JP6974083B2 - EGR cooler - Google Patents

Description

The present invention relates to an EGR cooler that cools exhaust gas with cooling water, and in particular, a headerless type EGR cooler in which both ends of the exhaust gas in the flow direction bulge in the thickness direction and flat tubes are laminated at the bulging portions. Regarding.

The heat exchanger described in Patent Document 1 below has a core formed of a laminated body of flat tubes. In this flat tube, both ends in the exhaust gas flow direction bulge in the thickness direction, and the ends of the flat tubes are laminated at the bulge. As a result, it is a headerless type heat exchanger that does not require a header plate and is used as an EGR cooler. Then, the high-temperature exhaust gas flows inside the flat tube, and the cooling water flows to the outside of the flat tube via the casing that fits the outer circumference of the core. Then, heat exchange is performed between the exhaust gas and the cooling water.

Japanese Unexamined Patent Publication No. 2013-148319

Such a flat tube is composed of a fitting body of a pair of plates formed in a shallow groove shape, and the flat tubes are brazed to each other at both ends in the exhaust gas flow direction. Further, an inner fin is interposed inside the flat tube.
In such a headerless type EGR cooler, the temperature becomes high especially at the inflow end of the exhaust gas, deterioration occurs in the brazed portions between the ends of the flat tubes, and the base metal tends to crack.
Therefore, it is an object of the present invention to absorb the thermal stress generated at the inflow end of the exhaust gas to prevent deterioration of the EGR cooler and cracking of the base metal.

The present invention according to claim 1 has a plurality of flat tubes (3) in which bulging portions (2) bulging in the thickness direction are formed at both ends of the exhaust gas (1) in the flow direction. The flat tubes (3) are laminated with each other in the thickness direction at the bulging portion (2) to form a core (4), and a casing (5) is fitted on the outer periphery of the core (4) to form a flat tube (3). ), And the cooling water (6) is introduced into the outer surface side of the flat tube (3) via the casing (5) in the EGR cooler.
On the inlet side of the exhaust gas (1), the bulging portion is partially recessed in the thickness direction of the flat tube (3) toward the inner surface side of the bulging portion (2) of each flat tube (3). A thermal stress absorbing portion (7) that can be deformed in the width direction of (2) is provided .
The thermal stress absorbing portion (7) is an EGR cooler formed at the opening end on the inlet side of the bulging portion (2).

The present invention according to claim 2 is a plurality of heats that are intermittently recessed in the thickness direction on the inner surface side of the bulging portion (2) of each flat tube (3), separated in the width direction of the tube. The EGR cooler according to claim 1, which has a stress absorbing portion (7).
The present invention according to claim 3 has an inner fin (8) inserted into the flat tube (3) so that the tip of the inner fin (8) reaches the thermal stress absorbing portion (7). 1 or the EGR cooler according to claim 2.

The EGR cooler of the present invention is partially recessed in the thickness direction of the flat tube 3 toward the inner surface side of the bulging portion 2 of each flat tube 3 on the inlet side of the exhaust gas 1, and is deformed in the width direction thereof. A possible heat stress absorbing portion 7 is provided , and the heat stress absorbing portion 7 is formed at the opening end of the bulging portion 2 on the inlet side . Therefore, the thermal stress generated in the width direction of the flat tube 3 can be absorbed by the deformation of the heat stress absorption unit 7 in the width direction at the inlet portion of the exhaust gas 1 which becomes particularly hot, and deterioration of the EGR cooler can be prevented. As a result, cracking of the base metal of the flat tube and the core is prevented.

The invention according to claim 2 has a plurality of thermal stress absorbing portions 7 separated in the width direction of the bulging portion 2 of the flat tube 3, so that the thermal stress is absorbed more effectively and the EGR cooler is deteriorated. Can be prevented.
In the invention according to claim 3, since the tip of the inner fin 8 of the flat tube 3 reaches the heat stress absorbing portion 7, the tip of the bulging portion 2, which becomes particularly hot, is cooled by the inner fin 8. , EGR cooler deterioration can be prevented.

Exploded view (A) showing the first embodiment of the flat tube 3 constituting the EGR cooler of the present invention, the assembled view (B), the explanatory view (C) showing the laminated state thereof, and the DD cross section of (C). It is a figure (D). It is an exploded view (A) which shows the 2nd Example of the flat tube 3, the assembly drawing (B), the explanatory view (C) which shows the laminated state, and the DD sectional view (D) of (C). Explanatory drawing which shows the operation of the 1st Example. Explanatory drawing which shows the operation of the 2nd Example. It is a cross-sectional plan view of the EGR cooler 10 in which the core 4 is formed by the laminated body of the flat tube 3 of the first embodiment, and is along the plane of the flat tube 3.

Next, each embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a vertical cross-sectional view of the EGR cooler 10 of the present invention, which is along the plane of the flat tube 3. The EGR cooler 10 constitutes a core 4 by a laminated body of flat tubes 3, a casing 5 is fitted on the outer periphery of the core 4, and an inlet tank 16 and an outlet tank 17 are integrally formed with the casing 5. It is placed at both ends of.
As shown in FIG. 1, the flat tube 3 constituting the core 4 is formed by facing a pair of groove-shaped plates 3a and groove-shaped plates 3b formed in a groove shape, respectively, and fitting both edges thereof. ..

Each of the grooved plates 3a and 3b has bulging portions 2 projecting in the thickness direction at both ends in the X direction in FIG. 1 which is the flow direction of the exhaust gas 1. In this example, as shown in FIG. 1C, both edges of the upper grooved plate 3a are fitted to stepped portions provided at the ends of the lower grooved plate 3b. Further, dimples 9 are projected on the outer surface side of the grooved plate 3a and the grooved plate 3b except for the bulging portion 2. Further, the heat stress absorbing portion 7 is recessed at the center position in the width direction (Y direction) of the bulging portion 2 of the grooved plate 3a and the grooved plate 3b.
An inner fin 8 having a length matching the flow direction of the exhaust gas 1 is inserted into the grooved plate 3a and the grooved plate 3b thus formed.

As shown in FIGS. 1 (C) and 1 (D), the flat tubes 3 are laminated with each other at the bulging portions 2 to form a core. As shown in FIG. 5, a casing 5 is fitted on the outer periphery of the core 4, and a pair of exhaust gas inlet tanks 16 and outlet tanks 17 are arranged at both ends thereof. In the figure, a flange is provided at the inlet 11 into which the exhaust gas 1 flows in, and an outlet 12 is formed at the outlet tank 17.
The EGR cooler 10 thus assembled is brazed integrally in the furnace.
The flat tube 3 and the inner fin 8 can be brazed to each other. Further, the flat tube 3 and the inner fin 8 may be partially brazed so that the tip portion of the inner fin 8 and the bulging portion 2 can move relative to each other without brazing. can.

As shown in FIGS. 1 and 3, the thermal stress absorbing portion 7 may be recessed by the height of the bulging portion 2. In this example, as shown in FIG. 5, the thermal stress absorbing portion 7 is formed only on the inflow side of the exhaust gas 1. This is because the gas temperature on the inlet side is higher than that on the outlet side. On the inflow side of the exhaust gas 1 of the flat tube 3, the bulging portion 2 becomes particularly hot due to the high temperature exhaust gas 1, and thermal stress is generated. Then, the rising edge portion of the thermal stress absorbing portion 7 is deformed and absorbs the stress. Thereby, deterioration and cracking of the brazed portion of each flat tube 3 are prevented.

[Action]
In FIG. 5, the high-temperature exhaust gas 1 flowing in from the leftmost inlet 11 flows in from the bulging portion 2 of each flat tube 3 constituting the core 4. Further, the cooling water 6 is supplied from the inlet pipe 13 at the right end to the outer surface side of each flat tube 3 via the manifold 15, and becomes a countercurrent flow to the exhaust gas 1 from the manifold 15 to the outside via the outlet pipe 14. leak. Then, heat exchange is performed between the exhaust gas 1 and the cooling water 6.

At this time, the bulging portion 2 of each flat tube 3 on the inflow side of the exhaust gas 1 is subjected to thermal stress due to the high temperature exhaust gas 1 and tends to expand the bulging portion 2 in the width direction. Then, as shown in FIG. 3, thermal strain is generated in the thermal stress absorbing portion 7, and the state of the solid line is deformed to the state of the chain line. As a result, the strain applied to the bulging portion 2 of each flat tube 3 is absorbed, and in particular, the strain generated in the bulging portion 2 of the flat tube 3 is released, and the deterioration thereof and the cracking of the brazed portion between the flat tubes 3 are released. Can be prevented.

Next, FIG. 2 is a second embodiment of the present invention, and the difference between this example and that of FIG. 1 is that the bulging portions 2 are separated from each other in the longitudinal direction, and the plurality of thermal stress absorbing portions 7 are separated from each other in the thickness direction. It is formed on the inner surface side of. Further, the tip of the inner fin 8 is separated from the heat stress absorbing portion 7.
By providing the plurality of thermal stress absorbing portions 7 in the bulging portion 2 in this way, the thermal stress can be absorbed more effectively.
FIG. 4 is an explanatory diagram showing a deformed state when thermal stress is generated in the thermal stress absorbing portion 7.
That is, it changes from the state of the solid line to the state of the chain line and absorbs the thermal stress.

1 Exhaust gas 2 Swelling part 3 Flat tube 3a Groove type plate 3b Groove type plate 4 Core 5 Casing 6 Cooling water 7 Thermal stress absorption part

8 Inner fin 9 Dimple 10 EGR cooler 11 Inlet 12 Outlet 13 Inlet pipe 14 Outlet pipe 15 Manifold 16 Inlet tank 17 Outlet tank

Claims (3)

A plurality of flat tubes (3) having bulging portions (2) formed in the thickness direction are formed at both ends of the exhaust gas (1) in the flow direction, and each flat tube (3) has the bulging. The core (4) is formed by laminating each other in the thickness direction at the portion (2), the casing (5) is fitted on the outer periphery of the core (4), and the exhaust gas (1) is guided into the flat tube (3). In the EGR cooler in which the cooling water (6) is introduced to the outer surface side of the flat tube (3) via the casing (5).
On the inlet side of the exhaust gas (1), the bulging portion is partially recessed in the thickness direction of the flat tube (3) toward the inner surface side of the bulging portion (2) of each flat tube (3). A thermal stress absorbing portion (7) that can be deformed in the width direction of (2) is provided .
An EGR cooler in which the thermal stress absorbing portion (7) is formed at the opening end on the inlet side of the bulging portion (2). Claimed to have a plurality of thermal stress absorbing portions (7) on the inner surface side of the bulging portion (2) of each of the flat tubes (3), which are spaced apart in the width direction of the tube and intermittently recessed in the thickness direction. The EGR cooler according to 1. The EGR cooler according to claim 1 or 2, wherein the inner fin (8) is inserted into the flat tube (3) so that the tip of the inner fin (8) reaches the thermal stress absorbing portion (7). ..

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