BATTERY ASSEMBLY

Abstract

A battery assembly comprises at least one electrochemical cell, a protective housing (11) surrounding the at least one electrochemical cell, and a heat exchanger which is in thermal contact with the at least one electrochemical cell and can be supplied with a heat transfer medium via a connecting piece (2) which extends through an opening (13) in a wall (12) of the protective housing (11), wherein the wall (12) is movable along the connecting piece (2) under the effect of an overpressure in the protective housing (11), and wherein a flexible sealing bellows (15) is fastened with a radially inner side to the connecting piece (2) and with a radially outer side to an edge (14) of the wall (12) which surrounds the opening (13) penetrated by the connecting piece (2), and defines a maximum deflection up to which the wall (12) can be deflected along the connecting piece (2) without destroying the sealing bellows (15).A travel limiter (20), which overlaps with the wall (12) in the direction of the deflection, is anchored to the connecting piece (2) outside the protective housing (11) in order to block the deflection of the wall (12) before the maximum deflection is reached.

Description

The present invention relates to a battery assembly having at least one electrochemical cell.Electrochemical cells can reach high temperatures in the event of a technical fault such as a short circuit. In the case of cells with high energy density, as are required for electromobility applications, these temperatures can become so high that, with sufficient fresh air supply, there is the possibility that the battery may get in fire or exhaust gases released.To prevent such accidents, it is common to enclose the electrochemical cells in a protective housing that shields them from the ambient air. Such a housing is exposed to high thermal loads on account of temperatures of the cells which fluctuate greatly between operation and idle state. In order to prevent the housing from leaking through operating medium passages, such as connecting pieces for heat transfer media running through a wall of the housing, the latter are not rigidly connected to the wall but rather via flexible sealing bellows, which each bridge an intermediate space between the connecting piece and the edges of the wall opening surrounding the connecting piece. However, especially if a technical fault leads to overheating of the battery, also referred to as "thermal runaway", the pressure inside the sealed housing also increases. If the wall is thereby expanded to such an extent that one of the sealing bellows tears, fresh air oxygen can abruptly reach the cells, so that it is still possible for the cells to fire. It is therefore necessary to enclose the electrochemical cells in such a way that they are still reliably protected from the access of atmospheric oxygen even in the event of overheating.It is therefore an object of the invention to provide a battery assembly in which the tightness of a protective housing is ensured even at high temperatures and / or elevated internal pressure.According to one aspect of the invention, the object is achieved in that, in a battery assembly having at least one electrochemical cell, a protective housing surrounding the at least one electrochemical cell and a heat exchanger which is in thermal contact with the at least one electrochemical cell and can be charged with a heat carrier via a connecting piece which extends through an opening in a wall of the protective housing, wherein the wall can be moved along at least one of the connecting pieces under the action of an overpressure in the protective housing, and wherein a flexible sealing bellows is fastened by a radially inner side to the connecting piece and by a radially outer side to an edge of the wall which surrounds the opening through which the connecting piece passes and defines a maximum deflection until which the wall can be deflected along the connecting piece without destroying the sealing bellows, a travel limiter overlapping the wall is anchored to the connecting piece outside the housing in order to block the deflection of the wall before the maximum deflection is reached.In order to prevent the travel limiter from loading the connecting piece with a high torque when it becomes effective, it should overlap with the wall on both sides of a plane running along an axis of the connecting piece.In particular, the travel limiter can comprise a flange radially protruding from the connecting piece all around.In order to achieve a high load-bearing capacity with a small material thickness, the flange can be reinforced by at least one embossed bead. For example, one or more such beads may form a ring around the connector, or they may extend radially outward from the connector.In order to fix the travel limiter axially to the connecting piece, the connecting piece can have a groove which is open radially outwards and which receives a spring clip, for example in the form of a wire bent in the form of a hairpin, wherein the travel limiter is supported in the axial direction on parts of the spring clip which project out of the groove.If the connecting piece is designed as a plug, the spring clip can fulfil a dual function by additionally fixing a socket to the plug by engaging in slots of the socket which axially overlap the groove.The travel limiter may comprise a ring portion having an upper side facing the spring clip and a lower side facing the sealing bellows, which ring portion is dimensioned to receive a part of the bushing projecting under the spring clip. On the underside of the ring section, a radially inwardly projecting centering section can be provided. This can be tolerated in particular sufficiently tightly and be matched to the dimensions of the ring section such that, when the travel limiter is placed over the plug, the ring section is centered such that it is not in the way of the socket being plugged onto the plug.The construction according to the invention is particularly expediently applicable to a lithium ion cell as an electrochemical cell.Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the appended figures. FIG. 1 shows a section through a part of a battery assembly according to a first embodiment of the invention; and FIG. 2 shows a part of a battery assembly according to a second embodiment of the invention in a perspective view.FIG. 1 shows a section along the axis of a connecting piece 2, via the central passage 3 of which a battery 1 with a plurality of rechargeable electrochemical cells is supplied with cooling water. The connector 2 includes a plug 4 fixedly connected to the electrochemical cells (not shown in the figure) and communicating with a heat exchanger extending between the cells, and a socket 5 fitted over the plug 4 and connected to an external supply line such as a cooling water hose. Both are fixed to one another in the axial direction by a substantially U-shaped spring clip 6, of which two limbs 7 extend perpendicular to the sectional plane of FIG. 1. The legs 7 are received in laterally open slots 8 of the bushing 5. The slots 8 define a rest position of the legs 7, in which they abut against a conical surface 9 of the plug 4 when the socket 5 is placed on the plug 4, so that they are elastically spread apart when the socket 5 is subsequently pressed down. By finally engaging in a circumferential groove 10 of the plug 4, the plug 4 and the socket 5 are fixed to one another in the axial direction.A protective housing 11 encloses the battery 1; a wall 12 of the protective housing 11 is shown in detail in FIG. 1. An opening 13 of the wall 12 surrounds the connecting piece 2; the wall 12 and the connecting piece 2 do not touch one another; an intermediate space between the connecting piece 2 and an edge 14 of the opening 13 is bridged by a sealing bellows 15 and is closed in a substantially air-tight manner. The wall 12 may be stiffened as shown in Figure 1 by the rim 14 being shaped as a skirt extending around the opening.As long as the protective housing 11 and the sealing bellows 15 are intact, the access of fresh oxygen of the ambient air to the battery 1 is too low to keep a fire in progress. However, this tightness also entails that an overpressure which forms in the protective housing 11 as a result of a release of gas or overheating of the battery 1 tends to inflate the protective housing 11 and to displace the wall 12 upwards in the direction of its longitudinal axis in the illustration of FIG. 1 relative to the immovable connecting piece 2.The sealing bellows 15 comprises a hose- or annular inner portion 16 which sealingly abuts the plug 4 and a circumferential membrane 17 extending substantially radially outwards from the inner portion 16. In order to fix the inner portion 16 axially to the plug 4, the inner portion 16 may have on an inner surface a circumferential rib 30 which is prevented from disengaging from a groove of the plug 4 by a non-stretchable ring 31 extending outwards around the portion 16.An outer edge of the diaphragm 17 is connected to a base plate 18 which is fixed to the wall 12 by means of threaded studs 19 projecting from the wall 12 on either side of the opening 13 and nuts, not shown. The base plate 18 can be tightly glued to the edge of the membrane 13; it is also conceivable that the base plate 18 and the sealing bellows 15 are injection-molded in one piece and the base plate 18 is not elastic and flexible like the sealing bellows 15 only because of its greater wall thickness.The extensibility of the diaphragm 17 is limited; if the deflection of the wall 12 from the rest position shown in FIG. 1 exceeds a limit, this leads to tearing of the diaphragm 17 or its detachment from the base plate 18 and thus to leakage of the protective housing 11.The travel limiter 20 comprises, in the embodiment of Fig. 1, a flange 21, typically of sheet metal, having a central opening 22 which is dimensioned to receive the plug 4 with little play. Flange 21 may be placed on diaphragm 17 during assembly of the battery assembly. A ring section 23 is mounted on the flange 21 concentrically with the central opening 22 in such a way that parts of the flange 21 form a centering section 29 projecting into the opening of the ring section 23 and the interior of the ring section 23 offers space above the centering section 29 for a lower end of the socket 5. The axial extent of the ring section 23 is selected in such a way that, when the lower end of the socket 5 is engaged into the ring section 23 and the legs 8 are engaged into the groove 10 of the plug 4, parts of the spring clip 6 projecting from the slots 8 of the socket 5 are situated opposite an upper side 24 of the ring section 23 at such a small distance that a slight deflection of the wall 12 is sufficient to bring both into contact and thus axially fix the travel limiter 20.The flange 21 extends on both sides of the connecting piece 2 as far as over the base plate 18 and / or as far as over the wall 12, In the event of a deflection of the wall 12 upwards by overpressure in the protective housing 11, the base plate 18 abuts against the flange 21, optionally via a spacer 25, the freedom of movement of the wall 12 is limited such that damage to the sealing bellows 15 by the deflection of the wall 12 can be prevented as long as the plug 4 remains anchored to the battery 1.According to a variant, the flange 21 and the annular portion 23 can be replaced by a strong plate, for example made of plastic, the thickness of which corresponds to the cumulative thickness of the flange and annular portion and the base area of which corresponds to that of the flange 21.FIG. 2 shows a perspective view of the base plate 18 and the travel limiter 20 according to a second embodiment of the invention. The base plate 18 is the same as in FIG. 1 ; as here too, the sealing bellows 15 comprises an inner section 16 and a membrane 17 connected to the base plate 18.The ring section 23 of the travel limiter 20 is omitted here; instead, the axial freedom of movement of the travel limiter 20 is limited in that the centering section 29 of the flange 21 extending annularly around the opening 22 abuts a lower end of the bushing 5 when the wall 12 is raised by an internal overpressure.The annular centering portion is interrupted by a plurality of bulges 26 of the central opening 22. The sheet metal of the flange 21 is here notched downward in order to form hooks which interact with elastic latching hooks 32 which extend the inner section 16 upward in one piece. Since the locking hooks are initially elastically deflected inward when the travel limiter 20 is pushed onto the sealing bellows 15 from above, and then engage behind the hook of the flange 21, the travel limiter 20 is fixed to the sealing bellows 15 in a rotationally secure manner.It can thus be ensured that during assembly corners 27 of the flange 21 come to lie exactly opposite spacers 25 of the base plate 18. Depressions 28 embossed in the flange 21 extend from one of the corners 27 to the other and thus reinforce the flange 21.The assembly shown in FIG. 2 can be placed over a plug 4 of a battery as shown in FIG. 1; subsequently, by engaging the socket 5, the axial freedom of movement of the travel limiter 20 is limited to such an extent that it prevents the sealing bellows 15 from breaking under the action of an overpressure in the protective housing.Reference numerals denote reference numerals1 Battery 2 Connecting piece 3 Central passage 4 Plug 5 Socket 6 Spring clip 7 Leg 8 Slot 9 Conical surface 10 Groove 11 Protective housing 12 Wall 13 Opening 14 Edge 15 Sealing bellows 16 Inner section 17 Membrane 18 Base plate 19 Threaded pin 20 Travel limiter 21 Flange 22 Central opening 23 Ring section 24 Upper side 25 Spacer 26 Bulge 27 Corner 28 Bead 29 Centering section 30 Rib 31 Ring 32 Latching hooks

Claims

Battery assembly having at least one electrochemical cell, a protective housing (11) surrounding the at least one electrochemical cell and a heat exchanger which is in thermal contact with the at least one electrochemical cell and can be supplied with a heat carrier via a connecting piece (2) which extends through an opening (13) in a wall (12) of the protective housing (11), wherein the wall (12) is movable along the connecting piece (2) under the action of an overpressure in the protective housing (11), and wherein a flexible sealing bellows (15) is fastened by a radially inner side to the connecting piece (2) and by a radially outer side to an edge (14) of the wall (12) which surrounds the opening (13) through which the connecting piece (2) passes, and which defines a maximum deflection until which the wall (12) can be deflected along the connecting piece (2), Without destroying the sealing bellows (15), characterized in that a travel limiter (20), which overlaps the wall (12) as viewed in the direction of the deflection, is anchored to the connecting piece (2) outside the protective housing (11) in order to block the deflection of the wall (12) before the maximum deflection is reached.Battery assembly according to Claim 1, in which the travel limiter (20) overlaps the wall (12) on both sides of a plane running along an axis of the connecting piece (2).Battery assembly according to Claim 1, in which the travel limiter (20) comprises a flange (21) which projects radially all around the connection piece (2).The battery assembly of claim 1, 2 or 3, wherein the flange (21) is stiffened by at least one embossed bead (28).Battery assembly according to one of the preceding claims, in which the connecting piece (2) has a radially outwardly open groove (10) which accommodates a spring clip (6), wherein the travel limiter (20) is supported in the axial direction on parts of the spring clip (6) protruding from the groove (10).Battery assembly according to one of the preceding claims, in which the connecting piece (2) comprises a plug (4) and a socket (5) plugged onto the plug (4).Battery assembly according to Claim 5 and Claim 6, in which the spring clip (6) fixes a socket (5) to the plug (4) by engaging in slots (8) of the socket (5) which axially overlap the groove (10), and optionally the travel limiter (20) has a ring section (23) with an upper side (24) facing the spring clip (6) and a lower side facing the sealing bellows (15), which is dimensioned in order to receive a part of the socket (5) which projects under the spring clip (6), and a centring section (29) which projects radially inwards on the lower side of the ring section (23).The battery assembly of claim 6, wherein the flange (21) has a central opening (22), the cross section of which is large enough to allow a distal portion of the plug (4) to pass and small enough to not allow at least a portion of the receptacle (5) to pass.Battery assembly according to Claim 3 or one of Claims 4 - 8, insofar as it relates back to Claim 3, in which the flange is latched to the sealing bellows (15).The battery assembly of any preceding claim, wherein the electrochemical cell is a lithium ion cell.

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