WO2015117878A1

WO2015117878A1 - Pyrotechnic circuit breaker

Info

Publication number: WO2015117878A1
Application number: PCT/EP2015/051753
Authority: WO
Inventors: François GAUDINAT; Alain Magne
Original assignee: Autoliv Development Ab
Priority date: 2014-02-04
Filing date: 2015-01-29
Publication date: 2015-08-13
Also published as: FR3017239A1; FR3017239B1

Abstract

A circuit breaker comprising: - a casing, - at least one electric circuit portion comprising two connection terminals and an electric conductor arranged between the two connection terminals, - a piston arranged movably so as to shift from a first position to a second position, cutting said at least one electric circuit portion into at least two separate electric conductor sections, and each section being connected to one of the connection terminals, - a pyrotechnic actuator arranged to shift the piston from the first position to the second position when it is ignited, characterised in that, when the piston is in the second position, the casing and the piston are arranged to define two distinct cutoff chambers separated by the piston, and in that each of the two sections is separated by the piston.

Description

NECK ICE RCU IT PYROTECH N IQU E

The present invention generally relates to a circuit breaker comprising a pyrotechnic actuator, intended to be mounted on a motor vehicle, and in particular on an electric vehicle.

In such electric vehicles, it is necessary to be able to cut the power lines connecting the electrical energy storage devices (batteries, super capacitors, ...) to the rest of the vehicle, to put it safe, if an accident occurs. for example. Because of the powers involved, and the characteristics of the electrical circuits, electric arcs will occur during the cut and call into question the cut of the circuit or even the integrity of the circuit breaker if these arcs are not controlled. It is known in the prior art circuit breakers such as that disclosed in EP0359467A2, and which propose specific arrangements to extinguish the arcs. In return, this system has the particular disadvantage of being bulky.

An object of the present invention is to meet the disadvantages of the documents of the prior art mentioned above and in particular, first of all, to provide a compact circuit breaker and which provides a fast cut.

For this, a first aspect of the invention relates to a circuit breaker comprising:

- a housing,

at least one electrical circuit portion comprising two connection terminals and an electrical conductor arranged between the two connection terminals,

a piston arranged to move from a first position to a second position by cutting off said at least one circuit portion; in at least two independent sections of electrical conductor, and each section being connected to one of the connection terminals, a pyrotechnic actuator arranged to move the piston from the first position to the second position when it is fired,

characterized in that, when the piston is in the second position, the housing and the piston are arranged to define two separate breaking chambers separated by the piston, and in that said at least two sections are separated by the piston.

The circuit breaker according to the present invention makes it possible to limit the formation of electric arcs between the two conductor sections, since they are separated by the piston when it is in the second position, and each conductor section opens into a single two break chambers that are separate once the pyrotechnic actuator has operated. Such arcs can be created when the circuit breaker is connected to a live electrical circuit, with voltages ranging from 0V to 600V and currents ranging from 0A to 5000A on inductive loads up to 2500μΗ (micro-Henry) for an intensity lower than 500A and up to 150μΗ for an intensity of 5000A. The circuit breaker according to the invention makes it possible to cut the current reliably in less than 10ms and even less than 5ms, in a definitive manner, since the circuit breaker, comprising a pyrotechnic actuator, can only serve times.

Advantageously, the piston is arranged to cut a bridge of said at least one circuit portion into two distinct cutoff points, and to move the cut bridge during its passage to the second position. According to this implementation, the circuit breaker cuts a bridge and the latter is led by the piston. Therefore, to ensure electrical continuity once the bridge is cut, it is necessary to form two arcs between the bridge and each conductor section, and these two arcs are in series, which automatically increases the total arc voltage, once the bridge separated from the electrical circuit portion. Advantageously, the bridge has at least one thinned portion to facilitate cutting.

Advantageously, the circuit breaker comprises at least a portion of plastic material arranged to be removed by ablation by an electric arc created during the cutting of said at least a portion. The plastic material that is removed by ablation by the electric arc is vaporized and changes the conductivity of the medium in which the electric arc is propagated, which further increases the voltage of the arc. This makes it possible to reach more quickly a total arc voltage higher than the supply voltage. The surface of the plastic material part can for example be sublimated under the action of the high heat flux created by the electric arc.

Advantageously, the housing comprises a cutting die arranged to cut in cooperation with the piston said at least a portion when the piston passes in the second position.

Advantageously, the plastic material portion at least partially covers the matrix. The plastic part partially covers the matrix, it is therefore in the immediate vicinity or is even in contact with the circuit portion at the rupture zone, that is to say where the electric arc will be formed. By being closer to the electric arc, the plastic part can be more easily removed by ablation by the electric arc confined between the piston and the plastic material.

Advantageously, each breaking chamber comprises means of extinction of the electric arc, formed by at least one stack of ferromagnetic plates electrically insulated from each other. Such an extinguishing device with ferromagnetic plates tends to divide the electric arc into a multitude of electric arcs between the ferromagnetic plates. These plates may comprise V-shaped cuts favoring movement of the arc in the plates and its division. It should be noted that the two stacks of ferromagnetic plates are separated by the piston when it is in the second position. Advantageously, the circuit breaker comprises:

a distal, conductive part forming a distal wall of each of the two chambers,

two proximal, conductive parts each forming another wall of one of each interrupting chamber,

- Two stack of ferromagnetic plates, each sandwiched between the distal part and one of the proximal parts.

Advantageously, the circuit breaker comprises plastic plates inserted between the ferromagnetic plates. The electric arcs will meet the plastic plates, part of which will be removed by ablation. It is possible to overmould or inject the plastic plates between the ferromagnetic plates. The cut is improved because the electric arcs formed between the ferromagnetic plates can easily remove plastic by ablation plastic plates which will increase the voltage of the arcs, and thus which will improve the circuit break.

Advantageously, the plastic plates comprise a central groove. The central groove forces the divided arcs to pass along the groove and ablatively remove more plastic from each plastic plate. The groove may be arranged all along each plastic plate or not.

Advantageously, one of the piston and / or the distal piece comprises an imprint arranged to receive the cut bridge, once the piston in the second position. The cut bridge is thus received by a complementary female part (impression on the piston and / or distal piece) when the piston is in the second position, so that the electric arc will preferentially be transferred to the distal piece. With no protruding part, the cut bridge can not be the starting point of an electric arc.

Advantageously, the distal piece is arranged facing all the ferromagnetic plates and / or proximal parts. Advantageously, when the piston is in the second position. The cut bridge touches the distal piece. Since the distal part is conductive, this contact with the cut bridge results in the arc being established in each interrupting chamber between the distal part and either the ferromagnetic plates or the proximal part. Even if the piston then recoils, the electric arc will remain established between the distal part and the ferromagnetic plates or the proximal part since the arc will no longer pass through the cut bridge. Thus, the entire length of each interrupting chamber is used for the expansion of the arc which optimizes the compactness of the device.

Advantageously, the piston separates the breaking chambers of a combustion chamber arranged to contain gases produced by the pyrotechnic actuator and the piston is arranged to contain the gases produced by the pyrotechnic actuator so as to avoid any increase in the conductivity. in break rooms.

Advantageously, the circuit breaker is arranged to block or hold the piston in place when the latter is in the second position. The piston can not go back to avoid the risk of electrical contact between the two sections during a possible return back. For this purpose, it is conceivable to provide sufficient sealing of the combustion chamber to obtain a maintenance of the gas pressure of the igniter and / or tight fitting of the piston in the second position.

Advantageously, the circuit breaker comprises braking means arranged to brake the piston after cutting, to prevent it from gaining speed and to limit the risk of damage to the structure (it is conceivable for example to implant ribs on the piston or on the chamber).

Advantageously, the housing and the piston comprise means for guiding the piston in the housing, and these guide means are arranged to lengthen a path for an electric arc formed directly between said at least two sections. The guide means may be a groove and an index, and by arranging them between the two breaking chambers, the path from one chamber to the other is elongated, which increases the difficulty of forming an electric arc between the two chambers. .

It is conceivable to limit the clearance between the piston and the casing to increase a plastic withdrawal by ablation of at least one of these components if an electric arc is formed between them. A clearance of less than or equal to 0.4 millimeters favors such erosion.

Advantageously, when the piston is in the second position, the bridge is placed between the piston and the distal piece. This ensures that the created arc will be cut by the stack of ferromagnetic plates. Indeed, the contact between the bridge and the distal part will have the effect of eliminating any risk of maintaining an arc between a ferromagnetic plate and the bridge that would keep the arc at the edge of the ferromagnetic plates and prevent it from dividing. The path from the bridge arc to the ferromagnetic plates is facilitated because the distal part is conductive.

Advantageously, the matrix is metallic and in contact with the two sections of the electric circuit portion and the proximal portions which makes it possible to withstand the operating constraints and to guarantee electrical continuity (with the two proximal parts) so as to facilitate the arcing between the distal and proximal portions and thereby ensuring effective cutting of said arches in the stacks of ferromagnetic plates.

Advantageously, the piston cuts a bridge of the circuit portion at two distinct cutoff points, and the piston in the second position places the bridge in abutment on the distal piece.

Advantageously, the circuit breaker comprises a vent by cutoff chamber, sealed with a cap arranged to break beyond a predetermined pressure of each breaking chamber. This implementation improves the resistance of the circuit breaker in the event of a sharp rise in temperature, which could generate too much pressure in the breaking chambers. The predetermined pressure is of course the pressure difference between the breaking chamber in question and the pressure outside the cut-off circuit (generally the atmospheric pressure).

A second aspect of the invention is a current distribution device comprising at least one circuit breaker according to the first aspect of the invention.

A third aspect of the invention is a motor vehicle comprising at least one circuit breaker according to the first aspect of the invention.

Advantageously, the vehicle comprises an electric propulsion device.

Advantageously, the vehicle comprises at least one electrical energy storage device connected to the propulsion device via said at least one circuit breaker.

Other features and advantages of the present invention will appear more clearly on reading the following detailed description of an embodiment of the invention given by way of non-limiting example and illustrated by the appended drawings, in which:

- Figure 1 shows a sectional view of a circuit breaker according to the present invention, before operation;

- Figure 2 shows the circuit breaker of Figure 1, after operation;

FIG. 3 represents an isometric view of plates included in the circuit breaker of FIG. 1.

FIG. 1 represents a circuit breaker comprising:

a housing 10,

a portion 20 of electrical circuit comprising two connection terminals 23a, 23b and an electrical conductor arranged between the two connection terminals 23a, 23b,

a piston 30 in a first position,

a pyrotechnic actuator 40 arranged to move the piston 30 from the first position to a second position (visible in FIG. 2) when it is fired.

The electrical circuit portion 20 is located between the piston 30 and a die 31, which gives into a main chamber 60. The main chamber 60 contains two separate stacks of ferromagnetic plates 51 which are separated from each other by air. As shown in FIG. 3, these ferromagnetic plates 51 each have a V-shaped end, directed towards the central part of the main chamber 60. These stackings of ferromagnetic plates 51 serve to extinguish an electric arc, as will be explained in the passages relating to Figure 2.

These ferromagnetic plates 51 are sandwiched firstly by a distal part 53 which covers at least a portion of a wall of the main chamber opposite the piston 30, and secondly by two proximal parts 54 which covers the wall of the main chamber 60 close to the matrix 31. In other words, the distal piece 53 extends above the two ferromagnetic plate stacks 51, and a proximal piece 54 is below each stack of ferromagnetic plates 51 near the matrix 31.

Figure 2 shows the circuit breaker of Figure 1, after operation. If it is necessary to open or cut the portion 20 of electrical circuit, then the pyrotechnic actuator (an electro-pyrotechnic igniter for example, well known in the technical field of air bags) is fired. The hot gases emitted by the pyrotechnic actuator have the effect of pushing the piston 30 in the housing 10, and the piston 30 passes from the first position of Figure 1 to go to a second position as shown. During its movement, the piston 30 will shear a bridge 22 of the electrical circuit portion 20, providing a punch function which cooperates with the matrix 31. Once the bridge 22 is cut, it is moved by the piston 30 , parallel to its initial position before cutting. The portion 20 of electrical circuit being subjected to a voltage, two electric arcs will be created between the sections 21a, 21b and each end of the bridge 22. The piston 30 is obviously made of insulating material and may be made of polyoxymethylene (or polyformaldehyde) ( POM), polyamide (PA6.6), or polymethylmethacrylate (PMMA).

To break the circuit, the arc voltage must be greater than the circuit voltage. The objective is therefore to achieve as soon as possible an arc voltage higher than the mains voltage, which tends to make the circuit breaker according to the invention by forming two electric arcs in series since the voltage across the terminals of the circuit breaker will be the sum of the voltages of the arcs formed.

In addition, optionally, the matrix 31 comprises an outer skin made of polyoxymethylene (or polyformaldehyde (POM) or polymethylmethacrylate (PMMA)) plastic material, and any arc created between the bridge 22 and the sections 21a, 21b must pass between the piston 30 and the matrix 31, which ablates the plastic of the matrix 31 and / or the piston 30. This ablation is due to the high heat of the electric arc and results in a gas generation ( combustion of the plastic material, or vaporization), which increases the voltage of the electric arc by reducing the conductivity of the gases present near the matrix 31.

To promote this ablation at the level of the matrix 31, one can consider choosing an adjustment between the piston 30 and the matrix 31 less than or equal to 0.4 millimeters, or even better, a tight fit (negative clearance) between these two components under condition to leave at least one controlled passage between the piston and the die 31 for the passage of the two electric arcs created. Once the piston 30 in the second position as shown in Figure 2, it separates the main chamber 60 of Figure 1 into two separate cutting chambers, and the piston thus separates the two sections 21a and 21b. The piston 30 thus forms a physical barrier between the two sections 21a and 21b and prevents the formation of electric arc between them. This makes it possible to reduce the distance between the two sections 21a and 21b, and a piston dimension of 5 millimeters ± 0.5 millimeters is quite satisfactory. The invention is however not limited to this value range, and a reduction in size is still possible.

Following the formation of the two electric arcs during the cut, each of them will be trapped in one of the breaking chambers when the piston is in the second position. As explained above, each interrupting chamber comprises a stack of ferromagnetic plates 51 electrically insulated from each other, with a Vee notch facing the piston 30, and arranged between the distal piece 53 and a proximal piece 54. This arrangement has the effect of causing a Laplace force on each electric arc, which tends to push the arches towards the bottom of the V-notch and cut them into sub-arcs.

As seen in FIG. 2, the piston 30 pushes the bridge 22 into contact with the distal piece 53. In each chamber, this has the effect of allowing the electric arc to pass from the bridge 22 to the distal piece 53. to be established between the latter and the ferromagnetic plates 51 or the proximal piece 54.

This passage from the electric arc of the bridge 22 to the distal part 53 is favored by the fact that the distal piece is arranged opposite each stack of ferromagnetic plates 51 and the proximal parts, as shown in FIG.

In case of recoil of the piston 30, the electric arc will remain established between the distal part 53 and either the ferromagnetic plates 51 or the proximal part 54 since the arc will then no longer pass through the cut bridge. it makes it possible to improve the robustness of the device and the extinction of the electric arc in each interrupting chamber, since this guarantees that the length of the arc remains maximal regardless of the position of the bridge 22 once this touched the distal piece.

The invention further proposes optionally to insert between each ferromagnetic plate 51 a plastic plate 52 of the polyoxymethylene (or polyformaldehyde (POM) or polymethyl methacrylate (PMMA) type.These plastic plates 52 are shown in FIG. comprise a central groove preferably in the axis of the V-notches for passing the electric arc between the ferromagnetic plates 51. A typical thickness of each plastic plate 52 is from 0.5 millimeters to 2 millimeters, and the central groove may have a width between 0.5 millimeters and 2 millimeters.

It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to the various embodiments of the invention described in the present description without departing from the scope of the invention defined by the appended claims. In particular, certain plastics have been cited as examples for the piston 30, the matrix 31 and the plastic plates 52, and it should be noted that each component having its specificities, different materials can be chosen for each piece .

Claims

1. Circuit breaker comprising:

a housing (10),

at least one portion (20) of electrical circuit comprising two connection terminals (23a, 23b) and an electrical conductor arranged between the two connection terminals (23a, 23b),

a piston (30) arranged movable to move from a first position to a second position by cutting said at least one portion (20) of electrical circuit into at least two independent electric conductor sections (21a, 21b), and each section being connected to one of the connection terminals (23a, 23b),

a pyrotechnic actuator (40) arranged to move the piston (30) from the first position to the second position when it is fired,

characterized in that, when the piston (30) is in the second position, the housing (10) and the piston (30) are arranged to define two separate breaking chambers separated by the piston (30), and in that said at least two sections (21a, 21b) are separated by the piston (30).

2. Circuit breaker according to the preceding claim, wherein the piston (30) is arranged to cut a bridge (22) of said at least one portion (20) of circuit at two distinct cut-off points, and to move the bridge ( 22) cut when passing to the second position.

3. Circuit breaker according to one of the preceding claims, comprising at least a portion of plastic material arranged to be removed by ablation by an electric arc created during the cutting of said at least a portion (20).

4. Circuit breaker according to the preceding claim, wherein the housing (10) comprises a cutting die (31) arranged to cut in cooperation with the piston said at least a portion when the piston (30) passes into the second position, and wherein the plastic material portion at least partially covers the die (31).

5. A circuit breaker according to one of claims 1 to 4, wherein each arc chute comprises means for extinguishing the electric arc, formed by at least one stack of ferromagnetic plates (51) electrically isolated from each other. other.

6. Circuit breaker according to the preceding claim comprising:

a distal piece (53), conducting and forming a distal wall of each of the two chambers

two proximal pieces (54), each conducting and forming another wall of one of each interrupting chamber,

- Two stack of ferromagnetic plates (51), each sandwiched between the distal part (53) and one of the proximal parts (54).

7. Circuit breaker according to one of claims 5 or 6, comprising plastic plates (52) inserted between the ferromagnetic plates.

(51).

8. Circuit breaker according to the preceding claim, wherein the plastic plates (52) comprise a central groove.

9. Circuit breaker according to one of claims 6 to 8, wherein one of the piston (30) and / or the distal piece (53) comprises a recess arranged to receive the cut bridge (22), once the piston (30) in the second position.

10. Circuit breaker according to one of the preceding claims, wherein the housing (10) and the piston (30) comprise guide means of the piston (30) in the housing (10), and these guide means are arranged to lengthen a path for an electric arc formed directly between said at least two sections (21a, 21b).

11. Circuit breaker according to one of the preceding claims, comprising a vent of each interrupting chamber, sealed with a operculum arranged to break beyond a predetermined pressure of each breaking chamber.

12. Current distribution device comprising at least one circuit breaker according to one of the preceding claims.

Motor vehicle comprising at least one circuit breaker according to one of claims 1 to 11.

14. Motor vehicle according to the preceding claim, comprising an electric propulsion device.