JPH11237192A - Egr gas cooler for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To share a cooler element while preventing troubles, e.g. pitting, due to welding. SOLUTION: A cooler element 2 comprises a tubular body 5, end plates 6, 6 closing the opposite ends of the body 5, four heat exchanging tubes 7 having opposite ends connected with respective end plates 6, and a partitioner 8 arranged to define a U-turn cooling water channel in the body 5 integrated previously by brazing. Each of cap members 3 being welded to the inlet and outlet ends of the cooler element 2 has a tubular section 3b being fitted to the outer circumferential surface at the first bend 6a of the end plate 6. A part 3c being bend to the outer circumferential side is provided on the farther forward end side of the tubular section 3b and forward end 6C of the second bend 6b is welded, over the entire circumference, to forward end 3d of the bend 3c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR gas cooler for cooling EGR gas (recirculated exhaust gas) with cooling water in an exhaust gas recirculation system for an internal combustion engine.

[0002]

2. Description of the Related Art Exhaust gas recirculation devices that recirculate a part of exhaust gas discharged from an internal combustion engine to an intake system to suppress nitrogen oxides discharged from the internal combustion engine have been widely used. ing. In this exhaust gas recirculation device,
Generally, high-temperature exhaust gas extracted from the exhaust system is introduced into the intake system as it is without cooling, but the exhaust gas extracted from the exhaust system is extremely hot and the gas itself is Because of the expansion, if an attempt is made to introduce a sufficient amount of EGR gas, the volumetric efficiency of the internal combustion engine is reduced, leading to a decrease in output and a decrease in fuel efficiency.

Therefore, an EGR gas cooler that cools EGR gas by circulating cooling water has been proposed, and some of them have been put to practical use.

FIG. 6 shows a conventional E using a multi-tube structure.
This shows an example of the configuration of a GR gas cooler, in which cooling water flows through a cooling water inlet 32 and a cooling water outlet 33 on the side surface of a cylindrical body 31. Inside, a plurality of heat exchange tubes 34 are provided. The ends of the heat exchange tubes 34 are connected to a pair of end plates 35 that close both ends of the body 31, respectively, and the body 31 is used to introduce exhaust gas into the heat exchange tubes 34. Cap-shaped members 3 serving as a gas inlet and a gas outlet respectively at both ends of
6 is fixed. Therefore, the exhaust gas serving as the EGR gas flows in the plurality of heat exchange tubes 34 in parallel, and is cooled by the cooling water surrounding the periphery.

[0005]

SUMMARY OF THE INVENTION Such a multi-tubular E
The GR gas cooler is generally manufactured by a brazing method, in particular, an in-furnace brazing method in which all parts are simultaneously brazed by heating the whole inside the furnace. However, the layout and the like of the EGR gas pipes from the exhaust system to the intake system of the internal combustion engine differ depending on the internal combustion engine and the type of vehicle. As a result, the cap-shaped member 36 actually requires various shapes. Therefore, brazing the inside of the furnace including the cap-shaped member 36 is very inefficient in work efficiency. When the exhaust pipe is integrated with the cap-like member 36,
Since the size of the entire cap-shaped member 36 is large, it is difficult to braze the inside of the furnace.

On the other hand, in order to avoid such a problem,
Only the cap-like member 36 is used in a
Although it is possible to weld to both ends, since the plate thickness of the body 31 is relatively thin, a problem such as puncturing during welding is likely to occur, and there is a problem that workability of welding work is poor.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a cylindrical body having a cooling water inlet and a cooling water outlet provided on the side so that cooling water flows therein, and the both ends of the body. An end plate to be closed, a plurality of heat exchange tubes disposed in the body, and both ends respectively connected to mounting holes of the end plate, and an exhaust gas flowing therein; An inlet side and an outlet side cap-shaped member respectively forming a gas inlet and a gas outlet, respectively, wherein the body, the end plate, and the heat exchange tube are integrated in advance by brazing as a cooler element. In the EGR gas cooler of the internal combustion engine in which the cap-shaped members are fixed to both ends of the cooler element by welding, the end plate is It has a first bent portion obtained by bending the outer peripheral portion into a cylindrical shape. The first bent portion is fitted to the outer periphery of the end of the body, and further includes a first bent portion. The distal end is bent outward as a second bent portion, and the cylindrical opening of the flange member is fitted to the outer peripheral surface of the first bent portion. A tip edge is welded to the second bent portion.

That is, in the present invention, the body, the end plate, and the heat exchange tube are previously integrated as a cooler element by brazing, for example, brazing in a furnace. Cap-shaped members are fixed to both ends of the brazed cooler element by welding. Here, since the cap-shaped member has a cylindrical opening fitted over the cylindrical first bent portion of the end plate, both are reliably positioned and welding is facilitated. The outer peripheral edge of the end plate extends to the outer peripheral side as a second bent portion, and the distal end edge of the cap-shaped member is welded to the second bent portion of the end plate. That is, since the welding is not performed directly on the body but is performed at a position away from the body toward the outer peripheral side, the thermal influence on the body is very small.

According to a second aspect of the present invention, which is a further embodiment of the present invention, the cap-shaped member is bent outward at the distal end of the cylindrical opening along the second bent portion. A bent portion is formed, and the bent portion and the second
Adjacent leading edges of the bent portion are welded.
In other words, the bent portion at the tip of the cap-shaped member and the second bent portion of the end plate both extend toward the outer peripheral side, and their leading edges are welded to each other. This is particularly suitable when the cap-shaped member is formed in a thin plate shape.

According to the third aspect of the present invention, the distal end of the cylindrical opening of the cap-like member abuts against the side surface of the second bent portion. The bent part side surface is welded. This is particularly suitable when the cap-shaped member is made relatively thick, such as a cast product.

[0011]

Preferred embodiments of the present invention will be described below.

FIG. 1 is a cross-sectional view showing the overall configuration of an EGR gas cooler 1 according to the present invention, FIG. 2 is a side view, and FIG. 3 is a cross-sectional view showing a main part thereof.

The EGR gas cooler 1 has a central cooler element 2 previously integrated by brazing, and a pair of cap-like members 3 and 3 welded to the inlet and outlet ends of the cooler element 2, respectively. And, it is roughly divided into.

The cooler element 2 has a cylindrical body 5 having a substantially square cross section, a pair of end plates 6 and 6 for closing both ends of the body 5, respectively, and is accommodated in the body 5 and has both ends. The heat exchanger includes a heat exchange tube 7 connected to the end plate 6 and a partition plate 8 arranged in the body 5 to form a U-shaped cooling water flow path.

The body 5 is made of stainless steel and has a thickness of, for example, about 0.8 mm, and a cooling water inlet 11 and a cooling water outlet 12 are provided at opposing positions on the side surfaces. At the cooling water inlet 11 and the cooling water outlet 12, a connector 13 for connecting a cooling water pipe is fixed by brazing. The cooling water inlet 11 and the cooling water outlet 12
Are formed at positions offset from one end of the body 5 on the inlet side of the EGR gas.

The end plate 6 is made of a stainless steel plate having a thickness of, for example, about 1.5 mm, which is thicker than the body 5, and has circular mounting holes 9 formed in four places in advance and an outer peripheral portion. Is bent in a tubular shape as a first bent portion 6a, and the first bent portion 6a is fitted on the outer periphery of the end of the body 5, and is brazed at the fitted portion. Further, as shown in detail in FIG. 3, a further distal end portion of the first bent portion 6a is bent outward as a second bent portion 6b. The second bent portion 6 b is formed to have a constant projection width over the entire circumference of the end plate 6.

The heat exchange tube 7 is also made of stainless steel, has a very thin thickness of, for example, about 0.3 mm, and has a bellows shape or a spiral shape to increase the surface area. The shape is provided. As shown in detail in FIG. 3, both ends of the heat exchange tube 7 penetrate the mounting hole 9 of the end plate 6, are caulked from the outside, and are brazed to the opening edge of the mounting hole 9. . In this embodiment, a fin 10 formed by twisting a strip-shaped metal plate is fixed in the heat exchange tube 7 in order to improve the heat exchange efficiency. In addition, this fin 10
Is provided only in the upstream portion of the heat exchange tube 7.

As shown in FIG. 2, four heat exchange tubes 7 are disposed in the body 5, and two heat exchange tubes 7 are accommodated in the space in the body 5 respectively.
A partition plate 8 is disposed at the center of the body 5 in parallel with the heat exchange tube 7 so as to partition the two flow paths 14a and 14b. The partition plate 8 has both side edges bent in an L shape, and is brazed to the inner wall surface of the body 5 at this portion. The partition plate 8 is shorter than the entire length of the body 5 and has one end in contact with one end plate 6 on the EGR gas inlet side. In other words, on the EGR gas outlet side of the body 5, the partition plate 8 does not exist, and the two flow paths 14a and 14b in the body 5 communicate with each other. Thus, a cooling water flow path that is continuous in a U-turn shape from the cooling water inlet 11 to the cooling water outlet 12 is formed in the body 5.

The cooler element 2 constructed as described above is integrated by brazing as described above. For this brazing, for example, nickel brazing is used, and the members are assembled in a so-called furnace brazing in which each member is assembled in a furnace and heated in a furnace.

On the other hand, since the cap-shaped member 3 needs to have various configurations according to the type of vehicle and the like, it is welded to the cooler element 2 integrated by brazing in a later step. The cap-shaped member 3 has a pyramid shape covering the end of the body 5 and has a single opening 15 at the center serving as a gas inlet or a gas outlet. FIG.
In the embodiment shown in FIG.
Is formed of a thin stainless steel plate, a flange 16 is directly fixed to the main body portion 3a at the inlet-side cap-shaped member 3, and an exhaust pipe 17 is connected to the outlet-side cap-shaped member 3. A flange 18 is fixed via the exhaust pipe 17. These flanges 1
6 and the exhaust pipe 17 are previously welded to the main body portion 3a of the cap-shaped member 3 to be integrated.

FIG. 3 shows the details of the cap-like member 3 on the inlet side of the EGR gas, but the basic structure is the same on the outlet side. As shown in FIG. 3, a cylindrical portion 3b having an appropriate length is formed on the opening side of the cap-like member 3, and the cylindrical portion 3b is formed by the first bending of the end plate 6. It is fitted on the outer peripheral surface of the portion 6a. Also, this cylindrical portion 3
Further, a bent portion 3c that is bent toward the outer peripheral side is provided on the distal end side of b. That is, the bent portion 3c is bent along the second bent portion 6b of the end plate 6, and
The projection width of the bent portion 3c is set so as to match the position of the leading edge 6c of the bent portion 6b. The leading edge 6c of the second bent portion 6b and the leading edge 3d of the bent portion 3c that are adjacent to each other are welded to each other over the entire circumference. As this welding, for example, TIG welding is used.

According to the structure of this embodiment, the cap-shaped member 3 is welded to the relatively thick end plate 6 instead of the thin body 5, and the welding is performed at a position away from the outer periphery of the body 5. Since welding is performed, there is no problem that a hole is formed in the body 5 and welding work is facilitated. In addition, the cap-shaped member 3 has the cylindrical portion 3b formed by the first bent portion 6a of the end plate 6.
, The temporary assembly state to the cooler element 2 is maintained, so that the welding operation is further facilitated.
In this embodiment, the cap-like member 3 also
Since the leading edge 3d of the bent portion 3c is welded, a relatively thin configuration made of a metal plate can be obtained.

Next, FIG. 4 shows an embodiment in which the configuration of the cap-shaped member 3 is different. The cooler element 2
Although the configuration of itself is not particularly different from the embodiment described above,
In this embodiment, the fin 10 is not provided in the heat exchange tube 7.

The cap-like member 3 shown in FIG. 4 has a main body 3e and a flange 3f integrally cast, and has a single opening 15 at the center which also serves as a gas inlet or a gas outlet. It has. A cylindrical portion 3g having an appropriate length is provided on the opening side of the cap-shaped member 3.
The cylindrical portion 3g is fitted on the outer peripheral surface of the first bent portion 6a of the end plate 6. 3 g of this cylindrical part
Of the second bent portion 6b of the end plate 6, and the leading edge 3h and the side surface of the second bent portion 6b are welded to each other by, for example, TIG welding or the like. ing.

According to the structure of this embodiment, similarly to the above-described embodiment, the cap-like member 3 is welded not to the thin body 5 but to the relatively thick end plate 6.
Since welding is performed at a position distant from the outer periphery, there is no problem that a hole is formed in the body 5 and welding work is facilitated. Moreover, since the cap-shaped member 3 is maintained in a state of being temporarily assembled to the cooler element 2 by fitting the cylindrical portion 3b into the first bent portion 6a of the end plate 6, the welding operation is further improved. It will be easier.

The cooler element 2 is the same whether the cap-shaped member 3 made of casting is used as in this embodiment or the cap-shaped member 3 made of a metal plate as in the above-described embodiment. Therefore, various cap-shaped members 3 can be appropriately combined with the same cooler element 2, and the versatility of the cooler element 2 is further improved.

FIG. 5 shows an example of a preferred layout of the EGR gas cooler 1 in the internal combustion engine cooling water circulation system. In FIG. 5, reference numeral 21 denotes a water jacket on the cylinder block side, reference numeral 22 denotes a water jacket on the cylinder head side, and reference numeral 23 denotes these water jackets 2.
Water pump for sending cooling water to 1, 22
Numeral 4 denotes a radiator for radiating cooling water. High-temperature cooling water is fed from the cylinder head side water jacket 22 through an outlet tube 25, and cooling water whose temperature has fallen is reduced through a water pump 23 through an inlet tube 26. It is to be returned to the side. In addition, a known thermostat 27 that switches a flow path to a bypass passage (not shown) at a low temperature is provided upstream of the water pump 23.

A heater passage 28 is provided from the water jacket 21 on the cylinder block side to the thermostat housing 27a downstream of the thermostat 27. The heater passage 28 has a heater core 2 for heating the vehicle interior.
9 are interposed. Then, the EGR gas cooler 1
Are arranged on the upstream side of the heater core 29 in the heater passage 28. In this embodiment, the oil cooler 3 is provided in a flow path branched from the upstream side of the EGR gas cooler 1.
A switching valve 29a is provided between the heater core 29 and the EGR gas cooler 1 to bypass the high-temperature cooling water when a heater is not required.

As described above, the EG is provided upstream of the heater core 29.
If the R gas cooler 1 is arranged, the amount of heat recovered from the exhaust gas in the EGR gas cooler 1 will be reduced by the amount of heat in the downstream heater core 2.
As a result, the heating performance of the passenger compartment is improved, and the exhaust heat can be effectively used.

[0030]

As is apparent from the above description, according to the EGR gas cooler for an internal combustion engine according to the present invention, the cooler element is integrated by brazing and the cap-shaped member is attached thereto by welding, so that the cooler It is possible to combine a cap-shaped member having an appropriate configuration according to a vehicle type or the like while sharing the element, thereby improving workability and reducing costs. In addition, at the time of the welding, the thermal effect on the cylindrical body is reduced, so that a problem that a hole is formed in the body can be prevented, and the welding operation is facilitated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an overall configuration of an EGR gas cooler according to the present invention.

FIG. 2 is a side view of the EGR gas cooler.

FIG. 3 is a sectional view of a main part.

FIG. 4 is a sectional view of a main part showing a different embodiment.

FIG. 5 is a circuit diagram showing a layout of an EGR gas cooler in an internal combustion engine cooling water circulation system.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... EGR gas cooler 2 ... Cooler element 3 ... Cap-shaped member 5 ... Body 6 ... End plate 6a ... 1st bending part 6b ... 2nd bending part 7 ... Heat exchange tube 8 ... Partition plate

Claims (3)

[Claims] 1. A tubular body provided with a cooling water inlet and a cooling water outlet on a side surface to allow cooling water to flow therein, an end plate for closing both ends of the body, and A plurality of heat exchange tubes disposed and connected at both ends to respective mounting holes of the end plate, and through which exhaust gas flows; and a gas inlet and a gas outlet respectively connected to both ends of the body. And a cap-shaped member on the inlet side and the outlet side respectively configuring
The EG of an internal combustion engine in which the body, the end plate, and the heat exchange tube are previously integrated by brazing as a cooler element, and the cap-shaped members are fixed to both ends of the cooler element by welding.
In the R gas cooler, the end plate has a first bent portion obtained by bending an outer peripheral portion of the end plate into a cylindrical shape, and the first bent portion is fitted to an outer peripheral portion of an end portion of the body. A further distal end of the first bent portion is bent outward as a second bent portion, and a cylindrical opening of the cap-shaped member is fitted to an outer peripheral surface of the first bent portion. An EGR gas cooler for an internal combustion engine, wherein the EGR gas cooler is fitted and the leading edge of the opening is welded to the second bent portion. 2. A bent portion which is bent to the outer peripheral side along the second bent portion is formed at a tip end of a cylindrical opening of the cap-shaped member. 2. An EGR gas cooler for an internal combustion engine according to claim 1, wherein the mutually adjacent leading edges of said second bent portion and said second bent portion are welded to each other. 3. A front end edge of the cylindrical opening of the cap-like member abuts against a side surface of the second bent portion, and the front end edge of the opening and the side surface of the second bent portion are formed. The EGR of an internal combustion engine according to claim 1, wherein the EGR is welded.
Gas cooler.