Hydraulic accumulator

A hydraulic accumulator, comprising a base body (2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i) having a first component (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i) and a second component (4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i) which are connected to one another by a form fit and/or a material join, is, with the aim of specifying a hydraulic accumulator which, after fabrication without difficulty, exhibits a very reliable seal, a high level of strength, an as far as possible undamaged surface and an as far as possible rotationally symmetrical design in the joining region of the components, characterized in that at least one component (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i) is deformed by a contactless shaping method in such a way that it enters into the form fit and/or material join with the other component (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a United States national phase application based on PCT/EP2012/002509 filed Jun. 14, 2012 which claims the benefit of European Patent Application Serial No. 11009128.7 filed Nov. 17, 2011. The entire disclosures of the above applications are hereby incorporated herein by reference.

TECHNICAL BACKGROUND

The invention relates to a hydraulic accumulator according to the preamble of patent claim1.

PRIOR ART

Hydraulic accumulators, in particular diaphragm accumulators, can be used in hydraulic systems for storing energy. The hydraulic accumulators are pressure containers having receptacle spaces in which a specific usable volume of a liquid medium can be stored. The compressibility of a gaseous medium is used to apply pressure to the liquid medium.

In a diaphragm accumulator, a diaphragm usually divides off a receptacle space, in which the liquid medium can be accommodated, from a storage space. A gaseous, compressible medium is accommodated in the storage space. The receptacle space in which the liquid medium is accommodated can be connected to a hydraulic circuit.

As soon as the liquid medium is pressed under pressure into the diaphragm so accumulator, the gaseous medium in the storage space is compressed. In the case of a drop in pressure in the hydraulic circuit, the compressed gaseous medium can expand and can force the liquid medium accommodated in the receptacle space back into the hydraulic circuit.

A currently commercially available diaphragm accumulator is generally composed of two housing shells in which a diaphragm is mounted using a clamping ring. The mounting of the clamping ring is carried out in manufacturer-specific fashion.

After this, the two housing shells are closed off using a welding method. Furthermore, the diaphragm accumulator is filled with a gas via an inflow line. The storage space of the diaphragm accumulator which contains the gas is then closed off.

Against this background, WO 2010/130 332 A1 has already disclosed a diaphragm accumulator which comprises as components two housing shells which are connected to one another with a form fit.

The form fit is manufactured by shaping at least one of the components. In this context, tools usually act with considerable forces on the components. These tools can lead to damage to the outer surface of the components. Specifically, scratches, dents or scuffing can occur. Furthermore, joining with a form fit is difficult to implement within a pressure chamber.

When a form fit is manufactured on a hydraulic accumulator, it is necessary, owing to its substantially rotationally symmetrical design, that identical forces act in the radial direction in order to prevent non-uniform deformation.

In production it may easily be the case that the tools which act on the components bring about non-uniform and “non-round” deformation of the components. In this respect, a type of geometric unbalance may be impressed on a hydraulic accumulator. This can lead, in particular, to problems with respect to the seal and/or the strength.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of specifying a hydraulic accumulator which, after fabrication without difficulty, exhibits a very reliable seal, a high level of strength, an as far as possible undamaged surface and an as far as possible rotationally symmetrical design in the joining region of the components.

According to the invention, the above object is achieved by means of a hydraulic accumulator having the features of patent claim1.

According to the invention it has been recognized that a contactless shaping method can ensure that the external surface of the hydraulic accumulator remains substantially undamaged. The external surface of the hydraulic accumulator is free of dents, scratches or other irregularities. Furthermore, it has been recognized that such a shaping method allows forces to act uniformly on a rotationally symmetrical component of the hydraulic accumulator in such a way that it is deformed uniformly without unbalance in the radial direction.

Moreover, such a shaping method can apply such a prestress to a sealing surface of the diaphragm that it is possible to dispense with a clamping ring. The shaping method reduces the parts and the mounting steps which are necessary to fabricate a hydraulic accumulator, in particular a diaphragm accumulator.

In this respect, a hydraulic accumulator is specified which, after fabrication without difficulty, exhibits a very reliable seal, a high level of strength, an as far as possible undamaged surface and an as far as possible rotationally symmetrical design in the joining region of the components.

Consequently, the object mentioned at the beginning is achieved.

The shaping method could be an electromagnetic pulse joining operation. The Lorentz force which acts on a conductor through which a current flows in a magnetic field can advantageously be used for joining with a form fit. This force is surprisingly strong and precise to the extent that a metallic component with a considerable wall thickness can be deformed in a defined and uniform fashion. A metallic component can be surprisingly bent or pressed onto another component in the radial direction, as it were shrunk on. The forces which arise act on the hydraulic accumulator along the circumference thereof in a uniformly radial fashion in such a way that the components can be connected to one another in a fluidtight fashion with a form fit and/or material join.

The components could also be connected to one another in a materially joined fashion. In addition to the form fit, a material join could also be provided in order to further increase the seal of the hydraulic accumulator.

At least one component could be fabricated from a metal. Metals can be joined by an electromagnetic pulse joining operation owing to their electrical conductivity. In particular, all the electrically conductive iron metals and non-iron metals can be joined.

Against this background, at least one component could be fabricated from aluminum. By means of the contactless shaping method, this material, which per se can only be welded at high cost, is used for the manufacture of hydraulic accumulators, in particular diaphragm accumulators. Furthermore, at least one component could be fabricated from steel. The steel could be cold formed.

A component could be fabricated from plastic. In this context it is conceivable to use thermoplasts or duroplasts. A reduction in weight of the hydraulic accumulator is possible in this way. The fixed or static component during the electromagnetic pulse joining operation can be fabricated from plastic, while the other component is fabricated from a metal.

The components could form a storage space for a gaseous medium and a receptacle space for a liquid medium, wherein the storage space is separated off from the receptacle space by a diaphragm, and wherein the volumes of the storage space and of the receptacle space are variable. The hydraulic accumulator can therefore function as a diaphragm accumulator. The diaphragm can advantageously form sealing faces with the components by being clamped in between them under prestress. It is possible to dispense with a clamping ring for the diaphragm.

The storage space could be embodied without an inflow line. It is therefore possible to fabricate a compact hydraulic accumulator, which is provided with as few cumbersome connections as possible. Such a hydraulic accumulator has closure of the storage space with a high level of process reliability. The hydraulic accumulator can be joined in an installation space under pressure. The pressure in the installation space then corresponds substantially to the pressure in the storage space in the unloaded state of the hydraulic accumulator.

The receptacle space could have a connector which is integrally formed onto a first component. The connector is advantageously embodied as a hexagon and therefore permits the hydraulic accumulator to be easily connected by flanges to a hydraulic system.

The storage space could have an inflow line which is integrally formed onto a second component. By virtue of this configuration, the pressure in the storage space can be adjusted by refilling.

A first component could be embodied as a housing lower shell and a second component as a housing upper shell, wherein the edges of the housing lower shell and of the housing upper shell overlap one another and clamp in a diaphragm between them. The hydraulic accumulator can therefore function as a diaphragm accumulator. The diaphragm can advantageously form sealing faces with the components by being clamped in between them under prestress. It is possible to dispense with a clamping ring for the diaphragm.

A method for fabricating a hydraulic accumulator of the type described here could use an electromagnetic pulse joining operation as a shaping method.

In order to avoid repetitions with respect to the advantages of the contactless shaping method, reference is made to the statements relating to the hydraulic accumulator as such.

A system for carrying out an electromagnetic pulse joining operation is composed essentially of a pulse generator and a tool coil.

The pulse generator generates an electric current which flows through the tool coil. In this context, a magnetic field is generated which in turn induces a current in a component made of electrically conductive material.

What are referred to as Lorentz forces act on bodies through which a current flows in magnetic fields. These forces can, given sufficient strength, plastically deform the component and fit snugly onto another component or be integrally formed thereon. This shaping method is contactless and does not damage the surfaces of the components.

Moreover, this shaping method can also manufacture a materially joined connection between two components without the components being fused on. Metals can be moved close to one another in such a way that electrons can be exchanged between them.

Against this background, a first component could be made available, a diaphragm or a sealing means could be arranged between the first component and a second component, and the second component and/or the first is component could be deformed by the shaping method. By virtue of such a method it is possible to dispense with welding processes.

The diaphragm or the sealing means could be placed under prestress without using a damping ring by deforming one of the components. In this way it is possible to achieve a saving in terms of components. A prestress can specifically be applied to the sealing bead of a diaphragm by deforming a housing lower shell during a joining process.

The hydraulic accumulator could be joined together by the shaping method in an installation space in which there is a pressure which is above or below the atmospheric pressure.

This method for manufacturing a hydraulic accumulator is advantageously carried out in an installation space in which a pressurized gas is accommodated. The gas which is to be accommodated in the storage space is present in the installation space.

It is therefore possible to dispense with inflow lines to the storage space. An inert gas is preferably used as the gas. The pressure which is clearly above atmospheric pressure and which is present in the installation space can be adjusted as a function of the purpose of use of the hydraulic accumulator.

EMBODIMENT OF THE INVENTION

In the drawing,FIG. 1shows a hydraulic accumulator1acomprising a base body2awith a first component3aand a second component4awhich are connected to one another by a form fit and/or material join.

At least one component, specifically the first component3a, is deformed by a contactless shaping method such that it enters into the form fit and/or material join with the other component4a.

A wave structure is formed in the first component3a, said wave structure being made complementary to elevated portions and depressions in the second component4a.

The shaping method which has been used to produce the form fit and/or material join is an electromagnetic pulse joining operation.

The first component3ais fabricated from aluminum or steel.

The components3a,4aform a storage space5afor a gaseous medium and a receptacle space6afor a liquid medium, wherein the storage space5ais separated off from the receptacle space6aby a diaphragm7a, and wherein the volumes of the storage space5aand of the receptacle space6aare variable. The diaphragm7ais accommodated between the components3a,4awithout a clamping ring.

The storage space5ais embodied without an inflow line. The receptacle space6ahas a connector8awhich is integrally formed onto the first component3a.

The first component3ais embodied as a housing lower shell and the second component4aas a housing upper shell, wherein the edges9a,10aof the housing lower shell or housing upper shell overlap one another and clamp in the diaphragm7abetween them. There is no clamping ring provided for the diaphragm7a.

The housing upper shell is provided with grooves. The diaphragm7ais arranged between the housing upper shell and the housing lower shell. The joined-together hydraulic accumulator la withstands a defined burst pressure. Furthermore, it is gastight and oiltight. The fitting of the housing lower shell into the grooves of the housing upper shell occurs by partially reducing the diameters of the housing lower shell.

In the drawing,FIG. 2shows a hydraulic accumulator lb comprising a base body2bwith a first component3band a second component4bwhich are connected to one another by a form fit.

At least one component, specifically the first component3b, is deformed by a contactless shaping method such that it enters into the form fit with the other component4b.

The shaping method which has been used to manufacture the form fit is an electromagnetic pulse joining operation.

The first component3bis fabricated from aluminum or steel.

The components3b,4bform a storage space5bfor a gaseous medium and a receptacle space6bfor a liquid medium, wherein the storage space5bis separated off from the receptacle space6bby a diaphragm7b, and wherein the volumes of the storage space5band of the receptacle space6bare variable.

The storage space5bis embodied without an inflow line. The receptacle space6bhas a connector8bwhich is integrally formed onto the first component3b.

The first component3bis embodied as a housing lower shell and the second component4bas a housing upper shell, wherein the edges9b,10bof the housing lower shell and housing upper shell overlap one another and clamp in the diaphragm7bbetween them. There is no clamping ring provided for the diaphragm7b.

The edge9b, directed toward the second component4b, of the first component3bis bent radially inward and in the process engages over a circumferential, arcuate shoulder of the second component4b.

In the drawing,FIG. 3shows a hydraulic accumulator1ccomprising a base body2cwith a first component3cand a second component4cwhich are connected to one another by a form fit.

At least one component, specifically the first component3c, is deformed by a contactless shaping method such that it enters into the form fit with the other component4c.

The shaping method, which was used to manufacture the form fit, is an electromagnetic pulse joining operation.

The first component3cis fabricated from aluminum or steel.

The components3c,4cform a storage space5cfor a gaseous medium and a receptacle space6cfor a liquid medium, wherein the storage space5cis separated off from the receptacle space6cby a diaphragm7c, and wherein the volumes of the storage space5cand of the receptacle space6care variable.

The storage space5cis embodied without an inflow line. The receptacle space6chas a connector8cwhich is integrally formed onto the first component3c.

The first component3cis embodied as a housing lower shell and the second component4cas a housing upper shell, wherein the edges9c,10cof the housing lower shell and of the housing upper shell overlap one another and clamp in the diaphragm7c. A clamping ring11c is provided for the diaphragm7c.

The diaphragm7cis pressed between the clamping ring11c and the edge10cof the second component4c. The edge9cof the first component3chas a radially inwardly directed constriction12c.

In the drawing,FIG. 4shows a hydraulic accumulator1dcomprising a base body2dwith a first component3dand a second component4dwhich are connected to one another by a form fit.

At least one component, specifically the second component4d, is deformed by a contactless shaping method in such a way that it enters into the form fit with the other component3d.

The shaping method which was used to manufacture the form fit is an electromagnetic pulse joining operation.

The second component4dis fabricated from aluminum or steel.

The components3d,4dform a storage space5dfor a gaseous medium and a receptacle space6dfor a liquid medium, wherein the storage space5dis separated off from the receptacle space6dby a diaphragm7d, and wherein the volumes of the storage space5dand of the receptacle space6dare variable.

The storage space5dis embodied without an inflow line. The receptacle space6dhas a connector8dwhich is integrally formed onto the first component3d.

The first component3dis embodied as a housing lower shell and the second component4das a housing upper shell, wherein the edges9d,10dof the housing lower shell and of the housing upper shell overlap one another and clamp in the diaphragm7d. A clamping ring lid is provided for the diaphragm7d.

The clamping ring11dengages over the edge9dof the first component3d,projects into it and tapers in the direction of the receptacle space6d. The edge10dof the second component4dis bent radially inward and is pressed, together with the edge9dof the first component3d, against the clamping ring11d. The diaphragm7dis pressed here between the clamping ring11dand the edge9dof the first component3d.

In the drawing,FIG. 5shows a hydraulic accumulator1ecomprising a base body2ewith a first component3eand a second component4ewhich are connected to one another by a form fit.

At least one component, specifically the first component3e, is deformed by a contactless shaping method in such a way that it enters into the form fit with the other component4e.

The shaping method which was used to manufacture the form fit is an electromagnetic pulse joining operation.

The first component3eis fabricated from aluminum or steel.

The components3e,4eform a storage space5efor a gaseous medium and a receptacle space6efor a liquid medium, wherein the storage space5eis separated off from the receptacle space6eby a diaphragm7e, and wherein the volumes of the storage space5eand of the receptacle space6eare variable.

The storage space5eis embodied without an inflow line. The receptacle space6ehas a connector8ewhich is integrally formed onto the first component3e.

The first component3eis embodied as a housing lower shell and the second component4eas a housing upper shell, wherein the edges9e,10eof the housing lower shell and of the housing upper shell overlap one another and clamp in the diaphragm7ebetween them. There is no clamping ring provided for the diaphragm7e. The diaphragm7eprojects with a bead in a positively locking fashion into a hollow in the edge10eof the second component4e.

In the drawing,FIG. 6shows a hydraulic accumulator If comprising a base body2fwith a first component3fand a second component4fwhich are connected to one another by a form fit.

At least one component, specifically the first component3f, is deformed by a contactless shaping method in such a way that it enters into the form fit with the other component4f.

The shaping method which was used to manufacture the form fit is an electromagnetic pulse joining operation.

The first component3fis fabricated from aluminum or steel.

The components3f,4fform a storage space5ffor a gaseous medium and a receptacle space6ffor a liquid medium, wherein the storage space5fis separated off from the receptacle space6fby a diaphragm7f, and wherein the volumes of the storage space5fand of the receptacle space6fare variable.

The storage space5fis embodied without an inflow line. The receptacle space6fhas a connector8fwhich is integrally formed onto the first component3f.

The first component3fis embodied as a housing lower shell and the second component4fas a housing upper shell, wherein the edges9f,10fof the housing lower shell and of the housing upper shell overlap one another and clamp in the diaphragm7fbetween them. There is no clamping ring provided for the diaphragm7f. The diaphragm7fprojects with a bead in a positively locking fashion into a hollow in the edge10fof the second component4f. The edge9fof the first component3fbears against an edge seal131which lies in a stop14fof the second component4f.

The diaphragms shown inFIGS. 1 to 9are fabricated from an elastomer.

FIG. 7shows a hydraulic accumulator1gcomprising a base body2gwith a first component3gand a second component4gwhich are connected to one another by a form fit and/or material join.

At least one component3gis deformed by a contactless shaping method in such a way that it enters into the form fit and/or material join with the other component4g. The shaping method is an electromagnetic pulse joining operation.

FIG. 7illustrates that the components3g,4gare multiply interlocked with one another. Specifically, the edges9g,10gare multiply interlocked with one another. In addition to a form fit, the edges9g,10gand/or the components3g,4gcould be additionally connected to one another by a material join.

FIG. 8shows a hydraulic accumulator1hcomprising a base body2hwith a first component3hand a second component4hwhich are connected to one another by a form fit and/or material join.

At least one component3his deformed by a contactless shaping method in such a way that it enters into the form fit and/or material join with the other component4h. The shaping method is an electromagnetic pulse joining operation.

The form fit is produced by a sharp transition between two diameters of the second component4h. The sharp transition is implemented by a step15hwhich is partially rectangular in cross section. The sharp transition is formed in the edge10hof the second component4h.

In addition to a form fit, the edges9h,10hor the components3h,4hcould be additionally connected to one another by a material join.

FIG. 9shows a hydraulic accumulator1icomprising a base body2iwith a first component3iand a second component4iwhich are connected to one another by a form fit and/or material join.

At least one component3iis deformed by a contactless shaping method in such a way that it enters into the form fit and/or material join with the other component4i. The shaping method is an electromagnetic pulse joining operation.

The form fit is generated by a recess16iwhich is made in the first component3ior in the edge9ithereof before the pulse joining operation. During the pulse joining operation, the first component3iis fitted with the recess16ionto a projection17ion the second component4ior on the edge10ithereof. This brings about better interlocking of the components3i,4i.