Battery module and method for manufacturing the battery module

Abstract

To securely weld lead plates to sealing bodies and caulking protrusion strips arranged on the same plane while arranging a plurality of cylindrical batteries in parallel postures facing the same direction.SOLUTION: A battery module includes a plurality of cylindrical batteries 1 that are stored in a battery holder 2 in postures in parallel with each other and are connected using lead plates 3, each of the cylindrical batteries 1 comprising a caulking protrusion strip 15 at an outer peripheral edge part of a first end surface 1A. The battery holder 2 has first electrode windows 25 for exposing sealing bodies 12 and second electrode windows 26 for exposing caulking protrusion strips 15, the first and second electrode windows being open at surface plate parts 22 facing first end surfaces 1A, the second electrode windows 26 being slits having a curved shape. The lead plates 3 each comprise: a first connection piece 31 welded to a sealing body 12 at a first electrode window 25; and a second connection piece 32 welded to a caulking protrusion strip 15 at a second electrode window 26, the second connection piece 32 having a belt-like shape curved in a shape along the caulking protrusion strip 15 and being partially welded to a region that partially covers at least the caulking protrusion strip.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a battery module formed by connecting cylindrical batteries with a metal lead plate. In particular, the present invention relates to a battery module in which a plurality of cylindrical batteries are arranged side by side in a parallel posture such that their first end faces face the same direction, and the plurality of cylindrical batteries are connected with a lead plate on the first end face side, and a method for manufacturing the same.

Background Art

[0002] Battery modules have been developed in which lead plates are welded to electrode terminals at the ends to connect a plurality of cylindrical batteries in series or in parallel. Such battery modules are used as power sources for portable electric devices such as electric cleaners and electric tools, or as backup power sources for servers, household, commercial, and industrial power supply devices in stationary energy storage applications. Further, they are used as drive power sources for assist bicycles, electric scooters, electric carts, or drive power sources for vehicles such as hybrid vehicles and electric vehicles.

[0003] As such cylindrical batteries used in such battery modules, secondary batteries in which the opening of a bottomed cylindrical outer can is caulked and closed with a sealing body, with the sealing body as the positive electrode and the outer can as the negative electrode, are frequently used. In recent years, an improvement in the energy density of battery modules has been called for. As a means for coupling cylindrical batteries, from connecting a lead plate to the bottom of the can to connecting a lead plate to a caulked ridge provided by caulking on the outer peripheral edge portion on the sealing body side, reducing the required volume and improving the volume energy density have been promoted. Conventionally, wire bonding has been used as a means for connecting a lead plate to the caulked ridge on the sealing body side of a cylindrical battery.

[0004] Wire bonding has a wire diameter of usually about φ500μm, and since the current capacity is determined by the wire diameter, there are restrictions on how it can be used because the current value that can be taken out from one cell can be limited (see Patent Document 1). By using a lead plate instead of wire bonding for connection, the limitation of the current value can be eliminated. However, there is a problem that it is difficult to accurately and reliably weld the lead plate to the narrow caulking ridge due to variations in tolerances of each component part.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The present invention has been developed for the purpose of solving the above problems. One of the objects of the present invention is to provide a battery module capable of reliably welding a lead plate to a sealing body and a caulking ridge arranged on the same surface while arranging a plurality of cylindrical batteries in a parallel posture with the positive electrodes facing the same direction, and a method for manufacturing the same. Means for Solving the Problems and Effects of the Invention

[0007] A battery module according to an aspect of the present invention includes a plurality of cylindrical batteries each having a bottomed cylindrical outer can with one open end, a battery holder that houses the plurality of cylindrical batteries in a parallel posture with respect to each other, and a lead plate that is connected to the cylindrical batteries to electrically connect the plurality of cylindrical batteries. The cylindrical battery caulks the opening of the outer can and closes it with a sealing body, and designates the end face closed with the sealing body as the first end face, and provides a caulked ridge by caulking on the outer peripheral edge of the first end face. The battery holder holds the plurality of cylindrical batteries so that the first end faces are aligned on the same plane, and includes a surface plate portion on the surface facing the first end face. The surface plate portion has a first electrode window that partially exposes the sealing body of the cylindrical battery and a second electrode window that partially exposes the caulked ridge, and the second electrode window is a curved slit along the caulked ridge. The lead plate includes a first connection piece disposed in the first electrode window and welded to the sealing body, and a second connection piece disposed in the second electrode window and welded to the caulked ridge. The second connection piece is in a strip shape curved along the caulked ridge, and is partially welded to the caulked ridge at least in a region covering the caulked ridge.

[0008] According to the above configuration, while arranging a plurality of cylindrical batteries formed by caulking the opening of the outer can and closing it with a sealing body in a parallel posture with the first end faces facing the same direction, there is a feature that the lead plate can be reliably welded to the sealing body and the caulked ridge arranged on the same plane. This is because the above battery module is provided with a first electrode window that exposes the sealing body of the cylindrical battery and a second electrode window in a curved slit shape that exposes the caulked ridge in the surface plate portion facing the first end face of the cylindrical battery, the first connection piece of the lead plate is arranged in the first electrode window and welded to the sealing body, and the second connection piece is arranged in the second electrode window and welded to the caulked ridge. In particular, the second connection piece of the lead plate is in a curved shape along the caulked ridge and is partially welded to the caulked ridge at least in a region covering the caulked ridge, so that the second connection piece can be reliably welded to the caulked ridge and the lead plate can be connected.

[0009] The battery module according to another aspect of the present invention has a caulking ridge that is ring-shaped with a predetermined lateral width (D) and has a planar connection region, and the second connection piece is arc-shaped along the connection region and is welded to the connection region.

[0010] According to the above configuration, a ring-shaped connection region having a predetermined lateral width (D) is provided on the caulking ridge, and the second connection piece is formed in an arc shape along the connection region and welded to the connection region, so that the second connection piece can be more accurately welded to the connection region.

[0011] The battery module according to another aspect of the present invention has a welding region where the second connection piece is partially welded to the caulking ridge, and the welding region has a lateral width (a) that is less than or equal to the lateral width (D) of the connection region, and a longitudinal width (b) of the welding region is set to 1 / 4 or less of the total length (L) of the second connection piece.

[0012] According to the above configuration, by setting the welding region of the second connection piece within a specific range, the second connection piece can be more accurately welded to the connection region of the caulking ridge. Here, the total length (L) of the second connection piece indicates the length of the center line passing through the center in the width direction of the second connection piece.

[0013] Note that FIG. 6A shows a plan view of the first end face of the cylindrical battery 1, and FIG. 6B shows a plan view of the second connection piece 32, and the welding region 35 is indicated by cross-hatching. In the welding example shown in the figure, the lateral width (a) of the welding region 35 is made equal to the lateral width (D) of the connection region, and the longitudinal width (b) of the welding region is 1 / 4 or less of the total length of the second connection piece and 1.5 times the lateral width (D) of the connection region. However, the longitudinal width (b) of the welding region can also be set to 0.8 to 3 times the lateral width (D) of the connection region. When the longitudinal width (b) of the welding region is made larger than the lateral width (D) of the connection region and ultrasonic welding is performed, the ultrasonic horn for welding may be applied multiple times while shifting the position with respect to the welding region.

[0014] The battery module according to another aspect of the present invention is such that cylindrical batteries are insulated from each other by providing an insulating material between the outer can and the sealing body, and in a plan view of the first end face, the insulating material protrudes inside the caulking ridge to provide a ring-shaped insulating region, and the lateral width (S) of the insulating region is 0.8 to 1.5 times the lateral width (D) of the connection region of the caulking ridge.

[0015] According to the above configuration, even if the second connection piece arranged on the caulking ridge is displaced in the direction of the center of the sealing body due to the insulating region provided inside the caulking ridge, it is possible to effectively prevent the second connection piece from directly contacting the sealing body, and avoid the situation where the caulking ridge and the sealing body are short-circuited through the second connection piece.

[0016] The battery module according to another aspect of the present invention is such that the lateral width (W) of the second connection piece is 1 to 3 times the lateral width (D) of the connection region of the caulking ridge, the radius of curvature (R1) of the arc-shaped outer edge is larger than the radius of curvature (r1) of the outer peripheral edge of the connection region, the radius of curvature (R2) of the arc-shaped inner edge is smaller than the radius of curvature (r2) of the inner peripheral edge of the connection region, and larger than the radius of curvature (r3) of the inner peripheral edge of the insulating region, and the central angle (α) with respect to the arc-shaped second connection piece is 135 degrees to 180 degrees.

[0017] According to the above configuration, by widely designing the second connection piece arranged in a laminated state with respect to the connection region of the caulking ridge protruding from the second electrode window, while widening the weldable region, even when the relative position of the second connection piece with respect to the cylindrical battery is displaced, a welding region can be ensured.

[0018] The battery module according to another aspect of the present invention is such that the battery holder is arranged with the opening edge on the inner peripheral side of the second electrode window inside the inner peripheral edge of the caulking ridge and outside the inner peripheral edge of the insulating region, and the opening edge on the outer peripheral side of the second electrode window is arranged outside the outer peripheral edge of the caulking ridge, and the opening width (K) of the second electrode window is 1 to 2 times the lateral width (W) of the second connection piece.

[0019] According to the above configuration, by defining the positions of the inner peripheral edge and the outer peripheral edge of the second electrode window provided in the battery holder, while arranging the second connection piece disposed in the second electrode window at a position where it can be welded to the caulking ridge, it is possible to avoid the adverse effect that the second connection piece contacts the sealing body.

[0020] In the battery module according to another aspect of the present invention, in a plan view of the first end face of the cylindrical battery, depending on the relative position of the second connection piece with respect to the cylindrical battery, the position of the welding region for welding the second connection piece to the caulking ridge is changed.

[0021] With the above configuration, even when the position of the second connection piece is displaced with respect to the caulking ridge due to dimensional errors or the like, the second connection piece can be surely welded to the caulking ridge for connection.

[0022] A method for manufacturing a battery module according to an aspect of the present invention includes a plurality of cylindrical batteries each having a bottomed cylindrical exterior can with one open end, a battery holder that houses the plurality of cylindrical batteries in a parallel posture with respect to each other, and a lead plate that is connected to the cylindrical batteries to electrically connect the plurality of cylindrical batteries. The method includes: preparing a cylindrical battery in which the opening of the exterior can is caulked and closed with a caulked body, and a caulking ridge is provided by caulking on the outer peripheral edge of the end face closed by the caulked body as a first end face; preparing a battery holder having a first electrode window that exposes the caulked body and a second electrode window that exposes the caulking ridge, the second electrode window being a slit having a curved shape along the caulking ridge, the first electrode window and the second electrode window being provided by opening on a surface plate portion disposed opposite to the first end face of the cylindrical battery; preparing a lead plate including a first connection piece that is disposed in the first electrode window and welded to the caulked body, and a second connection piece that is curved in a shape along the caulking ridge and is a strip shape, the second connection piece being disposed in the second electrode window and welded to the caulking ridge; disposing the plurality of cylindrical batteries at fixed positions in the battery holder, holding the plurality of cylindrical batteries such that the first end faces are aligned on the same plane, exposing the caulked body of the cylindrical battery from the first electrode window, and exposing the caulking ridge from the second electrode window; disposing the lead plate at a fixed position in the battery holder, disposing the first connection piece in the first electrode window, and disposing the second connection piece in the second electrode window; and welding the first connection piece disposed in the first electrode window to the caulked body and welding the second connection piece disposed in the second electrode window to the caulking ridge. In the lead plate welding step, the position of the welding region for welding the second connection piece to the caulking ridge is changed according to the relative position of the second connection piece with respect to the cylindrical battery.

[0023] According to the above method, while arranging a plurality of cylindrical batteries in a parallel posture with the first end faces facing the same direction, the lead plate can be reliably welded to the caulked body and the caulking ridge arranged on the same plane. In particular, even when the second connection piece is disposed in a misaligned state with respect to the caulking ridge, good welding can be realized by changing the position of the welding region, and reliable connection can be achieved.

[0024] The manufacturing method of a battery module according to an aspect of the present invention includes a step of welding a second connection piece to a caulking ridge, which includes a photographing step, a calculation step, a determination step, and a second connection piece welding step. The photographing step photographs a cylindrical battery on which a lead plate is disposed and the second connection piece from the first end face side with a camera. The calculation step calculates the center position of the cylindrical battery and the center position with respect to the arc-shaped second connection piece from the photographed image. The determination step identifies a welding region for welding the second connection piece to the caulking ridge from the relative position of the center position of the second connection piece with respect to the center position of the cylindrical battery detected in the calculation step. The second connection piece welding step welds the second connection piece to the caulking ridge in the welding region determined in the determination step.

[0025] In the determination step of the manufacturing method of a battery module according to an aspect of the present invention, the welding region of the second connection piece is identified based on the following conditions. In a plan view of the first end face of the cylindrical battery, in the XY plane with the center of the cylindrical battery as the origin, where one end of the second connection piece is located in the positive direction on the Y axis and the other end of the second connection piece extends to the negative direction of the Y axis beyond the positive direction of the X axis to form a central angle (α), Taking the center of the cylindrical battery as the first center (O1) and the center of the arc-shaped second connection piece as the second center (O2), the welding region at the relative position of the second center (O2) with respect to the first center (O1) is specified within the range of an angle (θ) indicated by a radial line starting from the positive direction of the X axis. (1) When the second center (O2) coincides with the first center (O1), the welding region is set to any position on the second connection piece. (2) When the second center (O2) is located in the negative direction of the X axis with respect to the first center (O1), the welding region is within the range of 55 degrees ≤ θ ≤ 90 degrees on the second connection piece. (3) When the second center (O2) is located in the positive direction of the X axis with respect to the first center (O1), the welding region is in the range of 55 degrees ≤ θ ≤ 85 degrees on the second connection piece. (4) When the second center (O2) is located in the positive direction of the Y axis with respect to the first center (O1), the welding region is in the range of -35 degrees ≤ θ ≤ 35 degrees on the second connection piece. (5) When the second center (O2) is located in the negative Y-axis direction with respect to the first center (O1), the welding area shall be in the range of -35° ≤ θ ≤ 35° on the second connecting piece. (6) When the second center (O2) is located in the positive X-axis direction and positive Y-axis direction with respect to the first center (O1), the welding area shall be in the range of -65° ≤ θ ≤ -20° on the second connecting piece. (7) When the second center (O2) is located in the negative X-axis direction and positive Y-axis direction with respect to the first center (O1), the welding area shall be in the range of 25° ≤ θ ≤ 70° on the second connecting piece. (8) When the second center (O2) is located in the negative X-axis direction and negative Y-axis direction with respect to the first center (O1), the welding area shall be in the range of -70° ≤ θ ≤ -25° on the second connecting piece. (9) When the second center (O2) is located in the positive X-axis direction and negative Y-axis direction with respect to the first center (O1), the welding area shall be in the range of 20° ≤ θ ≤ 65° on the second connecting piece.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. Also, this specification does not at all specify the members shown in the claims as the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present invention only to those, but are merely illustrative examples. Note that the sizes and positional relationships of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same names and reference numerals indicate the same or similar members, and detailed descriptions will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are formed of the same member and one member serves as a plurality of elements, or conversely, the function of one member may be realized by sharing it among a plurality of members.

[0028] The battery module of the present invention can be used for various purposes such as a power source for portable electric devices such as electric cleaners and power tools, or as a backup power source for servers in stationary energy storage applications, a power source for storing the generated power of natural energy such as solar power generation and wind power generation, or a power source for storing late-night power, as a power supply device for home, business, and factory use, and further as a drive power source for assist bicycles, electric scooters, electric carts, or vehicles such as hybrid vehicles and electric vehicles. Hereinafter, as an embodiment of the present invention, a battery module used as a power source for electric devices will be described.

[0029] [Embodiment 1] The battery module 100 according to Embodiment 1 of the present invention is shown in FIGS. 1 to 5. FIG. 1 is a schematic perspective view of the battery module, FIGS. 2 and 3 are an exploded perspective view and a plan view of the battery unit of the battery module of FIG. 1, FIG. 4 is an enlarged cross-sectional perspective view taken along line IV-IV of the battery unit shown in FIG. 3, and FIG. 5 is an enlarged cross-sectional view taken along line IV-IV of the battery unit shown in FIG. 3. The battery module 100 shown in these figures includes a plurality of cylindrical batteries 1, a battery holder 2 that houses the plurality of cylindrical batteries 1 in a parallel posture with each other, and a lead plate 3 that is connected to the cylindrical batteries 1 and electrically connects the plurality of cylindrical batteries 1. The battery module 100 shown in FIG. 1 connects the plurality of cylindrical batteries 1 through a lead plate 3 disposed at a fixed position of the battery holder 2 in which the plurality of cylindrical batteries 1 are housed to form a battery unit 10, and this battery unit 10 is housed in an outer case 9.

[0030] (Cylindrical battery 1) The cylindrical battery 1 preferably uses a non-aqueous electrolyte battery such as a lithium-ion battery. Since a lithium-ion battery has a large capacity with respect to weight and volume, the battery module 100 using the cylindrical battery 1 as a lithium-ion battery can be reduced in size and weight and increased in charge and discharge capacity. However, the present invention does not specifically specify the non-aqueous electrolyte battery for the cylindrical battery, and all rechargeable batteries such as nickel-metal hydride batteries and nickel-cadmium batteries can also be used.

[0031] As shown in FIG. 5, the cylindrical battery 1 houses a spiral electrode body 13 formed by laminating positive and negative electrode plates 13A and 13B with a separator 13C in a bottomed cylindrical metal exterior can 11, fills it with an electrolytic solution, and caulks the opening of the exterior can 11 to close it with a sealing body 12. The sealing body 12 is insulated from the exterior can 11 through an insulating material 14 and is airtightly fixed thereto. The cylindrical battery 1 has a caulking ridge 15 provided by caulking on the outer peripheral edge of the first end face 1A with the end face closed by the sealing body 12 as the first end face 1A. In the cylindrical battery 1 of the lithium-ion battery, the sealing body 12 serves as the positive electrode and the caulking ridge 15 of the exterior can 11 serves as the negative electrode. As the cylindrical battery 1, a lithium-ion battery called "18650" having a diameter of 18 mm and a total length of 65 mm, or a lithium-ion battery having dimensions close to or larger than this can be used.

[0032] The caulking ridge 15 is provided with a planar connection region 15A in order to improve the connection with the lead plate 3. The connection region 15A is ring-shaped with a predetermined lateral width (D) and is provided in the inner region excluding the caulked outer peripheral edge. By providing the planar connection region 15A having a predetermined width on the surface of the caulking ridge 15 in this way, the second connection piece 32 of the lead plate 3 described later can be welded while being arranged in a surface contact state.

[0033] Furthermore, in the cylindrical battery 1 of FIG. 5, a gasket is interposed as the insulating material 14 between the upper end opening of the exterior can 11 and the sealing body 12, and the sealing body 12 and the exterior can 11 are insulated through this gasket. In the cylindrical battery 1 shown in FIGS. 5 and 6A, in a plan view of the first end face 1A, the insulating material 14 arranged between the caulked caulking ridge 15 and the sealing body 12 is extended to the inside of the caulking ridge 15 and exposed to provide a ring-shaped insulating region 16. By providing the insulating region 16 inside the caulking ridge 15 in this way, there is a feature that a short circuit due to contact between the caulking ridge 15 and the sealing body 12 can be effectively prevented. The lateral width (S) of this insulating region 16 can be, for example, 0.8 to 1.5 times the lateral width (D) of the connection region 15A of the caulking ridge 15.

[0034] The cylindrical battery 1 shown in Fig. 5 forms an insulating region 16 by exposing a gasket interposed between the sealing body 12 and the outer can 11. However, in the plan view of the first end face 1A of the cylindrical battery 1, a material different from the gasket, such as a resin material, etc., can be arranged inside the caulking ridge 15 to insulate the sealing body 12 and the caulking ridge 15, or an insulating paint can be applied to the surface of the sealing body 12 inside the caulking ridge 15 to insulate the sealing body 12 and the caulking ridge 15.

[0035] Furthermore, although not shown in the figure, as the sealing body, the cylindrical battery can also adopt a structure in which a cap is connected to a sealing plate to form a convex electrode. In this sealing body, the central portion of the cap is connected to the lead plate as the positive electrode.

[0036] In the above cylindrical battery 1, since the sealing body 12 and the caulking ridge 15 arranged on the first end face 1A are connected to the lead plate 3 as positive and negative electrodes, the region on the bottom side of the outer can 11 excluding the first end face can also be covered and insulated with an insulating tube or the like.

[0037] (Battery Holder 2) The battery holder 2 is formed of a thermoplastic resin such as plastic, which is an insulating material. As shown in Fig. 4, the battery holder 2 integrally forms and connects surface plate portions 22 and 23 at both ends of a holding portion 21 that inserts and holds the cylindrical battery 1. This battery holder 2 is provided with the holding portion 21 on the opposing inner sides of a pair of surface plate portions 22 and 23 to form a battery storage portion. The holding portion 21 shown in Figs. 2 and 4 is in a cylindrical shape along the outer peripheral surface of the cylindrical battery 1, or a cylindrical shape with a partially opened portion. A pair of surface plate portions 22 and 23 are located at both ends of the holding portion 21 and are provided in a parallel posture to each other. The surface plate portions 22 and 23 are formed in a plate shape orthogonal to the holding portion 21. As shown in Figs. 1 and 2, the battery holder 2 arranges a plurality of cylindrical batteries 1 inserted into each holding portion 21 in multiple stages and multiple rows and holds them in a fixed position.

[0038] The battery holder 2 shown in FIGS. 2 and 4 divides the holding portion 21 into two parts axially in the middle, and integrally forms the ends of the divided holding portions 21 with the surface plate portions 22 and 23 respectively to form a pair of holder units 2A and 2B. This battery holder 2 holds a plurality of cylindrical batteries 1 such that the first end faces 1A are aligned on the same plane. Therefore, the holder unit 2A where the first end face 1A of the cylindrical battery 1 is disposed is provided with an electrode window on the surface plate portion 22 to expose the sealing body 12 and the caulking ridge 15, which are the positive and negative electrodes disposed on the first end face 1A. On the other hand, the holder unit 2B where the bottom side of the can of the cylindrical battery 1 is disposed closes one end of the holding portion 21 with the surface plate portion 23 without providing an opening on the surface plate portion 23. With the cylindrical batteries 1 housed in the holding portions 21 of the respective holder units 2A and 2B, a battery housing portion for holding the cylindrical batteries 1 in a fixed position is formed by connecting the pair of holder units 2A and 2B. The pair of holder units 2A and 2B are connected and fixed to each other. The divided holder units can be connected via connectors such as ultrasonic welding, adhesion, locking structures, and set screws. The above battery holder 2 integrally forms half of the holding portion 21 and the surface plate portions 22 and 23 as the holder units 2A and 2B, but the battery module 100 does not specify the battery holder to have the above structure. The battery holder can have any other structure that can hold a plurality of batteries in a predetermined position.

[0039] The holder unit 2A is provided with a first electrode window 25 for exposing the sealing body 12 of the cylindrical battery 1 and a second electrode window 26 for exposing the caulking ridge 15 in a surface plate portion 22 disposed on a surface facing the first end face 1A. The first electrode window 25 is a circular through-hole opened at a position facing the central portion of the sealing body 12. The first electrode window 25 has a size for exposing the central portion of the sealing body 12, and in this portion, the first connection piece 31 of the lead plate 3 described later is welded. Further, by opening the first electrode window 25 widely, the feature of quickly discharging the gas discharged from the sealing body 12 of the cylindrical battery 1 to the outside of the cylindrical battery 1 is also realized. However, the first electrode window 25 does not necessarily have to be opened in a large circular shape, and it can be polygonal or opened in a size where only the first connection piece can be arranged.

[0040] The second electrode window 26 is in the shape of a curved slit along the caulking ridge 15 formed on the first end face 1A. As shown in FIG. 3, the slit-shaped second electrode window 26 is formed in a curved shape along approximately half of the outer peripheral region of the cylindrical battery 1 in a plan view. As shown in FIG. 5, the inner peripheral opening edge 26a of the second electrode window 26 is disposed inside the inner peripheral edge of the caulking ridge 15 and outside the inner peripheral edge of the insulating region 16, and the outer peripheral opening edge 26b of the second electrode window 26 is disposed outside the outer peripheral edge of the caulking ridge 15. Further, the second electrode window 26 shown in the figure is in the shape of a slit along the outer shape of the second connection piece 32 extending in a strip shape, and by inserting the second connection piece 32 along the inner surface of the second electrode window 26, the second connection piece 32 can be positioned. The opening width (K) of the second electrode window 26 can be 1 to 2 times the lateral width (W) of the second connection piece 32 guided here.

[0041] Furthermore, the surface plate portion 22 shown in FIG. 4 is provided with a boss 24 for arranging the lead plate 3 at a fixed position. The boss 24 is formed in a posture protruding from the surface of the surface plate portion 23. The lead plate 3 has a positioning hole 34 through which the boss 24 is guided, and the boss 24 is guided into the positioning hole 34 so that the lead plate 3 is arranged at a fixed position on the surface plate portion 23.

[0042] (Lead plate 3) The lead plate 3 is arranged at a fixed position on the surface plate portion 22 and is connected to the positive and negative electrodes of the plurality of cylindrical batteries 1 to connect the plurality of cylindrical batteries 1 in a predetermined arrangement. The lead plate 3 is a thin metal plate and is connected to the sealing body 12 and the caulking rib 15 provided on the first end face 1A of each cylindrical battery 1. The lead plate 3 shown in the figure includes a first connection piece 31 arranged in the first electrode window 25 and welded to the sealing body 12, and a second connection piece 32 arranged in the second electrode window 26 and welded to the caulking rib 15. The lead plate 3 shown in the figure includes a main body portion 30 arranged on the surface of the surface plate portion 22. A plurality of first connection pieces 31 are integrally provided protruding from one side of the main body portion 30, and a plurality of second connection pieces 32 are integrally provided protruding from the opposite side of the main body portion 30. The main body portion 30 shown in the figure extends along the extending direction of the plurality of cylindrical batteries 1 arranged in a plurality of rows and has an arch shape along the opening edge of the second electrode window 26. The lead plate 3 is made of a metal plate made of aluminum, nickel, copper, or an alloy thereof that can be elastically deformed. Also, for the lead plate 3, for example, a sheet made of polycarbonate with a thickness of about 0.2 mm, on which the main body portion 30, the first connection piece 31, and the second connection piece 32 are initially pasted and integrated, can be used. The sheet is preferably aramid paper or the like.

[0043] The first connection piece 31 is provided with a connection portion at the tip of an arm portion extending from the main body portion 30, and this connection portion is welded and connected to the central portion of the sealing body 12. The first connection piece 31 connected to the sealing body 12 is connected by spot welding, for example. As shown in FIG. 4, the lead plate 3 is connected to the sealing body 12 via the first connection piece 31 connected to the main body portion 30.

[0044] As shown in FIGS. 3 and 4, the second connecting piece 32 is in the shape of a strip curved along the caulking ridge 15. The second connecting piece 32 shown in FIG. 6B is in an arc shape along the connecting region 15A of the caulking ridge 15 shown in FIG. 6A. The second connecting piece 32 formed in an arc shape has a curvature radius (R1) of the outer edge of the arc larger than the curvature radius (r1) of the outer peripheral edge of the connecting region 15A, a curvature radius (R2) of the inner edge of the arc smaller than the curvature radius (r2) of the inner peripheral edge of the connecting region 15A, and larger than the curvature radius (r3) of the inner peripheral edge of the insulating region 16. Thereby, the second connecting piece 32 can widen its lateral width (W) with respect to the connecting region 15A of the caulking ridge 15. The lateral width (W) of the second connecting piece 32 can be 1 to 3 times the lateral width (D) of the connecting region 15A of the caulking ridge 15. Further, the second connecting piece 32 shown in FIG. 6B has a central angle (α) with respect to the arc-shaped second connecting piece 32 of 135 degrees to 180 degrees, preferably 145 degrees to 170 degrees. By setting the central angle (α) of the second connecting piece 32 within the above range, there is a feature that the welding region 35 can be secured against displacement in any direction.

[0045] The second connecting piece 32 is partially welded to the caulking ridge 15 at least in the region covering the caulking ridge 15. The second connecting piece 32 can be provided with a welding region 35 so as to be partially welded to the caulking ridge 15. As shown in FIG. 6, the lateral width (a) of the welding region 35 is equal to or less than the lateral width (D) of the connecting region 15A, and the longitudinal width (b) of the welding region 35 is equal to or less than 1 / 4 of the total length (L) of the second connecting piece 32. Here, the total length (L) of the second connecting piece 32 indicates the length of the center line passing through the center in the width direction of the second connecting piece 32 as shown in FIG. 6B. In this way, by setting the welding region 35 of the second connecting piece within a specific range, the second connecting piece 32 can be welded more accurately to the connecting region 15A of the caulking ridge 15.

[0046] The second connecting piece 32 is ultrasonically welded and connected to the caulking ridge 15. Ultrasonic welding presses an ultrasonic horn against the surface of the second connecting piece 32, ultrasonically vibrates the second connecting piece 32 while pressing the second connecting piece 32 against the caulking ridge 15, and connects the second connecting piece 32 to the caulking ridge 15. Ultrasonic welding ultrasonically vibrates the second connecting piece 32 in a direction parallel to the surface of the caulking ridge 15 to connect the second connecting piece 32 to the caulking ridge 15. Since ultrasonic welding molecularly bonds the metal at the interface to connect the second connecting piece 32 to the caulking ridge 15, dissimilar metals can be stably connected. Therefore, the aluminum lead plate 3 can be reliably and stably fixed to the caulking ridge 15 of the iron outer can 11. The long and easily deformable second connecting piece 32 is flexibly deformed in the process of ultrasonically welding the welding region 35 to the caulking ridge 15, so it has the characteristic of being able to be reliably connected with smaller ultrasonic vibration energy.

[0047] The battery unit 10 in FIG. 3 has a plurality of lead plates 3 arranged on the first end face 1A side of the cylindrical battery 1, and a plurality of cylindrical batteries 1 arranged in multiple stages and multiple rows are connected in multiple parallel and multiple series. The battery unit 10 shown in the figure has a plurality of cylindrical batteries 1 arranged in a posture parallel to each other and with their first end faces located on the same plane, and are connected in series and in parallel on the first end face 1A side. The battery unit 10 shown in the figure arranges 12 cylindrical batteries 1 in 4 rows and 3 stages, and connects them in 4 parallel and 3 series.

[0048] One lead plate 3 is provided with four first connection pieces 31 and four second connection pieces 32 respectively. The four first connection pieces 31 are connected to the sealing bodies 12 of four adjacent cylindrical batteries 1, connecting these four cylindrical batteries 1 in parallel. The four second connection pieces 32 are connected to the caulking ridges 15 of four cylindrical batteries 1 adjacent to the four cylindrical batteries 1 connected in parallel, connecting these four cylindrical batteries 1 in parallel and connecting the four cylindrical batteries 1 connected in parallel in series. That is, the lead plate 3 connects a plurality of cylindrical batteries 1 arranged in each stage in parallel with each other and connects a plurality of cylindrical batteries 1 arranged in adjacent stages in series with each other. In this way, while connecting the four cylindrical batteries 1 arranged in one row in parallel with each other, the two stages of cylindrical batteries 1 adjacent to each other are connected in series.

[0049] Furthermore, for the cylindrical batteries 1 arranged in a plurality of stages and connected in series, an output lead plate 3A is connected to the cylindrical battery 1 arranged in the frontmost stage in the figure, and an output lead plate 3B is connected to the cylindrical battery 1 arranged in the rearmost stage. One output lead plate 3A is provided with four first connection pieces 31 connected to the sealing plate 12, and the first connection pieces 31 are respectively connected to the four cylindrical batteries 1 arranged on the front side among the plurality of stages of cylindrical batteries 1 connected in series with each other, connecting these four cylindrical batteries 1 in parallel with each other. The output lead plate 3A in FIG. 1 bends the end portion on the side opposite to the first connection piece 31 at a right angle to provide a bent terminal portion 3a, and arranges this bent terminal portion 3a on the side surface of the battery holder 2. Also, the other output lead plate 3B is provided with four second connection pieces 32 connected to the caulking ridges 15, and the second connection pieces 32 are respectively connected to the four cylindrical batteries 1 arranged on the rear side among the plurality of stages of cylindrical batteries 1 connected in series with each other, connecting these four cylindrical batteries 1 in parallel. The output lead plate 3B bends the end portion on the side opposite to the second connection piece 32 at a right angle to provide a bent terminal portion 3b, and arranges this bent terminal portion 3b on the side surface of the battery holder 2.

[0050] Furthermore, although not shown in the figure, the battery module can also connect the plurality of battery units 10 in the vertical direction (the up-and-down direction in FIG. 3), and directly or through a bus bar or the like connect the bent terminal portions 3a and 3b of the output lead plates 3A and 3B arranged on the side surface of the battery holder 2 to connect the plurality of battery units 10 in series to increase the output voltage. It is also possible to arrange the plurality of battery units 9 in the horizontal direction (the left-and-right direction in FIG. 3), and connect the bent terminal portions 3a and 3b of the output lead plates 3A and 3B arranged on the side surface of the battery holder 2 with a bus bar or the like to connect the plurality of battery units 10 in parallel.

[0051] Here, the cylindrical battery 1 is arranged in a fixed position while being inserted into the holding portion 21 of the battery holder 2. However, due to the dimensional differences of the batteries and the dimensional differences of the battery holder 2, the position of the cylindrical battery 1 may shift with respect to the fixed position of the battery holder 2. Also, the position of the second connection piece 32 arranged in the second electrode window 26, which is a curved slit, may shift from the accurate position. In particular, since the second connection piece 32 is composed of a curved metal plate, it may be displaced with respect to the cylindrical battery 1 even when arranged in the curved window of the battery holder. In order to surely weld the second connection piece 32 arranged in such a displaced manner to the caulking ridge 15 of the cylindrical battery 1, in the battery module 100 shown in the figure, when the second connection piece 32 is displaced with respect to the cylindrical battery 1, the welding region 35 is shifted so that the second connection piece 32 can be surely welded to the caulking ridge 15.

[0052] The above battery module is manufactured in the following steps. (1) Cylindrical battery preparation step In this step, as the cylindrical battery, a cylindrical battery is prepared by caulking the opening of a bottomed cylindrical outer can and closing it with a sealing body, and providing a caulking ridge by caulking on the outer peripheral edge of the first end face closed by the sealing body. (2) Battery holder preparation step In this step, a battery holder is prepared which has a first electrode window for partially exposing the sealing body of the cylindrical battery on the surface plate portion disposed opposite to the first end face of the cylindrical battery, and a second electrode window for partially exposing the caulking ridge, the second electrode window being formed by opening a slit having a curved shape along the caulking ridge. (3) Lead plate preparation step In this step, as the lead plate 3, a lead plate 3 is prepared which includes a first connection piece 31 disposed in the first electrode window 25 and welded to the sealing body 12, and a second connection piece 32 which is strip-shaped and curved along the shape of the caulking ridge 15 and is disposed in the second electrode window 26 and welded to the caulking ridge 15. The lead plate 3 is prepared by arranging a plurality of first connection pieces and second connection pieces in a predetermined arrangement according to the connection state of the cylindrical batteries 1 to be connected. (4) Cylindrical battery arrangement step A plurality of cylindrical batteries are arranged at the fixed positions of the battery holder, and the plurality of cylindrical batteries are held such that their first end faces are aligned on the same plane. The sealing body 12 of the cylindrical battery 1 is exposed from the first electrode window 25, and the caulking ridge 15 is exposed from the second electrode window 26. (5) Lead plate arrangement step The lead plate 3 is arranged at the fixed position of the battery holder 2, the first connection piece 31 is arranged in the first electrode window 25, and the second connection piece 32 is arranged in the second electrode window 26. (6) Lead plate welding step The first connection piece 31 arranged in the first electrode window 25 is welded to the sealing body 12, and the second connection piece 32 arranged in the second electrode window 26 is welded to the caulking ridge 15. Further, in this step, the position of the welding region for welding the second connection piece 32 to the caulking ridge 15 is changed according to the relative position of the second connection piece 32 with respect to the cylindrical battery 1.

[0053] Furthermore, in the lead plate welding step of welding the second connection piece 32 to the caulking ridge 15, in the steps shown below, the second connection piece 32 is accurately welded to the connection region 15A of the caulking ridge 15. (a) Photographing step As shown in Fig. 7, the cylindrical battery 1 with the lead plate 3 disposed therein and the second connection piece 32 are photographed by the camera 41 from the side of the first end face 1A. The camera 41 is disposed at a distance in the central axis direction of the cylindrical battery 1 so as to be able to photograph the sealing body 12 of the cylindrical battery 1 and the second connection piece 32 set at a fixed position. The camera 41 detects images of the sealing body 12 of the cylindrical battery 1 and the second connection piece 32. As such a camera 41, a camera used for various sensors or the like, for example, a CCD camera or the like can be used. The data of the ring-shaped image photographed by the camera 41 is input to the arithmetic circuit of the control circuit. (b) Arithmetic step The image photographed by the camera 41 is arithmetically processed by the arithmetic circuit to detect the central position of the cylindrical battery 1 and the central position with respect to the arc-shaped second connection piece 32. (c) Judgment step In this step, the judgment circuit 43 specifies the welding region for welding the second connection piece 32 to the caulking ridge 15 based on the relative position of the central position of the second connection piece 32 with respect to the central position of the cylindrical battery 1 detected by the arithmetic circuit 42.

[0054] The judgment circuit stores the optimum welding position with respect to the relative position of the cylindrical battery 1 and the second connection piece 32 as a table or a function, determines the optimum welding position based on these, and welds the second connection piece 32 to the caulking ridge 15 at the determined welding position. The judgment circuit specifies the welding region based on the conditions shown in Figs. 8 and 9, for example.

[0055] Figures 8 and 9 show the results of verification in a state where, in a plan view of the first end face 1A of the cylindrical battery 1, it is an XY plane with the center of the cylindrical battery 1 as the origin, one end of the second connection piece 32 is located in the positive direction on the Y axis, and the other end of the second connection piece 32 extends to the negative direction of the Y axis beyond the positive direction of the X axis so as to have a central angle (α). Taking the center of the cylindrical battery as the first center (O1) and the center for the arc-shaped second connection piece 32 as the second center (O2), the welding region 35 at the relative position of the second center (O2) with respect to the first center (O1) is specified within the range of the following angle (θ) indicated by a radial line starting from the positive direction of the X axis. (1) When the second center (O2) coincides with the first center (O1), the welding region 35 is set at an arbitrary position on the second connection piece 32. (2) When the second center (O2) is located in the negative direction of the X axis with respect to the first center (O1), the welding region 35 is within the range of 55 degrees ≤ θ ≤ 90 degrees on the second connection piece 32. (3) When the second center (O2) is located in the positive direction of the X axis with respect to the first center (O1), the welding region 35 is in the range of 55 degrees ≤ θ ≤ 85 degrees on the second connection piece 32. (4) When the second center (O2) is located in the positive direction of the Y axis with respect to the first center (O1), the welding region 35 is in the range of -35 degrees ≤ θ ≤ 35 degrees on the second connection piece 32. (5) When the second center (O2) is located in the negative direction of the Y axis with respect to the first center (O1), the welding region 35 is in the range of -35 degrees ≤ θ ≤ 35 degrees on the second connection piece 32. (6) When the second center (O2) is located in the positive direction of the X axis and the positive direction of the Y axis with respect to the first center (O1), the welding region 35 is in the range of -65 degrees ≤ θ ≤ -20 degrees on the second connection piece 32. (7) When the second center (O2) is located in the negative direction of the X axis and the positive direction of the Y axis with respect to the first center (O1), the welding region 35 is in the range of 25 degrees ≤ θ ≤ 70 degrees on the second connection piece 32. (8) When the second center (O2) is located in the negative direction of the X axis and the negative direction of the Y axis with respect to the first center (O1), the welding region 35 is in the range of -70 degrees ≤ θ ≤ -25 degrees on the second connection piece 32. When the second center (O2) is located in the positive X-axis direction and the negative Y-axis direction with respect to the first center (O1), the welding region 35 shall be in the range of 20° ≤ θ ≤ 65° on the second connecting piece 32.

[0056] (d) Second connecting piece welding process In this process, in the welding region 35 determined in the determination process, the second connecting piece 32 is welded to the caulking rib 15. FIG. 7 shows a state where the control unit 44 drives the ultrasonic welder based on the determination of the determination circuit 43. The control unit 44 controls the moving mechanism 46 to move the ultrasonic horn 45 to the welding position. With the tip of the ultrasonic horn 45 arranged at the welding position, a drive signal is output from the control unit 44 to the output unit 47 for ultrasonic welding. Through the above processes, the second connecting piece 32 is welded to the caulking rib 15 at an optimal position to ensure a reliable connection.

Industrial Applicability

[0057] The present invention is a battery module formed by connecting a plurality of cylindrical batteries with a metal lead plate. In particular, it can be preferably used as a battery module in which the first end faces of the cylindrical batteries are arranged side by side in a parallel posture so as to face the same direction, and the plurality of cylindrical batteries are connected with a lead plate on the first end face side.

Explanation of Signs

[0058] 100…Battery module 1…Cylindrical battery 1A…First end face 2…Battery holder 2A, 2B…Holder unit 3…Lead plate 3A, 3B…Output lead plate 3a, 3b…Bending terminal part 9…Outer case 10…Battery unit 11…Outer can 12…Sealing body 13…Electrode body 13A…Electrode plate 13B…Electrode plate 13C…Separator 14…Insulating material 15…Crimping rib 15A…Connection area 16…Insulation area 21…Holding part 22…Surface plate part 23…Surface plate part 24…Boss 25…First electrode window 26…Second electrode window 26a, 26b…Opening edge 30…Main body part 31…First connection piece 32…Second connection piece 34…Positioning hole 35…Welding area 41…Camera 42…Arithmetic circuit 43…Judgment circuit 44…Control part 45…Ultrasonic horn 46…Moving mechanism 47…Output part

Claims

1. A plurality of cylindrical batteries having a bottomed cylindrical outer can with one open end, a battery holder for housing the plurality of cylindrical batteries in a parallel posture with each other, a lead plate connected to the cylindrical battery for electrically connecting the plurality of cylindrical batteries, A battery module comprising: The cylindrical battery caulks the opening of the outer can and closes it with a caulked body. Taking the end face closed by the caulked body as the first end face, a caulked ridge is provided by caulking on the outer peripheral edge of the first end face. The battery holder holds the plurality of cylindrical batteries such that the first end faces are aligned on the same plane, and has a surface plate portion on the facing surface with the first end face. On the surface plate portion, a first electrode window for partially exposing the caulked body of the cylindrical battery, and a second electrode window for partially exposing the caulked ridge are opened, The second electrode window is a curved slit along the caulked ridge, The lead plate, a first connection piece disposed in the first electrode window and welded to the caulked body, and a second connection piece disposed in the second electrode window and welded to the caulked ridge comprising, The second connection piece is a strip curved in a shape along the caulked ridge, and is partially welded to the caulked ridge at least in a region covering the caulked ridge. A battery module in which, in a plan view of the first end face of the cylindrical battery, the position of the welding region for welding the second connection piece to the caulked ridge is changed according to the relative position of the second connection piece with respect to the cylindrical battery.

2. The battery module according to Claim 1, wherein the caulked ridge is a ring shape having a predetermined width (D) and has a planar connection region, and the second connection piece is an arc shape along the connection region and is welded to the connection region.

3. The battery module according to Claim 2, wherein the second connection piece has a welding region that is partially welded to the caulked ridge, the width (a) of the welding region is less than or equal to the width (D) of the connection region, and the longitudinal width (b) of the welding region is less than or equal to 1 / 4 of the total length (L) of the second connection piece.

4. The battery module according to Claim 2 or 3, The cylindrical battery arranges an insulating material between the outer can and the sealing body to insulate them from each other, and in a plan view of the first end face, the insulating material is exposed inside the caulking ridge to provide a ring-shaped insulating region. A battery module in which a lateral width (S) of the insulating region is 0.8 to 1.5 times a lateral width (D) of the connection region of the caulking ridge.

5. The battery module according to claim 4, wherein the second connection piece has a lateral width (W) that is 1 to 3 times the lateral width (D) of the connection region of the caulking ridge, a radius of curvature (R1) of an arcuate outer edge that is larger than a radius of curvature (r1) of an outer peripheral edge of the connection region, a radius of curvature (R2) of an arcuate inner edge that is smaller than a radius of curvature (r2) of an inner peripheral edge of the connection region, and larger than a radius of curvature (r3) of an inner peripheral edge of the insulating region, and a central angle (α) with respect to the arcuate second connection piece is 135 degrees to 180 degrees.

6. The battery module according to claim 4 or 5, wherein an opening edge on an inner peripheral side of the second electrode window of the battery holder is arranged inside an inner peripheral edge of the caulking ridge and outside an inner peripheral edge of the insulating region, an opening edge on an outer peripheral side of the second electrode window is arranged outside an outer peripheral edge of the caulking ridge, and an opening width (K) of the second electrode window is 1 to 2 times a lateral width (W) of the second connection piece.

7. A plurality of cylindrical batteries, a battery holder formed by housing the plurality of cylindrical batteries in a parallel posture to each other, a lead plate connected to the cylindrical battery to electrically connect the plurality of cylindrical batteries, and a method for manufacturing a battery module comprising: a step of caulking an opening of a bottomed cylindrical outer can and closing it with a sealing body, using the end face closed by the sealing body as a first end face, and preparing the cylindrical battery provided with a caulking ridge by caulking on an outer peripheral edge portion of the first end face; a step of preparing a battery holder having a first electrode window for exposing the sealing body of the cylindrical battery and a second electrode window for exposing the caulking ridge, the second electrode window being a curved slit along the caulking ridge, on a surface plate portion arranged to face the first end face of the cylindrical battery. A step of preparing a lead plate including a first connection piece disposed in the first electrode window and welded to the sealing body, and a second connection piece that is strip-shaped and curved along the caulking ridge, disposed in the second electrode window and welded to the caulking ridge. A step of arranging a plurality of the cylindrical batteries at fixed positions in the battery holder, holding the plurality of cylindrical batteries such that the first end faces are aligned on the same plane, exposing the sealing body of the cylindrical battery from the first electrode window, and exposing the caulking ridge from the second electrode window. A step of arranging the lead plate at a fixed position in the battery holder, arranging the first connection piece in the first electrode window, and arranging the second connection piece in the second electrode window. A step of welding the first connection piece disposed in the first electrode window to the sealing body, and welding the second connection piece disposed in the second electrode window to the caulking ridge, including: A method for manufacturing a battery module, in the lead plate welding step, changing the position of a welding region for welding the second connection piece to the caulking ridge according to the relative position of the second connection piece with respect to the cylindrical battery.

8. A method for manufacturing a battery module according to claim 7, wherein: The step of welding the second connection piece to the caulking ridge includes: A photographing step of photographing the cylindrical battery on which the lead plate is disposed and the second connection piece from the first end face side with a camera; A calculation step of calculating the center position of the cylindrical battery and the center position with respect to the arc-shaped second connection piece from the photographed image; A determination step of specifying a welding region for welding the second connection piece to the caulking ridge from the relative position of the center position of the second connection piece with respect to the center position of the cylindrical battery detected in the calculation step; A second connection piece welding step of welding the second connection piece to the caulking ridge in the welding region determined in the determination step. A method for manufacturing a battery module including:

9. A method for manufacturing a battery module according to claim 8, wherein: In the determination step, a method for manufacturing a battery module for specifying a welding region of the second connection piece based on the following conditions. In a plan view of the first end face of the cylindrical battery, in an XY plane with the center of the cylindrical battery as the origin, when one end of the second connection piece is located in the positive direction on the Y axis and the other end of the second connection piece extends to the negative direction of the Y axis beyond the positive direction of the X axis to form a central angle (α), Taking the center of the cylindrical battery as the first center (O1) and the center of the arc-shaped second connecting piece as the second center (O2), the welding area at the relative position of the second center (O2) with respect to the first center (O1) is specified within the range of the angle (θ) indicated by the radius vector starting from the positive direction of the X-axis. (1) When the second center (O2) coincides with the first center (O1), the welding area is set at any position on the second connecting piece. (2) When the second center (O2) is located in the negative direction of the X-axis with respect to the first center (O1), the welding area is within the range of 55 degrees ≤ θ ≤ 90 degrees on the second connecting piece. (3) When the second center (O2) is located in the positive direction of the X-axis with respect to the first center (O1), the welding area is within the range of 55 degrees ≤ θ ≤ 85 degrees on the second connecting piece. (4) When the second center (O2) is located in the positive direction of the Y-axis with respect to the first center (O1), the welding area is within the range of -35 degrees ≤ θ ≤ 35 degrees on the second connecting piece. (5) When the second center (O2) is located in the negative direction of the Y-axis with respect to the first center (O1), the welding area is within the range of -35 degrees ≤ θ ≤ 35 degrees on the second connecting piece. (6) When the second center (O2) is located in the positive direction of the X-axis and the positive direction of the Y-axis with respect to the first center (O1), the welding area is within the range of -65 degrees ≤ θ ≤ -20 degrees on the second connecting piece. (7) When the second center (O2) is located in the negative direction of the X-axis and the positive direction of the Y-axis with respect to the first center (O1), the welding area is within the range of 25 degrees ≤ θ ≤ 70 degrees on the second connecting piece. (8) When the second center (O2) is located in the negative direction of the X-axis and the negative direction of the Y-axis with respect to the first center (O1), the welding area is within the range of -70 degrees ≤ θ ≤ -25 degrees on the second connecting piece. (9) When the second center (O2) is located in the positive direction of the X-axis and the negative direction of the Y-axis with respect to the first center (O1), the welding area is within the range of 20 degrees ≤ θ ≤ 65 degrees on the second connecting piece.

Images