JPH08338321A - Exhaust gas recirculating pipe for internal combustion engine - Google Patents

Abstract

PURPOSE: To lower running temperature with its heat radiation effect accelerated at the circulating pipe, effectively restrain NOX in exhaust gas from being exhausted outside, reasonably facilitate mounting works for the aforesaid pipe in a narrow space close to an engine by making the pipe itself flexible even if it is scattered in a bending shape, and let the pipe also exhibit vibration proofs and absorptivity. CONSTITUTION: The circulating pipe 1 is formed out of a stainless pipe the thickness of which is comparatively thin, provided with mounting parts 2 and 2' at both sides of it, formed out of heat radiating fin parts 3 each of which is located in place over the length of the pipe, and formed in a spiral shape or in a plurality of ring shapes, and formed out of flexible bellows parts 4 formed integrally or separately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an internal combustion engine of an automobile or the like, in order to reduce NOx in exhaust gas discharged in connection with pollution control measures, a part of the exhaust gas is again returned to the intake passage side of the engine. The present invention relates to an exhaust gas recirculation pipe (hereinafter referred to as an EGR pipe) by an exhaust gas recirculation method in which the mixed gas is returned to the above.

[0002]

2. Description of the Related Art Conventionally, as this kind of EGR pipe,
The tubular body made of a stainless steel material is simply placed as it is between the exhaust system passage and the intake system passage to increase the inactive ratio of H ₂ O, N ₂ , CO _2, etc. in the combustion mixture to increase the combustion temperature. And NOx discharged to the outside are suppressed.

[0003]

However, such an EGR pipe according to the conventional technique has a heat dissipating effect in the EGR system components such as the stainless steel pipe body and the EGR valve because the stainless steel pipe body is simply left as it is. Scarce,
Therefore, the temperature of the recirculated exhaust gas cannot be sufficiently lowered, the heat resistance of the EGR system components may be deteriorated, and the fuel consumption is deteriorated, and the EGR amount cannot be increased and is naturally discharged. There was a problem that NOx could not be effectively suppressed. Furthermore, in connection with the complicated bending shape at the squeezing point near the engine, the pipe itself does not have flexibility, and the variation in bending shape makes the installation work difficult at the time of installation, and it is impossible to install it. In addition to the vibration under the condition, there was a problem that the vibration resistance was generally poor, such as cracking near the brazing part formed between the mounting parts such as flanges and nipples at both ends.

The present invention has been made in view of the above problems of the prior art, and promotes the heat radiation effect in the EGR pipe to lower the temperature of the exhaust gas to be recirculated to reduce the EGR.
The heat resistance of the system components can be increased, NOx in the exhaust gas discharged to the outside can be suppressed more effectively to improve fuel efficiency, and the pipe itself has a flexible function to improve the heat resistance. In addition, it is possible to provide an exhaust gas recirculation pipe for an internal combustion engine that can be easily installed without difficulty even if there is variation in the bending shape, and can also exhibit vibration absorption resistance. It is intended.

[0005]

In order to achieve the above object, the present invention is an exhaust gas recirculation pipe for returning a part of exhaust gas to the intake passage side of an engine, and a stainless pipe material having a relatively thin wall for the circulation pipe. However, a flexible portion formed integrally or separately with a radiation fin portion having a spiral shape or a plurality of ring shapes fixed at appropriate positions of the pipe length at both ends of the radiation fin portion. The gist of the invention is an exhaust gas re-EGR pipe of an internal combustion engine, which is composed of a bellows part, and further, the fin part is formed by being fixed to the outer peripheral surface of the pipe by welding, brazing or caulking.

[0006]

Since the present invention is constructed as described above, since it has a heat dissipating fin portion and a flexible bellows portion in association with the thin stainless pipe material, the fin portion as well as the bellows portion can be used. The expansion of the surface area formed by the part promotes the heat dissipation effect in the pipe, resulting in a decrease in the temperature of the exhaust gas flowing inside, and therefore, the heat resistance of the EGR system constituent parts can be increased and the exhaust gas is discharged. NOx in the exhaust gas can be suppressed more effectively, and further, the flexible function at the bellows part, especially by providing the bellows part at the bent part, it becomes possible to perform bending work with a small bending radius. In addition, even if there are variations in the bending shape, it is possible to easily and easily perform the mounting work, and it is also possible to exhibit vibration absorption resistance.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a plan view of an exhaust gas re-EGR pipe for an internal combustion engine of the present invention, and FIG. 2 is a view of another embodiment corresponding to FIG. 3 is a half cutaway view of yet another embodiment, and FIG.
FIG. 5 is a sectional view for explaining a method for caulking and fixing the outer peripheral surface of the R pipe, FIG. 5 is a half sectional view for explaining a method for caulking and fixing the flange, and (1) shows various bending shapes E
GR pipe, made of austenitic stainless steel such as SUS 304, 316 or ferritic stainless steel with Si 1.5 wt% to 3.0 wt% and C ≧ 0.02 wt%, with a pipe diameter of about 20 m / m or less , Wall thickness 0.2m / m ~
It is made of a relatively thin stainless steel tube material having a thickness of about 0.5 m / m, and preferably has a surface plated with Ni.
At both ends, mounting parts consisting of mounting flanges (2, 2 ') connecting to the exhaust system passage, EGR valve and intake system passage are welded or brazed for TIG, MIG, etc. as shown in Figs. 1 and 2. It is fixed by plastic working such as caulking shown in FIGS. 3 and 5 and Japanese Utility Model Laid-Open No. 6-34157.

(3) is a radiation fin portion, for example, a wall thickness of 0.6 m / m, a pitch of 3.0 m / m, and a height of 6.5 m / m.
Made of SUS SPCC, SPHC, etc., the outer surface of which is Cu-plated or Ni-plated if desired.
A flexible bellows part which is located at a proper position of the pipe length of (1) and is fixed to the outer peripheral surface of the pipe in a spiral shape or a plurality of ring shapes by welding, brazing or caulking, and is integrally formed (4) And is formed. The flexible bellows (4) is preferably close to both ends of the pipe (1) in relation to the flexible function and the vibration absorbing effect (Fig. 1).
In addition, if it is necessary to perform bending with a small bending radius, it is desired to form it at the bending position, and similarly, if desired, the fin portion (3) and the bellows portion (4) are alternately ( 1) can also be formed.

Further, as shown in FIG. 3, heat radiation fins (3) are provided at both ends, and the flexible bellows (4) formed separately from the heat radiation fins (3) are brazed or welded to the EGR. The pipe (1) can be constructed. In this case, when the flexible bellows portion (4) is arranged in the bent portion, the flexible bellows portion can be bent in advance, and the productivity is improved. In FIG. 3, the flange (2) is fixed to one end by caulking as a mounting portion, and the elbow nipple (2 ') is fixed to the other end by welding or brazing as a mounting portion to the mating member. It will be.

The above-mentioned flexible bellows portion (4) is formed by a usual method such as a bi-pitch method or a hydraulic bulge process. On the other hand, E
When winding the fin part (4) around the outer peripheral surface of the GR pipe (1), in the case of a spiral fin part, the fin part (4) may be wound while rotating the pipe (1), or the spiral part may be wound in advance. The fins are molded and then fitted onto the outer peripheral surface of the pipe (1), and in the case of ring-shaped fins, the donut-shaped fins are sequentially fitted onto the outer peripheral surface of the pipe (1). .

The method of fixing the wound or externally fitted fin portion (4) to the outer peripheral surface of the EGR pipe (1) is as follows: welding by TIG, MIG, CO ₂ , plasma, laser, etc., vacuum or Cu-based and Ni in reducing atmosphere
Brazing using brazing filler metal, or fins as shown in Fig. 4.
The burring part (4 ') is provided on the inner peripheral side of (4) and this part is E
The GR pipe (1) is fixed by caulking to the outer peripheral surface of the GR pipe (1), but the caulking portion can be further spot-welded.

[0012]

As described above, the exhaust gas recirculation pipe of the internal combustion engine according to the present invention is particularly suitable for the heat radiation fin portion (3) in the pipe (1) made of the thin stainless pipe material.
And the flexible bellows portion (4), the fin portion and the bellows portion can promote the heat dissipation effect in the pipe (1) to lower the temperature of the exhaust gas to be recirculated. The heat resistance of the components of the EGR system can be increased, NOx in the exhaust gas discharged to the outside can be suppressed more effectively, and fuel consumption can be improved, and the flexible function of the bellows part (4) can be improved. , In particular, by providing the bellows part in the bent part, it is possible to perform bending work with a small bending radius, and therefore, it is possible to easily perform the mounting work easily at a narrow place and even if there is variation in the bending shape, In addition, it is an extremely useful exhaust gas recirculation pipe for an internal combustion engine because it can also exhibit vibration absorption resistance.

[Brief description of drawings]

FIG. 1 is an exhaust gas re-EGR of an internal combustion engine according to an embodiment of the present invention.
It is a top view of a pipe.

FIG. 2 is a view corresponding to FIG. 1 of the same as another embodiment.

FIG. 3 is a half cutaway view of still another embodiment.

FIG. 4 is a cross-sectional view illustrating a method of crimping and fixing a heat radiation fin portion to an outer peripheral surface of an EGR pipe.

FIG. 5 is a half-cut sectional view illustrating a method of crimping and fixing a flange.

[Explanation of symbols]

 1 EGR pipe 2, 2'mounting part 3 radiating fin part 4 flexible bellows part

Claims (2)

[Claims] 1. An exhaust gas recirculation pipe for returning a part of exhaust gas to the intake passage side of the engine again,
(1) is made of a relatively thin-walled stainless steel tube and mounting parts (2, 2 ') are provided at both ends of the tube, and the spiral shape or multiple ring shapes fixed at appropriate positions of the pipe length are used. A pipe for exhaust gas recirculation of an internal combustion engine, comprising: a heat radiation fin portion (3) and a flexible bellows portion (4) formed integrally or separately. 2. The exhaust gas recirculation of an internal combustion engine according to claim 1, wherein the fin portion (3) is fixed to the outer peripheral surface of the pipe (1) by welding, brazing or caulking. Pipes.