Vehicle traction battery flat box provided with a cover with inclined reinforcing ribs

Abstract

The invention relates to traction battery box for an electric or hybrid motor vehicle forming a substantially rectangular flat assembly having a longitudinal axis (A) comprising a forward direction of the vehicle (AV), this box (8) being provided with a sheet-metal cover attached by its edges to a battery tray that has ribs formed in the thickness thereof, comprising, in a central portion, a reinforcement (20), the sheet-metal cover comprising, on each side with respect to the longitudinal axis (A), over at least one portion of the length of this cover, starting towards the outside of the vehicle, longitudinal ribs (30) followed by ribs (16) that are inclined in an outward direction towards the rear of this vehicle.

Description

[0001] DESCRIPTION

[0002] Title: FLAT VEHICLE TRACTION BATTERY BOX EQUIPPED WITH A COVER WITH INCLINED REINFORCING RIBS

[0003] 001. The present invention claims priority from French application No. 2304205 filed on 04 / 26 / 2023, the content of which (text, drawings and claims) is incorporated here by reference.

[0004] 002. The present invention relates to a flat battery box for an electric or hybrid motor vehicle traction battery equipped with a cover having stiffening ribs, as well as a motor vehicle comprising such a battery box.

[0005] 003. Some electric or hybrid motor vehicles have a battery powering an electric traction machine which is installed flat under the floor of the vehicle to use a large available surface area while arranging the mass in the lower part of the body in order to obtain a low height of the vehicle's center of gravity.

[0006] 004. A known type of electric vehicle battery, presented in particular by document CN-Y-200969361, comprising a flat, rectangular shape elongated in the longitudinal direction of the vehicle, comprises a box having a lower tray receiving the electrochemical elements. A cover formed by a substantially flat sheet covering the entire battery, has a contour fixed on an upper edge of the tray to seal the box.

[0007] 005. Generally speaking, to limit the mass of the vehicle and its cost, and to optimize the interior volume available in the battery box, the cover is made from a relatively thin metal sheet. In order to improve the rigidity of the cover, in particular to reduce the amplitude of the first-order vertical oscillations of its central part, the sheet comprises a network of stamped ribs giving it greater rigidity without increasing the mass. 006. According to an embodiment presented in this document, the battery cover comprises in its central part two parallel longitudinal ribs, and on each side, symmetrically with respect to the longitudinal median axis, front ribs and rear ribs arranged diagonally, each having a perpendicular direction which is turned towards the center of the cover. 007.Furthermore, for their approval, motor vehicles undergo standardized side impact tests on a small diameter post which concentrates the force on a reduced surface area on the side of the vehicle. Depending on the geographical regions and the manufacturers, one type of test involves a side impact along an inclined axis, forming the rear of the vehicle at an angle of 15° relative to its transverse direction. Some tests apply this impact to a single point on the side of the vehicle positioned on the axis passing through the driver, others repeat this test several times with the same inclination along the length of the side of the battery box in order to test its resistance at every lateral point.

[0008] 008. Furthermore, the side rails of the vehicle body, located outside the battery box, have significant resistance in order to protect the box behind it, which has a rigid profile on each side protecting the electrochemical cells.

[0009] 009. However, for this type of side impact test, even if the box is not plastically deformed, energy transmission can occur in the box cover from the impact, which propagates substantially in the forward direction of this impact on the flat parts between the ribs, without being effectively stopped by these ribs.

[0010] 010. In particular for the battery box cover presented by the prior art document, comprising ribs arranged diagonally and inverted between the front and the rear, with a series of inclined lateral impacts distributed over the entire side of the battery box, some of these impacts will emit energy in a direction substantially parallel to the ribs.

[0011] 011. This energy can propagate in the flat part between these ribs, and directly reach the center of the cover sheet, making it vibrate vertically with a high amplitude. A vibration of too high amplitude of the center of the cover can cause problems of contact of its sheet with the electrochemical elements contained inside, and lead to incidents including risks of electrical damage and fire.

[0012] 012. An increase in the height of the ribs to improve the rigidity of the cover sheet, takes up more space and reduces the space available for the battery arranged below. 013. The present invention aims in particular to avoid these problems of the prior art.

[0013] 014. To this end, it proposes a traction battery box for an electric or hybrid motor vehicle forming a substantially rectangular flat assembly, having a longitudinal axis comprising a forward direction of the vehicle, the box comprising a metal cover sheet, fixed by its contour to a battery tray, which has ribs made in its thickness, this box being remarkable in that the cover comprises in a central part a reinforcement, and comprises on each side relative to the longitudinal axis, over at least part of the length of this cover, starting towards the outside of the vehicle, first longitudinal ribs, then ribs inclined in a direction which towards the outside is turned towards the rear of this vehicle.

[0014] 015. An advantage of this battery box is that in the event of a side impact with a rearward tilt at any point on the side of the vehicle, which transmits energy to the side of the cover of this box in this same direction, we obtain a transmission of energy passing mainly through the flat surfaces of the sheet metal of this cover, which arrives substantially perpendicularly on the diagonal ribs.

[0015] 016. The direction of propagation of the energy blocked by the inclined ribs is then distributed on each side over the flat areas. The energy going towards the center meets the longitudinal ribs which in turn deflect them, avoiding direct access to the center. In the end, a low level of energy is obtained which reaches the central reinforcement, which avoids a large amplitude vibration of this central part.

[0016] 017. A cover sheet with limited thickness can be used, which reduces mass and costs, and the cover can be positioned as close as possible to the battery, which optimizes the volume of the box. Protection of the battery cells inside is provided simply and effectively, without adding a stiffening component to the cover, which would increase mass and costs.

[0017] 018. The electric or hybrid vehicle traction battery box according to the invention may further comprise one or more of the following characteristics, which may be combined with each other. 019. Advantageously, the ribs have symmetry with respect to the longitudinal axis.

[0018] 020. Advantageously, the central reinforcement forms a rib which extends along the longitudinal axis over more than half the length of the cover, presenting similar inclinations.

[0019] 021. In this case, advantageously the rib of the central reinforcement has in its cross section a width of between 60 and 120mm, and a height of between 5 and 15mm.

[0020] 022. Advantageously, the box comprises at least two longitudinal ribs distributed along the length of the cover.

[0021] 023. Advantageously, the box has several inclined ribs distributed along the length of the cover.

[0022] 024. In this case, the inclined ribs may have an inclination of between 30 and 60° relative to the transverse direction of the vehicle.

[0023] 025. Advantageously, each inclined or longitudinal rib has in its cross section a height of between 2 and 6mm and a width of between 30 and 50mm.

[0024] 026. Advantageously, the cover sheet made of steel has a surface area greater than 1 m 2and a thickness less than 1mm.

[0025] 027. The invention also relates to an electric or hybrid motor vehicle comprising a battery integrated into a box comprising any one of the preceding characteristics, remarkable in that this box is arranged flat under the floor of the vehicle between the front and rear axles.

[0026] 028. The invention will be better understood and other characteristics and advantages will appear more clearly on reading the description below given by way of example, with reference to the appended drawings in which:

[0027] 029. [Fig. 1] is a top view of an inclined side impact test on an electric vehicle comprising a battery box according to the invention;

[0028] 030. [Fig. 2] is a cross-sectional view of this battery box;

[0029] 031. [Fig. 3] is a top view of the box cover showing an inclined side impact transmitted to this cover; and

[0030] 032. [Fig. 4] is a detailed view in cross-section successively of the longitudinal reinforcement and the lateral ribs of this cover. 033. Throughout the document the upper side or top is relative to the vertical direction for a vehicle placed on horizontal ground.

[0031] 034. Figure 1 shows an electric motor vehicle 2 arranged along a longitudinal axis A having a front side corresponding to the direction of travel of the vehicle, which comprises a traction battery integrated in a sealed box 8 comprising a substantially rectangular flat shape arranged under the floor of the vehicle, between the front and rear axles. The lateral edges of the battery box 8 arrive at a small distance from the sides of the vehicle 2 in order to occupy a major part of the surface of the floor.

[0032] 035. A standardized test bench for resistance to inclined side impacts of the vehicle 2, comprises a vertical bar 4 rigidly connected to a mass 6 which is projected with a speed V on the side of the vehicle, in a direction facing backwards forming an angle of 15° relative to a transverse axis of this vehicle.

[0033] 036. A penetration of the bar 4 is obtained on the side of the vehicle 2 with a deformation of the side member of the body which absorbs at least part of the transmitted energy, avoiding a plastic deformation of the battery box 8 located behind. However, a part of the energy is transmitted to this battery box 8, in the form of a shock wave which generates an elastic deformation of its cover.

[0034] 037. Figures 2, 3 and 4 show the battery box 8 comprising a tray comprising a lower sheet 10 and two lateral side members 12 formed by aluminum profiles having closed cells in order to present great resistance.

[0035] 038. An upper cover plate 14 covering this container, comprises a longitudinal central reinforcement 20, and on each side longitudinal ribs 30 and inclined lateral ribs 16 arranged symmetrically with respect to the longitudinal axis A. The space between the central reinforcement 20 and the different ribs 16, 30 constitutes a flat intermediate zone 26.

[0036] 039. The box 8 receives electrochemical battery cells 18 which are fixed to the floor plate 10.

[0037] 040. The cover plate 14 has on its periphery a series of holes 32 receiving tightening screws on the contour of the box 8 in order to ensure a seal on this contour, to protect the interior cells 18 from projections and impacts.

[0038] 041. The central cover reinforcement 20, symmetrical with respect to the longitudinal axis A, forms a rib starting from the front side of the cover 14 to extend over approximately three-quarters of its length.

[0039] 042. The central reinforcement 20, detailed in figure 4 above, has in cross section a circular arc shape curved upwards, comprising in the middle a maximum height H of between 5 and 15mm, and on each side a rise to a height H1 of less than 10mm to reach the intermediate flat area of ​​the cover 26. The width L1 of the central reinforcement 20 separating the two ends of its circular arc is between 60 and 120mm.

[0040] 043. Each longitudinal rib 30 or inclined rib 16 has, in detailed cross-section in Figure 4 below, a flat upper face comprising a height of between 2 and 6 mm, which ends on each side with a slope to arrive at the intermediate flat area of ​​the cover 26. The total width L2 of the longitudinal ribs 30 or inclined ribs 16 is between 30 and 50 mm. 044. For each side of the cover 14, the inclined ribs 16 have an inclination relative to the transverse direction of the vehicle forming an angle of between 30 and 60°, advantageously approximately 45°, with a direction which, starting outwards, is turned towards the rear of this vehicle.

[0041] 045. Each side of the cover 14 has two short longitudinal ribs 30 distributed along the length of this cover, which are aligned on the same axis arranged starting from the rib 20 approximately in the first third of this side.

[0042] 046. Starting from the rear there are two short inclined ribs, the first 16a arranged opposite the first longitudinal rib 30a, the second 16b arranged between the two longitudinal ribs 30a, 30b.

[0043] 047. Along a transverse direction aligned with the front of the reinforcement 20, there are three inclined front ribs 16 distributed across the width, comprising firstly, starting from the centre, a long inclined rib 16c then two short inclined ribs 16d.

[0044] 048. Figure 3 shows three lateral impacts inclined towards the rear 40a, 40b, 40c, on the left side of the vehicle, according to the standardized tests presented in figure 1, causing a deformation of the body of the vehicle, without deforming the box 8 but with a shock wave 34 transmitted to the cover 14 following the direction of these impacts. The cover plate 14 forming a substantially flat assembly having a large surface area, comprises a vertical vibrational natural mode of its central part which will be excited with the received energy. 049. The intermediate flat zones 26 of the cover plate 14 between the ribs 16, 30 can vibrate more easily due to their flexibility while transmitting the energy by propagation, whereas the various highly rigid ribs constitute obstacles to this propagation.

[0045] 050. For the most forward impact 40a the wave comes directly into contact with the most forward inclined rib 16a arranged substantially perpendicularly, it must be distributed on both sides parallel to this rib, the part facing the inside of the vehicle not reaching the center of the cover 14.

[0046] 051. For the impact of the middle 40b in a similar manner the wave comes directly into contact with the second inclined rib 16b, then is distributed on both sides, the part facing the interior of the vehicle arriving on the first longitudinal rib 30a which prevents it from reaching the center of the cover 14.

[0047] 052. For the rear shock 40c the wave arrives on the two inclined rear ribs 16d, a part of the wave goes towards the center of the cover 14 to be stopped by the second longitudinal rib 30b.

[0048] 053. In all cases of inclined lateral impact 40, a blocking of the wave is obtained which allows little energy to reach the center of the cover 14, and a dispersion of this energy towards the front and the rear, far from this center. The central part of the cover 14 receives a low level of energy, its natural vibration mode is little excited with a limited oscillation amplitude.

[0049] 054. In particular, a cover 14 can be formed comprising a surface area of ​​more than 1 m 2 , formed with a steel sheet less than one millimeter thick. A cover 14 is thus produced with a sheet of limited thickness which is arranged near the internal electrochemical elements 18 while ensuring their protection, which makes it possible to reduce the mass and costs of this cover, and optimizes the use of the internal volume of the box 8.

Claims

CLAIMS 1. Traction battery box for an electric or hybrid motor vehicle forming a substantially rectangular flat assembly, having a longitudinal axis (A) comprising a forward direction of the vehicle (AV), the box (8) comprising a metal cover sheet (14), fixed by its contour to a battery tray, which has ribs (16, 30) made in its thickness, characterized in that the cover (14) comprises in a central part a reinforcement (20), and comprises on each side relative to the longitudinal axis (A), over at least part of the length of this cover (14), starting towards the outside of the vehicle, first longitudinal ribs (30), then inclined ribs (16) in a direction which towards the outside is turned towards the rear of this vehicle.

2. Battery box according to claim 1, characterized in that the ribs (16, 30) have symmetry with respect to the longitudinal axis (A).

3. Battery box according to claim 1 or 2, characterized in that the central reinforcement (20) forms a rib which extends along the longitudinal axis (A) over more than half the length of the cover (14).

4. Battery box according to claim 3, characterized in that the rib of the central reinforcement (20) has in its cross section a width of between 60 and 120 mm, and a height of between 5 and 15 mm.

5. Battery box according to any one of the preceding claims, characterized in that it comprises at least two longitudinal ribs (30) distributed along the length of the cover (14).

6. Battery box according to any one of the preceding claims, characterized in that it comprises several inclined ribs (16) distributed along the length of the cover (14), having similar inclinations.

7. Battery box according to claim 6, characterized in that the inclined ribs (16) have an inclination of between 30 and 60° relative to the transverse direction of the vehicle.

8. Battery box according to any one of the preceding claims, characterized in that each inclined (16) or longitudinal (30) rib has in its cross section a height of between 2 and 6 mm and a width of between 30 and 50 mm.

9. Battery box according to any one of the preceding claims, characterized in that the cover sheet (14) made of steel has a surface area greater than 1m 2 and a thickness of less than 1 mm.

10. Electric or hybrid motor vehicle comprising a battery integrated in a box (8) according to any one of the preceding claims, characterized in that this box (8) is arranged flat under the floor of the vehicle (2) between the front and rear axles.

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