WO2000043663A1

WO2000043663A1 - Egr cooler

Info

Publication number: WO2000043663A1
Application number: PCT/JP2000/000218
Authority: WO
Inventors: Makoto Tsujita; Keiichi Nakagome; Katsuji Inoue; Yoji Yamashita
Original assignee: Hino Motors, Ltd.; Sankyo Radiator Co., Ltd.
Priority date: 1999-01-20
Filing date: 2000-01-19
Publication date: 2000-07-27
Also published as: EP1148231A1; KR20010102981A; EP1148231A4

Abstract

A shell and tube type water-cooled EGR cooler capable of increasing an efficiency of heat exchange between exhaust gas and cooling water, wherein a plurality of spiral projection lines are formed on the inner peripheral surfaces of tubes passing through plates and spiral wire material is closely fitted into the tubes, a bonnet located on an exhaust gas inlet side is formed in a bell mouth shape of which the bore increases gradually toward the flow direction of the exhaust gas; a flat box-shaped shell and tube type water-cooled EGR cooler, wherein a bonnet (6A) on an exhaust gas inlet side is formed in a bell mouth shape, and a truncated-chevron guide plate (21) is disposed in the bonnet and a round bar (22) is disposed at the intermediate position of each guide plate.

Description

Specification

EGR Cooler Technical Field

The present invention relates to an EGR cooler that is attached to an EGR device that recirculates engine exhaust gas to reduce generation of nitrogen oxides and cools exhaust gas for recirculation. Background art

FIG. 1 is a cross-sectional view showing an example of a conventional EGR cooler. In FIG. 1, reference numeral 1 denotes a shell formed in a cylindrical shape. Plates 2 and 2 are fixed so that both ends of a large number of tubes 3 extending in parallel with the axial extension line X of the shell 1 are fixed to each of the plates 2 and 2 in a penetrating state. Tube 3 extends axially inside shell 1.

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

Further, bonnets 6A and 6B are fixed to the opposite sides of the shells 1 of the plates 2 and 2 so as to cover the end faces of the plates 2 and 2, respectively. An exhaust gas inlet 7 is provided at the center of the other hood 6B, and an exhaust gas outlet 8 is provided at the center of the other bonnet 6B. Through tube 3 of After being cooled by heat exchange with the cooling water 9 flowing outside the tube 3 in the meantime, it is discharged into the other bonnet 6B and recirculated from the exhaust gas outlet 8 to the engine. .

However, in such a conventional EGR cooler, the heat exchange efficiency is poor because the exhaust gas 10 flows straight through the tube 3 and the exhaust gas 10 does not sufficiently contact the inner peripheral surface of the tube 3. There was a problem. Further, as shown in FIG. 2 on an enlarged scale, one bonnet 6 A has a taper section 6 X extending from the exhaust gas inlet 7 to the shell 1 side in a straight outline, and a shell 1. However, in such a shape, the flow of the exhaust gas 10 introduced from the exhaust gas inlet 7 flows from the inner peripheral surface of the tapered portion 6X. It is easy to peel off, and turbulence occurs in the inner portion from the tapered portion 6X to the cylindrical portion 6y, so that it becomes difficult for the exhaust gas 10 to be introduced into the tube 3 arranged on the outer peripheral side of the plate 2. Such uneven distribution of the exhaust gas 10 to each tube 3 also has a problem that the heat exchange efficiency is deteriorated.Furthermore, the center tube 3 becomes higher in temperature than the outer tube 3 and is locally heated. There is also a risk that excessive thermal deformation may occur. On the other hand, as shown in FIG. 3 in an enlarged manner, the other bonnet 6B was formed in the same manner as the one bonnet 6A described above, so that the exhaust gas 10 from which the tube 3 on the outer peripheral side was extracted was removed. Collides with the tapered portion 6X of the bonnet 6A and rapidly changes the direction of the flow, causing a pressure rise at the outlet of the tube 3 on the outer peripheral side. The ventilation resistance of the gas 10 causes the exhaust gas 10 to be more difficult to be introduced into the tubes 3 on the outer peripheral side. For this reason, the uneven distribution of the exhaust gas 10 to each tube 3 is also prevented. Heat exchange efficiency is worsened, or the center tube 3 becomes hotter than the outer tube 3 and local thermal deformation occurs. Was caused.

Furthermore, as shown in FIG. 4, the conventional arrangement of the tubes 3 is arranged in a staggered pattern based on a triangle as shown by a two-dot chain line in the figure, so that the tubes 3 are formed in a cylindrical shape. A relatively large gap is formed between the shell 1 thus formed and the outer tube 3, and the cooling water 9 introduced from the cooling water inlet 4 tends to preferentially flow on the outer periphery having less flow resistance. Because the cooling water 9 does not reach the center side where the tubes 3 are densely arranged, the heat exchange efficiency of the center tube 3 is worse than that of the outer tube 3 for such a reason. However, the temperature of the center tube 3 becomes higher than that of the outer tube 3, which may cause local thermal deformation. Further, in the conventional EGR cooler as described above, the cooling water 9 supplied from the cooling water inlet 4 to the inside of the shell 1 does not flow uniformly toward the cooling water outlet 5 with respect to the inner cross section of the shell 1. As shown by the path 12 in Fig. 1, after flowing into the inside of the shell 1 from the cooling water inlet 4, it bends toward the cooling water outlet 5 and diagonally turns to the cooling water outlet 5. The main flow is toward the cooling water inlet 4 and the cooling water outlet 5 in the shell 1, and the cooling water 9 stagnates near the corner on the side facing the cooling water outlet 5 to form a cooling water stagnation section 13. In particular, at a position diametrically opposite the cooling water inlet 4 into which the high-temperature exhaust gas 10 is introduced, a tube near the cooling water stagnant portion 13 There was also a risk that the temperature of 3 would become locally high and cause thermal deformation.

Figs. 5 and 6 show another example of a conventional EGR cooler. In the EGR cooler shown here, the shell 1 is moved vertically (the axis It is formed in a flat box shape (direction perpendicular to the extension line X), and each bonnet 6A, 6B is connected to the exhaust gas inlet 7 or the exhaust gas. The end face of the shell 1 extends from the outlet 8 toward the shell 1 side in the long side direction (vertical direction in the illustrated example) to cover the entire end face of the plate 2.

In such a flat box-shaped EGR cooler, the exhaust gas 10 introduced into the bonnet 6A from the exhaust gas inlet 7 tends to flow straight while maintaining the flow direction at the time of introduction. Is weakened, so that it is difficult to diffuse to the outside of the end face of the shell 1 in the long side direction.In addition, the gas flow is separated at the portion near the exhaust gas inlet 7 in the bonnet 6A, and turbulence is likely to occur. As a result, the exhaust gas 10 flows into the tube 3 at the center in the long side direction of the end surface of the shell 1, and the tube 3 becomes hot mainly on the exhaust gas 10 inlet side, causing local thermal deformation. On the other hand, the amount of exhaust gas 10 distributed to the tube 3 on the outer side in the long side direction of the end face of the shell 1 is insufficient, which causes a problem that the heat exchange efficiency in this portion is deteriorated. Was.

Fig. 7 shows yet another example of a conventional EGR cooler.In the EGR cooler shown here, the bonnet is omitted due to the problem of mounting on the vehicle, and the axial center of the seal 1 is extended. The gas pipes 11, 11 extending in a direction substantially perpendicular to the line X are bent about 90 ° to both ends of the shell 1 and are directly connected to each other. The shape of the connection-side end of the shell 1 with respect to the shell 1 is a bowl-like shape that simulates the bonnets 6A and 6B (see FIG. 1) in the prior art examples of FIGS.

In this type of EGR cooler, the gas pipes 11 and 11 are connected to both ends of the shell 1 by bending them at substantially right angles. Due to the sharp bending of the gas pipe 11 on the side, the gas flow separates inside the corner and turbulence occurs, and the exhaust gas 10 tends to flow unevenly to the tube 3 facing the outside of the corner , There is a risk that the UBE 3 may become hot on the inlet side of the exhaust gas 10 and cause local thermal deformation, while the amount of the exhaust gas 10 distributed to the tube 3 facing the inside of the corner portion may decrease. Insufficient heat exchange caused the problem of poor heat exchange efficiency in this area.

The present invention has been made in view of the above-described circumstances, and provides an EGR cooler capable of improving the heat exchange efficiency between exhaust gas and cooling water as compared with the conventional EGR cooler. If there is a concern, we provide an EGR cooler that can prevent thermal deformation at the same time. Disclosure of the invention

The EGR cooler according to claim 1 of the present invention includes a tube, and a shell surrounding the tube, supplies and discharges cooling water inside the seal, and allows exhaust gas to pass through the tube through exhaust gas. An EGR cooler for exchanging heat with the cooling water, wherein a plurality of spiral projections are formed on an inner peripheral surface of the tube.

By forming a plurality of spiral projections on the inner peripheral surface of the tube in this way, the exhaust gas flowing through the tube is swirled along the plurality of spiral projections and becomes turbulent. As a result of the increase in the frequency and distance of contact with the exhaust gas, the exhaust gas contacts the inner peripheral surface of the tube evenly and sufficiently, and the heat exchange efficiency of the EGR cooler is greatly improved.

When the pitch of the spiral projection formed on the inner peripheral surface of the tube is reduced, the inclination angle of the spiral projection with respect to the flow of the exhaust gas 10 becomes large and approaches a right angle. However, in the present invention, since a plurality of spiral projections are formed in particular, even when the pitch of the spiral projections is reduced, the spiral with respect to the flow of the exhaust gas is reduced. The inclination angle of the projection can be kept small, and the turning force can be increased without increasing the pressure loss.

An EGR cooler according to a second aspect of the present invention includes a tube, and a shell surrounding the tube, for supplying and discharging cooling water inside the shell, and passing exhaust gas into the tube. An EGR cooler configured to exchange heat between the exhaust gas and the cooling water, wherein a spiral wire is inserted into the tube.

When the spiral wire is fitted into the tube in this manner, the exhaust gas flowing in the tube is swirled along the spiral wire and turbulent, thereby increasing the frequency and distance of contact with the inner peripheral surface of the tube. As a result, the exhaust gas comes into even and sufficient contact with the inner peripheral surface of the tube, and the heat exchange efficiency of the EGR cooler is greatly improved.

Further, the invention according to claim 3 of the present invention provides a shell formed in a cylindrical shape, a plate fixed to both ends in the axial direction of the shell so as to close a shell end face, and an opposite shell side of the plate. A shell fixed to cover the end face of the plate, and a tube extending in the axial direction through the inside of the shell and having both ends fixed to the respective plates. An EGR cooler for supplying and discharging water and passing heat through the exhaust gas from one bonnet side to the other bonnet side in the tube to exchange heat between the exhaust gas and the cooling water, wherein the exhaust gas inlet side The bonnet has a concave shape with the bonnet facing outward, and has a bell-mouth shape whose diameter gradually increases in the flow direction of exhaust gas.

By doing so, the tendency of the exhaust gas to flow in a laminar flow without separating along the inner peripheral surface of the bonnet increases, and turbulence is less likely to occur in the outer peripheral portion in the bonnet, and Same as the center side for the placed tube As described above, the exhaust gas is easily introduced, so that the exhaust gas is evenly distributed to each tube, and the heat exchange efficiency is greatly improved.In addition, the center tube and the outer tube are uniformly heated. Thermal deformation due to local high temperature is avoided.

Further, the invention according to claim 4 of the present invention provides a shell formed in a cylindrical shape, a plate fixed to both ends of the shell in the axial direction so as to close a shell end face, and a plate opposite to the shell. A bonnet fixed so as to enclose the end face of the plate, and a tube extending in the axial direction inside the shell and having both ends penetrating and fixed to the respective plates, and a cooling water inside the shell. An EGR cooler for supplying and discharging air and passing the exhaust gas from one bonnet side to the other bonnet side in the tube to exchange heat between the exhaust gas and the cooling water, wherein the exhaust gas outlet side The hood has a bowl-like shape with a convex surface facing outward and the diameter gradually decreases in the exhaust gas flow direction.

By doing so, the exhaust gas that has escaped from the tube on the outer circumferential side forms a laminar flow along the inner circumferential surface of the bonnet and can smoothly change its direction, so that the pressure rise at the outlet of the tube on the outer circumferential side As a result, the ventilation resistance of the exhaust gas in the tubes on the outer peripheral side decreases, and it becomes easier for the exhaust gas to be introduced into the tubes arranged on the outer peripheral side as in the center side. Exhaust gas is evenly distributed and heat exchange efficiency is greatly improved.In addition, both the center tube and the outer tube are heated uniformly, so that thermal deformation due to local high temperature is avoided. .

Further, the invention according to claim 5 of the present invention provides a shell formed in a cylindrical shape, a plate fixed to both ends of the shell in the axial direction so as to close a seal end face, and a plate opposite to the shell. To secure the end face of the plate And a tube extending axially through the inside of the shell and having both ends penetratingly fixed to the respective plates, supplying and discharging cooling water to the inside of the shell, and one of the tubes in the tube. An EGR cooler for exchanging heat between the exhaust gas and the cooling water by passing the exhaust gas from the bonnet side to the other bonnet side, wherein each tube has a concentric multiple circumferential shape centered on the axis of the shell. It is characterized by being arranged in.

In this way, the outer peripheral tube can be arranged along the cylindrical shell, and the gap between the two can be significantly reduced. The tendency for the cooling water to flow preferentially on the outer peripheral side is greatly suppressed, and when arranging the same number of tubes with the same diameter as in the past, the gap between each tube is secured wider than before, and the center Since the cooling water reaches the tube on the side as well, the tube on the center side and the tube on the outer side are cooled uniformly, so that the local rise in temperature of the tube is avoided. The efficiency of heat exchange between exhaust gas and cooling water will also be greatly improved.

The invention according to claim 6 of the present invention is directed to a shell formed into a cylindrical shape, a plate fixed to both ends of the shell in the axial direction so as to close a shell end face, and a plate opposite to the shell side of the plate. A bonnet fixed so as to enclose the end face of the plate; and a tube extending in the axial direction inside the shell and having both ends penetrating and fixed to the respective plates. An EGR cooler for exchanging heat between the exhaust gas and the cooling water through the exhaust gas from one bonnet side to the other bonnet side in the supply / discharge tube, and one end of the shell in the axial direction of the shell. A cooling water inlet for introducing cooling water into the shell, and a cooling water outlet for discharging cooling water from the inside of the shell at the other axial end of the shell; and Axial end of At a position diametrically opposite to the cooling water inlet on the side, a bypass outlet is provided for extracting a part of the cooling water introduced from the cooling water inlet.

Thus, when the cooling water is introduced into the inside of the shell from the cooling water inlet and a part of the introduced cooling water is extracted from the bypass outlet, the cooling water inlet at one axial end of the shell can be removed. Cooling water does not stagnate at the position facing the diametrical direction, and the cooling water stagnation does not occur here, so that the local increase in the temperature of the tube at one axial end of the shell can be avoided. As a result, the heat exchange efficiency between the exhaust gas and the cooling water will be greatly improved.

The invention according to claim 7 of the present invention is characterized in that the shell is formed in a flat box shape and has both ends opened in the axial direction, and is fixed to both ends in the axial direction of the shell so as to close the shell end faces. A plate, a bonnet fixed to the shell opposite to the shell so as to enclose the plate end face, and a tube extending axially inside the shell and having both ends fixed to the respective plates. An EGR cooler that supplies cooling water to the inside of the shell and passes exhaust gas from one bonnet side to the other bonnet side in the tube to exchange heat between the exhaust gas and the cooling water. The exhaust-gas inlet-side ponnet is rapidly expanded from the exhaust gas inlet, which opens on the extension of the axis of the shell, toward the shell side toward the long side of the seal end face to cover the entire plate end face. And A portion close to the exhaust gas inlet is formed to have a bell-mouth-shaped cross-sectional shape with a concave surface facing outward so that gas flow does not separate, and faces the exhaust gas inlet in the bonnet on the exhaust gas inlet side At the position, a pair of guide plates that are curved in an arc shape outward in the long side direction of the shell end surface from the direction along the extension of the axis of the shell are arranged in an eight-shape, and sandwiched between the guide plates. In the middle position, the shell end It features a round bar that extends in the direction of the short side of the surface and cuts off the main flow of exhaust gas.

In this way, the exhaust gas introduced into the bonnet from the exhaust gas inlet is smoothly changed in flow direction by each guide plate, and is well diffused outward in the long side direction of the shell end face. The flow of the exhaust gas passing between the guide plates is also diffused well by hitting the round bar and being divided, and furthermore, at the portion of the hood on the exhaust gas inlet side close to the exhaust gas inlet. The tendency of the gas flow to flow as a laminar flow without separating along the curved surface is strengthened, and the turbulence of the gas flow in the bonnet on the exhaust gas entry side is less likely to occur. The exhaust gas can be easily introduced into the tubes arranged in the pipes, so that the exhaust gas can be introduced and distributed almost uniformly to all the tubes, and the local increase in the temperature of the tubes can be avoided. Becomes, the heat exchange efficiency between the exhaust gas and the cooling water also will be greatly improved.

The invention according to claim 8 of the present invention provides a shell formed in a cylindrical shape, a plate fixed to both ends in the axial direction of the shell so as to close a shell end face, and a shaft inside the shell. A tube extending in the axial direction and having both ends penetrated and fixed to the respective plates, for supplying and discharging cooling water inside the shell, and inside the tube, from one end to the other end in the axial direction of the shell. An EGR cooler that exchanges heat between the exhaust gas and the cooling water through the exhaust gas toward the shell, and extends at both ends in the axial direction of the shell in a direction substantially perpendicular to the axial extension of the shell. While gradually increasing the diameter of the gas pipe, the gas pipe is gently bent so as not to cause separation of the gas flow, and the axis extension of the shell and the axis of each gas pipe intersect at a required angle. The connection is characterized in that: In this way, the exhaust gas guided toward one end in the axial direction of the shell forms a laminar flow along the inner peripheral surface of the gas pipe and can smoothly change its direction. The direction of the flow after the change does not completely match the axial direction of the shell, and the plate is abutted against the plate at one end in the axial direction of the shell with uniform flow velocity distribution. Therefore, it is possible to introduce and distribute exhaust gas substantially evenly to all the tubes while suppressing turbulence of the gas flow at one end in the axial direction of the shell. Exhaust gas that has escaped to the other end in the center direction also forms a laminar flow along the inner peripheral surface of the gas pipe, can be smoothly changed in direction, and receives local ventilation at the outlet of each tube. Since the tube is discharged smoothly without any trouble, the local high temperature of the tube is avoided, and the heat exchange efficiency between the exhaust gas and the cooling water is greatly improved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing an example of a conventional EGR cooler, FIG. 2 is a cross-sectional view showing details of an exhaust gas inlet side bonnet of FIG. 1, and FIG. 3 is an exhaust gas outlet side of FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 2, FIG. 5 is a cross-sectional view showing another example of the conventional EGR cooler, and FIG. 6 is a cross-sectional view of FIG. 7 is a cross-sectional view showing still another example of the conventional EGR cooler, and FIG. 8 is an example of a mode for carrying out the invention described in claim 1 of the present invention. FIG. 9 is a schematic diagram showing the case where the spiral projections of FIG. 8 are one-row, FIG. 10 is a schematic diagram showing the case where the pitch of the spiral projections of FIG. 9 is reduced, FIG. 11 is a schematic view showing a case where the spiral projections of FIG. 8 are two-row, and FIG. 12 is an enlarged view showing an example of an embodiment for carrying out the invention described in claim 2 of the present invention. FIG. 13 is a sectional view showing an example of an embodiment of the invention described in claim 3 of the present invention. FIG. 14 is a cross-sectional view showing an embodiment of the invention described in claim 4 of the present invention. FIG. 15 is a sectional view showing an example of the present invention. FIG. 16 is a sectional view showing an example of an embodiment of the invention described in claim 5, FIG. 16 is a sectional view showing an example of an embodiment of the invention described in claim 6 of the present invention, and FIG. FIG. 18 is a cross-sectional view showing an example of an embodiment of the invention described in claim 7 of the present invention. FIG. 18 is a cross-sectional view showing an example of the embodiment of the invention described in claim 8 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 8 is an enlarged sectional view showing an example of an embodiment of the invention described in claim 1 of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. In the present embodiment, in the EGR cooler configured substantially in the same manner as the EGR cooler described earlier with reference to FIG. In the form, spiral projections 14 and 15 are formed.

In the case of the thin-walled tube 3, when forming the plurality of spiral projections 14, 15, by performing a pressing process for spirally recessing the tube 3 from the outside with a roll having a spiral ridge, A portion pressed from the outside is formed as a plurality of spiral projections 14 and 15 on the inner peripheral surface of the tube 3.

Then, as shown in FIG. 8, for example, the two spiral projections 14 and 15 are arranged so as to coexist on the inner peripheral surface of the tube 3 by changing the phase by 180 ° in the circumferential direction. For example, at each position in the longitudinal direction, the spiral projections 14 and 15 facing each other in the diametric direction cross each other in opposite directions, and the strength of the tube 3 against bending stress increases. Become.

However, in the case of the thick tube 3, multiple spiral projections In forming 14 and 15, the inner peripheral surface of the tube 3 may be cut so as to leave a plurality of spiral projections 14 and 15.

Thus, when a plurality of spiral projections 14 and 15 are formed on the inner peripheral surface of the tube 3 as described above, the exhaust gas 10 passing through the tube 3 flows along the spiral projections 14 and 15. As a result of the swirling flow and turbulence, the frequency of contact and the contact distance with the inner peripheral surface of the tube 3 increase, so that the exhaust gas 10 uniformly and sufficiently contacts the inner peripheral surface of the tube 3, The heat exchange efficiency of the cooler can be greatly improved.

For example, as shown schematically in FIG. 9, when only one spiral projection 14 is formed on the inner peripheral surface of the tube 3 at an inclination angle α with respect to the flow of the exhaust gas 10, a spiral shape is formed. When the pitch Ρ of the projections 14 is reduced, as shown in FIG. 10, the inclination angle β of the spiral projections 14 increases and approaches a right angle, and as a result, it is assumed that the pressure loss increases. In the embodiment, in particular, since a plurality of spiral projections 14 and 15 are formed, as shown in FIG. 11, even if the pitch 間の between the spiral projections 14 and 15 is reduced, The inclination angle a of the spiral projections 14 and 15 with respect to the flow of the exhaust gas 10 can be kept small, and the turning force can be increased without increasing the pressure loss.

FIG. 12 is an enlarged sectional view showing an example of an embodiment of the invention described in claim 2 of the present invention. In this embodiment, the shell 1 is formed in a cylindrical container shape, A structure is adopted in which both ends of the tube 3 are penetrated and fixed to both end surfaces in the axial direction of the shell 1, and the diameter and the wall thickness of the tube 3 are increased to increase the cross-sectional area and the strength of the flow path. However, the number of tubes 3 is reduced to the minimum necessary.

A gas flange 1 is attached to the tip of the tube 3 that protrudes outside the shell 1. A line for recirculating the exhaust gas 10 is appropriately branched and directly connected to the gas flange 16.

Then, a coil spring-shaped spiral wire 17 is inserted into the EGR cooler having such a structure over substantially the entire length in the tube 3, and both ends of the spiral wire 17 are welded 18 to the tube 3. It is fixed to the inner peripheral surface. That is, the embodiment shown in FIG. 12 is suitable when the diameter of the tube 3 is large and the wall thickness is large, and forms the spiral projections 14 and 15 as described above with reference to FIG. There is an advantage that processing is easier than doing. Then, the exhaust gas 10 passing through the tube 3 is swirled along the spiral wire 17 and becomes turbulent. As a result, the frequency of contact and the contact distance to the inner peripheral surface of the tube 3 are increased, and the exhaust gas 10 10 is uniformly and sufficiently in contact with the inner peripheral surface of the tube 3, so that the heat exchange efficiency of the EGR cooler can be greatly improved.

FIG. 13 shows an example of an embodiment for carrying out the invention described in claim 3 of the present invention. In this embodiment, the configuration is substantially the same as the EGR cooler described above with reference to FIG. Regarding the EGR cooler, the bonnet 6A on the inlet side of the exhaust gas 10 has a concave surface facing outward and is formed in a bell-mouth shape whose diameter gradually increases in the flow direction of the exhaust gas 10.

By doing so, the tendency that the exhaust gas 10 introduced from the exhaust gas inlet 7 flows in a laminar flow without separating along the inner peripheral surface of the bonnet 6A becomes stronger. Turbulence is less likely to occur in the outer peripheral portion, and the exhaust gas 10 is easily introduced into the tubes 3 arranged on the outer peripheral side as in the center side. Is distributed evenly, and the heat exchange efficiency is greatly improved.Moreover, both the center tube 3 and the outer tube 3 are uniformly heated to avoid thermal deformation due to local high temperature. become.

FIG. 14 shows an example of an embodiment for carrying out the invention described in claim 4 of the present invention. In this embodiment, substantially the same as the EGR cooler described above with reference to FIG. In the EGR cooler configured as described above, the ponnet 6B on the exit side of the exhaust gas 10 is formed to have a bowl-like shape having a convex surface facing outward and having a diameter gradually decreasing in the flow direction of the exhaust gas 10.

In this way, the exhaust gas 10 that has escaped from the outer tube 3 can form a laminar flow along the inner surface of the bonnet 6B and smoothly change its direction. The pressure rise is less likely to occur at the outlet part of 3, so that the ventilation resistance of the exhaust gas 10 in the outer tube 3 is reduced, and the outer tube 3 is also exhausted similarly to the center. Since the gas 10 is easily introduced, the exhaust gas 10 is evenly distributed to each of the tubes 3 and the heat exchange efficiency is greatly improved. Thus, heat deformation due to local high temperature is avoided.

FIG. 15 shows an example of an embodiment for carrying out the invention described in claim 5 of the present invention. In this embodiment, substantially the same as the EGR cooler described earlier with reference to FIG. In the EGR cooler configured as shown in Fig. 15, the tubes 3 are arranged in a concentric multiple circumference centered on the axis 〇 of the shell 1, and the same diameter and the same diameter as in Fig. 4 are shown in Fig. 15 The number of tubes 3 is arranged.

By doing so, the tubes 3 on the outer peripheral side can be arranged along the cylindrical shell 1 and the gap between the two can be significantly reduced, so that the cooling water inlet The tendency of the cooling water 9 introduced into the shell 1 from 4 to flow preferentially on the outer peripheral side is greatly suppressed.Moreover, when the same number of tubes 3 having the same diameter as the conventional one are arranged, the space between the tubes 3 is reduced. Gap The cooling water 9 is sufficiently secured to reach the center tube 3 more than before, so that both the center tube 3 and the outer tube 3 are cooled uniformly and the tube 3 Local high temperature is avoided, and the heat exchange efficiency between the exhaust gas 10 and the cooling water 9 is greatly improved.

FIG. 16 shows an example of an embodiment for carrying out the invention described in claim 6 of the present invention. In this embodiment, the configuration is substantially the same as that of the EGR cooler described above with reference to FIG. Regarding the EGR cooler, a bypass outlet 19 for extracting a part of the cooling water 9 introduced from the cooling water inlet 4 is provided at a position diametrically opposite to the cooling water inlet 4 at one axial end of the shell 1. Provided.

Thus, the exhaust gas 10 of the engine is dispersed from the exhaust gas inlet 7 through the inside of one bonnet 6A, passes through a number of tubes 3, and enters the inside of the other bonnet 6B. While cooling water 9 is recirculated from the exhaust gas outlet 8 to the engine, cooling water 9 is supplied from the cooling water inlet 4 to the inside of the shell 1 and flows toward the cooling water outlet 5. By introducing a part of the introduced cooling water 9 from the bypass outlet 19 while introducing the cooling water 9 into the inside of the shell 1 from the cooling water inlet 4, the cooling water inlet 4 at one axial end of the shell 1 On the other hand, the cooling water 9 does not stagnate at the position facing the diametrical direction, and the cooling water stagnation portion does not occur here, so the local high temperature of the tube 3 at one end of the shell 1 in the axial direction is reduced. Will be avoided and exhaust Heat exchange efficiency of the scan 1 0 and the cooling water 9 also will be greatly improved.

FIG. 17 shows an example of the embodiment of the invention described in claim 7 of the present invention. In this embodiment, the EGR cooler described above with reference to FIGS. 5 and 6 is omitted. Regarding the EGR cooler with the same configuration, the bonnet 6 A on the exhaust gas 10 inlet side was moved from the exhaust gas inlet 7 opened on the axial extension X of the shell 1. It expands abruptly toward the shell 1 end in the long side direction of the end face of the shell 1 (upward and downward in the example shown) to cover the entire end face of the plate 2 and to separate the gas flow at the portion near the exhaust gas inlet 7 To form a bell mouth-shaped cross-sectional shape with a curved surface portion 20 that is concave toward the outside so as to prevent the occurrence of the exhaust gas inlet 7 in the bonnet 6 A at the position facing the exhaust gas inlet 7. A pair of guide plates 21, 21, which are curved in an arc shape outward from the direction along the long side of the end face of the shell 1, are arranged in an eight-shape, and are sandwiched between the guide plates 21, 21. At the intermediate position, a round bar 22 extending in the short side direction of the end face of the shell 1 (corresponding to the horizontal direction in FIG. 6) and dividing the main flow of the exhaust gas 10 is provided.

In this way, the exhaust gas 10 introduced into the bonnet 6A from the exhaust gas inlet 7 is smoothly changed in flow direction by the guide plates 21 and 21 so that the long side of the end face of the shell 1 Direction, and the flow of exhaust gas 10 that has passed between the guide plates 21, 21 collides with the round bar 22, and is separated well. The gas flow in the bonnet 6A near the exhaust gas inlet 7 is more likely to flow in a laminar flow without separating along the curved surface portion 20 at the portion near the exhaust gas inlet 7. The turbulence of the gas flow in 6 A is less likely to occur, and the exhaust gas 10 is easily introduced into the tubes 3 arranged on the outer side in the long side direction of the shell 1 end face. Exhaust gas 10 is introduced and distributed almost evenly and the local high temperature of tube 3 There would be avoided, the heat exchange efficiency between the exhaust gas 1 0 and the cooling water 9 also will be greatly improved.

FIG. 18 shows an example of an embodiment for carrying out the invention described in claim 8 of the present invention. In this embodiment, the configuration is substantially the same as that of the EGR cooler described earlier with reference to FIG. With respect to the EGR cooler, gas pipes 11 extending in a direction substantially perpendicular to the axial extension line X of the shell 1 are provided at both axial ends of the shell 1. While gradually increasing the aperture, the gas flow is gently bent so as not to cause separation of the gas flow, and the required extension angle S between the axial extension line X of the shell 1 and the axial center line y of each of the gas pipes 11 and 11 is set. And are connected so as to intersect.

In this way, the exhaust gas 10 guided toward one axial end of the shell 1 forms a laminar flow along the inner peripheral surface of the gas pipe 11 and smoothly changes its direction. However, the flow direction after the change is not completely matched with the axial direction of the shell 1 and is made to strike the plate 2 at one axial end of the shell 1 while maintaining a uniform flow velocity distribution. As a result, it is possible to introduce and distribute the exhaust gas 10 almost equally to all the tubes 3 while suppressing turbulence of the gas flow at one axial end of the shell 1, Exhaust gas 10 that has passed through the tube 3 to the other axial end of the shell 1 also forms a laminar flow along the inner peripheral surface of the gas pipe 11 and can smoothly change its direction. Since it will be discharged smoothly without receiving local ventilation resistance at the exit part, Exhaust gas 10 flows almost evenly for all tubes 3, which avoids local rise in temperature of tube 3, and greatly improves the heat exchange efficiency between exhaust gas 10 and cooling water 9. Will be done.

Note that the EGR cooler of the present invention is not limited to the above-described embodiment, and the structures shown in the drawings may be applied individually, but may be appropriately combined with each other. By using this, it is possible to synergistically obtain the effect of improving the heat exchange efficiency between the exhaust gas and the cooling water. Although the case where the heat exchange is performed has been described, heat exchange may be performed as a counter flow, and various changes may be made without departing from the spirit of the present invention. Industrial applicability

As described above, the EGR cooler according to the present invention is suitable for being attached to an EGR device that recirculates engine exhaust gas to reduce the generation of nitrogen oxides.

Claims

The scope of the claims

1. A tube and a shell surrounding the tube are provided, and cooling water is supplied / discharged inside the shell, and exhaust gas is passed through the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler, wherein a plurality of spiral projections are formed on an inner peripheral surface of the tube.

2. A tube and a shell surrounding the tube are provided, and cooling water is supplied to and discharged from the inside of the shell, and exhaust gas is passed through the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler, wherein a spiral wire is inserted into the tube.

3. A shell formed in a cylindrical shape, a plate fixed to both ends in the axial direction of the shell so as to close the shell end surface, and a plate fixed to the opposite side of the plate to cover the plate end surface. And a tube extending axially through the inside of the shell and having both ends penetrating and fixed to the respective plates, supplying and discharging cooling water to the inside of the shell, and An EGR cooler for exchanging heat between the exhaust gas and the cooling water by passing exhaust gas from one bonnet side to the other bonnet side, wherein the bonnet on the exhaust gas inlet side faces outward and has a concave surface. An EGR cooler characterized by a bell mouth shape that gradually increases in diameter in the exhaust gas flow direction.

4. A shell formed in a cylindrical shape, a plate fixed to both ends in the axial direction of the shell so as to close the shell end surface, and a plate end surface enclosing the plate on the side opposite to the shell. A fixed bonnet; and a tube extending axially through the inside of the shell and having both ends penetrating and fixed to the respective plates, supplying and discharging cooling water to the inside of the shell, and Is one side An EGR cooler configured to exchange heat between the exhaust gas and the cooling water by passing exhaust gas from the bonnet side of the exhaust gas to the other bonnet side, wherein the exhaust gas outlet side hood has a convex surface facing outward. The EGR cooler is characterized in that it has a bowl-like shape whose diameter gradually decreases in the exhaust gas flow direction.

5. A shell formed in a cylindrical shape, a plate fixed to both ends in the axial direction of the shell so as to close the shell end surface, and a plate fixed to the opposite side of the plate to cover the plate end surface. And a tube extending axially through the inside of the shell and having both ends penetratingly fixed to the respective plates, supplying and discharging cooling water inside the shell and filling the inside of the tube with cooling water. Is an EGR cooler for exchanging heat between the exhaust gas and the cooling water through the exhaust gas from one bonnet side to the other bonnet side, wherein each tube is centered on the axis of the shell. An EGR cooler characterized by being arranged in concentric multiple circumferences.

6. A shell formed in a cylindrical shape, a plate fixed to both ends in the axial direction of the shell so as to close the shell end surface, and a plate fixed to the opposite side of the plate to cover the plate end surface. And a tube extending in the axial direction through the inside of the shell and having both ends penetratingly fixed to the respective plates, supplying and discharging cooling water inside the shell, and one inside the tube. An EGR cooler in which heat is exchanged between the exhaust gas and the cooling water through the exhaust gas from the ponnet side to the other bonnet side, wherein the cooling water is introduced into the seal at one end in the axial direction of the shell. A cooling water inlet for introducing cooling water, a cooling water outlet for discharging cooling water from the inside of the shell at the other axial end of the shell, and cooling at one axial end of the shell. Direct to water inlet At a position facing the direction, EGR cooler, characterized in that a bypass outlet for out punching a portion of the cooling water introduced from the cooling water inlet.

7. A shell formed in a flat box shape and open at both ends in the axial direction, a plate fixed to both ends in the axial direction of the shell so as to close the shell end surface, and a plate end surface on the opposite side of the plate from the shell And a tube extending in the axial direction through the inside of the shell and having both ends penetrating and fixed to each of the plates, and supplying and discharging cooling water to the inside of the shell. An EGR cooler in which heat is exchanged between the exhaust gas and the cooling water by passing the exhaust gas from one bonnet side to the other bonnet side in the tube, wherein the bonnet on the exhaust gas inlet side is provided with: From the exhaust gas inlet opening on the extension of the axis of the shell, the shell expands abruptly outward in the long side direction toward the shell side to cover the entire plate end surface and the gas near the exhaust gas inlet is covered. A bell mouth-shaped cross-sectional shape with a concave surface facing outward so as not to cause peeling of the shell, at the position facing the exhaust gas inlet in the bonnet on the exhaust gas entry side, along the extension of the axis of the shell A pair of guide plates, which are curved in an arc shape from the direction along the length of the shell end surface to the long side direction, are arranged in an eight-shape, and an intermediate position sandwiched between the guide plates has a short side direction of the shell end surface. The EGR cooler is characterized by a round bar that extends to the main flow and separates the main flow of exhaust gas.

8. A shell formed in a cylindrical shape, plates fixed to both ends in the axial direction of the shell so as to close the shell end surfaces, and plates extending in the axial direction inside the shell and having both ends in the respective plates A cooling water supply / discharge system inside the shell, and an exhaust gas is passed through the shell from one axial end to the other axial end of the shell to heat the exhaust gas and the cooling water. In the EGR cooler which is to be replaced, gas flow separation occurs at both axial ends of the shell while gradually increasing the diameter of gas pipes extending in a direction substantially perpendicular to the axial extension of the shell. Gently bent so that the extension of the axis of the shell and the axis of each gas pipe intersect at a required angle. EGR cooler characterized by: