Underbody protection device, housing lower part, vehicle underbody device, and motor vehicle

Abstract

The invention relates to a vehicle underbody device (10) for an electrically drivable motor vehicle, comprising a battery housing (12) for a power battery, the battery housing (12) having a housing lower part (20) and / or an underbody protection device (16) being reversibly fastened to the battery housing (12), the vehicle bottom protection device at least partially covers the battery housing (12) downwards in the vehicle height direction (z) in the installation position.

Description

Technical Field

[0001] The invention relates to an underbody protection device for an electrically driven motor vehicle, a housing lower part of a battery housing of a power battery for an electrically driven motor vehicle, a vehicle bottom device for an electrically driven motor vehicle, and a motor vehicle. Background Art

[0002] The underbody of a motor vehicle is a component of the high-voltage storage housing in many high-voltage storage devices and cannot be replaced in the event of damage. In a storage architecture consisting of connected battery cell modules, which is called the so-called C2M (cell to module) storage architecture, the lower housing part of the housing is usually reinforced by a supporting structure for the battery cell modules, thereby supporting underbody protection against intrusion (e.g., pile intrusion). In the so-called C2P (cell to pack) storage architecture, the housing parts are basically implemented without additional reinforcements, so that underbody protection is more difficult to meet. In addition to the risk of intrusion, there is a risk of corrosion, especially in the case of steel components, even in the case of minor damage or scratches. When the lower part of the high-voltage storage housing is damaged, it cannot be replaced or can only be replaced with difficulty. In the worst case, the entire high-voltage storage device must be replaced.

[0003] WO 2018 / 029168 A1 discloses a battery box for accommodating one or more battery elements, comprising: a box profile forming an inner area, the box profile at least partially providing the outer side walls of the battery box; a cover; a bottom and a connecting profile for connecting the battery box to a motor vehicle. An underbody protection piece is arranged below the bottom. The underbody protection piece is essentially plate-shaped and extends horizontally at the installation position of the battery box. The underbody protection piece is screwed to the box profile. Summary of the invention

[0004] The object of the present invention is to provide a solution which allows particularly good protection of the underbody of a motor vehicle, in the underbody region of which the traction battery is arranged, from damage.

[0005] The object is achieved by the subject matter of the independent claims. Other possible solutions of the invention are disclosed in the dependent claims, the description and the drawings. The features, advantages and possible solutions set out in the description for one of the subject matters of the independent claims can be regarded at least similarly as the features, advantages and possible solutions of the corresponding subject matter of the other independent claims and as the features, advantages and possible solutions of each possible combination of the subject matter of the independent claims (possibly in combination with one or more dependent claims).

[0006] The present invention relates to an underbody protection device for an electrically driven motor vehicle. The underbody protection device is configured to be reversibly fixed on a battery housing of a power battery of the motor vehicle. To this end, the underbody protection device can be threaded and / or bonded to the battery housing. The power battery is configured to provide electrical energy to an electric drive train of a motor vehicle, so that the motor vehicle can be electrically driven with electrical energy from the power battery. The battery housing surrounds a storage volume, in which a plurality of battery cells of the power battery can be accommodated. “The underbody protection device is reversibly fixed on the battery housing” can be understood as the underbody protection device being reversibly fixed to the battery housing, so that the underbody protection device can be replaced. The underbody protection device is configured to cover the battery housing at least partially downward in the vehicle height direction at a prescribed installation position. Therefore, the underbody protection device protects the battery housing from mechanical influences from below at the installation position, so that the battery cells of the power battery can be protected from damage.

[0007] The underbody protection device comprises a first underbody element and a second underbody element, and a spacer is arranged between the first underbody element and the second underbody element, so that each underbody element and the spacer form a sandwich structure. In other words, the first underbody element and the second underbody element define an intermediate space between each other, and the intermediate space is a closed cavity. The first underbody element can define the intermediate space upward in the vehicle height direction, and conversely, the second underbody element defines the intermediate space downward in the vehicle height direction. The intermediate space can be defined in particular completely by each underbody element. In order to allow particularly good protection of the battery cells of the power battery, the two underbody elements cover all the battery cells downward in the vehicle height direction.

[0008] The spacer is arranged in the intermediate space and is used to maintain the minimum spacing between the underbody elements. The spacer can be formed, for example, by a spacing foam. The spacer can be formed completely or partially by plastic. In particular, the spacer is porous or has a hollow structure or a honeycomb structure. Therefore, the underbody protection device has a sandwich structure, which includes a first underbody element, a spacer and a second underbody element, which are arranged in this order along the height direction of the vehicle. Since the first underbody element and the second underbody element are arranged spaced apart from each other by means of the spacer, a particularly high Steiner share can be achieved, and therefore the underbody protection device has a particularly high stability. In the plane moment of inertia, the product of the cross-sectional area and the square of the distance from the center of gravity of the surface to the axis of rotation is called the Steiner share.

[0009] Since the underbody protection device can be reversibly fastened to the battery housing, the underbody protection device can be replaced particularly easily and quickly, for example if the underbody protection device is damaged. Therefore, in the event of damage to the underbody protection device, it is not necessary to replace the entire underbody of the motor vehicle including the power battery. Due to the sandwich structure, the underbody protection device has a particularly high stability, so that the battery housing can be particularly well protected from damage.

[0010] In a possible extension of the present invention, it is provided that each underbody element comprises fiber-reinforced plastic (FRP). In particular, at least one of the underbody elements can be configured as a metal-FRP hybrid. Here, the plastic can be reinforced with glass fibers and / or carbon fibers, in particular. For example, the plastic is reinforced with unidirectional fibers. In particular, the plastic is a plastic reinforced with continuous glass fibers. The corresponding underbody elements can be manufactured in a wet pressing method, in which the glass fiber fabric is impregnated with liquid resin, followed by molding and hardening. The underbody elements can be manufactured separately from each other and stacked with spacers to form a sandwich structure. The underbody elements are manufactured from fiber-reinforced plastic, which allows particularly good protection of the battery housing to avoid damage, while the weight of the underbody protection device is particularly low.

[0011] The present invention also relates to a lower housing part of a battery housing for a power battery of an electrically driven motor vehicle. The lower housing part is provided to define a storage volume for a plurality of battery cells of the power battery. Here, the lower housing part defines a storage volume downwardly along the vehicle height direction at a prescribed installation position. The lower housing part has a storage area on which the battery cells can be accommodated. In the storage area, the lower housing part has at least one rated breaking point, and an opening is formed in the lower housing part when the rated breaking point fails. The gas discharged from the battery cell can be output from the storage volume via the opening. The gas can be released in particular during the so-called thermal breakdown of the battery cell. Therefore, in order to avoid damaging other battery cells of the power battery due to propagation during the thermal breakdown of the battery cell, the gas is output from the storage volume via the opening formed due to the failure of the at least one rated breaking point. Therefore, the risk of propagation and therefore the risk of thermal breakdown of other battery cells due to heat development can be kept particularly small. The rated breaking point of the lower housing part is provided to fail during the thermal breakdown of at least one battery cell among the battery cells. Gases generated during thermal breakdown of a battery cell can thus be reliably discharged from the receiving volume via the openings produced in the housing lower part, thus avoiding a strong temperature increase in the receiving volume. This achieves particularly good protection of the power battery from the spread of a fire to a plurality of battery cells.

[0012] In a possible extension of the present invention, it is provided that the housing lower part has a separate rated breaking point for each battery cell, and each rated breaking point is arranged below the correspondingly assigned battery cell in the vehicle height direction at the prescribed installation position. For example, the battery cell can be a round battery cell, which includes a gas exhaust opening oriented downward in the installation position. Since the rated breaking point is provided accordingly for each battery cell, it is allowed that the gas generated during the thermal breakdown of a battery cell can be discharged over a short distance through the opening (which is generated due to the failure of the assigned rated breaking point) and thus discharged from the storage volume particularly quickly. Therefore, it is ensured that the gas is reliably discharged from the storage volume during the thermal breakdown of the battery cell.

[0013] The present invention also relates to a vehicle underbody device for an electrically driven motor vehicle, comprising a battery housing for a power battery, the battery housing having a housing lower part, as has been described in relation to the housing lower part according to the present invention. As an alternative or in addition, an underbody protection device is reversibly fixed to the battery housing and covers the battery housing downward at least partially in the vehicle height direction at a prescribed installation position. The underbody protection device may correspond to the underbody protection device described in relation to the underbody protection device according to the present invention. Alternatively, the underbody protection device may be integrally formed and thus formed in a single piece. The battery housing and the underbody protection device seal the inner chamber of the battery housing. "The underbody protection device is reversibly fixed to the battery housing" can be understood as meaning that the underbody protection device can be removed from the battery housing, so that, for example, the underbody protection device can be replaced on the battery housing when the underbody protection device is damaged. Here, it can be provided that at least one of the components is removed without destruction or removed in the event of destruction. In particular, the vehicle underbody device can include both the housing lower part according to the invention and the underbody protection device according to the invention, so that the housing lower part is particularly well protected from damage by means of the underbody protection device. This makes it possible for the housing lower part to be particularly thin and therefore particularly low-weight and / or to be made of plastic. The housing lower part allows, in the event of a thermal breakdown of a battery cell, the other battery cells to be particularly well protected from damage by allowing the gases generated in the thermal breakdown of the battery cell to escape from the receiving volume through the opening generated in the event of failure of the at least one predetermined breaking point.

[0014] In a possible extension of the present invention, it is provided that the vehicle bottom device includes not only the lower shell part but also the underbody protection device, and the lower shell part and the underbody protection device jointly define an exhaust chamber, into which gas can flow via the opening, and gas can be discharged from the storage volume via the exhaust chamber. The exhaust chamber allows that gas can be discharged from the storage volume particularly quickly, can be collected in the exhaust chamber, and can be collected and led out of the underbody device via the exhaust chamber. The exhaust chamber extends between the lower shell part and the underbody protection device. In particular, the exhaust chamber covers all battery cells of the power battery downward in the vehicle height direction. This ensures that the gas generated by each battery cell during thermal breakdown can be discharged over a particularly short distance through the opening generated when the assigned rated breaking point fails. Therefore, the accumulation of the generated gas in the storage volume can be at least substantially avoided.

[0015] In another extension of the present invention, it is provided that a collision absorbing structure is arranged in the exhaust chamber. The collision absorbing structure is a so-called impact absorber structure. The collision absorbing structure is provided to deform when a mechanical action is applied to the underbody protection device, thereby resisting damage to the lower part of the housing and the battery cells. The collision absorbing structure may, for example, include foam. The collision absorbing structure may be abutted against the underbody protection device with a first side and against the lower part of the housing with a second side opposite to the first side, so that the underbody protection device is supported on the lower part of the housing by the collision absorbing structure. It can therefore be ensured that the minimum spacing between the underbody protection device and the lower part of the housing is observed. In particular, it is provided that the collision absorbing structure covers all the battery cells of the power battery downward in the vehicle height direction at a prescribed installation position, so that each battery cell can be particularly well protected by means of the collision absorbing structure to avoid damage by mechanical action.

[0016] In another possible solution of the present invention, it is provided that the collision absorbing structure has at least one gas guiding channel, which is provided for discharging gas from the battery cell. The at least one gas guiding channel can extend in particular from the opening generated when the at least one rated fracture site fails, so that the gas flowing into the exhaust chamber through the opening can be discharged from the opening particularly quickly and reliably. Therefore, the at least one gas guiding channel allows particularly reliable and targeted guidance of the gas in the exhaust chamber, and at the same time, with the aid of the collision absorbing structure, the lower part of the housing and each battery cell can be particularly well protected from damage. The collision absorbing structure can, for example, have a separate gas guiding channel for each rated fracture site. Alternatively, the collision absorbing structure can have a common gas guiding channel for multiple rated fracture sites, and the gas flowing into the exhaust chamber through multiple openings can be transported in a collective manner through the common gas guiding channel. Therefore, overheating of other battery cells arranged next to the battery cell with thermal breakdown can be prevented.

[0017] In a further possible embodiment of the invention, it is provided that the underbody protection device is held on the housing lower part via at least one screw connection. The at least one screw connection allows particularly simple fastening of the underbody protection device on the battery housing and particularly simple release of the underbody protection device from the battery housing, so that the underbody protection device can be replaced particularly easily. At the same time, the at least one screw connection allows particularly reliable holding of the underbody protection device on the housing lower part.

[0018] The invention also relates to a motor vehicle, which comprises a vehicle underbody device, as has already been described in relation to the vehicle underbody device according to the invention. The vehicle underbody device is arranged in the underbody region of the motor vehicle. Here, the vehicle underbody device can at least partially form the underbody of the motor vehicle. The motor vehicle is in particular a car, in particular a sedan. The motor vehicle is arranged to be driven by means of electrical energy from a power battery. This means that the motor vehicle is a hybrid vehicle or a pure electric vehicle.

[0019] Other features of the invention can be derived from the claims, the drawings and the description of the drawings. The features and feature combinations mentioned above in the description and the features and feature combinations shown separately in the following description of the drawings and / or in the drawings can be used not only in the combination described respectively, but also in other combinations or can be used alone without departing from the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The attached pictures are as follows:

[0021] Figure 1A schematic sectional view showing a region of a vehicle underbody device, which comprises a battery housing and an underbody protection device, the battery housing having a housing lower part, the underbody protection device being reversibly held on the housing lower part;

[0022] Figure 2 A schematic cross-sectional view showing an area of ​​the vehicle underbody arrangement; and

[0023] Figure 3 The cross-sectional view shows the region of the underbody protection device, on which the impact-absorbing structure is arranged.

[0024] In the figures, identical elements or elements having the same function are provided with the same reference symbols. DETAILED DESCRIPTION

[0025] exist Figure 1 , a vehicle underbody device 10 for an electrically drivable motor vehicle is described in a partial sectional view. The vehicle underbody device 10 is configured to be arranged in the underbody area of ​​the motor vehicle. The motor vehicle comprises an electric drive train, by which the motor vehicle can be driven by means of electric energy from a power battery of the motor vehicle. The power battery comprises a plurality of battery cells 14 accommodated in a battery housing 12. At present, the battery cells 14 are correspondingly round battery cells. At present, the battery cells 14 are lithium-ion battery cells. Each battery cell 14 is configured to store electric energy and to provide electric energy for the electric drive train of the motor vehicle.

[0026] The vehicle floor device 10 comprises a battery housing 12 of a power battery and an underbody protection device 16 reversibly held on the battery housing 12. The battery housing 12 comprises an upper housing part 18 and a lower housing part 20, which together define a storage volume 22. Here, in the prescribed installation position of the vehicle floor device 10, the upper housing part 18 defines the storage volume 22 upward in the vehicle height direction z, and the lower housing part 20 defines the storage volume downward in the vehicle height direction z. All battery cells 14 of the power battery can be accommodated in the storage volume 22. The lower housing part 20 has a storage area 24, on which each battery cell 14 can be accommodated. This means that in the power battery, each battery cell 14 is placed on the lower housing part 20 in the storage area 24. In addition, the upper housing part 18 and the lower housing part 20 are held together by at least one first screw connection device 26. By means of the first screw connection device 26, the upper housing part 18 and the lower housing part 20 are additionally fixed to the door sill 28 of the motor vehicle.

[0027] The underbody protection device 16 is held on the housing lower part 20 via at least one second screw connection 30. The underbody protection device 16 is provided to protect the housing lower part 20 and the battery cells 14 from damage from below, for example due to mechanical effects. Since the underbody protection device 16 is reversibly fixed to the housing lower part 20 via the at least one second screw connection 30, the underbody protection device 16 can be removed from the housing lower part 20 and replaced by another underbody protection device. Therefore, for example, if the underbody protection device 16 is damaged, it is particularly easy to replace the underbody protection device 16.

[0028] The housing lower part 20 is designed in the present case in the form of a high-voltage storage tank and is Figure 2 is shown in more detail in Figure 2 2 shows the housing lower part 20 in a partial sectional view. In the present case, the housing lower part 20 is made of plastic, in particular long-fiber thermoplastic and / or lightweight structural plastic. Alternatively, the housing lower part 20 can be made of metal or an alloy.

[0029] As in Figure 2 It can be seen particularly clearly in the figure that the housing lower part 20 has a plurality of predetermined breaking points 32 in the receiving area 24, of which, for reasons of clarity, only a few are indicated by reference numerals in the figure. In the present case, a corresponding predetermined breaking point 32 is provided for each battery cell 14, which is provided below the corresponding assigned battery cell 14 in the vehicle height direction z at the prescribed installation position of the vehicle floor device 10. In the present case, each corresponding predetermined breaking point 32 is formed in a smooth manner, but any other shape is also conceivable. Each predetermined breaking point 32 is provided to fail in the event of a thermal breakdown of the corresponding assigned battery cell 14. When the corresponding predetermined breaking point 32 fails, an opening is formed in the housing lower part 20. This means that when a battery cell 14 is thermally broken, the predetermined breaking point 32 assigned to the battery cell 14 fails, and therefore an opening is formed at the predetermined breaking point 32. Thus, if a plurality of predetermined breaking points 32 fail, a corresponding opening can be formed in the housing lower part 20 by each of these predetermined breaking points 32. Through these formed openings, gases 36 generated during thermal breakdown of the battery cells 14 can escape from the receiving volume 32. In the present case, the gases 36 are conducted through at least one formed opening into a ventilation chamber 34 arranged between the housing lower part 20 and the underbody protection device 16, through which the gases 36 are discharged from the vehicle underbody device 10.

[0030] At present, a collision absorbing structure 38 is arranged in the exhaust chamber 34. The collision absorbing structure 38 is used to absorb energy by deformation when a mechanical action (such as impact) is applied to the underbody protection device 16, and is used to support the underbody protection device 16 on the housing lower part 20. At present, the collision absorbing structure 38 is provided by a collision absorber foam. In order to ensure that the gas 36 is reliably guided in the exhaust chamber 34, the collision absorbing structure 38 has a plurality of gas guiding channels 40, which are provided to guide the gas 36 flowing into the exhaust chamber 34 through the opening. At present, a gas guiding channel 40 is provided for each predetermined breaking point 32, and the corresponding inlet openings of each gas guiding channel 40 are arranged to abut against the assigned predetermined breaking point 32, so as to ensure the reliable guidance of the gas 36 flowing into the exhaust chamber 34 through the corresponding opening when the opening is formed. The collision absorbing structure 38 allows each gas guiding channel 40 to be integrated into the vehicle bottom device 10, so that in the case of a thermal event of the battery cell 14, the gas 36 can be discharged from the battery cell 14 particularly well.

[0031] If one of the battery cells 14 explodes, the housing lower part 20 breaks at the assigned predetermined breaking point 32, so that the gas generated when the battery cell 14 explodes can be discharged into the exhaust chamber 34 through the generated opening. The exhaust chamber 34 is formed by the intermediate space between the housing lower part 20 and the underbody protection device 16. Since the housing lower part 20 is covered downwardly in the vehicle height direction z by the underbody protection device 16, there are only particularly low strength requirements on the housing upper part 20. In the present case, the corresponding predetermined breaking point 32 is formed by a local particularly thin area of ​​the housing lower part 20. Therefore, the housing lower part 20 and thus the battery housing 12 can be manufactured with particularly low weight.

[0032] exist Figure 3 , the underbody protection device 16 is shown in a partial sectional view, on which a collision absorbing structure 38 with a plurality of gas guide channels 40 is arranged. The underbody protection device 16 has a sandwich structure, which includes a first underbody element 42 at the top, a second underbody element 44 at the bottom, and a spacer 46 between the underbody elements 42, 44. The spacer 46 is currently made of foam. Therefore, the underbody protection device 16 has a foam core. Both the first underbody element 42 and the second underbody element 44 are made of glass fiber reinforced plastic. As shown in Figure 3It can be seen particularly clearly that the underbody elements 42, 44 are designed as flat plates in the entire region, in which the underbody elements 42, 44 cover the impact absorption structure 38 downward in the vehicle height direction z. These flat plate-shaped areas of the underbody elements 42, 44 are arranged parallel to each other and overlap in the vehicle height direction z. Therefore, a particularly high stability of the underbody protection device 16 can be achieved. This makes it possible to intercept the impact on the underbody protection device 16 particularly well, so that the lower shell part 20 can be protected particularly well from damage. Therefore, the underbody protection device 16 is an underbody protection component for the battery housing 12 that can be replaced particularly easily in the event of damage. At present, the underbody protection device 16 is a glass fiber component with a sandwich structure having a foam core and reinforced with unidirectional fibers.

[0033] In general, the invention relates to an underbody protection element for a high-voltage storage housing.

[0034] Reference numerals list

[0035] 10 Vehicle bottom device

[0036] 12 Battery housing

[0037] 14 Battery Cells

[0038] 16 Underbody protection

[0039] 18 Housing upper part

[0040] 20 Housing lower part

[0041] 22 Capacity

[0042] 24 Accommodation Area

[0043] 26 First threaded connection device

[0044] 28 Threshold

[0045] 30 Second threaded connection device

[0046] 32 Rated breaking point

[0047] 34 Exhaust Chamber

[0048] 36 Gas

[0049] 38 Impact absorbing structure

[0050] 40 Gas guide channel

[0051] 42 First underbody element

[0052] 44 Second underbody element

[0053] 46 Spacer

[0054] z Vehicle height direction

Claims

1. An underbody protection device (16) for an electrically driven motor vehicle, the underbody protection device being configured to be reversibly fixed to a battery housing (12) of a power battery of the motor vehicle and to at least partially cover the battery housing (12) downward in the vehicle height direction (z) in the installed position, the underbody protection device comprising a first underbody element (42) and a second underbody element (44), a spacer (46) being arranged between the first underbody element and the second underbody element, so that each underbody element (42, 44) and the spacer (46) form a sandwich structure.

2. The underbody protection device (16) according to claim 1, characterized in that: Each underbody element (42, 44) comprises fiber-reinforced plastic.

3. A housing lower part (20) of a battery housing (12) for a power battery of an electrically driven motor vehicle, the housing lower part being configured to define a storage volume (22) for a plurality of battery cells (14) of the power battery, the housing lower part having a storage area (24) on which the battery cells (14) can be stored, the housing lower part (20) having at least one rated breaking point (32) in the storage area (24), and forming an opening in the housing lower part (20) when the rated breaking point fails, so that gas (36) discharged from the battery cells (14) can be discharged from the storage volume (22) via the opening.

4. The housing lower part (20) according to claim 3, characterized in that The housing lower part (20) has a separate predetermined breaking point (32) for each battery cell (14), each predetermined breaking point (32) being arranged in the installed position in the vehicle height direction (z) below the correspondingly assigned battery cell (14).

5. A vehicle underbody device (10) for an electrically driven motor vehicle, comprising a battery housing (12) for a power battery, the battery housing (12) having a housing lower part (20) according to claim 3 or 4, and / or a vehicle underbody protection device (16), in particular a vehicle underbody protection device (16) according to claim 1 or 2, being reversibly fixed to the battery housing (12), and the vehicle underbody protection device at least partially covering the battery housing (12) downward in the vehicle height direction (z) in the installed position.

6. The vehicle bottom device (10) according to claim 5, characterized in that: The housing lower part (20) and the underbody protection device (16) jointly define an exhaust chamber (34), into which gas (36) can flow via the opening and through which gas (36) can be discharged from the receiving volume (22).

7. The vehicle bottom device (10) according to claim 6, characterized in that: A collision absorbing structure (38) is disposed in the exhaust chamber (34).

8. The vehicle bottom device (10) according to claim 7, characterized in that: The impact absorbing structure (38) has at least one gas conducting channel (40) which is provided for discharging gas (36) from the battery cell (14).

9. The vehicle underbody device (10) according to any one of claims 5 to 8, characterized in that The underbody protection device (16) is held on the housing lower part (20) via at least one screw connection (30).

10. A motor vehicle comprising a vehicle underbody device (10) according to any one of claims 5 to 9.

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