JP3861968B2 - EGR cooler installation structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an arrangement structure of an EGR cooler.
[0002]
[Prior art]
NOx in the exhaust gas is generated by combining nitrogen and oxygen in the mixture at a high temperature when the mixture burns. Therefore, NOx can be reduced by lowering the combustion temperature. One method for reducing NOx in exhaust gas is an exhaust gas recirculation device (hereinafter referred to as “EGR device”). In this EGR device, a part of the combusted exhaust gas is introduced into the intake side to slow down the combustion, thereby lowering the maximum combustion temperature and reducing the generation of NOx.
[0003]
By the way, when exhaust gas (hereinafter referred to as “EGR gas”) is introduced to the intake side, NOx is reduced as described above. However, since the amount of intake air of fresh air is reduced by that amount, oxygen is insufficient and smoke or HC There is a problem that the amount of PM (hazardous particulate matter) increases. In order to reduce PM, it is necessary to reduce the volume of the EGR gas introduced to the intake side to reduce the volume, and to increase the amount of fresh intake air accordingly. That is, in order to reduce NOx while suppressing PM in the exhaust gas by the EGR device, it is necessary to lower the temperature of the EGR gas introduced to the suction side.
[0004]
Therefore, in recent years, a technique has been implemented in which EGR gas is cooled by an EGR cooler to suppress PM and reduce NOx. The EGR cooler includes a plurality of pipes as EGR gas passages through which EGR gas passes and a cooling medium (cooling water) that cools the EGR gas in these pipes, and communicates the exhaust passage and the intake passage of the engine. The EGR gas passage that introduces a part of the exhaust gas to the suction side is configured to cool the EGR gas by enabling heat exchange between the EGR gas and the cooling medium.
[0005]
An EGR device equipped with such an EGR cooler is disclosed in, for example, Japanese Patent Application Laid-Open No. 10-2256. This EGR device is provided with an EGR cooler for cooling exhaust gas that is integrated with the EGR valve and returned to the EGR valve and the intake manifold on the side surface of the cylinder block of the engine, and the cooling water flow path of the EGR cooler is connected to the cylinder. The structure is directly attached so as to communicate with the cooling water passage of the block.
[0006]
[Problems to be solved by the invention]
The water-cooled EGR cooler requires a large heat transfer area in order to improve the heat exchange rate. However, in the structure in which the EGR device is directly attached to the side surface of the conventional cylinder block, it is difficult to secure a heat transfer area sufficient for exhibiting a cooling effect due to limited mounting space.
[0007]
For this reason, the present invention provides an EGR cooler arrangement structure in which the EGR cooler is arranged on the cylinder head of the engine as a rocker cover, and the heat transfer area is widened to improve the heat exchange rate. The purpose is to do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a part of the exhaust gas discharged to the exhaust passage of the engine is introduced into the EGR cooler through the EGR gas passage. On the other hand, part of the engine coolant supplied from the coolant passage flows into the EGR cooler. The hot EGR gas flowing through the EGR gas passage in the EGR cooler is cooled by the cooling water and supplied to the intake passage of the engine. EGR cooler, said has substantially the same size as the cooling water passage and the EGR passage defined in a plurality of flat space between the cylinder head upper surface of the engine is formed to form a layered alternately, the EGR cooler, A large heat transfer area is ensured by being arranged on the cylinder head and also serving as a rocker cover. Thereby, a heat exchange rate improves significantly and EGR gas is cooled very well. The cooled EGR gas is supplied to the intake passage of the engine, and the cooling water that has cooled the EGR gas flows to the engine.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.
Example 1
FIG. 1 is a front view of an engine to which an EGR cooler arrangement structure according to the present invention is applied, and FIG. 2 is a plan view of FIG. As shown in FIGS. 1 and 2, the engine 1 has a cylinder head 3 mounted on a cylinder block 2, an intake manifold 4 mounted on one side of the cylinder head 3, and an exhaust manifold 5 mounted on the other side. The intake manifold 4 is connected to the intake passage 6, and the exhaust manifold 5 is connected to the exhaust passage 7.
[0010]
The EGR cooler 11 is a flat box having approximately the same size as the cylinder head 3, is arranged and fixed on the cylinder head 3, and is also used as a rocker cover. The EGR cooler 11 is interposed in an EGR gas passage composed of EGR gas passages 12 and 13, and an EGR gas inlet 11 a is connected to the vicinity of the outlet of the exhaust manifold 5 of the exhaust passage 7 via the EGR passage 12. The gas outlet 11 b is connected to the vicinity of the inlet of the intake manifold 4 in the intake passage 6 via the EGR passage 13, and an EGR valve 14 is interposed in the EGR passage 13. Further, the cooling water passage of the EGR cooler 11 is inserted into the cooling water passage of the engine 1, and the cooling water inlet 11 c is connected to the cooling water passage (not shown) of the cylinder block 2 via the cooling water passage 15. The cooling water outlet 11 d is connected to a cooling water passage (not shown) of the cylinder head 3 through the cooling water passage 16.
[0011]
As shown in FIGS. 3 and 4, the interior of the EGR cooler 11 is defined by a plurality of partition plates 17 into a plurality of flat spaces at predetermined intervals, and the EGR gas passages 18 and the cooling water passages 19 are alternately arranged. A plurality of layers are formed, and has the same configuration as a known stacked EGR cooler.
In the EGR cooler 11, the EGR gas passage 18 and the cooling water passage 19 are flat, have a large heat transfer area substantially the same size as the cylinder head 3, and the EGR gas passage 18 and the cooling water passage 19 are The heat exchange rate is greatly improved by being defined by the partition plates 17 having excellent heat conductivity and being alternately formed in layers.
[0012]
The operation will be described below.
As shown in FIGS. 1 to 4, a part of the exhaust gas discharged into the exhaust passage 7 of the engine 1 is introduced from the EGR gas inlet 11a side of the EGR cooler 11 through the EGR gas passage 12, and the EGR gas is flattened. The gas flows through the EGR gas passage 18 to the EGR gas outlet 11b. On the other hand, a part of the cooling water that has cooled the cylinder block 2 of the engine 1 flows from the cooling water inlet 11 c side of the EGR cooler 11 through the cooling water passage 15 and flows to the cooling water outlet 11 d through the flat cooling water passages 19. .
[0013]
Then, the cooling water flowing through each cooling water passage 19 cools the EGR gas flowing through each EGR gas passage 18. The EGR gas passage 18 and the cooling water passage 19 are flat and have a large heat transfer area, and the EGR gas passage 18 and the cooling water passage 19 are alternately formed in layers by the partition plates 17 having excellent heat conductivity. As a result, the heat exchange rate is greatly improved, and the EGR gas is cooled extremely well. The EGR gas cooled in each EGR gas passage 18 is supplied to the intake passage 4 of the engine 1 through the EGR gas passage 13 and the EGR valve 14. The cooling water that has cooled the EGR gas flows to the cylinder head 3 through the cooling water passage 16.
[0014]
In the above-described embodiment, the laminated EGR cooler has been described. However, the present invention is not limited to this, and a multi-tube EGR cooler may be applied.
[0015]
【The invention's effect】
According to the present invention, an EGR cooler that is interposed in an EGR passage that supplies EGR gas from an exhaust passage of an engine to an intake passage and that can exchange heat between the cooling water of the engine and the EGR gas is provided in the engine. By arranging the rocker cover on the cylinder head, the heat exchange rate of the EGR can be greatly improved, and the EGR gas can be cooled well. Further, by using the same as the rocker cover, the cost can be reduced and the number of assembling steps can be reduced.
[Brief description of the drawings]
FIG. 1 is a front view of an engine to which an EGR cooler arrangement structure according to the present invention is applied.
FIG. 2 is a plan view of an arrangement structure of the EGR cooler shown in FIG.
FIG. 3 is a partially cutaway plan view of the EGR cooler shown in FIG. 1;
4 is a partially cutaway front view of the EGR cooler shown in FIG. 3; FIG.
[Explanation of symbols]
1 Engine 2 Cylinder block 3 Cylinder head 4 Intake manifold 5 Exhaust manifold 6 Intake passage 7 Exhaust passage 11 EGR coolers 12, 13 EGR gas passage 18 EGR gas passage 19 Cooling water passage

Claims (1)

An EGR cooler provided in an EGR passage for supplying EGR gas from an exhaust passage of the engine to an intake passage and provided to enable heat exchange between the cooling water of the engine supplied from the cooling water passage and the EGR gas; was formed to form a layered substantially equal to the cooling water passage and the EGR passage alternately which is defined in a plurality of flat space between the cylinder head upper surface of the engine, the rocker with and disposed on the cylinder head An arrangement structure of an EGR cooler characterized by being configured as a cover.

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