COOLING DEVICE FOR A BATTERY COMPRISING VARIABLE DENSITY METALLIC FOAM

Abstract

The invention relates to a battery (30) comprising a battery cell frame (20) and an air duct (10). The air duct (10) includes an air inlet having a first section (10A), and the air duct (10) includes an air outlet having a second section (10B). An airflow (F) from the first section (10A) to the second section (10B) cools a mounting wall (12) of the battery (30). The air duct (10) includes a variable-density metallic foam (40) having pores and walls between the pores, the variable-density metallic foam (40) having a first portion (41) adjacent to the first section (10A) and a second portion (42) adjacent to the second section (10B), the volumetric density of the second portion (42) being greater than the volumetric density of the first portion (41). Figure 1

Description

Title of the invention: COOLING DEVICE FOR A BATTERY COMPRISING A VARIABLE DENSITY METALLIC FOAM

[0001] The invention relates to electric vehicles, that is to say, those equipped with at least one battery for storing electrical energy intended for their propulsion. This includes vehicles with a single means of electric propulsion, as well as hybrid vehicles incorporating at least one mode of electric propulsion.

[0002] It is known from the prior art that the battery of an electric vehicle heats up during use. Patent application FR2965042 A1 describes a heat exchange device for a motor vehicle. The device comprises a metallic foam and a heating element in contact with the metallic foam. The metallic foam has pores separated by walls. An airflow circulates between the pores of the metallic foam. Thus, the airflow extracts heat from the metallic foam by convection. In turn, the metallic foam exchanges heat by thermal conduction to the heating element. Therefore, the metallic foam allows for excellent heat exchange, due to its large exchange surface area and the chaotic air movement within the pores.

[0003] However, the walls of such a metallic foam can excessively obstruct the passage of airflow. As a result, the airflow is slowed. Thus, heat exchange is reduced. Moreover, since heat transport is less, the airflow can exhibit significant temperature gradients. In particular, temperature differentials can create thermal stresses between battery cells. This impairs the battery's durability and performance.

[0004] The objective of the present invention is to remedy these drawbacks and to improve the performance and cooling of the electric vehicle battery.

[0005] To achieve this objective, the invention proposes an electric or hybrid vehicle battery, the battery having a longitudinal axis, the battery comprising: - an air duct having an air inlet having a first section, the air duct having an air outlet having a second section, the air duct being configured to circulate an airflow from the first section to the second section; and, - a battery cell chassis, the air duct comprising: - a mounting plate attached to the battery cell chassis; and, - a variable density metallic foam in contact with the fixing wall and comprising pores and walls between the pores, the variable density metallic foam having a density increasing longitudinally from the first section to the second section.

[0006] Such a coil features an enhanced thermal retention wall so that the airflow extracts more heat from the coil. Furthermore, as the airflow is gradually heated, the variable-density metallic foam thus designed compensates for the reduction in heat transfer in order to maintain a homogeneous temperature within the coil. In addition, the architecture of the variable-density metallic foam limits its obstruction to the airflow, thereby facilitating airflow within the coil. Moreover, the variable-density metallic foam is designed to impart turbulent, chaotic movements to the airflow. Consequently, the airflow effectively cools the coil. Furthermore, the variable-density metallic foam is easy to insert into the confined space of the air duct.Consequently, the manufacture of such batteries is easier and less expensive to implement compared to, for example, cooling fins.

[0007] Advantageously, the variable density metallic foam has a first portion, adjoining the first section, having a first density, and the variable density metallic foam has a second portion, adjoining the second section, having a second density, the second density being greater than the first density.

[0008] Such a configuration of the variable density metallic foam is easy to manufacture and assemble.

[0009] Advantageously, the second density is 2 to 5 times greater than the first density.

[0010] Such a density ratio range promotes airflow without compromising battery performance and cooling. Indeed, a density ratio exceeding this range can lead to excessive airflow restriction and, consequently, battery overheating. Conversely, a density ratio below this range can leave some pores insufficiently cooled, resulting in premature battery degradation.

[0011] Advantageously, the average volume of pores in the first portion is greater than in the second portion.

[0012] Reducing the average pore volume ensures that, as the airflow heats up, heat transfer tends to remain at a uniform level throughout the air duct. This results in a more homogeneous battery temperature and more efficient airflow cooling.

[0013] Advantageously, the average wall thickness in the first portion is smaller than in the second portion.

[0014] Due to their thickness, the walls form a more rigid lattice for the variable-density metal foam. This rigidity is sufficient so that, where the mechanical stresses of the airflow are greatest, the wall structure provides solid support, particularly against mechanical fatigue stresses such as vehicle vibrations or gusts in the airflow.

[0015] Advantageously, the pores have an ellipsoidal shape, the principal axis of the ellipsoid forming an angle with respect to the longitudinal axis, the angle being substantially 0 degrees.

[0016] This distribution of variable density metallic foam, simple and inexpensive to set up, has the advantage of directing the airflow along the longitudinal axis, which improves battery cooling.

[0017] Advantageously, the pores have a cuboid shape.

[0018] This variable density metallic foam distribution system is easy to set up.

[0019] Advantageously, the air duct has a first part and a second part extending between the first section and the second section, the variable density metallic foam occupying the first part, a volume of air occupying the second part.

[0020] The size of the metal foam can be determined so that it remains generally close to the mounting wall, avoiding excessive interference with the airflow. In this case, the partial occupancy of the variable-density metal foam within the air duct facilitates airflow circulation while promoting heat exchange.

[0021] Advantageously, the variable density metallic foam is welded to the fixing wall.

[0022] This weld can be achieved by any known means, in particular by partial melting of the variable-density metallic foam. Furthermore, due to their small surface area, the weld points contribute very little to heat exchange, but they nevertheless guarantee good mechanical resistance against stresses that the variable-density metallic foam might undergo, such as thermal shock or stress relaxation.

[0023] The invention also relates to an electric or hybrid vehicle comprising a battery as defined above.

[0024] The invention will be further detailed by describing a non-limiting embodiment, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates a longitudinal cross-sectional view of a battery comprising a variable density metallic foam, according to an embodiment of the invention. - [Fig. 2] schematically illustrates a detailed view of a metallic foam with variable density exhibiting ellipsoidal pores.

[0025] Figure 1 illustrates a battery 30 for an electric or hybrid vehicle, having a longitudinal axis X, according to an embodiment of the invention. The battery 30 comprises an air duct 10 and a battery cell frame 20. The air duct 10 is attached to the battery cell frame 20 by means of fasteners. Consequently, the contact between the air duct 10 and the battery cell frame 20 defines a mounting wall 12. Furthermore, the mounting wall 12 preferably has a planar shape extending longitudinally.

[0026] The air duct 10 is configured to circulate an airflow F. The airflow F cools the fixing wall 12 by thermal convection, which contributes to the cooling of the battery 30.

[0027] The air duct 10 extends between a first section 10A, forming an air inlet, and a second section 10B, forming an air outlet. Thus, the airflow F can circulate in the air duct 10 so as to flow from the first section 10A to the second section 10B. The longitudinal axis X is oriented from the first section 10A to the second section 10B.

[0028] The first section 10A is connected to an air passage, injecting an airflow F into the air duct. The airflow F heats up in the air duct. The second section 10B is connected to an air outlet, expelling the heated airflow outside the vehicle.

[0029] In the following, the terms "upstream" and "downstream" are defined with respect to the direction of the airflow F. Thus, upstream refers to the side from which the airflow F originates, i.e., the side of the air passage. Conversely, downstream refers to the side toward which the airflow F is directed, i.e., the side of the air exhaust. Thus, the airflow F flows from upstream to downstream of the air duct 10.

[0030] The air duct 10 preferably has a constant cross-section. The air duct 10 comprises a variable-density metallic foam 40 comprising a plurality of foam portions. The plurality of foam portions comprises a first portion 41 and a second portion 42. The first portion 41 is adjacent to the first section 10A, while the second portion is adjacent to the second section 10B. The metallic foam is preferably made of aluminum. The metallic foam comprises pores 43 and walls 44 between the pores 43. The airflow F can flow from one pore 43 to a neighboring pore 43. Thus, the airflow F flows progressively through the variable-density metallic foam 40.

[0031] Each foam portion of the plurality of portions preferably has a uniform volumetric density distribution. The foam portions are arranged so as to exhibit densities increasing along the longitudinal axis X. Thus, the first portion 41 is less dense than the second portion 42. According to one embodiment, the variable-density metallic foam 40 may exhibit substantially a continuum of volumetric density increasing from the first section 10A to the second section 10B.

[0032] The variable-density metallic foam 40 fills the air duct 10. Furthermore, the variable-density metallic foam 40 is in contact with the mounting wall 12. The battery cell frame 20 extends along the direction of the longitudinal axis X. The battery cell frame 20 comprises a first longitudinal end 20A arranged upstream and a second longitudinal end 20B arranged downstream. The first longitudinal end 20A lies in a first plane perpendicular to the longitudinal axis X. The second longitudinal end 20B lies in a second plane perpendicular to the longitudinal axis X. The first section 10A is arranged in the first plane. The second section 10B is arranged in the second plane. Thus, the fixing wall 12 extends along the entire length of the battery cell frame 20 along the longitudinal axis X. As a result, the ratio between the fixing wall 12 and the length of the air duct is maximized.In this way, the airflow F efficiently cools the battery 30 relative to the battery 30's size.

[0033] According to one embodiment, the volume of the air duct 10 is divided into a first part and a second part. Variable density metallic foam 40 fills the first part. A volume of air occupies the second part.

[0034] The average volume of the pores 43 of the first portion 41 is preferably twice as large as the average volume of the pores 43 of the second portion 42. Furthermore, the average thickness of the walls 44 of the second portion 42 is preferably twice as large as the average thickness of the walls 44 of the first portion 4L.

[0035] According to one embodiment, the average volume of the pores 43 is constant between the first portion 41 and the second portion 42. However, the average thickness of the walls 44 is twice as large in the second portion 42 as in the first portion 4L.

[0036] According to another embodiment, the average thickness of the walls 44 is constant between the first portion 41 and the second portion 42. However, the average volume of the pores 43 of the first portion 41 is twice as large as in the second portion 42.

[0037] As illustrated in [Fig. 2], the shape of the pores is preferably ellipsoidal. The major axis of the ellipsoids forms an angle α with the longitudinal axis X. The angle α is approximately 0 degrees. Thus, the pores 44 are oriented approximately in the direction of the longitudinal axis X. Thus, the airflow F is oriented in the direction of the longitudinal axis X.

[0038] According to one variant, the shape of the pores is cuboid.

[0039] The variable density metallic foam 40 is held on the fixing wall 12 preferably by local welding points.

[0040] According to one variant, one or more screws hold the variable density metallic foam 40 onto the fixing wall 12.

Claims

Demands

1. Battery (30) of an electric or hybrid vehicle, the battery (30) having a longitudinal axis (X), the battery (30) comprising: - an air duct (10) having an air inlet having a first section (10A), the air duct (10) having an air outlet having a second section (10B), the air duct (10) being configured to circulate an airflow (F) from the first section (10A) to the second section (10B); and, - a battery cell frame (20), the air duct (10) comprising: - a mounting wall (12) fixed to the battery cell frame (20); and, - a variable density metallic foam (40) in contact with the fixing wall (12) and comprising pores (43) and walls (44) between the pores (43), the battery (30) being characterized in that the variable density metallic foam (40) has a density increasing longitudinally from the first section (10A) to the second section (10B).

2. Battery (30) according to claim 1, characterized in that the variable density metallic foam (40) has a first portion (41), adjoining the first section (10A), having a first density, and the variable density metallic foam (40) has a second portion (42), adjoining the second section (10B), having a second density, the second density being greater than the first density.

3. Battery (30) according to claim 2, characterized in that the second density is 2 to 5 times greater than the first density.

4. Battery (30) according to any one of claims 2 to 3, characterized in that the average volume of pores (43) in the first portion (41) is greater than in the second portion (42).

5. Battery (30) according to any one of claims 2 to 4, characterized in that the average thickness of the walls (44) in the first portion (41) is smaller than in the second portion (42).

6. Battery (30) according to any one of claims 1 to 5, characterized in that the pores (43) have an ellipsoidal shape, the principal axis of the ellipsoid forming an angle (a) with respect to the longitudinal axis (X), the angle (a) being substantially 0 degrees.

7. Battery (30) according to any one of claims 1 to 5, characterized in that the pores (43) have a cuboid shape.

8. Battery (30) according to any one of claims 1 to 7, the air duct (10) has a first part and a second part extending between the first section (10A) and the second section (10B), the variable density metallic foam (40) occupying the first part.

9. Battery (30) according to any one of claims 1 to 8, characterized in that the variable density metallic foam (40) is welded to the fixing wall (12).

10. Electric or hybrid vehicle comprising an electric vehicle battery (30) according to any one of claims 1 to 9.

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