Heat exchanger reinforcement structure

Abstract

To provide a reinforcement structure of a heat exchanger using a reinforcement member, which prevents occurrence of a crack at a connection part between a flat tube and a header plate in a heat exchanger.SOLUTION: A bend part 5c of a reinforcement member 5 comprises a notch part 5d that is shorter than a longitudinal width of a flat tube 1 of a flat part 5a. An edge 5dd of the notch part 5d is located closer to a center side of a heat exchanger core than an intersection 4b between a surface of a header plate 3 on the center side of the heat exchanger core and an outer surface of the flat tube 1 in a tube insertion hole 3a. A length x in the longitudinal direction from the intersection 4b to the edge 5dd of the notch part 5d of the reinforcement member 5 is within a range of 0.3 mm≤x≤2.7 mm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention is ideal for heat exchangers such as charge air coolers, and prevents cracks from occurring when high-temperature fluid flows inside the flat tubes, particularly at the joints between the flat tubes and the header plate. This type of heat exchanger has a heat exchanger core formed by alternately stacking flat tubes and corrugated fins, with core supports attached to both sides of the core. A high-temperature first fluid, such as charge air, flows through the flat tubes, while a second fluid, such as air, flows through the outer surfaces of the flat tubes and the corrugated fins, exchanging heat between them. When a high-temperature first fluid flows through the flat tubes, the flat tubes expand in their longitudinal direction. However, in a low-temperature environment, a temperature difference occurs between the core support and the flat tubes when the high-temperature first fluid flows inside, resulting in a thermal expansion difference. The high-temperature flat tubes attempt to expand in their longitudinal direction, but the core support restricts this expansion, generating a bending force near the joints. This causes the flat tubes to bend near their joints. This results in a large thermal stress being applied to at least one row of flat tubes at the end of the flat tubes in the parallel direction closest to the core support, causing cracks to form at the joints between the flat tubes and the header plate. [Background technology]

[0002] As mentioned above, one of the damage modes of a heat exchanger using flat tubes is the formation of cracks due to thermal stress at the longitudinal ends of the flat tubes, which causes leakage of the first fluid. As a countermeasure to this, a proposal to insert a reinforcing member into the opening of the flat tube to prevent bending of the flat tube and cracking is disclosed in Patent Document 1 listed below and elsewhere. As an example, as shown in FIG. 6A, a conventional reinforcing member 7 has a flat portion 7a, a pair of folded portions 7b bent at both ends thereof, a bent portion 7c bent between the flat portion 7a, and a pair of flange portions 7e provided on the upper edge of each folded portion 7b. 6B, the conventional reinforcing member 7 thus constructed is inserted into both the upper and lower ends of the flat tube 1 located at the end of the header plate 3, with the bent portion 7c coming into contact with the long side portion 1a of the flat tube 1. In this state, the conventional reinforcing member 7 and the flat tube 1, and the flat tube 1 and the header plate 3 are brazed together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5706666 specification Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional reinforcing structure shown in FIG. 6A, it is desirable that the conventional reinforcing member 7 is inserted into the flat tube 1 parallel to the longitudinal direction as shown in FIG. 6B. However, depending on the construction of the reinforcing member 7 and the flat tube 1, when the conventional reinforcing member 7 is inserted, the conventional reinforcing member 7 and the flat tube 1 may tilt as shown in FIG. 6C, and only the tip of the bend portion 7c may be joined in contact with the flat tube 1 as shown in FIG. 6C. This will lead to stress concentration when a high-temperature first fluid flows in a low-temperature environment, generating thermal stress. 6D, the tip of the bent portion 7c of the conventional reinforcing member 7 presses strongly against the inner surface of the flat tube 1, deforming the flat tube 1. Stress is then concentrated at the deformed portion 9 of the flat tube 1.

[0005] As a result, cracks 9a may occur in the flat tube 1 near the tip of the bent portion 7c of the conventional reinforcing member 7, which may cause leakage of the first fluid. Therefore, an object of the present invention is to solve these problems. [Means for solving the problem]

[0006] The present invention provides a heat exchanger core made of aluminum or an aluminum alloy, which includes a large number of flat tubes 1 arranged in parallel and spaced apart from each other, and a pair of header plates 3 in which both ends of each flat tube 1 are inserted into tube insertion holes 3a, and in which the flat tubes 1 and the header plates 3 are brazed together, the flat tubes 1 have a thickness of 0.3 mm to 0.6 mm, and the header plate 3 has a thickness of 1.5 mm to 3.5 mm; The flat tube 1 has a cross section perpendicular to its longitudinal direction, which has a pair of opposing long side portions 1a and a pair of short side portions 1b connecting both ends of each long side portion 1a, A reinforcing member (5) is inserted inside an end portion in the longitudinal direction of at least one flat tube (1), the reinforcing member (5) having a flat portion (5a) that is approximately aligned with the long side portion (1a), a pair of folded portions (5b) bent at both ends and approximately aligned with the short side portion (1b), and a bent portion (5c) that contacts the long side portion (1a) at the flat portion (5a) and has an arc-shaped cross section perpendicular to the longitudinal direction, and reinforcing the inner surfaces of the long side portion (1a) and the short side portion (1b) of the flat tube (1), The bent portion 5c of the reinforcing member 5 includes a notched portion 5d that is shorter than the width of the flat portion 5a in the longitudinal direction, When the reinforcing member 5 is inserted into the flat tube 1, the notch 5d is formed on the center side of the heat exchanger core, An edge 5dd of the notch 5d is located closer to the center of the heat exchanger core than an intersection 4b of the surface of the header plate 3 at the tube insertion hole 3a that is closer to the center of the heat exchanger core and the outer surface of the flat tube 1, The length x in the longitudinal direction from the intersection 4b to the edge 5dd of the notch 5d of the reinforcing member 5 is 0.3mm≦x≦2.7mm This is a reinforcing structure for a heat exchanger in the range of (see claim 1).

[0007] In the present invention, the length x is defined as: 0.7mm≦x≦2.7mm (See claim 2.)

[0008] In the present invention, the heat exchanger can be a charge air cooler (see claim 3). [Effects of the Invention]

[0009] In the present invention, in a heat exchanger core in which the thickness of the flat tubes 1 is 0.3 mm to 0.6 mm and the thickness of the header plate 3 is 1.5 mm to 3.5 mm, a notch 5d is provided in the bend portion 7c of the conventional reinforcing member 7, and its edge 5dd is brought close to the intersection 4b of the surface of the header plate 3 on the center side of the heat exchanger core at the tube insertion hole 3a and the outer surface of the flat tube 1. The length x in the longitudinal direction from the intersection 4b of the joint 4 between the header plate 3 and the flat tube 1 to the edge 5dd of the notch 5d of the reinforcing member 5 is set in the range of 0.3 mm≦x≦2.7 mm. Here, the edge 5dd of the notch 5d drawn with a solid line in Fig. 5A indicates the position of the edge 5dd where the length x is 0.3 mm, and the edge 5dd of the notch 5d drawn with a dashed line indicates the position of the edge 5dd where the length x is 2.7 mm (the flat portion 5a is not shown in this figure) (see claim 1).

[0010] Setting the upper limit of length x to 2.7 mm or less prevents edge 5dd of notch 5d of bent portion 5c from being inserted too deeply into flat tube 1. This reduces stress generated in bent portion 5c when a high-temperature first fluid flows inside in a low-temperature environment, even if reinforcing member 5 and flat tube 1 are tilted when reinforcing member 5 is inserted and only the tip of bent portion 5c is joined in contact with flat tube 1. Furthermore, the tip of bent portion 5c is prevented from pressing too hard against the inner surface of flat tube 1, preventing deformation of flat tube 1. 5C, in the range where length x exceeds 2.7 mm, when a high-temperature first fluid flows inside in a low-temperature environment, the stress generated in bent portion 5c is higher than the stress generated in short side portion 1b of flat tube 1. In contrast, when the upper limit of length x is set to 2.7 mm or less, the stress generated at the joint between bent portion 5c of flat tube 1 and reinforcing member 5 can be kept lower than the stress generated in short side portion 1b (100%), and a reinforcing effect can be obtained. On the other hand, the position of the end edge 5dd overlaps with the position of the flat tube 1 where the rigidity is increased by joining the header plate 3, creating a portion with increased rigidity and a portion of the flat tube 1 that is not in contact with either the header plate 3 or the bend 5c, and these portions are adjacent to each other. As a result, when the heat exchanger reaches a high temperature, stress concentrates at the boundary between the high-rigidity and low-rigidity portions. By setting the lower limit of the length x to 0.3 mm or more, the position of the edge 5dd of the cutout portion 5d can be positioned closer to the center of the core than the intersection 4b of the joint 4, as shown in Figure 5A, thereby reducing the change in rigidity and reducing stress concentration when the heat exchanger reaches a high temperature, thereby preventing the occurrence of cracks. As shown in FIG. 5B, when the length x is in the range of 0 mm to less than 0.3 mm, the stress increases sharply as the length x approaches 0. However, by setting the lower limit of the length x to 0.3 mm or more, stress concentration can be avoided.

[0011] In the present invention, the length x is defined as: The range of x can be 0.7 mm≦x≦2.7 mm (see claim 2). This makes it possible to further avoid stress concentration when the heat exchanger reaches a high temperature by making the lower limit of length x greater than 0.3 mm and positioning edge 5dd of notch 5d closer to the center of the core than intersection 4b of joint 4. Also, fillets 4a made of brazing material are formed at joints 4 between the header plate 3 and flat tubes 1 by brazing, but in a heat exchanger in which the thickness of the flat tubes 1 is 0.3 mm to 0.6 mm and the thickness of the header plate 3 is 1.5 mm to 3.5 mm, setting the lower limit of length x to 0.7 mm can reduce stress concentration even when taking into account the increased rigidity due to fillets 4a.

[0012] The present invention can be applied to a charge air cooler (see claim 3). Therefore, the effects of the invention as set forth in claims 1 and 2 can also be obtained in a charge air cooler. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an exploded perspective view of a main part of a reinforcement structure for a heat exchanger according to the present invention; [Figure 2] Cross-sectional view of line II-II in Figure 1. [Figure 3A] Enlarged view of the main part of Figure 2. [Figure 3B] Enlarged view of part B in Figure 3A. [Figure 4A] FIG. 2 is a front view of a reinforcing member 5 of the present invention. [Figure 4B] The same bottom view. [Figure 5A] 10 is an explanatory diagram of each length x from the intersection 4b of the joint 4 to the edge 5dd of the notch 5d of the bent portion 5c. FIG. [Figure 5B] This is a relationship diagram between the length x from the intersection 4b of the joint 4 to the edge 5dd of the notch 5d of the bend 5c and the ratio of the stress generated at the bend 5c to the stress when the heat exchanger becomes hot and the length x is long. [Figure 5C] 10 is a graph showing the relationship between the length x from the intersection 4b of the joint 4 to the edge 5dd of the notch 5d of the bend 5c and the ratio of the stress generated in the bend 5c to the stress generated in the short side 1b in a low-temperature environment. [Figure 6A] FIG. 10 is a perspective view of a conventional reinforcing member 7, illustrating how it is inserted into the end of a flat tube 1 of a heat exchanger. [Figure 6B] BB arrow cross-sectional view of FIG. 6A. [Figure 6C] 6B, and is an explanatory diagram of a gap 8 formed when the flat tube 1 and the conventional reinforcing member 7 provided at the end of the flat tube 1 are tilted during insertion. FIG. [Figure 6D] 6B is an explanatory diagram showing how the tip of the bent portion 7c of the conventional reinforcing member 7 deforms the flat tube 1 at the same location as FIG. 6B. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a main part of the reinforcement structure of a heat exchanger of the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, FIG. 3A is an enlarged view of a main part of FIG. 2, FIG. 3B is an enlarged view of part B in FIG. 3A, FIG. 4A is a front view of a reinforcement member 5 used in the same embodiment, and FIG. 4B is a bottom view thereof. As shown in Fig. 4A, the reinforcing member 5 of this embodiment has a flat portion 5a, a pair of folded portions 5b formed at both ends of the flat portion 5a that approximately align with the short side portion 1b of the flat tube 1, and a bent portion 5c formed in the center of the flat portion 5a as shown in Fig. 4B. The folded portion 5b has a flange 5e formed near the short side portion 1b of the flat tube 1 for hooking the reinforcing member 5.

[0015] The reinforcing member 5 of this embodiment differs from the known conventional reinforcing member 7 shown in Figures 6A to 6D in that, as shown in Figure 4A, a notch 5d is formed in the center of the flat portion 5a by cutting out a part of the bent portion 5c. That is, as shown in Figures 2, 3A, and 3B, the notch 5d is formed on the center side of the heat exchanger core when the reinforcing member 5 is inserted into the flat tube 1. Note that Figures 3A and 3B omit the flat portion 5a of the reinforcing member 5.

[0016] As shown in FIG. 1, the heat exchanger of this embodiment has a core formed by alternately stacking flat tubes 1 and corrugated fins 2, and core supports 6 are joined to both sides of the core. Both ends of each flat tube 1 are inserted into a tube insertion hole 3a of the header plate 3. The edge of the tube insertion hole 3a has a burring portion 3aa that protrudes away from the center of the heat exchanger core. At the intersection 4b of the connection portion 4 between the flat tube 1 and the header plate 3, a fillet portion 4a is formed, as shown in FIG. 3B.

[0017] The reinforcing member 5 is inserted into an opening of the flat tube 1 located at the end of the flat tube 1 in the parallel direction. When the reinforcing member 5 is inserted, the reinforcing member 5 is inserted into the opening of the flat tube 1 in a state in which the portions between the folded-back portions 5b at both ends of the reinforcing member 5 are compressed toward the bent portions 5c, and by releasing this compressed state, the folded-back portions 5b come into contact with the short side portions 1b of the flat tube 1. The bent portion 5c of the reinforcing member 5 contacts the long side portion 1a of the flat tube 1, as shown in FIG. In this state, the contacting portions of the components are brazed together.

[0018] Figure 5A is an explanatory diagram of the longitudinal length x of each flat tube 1 from the intersection 4b of the joint 4 on the heat exchanger core side to the edge 5dd of the notch 5d of the bend 5c, Figure 5B is a diagram showing the relationship between the longitudinal length x of the flat tube 1 from the intersection 4b of the joint 4 to the edge 5dd of the notch 5d of the bend 5c and the ratio of the stress generated at the bend 5c to the stress when the length x is long, and Figure 5C is a diagram showing the relationship between the length x from the intersection 4b of the joint 4 to the edge 5dd of the notch 5d of the bend 5c and the ratio of the stress generated at the bend 5c to the stress generated at the short side 1b when a high-temperature first fluid flows inside the flat tube 1 in a low-temperature environment. In addition, in FIG. 5A, the flat portion 5a of the reinforcing member 5 is not shown. 5A to 5C do not take into consideration the fillet portions 4a formed at the intersections 4b of the joints 4. The figures show the relationship between the longitudinal length x of the flat tubes 1 from the intersections 4b on the center side of the heat exchanger core to the edge 5dd of the notch 5d of the reinforcing member 5, excluding the fillet portions 4a formed at the intersections 4b of the joints 4 between the header plate 3 and the flat tubes 1. 5A, the reinforcing member 5 is inserted so that the edge 5dd of the notch 5d is positioned further toward the center of the core than the intersection 4a, on the center side of the core, of the joint 4 between the flat tube 1 and the header plate 3. Here, the solid line in Fig. 5A indicates the position of the edge 5dd where the length x is 0.3 mm, and the dashed line indicates the position of the edge 5dd where the length x is 2.7 mm. Stress concentration is alleviated in the range of 0.3 mm≦x≦2.7 mm.

[0019] As shown in FIG. 5B, when the length x is in the range of 0 mm to less than 0.3 mm, as the length x approaches 0, the stress in the bent portion 5c increases rapidly when the heat exchanger reaches a high temperature state. However, by setting the lower limit of x to 0.3 mm or more, it is possible to avoid a rapid change in rigidity. 5C, when length x exceeds 2.7 mm, the stress is higher than that at short side 1b of flat tube 1, and the thermal stress generated in this area increases when a high-temperature first fluid flows inside flat tube 1 in a low-temperature environment. When the upper limit of length x is set to 2.7 mm or less, the stress generated at the joint between flat tube 1 and bent portion 5c of reinforcing member 5 can be kept lower than the stress (100%) generated at short side 1b. This avoids stress concentration due to changes in rigidity occurring at the bent portion 5c of the flat tube 1 and the reinforcing member 5, thereby preventing the occurrence of cracks. At the same time, the stress generated in the bent portion 5c of the present invention can be kept smaller than the stress generated in the bent portion 7c of the conventional reinforcing member 7, thereby reducing deformation of the flat tube 1 due to thermal stress and maintaining the reinforcing effect.

[0020] The range of the value of the length x in this embodiment can be 0.7 mm≦x≦2.7 mm. This makes it possible to further avoid stress concentration that occurs when the heat exchanger is in a high temperature state by making the lower limit of the length x greater than 0.3 mm and shifting the position where the stiffness of the end of the flat tube 1 changes due to the reinforcing member 5. Also, by brazing, a fillet portion 4a is formed by the brazing material at the joint 4 between the header plate 3 and the flat tube 1, By setting the lower limit of the length x to 0.7 mm, stress concentration can be reduced even when the increase in rigidity due to the fillet portion 4a is taken into consideration. [Industrial Applicability]

[0021] The present invention can be used as a heat exchanger such as a charge air cooler. [Explanation of symbols]

[0022] 1 Flat tube 1a Long side 1b Short side 2 Fins 3 Header Plate 3a Tube insertion hole 3aa Burring section 4 Joint 4a Fillet part 4b intersection 5 Reinforcing members 5a Flat area 5b Folded part 5c Bend 5d Notch 5dd edge 5e Tsubabe

[0023] 6 Core Support 7 Conventional reinforcement members 7a Flat area 7b Folded part 7c Bend 7e Tsubabe 8. Gap 9 Deformation section 9a Crack x: The length in the longitudinal direction of the flat tube 1 from the intersection 4b of the central surface of the heat exchanger core and the outer surface of the flat tube 1 to the edge 5dd of the notch 5d of the reinforcing member 5

Claims

1. A heat exchanger core made of aluminum or an aluminum alloy, comprising a number of flat tubes (1) arranged in parallel and spaced apart from one another, and a pair of header plates (3) in which both ends of each flat tube (1) are inserted into tube insertion holes (3a), and the flat tubes (1) and the header plates (3) are brazed together, The thickness of the flat tube (1) is 0.3 mm to 0.6 mm, and the thickness of the header plate (3) is 1.5 mm to 3.5 mm, The flat tube (1) has a cross section perpendicular to its longitudinal direction, which has a pair of opposing long side portions (1a) and a pair of short side portions (1b) connecting both ends of each long side portion (1a), A reinforcing member (5) is inserted inside an end portion of at least one flat tube (1) in the longitudinal direction, The reinforcing member (5) has a flat portion (5a) that is approximately aligned with the long side portion (1a), a pair of folded portions (5b) that are bent at both ends and are approximately aligned with the short side portion (1b), and a bent portion (5c) that is in contact with the long side portion (1a) at the flat portion (5a) and has an arc-shaped cross section perpendicular to the longitudinal direction, and the reinforcing member (5) has a flat portion (5a) that is approximately aligned with the long side portion (1a), and the reinforcing member (5) has a flat portion (5a) that is approximately aligned with the short side portion (1b), and the reinforcing member (5) has a flat portion (5a) that is in contact with the long side portion (1a), and a bent portion (5c) that is arc-shaped in cross section perpendicular to the longitudinal direction, and the reinforcing member (5) reinforces the inner surfaces of the long side portion (1a) and the short side portion (1b) of the flat tube (1). the vent portion (5c) of the reinforcing member (5) is provided with a notch portion (5d) that is shorter than the width of the flat portion (5a) in the longitudinal direction, and the notch portion (5d) is formed on the center side of the heat exchanger core when the reinforcing member (5) is inserted into the flat tube (1); an edge (5dd) of the notch (5d) is located closer to the center of the heat exchanger core than an intersection (4b) of the surface of the header plate (3) at the tube insertion hole (3a) that is closer to the center of the heat exchanger core and the outer surface of the flat tube (1); The length x in the longitudinal direction from the intersection (4b) to the edge (5dd) of the notch (5d) of the reinforcing member (5) is 0.3mm≦x≦2.7mm Reinforcement structure for heat exchangers in the range.

2. The reinforcing structure for a heat exchanger according to claim 1, The length x is 0.7mm≦x≦2.7mm Reinforcement structure for heat exchangers in the range.

3. The reinforcement structure for a heat exchanger according to claim 1 or 2, The heat exchanger is a reinforced structure that is a charge air cooler.

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