GAS SPRING WITH TEMPERATURE COMPENSATION, METHOD FOR MANUFACTURING THE GAS SPRING

Description

Technical field

[0001] The invention relates to a gas pressure spring according to the preamble of claim 1 and a method for producing the gas pressure spring. State of the art

[0002] Gas pressure springs are known from the state of the art in which a temperature dependence of the spring force is to be compensated by a compensating medium.

[0003] Document EP 1 795 777 A2 describes a gas spring with a working cylinder in which a working piston is slidably guided. The annular space formed between the working cylinder and a compensating cylinder is filled with a compensating medium that expands when the temperature rises. The open end of the working cylinder, opposite the piston outlet end, is closed by a cup-shaped compensating piston. As the compensating medium expands, it displaces the compensating piston, increasing the volume of the working cylinder.

[0004] The document DE 31 41 295 A1 relates to a gas spring consisting of a container, along whose inner wall a piston connected to the piston rod slides. A space filled with an expanding material is located between a partition wall fixed to the container and a disc piston, with this disc piston forming a movable partition wall for the space filled with expanding material. The gas spring further comprises a working chamber with a pressurized gas filling. As the temperature increases, the expanding material expands and causes the disc piston to move further away from the partition wall fixed to the container, thereby enlarging the working space.

[0005] Known gas springs with temperature compensation are usually complex in design, require a significantly larger installation space than gas springs without temperature compensation, or cannot compensate for the temperature dependence over the entire application-relevant temperature range. Technical task

[0006] The object of the invention is to provide a cost-effective and simply constructed gas spring and a cost-effective and reliable method for its production, wherein the spring force of the gas spring is independent of the temperature over the widest possible temperature range. Technical solution

[0007] The present invention provides a gas spring according to claim 1, which solves the technical problem. The problem is also solved by a method for producing the gas spring according to claim 12. Advantageous embodiments emerge from the dependent claims.

[0008] The gas spring comprises a working piston that is displaceably guided in a working cylinder along a stroke axis over a stroke range. The working piston is preferably displaceable relative to the working cylinder along the stroke axis. The working cylinder is preferably hollow-cylindrical in shape and / or arranged coaxially with the stroke axis.

[0009] The gas spring comprises a compensating cylinder that surrounds the working cylinder radially relative to the stroke axis. The compensating cylinder is preferably hollow-cylindrical and / or arranged coaxially with the stroke axis. The compensating cylinder is preferably rigidly attached to the working cylinder. The compensating cylinder is preferably made of one piece, making the gas spring particularly easy to manufacture.

[0010] The working cylinder has one open end along the stroke axis. "Open" means at least that gas can freely exit and enter the working cylinder through the open end. Preferably, the open end is completely open.

[0011] At a piston rod end of the working cylinder opposite the open end along the stroke axis, a piston rod of the gas spring, preferably attached to the working piston, extends out of the working cylinder through a sealing device. The sealing device preferably seals off the piston rod end to prevent gas from entering or escaping from the working cylinder. "Closed" means that no gas can escape from the working cylinder at the piston rod end.

[0012] The compensating cylinder forms a projection over the working cylinder at the open end with a closed end along the stroke axis.

[0013] At a piston rod end of the compensating cylinder opposite the closed end along the stroke axis, the piston rod of the gas spring is preferably guided out of the compensating cylinder through a sealing device. The sealing device preferably closes the piston rod end to a gas.

[0014] The sealing device preferably seals the piston rod end of the compensating cylinder and the piston rod end of the working cylinder. The sealing device preferably also serves as a guide device for guiding the piston rod along the stroke axis. The working cylinder is preferably attached to the compensating cylinder via the sealing device.

[0015] The sealing device can comprise a preferably one-piece fastening element, for example made of aluminum, which is fastened to the compensating cylinder and to the working cylinder, for example, by positively locking and / or materially bonding, in particular by deformation of the compensating cylinder and / or the working cylinder. The sealing device can comprise a number of sealing elements, for example sealing rings, which seal the fastening element of the sealing device to the working cylinder, the compensating cylinder, and / or the piston rod.

[0016] The sealing device can comprise an outer part that seals the piston rod end of the compensating cylinder and an inner part that seals the piston rod end of the working cylinder. The advantage of this two-part design is that the inner part can be constructed without a compensating cylinder, just like a standard gas spring.

[0017] The outer part of the sealing device can comprise at least one external fastening element, for example a sleeve, which fastens the compensating cylinder to the working cylinder, for example in a form-fitting, force-fitting, and / or material-fitting manner. The outer part of the sealing device can comprise at least one external sealing element, for example a sealing ring, which seals the working cylinder to the compensating cylinder.

[0018] The inner part of the sealing device can comprise at least one guide element, for example a guide bushing, which guides the piston rod along the stroke axis. The inner part of the sealing device can comprise at least one internal sealing element, for example a sealing ring, which seals the working cylinder to the piston rod.

[0019] A disc, particularly a metal disc with a corrosion-resistant surface, can be arranged between the piston rod end of the working cylinder and the piston rod end of the compensating cylinder. The disc can increase the strength of the sealing device, particularly so that the sealing device is not damaged when the compensating cylinder is rolled shut. The disc can be connected, for example, to the external fastening element of the sealing device via a snap-in connection.

[0020] The compensating piston separates, preferably in a gas-tight manner, a working chamber arranged in the working cylinder, a compensating chamber arranged between the working cylinder and the compensating cylinder, and a return chamber arranged in the projection.

[0021] A compensating medium is preferably arranged in the compensating chamber, which moves the compensating piston toward the closed end when the compensating medium heats up. The pressure of the compensating medium is, for example, between 70 bar and 350 bar.

[0022] The compensating medium preferably comprises an expansion material, in particular an expansion wax, particularly preferably a mixture of an expansion wax and an oil. The compensating medium can consist in particular of the expansion material, the expansion wax, or the mixture of expansion wax and oil. The compensating medium can, for example, be configured like the compensating medium described in document EP 1 795 777 A2. The expansion wax can, for example, be configured like the expansion wax described in application DE 10 2020 113 749.

[0023] A return means is preferably arranged in the return chamber, which moves the compensating piston away from the closed end when the compensating medium cools down.

[0024] The reset means preferably comprises or is a reset gas, wherein the reset gas is preferably the same gas that fills the working chamber as the working gas. The reset gas and / or the working gas is, for example, nitrogen. The reset means can comprise or be formed from a mechanical reset element, for example, a spring, in particular a helical compression spring.

[0025] The working gas pressure, for example, ranges from 20 bar to 250 bar. The return gas pressure, for example, ranges from 20 bar to 350 bar.

[0026] A distance of the compensating cylinder from the working cylinder, measured radially to the stroke axis, is preferably greater in the stroke area than in an end area of ​​the working cylinder located between the stroke area and the open end of the working cylinder.

[0027] The smaller distance at the end results in a smaller cross-sectional area of ​​the compensation chamber perpendicular to the stroke axis at the end. As a result, for a given temperature increase, the compensation piston is displaced further toward the closed end of the compensation cylinder due to the expansion of the compensation medium, thus increasing the working space and providing greater compensation for the temperature dependence of the gas spring's spring force.

[0028] Since the distance in the stroke area is not reduced, the compensation chamber can still accommodate a sufficient amount of compensation medium for effective temperature compensation.

[0029] The disadvantage of designing different distances between the stroke range and the end range is that it makes the production of the gas spring more complex. Furthermore, in the transition area between the stroke range and the end range, material weakening can occur due to deformation of the working cylinder and / or compensating cylinder, or leaks can occur at the joints between parts of the working cylinder and / or compensating cylinder. Thus, the different distances could jeopardize the reliable functioning of the gas spring.

[0030] The distance is, for example, 10% to 50%, preferably 20% to 40%, particularly preferably 30% smaller in the end region than in the stroke region. The distance is, for example, 1 mm to 8 mm, preferably 2 mm to 4 mm, particularly preferably 2.5 mm in the end region. The distance is, for example, 2 mm to 12 mm, preferably 3 mm to 6 mm, particularly preferably 3 mm to 3.5 mm in the stroke range. With the stated distance values, extensive, in particular complete, compensation of the temperature dependence of the spring force of the gas spring can be achieved over a typical operating temperature range of the gas spring, for example from -10 °C to +60 °C.

[0031] Preferably, the distance between the compensating cylinder and the working cylinder in the end region and / or in the stroke region is independent of a position along the stroke axis. In this embodiment, the distance is constant in the end region and / or in the stroke region along the stroke axis, making the gas spring particularly easy to manufacture. Description of the execution types

[0032] An end region outer diameter of the working cylinder, measured radially to the stroke axis, is preferably larger in the end region of the working cylinder than a stroke region outer diameter of the working cylinder, measured radially to the stroke axis, in the stroke region. Such an expansion of the working cylinder in the end region results in a reduced distance between the working cylinder and the compensating cylinder without changing the compensating cylinder or the shape of the working cylinder in the stroke region. Thus, the reduced distance is achieved with as few changes as possible compared to a prior art gas spring. The gas spring can therefore be manufactured particularly easily and cost-effectively, in particular using known components and methods.

[0033] The end-range outer diameter of the working cylinder is preferably from 101% to 150%, preferably from 105% to 130%, particularly preferably from 110% to 120%, most preferably 112% to 113%, of the stroke-range outer diameter of the working cylinder. The end-range outer diameter is, for example, from 15 mm to 25 mm, preferably from 16 mm to 22 mm, particularly preferably from 18 mm to 21 mm. The stroke-range outer diameter is, for example, from 10 mm to 20 mm, preferably from 15 mm to 19 mm, particularly preferably 17 mm to 18 mm. With the stated outer diameter values, extensive compensation of the temperature dependence of the spring force of the gas spring can be achieved over a typical operating temperature range of the gas spring.

[0034] Preferably, the outer diameter of the working cylinder in the end region and / or in the stroke region is independent of a position along the stroke axis. In this embodiment, the outer diameter is constant in the end region and / or in the stroke region along the stroke axis, making the gas spring particularly easy to manufacture.

[0035] The compensating cylinder's inner diameter, measured radially to the stroke axis, is preferably from 110% to 200%, preferably from 140% to 170%, particularly preferably from 150% to 160%, most preferably 155% to 157%, of the working cylinder's stroke range outer diameter. The compensating cylinder's inner diameter is, for example, from 20 mm to 30 mm, preferably from 23 mm to 27 mm, particularly preferably 25 mm. With the stated values ​​of the compensating cylinder's inner diameter, a substantial compensation of the temperature dependence of the gas spring's spring force can be achieved over a typical operating temperature range of the gas spring.

[0036] Preferably, the inner diameter of the compensating cylinder is independent of a position along the stroke axis. In this embodiment, the inner diameter of the compensating cylinder is constant along the stroke axis, making the gas spring particularly easy to manufacture.

[0037] The stroke area and the end area of ​​the working cylinder are preferably connected in one piece, making the gas spring particularly easy to manufacture. For example, the working cylinder can be widened in the end area transverse to the stroke axis relative to the stroke area.

[0038] The stroke area and the end area can, for example, be connected to one another in a materially bonded manner, in particular welded, soldered, and / or glued. The stroke area and the end area can, for example, be connected to one another in a form-fitting and / or force-fitting manner, in particular screwed, latched, and / or clamped.

[0039] The working cylinder may, for example, comprise or consist of a metal, in particular a steel, and / or a plastic.

[0040] The wall thickness of the working cylinder radially to the stroke axis is preferably the same in the stroke region and in the end region of the working cylinder. The wall thickness is considered to be the same in particular if it is the same except for a reduction in wall thickness caused by an expansion of the working cylinder in the end region, for example, a reduction of up to 0.2 mm. The wall thickness is preferably independent of a position along the stroke axis. In this embodiment, the wall thickness of the working cylinder is constant along the stroke axis, which makes the gas spring particularly easy to manufacture.

[0041] The wall thickness of the compensating cylinder radially to the stroke axis is preferably independent of the position along the stroke axis. In this embodiment, the wall thickness of the compensating cylinder is constant along the stroke axis, making the gas spring particularly easy to manufacture.

[0042] The compensating piston is preferably made in one piece, making the gas spring particularly easy to manufacture.

[0043] The compensating piston preferably comprises aluminum or a plastic. The compensating piston is particularly preferably made of aluminum or a plastic.

[0044] The compensating piston is preferably hollow-cylindrical in shape and is arranged in particular coaxially to the stroke axis.

[0045] The compensating piston preferably has a cylinder base on its underside. The cylinder base is preferably aligned perpendicular to the stroke axis and / or closed.

[0046] The compensating piston preferably comprises a cylinder jacket that extends around the stroke axis. The cylinder jacket is preferably closed.

[0047] The compensating piston is open at the top of the compensating piston, opposite the cylinder base along the stroke axis. This offers the advantage that the interior of the compensating piston can serve as part of the working chamber or the return chamber, allowing the gas spring to be designed particularly compactly.

[0048] The compensating piston is preferably pot-shaped, with the cylinder bottom corresponding to a pot bottom and the cylinder jacket corresponding to a pot wall.

[0049] A hollow cylindrical or pot-shaped compensating piston has the advantage that it can separate the working chamber, the compensation chamber and the return chamber with a particularly low mass.

[0050] A compensating cylinder seal is preferably arranged on the compensating piston, sealing the compensating piston to the compensating cylinder, in particular in a gas-tight manner. The compensating cylinder seal can be attached to the compensating piston. The compensating cylinder seal can comprise or be formed by a sealing ring, in particular an O-ring, that runs, in particular coaxially, around the stroke axis.

[0051] The compensating piston preferably comprises a cylinder flange, preferably adjacent to the top side and projecting radially outward beyond the cylinder jacket relative to the stroke axis. The compensating cylinder seal is arranged, in particular secured, to the cylinder flange. With the aid of the cylinder flange, the compensating cylinder seal can be brought into reliable sealing contact with the compensating cylinder with minimal material expenditure.

[0052] The top of the compensating piston is preferably open to the return chamber. This makes the interior of the compensating piston part of the return chamber, allowing more volume for the return fluid relative to the working gas. With a smaller working gas volume relative to the return fluid volume, the temperature dependence of the spring force can be more easily compensated.

[0053] A working cylinder seal that seals the compensating piston to the working cylinder, in particular in a gas-tight manner, is preferably arranged, in particular attached, on the compensating piston, preferably on the cylinder jacket of the compensating piston, or on the working cylinder. The working cylinder seal can comprise or be formed by a sealing ring, in particular an O-ring, that runs, in particular coaxially, around the stroke axis.

[0054] The compensating piston, preferably the cylinder barrel of the compensating piston and particularly preferably also the cylinder base of the compensating piston, is preferably arranged at least partially in the end region of the working cylinder. This increases the volume of the compensating chamber and / or the reset chamber relative to the volume of the working chamber, thereby achieving more effective compensation for the temperature dependence of the spring force of the gas spring.

[0055] The compensating piston is preferably completely enclosed within the compensating cylinder. This has the advantage that the length of the gas spring measured along the stroke axis does not change when the compensating piston moves. The length of the gas spring is therefore not temperature-dependent.

[0056] The gas spring preferably comprises a number of support elements, for example one, two, three, four, five, or more, wherein the number of support elements supports the working cylinder on the compensating cylinder. The support elements advantageously prevent relative movements of the working cylinder relative to the compensating cylinder that could impair the sealing of the compensating piston with respect to the working cylinder or the compensating cylinder, or the displaceability of the compensating piston along the stroke axis.

[0057] The support elements are preferably arranged spaced apart from one another around the stroke axis, and / or the support elements preferably have openings along the stroke axis. As a result, the support elements do not significantly impede the expansion or compression of a compensating medium in the compensation chamber along the stroke axis between the working cylinder and the compensating cylinder.

[0058] The support elements are preferably evenly distributed around the lifting axis. This allows the support elements to support the working cylinder particularly reliably against the compensating cylinder.

[0059] The support elements are preferably arranged at the end of the working cylinder. Since the end is adjacent to the compensating piston, the support elements at the end can particularly effectively ensure the sealing and mobility of the compensating piston.

[0060] The support elements can be designed as a ring with a perforation along the stroke axis, which is arranged coaxially to the stroke axis and mechanically connects the working cylinder to the compensating cylinder. The ring is preferably arranged in the stroke region of the working cylinder. At the stroke region, the ring impedes the expansion or compression of a compensating medium in the compensating chamber along the stroke axis to a particularly small extent.

[0061] The number of support elements is preferably integral with the working cylinder or the compensating cylinder. This reduces the number of components of the gas spring, making it particularly easy, quick, and cost-effective to manufacture.

[0062] The support elements can be formed, for example, by deforming the working cylinder and / or the compensating cylinder. This allows the support elements to be formed particularly quickly and easily. The deformations include, for example, widenings of the working cylinder to fit the compensating cylinder and / or, in particular, point-shaped depressions of the compensating cylinder to fit the working cylinder. Due to the short distance between the working cylinder and the compensating cylinder in the end region, the support elements can be formed particularly easily in the end region by the deformations.

[0063] The method for producing the gas spring preferably comprises providing a working cylinder blank, wherein the working cylinder blank is shaped like a hollow cylinder and has an outer diameter transverse to the longitudinal axis that is independent of a position along its longitudinal axis. The outer diameter is therefore constant along the stroke axis. The working cylinder blank can in particular be a working cylinder of a known gas spring. The working cylinder blank preferably has material properties that are dependent on an azimuth with respect to its longitudinal axis, for example by means of a weld seam along the longitudinal axis. Such a working cylinder blank is particularly simple and cost-effective to produce, for example by drawing and welding it from steel.

[0064] The method preferably comprises forming the working cylinder blank into the working cylinder of the gas pressure spring, wherein the forming comprises widening the outer diameter of the working cylinder blank in an end region of the working cylinder blank.

[0065] The method preferably comprises arranging the compensating piston of the gas pressure spring at least in sections in the end region of the working cylinder of the gas pressure spring.

[0066] The expansion preferably comprises inserting a mandrel into the end region and preferably arranging a sleeve extending around the longitudinal axis around the end region of the working cylinder blank prior to inserting the mandrel, such that the end region rests against the sleeve after expansion. This advantageously allows the diameter of a working cylinder blank, whose material properties depend on an azimuth relative to its longitudinal axis, to be expanded to a diameter independent of the azimuth.

[0067] The method preferably comprises forming the working cylinder of the gas spring and / or the compensating cylinder of the gas spring to produce a number of support elements, wherein the number of support elements supports the working cylinder on the compensating cylinder. The support elements can be configured as described above, resulting in the advantages mentioned therein.

[0068] The forming process for producing the support elements comprises, for example, widening the working cylinder to the compensating cylinder and / or deepening the compensating cylinder to the working cylinder, in particular in a point-like manner.

[0069] Particularly preferably, the expansion of the working cylinder to produce the support elements takes place in the same step as the expansion of the end region of the working cylinder blank to form the working cylinder. For this purpose, for example, a mandrel can be inserted into the end region of the working cylinder blank, wherein the mandrel preferably has a number of projections for producing the support elements during the expansion of the end region of the working cylinder blank to form the working cylinder.

[0070] The method preferably comprises forming or machining a balance piston blank to produce the balance piston. Forming allows the balance piston to be manufactured with particularly low material requirements. The balance piston can be produced, for example, by deep-drawing a balance piston blank made of aluminum. The balance piston can be produced, for example, by forming a balance piston blank made of steel.

[0071] The balance piston blank can, for example, be shaped like a hollow cylinder. The hollow cylindrical balance piston blank can be expanded at one end along its longitudinal axis, for example, from an inner diameter of 18 mm to an inner diameter of 23 mm, to form an outwardly projecting cylinder rim. The hollow cylindrical balance piston blank can be closed at its other end by roll closing and / or plasma welding to form a closed cylinder base. Beads can be rolled into the cylinder jacket of the balance cylinder blank around its longitudinal axis to partially accommodate the balance cylinder seal and / or the working cylinder seal.

[0072] The working cylinder of the gas pressure spring preferably has a groove on an inner side of a jacket wall of the working cylinder through which a gas contained in the working cylinder can flow along the stroke axis of the gas pressure spring past the working piston of the gas pressure spring.

[0073] A cross-sectional area of ​​the groove aligned orthogonally to the stroke axis preferably varies along the stroke axis. The cross-sectional area is preferably minimal at the ends of the stroke range of the working cylinder and maximum in a central section between the ends of the stroke range. This results in greater flow resistance to the gas at the ends of the stroke range. Consequently, the gas spring produces a higher damping force near a maximum insertion of the piston rod into the gas spring and near a maximum extension of the piston rod from the gas spring than in intermediate positions of the piston rod. The increased damping force near the maximum insertion and maximum extension means that movement of the piston rod is decelerated more strongly at those points, thus preventing damage to the gas spring due to reaching the maximum insertion or extension at high speed.

[0074] The cross-sectional area of ​​the groove preferably varies by a variable depth of the groove perpendicular to the inside of the jacket wall of the working cylinder.

[0075] In a particularly advantageous embodiment, particularly for the use of the gas pressure spring in a drive system described below, the cross-sectional area of ​​the groove increases along the stroke axis from an extension end of the stroke range of the working cylinder facing the piston rod end of the working cylinder in the direction of the open end of the working cylinder in an extension transition area, preferably linearly; runs constantly in a central area adjoining the extension transition area, falls, preferably linearly, in an insertion transition area adjoining the central area and runs constantly in an insertion end area adjoining the insertion transition area up to an insertion end of the stroke range facing the open end of the working cylinder.

[0076] The aforementioned cross-sectional shape achieves a high damping force when the piston rod is inserted into the gas spring and approaches maximum insertion. This prevents, in particular, a flap supported by the gas spring from closing completely too quickly, which could otherwise lead to damage to the flap or injury to the flap operator.

[0077] The working piston of the gas spring preferably comprises a seal, in particular a sealing ring, which seals the piston to the inside of a casing wall of the working cylinder. The seal is preferably rigid enough that it does not penetrate a groove arranged on the inside of the casing wall. This prevents the seal from closing the groove, which would otherwise block the gas spring.

[0078] The invention relates to a drive system for a flap with a. a gas pressure spring according to the invention for supporting the flap and b. an electromechanical drive, for example a linear drive, in particular a spindle drive, for driving the flap.

[0079] The flap can be, for example, a flap of a vehicle, in particular a bonnet, a trunk lid, a luggage compartment lid or a wing door.

[0080] Drive systems for a flap with a gas spring to support the flap and an electromechanical drive to drive the flap are known in the prior art. Except for the use of a gas spring according to the invention instead of a generic gas spring, the drive system according to the invention can be constructed like a corresponding drive system from the prior art, for example, from DE 103 13 440 A1 or DE 10 2008 045 903 A1.

[0081] The gas spring of the drive system serves to hold the flap in any position against gravity, while the electromechanical drive is used to open and close the flap. Additionally, manual operation of the flap can be provided, as described in DE 103 13 440 A1 and DE 10 2008 045 903 A1.

[0082] The gas spring must have such a high spring force that it can hold the flap closed even at low ambient temperatures. Since the spring force of conventional gas springs increases with temperature, this means that at high temperatures, a very high force must be applied by the electromechanical drive or an operator to close the flap. Therefore, the drive system must include a very powerful electromechanical drive, which is expensive, requires a lot of space, and consumes a lot of energy during operation. Furthermore, this leads to significant wear on the electromechanical drive and other parts mechanically connected to the flap, such as hinges.

[0083] In the prior art, these problems are circumvented by using a spring strut instead of a gas spring (e.g., DE 10 2008 045 903 A1, paragraph

[0021] ). Although a spring strut has a spring force that is virtually independent of temperature, it is larger, heavier, and more expensive than a gas spring with comparable spring force.

[0084] Compared to a strut designed to support a given load, a gas spring designed to support the same load has a higher damping force due to its high gas pressure. This is especially true at high retraction speeds due to the fluid dynamic flow resistance of the gas in the gas spring, which increases with the speed at which the piston rod is inserted into the gas spring. As a result, a gas spring only slightly slows down slow movements of the flap that occur when the flap is actuated as intended by the drive. However, the gas spring significantly slows down rapid movements of the flap, which can occur, for example, if the flap falls due to incorrect operation or a malfunction of the drive.

[0085] Thus, by using a gas spring instead of a strut, the drive system is particularly lightweight, cost-effective, space-saving, and safe. By using a temperature-compensated gas spring according to the invention instead of a conventional gas spring, the aforementioned disadvantages of conventional gas springs are overcome. Short description of the drawings

[0086] Figure 1 shows, by way of example, a schematic longitudinal section along the stroke axis of an embodiment of the gas pressure spring according to the invention. Figure 2 shows a schematic longitudinal section of an alternative embodiment of the sealing device of a gas pressure spring according to the invention. Figure 3 shows schematically a profile of a depth of a groove on an inner side of a casing wall of the working cylinder of a gas pressure spring according to the invention. Fig.1

[0087] Figure 1shows a schematic longitudinal section along the stroke axis H of an embodiment of the gas pressure spring 50 according to the invention.

[0088] The gas pressure spring 50 shown comprises a working piston 2 which is displaceably guided in a working cylinder 1 along a stroke axis H over a stroke range HB, a compensating cylinder 12 which surrounds the working cylinder 1 radially to the stroke axis H, and a hollow-cylindrically shaped compensating piston 10 which is displaceably guided in the compensating cylinder 12 along the stroke axis H relative to the working cylinder 1 and the compensating cylinder 12.

[0089] The working cylinder 1 has an open end 1b along the stroke axis H, wherein the compensating cylinder 12 forms a projection 15 at the open end 1b over the working cylinder 1 with a closed end 15b along the stroke axis H.

[0090] The compensating piston 10 separates a working chamber 1a arranged in the working cylinder 1, a compensating chamber 12a arranged between the working cylinder 1 and the compensating cylinder 12 and a return chamber 15a arranged in the projection 15.

[0091] The compensating piston 10 comprises a cylinder base 10b and a cylinder jacket 10c extending around the stroke axis H on an underside of the compensating piston 10 facing the working chamber 1a. The cylinder base 10b and a part of the cylinder jacket 10c are arranged in the working cylinder 1. The compensating piston 10 is open on an upper side 10a of the compensating piston 10 facing the return chamber 15a.

[0092] A compensating cylinder seal 8 is arranged on the compensating piston 10, sealing the compensating piston 10 to the compensating cylinder 12.

[0093] The compensating piston 10 comprises a cylinder rim 10d projecting radially outwards beyond the cylinder jacket 10c relative to the stroke axis H, wherein the compensating cylinder seal 8 is arranged on the cylinder rim 10d.

[0094] A working cylinder seal 18 sealing the compensating piston 10 to the working cylinder 1 is arranged on the cylinder jacket 10c of the compensating piston 10.

[0095] At a piston rod end 1c of the working cylinder 1 opposite the open end 1b along the stroke axis H, a piston rod 6 fastened to the working piston 2 is led out of the working cylinder 1 through a sealing device 20.

[0096] The sealing device 20 comprises a fastening element 21, for example made in one piece from aluminum, which is fastened, for example in a form-fitting manner, to the compensating cylinder 12 and to the working cylinder 1. The sealing device 20 comprises a number of sealing elements 22, for example four sealing rings, which seal the fastening element 21 of the sealing device 20 to the working cylinder 1, the compensating cylinder 12, and the piston rod 6.

[0097] A distance of the compensating cylinder 12 from the working cylinder 1 measured radially to the stroke axis H in the stroke range HB is greater than in an end region EB of the working cylinder 1 lying between the stroke range HB and the open end 1b of the working cylinder 1.

[0098] The reduced distance in the end region EB is due to the fact that an end region outer diameter EAD of the working cylinder 1, measured radially to the stroke axis H, is larger than a stroke region outer diameter HAD of the working cylinder 1 in the stroke region HB, measured radially to the stroke axis H. The end region outer diameter EAD is, for example, 18 mm to 20 mm. The stroke region outer diameter HAD is, for example, 16 mm.

[0099] For example, the compensating cylinder inner diameter AID of the compensating cylinder 12 is 25 mm. Fig.2

[0100] Figure 2 shows a schematic longitudinal section along the stroke axis H of an alternative embodiment of the sealing device 20 of a gas pressure spring 5 according to the invention.

[0101] The Figure 2The sealing device 20 shown comprises an outer part which closes the piston rod end 12c of the compensating cylinder 12 and an inner part which closes the piston rod end 1c of the working cylinder 1.

[0102] The outer part of the sealing device 20 comprises an external fastening element 23, for example a sleeve, which fastens the compensating cylinder 12 to the working cylinder 1, for example by means of a material bond, in particular by means of an adhesive. The outer part of the sealing device comprises an external sealing element 24, for example a sealing ring, which seals the working cylinder 1 to the compensating cylinder 12.

[0103] The inner part of the sealing device 20 comprises a guide element 26, for example a guide bushing, which guides the piston rod 6 of the gas spring 5 along the stroke axis H. The inner part of the sealing device 20 comprises at least one inner sealing element 27, for example a sealing ring or two sealing rings, which seals the working cylinder 1 to the piston rod 6.

[0104] For example, a disc 25, in particular a metal disc with a corrosion-protected surface, is arranged between the piston rod end 1c of the working cylinder 1 and the piston rod end 12c of the compensating cylinder 12. Fig.3

[0105] Figure 3 shows schematically a profile of a depth d of a groove on an inner side of a casing wall of the working cylinder of a gas pressure spring according to the invention depending on a position x along the stroke axis of the gas pressure spring.

[0106] In the example shown, the depth of the groove increases linearly along the stroke axis from an extension end AE of the stroke range of the working cylinder facing the piston rod end of the working cylinder in the direction of the open end of the working cylinder in an extension transition area AUB; it is constant in a central area ZB adjoining the extension transition area AUB, decreases linearly in an insertion transition area EUB adjoining the central area ZB and is constant in an insertion end area EEB adjoining the insertion transition area EUB up to an insertion end EE of the stroke range facing the open end of the working cylinder. List of reference symbols 1 Working cylinder 23 External fastener 1a Inner workspace 24 External sealing element 1b open ending 25 disc 1c Piston rod end 26 Guide element 2 Working piston 27 Internal sealing element 6 piston rod 50 Gas spring 8 Compensating cylinder seal 10 compensating piston AE End of extension 10b Cylinder base AID Compensating cylinder inner diameter 10c cylinder jacket AUB Extension transition area 10d cylinder brim d depth 12 compensating cylinder EAD End area outer diameter 12a Compensation space EB End area 12c Piston rod end EE Insert end 15 Overhang EEB Insertion end area 15a storage room EUB Insertion transition area 15b closed end H lifting axis 18 Working cylinder seal HAD Stroke range outer diameter 20 Sealing device HB Lifting range 21 Fastening element x Position along the lifting axis 22 Sealing element E.g. Central area

Claims

1. A gas pressure spring (50), comprising a. a working piston (2) which is displaceably guided in a working cylinder (1) along a stroke axis (H) over a stroke range (HB), b. a compensating cylinder (12) surrounding the working cylinder (1) radially to the stroke axis (H), and c. a compensating piston (10) which is displaceably guided in the compensating cylinder (12) along the stroke axis (H), d. wherein the working cylinder (1) has an open end (1b) along the stroke axis (H), e. wherein the compensating cylinder (12) forms a projection (15) along the stroke axis (H) beyond the working cylinder (1) at the open end (1b), the projection (15) having a closed end (15b), f. wherein the compensating piston (10) separates a working chamber (1a) arranged in the working cylinder (1), a compensating chamber (12a) arranged between the working cylinder (1) and the compensating cylinder (12) and a restoring chamber (15a) arranged in the projection (15) from one another, g. wherein a distance of the compensating cylinder (12) from the working cylinder (1) measured radially to the stroke axis (H) is greater in the stroke range (HB) than in an end region (EB) of the working cylinder (1) lying between the stroke range (HB) and the open end (1b) of the working cylinder (1), characterized in that h. the compensating piston (10) is arranged at least in sections in the end region (EB) of the working cylinder (1).

2. The gas pressure spring (50) according to claim 1, characterized in that a wall thickness (WS) of the working cylinder (1) measured radially to the stroke axis (H) is the same in the stroke range (HB) and in the end range (EB) of the working cylinder (1).

3. The gas pressure spring (50) according to one of claims 1 to 2, characterized in that the compensating piston (10) is in one piece.

4. The gas pressure spring (50) according to one of claims 1 to 3, characterized in that the compensating piston (10) comprises aluminium or a plastic.

5. The gas pressure spring (50) according to one of claims 1 to 4, characterized in that the compensating piston (10) is hollow cylindrical in shape, wherein the compensating piston (10) a. comprises a closed cylinder base (10b) at an underside of the compensating piston (10), b. comprises a cylinder jacket (10c) arranged around the stroke axis (H), and c. is open on an upper side of the compensating piston (10) being arranged opposite the cylinder base (10b) along the stroke axis (H), d. wherein a compensating cylinder seal (8) sealing the compensating piston (10) to the compensating cylinder (12) is arranged on the compensating piston (10).

6. The gas pressure spring (50) according to claim 5, characterized in that a. the compensating piston (10) comprises a cylinder brim (10d) projecting radially to the stroke axis (H) outwards over the cylinder jacket (10c), b. wherein the compensating cylinder seal (8) is arranged on the cylinder brim (10d).

7. The gas pressure spring (50) according to one of claims 5 to 6, characterized in that the upper side of the compensating piston (10) is open to the restoring chamber (15a).

8. The gas pressure spring (50) according to one of claims 1 to 7, characterized in that a working cylinder seal (18) sealing the compensating piston (10) to the working cylinder (1) is arranged on the compensating piston (10).

9. The gas pressure spring (50) according to one of claims 1 to 8, characterized in that the gas pressure spring (50) comprises a number of support elements, the number of support elements supporting the working cylinder (1) on the compensating cylinder (12).

10. The gas pressure spring (50) according to claim 9, characterized in that the number of support elements is integral with the working cylinder (1) or with the compensating cylinder (12).

11. The gas pressure spring (50) according to one of claims 1 to 10, characterized in that the compensating piston (10) is arranged completely in the compensating cylinder (12).

12. A method for producing a gas pressure spring (50) according to one of claims 1 to 11, characterized by the following steps: a. providing a working cylinder blank, wherein the working cylinder blank is shaped like a hollow cylinder and has an outer diameter transverse to its longitudinal axis that is independent of a position along the longitudinal axis, b. forming the working cylinder blank into the working cylinder (1) of the gas pressure spring (50), the forming comprising an expansion of the outer diameter of the working cylinder blank in an end region of the working cylinder blank, and c. arranging the compensating piston (10) of the gas pressure spring (50) at least in sections in the end region (EB) of the working cylinder (1) of the gas pressure spring (50).

13. The method according to claim 12, characterized in that the expansion includes inserting a mandrel into the end region and preferably arranging a sleeve around the longitudinal axis around the end region before inserting the mandrel, so that the end region lies against the sleeve after the expansion.

14. The method according to one of claims 12 to 13, characterized by the following step: forming the working cylinder (1) of the gas pressure spring (50) and / or the compensating cylinder (12) of the gas pressure spring (50) to produce a number of support elements, the number of support elements supporting the working cylinder (1) on the compensating cylinder (12).

15. A drive system for a flap comprising a. a gas pressure spring (50) according to one of claims 1 to 11 to support the flap and b. an electromechanical drive, preferably a spindle drive, to drive the flap.