JP2012241597A - Exhaust gas cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas cooler that easily warms up cooling water even at a low temperature by the heat of a recirculated exhaust gas, and reliably prevents corrosion caused by condensate water.SOLUTION: The exhaust gas cooler cools the recirculated exhaust gas by heat exchange between the recirculated exhaust gas flowing in an EGR gas passage 13 and engine cooling water flowing in a cooling water passage 14. The exhaust gas cooler is equipped with: a plurality of opposite partition walls 21, 22 arranged so as to partition the gas passage 13 and the cooling water passage 14 and face each other at a distance; and a spacer 16 inserted between a plurality of the opposite partition walls 21, 22 and disposed in the cooling water passage 14 so as to partially regulate the flow of the cooling water in a specific passage zone 14a in the cooling water passage 14. The spacer 16 is made of a material of a higher thermal conductivity than a plurality of opposite partition walls 21, 22.

Description

  The present invention relates to an exhaust cooler, and more particularly to an exhaust cooler suitable for an EGR cooler installed in an exhaust gas recirculation system of an internal combustion engine.

  Many internal combustion engines for vehicles are equipped with an exhaust gas recirculation (EGR) system that performs exhaust gas recirculation that is effective in reducing NOx (nitrogen oxides), so that lean combustion is possible and the EGR flow rate is high. In many engines, an EGR cooler (exhaust cooler) is frequently used to lower the temperature of the recirculated exhaust gas that is recirculated.

  In the EGR cooler, condensed water is generated when the moisture in the exhaust gas is cooled, but exhaust gas components such as sulfur compounds dissolve in the condensed water, and it tends to become highly acidic condensed water. The device which suppresses is made.

  As such an EGR cooler, for example, a cooling water passage is formed between a plurality of flat tubes through which EGR gas passes, and a rectifying plate for rectifying the flow of the cooling water through the cooling water passage is installed. It is known (see, for example, Patent Document 1). In this EGR cooler, by disposing the gas inflow portion below the gas outflow portion, even if acidic condensed water is generated when the exhaust gas is cooled by the heat exchange portion, the condensed water is The gas flows down and is discharged from the gas inflow portion to the exhaust pipe side.

JP 2010-190064 A

  However, in the conventional exhaust cooler, the main components such as the heat exchange tube that partitions the cooling water passage and the EGR gas passage in the EGR cooler are aluminum alloys having excellent thermal conductivity and stainless steel having excellent corrosion resistance. As a result, the following problems existed.

  That is, when the EGR gas is introduced into the EGR cooler in a state where the engine coolant temperature is low, it is preferable to suppress the generation of condensed water in the EGR cooler by raising the temperature of the EGR cooler by the heat of the EGR gas. In the conventional exhaust cooler in which the EGR cooler is made of stainless steel having excellent corrosion resistance, the heat conductivity of the stainless steel is low, so that the EGR cooler is uniformly and rapidly raised by the heat of the EGR gas. The temperature was not easy.

  On the other hand, in the conventional exhaust cooler in which the EGR cooler is formed of a material such as an aluminum alloy having excellent thermal conductivity, when the EGR gas is introduced into the EGR cooler under a condition where the engine coolant temperature is low, the heat of the EGR gas Thus, the temperature of the EGR cooler can be easily and uniformly raised, and the generation of condensed water in the EGR cooler can be suppressed. However, in this case, the main components of the EGR cooler are easily corroded by acidic condensed water in which sulfur compounds in the exhaust gas are dissolved. In particular, condensed water is generated in the portion of the EGR cooler where the temperature is low. As a result, the EGR cooler is easily corroded by the condensed water.

  Accordingly, the present invention provides an exhaust cooler that can be easily heated by the heat of the recirculated exhaust gas even when the cooling water temperature is low, and that can reliably prevent corrosion due to condensed water. .

  In order to solve the above problems, an exhaust cooler according to the present invention includes (1) a gas passage forming a part of an exhaust gas recirculation passage of an internal combustion engine and a cooling water passage through which cooling water of the internal combustion engine passes. An exhaust cooler that cools the recirculated exhaust gas by heat exchange between the recirculated exhaust gas that passes through the gas passage and the cooling water, and that is disposed to face and separate the gas passage and the cooling water passage A plurality of opposed wall surface portions, and interposed between the plurality of opposed wall surface portions and disposed in the cooling water passage, and partially restricts the flow of the cooling water in a specific passage region of the cooling water passage. And the spacer is made of a material having a higher thermal conductivity than the plurality of opposing wall surface portions.

  In the operation of the exhaust cooler, a plurality of opposing wall surfaces are in a state of receiving the heat from the recirculated exhaust gas entirely on the wall surface on the gas passage side, but on the wall surface on the specific passage region side of the cooling water passage, Heat is taken away by the cooling water within a range not contacting the spacer, and heat is hardly taken away by the cooling water within a range coming into contact with the spacer, so that heat conduction is easily achieved. Therefore, by arranging a spacer on the other surface side (cooling water passage side) of the opposing wall surface portion having a portion on the one surface side where condensed water is likely to be generated, the generation of condensed water can be effectively suppressed. Even if condensed water is generated, it can be quickly evaporated. In addition, it is desirable that the plurality of opposing wall surface portions described here have at least a wall portion on the gas passage side that has better acid corrosion resistance than the spacer.

  In the exhaust cooler of the present invention having the above-described configuration, (2) the gas passage has a low-temperature passage portion in which the temperature of the recirculated exhaust gas during heat exchange is lower than the other passage portions, It is preferable that the wall surface portion is disposed so as to be in contact with the low temperature passage portion on one surface side and in contact with the spacer on the other surface side. In this case, the spacer is disposed adjacent to the low temperature portion where the condensed water is likely to be generated in the gas passage, and the flow is limited by the spacer so that the flow of the cooling water bypasses the low temperature portion. Water generation is effectively suppressed. Note that the low temperature passage portion referred to here is because the flow rate of cooling water in adjacent cooling water passages is increased, or the flow rate of the recirculated exhaust gas is locally reduced or the temperature of the cooling water is lowered. Therefore, unless the flow of the cooling water is partially limited, the passage portion is likely to be excessively cooled as compared with other passage portions, and the temperature of the recirculated exhaust gas during heat exchange is likely to be low.

  In the exhaust cooler of the present invention, (3) the plurality of opposed wall surface portions are configured by mutually facing portions of the plurality of flat tubes forming the gas passages in the respective interiors, and are in contact with the spacer A plate-like shape having a wall surface portion, wherein the specific passage region of the cooling water passage is formed between the plurality of flat tubes, and the spacer is sandwiched between the plurality of flat tubes and is in contact with the low temperature wall surface portion. It is preferably constituted by a body. Thereby, arrangement | positioning and support of a spacer become easy.

  In the exhaust cooler having the configuration of the above (2) or (3), (4) the low temperature passage portion has a flow rate of the cooling water other than the specific passage region of the cooling water passage during the heat exchange. It may be close to the cooling water concentration portion that is larger than the cooling water passage portion. In this case, the flow rate of the cooling water in the vicinity of the low temperature passage portion is limited by the spacer, and since the amount of the cooling water is large, the low temperature passage portion is reliably prevented from being overcooled.

  In the exhaust cooler having the configuration of (4), (5) the plurality of flat tubes have three or more parallel flat tube portions that are separated from each other in the separation direction of the plurality of opposing wall surface portions, The low-temperature wall surface portions of the plurality of opposing wall surface portions are a first parallel flat tube portion positioned on the extreme end side in the separation direction among the parallel flat tube portions, and a second parallel flat tube adjacent to the first parallel flat tube portion. It is preferable that the tube portion is constituted by a portion facing the tube portion. Accordingly, it is possible to accurately limit the cooling of the first parallel flat tube portion on the extreme end side where there is no gas passage on the outside and the cooling with the cooling water is likely to be excessive.

  In the exhaust cooler having the configuration of (5) above, (6) the low temperature wall surface portion of the plurality of opposed wall surface portions is located on the lower side in the vertical direction among the plurality of opposed wall surface portions. There may be. In this case, even if the recirculated exhaust gas in the flat gas passage or the recirculated exhaust gas or the cooling water in the specific passage area of the flat cooling water passage convects and tends to be low in the vertical direction, the gas locally It can prevent that the inner wall part of a channel | path becomes low temperature.

  In the exhaust cooler of the present invention, (7) it is preferable that the spacer is made of an aluminum-based alloy, and the plurality of opposing wall surfaces are made of stainless steel. As a result, the low-temperature wall surface portion in contact with the low-temperature passage portion where the condensed water is easily generated in the gas passage is limited by the cooling by the cooling water by the spacer and the heat transfer from the adjacent gas passage side is promoted to condense. Generation of water can be effectively suppressed.

  According to the present invention, the plurality of opposing wall surface portions are disposed within the range in contact with the spacer by disposing the spacer on the other surface side of the opposing wall surface portion having a portion on the one surface side where condensed water is easily generated in the gas passage. The cooling water is not easily deprived of heat, and it is easy to conduct heat mutually, so that the generation of condensed water is effectively suppressed, and even if condensed water is generated, it is evaporated quickly. It is possible to provide an exhaust cooler that can be easily heated by the heat of the recirculated exhaust gas even when the water temperature is low, and that can reliably prevent corrosion due to condensed water.

It is the front view seen in the mounting direction to the engine of the exhaust cooler concerning one embodiment of the present invention. It is AA arrow sectional drawing of FIG. It is BB arrow sectional drawing of FIG. It is CC sectional view taken on the line of FIG. It is a schematic block diagram of the cooling system of the water cooling engine provided with the exhaust cooler which concerns on one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(One embodiment)
1 to 5 are schematic block configuration diagrams of an exhaust cooler according to an embodiment of the present invention and a cooling system of a water-cooled engine including the exhaust cooler.

  First, the configuration will be described.

(First embodiment)
1 to 5 show an exhaust gas recirculation device for an internal combustion engine according to a first embodiment of the present invention.

  The exhaust cooler of the present embodiment is configured to exchange heat between exhaust gas and engine coolant in an EGR (exhaust gas recirculation) system of an engine 1 (see FIG. 5) that is a water-cooled internal combustion engine mounted on a vehicle. Is implemented as an EGR cooler 10 that lowers the temperature of the recirculated exhaust gas that is recirculated by the exhaust gas. The configuration of the EGR system other than the EGR cooler 10 is the same as a known one. Although the engine 1 is a four-cycle gasoline engine here, it is needless to say that the engine 1 may be another engine having a different fuel.

  First, the engine cooling system shown in FIG. 5 will be described. The engine 1, although not shown in detail, is cooled by cooling water passing through an internal water jacket. The engine 1 includes an EGR device that recirculates and recirculates a part of the exhaust gas from the exhaust device side to the intake device side. In the EGR device, each combustion chamber (not shown) of the engine 1 is provided. An exhaust gas recirculation EGR gas passage 51 (a recirculation exhaust gas passage; see FIG. 1) that bypasses and connects the exhaust passage and the intake passage, a cooling water passage 9 that passes the cooling water of the engine 1, and an EGR gas passage 51 An EGR valve 53 that adjusts the exhaust gas recirculation amount in the middle, and an EGR cooler 10 that cools the exhaust gas recirculated through the EGR gas passage 51 with engine cooling water are provided.

  The cooling water that has passed through the water jacket of the engine 1 flows out from a cooling water outlet e1 formed in the cylinder head 1h of the engine 1, and the cooling water that flows out of the engine 1 is separated from the outside air by the radiator 2. It is cooled by heat exchange. For example, a completely sealed reserve tank 3 is mounted on the radiator 2. A water pump (not shown) is disposed on the upstream end side of the water jacket of the engine 1, and a thermostat 4 that opens and closes in response to the temperature of the cooling water is disposed on the suction side of the water pump. Yes.

  The cooling water that has flowed out of the engine 1 is also supplied to the heater core 5 that performs heat exchange between the cooling water and the air for heating the passenger compartment, and the engine cooling that has passed through the heater core 5 is performed. The water recovers exhaust heat by heat exchange between the EGR cooler 10 and the exhaust gas passing through the exhaust pipe of the engine 1 and the engine cooling water via the two branch passages 9a and 9b of the cooling water passage 9. Thus, the heater core 5 and the exhaust heat recirculation device 6 that can improve the warm-up performance of the engine 1 are respectively supplied.

  Here, the EGR cooler 10 has a function of cooling the recirculated exhaust gas by heat exchange between the engine cooling water that has passed through the heater core 5 and the recirculated exhaust gas that passes through the EGR gas passage 51. Further, the exhaust heat recirculation device 6 is configured to control the exhaust heat recirculation amount by variably controlling the flow rate of engine cooling water by the control actuator 6a. The cooling water flowing out from the engine 1 is further passed through a throttle body 7 that forms part of the intake passage and forms part of the throttle valve.

  As shown in FIGS. 1 to 4, the EGR cooler 10 includes a substantially rectangular tube case 11 that is an outer shell, and a plurality of flat heat exchange tubes 12 (flat tubes) housed in the case 11 in parallel with each other. ) And.

  The case 11 protrudes outward from the case body 11a so as to be connected to a tank-like case body 11a that forms a cooling water passage 11h through which the engine coolant that has passed through the heater core 5 passes, and a cooling water pipe such as a hose, The first and second cooling water introduction pipe portions 11b and 11c that connect the cooling water passage 11h and the two branch passages 9a and 9b of the cooling water passage 9 and a plurality of EGR gases from the exhaust device side of the engine 1 An EGR gas introduction pipe portion 11d to be introduced into the heat exchange tube 12, an EGR gas discharge pipe portion 11e for returning the EGR gas after passing through the plurality of heat exchange tubes 12 to the intake device side of the engine 1, and a cooling water passage 11h The cooling water discharge pipe part 11g which recirculates the cooling water which passed through to the engine 1 side and mounting brackets 11j and 11k to the engine 1 are provided.

  The EGR cooler 10 includes a gas passage 13 that forms a part of the EGR gas passage 51 by the EGR gas introduction pipe portion 11 d and the EGR gas discharge pipe portion 11 e of the case 11 and the plurality of heat exchange tubes 12. And a plurality of heat exchange tubes 12 form a cooling water passage 14 through which the cooling water of the engine 1 passes, and heat exchange between the recirculated exhaust gas passing through the gas passage 13 and the cooling water passing through the cooling water passage 14 Thus, the recirculated exhaust gas is cooled.

  Specifically, the plurality of heat exchange tubes 12 are formed in a flat tube shape having a constant thickness with a metal having high thermal conductivity. The plurality of heat exchange tubes 12 are connected to the EGR gas introduction pipe portion 11d and the EGR gas discharge pipe portion 11e of the case 11 at both ends thereof, thereby being orthogonal to the extending direction of the gas passage 13. It is supported by the case 11 with a predetermined gap g from each other in the thickness direction Dt. A plurality of flat gas passages 13a through which the recirculated exhaust gas passes are formed in parallel to each other by the plurality of heat exchange tubes 12. The plurality of gas passages 13 a form a plurality of branch passages in the middle of the gas passage 13 as a part of the gas passage 13. Each heat exchange tube 12 contains an inner fin 17 having a plurality of concave and convex bent portions 17a so as to promote the heat exchange by disturbing the flow of EGR gas.

  More specifically, as shown in FIGS. 2 to 4, the case body 11 a of the case 11 is formed by firmly bonding a pair of case members 111 and 112 having a substantially U-shaped cross section by brazing or the like. The first and second cooling water introduction pipe parts 11b and 11c, the EGR gas introduction pipe part 11d, the EGR gas discharge pipe part 11e, the cooling water discharge pipe part 11g, and the engine 1 with respect to the case main body part 11a. Mounting brackets 11j and 11k are fixed to each other.

  Each of the plurality of heat exchange tubes 12 has a substantially flat wall surface portion 21 (which may have small irregularities or grooves) on one surface side, and a substantially flat wall surface portion 22 on each other surface side. These wall surface portions 21 and 22 are a plurality of opposed wall surface portions facing each other with a predetermined gap g. That is, of each pair of heat exchange tubes 12 adjacent to each other in the thickness direction Dt, the pair of wall surface portions 21 and 22 that face each other are between the gas passages 13 a inside the heat exchange tubes 12 and the heat exchange tubes 12. While partitioning the specific passage area 14a of the cooling water passage 14 corresponding to the predetermined interval g, parallel wall portions spaced apart in parallel are configured.

  In addition, between the plurality of heat exchange tubes 12, a substantially flat plate shape (small unevenness and so on) is partially restricted between the opposing wall surface parts 21 and 22 in the specific passage region 14 a of the cooling water passage 14. Spacers 15 and 16 (which may have grooves) are provided. The restriction of the flow of the cooling water here means that the flow of the cooling water in the specific passage area 14a is partially blocked within the installation range of the spacers 15 and 16, and is restricted by the spacers 15 and 16, or different directions. The spacers 15 and 16 significantly reduce the flow rate of the cooling water in the respective installation ranges as compared with the surrounding cooling water passage portion (in this embodiment, the flow rate is zero). This hinders the flow of cooling water.

  The spacers 15 and 16 are fixed to a pair of adjacent wall surfaces 21 and 22 adjacent to each other by brazing, for example, and are in contact with each other so as to be able to conduct heat. In addition, each spacer 15, 16 is made of a material having higher thermal conductivity than the plurality of opposing wall surface portions 21, 22. In this embodiment, the wall surface portions 21 and 22 of the plurality of heat exchange tubes 12 are each formed of stainless steel, whereas the spacers 15 and 16 are aluminum alloys for heat exchangers each having a higher thermal conductivity than stainless steel. (Aluminum alloy). In addition, in the plurality of heat exchange tubes 12 made of stainless steel, at least the wall surface portion on the gas passage 13 side of the opposed wall surface portions 21 and 22 has better acid corrosion resistance than the spacers 15 and 16. .

  On the other hand, in the EGR cooler 10, the connection positions of the first and second cooling water introduction pipe portions 11b and 11c and the cooling water discharge pipe portion 11g with respect to the case main body portion 11a of the case 11 are on the end side of the case main body portion 11a. They are biased and their connecting directions are also different from each other. Therefore, the gas passage 13 has low-temperature passage portions 13e and 13f in which the temperature of the recirculated exhaust gas during heat exchange is lower than that of the other passage portions.

  The low temperature passage portion 13e of the gas passage 13 passes through the heater core 5 and the exhaust heat recirculation device 6 in the width direction (vertical direction in FIG. 3) of the plurality of heat exchange tubes 12, as shown in FIGS. The cooling water flow rate along the wall surface portions 21 and 22 on both sides of the second cooling water introduction pipe portion 11c to which the cooling water is introduced is most likely to increase. This low-temperature passage portion 13e is a cooling water in which the flow rate of the cooling water during heat exchange in the specific passage region 14a of the cooling water passage 14 is larger than that of the other cooling water passage portion 14a2 (the lower portion in FIG. 3). It is close to the concentrated portion 14a1 (the upper portion in FIG. 3).

  As shown in FIG. 4, the low-temperature passage portion 13 f of the gas passage 13 is disposed on the lower side in the vertical direction inside the case 11 in the vicinity of the first cooling water introduction pipe portion 11 b into which the cooling water that has passed through the heater core 5 is introduced. The gas passage portion is located and located inside the heat exchange tubes 12 (shown by 12E in FIG. 2) on both ends in the separating direction of the plurality of heat exchange tubes 12. Note that a large amount of cooling water that passes through the heater core 5 and is introduced into the case 11 through the first cooling water introduction pipe portion 11b flows along the inner wall surface of the case 11 to the lower side in FIG. The temperature of the cooling water in contact with the wall surface portions 21 and 22 in the vicinity of the left and right low-temperature passage portions 13f is lower than other cooling water passage portions inside the case 11 (other portions of the specific passage region 14a).

  The low-temperature passage portions 13e and 13f of the gas passages 13 are used for increasing the flow rate of the cooling water in the specific passage region 14a of the adjacent cooling water passage 14, or locally for the recirculated exhaust gas in the gas passage 13a. If the flow rate of the cooling water is not partially limited because the flow rate is reduced or the temperature of the cooling water is lowered, the recirculation exhaust during heat exchange becomes excessively cooled as compared with the other gas passage portions 13g. It is a passage portion where the temperature of the gas tends to be low.

  And a pair of heat exchange tube 12E located in the both ends side in thickness direction Dt and a pair of heat exchange tube 12 adjacent to them are the outer surface side (one surface side) of a pair of wall surface parts 21 and 22 mutually opposed. Low-temperature wall surface portions 21a and 22a are in contact with either one of the low-temperature passage portions 13e and 13f and are in contact with the spacers 15 and 16 on the inner surface side (other surface side). Each of the spacers 15 and 16 is a plate-like body that is sandwiched between the plurality of heat exchange tubes 12 and is in contact with the low-temperature wall portions 21a and 22a, and one of the plurality of spacers 15 adjacent to the low-temperature passage portion 13e. And the other plurality of spacers 16 adjacent to the low temperature passage portion 13f have substantially the same thickness, but the shape and width of their plate surfaces may be different from each other.

  That is, in this embodiment, as shown in FIGS. 2 to 4, the plurality of heat exchange tubes 12 includes three or more parallel flat tube portions 12 p that are separated from each other in the separation direction of the plurality of opposing wall surface portions 21 and 22. The low-temperature wall surface portions 21a and 22a of the plurality of opposing wall surface portions 21 and 22 are the first parallel flat tube portion 12p1 positioned on the extreme end side in the separation direction among the plurality of parallel flat tube portions 12p and the The second parallel flat tube portion 12p2 adjacent to the first parallel flat tube portion 12p1 is configured to be opposed to the first parallel flat tube portion 12p1.

  The EGR valve 53 can be switched between a valve open state in which the EGR gas passage 51 communicates with the intake passage side and a closed / closed state in which the communication / connection state is limited, for example, shut off. The electronic control unit) is controlled according to the operating state of the engine 1 by a known method.

  Next, the operation will be described.

  In the EGR cooler 10 of the present embodiment configured as described above, the EGR valve 53 is controlled according to the operation state during the operation of the engine 1, and passes through the EGR gas passage 51 when the EGR valve 53 is opened. The recirculated exhaust gas is cooled by the EGR cooler 10.

  During operation of the EGR cooler 10, the opposing wall surface portions 21 and 22 of the plurality of heat exchange tubes 12 are in a state of receiving the heat from the recirculated exhaust gas entirely on the wall surface on the gas passage 13 side, but the cooling water passage 14 The wall on the side of the specific passage area 14a is deprived of heat by the cooling water within a range not in contact with the spacers 15 and 16, whereas the heat is not easily deprived by the cooling water within a range of contact with the spacers 15 and 16, and heat conduction between them. It becomes easy to do.

  Accordingly, by disposing the spacers 15 and 16 on the other surface side (cooling water passage side) of the opposing wall surface portions 21 and 22 having a portion on the one surface side where the condensed water is likely to be generated in the gas passage 13, the specific passage region. It is possible to prevent the cooling water flow rate in 14a from locally increasing and the cooling water temperature from locally lowering, effectively suppressing the generation of condensed water and generating condensed water. Even then, it can be quickly evaporated.

  In addition, since the plurality of opposed wall portions 21 and 22 are more excellent in acid corrosion resistance than the spacers 15 and 16 at least on the wall portion on the gas passage 13 side, it is possible to prevent the occurrence of condensed water and promote evaporation as described above. Thus, corrosion due to acidic condensed water can be effectively suppressed.

  Moreover, in this embodiment, the some opposing wall surface parts 21 and 22 have the low temperature wall surface parts 21a and 22a which contact | connect the spacers 15 and 16 on the other surface side while contacting the low temperature channel | path parts 13e and 13f on the one surface side. Therefore, the plate-like spacers 15 and 16 are disposed adjacent to the low-temperature passage portions 13e and 13f in which the condensed water is easily generated in the gas passage 13, and the flow of the cooling water is lowered by the spacers 15 and 16. It is limited to bypass the wall surface portions 21a and 22a, and the opposed wall surface portions 21 and 22 are less likely to be deprived of heat by cooling water within a relatively wide range in contact with the spacer 15 and easily conduct heat to each other. Thus, the generation of condensed water is more effectively suppressed.

  Further, each spacer 15, 16 is sandwiched between a plurality of flat heat exchange tubes 12 and is a plate-like body in contact with the low temperature wall surface portions 21 a, 22 a of the opposing wall surface portions 21, 22. , 16 is easy to arrange and support.

  In addition, the low-temperature passage portion 13e is close to the cooling water concentration portion in the specific passage region 14a of the cooling water passage 14 where the cooling water passage flow rate during heat exchange is larger than that of other cooling water passage portions. 15 effectively restricts the flow rate of the cooling water in the vicinity of the low temperature passage portion 13e and increases the flow rate of the cooling water in the other cooling water passage portion located on the lower side in FIG. In addition, it is possible to reliably prevent the low temperature passage portion 13e from being overcooled.

  In addition, the plurality of heat exchange tubes 12 have three or more parallel flat tube portions 12p that are separated from each other in the separation direction of the opposed wall surface portions 21 and 22, and the low-temperature wall surface portions 21a of the plurality of opposed wall surface portions 21 and 22 are. , 22a is a first parallel flat tube portion 12p1 located on the most end side in the separating direction of the parallel flat tube portions 12p, and a second parallel flat tube portion 12p2 adjacent to the first parallel flat tube portion 12p1. Since it is comprised by the part which opposes, the cooling of the 1st parallel flat tube part 12p1 of the endmost side which does not have the gas channel 13 on the outer side, and is easy to be cooled by cooling water excessively can be restrict | limited exactly.

  Moreover, since the low-temperature wall surface parts 21a and 22a of the some opposing wall surface parts 21 and 22 are the lower part of the perpendicular direction among the some opposing wall surface parts 21 and 22 in the case 11, the flat gas passage 13a is used. Even if the recirculated exhaust gas or the cooling water convects in the specific recirculation exhaust gas or the specific passage region 14a of the flat cooling water passage 14 and tends to be low in the lower side in the vertical direction, the gas passage 13 locally. It can prevent that the inner wall part of this becomes low temperature.

  In the present embodiment, the spacers 15 and 16 are made of an aluminum alloy for a heat exchanger, and the plurality of opposing wall surfaces 21 and 22 are made of stainless steel, so that a low temperature passage that easily generates condensed water in the gas passage 13a. For the low-temperature wall surface portions 21a and 22a in contact with the portions 13e and 13f, the cooling by the cooling water is limited by the spacers 15 and 16, and the heat transmission from the adjacent gas passage 13a side is promoted to effectively generate the condensed water. Can be suppressed.

  As described above, according to the exhaust cooler of the present embodiment, the plurality of opposing wall surface portions 21 and 22 have the portions of the opposing wall surface portions 21 and 22 that have a portion on the one surface side that easily generates condensed water in the gas passage 13a. Since the spacers 15 and 16 are arranged on the other surface side, the opposing wall surface portions 21 and 22 are not easily deprived of heat by the cooling water within a range in contact with the spacers 15 and 16 and are easy to conduct heat mutually. In this way, it is possible to effectively suppress the generation of condensed water or to rapidly evaporate even if condensed water is generated. Therefore, the temperature of the EGR cooler 10 can be easily raised by the heat of the recirculated exhaust gas from the stage where the temperature of the engine cooling water is low, and the temperature can be increased uniformly at each part of the opposing wall surface parts 21 and 22, and corrosion caused by the condensed water can be ensured. The EGR cooler 10 that can be prevented can be provided.

In the exhaust cooler according to the above-described embodiment, the plurality of heat exchange tubes 12 are made of stainless steel, and the spacers 15 and 16 are made of an aluminum alloy. As long as it is made of a material having a higher thermal conductivity than the wall surfaces 21 and 22 and the material of the plurality of heat exchange tubes 12 is excellent in corrosion resistance, other materials may be used. Different materials may be used.
Moreover, although the several heat exchange tube 12 was a plate-shaped flat tube, the flat tube which has arbitrary cross-sectional shapes, such as circular, a polygon, a substantially U shape, or a substantially E shape, opposes partially. It may have at least a pair of opposing wall surfaces. The installation posture of the EGR cooler 10 is not limited to the horizontal position as shown in FIG. 1, and it is needless to say that one end side may be inclined so as to be positioned vertically above the other end side.
Furthermore, the spacers 15 and 16 can adjust the flow of the cooling water to a suitable state by suppressing the concentration of the cooling water amount in the specific passage region 14a of the cooling water passage 14 or suppressing the uneven flow. If so, the shape is not limited to a flat plate shape, and may have a plurality of holes, grooves, irregularities, and the like.
The case 11 has a substantially rectangular cross section, but may be a noncircular cross section such as a circular or oval cross section. It is also conceivable that the case 11 is directly attached to the rear end portion of the cylinder head 1h without passing through the cooling water pipe, and the cooling water passage 14 is directly connected to the water jacket of the engine 1.

  As described above, in the exhaust cooler according to the present invention, the plurality of opposing wall surfaces have a spacer on the other surface side of the opposing wall surface having a portion on the one surface side where condensed water is easily generated in the gas passage. In this way, heat is not easily taken away by the cooling water within the range in contact with the spacer, making it easy to conduct heat to each other, effectively suppressing the generation of condensed water and allowing it to evaporate quickly even if condensed water is generated. To provide an exhaust cooler that can be easily heated by the heat of the recirculated exhaust gas even when the cooling water temperature is low, and that can reliably prevent corrosion due to condensed water. It is useful for general exhaust gas coolers suitable for an EGR cooler equipped in an exhaust gas recirculation system of an internal combustion engine.

1 engine (internal combustion engine)
2 Radiator 5 Heater core 6 Exhaust heat recirculation device 9 Cooling water passage 9a, 9b Branch passage 10 EGR cooler (exhaust cooler)
DESCRIPTION OF SYMBOLS 11 Case 11a Case main-body part 11b 1st cooling water introduction pipe part 11c 2nd cooling water introduction pipe part 11d EGR gas introduction pipe part 11e EGR gas discharge pipe part 11g Cooling water discharge pipe part 11h Cooling water path 12 Heat exchange tube (Multiple flat tubes)
12E heat exchange tube (flat tube on the end side in the separation direction)
12p, 12p1, 12p2 Parallel flat tube part 13 Gas passage (EGR gas passage)
13a Gas passage (flat gas passage in the heat exchange tube)
13e, 13f Low-temperature passage portion 13g Other gas passage portion 14 Cooling water passage 14a Specific passage region 14a1 Cooling water concentration portion 14a2 Other cooling water passage portions 15, 16 Spacers 21, 22 Wall portion (opposing wall portion)
21a, 22a Low temperature wall portion 51 EGR gas passage 52 Cooling water passage 53 EGR valve e1 Cooling water outlet

Claims (7)

A gas passage forming a part of an exhaust gas recirculation passage of the internal combustion engine and a cooling water passage for passing the cooling water of the internal combustion engine are formed, and the heat exchange between the recirculated exhaust gas passing through the gas passage and the cooling water An exhaust cooler for cooling the reflux exhaust gas,
A plurality of opposing wall surfaces arranged to face the gas passage and the cooling water passage and to be separated from each other;
A spacer that is interposed between the plurality of opposing wall surfaces and is disposed in the cooling water passage, and partially restricts the flow of the cooling water in a specific passage region of the cooling water passage,
The exhaust cooler, wherein the spacer is made of a material having higher thermal conductivity than the plurality of opposed wall surface portions. The gas passage has a low temperature passage portion in which the temperature of the recirculated exhaust gas during the heat exchange is lower than the other passage portions;
2. The exhaust cooler according to claim 1, wherein the plurality of opposed wall surface portions are arranged so as to contact the low temperature passage portion on one surface side and to contact the spacer on the other surface side. The plurality of opposing wall surface portions are constituted by portions facing each other of a plurality of flat tubes that form the gas passages inside thereof, and have a low temperature wall surface portion in contact with the spacer,
A specific passage region of the cooling water passage is formed between the plurality of flat tubes;
The exhaust cooler according to claim 2, wherein the spacer is configured by a plate-like body that is sandwiched between the plurality of flat tubes and is in contact with the low-temperature wall surface portion.   The low temperature passage portion is close to a cooling water concentration portion where a flow rate of the cooling water during the heat exchange is larger than that of other cooling water passage portions in a specific passage region of the cooling water passage. The exhaust cooler according to claim 2 or claim 3. The plurality of flat tubes have three or more parallel flat tubes separated from each other in the separation direction of the plurality of opposing wall surfaces;
The low-temperature wall surface portions of the plurality of opposed wall surface portions are a first parallel flat tube portion positioned on the extreme end side in the separation direction among the parallel flat tube portions and a second parallel adjacent to the first parallel flat tube portion. The exhaust cooler according to claim 2 or 3, wherein the exhaust cooler is configured by a portion facing the flat tube portion.   The exhaust cooler according to claim 5, wherein the low temperature wall surface portions of the plurality of opposed wall surface portions are positioned on a lower side in a vertical direction among the plurality of opposed wall surface portions. The spacer is made of an aluminum-based alloy,
The exhaust cooler according to any one of claims 1 to 6, wherein the plurality of opposing wall surface portions are made of stainless steel.

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