EP2519747B1 - Guiding device for metal bellows - Google Patents

Description

The invention relates to a guide device for a metal bellows, which has on at least one Balgende a movable upon extension and contraction of the bellows along the wall of a housing end body, between which and the housing, a guide means is provided, wherein the guide means at least one peripheral portion of the end body having surrounding ring body, which forms on its outer circumference first annular surface parts which have a radial distance from the wall of the housing and are separated from one another by distributed over the outer circumference, radially projecting over the first annular surface parts second annular surface parts.

Metal bellows are used in various technical fields as a variable-length component, for example, if a length compensation for lines or coupling connections for fluid media is required. Metal bellows are also frequently used in hydraulic accumulators as a movable separating element between the gas side and the fluid side. In particular, in applications in which the movements take place during expansion and contraction of the bellows relatively widely or if, as is the case with pulsation dampers or shock absorbers, reciprocating movements with relatively high frequency and / or higher acceleration values, it is for the Life of the bellows essential that the respective End of the bellows, which moves in operation along a housing wall, is guided safely.

In this regard, it is therefore prior art to provide a guide means at the movable end of the respective bellows. In a post-published state of the art representing solution described in the German patent application DE 10 2007 036 487.5 is disclosed, the guide arrangement is formed in such a way that at the peripheral edge of the movable end body of the bellows, individual, distributed around the circumference of the end body guide body are mounted, which form sliding bodies, which are guided with an outer sliding surface on the housing wall. The sliding surfaces of these bodies have a radial distance from the outer periphery of the end body, so that between the individual guide bodies fluid passages along the housing wall are formed.

These guide bodies are designed as guide shoes, which engage over the peripheral edge of the pot in the cup-shaped end body whose circular cylindrical side wall extends into the interior of the bellows. When formed from a plastic material good sliding properties guide bodies good leadership properties are achieved, ie the guide allows safe long-term operation with favorable friction conditions between the guide body and housing wall. On the other hand, the production is complicated and expensive. The individual guide body, which are made in a separate manufacturing step, must be brought to the installation site and mounted on the end edge of the end body of the bellows concerned. In order to ensure a secure anchoring of the guide body, the guide body are designed as guide shoes with a cross-sectionally U-shaped profile, whose legs engage over the end edge of the pot-like end body. In this case, both at the end edge of the pot a detent and inside the profile of the guide shoes at least one undercut must be present to the fuse to allow the guide body by clipping. The formation of undercuts requires a complex production of the guide shoes by compression molding.

The JP 02-195001 shows a bellows, which is supported via an annular guide member relative to a housing wall. The guide element has radial projections and inter-projection fluid passages. The guide element is L-shaped in cross-section and engages in a fold of the bellows.

From the JP 10-019001 goes out a bellows, the end is welded to an end piece. At the tail turn, a guide element is attached to the end. The guide element has projections that space the bellows end away from the housing wall.

With the JP 02-113139 and the JP 2009-228715 Bellows belong to the prior art, in each of which a U-shaped guide element in cross-section encompasses an end piece and an end fold of the bellows.

In view of this, the object of the invention is to provide a guide device which, while maintaining the good guiding and operating properties of the mentioned solution of the prior art, is characterized by a substantial simplification of the production and thus a reduction of the production costs.

According to the invention this object is achieved by a guide device having the features of claim 1 in its entirety.

The respective annular body engages with a ring part forming the first annular surface parts in a circumferential annular groove which is arranged on the end body. This enlargement of the distance of the guidance point from immovable Balgende favors the tilting security of the leadership. The securing of the ring body by snapping into an annular groove allows a particularly simple installation.

The guide means has a ring body surrounding a peripheral region of the end body of the bellows and this forms on its outer circumference both annular surface parts which have a radial distance from the wall of the housing, and distributed over the outer circumference, radially above the first annular surface parts projecting second annular surface parts. These radially projecting annular surface parts in this case form the guided on the housing wall sliding surfaces which separate the radially radially withdrawn first annular surface parts in the circumferential direction from each other. A uniform ring body thus assumes not only the function of the guide body of the solution according to the prior art, but also the formation of the fluid passages between the housing wall and the end body of the bellows at the radially located between the second Ringflächenteilen first Ringflächenteilen.

Preferably, the ring body is formed of a plastic material with good sliding properties, resulting in a lightweight, easy to produce by injection molding construction.

In preferred embodiments, the bellows is fixed to the housing opposite the movable end body to a housing-fixed retaining ring which seals the interior of the bellows against the wall of the housing, wherein the end body forms a the interior of the bellows at the associated bellows tightly sealing closure body. Such a design is particularly advantageous if the metal bellows is used as a movable separating element between the gas side and the fluid side of a hydraulic accumulator.

In particularly advantageous embodiments, the annular body may have an inner ring part with at least one radially inwardly into the associated annular groove projecting inner edge and an outer ring part, on the outside of the first and second Ringflächenteile are formed, wherein the outer ring part and first and second annular surface part has a greater axial width having the width of the annular groove and the width of the inner edge of the inner ring part received therein. Such a configuration of the annular body opens up the possibility of forming the axial dimension of the second annular surface parts formed on the outer ring part, which form the actual sliding surfaces on the housing wall, with an axially much larger dimension than corresponds to the width of the annular groove securing the annular body. As a result, optimal guide properties on the housing wall result for the sliding surfaces which are correspondingly extended in the axial direction.

With particular advantage, the arrangement can be made such that the bottom of the housing nearest end of the inner ring part of the annular body forms a radially inwardly projecting lip which extends from the radially outer edge region inwards and limits the edge region on a narrow annular surface. During operation of the device thus forms a narrow, axially projecting edge region of the contact surface in the system on the surface of the housing bottom in the fully extended state of the bellows. The resilience of the plastic material from which the ring body is formed, thus acting as a damping element when hitting the bottom surface, which is given due to the contact surface formed by the inclined surface of reduced size no risk of sticking to the housing bottom.

Preferably, the second Ringflächenteile are arranged at equal angular intervals from each other, for a low-friction but safe Guide preferably 4 to 12 second ring surface parts on the relevant ring body are present.

The invention is according to claim 8, a hydraulic accumulator with a storage housing, in which a metal bellows is provided as a movable separating element between a gas side and a fluid side, for which a guide device according to one of claims 1 to 7 is present.

Fig. 1

einen gegenüber einer praktischen Ausführungsform geringfügig verkleinert und schematisch vereinfacht gezeichneten Längsschnitt eines für einen Einsatz als Schockabsorber vorgesehenen Hydrospeichers mit einem als bewegliches Trennelement zwischen Gasseite und Fluidseite dienenden Metallbalg, versehen mit einer Führungseinrichtung gemäß einem Ausführungsbeispiel der Erfindung;

Fig. 2

eine teilweise aufgeschnitten dargestellte Draufsicht des Hydrospeichers von Fig. 1;

Fig. 3

eine perspektivische Schrägansicht lediglich des Ringkörpers als Bestandteil der Führungseinrichtung des Ausführungsbeispieles ;

Fig. 4

eine Draufsicht des Ringkörpers von Fig. 3;

Fig. 5

eine Schnittdarstellung entsprechend der Schnittlinie XII-XII von Fig. 4 und

Fig. 6

einen gegenüber Fig. 5 größer gezeichneten Teilausschnitt lediglich des in Fig. 5 mit XIII bezeichneten Bezirks.

The invention with reference to an embodiment shown in the drawing will be explained in detail. Show it:

Fig. 1

a comparison with a practical embodiment slightly smaller and schematically simplified drawn longitudinal section of a planned for use as a shock absorber hydraulic accumulator serving as a movable separating element between the gas side and fluid side metal bellows, provided with a guide device according to an embodiment of the invention;

Fig. 2

a partially cutaway top view of the hydraulic accumulator of Fig. 1 ;

Fig. 3

a perspective oblique view only of the annular body as part of the guide device of the embodiment;

Fig. 4

a plan view of the ring body of Fig. 3 ;

Fig. 5

a sectional view corresponding to the section line XII-XII of Fig. 4 and

Fig. 6

one opposite Fig. 5 larger drawn partial section only of in Fig. 5 district designated XIII.

The Fig. 1 to 6 show an embodiment of the guide device according to the invention in a hydraulic accumulator in the form of a shock absorber. A designated as a whole with 1 storage enclosure has a housing main part 3 in the form of a circular cylindrical pot, which is closed at the top of the drawing in the drawing up to a filling opening 7, which is aligned with the housing longitudinal axis 9 and in the representation of Fig. 1 is sealed fluid-tight by a welding core. For closing the upper end of the pot, a closing part 13 is welded tightly to the housing main part 3 along a welding line 16. Concentric with the axis 9 is located in the bottom 69 of the pot, a fluid inlet 15 with an outer connecting piece 17. In the representation of Fig. 1 is screwed onto the external thread of the connecting piece 17, a threaded cap 20.

In the interior of the storage housing, a metal bellows unit forms a movable separating element between a gas side 21, which adjoins the closing part 13 and can be filled via the filling opening 7 with a working gas, preferably N ₂ , with a gas pre-filling pressure. In the presentation of Fig. 1 the bellows 19 is in its fully extended state, wherein the volume of the gas side 21 has the largest value, while the adjacent to the fluid inlet 15 fluid side 23 has its smallest volume. The bellows unit is welded in a fluid-tight manner to the bellows end 29 adjacent the housing end part 13, more precisely to the radially outer edge of the last bellows fold, with a metallic retaining ring 25. The retaining ring 25 in turn is welded to the storage housing at the separation point between the end part 13 and the main part 3 at the weld line 16. When assembling the storage housing and the installation of the bellows unit, therefore, the welding line 16 is thermally insulated at least partially via the retaining ring 25 from the bellows 29. The welding region of the bellows 29 on the retaining ring 25 is indicated in the figure by 27, the point where the retaining ring 25 forms an axial bulge as a welding area.

The housing-fixed Balgende 29 opposite, movable bellows 31 is welded to the radially outer end edge of the last Balgfalte with a metallic end body 35 which forms a closure body which closes the interior of the bellows 19 fluid-tight and thus forms the separation between the gas side 21 and fluid side 23.

A cylindrical insert body 73 which extends from the end portion 13 into the interior of the bellows 19, causes a corresponding reduction in the volume of the gas side 21 and at the same time forms an end stop against which the movable end body 35 of the bellows 19 starts in the fully contracted state. In Fig. 1 the bellows 19 is shown in its almost fully extended position, in which the end body 35 is located at a small distance from the flat bottom surface 71 of the bottom 69.

The end body 35 is on the inside of the bellows 19 side facing substantially planar, except for an axially slightly protruding peripheral edge 75, which forms the weld at the associated bellows 31. Axially offset from the peripheral edge 75, the end body 35 forms an annular groove 77 as a seat for an inner ring part 79 of the annular body 47 of the guide device. Opposite the annular groove 77 axially offset, the end body 35 forms a step at the step surface of a radially inwardly projecting lip 81 of the ring member 79 is present. The in Fig. 3 to 6 illustrated annular body 47 has, radially outward on the inner ring member 79, an outer ring member 83 which forms inner annular surfaces 51 which are separated by outer annular surfaces 53 from each other on radially outer guide members 55 on the outside sliding surfaces for engagement with the housing wall. The ring body 47 is formed of a plastic material with good sliding properties and can be made by turning or milling, but also be formed as a molded component.

A peculiarity of the ring body 47 is, as best of Fig. 6 can be seen in that the lip 81 between the radially outer end 85 and its inner end forms an inclined surface 87, such that the annular body 47 at the end 85 forms a relatively narrow edge region. When attached to the end body 35 of the bellows annular body 47 thus forms this axially projecting edge region at the end 85, the contact surface when resting against the bottom surface 71 of the bottom 69 in the fully extended state of the bellows 19. The compliance of the plastic material from which the annular body 47 formed is acting as a damping element when striking the bottom surface 71, wherein due to the increased surface formed by the inclined surface 87 reduced size no risk of adherence to the bottom surface 71 is given. In addition to support via the guide can be caused by the bellows body, in particular in the end regions, a support. Accordingly, then the guide could be shorter from their axial length ago.

For large diameters of the bellows 19 more ring surface parts 53 are required for support than for smaller diameters. In the case of very small diameters, three annular surface parts 53 arranged offset by 120 ° from one another are preferably provided on the annular body 47.

Another special feature is that the guide body 55 and thus the sliding surfaces formed by the outer annular surfaces 53 have a much greater axial length than would be the case with a ring 47 forming a flat ring.

When using the hydraulic accumulator provided with the guide device according to the invention as a pulsation damper, the fluid side 23 via the inlet 15 with a pressurized fluid, in particular hydraulic fluid, a fuel or lubricant in fluid communication around occurring Smooth pressure surges. It has proved to be favorable if, as in DE 10 2004 004 341 A1 is shown, the gas side 21 is not only filled with working gas, but also contains a predetermined volume fraction of a fluid. A combination of nitrogen gas as the working gas and ethylene alcohol as the fluid on the gas side 21 of the storage has proved to be particularly advantageous. In operation, the fluid between folds and deflections of the bellows 19 form a damping support medium, on which the folded wall parts of the bellows 19 can be supported on the fluid as an abutment, which leads to an increase in the life of the bellows and thus to an increase in reliability. This is especially true for rapid pulsations and rapid pressure surges.

Claims (7)

1. A guiding device comprising a metal bellows (19) which has an end body (35) on at least one end (31) of the bellows, said end body being moveable along the wall of a housing (1) during expansion and compression of the bellows (19), there being between this end body and the housing (1) a guiding means (47) forming part of the guiding device, the guiding means having at least one annular body (47) surrounding a peripheral region of the end body (35) which forms on its outer periphery first annular surface parts (51) which are radially spaced apart from the wall of the housing (1) and are separated from one another by second annular surface parts (53) distributed over the outer periphery and projecting radially beyond the first annular surface parts (51), characterised in that the respective annular body (47) engages with an annular part (79) forming the first annular surface parts (51) in a peripheral annular groove (77) located on the end body (35).
2. The guiding device according to Claim 1, characterised in that the annular body (47) is made of a plastic material with good sliding properties.
3. The guiding device according to Claim 1 or 2, characterised in that the bellows (19) is secured at the bellows end (29) lying opposite the moveable end body (35) at a retaining ring (25) forming part of the guiding device, that is rigidly mounted on the housing and seals off the interior of the bellows (19) relative to the wall of the housing (1), and that the end body (35) forms a closure body that tightly closes off the interior of the bellows (19) at the assigned end (31) of the bellows.
4. The guiding device according to any of Claims 1 to 3, characterised in that the respective annular body (47) has an internal ring part (79) with at least one inner edge which projects radially inwards into the assigned annular groove (77) and an external ring part (83) on the exterior of which are formed the first and the second ring surface parts (51, 53), and that the external ring part (83) and the first and the second annular surface parts (51, 53) have a larger axial width than the width of the annular groove (77) and the width of the inner edge of the internal ring part (79) accommodated within.
5. The guiding device according to Claim 4, characterised in that the end of the internal ring part (79) that lies closest to the bottom (69) of the housing (1) forms a radially inwardly projecting lip (81) which extends inwards from the radially external edge region (85) and limits the edge region (85) to a narrow annular surface.
6. The guiding device according to any of Claims 1 to 5, characterised in that the second annular surface parts (53) are arranged the same angular distances apart from one another, and that preferably three to twelve second annular surface parts (53) are provided on the annular body (47).
7. A hydraulic accumulator with an accumulator housing (1) in which a metal bellows (19) is provided as a moveable separating element between a gas side (21) and a fluid side (23), a guiding device (47) according to any of Claims 1 to 6 being provided for said metal bellows.

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