Traction battery for a motor vehicle, method for producing a traction battery and motor vehicle

Abstract

The invention relates to a traction battery (12) for a motor vehicle, comprising a housing (22), a battery complex (10) and at least one fixing element (28) which is designed to fix a position of the battery complex (10) in the housing (22) by pressing the at least one fixing element (28) between the battery complex (10) and the housing (22), wherein the fixing element (28) comprises a foam.

Description

The invention relates to a traction battery for a motor vehicle, to a method for producing a traction battery for a motor vehicle, and to a motor vehicle having a traction battery.DE 20 2005 010 708 U1 discloses a housing for a starter battery. This housing comprises outer walls and intermediate walls integrally formed therewith, said walls having at least partially a foam structure.Furthermore, DE 10 2015 119 156 A1 discloses a battery assembly having a battery formation and a foam shell which surrounds the battery formation. The assembly includes a guard attached to the foam shell. The protective device is made of polyamide, polyethylene or polypropylene.It is an object of the present invention to provide a solution which enables particularly good protection of battery cells of a traction battery in a housing.This object is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description and the figures. Features, advantages and possible configurations which are set forth in the context of the description for one of the subject matters of the independent claims are to be regarded at least analogously as features, advantages and possible configurations of the respective subject matter of the other independent claims and of each possible combination of the subject matters of the independent claims, optionally in conjunction with one or more of the dependent claims.The invention relates to a traction battery for a motor vehicle, in particular a motorcycle, such as a motorcycle, or a motor vehicle, in particular a passenger car. The traction battery is configured to provide electrical energy to an electric powertrain of the motor vehicle. The motor vehicle can thus be driven by means of the electric drive train and the electrical energy provided by the traction battery. The traction battery is in particular a so-called high-voltage battery. The traction battery includes a housing, a battery complex, and at least one fixation element. The housing can comprise a plurality of housing parts, for example an upper housing part and a lower housing part, which together delimit a receiving space. The battery complex can be accommodated in this accommodation space. The battery complex comprises a plurality of battery cells which are connected to one another to form the battery complex. In particular, the respective battery cells are designed as round cells. The fixing element is configured to fix the position of the battery complex in the housing, in particular in the receiving space of the housing. For this purpose, the at least one fixing element is pressed between the battery complex and the housing, wherein the fixing element comprises a foam. Because the fixation element comprises a foam, the fixation element yields before the battery complex yields. As a result, the fixing element can be compressed at least in regions during the pressing between the battery complex and the housing and thus compressed. As a result, the battery complex is clamped in the housing without play by means of the at least one fixing element, as a result of which a relative movement of the battery complex with respect to the housing can be prevented particularly well. Because the at least one fixing element comprises the foam material, the at least one fixing element simultaneously serves to absorb mechanical forces introduced into the traction battery. This means that when mechanical forces are introduced into the traction battery, the at least one fixing element deforms, as a result of which a force effect on the battery complex and consequently a risk of damage to the battery complex can be kept particularly low. By means of the at least one fixing element which comprises the foam, it is thus possible, on the one hand, for the battery complex to be positioned and fixed securely and precisely in the housing and, moreover, for the battery complex to be protected particularly well from damage. The pressing of the fixing element has two important tasks: on the one hand, all component tolerances and assembly tolerances can be compensated and thus a play-free mounting of the battery cells in the housing can be ensured. On the other hand, the required mechanical properties or characteristic values for satisfying legal requirements or safety features for high-voltage accumulators or the overall vehicle, such as Euro-NCAP, are achieved.In a possible development of the invention, it is provided that the at least one fixing element comprises an expanded polypropylene. Expanded polypropylene is a plastic which is also used in what are known as crash pads. The battery cells of the battery complex can be protected particularly well from damage by means of the expanded polypropylene, since the expanded polypropylene can shield mechanical forces acting on the traction battery from the outside particularly well from the battery complex by forming.In a further possible embodiment of the invention, it is provided that the at least one fixing element has a wedge-shaped geometry at least before the pressing. The wedge-shaped geometry is to be understood to mean that two mutually different side surfaces of the fixing element converge at an acute angle. In this case, these two side surfaces can directly adjoin one another or adjoin a further side surface at respectively mutually opposite side edges. In other words, the at least one fixing element tapers to a point at least in regions. The wedge-shaped geometry of the fixing element allows the fixing element to be inserted into a gap between the battery complex and the housing, wherein the wedge-shaped fixing element is inserted into the gap until the wedge-shaped geometry of the fixing element is clamped between the battery complex and the housing in such a way that the battery complex is fixed in its position relative to the housing. The wedge-shaped geometry of the fixing element enables tolerances between the battery complex and the housing to be compensated particularly well by adjusting a depth of insertion of the fixing element into the gap, whereby it can be ensured that the battery complex is securely fixed relative to the housing.In a further possible embodiment of the invention, it is provided that the at least one fixing element completely covers the battery complex on the side against which the fixing element abuts, toward the housing. As a result, the battery cells of the battery complex on the side on which the fixing element abuts are particularly well protected against damage by means of the fixing element, since the battery complex on this side is completely covered by the fixing element. A risk of damage to the battery cells of the battery complex can thus be kept particularly low.In a further possible embodiment of the invention, it is provided that the at least one fixing element has, on its outer side facing the housing, at least one groove in which a guide rib of the housing engages. In this case, the groove and the guide rib are aligned, in particular with their longitudinal extension directions, parallel to an insertion direction in which the fixing element has been inserted into the gap between the battery complex and the housing during the production of the traction battery. In particular, the insertion direction runs parallel to the longitudinal extension direction of the respective central axes of the battery cells configured as round cells. As a result, the at least one fixing element is guided relative to the housing by the engagement of the guide rib in the groove when it is pushed into the gap. In this way, it can be achieved that the fixing element, in its end position relative to the housing, has a predetermined orientation or a predetermined position. Furthermore, the fixing element is held in its end position particularly securely relative to the housing by the engagement of the guide rib of the housing in the groove of the fixing element. The fixing element is thus clamped between the battery complex and the housing on the one hand and is secured relative to the housing via the engagement of the guide rib in the groove on the other hand. A risk of a relative movement of the at least one fixing element relative to the housing and thus, if appropriate, of a movement of the battery complex relative to the housing can thus be kept particularly low.In a further possible embodiment of the invention, it is provided that the battery complex comprises a plurality of round cells which are arranged with their respective central axes parallel to one another and next to one another. In particular, respective end faces of the round cells are aligned flush with one another. Furthermore, in this embodiment, it is provided that the at least one fixing element abuts laterally on the round cells of an outermost row of the round cells. This means that the at least one fixing element abuts on respective lateral surfaces of the outermost row of round cells. Furthermore, it is provided that the fixing element has a wave geometry on its side surface facing the round cells, as a result of which the outer contour of this side surface of the fixing element corresponds to the outer contour of the battery complex provided by the round cells. In particular, respective radii of the shafts of the shaft geometry of the at least one fixing element correspond to respective outer radii of the lateral surfaces of the outermost row of battery cells, as a result of which the at least one fixing element can be placed on the respective lateral surfaces of the outermost row of round cells in a particularly large area. Due to the wave geometry, the at least one fixing element thus extends in a transverse direction, which extends both perpendicularly to the respective central axes of the round cells and also perpendicularly to a longitudinal extension direction of the outermost row of battery cells, between adjacent round cells of this outermost row of battery cells. As a result, the respective round cells of the outermost row of battery cells are fixed in their position along the longitudinal direction of extent of the outermost row of battery cells by the at least one fixing element, as a result of which relative movements of these round cells with respect to the at least one fixing element along the longitudinal direction of extent of the outermost row of battery cells can be particularly well prevented. In other words, it can be avoided that the at least one fixing element is moved laterally along the outermost row of battery cells or is moved past it, since the shaft geometry engages the fixing element at least in regions between the round cells. This engagement thus results in a fixing of the relative position of the battery complex to the at least one fixing element along the longitudinal extension direction of the outermost row of battery cells. Alternatively, the at least one fixing element can bear laterally only on a cell carrier carrying the battery cells-and in this case not on the battery cells-or both on the cell carrier and on the battery cells, in particular the round cells.In a further possible embodiment of the invention, it is provided that the traction battery comprises three fixing elements, one of which rests on the top side of the battery complex and the other two of which rest on mutually opposite side surfaces of the battery complex. As a result, the battery complex can be covered on particularly many different sides by respective fixing elements and thereby protected from damage. In addition, the plurality of fixing elements enable a particularly precise and secure fixing of the position of the battery complex within the housing.The invention furthermore relates to a method for producing a traction battery for a motor vehicle, as has already been described in connection with the traction battery according to the invention. In the method, a battery complex is arranged in a housing. To fix the position of the battery complex in the housing, at least one fixing element which comprises a foam is pressed between the battery complex and the housing, in particular in a gap between the battery complex and the housing. In particular, for producing the traction battery, the battery complex is first placed inside the housing and the at least one fixing element is subsequently pressed into a gap between the battery complex and the housing in order to clamp the battery complex in the housing at its lateral position. As a result, the battery complex is particularly securely fixed within the housing.In a possible development of the invention, it is provided that the at least one fixing element is compressed in at least one dimension by at least ten percent and at most 30 percent during pressing, in particular is compressed by at least 20 percent and at most 25 percent. The compression of the fixing element when it is inserted into the gap between the battery complex and the housing ensures that, depending on the degree of compression of the fixing element, tolerances between the battery complex and the housing can be compensated and in the process the battery complex is held in the housing reliably without play.In a further possible embodiment of the invention, it is provided that the at least one fixing element is compressed in at least one dimension during pressing until a predefined value for a predefined parameter is reached. The predefined parameter can be, for example, a compressive strength to be achieved. For example, the fixing element can be inserted so deeply into the gap between the battery complex and the housing in the insertion direction until the predetermined value for the predetermined parameter is reached. As a result, legal requirements can be complied with particularly easily and reliably.Furthermore, the invention comprises a motor vehicle having a traction battery as has already been described in connection with the traction battery according to the invention. The motor vehicle can be a motor vehicle or a motorcycle. The traction battery is configured to provide electrical energy for an electric drive train of the motor vehicle, as a result of which the motor vehicle can be driven by means of electrical energy by means of an electric traction machine.Further features of the invention can be derived from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description and the features and combinations of features shown below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the invention.The drawing shows in: FIG. 1 is a schematic perspective view of a battery complex for a traction battery of a motor vehicle; FIG. 2 is a schematic perspective view of the battery complex to which a fixing element is applied and which is inserted into a housing lower part of a housing; FIG. 3 is a schematic perspective view of the traction battery during a manufacturing step; FIG. 4 is a schematic perspective view of the traction battery during a further manufacturing step; FIG. 5 shows a schematic perspective view of the battery complex, which is deposited on a housing lower part of the housing and on which respective fixing elements are laterally placed on opposite sides; and FIG. 6 is an exploded view of the traction battery.In the figures, identical and functionally identical elements are provided with the same reference numerals.FIG. 1 shows a battery complex 10 for a traction battery 12 of a motor vehicle, in the present case a motorcycle. This traction battery 12 is shown in an exploded illustration in FIG. 6. The traction battery 12 is configured to provide electrical energy to a powertrain of the motor vehicle. For this purpose, the battery complex 10 comprises a plurality of battery cells which are designed in the present case as round cells 14. For reasons of clarity, only individual ones of the round cells 14 in FIG. 1 are provided with the associated reference sign. The battery complex 10 in the present case furthermore comprises a cell carrier 16, on which the round cells 14 are deposited, a cooling system 18, which is configured to be flowed through by a cooling fluid, as a result of which the round cells 14 can be cooled, and a cell contacting system 20.In addition to the battery complex 10, the traction battery 12 comprises, as can be seen in FIG. 6, a housing 22, which housing 22 comprises in the present case an upper housing part 24 and a lower housing part 26. In order to prevent the battery complex 10 from being accommodated loosely within the receiving space of the housing 22 and as a result could be damaged by collisions with respective inner walls of the housing 22, the traction battery 12 comprises at least one fixing element 28, in the present case three fixing elements 28. These fixing elements 28 are pressed between the battery complex 10 and the housing 22, insbesonderjeweiligen inner walls of the housing 22, as a result of which the battery complex 10 is clamped in the housing 22 and is thereby fixed in its position. The respective fixing elements 28 each comprise a foam material, in particular an expanded polypropylene.The assembly of the traction battery 12 is explained below with reference to FIGS. 2 to 4. For producing the traction battery 12, a first fixing element 28 is placed on an upper side 30 of the battery complex 10. In this case, the first fixing element 28 covers the upper side 30 of the battery complex 10 at least substantially completely upwards. The upper housing part 24 of the housing 22 is then placed over the battery complex 10, starting with its upper side 30. this means that the battery complex 10 is moved with the first fixing element 28 arranged on the upper side 30 in front into the receiving space of the housing 22 defined by the upper housing part 24. Subsequently, the battery complex 10 inserted into the upper housing part 24 is rotated together with the upper housing part 24 about a horizontal axis, so that the upper side 30 of the battery complex 10 is oriented downward and the lower side 32 of the battery complex 10 is oriented upward, whereby the arrangement shown in FIG. 3 is achieved. Respective wedge-shaped second fixing elements 28 are subsequently inserted in an insertion direction 36, into respective gaps 34 laterally kept free between the battery complex 10 and the housing upper part 24. In this case, the wedge-shaped second fixing elements 28 are inserted with their respective tips first into the gaps 34. A thickness of the respective wedge-shaped second fixing elements 28 widens counter to the insertion direction 36, as a result of which the deeper the respective second fixing elements 28 are inserted into the respectively associated gaps 34 in the insertion direction 36, the stronger the battery complex 10 is clamped to the upper housing part 24 of the housing 22. In this case, it is provided that the respective second fixing elements 28 are compressed in at least one dimension during pressing until a predefined value for a predefined parameter of the respective second fixing elements 28 is reached. The predefined parameter can be, for example, a compressive strength to be achieved. Thus, the second fixing elements 28 can each be inserted so deeply in the insertion direction 36 into the respectively associated gap 34 between the battery complex 10 and the housing 22 until the predetermined value for the predetermined parameter is reached for each of the second fixing elements 28. When the battery complex 10 is inserted into the upper housing part 24 with the upper side 30 first, the first fixing element 28 can be compressed depending on the depth of insertion of the battery complex 10 into the upper housing part 24. Here, too, the insertion depth of the battery complex 10 can be selected such that the resulting compression of the first fixing element 28 is sufficient to achieve the predefined value for the predefined parameter. Depending on the insertion depth of the second fixing elements 28 into the respectively assigned gaps 34, the second fixing elements 28 can be compressed in the width direction between a respective inner wall of the upper housing part 24 and the battery complex 10. In this case, the fixing elements 28 are compressed, in particular in at least one dimension, by at least ten percent and at most 30 percent, in particular compressed by at least 20 percent and at most 25 percent. In the present case, a first fixing element 28 is thus provided in the traction battery 12, which is placed on the top side of the battery complex 10, and two second fixing elements 28 are provided, which bear against mutually opposite side surfaces of the battery complex 10. As a result, the battery complex 10 is held particularly securely in the upper housing part 24 of the housing 22 by means of the fixing elements 28 by clamping. In addition, because they are made of the foam material, in particular the expanded polypropylene, the fixing elements 28 are in the present case particularly well configured to be deformed in the event of mechanical actions on the upper housing part 24, as a result of which a force introduction into the battery complex 10 can be kept particularly low on account of mechanical actions on the upper housing part 24.As can be seen in FIG. 4, a mica plate 38 is placed on the underside 32 of the battery complex 10 in order to complete the traction battery 12. Mica is a group of minerals from the division of the sheet silicates. Micas have a layered structure, with a very weak bond between the layers of this layered structure. This mica plate 38 is then covered by placing the housing lower part 26 outwards. The mica plate 38 serves to protect propagation when a single round cell 14 of the battery complex 10 passes through. The housing lower part 26 has, as can be seen particularly well in FIG. 4, a plurality of degassing openings 40, which are covered from the mica plate 38 toward the battery complex 10. For reasons of clarity, only individual ones of the degassing openings 40 are provided with the associated reference sign. When one of the round cells 14 of the battery complex 10 passes through, the mica plate 38 which covers this round cell 14 downward fails, as a result of which the mica plate 38 enables a passage from the thermally overheating round cell 14 to the degassing opening 40 assigned to this round cell 14. Hot gases which are produced during this thermal overheating and thus thermal passage of the round cell 14 can be conducted away from the battery complex 10 via the degassing opening 40, as a result of which overheating of further round cells 14 as a result of contact with these hot battery cells can be particularly easily avoided. For a particularly secure connection of the lower housing part 26 to the upper housing part 24, the lower housing part 26 is screwed to the upper housing part 24 by means of screws 42. For reasons of clarity, only individual screws 42 are provided with the associated reference sign.In the illustration shown in FIG. 5, the traction battery 12 is illustrated without the upper housing part 24 and without the first fixing element 28. It can be recognized here that the respective second fixing elements 28 each bear against a side surface of the battery complex 10, wherein the second fixing elements 28 bear against mutually opposite side surfaces of the battery complex 10. The respective second fixing elements 28 have, on their side facing the round cells 14, a wave geometry 44 which corresponds to an external geometry of the battery complex 10 on the associated side surface of the battery complex 10, on which this second fixing element 28 bears. The corrugations of the corrugation geometry 44 project into respective cell interspaces between adjacent round cells 14 of the battery complex 10. As a result, the respective second fixing element 28 is fixed relative to the battery complex 10 along a longitudinal extent direction L of that outermost row of round cells 14 on which this second fixing element 28 bears. This means that, due to the engagement of the respective shafts in a transverse direction Q running perpendicular to the longitudinal direction L of the respective row of round cells 14 and perpendicular to respective central axes of the round cells 14 between respective adjacent round cells 14 of this outermost row of round cells 14, a relative movement of the second fixing element 28 along the longitudinal direction L relative to the battery complex 10 is prevented. In order to further prevent a relative movement of the respective second fixing elements 28 with respect to the upper housing part 24 along the longitudinal extension direction L of the respective outermost rows of round cells 14 on which the second fixing elements 28 abut, the respective second fixing elements 28 have at least one groove 46 on their outer wall facing the upper housing part 24 and opposite the shaft geometry 44. In the present case, the respective second fixing elements 28 have a plurality of grooves 46 on their outer wall, which grooves are oriented with their respective longitudinal extension direction parallel to one another and parallel to the insertion direction 36. The insertion direction 36 runs parallel to a longitudinal extension direction of respective center axes of the round cells 14. The upper housing part 24 has on its inner walls, against which the respective second fixing elements 28 abut in the finished traction battery 12, respective guide ribs 48 corresponding to the grooves 46, which can be recognized in FIG. 6. These guide ribs 48 engage in the respectively associated grooves 46 of the respective second fixing elements 28 bearing against the respective inner wall when the traction battery 12 is assembled. When the respective second fixing elements 28 are inserted in the insertion direction 36 into the respectively assigned gaps 34, the guide ribs 48 are inserted into the respectively assigned grooves 46 counter to the insertion direction 36. By the engagement of the respective guide ribs 48 with the respectively associated grooves 46, the respective second fixing elements 28 are guided relative to the upper housing part 24 in the insertion direction 36. In addition, the respective second fixing elements 28 are fixed in their movement relative to the upper housing part 24 along the longitudinal extension direction of the outermost row of round cells 14 on which the respective second fixing element 28 abuts, by the engagement of the respective guide ribs 48 in the associated grooves 46.In the present case, the housing 22 is designed as a plastic housing. The respective fixing elements 28 take over a play-free mounting of the battery complex 10 within the housing 22 and shock absorption.It is already known to glue or foam round cells into a battery module or directly into a high-voltage accumulator. However, gluing / foaming processes are very expensive and difficult to industrialize. In the traction battery 12 described, the structural integration of the round cells 14 into the housing 22 is substantially simpler and more cost-effective. In this case, the structural integration of the round cells 14 takes place by the use of the fixing elements 28, which in the present case are embodied as so-called EPP pads. In the event of an accident, these EPP pads securely mount the round cells 14 and at the same time take over a play-free mounting of the round cells 14 by means of a tolerance compensation function. The EPP pads are inserted into the upper housing part 24 during the assembly of a single battery module or the entire traction battery 12 and produce a structural connection between the round cells 14 and the housing 22. The housing 22 may be a module housing or an overall housing of the traction battery 12 and thus a high-voltage accumulator housing. During joining of the housing lower part 26, the EPP pads are pressed together in a defined manner, so that a necessary tolerance compensation for the play-free mounting of the round cells 14 in the housing 22 takes place. The round cells 14 can be positioned in particular by means of a support geometry in the housing 22, which can be in particular a housing made of a glass fibre-reinforced plastic. On the side of the battery complex 10, an installation space requirement, in the present case the gaps 34, in which the EPP pads are inserted, can be found. The EPP pads formed as the second fixing elements 28 have a wedge-shaped geometry, so that they can slip optimally between the respective round cells 14 and the housing 22 in the end position. In particular, the EPP pads are pressed in a defined manner only by the mounting of the housing lower part 26, which can also be referred to as housing cover, on the housing upper part 24. In this case, the EPP pads can be pressed by approximately 25 percent, for example. This assembly step results in two functions of the EPP pad. On the one hand, all component and bearing tolerances between round cells 14, supporting structure and housing 22 are eliminated and, on the other hand, the EPP pads obtain a desired compressive strength for a predefined accident scenario by the pressing.Overall, the invention shows how a crash pad with tolerance compensation can be used in a traction battery 12.List of reference characters10 Battery complex 12 Traction battery 14 Round cell 16 Cell carrier 18 Cooling system 20 Cell contacting system 22 Housing 24 Upper housing part 26 Lower housing part 28 Fixing element 30 Upper side 32 Lower side 34 Gap 36 Insertion direction 38 Mica plate 40 Degassing opening 42 Screw 44 Wave geometry 46 Groove 48 Guide rib L Longitudinal direction of an outermost cell row Q Transverse directionReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 20 2005 010 708 U1

[0002] DE 10 2015 119 156 A1

[0003]

Claims

Traction battery (12) for a motor vehicle, having a housing (22), a battery complex (10) and at least one fixing element (28) which is configured to fix a position of the battery complex (10) in the housing (22) by the at least one fixing element (28) being pressed between the battery complex (10) and the housing (22), wherein the fixing element (28) comprises a foam.The traction battery (12) of claim 1, characterized in that the at least one fixation element (28) comprises an expanded polypropylene.Traction battery (12) according to Claim 1 or 2, characterized in that the at least one fixing element (28) has a wedge-shaped geometry at least before it is pressed.Traction battery (12) according to one of the preceding claims, characterized in that the at least one fixing element (28) completely covers the battery complex (10) towards the housing (22) on the side on which the fixing element (28) bears.Traction battery (12) according to one of the preceding claims, characterized in that the at least one fixing element (28) has, on its outer side facing the housing (22), at least one groove (46), in which a guide rib (48) of the housing (22) engages.Traction battery (12) according to one of the preceding claims, characterized in that the battery complex (10) comprises a multiplicity of round cells (14) which are arranged with their respective central axes parallel to one another and next to one another, the fixing element (28) bears laterally against the round cells (14) of an outermost row of round cells (14), and the fixing element (28) has a wave geometry (44) on its side face facing the round cells (14), as a result of which the outer contour of this side face corresponds to the outer contour of the battery complex (10) provided by the round cells (14).Traction battery (12) according to one of the preceding claims, characterized in that three fixing elements (28) are provided, one of which rests on the top side of the battery complex (10) and the other two of which rest on mutually opposite side faces of the battery complex (10).Method for producing a traction battery (12) for a motor vehicle according to one of the preceding claims, in which a battery complex (10) is arranged in a housing (22) and, in order to fix the position of the battery complex (10) in the housing (22), at least one fixing element (28) which comprises a foam is pressed between the battery complex (10) and the housing (22).Method according to claim 8, characterised in that the at least one fixing element (28) is compressed in at least one dimension by at least 10 percent and at most 30 percent during pressing, in particular is compressed by at least 20 percent and at most 25 percent.Method according to claim 8 or 9, characterised in that the at least one fixing element (28) is compressed in at least one dimension during pressing until a predetermined value for a predetermined parameter is reached.Motor vehicle having a traction battery (12) according to one of Claims 1 to 7.

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