Dampening device for vehicles

The present invention relates to a damping device for vehicles according to the preamble of claim 1.

Damping devices are well known from numerous publications. As a rule, is in a vehicle for each wheel a damper unit available.

A corresponding to the preamble of claim 1. damping device is in the document <patcit id="pcit0001" dnum="JP2005188601A"><text>JP 2005 188 601 A</text></patcit> described. It is a hydraulic shock absorber with a telescopic cylinder, wherein a damper piston flow passages with damping valves having. This known shock absorber is a so-called "twin-tube dampers" formed with a hydraulic accumulator surrounds the telescopic cylinder coaxially. The thus cross-sectionally annular storage space is connected via a passage arranged in the lower region with the lower cylinder chamber. Within the memory space is an annular intermediate wall is arranged as a cooling element, that heat is transferred from the inside to the outside via an outer tubular housing to the environment. Within the memory space in each case the variable volume of the hydraulic damping medium is directly acted upon by a gas in an upper space. As a result, the shock absorber can not be mounted and operated in any orientation in space.

A very similar design is by the title <patcit id="pcit0002" dnum="JP2005155793A"><text>JP 2005 155 793 A</text></patcit> known, but within the cylinder surrounding the telescopic hydraulic accumulator above the respective volume of the damping medium a vented to the outside space is formed in which air is thus arranged with atmospheric pressure.

The document <patcit id="pcit0003" dnum="EP0425858B1"><text>EP 425 858 B1 0</text></patcit> describes a hydropneumatic suspension system, in which a piston-cylinder unit as a shock absorber between a sprung mass (vehicle body) and an unsprung mass (vehicle) is arranged. The strut is hydraulically connected to a hydropneumatic spring accumulator, so that during compression displaces a certain volume of a hydraulic medium against a spring kompressibes medium (compressed gas) in the spring accumulator. The pressurized gas is compressed by the gas pressure and causes the pneumatic spring via the spring medium associated hydraulic medium load capacities in the strut. This known suspension system has proven itself very well in practice, particularly in embodiments wherein the strut with two spring Save cooperates that a piston of the shock absorber is applied on both sides with a spring pressure. Consequently, the carrying capacity results from the difference of two oppositely acting on the piston forces.

However, while for damping the suspension movements that acting against the pneumatic pressure medium hydraulic medium is guided through a damping valve. By attenuation (reduction) which the spring medium associated hydraulic medium but is strongly heated rapidly and in part. This heating also has an effect on the gas pressure, so that its pressure and thus also the supporting spring force increase. This results depending on the situation quite unfavorable, varying suspension and damping properties.

The <patcit id="pcit0004" dnum="WO03106202A1"><text>WO 03/106202 A1</text></patcit> describes a suspension device, in some embodiments, a damping device has a separate, true of the spring cylinder and the spring medium independent circuit of a hydraulic damping medium. For this purpose, at least one separate damping cylinders with a cylinder in a relatively movably guided damper piston and at least one hydraulically connected to the damper cylinder damping valve is required. The piston of the spring cylinder is driven via a gear formed by a gear drive device, which converts the pivotal movements of a wheel-in Schwingentragarms linear relative movements between the cylinder and piston of the spring cylinder. The damping device is intended to cooperate with the same drive means as well as the spring cylinder, but the media, ie, media spring and damping medium are completely separated from each other. The background is that by virtually no thermal dependency so that damping induced heating of the damping medium are far uncritical of the temperature of the spring medium and thus also the pressure and the pressure-dependent supporting spring force remain as virtually unaffected. This known suspension and damping device, however, has a rather complex construction, which is reflected by a relatively large installation volume and weight.

The document <patcit id="pcit0005" dnum="EP1584502A1"><text>EP 1584502 A1</text></patcit> describes another suspension and damping device with a fairly simple telescopic spring cylinder, indirectly affects its in a cylinder movable piston guided directly to produce a load bearing supporting spring force or a hydraulic medium against an elastically compressible spring medium. Here, for attenuating a separate and independent of the spring medium circuit of a hydraulic damping medium is also provided. Given separates the piston within the cylinder two working chambers from each other, said first working chamber to the spring medium and the second working chamber associated with the damping medium. The filled with the damping medium second working space is connected via a damping valve arrangement to a hydraulic tank (hydraulic accumulator). This hydraulic reservoir is arranged so that the damping medium gravity in a lower range is. Above the air damping medium can be arranged with atmospheric pressure. However, it can also be provided to set this space above the damping medium below a certain bias pressure during compression in supporting the flow in the second working chamber (acceleration of the return flow). This known system is well proven because there is a very extensive thermal decoupling between the hydraulic damping medium and the medium spring ensured in a structurally simple and compact design. However, since the two media are separated only on the piston of the spring cylinder, it may yet come to a minor heat transfer to the spring medium especially with very strong heating of the damping medium.

Therefore, the present invention is based on the object to provide a damping device of the aforementioned type, with at still simple and compact design of the components to further improve the performance characteristics can be achieved.

This is achieved by the features of independent claim 1. According to the invention. Further advantageous embodiments of the invention are contained in the dependent claims and in the following description.

Due to the design according to the invention, a high proportion of the resultant by throttling heat is dissipated from the damping medium through the cooling element from the hydraulic accumulator to the outside to the environment. By this cooling of the damping medium, a heat transfer is reduced to a spring medium when the damping device is used in combination with a hydro-pneumatic spring cylinders. In this case, the damper unit on a telescopic spring cylinder, consisting of a cylinder in a relatively movably guided piston which acts to produce a load bearing supporting spring force against an elastically compressible spring medium. This can be claimed later by the inventive cooling action of the spring cylinder, since this is heated less overall. Due to the higher allowable stress of the suspension system, the driving performance can be significantly increased especially in off-road vehicles.

Based on illustrated in the drawing, preferred embodiments of the invention will be explained in detail. They show:<dl id="dl0001"><dt>Fig. 1</dt><dd>a suspension device for a vehicle with a telescopic spring cylinder and with a non-inventive damping device, wherein all the components are shown in longitudinal section, and</dd><dt>FIG. 2</dt><dd>an illustration as in <figref idrefs="f0001">Fig. 1</figref> in a Auführung invention.</dd></dl>

In the two figures of the drawing, the same parts are always provided with the same reference numerals.

As from first <figref idrefs="f0001">Fig. 1</figref> incl is a damping device 1 comprises at least one damper unit 2 for damping wheel suspension movements within a vehicle. Typically, each wheel is equipped with its own damper unit 2 in a wheeled vehicle, so that a four-wheel vehicle having four damper units. 2 The damper unit 2 has a hydraulic damping valve 4 for throttling - on flows of a hydraulic damping medium DM - caused respectively by suspension movements. The damping valve 4 is a hydraulic accumulator 6 arranged downstream, that is downstream hydraulically.

This hydraulic accumulator 6 has a storage space 8 for varying at damping the suspension movements volume Shares of the damping medium DM. The located in the memory space 8 DM damping medium is subjected to a biasing pressure p. For this purpose, the hydraulic accumulator 6 adjacent to the storage space 8 a pressure chamber 10 which contains a damping medium, the DM with the biasing pressure P acting upon pressurized gas DG. The initial pressure of the compressed gas p DG may be cash in the order of 2 to 20 bar, especially in the area 3 to 10 This bias pressure p supports the respective back-flow of the damping medium DM from the storage space 8 back over the respective damping valve fourth

Furthermore, the hydraulic accumulator 6, a cooling element 12 for dissipating heat of the damping medium DM outwards to the environment on. In a preferred embodiment, the cooling element 12 is arranged from a within a particular cylindrical housing 14 of the hydraulic accumulator 6 and a plurality of through flow openings 16 having intermediate wall 18. This intermediate wall 18 and the housing 14 each consist of a material with good thermal conductivity, in particular metal, and are connected thermally conductively with each other. In this way, heat generated by throttling (internal molecular friction) of the damping medium DM produced, derived from the interior of the hydraulic accumulator 6 via the cooling element 12 and the intermediate wall 18 to the housing 14 and then radiated through the outer surface of the casing 14 outwardly to the surrounding environment ,

In the first embodiment according to <figref idrefs="f0001">Fig. 1</figref> the damping medium DM is directly acted upon by the pressurized gas DG. Here, the hydraulic accumulator 6 is to orient in space, that the storage space 8 of the pressure chamber are vertically arranged below and 10 above. In this embodiment the intermediate wall 18 may be anywhere in the range of the memory space 8 and / or arranged in the region of the pressure chamber 10 may be (depending on the degree of filling of the memory space 8). The flow openings 16 of the intermediate wall 18 are thus flows through the suspension in-related currents of the damping medium DM each of the damping medium DM and / or the compressed gas DG. When in<figref idrefs="f0001">Fig. 1</figref> illustrated embodiment, the intermediate wall 18 - regardless of the degree of filling of the memory space 8 - always arranged inside the pressure chamber 10 so that the flow openings flows through 16 only from the pressurized gas DG. Here, the heat is transferred from the damping medium DM via the pressure gas DG in the intermediate wall 18 and discharged from there outward to the housing fourteenth

In the invention according to embodiment <figref idrefs="f0002">FIG. 2</figref> is the storage space 8 of the pressure chamber 10 via a separator media-tight separately. As shown as a separator within the cylindrical hydraulic accumulator 6 a freely movable (floating) arranged guided separating piston 20th By the separating element of the hydraulic accumulator 6 can be advantageously placed in any orientation in space, for example - other than as shown in<figref idrefs="f0002">FIG. 2</figref> - So that the memory space 8 "above" and the pressure chamber 10 are arranged "below". according to In this embodiment,<figref idrefs="f0002">FIG. 2</figref> is also preferably disposed within the pressure chamber 10, namely at such a position that at all occur in practice, suspension-related currents of the damping medium DM remains ensured, the mobility of the floating piston 20, the intermediate wall 1B. In this embodiment, the resulting in the damping medium DM heat is transferred via the floating piston 20 in the compressed gas DG and then dissipated via the cooling element 12th Alternatively, according to this embodiment<figref idrefs="f0002">FIG. 2</figref> it is basically also possible to arrange the intermediate wall 18 within the memory space. 8

It should be noted that the hydraulic accumulator 6 acts solely as a reservoir for the flowing back and forth for damping damping medium DM. This means that the hydraulic accumulator 6 is exclusively associated with the damping circuit and consequently has no spring action to the wheel support in the vehicle.

In a further advantageous embodiment, however, the damping device 1 is practically combined with a suspension system. For this purpose, the damper unit 2 preferably proportionally part of a telescopic spring cylinder 22, which is provided (not shown) particular for the arrangement as a so-called leg spring between a vehicle wheel and a wheel suspension and a vehicle frame. The spring cylinder 22 consists of a cylinder 24 and a piston guided therein linearly movable relative to 26, which acts to produce a load-carrying supporting spring force F against the pressure of an elastically compressible spring medium FM. The piston 26 divides within the cylinder 24 two working chambers 28 and 30 medium-tight from each other; the first working chamber 28 is assigned to the spring medium FM, while the second working chamber 30 is assigned to the hydraulic damping medium DM. This two independent circuits on the one hand the spring medium FM for the suspension and the other part of the damping medium DM are formed on the attenuation. Thus, a substantial thermal independence between the media DM and FM is achieved. The piston 26 is connected to a piston side with a piston rod 32 which is guided sealed circumferentially from the cylinder 24 to the outside. This one of the two working chambers is designed as a piston rod 32 enclosing annulus.

In the illustrated, preferred embodiments of the piston rod 32 forms the annular space enclosing the damping medium DM the associated second working space 30, while an opposite cylinder chamber forms the said spring medium FM associated first working space 28th

The first working chamber 28 is filled with the FM elastically compressible spring medium and connected in particular via a line 34 with an additional, likewise filled with spring medium FM spring store 36th The spring FM medium is at a correspondingly high pressure designed to generate by acting on the piston 26, the supporting spring force F.

As an alternative to this embodiment, it is also possible to fill the first working chamber 28 with a hydraulic medium and hydraulically connected to the spring brake 36, wherein the spring 36 is then be formed as a hydropneumatic storage z. B. with a separating piston between the hydraulic fluid and the spring medium ,

The second working chamber 30 is filled with the DM hydraulic damping medium and connected to the damping valve fourth The damping valve 4 can in principle be arranged at the outside or inside in the spring cylinder 22 (not shown). In the shown advantageous embodiments, but the damping valve 4 is formed as a separate component with its own remote from the spring cylinder 22 to be disposed housing 14 and connected to the spring cylinder 22 via a hydraulic line 38th

The damping valve 4 is composed of two sub-valves, namely a first part of valve with a relatively higher ballast resistance for the flow of the damping medium DM in the hydraulic accumulator 6 and a second part of valve with a relatively lower throttle resistance of the reverse flow from the hydraulic reservoir 6 back into the spring cylinder 22 . This is achieved in a conventional manner that the deflection of the spring cylinder 22 is attenuated slightly, while the rebound is more attenuated.

As a pressure gas DG for the hydraulic accumulator 6, and / or as a spring medium FM for the spring cylinder 22 and / or optional additional spring for the memory 36, in particular nitrogen.

By preferably external, separate from the spring cylinder 22 arrangement of the damping valve 4, and in particular by the inventive cooling element 12 is a very effective cooling of warming with throttling damping medium DM is reached. This heat transfer within the cylinder spring 22 to the spring medium FM is kept extremely low so that the equipped with the damping device according to the invention suspension system guarantees constant suspension and damping properties.

In a further advantageous embodiment of the invention, the hydraulic accumulator 6, an overpressure valve 40, which is in particular designed such that it opens at a certain excess pressure which corresponds to the respective maximum value of the priming pressure p. Thus, the pressure relief valve 40 opens bar from about 20, preferably from about 10 bar. Through the pressure relief valve 40 is advantageously prevented in the event of a leak in the seals of the piston 26, the higher pressure of the spring medium FM could cause an excessive pressure in the hydraulic accumulator. 6

The hydraulic accumulator 6 may further comprise at a suitable location of the housing 14 a filling valve 42nd Furthermore, the spring 36 is equipped with a filling valve 44th