JP2001182627A - Egr gas cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR gas cooling system which prevents degradation of its cooling performance by reducing accumulation quantity of condensed water generated by cooling EGR gas. SOLUTION: This EGR gas cooling system comprises an upstream EGR gas chamber, a downstream EGR gas chamber, multiple heat-transfer tubes which connect the internal space of both EGR gas chambers and in which EGR gas flows, and cooling water passage formed around the heat-transfer tubes. The EGR gas chambers are so formed that the maximum level of condensed water which may accumulate in the EGR gas chambers is flush with the lowest point of the peripheral edge inside the water-surface side opening end of the heat-transfer tube located vertically lowest among all the heat transfer tubes, or the maximum level of condensed water which may accumulate in the EGR gas chambers is located vertically below the lowest point of the peripheral edge inside the water-surface side opening end of the heat-transfer tube located vertically lowest among all the heat transfer tubes when the EGR gas cooling system is mounted on a vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR gas cooling device for cooling EGR gas of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in a diesel engine or the like, in order to reduce nitrogen oxides (NOx) generated during combustion, a part of exhaust gas is taken out of an exhaust system and returned to an intake system by EGR (Exhaust Gas Reci.).
2. Description of the Related Art Devices for recirculation are known. Since nitrogen oxides are produced by the reaction of oxygen and nitrogen in the gas under high-temperature combustion gas, this EGR device lowers the combustion temperature by returning the exhaust gas to the intake system to reduce the nitrogen oxidation. It is to reduce the generation of products. In this EGR device, E is recirculated to the intake side.
If the temperature of the GR gas is too high, the volume of the EGR gas increases, the proportion of the new intake air amount decreases, and the intake air temperature does not decrease, so that the suppression of the generation of nitrogen oxides is not promoted and the fuel efficiency deteriorates. , EGR gas needs to be cooled.

Therefore, in recent years, in order to cool the EGR gas, an engine connecting an intake passage and an exhaust passage of an engine has been developed.
An EGR device in which an EGR gas cooling device is installed in a GR passage is provided. Generally, a multi-tube EGR gas cooling device is used as the EGR gas cooling device. FIG.
Shows an example of a conventional multi-tube type EGR gas cooling device, in which a cooling medium is supplied through a cooling medium inlet 76a and a cooling medium outlet 76b provided on the side surface of the cylindrical heat exchange unit 70. A plurality of heat transfer tube groups 74 are provided so as to allow the flow to flow, and the ends of the heat transfer tubes 70 are fixed to partition walls 72a and 72b closing both ends of the cylindrical heat exchange section 70, respectively. Here, considering the pressure loss of the EGR gas,
It is desirable that the sum of the cross-sectional area of the inner circumference of the EGR pipe 4 and the cross-sectional area of the inner circumference of each heat transfer tube 74 be at least equal, and that a space through which the cooling medium flows is provided inside the cylindrical heat exchange unit 70. Since it is necessary to secure the cross-sectional area, the cross-sectional area of the cylindrical heat exchange unit 70 is necessarily larger than the cross-sectional area of the EGR pipe 4. Further, in order to allow a large amount of cooling medium to flow into the heat exchange unit 70 in order to improve the cooling efficiency, it is necessary to ensure a sufficient space for the cooling medium to flow in the heat exchange unit 70. The cross-sectional area of the replacement unit 70 is larger than the cross-sectional area of the EGR pipe 4. Therefore, in order to distribute and introduce the EGR gas into the heat transfer tube 74 in the tubular heat exchange unit 70, and to collect and discharge the EGR gas inside the heat transfer tube 74 to the EGR pipe 4, Bonnet members 80a, 80b are fixed to the outside of the partition walls 72a, 72b at both ends of the heat exchange section 70. The inner peripheral surfaces of the bonnet members 80a and 80b are enlarged toward both ends of the heat exchange unit 70, and the EGR pipe 4 and the heat exchange unit 7
0 are connected to both ends. And the partition wall 72
a and the bonnet member 80a and the upstream EGR gas chamber 90.
a, and the downstream EGR gas chamber 90b is formed by the partition wall 72b and the bonnet member 80b. Therefore, the EGR gas introduced into the tubular heat exchange unit 70 via the upstream EGR gas chamber 90a is supplied to the plurality of heat transfer tubes 74.
After being cooled by a cooling medium surrounding the periphery thereof, and then discharged to the EGR pipe 4 via the downstream EGR gas chamber 90b (see JP-A-10-318050 and JP-A-9-89491). ).

[0004]

Incidentally, since the EGR gas contains a large amount of water, condensed water is generated when the EGR gas is cooled. In particular, when the temperature of the cooling medium is low and the EGR gas cooling device itself is cold, such as in winter or immediately after the start of the engine, the temperature difference between the EGR gas and the cooling medium is large. A large amount of condensed water is generated. And EG is added to this condensed water.
The sulfur component contained in the R gas is dissolved to generate sulfuric acid. In the conventional multi-pipe EGR gas cooling device as described above, the upstream EGR gas chamber 90a, the downstream EGR gas chamber 9
0b, the partition walls 72a and 72b and the bonnet member 80
a, a concave space C is formed with the inner peripheral surface of 80b,
The condensed water 10 containing sulfuric acid is stored in the concave space C. Condensed water 10 accumulated in this concave space C
Although the EGR gas evaporates to a certain extent as the temperature of the EGR gas increases, the entire amount of the EGR gas remains in the concave space C without being completely evaporated.

When a large amount of the condensed water 10 generated by cooling the EGR gas accumulates in the concave space C in the EGR gas chamber, the EGR gas cooling device itself has its axis inclined with respect to the horizontal direction. When the heat exchanger is mounted on a vehicle, the opening end of the heat transfer tube 74 is blocked by the condensed water 10 so that the flow of the EGR gas in the heat exchange unit 70 is obstructed, and the cooling of the EGR gas cooling device is performed. There is a problem that the performance is reduced.

The present invention has been made in view of the above-mentioned problems, and reduces the amount of condensed water generated by cooling EGR gas to prevent the deterioration of cooling performance.
An object of the present invention is to provide a GR gas cooling device.

[0007]

In order to solve the above problems, an EGR gas cooling device according to the present invention is provided in an EGR gas passage for extracting a part of exhaust gas from an exhaust system of an internal combustion engine and recirculating the exhaust gas to an intake system. An EGR gas cooling device provided at the upstream includes an upstream EG communicating with the upstream side of the EGR gas passage.
An R gas chamber, a downstream EGR gas chamber communicating with a downstream side of the EGR gas passage, an internal space of the upstream EGR gas chamber, and an internal space of the downstream EGR gas chamber, and an EGR gas inside. And a cooling medium passage formed around the heat transfer tube between the upstream EGR gas chamber and the downstream EGR gas chamber, wherein the upstream EGR gas At least one of the chamber and the downstream EGR gas chamber is the EGR gas chamber.
When the gas cooling device is mounted on a vehicle, the EG
Whether the water surface of the maximum amount of condensed water that can accumulate in the R gas chamber coincides with the lowest point of the inner peripheral edge of the opening end on the water surface side of the heat transfer tube located at the lowest position among the heat transfer tubes,
Alternatively, it is characterized in that the water surface is formed so as to be separated vertically below the lowermost point.

[0008]

According to the EGR gas cooling device of the present invention, when the EGR gas chamber is mounted on a vehicle,
The maximum surface of the condensed water that can accumulate in the R gas chamber coincides with the lowest point of the inner peripheral edge of the opening end on the water surface side of the heat transfer tube located at the lowest position among the heat transfer tubes, or Since the water surface is located vertically below the lowest point of the inner peripheral edge of the opening end of the heat transfer tube located at the lowest position among the heat transfer tubes, the opening end of the heat transfer tube is not blocked by condensed water. , The flow of the EGR gas is not hindered, and a decrease in cooling performance can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) A first embodiment will be described below with reference to FIGS.

FIG. 1 is a vertical sectional side view showing the entire structure of an EGR gas cooling apparatus according to the first embodiment, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. FIG. 4 is a partially longitudinal side view in which a portion is omitted, and FIG.
FIG. 5 is a perspective view showing the entire bonnet member 30a, and FIG. 6 is a perspective view showing an E of the first embodiment.
FIG. 4 is a vertical sectional side view showing a state in which a maximum amount of condensed water has accumulated in a concave space A when the GR gas cooling device is mounted on a vehicle.

As shown in FIG. 1, the EGR gas cooling device 1 generally includes a heat exchange section 2 and an upstream EGR gas chamber 3.
a and a downstream EGR gas chamber 3b.

The heat exchange section 2 is mainly composed of a tubular body 20, tube sheets 22a and 22b, heat transfer tubes 24 and the like.

The cylindrical body 20 is made of austenitic stainless steel, and is formed of a hollow cylindrical member having both ends open and a circular cross section. A cooling water inlet and a cooling water outlet are formed in the side surfaces near both ends of the cylindrical body 20, and a cooling water inlet made of austenitic stainless steel is provided around the cooling water inlet and the cooling water outlet. The flanges formed by enlarging the open ends of the introduction pipe 26a and the cooling water discharge pipe 26b are brazed with Ni so that engine cooling water as a cooling medium is introduced and discharged into the cylindrical body 20. It is configured. The inner peripheral edges of the tube sheets 22a and 22b are Ni-brazed to the outer peripheral edges of both ends of the cylindrical body 20, and the openings at both ends of the cylindrical body 20 are closed respectively, so that the cylindrical body 2 is closed.
The cooling water is configured to flow through the inside.

[0014] As shown in FIG.
The through holes 2a and 22b are formed of austenitic stainless steel and have a diameter substantially equal to the outer diameter of the heat transfer tube 24 so that the heat transfer tubes 24 are radially arranged and inserted and fixed.
3 are pierced radially.

The heat transfer tube 24 is formed of a hollow cylindrical member made of austenitic stainless steel. As shown in FIG. 3, the opening end on the upstream side of the EGR gas is EGR gas.
The pipe is expanded in a tapered shape toward the upstream side of the gas.
The configuration is such that the GR gas easily flows into each heat transfer tube 24. Further, a spiral ridge 27 is formed on the inner peripheral surface side by applying a spiral groove processing from the outer peripheral surface side to the side surface, and the swirling force is applied to the EGR gas flowing in the heat transfer tube 24 to forcibly apply the whirl force. By generating the turbulent flow, the heat transfer performance is enhanced. The outer peripheral surfaces near both ends are formed with through holes 23 formed in the tube sheets 22a and 22b, respectively.
Are brazed to the inner peripheral surface of the cylinder E, and are arranged in parallel along the axis 21 of the cylindrical body 20 to form an upstream EGR gas chamber 3 described later.
a and the internal space of the downstream EGR gas chamber 3b. Further, a space around the heat transfer tube 24 becomes a cooling water passage 28 as a cooling medium passage, and the periphery of the heat transfer tube 24 is surrounded by the cooling water.

The upstream EGR gas chamber 3a and the downstream EGR gas chamber 3b are constituted by tube sheets 22a, 22b and bonnet members 30a, 30b.

The bonnet members 30a and 30b are made of austenitic stainless steel, and the inner peripheral surface is enlarged from the open end at one end to the open end at the other end while maintaining a circular cross-sectional shape. The inner periphery of the opening end on the small diameter side of the bonnet member 30a is Ni-brazed on the outer periphery of the opening end of the upstream EGR pipe 4a communicating with the exhaust passage (not shown) of the internal combustion engine (not shown), and EGR gas is supplied. Inlet 31
a is formed, and the inner circumference of the opening end on the small diameter side of the bonnet member 30b is formed in an intake passage (not shown) of an internal combustion engine (not shown).
N around the opening end of the downstream EGR pipe 4b communicating with the
i, which are brazed to form the EGR gas discharge port 31b. The inner circumferences of the large-diameter-side open ends of the bonnet members 30a and 30b are Ni-brazed to the tube sheets 22a and 22b fixed to both ends of the heat exchange unit 2. Therefore, the upstream EGR gas chamber 3 is formed by the tube sheets 22a and 22b and the bonnet members 30a and 30b.
a, a downstream EGR gas chamber 3b is formed.

As shown in FIG. 1, in the first embodiment, the EGR pipes 4a and 4b have their axes aligned with the cylinder 2 near the location where the EGR gas cooling device 1 is provided.
The EGR pipe 4a is formed in a straight line so as to be parallel to the axis 21 of 0, and the EGR pipe 4a is bent so that the upstream side of the EGR gas is lower than the straight line portion.
b is bent so that the downstream side of the EGR gas is lower than the straight portion. Therefore, in the system formed by the EGR gas cooling device 1 and the EGR pipes 4a and 4b, the EGR gas cooling device 1 is disposed at the highest position. Further, as shown in FIG. 4, the EGR pipes 4a and 4b are slightly inclined with respect to the horizontal direction so that the straight portion where the EGR gas cooling device 1 is disposed is lower on the upstream side of the EGR gas than on the downstream side. And is mounted on the vehicle. Therefore, the EGR gas cooling device 1 is
The R gas chamber 3a is located vertically below the downstream EGR gas chamber 3b, and the axis 21 of the cylindrical body 20 and the axis (not shown) of the heat transfer tube 24 are slightly inclined with respect to the horizontal direction to the vehicle. It is installed.

Here, the shapes of the bonnet members 30a and 30b will be described in detail.

As shown in FIGS. 4 and 5, of the bonnet members 30a and 30b, the bonnet member 30a disposed on the upstream side of the EGR gas has a large diameter (the heat exchange section 2).
The center 32a of the opening is located on the axis 21 of the cylindrical body 20, and the center 34a of the opening on the small diameter side (the EGR pipe 4a side) is vertically offset from the axis 21 of the cylindrical body 20. It is formed. Further, the bonnet member 30a is composed of a first cylindrical portion T1, an oblique truncated cone-shaped portion T2, and a second cylindrical portion T3 from the opening on the small diameter side to the opening on the large diameter side (here, the cylindrical portion T3). , With the oblique frustum shape, cut the oblique cone with a plane parallel to the bottom surface that does not pass through the apex,
This shows the shape that can be formed except for the part including the vertices.) In the first cylindrical portion T1, the axis is parallel to the axis 21 of the cylinder 20, the inner diameter is formed substantially equal to the outer diameter of the EGR pipe 4a, and the EGR pipe 4a is fixed at this portion. In the oblique truncated cone-shaped portion T2, the inner peripheral surface is expanded in a truncated conical shape such that the generatrix and the circular bottom face are perpendicular from the small-diameter opening to the large-diameter opening. A generatrix perpendicular to the circular bottom surface is formed so as to be parallel to the axis 21 of the cylindrical body 20 and to be positioned at the lowest vertically among the generatrix. In the lower part near the boundary with the second cylindrical portion T3, the pipe is slightly expanded in a stepped manner at a predetermined inclination angle with respect to the generatrix. In the second cylindrical portion T3, its axis is located coaxially with the axis 21 of the cylinder 20,
The inner diameter is substantially equal to the outer diameter of the tube sheet 22a, and the tube sheet 22a is fixed at this portion. Then, of the two inner lines in the vertical vertical section including the center 32a of the large-diameter side opening and the center 34a of the small-diameter side opening of the bonnet member 30a, the inner line 36a on the vertically lower side is used.
Is the heat transfer tube 2 located at the most vertically lower position of the heat transfer tubes 24.
4a, it is configured to be located vertically below the lowest point 25a of the inner peripheral edge of the opening end on the upstream side of the EGR gas.
In addition, the inner line 36a is parallel to the axis 21 of the cylindrical body 20 in most parts other than the part where the pipe is expanded stepwise at the oblique frustoconical portion T2, and is slightly parallel to the horizontal direction. It is inclined. The inner peripheral surface of each boundary between the first cylindrical portion T1, the oblique-cone-shaped portion T2, and the second cylindrical portion T3 is formed smoothly and continuously.

Therefore, in the upstream side EGR gas chamber 3a, the lower portion of the bonnet member 30a is expanded stepwise at the oblique frustoconical portion T2, so that the portion where the stepped expansion falls and the tube sheet 22a. Between the inner peripheral surface of the bonnet member 30 a and the tube sheet 2.
2a form a concave space A.

On the other hand, the bonnet member 30b disposed downstream of the EGR gas has basically the same configuration as the bonnet members 80a and 80b of the conventional EGR gas cooling device, and Center 32 of opening of exchange unit 2)
b and the center 34 of the opening on the small diameter side (the EGR pipe 4b side)
b is coaxial with the axis 21 of the cylinder 20,
The lower end of the opening on the smaller diameter side, that is, the lowermost point of the inner peripheral edge of the EGR gas discharge port 31b is the lowermost point 25b of the inner peripheral edge of the opening end on the downstream side of the EGR gas in the heat transfer tube 24a located at the lowest position among the heat transfer tubes 24. It is located more vertically above. Further, the bonnet member 30b is composed of a first cylindrical portion S1, a truncated cone-shaped portion S2, and a second cylindrical portion S3 from the opening on the small diameter side to the opening on the large diameter side (here,
The truncated cone shape refers to a shape formed by cutting a straight cone with a plane parallel to the bottom surface that does not pass through the apex and excluding a portion including the apex). In the first cylindrical portion S1, the axis is located coaxially with the axis 21 of the cylindrical body 20, and the inner diameter is the EGR pipe 4b.
And the EGR pipe 4b is fixed at this portion. In the truncated cone-shaped portion S2, the inner peripheral surface is expanded in a truncated cone shape coaxial with the axis 21 of the cylindrical body 20 from the opening on the small diameter side to the opening on the large diameter side.
In the second cylindrical portion S3, the axis is located coaxially with the axis 21 of the cylindrical body 20, the inner diameter is formed substantially equal to the outer diameter of the tube sheet 22b, and the tube sheet 22b is fixed at this portion. I have. The inner peripheral surface of the boundary between the first cylindrical portion S1, the oblique-cone-shaped portion S2, and the second cylindrical portion S3 is smoothly and continuously formed.

Therefore, in the downstream side EGR gas chamber 3b, the inner peripheral surface of the bonnet member 30b is expanded in a truncated cone shape at the truncated cone shape S2, so that the truncated cone shape portion S2 and the second cylinder are formed. In the part S3, the bonnet member 30
A concave space B is formed by the inner peripheral surface of the tube b and the tube sheet 22b.

The length of the concave space A in the upstream EGR gas chamber 3a in the direction of the axis 21 is equal to the length of the downstream EGR gas chamber 3a.
It is formed shorter than the length of the concave space B in the direction of the axis 21 at b.

Further, E in the bonnet member 30a
The distance La between the open end on the GR pipe 4a side and the open end on the heat exchange section 2 side is equal to the EGR in the bonnet member 30b.
The distance is set to be longer than the distance Lb between the open end on the pipe 4b side and the open end on the heat exchange section 2 side.

The operation and effect of the EGR gas cooling device having the above configuration will be described below.

According to the EGR gas cooling device 1 configured as described above, EGR gas is transferred from the upstream EGR pipe 4a to each heat transfer tube 24 in the heat exchange unit 2 via the internal space of the upstream EGR gas chamber 3a. After being distributed and cooled by the cooling water surrounding the periphery of the heat transfer tube 24 while passing through the heat transfer tube 24, they are collected in the internal space of the downstream EGR gas chamber 3 b and discharged to the downstream EGR pipe 4 b. On the other hand, the cooling water is introduced into the cylindrical body 20 from the cooling water inlet 26a, and flows through the cooling water passage 28 around the heat transfer tube 24.
It is discharged from the cooling water discharge port 26b.

When the EGR gas is cooled in this manner, the condensed water 10 is generated as described above. However, according to the EGR gas cooling device 1 according to the first embodiment, as shown in FIG. Seat 22a and bonnet member 30a
When the concave space A formed by the inner peripheral surface of the inner line 3 is filled with the condensed water 10, that is, when the maximum amount of condensed water that can be stored in the upstream EGR gas chamber 3a is stored, the inner line 3
Because most of 6a is slightly inclined with respect to the horizontal direction, the water surface 12 of the condensed water 10 is on the inner line 36a,
And it reaches the part where the step-shaped expansion pipe falls. However, since the inner line 36a is formed vertically below the lowest point 25a of the inner peripheral edge of the open end of the heat transfer tube 24a on the upstream side of the EGR gas, the water surface 12 of the condensed water 10
Are spaced vertically below the lowest point 25a of the inner peripheral edge of the open end of the heat transfer tube 24a. Therefore, the heat transfer tube 24a
Is not blocked by the condensed water 10, the flow of the EGR gas is not hindered, and a decrease in the cooling efficiency of the EGR gas cooling device 1 can be prevented.

Furthermore, when the condensed water continues to be generated even after the concave space A is filled with the condensed water 10, the portion on the inner line 36a where the step-shaped expansion tube falls is defined as follows.
Since the EGR pipe 4a is formed vertically below the lowest point 25a of the inner peripheral edge of the open end of the heat transfer tube 24a and the EGR pipe 4a is bent so that the upstream side of the EGR gas is lower than the straight portion, condensation occurs. The water 10 overflows to the EGR pipe 4a side, that is, to the exhaust passage side of the internal combustion engine. Therefore, the condensed water 10 generated in the upstream EGR gas chamber 3a passes through the heat transfer tube 24, and flows into the downstream EGR gas chamber 3b.
Since the water does not flow to the side, the water surface 12 of the condensed water 10 that accumulates in the concave space B can be kept low, the flow of the EGR gas is prevented from being inhibited, and the cooling efficiency of the EGR gas cooling device 1 is reduced. Can be prevented. Further, when the condensed water 10 overflowing from the concave space A flows to the exhaust passage side, since the temperature in the exhaust passage is high, there is an advantage that the overflowed condensed water 10 is easily evaporated.

Further, the axis 21 of the cylinder 20 and the axis of the heat transfer tube 24 are slightly inclined with respect to the horizontal direction so that the upstream EGR gas chamber 3a is located vertically below the downstream EGR gas chamber 3b. Since the condensed water 10 generated in the heat transfer tube 24 by being mounted on the vehicle flows along the slope toward the upstream EGR gas chamber 3a, the downstream EG
The condensed water 10 does not flow to the R gas chamber 3b side. Accordingly, the EGR gas cooling device 1 is
The amount of condensed water 10 flowing into the downstream EGR gas chamber 3b is reduced as compared with the case where the axis of the heat transfer tube 24 is mounted on the vehicle in the horizontal direction. Of the EGR gas cooling device 1
Of the cooling efficiency can be prevented.

Further, the inner line 3 of the bonnet member 30a
6a is located vertically below the lowest point 25a of the inner peripheral edge of the opening end of the heat transfer tube 24a on the upstream side of the EGR gas, whereas the lowermost point of the inner peripheral edge of the EGR gas outlet 31b of the bonnet member 30b is located. The point is EG in the heat transfer tube 24a.
The length of the concave space A of the bonnet member 30a in the direction of the axis 21 is located vertically above the lowest point 25b of the inner peripheral edge of the opening end on the downstream side of the R gas, and the axis of the concave space B of the bonnet member 30b. By being formed shorter than the length in the 21 direction, the volume of the concave space A in the upstream EGR gas chamber 3a is substantially equal to the volume of the concave space B in the downstream EGR gas chamber 3b having basically the same configuration as the conventional one. It is much smaller than its volume. As a result, a small amount of the condensed water 10 accumulated in the concave space A is
Since the gas evaporates easily as the temperature becomes high and does not remain, the water surface 12 of the condensed water 10 can be kept lower, and the flow of the EGR gas is suppressed from being hindered as compared with the conventional one. Thus, a decrease in the cooling efficiency of the EGR gas cooling device 1 can be prevented.

Further, in general, when the center 34a of the opening on the EGR pipe 4a side of the bonnet member 30a is offset from the center 32a of the opening on the side of the heat exchange section 2, the EGR pipe is like the bonnet member 30b. The center of the opening on the side of the heat exchange section and the center of the opening on the side of the heat exchange section are EG,
The diffusion of the R gas becomes non-uniform. However, according to the EGR gas cooling device 1 according to the first embodiment, the distance La between the opening end of the bonnet member 30a on the EGR pipe 4a side and the opening end of the heat exchange unit 2 side is the same as the conventional one. It is set longer than the distance Lb between the open end on the EGR pipe 4b side and the open end on the heat exchange section 2 side in the bonnet member 30b having basically the same configuration as that of the bonnet member 30b. As a result, the EGR gas is prevented from being unevenly diffused, and the EGR gas is uniformly distributed to each of the heat transfer tubes 24. (Second Embodiment) Next, a second embodiment will be described with reference to FIG.

In the second embodiment, similarly to the first embodiment, the present invention is applied to an EGR gas cooling device for cooling the EGR gas. In general, they have the same configuration. The same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 7 is a vertical sectional side view of a main part of the EGR gas cooling apparatus according to the second embodiment, in which the center is omitted, and FIG. 8 shows that the maximum amount of condensed water is stored in the concave spaces A 'and B'. FIG.

As shown in FIG. 7, in the EGR gas cooling device 1 according to the second embodiment, the heat exchange section 2 and the bonnet member 5 disposed upstream of the EGR gas are provided.
0a has the same configuration as that of the first embodiment, but has a bonnet member 5 disposed downstream of the EGR gas.
0b has the same shape as the bonnet member 50a disposed on the upstream side of the EGR gas.
Although a and 4b have the same shape as the first embodiment, the straight portion is mounted on the vehicle parallel to the horizontal direction, and the axis 21 of the cylindrical body 20 is inclined so as to be along the horizontal direction. The first embodiment is different from the first embodiment in that the first embodiment is mounted on a vehicle without using the first embodiment.

That is, the bonnet members 50a and 50b are
Centers 52a, 52b of openings on the large diameter side (heat exchange unit 2 side)
Are located on the axis 21 of the cylindrical body 20, and the small diameter side (EG
Centers 54a, 54b of openings of R pipes 4a, 4b side)
Are offset vertically downward with respect to the axis 21 of the cylindrical body 20. Further, the bonnet members 50a, 5
0b, the first cylindrical portions T1 ′ and S1 ′ and the oblique frustoconical portion T from the small-diameter side opening toward the large-diameter side opening.
2 ', S2' and second cylindrical portions T3 ', S3'. In the first cylindrical portions T1 'and S1', the axis is parallel to the axis 21 of the cylinder 20, and the inner diameter is EGR.
The EGR pipes 4a, 4b are formed to be substantially equal to the outer diameters of the pipes 4a, 4b, and the EGR pipes 4a, 4b are fixed at this portion. In the oblique truncated cone-shaped portions T2 'and S2', the inner peripheral surface is enlarged in a truncated cone shape such that the generatrix and the circular bottom face are perpendicular from the small-diameter opening to the large-diameter opening. At the same time, a generating line perpendicular to the circular bottom surface is formed so as to be parallel to the axis 21 of the cylindrical body 20 and to be located at the most vertically lower position among the generating lines. In the lower part near the boundary between the second cylindrical portions T3 'and S3', the pipe is slightly expanded in a stepped manner at a predetermined inclination angle with respect to the generatrix. 2nd cylindrical part T
In 3 ′ and S3 ′, the axis is located coaxially with the axis 21 of the cylindrical body 20, and the inner diameters of the tube sheets 22a, 2
The tube sheets 22a and 22b are formed to be substantially equal to the outer diameter of the tube sheet 2b, and the tube sheets 22a and 22b are fixed at this portion. Then, the center 52 of the large diameter side opening of the bonnet members 50a, 50b.
Among the two inner lines in the vertical vertical section including the centers a and 52b and the centers of the small-diameter-side openings, the inner lines 56a and 56b on the vertically lower side are the heat transfer tubes located at the most vertically lower position among the heat transfer tubes 24. The lowermost point 25a of the inner peripheral edge of the opening end on the upstream side of the EGR gas and the lowermost point 25b of the inner peripheral edge of the opening end on the downstream side of the EGR gas in 24a are configured to be located vertically below. The thickness of the EGR pipes 4a, 4b is set such that the lowermost points 42a, 42b of the inner peripheral edge of the open end are located vertically below the lowermost points 25a, 25b of the inner peripheral edge of the open end of the heat transfer tube 24a. ing. The first cylindrical portion T1 ′, S1 ′, the oblique truncated cone-shaped portion T2 ′, S2 ′, the second
The inner peripheral surface of each boundary between the cylindrical portions T3 'and S3' is formed smoothly and continuously.

Accordingly, the bonnet member 50a, the upstream EGR gas chamber 5a, and the downstream EGR gas chamber 5b are provided in the upstream EGR gas chamber 5b.
The EGR pipes 4a, 4b are provided with the oblique truncated cone-shaped portions T2 ', S2', and the lower portion is expanded in a stepped manner.
Open end wall surfaces 44a, 44b and bonnet member 50
Concave spaces A 'and B' are formed by the inner peripheral surfaces of the a and 50b and the tube sheets 22a and 22b.

According to the EGR gas cooling device 1 configured as described above, as shown in FIG. 8, when the concave spaces A 'and B' are filled with the condensed water 10, that is, the upstream EGR gas chamber 5a When the maximum amount of condensed water that can accumulate in the downstream-side EGR gas chamber 5b accumulates, the EGR pipes 4a and 4b are arranged upstream of a straight portion parallel to the horizontal direction in which the EGR gas cooling device 1 is disposed. The condensed water 10 and the downstream side are bent so as to be lower.
The water surface 12 reaches the lowermost points 42a, 42b of the inner peripheral edges of the open ends of the EGR pipes 4a, 4b. However, the inner lines 56a and 56b are configured to be located vertically below the lowest points 25a and 25b of the inner peripheral edge of the open end of the heat transfer tube 24a, and the EGR pipes 4a and 4b are connected to the inner peripheral edge of the open end. The water surface 12 of the condensed water 10 is conveyed by setting the wall thickness so that the lowermost points 42a and 42b are located vertically below the lowermost points 25a and 25b of the inner peripheral edge of the open end of the heat transfer tube 24a. The lower end points 25a and 25b of the inner circumference of the open end of the heat pipe 24a are separated vertically below. Therefore, on both the upstream EGR gas chamber 5a side and the downstream EGR gas chamber 5b side, the opening end of the heat transfer tube 24a is not blocked by the condensed water 10, and compared with the first embodiment. Further, it is possible to further prevent the cooling performance of the EGR gas cooling device 1 from lowering.

Further, when the condensed water continues to be generated even after the concave space A 'in the upstream EGR gas chamber 5a is filled with the condensed water 10, the EGR pipe 4a is connected to the lowermost point 42a of the inner peripheral edge of the open end. Is positioned so as to be located vertically below the lowermost point 25a of the inner peripheral edge of the open end of the heat transfer tube 24a, and bent so that the upstream side is lower than a straight line portion parallel to the horizontal direction. As a result, the condensed water 10 overflows toward the EGR pipe 4a, that is, toward the exhaust passage of the internal combustion engine. Therefore, since the temperature in the exhaust passage is high, there is an advantage that the overflowed condensed water 10 is easily evaporated. (Third Embodiment) Next, a third embodiment will be described with reference to FIG.

In the third embodiment, similarly to the first and second embodiments, the present invention is applied to an EGR gas cooling device for cooling the EGR gas. The configuration is basically the same as that of the embodiment. The same members as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 9 is a vertical sectional side view showing a main part of the EGR gas cooling apparatus according to the third embodiment, in which the center is omitted. FIG. 10 shows that the maximum amount of condensed water is stored in the concave spaces A "and B". FIG.

In the EGR gas cooling apparatus 1 according to the third embodiment, the heat exchange section 2 and the EGR pipe 4
Although a and 4b have the same configuration as those of the first and second embodiments, the shapes of the bonnet members 60a and 60b are different from those of the first and second embodiments. The EGR gas cooling device 1 according to the third embodiment is mounted on a vehicle without tilting so that the axis 21 of the cylindrical body 20 extends along the horizontal direction, similarly to the second embodiment. I have.

As shown in FIG. 9, the bonnet member 6
Reference numerals 0a and 60b denote openings 62a and 62b on the large-diameter side (heat exchange unit 2 side) centered on the axis 21 of the cylindrical body 20 and small-diameter sides (EGR pipes 4a and 4b side). Are formed vertically offset vertically below the axis 21 of the cylindrical body 20. Further, the bonnet members 60a and 60b are arranged such that the first cylindrical portions T1 "and S1", the truncated cone-shaped portions T2 "and S2", and the second cylindrical portions are arranged from the small-diameter opening to the large-diameter opening. T3 "and S3". In the first cylindrical portion T1 ″, S1 ″,
The axis is parallel to the axis 21 of the cylinder 20, the inner diameter is formed substantially equal to the outer diameter of the EGR pipes 4a, 4b, and the EGR pipes 4a, 4b are fixed at this portion. In the oblique truncated cone-shaped portions T2 ″ and S2 ″, the inner peripheral surface is enlarged in a truncated conical shape such that the generatrix and the circular bottom face are perpendicular from the small-diameter opening to the large-diameter opening. At the same time, a generatrix perpendicular to the circular bottom surface is formed so as to be parallel to the axis 21 of the cylindrical body 20 and to be positioned at the lowest vertically among the generatrix. Second cylindrical portion T3 ″, S3 ″
In this example, the axis is located coaxially with the axis 21 of the cylindrical body 20, and the inner diameter is formed substantially equal to the outer diameter of the tube sheets 22a and 22b.
a and 22b are fixed. Then, of the two inner lines in the vertical vertical section including the centers 62a, 62b of the large-diameter side openings of the bonnet members 60a, 60b and the centers 64a, 64b of the small-diameter side openings, the inner line 66a, vertically lower, of the two inner lines.
66b is vertically lower than the lowest point 25a of the inner peripheral edge of the opening end on the upstream side of the EGR gas and the lowermost point 25b of the inner peripheral edge of the opening end on the downstream side of the EGR gas in the heat transfer tube 24a located at the lowest position among the heat transfer tubes 24. Side. The thickness of the EGR pipes 4a, 4b is set such that the lowermost points 42a, 42b of the inner peripheral edges of the open ends are vertically lower than the lowermost points 25a, 25b of the inner peripheral edges of the heat transfer tubes 24a. ing. The first cylindrical portion T1 ″, S
1 ″, oblique frustoconical portion T2 ″, S2 ″, second cylindrical portion T
The inner peripheral surface of each boundary portion of 3 ″ and S3 ″ is formed smoothly and continuously.

Therefore, the EGR pipes 4a, 4b are provided in the upstream EGR gas chamber 6a and the downstream EGR gas chamber 6b.
Open end wall surfaces 44a, 44b and bonnet member 60
A minute concave space A ", B" is formed between the inner peripheral surfaces of the a and 60b and the tube sheets 22a and 22b.

According to the EGR gas cooling device 1 configured as described above, as shown in FIG. 10, the concave spaces A ", B"
Is filled with the condensed water 10, that is, when the maximum amount of condensed water that can be accumulated in the upstream EGR gas chamber 6a and the downstream EGR gas chamber 6b is accumulated, the EGR pipe 4a
And 4b are bent so that the upstream and downstream sides are lower than the straight portion parallel to the horizontal direction in which the EGR gas cooling device 1 is provided, so that the condensed water 1
The zero water surface 12 reaches the lowest points 42a and 42b of the inner peripheral edges of the open ends of the EGR pipes 4a and 4b. However, the inner lines 66a, 66b are configured to be located vertically below the lowest points 25a, 25b of the inner peripheral edge of the open end of the heat transfer tube 24a, and the EGR pipes 4a, 4b are connected to the inner peripheral edge of the open end. The water surface 12 of the condensed water 10 is conveyed by setting the wall thickness so that the lowermost points 42a and 42b are located vertically below the lowermost points 25a and 25b of the inner peripheral edge of the open end of the heat transfer tube 24a. The lower end points 25a and 25b of the inner circumference of the open end of the heat pipe 24a are separated vertically below. Therefore, the upstream EGR gas chamber 5a and the downstream EGR
On both sides of the gas chamber 5b, the open end of the heat transfer tube 24a is not blocked by the condensed water 10, and the first
As compared with the embodiment, it is possible to further prevent the cooling performance of the EGR gas cooling device 1 from lowering.

Further, the EGR according to the third embodiment
The gas cooling device 1 has a concave space A due to the truncated conical portions T2 ″ and S2 ″ of the bonnet members 60a and 60b not having the lower portion expanded in a stepped shape as in the first and second embodiments. ", B" is extremely smaller than the concave spaces A, A ', B' in the first and second embodiments. Therefore, only a very small amount of the condensed water 10 accumulates in the concave spaces A "and B", and when the condensed water 10 evaporates with the high-temperature EGR gas, the first and second condensed water 10 are removed.
And hardly remain as compared with the embodiment of FIG.
It is possible to promote prevention of deterioration in the cooling performance of the R gas cooling device 1.

Further, when the condensed water continues to be generated even after the concave space A "in the upstream EGR gas chamber 6a is filled with the condensed water 10, the EGR pipe 4a is connected to the lowermost point 42a of the inner peripheral edge of the open end. Is positioned so as to be located vertically below the lowermost point 25a of the inner peripheral edge of the open end of the heat transfer tube 24a, and bent so that the upstream side is lower than a straight line portion parallel to the horizontal direction. As a result, the condensed water 10 overflows to the EGR pipe 4a side, that is, to the exhaust passage side of the internal combustion engine. Is easily evaporated.

It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented as follows with appropriate modifications without departing from the spirit of the invention. (1) In the first and second embodiments, when the concave spaces A, A ', B' are filled with condensed water, that is, when the upstream EGR gas chambers 3a, 5a, In the case where the maximum amount of condensed water 10 that can be accumulated in 5b is accumulated,
Although the example in which the water surface 12 of the condensed water 10 is vertically separated from the lowermost points 25a and 25b of the inner peripheral edge of the open end of the heat transfer tube 24a, the water surface 12 of the condensed water 10 is Even if the lower end points 25a and 25b of the inner peripheral edge are configured to coincide with each other, the opening end of the heat transfer tube 24a is not closed, and the prevention of a decrease in cooling efficiency is promoted as compared with the related art. (2) In the first embodiment and the second embodiment, in the first cylindrical portions T1, T1 ′, S2 ′ of the bonnet members 30a, 50a, 50b, the inner peripheral surface is the EGR pipe 4a, Although the Ni brazing is performed on the outer periphery of the opening end of the EGR pipes 4a and 4b, the inner wires 36a and 56a are formed even if the outer peripheral surfaces of the bonnet members 30a, 50a and 50b are Ni brazed on the inner periphery of the opening ends of the EGR pipes 4a and 4b. , 56b are located vertically below the lowermost points 25a, 25b of the inner peripheral edge of the open end of the heat transfer tube 24a.
The concave spaces A, A ', B' are located vertically below the lowest points 25a, 25b of the inner peripheral edge of the open end of the heat transfer tube 24a, and the water surface 12 of the condensed water 10 is located inside the open end of the heat transfer tube 24a. The lowermost points 25a and 25b of the peripheral edge are not reached, so that a decrease in cooling efficiency can be prevented. (3) In the first embodiment, the EGR gas cooling device 1 controls the axis 21 of the cylinder 20 so that the upstream EGR gas chamber 3a is located vertically below the downstream EGR gas chamber 3b.
And the axis 28 of the heat transfer tube 24 is mounted on the vehicle with a slight inclination with respect to the horizontal direction.
Even when mounted on the vehicle such that the axis 28 of the heat transfer tube 1 and the heat transfer tube 24 extend along the horizontal direction, prevention of a decrease in cooling efficiency is promoted as compared with the related art. (4) In the first to third embodiments, when the concave spaces A, A ′, A ″ are filled with the condensed water, that is, the maximum amount that can be stored in the upstream EGR gas chambers 3a, 5a, 6a. When the condensed water 10 accumulates, the water surface 12 of the condensed water 10 becomes lowermost point 25a of the inner peripheral edge of the open end of the heat transfer tube 24a.
Because they are more vertically separated, the concave spaces A, A ',
When the condensed water 10 continues to be generated even after the A ″ is filled with the condensed water 10, the condensed water 10 is supplied to the upstream EGR pipe 4a to which the upstream EGR gas chambers 3a, 5a, and 6a communicate.
An example has been shown in which the fuel can easily be evaporated by overflowing into the exhaust gas side of the internal combustion engine. Therefore, when the water surface 12 of the maximum amount of condensed water 10 that can accumulate in the upstream EGR gas chambers 3a, 5a, and 6a coincides with the lowermost point 25a of the inner peripheral edge of the upstream end of the heat transfer tube 24a, The heat transfer tube 24a has an EGR gas
By inclining the downstream side of the gas to be higher, the condensed water 1 is filled after the concave spaces A, A ′, A ″ are filled with the condensed water 10.
If 0 continues to be generated, the condensed water 10 flows into the upstream EGR pipe 4a to which the upstream EGR gas chambers 3a, 5a, 6a communicate.
Side, that is, to the side of the exhaust passage of the internal combustion engine, and can be easily evaporated.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an overall configuration of an EGR gas cooling device according to a first embodiment.

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

FIG. 3 is a partially longitudinal side view in which a part of a heat transfer tube 24a is omitted.

FIG. 4 is a vertical sectional side view of a main part when the EGR gas cooling device according to the first embodiment is mounted on a vehicle, with a center omitted in FIG.

FIG. 5 is a perspective view showing the entire bonnet member 30a.

6 is a vertical sectional side view showing a state in which a maximum amount of condensed water is accumulated in a concave space A. FIG.

FIG. 7 is a vertical cross-sectional side view of a main part of an EGR gas cooling device according to a second embodiment, in which the center is omitted.

FIG. 8 is a vertical sectional side view showing a state in which a maximum amount of condensed water has accumulated in the concave spaces A ′ and B ′.

FIG. 9 is a vertical cross-sectional side view of a main part of an EGR gas cooling device according to a third embodiment, with the center omitted.

FIG. 10 is a vertical sectional side view showing a state where a maximum amount of condensed water has accumulated in the concave spaces A ″ and B ″.

FIG. 11 is a vertical sectional side view showing an overall configuration of an example of a conventional multi-tube EGR gas cooling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 EGR gas cooling device 2 Heat exchange part 3a Upstream EGR gas chamber 3b Downstream EGR gas chamber 4a, 4b EGR gas passage 10 Condensed water 12 Water surface 24 Heat transfer tube 24a Heat transfer tube most vertically located 25a Lowermost point 28 Cooling medium passage A Concave space

Claims (1)

[Claims] An EGR gas cooling device provided in the middle of an EGR gas passage for extracting a part of exhaust gas from an exhaust system of an internal combustion engine and recirculating the exhaust gas to an intake system has an upstream EGR communicating with an upstream side of the EGR gas passage. A gas chamber communicates with a downstream EGR gas chamber communicating with the downstream side of the EGR gas passage, an internal space of the upstream EGR gas chamber, and an internal space of the downstream EGR gas chamber, and an EGR gas is formed therein. The upstream EGR gas chamber, comprising: a plurality of heat transfer tubes flowing therethrough; and a cooling medium passage formed around the heat transfer tube between the upstream EGR gas chamber and the downstream EGR gas chamber. And at least one of the downstream EGR gas chambers has a surface of a maximum amount of condensed water that can accumulate in the EGR gas chamber when the EGR gas cooling device is mounted on a vehicle. The lowermost point of the inner peripheral edge of the open end on the water surface side of the heat transfer tube located at the most vertically lower position among the heat transfer tubes, or the water surface is vertically separated from the lowermost point An EGR gas cooling device characterized by being formed as described above.