JPH11287571A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat dissipating property of EGR gas. SOLUTION: An EGR cooler 1 is formed of an inlet port side gas chamber 7, an outlet port side gas chamber 19 and a cooling liquid chamber 8, which are defined by partitioning the inside of a casing 2, and intermediate gas chambers 20, 21 are formed in the cooling liquid chamber 8 by defining the same while the inlet port side gas chamber 7 communicates with the intermediate gas chambers 20, 21 and the outlet port side gas chamber 19 communicates with the intermediate gas chambers 20, 21 through cooling pipes 29, 30, 31 respectively. In this case, the cooling pipes 20, 30, 31 are penetrated through and fixed to respective plates 9,... while respective chambers communicate with each other.

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.
EG during gas recirculation)
The present invention relates to an EGR cooler for cooling R gas.

[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. 22 is a configuration diagram of an engine to which an EGR cooler is applied. An EGR cooler 51 has an EGR passage E
Provided in the middle of the GR pipe 52, circulates cooling water (cooling liquid) between the engine 53 and the engine 53 through a cooling water pipe 54,
The cooling water is used as a coolant to cool the EGR gas inside. The EGR pipe 52 extracts a part of the exhaust gas (EGR gas) from the exhaust path including the exhaust manifold 55 and the exhaust pipe 56 and returns it to the intake path including the intake manifold 57 and the intake pipe 58. In the middle of the EGR pipe 52, a flow control valve 5 for controlling the EGR amount is provided.
9 are provided.

The structure of a general EGR cooler is shown in FIGS.
0 and 21. The EGR cooler 51 has a cylindrical casing 60 extending in one direction and narrowed at both ends. An inlet flange 61 and an outlet flange 62 are integrally provided at both longitudinal ends of the casing 60. The inlet-side flange 61 and the outlet-side flange 62 define a gas inlet 63 and a gas outlet 64, respectively, to form the above-described E.
Each is connected to the GR pipe 52. A pair of end plates separated in the longitudinal direction (gas flow direction), that is, an inlet end plate 65 and an outlet end plate 66 are provided inside the casing 60. These end plates 65 and 66 partition the inside of the casing 60 into an inlet gas chamber 67 at both ends, an outlet gas chamber 68 and a central water chamber 69 (coolant chamber). In the water chamber 69,
A cooling water inlet 70 and a cooling water outlet 71 are provided apart from each other in the longitudinal direction. These are provided on the radially opposite side.

[0006] A plurality of straight tubular cooling pipes 72 are provided so as to bridge both end plates 65 and 66. The cooling pipe 72 is inserted and fixed to both end plates 65 and 66, communicates the inlet side and outlet side gas chambers 67 and 68, and passes through the water chamber 69 between the both end plates 65 and 66. .

The EGR gas introduced from the gas inlet 63 into the inlet gas chamber 67 in this manner is supplied to the inlet gas chamber 67.
Inside, it is diffused in the radial direction and distributed to each cooling pipe 72. Then, after passing through each cooling pipe 72, they are gathered again in the outlet side gas chamber 68 and are led out from the gas outlet 64. In particular, when passing through the water chamber 69, heat is exchanged with cooling water to be cooled.

The cooling pipe 72 is made as thin as possible (about 0.5 to 1 mm) in order to increase the cooling efficiency. Further, since the EGR gas contains sulfur at high temperature, a material such as stainless steel excellent in high-temperature strength and corrosion resistance is employed. Although this cooler is made by joining a plurality of parts, all parts are assembled at once by brazing in the furnace to simplify manufacturing. For this reason, parts other than the cooling pipe 72 are formed of the same material as the cooling pipe 72.

[0009]

Immediately after the EGR gas flows from the inlet side gas chamber 67 into the cooling pipe 72, the EGR gas is affected by a sudden change in cross-section, and becomes a turbulent flow in which the speed and direction are not constant. In this turbulent region, the cooling pipe 72
Active heat dissipation is performed.

On the other hand, after passing through the turbulent flow region, the gas flow becomes a laminar flow flowing in the axial direction of the cooling pipe 72. For this reason, the flow velocity of the gas is higher on the axial center side and is lower in the vicinity of the inner wall of the cooling pipe 72, so that heat is not actively radiated.

As a countermeasure, there are methods of increasing the heat radiation area by providing thin fins inside the cooling pipe 72 and providing irregularities inside the cooling pipe 72 to disturb the boundary layer of the laminar flow portion.
Soot contained in the GR gas adheres to the fins and the like, where E
Since sulfuric acid is formed by the sulfur content and water contained in the GR gas, a problem occurs in terms of durability.

Since the EGR gas flow rate (EGR rate) changes according to the engine operating conditions such as the engine speed and the engine load, and the EGR gas also pulsates due to the exhaust pulsation of each cylinder, the above-described disturbance is caused. The extent or length of the flow region is not constant.

[0013]

An EGR cooler according to the present invention partitions an inlet side gas chamber, an outlet side gas chamber, and a coolant chamber by partitioning the inside of a casing, and forms an intermediate gas chamber in the coolant chamber. And the inlet gas chamber and the intermediate gas chamber,
The intermediate gas chamber and the outlet gas chamber are connected by a cooling pipe.

According to this, the EGR gas introduced into the cooling pipe from the inlet gas chamber can be discharged to the intermediate gas chamber and introduced again into the cooling pipe. Therefore, the turbulence region can be increased, and the heat radiation can be activated.

Here, a plurality of the intermediate gas chambers are provided,
It is preferable that these intermediate gas chambers are connected by another cooling pipe.

Preferably, the intermediate gas chamber divides the cooling liquid chamber, and the divided cooling liquid chambers are connected to each other by a communication passage.

Preferably, the communication passage is formed by a communication pipe passing through the intermediate gas chamber, and the communication pipe extends in a direction crossing the cooling pipe.

Further, it is preferable that a guide means for flowing the cooling liquid in the cooling liquid chamber in a direction intersecting with the cooling pipe is provided.

[0019]

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

[First Embodiment] FIGS. 1, 2 and 3 show an EGR cooler according to a first embodiment. As in the related art, the EGR cooler 1 has a cylindrical casing 2 that is long in one direction (the left-right direction in the drawing). The casing 2 has an outer cylindrical portion 3 formed to have a predetermined constant diameter, and an inlet side narrowed hemispherically from the outer cylindrical portion 3 toward a gas inlet side (left side in the figure) and an outlet side (right side in the figure). It comprises a tank part 4 and an outlet side tank part 13. Inlet end of outlet side tank part 4 and outlet side tank part 13
Are provided with flange portions 5 and 14 for connection to the aforementioned EGR pipe. These flange parts 5, 1
4 has a gas inlet 15 and a gas outlet 16 and a pair of bolt holes (female screw holes) 17 respectively. These outer cylinder part 3, tank parts 4, 13 and flange parts 5, 14
Are arranged coaxially.

At the joint position between the outer cylindrical portion 3 and the tank portions 4 and 13, a pair of end plates partitioning the inside of the casing 2 between the inlet side and the outlet side, that is, the inlet side end plate 9 and the outlet side end plate 18, Is provided. Thus, in the casing 2, an inlet gas chamber 7 is provided on the left side of the inlet end plate 9, and a water chamber 8 (coolant chamber) for passing cooling water (coolant) between the end plates 9 and 18. But,
An outlet side gas chamber 19 is provided on the right side of the outlet side end plate 18.
Are respectively formed.

However, two intermediate gas chambers 20, 21 are formed in the water chamber 8, and these two intermediate gas chambers 20, 21 are formed.
The water chamber 8 is divided into three by 21.

That is, four intermediate plates 22, 23, 24, and 25 are provided between the end plates 9 and 18, and these intermediate plates 22 partition the inside of the outer cylinder portion 3 so that the upstream side in the gas flow direction. A first water chamber 26, a second water chamber 27, and a third water chamber 28 are formed in this order from
, A first intermediate gas chamber 20 and a second intermediate gas chamber 21 are defined between them.

As described above, in the present cooler 1, the gas chamber and the water chamber are provided alternately in series along the gas flow direction.

Each end plate 9 and the intermediate plate 2
Are arranged perpendicular to the longitudinal direction of the casing. Each of the water chambers 26 or each of the intermediate gas chambers 20 has the same length in the casing longitudinal direction. Further, each of the water chambers 26 is made longer than each of the intermediate gas chambers 20 to secure a heat radiation area.

The inlet-side gas chamber 7 and the first intermediate gas chamber 20, the first intermediate gas chamber 20 and the second intermediate gas chamber 21, the second intermediate gas chamber 21 and the outlet-side gas chamber 19 are plural and equal in number, respectively. First cooling pipe 29, second cooling pipe 30, third cooling pipe 31
Has been contacted. These cooling pipes 29 ...
... are fixed to each other so as to communicate with each other.

Similarly, the first water chamber 26 and the second water chamber 27 are connected to each other, and the second water chamber 27 and the third water chamber 28 are connected to each other by a first communication pipe 32 and a second communication pipe 33 forming communication paths. Are communicated with each other. The first connecting pipe 32 passes through the first intermediate gas chamber 20, and the second connecting pipe 33 passes through the second intermediate gas chamber 21. These connecting pipes 32 are straight pipes, and each cooling pipe 2
9 ... are extended in the same direction. A cooling water inlet 12 is provided at a lower part of the first water chamber 26, and a cooling water outlet 1 is provided at an upper part of the third water chamber 28.
0 is provided. As a result, the cooling water introduced from the cooling water inlet 12 into the first water chamber 26 flows through the first connecting pipe 32, the second water chamber 27, the second connecting pipe 33, and the third water chamber 28 in this order. It is derived from the outlet 10.

The cooling pipes 29 and the communication pipes 32 are:
As shown in FIG. 3, they have the same diameter as each other, and are staggered so as to spread over the entire casing 2 together. However, as shown by hatching in the figure, the first and second communication pipes 32 and 33 are provided only at the outermost periphery at intervals of 120 °, and as shown in FIG. 29 ... has been removed. The reason why the number of the connecting pipes 32 is small and the total cross-sectional area of the connecting pipes 32 is smaller than the total cross-sectional area of the cooling pipes 29 is that the volume flow rate of the cooling water is smaller than the volume flow rate of the EGR gas. Because. First to third
The cooling pipes 29 or the first and second communication pipes 32 are linearly arranged along the longitudinal direction of the casing.

Now, in this configuration, the gas inlet 1
After the EGR gas introduced from 5 diffuses in the inlet side gas chamber 7 and is distributed and introduced into each first cooling pipe 29,
It flows through the cooling pipe 29. Then, first cooling is performed when passing through the first water chamber 26, and thereafter, the first intermediate gas chamber 2
It is released and diffused within zero. And after being assembled here,
Further, it is distributed and introduced into the next second cooling pipes 30. Next, similarly, the second cooling in the second water chamber 27, the discharge into the second intermediate gas chamber 21, the third cooling in the third water chamber 28,
After passing through the process of discharge to the outlet side gas chamber 19, the gas is drawn out from the gas outlet 16.

As described above, in the present cooler, the intermediate gas chamber is provided, and the gas distribution and introduction to the cooling pipe are performed again.
Heat radiation from the gas is activated, and the cooling efficiency of the cooler can be improved. In particular, in the present embodiment, since a plurality of intermediate gas chambers are provided, gas can be introduced into the cooling pipe a plurality of times, and the cooling efficiency can be further improved.

Further, the intermediate plates 22 and the connecting pipes 32 are provided.
Is cooled by contact with the cooling water.
The gas can be cooled in the inside of.

Here, in order to make the figure easy to understand,
The communication pipes 32 are added without changing the dimensions of the casing and the arrangement of the cooling pipes, and the number of cooling pipes is reduced by the corresponding amount (FIGS. 19 to 2).
1) and the gas passage area is also reduced. However, when problems such as a pressure loss and an increase in the amount of heat radiation occur, this can be dealt with by reviewing the number and diameter of the cooling pipes. However, if this does not solve the problem, it is necessary to take measures such as enlarging the casing and increasing the number of cooling pipes.

[Second Embodiment] FIGS. 4, 5, 6, and 7 show a second embodiment.
1 shows an EGR cooler according to an embodiment. The same applies to the embodiments described below, but the description of the same components will be omitted. This embodiment is different from the first embodiment in that each cooling pipe 29 ...
And the arrangement of the communication tubes 32 are different.

That is, as shown in FIG. 1, in the first embodiment, since the first and second communication pipes 32 and 33 are linearly arranged, the axial direction of the cooling water in the second water chamber 27 is increased. There is a possibility that the components become strong and the contact with each second cooling pipe 30 becomes weak. Also, since one of the second connecting pipes 33 opens near the cooling water outlet 10, the third water chamber 28 also has a third
The contact with the cooling pipe 31 may be weakened.

In the present embodiment, as shown in FIGS. 4, 6 and 7, the first and second connecting pipes 32 and 33 are arranged so as to be opposite to each other as a whole while having the same number. That is, three first communication pipes 32 are arranged in parallel in the upper and outermost periphery in the casing 2, and three second communication pipes 33 are arranged in parallel in the lower and outermost periphery in the casing 2. As a result, the connecting pipes 32 and the cooling water inlets 12 and the cooling water outlets 10 are alternately arranged on the opposite sides, respectively. In each of the water chambers 26. 29, so that the cooling water can be sufficiently applied to the cooling pipes 29. Thereby, the heat radiation of the gas can be further activated, and the cooling efficiency can be improved.

However, in the present embodiment, as shown in FIG. 5, the cooling pipes 29 where the first and second communication pipes 32 and 33 are located are removed, and the number of the cooling pipes 29 is further reduced. ing. As a result, the gas passage area is reduced, and problems such as pressure loss may be promoted.

Therefore, the third embodiment described below can solve this problem.

[Third Embodiment] A third embodiment shown in FIGS. 8, 9, 10 and 11 is configured as follows. That is, the cooling water inlet 12 and the cooling water outlet 10 are respectively provided above the first water chamber 26 and the third water chamber 28, and the first and second communication pipes 32 and 33 are respectively provided only in the lower part of the casing 2. Are arranged in parallel. These connecting pipes 3
The first inside the casing 2 except for the positions where
The third cooling pipes 29, 30, 31 are arranged in a staggered manner. Then, an intermediate plate 34 is added in the second water chamber 27.
The intermediate plate 34 is disposed so as to partition the second water chamber 27 at an intermediate position in the axial direction of the casing. An opening 35 is provided at an upper portion of the intermediate plate 34 so as to allow the cooling water to flow therethrough. The opening 35 is formed by cutting a part of the intermediate plate 34 straight, but may be formed by another method, for example, by drilling a hole.

According to this, the same number of cooling pipes 29 as in the first embodiment is ensured, and the problem of reducing the gas passage area can be prevented. The cooling water flowing out of the first connecting pipe 32 can be meandered in the direction orthogonal to the second cooling pipe 30 without being directly directed to the second connecting pipe 33 by the intermediate plate 34. We can pour water enough. Of course, in the first water chamber 26 and the third water chamber 28 as well, the inlet and outlet of the cooling water are formed on opposite sides, and the cooling pipes 29,
The flow can be orthogonal to 31. If an intermediate plate is provided in the first water chamber 26 or the third water chamber 28, the cooling water inlet 1
The position or direction of the outlet 2 or the outlet 10 can be changed, and these directions can be made different directions.

However, this embodiment has a disadvantage that the number of intermediate plates increases and the number of parts increases.

[Fourth Embodiment] FIGS. 12, 13, 14, 1
As shown in FIG. 5, in this embodiment, the second embodiment (FIG.
7) Similarly, the first to third cooling pipes 29 are arranged, and each of the water chambers 26 has three empty spaces in the upper part and the lower part. Therefore, three crank-shaped first and second connecting pipes 32 and 33 are provided so as to connect the upper empty space on the upstream side to the empty space on the lower downstream side.

In this embodiment, the first and second connecting pipes 32 and 33 extend in the first and second intermediate gas chambers 20 and 21 in a direction orthogonal to the gas flow direction. Therefore, heat radiation from the gas in these gas chambers 20 and 21 is promoted,
Cooling performance is improved.

Since the number of components is the same as that of the second embodiment, there is no increase in the number of components compared to the second embodiment. However, when the first and second connecting pipes 32 and 33 are formed, bending of the pipes and the like are required, and the assembling of the pipes is not easy, so that an increase in manufacturing cost is inevitable. Further, since the number of cooling pipes 29 is smaller than in the conventional case, problems such as pressure loss cannot be solved.

[Fifth Embodiment] As shown in FIGS. 16, 17, and 18, in this embodiment, unlike the previous embodiment, the inside of the casing 2 is not completely partitioned by the intermediate plates 22. That is, in the water chamber 8, a cooling water inlet 12 is provided at a lower portion on the gas inlet side, and a cooling water outlet 10 is provided at an upper portion on the gas outlet side. As a result, the cooling water flows as the main flow in the same direction as the gas flow direction.
The four intermediate plates 22, 23, and 2 partition the inside of the water chamber 8 from the upstream side to the downstream side in the cooling water flow direction.
4 and 25 are provided, the former two sheets and the latter two sheets are connected by cylindrical plates 36 and 37, respectively, and the first intermediate gas chamber 20 and the second intermediate gas chamber 21 are defined by these plates. .

Intermediate plate 2 forming each gas chamber 20, 21
Of the two, the upstream one has an opening 38 at the top, and the downstream one has an opening 39 at the bottom. These openings 38 and 39 are formed by linearly cutting a part of each plate. Except for the openings 38 and 39, the intermediate plates 22 are fixed to the inner wall of the casing to partition the inside of the casing. On the other hand, the cylindrical plates 36 and 37 are
As shown in FIGS. 7 and 18 (only 37 is shown), it is formed in a cylindrical shape and has an outer diameter equal to the distance between the linear cut edges of the adjacent intermediate plates 22. As a result, first and second communication passages 40 and 41 are formed around the entire circumference of the cylindrical plates 36 and 37 in place of the communication pipes 32. The water chamber 8 is divided into a first water chamber 26, a second water chamber 27, and a third water chamber 28 by the intermediate gas chambers 20.
The water chamber 26 and the second water chamber 27 are communicated or communicated by the first communication passage 40, and the second water chamber 27 and the third water chamber 28 are communicated or communicated by the second communication passage 41.

In this configuration, the same number of cooling pipes 29, 30, and 31 as in the conventional case (see FIGS. 19 to 21) can be provided within a range radially inside the cylindrical plates 36 and 37. Therefore, although the casing outer diameter is slightly increased, the gas passage area does not need to be reduced, and problems such as pressure loss do not occur.

The flow of the cooling water from the first water chamber 26 to the second water chamber 27 (from the second water chamber 27 to the third water chamber 28) is as follows.
The flow enters the first communication passage 40 (the second communication passage 41) from the upper opening 38 and exits from the lower opening 39. Since the cooling water enters the first water chamber 27 from the lower cooling water inlet 12 and the second water chamber 28, the cooling water exits from the upper cooling water outlet 10, so that each of the water chambers 26. Is a flow from the bottom to the top, that is, a flow orthogonal to each cooling pipe 29. Thereby, heat radiation from the gas is promoted, and the cooler cooling efficiency can be improved.

As can be seen from the above description, according to the present invention, the turbulence region of the EGR gas is increased to increase the heat radiation amount,
Cooler cooling efficiency can be improved. The EGR gas temperature can be reduced to achieve NOx reduction due to a decrease in intake air temperature, and the amount of fresh air can be increased by the volume reduction of the EGR gas to reduce smoke.

Further, since the present invention has a shape in which the cooling pipe is divided in the longitudinal direction, preferable characteristics are given to each of them, and it is possible to greatly contribute to improvement of heat radiation. For example, when the inflow gas has a high temperature and a high flow rate in the vicinity of the inlet-side end plate 9, the cooling water may boil and the heat transfer may be deteriorated. Therefore, in this case, the cooling pipe on the gas inlet side can be made thicker to limit heat radiation and prevent boiling before it occurs. Conversely, the cooling pipe on the downstream side can secure high heat dissipation by reducing the thickness. In this way, the restrictions on the flow rate and temperature of the EGR gas are relaxed, and good engine performance can be secured.

In the above embodiment, the inlet end plate 9, the outlet end plate 18, the intermediate plates 2
2, ... cooling water inlet 12 and outlet 10, connecting pipe 32 ...
And the openings 35 constitute the guide means of the present invention.

The present invention is not limited to the above embodiment, and various embodiments are possible. For example, the number, length, arrangement, and the like of the intermediate gas chambers and water chambers may be changed, and the intersection angle between the cooling water flow direction and the cooling pipe may be other than 90 ° (orthogonal). The same can be said for the relationship between the communication pipe and the cooling pipe. It is also possible to add a baffle plate in the water chamber to further meander the cooling water, or to use a liquid other than the engine cooling water as the cooling liquid.

[0052]

In summary, according to the present invention, the following excellent effects are exhibited.

(1) The turbulence region of the EGR gas is increased to increase the amount of heat radiation, and the cooler cooling efficiency can be improved.

(2) The gas can be suitably cooled even in the intermediate gas chamber, and the amount of heat radiation can be increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an EGR cooler according to a first embodiment.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a longitudinal sectional view of an EGR cooler according to a second embodiment.

FIG. 5 is a sectional view taken along line CC of FIG. 4;

FIG. 6 is a sectional view taken along line DD of FIG. 4;

FIG. 7 is a sectional view taken along the line EE of FIG. 4;

FIG. 8 is a longitudinal sectional view of an EGR cooler according to a third embodiment.

FIG. 9 is a sectional view taken along line FF of FIG. 8;

FIG. 10 is a sectional view taken along line GG of FIG. 8;

FIG. 11 is a sectional view taken along the line HH in FIG. 8;

FIG. 12 is a longitudinal sectional view of an EGR cooler according to a fourth embodiment.

FIG. 13 is a sectional view taken along the line II of FIG. 12;

FIG. 14 is a sectional view taken along the line JJ of FIG. 12;

FIG. 15 is a sectional view taken along line KK of FIG.

FIG. 16 is a longitudinal sectional view of an EGR cooler according to a fifth embodiment.

FIG. 17 is a sectional view taken along line LL of FIG. 16;

FIG. 18 is a sectional view taken along line MM of FIG. 16;

FIG. 19 is a longitudinal sectional view showing a conventional EGR cooler.

FIG. 20 is a right side view of FIG. 19;

21 is a sectional view taken along line XX of FIG.

FIG. 22 is a configuration diagram of an engine to which an EGR cooler is applied.

[Explanation of symbols]

 Reference Signs List 1 EGR cooler 2 Casing 7 Inlet gas chamber 8 Water chamber 9 Inlet end plate 10 Cooling water outlet 12 Cooling water inlet 18 Outlet end plate 19 Outlet gas chamber 20 First intermediate gas chamber 21 Second intermediate gas chamber 22, 23, 24, 25 Intermediate plate 26 First water chamber 27 Second water chamber 28 Third water chamber 29 First cooling pipe 30 Second cooling pipe 31 Third cooling pipe 32 First connecting pipe 33 Second connecting pipe 35 , 38, 39 Opening 36, 37 Tubular plate 40 First communication passage 41 Second communication passage

Claims (5)

[Claims] 1. An inlet-side gas chamber which partitions the inside of a casing,
An outlet gas chamber and a cooling liquid chamber are defined, and an intermediate gas chamber is formed in the cooling liquid chamber, and the inlet gas chamber and the intermediate gas chamber, and the intermediate gas chamber and the outlet gas chamber are connected by cooling pipes. An EGR cooler, characterized in that: 2. The EGR cooler according to claim 1, wherein a plurality of the intermediate gas chambers are provided, and the intermediate gas chambers are connected to each other by another cooling pipe. 3. The EGR cooler according to claim 1, wherein the intermediate gas chamber divides the cooling liquid chamber, and the divided cooling liquid chambers are connected to each other by a communication passage. 4. The EGR cooler according to claim 3, wherein the communication passage is formed by a communication pipe passing through the intermediate gas chamber, and the communication pipe extends in a direction crossing the cooling pipe. 5. The EGR cooler according to claim 1, further comprising guide means for flowing the coolant in the coolant chamber in a direction intersecting with the cooling pipe.