Pyrotechnic circuit breaker

Abstract

The invention relates to a pyrotechnic circuit breaker, comprising: - a housing (10), - an electrical conductor (20) to be interrupted, - a piston (30) which is arranged in the housing (10) to interrupt the electrical conductor (20) and which can be moved between an idle position and an activated position in which the electrical conductor (20) is interrupted, - a pyrotechnic actuator (40) arranged in the housing (10) to cause the piston (30) to move from the idle position to the activated position, the piston (30) comprising a proximal end (30A) arranged on the side of the pyrotechnic actuator (40) and a distal end (30B) opposite to the proximal end (30A), characterised in that the piston (30) comprises at least one gas passage (31) arranged between the distal end (30B) and the proximal end (30A).

Description

DESCRIPTION TITLE: Pyrotechnic Circuit Breaker Technical field of the invention

[0001] The present invention relates generally to pyrotechnic circuit breakers intended for use in electric vehicles to quickly interrupt electrical circuits (in particular traction circuits with high currents, and / or high voltages, and / or high inductances). The currents flowing through such electrical circuits in electric vehicles can reach intensities of several thousand or tens of thousands of amperes, with voltages ranging from a few tens to several thousand volts. Prior art

[0002] It is known in the prior art of circuit breakers to incorporate a gas passage within the housing between a breaking chamber, which initially contains the electrical conductor to be interrupted, and a pyrotechnic chamber designed to receive combustion gases from the pyrotechnic actuator. However, this system can have the disadvantage of being large and / or exhibiting insufficient insulation resistance after operation (due to conductive deposits left by the combustion gases). Document DE102019135591 illustrates such a circuit breaker, for example.

[0003] Document DE102018125059A1 illustrates, for example, a circuit breaker with a cooling channel. Description of the invention

[0004] One aim of the present invention is to address the disadvantages of the prior art mentioned above and in particular, first of all, to offer a compact circuit breaker and / or one that provides high operational safety.

[0005] To this end, a first aspect of the invention relates to a pyrotechnic circuit breaker, comprising: - a case, - an electrical conductor to be cut, - a piston arranged in the housing to cut the electrical conductor and movable between a rest position and an activated position in which the electrical conductor is cut, - a pyrotechnic actuator arranged in the housing to move the piston from the rest position to the activated position, the piston comprising a proximal end arranged on the side of the pyrotechnic actuator and a distal end opposite the proximal end, characterized in that the piston includes at least one gas passage arranged between the distal and proximal ends. According to the above embodiment, the circuit breaker includes at least one gas passage arranged on or within the piston, thus providing a compact solution. Furthermore, the fluidic communication between the distal and proximal ends limits or prevents compression of the gases located above the piston during its movement, thereby increasing operational safety by preventing the piston from retracting due to excessive pressure exerted by gases compressed by the distal end.

[0006] According to one embodiment, the piston (or passage) may include at least one orifice provided on the distal end side and / or on the proximal end side, so as to establish fluidic communication between the distal end and the proximal end.

[0007] In one embodiment, the fluidic communication can be permanent and / or independent of the piston position. In other words, the passage can be designed to be constantly open to facilitate / allow the passage of gas from one side of the piston to the other. Such a passage can be considered a means of increasing the volume available for gases located within the chamber that contains the conductor (to be cut off before the circuit breaker is activated, cut off after the circuit breaker is activated).

[0008] In one embodiment, the piston and / or the passage and / or the circuit breaker may be without filtration means. The gases do not need to be cooled or filtered to guarantee the absence of piston backflow or recoil.

[0009] In one embodiment, the piston and / or the passage and / or the circuit breaker may be without a vent and / or venting means. Thus, environmental resistance is easily guaranteed.

[0010] According to one embodiment, the proximal end can be directly opposite the pyrotechnic actuator at least when the piston is in the rest position.

[0011] According to one embodiment, the distal end can be directly opposite the electrical conductor to be cut, when the piston is in the rest position.

[0012] According to one embodiment, the piston (or passage) may include at least one orifice provided on the distal end side and directly opposite the electrical conductor to be cut, when the piston is in the rest position.

[0013] According to one embodiment, the proximal end can be a first end of the piston in a direction of piston movement, and the distal end can be a second end of the piston in a direction of piston movement.

[0014] According to one embodiment, when the piston is in its rest position, the housing can form with the piston: - a breaking chamber comprising a portion of the electrical conductor to be broken, - a pyrotechnic chamber, designed to receive combustion gases of the pyrotechnic actuator, - a side chamber, separated from the cut-off chamber by the piston and isolated from the pyrotechnic chamber, and the gas passage can establish fluidic communication between the cut-off chamber and the side chamber. According to the above implementation, the pyrotechnic chamber is isolated from the side chamber and the cut-off chamber by the piston, so that the combustion gases remain confined within the pyrotechnic chamber: operational safety is improved, notably with high insulation resistances after operation.

[0015] According to one embodiment: - the housing may include an ignition well, and - The piston may include a skirt that engages in the igniter well and separates the side chamber from the pyrotechnic chamber. This design is simple, and the skirt provides additional guidance. A sealing gasket may be fitted to the skirt.

[0016] According to one embodiment: - the casing may include a main cylinder, and - the piston may include a peripheral surface engaged in the main cylinder, and the gas passage may be arranged between the peripheral surface and the piston skirt.

[0017] In one embodiment, the piston in the activated position can divide the cut-off chamber into several sub-chambers, and the piston can have at least one gas passage per sub-chamber leading to the lateral chamber. Even though the cut-off chamber is partitioned once the piston is moved, the presence of multiple gas passages ensures the absence of overpressures at the distal end, thus guaranteeing that the piston remains in its final position without recoiling.

[0018] In one embodiment, the pyrotechnic circuit breaker may include at least one cooler arranged to cool gases heated by an electric arc generated during the interruption of the electrical conductor. Such coolers further improve operational safety by preventing the gases from remaining hot, even if electric arcs are created during operation: the pressure drops rapidly.

[0019] According to one embodiment, said at least one cooler can be arranged in the cut-off chamber and / or in the side chamber.

[0020] In one embodiment, at least one cooler may be attached to the housing and / or the piston. At least one cooler may be arranged in the gas path to force passage through it, thereby providing more efficient cooling. For example, the gas passage may supply or direct a cooler.

[0021] According to one embodiment, the gas passage can be: - a through hole made in the piston, or - an external groove managed in a lateral surface of the piston.

[0022] According to one embodiment, the gas passage may have a transverse passage area greater than or equal to 15, or even 25 mm 2 This surface can be obtained by one, two, or more passes. It should be noted that the passage has a dimension much larger than the mechanical clearance between two parts that must move relative to each other. Furthermore, manufacturing tolerances can cause significant variations in the mechanical clearance between two moving parts, whereas the gas passage has a relatively constant surface area, thus providing better repeatability.

[0023] According to one embodiment, said at least one gas passage allows gas communication within the housing so as to impose, within the housing and for 1 ms after a peak maximum pressure Pmax, a pressure between Pmax and 0.9Pmax. The maximum pressure Pmax may The maximum pressure Pmax can be a maximum pressure measured during a functional test, and 0.9Pmax can represent 90% of the maximum pressure. The maximum pressure Pmax can be a maximum pressure measured in a circuit breaker interruption chamber, i.e., in a chamber containing the conductor to be interrupted and delimited at least partially by the distal end of the piston. According to this implementation, the gas passage prevents an excessively high peak pressure, resulting in a flatter pressure curve: the pressure varies little after the peak pressure. The piston is therefore under minimal stress and does not retract once it reaches its maximum stroke.

[0024] According to one embodiment, the electrical conductor can pass through the housing.

[0025] According to one embodiment, the gas passage can be arranged to allow, when the electrical conductor is cut off, a displacement of gases present from one side of the piston opposite the electrical conductor when the piston is in the rest position to one side of the piston opposite the pyrotechnic actuator when the piston is in the activated position.

[0026] A second aspect of the invention relates to a motor vehicle comprising at least one pyrotechnic circuit breaker according to the first aspect of the invention. Description of the figures

[0027] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of an embodiment of the invention given by way of non-limiting example and illustrated by the accompanying drawings, in which:

[0028] [fig. 1] represents a cross-sectional view of a pyrotechnic circuit breaker according to the invention after activation of the pyrotechnic device, with a piston having cut an electrical conductor;

[0029] [fig. 2] represents a perspective view of the piston alone;

[0030] [fig. 3] represents voltage, current and pressure curves measured during operation in a prior art circuit breaker;

[0031] [fig. 4] represents voltage, current and pressure curves measured during operation in a circuit breaker according to the invention. Detailed description of implementation method(s)

[0032] Figure 1 represents a circuit breaker comprising: - a 10-inch case, - an electrical conductor to be cut 20, - a piston 30 arranged in the housing to cut the electrical conductor 20 and movable between a rest position and an activated position in which the electrical conductor 20 is cut, - a pyrotechnic actuator 40 arranged in the housing 10 to move the piston 30 from the rest position to the activated position, the piston 30 comprising a proximal end 30A arranged on the side of the pyrotechnic actuator 40 and a distal end 30B opposite the proximal end 30A.

[0033] In detail, the housing 10 of the circuit breaker shown in Figure 1 comprises a first half-shell 11 and a second half-shell 12. The first half-shell 11 receives an igniter support 15 which allows the attachment of an electro-pyrotechnic igniter forming the pyrotechnic actuator 40. The electrical conductor 20 is mainly made up of an electrically conductive bar, which can be overmolded by a frame 21, sandwiched between the first half-shell 11 and the second half-shell 12. Note the presence of several sealing gaskets 18 and 16 between the parts to ensure good environmental resistance.

[0034] Generally speaking, the piston 30 is housed in the casing 10, so as to form: - a breaking chamber 130 comprising a portion of the electrical conductor 20 to be broken, - a pyrotechnic chamber 110, designed to receive gases of combustion of pyrotechnic actuator 40, - a side chamber 120, separated from the cut-off chamber 130 by the piston 30, and isolated from the pyrotechnic chamber 110 by the piston 30.

[0035] For this purpose, the housing 10 has a main cylinder and the piston 30 has a peripheral surface 33 housed in the main cylinder arranged to allow the piston 30 to slide in the housing 10. Piston 30 also features: - a skirt 36 and a joint 35 on the side of the proximal end 30A; - a plurality of knives 34 separated by grooves 37 on the distal end side 30B, - passages 31 (orifices) establishing a fluidic communication between the proximal end 30A and the distal end 30B. Opposite the grooves 37 separating the plurality of knives 34 from the piston 30, the second half-shell 12 has dies 17 which are designed to interlock with the piston 30 in order to cut the electrical conductor 20.

[0036] Indeed, as shown in Figure 1, the pyrotechnic actuator 40 has been triggered, and the piston 30 is therefore in an activated position in which the electrical conductor 20 has been cut into several pieces. Specifically, as can be seen in Figure 1, the electrical conductor 20 consists of the two external ends 24 of the electrical conductor 20, a first cut piece 22, and a second cut piece 23. The piston 30, initially in its rest position in the first half-shell 11, was moved by the pressurized gases of the pyrotechnic actuator 40 expelled into the pyrotechnic chamber 110 to occupy the activated position shown in Figure 1.During the transition from the rest position to the activated position, the piston 30 cut the electrical conductor 20; the first cut piece 22 and the second cut piece 23 were then separated from the two external ends 24 and sandwiched between the piston 30 (the knives 37 and grooves 37) on one side and the housing 10 (the dies 17) on the other.

[0037] The circuit breaker includes coolers 13, 14 arranged to cool gases and the breaking chamber 130 also contains coolers arranged to cool gases heated by an electric arc generated during the breaking of the electrical conductor 20. Indeed, first coolers 13 are housed in the breaking chamber 130, and second coolers 14 are housed in the side chamber 120.

[0038] The coolers can be metallic components. Porous components or components with internal voids are possible. Coolers can be formed from metal wire. The metal wire can be compacted to form the coolers. In other words, each cooler is formed from one or more compacted wires. Compacted knit materials, or even porous sintered components, are also possible. Such components can dissipate energy from gases heated by an electric arc.

[0039] Indeed, according to one embodiment, the coolers can be porous parts and / or have voids and / or passages and / or interstices, and / or have a density much lower than that of the metal from which they are formed, and which can be easily traversed by the gases, thus providing a large exchange surface and an interesting cooling capacity for the gas in the cut-off chamber 130. It can be noted that during operation, the gases in the cut-off chamber 130 can be compressed / displaced by the movement of the piston 30, so that there is movement of these gases in the coolers, within the free spaces, and this allows efficient heat exchange to cool the gases in the cut-off chamber 130. In other words, the coolers can be designed to perform convection cooling (heat exchange between a gas and a solid).

[0040] Figure 2 shows a perspective view of the distal end 30B, i.e., the face of the piston 30 which carries the knives 34 separated by the grooves 37. It can be noted that the piston 30 has a surface The peripheral 33 is non-circular, which ensures that the piston 30 slides without rotating around its axis: the assembly is a sliding joint. Thus, the knives 34, separated by the grooves 37, can perform an effective mechanical cut (shear) of the electrical conductor 20 in cooperation with the dies 17 of the housing 10, which are precisely aligned with the grooves 37.

[0041] We can also note the presence of two passages 31 which are placed in the plane of the section of figure 1, and four passages 32 which are placed on either side of the plane of the section of figure 1 and each open into a groove 37 of the piston 30.

[0042] As seen above and clearly visible in Figure 1, the housing 10 defines: - on the proximal end side 30A: the pyrotechnic chamber 110, and the lateral chamber 120 isolated from the pyrotechnic chamber 110 by the skirt 36 and the seal 35 of the piston 30, - on the distal end side 30B: the cut-off chamber 130, isolated or separated from the pyrotechnic chamber 110 and the lateral chamber 120 by the piston 30. However, the passages 31 and 32 provided in the piston 30 ensure gas communication between the cut-off chamber 130 and the lateral chamber 120. Consequently, the gas passages 31 and 32 are arranged to allow, when the electrical conductor 20 is cut off, a displacement of gases present on the side of the piston 30 opposite the electrical conductor 20 when the piston 30 is in the rest position towards the side of the piston 30 opposite the pyrotechnic actuator 40 when the piston 30 is in the activated position.This helps to avoid gas overpressures in the cut-off chamber 130, because it should be remembered that the gases in the cut-off chamber 130 are compressed by the movement of the piston 30 which reduces their volume, and by possible electrical arcs which are established between the different pieces of the electrical conductor 20 and which heat the gases in the cut-off chamber 130. The piston 30 therefore undergoes little or no stress or pressure forces. applied to the distal end 30B, which would tend to cause it to retract. The activated position of piston 30 is more robust and stable.

[0043] It can also be noted that during the movement of the piston 30, due to the interlocking of the dies 17 with or within the grooves 37, the cut-off chamber 130, initially a single unit, is progressively segmented into sub-cut-off chambers. However, the various passages 31 and 32 are arranged on the piston 30 to ensure proper communication between the lateral chamber 120 and each of the sub-cut-off chambers. Thus, any risk of overpressure is avoided.

[0044] It can also be noted that the side chamber 120 is well insulated from the pyrotechnic chamber 110, so that the combustion gases and residues from the pyrotechnic actuator 40 remain confined within the pyrotechnic chamber 110 and do not enter the side chamber 120 or the cut-off chamber 130, and vice versa. Thus, the combustion gases and residues from the pyrotechnic actuator 40 do not affect the insulation resistance between the ends 24, and the gases and residues resulting from the cutting of the electrical conductor 20 do not affect the insulation resistance at the pins of the pyrotechnic actuator 40.

[0045] Figure 3 shows measurements taken during the operation of a prior art circuit breaker, i.e., without gas passing through the piston. The graph in Figure 3 shows: - a voltage curve across the terminals of the electrical conductor, - a curve of the current intensity passing through the electrical conductor, - a curve of the pressure that prevails in the cut-off chamber.

[0046] At T = 0 ms, current flows through the electrical conductor while the voltage across its terminals is zero, because the electrical conductor is intact and conducts current perfectly. The igniter is fired, and the piston begins to move.

[0047] At T=0.35 ms, the pressure begins to increase in the cutting chamber, the current intensity decreases and the voltage increases: the piston has begun to physically cut the electrical conductor and an electric arc has been established.

[0048] At T = 0.40 ms, the pressure in the breaking chamber continues to increase, the current continues to decrease, and the voltage increases as the piston continues to separate the electrical conductor into several cut pieces. Between T = 0.5 ms and T = 0.65 ms, the voltage is at its maximum, a pressure peak is reached, and the voltage then drops to stabilize at the DC voltage of the open electrical circuit, while the current becomes zero: the electrical circuit is open and the electric arc is broken. It can be noted that the pressure peak in this test was approximately 80 bar at 0.5 ms, and that at 1.5 ms (i.e., 1 ms after the pressure peak), the pressure is slightly less than 60 bar.

[0049] Figure 4 shows the same measurements as Figure 3, but taken during the operation of a circuit breaker according to the invention, i.e., as in Figure 1, with at least one gas passage provided in the piston, between the distal end 30B and the proximal end 30A. The rest of the structure and geometry of the circuit breaker are identical to the circuit breaker used for the measurements in Figure 3. The graph in Figure 4 shows: - a voltage curve across the terminals of the electrical conductor, - a curve of the current intensity passing through the electrical conductor, - a curve of the pressure that prevails in the cut-off chamber.

[0050] At T = 0 ms, current flows through the electrical conductor while the voltage across its terminals is zero, because the electrical conductor is intact and conducts current perfectly. The igniter is fired, and the piston begins to move.

[0051] At T=0.35 ms, the pressure begins to increase in the cutting chamber, the current intensity decreases and the voltage increases: the piston has begun to physically cut the electrical conductor and an electric arc has been established.

[0052] At T = 0.40 ms, the pressure in the breaking chamber continues to increase, the current continues to decrease, and the voltage increases as the piston continues to separate the electrical conductor into several cut pieces. Between T = 0.5 ms and T = 0.65 ms, the voltage is at its maximum, a pressure peak is reached, and the voltage then drops to stabilize at the DC voltage of the open electrical circuit, while the current becomes zero: the electrical circuit is open and the electric arc is broken. It can be noted that the pressure peak in this test was approximately 60 bar at 0.5 ms, and that at 1.5 ms (i.e., 1 ms after the pressure peak), the pressure is slightly less than 60 bar.

[0053] Compared to the curves in Figure 3, it can be noted that the duration for which the electric arc is present is shorter (an electric arc can be considered present as soon as the voltage is above zero, and the electric arc is broken when the voltage stabilizes at the open circuit voltage, i.e., the battery voltage). Figure 4 also shows that the peak maximum pressure is lower than that of Figure 3, which is explained by the presence of gas passages, which prevent the breaking chamber from becoming pressurized. Due to this lower pressure, the piston cuts the electrical conductor more effectively and more quickly, and it remains better positioned in its final position, without recoiling: the partitioning performed by the piston is effective and limits the formation of the electric arc, resulting in a faster breaking action.

[0054] It will be understood that various modifications and / or improvements obvious to a person skilled in the art can be made to the different embodiments of the invention described in this description without departing from the scope of the invention.

[0055] In particular, it can be noted that passages 31 and 32 are orifices formed in the piston 30, but grooves could be provided in the lateral wall 33 of the piston 30. It should be noted, however, that the gas passage area, equal to the sum of the areas of passages 31 and 32, is much greater than the peripheral clearance of the piston 30. In particular, the gas passage area can be greater than 6 mm². 2 preferably greater than 9 mm 2 and even greater than 12 mm 2 by gas passing between a sub-chamber and the lateral chamber.

[0056] Furthermore, the distributor can, for example, be overmolded or crimped onto the housing 10 or the distributor support 15 depending on the materials chosen for the latter.

[0057] Apart from the electrical conductor 20 and the coolers 13 and 14, it can be assumed that all or part of the components in Figure 1 are made of plastic, and / or polymer, and / or contain a filler material. Polyamide, glass fibers, or any other reinforcing material are possible.

[0058] Plastic parts can be overmolded onto or reinforced with metal elements depending on the stresses they must withstand.

[0059] We can foresee other shapes for the piston 30, we can foresee more or fewer knives 34 / grooves 37 / dies 17.

[0060] It is possible to plan to place the coolers on or in the piston 30. For example, it is possible to plan to place at least one cooler on or in or near at least one passage, so as to force a passage of gas into the cooler and thus improve the cooling of the gases in the cut-off chamber. Industrial application

[0061] A circuit breaker according to the present invention, and its manufacture, are capable of industrial application.

Claims

DEMANDS

1. Pyrotechnic circuit breaker, comprising: - a case (10), - an electrical conductor (20) to be cut, - a piston (30) arranged in the housing (10) to cut the electrical conductor (20) and movable between a rest position and an activated position in which the electrical conductor (20) is cut, - a pyrotechnic actuator (40) arranged in the housing (10) to move the piston (30) from the rest position to the activated position, the piston (30) comprising a proximal end (30A) arranged on the side of the pyrotechnic actuator (40) and a distal end (30B) opposite the proximal end (30A), characterized in that the piston (30) comprises at least one gas passage (31, 32), arranged between the distal end (30B) and the proximal end (30A).

2. Pyrotechnic circuit breaker according to claim 1, wherein said at least one gas passage (31, 32) permits gas communication in the housing (10) so as to impose in the housing (10) and for 1 ms after a peak maximum pressure Pmax a pressure between Pmax and 0.9Pmax.

3. Pyrotechnic circuit breaker according to claim 1 or 2, wherein, when the piston (30) is in the rest position, the housing (10) forms with the piston (30): - a breaking chamber (130) comprising a portion of the electrical conductor (20) to be broken, - a pyrotechnic chamber (110), arranged to receive combustion gases from the pyrotechnic actuator (40), - a lateral chamber (120), separated from the cut-off chamber (130) by the piston (30), and isolated from the pyrotechnic chamber (110), in which the gas passage (31, 32) puts the cut-off chamber (130) into fluidic communication with the lateral chamber (120).

4. Pyrotechnic circuit breaker according to claim 3, wherein: - the housing (10) includes an ignition well, and - the piston (30) includes a skirt (36) engaged in the igniter well and separating the lateral chamber (120) from the pyrotechnic chamber (110).

5. Pyrotechnic circuit breaker according to claim 4, wherein: - the casing (10) includes a main cylinder, and - the piston (30) includes a peripheral surface (33) engaged in the main cylinder, and the gas passage (31, 32) is arranged between the peripheral surface (33) and the skirt (36) of the piston (30).

6. Pyrotechnic circuit breaker according to any one of claims 3 to 5, wherein the piston (30) in the activated position splits the cutting chamber (130) into several sub-chambers, and wherein the piston (30) has at least one gas passage (31, 32) per sub-chamber to the lateral chamber (120).

7. Pyrotechnic circuit breaker according to any one of claims 1 to 6, comprising at least one cooler (13, 14) arranged to cool gases heated by an electric arc generated during the interruption of the electrical conductor (20).

8. Pyrotechnic circuit breaker according to claim 7 in its dependence on any one of claims 3 to 6, wherein said at least one cooler (13, 14) is arranged in the breaking chamber (130) and / or in the side chamber (120).

9. Pyrotechnic circuit breaker according to any one of claims 7 or 8, wherein said at least one cooler (13, 14) is fixed to the housing (10) and / or to the piston (30).

10. Pyrotechnic circuit breaker according to any one of claims 1 to 9, wherein the gas passage (31, 32) is: - a through hole made in the piston (30), or - an external groove managed in a lateral surface of the piston (30).

11. Pyrotechnic circuit breaker according to any one of claims 1 to 10, wherein the gas passage (31, 32) has a transverse passage area greater than or equal to 15 mm, or even 25 mm 2 .

12. Pyrotechnic circuit breaker according to any one of claims 1 to 11, wherein the electrical conductor (20) passes through the housing (10).

13. Pyrotechnic circuit breaker according to any one of claims 1 to 12, wherein the gas passage (31, 32) is arranged to permit, upon interruption of the electrical conductor (20), a displacement of gases present from one side of the piston (30) opposite the electrical conductor (20) when the piston (30) is in the rest position to one side of the piston (30) opposite the pyrotechnic actuator (40) when the piston (30) is in the activated position.

14. Motor vehicle comprising at least one pyrotechnic circuit breaker according to any one of claims 1 to 13.

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