Spring device for a vehicle

ES 2 329 162 T3

DESCRIPTION

Suspension device for cars.

The invention relates to a suspension device according to the general concept of claim 1 for a wheel support, load bearing and elastic, in an automobile.

Such a suspension device is known, for example, from patent EP 0 425 885 B1 (descriptions starting from FIG. 5). It is a hydropneumatic suspension system, in which the cylinder unit and the annular space of the suspension cylinder are respectively connected with a hydropneumatic spring accumulator, so that a pneumatic pressure from both sides acts on the cylinder piston respectively. suspension. This generates two forces that act in the opposite direction on the piston, the difference of which results in a suspension force to support the load.

This known suspension system has been tested successfully in practice. However, pneumatic spring tongues always have the disadvantage that changes in temperature have a rather strong influence on the pressure of an air spring means, so that the bearing and suspension properties also change as a function of temperature. This also applies to the level of the vehicle in its static state. However, in the suspension system according to EP 0 425 885 B1, this temperature influence is somewhat reduced because two pressures act in opposite directions on the piston of the suspension cylinder.

However, there is a need for improvement.

Document DE 30 27 124 A1 describes a shock absorber, particularly for travel mechanisms of airplanes, for example helicopters. In this case, the particular problem of configuring a "suspension damper" for landing in the event of a catastrophe, that is to say for a landing with damage, is particularly important, producing a vertical impact velocity of about 10 to 12 m / s. The document does not contain anything about the above-described problem of a temperature dependence of the support and suspension properties. As regards its construction, the known suspension damper consists of a cylinder, a damping piston and a damping rod connected to the piston, which is therefore a piston rod guided from the cylinder outwards. In some embodiments, an additional movable bottom is arranged within the cylinder in an enlarged lower portion which is connected to a counter rod. The bottom separates a high pressure gas chamber in the enlarged part of the cylinder. In further embodiments, the counter stem is connected to a bottom fixedly arranged as a septum in the cylinder. In all cases, the damping piston slides with an opening on the counter rod connected to the fixed or movable bottom.

The object of the present invention is to improve a suspension device of the type indicated in such a way that the properties of use are practically independent of changes in temperature. This is especially true for a static level position of the suspension cylinder, so that the respective level of the vehicle remains practically constant at different temperatures.

According to the invention, this is achieved with the features of claim 1. Advantageous features of embodiment are contained in the dependent claims.

Accordingly, according to the invention, provision is made for an additional suspension cylinder to be positioned in the piston rod region of the suspension cylinder in such a way that the length of the piston rod can be changed in the manner of a telescope. The additional suspension cylinder consists of an additional cylinder and an additional piston guided therein with an additional piston rod guided outwardly, the additional suspension cylinder with these elements forming a part of the piston rod. Preferably, in this case the additional cylinder is fixedly (rigid) connected to the part of the piston rod facing the piston, while the additional piston rod guided outwards with its free end practically forms the end of the piston rod variable in length and, for this purpose, has at its end end a connection element for the mounting connection on the vehicle side. However, the additional suspension cylinder can also be arranged upside down, that is, the additional piston rod can be connected with the piston rod and the additional cylinder with the connecting element on the vehicle side.

According to the invention, in this case the additional suspension cylinder is supplied with at least a counter pressure of an elastically compressible, especially pneumatic counter-spring means, in the region of an additional annular space and / or an additional working space. . Thanks to this constructional configuration, it is possible to configure, depending on the load that occurs in each respective case of application, the working pressure, the back pressure as well as the respective surfaces of the piston and the additional piston, supplied by these pressures, in such a way so that, in a static state powered by the load, on the one hand, the piston is at a rebound end stop with respect to the cylinder and / or on the other hand, the additional piston is at a compression end stop with respect to the additional cylinder. In this static position, in the event of a rise in temperature, the pressures which also increase as a result, advantageously, cannot cause a change in the static level. In case of a dynamic compression from the static position, it is only the piston that is propelled inside the cylinder against the working pressure, while the additional piston remains at its compression end stop in the additional cylinder. In the event of a dynamic rebound from the static position, the piston remains at its rebound end stop, and only the additional piston moves with the additional piston rod in the rebound direction in the additional cylinder.

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In the following, the invention is described in more detail by means of preferred embodiments with reference to the drawings. In the drawings:

Figure 1 shows a first embodiment of a suspension device according to the invention, in its representation of axial section of the components, in a static position,

Figure 2 shows the suspension device according to Figure 1 in a state of compression from the static position, and

Figure 3 shows a variant of the suspension device according to Figure 1 in a rebound state from the static position,

Figure 4 shows another variant of the suspension device in a certain state of suspension, and

Figure 5 shows a variant of the embodiment according to figure 4 in a corresponding position.

In the various figures of the drawings, the identical parts and components or whose functions correspond, are always identified with the same references.

A suspension device 1 according to the invention consists of (at least) a suspension cylinder 2, consisting of a part of a cylinder 4 in the manner of a telescope, and a piston 6, guided therein in such a way linearly movable, with a piston rod 8. The piston rod 8 is guided from the cylinder 4 outwards, sealed at its circumference on one side. The suspension cylinder 2 is provided for direct arrangement between a non-spring mass (vehicle wheel or axle) and a spring mass (vehicle frame or body construction). For this purpose, the cylinder 4 and the piston rod 8 have suitable connecting elements 10 at their opposite ends, remote from each other.

The piston 6 is adjacent to the inner surface of the cylinder 4 through (at least) one circumferential seal. Due to this, the piston 6 separates within the cylinder 4 a cylindrical working space 12 from an annular space 14 that surrounds the piston rod 8. On the side of the working space 12, the piston 6 acts with its working surface A1 oriented towards it, to generate a supporting spring force F that supports the respective load against a working pressure p_TO of an elastically compressible spring medium FM, especially pneumatic (for example nitrogen).

According to the invention, the piston rod 8 is configured in such a way that its length can be varied in the manner of a telescope through an additional suspension cylinder 16. In this case, the additional suspension cylinder 16 is supplied with al minus one back pressure p_G of an elastically compressible counter spring means GM, especially also pneumatic.

The additional suspension cylinder 16 consists of an additional cylinder 18 and an additional piston 20 guided therein in relative motion, with an additional piston rod 22 sealed at its circumference and guided outward from the additional cylinder 18. In preferred embodiments, the additional cylinder 18 is rigidly connected to the piston rod 8 of the suspension cylinder 2, while the additional piston rod 22 has at its free end the connection element 10 for the mounting connection on the side of the vehicle.

The additional piston 20 remains adjacent to the inner wall of the additional cylinder 18 through a circumferential seal consisting of several seals, and thereby separates within the additional cylinder 18 an additional cylindrical working space (see Figures 3 to 5). of an additional annular space 26 surrounding the additional piston rod 22.

In the embodiment according to Figures 1 and 2, the additional annular space 26 is immediately supplied with the counter spring means GM and, preferably, is further connected via a pipe 28 with an external accumulator 30. According to FIG. 1, the pipe 28 opens directly into the additional annular space 26 through a radial opening in the wall of the additional cylinder 18, whereas, in the variant according to FIG. 2, the pipe 28 opens only through of outlined channels or bores of the connecting element 10 or respectively of the additional piston rod 22 in a hollow space 32 of the additional piston rod 22. This hollow space is connected to the additional annular space 26 through transverse bores, also only outlined, of the additional piston rod 22.

In the variant embodiment according to FIG. 3, the additional working space 24 is directly connected to the counter spring means GM and, also in this case, it is preferably connected to an external accumulator 30 via a pipe 28. The pipe 28 empties, similarly to the manner of FIG. 2, into a hollow space 32 of the additional piston rod 22, the hollow space 32 being however open axially in the direction of the additional working space 24.

In the embodiments according to Figures 4 and 5, both the additional working space 24 and the additional annular space 26 are supplied with the counter spring means GM, producing a force resulting from the difference of two opposite partial forces, which result from the pressures p_G1 And p_G2.

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On the side of the additional annular space 26, the additional piston 20 has an annular surface A2 that can be fed with pressure, and on the side of the additional working space 24 its entire front surface A3 can be fed with pressure.

According to the invention, it is envisaged in this case to configure, depending on the load expected for each respective case of application, the working pressure p_TO, the back pressure (p_G, p_G1, p_G2) and the respective surfaces A1 as well as A2 and / or A3, supplied with these pressures, of the piston 6 and the additional piston 20 in such a way that, in the static state represented in FIG. 1, on the one hand the piston 6 is at a rebound end stop 34 with respect to cylinder 4 and on the other hand the additional piston 20 is in compression end stop 36 with respect to the additional cylinder 18. In this case, the rebound end stop 34 is formed by an annular step of the piston rod 8 which is adjacent to an annular rim of the cylinder 4, while in the compression end stop 36 the additional piston 20 is adjacent to its surface. front A3 to additional cylinder 18.

When the suspension cylinder 2 according to FIG. 2 is in the dynamic compression phase from the static position according to FIG. 1, only the piston 6 in the cylinder is propelled through the piston rod 8 against the pressure of work pA. The additional piston 20 remains at its compression end stop 36. Therefore, in the event of compression in the direction of the arrow X, only the true supporting spring force F = p acts on the piston_TO-A1.

In figure 3 a dynamic rebound from the static position is represented. In this case, the piston 6 remains at its rebound end stop 34 in the cylinder 4. The additional piston 20 is moved exclusively with the additional piston rod 22 in the direction of the arrow Y in the rebound direction. When, according to Figures 1 and 2, the additional annular space 26 is supplied with the counter spring means GM, in the event of rebound the counter force pG increases by compression, leading to a damping of the rebound. In the embodiments according to Figures 4 and 5, the effect depends on the ratio of the respective pressures in the spaces 24 and 26.

In the preferred embodiments shown, the working space 12 of the cylinder 4 is filled directly with the compressible spring medium FM. Preferably, in this case the working space 12 is connected via a pipe 38 with an external accumulator 40, the working space 12 containing a first volume K1.1 of the spring means FM and the accumulator 40 containing a second volume K1.2 of the spring medium FM. Additionally, preferably also the counter spring means GM is arranged with a first volume K2.1 in the additional annular space 26 and with a second volume K2.2 in the accumulator 30 (FIGS. 1, 2) or respectively with a first volume K3.1 in additional workspace 24 and with a second volume K3.2 in accumulator 30 (Figures 3, 4).

As an alternative to these preferred embodiments, an indirect supply with pressure, via hydraulic means (hydropneumatic embodiment) would also be possible.

In preferred embodiments, annular space 14 surrounding piston rod 8 within cylinder 4 is preferably a component of a hydraulic damping device 42. For this purpose, annular space 14 is filled with a hydraulic damping means DM and is connected with an external accumulator 48 through a pipeline 44 and a damping valve 46. From FIGS. 1 and 2 it can be understood that dynamic suspension movements of the piston 6 cause changes in the volume of the annular space 14, so that the hydraulic medium DM flows respectively through the damping valve 46. By means of a configuration appropriate damping valve 46 different damping forces can be achieved during the compression and rebound phases.

Alternatively, the annular space 14 could also be ventilated, that is, connected to the atmosphere, and therefore be basically functionless.

The invention leads, inter alia, to the advantage that the suspension work is distributed over two pneumatic springs. Because of this, the respective spring volume has a "rest", when the movement takes place in the region of the other respective volume. As a result, the temperature of the respective medium is advantageously kept low, since each volume is less compressed.

Regarding the embodiment according to figure 3, it should be noted that the pressure of the volume K3.1 can be adjusted in such a way that this pressure, by feeding the surface A3 of the additional piston 20, results in a force that is equal to the force that results from the pressure p_TO of the volume K1.1 in the workspace 12 on the piston 6 in its static position. As a result, the additional piston 20 can advantageously abut the mechanical compression end stop 36 in the compression phase almost without jerks.

The embodiment according to figure 4 represents practically a combination of the previous embodiments according to figures 1 to 3. Thanks to it, also the expansion can be reduced and the mechanical shock can be minimized. In FIG. 5 it can be seen that an embodiment is also possible without additional accumulators in the area of ​​the additional suspension cylinder 16. In this case, the volumes K2.1 and / or K3.1 are only included separately in spaces 26, 24. As results from the representations in figures 4 and 5, in discrepancy of the static position according to Figure 1, the pressure can also be configured in such a way that the piston 6 and the additional piston 20 are "floating" in their static position, that is, positioned at a distance from the mechanical stops 34, 36.