Heat exchanger for cooling a flow of charge air, and method of assembling the same

A heat exchanger for cooling a flow of charge air includes a heat exchanger core that is inserted through an aperture of a housing. A leak-free seal is maintained along the periphery of the aperture by the compression of a gasket between a top plate of the heat exchanger core and a planar bearing surface of the housing. Compression of the gasket is maintained by one or more deformable retaining members that are disposed against the top plate.

BACKGROUND

Charge air coolers are used in conjunction with turbocharged internal combustion engine systems. In such systems, residual energy from the combustion exhaust is recaptured through an exhaust expansion turbine, and the recaptured energy is used to compress or “boost” the pressure of the incoming air (referred to as the “charge air”) being supplied to the engine. This raises the operating pressure of the engine, thereby increasing the thermal efficiency and providing greater fuel economy.

The compression of the charge air using the exhaust gases typically leads to a substantial increase in temperature of the air. Such a temperature increase can be undesirable for at least two reasons. First, the density of the air is inversely related to its temperature, so that the amount of air mass entering the combustion cylinders in each combustion cycle is lower when the air temperature is elevated, leading to reduced engine output. Second, the production of undesirable and/or harmful emissions, such as oxides of nitrogen, increases as the combustion temperature increases. The emissions levels for internal combustion engines is heavily regulated, often making it necessary to control the temperature of the air entering the combustion chambers to a temperature that is relatively close to the ambient air temperature. As a result, cooling of the charge air using charge air coolers has become commonplace for turbocharged engines.

In some applications, the charge air is cooled using a liquid coolant (for example, engine coolant). Some known types of these liquid cooled charge air coolers include a metallic core with sealed liquid passages arranged in heat transfer relation to air passages, and a housing surrounding the core to direct the flow of charge air through the air passages.

SUMMARY

According to one embodiment of the invention, a heat exchanger for cooling a flow of charge air includes a heat exchanger core with alternating coolant plates and air fins arranged in a core stacking direction, and a top plate at one end of the core in the core stacking direction. A housing of the heat exchanger has an air inlet, an air outlet, and an aperture through which the coolant plates and air fins are received into the housing. The aperture is bounded by a generally planar bearing surface, and a gasket is compressed between a face of the top plate and the housing to provide an air seal at the aperture. A retaining member is disposed against a face of the top plate to compress the gasket.

In some embodiments, the retaining member engages recesses along the periphery of the bearing surface in order to maintain the force for compressing the gasket. In some such embodiments, the retaining member is one of several retaining members. In some embodiments the recesses are provided in a wall of the housing that is disposed along a periphery of the generally planar bearing surface.

In some embodiments, the retaining member includes a deformable metal component. In some embodiments the retaining member is plastically deformed in order to be disposed against the top plate. In other embodiments the retaining member is elastically deformed to secure the retaining member to the housing.

In some embodiments the retaining member is of a generally planar shape, and in some such embodiments it is elastically deformed from an arcuate shape to the generally planar shape during the installation process.

According to another embodiment of the invention, a method for assembling a heat exchanger includes inserting a heat exchanger core through an aperture of a housing into a cavity of the housing. A gasket is compressed between a top plate of the heat exchanger core and the housing along the periphery of the aperture. At least one retaining member is elastically deformed and is secure to the housing in order to maintain the compression of the gasket.

In some embodiments the retaining members are secured by engaging recesses along the periphery of a generally planar bearing surface that surrounds the aperture.

DETAILED DESCRIPTION

A heat exchanger1for cooling a flow of charge air according to an embodiment of the invention is depicted inFIG. 1. The heat exchanger1is especially well suited for use as a charge air cooler for turbo-charged combustion engine powered passenger cars, but it should be understood that its use is not limited to such an application. The heat exchanger1might also be applicable to the cooling of charge air for other types of processes, as well as to the cooling or heating of other fluids.

Referring still toFIG. 1, and with additional reference toFIGS. 3 and 5A-B, the heat exchanger1includes a heat exchange core2that is inserted into, and retained within, a cavity16of a heat exchanger housing6. The housing6is preferably a molded or cast part, or an assembly of such parts, although other construction methods might be used as well. In some preferable embodiments the housing6can be formed of a plastic material, although aluminum or other metallic alloys can be used as well. The housing6includes an air inlet7and an air outlet8, with an air flow passage established though the housing6between the inlet7and outlet8. The cavity6is provided along the flow path, and is generally of a shape and size that closely conforms to the heat exchange core2so that substantially all of the charge air received into the heat exchanger1through the inlet port7is directed through the core2to be cooled.

The heat exchanger core2includes a top plate5and an alternatingly stacked arrangement of coolant plates3and air fins4, typically made of aluminum and brazed together so that the core2is of a unitary construction. The coolant plates are of a two-piece construction, with a coolant flow passage provided within interior spaces of each coolant plate. Ends of the coolant flow passages are fluidly joined to coolant ports25that extend out of the heat exchanger1and can be used to couple the heat exchanger1into a coolant circuit (not shown). The air fins4can be of any of the multiple styles of fins known in the art, including but not limited to serpentine fins, lanced-offset fins, square wave fins, etc.

During typical operation of the heat exchanger1as a charge air cooler, a flow of compressed air is received into the heat exchanger1through the air inlet port7. Liquid coolant is directed into the core2through one of the coolant ports25, and is distributed to the coolant flow passages provided within the interior spaces of the coolant plates. The coolant is circuited through the coolant flow passages, and is collected and removed from the core2through the other of the coolant ports25. The charge air flows through the spaces between the coolant plates3, in channels defined by the air fins4. Heat is transferred from the charge air to the coolant passing through the coolant flow passages, the coolant being at a lower temperature than the charge air, so that the charge air exits the core2at a substantially lower temperature than when it entered the air inlet7. Having been cooled down to an acceptable temperature, the charge air exits the heat exchanger1through the air outlet port8.

As best seen inFIGS. 1, 2, 3 and 5A-B, the housing6includes an aperture9disposed above the cavity16, through which the core2can be inserted into the housing6. The aperture9is preferably slightly larger than the outer periphery of the stack of coolant plates3and air fins4, and is smaller than the outer periphery of the top plate5. The aperture9is bounded by a generally planar bearing surface10of the housing, and a bottom face of the top plate5is disposed against, or adjacent to, the bearing surface10to close off the aperture9. A gasket23is compressed between the bottom face of the top plate5and the housing6to create an air seal, so that compressed air is prevented from leaking out through the aperture9during operation of the heat exchanger1. In the exemplary embodiment the gasket23is retained within a groove24that is formed into the bearing surface10along the periphery of the aperture9. Alternatively, a flat gasket can be used to provide a face seal between a bottom face of the top plate5and the bearing surface10.

Once the core2has been inserted into the housing6, one or more retaining members are used to both retain the core within the housing and maintain the requisite compression of the gasket. In the heat exchanger1shown inFIG. 1, three retaining members13are provided for that purpose. The exemplary retaining members13are thin metallic parts that operate on a leaf spring principle. In their free state (shown inFIG. 4), the retaining members13define an arcuate profile, with a concave side and a convex side. The retaining members13can be elastically deformed from their arcuate free shape to a planar shape by the application of appropriate force. Elastically deformed, in this context, means that the stresses induced within the retaining member13as a result of such a deformation are below the yield strength of the material, such that the retaining member13would revert back to its arcuate free state upon the removal of the deforming force.

The installation of the retaining members13into the heat exchanger1can best be understood with reference toFIGS. 5A and 5B. A downward force is applied to a top surface of the top plate5in order to compress the gasket23. A retaining member13is positioned in alignment with a pair of opposing recesses14provided in a wall15of the housing6, the wall15at least partially surrounding the generally planar bearing surface10, as shown inFIG. 5A. A force (indicated by the arrow inFIG. 5A) is applied to the convex surface of the retaining member13in order to flatten the retaining member13, thereby directing ends of the retaining member13into the recesses14. A locking tang17is provided near each of the opposing ends of the retaining member13, and is formed outwardly to extend towards the concave side of the retaining member13. As the retaining member13is flattened, the free ends of the tangs17contact the top surface of the top plate5and translate along that surface as the retaining member13continues to be deformed.FIG. 5Bshows one such retaining member13in its installed, flattened state. In that state, the locking tangs17have translated to a position immediately beyond the outer edges of the top plate5, and are disposed directly adjacent to those edges. Both the compressive force applied to the top plate5to compress the gasket, and the force applied to elastically deform the retaining member13, can be removed, leaving the elastically deformed retaining member(s)13engaging the recesses14to maintain the gasket compression force.

The installed retaining members13are prevented from returning to their arcuate pre-installation shape by the presence of the locking tangs17. As an installed retaining member13attempts to spring back to its arcuate shape, the edges of the locking tangs17contact the edges of the top plate5, their movement being thereby halted. Movement of the retaining member13in a direction normal to and away from the top plate5is restricted by edges of the recesses14, such that the retaining member13is captured. The installed retaining members13thus maintain the position of the top plate5relative to the bearing surface10, and thereby also maintain the compression force on the gasket23in order to preserve the air-tight seal around the aperture9.

Each of the recesses14includes a slot22along a portion of its length, with the slots22extending to the bearing surface10. The slots22are each aligned with a locking tang17of an installed retaining member13. Disassembly of the retaining members13from the heat exchanger1is accomplished by inserting a tool inwardly through the slots22corresponding to that retaining member13, thereby deforming the corresponding locking tangs17so that the tangs17can pass over the edges of the top plate5. In so doing, the retaining member13becomes free to return to its un-deformed, arcuate shape, and is freed from the heat exchanger1.

An alternative embodiment of a heat exchanger101is depicted inFIG. 6, and uses the same heat exchanger core2in a slightly modified housing106. Retention of the core102in the housing106, and compression of the gasket seal, is maintained in a similar fashion to that described above with respect to the heat exchanger1. Again, a force is applied to a top surface of the top plate105in order to compress a gasket and retaining members113are used to maintain the compression upon removal of the force. Two such retaining members113are shown in an installed state, while a third is shown un-installed from the heat exchanger1.

The retaining members113are preferably stamped metal parts of a planar C-shape design, with arms126extending from opposing ends of an arcuate center portion127. Locking extensions120are provided on outermost edges of the arms126, and are sized to allow for insertion into recesses114provided at select locations along a wall115of the housing106, similar to the recesses14and wall15of the heat exchanger1. Assembly of a retaining member113into the heat exchanger101is accomplished by elastically deforming the retaining member113within its own plane so that the arms126move inwardly, thereby causing bending to occur within the arcuate center portion127. Such deformation of the retaining member113can be facilitated through the use of an insertion tool (not shown) that engages holes121provided at each of the arms126and applies the required force. During installation the retaining member113is deformed sufficiently to allow the retaining member113to pass within the peripheral wall115to the top plate105. Upon removal of the force used to elastically deform the retaining member113, the locking extensions120seat within the recesses114and prevent removal of the retaining member113. Removal of the retaining members113, if desired, can be accomplished by reversing the installation process.

Yet another alternative embodiment of a heat exchanger201is depicted inFIGS. 7-9, also using the same heat exchanger core2, in an again slightly modified housing202. The housing202includes a peripheral wall215surrounding the aperture into which the heat exchange core2is received, but the peripheral wall215extends along only the two long sides of the core2and the short side of the core2adjacent to the coolant ports25. Track-like recesses229are provided along those lengths of the wall215adjacent the long sides of the core2, and are sized to receive a frame portion228of a retaining member213.

The retaining member213is preferably a stamped metal part having an outer frame228formed in a U-shape, with a length and width that are similar to, but slightly larger than, the top plate5of the core2. The retaining member213is assembled to the heat exchanger201by sliding, from the open end of the wall215, along the top surface of the top plate5while a force is applied to that top surface in order to compress a gasket, as previously described with respect to the embodiments ofFIGS. 1 and 6. The long portions of the outer frame228are received within the recesses229, so that compression of the gasket is maintained after removal of the compression force used during assembly.

Arms218extend from end portions of the outer frame228to surround the coolant ports25, with locking hooks219provided at the ends of the arms228. The locking hooks219are received into a recess214provided along a portion of the wall215adjacent the ports25, as best seen inFIG. 9. The recess214is sized so that, upon assembly of the retaining member213into the heat exchanger1, an angled profile of each locking hook219contacts an edge of the recess214, thereby causing the outer frame228to elastically deform within the plane of the retaining member213and allowing the hooks219to enter into the recess214. Once the locking hooks219extend fully though the wall215, the frame228is allowed to spring back to its un-deformed shape, and the hooks219engage against the exterior of the wall215to prevent removal of the retaining member213. When desired, however, the retaining member213can be readily removed by squeezing together the locking hooks219, thereby allowing them to be withdrawn back through the recess214.

FIGS. 10A and 10Bshow two additional embodiments of a heat exchanger. The heat exchanger301ofFIG. 10Aand the heat exchanger301′ ofFIG. 10Bare similar to the previously described embodiments in that a retaining member is deformed to secure the heat exchanger core2within the housing6in a leak-free manner. The heat exchanger core2is not shown in detail, but is essentially unchanged from the previously described embodiments, and again includes a top plate5arranged at an uppermost end of the core2. The top plate5again is disposed against a bearing surface310of the housing6, and a leak-free seal is thereby created through the compression of the gasket23.

The peripheral wall315extends around the aperture of the housing6into which the core2is received, but in these particular embodiments that wall315extends outward from the core instead of extending upward. A retaining clip313,313′ is partially received into a recess314that is provided along the wall315. The retaining clip can be secured into the recess314in a variety of ways, including insert molding, heat staking, ultrasonic welding, and friction fitting, among others. In order to secure the top plate5against the bearing surface310and create the leak-free seal, a portion330,330′ of the retaining clip313,313′ is plastically deformed in order to provide a permanent downward acting force upon the top plate5, thereby preventing movement of the heat exchanger core2in a direction opposite to the insertion direction.

The two embodiments301,301′ differ slightly in the design of the retaining clip. The retaining clip313of the heat exchanger301is crimped over to that a top edge of the retaining clip313bears directly on the top plate5. The deformed portion330is depicted inFIG. 10Aits un-deformed state using dashed lines. The heat exchanger301′, depicted inFIG. 10B, uses a retaining clip313′ which has pre-pierced deformable features330′ arranged along the periphery of the housing6. After insertion of the core2into the aperture of the housing6, the features330′ are deformed inwardly to partially overlay the top plate5, as illustrated inFIG. 10B.

As was the case in the previously described embodiments, the heat exchanger core2can be removed from the housing6by restoring the deformed portion330,330′ to its un-deformed state, thereby allowing for service or replacement of the core2.

Various alternatives to the certain features and elements of the present invention are described with reference to specific embodiments of the present invention. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with each embodiment described above, it should be noted that the alternative features, elements, and manners of operation described with reference to one particular embodiment are applicable to the other embodiments.