Battery pack

Abstract

The battery pack (1) includes: a battery (3); and a flexible printed circuit board (7) for detecting the voltage and temperature of the battery (3). The FPC (7) includes: a base material (70) having a front side and a back side; a thermistor (79) for detecting the temperature of the battery (3); a temperature detection line (71); and a voltage detection line (72). The temperature detection line (71) is electrically connected to the thermistor (79) and is disposed between the back side and the battery (3). The voltage detection line (72) is disposed on the front side so as to overlap the temperature detection line (71) when the FPC (7) is viewed in a plane from the back side to the front side.

Description

[0001] Cross - reference to related applications

[0002] This application is based on Japanese Patent Application No. 2020 - 169109 filed on October 6, 2020, and incorporates the entire contents of the basic application by reference. Technical field

[0003] The present disclosure relates to a battery pack, and more particularly to a battery pack including a flexible printed circuit board. Background art

[0004] In recent years, FPC (Flexible Printed Circuit), which is a flexible printed circuit board, has been used in a large number of electrical devices. There is a possibility that electromagnetic wave noise is superimposed on wiring patterns such as signal lines arranged on the FPC. Therefore, an FPC capable of suppressing the superimposition of noise has been proposed.

[0005] For example, the FPC disclosed in Japanese Patent Laid - Open No. 2019 - 192806 (Patent Document 1) includes a laminated wiring board extending in one direction and a shielding film. In the above - mentioned shielding film, a conductive shielding layer is formed on one side of an insulating insulating coating layer. The shielding film is configured to cover the upper surface and the lower surface of the laminated wiring board through the shielding layer side, and cover at least a part of two end faces in the other direction in the plane parallel to the upper surface of the laminated wiring board through the shielding layer side. The other direction is a direction orthogonal to the above - mentioned one direction.

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Laid - Open No. 2019 - 192806 Summary of the invention

[0009] In an FPC, a temperature detection line is sometimes arranged. The temperature detection line is electrically connected to a thermistor for detecting the temperature of an electrical device. When noise is superimposed on the temperature detection line, since the current caused by the noise flows to the thermistor, the thermistor may heat up. As a result, a detection error may occur in the temperature of the battery pack. The electrical device is, for example, a battery pack arranged in a battery pack.

[0010] The FPC disclosed in Patent Document 1 suppresses the superimposition of noise through a shielding film. Therefore, it is necessary to add a layer (shielding layer) dedicated to shielding on the upper surface and the lower surface (i.e., the front and back surfaces of the FPC) of the laminated wiring board. As a result, compared with the structure without a shielding layer, the cost of the FPC increases. In order to reduce the cost, it is desirable to suppress the superimposition of noise with a simpler structure.

[0011] The present disclosure is completed to solve the above technical problems, and the object of the present disclosure is to provide a technology that can suppress the superimposition of noise on a temperature detection line with a simple structure in a battery pack including a flexible printed circuit board.

[0012] A battery pack according to an aspect of the present disclosure includes: a battery group; and a flexible printed circuit board that is arranged along the battery group and is used to detect the voltage and temperature of the battery group. The flexible printed circuit board includes: a base material having a front surface (surface) and a back surface; a thermistor for detecting the temperature of the battery group; a temperature detection line electrically connected to the thermistor and arranged between the back surface and the battery group; and a voltage detection line arranged on the front surface so as to overlap the temperature detection line when the flexible printed circuit board is viewed in a plane from the back surface to the front surface.

[0013] In the above structure, the voltage detection line is arranged to overlap the temperature detection line when the flexible printed circuit board is viewed in a plane. In other words, the voltage detection line is arranged to cover the temperature detection line. That is to say, the temperature detection line is sandwiched between the voltage detection line and the electrical equipment. Since the voltage detection line functions as a shielding member, the noise superimposed on the temperature detection line can be suppressed. The above flexible printed circuit board is composed of a simple structure without a specially provided shielding layer. Therefore, according to the above structure, the superimposition of noise on the temperature detection line can be suppressed with a simple structure.

[0014] According to the present disclosure, in a battery pack including a flexible printed circuit board, the superimposition of noise on the temperature detection line can be suppressed with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a circuit block diagram schematically showing the overall structure of a vehicle to which a flexible printed circuit board according to an embodiment of the present disclosure is applied.

[0016] Figure 2 It is a circuit block diagram showing an example of a circuit structure for detecting the temperature of a battery.

[0017] Figure 3 It is a diagram showing an example of the structure of a battery pack.

[0018] Figure 4 is along Figure 3 A cross-sectional view of the cover, the monomer, and the flexible printed circuit board along the IV line of.

[0019] Figure 5 It is a top view schematically showing an example of the outer shape of the flexible printed circuit board according to the present embodiment.

[0020] Figure 6It is a diagram showing an example of a wiring pattern of a temperature detection line.

[0021] Figure 7 It is a diagram showing an example of a wiring pattern of a voltage detection line.

[0022] Figure 8 It is a diagram showing an example of a virtual pattern disposed on a flexible printed circuit board. Detailed implementation

[0023] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0024] Hereinafter, an example in which the flexible printed circuit board of the present disclosure is applied to a vehicle structure will be described. However, the use of the flexible printed circuit board of the present disclosure is not limited to vehicle use, and all electrical devices can be targeted.

[0025] [Embodiment]

[0026] <Vehicle structure>

[0027] Figure 1 It is a circuit block diagram schematically showing the overall structure of a vehicle to which the flexible printed circuit board according to the embodiment of the present disclosure is applied. Refer to Figure 1 , the vehicle 100 includes a battery pack 1. The battery pack 1 includes a battery ECU (Electronic Control Unit) 2, a battery 3, and a monitoring unit 4. The vehicle 100 further includes a system main relay (SMR: System Main Relay) 101, a converter 102, an inverter 103, and a vehicle drive unit 104.

[0028] The battery ECU 2 manages the state of the battery 3. Specifically, the battery ECU 2 calculates the remaining battery level (SOC: State of Charge) of the battery 3 and infers the deterioration state (SOH: State of health) of the battery 3.

[0029] The battery 3 is a battery pack. Each single battery (monomer) constituting the battery pack is a rechargeable battery such as a lithium-ion battery or a nickel-metal hydride battery. The battery 3 stores electric power for supplying to the vehicle drive unit 104. In addition, the battery 3 is charged with the electric power generated by the vehicle drive unit 104. Alternatively, a large-capacity capacitor such as an electric double-layer capacitor may be used instead of the battery 3.

[0030] The monitoring unit 4 includes various sensors for monitoring the state of the battery 3. Specifically, the monitoring unit 4 includes a voltage sensor, a current sensor, and a temperature sensor (none of which are shown). The voltage sensor detects the voltage VB of the battery 3. The current sensor detects the current IB input to or output from the battery 3. The temperature sensor detects the temperature TB of the battery 3. Each sensor outputs a signal representing its detection result to the battery ECU 2.

[0031] In the present embodiment, the battery pack 1 includes a cover 5, a plurality of cells 6, and an FPC 7 (both are referred to Figure 3 ). The FPC 7 transmits signals from the respective sensors to the battery ECU 2. The structure of the FPC 7 will be described later.

[0032] The SMR 101 is electrically connected between the battery 3 and the converter 102. By turning on the SMR 101, power transmission between the battery 3 and the converter 102 can be achieved.

[0033] The converter 102 is electrically connected between the SMR 101 and the inverter 103. When the vehicle 100 is running and driving, the converter 102 raises the voltage of the direct current power supplied from the battery 3 and outputs it to the inverter 103. When the vehicle 100 is running and driving, it is the discharge time of the battery 3. In addition, when the vehicle drive unit 104 generates electricity (during charging of the battery 3), the converter 102 lowers the voltage of the direct current power supplied from the inverter 103 and outputs it to the battery 3.

[0034] The inverter 103 is electrically connected between the converter 102 and the vehicle drive unit 104. The inverter 103 converts the direct current power from the converter 102 into alternating current power and outputs the alternating current power to the vehicle drive unit 104. The vehicle drive unit 104 is, for example, an electric generator. In addition, the inverter 103 converts the alternating current power generated by the vehicle drive unit 104 into direct current power and outputs the direct current power to the inverter 103.

[0035] The vehicle drive unit 104 is a device for driving the vehicle 100. The vehicle drive unit 104 includes an electric generator. In addition to this, the vehicle drive unit 104 can also include an engine, a power distribution device, and drive wheels (none of which are shown), etc.

[0036] Figure 2 is a circuit block diagram showing an example of the circuit structure for detecting the temperature TB of the battery 3. Refer to Figure 2 , the FPC 7 includes a thermistor 79 provided on the battery 3 (the cell 6 described later). The thermistor 79 is, for example, a negative temperature coefficient (NTC: Negative Temperature Coefficient) thermistor. However, the thermistor 79 is not necessarily an NTC thermistor.

[0037] The thermistor 79 and the battery ECU 2 are electrically connected to the temperature detection line 71 formed on the FPC 7. The temperature TB of the battery 3 detected by the thermistor 79 is transmitted to the A / D converter 20 in the battery ECU 2 via the temperature detection line 71. By Figures 5 to 7 The characteristics of the temperature detection line 71 will be described in detail.

[0038] <Battery Pack Structure>

[0039] Figure 3 is a diagram showing an example of the structure of the battery pack 1. In Figure 3 a side view of the battery pack 1 is schematically shown. In Figure 3 in each of the subsequent figures, the x-direction, y-direction, and z-direction are orthogonal to each other. The x-direction and the y-direction are horizontal directions. The vertical direction is the z-direction downward. Hereinafter, the upper side in the z-direction may be simply referred to as "upper side", and the lower side in the z-direction may be simply referred to as "lower side". As Figure 3 shown, the battery pack 1 includes a cover 5, a plurality of cells 6, and an FPC 7.

[0040] The cover 5 is disposed above the plurality of cells 6. In this example, the structure of the battery pack 1 is not a closed structure, and both ends in the horizontal direction (in Figure 2 the x-direction) are open. Therefore, electromagnetic wave noise generated outside the battery pack 1 and propagating in the horizontal direction can invade the inside of the battery pack 1. In addition, when the material of the cover 5 is a non-metal such as resin, the battery pack 1 is easily affected by electromagnetic wave noise even if it has a closed structure.

[0041] The plurality of cells 6 are arranged along the horizontal direction (x-direction). The number of cells 6 is not particularly limited, and typically ranges from several tens to several hundreds. In Figure 3 a part of many cells 6 constituting the battery pack 1 is illustrated.

[0042] The FPC 7 is disposed directly above the plurality of cells 6. The FPC 7 is disposed between the cells 6 and the cover 5. As described above, the FPC 7 transmits signals from the voltage sensor and the thermistor (not shown) to the battery ECU 2.

[0043] Figure 4 is a cross-sectional view of the cover 5, the cell 6, and the FPC 7 along the IV line of Figure 3 . Referring to Figure 4 , the FPC 7 includes a base material 70, a temperature detection line 71, a voltage detection line 72, and cover layers 73, 74.

[0044] The base material 70 is a thin and flexible (flexible) base film. In addition, the base material 70 has insulating properties. As the material of the base material 70, polyimide is typically used.

[0045] The temperature detection line 71 is a wiring pattern formed on a conductive layer such as a copper foil. The temperature detection line 71 is disposed below the base material 70. The temperature detection line 71 is disposed on the back surface of the base material 70.

[0046] The voltage detection line 72 is the same as the temperature detection line 71 and is a wiring pattern formed on the conductive layer. The voltage detection line 72 is disposed above the base material 70. The voltage detection line 72 is disposed on the front surface of the base material 70.

[0047] The cover layers 73 and 74 are cover films that cover the wiring patterns respectively. The cover layers 73 and 74 have insulating properties. Polyimide can also be used as the material for the cover layers 73 and 74. The cover layer 73 is disposed further below the temperature detection line 71. The cover layer 74 is disposed further above the voltage detection line 72.

[0048] <Wiring Pattern of FPC>

[0049] When electromagnetic wave noise is superimposed on the temperature detection line 71, current will flow through the thermistor 79, and thus the thermistor 79 may heat up. As a result, there may be a detection error in the temperature TB of the battery 3. In particular, when Figure 2 the thermistor 79 described is an NTC thermistor, when the thermistor 79 heats up due to the superimposition of electromagnetic wave noise, the resistance value of the thermistor 79 will decrease. Then, the positive feedback that current is more likely to flow to the thermistor 79 takes effect, which may lead to thermal runaway of the thermistor 79. As a result, there is also a possibility that the thermistor 79 is damaged.

[0050] Currently, various shielding films have been put into use. It is conceivable to suppress the superimposition of electromagnetic wave noise on the temperature detection line 71 by selecting an appropriate shielding film (not shown) and disposing it on the FPC 7 (for example, refer to Patent Document 1). However, in the case of adding a shielding film, the component cost and / or manufacturing cost of the FPC 7 will increase accordingly. In order to reduce costs, it is preferable to suppress the superimposition of electromagnetic wave noise through a simpler structure.

[0051] Therefore, in the present embodiment, the following structure is adopted: the temperature detection line 71 is sandwiched by the voltage detection line 72 and the battery 3 (multiple monomers 6) to suppress the superimposition of electromagnetic wave noise on the temperature detection line 71.

[0052] Figure 5 is a top view schematically showing an example of the outer shape of the FPC of the present embodiment. Figure 6 is a diagram showing an example of the wiring pattern of the temperature detection line 71. Figure 7 is a diagram showing an example of the wiring pattern of the voltage detection line 72.

[0053] As Figure 4As described above, the wiring pattern of the temperature detection line 71 is disposed on the back surface (the back surface of the FPC 7) of the base material 70, and the wiring pattern of the voltage detection line 72 is disposed on the front surface (the front surface of the FPC 7) of the base material 70. In Figure 6 shows the wiring pattern of the temperature detection line 71 as confirmed when observing the FPC 7 from below (the back surface side) to above (the front surface side). On the other hand, in Figure 7 shows the wiring pattern of the voltage detection line 72 as confirmed when the FPC 7 is viewed in a plane perspective from below to above.

[0054] From Figure 6 and Figure 7 it can be understood that although the wiring patterns of the temperature detection 71 and the voltage detection line 72 are different because the surfaces on which they are disposed are the front and back surfaces of the base material 70, they are substantially the same. Thus, a structure is realized in which the temperature detection line 71 is sandwiched from both sides by the voltage detection line 72 and the monomer 6.

[0055] The voltage detection line 72 functions as a shield wire that electrically shields the temperature detection line 71, which improves the noise resistance of the temperature detection line 71. On the other hand, there is a possibility that electromagnetic wave noise is superimposed on the voltage detection line 72. The electromagnetic wave noise superimposed on the voltage detection line 72 is the same as the electromagnetic wave noise superimposed on the voltage detection line 72 and can be transmitted to the battery ECU 2. However, the electromagnetic wave noise reaching the battery ECU 2 can be reduced to a level where the detection error of the voltage VB is not a problem by providing an appropriate filter circuit (not shown) in the battery ECU 2. Moreover, since this filter circuit can be a general RC circuit, it can be realized at a lower cost than a shielding film. Therefore, according to the present embodiment, the cost required for electromagnetic wave noise countermeasures can be reduced.

[0056] In addition, a thermistor is not connected to the voltage detection line 72 for detecting the voltage VB of the battery 3. Therefore, even if electromagnetic wave noise is superimposed on the voltage detection line 72, it is different from the situation where electromagnetic wave noise is superimposed on the temperature detection line 71, and it will not cause the thermistor to heat up. Furthermore, the thermistor will not be damaged due to thermal runaway. Therefore, according to the present embodiment, the thermistor 79 can be more reliably protected.

[0057] In addition, in Figure 6 and Figure 7 the structure in which the temperature detection line 71 is shielded by the voltage detection line 72 has been described, but a wiring pattern not used for signal transmission (so-called virtual pattern) can be provided instead of the voltage detection line 72.

[0058] Figure 8 is a diagram showing an example of the virtual pattern disposed on the FPC 7. In Figure 8 is the same as in Figure 7The same represents the wiring pattern confirmed when the FPC 7 is viewed in a planar perspective from below upward. As Figure 8 shown, a dummy pattern 75 can also be provided in such a way as to cover the wiring pattern of the temperature detection line 71. Although not shown, for example, a single cell discrimination signal line or a ground line can be used instead of the dummy pattern 75, or in addition to the dummy pattern 75, for example, a single cell discrimination signal line or a ground line can also be used.

[0059] However, the dummy pattern 75 requires a larger wiring area than the voltage detection line 72. Therefore, by using the voltage detection line 72, the noise resistance of the temperature detection line 71 can be improved even in an area where there is no surplus in the layout wiring area.

[0060] As described above, in the present embodiment, the voltage detection line 72 is arranged so as to overlap with the temperature detection line 71 when the FPC 7 is viewed in a plane. In other words, the voltage detection line 72 is arranged so as to cover the temperature detection line 71. Since the temperature detection line 71 is formed between the voltage detection line 72 and the single cell 6 in the above-described manner, the voltage detection line 72 functions as a shield wire, and thus, the noise resistance of the temperature detection line 71 can be improved. In addition, the FPC 7 has a simple structure without a dedicated shielding layer (such as a shielding film), and thus, can be manufactured at low cost. Therefore, according to the present embodiment, the superimposition of electromagnetic wave noise on the temperature detection line 71 can be suppressed by a simple structure.

[0061] In addition. In the present embodiment, the structure in which the temperature detection line 71 is used to detect the temperature TB of the battery 3 has been described. However, the temperature detection line 71 can also be used, for example, to detect the intake temperature of the cooling air for cooling the battery pack 1. In addition, the installation position of the FPC 7 is not limited to the upper surface of the battery 3, and can also be the side surface or the lower surface of the battery 3, or the front surface (surface) of the metal case for housing the battery 3.

[0062] It should be understood that all points of the embodiments disclosed this time are illustrative and not restrictive. The scope of the present disclosure is shown by the claims rather than the description of the above embodiments, and is intended to include the meaning equivalent to the scope of the claims and all changes within the scope.

Claims

1. A battery pack, comprising: a battery group; and a flexible printed circuit board, which is arranged along the battery group and is used for detecting the voltage and temperature of the battery group, wherein the flexible printed circuit board includes: a base material having a front side and a back side; a thermistor for detecting the temperature of the battery group; a temperature detection line electrically connected to the thermistor and arranged between the back side and the battery group; and a voltage detection line arranged on the front side in a manner that overlaps with the temperature detection line when the flexible printed circuit board is viewed in a plane from the back side to the front side.

2. The battery pack according to claim 1, wherein the battery group is composed of a plurality of monomers, the plurality of monomers are arranged along the x direction, and the flexible printed circuit board is arranged directly above the plurality of monomers.

3. A battery pack, comprising: a battery group; and a flexible printed circuit board, which is arranged along the battery group and is used for detecting the voltage and temperature of the battery group, wherein the flexible printed circuit board includes: a base material having a front side and a back side; a thermistor for detecting the temperature of the battery group; a temperature detection line electrically connected to the thermistor and arranged between the back side and the battery group; and a virtual pattern arranged on the front side in a manner that overlaps with the temperature detection line when the flexible printed circuit board is viewed in a plane from the back side to the front side.

4. The battery pack according to claim 3, wherein the virtual pattern is a wiring pattern not used for signal transmission.

5. The battery pack according to claim 3 or 4, wherein the battery group is composed of a plurality of monomers, the plurality of monomers are arranged along the x direction, and the flexible printed circuit board is arranged directly above the plurality of monomers.

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