Patent Application
20100207347
This invention relates to a suspension strut bearing.
A suspension strut bearing, for vibration-damping support of the top end of a suspension strut in a motor vehicle, is disclosed in DE 10 2004 051 112 B3, for example. This known design has a casing that enables the suspension strut bearing to be installed into a motor vehicle. An inner part is used to connect the top end of the suspension strut to the suspension strut bearing. The inner part in turn is accommodated in a working spring formed by at least one elastomeric body. In order to accommodate the inner part in a vibration-damping manner, the elastomeric body has a constant force-displacement characteristic and/or torsional moment-angle characteristic, which depends on the material used. These characteristics of the elastomeric part are determined with great expenditure in road tests. When doing this, the vehicle has to meet the imposed requirements both with regard to driving comfort and driving safety. The support of the top end of a suspension strut in a motor vehicle is of critical importance for the entire wheel suspension of a motor vehicle. It is a drawback of the existing designs that a change of damping is possible only by replacing the entire suspension strut bearing. No desirable adaptation to the specific driving behavior of the driver or to changing road conditions can be accomplished in this way.
DE 10 2004 032 470 A1 also discloses a support of the top end of a suspension strut by means of a suspension strut bearing present on each wheel of the vehicle, wherein an electromagnet is used to set the height level of the vehicle wheel. In this case, the inner part of the suspension strut bearing is mounted as a mobile armature between two coils surrounding the armature. In this embodiment, the motor vehicle as a whole can be lowered or raised. Changing the bearing characteristic or the damping characteristics of the suspension strut bearing, however, is likewise impossible.
Furthermore, DE 101 53 007 A1 discloses a design for a suspension strut bearing that comprises an inner part to support the top end of a suspension strut. This inner part is embedded in an elastomeric bearing body. The elastomeric body is accommodated with the inner part in a hydraulically adjustable piston. The piston can be displaced, in the axial direction, relative to the bearing center line between an upper and a lower position. In this embodiment, it is possible to raise or lower the motor vehicle. It is likewise not possible to change the bearing characteristics with this variant.
DE 199 51 693 C1 also discloses a suspension strut bearing for supporting the top end of a suspension strut in a motor vehicle. This design has an inner part for fastening the suspension strut bearing to the top end of the suspension strut. The suspension strut bearing is connected to the motor vehicle by way of the casing thereof. An elastomeric body serves to dampen the vibrations caused by the road. This body is designed as a working spring and represents a connection between the inner part and the casing. Suspension strut bearings are additionally equipped with a hydraulic damper, since only rising dynamic rigidities can be achieved with simple elastomeric bearings. This damper has a specific damping characteristic. The suspension strut bearing, disclosed in DE 199 51 693 C1, is equipped with at least two chambers filled with a fluid and a channel for a fluid-conducting connection of the chambers. In a model concept, such a suspension strut bearing links different springs, with one spring being formed by the working spring and the other spring by the hydraulic system, comprising the chambers that are connected to one another by a channel. However, it is a drawback of this embodiment that there is no flexible adaptation to changing road conditions.
The problem underlying the invention is to create a suspension strut bearing that has a simple design and, in addition, provides at least two different damping characteristics. The suspension strut bearing should be able to adapt flexibly to changing influences of the road, including those associated with steering motions, and should allow the driver to preset the damping.
A suspension strut bearing for supporting the top end of a suspension strut in a motor vehicle, comprising:
A very simple possibility to regulate the flow through the channel, which is to say the flow rate inside the channel, is provided by the solution according to the invention. The valve switching unit serves the purpose of completely or partially closing off or opening the channel. In this way, when the channel is closed, the vibrations are damped exclusively by the elastomeric body designed as a working spring, while when the channel is opened, the advantages of hydraulic damping can additionally be utilized, depending on the cross-section of the channel available. Cost-intensive methods that are difficult to control, such as those using rheological fluids, for example, can be avoided by the solution according to the invention.
According to a first embodiment of the invention, the valve switching unit has an electromagnet. By connecting the valve switching unit to an electromagnet, the partially mechanical solution can be suitably supplemented with an electromagnet and thus represents an electromagnetic valve or an electromagnetically assisted valve. The electromagnet has the advantage that it enables the channel to be completely or partially opened and closed, with very short switching times. Thus, the damping characteristics of the suspension strut bearing, according to the invention, can be adapted to influences from the road changing at very short time intervals. In the same way, damping can be adapted to any definable values. The chassis can thus be set by the driver, for example, to be oriented to damp toward sportiness or comfort.
Furthermore, a particularly simple embodiment of the solution, according to the invention, is to equip the electromagnet with a coil and an armature moveable in the channel against the force of a spring. The armature is thus integrated directly in the channel. Consequently, no additional components are necessary to regulate the channel cross-section. The direct influencing of the volume flowing through the channel thus obtained leads to a change of the damping characteristics in real time.
It is particularly advantageous if the armature is designed as a piston. The armature corresponding in the structure thereof to a piston leads to a solution which is very easy to manufacture. Thus, the guide and the armature designed as a piston can be configured as rotationally symmetrical components, which also advantageously simplifies sealing them from the surroundings. The spring, which is present in the valve switching unit and against which the armature can be moved, can be used to return the armature to the neutral position thereof.
By designing the armature as a piston, the idea according to the invention is for the piston to be moveable back and forth between the end “channel completely open” and “channel completely closed” positions. The particular advantage of the solution according to the invention, however, is that any arbitrary or necessary intermediate position can be reached and set, so that a partial closure of the channel and with it only a partial reduction of the flow rate of hydraulic fluid between the chambers can be achieved.
In order to implement the previously described possibilities, it is also proposed that the suspension strut bearing has a load-dependent regulator for the coil current of the electromagnetic valve switching unit. In this case, regulation of the coil current, as a function of the oscillations and vibrations acting on the suspension strut bearing and originating from the wheel suspension, is also within the scope of the concept of the invention. Therefore, load-dependent regulation in the context of the invention means, for example, that the intensity of the coil current is regulated as a function of the frequencies introduced into the suspension strut bearing by way of the suspension strut. The vibrations to be damped here represent the disturbances of a control system. By means of adapted electronics suitable for this purpose, signals from the sensors present on the wheel suspension can be used advantageously to control the electromagnet, in order to ensure optimal regulation of the suspension strut bearing.
Active regulation of the suspension strut bearing can be achieved, for example, in that sensors on the vehicle wheels and the steering system capture information in the form of signals, which are collected in suitable processing units and linked, for example, to information on road conditions and/or driving conditions. Optimal damping values for the suspension strut bearing can be determined based the collected information. In addition, the driver can also here preset the damping, for example, to perform a sporty- or comfort-oriented adjustment of the chassis.
Another proposal pursuant to the invention involves fastening the valve switching unit to the outside of the casing of the suspension strut bearing. Thus, the valve switching unit does not otherwise affect the properties of the suspension strut bearing. The suspension strut bearing can be made compact in this way. This is particularly important because in a motor vehicle the available installation space, in the area of the suspension strut bearing, is limited.
In order to protect the valve switching unit against mechanical damage, according to an advantageous embodiment of the invention, the valve switching unit is fastened to the suspension strut bearing in a manner that offers protection by a cap against mechanical damage. This cap, in turn, can be protected against external effects by buffer elements made of elastomeric materials, such as rubber.
Overall the suspension strut bearing, according to the invention, has considerable advantages with regard to noise development, vibration damping, and the necessary hardness. At least two different damping characteristics can be achieved with the suspension strut bearing. These are provided at least in an axial and/or radial direction. However, damping that originates from rotational motions of the piston rod can also be achieved. This represents another advantage over existing solutions. It is possible thereby to provide a wheel suspension for a motor vehicle which can be flexibly adapted to the vibrations originating from the road and the damping characteristics of which can be varied. Supporting electronic sensor units or sensors can be used for this purpose. A particularly advantageous combination is the use of electronically controllable shock absorbers or electronically controllable steering systems. The damping characteristics can be optimized, in this way, in any driving condition.
Another special advantage consists of the direct effect of steering on the characteristic of the suspension strut bearing. Thus, differentiation between a high and a low vehicle speed and the steering actions required to do so is enabled. In addition, the advantages of electromagnetically switchable valves are used for the invention. They have a very short response time, of less than 0.1 second, and an exceptional service life.
The invention will be described below in further detail with reference to the drawings. The embodiments shown do not represent any limitation to the illustrated variants, but serve only to explain the principle of the invention. Identical or nearly identical components are denoted with the same reference numerals. In order to be able to illustrate the principle of operation according to the invention, only greatly simplified sketches are shown in the figures, in which the components not essential for the invention have been omitted. However, this does not mean that such components are not present in a solution according to the invention.
Shown are:
In the illustration of
The very simplified schematic illustration of the valve switching unit 8, in detail in
For reasons of clarity,
Individual metallic reinforcing inserts in the elastomeric body are of subordinate importance for the invention and are therefore not shown in detail. The suspension strut bearing 2 comprises the valve switching unit 8 projecting laterally, which is present on the outside of the casing 4 of the suspension strut bearing 2. Furthermore, a strut mount 16 is present which has a buffer 18 made of an elastomer and is fastened by nuts to the piston rod 14. In order to offer protection against mechanical stresses, the shown embodiment of the suspension strut bearing has a cap 17 that covers at least the region of the valve switching unit 8. A rubber buffer 15 is provided above the cap 17 and keeps mechanical shocks away from the components below it.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 048 784.5 | Oct 2007 | DE | national |
This application is a National Stage completion of PCT/DE2008/050030 filed Oct. 9, 2008, which claims priority from German patent application serial no. 10 2007 048 784.5.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE08/50030 | 10/9/2008 | WO | 00 | 3/17/2010 |
