AUTOMOBILE TRACTION BATTERY WITH THERMAL CONDUCTOR BETWEEN CELLS

Abstract

A motor vehicle traction battery comprising cylindrical electrochemical cells (2) arranged parallel to each other in rows (4) including a staggered arrangement between two rows (4), and comprising at least one thermal conductor (10) forming a flat strip interposed between two rows (4) giving a sinusoidal shape surrounding each cell (2) with support on a portion of its contour, this battery comprising intermediate heat exchange bars (20) elongated along the axis of the cells (4), having a three-sided cross-section (22, 24) comprising a first bearing face (24) on the thermal conductor (10) and two bearing faces (22) on two adjacent cells (2). Figure 3

Description

Title of the invention: MOTOR VEHICLE TRACTION BATTERY WITH THERMAL CONDUCTOR BETWEEN THE CELLS

[0001] The present invention relates to a traction battery for an electric or hybrid motor vehicle comprising a thermal conductor arranged between the electrochemical cells, as well as a method of assembling this battery and a motor vehicle comprising such a battery.

[0002] The electrochemical cells of motor vehicle traction batteries, in particular cells using lithium-ion technology, have a particular operating temperature range providing both optimization of the charging power, the charging capacity and the service life. In addition, excessive heating of the cells can lead to destruction of these cells with a risk of fire.

[0003] The battery compartment generally has a heat exchange system for cooling, or heating in certain cases, using air or a liquid, and thermal conductors of this flow in contact with the cells in order to regulate their temperatures.

[0004] A known type of vehicle traction battery, presented in particular by document EP-A1-3878045, comprises electrochemical cells of cylindrical shape arranged vertically in aligned rows, comprising a staggered assembly making it possible to optimize the use of the volume available in a battery compartment.

[0005] A fluid conductor comprising a flat continuous strip having a vertically arranged width, is inserted between two rows of cells to form a sinusoidal channel. In this way by adding a small thickness of strip between two rows, the sinusoid with its successive opposite curvatures follows the cells arranged in a staggered fashion, bypassing each cell with contact on a part of its contour. However, the sinusoidal strip inserted between two rows remains in contact with each cell at an angle of approximately 90°, i.e. a quarter of the cell's contour.

[0006] In addition, in order to limit the size of the battery, a thermal conductor is placed every two rows, which gives each cell contact on a single side, with three-quarters of the contour remaining without exchange. The cell with cooling on a limited part of its surface can pose problems of internal temperature difference.

[0007] Furthermore, the continuous strips of thermal conductor interposed between rows of cells, giving a flow uniformly passing through the compartment, comprising over its entire length the same exchange surface with the cells, does not make it possible to differentiate the heat exchange capacity according to the positioning of each cell.

[0008] In particular, the heat exchange requirement of each cell may be different depending on its arrangement, more or less close to the outline of the assembly benefiting from more exchange with the exterior. In addition, the flow of fluid advancing in the conductor heats up following its progression along the channel formed by the strip, with a thermal difference relative to the cells which decreases. The heat exchange capacity is reduced at the end of this channel.

[0009] There is no possibility of individually modifying the heat exchange of the cells according to their position in the battery, which poses problems of optimizing the thermal regulation range of their temperatures.

[0010] The present invention aims in particular to avoid these problems of the prior art.

[0011] For this purpose, it proposes a motor vehicle traction battery comprising cylindrical electrochemical cells arranged parallel to each other in rows comprising a staggered assembly between two rows, and comprising at least one thermal conductor forming a flat strip inserted between two rows giving a sinusoidal shape going around each cell with support on part of its outline, this battery being remarkable in that it comprises intermediate thermal exchange bars elongated along the axis of the cells, having a three-sided section comprising a first support face on the thermal conductor and two support faces on two nearby cells.

[0012] An advantage of this traction battery is that a thermal conductor of substantially constant section can be provided, forming a continuous fluid passage over the entire length between two rows of cells, then intermediate bars can be adjusted punctually between certain particular cells, on one side or the other of the thermal conductor. Each bar in contact with both two nearby cells and the conductor increases the heat exchange between these nearby cells and the fluid of the conductor.

[0013] It is thus possible to obtain, from identical cells and a thermal conductor substantially equivalent to those used in batteries according to the prior art, by locally adding intermediate bars, the possibility of increasing the heat exchange capacity of certain cells in places so as to obtain greater regularity of the temperature range across the whole. The larger heat exchange surface of the cells in contact with the conductive bars also makes it possible to improve the regularity of the internal temperature in these cells.

[0014] The charging capacity of the cells, the charging power and the service life of these cells are improved.

[0015] The motor vehicle traction battery according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

[0016] Advantageously, the intermediate bars comprise two faces of concave section fitting the contour of the cells.

[0017] According to a first embodiment, the first face of the intermediate bars comprises along its length grooves fitting onto a corresponding surface of the thermal conductor.

[0018] In this case, advantageously the striations have a succession of triangular or rectangular sections.

[0019] According to another embodiment, the first face of the intermediate bars comprises a smooth surface fitting onto the surface of the thermal conductor.

[0020] In particular, the first face of the strips may comprise a generally flat shape fitting onto a flat side of the thermal conductor.

[0021] Advantageously, the intermediate bars have a constant section formed by an extrusion process.

[0022] The invention also relates to a method for assembling a traction battery comprising any one of the preceding characteristics, remarkable in that it comprises a step of assembling the cells by arranging the thermal conductors between certain rows of cells, then a step of inserting intermediate bars between cells.

[0023] In addition, the method can carry out a selection of the intermediate spaces between the cells receiving the bars, as a function of the position of these cells relative to the edge of the set of cells, or of their position relative to the direction of a flow contained in the thermal conductor.

[0024] The invention further relates to an electric or hybrid motor vehicle equipped with an electric traction machine, remarkable in that it comprises a traction battery comprising any one of the preceding characteristics, which powers the electric machine.

[0025] 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:

[0026] [Fig.l] shows in top view a set of electrochemical cells of a battery according to the prior art, comprising thermal conductors interposed every two rows;

[0027] [Fig.2] is a diagram showing in detail the thermal conductor of this battery; And

[0028] [Fig.3] is a diagram showing in detail the thermal conductor of a battery according to the invention.

[0029] Throughout the document, the vertical direction relates to a battery placed on a horizontal plane, this battery being able to take any orientation during its use in the motor vehicle.

[0030] Figures 1 and 2 show a set of cylindrical cells 2 of a traction battery of an electric or hybrid motor vehicle, aligned vertically in parallel rows 4 arranged in a longitudinal direction, close together in the same row and between these rows.

[0031] A cell compartment 6 containing all of the cells 2 is arranged in a battery box receiving other elements necessary for the operation of this battery, in order to form a flat assembly generally fixed under the floor of a motor vehicle to power an electric traction machine.

[0032] Between two close parallel rows 4, the cells 2 are offset in the longitudinal direction by a distance equal to the radius of the cells so as to form a staggered arrangement which optimizes the number of cells in a given space.

[0033] With adjoining parallel rows 4, intermediate spaces 12 are obtained having a shape with three concave faces corresponding to parts of the contour of the three cells 2 which are in contact.

[0034] Every two rows 4 a fluid thermal conductor 10 forms a channel fitted between two rows, which extends in the longitudinal direction over the complete length of the whole of the cells.

[0035] Each thermal conductor 10 forms a relatively flexible flat continuous strip, having a vertically arranged width, and a thickness which is inserted between the two rows 4 of cells 2, forming a sinusoid which successively goes around a cell of one row and then a cell of the other row. In this way, contact is obtained between each cell of the battery 2 and the thermal conductor 10, following an angular sector of its contour which is approximately 90°.

[0036] [Fig. 3] shows an intermediate strip 20 forming a thermal conductor which is inserted vertically into an intermediate space 12 over its entire height. The constant section of the intermediate strip 20, generally triangular, has a first face 24 for exchange with the thermal conductor 10, generally flat, comprising along its length vertical grooves of square section constituting a comb which fits onto a corresponding grooved surface formed on the side of the conductor, and has two concave faces 22 resting on the contours of two close cells 2 of the same row 4.

[0037] Alternatively, the exchange face 24 may be generally rounded so as to follow the sinusoid of the thermal conductor 10, which makes it possible to maintain the sinusoidal shape on both faces of this conductor. The grooves may have a square section, or any other section such as triangular notches, with the aim of increasing the conduction surface between the bar 20 and the conductor 10, while allowing vertical sliding of insertion of this bar.

[0038] Alternatively, the exchange face 24 of the strip 20 may be concave and smooth so as to follow the sinusoidal surface of the thermal conductor 10 which is also smooth in this case. The heat exchange surface between the strip 20 and the thermal conductor 10 is reduced, but the faces of this conductor are kept which are smooth and constant over its entire length, allowing in particular to be produced by extrusion.

[0039] Advantageously, the intermediate bars 20 comprising a constant section profile are produced by extrusion of a material having high thermal conductivity, such as an aluminum alloy.

[0040] The method of assembling the battery according to the invention is as follows. After the complete assembly of the cells 2 and the thermal conductors 10 fitted between the rows of cells 4, intermediate bars 20 are slid vertically into certain intermediate spaces 12 depending on the need to increase the heat exchange between the two contiguous cells and this conductor.

[0041] In particular, it is possible to promote the heat exchange of the cells 2 distant from the edges of the battery, benefiting from less heat exchange with the exterior of this battery. It is also possible to promote the heat exchange of the cells 2 with those arranged at the end of the path of the flow of the thermal conductor 10, containing an internal fluid which is hotter.

[0042] In all cases, the intermediate bars 20 constitute standard elements which can be added in all the intermediate spaces 12 of each battery, depending on its own characteristics which can be different from one battery to another, which gives great flexibility of individual adaptation to these batteries.

Claims

Claims

1. Motor vehicle traction battery comprising cylindrical electrochemical cells (2) arranged parallel to each other in rows (4) comprising a staggered assembly between two rows (4), and comprising at least one thermal conductor (10) forming a flat strip interposed between two rows (4) giving a sinusoidal shape going around each cell (2) with a support on a part of its contour, characterized in that it comprises intermediate thermal exchange bars (20) elongated along the axis of the cells (4), having a three-sided section (22, 24) comprising a first support face (24) on the thermal conductor (10) and two support faces (22) on two nearby cells (2).

2. Traction battery according to claim 1, characterized in that the intermediate bars (20) comprise two faces of concave section (22) fitting onto the contour of the cells (2).

3. Traction battery according to claim 2, characterized in that the first face (24) of the intermediate bars (20) has along its length grooves fitting onto a corresponding surface of the thermal conductor (10).

4. Traction battery according to claim 3, characterized in that the grooves have a succession of triangular or rectangular sections.

5. Traction battery according to any one of claims 1 or 2, characterized in that the first face (24) of the intermediate bars (20) has a smooth surface fitting onto the surface of the thermal conductor (10).

6. Traction battery according to any one of the preceding claims, characterized in that the first face (24) of the intermediate bars (20) has a generally flat shape.

7. Traction battery according to any one of the preceding claims, characterized in that the intermediate bars (20) have a constant section formed by an extrusion process.

8. Method for assembling a traction battery according to any one of the preceding claims, characterized in that it comprises a step of assembling the cells (2) by arranging the thermal conductors (10) between certain rows of cells (4), then a step of inserting intermediate bars (20) between cells (2).

9. Assembly method according to claim 8, characterized in that it carries out a selection of the intermediate spaces (12) between cells (2) receiving the intermediate bars (20), as a function of the position of these cells (2) relative to the edge of the set of cells, or of their position relative to the direction of a flow contained in the thermal conductor (10).

10. Electric or hybrid motor vehicle equipped with an electric traction machine, characterized in that it comprises a traction battery according to any one of claims 1 to 7, which powers the electric machine.

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