DE102017215231B4 - Shock absorber for a motor vehicle - Google Patents

Abstract

Shock absorber (1) for a motor vehicle, with a damper tube (10) for receiving a damping medium, in which a piston rod (11) with a piston (12) is guided in a longitudinally movable manner, the piston rod (11) having an upper damper bearing (13a) and the damper tube (10) is connected to a lower damper bearing (13b) and to a protective tube (15, 15', 15"), which protectively surrounds the piston rod (11) and the damper tube (10) at least in certain areas, the protective tube ( 15, 15', 15"), starting from a lower end (20), has a plurality of elongated material interruptions (21) in such a way that there are at least two material segments (22) that are separate from one another, characterized in that the protective tube (15, 15 ', 15") has a circumferential, funnel-shaped widening (23) at its end (20) having the material interruptions (21), the opening diameter of which increases from the start of the funnel-shaped widening (23) to the end of the protective tube (15, 15', 15") cont gradually increased to a maximum opening diameter, with the funnel-shaped widening (23) in the direction of the upper damper bearing (13a) merging directly into a hollow-cylindrical section of the protective tube (15, 15', 15"), into which the material interruptions (21) protrude.

Description

The invention relates to a shock absorber for a motor vehicle with the features of the preamble of patent claim 1.

Such shock absorbers are primarily used in the rear axle of motor vehicles and are used to dampen spring movements of the motor vehicle caused by bumps in the road surface, thus ensuring safe road holding and a high level of driving comfort for the motor vehicle.

A protective tube, which protectively surrounds a piston rod and a damper tube of the shock absorber, serves to protect against the ingress of dirt.

In most cases, the damper tube is also covered with a cover cap (also known as a buffer cap), which is arranged radially between the protective tube and the damper tube. Such a covering cap serves to prevent damage to the paint layer on the damper tube due to relative movements occurring between the protective tube and the damper tube.

In everyday use, especially in the cold season, ice sometimes forms in the lower area of the cover cap. This causes a disturbing noise on the rear axle, which is caused by a so-called stick-slip effect between the protective tube and the icing. In the extreme case, damage to the protective tube by touching down on the ice adhering to the buffer cap is also conceivable.

From the DE 10 2010 024 601 A1 a suspension strut bearing and a manufacturing method for a friction-reducing component of a suspension strut bearing are known. In order to avoid the above-mentioned stick-slip effect and for the purpose of making a suspension strut bearing more economical to produce, this document proposes a suspension strut bearing with a sliding bearing which has a number of friction-reducing elements on its sliding disk. Polytetrafluoroethylene (PTFE) is proposed as the material for the friction-reducing elements.

The forming the preamble of the main claim DE 18 74 288 U describes a protective casing tube for hydraulic vibration dampers with a casing tube body. At its lower end, the casing tube body has slots which run uniformly around its circumference and which extend somewhat upwards in a straight line starting from the end.

From the DE 20 2006 006 021 U1 a protective tube for a shock absorber is known, which has a cap in a head area for connection to an upper bearing element of the shock absorber.

In the DE 101 22 796 A1 describes a shock absorber with a protective element designed as a bellows. The protective element also surrounds a bump stop which, during deflection, strikes the support surface of an end cap located on the damper tube. The bump stop, the protective element and the end cap form a pre-assembled unit.

Of the JP 2016 048 081 A a protective element designed as a bellows can also be seen. The protective element has at the upper end formed by slots, right-angled segments of material with which it is attached to an upper fastener.

Of the DE 71 11 851 U a shock absorber with a protective tube can be removed. A piston rod guided in a damper tube has a thread at its free end for receiving a fastening nut. The piston rod also carries the protective tube that covers the damper tube. To reduce weight, it is proposed to manufacture the protective tube from thermoplastic material and to secure the protective tube and the piston rod against twisting relative to one another in order to facilitate assembly.

the DE 10 2010 018 044 A1 describes a shock absorber with a bellows-like protective element. The protective element also surrounds a spring element which, when the shock absorber deflects, strikes a cap with spring tongues which is located on a damper tube. A spreading element on the spring tongues serves to spread the spring tongues in the radial direction during assembly of the protective element on the damper tube together with the spring element and cap and to hold them securely in the protective element.

From the DE 18 11 684 U a shock absorber with a protective tube is known, which also includes a spring element. During deflection, the spring element strikes against a damper tube and, as a hollow spring, encloses a piston rod that slides in the damper tube.

through the DE 10 2015 216 075 A1 discloses a shock absorber with an auxiliary spring. An end cap on a damper tube forms a stop surface for the additional spring during deflection and is provided with a sliding layer made of PTFE.

the JP 2007 327 627 A shows a shock absorber with a protective cover formed from a spiral band.

through the DE 10 2006 010 332 A1 a vibration damper with a protective tube is shown. A guide element made of a low-friction material is arranged at the lower end of the protective tube between the protective tube and a damper tube partially covered by it.

In the JP S60-122 036 U describes a shock absorber with a damper tube in which a piston rod is guided in a longitudinally movable manner. The shock absorber is surrounded by a protective tube whose circumferential, cylindrical wall merges into a bellows-like profile in the lower area. Specifically, a labyrinthine seal is created between the wall of the protective tube and the outer diameter of the damper tube by protuberances pointing radially outwards and lobe-like projections pointing radially inwards.

Of the JP 2011 052 702 A a shock absorber with a dust cover can be seen. The dust protection has a bellows-like area that is divided into a lower area and an upper area. The lower section has an inner diameter that is smaller than an inner diameter of the upper section.

From the JP H07-63 236 A a shock absorber with a bellows protection is known. An upper end of the bellows is connected to an upper spring bearing. With a lower end, which has slots, the bellows rests on a lower spring bearing.

Finally is out of the JP S63-51 948 U a shock absorber with a damper tube and a piston rod is known, with a bellows protectively surrounding the damper tube and the piston rod in some areas.

The object of the present invention is to provide a shock absorber for a motor vehicle in which the occurrence of disturbing noises is reduced. In particular, it should be possible for the material segments of the protective tube to slide outwards easily when they hit an ice buildup that has formed.

The present problem is solved by a shock absorber with the features of patent claim 1 . Advantageous configurations or developments of the invention can be found in the dependent claims.

The invention is initially based on a shock absorber for a motor vehicle, with a damper tube for receiving a damping medium, which can be air or oil, for example. A piston rod with a piston is guided in a longitudinally movable manner in the damper tube, the piston rod being connected to an upper damper bearing and the damper tube being connected to a lower damper bearing. Furthermore, the shock absorber has a protective tube which protectively surrounds the piston rod and the damper tube at least in certain areas.

The protective tube also has at least one elongate material interruption, starting from one end. This is done in such a way that at least two separate material segments are present.

Due to the separate material segments, the resilience of the protective tube is increased in the critical area, i.e. where ice often forms. If the protective tube hits a layer of ice while the damper is moving, the material segments can deviate radially outwards. In this way, the occurrence of a stick-slip effect is effectively prevented. Disturbing operating noises can be reduced.

The material segments are preferably designed like tongues, so that good flexibility can be achieved.

According to a further development of the invention, it is proposed that the at least one material interruption is designed in the manner of a slot. As a result, the greatest possible coverage of the damper tube by the protective tube is still ensured despite the introduction of the material interruption.

In order to optimize the radial yielding capacity of the protective tube on all sides, there are several material interruptions that are evenly distributed around the circumference of the protective tube.

According to another expedient embodiment of the idea of the invention, the at least one material interruption runs in a straight line. Starting from one end of the protective tube, the material interruption thus runs parallel to the longitudinal axis of the shock absorber.

In this way, the material interruption can be produced particularly easily.

According to the invention, it is proposed that the protective tube has a peripheral expansion at its end having the at least one material interruption. This allows the material segments of the protective tube to slide outwards when they hit ice buildup. In other words, this effectively prevents the lower edge of the protective tube from “wedging” with ice and ensures that the material segments deviate radially.

Furthermore, friction noises that occur can be further reduced if the protective tube has a receiving space, facing the upper damper bearing, for a resilient additional element, which is provided at least in regions with a friction-reducing layer.

Instead of the friction-reducing layer, it is also expedient if the protective tube has a receiving space for a resilient additional element facing the upper damper bearing, with a friction-reducing, preferably sleeve-like molded part being introduced between the wall of the receiving space and the resilient additional element. In this way, too, noises occurring in the area of the resilient additional element can be effectively reduced.

Preferred exemplary embodiments of the invention are illustrated in the figures and are explained in more detail in the following description with reference to the figures. As a result, further advantages of the invention also become clear. Identical reference symbols, even in different figures, refer to identical, comparable or functionally identical components. Corresponding or comparable properties and advantages are thereby achieved, even if a repeated description or reference thereto does not occur. The figures are not always to scale. Proportions may be exaggerated in some figures in order to be able to emphasize features of an exemplary embodiment more clearly.

• 1 einen Längsschnitt durch einen erfindungsgemäßen Stoßdämpfer,
• 2 die Darstellung des Schutzrohrs vom Stoßdämpfer in Alleinstellung,
• 3 die Darstellung des Schutzrohrs, in einer weiteren Ausführungsform,
• 4 die Darstellung des Schutzrohrs, in noch einer weiteren Ausführungsform,
• 5a die Darstellung des Stoßdämpfers gemäß Einzelheit V aus 1, mit einer reibungsvermindernden Beschichtung der Innenwandung des Schutzrohrs und
• 5b eine Darstellung des Stoßdämpfers gemäß Detailansicht V aus 1, mit einem reibungsvermindernden Formteil zwischen der Innenwandung des Schutzrohrs und einem federnden Zusatzelement.

Show it, each schematically

• 1 a longitudinal section through a shock absorber according to the invention,
• 2 the representation of the protective tube of the shock absorber on its own,
• 3 the representation of the protective tube, in a further embodiment,
• 4 the representation of the protective tube, in yet another embodiment,
• 5a the representation of the shock absorber according to detail V 1 , with a friction-reducing coating on the inner wall of the protective tube and
• 5b a representation of the shock absorber according to detail view V 1 , with a friction-reducing molded part between the inner wall of the protective tube and a resilient additional element.

the 1 shows a shock absorber 1, which is preferably used for rear axle damping of a motor vehicle.

The shock absorber 1 has a damper tube 10 which is filled with a damping medium such as oil or air.

A piston rod 11 with a piston 12 is moved longitudinally in the damper tube 10 . The desired damping effect is achieved by a relative movement (damper movement V) between the piston 12 and the damper tube 10 and the associated displacement of the damping medium.

The piston rod 11 and partially also the damper tube 10 are protectively surrounded by a protective tube 15 .

The piston rod 11 is fixed at its upper end with an upper cushion bearing 13a. The attachment point is covered with a protective cap 14.

Furthermore, the upper end of the protective tube 15 is fixed to the upper damper bearing 13a by means of fastening means 16 (for example a pipe clamp). The protective tube 15 is at least so long that it can protectively enclose the upper area of the damper tube 10 even when the shock absorber 1 is not compressed.

The damper tube 10 in turn is connected at the lower end to a lower damper bearing 13b.

In a known manner, when using the shock absorber 1, the upper damper bearing 13a is connected to the structure and the lower damper bearing 13b is connected to the rear axle of a motor vehicle, not shown in detail.

It can also be seen that the upper area of the protective tube 15 has a receiving space 15a for an additional resilient element 17 . To put it more precisely, the resilient additional element 17 is partially accommodated with its upper end in the upper damper bearing 13a and is supported upwards against this. A through-opening 17a allows the piston rod 11 to pass through. A retaining ring 17b, which surrounds the additional element 17 at the lower end, can also be seen in the receiving space 15a.

The resilient additional element 17 can be made of foamed polyurethane (PU), for example. It serves to ensure that a progressive spring characteristic is achieved or supported in the event of a very strong deflection of a motor vehicle.

A cover cap 18 (buffer cap) is applied to the damper tube 10 . The cover cap 18 is used on the one hand to ensure that the sealed entry area from the piston rod 11 into the damper tube 10 is not damaged and on the other hand as a lower stop for the additional element 17 in the event of strong deflection of the shock absorber 1.

The cap 18 is (like the protective tube 15) preferably made of plastic.

As can also be seen from the figure, the cover cap 18 is connected in one piece to a cage-like extension 18a, which extends to the lower end of the protective tube 15 in the exemplary embodiment. Deviating from the exemplary embodiment, the covering cap 18 and the extension 18a can also be present as separate components. The cage-like extension 18a extends radially between the protective tube 15 and the damper tube 10. It serves to ensure that a painted surface of the damper tube 10 is not damaged by relative movements between the protective tube 15 and the damper tube 10. Deviating from the exemplary embodiment, the extension 18a can also be longer or shorter, that is to say, for example, protrude downwards from the protective tube 15 .

In the 2 the protective tube is shown on its own. The protective tube 15 has an upper end 19 and a lower end 20 . The receiving space 15a already mentioned is only indicated by dashed lines. Bellows-like protuberances 15b allow slight compensating movements of the protective tube 15 during a cardanic deflection movement of the shock absorber 1 during its compression/extension, which the protective tube 15 must also carry out. A fastening groove 15c serves to accommodate the fastening means 16 mentioned.

It is now essential that the protective tube 15 is provided with a plurality of elongated material interruptions 21 . The material interruptions 21 start from the lower end 20 of the protective tube 15 and extend in a straight line in the longitudinal direction of the protective tube 15 upwards. In other words, the material interruptions 21 run parallel to a longitudinal axis of the protective tube 15.

In particular, the material interruptions 21 are designed in the manner of slots.

The material interruptions 21 result in tongue-like material segments 22.

The material segments 22 are more flexible than the rest of the protective tube 15 and are able to perform radial deflection movements A.

In the exemplary embodiment, six material interruptions 21 are evenly distributed around the circumference of the protective tube 15 . However, a larger or smaller number of material interruptions 21 is also conceivable. At least one material interruption 21 should be present in order to achieve the desired effect.

Finally, the lower end 20 of the protective tube 15 is provided with a circumferential, funnel-shaped widening 23 in the exemplary embodiment (cf. also 1 ). The widening 23 also contributes to supporting the evasive movement A when the lower end 20 is placed on ice, dirt or the like.

In the 3 another exemplary embodiment of a protective tube 15' is described. In contrast to the previous exemplary embodiment, the material interruptions 21 here are not straight but curved. Equally, however, tongue-like material segments 22 are also produced here, which can perform a radial deflection movement A.

This in 4 The protective tube 15" shown has, in contrast to the previous examples, a different form of a material interruption 21. In this exemplary embodiment, the (single) material interruption 21 has a serpentine course.

At least one of the material interruptions 21 shown should also be introduced in the protective tubes 15 ′ and 15 ″. However, several material interruptions 21 are preferably arranged evenly distributed around the circumference of the protective tube 15 .

Based on 5 It is shown that to achieve a further noise reduction in the area of the receiving space 15a, the surface of the receiving space 15a, ie the inner surface of a wall 15d of the protective tube 15, can be provided with a friction-reducing layer 24 (cf 5a) . The friction reducing layer 24 is preferably a layer of polytetrafluoroethylene (PTFE). However, other friction-reducing materials are also conceivable.

Alternatively, between the surface of the receiving space 15a, ie between the wall 15d and the resilient additional element 17, however, a friction-reducing molded part 25 can also be introduced, which is preferably designed like a sleeve.

Reference List

1

shock absorber

10

damper tube

11

piston rod

12

Pistons

13a

upper damper bearing

13b

lower shock mount

14

protective cap

15, 15', 15"

protective tube

15a

recording room

15b

bellows-like protuberances

15c

mounting groove

15d

wall of the protective tube

16

fasteners

17

resilient additional element

17a

passage opening

17b

retaining ring

18

cover cap (buffer cap)

18a

cage-like extension

19

top end

20

lower end

21

elongated material interruptions

22

material segments

23

circumferential, funnel-shaped widening

24

friction-reducing layer

25

friction-reducing molded part

A

evasive movement

V

damper movement

Claims (6)

Shock absorber (1) for a motor vehicle, with a damper tube (10) for receiving a damping medium, in which a piston rod (11) with a piston (12) is guided in a longitudinally movable manner, the piston rod (11) having an upper damper bearing (13a) and the damper tube (10) is connected to a lower damper bearing (13b), and to a protective tube (15, 15', 15"), which protectively surrounds the piston rod (11) and the damper tube (10) at least in certain areas, the protective tube ( 15, 15', 15"), starting from a lower end (20), has a plurality of elongate material interruptions (21), such that there are at least two material segments (22) separated from one another, characterized in that the protective tube (15, 15 ', 15") has a circumferential, funnel-shaped widening (23) at its end (20) having the material interruptions (21), the opening diameter of which increases from the start of the funnel-shaped widening (23) to the end of the protective tube (15, 15', 15") cont gradually enlarged to a maximum opening diameter, the funnel-shaped widening (23) in the direction of the upper damper bearing (13a) merging directly into a hollow-cylindrical section of the protective tube (15, 15', 15"), into which the material interruptions (21) protrude. shock absorber after claim 1 , characterized in that the material interruptions (21) are formed like slots. shock absorber after claim 1 or 2 , characterized in that the material interruptions (21) are distributed evenly around the circumference of the protective tube (15, 15', 15"). Shock absorber according to one of the preceding claims, characterized in that the material interruptions (21) run in a straight line. Shock absorber according to one of the preceding claims, characterized in that the protective tube (15, 15', 15") has a receiving space (15a) facing the upper damper bearing (13a) for a resilient additional element (17), the receiving space (15a) having at least is partially provided with a layer (24) of polytetrafluoroethylene. Shock absorber according to any of the preceding Claims 1 until 4 , characterized in that the protective tube (15, 15', 15") has a receiving space (15a) facing the upper damper bearing (13a) for a resilient additional element (17), with between the wall of the receiving space (15a) and the resilient additional element (17) a sleeve-like molded part (25) is introduced.

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