JP2000130964A - Double-pipe heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double-pipe heat exchanger to prevent the occurrence of a crack due to thermal fatigue of a radiation fin. SOLUTION: An EGR cooler 10 comprises an inner pipe 11 through the inner side of which cooling water flows; an outer pipe 12 surrounding the outer periphery of the inner pipe 11 apart therefrom and partitioning a flow passage 13 between the inner pipe 11 and the outer pipe; a radiation fin 16 securely contained in the inner pipe 11; and an EGR cooler 10 provided with an introduction pipe 14 and a discharge pipe 15. In the EGR cooler 10, the radiation fin 16 is arranged in the inner pipe 11 such that an end part A on the cooling water inflow side is positioned downstream from a central axis 01 of the introduction pipe 14 in the direction of a flow of EGR gas. Therefore, the heat of the end part A on the EGR gas inflow side of the radiation fin 16 is transmitted to cooling water before heating flowing in the flow passage 13 through the introduction pipe 14. Thus, the end part on the EGR gas inflow side of the radiation fin 16 is further efficiently cooled, and a thermal stress generated at the end part A is relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-pipe heat exchanger for cooling high-temperature exhaust gas extracted from an exhaust system, for example, in an exhaust gas recirculation system for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in order to reduce nitrogen oxides in exhaust gas of an internal combustion engine, a part of the exhaust gas is taken out from an exhaust system (exhaust manifold) and recirculated to an intake system (intake manifold). A recirculation device (hereinafter, referred to as an “EGR device”) is known. The EGR device has a double-pipe heat exchanger (hereinafter, referred to as "EGR gas") for cooling high-temperature exhaust gas (hereinafter, referred to as "EGR gas") taken out of an exhaust system before re-introducing it into an intake system.
"GR cooler". ) Is provided.

[0003] As shown in FIGS. 4 and 5, an E is disposed in the exhaust passage (not shown) in the EGR device.
The GR cooler 50 has an inner tube 51 through which EGR gas flows, and an outer peripheral surface of the inner tube 51, the ends of which are fixed to the outer peripheral surface of the inner tube 51. It is configured as a double piping structure with an outer pipe 53 that partitions the flow passage 52. A radiation fin 54 for promoting heat transfer is housed in the inner tube 51, and the outer periphery of the radiation fin 54 is fixed to the inner periphery of the inner tube 51 by brazing.

[0004] Cooling water is supplied to the outer pipe 53 through the flow passage 52.
And a discharge pipe 56 for discharging the cooling water in the flow passage 52. Cooling water for cooling the internal combustion engine is introduced into the flow passage 52 through an inlet pipe 55.
The cooling water flows through the flow passage 52, and flows through a discharge pipe 56 to a cooling water circulation circuit (not shown) of the internal combustion engine.
Is returned to. Heat exchange is performed between the high-temperature EGR gas and the cooling water via the inner pipe 51. As a result, EGR
The gas is cooled and reintroduced into the intake system of the internal combustion engine.

[0005]

However, the end A of the radiating fin 54 at the highest temperature on the EGR gas inflow side is located upstream of the introduction pipe 55. For this reason, the EGR gas inflow side end A of the radiation fin 54 is not sufficiently cooled, and the EGR gas inflow side end of the radiation fin 54 is EGR gas.
The temperature will be as high as the gas temperature. When the EGR device is turned on or off, the engine is stopped, or the like, a large temperature difference occurs between the end A of the radiation fin 54 on the EGR gas inflow side and the downstream side of the end A. Therefore, a large thermal stress is generated in the heat radiation fins 54, and there is a possibility that cracks K may be generated in the heat radiation fins 54 due to thermal fatigue.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a double-pipe heat exchanger capable of preventing a heat radiation fin from being cracked due to thermal fatigue. It is in.

[0007]

According to a first aspect of the present invention, a first cylindrical member through which a medium to be cooled is circulated and an outer periphery of the first cylindrical member are separated from each other to surround the first cylindrical member. A second cylindrical member that defines a circulation section for a cooling medium between the first cylindrical member and a radiating member that is accommodated and fixed in the first cylindrical member; and a cooling medium that is provided in the second cylindrical member and that is provided in the flow passage. In a double-pipe heat exchanger provided with an inlet pipe for introducing heat and a discharge pipe for discharging the cooling medium in the flow passage, the heat radiating member is provided with a first cooling medium which is ejected from the introducing pipe. The gist of the present invention resides in that the cylindrical member is disposed on the downstream side in the flow direction of the medium to be cooled with respect to the jet collision portion.

According to a second aspect of the present invention, in the first aspect of the present invention, the heat radiating member is disposed downstream of the mounting portion of the introduction pipe in the flow direction of the medium to be cooled. I do.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the cooling medium inflow side end of the heat radiating member has a mounting portion for an introduction pipe and a mounting portion for a discharge pipe. The point is that it is located between

According to a fourth aspect of the present invention, in the first aspect of the present invention, the second tubular member includes a first body connected to an introduction pipe; When the inside diameter of the first body portion is D1 and the inside diameter of the second body portion is D2, "D1 <D2" is provided, the second body portion being provided on the downstream side of the cooling medium and connected to the discharge pipe. And the end of the heat dissipating member on the cooling medium inflow side is set to the first position.
The gist of the invention is that it is arranged in the first tubular member so as to be located in a section corresponding to the body portion. (Operation) Therefore, according to the first aspect of the present invention, the cooling medium flowing-in end of the heat-radiating member having the highest temperature among the heat-radiating members, and the jet of the first cylindrical member hit by the cooling medium ejected from the introduction pipe. Since the thermal gradient is larger in the downstream area than the collision portion, the cooling medium inflow end of the heat radiating member is cooled with high efficiency, and the temperature of the same end is reduced. As a result, the thermal stress generated at the cooling medium inflow side end is reduced.

According to a second aspect of the present invention, in the second aspect of the present invention, a large heat is generated between the end of the heat dissipating member having the highest temperature on the inflow side of the medium to be cooled and the area downstream of the mounting portion of the introduction pipe. Because of the gradient, the cooling medium inflow end of the heat radiation member is cooled with high efficiency.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the cooling medium inflow side end of the heat radiating member is provided in a process in which the cooling water flows from the introduction pipe to the discharge pipe. Cooled. For this reason, the cooling medium inflow side end of the heat radiating member is cooled with high efficiency, and the temperatures of the central portion and the outer peripheral portion of the cooling medium inflow side end are made substantially uniform.

According to a third aspect of the present invention, in any one of the first to third aspects of the present invention, the flow velocity of the cooling medium in the section corresponding to the first body portion of the flow passage is:
The flow rate of the cooling medium in another section corresponding to the second body portion of the flow passage is larger than that of the other, and the heated cooling medium and the unheated cooling medium are switched at a high speed. For this reason, the cooling medium inflow end of the heat radiating member is cooled with higher efficiency, and the thermal stress generated in the heat radiating member is further alleviated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, the present invention relates to an exhaust gas recirculation device for an internal combustion engine (hereinafter referred to as an "EGR device").
That. An embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1 and FIG.
A double-pipe heat exchanger (hereinafter, referred to as an “EGR cooler”) 10 provided in the middle of an exhaust circulation passage (not shown) in the GR device has a cooling medium taken out from the exhaust system of the internal combustion engine inside. Pipe 1 as a first cylindrical member through which high-temperature exhaust gas (hereinafter, referred to as “EGR gas”) flows
1 is provided.

An outer tube 1 as a second cylindrical member is provided on the outer periphery of the inner tube 11 so as to surround the outer periphery of the inner tube 11 at a distance.
2 are arranged. Both ends of the outer tube 12 are gradually reduced in diameter, and are fixed to the outer peripheral surface of the inner tube 11 by welding or the like. A flow passage 13 is formed between the outer peripheral surface of the inner tube 11 and the inner peripheral surface of the outer tube 12 for flowing cooling water as a cooling medium having an annular cross section. That is, the EGR cooler 10 is configured as a double pipe structure of the inner pipe 11 and the outer pipe 12.

The outer pipe 12 is provided with an introduction pipe 14 for introducing cooling water into the flow path 13 and a discharge pipe 15 for discharging cooling water in the flow path 13. Cooling water for cooling the internal combustion engine is supplied to the flow passage 13 through an introduction pipe 14, and the cooling water flows through the flow passage 13, and then flows through a discharge pipe 15 to a cooling water circulation circuit (not shown in the drawing) of the internal combustion engine. )
Is returned to. The EGR cooler 10 can cool the EGR gas passing through a coolable range C where the cooling water flowing through the flow passage 13 and the outer peripheral surface of the inner pipe 11 come into contact.

The cooling water that has flowed into the flow passage 13 through the introduction pipe 14 collides with the outer peripheral wall of the inner pipe 11 facing the introduction pipe 14, and then spreads in all directions in the flow passage 13. For this reason, a part of the outer peripheral wall of the inner pipe 11 in a predetermined range where the cooling water collides (hereinafter, referred to as a “jet collision part P”).
The temperature is the lowest in the inner tube 11.

A radiating fin 16 as a radiating member is accommodated and fixed in the inner tube 11. The radiation fin 16
Is formed to have a substantially radial cross section (substantially star-shaped cross section) in the radial direction of the inner tube 11 and to have a predetermined length in the tube axis direction of the inner tube 11. Fixed.

That is, the heat dissipating fins 16 are formed by bending a single metal plate such as stainless steel (for example, SUS304) having high heat resistance, high corrosion resistance, and high heat conductivity into a wave shape (approximate bellows shape) by pressing or the like. Each mountain part 16a of the one
Is rounded (corrugated cylindrical shape) so as to be in contact with the inner peripheral surface of the inner tube 11, and inserted into the inner tube 11. And
The heat radiation fins 16 are fixed to the inner peripheral surface of the inner tube 11 by brazing the respective peak portions 16 a to the inner peripheral surface of the inner tube 11.

The radiation fins 16 are arranged such that the EGR gas inflow side end A is located downstream of the jet impingement portion P, and the EGR gas inflow side end A is connected to the mounting portion Y1 of the introduction pipe 14. It is arranged so as to be located further downstream and further upstream than the attachment site Y2 of the discharge pipe 15. That is, the end A of the radiation fin 16 on the EGR gas inflow side is connected to the central axis O1 of the introduction pipe 14 and the central axis O1 of the discharge pipe 15.
It is located between the two. The end A of the radiating fin 16 on the EGR gas inflow side and the central axis O1 of the introduction pipe 14 are spaced apart from each other with an interval X.

Therefore, the heat at the end A of the radiating fin 16 on the EGR gas inflow side is transferred to the cooling water via the inner pipe 11 before the heat of the downstream body of the radiating fin 16 is transmitted to the cooling water. Is transmitted. That is, first, the cooling water that has flowed into the flow passage 13 has an end A A on the EGR gas inflow side of the radiation fin 16.
Heat is transmitted. Then, as the cooling water flows downstream in the flow passage 13, the heat of the body of the radiation fin 16 is transmitted to the cooling water. For this reason, the EG of the radiation fin 16
The R gas inflow side end A is efficiently cooled.
In the present embodiment, the side where the EGR gas flows into the inner pipe 11 is defined as the upstream side, and the side where the EGR gas flows out of the inner pipe 11 is defined as the downstream side.

When high-temperature EGR gas flows into the inner tube 11 of the EGR cooler 10 and the EGR gas comes into contact with the radiating fins 16, the heat of the high-temperature EGR gas is taken by the radiating fins 16 and 11 is transmitted. Then, the heat transmitted to the inner pipe 11 is transmitted to the cooling water flowing through the flow passage 13 and is discharged. That is, the high-temperature EGR gas flows between the radiation fin 16 and the inner pipe 1 between the EGR gas and the cooling water.
The heat is exchanged through 1 to be cooled.

The cooling water flowing from the introduction pipe 14 includes:
After the heat of the EGR gas inflow side end A of the radiation fin 16 is transmitted, the heat of the downstream body portion of the radiation fin 16 is transmitted. Then, the cooling water to which the heat of the radiation fins 16 has been transmitted is discharged from the discharge pipe 15. That is, the radiation fin 1
6, there is a large thermal gradient between the cooling water inflow side end A of the radiating fin 16 having the highest temperature and the area downstream of the jet collision portion P of the inner pipe 11 where the cooling water jetted from the introduction pipe 14 hits. . For this reason, the heat of the EGR gas inflow side end A of the radiation fin 16 is transmitted to the cooling water with high efficiency, and is efficiently cooled. Therefore, the temperature of the EGR gas inflow side end A of the radiation fin 16 decreases, and the thermal stress generated at the EGR gas inflow side end A is reduced. As a result, the radiation fins 1
6 is prevented from being cracked due to thermal fatigue.

Therefore, according to the present embodiment, the following effects can be obtained. (1) EGR gas inflow side end A of the radiation fin 16
Is located downstream of the jet collision portion P,
The radiation fin 16 having the highest temperature among the radiation fins 16
Has a large thermal gradient between the cooling water inflow side end A and the area downstream of the jet collision portion P of the inner pipe 11, which is hit by the cooling water jetted from the introduction pipe 14. For this reason, the EG of the radiation fin 16
The heat of the R gas inflow side end A is transferred to the cooling water with high efficiency and is cooled efficiently. Therefore, E of the radiation fin 16
The temperature of the GR gas inflow side end A decreases, and the thermal stress generated in the EGR gas inflow side end A is reduced. As a result, it is possible to prevent the heat radiation fins 16 from cracking due to thermal fatigue.

(2) The thermal stress generated at the EGR gas inflow side end A of the radiation fin 16 only by arranging the heat radiation fin 16 so that the end A of the EGR gas inflow side is located downstream of the introduction pipe 14. Can be alleviated. That is, E
Cracks due to thermal fatigue of the radiation fins 16 can be prevented with a simple configuration without increasing the number of parts of the GR cooler 10.

(3) Since the radiation fin 16 is formed of a metal plate having high heat resistance and high corrosion resistance, the radiation fin 16
Thus, oxidative corrosion and the like due to corrosive EGR gas can be suppressed as much as possible, and the product life of the EGR cooler 10 can be extended. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 3, in the second embodiment, the outer tube 12 has a first body portion 20 and a second body portion having different diameters.
The configuration is different from that of the first embodiment only in that a body portion 21 is provided. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

On the upstream side of the outer tube 12, a first body 20
Is provided, and a second body portion 21 is provided downstream thereof. The first body part 20 and the second body part 21
Is set such that “D1 <D2” when the inside diameter of the first body portion 20 is D1 and the inside diameter of the second body portion 21 is D2. The downstream end of the first body part 20 is gradually enlarged in diameter and is formed integrally with the second body part 21. The first body portion 20 is provided with an introduction pipe 14, and the second body portion 21 is provided with a discharge pipe 15.

Accordingly, the outer diameter of the inner tube 11 is constant, and the distance between the first body portion 20 and the inner tube 11 is smaller than that between the second body portion 21 and the inner tube 11. I have. For this reason, the flow rate of the cooling water in the section D corresponding to the first body section 20 in the flow passage 13 is larger than the flow rate of the cooling water in the section E corresponding to the second body section 21 in the flow path 13. That is, the cooling water that has flowed into the section D of the flow passage 13 via the introduction pipe 14 is moved at a high speed in the section E downstream of the flow passage 13.
The cooling water passes through the section E of the flow passage 13 and is discharged through the discharge pipe 15.

The radiation fin 16 has an end A on the EGR gas inflow side corresponding to the first body portion 20 (section D of the flow passage 13), and the end A has a mounting portion Y1 for the introduction pipe 14. Is disposed in the inner tube 11 so as to be located on the downstream side of the inner tube. That is, the radiation fin 16 has a distance X between the end A of the EGR gas inflow side and the extension of the central axis O1 of the introduction pipe 14.
The EGR gas inflow side end A is disposed in the inner pipe 11 such that the EGR gas inflow side end A is located downstream of the central axis O1 of the introduction pipe 14.

When high-temperature EGR gas flows into the inner tube 11 of the EGR cooler 10 and the EGR gas comes into contact with the radiating fins 16, heat of the high-temperature EGR gas is taken by the radiating fins 16 and 11 is transmitted. Then, the heat transmitted to the inner pipe 11 is transmitted to the cooling water flowing through the flow passage 13 and is discharged. That is, the high-temperature EGR gas flows between the radiation fin 16 and the inner pipe 1 between the EGR gas and the cooling water.
The heat is exchanged through 1 to be cooled.

The cooling water flowing from the introduction pipe 14 includes:
After the heat of the EGR gas inflow side end A of the radiation fin 16 is transmitted, the heat of the downstream body portion of the radiation fin 16 is transmitted. Then, the cooling water to which the heat of the radiation fins 16 has been transmitted is discharged from the discharge pipe 15.

The heated cooling water in the section D of the flow passage 13 flows downstream at a high speed, and the unheated cooling water flows into the section D. That is, the heated cooling water and the non-heated cooling water are switched at a high speed, so that the EGR gas inflow side end A of the radiation fin 16 is cooled with higher efficiency.

Accordingly, the temperature of the end A of the radiating fin 16 on the EGR gas inflow side is further lowered, and the thermal stress generated at the end A on the EGR gas inflow side is alleviated. As a result, generation of cracks due to thermal fatigue of the radiation fins 16 is prevented.

Therefore, according to the present embodiment, the following effects can be obtained in addition to the effects (1) to (3) of the first embodiment. A first body portion 20 having a small diameter and a second body portion 21 having a large diameter are provided on the outer tube 12, and the introduction tube 1 is provided in each of the body portions 20 and 21.
4 and a discharge pipe 15 were provided. In addition, the radiation fin 16 is connected to the EGR gas inflow side end portion A by the first body portion 20.
(Section D of the flow passage 13) and the introduction pipe 14
In the inner tube 11 so as to be located downstream of the inner tube. That is, the heated cooling water and the cooling water before the heating are exchanged at a high speed, and the heat of the EGR gas inflow side end A of the radiation fin 16 is always transmitted to the unheated cooling water flowing from the introduction pipe 14. Will be. Therefore, the end A of the radiating fin 16 on the EGR gas inflow side can be cooled with higher efficiency.

The above embodiments may be modified as follows. In the first embodiment, the radiation fins 16 are
The GR gas inflow side end A and the central axis O1 of the introduction pipe 14 are arranged in the inner pipe 11 so that a space X is formed between them.
The radiation fins 16 may be arranged in the inner tube 11 such that the EGR gas inflow side end A coincides with the central axis O1 of the introduction tube 14 (that is, X = 0). Also, the EGR gas inflow side end A
The radiation fins 16 may be arranged in the inner tube 11 so that the heat radiation fins slightly exceed the central axis O1 of the introduction tube 14 on the upstream side. Even in this case, the end portion A of the radiating fin 16 on the EGR gas inflow side is formed.
Is transferred to the unheated cooling water from the introduction pipe 14, and the radiating fins 16 can be efficiently cooled.

In the first and second embodiments, the EGR cooler 10 is used for cooling the EGR gas of the internal combustion engine. However, the EGR cooler 10 is not used for cooling the EGR gas or the like but for cooling a liquid or the like. You may. Even in this case, the same effects as those of the above embodiments can be obtained.

In the first and second embodiments, the EGR cooler 10 is provided with a substantially cylindrical inner pipe 11 and an outer pipe 1.
Although at least one of the inner tube 11 and the outer tube 12 may be formed in a square tube shape. Even in this case, the same effects as those of the above embodiments can be obtained.

Next, technical ideas other than the claimed invention which can be understood from the present embodiment will be described below together with their effects. A double-pipe heat exchanger in which the inlet pipe is located upstream of the cooling medium inflow side end of the heat radiating member. Even in this case, the same effect as the effect of the invention described in any one of claims 1 to 3 can be obtained.

An exhaust gas recirculation apparatus comprising the double-pipe heat exchanger according to claim 1 or 2. 3. The double-pipe heat exchanger according to claim 1, wherein the heat radiating member is formed of a metal plate having high heat resistance, high corrosion resistance, and high thermal conductivity. 4. In this way, the heat radiation member can be prevented from being deteriorated by the medium to be cooled, and the product life of the double-pipe heat exchanger can be improved.

[0042]

According to the first aspect of the invention, the thermal stress generated at the cooling medium inflow side end of the heat radiating member is reduced,
The generation of cracks due to thermal fatigue of the heat radiating member can be prevented.

According to the second aspect of the present invention, it is possible to cool the end of the heat dissipation member on the inflow side of the medium to be cooled with high cooling efficiency in a process in which the cooling water flows from the introduction pipe to the discharge pipe.

According to the invention described in claim 3, according to claim 1
Alternatively, in addition to the effect of the invention described in claim 2, the heated cooling medium and the unheated cooling medium are circulated at a high speed to cool the cooling medium inflow side end of the heat radiation member with higher efficiency. be able to.

[Brief description of the drawings]

FIG. 1 is a front sectional view of an EGR cooler according to an embodiment.

FIG. 2 is a sectional view taken along line 1-1 in FIG. 1;

FIG. 3 is a front sectional view of an EGR cooler according to another embodiment.

FIG. 4 is a front sectional view of a conventional EGR cooler.

FIG. 5 is a sectional view taken along line 2-2 in FIG. 4;

[Explanation of symbols]

10 EGR cooler (double-pipe heat exchanger), 11 inner pipe (first cylindrical member), 12 outer pipe (second cylindrical member), 13 ...
Flow passage, 14 ... introduction pipe, 15 ... discharge pipe, 16 ... heat radiation fin (heat radiation member), 20 ... first body part, 21 ... second body part, D1 ... inner diameter of first body part, D2 ... second body Inner diameter of part, O1 ... central axis of introduction pipe, O2 ... central axis of discharge pipe, A
... EGR gas inflow end of the radiation fins, D. a section corresponding to the first body in the flow passage, E. section corresponding to the second body in the flow passage.

Claims (4)

[Claims] 1. A first cylindrical member through which a medium to be cooled is circulated, and an outer periphery of the first cylindrical member is separated from the first cylindrical member, and a cooling medium flow portion is defined between the first cylindrical member and the first cylindrical member. A second tubular member, a heat dissipating member housed and fixed in the first tubular member, and an introduction pipe provided in the second tubular member for introducing a cooling medium into the flow passage and cooling in the flow passage. And a discharge pipe for discharging the medium, wherein the heat radiating member is formed of a medium to be cooled more than a jet impinging portion of the first cylindrical member hit by the cooling medium ejected from the introduction pipe. A double-pipe heat exchanger arranged downstream in the flow direction. 2. The double-pipe heat exchanger according to claim 1, wherein the heat radiating member is disposed downstream of a mounting portion of the introduction pipe in a flow direction of the medium to be cooled. 3. The double-pipe heat exchanger according to claim 1, wherein the cooling medium inflow side end of the heat radiating member is located between a mounting part of the introduction pipe and a mounting part of the discharge pipe. . 4. The second body member includes a first body portion connected to an introduction pipe, and a second body portion provided downstream of the cooling medium and connected to a discharge pipe. When the inside diameter of the portion is D1 and the inside diameter of the second body portion is D2, "D1 <D2" is set and provided, and the cooling medium inflow side end of the heat radiation member corresponds to the first body portion. The double-pipe heat exchanger according to any one of claims 1 to 3, wherein the double-pipe heat exchanger is disposed in the first tubular member so as to be located in a section where the heat exchanger is located.