DE102022126359A1 - Pyrotechnic actuator - Google Patents

Abstract

To increase the diameter, i.e. to increase Impingement surface, another component (14) attached. The other component (14) is positively fixed to the piston rod (6) by plastic deformation. According to the invention, the piston rod (6) consists of solid material and a projection (13) is provided at the end of the piston rod (6) remote from the igniter, which protrudes through an opening in the further component (14), this projection (13) being widened by plastic deformation, so that the further component (14) is positively fixed. For this purpose, the projection (13) can be tubular and bent outwards on the side of the additional component (14) facing away from the igniter, but the projection (13) can also be fully cylindrical and the additional component (14) can be formed by twisting or riveting the projection ( 13) must be positively fixed. The piston rod (6) is preferably made of aluminum. The other component (14) is preferably a stamped disc that can be curved or cambered.

Description

The present invention relates to a pyrotechnic actuator, in particular for lifting an engine hood, with a housing and a piston, which can be displaced in the housing by means of an igniter, with a piston rod which projects out of the housing at the end remote from the igniter through an outlet opening of the housing, with another component being attached outside the housing is, the radial extent of which is greater than the radial extent of the piston rod in the region of the end remote from the igniter, the further component being fixed in a form-fitting manner on the piston rod by plastic deformation.

Pyrotechnic actuators are widely used in automotive safety technology when it comes to releasing high forces in a short time. A typical application is active pedestrian protection systems, which raise the hood in the event of a vehicle collision with a pedestrian, thus providing additional deformation space to the hard components in the engine compartment. Before the actual adjustment, a fixation of the starting position must be released, this often involves tear-off elements in the hinge.

In the EP 2699455 B1 Autoliv shows a cost-effective solution for an actuator that only allows for a small diameter end of the piston rod. Due to tolerances in the body shell and the assembly of the actuator, it is difficult to always reliably hit the release positions in the hinge. To counteract this, the plunger tip is often enlarged, which involves a great deal of effort. In the US9956938B2 Takata, for example, discloses a nut that threads onto a thread on the end of the piston rod. Likewise, reverse solutions are known, in which another component is screwed or crimped into the piston.

However, all of these solutions are very complex.

In many actuator concepts, the target area can only be enlarged after the piston and piston rod have been installed in the

Housing take place because usually neither the piston nor the other component can be pushed through the housing. When screwing in, this makes it necessary to fix the piston in the housing so that the piston or the piston rod cannot rotate, and this fixation must withstand the torque required for screwing on the other component. The screwing process often requires additional security, for example in the form of a locking varnish.

From the generic AT522245B1 is already known to fix a kind of plug on a tubular piston rod. The stopper protrudes with a pin into the interior of the piston rod. This pin has an outside diameter that essentially corresponds to the inside diameter of the tubular piston rod. This pin has a neck of reduced diameter and in this area the end of the tubular piston rod is bent inwards so that the plug is positively fixed. However, this solution is not suitable for massive piston rods. In many actuator concepts, the piston must not be pushed beyond its starting position during assembly, for example because otherwise the lock in the initial position of the piston rod would be destroyed - this means that lateral pressing is associated with major design restrictions.

It is the object of the present invention to find a way of fastening the further component on the piston rod which is suitable for solid piston rods and which is less complex than the known solutions.

This object is achieved according to the invention by an actuator of the type mentioned at the outset in that the piston rod is made of solid material, that a projection is provided on the end of the piston rod remote from the igniter, which protrudes through an opening in the further component, this projection being widened by plastic deformation, so that the other component is positively fixed.

According to the invention, the form-fit fixing is thus effected on the end face of the piston rod (protruding from the housing), and this area is very easily accessible. It is easiest if the projection is reshaped on the side of the additional component that is remote from the igniter. However, it is also conceivable that the plastic deformation takes place in an inner recess of the further component.

If the projection is tubular, it can be bent outwards on the side of the additional component facing away from the igniter, which is easily possible, for example, by inserting a conical tool into the interior of the tubular projection. During deformation, this cone-shaped tool is located outside and in the extension of the actuator, where there are no space problems.

As an alternative to this, the projection can also be fully cylindrical, that is to say solid (not hollow) and be wobbled or riveted, so that the further component is fixed in a form-fitting manner. wobbling and riveting are similar cold forming processes. During wobbling, a wobbling movement of the upper die on a rotationally symmetrical workpiece only ever deforms a partial surface of the workpiece, which means that a large deformation can be achieved with relatively little effort. When riveting, on the other hand, the entire workpiece is deformed at the same time, which requires a correspondingly higher expenditure of force.

In both cases, the positive connection is particularly effective when the opening in the other component is countersunk, i.e. widens conically. As a result, the deformed projection can bear over the entire surface in this countersink of the further component.

The piston rod is advantageously produced by cold forming, production from an aluminum wire by so-called “beating” being particularly preferred. Classic extrusion of stainless steel, for example, is also possible.

The further component is preferably disc-shaped and can be produced cheaply by a stamping process. If necessary, this disc can also be bent. It is preferred that the outer diameter of the disk is 1 mm to 3 mm, particularly preferably about 2 mm, larger than the diameter of the piston rod. Larger differences than 3 mm are normally not necessary, and if, in exceptional cases, a larger disc had to absorb the full force (up to 7 kN) at its edge, it would deform. According to the invention, it is therefore a matter of a relatively small increase in the impact area in order to allow greater manufacturing tolerances in vehicle construction.

Alternatively, the further component can also be an (extruded) pressed or stamped part; a shape with at least one-sided camber is preferred here.

The protrusion of the piston rod has the advantage during production that the piston rod can be "fetched" with a mandrel. The housing has an outlet opening for the piston rod. A mandrel is inserted into the housing from the outside through this outlet opening and pushed until it comes out again at the end of the housing on the ignition side. In this position you press the projection of the piston rod against the mandrel and then move both parts simultaneously in the opposite direction until the piston rod slides through the exit opening.

A method for producing an actuator according to the invention is therefore characterized in that a mandrel is inserted from the outside through the outlet opening of the housing for the piston rod into the housing and is displaced until it emerges at the fuze-side end of the housing so that in this position pushes the projection of the piston rod against the mandrel and then moves both parts simultaneously in the opposite direction until the piston rod slides through the exit opening, after which the further component is placed with its opening on the projection and the protruding part of the projection is reshaped so that a bent area is formed arises and the further component is positively connected to the piston rod, and that one mounts the propellant charge and the igniter in the usual way before or after the fixing of the further component.

The term “mandrel” is to be understood in general terms and should in particular also include a hollow mandrel whose cavity can encompass a fully cylindrical projection.

In a variant of this sequence, the passage and form-fitting connection can take place by forming in one operation.

The present invention is explained in more detail with reference to the accompanying drawings. It shows: 1 an actuator according to the invention in section; 2 the detail A of 1 on an enlarged scale; and 3 a perspective external view of the pyrotechnic actuator.

According to 1 the actuator 1 consists of a tubular housing 2 in which a piston rod 6 can be displaced. This piston rod 6 is expanded at the bottom to form a piston 6'. At its end opposite the piston 6 ′, the piston rod 6 is guided in an intermediate piece 3 . The intermediate piece 3 has two O-rings 5a, 5b (see 2 ) for sealing between the housing 2 and the piston rod 6.

Behind the end of the piston 6' facing away from the piston rod 6 (see 1 ) there is an igniter 11 with connection wires 18, which are continued in a cable 17. A propellant charge 16 is located adjacent to the igniter 11.

If the detonator 11 is ignited by applying a corresponding voltage pulse via the cable 17 or the connecting wires 18, the propellant charge 16 also explodes and thereby generates high pressure, so that the piston 6' together with the piston rod 6 extends (upwards, as in 1 and 2 shown).

Since the piston rod 6 has a relatively small diameter (because of the intermediate piece 3, it must be significantly smaller than the diameter of the piston 6'), there is a risk that the element to be actuated will not be hit. For this reason, another component 14 is provided, which has a larger diameter than the piston rod 6.

To fix this additional component 14 (see 2 ) has the end face of the piston rod 6 facing away from the piston 6 ′ has a projection 13 which protrudes through a corresponding opening in the further component 14 . In the exemplary embodiment, this projection is tubular (hollow cylindrical). Above the opening (as in 1 and 2 seen) the projection 13 is bent outwards, it forms a bent region 15. As a result, the component 14 is held in a form-fitting manner.

As can be seen from the figures, the diameter of the further component 14 is only slightly larger than the diameter of the piston rod 6, in particular it is smaller than the diameter of the housing 2 in its upper area, i.e. in the area of the outlet opening for the piston rod 6. General the outer diameter of the further component 14 should be 1 mm to 3 mm, preferably about 2 mm, larger than the diameter of the piston rod.

The housing 2 has a taper 21 at the upper end, i.e. the end facing away from the igniter 11, with which it is inserted into an opening of a holder 12. For fixing in the holder 12, the housing 2 is bent outwards above the holder 12, so that a bent region 22 results.

The actuator 1 is manufactured as follows: first the housing 2 is inserted with its taper 21 into the opening of the holder 12 . Then the case is deformed to form the bent portion 22 . The housing is now firmly (positively) connected to the holder 12 . Then the intermediate piece 3 with the O-rings 5a, 5b is inserted into the housing (from below, as in 1 seen) is pushed in, after which the piston 6' is inserted into the housing 2 with the piston rod 6 in front (again from below, as in 1 seen). This can be done with a mandrel as described above. If the piston rod 6 the in 1 and 2 has reached the position shown, i.e. protrudes slightly from the housing 2, the further component 14 is placed with its opening on the projection 13, after which the protruding part of the projection 13 is bent outwards so that the bent region 15 is formed and the further component 14 is firmly (positively) connected to the piston rod 6. Finally, the propellant charge and the igniter are mounted in the usual way.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2699455 B1 [0003]
• US9956938B2 [0003]
• AT 522245 B1 [0007]

Claims (13)

Pyrotechnic actuator (1), in particular for raising an engine hood, with a housing (2) and a piston (6') which can be displaced in the housing (2) by means of an igniter (11) and has a piston rod (6) which passes through an outlet opening at the end remote from the igniter of the housing (2) protrudes from this, with a further component (14) being fastened outside the housing (2), the radial extent of which is greater than the radial extent of the piston rod (6) in the region of the end remote from the igniter, the further component ( 14) is positively fixed to the piston rod (6) by plastic deformation, characterized in that the piston rod (6) consists of solid material, that a projection (13) is provided at the end of the piston rod (6) remote from the igniter, which protrudes through an opening in the further component (14) protrudes, this projection (13) being widened by plastic deformation, so that the further component (14) is fixed in a form-fitting manner. Pyrotechnic actuator claim 1 , characterized in that the projection (13) is tubular and bent outwards on the side of the further component (14) facing away from the igniter. Pyrotechnic actuator claim 1 , characterized in that the projection (13) is fully cylindrical and the further component (14) is positively fixed by wobbling or riveting the projection (13). Pyrotechnic actuator claim 2 or 3 , characterized in that the opening of the further component (14) is countersunk. Pyrotechnic actuator according to one of Claims 1 until 4 , characterized in that the piston rod (6) consists of aluminum. Pyrotechnic actuator according to one of Claims 1 until 5 , characterized in that the piston rod (6) is an extruded part or a forged part. Pyrotechnic actuator according to one of Claims 1 until 6 , characterized in that the further component (14) is a stamped part. Pyrotechnic actuator according to one of Claims 1 until 6 , characterized in that the further component (14) is a pressed or beaten part. Pyrotechnic actuator according to one of Claims 1 until 8th , characterized in that the further component (14) is a disc. Pyrotechnic actuator claim 9 , characterized in that the outer diameter of the disc is 1 mm to 3 mm, particularly preferably about 2 mm, larger than the diameter of the piston rod (6). Pyrotechnic actuator claim 9 or 10 , characterized in that the disc is curved. Pyrotechnic actuator according to one of Claims 1 until 11 , characterized in that the further component (14) is cambered on at least one side. Method for producing a protechnical actuator according to one of Claims 1 until 12 , characterized in that a mandrel is inserted from the outside into the housing (2) through the outlet opening of the housing (2) for the piston rod (6) and is displaced until it emerges at the igniter-side end of the housing (2), that in this position the projection of the piston rod (6) is pressed against the mandrel and then both parts are moved simultaneously in the opposite direction until the piston rod (6) slides through the outlet opening, after which the other component (14) is pushed onto the projection with its opening (13) and reshapes the protruding part of the projection (13) so that a bent area (15) is created and the further component (14) is positively connected to the piston rod (6), and that before or after fixing the further Component (14) mounted in the usual way, the propellant charge (16) and the igniter (11).

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