JP3781386B2 - EGR gas cooling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus that cools EGR gas using engine coolant, a car air conditioner refrigerant, cooling air, or the like.
[0002]
[Prior art]
A method of taking a part of the exhaust gas from the exhaust system, returning it to the intake system of the engine again, and adding it to the air-fuel mixture is called EGR (Exhaust Gas Recirculation). EGR suppresses the generation of NOx (nitrogen oxide), reduces pump loss, reduces heat dissipation loss to the coolant due to lowering of combustion gas temperature, and increases specific heat ratio due to changes in working gas amount / composition. It is considered an effective method for improving the thermal efficiency of an engine because it has many effects such as improvement of cycle efficiency.
[0003]
However, it is recognized that when the temperature of the EGR gas increases, the durability of the EGR valve deteriorates due to its thermal action, which may cause premature breakage, or it may be necessary to have a water cooling structure to prevent this. ing.
In order to avoid such a situation, an apparatus that cools EGR gas with engine coolant or the like is used. As this apparatus, a multi-tube heat exchanger is generally used.
[0004]
As shown in FIG. 5, an example of the multitubular heat exchanger used in this case is a partition wall 15 on an end cap 14 having EGR gas inlets 14a or outlets 14b on one or both of the left and right sides. Is connected to and fixed to a head member (hub) 16 having a cooling medium inflow port 16a separately, and a heat transfer tube group constituted by a large number of tubes 12 inside the cylinder tube 11. Are fixedly arranged at the assembly holes provided in the partition walls 15 on both sides, and the nipple 18 screwed into the cooling medium inlet 16a and the cooling medium outlet 16b provided in the head member 16 is provided with a rubber hose or the like. A structure is known in which the EGR gas flowing through the heat transfer tube group is cooled by an engine coolant or the like connected to the branch pipe 17 and introduced or discharged from the branch pipe 17. Japanese Utility Model reference No. 57-309).
[0005]
However, the above-described multi-tube heat exchanger has a problem in that a large flow resistance is generated because the flow of engine coolant or the like is suddenly bent at the coolant inlet 16a. In addition, since the head member 16 and the partition wall 15 for fixing the large number of tubes 12 constituting the heat transfer tube group are both made of casting or forging, the weight of the heat exchanger body becomes excessive. In addition, since it is necessary to process a connection hole for screwing the nipple 18 for connecting the branch pipe 17 to the cooling medium outlet 16b and work to fix the heat transfer tube group to the partition wall 15, assembly is performed. The man-hours are excessive, and there is a problem that workability is deteriorated. Further, since the brazing operation is adopted as the joining means of the heat transfer tube group, the tube body 12 and the partition wall 15 are different in thickness. Since the heat capacities were different, the reliability of brazing work part strength maintenance was poor, and product defects were likely to occur.
[0006]
The present applicant has proposed an apparatus disclosed in Japanese Patent Application No. 7-267691 in order to solve the above-mentioned problems. As shown in FIG. 6, this apparatus is a multi-tube type in which a heat transfer tube group is fixedly arranged inside the trunk tube 1, and an EGR gas inlet 5a and an EGR gas outlet 5b are provided at the end of the trunk tube 1. In the EGR gas cooling apparatus, a cooling medium inflow port 6a and a cooling medium outflow port 6b are provided in the barrel tube 1 by burring outward, and the cooling medium inflow port 6a and the cooling medium outflow port provided by this burring are provided. In Fig. 6b, an EGR gas cooling apparatus having a structure in which the branch pipes 7a and 7b are directly joined by brazing or welding is presented.
[0007]
[Problems to be solved by the invention]
Although the EGR gas cooling device proposed in Japanese Patent Application No. 7-267691 was effective in improving the above-mentioned difficulty, the trunk tube 1 itself seems to have a uniform inner diameter over the entire length in the longitudinal direction. The outer diameter of the tube sheet 3 which is constructed and fitted to the barrel 1 is preferably substantially the same as the inner diameter of the barrel 1, and the barrel 1 in order to maximize the heat transfer area. Since the space between the cooling pipe 2 and the cooling pipe 2 is arranged close to each other, the space region 8 formed by the end cap 4 serving as the EGR gas inlet / outlet and the sheet metal tube sheet 3 is narrowed. The EGR gas that has flowed into the narrow space region 8 is likely to stay in the space region 8, and as a result, the flow into the cooling pipe 2 is prevented and the flow velocity is reduced, and the particulate matter contained in the EGR gas in this space region. 9 was caused, and the cooling phenomenon of the heat exchanger might be further deteriorated by the clogging of the cooling pipe 2 due to the accumulation phenomenon of the particulate matter 9.
[0008]
7 and FIG. 8, the space region 8 formed by the end cap 4 serving as the EGR gas inlet / outlet and the sheet metal tube sheet 3 is narrowed. The EGR gas that has flowed into the narrow space region 8 tends to stay in the narrow space region 8, so that the flow into the cooling pipe 2 is prevented and the flow velocity is slowed down, and the particulate matter 9 contained in the EGR gas enters the space region 8. It tends to be accumulated. This stagnant phenomenon of the particulate matter 9 has shortened the performance of the heat exchanger in a short time by accelerating the closing time of the cooling pipe 2, particularly the outermost cooling pipe 2.
[0009]
The present invention improves the above-mentioned drawbacks and expands a space region formed by an end cap serving as an EGR gas inlet / outlet and a sheet metal tube sheet to smoothly and smoothly flow into the cooling pipe. An EGR gas cooling device is provided in which the flow velocity in the cooling pipe near the outside is increased to prevent the reduction of the heat transfer coefficient in the pipe, and the particulate matter is stagnated here, and the closing time of the cooling pipe is greatly extended. It is for the purpose.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a heat transfer tube group fixedly arranged on a tube sheet fixed in the vicinity of both ends of the inner wall of the trunk tube, and end caps are fixed to the outside of both ends of the trunk tube. Also, in the multi-tube EGR gas cooling device in which the end cap is provided with an EGR gas inlet and outlet, the end of the barrel tube is enlarged, and the end of the barrel tube is enlarged. The EGR gas cooling device is characterized in that the heat transfer tube group is fixedly arranged by a sheet metal tube sheet fitted to the tube sheet, and the space region formed between the tube sheet and the inner peripheral surface of the end cap is expanded. It is what.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a partially broken plan view of one embodiment of the present invention, and FIG. 3 is a cross-sectional view of a main part of another embodiment of the present invention, and FIG. 4 is a cross-sectional view of a main part of still another embodiment of the present invention.
[0012]
As shown in FIG. 1, the multi-tube EGR gas cooling device 30 according to the present invention has both ends of a group of heat transfer tubes 32 fixed to a tube sheet 33 made of sheet metal by brazing or welding inside the trunk tube 31. On the other hand, the tube sheet 33 is arranged with its outer peripheral portion fixed to the inner wall 34 of the barrel tube 31 by brazing or welding, and an EGR gas inlet 35 is provided at one end of the barrel tube 31. An end cap 36a is fixed, and an end cap 36b provided with an EGR gas outlet 37 is fixed to the other end.
In the above description, a multi-tube EGR gas cooling device in which the inlet 35 is provided in one end cap 36a and the outlet 37 is provided in the other end cap 36b is shown. The present invention can also be applied to a multi-tube EGR gas cooling device of a type in which the group of heat tubes 32 is bent in a substantially U shape and an inlet and an outlet are provided in one end cap.
[0013]
In the gas cooling device 30, the trunk tube 31 has an end portion 40 in which both or one of the end portions is enlarged in diameter, and the enlarged diameter end portion 40 of the trunk tube 31 is made of a sheet metal tube. The sheet 33 is fitted, and the outer periphery of the sheet metal tube sheet 33 is fixed to the inner surface of the end portions of the end caps 36a and 36b together with the enlarged diameter end portion 40 of the body tube 31 by brazing or welding. A group of heat transfer tubes 32 is fixedly arranged inside the body tube 31, and an inner peripheral surface of an end cap 36 a provided with an EGR gas inlet 35 or an end cap 36 b provided with an outlet 37. The space region 38 formed between the tube sheet 33 made of sheet metal is expanded, and therefore the space between the outermost heat transfer tube opening 32a and the inner peripheral surfaces of the end caps 36a and 36b in the heat transfer tube 32 group. Region 38 is It is intended to be Zhang.
[0014]
That is, the EGR gas cooling device 30 according to the present invention includes an end cap 36a provided with an EGR gas inlet 35 or an inner peripheral surface of an end cap 36b provided with an EGR gas outlet 37, and a sheet metal The space region 38 between the tube sheet 33 is expanded, and therefore the inner peripheral surfaces of the end caps 36a and 36b and the heat transfer tube opening 32a of the heat transfer tube 32 group, particularly the outermost of the heat transfer tube 32 group. Since the space region 38 formed between the heat transfer tube opening 32a and the heat transfer tube opening 32a is expanded, the EGR gas flowing in from the EGR gas inlet 35 smoothly flows into the heat transfer tube 32 through the space region 38. The EGR gas flowing into or out of the heat transfer tube 32 flows out smoothly and out of the outlet 37, and the EGR gas at that time flows out through the space region 38. Flow without causing a decrease in flow rate to obtain a substantially same flow rate as the heat transfer tubes disposed in the central portion vicinity, thus nearly identical tube heat transfer coefficient (thermal communication rate ^{(kcal / m 2 hr ℃)} ) The space region 38 where the particulate matter 39 contained in the EGR gas stagnates is expanded, so that the particulate matter 39 flows into the heat transfer tube 32 and the inside of the heat transfer tube 32. The particulate matter 39 is prevented from flowing out for a long period of time, and it is possible to easily prevent the heat exchange capacity from being lowered due to the clogging phenomenon of the heat transfer tube 32 caused by the accumulation of the particulate matter 39 in the past. Is.
[0015]
2 to 4 are cross-sectional views of the main part of an EGR gas cooling device 30 according to another embodiment of the present invention. In FIG. 2, the end portion of the trunk tube 31 is bent in a direction perpendicular to the central axis. Then, the tube sheet 33 is fitted so as to overlap with the outer peripheral portion of the tube sheet 33, and has the same diameter as that of the outer peripheral end surface of the tube sheet 33. Alternatively, as shown in FIG. 3, the end portion of the trunk tube 31 is expanded to substantially match the outer diameter of the tube sheet 33, and the tube sheet is fitted to the expanded end portion of the trunk tube. The inner ends of the ends of 36a and 36b are fitted and fixed together, or the outer peripheral end of the tube sheet 33 is bent in parallel with the central axis of the barrel 31 as shown in FIG. It is fitted to the end of the diameter, and these are further connected to the end cap 3 a, it is constructed by fixing them integrally fitted to the inner surface of the end portion of 36b.
[0016]
【The invention's effect】
As described above, according to the present invention, the stagnant region of the particulate matter contained in the EGR gas is expanded. Therefore, the attachment of the particulate matter inside the heat transfer tube or the blockage of the heat transfer tube is prolonged. It is easy to prevent the heat exchange capacity from being lowered due to the clogging phenomenon of the heat transfer tube that has been caused by the particulate matter in the past, and to smoothly flow in and out of the EGR gas. Uniformity and uniform heat transfer coefficient can be achieved, and variations in heat exchange capacity can be reduced.
[Brief description of the drawings]
FIG. 1 is a partially broken plan view of an embodiment of an EGR gas cooling device of the present invention.
FIG. 2 is a cross-sectional view of another embodiment of the main part of the present invention.
FIG. 3 is a cross-sectional view of still another embodiment of the essential part of the present invention.
FIG. 4 is a cross-sectional view of still another embodiment of the essential parts of the present invention.
FIG. 5 is a partially broken plan view of a conventional example.
FIG. 6 is a partially broken plan view of another conventional example.
FIG. 7 is a cross-sectional view of a main part of another conventional example.
FIG. 8 is a cross-sectional view of a main part of another conventional example.
[Explanation of symbols]
30 EGR gas cooling device 31 trunk tube 32 heat transfer tube 33 tube sheet 34 trunk tube inner wall 35 EGR gas inlet 36a end cap 36b end cap 37 EGR gas outlet 38 space region 39 particulate matter 40 expanded end

Claims (1)

A heat transfer tube group is fixedly arranged on a tube sheet fixed near both ends of the inner wall of the trunk tube, and end caps are fixed to the outer sides of both ends of the trunk tube, and EGR gas is attached to the end cap. In the multi-tube type EGR gas cooling apparatus provided with an inflow port and an outflow port, the end portion of the trunk tube is enlarged, and a sheet metal tube sheet fitted to the enlarged end portion of the trunk tube is used. An EGR gas cooling device characterized in that a space region formed between the tube sheet and the inner peripheral surface of the end cap is expanded by firmly arranging heat transfer tube groups.

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