Patent Application
20080048370
The invention relates to a bump stop for a vehicle Macpherson strut, in particular for a telescopic Macpherson strut of a motor vehicle steering wheel, equipped with filtration elements for the vibrations transmitted by the spring and by the telescopic damper to the superstructure of the vehicle.
1. Prior Art
In document FR 2 793 732 is described an upper attachment device of a Macpherson strut with a coil spring and a telescopic damper for a motor vehicle steering wheel. Said device comprises an antifriction bearing the lower washer of which forms a spring support and the upper washer forms a cylindrical core on which is supported a dampening pad of the travel limit of the telescopic damper. Between the lower washer and the coil spring is interposed an elastomeric mass which covers, for example by moulding, the inner face of the washer rotated towards the coil. Said elastomeric mass is used to restrain and filter the upper coil of the spring. The elastomeric mass is placed under stress not only in the axial direction but also during shearing, due to the deformations and complex movements of the end of the spring during deflections. In addition, the thickness of the elastomeric mass is not constant because it compensates the offset between the damper rod and the spiral spring, and said variable thickness hinders the filtration. Finally, the elastomeric mass is directly exposed to external contaminations, and is in constant friction against the coil of the spring, which causes rapid wear.
In document U.S. Pat. No. 6,257,605 is described a bump stop consisting of a lower support element, an antifriction bearing and a housing cover for the bearing, equipped with a skirt engaging with the lower support element for defining a labyrinth seal. The stop thus constituted forms a sub-assembly which is mounted between the coil spring and an upper support element constituting the interface with the superstructure of the vehicle. Between the cover and the upper support is interposed an annular dampening block. Said block is not however built into the sub-assembly consisting of the stop, which is not optimal in terms of function integrations.
2. Description of the Invention
The invention therefore aims to resolve the disadvantages of the prior art, so as to propose a bump stop which forms a compact single sub-assembly including the vibration filtration function of the spring in a protect environment.
To this effect, the purpose of the invention is a bump stop device for a Macpherson strut of a vehicle, the strut being equipped with a coil spring and a telescopic damper, the device comprising:
The presence of two filtration elements, one dedicated to the vibrations transmitted by the telescopic damper and the other to the spring, allows each filtration element to be individually adapted. The vibration filtration block of the spring may thus be relatively compact, because the vibrations of the spring requiring a filtration are in a relatively high frequency range, above 30 Hz, in particular in the frequency range between 40 and 100 HZ.
The bump stop constitutes a pre-assembled sub-assembly including the filtration function of the spring and filtration of vibrations of the damper.
Due to its positioning above the upper washer, the vibration filtration block of the spring is interposed between the parts which are fixed in rotation in relation to the upper support element and the superstructure of the vehicle. The filtration block is not subjected to any torque and may be optimised for essentially axial stresses. In addition, the block may if necessary also filter the vibrations produced by the bearing itself.
According to one embodiment, the filtration block is disposed between the upper washer and the cover. Said layout allows the filtration block to be further protected from external contaminations. It also facilitates the assembly.
It can also be envisaged that the cover is made of elastomeric material and constitutes the upper support.
Preferentially, the cover is equipped with a skirt covering without touching a peripheral area of the support element and delimiting with the peripheral area of the support element an annular labyrinth, disposed radially outside of the housing and connecting the housing to the outside.
Other advantages and characteristics will emerge more clearly from the description which will follow of the specific embodiments of the invention, given by way of non-limitative example, and shown in the appended drawings on which:
In order to simplify the presentation, the elements common to the various embodiments will be designated by the same reference signs and their description will not be systematically repeated.
In reference to
The bearing 24 consists of an upper washer 26 and a lower washer 28, both made of pressed steel, and forming rolling paths with oblique contact for rolling bodies such as balls 30 or tapered rollers. The bearing thus defines a rotational axis 31 of the stop. The upper washer 26 is supported by a filtering block made of elastomeric material 32 itself supported by the bottom 33 of the cover 22. The lower washer 28 is supported by a support area 34 constituting a positioning relief at the upper surface 36 of a supporting part 38 made of synthetic material. The supporting part 38 comprises, on the side of its lower surface 42, a cylinder-shaped skirt 44 which separates an outer transversal support shoulder 46 of the spring 10 and an inner transversal support shoulder 48 of the dampening pad 14.
The cover 22 delimits with the supporting part a housing for the bearing 24. The cover 22 is equipped with a skirt 56 covering without touching a peripheral area 58 of the supporting part 38 and delimiting with the peripheral area 58 of the supporting part an annular labyrinth connecting the housing to the outside.
It should be noted that the washers 26, 28 constituting the bearing 22 have a high rigidity, which allows very small clearances to be maintained at the level of the pressure drops. Said washers 26, 28 are preferentially made of 1.2 to 2 mm thick pressed sheet metal. In the example of embodiment, a 1.5 mm sheet metal is used.
The elastomeric material constituting the filtration block is selected in order to allow effective filtering of the specific vibration modes of the spring, in particular in a frequency range located between 40 and 100 Hz. Good results have been obtained with a rubber ring between 2 mm and 10 mm thick, and more specifically between 3 mm and 5 mm.
A second embodiment of the invention is shown in
Naturally, various modifications are possible.
The rolling bodies may be rollers. The antifriction bearing may be replaced with a plain bearing.
The lower supporting part may be strengthened with a metal insert. Its lower face may be partially covered with a metal cup.
Between the outer shoulder and the spring may be interposed the annular end of a concertinaed sleeve designed for protecting the damper against external contaminations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0606853 | Jul 2006 | FR | national |
