Power storage device

Abstract

To improve a heat dissipation of a heating component and an attachment property of a bus bar.SOLUTION: A power storage device 10 of a present disclosure, comprises: a power storage element unit 20 that contains a plurality of power storage elements 21; a holding member 80 that holds the power storage element unit 20; a circuit board 60 that is fixed oppositely to an outside surface of the holding member 80; a heating component that is provided to the circuit board 60 and is thermally connected to the holding member 80; and a bus bar 40 that includes a fit part 45, and is connected to the circuit board 60. The circuit board 60 includes: a first surface 60A that is opposite to the holding member 80; and a second surface 60B on the side opposite to the first surface 60A. The bus bar 40 is connected to the circuit board 60 by press-fitting the fit part 45 to the second surface 60B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power storage device.

Background Art

[0002] In order to electrically connect a bus bar to a circuit board, bolt fastening, soldering, etc. are performed. As an example of bolt fastening, in Japanese Unexamined Patent Application Publication No. 2023-32753, a bus bar and a circuit board are electrically connected via a conductive terminal block.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Bolt fastening of a bus bar requires manual tightening due to the difficulty of tightening torque management, and involves laborious tasks such as bolt alignment, torque management, and burr removal (Fig. 9 shows a state where a bus bar 1 and a circuit board 2 are connected by a bolt 3). In soldering, since the heat capacity of the bus bar is large, it is difficult to solder and it takes time to complete, and laborious tasks such as removing solder balls are involved (Fig. 10 shows a state where a bus bar 4 and a circuit board 5 are connected by solder 6).

[0005] A power storage device such as an in-vehicle battery includes a management device, and on the circuit board of the management device, in addition to a bus bar, heat-generating components such as semiconductor switches are mounted. Although it is known that a semiconductor switch can suppress heat generation by sacrificing its current-carrying capacity in a dilating operation or the like, there is room for improvement in the heat dissipation of such heat-generating components.

[0006] The present disclosure has been completed based on the above circumstances, and an object thereof is to improve the heat dissipation performance of heat-generating components and the mountability of bus bars.

Means for Solving the Problem

[0007] The energy storage device of the present disclosure includes an energy storage element unit including a plurality of energy storage elements, a holding member that holds the energy storage element unit, a circuit board fixed to face the outer surface of the holding member, a heat generating component provided on the circuit board and thermally connected to the holding member, and a bus bar having a fitting portion and connected to the circuit board. The circuit board has a first surface facing the holding member and a second surface opposite to the first surface, and the bus bar is connected to the circuit board by press-fitting the fitting portion into the second surface.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to achieve both improvement in the heat dissipation performance of the heat generating component and the mounting property of the bus bar.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0010] (Summary of this Embodiment) (1) The power storage device of the present disclosure includes a power storage element unit including a plurality of power storage elements, a holding member that holds the power storage element unit, a circuit board fixed to face the outer surface of the holding member, a heat generating component provided on the circuit board and thermally connected to the holding member, and a bus bar having a fitting portion and connected to the circuit board. The circuit board has a first surface facing the holding member and a second surface opposite to the first surface, and the bus bar is connected to the circuit board by press-fitting the fitting portion into the second surface.

[0011] The holding member is a member for suppressing expansion due to temperature change or aging deterioration of a plurality of power storage elements, and suppresses expansion of the plurality of power storage elements by holding the power storage element unit. Further, the holding member has a large volume inside the power storage device, and when configured with, for example, metal, it can function as a heat radiating component having a high heat conductivity peculiar to metal. In the above power storage device, by thermally connecting the heat generating component to the holding member (for example, sandwiching the heat generating component between the holding member and the circuit board, or connecting the heat generating component and the holding member with a member having high thermal conductivity (such as a metal member)), heat can be transferred from the heat generating component to the circuit board or the holding member, and the heat generating component can be radiated. In this way, by using the holding member for heat dissipation of the heat generating component, an increase in the temperature of the heat generating component can be suppressed.

[0012] Conventionally, in order to connect the bus bar to the circuit board, bolt fastening or soldering has been performed. However, in the above power storage device, the fitting portion (for example, a convex portion) of the bus bar may be press-fitted into the second surface of the circuit board, so the mountability is good. If the bus bar and the circuit board are connected by bolt fastening, a space for arranging the nut is required on the circuit board, which makes it difficult to bring the circuit board close to the holding member and makes it difficult to bring the heat generating component into contact with the holding member. On the other hand, in the above power storage device, since the nut is not required, it is easy to bring the heat generating component into contact with the holding member. Therefore, it is possible to provide a power storage device that achieves both improved heat dissipation of the heat generating component and improved mountability of the bus bar.

[0013] (2) In the power storage device according to (1), it is preferable that the holding member is formed in an annular shape surrounding the power storage element unit. As the holding member, a structure in which a U-shaped holding member surrounds the power storage element unit from three directions can also be considered. In that regard, since the above holding member is formed in an annular shape surrounding the power storage element unit, it surrounds the power storage element unit from four directions. Therefore, compared with the holding member that surrounds from three directions, the holding member that surrounds from four directions can have a larger heat dissipation area and can have higher heat dissipation performance.

[0014] (3) In the power storage device according to (1) or (2), the holding member has a pair of restraint plates that sandwich the power storage element unit in a first direction in which the plurality of power storage elements are arranged, and it is preferable that the circuit board is fixed facing the outer surface of one of the restraint plates. Since the restraint plate is in contact with the power storage element unit, it is easy to dissipate heat from the heat-generating component to the power storage element unit through the restraint plate. Therefore, compared with the case where the circuit board is fixed facing the outer surface of the portion of the holding member that is not in contact with the power storage element unit, the heat dissipation performance can be higher.

[0015] (4) In the power storage device according to any one of (1) to (3), each of the power storage elements preferably has a pair of terminals, and the bus bar preferably has a fixing surface that is fixed to one of the terminals. According to the above configuration, the bus bar can be connected to the power storage element unit by fixing the fixing surface of the bus bar to the terminal.

[0016] (5) In the power storage device according to any one of (1) to (4), through holes are formed in the circuit board, and it is preferable that the fitting portion is a press-fit pin that fits into the through holes. According to the above configuration, the bus bar can be fixed to the circuit board simply by press-fitting the press-fit pins into the through holes. The connection by the press-fit pins enables energization at high density within a narrow range, and the protrusion of the press-fit pins from the first surface of the circuit board can be minimized. Therefore, it becomes easier to bring the first surface of the circuit board into close contact with the holding member, and the heat dissipation performance can be further enhanced.

[0017] <Embodiment> Hereinafter, a specific description will be given with reference to the drawings showing embodiments. Hereinafter, a configuration example of the power storage device 10 will be described with reference to the directions of "front and rear", "left and right", and "up and down" shown in the drawings.

[0018] 1. Overall configuration of the power storage device 10 The power storage device 10 is a battery that is preferably mounted on vehicles such as engine vehicles, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and other moving bodies. The power storage device 10 of the present embodiment is used in place of a lead-acid battery and has a rated voltage of 12 volts (V). Alternatively, the power storage device may have a rated voltage of 24V or 48V, or may be applied to stationary applications.

[0019] The power storage device 10 includes a power storage element unit 20, a plurality of bus bars 40, a circuit board 60, and a holding member 80. The power storage element unit 20, the plurality of bus bars 40, and the circuit board 60 (battery management unit: BMU) are housed inside a housing case (not shown).

[0020] The energy storage element unit 20 includes a plurality of energy storage elements 21 and a spacer (not shown) disposed between adjacent energy storage elements 21. The spacer may not be provided. The energy storage element 21 is, for example, a lithium-ion secondary battery (battery cell). The energy storage element 21 includes a hollow rectangular parallelepiped case 22. A positive terminal 23 and a negative terminal 24 of the energy storage element 21 are provided on the upper surface (terminal surface) of the case 22. An electrode body, an electrolytic solution, etc. are accommodated inside the case 22. Alternatively, the energy storage element 21 may be a battery cell such as an all-solid-state battery or a nickel-metal hydride battery, or may be a capacitor.

[0021] The energy storage element 21 is a rectangular battery cell having a wound electrode body. Alternatively, the energy storage element 21 may be a cylindrical battery cell or a laminated (pouch-type) battery cell, and may be a battery cell having a stacked electrode body.

[0022] Four energy storage elements 21 are connected in series to form a battery pack. Alternatively, some of the energy storage elements 21 may be connected in parallel. For example, the battery pack may have eight energy storage elements 21 connected in 2 parallel and 4 series, or may have twelve energy storage elements 21 connected in 3 parallel and 4 series.

[0023] Hereinafter, the energy storage element 21 is also referred to as a first energy storage element 21A, a second energy storage element 21B, a third energy storage element 21C, and a fourth energy storage element 21D in order from the front. The second energy storage element 21B is disposed adjacent to the rear surface of the first energy storage element 21A, the third energy storage element 21C is disposed adjacent to the rear surface of the second energy storage element 21B, and the fourth energy storage element 21D is disposed adjacent to the rear surface of the third energy storage element 21C.

[0024] The first energy storage element 21A and the third energy storage element 21C are arranged with the positive terminal 23 on the left and the negative terminal 24 on the right, and the second energy storage element 21B and the fourth energy storage element 21D are arranged with the positive terminal 23 on the right and the negative terminal 24 on the left.

[0025] A plurality of bus bars 40 are arranged on the terminal surface of the energy storage element 21. The plurality of bus bars 40 may be configured as one bus bar unit by being housed in a resin case.

[0026] The holding member 80 holds the outer surface of the energy storage element unit 20. As shown in FIG. 2, the holding member 80 is formed in an annular shape surrounding the energy storage element unit 20. The energy storage element unit 20 is constrained by the holding member 80. Thereby, the expansion due to the temperature change or the aging deterioration of each of the plurality of energy storage elements 21 is suppressed, and the performance deterioration or the occurrence of defects of the energy storage device 10 is suppressed.

[0027] Specifically, the holding member 80 includes a front restraint plate 81A and a rear restraint plate 81B that sandwich the energy storage element unit 20 in the front-rear direction in which the plurality of energy storage elements 21 are arranged, a left connection plate 82A that connects the left side edge of the front restraint plate 81A and the left side edge of the rear restraint plate 81B, a right connection plate 82B that connects the right side edge of the front restraint plate 81A and the right side edge of the rear restraint plate 81B, and an upper connection plate 82C that connects the center of the upper edge of the front restraint plate 81A and the center of the upper edge of the rear restraint plate 81B, and is integrally provided. The front restraint plate 81A and the rear restraint plate 81B hold a pair of outer surfaces located at both front and rear ends of the energy storage element unit 20 by sandwiching them from the front-rear direction. Each of the restraint plates 81A, 81B and each of the connection plates 82A, 82B are integrally formed so as to form an annular shape when viewed from above. As the material of the holding member 80, a metal such as iron is used.

[0028] As shown in FIG. 1, the circuit board 60 has a first surface 60A facing the holding member 80 and a second surface 60B on the side opposite to the first surface 60A. The circuit board 60 is arranged parallel to the pre-restraint body 81A of the holding member 80 and is arranged facing the outer surface of the pre-restraint body 81A. As shown in FIG. 5, the circuit board 60 includes a circuit breaker 61 for cutting off the power line, a shunt resistor 62, and an IC 63 on the first surface 60A. The circuit breaker 61 may be constituted by a plurality of semiconductor switches connected in series-parallel or a relay. From the viewpoints of miniaturization and cost reduction, it is preferable to configure the circuit breaker 61 with semiconductor switches. The circuit breaker 61, the shunt resistor 62, and the IC 63 are an example of the "heat-generating components" of the present disclosure and may be referred to as "heat-generating components" hereinafter.

[0029] A plurality of through holes 64 are formed in the circuit board 60 so as to penetrate in the plate thickness direction between the first surface 60A and the second surface 60B. Through-hole plating is formed inside the through holes 64. The through-hole plating is connected to a conductor formed on the upper surface of the circuit board 60.

[0030] For example, five through holes are arranged vertically and five through holes are arranged horizontally, and a total of 25 through holes 64 are formed. One bus bar connection portion 65 is constituted by the total 25 through holes 64. In the example of FIG. 5, three of the bus bar connection portions 65 are arranged above the circuit breaker 61 in the drawing, and are the first bus bar connection portion 65A, the second bus bar connection portion 65B, and the third bus bar connection portion 65C in order from the left in the drawing. Also, one of the bus bar connection portions 65 is arranged below the circuit breaker 61 in the drawing and is the fourth bus bar connection portion 65D.

[0031] As shown in FIG. 1, the bus bar 40 includes a pair of first bus bars 41 connecting the circuit board 60 and an external power cable (not shown), a second bus bar 42 connecting the circuit board 60 and the positive terminal 23 of the fourth energy storage element 21D, a third bus bar 43 connecting the circuit board 60 and the negative terminal 24 of the first energy storage element 21A, and a fourth bus bar 44 connecting the positive terminal 23 and the negative terminal 24 of adjacent energy storage elements 21.

[0032] In each of the bus bars 41, 42, and 43, the connection portions with the circuit board 60 are the board connection portions 41A, 42A, and 43A. Although FIG. 6 illustrates the board connection portion 43A of the third bus bar 43, the same applies to the board connection portion 41A of the first bus bar 41 and the board connection portion 42A of the second bus bar 42. Therefore, in the following, the board connection portion 43A of the third bus bar 43 will be described as a representative.

[0033] The board connection portion 43A of the third bus bar 43 includes a board facing surface 43A1 facing the circuit board 60 and a plurality of convex portions 45 protruding from the board facing surface 43A1. The convex portion 45 in FIG. 6 is a press-fit pin that fits into the through hole 64 of the circuit board 60. A press-fit pin has an elastic structure by making the shape of the center part of the terminal punched out, and has a shape with contact performance that can sufficiently maintain electrical connection and mechanical connection with the through-hole plating formed on the inner wall of the through hole 64. The board connection portion 43A is formed, for example, with 5 convex portions 45 arranged vertically and 5 convex portions 45 arranged horizontally, including a total of 25 convex portions 45. The total of 25 convex portions 45 are arranged corresponding to the 25 through holes 64 that constitute the bus bar connection portion 65 of the circuit board 60.

[0034] In the second bus bar 42 and the third bus bar 43, the connection portions with the respective terminals 23, 24 are the terminal connection portions 42B, 43B. The surfaces fixed to the respective terminals 23, 24 in the respective terminal connection portions 42B, 43B are the fixing surfaces 42C, 43C. Each of the fixing surfaces 42C, 43C in FIG. 1 is fixed to the respective terminals 23, 24 by welding, but may be fixed by bolt fastening.

[0035] 2. Assembly of the power storage device 10 First, the bus bar 40 is assembled to the circuit board 60. As shown in FIG. 7, by press-fitting each convex portion 45 into the second surface 60B, the pair of first bus bars 41 are assembled to the first bus bar connection portion 65A and the second bus bar connection portion 65B. Similarly, by press-fitting each convex portion 45 into the second surface 60B, the third bus bar 43 is assembled to the third bus bar connection portion 65C, and the second bus bar 42 is assembled to the fourth bus bar connection portion 65D. Thereby, each of the bus bars 41, 42, 43 is connected to the circuit board 60. As shown in FIG. 8, by these assemblies, the convex portion 45 penetrates the through hole 64 and slightly protrudes from the surface of the circuit board 60, but this protruding dimension is smaller than the height dimension of each heat generating component (circuit breaker 61, shunt resistor 62, IC 63) from the surface of the circuit board 60.

[0036] Next, the heat dissipation sheet 70 is disposed so as to cover each heat generating component. The heat dissipation sheet 70 is, for example, a heat conductive silicone rubber obtained by compounding a heat conductive material into silicone rubber and processed into a sheet shape. The heat dissipation sheet 70 can efficiently transfer heat from the heat generating component to the heat dissipation member by being sandwiched between the heat generating component (circuit breaker 61 in FIG. 8) and the heat dissipation member (front restraint plate 81A in FIG. 8). In this way, the heat generating component is thermally connected to the holding member 80 via the heat dissipation sheet 70. Generally, it is known that the thinner the heat dissipation sheet 70, the higher the heat dissipation effect, and the thicker the heat dissipation sheet 70, the lower the heat dissipation effect. For this reason, as shown in FIG. 8, the heat dissipation sheet 70 is made as thin as possible within a range where the convex portion 45 does not contact the front restraint body 81A of the holding member 80.

[0037] Next, the circuit board 60 to which the bus bars 41, 42, and 43 are assembled is attached to the front restraint plate 81A of the holding member 80. When attaching, while maintaining the state in which each heat generating component and each heat dissipation sheet 70 are sandwiched between the circuit board 60 and the front restraint body 81A of the holding member 80, the fixing surfaces 42C and 43C are welded to the terminals 23 and 24. FIG. 8 illustrates a state in which the circuit breaker 61 and the heat dissipation sheet 70 are sandwiched between the circuit board 60 and the holding member 80, and the same applies to the shunt resistor 62 and the IC 63. The welding of the fixing surfaces 42C and 43C to the terminals 23 and 24 may be performed before pressing each convex portion 45 into each through hole 64.

[0038] In parallel with the attachment of the first bus bar 41 to the third bus bar 43, the positive terminal 23 and the negative terminal 24 of the adjacent power storage elements 21 are connected by the fourth bus bar 44. When making this connection, the fourth bus bar 44 is welded to the terminals 23 and 24. As a result, the circuit board 60 adheres to the front restraint body 81A of the holding member 80 via the heat dissipation sheet 70. If the bus bars 40 and the circuit board 60 were fixed by bolt fastening, a bolt fastening work space and a space for arranging nuts would be required, so the circuit board 60 and the holding member 80 could not be made to adhere closely.

[0039] 3. Effects of this Embodiment In conventional power storage devices, an assembly method has been adopted in which a battery module to which a plurality of battery cells are connected and a circuit board are assembled separately. Since the power storage device includes a cutoff circuit to which a power line (bus bar) through which a large current flows is connected separately from the circuit board, the power line has never been directly fastened to the circuit board. However, in a cutoff circuit using a semiconductor switch, since the semiconductor switch is directly mounted on the circuit board, it is necessary to directly fasten the power line to the circuit board. For this reason, after inserting the battery module into a housing (a case for housing the battery module and the circuit board), an assembly method has been adopted in which the circuit board is attached to the housing and the power line is fastened to the circuit board. In this assembly method, bolt fastening or soldering is required to electrically connect the power line and the circuit board.

[0040] According to the power storage device 10 of the present embodiment, since the heat generating component and the heat dissipation sheet 70 are sandwiched between the circuit board 60 and the holding member 80, it becomes easier to transfer the heat of the heat generating component to the holding member 80. Since the holding member 80 is much larger than the circuit board 60, the heat of the heat generating component can be transferred over a wide area, and high heat dissipation performance can be exhibited. To assemble the bus bar 40 to the circuit board 60, it is only necessary to press-fit each convex portion 45 of the bus bar 40 into each through hole 64 of the circuit board 60, so that bolt fastening and soldering are not required, and the attachability of the bus bar 40 can be improved. Therefore, it is possible to provide the power storage device 10 that achieves both high heat dissipation performance of the heat generating component and high attachability of the bus bar 40.

[0041] As the holding member, a structure in which the power storage element unit is surrounded from three directions by a U-shaped holding member can also be considered. In that regard, since the holding member 80 described above is formed in an annular shape surrounding the power storage element unit 20, the power storage element unit 20 is surrounded from four directions. Therefore, compared with the holding member surrounding from three directions, the holding member 80 surrounding from four directions can take a wider heat dissipation area and can achieve higher heat dissipation performance.

[0042] Since the front restraint plate 81A of the holding member 80 is in contact with the power storage element unit 20, it is easy to dissipate the heat from the heat generating component to the power storage element unit 20 through the front restraint plate 81A. Therefore, compared with the case where the circuit board 60 is fixed facing the portion of the holding member 80 that is not in contact with the power storage element unit 20, higher heat dissipation performance can be achieved.

[0043] Since the convex portion 45 is a press-fit pin, the bus bar 40 can be fixed to the circuit board 60 simply by fitting the press-fit pin into the through hole 64. Connection by the press-fit pin can conduct electricity at high density in a narrow range, and the amount of protrusion from the through hole 64 can be minimized. Therefore, it becomes easier to bring the heat generating component and the holding member 80 into close contact, and higher heat dissipation performance can be achieved.

[0044] <Other Embodiments> The present disclosure is not limited to the embodiments described by the above description and drawings, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. The technical scope of the present disclosure includes, for example, the following embodiments.

[0045] In the above embodiment, the convex portion 45 is press-fitted into the through hole 64 as an example, but it is not necessarily the through hole 64, and the convex portion 45 may be press-fitted into a bottomed recess. A convex portion (for example, a press-fit pin) may be provided on the circuit board 60, and a through hole may be provided on the bus bar.

[0046] In the above embodiment, the holding member 80 is formed in an annular shape surrounding the power storage element unit 20 as an example, but the holding member may be U-shaped or C-shaped when viewed from above.

[0047] In the above embodiment, the circuit board 60 is fixed facing the outer surface of the front restraint plate 81A of the holding member 80, but the circuit board 60 may be fixed facing each connecting plate 82A, 82B of the holding member 80.

[0048] In the above embodiment, a press-fit pin is exemplified as the convex portion 45, but the convex portion may be constituted by a protrusion that does not elastically deform.

Explanation of Reference Numerals

[0049] 10: Power storage device 20: Power storage element unit 21: Power storage element 40: Bus bar 45: Convex portion (fitting portion) 60: Circuit board 60A: First surface 60B: Second surface 80: Holding member

Claims

1. A power storage device unit including a plurality of power storage elements, a holding member that holds the power storage device unit, a circuit board fixed facing an outer surface of the holding member, a heat generating component provided on the circuit board and thermally connected to the holding member, and a bus bar having a fitting portion and connected to the circuit board, the power storage device comprising: the circuit board has a first surface facing the holding member and a second surface opposite to the first surface, the bus bar is connected to the circuit board by press-fitting the fitting portion into the second surface.

2. The power storage device according to claim 1, wherein the holding member is formed in an annular shape surrounding the power storage device unit.

3. The power storage device according to claim 1 or claim 2, wherein the holding member has a pair of restraint plates sandwiching the power storage device unit in a first direction in which the plurality of power storage elements are arranged, and the circuit board is fixed facing an outer surface of one of the restraint plates.

4. Each of the power storage elements has a pair of terminals, The power storage device according to claim 1 or claim 2, wherein the bus bar has a fixing surface fixed to one of the terminals.

5. A through hole is formed in the circuit board, The power storage device according to claim 1 or claim 2, wherein the fitting portion is a press-fit pin fitted into the through hole.

Images