Method for joining metal members and joined metal members
By clamping a first metal member with a second member and using a bent portion on the first member to absorb thermal expansion, the method addresses thermal deformation issues, improving joint strength and alignment in metal member joining.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- RYOBI
- Filing Date
- 2024-03-29
- Publication Date
- 2026-05-29
Smart Images
Figure 0007867516000001 
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for joining metal members to each other and a joined body.
Background Art
[0002] When two metal members are overlapped and joined by, for example, laser welding, among the two members, particularly the first member on the laser irradiation side is likely to be thermally deformed by heating. That is, there is a problem that the first member is likely to thermally expand or thermally contract during laser irradiation, and the joining planned position is likely to be displaced. There is a limit to firmly clamping the first member and the second member to prevent the displacement of the first member. Also, even if it can be firmly clamped, there is a risk that distortion may occur in the first member or residual stress may occur, and the desired joining strength may not be obtained.
[0003] In Patent Document 1 below, a method of overlapping two zinc-based plated steel sheets and laser welding them has been proposed. In this method, the welding planned portion of the first member on the laser irradiation side is preliminarily curved and deformed toward the torch side, and a gap is formed between the members at the welding planned portion by the curved portion of the first member. However, since a gap is generated between the members at the welding planned portion, heat is difficult to be transmitted to the second member on the side opposite to the torch.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] An object of the present invention is to improve the joining strength.
Means for Solving the Problems
[0006] The present invention relates to a method for joining metal members, in which a first metal member and a second metal member are overlapped and clamped at a clamping point, and the first and second members are joined by heating them from the first member side at a joining point away from the clamping point, wherein, prior to joining, an excess portion is provided in the first member at a position between the joining point and the clamping point to absorb thermal deformation during joining.
[0007] In this method, the temperature rises from the first member side during joining. A typical example of heating from the first member side during joining is welding by irradiating the first member with laser light, in which case the temperature rise of the first member will be greater than that of the second member. In addition to laser welding, other joining methods include, for example, friction stir welding. In the case of friction stir welding, the tool is pressed from the first member side.
[0008] The following explanation uses laser welding as an example. When a laser is irradiated from the first member towards the joint, the temperature of the first member rises rapidly, and the first member expands due to thermal expansion. The first member and the second member are clamped at the clamp point, but the first member expands in the region between the joint point and the clamp point. In the region between the joint point and the clamp point, the first member tries to stretch from the joint point towards the clamp point, but because an excess portion is provided at the position between the joint point and the clamp point, the excess portion absorbs the stretching of the first member. Therefore, it is possible to prevent excessive stress from acting on the clamp point. It is also possible to suppress displacement of the clamp point. When the welding process is completed, the first member shrinks as the temperature drops. At that time, the absorbed portion in the excess portion that was absorbed during joining acts as a buffer, and the first member smoothly returns to its original state. Therefore, even when the first member shrinks, excessive stress is not placed on the clamp point. As a result, it is possible to suppress the occurrence of large residual stress or distortion in the first member after joining, enabling accurate joining and ensuring the desired joint strength.
[0009] In particular, the excess portion is preferably a bent portion that protrudes in the direction of overlap between the first and second members. With this method, when the first member expands and contracts due to heat, the bent portion changes its bent shape, so that the thermal deformation of the first member can be absorbed smoothly and reliably.
[0010] In particular, it is preferable that the joint portion has a shape that extends along a predetermined direction, and the bent portion is a bent projection that extends along the extension direction of the joint portion. With this method, when joining the joint portions along a predetermined direction, the bent projection deforms smoothly to expand and contract the spacing of its openings. Therefore, the joint portion can be accurately formed along a predetermined direction.
[0011] Furthermore, a recess is provided on the surface of the second member that faces the first member, and the bent ridge protrudes toward the second member. When overlapping the first and second members, it is preferable to insert the bent ridge into the recess and bring the side of the bent ridge furthest from the joining point into contact with the wall of the recess. According to this method, when joining the first and second members, the bent ridge is inserted into the recess and the side of the bent ridge furthest from the joining point into contact with the wall of the recess. Therefore, the bent ridge can be used for positioning, and the first member can be accurately overlapped with the second member at a predetermined position. Moreover, when the first member expands due to heat during joining, the side of the bent ridge is in contact with the wall of the recess, so the bent ridge deforms in a way that reliably shrinks its opening. Therefore, the thermal deformation of the first member can be smoothly and reliably absorbed by the bent ridge.
[0012] Furthermore, it is preferable to interpose a sealing material between the bent ridge and the wall surface of the recess. Interposing a sealing material in this way improves the airtightness between the first member and the second member. Therefore, it is suitable, for example, when a medium such as liquid is placed in the recess. Moreover, even if the joint is discontinuous, for example, divided in a part along its extension direction, airtightness can be easily ensured.
[0013] Furthermore, the metal member joint according to the present invention is a metal member joint in which a first metal member and a second metal member are overlapped and a joint is provided which is heat-bonded from the first member side, wherein a bent portion is provided on the first member at a location away from the joint so as to protrude toward the second member, and a recess is provided on the surface of the second member on the side facing the first member, the bent portion fits into the recess, and the side of the bent portion furthest from the joint abuts against the wall surface of the recess. Note that heat bonding includes laser welding as well as friction stir welding, etc.
[0014] With this configuration, the side of the bent portion furthest from the joint contacts the wall surface of the recess, ensuring accurate positioning between the first and second members. Furthermore, during heat joining such as laser welding, the bent portion smoothly absorbs the thermal deformation of the first member. As a result, it is possible to suppress large residual stresses and strains in the joint, thereby ensuring joint strength. [Effects of the Invention]
[0015] As described above, the thermal deformation of the first member between the joining point and the clamping point during joining is absorbed by the excess portion, thereby improving the joint strength. [Brief explanation of the drawing]
[0016] [Figure 1] A cross-sectional view showing the main part of the joint in one embodiment of the present invention. [Figure 2] A cross-sectional view showing the joining process of the jointed body. [Figure 3] A cross-sectional view showing the joining process of the jointed body. [Figure 4] A cross-sectional view showing the state of the joint after it has been joined. [Figure 5] (a) and (b) are enlarged views of the main parts of Figure 4. [Figure 6] (a) and (b) are cross-sectional views of the main parts of the joint in another embodiment of the present invention. [Figure 7] A cross-sectional view showing the joining process of a joint in another embodiment of the present invention. [Figure 8] Cross-sectional view showing the main part of the first member in another embodiment of the present invention. [Figure 9] (a) to (c) are cross-sectional views showing the main part of the first member in another embodiment of the present invention. [Figure 10] Cross-sectional view showing the main part of the first member in another embodiment of the present invention.
Mode for Carrying Out the Invention
[0017] Hereinafter, a joining method and a joined body according to an embodiment of the present invention will be described with reference to the drawings. The joined body is made of metal. The joined body is formed by joining two metal members. That is, the joined body includes a first member and a second member made of metal, and the first member and the second member are joined and integrated at a predetermined joining location. The forms of the joined body, the first member, and the second member may be various. In this embodiment, as an example, the case where the joined body is a battery case will be described.
[0018] As shown in FIG. 1, the battery case is for accommodating a plurality of batteries 3. The upper surface of the battery case is open, and the batteries 3 are inserted into the battery case through the upper surface opening. The battery case includes a bottomed case body 2 having an upper surface opening, and a bottom cover 1 attached to the lower surface of the case body 2 from below. The case body 2 is made by casting, specifically die-cast, and more specifically made of aluminum die-cast. The bottom cover 1 is plate-shaped and is preferably made of an aluminum expanded material. The case body 2 is the second member, and the bottom cover 1 is the first member.
[0019] To describe the details of the case body 2, the case body 2 has a storage space for housing batteries 3, and the storage space can accommodate one or more batteries 3. The number of batteries 3 to be housed is arbitrary. The case body 2 is, for example, rectangular in plan view. The case body 2 comprises a bottom portion 10 and side portions 11 that rise upward from the periphery of the bottom portion 10. The batteries 3 are placed on the upper surface of the bottom portion 10. A recess 12 that opens downward is formed on the lower surface of the bottom portion 10. The recess 12 can be used as a cooling space.
[0020] The lower surface of the bottom portion 10 has a mounting surface portion 13 provided around the recess 12 and a placement surface portion 15 provided outside the mounting surface portion 13 via a stepped portion 14. The mounting surface portion 13 is provided at the opening edge of the recess 12 and encircles the recess 12. The bottom cover 1 is mounted on top of the mounting surface portion 13. The placement surface portion 15 is located below the mounting surface portion 13. The placement surface portion 15 constitutes the peripheral edge of the lower surface of the bottom portion 10. The placement surface portion 15 is the part that becomes the legs when the battery case is placed on the placement surface P and contacts the placement surface P. Preferably, the vertical dimension between the placement surface portion 15 and the mounting surface portion 13 is greater than the thickness of the bottom cover 1, and preferably the placement surface portion 15 is located below the bottom cover 1, so that the bottom cover 1 does not contact the placement surface P when the battery case is placed on the placement surface P. Furthermore, the bottom cover 1 and the mounting surface 15 may be flush with each other.
[0021] By attaching the bottom cover 1 to the bottom surface 10 of the case body 2, the lower opening of the recess 12 is closed. The recess 12 of the case body 2 and the bottom cover 1 form a cooling passage. A coolant for cooling the battery 3 flows through the cooling passage. The configuration of the recess 12 is arbitrary, but as an example, the recess 12 extends along the direction normal to the paper (depth and front direction) in Figure 1. The direction normal to the paper in Figure 1 is simply referred to as the direction normal to the paper. In addition, a partition wall 20 is provided projecting downward from the lower surface of the bottom surface 10 to form the recess 12 and to divide the recess 12 into left and right sections. Both sides of the partition wall 20 constitute the wall surface of the recess 12. The lower surface of the partition wall 20 constitutes the mounting surface 13.
[0022] The partition wall 20 extends in the direction normal to the plane of the paper. It is preferable that the cooling passages reciprocate in the direction normal to the plane of the paper, with one of the cooling passages on the left and right sides of the partition wall 20 being the forward path and the other being the return path. It is also preferable that ribs 21 are provided projecting downward from the lower surface of the bottom portion 10. The ribs 21 are formed parallel to the partition wall 20 and preferably formed in the center of each cooling passage. The amount of protrusion of the ribs 21 is smaller than the amount of protrusion of the partition wall 20. A pair of communication holes 22 are formed at the lower part of the side portion 11. One communication hole 22 is for the refrigerant inlet, and the other communication hole 22 is for the refrigerant outlet. Refrigerant is sent into the cooling passage from the inlet communication hole 22 and discharged from the outlet communication hole 22.
[0023] The bottom cover 1 is joined to the case body 2 by laser welding. The battery case is formed by overlapping the case body 2 and the bottom cover 1 and welding them together. A joint is formed at the welded location, and a weld bead is formed at the joint. The locations where the joint is formed, i.e., the joint locations, may vary, but in this embodiment, they are the partition wall 20 and both ends of the bottom cover 1. The location of the partition wall 20 is the first joint location 51, and the first joint 61 is formed at the location of the partition wall 20. Both ends of the bottom cover 1 are the second joint locations 52, and the second joint 62 is formed at both ends of the bottom cover 1. The first joint 61 is an overlap weld, and the second joint 62 is an overlap fillet weld. The first joint 61 and the second joint 62 have a shape that extends along a predetermined direction, and the direction of extension is the direction normal to the plane of the paper.
[0024] The bottom cover 1 has a first surface 1a, which is a first plate surface, and a second surface 1b, which is a second plate surface facing the first surface 1a. Of the first surface 1a and the second surface 1b of the bottom cover 1, the first surface 1a is the surface facing the case body 2. That is, the first surface 1a is the surface facing upwards when the battery case is in place. The first surface 1a is superimposed on the lower surface of the bottom portion 10 of the case body 2. When the battery case is in place, the first surface 1a of the bottom cover 1 is the upper surface of the bottom cover 1, and the second surface 1b is the lower surface. More specifically, the bottom cover 1 is attached to the mounting surface 13 of the lower surface of the bottom portion 10 of the case body 2, and the first surface 1a of the bottom cover 1 is superimposed on the mounting surface 13 of the case body 2.
[0025] Near both ends of the bottom cover 1, there are bent ridges 30 that are bent upwards. In this embodiment, the bent ridges 30 are the bent portion and the excess portion. The bent ridges 30 are bent in half toward the upwards, that is, toward the case body 2. The bent ridges 30 are formed so that the first surface 1a side of the bottom cover 1 is convex. The cross-sectional shape of the bent ridges 30 can vary, but in this embodiment it is U-shaped, and the folded portion 30a of the bent ridge 30 is curved. The bent ridges 30 have a ridge opening 30b that opens toward the second surface 1b side.
[0026] The folded ridge 30 is provided at a distance from the first joint 61 in the horizontal direction (a direction perpendicular to the direction normal to the paper plane and the overlapping direction). The folded ridge 30 extends along the recess 12, that is, it is formed along the direction normal to the paper plane. The direction of extension of the folded ridge 30 is the direction of extension of the first joint 61. The folded ridge 30 is recessed into the recess 12. The amount of protrusion of the folded ridge 30 is less than the amount of recess in the recess 12.
[0027] Of the two sides of the bent projection 30, the side furthest from the first joint 61 is designated as the first side 30c, and the side closer to the first joint 61 is designated as the second side 30d. Furthermore, of the walls of the recess 12, the wall facing the partition wall 20 is designated as the first wall 12a, and the wall opposite the partition wall 20 is designated as the second wall 12b. Note that the first wall 12a of the recess 12 constitutes the side of the partition wall 20.
[0028] The first side surface 30c of the folded ridge 30 abuts against the second wall surface 12b of the recess 12. The contact between the first side surface 30c of the folded ridge 30 and the second wall surface 12b of the recess 12 is preferably a line contact along the direction normal to the paper, and more preferably a surface contact. In this embodiment, both the second wall surface 12b of the recess 12 and the folded ridge 30 are formed continuously along the direction normal to the paper. Therefore, it is preferable that the first side surface 30c of the folded ridge 30 and the second wall surface 12b of the recess 12 are in continuous contact along the direction normal to the paper. However, for example, there may be discontinuous portions in the folded ridge 30 or discontinuous portions in the second wall surface 12b of the recess 12.
[0029] Figure 2 shows the state before joining. In Figure 2, the case body 2 is shown upside down, with the bottom surface 10 of the case body 2 facing upwards. The bottom cover 1 has a pre-formed bent projection 30 before joining. Then, as shown in Figure 3, the bottom cover 1 is placed on top of the mounting surface 13 on the bottom surface 10 of the case body 2. At this time, the first side surface 30c of the bent projection 30 is brought into contact with the second wall surface 12b of the recess 12, and the bent projection 30 is inserted into the recess 12. By bringing the first side surface 30c of the bent projection 30 into contact with the second wall surface 12b of the recess 12 in this way, the bottom cover 1 is positioned relative to the case body 2. In particular, in Figure 2, the left-right positioning of the bottom cover 1 relative to the case body 2 can be performed. Therefore, the bottom cover 1 can be easily and accurately placed on top of the case body 2. Furthermore, since the folded projection 30 of the bottom cover 1 fits into the recess 12 of the case body 2, the bottom cover 1 is less likely to shift position and less likely to come off the case body 2. In other words, the bottom cover 1 is temporarily fixed to the case body 2. Therefore, when clamping the bottom cover 1 to the case body 2 in the next step, it can be easily clamped.
[0030] With the bottom cover 1 placed on top of the case body 2, the bottom cover 1 and the case body 2 are clamped together from above and below. The clamping points 70 are indicated by arrows in Figure 3. The clamping points 70 are near the second wall surface 12b of the recess 12 and are at both ends of the bottom cover 1. With the bottom cover 1 clamped to the case body 2 in this manner, the laser 100 is shone onto the joint. The laser 100 is shone from the second surface 1b side of the bottom cover 1. First, the first joint point 51 is joined, and then the second joint point 52 is joined.
[0031] By irradiating the bottom cover 1 at the first joint 51 with the laser 100, the bottom cover 1 is heated with the first joint 51 as the center. Because the laser 100 is irradiating the bottom cover 1, the temperature of the bottom cover 1 rises rapidly and becomes hotter than that of the case body 2. As the temperature of the bottom cover 1 rises, the bottom cover 1 stretches in the left-right direction between the first joint 51 and the clamp 70. That is, the bottom cover 1 stretches from the first joint 51 outwards to both the left and right sides. The stretching of the bottom cover 1 is absorbed by the bent ridge 30. The bent ridge 30 deforms so as to contract its ridge opening 30b, thereby absorbing the stretching of the bottom cover 1. In particular, since the first side surface 30c of the bent ridge 30 is in contact with the second wall surface 12b of the recess 12, the bent ridge 30 deforms to contract smoothly. In this way, the bent ridge 30 contracts to narrow the width of the ridge opening 30b, absorbing the expansion of the bottom cover 1, so that no excessive stress is applied to the clamping point 70. Once the joining of the first joint point 51 is complete, the temperature of the bottom cover 1 at the first joint point 51 decreases. As the temperature of the bottom cover 1 decreases, the bottom cover 1 contracts in the opposite direction, and at that time, the bent ridge 30 deforms in the opposite direction to widen the ridge opening 30b. Therefore, the bottom cover 1 can smoothly return to its original state. After joining the first joint point 51 in this manner, the second joint point 52 is joined, and the bottom cover 1 is joined to the case body 2 as shown in Figure 4.
[0032] Figure 5(a) shows an enlarged view of the first joint 61. If the first joint 61 is formed to protrude downward (upward in the drawing) from the second surface 1b of the bottom cover 1, as shown by the dashed line, the protruding portion 61a that bulges out from the second surface 1b of the bottom cover 1 may be cut off after the joining process. However, if the protruding portion 61a of the first joint 61 does not protrude beyond the mounting surface 15, the protruding portion 61a does not need to be cut off. Figure 5(b) shows an enlarged view of the second joint 62. Similarly, in the second joint 62, the protruding portion 62a that bulges out from the second surface 1b of the bottom cover 1 may be cut off, but if the protruding portion 62a does not protrude beyond the mounting surface 15, the protruding portion 62a does not need to be cut off.
[0033] Alternatively, as shown in Figure 6, a sealing material 65 may be interposed between the folded ridge 30 and the second wall surface 12b of the recess 12. In the case of Figure 6(a), after casting the case body 2, a groove 66 is formed in the second wall surface 12b of the recess 12 by post-processing, and the sealing material 65 is interposed in the groove 66. By interposing the sealing material 65, the airtightness between the first side surface 30c of the folded ridge 30 and the second wall surface 12b of the recess 12 is improved. Alternatively, as shown in Figure 6(b), a chamfered portion 67 may be provided at the corner of the second wall surface 12b of the recess 12, and the sealing material 65 may be interposed in the chamfered portion 67. In this case, the chamfered portion 67 can be formed when casting the case body 2. However, the chamfered portion 67 may also be formed by post-processing.
[0034] In the above embodiment, the bent ridge 30 is projected toward the second member, but conversely, as shown in Figure 7, when overlapping the first member 81 and the second member 82 to form one or more third joints 83, the bent ridge 30 may be projected toward the opposite side from the second member 82. Furthermore, as shown by the dashed line in Figure 7, an auxiliary clamping point 70 may be provided in the left-right center of the first member 81.
[0035] Furthermore, the direction of the bent protrusions 30 may be mixed between those that protrude towards the second member 82 and those that protrude on the opposite side of the second member 82. For example, as shown in Figure 8, the first member 81 may be alternately provided with a first bent protrusion 85 that protrudes in the first overlapping direction and a second bent protrusion 86 that protrudes in the second overlapping direction, which is on the opposite side of the first direction. In that case, the first member 81 may be formed in a corrugated shape in cross-section by continuously forming the second bent protrusion 86 next to the first bent protrusion 85.
[0036] Furthermore, the folded portion 30a of the folded ridge 30 does not have to be curved. For example, as shown in Figure 9(a), the folded portion 30a of the folded ridge 30 may be pointed, and the folded ridge 30 may have a V-shape in cross-section. Also, as shown in Figure 9(b), the folded ridge 30 may have a U-shape in cross-section. As shown in Figure 9(c), U-shaped folded ridges 30 may be formed continuously, and the protruding directions of adjacent U-shaped folded ridges 30 may be opposite to each other. Moreover, as shown in Figure 10, a folded step portion 90 may be provided on the first member 81 as a folded portion, and the first member 81 may have an upper step portion 91 and a lower step portion 92 via the folded step portion 90. Thus, the shape of the folded portion can be varied. Also, for example, an uneven portion may be formed by embossing a predetermined location on the first member 81, and this uneven portion may be used as an excess portion.
[0037] As mentioned above, the shapes of the first member 81 and the second member 82 can vary; for example, both the first member 81 and the second member 82 may be plate-shaped. [Explanation of Symbols]
[0038] 1. Bottom cover (first component) 1a 1st page 1b 2nd side 2. Case body (second component) 3 Batteries 10 Bottom part 11 Side part 12 recesses 12a First wall 12b Second wall 13 Mounting surface 14 Stepped section 15 Placement surface 20 Bulkhead 21 Ribs 22 Communication hole 30. Folded protrusions (folded portion, excess portion) 30a Folded section 30b Projection opening 30c 1st side 30d Second side 51. First joint 52 Second joint 61 1st joint 61a Bulge 62 Second joint 62a Bulge 65 sealing material 66 Groove 67 Chamfered section 70 clamping points 81 First Member 82 Second Member 83 Third joint 85 First Folding Protrusion 86. Second Folding Protrusion 90 Folded section (folded part, excess part) 91 Upper step 92 step bottom 100 lasers P mounting surface
Claims
1. A method of joining a first metal member and a second metal member by overlapping them and clamping them at a clamping point, and then heating the first metal member from the first metal member side at a joint point away from the clamping point, Before joining, an excess portion is provided in the first member at the position between the joining point and the clamping point to absorb thermal deformation during joining. The excess portion is a bent portion that is bent so as to protrude in the direction in which the first member and the second member overlap. The joint has a shape that extends along a predetermined direction. The bent portion is a bent projection that extends along the direction of extension of the joint. A recess is provided on the surface of the second member that is on the side of the first member. The bent ridge protrudes toward the second member side. When overlapping the first and second members, the folded projection is inserted into the recess, and the side of the folded projection furthest from the joint is brought into contact with the wall of the recess. A method for joining metal members, comprising interposing a sealing material between a bent ridge and the wall surface of a recess.
2. A metal member joint comprising a first metal member and a second metal member superimposed on each other, with a joint formed by heat bonding from the first member side, A bent portion is provided in the first member at a location away from the joint, so as to protrude toward the second member. The joint has a shape that extends along a predetermined direction. The bent portion is a bent projection that extends along the direction of extension of the joint. A recess is provided on the surface of the second member that is on the side of the first member. The folded ridge is recessed into the recess, and the side of the folded ridge furthest from the joint is in contact with the wall surface of the recess. A joint of metal members in which a sealing material is interposed between a bent projection and the wall surface of a recess.