WO2016193211A1

WO2016193211A1 - Vibration damper with a traction stop

Info

Publication number: WO2016193211A1
Application number: PCT/EP2016/062164
Authority: WO
Inventors: Michael Fritz
Original assignee: Thyssenkrupp Bilstein Gmbh; Thyssenkrupp Ag
Priority date: 2015-06-01
Filing date: 2016-05-30
Publication date: 2016-12-08
Also published as: DE102015210078A1

Abstract

The invention relates to a vibration damper for motor vehicles, in particular commercial vehicles, having a damper tube (1), a piston rod (2) which can be moved to and fro in the damper tube (1) along a shock absorber longitudinal axis, wherein a piston rod guide (3) is arranged on the damper tube (1) in order to guide the movements of the piston rod (2), wherein a stop ring (4) is provided on the piston rod (2), wherein a stop element (5) is arranged on that side of the piston rod guide (3) which faces the stop ring (4), wherein the stop element (5) is configured as an insert part (6) and is connected to the piston rod guide (3), wherein the stop ring (4) comes into contact with the insert part (6) after a defined extending travel during an extending movement of the piston rod (2) out of the damper tube (1), and limits the extending movement. In order to develop a vibration damper of the type mentioned at the outset in such a way that damage of the piston rod surface is avoided effectively even in the case of very high stop forces, it is proposed that the piston rod guide (3) has a main body (7) made from sintered material which has a receptacle (8) for the insert part (6), wherein the insert part (6) is inserted into the receptacle (8) and is connected to the main body (7), wherein the insert part (6) has, at least in the region in which it comes into contact with the stop ring (4) after a defined extending travel of the piston rod (2), a material which has a higher yield point R_p0.2 and a higher tensile strength R_m than the sintered material of the main body (7).

Description

DESCRIPTION

Vibration damper with cable stop

State of the art

The invention relates to a vibration damper having the features of the preamble of patent claim 1.

Such a vibration damper is known from document EP 1 544 499 B1. There, a vibration damper is described with a stop acting in the pulling direction (ie, in the direction of an extension movement of the piston rod out of the damper tube) (also referred to as "pull stop" for short) .The movements of the piston rod are guided by the piston rod guide via a guide surface enclosing the piston rod The stop stop comprises a stop ring located on the piston rod and a stop shoulder provided on the piston rod guide The stop stop is used, on the one hand, to limit an extension movement of the piston rod out of the damper tube (a so - called rebound stroke of the piston rod) This function is described in EP 1 544 499 Bl referred to as "stroke limitation". Another object of the Zuganschlags known from EP 1 544 499 Bl, it is on the other hand, even in case of overload, d .h. at very high impact forces, which cause a plastic deformation of the material of the piston rod guide, to avoid mechanical damage to the piston rod surface by the deformed material of the piston rod guide. At the same time a low height in the axial direction should be achieved.

In order to achieve these objectives, the invention underlying EP 1 544 499 B1 proposes that the piston rod guide between the stop shoulder and the guide surface has an annular deformation zone with a recess which, in the event of overloading, permits deformation of the stop shoulder while absorbing axial forces. A plastic deformation of the stop shoulder in case of overload is therefore deliberately accepted in the subject matter of EP 1 544 499 B1. Deformations and settlements which the stop ring leaves on the piston rod guide are referred to as "unavoidable" in EP 1 544 499 B1 (cf, paragraph [0008].) The deformation zone is intended to protect the guide surface against deformations and settling phenomena In order to achieve this, the deformation zone should absorb the plastic deformations of the stop shoulder, as stated in paragraph [0008]: "In particular, those in continuous operation are avoidable settlements or deformations, which leaves the stop ring on the piston rod guide, absorbed and absorbed by the stop shoulder. "

In the first sentence of paragraph [0018] of EP 1 544 499 B1, an exemplary embodiment which is not described or illustrated in detail in the remaining text is casually mentioned, in which the stop shoulder is mounted on the front side of the piston rod guide as an insert part and in the extension direction if necessary, located at a distance in front of the guide surface for the piston rod. Also in this embodiment, the deformation zone is provided to absorb the plastic deformations of the stop shoulder according to the technical teaching of EP 1 544 499 Bl. The technical teaching of EP 1 544 499 B1 thus presupposes in this embodiment as well regarded as "unavoidable" deformations and settlements, which leaves the stop ring on the piston rod guide.

For vibration absorbers of the type described above, there is a requirement on the part of the vehicle manufacturer that the cable stop must be able to absorb high impact forces of up to 80 kN without mechanically damaging the surface of the piston rod by plastically deformed material of the piston rod guide. A disadvantage of the solution known from EP 1 544 499 B1 is that still so great plastic deformations of the piston rod guide are possible that the deformation zone is insufficient to absorb the deformations and to protect the piston rod effectively against damage to the surface.

Disclosure of the invention

The present invention is based on the object, a vibration damper of the type mentioned in such a way that damage to the piston rod surface is effectively avoided even at very high impact forces.

This object is achieved by a vibration damper with the features of claim 1. Meaningful further developments of the invention are specified in the subclaims.

According to the invention, it is provided that the piston rod guide has a base body made of sintered metal, which has a receptacle for the insert part, wherein the insert part is inserted into the receptacle and connected to the base body, wherein the insert part at least in the area in which it from a certain extension path the piston rod comes into contact with the stop ring, _comprising a material having a higher yield point R _p o _i2 and a higher tensile strength R _m than the sintered metal of the main body. The present invention thus proposes to form the piston rod guide from elements which consist of different materials. The measure according to the invention that the main body and the insert part have different materials, allows the designer to optimally adapt these components by appropriate choice of materials to the particular requirements that are placed on these components.

The main body is made of sintered metal and can therefore be produced inexpensively by a sintering process. The sintering process allows both the guide surface for guiding the piston rod movements and the receptacle required for the insert part to be easily and without additional operations such as e.g. To provide machining operations on or in the body. Furthermore, the sintered metallic material of the base body has a certain elasticity, so that the piston rod guide is not altogether too rigid.

On the other hand, at least in the region in which it comes into contact with the stop _ring after a certain extension of the piston rod, the insert part has a material which has a higher yield strength R _p0i 2 and a higher tensile strength R _m than the sintered metal of the main body. The targeted selection of a material for the insert with a significantly higher yield strength and tensile strength ensures that the insert does not plastically deform even with very large impact forces. In marked contrast to the solution known from EP 1 544 499 B1, according to which deformation of the insert part is absorbed / absorbed by a deformation zone, plastic deformation of the insert part and the piston rod guide is thus avoided in the present invention. In this respect, the solution according to EP 1 544 499 B1 fundamentally differs from the solution approach of the present invention, so that EP 1 544 499 B1 points in a completely different direction than the present invention.

According to one embodiment of the invention, the insert part consists of a hard metal, e.g. from 42CrMo4. This has the advantage that is achieved by the targeted selection of a material for the insert with a significantly higher yield strength and tensile strength than the material of the body that the insert does not plastically deform even with very large impact forces.

According to one embodiment of the invention, the insert part is formed as an annular element which is inserted into the receptacle of the base body and connected to the base body. The insert part may be connected in different ways with the base body, in particular, the insert part with the main body form a non-positive / positive and / or a cohesive connection. Thus, the insert can be pressed into a cylindrically shaped receptacle of the body, glued, soldered or welded.

If the insert part is pressed into the receptacle of the main body, then the diameter of the annular insert part in relation to the cylindrical receptacle of the main body is dimensioned such that the insert part forms an at least frictional connection with the main body. per is pressed into the receptacle.

As a suitable welding method for the connection between the insert part and the base body, friction welding is recommended due to the rotational symmetry of the annular insert part and the cylindrical receptacle. Alternatively, other welding methods may be used, such as e.g. Laser beam welding.

According to one embodiment of the invention, the material characteristic flow limit R _p o _i2 and tensile strength R _{m of} the insert part are greater than the corresponding material properties of the piston rod material. This means that the said material characteristic values of the material of the insert part in this embodiment not only relative to the material values of the main body of the piston rod guide are selected, but also relative to the material values of the piston rod material. This ensures that no deformations of the insert occur even at high impact forces, which can lead to a leak or malfunction due to increased piston rod friction.

In the following the invention will be explained in more detail with reference to a drawing. Brief description of the drawings

Figure 1 shows a vibration damper according to the invention in an axial half section in an engaged position of the stopper ring 4 with the piston rod guide 3;

Embodiments of the invention

In Figure 1, a vibration damper according to the invention is shown in axial half section. The damper tube 1 receives a reciprocating in the damper tube 1 in the axial direction piston rod 2. On the piston rod 2, a working piston 10 is arranged. The working piston 10 divides the interior of the damper tube 1 in a piston rod-side working space 11 and a piston rod remote working space 12. The piston rod side working space 12 is closed by a piston rod guide 3, which is connected to the damper tube 1. By the piston rod guide 3, the piston rod 2 is guided in its oscillating entry and exit movement in the damper tube 1. On the piston rod 2, a stop ring 4 is arranged, which is designed for example as a snap ring or spring ring. The stop ring 4 is inserted into a receiving groove 13 provided in the piston rod 2. From a certain Ausfahrweg by which the piston rod 2 is extended from the damper tube 1, the stop ring 4 enters into contact with the piston rod guide. 3 Fig. 1 shows the situation in which the stop ring 4 comes into contact with the piston rod guide 3. The piston rod guide 3 comprises a base body 7, which is made, for example, of a sintered metal as a sintered component. At the side facing the piston rod-side working space 11 in the installed state, the main body 7 has a receptacle 8 for a stop element 5. The stop element 5 is formed as an insert 6, that is, it is inserted into the receptacle 8. The stop element 5 is firmly connected to the base body 7. The fixed connection between the stop element 5 and the main body 7 can be achieved by pressing the stop element 5 into the receptacle 8. In the illustrated embodiment, the stop element is annular and the receptacle 8 has a cylindrical cross-section. In order to press the stopper member 5 in the receptacle 8 and to achieve a solid non-positive connection between the base body 7 and the stop element 5, the diameter of the receptacle 8 and the outer diameter of the annular stop element 5 are coordinated so that there is a diameter coverage, the leads to a sufficiently tight interference fit. Alternatives to pressing the stop element 5 into the receptacle 8 are possible. Thus, the stop element 5 can also be materially inserted by a welding process, for example, a friction welding process such as rotary friction welding or a beam welding process such as laser beam welding or electron beam welding in the recording. Or the stop element 5 is integrally inserted by an adhesive bond or a solder joint in the receptacle 8 and thereby firmly connected to the piston rod guide 3.

In a specific embodiment, the main body 7 of the piston rod guide 3 is made of a sintered metal material, for example of sintered steel Sint-Cl l as a sintered component. This material has a yield point R _p o _i2 of 290 MPa and a tensile strength R _m of 390 MPa. The elongation at break, d .h. the elongation A occurring up to a fraction of the sample is 1% for this material. The stop element 5 consists of the steel material 42CrMo4. This material has a yield point R _p o _{, 2} of 750 MPa and a tensile strength R _m of 1100 MPa. The elongation at break A is 11% for this material. As material for the piston rod, the material WNB 791 A2 is used in the concrete embodiment. This material has a yield strength R _p o _i2 of 500 MPa, a tensile strength R _m of 775 MPa and an elongation at break of 6%. The snap ring consists of the material according to DIN EN 10270-1 or 2 and has a tensile strength R _m in the range 1840 MPa to 2040 MPa. LIST OF REFERENCE NUMBERS

1 damper tube

2 piston rod

3 piston rod guide

4 stop ring

5 stop element

6 insert part

7 basic body

8 recording

10 working pistons

11 piston rod side working space

12 piston rod remote working space

13 receiving groove

Claims

1. Vibration dampers for motor vehicles, in particular commercial vehicles,

a. with a damper tube (1),

b. a piston rod (2) which can be moved back and forth in the damper tube (1) along a shock absorber longitudinal axis,

c. wherein a piston rod guide (3) for guiding the movements of the piston rod (2) is arranged on the damper tube (1),

d. wherein a stop ring (4) is provided on the piston rod (2),

e. wherein on the side facing the stop ring (4) side of the piston rod guide (3) a stop element (5) is arranged,

f. wherein the stop element (5) is designed as an insert part (6) and connected to the piston rod guide (3),

g. wherein the stop ring (4) in an extension movement of Kolbenstrange (2) from the damper tube (1) from a certain extension path with the insert part (6) comes into contact and limits the extension movement, characterized in that h. the piston rod guide (3) has a base body (7) made of sintered metal, which has a receptacle (8) for the insert part (6),

i. wherein the insert part (6) is inserted into the receptacle (8) and connected to the base body (7),

j. wherein the insert (6) at least in the region in which it comes into contact with the stop ring (4) from a certain extension of the piston rod (2), a material having a higher yield point R _p o _{, 2} and a higher tensile strength R _m as the sintered metal of the main body (7).

2. Vibration damper according to claim 1, wherein the insert part (6) consists of a hard metal.

3. Vibration damper according to claim 2, wherein the insert consists of 42CrMo4.

4. Vibration damper according to one of the preceding claims, wherein the insert part (6) is designed as an annular element which is inserted into the receptacle (8) of the base body (7) and connected to the base body (7).

5. Vibration damper according to one of the preceding claims, wherein the material _properties yield point R _p0 , ₂ and tensile strength R _{m of} the insert part (6) are greater than the corresponding material characteristic values of the piston rod material.