JP4565493B2 - EGR gas cooling device - Google Patents

Description

  The present invention relates to a heat exchange type gas cooling device, and more specifically, a part of exhaust gas is extracted from an exhaust system of a diesel engine or the like, returned to an intake system of an engine via an EGR pipe, and exhaust recirculation applied to a mixer ( Hereinafter, the present invention relates to an apparatus for cooling EGR gas in the EGR pipe.

  A method of taking a part of the exhaust gas from the exhaust system of the diesel engine, returning it to the intake system of the engine again, and adding it to the air-fuel mixture is called EGR (Exhaust Gas Recirculation), which is the NOx (nitrogen oxide) Many effects such as suppression of generation, reduction of pump loss, reduction of heat dissipation loss to coolant due to lowering of combustion gas temperature, increase of specific heat ratio due to change of working gas amount and composition, and improvement of cycle efficiency associated with it Therefore, it is widely adopted as an effective method for purifying exhaust gas from diesel engines and improving thermal efficiency.

  However, when the temperature of the EGR gas rises and the amount of EGR gas increases, the durability of the EGR valve deteriorates due to its thermal action, and there is a risk of early damage. Therefore, as a preventive measure, the cooling system has a water cooling structure. This leads to a phenomenon in which the fuel efficiency is lowered due to a decrease in the charging efficiency as the intake air temperature rises. In order to avoid such a situation, an EGR gas cooling device is used with engine coolant, car air conditioner refrigerant, or cooling air.

Under such circumstances, various types of heat exchanger type cooling devices have been proposed as cooling means for EGR gas. For example, a double pipe type in which an outer pipe through which a liquid is passed is disposed outside an inner pipe through which a gas passes, and a metal corrugated plate is inserted as a fin in the inner pipe in an exchanger for exchanging heat between the gas and the liquid. 2 provided with a heat exchanger (for example, refer to Patent Document 1), an inner tube and an outer tube, and each having either a high-temperature side fluid passage or a low-temperature side fluid passage on the inner tube side and the outer tube side, respectively. A double-pipe heat exchanger (see, for example, Patent Document 2), an inner pipe through which a medium to be cooled is circulated, an outer pipe provided so as to surround and surround the outer circumference of the inner pipe, and the inner pipe A double-pipe heat exchanger (see, for example, Patent Document 3) composed of a heat dissipating fin having a thermal stress relaxation function disposed inside, an inner pipe for circulating a medium to be cooled, and the inner pipe An outer tube provided so as to surround the outer periphery of the outer space and an inside of the inner tube. EGR gas in which a cooling pipe (heat transfer pipe) is spirally wound around the outer peripheral surface of a double-pipe heat exchanger (for example, see Patent Document 4) composed of a cross fin and an EGR gas pipe A cooling device (for example, see Patent Document 5), an EGR gas cooler having a structure in which a cooling pipe (heat transfer tube) is inserted into the EGR gas pipe through the outer peripheral wall of the EGR gas pipe (for example, Patent Document 6) See).
Japanese Patent Laid-Open No. 11-23181 (pages 1-6, FIGS. 1-2) JP 2002-350071 A (pages 1-6, FIGS. 1-4) JP 2000-1111277 A (pages 1 to 12, FIGS. 1 to 12) JP 2003-21478 A (pages 1-8, FIGS. 1-7) JP-A-9-88730 (pages 1 to 4, FIGS. 1 to 4) Japanese Patent Laid-Open No. 9-88731 (pages 1 to 5, FIGS. 1 to 8)

  In each of the above prior arts, in the case of the double-tube type EGR gas cooler disclosed in Patent Documents 1 to 4, the inner surface of the pipe constituting the EGR gas flow path extends over the entire length in the length direction. In many cases, the inner peripheral surface is smooth, heat transfer in the vicinity of the center of the pipe is insufficient, and the cooling efficiency of the EGR gas is low. In addition, the EGR gas cooling device disclosed in Patent Documents 5 and 6 has the advantage that the device is easy to manufacture and inexpensive, but the heat transfer performance required because the heat transfer area is small. In order to secure the vehicle, it is indispensable to increase the length in the axial direction, and in the case of an automobile or the like, which is an indispensable requirement to mount it in a limited space, a layout problem arises and gas Since the flow flows along the EGR gas pipe, the turbulent flow of the gas flow becomes insufficient, the boundary layer of the heat transfer surface is not sufficiently thin, and the heat transfer performance is slightly insufficient.

 Furthermore, as shown in FIGS. 7 and 8, a plurality of flat tubes 30 whose cross-sections have been expanded to have a flat cross section are arranged in order within the shell main body 10 formed of an elongated rectangular cylindrical body at a specific interval. Then, a pair of header plates 20 that close the opening portions at both ends of the shell body 10 are liquid-tightly penetrated and welded, and a pair of ducts 70 are connected to both ends of the header plate 20 to form a gas flow path, The cooling water 18 flows in from the cooling water inlet / outlet 40 provided in the pair of annular bulging portions 50 at both ends of the shell body 10, and the high-temperature gas flowing through the flat tube 30 is effectively heat-exchanged. And a shell-and-tube type multi-tube heat exchanger that is cooled by cooling is proposed (Japanese Patent Laid-Open No. 2002-107091), and the outer periphery of the flat tube 30, the inner wall of the shell body 10, the outer periphery of the flat tube 30, etc. The specific interval which is formed, by controlling the flow rate of the cooling water flowing in the shell body 10 suitably are disclosed effectively that which may be heat exchange. However, in the heat exchanger having such a structure, as shown in FIG. 9, the end portion of the flat tube tube 30 that forms the gas flow path and the header plate 20 that blocks the cooling water flow path are the same joint 90. Therefore, in the unlikely event that leakage occurs at the joint 90, there is a concern that cooling water may enter the gas flow path and lead to a serious accident.

 Further, in a conventional heat exchanger in which gas flow paths are arranged on both sides of a heat transfer tube through which cooling water flows, the end of the heat transfer tube 120 is blocked by a cover 140 as shown in FIG. In this case, the structure is separated from the side case 170 that forms the gas flow path, but at this time, the open portions of both end faces of the heat transfer tube 120 are closed so as to be covered by the covers 140 (FIG. 10B and FIG. (See (c)) or closed so as to be fitted in the heat transfer tube (see FIGS. 10 (d) and (e)), the side cases respectively forming gas flow paths. Are joined by welding or brazing at the same position as shown in FIG. 10 (c) or (e). Accordingly, in this case as well, in the unlikely event that leakage occurs in the joint 90, there is a concern that the cooling water may enter the gas flow path and cause serious troubles, which can be solved quickly. It was a big issue that was desired. SUMMARY OF THE INVENTION An object of the present invention is to solve such problems and to provide an EGR gas cooling device that has excellent cooling efficiency despite its simple structure and can be easily installed in a limited space. It is.

  An EGR gas cooling apparatus according to the present invention for solving the above-mentioned problems is provided with a heat transfer tube having a flat or rectangular cross section having an inlet and an outlet for a cooling medium, and a gas flow path adjacent to the heat transfer tube. In the multi-tube heat exchange type gas cooling apparatus in which a plurality of side cases to be formed are alternately arranged, the heat transfer tubes and the side cases are formed independently, and their joint portions do not coincide with each other. It is a characteristic constituent feature to be arranged in such a manner.

  In the present invention, the heat transfer tube incorporated in the EGR gas cooling device is molded into a container shape by deep drawing, and the edge portion of the upper open portion and the upper lid portion are joined in a liquid-tight manner by welding or fitting, The joining portion is arranged so as not to coincide with the joining portion of the side case forming the gas flow path.

  According to the present invention, the heat transfer tube incorporated in the EGR gas cooling device is formed in a rectangular tube shape whose upper and lower portions are open, and an edge portion of the upper and lower open portion, an upper lid portion, and a bottom portion are welded or fitted into the liquid. It is characterized in that it is tightly joined, and the joint is arranged so as not to coincide with the joint of the side case forming the gas flow path.

  In the EGR gas cooling device according to the present invention, it is preferable that inner fins and / or embossing be performed in the side case forming the gas flow path.

  Furthermore, in the EGR gas cooling device according to the present invention, it is preferable that the inner fin is provided with louvers, through holes, irregularities, corrugations, and the like.

  In a preferred aspect of the present invention, the welding means of each part constituting the EGR gas cooling device including the inner fin is welding and / or brazing.

  The EGR gas cooling device according to the present invention includes a heat transfer tube having a flat or rectangular cross-sectional shape having an inlet and an outlet for a cooling medium, and a side case that forms a gas flow path adjacent to the heat transfer tube. However, in the multi-tube heat exchange type gas cooling apparatus in which a plurality are alternately arranged, the heat transfer tubes and the side cases are formed independently, and the joint portions are arranged so as not to coincide with each other. Is a basic configuration requirement. Further, the heat transfer tube according to the present invention is formed into a container shape by deep drawing, and the edge portion of the upper open portion and the upper lid portion are joined in a liquid-tight manner by either welding, brazing or fitting, The joining portion is formed so as not to overlap with the joining portion of the side case forming the gas flow path. With such a configuration, the EGR gas cooling device according to the present invention has an extremely omitted connection between the heat transfer tubes themselves, and in addition, the gas flow path and the flow path of the cooling medium are completely cut off. Even if pinholes or cracks occur in the joints of the heat pipes and leakage of the cooling medium occurs, entry into the gas flow path is prevented in advance, and there are concerns about serious problems such as engine damage due to that. Is definitely resolved. In the EGR gas cooling apparatus according to the present invention, a cooling medium in which engine coolant is mainly used is narrowed by the flat heat transfer tube, passes through the tube while increasing the flow velocity thereof, and is disposed adjacent to the cooling medium. In the side case that expands the heat transfer area with the side case, promotes heat exchange efficiency for high-temperature gas flowing through the side case to increase its cooling efficiency, and additionally forms the gas pipe The high-temperature gas flow obstructed by the inner fin, which is arbitrarily provided, passes through the gas flow channel as an irregular flow accompanied by turbulent flow or vortex flow. Therefore, the heat of the EGR gas is surely transferred to the cooling medium passing through the flat heat transfer tube at high speed during this time, and is efficiently exchanged. Note that the EGR gas cooling device according to the present invention uses the engine cooling water as a cooling medium as described above, so that the heat transfer coefficient of the outer surface of the flat heat transfer tube is almost 10 times that of the EGR gas. The gas in contact with the outer surface is reliably cooled and excellent heat exchange performance can be obtained.

  Furthermore, in the EGR gas cooling device according to the present invention, since the heat transfer tube is formed into a single container by deep drawing, the single structure acts as a strong support and exhibits a reinforcing effect. As the EGR gas cooling device arranged under severe operating conditions, it can be installed as it is without adding another support or the like, so that the device can be reduced in weight and size. Therefore, the obtained EGR gas cooling device is extremely compact and can be easily installed in a limited space.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings and examples.
FIG. 1 is a schematic partial perspective view for explaining an embodiment of the EGR gas cooling apparatus according to the present invention, and FIG. 2 is a schematic view for explaining another embodiment of the EGR gas cooling apparatus according to the present invention. FIG. 3 is a schematic front view for explaining still another embodiment of the EGR gas cooling device according to the present invention, and FIG. 4 is still another example of the EGR gas cooling device according to the present invention. FIG. 5 is a schematic front view for explaining the embodiment, FIG. 5 is an enlarged sectional view for explaining a joined state of the heat transfer tube and the upper lid portion in the embodiment, and FIG. 6 is another embodiment according to the present invention. FIG. 7 is a partially broken front view of a conventional EGR gas cooling device, and FIG. 8 is a cross-sectional view taken along the line BB in FIG. 9 is a partially enlarged view of the C frame in FIG. 7, and FIG. 10 illustrates another example of a conventional EGR gas cooling device. FIG. 4 is a schematic partial perspective view for the purpose of the present invention, in which FIG. (D) is a partial perspective view showing another example when the cover is joined, (e) is one of the joined state of the heat transfer tube and the cover in (d). FIG.

[Example]
Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited thereto, and can be freely modified within the scope of the gist of the present invention.

  As shown in FIG. 1, the main body 1 of the EGR gas cooling device according to the present example has a heat transfer pipe 2 having a substantially flat cross section having an inlet P1 and an outlet P2 for the cooling medium, and adjacent to the heat transfer pipe 2. And the tubular side case 6 used as a gas flow path is arrange | positioned. The heat transfer tubes 2 and the side cases 6 adjacent to each other are tubular bodies formed independently of each other, and are arranged so that their joint portions do not coincide with each other. The heat transfer tubes 2 are a kind of press forming means. Is formed into a container shape having an open portion on the upper side by the deep drawing method, and the upper open portion is liquid-tightly closed by the upper lid portion 3-1, and the cooling medium W outlet P- 2, the bottom 3-2 of the heat transfer tube 2 formed by deep drawing is similarly provided with an inlet P-1 of the cooling medium W as a single body, and the cooling medium W mainly using engine cooling water is The heat transfer tube 2 is configured to flow independently. In the present embodiment, the upper lid portion 3-1 that covers and closes the upper open portion of the heat transfer tube 2 is liquid-tightly joined by welding with the edge portion 5 of the heat transfer tube 2 as shown in FIG. The end portion 4 of the side case 6 parallel to the gas flow direction g is formed in a container shape by a deep drawing method, and therefore there is no joint portion. Accordingly, the cooling medium W cannot flow out from the end 4, and a pinhole or a crack is generated in the joint portion between the heat transfer tube 2 and the upper lid 3-1, and the cooling medium W leaks. Even in this case, the joint portions do not coincide with each other independently of the side case 6 forming the gas flow path, and the inflow of the cooling medium W into the gas flow path is prevented in advance. The concerns of various engine troubles are also eliminated. In addition, although the wave-shaped inner fin 7 was provided in the side case 6 in this example as shown in FIG. 1, turbulent flow is generated in the flow of high-temperature gas flowing through the side case 6, The flow velocity of the cooling medium W flowing through the heat transfer pipe 2 is accelerated by having an independent inlet / outlet, effectively cooling with excellent heat exchange performance. It was confirmed that In the figure, reference numeral 100 denotes a bonnet.

  As shown in FIG. 2, the main body 1a of the EGR gas cooling device in the present embodiment is formed in a tubular body having a rectangular cross section of the heat transfer tube 2a and having an open portion at the top and bottom. The EGR gas cooling device 1a is similar to the first embodiment except that the upper lid portion 3a-1 having the outlet Pa-2 and the bottom portion 3a-2 having the inlet Pa-1 are liquid-tightly closed. The EGR gas cooling test was carried out under the same conditions as in Example 1. As a result, the joints between the heat transfer tube 2a and the tubular side case 6a do not coincide with each other independently, and the joints between the heat transfer tube 2a, the upper lid 3a-1 and the bottom 3a-2 are Even when one leak occurs, it is confirmed that the cooling medium W can be prevented from entering the gas flow path, and the heat exchange performance is equivalent to that of the first embodiment. In the figure, reference numeral 100 denotes a bonnet as in FIG.

  As shown in FIG. 3, the EGR gas cooling device is configured in the same manner as in Example 1 except that the tubular side cases 6b are arranged on both sides of the heat transfer tube 2b. An EGR gas cooling test was performed. As a result, the joints between the heat transfer tube 2b and the tubular side case 6a do not match each other independently, and even if a leak occurs in the joint of the heat transfer tube 2b, the cooling medium W It was confirmed that intrusion into the gas flow path could be prevented and the heat exchange performance was maintained at an excellent level according to Example 1.

 As shown in FIG. 4, an EGR gas cooling device is configured in the same manner as in Example 1 except that a plurality of heat transfer tubes 2c and tubular side cases 6c are alternately arranged. An EGR gas cooling test was performed. As a result, the joint between the heat transfer tube 2c and the side case 6c does not match each other independently, and even if a leak occurs in the joint of the heat transfer tube 2c, the gas of the cooling medium W It was confirmed that intrusion into the flow path can be prevented and the heat exchange performance is maintained at the same level as in Example 1.

  In each said Example which concerns on this invention, the joining means of the heat exchanger tube main body 2, 2a, 2b, 2c, the upper cover part 3-1, 3a-1, 3b-1, 3c-1, and the bottom part 3a-2, Although it is carried out by welding, for example, brazing using nickel brazing may be adopted instead of the welding, and in the range where liquid-tight connection is possible, it is also hindered to adopt a fitting method as shown in FIG. Absent. Further, in addition to 7, 7a, 7b, 7c, the inner fins provided on the side cases 6, 6a, 6b, 6c serving as gas flow paths are not disturbed by embossing or using corrugated fins. In addition to the inner fins, provision of louvers, through holes, irregularities, and the like can be arbitrarily selected.

  The EGR gas cooling device according to the present invention in each of the above embodiments is a gas heat exchange device such as an EGR cooler in which a tubular body having a flat or rectangular cross section is used as a flow path for a cooling medium such as engine cooling water. A flat or rectangular tube body that forms the flow path of the cooling medium is formed into a container-like tubular body by deep drawing to form a heat transfer tube, and flows through the adjacent tubular side case. The high-temperature gas is cooled by efficiently exchanging heat. The heat transfer tube according to the present invention formed by deep drawing is formed in either a container shape having a bottom portion integrally formed and having an open portion above it, or a tubular body having open portions above and below. However, in the former, the upper open portion is closed by the upper lid portion, and in the latter, the upper and lower open portions are liquid-tightly closed by the upper lid portion and the bottom portion, respectively, so that the cooling medium flows through the upper lid portion and the bottom portion. However, the inflow port and the outflow port do not need to be specified individually, and can be arbitrarily changed by, for example, reversing the outflow port for design reasons.

  In the heat transfer tube according to the present invention, the upper open portion or the upper and lower open portions are liquid-tightly closed using the upper lid portion or the upper lid portion and the bottom portion, and are disposed adjacent to each other. The gas flowing in the tubular side case serving as the gas flow path is shaped so that there is no joint portion as well as an end portion parallel to the flow direction. Therefore, the cooling medium flowing through the heat transfer tube flows out of the end portion and enters the gas flow path in the tubular side case that is opened in parallel. Has been. The heat transfer tube according to the present invention has such a structure that the joint portion is omitted as much as possible, and the joint portion does not coincide with the portion forming the gas flow path in the tubular side case. Since it is designed, the trouble that the cooling medium flows into the gas flow path is avoided in the event of a leak from the joint.

  On the other hand, the side case according to the present invention disposed adjacent to the heat transfer tube to form a gas flow path is substantially a tubular body similar to the heat transfer tube, and is disposed adjacent to the heat transfer tube. In addition, there is a demand for heat exchange of high-temperature gas flowing through the pipe through the gas pipe to the heat transfer pipe, and cooling to a substantially predetermined temperature between the inlet and the outlet. In order to achieve efficient heat exchange, the contact area between the side case and the heat transfer tube is expanded, the flow of gas flowing through the gas flow path is agitated, and a thin layer provides contact with the heat transfer surface. Since it is desirable to repeat, it is devised to generate turbulent flow and vortex flow by providing an inner fin in the flow path. Further, by arranging a plurality of heat transfer tubes and side cases alternately rather than being normally provided as a pair, they can complement each other to promote better heat exchange performance, and an efficient cooling effect can be expected.

  As is clear from each of the above embodiments, the heat transfer tube according to the present invention is formed into a container shape by deep drawing, and the edge of the upper open portion and the upper lid portion abut each other for welding, brazing or fitting welding. These are joined in a liquid-tight manner by either brazing, and the joined portions are formed so as not to overlap with the joined portions of the side cases forming the gas flow paths. Therefore, the joint part of the heat transfer tube itself is extremely omitted, and in addition, the gas flow path and the cooling medium flow path are completely cut off. Even if a leak occurs, the intrusion of the cooling medium into the gas flow path is prevented in advance, and the concern about the trouble caused by it is surely eliminated. In the EGR gas cooling device according to the present invention, a cooling medium mainly using engine cooling water is narrowed by the flat heat transfer tube, passes through the tube while increasing its flow rate, and is disposed adjacent to the cooling medium. The heat transfer area with the side case is increased to increase the cooling efficiency. In addition, the gas flow at a high temperature blocked by the inner fin arbitrarily provided in the side case is brought about by the inner fin. It passes through the irregular gas flow path over time with turbulent flow and vortex flow, and heat is reliably transferred to the cooling medium passing through the adjacent flat heat transfer tube, thereby efficiently exchanging heat. Note that the EGR gas cooling device according to the present invention uses the engine cooling water as a cooling medium as described above, so that the heat transfer coefficient of the outer surface of the flat heat transfer tube is almost 10 times that of the EGR gas. The gas in contact with the outer surface is reliably cooled and excellent heat exchange performance can be obtained. Furthermore, in the EGR gas cooling device according to the present invention, since the heat transfer tube is formed into a single container by deep drawing, the single structure acts as a strong support and exhibits a reinforcing effect. As the EGR gas cooling device arranged under severe operating conditions, it can be installed as it is without adding another support or the like. As described above, the EGR gas cooling device according to the present invention exhibits an excellent cooling efficiency despite the fact that its structure is simple, and at the same time, the EGR gas for automobiles can be reduced in weight and size. A wide range of applications is expected, including not only cooling devices but also other gas cooling devices and gas heating devices.

It is a typical partial perspective view for demonstrating one Example of the EGR gas cooling device which concerns on this invention. It is a typical partial perspective view for demonstrating the other Example of the EGR gas cooling device which concerns on this invention. It is a typical front view for demonstrating the further another Example of the EGR gas cooling device which concerns on this invention. It is a typical front view for demonstrating the further another Example of the EGR gas cooling device which concerns on this invention. It is an expanded sectional view for demonstrating the joining state of the heat exchanger tube and upper cover part in the Example. It is an expanded sectional view for demonstrating the joining state of the heat exchanger tube and upper cover part of the other Example which concerns on this invention. It is a partially broken front view of the conventional EGR gas cooling device. FIG. 8 is a cross-sectional view taken along line BB in FIG. It is a partially enlarged view front view in the C frame in FIG. It is a typical fragmentary perspective view for demonstrating the other example of the conventional EGR gas cooling device, (a) is a partial abbreviation perspective view of the whole structure, (b) is a part which shows an example at the time of joining a cover (C) is a partially enlarged sectional view of the joined state of the heat transfer tube and cover in (b), (d) is a partial perspective view showing another example when joining the cover, (e) It is a partially expanded sectional view of the joining state of the heat exchanger tube and cover in (d).

Explanation of symbols

1, 1a, 1b, 1c EGR gas cooling device main body 2, 2a, 2b, 2c Heat transfer tube 3-1, 3a-1 Upper lid portion 3-2, 3a-2 Bottom portion 4, 4a End portion 5, 5a-1, 5a -2, 5b Edge 6, 6a, 6b, 6c Side case 7, 7a, 7b, 7c Inner fin 8, 8-1 Joint P-1, Pa-1 inlet P-2, Pa-2 outlet Pb , Pc Outflow inlet g Gas flow direction W Cooling medium 100 Bonnet

Claims (1)

And a cross-sectional shape is flat or rectangular heat transfer tube having an inlet and outlet of its own cooling medium, and side case forming a gas flow path adjacent to the heat transfer tubes, a plurality of alternately disposed independently In the multi-tube heat exchange type gas cooling device, the heat transfer tube is formed into a container shape by deep drawing, and the edge of the upper open portion and the upper lid portion are welded or fitted together and liquid-tightly joined Or formed into a rectangular tube open at the top and bottom, and the edge portion of the upper and lower open portion, the upper lid portion and the bottom portion are welded or fitted in a liquid-tight manner, and the heat transfer tubes are joined together. The EGR gas cooling device is characterized in that the portion is arranged so as not to coincide with the joint portion of the side case forming the gas flow path.

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