JP2000345925A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency in heat exchanging of an EGR cooler by bringing exhaust gas into even-contact with the inner peripheral surface of a tube. SOLUTION: An EGR cooler is provided with a tube 3 and a shell 1 for surrounding the tube 3, and heat-exchanges exhaust gas 10 and cooling water by allowing the exhaust gas 10 to flow in the tube 3. A plurality of spiral protrusions 11, 12 are formed on the inner peripheral surface of the tube 3.

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. 6 is a cross-sectional view showing an example of the EGR cooler. In FIG. 6, reference numeral 1 denotes a shell formed in a cylindrical shape. 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, the exhaust gas 10 flows straight through the tube 3 and the exhaust gas 10 does not sufficiently contact the inner peripheral surface of the tube 3. Had a problem that the heat exchange efficiency was poor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve the heat exchange efficiency of an EGR cooler by allowing exhaust gas to uniformly and sufficiently contact the inner peripheral surface of a tube. And

[0008]

In order to achieve the above object, an EGR cooler according to a first aspect of the present invention includes a tube and a shell surrounding the tube, and cooling water is provided inside the shell. An EGR cooler configured to supply and discharge air and exchange heat between the exhaust gas and the cooling water by passing the exhaust gas into the tube, wherein a plurality of spiral projections are formed on an inner peripheral surface of the tube. It is a feature.

If a plurality of spiral projections are formed on the inner peripheral surface of the tube in this way, the exhaust gas flowing through the tube is swirled along the plurality of spiral projections to be turbulent, so that the exhaust gas flows in the tube. As a result of an increase in the frequency and distance of contact with the inner peripheral surface, the exhaust gas uniformly and sufficiently contacts the inner peripheral surface of the tube, and the heat exchange efficiency of the EGR cooler is greatly improved.

When the pitch of the spiral projection formed on the inner peripheral surface of the tube is reduced, the exhaust gas 1
It is assumed that the inclination angle of the spiral projection with respect to the flow of zero increases and approaches a right angle, and as a result, the pressure loss increases. However, in the present invention, in particular, since a plurality of spiral projections are formed, the spiral projection is formed. Even if the pitch of the projections is reduced, the inclination angle of the spiral projections with respect to the flow of the exhaust gas can be kept small, and the turning force can be increased without increasing the pressure loss.

According to a second aspect of the present invention, there is provided an EGR cooler including a tube and a shell surrounding the tube, supplying and discharging cooling water inside the shell, and passing exhaust gas through the tube. An EGR cooler configured to exchange heat between the exhaust gas and the cooling water, wherein a spiral wire is inserted into the tube.

When the spiral wire is inserted into the tube as described above, the exhaust gas flowing in the tube forms a swirling flow along the spiral wire and becomes turbulent, and the frequency and distance of contact with the inner peripheral surface of the tube. As a result, the exhaust gas comes to contact the inner peripheral surface of the tube evenly and sufficiently,
The heat exchange efficiency of the EGR cooler is greatly improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged sectional view showing an example of an embodiment for carrying out the invention according to claim 1 of the present invention, and the same parts as those in FIG. 6 are denoted by the same reference numerals.

In the present embodiment, an EGR cooler having substantially the same configuration as the EGR cooler described above with reference to FIG.
A plurality of (two in the embodiment shown in FIG. 1) spiral projections 11 and 12 are formed on the inner peripheral surface of a tube 3 that penetrates the plate 2.

In the case of the thin tube 3, when forming the plurality of spiral projections 11, 12, a pressing process for spirally recessing the tube 3 from the outside is performed by a roll or the like having a spiral ridge. , The part pressed from the outside,
A plurality of spiral projections 11 on the inner peripheral surface of the tube 3,
12 will be formed.

As shown in FIG. 1, for example, if the two spiral projections 11 and 12 are arranged on the inner peripheral surface of the tube 3 so as to be parallel to each other with a phase difference of 180 ° in the circumferential direction, the longitudinal direction can be improved. At each position in the direction, the diametrically opposed spiral projections 11 and 12 are opposite in direction and cross each other, and the strength of the tube 3 against bending stress is increased.

However, when forming the plurality of spiral projections 11 and 12 in the thick tube 3, the inner peripheral surface of the tube 3 is cut so as to leave the plurality of spiral projections 11 and 12. You may.

When a plurality of spiral projections 11 and 12 are formed on the inner peripheral surface of the tube 3 as described above, the exhaust gas 10 passing through the tube 3 is subjected to the spiral projection 1.
As a result, the exhaust gas 10 uniformly and sufficiently contacts the inner peripheral surface of the tube 3 as a result of the turbulence of the swirling flow along the tubes 1 and 12 and the increase in the contact frequency and the contact distance with the inner peripheral surface of the tube 3. Thus, the heat exchange efficiency of the EGR cooler can be greatly improved.

For example, as shown schematically in FIG. 2, when only one spiral projection 11 is formed on the inner peripheral surface of the tube 3 at an inclination angle α with respect to the flow of the exhaust gas 10, the spiral projection When the pitch P of 11 is reduced, FIG.
As shown in FIG. 5, it is assumed that the inclination angle β of the spiral projection 11 becomes large and approaches a right angle, and as a result, the pressure loss becomes large. In this embodiment, a plurality of spiral projections 11 and 12 are particularly formed. As shown in FIG. 4, the pitch P between the spiral projections 11 and 12 is
However, the inclination angle γ of the spiral projections 11 and 12 with respect to the flow of the exhaust gas 10 can be kept small, and the turning force can be increased without increasing the pressure loss.

FIG. 5 is an enlarged sectional view showing an example of an embodiment for carrying out the invention according to claim 2 of the present invention. In this embodiment, a shell 1 is formed in a cylindrical container shape, and a tube 3 is formed. Are fixed to both ends of the shell 1 in the axial direction thereof.
The diameter and thickness of the tube 3 are increased to increase the cross-sectional area and the strength of the flow path, and the number of the tubes 3 is reduced to a necessary minimum.

A gas flange 13 is provided at the end of the tube 3 projecting outside the shell 1 so that a line for recirculating the exhaust gas 10 can be appropriately branched and connected directly to the gas flange 13. It is.

The spiral wire 14 having a coil spring shape is inserted into the EGR cooler having such a structure over substantially the entire length of the tube 3.
Are fixed to the inner peripheral surface of the tube 3 by welding 15.

That is, the embodiment shown in FIG. 5 is suitable for the case where the tube 3 has a large diameter and a large wall thickness, and the spiral projections 11, 1 as described above with reference to FIG.
There is an advantage that processing is easier than forming No. 2.

The exhaust gas 1 passing through the tube 3
0 is turbulent as a swirling flow along the spiral wire 14,
As a result of the increase in the frequency of contact and the contact distance with the inner peripheral surface of the tube 3, the exhaust gas 10 uniformly and sufficiently contacts the inner peripheral surface of the tube 3, and the heat exchange efficiency of the EGR cooler is greatly improved. Becomes 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.

[0027]

As described above, according to the EGR cooler of the present invention, the exhaust gas flowing in the tube can be made into a turbulent flow as a swirling flow, and the frequency and distance of contact with the inner peripheral surface of the tube can be greatly reduced. Can be increased to
An excellent effect that the exhaust gas can be uniformly and sufficiently contacted with the inner peripheral surface of the tube to significantly improve the heat exchange efficiency of the EGR cooler can be obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing an example of an embodiment for carrying out the invention described in claim 1 of the present invention.

FIG. 2 is a schematic view showing a case where the spiral projection of FIG.

FIG. 3 is a schematic diagram showing a case where the pitch of the spiral protrusions in FIG. 2 is reduced.

FIG. 4 is a schematic view showing a case where the number of spiral protrusions in FIG. 1 is two.

FIG. 5 is an enlarged sectional view showing an example of an embodiment for carrying out the invention described in claim 2 of the present invention.

FIG. 6 is a sectional view showing an example of a conventional EGR cooler.

[Description of Signs] 1 Shell 3 Tube 9 Cooling Water 10 Exhaust Gas 11,12 Spiral Projection 14 Spiral Wire

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Katsuharu Inoue 3-1-1, Hinodai, Hino-shi, Tokyo Hino Automotive Industry Co., Ltd. (72) Yoji Yamashita 6-28, Owada-cho, Hachioji-shi, Tokyo F term in Sankyo Radiator Co., Ltd. (reference) 3G062 ED08 GA08 GA10

Claims (2)

[Claims] 1. A cooling system comprising: a tube; and a shell surrounding the tube, wherein cooling water is supplied to and discharged from the inside of the shell, and exhaust gas is passed through the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler characterized in that a plurality of spiral projections are formed on the inner peripheral surface of the tube. 2. A cooling apparatus comprising: a tube; and a shell surrounding the tube, for supplying and discharging cooling water to the inside of the shell, and passing exhaust gas into the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler, wherein a spiral wire is inserted into the tube.
GR cooler.