Pyrotechnic switch

Abstract

Pyrotechnic switch, comprising: - a housing (10), - at least one electrical conductor (20) passing through the housing (10), - a piston (30) housed in the housing (10), the piston (30) - housing (10) assembly being arranged to cut the electrical conductor (20) at least at three distinct locations, so as to form at least two free conductive strands (21, 22), distinct from the rest of the electrical conductor (20), - a pyrotechnic actuator arranged to force the piston (30) to cut the electrical conductor (20), characterized in that the piston (30) - housing (10) assembly is arranged to - cut the electrical conductor (20) so that each free strand (21, 22) has at least one base portion with either none or two folded wings (22B, 22C) arranged on either side of the base portion and to - generate at least one free strand (22) with two wings folded (22B, 22C).

Description

[0001] The present invention generally relates to a pyrotechnic switch for cutting an electrical circuit, for example for cutting an electrical power circuit of a motor vehicle in the event of an accident.

[0002] Pyrotechnic switches are known in the prior art, such as that disclosed in document DE102012212509. In return, this system has the disadvantage of presenting a risk of variable operation (depending on the cutting conditions of the electrical conductor).

[0003] An aim of the present invention is to address the drawbacks of the prior art mentioned above and in particular, first of all, to propose a pyrotechnic switch which has a reliable circuit break with predictable and controlled current cut-off conditions.

[0004] For this, a first aspect of the invention concerns a pyrotechnic switch, comprising: a housing, at least one electrical conductor passing through the housing, a piston housed in the housing, the piston-housing assembly being arranged to cut the electrical conductor at least at three distinct locations, so as to form at least two free conductive strands, distinct from the rest of the electrical conductor, a pyrotechnic actuator arranged to force the piston to cut the electrical conductor, characterized in that the piston-housing assembly is arranged to cutting the electrical conductor so that each free strand has at least one base portion with either none or two folded wings arranged on either side of the base portion and to generate at least one free strand with two folded wings.

[0005] The pyrotechnic switch according to the above implementation cuts the electrical conductor into several strands, which improves the cutting capacity of the switch. Indeed, cutting in several places amounts to extending the length of a possible electric arc. In addition, each free strand comprises either only a base portion (not deformed), or a base portion with two folded wings. In other words, each free strand is either a straight or flat base portion, or a base portion framed by two folded wings. Thus, the free strands are symmetrical, which guarantees a balanced cut on each side: the forces are similar at each end of the free strands, which limits the risks of displacement during cutting and therefore of erratic operation which can affect the performance and / or integrity of the switch.Indeed, similar or symmetrical forces at the ends of each free strand will guarantee stability and the absence of untimely movements during or after the cut. Such untimely movements of conductive elements can either cause unwanted arcing conditions that can affect the performance of the device and / or cause mechanical stresses, due to jamming for example, that can affect the integrity of components.

[0006] The pyrotechnic switch according to the above implementation therefore comprises a piston which is movable between a rest position (in which the electrical conductor is a continuous part and can conduct electricity), and an activated position (in which the electrical conductor is no longer intact and can no longer conduct electricity). The transition from the rest position to the activated position is caused by the pyrotechnic actuator, itself triggered or ignited, for example by an electronic unit or card of the vehicle. Finally, the transition from the rest position to the activated position therefore causes the electrical conductor to be cut, the formation of several free strands, and the bending of some of the free strands. The bent free strands therefore have a different shape before and after being cut.

[0007] However, each free strand includes a base portion (with or without bent wings) and this base portion is undeformed. That is, the base portion is a portion of the electrical conductor having the same shape before and after activation of the circuit breaker. In other words, each free strand includes a portion (the base portion) that has the same geometry as the initial electrical conductor before cutting.

[0008] In particular, the base portion may not undergo plastic deformation when cutting the initial electrical conductor.

[0009] In particular, the base portion may simply undergo a translation during the cut, and in the final position, may end up parallel to its initial position.

[0010] In particular, the base portion may be parallel to a bearing surface of the piston, itself preferably perpendicular to a direction of movement of the piston.

[0011] According to one implementation, the circuit breaker may be arranged to cut the electrical conductor by shearing. In particular, the piston of the circuit breaker may comprise a bearing surface which receives the base portion of each free strand without deforming it, and at least two cutting angles arranged on either side of the bearing surface, arranged to cut the electrical conductor by shearing.

[0012] According to one implementation, the bearing surface can be framed by two protrusions of the piston, and the two cutting angles can each be arranged on one of the protrusions, and preferably on a flank of each protrusion opposite the bearing surface, so as to form a free strand with an undeformed base portion and two folded wings, or preferably on a flank of each protrusion adjacent to the bearing surface, so as to form a free strand with an undeformed base portion and without any folded wings.

[0013] According to one implementation, at least one free strand, and preferably each free strand, may have at least one reference portion which may occupy the same position in the housing before and after cutting. Such an implementation makes it possible to limit the movements of the electrical conductor and the free strands during cutting, which further limits the risks of non-reproducibility.

[0014] According to one implementation, the piston-housing assembly may be arranged to block at least one movement of each free strand after cutting. In other words, each free strand, whether it consists of a single base portion or of a base portion and two folded wings, is held, retained or blocked in place by the piston-housing assembly.

[0015] According to one implementation, the piston-housing assembly may have cutting protrusions, so that after cutting: a free strand with no bent wings may be arranged between two cutting protrusions with a clearance of less than 1 mm and preferably a clearance of less than 0.5 mm, and / or a free strand with two bent wings may be arranged with a cutting protrusion of one of the piston-housing assembly between the two bent wings, and with two adjacent cutting protrusions of the other of the piston-housing assembly each capable of contacting one end of each bent wing.

[0016] According to the above implementation, a cutting protrusion means a protrusion or projection which exerts a cutting force, and / or on which the electrical conductor rests at least for a moment of cutting. These protrusions can be on the housing or integral with the latter (therefore considered static), or on the piston or integral with the latter (therefore considered mobile).

[0017] According to the implementation above: a free strand without bent wings has a cutting protrusion from one of the piston-housing assembly opposite or at its base portion, and has its ends in contact or nearly in contact with two adjacent cutting protrusions from the other of the piston-housing assembly: it cannot move in the direction of its length; a free strand with two bent wings has a cutting protrusion from one of the piston-housing assembly opposite or at its base portion, and two adjacent cutting protrusions from the other of the piston-housing assembly each in contact with one end of the free strand (the free ends of each bent wing). Thus each free strand, once separated from the electrical conductor, is held at its ends by cutting protrusions.

[0018] According to one implementation, a free strand with no folded wings may be arranged in an enclosed space defined between at least: a cutting protrusion of one of the piston-housing assembly, and two cutting protrusions of the other of the piston-housing assembly.

[0019] Depending on an implementation, the cutting protrusions may have clearance angles.

[0020] According to an implementation: the piston may include cutting protrusions forming knives, the housing may include cutting protrusions forming dies, and, after cutting, each knife of the piston may be arranged between two dies.

[0021] According to one implementation, after cutting, at least one relief face, and preferably each relief face, of each knife may be opposite a relief face of a die. This implementation ensures that the piston reliably closes a volume around the free strands. Indeed, the relief faces bear on each other, and since the reliefs are reversed, the contact between the knives of the piston and the dies of the housing is a surface type contact. Any electric arc is then reliably confined, and any leakage path is over a long distance, between two parts in surface contact.

[0022] According to one implementation, after cutting, each knife of the piston can be arranged between two faces of a die, and preferably between two relief faces of a die. In other words, a die can be provided on either side of each knife, even with regard to the side knives: a side die can be provided on each side of the housing to provide a relief face opposite each side knife.

[0023] Depending on the implementation, the dies may be integral or formed directly with the housing.

[0024] According to one implementation, the clearance angle of one of the piston / housing assembly is equal to the clearance angle of the other of the piston / housing assembly. According to this implementation, the side faces (in clearance) of the piston and the housing are parallel to each other.

[0025] In one implementation, the clearance angle of one of the piston / housing assembly is different from the clearance angle of the other of the piston / housing assembly, and contained within the friction cone of the contacting clearance surfaces. In this implementation, the side (clearance) faces of the piston and the housing are not parallel to each other, but the difference in angle is less than the friction angle, so that there is wedging between the surfaces once the piston is in the activated position, so that it remains in this position. In particular, if the surfaces are made of plastic, then the difference in clearance angles will remain less than 5°.

[0026] According to one implementation, the folds of a free strand with two folded wings can be symmetrical.

[0027] According to one implementation, the pyrotechnic switch may comprise, after cutting, two separate elements including: a free strand with a base portion without folded wings, a free strand with a base portion with two folded wings.

[0028] In other words, there is a free strand that is straight, rectilinear or not deformed by the passage of the piston (base portion only) and a bent strand with two bent wings. Generally speaking, the cut is made by generating an alternation of free strands without bent wings and free strands with two bent wings.

[0029] According to an implementation: the piston may have an axis for applying a thrust force of the pyrotechnic actuator, the piston-housing assembly may be arranged to cut the electrical conductor at points located at a predetermined distance from the axis for applying force, and the sum of the predetermined distances of the points located on one side of the force application axis may be equal to the sum of the predetermined distances of the points located on the other side of the force application axis. The position of the cutting points along the electrical conductor is distributed so that the force application axis passes through the middle, which guarantees an absence of overturning torque on the piston. The latter will therefore have a regular and easy movement from the rest position to the activated position, with a limited risk of buckling or jamming.

[0030] According to one implementation, the electrical conductor may have at least a first portion anchored in the housing, and a second portion facing the piston, and the second portion may have a cross-sectional area smaller than a cross-sectional area of ​​the first portion. The second portion is typically the one on which the piston will exert its cutting force, it is weaker, so the first portion will be subjected to little stress. Breakage is guaranteed in the second portion.

[0031] According to one implementation, the first portion may be overmolded in a material forming a separate part of the housing. In conjunction with the implementation where the piston knives come between dies of the housing, this implementation makes it possible to facilitate manufacturing with adequate clearances even for overmolding the electrical conductor, while ensuring that the piston comes into surface contact on the housing, in the activated position.

[0032] According to one implementation, the piston and / or the housing may comprise at least one insert at a cutting protrusion.

[0033] Depending on one implementation, after cutting, the free strands can be trapped in the housing.

[0034] Depending on the implementation, the pyrotechnic switch may include non-return elements. It is possible to consider a tight mounting, a wedging at the end of the piston stroke, or even an engagement with a non-return tab, for example.

[0035] A second aspect of the invention relates to a motor vehicle comprising at least one pyrotechnic switch according to the first aspect of the invention.

[0036] It is understood that all the above technical characteristics may be combined with each other or separated from each other as long as there is no technical inconsistency or incompatibility.

[0037] Other characteristics and advantages of the present invention will appear more clearly on reading the following detailed description of embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which: [ fig. 1 ] represents a schematic view of a first implementation of a pyrotechnic switch according to the invention, before triggering; [ fig. 2 ] represents the pyrotechnic switch of the figure 1 , after triggering; [ fig. 3 ] represents a schematic view of a second implementation of a pyrotechnic switch according to the invention, before triggering; [ fig. 4 ] represents the pyrotechnic switch of the figure 3 , after triggering; [ fig. 5 ] represents a schematic view of a third implementation of a pyrotechnic switch according to the invention, before triggering; [ fig. 6 ] represents the pyrotechnic switch of the figure 5 , after triggering; [ fig. 7 ] represents a detailed section of the pyrotechnic switch of the figure 1 ; [ fig. 8 ] represents a detail of the figure 7 to show an aspect of the invention; [ fig. 9 ] represents the detail of the figure 8 , to show another aspect of the invention.

[0038] There figure 1 represents a pyrotechnic switch which comprises a housing 10 consisting of an upper housing part 10A and a lower housing part 10B. An electrical conductor 20 passes through the housing 10 and a piston 30 is located under the electrical conductor 20, and a pyrotechnic actuator (an electro-pyrotechnic igniter 40) is provided integral with the lower housing part 10B.

[0039] In reference to the figure 7 , more detailed, the piston 30 is mounted mobile relative to the housing 10, between a rest position (on the figures 1 And 7 ) and an activated position (on the figure 2 ). The electro-pyrotechnic igniter 40 opens onto a combustion or pressurization chamber 41, so that the triggering of the electro-pyrotechnic igniter 40 causes a sudden rise in pressure in the combustion chamber 41, which causes the piston 30 to move from the rest position to the activated position.

[0040] Typically, the triggering of the electro-pyrotechnic igniter 40 is caused by an electronic control unit, after detection of a situation where the electrical conductor 20 must be cut (for example a vehicle impact, if the electrical conductor 20 is part of an electrical circuit comprising batteries to be isolated after impact).

[0041] During this passage of the piston 30 from the rest position to the activated position, the electrical conductor 20 is cut by cutting protrusions provided on the piston 30 - housing 10 assembly. In detail, the piston 30 - housing 10 assembly comprises cutting protrusions (or cutting and folding as explained below) which are dies 11 on the housing 10 (11A, 11B, 11C, 11D on the figure 7 only) and knives 31 on piston 30 (31A, 31B, 31C on the figure 7 ). As visible figures 1 And 7, before triggering, the electrical conductor 20 is arranged between the cutting protrusions of the housing 10, i.e. the dies 11 (11a, 11B, 11C, 11D on the figure 7 , this will not be repeated in the rest of the description) of the housing 10, and the cutting protrusions of the piston 30, that is to say the knives 31 (31A, 31B, 31C on the figure 7 , this will not be repeated in the rest of the description) on the piston 30.

[0042] When the piston 30 rises after triggering, the knives 31 will cut the electrical conductor 20 then resting on the dies 11.

[0043] The electrical conductor 20 is then cut at three points and two free strands 21 and 22 are created or formed, as shown in figure 2 . These free strands 21 and 22 are detached from the rest of the electrical conductor and as visible on the figure 2 , the free strand 21 comprises only a rectilinear base portion (or not deformed by the knives / dies, i.e. whose shape is identical before and after cutting), and the free strand 22 comprises a base portion 22A, with two folded wings 22B and 22C.

[0044] In addition, each end of the free strand 21 is in contact with one of two adjacent punches 31 of the piston 30, and the ends of the folded wings 22B and 22C are also each in contact with one of two adjacent punches 31 of the piston 30. Thus, each free strand is locked in the position occupied on the figure 2 . In particular, the free strands 21 and 22 cannot move in the axial direction of the conductor 20 before triggering (the horizontal direction of the figure 2 ).

[0045] Safety and reliability are improved because the path of a possible arc is that between the ends in the position shown figure 2 . In fact, the unforeseen movements and displacements of the free strands 21 and 22 are eliminated, because the free strands 21 and 22 are held in position or blocked by the cutting protrusions (the dies 11 and the knives 31 which bear on each other to form closed spaces, and which touch the free strands so as to block them). The conditions for establishing an arc will thus always be the same on a series of switches. Furthermore, there is no risk of the piston 30 becoming stuck due to a free strand not remaining in place.

[0046] Furthermore, back to the figure 7 , it should be noted that the electrical conductor 20 is overmolded in an attached portion 23, which is distinct from the upper 10A and lower 10B housing parts. As shown in the figure 8 , this construction, makes it possible to provide reliefs on the cutting protrusions located on the housing 10 which allow an additional technical effect.

[0047] Indeed, by focusing on the right cutting protrusions (the 11D die and the 31C knife of the figure 8 ), we see that the side face 31Cs of the knife 31C has a draft angle, which improves the manufacturing of the part by injection molding. In the same way, the side face 11Ds of the die 11D has a draft angle. Since the die 11D is not overmolded on the electrical conductor 20 (since it is the added portion 23 which is overmolded on the electrical conductor 20), then the draft angle of the side face 11Ds of the die 11D is effectively complementary to the draft angle of the side face 31Cs of the knife 31C. It should be noted that such a complementary angle cannot be obtained on the added portion 23 by injection molding.

[0048] Consequently, when the piston 30 is in the activated position, then the lateral face 11Ds of the die 11D can be in surface contact with the lateral face 31Cs of the knife 31C (and not in linear contact). It should be noted that what is said here is valid for each cutting protrusion: each punch 31 of the piston 30 of the switch has at least one lateral face which will come into surface contact with a lateral face of a die 11 of the housing 10 (that is to say with a relief complementary to a relief of the lateral face of the die concerned). This creates a succession of closed spaces with surface contacts. This makes it possible to control the path of an electric arc by defining a specific non-contact zone such as a groove to force the arc path always in the same place.

[0049] It should be noted that in this first embodiment, the cutting of the electrical conductor 20 is a shearing carried out at the level of the die 11B with the knives 31A and 31B, and at the level of the die 11D with the knife 31C. The dies 11A and 11C serve as a fulcrum to force the bending of the electrical conductor 20 and the free strand 22. Consequently, the cutting protrusions mentioned above participate either in the shearing cutting or in the bending of the electrical conductor 20.

[0050] There figure 9 shows in detail the position of the shear cutting points, and their distance from an axis 100. In particular, the axis 100 is the axis of application of the thrust force on the piston 30. On one side of the axis 100, the electrical conductor 20 is cut at points distant from the axis 100 by a distance x1 and x2, while on the other side of the axis 100, the electrical conductor 20 is cut at the point distant from the axis 100 by a distance x3. It is intended to have x1+x2 = x3±20%; so as to avoid any tilting torque of the piston 30 in the housing 10. Thus the movement of the piston 30 is reliable, with forces distributed equally on each side of the axis of application of the pressure force, even when shear cutting at several points.

[0051] Generally, it is intended to maintain the piston 30 in the activated position, for example by non-return means, such as a tight mounting at the end of the stroke, clipping, or locking by a flexible tab.

[0052] In summary of this first embodiment, the piston 30 - housing 10 assembly is arranged to cut the electrical conductor by shearing at three separate points, so that: that two separate free strands are formed, which lengthens the path of an electric arc, that a first free strand 21 is without folded wings and symmetrical, that a second free strand 22 is with two folded wings and symmetrical, which avoids any asymmetrical force which could lead to an untimely or random movement of the free strands 21, 22, that each free strand 21, 22 has its end in contact with a cutting protrusion, which maintains or blocks in place the free strands 21, 22 in the housing 10, that, in the final position or activated position, the piston 30 contacts the housing 10 according to a surface contact, so as to close an arcing chamber with a leakage path or arc path of several millimeters between two surfaces in contact with each other.

[0053] There figure 3 shows a second exemplary embodiment, in which the piston 30 comprises four knives 31, so that the electrical conductor 20 will be cut into three separate free strands 21 and 22. In this implementation, one free strand 21 (without a folded wing) and two free strands 22 (with two folded wings) are formed, as shown in figure 4 The rest of the technical details and advantages remain identical to the first embodiment.

[0054] There figure 5 shows a third exemplary embodiment, in which the piston 30 comprises four knives 31, so that the electrical conductor 20 will be cut into three separate free strands 21 and 22. In this third implementation, two free strands 21 (without folded wings) and one free strand 22 (with two folded wings) are formed, as shown in figure 6 The rest of the technical details and advantages remain identical to the first embodiment.

[0055] It will be understood that various modifications and / or improvements obvious to those skilled in the art may 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, reference is made to wings folded at a single point, but it is possible to envisage folding the free strands along a large radius of curvature, or along several folds.

Claims

1. Pyrotechnic switch, comprising: - a housing (10), - at least one electrical conductor (20) passing through the housing (10), - a piston (30) housed in the housing (10), the piston (30) - housing (10) assembly being arranged to cut the electrical conductor (20) at least at three separate locations, so as to form at least two free conductive strands (21, 22), separate from the rest of the electrical conductor (20), - a pyrotechnic actuator arranged to force the piston (30) to cut the electrical conductor (20), characterized in that the piston (30) - housing (10) assembly is arranged to - cut the electrical conductor (20) so that each free strand (21, 22) has at least one base portion with either none or two folded wings (22B, 22C) arranged on either side of the base portion and to - generate at least one free strand (22) with two folded wings (22B, 22C), - generate at least one free strand (21) without folded wings (22B, 22C).

2. Pyrotechnic switch according to claim 1, in which the piston (30) - housing (10) assembly is arranged to block at least one movement of each free strand (21, 22) after cutting.

3. Pyrotechnic switch according to one of claims 1 to 2, in which the piston (30) - housing (10) assembly has cutting protrusions, so that after cutting: - a free strand (21) with no folded wings is arranged between two cutting protrusions with a clearance of less than 1 mm and preferably a clearance of less than 0.5 mm, and / or - a free strand (22) with two folded wings (22B, 22C) is arranged with a cutting protrusion of one of the piston (30) - housing (10) assembly between the two folded wings (22B, 22C), and with two adjacent cutting protrusions of the other of the piston (30) - housing (10) assembly each in contact with one end of each folded wing.

4. Pyrotechnic switch according to claim 3, wherein a free strand (21) with no bent wings is arranged in an enclosed space defined between at least: - one cutting protrusion of one of the piston (30) - housing (10) assembly, and - two cutting protrusions of the other of the piston (30) - housing (10) assembly.

5. Pyrotechnic switch according to one of claims 3 to 4, in which the cutting protrusions have clearance angles.

6. Pyrotechnic switch according to one of claims 3 to 5, in which: - the piston (30) comprises cutting protrusions forming knives (31), - the housing (10) comprises cutting protrusions forming dies (11), and in which, after cutting, each knife (31) of the piston (30) is arranged between two dies (11).

7. Pyrotechnic switch according to claim 6 in its dependency on claim 5, in which, after cutting, at least one undercut face, and preferably each undercut face, of each knife (31) is opposite an undercut face of a die (11).

8. Pyrotechnic switch according to one of claims 1 to 7, in which the folds of a free strand (22) with two folded wings (22B, 22C) are symmetrical.

9. Pyrotechnic switch according to one of claims 1 to 8, comprising, after cutting, two separate elements including: - a free strand (21) with a base portion without folded wings, - a free strand (22) with a base portion with two folded wings (22B, 22C).

10. Pyrotechnic switch according to one of claims 1 to 9, in which: - the piston (30) has an axis (100) for applying a thrust force of the pyrotechnic actuator, - the piston (30) - housing (10) assembly is arranged to cut the electrical conductor (20) at points located at a predetermined distance (x1, x2, x3) from the force application axis, and in which the sum of the predetermined distances of the points located on one side of the force application axis (100) is equal to the sum of the predetermined distances of the points located on the other side of the force application axis (100).

11. Pyrotechnic switch according to one of claims 1 to 10, in which the electrical conductor (20) has at least a first portion anchored in the housing (10), and a second portion facing the piston (30), and in which the second portion has a cross-sectional area smaller than a cross-sectional area of ​​the first portion.

12. Pyrotechnic switch according to claim 11, in which the first portion is overmolded in a material forming a separate part of the housing (10).

13. Pyrotechnic switch according to one of claims 1 to 12, wherein the piston (30) and / or the housing (10) comprises at least one insert at a cutting protrusion.

14. Pyrotechnic switch according to one of claims 1 to 13, in which after cutting, the free strands (21, 22) are trapped in the housing (10).

15. Motor vehicle comprising at least one pyrotechnic switch according to one of claims 1 to 14.

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