Patent Application
20110290605
1. Field of the Invention
The invention is directed to a Vibration damper comprising a cylinder in which a piston fastened to a piston rod executes a translational and a rotational movement relative to the cylinder.
2. Description of the Related Art
In a vibration damper, the piston executes an axial relative movement relative to the cylinder. As a rule, a piston nut causes a pre-loading between the piston and the piston rod so that the connection between the piston and piston rod is not loosened.
Particularly in vibration dampers on articulated axles, the piston, together with the piston rod, also carries out a rotational relative movement relative to the cylinder. The piston can also execute a rotational relative movement relative to the cylinder in vibration dampers arranged at an inclination to the swiveling axis of an axle part. In this way, it can come about that the friction force between the inner wall of the cylinder and the piston exerts a loosening torque on the piston nut.
Particularly in vibration dampers for upscale vehicle types, bearings are provided which allow a relative movement of the piston rod relative to the vehicle body, as is disclosed in DE 37 16 819 A1, for example. The problem of loosening of the piston does not arise in vibration dampers of this kind.
As an alternative measure, for example, piston nuts are used whose thread pitch diverges slightly from a fastening thread of the piston rod. In this connection, reference is had to DE 34 29 473 A1, for example.
DE 101 61 801 A1 suggests a deliberate deformation of the piston nut as a solution for securing the piston. Further, self-locking nuts are also known.
In principle, the problem of loosening described above arises not only when pistons are secured by screwing, but also in pistons that are riveted to the piston rod. The method for fastening the piston to the piston rod is secondary, since every rotational movement of the piston relative to the piston rod shortens the life of the vibration damper.
it is an object of the present invention to provide another solution for the problem of securing the piston.
According to one embodiment of the invention, a device for preventing rotation by positive engagement is formed between the piston and the piston rod.
The great advantage is that a rotational movement of the piston relative to the piston rod is reliably prevented. On the other hand, the axial pre-loading force on the piston can be reduced. As a result, smaller piston nut diameters can be used.
The device for preventing rotation is formed by a through-opening in the piston and a lateral surface of the piston rod so that no additional structural component parts need be used for the device for preventing rotation.
In principle, the positive-engagement connection between the piston and the piston rod can be produced by a profile of optional geometry. However, the lateral surface and the through-opening are preferably constructed as a multi-wedge profile.
To simplify assembly, the multi-wedge profile of the piston rod is constructed so as to be in an integer ratio to the multi-wedge profile in the region of the through-opening of the piston. The quantity of possible assembly positions of the piston on the piston rod is appreciably increased by this step so that assembly times are shortened.
In a further construction, the rotation-preventing profile is limited to only one axial portion of the through-opening.
Further, it is provided that the through-opening in the piston has an axial guide portion and a portion for the rotation-preventing profile, an assembly bevel being formed between these two portions. Owing to the assembly bevel, the piston also executes a slight rotational movement automatically when imprecisely guided onto the piston rod and, consequently, the positive engagement connection is closed.
The guide portion has a greater diameter than the rotation-preventing profile. The rotation-preventing profile need only support a turning torque. Transverse forces acting on the piston, which are appreciably larger, are taken over by the guide portion.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
The invention will be described more fully with reference to the following description of the drawings. In the drawings:
The piston 7 has an axial through-opening 31 for receiving the piston rod 1 according to
When viewed in combination,
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 029 252.4 | May 2010 | DE | national |
