced relation with respect to the engine (13) thereby cooling the liquid, the air being directed from a front side (21) of the heat exchanger through a rear side (15) of the heat exchanger, directing the air from the rear side of the heat exchanger into a duct structure covering at least a portion of said rear side, characterised in that the method further comprises the steps of: directing the air through the duct structure into at least one end portion extending beyond the bounds of opposing sidewalls (19) of the heat exchanger at an upper portion of the duct structure; and directing the air through the end portion(s) and into an exhaust passage of the duct structure, respectively downwardly away from the or each end portion, adjacent a respective sidewall of the heat exchanger and into the atmosphere, by operation of at least one motor-driven centrifugal-flow fan mounted in the end portion(s) of the duct structure beyond the bounds of the sidewalls of the heat exchanger.

Inventors: GALLIVAN WILLIAM P, KERSHAW P, GALLIVAN, WILLIAM P., KERSHAW, P.
Applicants: SIEMENS VDO AUTOMOTIVE INC, SIEMENS VDO AUTOMOTIVE INC.
Application year: 1998
Main classification: F01P11
IPC codes: F01P5, F01P11