JP2005317454A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply, easily, efficiently, and inexpensively conduct mass production while thermal resistance of a battery and a temperature sensor accurately keeps constant. <P>SOLUTION: A battery pack is equipped with a secondary battery 2, the temperature sensor 3 thermally connected to the secondary battery 2 and detecting battery temperature, and a case 1 housing the temperature sensor 3 and the secondary battery 2. The case 1 has a pair of ribs 5 integrally formed so as to position between a circuit board 4 and the secondary battery 2, a housing part 6 housing the temperature sensor 3 is installed between the pair of ribs 5, and the temperature sensor 3 fixed to the circuit board 4 is arranged in the housing part 6. A fitting part 7 for arranging the circuit board 4 is installed between the pair of ribs 5 and a case body 10, the circuit board 4 is arranged in the fitting part 7, and the circuit board 4 is arranged in a home position. A thermal binder 8 is filled in the housing part 6, and the temperature sensor 3 and the secondary battery 2 are thermally bonded with the thermal binder 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery pack in which a secondary battery and a temperature sensor are built in a case.

  A battery pack incorporating a temperature sensor for detecting the temperature of the secondary battery can be used while protecting the secondary battery by controlling the charge / discharge current according to the battery temperature. It is important for this battery pack to accurately detect the battery temperature with a temperature sensor. For this reason, the temperature sensor is disposed in contact with or close to the secondary battery.

  In a battery pack in which the temperature sensor is fixed to the secondary battery with a simple structure, the temperature sensor is fixed to the surface of the secondary battery with a tape. This battery pack takes time and effort to fix the temperature sensor. In addition, there is a drawback that the position where the temperature sensor is fixed is easily displaced. Battery packs produced in large quantities are required to fix a temperature sensor at a position determined by a simple method. In particular, it is particularly important that the temperature sensor quickly detects the battery temperature and that the thermal resistance between the secondary battery and the temperature sensor is uniform. If the temperature detection of the temperature sensor is delayed, the secondary battery cannot be safely protected from the temperature rise when the temperature of the secondary battery rises rapidly. In addition, if there is variation in pack batteries produced in large quantities without making the thermal resistance constant, in all pack batteries, secondary batteries cannot be charged / discharged normally within a specified temperature range. Even if the battery pack with increased thermal resistance controls charge / discharge in the same manner with a signal from the temperature sensor, the battery temperature becomes higher and it is more susceptible to thermal failure. On the other hand, the battery pack having a low thermal resistance has a drawback that the charge / discharge current of the secondary battery becomes stronger and the charge / discharge current is limited in a state where the charge / discharge can be performed.

The applicant of the present application has developed a battery pack shown in FIG. 1 in order to solve this drawback (see Patent Document 1).
Japanese Utility Model Publication No. 7-29741

  In this battery pack, a U-shaped rib 25 is integrally formed on a plastic case 21 in order to place the temperature sensor 23 at a fixed position. The U-shaped rib 25 opens on the side facing the secondary battery 22, and the temperature sensor 23 is disposed here with the inside serving as a storage portion 26. Further, the storage portion 26 is filled with a silicon resin as the thermal bonding material 28, and the thermal resistance between the secondary battery 22 and the temperature sensor 23 is reduced with the silicon resin.

  In the battery pack having this structure, the temperature sensor 23 is fixed to the flexible substrate 27. The flexible substrate 27 is disposed on the surface of the secondary battery 22, and the temperature sensor 23 that is bent at the tip and fixed to the bent end is disposed in the storage portion 26 of the rib 25. According to this structure, it is difficult to position the temperature sensor with high accuracy and make the relative position between the secondary battery and the temperature sensor constant. For this reason, mass production cannot be performed while keeping the thermal resistance between the secondary battery and the temperature sensor constant with high accuracy. This is because the position of the temperature sensor is shifted due to deformation of the bent end of the flexible substrate or the fixing position of the flexible substrate is shifted, and the thermal resistance between the temperature sensor and the secondary battery changes and becomes non-uniform. .

  The present invention has been developed for the purpose of solving such drawbacks. An important object of the present invention is to provide a battery pack that can be mass-produced efficiently and inexpensively while keeping the thermal resistance between the secondary battery and the temperature sensor constant with high accuracy.

  The battery pack according to the present invention includes a secondary battery 2, a temperature sensor 3 that is thermally coupled to the secondary battery 2 and detects a battery temperature, and a case 1 that houses the temperature sensor 3 and the secondary battery 2. . The case 1 is formed by integrally forming a pair of ribs 5 so as to be positioned between the circuit board 4 and the secondary battery 2, and the housing portion 6 of the temperature sensor 3 is interposed between the pair of ribs 5. And the temperature sensor 3 fixed to the circuit board 4 is disposed in the storage portion 6. Further, a fitting portion 7 for arranging the circuit board 4 is provided between the pair of ribs 5 and the case main body 10, and the circuit board 4 is arranged on the fitting portion 7 so that the rib 5 and the case main body 10 Thus, the circuit board 4 is arranged at a fixed position. Furthermore, the housing 6 is filled with a thermal bonding material 8, and the temperature sensor 3 and the secondary battery 2 are thermally coupled with the thermal coupling material 8.

  In the battery pack of the present invention, the secondary battery 2 can be a thin battery, and the circuit board 4 can be disposed facing the outer peripheral surface of the thin battery. Furthermore, the battery pack of the present invention can be provided with a peripheral wall 11 formed integrally with the case 1. In this battery pack, the fitting portion 7 is provided between the peripheral wall 11 and the rib 5, and the circuit board 4 can be arranged inside the peripheral wall 11 in a posture parallel to the peripheral wall 11. Further, in the battery pack of the present invention, the output terminal 9 can be fixed to the circuit board 4 and a terminal window 13 for exposing the output terminal 9 to the outside can be provided in the case body 10. Furthermore, in the battery pack of the present invention, the thermal bonding material 8 can be a silicon-based resin containing a filler or not containing a filler.

  The battery pack of the present invention has a feature that it can be mass-produced efficiently and inexpensively while keeping the thermal resistance between the secondary battery and the temperature sensor constant with high accuracy. The battery pack of the present invention is provided with a pair of ribs formed integrally with the case so that the battery pack of the present invention is located between the circuit board and the secondary battery, and a storage portion provided between the pair of ribs. In addition, the circuit board is disposed in the fitting portion provided between the pair of ribs and the case body, and the temperature sensor and the secondary battery are filled with a thermal coupling material in the housing portion. This is because they are thermally coupled. The battery pack with this structure has the rib and case body so that the secondary battery and the circuit board are arranged at the fixed positions of the case. Therefore, the distance between the secondary battery and the circuit board can be easily and easily adjusted with high accuracy. The temperature sensor and the secondary battery can be thermally coupled while being kept constant. Therefore, mass production can be performed at low cost while minimizing variation in thermal resistance between the secondary battery and the temperature sensor of the battery pack that is mass-produced.

  Embodiments of the present invention will be described below with reference to the drawings. However, the examples shown below exemplify a battery pack for embodying the technical idea of the present invention, and the present invention does not specify the battery pack as follows.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The battery pack shown in FIGS. 2 to 10 includes a secondary battery 2, a temperature sensor 3 that is thermally coupled to the secondary battery 2 and detects the battery temperature, and a case that houses the temperature sensor 3 and the secondary battery 2. 1 and a circuit board 4 that is disposed at a fixed position of the case 1 and thermally couples the temperature sensor 3 to the secondary battery 2.

  The secondary battery 2 is a thin lithium-ion secondary battery. However, the secondary battery is not necessarily a thin battery, and may be a square battery or a cylindrical battery. Furthermore, the secondary battery 2 is not limited to a lithium ion secondary battery, and can be a nickel metal hydride battery or a nickel cadmium battery. In the illustrated battery pack, one secondary battery 2 is accommodated in the case 1, but a plurality of secondary batteries can be accommodated in the case.

  The temperature sensor 3 is disposed in a state of being close to the secondary battery 2 and thermally coupled. The temperature sensor 3 is a thermistor. However, for the temperature sensor, all elements whose electrical resistance changes with battery temperature, such as PTC, varistor, or transistor, can be used.

  The case 1 is manufactured by molding plastic. The case 1 shown in FIGS. 2 and 8 has an overall outer shape of a rectangular box shape. In this case 1, the upper case 1 </ b> A and the lower case 1 </ b> B are separately molded from plastic to connect the peripheral wall 11 in order to store the secondary battery 2 and the circuit board 4 in place. The upper case 1A and the lower case 1B are manufactured by molding plastic into a shape in which the peripheral wall 11 is integrally molded around the surface plate 12. In the upper case 1A and the lower case 1B in the figure, a peripheral wall 11 is integrally formed around a surface plate 12 having a rectangular outer shape. The upper case 1A and the lower case 1B are connected to each other by connecting the contact edges of the peripheral wall 11. The contact edges of the peripheral wall 11 are connected by ultrasonic welding or bonded. Since the battery pack shown in the figure accommodates a thin battery having a rectangular outer shape, the outer shape of the surface plate 12 is also rectangular.

  In order to arrange the secondary battery 2 and the circuit board 4 at a fixed position, the case 1 is provided with a rib 5 integrally formed so as to protrude inside. In the illustrated battery pack, a rib 5 is integrally formed on one case 1. In the figure, the rib 5 is integrally formed on the lower case 1B. The rib 5 is provided so as to protrude from the surface plate 12 to the inside. The pair of ribs 5 are provided between the secondary battery 2 and the circuit board 4 because the temperature sensor 3 is accommodated therebetween. In the case 1 shown in the figure, a pair of ribs 5 are provided in parallel to each other, and a storage portion 6 is provided therebetween. The pair of ribs 5 are provided with storage portions 6 having a predetermined width, with inner surfaces facing each other being parallel surfaces. The storage unit 6 can fill the thermal bonding material 8 to be filled without slipping with respect to the rib 5. In particular, it is possible to fill the storage portion 6 with the thermal bonding material 8 in which the adhesive force to the rib 5 is reduced by mixing a large amount of filler without moving with respect to the rib 5. Further, even if the adhesive force of the thermal bonding material 8 to the rib 5 decreases with time, the thermal bonding material 8 can be filled in a fixed position of the storage portion 6.

  The rib 5 disposed between the secondary battery 2 and the circuit board 4 has one side edge abutted on the surface of the secondary battery 2 and the other side edge abutted on the surface of the circuit board 4. Then, the secondary battery 2 and the circuit board 4 are stored in the case 1 at a constant interval. Therefore, the rib 5 is disposed between the secondary battery 2 and the circuit board 4 so as to face the direction of the secondary battery 2 from the circuit board 4. The rib 5 in the figure is in a posture orthogonal to the surface of the circuit board 4 and the secondary battery 2. Although not shown, the rib can be provided in a posture inclined with respect to the surface of the circuit board or the secondary battery.

  The rib 5 arranges the secondary battery 2 at a fixed position of the case 1, and further arranges the circuit board 4 at a fixed position of the case 1. Further, the interval between the secondary battery 2 and the circuit board 4 is constant To do. In order to arrange the circuit board 4 at a fixed position of the case 1, a fitting portion 7 for arranging the circuit board 4 is provided between the rib 5 and the case body 10. In the case 1 shown in the figure, a rib 5 having a shape protruding inward from the surface plate 12 is integrally formed on a case body 10 including a surface plate 12 and a peripheral wall 11. The width of the fitting portion 7, which is a gap provided between the rib 5 and the case body 10, is substantially equal to the thickness of the circuit board 4. The fitting portion 7 having this width guides the circuit board 4 and is disposed at a fixed position by the rib 5 and the case body 10. The lower case 1B in the figure has a fitting portion 7 between the peripheral wall 11 of the case main body 10 and the rib 5, so that the circuit board 4 guided by the fitting portion 7 is connected to the peripheral wall 11 and the rib 5. In a state of being sandwiched, it is arranged at a fixed position.

  In the case 1 shown in FIGS. 6 and 7, the surface plate 12 of the lower case 1 </ b> B is protruded inside the rib 5, and a protruding portion 14 is provided between the ribs 5. In the case 1 having this shape, the storage portion 6 becomes shallow at the protruding portion 14. Therefore, the volume of the storage portion 6 formed between the ribs 5 is reduced, and the filling amount of the thermal bonding material 8 is reduced. Moreover, since the protrusion part 14 connects and reinforces the rib 5 inside, the rib 5 can be made into a strong structure. For this reason, the rib 5 can also be formed thin.

  The rib 5 shown in FIGS. 4 to 7 has an upper end that is close to the inner surface of the surface plate 12 of the upper case 1A. The rib 5 can hold the circuit board 4 and the secondary battery 2 firmly. However, the rib does not necessarily need to be raised to the inner surface plate of the upper case, the circuit board guided to the fitting portion can be held in place so as not to move, and the secondary battery can be held in place. Can be as high as possible. Therefore, the height of the rib is, for example, 1/3 or more, preferably 1/2 or more of the width of the circuit board, and 1/3 or more, preferably 1 of the dimension in the width direction of the circuit board of the secondary battery. / 2 or more.

  The battery pack shown in FIGS. 3 and 10 has a rib 5 between one side of the secondary battery 2 and the peripheral wall 11 of the case 1. Furthermore, this battery pack is provided with a pair of ribs 5 at the central portion of the side portion. The battery pack shown in FIG. 9 is provided between the end of the secondary battery 2 where the convex electrode 2 </ b> A is provided and the peripheral wall 11 of the case 1. In this battery pack, a pair of ribs 5 are provided between the flat portion 2 </ b> B and the peripheral wall 11, which are separated from the convex electrode 2 </ b> A.

  The circuit board 4 is a hard printed board such as a glass epoxy board or a phenol board, and the temperature sensor 3 is fixed to the surface by reflow soldering. The circuit board 4 is fitted into the fitting portion 7 between the rib 5 and the peripheral wall 11 of the case 1, and is disposed at a fixed position of the case 1 so as to face the secondary battery 2 and the side portion. The temperature sensor 3 is fixed to the surface facing the secondary battery 2 and is disposed in the storage portion 6 of the rib 5. 3 and 9 has an electronic component 15 fixed to the surface of the circuit board 4. The electronic component 15 is a protection IC that realizes a protection circuit for the secondary battery 2 or a semiconductor switching element such as an FET or a transistor that is switched to the protection IC. FIG. 11 shows a circuit diagram of a battery pack in which the protection circuit is mounted. In the battery pack of this figure, the protection IC 16 detects overcharge or overdischarge of the secondary battery 2 and switches the semiconductor switching element 17 on and off so that the secondary battery 2 is not overcharged or overdischarged. Accordingly, the secondary battery 2 can be charged and discharged while being protected.

  The circuit board 4 to which the electronic component 15 is fixed fixes the electronic component 15 to the surface facing the secondary battery 2 as shown in FIGS. 3 and 9. In this battery pack, the electronic component 15 can be arranged by effectively using the space formed by providing the rib 5 between the secondary battery 2 and the circuit board 4. Furthermore, the circuit board 4 fixes the output terminal 9 of the battery pack. The output terminal 9 is fixed to the surface facing the peripheral wall 11. The case 1 is provided with a terminal window 13 on the peripheral wall 11 in order to expose the output terminal 9 to the outside. In this battery pack, the back surface of the circuit board 4 that fixes the output terminal 9 is supported by the rib 5. Therefore, even if the battery pack is mounted on the electric device and the connection terminal of the electric device presses the output terminal 9, the position of the circuit board 4 does not shift. This is because the rib 5 supports the circuit board 4 from the back surface. In particular, as in the battery pack shown in FIGS. 3 and 9, the structure in which the rib 5 is disposed on the back surface of the portion of the circuit board 4 where the output terminal 9 is provided firmly holds the circuit board 4 pressed by the connection terminal. It can be supported so as not to be displaced.

  The battery pack shown in the circuit diagram of FIG. 11 has the temperature sensor 3 connected to the output terminal 9. The temperature sensor 3 outputs a temperature signal to be detected via an output terminal 9 to an electric device in which the battery pack is mounted. The electric device detects the battery temperature by the temperature signal, and when the battery temperature becomes higher than the set temperature, the charge / discharge current of the battery pack is limited, or the charge / discharge current is interrupted to stop the charge / discharge. As described above, the circuit configuration in which the temperature sensor 3 is connected to the output terminal 9 and the temperature signal is output to the electric device in which the pack battery is mounted can simplify the circuit configuration of the protection IC 16 for the pack battery. For this reason, the power consumption of the protection IC 16 can be reduced, and the consumption of the secondary battery 2 by the protection IC 16 can be reduced. However, the semiconductor switching element can also be controlled so that the temperature sensor is connected to the protection IC and the secondary battery is protected by the protection IC. Although not shown, the temperature sensor connected to the output terminal and the temperature sensor connected to the protection IC can be fixed to the circuit board, and both temperature sensors can be arranged in the storage portion. A battery pack having a plurality of temperature sensors is arranged in a single storage part provided with a plurality of temperature sensors between ribs, or provided with a plurality of storage parts by providing a plurality of pairs of ribs on the case. A temperature sensor can be arranged in the part.

  The temperature sensor 3 disposed in the storage unit 6 via the circuit board 4 is thermally coupled to the secondary battery 2 by the thermal coupling material 8 with a small thermal resistance. The thermal bonding material 8 is a synthetic resin such as a silicon-based resin that contains a filler or does not contain a filler. As the filler mixed with the thermal bonding material 8, a filler having a higher thermal conductivity than that of a synthetic resin such as a silicon-based resin is used. For example, an inorganic powder such as silica or alumina is used as the filler. In particular, silica and alumina are excellent as insulating materials unlike metal powders, and are therefore most suitable as fillers to be filled in the thermal bonding material. As described above, the thermal bonding material including the filler having high thermal conductivity can thermally couple the secondary battery and the temperature sensor while reducing the thermal resistance, so that the battery temperature can be accurately and quickly detected by the temperature sensor. There is. The thermal bonding material 8 is in a paste form in an uncured state. A paste-like thermal bonding material 8 is filled in the storage unit 6 in which the temperature sensor 3 is arranged. The thermal bonding material 8 filled in the storage unit 6 is filled in the gap between the temperature sensor 3 and the secondary battery 2 and is cured. The cured thermal bonding material 8 thermally couples the secondary battery 2 and the temperature sensor 3 with a small thermal resistance.

The above battery pack is assembled in the following steps.
(1) The temperature sensor 3 and the electronic component 15 are arranged at fixed positions on the circuit board 4, and these components are fixed to the circuit board 4 by reflow soldering. The leads 18 are also connected to the circuit board 4 by reflow soldering.
(2) The tip of the lead 18 is connected to the secondary battery 2, and the circuit board 4 is connected to the secondary battery 2 through the lead 18. The lead 18 is connected to the secondary battery 2 by a method such as spot welding.
(3) The secondary battery 2 and the circuit board 4 connected to each other by the lead 18 are arranged at a fixed position of the lower case 1B. The circuit board 4 is placed in a fixed position by being placed in a fitting portion 7 provided between the rib 5 and the peripheral wall 11, and the secondary battery 2 is placed in a fixed position by being inserted between the lead 18 and the peripheral wall 11. Deploy. When the circuit board 4 is inserted into the fitting portion 7 between the rib 5 and the peripheral wall 11 and arranged at a fixed position, the temperature sensor 3 fixed to the surface of the circuit board 4 is formed integrally with the lower case 1B. It arrange | positions in the accommodating part 6 between the ribs 5 which are. In this process, the circuit board 4, the secondary battery 2, and the temperature sensor 3 are arranged at fixed positions of the case 1. The output terminal 9 fixed to the circuit board 4 is disposed on the inner surface of the terminal window 13 provided on the peripheral wall 11.
(4) The storage portion 6 between the ribs 5 is filled with an uncured thermal bonding material 8 in the form of a paste, and the thermal bonding material 8 is cured.
(5) Connect the upper case 1A to the lower case 1B. The lower case 1B and the upper case 1A are connected by ultrasonic welding of the edge of the peripheral wall 11.
(6) A label is attached or printed on the surface of the lower case 1B and the upper case 1A connected to each other, and characters and symbols are written.

It is a perspective view which shows the internal structure of the conventional battery pack. 1 is a perspective view of a battery pack according to an embodiment of the present invention. FIG. 3 is a horizontal sectional view of the battery pack shown in FIG. 2. FIG. 4 is a cross-sectional view of the battery pack shown in FIG. 3 taken along line AA. FIG. 5 is a cross-sectional view of the battery pack shown in FIG. 4 taken along the line BB. FIG. 6 is a vertical cross-sectional view of a battery pack according to another embodiment of the present invention. FIG. 7 is a cross-sectional view of the battery pack shown in FIG. 6 taken along line BB. It is a perspective view of the pack battery concerning the other Example of this invention. It is a horizontal sectional view of the battery pack shown in FIG. It is a horizontal sectional view of a battery pack according to another embodiment of the present invention. 1 is a circuit diagram of a battery pack according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Case 1A ... Upper case 1B ... Lower case 2 ... Secondary battery 2A ... Convex part electrode 2B ... Planar part 3 ... Temperature sensor 4 ... Circuit board 5 ... Rib 6 ... Storage part 7 ... Insertion part 8 ... Thermal coupling material DESCRIPTION OF SYMBOLS 9 ... Output terminal 10 ... Case main body 11 ... Perimeter wall 12 ... Surface plate 13 ... Terminal window 14 ... Projection part 15 ... Electronic component 16 ... Protection IC
DESCRIPTION OF SYMBOLS 17 ... Semiconductor switching element 18 ... Lead 21 ... Plastic case 22 ... Secondary battery 23 ... Temperature sensor 25 ... Rib 26 ... Storage part 27 ... Flexible board 28 ... Thermal coupling material

Claims (5)

A secondary battery (2), a temperature sensor (3) that is thermally coupled to the secondary battery (2) to detect the battery temperature, and a case for housing the temperature sensor (3) and the secondary battery (2) ( 1)
The case (1) is formed by integrally forming a pair of ribs (5) so as to be positioned between the circuit board (4) and the secondary battery (2). Is provided with a storage portion (6) for the temperature sensor (3), a temperature sensor (3) fixed to the circuit board (4) is disposed in the storage portion (6), and a pair of ribs (5 ) And the case body (10), a fitting part (7) for arranging the circuit board (4) is provided, and the circuit board (4) is arranged on the fitting part (7), and the rib ( 5) and the case body (10), the circuit board (4) is placed in a fixed position, and the storage part (6) is filled with a thermal bonding material (8), and this thermal bonding material ( 8) A battery pack in which the temperature sensor (3) and the secondary battery (2) are thermally coupled.   The battery pack according to claim 1, wherein the secondary battery (2) is a thin battery, and the circuit board (4) is arranged opposite to the outer peripheral surface of the thin battery.   The case (1) is provided with a peripheral wall (11) formed integrally, and a fitting portion (7) is provided between the peripheral wall (11) and the rib (5), and the circuit board (4) is connected to the peripheral wall. The battery pack according to claim 1, wherein the battery pack is arranged in a posture parallel to the peripheral wall (11) on the inner side of (11).   The output terminal (9) is fixed to the circuit board (4), and a terminal window (13) for exposing the output terminal (9) to the outside is provided in the case body (10). Pack battery. The battery pack according to claim 1, wherein the thermal bonding material (8) is a silicon-based resin containing a filler or not containing a filler.

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