Method

Abstract

1. Method 2. The invention relates to a method for producing at least one part of a hydraulic accumulator, said method having at least the following method steps: - providing an accumulator housing part (20) that has at least one fluid connection point (28), - providing a connection element (30) with a fluid passage (60) that has a material agglomeration (64) on its one free end face, - placing the material agglomeration (64) against the accumulator housing part (20) such that the fluid connection (28) in the accumulator housing part (20) comes into fluidic connection with the fluid passage (60) of the connection element (30), - melting the material agglomeration (64) by means of a welding method, - joining the connection element (30) and accumulator housing part (20) under a predefinable pressing force and a predefinable path and - allowing the resulting weld connection to cool.

Description

[0001] HYDAC TECHNOLOGY GMBH

[0002] Industriestraße, 66280 Sulzbach / Saar, Germany

[0003] Proceedings

[0004] The invention relates to a method for producing at least part of a hydraulic accumulator and to a hydraulic accumulator produced in particular according to this method.

[0005] DE 10 2009 049 547 B3 discloses a method for producing a hydropneumatic pressure accumulator, including the method steps: providing a valve body with a projection located on the surface facing the valve seat,

[0006] Placing the valve body in an injection mold for forming a flexible membrane forming a movable separating element, and - injecting an elastomer forming the membrane in such a way that the valve body is incorporated into the elastomer while leaving the surface facing the valve seat free.

[0007] To complete the hydropneumatic pressure accumulator, the assembly is installed in an accumulator housing. The accumulator housing features a housing opening that provides access to the fluid chamber. Adjacent to this opening is a connecting body for connecting the accumulator to a conventional hydraulic system. For this purpose, the connecting body, with its fluid passage, is firmly connected to the accumulator housing via a circumferential fillet weld, in a coaxial arrangement with the housing opening in the accumulator housing.

[0008] From DE 10 2015 012 357 A1 a comparable hydraulic accumulator, in particular in the form of a diaphragm accumulator, is known, consisting of at least two housing parts of an accumulator housing, in which a separating element in the form of a separating diaphragm separates two media spaces from one another and with at least one media connection part which is connected to one housing part along a weld seam and which, as a connection body for connecting the hydraulic accumulator to a hydraulic system, engages at least partially in a receiving space which is formed in one housing part along a housing opening, wherein the wall surfaces of the housing and the connection body which are adjacent to one another in the receiving space and face one another are firmly connected to one another by means of the weld seam.

[0009] In a comparable hydraulic accumulator structure according to DE 10 2021 000 139 A1, the accumulator housing in turn has a fluid connection point which opens into an adjacent media chamber of the housing and which has a connecting body with a fluid passage point which is firmly connected to the accumulator housing via a weld seam, wherein the connecting body has an annular outer circumferential surface on its connection area facing the accumulator housing, which forms a transition point along which the weld seam runs when the connecting body is placed on the accumulator housing at the front.

[0010] Proceeding from this, the object of the invention is to further improve the relevant prior art while retaining its advantages, namely to achieve a secure connection between a connecting body for connecting a hydraulic accumulator to a fluid system, in particular a hydraulic system, and an accumulator housing of the relevant hydraulic accumulator, in such a way that large quantities of hydraulic accumulators with accumulator housings and connecting bodies can be reliably manufactured in a particularly cost-effective manner.

[0011] A corresponding object is achieved by a method having the features of patent claim 1 in its entirety and by a hydraulic accumulator, which is produced in particular by a corresponding method, having the features of patent claim 5.

[0012] The method according to the invention for producing at least part of a hydraulic accumulator is characterized by the following method steps:

[0013] Providing a storage housing part having at least one fluid connection point,

[0014] Providing a connecting body with a fluid passage which has a material accumulation on its one free end face,

[0015] - Applying the material accumulation to the storage housing part in such a way that the fluid connection point in the storage housing part comes into fluid connection with the fluid passage of the connection body,

[0016] Melting the accumulation of material by means of a welding process, joining the connecting body and the storage housing part under a predeterminable contact force and a predeterminable path, and allowing the welded joint to cool.

[0017] By melting the material accumulation, which is preferably an integral part of the connecting body, the welding process can be carried out without additional welding materials, creating a particularly homogeneous weld between the storage housing part and the connecting body. The high contact force when joining the connecting body and the storage housing part also creates a very strong connection between the components, which can reliably withstand even greater stresses during later practical operation. Resistance pressure welding, in particular resistance projection welding, is particularly preferred as the welding process. The latter welding process is also referred to as projection welding in technical terms and is a variant of resistance pressure welding.The welded joint is created by introducing electrical current into the components to be joined in the form of the storage housing part together with the associated connecting body and the contact pressure that is applied to the workpieces to be joined by using large-area electrodes.

[0018] The accumulation of material on the free end face of the connection body, which can also be divided into individual joining parts, appears as a projection. The energy input, i.e. the current concentration at the welding point, is then achieved via this accumulation of material, which melts in the process. During the actual welding process, the molten accumulation of material is therefore largely reshaped by the electrode force and the heating resulting from the current flow between the storage housing part and the connection body. However, this reshaping is often not complete, and the projection reshaped during welding then regularly forms a weld joint in the shape of a flat lens, which in this specific case has a central passage for fluid. In principle, the reshaped accumulation of material could additionally or alternatively be arranged on the storage housing part opposite the connection body to be welded before the welding process.For projection welding itself, however, it is advantageous to provide the material accumulation on the connecting body, which can then be applied in a particularly simple manner to the storage housing part designed as a cathode by means of a contact anode.

[0019] A separating element, usually in the form of a separating membrane, can then be inserted into the dome-shaped accumulator housing part with the welded-on connecting body by means of a holder, and then another dome-shaped accumulator housing part is welded to the one accumulator housing part to form the hydraulic accumulator, for which various welding processes can be used, in particular a laser welding process that does not require additional welding material.In this way, the interior of the accumulator housing of the hydraulic accumulator can be manufactured at various manufacturing locations and the pre-welded semi-finished product, consisting of the accumulator housing part and the welded-on connection body, can be completed in a further welding process step after inserting the separating element using the holding device to form the entire hydraulic accumulator, which can be closed on its further media side, in particular the gas side, with a sealing plug or a sealing screw that is inserted into another fluid connection point of the accumulator housing.In this respect, it is also possible to fix the said connecting body not only on the liquid side of the storage housing, but also on its gas side with a corresponding material accumulation or projection by means of projection welding, whereby the further connecting body on the gas side then represents a closure body, which can, however, for example, be provided with a refilling device for gas.

[0020] The invention further relates to a hydraulic accumulator, in particular manufactured using a method according to one of the preceding claims, having an accumulator housing and a separating element arranged therein, which separates two media spaces from one another, wherein the accumulator housing has at least one fluid connection point that opens into an adjacent media space and having a connecting body with a fluid passage that is firmly connected to the accumulator housing by means of a welded connection such that the fluid connection point of the accumulator housing is in fluid communication with the fluid passage of the connecting body, wherein the welded connection between the accumulator housing part and the connecting body is formed from a reshaped material accumulation that forms a type of lens with a through-opening as part of the fluid connection. In particular, the mentioned material accumulation is part of the connecting body before its reshaping as a so-called hump.The electrical contact resistance and the material or substance resistance of the joining partners involved, here in the form of one storage housing part and the associated connecting body, contribute significantly to the formation of the weld nugget, which has a fluid passage. The contact resistance mentioned between these joining partners is essentially influenced by the projection geometry, the contact force via at least one of the electrodes, and the surface condition of the storage housing part and connecting body. The weld nugget itself is surrounded by a heat-affected zone, whereby the material structure of the respective joining partner is changed, in particular homogenized, by the effect of heat in this heat-affected zone. The setting parameters for creating the appropriate weld nugget are ultimately the welding current, the welding current time, and the applied electrode force.

[0021] In a preferred embodiment of the hydraulic accumulator according to the invention, the material accumulation is formed from an annular boss which encloses the fluid passage on the connecting body and which is an integral part of the connecting body. The annular material accumulation is preferably triangular in cross-section, and an opening angle of between 70° and 110°, preferably between 80° and 100°, and particularly preferably approximately 90°, is created at the tip of the triangle. It has been shown that the geometric triangular shape for the boss is particularly suitable, in particular with regard to material thickness and material strength, for ensuring good force introduction and optimized recovery for the material accumulation in the direction of production of the weld nugget between the said joining partners.

[0022] It is also advantageous if the material accumulation on the outer and / or inner circumference merges into a boundary surface that is perpendicular to the longitudinal axis of the connecting body. This boundary surface also provides additional support during the reshaping process, resulting in improved weld seam bonding. Alternatively, it is also possible to have the boundary surface on the outer circumference merge at a predefined angle into an inclined surface that is part of one of the free end faces of the connecting body. This also reliably supports the reshaping process, preventing an unacceptably high reshaping of the material accumulation or projection before the actual welding process begins.

[0023] It is particularly preferred that the boundary surface on the inner circumference, viewed in a vertical extension parallel to the longitudinal axis of the connecting body, merges into a threaded region of the same, which helps to significantly facilitate the connection of the hydraulic accumulator as a whole to a fluid or hydraulic system via an associated threaded connection.

[0024] A further advantage is that the weld seam / joining zone can be inspected using non-destructive testing methods, such as ultrasound. The inside of the half-shell provides an ideal surface for irradiation. This makes it possible to detect pores or fusion defects in the joining zone. The solution according to the invention is explained in more detail below using an exemplary embodiment according to the drawing. In this case, the

[0025] Figure 1 shows the essential joining partners for producing a

[0026] Welded connection in the form of a storage housing part and a connecting body;

[0027] Figure 2 shows a modified embodiment of a connecting body according to Figure 1;

[0028] Figures 3 and 4, viewed from the outside, show for a basic explanation the attachment of a connecting body to a storage housing using a welding electrode and the welded connection between the storage housing and the connecting body; and

[0029] Figure 5 shows a longitudinal section through the hydraulic accumulator as shown in Figure 4.

[0030] The hydraulic accumulator shown in Figure 5 in longitudinal section is a so-called diaphragm accumulator with a separating element 12 in the form of a diaphragm made of elastomer material arranged in an accumulator housing, designated as a whole by 10. This diaphragm divides the housing 10 into a media space 14 in the form of a fluid space for storing a liquid, in particular in the form of hydraulic oil, and a further media space 16 in the form of a gas space for storing a working gas, in particular in the form of nitrogen gas.

[0031] As viewed in the direction of Figure 5, the housing 10 consists of an upper accumulator housing part 18 and a lower accumulator housing part 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 part 18 has a flatter shell shape than the lower accumulator housing part 20. At the end of the accumulator housing 10 opposite the fluid chamber 14, i.e., at the end associated with the gas chamber 16, the upper accumulator housing part 18 has an upper fluid connection point 24 concentric with the axis 22, which can be closed by means of a plug or solder 26 after the gas chamber 16 has been filled.On the lower accumulator housing part 20, a lower fluid connection point 26 is provided concentrically to the axis 22, at which a lower connection body 30 is attached as an oil connection, via which the accumulator can be connected to a hydraulic system (not shown) in the usual way.

[0032] The upper 18 and the lower 20 accumulator housing part have a central upper 32 and lower 34 fluid channel, which each extends centrally along the longitudinal axis 22 through an accumulator housing wall 36 of the upper accumulator housing part 18 and opens into the gas chamber 16, or starting from the lower fluid connection point 28, extends centrally through an accumulator housing wall 38 of the lower accumulator housing part 20 and opens into the fluid chamber 14. The respective channel 32, 34 is part of the upper 24 and the lower 28 fluid connection point. 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 outwards towards the longitudinal axis 22 of the hydraulic accumulator up 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 initially extends away from the upper accumulator housing part 18 and curves outwards towards the longitudinal axis 22 of the hydraulic accumulator, then transitions into a disk-shaped plate 40 that is flat on both sides and through which the lower fluid channel 34 extends centrally as the lower fluid connection point 28. The upper 18 and lower 20 accumulator housing parts, which abut one another along a weld seam 42, are connected to one another by means of a laser or electron beam welding process. In order to protect the interior of the accumulator housing 10 from welding spatter and / or heat input during welding, the upper accumulator housing part 18 is provided on its inner circumference with a downwardly projecting annular edge 44 that protectively covers the weld seam 42 inwards as an edge projection as soon as the two housing parts 18, 20 are placed against one another.

[0033] Provided beneath and adjacent to the annular rim 44 is a holder designated as a whole by 46, which has a securing ring 48 with a ring receptacle 49 for receiving a thickened, circumferential edge bead 50 of the membrane-like separating element 12. Furthermore, the edge bead 50 is supported on the outer circumference in a groove-shaped receptacle 52 or notch on the inner wall of the lower storage housing wall 38, so that the receptacle 52, together with the annular receptacle 49 in the securing ring 48, form a seat for the thickened edge bead 50. If the securing ring 48 is formed from a metallic sheet metal part, the inherent elasticity of the securing ring 48 can prestress the edge bead 50 and thus the separating element 12 to the lower storage housing wall 38.

[0034] Furthermore, the separating element 12 has a solid valve body 54 as a separating membrane, which can cover an edge 56 of the opening of the lower fluid connection point 28, forming a type of valve seat, provided that the valve body 54 comes into contact with the aforementioned edge 56 in the lowest deflected position of the separating element 12. The connecting body 30 can, as shown in particular in Figures 3 and 4, have engagement surfaces 58 for engagement with an actuating tool, for example in the form of a conventional hexagon wrench, for improved assembly of the hydraulic accumulator to a hydraulic system. As shown in particular in Figures 1, 2 and 5, the connecting body 30 also has a fluid passage 60 which runs concentrically to the longitudinal axis 22 of the hydraulic accumulator, provided that the connecting body 30 is firmly connected to the accumulator housing 10.In particular, the free cross-section of the fluid passage 60 is dimensioned larger than the channel diameter for the lower fluid connection point 28. As can further be seen from Figures 1 and 2, the fluid passage 60 is at least partially provided with a conventional internal thread as a threaded area 62, which enables the hydraulic accumulator according to Figure 5 to be screwed onto connecting parts of the hydraulic system. Such a connection between the hydraulic accumulator and the hydraulic system is common, so it will not be discussed in more detail here. Starting from the conventional design of a hydraulic accumulator according to Figure 5, the manufacturing method according to the invention will now be explained in more detail with reference to Figures 1 to 4, wherein the components described so far and used are provided with the same reference numerals as in Figure 5, and the statements made in this regard also apply to the process sequence description according to Figures 1 to 4.

[0035] In the manufacturing method according to the invention, the lower accumulator housing part 20 is first connected to the connecting body 30, as shown in more detail in Figure 1. First, the lower accumulator housing part 20 is provided, which has the lower fluid connection point 28. Furthermore, the connecting body 30 is provided with its fluid passage 60, which has a material accumulation 64 on its one free, upper end face, which is also referred to in technical terms as a hump. In a further method step, the material accumulation 64 of the connecting body 30 is then fixed to the lower accumulator housing part 20 such that the fluid connection point 28 in the accumulator housing part 20 is in fluid communication with the fluid passage 60 of the connecting body 30, with both the fluid connection point 28 and the fluid passage 60 of the connecting body 30 being arranged concentrically with the longitudinal axis 22 of the hydraulic accumulator.

[0036] The material accumulation 64 is then melted using a special welding process, which will be explained in more detail below. The basic prerequisite for welding, however, is the joining of the connecting body 30 and the lower storage housing part 28 under a predeterminable contact force, which, as shown in Figure 3, is preferably applied by a vertically movable electrode in the form of an anode 66, which is only partially shown in Figure 3 and which, at its upper end or at its upper free end, merges into a flat contact surface 80, which can be brought into flat contact with the underside of the connecting body 30. The welded connection 70 thus produced, as shown in Figures 3 and 5, is then allowed to cool, with the result that a firm connection is created between the storage housing part 20 and the connecting body 30.

[0037] According to the invention, so-called resistance pressure welding, in particular resistance projection welding, is used as the welding method. In resistance projection welding, as already explained, the connecting body 30 is pressed against the storage housing part 18 as the cathode 72 by means of the anode 66 with a predeterminable contact force. Upon appropriate application of an electrical voltage or current to both the anode 66 and the cathode 72, the material accumulation 60 is melted on the underside of the storage housing part 20 due to the associated contact resistance when the connecting body 30 is applied. Due to the contact force via the anode 66, the material accumulation 64 is reformed until an annular weld nugget 74 is obtained, which creates the actual welded connection 70 between the storage housing part 20 and the connecting body 30 after it has cooled.The welding lens 74 has a through-opening 76 in the form of a circular ring, which, with optimal welding, corresponds to the inner diameter of the fluid passage 60 of the connecting body 30, which is particularly evident from the illustration in Figure 5.

[0038] As Figure 1 shows, the material accumulation 64 is formed from an annular boss that encloses the fluid passage 60 on the connecting body 30 and is a one-piece component of the connecting body 30. Furthermore, the annular material accumulation 64 is triangular in cross-section, and the two adjacent triangular legs define an opening angle a of approximately 80° at their apex. Furthermore, in the solution according to Figure 1, the material accumulation 64, which is triangular in cross-section, merges on both the outer and inner circumferences into a boundary surface 78, 80, which is perpendicular to the longitudinal axis 22. In this way, the annular boundary surfaces 78, 80, which adjoin the base of the material accumulation 64, provide support during reshaping during the welding process.Furthermore, the outer peripheral boundary surface 78 is adjoined by a further annular support surface 82 which, as viewed in the direction of Figure 1, has an inclination angle β of approximately 30° relative to the horizontal. This support surface 82 also contributes to favorable recovery behavior of the material accumulation 64 during the welding process. On the outer peripheral side, the support surface 82 then merges into the adjacent tool engagement surfaces 58, and on the inner peripheral side, the inner boundary surface 80 delimits the threaded area 62 of the connecting body 30. The inclined support surface 82 also allows trouble-free flow of material in the edge area of ​​the triangular material accumulation 64 during recovery during the welding process, in order to thus obtain a geometrically optimally formed weld nugget 74. The two boundary surfaces 78, 80 lie in a common plane.The embodiment of a connecting body 30 according to Figure 2 largely corresponds to the embodiment according to Figure 1, with the proviso that the triangular material accumulation 64, seen in cross-section, is smaller than the material accumulation 64 according to Figure 1. Thus, the reduced material accumulation according to Figure 2 can be sufficient to be able to produce a strong welded connection between the connecting body 30 and the storage housing part 20 during projection welding. In a further manufacturing process step, the separating element 12, together with the holder 46, is then introduced from above into the lower storage housing part 20, and the edge bead 50 of the separating element 12 is clamped in the receptacle 52 of the lower storage housing part 20 by means of the fixing ring 48.Subsequently, the upper accumulator housing part 18 is placed on top, and a fixed connection between the two accumulator housing parts 18, 20 is created along the weld seam 42, as already described, by means of laser welding or the like. The thus completed hydraulic accumulator can then be filled on its gas side, or the additional media chamber 16, with a working gas, such as nitrogen gas, via the upper fluid connection point 24 at a predeterminable pressure, which is then sealed gas-tight by a plug or the solder 26.

[0039] In principle, it is possible to arrange a connecting body 30 on the gas side as presented, i.e. the solder 26 can be omitted and the connecting body 30 is fixed in a similar way to the presentation by projection welding on the top side of the upper accumulator housing part 18 in the edge area of ​​the upper fluid connection point 24. Using a connecting body (not shown), the hydraulic accumulator can also be refilled with working gas if necessary and the gas side can be closed, for example by inserting a screw-in plug into the fluid passage 60 of the connecting body 30 (not shown). In principle, it is also possible to fix a gas valve on the gas side of the accumulator using the resistance welding described, which is particularly advantageous for accumulators that can be refilled on the gas side.When the term fluid is mentioned above, this includes not only liquids such as hydraulic oil, but also gases such as nitrogen gas.

[0040] It should be emphasized at this point that the solution according to the invention does not need to be restricted to hydraulic accumulators in the form of diaphragm accumulators, but rather can always be used when corresponding connecting bodies with fluid passage are to be fixed to accumulator housings of pressure accumulators that have corresponding fluid connection points.

Claims

Patent claims Method for producing at least part of a hydraulic accumulator with at least the following method steps: Providing a storage housing part (20) having at least one fluid connection point (28), Providing a connecting body (30) with a fluid passage (60) which has a material accumulation (64) on its one free end face, - applying the material accumulation (64) to the storage housing part (20) such that the fluid connection point (28) in the storage housing part (20) comes into fluid connection with the fluid passage (60) of the connection body (30), Melting the material accumulation (64) by means of a welding process, Joining the connecting body (30) and the storage housing part (20) under a predeterminable contact force and a predeterminable path and Allowing the resulting welded joint (70) to cool. The method according to claim 1, characterized in that resistance pressure welding, in particular resistance projection welding, is used as the welding method. The method according to claim 1 or 2, characterized in that, during the resistance projection welding, the connecting body (30) is applied by means of an anode (66) against the storage housing part (20) as a cathode (72) with the predeterminable contact force. Method according to one of the preceding claims, characterized in that a separating element (12) is inserted into the accumulator housing part (20) with the welded connecting body (30) by means of a holder (46), and that subsequently a further accumulator housing part (18) is welded to the one accumulator housing part (20) to form the hydraulic accumulator. Hydraulic accumulator, in particular produced by a method according to one of the preceding claims, with an accumulator housing (10) and a separating element (12) arranged therein, which separates two media spaces (14, 16) from each other, wherein the accumulator housing (10) has at least one fluid connection point (28) which opens into an adjacent media space (14), and with a connecting body (30) with a fluid passage (60) which is firmly connected to the accumulator housing (10) by means of a welded connection such that the fluid connection point (28) of the accumulator housing (10) is in fluid communication with the fluid passage (60) of the connecting body (30), characterized in that the welded connection (70) between the accumulator housing part (20) and the connecting body (30) is formed from a reshaped material accumulation (64) of the connecting body (30), which forms a lens (74) with a through-opening (76) as part of the fluid connection. Hydraulic accumulator according to claim 5, characterized in that the material accumulation (64) is formed from an annular boss which surrounds the fluid passage (60) on the connecting body (30) and which is an integral part of the connecting body (30). Hydraulic accumulator according to claim 5 or 6, characterized in that the annular material accumulation (64) seen in cross-section is triangular and has an opening angle (θ) at the tip of 70° to 110°, preferably of 80° to 100°, particularly preferably of 90°.

8. Hydraulic accumulator according to one of claims 5 to 7, characterized in that the material accumulation (64) merges on the outer and / or inner circumference into a boundary surface (78, 80) which is perpendicular to the longitudinal axis (22) of the connecting body (30).

9. Hydraulic accumulator according to claim 8, characterized in that the outer boundary surface (75) merges on the outer circumference at a predeterminable angle (β) into a support surface (82) which is part of one free end face of the connecting body (30).

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

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