AT527248B1 - Pyrotechnic current isolator - Google Patents

Abstract

The pyrotechnic current isolator (1) has a separating piston (17) which can be moved in a central recess (13) of the current isolator (1) and can be driven by an igniter (7). When triggered, a circuit board (4) between a first separating point (5) and a second separating point (6) of a conductor (2) is separated from the separating piston (17). A fuse (15) is also provided which is normally only in contact with one side of the first separating point (5) and is only connected to the other side of the first separating point (5) during the pyrotechnic separating process, so that the fuse (15) is only connected in parallel to the first separating point (5) after contact has been made. According to the invention, when the current isolator (1) is triggered, the separating piston (17) first separates the first separating point (5) and bends the circuit board (4) around the second separating point (6) so that the bent circuit board creates an electrical connection to the fuse. Only then is the second separation point (6) also cut through, so that the fuse is no longer connected in the current path of the conductor. In any case, after the separation process, a galvanic separation of the two ends of the conductor (2) is ensured.

Description

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Description

[0001] The present invention relates to a pyrotechnic current isolator with reduced external effect for severing a conductor by means of a separating piston which can be moved in a central recess of the current isolator and driven by an igniter, wherein two separating points are provided in the conductor, namely a first separating point and a second separating point, so that when the current isolator is triggered, a circuit board between these two separating points is separated from the separating piston, wherein a fuse is provided which is normally in contact with at most one side (conductor end or circuit board) of the first separating point and is only connected to the other side (circuit board or conductor end) of the first separating point during the pyrotechnic separating process or immediately before the pyrotechnic separating process, so that the fuse is connected in parallel only to the first separating point after contact during the pyrotechnic separating process or immediately before the pyrotechnic separating process and thus after the separation of both separating points and extinguishing of any arcs, galvanic separation is provided even when the fuse is intact.

[0002] Electric vehicles are powered by a so-called high-voltage battery - this means operating voltages in the range of approx. 200-1000 V. To protect against short circuits, either fuses for lower drive power in the range of around 100 kW or so-called circuit breakers for higher power are used. With these circuit breakers, a piece, the so-called circuit board, is punched out of a conductor. This type of protection works very well for the vehicle on its own, but short circuits can also occur when charging the battery. In this case, the energy introduced is much higher because the inductance of the charging cable - the value can be 100 uH or more - must be taken into account. For the same short-circuit current, the energy is many times greater than the short circuit in the vehicle, and this must also be taken into account in the design of the circuit breakers. The energy absorption is best ensured by connecting a fuse in parallel.

[0003] In the simplest case, the fuse is constantly connected in parallel to the current isolator, as described, for example, in WO 2018/206273 A1. In the current isolator described there, the conductor is divided into three parallel strips: the two edge strips are penetrated by the isolating piston when the current isolator is triggered, but the middle strip is not; this middle strip has cross-sectional reductions that act as fuses. The fuse (the middle strip) is therefore also located inside the housing of the current isolator.

[0004] Due to the division of the operating current before the separation between the conductor (bus bar) and the fuse, a large surface of the fuse element in contact with sand as a coolant is required at high currents in order to achieve the required current-carrying capacity, which is not possible with the design described. This solution leads to large and complex designs.

[0005] A better solution is shown in US 11056306 B2 by Autoliv in Fig. 1, the fuse is only contacted when it is triggered. This avoids the problems with the permanent current load on the fuse, but there is no separation if the current is applied for too short a time or is too small to separate the fuse, because the fuse is connected to the two conductor ends after it is triggered, i.e. after the circuit board has been punched out. Furthermore, this structure is also complex.

[0006] An alternative concept is shown in the generic AT 521150 B1 from Hirtenberger. Here, after the fuse has been triggered, it is connected to the circuit board and to one end of the conductor. At low current loads, the fuse remains ineffective, an arc is created between the end of the conductor that is not connected to the fuse and the circuit board, which is extinguished due to the design of the current isolator. No arc is created between the circuit board and the end of the conductor that is connected to the fuse because the current can flow through the fuse. At high current loads, where the arc would not extinguish quickly enough due to the design of the current isolator, the fuse is triggered, which interrupts the flow of current.

x hes AT 527 248 B1 2025-01-15

8 NN

and the arc is extinguished. In both cases, the two conductor ends are galvanically separated. The disadvantage of this solution is that the arc between one conductor end and the circuit board creates a current-dependent external effect, which is correspondingly severe at high currents despite the fuse.

[0007] EP 2660842 A1 discloses a separating device whose conductor is separated by a separating piston with a shoulder in such a way that first a part of the conductor is separated and only then a second part of the conductor is separated, so that only half the force is required for the separation.

[0008] It is an object of the present invention to avoid all the above-mentioned disadvantages and to provide a cost-effective solution which has only a small external impact and in which a galvanic separation of the conductor ends is provided in any case after triggering.

[0009] This object is achieved according to the invention by a pyrotechnic current isolator of the type mentioned at the outset in that the isolating piston, when the current isolator is triggered, first separates the first isolating point and bends the circuit board around the second isolating point, so that the bent circuit board creates an electrical connection to the fuse and only then also separates the second isolating point, so that the fuse is no longer connected in the current path of the conductor. In this way, an arc can only form between the end of the conductor that is not connected to the fuse and the circuit board (i.e. around the second isolating point) when the conductor is also separated from the isolating piston at the second isolating point, and by this time the fuse should already have interrupted the flow of current if a high current had to be interrupted. If only a small current had to be interrupted that could not trigger the fuse, then the arc is only moderately strong anyway and thus the external effect is low.

[0010] There are various ways of causing the separating piston to separate the two separation points one after the other. In principle, this is achieved by the separating piston having two separation surfaces, namely a first separation surface for the first separation point and a second separation surface for the second separation point, the distance of the first separation surface from the first separation point being smaller than the distance of the second separation surface from the second separation point. The distance of the separating piston (seen in its direction of movement) from the first separation point is therefore smaller than the distance to the second separation point, so that the separating piston reaches the first separation point earlier than the second separation point. One way of achieving this different distance is to arrange the conductor not at a right angle to the direction of movement of the separating piston as is usual, but at an angle to it.

[0011] However, it is preferred that the two separating surfaces are offset from one another in the direction of movement of the separating piston, with the second separating surface being located behind the first separating surface. The separating piston therefore has a type of step, which makes it possible to arrange the conductor at right angles to the direction of movement of the separating piston, as is usual.

[0012] In order to ensure that the first separating surface reliably meets the first separating point, it is expedient if the separating piston is secured against rotation in the central recess, which can be achieved by having at least one point where its cross-section deviates from the circular shape.

[0013] In principle, this can be achieved by the separating piston having a lateral projection, with a corresponding groove then being provided in the central recess (or vice versa). However, this has the disadvantage that the sealing of the separating piston with respect to the central recess is thereby impaired.

[0014] It is therefore preferably provided that the igniter has an igniter overmolding and that the anti-twisting device is implemented by a point on the separating piston that interacts with a complementary point on the igniter overmolding. An igniter overmolding is normally provided anyway, so that a projection or a recess can easily be provided. A complementary recess or a complementary projection can then be provided on the separating piston, and since the igniter overmolding is rotationally fixed relative to the separator housing

The separating piston is thus fixed in a rotationally fixed manner relative to the housing, even if it has an exactly circular cross-section - which is optimal for sealing with an O-ring.

[0015] In order to ensure that the contact between the circuit board and the fuse is only established after the current isolator has been triggered, a preferred embodiment provides that a hollow cylindrical contact element is provided on the side of the circuit board facing away from the isolating piston, which is spaced apart from the circuit board when the current isolator is not triggered and is connected to one side of the fuse, the other end of which is connected to the end of the conductor adjacent to the first isolating point.

[0016] The connection to the fuse can preferably be established in that the contact element is in electrical connection at its end facing away from the circuit board with a ground contact, which in turn is connected to the fuse.

[0017] The present invention is explained in more detail with reference to the accompanying drawings. Fig. 1 shows a current isolator according to the invention before tripping, Fig. 2 shows an intermediate state; Fig. 3 shows the final state after separation; and Figs. 4-6 show another embodiment analogous to Figs. 1-3.

[0018] The current isolator 1 has a conductor 2, the middle area of which, called the circuit board 4, is delimited on the one hand by a predetermined breaking point or first separation point 5 and on the other hand by a second separation point 6 or joint point, which is achieved by reducing the thickness of the conductor cross-section. In a preferred embodiment, the weakening takes place from one side, particularly preferably with an extension of at least 1 mm, the area can also contain a further linear weakening of the thickness. These methods are particularly advantageous for thick conductors 2 (> 2 mm) in order to facilitate bending.

[0019] The conductor 2 is provided with a conductor overmolding 3 which has a central bore. The conductor overmolding 3 is closed at the bottom by a housing base 10. Above the conductor 2 there is a support ring 11 which fixes an igniter 7 and supports the conductor overmolding 3 in the radial direction.

[0020] The housing base 10 and the support ring 11 are connected by four screws (not visible in the sections through the middle of the current isolator). Polymer screws are preferred here, i.e. screws made of metal with a thread profile that is particularly optimized for the tear-out force in plastics.

[0021] The igniter 7 has an igniter overmolding 8 and an electrical interface 9, consisting of a retainer (= short-circuit ring) and igniter pins.

[0022] To transfer the pressure of the igniter 7 to the conductor 2 and to shield the separation area from the igniter gases and combustion products of the igniter 7, a separation piston 17 is provided in the central recess 13 of the conductor overmolding 3.

[0023] This separating piston 17 is either essentially rectangular in cross-section, or it has at least one point that deviates from the circular shape so that its orientation can be determined. In the example shown, this point that deviates from the circular shape is arranged at right angles to the plane of view and is therefore not visible. In the recess 13 of the conductor overmolding 3 near the igniter or particularly preferably on the igniter overmolding 8, there is a complementary point so that the separating piston 17 is held in the central recess 13 in a rotationally fixed manner. In the latter case, the two flat surfaces of the separating piston 17 and igniter 7 are oriented towards each other, and the igniter 7 is in turn oriented towards the conductor 2 during assembly.

[0024] The separating piston 17 has a first separating surface 18 and a second separating surface 19. The first separating surface 18 has a flat edge region of 1-4 mm, followed by a radius or a chamfer 20 in the direction of the second separating surface 19. The symmetrical division of the separating piston 17 between the two separating surfaces 18 and 19 is to be understood only as an example.

[0025] In order to keep the ignition gases and combustion products away from the separation area, the separating piston 17 has an O-ring 21 which, together with an O-ring 22, is mounted on the ignition encapsulation.

tongue 8 seals the pressure chamber.

[0026] If the separating piston 17 has a substantially round cross-section, the second separating point 6 (which acts as a hinge point) can be made more efficient by an incision on both sides.

[0027] If the separating piston 17 has a substantially rectangular cross-section, the two separating points 5 and 6 are straight and at right angles to the longitudinal axis of the conductor 2.

[0028] In the area of the recess 13 remote from the igniter there is a contact element 12. As can be seen in Fig. 1, there is a gap between the circuit board 4 and the contact element 12, the two parts are not electrically connected to each other.

[0029] Below the contact element 12, which can also be used to dampen the board movement, there is a ground contact 14, which is connected via a fuse 15 to the conductor end 16 of the conductor 2 facing away from the second separation point 6 (the articulation point).

[0030] The contact element 12 is preferably fixed in the housing lower part 10, for example by means of a few crimp ribs or by molding it together with the base contact 14 in the housing lower part 10.

[0031] The fuse 15 is either an external fuse (Fig. 1-3) or a fuse structure housed in the disconnector housing (Fig. 4-6).

[0032] It is particularly helpful if the ground contact 14 is made of a resilient material, such as copper-beryllium, and has a thickness of less than one millimeter. The ground contact 14 can thus be designed as a spring in the area of contact with the fuse, for example by folding up a partial area.

[0033] When the ignition pulse is applied to the electrical interface 9, the igniter 7 ignites and applies pressure to the separating piston 17. This moves away from the igniter 7 until the first separating surface 18 makes contact with the circuit board 4 and breaks through the predetermined breaking point or separating point 5. This state is shown in Fig. 2. By moving the side of the circuit board 4 away from the second separating point 6 (the hinge point) downwards, contact is made with the contact element 12 and the circuit to the fuse 15 is thus closed.

[0034] In the initial state, the contact element 12 can also be connected to the circuit board 4 instead of the ground contact 14; in this case, when the circuit board 4 is separated at the separation point 5, the connection to the ground contact 14 is established.

[0035] In both cases, it is advantageous to use the contact element 12 as a braking element in order to increase the time between the separation of the first separation point 5 and the separation of the second separation point 6. The temporal control of the separation process is carried out via the flexibility of the contact element 12.

[0036] Fig. 3 shows the final state of the separation, as in Fig. 2, the opening of the igniter 7 is not shown here either. The contact element 12 is compressed under the circuit board 4. The circuit board 4 has now also been separated at the second separation point 6 by the second separation surface 19 of the separating piston 17. If the energy in the circuit has not yet been completely used up by the fuse 15 or the fuse element, a small arc can arise which is squeezed and extinguished between the inner wall of the recess 13 and the separating piston 17.

[0037] If no current or only a small current flows in the circuit, the fuse 15 does not respond and the separation takes place by interrupting the separation point 5 and squeezing any arc that may occur after separation of the second separation point 6.

[0038] Figs. 4-6 correspond to Figs. 1-3, corresponding parts have the same reference numerals. The only difference is that in this embodiment the fuse is provided inside the housing of the current isolator. In this case the conductor overmolding 3 is pulled further downwards at least on the side remote from the second isolating point 6 (the articulation point) in order to create a chamber for the fuse 15. The fuse 15 or the fuse

The sealing structure and sand are then located within the conductor overmolding 3, and the fuse 15 is fixed by tightening the screws.

REFERENCE SYMBOL LIST:

1 current isolator

2 conductors, also called busbar

3 conductor overmolding

4 Circuit board (middle area of the conductor) 5 First separation point

6 Joint or second separation point 7 Detonator

8 igniter overmolding

9 Electrical Interface

10 housing base

11 support ring

12 contact element

13 Central recess of the conductor overmolding 14 Ground contact

15 fuse

16 Ladder end remote from the joint

17 separating pistons

18 First dividing surface

19 Second dividing surface

20th phase

21 O-ring in the separating piston

22 O-ring in the igniter overmolding

Claims (7)

patent claims 1. Pyrotechnic current isolator (1) with reduced external effect for severing a conductor (2) by means of a separating piston (17) which can be moved in a central recess (13) of the current isolator and can be driven by an igniter (7), wherein two separating points (5, 6) are provided in the conductor (2), namely a first separating point (5) and a second separating point (6), so that when the current isolator (1) is triggered, a circuit board (4) between these two separating points (5, 6) is separated from the separating piston (17), wherein a fuse (15) is provided which is normally in contact with at most one side (conductor end 16 or circuit board 4) of the first separating point (5) and is only connected to the other side (circuit board 4 or conductor end 16) of the first separating point (5) during the pyrotechnic separating process or immediately before the pyrotechnic separating process, so that the fuse (15) after the Contacting during the pyrotechnic separation process or immediately before the pyrotechnic separation process is connected in parallel only to the first separation point (5) and thus after separation of both separation points (5, 6) and extinguishment of any arcs even when the fuse (15) is intact, a galvanic separation is provided, characterized in that the separating piston (17) first separates the first separation point (5) when the current isolator (1) is triggered and bends the circuit board (4) around the second separation point (6) so that the bent circuit board (4) creates an electrical connection to the fuse (15) and only then also separates the second separation point (6) so that the fuse (15) is no longer connected in the current path of the conductor (2). 2. Pyrotechnic current separator according to claim 1, characterized in that the separating piston (17) has two separating surfaces (18, 19), namely a first separating surface (18) for the first separating point (5) and a second separating surface (19) for the second separating point (6), wherein the distance of the first separating surface (18) from the first separating point (5) is smaller than the distance of the second separating surface (19) from the second separating point (6). 3. Pyrotechnic current separator according to claim 2, characterized in that the two separating surfaces (18, 19) are offset from one another as seen in the direction of movement of the separating piston (17), the second separating surface (19) being located behind the first separating surface (18). 4. Pyrotechnic current separator according to claim 3, characterized in that the separating piston (17) is secured against rotation in the central recess (13). 5. Pyrotechnic current separator according to claim 4, characterized in that the igniter (7) has an igniter coating (8) and that the anti-twisting device is realized by a point on the separating piston (17) which interacts with a complementary point on the igniter coating. 6. Pyrotechnic current isolator according to one of claims 3 to 5, characterized in that on the side of the circuit board (4) facing away from the isolating piston (17) a hollow cylindrical contact element (12) is provided which, in the non-triggered state of the current isolator, is at a distance from the circuit board (4) and is connected to one side of the fuse (15), the other end of which is connected to the end of the conductor (2) which is adjacent to the first isolating point (5). 7. Pyrotechnic current isolator according to claim 6, characterized in that the contact element (12) is in electrical connection at its end facing away from the circuit board (4) with a ground contact (14), which in turn is connected to the fuse (15). Here 3 sheets of drawings