method

Abstract

The present invention relates to a method for manufacturing at least part of a hydraulic accumulator, characterized in that the method comprises the steps of: providing an accumulator housing part (20) having at least one fluid connection point (28); providing a connecting body (30) with a fluid passage (60) having a material deposit (64) on one free end face thereof; positioning the material deposit (64) relative to the accumulator housing part (20) such that the at least one fluid connection point (28) in the accumulator housing part (20) is in fluid communication with the fluid passage (60) of the connecting body (30); melting the material deposit (64) by a welding process; joining the connecting body (30) and the accumulator housing part (20) with a predetermined pressing force and along a predetermined path; and allowing the resulting welded joint (70) to cool.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing at least part of a hydraulic accumulator and in particular to a hydraulic accumulator manufactured by said method. [Background technology]

[0002] Patent Document 1 (German Patent Invention No. 102009049547) describes a method for manufacturing a hydro-pneumatic accumulator, The method comprises: providing a protrusion on a surface of the valve body facing the valve seat; inserting the valve body into a projection mold to form a flexible membrane that forms a movable separation element; and injecting a membrane-forming elastomer such that the valve body is embedded in the elastomer, leaving the surface facing the valve seat exposed.

[0003] To complete the hydro-pneumatic accumulator, the above-described arrangement is inserted into an accumulator housing, on which a housing opening is located, providing access to the fluid chamber, for the purpose of connecting the accumulator to a conventional hydraulic system, and a connector is adjacent to the housing opening, for which purpose the connector, having a fluid passage coaxially arranged with the housing opening in the accumulator housing, is rigidly connected to the accumulator housing via a circumferential fillet weld joint.

[0004] DE 10 2015 012 357 A1 discloses a comparable hydraulic accumulator, in particular in the form of a diaphragm accumulator, which comprises at least two housing parts of an accumulator housing, with a separating element in the form of a separating membrane separating two medium chambers from one another, which separating element has at least one medium connection which is connected to one housing part along a welded joint and which serves as a connecting body for connecting the hydraulic accumulator to a hydraulic system and which at least partially engages in a receiving space formed in one housing part along a housing opening, facing towards and adjacent to one another in the receiving space, the housing wall and the connecting body being firmly connected to one another by the welded joint.

[0005] In a comparable hydraulic accumulator construction described in patent document 3 (DE 102021000139 A1), the accumulator housing further has a fluid connection point, which has a connecting body that opens into an adjacent medium chamber of the housing and has a fluid passage point, which connecting body is firmly connected to the accumulator housing via a welded joint, and which connecting body has an annular outer circumferential surface in its connection area facing the accumulator housing, which annular outer circumferential surface forms a transition point along which the welded joint extends when the connecting body is arranged on the end face of the accumulator housing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent No. 102009049547 [Patent Document 2] German Patent Application Publication No. 102015012357 [Patent Document 3] German Patent Application Publication No. 102021000139 Summary of the Invention [Problem to be solved by the invention]

[0007] Based on the above, the object of the present invention is to further improve upon the relevant prior art while realizing its advantages, namely a reliable connection between a connector for connecting a hydraulic accumulator to a fluid system, in particular a hydraulic system, and the accumulator of the associated hydraulic accumulator, so that a large number of hydraulic accumulators comprising an accumulator housing and a connector can be produced in a particularly cost-effective and functionally reliable manner. [Means for solving the problem]

[0008] The above object is achieved by a method having all the features of claim 1 and in particular by a hydraulic accumulator having the features of claim 5, which is manufactured by a corresponding method.

[0009] A method of manufacturing at least part of a hydraulic accumulator according to the present invention comprises the steps of: providing an accumulator housing portion having at least one fluid connection point; providing a connector comprising a fluid passageway having a material deposit portion on one free end surface thereof; positioning the material deposit relative to the accumulator housing portion such that the at least one fluid connection point in the accumulator housing portion is in fluid communication with the fluid passage of the connection body; fusing the material deposit by a welding process; joining the connecting body and the accumulator housing part with a predetermined pressing force and along a predetermined path; and allowing the weld joint to cool.

[0010] By melting the material deposit, which is preferably an integral part of the connecting body, the welding process can be carried out without additional filler metal, so that a particularly homogeneous weld joint is produced between the accumulator housing part and the connecting body. The high contact pressure when joining the connecting body and the accumulator housing part results in a very strong joint between the components, which can also withstand greater stresses in subsequent practical operation.

[0011] The welding process used is particularly preferably resistance welding, in particular resistance projection welding. In technical terms, resistance projection welding, also known for short as projection welding, is a variant of resistance welding. The weld joint is created by applying an electric current to the parts to be joined, in the form of an accumulator housing part with the associated connections, and a pressing force applied to the workpieces to be joined by using a large-area electrode.

[0012] The material deposit on the free end face of the connecting body can be divided into individual joint sections and function as protrusions. Energy input, i.e., current concentration at the welding point, is then achieved through the material deposit, which melts during this process. Therefore, during the actual welding process, the molten material deposit is primarily reshaped by the electrode force between the accumulator housing part and the connecting body and heating due to the current flow. This reshaping is often incomplete; the protrusions are reshaped during welding, subsequently forming a weld joint in the form of a regular flat nugget, which in this particular case has a central passage for fluid. In principle, the reshaped material deposited before the welding process can additionally or alternatively be placed on the accumulator housing part opposite the connecting body to be welded. However, for the projection welding itself, it is advantageous to provide the material deposit on the connecting body, which can then be applied in a particularly simple manner to the accumulator housing part designed as a cathode using a contact anode.

[0013] The separating element, usually in the form of a separating membrane, can then be inserted into the dome-shaped accumulator housing section with the welded connecting members by means of a holder. Next, another dome-shaped accumulator housing section is welded to one accumulator housing section to form the hydraulic accumulator. The hydraulic accumulator can be manufactured using various welding processes, particularly laser welding processes that do not require additional filler metal. In this way, the interior of the accumulator housing of the hydraulic accumulator can be manufactured at various manufacturing locations. After the separating element is inserted by the holding device, the welded pre-assembled part consisting of the accumulator housing section and the welded connecting members can be completed in a further welding process step to form the entire hydraulic accumulator. This can be closed on its further medium side, particularly the gas side, with a sealing plug or sealing screw inserted into another fluid connection point of the accumulator housing. In this respect, it is also possible to fasten the connection not only to the liquid side of the accumulator housing but also to its gas side by means of a corresponding deposit or projection of material by projection welding, whereby the further connection on the gas side represents a closure, which can however be provided with, for example, a refilling device for the gas.

[0014] The present invention also relates to a hydraulic accumulator, in particular a hydraulic accumulator manufactured by a method according to one of the preceding claims, comprising an accumulator housing and a separating element arranged therein, separating two medium chambers from each other, the accumulator housing having at least one fluid connection point opening into an adjacent medium chamber and a connecting body with a fluid passage, the connecting body being rigidly connected to the accumulator housing by a welded joint so that the fluid connection point of the accumulator housing is in fluid communication with the fluid passage of the connecting body, in which the welded joint between the accumulator housing part and the connecting body is formed from a reshaped material deposit of the connecting body, forming a so-called nugget with a through opening as part of the fluid connection, in particular the material deposit being part of the connecting body before its reshaping as a so-called protrusion. The electrical contact resistance and material or substance resistance of the associated joining partners, including the configuration of one accumulator housing part and the associated connecting body, significantly contribute to the formation of a weld nugget with a fluid passage. The contact resistance between these joining partners is essentially influenced by the projection shape, the pressing force applied by at least one of the electrodes, and the surface condition of the accumulator housing part and the connecting body. The weld nugget itself is surrounded by a heat-affected zone, whereby the material structure of each joining partner within said heat-affected zone is particularly homogenized and altered by the heat influence. The setting parameters for creating a suitable weld nugget are ultimately the welding current, welding current time, and applied electrode force.

[0015] In a preferred embodiment of the hydraulic accumulator according to the invention, the material deposit is formed by an annular protrusion that surrounds the fluid passage on the connecting body and is an integral part of the connecting body. Preferably, the annular material deposit has a triangular cross section, with an opening angle at the apex of the triangle between 70° and 110°, preferably between 80° and 100°, and particularly preferably about 90°. The geometric triangular shape of the protrusion, particularly in terms of material thickness and strength, has been shown to be particularly suitable for ensuring good force introduction as well as optimized reshaping for material deposition in the direction of production of the weld nugget between the joining partners.

[0016] It is also advantageous if the material deposits on the outer and / or inner periphery merge into an interface perpendicular to the longitudinal axis of the connecting body. The respective interface also provides support during the reshaping process, resulting in an improved weld connection. Alternatively, the interface on the outer periphery can merge into an inclined surface with a predetermined angle that is part of one of the free end faces of the connecting body. In this way, the reshaping can be safely supported before the actual welding process begins, preventing unacceptably high material deposits or protrusions from reshaping.

[0017] It is particularly preferred that the boundary surface on the inner circumference merges into the threaded region in a vertical extension parallel to the longitudinal axis of the connecting body, thereby serving to significantly facilitate connection of the hydraulic accumulator as a whole to a fluid or hydraulic system via an associated threaded mounting assembly.

[0018] A further advantage is that the weld / joint zone can be inspected using non-destructive testing methods such as ultrasound. The inside of the half-shell provides an ideal surface for irradiation, allowing pores and fusion defects to be detected.

[0019] In the following the solution according to the invention will be explained in more detail by means of an embodiment according to the drawings, which illustrate the principle and are not to scale. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 shows the necessary joining partners for producing a welded joint in the form of an accumulator housing part and a connection. [Figure 2] FIG. 2 shows a variant of the connector according to FIG. [Figure 3] FIG. 3 is a basic illustration showing, from the outside, the attachment of the connector to the accumulator housing using a welding electrode and the welded joint between the accumulator housing and the connector. [Figure 4] FIG. 4 is a basic illustration showing, from the outside, the attachment of the connector to the accumulator housing using a welding electrode and the welded joint between the accumulator housing and the connector. [Figure 5] FIG. 5 shows a longitudinal section through a hydraulic accumulator such as that shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] The hydraulic accumulator shown in longitudinal section in Figure 5 is a so-called diaphragm accumulator, comprising a separating element 12 in the form of a membrane (diaphragm) made of elastomeric material arranged in an accumulator housing generally designated by the reference numeral 10. This membrane separates the interior of the housing 10 into a medium chamber 14 in the form of a fluid chamber for storing a liquid, in particular in the form of a hydraulic oil, and a further medium chamber 16 in the form of a gas chamber for storing a working gas, in particular in the form of nitrogen gas.

[0022] 5, the housing 10 comprises an upper accumulator housing portion 18 and a lower accumulator housing portion 20, each of which has a circular shell or dome shape with a central axis 22 corresponding to the longitudinal axis of the hydraulic accumulator. The upper accumulator housing portion 18 has a flatter (shallower) shell shape than the lower accumulator housing portion 20. At the end of the accumulator housing 10 opposite the fluid chamber 14, i.e., the end associated with the gas chamber 16, the upper accumulator housing portion 18 has an upper fluid connection point 24 concentric with the central axis 22, which can be closed by a plug or by solder 26 after the gas chamber 16 has been filled. On the lower accumulator housing part 20, a lower fluid connection point 28 is provided concentrically on the central axis 22, to which a lower connector 30 is attached as an oil connection, via which the accumulator can be connected in the usual way to a hydraulic system (not shown).

[0023] The upper accumulator housing part 18 and the lower accumulator housing part 20 each have a central upper fluid channel 32 and a lower fluid channel 34 that extend centrally along the longitudinal axis 22 through an accumulator housing wall 36 of the upper accumulator housing part 18 and open into the gas chamber 16, or that start from the lower fluid connection point 28 and extend centrally through the accumulator housing wall 38 of the lower accumulator housing part 20 and open into the fluid chamber 14. The respective channels 32, 34 are part of the upper fluid connection point 24 or the lower fluid connection point 28. The housing wall 36 of the upper accumulator housing part 18 extends from a constant outer diameter away from the lower accumulator housing part 20 and curves outward toward the longitudinal axis 22 of the hydraulic accumulator to the central upper fluid channel 32. In contrast, starting from a constant outer diameter, the housing wall 38 of the lower accumulator housing part 20 is first curved outward, away from the upper accumulator housing part 18, towards the longitudinal axis 22 of the hydraulic accumulator, and then merges into a plate 40 shaped like a disk, with flat sides and a lower fluid channel 34 extending through the center as the lower fluid connection point 28.

[0024] The upper and lower accumulator housing parts 18, 20, which abut each other along a weld 42, are connected to each other by a laser or electron beam welding process, and in order to protect the interior of the accumulator housing 10 from weld spatter and / or heat input during welding, the upper accumulator housing part 18 is provided with a downwardly projecting annular rim 44 on its inner periphery that protectively covers the weld 42 inwardly as a rim protrusion once the two housing parts 18, 20 are placed against each other.

[0025] Below and adjacent to the annular rim 44 is a holder, generally designated 46, which has a retaining ring 48 with an annular receptacle 49 for receiving a thickened circumferential rim bead 50 of the membrane-like separation element 12. The rim bead 50 is in turn supported on its outer periphery in a groove-shaped receptacle 52 or depression in the inner wall of the lower accumulator housing wall 38, so that the receptacle 52, together with the annular receptacle 49 in the retaining ring 48, forms a seat for the thickened rim bead 50. If the retaining ring 48 is formed from a metal sheet, the inherent elasticity of the retaining ring 48 can be used to secure the rim bead 50, and thus the separation element 12, to the lower accumulator housing wall 38.

[0026] Furthermore, the separation element 12 as a separation membrane has a solid valve body 54 which can cover the rim 56 of the inlet of the lower fluid connection point 28, forming a kind of valve seat, if the valve body 54 comes into contact with said rim 56 in the lowest deflection position of the separation element 12. As shown in particular in Figures 3 and 4, the connection body 30 can have an engagement surface 58 for engagement with an operating tool, for example in the form of a conventional hexagonal wrench, to improve the assembly of the hydraulic accumulator into the hydraulic system. As shown in particular in Figures 1, 2 and 5, the connection body 30 is rigidly connected to the accumulator housing 10 and further has a fluid passage 60 extending concentrically with the longitudinal axis 22 of the hydraulic accumulator. In particular, the free cross-section of the fluid passage 60 is larger than the channel diameter for the lower fluid connection point 28. As can be further seen from Figures 1 and 2, the fluid passage 60 is at least partially provided with a conventional internal thread as threaded region 62, by means of which the hydraulic accumulator according to Figure 5 can be screwed into a connection of a hydraulic system. Such a connection between a hydraulic accumulator and a hydraulic system is common practice and will not be discussed in further detail here. Starting from the usual structure of the hydraulic accumulator according to Figure 5, the manufacturing method according to the invention will now be described in more detail with reference to Figures 1 to 4. In this document, components previously described and used are provided with the same reference numerals as in Figure 5, and the wording made in this regard also applies to the description of the method sequence based on Figures 1 to 4.

[0027] In the manufacturing method according to the invention, the lower accumulator housing part 20 is first connected to the connecting body 30, which is shown in more detail in FIG. 1. First, the lower accumulator housing part 20 is provided with a lower fluid connection point 28. Furthermore, the connecting body 30 is provided with its fluid passage 60, which has a material deposit 64, also technically called a protrusion, on one free upper end face thereof. In a further method step, the material deposit 64 of the connecting body 30 is then fixed to the lower accumulator housing part 20 in such a way that the fluid connection point 28 in the accumulator housing part 20 is fluidly connected with the fluid passage 60 of the connecting body 30 and that both the fluid connection point 28 and the fluid passage 60 of the connecting body 30 are arranged concentrically with the longitudinal axis 22 of the hydraulic accumulator.

[0028] The material deposit 64 is then melted by a special welding process, which will be explained in more detail. However, a basic prerequisite for welding is the joining of the connecting body 30 and the lower accumulator housing part 28 under a predetermined contact pressure, which, according to the illustration in Fig. 3, is preferably exerted by a vertically movable electrode in the form of an anode 66, which is only partially shown in Fig. 3 and which merges into a flat contact surface 80, which at its upper end or upper free end face can be brought into flat contact with the lower surface of the connecting body 30. The weld joint 70 produced in this way is then cooled, as shown in Figs. 3 and 5, as a result of which a solid connection is formed between the accumulator housing part 20 and the connecting body 30.

[0029] According to the present invention, the welding process used is so-called resistance pressure welding, in particular resistance projection welding. During resistance projection welding, as already explained, the connecting body 30 is pressed by the anode 66 with a predetermined pressure force against the accumulator housing part 18 as the cathode 72. When a voltage or current is applied to both the anode 66 and the cathode 72, the material deposit 64 melts due to the associated contact resistance when the connecting body 30 is applied. Due to the pressure via the anode 66, the material deposit 64 is reshaped until an annular weld nugget 74 is obtained, thereby forming the actual weld joint 70 between the accumulator housing part 20 and the connecting body 30 after cooling. The weld nugget 74 in the form of a circular ring has a through opening 76 that, with optimal welding, corresponds to the inner diameter of the fluid passage 60 of the connecting body 30, as is particularly clear from the illustration in FIG. 5.

[0030] As shown in FIG. 1 , the material deposit 64 is formed from an annular protrusion that surrounds the fluid passage 60 on the connecting body 30 and is an integral part of the connecting body 30. Furthermore, the annular material deposit 64 is triangular in cross section, with two adjacent legs of the triangle defining an opening angle α at their vertices, which is approximately 80°. Furthermore, in the solution according to FIG. 1 , when viewed in cross section, the triangular material deposit 64 merges on both the outer and inner sides into boundary surfaces 78, 80 that are perpendicular to the longitudinal axis 22. In this way, the annular boundary surfaces 78, 80 adjacent to the base of the material deposit 64 provide support for the base of the material deposit 64 during reshaping during the welding process. Furthermore, a further annular support surface 82 adjoins the outer boundary surface 78, which, when viewed from the orientation of FIG. 1 , has an inclination angle β of approximately 30° with respect to the horizontal. The corresponding support surface 82 also contributes to the favorable reshaping behavior of the material deposit 64 during the welding process. In turn, at the outer periphery, the support surface 82 meets the adjacent tool-engagement surface 58, and the inner interface 80 defines the thread region 62 of the connector 30 at the inner periphery. The inclined support surface 82 also allows for smooth material flow at the edge region of the triangular material deposit 64 as part of the reshaping during the welding process to obtain a geometrically optimally formed weld nugget 74. The two interface surfaces 78, 80 lie in a common plane.

[0031] The embodiment of the connecting body 30 according to Fig. 2 generally corresponds to the embodiment according to Fig. 1, except that the triangular material deposit 64 seen in cross section is smaller than the material deposit 64 according to Fig. 1. The reduced material deposit according to Fig. 2 may therefore be sufficient to create a permanent welded joint between the connecting body 30 and the accumulator housing part 20 during projection welding. Then, in a further manufacturing method step, the separation element 12 together with the holder 46 is inserted from above into the lower accumulator housing part 20, and the edge bead 50 of the separation element 12 is firmly clamped in the receptacle 52 of the lower accumulator housing part 20 by the retaining ring 48. Subsequently, the upper accumulator housing part 18 is placed in place, and a permanent connection between the two accumulator housing parts 18, 20 is made along the weld 42, as already described, e.g. by laser welding. The hydraulic accumulator thus completed can then be filled with a working gas, such as nitrogen gas, at a predetermined pressure through the upper fluid connection point 24 into its gas side or further chamber 16, which is then gas-sealed by a plug or solder 26.

[0032] In principle, it is also possible to arrange the connection 30 so that it is also presented on the gas side, i.e. the solder 26 can be omitted and the connection 30 is fixed in a similar manner to that presented by projection welding to the upper side of the upper accumulator housing part 18 in the edge region of the upper fluid connection point 24. For this purpose, a connection not shown can be used to refill the hydraulic accumulator with working gas as required and close the gas side, for example by inserting a threaded plug into the fluid passage 60 (not shown) of the connection 30.

[0033] In principle, it is also possible to fasten the gas valve to the gas side of the accumulator using the described resistance welding, which is particularly advantageous for accumulators that can be refilled on the gas side.When the term fluid is used above, it includes not only liquids such as hydraulic oils, but also gases such as nitrogen gas.

[0034] It should be emphasized at this point that the solution according to the invention does not have to be limited to hydraulic accumulators in the form of diaphragm accumulators, but rather can be used whenever a corresponding connection body with a fluid passage is to be fixed to the accumulator housing of a pressure accumulator with a corresponding fluid connection point.

Claims

1. 1. A method of manufacturing at least a portion of a hydraulic accumulator, comprising: The method comprises: providing an accumulator housing portion (20) having at least one fluid connection point (28); providing a connection body (30) having a fluid passageway (60) with a material deposit (64) on one free end face thereof; positioning the material deposit portion (64) relative to the accumulator housing portion (20) such that the at least one fluid connection point (28) in the accumulator housing portion (20) is in fluid communication with the fluid passage (60) of the connection body (30); fusing said material deposit (64) by a welding process; joining the connecting body (30) and the accumulator housing part (20) with a predetermined pressing force and along a predetermined path; and allowing the resulting weld joint (70) to cool.

2. 2. A method according to claim 1, characterized in that the welding process used is resistance welding, in particular resistance projection welding.

3. 3. The method according to claim 1, wherein during resistance projection welding, the predetermined pressing force of the connecting body (30) is applied by an anode (66) against the accumulator housing part (20) as a cathode (72).

4. a separating element (12) is inserted into the accumulator housing part (20) together with the connecting body (30) to be welded by means of a holder (46); 4. A method according to any one of claims 1 to 3, characterized in that a further accumulator housing part (18) is subsequently welded to the one accumulator housing part (20) to form the hydraulic accumulator.

5. A hydraulic accumulator, in particular manufactured by a method according to any one of claims 1 to 4, The hydraulic accumulator comprises an accumulator housing (10) and a separation element (12) arranged in the accumulator housing (10) that separates two medium chambers (14, 16) from each other, the accumulator housing (10) having at least one fluid connection point (28) opening into an adjacent medium chamber (14) and a connecting body (30) with a fluid passage (60), the connecting body (30) being rigidly connected to the accumulator housing (10) by a welded joint such that the fluid connection point (28) of the accumulator housing is in fluid communication with the fluid passage (60) of the connecting body (30), 1. A hydraulic accumulator comprising: a housing portion (20) and a connecting body (30) having a welded joint (70) formed from a reshaped material deposit (64) of the connecting body (30), the welded joint (70) being formed from a nugget (74) having a through opening (76) as part of a fluid connection.

6. 6. The hydraulic accumulator according to claim 5, wherein the material deposit (64) is formed from an annular protrusion that surrounds the fluid passage (60) on the connecting body (30) and is an integral part of the connecting body (30).

7. 7. A hydraulic accumulator according to claim 5 or 6, characterized in that the annular material deposit (64) has a triangular cross section and a tip opening angle (α) of 70° to 110°, preferably 80° to 100°, particularly preferably 90°.

8. 8. The hydraulic accumulator according to claim 5, wherein the material deposit portion (64) meets at an outer periphery and / or an inner periphery a boundary surface (78, 80) perpendicular to the longitudinal axis (22) of the connecting body (30).

9. 9. A hydraulic accumulator according to claim 8, characterized in that the outer boundary surface (78) meets, on the outer periphery, a support surface (82) which is part of the one free end face of the connecting body (30) at a predetermined angle (β).

10. 10. The hydraulic accumulator according to claim 8 or 9, characterized in that the inner peripheral boundary surface (80) merges into a threaded region (62) on a vertical extension when viewed in a direction parallel to the longitudinal axis (22) of the connecting body (30).

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