JP2000038963A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance layout properties, and make a structure light in weight by dividing a casing petitioning and forming a cooling fluid chamber with cooling pipes enclosed from the side of an outer circumference, into the longer direction of each cooling pipe and the direction normal to the cooling pipe. SOLUTION: In this EGR cooler 1, a casing 2 petitioning a cooling fluid chamber 9 with cooling tubes enclosed from the side of an outer circumference, is divided into the longer direction of each cooling pipe, and the direction normal to the cooling pipe. A cooling pipe bent in any shape can be entered into the inside of the casing so as to be increased in the degree of freedom in shape, so that their layout properties can thereby be enhanced. In addition, since each cooling pipe can be extended, its thermal conduction is made excellent, and its heat radiating area cna thereby be substantially reduced, so that its structure can thereby be made light in weight.

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. 4 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 each other. A pair of end plates separated in the longitudinal direction (gas flow direction) inside the casing 60;
That is, an inlet side end plate 65 and an outlet side end plate 66 are provided. These end plates 65, 66
The inside of the casing 60, the inlet side gas chamber 67 at both ends,
This is for partitioning into an outlet gas chamber 68 and a central water chamber 69 (cooling liquid chamber). 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 casing that surrounds the cooling pipe from the outer peripheral side and forms a cooling liquid chamber is divided in a direction perpendicular to the longitudinal direction of the cooling pipe.

It is preferable that the cooling pipe has a bent shape, and the casing is bent along the bent shape.

[0012]

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 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 gas chamber 7 is defined on the upstream side of the end plate 5 in the gas flow direction, and an outlet gas chamber 8 is defined on the downstream side of the outlet end plate 6 in the gas flow direction. A water chamber 9 (coolant chamber) is defined. A plurality of cooling pipes 10 are provided by bridging the two end plates 5 and 6. The cooling pipes 10 are fixedly inserted into the two end plates 5 and 6 to communicate the gas chambers 7 and 8, And radiates 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. 3), and the casing 2 surrounding the outer periphery of the cooling pipe 10 is made to have a small diameter substantially equal to that of the EGR pipe (see FIG. 4). 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, the length of the cooling pipe 10 is extended in order to secure a heat radiation area equivalent to the conventional one. Along with this, the casing 2 (water chamber 9) is also extended. 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, the total length of the cooling pipes 10 of the present cooler can be made shorter than the total length of the conventional cooling pipes, and the length of each of the cooling pipes 10 can be made shorter, so that the weight can be reduced. In addition, the cooling water flow rate can be reduced by improving the heat transfer efficiency.

However, if the linear shape is too long, the layout becomes impossible. Therefore, 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. 3, 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 the outer pipe 73 of the cylindrical casing 60 is axially attached to the outer pipe 73. Then, 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 the cooler, the cooling pipe 10
If is bent, it cannot be inserted into the casing in the same manner as in the prior art, and cannot be assembled.

Therefore, in the present cooler, as shown in FIG. 1, the casing 2 is divided in a direction orthogonal to the longitudinal direction.
Assembly is possible.

Here, the casing 2 is of a so-called Monaka type, which is divided into two parts, an outer side and an inner side of a U-shape, and is joined after the cooling pipe 10 is inserted. The casing 2 includes an outer casing 13 and an inner casing 14 having a semicircular cross section.
And these are butted together and brazed integrally. This allows the cooling pipe 10 to be inserted perpendicularly to the longitudinal direction from the outward opening of the inner casing 14. After that, the outer casing 13 may be covered and brazed to the inner casing 14.

Here, the edge of the outer casing 13 is overlapped and joined to the back side of the edge of the inner casing 14, but this may be reversed, or a different joining structure such as flange joining may be used. May be adopted. Also, here, both ends of the casing 2 are not in the conventional drawn shape. The casing 2 is a straight tube having a uniform overall length. However, the whole shape is U-shaped or U-shaped. The inlet gas chamber 7 and the outlet gas chamber 8 are small, and the EGR gas is supplied to each cooling pipe 10.
Is the smallest size that can be distributed to

The cooling pipe 10 is connected by a baffle plate 15 at a position spaced a predetermined distance in the longitudinal direction of the casing. The baffle plate 15 is fixed to the inner wall of the casing 2 to meander the flow of the cooling water in the water chamber 9, and appropriately separates the cooling pipes 10 from each other or the cooling pipe 10 and the casing 2 to form the entire surface of the cooling pipe 10. Is exposed 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 pipe 10 are fixed and integrated, and in this state, they are inserted into the inner casing 14, and the baffle plate 15 is fixed to the inner casing 14. By doing so, the positioning of the cooling pipe 10 can be performed easily and accurately before the outer casing 13 is covered, and the assembly becomes easy.

With the above configuration, the cooling pipe 10 having any bent shape can be put in the casing 2.
Since the degree of freedom in shape is increased and the cooler can be made thinner with a minimum outer diameter, 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.

The present invention is not limited to the above embodiment, but various embodiments are possible. For example, the cross section of the casing is not limited to a circle, and the number of divisions is not limited to two. The shapes of the cooling pipe and the casing are not limited to the U-shape. The cooling water may not be the engine cooling water.

[0025]

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 partial longitudinal sectional view of an EGR cooler according to an embodiment of the present invention, and is a sectional view taken along line AA of FIG.

FIG. 2 is a longitudinal sectional view showing the entirety of an EGR cooler according to the embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a conventional EGR cooler.

FIG. 4 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 9 Water chamber 10 Cooling pipe 13 Outer casing 14 Inner casing

Claims (2)

[Claims] 1. An EGR cooler, wherein a casing surrounding a cooling pipe from an outer peripheral side and defining a cooling liquid chamber is divided in a direction perpendicular to a longitudinal direction of the cooling pipe. 2. The EG according to claim 1, wherein the cooling pipe has a curved shape, and the casing is bent along the curved shape.
R cooler.