DE102021124843A1 - Temperature compensated gas spring, method of manufacturing the gas spring - Google Patents

Abstract

The invention relates to a gas pressure spring (50), comprising a working piston (2) that is displaceably guided in a working cylinder (1) along a stroke axis (H), a compensating cylinder (12) surrounding the working cylinder (1), and a compensating cylinder (12) compensating piston (10) which is movably guided along the stroke axis (H) and is hollow-cylindrical in shape. The working cylinder (1) has an open end (1b) on which the compensating cylinder (12) forms a projection (15) over the working cylinder (1) with a closed end (15b). 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 overhang (15). from each other. A distance radially to the stroke axis (H) of the compensating cylinder (12) from the working cylinder (1) is greater in the stroke area (HB) than in an end area lying between the stroke area (HB) and the open end (1b) of the working cylinder (1). (EB) of the working cylinder (1).

Description

technical field

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

Gas pressure springs are known from the prior art, in which a temperature dependency of the spring force is to be compensated for by a compensating medium.

The pamphlet 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 increases. The open end of the working cylinder opposite a piston outlet end is closed by means of a pot-shaped compensating piston. When the compensating medium expands, it moves the compensating piston in such a way that the volume of the working cylinder increases.

The pamphlet DE 31 41 295 A1 relates to a gas spring consisting of a container on the inside wall of which slides a piston connected to the piston rod. A space filled with expansion material is located between a container-fixed partition and a disc piston, this disc piston representing a movable partition wall for the space filled with expansion material. The gas spring also includes a working space with a pressurized gas filling. When the temperature rises, the expansion material expands and causes the disk piston to move further away from the partition fixed to the container, which increases the working space.

Known gas pressure springs with temperature compensation usually have a complicated structure, require a significantly larger installation space than gas pressure springs without temperature compensation, or cannot compensate for the temperature dependency over the entire application-relevant temperature range.

Technical task

The object of the invention is to create a cost-effective and simply constructed gas pressure spring and a cost-effective and reliable method for its manufacture, the spring force of the gas pressure spring being independent of the temperature over the widest possible temperature range.

Technical solution

The present invention provides a gas spring according to claim 1 that solves the technical problem. The object is also achieved by a method for producing the gas pressure spring according to claim 12. Advantageous configurations result from the dependent claims.

The gas pressure spring includes a working piston that is displaceably guided in a working cylinder along a lifting axis over a lifting range. The working piston is preferably displaceable relative to the working cylinder along the stroke axis. The working cylinder is preferably formed as a hollow cylinder and/or arranged coaxially to the lifting axis.

The gas pressure spring comprises a compensating cylinder which encloses the working cylinder radially to the lifting axis. The compensating cylinder is preferably shaped as a hollow cylinder and/or arranged coaxially to the lifting axis. The compensating cylinder is preferably rigidly attached to the working cylinder. The compensating cylinder is preferably in one piece, so that the gas pressure spring is particularly easy to produce.

The power cylinder has an open end along the stroke axis. "Open" means at least that a gas can freely exit the working cylinder and enter the working cylinder through the open end. Preferably the open end is fully open.

At a piston rod end of the working cylinder opposite the open end along the stroke axis, a piston rod of the gas pressure spring, which is fastened to the working piston, is preferably led out of the working cylinder through a sealing device. The sealing device preferably closes the end of the piston rod to a gas. "Closed" means that no gas can escape from or enter the working cylinder at the end of the piston rod.

The compensating cylinder forms an overhang at the open end over the working cylinder with a closed end along the stroke axis.

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

The compensating piston separates 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 overhang, preferably in a gas-tight manner.

A compensating medium is preferably arranged in the compensating chamber, which moves the compensating piston toward the closed end when the compensating medium is heated. A pressure of the compensation medium is, for example, from 70 bar to 350 bar.

The compensating medium preferably comprises an expanding material, in particular an expanding wax, particularly preferably a mixture of an expanding wax and an oil. The leveling medium can consist in particular of the expanding material, the expanding wax or the mixture of expanding wax and oil. The compensation medium can be designed, for example, like that in the publication EP 1 795 777 A2 described compensation medium. The stretch wax can, for example, be designed like that in the application DE 10 2020 113 749 described stretch wax.

A restoring means is preferably arranged in the restoring space, which displaces the compensating piston away from the closed end when the compensating medium cools.

The restoring means preferably comprises or is a restoring gas, with the restoring gas preferably being the same gas that fills the working space as the working gas. The reset gas and/or the working gas is nitrogen, for example. The restoring means can include or be formed by a mechanical restoring element, for example a spring, in particular a helical compression spring.

A gas pressure of the working gas is, for example, from 20 bar to 250 bar. A gas pressure of the reset gas is, for example, from 20 bar to 350 bar.

A distance of the compensating cylinder from the working cylinder, measured radially to the lifting axis, is preferably greater in the lifting area than in an end area of the working cylinder lying between the lifting area and the open end of the working cylinder.

The smaller distance in the end area results in a smaller cross-sectional area of the compensating space perpendicular to the lifting axis in the end area. As a result, the compensating piston is pushed further towards the closed end of the compensating cylinder for a given temperature increase due to an expansion of the compensating medium, so that the working chamber is enlarged more and the temperature dependence of the spring force of the gas pressure spring is compensated more.

Since the distance in the stroke area is not reduced, the compensating chamber as a whole can still accommodate an amount of compensating medium that is sufficient for effective temperature compensation.

Designing the distance in the lifting area and in the end area to be different from one another has the disadvantage that this makes the production of the gas pressure spring more complex. In addition, in a transition area between the lifting area and the end area, the material can be weakened due to deformation of the working cylinder and/or compensating cylinder or leaks can occur due to connection points between parts of the working cylinder and/or compensating cylinder. The different distance could thus jeopardize the reliable functioning of the gas pressure spring.

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

The distance between the compensating cylinder and the working cylinder in the end area and/or in the lifting area is preferably independent of a position along the lifting axis. In this configuration, the distance is constant in the end area and/or in the lifting area along the lifting axis, as a result of which the gas pressure spring is particularly easy to produce.

Description of execution types

An end area outer diameter of the working cylinder measured radially to the stroke axis is preferably larger in the end area of the working cylinder than a stroke area outer diameter of the working cylinder measured radially to the stroke axis in the stroke area. Such a widening of the working cylinder in the end area causes a reduced distance between the working cylinder and the outlet balancing cylinder without changing the balancing cylinder or the shape of the working cylinder in the lifting area. Thus, the reduced distance is achieved with as few changes as possible compared to a gas pressure spring from the prior art. The gas pressure spring can thus be produced in a particularly simple and cost-effective manner, in particular using known components and methods.

The end area 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 area outer diameter of the working cylinder. The outer diameter of the end area 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 outer diameter of the stroke area 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 values of the outside diameter, extensive compensation of the temperature dependency of the spring force of the gas pressure spring can be achieved over a typical temperature range of use of the gas pressure spring.

The outer diameter of the working cylinder in the end area and/or in the lifting area is preferably independent of a position along the lifting axis. In this configuration, the outer diameter is constant in the end area and/or in the lifting area along the lifting axis, as a result of which the gas pressure spring is particularly easy to produce.

A compensation cylinder inner diameter of the compensation cylinder 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 outer diameter of the stroke area of the working cylinder . The inner diameter of the compensating cylinder is, for example, from 20 mm to 30 mm, preferably from 23 mm to 27 mm, particularly preferably 25 mm. With the specified values for the inner diameter of the compensating cylinder, extensive compensation of the temperature dependency of the spring force of the gas pressure spring can be achieved over a typical temperature range of use of the gas pressure spring.

The inner diameter of the compensating cylinder is preferably independent of a position along the stroke axis. In this configuration, the inside diameter of the compensating cylinder is constant along the stroke axis, as a result of which the gas pressure spring is particularly easy to produce.

The lifting area and the end area of the working cylinder are preferably connected to one another in one piece, so that the gas pressure spring is particularly easy to produce. For example, the working cylinder can be widened in the end area transversely to the lifting axis relative to the lifting area.

The lifting area and the end area can, for example, be connected to one another with a material fit, in particular welded, soldered and/or glued to one another. The lifting 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 to one another.

The working cylinder can, for example, comprise or consist of a metal, in particular a steel, and/or a plastic.

A wall thickness of the working cylinder radially to the lifting axis is preferably the same in the lifting area and in the end area 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 area, for example up to a reduction of up to 0.2 mm. The wall thickness is preferably independent of a position along the stroke axis. In this configuration, the wall thickness of the working cylinder is constant along the stroke axis, as a result of which the gas pressure spring is particularly easy to produce.

A wall thickness of the compensating cylinder radially to the stroke axis is preferably independent of a position along the stroke axis. In this configuration, the wall thickness of the compensating cylinder is constant along the lifting axis, as a result of which the gas pressure spring is particularly easy to produce.

The compensating piston is preferably in one piece, so that the gas pressure spring is particularly easy to produce.

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

The compensating piston is preferably in the form of a hollow cylinder and is in particular arranged coaxially with the stroke axis.

The compensating piston preferably has a cylinder bottom on an underside of the compensating piston. The cylinder base is preferably aligned and/or closed perpendicularly to the stroke axis.

The compensating piston preferably includes a cylinder jacket running around the stroke axis. The cylinder jacket is preferably closed.

The compensating piston is open on an upper side of the compensating piston opposite the cylinder base along the stroke axis. This results in the advantage that the interior of the compensating piston can serve as part of the working space or the return space, so that the gas pressure spring can be constructed in a particularly compact manner.

The compensating piston is preferably pot-shaped, with the cylinder base corresponding to a pot base and the cylinder jacket to a pot wall.

A hollow-cylindrical or pot-shaped compensating piston has the advantage that it can separate the working space, the compensating space and the return space from one another with a particularly low mass.

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

The compensating piston preferably comprises a cylinder rim which preferably adjoins the upper side and protrudes radially to the stroke axis outwards beyond the cylinder jacket, the compensating cylinder seal being arranged, in particular fastened, on the cylinder rim. With the help of the cylinder brim, the compensating cylinder seal can be brought into reliable sealing contact with the compensating cylinder with little material expenditure.

The top of the compensating piston is preferably open to the reset space. As a result, the interior of the compensating piston becomes part of the reset space, so that more volume is available for the reset means relative to the working gas. The temperature dependency of the spring force can be compensated for more easily with a working gas volume that is smaller in relation to the volume of the restoring medium.

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

The compensating piston, preferably the cylinder jacket of the compensating piston and particularly preferably also the cylinder base of the compensating piston, is preferably arranged at least in sections in the end region of the working cylinder. As a result, the volume of the compensating space and/or the return space is increased relative to the volume of the working space, as a result of which more effective compensation of the temperature dependency of the spring force of the gas pressure spring is achieved.

The compensating piston is preferably arranged entirely in the compensating cylinder. This results in the advantage that a length of the gas pressure spring measured along the stroke axis does not change when the compensating piston moves. The length of the gas pressure spring is therefore not temperature-dependent.

The method for producing the gas pressure spring preferably includes providing a working cylinder blank, the working cylinder blank being shaped as a hollow cylinder and having an outside 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 pressure spring. The working cylinder blank preferably has material properties that are dependent on an azimuth with respect to its longitudinal axis, for example due to a weld seam along the longitudinal axis. Such a working cylinder blank is particularly easy and inexpensive to produce, for example by being drawn from steel and welded.

The method preferably includes forming the working cylinder blank into the working cylinder of the gas pressure spring, wherein the forming includes expanding the outer diameter of the working cylinder blank in an end region of the working cylinder blank.

The widening preferably includes inserting a mandrel into the end area and preferably arranging a sleeve running around the longitudinal axis around the end area of the working cylinder blank before inserting the mandrel, so that the end area rests against the sleeve after the widening. As a result, the diameter of a working cylinder blank, the material properties of which are dependent on an azimuth with respect to its longitudinal axis, can advantageously be expanded to a diameter that is independent of the azimuth.

The method preferably includes forming or machining a compensating piston blank to form the compensating piston. Reshaping allows the compensating piston to be manufactured with a particularly low material requirement. The compensating piston can be produced, for example, by deep-drawing a compensating piston blank made of aluminum. The compensating piston can be produced, for example, by forming from a compensating piston blank made of steel.

The compensating piston blank can be shaped as a hollow cylinder, for example. 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 compensating piston blank can be closed at its other end by roll closing and/or plasma welding in order to form a closed cylinder base. Beads running around its longitudinal axis can be rolled into the cylinder jacket of the compensating cylinder blank in order to partially accommodate the compensating cylinder seal and/or the working cylinder seal.

character list

• 1 shows an example of a schematic longitudinal section along the stroke axis of an embodiment of the gas pressure spring according to the invention.

Fig.1

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

The gas pressure spring 50 shown comprises a working piston 2, which is guided in a working cylinder 1 along a lifting axis H for displacement over a lifting range HB, a compensating cylinder 12 which encloses the working cylinder 1 radially to the lifting axis H, and a compensating cylinder 12 in the compensating cylinder 12 along the lifting axis H relative to the working cylinder 1 and the compensating cylinder 12, which is displaceably guided and hollow-cylindrical in shape.

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

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 overhang 15 from one another.

The compensating piston 10 comprises a cylinder base 10b and a cylinder casing 10c running around the stroke axis H on an underside of the compensating piston 10 facing the working chamber 1a. The cylinder bottom 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 restoring space 15a.

A compensating cylinder seal 18 that seals the compensating piston 10 to the compensating cylinder 12 is arranged on the compensating piston 10 .

The compensating piston 10 includes a cylinder rim 10d which protrudes radially to the stroke axis H outwards beyond the cylinder jacket 10c, the compensating cylinder seal 18 being arranged on the cylinder rim 10d.

A working cylinder seal 8 sealing the compensating piston 10 to the working cylinder 1 is arranged on the cylinder jacket 10c of the compensating piston 10 .

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 guided out of the working cylinder 1 through a sealing device 20 .

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

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

A compensating cylinder inner diameter AID of the compensating cylinder 12 is 25 mm, for example.

Reference List

1

working cylinder

1a

inner working space

1b

open end

1c

piston rod end

2

working piston

6

piston rod

8th

balancing cylinder seal

10

balance piston

10b

cylinder bottom

10c

cylinder jacket

10d

cylinder brim

12

balancing cylinder

12a

balancing room

15

Got over

15a

reset room

15b

closed end

18

working cylinder seal

20

sealing device

50

gas spring

aid

Compensation cylinder inside diameter

EAD

End Section Outside Diameter

EB

end area

H

lifting axis

HAD

Stroke Range Outside Diameter

hb

lifting range

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1795777 A2 [0003, 0016]
• DE 3141295 A1 [0004]
• DE 102020113749 [0016]

Claims (15)

Gas spring (50) comprising a. a working piston (2) displaceably guided in a working cylinder (1) along a lifting axis (H) over a lifting range (HB), b. a compensating cylinder (12) surrounding the working cylinder (1) radially to the lifting axis (H), and c. a compensating piston (10) 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) at the open end (1b) forms a projection (15) over the working cylinder (1) with a closed end (15b) along the stroke axis (H), f. wherein the compensating piston (10) has a in the 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 overhang (15) separates one another, characterized in that g. a distance of the compensating cylinder (12) from the working cylinder (1), measured radially to the stroke axis (H), is greater in the stroke area (HB) than in one between the stroke area (HB) and the open end (1b) of the working cylinder (1). End area (EB) of the working cylinder (1). Gas pressure spring (50) after claim 1 , characterized in that an end area outer diameter (EAD) of the working cylinder (1) measured radially to the stroke axis (H) is greater than a stroke area outer diameter (HAD) of the working cylinder (1) measured radially to the stroke axis (H) in the stroke area ( HB). Gas spring (50) according to one of Claims 1 until 2 , characterized in that the lifting area (HB) and the end area (EB) of the working cylinder (1) are connected to one another in one piece. Gas spring (50) according to one of Claims 1 until 3 , characterized in that a wall thickness (WS) of the working cylinder (1) radially to the lifting axis (H) in the lifting area (HB) and in the end area (EB) of the working cylinder (1) is the same. Gas spring (50) according to one of Claims 1 until 4 , characterized in that the compensating piston (10) is in one piece. Gas spring (50) according to one of Claims 1 until 5 , characterized in that the compensating piston (10) comprises aluminum or a plastic. Gas spring (50) according to one of Claims 1 until 6 , characterized in that the compensating piston (10) is formed as a hollow cylinder, wherein the compensating piston (10) a. comprises a cylinder base (10b) on an underside of the compensating piston (10), b. comprises a cylinder casing (10c) running around the lifting axis (H), c. is open on an upper side of the compensating piston (10) opposite the cylinder base (10b) along the stroke axis (H), and d. A compensating cylinder seal (18) sealing the compensating piston (10) to the compensating cylinder (12) is arranged on the compensating piston (10). Gas pressure spring (50) after claim 7 , characterized in that the compensating piston (10) a. a cylinder rim (10d) which protrudes radially to the stroke axis (H) outwards beyond the cylinder jacket (10c), b. wherein the balance cylinder seal (18) is located on the cylinder rim (10d). Gas spring (50) according to one of Claims 7 until 8th , characterized in that the upper side of the compensating piston (10) is open to the return space (15a). Gas spring (50) according to one of Claims 1 until 9 , characterized in that a working cylinder seal (8) sealing the compensating piston (10) to the working cylinder (1) is arranged on the compensating piston (10). Gas spring (50) according to one of Claims 1 until 10 , characterized in that the compensating piston (10) is arranged at least in sections in the end region (EB) of the working cylinder (1). Gas spring (50) according to one of Claims 1 until 11 , characterized in that the compensating piston (10) is arranged entirely in the compensating cylinder (12). Method for producing the gas pressure spring (50) according to one of Claims 1 until 12 , characterized by the following steps: a. Providing a working cylinder blank, wherein the working cylinder blank is shaped as a hollow cylinder and has an outer diameter transverse to the longitudinal axis that is independent of a position along its longitudinal axis, and b. Reshaping of the working cylinder blank to form the working cylinder (1) of the gas pressure spring (50), c. wherein the forming comprises expanding the outer diameter of the working cylinder blank in an end region of the working cylinder blank. procedure after Claim 13 , characterized in that the widening comprises inserting a mandrel into the end region and preferably arranging a sleeve running around the longitudinal axis around the end region before inserting the mandrel, so that the end region bears against the sleeve after the widening. procedure after Claim 13 or 14 , characterized by the following step: forming or machining a compensating piston blank to form the compensating piston (10) of the gas pressure spring (50).

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