The invention relates to a controllable vibration damper having a damping force control system, having a damper housing tube, which is at least partially filled with damping medium, and a damping valve for damping force control, which is arranged on and fluidically connected to the damper housing tube, having an inner tube, which is inserted into the tubular damper housing via a bottom valve element, and having a piston rod, which can be moved longitudinally in the inner tube and has a working piston, wherein the bottom valve element divides the tubular damper housing into a low-pressure working chamber and a high-pressure working chamber, which is acted upon by means of the working piston, and an inlet opening of the damping valve element is fluidically connected to the high-pressure working chamber, and an outlet opening of the damping valve element is fluidically connected to the low-pressure region.
The prior art discloses vibration dampers in which two control valves arranged hydraulically in parallel with the working piston are provided, through one of which the damping medium flows in the compression stage, during the retraction movement of the piston rod, and through the other of which it flows in the rebound stage, during the extension movement of the piston rod. For this purpose, EP 1 538 399 A1 provides control valves, each accommodated in separate housings. DE 10 2008 015 412 A1 describes a solution in which the two control valves are accommodated in a common housing and are flowed through by suitable inflow in the compression stage or rebound stage. These vibration dampers are constructed as a 2-tube configuration, with an inner tube and a tubular damper housing surrounding the latter. Furthermore, vibration dampers are known which operate according to the “uniflow” principle and are constructed in a 3-tube configuration. In this case, only one control valve is provided, through which the flow is always unidirectional as a result of the uniflow principle, irrespective of the compression stage and rebound stage. While it would therefore be desirable, for the sake of simplification, in the case of vibration dampers of 2-tube configuration, to provide just one control valve, it would be desirable in the case of vibration dampers based on the uniflow principle to embody this in a 2-tube configuration.
Proceeding from this, the object of the present invention is to provide a vibration damper which, as outlined above, makes use of both embodiments.
The object is achieved by a controllable vibration damper having a damping force control system, comprising a damper housing tube, which is at least partially filled with damping medium, and a damping valve for damping force control, which is arranged on and fluidically connected to the damper housing tube, an inner tube, which is inserted into the tubular damper housing via a bottom valve element, a piston rod, which can be moved longitudinally in the inner tube and has a working piston, wherein according to the invention a separating piston seated in the tubular damper housing separates the damping medium in the low-pressure region from a gas volume held in the tubular damper housing, and the bottom valve element divides the tubular damper housing into a low-pressure working chamber and a high-pressure working chamber, which is acted upon by means of the working piston, and an inlet opening of the damping valve element is fluidically connected to the high-pressure working chamber, and an outlet opening of the damping valve element is fluidically connected to the low-pressure region, such that the damping valve element is connected in parallel with the working piston.
A vibration damper configured according to the invention functions according to the uniflow principle and is designed as a 2-tube configuration. In addition, just one damping valve element or control valve is provided. Overall, a radially slender construction is thus ensured. By arranging a gas volume and separating this gas volume from the low-pressure region, it is possible to dispense with a third cylinder tube.
An advantageous embodiment of the invention provides for the gas volume to be arranged inside the damping valve element or on the outer circumference of the damping tube.
An advantageous embodiment of the invention envisages that the inner tube is inserted into the tubular damper housing via the bottom valve element in such a way that the bottom valve element is inserted into the tubular damper housing on the inner circumference and forms a hydraulic seal with the inner tube. It is advantageous if the inner tube and the bottom valve element form a mounting unit and can be inserted jointly in the axial direction into the tubular damper housing.
An advantageous embodiment of the invention envisages that the damping valve element can be adjusted continuously between a minimum damper characteristic and a maximum damper characteristic. It is thereby possible to set different damping characteristics.
An advantageous embodiment of the invention envisages that the damping valve has at least one controllable valve unit, by means of which the damper characteristic can be switched. It is thereby possible to increase further the number of damping characteristics that can be set.
In one specific embodiment of the invention, provision can be made for the valve unit to comprise a manually, electrically or electromagnetically adjustable valve for switching the damper characteristic.
An advantageous embodiment of the invention envisages that a second valve unit with a defined flow cross section is connected upstream or downstream of the first valve unit in the flow direction of the damping medium. Furthermore, it is deemed expedient if a further, passive valve unit is provided, which is connected in parallel or in series with the first and/or the second valve unit.
The invention is explained below with further features, details and advantages with reference to the appended figures. The figures illustrate only illustrative embodiments of the invention. More specifically:
During operation, a high-pressure working chamber 26 is formed in the inner tube 18, wherein the working piston 22 divides this chamber into a region 26a on the piston-rod side and a region 26b remote from the piston rod. The high-pressure working region 26 extends via openings 44 in the wall of the inner tube 18 as far as the intermediate space between the inner tube 18 and the tubular damper housing 12. By means of the bottom valve element 16, the high-pressure working chamber 26 is delimited with respect to a low-pressure working region 26, which forms within the tubular damper housing 12 during operation. Furthermore, a gas volume 42 is provided in the tubular damper housing 12, which is delimited with respect to the low-pressure working region 26 by means of a separating piston 40, which can be moved axially in the tubular damper housing 12.
Mounted on the outside of the tubular damper housing 12 is a damping valve element 14, the function of which is described further below in conjunction with the working movement of the working piston 22. The damping valve element 14 has an inlet opening 28 and an outlet opening 30 and is fluidically connected to the high-pressure working chamber 26 via the inlet opening 28 and fluidically connected to the low-pressure working chamber 24 via the outlet opening 30 via bores correspondingly formed in the tubular damper housing 12.
The damping valve element 14 in the embodiment shown comprises a controllable valve unit 34, a second valve unit 36 with a defined flow cross section, which is arranged downstream of the first controllable valve unit 34 in the flow direction of the damping medium, and an hydraulic intermediate chamber 38 arranged between the two valve units. By means of the controllable valve unit 34, the damping valve element 14 can be positioned between an open position and a closed position.
The circulation of the damping medium in the vibration damper 10 in the compression stage, the rebound stage and with the damping valve element 14 open and closed in each case is described with reference to
The flow of the damping medium then continues via the check valve 50 in the bottom valve element 16 into the region of the high-pressure working chamber 26 remote from the piston rod. The flow of the damping medium is symbolized by the arrow Q2. To compensate for the piston rod volume, damping medium flows from the high-pressure working chamber 24 on the piston-rod side into the high-pressure working chamber 26 remote from the piston rod through the valve element 48 in the working piston 22. As a result, a small damping force is produced. This flow of the damping medium is symbolized by the arrow Q1. In this operating range of the vibration damper 10, the damping medium flows primarily via the damping valve element 14, i.e. Q1<<Q2. The separating piston 40 moves upward in order to compensate for the volume of the piston rod 20 extending out of the tubular damper housing 12. The division between flows Q1 and Q2 can be varied by means of intermediate positions of the valve unit 34 between the open and closed positions, thus enabling different damper characteristics to be set in the rebound stage.
Number | Date | Country | Kind |
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10 2020 211 490.0 | Sep 2020 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2021/074007 | 8/31/2021 | WO |