Pneumatic strut, method for producing a pneumatic strut, drive for a flap having a pneumatic strut

Abstract

The present invention relates to a pneumatic strut comprising: an external working space disposed radially to a stroke axis between a working cylinder and a balancing cylinder, the external working space being connected to an internal working space in a pneumatically guided manner; a balancing piston radially surrounding the working cylinder along the stroke axis, the balancing piston being movably mounted along the stroke axis, defining the external working space on a side transverse to the stroke axis, and being subjected to working medium pressure and balancing medium pressure to increase the volume of the external working space; and a restoring medium disposed in a restoring space radially to the stroke axis between the working cylinder and the balancing cylinder, the restoring medium being subjected to pressure from the restoring medium to reduce the volume of the external working space. The present invention also relates to a method for manufacturing the pneumatic strut and a drive for a flap having the pneumatic strut.

Description

Technical Field

[0001] The invention relates to a pneumatic strut comprising a working cylinder which encloses an inner working space filled with working gas; a working piston which is mounted movably along a stroke axis in the inner working space; a balancing cylinder which encloses the working cylinder along the stroke axis at least over a portion of its length; and a balancing medium which expands when the temperature rises and is arranged in the balancing space radially to the stroke axis between the working cylinder and the balancing cylinder.

[0002] The invention further relates to a method for producing a pneumatic strut and a drive for a flap having such a pneumatic strut. Background Art

[0003] The gas contained in a pneumatic strut expands as the temperature T increases and contracts as the temperature T decreases, or, if the volume V is constant, the gas pressure p increases or decreases (for an ideal gas, p × V = n × R × T). Therefore, the spring force provided by the pneumatic strut is also temperature-dependent. In many applications, this can cause problems, which is why it is advantageous to compensate for this effect.

[0004] For example, when used in vehicle tailgates, the temperature dependence of the spring force necessitates that the pneumatic strut be configured to be more powerful than necessary at most temperatures in order to provide sufficient spring force to keep the tailgate securely open even at low temperatures (e.g., -30°C to 0°C). However, this generally increases the required motor power of the automatic actuator designed to close the tailgate against the pneumatic strut, as the pneumatic strut typically operates at moderate temperatures (e.g., from 0°C to 25°C) and its spring force is higher than necessary. The high motor power requires an undesirably large and heavy motor and results in an undesirably high power consumption. Furthermore, due to the temperature dependence of the spring force during manual operation, ease of operation is reduced at moderate to high temperatures (e.g., above 25°C) because a significant force is required to compress the pneumatic strut when closing the tailgate.

[0005] Patent application EP 1 795 777 A1 describes a pneumatic strut comprising a working cylinder that, together with a balancing piston, defines a working space filled with a working medium. The balancing piston is pressurized by the pressure of the working medium and by a balancing medium, which expands with increasing temperature. The balancing medium is arranged in the balancing space to increase the volume of the working space. The balancing medium thus adjusts the available volume of the working medium according to temperature, thereby reducing the temperature dependence of the pneumatic strut's spring force.

[0006] Currently, the prior art offers several non-optimal solutions to compensate for the temperature dependence of the gas strut spring force:

[0007] a. When the temperature is low, temperature compensation is performed by providing additional volume, for example by a tempering drive valve as described in DE 11 2006000335T5,

[0008] b. The use of spring struts, especially a combination of pneumatic struts and mechanical springs, and

[0009] c. As described in EP 1 795 777 A1, a balancing medium is used to reduce the temperature dependence.

[0010] Option A provides limited temperature compensation, and the spring rate changes due to the additional capacity provided. In addition, the overall length is much greater than when using a simple pneumatic strut.

[0011] The disadvantage of option b is that a sufficiently large spring strut is very expensive to produce, is heavy, and has an unsatisfactory spring stiffness. Furthermore, the temperature dependence cannot be completely overcome.

[0012] Option C is technically very complex and, most importantly, uneconomical to implement in terms of assembly. Furthermore, under certain operating conditions, very high pressures can occur in the compensating chamber, which can lead to significant stresses on the sealing elements and piping of the pneumatic strut. Furthermore, the overall length of the pneumatic strut, which is achieved by temperature compensation due to the extended operating chamber, is significantly longer than that of an uncompensated pneumatic strut, significantly limiting the possible applications. Summary of the Invention

[0013] The object of the present invention is to provide an inexpensive, durable pneumatic strut which is versatile in use and has the lowest possible temperature dependence of the spring force. Furthermore, the object of the present invention is to create a production method for the pneumatic strut which is as inexpensive and reliable as possible.

[0014] The subject of the present invention provides a pneumatic strut which achieves the technical objectives. Likewise, the objectives are achieved by a production method and a drive system.

[0015] The pneumatic strut according to the present invention comprises at least one working cylinder enclosing an internal working space filled with a working gas. For example, the working cylinder may be substantially hollow cylindrical and / or coaxially arranged with a stroke axis (defined further below), and / or may enclose the working space in a gas-tight manner, except for a plurality of connections to an external working space for the working gas (described further below). For example, the working gas may be nitrogen or another gas known for filling pneumatic struts. The working cylinder is preferably integral to facilitate the manufacture of the pneumatic strut.

[0016] The pneumatic strut comprises at least one working piston that is movably mounted along a stroke axis within the internal working space. As is conventional with pneumatic struts, the working piston can divide the working space into two chambers and / or be connected to a piston rod that transmits the movement of a component connected to the pneumatic strut relative to the working cylinder to the working piston.

[0017] The pneumatic strut includes at least one balancing cylinder, which surrounds the working cylinder along the stroke axis over at least part of its length, in particular in a gas-tight manner with respect to the working gas. The balancing cylinder is, for example, rotationally symmetrical with respect to the stroke axis and / or surrounds the working cylinder along the stroke axis or over its entire length, so that it provides at least one additional length relative to the working cylinder along the stroke axis. The balancing cylinder is, for example, substantially hollow-cylindrical in shape. The balancing cylinder is preferably integral to facilitate the production of the pneumatic strut.

[0018] The pneumatic strut comprises at least one balancing medium that expands when the temperature rises, the balancing medium being arranged in at least one balancing space located at least radially on the stroke axis between the working cylinder and the balancing cylinder. The balancing medium preferably fills the balancing space.

[0019] The equilibration medium is preferably a swelling substance, such as a swelling wax, in particular a mixture of paraffins and / or alkanes, an oil or a two-phase medium, which can in particular be configured as described in EP 1 795 777 A1 or DE 10 2020 113 749 A1, wherein the advantages described therein emerge.

[0020] The pneumatic strut comprises at least one external working space, which is arranged at least radially on the stroke axis between the working cylinder and the balancing cylinder and is connected to the internal working space in a gas-conducting manner. The external working space is, for example, formed as a substantially hollow cylinder and / or arranged coaxially with the stroke axis. The external working space is connected to the internal working space in a gas-conducting manner via a number of openings, in particular holes in the side wall of the working cylinder radially to the stroke axis. The side wall preferably runs around the stroke axis. The advantage of connecting the external working space and the internal working space via the side wall is that the external working space can be arranged completely along the internal working space or surround the internal working space relative to the stroke axis. This advantageously results in a particularly short length of the pneumatic strut along the stroke axis. The end wall of the working cylinder, which is aligned transversely with the stroke axis, is preferably closed to the working gas.

[0021] The pneumatic strut includes at least one balancing piston, which radially surrounds the working cylinder along the stroke axis. The balancing piston is movably installed along the stroke axis, defines an external working space on at least one side transverse to the stroke axis, and is pressurized by the working medium pressure and the balancing medium pressure to increase the volume of the external working space.

[0022] The balancing piston is, for example, designed as a hollow cylinder and / or arranged coaxially with the stroke axis. It is preferably integral to facilitate the production of the pneumatic strut. The balancing piston is preferably completely disposed within the balancing cylinder. This has the advantage that the length of the pneumatic strut measured along the stroke axis does not change as the balancing piston moves along the stroke axis. Therefore, the length is independent of temperature.

[0023] When the temperature rises, the balancing medium expands, displacing the balancing piston along the stroke axis and thus increasing the external working space. Consequently, the volume available to the working gas in both the internal and external working spaces increases, counteracting the increase in working gas pressure due to the temperature increase. By appropriately selecting the balancing medium and / or the geometry of the pneumatic strut, the temperature dependence of the working gas pressure and the resulting spring force of the pneumatic strut can be reduced or even completely compensated. This, in particular, allows for better compensation compared to a spring strut.

[0024] The arrangement of the external working space radially along the stroke axis between the working cylinder and the compensating cylinder according to the present invention has the particular advantage that the overall length of the pneumatic strut along the stroke axis does not need to be extended compared to a pneumatic strut without the external working space. Consequently, the overall length of the pneumatic strut can be significantly reduced compared to EP 1 795 777 A2, allowing the pneumatic strut to be used in a more versatile manner.

[0025] The pneumatic strut preferably includes at least one restoring medium arranged in at least one restoring space, the restoring space being arranged at least radially on the stroke axis between the working cylinder and the balancing cylinder. The balancing piston is pressurized by the pressure of the restoring medium in order to reduce the volume of the outer working space. The restoring medium preferably fills the restoring space.

[0026] The return space is, for example, configured rotationally symmetrically with respect to the stroke axis. The external working space is preferably arranged along the stroke axis between the balancing space and the return space. The return space is preferably arranged at one end of the pneumatic strut, while the balancing space is arranged at the other end of the pneumatic strut along the stroke axis. By arranging the external working space between the balancing space and the return space, the balancing medium and the return medium can act on the volume of the external working space in opposite directions in a particularly simple manner, thereby compensating for the temperature dependence of the pneumatic strut spring force during heating and cooling.

[0027] The restoring medium advantageously ensures that if the balancing medium contracts during a temperature drop, the balancing piston is displaced, thereby reducing the external working volume. Consequently, the available volume of working gas in the internal and external working volumes is smaller, which offsets the decrease in working gas pressure due to the temperature drop. Ideally, in the event of temperature fluctuations, the balancing piston is reversibly displaced by the balancing medium, working gas, and restoring medium, thereby permanently compensating for the temperature dependence of the gas spring's spring force.

[0028] The arrangement of the return space between the working cylinder and the compensating cylinder radially relative to the stroke axis according to the present invention has the particular advantage that the overall length of the pneumatic strut along the stroke axis does not need to be extended compared to a pneumatic strut without a return space. Consequently, the overall length of the pneumatic strut can be significantly reduced compared to EP 1 795 777 A2, allowing the pneumatic strut to be used in a more versatile manner.

[0029] The pneumatic strut preferably comprises at least one tappet, which can displace the balancing space along the stroke axis toward the balancing piston by the pressure of the balancing medium.

[0030] The tappet can, for example, be designed as a hollow cylinder and / or be arranged coaxially with the stroke axis. The tappet preferably has a smaller cross-sectional area transversely to the stroke axis than the balancing piston. Consequently, a given change in the balancing medium volume results in a further displacement of the balancing piston than would be the case without the tappet, thereby more effectively compensating for the temperature dependence of the pneumatic strut spring force.

[0031] If the balancing piston is arranged on the side of the outer working space facing away from the balancing space, the tappet can advantageously connect the balancing piston to the balancing medium. Thus, the expansion of the balancing medium can bring about an increase in the outer working space in a particularly simple manner.

[0032] The compensating cylinder preferably forms at least one additional length on the working cylinder along the stroke axis, the at least one additional length encompassing a partial region of the compensating space and / or the restoring space.

[0033] By arranging a portion of the balancing and / or restoring space in the additional length, the pneumatic strut can contain more balancing and / or restoring medium without having to increase the diameter of the pneumatic strut laterally relative to the stroke axis. The pneumatic strut can thus be adapted to the varying requirements of the pressure exerted by the balancing and / or restoring medium and the available installation space for the pneumatic strut.

[0034] For practical use of the pneumatic strut in vehicle construction, it has proven particularly advantageous to arrange a portion of the restoring space within the excess length. This allows the restoring space to be sufficiently large so that during operation of the pneumatic strut, the pressure of the restoring medium is limited to a value that is not critical for the conventional sealing arrangements and materials of the compensating and working cylinders, for example, below 250 bar.

[0035] The pneumatic strut preferably comprises a piston rod fixed to a working piston, the piston rod being movably mounted along a stroke axis in a working cylinder, with the excess length being arranged at an end of the working cylinder, distal from the piston rod along the stroke axis. This has the advantage that the stroke movement of the piston rod and the connection of the piston rod to other components are not hindered by the excess length.

[0036] The pneumatic strut preferably comprises a piston rod fixed to a working piston, said piston rod being movably mounted along a stroke axis in a working cylinder, the return space being arranged at an end of the working cylinder which is remote from the piston rod along the stroke axis.

[0037] Typically, a pneumatic strut is created by inserting the working piston forward into the working cylinder with the side facing away from the piston rod, and injecting the working gas into the working cylinder from the side of the piston rod that projects out of the working cylinder. If the balancing chamber is arranged on the side of the working cylinder facing away from the piston rod, the filling of the special gaseous restoring medium and the special wax-like balancing medium can be integrated particularly easily into this process.

[0038] The external working volume is preferably transverse to the stroke axis and has a smaller diameter than the balancing and / or restoring volume. This ensures that the volume of balancing and / or restoring medium in the balancing and / or restoring volume is sufficiently large to ensure reliable operation under typical conditions of pneumatic strut use and to broadly compensate for the temperature dependence of the spring force. At the same time, the length of the pneumatic strut, measured along the stroke axis, should be as small as possible.

[0039] The balancing cylinder preferably encloses a balancing space, an external working space, and a restoring space radially to the stroke axis, wherein the diameter of the balancing cylinder, measured transversely to the stroke axis, widens in the region of the balancing space and / or the restoring space relative to the region of the external working space. In this embodiment, different diameters of the external working space and the balancing space and / or the restoring space are particularly easy to produce.

[0040] In particular, a sufficiently large restoring space ensures that the pressure of the restoring medium remains at a value that is not critical for conventional sealing devices and materials of the balancing cylinder and the working cylinder, for example, below 250 bar. A sufficiently large restoring space ensures that the restoring medium expands sufficiently when the temperature rises to increase the external working space, so that the pressure of the working gas does not increase significantly.

[0041] In one embodiment, the restoring medium is a gas, particularly a working gas. Gas offers advantages over mechanical springs, such as reduced mass and quiet operation. Using a working gas as the restoring medium simplifies the production of the pneumatic strut, as only one type of gas is used. In addition to or as an alternative to a gaseous restoring medium, the restoring medium may include a mechanical restoring spring in the restoring space.

[0042] The reset space preferably contains a multiplier piston which is movably mounted along the stroke axis and which divides the reset space into a liquid space in contact with the compensating piston and a gas space which is separated from the compensating piston in a gas-tight manner.

[0043] The liquid space is filled with a hydraulic fluid, in particular hydraulic oil, and the gas space is filled with a restoring medium in the form of a gas, in particular a working gas.

[0044] The cross-sectional area of ​​the multiplier piston transverse to the stroke axis is preferably greater than the cross-sectional area of ​​the balancing piston transverse to the stroke axis, for example, two to ten times, in particular five times. Thus, the multiplier piston and the balancing piston, along with the hydraulic oil located therebetween, act as a hydraulic multiplier. Consequently, when using hydraulic multiplication, the pressure in the reset space needs to be lower than when it is not, in order to compress the balancing medium during cooling. This helps protect the seals and walls that separate the reset space.

[0045] The outer diameter of the multiplier piston transverse to the stroke axis is larger or smaller than that of the balancing piston, or is the same as that of the balancing piston.

[0046] The multiplier piston is preferably a disc-shaped structure, with the plane of the disc oriented transversely to the stroke axis and / or arranged along the stroke axis in front of the end of the working cylinder distal to the piston rod. Compared to a balancing piston arranged annularly around the working cylinder, the disc-shaped multiplier piston can also have a larger cross-sectional area, provided that the outer diameter of the balancing piston is not larger than that of the balancing piston.

[0047] The present invention relates to a method for manufacturing a pneumatic strut according to the present invention. The method comprises at least the following steps:

[0048] a. The working cylinder of the pneumatic strut is arranged in the balance cylinder of the pneumatic strut;

[0049] b. After the arrangement is completed, the resetting medium, the balancing medium of the balancing piston and the pneumatic strut are filled in the space between the working cylinder and the balancing cylinder;

[0050] c. After the arrangement step, the working gas of the working piston and the pneumatic strut is introduced into the working cylinder, and

[0051] d. After the filling and introduction steps, the working cylinder and the balancing cylinder are closed airtight.

[0052] The method preferably includes simultaneously introducing working gas into the inner and outer working spaces, filling the return space of the pneumatic strut with the working gas as return medium, in particular via a non-return valve from the working space to the return space, and discharging part of the working medium from the inner and outer working spaces after the introduction and filling.

[0053] The advantage of simultaneous introduction and filling is that assembly of the pneumatic strut is accelerated and simplified. By partially removing the working medium from the working space, the pressure of the working medium acting as the resetting medium in the resetting space is higher than that of the working medium in the inner and outer working spaces. As a result, the resetting medium, at a low temperature and opposite to the working and balancing medium pressures, resets the balancing piston to the position with the smallest outer working space.

[0054] The method preferably comprises measuring the diameter of the balancing cylinder transversely in the region of the balancing volume and / or the reset volume relative to the region of the external working volume.

[0055] The present invention relates to a drive system for a flap having the following structure:

[0056] a. a pneumatic strut for supporting a flap according to the present invention, and

[0057] b. Electromechanical drives for driving the flaps, such as linear drives, in particular spindle drives.

[0058] For example, the flap may be a flap of a vehicle, in particular a hood, a trunk lid, a trunk door or a fender door.

[0059] Drive systems for flaps having pneumatic struts for supporting the flaps and electromechanical drives for driving the flaps are known in the prior art. The drive system according to the invention can be constructed similarly to corresponding drive systems of the prior art, such as those from DE 103 13 440 A1 or DE 10 2008 045 903 A1, except that the pneumatic struts according to the invention are used instead of conventional struts.

[0060] The pneumatic struts of the drive system are used to fix the flaps in any position against gravity, while the electromechanical drive is used to open and close the flaps. In addition, as described in DE 103 13 440 A1 and DE 10 2008 045 903 A1, manual operation of the flaps can be provided.

[0061] The spring force of the pneumatic struts must be high enough to hold the flap in place even at low ambient temperatures. Since the spring force in conventional pneumatic struts increases with temperature, the electromechanical actuator or the operator must apply very high forces to close the flap at high temperatures. Consequently, the drive system must include a very powerful electromechanical actuator, which is expensive, takes up a lot of installation space, and consumes a lot of energy during operation. Furthermore, the electromechanical actuator and other components mechanically connected to the flap, such as the hinges, are subject to significant wear.

[0062] In the prior art, these problems are avoided by using spring struts instead of pneumatic struts (e.g., DE 10 2008 045 903 A1, paragraph

[0021] ). Although spring struts have a temperature-independent spring force, they are larger, heavier, and more expensive than pneumatic struts with the same spring force.

[0063] Due to the use of the temperature-compensated aerodynamic struts according to the invention instead of the aerodynamic struts customary in the art, a particularly cheap, durable, compact and energy-efficient drive system is created, which is easy to manufacture and operate for the flap. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Further advantages, objects and features of the invention will be discussed with reference to the following description and the accompanying drawings, in which the subject matter according to the invention is illustrated by way of example. Features that correspond at least substantially to their function in the drawings may be given the same reference numerals here: it is not necessary to indicate and discuss these features in all drawings.

[0065] Figure 1 A schematic longitudinal section through a pneumatic strut according to the present invention is shown.

[0066] Figure 2 FIG2 shows a schematic longitudinal section of another pneumatic strut according to the present invention along its stroke axis. DETAILED DESCRIPTION

[0067] Figure 1

[0068] Figure 1 A schematic longitudinal section of a pneumatic strut 50 according to the present invention along its stroke axis H is shown.

[0069] The pneumatic strut 50 includes a working cylinder 1, which encloses an internal working space 1a filled with a working gas (not shown), such as nitrogen. For example, the working cylinder 1 is substantially hollow cylindrical and coaxially arranged with the stroke axis H. For example, the length of the working cylinder 1 along the stroke axis H is 230 mm, and the inner diameter transverse to the stroke axis is 16 mm, and the outer diameter is 19 mm.

[0070] The pneumatic strut 50 includes a working piston 2 , which is mounted in an inner working space 1 a so as to be displaceable along a stroke axis H. The working piston 2 is, for example, substantially cylindrical in shape and is arranged coaxially with the stroke axis H.

[0071] The working piston 2 preferably subdivides the interior 1 a of the working cylinder 1 into a first working chamber 3 and a second working chamber 4 , which are arranged one behind the other along the stroke axis H. The working piston 2 can have a special annular seal 9 , which contacts the inner side of the working cylinder 1 , so that the working medium cannot flow around the working piston 2 when the working piston 2 moves along the stroke axis H.

[0072] The working piston 2 may have a throttle opening 5 which connects the first working chamber 3 to the second working chamber 4 in order to enable a controlled pressure equalization between the first working chamber 3 and the second working chamber 4 .

[0073] Preferably, a piston rod 6 is fastened to the working piston 2 , said piston rod 6 being passed along the stroke axis H through the second working chamber 4 and being removed from the pneumatic strut 50 , for example by closing the closure element 14 of the working cylinder 1 .

[0074] The pneumatic strut 50 includes a balancing cylinder 12 that surrounds the working cylinder 1 along the stroke axis H over a portion of its length. The balancing cylinder 12 can be formed substantially rotationally symmetrically with respect to the stroke axis H. The balancing cylinder 12 can surround the working cylinder 1 along the stroke axis H over its entire length and, in particular, along the stroke axis H, form an additional length 12b of the working cylinder 1 at the end of the working cylinder 1 (away from the piston rod 6). For example, the additional length can have a length of 20 mm along the longitudinal axis.

[0075] The pneumatic strut 50 includes a balancing medium (not shown) disposed in a balancing space 16a radially relative to the stroke axis H between the working cylinder 1 and the balancing cylinder 12. The balancing medium expands as the temperature increases. The balancing medium preferably fills the balancing space. The balancing medium is, for example, expansion wax. The balancing space 16a is, for example, formed substantially rotationally symmetrically with respect to the stroke axis H. For example, the balancing space 16a has a length of 113 mm along the stroke axis.

[0076] The pneumatic strut 50 includes an outer working space 12a, which is arranged radially on the stroke axis H between the working cylinder 1 and the balancing cylinder 12. The outer working space 12a is connected to the inner working space 1a, in particular the first working chamber 3, in a gas-conducting manner, for example, via a plurality of openings 1b in the side wall of the working cylinder 1. The outer working space 12a is, for example, formed substantially rotationally symmetrically with respect to the stroke axis H.

[0077] The pneumatic strut 50 includes a balancing piston 10 radially surrounding the working cylinder 1 along the stroke axis H. The balancing piston 10 is movably mounted along the stroke axis H, defining an external working space 12a on one side transverse to the stroke axis H. The balancing piston 10 is subjected to pressure from the working medium and the balancing medium, thereby increasing the volume of the external working space 12a. The balancing piston 10 is, for example, substantially hollow cylindrical and arranged coaxially with the stroke axis H. For example, the balancing piston 10 is movable along the stroke axis H by a balancing distance of 84 mm.

[0078] The pneumatic strut 50 includes a restoring medium (not shown) disposed in a restoring space 15a radially relative to the stroke axis H between the working cylinder 1 and the balancing cylinder 12. The balancing piston 10 is pressurized by the pressure of the restoring medium to reduce the volume of the external working space 12a. The restoring medium is, for example, a gas, particularly a working gas.

[0079] The return space 15a is formed, for example, substantially rotationally symmetrically with respect to the stroke axis H. The return space 15a may be arranged in the excess length 12b of the balancing cylinder 12 along the portion of the stroke axis H outside the working cylinder 1. For example, at the maximum displacement of the balancing piston 10 toward the return space 15a, the minimum length of the return space 15a along the stroke axis H is 60 mm.

[0080] Preferably, the balancing space 16a, the external working space 12a and the reset space 15a are arranged one after another along the stroke axis H, especially the reset space 15a may be arranged at one end of the pneumatic strut 50 away from the piston rod 6, the balancing space 16a at one end of the pneumatic strut 50, the piston rod 6 is removed from the pneumatic strut 50, and the external working space 12a between the reset space 15a and the balancing space 16a.

[0081] The diameters of the balancing space 16a and the reset space 15a transverse to the stroke axis can be larger than the external working space 12a. For example, the outer diameter of the balancing space 16a is 30mm, the outer diameter of the reset space 15a is 25mm to 30mm, and the outer diameter of the external working space 12a is 25mm.

[0082] The balancing space 16a and the reset space 15a can be sealed from the outer working space 12a using in each case at least one seal 9 , for example using in each case at least one O-ring.

[0083] The balancing space 16a can be closed at the end remote from the external working space 12a by a closing element 14, in particular a closing disk. The working cylinder 1 and the balancing space 16a can be closed in particular using a common closing element 14.

[0084] The pneumatic strut 50 preferably includes a tappet 110 that can discharge the balancing space 16 a along the stroke axis H toward the balancing piston 10 due to the pressure of the balancing medium. The tappet 110 is, for example, substantially in the form of a hollow cylinder and is arranged coaxially with the stroke axis H. The tappet 110 can be guided from the balancing space 16 a through the external working space 12 a to the balancing piston 10 and, in particular, can be fixed to the balancing piston 10 or formed integrally therewith.

[0085] exist Figure 1In FIG, the pneumatic strut 50 is shown at a low temperature, when the volume of the external working space 12a is small. When the pneumatic strut 50 is heated, the balancing medium expands in the balancing space 16a, thereby moving the balancing piston 10 along the stroke axis H, thereby increasing the volume of the external working space 12a ( Figure 1 As a result, the pressure increase caused by the temperature increase of the working gas in the inner working space 1a and the outer working space 12a can be compensated.

[0086] When the pneumatic strut 50 cools, the balancing medium contracts in the balancing space 16a, so that the resetting medium pressure in the resetting space 15a moves the balancing piston 10, thereby reducing the volume of the external working space 12a ( Figure 1 As a result, the pressure drop caused by the cooling of the working gas in the inner working space 1a and the outer working space 12a can be compensated.

[0087] Figure 2

[0088] Figure 2 FIG. 1 is a schematic longitudinal section of another pneumatic strut 50 according to the present invention along its stroke axis H. FIG.

[0089] Figure 1 The features of the pneumatic strut 50 shown in FIG. Figure 1 The same reference number as in Figure 1 Configure the relevant description.

[0090] Figure 2 The return space 15a of the pneumatic strut 50 shown contains a multiplier piston 17 which is mounted movably along the stroke axis H and which divides the return space 15a, for example by means of a seal 9, into a liquid space 18a which is in contact with the balancing piston 10 and a gas space 19a which is separated from the balancing piston 10 in a gas-tight manner.

[0091] In this configuration, the liquid space 18 a is filled with a hydraulic fluid and the gas space 19 a is filled with a restoring medium in gaseous form.

[0092] The cross-sectional area of ​​the multiplication piston 17 transversely to the stroke axis H is greater than the cross-sectional area of ​​the balancing piston 10 transversely to the stroke axis H, so that the multiplication piston 17 with the balancing piston 10 and the hydraulic fluid arranged therebetween form a hydraulic multiplication.

[0093] For example, the outer diameter of the multiplier piston 17 transversely to the stroke axis H is larger than that of the compensating piston 10 .

[0094] The multiplication piston 17 is preferably a disk-shaped structure, for example, with the disk plane facing transversely to the stroke axis H and arranged along the stroke axis H in front of an end of the working cylinder 1 away from the piston rod 6 .

[0095] List of Reference Numerals

[0096] 1 working cylinder 12 balancing cylinders

[0097] 1a Internal working space 12a External working space

[0098] 1b opening 12b extra length

[0099] 2 Working piston 14 Closing element

[0100] 3. Reset space of the first working chamber 15a

[0101] 4 Second working chamber 16a balance space

[0102] 5 throttle holes 17 times the piston

[0103] 6 Piston rod 18a liquid space

[0104] 9 Seal 19a Gas space

[0105] 10 balanced piston 50 pneumatic strut

[0106] 110 tappet

[0107] H stroke axis

Claims

1. A pneumatic strut (50), comprising a. a working cylinder (1), which encloses an inner working space (1a) filled with working gas, b. a working piston (2) which is movably mounted along a stroke axis (H) in the inner working space (1a), c. a balancing cylinder (12) which surrounds the working cylinder (1) along the stroke axis (H) at least over part of its length, d. a balancing space (16a) arranged between the working cylinder (1) and the balancing cylinder (12) in the radial direction of the stroke axis (H), and e. a balancing medium which expands when the temperature rises, said balancing medium being arranged in the balancing space (16a), It is characterized by f. External workspace (12a), i. The external working space (12a) is arranged between the working cylinder (1) and the balancing cylinder (12) along the radial direction of the stroke axis, ii. Among them, The external working space (12a) is connected to the internal working space (1a) in an air-conducting manner through the side wall of the working cylinder (1) via a plurality of openings (1b). g. A balancing piston (10) which surrounds the working cylinder (1) in the radial direction of the stroke axis, wherein the balancing piston (10) i. Movable installation along the stroke axis (H), ii. defining an external working space (12a) on one side transverse to the stroke axis (H), and iii. pressurizing the external working space (12a) by the working medium pressure and the balance medium pressure, and h. a reset space (15a) arranged between the working cylinder (1) and the balancing cylinder (12) in the radial direction of the stroke axis (H), and i. A resetting medium is arranged in the resetting space (15a), wherein the balancing piston (10) is pressurized by the pressure of the resetting medium to reduce the volume of the external working space (12a).

2. The pneumatic strut (50) according to claim 1, It is characterized by The balancing piston (10) is completely installed in the balancing cylinder (12).

3. The pneumatic strut (50) according to claim 1, It is characterized by The external working space (12a) is arranged between the balancing space (16a) and the reset space (15a) along the radial direction of the stroke axis (H).

4. The pneumatic strut (50) according to claim 1, It is characterized by A tappet (110) is capable of being displaced from the balancing space (16a) by the pressure of a balancing medium along a stroke axis (H) in the direction of the balancing piston (10), wherein the tappet (110) has a smaller cross-sectional area than the balancing piston (10) measured in a direction transverse to the stroke axis (H).

5. The pneumatic strut (50) according to claim 1, It is characterized by The balancing cylinder (12) forms at least one extra length (12b) on the working cylinder (1) along the direction of the stroke axis (H), wherein the at least one extra length (12b) includes a portion of the reset space (15a).

6. The pneumatic strut (50) according to claim 5, It is characterized by A piston rod (6) is fixed to the working piston (2) and is mounted movably along a stroke axis (H) in the working cylinder (1), wherein the excess length (12b) is arranged at an end of the working cylinder (1) that is remote from the piston rod (6) in the direction of the stroke axis (H).

7. The pneumatic strut (50) according to claim 1, It is characterized by The outer working space (12a) has a smaller diameter measured in a direction transverse to the stroke axis (H) than the balancing space (16a) and / or the reset space (15a).

8. The pneumatic strut (50) according to claim 7, It is characterized by The balancing cylinder (12) surrounds a balancing space (16a), an external working space (12a) and a reset space (15a) in a radial direction of the stroke axis (H), wherein a diameter of the balancing cylinder (12) measured in a direction transverse to the stroke axis (H) is wider in the region of the balancing space (16a) and / or the reset space (15a) than in the region of the external working space (12a).

9. The pneumatic strut (50) according to claim 1, It is characterized by The resetting medium is gas.

10. The pneumatic strut (50) according to claim 1, It is characterized by a. The reset space (15a) contains a multiplier piston (17) movably mounted along the stroke axis (H), b. wherein the multiplying piston (17) divides the reset space (15a) into a liquid space (18a) in contact with the balancing piston (10) and a gas space (19a) separated from the balancing piston (10) in an airtight manner, c. wherein the liquid space (18a) is filled with a hydraulic fluid, the gas space (19a) is filled with a resetting medium in gaseous form, and d. wherein the cross-sectional area of ​​the multiplying piston (17) measured in a direction transverse to the stroke axis (H) is greater than the cross-sectional area of ​​the balancing piston (10) measured in a plane transverse to the stroke axis (H).

11. A method for manufacturing a pneumatic strut (50) according to any one of claims 1 to 10, It is characterized by The following steps: a. Arrange the working cylinder (1) of the pneumatic strut (50) in the balancing cylinder (12) of the pneumatic strut (50), b. After the arrangement step, the resetting medium, the balancing medium of the balancing piston (10) and the pneumatic strut (50) are filled in the space between the working cylinder (1) and the balancing cylinder (12), c. After the arrangement step, the working gas of the working piston (2) and the pneumatic strut (50) is introduced into the working cylinder (1), and d. After the filling and introduction steps, the working cylinder (1) and the balancing cylinder (12) are closed airtight.

12. The method according to claim 11, It is characterized by The following steps: a. simultaneously introducing the working gas into the internal working space (1a) of the pneumatic strut (50) and into the external working space (12a) of the pneumatic strut (50), and filling the resetting space (15a) of the pneumatic strut (50) with the working gas as a resetting medium, and b. After the introduction and filling steps, part of the working medium is discharged from the inner working space (1a) and the outer working space (12a).

13. The method according to claim 11 or 12, It is characterized by The following steps: The diameter of the balancing cylinder (12), measured transversely to the stroke axis (H), is widened in the region of the balancing space (16a) and / or in the region of the reset space (15a) relative to the region of the outer working space (12a).

14. A drive system for a flap, comprising a. A pneumatic strut (50) according to any one of claims 1 to 10 for supporting the flap, and b. An electromechanical drive for driving the flaps.

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