JPH11303688A - EGR cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance heat radiation in EGR(exhaust gas recalculation) gas by partitioning the interior of a casing to define an inlet side gas chamber, an outlet side gas chamber, and a coolant chamber, by defining and forming intermediate gas chambers for partitioning the coolant chamber, and by separate ly connecting the inlet side gas chamber to the intermediate gas chambers, and the intermediate chambers to the outlet gas chamber through cooling tubes, respectively. SOLUTION: This EGR cooler 1 partitions the interior of a casing 2 to define an inlet side gas chamber 7, an outlet side gas chamber 19, and a coolant chamber 8. Intermediate gas chambers 20, 21 are defined and formed to partition the coolant chamber 8. In addition, connection is made to the inlet gas chamber 7 to the intermediate gas chambers 20, 21, and the intermediate gas chambers 20, 21 to the outlet gas chamber 19 through cooling tubes 29, 30, 31 respectively. Each coolant chamber 26, 27, 28 is provided with a cooling water inlet 12 and a cooling water outlet 10.

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. 7 is a configuration diagram of an engine to which an EGR cooler is applied. An EGR cooler 51 is an EG that forms an EGR passage.
The cooling water (cooling liquid) is circulated between the engine 53 and the engine 53 via a cooling water pipe 54, and the cooling water is used as a refrigerant to cool the EGR gas inside. . The EGR pipe 52 is connected to the exhaust manifold 5
A part of the exhaust gas (EGR gas) is extracted from an exhaust path including the exhaust pipe 5 and the exhaust pipe 56 and returned to an 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.
6. 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 flange 61 and the outlet flange 62 define a gas inlet 63 and a gas outlet 64, respectively, and are connected to the EGR pipe 52, respectively. 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 6
Reference numerals 5 and 66 are used to partition the inside of the casing 60 into an inlet-side gas chamber 67 at both ends, an outlet-side gas chamber 68, and a central water chamber 69 (coolant chamber). The water chamber 69 is provided with a cooling water inlet 70 and a cooling water outlet 71 spaced apart 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 partitions an intermediate gas chamber which divides the coolant chamber. At the same time, the inlet gas chamber and the intermediate gas chamber, and the intermediate gas chamber and the outlet gas chamber were separately connected by cooling pipes, and each cooling liquid chamber was provided with a cooling water inlet and a cooling water outlet. Things.

According to this, E is transferred from the intermediate gas chamber to the cooling pipe.
The GR gas can be re-introduced, the turbulence region can be increased, and heat radiation can be activated. In addition, since a new coolant is introduced into each coolant chamber, the gas can be cooled with relatively low-temperature cooling water in the entire region in the gas flow direction, and the heat radiation can be improved.

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 cooling water inlet and the cooling water outlet are provided in a direction orthogonal to the cooling pipe and on opposite sides of each other.

Preferably, the cooling pipes on the upstream and downstream sides in the gas flow direction are offset from each other.

It is preferable that a portion of the casing that defines the intermediate gas chamber is bent.

It is preferable that the casing is divided into portions that define an inlet gas chamber, an outlet gas chamber, a coolant chamber, and an intermediate gas chamber.

[0020]

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

FIGS. 1 and 2 show an EGR cooler according to this 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 includes an outer cylindrical portion 3 formed to have a predetermined constant diameter,
It is formed integrally with an inlet-side tank portion 4 and an outlet-side tank portion 13 squeezed hemispherically from the outer cylinder portion 3 toward a gas inlet side (left side in the figure) and an outlet side (right side in the figure). Flanges 5 and 14 for connecting to the aforementioned EGR pipe are provided at the inlet end of the inlet-side tank unit 4 and the outlet end of the outlet-side tank unit 13. Each of the flange portions 5 and 14 is provided with a gas inlet 15 and a gas outlet 16 and a pair of bolt holes (female screw holes) 17. The outer cylinder 3, the tanks 4, 13 and the flanges 5, 14 are coaxially arranged.

At the joint position between the outer cylindrical portion 3 and the tank portions 4 and 13, a pair of end plates that partition the inside of the casing 2 between an inlet side and an outlet side, that is, an inlet side end plate 9 and an outlet side end plate 18 are provided. 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 and 21 are defined in the water chamber 8, and these two intermediate gas chambers 20 and 21 are formed.
The water chamber 8 is divided into three by 21.

That is, four intermediate plates 22, 23, 24, 25 are provided between the end plates 9, 18, and the intermediate plates 22... First water chamber 26 in order from the upstream side,
A second water chamber 27 and a third water chamber 28 are defined, and the first intermediate gas chamber 20 and the second intermediate gas chamber 21 are interposed between the water chambers 26.
Are formed.

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. However, the length of each of the water chambers 26 is longer than the length of 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, and 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 ...
, And pass through the water chambers 26 along the longitudinal direction of the casing.

These cooling pipes 29 have the same diameter.
As shown in FIG. 2, they are arranged in a zigzag pattern so as to spread throughout the casing 2. The first to third cooling pipes 29 are linearly coaxially arranged along the longitudinal direction of the casing.

On the other hand, a cooling water inlet 12 is provided at a lower portion of each of the water chambers 26, and a cooling water outlet 10 is provided at an upper portion. That is, the inlet 12 and the outlet 10 are provided in a direction orthogonal to the cooling pipes 29 and on opposite sides of each other. As a result, the cooling water is introduced from the cooling water inlet 12 and comes out of the cooling water outlet 10 while hitting the cooling pipes 29 in an orthogonal or vertical direction. The cooling water pipe (see FIG. 7) connected to the inlet 12 and the outlet 10 is branched into three branches.

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 and diffusion into the second intermediate gas chamber 21, the third introduction into the third water chamber 28, and the cooling, the outlet side After being discharged and diffused into the gas chamber 19, the gas is discharged from the gas outlet 16.

As described above, in the present cooler, the intermediate gas chamber is provided and the gas is introduced into the cooling pipe again.
The turbulence region can be increased by increasing the number of places where the cross section changes, and the heat radiation from the gas can be 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, the number of gas introductions to the cooling pipe increases, and the turbulent flow region can be further expanded.

Since each of the intermediate plates 22 contacts the cooling water and is cooled, the gas can be cooled also in each of the intermediate gas chambers 20.

Since the cooling water inlets 12 and the cooling water outlets 10 are individually provided in the respective water chambers 26, the gas can be cooled by the new relatively low-temperature cooling water in the entire region in the gas flow direction. Heat dissipation can be improved.

That is, in general, in the EGR cooler, when the temperature of the gas is high and the flow rate is high, the cooling water tends to boil in the vicinity of the end plate on the inlet side, and the heat transfer tends to deteriorate. Therefore, in the related art (see FIG. 4), a cooling water inlet 70 is provided near the inlet side end plate 65, and the vicinity of the inlet is actively cooled with new cooling water that comes out of the cooling water inlet 70. However, since the cooling water that has already been used for heat exchange and has been heated also cools the downstream side, there is a problem that the heat radiation on the gas downstream side is not very good.

In the present invention, good cooling performance can be obtained because new cooling water is used also on the downstream side of the gas. In particular, since the inlet 12 and the outlet 10 are provided at the above-described positions, the cooling water can be strongly applied to the cooling pipes 29 from the orthogonal direction, thereby improving the cooling performance.

Here, in the present embodiment, the first to third cooling pipes 29 are arranged linearly and coaxially. For this reason,
The gas easily enters the cooling pipe on the downstream side from the cooling pipe on the upstream side in the gas flow direction, and the effect due to the change in cross section may be lost. For this reason, there is a method in which the outlet and the inlet of the cooling pipe are separated, that is, a method in which the distance between the intermediate plates 22 is increased or the length of the intermediate gas chamber 20 is increased to suppress the direct introduction of gas. The overall length becomes longer.

Therefore, as shown in FIG. 3, the cooling pipes on the upstream and downstream sides in the gas flow direction may be offset from each other (in the illustrated example, the first cooling pipe 29 is on the upstream side and the second cooling pipe 30 is on the downstream side). In other words, the cooling pipes on the upstream and downstream sides are not coaxial, but are arranged with their axes shifted from each other. This makes it difficult for the gas to directly enter the cooling pipe on the downstream side even when the outlet and the inlet of the cooling pipe are close to each other.As a result, the gas exiting from the cooling pipe on the upstream side is surely diffused, introduced again, and turbulent A flow region is formed. As a result, it is possible to reduce the overall length of the cooler without losing the effect due to the change in cross section.

FIG. 3 shows an example of offset in the circumferential direction. However, the present invention is not limited to this, and offset in a radial direction or even a random direction may be performed.

As can be understood 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, as described above, boiling of the cooling water is likely to occur near the inlet-side end plate 9. Therefore, in this case, the thickness of the cooling pipe (first cooling pipe 29) on the gas inlet side can be increased to limit heat radiation and prevent boiling before it occurs. Conversely, cooling pipes on the downstream side (second cooling pipe 30, third cooling pipe 31)
Can secure high heat dissipation by thinning. Thus E
Restrictions on the flow rate and temperature of the GR gas are relaxed, and good engine performance can be secured.

Next, another embodiment will be described.

In general, in an EGR cooler, when the length of the cooling pipe is increased, the amount of heat radiation increases, and preferable characteristics can be obtained. However, it is sometimes difficult to secure a long linear space on the layout.

Therefore, conventionally, a plurality of EGR coolers 51 are arranged in series with a bent EGR pipe 74 as shown in FIG. The illustrated example shows two EGR coolers 5
This is an example in which 1 are connected in the orthogonal direction.

However, in this case, since the gas flow is restricted on the way, the pressure loss increases, the number of parts increases, and the cost increases.

Therefore, as shown in FIG. 9, in the present embodiment, a portion 37 of the casing 35 that defines the intermediate gas chamber 36 is bent. By doing so, the EGR cooler can be formed in a bent shape without reducing the gas flow and without increasing the number of parts, thereby increasing the degree of freedom in layout. In particular, while maintaining the same external dimensions as the prior art, the length of the cooling pipe (length of the radiator portion) can be a longer L ₂ than the conventional L _1, attained a significant increase in heat dissipation. In this embodiment, only one intermediate gas chamber 36 is provided, and the partition 37 is bent at a right angle. However, these numbers and bending angles are arbitrary.

Next, FIGS. 10, 11, 12, and 13 show another embodiment. However, this embodiment is substantially the same as that shown in FIGS. 1 and 2, and therefore, the same portions will be described using the same reference numerals.

Here, the casing 2 is composed of the inlet gas chamber 7,
The outlet side gas chamber 19, each of the water chambers 26, 27, 28 and each of the intermediate gas chambers 20, 21 are divided.
That is, the above-described inlet-side tank portion 4, outlet-side tank portion 13, and outer cylinder portion 3 are not integrated but divided, and the outer cylinder portion 3 is further divided for each of the chambers 26 and assembled. I have.

As shown in FIG. 11, the inlet side tank 4 is provided integrally with a flange 38 for assembling the divided casings in addition to the flange 5 described above.
The flange portion 38 is provided with a plurality of bolt insertion holes 39 for inserting a long bolt 47 (see FIG. 10). The same configuration is also applied to the outlet-side tank section 13, whereby a common tank unit 40 is formed on the inlet side and the outlet side.

Each of the water chambers 26 is also formed by a common water chamber unit 41 as shown in FIG. For example, the first water chamber 26
In place of the inlet-side end plate 9 and the intermediate plate 22 of the above-described embodiment, relatively thick partition plates 42 are provided at both ends of the first water chamber outer cylindrical portion 43 that defines the first water chamber. The first cooling pipes 29 are inserted and fixed to these partition plates 42. The partition plate 42 also serves as a joining flange, and slightly protrudes radially outward of the first water chamber outer cylindrical portion 43. A cooling water inlet 12 and a cooling water inlet 10 are provided at an intermediate position in the longitudinal direction of the outer cylinder portion 43 for the first water chamber.

Similarly, the intermediate gas chambers 20 are formed by a common intermediate gas chamber unit 44 shown in FIG. For example, a flange plate 46 to be joined to the partition plate 42 is integrally provided at both ends of a first intermediate gas chamber outer cylinder portion 45 that partitions the first intermediate gas chamber 20.

As shown in FIG. 10, each unit 40, 4
If the flanges 38 on the inlet side and the outlet side are connected to each other with long bolts 47 and nuts 48, the flanges 38, the partition plate 42 and the flange plates 46 are strongly joined together, These are assembled together without leakage or gas leakage. It is optional to sandwich a gasket at each joint or to bolt each joint individually.

According to this configuration, the unit as described above can be configured by dividing the casing 2, and the following effects can be particularly obtained. That is, in this embodiment, the number of parts is increased as compared with the embodiment of FIGS. 1 and 2, and the cost is increased as a single product. However, the engine can be replaced in units of each engine to be applied. Can be lowered. That is, since only a part of the units needs to be changed according to the engine, the cost can be reduced by using common parts rather than making several types of coolers corresponding to several types of engines. In this embodiment, since the unit is shared for each gas chamber and water chamber even in a single product, the cost can be minimized.

As described above, the present invention is not limited to the above embodiments, and various embodiments are possible. For example, the number, shape, length, arrangement, etc. of the cooling pipes, intermediate gas chambers, water chambers and the like may be changed. It is also possible to add a baffle plate in the water chamber to meander the cooling water, or to use a liquid other than the engine cooling water as the cooling liquid.

[0054]

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

(1) The turbulent flow region of the EGR gas is increased to increase the amount of heat radiation, thereby improving the cooler cooling efficiency.

(2) Cooling with new cooling water can be performed over the entire area in the gas flow direction, and the heat radiation can be improved.

(3) The overall length of the cooler can be shortened.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an EGR cooler according to an embodiment of the present invention.

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

FIG. 3 is a sectional view taken along line AA of FIG. 1 according to another embodiment.

FIG. 4 is a longitudinal sectional view showing a conventional EGR cooler.

FIG. 5 is a right side view of FIG.

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

FIG. 7 is a configuration diagram of an engine to which an EGR cooler is applied.

FIG. 8 is a diagram showing an example in which conventional EGR coolers are connected in series.

FIG. 9 is a diagram showing another embodiment.

FIG. 10 is a diagram showing another embodiment.

FIG. 11 is a longitudinal sectional view showing a tank unit.

FIG. 12 is a longitudinal sectional view showing a water chamber unit.

FIG. 13 is a longitudinal sectional view showing an intermediate gas chamber unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 EGR cooler 2, 35 Casing 3 Outer cylinder part 4 Inlet side tank part 7 Inlet side gas chamber 8 Water chamber 9 Inlet side end plate 10 Cooling water outlet 12 Cooling water inlet 13 Outlet side tank part 18 Outlet side end plate 19 Outlet side gas chamber 20 First intermediate gas chamber 21 Second intermediate gas chamber 26 First water chamber 27 Second water chamber 28 Third water chamber 29 First cooling pipe 30 Second cooling pipe 31 Third cooling pipe 37 Part 43 First 1 outer cylinder for water chamber 45 outer cylinder for first intermediate gas chamber

Claims (6)

[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 that divides the cooling liquid chamber is formed, and the inlet gas chamber and the intermediate gas chamber, and the intermediate gas chamber and the outlet gas chamber are separately cooled. An EGR cooler, characterized in that a cooling water inlet and a cooling water outlet are provided in each of the cooling liquid chambers, each being connected by a pipe. 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 cooling water inlet and the cooling water outlet are provided on a direction orthogonal to the cooling pipe and on opposite sides of each other. 4. The EG according to claim 1, wherein the cooling pipes on the upstream and downstream sides in the gas flow direction are offset from each other.
R cooler. 5. The EGR cooler according to claim 1, wherein a portion of the casing that partitions the intermediate gas chamber is bent. 6. The EGR cooler according to claim 1, wherein the casing is divided into portions that define an inlet gas chamber, an outlet gas chamber, a coolant chamber, and an intermediate gas chamber.