JPH1113551A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cooling water from boiling in the vicinity of an inlet side end plate, and improve cooling performance by inserting a plurality of cooling pipes in an end plate at an EGR gas inlet side, fixing them, and separating the end surface on the water chamber side of the end plate from the inlet end of the cooling pipe by a length equivalent to or more than the length of a turbulent zone. SOLUTION: A casing 2 of an EGR cooler 1 is formed by coaxially-disposing a flange part 5, an inlet side tank part 4, and an outer cylindrical part 3, and partitioning a gas introduction opening 6, an inlet side gas chamber 7, and a water chamber 8 toward its inside in a radial direction. The inlet side gas chamber 7 and the water chamber 8 are partitioned by an inlet side end plate 9, and the inlet side gas chamber 7 is communicated with an outlet side gas chamber by a plurality of cooling pipes 10 formed at the inlet side end plate 9. In the respective cooling pipes 10, a protruding part 10d protruding from the inlet side end plate 9 by a prescribed length F in the inlet side gas chamber 7 is formed, thus it is possible to separate the inlet end 10b of the cooling pipe 10 from the end surface 9a on the water chamber 8 side of the inlet side end plate 9 by the length E equivalent to or more than the length of a turbulent zone L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR cooler, and more particularly, to an EGR (Exhaust) system for extracting a part of exhaust gas from an engine from an exhaust path and returning the exhaust gas to an intake path of the engine again.
The present invention relates to an EGR cooler that cools EGR gas by using engine cooling water as a coolant when performing Gas Recirculation.

[0002]

2. Description of the Related Art NOx in exhaust gas from diesel engines, etc.
It is known that EGR is effective to reduce the EGR. That is, it is considered that when EGR is performed, the oxygen concentration in the intake air decreases and combustion becomes slow, and the generation of NOx is suppressed by the decrease in combustion temperature.

On the other hand, mixing EGR gas into the intake air causes a problem that the fresh air amount is reduced by that amount and the smoke is deteriorated. In order to solve this, the EGR
It has been proposed to provide a cooler and cool the high-temperature EGR gas to reduce the volume, thereby increasing the amount of fresh air and preventing the generation of smoke (Japanese Patent Laid-Open No. 6-14).
No. 7028).

FIG. 14 is a block diagram of an engine to which an EGR cooler is applied.
The cooling water is circulated between the engine 53 and the engine 53 via a cooling water pipe 54, and the cooling water is used as a coolant to cool the EGR gas inside the GR pipe 52. The EGR pipe 52 takes out a part of the exhaust gas (EGR gas) from an exhaust path including an exhaust manifold 55 and an exhaust pipe 56, and takes the intake manifold 57 and the intake pipe 58.
Return it to the intake path consisting of A flow control valve 59 for controlling the EGR amount is provided in the middle of the EGR pipe 52.

The structure of a general EGR cooler is shown in FIGS.
6. The EGR cooler 51 has a cylindrical casing 60, and an inlet side flange 61 and an outlet side flange 62 are integrally provided at both ends in the longitudinal direction of the casing 60. Inlet flange 61 and outlet flange 62
Separates a gas inlet 63 and a gas outlet 64, respectively, into an upstream EGR pipe 52a and a downstream EGR pipe 52.
b. Inside the casing 60, a pair of end plates spaced apart in the longitudinal direction (gas flow direction), that is, an inlet end plate 65 and an outlet end plate 66
Is provided. These end plates 65 and 66 divide the inside of the casing 60 into inlet and outlet gas chambers 6 at both ends.
7, 68 and a central water chamber 69. The water chamber 69 is provided with a cooling water inlet 70 and a cooling water outlet 71 that are separated from each other in the longitudinal direction. The cooling water inlet 70 and the cooling water outlet 71 are defined by a cooling water inlet 70a and a cooling water outlet 71a, respectively. A cooling water outlet pipe 71 a is provided near the outlet side end plate 66. However, these may be reversed as shown by the imaginary line. Also in this case, the cooling water introduction pipe 70a is provided on the lower side, and the cooling water outlet pipe 71a is provided on the upper side. On the other hand, a plurality of cooling pipes 72 are provided by bridging both end plates 65 and 66. The cooling pipe 72 communicates the inlet-side and outlet-side gas chambers 67 and 68, and allows a high-temperature EGR gas to flow therein, and the EGR gas and the water chamber 69.
Heat exchange is performed with the cooling water inside.

A portion of the casing 60 that divides the water chamber 69 includes an outer cylinder 73, inlet-side and outlet-side gas chambers 67, 6.
8 are tank portions 74 and 75. While the outer cylinder 73 is cylindrical with a constant diameter, the tanks 74, 7
5 is narrowed at both ends. Thereby, the gas inlet 63
The EGR gas introduced from the cooling pipe 72 spreads in the radial direction and is distributed to each cooling pipe 72, and the EGR gas coming out of each cooling pipe 72 is collected and led out from the gas outlet 64.

The cooling pipe 72 has a relatively small thickness (about 0.5 to 1 mm) in order to enhance the cooling efficiency, and has an inner diameter of 6 to 10 mm.
It is about 8mm. Further, as the material, since EGR gas contains sulfur at a high temperature, stainless steel or the like excellent in high-temperature strength and corrosion resistance is employed. In order to reduce the assembly cost, all parts are assembled by brazing in the furnace. Therefore, other parts than the cooling pipe 72 are formed of the same material as the cooling pipe 72. Both end plates 65 and 66 have a relatively large wall thickness (about 3 mm) in order to secure the connection with the cooling pipe 72 and the casing 60 (the outer cylindrical portion 73) by brazing. The outer cylinder 73 and the tanks 74 and 75 of the casing 60 have a thickness of about 1.5 to 3 mm in order to obtain sufficient strength, since the thickness is not related to the efficiency of the cooler.

In the EGR cooler 51, the flow of the cooling water in the water chamber 69 is changed from the cooling water inlet 70 to the cooling water outlet 7
The flow is obliquely upward toward 1. On the other hand, separately from this, in order to increase the cooling efficiency, as shown in FIG.
In some cases, a plurality of baffle plates 76 are provided in the chamber 9 so that the cooling water meanders in the water chamber 69.

The number, diameter, and length of the cooling pipes 72 are determined based on the temperature and flow rate of the EGR gas, the required heat radiation, and the like. The wall resistance of the cooling pipe 72 with respect to the gas flow rate and the inlet-side gas chamber 67
It is necessary to determine the total passage area in consideration of the drawing loss due to the cross-sectional change from the cooling pipe 72 to the cooling pipe 72. In order to increase the amount of heat radiation, it is necessary to increase the total surface area of the cooling pipe 72. That is, for a cooler having the same diameter, if the pipe diameter is reduced and the number of tubes is increased, the surface area per unit length of the cooler can be increased while securing the total passage area, and the overall length of the cooler can be shortened. Such specifications need to be determined in consideration of the mountability to the engine.

The specific heat of water is larger than that of EGR gas,
Since the difference between the inlet and outlet temperatures of the cooling water is smaller than the difference between the inlet and outlet temperatures of the GR gas, there is no great difference in the amount of heat radiation regardless of the position of the cooling water inlet 70 and outlet 71. For example, even if the EGR gas at 1.0 kg / min and 500 ° C is cooled to 200 ° C with 10 kg / min cooling water, the difference
° C, which is sufficiently smaller than the temperature difference of the EGR gas.

[0011]

Although the boiling point of engine cooling water is generally raised to about 120 ° C. by pressurization, when used as a refrigerant in the EGR cooler 51, the temperature and flow rate of EGR gas are reduced. Boiling may occur due to rising. When the boiling occurs, the components dissolved in the cooling water adhere to the surface of the cooling pipe 72 and the like, and the heat transfer (radiation) from the EGR gas to the cooling water is hindered, so that the initial performance cannot be maintained. In this case, the temperature of the EGR gas becomes high, and the problem of increase in NOx and smoke occurs. Conversely, the temperature and flow rate of the EGR gas are limited to a range where boiling in the EGR cooler 51 does not occur.

The earliest boiling occurs due to an increase in the temperature and flow rate of the EGR gas is caused by the inlet end plate 65.
And the surface of the cooling pipe 72 in the vicinity thereof. The reason is E
This is because the GR gas temperature is higher than the downstream or outlet side. In particular, as shown in FIG. 15, in the inlet side gas chamber 67, the central portion S of the inlet side end plate 65 is a portion where the high temperature gas introduced from the gas inlet 63 hits at a relatively high speed. Easily.

The flow of the EGR gas in the cooling pipe 72 is defined by a section L from the pipe end on the inlet side to a downstream side by a predetermined distance.
So becomes turbulent orientation is not constant under the influence of sudden cross-section variation, the orientation in the section L ₀ downstream of the section L is in line with the cooling pipe 72 (hereinafter, the former segment L
Is referred to as a “turbulent section” and the latter section L _{0 is referred} to as a “stable section”). In the stable section L ₀ , the temperature distribution and the velocity distribution of the flow are larger toward the center of the pipe and smaller at the pipe wall. On the other hand, in the turbulent flow section L, there is no such a temperature gradient and a velocity gradient from the pipe center side to the pipe wall side. For this reason,
In the turbulent flow section L, heat transfer to the cooling pipe 72 is more active than in the stable section L ₀ , so that the temperature of the inlet end plate 65 in contact with the cooling pipe 72 also becomes high.

The length of the turbulence section L is determined by the length of the upstream EGR pipe 5.
It varies depending on the inner diameter and the number of cooling pipes 72 with respect to the inner diameter of 2 a and the inner diameter of the inlet side gas chamber 67. Further, the flow rate, temperature, and pressure of the EGR gas change depending on the operating state of the engine, and also change during the cycle due to the exhaust pulsation. Therefore, the length of the turbulent flow section L also changes accordingly. Usually, the turbulent section L
Is about 1 to 3 times the inner diameter of the cooling pipe 72.

Further, in the water chamber 69, the temperature near the surface of the inlet-side end plate 65 tends to be high because the cooling water easily flows.

As can be seen from these descriptions, it is difficult to prevent boiling in the turbulent flow section L even if the number of cooling pipes 72 is increased.

Here, as shown in FIGS.
The adhesion of the dissolved component in the cooling water introduction port 7 is not only caused in the region A near the inlet side end plate 65 where boiling easily occurs.
0 and depending on the positional relationship between the outlet port 71, or going on a steam Todokoryu region V ₂ when passing path V ₁ of the steam shown in FIG. 18, or the derivation of the coolant as shown in FIG. 19 is not performed smoothly. Therefore, heat transfer is also prevented in the path V ₁ and the region V ₂ , and the cooler performance is deteriorated.

As described above, for the EGR cooler, it is urgently necessary to take measures against boiling near the end plate on the inlet side.

[0019]

In the EGR cooler according to the present invention, a plurality of cooling pipes are inserted into and fixed to the end plate on the EGR gas inlet side, and the end face of the end plate on the water chamber side and the cooling pipe are provided. The inlet end is separated by at least the length of the turbulent section.

According to the above configuration, the end of the water chamber on the gas inlet side can be set at least in the stable section. Thus, contact between the high-temperature portion and the cooling water can be avoided, and boiling of the cooling water can be prevented.

Here, it is preferable that the end plate has a thickness equal to or greater than the length. Preferably, the end plate has a slit for exposing the cooling pipe to the outside. Preferably, the cooling pipe projects from the end plate toward the gas inlet. Preferably, the inlet side end of the cooling pipe is expanded in a funnel shape. Preferably, the projecting portions of the cooling pipes are connected by a heat transfer plate. Preferably, a gas chamber is provided at a predetermined distance from the end plate on the gas inlet side, and the cooling pipe connects the end plate to the gas chamber and is exposed to the outside between them. Further, it is preferable that a radiation fin is provided on an exposed portion of the cooling pipe.
Preferably, the exposed part of the cooling pipe is covered with a protective tube. A gas chamber is provided at a predetermined distance from the end plate on the gas inlet side, and the cooling pipe connects the end plate and the gas chamber, and a coolant chamber is provided between the end plate and the gas chamber. Is preferably provided.

[0022]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an EGR cooler E according to this embodiment.
The portion on the GR gas inlet side is shown. EGR as before
The cooler 1 has a casing 2 formed in a substantially cylindrical shape. The casing 2 includes an outer cylindrical portion 3 formed to have a predetermined constant diameter, and an inlet-side tank portion 4 sequentially narrowed from the outer cylindrical portion 3 toward the gas inlet side (left side in the figure). At the inlet end of the inlet side tank portion 4, a flange portion 5 for connecting to the above-mentioned upstream EGR pipe is provided (see FIG. 15), and the flange portion 5 has a plurality of bolt mounting holes (not shown). They are provided at predetermined intervals in the circumferential direction.

The flange portion 5, the inlet side tank portion 4 and the outer cylinder portion 3 are coaxially arranged, and define a gas inlet 6, an inlet side gas chamber 7 and a water chamber 8 radially inward. The gas inlet 6 and the inlet gas chamber 7 are continuous,
The inlet gas chamber 7 and the water chamber 8 are separated by an inlet end plate 9. That is, the water chamber 8 is provided with the inlet-side end plate 9.
And an exit-side end plate on the right side in the figure, which is divided in the axial direction. The inlet end plate 9 and the outlet end plate are circular flat plates perpendicular to the casing axial direction, and are bridged by a plurality of cooling pipes 10 extending in the axial direction. The cooling pipes 10 are arranged in a staggered manner, and a portion on the gas inlet side is inserted into and fixed to the inlet side end plate 9.
Thus, the cooling pipe 10 communicates the inlet-side gas chamber 7 with the outlet-side gas chamber on the right side in the figure.

In particular, the cooling pipe 10 has a protruding portion 10 d that protrudes from the inlet end plate 9 by a predetermined length F in the inlet gas chamber 7. And by this, the cooling pipe 1
0 and the water chamber 8 of the inlet-side end plate 9
Side end surface 9a is separated from the turbulent flow section L by a length equal to or longer than the length (separation distance E). Here, the projection length F itself is made larger than the length of the turbulent flow section L, and the distance between the inlet end 10b and the end face 9a is set to be sufficiently larger than the length of the turbulent flow section L.

Here, a cooling water inlet 11 is opened in the water chamber 8 near the inlet end plate 9. The cooling water inlet 11 is formed by a cooling water inlet pipe 12 protruding from a lower portion of the outer cylindrical portion 3. Cooling water inlet 1
1 has a directivity direction perpendicular to the casing axial direction.

The configuration on the right outside the drawing is the same as the conventional configuration shown in FIG. Therefore, a cooling water outlet is opened on the gas outlet side of the water chamber 8. The cooling water outlet is formed by a cooling water outlet pipe, and the cooling water outlet pipe is provided so as to protrude above the outer cylindrical portion 3. A cooling water pipe such as a hose leading to the engine is connected to the cooling water inlet pipe 12 and the cooling water outlet pipe. An outlet side EGR pipe is connected to the outlet side flange. Other manufacturing methods, dimensions of each part, and the like are the same as those in the related art.

In this configuration, the EGR gas is introduced from the gas inlet 6 and enters each cooling pipe 1 in the inlet side gas chamber 7.
Distributed to zero. And after passing through each cooling pipe 10,
They are gathered in the outlet gas chamber and led out from the gas outlet. In addition, the cooling water is introduced into the water chamber 8 from the cooling water inlet 11 and flows toward the cooling water outlet.

In particular, in the above configuration, since the end face 9a of the inlet end plate 9 and the inlet end 10b of the cooling pipe 10 are separated by the length of the turbulence section L or more, the end face 9a, that is, the gas in the water chamber 8 the position of the inlet side of the chamber end, can be set in the stable section L ₀ deviated from turbulence interval L. As described above, the temperature inside the turbulent flow section L becomes high due to the unsteady flow of the EGR gas. However, with such a configuration, the cooling water is positioned so as to avoid the high temperature section, and the high temperature section and the cooling water Contact with water, and the boiling of the cooling water can be prevented.

In the above configuration, the inlet-side end plate 9 is also located outside the turbulent section L. Therefore, heating of the inlet side end plate 9 due to heat transfer from the cooling pipe 10 can be suppressed, and boiling on the plate surface can be prevented. As can be seen from this, as the distance E and the protrusion length F are increased, the effect of preventing boiling is increased.

In the case of this configuration, the flow of the EGR gas in the inlet side gas chamber 7 mainly flows toward each cooling pipe 10, and the gas stays around the projecting portion 10 d of the cooling pipe 10. Therefore, the gas introduced from the gas inlet 6 does not directly collide with the inlet side end plate 9,
As a result, the heating of the inlet-side end plate 9 is prevented, and the boiling of the cooling water is also prevented.

In this way, performance deterioration due to adhesion of dissolved components due to boiling is prevented, restrictions on prevention of boiling of gas temperature and gas flow rate are suppressed, and the EGR rate and the EGR region can be expanded.

Next, a modified example will be described. FIG. 2 shows an example in which a heat transfer plate 13 is added to the configuration of FIG. The heat transfer plate 13 is connected to the inlet end 1 of the cooling pipe 10.
Oa is connected to disperse heat to equalize heating. As described above, the cooling pipe 10 in the central portion S facing the gas inlet 6 receives a gas having a relatively high flow rate, and thus tends to become high in temperature. Therefore, if the heat transfer plate 13 is provided, the heat is distributed to the cooling pipes 10 on the radially outer side, and an excessive rise in the temperature of the cooling pipes 10 in the central portion S can be suppressed. Further, the heat transfer plate 13 prevents the gas from directly colliding with the inlet side end plate 9, so that the heating of the inlet side end plate 9 can be suppressed. Further, here, since the heat transfer plate 13 is arranged flush with the inlet end 10b of the cooling pipe 10, the heat transfer plate 13 is located in the turbulent flow section L, and the heat is equalized and dispersed in the turbulent flow section L. Can also be planned.

In the example shown in FIG. 3, the inlet side end 10a of the cooling pipe 10 in the configuration of FIG. 1 is enlarged in a funnel shape. In this way, the introduction of gas into the cooling pipe 10 becomes smooth, the length of the turbulent flow section L is shortened, and the temperature rise of the cooling pipe 10 can be suppressed. Further, the enlarged diameter portion becomes an obstacle to the gas directed to the inlet end plate 9, and at the same time, maintains the stagnation of the gas and suppresses the direct collision of the gas with the inlet end plate 9.

In the example shown in FIG. 4, the inlet gas chamber 7 is separated from the water chamber 8 by a predetermined distance toward the gas inlet.
The inlet-side gas chamber 7 and the water chamber 8 are connected by a cooling pipe 10, and the cooling pipe 10 is exposed between them. That is, here, a central casing 2a composed of the outer cylinder 3a and the inlet side end plate 9 is provided, the inlet side end plate 9 partitions the water chamber 8, and the cooling pipe 10 extends from the inlet side end plate 9 to the gas inlet side. The inlet end 10a of the cooling pipe 10 is inserted and fixed to a rear end plate 15 of an inlet-side tank casing 14 defining the inlet-side gas chamber 7. Inlet end 1 of cooling pipe 10
0b is flush with the rear end plate 15. Even in this case, the separation distance E can be sufficiently secured, and boiling can be prevented. In this example, the rear end plate 15, the inlet end plate 9, and the exposed portion 10c of the cooling pipe 10 can be air-cooled,
Boiling can be prevented by setting the vicinity of the inlet side end plate 9 to a low temperature. It is effective to guide the air to the exposed portion 10c of the cooling pipe 10 with a fan or to apply a traveling wind.

In the example shown in FIG. 5, a radiation fin 16 is provided on the exposed portion 10c of the cooling pipe 10 in addition to the configuration shown in FIG. The radiation fins 16 are formed of a thin circular plate, are arranged at equal pitches in the longitudinal direction of the exposed portion 10c, and are arranged perpendicularly to the longitudinal direction of the exposed portion 10c so that all the cooling tubes 10 are inserted and fixed. . In this way, air cooling of the cooling pipe 10 can be further promoted, and the effect of preventing boiling can be further enhanced.

In the example shown in FIG. 6, in addition to the configuration of FIG.
Another radiation fin (orthogonal fin) 17 extending in the longitudinal direction of the exposed portion 10c is provided. The orthogonal fins 17 are orthogonal to the heat radiating fins 16 and connect the central casing 2a and the inlet-side tank casing 14, and are provided at a predetermined interval in the circumferential direction. In this case, the air cooling effect is further enhanced, and a further boiling prevention effect can be expected. It is also advantageous in strength.

In the example shown in FIG.
0c is covered with a protective tube 18. The protective cylinder 18 connects the central casing 2a and the inlet-side tank casing 14, and has a plurality of air cooling holes 19 that allow air to flow. By doing so, the strength can be secured without hindering the heat radiation in the exposed portion 10c. As for the protection of the exposed portion 10c, the cooling pipe 10 may be formed to be thick instead of providing the protection tube 18.

In the example shown in FIG. 8, the inlet side end plate 9 is formed of a material having a thickness T larger than the length of the turbulent flow section L, and a plurality of slits 20 are provided.
Is partially exposed. Slit 20
The openings that open upward or downward are provided alternately to prevent local heat storage of the inlet-side end plate 9. Even in this case, the separation distance E can be made large to be effective in preventing boiling.

In the example shown in FIG. 9, the inlet side end plate 9 is merely formed with a thickness T larger than the length of the turbulent flow section L. Here, the inlet end 10 b of the cooling pipe 10 is flush with the surface 9 e of the inlet end plate 9 facing the inlet gas chamber 7. Even in this case, the water chamber 8 is located at a position deviating from the turbulent flow section L, and boiling can be prevented. Here, the inlet-side end plate 9 can be air-cooled by exposing the outer peripheral edge to the outside of the casing 2. Even if the inlet end 10b of the cooling pipe 10 is positioned inside the thickness direction of the inlet-side end plate 9, the turbulent flow section L is located on the surface 9 of the inlet-side end plate 9.
There is no particular problem because it starts from e.

In the example shown in FIG. 10, the inlet side gas chamber 7 is provided at a predetermined distance from the inlet side end plate 9 to the gas inlet side, and the cooling pipe 10 is connected to the inlet side end plate 9 and the inlet side gas chamber 7. And a coolant chamber, that is, the inlet water chamber 2, between the inlet end plate 9 and the inlet gas chamber 7.
1 is provided. The inlet-side water chamber 21 is provided for the purpose of water-cooling a portion on the gas inlet side from the inlet-side end plate 9, and is partitioned by the main water chamber 8 and the inlet-side end plate 9 in the casing 2. 7 and an inlet end plate 22. In the main water chamber 8, the cooling water inlet 1 is located near the outlet side end plate 23.
1 is a cooling water outlet 2 near the inlet side end plate 9.
4 are opened at the lower part and the upper part, respectively. on the other hand,
An inlet-side cooling water inlet 25 and an inlet-side cooling water outlet 26 are also opened in the lower and upper portions of the inlet-side water chamber 21, respectively. The cooling pipe 10 is inserted through and fixed to the inlet-side end plate 9 and the inlet-end end plate 22, and has an inlet end 10b.
Are flush with the surface 22 a of the inlet end plate 22. The inlet side water chamber 21 has a relatively short chamber length, and has an inlet side cooling water inlet 25 and an inlet side cooling water outlet 2.
6 allows the cooling water to be introduced and discharged linearly.

According to this configuration, the vicinity of the inlet end plate 22 at which the temperature becomes high can be efficiently cooled in the inlet-side water chamber 21 where the introduction and discharge (metabolism) of the cooling water is active. Thereby, boiling near the inlet side end plate 9 in the water chamber 8 can be prevented. The cooling water may be branched and introduced into the inlet-side water chamber 21 and the main water chamber 8, and may be collected and led out. Also in this case, the separation distance E can be made sufficiently large.

Here, when the high temperature and high flow rate EGR gas is introduced, even if boiling occurs in the inlet side water chamber 21, bubbles are immediately drawn out and diffusion of the bubbles into the main water chamber 8. Because it is completely prevented, heat transfer degradation is minimized. In addition, even if the dissolved matter adheres to the surface of the cooling pipe 10 due to boiling and the amount of heat radiation is reduced, the specifications of the cooler may be determined in advance in consideration of the amount of heat radiation. Further, when there is a concern about corrosion or the like due to frequent boiling, the cooling pipe 10 in the inlet-side water chamber 21 may be made thick or a double pipe. In the latter case, care must be taken when brazing to ensure that the intermediate gap is filled. Here, the inlet-side water chamber 21 into which the cooling water flows is set as the cooling liquid chamber.
Instead, another cooling liquid chamber into which lubricating oil or light oil having a higher boiling point than water flows can be used.

FIG. 11 shows a general EGR cooler 81 employing a so-called two-pass system. The EGR cooler 81 has a gas inlet 82 and a gas outlet 83 at one end in the longitudinal direction on the lower side and the upper side, so that the EGR gas is U-turned in the longitudinal direction, and the EGR cooler 81 communicates with the internal cooling water. A heat exchange is performed between them. The inside of the casing 84 is partitioned by a pair of end plates 85 and 86 and a partition 95, whereby the inlet gas chamber 87, the water chamber 88, and the reverse gas chamber 89 are provided.
And an outlet-side gas chamber 90 is defined. A plurality of cooling pipes 91 are bridged between the end plates 85 and 86, and the lower one of the cooling pipes 91 serves as a gas flow path toward the reversal gas chamber 89, and the upper one serves as a gas flow path toward the outlet gas chamber 90. Used as a road. A lower portion of the one end-side end plate 85 that divides the inlet-side gas chamber 87 forms an inlet-side end plate 92. A cooling water inlet 93 is provided near the end plate 85 on one end, and the end plate 8 is provided on the other end.
In the vicinity of 6, cooling water outlets 94 are respectively opened.

In the case of the two-pass cooler, there is a problem that the partition wall 95 is heated by the high-temperature gas in the inlet-side gas chamber 87 and the low-temperature gas in the outlet-side gas chamber 90 is heated. In this case, the end plate 85 at one end is also heated by the high-temperature gas, and is heated when the low-temperature gas approaches the end plate 85.

In order to solve this problem, as shown in FIG. 12, the above problem can be solved by applying the same structure as that of FIG. 4 to the cooler inlet side. That is, the lower cooling pipe 91 is connected to the end plate 85 at one end (the inlet end plate 92).
From the gas to the gas inlet side to be cooled by air, so that the temperature of the end plate 85 can be lowered and the end plate 85 can be cooled.
Can suppress the heating of the low-temperature gas. Further, since the inlet side gas chamber 87 and the outlet side gas chamber 90 are separated by separate tank casings 96 and 97 separated from each other, the heating of the low temperature gas in the outlet side gas chamber 90 by the high temperature gas in the inlet side gas chamber 87 is prevented. it can. Here, as shown in FIG. 13, it is naturally possible to apply the configuration shown in FIG. 3 to the cooling pipe 91 on the inlet side.

The present invention may have various other embodiments, and the above embodiments can be appropriately combined.

[0048]

The present invention exhibits the following excellent effects.

(1) Boiling of cooling water near the inlet-side end plate can be prevented, and cooling performance can be improved.

(2) Use restrictions on coolers due to increases in gas temperature and gas flow rate are suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a main part of an EGR cooler according to the present invention.

FIG. 2 is a longitudinal sectional side view showing a modification of the EGR cooler.

FIG. 3 is a longitudinal sectional side view showing a modification of the EGR cooler.

FIG. 4 is a longitudinal sectional side view showing a modification of the EGR cooler.

FIG. 5 is a side view showing a modification of the EGR cooler.

FIG. 6 is a side view showing a modification of the EGR cooler.

FIG. 7 is a side view showing a modification of the EGR cooler.

FIG. 8 is a side view showing a modification of the EGR cooler.

FIG. 9 is an enlarged vertical sectional side view showing a modification of the EGR cooler.

FIG. 10 is a longitudinal sectional side view showing a modification of the EGR cooler.

FIG. 11 is a longitudinal sectional side view showing a modification of the EGR cooler.

FIG. 12 is a vertical sectional side view showing a modification of the EGR cooler.

FIG. 13 is an enlarged vertical sectional side view showing a modification of the EGR cooler.

FIG. 14 is a configuration diagram of an engine to which an EGR cooler is applied.

FIG. 15 is a vertical sectional side view showing a conventional EGR cooler.

FIG. 16 is a sectional view taken along line XX of FIG. 15;

17A and 17B show a conventional EGR cooler, wherein FIG. 17A is a schematic side view (cooling tube omitted), and FIG. 17B is a sectional view taken along line YY of FIG.

FIG. 18 is a schematic side view showing a steam passage in a conventional EGR cooler.

FIG. 19 is a schematic side view showing a steam region in a conventional EGR cooler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 EGR cooler 7,87 Inlet side gas chamber 8 Water chamber 9,92 Inlet side end plate 9a End face 10,91 Cooling tube 10a Inlet side end 10b Inlet end 10c Exposed part 10d Projection part 13 Heat transfer plate 16,17 Radiation fin 18 protection cylinder 20 slit 21 inlet side water chamber E separation distance L turbulence section T thickness

Claims (10)

[Claims] 1. A plurality of cooling pipes are inserted into and fixed to an end plate on the EGR gas inlet side, and the end face of the end plate on the water chamber side and the inlet end of the cooling pipe are longer than the length of the turbulent flow section. An EGR cooler characterized by being separated from the EGR cooler. 2. The EGR cooler according to claim 1, wherein said end plate has a thickness equal to or greater than said length. 3. The EGR cooler according to claim 1, wherein the end plate has a slit for exposing the cooling pipe to the outside. 4. The EGR cooler according to claim 1, wherein the cooling pipe projects from the end plate toward a gas inlet. 5. The EGR cooler according to claim 4, wherein the inlet end of the cooling pipe is expanded in a funnel shape. 6. The EGR cooler according to claim 4, wherein the projecting portion of the cooling pipe is connected by a heat transfer plate. 7. A gas chamber is provided at a predetermined distance from the end plate on the gas inlet side, and the cooling pipe connects the end plate and the gas chamber and is exposed to the outside between them. EG according to any one of 1 to 6
R cooler. 8. The EGR cooler according to claim 1, wherein a radiation fin is provided on an exposed portion of the cooling pipe. 9. The EGR cooler according to claim 1, wherein an exposed portion of the cooling pipe is covered with a protective tube. 10. A gas chamber is provided at a predetermined distance from the end plate to a gas inlet side, and the cooling pipe connects the end plate and the gas chamber, and a gas pipe is provided between the end plate and the gas chamber. The EGR cooler according to any one of claims 1 to 6, wherein a coolant chamber is provided in the EGR cooler.