Pyrotechnic circuit breaker

Abstract

Pyrotechnic circuit breaker, comprising: - a housing (10), - an electrical conductor (20) to be interrupted, - a piston (30) arranged in the housing (10) for interrupting the electrical conductor (20) and movable between a rest position and an activated position in which the electrical conductor (20) is interrupted, - a pyrotechnic actuator (40) arranged in the housing (10) for moving 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), arranged between the distal end (30B) and the proximal end (30A). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Pyrotechnic circuit breaker Technical field of the invention

[0001] The present invention relates generally to pyrotechnic circuit breakers, intended to equip electric vehicles in order to quickly cut electrical circuits (in particular traction circuits with high current intensities, and / or high electrical voltages, and / or with high inductances). The currents flowing through such electric vehicle electrical circuits may have intensities of several thousand or tens of thousands of amperes, with voltages ranging from a few tens to several thousand volts State of the art

[0002] It is known in the prior art of circuit breakers to provide a gas passage in the housing between a breaking chamber which initially comprises the electrical conductor to be cut and a pyrotechnic chamber intended to receive combustion gases from the pyrotechnic actuator. On the other hand, this system may have the disadvantage of having large dimensions and / or problems of insufficiently high insulation resistance after operation (due to conductive deposits left by the combustion gases). Document DE102019135591 illustrates for example such a circuit breaker. Statement of the invention

[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 compact circuit breaker and / or which makes it possible to propose high operational safety.

[0004] For this purpose, 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 for cutting the electrical conductor and moving 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 pyrotechnic actuator side and a distal end opposite the proximal end, characterized in that the piston comprises at least one gas passage, arranged between the distal end and the proximal end. According to the above implementation, the The circuit breaker comprises at least one gas passage arranged on or in the piston, which provides a compact solution. In addition, the fluid communication between the distal end and the proximal end limits or prevents compression of the gases located above the piston during its movement, which increases operational safety by preventing the piston from moving backward due to excessive pressure exerted by the gases compressed by the distal end.

[0005] According to one embodiment, when the piston is in the rest position, the housing can form with the piston: - a cutting chamber comprising a portion of the electrical conductor to be cut, - a pyrotechnic chamber, arranged to receive combustion gases from the pyrotechnic actuator, - a side chamber, separated from the cutting chamber by the piston, and isolated from the pyrotechnic chamber, and the gas passage can put the interrupting chamber into fluid communication with the side chamber. According to the above implementation, the pyrotechnic chamber is isolated from the side chamber and the interrupting chamber by the piston, so that the combustion gases remain confined in the pyrotechnic chamber: operational safety is improved, with in particular high insulation resistances after operation.

[0006] According to one embodiment: - the housing may include an igniter well, and - the piston may include a skirt engaged in the igniter well and separating the side chamber from the pyrotechnic chamber. This construction is simple, the skirt provides additional guidance. A seal may be provided on the skirt.

[0007] According to one embodiment: - the housing may include a main cylinder, and - the piston may comprise a peripheral surface engaged in the main cylinder, and the gas passage may be arranged between the peripheral surface and the skirt of the piston.

[0008] According to one embodiment, the piston in the activated position can divide the cutting chamber into several sub-chambers, and the piston can have per sub-chamber at least one gas passage towards the lateral chamber. Even if the cutting chamber is partitioned once the piston has been moved, the presence of multiple gas passages guarantees the absence of overpressures on the distal end, which guarantees that the piston remains in the final position, without moving back.

[0009] According to one embodiment, the pyrotechnic circuit breaker may comprise at least one cooler arranged to cool gases heated by an electric arc. generated during the electrical conductor cut-off. Such coolers further improve operational safety by preventing the gases from remaining hot, even if electric arcs are created during operation: the pressure drops quickly.

[0010] According to one embodiment, said at least one cooler can be arranged in the cutting chamber and / or in the side chamber.

[0011] According to one embodiment, said at least one cooler may be fixed to the housing and / or to the piston. Provision may be made to arrange at least one cooler in the gas path, to force a passage therethrough, in order to cause more efficient cooling. For example, the gas passage may give or direct onto a cooler.

[0012] According to one embodiment, the gas passage may be: - a through hole provided in the piston, or - an external groove provided in a lateral surface of the piston.

[0013] According to one embodiment, the gas passage may have a transverse passage surface greater than or equal to 15, or even 25 mm2. This surface may be obtained by one passage, by two passages or more. It may be noted that the passage has a dimension much greater than a mechanical clearance present between two parts which must move relative to each other. Furthermore, manufacturing tolerances can cause a mechanical clearance between two moving parts to vary greatly, whereas the gas passage has a relatively variable surface, which provides better repeatability.

[0014] According to one embodiment, said at least one gas passage allows gas communication in the housing so as to impose in the housing and for 1 ms after a maximum pressure peak Pmax a pressure between Pmax and 0.9Pmax. According to this implementation, the gas passage makes it possible to avoid a maximum pressure peak that is too high, which provides a flatter pressure curve: the pressure varies little after the maximum pressure peak. The piston is therefore not subjected to much stress and does not move back once it has reached its maximum displacement.

[0015] According to one embodiment, the electrical conductor can pass through the housing.

[0016] According to one embodiment, the gas passage can be arranged to allow, during from the cutting of the electrical conductor, a displacement of gases present on one side of the piston opposite the electrical conductor when the piston is in the rest position towards one side of the piston opposite the pyrotechnic actuator when the piston is in the activated position.

[0017] 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

[0018] Other characteristics 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:

[0019] [Fig-1] represents a 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;

[0020] [Fig.2] represents a perspective view of the piston alone;

[0021] [Fig.3] represents voltage, current and pressure curves measured during the func operation in a circuit breaker of the prior art;

[0022] [Fig.4] represents voltage, current and pressure curves measured during operation in a circuit breaker according to the invention.

[0023] Detailed description of embodiment(s)

[0024] [Fig.l] represents a circuit breaker comprising: - a 10 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.

[0025] In detail, the housing 10 of the circuit breaker shown [Fig.l] 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 fixing 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. It is possible to note the presence of several seals 18 and 16 between the parts to guarantee good environmental resistance.

[0026] Generally speaking, the piston 30 is housed in the housing 10, so as to form: - a cutting chamber 130 comprising a part of the electrical conductor 20 to be cut, - a pyrotechnic chamber 110, arranged to receive combustion gases from the pyrotechnic actuator 40, - a side chamber 120, separated from the cutting chamber 130 by the piston 30, and isolated from the pyrotechnic chamber 110 by the piston 30.

[0027] 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 has: - a skirt 36 and a seal 35 on the side of the proximal end 30A; - a plurality of knives 34 separated by grooves 37 on the side of the distal end 30B, - passages 31 (orifices) establishing fluid 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 intended to fit together with the piston 30 in order to cut the electrical conductor 20.

[0028] Indeed, as shown in [Fig. 1], the pyrotechnic actuator 40 has been triggered and the piston 30 is therefore an activated position in which the electrical conductor 20 has been cut into several pieces. Indeed, it can be noted [Fig.l] that the electrical conductor 20 is constituted by 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 the rest position in the first half-shell 11, has been moved by the pressurized gases of the pyrotechnic actuator 40 expelled into the pyrotechnic chamber 110 to occupy the activated position shown [Fig.l].When moving 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 then being separated from the two external ends 24 and sandwiched between the piston 30 (the knives 37 and grooves 37) on the one hand and the housing 10 (the dies 17) on the other hand.

[0029] The circuit breaker comprises 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. In fact, first coolers 13 are housed in the breaking chamber 130, and second coolers 14 are housed in the lateral chamber 120.

[0030] The coolers may be metal parts. Porous parts or parts with internal voids may be provided. The coolers may be formed with a metal wire. The metal wire may be compacted on itself to form the coolers. In other words, each cooler is formed with one or more compacted wire(s). A compacted knit, or even porous sintered parts, may also be provided. Such parts can dissipate energy from gases heated by an electric arc.

[0031] Indeed, according to one embodiment, the coolers may be porous parts and / or with voids and / or with passages and / or with interstices, and / or with a density much lower than that of the metal from which they are formed, and which can be easily crossed by the gases, which provides a large exchange surface and an interesting cooling capacity for the gas of the cutting chamber 130. It may be noted that during operation, the gases of the cutting chamber 130 may 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 an effective heat exchange to cool the gases of the cutting chamber 130. In other words, the coolers may be designed to carry out cooling by convection (heat exchange between a gas and a solid).

[0032] [Fig. 2] represents a perspective view of the distal end 30B, that is to say 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 non-circular peripheral surface 33, which guarantees sliding of the piston 30 without rotation around its axis: the assembly is a sliding connection. 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 well aligned with the grooves 37.

[0033] It is also possible to note the presence of two passages 31 which are placed in the plane of the section of [Fig.l], and four passages 32 which are placed on either side of the plane of the section of [Fig.l] and each open into a groove 37 of the piston 30.

[0034] As seen above and clearly visible [Fig.l], the housing 10 defines: - on the side of the proximal end 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 side of the distal end 30B: the cutting 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 make it possible to guarantee gas communication between the cutting 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, a movement of gas 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 makes it possible to avoid excess gas pressures in the cutting chamber 130, because it will be remembered that the gases in the cutting chamber 130 are compressed by the movement of the piston 30 which reduces their volume, and by possible electric arcs which are established between the different pieces of the electrical conductor 20 and which heat the gases in the cutting chamber 130. The . piston 30 therefore experiences little or no stress or pressure forces applied to the distal end 30B which would tend to cause it to move back. The activated position of the piston 30 is more robust and more stable.

[0035] It may further be noted that during the movement of the piston 30, due to the interlocking of the dies 17 with or in the grooves 37, the initially single-piece cutting chamber 130 is progressively segmented into cutting sub-chambers. However, the different passages 31 and 32 are arranged on the piston 30 to properly place the lateral chamber 120 in communication with each of the cutting sub-chambers. Thus, any risk of overpressure is avoided.

[0036] It may also be noted that the lateral chamber 120 is well insulated from the pyrotechnic chamber 110, so that the combustion gases and residues from the pyrotechnic actuator 40 remain confined in the pyrotechnic chamber 110 and do not go into the lateral chamber 120 or into the cut-off chamber 130 and vice versa. Thus, the combustion gases and residues from the pyrotechnic actuator 40 do not impact the insulation resistance between the ends 24 and the gases and residues from the cutting of the electrical conductor 20 do not impact the insulation resistance at the pins of the pyrotechnic actuator 40.

[0037] [Fig. 3] represents measurements carried out during the operation of a prior art circuit breaker, i.e. without gas passing through the piston. The graph in [Fig. 3] shows: - a curve of the voltage at the terminals of the electrical conductor, - a curve of the intensity of the current passing through the electrical conductor, - a curve of the pressure prevailing in the breaking chamber.

[0038] At T= Oms, current flows through the electrical conductor while the voltage across its terminals is zero, because the electrical conductor is intact and conducts the current perfectly. The igniter is ignited, the piston begins to move.

[0039] At T=0.35 ms, the pressure begins to increase in the breaking 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.

[0040] At T = 0.40 ms, the pressure increases further in the breaking chamber, the current intensity still decreases and the voltage increases, 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 maximum, a pressure peak is reached and the voltage then drops to stabilize at the DC voltage of the open electrical circuit, while the intensity 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 bars at 0.5 ms, and that at 1.5 ms (i.e. 1 ms after the pressure peak), the pressure is slightly lower than 60 bars.

[0041] [Fig.4] represents the same measurements as [Fig.3], but carried out during the operation of a circuit breaker according to the invention, that is to say as in [Fig.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 the geometry of the circuit breaker is identical to the circuit breaker used for the measurements in [Fig.3]. We can see on the graph in [Fig.4]: - a curve of the voltage across the terminals of the electrical conductor, - a curve of the intensity of the current passing through the electrical conductor, - a curve of the pressure prevailing in the cutting chamber.

[0042] At T= Oms, current flows through the electrical conductor while the voltage across its terminals is zero, because the electrical conductor is intact and conducts the current perfectly. The igniter is ignited, the piston begins to move.

[0043] At T=0.35 ms, the pressure begins to increase in the breaking 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.

[0044] At T = 0.40 ms, the pressure increases further in the breaking chamber, the current intensity still decreases and the voltage increases: 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 maximum, a pressure peak is reached and the voltage then drops to stabilize at the DC voltage of the open electrical circuit, while the intensity 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 bars 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 bars.

[0045] Compared to the curves of [Fig.3], it can be noted that the duration during which the electric arc is present is lower (it can be considered that an electric arc is present as soon as the voltage is greater than zero and that the electric arc is cut when the voltage is stabilized at the open circuit voltage, i.e. the battery voltage). It can also be noted [Fig.4] that the maximum pressure peak is lower than that of [Fig.3], which is explained by the presence of the gas passages, which prevent the breaking chamber from being pressurized. Because of this lower pressure, it can be noted that the piston cuts the electrical conductor more efficiently and more quickly, and that the piston remains better in place in its final position, without moving back: the partitioning carried out by the piston is effective and limits the formation of the electric arc, which makes the cut-off faster.

[0046] 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.

[0047] In particular, it can be noted that the passages 31 and 32 are orifices provided in the piston 30, but it is possible to envisage providing grooves in the side wall 33 of the piston 30. It will be noted, however, that the gas passage surface, equal to the sum of the surfaces of the passages 31 and 32, is much greater than the peripheral clearance of the piston 30. In particular, the gas passage surface can be greater than 6 mm2, preferably greater than 9 mm2, and even greater than 12 mm2 per gas passage between a sub-chamber and the side chamber.

[0048] Furthermore, the igniter may for example be overmolded or crimped onto the housing 10 or the igniter support 15 depending on the materials chosen for the latter.

[0049] Apart from the electrical conductor 20 and the coolers 13 and 14, it may be provided that all or part of the parts of [Fig.l] are made of plastic, and / or polymer, and / or with a filler material. Polyamide may be provided, with glass fibers or any other reinforcing material.

[0050] Plastic parts can be overmolded onto or reinforced with metal elements depending on the stresses they have to withstand.

[0051] Other shapes can be provided for the piston 30, more or fewer knives 34 / grooves 37 / dies 17 can be provided.

[0052] Provision may be made to place the coolers on or in the piston 30. For example, provision may be made 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 interrupting chamber. Industrial application

[0053] A circuit breaker according to the present invention, and its manufacture, are capable of industrial application.

Claims

Claims

1. Pyrotechnic circuit breaker, comprising: - a housing (10), - an electrical conductor (20) to be cut, - a piston (30) arranged in the housing (10) for cutting 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) for moving 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) and comprising at least one orifice provided on the side of the distal end, so to establish fluid communication 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) allows gas communication in the housing (10) so as to impose in the housing (10) and for 1 ms after a maximum pressure peak 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 cut-off chamber (130) comprising a portion of the electrical conductor (20) to be cut, - 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) places the cut-off chamber (130) in fluid communication with the lateral chamber (120).

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

5. Pyrotechnic circuit breaker according to claim 4, wherein: - the housing (10) comprises a main cylinder, and - the piston (30) comprises 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 one of claims 3 to 5, in which the piston (30) in the activated position divides the cutting chamber (130) into several sub-chambers, and in which the piston (30) has per sub-chamber at least one gas passage (31, 32) towards the lateral chamber (120).

7. Pyrotechnic circuit breaker according to 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 cutting of the electrical conductor (20).

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

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

11. Pyrotechnic circuit breaker according to one of claims 1 to 10, in which the gas passage (31, 32) has a transverse passage surface greater than or equal to 15 mm, or even 25 mm2.

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

13. Pyrotechnic circuit breaker according to one of claims 1 to 12, in which the gas passage (31, 32) is arranged to allow, when the electrical conductor (20) is cut, a displacement of gases present on one side of the piston (30) opposite the electrical conductor (20) when the piston (30) is in the rest position towards one side of the piston (30) opposite the pyrotechnic actuator (40) when the piston (30) is in

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

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