JP2015017508A - EGR cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR (Exhaust Gas Recirculation) cooler capable of securing its high brazing quality even when adopting flat tubes.SOLUTION: There is provided the EGR cooler in which: the diameter of the end of each flat tube 12 is enlarged into a rectangular shape to form a header part 12a; a heat exchange core 13 is constituted by arranging a plurality of rows of the flat tube 12 in such a way that the header parts 12a neighbor each other; and clearances formed between body parts 12b which are not diametrically enlarged, of the flat tubes 12 serve as flow paths for cooling water 9 to make a heat exchange between exhaust gas 10 flowing in the flat tubes 12 and the cooling water 9. In the EGR cooler, a level difference part 19 is provided in a joint member 18 (a housing member) embracing an area around the header parts 12a. Under the level difference part 19, adjacent sites of corner portions of the header parts 12a are buried to block the clearances between the adjacent sites.

Description

  The present invention relates to an EGR cooler.

  Conventionally, EGR devices that reduce the generation of NOx (nitrogen oxides) by recirculating a part of the exhaust gas of an engine of an automobile or the like to the engine are known. In such an EGR device, recirculation to the engine is known. When the exhaust gas to be cooled is cooled, the temperature of the exhaust gas is lowered and the volume of the exhaust gas is reduced, so that the combustion temperature can be lowered and the generation of NOx can be effectively reduced without significantly reducing the output of the engine. For this reason, some engines are equipped with an EGR cooler for cooling the exhaust gas in the middle of the line for recirculating the exhaust gas to the engine.

  FIG. 6 is a cross-sectional view showing an example of the EGR cooler. In FIG. 6, reference numeral 1 denotes a shell formed in a cylindrical shape, and a plate is formed at both ends in the axial center direction of the shell 1 so as to close the end face of the shell 1. 2 are fixed, and both ends of a large number of tubes 3 are fixed to each plate 2 in a penetrating state. The large number of tubes 3 extend in the axial direction inside the shell 1.

  A cooling water inlet pipe 4 is attached from the outside near one end of the shell 1, and a cooling water outlet pipe 5 is attached from the outside near the other end of the shell 1. 9 is supplied from the cooling water inlet pipe 4 to the inside of the shell 1, flows outside the tube 3, and is discharged from the cooling water outlet pipe 5 to the outside of the shell 1.

  Further, a bonnet 6 formed in a bowl shape is fixed to the side of the anti-shell 1 of each plate 2 so as to enclose the end face of each plate 2, and an exhaust gas inlet 7 is provided at the center of one bonnet 6. An exhaust gas outlet 8 is provided in the center of the other bonnet 6, and the exhaust gas 10 of the engine enters the inside of one bonnet 6 from the exhaust gas inlet 7 and passes through the tubes 3. After being cooled by heat exchange with the cooling water 9 flowing outside, the exhaust gas is discharged into the other bonnet 6 and recirculated from the exhaust gas outlet 8 to the engine.

  In the figure, reference numeral 11 denotes a bypass outlet pipe provided at a position facing the cooling water inlet pipe 4 in the diameter direction of the shell 1. By extracting a part of the cooling water 9 from the bypass outlet pipe 11, The stagnation of the cooling water 9 is prevented from occurring at a location facing the inlet pipe 4.

  According to such an EGR cooler, the exhaust gas 10 recirculated from the exhaust side to the intake side is cooled by the cooling water 9 while passing through the tube 3, and the temperature and volume thereof are reduced to effectively reduce NOx. However, in order to respond to further strengthening of exhaust gas regulations in the future, it is required to increase the recirculation amount of the exhaust gas 10 and increase the EGR rate more than ever.

  However, in the structure in which a plurality of tubes 3 as described above are uniformly arranged and accommodated in the shell 1, the total amount of heat exchanged per unit volume is small, so that the entire EGR cooler becomes too large and is difficult to mount on the vehicle. Therefore, a flat tube 12 as shown in FIG. 7 has been devised, and it is considered to make the EGR cooler compact by arranging a plurality of flat tubes 12 to form a heat exchange core 13. .

  Here, the end portion of the flat tube 12 is expanded in a rectangular shape to form a header portion 12a, and the main body portion 12b sandwiched between the header portions 12a has a plurality of circular tubes close to each other. The circular pipe portions 15 are arranged in a plane and connected in proximity to each other as the communication portion 14 (see FIG. 8), and are arranged so that the header portions 12a are adjacent to each other. Occasionally, a gap formed between the non-expanded main body portions 12b forms a flow path 16 for cooling water (not shown in FIG. 7).

  As prior art document information related to this type of flat tube, for example, the following Patent Document 1 has already been proposed.

JP 2013-79779 A

  However, when the flat tubes 12 as described above are arranged so that the header portions 12a are adjacent to each other, no matter how the radius of curvature of the corner portion of the header portion 12a is minimized, the portion A of FIG. As shown in the drawing, it is inevitable that the substantially triangular gap S is formed at the adjacent corners of the header portion 12a, and the brazing material that has melted during brazing is sucked into the gap S by capillary action. In addition, since the sucked brazing material flows out from the open end face of the gap S and continuously sucks the brazing material necessary for the joint portion, it is easy to cause a shortage of the brazing material at the joint portion. There was a possibility that brazing quality might fall.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an EGR cooler that can ensure high brazing quality even when a flat tube is employed.

  In the present invention, the end of the flat tube is expanded in a rectangular shape to form a header portion, and a plurality of the flat tubes are arranged so that the header portions are adjacent to each other to constitute a heat exchange core. An EGR cooler configured to exchange heat between the exhaust gas flowing in each of the flat tubes and the cooling water using a gap formed between the main body portions of the tube not expanded as a flow path of the cooling water, The housing member that holds the periphery of each header portion is provided with a step portion, and the step portion is configured so that the adjacent portion of the corner portion of each header portion is buried and the gap between the adjacent portions is closed. It is characterized by.

  Thus, since the adjacent portions of the corner portions between the header portions are buried in the step portion of the housing member and the gap between the adjacent portions is closed, the brazing material melted at the time of brazing is capillarity. Even if the gap is sucked into the gap between the adjacent portions by the step, the open end surface of the gap is blocked by the step portion of the housing member. As a result, the suction of the brazing material does not continue, and a shortage of the amount of the brazing material at the joint is avoided.

  Further, in the present invention, the main body portion sandwiched between both header portions of the flat tube is arranged in a planar shape with a plurality of circular tubes in close proximity to each other, and a proximity portion between them is connected as a communication portion. A swirl flow forming projection is formed on the inner peripheral surface of the circular pipe portion along a spiral orbit concentric with the central axis of the circular pipe portion, and the circular pipe portions are individually evacuated. It is preferable to configure so that a swirl flow of gas can be formed.

  In this way, when the exhaust gas flows through each circular pipe portion in the main body portion of the flat tube, the flow is guided in the direction along the spiral orbit by the swirl flow forming protrusion on the inner peripheral surface of each circular pipe portion, As a result, the swirling flow of the exhaust gas is individually formed in each circular pipe part. As a result, the contact frequency and the contact distance of the exhaust gas with respect to the inner peripheral surface in each circular pipe part increase, and the heat exchange efficiency is improved. In addition, the circular pipe portions are in communication with each other via a communication portion, and a large cross-sectional area for passage of exhaust gas is ensured. As a result, the amount of exchange heat increases and pressure loss is reduced.

  Furthermore, in the present invention, it is preferable that the direction of the swirl flow forming projections of the adjacent circular pipe portions is formed so as to be along the spiral trajectories of the opposite directions. The swirl flows in the same direction flow in the same direction and accelerate each other, and even if there is a communication part between each circular pipe part, it is possible to more reliably form exhaust gas as a swirl flow Become.

  According to the EGR cooler of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, since the open end surface of the gap formed at the adjacent portion of the corner portion between the header portions can be closed by the step portion of the housing member, It is possible to prevent further inhalation of the brazing filler metal due to the capillary phenomenon after the gap between the adjacent portions is filled with the brazing filler metal. Even if it is adopted, high brazing quality can be secured.

  (II) According to the invention described in claim 2 of the present invention, the amount of heat exchange per unit volume can be greatly improved as compared with the prior art while providing a swirl flow to the exhaust gas and realizing high heat exchange efficiency. In addition, the overall configuration of the EGR cooler can be made compact to improve the mountability on a vehicle or the like.

  (III) According to the invention described in claim 3 of the present invention, the swirl flows can be accelerated in the same direction at the communicating portions of the adjacent circular pipe portions, and each circular pipe portion can be accelerated. The formation of the swirling flow can be made more reliable.

It is the perspective view which notched a part which shows an example of the form which implements this invention. It is a general view of the EGR cooler of FIG. It is sectional drawing explaining the structure of the main-body part of the flat tube of FIG. It is sectional drawing which expands and shows the principal part of FIG. It is a perspective view which shows the example which formed the notch part in the four corners of the one end side of the coupling member of FIG. It is sectional drawing which shows an example of the conventional EGR cooler. It is a perspective view which shows an example of the core for heat exchange which employ | adopted the flat tube. FIG. 8 is a perspective view showing the structure of the main body portion of FIG. It is a front view which expands and shows the A section of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 5 show an example of an embodiment for carrying out the present invention, and the portions denoted by the same reference numerals as those in FIGS. 6 to 9 represent the same items.

  As shown in FIGS. 1 and 2, in the EGR cooler of this embodiment, the end of the flat tube 12 is expanded in a rectangular shape to form a header portion 12a, and the header portions 12a are adjacent to each other. A plurality of rows of flat tubes 12 are arranged vertically to form the heat exchange core 13, and a gap formed between the non-expanded main body portions 12 b of the flat tubes 12 is used as a flow path for the cooling water 9. 16 (see FIG. 7).

  That is, the heat exchanging core 13 is held in its entirety by a rectangular cylindrical shell 1, and the cooling introduced into the shell 1 from the cooling water inlet pipe 4 provided on the lower surface on the entrance side of the shell 1. The water 9 passes through the flow path 16 between the main body portions 12b and is extracted from the cooling water inlet pipe 4 provided on the outlet side upper surface of the shell 1.

  Here, as shown in FIG. 3, the main body portion 12b sandwiched between the header portions 12a of the flat tube 12 has a plurality of circular tubes placed close to each other and arranged in a plane, and the adjacent portions between them communicate with each other. The circular tube portion 15 is connected as the portion 14, and the swirl flow forming protrusion is formed on the inner peripheral surface of the circular tube portion 15 along a spiral orbit concentric with the central axis O of the circular tube portion 15. 17 is formed, and a swirling flow of the exhaust gas 10 is individually formed in each of the circular pipe portions 15. In particular, in this embodiment, the direction of the swirl flow forming projections 17 of the adjacent circular pipe portions 15 is formed so as to be along mutually opposite spiral trajectories.

  As shown in FIGS. 1 and 4, bonnets 6 formed in a bowl shape like the conventional case are provided at both ends of the shell 1 so as to enclose the end face of the shell 1. Between the bonnet 6 and the shell 1, a joint member 18 is provided so that the bonnet 6 can be fitted inside at one end and the shell 1 can be fitted outside at the other end. It is a housing member that holds the periphery of each header portion 12a.

  On the inner peripheral surface of the other end side of the joint member 18 where the shell 1 can be fitted, the adjacent portion of the corner portion of each header portion 12a is buried and the gap S between the adjacent portions (see FIG. 9). ) Is formed so as to block at least the thickness of the header 12a (see FIG. 4).

  Note that notches 20 as shown in FIG. 5 may be formed at four corners on one end side of the joint member 18, and in this way, the joint member 18 after the bonnet 6 is fitted inside. It is possible to reduce the gap by caulking one end side of the joint, and it is possible to greatly improve the joint quality between the joint member 18 and the bonnet 6.

  Thus, since the adjacent portions of the corner portions of the header portion 12a are buried in the step portion 19 and the gap S between the adjacent portions is closed, the brazing material melted at the time of brazing is capillarity. Even if the clearance S is sucked into the gap S of the adjacent portion, the open end surface of the gap S is blocked by the step portion 19 of the joint member 18, so that the gap S of the adjacent portion is filled with the brazing material. Further, the suction of the brazing filler metal due to the capillary phenomenon is not continued, and the shortage of the brazing filler metal at the joining portion is avoided in advance.

  Further, when the exhaust gas 10 flows through each circular pipe portion 15 in the main body portion 12 b of the flat tube 12, the flow is guided in a direction along the spiral trajectory by the swirl flow forming projections 17 on the inner peripheral surface of each circular pipe portion 15. As a result, the swirl flow of the exhaust gas 10 is individually formed in each circular pipe portion 15, and as a result, the contact frequency and the contact distance of the exhaust gas 10 with respect to the inner peripheral surface in each circular pipe portion 15 increase, and heat exchange is performed. The efficiency is improved, and the circular pipe parts 15 are in communication with each other via the communication part 14 so that a large cross-sectional area for the passage of the exhaust gas 10 is ensured. Therefore, the amount of exchange heat per unit volume is increased and the pressure loss is reduced. Especially, as in this embodiment, the directions of the swirl flow forming projections 17 of the adjacent circular pipe portions 15 are mutually different. Along the reverse spiral trajectory If they are formed in this way, the swirling flows in the communication portions 14 of the adjacent circular pipe portions 15 become flows in the same direction and accelerate each other, and even if the communication portions 14 exist between the circular pipe portions 15. Thus, the exhaust gas 10 can be more reliably formed as a swirling flow.

  Therefore, according to the above embodiment, the open end surface of the gap S formed at the adjacent portion of the corner portion of the header portion 12a can be closed by the step portion 19 of the joint member 18, so that the gap at the adjacent portion at the time of brazing. It is possible to prevent further inhalation of the brazing material due to the capillary phenomenon after S is filled with the brazing material, thereby avoiding an insufficient amount of the brazing material at the joining portion, and adopting the flat tube 12. Even high brazing quality can be ensured.

  In addition, the amount of heat exchange per unit volume can be greatly improved as compared with the prior art while providing a swirl flow to the exhaust gas 10 flowing through each circular pipe portion 15 in the main body portion 12b of the flat tube 12 to achieve high heat exchange efficiency. Thus, the overall configuration of the EGR cooler can be made compact to improve the mountability on a vehicle or the like.

  In particular, in the case of this embodiment, the direction of the swirl flow forming projections 17 of the adjacent circular pipe portions 15 is formed so as to be along mutually opposite spiral trajectories. In FIG. 14, the swirl flows can be accelerated by making the swirl flows flow in the same direction, and the formation of the swirl flow in each circular pipe portion 15 can be made more reliable.

  The EGR cooler according to the present invention is not limited to the above-described embodiment. The housing member that holds the periphery of each header portion does not necessarily have to be a joint member in the illustrated example. Of course, it is possible that the end portion of the housing constitutes a housing member, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 9 Cooling water 10 Exhaust gas 12 Flat tube 12a Header part 12b Main body part 13 Core for heat exchange 14 Communication part 15 Circular pipe part 16 Flow path 17 Swirling flow formation protrusion 18 Joint member (housing member)
19 Stepped portion O Center axis S Clearance

Claims (3)

  The end of the flat tube is expanded in a rectangular shape to form a header portion, and a plurality of the flat tubes are arranged so that the header portions are adjacent to each other to form a heat exchange core, and each flat tube is expanded. The EGR cooler is configured to exchange heat between the exhaust gas flowing in the flat tubes and the cooling water, with a gap formed between the main body portions not being used as a flow path of the cooling water. A step portion is provided in a housing member that holds the periphery of the housing, and the adjacent portion of the corner portion of each header portion is buried by the step portion so that a gap between the adjacent portions is closed. EGR cooler.   The main body part sandwiched between both header parts of the flat tube is constituted by a circular pipe part having a shape such that a plurality of circular pipes are arranged in a plane in close proximity to each other and their adjacent parts are connected as communication parts. A swirl flow forming projection is formed on the inner peripheral surface of the circular tube portion along a spiral orbit concentric with the central axis of the circular tube portion, and a swirl flow of exhaust gas is individually formed in each circular tube portion. The EGR cooler according to claim 1, wherein the EGR cooler is configured to be obtained.   The EGR cooler according to claim 1 or 2, wherein the direction of the swirl flow forming projections of adjacent circular pipe portions is formed so as to be along spiral trajectories opposite to each other.

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