Brakes – Internal-resistance motion retarder – Having a thrust member with a variable volume chamber
Patent
1993-09-13
1995-11-07
Oberleitner, Robert J.
Brakes
Internal-resistance motion retarder
Having a thrust member with a variable volume chamber
188280, 18832214, B60G 1708, F16F 946
Patent
active
054640792
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention is related to a controllable two-tube shock absorber with controllable variable shock absorbing power for automotive vehicles, and more particularly relates to shock absorbers comprised of a power cylinder wherein the interior space is subdivided into a first and a second power chambers by means of a piston slidable by a piston rod; storage tank partly filled with oil, wherein hydraulic connections afford a compensation of volume between the power chambers and the storage tank.
BACKGROUND OF THE INVENTION
A two-tube shock absorber of this kind is known from the international patent application No. WO 89/09891. A particular feature of this prior art two-tube shock absorber is its shock absorbing power that is predetermined exclusively by means of a two-stage controllable shock absorber valve which is disposed at the lower end of the central tube and through which the fluid flows in one direction only. With this arrangement, the pilot control stage of the shock absorber valve serves exclusively to control the main stage wherein the flow cross-sectional area determines the variance of absorbing power.
In the state of the art controllable shock absorber however, a disadvantage is that beyond the electromagnetic actuating power at the pilot control stage a minimum hydraulic pressure is required in the system in order to safeguard the functioning of the shock absorber in the customary range of application. Furthermore, the control times which are achievable by this arrangement and which are too long for a quick-acting shock absorber system are less advantageous. The "soft" characteristic and the quick adjustability, which are desired for driving comfort, cannot be attained for the aforementioned reasons.
It is, therefore, the object of the present invention to provide a two-tube shock absorber of the kind discussed which overcomes the aforementioned disadvantages. Moreover, a two-tube shock absorber is provided which affords the adjustment of a special desired characteristic, wherein the shock absorbing power is dependent on the piston speed, out of a field of potential characteristic curves.
According to the invention this object is achieved in that in a lower range of piston speed the shock absorbing power is exclusively determined by the variable flow cross-sectional area of the pilot control stage, while the main stage remains closed, and in that in an upper range of piston speed the shock absorbing power is determined by the variable flow cross-sectional areas both in the main stage and in the pilot control stage.
With this arrangement, it is of advantage that in the upper range of piston speed the main stage follows the position of the pilot control stage. Due to this provision, a more elevated dynamic ratio of the valve adjustment jointly with a simultaneous reduction of the vibration tendency of the shock absorber, particularly when utilized in a moving gear control process, is achieved.
A further advantage of this invention is that the main stage as well as the pilot control stage are arranged so as to be separate from the second non-return valve in a valve housing, wherein the main stage includes a main slide valve interacting with a control edge which is configured within the valve housing. The pilot control stage includes an electromagnetically actuatable control slide valve interacting with control bores which are provided in the main slide valve. A shock absorber valve having this set-up and presenting a two-stage configuration requires less actuating capacity, and affords a better handling of more elevated absorbing power levels.
The control edge is preferably positioned in proximity to the flow-off bores which are configured in the valve housing and which are used in connection with the storage tank. The flow-off bore's size and geometric shape influence the performance characteristics of the main stage. In its upper part, the main slide valve is configured open and is furnished with slide valve bores which allow the bores to be brought into connection with the f
REFERENCES:
patent: 3874485 (1975-04-01), Smith
patent: 4597411 (1986-07-01), Lizell
Bayer Ronald
Halat Siegfried
Kircher Dieter
Lohberg Peter
Perez Diogenes
Alfred Teves GmbH
Oberleitner Robert J.
Poon Peter M.
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