JP2000097113A - Egr gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR(exhaust gas recirculation) gas cooling device which can reduce a stress applied to a pipe for heat exchange in a simple structure, as to the EGR gas cooling device in order to cool the EGR gas recirculated to a suction system from the exhaust system of an engine. SOLUTION: This EGR gas cooling device is provided with an outer tube 21 furnishing the inlet 33 and the outlet 35 of the cooling water, a partition plate 23 to block the opening 21b of the outer tube 21, plural pipes 37 extended in the outer tube 21 by penetrating the partition plate 23, whose both ends 37b and 37c are fixed to the partition plate 23, and an inlet cap 27 and an outlet cap 29 of the EGR gas 25 provided by covering the both ends 37b and 37c of the plural pipes 37 respectively. In such an EGR gas cooling device, the pipes 37 have bending parts 37a which are displaced following to the expansion and the contraction of the pipes 37 by the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EGR gas cooling device for cooling EGR gas recirculated from an exhaust system of an engine to an intake system.

[0002]

2. Description of the Related Art Conventionally, in order to reduce nitrogen oxides (NOx) in exhaust gas discharged from an engine, part of the exhaust gas is taken out of an exhaust system and added to an air-fuel mixture.
(Exhaust Gas Recirculation).

In an EGR apparatus for performing such EGR, when high-temperature EGR gas expanded by heat is directly taken into an intake system, an air-fuel mixture becomes lean, combustion efficiency deteriorates, and engine output decreases. Resulting in. For this reason,
An EGR device generally includes an EGR gas cooling device that cools EGR gas.

[0004] This type of EGR gas cooling device is generally
A device in which a pipe for distributing cooling water is disposed inside or outside the outer cylinder for flowing EGR gas, and a device in which a pipe for distributing EGR gas is disposed in the outer cylinder for distributing cooling water. . EG in which a pipe for cooling water distribution is arranged in an outer cylinder
JP-A-9-88730 discloses an R gas cooling device,
Japanese Unexamined Patent Application Publication No. 8-165925 and the like are known.

[0005] The EGR gas cooling device disclosed in Japanese Patent Application Laid-Open No. 9-88730 discloses a long cooling water pipe spirally wound around an outer cylinder through which EGR gas flows. The heat exchange of the EGR gas is performed on the outer surface of the EGR gas. The EGR gas cooling device disclosed in this publication has a simple structure, but heat exchange of the EGR gas is performed through the outer surface of the outer cylinder, so that the heat exchange efficiency is poor and is not practical.

The EGR gas cooling device disclosed in Japanese Patent Application Laid-Open No. 8-165925 has a long cooling water pipe arranged in a meandering manner in an outer cylinder through which EGR gas flows. The heat exchange of the EGR gas is performed. The EGR gas cooling device disclosed in this publication includes an outer cylinder having a limited volume,
Since the pipes are arranged in a meandering manner, long pipes cannot be arranged, and it is difficult to obtain high heat exchange efficiency.

On the other hand, there is known an EGR gas cooling apparatus having an EGR gas distribution pipe disposed in an outer cylinder as shown in FIG. In the figure, a circular plate-shaped partition plate 2 is provided at both ends of a cylindrical outer cylinder 1 and brazed, respectively.

An inlet cap 4 and an outlet cap 5 through which the EGR gas 3 flows are fixed to both ends of the outer cylinder 1. An inlet 7 and an outlet 8 for flowing the cooling water 6 into the outer cylinder 1 are formed in the outer cylinder 1 at intervals. A plurality of copper pipes 9 for circulating the EGR gas 3 are provided in the outer cylinder 1 along the axial direction.

Both ends of the pipe 9 penetrate the partition plate 2, and the end 9 a of the pipe 9 projects toward the inlet cap 4 and the outlet cap 5.
It is brazed to 10. In the above-described EGR gas cooling device, the EGR gas 3 discharged from the exhaust system of the engine 3
Flows into the pipe 9 through the inlet cap 4.

The temperature of the EGR gas 3 in the vicinity of the inlet cap 4 is as high as 200 to 300 ° C., and constantly changes depending on the degree of combustion of the engine. Since the EGR gas 3 is directly blown to the end 9a of the pipe 9 on the inlet cap 4 side, the temperature of the pipe 9 on the inlet cap 4 side is EGR.
The temperature rises to almost the same temperature as the gas 3.

The EGR gas 3 flowing into the pipe 9 undergoes heat exchange with the cooling water 6 flowing through the outer cylinder 1 and
Cool to 150 ° C. EG with cooled volume
The R gas 3 is sent through the outlet cap 5 to the intake system of the engine.

[0012]

However, in such a conventional EGR gas cooling device, the pipe 9 thermally expands in the axial direction along with the inflow of the EGR gas 3, while both ends of the pipe 9 are partitioned. Since the brazing 10 is performed on the plate 2 and the extension in the axial direction is regulated, the pipe 9 is deformed, and a large stress is applied to the brazing portion 10 between the pipe 9 and the partition plate 2. .

In particular, the temperature of the pipe 9 on the inlet cap 4 side is always 200 to 30 in accordance with the temperature of the EGR gas 3.
Since the temperature changes to 0 ° C., this temperature change causes the pipe 9 to constantly expand and contract, and the stress applied to the brazing portion 10 changes irregularly. For this reason, when such expansion and contraction are repeated for a long period of time, there is a possibility that a crack may be generated in the brazing portion 11.

The EGR gas cooling system disclosed in Japanese Patent Application Laid-Open No. 8-165925, in which a pipe for distributing cooling water is disposed inside or outside the outer cylinder, circulates cooling water through the pipe. Since the EGR gas does not blow directly onto the end face of the pipe, the expansion and contraction of the pipe is smaller than that of an EGR gas cooling device in which an EGR gas distribution pipe is provided in an outer cylinder, and the stress applied to the pipe is small.

[0015] Therefore, problems such as the above-described EGR gas cooling device hardly occur. The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an EGR gas cooling device capable of reducing stress applied to a heat exchange pipe with a simple structure.

[0016]

According to a first aspect of the present invention, there is provided an EGR gas cooling apparatus, comprising: an outer cylinder provided with an inlet and an outlet for cooling water; a partition plate for closing an open end of the outer cylinder; EGR comprising: a plurality of pipes extending into the outer cylinder and having both ends fixed to the partition plate; and an EGR gas inlet cap and an outlet cap provided to respectively cover both ends of the plurality of pipes. In the gas cooling device,
The pipe is provided with a curved portion that is displaced following the expansion and contraction of the pipe due to a temperature change.

The EGR gas cooling device according to a second aspect is the EGR gas cooling device according to the first aspect, wherein the opening end is:
Formed at one end of the outer cylinder, the curved portion of the pipe is a folded portion of the pipe formed in a U-shape,
Both ends of the pipe are fixed to the partition plate closing the opening end, respectively, and the inlet cap and the outlet cap are fixed to the partition plate so as to be adjacent to each other.

According to a third aspect of the present invention, there is provided the EGR gas cooling apparatus according to the first or second aspect,
The curved portion of the pipe is formed in a bellows shape in which a diameter expansion and a diameter reduction are repeated.

(Operation) In the EGR gas cooling device of the first aspect, the engine is started, and the EGR gas flows through the pipe whose both ends are fixed to the partition plate.

The temperature of the EGR gas constantly changes depending on the degree of combustion of the engine, and the pipe is repeatedly expanded and contracted in accordance with the temperature change. The curved portion formed in the pipe follows the expansion and contraction of the pipe. Therefore, stress is prevented from being applied to a fixed portion between both ends of the pipe and the partition plate. As a result, it is possible to prevent cracks from being generated in the fixed portion between the both ends of the pipe and the partition plate.

In the EGR gas cooling device according to the second aspect, when the EGR gas flows through the pipe which is bent in a U-shape and has a folded portion, the pipe expands and contracts with a change in the temperature of the EGR gas. Then, the folded portion is displaced following the expansion and contraction of the pipe, so that stress is prevented from being applied to the fixed portion between the both ends of the pipe and the partition plate.

Further, since the U-shaped pipe is provided in the outer cylinder having one end opened, the outer cylinder can be made shorter.
The degree of freedom in layout when installing the apparatus in an engine room or the like is increased. In the EGR gas cooling device according to the third aspect, the EGR gas is formed in the pipe in which the bellows-like curved portion is formed.
When the gas is circulated, the pipe expands and contracts with a change in the temperature of the EGR gas.

Then, the curved portion is displaced following the expansion and contraction of the pipe, so that stress is prevented from being applied to the fixed portion between the both ends of the pipe and the partition plate. Further, by processing the pipe into a bellows shape, the inner surface of the pipe becomes uneven, so that the contact area of the EGR gas on the inner surface of the pipe is increased, and the heat exchange efficiency of the EGR gas is improved.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment (corresponding to claims 1 and 2) of an EGR gas cooling device of the present invention. In the figure, an opening 21b is formed at one end 21a in the axial direction of a flat container-shaped outer cylinder 21 having an oval cross section.

The outer cylinder 21 has an elliptical partition plate 2 covering the opening 21b and corresponding to the cross-sectional shape of the outer cylinder 21.
3 is brazed. In the partition plate 23, an inlet cap 27 and an outlet cap 29 through which the EGR gas 25 flows are disposed on an outer surface 23a located on the opposite side of the outer cylinder 21. These inlet cap 27 and outlet cap 29 are brazed at intervals along the longitudinal direction of the partition plate 23.

The outer cylinder 21, the partition plate 23, the inlet cap 27 and the outlet cap 29 are made of stainless steel such as SUS. Further, the outer cylinder 21 is provided with the cooling water 3.
The inlet 33 and the outlet 35 that allow the fluid 1 to flow into the outer cylinder 21 are
They are formed at intervals in the axial direction.

Inside the outer cylinder 21, a copper pipe 37 having a U-shape and having a circular cross section having a folded portion 37a is provided.
Are provided. One end 37b and the other end 37c of each pipe 37 penetrate the partition plate 23 and protrude toward the outer surface 23a of the partition plate 23 covered with the inlet cap 27 and the outlet cap 29, respectively.

One end 37b and the other end 37 of each pipe 37
c is brazed 39 to the partition plate 23. In the above-described EGR gas cooling device, the EGR gas 25 discharged from the exhaust system of the engine flows into each pipe 37 from the inlet cap 27. The temperature of the EGR gas 25 near the inlet cap 27 is as high as 200 to 300 ° C., and constantly changes depending on the degree of combustion of the engine.

For this reason, the temperature at the one end 37b side of the pipe 37 to which the EGR gas 25 is directly blown depends on the temperature of the EGR gas 25.
And the temperature is almost the same. EG flowing into the pipe 37
The R gas 25 undergoes heat exchange with the cooling water 31 flowing in the outer cylinder 21, and in the vicinity of the outlet cap 29, 100 to 15 R
Cool to 0 ° C.

The cooled EGR gas 25 whose volume has been reduced
Is passed through the outlet cap 29 to the intake system of the engine. Here, the temperature of the pipe 37 changes according to the temperature of the EGR gas 25 flowing in the pipe 37. On the one end 37b side of the pipe 37 located on the inlet cap 27 side, the temperature of the pipe 37 changes to 200 to 300 ° C.

The pipe 37 located on the outlet cap 29 side
On the other end 37c side, the temperature of the pipe 37 is 100 to 1
Changes to 50 ° C. As the temperature of the pipe 37 changes,
Repeats expansion and contraction in the axial direction. Folded part 3 of pipe 37
Since there is nothing in 7a that restricts the expansion and contraction of the pipe 37, the folded portion 37a moves in the axial direction of the outer cylinder 21 following the expansion and contraction of the pipe 37.

As a result, stress is not applied to the brazing portions 39 at the one end 37b and the other end 37c of the pipe 37, and the occurrence of cracks in the brazing portion 39 due to expansion and contraction of the pipe 37 is prevented. In the EGR gas cooling device configured as described above, the pipe 37 is disposed in the outer cylinder 21 and has one end 37b and the other end 37c fixed to the partition plate 23.
Since the U-shaped folded portion 37a is formed on the
Following the expansion and contraction of the pipe 37 due to the temperature change of the gas 25, the folded portion 37 a can be moved in the axial direction of the outer cylinder 21, and one end 37 b and the other end 37 of the pipe 37 can be moved.
It is possible to prevent stress from being applied to the brazing portion 39 between the c and the partition plate 23.

As a result, it is possible to prevent the occurrence of cracks in the brazing portion 39 and the cooling water 31 from flowing into the intake system of the engine. In addition, the outer cylinder 21 is formed in a flat container shape having an oblong cross section having an opening 21b at one end 21a, and a U-shaped pipe 37 is provided in the outer cylinder 2. The length can be shortened, and the degree of freedom in layout when installing the device in an engine room or the like can be increased.

FIG. 2 shows a second embodiment (corresponding to claim 1) of the EGR gas cooling device of the present invention. In the figure, openings 4 are provided at both ends of an outer cylinder 41 having a circular cross section.
1a is formed. In the opening 41a of the outer cylinder 41,
Circular plate-shaped partition plates 43 are respectively provided and brazed.

The opening 41a of the outer cylinder 41 has an EG
The inlet cap 47 and the outlet cap 49 through which the R gas 45 flows are brazed, respectively. Outer cylinder 41
, A cylindrical inlet 53 and an outlet 55 for flowing the cooling water 51 into the outer cylinder 41 are formed at intervals in the axial direction. In the outer cylinder 41, a plurality of copper pipes 57 having a circular cross section for circulating the EGR gas 45 are arranged along the axial direction.

The pipe 57 has both ends penetrating through the partition plate 43, and is brazed 59 to the partition plate 43 with the end 57a of the pipe 57 protruding toward the inlet cap 47 and the outlet cap 49. ing. A curved portion 57 which is curved in an arc shape is provided substantially at the center of each pipe 57.
b is formed.

Here, the axes of the pipes 57 extending on both sides of the curved portion 57b are aligned. In the above-described EGR gas cooling device, the curved portion 57 follows the expansion and contraction of the pipe 57 due to the temperature change of the EGR gas flowing into the pipe 57.
The shape of b changes and the brazing portions 59 at both ends of the pipe 47 are changed.
In addition, stress due to expansion and contraction of the pipe 57 is prevented.

In the EGR gas cooling device of this embodiment, the same effect as in the first embodiment can be obtained. However, in this embodiment, a plurality of pipes 57 are provided in the outer cylinder 41 having a circular cross section. Since a curved portion 57b curved in an arc shape was formed substantially at the center of the pipe 57,
Following the expansion and contraction of the pipe 57 due to the temperature change of the GR gas 45, the shape of the curved portion 57b can be changed, and the brazing portion 59 between the both ends 57a of the pipe 57 and the partition plate 43 can be formed.
Can be prevented from being stressed.

FIG. 3 shows a third embodiment (corresponding to claim 1) of the EGR gas cooling device of the present invention. In this embodiment, a curved portion 61a which is bent in a step with a predetermined curvature is formed substantially at the center of a pipe 61 which is disposed in the outer cylinder 41 and brazed 59 to the partition plate 43.

Here, the axes of the pipes 61 extending on both sides of the curved portion 61a are shifted from each other, so that when the pipes 61 expand, the pipes 61 mutually stick toward the brazing portion 59. Is prevented. EGR of this embodiment
The same effect as in the second embodiment can be obtained in the gas cooling device.

FIG. 4 shows a fourth embodiment (corresponding to claim 3) of an EGR gas cooling device according to the present invention. In this embodiment, a bellows-like curved portion 63a that is repeated a plurality of times of diameter expansion and contraction is formed substantially at the center of a pipe 63 that is disposed in the outer cylinder 41 and brazed 59 to the partition plate 43. ing.

In the EGR gas cooling device of this embodiment, the same effects as those of the second and third embodiments can be obtained. In this embodiment, a bellows-like curved portion 63a is provided at the center of the pipe 63. Since the pipe 63 is formed, the contact surface of the EGR gas 45 can be increased by making the inner surface of the pipe 63 uneven, so that the stress of the pipe 37 can be absorbed and the heat exchange efficiency of the EGR gas can be improved. .

In the above-described second and third embodiments, the example in which the curved portion is formed by bending the pipe through which the EGR gas flows is described, but the present invention is limited to such an embodiment. Instead, for example, the pipe may be bent and processed into a bellows shape. In this case, the expansion and contraction of the pipe can be absorbed more reliably.
Further, in the above-described second embodiment, an example has been described in which the axes of the pipes 57 extending on both sides of the curved portion 57b are aligned, but the present invention is not limited to such an embodiment.
For example, as shown in FIG. 5, the pipes 57 extending on both sides of the curved portion 57b may be shifted from each other to form the pipes 57. In this case, when the pipes 57 expand, Since the pipes 57 are prevented from sticking to each other toward the brazing 59, stress applied to both ends 57a of the pipe 57 can be more reliably prevented.

[0044]

According to the EGR gas cooling device of the first aspect, the pipe disposed in the outer cylinder and having both ends fixed to the partition plate is provided with:
Since the curved portion is formed, the curved portion can be displaced by following the expansion and contraction of the pipe due to the temperature change of the EGR gas, and it is possible to prevent stress from being applied to the fixed portion between both ends of the pipe and the partition plate. it can.

As a result, it is possible to prevent the occurrence of cracks at the fixed portion between the both ends of the pipe and the partition plate. In the EGR gas cooling device according to the second aspect, the pipe bent in a U-shape and having the folded portion is disposed in the outer cylinder.
The folded portion can be displaced following the expansion and contraction of the pipe due to the temperature change of the R gas, and it is possible to prevent stress from being applied to the fixed portion between both ends of the pipe and the partition plate.

Further, since one end of the outer cylinder is opened and a U-shaped pipe is disposed in the outer cylinder, the outer cylinder can be made shorter, which is useful when the apparatus is installed in an engine room or the like. Layout flexibility can be increased. E of claim 3
In the GR gas cooling device, a bellows-like curved portion is formed in a pipe disposed in the outer cylinder and fixed at both ends to a partition plate, so that the pipe follows the expansion and contraction of the pipe due to a temperature change of the EGR gas. The portion can be displaced, so that stress can be prevented from being applied to a fixed portion between both ends of the pipe and the partition plate.

Further, by processing the pipe into a bellows shape,
Since the inner surface of the pipe becomes uneven, EG on the inner surface of the pipe
The contact area of the R gas can be increased, and the heat exchange efficiency of the EGR gas can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of an EGR gas cooling device of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the EGR gas cooling device of the present invention.

FIG. 3 is a perspective view showing a third embodiment of the EGR gas cooling device of the present invention.

FIG. 4 is a perspective view showing a fourth embodiment of the EGR gas cooling device of the present invention.

FIG. 5 is a cross-sectional view showing an example in which the axes of pipes extending on both sides of a curved portion are shifted in the second embodiment.

FIG. 6 is a sectional view showing a conventional EGR gas cooling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Outer cylinder 21a One end 21b Opening 23 Partition plate 25 EGR gas 27 Inlet cap 29 Outlet cap 31 Cooling water 33 Inlet 35 Outlet 37 Pipe 37a Folding part 37b One end 37c Other end 39 Brazing part (brazing) 41 Outer cylinder 41a Opening Part 43 Partition plate 45 EGR gas 47 Inlet cap 49 Outlet cap 51 Cooling water 53 Inlet 55 Outlet 57 Pipe 57a End 57b Curved part 59 Brazing part (brazing) 61 Pipe 61a Curved part 63 Pipe 63a Curved part

Claims (3)

[Claims] An outer cylinder provided with an inlet and an outlet for cooling water; a partition plate closing an open end of the outer cylinder; a partition penetrating the partition plate and extending into the outer cylinder; A plurality of pipes fixed to the plate; and E provided to cover both ends of the plurality of pipes, respectively.
An EGR gas cooling apparatus comprising a GR gas inlet cap and an outlet cap, wherein the pipe is provided with a curved portion which is displaced in accordance with expansion and contraction of the pipe due to a temperature change.
Gas cooling device. 2. The EGR gas cooling device according to claim 1, wherein the open end is formed at one end of the outer cylinder, and the curved portion of the pipe is formed as a U-shaped bent portion of the pipe. Wherein both ends of the pipe are fixed to the partition plate closing the open end, respectively, and the inlet cap and the outlet cap are fixed on the partition plate so as to be adjacent to each other. EGR gas cooling device. 3. The EGR gas cooling device according to claim 1, wherein the curved portion of the pipe is formed in a bellows shape in which a diameter increase and a diameter decrease are repeated. Cooling system.