JP2009070736A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack capable of surely performing fastening of a circuit board and outer insulation, and yet, reducing total cost by simplifying a fastening structure of the circuit board to save time and effort for assembly. <P>SOLUTION: An outer package cover 2 made of a plastic mold product is fastened at one end of a unit battery 1, and a circuit board 3 is arranged inside the outer package cover 2. A metal welding piece 28 is fixed to an opposing face of the circuit board 3 to the outer package cover 2. A thin joint part 19 is formed at an end wall 14 of the outer package cover 2 opposed to the welding piece 28. By irradiating laser light on the joint part 19 from an outside face of the outer package cover 2, the welding piece 28 and the joint part 19 are directly welded to fasten the circuit board 3 to the outer package cover 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery pack in which a circuit board constituting a protection circuit is arranged at one end of a unit cell.

  In this type of battery pack, a form in which electrical components such as a circuit board, a protective element, or a positive electrode lead and a negative electrode lead are collectively arranged on the sealing side of the unit cell is becoming mainstream. Several forms have been proposed as a circuit board fixing structure in this type of battery pack. For example, after temporarily assembling a circuit board, a protective element, etc. and a unit cell, the outer surface of the circuit board is covered with an exterior cover to form an intermediate assembly, and the obtained intermediate assembly is placed inside a molding die. A battery pack is known in which the periphery of the circuit board and the periphery of the unit cell are covered with a resin mold by loading and filling the periphery of the circuit board with a molten resin (see Patent Document 1).

  In another battery pack, a circuit board is assembled with a circuit board holder and a unit cell, and the circuit board is sandwiched and fixed between the circuit board holder and the exterior frame (see Patent Document 2). . The substrate holder and the exterior frame are each formed of a plastic molded product, and the circuit board is mechanically fitted and attached to the substrate holder. Moreover, the engagement claw provided in the board | substrate holder engages with the engagement hole provided in the exterior frame, and the connection state of both is maintained.

JP 2006-147329 A (paragraph number 0035, FIG. 7) JP 2007-73204 A (paragraph number 0019, FIG. 2)

  A battery pack that fixes a circuit board or the like with a resin mold as described above is excellent in that the circuit board can be securely fixed, and can be reliably isolated and insulated from the outside. However, it is necessary to prepare molds for molding individually according to the difference in the size of the unit cells, and to perform molding for each intermediate assembly. It takes time and inevitably increases the overall cost.

  In that respect, the battery pack of Patent Document 2 that mechanically engages and fixes the board holder and the exterior frame assembled with the circuit board simplifies the assembly work as compared with the battery pack of the mold structure, and the battery pack accordingly. Manufacturing costs can be reduced. However, the circuit board is mechanically fitted to the board holder, and the board holder and the outer frame are mechanically engaged and connected. There is a problem in that the assembled state of the three substrate holders tends to vary.

  For example, in an assembled state in which an excessive gap is generated between the exterior frame and the circuit board, there is a possibility that foreign matter may enter the gap between the two. Furthermore, if the invading foreign material has conductivity, it may cause a serious accident such as an external short circuit, and there is a problem in isolation and insulation of the circuit board. Conversely, in a joined state where there is no margin between the exterior frame, the circuit board, and the substrate holder, the substrate holder and the exterior frame cannot be properly engaged and connected. Further, if the engaging claw and the engaging hole are forcibly engaged in a state where there is no margin gap, either the engaging claw or the engaging hole is deformed and the appearance of the battery pack is impaired. Since the circuit board is assembled to the board holder and then the board holder is integrated with the exterior frame, there is a disadvantage that the overall cost of the battery pack increases by the amount of the board holder and the exterior frame.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a battery pack that can reliably fix a circuit board and insulate it from the outside, simplify the structure for fixing the circuit board, and reduce the total cost by omitting assembly work. It is in.

  In the battery pack of the present invention, a circuit board 3 on which an outer cover 2 made of a plastic molded product is fixed to one end of a unit cell 1 and a protective circuit for controlling charge / discharge current is mounted inside the outer cover 2 is arranged. is there. A metal welding piece 28 is fixed to the surface of the circuit board 3 facing the exterior cover 2. Therefore, the circuit board 3 is fixed to the exterior cover 2 by directly welding the weld piece 28 and the joint portion 19 of the exterior cover 2 that is in close contact with the weld piece 28 by laser welding. .

  A recess 16 is formed in the wall portion of the exterior cover 2 facing the weld piece 28, and a thin joint portion 19 is formed in the bottom wall of the recess 16.

  The exterior cover 2 is fixed to the outer surface of the sealing plate 10 of the unit cell 1. The exterior cover 2 is integrally provided with an end wall 14 that faces the sealing plate 10 and a peripheral wall 15 that continues to the periphery of the end wall 14. A weld piece 28 and a joint portion 19 are formed at a plurality of locations on the joint surface between the circuit board 3 and the end wall 14.

  The unit cell 1 and the circuit board 3 are electrically connected to each other through a pair of positive electrode side lead bodies 25 and 36 fixed to the facing surfaces of the sealing plate 10 and the circuit board 3, and a pair of negative electrode side lead bodies 26 and 34. Conducted to. A welding window 21 is opened in the peripheral wall 15 of the exterior cover 2 facing each other with the pair of positive electrode side lead bodies 25 and 36 and the pair of negative electrode side lead bodies 26 and 34 therebetween. Thus, in a state where the exterior cover 2 to which the circuit board 3 is fixed is assembled to the unit cell 1, the pair of positive electrode side lead bodies 25 and 36 and the pair of negative electrode side lead bodies 26 and 34 are respectively connected to the welding window 21. Fixed by welding.

  The weld piece 28 is formed as an independent part separate from the circuit board 3. The engagement portion 28 a provided on the weld piece 28 is engaged and attached to the peripheral edge of the circuit board 3.

  A mounting recess 18 is formed on the inner surface of the end wall 14 of the exterior cover 2, and a plurality of engaging claws 23 are formed on the inner surface of the peripheral wall 15 facing the mounting recess 18. Thus, the peripheral edge of the circuit board 3 is engaged and held by the engaging claws 23 in a state in which the circuit board 3 is fitted and mounted in the mounting recess 18.

  A lid recess 20 including a welding window 21 is formed on the outer surface of the peripheral wall 15 of the exterior cover 3. The outer surface of the welding window 21 is closed with the lid 40 fitted and fixed in the lid recess 20. The periphery of the unit cell 1 and the periphery of the exterior cover 2 including the lid body 40 are covered with the cover label 6.

  In the battery pack of the present invention, the circuit board 3 is arranged inside the plastic-molded outer cover 2, and both of these 2 and 3 are directly welded by a laser welding method. Specifically, a metal weld piece 28 is provided on the circuit board 3, the laser beam L is applied to the joint portion 19 of the exterior cover 2 that is in close contact with the weld piece 28, and the previous joint portion 19 is melted and solidified. By doing so, the circuit board 3 was fixed to the exterior cover 2.

  As described above, according to the fixing structure in which the joining portion 19 formed of the plastic material and the metal welding piece 28 are directly welded by the laser welding method, the conventional battery pack in the form of fixing the circuit board with the resin mold is used. In comparison, the circuit board 3 can be securely fixed to the outer cover 2 with a simpler structure. Since the circuit board 3 is disposed inside the exterior cover 2, insulation from the outside can be performed reliably. Further, since the circuit board 3 and the outer cover 2 are directly welded and fixed by laser welding, the circuit board 3 and the outer cover 2 are fixed by mechanically engaging and fixing the board holder assembled with the circuit board and the outer frame. The assembled state of the substrate 3 with respect to the exterior cover 2 can be wiped out, and both 2 and 3 can always be properly adhered and fixed, and a battery pack having a stable shape and function can be obtained. Furthermore, the overall cost of the battery pack can be reduced by the amount that the substrate holder can be omitted.

  When the concave portion 16 is formed in the wall portion of the exterior cover 2 facing the weld piece 28 and the joint portion 19 is thinned, the joint portion 19 is removed even when the exterior cover 2 is formed of an opaque plastic material. The joining portion 19 and the weld piece 28 can be reliably fixed by reliably melting and solidifying on the surface of the metal weld piece 28. Incidentally, in the state where the thickness of the joint portion 19 is thick, it is difficult to melt the essential portion, that is, the boundary portion between the joint portion 19 and the weld piece 28 only by melting the surface of the joint portion 19 unnecessarily. .

  The exterior cover 2 is configured in a hollow container shape by the end wall 14 facing the sealing plate 10 and the peripheral wall 15 continuing to the periphery of the end wall 14, and at a plurality of locations on the joint surface between the circuit board 3 and the end wall 14. According to the fixing structure in which the formed weld piece 28 and the joint portion 19 are welded, the weld piece 28 may be formed on the wall facing the end wall 14 of the circuit board 3. In addition, the space occupied by the weld piece 28 can be minimized, and the battery pack can be made compact accordingly. By providing welding pieces 28 and joint portions 19 at a plurality of locations on the joint surface between the circuit board 3 and the end wall 14 and welding, the circuit board 3 can be more firmly and firmly fixed to the exterior cover 2. At the time of welding, by supporting the circuit board 3 from the opening surface side of the exterior cover 2, the welding piece 28 and the joint portion 19 can be fixed and held easily and accurately, and the welding accuracy can be improved.

  In a state where the welding window 21 is opened in the peripheral wall 15 of the exterior cover 2 and the exterior cover 2 to which the circuit board 3 is fixed is assembled to the unit cell 1, a pair provided on each of the unit cell 1 and the circuit board 3. According to the battery pack in which the positive electrode side lead bodies 25 and 36 and the pair of negative electrode side lead bodies 26 and 34 are welded and fixed via the welding window 21, the lead bodies 25, 36, 26 and 34 are spot welded, for example. Thus, the outer cover 2 can be combined with the unit cell 1 to be surely integrated. The connection strength between the outer cover 2 and the unit cell 1 can also be sufficient. Thus, according to the battery pack in which the exterior cover 2 and the unit cell 1 are integrated by welding the lead bodies 25, 36, 26, and 34, the structure for coupling and connecting both the members 1 and 2 is provided. There is no need to provide a separate battery, and it is possible to save the labor required for assembly, thereby simplifying the structure of the battery pack and reducing the labor of assembly at the same time, further reducing the overall cost of the battery pack. Can be

  When the weld piece 28 is formed as an independent component separate from the circuit board 3, the circuit board 3 is attached to the exterior cover 2 by engaging and attaching the engaging portion 28 a provided on the weld piece 28 to the periphery of the circuit board 3. Can be fixed by welding. Therefore, the circuit board 3 on which the weld piece 28 is not formed, for example, an existing circuit board can be effectively used and welded to the exterior cover 2 without any problem.

  A board mounting structure in which the mounting recess 18 and the engaging claw 23 are formed on the inner surface of the exterior cover 2, and the peripheral edge of the circuit board 3 is engaged and held by the engaging claw 23 in a state where the circuit board 3 is fitted and mounted in the mounting recess 18. According to this, the circuit board 3 can be fixed to the exterior cover 2 in multiple layers by the mechanical engagement structure by the mounting recess 18 and the engagement claw 23 and the welding structure. Therefore, the circuit board 3 can be more accurately fixed to the exterior cover 2 and the circuit board 3 is separated from the exterior cover 2 even if the welded state between the joint portion 19 and the weld piece 28 is incomplete. The battery pack can be prevented from wobbling and the reliability of the battery pack can be improved.

  A lid concave portion 20 including a welding window 21 is formed on the outer surface of the peripheral wall 15 of the outer cover 3, and the outer surface of the welding window 21 is closed with a lid body 40 fitted and fixed in the lid concave portion 20. According to the battery pack that covers the periphery of the outer cover 2 including the outer cover 2 with the cover label 6, foreign matter can be prevented from entering the inside of the outer cover 3 from the welding window 21 in the use state of the battery pack, or the welding window 21. Therefore, it is possible to reliably prevent mischief such as a metal piece being inserted from the battery pack and improve the safety of the battery pack.

(Example) FIG. 1 thru | or FIG. 7 shows the Example of the battery pack based on this invention. In FIG. 2, the battery pack includes a unit cell 1, an exterior cover 2 disposed on the sealing surface side of the unit cell 1, a circuit board 3 and a thermal fuse 4 disposed between the unit cell 1 and the exterior cover 2. The battery is composed of a bottom cover 5 disposed on the bottom side of the unit cell 1 and a cover label 6 that covers the outer surfaces of these components.

  The unit cell 1 uses a flat cylindrical outer can 9 whose upper surface is open as a base, accommodates an electrode body and an electrolyte therein, and seals the opening of the outer can 9 with a metal sealing plate 10. Constitute. Both ends of the outer can 9 and the sealing plate 10 are rounded. As shown in FIG. 3, a negative electrode terminal 11 bulges in the center of the upper surface of the sealing plate 10, and the sealing plate 10 or the outer can 9 also serves as the positive electrode terminal. The outer can 9 is made of a deep-drawn product made of aluminum, aluminum alloy, or stainless steel. Similarly, the sealing plate 10 is made of a press-molded product made of aluminum or an aluminum alloy, and is fixed by laser welding in a state where the sealing plate 10 is fitted into the inner surface of the opening of the outer can 9.

The electrode body is formed by laminating a positive electrode sheet using LiCoO ₂ as an active material, a negative electrode sheet using graphite as an active material, and a separator sheet that insulates both the sheets, and then spirally winding the entire sheet to push the whole flat. It is crushed and formed. As can be understood from both active materials, the unit cell 1 is configured as a lithium ion battery that can be charged and discharged.

  1 and 3, the exterior cover 2 is made of an injection-molded product made of a thermoplastic plastic material, for example, polycarbonate, and is continuous with the end wall 14 facing the sealing plate 10 and the periphery of the end wall 14. The peripheral wall 15 forms a hollow container. A rectangular recess 16 is formed on the left and right sides of the upper surface of the end wall 14, and three electrode windows 17 are opened at regular intervals adjacent to the right recess 16. A mounting recess 18 for fitting and mounting the circuit board 3 is formed on the inner surface of the end wall 14.

  A thinned joint portion 19 is formed between the bottom surface of the previous concave portion 16 and the mounting concave portion 18. The joining part 19 is formed to have a thickness within a range of 0.1 to 0.2 mm with a reference dimension of 0.15 mm. Left and right horizontally long lid recesses 20 are formed in the front and rear wall surfaces of the peripheral wall 15, and square welding windows 21 are opened on the left and right sides of the concave surface. Both sides of the outer cover 2 are rounded in the same manner as the outer can 9, and a quarter-circular cutout 22 is formed at the upper part of the rounded portion. This notch 22 is provided to specify the loading direction and loading posture of the battery pack. Four engaging claws 23 for engaging and holding the circuit board 3 fitted in the mounting recess 18 are formed on the left and right sides facing the mounting recess 18 on the inner surfaces of the front and rear wall surfaces of the peripheral wall 15.

  The circuit board 3 is formed of a horizontally long printed circuit board, electronic components constituting a protection circuit are mounted on the lower surface side thereof, and a positive lead body 25 and a negative lead body 26 are soldered on both sides of the protection circuit. . The outer surface of the mounting component constituting the protection circuit is covered with a resin mold. This mold part is denoted by reference numeral 27. A square metal weld piece 28 is provided on the left and right sides of the upper surface of the circuit board 3, and three external output electrodes 29 are formed adjacent to the right weld piece 28. The formation position of the left and right weld pieces 28 is made to correspond to the formation position of the previous joining portion 19. Similarly, the formation position of the external output electrode 29 corresponds to the formation position of the previous electrode window 17. The weld piece 28 and the external output electrode 29 are formed simultaneously with the wiring pattern when the insulating substrate is etched to form the wiring pattern. Therefore, the weld piece 28 and the external output electrode 29 in this embodiment are formed of copper foil or aluminum foil.

  Of the external output electrodes 29, two adjacent ones are output terminals on the positive electrode side and the negative electrode side, and the remaining one is an input terminal for sending a control signal to the previous protection circuit. By sending a control signal from the outside to the protection circuit via this input terminal, the charging current and the discharging current can be controlled to an appropriate state to protect the unit cell. The thermal fuse 4 is provided to cut off the discharge current and the charging current of the unit cell 1 when the temperature of the unit cell 1 exceeds a predetermined value. The bottom cover 5 is made of a plastic molded product, and is attached and fixed to the bottom surface of the outer can 9 via a double-sided tape 32. This prevents the bottom surface of the outer can 9 from coming into contact with other objects.

  Next, an assembling procedure for each of the above constituent members will be described. Assembling is performed by assembling the unit cell 1 side and assembling the circuit board 3 with the exterior cover 2, and then assembling the exterior cover 2 with the unit cell 1. Specifically, a lead terminal 33 made of nickel plate is spot welded to one connection lead 4a of the thermal fuse 4, and a lead body 34 made of nickel plate bent in an L shape is spot welded to the other connection lead 4a. Next, as shown in FIG. 6, a plastic insulating plate 35 is bonded and fixed to the surface of the sealing plate 10 adjacent to the negative electrode terminal 11, and the previous lead terminal in a state where the thermal fuse 4 is closely bonded to the upper surface of the insulating plate 35. 33 is spot welded to the negative terminal 11. Further, a lead member 36 made of a nickel plate bent in an L shape is spot welded to the upper surface of the sealing plate 10 through a clad plate 37. The bottom cover 5 is attached to the bottom surface of the outer can 9 with a double-sided tape 32. Thus, the assembly on the unit cell 1 side is completed.

  As shown in FIGS. 4 and 5, lead bodies 25 and 26 made of nickel plates bent in an L-shape are spot-welded to the left and right sides of the mold portion 27 of the circuit board 3, respectively. The fixing positions of the lead bodies 25 and 26 correspond to the fixing positions of the leading lead bodies 34 and 36 with respect to the sealing plate 10. By fitting the circuit board 3 into the mounting recess 18 in a state where the external output electrode 29 faces the electrode window 17, as shown in FIG. 4 and FIG. Is held engaged. The circuit board 3 in this state is positioned in the front-rear and left-right directions by the mounting recess 18, and further, the vertical movement is restricted by the engaging claws 23.

  The exterior cover 2 and the circuit board 3 are welded and fixed by a laser welding method. When the circuit board 3 is assembled to the inner surface of the exterior cover 2 as described above, the weld piece 28 formed on the substrate side is bonded to the inner surface of the bonding portion 19 formed on the decorative cover 2 as shown in FIGS. 1 and 5. is doing. Therefore, as shown in FIG. 5, when the laser beam L is applied to the joint portion 19 from the outer surface side of the exterior cover 2, the contact surface side of the joint portion 19 with the weld piece 28 is mainly melted and integrated with the weld piece 28. it can.

  At this time, since the polycarbonate constituting the joint portion 19 is rapidly heated beyond the decomposition temperature, fine bubbles of decomposition gas are generated at the boundary portion between the joint portion 19 and the weld piece 28, and the melt around the bubbles is melted. The surface of the resin and the weld piece 28 becomes high temperature and high pressure. Therefore, at the time of welding, the molten resin can bite into the surface of the weld piece 28 and exhibit an anchor effect. Further, an oxide film is formed on the surface of the weld piece 28, and chemical bonds and hydrogen bonds are generated through the oxide film. Therefore, when the molten resin is solidified, the joint portion 19 and the weld piece 28 can be firmly connected. Since the joining of the surface of the weld piece 28 and the molten resin occurs at the boundary portion between the joint portion 19 and the weld piece 28, it is possible to suppress discharge of volatile organic compounds to the outside during welding.

  Since the spot diameter of the laser beam L is sufficiently smaller than the area of the joint portion 19, the welding portion can be drawn in one stroke at any position in the entire region of the joint portion 19 by continuously changing the irradiation position of the laser beam L. Can be formed. Further, spot-like welded portions can be formed at a plurality of locations of the joint portion 19 by intermittently irradiating the laser beam. In addition, the welding conditions at the time of said laser welding can be performed by selecting a laser output within the range of 75-1500W, when using a laser beam with a laser wavelength of 1.064 nm.

  The exterior cover 2 in which the circuit board 3 is integrated by laser welding is joined to the end of the unit cell 1 on the sealing side. As shown in FIG. 7, in a state where the exterior cover 2 is joined to the unit cell 1, the vertical wall portions of the positive and negative electrode lead bodies 34 and 36 provided on the unit cell 1 side and the positive and negative electrode provided on the circuit board 3 side are provided. The vertical wall portions of the lead bodies 25 and 26 are adjacent to each other in the front-rear direction. Accordingly, the pair of welding electrodes W are inserted into the exterior cover 2 from the front and rear welding windows 21 while the exterior cover 2 is pressed against the unit cell 1, and the corresponding lead bodies 36 and 25 (or the two electrodes W) are used. The outer cover 2 and the unit cell 1 can be integrated by spot welding with the vertical walls 34 and 26) sandwiched therebetween. In this assembled state, the circuit board 3 is lifted away from the sealing plate 10 and the outer surface of the mounting component constituting the protection circuit is covered with a resin mold. Therefore, even if the electrolytic solution in the unit cell 1 leaks out of the sealing plate 10, the circuit board 3 can be well prevented from being short-circuited.

  After the welding is completed, the lid 40 made of a plastic plate is adhered and fixed to the front and rear lid recesses 20 to close the welding window 21. Finally, as shown in FIG. 2, the surface label 6 is attached around the unit cell 1, the outer cover 2, and the bottom cover 6 to complete the battery pack. The cover label 6 is formed of a plastic sheet or a piece of paper laminated with a plastic film, on which the battery specifications, manufacturer name, etc. are printed.

  As described above, according to the battery pack in which the circuit board 3 is directly fixed to the outer cover 2 by the laser welding method, the time and effort of assembly are reduced as compared with the conventional battery pack in which the circuit board is fixed by the resin mold. Since it can be significantly reduced, the circuit board 3 can be fixed with a simpler structure and at a lower cost. Since the circuit board 3 is assembled and fixed inside the exterior cover 2, insulation from the outside can be performed reliably. Also, compared to the conventional battery pack in which the circuit board is assembled and the circuit board holder and the exterior frame are engaged and connected, the assembled state of the circuit board 3 and the exterior cover 2 is eliminated, and both 2 and 3 are accurately determined. A battery pack having a stable shape and function can be obtained. In addition, the overall cost of the battery pack can be reduced by omitting the board holder for fixing the circuit board.

  8 and 9 show another embodiment of the circuit board 3. In this case, a weld piece 28 having a U-shaped cross section is formed of a thin stainless steel plate, and an engagement portion 28a that is engaged with and attached to the periphery of the circuit board 3 is integrally formed at the bent portion. The engaging portion 28 a is engaged and attached to the short side portions at both ends of the circuit board 3. In a state where the circuit board 3 is assembled in the mounting recess 18 of the exterior cover 2, the upper surface wall of the weld piece 28 is in close contact with the joint portion 19 of the exterior cover 2. Therefore, the circuit board 3 can be constructed in a simpler structure and at a lower cost with respect to the exterior cover 2 by welding the joint portion 19 and the upper surface wall of the weld piece 28 by the laser welding method in the same manner as in the above embodiment. Can be tightly fixed. Further, since the weld piece 28 is formed as an independent component separate from the circuit board 3, the existing circuit board is externally mounted by assembling the weld piece 28 to the existing circuit board on which the weld piece is not formed by the etching process. The cover 2 can be fixed by welding. Since others are the same as the previous embodiment, the same reference numerals are assigned to the same members, and descriptions thereof are omitted.

  In addition to the above embodiments, the exterior cover 2 can be formed using a plastic material such as polyamide, polyethylene terephthalate, or polypropylene other than polycarbonate. When the entire outer cover 2 is formed of a transparent body or a translucent plastic material, it is not necessary to reduce the thickness of the joint portion 19 in the previous embodiment, and therefore the recess 16 can be omitted. The exterior cover 2 may be formed by a two-color molding method, and only the joint portion 19 may be formed of a transparent body or a translucent body.

  In the above embodiment, the joint portion 19 is formed on the end wall 14 of the exterior cover 2. However, if necessary, the joint portion 19 can be formed on the peripheral wall 15 of the exterior cover 2. In that case, L-shaped or gate-shaped welding pieces 28 are fixed to a plurality of locations on the circuit board 3, and the vertical wall portion of the welding pieces 28 and the joining portion 19 are welded by laser welding. The forming material of the lead bodies 25, 26, 34, 36, etc. may be any metal having electrical conductivity, and need not be the metal described in the embodiments. The lead bodies 25, 26, 34 and 36 need not be fixed by spot welding, but can be fixed by laser welding.

  The upper surface of the sealing plate 10 is located below the inner surface below the opening surface of the outer can 9, the lower end edge of the peripheral wall 15 of the outer cover 2 is fitted into the inner edge of the opening of the outer can 9, and the outer cover 2 is attached to the outer can 9. It is possible to engage and mount in a non-movable manner in the entire circumferential direction. Similarly, the lower end edge of the peripheral wall 15 of the outer cover 2 can be engaged and attached to the outer surface of the outer can 9. In addition, the outer cover 2 can be regulated freely by providing an engaging structure that engages with each other between the upper surface of the sealing plate 10 and the inner surface of the outer cover 2.

It is a vertical front view of the battery pack principal part. It is a front view of a battery pack. It is a disassembled perspective view of a battery pack. It is a vertical front view of the exterior cover of the state which assembled | attached the circuit board. It is the sectional view on the AA line in FIG. It is a disassembled perspective view which shows the state just before attaching an exterior cover to a unit cell. It is a vertical side view which shows the assembly | attachment state of an exterior cover and a unit cell. It is a disassembled perspective view which shows another Example of a circuit board. It is a vertical front view which shows the assembly | attachment state of the circuit board which concerns on another Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Unit cell 2 Exterior cover 3 Circuit board 6 Cover label 10 Sealing plate 14 End wall 15 Peripheral wall 16 Recess 18 Mounting recess 19 Joining portion 20 Lid recess 21 Welding window 23 Engagement claws 25/36 Side lead body 28 Welding piece 28a Engaging portion 40 Lid

Claims (7)

An outer cover made of a plastic molded product is fixed to one end of the unit cell, and a circuit board on which a protection circuit for controlling charge / discharge current is mounted is disposed inside the outer cover,
A metal welding piece is fixed to the surface of the circuit board facing the exterior cover,
A battery pack, wherein the circuit board is fixed to the exterior cover by directly welding the weld piece and a joint portion of the exterior cover that is in close contact with the weld piece by a laser welding method.   2. The battery pack according to claim 1, wherein a concave portion is formed in a wall portion of the exterior cover facing the weld piece, and the thin joint portion is formed on a bottom wall of the concave portion. The exterior cover is fixed to the outer surface of the sealing plate of the unit cell,
The exterior cover is integrally provided with an end wall facing the sealing plate and a peripheral wall continuous to the periphery of the end wall,
The battery pack according to claim 1, wherein the weld piece and the joint portion are formed at a plurality of locations on a joint surface between the circuit board and the end wall. The unit cell and the circuit board are electrically connected via a pair of positive electrode side lead bodies fixed to each of the sealing plate and the opposing surface of the circuit board, and a pair of negative electrode side lead bodies,
A welding window is opened in the peripheral wall of the outer cover facing the pair of positive electrode side lead bodies and the pair of negative electrode side lead bodies in between;
Each of the pair of positive electrode side lead bodies and the pair of negative electrode side lead bodies is welded and fixed via the welding window in a state where the exterior cover to which the circuit board is fixed is assembled to the unit cell. The battery pack according to claim 3. The weld piece is formed as an independent component separate from the circuit board,
The battery pack according to claim 3 or 4, wherein an engagement portion provided on the weld piece is engaged and attached to a peripheral edge of the circuit board. A mounting recess is formed on the inner surface of the end wall of the exterior cover, and a plurality of engaging claws are formed on the inner surface of the peripheral wall facing the mounting recess.
6. The battery pack according to claim 3, 4, or 5, wherein a peripheral edge of the circuit board is engaged and held by the engaging claw in a state in which the circuit board is fitted into the mounting recess. A lid recess including the welding window is formed on the outer surface of the peripheral wall of the exterior cover,
The outer surface of the welding window is closed with a lid fitted and fixed in the lid recess,
The battery pack according to any one of claims 3 to 6, wherein a periphery of the unit cell and a periphery of the exterior cover including the lid are covered with a cover label.

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