Pyrotechnic actuator, vehicle safety device and method for manufacturing a pyrotechnic actuator

Abstract

The present invention relates to a pyrotechnic actuator (1) with a cylindrical outer housing (2), at the first axial end section of which a connection (6) to a component is provided and at the second axial end section of which an ignition unit (14) is received, and a piston (4) guided axially displaceably in the outer housing (2), the axial movement of which in the outer housing (2) can be triggered by igniting propellant (20) by means of the ignition unit (14) in order to actuate the actuator (1), wherein the outer housing (2) has a radially outwardly projecting circumferential bead (30) in the region of the second axial end section, which forms a receiving space in which a retaining ring (28) for axially securing the ignition unit (14) is received. The present invention further relates to a vehicle safety device (8) and a method for manufacturing a pyrotechnic actuator (1).

Description

[0001] The present invention relates to a pyrotechnic actuator, in particular for a vehicle safety device, such as a bonnet lifter or belt tensioner, comprising a cylindrical outer housing, at the first axial end portion of which a connection to a component is provided and in the second axial end portion of which an ignition unit is accommodated, and a piston which is guided axially displaceably in the outer housing and whose axial movement in the outer housing can be triggered by igniting fuel by means of the ignition unit.

[0002] Pyrotechnic actuators are used to activate vehicle safety devices. When a triggering event occurs, such as exceeding a specified vehicle deceleration, a propellant charge is ignited. The resulting gas expands and drives the piston inside the outer casing, causing it to exit the outer casing. This activates the vehicle safety device, for example, by raising the hood or tightening the seat belt.

[0003] Previously known fastenings for the ignition unit are manufactured by first inserting the ignition unit into the outer casing, followed by a forming process, for example, by crimping or rolling. The outer casing must also be provided with an anti-corrosion coating, which could be damaged during the forming process, requiring additional downstream sealing. In other words, in known pyrotechnic actuators, the ignition units are usually fixed in the outer casing by forming it.

[0004] For example, US 3,987,729 A discloses a device for igniting an electric detonator, comprising a compression-deformable, sealed, and waterproof housing containing an electrical energy source for igniting a detonator and a device responsive to the deformation of the housing for actuating the energy source. The housing preferably consists of a bellows element, and the energy source (ignition unit) is preferably a piezoelectric element. The device is suitable for multiple detonations in which an explosive charge is ignited by the shock wave of a previously exploded charge. To secure the energy source, it is supported on a cap, which in turn is axially secured in the housing by a retaining ring.

[0005] In known actuators, the outer casing coated with an anti-corrosion coating is reshaped to fix the ignition unit, which can lead to damage of the coating and requires additional downstream sealing.

[0006] Therefore, the object of the present invention is to eliminate or at least mitigate the disadvantages of the prior art. In particular, it is intended to provide a simple-to-manufacture pyrotechnic actuator that prevents damage to an anti-corrosion coating during its assembly.

[0007] The above-mentioned object is achieved by a pyrotechnic actuator according to claim 1.

[0008] In particular, this is achieved in that the outer housing has, in the region of the second axial end section, a radially outwardly projecting, circumferential bead (bulge, projection, groove), which forms a receiving space in the interior in which a retaining ring for axially fixing the ignition unit is accommodated.

[0009] Advantageous and expedient embodiments of the pyrotechnic actuator are specified in the subclaims.

[0010] Preferably, the piston can form an expansion chamber inside it, into which a gas generated upon ignition of the fuel expands, thus causing the axial movement of the piston. The piston is thus a hollow body open axially on one side, which reduces installation space.

[0011] In an advantageous embodiment, the fuel can be stored in a fuel cap which is arranged on an end portion of the ignition unit facing the first end portion of the outer housing, which is also cost-effective.

[0012] The piston can be a tube that is axially closed on one side, i.e. it can be manufactured by forming.

[0013] Furthermore, it may be expedient if, in order to seal the outer housing, a circumferential groove is formed in an outer circumferential surface of the ignition unit, in which a sealing ring, in particular an O-ring, is arranged.

[0014] The invention also relates to a vehicle safety device, in particular a hood prop, with an actuator according to the invention, wherein the first axial end section is attached to a vehicle part to be moved.

[0015] The present invention further relates to a method for producing a pyrotechnic actuator according to the disclosure, comprising the following steps: a) Providing the outer casing with the bead, b) Applying a coating to the outer casing with an anti-corrosion coating, c) Inserting the ignition unit into the outer casing, and d) axially fixing the ignition unit in the outer casing by arranging the retaining ring in the bead.

[0016] Advantageously, the bead can be produced by primary forming of the outer casing.

[0017] Particularly preferably, process steps a) to d) can be carried out in this order.

[0018] In other words, the invention relates to the mounting or fixation of the ignition unit in the pyrotechnic actuator (e.g., for a hood lifter or belt tensioner). The mounting is formed by the retaining ring, which is mounted in a circumferential groove (bulge facing outwards) in the outer housing (tube) of the actuator. During the manufacture of the actuator, the circumferential groove in the outer housing is already formed. The ignition unit is then inserted axially into the tube, and the retaining ring is subsequently pushed toward the ignition unit until it is positioned in the groove, thus securing the ignition unit in its position.

[0019] Further features and advantages of the invention will become apparent from the following description of a preferred embodiment and from the accompanying drawings, to which reference is made. In the drawings: - Fig. 1 a longitudinal sectional view of a pyrotechnic actuator according to the invention and a vehicle safety device according to a preferred embodiment; - Fig. 2 a detailed view of the pyrotechnic actuator according to the invention according to the preferred embodiment; and - Fig. 3 a further detailed view of the pyrotechnic actuator according to the invention according to the preferred embodiment.

[0020] In Fig. 1 shows a vehicle safety device with a pyrotechnic actuator 1 according to a preferred embodiment. The pyrotechnic actuator 1 has a substantially tubular-cylindrical outer housing 2, within which a piston 4 is accommodated for axial displacement.

[0021] At a first axial end section, the pyrotechnic actuator 1 has a connection 6 to connect the pyrotechnic actuator 1, for example, to a hood 8.

[0022] In the preferred embodiment, the vehicle safety device is a hood lifter. Of course, the pyrotechnic actuator 1 can also be used for other vehicle safety devices, such as a seat belt pretensioner.

[0023] The connection seals the outer housing 6 and couples the piston 4 to the engine hood 8. In the area of ​​the connection 6, a tear-open point 10 is formed on the outer housing 2, so that the piston 4 can emerge from the outer housing 2 at this point upon actuation of the pyrotechnic actuator 1 as described below.

[0024] As in Fig. As can be seen in Figure 1, the piston 4 is designed in the form of a hollow cylinder open on one side. This means that the piston 4 is tubular, with one axial end closed and the other axial end open. Accordingly, the piston 4 defines an expansion chamber 12 within its interior, into which a gas can flow, as described in more detail below.

[0025] In a second axial end section of the pyrotechnic actuator 1 facing away from the connection 6, an ignition unit 14 is accommodated in the outer housing 2.

[0026] This ignition unit 14 protrudes, as shown particularly in the Fig. 2 and Fig. 3 can be seen, partly in the axial direction into the open end of the piston 4.

[0027] At this section projecting into the open end of the piston 4, a fuel cap 16 is arranged on the ignition unit 14, so that the ignition unit 14 and the fuel cap 16 form a fuel reservoir 18 for storing fuel.

[0028] In Fig. 2 and Fig. 3, the fuel is in the form of fuel pellets 20 in the fuel reservoir 18.

[0029] Upon actuation of the pyrotechnic actuator 1, the ignition unit 14 ignites, preferably electrically, the fuel stored in the fuel reservoir 18. For this purpose, the ignition unit 14 has contacts 22 at its end facing away from the fuel cap 16.

[0030] When the fuel is ignited and burned, gas is produced which flows into the expansion chamber 12 and causes an axial movement of the piston 4 in the outer housing 2 in the direction towards the connection 6.

[0031] Due to the axial movement of the piston 4, it exits the outer housing 2 at the tear-open point 10 and causes a displacement of the component to which the first axial end section is attached, in this case an erection of a bonnet 8. But the actuator 1 can also be used to tighten a belt.

[0032] To seal the expansion chamber 12 from the environment, in the preferred embodiment, a sealing ring 24 in the form of an O-ring is arranged between the ignition unit 14 and the outer housing 2. For this purpose, the ignition unit 14 has a circumferential groove 26 on an outer circumferential surface, in which the sealing ring 24 is received.

[0033] For axial fixing of the ignition unit 14 in the outer casing 2, as particularly shown in the Fig. 2 and Fig.3, a retaining ring 28 is provided, which holds the ignition unit 14 in the axial direction relative to the outer housing 2. The retaining ring 28 is received in a circumferential bead 30 formed in the outer housing 2.

[0034] As described in more detail below, the bead 30 is formed during the primary forming / forming of the outer housing 2. This means that during the manufacture and assembly of the disclosed pyrotechnic actuator 1, the outer housing 2 is first formed in a first step. The bead 30 is also formed in this first step.

[0035] Subsequently, the outer casing 2 must be coated for the first time with an anti-corrosion coating before the pyrotechnic actuator 1 can be mounted or assembled.

[0036] Because the bead 30 is formed as a receiving space for the retaining ring 28 during the molding step of the outer housing 2, i.e. before the coating, a complex post-processing step for repairing the coating is eliminated compared to molding the bead 30 after the coating.

[0037] During assembly of the disclosed pyrotechnic actuator 1, the piston 4 is first inserted into the outer housing 2. Subsequently, the ignition unit 14 is inserted axially into the outer housing 2, and the retaining ring 28 is pushed toward the ignition unit 14 until it engages in the bead 30, thus securing the ignition unit in the axial direction. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 3 987 729 A

[0004]

Claims

[1] Pyrotechnic actuator (1), in particular for a vehicle safety device (8), with a cylindrical outer housing (2), at the first axial end section of which a connection (6) to a component is provided and in the second axial end section of which an ignition unit (14) is accommodated, and with a piston (4) which is guided axially displaceably in the outer housing (2), the axial movement of which piston in the outer housing (2) can be triggered by igniting fuel (20) by means of the ignition unit (14), characterized in that the outer housing (2) has, in the region of the second axial end section, a radially outwardly projecting, circumferential bead (30) which forms a receiving space in the interior in which a retaining ring (28) for axially fixing the ignition unit (14) is accommodated. [2] Pyrotechnic actuator (1) according to claim 1, characterized bythat the piston (4) forms an expansion chamber (12) in its interior, in which a gas generated upon ignition of the fuel (20) expands in order to cause the axial movement of the piston (4). [3] Pyrotechnic actuator (1) according to claim 1 or 2, characterized by that the fuel (20) is stored in a fuel cap (16) which is arranged on an end portion of the ignition unit (14) facing the first end portion of the outer housing (2). [4] Pyrotechnic actuator according to claim 3, characterized by that the piston (4) is a tube closed on one side into which the fuel cap (16) projects. [5] Pyrotechnic actuator (1) according to one of the preceding claims 1 to 4, characterized by in that, for sealing the outer housing (2), a circumferential groove (26) is formed in an outer circumferential surface of the ignition unit (14), in which groove a sealing ring (24), in particular an O-ring, is arranged. [6] Vehicle safety device (8), in particular a bonnet prop, with an actuator (1) according to one of the preceding claims, characterized by that the first axial end section is attached to a vehicle part to be moved. [7] Method for producing a pyrotechnic actuator (1) according to one of claims 1 to 5, comprising the following steps: a) Providing the outer casing (2) with the bead (30), b) applying a coating to the outer casing (2), c) Inserting the ignition unit (14) into the outer casing (2), and d) axially fixing the ignition unit (14) in the outer casing (2) by arranging the retaining ring (28) in the bead (30). [8] Method according to claim 7, characterized by that the bead (30) is produced by primary shaping of the outer casing (2). [9] Method according to claim 7 or 8, characterized bythat the process steps a) to d) are carried out in this order.

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