JP2008041621A - Method for manufacturing battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a thin and light battery pack, which does not allow a unit cell to be exposed, and has a good production efficiency. <P>SOLUTION: All surfaces of a core pack 3 are insulative-coated, and then a U-shaped frame 4 made of a synthetic resin to be mounted on the outer periphery side surfaces of the core pack 3 is mounted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a battery pack suitable as a power source for driving a small electronic device such as a mobile phone.

  In recent years, various types of portable electronic devices such as mobile phones have become smaller and more portable, and lithium ion secondary battery packs that are small, light, and have high energy density have been used as power sources for driving these devices.

  In this battery pack, the outer peripheral side surface of the core pack is packaged with a synthetic resin frame. The core pack includes a unit cell having a flat rectangular metal case, and a protection circuit board module including a protection circuit board and a secondary protection element. The unit cell is a rechargeable lithium ion secondary battery, and aluminum is used as the metal case.

  The frame has a role of protecting the core pack from an external impact and facilitating incorporation into an electronic device, and is formed of a synthetic resin such as polycarbonate resin or acrylonitrile butadiene styrene resin.

  By the way, since the aluminum metal case of a unit cell is a positive electrode, since slight exposure may also lead to a short circuit, it needs to be insulated reliably.

  As a conventional method for insulating a core pack, a method of winding a decorative label after incorporating the core pack into a frame has been adopted. However, the user may easily peel the cosmetic label to expose the unit cell and cause a short circuit.

  Therefore, even if the battery pack is disassembled and modified by the user, there has been a demand for a structure in which the unit cell is not exposed and short-circuited.

  In addition, a method of insulating the core pack with a heat shrinkable tube after incorporating the core pack into the frame has been taken. However, since thermal stress is applied to the unit cell, the electrical characteristics may be deteriorated.

  Therefore, as a solution described above, Patent Document 1 proposes a battery pack in which an insulating coating layer is formed on the unit cell itself and no decorative label or heat shrinkable tube is used.

  In the technique described in Patent Document 1, a coating layer is formed on the outer surface of the metal case of the unit cell by baking. However, in baking painting, the unit cell is overheated to about 250 ° C. after painting. For this reason, there is a risk of thermal expansion of the unit cell and thermal deformation of the frame, and the unit cell is exposed to a high temperature state, so that the electrical characteristics may be deteriorated.

  Therefore, Patent Document 2 proposes a battery pack in which an insulating coating layer is formed on the front and back of a unit cell and no decorative label or heat shrinkable tube is used as a countermeasure against the above-described insulation method.

JP-A-11-149908 JP 2004-296334 A

  However, in the technique of Patent Document 2, after the core pack and the frame are fixed with a molten synthetic resin, insulating coatings are formed on the upper and lower surfaces by printing or the like. That is, since the outer peripheral side surface of the core pack is fixed by the frame, the insulating coating is not formed.

  Therefore, when the user peels off the frame to expose the core pack, the outer peripheral side surface of the unit cell that is not covered with insulation is exposed, which may cause a short circuit.

  In addition, when the core pack and the frame are fixed with a melted synthetic resin, heating is performed to cure the resin, so that thermal stress may be applied to the unit cell and the electrical characteristics may be deteriorated. In the production process, there are problems that it takes a long time to cure and the production efficiency is poor.

  As a countermeasure, there is an ultrasonic welding method as a fixing method with high production efficiency without heating when the core pack and the frame are fixed. However, in ultrasonic welding, a gap may occur at the joint between the core pack and the frame.

  Therefore, when trying to fix the outer peripheral surface of the core pack and the frame by ultrasonic welding, the side surfaces of the uninsulated unit cells are exposed if not only the front and back surfaces of the core pack but also the side surfaces are sufficiently insulated. Therefore, there is a problem that it may be short-circuited.

  Further, in small electronic devices that are rapidly becoming smaller, thinner, and lighter, demands for smaller, thinner, and lighter battery packs are increasing.

  An object of the present invention is to provide a method for manufacturing a thin and light battery pack with good production efficiency without exposing a unit cell.

  The present invention has been made as a result of studying a method for insulating a battery pack in order to solve the above problems.

  That is, in a battery pack comprising a core pack formed by connecting a protection circuit board and a secondary protection element for managing the charge / discharge state of the unit cell to a unit cell having a flat rectangular metal case, and a synthetic resin frame, In the battery pack manufacturing method, the frame is mounted on an outer peripheral side surface of the core pack after the entire surface of the core pack is insulation-coated.

  Further, in the battery pack manufacturing method, the frame is attached to the outer peripheral side surface of the core pack by ultrasonic welding.

  According to the present invention, since the entire surface of the core pack is coated with insulation, not only the front and back surfaces of the core pack but also the outer peripheral side surface of the core pack is insulated. When the frame is fixed to the outer peripheral side of the core pack by ultrasonic welding, there may be a gap at the joint, but the side of the core pack is also painted, so the cell is exposed even if a gap occurs. Do not short circuit. Therefore, it is possible to cope with ultrasonic welding.

  Further, unlike the fixing method using a molten synthetic resin, it can be manufactured without applying thermal stress to the unit cell, and there is no need for thermosetting time, so that a battery pack can be manufactured efficiently without deteriorating electrical characteristics.

  Furthermore, even if the U-shaped frame is fixed to the side surface of the core pack and the plane end adjacent to the side surface with a fixing tape, the core pack outer peripheral side surface is insulated, so the user peeled off the frame. However, the unit cell is not exposed and short-circuited. In addition, with this configuration, since the upper frame and the lower frame are not used, a thin and light battery pack that is very easy to manufacture and inexpensive can be manufactured.

  Therefore, by providing an insulating coating on the entire surface of the core pack and then attaching the frame, a battery pack manufacturing method is provided that does not expose the unit cell even when ultrasonic welding or tape fixing is performed, and has high productivity. can do.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a first embodiment according to the present invention. FIG. 1 (a) is an external perspective view, and FIG. 1 (b) is an exploded perspective view.

  The battery pack 10 includes a core pack 1, an upper frame 2a, and a lower frame 2b. The core pack 1 includes a unit cell 1a and a protection circuit module.

  The protection circuit module includes a protection circuit board 1b that protects the unit cell from overcharge and overdischarge, and a polyswitch 1g that is a secondary protection element that interrupts current when the unit cell is overheated or overcurrent. They are connected by spot welding using the tabs 1h and 1i.

  The core pack 1 is produced by attaching insulating paper 1j to the unit cell 1a, positioning the protection circuit module there, and spot welding the positive electrode 1c and the negative electrode 1d of the unit cell.

  Next, an epoxy resin or the like that does not chemically react with the above components is applied to the entire surface of the core pack 1 as an insulating paint.

  As a procedure for applying the insulating paint, first, masking tape is applied to the contact points 1e and 1f of the protective circuit board provided at two places on the core pack 1 so as not to be painted. Then, an insulating paint is applied by spraying or the like. After the insulating paint has dried, remove the masking tape.

  Here, after drying the insulating paint, it is possible to write a cautionary note by silk printing or design the appearance.

  Then, the coated core pack 1 is placed in the lower frame 2b, and the upper frame 2a is attached, and then fixed by ultrasonic welding.

  FIG. 2 is an explanatory view of a second embodiment according to the present invention, showing a form in which a frame is attached to a side surface of a core pack and a flat end adjacent to the side surface, and FIG. FIG. 2B is an exploded perspective view.

  The battery pack 20 has a configuration in which a U-shaped frame 4 is fixed with a fixing tape 5 at a side surface of the core pack 3 and an end of a plane adjacent to the side surface. The core pack 3 includes a unit cell 3a and a protection circuit module, and an output cable 3k is connected thereto.

  The protection circuit module was manufactured by connecting the polyswitch 3g and the tab 3h, which are secondary protection elements, to the protection circuit board 3b by spot welding and soldering the output cable 3k. Here, the functions of the protection circuit board 3b, the polyswitch 3g, and the tab 3h are the same as those in the first embodiment.

  The core pack 3 is produced by attaching insulating paper 3j to the unit cell 3a, positioning the above-described protection circuit module there, and spot welding the positive electrode 3c and the negative electrode 3d of the unit cell.

  Next, an epoxy resin or the like that does not chemically react with the above components is applied to the entire surface of the core pack 3 as an insulating paint.

  As a procedure for applying the insulating paint, first, a masking tape is applied so that the output cable 3k is not painted.

  Then, an insulating paint is applied to the entire surface of the core pack 3 by a method such as spraying. After the insulating paint has dried, remove the masking tape.

  Here, after the insulating paint is dried, it is possible to write a cautionary note by silk printing or design the appearance as in the first embodiment.

  Then, the U-shaped frame 4 is attached to the core pack 3 which is coated with insulation on the entire surface. Here, the U-shaped frame 4 is provided with an output cable takeout groove 6. With the output cable 3k of the core pack 3 taken out from the U-shaped frame through the output cable take-out groove 6, the U-shaped frame 4 is fixed to the side surface of the core pack 3 and the end of the plane adjacent to the side surface. Secure with.

Explanatory drawing of 1st Embodiment by this invention. FIG. 1A is an external perspective view. FIG. 1B is an exploded perspective view. Explanatory drawing of 2nd Embodiment by this invention. FIG. 2A is an external perspective view. FIG. 2B is an exploded perspective view.

Explanation of symbols

1, 3 Core pack 1a, 3a Cell 1b, 3b Protection circuit board 1c, 3c Cell positive electrode 1d, 3d Cell negative electrode 1e, 1f Protection circuit board contact 1g, 3g Polyswitch 1h, 3h, 1i Tab 1j 3j Insulating paper 2a Upper frame 2b Lower frame 3k Output cable 4 U-shaped frame 5 Fixing tape 6 Output cable take-out groove 10, 20 Battery pack

Claims (2)

  A core pack formed by connecting a protection circuit board and a secondary protection element for managing a charge / discharge state of a unit cell to a unit cell having a flat rectangular metal case, and a method of manufacturing a battery pack comprising a synthetic resin frame The method of manufacturing a battery pack according to claim 1, wherein the frame is attached to the core pack after the entire surface of the core pack is insulation-coated.   The battery pack manufacturing method according to claim 1, wherein the frame is attached to the core pack by ultrasonic welding.

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