JP2015113750A - EGR cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR cooler capable of suppressing the occurrence of crack in a ceramic heat exchanger when the heat exchanger is thermally expanded in the radial direction, while suppressing an increase in the manufacturing cost.SOLUTION: An EGR cooler (5) includes a ceramic heat exchanger (10) for EGR gas to pass therethrough, and a metallic housing (20) internally storing the heat exchanger, the heat exchanger being joined at both ends to the housing, wherein a refrigerant passage (40) is formed between the outer periphery of the heat exchanger and the inner periphery of the housing. The EGR cooler (5) further includes a constraining member (25) for constraining a portion between both ends of the heat exchanger when the heat exchanger is thermally expanded in the radial direction, the constraining member being formed integrally with the housing.

Description

  The present invention relates to an EGR cooler.

  Conventionally, an EGR cooler has been known as a device for cooling EGR gas passing through an EGR (Exhaust Gas Recirculation) passage. Patent Document 1 discloses a heat exchange device that can be applied as an EGR cooler. The heat exchange device according to Patent Document 1 includes a ceramic heat exchange element and a metal housing that houses the heat exchange element. If the heat exchange device according to Patent Document 1 is arranged in the EGR passage so that the EGR gas flows through the heat exchange body according to Patent Literature 1, the heat exchange device according to Patent Literature 1 can be used as an EGR cooler. .

  Here, the ceramic has better corrosion resistance against exhaust gas than a metal such as stainless steel. Therefore, when the heat exchanging device according to Patent Document 1 is used as an EGR cooler, it is considered that the corrosion resistance of the EGR cooler can be improved as compared with an EGR cooler having a metal heat exchanger.

International Publication No. 2010/110238

  By the way, the heat exchanging device according to Patent Document 1 has a structure in which both end portions of a ceramic heat exchanging body are joined to a metal housing. When such a heat exchange device according to Patent Document 1 is used as an EGR cooler as it is, when the EGR cooler becomes high temperature, the thermal expansion coefficient of the ceramic heat exchange element and the thermal expansion coefficient of the metal housing Due to this difference, the diameter of the intermediate part (the part between both end parts) of the heat exchange element is thermally expanded larger than the diameter of both end parts. In this case, stress concentration occurs at both ends of the heat exchange element, and as a result, cracks may occur particularly at both ends of the heat exchange element. Moreover, it is not preferable that the manufacturing cost of the EGR cooler rises in suppressing the occurrence of cracks. Therefore, it is desired to develop a technique for suppressing the occurrence of cracks in the heat exchanger while suppressing an increase in manufacturing cost, but such a technique has not been developed so far.

  An object of the present invention is to provide an EGR cooler that can suppress the occurrence of cracks in a heat exchanger when the ceramic heat exchanger is thermally expanded in the radial direction while suppressing an increase in manufacturing cost.

  An EGR cooler according to the present invention includes a ceramic heat exchanger through which EGR gas passes, and a metal housing in which the heat exchanger is accommodated, and both ends of the heat exchanger are the housing. In the EGR cooler in which a refrigerant passage is formed between the outer periphery of the heat exchange element and the inner periphery of the housing, when the heat exchange element is thermally expanded in the radial direction, the heat exchange element A restraint member that restrains a portion between both ends is provided, and the restraint member is formed integrally with the housing.

  According to the EGR cooler according to the present invention, when the ceramic heat exchanger is thermally expanded in the radial direction, the stress generated in the heat exchanger by the restraining member can be dispersed. Thereby, it can suppress that a crack generate | occur | produces in a heat exchange body. Further, according to the EGR cooler, since the restraining member is integrally formed with the housing, the number of parts of the EGR cooler can be reduced as compared with the case where the restraining member is not integrally formed with the housing. Thereby, an increase in the manufacturing cost of the EGR cooler can be suppressed.

  The said structure WHEREIN: The said restraint member may have the helical shape which restrains the part between the said both ends of the said heat exchange body helically. According to this configuration, it is possible to suppress the refrigerant in the refrigerant passage from being retained by the restraining member. Thereby, it can suppress that the cooling performance of EGR gas of an EGR cooler falls by a restraint member.

  The said structure WHEREIN: The said restraint member may restrain the part between the said both ends of the said heat exchange body before the said heat exchange body thermally expands to radial direction further. According to this structure, it can suppress that a refrigerant | coolant leaks from the clearance gap between the inner periphery of a restraint member and the outer periphery of a heat exchanger in the state before the thermal expansion of a heat exchanger. Thereby, according to this structure, a high cooling performance can be exhibited from the low temperature.

  ADVANTAGE OF THE INVENTION This invention can provide the EGR cooler which can suppress that a crack is generated in a heat exchange body, when the heat exchanger made from a ceramic is thermally expanded to radial direction, suppressing the raise of manufacturing cost.

FIG. 1A is a schematic perspective view of an EGR cooler according to the first embodiment. FIG.1 (b) is typical sectional drawing of a heat exchanger. FIG. 2A is a schematic perspective view of an EGR cooler according to a comparative example. FIG.2 (b) is typical sectional drawing which shows the mode of the heat exchange body and housing when the EGR cooler which concerns on a comparative example becomes high temperature. FIG. 3 is a schematic perspective view of an EGR cooler according to the first modification of the first embodiment. FIG. 4A is a schematic perspective view of the EGR cooler according to the second embodiment. FIG. 4B is a schematic diagram enlarging the portion A of FIG.

  Hereinafter, modes for carrying out the present invention will be described.

  An EGR cooler 5 according to Embodiment 1 of the present invention will be described. FIG. 1A is a schematic perspective view of the EGR cooler 5. In FIG. 1A, the inside of the EGR cooler 5 is seen through. The EGR cooler 5 according to the present embodiment is disposed in an EGR passage that communicates an exhaust passageway of an internal combustion engine mounted on a vehicle and an intake passageway. The EGR cooler 5 is a device that cools the EGR gas by exchanging heat between the refrigerant and the EGR gas passing through the EGR passage. Specifically, the EGR cooler 5 according to the present embodiment includes a ceramic heat exchange element 10 through which EGR gas passes and a metal housing 20 in which the heat exchange element 10 is accommodated. Further, the EGR cooler 5 includes a restraining member 25. Details of the restraining member 25 will be described later.

  The housing 20 according to the present embodiment includes a cylindrical member 21 having a substantially cylindrical shape, and a ring member 22a and a ring member 22b having a ring shape. The ring member 22a is disposed on the outer periphery of the first end portion on one side in the direction along the axis 100 of the heat exchange element 10 (hereinafter referred to as the axial direction). The inner periphery of the ring member 22 a and the outer periphery of the heat exchange element 10 are joined by a brazing material 30. The ring member 22a is fitted inside the cylindrical member 21. The ring member 22 b is disposed on the outer periphery of the second end portion on the other side in the axial direction of the heat exchange element 10. The inner periphery of the ring member 22 b and the outer periphery of the heat exchange element 10 are joined by a brazing material 30. The ring member 22b is fitted inside the cylindrical member 21. As described above, the heat exchange element 10 according to the present embodiment has both ends joined to the ring members 22 a and 22 b of the housing 20. In this embodiment, the EGR gas flows from the second end side to the first end side inside the EGR cooler 5, but the flow direction of the EGR gas is not limited to this. For example, the EGR gas may flow from the first end side to the second end side.

  In the present embodiment, the outer periphery of the housing 20 is not flat. Specifically, the outer periphery of the housing 20 according to the present embodiment is a concave portion 23 in which a portion of a restraining member 25 described later is recessed inward, and a portion corresponding to the outside of the refrigerant passage 40 of the cylindrical member 21 protrudes outward. Protrusions 24 are formed. However, the outer periphery of the housing 20 is not limited to such a configuration, and may be flat, for example.

  The material of the housing 20, specifically, the type of metal that is the material of the cylindrical member 21 and the ring members 22 a and 22 b is not particularly limited, but is preferably a metal having high corrosion resistance. As an example of such a metal, stainless steel (SUS) is used in this embodiment. The material of the brazing material 30 is not particularly limited as long as it can join the heat exchanger 10 and the ring members 22a and 22b, but in this embodiment, copper is used as an example.

  In the EGR cooler 5, a refrigerant passage 40 through which the refrigerant passes is formed between the outer periphery of the heat exchanger 10 and the inner periphery of the cylindrical member 21 of the housing 20. The cylindrical member 21 of the housing 20 is connected to a refrigerant supply passage 110 through which the refrigerant supplied to the refrigerant passage 40 passes and a refrigerant discharge passage 120 through which the refrigerant discharged from the refrigerant passage 40 passes. As an example, the refrigerant supply passage 110 according to the present embodiment is connected to the vicinity of the ring member 22a of the cylindrical member 21, and the refrigerant discharge passage 120 is connected to the vicinity of the ring member 22b of the cylindrical member 21 as an example. ing. However, the specific connection location to the cylindrical member 21 of the refrigerant supply passage 110 and the refrigerant discharge passage 120 is not limited to this. As another example, for example, the EGR cooler 5 includes a refrigerant supply passage 110 instead of the refrigerant discharge passage 120 illustrated in FIG. 1A, and the refrigerant supply illustrated in FIG. A configuration including a refrigerant discharge passage 120 instead of the passage 110 may be employed. In this case, the flow direction of the refrigerant is opposite to the flow direction of FIG.

  The heat exchanger 10 is a medium that exchanges heat between the refrigerant in the refrigerant passage 40 and the EGR gas. FIG. 1B is a schematic cross-sectional view of the heat exchange element 10. Specifically, FIG. 1B schematically illustrates a cross section of the heat exchanger 10 of FIG. 1A taken along a plane whose normal direction is the axial direction of the heat exchanger 10. The heat exchanger element 10 according to the present embodiment has a plurality of internal gas passages 11 through which EGR gas passes. The internal gas passage 11 is formed by partitioning the inside of a dense layer 12 made of dense ceramic by a plurality of partition members 13. When the EGR gas flows into the internal gas passage 11 of the heat exchange body 10, the heat of the EGR gas is conducted to the dense layer 12 through the partition wall member 13. The heat conducted to the dense layer 12 is then taken away by the refrigerant in the refrigerant passage 40. In this way, the heat exchanger 10 conducts the heat of the EGR gas to the refrigerant in the refrigerant passage 40. In addition, since the heat exchanger 10 has the dense layer 12, the refrigerant in the refrigerant passage 40 is suppressed from being mixed into the EGR gas passing through the internal gas passage 11.

  Although the specific component of the ceramic which is the material of the heat exchange element 10 (specifically, the material of the dense layer 12 and the partition wall member 13) is not particularly limited, SiC is preferable. SiC is particularly suitable as a material for the heat exchanger 10 for the EGR cooler 5 because it has good corrosion resistance against exhaust, good thermal conductivity, good workability, and low cost. is there. Therefore, in the present embodiment, as an example of the material of the heat exchange element 10, a ceramic containing SiC in the component is used. As specific examples of the ceramic containing SiC in its components, SiC (that is, a material in which no additive is added in addition to SiC), Si-impregnated SiC, (Si + Al) -impregnated SiC, metal composite SiC, or the like can be used. . In this embodiment, Si-impregnated SiC is used as an example of the material of the heat exchange element 10.

  Next, details of the restraining member 25 will be described. Referring to FIG. 1A, the restraining member 25 restrains a portion (hereinafter referred to as an intermediate portion) between both end portions of the heat exchange body 10 when the heat exchange body 10 is thermally expanded in the radial direction. It is a member. Here, in the present embodiment, the heat exchange element 10 is thermally expanded in the radial direction when the temperature of the heat exchange element 10 is equal to or higher than a predetermined temperature, so that the outer diameter of the heat exchange element 10 is It means increasing compared to a case where the temperature is lower than a predetermined temperature. The specific value of the predetermined temperature is not particularly limited, and an appropriate value may be used in consideration of the assumed use environment of the internal combustion engine on which the EGR cooler 5 is mounted.

  In addition, as described above, when the heat exchange element 10 is thermally expanded in the radial direction, the intermediate portion of the heat exchange element 10 is restrained at least when the heat exchanger 10 is thermally expanded in the radial direction. It means that the intermediate part of the heat exchanger 10 may be restrained by contacting the outer periphery of the intermediate part of the exchanger 10. Therefore, the restraining member 25 may be configured not to restrain the intermediate portion of the heat exchange body 10 in a state before the heat exchange body 10 is thermally expanded in the radial direction. However, the restraining member 25 according to the present embodiment restrains the intermediate portion of the heat exchange body 10 by contacting the intermediate portion of the heat exchange body 10 before the heat exchange body 10 thermally expands in the radial direction. That is, the restraining member 25 according to the present embodiment restrains the intermediate portion of the heat exchanger 10 from a low temperature when the temperature of the heat exchanger 10 is lower than a predetermined temperature.

  Note that, as described above, the restraining member 25 is disposed so as to restrain the intermediate portion of the heat exchange body 10, so that the restraining member 25 according to the present embodiment is a member constituting a part of the refrigerant passage 40. It also has the function of As a result, in the refrigerant passage 40 according to the present embodiment, the outer periphery of the heat exchanger 10 is the first wall portion, and the inner periphery of the cylindrical member 21 of the housing 20 is the second wall portion facing the first wall portion. The restraint member 25 is a third wall portion that connects the first wall portion and the second wall portion.

  The restraining member 25 is integrally formed with the housing 20. Specifically, the restraining member 25 according to the present embodiment is integrally formed with the cylindrical member 21 of the housing 20. The term “integrally formed” means that it is not formed by connecting separate members. Specifically, the restraining member 25 and the cylindrical member 21 according to the present embodiment are joined to the restraining member 25 and the cylindrical member 21 by a welding means such as welding or brazing material, or the restraining member 25 is installed inside the cylindrical member 21. It is not manufactured by connecting means such as fitting. The restraining member 25 and the cylindrical member 21 according to the present embodiment are manufactured by casting or pressing, or by performing cutting or the like to adjust the shape after these processing. The material of the restraining member 25 is the same metal as the material of the cylindrical member 21, specifically, stainless steel in this embodiment.

  Further, the restraining member 25 according to the present embodiment has a spiral shape that restrains the intermediate portion of the heat exchange element 10 in a spiral manner. Specifically, as shown in FIG. 1A, the restraining member 25 has a spiral shape that causes the refrigerant that has flowed into the refrigerant passage 40 from the refrigerant supply passage 110 to circulate spirally toward the second end side. doing. As a result, the refrigerant according to the present embodiment flows around the heat exchanger 10 from the first end side to the second end side of the heat exchanger 10 after flowing into the refrigerant passage 40 from the refrigerant supply passage 110. It circulates while spiraling around, and then flows into the refrigerant discharge passage 120. Since the restraining member 25 has a spiral shape, the recess 23 provided outside the restraining member 25 also has a spiral shape.

  The operation and effect of the EGR cooler 5 according to the present embodiment will be described as follows in comparison with the EGR cooler according to the comparative example. FIG. 2A is a schematic perspective view of an EGR cooler 200 according to a comparative example. The EGR cooler 200 is different from the EGR cooler 5 according to the present embodiment shown in FIG. 1A in that the restraining member 25 is not provided. The EGR cooler 200 is different from the EGR cooler 5 in that the outer periphery of the cylindrical member 21 is flat.

  FIG. 2B is a schematic cross-sectional view showing a state of the heat exchange element 10 and the housing 20 when the EGR cooler 200 according to the comparative example becomes high temperature. In addition, illustration of the cylindrical member 21 is abbreviate | omitted in FIG.2 (b). When the EGR cooler 200 reaches a high temperature, the diameter of the intermediate portion of the heat exchange body 10 is reduced at both ends due to the difference between the thermal expansion coefficient of the ceramic heat exchange body 10 and the thermal expansion coefficient of the metal housing 20. Thermal expansion is greater than the diameter of the part. Specifically, as shown in FIG. 2 (b), the heat exchange body 10 is thermally expanded so that the diameter of the central portion in the axial direction of the intermediate portion of the heat exchange body 10 becomes the largest. When the diameter of the intermediate part of the heat exchanger 10 is larger than the diameter of both ends, stress concentration occurs at both ends of the heat exchanger 10, and as a result, cracks particularly at both ends of the heat exchanger 10 occur. May occur. In order to suppress the occurrence of cracks in the heat exchange element 10, for example, a countermeasure is taken such that the intermediate part of the heat exchange element 10 is restrained by a member separate from the housing 20 such as a metal band. It is also possible. However, in this case, the manufacturing cost of the EGR cooler 200 is significantly increased.

  On the other hand, according to the EGR cooler 5 according to the present embodiment, the restraint member 25 is provided. Therefore, when the ceramic heat exchange body 10 is thermally expanded in the radial direction, the restraint member 25 causes the heat exchange body to be expanded. 10 can be dispersed. Thereby, it can control that a crack occurs in heat exchanging element 10. Further, according to the EGR cooler 5, since the restraining member 25 is integrally formed with the housing 20, the number of parts of the EGR cooler 5 can be reduced as compared with a case where the restraining member is not integrally formed with the housing 20. . Thereby, an increase in manufacturing cost of the EGR cooler 5 can be suppressed. In addition, since the restraining member 25 is integrally formed with the housing 20 in this way, it is possible to reduce the number of parts assembly steps. Also in this respect, an increase in the manufacturing cost of the EGR cooler 5 according to the present embodiment is suppressed.

  Further, according to the EGR cooler 5, since the restraining member 25 has a spiral shape, it is possible to suppress the refrigerant in the refrigerant passage 40 from being retained by the restraining member 25. Thereby, it can suppress that the cooling performance of the EGR gas of the EGR cooler 5 falls by the restraining member 25.

  The restraining member 25 according to the present embodiment restrains the intermediate portion of the heat exchange body 10 before the heat exchange body 10 thermally expands in the radial direction. However, as described above, the restraining member 25 is the heat exchange body. Before the thermal expansion of 10 in the radial direction, the intermediate portion of the heat exchanger 10 need not be constrained. If the restraint member 25 restrains the intermediate portion of the heat exchange body 10 at least when the heat exchange body 10 is thermally expanded in the radial direction, it is possible to suppress the occurrence of cracks in the heat exchange body 10. is there. However, for example, when the restraining member 25 does not restrain the intermediate portion of the heat exchanger 10 before the heat exchanger 10 expands in the radial direction, the heat exchanger 10 expands in the radial direction (that is, at a low temperature). In this case, the refrigerant may leak from the gap between the inner periphery of the restraining member 25 and the outer periphery of the heat exchange element 10. On the other hand, according to the EGR cooler 5 according to the present embodiment, the restraint member 25 restrains the intermediate portion of the heat exchange body 10 before the heat exchange body 10 thermally expands in the radial direction. It is possible to suppress leakage from the gap between the inner circumference of the restraining member 25 and the outer circumference of the heat exchange body 10 in a state before the thermal expansion of the heat exchange body 10. Thereby, the high cooling performance of EGR gas can be exhibited from a low temperature.

  Further, as described in FIG. 1A, according to the EGR cooler 5 according to the present embodiment, the concave portion 23 and the convex portion 24 are formed on the outer periphery of the housing 20, whereby the outer periphery of the housing 20 is flat. It is not. As a result, according to the EGR cooler 5, the surface area of the outer periphery of the housing 20 is larger than when the outer periphery of the housing 20 is flat. Thereby, according to the EGR cooler 5, a large contact area between the outside air and the housing 20 can be secured, so that the heat of the refrigerant in the refrigerant passage 40 can be effectively radiated to the outside air. As a result, the cooling performance of the EGR gas can be effectively improved.

(Modification 1)
FIG. 3 is a schematic perspective view of the EGR cooler 5a according to the first modification of the first embodiment. The EGR cooler 5a further includes a restraining member 25a. Further, in the EGR cooler 5 a, the connection portion of the refrigerant supply passage 110 to the housing 20 is a central portion in the axial direction of the housing 20. A refrigerant discharge passage 120a is further connected to the EGR cooler 5a. The EGR cooler 5a is different from the EGR cooler 5 shown in FIG.

  The refrigerant discharge passage 120 a is connected to the vicinity of the ring member 22 a of the cylindrical member 21. Specifically, the restraining member 25a is formed integrally with the cylindrical member 21 of the housing 20, and not only when the heat exchanging body 10 thermally expands in the radial direction but also before the heat exchanging in the radial direction. 10 is the same as the restraining member 25 in that the middle portion is restrained. The restraining member 25a is different from the restraining member 25 in the specific configuration of the spiral shape. Specifically, the restraining member 25 spirals a part of the refrigerant flowing into the refrigerant passage 40 from the refrigerant supply passage 110 toward the second end (the end on the side where the ring member 22b is disposed). In contrast to the spiral shape that circulates, the restraining member 25a has a part of the refrigerant flowing into the refrigerant passage 40 from the refrigerant supply passage 110 at the first end (the end on the side where the ring member 22a is disposed). It has a spiral shape that circulates in a spiral toward the side.

  As a result, in this modification, a part of the refrigerant flowing into the refrigerant passage 40 from the refrigerant supply passage 110 spirals around the heat exchange body 10 from the center of the heat exchange body 10 toward the second end side. And then flows into the refrigerant discharge passage 120. Further, the other part of the refrigerant that has flowed into the refrigerant passage 40 from the refrigerant supply passage 110 circulates while spirally surrounding the heat exchange body 10 from the central portion of the heat exchange body 10 toward the first end side, and thereafter. It flows into the refrigerant discharge passage 120a.

  Also in the EGR cooler 5a according to this modification, the same operational effects as those of the EGR cooler 5 according to the first embodiment described above can be achieved. Specifically, since the EGR cooler 5a also includes the restraining members 25 and 25a, when the ceramic heat exchange element 10 is thermally expanded in the radial direction while suppressing an increase in manufacturing cost, the heat exchange element 10 is cracked. Can be prevented from occurring. Also, in the EGR cooler 5a, since the restraining members 25 and 25a have a spiral shape, it is possible to suppress the refrigerant in the refrigerant passage 40 from being retained by the restraining members 25 and 25a. Thereby, the fall of the cooling performance of the EGR cooler 5a can be suppressed. Also in the EGR cooler 5a, the restraining members 25 and 25a restrain the intermediate portion of the heat exchange body 10 before the heat exchange body 10 thermally expands in the radial direction. be able to. Also in the EGR cooler 5a, since the outer periphery of the housing 20 is not flat, the heat of the refrigerant in the refrigerant passage 40 can be effectively radiated to the outside air. Thereby, cooling performance can be improved effectively.

  FIG. 4A is a schematic perspective view of an EGR cooler 5b according to the second embodiment of the present invention. The EGR cooler 5b differs from the EGR cooler 5 shown in FIG. 1 (a) in that the EGR cooler 5b is provided with a restraining member 25b instead of the restraining member 25 and further includes a bypass passage 41a and a bypass passage 41b. Yes. Since the other structure of the EGR cooler 5b is the same as that of the EGR cooler 5, detailed description thereof is omitted. The restraining member 25b is integrally formed with the housing 20, and is not only when the heat exchange body 10 is thermally expanded in the radial direction, but also before the heat exchange body 10 is thermally expanded in the radial direction. Is the same as the restraining member 25 according to the first embodiment. The restraining member 25b is different from the restraining member 25 in that it does not have a spiral shape. Specifically, the restraining member 25b according to the present embodiment has a cylindrical shape.

  FIG. 4B is a schematic diagram enlarging the portion A of FIG. 4 (a) and 4 (b), bypass passages 41a and 41b are refrigerant passages that allow the refrigerant on one side to pass to the other side in the axial direction of restraint member 25b. Specifically, the bypass passage 41a is not in contact with the cylindrical member 21 of the restraining member 25b disposed on the upstream side in the refrigerant flow direction out of the two restraining members 25b illustrated in FIG. It is provided in a portion between the outer periphery of the portion and the inner periphery of the cylindrical member 21. The bypass passage 41b is provided in a portion between the outer periphery of the portion of the restraining member 25b arranged on the downstream side in the refrigerant flow direction and not in contact with the cylindrical member 21 and the inner periphery of the cylindrical member 21. .

  Further, in the present embodiment, the bypass passage 41a on the upstream side in the refrigerant flow direction is located on one side (the lower side in FIG. 4A) with respect to the axis 100. The bypass passage 41b on the downstream side of the bypass passage 41a is located on the other side (the upper side in FIG. 4A) with respect to the axis 100. With this configuration, the refrigerant flow direction in the circumferential direction of the heat exchanger 10 is opposite before and after passing through the bypass passages 41a and 41b. Specifically, the refrigerant according to the present embodiment flows from the refrigerant supply passage 110 into the refrigerant passage 40, and then the heat exchanger 10 along the side surface on the first end side of the restraining member 25b (first restraining member). In the first circumferential direction, and then passes through the bypass passage 41a to form a portion between the restraining member 25b (first restraining member) and the restraining member 25b (second restraining member) adjacent thereto. It flows in the second circumferential direction opposite to the first circumferential direction. Thereafter, the refrigerant passes through the bypass passage 41b, flows in the first circumferential direction along the side surface on the second end side of the restraining member 25b (second restraining member), and flows into the coolant discharge passage 120.

  Since the EGR cooler 5b according to the present embodiment also includes the restraining member 25b, it is possible to disperse the stress generated in the heat exchanger 10 when the ceramic heat exchanger 10 is thermally expanded in the radial direction. Thereby, it can control that a crack occurs in heat exchanging element 10. Moreover, also in the EGR cooler 5b, since the restraining member 25b is integrally formed with the housing 20, an increase in manufacturing cost of the EGR cooler 5b can be suppressed. Also, in the EGR cooler 5b, the restraining member 25b restrains the intermediate portion of the heat exchanger 10 before the heat exchanger 10 thermally expands in the radial direction, and therefore exhibits high cooling performance from a low temperature. Can do. Also in the EGR cooler 5b, since the outer periphery of the housing 20 is not flat, the heat of the refrigerant in the refrigerant passage 40 can be effectively dissipated to the outside air, thereby effectively improving the cooling performance. Can do.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

5, 5a, 5b EGR cooler 10 Heat exchanger 20 Housing 25, 25a, 25b Restraining member 40 Refrigerant passage

Claims (3)

A heat exchanger made of ceramic through which EGR gas passes, and a metal housing that houses the heat exchanger, and both ends of the heat exchanger are joined to the housing, and the heat exchanger In an EGR cooler in which a refrigerant passage is formed between the outer periphery of the housing and the inner periphery of the housing,
When the heat exchange body is thermally expanded in the radial direction, comprising a restraining member that restrains a portion between the both ends of the heat exchange body,
The EGR cooler, wherein the restraining member is integrally formed with the housing.   The EGR cooler according to claim 1, wherein the constraining member has a spiral shape that constrains a portion between the both end portions of the heat exchange element in a spiral manner.   3. The EGR according to claim 1, wherein the restraining member restrains a portion between the both end portions of the heat exchange body before the heat exchange body is thermally expanded in a radial direction. Cooler.

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