The invention relates to a steering column, in particular for motor vehicles, with an impact energy absorbing element that is equipped with a container holding a flowable medium, with the medium, in the event of an impact, being forced through at least one opening whose counterforce is controllable.
Energy absorbing elements have been known in a multitude of embodiments. In recent years, elements containing an electrorheological or magnetorheological fluid that changes the viscosity under the influence of an electric or magnetic field have been used increasingly for energy absorption. Control of the counterforce exerted by the opening is of great importance since the energy absorption can be adapted to varying initial states and conditions, which means that such energy absorbing elements can be used particularly in the steering columns of motor vehicles. During a crash, several systems are being deployed one after the other or, respectively, simultaneously (seatbelt, airbag and ultimately the steering column) that are designed to slow down the driver with as little stress as possible. The seatbelt and the airbag oftentimes do not provide an ideal counterforce which is to be compensated by a controllable impact shock absorber in the steering column. The overall result thus becomes bearable for the occupant since the energy can be gently absorbed in the case of injury-critical surface pressure values and deceleration values. During this process, the individual components may follow rapidly changing courses that in sum, however, result in a gentle course of actions.
In accordance with U.S. Pat. No. 6,279,952 which shows such a steering column, the flowable medium is arranged in a cylinder-piston system and can stream out through overflow openings in the piston or in the cylinder. The overflow openings can be designed to open only when a certain excess pressure is reached in the medium.
In contrast with vibration absorbers and shock absorbers that are intended for permanent use, impact absorbers in steering columns are only provided for an emergency and are in most cases not used at all. Nevertheless, the operability of the impact absorber must be assured even after years of inactivity. In the case of cylinder-piston systems, years of inactivity may lead to problems since impermeability of the system as well as operability are critical. Seals lose their sealing properties and movable parts, their mobility.
The invention now has as its objective the creation of a steering wheel whose energy absorbing element does not contain any mechanically movable parts or seals; this is achieved through the fact that the container holding the flowable medium is deformable. In this context, it is assumed that it is irrelevant in the event of an impact that is to be absorbed, for example in the case of a traffic accident or the like, whether or not the energy absorbing element is damaged or becomes unusable.
In a preferred design, the container is equipped with a compressible container part and a non-compressible discharge channel in which the opening is located. In this way, the area surrounding the opening is not affected by the deformation, and the mechanism for controlling the counterforce can preferably envelop the discharge channel.
In an additional preferred embodiment, the compressible container part has a deformable container wall, in particular a bellows or a membrane bellows that is compressible in the axial direction of the discharge tube.
For a one-time use, the opening is preferably covered by a closing element that releases the opening when a certain excess pressure is exceeded.
As mentioned before, control of the counterforce is of great importance in order to adapt the energy absorption to varying initial states and conditions, for example to the mass and/or speed of the impacting object. The counterforce may, for example, be set or changed by enlarging or reducing the cross section of the discharge opening. Preferably, however, the compressible and/or deformable container is filled with a medium that changes its fluidity under the influence of an electric or magnetic field. Magnetorheological fluids are particularly well suited for this purpose because in contrast with electrorheological fluids, only lower, safe voltages are required for the creation or, respectively, for the changing of the field.
In the following, the invention will be described in detail by means of the attached drawing, without being limited thereto. Shown are:
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In an original embodiment, a steering column 9 as shown in
According to
In lieu of the permanent magnet as shown, a simple arrangement of an electromagnet all around the discharge channel 6 is possible as well. The closure device 3 prevents an accidental flowing off of the medium which means that the electromagnet needs to be activated only in the event of an accident in order to increase the viscosity of the magnetorheological medium and thus the counterforce.
When the compressible container part 4—whose wall is, for example, designed like a bellows—is compressed during an impact and the interior space is reduced, an initial excess pressure builds up that opens the closure device 3, thereby releasing the opening 2 on the discharge channel. The medium is forced out of the compressible container part 4 through the discharge channel 6. The displaced medium can be collected, if so desired, in a collection container. The container part 4 designed like a bellows can, for example, be made of metal or reinforced synthetics, with the rippling or, respectively, zigzag shape of the wall determining the bending and folding locations. The maximal compression of the container part 4 can be seen in
In the event of an accident, the compressible container part 4 connected to the steering wheel 8 is bulged and compressed through the impact of the upper part of the body; the closure device 3 is thrown from the opening 2, and the medium is ejected. The mechanism 10 controls the flow of the medium through the discharge channel by means of a corresponding change of the viscosity in dependence of signals of the electronic system 16 which processes various measuring data and parameters.
The illustrations show cylindrical containers 1 that are, for example, designed like a bellows and that are compressible. Of course, other compressible containers 1 can be designed as well. The size of the compressible volume of the container 1; the cross section of the discharge channel 6 which codetermines the extent of the energy absorption; as well as the viscosity and the type of fluid are determined by the intended use of the element whose essential advantages lie, in any event, in the fact that it is one single piece, and in the volume reduction of the container 1 without any moving parts.
In the event that magnetorheological fluids are used, a condenser 17 housed in the steering wheel or, respectively, in the vicinity of the impact energy absorbing element, or a similar power source will be sufficient, meaning that the system will remain functional even in the event of a power failure of the motor vehicle. The length of the compression may amount to 100 mm in the embodiment shown in
Number | Date | Country | Kind |
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A 1109/2005 | Jun 2005 | AT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/AT2006/000280 | 6/30/2006 | WO | 00 | 12/28/2007 |