JP2000213424A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of local thermal deformation by avoiding a state in which temperature of a central side tube is higher than that of an outer peripheral side tube. SOLUTION: In this EGR cooler, an enginehood 6A on an inlet side of exhaust gas 10 faces to outside to be a recess face, and formed into a bell mouth shape in which an aperture is gradually increased in an exhaust gas flowing direction. According to this constitution, the exhaust gas 10 introduced from an exhaust gas inlet 7 tends to flow forming laminar air flow along an inner peripheral surface of the enginehood 6A without separation, turbulence is unlikely to occur on an outer periphery in the enginehood 6A, and the exhaust gas 10 is likely to be introduced to a tube 3 disposed on an outer peripheral side like a central side. Accordingly, the tube 3 on the central side and the tube 3 on the outer peripheral side are heated in a uniform manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR cooler which is attached to an EGR device for recirculating exhaust gas of an engine to reduce the generation of nitrogen oxides and cools the exhaust gas for recirculation.

[0002]

2. Description of the Related Art Conventionally, an EGR device for reducing the generation of nitrogen oxides by recirculating a part of exhaust gas from an engine of an automobile or the like to the engine has been known.
In the device, when the exhaust gas recirculated to the engine is cooled, the temperature of the exhaust gas is reduced and its volume is reduced, so that the combustion temperature is reduced without significantly lowering the output of the engine and the nitrogen oxidation is effectively performed. In order to reduce the generation of substances, some engines are equipped with an EGR cooler for cooling the exhaust gas in the middle of a line for recirculating the exhaust gas to the engine.

FIG. 4 is a cross-sectional view showing an example of the EGR cooler. In the figure, reference numeral 1 denotes a cylindrical shell, and at both ends in the axial direction of the shell 1, the end faces of the shell 1 are closed. The plates 2 and 2 are fixed to each other, and both ends of a large number of tubes 3 are fixed to the respective plates 2 and 2 in a penetrating state.
Extends in the axial direction.

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

Further, bonnets 6A and 6B are fixed to the opposite sides of the plates 2 and 2 from the shell 1 so as to cover the end faces of the plates 2 and 2, respectively. An inlet 7 is provided with an exhaust gas outlet 8 at the center of the other bonnet 6B, and the exhaust gas 10 of the engine enters the inside of one bonnet 6A from the exhaust gas inlet 7 and passes through a number of tubes 3. After being cooled by heat exchange with cooling water 9 flowing outside the tube 3, the exhaust gas is discharged into the other bonnet 6B and recirculated to the engine from the exhaust gas outlet 8.

[0006]

However, in such a conventional EGR cooler, as shown in an enlarged view in FIG. 5, one of the bonnets 6A has a straight outline extending from the exhaust gas inlet 7 toward the shell 1 side. Of the exhaust gas 10 introduced from the exhaust gas inlet 7 with the tapered portion 6x and the cylindrical portion 6y having substantially the same diameter as the shell 1. Flow is tapered part 6
x from the inner peripheral surface of the plate 2, the turbulent flow occurs in the inner portion from the tapered portion 6 x to the cylindrical portion 6 y, and the exhaust gas 10 flows to the tube 3 arranged on the outer peripheral side of the plate 2.
Is difficult to be introduced, so that the temperature of the tube 3 on the center side becomes higher than that of the tube 3 on the outer peripheral side, and there is a possibility that local thermal deformation may occur.

On the other hand, as shown in an enlarged view in FIG. 6, the other bonnet 6B is also formed in the same manner as the above-mentioned one bonnet 6A. When the flow direction is suddenly changed by colliding with the portion 6x, a pressure rise occurs at an outlet portion of the outer tube 3, and this pressure rise becomes a resistance to the passage of the exhaust gas 10 in the outer tube 3, Since the exhaust gas 10 is more difficult to be introduced into the outer tube 3, the center tube 3 becomes higher in temperature than the outer tube 3, which may cause local thermal deformation. there were.

Further, as shown in FIG. 7, the conventional arrangement of the tubes 3 is arranged in a staggered manner based on a triangle, so that the cylindrical shell 1 and the outer peripheral side are arranged. A relatively large gap is formed between the tubes 3 and the cooling water 9 introduced from the cooling water inlet pipe 4 tends to preferentially flow on the outer peripheral side where the flow resistance is low, while the tubes 3 are densely arranged. Since the cooling water 9 does not reach the center side sufficiently, the center tube 3 may be heated to a higher temperature than the outer tube 3 due to such a reason, and local thermal deformation may occur.

The present invention has been made in view of the above circumstances, and prevents the center tube from becoming hotter than the outer tube, thereby preventing local thermal deformation from occurring. It is intended to be.

[0010]

According to a first aspect of the present invention, there is provided a shell having a cylindrical shape, plates fixed to both ends of the shell in the axial direction so as to close the shell end faces, A bonnet fixed to the side opposite to the shell of the plate 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 fixed to the respective plates. An EGR cooler for supplying and discharging cooling water therein 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. The gas inlet side bonnet has a concave surface facing outward and has a bell mouth shape whose diameter gradually increases in the flow direction of exhaust gas.

With this arrangement, 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 hardly occurs in the outer peripheral portion in the bonnet. Exhaust gas is easily introduced into the tubes arranged on the side similarly to the center side, so that both the tube on the center side and the tube on the outer peripheral side are uniformly heated.

[0012] The invention described in claim 2 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 the shell end surface, a bonnet fixed to cover the plate end surface on the side opposite to the shell of the plate; Tubes extending axially through the inside of the shell and having both ends fixed to the respective plates to supply and discharge cooling water to the inside of the shell, and inside the tubes from one bonnet side to the other. An EGR cooler configured to exchange heat between the exhaust gas and the cooling water through the exhaust gas toward the bonnet side,
The exhaust gas outlet side bonnet has a bowl-like shape in which a convex surface faces outward and the diameter gradually decreases in the flow direction of the exhaust gas.

With this configuration, the exhaust gas that has escaped from the tube on the outer peripheral side forms a laminar flow along the inner peripheral surface of the bonnet and can smoothly change its direction. Pressure rise is unlikely to occur, which reduces the ventilation resistance of the exhaust gas in the tubes on the outer peripheral side, and makes it easier for the exhaust gas to be introduced into the tubes arranged on the outer peripheral side as well as the center side, Both the outer tube and the outer tube are heated uniformly.

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 the shell end surface, a bonnet fixed to cover the plate end surface on the side opposite to the shell of the plate; Tubes extending axially through the inside of the shell and having both ends fixed to the respective plates to supply and discharge cooling water to the inside of the shell, and inside the tubes from one bonnet side to the other. An EGR cooler configured to exchange heat between the exhaust gas and the cooling water through the exhaust gas toward the bonnet side,
The tubes are arranged in a concentric multiple circumference around the axis of the shell.

[0015] With this configuration, it is possible to arrange the tubes on the outer peripheral side along the shell formed in a cylindrical shape, and it is possible to remarkably reduce the gap between the two. The tendency of the introduced cooling water to flow preferentially on the outer peripheral side is greatly suppressed, and furthermore, when arranging the same number of tubes with the same diameter as the conventional one, the gap between each tube is secured wider than before, Since the cooling water sufficiently reaches the center tube, both the center tube and the outer tube are cooled uniformly.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment for carrying out the invention described in claim 1 of the present invention, and the same parts as those in FIG. 4 are denoted by the same reference numerals.

In the present embodiment, an EGR cooler having substantially the same configuration as the EGR cooler described above with reference to FIG.
The bonnet 6 </ b> A on the inlet side of the exhaust gas 10 has a concave shape facing outward and is formed in a bell-mouth shape whose diameter gradually increases in the flow direction of the exhaust gas 10.

In this manner, 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 is enhanced, and the outer peripheral portion in the bonnet 6A is increased. As a result, the turbulence hardly occurs, and the exhaust gas 10 is easily introduced into the tubes 3 arranged on the outer peripheral side as well as the central side. Heating.

Therefore, according to this embodiment, the exhaust gas 1 is applied to the tube 3 arranged on the outer peripheral side in the same manner as the central side.
0 can be introduced and the center tube 3 can be prevented from becoming higher in temperature than the outer tube 3, so that local thermal deformation can be prevented from occurring, and EGR can be prevented. The strength reliability of the cooler can be greatly improved.

FIG. 2 shows an example of an embodiment for carrying out the invention according to the second aspect of the present invention. In this embodiment, the hood 6B on the outlet side of the exhaust gas 10 has a convex surface facing outward. It is formed as a bowl-shaped shape whose diameter gradually decreases in the flow direction of the exhaust gas 10.

In this way, the exhaust gas 10 which 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. Pressure rise hardly occurs at the outlet portion of the exhaust gas 1, and the exhaust gas 1
0, the exhaust gas 10 is easily introduced into the tubes 3 arranged on the outer peripheral side similarly to the central side, so that the tubes 3 on the central side are also replaced with the tubes 3 on the outer peripheral side.
Will also be uniformly heated.

Therefore, also in the case of this embodiment, the exhaust gas 10 can be introduced into the tube 3 arranged on the outer peripheral side in the same manner as the central side, and the central tube 3 has a higher temperature than the outer peripheral tube 3. Since it is possible to avoid the occurrence of local thermal deformation, it is possible to prevent local thermal deformation from occurring, and it is possible to greatly improve the strength reliability of the EGR cooler.

FIG. 3 shows an example of an embodiment for carrying out the invention according to claim 3 of the present invention. In this embodiment, each tube 3 is concentric about the axis O of the shell 1. The tubes 3 are arranged in a multi-circumferential shape, and in FIG. 3, the same number of tubes 3 having the same diameter as in FIG. 7 are arranged.

In this way, it is possible to arrange the tubes 3 on the outer peripheral side along the shell 1 formed in a cylindrical shape, and it is possible to remarkably reduce the gap between the two. The tendency of the cooling water 9 introduced into the shell 1 from the water inlet pipe 4 to flow preferentially on the outer peripheral side is greatly suppressed, and when arranging the same number of tubes 3 with the same diameter as the conventional one, Since the gap between the tubes 3 is wider than before, and the cooling water 9 reaches the center tube 3 sufficiently, the center tube 3 and the outer tube 3 are uniformly cooled. become.

Therefore, in the case of the present embodiment, the tendency of the cooling water 9 introduced into the shell 1 to preferentially flow on the outer peripheral side can be greatly suppressed, and the cooling water 9 also cools the central tube 3. Since the water 9 can be sufficiently distributed, it is possible to prevent the center tube 3 from becoming hotter than the outer tube 3, thereby preventing local thermal deformation from occurring. Can be EGR
The strength reliability of the cooler can be greatly improved.

The EGR cooler of the present invention is not limited to the above-described embodiment, and the structures shown in FIGS. 1, 2 and 3 may be applied individually. However, it is possible to obtain a synergistic effect of preventing the occurrence of local thermal deformation by using them appropriately in combination with each other. On the other hand, the case where the heat exchange is performed as the counter flow has been described, but it is needless to say that the heat exchange may be performed as the parallel flow, and that various changes may be made without departing from the gist of the present invention.

[0028]

According to the EGR cooler of the present invention described above, it is possible to prevent the center tube from becoming hotter than the outer tube, thereby preventing local thermal deformation from occurring. Therefore, an excellent effect that the reliability of the strength of the EGR cooler can be greatly improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an embodiment for carrying out the invention described in claim 1 of the present invention.

FIG. 2 is a sectional view showing an example of an embodiment for carrying out the invention described in claim 2 of the present invention.

FIG. 3 is a sectional view showing an example of an embodiment for carrying out the invention described in claim 3 of the present invention.

FIG. 4 is a sectional view showing an example of a conventional EGR cooler.

FIG. 5 is a cross-sectional view showing details of a bonnet on an exhaust gas entry side in FIG. 4;

FIG. 6 is a sectional view showing details of a bonnet on an exhaust gas outlet side in FIG. 4;

7 is a view in the direction of arrows VII-VII in FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 shell 2 plate 3 tube 6A bonnet 6B bonnet 9 cooling water 10 exhaust gas O axis

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoji Yamashita 6-28, Owada-cho, Hachioji-shi, Tokyo F-term in Sankyo Radiator Co., Ltd. (reference) 3G062 CA06 ED08 GA08 GA10 GA23

Claims (3)

[Claims] 1. 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 plate fixed to the opposite side of the plate to cover the plate end face. And a tube extending axially through the inside of the shell and having both ends penetratingly fixed to the respective plates, for supplying and discharging cooling water to the inside of the shell and having one inside the tube. An EGR cooler for exchanging heat between the exhaust gas and the cooling water through the exhaust gas from the bonnet side to the other bonnet side, wherein the exhaust gas inlet side bonnet has a concave surface facing outward and the exhaust gas is formed. An EGR cooler characterized in that it has a bell mouth shape whose diameter gradually increases in the flow direction of the EGR. 2. 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 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, wherein cooling water is discharged inside the shell, and one bonnet is provided inside the tube. An EGR cooler that exchanges heat between the exhaust gas and the cooling water through the exhaust gas from the side toward the other bonnet side. An EGR cooler characterized in that it has a bowl shape whose diameter gradually decreases in a flow direction. 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 a 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, for supplying and discharging cooling water to the inside of the shell and having one inside the tube. An EGR cooler for exchanging heat between the exhaust gas and the cooling water through the exhaust gas from the bonnet side to the other bonnet side, wherein each tube has a concentric multiple circumference centered on the axis of the shell. An EGR cooler characterized by being arranged.