JP2000038964A - Egr coller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance layout properties, and make its structure light in weight by inserting a flexible pipe acting as a casing, to the outer circumferential side of a cooling pipe in a bent shape, and letting the whole of them be formed into a bent shape. SOLUTION: In this EGR cooler 1, a flexible pipe 13 acting as a casing 2 is inserted in the outer circumferential side of a cooling pipe 10 in a bent shape so as to allow the whole of them to be formed into a bent shape. The degree of freedom in shape can thereby be increased, and layout properties can thereby be enhanced. In addition, since the cooling pipe can be extended, its thermal conduction is made excellent, its thermal radiation area can be substantially reduced, and weight saving can thereby be accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR cooler, and more particularly, to an EGR (Exhaust) system for extracting a part of exhaust gas from an engine from an exhaust path and returning the exhaust gas to an intake path of the engine.
EG during gas recirculation)
The present invention relates to an EGR cooler for cooling R gas.

[0002]

2. Description of the Related Art NOx in exhaust gas from diesel engines, etc.
It is known that EGR is effective to reduce the EGR. That is, it is considered that when EGR is performed, the oxygen concentration in the intake air decreases and combustion becomes slow, and the generation of NOx is suppressed by the decrease in combustion temperature.

On the other hand, mixing EGR gas into the intake air causes a problem that the fresh air amount is reduced by that amount and the smoke is deteriorated. In order to solve this, the EGR
It has been proposed to provide a cooler and cool the high-temperature EGR gas to reduce the volume, thereby increasing the amount of fresh air and preventing the generation of smoke (Japanese Patent Laid-Open No. 6-14).
No. 7028).

FIG. 6 is a configuration diagram of an engine to which an EGR cooler is applied. An EGR cooler 51 is an EG that forms an EGR passage.
The cooling water (cooling liquid) is circulated between the engine 53 and the engine 53 via a cooling water pipe 54, and the cooling water is used as a refrigerant to cool the EGR gas inside. . The EGR pipe 52 is connected to the exhaust manifold 5
A part of the exhaust gas (EGR gas) is extracted from an exhaust path including the exhaust pipe 5 and the exhaust pipe 56 and returned to an intake path including the intake manifold 57 and the intake pipe 58. In the middle of the EGR pipe 52, a flow control valve 5 for controlling the EGR amount is provided.
9 are provided.

[0005] The structure of a general EGR cooler is as shown in FIG. The EGR cooler 51 has a cylindrical casing 60 extending in one direction and narrowed at both ends. An inlet flange 61 and an outlet flange 62 are integrally provided at both longitudinal ends of the casing 60. The inlet side flange 61 and the outlet side flange 62 are connected to the gas inlet 6 respectively.
3 and the gas outlet 64 are divided into the above-mentioned EGR pipe 52.
Connected to. A pair of end plates separated in the longitudinal direction (gas flow direction), that is, an inlet end plate 65 and an outlet end plate 66 are provided inside the casing 60. These end plates 65 and 66 partition the inside of the casing 60 into an inlet-side gas chamber 67, an outlet-side gas chamber 68, and a central water chamber 69 (coolant chamber) at both ends. The water chamber 69 is provided with a cooling water inlet 70 and a cooling water outlet 71 spaced apart in the longitudinal direction.

[0006] A plurality of straight tubular cooling pipes 72 are provided so as to bridge both end plates 65 and 66. The cooling pipe 72 is inserted and fixed to both end plates 65 and 66, communicates the inlet side and outlet side gas chambers 67 and 68, and passes through the water chamber 69 between the both end plates 65 and 66. .

The EGR gas introduced from the gas inlet 63 into the inlet gas chamber 67 in this manner is supplied to the inlet gas chamber 67.
Inside, it is diffused in the radial direction and distributed to each cooling pipe 72. Then, after passing through each cooling pipe 72, they are gathered again in the outlet side gas chamber 68 and are led out from the gas outlet 64. In particular, when passing through the water chamber 69, heat is exchanged with cooling water to be cooled.

The EGR cooler 51 is made of a material such as stainless steel excellent in high-temperature strength and corrosion resistance because the EGR gas contains sulfur at a high temperature. The cooling pipe 72 is made as thin as possible (about 0.5 to 1 mm) in order to increase the cooling efficiency. Although this cooler is made by joining a plurality of parts, all parts are assembled at once by brazing in the furnace to simplify manufacturing.

[0009]

However, with this structure, the cooler is determined to be a thick straight tube, and the outer diameter is relatively large, which may make layout difficult. Was. In addition, there is also a problem that the weight increases because a large number of cooling tubes are used.

[0010]

In the EGR cooler according to the present invention, a flexible tube serving as a casing is inserted on the outer peripheral side of a curved cooling pipe, and the whole is bent.

Preferably, the flexible tube is a bellows-shaped stainless steel tube.

Preferably, the flexible tube is made of an elastomer resin or silicon.

[0013]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIGS. 1 and 2 show an EGR cooler according to this embodiment. The basic configuration of the EGR cooler 1 is substantially the same as the conventional one. That is, an inlet-side flange 3 and an outlet-side flange 4 are provided at both ends in the longitudinal direction of the cylindrical casing 2, and the inside of the casing 2 is partitioned by an inlet-side end plate 5 and an outlet-side end plate 6 at both ends in the longitudinal direction. An inlet side gas chamber 7 is defined on the upstream side of the end plate 5 in the gas flow direction, and the outlet side end plate 6 is formed.
An outlet gas chamber 8 is defined on the downstream side in the gas flow direction, and a water chamber 9 (coolant chamber) is defined between both end plates 5 and 6. A plurality of cooling pipes 10 are provided by bridging the two end plates 5 and 6.
8 and communicate with the water chamber 9 to radiate heat in the cooling water. The cooling water enters the water chamber 9 from the cooling water inlet 11 and is drawn out from the cooling water outlet 12.

However, the layout is improved here,
At the same time, the following configuration is adopted to achieve weight reduction.

First, the number of the cooling pipes 10 is reduced (four) as compared with the conventional case (FIG. 5), and the casing 2 surrounding the outer circumference of the cooling pipe 10 is made to have a small diameter substantially equal to that of the EGR pipe (see FIG. 6). I do. However, the total sectional area of the cooling pipe 10 is EGR
Make the cross-sectional area equal to or greater than the cross-sectional area of the pipe to prevent an increase in flow path resistance. As a result, the EGR cooler 1 becomes slender and can be inserted into a narrow gap around the engine.

Next, in order to secure a heat radiation area equivalent to the conventional one, the length of the cooling pipe 10 is extended, and the casing 2 (water chamber 9) is extended accordingly. Here, in the case of the same heat radiation area, it has been found that extending the cooling pipe 10 like the present cooler is more advantageous in heat transfer than dividing the cooling pipe 10 in the radial direction as in the conventional case. Therefore, compared to the total length of the conventional cooling pipe, the total length of the cooling pipe 10 of the present cooler can be shortened,
Weight reduction can be achieved. In addition, the cooling water flow rate can be reduced by improving the heat transfer efficiency.

However, since the layout becomes impossible if the linear shape is too long, the entire cooler is bent in a U shape or a U shape here. That is, the cooling pipe 10 is bent in a U shape or a U shape, and the casing 2 is bent accordingly. Thereby, the cooler 1 can be laid out in such a manner that a narrow gap around the engine is sometimes sewn. As a result, the inlet gas chamber 7 and the outlet gas chamber 8 face in the same direction. Cooling water inlet 11
The cooling water outlet 12 is also directed upward, and is disposed on the upper inlet side and the lower outlet side of the casing 2.

However, such a shape causes a problem in assembly. That is, as shown in FIG. 5, since the cooling pipe 72 is conventionally a straight pipe, a plurality of cooling pipes 72 are attached to one of the end plates 65 and 66, and a shaft is attached to the outer cylinder 73 of the cylindrical casing 60. And the other end plates 65 and 66 were attached, the two tank portions 74 and 75 of the casing 60 were attached and brazed, and assembly was possible. However, like this cooler, the cooling pipe 1
If 0 is a bent shape, it cannot be inserted into the casing in the same manner as in the related art, and cannot be assembled.

Therefore, in the present cooler, as shown in FIG. 1, the casing 2 is formed of a flexible tube 13 to enable assembly.

Here, a bellows-shaped stainless steel tube is used as the flexible tube 13. All other parts of the cooler are also made of stainless steel, so that the furnace can be collectively brazed. As an assembling method in this case, four cooling pipes 10 which are bent in advance are temporarily fixed, and the flexible pipes 13 are sequentially inserted into the outer peripheral side of these cooling pipes 10 from one end in the longitudinal direction. Even in the bent portion of the cooling pipe 10, the flexible pipe 13
Is guided by the cooling pipe 10 and bends without permission, so that insertion is possible. If the insertion of the bent portion is difficult, it may be assisted by hand bending. After the insertion is completed, other components such as the end plates 5 and 6 may be attached, and the shape of the flexible tube 13 and particularly the bent portion may be adjusted. Thus, the EGR cooler 1 having a curved shape as a whole
Is completed.

As described above, the cooling pipe 10 having any bent shape can be accommodated in the casing 2, so that the degree of freedom in shape is increased, the cooler can be made thinner with a minimum outer diameter, and the layout can be greatly improved. In addition, since the cooling pipe can be extended, the heat transfer becomes good, the heat radiation area can be substantially reduced, and the weight can be reduced.

Here, the flexible tube 13 made of stainless steel has sufficient rigidity (self-supporting property) to maintain its own shape, and comes into contact with the cooling tube 10 at a bent portion, or is in contact with the cooling tube 10. The gap is not narrowed and the flow of the cooling water is not deteriorated.

Note that both ends of the casing 2 are not in a bellows shape but in a straight tube shape, and do not have a conventional drawn shape. A pipe member 17 forming a cooling water inlet 11 and a cooling water outlet 12 is integrally fixed to the straight pipe portion. The inlet-side gas chamber 7 and the outlet-side gas chamber 8 are small and have the minimum size that can distribute and collect the EGR gas. Here, the shape of the EGR cooler 1 (the cooling pipe 10 and the casing 2) is not limited to the U-shape as shown in the figure, and various shapes are possible according to the engine layout.

Next, another embodiment will be described.
As shown in FIGS. 3 and 4, the flexible tube 13 is made of a heat-resistant elastomer resin or silicon.
Therefore, since brazing is impossible, the flexible tube 13 is used here.
Is a tube portion 14 provided integrally with the end plates 5 and 6.
The flexible tube 13 is fixed by the elasticity of the flexible tube 13 or by using a tightening band or the like. Also in this case, when the flexible tube 13 is inserted into the outer peripheral side of the cooling tube 10, the flexible tube 13 bends freely at the bent portion of the cooling tube 10, so that the insertion is possible. The flexible tube 13 is made relatively thick to ensure self-supporting properties.

Here, the cooling pipe 10 is connected by a baffle plate 15 at a position separated by a predetermined distance in the longitudinal direction. The baffle plate 15 makes the flow of the cooling water in the water chamber 9 meander, and separates the cooling pipes 10 from each other or the cooling pipe 10 and the inner wall of the casing 2 at a predetermined interval.
This is for exposing the entire surface of the cooling pipe 10 to cooling water. In particular, the baffle plate 15 here functions as a positioning or support member for the cooling pipe 10 when assembling the cooler, and functions as a steadying member for the cooling pipe 10 when using the cooler. At the time of assembling the cooler, the baffle plate 15 and the cooling tube 10 are fixed in advance, and the flexible tube 13 is inserted. Thereby, the variation of the cooling pipe 10 at the time of insertion is naturally prevented, and the insertion becomes easy.

In this case, the cooling water inlet 11 and the cooling water outlet 12 are connected to a tube 18 formed integrally with the flexible tube 13.
And is not a joint structure of separate members. Further, the outlet side flange is omitted, and the outlet end 16 itself of the flexible tube 13 is inserted and connected to a nipple or the like of another member. A feature of the present cooler is that a flange is not required. Insertion of the flexible tube 13 is performed from the side without the flange until the distal end abuts on the inlet side flange 3.

In addition to the above, various embodiments of the present invention are possible. For example, the cooling water may not be the engine cooling water.

[0029]

The present invention exhibits the following excellent effects.

(1) The layout can be improved.

(2) Weight reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an EGR cooler according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a longitudinal sectional view of an EGR cooler according to another embodiment of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a longitudinal sectional view showing a conventional EGR cooler.

FIG. 6 is a configuration diagram of an engine to which an EGR cooler is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 EGR cooler 2 Casing 10 Cooling pipe 13 Flexible pipe

Claims (3)

[Claims] 1. An EGR cooler characterized in that a flexible tube forming a casing is inserted into an outer peripheral side of a curved cooling pipe, and the whole is bent. 2. The EGR cooler according to claim 1, wherein said flexible tube is a bellows-shaped stainless steel tube. 3. The EGR cooler according to claim 1, wherein said flexible tube is made of an elastomer resin or silicon.