JP2000045882A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a piercing and fixing part between a plate facing exhaust gas on the inlet side, and tubes from cracking, by avoiding exposing the piercing and fixing part to exhaust gas. SOLUTION: On end part of tubes 3 is extended from one of face plates 2 facing exhaust gas 10 on the inlet side, by a predetermined length, and a shield plate 12 is provided on a side remote from a shell 1 so as to allow the thus extended front end parts of the tubes 3 to pierce therethrogh and to blazed parts 11 of the tubes, which are blazed to the plate 2 (that is, piercing and fixing parts). Thus, the shield plate 12 can prevent the blazed parts 11 from being directly exposed to exhaust gas having a high temperature.

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. 3 is a sectional view showing an example of the EGR cooler. In the figure, reference numeral 1 denotes a cylindrical shell, and both ends of the shell 1 in the axial direction are closed with end faces of the shell 1. 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 6 and 6 formed in a bowl shape 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. The exhaust gas inlet 7 is provided at the center of the bonnet 6, and the exhaust gas outlet 8 is provided at the center of the other bonnet 6, respectively.
After the exhaust gas 10 of the engine enters the inside of one bonnet 6 from the exhaust gas inlet 7 and is cooled by heat exchange with the cooling water 9 flowing outside the tubes 3 while passing through a number of tubes 3, the other one is cooled. The exhaust gas is discharged into the bonnet 6 and recirculated from the exhaust gas outlet 8 to the engine.

[0006]

However, in such a conventional EGR cooler, as shown in an enlarged view in FIG. 4, the end of the tube 3 is formed on the end face of the plate 2 on the side opposite to the shell 1 by a brazing portion. 11, the brazing portion 11 is directly exposed to the high-temperature exhaust gas 10, particularly on the inlet side of the exhaust gas 10 as shown in the figure. If the cooling water 9 leaks from there, the cooling water 9 will be led to the engine side, causing a serious trouble. There was also a risk of inviting.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to prevent a through-fixed portion between a plate and a tube facing an exhaust gas inlet side from being exposed to high-temperature exhaust gas.
It is an object of the present invention to prevent the occurrence of cracks in the penetration fixing portion.

[0008]

SUMMARY OF THE INVENTION The present invention provides a cylindrical shell, a plate fixed to both ends of the shell in the axial direction to close the shell end face, and a plate on the opposite side of the plate from the shell. A bonnet fixed so as to enclose the end surface; and a tube extending in the axial direction inside 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 an EGR cooler in which heat is exchanged between the exhaust gas and the cooling water by passing exhaust gas from one bonnet side to the other bonnet side in the tube, wherein the EGR cooler faces the exhaust gas inlet side. One end of the tube is extended from the plate to extend the required length, the tip of the extended tube is inserted therethrough, and the through-fixed portion of the tube to the one plate is formed. Providing the heat shield plate to the counter-shell side of the one plate to be overturned and is characterized in.

With this configuration, the exhaust gas introduced from the one bonnet side is blocked by the heat shield plate and does not directly hit the one plate, and the temperature of the through-fixed portion between the plate and the tube becomes high. Since this is avoided, it is possible to prevent the through-fixed portion from being reduced in strength and cracking.

Further, even in the event that a crack occurs in the through-fixed portion and water leakage occurs, the cooling water is blocked by the heat shield plate and the cooling water is interposed between the heat shield plate and the plate. The cooling water leaks inside the heat shield plate and is prevented from flowing into the tube because the exhaust gas inlet end of the tube is open outside the heat shield plate. You.

[0011]

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 of the present invention, and the same parts as those in FIGS. 3 and 4 are denoted by the same reference numerals.

In the EGR cooler of this embodiment, one end of the tube 3 is extended from one of the plates 2 facing the exhaust gas inlet 7 so as to extend a required length, and the tip of the extended tube 3 is inserted. Further, a heat shield plate 12 is provided on the side opposite to the shell 1 of the plate 2 so as to cover a brazing portion 11 of the tube 3 to the plate 2.

In the illustrated example, a drain hole 13 is formed at the lower end of the bonnet 6 which is the lowermost part of the space A formed between the heat shield plate 12 and the plate 2. A drain discharge pipe 14 is connected to the lower part of the fixed end of the bonnet 6 so as to communicate with the drain hole 13.

Thus, the exhaust gas 10 introduced from the exhaust gas inlet 7 of the one bonnet 6 is blocked by the heat shield plate 12 and does not directly hit the plate 2, so that the plate 2 and the tube Since the temperature of the brazing portion 11 with 3 is prevented from increasing to a high temperature, the strength of the brazing portion 11 is prevented from being reduced and the occurrence of a crack is prevented.

Also, even in the event that a crack is generated in the brazing portion 11 and water leakage occurs, the cooling water 9 is blocked by the heat shield plate 12 and 2 and is discharged from the drain hole 13 to an appropriate treatment place through the drain discharge pipe 14, and the end of the tube 3 on the exhaust gas 10 side is connected to the heat shield plate 12. , The cooling water 9 leaked into the heat shield plate 12 is reliably prevented from flowing into the tube 3.

Therefore, according to the above embodiment, the exhaust gas 1
The brazing portion 11 between the plate 2 and the tube 3 facing the inlet side of the exhaust gas 10 is covered with a heat shield plate 12 so that the hot exhaust gas 10
Since it is possible to protect the brazing portion 11 from high temperature, it is possible to prevent the brazing portion 11 from being heated to a high temperature and to prevent the occurrence of cracks due to a decrease in strength. Can be prevented from leaking.

Further, even if the brazing portion 11 of the plate 2 and the tube 3 facing the inlet side of the exhaust gas 10 is cracked due to a factor other than the decrease in strength due to the high temperature, and water leakage occurs, The cooling water 9 can be blocked by the heat shield plate 12 and stored between the heat shield plate 12 and the plate 2, and the end of the tube 3 on the exhaust gas 10 side is opened outside the heat shield plate 12. The structure can surely prevent the cooling water 9 leaking into the heat shield plate 12 from flowing into the tube 3, so that there is no possibility that the cooling water 9 is guided to the engine side. The occurrence of troubles of the engine can be prevented beforehand.

FIG. 2 shows another embodiment of the present invention.
In this embodiment, the penetrating portion between the heat shield plate 12 and the tube 3 is also fixed by the brazing portion 11 ',
Knowing that the brazing portion 11 ′ is exposed to the exhaust gas 10 to increase the temperature, the airtightness and the stability at the penetrating portion between the heat shield plate 12 and the tube 3 are improved as much as possible.

It should be noted that the EGR cooler of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0021]

According to the above-described EGR cooler of the present invention, various excellent effects as described below can be obtained.

(I) The through-fixed portion between the plate and the tube facing the exhaust gas inlet side can be covered with a heat shield to protect it from direct exposure to high-temperature exhaust gas. It is possible to avoid the high temperature of the part, it is possible to prevent the occurrence of cracks due to reduced strength,
The leakage of the cooling water to the outside of the shell can be prevented.

(II) Even if a crack is generated in the through-fixed portion between the plate and the tube facing the exhaust gas entry side due to a factor other than the decrease in strength due to the high temperature, and water leakage occurs,
Cooling water can be blocked by the heat shield plate and stored between the heat shield plate and the plate. In addition, the exhaust gas inlet side end of the tube is opened outside the heat shield plate, so that the heat shield plate has a structure. Since the inflow of cooling water leaking into the tube can be reliably prevented, there is no possibility that the cooling water will be guided to the engine side, and the occurrence of serious engine troubles will be prevented. Can be.

[Brief description of the drawings]

FIG. 1 is a partially enlarged sectional view showing an example of an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing an example of a conventional EGR cooler.

FIG. 4 is a partially enlarged cross-sectional view of the EGR cooler of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shell 2 Plate 3 Tube 6 Bonnet 9 Cooling water 10 Exhaust gas 11 Brazing part (penetration fixed part) 12 Heat shield plate

Claims (1)

[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. A hood, 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 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, and requires one end of a tube from one plate facing the inlet side of the exhaust gas. Extend to extend the length,
An EGR cooler characterized in that a heat shield plate is provided on a side opposite to the shell of the one plate so as to allow a tip of the extended tube to pass therethrough and cover a fixed portion of the tube penetrating to the one plate.