Battery pack

Abstract

To provide a battery pack capable of detecting the state of a battery with high accuracy.SOLUTION: A battery pack includes a housing that contains a battery, and a sensor attached to the housing and that detects distortion of the housing, and a plate-like member having higher rigidity than the housing is adhered to at least one side of the housing so as to cover the side, and one or more sensors are attached to the surface of the other side other than the at least one side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a battery pack. [Background technology]

[0002] Patent Document 1 discloses a battery pack including a battery and a sensor that detects the state of the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7008618 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for more accurate detection of the state of a battery, for example, expansion of the battery body.

[0005] An object of the present disclosure is to provide a battery pack capable of detecting the state of a battery with high accuracy. [Means for solving the problem]

[0006] The battery pack of the present disclosure comprises a housing that contains a battery, and a sensor that is attached to the housing and detects distortion of the housing, with a plate-like member that is more rigid than the housing being adhered to at least one side of the housing so as to cover the side, and one or more sensors being attached to the surface of the other side other than the at least one side. Effect of the Invention

[0007] According to the battery pack of the present disclosure, the state of the battery can be detected with high accuracy. [Brief description of the drawings]

[0008] [Figure 1]1 is a diagram illustrating a battery pack according to a first embodiment; [Diagram 2] 2A to 2C are diagrams illustrating an example of a housing in the battery pack according to the first embodiment. [Diagram 3] 2 is a plan view illustrating a strain gauge mounted on the battery pack according to the first embodiment. FIG. [Figure 4] 2 is a cross-sectional view illustrating a strain gauge mounted on the battery pack according to the first embodiment. FIG. [Diagram 5] 2 is a block diagram illustrating a circuit board mounted on the battery pack according to the first embodiment. FIG. [Figure 6] 11 is a diagram illustrating a battery pack according to a second embodiment. FIG. [Figure 7] 13 is a diagram illustrating a battery pack according to a third embodiment. FIG. [Figure 8] 13 is a diagram illustrating another example of the battery pack according to the third embodiment. FIG. [Figure 9] 11A and 11B are diagrams illustrating a first modified example of a housing in the battery pack according to the embodiment. [Figure 10] 11A and 11B are diagrams illustrating a first modified example of a housing in the battery pack according to the embodiment. [Figure 11] 11A and 11B are diagrams illustrating a first modified example of a housing in the battery pack according to the embodiment. [Figure 12] 11A and 11B are diagrams illustrating a first modified example of a housing in the battery pack according to the embodiment. [Figure 13] 11A and 11B are diagrams illustrating a second modified example of the housing of the battery pack according to the embodiment. [Figure 14] 13A and 13B are diagrams illustrating a third modified example of the housing of the battery pack according to the embodiment. [Figure 15] 13A and 13B are diagrams illustrating a third modified example of the housing of the battery pack according to the embodiment. [Figure 16] 13A and 13B are diagrams illustrating a fourth modified example of the housing of the battery pack according to the embodiment. [Figure 17] 13A and 13B are diagrams illustrating a fourth modified example of the casing of the battery pack according to the embodiment. [Figure 18] 13 is a diagram illustrating a battery pack according to a fourth embodiment. FIG. [Figure 19] 13 is a diagram illustrating a battery pack according to a fifth embodiment. FIG. [Figure 20] 13 is a cross-sectional view illustrating a battery pack according to a fifth embodiment. FIG. [Figure 21] 13A to 13C are diagrams illustrating a state in which a battery pack according to a fifth embodiment is used. [Figure 22] 13A to 13C are diagrams illustrating a method for manufacturing a battery pack according to a fifth embodiment. [Diagram 23] 13A to 13C are diagrams illustrating a method for manufacturing a battery pack according to a fifth embodiment. [Figure 24] 13A and 13B are diagrams illustrating modified examples of the battery pack according to the fifth embodiment. [Diagram 25] 13A and 13B are a plan view and a cross-sectional view showing an example of a detection element included in a strain gauge according to a sixth embodiment. [Figure 26] 13A to 13C are a perspective view, a plan view, and a cross-sectional view showing an example of a detection element included in a strain gauge according to a seventh embodiment. [Figure 27] 13A to 13C are a perspective view, a plan view, and a cross-sectional view showing another example of a detection element included in a strain gauge according to the seventh embodiment. [Figure 28] 13A to 13C are a perspective view, a plan view, and a cross-sectional view showing still another example of a detection element included in a strain gauge according to the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and duplicated explanations may be omitted.

[0010] In the following embodiments and modifications, examples are shown mainly of detecting battery expansion, but the invention is not limited thereto, and the strain gauges and sensors according to the embodiments and modifications can detect various battery states. Examples of various battery states include battery contraction, the presence or absence of protrusions or recesses, shape distribution, temperature, and the like, in addition to battery expansion.

[0011] First Embodiment Fig. 1 is a diagram showing a battery pack 1 which is an example of a battery pack according to the first embodiment. The battery pack 1 is used, for example, as a battery for an electric vehicle. The battery pack 1 includes a strain gauge 10, one or more batteries 20, a housing 30, and one or more (in the example of Fig. 1, a plate-shaped member 41 and a plate-shaped member 42). The strain gauge 10 may also be connected to a circuit board 60 (see Fig. 4) which will be described later.

[0012] [Battery 20] The battery 20 is, for example, a secondary battery such as a lithium ion battery. A plurality of the batteries 20 are appropriately connected in parallel and / or series and arranged inside the housing 30. Although five batteries 20 are illustrated in FIG. 1, the number of the batteries 20 can be appropriately determined as necessary. In the example of FIG. 1, the batteries 20 are mounted in the housing 30 so as to fit exactly in the housing 30 (i.e., so as to fill the housing 30 without any gaps). However, the housing 30 may have gaps in which no batteries 20 are arranged. The shape of the battery 20 is not limited to a square shape as shown in FIG. 1, and may be, for example, a cylindrical shape. The battery 20 may be a laminated (pouch) type battery.

[0013] [Case 30] The housing 30 is a member that houses the battery 20. The housing 30 is formed of, for example, metal or resin. FIG. 2 is a diagram illustrating the housing 30 in the battery pack 1, which is an example of the battery pack according to the first embodiment. The housing 30 has a hexahedral shape in appearance. The housing 30 has a space capable of housing the battery 20 therein. The housing 30 includes a box portion 31 and a lid portion 32. In the description of FIG. 2, for convenience, the surface 30T of the housing 30 will be referred to as the upper surface, the surface 30B as the lower surface, and the surfaces 30S1 to 30S4 as side surfaces.

[0014] The box portion 31 has a box-like shape with an open top. The lid portion 32 closes the open portion at the top of the box portion 31. By closing the top of the box portion 31 with the lid portion 32, the housing 30 has a hexahedral shape.

[0015] In the battery pack according to the first embodiment, the shape of the housing is not limited to the shape of the housing 30. For example, the housing 30 may not include the lid portion 32, and the battery 20 may be stored in the box portion 31 with the top open. Also, for example, the inside of the box may be divided into a plurality of rooms, and the battery 20 may be stored in each room. When the inside of the box is divided into a plurality of rooms, and the battery 20 is stored in each room, the walls constituting each room may be regarded as the housing. Also, for example, the housing may be formed of a film that seals the battery 20.

[0016] [Plate-shaped member 41 and plate-shaped member 42] Description will be given again with reference to FIG. 1. Each of the plate-shaped members 41 and 42 is a member having higher rigidity than the housing 30. Each of the plate-shaped members 41 and 42 is formed of, for example, a metal. The plate-shaped member 41 is adhered so as to cover the upper surface 30T of the housing 30. The plate-shaped member 42 is adhered so as to cover the lower surface 30B of the housing 30. Note that, in the example of FIG. 1, two plate-shaped members are adhered to two surfaces (the upper surface 30T and the lower surface 30B) of the housing 30, respectively, but in the battery pack according to this embodiment, the number of plate-shaped members and the adhesion surfaces are not important as long as at least one surface of the housing can be covered.

[0017] The strain gauge 10 is an example of a sensor that detects strain in the housing 30. The strain gauge 10 is attached to the housing 30. More specifically, the strain gauge 10 is attached to a surface of the housing 30 other than the surface to which a plate-shaped member (in the example of FIG. 1, the plate-shaped member 41 or the plate-shaped member 42) is bonded (hereinafter, for convenience, also referred to as the "surface without a plate-shaped member").

[0018] In the example of Fig. 1, the strain gauge 10 is attached to the center of the side surface 30S1. However, as long as one or more strain gauges 10 are attached to one or more surfaces that do not have a plate-like member, the surface to which the strain gauge 10 is attached, the position of the strain gauge 10 on the surface, and the number of strain gauges 10 attached are not limited. For example, the strain gauge 10 may be attached to any one of the side surfaces 30S2, 30S3, and 30S4. The strain gauge 10 may also be attached to two or more surfaces, the side surfaces 30S1, 30S2, 30S3, and 30S4.

[0019] [Strain gauge 10] The strain gauge 10 will be described in detail. FIG. 3 is a plan view of the strain gauge 10 mounted on the battery pack 1, which is an example of the battery pack according to the first embodiment. FIG. 4 is a cross-sectional view of the strain gauge 10 mounted on the battery pack 1, which is an example of the battery pack according to the first embodiment. Specifically, FIG. 4 is a cross-sectional view showing a cross section along the line AA in FIG. 2. Referring to FIGS. 3 and 4, the strain gauge 10 has a base material 11, a resistor 12, and a terminal portion 13. The strain gauge 10 can be attached to the housing 30, for example, by applying an adhesive to the lower surface 11b of the base material 11.

[0020] In this embodiment, for convenience, in the strain gauge 10, the side of the substrate 11 on which the resistor 12 is provided is referred to as the upper side or one side, and the side on which the resistor 12 is not provided is referred to as the lower side or the other side. Also, the surface on which the resistor 12 is provided in each portion is referred to as the one side or upper surface, and the surface on which the resistor 12 is not provided is referred to as the other side or lower surface. However, the strain gauge 10 can be used upside down or placed at any angle. Also, the planar view refers to the object being viewed from the normal direction of the upper surface 11a of the substrate 11, and the planar shape refers to the shape of the object being viewed from the normal direction of the upper surface 11a of the substrate 11.

[0021] The substrate 11 is an insulating member that serves as a base layer for forming the resistor 12 and the like, and has flexibility. The thickness of the substrate 11 is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, about 5 μm to 500 μm. In particular, it is preferable that the thickness of the substrate 11 is 5 μm to 200 μm, since it is possible to reduce the strain sensitivity error of the resistor 12.

[0022] The substrate 11 can be formed from an insulating resin film such as PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, etc. The film refers to a flexible member having a thickness of about 500 μm or less.

[0023] Here, "formed from an insulating resin film" does not prevent the base material 11 from containing fillers, impurities, etc. in the insulating resin film. The base material 11 may be formed from an insulating resin film containing fillers such as silica or alumina.

[0024] However, if the substrate 11 does not need to be flexible, the substrate 11 may be made of materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, perovskite ceramics (CaTiO3, BaTiO3), etc.

[0025] The resistor 12 is a thin film formed in a predetermined pattern on the substrate 11, and is a sensing part that generates a resistance change when strained. The resistor 12 may be formed directly on the upper surface 11a of the substrate 11, or may be formed on the upper surface 11a of the substrate 11 via another layer. For convenience, the resistor 12 is shown in Fig. 3 with a matte pattern.

[0026] The resistor 12 can be formed, for example, from a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 12 can be formed from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr mixed phase film. An example of a material containing Ni is Cu-Ni (copper nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0027] Here, the Cr mixed phase film is a film in which Cr, CrN, Cr2N, etc. are mixed. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0028] The thickness of resistor 12 is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, about 0.05 μm to 2 μm. In particular, a thickness of resistor 12 of 0.1 μm or more is preferable in that the crystallinity of the crystals constituting resistor 12 (for example, the crystallinity of α-Cr) is improved. Moreover, a thickness of resistor 12 of 1 μm or less is even more preferable in that film cracks and warping from substrate 11 caused by internal stress of the film constituting resistor 12 can be reduced.

[0029] For example, when the resistor 12 is a Cr mixed phase film, the stability of the gauge characteristics can be improved by making the resistor 12 mainly composed of α-Cr (alpha chromium), which is a stable crystal phase. In addition, by making the resistor 12 mainly composed of α-Cr, the gauge factor of the strain gauge 10 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C. Here, the main component means that the target substance accounts for 50 mass % or more of the total substance constituting the resistor, but from the viewpoint of improving the gauge characteristics, it is preferable that the resistor 12 contains α-Cr at 80 weight % or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0030] The terminal portions 13 extend from both ends of the resistor 12 and are formed in a generally rectangular shape in plan view, wider than the resistor 12. The terminal portions 13 are a pair of electrodes for outputting to the outside a change in the resistance value of the resistor 12 caused by distortion, and are connected to, for example, a flexible board or a lead wire for external connection.

[0031] For example, the resistor 12 extends from one of the terminal portions 13 while folding back in a zigzag pattern and is connected to the other terminal portion 13. The upper surface of the terminal portion 13 may be covered with a metal having better solderability than the terminal portion 13. Although the resistor 12 and the terminal portion 13 are denoted by different reference numerals for convenience, they can be integrally formed from the same material in the same process.

[0032] A cover layer 15 (insulating resin layer) may be provided on the upper surface 11a of the base material 11 so as to cover the resistor 12 and expose the terminal portion 13. By providing the cover layer 15, mechanical damage to the resistor 12 can be prevented. Furthermore, by providing the cover layer 15, the resistor 12 can be protected from moisture and the like. The cover layer 15 may be provided so as to cover the entire portion except for the terminal portion 13.

[0033] The cover layer 15 can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, or composite resin (e.g., silicone resin, polyolefin resin). The cover layer 15 may contain a filler or a pigment. There is no particular limit to the thickness of the cover layer 15 and it can be appropriately selected depending on the purpose, but it can be, for example, about 2 μm to 30 μm.

[0034] In the battery pack 1, when the battery 20 expands, the housing 30 is correspondingly deformed (the housing 30 is distorted). The strain gauge 10 detects the distortion of the housing 30 as a change in the resistance value of the resistor 12, and can output the detected distortion from the terminal portion 13 which is a pair of electrodes.

[0035] When the housing 30 expands, the resistor 12 of the strain gauge 10 becomes thinner and longer, and the resistance value increases. When the housing 30 contracts, the resistor 12 of the strain gauge 10 becomes thicker and shorter, and the resistance value decreases. Therefore, by monitoring the increase or decrease in the resistance value of the resistor of the strain gauge 10, it is possible to determine whether the housing 30 is expanding. In other words, it is possible to determine whether the battery 20 stored in the housing 30 is expanding.

[0036] To manufacture the strain gauge 10, first, a substrate 11 is prepared, and the resistor 12 and terminal portion 13 having a planar shape as shown in Fig. 3 are formed on the upper surface 11a of the substrate 11. The material and thickness of the resistor 12 and terminal portion 13 are as described above. The resistor 12 and terminal portion 13 can be integrally formed from the same material.

[0037] The resistor 12 and the terminal portion 13 can be formed, for example, by forming a film by magnetron sputtering using a raw material capable of forming the resistor 12 and the terminal portion 13 as a target, and patterning the film by photolithography. The resistor 12 and the terminal portion 13 may be formed by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like instead of magnetron sputtering.

[0038] From the viewpoint of stabilizing the gauge characteristics, it is preferable to vacuum-form a functional layer having a thickness of about 1 nm to 100 nm as a base layer by, for example, a conventional sputtering method on the upper surface 11a of the substrate 11 before forming the resistor 12 and the terminal portion 13. After the resistor 12 and the terminal portion 13 are formed on the entire upper surface of the functional layer, the functional layer is patterned into the planar shape shown in FIG. 3 together with the resistor 12 and the terminal portion 13 by photolithography.

[0039] In the present application, the functional layer refers to a layer having a function of promoting the crystal growth of at least the upper layer, the resistor 12. The functional layer preferably further has a function of preventing oxidation of the resistor 12 due to oxygen and moisture contained in the substrate 11, and a function of improving the adhesion between the substrate 11 and the resistor 12. The functional layer may further have other functions.

[0040] Since the insulating resin film constituting the substrate 11 contains oxygen and moisture, it is effective for the functional layer to have the function of preventing oxidation of the resistor 12, particularly when the resistor 12 contains Cr, since Cr forms a self-oxidized film.

[0041] The material of the functional layer is not particularly limited as long as it has the function of promoting the crystal growth of at least the upper layer, the resistor 12, and can be appropriately selected depending on the purpose. For example, Cr (chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn (zinc), Cu (copper), Bi (bismuth), Examples of the metal include one or more metals selected from the group consisting of Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), and Al (aluminum), an alloy of any of the metals in this group, or a compound of any of the metals in this group.

[0042] Examples of the alloy include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the compound include TiN, TaN, Si3N4, TiO2, Ta2O5, SiO2, etc.

[0043] The functional layer can be formed in vacuum by conventional sputtering, for example, using a raw material capable of forming the functional layer as a target and introducing Ar (argon) gas into a chamber. By using conventional sputtering, the functional layer is formed while etching the upper surface 11a of the substrate 11 with Ar, so that the amount of the functional layer formed can be minimized and the effect of improving adhesion can be obtained.

[0044] However, this is just one example of a method for forming the functional layer, and the functional layer may be formed by other methods. For example, a method may be used in which the upper surface 11a of the substrate 11 is activated by a plasma treatment using Ar or the like before forming the functional layer, thereby improving adhesion, and then the functional layer is vacuum-formed by magnetron sputtering.

[0045] There is no particular limitation on the combination of the material of the functional layer with the materials of the resistor 12 and the terminal portion 13, and it can be appropriately selected according to the purpose. For example, it is possible to use Ti for the functional layer, and form a Cr mixed phase film containing α-Cr (alpha chromium) as the main component for the resistor 12 and the terminal portion 13.

[0046] In this case, for example, the resistor 12 and the terminal portion 13 can be formed by magnetron sputtering using a raw material capable of forming a Cr mixed phase film as a target and introducing Ar gas into a chamber. Alternatively, the resistor 12 and the terminal portion 13 may be formed by reactive sputtering using pure Cr as a target and introducing an appropriate amount of nitrogen gas together with Ar gas into a chamber.

[0047] In these methods, the growth surface of the Cr mixed-phase film is determined by the functional layer made of Ti, and a Cr mixed-phase film containing α-Cr, which has a stable crystal structure, as a main component, can be formed. Furthermore, the Ti constituting the functional layer is diffused into the Cr mixed-phase film, thereby improving the gauge characteristics. For example, the gauge factor of the strain gauge 10 can be set to 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be set within the range of −1000 ppm / ° C. to +1000 ppm / ° C. In addition, when the functional layer is formed of Ti, the Cr mixed-phase film may contain Ti and TiN (titanium nitride).

[0048] When the resistor 12 is a Cr mixed phase film, the functional layer made of Ti has all of the following functions: promoting the crystal growth of the resistor 12, preventing oxidation of the resistor 12 due to oxygen and moisture contained in the substrate 11, and improving adhesion between the substrate 11 and the resistor 12. The same applies when Ta, Si, Al, or Fe is used as the functional layer instead of Ti.

[0049] In this way, by providing a functional layer under the resistor 12, it is possible to promote crystal growth of the resistor 12, and to produce a resistor 12 consisting of a stable crystal phase. As a result, it is possible to improve the stability of the gauge characteristics of the strain gauge 10. In addition, the material constituting the functional layer diffuses into the resistor 12, thereby improving the gauge characteristics of the strain gauge 10.

[0050] After forming the resistor 12 and the terminal portion 13, a cover layer 15 that covers the resistor 12 and exposes the terminal portion 13 is provided on the upper surface 11a of the substrate 11 as necessary, thereby completing the strain gauge 10. The cover layer 15 can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 11a of the substrate 11 so as to cover the resistor 12 and expose the terminal portion 13, and then heating and curing the film. The cover layer 15 may also be produced by applying a liquid or paste-like thermosetting insulating resin to the upper surface 11a of the substrate 11 so as to cover the resistor 12 and expose the terminal portion 13, and then heating and curing the film.

[0051] Fig. 5 is a block diagram illustrating a circuit board 60 connected to a strain gauge 10 of a battery pack 1, which is an example of a battery pack according to the first embodiment. As shown in Fig. 5, the strain gauge 10 is connected to an analog front-end section 61 mounted on the circuit board 60, and the output of the analog front-end section 61 is connected to an external output terminal 62. This allows information detected by the strain gauge 10 (information indicating the degree of expansion of the battery 20) to be output as a digital signal from the external output terminal 62.

[0052] Circuits (electronic components, etc.) having other functions may be mounted on the circuit board 60. Circuits having other functions include, for example, a voltage monitoring circuit, a protection circuit, a current detection circuit, etc. for the battery 20. There is no particular limitation on where the circuit board 60 is attached. For example, the circuit board 60 is attached near a device (for example, a specific location of a vehicle) in which the battery pack 1 is mounted. The circuit board 60 may be equipped with a power source necessary for driving the circuits included in the circuit board 60, or may be supplied with electricity from a separate power source.

[0053] The pair of terminals 13 of the strain gauge 10 are connected to the analog front end unit 61 using, for example, a flexible substrate, lead wires, or the like.

[0054] The analog front-end unit 61 includes, for example, a bridge circuit, an amplifier, an analog / digital conversion circuit (A / D conversion circuit), and an external communication function (for example, an I 2 The analog front-end unit 61 may be provided with a temperature compensation circuit. The analog front-end unit 61 may be formed as an IC or may be composed of individual components.

[0055] In the analog front-end section 61, for example, a pair of terminals 13 of the strain gauge 10 are connected to a bridge circuit. That is, one side of the bridge circuit is formed by the resistor 12 between the pair of terminals 13, and the other three sides are formed by fixed resistors. This makes it possible to obtain a voltage (analog signal) corresponding to the resistance value of the resistor 12 as the output of the bridge circuit.

[0056] The voltage output from the bridge circuit is amplified by the amplifier, and then converted into a digital signal by the A / D conversion circuit, which can be output from the external output terminal 62. If the analog front-end unit 61 includes a temperature compensation circuit, a temperature-compensated digital signal can be output from the external output terminal 62.

[0057] For example, in the battery pack 1, the battery 20 may expand due to a decrease in the life of the battery 20, leading to leakage, etc. In the battery pack 1, the expansion of the battery 20 is detected by the strain gauge 10 through the housing 30, and the detection result (information indicating the degree of expansion of the battery 20) is output from the external output terminal 62 as a digital signal from the analog front end unit 61.

[0058] For example, it is possible to connect a charging circuit to the external output terminal 62 outside the battery pack 1. In this case, the connected charging circuit can increase or decrease the charging current based on the digital signal from the analog front end unit 61. Furthermore, when the connected charging circuit determines that the degree of expansion of the battery 20 exceeds an allowable value, it can stop charging and emit an alarm or display a message such as "Charging not possible."

[0059] It is also possible to provide a control circuit including a CPU (Central Processing Unit) and the like inside the battery pack 1. The control circuit can be mounted on, for example, a circuit board 60. In this case, for example, a current cutoff switch is inserted in the line on the positive and / or negative side of the battery 20, and a digital signal output by an analog front-end unit 61 is input to the control circuit. When the control circuit determines, based on the digital signal from the analog front-end unit 61, that the degree of expansion of the battery 20 exceeds an allowable value, it can cut off the current cutoff switch to stop the operation of the battery pack 1.

[0060] In this way, by providing the strain gauge 10 in the battery pack 1, the degree of expansion of the battery 20 can be detected as a change in the resistance value of the resistor 12. This makes it possible to control the amount of charging current or stop the operation of the battery pack 1 according to the degree of expansion of the battery 20. As a result, when the degree of expansion of the battery 20 exceeds an allowable value, it becomes possible to prevent the battery pack 1 from being forcibly charged or from being continuously used, thereby preventing damage to the battery pack 1 and improving the safety of the battery pack 1.

[0061] In particular, when resistor 12 is formed from a Cr mixed phase film, the sensitivity of the resistance value to the expansion of battery 20 (the amount of change in the resistance value of resistor 12 with respect to the expansion of the same battery 20) is significantly improved compared to when resistor 12 is formed from Cu-Ni or Ni-Cr. When resistor 12 is formed from a Cr mixed phase film, the sensitivity of the resistance value to the expansion of battery 20 is approximately 5 to 10 times higher compared to when resistor 12 is formed from Cu-Ni or Ni-Cr. Therefore, by forming resistor 12 from a Cr mixed phase film, it becomes possible to accurately detect the expansion of battery 20.

[0062] Furthermore, since the resistance value has a high sensitivity to the expansion of the battery 20, it is possible to differentiate the operation to be performed depending on the degree of expansion of the battery 20. For example, it is possible to realize a control in which a predetermined operation is performed when it is detected that the expansion of the battery 20 is small, another operation is performed when it is detected that the expansion of the battery 20 is medium, and yet another operation is performed when it is detected that the expansion of the battery 20 is large.

[0063] Furthermore, if the resistance value is highly sensitive to the expansion of the battery 20, a signal with a high S / N ratio can be obtained. Therefore, even if the number of times averaging is performed in the A / D conversion circuit of the analog front-end unit 61 is reduced, the signal can be detected with high accuracy. By reducing the number of times averaging is performed in the A / D conversion circuit, the time required for one A / D conversion can be shortened.

[0064] Moreover, when the resistor 12 is made of a Cr mixed phase film, the strain gauge 10 can be made smaller, so that it can be used in a small battery pack 1. Furthermore, since the strain gauge 10 can be made smaller, it is possible to improve the degree of freedom in selecting the location where it is placed.

[0065] In the battery pack 1, the strain gauge 10 is attached to a surface of the housing 30 other than the surfaces to which the plate members 41 and 42 are attached (a surface on which no plate members are attached).

[0066] As described above, the plate-like member has higher rigidity than the housing. Therefore, the surfaces of the housing that do not have the plate-like member have lower rigidity relative to the surfaces to which the plate-like member is attached. Specifically, the side surfaces 30S1, 30S2, 30S3, and 30S4 that do not have the plate-like member have lower rigidity relative to the top surface 30T and the bottom surface 30B.

[0067] Therefore, the side surfaces 30S1, 30S2, 30S3, and 30S4 are more likely to be distorted due to the expansion of the battery 20 than the upper surface 30T and the lower surface 30B. In other words, when the battery 20 expands, the distortion of the housing 30 due to the expansion is concentrated on the side surfaces that do not have the plate-like members. Therefore, since the amount of distortion increases on the side surfaces 30S1, 30S2, 30S3, and 30S4, the distortion of the housing 30 can be detected with high accuracy by attaching one or more strain gauges 10 to at least one of these surfaces. Therefore, the battery pack according to the first embodiment has the effect of being able to detect the state of the battery with high accuracy.

[0068] Second Embodiment In the battery pack according to the present disclosure, the plate-shaped member may be provided on two or more of the side surfaces of the housing. A battery pack according to a second embodiment will be described below. The battery pack according to the second embodiment differs from the battery pack according to the first embodiment in that the surface to which the plate-shaped member is adhered is different. FIG. 6 is a diagram showing a battery pack 2, which is an example of the battery pack according to the second embodiment. The following description will focus on the differences from the battery pack according to the first embodiment.

[0069] The battery pack 2 includes a strain gauge 10, one or more batteries 20, a housing 30, and a plate-shaped member 141, a plate-shaped member 142, a plate-shaped member 143, and a plate-shaped member 144. The strain gauge of the battery pack 2 may be connected to a circuit board 60 (not shown).

[0070] [Plate-shaped member 141, plate-shaped member 142, plate-shaped member 143, and plate-shaped member 144] Plate-shaped member 141, plate-shaped member 142, plate-shaped member 143, and plate-shaped member 144 are each made of the same material as plate-shaped member 41 and plate-shaped member 42 according to the first embodiment. That is, plate-shaped members 141 to 144 are members having higher rigidity than housing 30, and are members made of metal or the like.

[0071] 6, plate-shaped member 141 is adhered so as to cover side surface 30S1 of housing 30. Plate-shaped member 142 is adhered so as to cover side surface 30S2 of housing 30. Plate-shaped member 143 is adhered so as to cover side surface 30S3 of housing 30. Plate-shaped member 144 is adhered so as to cover side surface 30S4 of housing 30.

[0072] In the battery pack 2, the strain gauge 10 is attached to a surface of the housing 30 other than the surface to which the plate-shaped member is attached (i.e., the upper surface 30T or the lower surface 30B). In the example of FIG. 6, the strain gauge 10 is attached to the upper surface 30T of the housing 30.

[0073] 6, the strain gauge 10 is attached to the upper surface 30T, but the surface to which the strain gauge 10 is attached may be the lower surface 30B. Also, for example, one or more strain gauges 10 may be attached to each of the upper surface 30T and the lower surface 30B.

[0074] In the battery pack according to this embodiment, the top and bottom surfaces of the housing (top surface 30T and bottom surface 30B in the example of FIG. 6) are surfaces without plate-like members, and therefore have a relatively low rigidity compared to the side surfaces of the housing to which plate-like members are attached. Therefore, according to the battery pack according to this embodiment, the top surface 30T and bottom surface 30B are more likely to be distorted due to the expansion of the battery 20 than the four side surfaces of the housing. In other words, when the battery 20 expands, the distortion of the housing 30 due to the expansion is concentrated on the side surfaces without plate-like members.

[0075] Therefore, by attaching one or more strain gauges 10 to the upper surface 30T and / or the lower surface 30B, it is possible to accurately detect the strain of the housing 30. Therefore, the battery pack according to the second embodiment has an effect of being able to accurately detect the state of the battery.

[0076] In addition, the arrangement of the plate-shaped members and the strain gauges in the battery pack according to the present disclosure is not limited to the examples in the first and second embodiments. In addition to the examples described in these embodiments, for example, the plate-shaped members may be arranged only on the lower surface of the housing, and the strain gauges may be attached to at least one side surface of the housing. Also, for example, five of the six surfaces of the housing may be covered with plate-shaped members, and the strain gauge may be attached to the remaining surface.

[0077] Third Embodiment In the battery pack according to the present disclosure, the number of strain gauges attached to the housing is not limited. The locations of the strain gauges may be determined appropriately depending on the shape of the housing, the positions and number of the surfaces of the plate-like members to which the plate-like members are attached, and whether the strain gauges are to detect "compressive strain" or "expansive strain" of the housing.

[0078] As an example, a case where a box-shaped housing as described in the first and second embodiments is adopted as the housing of the battery pack will be described. When the battery mounted in the battery pack expands, due to the relationship between the shape of the housing and the product strength, the degree of expansion is likely to be greater in the center part of the housing on the side where there is no plate-like member than in the sides and the vicinity of the four corners of each side. That is, the center part of the housing on the side where there is no plate-like member of the battery pack is likely to be subject to large expansion strain. Similarly, when the battery of the battery pack expands, the portion near the corner of the housing on the side where there is no plate-like member is likely to be subject to compressive strain due to the expansion of the center of the same side. However, the portion of the outermost periphery of each side (i.e., the portion corresponding to the "side" of each housing side) that is joined to the other side is highly rigid, and therefore is less likely to be subject to expansion strain or compressive strain than other portions of the same side.

[0079] Therefore, when it is desired to detect expansion strain of the housing using a strain gauge, it is desirable to place the strain gauge (more specifically, the grid of resistors which is the detection element of the strain gauge) near the center of the surface on which there is no plate-like member. On the other hand, when it is desired to detect compression strain using a strain gauge, it is desirable to place the strain gauge (more specifically, the grid of resistors of the strain gauge) near the edge of the surface on which there is no plate-like member (or near the four corners), excluding the part joined to the other surface. In both the case of expansion strain and the case of compression strain, by placing the strain gauge as described above, it is possible to detect the strain of the housing with high accuracy.

[0080] The battery pack according to the third embodiment will be described below. The battery pack according to the third embodiment is different from the battery pack according to the first embodiment in the number of strain gauges attached to the housing. Also, the battery pack according to the third embodiment is different from the battery pack according to the first embodiment in the attachment positions of the strain gauges.

[0081] 7 is a diagram showing a battery pack 3 which is an example of a battery pack according to the third embodiment. Here, differences from the battery pack according to the first embodiment will be mainly described, and descriptions of configurations similar to those of the battery pack according to the first embodiment may be omitted.

[0082] A plate-shaped member 41 is adhered to an upper surface 30T of a housing 30 of a battery pack 3 so as to cover the upper surface 30T. A plate-shaped member 42 is adhered to a lower surface 30B of the housing 30 so as to cover the lower surface 30B of the housing 30. Then, one or more strain gauges 10 are attached near corners of the surface of the housing 30 to which the plate-shaped member is not adhered.

[0083] 7, a total of four strain gauges 10 are attached near each of the four corners of the side surface 30S1 of the housing 30. Note that, in the battery pack according to this embodiment, the number of strain gauges 10 is not limited to the example in FIG.

[0084] According to the above configuration, the strain gauge is attached near the corner of the surface of the battery pack housing that does not have a plate-like member. Therefore, as described above, since the strain gauge is attached to the location where the compressive strain is concentrated (where the amount of compressive strain is greater), the strain gauge can accurately detect the strain of the housing. Therefore, the battery pack 3 can accurately detect the expansion of the battery 20.

[0085] The same can be said when the plate-like member is adhered to the side surface of the housing. Fig. 8 is a diagram showing a battery pack 4 which is another example of the battery pack according to this embodiment. The battery pack 4 differs from the battery pack 2 according to the second embodiment in the number of attached strain gauges and their attachment positions. Note that the number of strain gauges 10 in the battery pack 4 is not limited to two, and may be one, or three or more.

[0086] The battery pack 4 is provided with strain gauges 10 near two diagonal corners among the four corners of the top surface 30T. According to the above configuration, similar to the example of FIG. 7, the strain gauges are attached near the corners of the surface of the battery pack housing that does not have a plate-like member. Therefore, as described above, since the strain gauges are attached to the locations where compressive strain is concentrated (where the amount of compressive strain is greater), the strain of the housing can be detected with high accuracy. Therefore, the battery pack 4 can detect the expansion of the battery 20 with high accuracy.

[0087] <<Modifications of the casing in the battery pack according to the first to third embodiments>> Next, various modifications of the casings of the battery packs according to the above-mentioned first to third embodiments will be described.

[0088] <First Modification> In producing the battery pack according to this embodiment, when a method is adopted in which the battery is placed in the housing after the housing is produced, the housing may be produced larger than the battery. If the housing is produced larger than the battery, a gap may be formed between the housing and the battery, and the housing and the battery may not be in close contact with each other. If the housing and the battery are not in close contact with each other, even if the battery expands, the gap with the housing may simply be filled, and no distortion may occur in the housing (or, even if distortion occurs, it may be very small). Therefore, if the housing and the battery in a battery pack are not in close contact with each other, it may be difficult to detect the expansion of the battery even if a strain gauge is attached to the housing.

[0089] Hereinafter, as a first variation of the housing, a configuration for improving the adhesion between the battery and the housing after the battery is inserted into the housing will be described. Specifically, the housing has a slit for crimping the battery after it is inserted into the housing.

[0090] Each of Fig. 9 to Fig. 12 is a diagram illustrating a housing 130 which is a first modified example of the housing in the battery pack according to the present embodiment. Each of Fig. 9 to Fig. 11 is a perspective view of the housing 130. Fig. 12 is a top view of the housing 130.

[0091] The procedure for attaching the battery 20 to the housing 130 will be described. First, the housing 130 is formed in a rectangular tube shape that is larger than the battery 20. The housing 130 is formed by bending a plate-like member with slits 131 formed therein, forming it into a rectangular tube shape, and joining the ends. FIG. 9 is a diagram showing the housing 130 formed into a rectangular tube shape. The housing 130 has a plurality of slits 131 arranged in a row along the edge between adjacent side surfaces. Each of the plurality of slits 133 opens across the adjacent side surfaces.

[0092] Next, the battery 20 is inserted inside the housing 130. Fig. 10 is a diagram showing the state in which the battery 20 is inserted inside the housing 130. The housing 130 is formed with an interior that is larger than the battery 20. Therefore, when the battery 20 is inserted inside the housing 130, there is a gap between the housing 130 and the battery 20.

[0093] Next, the corners of the housing 130 between the adjacent side surfaces are crimped to bring the housing 130 into close contact with the battery 20. As described above, the housing 130 has slits 131 at the corners of the housing 130. Due to the presence of this slit structure, the housing 130 and the battery 20 can be brought into close contact when the corners of the housing 130 are crimped. Specifically, when the corners of the housing 130 are crimped, the outer shape of the housing 130 becomes smaller, and the battery 20 can be brought into close contact with the housing 130. FIG. 11 is a diagram showing the housing 130 in a crimped state. FIG. 12 is a plan view showing the housing 130 in a crimped state. In the first modified example, the corners are crimped from both sides (from the direction of the arrow in FIG. 12).

[0094] In the above description, the battery 20 is inserted into the housing 130 and then crimped, but the battery 20 may be inserted after or while crimping the housing 130. The number, position, shape, etc. of the slits may be determined as appropriate depending on the material properties of the housing 130 and the strength and direction of the crimping force, etc.

[0095] <Second Modification> The second modified housing has a different crimping method from the first modified housing. In the second modified housing, the corners are crimped so that one side is shifted.

[0096] Fig. 13 is a diagram illustrating a housing 230 which is a second modified example of the housing in the battery pack according to the present embodiment. Fig. 13 is a plan view showing a state in which the housing 230 is crimped. As shown in Fig. 13, by changing the crimping direction, the shape of the corners differs from that of the first modified example.

[0097] <Third Modification> A third variation of the housing is a housing having a bottom plate and side plates, the side plates being configured to press the battery inward.

[0098] Fig. 14 and Fig. 15 are diagrams illustrating a housing 330 which is a third modified example of the housing in the battery pack according to the present embodiment. Fig. 14 is a plan view showing metal plates 330m in a state where the housing 330 is unfolded. Fig. 15 is a diagram showing a state in the middle of assembling the metal plates 330m to form the housing 330.

[0099] The housing 330 is formed by bending a metal plate 330m. The housing 330 includes a bottom plate 330SB and a side plate 330SS1, a side plate 330SS2, a side plate 330SS3, and a side plate 330SS4. The metal plate 330m may be formed from a single metal plate, or may be formed by bonding multiple metal plates together.

[0100] In the metal plate 330m, at a connection portion 330L1 which is a connection portion between the bottom plate 330SB and the side plate 330SS1, the side plate 330SS1 is bent toward the front side of the paper of Fig. 14 to form a valley fold. When the side plate 330SS1 is valley folded, the side plate 330SS1 is made to be inclined toward the inside of the bottom plate 330SB when viewed from above. By making the side plate 330SS1 inclined toward the inside of the bottom plate 330SB when viewed from above, the side plate 330SS1 can push the battery placed on the bottom plate 330SB by the elasticity of the connection portion 330L1.

[0101] Similarly, side plate 330SS2 is valley-folded at connection portion 330L2, which is the connection portion between bottom plate 330SB and side plate 330SS2. Side plate 330SS3 is valley-folded at connection portion 330L3, which is the connection portion between bottom plate 330SB and side plate 330SS3. Furthermore, side plate 330SS4 is valley-folded at connection portion 330L4, which is the connection portion between bottom plate 330SB and side plate 330SS4.

[0102] Then, the housing 330 is formed from the metal plate 330m. By forming the housing 330 as described above, the side plate 330SS2 can press the battery placed on the bottom plate 330SB by the elasticity of the connection portion 330L2. Also, the side plate 330SS3 can press the battery placed on the bottom plate 330SB by the elasticity of the connection portion 330L3. The side plate 330SS4 can press the battery placed on the bottom plate 330SB by the elasticity of the connection portion 330L4.

[0103] <Fourth Modification> In the battery pack according to this embodiment, in order to make the housing more susceptible to distortion, the housing of the fourth modified example is provided with a thin-walled portion at a part of the housing where the material forming the housing is thin.

[0104] 16 is a diagram illustrating a housing 35 which is an example of a fourth modified example of the housing in the battery pack according to the present embodiment. Housing 35 differs from housing 30 in that a thin-walled portion 36 is provided on side surface 30S1 to which strain gauge 10 is attached. Thin-walled portion 36 is formed by thinning a material that forms side surface 30S1 to which strain gauge 10 is attached. Housing 35 has thin-walled portion 36 provided on side surface 35S1 at a portion to which strain gauge 10 is attached.

[0105] In particular, when detecting expansion strain with strain gauge 10, it is preferable to provide thin portion 36 near the center of side surface 35S1 and attach strain gauge 10 to thin portion 36.

[0106] In the above example, the strain gauge 10 is attached to the side surface 35S1, but the location where the strain gauge 10 is attached is not limited to the side surface 35S1, and the strain gauge 10 may be attached to another surface. The thin-walled portion described in this modification may be provided at the position where the strain gauge is attached to the housing of the battery pack according to the first and second embodiments. Then, the strain gauge may be attached to the thin-walled portion. In this way, by combining the two configurations of the thin-walled portion and the plate-shaped member, the strain gauge can more easily detect the strain of the housing caused by the expansion of the battery.

[0107] <Fifth Modification> The fifth modified housing has a different position of the thin-walled portion from the fourth modified housing. In the fifth modified housing, a thin-walled portion is provided on the surface on which the strain gauge is attached, where the strain gauge is not attached.

[0108] 17 is a diagram illustrating a housing 37 which is an example of a fifth modified example of the housing in the battery pack according to the present embodiment. Housing 37 is different from housing 35 in that a thin-walled portion 36 is provided at a position corresponding to strain gauge 10 on side surface 37S1 on which strain gauge 10 is attached. Thin-walled portion 38 is formed by thinning a material forming side surface 37S1 on which strain gauge 10 is attached. Housing 37 has thin-walled portion 38 provided at a portion of side surface 37S1 on which strain gauge 10 is not attached.

[0109] In particular, when detecting compressive strain with strain gauge 10, it is advisable to create thin portion 38 near the center of side surface 37S1 and attach strain gauge 10 to a corner of side surface 37S1. By providing thin portion 38 in the center, damage and the like can be prevented.

[0110] In the above example, the strain gauge 10 is attached to the side surface 37S1, but the place where the strain gauge 10 is attached is not limited to the side surface 37S1, and the strain gauge 10 may be attached to another surface. The thin-walled portion described in this modification may be provided in the center of the surface of the housing of the battery pack according to the third embodiment where the strain gauge is attached. In this way, by combining the two configurations of the thin-walled portion and the plate-shaped member, the strain of the housing due to the expansion of the battery can be made larger. Therefore, the strain of the housing can be detected more accurately using the strain gauge.

[0111] Fourth Embodiment In the above example, the battery is mounted so that it fills the box-shaped housing, but the battery and a monitoring unit that monitors the state of the battery may be mounted in the housing together. If a gap is formed between the housing and the monitoring unit, the strain gauge 10 is attached near the gap between the housing and the monitoring unit.

[0112] 18 is a diagram illustrating a battery pack 5 which is an example of a battery pack according to the fourth embodiment. The battery pack 5 includes a strain gauge 10, one or more batteries 20, a housing 30, and a monitoring unit 65. In the battery pack 5, the battery 20 is not housed in the portion that would house the battery 20, but a monitoring unit 65 smaller than the battery 20 is housed therein. By housing the monitoring unit 65 smaller than the battery 20 instead of the battery 20, a hollow portion is formed.

[0113] The strain gauge 10, the battery 20, and the housing 30 are described in the first embodiment and will not be described here. The battery pack 5 has one less battery 20 than the battery pack 1. The battery pack 5 houses a monitoring unit 65 in the portion where the battery 20 was housed.

[0114] [Monitoring Department 65] The monitoring unit 65 includes an ECU (Electronic Control Unit) for monitoring the state of the battery 20, and circuits such as the circuit board 60 described above. The monitoring unit 65 has a small shape compared to the battery 20. Therefore, a gap SP1 is formed between the monitoring unit 65 and the housing 30.

[0115] In a battery pack, when there is a gap between the case and the battery (or a group of batteries in the case of multiple batteries) all around, the case may not be easily distorted even if the battery expands, as described in the above embodiment. However, when the battery and the case are in close contact with each other and there is a gap only on a part of the inside of the case, when the battery expands, the strain caused by the expansion (expansion strain and compression strain) is significantly manifested in the gap.

[0116] Therefore, as in the battery pack 5 according to this embodiment, when there is a gap SP1 between the monitoring unit 65 and the housing 30 and the strain gauge 10 is provided on a surface and at a position corresponding to the gap, the accuracy of detecting the strain of the housing by the strain gauge 10 is improved. For example, if the strain gauge 10 is attached to the gap SP1 portion of the housing 30, it is easy to detect expansion strain. Also, if the battery 20 is located near the gap SP1, it is easy to detect compression strain if the strain gauge 10 is attached to the part of the battery 20 in the housing 30 that is near the gap SP1.

[0117] Fifth embodiment The battery pack according to the present disclosure may be configured to place a battery inside a housing, and then fill a gap between the housing and the battery with an inert liquid, thereby immersing the battery in the inert liquid. The battery pack according to the present disclosure may be configured to measure the level of the inert liquid and / or the internal pressure from the inert liquid due to the expansion of the battery, using a strain gauge attached to the outside of the housing. Hereinafter, a battery pack according to a fifth embodiment will be described.

[0118] Fig. 19 is a diagram illustrating a battery pack 6, which is an example of a battery pack according to the fifth embodiment. Fig. 20 is a cross-sectional view illustrating a battery pack 6, which is an example of a battery pack according to the fifth embodiment. The battery pack 6 includes one or more strain gauges 10, one or more batteries 120, and a housing 430.

[0119] The housing 430 includes a case 431 and a film 432. The case 431 has a box-like shape. The battery 120 is placed on the bottom surface of the case 431. The battery 120 is immersed in the inert liquid FIL. The inert liquid FIL is, for example, a fluorine-based inert liquid.

[0120] FIG. 21 is a diagram illustrating a state of use of a battery pack 6, which is an example of a battery pack according to the fifth embodiment. In the battery pack 6, (a) of FIG. 21 shows a case where the battery 120 is in a normal state. When the battery 120 is in a normal state, the liquid level of the inactive liquid FIL is H. Next, (b) of FIG. 21 shows a state where the battery 120 has expanded. When the battery 120 expands, the liquid level of the inactive liquid FIL rises by ΔH.

[0121] The battery pack 6 detects the expansion of the battery 120 by (1) detecting the level of the inert liquid FIL and / or (2) detecting the internal pressure of the casing 430, which changes due to a change in the level of the inert liquid FIL. When detecting the internal pressure of the casing 430, for example, the thickness of a part of the casing 430 may be thinned and a strain gauge 10 may be used to detect a change in stress applied to the casing 430.

[0122] Next, a method for manufacturing the battery pack 6 will be described. Figures 22 and 23 are diagrams illustrating a method for manufacturing the battery pack 6, which is an example of the battery pack according to the fifth embodiment.

[0123] First, the battery 120 is placed in the case 431 of the housing 430. Then, the case 431 is filled with the inert liquid FIL in which the battery 120 is immersed. Fig. 22 shows a process of filling the case 431 in which the battery 120 is placed with the inert liquid FIL.

[0124] Next, the upper surface of case 431 is sealed with film 432. Fig. 23 shows a state in which the upper surface of case 431 is sealed with film 432.

[0125] The inert liquid FIL may be circulated from the outside into the housing 430. For example, as shown in Fig. 24, the inert liquid FIL may be circulated by flowing the inert liquid FIL along the lines with arrows.

[0126] Sixth embodiment In the above-described embodiment and its modified example, an example was described in which the sensor according to the present disclosure is a strain gauge using a resistor. That is, in the above-described embodiment, a case was described in which the sensor according to the present disclosure is an electrical resistance type metal strain gauge. However, the sensor according to the present disclosure is not limited to a metal strain gauge. For example, the sensor according to the present disclosure may be a strain gauge that detects a magnetic change caused by a strain of a housing by a detection element included in the strain gauge.

[0127] Specifically, the sensor according to the present disclosure may be a strain gauge including a detection element utilizing the Villari phenomenon (described later). Also, the sensor according to the present disclosure may be a strain gauge including a detection element having a magnetic tunnel junction (described later) structure. In the sixth embodiment, a strain gauge including a detection element utilizing the Villari phenomenon will be described below. In the seventh embodiment, a strain gauge including a detection element having a magnetic tunnel junction structure will be described.

[0128] In each embodiment of this specification, members having similar functions are given similar names and numbers, and descriptions will not be repeated. In addition, the directions of the x-axis, y-axis, and z-axis in each drawing from FIG. 25 onwards are the same as the directions of the x-axis, y-axis, and z-axis shown in FIG. 25. In addition, in the following description, the positive direction of the z-axis is referred to as "upper", and the negative direction of the z-axis is referred to as "lower". That is, in the following description, "upper side" refers to the positive side of the z-axis, and "upper surface" refers to the surface on the positive side of the z-axis. In addition, "lower side" refers to the negative side of the z-axis, and "lower surface" refers to the surface on the negative side of the z-axis.

[0129] FIG. 25 is a diagram showing an example of a detection element 300 included in a strain gauge according to the sixth embodiment. FIG. 25(a) is a plan view of the detection element 300 when viewed from the positive to negative direction of the z-axis (i.e., from the top to the bottom). FIG. 25(b) shows a cross-sectional view of the detection element 300 shown in FIG. 25(a) along line α-α'. Note that, in FIG. 25(a) and (b), wiring extending from the detection element 300 is not shown. However, the detection element 300 may be connected to wiring connecting the drive coil 320 and a power source, which will be described later, and wiring for transmitting a current detected by the sensing coil 380.

[0130] As shown in FIG. 25(a), the detection element 300 includes a driving coil 320, a sensing coil 380, and a base layer 310. The base layer 310 is a layer that serves as a core material for the driving coil 320 and the sensing coil 380. The sensing coil 380 is a coil for detecting the intensity of magnetization of the base layer 310 (more precisely, a base metal 370 described later). The driving coil 320 is a coil for generating a magnetic field. The detection element 300 has a double structure in which the sensing coil 380 is wound on the inside and the driving coil 320 is wound on the outside, with the base layer 310 as the core material. The materials for the driving coil 320 and the sensing coil 380 are preferably conductive metals such as Cu, Ag, Al, and Au, and alloys of these metals. The number of turns and the size of the cross-sectional area of ​​the driving coil 320 and the sensing coil 380 may be appropriately designed according to the strain detection sensitivity required for the detection element 300.

[0131] As will be described in detail later, when stress is applied to the base layer 310, the strength of magnetization of a base metal 370 (described later) included in the base layer 310 changes. The detection element 300 can determine the strength of the stress applied to the base layer 310 (i.e., the degree of strain) by detecting this change in the strength of magnetization with the sensing coil 380.

[0132] The configuration of the detection element 300 will be further described with reference to the cross-sectional view of (b) in Fig. 25. In Fig. 25(b), the driving coil 320, the sensing coil 380, and the three insulating layers 340, 350, and 360 are each formed to surround the base metal 370, which is the core material. That is, the layers with the same component number in (b) in Fig. 25 are connected to surround the base metal 370.

[0133] The base metal 370 is a member that serves as a core material for various coils and insulating layers. The base metal 370 may be, for example, a substantially flat metal plate. The base metal 370 is covered so as to be surrounded by the insulating layer 360. The base metal 370 is desirably made of a soft magnetic material, for example, an Fe-Si-Al based alloy such as sendust, and an Ni-Fe based alloy such as permalloy. The aforementioned base layer 310 is made of the base metal 370 and the insulating layer 360, as shown in FIG. 25(b).

[0134] An insulating layer 350 is formed on the outside of the insulating layer 360 so as to surround the insulating layer 360. An insulating layer 340 is further formed on the outside of the insulating layer 350. The insulating layer 350 is a layer including the sensing coil 380, and is a layer in which the gaps in the sensing coil 380 are filled with an insulating material. The insulating layer 340 is a layer including the driving coil 320, and is a layer in which the gaps in the driving coil 320 are filled with an insulating material. The insulating layers 340, 350, and 360 are desirably made of a dry film that does not affect the magnetic field or a resist cured material such as photosensitive polyimide.

[0135] One surface of the detection element 300 may be attached to the substrate 110 as shown in FIG. 25(b). The substrate 110 is a member for fixing the detection element 300. For example, the substrate 110 may be a flexible substrate made of a plastic film or the like. The substrate 110 may be the same as the substrate 11 described in each of the above embodiments. The detection element 300 is attached to the housing of the battery pack via the substrate 110. The detection element 300 may be a flat or thin-film detection element as a whole. When the detection element 300 is flat or thin-film, the detection element 300 can be attached to the substrate 110 more easily. The substrate 110 is not an essential component of the detection element 300. For example, the detection element 300 may not be provided with the substrate 110, and the lower surface of the detection element 300 may be directly attached to the housing of the battery pack.

[0136] The housing of the battery pack according to this embodiment may basically have the same configuration and material as the housing according to the first to fifth embodiments and the modified examples of these embodiments. However, in this embodiment, it is more preferable that the housing of the battery pack is made of a non-magnetic material. The housing of the battery pack according to this embodiment can be made of, for example, non-magnetic stainless steel.

[0137] Next, the principle of detecting strain using the detection element 300 will be outlined. The detection element 300 includes a base metal 370, which is a magnetic body. When an alternating current is supplied from a power source to the drive coil 320, the drive coil 320 generates an alternating magnetic field around it. This generates a magnetic field, and the base metal 370 is magnetized. If the housing of the battery pack is deformed in this state, strain occurs. The strain is transmitted through the substrate 110, and stress is applied to the base metal 370. Note that if the detection element 300 is attached to the housing without the substrate 110, the stress is transmitted directly from the housing to the base metal 370 (and the insulating layers 340 to 360 covering it).

[0138] When stress is applied to the base metal 370, the magnetic permeability of the base metal 370 changes according to the stress. Therefore, the strength of magnetization (degree of magnetization) of the base metal 370 changes. The phenomenon in which the magnetic permeability and strength of magnetization of a magnetic body change when stress is applied to the magnetic body is called the "Villari phenomenon". According to the configuration of the detection element 300, an AC voltage corresponding to the strength of magnetization of the base metal 370 is induced in the sensing coil 380, which is a pickup coil. Therefore, based on the principle of the Villari phenomenon, the stress applied to the base metal 370 can be calculated from the value of this AC voltage. Then, the degree of distortion of the housing of the battery pack can be specified from the calculated stress. Note that when the detection element 300 has the shape shown in (a) and (b) of FIG. 25, the grid direction of the detection element 300 is equal to the α-α' direction in (a) of FIG. 25. Based on the principle described above, the detection element 300 can detect the distortion of the housing of the battery pack. That is, the sensing element 300 functions as a sensing element of a strain gauge.

[0139] It is desirable that the driving coil 320 is wound as uniformly as possible around the outside of the sensing coil 380 and over the entire area in which the sensing coil 380 exists. This allows an alternating magnetic field to be applied more uniformly to the entire area of ​​the base metal 370 in which the sensing coil 380 exists. This allows the change in the strength of magnetization of the base metal 370 due to the Villari phenomenon to be detected more precisely. This improves the performance of the detection element 300.

[0140] Furthermore, the insulating layer 360 may be formed on only a part of the base metal 370 rather than on the entirety of the base metal 370. For example, the region of the base metal 370 around which the sensing coil 380 and the driving coil 320 are wound may be covered with the insulating layer 360, the insulating layer 360 may be covered with the insulating layer 350 including the sensing coil 380, and the insulating layer 350 may be further covered with the insulating layer 340 including the driving coil 320.

[0141] In addition, when the base metal 370 is substantially plate-shaped, the insulating layer 360 may be formed to surround only the base metal 370 in the winding direction of the coil. That is, in (b) of FIG. 25, both ends of the base metal 370 in the x direction do not need to be covered with the insulating layer 360.

[0142] In the battery pack according to this embodiment, when the housing of the battery pack is deformed (i.e., strain occurs in the housing), the substrate 110 of the strain gauge (or the detection element 300 itself) is strained. The detection element 300 can detect the magnetic change caused by this strain based on the principle of the Villari phenomenon described above.

[0143] The strain gauge including the detection element 300 according to this embodiment can be arranged in the housing of the battery pack in any arrangement pattern shown in the first to fifth embodiments and the modified examples of these embodiments. That is, the detection element 300 according to this embodiment can be used to detect strain in the housing of the battery pack in the same manner as when an electrical resistance type strain gauge is used. Therefore, the strain gauge according to this embodiment has the same effects as the strain gauge 10 according to the first to fifth embodiments and the modified examples of these embodiments.

[0144] Seventh embodiment FIG. 26 is a diagram showing a detection element 500, which is an example of a detection element included in the strain gauge according to the seventh embodiment. FIG. 27 is a diagram showing a detection element 600, which is another example of the detection element according to the seventh embodiment. FIG. 28 is a diagram showing a detection element 700, which is yet another example of the detection element according to the seventh embodiment. (a) of FIG. 26 to FIG. 28 is a perspective view of the detection elements 500, 600, and 700, respectively. (b) of FIG. 26 to FIG. 28 is a plan view of the detection elements 500, 600, and 700 when viewed from the positive direction to the negative direction of the z axis, respectively. (c) of FIG. 26 to FIG. 28 is a cross-sectional view of the detection elements 500, 600, and 700 on a surface parallel to the zx plane. Note that wiring extending from the detection elements is not shown in any of FIG. 26 to FIG. 28. However, these detection elements 500, 600, and 700 may be connected to a wiring that connects the upstream electrode 510 to a power source, and a wiring that connects the downstream electrode 520 to a power source, which will be described later.

[0145] 26 to 28(a), the detection elements 500, 600, and 700 include an upstream electrode 510, a downstream electrode 520, a magnetic film 530, and an insulating film 540. The insulating film 540 is sandwiched between the magnetic films 530 as shown in the figures. A magnetic tunnel junction is formed by the magnetic film 530 and the insulating film 540. In other words, the detection elements 500, 600, and 700 have a structure in which electrodes are connected to a magnetic tunnel junction structure.

[0146] The lower surfaces of the detection elements 500, 600, and 700 may be attached to a substrate similar to the substrate 11 according to the sixth embodiment. The detection element 500 may be attached to the housing of the battery pack via the substrate. The detection elements 500, 600, and 700 may be flat or thin-film detection elements as a whole. When the detection elements 500, 600, and 700 are flat or thin-film, the detection elements 500, 600, and 700 can be attached to a substrate or housing more easily. For example, the lower surfaces of the detection elements 500, 600, and 700 may be directly attached to the housing.

[0147] The magnetic film 530 is a magnetic nano-thin film. The insulating film 540 is a nano-thin film of an insulator. As long as a magnetic tunnel junction structure can be formed, the materials of the magnetic film 530 and the insulating film 540 are not particularly limited. For example, the magnetic film 530 can be made of cobalt iron boron, or a 3d transition metal ferromagnetic material such as Fe, Co, or Ni, or an alloy containing these. The insulating film 540 can be made of silicon oxide, silicon nitride, aluminum oxide, magnesium oxide, or the like.

[0148] The upstream electrode 510 and the downstream electrode 520 are electrodes for applying a voltage to the magnetic tunnel junction structure. In the examples of Figs. 26 to 28, a current flows from the upstream electrode 510 to the downstream electrode 520. For example, in the case of Fig. 26(c), when a voltage is applied between the upstream electrode 510 and the downstream electrode 520, electrons flow from the upper magnetic film 530 (the positive z-axis side) over the insulating film 540 to the lower magnetic film 530 (the negative z-axis side). This is a phenomenon called the "tunnel effect", and the electrical resistance when electrons pass through the insulating film 540 is called the "tunnel resistance". In the examples of Figs. 26 to 28, the junctions of the electrodes are structured such that the ends are processed so that no current flows that short-circuits the magnetic tunnel junction structure.

[0149] When strain is applied to the detection element 500 through the substrate 11 or the like, a magnetic change occurs in the tunnel junction structure. More specifically, the magnetization directions of the upper and lower magnetic films 530 are shifted. When the magnetization directions of the upper and lower magnetic films 530 are shifted in this way, the tunnel resistance becomes larger than when the magnetization directions are parallel (tunnel magnetoresistance effect). Therefore, in the detection element 500 having the above-mentioned configuration, the current flowing between the electrodes becomes smaller according to the magnitude of the strain of the detection element 500 (more precisely, the magnetic tunnel junction part). That is, as the strain increases, the electric resistance increases. In this way, the detection element 500 can detect the strain based on the current value for the applied voltage. Therefore, by attaching the detection element 500 to the housing of the battery pack, the strain on the housing can be measured.

[0150] The detection element having the magnetic tunnel junction structure is not limited to the example shown in FIG. 26. For example, detection elements 600 and 700 shown in FIG. 27 and FIG. 28 can be adopted. The detection element 600 shown in FIG. 27 and the detection element 700 shown in FIG. 28 are both configured with an upstream electrode 510, a downstream electrode 520, a magnetic film 530, and an insulating film 540, and the principle of detecting strain by these configurations is the same as that of the detection element 500. The basic operation of the detection elements 600 and 700 is also the same as that of the detection element 500. The grid directions of the detection elements 500, 600, and 700 correspond to the x-axis direction (the positive direction of the x-axis and the negative direction of the x-axis) in FIG. 26 to FIG. 28, respectively. As shown in the figure, the detection element 600 shown in FIG. 27 has a structure in which the upper magnetic film 530 and the lower magnetic film 530 are partially connected. That is, a magnetic tunnel junction structure is formed only in a partial region of the magnetic film 530, and a tunnel magnetoresistance effect occurs in this structure. Meanwhile, a detection element 700 shown in Fig. 28 is attached to a base material 11 via a substrate 710. As shown in Figs. 26 to 28, the design of the detection element may be appropriately changed according to the required size, durability, magnitude of stress to be detected, and the like, as long as it does not exceed the above-mentioned principle.

[0151] The housing of the battery pack according to this embodiment may basically have the same configuration and material as the housing according to the first to fifth embodiments and their modified examples. However, in this embodiment, it is more preferable that the housing is made of a non-magnetic material. The housing according to this embodiment may be made of, for example, non-magnetic stainless steel. The detection elements 500, 600, and 700 may have a substantially flat shape such as a film type as the whole element. This allows the detection element 500 to be easily attached to the housing of the battery pack. The detection elements 500, 600, and 700 may have a structure for applying a weak magnetic field to the structural part of the magnetic tunnel junction, such as a drive coil. By applying a magnetic field to the structural part of the magnetic tunnel junction, the tunnel magnetoresistance effect described above can be measured more stably, and therefore the strain can be detected stably.

[0152] In addition, the "upstream electrode" and the "downstream electrode" in the detection elements 500, 600, and 700 are names for convenience, and the direction of current flow may be reversed. That is, the detection elements 500, 600, and 700 shown in Figs. 26 to 28 may be designed so that the current flows from the downstream electrode 520 to the upstream electrode 510.

[0153] In the battery pack according to this embodiment, when the housing of the battery pack is deformed (i.e., strain occurs in the housing), the substrate of the strain gauge (or the detection element 500, 600, or 700 itself) is strained. The detection element 500, 600, or 700 can detect the magnetic change caused by this strain based on the principle of the tunnel magnetoresistance effect described above.

[0154] The strain gauge including the detection elements 500, 600, and 700 according to this embodiment can be arranged in the housing of the battery pack in any arrangement pattern shown in the first to fifth embodiments and the modified examples of these embodiments. That is, the detection elements 500, 600, and 700 according to this embodiment can be used to detect strain in the housing of the battery pack in the same manner as when an electrical resistance type strain gauge is used. Therefore, the strain gauge according to this embodiment has the same effects as the strain gauge 10 according to the first to fifth embodiments and the modified examples of these embodiments.

[0155] Eighth embodiment The sensor according to the present disclosure may be a semiconductor strain gauge, a capacitance pressure sensor, or an optical fiber strain gauge. The sensor according to the present disclosure may also be a mechanical pressure sensor, a vibration pressure sensor, or a piezoelectric pressure sensor. The principles of various strain gauges and pressure sensors are described below.

[0156] (Semiconductor type strain gauge) A semiconductor strain gauge is a strain gauge that detects strain by utilizing the piezo-resistance effect of a semiconductor, that is, a semiconductor is used as a strain detection element.

[0157] It is known that when stress is applied to a semiconductor, distortion occurs in the semiconductor's crystal lattice, causing changes in the number and mobility of carriers in the semiconductor, resulting in a change in electrical resistance. Like electrical resistance-type metal strain gauges, semiconductor-type strain gauges can be attached directly to the housing of a battery pack. In this case, when the housing expands or contracts, the attached semiconductor (more specifically, the semiconductor's crystal lattice) is distorted, causing a change in electrical resistance. Therefore, the amount of strain in the housing can be identified by measuring this electrical resistance.

[0158] The semiconductor strain gauge can also be configured as a strain sensor with a diaphragm structure. In this case, the strain sensor has, for example, a non-metallic diaphragm (or a metal diaphragm with an electrically insulating layer formed thereon) and a semiconductor (for example, a silicon thin film semiconductor) formed on the diaphragm. In such a structure including a diaphragm, when the diaphragm is distorted by a normal stress applied to the diaphragm, the electrical resistance of the semiconductor changes. Therefore, the amount of strain of the diaphragm (and thus the amount of strain of the battery pack housing) can be identified by measuring the electrical resistance.

[0159] (Capacitive pressure sensor) A capacitance type pressure sensor is a pressure sensor that measures the pressure applied to a diaphragm as a change in the capacitance of a pair of electrodes. That is, a capacitance type pressure sensor is a pressure sensor that uses a pair of electrodes as a detection element. A capacitance type pressure sensor includes, for example, a diaphragm as a movable electrode and one or more fixed electrodes. The diaphragm is formed of, for example, silicon containing impurities (i.e., silicon that functions as a conductor).

[0160] When pressure is applied to the diaphragm, the diaphragm is displaced, and the distance between the fixed electrode and the movable electrode changes. It is known that the capacitance between the electrodes is determined according to the distance between the electrodes, provided that the dielectric constant of the interelectrode medium and the area of ​​the electrodes are constant. Therefore, the amount of displacement of the diaphragm (i.e., the magnitude of the pressure) can be determined by measuring the capacitance.

[0161] (Optical fiber strain gauge) An optical fiber strain gauge is a strain gauge that detects strain using an optical fiber on which a fiber Bragg grating (FBG) is formed. In other words, an optical fiber strain gauge is a strain gauge that uses an optical fiber as a strain detection element. An FBG is a diffraction grating that reflects light differently from other parts of the optical fiber, and each grating is formed at a fixed interval. When an optical fiber is distorted and stretched, the lattice interval of the FBG widens, and the wavelength of the reflected light of light (e.g., laser light) that is incident on the optical fiber changes. When an optical fiber is distorted and contracted, the lattice interval of the FBG narrows, and the wavelength of the reflected light of light (e.g., laser light) that is incident on the fiber changes.

[0162] By attaching an optical fiber having such characteristics to the housing of a battery pack and measuring the wavelength spectrum of the reflected light of the optical fiber, the amount of strain in the optical fiber (i.e., the amount of strain in the housing) can be determined. Note that the optical fiber type strain gauge may be a strain gauge that determines the amount of strain in the optical fiber from the change in frequency of the Brillouin scattered light generated in the optical fiber.

[0163] (Mechanical pressure sensor) A mechanical pressure sensor is a sensor that measures the amount of displacement of a mechanical structure to determine the pressure applied to the structure. A mechanical pressure sensor includes, for example, a spring or a bent tube, and measures the amount of expansion and contraction of the spring or the amount of expansion and contraction of the bent tube. These amounts of expansion and contraction (i.e., the amount of displacement) change depending on the magnitude of pressure applied to the spring or bent tube. Therefore, by measuring the amount of expansion and contraction, it is possible to determine the pressure applied to the spring or bent tube. The shape and size of the spring or bent tube may be determined appropriately depending on the size and shape of the object to which the mechanical pressure sensor is attached.

[0164] (Vibration pressure sensor) A vibration pressure sensor is a sensor that detects pressure by utilizing the phenomenon that the natural frequency of an elastic beam changes depending on the pressure (i.e., axial force) generated along the axis of the elastic beam. The vibration pressure sensor can be directly attached to the housing of a battery pack for use, similar to an electrical resistance type metal strain gauge. For example, the vibration pressure sensor may be a pressure sensor composed of a diaphragm formed on a substrate and a beam-shaped vibrator formed on the surface of the diaphragm.

[0165] In either case, when the battery pack housing is distorted, the pressure is transmitted directly or indirectly to the vibrator, generating an axial force in the vibrator. The natural frequency of the vibrator changes depending on the axial force. Therefore, by measuring the natural frequency of the vibrator, it is possible to determine the magnitude of the pressure on the battery pack housing.

[0166] (Piezoelectric pressure sensor) A piezoelectric pressure sensor is a sensor that contains a piezoelectric element (also called a piezo element) and detects pressure using the characteristics of this piezoelectric element. When a force is applied to a piezoelectric element and it deforms (strains), it generates an electromotive force according to that force. In addition, when a voltage is applied to a piezoelectric element, it expands and contracts, generating a force according to that voltage.

[0167] A piezoelectric pressure sensor can determine the force applied to a piezoelectric element (i.e., the amount of strain of the piezoelectric element) by measuring the electromotive force of the piezoelectric element. Therefore, by attaching a piezoelectric pressure sensor to the housing of a battery pack, the amount of strain of the battery pack housing can be determined.

[0168] As described above, even when a semiconductor strain gauge, a capacitance pressure sensor, an optical fiber strain gauge, a mechanical pressure sensor, a vibration pressure sensor, or a piezoelectric pressure sensor is used, the same effects as those of the strain gauge 10 according to the first to fifth embodiments and the modified examples of these embodiments can be obtained.

[0169] The preferred embodiments and the like have been described above in detail. However, the battery pack according to the present disclosure is not limited to the above-described embodiments and modifications. For example, various modifications and substitutions can be made to the battery pack according to the above-described embodiments and the like without departing from the scope of the claims. [Explanation of symbols]

[0170] 1, 2, 3, 4, 5, 6 battery pack, 10, 10A, 10B strain gauge, 12, 12A, 12B resistor, 12Aa, 12Ab, 12Ba, 12Bb resistor section, 20, 120 battery, 30, 130, 230, 330, 430 housing, 30B bottom surface, 30S1, 30S2, 30S3, 30S4 side, 30T top surface, 35 housing, 35S1 side, 36 thin section, 37 housing, 37S1 side, 38 thin section, 41 plate-shaped member, 42 plate-shaped member, 65 monitoring section, 141, 142, 143, 144 plate-shaped member, 330L1, 330L2, 330L3, 330L4, connection section, 330SB Bottom plate, 330SS1, 330SS2, 330SS3, 330SS4 Side plate, 500, 600, 700 Detection element, 530 Magnetic film, 540 Insulating film

Claims

1. A casing that houses the battery, The system includes a sensor attached to the housing for detecting strain on the housing, A plate-like member with higher rigidity than the housing is bonded to at least one surface of the housing so as to cover that surface. The battery pack has one or more sensors attached to the surface of a surface other than the at least one surface.

2. The battery pack according to claim 1, wherein the plate-shaped member is provided on the upper and / or lower surface of the housing.

3. The battery pack according to claim 1, wherein the plate-shaped member is provided on two or more of the sides of the housing.

4. A housing that houses a battery and a monitoring unit that monitors the state of the battery, The system includes a sensor attached to the housing for detecting strain on the housing, The monitoring unit is housed such that there is a gap between it and the housing. The aforementioned sensors are attached one or more times near the gap. Battery pack.

5. The battery pack according to any one of claims 1 to 4, wherein a thin portion is provided on the surface of the housing to which the sensor is attached.

6. The battery pack according to any one of claims 1 to 4, comprising a plurality of slits arranged along the sides between adjacent sides of the housing and opening across the adjacent sides.

7. The housing comprises a bottom plate and a side plate formed integrally with the bottom plate and extending in a direction intersecting the bottom plate. The side plate, due to the elasticity at the connection point between the bottom plate and the side plate, pushes the battery inward. The battery pack according to any one of claims 1 to 4.

8. The aforementioned sensor is Insulating layer and, A functional layer formed directly on one surface of the insulating layer from a metal, alloy, or metal compound, On one side of the functional layer, Cr, CrN, and Cr ２ A resistor formed from a film containing N, The state of the battery is detected as a change in the resistance value of the resistor, The resistor mainly consists of α-Cr, The functional layer has the function of promoting the crystal growth of α-Cr and forming a film mainly composed of α-Cr. The battery pack according to any one of claims 1 to 4.

9. The resistor contains 80% by weight or more of α-Cr. The battery pack according to claim 8.

10. The battery pack according to any one of claims 1 to 4, wherein the sensor has a detection element that detects magnetic changes caused by distortion of the housing.

11. The aforementioned detection element includes a magnetic material, The battery pack according to claim 10, wherein the detection element is a detection element that detects a change in the magnetization strength of the magnetic material when pressure is applied to the magnetic material due to the strain of the housing.

12. The detection element includes a magnetic tunnel junction structure in which an insulating film is sandwiched between magnetic films. The battery pack according to claim 10, wherein the detection element is an output element that detects magnetic changes generated in the structure due to distortion of the housing.

13. The battery pack according to any one of claims 1 to 4, wherein the sensor is a semiconductor strain gauge.

14. The battery pack according to any one of claims 1 to 4, wherein the sensor is a capacitive pressure sensor.

15. The battery pack according to any one of claims 1 to 4, wherein the sensor is an optical fiber strain gauge.

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