Damping cylinder assembly

Abstract

The invention relates to a damping cylinder assembly, comprising a hydraulic cylinder (10) and a damping accumulator (20), wherein: the hydraulic cylinder comprises a cylinder pipe (30), a guide closure part (40), a base closure part (50) and a piston unit (60); the cylinder pipe (30) comprises a guide-side cylinder pipe end (31) and a base-side cylinder pipe end (32); the guide closure part (40) is located on the guide-side cylinder pipe end (31); the base closure part (50) comprises a cylinder pipe receiving portion (51), a damping accumulator receiving portion (52) and a fluid channel (53), which connects the cylinder pipe receiving portion (51) and the damping accumulator receiving portion (52); the cylinder pipe (30) is located with the base-side cylinder pipe end (32) on the cylinder pipe receiving portion (51); the piston unit (60) slidingly passes through the guide closure part (40) and, together with the cylinder pipe (30) and the base closure part (50), forms a working space which is connected to the fluid channel (53); the damping accumulator (20) comprises a pressure capsule and, accommodated thereby, a fluid chamber and pressure-deformable air chamber that is membrane-separated from the fluid chamber, as well as a damping accumulator fluid connection (21) which is located on the base closure part (50); and the damping fluid connection (21) is connected to the fluid channel (53).

Description

[0001] Damping cylinder assembly

[0002] The invention relates to a damping cylinder assembly, in particular for demanding applications with high dynamic loads, such as in agricultural machinery.

[0003] According to the state of the art, it is known, for example, in agricultural machinery for soil cultivation, to provide damping devices that use heavy compression springs. This solution is disadvantageous due to the low absorbable force and the poor characteristic curve.

[0004] Hydraulic damping cylinders have proven to be more advantageous in the state of the art. This is particularly true when equipped with a diaphragm or bladder accumulator. The high dynamic loads and the resulting pressure peaks are problematic, requiring particularly strong couplings. A disadvantage is the complex manufacturing process required for this, as extensive machining is required to produce the damping cylinder, and the high thermal stresses associated with MAG welding, for example, can adversely affect quality and service life and require high energy consumption. Furthermore, cleaning the cylinder interior after MAG welding is disadvantageous. Therefore, it is known in the state of the art to alternatively couple the guide closure part by means of a screw connection.

[0005] The object of the invention is to provide a damping cylinder assembly that can be manufactured in a resource-saving manner, with high quality and with little time expenditure.

[0006] The problem is solved by the features listed in claim 1. Preferred developments emerge from the subclaims. The damping cylinder assembly according to the invention has a hydraulic cylinder and a damping accumulator as basic components. The hydraulic cylinder acts as a pressure flow generator during an inward movement and as a pressure flow consumer during an outward movement. During the inward movement, which is caused by a force introduced by a coupled device component and is intended to be damped, a fluid flow is generated and the fluid is pressed into the damping cylinder and absorbed there. Conversely, during an outward movement, the fluid is pressure-based and guided out of the damping accumulator and absorbed by the hydraulic cylinder. In at least one direction of movement of the fluid, the fluid flow is throttled, thus resulting in damping.The hydraulic cylinder and the damping accumulator are also referred to below as the hydraulic units.

[0007] The hydraulic cylinder has a cylinder tube, a guide closure part, a bottom closure part and a piston unit.

[0008] The cylinder tube has a guide-side cylinder tube end and a base-side cylinder tube end. The guide closure part is arranged at the guide-side cylinder tube end.

[0009] The bottom closure part of the hydraulic cylinder is designed in a special way and has a cylinder tube receiving section, a damping accumulator receiving section and a fluid channel.

[0010] The cylinder tube is arranged with its bottom-side cylinder tube end on the cylinder tube receiving section and forms a bottom-side axial boundary of the cylinder interior, which is opposite the guide-side axial boundary of the cylinder interior.

[0011] The piston unit slides through the guide closure part and, together with the cylinder tube and the base closure part, forms a working chamber. This working chamber is connected to the fluid channel, so that during an inward movement, the fluid is displaced from the shrinking working chamber and pressed into the fluid channel. Conversely, it can flow into the working chamber via the fluid channel and generate an outward movement. The piston unit can, in particular, be designed as a unit consisting of a piston and piston rod. However, it can also be designed as a plunger piston, so that in this case the hydraulic cylinder is a plunger cylinder.

[0012] The fluid channel arranged in the bottom closure part connects the cylinder tube receiving section and the damping accumulator receiving section.

[0013] The damping accumulator comprises a pressure capsule, a fluid chamber accommodated by the pressure capsule, and a pressure-deformable air chamber separated from the fluid chamber by a membrane. A membrane-separated, pressure-deformable air chamber is understood here to be a structural design in which, depending on the fluid pressure, compression of the air enclosed in the air chamber is effected, thus pre-tensioning the air that acts on the fluid. The compression causes a reduction in the volume of the air chamber, so that the fluid chamber can accommodate more fluid in the same way. It is preferably a membrane accumulator, although other structural designs, such as a metal bellows accumulator, are also encompassed by the solution according to the invention.

[0014] The damping accumulator further comprises a damping accumulator fluid connection located on the bottom closure part. There, the damping accumulator is coupled to the bottom closure part in such a way that a sealed connection exists and, at the same time, a fixed positional relationship is established between the bottom closure part and the damping accumulator. This coupling can preferably be formed as a laser-welded connection.

[0015] The bottom closure part is functionally integrated, firstly, to create space for the working space of the hydraulic cylinder, secondly, to act as a base body for power transmission and for mounting, for example, on a machine part, and thirdly, to act as a support for the damping accumulator.

[0016] The damping fluid connection is connected to the fluid channel of the bottom closure part in a fluid-conducting manner, so that the fluid displaced from the hydraulic cylinder during an inward movement can be pressed into the damping cylinder via this path and, conversely, can be returned again during an outward movement.

[0017] The damping cylinder assembly according to the invention is particularly characterized in that a combination of two beam welding processes is used in the production of a hydraulic unit consisting of the hydraulic cylinder and the damping accumulator and thus of two different hydraulic units for their permanent coupling.

[0018] It was found that by combining two beam welding processes, both based on exposing the coupling partners to high-energy radiation, but which can simultaneously meet different specific requirements as electron beam welding and laser beam welding, a particularly high-quality and energy-efficient production of a damping cylinder unit can be demonstrated. This advantageously meets the special requirements arising from the different functions and design features of the two hydraulic units.

[0019] For this purpose, the damping cylinder assembly is characterized in that the damping accumulator is welded to its pressure capsule according to the invention using an electron beam ring weld. Optionally, multiple electron beam welds can also be present on the damping accumulator.

[0020] Furthermore, the damping cylinder assembly is characterized in that the guide closure part is integrally connected to the cylinder tube by means of a first circumferential laser ring weld seam, and in that the bottom closure part is integrally connected to the cylinder tube by means of a second circumferential laser ring weld seam.

[0021] The coupling according to the invention using two circumferential laser ring welds makes it possible for the first time to manufacture the hydraulic cylinder, including its components with limited thermal loads, such as piston seals and guides on the piston or on the guide closure part, with such high quality assurance that it is not necessary to revise the guide closure part, for example, by means of a screw coupling. While the particularly high dynamic loads caused by the connected components to be damped required massive MAG welds between the cylinder barrel and the base closure part according to the prior art, which adversely affected the coupling partners with significant thermal stress, a surprising way was found here to apply laser welding using the special arrangement of the laser ring welds.

[0022] Preferably, the first laser ring weld seam is radial and butt-jointed and the second laser ring weld seam is conical with an inclination angle.

[0023] According to the invention, the electron beam welding process on the damping accumulator and the laser welding process on the hydraulic cylinder are advantageously combined in the damping cylinder assembly. By combining the electron beam welding process and the laser welding process, a solution was found that enables a time- and energy-saving manufacturing process while simultaneously ensuring high-quality and process-reliable production of a damping cylinder assembly.

[0024] This is based on the fact that, on the one hand, the laser beam welding process is energetically advantageous for smaller weld seams, especially those below 5 mm, while, on the other hand, high energy efficiency can be achieved when welding larger seams, such as those found in the manufacture of the damping accumulator, using the electron beam welding process. Furthermore, the electron beam welding process is easier to control, allowing the power density to be adjusted. Furthermore, the advantages offered by combining the two beam welding processes cannot be achieved when using only one of the two beam welding processes alone.

[0025] Furthermore, there is a particular manufacturing advantage, since process-related and occupational safety-related provisions for one of the welding processes, such as an enclosure of the process area or shielding, can be used at the same time for carrying out the other welding process, so that multiple provisions can be avoided.

[0026] Laser welding advantageously allows the cylinder tube to be formed with a thinner wall thickness, as otherwise the allowances required to compensate for thread wear, as required by the current state of the art, are no longer necessary. Eliminating minimum lengths for threaded sections also allows for shorter cylinder tube lengths.

[0027] There are many possible applications for the damping cylinder assembly according to the invention, particularly in agricultural machinery, vehicles and mechanical engineering.

[0028] According to an advantageous development, the damping cylinder assembly is characterized in that the cylinder tube receiving section of the base closure part has a conical receiving contour and in that the cylinder tube has a corresponding conical annular surface, and in that the second laser ring weld seam is formed with a laser weld seam inclination angle of 20 to 70 degrees. Due to the conical receiving contour and the corresponding conical annular surface, two surfaces lie opposite each other essentially without a gap, so that the laser, with a penetration depth matched thereto, brings about a full-surface weld with, at the same time, low linear energy. Furthermore, according to this advantageous development, the cylinder tube has an end section which projects axially distally beyond the conical annular surface and has an axial annular surface. This axial annular surface rests against an axial counter-anular surface of the cylinder tube receiving section.

[0029] In a further advantageous development, the distally projecting end section has a reduced wall thickness compared to the wall thickness of the cylinder tube. The wall thickness of the distally projecting end section is preferably between 10 and 30 percent of the full wall thickness of the cylinder tube. Furthermore, the distally projecting end section forms an outer circumferential surface radially outward, which bears against an opposite inner circumferential surface of the cylinder tube receiving section.

[0030] These developments have the particular advantages described below. The conical receiving contour on the base closure part and the corresponding conical annular surface on the cylinder tube can advantageously be manufactured simply and with minimal material removal by turning and milling. In terms of manufacturing technology, this also enables a self-centering joining of the cylinder tube and the base closure part to form a pre-assembly before laser welding. Preferably, the length of the distally projecting end section is also selected such that it is subjected to axial prestress during joining by means of elastic compression when the conical receiving contour and the conical annular surface are in contact with one another in an assembly position ready for welding. Laser welding is then carried out. The elastic prestress is retained even after laser welding has been completed.Advantageously, the axial ring surface thus already forms a metallic seal against the axial counter-ring surface during welding, reliably protecting the cylinder interior from contamination during welding. Welding on the conical surface pairing with a laser weld seam inclination angle advantageously creates a larger weld seam surface, provides unobstructed spatial access for the laser to the weld seam, and, in conjunction with the distally projecting end section, ensures that the weld root does not touch the cylinder interior.

[0031] The geometry of the conical receiving contour of the base closure part and its continuation on the inner surface, in conjunction with the conical annular surface and its continuation through the outer surface and the distally projecting end section, enables a particularly stable coupling despite the high dynamic loads. The pressure fluctuations with sudden pressure peaks that occur during the impacts to be dampened place a strain on the coupling. Due to the prestress on the axial annular surface, a barrier is also present there, separating the fluid from the second laser ring weld seam. Furthermore, the fluid acts radially on the inner surface of the distally projecting end section.A particularly advantageous feature here is that the reduced wall thickness of the distally protruding end section, on the one hand, enables its elastic compression and prestressing. On the other hand, during radial force application, this section is pressed outward against the inner surface of the cylinder tube receiving section by pressure peaks. Thus, in this operating state, there is increased friction between the outer surface of the distally protruding end section and the inner surface, and the distally protruding end section is radially supported. These factors together effectively relieve the stress on the laser weld seam.

[0032] According to a further advantageous development, the damping cylinder assembly is characterized in that the guide closure part has a stepped hollow-cylindrical receiving contour, that a radial outer ring surface of the hollow-cylindrical receiving contour bears against an inner circumferential surface of the cylinder tube, and that the guide closure part has a proximal axial ring surface which, together with a distal axial counter-ring surface of the cylinder tube, forms the first laser ring weld seam in a butt-joint manner. This further advantageous development relates to the formation of the coupling between the guide closure part and the cylinder tube and thus concerns the first laser ring weld seam.

[0033] Advantageously, the radial outer ring surfaces of the hollow cylindrical receiving contour and the inner surface of the cylinder tube form a separation that prevents a direct connection of the first laser weld seam, including its weld root, to the cylinder interior, thus preventing contamination of the interior during welding. Furthermore, the radial form fit supports the coupling of the guide closure part to the cylinder tube.

[0034] The invention is illustrated by way of example with reference to

[0035] Fig. 1 Longitudinal section of a damping cylinder unit

[0036] Fig. 2 Enlarged section of the bottom cylinder section

[0037] Fig. 3 Enlarged section of the area of ​​the second laser ring weld

[0038] Fig. 4 Enlarged section of the guide-side cylinder section explained in more detail.

[0039] Identical reference numerals in the various figures refer to identical features or components. These reference numerals are used in the description even if they are not shown in the respective figure. Fig. 1 shows an exemplary embodiment of the hydraulic cylinder 10 and the damping accumulator 20 as the basic components in the positional relationship defined by the bottom closure part 50.

[0040] In this exemplary embodiment, the bottom closure part 50 is manufactured as a so-called burn-in part, and the cylinder tube receiving section 51, the damping accumulator receiving section 52, and the fluid channel 53 are subtractively machined. A filling and venting opening (without reference symbol) is assigned to the top of the fluid channel.

[0041] The hydraulic cylinder 10 is formed by the cylinder tube 30 together with the guide closure part 40 arranged at its guide-side cylinder tube end 31 and the bottom closure part 50 arranged at its bottom-side cylinder tube end 32 as well as the piston unit 60, which is present here as a plunger piston.

[0042] In this embodiment, the damping accumulator 20 is in the form of a diaphragm accumulator and has (not shown) a diaphragm in its pressure capsule 21 which separates an air chamber from the fluid in a fluid chamber, wherein the air chamber is compressible by means of the fluid pressure and the volume of the fluid chamber is increased depending on the pressure and the resulting degree of compression.

[0043] According to the inventive combination of two different beam welds, both laser beam welding and electron beam welding are present. The guide closure part 40 is integrally connected to the cylinder tube 30 by the first laser ring weld 71. Furthermore, the base closure part 50 is also integrally connected to the cylinder tube 30 by means of the second laser ring weld 72. At the same time, the pressure capsule 21 of the damping accumulator 20 is welded by means of the electron beam ring weld 22. Fig. 2 and Fig. 3 each show an enlarged section of the base closure part-side region of the hydraulic cylinder 10 in a preferred embodiment. The cylinder tube 30 has a conical annular surface 34, to which a distally projecting end section 33 adjoins. The conical receiving contour 54 lies opposite the conical annular surface 34 with the same conicity angle.The second laser ring weld seam 72 is arranged on the joining surface between the conical ring surface 34 and the conical receiving contour 54, which, according to the conicity in the exemplary embodiment, has a laser weld seam angle a of approximately 30 degrees.

[0044] The distally projecting end section 33 is significantly tapered compared to the full cylinder tube wall thickness present in the other areas and also has a slight excess length. This makes it possible to prestress the end section 33 by means of elastic compression even before the second laser ring weld seam 72 is created. The axial ring surface 35 and the axial counter-ring surface 55 abut one another. Furthermore, the radial outer surface 36 and the radial inner surface 56 lie opposite one another, so that at high pressures, the end section 33, which is tapered for elastic prestressing, comes into pressure contact with the radial inner surface 56 and is supported by it.

[0045] Fig. 4 shows, in another enlarged section, the bottom closure part-side area of ​​the hydraulic cylinder 10 in a preferred embodiment. The guide closure part has a stepped hollow cylindrical receiving contour 41 at the connection point to the cylinder tube 30, so that the radial outer ring surface 42 of the guide closure part 40 and the guide-side inner surface 37 of the cylinder tube 30 are opposite each other in the radial direction, and the proximal axial ring surface 43 of the guide closure part and the guide-side axial counter-ring surface 38 are opposite each other in the axial direction. The proximal axial ring surface 43 and the guide-side axial counter-ring surface 38 form a butt joint. The first laser ring weld seam 71 is arranged there in a radial orientation—represented by the dashed line. Reference numerals used

[0046] 10 hydraulic cylinders

[0047] 20 damping accumulators

[0048] 21 pressure capsule

[0049] 22 Electron beam ring weld

[0050] 30 cylinder barrel

[0051] 31 guide-side cylinder tube end

[0052] 32 bottom cylinder tube end

[0053] 33 protruding end section

[0054] 34 conical ring surface

[0055] 35 axial ring surface

[0056] 36 radial outer surface

[0057] 37 guide-side inner surface

[0058] 38 guide-side axial counter ring surface

[0059] 40 Guide closure part

[0060] 41 stepped hollow cylindrical receiving contour

[0061] 42 radial outer ring surface

[0062] 43 proximal axial ring surface

[0063] 50 bottom closure part

[0064] 51 Cylinder tube receiving section

[0065] 52 Damping storage receiving section

[0066] 53 Fluid channel

[0067] 54 conical receiving contour

[0068] 55 axial counter ring surface

[0069] 56 radial inner surface

[0070] 60 piston unit

[0071] 71 first laser ring weld

[0072] 72 second laser ring weld a laser weld inclination angle

Claims

Patent claims 1. A damping cylinder assembly comprising a hydraulic cylinder (10) and a damping accumulator (20), wherein the hydraulic cylinder comprises a cylinder tube (30), a guide closure part (40), a bottom closure part (50), and a piston unit (60), wherein the cylinder tube (30) has a guide-side cylinder tube end (31) and a bottom-side cylinder tube end (32), wherein the guide closure part (40) is arranged at the guide-side cylinder tube end (31), wherein the bottom closure part (50) has a cylinder tube receiving section (51), a damping accumulator receiving section (52), and a fluid channel (53) connecting the cylinder tube receiving section (51) and the damping accumulator receiving section (52), wherein the cylinder tube (30) is arranged with the bottom-side cylinder tube end (32) at the cylinder tube receiving section (51),wherein the piston unit (60) slidably passes through the guide closure part (40) and, together with the cylinder tube (30) and the base closure part (50), forms a working chamber which is connected to the fluid channel (53), wherein the damping accumulator (20) has a pressure capsule and, received therein, a fluid chamber and a pressure-deformable air chamber separated from the fluid chamber by a membrane, as well as a damping accumulator fluid connection (21) which is arranged on the base closure part (50), wherein the damping fluid connection (21) is connected to the fluid channel (53), characterized in that the damping cylinder assembly is coupled by means of a combination of two beam welding processes, that the pressure capsule (21) of the damping accumulator (20) has an electron beam ring weld seam (22), and, that the guide closure part (40) is integrally connected to the cylinder tube (30) by means of a first circumferential laser ring weld seam (71), and that the bottom closure part (50) is integrally connected to the cylinder tube (30) by means of a second circumferential laser ring weld seam (72). Damping cylinder assembly according to claim 1, characterized in that the cylinder tube receiving section (51) has a conical receiving contour (54) that the cylinder tube (30) has a conical annular surface (34) corresponding thereto, that the second laser ring weld seam (72) is formed with a laser weld seam inclination angle (α) which is 20 to 70 degrees and that the cylinder tube (30) has an end section (33) projecting axially distally beyond the conical annular surface (34), which has an axial annular surface (35) which is connected to an axial counter-ring surface (55) of the cylinder tube receiving section (51). Damping cylinder assembly according to claim 2, characterized in that the distally projecting end section (33) has a wall thickness of 10 to 30 percent of the wall thickness of the cylinder tube (30) and a radial outer surface (36) that bears against a radial inner surface (56) of the cylinder tube receiving section (51). Damping cylinder assembly according to one of the preceding claims, characterized in that the guide closure part (40) has a stepped hollow cylindrical receiving contour (41), that a radial outer ring surface (42) of the hollow cylindrical receiving contour (41) bears against a guide-side inner surface (37) of the cylinder tube (30), and that the guide closure part (40) has a proximal axial annular surface (43) that, together with a guide-side distal axial counter-ring surface (38), of the cylinder tube (30) the first laser ring weld seam (71) is butt-jointed.

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