JP2016128181A - Welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method which can achieve excellent airtightness.SOLUTION: The welding method is a method for welding a first member to a second member by the full-circled welding, by radiating welding beam. In the method, the welding beam has two peak parts and peripheral parts positioned at peripheries of the two peak parts in a power density distribution. The two peak parts are arranged at an interval along a direction crossing a processing direction of welding in the full-circled welding. Further respective spot diameters in the two peak parts are equal to 80 μm or less, and the interval between the two peak parts is within 0.4 mm-0.9 mm.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a welding method.

  As welding methods for two metal members, various welding methods such as laser welding are widely known. Also in the manufacture of a battery, a welding technique is used for joining the battery case and the lid (see Patent Document 1).

JP 2013-143332 A

  In manufacturing the battery, for example, all-around welding is performed when the reversing plate is attached in a current interruption mechanism (CID). The all-round welding refers to a welding method in which welding is continuously advanced from a welding start position, and then returns to the original start position after making a circle, and a welding state obtained by the method. All-around welding is preferably used when the outer periphery or outer edge of one member is joined to another member. In all-around welding, when the welding beam that has traveled from the start position makes a round, returns to the original position, and overlaps with the start position, pinholes may occur, leading to a decrease in airtightness. The same phenomenon may occur when the main welding crosses the temporarily fixed weld portion that is used to temporarily fix the welding member. For example, in the manufacture of a battery, the above-described decrease in airtightness may cause a decrease in CID operating accuracy and a decrease in safety, and improvement thereof has been demanded.

  As a result of the examination, it was found that the decrease in the airtightness is caused by explosions derived from air or the like confined to the planned welding place without any escape during all-round welding. Specifically, when the welding beam makes a round in the all-around welding and tries to overlap the original welding start position, or when the main welding is going to straddle the temporarily fixed welded part (typical) Air between the welded members) is compressed and heated to cause explosions. This generates pinholes and the like, causing a decrease in airtightness. Based on this knowledge, the present invention has been completed as a result of further studies on countermeasures against air and the like causing the explosion. That is, an object of the present invention is to provide a welding method capable of realizing excellent airtightness.

In order to achieve the above object, the present invention provides a method of welding a first member to a second member by irradiating a welding beam. The welding is preferably all-around welding. In this method, the welding beam has two peaks in the power density distribution. The two peak portions are arranged at intervals along a direction that intersects the welding progress direction in the all-around welding. Each spot diameter at the two peak portions is 80 μm or less. The interval between the two peak portions is in the range of 0.4 mm to 0.9 mm. Furthermore, it is preferable that the welding beam has a peripheral portion that is typically located around two peak portions. More preferably, the outer diameter of the peripheral portion is typically in the range of 0.5 mm to 1.0 mm. Furthermore, the power density of the two peak portions is preferably 50 times or more the power density of the peripheral portion.
According to said structure, since two peak parts which comprise a welding beam have predetermined size and space | interval, gas components, such as air which exists ahead of the advancing direction of welding, are weld parts derived from said two peak parts. It can move between (deep parts). Specifically, the shape of the melted portion by the welding beam is W-shaped in a cross section orthogonal to the welding progress direction, and air or the like can move in the central portion of the W-shape. As a result, the occurrence of explosions originating from the air or the like is prevented, and welding with excellent airtightness is realized. The method of the present invention is advantageous compared to the method of Patent Document 1 in that it is not necessary to form grooves in advance.

  Moreover, according to this specification, the manufacturing method of a sealed battery provided with a first member and a second member is provided. The first member and the second member are typically arranged at a site where the internal pressure of the sealed battery acts. The said manufacturing method includes the process (welding process) of irradiating a welding beam and welding a 1st member to a 2nd member. The welding is preferably all-around welding. As the welding process, the technique of the welding method disclosed herein is preferably employed.

  In a preferred aspect of the technology disclosed herein, a sealed battery includes positive and negative electrodes and a case that accommodates the electrodes. The sealed battery may be formed with a conductive path that connects at least one of the electrodes and an external terminal exposed outside the case. Moreover, the sealed battery typically includes a current interrupt mechanism (pressure type CID) configured to disconnect the conductive path when the case internal pressure increases.

  In a preferred aspect of the technology disclosed herein, the current cutoff mechanism may include a cutoff valve that constitutes a part of the conductive path and blocks gas flow to the outside of the case. Typically, the shut-off valve may be one that at least part of the shut-off valve moves or deforms toward the outside of the case when the internal pressure of the case increases, thereby dividing the conductive path. The shut-off valve corresponds to one of the first member and the second member. More specifically, the current cutoff mechanism may include a connection member that is electrically connected to the positive electrode, a cutoff valve that is electrically connected to the connection member, and a rivet in which the cutoff valve is joined by welding. . In this case, the first member can be a shut-off valve and the second member can be a rivet.

  Furthermore, according to this specification, a sealed battery including a first member and a second member is provided. The sealed battery may be manufactured by a method including the welding method disclosed herein. Alternatively, in the sealed battery according to the technology disclosed herein, there is a gap below the welded portion between the first member and the second member (the welding beam irradiation side is the top), and the gap is The first member and the second member extend along the welding direction. Typically, the gap is formed in an annular shape along the outer peripheral end surface of the first member. Moreover, it is preferable that a welding part has a W shape in the cross section orthogonal to the longitudinal direction (it is fundamentally corresponded with the advancing direction of welding) of this welding part. Thereby, even after welding, the gap can be extended and can be separated from the outside.

  Since the sealed battery disclosed herein can be excellent in airtightness and safety, a motor mounted on a vehicle such as an automobile equipped with an electric motor such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle. It can be suitably used as a power source for (motor). Therefore, according to the technology disclosed herein, a vehicle including the sealed battery is provided.

1 is a schematic perspective view of a secondary battery according to an embodiment. It is a schematic cross section which expands and shows the electric current interruption mechanism in the II-II line | wire of FIG. It is a figure corresponding to the cross section of the electric current interruption mechanism in the III-III line of FIG. 2, Comprising: It is a schematic diagram for demonstrating the perimeter welding method of an interruption | blocking valve. FIG. 4 is an enlarged view showing the IV part of FIG. 2 upside down. It is a schematic cross section along the traveling direction of welding, and is a diagram showing a state when the welding beam returns to the original starting position. It is a schematic cross section along the traveling direction of welding, and is a diagram showing a state when main welding straddles a temporarily fixed welded portion. It is a schematic diagram which shows the power density distribution of a welding beam. It is a schematic diagram which shows the welding state in the cross section orthogonal to the advancing direction of welding.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, members and parts having the same action are denoted by the same reference numerals, and redundant description may be omitted or simplified. Moreover, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship. Further, matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, matters relating to general battery production other than the welding method) are based on conventional technologies in the field. It can be grasped as a design item of the trader.

  As a preferred embodiment of the sealed battery disclosed herein, a lithium secondary battery will be described as an example, but the application target of the present invention is not intended to be limited to this type of battery. In the present specification, the “battery” is a term indicating a general power storage device capable of taking out electric energy, and is a concept including a primary battery and a secondary battery. The “secondary battery” includes not only a storage battery such as a lithium secondary battery but also a capacitor such as an electric double layer capacitor. The technique disclosed here is preferably applied to a sealed secondary battery typically.

  FIG. 1 is a schematic perspective view of a secondary battery according to an embodiment, and FIG. 2 is a schematic cross-sectional view showing an enlarged current interruption mechanism in the II-II cross section of FIG.

  As shown in FIGS. 1 and 2, the secondary battery 10 according to the present embodiment typically includes predetermined battery constituent materials (a positive electrode, a negative electrode, a separator, and the like) as in the case of a conventional general lithium secondary battery. A wound electrode body (not shown) provided is housed in a case 20 together with an appropriate electrolyte (not shown). The shape of the secondary battery is not particularly limited, and may be a square shape or a cylindrical shape. In addition, the configurations of the battery constituent material, the electrode body, and the electrolytic solution do not characterize the present invention, and thus the description thereof is omitted.

  The case 20 includes a case main body 21 having an opening and a lid 22 that closes the opening. The case main body 21 is formed in a rectangular parallelepiped box shape whose upper surface is open. The lid 22 is a rectangular plate-like body, and has a positive external terminal 15 electrically connected to a positive electrode (not shown) of the electrode body, and a negative external terminal 16 electrically connected to a negative electrode (not shown). Is exposed on the upper surface (outside of the case 20). The lid 22 is also provided with a liquid injection port 17 for injecting an electrolytic solution and a safety valve 18. The material which comprises case 20 is not specifically limited, Aluminum and aluminum alloy are used preferably.

  Inside the case 20 is provided a current interrupt mechanism 30 that operates when the internal pressure of the case increases. When the secondary battery 10 is overcharged or the like, gas is generated inside the case 20 and the internal pressure of the case increases, the current interruption mechanism 30 separates the conductive path from the positive external terminal 15 to the positive electrode, thereby charging current. It is comprised so that it can interrupt | block.

  Specifically, as shown in FIG. 2, the current cutoff mechanism 30 is electrically connected to the positive electrode, and has a connection member 32 that functions as a positive electrode current collecting terminal, and a cutoff valve 34 that is electrically connected to the connection member 32. The rivet 35 is electrically connected to the shut-off valve 34 and communicates with the inside and outside of the case. The connection member 32, the shut-off valve 34, and the rivet 35 are disposed in order from the inside of the case to the outside, and all are metal conductive members (members with hatching in the drawing). These members play a role of a conductive path that conducts between the positive electrode and the positive electrode external terminal 15 exposed to the outside of the case, and each constitutes a part of the conductive path. The secondary battery 10 is charged / discharged through the conductive path. As the conductive member, aluminum or an aluminum alloy is preferably used.

  The connection member 32 includes a plate-shaped portion (plate-shaped portion), and a connection portion 33 connected to the shut-off valve 34 is formed on the plate-shaped portion. The connecting portion 33 has a thin stamped portion (not shown). When the battery internal pressure rises, the shut-off valve 34 reverses to the rivet 35 side, so that the stamped portion breaks and the connecting portion 33 and The electrical connection with the shutoff valve 34 is disconnected.

  The shut-off valve 34 is affected by atmospheric pressure through the space of the shaft portion of the rivet 35. Specifically, the first surface (the upper surface in FIG. 2) of the shutoff valve 34 receives atmospheric pressure. On the other hand, the second surface (the lower surface in FIG. 2) opposite to the first surface of the shut-off valve 34 receives battery internal pressure.

  The shut-off valve 34 is electrically connected to a connection portion 33 having a thin stamped portion. In the present embodiment, the shut-off valve 34 is a circular plate. Further, the central portion 40 of the shut-off valve 34 located at the center of the shut-off valve 34 projects relatively inward of the case (downward in FIG. 2). The lower surface (top surface) of the central portion 40 is joined to the connection portion 33 of the connection member 32 by welding. A peripheral portion 41 located around the central portion 40 is inclined upward toward the outside of the case as it goes outward of the shutoff valve 34. The shut-off valve 34 is joined to the rivet 35 at the outer edge 42 by welding. The outer shape of the shut-off valve is not limited to a circular shape, and may be a rectangular shape or the like.

  The shut-off valve 34 is configured such that the central portion 40 can move away from the connection member 32 toward the outside of the case, and the conductive path is divided between the shut-off valve 34 and the connection member 32 by this movement. It is configured as follows. As the shut-off valve 34, a valve that cuts off the conductive path when the shut-off valve itself or a part thereof is deformed is preferably used. In the present embodiment, as the shut-off valve 34, a reversing plate configured so that the central portion 40 protruding inward of the case is reversed outwardly of the case by increasing the internal pressure of the case is used.

  The rivet 35 is fitted in a perforation formed in the lid 22 and communicates with the inside and outside of the case. A concave space (opening) having a U-shaped cross section is formed on the inner side of the case of the rivet 35. A step 50 is formed at the upper end (shoulder) of the outer peripheral wall surface of the recessed space. The outer edge 42 of the shutoff valve 34 is joined to the step portion 50. The step portion 50 has a shape capable of accommodating the shut-off valve 34 on the inside thereof, and specifically includes a planar bottom surface and a wall surface. The depth of the stepped portion 50 is substantially the same as the thickness of the outer edge 42 of the shutoff valve 34.

  Further, the rivet 35 is in contact with the positive external terminal 15 at a part of the outer peripheral surface thereof, so that both are electrically connected. The rivet 35 has a communication hole that communicates with the inside and outside of the case. The rivet 35 may be composed of a single member or may be formed by fitting a plurality of members.

  In addition, although the electric current interruption mechanism 30 is provided between the positive electrode external terminal 15 fixed to the cover body 22 and a positive electrode (not shown), it is not limited to this. The current interruption mechanism 30 may be provided on either the positive electrode side or the negative electrode side, or may be provided on both of them. Since the configuration and method in the case of applying the current interrupt mechanism to the conductive path of the negative electrode are basically the same as those of the positive electrode, description thereof will not be repeated here.

  Next, the welding method in this embodiment is demonstrated. As a preferred embodiment, a method for welding members (specifically, the shut-off valve 34 and the rivet 35) constituting the current cut-off mechanism will be described.

  FIG. 3 is a diagram corresponding to a cross section of the current interrupting mechanism taken along line III-III in FIG. 2, and is a schematic diagram for explaining the entire circumference welding method of the shutoff valve. FIG. 4 is an enlarged view showing the IV portion of FIG. 2 upside down. FIG. 5 is a schematic cross-sectional view along the welding direction, showing a state when the welding beam returns to the original starting position. FIG. 6 is a schematic cross-sectional view along the welding direction, and shows a state when the main welding straddles the temporarily fixed welded portion.

  As shown in FIG. 3, in the welding method according to the present embodiment, the entire circumference of the outer edge 42 of the shutoff valve 34 is rivet 35 in a state where the end face of the outer edge 42 of the shutoff valve 34 and the stepped portion 50 wall surface of the rivet 35 face each other. All-around welding to be joined. In the welding method, first, the outer edge 42 of the shut-off valve 34 is disposed at the stepped portion 50 located at the upper end portion of the outer peripheral wall surface of the opening of the rivet 35 (arrangement step). Next, a plurality of temporary fixing welds 100 are performed on the same circumference of the outer edge 42 of the shutoff valve 34 at predetermined intervals in the circumferential direction (temporary fixing welding process). And the above-mentioned all-around welding (main welding) is performed (main welding process).

  In the arrangement step of the shut-off valve 34, the rivet 35 is installed so that the opening side becomes the upper surface as shown in FIG. 4, and the shut-off valve 34 is placed on the stepped portion 50 of the rivet 35. The shut-off valve 34 is designed so that a clearance 200 is formed between the outer peripheral end surface and the stepped portion 50 wall surface in consideration of variation in shape, variation in CID operating pressure, and the like.

  In the temporary fixing welding process, the welding beam is melted to a position exceeding the bottom surface of the stepped portion 50 of the rivet 35 to prevent the shutoff valve 34 from being deformed or displaced. By performing the temporary fixing welding, the airtightness in the case is improved and the accuracy of the operating pressure of the current interrupt mechanism is improved.

  As shown in FIG. 3, all-around welding starts from a welding start position 125 and proceeds in the direction indicated by the arrow in FIG. And it goes around along the outer edge 42 of the shutoff valve 34, returns to the original welding start position 125, and is performed until the welding start position 125 and the welding end position (not shown) overlap.

  Referring to FIG. 4, in the all-around welding, a welding beam is irradiated to a region centered on clearance 200 to melt stepped portion 50 of rivet 35, outer edge 42 of shutoff valve 34, and the vicinity thereof, and The clearance 200 is closed by making a round along the line 42. Thereby, the airtightness of a welding part is acquired. For reference, in FIG. 4, a conventional weld is denoted by reference numeral 130 ′.

  Further, a gap 210 exists between the lower surface of the outer edge 42 of the shut-off valve 34 and the bottom surface of the step portion 50 of the rivet 35. The gap 210 is mainly caused by molding of a constituent member such as a sag generated when the shut-off valve 34 is molded. The gap 210 is normally closed similarly to the clearance 200 in the conventional all-around welding. At this time, the air existing in the clearance 200 or the like is basically pushed out from an unwelded portion in front of the welding direction. However, in the conventional all-around welding, as shown in FIG. 5, when the welding beam WB that has made a round return from the welding start position 125 tries to overlap the original welding start position 125, it exists in the gap 210 or the like. The air to be blocked is blocked by the weld 130 at the welding start position 125 and is confined without escape, and is compressed and heated by the approach of the welding beam WB. As a result, explosion occurs. This causes underfill, pinholes, and the like, resulting in a decrease in airtightness. When scattered matter adheres to a constituent member (for example, a resin member), in addition to a decrease in airtightness, it may affect the operation accuracy of the current interrupt mechanism. A similar event may occur when the main weld 120 is going to straddle the temporarily fixed weld 110 as shown in FIG. In addition, the arrow in FIG. 5, 6 shows the advancing direction of welding.

  Therefore, in this embodiment, a welding beam having a predetermined beam profile is employed to prevent or suppress the occurrence of the above-mentioned explosion. FIG. 7 is a schematic diagram showing the power density distribution of the welding beam. FIG. 8 is a schematic diagram showing a welded state in a cross section orthogonal to the welding direction.

Specifically, as schematically shown in FIG. 7, the welding beam WB is positioned around the two peak portions 300A and 300B and the two peak portions 300A and 300B in the power density distribution (power density reference). Peripheral portion (which may be a peripheral heating portion) 320. The peak portions 300 </ b> A and 300 </ b> B exist within the outer periphery of the peripheral portion 320. The peak portions 300A and 300B are arranged at intervals along a direction substantially perpendicular to the welding progress direction (the direction indicated by the arrow in FIG. 7), and each spot diameter (each peak in the peak portions 300A and 300B). Each spot diameter corresponding to the part) is set to 80 μm or less. Further, the interval I between the peak portions 300A and 300B is set to be within a range of 0.4 mm to 0.9 mm. Here, the interval between the peak portions 300A and 300B is the distance between the center points of the respective peak portions on the basis of the irradiation point. Moreover, the outer diameter D of the peripheral part 320 is set in the range of 0.5 mm to 1.0 mm on the basis of the irradiation point. And the power density of each peak part 300A, 300B is set to 50 times or more of the power density of the peripheral part 320. FIG. The power density is based on the irradiation point, and W (for example, W / cm ² ) per unit area may be adopted as the unit.

  In the present embodiment, a laser beam is used as the welding beam WB. Therefore, the welding is laser welding. The type of laser is not particularly limited, and various lasers such as a gas laser, a solid laser, and a liquid laser can be used without particular limitation. When laser welding is employed, the peak portions 300 </ b> A and 300 </ b> B are also referred to as high-intensity laser portions in relation to the peripheral portion 320. The peripheral portion 320 is also referred to as a low-intensity laser portion in the relative relationship with the peak portions 300A and 300B. The welding beam having the beam profile described above can be implemented based on the common general knowledge of those skilled in the art using a commercially available laser welding apparatus or an apparatus in which a part thereof (oscillator, optical system, etc.) is modified. Description is omitted. In addition, the conditions affecting the welding speed and the welding quality (for example, laser output) can be appropriately set based on the common general knowledge of those skilled in the art according to the welding object.

  By irradiating the welding beam WB, a welded portion (melted portion at the time of welding) 130 as schematically shown in FIG. 8 is formed. Specifically, the welded portion 130 has a W shape in a cross section orthogonal to the traveling direction of the weld 120. The W-shaped welded portion 130 has two deep portions 150A and 150B (which may be keyhole welded portions) derived from the peak portions 300A and 300B of the welding beam WB. These deep portions 150 </ b> A and 150 </ b> B extend so as to taper in a direction parallel to the thickness direction of the shutoff valve 34, and the penetration depth exceeds the bottom surface of the stepped portion 50 of the rivet 35.

  In addition, the welded portion 130 has a shallow portion 160 (which may be a heat conduction welded portion) derived from the peripheral portion 320 of the welding beam WB. The shallow portion 160 is located between the deep portions 150A and 150B, and constitutes the W-shaped central portion. The shallow portion 160 typically closes the upper portion of the clearance 200, but the deepest portion of the shallow portion 160 is located above the bottom surface of the stepped portion 50. 210 may remain. As a result, air that causes explosions when the welding beam makes a round in all-around welding and tries to overlap the original welding start position, or when main welding is going to straddle the temporarily fixed welded part, etc. Can move from the welding location, and the occurrence of explosions and the occurrence of welding defects resulting from explosions are prevented or suppressed.

  In addition, the application object of the welding method disclosed here is not specifically limited, It can apply to joining of various members (for example, a case and a lid) which comprise a battery, and joining in various products other than a battery. Moreover, the welding method disclosed here is not limited to all-around welding. For example, the present invention can also be applied to a welding method that is carried out in a mode in which the main welding extends over the temporarily fixed weld portion formed prior to the main welding.

  Moreover, the welding beam does not need to have the peripheral part in power density distribution. Instead of the peripheral part, it may have an intermediate part located between at least two peak parts. The power density in the intermediate portion may be approximately the same as that in the peripheral portion, and the outer diameter may be in a range approximately equal to the interval between the peak portions. Even with such a configuration, a melted portion having a W-shaped cross section can be formed. Furthermore, the welding beam may have additional peak portions in addition to the two peak portions. In this case, the additional peak portion typically does not exist between the two peak portions.

DESCRIPTION OF SYMBOLS 10 Secondary battery 15 Positive electrode external terminal 16 Negative electrode external terminal 20 Case 30 Current interruption | blocking mechanism 32 Connection member 34 Shutoff valve 35 Rivet 100 Temporary fixation welding 110 Temporary fixation welding part 120 Whole circumference welding (main welding)
125 Welding start position 130 Welded part (melted part)
150A, 150B Deep part 160 Shallow part 200 Clearance 210 Air gap WB Welding beam 300A, 300B Peak part 320 Peripheral part

Claims (1)

It is a method of irradiating a welding beam to weld the first member to the second member by full circumference welding,
The welding beam has two peak portions and a peripheral portion located around the two peak portions in a power density distribution,
The outer diameter of the peripheral portion is in the range of 0.5 mm to 1.0 mm,
The two peak portions are arranged at intervals along a direction crossing a welding traveling direction in the all-around welding,
The power density of the two peak parts is 50 times or more the power density of the peripheral part,
Each spot diameter at the two peak portions is 80 μm or less,
The welding method, wherein an interval between the two peak portions is in a range of 0.4 mm to 0.9 mm.

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