JP7612405B2 - Battery pack structure - Google Patents

Description

The present invention relates to a battery pack structure.

The following Patent Document 1 discloses a battery pack having a battery, a housing for housing the battery, and a thermal expansion part that can reduce the internal gap between the battery and the housing in response to the application of heat.

WO2008-152803 publication

However, when a battery cell in a battery pack releases high-temperature gas, the heat of the gas can be transferred to the battery pack's housing, causing the temperature of the housing to rise. Furthermore, the release of gas can increase the pressure inside the housing, which can cause the housing to receive pressure from the inside and deform.

The purpose of the present invention is to suppress the temperature rise and deformation of the housing when the battery cell releases high-temperature gas.

In a battery pack structure according to one aspect of the present invention, the opposing wall portion of the housing that faces at least the gas release portion includes at least a portion of the wall portion surrounding one or more battery cells of the housing, a fiber-reinforced resin layer that reinforces the opposing wall portion, and a thermal expansion portion that is disposed in the layer of the opposing wall closest to the gas release portion and expands by absorbing the heat of the gas released from the gas release portion.

The present invention makes it possible to suppress temperature rise and deformation of the housing when the battery cell releases high-temperature gas.

1 is a perspective view of a battery pack according to an embodiment, seen from above and on the front left. FIG. FIG. 2 is an exploded perspective view showing the structure of the battery pack shown in FIG. 1 . 1 is a perspective view of a battery cell in a battery pack structure according to an embodiment, viewed from above and on the front left. FIG. 3 is a schematic partial cross-sectional view taken along line AA in FIG. 2, showing the arrangement relationship of a wall portion, a fiber-reinforced resin layer, and a thermal expansion portion in the battery pack structure according to the first embodiment. FIG. FIG. 5 is a diagram for explaining the function of the battery pack structure according to the first embodiment, and is a schematic partial cross-sectional view showing the state after gas has been released from the gas release portion of the battery cell in the cross-section shown in FIG. 5 is a schematic partial cross-sectional view corresponding to FIG. 4 , showing the arrangement relationship of a wall portion, a fiber-reinforced resin layer, and a thermal expansion portion in a battery pack structure according to a modified example of the first embodiment. FIG. 5 is a schematic partial cross-sectional view corresponding to FIG. 4 , showing the arrangement relationship of a wall portion, a fiber-reinforced resin layer, and a thermal expansion portion in a battery pack structure according to a second embodiment. FIG.

The battery pack structure according to the embodiment will be described below with reference to the drawings. In each figure, FR and RR indicate the front and rear in the longitudinal direction of the vehicle, LH and RH indicate the left and right in the width direction of the vehicle, and UP and DN indicate the top and bottom in the vertical direction of the vehicle. In the following description, the front and rear in the longitudinal direction of the vehicle, the top and bottom in the vertical direction of the vehicle, and the left and right in the lateral direction of the vehicle will be simply referred to as "front of the vehicle," "rear of the vehicle," "upper of the vehicle," "lower of the vehicle," "left side of the vehicle," and "right side of the vehicle," respectively. Elements having the same function will be given the same reference numerals, and duplicate descriptions will be omitted.

The battery pack 1 according to the embodiment is used as a vehicle drive battery for a vehicle, such as an electric vehicle (EV) driven by an electric motor (not shown).

As shown in Figures 1 and 2, the battery pack structure according to the embodiment includes a housing 10, a battery cell 22, and an opposing wall portion 15 of the housing 10.

The housing 10 is a rectangular box-shaped hollow member that houses the battery module 20 inside, and forms the exterior of the battery pack 1. The housing 10 has a flat shape in which the dimensions in the vehicle vertical direction are smaller than the dimensions in the vehicle front-rear direction or left-right direction. The housing 10 has a wall portion 10a that forms the exterior of the battery pack 1, and the battery module 20 includes one or more battery cells 22. Thus, the housing 10 houses one or more battery cells 22. In the illustrated example, the wall portion 10a of the housing 10 surrounds the battery module 20 above, below, left, and right of the battery module 20. In other words, the housing 10 has a wall portion 10a that surrounds one or more battery cells 22. The shape of the housing 10 can be set appropriately depending on the shape and dimensions of the battery pack 1, or the arrangement method in the vehicle.

As shown in FIG. 2, the housing 10 includes an upper casing 11 and a lower casing 12. The upper casing 11 and the lower casing 12 are fastened to each other at their peripheries by fasteners such as bolts (not shown). A seal member made of a rubber material or the like may be interposed at the contact area between the upper casing 11 and the lower casing 12.

The lower casing 12 is a box-shaped member with a bottom that opens toward the top of the vehicle and has a roughly rectangular shape in a plan view. Battery modules 20 are arranged at the bottom of the lower casing 12. In the illustrated example, eight battery modules 20 are arranged in two rows in the vehicle width direction and four rows in the vehicle front-to-rear direction in the region of the lower casing 12 on the front side of the vehicle. Additionally, the battery modules 20 are stacked in two tiers, one above the other, in the region of the lower casing 12 on the rear side of the vehicle, and eight two-tiered battery modules 20 are arranged in two rows in the vehicle width direction and two rows in the vehicle front-to-rear direction.

When multiple battery modules 20 are arranged, a partition 50 may be provided to separate the battery modules 20 from each other at the bottom of the lower casing 12. This fixes the position of the battery modules 20 inside the housing 10, restricting the movement of the battery modules 20 when an external force is applied to the battery pack 1, and preventing the battery modules 20 from coming into contact with each other. In the illustrated example, wiring members (not shown) such as bus bars that electrically connect the battery modules to each other are arranged between the battery module 20 arranged on the left side of the vehicle and the battery module 20 arranged on the right side of the vehicle.

The upper casing 11 is a plate-like member having a generally rectangular shape in a plan view. The upper casing 11 closes the opening of the lower casing 12 above the vehicle, thereby sealing the inside of the housing 10. In the illustrated example, the region on the rear side of the vehicle of the upper casing 11 is formed to protrude further above the vehicle than the region on the front side of the vehicle, depending on the number of stages of the battery modules 20 arranged in the lower casing 12. In this way, it is possible to create space on the rear side of the vehicle for arranging more battery modules 20. This makes it possible to ensure more battery capacity while making the battery pack 1 thinner and more space-saving overall.

The upper casing 11 or the lower casing 12 is formed, for example, by pressure molding a molding material. In one embodiment, the molding material may be sheet molding compound (SMC), which is made by impregnating glass fibers with resin and molding them into a sheet. For example, the upper casing 11 or the lower casing 12 can be formed by stacking multiple pieces of SMC molding material cut to the desired size in a mold and heating and pressure molding them. Thus, the wall 10a of the housing 10 may be formed by pressure molding SMC.

In this manner, the battery pack 1 is constructed by disposing the battery cells 22 in the lower casing 12 and covering it from above with the upper casing 11. The battery pack 1 constructed in this manner is fixed to the vehicle, for example, by fastening the peripheral portion of the housing 10 to the bottom of the vehicle body (not shown) via fasteners such as bolts (not shown).

In the battery pack 1 illustrated in Figs. 1 and 2, the housing 10 houses multiple battery modules 20 therein, but this is not limited to this. The number of battery modules 20 can be set according to the dimensions of the battery pack 1, or the dimensions or installation method of the battery modules 20. Therefore, the number of battery modules 20 may be one or more.

As shown in FIG. 3, the battery module 20 is a modularized component in which multiple flat battery cells 22, whose width dimension is shorter than their longitudinal dimension, are arranged in parallel in the width direction of the vehicle. The electrode tabs (not shown) of the multiple battery cells 22 are arranged in a state in which they are electrically connected to each other by wiring members such as a bus bar unit (not shown). Furthermore, the anode terminal and cathode terminal (neither shown) of the battery cells 22 are exposed to the outside on the outer periphery of the battery module 20 via the bus bar unit.

In the illustrated example, the battery module 20 includes multiple battery cells 22, but may include only one battery cell 22. In other words, the battery module 20 may house one or more battery cells. The battery module 20 may also include a module case that integrally houses the multiple battery cells 22 and serves as an exterior member of the battery module 20.

The battery cell 22 is constructed by, for example, laminating a positive electrode plate and a negative electrode plate with a separator between them, sealing the power generating element together with an electrolyte in an exterior member such as an aluminum can. In one embodiment, the battery cell 22 is a lithium ion secondary battery.

Each of the one or more battery cells 22 has a gas release section 25 on its upper surface that releases gas toward the top of the vehicle. When gas is generated inside the battery cell 22, the gas release section 25 releases the gas. For example, the gas release section 25 can be an explosion-proof valve that opens to release the gas when the internal pressure of the battery cell 22 exceeds a predetermined pressure, or a sealing member that breaks to release the gas.

In the illustrated example, the gas release section 25 has a substantially circular shape in plan view, but may have, for example, a substantially elliptical, rectangular, or polygonal shape in plan view. The position of the gas release section 25 can be set appropriately depending on the shape and dimensions of the battery pack 1, the arrangement method of the battery cells 22, etc. For example, the gas release section 25 may be set on the underside or side of the battery cells 22.

As shown in Figures 1 and 2, an opposing wall portion 15 is provided in at least the area of the housing 10 that faces the gas release portion 25 in the gas release direction. The opposing wall portion 15 is a region that is provided in a plurality of portions on the wall portion 10a above the vehicle of the upper casing 11 (housing 10) and has a substantially rectangular shape that extends in the vehicle width direction in a plan view.

The position of the opposing wall portion 15 can be set according to the position where the gas release portion 25 is set. For example, if the gas release portion 25 is provided on the side surface of the battery cell 22, the opposing wall portion 15 may be set on the side portion of the housing 10.

In the illustrated example, the battery cells 22 are arranged in parallel in the vehicle width direction, so that the gas release sections 25 are arranged in a substantially linear fashion in the vehicle width direction. Therefore, the opposing wall section 15 extends in the vehicle width direction from the vehicle left end to the vehicle right end of the wall section 10a so as to cover the gas release sections 25 arranged in a substantially linear fashion. The opposing wall section 15 may extend in the vehicle front-rear direction from the vehicle front end to the vehicle rear end of the wall section 10a. In other words, the opposing wall section 15 may extend continuously from one end to the other end of the wall section 10a of the housing 10.

As shown in Fig. 4 and Figs. 6 to 7, the opposing wall portion 15 includes at least a portion of the wall portion 10a surrounding one or more battery cells 22 of the housing 10, a fiber reinforced resin layer 30, and a thermal expansion portion 45. In addition to the wall portion 10a, the fiber reinforced resin layer 30, and the thermal expansion portion 45, the opposing wall portion 15 may also include, as appropriate, an adhesive layer for joining the wall portion 10a and the fiber reinforced resin layer 30, a resin layer 40a including the thermal expansion portion 45, etc.

The fiber-reinforced resin layer 30 is formed by arranging an FRP material composed of multiple reinforced fiber layers (not shown) stacked in the thickness direction and matrix resin 40b impregnated in the reinforced fiber layers in the wall portion 10a.

The reinforcing fiber layer is made of reinforcing fiber bundles that are aligned in one direction or at different angles, stacked, and bound with stitch thread, or that are shaped by heat fusion without using stitch thread, or made of a woven reinforcing fiber. The reinforcing fiber may be continuous fiber such as carbon fiber, glass fiber, boron fiber, or aramid fiber. The matrix resin 40b may be a thermosetting resin such as epoxy resin, unsaturated polyester resin, or phenolic resin, and may also include thermoplastic resins such as nylon resin, polyether ether ketone resin (PEEK), and polyetherimide resin (PEI).

The opposing wall portion 15 is reinforced by including the fiber-reinforced resin layer 30 in the opposing wall portion 15. In this embodiment, the fiber-reinforced resin layer 30 has substantially the same shape as the opposing wall portion 15 in a plan view and has a substantially rectangular shape extending in the vehicle width direction, but may have, for example, a substantially elliptical, substantially rectangular, or substantially polygonal shape, and may be larger than the opposing wall portion 15.

The reinforcing fibers contained in the fiber-reinforced resin layer 30 may include continuous fibers oriented in the longitudinal direction of the fiber-reinforced resin layer 30. The longitudinal direction refers to the long dimension direction of the fiber-reinforced resin layer 30 in a planar view. For example, when the shape of the fiber-reinforced resin layer 30 in a planar view is approximately rectangular, the longitudinal direction refers to the long side direction, and when the shape is approximately elliptical, the longitudinal direction refers to the long axis direction. Carbon fibers may also be used as the reinforcing fibers. For example, polyacrylonitrile (PAN-based), pitch-based, cellulose-based, and other carbon fibers may be used alone or in combination.

In the example shown in FIG. 4 and FIGS. 6 to 7, the fiber-reinforced resin layer 30 extends continuously in the vehicle width direction from the vehicle left end to the vehicle right end of the wall portion 10a of the housing 10 without being divided. The fiber-reinforced resin layer 30 may extend continuously in the vehicle front-rear direction from the vehicle front end to the vehicle rear end of the wall portion 10a. In other words, the fiber-reinforced resin layer 30 may extend continuously from one end to the other end of the wall portion 10a of the housing 10.

The thermal expansion section 45 has the property of expanding by absorbing the heat of the gas released from the gas release section 25. The thermal expansion section 45 is disposed in the layer of the opposing wall section 15 closest to the gas release section 25 in order to receive the gas released from the gas release section 25 of the battery cell 22. In this embodiment, as illustrated in Figs. 1 to 3, the gas release section 25 is provided on the upper surface of the battery cell 22, and therefore the opposing wall section 15 is set above the battery cell 22 in the vehicle. Therefore, as shown in Figs. 4 and 6 to 7, the thermal expansion section 45 is disposed in the layer of the opposing wall section 15 closest to the vehicle bottom.

Expanded graphite, which has high thermal expansion and flame retardancy, can be used for the thermal expansion portion 45. In this way, by including the thermal expansion portion 45 in the opposing wall portion 15, heat resistance or flame retardancy is imparted to the wall portion 10a of the housing 10.

Expanded graphite is an intercalation compound in which reactive molecules such as sulfuric acid are held between layers of carbon crystals by, for example, treating flake graphite powder with an inorganic acid such as sulfuric acid or nitric acid, and then further treating it with an oxidizing agent such as concentrated nitric acid or potassium chlorate, and the crystal as a whole has a layered structure in which layers of carbon crystals are stacked. The shape of the expanded graphite is not particularly limited, and it may be in the form of powder, flakes, or particles. When the expanded graphite obtained in this way is heated, the reactive molecules between the crystal layers are gasified, and the pressure causes the expanded graphite to expand tens to hundreds of times in the stacking direction of the crystal layers, resulting in a fibrous form. The resin layer 40a and matrix resin 40b described later contain such expanded graphite as the thermal expansion portion 45.

The arrangement of the wall 10a of the housing 10, the fiber-reinforced resin layer 30, and the thermal expansion section 45 in the opposing wall 15 will be described below with reference to Figures 4, 6, and 7.

First Embodiment
4, the wall portion 10a, the fiber reinforced resin layer 30, and the thermal expansion portion 45 included in the resin layer 40a are laminated in this order from the top of the vehicle. In other words, the fiber reinforced resin layer 30 is disposed between the wall portion 10a and the thermal expansion portion 45. Moreover, the expandable graphite as the thermal expansion portion 45 is contained in the resin layer 40a laminated on the fiber reinforced resin layer 30.

The fiber-reinforced resin layer 30 is formed by disposing FRP material on the wall portion 10a. The FRP material has a shape with thickness, such as a sheet, film, or plate shape.

The resin layer 40a is formed by disposing a thermally expandable resin material composed of expanded graphite and a thermoplastic resin containing the expanded graphite in the fiber reinforced resin layer 30. The thermally expandable resin material can be obtained, for example, by injecting a molten thermoplastic resin to which powdered expanded graphite has been added into a mold and cooling it. The thermally expandable resin material has a shape having a thickness, such as a sheet shape, a film shape, or a plate shape. In this embodiment, the resin layer 40a has approximately the same shape as the opposing wall portion 15 in a plan view and has an approximately rectangular shape extending in the vehicle width direction, but may have, for example, an approximately elliptical, approximately rectangular, or approximately polygonal shape, and may be larger than the opposing wall portion 15.

The illustrated opposing wall portion 15 may be formed by integrally molding the fiber reinforced resin layer 30 or the resin layer 40a including the thermal expansion portion 45 when pressure molding the wall portion 10a. For example, the thermally expandable resin material, the prepreg that is the material of the FRP material, and SMC are laminated and pressure molded inside the mold used to mold the wall portion 10a. As a result, the opposing wall portion 15 is formed in which the resin layer 40a including the thermal expansion portion 45, the fiber reinforced resin layer 30, and the wall portion 10a are integrally molded. In this way, the battery pack structure according to this embodiment can be constructed with a simple manufacturing process. The opposing wall portion 15 may be formed by bonding the FRP material to the lower surface of the wall portion 10a with an adhesive layer interposed therebetween, and bonding the thermally expandable resin material to the lower surface of the FRP material.

(Modification)
6, the opposing wall 15 may be formed by stacking the fiber reinforced resin layer 30, the wall 10a, and the thermal expansion portion 45 included in the resin layer 40a in this order from the top of the vehicle. In other words, the fiber reinforced resin layer 30 may be disposed on the surface opposite the resin layer 40a including the thermal expansion portion 45 across the wall 10a. The expandable graphite as the thermal expansion portion 45 is contained in the resin layer 40a disposed in the wall 10a.

Similar to the case of forming the opposing wall portion 15 illustrated in FIG. 4, such opposing wall portion 15 may be formed by integrally molding the fiber reinforced resin layer 30 and the resin layer 40a including the thermal expansion portion 45 when pressure molding the wall portion 10a. This allows the battery pack structure according to this embodiment to be constructed with a simple manufacturing process. The opposing wall portion 15 may be formed by interposing an adhesive layer between the wall portion 10a and the fiber reinforced resin layer 30, or between the wall portion 10a and the resin layer 40a.

Second Embodiment
7 , the opposing wall portion 15 may include, in this order from the upper side of the vehicle, a wall portion 10a and a fiber reinforced resin layer 30. The expandable graphite serving as the thermal expansion portion 45 is contained in the matrix resin 40b of the fiber reinforced resin layer 30. In other words, the thermal expansion portion 45 is expandable graphite contained in the matrix resin 40b of the fiber reinforced resin layer 30.

The matrix resin 40b of the FRP material that constitutes the fiber-reinforced resin layer 30 contains expandable graphite as the thermal expansion portion 45. Such an FRP material is obtained by hardening a prepreg obtained by impregnating a reinforced fiber layer with molten matrix resin 40b to which powdered expandable graphite has been added.

The illustrated opposing wall 15 may be formed by integrally molding the fiber reinforced resin layer 30 when pressure molding the wall 10a. Specifically, prepreg, which is an FRP material having a matrix resin 40b containing expanded graphite, and SMC are stacked and arranged inside a mold used to mold the wall 10a, and pressure molded. This forms the opposing wall 15 in which the wall 10a and the fiber reinforced resin layer 30 are integrally molded. This allows the battery pack structure according to this embodiment to be constructed with a simple manufacturing process. The opposing wall 15 may be formed by joining the FRP material having the matrix resin 40b containing expanded graphite to the underside of the wall 10a by interposing an adhesive layer therebetween.

In the examples shown in Figs. 1 and 2, the opposing wall portion 15 has a substantially rectangular shape in plan view, but is not limited to this. The opposing wall portion 15 may have, for example, a notch, a protrusion, a curved portion, or an opening in plan view. In addition, in the examples shown in Figs. 4 and 6, the fiber reinforced resin layer 30 and the resin layer 40a have substantially the same cross-sectional dimensions, but is not limited to this. For example, the cross-sectional dimensions of the fiber reinforced resin layer 30 may be larger or smaller than the cross-sectional dimensions of the resin layer 40a.

The state of the opposing wall portion 15 after the gas release portion 25 of the battery cell 22 releases gas is described below.

In the facing wall 15 according to the first embodiment shown in FIG. 4, a battery cell 22 is disposed below the vehicle. When high-temperature gas is released from the gas release section 25 provided on the upper surface of the battery cell 22, the gas is released toward the facing wall 15 located above the vehicle from the gas release section 25. Since the facing wall 15 has a resin layer 40a as the layer of the facing wall 15 closest to the gas release section 25, the gas hits the resin layer 40a.

Figure 5 is a diagram showing the state of the opposing wall portion 15 shown in Figure 4 after gas has been released from the gas release portion 25. In the following explanation, expanded graphite after thermal expansion is referred to as expanded graphite.

Since the resin layer 40a contains expanded graphite as the thermal expansion portion 45, when the high-temperature gas discharged from the gas discharge portion 25 hits the resin layer 40a, the heat of the gas heats the expanded graphite contained in the resin layer 40a. The heated expanded graphite then expands into fibers at multiple locations on the vehicle lower side surface of the resin layer 40a, forming expanded graphite 45a. As shown in FIG. 5, the expanded graphite 45a entangles with each other to form many air layers 47 between the expanded graphite 45a. The air layers 47 thus formed function as a heat insulating layer. Therefore, the heat of the high-temperature gas discharged from the gas discharge portion 25 is insulated, and the transfer of the heat of the gas to the wall portion 10a (housing 10) is suppressed. Therefore, the temperature rise of the housing 10 is suppressed.

In addition, in the opposing wall portion 15 shown in FIG. 6, a resin layer 40a containing expandable graphite as a thermal expansion portion 45 is disposed on the vehicle lower surface of the wall portion 10a.

Even with this configuration, when the high-temperature gas released from the gas release section 25 hits the resin layer 40a, an insulating layer composed of an air layer 47 is formed on the vehicle lower surface of the resin layer 40a, as in the example shown in Figure 5. Therefore, the heat of the high-temperature gas released from the gas release section 25 is insulated, and the transfer of the heat of the gas to the wall section 10a (housing 10) is suppressed. Therefore, the temperature rise of the housing 10 is suppressed.

In the opposing wall portion 15 according to the second embodiment shown in FIG. 7, a fiber-reinforced resin layer 30 having a matrix resin 40b containing expandable graphite as a thermal expansion portion 45 is disposed on the vehicle lower surface of the wall portion 10a.

In this configuration, when the high-temperature gas discharged from the gas discharge section 25 hits the fiber-reinforced resin layer 30, the expanded graphite contained in the matrix resin 40b is heated by the heat of the gas. The heated expanded graphite then expands into a fibrous form, forming expanded graphite 45a at multiple locations on the vehicle lower side surface of the fiber-reinforced resin layer 30. The expanded graphite 45a entangles with each other as in the example shown in FIG. 5, forming many air layers 47 between the expanded graphite 45a. The air layers 47 thus formed function as a heat insulating layer. Therefore, the heat of the high-temperature gas discharged from the gas discharge section 25 is insulated, and the transfer of the heat of the gas to the wall section 10a (housing 10) is suppressed.

Furthermore, the opposing wall portion 15 shown in FIG. 4 and FIGS. 6 to 7 is reinforced with a fiber-reinforced resin layer 30. More specifically, the area of the housing 10 where the temperature may increase and the strength may decrease due to the impact of the released gas is reinforced with a fiber-reinforced resin layer 30 containing reinforcing fibers. Therefore, even if the pressure inside the housing 10 increases due to the release of the gas, deformation of the wall portion 10a (housing 10) is suppressed.

The effects of this embodiment are explained below.

(1) The battery pack structure according to the embodiment includes one or more battery cells 22, each having a gas release section 25 that releases gas, and a housing 10 that houses the one or more battery cells 22. The opposing wall section 15 of the housing 10 that faces at least the gas release section 25 includes at least a portion of the wall section 10a that surrounds the one or more battery cells 22 of the housing 10, a fiber-reinforced resin layer 30 that reinforces the opposing wall section 15, and a thermal expansion section 45 that is disposed in the layer of the opposing wall section 15 closest to the gas release section 25 and expands by absorbing heat from the gas released from the gas release section 25.

As a result, when the battery cell 22 releases high-temperature gas, the thermal expansion section 45 absorbs the heat of the gas and expands, forming an insulating layer inside the housing 10. Therefore, the heat of the gas is insulated by the insulating layer, and the transfer of the heat of the gas to the housing 10 is suppressed. This makes it possible to suppress an increase in the temperature of the housing due to the transfer of the heat of the gas to the housing. Furthermore, the area of the housing 10 that may be exposed to the released gas and have its temperature increase and strength decrease is reinforced by the fiber-reinforced resin layer 30 containing reinforcing fibers. Therefore, when the pressure inside the housing 10 increases due to the release of the gas and pressure is input from the inside to the housing 10, the fiber-reinforced resin layer 30 suppresses deformation of the housing.

(2) In the battery pack structure according to the first embodiment, the fiber-reinforced resin layer 30 is disposed between the wall portion 10a and the thermal expansion portion 45, and the thermal expansion portion 45 is expanded graphite contained in the resin layer 40a that is laminated on the fiber-reinforced resin layer 30.

Since the thermal expansion section 45 is made of expanded graphite, when the high-temperature gas released by the battery cell 22 hits the resin layer 40a, the expanded graphite absorbs the heat of the gas and thermally expands several tens to several hundreds of times, becoming fibrous. The thermally expanded expanded graphite (expanded graphite 45a) then entangles with each other to form an air layer 47 (thermal insulation layer). This more reliably insulates the heat of the gas, and suppresses the transfer of the heat of the gas to the housing 10.

(3) In the battery pack structure according to the modified example of the first embodiment, the fiber-reinforced resin layer 30 is disposed on the surface opposite the thermal expansion portion 45 across the wall portion 10a, and the thermal expansion portion 45 is expanded graphite contained in the resin layer 40a disposed on the wall portion 10a.

Since the thermal expansion section 45 is made of expanded graphite, when the high-temperature gas released by the battery cell 22 hits the resin layer 40a, the expanded graphite absorbs the heat of the gas and thermally expands several tens to several hundreds of times to become fibrous expanded graphite 45a. The expanded graphite 45a then entangles with each other to form an air layer 47 (thermal insulation layer). This more reliably insulates the heat of the gas and suppresses the transfer of the heat of the gas to the housing 10.

(4) In the battery pack structure according to the second embodiment, the thermal expansion portion 45 is expanded graphite contained in the matrix resin 40b of the fiber reinforced resin layer 30.

Since the thermal expansion portion 45 is expanded graphite, when the high-temperature gas emitted by the battery cell 22 hits the fiber reinforced resin layer 30, the expanded graphite contained in the matrix resin 40b absorbs the heat of the gas and expands several tens to several hundreds of times to become fibrous expanded graphite 45a. The expanded graphite 45a then entangles with each other to form an air layer 47 (insulating layer). Therefore, the heat of the gas is more reliably insulated and the transfer of the heat of the gas to the housing 10 is suppressed. Furthermore, since the expanded graphite is contained in the matrix resin 40b of the fiber reinforced resin layer 30, the thermal expansion portion 45 and the fiber reinforced resin layer 30 can be handled as a single unit. Therefore, the thermal expansion portion 45 and the fiber reinforced resin layer 30 can be easily arranged on the wall portion 10a of the housing 10. This makes it possible to easily configure the battery pack structure according to the embodiment.

(5) In the battery pack structure according to the embodiment, the reinforcing fibers contained in the fiber-reinforced resin layer 30 include continuous fibers oriented in the longitudinal direction of the fiber-reinforced resin layer 30.

As a result, the fiber-reinforced resin layer 30 has a higher tensile strength in the longitudinal direction. Therefore, the fiber-reinforced resin layer 30 can more reliably suppress deformation of the housing 10 caused by an increase in pressure inside the housing 10.

(6) In the battery pack structure according to the embodiment, the reinforcing fibers contained in the fiber-reinforced resin layer 30 are made of carbon fibers.

The fiber reinforced resin layer 30 is a carbon fiber reinforced resin (CFRP) that contains reinforcing fibers made of carbon fibers. Therefore, the fiber reinforced resin layer 30 has a higher tensile strength. As a result, the fiber reinforced resin layer 30 can more reliably suppress deformation of the housing caused by an increase in pressure inside the housing.

(7) In the battery pack structure according to the embodiment, the fiber-reinforced resin layer 30 extends continuously from one end to the other end of the wall portion 10a of the housing 10.

As a result, the fiber-reinforced resin layer 30 can more reliably reinforce the housing 10 between one end and the other end of the wall portion 10a of the housing 10. Therefore, the fiber-reinforced resin layer 30 can more reliably suppress deformation of the housing 10 caused by an increase in pressure inside the housing 10.

In the above embodiment, an electric vehicle (EV) is used as an example, but the battery pack 1 can of course also be used in hybrid vehicles (HVs) and the like.

Reference Signs List 1 Battery pack 10 Housing 10a Wall portion 15 Opposing wall portion 20 Battery module 22 Battery cell 25 Gas release portion 30 Fiber reinforced resin layer 40a Resin layer 40b Matrix resin 45 Thermal expansion portion

Claims (7)

One or more battery cells each having a gas release portion that releases gas;
a housing that houses the one or more battery cells;
Equipped with
At least a facing wall portion of the housing facing the gas release portion is
At least a portion of a wall portion of the housing that surrounds the one or more battery cells;
A fiber reinforced resin layer that reinforces the opposing wall portion;
a thermal expansion section that is disposed in a layer of the opposing wall section closest to the gas discharge section and expands by absorbing heat of the gas discharged from the gas discharge section,
The fiber reinforced resin layer is disposed between the wall portion and the thermal expansion portion . One or more battery cells each having a gas release portion that releases gas;
a housing that houses the one or more battery cells;
Equipped with
At least a facing wall portion of the housing facing the gas release portion is
At least a portion of a wall portion of the housing that surrounds the one or more battery cells;
A fiber reinforced resin layer that reinforces the opposing wall portion;
a thermal expansion section that is disposed in a layer of the opposing wall section closest to the gas discharge section and expands by absorbing heat of the gas discharged from the gas discharge section,
The fiber-reinforced resin layer is disposed on a surface of the wall opposite the thermal expansion portion . 2. The battery pack structure according to claim 1, wherein the thermal expansion portion is expanded graphite contained in a resin layer laminated on the fiber reinforced resin layer. 3. The battery pack structure according to claim 2 , wherein the thermal expansion portion is expanded graphite contained in a resin layer disposed on the wall portion. 5 . The battery pack structure according to claim 1 , wherein the reinforcing fibers contained in the fiber-reinforced resin layer include continuous fibers oriented in a longitudinal direction of the fiber-reinforced resin layer. 6 . 6. The battery pack structure according to claim 1, wherein the reinforcing fibers contained in the fiber-reinforced resin layer are made of carbon fibers. 7. The battery pack structure according to claim 1 , wherein the fiber-reinforced resin layer extends continuously from one end to the other end of the wall of the housing.

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