WO2011079852A1

WO2011079852A1 - Hydraulic accumulator, especially bellows accumulator

Info

Publication number: WO2011079852A1
Application number: PCT/EP2009/009331
Authority: WO
Inventors: Herbert Baltes
Original assignee: Hydac Technology Gmbh
Priority date: 2009-12-30
Filing date: 2009-12-30
Publication date: 2011-07-07
Also published as: DK2519748T3; EP2519748B1; EP2519748A1

Abstract

A hydraulic accumulator, especially a bellows accumulator, wherein the bellows serving as the mobile separating element between the gas side (21) and the fluid side (23) comprises a closing element (35) that closes the interior of the bellows in a fluid-tight manner on the bellows end (31) that can be axially displaced in the accumulator housing (1) during expansion and compression and is immobilized on the other bellows end (29) relative to the accumulator housing (1), is characterized in that a sealing system (37) sealing the interior of the bellows from the accumulator housing (1) on the immobile bellows end comprises, in addition to a first functional area (63) having a sealing effect, a second functional area in the form of an attachment projecting into the interior of the bellows, at least one bulge (73) projecting axially towards the mobile bellows end (31) forming a flexible buffer for the contact of the closing element (35) of the bellows when the latter is completely compressed.

Description

Hydraulic accumulator, in particular bellows accumulator

The invention relates to a hydraulic accumulator, in particular bellows accumulator, in which the serving as a movable separating element between the gas side and fluid side bellows on its pull-out and contraction in the storage housing in the axial direction movable bellows a fluid-tight closure of the interior of the bellows sealing body and at its other Balgende relative to the storage housing is fixed immovable.

Hydraulic accumulator with serving as a movable separator bellows are known and find application in various technical fields, for example in hydraulic brake systems for vehicles and various industrial hydraulic systems. For example, EP 1 052 412 A2 shows a bellows accumulator in which a metal bellows is provided as a movable separating element between the gas side and the fluid side.

In view of the prior art, the invention has the object to provide a hydraulic accumulator in the form of a bellows storage available, which is characterized by a particularly favorable performance, in particular ensures safe long-term operation.

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

CONFIRMATION COPY Characterized in that according to the characterizing part of claim 1, a sealing the interior of the bellows on immovable Balgende relative to the storage enclosure seal assembly in addition to a first, the sealing effecting functional area has a second functional area in the form of a projecting into the interior of the bellows approach, which opens advantageous possibility to use the seal assembly for an additional function by the resilience of the sealing material is used to form a resilient buffer, more precisely, by forming a projecting against the movable Balgende protrusion is formed on the projecting into the interior of the bellows approach which starts the closure body of the bellows in its fully contracted state. In particular, in applications in which it comes to oscillating movements of the movable closure body of the bellows, as is the case for example with pulsation dampers, the resilient, formed by the second functional area of the seal assembly, resilient buffer acts not only as a compliant, stroke limiting end stop the movement of the Closure body, but avoids any resulting operating noise by hitting moving parts of the bellows to unyielding components.

Preferably, a bellows is provided in the form of a metal bellows with a metallic closure body welded to the respective bellows end.

In particularly preferred embodiments, the immovable bellows end is fixed by means of a fluid-tight welded connection to a housing-fixed retaining ring, the inner annular opening adjacent to the fluid side forming the interior of the bellows, the seal assembly with its first functional area forms the seal between the inner ring opening of the retaining ring and the storage housing , Thereby, the sealing arrangement on the inner ring opening of the retaining ring directly forms a seal with the accumulator housing, resulting in a sealing of the interior of the bellows with respect to its outside, irrespective of whether the retaining ring is itself sealed fluid-tight against the accumulator housing. In other words, it is sufficient if the retaining ring is immovably fixed via a welded connection to the housing wall, wherein such a welded connection need not be continuously fluid-tight. In particularly advantageous embodiments, the storage housing has a main part and a bottom housing end part with a central, fluid side in communication with the fluid inlet, wherein the seal assembly comprises an annular body, the first functional area forms an annular, radially outer sealing lip, with lying in radial planes sealing surfaces causes the seal against a seat on the housing end part and an annular surface on the retaining ring.

Furthermore, the arrangement may advantageously be such that the closure body of the bellows has the shape of a pot with a circular-cylindrical side wall which extends away from the movable bellows end into the interior of the bellows and is delimited by a flat pot bottom, wherein the annular body at the forming the second functional area approach as a bulge has a rounded annular rib, the axial elevation is chosen such that the outside of the pot bottom rests with fully compressed bellows on the annular rib. This design of the closure body in the form of a projecting into the interior of the bellows pot leads to a significant increase in the volume of the gas side. At the same time, the planting of the flat pot bottom on the annular rib forming the flexible buffer results in a centering of the bellows in the fully contracted end position. The annular body forming the sealing arrangement may advantageously be shaped such that the end surface of the annular body facing the seating surface on the housing end part forms a radial plane extending from the radially outer sealing surface of the sealing lip to the annular opening, wherein the annular body has a stepped shape on the opposite side.

If the arrangement is made such that the stepped shape from the outer sealing lip radially inwardly from a first stage at the transition to the second functional part forming approach, where the buffer forming annular rib projects axially, the further inwardly to a second stage drops, on which an inner ring edge is formed, this can engage in an annular space which is formed between the seat in the Gehäuseab- closing part and an undercut in the retaining ring. As a result, the seal assembly is secured to the seat of the housing end part against axial lifting.

As materials for the production of the seal assembly forming annular body are polytetrafluoroethylene, a hydrolysis resistant polyurethane elastomer or other elastomer into consideration. Particularly suitable polyurethane elastomer has been found, which is marketed by the company Economos Austria Gesellschaft mbH under the product Eco-Pure ^®.

The invention with reference to an embodiment shown in the drawing will be explained in detail. It shows: a comparison with a practical embodiment slightly reduced and drawn schematically simplified Longitudinal section of an intended for use as a pulsation damper hydraulic accumulator;

Fig. 2 is a plan view of only one seal assembly of the hydraulic accumulator of Fig. 1;

Fig. 3 is a section along the section line III-III of Fig. 2;

Fig. 4 is a comparison with Figure 3 greatly enlarged drawn partial detail only of the designated in Figure 3 with IV district.

FIG. 5 shows a plan view of an annular body which is approximately in the natural size of a practical embodiment and forms part of a guide device of the bellows of the hydraulic accumulator of FIG. 1, and FIG

Fig. 6 is a sectional view of the ring body according to the line Vl-Vl of Fig. 5. In the drawing, the invention is described with reference to an embodiment in the form of a pulsation damper. A designated as a whole with 1 memory housing has a housing main part 3 in the form of a circular cylindrical pot with lying in the drawing above end 5, which is closed except for a filling opening 7, which is aligned with the housing longitudinal axis 9 and in the illustration of FIG a plug 1 1 media-tight is completed. At the opposite end, lying at the bottom in FIG. 1, the housing 1 is closed by a housing end part 13, which is welded tightly to the housing main part 3 along a welding line 16. A fluid inlet 15 with an outer connecting piece 17 is located concentrically with the axis 9 in the end part 13. In the illustration of FIG. 1, a threaded protective cap 20 is screwed onto the external thread of the connecting piece 1 7.

In the interior of the storage housing, a metal bellows unit forms a movable separating element between a gas side 21, which adjoins the housing end 5 and via the filling opening 7 with a working gas, preferably N2, with a gas pre-filling pressure can be filled, and one adjacent to the fluid inlet 15 fluid side 23. In the illustration of Fig. 1, the bellows 19 is in its fully contracted 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 fluid-tight to the housing end part 1 3 adjacent bellows 29, more precisely, at 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 1 3 and main part 3 at the weld line 16. During the welding process for the assembly of the storage housing 1 and the installation of the bellows unit, therefore, the welding line 1 6 is thermally insulated at least partially via the retaining ring 25 from the bellows 29. The welding region of the bellows end 29 itself on the retaining ring 25 is designated in the figure by 27, where the retaining ring 25 forms an annular axial elevation.

The housing-fixed Balgende 29 opposite, movable bellows 31 is welded at the radially outer end edge of the last Balgfalte at 33 with a metallic end body 35 which forms a closure body which closes the interior of the bellows 19 at the movable end 31 fluid-tight and thus the separation between the gas side 21 and fluid side 23 bi ldet. The sealing of the outside of the bellows 1 9 takes place by a sealing arrangement 37 in the form of an annular sealing element, which seals the retaining ring 25 with respect to the housing end part 1 3. The detailed design and the additional function fulfilled by the sealing arrangement 37 are explained in more detail below with reference to FIGS. 2 to 4. The end body 35 has in the illustrated embodiment, the shape of a pot with a circular cylindrical side wall 39, of the on Balgende 31 pot opening extending into the interior of the bellows 1 9 to a flat bottom of the pot 41. Compared to a planar design of the end body 35, the pot shape results in an enlargement of the gas volume of the gas side 21.

At the opening edge of the pot, the end body 35 extends beyond the adjacent Balgende 31 away radially outward to the weld 33 of the Balgendes and runs from there Balgende 31 away radially and axially to form an approximated to the housing wall peripheral edge 43. In the peripheral edge 43 is a circumferential annular groove 45, which forms the seat for an annular body 47, see FIGS. 5 and 6, as part of a guide device. These are, as shown in Fig. 5 and 6, a flat ring made of a plastic good sliding properties, in particular of polytetrafluoroethylene. This annular body 47 has a seated in the annular groove 45 ring member 49 which forms on its outer circumference first annular surface parts 51 which are separated by second annular surface portions 53 from each other. The second annular surface parts 53 are radially outwardly offset relative to the annular surface parts 51, see FIG. 5, such that the second annular surface parts 53 form sliding surfaces bearing on the housing wall on guide bodies 55 projecting radially from the inner annular part 49. During operation, when the fluid side 23 and thus the interior of the bellows 19 are acted upon by the inlet 15 with a pressurized fluid, for example hydraulic oil, so that the bellows 19 extends and the end body 35 thereby emerges from that shown in FIG Position is moved axially, thereby reducing the volume of the gas side 21, then form the radially outer annular surfaces 53 sliding surfaces of the guide body 55, with which the movable end body 35 of the bellows 19 is guided on the housing wall. The inner annular surface portions 51 radially offset from the outer annular surface portions 53 form fluid passages on the outside of the bellows 19, whereby the gas side 21 continues on the outer side of the bellows 19 as far as the retaining ring 25, the seal being opposite to that of FIG Fl uidseite 23 takes place through the seal assembly 37 which is inserted between the retaining ring 25 and housing end portion 13.

2 to 4 show the details of the shape of the annular body 61 of the seal assembly 37. It is a profiled or stepped sealing ring made of a material having a certain flexibility, for example polytetrafluoroethylene or an elastomeric polyurethane or other elastomeric material, such as synthetic rubber. ECOPUR ^{® has} proven to be particularly suitable as a sealing material.

As shown in FIGS. 2 to 4, the annular body 61 is profiled such that an annular, radially outer sealing lip 63 is formed on the radially outer edge region as the first functional region, which forms an upper sealing surface 65 and a lower sealing surface 67, the upper one , annular sealing surface 65 merges into a step 69 at the radially inner end, while the other sealing surface 67 lies in the continuous radial plane of the annular body 61. At the step 69, the annular body 61 merges into a radially further inward projection 71, which forms the second functional region of the sealing arrangement, wherein a curved annular rib 73 projects axially from the upper side of this projection 71. Radially inwardly the annular rib 73 merges into a sloping second step 75, to which a radially inner annular rim 77 connects. In the installed state shown in Fig. 1, the annular body 61 forms the

Seal assembly 37 between the retaining ring 25, which is connected at the weld 27 tightly connected to the interior of the bellows 19, and the Gehäuseabschl nozzle 13, the fluid-tight seal. For this purpose, the seal assembly 37 is received in a seat on the housing end portion 13, at the base surface of the annular body 61 with the continuation of the sealing surface 67 forming radial plane is applied over the entire surface. To the the lip 63 opposite, radially inner edge, the projection 71 forms a radially inwardly projecting annular rim 77, which is received in an undercut 79 of the housing end part 13 and thereby secured against axial lifting. The sealing lip 63 seals with its sealing surfaces 67 and 65 relative to the housing end part 13 and the retaining ring 25, wherein the annular edge 77 engages in a sealing space between the seat on the housing end part 13 and an inner annular surface 81 formed by a step on the retaining ring 25. As shown in FIG. 1, the depth of the pot on the end body 35 and the axial elevation of the formed as a buffer on the seal assembly 37, curved annular rib 73 are selected so that in the shown in Fig. 1, fully contracted state of the bellows 19 of the bottom of the pot 41 rests on the one yielding end stop forming rib 73 of the seal arrangement 37.

When the hydraulic accumulator is used as a pulsation damper, the fluid side 23 is in fluid communication via the inlet 15 with a pressure fluid, in particular hydraulic fluid, a fuel or lubricant, in order to smooth out occurring pressure surges. It has proven to be advantageous if, as shown in DE 10 2004 004 034 A1, 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 1 9 form a damping support medium on which the folded wall parts of the bellows 19 can support the fluid as an abutment, resulting in an increase in the life of the bellows 19 and thus to increase the reliability leads. This is especially true for rapid pulsations and rapid pressure surges. Due to the two-sided projecting Jumps on the seal assembly 37 is so far avoided due to the resulting undercuts an unintentional withdrawal of the assembly 37 during operation of the memory with certainty.

Claims

P a n t a n s p r e c h e

Hydraulic accumulator, in particular bellows accumulator, in which the bellows (19) serving as a movable separating element between the gas side (21) and the fluid side (23) forms the interior of the bellows (31) which can be moved axially in the storage housing (1) in the storage housing (1). 19) has a closure body (35) which closes in a fluid-tight manner and is immovably fixed at its other bellows end (29) relative to the storage housing (1), characterized in that an interior of the bellows (19) on the immovable bellows end (29) opposite the storage housing (1 ) sealing sealing arrangement (37) in addition to a first, the sealing effecting functional area (63) has a second functional area in the form of a in the interior of the bellows (19) projecting lug (71) on which at least one in the axial direction against the movable Balgende ( 31) projecting bulge (73) a resilient buffer for the system of the closure body (35) of the fully together Formed state located bellows (19) forms.

Hydraulic accumulator according to claim 1, characterized in that a metal bellows with a with the respective bellows end (31) welded, metallic closure body (35) is provided.

A hydraulic accumulator according to claim 2, characterized in that the immovable bellows end (29) by means of a fluid-tight welded connection to a housing-fixed retaining ring (25) is fixed, the inner annular opening adjacent to the fluid side (23) forming the interior of the bellows (19), and that the sealing arrangement (37) with its first functional region (63) forms the seal between the inner annular opening of the retaining ring (25) and the storage housing (1). Hydraulic accumulator according to claim 3, characterized in that the storage housing (1) has a main part (3) and a bottom-side housing end part (13) with a central, with the fluid side in communication fluid inlet (1 5) and that the seal assembly (37) has a Ring body (61), whose first functional area forms an annular, radially outer sealing lip (63), with sealing surfaces lying in radial planes (65, 67) sealing against a seat on the Gehäuseabschlussteil (13) and an annular surface (81) on the retaining ring ( 25) causes.

A hydraulic accumulator according to claim 4, characterized in that the closure body (35) of the bellows (19) has the shape of a pot with a circular cylindrical side wall extending from the movable bellows end (31) in the interior of the bellows (1 9) and of a planar pot bottom (41) is limited, and that the annular body (61) on the second functional region forming projection (71) as a bulge a rounded annular rib (73) whose axial elevation is selected such that the outside of the pot bottom (41 ) rests with fully compressed bellows (1 9) on the annular rib (73).

Hydraulic accumulator according to claim 4 or 5, characterized in that the seat surface on the Gehäuseabschlussteil (13) facing the end surface of the annular body (61) forms one of the radially outer sealing surface (67) of the sealing lip (63) to the ring opening continuous radial plane and that the annular body (61) has a stepped shape on the opposite side.

Hydraulic accumulator according to one of claims 4 to 6, characterized in that the stepped shape of the outer sealing lip (63) radially inwardly from a first stage (69) at the transition to the second functional part forming the projection (71) on which the the Buffer-forming annular rib (73) protrudes axially, the radially further inwardly to a second stage (75) drops, on which an inner annular edge (77) is formed, which engages in an annular space (81) between the seat in the housing end part ( 1 3) and an undercut (79) in the retaining ring (25) is formed.

Hydraulic accumulator according to one of claims 1 to 7, characterized in that the sealing arrangement (37) forming ring body (61) is formed of polytetrafluoroethylene, a hydrolysis resistant polyurethane elastomer or of another elastomer.