Pyrotechnic actuator, vehicle safety device and method for producing pyrotechnic actuator

Abstract

The invention relates to a pyrotechnic actuator (1) comprising a cylindrical housing (2), on a first axial end section of which a connecting device (6) for connecting to a component is provided and in a second axial end section of which an ignition unit (14) is accommodated, the pyrotechnic actuator comprises a piston (4) which is guided in an axially displaceable manner in a housing (2), the axial movement of which in the housing (2) can be triggered by igniting a propellant (20) by means of an ignition unit (14) in order to actuate the actuator (1) in such a way that the propellant (20) can be ignited by the ignition unit (14). According to the invention, the housing (2) has, in the region of the second axial end section, a circumferential projection (30) which projects radially outward and which forms in the interior a receiving space in which a fastening ring (28) for axially fastening the ignition unit (14) is received. The invention also relates to a vehicle safety device (8) and to a method for producing a pyrotechnic actuator (1).

Description

Technical Field

[0001] The present invention relates to a pyrotechnic actuator, particularly for vehicle safety devices such as hood lifters or seatbelt pretensioners, the pyrotechnic actuator comprising a cylindrical housing, a connecting device for connection to a component being provided on a first axial end section of the housing and an ignition unit being housed in a second axial end section of the housing, and the pyrotechnic actuator including a piston axially movable and guided within the housing, the axial movement of the piston within the housing being triggered by igniting propellant by means of the ignition unit. Background Technology

[0002] Pyrotechnic actuators are used to operate vehicle safety devices. For this purpose, a propellant charge is ignited upon the occurrence of a triggering event (such as exceeding a predetermined vehicle deceleration). The resulting gas expansion drives a piston inside the housing, which then extends out of the housing, thereby operating the vehicle safety devices, such as by lifting the hood or tightening the seatbelts.

[0003] The known methods for securing the ignition unit to date involve first pushing the ignition unit into the housing and then deforming the housing, for example, by curling or rolling. Furthermore, the housing must have an anti-corrosion coating, which may be damaged during deformation, requiring additional subsequent sealing. In other words, in known pyrotechnic actuators, the ignition unit is typically secured within the housing by deformation.

[0004] For example, US 3,987,729 A discloses a device for igniting an electric igniter, comprising a pressure-deformable, sealed, and waterproof housing, the housing including an electrical energy source for igniting the igniter and a mechanism for operating the energy source in response to housing deformation. The housing preferably includes a bellows element, and the energy source (ignition unit) is preferably a piezoelectric element. The device is suitable for multiple blasts, wherein the explosive charge is detonated by the shock wave of a previous explosive charge. To secure the energy source, it is supported on a cap, which is in turn axially secured within the housing by a retaining ring.

[0005] In known actuators, the housing coated with an anti-corrosion coating is molded to secure the ignition unit, which may damage the coating and require additional subsequent sealing. Summary of the Invention

[0006] Therefore, the objective of this invention is to eliminate or at least reduce the disadvantages of the prior art. In particular, it is intended to provide an easily manufactured pyrotechnic actuator that prevents damage to the anti-corrosion coating during its installation.

[0007] The above task is accomplished by the pyrotechnic actuator according to claim 1.

[0008] Therefore, this is particularly addressed by having a radially outwardly projecting, circumferential protrusion (raise, protrusion, groove) in the region of the second axial end section of the housing, which forms an internal receiving space in which a retaining ring for axially fixing the ignition unit is accommodated.

[0009] Advantageous and suitable designs for pyrotechnic actuators are given in the dependent claims.

[0010] Preferably, the piston can have an expansion space formed inside it, into which the gas generated when the propellant is ignited expands, thus causing axial movement of the piston. Therefore, the piston is a hollow body that is axially open on one side, which reduces the installation space required.

[0011] In an advantageous design, the propellant can be stored in a propellant cap disposed on the end section of the first end section of the ignition unit facing the outer casing, which is also low-cost.

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

[0013] In addition, it is suitable to construct a circumferential groove in the outer peripheral surface of the ignition unit in order to seal the housing, and a sealing ring, especially an O-ring, is provided in the groove.

[0014] The present invention also relates to a vehicle safety device, particularly an engine hood lifter, which includes an actuator according to the invention, wherein the first axial end section is mounted on the vehicle component to be moved.

[0015] The present invention also relates to a method for manufacturing a pyrotechnic actuator according to the invention, the method comprising the following steps:

[0016] a) Provide a housing with protrusions,

[0017] b) Apply a coating with anti-corrosion properties to the outer casing.

[0018] c) Insert the ignition unit into the housing, and

[0019] d) The ignition unit is axially fixed in the housing by setting the retaining ring in the protrusion.

[0020] Advantageously, the protrusion can be formed by native molding of the housing.

[0021] It is particularly preferred that steps a) to d) of the method be performed in this order.

[0022] In other words, the present invention relates to the retention or fixation of an ignition unit in a pyrotechnic actuator (e.g., for an engine hood lifter or seatbelt pretensioner). Retention is achieved here by a retaining ring mounted in a circumferential groove (outwardly projecting protrusion) within the actuator housing (tube). The circumferential groove is formed in the housing during actuator manufacturing; the ignition unit is then axially pushed into the tube, and the retaining ring is subsequently pushed in toward the ignition unit until it is positioned within the groove, thus securing the ignition unit in its position. Attached Figure Description

[0023] Other features and advantages of the present invention will become apparent from the following description of preferred embodiments and the accompanying drawings. The drawings are as follows:

[0024] Figure 1 A longitudinal sectional view of the pyrotechnic actuator and vehicle safety device of the present invention according to a preferred embodiment is shown.

[0025] Figure 2 Detailed diagrams of the pyrotechnic actuator of the present invention according to a preferred embodiment are shown; and

[0026] Figure 3 Another detailed view of the pyrotechnic actuator of the present invention according to a preferred embodiment is shown. Detailed Implementation

[0027] exist Figure 1 The image shows a vehicle safety device with a pyrotechnic actuator 1 according to a preferred embodiment. The pyrotechnic actuator 1 has a generally tubular housing 2, in which a piston 4 is movably housed in the axial direction.

[0028] The pyrotechnic actuator 1 has a connecting device 6 on the first axial end section for connecting the pyrotechnic actuator 1, for example, to the engine hood 8.

[0029] In the preferred embodiment, the vehicle safety device is an engine hood lifter. Of course, the pyrotechnic actuator 1 can also be used for other vehicle safety devices, such as seatbelt pretensioners.

[0030] The connecting device seals the housing 6 and couples the piston 4 to the engine cover 8. A tear point 10 is constructed on the housing 2 in the area of ​​the connecting device 6 so that the piston 4 can extend out of the housing 2 at that position when the pyrotechnic actuator 1 is operated as described below.

[0031] like Figure 1As can be seen, piston 4 is constructed as a hollow cylinder with one side open. That is, piston 4 is tubular, with one axial end closed and the other axial end constructed to be open. Therefore, piston 4 defines an expansion space 12 inside, into which gas can flow (as will be described in detail below).

[0032] In the second axial end section of the pyrotechnic actuator 1 away from the connecting device 6, an ignition unit 14 is housed in the housing 2.

[0033] The ignition unit 14 is here (as is especially true in) Figure 2 and 3 (As can be seen in the image) it extends partly into the open end of piston 4 along the axial direction.

[0034] On the section of the open end of the piston 4, a propellant cap 16 is provided on the ignition unit 14, such that the ignition unit 14 and the propellant cap 16 together form a propellant reservoir 18 for storing propellant.

[0035] exist Figure 2 and 3 In this process, the propellant exists in the form of propellant pellets 20 within the propellant reservoir 18.

[0036] When the pyrotechnic actuator 1 is operated, the ignition unit 14 (preferably electrically) ignites the propellant stored in the propellant reservoir 18. For this purpose, the ignition unit 14 has a contact 22 on its end opposite to the propellant cap 16.

[0037] Gas is generated when the propellant is ignited and burned. This gas flows into the expansion space 12, and causes the piston 4 to move axially in the housing 2 toward the connecting device 6.

[0038] Based on the axial movement of piston 4, the piston extends from housing 2 at tear point 10 and causes the component (on which the first axial end section is fixed) to move, thereby lifting the engine hood 8. However, actuator 1 can also be used to tighten seat belts.

[0039] To seal the expansion space 12 relative to the environment, in the preferred embodiment, a sealing ring 24 in the form of an O-ring is provided between the ignition unit 14 and the housing 2. The ignition unit 14 has a circumferential groove 26 on its outer peripheral surface, in which the sealing ring 24 is accommodated.

[0040] In order to axially fix the ignition unit 14 in the housing 2, especially in particular Figure 2 and 3 As can be seen, according to the present invention, a retaining ring 28 is provided, which holds the ignition unit 14 relative to the housing 2 in the axial direction. The retaining ring 28 is accommodated in a surrounding protrusion 30 formed on the housing 2.

[0041] As will be described in more detail below, the protrusion 30 is constructed concurrently with the initial molding / forming process of the housing 2. That is, in the manufacture and installation of the pyrotechnic actuator 1 according to the invention, the housing 2 is formed first in a first step. The protrusion 30 is also formed concurrently in this first step.

[0042] Subsequently, the outer casing 2 must be coated with an anti-corrosion coating for the first time, that is, before the pyrotechnic actuator 1 is installed or assembled.

[0043] Since the protrusion 30, which serves as a receiving space for the retaining ring 28, is formed together with the outer shell 2 during the molding step, i.e. before the coating, the expensive reprocessing step for restoring the coating is eliminated compared to forming the protrusion 30 after the coating.

[0044] When assembling the pyrotechnic actuator 1 according to the invention, the piston 4 is first inserted into the housing 2. Then, the ignition unit 14 is pushed axially into the housing 2 and the retaining ring 28 is pushed in toward the ignition unit 14 until the retaining ring engages with the protrusion 30 and thus fixes the ignition unit in the axial direction.

Claims

1. A pyrotechnic actuator (1), particularly for a vehicle safety device (8), comprising a cylindrical housing (2), a connecting device (6) for connecting to a component is provided on a first axial end section of the housing, and an ignition unit (14) is housed in a second axial end section of the housing, and the pyrotechnic actuator includes a piston (4) axially movable within the housing (2), the axial movement of which is triggered by igniting a propellant (20) by means of the ignition unit (14), characterized in that, The housing (2) has a radially outwardly projecting, circumferential protrusion (30) in the region of the second axial end section, which forms an internal receiving space in which a retaining ring (28) for axially fixing the ignition unit (14) is received.

2. The pyrotechnic actuator (1) according to claim 1, characterized in that, The piston (4) forms an expansion space (12) inside it, into which the gas generated when the propellant (20) is ignited expands, thereby causing axial movement of the piston (4).

3. The pyrotechnic actuator (1) according to claim 1 or 2, characterized in that, The propellant (20) is stored in a propellant cap (16) which is disposed on the end section of the first end section of the ignition unit (14) facing the outer casing (2).

4. The pyrotechnic actuator according to claim 3, characterized in that, The piston (4) is a single-sided closed tube into which the propellant cap (16) extends.

5. The pyrotechnic actuator (1) according to any one of claims 1 to 4, characterized in that, In order to seal the housing (2), a circumferential groove (26) is constructed in the outer peripheral surface of the ignition unit (14), and a sealing ring (24), especially an O-ring, is provided in the groove.

6. A vehicle safety device (8), particularly an engine hood lifter, the vehicle safety device comprising an actuator (1) according to any one of the preceding claims, characterized in that, The first axial end section is mounted on the vehicle component to be moved.

7. A method for manufacturing a pyrotechnic actuator (1) according to any one of claims 1 to 5, the method comprising the following steps: a) Provide a housing (2) with a protrusion (30). b) Apply the coating to the outer casing (2), c) Insert the ignition unit (14) into the housing (2), and d) The ignition unit (14) is axially fixed in the housing (2) by setting the retaining ring (28) in the protrusion (30).

8. The method according to claim 7, characterized in that, The protrusion (30) is formed by the original molding of the outer shell (2).

9. The method according to claim 7 or 8, characterized in that, The method steps a) to d) are performed in this order.

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