Pyrotechnic device with riveted housing

Abstract

The present invention relates to a pyrotechnic switch, comprising: a housing (10), the housing being formed by a first housing part (11) and a second housing part (12); at least one rivet (40), the first housing part (11) being riveted to the second housing part (12) by means of the at least one rivet so as to form the housing (10); and at least one pyrotechnic actuator (32), the at least one pyrotechnic actuator being arranged in the housing (10); characterized in that: at least one of the first housing part (11) or the second housing part (12) comprises a metal insert (16) and a plastic body (C1, C2) overmolded onto the metal insert (16); the metal insert (16) comprises a passage opening for the rivet (40); and the rivet (40) is in contact with the passage opening of the metal insert (16).

Description

Technical Field

[0001] The present invention generally relates to pyrotechnic devices, such as pyrotechnic switches, intended to be installed in motor vehicles. Background Art

[0002] Such devices usually comprise a housing of two or more parts, which are fastened to each other by clamping, bolts or rivets in order to enclose the pyrotechnic actuator. Document CN205943939 shows such a device with a housing. Then, this system with a housing of multiple parts has the disadvantage of having weak points, so that it is difficult to provide a good seal and a good resistance to the pressure generated by the pyrotechnic actuator during operation. Therefore, its manufacturing method is complicated, because the weakness of the components must be taken into account. Document EP0929090 (A2) discloses a pyrotechnic circuit breaker having a support bracket riveted to the housing part. Summary of the invention

[0003] The object of the present invention is to address the drawbacks of the above-mentioned background art documents and in particular to first propose a pyrotechnic device with a casing in several parts which obtains good sealing and good resistance to operating pressures while remaining easy to assemble.

[0004] Thus, a first aspect of the present invention relates to a pyrotechnic switch comprising:

[0005] - a housing formed by a first housing part and a second housing part;

[0006] at least one rivet, by means of which the first housing part is riveted together with (or to) the second housing part in order to form the housing;

[0007] - at least one pyrotechnic actuator, the at least one pyrotechnic actuator being arranged in the housing;

[0008] Features:

[0009] At least one of the first housing portion or the second housing portion includes a metal insert and a plastic body overmolded onto the metal insert,

[0010] The metal insert comprises a passage opening for the rivet,

[0011] And the rivet is in contact with the passage opening of the metal insert. According to the above embodiment, the rivet is in contact with the metal insert so that the rivet rests on the part made of resistant metal. Therefore, the plastic body does not receive riveting forces or position retention forces. The weakness of the plastic part is no longer a problem.

[0012] Advantageously, the rivet is in contact with the first housing part on the one hand and with the second housing part on the other hand. In other words, the first end of the rivet is in contact with the first housing part and the second end of the rivet is in contact with the second housing part.

[0013] Advantageously, the rivet is in contact with the side wall of the passage opening. That is, the expansion of the rivet is borne by the passage opening of the metal insert.

[0014] Advantageously, the entire periphery of the rivet is in contact with the side wall of the passage opening. Thus, the rivet is optimally retained.

[0015] Advantageously, the rivet comprises a base opposite the contact area with the passage opening, the base having a shoulder perpendicular to the axial direction of the rivet in order to form a support on or for the other of the first or second housing parts. Such a base with a shoulder obtains a large support surface, which thus limits the contact pressure. The perpendicular shoulder prevents radial stresses from being generated in the opening of the other of the first or second housing parts.

[0016] According to the convention in this patent application, the base forms the rivet tail and is formed before assembling the pyrotechnic switch. In contrast to the base, the head of the rivet is initially cylindrical so as to be inserted into the passage opening. During assembly, the riveting tool deforms the head to flatten and widen it.

[0017] Advantageously, the rivet is not in full contact with the plastic body of at least one of the first or second housing parts, including the metal insert, the metal insert having in particular a passage opening in the region of the housing between the metal insert and the base of the rivet, which is in contact with the rivet. In other words, the rivet only contacts the metal insert of the housing part including the rivet. The radial forces generated by the riveting operation are therefore first and mainly borne by the metal insert. The head of the rivet, once deformed, provides contact between the head of the rivet and the housing, or provides a recess (e.g. a countersunk hole) at this height.

[0018] Advantageously, at the height of the passage opening, the metal insert has a passage having a size smaller than a passage around a rivet in said at least one of the first housing part or the second housing part comprising the metal insert. In other words, the insert has a passage hole having a size smaller than the passage hole of the plastic body, which ensures that the rivet does not come into contact with the plastic body. This ensures that the rivet first contacts the metal insert when deforming. In particular, the insert has a passage hole having a diameter smaller than that implemented in the plastic body.

[0019] Advantageously, the metal insert comprises a plurality of overmolding openings to enable overmolding of the plastic body on both sides of the metal insert and to allow the material of the plastic body to be continuous through the overmolding openings. Thus, the plastic body is tightly coupled to the metal insert and the manufacturing method (usually by injection molding) remains easy to implement.

[0020] Advantageously, the area of ​​the rivet in contact with the passage opening is the area that is deformed by the riveting operation when assembling the pyrotechnic switch. Typically, the riveting operation is a crimping operation, radial crimping or radial riveting, or orbital crimping or orbital riveting, or even rotary riveting. A snap die (a cylindrical tool inclined relative to the rivet) is pushed onto the head of the rivet to crush, flatten and radially widen it by plastic deformation. By this operation, the rivet portion in the opening changes from a generally cylindrical shape to a generally conical shape.

[0021] Advantageously, the other of the at least one of the first housing part or the second housing part comprising the metal insert having the passage opening in contact with the rivet is in contact with the rivet only via an electrically insulating material, such as a plastic material.

[0022] Advantageously, the other of the first or second housing parts, other than the at least one of the first or second housing parts comprising a metal insert with a passage opening in contact with the rivet, has a further passage opening for the rivet and does not contain a metal insert at the level of the further passage opening. In other words, the other housing part (which is in contact with the base of the rivet) is made completely of plastic, since no insert is required.

[0023] Advantageously, the further passage opening has a passage cross section which is greater than the passage cross section of the metal insert.

[0024] Advantageously, the pyrotechnic switch comprises an electrical conductor extending through the housing and arranged between the first housing part and the second housing part.

[0025] Advantageously, the electrical conductor is sandwiched and compressed between the first housing part and the second housing part. Thus, the rivet applies a compressive force to the electrical conductor (sandwiched between the first housing part and the second housing part, which themselves are fastened to each other by the rivet).

[0026] Advantageously, the electrical conductor comprises a passage opening through which the rivet passes. In addition, a ring made of an insulating material, such as an overmoulded or attached plastic, may be arranged between the rivet and the electrical conductor.

[0027] A second aspect of the invention relates to a motor vehicle comprising a pyrotechnic switch according to the first aspect of the invention.

[0028] A third aspect of the present invention relates to a method of manufacturing a pyrotechnic switch according to the first aspect of the present invention, the method comprising the following steps:

[0029] - coupling, assembling or positioning the first housing part and the second housing part together,

[0030] - pass the free end of the rivet through the passage opening,

[0031] - The free end is deformed by a crimping operation so that the rivet contacts the passage opening over its entire periphery.

[0032] Advantageously, the step of deforming the free end is long enough to radially deform the free end at the level of the passage opening and short enough not to radially deform the base of the rivet situated opposite the free end and facing the other passage opening.

[0033] Advantageously, the step of deforming the free end is preceded by a step consisting of flattening or compressing the housing parts towards each other. A tool called a "blank holder" can be used which is mounted on a spring and is lowered simultaneously with the riveting tool (snapping die) and contacts one of the housing parts before the riveting tool contacts the rivet to be crimped or deformed.

[0034] Thus, in a more general manner, the present invention relates to a pyrotechnic device comprising:

[0035] - a housing formed by a first housing part and a second housing part;

[0036] at least one rivet, by means of which the first housing part is riveted to the second housing part in order to form the housing;

[0037] - at least one pyrotechnic actuator, the at least one pyrotechnic actuator being arranged in the housing;

[0038] Features:

[0039] At least one of the first housing portion or the second housing portion includes a metal insert and a plastic body overmolded onto the metal insert,

[0040] The metal insert comprises a passage opening for the rivet,

[0041] And the rivet is in contact with the channel opening of the metal insert.

[0042] Advantageously, the pyrotechnic device forms a pyrotechnic switch.

[0043] Generally, a pyrotechnic switch may be a component for cutting off an electric circuit, or for closing an electric circuit of a motor vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features and advantages of the present invention will become more apparent upon reading the detailed description of embodiments of the present invention, which are provided by way of example, but by no means limiting, and are illustrated by the accompanying drawings, in which:

[0045] - Figure 1 depicts a perspective view of a pyrotechnic device according to the present invention;

[0046] - Figure 2 Depicted Figure 1 A cross-sectional view of a pyrotechnic device;

[0047] - Figure 3 Depicted Figure 1 Another cross-sectional view of the device;

[0048] - Figure 4 Depicted Figure 1 A view of a metal insert of the device;

[0049] - Figure 5 Depicts the first manufacturing stage Figure 1 a cross-section of a portion of a housing of a pyrotechnic device;

[0050] - Figure 6 Depicts the second manufacturing stage Figure 1 a cross-section of a portion of a housing of a pyrotechnic device;

[0051] - Figure 7 Depicted Figure 1 An alternative to the manufacture of pyrotechnic devices. DETAILED DESCRIPTION

[0052] Figure 1 A perspective view of a pyrotechnic device according to the invention is depicted, the pyrotechnic device comprising a housing 10 formed by a first housing part 11 and a second housing part 12. An electrical conductor 20 is sandwiched between the first housing part 11 and the second housing part 12.

[0053] Figure 1 The lower part of the housing 10 is shown mounted in the housing 10 and is shown in FIG. Figure 3 A connection interface 31 of a pyrotechnic actuator 32 is provided.

[0054] this Figure 3 The internal structure of a pyrotechnic device is shown, which is arranged here as a switch intended to cut off the electrical conductor 20 when necessary (for example, to cut off the power supply circuit of the vehicle in the event of an accident).

[0055] For this purpose, the electrical conductor 20 holds an overmolded guide 21 which forms a hole in which the punch 33 is placed and which, together with the second housing part 12, forms a combustion chamber C facing the pyrotechnic actuator 32 (the pyrotechnic actuator is here an electric pyrotechnic igniter, but an additional pyrotechnic relay is conceivable if necessary). Figure 3 In the embodiment, the punch 33 is in a static position.

[0056] The first housing part 11 comprises, facing the punch 33 and on the other side of the electrical conductor 20 , a counter-form component 34 , which may be considered an anvil or a die.

[0057] It is therefore necessary to cut the electrical conductor 20, ignite the pyrotechnic actuator 32, which causes a substantial increase in the pressure in the combustion chamber, so that the punch 33 is pushed toward the end position according to a translation movement from the rest position toward the end position in which the electrical conductor 20 has been cut. Figure 3 top.

[0058] Considering that the pyrotechnic device is intended to be able to operate even after a service life of several years and that, in operation, pressures of several tens of bars or more are expected, according to the example depicted, a sealing member with gaskets 13 and 14 is intended to be located between the first housing part 11, the second housing part 12, the guide part 21. A sealing gasket 15 is also intended to be located between the punch 33 and the second housing part 12.

[0059] It is therefore understood that a good fastening between the first housing part 11 and the second housing part 12 is ensured. However, in order to ensure good electrical insulation, it must also be provided that the housing 10 is non-conductive between, for example, the electrical conductor 20 and the mass of the vehicle. In order to meet this last condition, each housing part 11 and 12 has a plastic body C1 or C2. In order to meet this fastening condition, by means of Figure 1 and Figure 2 The rivets 40 shown are intended to rivet together the housing parts 11 and 12. Before assembling the housing, and by assembling the housing to ensure effective maintenance of the electrical conductors 20 and sealing of the device, the first housing part 11 and the second housing part 12 are not in contact.

[0060] Figure 2 A section is depicted at the height of the rivet 40 to illustrate the assembly. In particular, the metal insert 16 is intended to be arranged in the second housing part 12 in order to limit the stresses on the plastic body of this second housing part 12 .

[0061] The rivets 40 are shouldered rivets. That is, before riveting, they have a base 40E and a cylindrical body so as to be able to be inserted into each housing part 11 and 12 having a passage opening for the rivet 40. Each rivet 40 is then deformed at the level of its head 40T so as to complete the assembly, thus ensuring the sealing of the device and preventing any subsequent disassembly. According to this embodiment, the head 40T is buried below the surface of the second housing part 12 or flush with it.

[0062] In practice, during this riveting operation, the base 40E of each rivet 40 abuts against a base tool and a snap die (riveting tool) that can be moved according to a specific movement so that it is at least temporarily tilted relative to the axis of the rivet 40 contacts the head 40T of the rivet 40 so as to exert a vertical force thereon so as to crush and widen the head 40T by plastic deformation through the rotation and / or swinging movement of the snap die.

[0063] The riveting operation causes the head 40T to deform in order to ensure the axial stop of the second housing part 12 , without deforming the entire cylindrical portion of the rivet 40 , ie at the level of the base 40E.

[0064] like Figure 2 As can be seen, the plastic body C2 of the second housing part 12 has a passage opening that is larger than the passage opening of the metal insert 16, so that the rivet 40 contacts the second housing part 12 only via the metal insert 16 at the height of the head 40E. Therefore, the rivet 40 does not exert radial forces on the plastic body C2. The risk of cracking, breaking, damage to the plastic is thus avoided. In other words, the passage diameter of the rivet 40 in the plastic bodies C1 and C2 is larger than the passage diameter in the metal insert 16.

[0065] This embodiment ensures that the rivet 40 contacts the second housing portion 12 only via the metal insert 16 and that expansion of the diameter of its shank does not cause the rivet 40 to contact one or the other of the plastic bodies C1 or C2 .

[0066] Furthermore, since the rivet 40 is not deformed at the level of its base 40E, according to a preferred and optional embodiment, it is not necessary to provide a metal insert in the first housing part 11 in order to resist the riveting operation. Thus, according to this embodiment, the first housing part consists only of the plastic body C1.

[0067] Figure 4 An example of a metal insert 16 is shown, which has a hole 16T (in Figure 4 , Figure 5 and Figure 6 ), so as to achieve continuity of the plastic material of the plastic body C2 of the second housing part 12, so as to facilitate the overmolding operation and obtain a solid plastic body C2.

[0068] The metal insert 16 may be made of stamped steel of type DC04-1.0338 (Re: 210 MPa to 220 MPa, Rm: 270 MPa to 350 MPa, A%>38%).

[0069] The plastic body C1 of the first housing part 11 can be made of a polymer such as polyamide (PA, PA6.6, PA6.12) or polyoxymethylene (POM), optionally loaded with reinforcing fibers such as glass fibers, for example, at a ratio of 25% to 35% by weight. The rivet 40 can be made of steel, copper, aluminum with a significant elongation at break (e.g., A%>20%).

[0070] As for the second housing portion 12 , it is made of two plastic materials: a first portion 12 a made of a first plastic material and a second portion 12 b made of a second plastic material.

[0071] Therefore, the connection interface 31 is implemented in the second part 12B of the second housing part 12, which is made of a second plastic material, and for example polyamide (PA, PA6, PA6-12, PA6-6) can be used, and it contains between 10% and 50% by weight of reinforcing fibers, such as glass fibers. Specifically, polyamide PA6 with 30% by weight of glass fibers can be selected. Therefore, a small size but accurate shape (groove, recess) at the height of the connection interface 31 can be provided, and the selected second plastic material is easy to inject into a mold with a complex shape. In addition, the selected second material can also correctly withstand the pressure present in the combustion chamber C due to the added reinforcing fibers.

[0072] Furthermore, the first part 12A of the second housing part 12 made of the first plastic material may be intended to be exposed to a medium in which an arc is formed during operation of the switch. According to such a case of the figure, a portion of the first plastic material is arranged to be removed by ablation, and the first plastic material is selected from polyphthalamide (PPA), polyoxymethylene (POM), poly(methyl methacrylate) (PMMA).

[0073] Figure 5 The second housing portion 12 is shown after a first injection molding operation, during which the first portion 12A has been injection molded with a first plastic material.

[0074] Figure 6 The second housing part 12 is shown after a second injection moulding operation, during which the second portion 12B has been injection moulded with a second plastic material.

[0075] Figure 5Also shown is the height at which the first plastic material is molded to the shoulder of the metal insert 16, with an offset of limit F between the two sides of the metal insert 16. In practice, ( Figure 5 The lower limit Fi of the lower side of the metal insert 16 has an inner diameter that is smaller than the upper limit Fs of the other side. This configuration provides several advantages. In fact, the shoulder of the metal insert 16 does not contain holes, and combined with the limited deflection, this enables good rigidity and low deformation of the second housing part 12 to be obtained. This limits the risks of breakage, delamination and cracking.

[0076] It may also be mentioned that the manufacturing mould for the second injection moulding operation of the second plastic material may rest on the surface 12As and / or 12Ai of the first plastic material at the height of the limit F, which also simplifies manufacturing.

[0077] Regarding the metal insert 16, the metal insert has Figure 4 , Figure 5 and Figure 7 The hole 16T visible in FIG. 1 includes holes 16T1 and 16T2 (these holes are each dedicated to making the first plastic material and the second plastic material continuous, respectively). Finally, the metal insert 16 is shown in FIG. Figure 6 The lower portion of the housing includes a shoulder 16E having a passage hole 16P for a pyrotechnic actuator 32 (for clarity, the pyrotechnic actuator is shown in FIG. Figure 3 It can be seen in Figure 6 The shoulder 16E contains no holes or recesses other than the passage hole 16P, so as to have suitable resistance to the forces and stresses present in this region during operation (ie due to the pressure in the combustion chamber C).

[0078] Figure 7 A manufacturing alternative is depicted whereby the second plastic material is injected first. At the same time, the limit F still includes the offset (Fs, Fi) between the two sides of the metal insert 16 and the support surfaces 12Bs, 12Bi with continuous perimeter to obtain a sealed support on the manufacturing mold for the subsequent overmolding operation.

[0079] It should be understood that various modifications and / or improvements obvious to those skilled in the art may be made to the various embodiments of the invention described in this specification without departing from the scope of the invention.

Claims

1. A pyrotechnic switch, comprising: - a housing (10), which is formed by a first housing part (11) and a second housing part (12); - at least one rivet (40), by means of which the first housing part (11) is riveted to the second housing part (12) to form the housing (10); - at least one pyrotechnic actuator (32), said at least one pyrotechnic actuator being arranged in said housing (10); Features: At least one of the first housing part (11) and the second housing part (12) comprises a metal insert (16) and a plastic body (C2) overmolded onto the metal insert (16), The metal insert (16) comprises a passage opening for the rivet (40), And the rivet (40) has a contact area that contacts the passage opening of the metal insert (16).

2. The pyrotechnic switch according to claim 1, wherein the rivet (40) is in contact with a side wall of the passage opening.

3. The pyrotechnic switch according to claim 1, wherein the entire periphery of the rivet (40) is in contact with the side wall of the passage opening.

4. The pyrotechnic switch according to claim 1, wherein the rivet (40) comprises a base (40E) opposite the contact area with the passage opening, the base having a shoulder perpendicular to the axial direction of the rivet (40) so as to form a support for the other of the first housing part (11) and the second housing part (12).

5. The pyrotechnic switch according to claim 4, wherein the rivet (40) is not in full contact with the plastic body (C2) of the at least one of the first housing part (11) and the second housing part (12), including the metal insert (16), the metal insert having the passage opening in contact with the rivet (40) in the region of the housing (10) between the metal insert (16) and the base (40E).

6. The pyrotechnic switch according to claim 1, wherein: At the height of the channel opening, the metal insert (16) has a channel having a smaller dimension than the channel of the at least one of the first housing part (11) and the second housing part (12) including the metal insert (16).

7. The pyrotechnic switch according to claim 1, wherein the metal insert (16) includes a plurality of overmolding openings (16T) to enable overmolding of the plastic body (C2) on both sides of the metal insert (16) and to allow the material of the plastic body (C2) to be continuous through the overmolding openings (16T).

8. The pyrotechnic switch according to claim 1, wherein the contact area of ​​the rivet (40) that contacts the passage opening is an area that is deformed by a crimping operation when assembling the pyrotechnic switch.

9. The pyrotechnic switch according to claim 1, wherein the other of the first housing portion (11) and the second housing portion (12) other than the at least one including the metal insert (16) having the passage opening in contact with the rivet (40) is in contact with the rivet (40) only via an electrically insulating material.

10. The pyrotechnic switch of claim 9, wherein the electrically insulating material is a plastic material.

11. The pyrotechnic switch according to claim 4, wherein the other of the first housing portion (11) and the second housing portion (12) other than the at least one including the metal insert (16) having the passage opening in contact with the rivet (40) has another passage opening for the rivet (40) and does not contain the metal insert (16) at the height of the other passage opening.

12. The pyrotechnic switch according to claim 11, wherein the further passage opening has a passage cross section which is larger than the passage cross section of the metal insert (16).

13. The pyrotechnic switch according to any one of claims 1 to 3 and 5 to 10, comprising an electrical conductor passing through the housing (10) and arranged between the first housing part and the second housing part (12).

14. A motor vehicle comprising a pyrotechnic switch according to any one of claims 1 to 13.

15. A method of manufacturing a pyrotechnic switch according to any one of claims 1 to 3, 5 to 10 and 13, the method comprising the steps of: - positioning the first housing part (11) and the second housing part (12) together, - passing the free end of the rivet (40) through the passage opening, - Deforming the free end by a crimping operation so that the rivet (40) contacts the passage opening over its entire periphery.

16. A method of making a pyrotechnic switch according to claim 15, wherein the step of deforming the free end deforms the free end radially at the level of the passage opening.

17. A method of manufacturing a pyrotechnic switch according to claim 11 or 12, the method comprising the following steps: - positioning the first housing part (11) and the second housing part (12) together, - passing the free end of the rivet (40) through the passage opening, - deforming the free end by a crimping operation so that the rivet (40) contacts the passage opening over its entire periphery; The step of deforming the free end radially deforms the free end at the level of the passage opening and does not radially deform the base (40E) of the rivet (40) situated opposite the free end and facing the other passage opening.

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