Pyrotechnic circuit breaker and motor vehicle with such a circuit breaker

Abstract

Disclosed is a pyrotechnic circuit breaker comprising: - a housing (10), - at least two connection terminals (21, 22); - an internal electrical circuit linking the two connection terminals (21, 22) and consisting, for example, of an electrical conductor; - an opening member (40) that is movable and configured, when moving between an initial position and a final position, to open a section of the internal electrical circuit intended to be opened, thus forming at least two separate conductor portions (32, 33) after opening; - a pyrotechnic actuator (50) for moving the opening member (40) from the initial position to the final position; - an internal chamber (60) receiving the section to be opened, characterised in that the internal chamber includes or contains at least one inner surface formed by a wall consisting of a plastic material including a flame retardant.

Description

[0001] DESCRIPTION

[0002] TITLE: Pyrotechnic circuit breaker Technical field of the invention

[0003] The present invention generally relates to a pyrotechnic circuit breaker intended to be mounted on a motor vehicle, and in particular in an electrical power circuit of a motor vehicle, for example a hybrid vehicle or an electric vehicle.

[0004] State of the art

[0005] Circuit breaker devices are known in the prior art, such as that described in document US20130175144, which proposes using an insulating material that can flow. On the other hand, this system has the disadvantage of requiring a lot of insulating material that can flow, which requires large quantities and can generate leaks. In the case of a material containing silicone, precautions and authorizations will be necessary for automotive use (due to incompatibility with paint, for example). In addition, the applicant has noted that such an insulating material that can flow can generate longer opening times and / or degraded performance during operation of the circuit breaker (the time taken to actually cut off the flow of a high-power current (for example, at least 100 A / 100 V, or for example, 800 A / 450 V).Finally, it is important to be able to guarantee, after operation, good insulation resistance.

[0006] Document W02020099486A1 discloses a pyrotechnic circuit breaker with an internal wall made of plastic material that may contain reinforcing fibers, such as glass fibers. With such a device, the applicant realized that the insulation resistances after operation may not be sufficient to meet specific or severe demands.

[0007] Statement of the invention 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 circuit breaker which is simple to manufacture, having high cutting capacities, a rapid opening time during operation, and good insulation resistance after opening.

[0008] For this, a first aspect of the invention concerns a pyrotechnic circuit breaker comprising:

[0009] - a case,

[0010] - at least two connection terminals,

[0011] - an internal electrical circuit connecting the two connection terminals and formed for example by an electrical conductor,

[0012] - an opening member, movable and arranged to open a part to be opened of the internal electrical circuit during a movement between an initial position and a final position, so as to form at least two distinct conductor portions after opening,

[0013] - a pyrotechnic actuator arranged to move the opening member from the initial position to the final position,

[0014] - an internal chamber receiving the part to be opened, characterized in that the internal chamber comprises or contains at least one internal surface formed by a wall formed with a plastic material comprising a flame retardant.

[0015] According to the above implementation, the circuit breaker comprises a wall arranged in the internal chamber, i.e. opposite the part to be cut, and which contains a flame retardant. The applicant noticed that the insulation resistances after operation were higher than those measured on circuit breakers having the same geometric configuration, but not made of a material with a flame retardant. In other words, providing a flame retardant in the material of one of the walls exposed to the electric arc formed during the cut makes it possible to significantly reduce the leakage currents once the cut has been made.

[0016] In other words, the internal chamber comprises or contains at least one internal surface formed by a wall formed:

[0017] - with a plastic material added with a flame retardant, or

[0018] - with a plastic material comprising an additive chosen to be a flame retardant. According to this implementation, it can be provided that the flame retardant additive is directly integrated or incorporated into the granules which will be melted to be used, for example, to inject the surface of the wall into the internal chamber.

[0019] According to one embodiment, said plastic material comprising the flame retardant may be a polymer, such as a polyamide, and preferably a polyphthalamide (PA 6T / 66).

[0020] According to one embodiment, said plastic material comprising the flame retardant may be a polymer forming a matrix, and comprising a filler material, such as fibers, preferably inorganic fibers, for example glass fibers, in a proportion ranging from 10% to 70% by weight and preferably in a proportion ranging from 45% to 55% by weight.

[0021] According to one embodiment, said plastic material comprising the flame retardant can self-extinguish after 10 seconds, during a flammability test according to the UL94 standard (6th edition of March 28, 2013) carried out on a vertical test piece, particle losses being permitted as long as the lost particles are not ignited.

[0022] According to one embodiment, the flame retardant may be a non-halogenated compound, selected from:

[0023] - conversion or reaction products of melamine with cyanuric acid,

[0024] - condensation products of melamine, - conversion or reaction products of melamine with polyphosphoric acid,

[0025] - conversion or reaction products of condensation products of melamine with polyphosphoric acid, - metal phosphinates,

[0026] - phosphoric acid esters,

[0027] - mixtures of these materials.

[0028] According to one embodiment, the flame retardant may be a non-halogenated compound, selected from the following compounds and mixtures thereof: melamine cyanurate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, melem phosphate (i.e., 2,5,8-triaminoheptazine phosphate), melem pyrophosphate, dimelamine pyrophosphate, dimelamine phosphate, melem polyphosphate, phosphaphenanthrenes, metal hydroxides, phosphinic acid salts, diphosphinic acid salts.

[0029] It may be noted that glass fibers used in a known manner to reinforce a plastic material, even if they do not burn or burn with difficulty, will in no way limit or delay ignition or combustion of said plastic material. According to one embodiment, the pyrotechnic circuit breaker may comprise a base portion formed by a second plastic material, and said plastic material comprising the flame retardant may be attached or overmolded onto the base portion. Such an implementation makes it possible to locate the plastic material comprising the flame retardant only where it will be correctly exposed to the electric arc, without providing an additional part.

[0030] According to one embodiment, the opening member may comprise:

[0031] - an opening body formed by a second plastic material,

[0032] - an exposed face, formed by the plastic material comprising the flame retardant overmolded or added to the opening body and arranged opposite the part to be opened and / or on the internal chamber side. Such a location on the opening member guarantees that the plastic material comprising the flame retardant will be as close as possible to the electric arc, and will therefore be well exposed to the latter to then guarantee that the insulation resistances are high and reproducible.

[0033] According to one embodiment, said second material may be a polyamide, preferably a polyphthalamide (PA 6.T / XT) forming a matrix, and which may comprise glass fibers, in a proportion ranging from 40% to 50% by weight. The second material makes it possible to provide a robust opening body which is highly resistant to mechanical stress.

[0034] According to one embodiment, the pyrotechnic circuit breaker may be arranged to generate an electric arc between the two separate conductor portions when the opening member moves between the initial position and a final position, when the circuit breaker is connected to a live electrical circuit, and the plastic material comprising the flame retardant may be arranged to be removed by ablation by the electric arc. In detail, the plastic material comprising the flame retardant arranged to be removed by ablation is transformed (for example sublimated) under the action of the intense heat flow of the electric arc. This material removed by ablation may then condense or be deposited on the walls of the internal chamber, and this provides high insulation resistances. Furthermore, such an implementation may modify the composition of the electric arc plasma and its conductivity, and makes it possible to increase the electric arc voltage.Such electric arcs can be created when the circuit breaker is connected to a live electrical circuit, with voltages ranging from 0V to 1000V and currents ranging from 0A to 25000A on inductive loads of up to 2500mH (micro-Henry) for an intensity of less than 500A and up to 5mH for an intensity of 25000A. The circuit breaker according to the invention makes it possible to cut the current reliably in less than 10ms and even less than 5ms, permanently, because the circuit breaker, comprising a pyrotechnic actuator, can only be used once. Once used, the circuit breaker also has good insulation resistance.

[0035] According to one embodiment, the pyrotechnic circuit breaker may comprise at least one passage arranged to guide the electric arc between the two separate conductor portions, and the plastic material comprising the flame retardant may be arranged to form or at least partially delimit the passage. According to this implementation, the plastic material comprising the flame retardant is necessarily exposed to the electric arc.

[0036] According to one embodiment, the passage may be at least partially formed on the opening member.

[0037] According to one embodiment, the internal chamber may comprise or contain at least one wall formed with a third plastic material comprising silicone. According to this implementation, at least one other wall of the internal chamber comprises silicone. The applicant has noticed that adding silicone to a material forming the wall makes it possible to guarantee high insulation resistances after use. In addition, the applicant has noticed that if another wall comprises the flame retardant, then the effect on the insulation resistances is amplified.

[0038] According to one embodiment, the pyrotechnic circuit breaker may comprise at least one support, and the third plastic material comprising silicone may be overmolded or attached to the support. Such an implementation makes it possible to locate the third plastic material comprising the silicone only where it will have a significant effect on the insulation resistance, without providing an additional part.

[0039] According to one embodiment, the support may include a portion of the electrical conductor. According to one embodiment, the support may include a portion of the housing.

[0040] According to one embodiment, the support may comprise a portion of the opening member.

[0041] According to one embodiment, the wall formed with the third plastic material comprising silicone can support a leakage current path between the two separate conductor portions after opening, and preferably the shortest leakage current path between the two separate conductor portions after opening. Such an implementation, with the addition of silicone in the wall supporting the shortest leakage current path, makes it possible to effectively cut off the leakage current path that would be taken by a leakage current.

[0042] According to one embodiment, the wall formed with the third plastic material comprising silicone may cover less than 50% of a total surface area of ​​the internal chamber. Such an implementation makes it possible to limit the use or addition of silicone only where it will have a significant effect on the insulation resistances.

[0043] According to one embodiment, the third plastic material comprising silicone may comprise a polyamide-type polymer, preferably a polyphthalamide of the PA6T / XT type.

[0044] According to one embodiment, the third plastic material comprising silicone may comprise silicone and / or polysiloxane, in a proportion ranging from 3.5% to 6.5% by weight, and preferably from 4.25% to 5.75% by weight.

[0045] According to one embodiment, once the opening member is in the final position, an insulation resistance between the connection terminals may be greater than 30 Mohms, preferably greater than 500 Mohms, preferably greater than 100 Mohms, preferably greater than 500 Mohms, and very preferably greater than 1000 Mohms. Another aspect of the invention relates to a method for manufacturing a circuit breaker according to the first aspect, comprising the steps of:

[0046] - form a box,

[0047] - form an internal electrical circuit connecting the two connection terminals and formed for example by an electrical conductor,

[0048] - providing a movable opening member arranged to open a part to be opened of the internal electrical circuit during a movement between an initial position and a final position, so as to form at least two distinct conductor portions after opening, - providing a pyrotechnic actuator arranged to move the opening member from the initial position to the final position,

[0049] - forming an internal chamber receiving the part to be opened, characterized in that the method comprises a step consisting of forming the internal chamber with at least one wall formed with a plastic material comprising silicone, by adding to a first raw material, for example in granules, intended to form the internal chamber a second raw material, for example in granules, comprising between 40% and 60% by weight of silicone.

[0050] In other words, the method according to the invention comprises a step consisting of mixing, before manufacturing the internal chamber, the first raw material, for example in granules, intended to form the internal chamber, with the second raw material, for example in granules, comprising between 40% and 60% by weight of silicone. Typically, the wall comprising the silicone is formed by an injection-molding process, and the manufacturing method comprises a step of preparing the material to be injected by mixing two types of granules: the first raw material and the second raw material which contains the silicone. There is therefore no pure silicone to provide or handle, simply solid granules already comprising the silicone. This implementation makes it possible to keep the process simple. Another aspect of the invention relates to a motor vehicle comprising at least one circuit breaker according to the first aspect.

[0051] Description of figures

[0052] 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:

[0053] [fig. 1] represents a sectional view of a pyrotechnic circuit breaker, comprising in particular a housing crossed by an electrical conductor forming an internal electrical circuit, a pyrotechnic actuator and an opening member arranged to open the internal electrical circuit when the pyrotechnic actuator is actuated or triggered;

[0054] [fig. 2] represents a detail of the circuit breaker housing of figure 1;

[0055] [fig. 3] represents a detail of the opening member of the circuit breaker of figure 1;

[0056] [fig. 4] represents a detail of a section of the circuit breaker of figure 1 after actuation or triggering of the pyrotechnic actuator;

[0057] [fig. 5] schematically represents a top view section of the circuit breaker of figure 1. Detailed description of embodiment(s)

[0058] Figure 1 represents a circuit breaker comprising in particular:

[0059] - a housing 10 formed by a lower housing portion 12 and an upper housing portion 11,

[0060] - two connection terminals 21 and 22, - an internal electrical circuit connecting the two connection terminals 21 and 22 and formed by an electrical conductor 31,

[0061] - an opening member 40, movable and arranged to open a part to be opened 31 A of the internal electrical circuit during a movement between an initial position (according to figure 1) and a final position (according to figure 4), so as to form at least two distinct conductor portions 32 and 33 (visible in figure 4) after opening,

[0062] - a pyrotechnic actuator 50 arranged to move the opening member 40 from the initial position to the final position,

[0063] - an internal chamber 60 (comprising a lower chamber 62 and an upper chamber 61), defined by one or more internal walls formed in the housing 10, and receiving the part to be opened 31 A,

[0064] - coolers 70 arranged inside the housing 10 and designed to lower the gas temperatures during operation and thus increase the cutting capacity of the circuit breaker.

[0065] The circuit breaker in Figure 1 is typically integrated into a power circuit of a motor vehicle (e.g., an electric vehicle) and can be used to cut off the power circuit if an emergency situation arises. One of the functions of this circuit breaker is therefore to be able to cut off a power circuit quickly, even if high currents are present (e.g., more than 500 amps). Another function of this circuit breaker is to ensure good insulation resistance between the connection terminals 21 and 22 after opening the internal electrical circuit.

[0066] To fulfill the opening function, the pyrotechnic actuator 50 (typically an electro-pyrotechnic igniter) is triggered and a high pressure is generated in the space between the pyrotechnic actuator 50 and the opening member 40, which pushes the latter upwards in FIG. 1, to move from the initial position shown to the final position in FIG. 4.

[0067] During this movement, the opening member 40 comes into contact with the part to be opened 31A of the electrical conductor, and therefore opens the internal electrical circuit by cutting the electrical conductor 31, by mechanical shearing. However, it is possible to alternatively provide an opening by pushing one of two initially separate strands in contact with each other, to separate them.

[0068] As shown in Figure 3, the opening member 40 comprises two projections 45, separated by a groove 46, and which form knives for cutting the part to be opened 31 A. In detail, and as shown in Figure 1, the part to be opened 31 A comprises a central portion supported by a return 13 of the upper housing portion 11, engaged with a bar 14 overmolded on the central portion of the part to be opened 31 A and secured to an overmolded body 15, overmolded on the electrical conductor 31.

[0069] When the opening member 40 is moved from the initial position to the final position, the projections 45 of the opening member 40 bear on the unsupported parts of the electrical conductor 31 and shear it on either side of the bar 14 and the return 13 (at the part to be opened 31A opposite the upper chamber 61). However, it is possible to alternatively have a single projection 45 or more than two projections 45, the number of projections 45 defining the number of cuts made on the electrical conductor 31 when the opening member 40 is moved.

[0070] As shown in Figure 4, the shear of the electrical conductor 31 forms:

[0071] - two distinct lateral portions 32 each having an internal end 34 in the internal chamber 60 (and in particular in the upper chamber 61), and

[0072] - a central portion 33, remaining engaged with the bar 14.

[0073] Furthermore, at the very start of opening, when the internal ends 34 are still close to the central portion 33, an electric arc can form (depending on whether current is passing through the electrical conductor 31 or not) between each internal end 34 and the central portion 33, at the level of an arc path TA shown in dotted lines in Figure 4. During the movement from the initial position to the final position, the opening member 40 pushes and causes a bending of each separate lateral part 32, so that the arc path TA “stretches” or “lengthens” to present at the end of operation a sufficient free distance to guarantee extinction of the electric arc and rapid cutting or opening of the internal electrical circuit.

[0074] Figures 2 and 3 show the mounting of the opening member 40 in the housing 10, and in particular, guide units are provided between the opening member 40 and the housing 10, at the level of the overmolded body 15. Indeed, the opening member 40 (figure 3) is provided with lateral projections 43 forming guide protrusions, and the overmolded body 15 with lateral grooves 613 forming guide grooves, formed in side walls 611 of the upper chamber 61 (visible in figure 2).

[0075] The opening member 40 is therefore mounted in sliding connection or in translation relative to the housing 10 and slides during its movement from the initial position to the final position, which provides reproducible and controlled operation and final position to guarantee rapid opening and arc extinction at the end of operation with a sufficient free distance.

[0076] However, the operation of the pyrotechnic actuator 50 can generate numerous particles and hot gases which are projected into the internal chamber 60, and which typically cover or condense on the walls of the latter, and in particular the walls 611, the lateral projections 43 and the lateral grooves 613. Such deposits can form a conductive or weakly conductive layer of electricity, and an insulation resistance, after opening of the electrical conductor 31, can be affected.

[0077] In addition, the electric arc can remove material from the opening member 40 and / or the housing 10 (return 13 or bar 14 in particular) by ablation, which can generate gases or particles which will also cover and / or condense on the walls of the internal chamber 60 and also affect the insulation resistance.

[0078] Such insulation resistance, measured after operation, between the connection terminals 21 and 22 must be high, to guarantee the absence of leakage current between the connection terminals 21 and 22 after opening of the internal electrical circuit of the circuit breaker.

[0079] Such leakage currents typically travel along leakage current paths between the separate conductor portions after opening, which travel along the inner wall of the inner chamber 60.

[0080] Figure 5 shows a schematic section (therefore not showing all the details of Figure 1) of the circuit breaker of Figure 1 after opening, in a plane passing through the upper face of the electrical conductor 31, seen from above.

[0081] The electrical conductor 31 has therefore been opened into three distinct conductor portions, i.e. two distinct lateral portions 32 and a central portion 33. The central portion 33 is separated from the two distinct lateral portions 32 by the lateral projections 45 of the opening member 40.

[0082] Detail A and detail B of Figure 5 show that a leakage current can travel a leakage current path CCF formed along the inner wall of the inner chamber 60, in particular between the lower corner 32A of the separate lateral portion 32 and the lower corner 33A of the central portion 33 which is the shortest leakage current path.

[0083] It should be noted that the function of providing good insulation resistance must be ensured after operation, once the electrical conductor 31 has been cut or opened. Typically, a leakage current cannot be established along the arc path TA because the resistivity of the air is too high. Consequently, a leakage current can only travel along the walls of the circuit breaker, in particular the internal walls of the internal chamber 60 or the walls of the opening member 40, and this preferably on the shortest path, which has the lowest insulation resistance.

[0084] As shown in details A and B of Figure 5, the leakage current path CCF travels or extends along the wall of the inner chamber 60.

[0085] In practice, it is expected or desired that the insulation resistance between the connection terminals be greater than 30Mohms, preferably greater than SOMohms, preferably greater than 100Mohms, preferably greater than SOOMohms, and very preferably greater than IGohms, even if particles or condensed gases have been deposited on the internal wall of the internal chamber.

[0086] In order to guarantee good insulation resistance, it may be, in a first alternative, proposed to provide in the internal chamber 60 a wall formed with a plastic material comprising a flame retardant. Indeed, the applicant has noticed that the addition of a flame retardant, in particular in a wall forming a surface exposed to the electric arc during operation of the circuit breaker, makes it possible to significantly increase the insulation resistances after operation.

[0087] The plastic material comprising the flame retardant may typically be a polyamide, and preferably a polyphthalamide (such as PA 6T / 66). Reinforcing fibers may be provided, for example glass fibers in a ratio of 45% to 55% by weight.

[0088] The flame retardant is typically a non-halogenated compound, selected from the following materials and their mixtures:

[0089] - conversion or reaction products of melamine with cyanuric acid,

[0090] - melamine condensation products,

[0091] - conversion or reaction products of melamine with polyphosphoric acid,

[0092] - conversion or reaction products of condensation products of melamine with polyphosphoric acid,

[0093] - metal phosphinates,

[0094] - phosphoric acid esters.

[0095] In particular, it can be provided that the flame retardant is a non-halogenated compound, selected from the following compounds and mixtures thereof: melamine cyanurate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, melem phosphate, melem pyrophosphate, dimelamine pyrophosphate, dimelamine phosphate, melem polyphosphate, phosphaphenanthrenes, metal hydroxides, phosphinic acid salts, diphosphinic acid salts.

[0096] The plastic material comprising the flame retardant may comprise the flame retardant between 2% and 30% by mass, and preferably between 5% and 30% by mass and more preferably between 8% and 25% by mass.

[0097] The flame retardant may further comprise at least one synergist (or synergistic compound, which further improves the resistance to ignition), said at least one synergist being selected from the group consisting of nitrogen-containing compounds, nitrogen-phosphorus-containing compounds, metal borates, metal carbonates, metal hydroxides, metal hydroxides, metal nitrides, metal oxides, metal phosphates, metal sulfides, metal stannates, metal hydroxystannates, silicates, zeolites, basic zinc silicates, silicic acids and combinations thereof, in particular triazine derivatives, melamine, guanidine, guanidine derivatives, biuret, triuret, tartrazine, glycoluril, acetoguanamine, butyroguanamine, caprinoguanamine, benzoguanamine, melamine derivatives of cyanuric,melamine derivatives of isocyanuric acid, melamine cyanurate, melamine condensation products, melamine pyrophosphate, pyrophospates of melamine condensation products, dimelamine phosphate, dimelamine pyrophosphate, melamine polyphosphate, dicyandiamide, ammonium polyphosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, polyphosphates of melamine condensation products, melamine sulfate, allantoin, aluminum hydroxide, synthetic aluminum hydroxide, synthetic aluminum metahydroxide, natural aluminum hydroxide, natural aluminum metahydroxide, aluminum oxide, calcium borate, calcium carbonate, calcium magnesium carbonate, calcium oxide, calcium sulfide, iron oxide, magnesium borate, magnesium carbonate, magnesium hydroxide, magnesium nitride, magnesium oxide, magnesium sulfide, hydroxide manganese, manganese oxide, titanium nitride,titanium dioxide, zinc borate, zinc metaborate, zinc carbonate, zinc hydroxide, zinc nitride, zinc oxide, zinc phosphate, zinc sulfide, zinc stannate, zinc hydroxystannate, basic zinc silicate, hydrated tin oxide and combinations thereof. Typically, the plastic material comprising the flame retardant self-extinguishes after 10 seconds, when tested for flammability according to UL94 (6th edition dated March 28, 2013) and carried out on a vertical test piece, with particle losses being permitted as long as the lost particles are not ignited. In particular,The length of the specimen is 5" (127 mm) and its width is 0.5" (12.7 mm). Its thickness must not exceed 0.5' (12.7 mm). It is fixed at 1 / 4 of its upper end in a vertical position. A metal net covered with surgical cotton is placed 12" (305 mm) below the specimen. The burner is adjusted to form a blue flame of 3 / 4" (19 mm). This flame is directed from below on the lower edge of the plastic specimen at a distance of 3 / 8" (9.5 mm). It is applied for 10 seconds, then withdrawn. The combustion time of the specimen is measured. As soon as the combustion stops, the flame is reapplied for 10 seconds. As soon as it is withdrawn, the combustion and incandescence time are again measured. The complete test is carried out on five specimens.,

[0098] The tested material is classified UL 94 V-0 if:

[0099] A) None of the five samples burns for more than 10 seconds after the burner flame is removed.

[0100] B) The total combustion time over the 5 tests does not exceed 25 seconds. C) None of the samples tested burn, either with a flame or by incandescence, up to the holding jaw.

[0101] D) No incandescent drop, which could ignite the cotton placed below, falls from any sample.

[0102] E) No sample has an incandescence time exceeding 30 seconds.

[0103] In the example shown, the opening member 40 may be provided with an opening body 41 (forming a base portion), onto which is overmolded an exposed face 42, formed with the plastic material comprising the flame retardant. Alternatively, the plastic material comprising the flame retardant could be provided at another wall opening into the internal chamber, such as on the housing 10 or on the overmolded body 15.

[0104] The base part, i.e. here the opening body 41, may be a second plastic material, such as a polyamide, preferably a polyphthalamide such as PA 6.T / XT forming a matrix, and comprising glass fibers, in a proportion ranging from 40% to 50% by weight.

[0105] For example, after operating tests (breaking a live circuit) carried out under various conditions, insulation resistances were measured on reference circuit breakers, and circuit breakers with an opening member comprising flame retardant (to form an exposed face 42 attached to the opening member 40). The results are shown in Tables 1, 2 and 3:

[0106] Tests carried out under 450V / 8000A / 15mH / +125°C

[0107] [table 1]

[0108] Tests carried out at 475V / 8000A / 20mH / +125°C [table 2] Tests carried out at 450V / 8000A / 20mH / +125°C [table 3]

[0109] It can be noted that in each series of tests, the insulation resistances after opening are significantly higher with the parts whose internal chamber includes a surface exposed to the electric arc formed by the material comprising the flame retardant, than on the reference parts not comprising flame retardant.

[0110] It should be noted that the plastic material containing the flame retardant is positioned as close as possible to the arc path TA, and for this purpose, a passage 44 is provided on the opening member 40 to guide the electric arc, the passage 44 being directly formed in the plastic material containing the flame retardant. In practice, the passage 44 is a groove of small dimensions (a few tenths of a millimeter in width and / or depth) formed in the plastic material containing the flame retardant, to provide a free space even when the opening member 40 is in the final position in abutment on the return 13, so that an electric arc will preferentially pass through this passage 44 and remove by ablation the plastic material containing the flame retardant.

[0111] In order to guarantee good insulation resistance, it may be, in a second alternative, proposed to provide in the internal chamber 60 a wall formed with a third plastic material comprising silicone.

[0112] In fact, the applicant noticed that the addition of silicone, in particular in a wall through which a leakage current could flow after operation of the circuit breaker, makes it possible to significantly increase the insulation resistances after operation.

[0113] In particular, the third plastic material comprising silicone comprises a polyamide-type polymer, preferably a polyphthalamide, such as PA6T / XT. In detail, the third plastic material comprising silicone comprises silicone and / or polysiloxane, in a proportion ranging from 3.5% to 6.5% by weight, and preferably from 4.25% to 5.75% by weight.

[0114] In the example shown, it can be provided that the third plastic material comprising the silicone is used for the overmolding of the electrical conductor 31, that is to say to produce the overmolded body 15 visible in FIG. 1. Indeed, according to the embodiment example shown here, it is on the wall of this component (the overmolded body 15) that the shortest leakage current path is located, as explained above with reference to FIG. 5. However, it could be provided to add silicone to other parts forming walls contained in the internal chamber 60, such as the housing 10 or the cutting member 40.

[0115] The applicant noticed that the addition of silicone in this overmolding made it possible to increase the insulation resistances. For example, after operating tests (cutting a live circuit), insulation resistances were measured on reference circuit breakers, and circuit breakers with overmolded body 15 comprising 10% silicone. The results are shown in Table 4:

[0116] Tests carried out under 450V / 8000A / 20mH / +125°C

[0117] [table 4]

[0118] It can be noted that the insulation resistances after openings are significantly higher with the parts whose overmolded body 15 comprises 10% silicone, than on the reference parts whose overmolded body 15 does not comprise silicone. Finally, the applicant noticed that there was a strong increase in the insulation resistances if the two alternatives are combined, i.e. provided in the internal chamber;

[0119] - a wall with the plastic material including the flame retardant, and

[0120] - a wall with the third plastic material including silicone.

[0121] Indeed, in the context of the tests reported in tables 3 and 4, the applicant also tested circuit breakers with one wall of the internal chamber comprising flame retardant (the exposed face 42 of the opening member 40) and another wall comprising silicone (in the overmolded body 15), and the results are reported in table 5.

[0122] Tests carried out at 450V / 8000A / 20mH / +125°C [table 5]

[0123] It can be noted from the results in Table 5 that the effect on the insulation resistance by combining one wall of the internal chamber comprising flame retardant and another wall comprising silicone goes well beyond the simple addition of the effects measured on parts comprising only one or the other of the alternatives. Consequently, a synergy was observed and this configuration (one wall of the internal chamber comprising flame retardant and another wall comprising silicone) is of demonstrated interest. It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to the different embodiments of the invention described in the present description without departing from the scope of the invention.

Claims

DEMANDS

1. Pyrotechnic circuit breaker comprising: - a case (10), - at least two connection terminals (21, 22), - an internal electrical circuit connecting the two connection terminals (21, 22) and formed for example by an electrical conductor (31), - an opening member (40), movable and arranged to open a portion to be opened of the internal electrical circuit during a movement between an initial position and a final position, so as to form at least two distinct conductor portions (32, 33) after opening, - a pyrotechnic actuator (50) arranged to move the opening member (40) from the initial position to the final position, - an internal chamber (60) receiving the part to be opened, characterized in that the internal chamber (60) comprises or contains at least one internal surface formed by a wall made with a plastic material comprising a flame retardant.

2. Pyrotechnic circuit breaker according to claim 1, wherein said plastic material comprising the flame retardant is a polymer, such as a polyamide, and preferably a polyphthalamide (PA 6T / 66).

3. Pyrotechnic circuit breaker according to any one of claims 1 to 2, wherein said plastic material comprising the flame retardant is a matrix-forming polymer, and comprising a filler material, such as fibers, preferably inorganic fibers, for example glass fibers, carbon fibers, in a proportion from 10% to 70% by weight and preferably in a proportion from 45% to 55% by weight.

4. Pyrotechnic circuit breaker according to any one of claims 1 to 3, wherein said plastic material comprising the flame retardant self-extinguishes after 10 seconds, during a Flammability test according to UL94 standard (6th edition of March 28, 2013) carried out on a vertical test specimen, particle loss being permitted as long as the lost particles are not ignited.

5. Pyrotechnic circuit breaker according to any one of claims 1 to 4, wherein the flame retardant is a non-halogenated compound, selected from: - the conversion or reaction products of melamine with cyanuric acid, - the condensation products of melamine, - the conversion or reaction products of melamine with polyphosphoric acid, - the conversion or reaction products of the condensation products of melamine with polyphosphoric acid, - metallic phosphinates, - phosphoric acid esters, - mixtures of these materials.

6. A pyrotechnic circuit breaker according to any one of claims 1 to 4, wherein the flame retardant is a non-halogenated compound selected from the following compounds and mixtures thereof: melamine cyanurate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, melem phosphate, melem pyrophosphate, dimelamine pyrophosphate, dimelamine phosphate, melem polyphosphate, phosphaphenanthrenes, metal hydroxides, phosphinic acid salts, diphosphinic acid salts.

7. A pyrotechnic circuit breaker according to any one of claims 1 to 6, comprising a base portion formed from a second plastic material, wherein said plastic material comprising the flame retardant is attached to or overmolded onto the base portion.

8. Pyrotechnic circuit breaker according to any one of claims 1 to 7, arranged to generate an electric arc between the two distinct conductor portions (32, 33) during the movement of the opening member (40) between the initial position and a final position, when the circuit breaker is connected to a live electrical circuit, in which the plastic material comprising the flame retardant is arranged to be removed by ablation by the electric arc.

9. Pyrotechnic circuit breaker according to claim 8, comprising at least one passage (44) arranged to guide the electric arc between the two separate conductor portions (32, 33), in which the plastic material comprising the flame retardant is arranged to form or delimit at least partially the passage (44).

10. A pyrotechnic circuit breaker according to any one of claims 1 to 9, wherein the internal chamber (60) comprises or contains at least one wall formed with a third plastic material comprising silicone.

11. A pyrotechnic circuit breaker according to claim 10, comprising at least one support, and wherein the third plastic material comprising silicone is overmolded or attached to the support.

12. Pyrotechnic circuit breaker according to any one of claims 10 to 11, wherein the wall formed with the third plastic material comprising silicone supports a leakage current path between the two separate conductor portions (32, 33) after opening, and preferably the shortest leakage current path between the two separate conductor portions (32, 33) after opening.

13. Pyrotechnic circuit breaker according to any one of claims 10 to 12, wherein the wall formed with the third plastic material comprising silicone covers less than 50% of a total surface of the internal chamber (60).

14. Pyrotechnic circuit breaker according to any one of claims 10 to 13, wherein the third plastic material comprising silicone includes silicone and / or polysiloxane, in a proportion ranging from 3.5% to 6.5% by weight, and preferably from 4.25% to 5.75% by weight.

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