Damper cap, kit and air spring unit

Abstract

Damper cap (16; 16''; 16'''') of a strut (4), in particular an air strut (4), wherein the strut (4) comprises a spring (5), in particular an air spring (5), an auxiliary spring (12), and a shock absorber (6), wherein the damper cap (16; 16''; 16'''') is provided for mounting on the shock absorber (6), wherein the damper cap (16; 16''; 16''') has a contact surface (26) for the auxiliary spring (12), wherein the damper cap (16; 16''; 16''') has a base body (18; 18''; 18''') which has a hollow cylindrical shell section (30) and a cover section (34), wherein an attachment (20; 20'; 20''; 20''') is fixed to the base body (18; 18''; 18'''). is, wherein the attachment (20; 20'; 20''; 20'''') is arranged coaxially to the base body (18; 18''; 18''''), wherein the contact surface (26) is formed on the attachment (20; 20'; 20''; 20''''), wherein the cover section (34) forms a connection to the attachment (20; 20'; 20'';20''') oriented outer surface (36) and an opposing inner surface (40), wherein a metal insert (28) is arranged on the inner surface (40), wherein axially extending webs (58) are provided on an inner surface (56) of the base body (18; 18''; 18''').

Description

[0001] The invention relates to a damper cap, a kit and an air spring unit.

[0002] Damper caps, kits, and air spring units of the type mentioned above are generally known. Known air spring units comprise an air spring and a shock absorber for suspending and damping vibrations of a motor vehicle chassis, wherein the air spring has a rolling diaphragm attached to an air spring cover and a rolling piston, the rolling diaphragm at least partially delimiting a first working chamber filled with compressed air. In some embodiments, the rolling piston provides two working chambers separated from each other by a partition and connectable to the first working chamber via switchable valves arranged in the rolling piston.

[0003] Air suspension systems in motor vehicles, in particular, often feature elastomeric auxiliary springs, which are an important component of the suspension system and its design. Auxiliary springs protect the suspension during high compression strokes by providing a more progressive spring characteristic just before maximum travel than would be possible without them. When a wheel encounters a bump and the suspension compresses sufficiently, the auxiliary spring engages shortly before reaching its maximum travel. The auxiliary spring then compresses against a stop surface within the suspension, which can be a damper cap. The auxiliary spring absorbs some of the kinetic energy and converts it into heat, which is stored in the spring material and dissipated into the environment over time.This prevents the wheel suspension from compressing too quickly to its maximum spring travel, causing the moving chassis components to collide harshly and thus protecting passengers, bodywork and other chassis components from damage.

[0004] WO 2020 / 165 247 A1 discloses a shock absorber arrangement for a vehicle suspension, comprising a shock absorber with a damper cap and a piston rod, and an auxiliary spring arranged on the piston rod opposite the shock absorber. This auxiliary spring has a lateral surface facing the damper cap and an inner surface facing the piston rod, and is designed to dampen the movement of the shock absorber towards the piston rod upon contact with the damper cap. It is proposed that the lateral surface and / or the inner surface be at least partially coated with a lubricant.

[0005] US Patent 2021 / 0 332 867 A1 discloses an air suspension arrangement consisting of a top and a bottom surface arranged on a central axis and spaced apart from each other. A bellows made of an elastomeric material extends between a first end attached to the top surface and a second end attached to the bottom surface, defining a chamber. The chamber extends between the top surface, the bottom surface, and the bellows to receive compressed air, the pressure of which is controlled based on an applied force. The bellows has an inner and an outer surface and comprises a plurality of coils extending between the first and second surfaces.Each bundle of the plurality of bundles comprises a pair of outer lobes and an inner lobe, each outer lobe of the pair of outer lobes having an outer lobe thickness extending between the inner surface and the outer surface of the bellows. US 2018 / 0154725A1 discloses an air spring assembly for a vehicle with a damper body that is decoupled from a piston, allowing the damper to rotate freely without that torsion is induced in the piston. The air spring assembly comprises a damper body and a decoupling mechanism connected to the damper body, with part of the decoupling mechanism surrounding the damper body. A piston is connected to the decoupling mechanism such that the decoupling mechanism allows rotation of the damper body relative to the piston, thereby preventing torsion from being transferred from the damper body to the piston. The decoupling mechanism also includes a rotatable machine element, such as a bearing, surrounding the damper body. The bearing is located adjacent to the spring shell section, so that the rotatable machine element facilitates relative rotation between the damper body and the spring shell section to limit the torsion exerted by the damper body on the piston.

[0006] It is also known that different vehicle variants require different suspension setups, which sometimes involve different ride heights. In some configurations, the suspension stiffness and / or the so-called resting position of the suspension is modified. A changed resting position results in a change to the engagement point of the auxiliary spring and, consequently, to the characteristic curve of the strut or air spring. This has a negative impact on ride comfort.

[0007] Adapting the system to different vehicle variants requires modifying the components that define the auxiliary spring's activation point, such as the damper cap. However, this is only possible to a limited extent due to cost and manufacturing constraints. To restore the activation point of the characteristic curve, the auxiliary spring tip and the damper cap must be moved closer together or further apart by the modified amount. This can be achieved, for example, by modifying the shock absorber, the position of the auxiliary spring pot, or by using a different auxiliary spring design. However, these solutions necessitate relatively complex component modifications and recalibrations of the chassis setup, which consequently involve high costs and additional development time.

[0008] The task therefore is to further develop damper caps, kits and air spring units of the type mentioned above in such a way that an air spring unit of a motor vehicle can be built in a more modular way in order to be usable for different chassis setups.

[0009] The problem is solved by a damper cap according to claim 1, a kit according to dependent claim 10, and an air spring unit according to dependent claim 11. Embodiments are the subject of the dependent claims.

[0010] A damper cap for a strut, in particular an air strut, is described, wherein the strut has a spring, in particular an air spring, an auxiliary spring, and a shock absorber, wherein the damper cap is provided for mounting on the shock absorber, wherein the damper cap has a contact surface for the auxiliary spring, wherein the damper cap has a base body having a substantially hollow cylindrical shell section and a cover section, wherein a mounting is fixed to the base body, wherein the mounting is arranged coaxially to the base body, and wherein the contact surface is formed on the mounting.

[0011] The strut comprises a spring or air spring and a shock absorber. A suitable air spring may have a rolling diaphragm that rolls along a piston. The shock absorber may have a cylindrical housing or a tube into which a piston rod extends through a cap on the end face.

[0012] The damper cap is designed to rest on the shock absorber housing, covering both the cover and a portion of the damper tube adjacent to the cover. The damper cap is designed to be pushed into its final position over the shock absorber piston rod during assembly of the strut.

[0013] The auxiliary spring is attached to an auxiliary spring pot, which is fixed relative to the shock absorber piston rod. When the piston rod compresses, the auxiliary spring moves towards the damper cap, and when it rebounds, it moves away from the damper cap. The auxiliary spring has a tip or end face oriented towards the damper cap, designed to abut the contact surface of the damper cap's mounting surface.

[0014] The attachment is permanently fixed to the outside of a cover section using suitable fastening methods. Suitable fastening methods include, among others, gluing, screwing, welding, snap-fit, and / or crimping. The attachment can be pre-mounted on the damper cap so that the damper cap can be installed as a single unit.

[0015] The damper cap can be modularly constructed using the attachment. By using attachments of varying heights, which are fixed to the base body, a consistent distance between the auxiliary spring and the mounting surface can be achieved for different vehicle variants by selecting the appropriate attachment height in the strut's rest position. Due to the modular design of the damper cap, it is therefore possible to ensure the same relative rest positions or distances between the auxiliary spring tip and the damper cap for different vehicle variants with adapted suspensions simply by selecting the appropriate attachment on the base body. This ensures that the air strut characteristics, based on the auxiliary spring force-suspension travel curve, remain consistent across multiple vehicle variants. This is very cost-efficient and, in many cases, eliminates the need for redesigning certain suspension components as well as for complex suspension retuning.

[0016] The lid section is designed to have an outer side facing the attachment and an opposite inner side, with a metal insert arranged on the inner side.

[0017] The metal insert transfers additional spring forces to the shock absorber housing by distributing these forces over a relatively large area from the plastic cover section to the metal insert, ensuring that the surface pressures on the plastic do not exceed acceptable limits. The metal insert then transfers these forces to the shock absorber housing, although the contact area is relatively small. However, the metal insert can withstand significantly higher surface pressures than plastic. Thus, the metal insert supports the cover section of the shock absorber cap, preventing damage to the plastic caused by high additional spring forces. The metal insert prevents the cover section from deflecting to such an extent under these high spring forces that cracking and damage to the shock absorber housing cover would occur.Damage to the shock absorber housing cover could lead to damage to the sealing components normally present there, which are designed to prevent the damper oil contained within the damper from leaking out. Leaking damper oil reduces the lifespan of the air spring, as it can be chemically attacked by the damper oil.

[0018] The metal insert can be permanently attached to the base body, for example, by having a larger diameter than the clear inner diameter of the damper cap's outer section. When the damper cap is installed, the metal insert comes into contact with the cover of the shock absorber housing.

[0019] The metal insert can essentially be flat disc-shaped and thus lie flat against the cover section of the base body as well as flat against the cover of the shock absorber housing.

[0020] Alternatively, the metal insert can be essentially wave-disc-shaped and thus, in an unloaded state, bear against several areas of the shock absorber housing cover. The metal insert can be designed to lie flat against the base body. If the metal insert is wave-disc-shaped on its side facing the shock absorber housing, the disc exhibits higher bending stiffness compared to a flat disc of the same thickness. This allows the disc thickness, and therefore the material used, to be minimized for a given bending stiffness.

[0021] Furthermore, it is provided that axially extending webs are provided on an inner surface of the base body.

[0022] These webs can be designed as guide webs that can be inserted into corresponding guide contours formed on the damper tube.

[0023] In addition or alternatively, the webs or parts of the webs can be designed as compression webs to enable a rattle-free fit of the base body to the damper tube while simultaneously allowing for large tolerance compensation capabilities.

[0024] According to a further embodiment, a first locking contour is formed on the base body, and a second locking contour is formed on the attachment, wherein the first locking contour and the second locking contour are interlocked.

[0025] The locking contours can be designed such that the base body and the attachment have essentially or completely the same outer diameter. For this purpose, a tapered section can be provided on the base body towards the attachment, which is at least partially overlapped by the attachment. Such a taper can essentially correspond to the material thickness of the locking contour of the attachment.

[0026] According to a further embodiment, the first locking contour has at least one radially circumferential groove, and the second locking contour is formed on at least one axially oriented projection or an axially protruding ring.

[0027] The radially circumferential groove can be arranged in the area of ​​the tapering of the base body, in particular at the level of a transition from tapering to the shell section.

[0028] The radially circumferential groove can be formed on the shell section at a distance from the cover section. The distance of the groove to the cover section, measured from the top edge of the groove to the top of the cover, can be 3 to 5 mm.

[0029] One or more locking projections or locking hooks allow easy mounting of the attachment to the base body, the locking projections having corresponding locking contours that form an undercut with the circumferential groove of the base body.

[0030] Alternatively, instead of a circumferential groove, a plurality of groove segments with corresponding detent contours can be provided.

[0031] A closed detent ring allows for a virtually smooth outer surface of the mounted damper cap. Such a detent ring also exhibits high structural stability, making it difficult to damage and capable of withstanding high radial forces. Furthermore, it allows for high detent forces. The detent ring can have one or more inwardly projecting detent segments or a circumferential, inwardly projecting ring that forms an undercut with the second detent contour of the base body. During assembly, the ring is elastically expanded and, in the installed position, finally snaps into the circumferential groove.

[0032] According to a further embodiment, it is provided that the attachment has a plurality of axially aligned projections that are distributed over the circumference of the attachment.

[0033] According to a further embodiment, a rib structure with a plurality of radially extending ribs is formed on an underside of the attachment oriented towards the outside of the base body.

[0034] The rib structure can have an inner and / or an outer ring, between which the radially extending ribs run.

[0035] The ribbed structure makes it possible to produce attachments at great heights with moderate material usage, high stiffness and wall thicknesses suitable for injection molding.

[0036] According to a further refinement, the attachment is selected from a kit of attachments with different axial heights.

[0037] This means that the appropriate attachment can always be selected for different chassis configurations, ensuring a constant distance between the auxiliary spring and the contact surface and thus resulting in consistent spring behavior with respect to the auxiliary spring and its point of application.

[0038] According to a further refinement, the attachment and base body each have a central through-opening.

[0039] The central through-hole serves to guide the piston rod. The central through-hole has a clear diameter larger than the diameter of the piston rod, ensuring that the piston rod passes through the damper cap without contact and that the damper cap neither creates friction against the piston rod nor can it become jammed against it.

[0040] According to a further refinement, the base body and / or attachment are injection molded from a plastic.

[0041] Suitable plastics are PA6, PA6.6 or mixtures of PA6 and PA66. These plastics can each be reinforced with approximately 30 to 60% glass fibers, i.e., for example PA6 GF35, PA6 GF50, PA66 GF30, PA66 GF50 or PA6 / 66GF60.

[0042] According to a further refinement, a centering mechanism is provided on the base body.

[0043] The centering mechanism can be a centering projection or a centering recess, which interacts with a complementary centering structure on the attachment. In the case of a centering projection on the base body, a centering recess can be provided on the attachment. Conversely, in the case of a centering recess on the base body, a centering projection can be provided on the attachment.

[0044] A corresponding centering leads to a better transmission of radial forces between the base body and the attachment, thereby relieving the mounting structures, for example the corresponding locking contours, and increasing the radial forces required to destroy the damper cap.

[0045] A first independent item relates to a kit comprising at least one damper cap of the type described above and at least one further attachment, wherein the attachments have different axial heights.

[0046] A second independent item concerns an air spring unit with a damper cap of the type described above.

[0047] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. The drawings show: Fig. 1 a sectional view through a strut with a damper cap; Fig. 2 a perspective view of a kit of a damper cap in a first embodiment with a base body and an attachment; Fig. 3 a perspective view of the damper cap made of Fig. 2 in assembled state; Fig. 4 a side view of the damper cap Fig. 3; Fig. 5 a sectional view of the damper cap Fig. 3; Fig. 6 a perspective presentation of the essay from Fig. 2 from a bottom side; Fig. 7 a perspective presentation of an alternative essay; Fig. 8 a perspective view of a damper cap attachment in a second embodiment viewed from below; Fig. 9 a perspective view of a basic body of the damper cap in the second embodiment; Fig. 10 a sectional view of the damper cap of the second embodiment; Fig. 11 a perspective view of a damper cap attachment in a third embodiment viewed from below; Fig. 12 a perspective view of a basic body of the damper cap in the third embodiment; Fig. 13 a sectional view of the damper cap of the third embodiment.

[0048] In the following exemplary embodiments, identical or equivalent components are provided with the same reference numerals for better readability.

[0049] Fig. Figure 1 shows a sectional view through an air spring unit 2 with an air spring strut 4.

[0050] The air spring strut 4 has an air spring 5 which includes a rolling diaphragm 5.1 enclosing an air volume 5.2. The rolling diaphragm 5.1 is designed to roll on a rolling piston 5.3 of the air spring strut 4.

[0051] Furthermore, a shock absorber 6 is provided, comprising a damper rod 8 and a damper tube 10. The damper rod 8 extends through an opening (not shown) in a damper tube cap 10.1 attached to the damper tube 10. Damping elements are provided on the damper rod 8 inside the damper tube 10. These elements interact with a damping fluid contained within the damper tube 10 and generate a defined, relative-velocity-dependent friction that reduces the compression velocity and absorbs and dissipates energy.

[0052] The damper rod 8 is fixed to a first support bearing (not shown), and the damper tube 10 to a wheel carrier-side connection (not shown). The first support bearing and the wheel carrier-side connection can be fixed to components of the vehicle that are movable relative to each other, for example, a body and a wheel carrier or suspension link. During compression, the damper rod 8 moves further into the damper tube 10 and is pulled out of the damper tube 10 during rebound. During compression in the opposite direction z, the air volume 5.2 decreases, and the rolling diaphragm 5.1 rolls along the rolling piston 5.3 in the opposite direction z. During rebound in the axial direction z, the air volume 5.2 increases, and the rolling diaphragm 5.1 rolls along the rolling piston 5.3 in the axial direction z.

[0053] On the side of the first support bearing, an elastomeric auxiliary spring 12 is fixed to an auxiliary spring plate 12.1.

[0054] On the side facing the auxiliary spring, a damper cap 16 is arranged on the damper tube 10, the damper cap 16 having a base body 18 and an attachment 20 that is snapped into place with the base body 18. The attachment 20 forms a contact surface 26 for an auxiliary spring tip 12.2.

[0055] During compression, the auxiliary spring 12 moves ever closer to the contact surface 26 of the damper cap 16 until the tip of the auxiliary spring 12.2 makes contact with the contact surface 26. With further compression, the auxiliary spring 12 is deformed and partially compressed, thereby absorbing kinetic energy and increasing the progression of the spring characteristic of the air spring 4. The distance G between the tip of the auxiliary spring 12.2 and the contact surface 26, together with the properties of the auxiliary spring 12, including material, hardness, porosity, and geometry, determines the spring behavior of the air spring 4 at high compression strokes.

[0056] The injection-molded base body 18 has a metal insert 28, which is partially embedded in the material of the base body 18 and thus held in place. The metal insert 28 rests against the damper tube cover 10.1.

[0057] The base body 18 has a shell section 30 and a cover section 34. The shell section 30 and the cover section 34 are formed in one piece. The shell section 30 rests at least partially against the damper tube 10, and the cover section 34 is bounded from below by the metal insert 28.

[0058] The cover section 34 of the base body 18 rests against the attachment 20 with an outer surface 36 and supports it axially, so that forces introduced via the auxiliary spring 12 can be transmitted via the base body 18 and the damper tube 10 to the connection on the wheel carrier side. The base body 18, with the metal insert 28, rests against the damper tube cover 10.1 of the damper tube 10 with an inner surface 40.

[0059] The attachment 20 has a central through-opening 44. The base body 18 has a through-opening 46. The through-openings 44 and 46 each have a clear diameter D that is larger than the damper rod diameter E of the damper rod 8, so that the damper rod 8 can move through the damper cap 16 without contact during compression and rebound.

[0060] The base body 18 has a tapered section 47 with a circumferential locking groove 48 formed in the tapered section 47. The tapered section 47 is radially at least partially covered by one or more projections 50 formed on the attachment 20, the projections 50 having locking edges 52 formed on them. The locking edges 52 engage in the locking groove 48 and form an undercut, thereby securing the attachment 20 to the base body 18.

[0061] The attachment 20 has an outer diameter that is essentially the same as the outer diameter of the base body 18.

[0062] The attachment 20 is offered in different axial heights in order to be able to use as many identical parts as possible in the air spring unit 2 for different chassis variants (see Fig. 5).

[0063] Fig. Figures 2 to 5 show part of a kit 53 of a damper cap 16 in a first embodiment with a base body 18 and an attachment 20.

[0064] Fig. Figure 2 shows a perspective view of part 53 of the kit. The damper cap 16 is shown with the base body 18 and the attachment 20 not interlocked.

[0065] Fig. Figure 3 shows a perspective view of the damper cap 16 with the components base body 18 and attachment 20 interlocked together.

[0066] Fig. Figure 4 shows a side view of the damper cap 16 and Fig. Figure 5 shows a sectional view of the damper cap 16.

[0067] Attachment 20 and base body 18 are injection-molded from plastic. In this case, PA6 GF35 is used; in other embodiments, depending on the stress, other materials such as PA6 GF50, PA66 GF30, or PA66 GF50, or compounds based on PA6 or a mixture of PA6 and PA66, can also be used.

[0068] The attachment 20 has six projections 50, evenly distributed around its circumference. Each projection extends approximately 30 degrees circumferentially. Other embodiments may have more or fewer projections with varying degrees of circumferential extension. Because the locking groove 48 is circumferential, the attachment 20 can be placed on the base body 18 in any radial orientation. When the attachment 20 is locked in place, the spacing between two adjacent projections 50 leaves openings 49 through which the tapered section 47 on the base body 18 remains open. The dimensions of the projections 50, as well as the locking groove 48 and the locking projections 52, depend, among other things, on the operating parameters.

[0069] Attachment 20 and base body 18 have the same outer diameters in order to create an essentially edge-free transition between attachment 20 and base body 18, with the exception of the openings 49.

[0070] The attachment 20 has a rounded section 42 which makes the transition between the contact surface 26 and the shell section 38 of the attachment 20 continuous, thereby reducing the risk of damage to the auxiliary spring 12 under high loads, since the rounded section 42 on the auxiliary spring 12 is less likely to be damaged by overworking and / or punching during large deflections, which could occur with a sharp transition.

[0071] To lock the attachment 20 to the base body 18 to form the damper cap 16, the attachment 20 is placed onto the base body 18 and pressed downwards in the opposite direction z. This causes the six projections 50 to expand due to a small chamfer (see figure). Fig. 6) at the locking edges 52 open far enough to be pushed over the tapering 47 of the base body 18 until they lock into the locking groove 48 on the base body 18, forming a positive fit.

[0072] The attachment 20 is available in kit 53 in various heights, with the Fig. Figures 2 to 5 show an attachment with a height H1, measured from the outer surface 36 of the base body 18 to the contact surface 26. Within the scope of kit 53, at least one further attachment (not shown) with a different height than H1 may be available, for example a lower height H2, as shown in Fig. 5 is indicated.

[0073] The damper cap 16 is primarily subjected to compressive stress, but during elastic relaxation after a pressure peak, it must not relax so much that the locking mechanism between the locking edges 52 and the locking groove 48 disengages. It must also be able to withstand minor lateral forces.

[0074] The metal insert 28 is partially embedded in the material of the base body 18. During the production of the base body 18 using injection molding, the metal insert 28 is placed in a holder within an injection mold and then overmolded. This results in the metal insert 28 having a flat contact surface with the inner surface 40 of the base body 18.

[0075] The metal insert 28 has a corrugated design to improve air circulation between the damper cap 16 and the shock absorber 6 as well as the auxiliary spring 12. For manufacturing reasons, the metal insert 28 has a slightly smaller inner diameter than the attachment 20.

[0076] On an inner surface 56 of the shell section 38 of the base body 18, axially z-oriented ribs 54 are provided, which have insertion ramps 57 on a lower surface 55 of the base body 18. The ribs 54 are arranged in groups of two closely spaced ribs 54 with an angular separation of less than 10 degrees, with six such pairs of ribs 54 distributed around the circumference of the inner surface 56 of the shell.

[0077] The ribs 54 help, on the one hand, to align the damper cap 16 on the damper tube 10 of the shock absorber 6 and, on the other hand, to hold the damper cap 16 rattle-free on the damper tube 10. In certain embodiments, the ribs 54 can be deformed to a certain extent to compensate for tolerances in the damper tube 10.

[0078] Fig. Figure 6 shows a subpage 60 of the essay 20 in perspective view.

[0079] On the illustrated underside 60, a plurality of ribs 58 are formed, some of which form closed rings 58.1, 58.2, and other ribs 58.3 (only one of which is provided with a reference numeral) are radially oriented. The rings 58.1 and 58.2 are connected to each other via the ribs 58.3. In the illustrated embodiment, 12 radially oriented ribs 58.3 are provided, which are evenly distributed around the circumference. The ribs 58 form a flat underside 60 to achieve a flat bearing surface for the attachment 20 on the base body 18.

[0080] The use of the webs 58 makes it possible to achieve greater heights H than without webs. The webs 58 allow the material thickness of the plastic material of the attachment 20 to be kept below 6 mm, in particular below 4 mm, in order to minimize the cooling times required during injection molding to achieve component dimensional stability, as well as the material usage, and to enable efficient production of the attachment 20.

[0081] The previously described radially inwardly pointing insertion chamfer 62 is provided at the locking edge 52, which leads to an elastic deformation of the projections 50 when the locking edge 52 comes into contact with the taper 47 of the base body 18 during the mounting of the attachment 20 on the base body 18.

[0082] Fig. Figure 7 shows a bottom side 60 of an attachment 20' in a second embodiment in perspective view.

[0083] In contrast to the essay 20 from the first embodiment according to Fig. In sections 1 to 6, instead of the axially protruding projections 50 there, an axially protruding ring 64 with a circumferential detent edge 52 and an insertion ramp 62 is provided.

[0084] Furthermore, the attachment 20' corresponds to the attachment 20, which is why reference is made here to the descriptions of the structure, function and mode of operation of the attachment 20 from the first embodiment.

[0085] The attachment 20' can be combined with the base body 18. When the attachment 20' is pushed onto the base body 18, the axially projecting ring 64 is elastically stretched until the circumferential detent edge 52 engages in the detent groove 48, whereby the axially projecting ring 64 elastically relaxes and forms a smooth surface without openings with the base body 18.

[0086] The invention is not limited to one of the embodiments described above, but can be modified in many different ways.

[0087] Fig. Figures 8 to 10 show a third embodiment of a damper cap 16".

[0088] The damper cap 16" is centered by means of a centering ring 70 formed on a 20" attachment and a centering groove 72 formed on a base body 18". When the base body 18" and attachment 20" are assembled, the centering ring 70 and centering groove 72 are in contact, allowing them to absorb radially acting forces and thus relieve the detent connection between the detent edge 52 and the detent groove 48 of such radially acting forces, as shown in Fig. 10 becomes understandable.

[0089] Furthermore, the damper cap 16" corresponds to the damper cap 16, which is why reference is made here to the descriptions of the construction, function and mode of operation of the damper cap 16 from the first embodiment.

[0090] Fig. Figures 11 to 13 show a fourth embodiment of a damper cap 16'''.

[0091] The damper cap 16''' is centered by means of a centering groove 74 formed on an attachment 20''' and a centering ring 76 formed on a base body 18'''. When the base body 18''' and attachment 20''' are assembled, the centering ring 76 and centering groove 74 are in contact, allowing them to absorb radially acting forces and thus relieve the detent connection between the detent edge 52 and the detent groove 48 of such radially acting forces, as shown in Fig. 13 becomes understandable.

[0092] Furthermore, the damper cap 16" corresponds to the damper cap 16, which is why reference is made here to the descriptions of the construction, function and mode of operation of the damper cap 16 from the first embodiment.

[0093] All features and advantages arising from the claims, the description and the drawing, including design details, spatial arrangements and process steps, can be essential to the invention both individually and in various combinations. Reference symbol list 2 air spring unit 4 air suspension strut 5 air spring 5.1 Rolling bellows 5.2 Air volume 5.3 Rolling piston 6 shock absorbers 8 damper rod 10 Damper tube 10.1 Damper tube cover 12 Additional spring 12.1 Additional spring plate 12.2 Additional spring tip 16, 16'', 16'' Damper cap 18, 18'', 18''' Basic body 20, 20', 20'', 20''' Essay 26 Plant area 28 metal inlays 30 Sheath section damper cap 34 Cover section 36 Outside 38 Section of the article 40 Inside 42 Rounding off the essay 44, 46 Passage opening 47 Rejuvenation 48 Locking groove 49 Opening 50 lead 52 locking edge 53 kit 54th rib 55 Underside 56 Inside of coat 57 Inlet ramp 58 Bridge 58.1, 58.2 Ring 58.3 radially oriented bridge 60 bottom 62 Inlet chamfer 64 axially projecting ring 70 Centering ring 72 Centering groove 74 Centering groove 76 Centering ring D clear diameter of through opening E Damper rod diameter G Distance between additional spring tip and contact surface H1, H2 height z axial direction

Claims

[1] Damper cap (16; 16''; 16'''') of a strut (4), in particular an air strut (4), wherein the strut (4) comprises a spring (5), in particular an air spring (5), an auxiliary spring (12), and a shock absorber (6), wherein the damper cap (16; 16''; 16'''') is provided for mounting on the shock absorber (6), wherein the damper cap (16; 16''; 16''') has a contact surface (26) for the auxiliary spring (12), wherein the damper cap (16; 16''; 16''') has a base body (18; 18''; 18''') which has a hollow cylindrical shell section (30) and a cover section (34), wherein an attachment (20; 20'; 20''; 20''') is defined, wherein the attachment (20; 20'; 20''; 20''') is arranged coaxially to the base body (18; 18''; 18'''), wherein the contact surface (26) is formed on the attachment (20; 20'; 20''; 20'''), wherein the cover section (34) forms a connection to the attachment (20; 20'; 20'';20''') oriented outer surface (36) and an opposing inner surface (40), wherein a metal insert (28) is arranged on the inner surface (40), wherein axially extending webs (58) are provided on an inner surface (56) of the base body (18; 18''; 18'''). [2] Damper cap (16; 16''; 16'''') according to claim 1, wherein a first locking contour (48) is formed on the base body (18; 18''; 18''''), wherein a second locking contour (52) is formed on the attachment (20; 20'; 20''; 20''''), wherein the first locking contour (48) and the second locking contour (52) are interlocked. [3] Damper cap (16; 16''; 16'''') according to claim 2, wherein the first detent contour (48) has at least one radially circumferential groove, wherein the second detent contour (52) is formed on at least one axially oriented projection (50) or an axially projecting ring (64). [4] Damper cap (16; 16''; 16''') according to claim 3, wherein a plurality of axially oriented projections (50) are formed on the attachment (20; 20''; 20''') which are arranged distributed over a circumference of the attachment (20; 20''; 20'''). [5] Damper cap (16; 16''; 16'''') according to one of the preceding claims, wherein a rib structure with a plurality of radially extending ribs (54) is formed on a bottom side (60) of the attachment (20; 20'; 20''; 20'''') oriented towards the outside (36) of the base body (18; 18''; 18''''). [6] Damper cap (16; 16''; 16''') according to one of the preceding claims, wherein the attachment (20; 20'; 20''; 20''') is selected from a kit (53) of attachments (20; 20'; 20''; 20''') with different axial heights (H1, H2). [7] Damper cap (16; 16''; 16''') according to one of the preceding claims, wherein the attachment (20; 20'; 20''; 20''') and the base body (18; 18''; 18''') each have a central through-opening (44, 46). [8] Damper cap (16; 16''; 16''') according to any of the preceding claims, wherein the base body (18; 18''; 18''') and / or attachment (20; 20'; 20''; 20''') are injection molded from a plastic. [9] Damper cap (16''; 16''') according to one of the preceding claims, wherein a centering (70, 72; 74, 76) is provided on the base body (18''; 18'''). [10] Kit (53) comprising at least one damper cap (16; 16''; 16''') according to one of the preceding claims and at least one further attachment (20; 20'; 20''; 20'''), wherein the attachments (20; 20'; 20''; 20''') have different axial heights (H1, H2). [11] Air spring unit (2) with a damper cap (16; 16''; 16'''') according to any one of the preceding claims 1 to 9.

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