JP2021085397A - EGR cooler - Google Patents

Abstract

To control a crack from being generated in an inlet-side end plate.SOLUTION: An EGR cooler 1 includes: a housing 2; multiple gas pipes 3 which are disposed inside the housing and through which an EGR gas flows; an inlet-side end plate 4 fixed to inlet-side end parts 3A of the multiple gas pipes and an inlet-side end part 2A of the housing to define a water chamber 6 through which coolant W flows; and an inlet-side flange 7 fixed to the inlet-side end part of the housing in a position separated on an outlet side as compared to the inlet-side end plate.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an EGR cooler, and more particularly to a water-cooled EGR cooler for cooling the EGR gas. Here, EGR (Exhaust Gas Recirculation) is an abbreviation for exhaust gas recirculation, and means taking out a part of the exhaust gas (called EGR gas) of an internal combustion engine and circulating it in an intake system.

In such a water-cooled EGR cooler, generally, a plurality of gas pipes through which EGR gas flows are arranged in the housing, and the inside of the housing is partitioned by an inlet side end plate and an outlet side end plate to house a water chamber through which cooling water flows. It is defined in (see, for example, Patent Document 1). Then, the EGR gas is cooled by removing the heat of the EGR gas from the cooling water in the water chamber. An inlet flange used for connection with the EGR tube is fixed to the inlet end of the housing.

JP-A-2007-224786

In such an EGR cooler, the EGR gas directly hits the surface of the inlet side end plate (inlet side surface), so that the inlet side end plate is heated, while the back surface of the inlet side end plate (outlet side side) is cooled water. Is contacted, so that the inlet side end plate is cooled.

Further, when the inlet side end plate is fixed to the inlet side flange, when the inlet side flange is heated by the EGR gas and stretches, the inlet side end plate also stretches accordingly.

When the flow of EGR gas is stopped while both the inlet side end plate and the inlet side flange are thermally expanded in this way, the inlet side end plate in contact with the cooling water is cooled before the inlet side flange. , Shrink. Then, thermal strain occurs between the two, and cracks may occur in the inlet side end plate, which is weak in strength.

Therefore, the present disclosure was devised in view of such circumstances, and an object thereof is to provide an EGR cooler capable of suppressing the occurrence of cracks in the inlet side end plate.

According to one aspect of the present disclosure
With the housing
A plurality of gas pipes arranged in the housing and through which EGR gas flows,
An inlet-side end plate fixed to an inlet-side end of the plurality of gas pipes and an inlet-side end of the housing to partition a water chamber through which cooling water flows.
An inlet flange fixed to the inlet end of the housing at a position separated from the inlet end plate on the outlet side.
An EGR cooler is provided that comprises.

Preferably, the fixing portion for fixing the inlet side flange is separated from the inlet side end plate on the outlet side.

Preferably, the inlet flange is brazed to the inlet end of the housing.

Preferably, the inlet side flange is formed in an L-shaped cross section.

According to the present disclosure, it is possible to suppress the occurrence of cracks in the inlet side end plate.

It is the schematic sectional drawing of the EGR cooler. It is an enlarged sectional view of the front end part of an EGR cooler. It is an enlarged sectional view of the rear end part of an EGR cooler.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the following embodiments.

FIG. 1 is a schematic cross-sectional view of the EGR cooler according to the embodiment of the present disclosure. The EGR cooler of the present embodiment is applied to an internal combustion engine mounted on a vehicle. For example, the vehicle is a large vehicle such as a truck, and the internal combustion engine (also referred to as an engine) is a diesel engine. However, the types and uses of the vehicle and the internal combustion engine are not particularly limited. For example, the vehicle may be a small vehicle such as a passenger car, and the engine may be a gasoline engine.

The engine may be mounted on a moving body other than a vehicle, for example, a ship, a construction machine, or an industrial machine. Further, the engine does not have to be mounted on a moving body, and may be a stationary engine.

In the illustrated EGR cooler 1, the right side in the figure is the inlet side into which the EGR gas G is introduced, and the left side in the figure is the outlet side in which the EGR gas G is discharged. Hereinafter, for convenience, the entrance side is defined as the front, the exit side is defined as the rear, and the other directions of up, down, left, and right are defined as shown in the figure. However, it should be noted that each of these directions is only defined for convenience of explanation.

The central axis of the EGR cooler 1, that is, the cooler axis is indicated by reference numeral C. Hereinafter, unless otherwise specified, the terms axial direction, radial direction, and circumferential direction mean the axial direction, radial direction, and circumferential direction with respect to the cooler axis C. The cooler shaft C is parallel to the front-rear direction. The EGR cooler 1 generally has an elongated shape extending linearly along the axial direction.

The EGR cooler 1 is fixed to the housing 2, a plurality of gas pipes 3 arranged in the housing 2 through which the EGR gas G flows, a front end portion 3A of the plurality of gas pipes 3, and a front end portion 2A of the housing 2. An inlet side end plate 4 and an outlet side end plate 5 fixed to a plurality of rear end portions 3B of gas pipes 3 and a rear end portion 2B of a housing 2 are provided. The inlet side end plate 4 and the outlet side end plate 5 partition a water chamber 6 through which the cooling water W flows between the two. The plurality of gas pipes 3 are housed in the water chamber 6, and the cooling water W in the water chamber 6 takes heat of the EGR gas in the gas pipe 3 to cool the EGR gas.

The EGR cooler 1 further includes an inlet flange 7 fixed to the front end 2A of the housing 2 and an outlet flange 8 fixed to the rear end 2B of the housing 2. These flanges 7 and 8 are used for connecting the upstream EGR pipe 9 and the downstream EGR pipe 10 arranged on the upstream and downstream sides of the EGR cooler 1.

The inlet-side flange 7 is joined to the flange 11 of the upstream-side EGR pipe 9 with the inlet-side gasket 12 interposed therebetween, and is fastened to the flange 11 by a plurality of bolts (not shown). Similarly, the outlet side flange 8 is joined to the flange 13 of the downstream side EGR pipe 10 with the outlet side gasket 14 interposed therebetween, and is fastened to the flange 13 by a plurality of bolts (not shown).

The EGR gas G is introduced from the upstream EGR pipe 9 into the EGR cooler 1, cooled through the EGR cooler 1, and then discharged from the EGR cooler 1 to the downstream EGR pipe 10.

Further, the EGR cooler 1 further includes a cooling water inlet pipe 15 fixed to the front end 2A of the housing 2 and a cooling water outlet pipe 16 fixed to the rear end 2B of the housing 2. The cooling water inlet pipe 15 and the cooling water outlet pipe 16 form an inlet and an outlet of the cooling water W with respect to the water chamber 6. The cooling water inlet pipe 15 and the cooling water outlet pipe 16 are arranged diagonally, that is, the cooling water inlet pipe 15 is arranged at the upper end of the front end portion 2A of the housing 2, and the cooling water outlet pipe 16 is arranged in the housing 2. It is arranged at the lower end of the rear end 2B.

The housing 2 is formed by a straight pipe having a circular cross section extending in the axial direction. The gas pipe 3 is also formed of a straight pipe having a circular cross section extending in the axial direction, and has a diameter smaller than that of the housing 2. The plurality of gas pipes 3 are arranged in a substantially staggered manner when viewed from the axial direction, but the arrangement method is arbitrary, and for example, they may be arranged in a grid pattern.

The inlet side end plate 4 and the outlet side end plate 5 are formed of a circular plate that is perpendicular to the axial direction and coaxial with the housing 2. The plates 4 and 5 are provided with a plurality of holes so as to allow the passage of the plurality of gas pipes 3. The outer shape of the inlet side flange 7 and the outlet side flange 8 is arbitrary, and may be triangular, circular, quadrangular, or the like.

Each of the above-mentioned parts constituting the EGR cooler 1 is made of metal, for example, stainless steel, and the EGR cooler 1 is manufactured by assembling each part by brazing.

The EGR cooler 1 is symmetrical in the front-rear direction except that the shapes and fixing methods of the inlet side flange 7 and the outlet side flange 8 are different and the arrangement of the cooling water inlet pipe 15 and the cooling water outlet pipe 16 is upside down. It is composed. First, the structure of the front end portion of the EGR cooler 1 will be described with reference to FIG.

As shown in FIG. 2, an inlet-side end plate 4 having the same outer diameter is fixed to the front end surface of the housing 2 in a liquid-tight and coaxial manner by brazing. A plurality of pipe insertion holes 21 are provided in the inlet side end plate 4. The front end of the gas pipe 3 is expanded in a flared shape, and after being inserted into the pipe insertion hole 21 from the front, the gas pipe 3 is brazed to the inlet side end plate 4 and fixed in a liquid-tight manner. The brazed portion (fixed portion) of the gas pipe 3 and the inlet side end plate 4 is indicated by reference numeral 22 for reference. The front end of the gas pipe 3 does not have to be flared.

The inlet-side flange 7 is generally formed in an annular shape extending in the circumferential direction and has an L-shaped cross section. The inlet-side flange 7 includes a housing fitting surface 23 formed on the inner peripheral portion of the rear end, a flange body 24 extending radially outward from the housing fitting surface 23, and then bending forward. It has a flange surface 25 formed on the front end surface of 24.

The housing fitting surface 23 is fitted to the outer peripheral surface of the front end portion 2A of the housing 2. After that, the flange body 24 is fixed to the outer peripheral surface by brazing at positions adjacent to the housing fitting surface 23 in the front-rear direction. In the case of the present embodiment, the flange body 24 is fixed from the front side by the front brazing portion (fixing portion) 26, and the flange body 24 is fixed from the rear side by the rear brazing portion (fixing portion) 27.

In particular, the inlet-side flange 7 is fixed to the front end portion 2A of the housing 2 at a position separated from the inlet-side end plate 4 on the rear side. Further, in the present embodiment, the front brazed portion 26 as a fixing portion for fixing the inlet side flange 7 closer to the inlet side end plate 4 is further separated to the rear side from the inlet side end plate 4. Therefore, the inlet side end plate 4 is not in direct contact with the inlet side flange 7 and is thermally isolated from the inlet side flange 7. Similarly, the inlet side end plate 4 is not in direct contact with the front brazing portion 26 and is thermally isolated from the front brazing portion 26.

The distance between the inlet side end plate 4 and the inlet side flange 7 in the front-rear direction X1 and the distance between the inlet side end plate 4 and the front brazing portion 26 in the front-rear direction X2 (<X1) are very small in the illustrated example. However, it may be larger than the illustrated example. Further, the inlet side end plate 4 and the inlet side flange 7 (flange body 24) are also separated in the radial direction, and the inlet side flange 7 is located radially outside the inlet side end plate 4.

As shown in FIG. 1, the flange surface 25 is a surface that is joined to the flange 11 of the upstream EGR pipe 9 with the inlet side gasket 12 interposed therebetween. The flange surface 25 is located in front of the inlet side end plate 4 and the plurality of gas pipes 3. A gas inlet 30 for introducing the EGR gas G is defined inside the flange body 24 in the radial direction. The EGR gas G introduced here is distributed and supplied to a plurality of gas pipes 3.

Next, the structure of the rear end portion of the EGR cooler 1 will be described with reference to FIG.

An outlet-side end plate 5 having the same outer diameter is fixed to the rear end surface of the housing 2 in a liquid-tight and coaxial manner by brazing. The rear end portions 3B of the plurality of gas pipes 3 are inserted into the plurality of pipe insertion holes 51 of the outlet side end plate 5, and are brazed to be liquidtightly fixed. The rear end of the gas pipe 3 has a flared diameter, but the diameter may not be increased. The brazed portion (fixed portion) is indicated by reference numeral 52 for reference.

The outlet side flange 8 is generally formed in an annular plate shape extending in the circumferential direction. The outlet side flange 8 has a housing fitting surface 53 formed on the inner peripheral portion of the front end thereof, a reduced diameter portion 54 adjacent to the rear of the housing fitting surface 53 and reduced in diameter in a stepped shape, and a reduced diameter portion 54. A tapered portion 55 adjacent to the rear of the housing is provided.

The housing fitting surface 53 is fitted to the outer peripheral surfaces of the housing 2 and the outlet side end plate 5 from the rear to the front until the outlet side end plate 5 abuts on the front end surface of the reduced diameter portion 54. The outlet side flange 8 is accurately positioned in the axial direction and the radial direction by such fitting, and then fixed to the housing 2 and the outlet side end plate 5 by brazing. In this way, the outlet side flange 8 is in contact with the outlet side end plate 5 and is fixed to the outlet side end plate 5.

A gas outlet 56 for discharging the EGR gas G is defined inside the outlet side flange 8 in the radial direction.

As shown in FIG. 2, the EGR gas G introduced into the gas inlet 30 flows rearward as it is and directly hits the surface, that is, the front surface of the inlet side end plate 4. As a result, the inlet side end plate 4 is heated from the front side. On the other hand, since the cooling water W is in contact with the back surface, that is, the rear surface of the inlet side end plate 4, the inlet side end plate 4 is cooled from the rear surface side. The inlet side flange 7 is heated from the inside in the radial direction by the EGR gas G introduced into the gas inlet 30.

Further, if the inlet side end plate 4 is fixed to the inlet side flange 7 similar to the structure of the rear end portion shown in FIG. 3, when the inlet side flange 7 is heated by the EGR gas and stretched, this becomes At the same time, the inlet side end plate 4 also extends.

When the inlet side end plate 4 and the inlet side flange 7 are both thermally expanded in this way and the flow of EGR gas is stopped due to, for example, EGR stop, the inlet side end plate 4 that comes into contact with the cooling water is better. It is cooled and contracted before the inlet side flange 7. Then, thermal strain occurs between the two, and cracks may occur in the inlet side end plate 4 which is weak in strength.

Therefore, in the present embodiment, the inlet-side flange 7 is fixed to the front-side end portion 2A of the housing 2 at a position separated from the inlet-side end plate 4 on the rear side. By doing so, the inlet side end plate 4 can be separated from the inlet side flange 7, so that the inlet side end plate 4 can be less susceptible to the influence of expansion and contraction due to the heat of the inlet side flange 7. In other words, the expansion and contraction due to the heat of the inlet side flange 7 and the expansion and contraction due to the heat of the inlet side end plate 4 can be performed separately and independently.

Therefore, even if the inlet-side end plate 4 is cooled by the cooling water before the inlet-side flange 7 and contracts, the contraction can be freely performed. Then, the thermal strain between the two can be suppressed, and the occurrence of cracks in the inlet side end plate 4 can be suppressed.

Further, in the present embodiment, since the inlet side flange 7 is fixed to the front end portion 2A of the housing 2 at a position separated from the inlet side end plate 4 on the rear side, the position separated from the inlet side end plate 4 on the front side. The flange surface 25 can be positioned rearward as compared with the case of fixing with, which is advantageous in shortening the total length of the EGR cooler 1 in the axial direction.

Further, in the present embodiment, the front brazing portion 26 for fixing the inlet side flange 7 is separated from the inlet side end plate 4 on the rear side. As a result, it is possible to suppress heat transfer and heat interference between the inlet side flange 7 and the inlet side end plate 4 via the front brazing portion 26, and the inlet side flange 7 and the inlet side end plate 4 can be more reliably connected. Can be thermally isolated. Then, it is advantageous for suppressing the occurrence of cracks in the inlet side end plate 4.

Since the inlet-side flange 7 is formed in an L-shaped cross section, the fixed portion of the inlet-side flange 7 is separated from the inlet-side end plate 4 to the rear side, and the inlet-side flange 7 is radially outward from the inlet-side end plate 4. The flange surface 25 can be positioned at a suitable position on the front side of the inlet side end plate 4 and the plurality of gas pipes 3 while being separated from each other.

Although the embodiments of the present disclosure have been described in detail above, various other embodiments and modifications of the present disclosure can be considered.

(1) For example, the fixing method of the inlet side flange 7 and the like is not limited to brazing. Other fixing methods such as normal welding and screwing are possible.

(2) A tapered portion symmetrical to the tapered portion 55 shown in FIG. 3 may be provided on the inner peripheral portion of the front end of the inlet side flange 7. When the tapered portion is provided, the EGR gas G introduced into the gas inlet 30 can be smoothly guided to the gas pipe 3 which is the outermost in the radial direction.

(3) The structure of the rear end portion of the EGR cooler 1 may be a structure symmetrical with the structure of the front end portion shown in FIG.

The configurations of the above-described embodiments and modifications can be combined partially or wholly, unless otherwise inconsistent. The embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the ideas of the present disclosure defined by the scope of claims are included in the present disclosure. Therefore, the present disclosure should not be construed in a limited manner and may be applied to any other technique belonging within the scope of the ideas of the present disclosure.

1 EGR cooler 2 Housing 2A Front end 3 Gas pipe 3A Front end 4 Inlet side end plate 6 Water chamber 7 Inlet side flange 26 Front brazed part G EGR gas W Cooling water

Claims (4)

With the housing
A plurality of gas pipes arranged in the housing and through which EGR gas flows,
An inlet-side end plate fixed to an inlet-side end of the plurality of gas pipes and an inlet-side end of the housing to partition a water chamber through which cooling water flows.
An inlet flange fixed to the inlet end of the housing at a position separated from the inlet end plate on the outlet side.
An EGR cooler characterized by being equipped with. The EGR cooler according to claim 1, wherein the fixing portion for fixing the inlet-side flange is separated from the inlet-side end plate on the outlet side. The EGR cooler according to claim 1 or 2, wherein the inlet-side flange is fixed to the inlet-side end of the housing by brazing. The EGR cooler according to any one of claims 1 to 3, wherein the inlet side flange is formed in an L-shaped cross section.

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