EP4004959B1 - Pyrotechnic cut-off device - Google Patents

Description

Technical area

The present invention relates to the general field of electrical cut-off devices, and more particularly those of the pyrotechnically actuated type.

Prior technique

Pyrotechnic cut-off devices are known comprising a body in which is present a pyrotechnic initiator configured to, when it is triggered, set in motion a piston provided with a relief in the direction of a conductive bar to be cut. The documents WO 2016/038043 And WO 2016/038050 show examples of such devices.

The known devices make it possible to obtain satisfactory results when breaking on low voltage circuits. However, as soon as the operating voltage increases, the reliability of known breaking devices decreases and the breaking time increases. We also know FR 2 471 662 which discloses improvements to cut-off devices with a conductor that can be destroyed by pyrotechnic effect with a branch fuse system, FR 3 017 240 which discloses a pyrotechnic circuit breaker, FR 3 005 200 which discloses an electrical switch and EP 3 724 908 which discloses a pyrotechnic system for interrupting an electrical circuit.

There is thus still a need for a pyrotechnic breaking device which is more reliable at high voltages while being of simple and economical design.

Disclosure of Invention

To this end, the invention proposes a pyrotechnic cut-off device comprising: a pyrotechnic initiator, a conductive portion and a movable piston, the piston being able to move in a cavity in a direction of movement following actuation of the pyrotechnic initiator between a first current passage position in the conductive portion and a second current cut-off position. The cut-off device is characterized in that the piston defines a first sealing portion having a narrowing in section along the direction of movement, and in that the cavity has a wall defining a second sealing portion which extends from either side of the conductive portion and which has a narrowing in section along the direction of movement, the first sealing portion being in contact with the second sealing portion along a contact surface extending on either side of the conductive portion when the piston is in the second position.

The first sealing portion of the piston and the second sealing portion defined by the wall of the cavity can cooperate in the second position of the piston so as to create a surface seal on either side of the conductive portion, which makes it possible to separate the two terminals of the device between which the conductive portion extends in a sealed manner. Thus, the breaking of the current and the reliability of the device are improved. In addition, the section narrowings of the sealing portions allow the piston to fit into the cavity in the manner of a Morse taper or fitting cone, which makes it possible to center the piston in the cavity, to prevent the piston to move once it is in the second position and also to maintain this seal.

When the current is cut off by section of the conductive portion by the piston, the device according to the invention makes it possible to obtain a characteristic short cut-off time, corresponding to the duration separating the moment when the conductive portion is cut off from the moment when current is effectively cut off, which can be typically between 50 µs and 150 µs.

In an exemplary embodiment, the sections of the piston and of the cavity can be of circular or oblong shape. These rounded section shapes make it possible to improve the seal between the piston and the wall of the cavity.

In an exemplary embodiment, the conductive portion can be broken by impact with the piston during passage from the first to the second position. In particular, the conductive portion can be broken into three parts, one of which is driven by the piston.

In an exemplary embodiment, the conductive portion may have at least one zone of weakness to facilitate the breakage of said conductive portion. The fragile zone can for example comprise a plurality of tabs, or even at least one groove.

In an exemplary embodiment, the first sealing portion may have a first surface and the second sealing portion may have a second surface, said surfaces each making an angle of between 1° and 10° with the direction of displacement of the piston. In particular, the angles made by the first surface and the second surface can be different to allow fitting of one sealing portion into the other, in order to further improve the sealing.

In an exemplary embodiment, the hardness of the material forming the first sealing portion and the hardness of the material forming the second sealing portion may be different. The difference in hardness between said materials can be between 50 Shore A and 100 Shore D. This characteristic allows a deformation of one sealing portion with respect to the other when the piston passes into the second position, which further improves sealing and power cut.

In an exemplary embodiment, in the first position, the piston may have a housing and the device may further comprise a relief which extends from a bottom of the cavity, said relief being housed in the housing when the piston is in the second position. In this configuration, the conductive portion can be cut into three parts, one of which is driven by the piston and then bent against the relief in the housing when the piston is in the second configuration. This configuration further improves the cut-off by isolating the bent part of the conductive portion in the housing from the remaining parts thereof.

The invention also relates to a secure electrical installation comprising a cut-off device such as that presented above and an electrical circuit connected to the conductive portion of said device.

The invention finally relates to a vehicle comprising a secure electrical installation such as that described above. Such a vehicle can for example be an electric motor vehicle.

Brief description of the drawings

• [ Fig. 1 ] There figure 1 is a perspective view of a switching device according to a first embodiment of the invention.
• [ Fig. 2 ] There figure 2 is an exploded view of the device of the figure 1 .
• [ Fig. 3 ] There picture 3 is a sectional and perspective view of part of the body of the cut-off device of the figure 1 .
• [ Fig. 4 ] There figure 4 shows a sectional and perspective view of the piston of the cut-off device of the figure 1 .
• [ Fig. 5A-5B ] THE figures 5A and 5B respectively show sectional views of the cut-off device of the figure 1 when the piston is in the first and in the second position.
• [ Fig. 6 ] There figure 6 is a sectional and perspective view of part of the body of a cut-off device according to a second embodiment of the invention.
• [ Fig. 7 ] There figure 7 is a sectional and perspective view of the piston of the cut-off device according to the second embodiment of the invention.
• [ Fig. 8A-8B ] THE figures 8A and 8B respectively show sectional views of the cut-off device according to the second embodiment of the invention when the piston is in the first and in the second position.
• [ Fig. 9 ] There figure 9 shows a secure electrical circuit in which a cut-off device according to the invention is present.

Description of embodiments

The cut-off device 100 according to a first embodiment illustrated in the figures 1 to 5B comprises: a body 10 in two parts 10a and 10b, a pyrotechnic initiator 20, a piston 30, and a conductive portion 40.

The device 100 comprises a first 41 and a second 42 electrical terminals intended to be connected to an electrical circuit to be cut and which correspond here to two ends of the conductive portion 40. The conductive portion 40 here takes the form of a bar or tab driver. In an embodiment not illustrated, the device 100 can comprise a plurality of conductive portions. An example of installation comprising an electrical circuit connected to terminals 41 and 42 will be described in connection with the figure 9 .

The body 10 has a generally parallelepipedic shape. The body 10 comprises a part 10a housing the various elements of the device 100 and a cover 10b which closes the body 10 at an upper end. THE cover 10b is fixed to part 10a by screws 10c. Part 10a of body 10 has an upper opening 11 into which piston 30 can be inserted. Cover 10b has an opening 12 to allow connectors 21 of pyrotechnic initiator 20 to pass. Part 10a of body 10 has two side openings 13 in which the conductive portion 40 can be inserted.

The pyrotechnic initiator 20 comprises a pyrotechnic charge connected to the connectors 21. The pyrotechnic charge is, when it is initiated for example using a current passing through the connectors 21, able to generate a pressurization gas by its combustion. Conductive elements 21 can be connected to a control device C ( figure 9 ) configured to actuate the pyrotechnic initiator 20 when an anomaly is detected.

The piston 30 has, in this example, a form of revolution around an axis Z. The axis Z corresponds to the axis of displacement of the piston 30. The axis Z is transverse, for example perpendicular, to the direction of passage current in the conductive portion 40. The piston 30 comprises a circumferential groove 31 in which a seal 32, for example an O-ring, is intended to be housed. The piston 30 can move in a direction of movement A along the axis Z inside the body 10 between a high position (first position) as on the figure 5A , and a low position (second position) as on the figure 5B . The direction of movement A is oriented from the pyrotechnic initiator 20 towards the conductive portion 40 or towards the second sealing portion 14b (downwards in the example illustrated). As long as the pyrotechnic initiator 20 has not been triggered, the piston 30 is in the first position.

The piston 30 comprises a first sealing portion 33, corresponding here to a lower part of the piston, which has a narrowing in section along the direction of movement A of the piston 30. The first sealing portion 33 here corresponds to an end of the piston 30 facing the conductive portion 40. In this example, the first sealing portion 33 is of frustoconical shape, for example of circular section. The angle a1 that the surface of the first sealing portion 33 makes with the direction of movement of the piston A can be between 1° and 10°. The angle a1 can be measured in a plane containing the direction of movement A (or the Z axis). Alternatively, the piston could have other sections, for example oblong, or even square. The upper part 34 of the piston where the groove 31 is present is itself cylindrical in shape here.

The body 10 defines a cavity 14 in which the piston 30 can move and which is crossed by the conductive portion 40. The cavity 14 is here divided into three parts: an upper part 14a where the wall of the cavity 14 is generally cylindrical, a second sealing portion 14b where the wall has a section narrowing in the direction of movement A of the piston 30, and a lower part 14c where the wall of the cavity is of generally cylindrical shape. The second sealing portion 14b extends the upper part 14a, and the lower part 14c extends the second sealing portion 14b. In this example, the second sealing portion 14b has a frustoconical shape. In this example, the internal diameter D1 of the cavity 14 at the level of the upper part 14a is greater than the internal diameter D2 of the cavity at the level of the lower part 14c, and the internal diameter of the cavity at the level of the second portion d sealing 14b is gradually reduced between the upper part 14a and the lower part 14c. The second sealing portion 14b extends on either side of the conductive portion 40, that is to say here on either side of the openings 13 which open into the cavity 14. The second portion d Sealing 14b has a surface which forms an angle α2 with the direction of movement A of piston 30 which may be between 1° and 10°. The angle a2 could be measured in a plane containing the direction of movement A (or the Z axis). Angle a1 and angle a2 may be the same or slightly different. For example, the angle a1 can be 3° and the angle a2 can be 4°, or vice versa.

The section of the cavity 14 and its dimensions will be adapted to those of the piston 30 so that the latter can move in order to cut the conductive portion 40, and that the sealing portions 33 and 14b of the piston and of the wall of the cavity can cooperate in the second position, that is to say be in contact along a contact surface which extends on either side of the conductive portion 40.

The conductive portion 40 has, in this example, two areas of weakness 43 ( figure 2 ) which make it possible to facilitate the cutting of the conductive portion 40 by the piston 30. In this example, each fragile zone 43 has a plurality of tabs 43a spaced apart between them which connect each terminal 41 and 42 of the conductive portion 40 to a part 44 which is intended to be separated from the terminals 41 and 42 and driven by the piston. Other types of fragile zones can be envisaged, for example grooves made in the conductive portion 40. In this example, the conductive portion 40 is cut into three parts by the piston 30. The conductive portion 40 has a width L0. As a variant, other cut-off configurations can be envisaged.

When the piston 30 is in the cavity 14, it separates the cavity 14 into a first pressurization chamber 15 and a second chamber 16 in which the conductive portion 40 is present.

In the examples illustrated, the conductive portion 40 is distinct from the body 10a. As a variant, the conductive portion 40 can be overmolded with the body 10 (here the part 10a) so as to improve the seal between the conductive portion 40 and the body 10.

The different operating steps of the device 100 will now be described in connection with the figures 5A and 5B which show sectional views, respectively when the piston 30 is in the first position and in the second position.

There figure 5A shows the device 100 before its triggering. Following the triggering of the pyrotechnic initiator 20, the chamber 15 is pressurized by the gases resulting from the combustion of the pyrotechnic charge, and the piston 30 starts moving towards the conductive portion 40 until the first portion of sealing 33 of piston 30 impacts conductive portion 40. More specifically, the first sealing portion 33 of piston 30 impacts part 44 of conductive portion 40 which then detaches from the parts of conductive portion 40 connected to terminals 41 and 42. When the piston 30 passes, the tabs 43a can fold up as can be seen on the enlargement of the figure 5B so as not to impede the stroke of the piston 30.

When the piston 30 is in the second position or low position as on the figure 5B , its first sealing portion 33 is in surface contact with the second sealing portion 14b of the cavity 14. In the second position, the piston 30 is interposed between the openings 13. In the second position, the piston 30 is interposed between the terminals 41 and 42 of the cut-off device. In the second position, the piston 30 is interposed between the fragments of the broken conductive portion 40. The piston 30 covers, in the second position, the openings 13 which open into the cavity. The contact surface between the piston 30 and the wall of the cavity 14 extends on either side of the initial location of the conductive portion 40 (or, equivalently, on either side of the openings 13 ) so as to create a seal preventing the passage of current between terminals 41 and 42. This contact surface may have a frustoconical shape. In this example, the entire surface of the second sealing portion 14b is in contact with the first sealing portion 33. In this example, the contact surface between the piston 30 and the wall of the cavity 14 surrounds the openings 13 which open into the cavity 14. In this way, the terminals 41 and 42 are insulated from each other in a sealed manner. The contact surface between the piston 30 and the wall of the cavity 14 extends around, in particular all around (at 360° around), the axis of displacement Z of the piston 30. The part 44 cut from the conductive portion 40 is housed in the lower part 14c of the cavity 14 on a bottom 14d thereof.

The materials of the first sealing portion 33 of the piston 30 and of the part of the body 10 forming the second sealing portion 14b can be identical. As a variant, these materials can advantageously have different hardnesses. The difference in hardness between these materials can be between 50 Shore A and 100 Shore D. Thus, the body 10 or the piston 30 can deform during the passage of the piston 30 from the first to the second position, which ensures even better contact between the two sealing portions, better sealing and therefore better breaking of the current.

THE figures 6 to 8B show views of a cut-off device 200 according to a second embodiment of the invention. Unless otherwise stated, the identical reference signs between the first and the second embodiment designate identical characteristics. Compared to the device 100, the piston 30 of the device 200 comprises a housing 35 and its cavity 14 has a relief 17.

The housing 35 of the piston 30 is present in the sealing portion 33 and opens opposite the conductive portion 40 when the piston 30 is in the first position. In this example, the housing 35 is cylindrical in shape.

The relief 17 extends from a bottom 14d of the cavity 14. In the first position, the relief 17 extends here more precisely between the bottom 14d of the cavity 14 and the conductive portion 40. The relief 17 has a triangular section in a plane containing the conductive portion 40 and the axis of displacement A of the piston. The relief 17 extends in a transverse direction T with respect to the longitudinal direction L in which the conductive portion 40 extends.

In this example, the conductive portion 40 has grooves as fragile zones 43, which delimit the part 44 of the conductive portion 40 which will be separated from the terminals 41 and 42 during the cut.

The internal diameter D3 of the housing 35 is greater than the width L0 of the conductive portion 40 so that the housing 35 can accommodate the part 44 after cutting.

The operation of device 200 is similar to that of device 100, except that when piston 30 is in the second position, the portion 44 of conductive portion 40 which is cut and driven by piston 30 is bent by the relief 17 in the housing 35. In the second position, the part 44 is located between the relief 17 and the piston 30 in the housing 35, which makes it possible to isolate the part 44 from the terminals 41 and 42, and to improve power cut again. In particular, with this device 200, the separation speed of the part 44 from the terminals 41 and 42 is increased, and the separation distance between the part 44 and the terminals 41 and 42 is greater while maintaining a reduced bulk.

There figure 9 schematically shows an example of a secure electrical installation 300 implementing a cut-off device 100 or 200 according to the invention.

The secure electrical installation 300 comprises a secure power supply system 310 comprising a cut-off device 100 or 200 (represented very schematically) and a power supply circuit 311. The power supply circuit 311 here comprises an electric generator G connected to the second terminal 42 of the conductive portion 40 of the cut-off device 100 or 200. The electric generator G may for example be a battery or an alternator.

The secure power system 310 further comprises a control element C configured to actuate the pyrotechnic initiator 20 when an anomaly is detected. Control element C is connected to pyrotechnic initiator 20 through connectors 21. The anomaly in response to which control element C can trigger pyrotechnic initiator 20 may be an electrical anomaly, such as a current threshold exceeded in the circuit, or a non-electrical anomaly such as the detection of a shock, for example a sudden deceleration of the control element, a change in temperature, pressure, etc. In the event of detection of an anomaly, the control element C is able to send an electric current to the pyrotechnic initiator 20 for its triggering in order to cut off the current, as described above.

The secure electrical installation 300 finally comprises an electrical device D connected here to the first terminal 41 of the conductive portion 40 of the cut-off device 100 or 200 to be powered by the secure power supply system 310.

By way of example, a motor vehicle may include a secure electrical installation 300.

Claims (9)

1. A pyrotechnic cut-off device (100 ; 200) comprising: a pyrotechnic igniter (20), a conductive portion (40) and a movable piston (30), the piston being able to be displaced in a cavity (14) along a direction of displacement (A) following the actuation of the pyrotechnic igniter between a first position of passage of the current in the conductive portion and a second position of cut-off of the current,
   the piston (30) defines a first sealing portion (33) having a narrowing of section along the direction of displacement (A), and the cavity (14) has a wall defining a second sealing portion (14b) which extends on either side of the conductive portion (40) and which has a narrowing of section along the direction of displacement (A), the first sealing portion (33) being in contact with the second sealing portion (14b) along a contact surface extending on either side of the conductive portion (40) when the piston is in the second position, characterized in that the first sealing portion and the second sealing portion cooperate in the second position such as to create a surface seal on either side of the conductive portion, which makes it possible to separate in a sealed manner the two terminals of the device between which the conductive portion extends.
2. The device (100 ; 200) as claimed in claim 1, wherein the sections of the piston (30) and of the cavity (14) are of circular or oblong shape.
3. The device (100 ; 200) as claimed in claim 1 or claim 2, wherein the conductive portion (40) is broken by impact with the piston (30 ; 30') when it passes from the first to the second position.
4. The device (100 ; 200) as claimed in claim 3, wherein the conductive portion (40) has at least one fragile area (43) to facilitate the breaking of said conductive portion.
5. The device (100 ; 200) as claimed in any of claims 1 to 4, wherein the first sealing portion (33) has a first surface and the second sealing portion (14b) has a second surface, said surfaces each forming an angle (a1, a2) between 1° and 10° with the direction of displacement (A) of the piston (30).
6. The device (100 ; 200) as claimed in any of claims 1 to 5, wherein the hardness of the material forming the first sealing portion (33) and the hardness of the material forming the second sealing portion (14b) are different.
7. The device (200) as claimed in any of claims 1 to 6, wherein, in the first position, the piston (30) defines a housing (35) and the device further comprises a protrusion (17) which extends from a floor (14d) of the cavity, said protrusion being housed in the housing (35) when the piston is in the second position.
8. A secure electrical installation (300) comprising a cut-off device (100 ; 200) as claimed in any of claims 1 to 7 and an electrical circuit connected to the conductive portion (40) of said device.
9. A vehicle comprising a secure electrical installation (300) as claimed in claim 8.

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