JP2006200490A - Exhaust gas cooling device for exhaust gas recirculating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a bellows part expandable along the axial direction at least on one of a cylinder body and a heat transmitting pipe, and thereby to restrain generation of thermal stress in a fixing part of the heat transmitting pipe and an end plate and a fixing part of the end plate and the cylinder body, and to prevent generation of cracks on the sections. <P>SOLUTION: The exhaust gas cooling device for the EGR system includes the cylinder body 1 having a cooling medium inflow port 9 and a cooling medium flow-out port 10, end plates 2a and 2b closing both ends of the cylinder body 1 respectively, and the heat transmitting pipe 3 extending in the cylinder body 1 almost in parallel with the axis and having both ends fixed to the end plates 2a and 2b so that EGR gas passes through it. The bellows part 8 expandable along the axial direction is formed at least on one of the cylinder body 1 and the heat transmitting pipe 3. Thereby, generation of the thermal stress in the fixing part of the heat transmitting pipe 3 and the end plates 2a and 2b and the fixing part of the end plates 2a and 2b and the cylinder body 1 is restrained when engine cooling water flows from the cooling medium inflow port 9a to the cooling medium outflow port 10 and the EGR gas passes through the heat transmitting pipe 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust cooling device provided in an EGR (Exhaust Gas Recirculation) system, and more particularly to a technique for preventing the exhaust cooling device from cracking due to thermal stress.

As described in JP 2000-54916 A (Patent Document 1), a heat transfer tube is used as an exhaust cooling device that cools exhaust gas (hereinafter referred to as “EGR gas”) that recirculates from an engine exhaust system to an intake system. A utilized EGR cooler is disclosed.
Such an EGR cooler includes a cylindrical body provided with a cooling medium inlet and a cooling medium outlet, an end plate that closes both ends of the cylindrical body, and extends substantially parallel to the axis of the cylindrical body, with both ends being end And a heat transfer tube penetrating the plate. Both ends of the heat transfer tube are fixed to the end plate by brazing or welding. The peripheral edge of the end plate is fixed to the cylinder by brazing, welding, or the like.

Then, the EGR gas and the cooling medium exchange heat by passing the EGR gas through the heat transfer tube while circulating the cooling medium such as engine cooling water from the cooling medium inlet to the cooling medium outlet.
JP 2000-54916 A

  At this time, the cylinder and the heat transfer tube tend to expand and contract in the axial direction according to the temperature of the EGR gas and the cooling medium. However, since the cylinder and the heat transfer tube are fixed via the end plate, they can expand and contract only in the axial direction. Therefore, if there is a difference in the amount of expansion and contraction in the axial direction between the cylinder and the heat transfer tube due to the temperature difference between the EGR gas and the cooling medium or the difference in the linear expansion coefficient between the cylinder and the heat transfer tube, the difference Therefore, expansion and contraction is suppressed, and thermal stress is generated in the fixing portion between the heat transfer tube and the end plate and the fixing portion between the end plate and the cylindrical body. And when this thermal stress becomes larger than the allowable stress according to the material, there is a possibility that cracks may occur in these portions.

  Therefore, in view of the conventional problems as described above, the present invention forms a bellows portion that is extendable in the axial direction on at least one of the cylindrical body and the heat transfer tube, and a fixing portion between the heat transfer tube and the end plate or the end plate. It is an object of the present invention to provide an exhaust cooling device for an exhaust gas recirculation system that suppresses generation of thermal stress at a fixing portion between a gas cylinder and a cylindrical body and prevents cracks from occurring at these portions.

  For this reason, the invention described in claim 1 is a cylinder provided with a cooling medium inlet and a cooling medium outlet, an end plate for closing both ends of the cylinder, and the cylinder substantially parallel to its axis. And an exhaust cooling device for an exhaust gas recirculation system including both ends fixed to the end plate and a heat transfer pipe through which exhaust gas recirculated from the engine exhaust system to the intake system passes. Thus, at least one of the cylindrical body and the heat transfer tube is formed with an accordion portion that is extendable in the axial direction.

The invention according to claim 2 is characterized in that fins are provided on the inner wall of the heat transfer tube.
In the third aspect of the invention, the cooling medium inlet is provided in the peripheral wall of the cylindrical body in the vicinity of one end of the cylindrical body, and the cooling medium outlet is formed of the cooling medium inlet with the axis of the cylindrical body interposed therebetween. It is provided on the opposite peripheral wall in the vicinity of the other end of the cylinder.

  According to the first aspect of the present invention, since the bellows portion formed on at least one of the cylinder and the heat transfer tube is extendable in the axial direction, the cooling medium flows from the cooling medium inlet to the cooling medium outlet. When the exhaust gas passes through the heat transfer tube, the bellows part absorbs the difference between the cylinder and the heat transfer tube when there is a difference in the amount of expansion and contraction in the axial direction. Thereby, since generation | occurrence | production of the thermal stress in the adhering part of a heat exchanger tube and an end plate and the adhering part of an end plate and a cylinder is suppressed, it can prevent that a crack generate | occur | produces in these parts.

According to the invention described in claim 2, since the contact area between the heat transfer tube and the exhaust gas passing through the heat transfer tube increases, the efficiency of heat exchange between the exhaust gas and the cooling medium can be improved.
According to the third aspect of the present invention, when the cooling medium is circulated from the cooling medium inlet to the cooling medium outlet, the cooling medium is less likely to stagnate in the cylindrical body, so that the efficiency of heat exchange between the exhaust and the cooling medium Can be further improved.

  An EGR cooler that is provided in an EGR system that recirculates part of the exhaust gas from the engine exhaust system to the intake system and cools the EGR gas includes a cylinder 1 and both ends of the cylinder 1 as shown in FIGS. Thin plate-like end plates 2a and 2b for closing the respective parts, a plurality of heat transfer tubes 3 extending substantially in parallel with the axial center in the cylindrical body 1, and a bowl-shaped end cap 4a for covering both ends of the cylindrical body 1 respectively. And 4b.

Both ends of the heat transfer tube 3 are fixed to the end plates 2a and 2b by brazing, welding, or the like, and the end cap 4a and the end cap 4b communicate with each other. The peripheral portions of the end plates 2a and 2b are fixed to the cylindrical body 1 by brazing, welding, or the like.
One end cap 4 a is provided with an EGR gas inlet 5, and the other end cap 4 b is provided with an EGR gas outlet 6. A flange 7 is provided around the EGR gas inlet 5 and the EGR gas outlet 6 to connect the EGR tube. When EGR gas is supplied from the EGR gas inlet 5, the EGR gas is divided in the end cap 4 a and flows into the heat transfer tube 3. Then, the EGR gas that has passed through the heat transfer tube 3 joins in the end cap 4 b and is discharged from the EGR gas outlet 6.

The cylindrical body 1 is formed with a bellows portion 8 that can be expanded and contracted in the axial direction. The bellows portion 8 is formed by bending the peripheral wall of the cylindrical body 1 into a bellows shape.
A cooling medium inlet 9 is provided on the peripheral wall of the cylinder 1 in the vicinity of one end of the cylinder 1, and a cooling medium outlet 10 is provided in the vicinity of the other end of the cylinder 1. The cooling medium outlet 10 is provided on the opposite side of the cooling medium inlet 9 across the axis of the cylinder 1. When engine cooling water as a cooling medium is supplied from the cooling medium inlet 9 to the inside of the cylinder 1, the engine cooling water flows along the heat transfer pipe 3 and is discharged from the cooling medium outlet 10 to the outside of the cylinder 1. The

  According to the above configuration, the EGR gas and the engine coolant are heated by passing the EGR gas into the heat transfer pipe 3 while circulating the engine coolant from the coolant inlet 9 to the coolant outlet 10. Exchange. At this time, since the bellows portion 8 is extendable in the axial direction, the bellows portion 8 absorbs the difference when there is a difference in the amount of expansion and contraction between the cylindrical body 1 and the heat transfer tube 3 in the axial direction. Thereby, since the generation | occurrence | production of the thermal stress in the adhering part of the heat exchanger tube 3 and the end plates 2a and 2b and the adhering part of the end plates 2a and 2b and the cylinder 1 is suppressed, a crack generate | occur | produces in these parts. Can be prevented.

  The cooling medium inlet 9 is provided on the peripheral wall of the cylinder 1 in the vicinity of one end of the cylinder 1, and the cooling medium outlet 10 is opposite to the cooling medium inlet 9 across the axis of the cylinder 1. Since the engine coolant is circulated from the coolant inlet 9 to the coolant outlet 10, the engine coolant is stagnated in the cylinder 1. It becomes difficult. Thereby, the efficiency of heat exchange between the EGR gas and the engine coolant is improved.

Further, fins 11 are provided on the inner wall of the heat transfer tube 3. The fin 11 increases the contact area between the EGR gas passing through the heat transfer tube 3 and the heat transfer tube 3. Thereby, the efficiency of heat exchange between the EGR gas and the engine coolant is further improved.
In the above embodiment, the bellows portion 8 is formed in the cylinder 1, but the bellows portion is formed in the heat transfer tube 3 in order to absorb the difference in the amount of expansion and contraction in the axial direction between the cylinder 1 and the heat transfer tube 3. Alternatively, a bellows portion may be formed on both the cylindrical body 1 and the heat transfer tube 3.

Explanatory drawing which shows the structure of the exhaust-air-cooling apparatus of this invention The perspective view which shows the structure of the exhaust-air-cooling apparatus of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical body 2a, 2b End plate 3 Heat exchanger tube 8 Bellows part 9 Cooling medium inflow port 10 Cooling medium outflow port 11 Fin

Claims (3)

A cylinder provided with a cooling medium inlet and a cooling medium outlet;
End plates for respectively closing both ends of the cylindrical body,
A heat transfer tube that extends substantially parallel to the axial center of the cylinder and has both end portions fixed to the end plate, and exhaust that recirculates from the exhaust system of the engine to the intake system.
An exhaust gas recirculation system for an exhaust gas recirculation system comprising:
An exhaust cooling apparatus for an exhaust gas recirculation system, wherein at least one of the cylindrical body and the heat transfer tube is formed with an accordion portion that can be expanded and contracted in an axial direction thereof.   The exhaust cooling device of the exhaust gas recirculation system according to claim 1, wherein fins are provided on an inner wall of the heat transfer tube.   The cooling medium inlet is provided on the peripheral wall of the cylinder close to one end of the cylinder, and the cooling medium outlet is on the opposite side of the cooling medium inlet across the axis of the cylinder. The exhaust cooling device of the exhaust gas recirculation system according to claim 1, wherein the exhaust cooling device is provided on the peripheral wall of the exhaust gas cylinder in proximity to the other end of the cylindrical body.

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