JP7810675B2 - Secondary battery pack - Google Patents

Description

The present invention relates to a secondary battery pack, and in particular to a secondary battery pack for use in a vehicle.

A secondary battery pack is known as a battery cell assembly, consisting of multiple secondary cells, placed inside a housing. The housing is equipped with a relief valve and a safety valve, and when the internal pressure of the housing increases, the secondary battery pack opens these valves to allow gas generated from the battery cell assembly to be discharged outside the housing. Furthermore, electronic components such as relays for controlling the battery cell assembly and electronic boards equipped with electronic circuits are housed inside the housing along with the battery cell assembly, protecting them from the environment outside the housing.

An example of this type of secondary battery pack is described in Japanese Patent Application Laid-Open No. 2014-49427.

JP 2014-49427 A

Conventional secondary battery packs have the problem of insufficient measures to prevent the electronic boards inside the housing from overheating. Therefore, the present invention aims to provide a secondary battery pack that can effectively cool the electronic boards inside the housing, thereby improving charge/discharge performance.

To achieve the above object, the present invention provides a secondary battery pack comprising a housing, an assembly of multiple secondary battery cells, and an electronic board for the assembly, wherein the housing is sealed, the assembly and the electronic board are disposed within the housing, the housing has an opening, the electronic board is attached to the housing so as to cover the opening while maintaining the sealing of the housing, and the back surface of the electronic board faces the outside of the housing.

The present invention provides a secondary battery pack that can effectively cool the electronic board inside the housing, thereby improving charge/discharge performance.

1 is a front view of a secondary battery pack according to an embodiment of the present invention, taken from the y direction, illustrating its internal configuration. FIG. 2 is a perspective view showing an external view of a secondary battery cell of the secondary battery pack according to FIG. 1 . 2 is an enlarged view of the electronic board of the secondary battery pack shown in FIG. 1 and the surrounding structure, drawn from the y direction. 2 is a plan view of the electronic board of the secondary battery pack shown in FIG. 1 and the surrounding structure, drawn from the z direction. FIG. 4 is an enlarged view of a fixing portion in FIG. 3A that positions the electronic board in the housing. 2 is an enlarged view of the electronic board of the secondary battery pack shown in FIG. 1 and the surrounding structure, drawn from the y direction. 10 is a partially enlarged view showing the state of the fixing portion of the electronic board when the electronic board is released due to an increase in pressure inside the housing. FIG. FIG. 2 is a front view of the electronic board and the blower unit, taken from the y direction of the housing. FIG. 2 is a schematic diagram of a battery pack showing a state in which an electronic board is mounted on a side surface of a housing. FIG. 2 is a schematic diagram of an electronic substrate. FIG. 10 is another schematic configuration diagram of the electronic substrate. FIG. 10 is still another schematic configuration diagram of the electronic substrate. FIG. 10 is a schematic diagram showing a modified example of the electronic substrate.

Next, we will explain an embodiment of a secondary battery pack according to the present invention. The secondary battery pack contains a battery cell assembly, an electronic board on which semiconductor relays for the battery cells are mounted, and a control device such as a BMS (Battery Management System) within an enclosed space within a housing.

In order to improve the charge/discharge performance of secondary battery packs, the number of battery cells mounted tends to increase. However, as the number of battery cells mounted increases, the current flowing through the electronic circuit board increases, causing the board to overheat, so it is desirable to cool the board.

However, cooling a circuit board inside a sealed housing is not easy in the first place, and limiting the current flowing through the board to prevent it from overheating can potentially limit charging and discharging performance. The secondary battery pack described below is designed to effectively cool an electronic board even when it is inside a sealed housing, without requiring a complex structure.

The secondary battery cells of the secondary battery pack are not particularly limited and may be lithium-ion secondary battery cells, as well as sodium-ion secondary batteries, magnesium-ion secondary batteries, calcium-ion secondary batteries, aluminum-ion secondary batteries, zinc secondary batteries, etc.

First, the overall configuration of this secondary battery pack will be explained using Figures 1 to 4. Elements that have the same function as other elements will be given the same reference numerals (in the drawings), and their explanations may be omitted.

Figure 1 is a front view of the secondary battery pack, drawn from the y direction, showing its internal configuration. Figure 2 is a perspective view of the exterior of a secondary battery cell of the secondary battery pack of Figure 1. Figure 3A is an enlarged view of the electronic board of the secondary battery pack of Figure 1 and its surrounding structure, drawn from the y direction. Figure 3B is a plan view of the electronic board of the secondary battery pack of Figure 1 and its surrounding structure, drawn from the z direction. Figure 4 is an enlarged view of the fixing portion in Figure 3A that positions the electronic board in the housing. As will be described later, the directions of the coordinate axes will be explained when explaining Figure 2.

The main components of the secondary battery pack 100 are a battery cell stack (battery cell assembly) 10 made up of multiple stacked secondary battery cells 11, a cooling unit 30 for cooling the battery cell stack 10, an electronic board 40, a control device 60, and a housing 70 that houses these components in an internal sealed space.

The electronic board 40 may be, for example, a semiconductor relay board, or other board on which circuits and electronic components through which a large current flows are mounted. Electronic components 42, such as multiple semiconductor chips, are mounted on the surface (flat surface) of the board portion 41 of the electronic board 40 that faces the inside of the housing 70. As previously mentioned, the control device 60 is, for example, a BMS (Battery Management System).

To cool the board 41, fins (heat transfer bodies) 43 are formed on the back surface of the board 41 (the outer surface of the housing 70) to dissipate heat transferred from the electronic components and electronic circuits 42 on the planar surface of the board 41. Ducts 85 (Figure 7) are formed around the fins 43 to allow cooling air to flow. Note that bus bars and electrical wiring for electrically connecting the multiple secondary battery cells 11 together, and bus bars and electrical wiring for electrically connecting the battery cells 11 to the electronic board 40 and the control device 60 are not shown in the figure.

As shown in FIG. 2, the main components of the secondary battery cell 11 are a battery cell can 17 having a roughly rectangular parallelepiped shape for housing a stack of multiple positive and negative electrode bodies (not shown), and electrode terminals 16 having positive and negative electrodes. The battery cell can 17 is formed into a roughly rectangular parallelepiped shape from, for example, aluminum, and has a wide surface 12 and narrow surfaces 13, 14, and 15. The electrode bodies are stacked roughly parallel to the wide surface 12 inside the battery cell can 17.

The battery cell stack 10 is constructed by stacking the secondary battery cells 11 with their wide surfaces 12 facing each other. The stacking direction of the secondary battery cells 11 is the x-axis direction. The x-axis, y-axis, and z-axis are all perpendicular to each other, with the z-axis direction being the vertical direction. Of the narrow surfaces of the secondary battery cells 11, narrow surface 13 is referred to as the "bottom of the can" and narrow surface 14 is referred to as the "side surface of the can."

As shown in Figure 1, the end plates 21 used to fasten and hold the battery cell stack 10 are positioned so that they come into contact with the wide faces 12 of the secondary battery cells 11, and the side plates (not shown) are positioned so that they come into contact with the narrow faces 14 (side faces of the can) of the battery cells 11. The two end plates 21 are fastened to the side plates, for example by screws, thereby holding the two end plates 21 to the side plates.

Because the fastening direction between the end plates 21 and side plates is the same as the stacking direction (x-axis direction) of the secondary battery cells 11, a nearly uniform surface pressure is applied across the wide surfaces 12 of the multiple secondary battery cells 11. This securely holds the multiple secondary battery cells 11 in the stacking direction (x-axis direction), increasing the rigidity of the battery cell stack 10. The end plates 21 and side plates are made of metal materials such as steel, iron, or aluminum.

As shown in FIG. 1 , the housing 70 includes a housing bottom 71 that houses the battery cell stack 10, electronic board 40, control device 60, etc., and a housing lid 72 that is shaped to cover the housing bottom 71. By covering the housing bottom 71 with the housing lid 72, the interior that houses the battery cell stack 10, etc., is sealed from the outside. The housing bottom 71 is made of a metal material such as steel, iron, or aluminum, and the housing lid 72 is made of a resin material such as plastic.

The can bottom side of the battery cell stack 10, i.e., the narrow side 13 (can bottom) of the secondary battery cell 11, is fixed to the inside of the housing 70 on the bottom surface of the housing bottom 71 via a thermally conductive material (not shown), such as heat-dissipating grease or a heat-dissipating adhesive. Furthermore, a cooling unit 30 for cooling the battery cell stack 10 is fixed to the outside of the bottom surface of the housing bottom 71. The cooling unit 30 may be a general heat sink, and has a shape in which multiple fins (heat dissipation heat transfer bodies) 32 are fixed to a fin base plate 31. The outside of the cooling unit 30 is provided with a duct (flow path) 33 for circulating cooling air to the fins 32. The cooling unit 30 may be made of a metal with relatively high thermal conductivity, such as aluminum or copper.

As shown in Figures 3A and 3B, an opening 73 is provided in a portion of the bottom surface of the housing bottom 71, and the substrate 41 is supported by the housing bottom 71 so as to cover the opening 73 while maintaining the interior of the housing 70 airtight. The fixing portions 50 of the substrate 41 position the substrate 41 relative to the opening 73 from the outside of the housing 70, allowing it to be supported by the housing bottom 71. Figure 3B shows that the shape of the opening 73 is, for example, rectangular, and the fixing portions 50 are provided at the four corners of the substrate 41. The shape of the opening is not particularly limited, and may be circular, elliptical, or the like. There are no particular restrictions on the size and area of the opening, as long as the substrate 41 can cover the opening. The lower limit may be determined within a range that allows the electronic components, electronic circuits, and semiconductor elements mounted on the substrate 41 to be exposed to the interior of the housing 70 through the opening.

The substrate portion 41 may be made of a metal with relatively high thermal conductivity, such as aluminum. An insulating layer 44 is provided on the side of the substrate portion 41 facing the inside of the housing 70, and a circuit pattern 45 is formed on the insulating layer 44. Multiple electronic components 42, such as semiconductor chips, are mounted on the substrate portion 41 via this circuit pattern 45.

The circuit pattern 45 is equipped with a bus bar 46, to which a flexible bus bar 49 is fixed via a terminal 47. The flexible bus bar 49 is a commonly used shunt wire or the like.

The other terminal 48 of the bus bar 49 is fixed by a support member (not shown) fixed inside the housing 70. Cut-and-raised fins 43 are molded directly onto the metal substrate 41 on the side opposite the surface on which the electronic components 42 are mounted (the side facing the outside of the housing 70, i.e., the back side), and serve as heat transfer bodies for heat dissipation. The fins 43 are, for example, commonly used skive fins. Ducts (cooling flow channels) 85 are provided on the outside of the fins 43 to direct cooling air toward the fins 43.

A blower is connected to the duct 85. The blower is, for example, a blower such as an axial fan or centrifugal blower. Therefore, even if the electronic board 40 is overheated by electronic components due to a large current in the electronic board 40, the electronic board can effectively dissipate heat. This allows for an increase in the number of battery cells mounted, improving the charging and discharging performance of the secondary battery pack.

As shown in FIG. 4 , the substrate unit 41 is positioned relative to the opening 73 so as to cover the opening 73 by a fixing unit 50 composed of fastening members 51, 52 such as screws and a spring 53, and is supported on the housing bottom 71 of the housing 70. The fastening members 51, 52 are male and female threads, respectively, and the fastening member 51 is fixed to the housing bottom 71 by a threaded portion 55 provided on the housing bottom 71.

Furthermore, the substrate portion 41 is pressed against the housing bottom portion 71 by the elastic stress of a spring (elastic body) 53 attached to the fastening member 51 as an actuator. As described in Figure 3B, multiple fixing portions 50 are installed near the outer edge of the substrate portion 41.

As shown in Figures 3A and 3B, a gasket 54 is interposed between the base plate 41 and the housing bottom 71. When the base plate 41 is pressed against the housing bottom 71 by the elastic stress of the spring (elastic body) 53, the gasket 54 seals the housing opening 73, maintaining an airtight environment inside the housing 70. The base plate 41 has a rectangular cross section in the width direction and a circumferential groove engraved into it, into which is fitted a gasket 54 that has a circular cross section in the width direction and protrudes from this groove toward the housing bottom 71. This groove is configured to avoid the fixed portion 50. The gasket 54 may be, for example, an O-ring, which is commonly used as a sealing member.

During normal operation of the secondary battery pack (charging and discharging), the electronic board 40 acts as a lid for the opening 73, keeping the housing 70 sealed. Meanwhile, in the event of abnormal operation of the secondary battery cell 11, if gas is generated and the pressure inside the housing 70 increases, the electronic board 40 will be pushed outward away from the housing 70 when the pressure inside the housing 70 exceeds a predetermined value. At this time, the seal provided by the gasket 54 is released, creating a path between the electronic board 40 and the housing 70 that opens the interior of the housing 70 to atmospheric pressure. Gas generated inside the housing 70 is released to the outside of the housing through this path. In other words, the board itself functions as a safety valve for the secondary battery pack 100.

By having the substrate itself function as a release valve, not only is there no need to provide a separate valve, but the path appears over a wide area around the substrate portion 41, allowing the gas pressure inside the housing 70 to be reduced quickly and sufficiently.

Figure 5 is an enlarged view of the electronic board of the secondary battery pack shown in Figure 1 and its surrounding structure, drawn from the y direction, showing the state when gas is generated inside the housing from the secondary battery cell 11. Figure 6 is an enlarged view of the fixing portion 50 of the electronic board 40 shown in Figure 5. When the pressure inside the housing 70 increases due to the generation of gas and the pressure (Pin) inside the housing 70 exceeds a certain predetermined value (Pf), the electronic board 40 is pushed toward the outside of the housing 70, creating a gap (path) 56 between the board portion 41 and the housing bottom 71. Gas 91 filling the housing 70 is released through the gap 56 and the opening 73 to the outside of the housing 70.

To ensure that the housing 70 can be sealed during normal operation of the secondary battery pack, and that gas can be released to the outside of the housing during abnormal operation of the secondary battery pack, the spring constant of the spring 53 of the fixing part 50 must be Ps, and the number of fixing parts 50 must be N, and Pin ≥ Pf = Ps × N must be satisfied.

If the specified value Pf is too small, for example, when the battery pack 100 is mounted on a vehicle, vibrations caused by the vehicle being driven may cause the board portion 41 to be pushed outward from the housing 70, even when no gas is being generated, causing the battery pack 100 to lose its sealed state and potentially deteriorating. Therefore, the reaction force Ps of the spring 53 must be strong enough to prevent the board portion 41 from moving outward from the housing 70 when the battery pack is operating normally and no gas is being generated from the battery cells.

When the gas is discharged outside the housing, the force of the spring 53 presses the substrate 41 against the housing bottom 71, closing the gap (path) 56 between them and sealing the housing again.

Figure 7 is a front view of the electronic board 40 and air blowing means 83, drawn from the y direction of the housing 70. The battery cell stack 10 and control device 60 are not shown. The air blowing means is composed of a blower 83 and ducts (flow paths) 84, 85, and 86. During normal operation of the secondary battery pack 100 (charging and discharging), the blower 83, located upstream of the flow path, is operated, causing cooling air 92 to pass through the fins 43 of the electronic board 40, exchanging heat with the heat transferred from the electronic components 42 to the fins 43, and the warmed air (exhaust air 93) is discharged.

On the other hand, if an abnormality occurs in the secondary battery pack 100, and the internal pressure Pin exceeds a predetermined value Pf due to an increase in pressure inside the housing 70 caused by gas generated from the secondary battery cells 11, the electronic board 40 is pushed outward from the housing 70, causing gas 91 to be released into the duct 85 through the gap 56 created between the board portion 41 of the electronic board 40 and the housing bottom 71. At this time, the gas 91 released from the housing 70 is guided by cooling air 92 from a blower 83 provided upstream of the flow path, and together with the cooling air 92, the gas 91 is exhausted as exhaust air 93 from the housing 70 and is ultimately efficiently discharged outside the system (e.g., outside the vehicle).

With the battery pack described above, the electronic board 40 itself can both cool the electronic board 40 and release gas from the housing. Furthermore, it is possible to share a common flow path for the cooling air and the gas exhaust from the housing, enabling high-density packaging of the battery pack and lower costs by reducing the number of components.

Figure 7 shows a configuration in which the blower 83 is placed on the inlet side of the cooling air 92 and pushes the cooling air 92 into the fins 43 of the electronic board 40, but the blower 83 may also be placed on the outlet side of the cooling air 92 and suck the cooling air 92 out through the fins 43.

As shown in Figure 8, the electronic board 40 may be provided in an opening on the side of the housing 70. The board portion 41 may be made of resin as well as metal. As shown in Figure 9, a general heat sink having a metal fin base plate 81 with multiple fins 43 can be attached to the surface of the resin board 41 facing the outside of the housing.

Alternatively, the electronic board 40 may be immovably fixed to the bottom 71 of the housing 70, as shown in Figures 10 and 11. Figure 10 shows the case where the electronic board 40 is fixed from the outside of the housing 70, while Figure 11 shows the case where the electronic board 40 is fixed from the inside of the housing 70.

Also, as shown in Figure 12, before the electronic board 40 is mounted, a simple plate 82 may be applied to the opening 73 instead of the electronic board 40, and the simple plate 82 may be used as a safety valve to open and close the opening.

As explained above, the openings can be used to expose the electronic components mounted on the board to the inside of the housing, while at the same time allowing the back of the board to face the outside of the housing. Therefore, by directing cooling air toward the back side of the electronic board, it is possible to cool the electronic board without relying on a complex configuration.

The present invention should not be limited to the above-described embodiments, and modifications and amendments by those skilled in the art are possible as long as they fall within the scope of the present invention. For example, the mechanism for releasing gas from within the housing 70 in the event of an abnormality in the battery pack 100 may be changed to one in which a pressure sensor is provided within the battery pack 100, and when the pressure within the housing 70 exceeds a predetermined value, a solenoid actuator moves the electronic board 40 outside the housing 70, thereby releasing the sealed state of the battery pack 100.

REFERENCE SIGNS LIST 10 Battery cell stack, 11 Battery cell, 12 Battery cell wide surface, 13 Battery cell narrow surface (bottom surface of can), 14 Battery cell narrow surface (side surface of can), 15 Battery cell narrow surface, 16 Electrode terminal, 17 Battery cell can, 21 End plate, 30 Cooling portion, 31 Fin base plate, 32 Fin, 33 Duct (flow path), 40 Electronic board, 41 Board portion, 42 Electronic component, 43 Fin, 44 Insulating layer, 45 Circuit pattern, 46 Bus bar, 47 Terminal, 48 Terminal, 49 Bus bar, 50 Fixing portion, 51 Fastening member (external thread), 52 Fastening member (internal thread), 53 Spring, 54 Gasket, 55 Threaded portion, 56 Gap, 60 Control device, 70 Housing, 71 Housing bottom, 72 Housing lid, 73 Housing opening, 81 Fin base plate, 82 Plate, 83 blower, 84, 85, 86 duct (flow path), 91 gas, 92 cooling air, 93 exhaust, 100 secondary battery pack.

Claims (6)

The housing and
an assembly of a plurality of secondary battery cells;
a substrate of electronic components for said assembly;
Equipped with
The inside of the housing is sealed,
The assembly is disposed within the housing;
the housing has an opening;
A secondary battery pack in which the substrate is attached to the housing so as to cover the opening from the outside of the housing toward the inside of the housing while maintaining the interior of the housing airtight , and the back surface of the substrate faces outside the housing. A plurality of heat dissipation heat transfer bodies are formed on the rear surface side of the substrate.
The secondary battery pack according to claim 1 . a flow path for sending cooling air toward the plurality of heat dissipation heat transfer bodies;
3. The secondary battery pack according to claim 2. an actuator that separates the substrate, which is attached to the housing so as to cover the opening, from the housing when the internal pressure in the housing reaches a predetermined level or higher;
The secondary battery pack according to claim 1 . The actuator is
an elastic body provided on a fixing portion that positions the substrate in the opening;
the elastic body presses the substrate against the housing when the pressure inside the housing is equal to or lower than a predetermined pressure, so that the opening is closed by the substrate;
When the pressure inside the housing exceeds a predetermined pressure, the substrate is pressed against the elastic body so as to move away from the housing, and a path connected to the opening is formed between the substrate and the housing, and the gas generated inside the housing is discharged to the outside of the housing through the path.
5. The secondary battery pack according to claim 4. the actuator has a path formed between the substrate and the housing that is connected to the opening, and gas generated within the housing is discharged to the outside of the housing via the path;
the secondary battery pack includes a flow path that sends cooling air toward the gas that is discharged to the outside of the housing;
The gas is guided by the cooling air and discharged to the outside of the system.
5. The secondary battery pack according to claim 4.