1. Field of the Invention
The present invention relates to an EGR cooler.
2. Related Background of the Invention
An EGR cooler is proposed by the Patent Document 1 given below. According to the proposed EGR cooler, a plurality of flat tubes is arranged in parallel, and both ends thereof penetrate through the respective header plates, thus structuring a core. A casing encloses the outer circumferential surface of the core to form a cooler body. A bypass pipe is laid along the cooler body. The bypass pipe and one end of the cooler body are connected via a tank, while the other end of the cooler body and the bypass pipe are connected to a tank having a gate valve.
Conventional EGR coolers are fabricated by a large number of parts, and have a complicated structure, resulting in expensive ones. In addition, they have a drawback of non-compactness. To solve the problems, the present invention aims to provide a compact EGR cooler integrated with a bypass valve with a small number of parts.
A first aspect of the present invention provides an EGR cooler having the structure of: a plurality of flat tubes (1), each having a bottom portion (1a) closing one end thereof, having an opening (1b) at the other end thereof, being arranged in parallel facing flat face thereeach; corrugated fins (2) formed in each of the flat tubes (1) while keeping a space (1c) against the bottom portion (1a) so as a ridgeline (2a) of each of the corrugated fins (2) to extend from the opening (1b) to the bottom portion (1a); a header plate (3) to which the opening (1b) of each of the flat tubes (1) penetrates therethrough and is fixed thereto, and a core (4) formed by the flat tubes, corrugated fins and header plate, wherein: the outer circumferential surface of the core (4) is enclosed by a casing (5); the header plate (3) closes an open end of a tank body (7) equipped with a partition (6); and the partition (6) is located at an intermediate position in the width direction of the opening (1b) of each of the flat tubes (1), and wherein a flue gas (9) is introduced to one side of the partition (6) in each of the flat tubes (1), and then takes a U-turn at the bottom portion (1a) to flow out from other side of the partition (6), while a cooling water (10) is introduced into the casing (5).
A second aspect of the present invention provides the EGR cooler according to the first aspect of the invention, further having an elastic support (11) which supports outer circumferential surface of the bottom portion (1a) of each of the flat tubes (1) at one end portion thereof, while the other end portion thereof is attached to the casing (5).
A third aspect of the present invention provides the EGR cooler according to the second aspect of the invention, wherein the casing (5) has a concave portion (21) at an intermediate position of the bottom portion thereof, and the other end portion of the elastic support (11) is fitted into the concave portion (21).
A fourth aspect of the present invention provides the EGR cooler according to any of the first to third aspects of the invention, wherein the partition (6) has a connection opening (6a) which is closed by a bypass valve (8) capable of being arbitrarily closed or opened.
A fifth aspect of the present invention provides the EGR cooler according to any of the first to fourth aspects of the invention, wherein each of the flat tubes (1) penetrating through the header plate (3) has a notched portion (25), at an intermediate position of an edge thereof in the width direction, cut to the face of the header plate (3), and an edge of the partition (6) contacts with the notched portion (25).
A sixth aspect of the present invention provides the EGR cooler according to any of the first to fourth aspects of the invention, wherein the header plate (3) has a protruded strip (3a) at a position facing an edge of the partition (6) so as the protruded strip (3a) and an edge of each of the flat tubes (1) to become flush with each other, and the edge of the partition (6) contacts with the protruded strip (3a).
A seventh aspect of the present invention provides the EGR cooler according to any of the first to fifth aspects of the invention, wherein the outer circumferential surface of the bottom portion (1a) of each flat tube (1) is formed in an arc shape, auxiliary fins (2b) are arranged at the bottom portion (1a), and the bottom portion (1a) and the auxiliary fins (2b) are brazed to fix them together.
An eighth aspect of the present invention provides the EGR cooler according to any of the first to sixth aspects of the invention, wherein each flat tube (1) is a brazed article structured by a pair of plates (29) and (30), having the respective side walls (29a) and (30a), erecting at the periphery thereof except at the opening of flat tube (1), while the side walls (29a) and (30a) have the respective concave portions (29b) and (30b) at the respective matching positions thereeach, thus fitting the concave portions (29b) and (30b) thereeach.
According to the EGR cooler of the present invention, corrugated fins 2 are located in the flat tube 1 having the bottom portion 1a, and the opening 1b of each of the plurality of flat tubes 1 penetrates to fix to the header plate 3, thereby forming the core 4. The outer circumferential surface of the core 4 is enclosed by the casing 5. The header plate 3 closes the opening at an end of the tank body 7 provided with the partition 6. Since the partition 6 is located at an intermediate position in the width direction of the opening 1b of the flat tube 1, the number of parts is small and the structure is quite simple, thus providing a U-turn flow compact EGR cooler at a low cost.
With the above structure, the one which locates the elastic support 11 between the bottom portion 1a of each flat tube 1 and the casing 5 smoothly absorbs the thermal expansion of the EGR cooler in operating state, and the elastic support 11 always supports each flat tube 1, thus providing a high strength EGR cooler enduring vibrations and other mechanical disturbances.
With the above structure, the one which forms the concave portion 21 at an intermediate position at the bottom portion of the casing 5 and which fits other edge portion of the elastic support 11 to the concave portion 21 provides a highly reliable EGR cooler with readily installation.
With the above structure, the one which has the connection opening (6a) on the partition (6) and which closes the connection opening (6a) with the arbitrarily closing and opening bypass valve (8) allows the flue gas to bypass the flat tube (1) by opening the bypass valve (8), at a low flue gas temperature, thus preventing supercooling of the flue gas.
With the above structure, the one which has the notched portion 25, at an intermediate position in the width direction of an edge of the flat tube 1 penetrating through the header plate 3, thus making an edge of the partition 6 contact with the notched portion 25, provides a compact EGR cooler with simple structure free of leakage.
With the above structure, the one which has the protruded strip 3a on the header plate 3 to make an edge of the partition 6 contact with the protruded strip 3a provides a highly reliable EGR cooler with simple structure and improved air-tightness of the partition 6.
With the above structure, it is possible that the face outer circumference of the bottom portion (1a) of the flat tube (1) is formed in an arc shape, that the auxiliary fins (2b) are arranged on the bottom portion (1a), and that the bottom portion (1a) and the auxiliary fins (2b) are brazed to fix them together. In that case, the pressure strength of the bottom portion (1a) of the flat tube (1) can be increased.
With the above structure, it is possible that the flat tube (1) is formed by a brazed article structured by combining a pair of plates (29) and (30) having the respective side walls (29a) and (30a) erecting at the periphery thereeach except at the opening of flat tube (1), and that the concave portions (29b) and (30b) are formed on the respective side walls (29a) and (30a) at the matching position thereeach, thus fitting the concave portions (29b) and (30b) thereeach. In that case, on assembling and brazing the core, the pair of plates (29) and (30) is prevented from misalignment in the flat direction thereof, thus providing a highly reliable EGR cooler.
Embodiments of the present invention will be described below referring to the drawings.
As illustrated in
As illustrated in
The corrugated fins 2 have a flat face at rise portion and at down portion of each fin, and there exists no louver such as cut-louver. With the configuration, the flue gas flowing through the inside space of the fin is prevented from moving in the width direction of the flat tube 1.
According to the example, the notched portion 25 is formed at an intermediate position in the width direction at an edge of the opening 1b of each flat tube 1, (although the position in this example is at the center of the width direction, the present invention does not limit the position to the center in the width direction).
The flat tube 1 configured as above is inserted into a tube penetration hole (not shown) in the header plate 3, and the inserted flat tube 1 and the header plate 3 are fixed by brazing or other means at the penetration portion, thus forming the core 4. The bottom of the notched portion 25 of each flat tube 1 is positioned to become flush with the face of the header plate 3. The casing 5 is enclosed to the outer circumferential surface of the core 4.
The casing 5 has an annular expanded portion 16 which slightly expands outward at each end in the longitudinal direction thereof. To each of both annular expanded portions 16, an inlet/outlet pipe 15 penetrates to fix them together. At the bottom portion of the annular expanded portion 16 of the casing 5, a concave portion 21 is formed. One end of the elastic support 11 is fitted to fix to the concave portion 21 via a bracket 22. As illustrated in
The header plate 3 closes an end opening of the tank body 7. The tank body 7 has the partition 6 at an intermediate position thereof to divide the inside space thereof into an inlet tank portion 7a and an outlet tank portion 7b. That is, the edge of the partition 6 contacts to fix with the header plate 3 at the position of the notched portion 25 of each flat tube 1. The partition 6 has the connection opening 6a, and the connection opening 6a is closed by the bypass valve 8 capable of being arbitrarily closed or opened. In concrete terms, the bypass valve 8 moves from the position of the solid line to the position of broken line. A rotary shaft 12 of the bypass valve 8 protrudes outward from the tank body 7, as shown in
The controller 17 according to the example generates a negative pressure when the flue gas temperature is relatively low, and the generated negative pressure enters the actuator 18 via a connection pipe 24, thus driving the second link 26 to open the bypass valve 8.
As described before in
The cooling water 10 enters the casing 5 through one inlet/outlet pipe 15 to cool the outer circumferential surface of each flat tube 1, then flows out from other inlet/outlet pipe 15.
The high temperature flue gas 9 flows through one side in the width direction of each flat tube 1, entering from an inlet 13 of the inlet tank portion 7a. Then, the flue gas takes a U-turn in a space 1c of the bottom portion 1a to flow through the other side in the width direction of the flat tube 1. After that, the flue gas flows out from the outlet pipe 14 of the outlet tank portion 7b. As a result, heat is exchanged between the cooling water 10 and the flue gas 9. During the heat exchange, the flat tube 1 extends, caused by the thermal expansion, relative to the casing 5 because the flue gas 9 flows inside the flat tube 1. The thermal expansion is, however, absorbed by the deformation of the elastic support 11. In addition, as illustrated in
The above bypass valve 8 may be eliminated. In that case, the connection opening 6a of the partition 6 is not required.
With the configuration, the inlet tank portion 7a and the outlet tank portion 7b are perfectly separated from each other.
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2007-164162 | Jun 2007 | JP | national |
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