JP2002180915A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress accumulation of soot in a tube, by suppressing a pressure loss of exhaust gas to a minimum limit while heat exchange efficiency of an EGR cooler is markedly improved, by forming a spiral-shaped protrusion in an internal peripheral surface of the tube. SOLUTION: Relating to this EGR cooler, making exhaust gas 10 pass through in a tube 3 so as to perform a heat exchange between this exhaust gas 10 and cooling water outside the tube 3, a spiral-shaped protrusion 11 is formed in an internal peripheral surface of the tube 3 so as to decrease a height H of upheaval to a center side of the tube 3 lower gradually toward the flow direction of the exhaust gas 10.

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 apparatus 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 R 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 gas is effectively reduced. 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 because the generation of oxides can be reduced.

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.

In the drawing, reference numeral 5a denotes a bypass outlet pipe provided at a position facing the cooling water inlet pipe 4 in the diametrical direction of the shell 1, and a part of the cooling water 9 is extracted from the bypass outlet pipe 5a. The stagnation of the cooling water 9 is prevented from occurring at a position facing the cooling water inlet pipe 4.

However, in such a conventional EGR cooler, the exhaust gas 10 flows straight through the tube 3 and the heat exchange efficiency is poor because the exhaust gas 10 does not sufficiently contact the inner peripheral surface of the tube 3. There is a problem that
Further improvement of the heat exchange efficiency of the EGR cooler is desired.

Therefore, as shown schematically in FIG. 7, the present inventors apply a pressing process to spirally depress the tube 3 from the outside by using a roll having a spiral ridge, or the like. Spiral projections 11 are formed on the peripheral surface, whereby the exhaust gas 10 flowing in the tube 3 is swirled along the spiral projections 11 to be turbulent, so that the exhaust gas 10 has an inner circumference of the tube 3. It has been invented that the frequency of contact and the contact distance with the surface are increased to greatly improve the heat exchange efficiency of the EGR cooler.

[0009]

However, when the spiral projection 11 is formed on the inner peripheral surface of the tube 3 as described above, the height H of the spiral projection 11 toward the center of the tube 3 is increased. Or tube 3
The heat exchange efficiency between the exhaust gas 10 and the cooling water 9 is reduced by decreasing the inclination angle θ formed between the surface D perpendicular to the axis of the On the other hand, the pressure loss of the exhaust gas 10 becomes large and the flow of the exhaust gas 10 becomes poor, soot contained in the exhaust gas 10
There is a risk that the heat exchange efficiency will be reduced due to the tendency to accumulate in the inside and use in a short time.

The present invention has been made in view of the above circumstances, and has a spiral projection formed on the inner peripheral surface of a tube.
It is an object of the present invention to significantly improve the heat exchange efficiency of a GR cooler and to minimize the pressure loss of exhaust gas to suppress the accumulation of soot in a tube.

[0011]

The invention according to claim 1 of the present invention comprises a tube and a shell surrounding the tube, and supplies and discharges cooling water to the inside of the shell and to the inside of the tube. An EGR cooler configured to exchange heat between the exhaust gas and the cooling water through the exhaust gas, wherein a height of a protrusion toward an inner peripheral surface of the tube toward a center of the tube decreases in a flow direction of the exhaust gas. The spiral projections are formed as described above.

[0012] According to this configuration, since the height of the spiral projection is relatively high on the inner peripheral surface of the tube on the inlet side of the exhaust gas, the height of the spiral protrusion is relatively shorter on the inlet side of the tube. In the section, a strong rotational force is applied to the exhaust gas, thereby performing efficient heat exchange over a wide range from the inlet side to the outlet side of the tube, and further, spiraling toward the outlet side of the tube. Since the height of the protrusions is relatively low,
The rise in pressure loss is suppressed to a minimum, and the accumulation of soot in the tube is well suppressed.

Further, the invention according to claim 2 of the present invention provides:
An EGR cooler comprising a tube and a shell surrounding the tube, supplying and discharging cooling water inside the shell, and passing exhaust gas into the tube to exchange heat between the exhaust gas and the cooling water. Further, a spiral projection is formed on the inner peripheral surface of the tube so as to increase the pitch in the flow direction of the exhaust gas.

In such a case, the pitch of the spiral projections is relatively small on the inner peripheral surface of the tube at the inlet side of the exhaust gas, so that the pitch of the spiral protrusions is relatively small within the relatively short section on the inlet side of the tube. A strong rotational force is applied to the exhaust gas, which results in efficient heat exchange over a wide range from the inlet side to the outlet side of the tube,
Moreover, since the pitch of the spiral projections becomes relatively large toward the outlet side of the tube, an increase in pressure loss is suppressed to a minimum, and the accumulation of soot in the tube is favorably suppressed.

The invention according to claim 3 of the present invention provides:
An EGR cooler comprising a tube and a shell surrounding the tube, supplying and discharging cooling water inside the shell, and passing exhaust gas into the tube to exchange heat between the exhaust gas and the cooling water. Further, a plurality of spiral projections are formed on the inner peripheral surface of the tube so that the number of the spiral projections is shifted from each other so as to decrease the number of the projections in the flow direction of the exhaust gas.

In this case, the number of spiral projections on the inner peripheral surface of the tube on the exhaust gas inlet side is relatively large. A strong rotational force is applied to the exhaust gas, whereby efficient heat exchange is performed over a wide range from the inlet side to the outlet side of the tube, and the spiral projections are formed toward the outlet side of the tube. Since the number of strips is relatively small, an increase in pressure loss is suppressed to a minimum, and the accumulation of soot in the tube is favorably suppressed.

[0017]

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

FIG. 1 is a cross-sectional view schematically showing a first embodiment of the present invention, in which the same reference numerals as in FIGS. 6 and 7 denote the same parts.

The first embodiment shown here relates to an EGR cooler having substantially the same configuration as the EGR cooler described above with reference to FIG. The spiral protrusion 11 is formed so that the height H of the protrusion toward the center of the tube 3 gradually decreases toward the center.

In this way, the height H of the spiral projection 11 on the inner peripheral surface of the tube 3 on the inlet side of the exhaust gas 10 is relatively high. In a relatively short section on the side, a strong rotational force is applied to the exhaust gas 10, whereby efficient heat exchange is performed over a wide range from the inlet side to the outlet side of the tube 3, and Since the height H of the spiral protrusion 11 is relatively lower toward the outlet side of the tube 3, the rise in pressure loss is suppressed to a minimum, and the accumulation of soot in the tube 3 is satisfactorily suppressed. Will be.

Here, it should be added that a strong rotational force is applied to the exhaust gas 10 in a relatively short section from the inlet side of the tube 3. In the case of FIG. Since the protrusion height H of the spiral projection 11 was formed uniformly over the entire length of the tube 3,
When the raised height H is determined in consideration of the increase in the pressure loss, although the rotational force of the exhaust gas 10 gradually increases from the inlet side to the outlet side of the tube 3, high heat exchange efficiency can be expected. By the time it reaches such a rotational force,
A certain length of the tube 3 was required, and efficient heat exchange could not be expected over a wide range of the tube 3.

It should be added that the accumulation of soot in the tube 3 is well suppressed. In the conventionally proposed one shown in FIG. 7, soot is deposited particularly on the outlet side of the tube 3. Although it was easy, in the first embodiment described with reference to FIG. 1, since the outlet side of the tube 3 is under the condition of the lowest airflow resistance, the accumulation of soot in the tube 3 is very effectively suppressed. It will be.

FIG. 2 is a cross-sectional view schematically showing a second embodiment of the present invention. In the example shown here, the exhaust gas 10 in FIG. Tube 3
Instead of reducing the height of the bulge H toward the center, the height of the bulge H is gradually reduced in each section of the tube 3 in the longitudinal direction. In this case, the same operation as in the first embodiment described with reference to FIG. 1 can be produced.

In FIG. 2, the raised height H is changed in two stages, but this is schematically shown, and the actual tube 3 extends longer than shown. Therefore, the raised height H may be changed in two or more steps.

FIG. 3 is a sectional view schematically showing a third embodiment of the present invention. In the example shown here, the inner peripheral surface of the tube 3 is directed toward the flow direction of the exhaust gas 10. The spiral projection 11 is formed so that the pitch P gradually increases.

In this case, since the pitch P of the spiral projection 11 is relatively small on the inner peripheral surface of the tube 3 on the inlet side of the exhaust gas 10, the pitch P on the inlet side of the tube 3 is relatively small. During a short section, a strong rotational force is applied to the exhaust gas 10, whereby the tube 3
Since efficient heat exchange is performed in a wide range from the inlet side to the outlet side of the tube 3 and the pitch P of the spiral projections 11 becomes relatively large toward the outlet side of the tube 3, The increase in pressure loss is suppressed to a minimum, and the accumulation of soot in the tube 3 is suppressed well.

FIG. 4 is a sectional view schematically showing a fourth embodiment of the present invention. In the example shown here, the exhaust gas 10 gradually flows in the flow direction of the exhaust gas 10 in FIG. Instead of increasing the pitch P, the pitch P is increased stepwise in each section sectioned in the longitudinal direction of the tube 3. In such a case, FIG. The same operation as in the third embodiment described above can be produced.

Although FIG. 4 shows the pitch P changed in two steps, this is a schematic illustration, and the actual tube 3 extends longer than shown. Therefore, the pitch P may be changed in two or more steps.

FIG. 5 is a sectional view schematically showing a fifth embodiment of the present invention. In the example shown here, the inner peripheral surface of the tube 3 is directed toward the flow direction of the exhaust gas 10. A plurality of spiral projections 11 so that the number of threads gradually decreases.
Are formed out of phase with each other.

In this case, the number of spiral projections 11 on the inner peripheral surface of the tube 3 on the inlet side of the exhaust gas 10 is relatively large.
Exhaust gas 10 in a relatively short section on the inlet side of
A strong rotational force is applied to the tube 3, whereby efficient heat exchange is performed over a wide range from the inlet side to the outlet side of the tube 3. Since the number of strips is relatively small, an increase in pressure loss is suppressed to a minimum, and the accumulation of soot in the tube 3 is favorably suppressed.

FIG. 5 illustrates a case where the number of spiral projections 11 is changed from two to one, but this is schematically shown, and the actual tube 3 is Since the length of the spiral projection 11 is longer than that shown in the drawing, the number of spiral projections 11 may be gradually reduced from two or more.

Therefore, in any of the above-described first to fifth embodiments, a strong rotational force is applied to the exhaust gas 10 within a relatively short section from the inlet side of the tube 3 to make the tube 3 wider. By performing efficient heat exchange within the range, the heat exchange efficiency of the EGR cooler can be significantly improved, and the pressure loss of the exhaust gas 10 can be minimized to reduce the accumulation of soot in the tube 3. Since it can also be suppressed, it is possible to maintain good heat exchange efficiency for a long period of time and cool the exhaust gas 10 well.

Incidentally, the EGR cooler of the present invention is not limited to the above-described embodiment, but includes a change in the height of the spiral projection to the center of the tube, a change in the pitch, and the like.
Furthermore, it is needless to say that changes in the number of rows may be used in a composite form in which they are combined with each other, and that various changes may be made without departing from the gist of the present invention.

[0034]

As described above, according to the EGR cooler of the present invention, a strong rotational force is applied to the exhaust gas within a relatively short section from the inlet side of the tube, so that efficient heat can be obtained over a wide range of the tube. By performing the replacement, the heat exchange efficiency of the EGR cooler can be greatly improved, and
Since it is also possible to suppress the accumulation of soot in the tube by minimizing the pressure loss of the exhaust gas, it is possible to maintain high heat exchange efficiency over a long period of time and perform excellent exhaust gas cooling. The effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a first embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a second embodiment of the present invention.

FIG. 3 is a sectional view schematically showing a third embodiment of the present invention.

FIG. 4 is a sectional view schematically showing a fourth embodiment of the present invention.

FIG. 5 is a sectional view schematically showing a fifth embodiment of the present invention.

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

7 is a cross-sectional view showing an example in which spiral projections are formed on the inner peripheral surface of the tube of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shell 2 Plate 3 Tube 9 Cooling water 10 Exhaust gas 11 Spiral projection H Rise height P Pitch

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoji Yamashita 6-3-28 Owadacho, Hachioji-shi, Tokyo F-term in Sankyo Radiator Co., Ltd. (reference) 3G062 ED08

Claims (3)

[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 spiral projection is formed on the inner peripheral surface of the tube so that the height of the protrusion toward the center of the tube decreases in the flow direction of the exhaust gas. 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 characterized in that spiral projections are formed on the inner peripheral surface of the tube so as to increase the pitch in the flow direction of exhaust gas. 3. 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, wherein a plurality of spiral projections are formed on the inner peripheral surface of the tube such that the number of spiral projections is shifted from each other so as to decrease the number of the projections in the flow direction of the exhaust gas. EGR cooler.