JP2000087812A - Egr gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool high temperature EGR gas without directly bringing it into contact with a cooling liquid pipe, and reduce thermal stress generated in the cooling liquid pipe by penetratingly forming a plurality of tubular spaces in a case wherein an EGR gas flows and inserting cooling liquid pipes circulating the cooling liquid into tubular spaces. SOLUTION: A gas 21 having an inflow port 23a and an outflow port 25a, through which an EGR gas flows is flat-tubularly formed of stainless steel. Flat-tubular spaces 27 are formed perpendicularly to the axial direction of the case 21 at prescribed intervals. EGR gas passages 29 are formed between the adjacent tubular spaces 27 for flowing of the EGR gas. A cooling liquid pipe 31 is inserted into each of the tubular spaces 27, whose inflow port 31a is connected to an inlet side tank 33, while whose outflow port 31b is connected to an outlet side tank 37. Cooling liquid is made to flow from an inflow pipe 35 to an outflow pipe 39, for cooling the EGR gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an EGR system for an exhaust system.
The present invention relates to an EGR gas cooling device for cooling EGR gas recirculated to an intake manifold via a pipe.

[0002]

2. Description of the Related Art Conventionally, in an engine, in order to reduce nitrogen oxides (NOx) in the exhaust gas, a part of the exhaust gas is taken out of an exhaust system and added to an air-fuel mixture.
(Exhaust Gas Recirculation). An EGR device for performing such EGR includes:
A part of the exhaust gas from the exhaust system is configured to be recirculated as an EGR gas to the air-fuel mixture sucked into the combustion chamber. For example, as shown in FIG. 3, an exhaust manifold (or exhaust pipe) 1 An EGR passage 3 connecting the intake manifold 2 and an EGR passage provided in the EGR passage 3
And a valve 4.

[0003] The ratio of the EGR gas to the intake air-fuel mixture is adjusted by appropriately controlling the opening of the EGR valve 4 according to the operating state of the engine. Such an E
In the GR device, since the EGR gas is taken into the combustion chamber together with the air-fuel mixture, it is necessary to maintain the temperature of the EGR gas at an appropriate temperature. In other words, the EGR gas is naturally high in temperature, but if the temperature of the EGR gas is too high, the air-fuel mixture is heated and thermally expanded, so that the air charging efficiency is deteriorated and the combustion rate of the air-fuel mixture is deteriorated. The output of the engine may be reduced.

On the other hand, if the temperature of the EGR gas is too low,
The viscosity of the adhering substance such as tar in the GR gas increases, so that the adhering substance easily adheres to the EGR passage, the EGR valve, and the like, which may reduce the reliability of the apparatus. Conventionally, as an EGR gas cooling device for cooling EGR gas, for example,
Japanese Unexamined Patent Publication No. -89491 is known.

FIG. 4 shows an EGR gas cooling device of this type, which comprises an exhaust manifold and an EGR gas cooling device.
It is arranged in a conduit connecting the valve. This cooling device is configured by arranging a number of pipes 6 in the axial direction of the outer cylinder 5, and both ends of the pipes 6 are supported by end plates 7 as shown in FIG. 5. An inlet pipe 8 and an outlet pipe 9 for the cooling water are opened on the outer periphery of the outer cylinder 5.

Further, flange portions 10 and 11 are formed at the upper end and the lower end of the outer cylinder 5, respectively. A pipe 12 from the exhaust manifold is connected to the upper flange 10 via a mounting flange 13, and a pipe 14 to the EGR valve is connected to the lower flange 11 via a mounting flange 15. In this cooling device, the EGR gas is introduced into the outer cylinder 5 from the pipe 12 on the exhaust manifold side, cooled by the cooling water flowing between the pipes 6 in the outer cylinder 5, and then led to the pipe 14 on the EGR valve side. Is done.

[0007]

However, in such a conventional EGR gas cooling device, high-temperature EGR gas flows into the outside of the flange portion 10 and the end plate 7 on the flange portion 10 side. Since low-temperature cooling water is circulated inside the end plate 7 on the 10 side, a large thermal stress is generated on the end plate 7 on the flange 10 side, and there is a possibility that cracks or the like may occur on the end plate 7 on the flange 10 side. There was a problem.

When the end plate 7 on the flange portion 10 is cracked, the cooling water flowing between the pipes 6 in the outer cylinder 5 flows out to the EGR gas side and greatly flows to the engine side. Serious damage. The present invention has been made in order to solve such a conventional problem, and it is possible to significantly reduce thermal stress generated in a case in which EGR gas is circulated and a cooling liquid pipe in which a cooling liquid is circulated. It is an object of the present invention to provide an EGR gas cooling device capable of reliably preventing a coolant from flowing to an EGR gas side when a crack is generated in a case or a coolant tube.

[0009]

According to a first aspect of the present invention, there is provided an EGR gas cooling apparatus, wherein a plurality of cylindrical spaces separated from the inside of the case by a partition member are provided in a case in which an inlet and an outlet for the EGR gas are formed. Is formed so as to penetrate the case, and a coolant pipe for circulating a coolant is inserted into the cylindrical space.

(Effect) In the EGR gas cooling device according to the first aspect, a cooling liquid pipe for circulating the cooling liquid is inserted into a plurality of cylindrical spaces formed in the case via the partition member. When passing through the vicinity of the cylindrical space, the EGR gas flowing into the case from the outlet of the case exchanges heat with the coolant in the coolant pipe via the partition member, is cooled, and flows out of the outlet of the case. You.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show one embodiment of the EGR gas cooling device of the present invention, and reference numeral 21 denotes a case 21 through which the EGR gas flows. The case 21 has a flat cylindrical shape and is made of stainless steel.

An inflow portion 23 having a tapered tip is formed on one side of the case 21, and an inflow port 23a through which EGR gas flows is formed at the tip of the inflow portion 23. An outlet 25 having a tapered tip is formed on the other side of the case 21, and an outlet 25a for discharging the EGR gas is formed at the tip of the outlet 25.

In this embodiment, a plurality of cylindrical spaces 27 are formed in the case 21. The cylindrical space 27 has a flat shape and extends in the axial direction of the case 21. Each cylindrical space 27 is formed at a predetermined interval in a direction perpendicular to the axial direction of the case 21, and an EGR gas through which EGR gas flows between the cylindrical spaces 27.
A gas passage 29 is formed.

The cylindrical space 27 is formed so as to penetrate one surface 21a and the other surface 21b of the case 21. The cylindrical space 27 is provided with one surface 21 a and the other surface 2 of the case 21.
The partition member 2 is inserted into the through holes 21c and 21d formed in
9 is formed by inserting and brazing or welding.

The partition member 29 is made of stainless steel.
It is formed in a flat cylindrical shape having a shape corresponding to the cylindrical space 27. And in this embodiment, in the cylindrical space 27,
A cooling liquid pipe 31 for circulating the cooling liquid is inserted. As shown in FIG. 2, the cooling liquid pipe 31 has a rectangular cross section, and a rectangular cooling liquid passage 32 is formed at the center.

As shown in FIG. 1, the cooling liquid pipe 31
It has a shape corresponding to the cylindrical space 27, and a cooling liquid inflow portion 31a is formed on one side, and a cooling liquid outflow portion 31b is formed on the other side.

The inflow portion 31a of each cooling liquid pipe 31 is connected to an inlet-side tank 33.
The coolant inflow pipe 35 is connected. The outlet 31b of each cooling liquid pipe 31 is connected to an outlet tank 37.
9 is connected. In this embodiment, the cooling liquid pipe 3
1, the inlet tank 33, the outlet tank 37, the coolant inflow pipe 35 and the coolant outflow pipe 39 are made of aluminum and brazed to each other.

After the coolant pipe 31 is inserted into the cylindrical space 27 of the case 21, the inlet tank 33 and the outlet tank 37 are fixed to the case 21 with screws (not shown) or the like. In the above-described EGR gas cooling device, the EG flowing into the case 21 from the outlet 23a of the case 21
When the R gas passes through the vicinity of the cylindrical space 27, the partition member 2
The heat is exchanged with the cooling liquid in the cooling liquid pipe 31 via the cooling pipe 9, the cooling liquid is cooled, and the cooling liquid flows out of the outlet 25 a of the case 21.

In the EGR gas cooling device configured as described above, a plurality of cylindrical spaces 27 separated from the inside of the case 21 by a partition member 29 are formed in the case 21, and the cooling space is formed in the cylindrical space 27. Since the cooling liquid pipe 31 that circulates the liquid is inserted, the high-temperature EGR gas does not directly contact the cooling liquid pipe 31, and the case 2 through which the EGR gas flows is used.
1, and the thermal stress generated in the cooling liquid pipe 31 through which the cooling liquid is circulated can be significantly reduced.

Further, since the cylindrical space 27 into which the cooling liquid pipe 31 is inserted is separated from the inside of the case 21 by the partition member 29, when the case 21 or the cooling liquid pipe 31 is cracked, the cooling liquid is supplied. Outflow to the EGR gas side can be reliably prevented. Further, in the above-described EGR gas cooling device, the EGR gas does not directly contact the cooling liquid pipe 31, so there is no possibility of corrosion. Thereby, the cooling liquid pipe 31 can be formed of, for example, aluminum. The weight of the device can be reduced.

In the embodiment described above, the cylindrical space 2
Although an example in which 7 is formed in a straight line has been described, the present invention is not limited to such an embodiment. For example, by forming the cylindrical space 27 in a wave shape, it is possible to further improve the heat exchange efficiency. it can. The EG in the case 21
By disposing a baffle plate or the like for stirring the EGR gas in the R gas passage 29, the heat exchange efficiency can be further improved.

[0022]

As described above, in the EGR gas cooling device according to the first aspect, a plurality of cylindrical spaces are formed in the case and are separated from the inside of the case by the partition member, and the cooling space is formed in the cylindrical space. Since the coolant pipe for circulating the liquid is inserted, the high-temperature EGR gas does not directly contact the coolant pipe,
The thermal stress generated in the case in which the EGR gas flows and the cooling liquid pipe in which the cooling liquid is circulated can be significantly reduced as compared with the related art.

Further, since the cylindrical space into which the cooling liquid pipe is inserted is separated from the inside of the case by the partition member, when the case or the cooling liquid pipe is cracked, the cooling liquid is supplied to the EGR.
Outflow to the gas side can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of an EGR gas cooling device of the present invention.

FIG. 2 is a cross-sectional view showing the EGR gas cooling device of FIG.

FIG. 3 is an explanatory view showing a conventional EGR device.

FIG. 4 is a side view showing a conventional EGR gas cooling device.

FIG. 5 is a sectional view showing details of a main part of the EGR gas cooling device of FIG. 4;

[Explanation of symbols]

 21 case 23a inflow port 25a outflow port 27 cylindrical space 29 partition member 31 coolant pipe

Claims (1)

[Claims] A case (21) in which an inlet (23a) and an outlet (25a) for EGR gas are formed, a plurality of cylindrical members isolated from the inside of the case (21) by a partition member (29). A space (27) is formed through the case (21), and a cooling liquid pipe (31) for circulating a cooling liquid is inserted into the cylindrical space (27). EGR gas cooling device.