DE212019000419U1 - Pyrotechnic isolator - Google Patents

Abstract

Pyrotechnic current isolator (1) with a housing in which an igniter (15), a pressure piston (11), an extinguishing agent (13) for extinguishing an arc that occurs during the cutting process and a cutting punch (14) are arranged one behind the other, the package of pressure piston (11), extinguishing agent (13) and separating punch (14) can be driven by the detonator (15), a conductor (2) also being passed through the housing, from which when the detonator (15) is ignited by the separating punch (14) a circuit board (3) can be separated so that after the separation process two conductor ends (2a, 2b) remain with a distance between them, characterized in that during the separation process the extinguishing agent (13) is already in the area where the conductor (2) passes the housing occurs before the current flow is completely interrupted.

Description

Technical area

The present invention relates to a pyrotechnic current isolator with a housing in which a separating ram is guided, which can be driven by an igniter, wherein a conductor is also passed through the housing, from which a circuit board can be separated when the igniter is ignited by the isolating ram, so that After the cutting process, two conductor ends remain with a distance between them, and furthermore - seen in the direction of movement of the cutting punch - an extinguishing agent is provided behind the cutting punch to extinguish an arc that occurs during the cutting process.

State of the art

Pyrotechnic current isolators have become a common part of the safety concept in electric vehicles in the event of an accident. While it was only the 12 V battery that was disconnected in conventional vehicles, batteries with voltages of up to 1000 V must be reliably disconnected in hybrid vehicles and fully electric vehicles. As a result of the need for greater efficiency, the internal resistances of the batteries decrease and the short-circuit currents that can be achieved, which have to be interrupted, also increase.

The market offers a wide variety of pyrotechnic current isolators, for example the one in the EP 3103131 A described current isolator, which is marketed under the name PSS 4 by Autoliv.

The applicant was also informed in WO 2017/066816 A such a current isolator described. This document discloses the preamble of claim 1. Although these current isolators can separate medium to high currents, they generate massive external effects during the separation process in the form of the escape of hot gases or particles that can cause short circuits in switch boxes and thus undermine or cancel the protective principle of the current isolator can even lead to fires.

As was established within the scope of the present invention, this is due, among other things, to the fact that the area where the conductor is led into or out of the housing cannot be adequately sealed (at least not with reasonable effort), so that hot gases and particles between the conductor and the housing can penetrate to the outside.

Presentation of the invention

It is therefore the object of the present invention to create a current isolator in which the external effect is reduced to a minimum.

This object is achieved according to the invention by a pyrotechnic current isolator of the type mentioned at the outset in that, during the cutting process, the extinguishing agent is already in the area where the conductor passes through the housing before the current flow is completely interrupted.

The extinguishing agent is under high pressure during the separation process. If it is already in the area where the conductor passes through the housing before the arc occurs, the separating agent acts as an additional seal that seals the gap between the conductor and the housing. Such a circuit breaker therefore has only a minor external effect.

One possible embodiment provides that the conductor is bent in a U-shape, the board to be punched out being in the back of the U and the back of the U - seen in the direction of movement of the cutting punch - lying in front of the area where the conductor passes through the housing .

Another possible embodiment provides that the conductor is essentially flat, and that the two conductor ends each have a contact that protrudes from the conductor ends in the direction of movement of the separating punch, so that an electrical connection continues to be made from one conductor end immediately after the circuit board has been separated whose contact to the board and from this board is via the contact of the other end of the conductor to the other end of the conductor. So there are two contacts attached to the conductor, namely at the edge of the (future) conductor ends, so that an electrical connection continues to exist immediately after the mechanical separation. The two contacts thus continue to enable a current to flow over the board even after the mechanical separation of the conductor with a maximum of short arcs between the contact and the board. When moving the board between the contacts, only arcs with a length of less than 2 mm should occur. The electrical separation only takes place after the circuit board has left the contacts. Since the arcs that occur here are only small, the energy released and thus the external effect are low. Only when the circuit board leaves the contacts does a large arc occur, but at this point the extinguishing agent is already in the plane of the conductor and seals the gap between the conductor and the housing. This also improves the separation efficiency because the gases are left in place step out of the housing through an opening, the separation performance is significantly impaired.

When the circuit board leaves the area of the contacts, electrical separation begins by elongating the arcs and interacting with the extinguishing agent. The release of the resulting gases is made more difficult because the extinguishing agent is already in the conductor level and seals the gap between the housing and conductor.

The distance between the cutting punch and the housing is preferably a maximum of 1 mm, preferably a maximum of 0.5 mm. As a result, the arcs are squeezed between the cutting punch and the housing wall, which improves the extinguishing effect. This means that there is only a narrow gap for the arcing between the separating piston and the housing wall after leaving the circuit board in the area of the contacts.

The contacts are preferably part of the conductor. This simplifies production.

The extinguishing agent preferably contains silicone. Silicone has the advantage of sealing gaps well in addition to the extinguishing effect. According to the invention, two effects are achieved: firstly, the at least partially closing of the area of the gap between the conductor and the housing with the extinguishing agent creates a higher internal pressure, and secondly the extinguishing agent cools any gases that may still be escaping.

The external effect can be further reduced if the circuit breaker has an additional housing. It is particularly favorable if there is energy-absorbing material in the additional housing, preferably glass, stone or mineral wool.

Brief description of the drawings

The present invention is explained in more detail with the aid of the accompanying drawings. It shows: 1 a current isolator according to the invention in the starting position; 2 the same immediately after its release; 3 the same in the end position after it has been triggered; 4th the current intensity as a function of time, both of a known current isolator and of the current isolator according to the invention; 5 shows the voltage as a function of time again of the known current isolator and the current isolator according to the invention; 6th shows the performance as a function of time again of the known current isolator and the current isolator according to the invention; and 7th the external effect as a function of time, in turn, of the known current isolator and the current isolator according to the invention.

Best way to carry out the invention

• 1 shows a current isolator according to the invention 1 in the starting position. The power isolator 1 owns a leader 2 . The head 2 has a middle area 3 through predetermined breaking points 4a , 4b from the rest of the leader 2 is delimited. This results in conductor ends 2a , 2 B . Will this middle area 3 from the head 2 broken out, it is also referred to as a circuit board. In the form shown, the circuit breaker has 1 an upper part of the housing 5 and a lower housing part 6th . These are made by reinforcement plates 7th , 8th and screws (only two screws are visible in the section 9a and 9b ) held together in an electrically conductive manner. All screws go on the side of the ladder 2 past. The power isolator 1 thus owns one from the head 2 insulated, electrically conductive housing that can be connected to vehicle ground if necessary.

The upper part of the housing 5 has a hole inside 10 in which there is a plunger 11 with O-ring 12th , an extinguishing agent 13th and a separator 14th with O-ring 14 ' is located. For tripping the circuit breaker 1 is an electric detonator 15th provided by an extrusion coating 16 who have favourited a steel washer 17th is held in position.

The lower part of the housing 6th also has a hole inside 18th , in which there is a braking element 19th and a floor 20th are located. The floor 20th can be a hole 21 own. This represents an additional volume when the braking element 19th is squeezed during triggering.

The head 2 has two electrical contacts 23a , 23b extending from the conductor in the direction away from the fuse. The distance between the two contacts 23a , 23b is designed to be the size of the board 3 is equivalent to.

2 shows the isolator 1 shortly after tripping. The pressure of the detonator 15th after the release presses over the plunger 11 , the extinguishing agent 13th and the separator 14th on the board 3 and breaks it along the predetermined breaking points 4a , 4b from the head 2 . The entire package (pressure piston 11 , Extinguishing agent 13th , Separator 14th , Circuit board 3 ) in the direction away from the ignition. The board moves 3 along the contacts 23a , 23b . The braking element 19th is compressed and stabilizes the movement of the board 3 . Is the head 2 when removing the board 3 When current flows through it, two arcs are formed between the conductor ends 2a , 2 B or the contacts 23a , 23b and the board 3 out. However, these have only a very short length and thus a low energy input. The leader is in this state though mechanically separated, but nevertheless - at least at higher currents - electrically connected.

In 2 is the circuit board 3 at the ends of the (sliding) contacts remote from the fuse 23a , 23b . The following leaves the board 3 the area of the (sliding) contacts 23a , 23b , the arcs between the ends of the (sliding) contacts 23a , 23b and the board 3 become longer and the actual deletion process begins. The extinguishing agent is at this point in time 13th already at the level of the head 2 and fills any gaps between the ends of the conductors 2a , 2 B and upper part of the housing 5 and lower part of the housing 6th off when pressurized. The ends of the ladder 2a , 2 B are means of holes 24a , 24b in which there are pens 25a , 25b are fixed in the housing. In this arrangement, the parting line is between the upper part of the housing 5 and lower part of the housing 6th separated from the location of the arcing and protected by the extinguishing agent. A direct escape of hot gases along the conductor 2 is thus avoided. Closing the housing with the extinguishing agent increases the pressure in the housing at the same time, which means that the arcs can be extinguished more easily.

3 shows the end position of the cutting punch 14th and board 3 . The braking element 19th is squeezed. The electrical resistance of the circuit breaker increases up to this position 1 by lengthening the arcs between the board 3 and ends of the (sliding) contacts 23a , 23b what results in an increase in the voltage curve (see below 5 ) indicates. It is particularly advantageous if the arc has already been extinguished when the board has reached the lower position.

In 4th the current curve 31 of a conventional, known circuit breaker and the current curve 32 of a circuit breaker according to the invention can be seen. Both curves start at a current strength of 17 kA. The starting point is the mechanical separation of the conductor, which can be recognized by a change in voltage on the current isolator. The curve of the known circuit breaker begins to decrease rapidly, while the curve of the circuit breaker according to the invention shows a kind of plateau as long as the board is in the area of the contacts. After leaving the area of the contacts, the current curve shows a strong drop, which speaks for a good extinguishing effect. The separation time is 0.65 ms for the known current isolator and 0.49 ms for the current isolator according to the invention.

The voltage curves in 5 show the same behavior pattern. In the case of curve 31 of the conventional current isolator, the voltage rises rapidly because the resistance increases due to the elongation of the arcs, while the resistance and thus also the voltage on the current isolator according to the invention (curve 32) remains largely constant for up to approx. 0.2 ms. After leaving the area of the contacts, the voltage, which represents the internal resistance, begins to rise sharply because the arcs elongate and they are in contact with the extinguishing agent. The final extinguishing peak of the curve of the current isolator according to the invention is cut off at approx. 2100 V, which is due to the measuring range of the devices used. After disconnection, the source voltage of 500 Van is applied to both current isolators.

The power curves, which are calculated from current multiplied by voltage, are also shown in 6th show the behavior of the two current isolators. While the power loss 31 of the known current isolator begins to rise rapidly, the power 32 of the current isolator according to the invention initially has a plateau and then begins to rise. The area under the power curves corresponds to the energy. It is significantly influenced by the energy E _Ind , which is stored in an inductance L at a current I (E _Ind = I ² · L / 2). In addition, there is an ohmic component that increases the longer the separation process lasts and the longer the arc continues to burn. The known current isolator shows a somewhat higher energy than the current isolator according to the invention.

To quantify the external effect, the power isolators were filmed using a high-speed camera under identical conditions (shutter, aperture, ...) with 120 k FPS. For the analysis, the pixels of each video frame were examined in the HSV color space (HSV = Hue Saturation Value, i.e. hue, saturation, brightness). The HSV color space is a cylindrical color coordinate system in contrast to the RGB color space, which is a Cartesian color coordinate system. The advantage of the HSV system is that the brightness (value) can be assessed independently of the hue (hue) and the color saturation (saturation). This makes it easier to detect the external impact, since only one value has to be assessed. The maximum value that the V value change can reach is by definition 1.

To evaluate the external effect, the number of pixels was counted that exceeded a lower limit of the V value change in the course of the recording and this number was set in relation to the total number of pixels.

The lower limit of the change in V value, from which an external effect is counted, was chosen so that the known current isolator has an external effect of almost 100%. The current isolator according to the invention only has a maximum value of 30%, i.e. the external effect is reduced by more than half.

7th shows the course of the external impact over time. While the normal power isolator ( Curve 31) shows the external effect immediately at the beginning of the separation process, in the case of the current isolator according to the invention (curve 32) this does not occur until later and with much lower intensity. Strictly speaking, most of the hot gases only appear after the separation process has been completed.

The reduction of the external effect can be further improved by housing the isolator, especially if there is energy-absorbing material in the housing, e.g. glass wool, rock wool or mineral wool. This allows the external effect to be suppressed under the visual observability.

List of reference symbols

1

Isolator

2

ladder

2a, 2b

Ladder ends

3

middle area of 2 or board

4a, 4b

Predetermined breaking points

5

Housing upper part

6th

Housing base

7th

Reinforcement plate

8th

Reinforcement plate

9a, 9b

Screws

10

drilling

11

Plunger

12th

O-ring

13th

Extinguishing agent

14th

Separator

14 '

O-ring

15th

Detonator

16

Encapsulation

17th

Steel washer

18th

drilling

19th

Braking element

20th

floor

21

drilling

23a, 23b

contacts

24a, 24b

Holes

25a, 25b

pencils

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 3103131 A [0003]
• WO 2017/066816 A [0004]

Claims (8)

Pyrotechnic current isolator (1) with a housing in which an igniter (15), a pressure piston (11), an extinguishing agent (13) for extinguishing an arc that occurs during the cutting process and a cutting punch (14) are arranged one behind the other, the package of pressure piston (11), extinguishing agent (13) and separating punch (14) can be driven by the detonator (15), a conductor (2) also being passed through the housing, from which when the detonator (15) is ignited by the separating punch (14) a circuit board (3) can be separated so that after the separation process two conductor ends (2a, 2b) remain with a distance between them, characterized in that during the separation process the extinguishing agent (13) is already in the area where the conductor (2) passes the housing occurs before the current flow is completely interrupted. Isolator after Claim 1 , characterized in that the conductor (2) is bent into a U-shape, with the board to be punched out being located in the back of the U and with the back of the U lying in front of the area where the conductor (2 ) passes through the housing. Isolator after Claim 1 , characterized in that the conductor (2) is essentially flat, and that the two conductor ends (2a, 2b) each have a contact (23a, 23b) which is separated from the conductor ends (2a, 2b) in the direction of movement of the cutting punch (14) ) so that immediately after the circuit board has been cut, an electrical connection continues from one conductor end (2a) via its contact (23a) to the circuit board (3) and from this circuit board (3) via the contact (23b) of the other conductor end (2b) to the other end of the conductor (2b). Isolator after Claim 3 , characterized in that the distance between the cutting punch (14) and the housing is a maximum of 1 mm, preferably a maximum of 0.5 mm. Isolator after Claim 3 or 4th , characterized in that the contacts (23a, 23b) are part of the conductor (2). Power isolator according to one of the Claims 1 until 5 , characterized in that the extinguishing agent (13) contains silicone. Power isolator according to one of the Claims 1 until 6th , characterized in that the current isolator (1) has an additional housing. Isolator after Claim 7 , characterized in that there is energy-absorbing material in the additional housing, preferably glass, stone or mineral wool.

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