Actuator, method for producing an actuator, and vehicle protection system

Abstract

An actuator (12) in a vehicle protection system (10) has a housing (26) and a displaceable piston (14). The piston (14) comprises a rigid piston tube (34) which is open at one end face (42), a rigid cap (48) which closes the end face (42) of the piston (14) and has a cover part (50), and an annular seal (64). The cap (48) has a pin-shaped projection (52) which extends into the piston tube (34), wherein the seal (64) surrounds the pin-shaped projection (52), and the end face (42) of the piston (14) has an axially tapering cutting structure (68) which protrudes into the seal (64) such that the cutting structure (68) delimits a radially inner portion (70) of the seal (64) between the pin-shaped projection (52) and the cutting structure (68) from a radially outer portion (72) of the seal (64) radially outside the cutting structure (68). In order to produce the actuator (12), the seal (64) is placed on the cutting structure (68) of the piston tube (34), the cap (48) is placed on the open end face (42) of the piston tube (34) such that the pin-shaped projection (52) protrudes into the piston tube (34) and such that the cover part (50) rests on the seal (64) and is positioned axially above the cutting structure (68), and the pin-shaped projection (52) is caulked to the inner circumferential surface (56) of the piston tube (34).

Description

[0001] ZF Airbag Germany GmbH Wernher-von-Braun-Straße 1 84544 Aschau a. Inn / DE

[0002] Actuator, method for producing an actuator and vehicle protection system

[0003] The invention relates to an actuator, in particular in a vehicle protection system, as well as a method for producing an actuator and a vehicle protection system.

[0004] Vehicle protection systems are known in which a pedestrian outside the vehicle is caught by a deliberately moved component on the vehicle's exterior panel, for example, by raising the hood. For this purpose, the component in question is connected to an actuator that can perform an axial movement by pushing a piston sectionally out of a housing. The actuator is pyrotechnically driven, for example, with the piston being moved axially within the housing by the generated gas pressure.

[0005] Such actuators are installed in an area of ​​the vehicle exposed to numerous environmental influences, while they must remain fully functional throughout the vehicle's service life. Therefore, it is necessary to protect the actuator well, for example, against the ingress of dirt and moisture.

[0006] The object of the invention is to present an actuator with a simple, cost-effective and reliable seal.

[0007] This object is achieved by an actuator, in particular in a vehicle protection system, comprising a housing in which a piston is accommodated such that it can move axially out of the housing when the actuator is activated, wherein a pressure-generating drive unit is provided which generates a compressed gas for displacing the piston, wherein the housing is open at a first axial end, the piston comprises a rigid piston tube which, in an unactuated initial state, is open at its end face near the first axial end, a rigid cap closing the end face of the piston, and an annular seal, the cap having a cover part and a pin-shaped projection protruding therefrom, which extends into the piston tube, the seal surrounding the pin-shaped projection, and wherein the end face of the piston has an axially tapered cutting structure that projects into the seal,so that the cutting structure delimits a radially inner portion between the pin-shaped projection and the cutting structure from a radially outer portion radially outside the cutting structure.,

[0008] Because the cutting edge penetrates the seal, displacing seal material into the gaps to be sealed, the sealing effect is improved. In the unactuated initial position before the actuator is activated, the seal prevents dirt and moisture from penetrating the interior of the piston tube, thus protecting the actuator from environmental influences. When the actuator is actuated, the seal largely retains the compressed gas in the piston tube, reducing compressed gas losses.

[0009] At the same time, the seal is securely held in its desired position by the pin-shaped projection and the cutting edge structure both before and during activation of the actuator.

[0010] As the piston moves out of the housing, the compressed gas is retained inside the piston tube, so less compressed gas is lost to the piston's advance. Since at least the radially inner section of the seal is moved along with the piston during the displacement, the sealing effect for the piston tube is maintained throughout the entire actuator actuation.

[0011] The radially inner portion of the seal preferably rests against an outer peripheral surface of the pin-shaped projection.

[0012] Such an actuator can be used in particular to lift a hood to protect a pedestrian outside the vehicle.

[0013] For this purpose, the housing is fixed to a suitable vehicle-fixed component section, e.g. an area of ​​the vehicle frame or the body, while the piston acts on a moving component, such as the bonnet. The vehicle-fixed component section holds the housing stationary relative to the vehicle when the actuator is activated. In its unactuated initial state, the piston can protrude axially from the housing, with the housing being fixed to a stationary component section. The component section has an opening into which the piston tube protrudes and through which the piston tube moves when activated, with the seal being clamped axially between the component section and the cover part before the actuator is activated. In this way, the seal simultaneously seals the piston tube and the housing against environmental influences.

[0014] The seal may extend radially from the outer peripheral surface of the pin-shaped projection of the cap beyond the inner edge of the opening in the component section.

[0015] The diameter of the opening in the component section is preferably smaller than an inner diameter of the housing and larger than an outer diameter of the piston tube, so that an inner edge of the opening projects radially into a gap between the piston tube and the housing.

[0016] In a preferred variant, an edge of the cap and a first axial end of the housing rest on opposite sides of the component section, wherein the seal is located entirely on the cover part side of the component section.

[0017] The cap is preferably made of a metal, in particular a steel.

[0018] The seal should be made of a suitable elastic and well-sealing material, e.g. EPDM (ethylene propylene diene (monomer) rubber).

[0019] Preferably, the seal is a flat seal, in particular a flat annular disc in the unloaded state.

[0020] The pin-shaped projection preferably sits in a form-fitting manner in the piston tube. Therefore, the cutting edge structure is generally positioned radially closer to the outer circumferential surface of the pin-shaped projection than to an outer edge of the seal. The radially larger part of the seal is thus located in the radially outer section. This has the advantage that a large surface area of ​​the seal is available for sealing between the cap and the component section. The cutting edge structure is formed, for example, by a singular, circumferentially encircling, axially directed cutting edge on the end face of the piston tube. In particular, the edge of the piston tube can taper axially in this area.

[0021] In a preferred variant, the cutting edge structure is pressed into the seal and / or axially severes the seal completely or partially. In any case, the cutting edge structure is intended not only to rest superficially on the seal, but also to penetrate axially into the seal. When the seal is completely or partially severed, the severed sections of the seal continue to rest against the cutting edge structure.

[0022] The pressing or cutting can occur during assembly of the actuator or only when the actuator is activated due to the then increased internal pressure inside the piston tube.

[0023] To further seal the housing, a sealing element, which in particular comprises an O-ring, is preferably arranged in the region of the first axial end of the housing between an outer circumferential surface of the piston tube and an inner side of the housing. The sealing element is spatially separated from the seal, for example, by the component section. In addition to the O-ring, the sealing element can also comprise a retaining ring that holds the O-ring in the desired axial position.

[0024] The sealing element prevents dirt or moisture from penetrating the gap between the piston tube and the housing. It can also help keep the piston in its non-actuated position.

[0025] The sealing element is preferably arranged in the region of the first end of the housing and in contact with the component section in order to seal the transition from the housing to the component section.

[0026] The piston tube is preferably tapered axially adjacent to the front side compared to an area positioned deeper in the housing.

[0027] In one possible variant, the taper occurs in two stages, between which lie straight, cylindrical axial sections. The shoulder formed by the second stage can be used, for example, to hold the sealing element in the desired axial position.

[0028] When the actuator is activated, the sealing element in this arrangement is pressed against the component section, which increases the sealing effect.

[0029] Normally, the piston tube is tapered on both its outer peripheral surface and its inner peripheral surface.

[0030] The pin-shaped projection of the cap is caulked, particularly in the tapered area of ​​the piston tube, in order to fix the cap to the piston tube.

[0031] The pressure-generating drive unit preferably contains a pyrotechnic drive charge, such as that known from conventional gas generators. The pyrotechnic drive charge is positioned in particular in the region of an axial end of the piston opposite the open end face and thus at a second axial end of the housing opposite the first axial end of the housing.

[0032] Preferably, the drive unit is connected via electrical connecting cables to a control unit, which transmits a corresponding trigger signal to the drive unit to activate the actuator.

[0033] The compressed gas generated by the pyrotechnic propulsion charge causes an increase in pressure in the piston tube, whereby the increased internal pressure in the piston tube pushes the piston out of the housing until it reaches an end stop.

[0034] The seal ensures that as little compressed gas as possible escapes from the piston, so that as much of the compressed gas as possible is available to move the piston.

[0035] The above-mentioned object is also achieved with a vehicle protection system having an actuator as described above, wherein the actuator is arranged in a vehicle such that it acts on a hood of the vehicle and raises it upon activation.

[0036] Even if the invention is described here in connection with a vehicle protection system, it is of course also conceivable to use an actuator described above in other areas, independently of a vehicle, and for purposes other than those described.

[0037] Furthermore, the above-described object is achieved with a method for manufacturing an actuator as described above. The method comprises the following steps:

[0038] Inserting an assembly comprising a housing, piston tube and seal into a component section fixed to the vehicle, so that the first end of the housing rests against the component section, the piston tube extends at least into the opening in the component section and the seal rests on the cutting edge structure of the piston tube,

[0039] - Placing the cap on the open end of the piston tube so that the pin-shaped projection protrudes into the piston tube and the cover part rests on the seal and is arranged axially above the cutting structure, and

[0040] Caulking the pin-shaped projection on an inner peripheral surface of the piston tube.

[0041] The caulking preferably creates a thickening on the pin-shaped projection in a transition to a tapered area of ​​the piston tube, which fixes the cap to the piston tube.

[0042] During the fitting of the cap and / or during the caulking of the cap, an axial force can be generated between the cap and the end face of the piston tube, thereby pressing and / or cutting the cutting structure into the seal.

[0043] The invention is described in more detail below using an exemplary embodiment with reference to the accompanying figures. The figures show:

[0044] Figure 1 is a schematic sectional view of an actuator according to the invention of a vehicle protection system according to the invention, manufactured according to a method according to the invention in an unactuated initial state before its activation;

[0045] Figures 2 and 3 show enlarged sections of Figure 1; and Figure 4 shows the actuator of Figure 1 in an actuated state.

[0046] For reasons of clarity, not all identical components are always provided with reference symbols.

[0047] The figures show a vehicle protection system 10 with an actuator 12 having a piston 14 displaceable along an axial direction A.

[0048] The actuator 12 is designed to act on and move a movable component 16 with its piston 14.

[0049] In the example shown here, the component 16 is, for example, a hood of a vehicle, and the vehicle protection system 10 serves to catch a pedestrian coming into contact with the vehicle in the event of an impact.

[0050] The actuator 12 comprises a pressure-generating drive unit 18, which in this case is pyrotechnically operated and has an igniter with a pyrotechnic drive charge 20. Electrical connecting lines 22, which are connected to the pyrotechnic drive charge 20, are connected to a suitable control unit 24, which transmits a trigger signal to the drive unit 18 when the actuator 12 is to be activated.

[0051] Figure 1 shows the actuator 12 before its activation in an unactuated initial state. Figures 2 and 3 show enlarged views of the actuator 12.

[0052] The actuator 12 has a dimensionally stable housing 26 that is elongated along the axial direction A and cylindrical in shape. At a first axial end 28, the housing 26 is open and rests with a front end surface 30 against a component section 32 fixed to the vehicle. The housing 26 is fixedly secured to the component section 32 (not shown), whereby the component section 32 and thus also the housing 26 remain fixed in position during the activation of the actuator 12.

[0053] The piston 14 is received in the housing 26 such that an internally hollow, rigid piston tube 34 extends largely within the housing 26. In the unactuated state, the piston 14 is pushed as far as possible into the housing 26. The piston tube 34 comprises a central section 36 that extends over a large part of the length of the piston tube 34 and is arranged entirely within the housing 26 with a radial gap 37 to an inner side 38 of the housing 26.

[0054] At its axial end near the first end 28 of the housing 26, the piston tube 34 has an open end face 42. The middle section 36 merges towards the end face 42 into an intermediate section 44, in which the piston tube 34 tapers. At the end face 42, the piston tube 34 therefore has a smaller diameter than in the middle section 36. The intermediate section 44 axially adjoins a cylindrical section 45 extending from the end face 42. Here, the cross-section of the piston tube 34 increases in two stages between the section 45 and the middle section 36 in the intermediate section 44.

[0055] In the example described here, the cross-section of the piston tube 34 is circular both at the end face 42 and in the intermediate section 44 and in the middle section 36, but the cross-sectional shape can be selected at the discretion of the person skilled in the art.

[0056] At an end 46 axially opposite the end face 42, the piston tube 34 is widened to the diameter of the inner side 38 of the housing 26. The drive unit 18 with the pyrotechnic propulsion charge 20 is arranged axially below the end 46, so that the compressed gas provided by the drive unit 18 largely enters the widened end 46 and from there into the remaining piston tube 34.

[0057] The piston 14 includes a rigid cap 48, which is mounted on the end face 42 of the piston tube 34. The cap 48 axially seals the piston 14 and forms the contact point between the piston 14 and the component 16.

[0058] The cap 48 is made of metal, in particular steel.

[0059] The cap 48 has a cover part 50, which forms an axial end of the piston 14, and a pin-shaped projection 52, which protrudes from a bottom side 54 of the cover part 50. The projection 52 projects into the piston tube 34 and rests in a form-fitting manner against an inner circumferential surface 56 of the piston tube 34. In this example, the projection 52 extends into the intermediate section 44, in which the piston tube 34 tapers from the central section 36 to the end face 42.

[0060] The cover part 50 of the cap 48 is located axially above the component section 32, i.e., on the side of the component section 32 remote from the housing 26. The component section 32 has an opening 58 into which the piston tube 34 projects. An outer edge 60 of the cover part 50 is positioned radially outside an inner edge 62 of the opening 58.

[0061] In addition, the piston 14 includes a seal 64, which in its initial state is designed as a flat seal in the form of an annular disc with a central opening. It is made of a suitable elastic and sealing material, for example, EPDM (ethylene propylene diene (monomer) rubber).

[0062] The seal 64 is arranged such that the projection 52 extends through the central opening and the seal 64 radially bears against an outer peripheral surface 66 of the projection 52.

[0063] The edge 60 of the cover part 50 optionally projects axially beyond the underside 54 in the direction of the component section 32. The seal 64 can be radially clamped in the annular space thus formed.

[0064] The outer peripheral surface 66 of the pin-shaped projection 52 lies directly against the inner peripheral surface 56 of the piston tube 34 in the section 45 of the piston tube 34.

[0065] The end face 42 of the piston tube 34 is formed as a cutting edge structure 68, which here consists of an axially extending, singular, radially completely circumferential cutting edge 69. The end face 42 of the piston tube 34 tapers axially to a point and ends in the cutting edge 69.

[0066] A radially inner portion 70 of the seal 64 extends between the outer peripheral surface 66 of the piston tube 34 and the cutting edge structure 68, while a radially outer portion 72 extends between the cutting edge structure 68 and a radially outer edge 74 of the seal 64. The cutting edge structure 68 engages the seal 64, with the cutting edge structure 68 being pressed into the seal 64 such that it lies in a recess 76 of the seal 64 (see Fig. 3).

[0067] The recess 76 can be caused by a deformation of the seal 64, whereby the seal 64 itself remains undamaged. However, it is also possible that the cutting edge 69 cuts into the seal 64, so that the seal 64 is cut into the recess 76 or even completely severed axially. In the latter case, the radially inner section 70 and the radially outer section 72 of the seal 64 are no longer connected.

[0068] As a result of the penetration of the cutting structure 68 into the seal 64, material of the seal 64 is displaced radially inwards and outwards, as can be seen in Figure 3. As a result, the radially inner section 70 completely seals the transition between the inner peripheral surface 56 of the piston tube 34 and the outer peripheral surface 66 of the projection 52. The radially outer section 72 of the seal 64 lies flat between the underside 54 of the cover part 50 of the cap 48 and a cover-side surface 78 of the component section 32. At the inner edge 62 of the opening 58, the seal 64 forms a bead on its axial side opposite the cover part 50, so that a gap 80 between an outer peripheral surface 82 of the piston tube 34 and the inner edge 62 of the opening 58 is also sealed.

[0069] In the radially outwardly adjoining region of the radially outer section 72, the seal 64 is axially clamped between the underside 54 of the cover part 50 and the cover-side surface 78 of the component section 32, so that a sealing effect also exists here.

[0070] The pin-shaped projection 52 here has a thickening 84 that fixes the projection 52 in the intermediate section 44 of the piston tube 34 and thus the cap 48 to the piston tube 34. The thickening 84 is formed here by caulking the projection 52 in the piston tube 34.

[0071] A sealing element 86 is arranged in the gap 37 between the housing 26 and the piston tube 34 in the region of the first axial end 28 of the housing 26. The sealing element 86 comprises an O-ring 88 and a retaining ring 90, which are positioned axially one above the other, with the O-ring resting against a housing-side surface 92 of the component section 32.

[0072] When the actuator 12 is activated, the control unit 24 sends an activation signal to the drive unit 18, and the pyrotechnic propulsion charge 20 is ignited. The resulting compressed gas flows into the interior of the piston tube 34, and due to the increased internal pressure compared to the ambient pressure, the entire piston 14 is displaced in the axial direction A. The piston tube 34 slides through the opening 58 in the component section 32, and the piston 14 lifts the component 16.

[0073] Figure 4 shows the actuator 12 in the actuated position and in the fully extended state of the piston 14. The end 46 of the piston tube 34 forms an end stop since its diameter is larger than the diameter of the opening 58.

[0074] When the piston 14 begins to slide through the opening 58, the sealing element 86 is pressed axially against the component section 32. The gap 37 thus remains sealed.

[0075] The seal 64 is carried along by the piston 14, maintaining the sealing effect between the cap 48 and the piston tube 34. If necessary, the pressure of the cutting edge structure 68 on the seal 64 increases, causing the cutting edge 69 to penetrate further into the seal 64. Optionally, the extension movement of the piston 14 also results in the seal 64 being cut or severed. If the seal 64 is completely severed, optionally only the radially inner portion 70 is carried along by the piston 14, while the radially outer portion 72 remains.

[0076] The sealing effect between the outer peripheral surface 82 of the piston tube 34 and the inner side 38 of the housing 26 is maintained by the sealing element 86.

[0077] To manufacture the actuator 12, an assembly is first formed from the housing 26, the piston tube 34, and the seal 64, which assembly is inserted into the component section 32 such that the axial end 28 of the housing 26 rests against the underside of the component section 32, radially outward of the inner edge 62 of the opening 58 in the component section 32. In this state, the housing 26 is firmly fixed in relation to the component section 32 in a suitable manner.

[0078] The piston tube 34 extends with its end face 42 into or just through the opening 58. The seal 64 is a single piece and rests on the cutting edge structure 68.

[0079] In addition, the sealing structure 86 is inserted into the gap 37 at the first end 28 of the housing 26.

[0080] Next, the cap 48 is placed on the piston tube 34 so that the pin-shaped projection 52 protrudes into the interior of the piston tube 34.

[0081] The cover part 50 is fixed to the piston tube 34 by caulking the projection 52 inside the piston tube 34. For this purpose, a suitable tool is inserted from the end 46. This caulking takes place here in the region of the tapered intermediate section 44, in which the inner circumferential surface 56 of the piston tube 34 also tapers corresponding to the outer circumferential surface 82. Therefore, an axially lower end of the projection 52 widens during caulking to form the thickened portion 84, which has a larger diameter than the piston tube 34 in the region of the end face 42. In this way, the projection 52 is positively fixed to the piston tube 34.

[0082] During this step, an axial force acts on the seal 64, pressing the cutting edge structure 68 against the seal 64. The cutting edge 69 of the cutting edge structure 68 penetrates axially into the seal 64 and forms the recess 76. As described above, the seal 64 can be cut or completely severed axially in the region of the recess 76. Furthermore, in this step, the radially outer section 72 of the seal 64 is axially clamped between the underside 54 of the cover part 50 of the cap 48 and the cover-side surface 78 of the component section 32.

[0083] Finally, the drive unit 18 is mounted in the housing 26.

Claims

Patent claims 1. Actuator (12), in particular in a vehicle protection system (10), with a housing (26) in which a piston (14) is accommodated displaceably in an axial direction (A), so that the piston (14) moves axially in the direction out of the housing (26) upon activation of the actuator (12), wherein a pressure-generating drive unit (18) is provided which generates a compressed gas for displacing the piston (14), wherein the housing (26) is open at a first axial end (28), the piston (14) comprises a rigid piston tube (34) which is open at its end face (42) near the first axial end (28) in an unactuated initial state, a rigid cap (48) closing the end face (42) of the piston (14) and an annular seal (64), the cap (48) having a cover part (50) and a pin-shaped projection (52) projecting therefrom, which extends into the piston tube (34),wherein the seal (64) surrounds the pin-shaped projection (52) and wherein the end face (42) of the piston (14) has an axially tapered cutting structure (68) which projects into the seal (64), so that the cutting structure (68) delimits a radially inner portion (70) of the seal (64) between the pin-shaped projection (52) and the cutting structure (68) from a radially outer portion (72) of the seal (64) radially outside the cutting structure (68).

2. Actuator (12) according to claim 1, wherein the piston (14) projects out of the housing (26) in the axial direction (A) in an unactuated initial state and the housing (26) is fixed to an immovable component section (32) which has an opening (58) into which the piston tube (34) projects and through which the piston tube (34) passes when activated, wherein the seal (64) is clamped axially between the component section (32) and the cover part (50) before the activation of the actuator (12).

3. Actuator (12) according to one of the preceding claims, wherein the seal (64) is a flat annular disc in the unloaded state.

4. Actuator (12) according to one of the preceding claims, wherein the cutting structure (68) is positioned radially closer to an outer peripheral surface (66) of the projection (52) than to an outer edge (74) of the seal (64).

5. Actuator (12) according to one of the preceding claims, wherein the cutting edge structure (68) is formed by a singular, circumferentially encircling, axially directed cutting edge (69) on the end face (42) of the piston tube (34).

6. Actuator (12) according to one of the preceding claims, wherein the cutting structure (68) is pressed into the seal (64) and / or completely or partially axially severed by the seal (64).

7. Actuator (12) according to one of the preceding claims, wherein a sealing element (86), which in particular comprises an O-ring (88), is arranged in the region of the first end (28) of the housing (26) between an outer peripheral surface (82) of the piston tube (34) and an inner side (38) of the housing (26).

8. Actuator (12) according to one of the preceding claims, wherein the piston tube (34) is tapered axially adjacent to the end face (42) compared to a region positioned deeper in the housing (26).

9. Actuator (12) according to claim 8, wherein the projection (52) of the cap (48) is caulked in the tapered region of the piston tube (34).

10. Actuator (12) according to one of the preceding claims, wherein the pressure-generating drive unit (18) contains a pyrotechnic drive charge (20).

11. Vehicle protection system (10) with an actuator (12) according to one of the preceding claims, wherein the actuator (12) is arranged in a vehicle such that it acts on a hood of the vehicle and raises it upon activation.

12. A method for manufacturing an actuator (12) according to one of claims 1 to 10, comprising the steps: Inserting an assembly consisting of the housing (26), piston tube (34) and Seal (64) in a vehicle-fixed component section (32) so that the the first end (28) of the housing (26) rests against the component section (32) at its end face, and the piston tube (34) projects into at least one opening (58) in the component section (32), and the seal (64) rests on the cutting edge structure (68) of the piston tube (34), - placing the cap (48) on the open end face (42) of the piston tube (34) so ​​that the pin-shaped projection (52) projects into the piston tube (34) and the cover part (50) rests on the seal (64) and is arranged axially above the cutting structure (68), and Caulking the pin-shaped projection (52) on an inner peripheral surface (56) of the piston tube (34).

13. The method according to claim 12, wherein the caulking in a transition to a tapered region of the piston tube (34) creates a thickening (84) on the pin-shaped projection (52) which fixes the cap (48) to the piston tube (34).

14. The method according to claim 12 or claim 13, wherein during the fitting of the cap (48) and / or during the caulking of the cap (48) an axial force is generated between the cap (48) and the end face (42) of the piston tube (34) and thereby the cutting structure (68) is pressed into and / or cuts into the seal (64).

Images