DE102018218509A1 - Shock absorber for a motor vehicle and protective tube for such - Google Patents

Abstract

The invention relates to a 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) is connected to an upper damper bearing (13a) and the damper tube (10) to a lower damper bearing (13b). A protective tube (15) surrounds the piston rod (11) and the damper tube (10) in a protective manner, at least in some areas, the protective tube (15), at least in the area of a lower end, having a longitudinally extending area (15d) in which a cross section The protective tube (15) is provided with a radial profile extending over its circumference. The invention proposes that the profile is formed by a radially changing radius of a wall of the protective tube (15) with mutually alternating indentations and bulges of the wall With the invention, a protective tube for such a shock absorber should also be placed under protection.

Description

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

Such shock absorbers are mainly used in the rear axle of motor vehicles and serve to dampen spring movements of the motor vehicle, which are caused by uneven road surfaces, and thus to ensure safe road holding and high driving comfort of the motor vehicle.

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

The damper tube is usually still covered with a cover cap (also called a buffer cap) which is arranged radially between the protective tube and the damper tube. Such a cover cap serves to prevent damage to the paint layer from the damper tube due to the relative movements occurring between the protective tube and the damper tube.

In everyday operation, 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 extreme cases, damage to the protective tube is also conceivable by placing it on the ice adhering to the buffer cap.

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 stick-slip effect mentioned and in order to be able to produce a suspension strut bearing at low cost, this document proposes a suspension strut bearing with a sliding bearing which has a plurality of friction-reducing elements on its sliding disk. Polytetrafluoroethylene (PTFE) is proposed as the material for the friction-reducing elements.

The one forming the preamble of the main claim DE 18 74 288 U describes a protective jacket tube for hydraulic vibration dampers with a jacket tube body. At its lower end, the casing tube body has slots which run uniformly around its circumference and extend straight upward in a straight line from the end. Furthermore, the casing tube body is provided with stiffening ribs running almost over its entire length, which give its cross section a radial profile that extends over its circumference.

From the DE 20 2006 006 021 U1 a protective tube for a shock absorber is known which has a cap in a head region 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 stop buffer which, when deflected, strikes the support surface of an end cap located on the damper tube. The stop buffer, the protective element and the end cap form a pre-assembled unit.

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

The DE 71 11 851 U a shock absorber with a protective tube can also 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 covering 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 relative rotation to make assembly easier. The protective tube has a circumferential widening at the lower end.

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 against a cap with spring tongues located on a damper tube. A spreading element on the spring tongues serves to spread the spring tongues in the radial direction when the protective element is mounted on the damper tube together with the spring element and cap and to hold it securely in the protective element.

From the DE 18 11 684 U a shock absorber with a protective tube is known, which also comprises a spring element. The spring element strikes a damper tube when it is deflected and, as a hollow spring, encloses a piston rod sliding in the damper tube.

Through the DE 10 2015 216 075 A1 discloses a shock absorber with an additional spring. An end cap on a damper tube forms at Deflection is a stop surface for the additional spring 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.

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

The present invention is based on the object of providing a shock absorber for a motor vehicle in which the occurrence of disturbing noises is reduced.

The present object is achieved by a shock absorber with the features of claim 1. Advantageous developments or further developments of the invention can be found in the dependent claims.

The invention is also based on the object of proposing a suitable protective tube for a shock absorber, which can contribute to noise reduction when the shock absorber is deflected.

This object is achieved with a protective tube with the features of claim 11.

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 surrounds the piston rod and the damper tube in a protective manner at least in some areas. The protective tube has, at least in the region of a lower end, a region which extends in the longitudinal direction and in which the cross section of the protective tube is provided with a radial profile which extends over its entire circumference or almost over its entire circumference,

The invention now proposes that the profiling is formed by a radially changing radius of the wall of the protective tube in the circumferential direction with mutually alternating indentations and bulges of the wall.

Such a profiling increases the compliance of the protective tube in the critical area, that is, where ice formation often occurs. If the protective tube strikes an ice layer during damper movements and thus in the event of radial force, the indentations can easily escape radially outwards or be pushed slightly outwards. In this way, the occurrence of a stick-slip effect is effectively prevented. Disturbing operating noises can be reduced.

In order to support this effect, the wall of the protective tube in the said area of the profiling can be made very thin, for example only in the range of approximately one millimeter. An elastic material, such as plastic, is recommended as the material for the protective tube.

According to a development of the invention, it is proposed that all indentations with radially inner valley points of the wall lie on an imaginary, common inner diameter and all bulges with radially outer mountain points of the wall lie on an imaginary, common outer diameter. All indentations and all indentations, in particular in the radial direction, are of approximately the same dimensions. With such a further development, a good force distribution in the event of an expansion occurring and a high degree of reliability in operation can be achieved.

In order to enable the protective tube to deflect radially on all sides, however, different configurations of the profiling are conceivable. For example, the profiling can preferably be wavy, star-shaped or polygonal. Combinations of these profiles are also conceivable.

According to another expedient development of the inventive concept, the wall has different wall thicknesses, with a first, smaller wall thickness and a second, higher wall thickness. The wall thicknesses alternate in the circumferential direction. In this way, the protective tube can have a greater material thickness in the form of a strip in the axial direction. In this way, a higher axial rigidity of the protective tube can be achieved despite radial compliance.

In order to optimize this effect, it is proposed that the first, smaller thickness lies on the bulges and the second, higher thickness on the bulges.

It is also conceivable that the wall thickness of the wall changes from a minimum value to one Maximum value or vice versa continuously changed. The minimum value can preferably lie at a radially outer mountain point of a bulge and the maximum value at a radially inner valley point of a bulge.

Another expedient embodiment of the invention proposes that the indentations and bulges, viewed in the longitudinal direction of the protective tube, have a changing width. As a result, the change in the compliance behavior along the longitudinal direction of the protective tube can be changed in the desired manner.

For example, the width of the indentations can continuously increase towards the upper end of the protective tube. This is associated with a corresponding decrease in the width of the bulges towards the upper end.

According to another development, it is proposed that the protective tube have a circumferential, conical widening at its lower end. The wall of the protective tube widens continuously from a first diameter to a larger diameter at the outermost lower end. This enables the protective tube to slide off even more easily when it encounters ice build-up. A jamming of the protective tube or a high pressure force of the protective tube on the ice layer and the associated noise generation are avoided even more effectively.

As mentioned at the beginning, the invention is also intended to provide a protective tube which is suitable for mounting on a shock absorber according to the invention. Such a protective tube has, at least in the region of a lower end, an area which extends in the longitudinal direction of the protective tube and in which a cross section of the protective tube is provided with a radial profile which extends over its entire or almost the entire circumference.

The protective tube is characterized in that the profiling is formed by a radially changing radius of a wall of the protective tube in the circumferential direction with mutually alternating indentations and bulges of the wall.

Preferred exemplary embodiments of the invention are shown in the figures and are explained in more detail with reference to the figures in the following description. This also makes further advantages of the invention clear. The same reference numerals, also in different figures, refer to the same, comparable or functionally identical components. Corresponding or comparable properties and advantages are achieved, even if there is no repeated description or reference to them. The figures are not always to scale. In some figures, proportions can be exaggerated in order to be able to emphasize features of an exemplary embodiment more clearly.

• 1 einen teilweisen Längsschnitt durch einen erfindungsgemäßen Stoßdämpfer,
• 2 a eine Schnittansicht des Schutzrohrs vom Stoßdämpfer im Bereich der Profilierung gemäß Schnittverlauf II aus 1, in einem radial nicht aufgeweiteten, ursprünglichen Zustand,
• 2 b eine Schnittansicht des Schutzrohrs vom Stoßdämpfer im Bereich der Profilierung gemäß Schnittverlauf II aus 1, in einem radial aufgeweiteten Zustand,
• 2 c eine prinziphafte Darstellung der radialen Aufweitung der Einbuchtungen,
• 3 weitere Ausführungsformen der Profilierung des Schutzrohrs,
• 4 die Darstellung des Schutzrohrs in Alleinstellung, in einer weiteren Ausführungsform,
• 5 die Darstellung des Schutzrohrs in Alleinstellung, in noch einer weiteren Ausführungsform und
• 6 die Darstellung einer umlaufenden, konischen Aufweitung des Schutzrohrs im Bereich seines unteren Endes.

It shows, each schematically

• 1 a partial longitudinal section through a shock absorber according to the invention,
• 2 a a sectional view of the protective tube from the shock absorber in the area of the profile according to the course of the cut II out 1 , in a radially unexpanded, original condition,
• 2 B a sectional view of the protective tube from the shock absorber in the area of the profile according to the course of the cut II out 1 , in a radially expanded state,
• 2 c a basic representation of the radial expansion of the indentations,
• 3rd further embodiments of the profiling of the protective tube,
• 4th the representation of the protective tube in isolation, in a further embodiment,
• 5 the representation of the protective tube in isolation, in yet another embodiment and
• 6 the representation of a circumferential, conical widening of the protective tube in the region of its lower end.

The 1 shows a shock absorber 1 , which is preferably used for rear axle damping of a motor vehicle, not shown. The shock absorber 1 has a damper tube 10th on, which is filled with a damping medium such as oil or air.

In the damper tube 10th is a piston rod longitudinally movable 11 with a piston 12th emotional. Through a relative movement (damper movement V ) between the pistons 12th and the damper tube 10th and the associated displacement of the damping medium, the desired damping effect is achieved.

The piston rod 11 and partly also the damper tube 10th are protective from a protective tube 15 surround. The piston rod 11 is at its upper end with an upper shock mount 13a attached. The attachment point is with a protective cap 14 covered.

Furthermore, the protective tube 15 at its upper end via fasteners 16 ( for example a pipe clamp) on the upper damper bearing 13a fixed. The protective tube 15 is at least so long that it is even when the shock absorber is not compressed 1 the top of the damper tube 10th can protectively surround. The damper tube 10th in turn is at the lower end with a lower damper bearing 13b connected.

In a known manner when using the shock absorber 1 the upper damper bearing 13a with the body and the lower damper bearing 13b connected to the rear axle of a motor vehicle.

On the damper tube 10th is a cover cap 18th (Buffer cap) applied. The cover cap 18th serves to seal the entrance area from the piston rod 11 into the damper tube 10th is not damaged. The cover cap 18th is (like the protective tube 15 ) preferably made of plastic.

The cover cap 18th is with a cage-like extension 18a integrally connected, which is towards the lower end of the protective tube 15 moves there. The extension 18a extends radially between the protective tube 15 and the damper tube 10th . It serves to paint the damper tube 10th not through relative movements between the protective tube 15 and damper tube 10th is damaged. The extension 18a can deviate from the exemplary embodiment also be longer or shorter, for example downward from the protective tube 15 stepping out.

It is now essential that the protective tube 15 in the lower area one in its longitudinal direction I. extending area 15d has, in which the cross section of the protective tube 15 (i.e. its wall W ) with a radial profile extending over its entire or almost entire circumference 15f is provided (see also 2a) .

In the 2a is the cross section of the protective tube 15 in the area 15d with the profiling 15f shown. It is clear that the profiling 15f itself in the circumferential direction U extends over the entire circumference. The profiling 15f is by a radius r the wall W of the protective tube 15 formed, which is in the circumferential direction U changed.

Specifically, that changes from a longitudinal center axis or from a center point M outgoing radius r such that multiple bulges A and several indentations E arise in the circumferential direction U take turns. In the embodiment, there are four bulges A and four indentations E available. In the area of each bulge A takes the radius r a maximum radius ra in the area of each indentation E a minimal radius re .

All dents E lie with their radius re or with a valley point TP on an imaginary, common inner diameter Tue . The radius ra or a mountain point formed thereby BP all bulges A or lies on an imaginary, common outer diameter There .

The 2a shows the profiling 15f the wall W in an undeformed, original condition. A radial force now occurs due to ice formation Fr radial deformation of the wall can easily occur W occur.

This is based on 2 B shown. Be specific through the radial force Fr the indentations E pushed radially outwards (cf. re' , E ' , 15f ' ) and on a new imagined, common inner diameter Di ' positioned. The profiling 15f gives the protective tube 15 so great radial flexibility. The dents E bring the radial force Fr little resistance to it. If there is no radial force Fr the protective tube forms 15 again elastic in the original shape or profile 15f back. The radial widening of the indentations took place E is also made by widening a between flanks F1 and F2 formed angle α towards an enlarged angle α ' clear.

The "expansion" of the inner diameter Tue (undeformed) towards a larger diameter Di ' (expanded) is again based on the 2c outlined.

Based on 3rd are alternative embodiments for the design of the profiling 15f evident. So the profiling 15f the wall W of the protective tube 15 for example, wavy ( 3a) , star-shaped ( 3b) or be polygonal ( 3c ).

It is also conceivable that the profiling 15f additionally one in the circumferential direction U variable wall thickness of the wall W having. So it is possible that the wall W at the radially outermost points (mountain points BP ) of the bulges A a minimal wall thickness d1 and at the radially innermost points (valley points TP ) the indentations E a maximum wall thickness d2 having. The transition from one wall thickness to another wall thickness is constant (cf. 3d ).

The 3e shows an embodiment in which each bulge A a minimal wall thickness over its entire circumferential length d1 and every indentation E a maximum wall thickness over its entire circumferential length d2 having. In addition, the transition from one wall thickness to the other is discontinuous, i.e. abrupt.

Through the indentations E with greater wall thickness d2 becomes a stiffening of the protective tube 15 in the axial direction, i.e. in the longitudinal direction I. reached.

In 4th is a protective tube 15 ' shown in isolation. It has an upper end 19th and a lower end 20th on. Bellows-like protuberances 15a allow slight compensatory movements of the protective tube 15 with a cardanic deflection movement of the shock absorber 1 during its deflection / rebound. This must also be the protective tube 15 ' can accomplish with. A mounting groove 15b is used to hold the fastener mentioned 16 . It can also be seen that both the indentations E as well as the bulges A starting from the lower end 20th rectilinear and parallel to the longitudinal direction I. run upwards and a constant width over almost their entire length b1 respectively. b2 exhibit.

Finally, the bottom is 20th of the protective tube 15 ' with a circumferential, in the exemplary embodiment funnel-shaped, in particular conical widening 21 Mistake. The expansion too 21 contributes to the lower end 20th on ice, dirt or the like to support a radial evasive movement or expansion of the protective tube 15 ' at. Such an expansion can preferably be used in addition to all designs of the protective tube.

In the 5 is yet another embodiment of a protective tube 15 " described. In contrast to the previous exemplary embodiment, the indentations point here E and the bulges A Widths b1 and b2 on that is in the longitudinal direction I. of the protective tube 15 " change. Specifically, the width is increasing b1 of every indentation E to the top end 19th towards and the width b2 of every bulge A to the top end 19th down.

The in the 4th and 5 shown, tapered widening 21 extends in the longitudinal direction I. only over a short end section 15e . As already mentioned, the expansion is ongoing 21 conical. It starts with a first diameter D1 the wall W of a protective tube, expands steadily and finally reaches the outer lower end 20th to a second, larger diameter D2 (see. 6 ). The expansion 21 overlapping indentations E and bulges A are not shown here for the sake of simplicity.

Reference list

1

Shock absorber

10th

Damper tube

11

Piston rod

12th

piston

13a

upper damper bearing

13b

lower damper bearing

14

protective cap

15, 15 ', 15 "

Protective tube

15a

bellows-like protuberances

15b

Mounting groove

15d

Area with a profiled cross-section

15e

expanding section

15f

Profiling

16

Fasteners

18th

Cover cap (buffer cap)

18a

cage-like extension

19th

top end

20th

lower end

21

circumferential, conical widening

α, α '

angle

A

bulge

BP

Mountain point

b1

Width of the indentations

b2

Width of the bulges

d1

Wall thickness

d2

Wall thickness

Tue, Tue

inner diameter

There, there

outer diameter

D1

first diameter

D2

second diameter

E, E '

indentation

F1, F2

Flanks

Fr

Radial force

I.

Longitudinal direction

M

Center point, longitudinal center axis

r

Radius of the wall from the protective tube

ra

Radius in a bulge

re, re '

Radius in a recess

TP

Valley point

U

Circumferential direction

V

Damper movement

W

Wall of the protective tube

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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

• DE 102010024601 A1 [0006]
• DE 1874288 U [0007]
• DE 202006006021 U1 [0008]
• DE 10122796 A1 [0009]
• JP 2016048081 A [0010]
• DE 7111851 U [0011]
• DE 102010018044 A1 [0012]
• DE 1811684 U [0013]
• DE 102015216075 A1 [0014]
• JP 2007327627 A [0015]
• DE 102006010332 A1 [0016]

Claims (11)

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 ') which surrounds the piston rod (11) and the damper tube (10) in a protective manner at least in certain areas, the protective tube (15, 15 '), at least in the area of a lower end (20), has an area (15d) extending in the longitudinal direction (I), in which the cross section of the protective tube (15) is provided with a radial profile (15f) extending over its circumference , characterized in that the profiling (15f) by a radially changing in the circumferential direction (U) radius (r) of a wall (W) of the protective tube (15) with mutually alternating indentations (E) and bulges (A) of the Wa ndung (W) is formed. Shock absorber (1) after Claim 1 , characterized in that all indentations (E) with radially inner valley points (TP) of the wall (W) on an imaginary, common inner diameter (Di) and all bulges (A) with radially outer mountain points (BP) of the wall (W) lie on an imaginary, common outer diameter (Da). Shock absorber (1) after Claim 1 or 2nd , characterized in that the profiling (15f) is undulating. Shock absorber (1) after Claim 1 or 2nd , characterized in that the profiling (15f) runs in a star shape. Shock absorber (1) after Claim 1 or 2nd , characterized in that the profiling (15f) is polygonal. Shock absorber (1) according to one of the preceding claims, characterized in that the wall (W) has different wall thicknesses (d1, d2) with a first, smaller wall thickness (d1) and a second, higher wall thickness (d2), the wall thicknesses (d1, d2) alternate with each other. Shock absorber (1) after Claim 6 , characterized in that the first wall thickness (d1) on the bulges (A) and the second wall thickness (d2) on the indentations (E). Shock absorber (1) according to one of the preceding claims, characterized in that the indentations and bulges (E and A), viewed in the longitudinal direction (I) of the protective tube (15, 15 '), have a changing width (b1 and b2) . Shock absorber (1) after Claim 8 , characterized in that the width (b1) of the indentations (E) increases continuously towards the upper end (19) of the protective tube (15). Shock absorber (1) according to one of the preceding claims, characterized in that the protective tube (15, 15 ') has a circumferential, conical widening (21) at its lower end (20), the wall (W) of the protective tube ( 15) from a first diameter (D1) to a diameter (D2) lying at the outermost lower end (20). Protective tube (15, 15 ') for a shock absorber (1) according to one of the preceding claims, wherein the protective tube (15, 15'), at least in the region of a lower end (20), a region (15d) extending in the longitudinal direction (I) ), in which a cross section of the protective tube (15) is provided with a radial profile (15f) extending over its circumference (U), characterized in that the profile (15f) has a radially changing radius (r ) a wall (W) of the protective tube (15) with mutually alternating indentations (E) and bulges (A) of the wall (W) is formed.

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