Gas spring system having at least one gas spring

Abstract

The invention relates to a gas spring system having at least one gas spring (1) with a piston (3) arranged in a displaceable manner in the cylinder. The piston arrangement (3) is designed as a piston packet that is closed depending on direction, wherein the piston packet is designed in a spring-less manner and has at least one annular sealing element (12) which is provided for sealing between the retaining region (10) of the cylinder (2) and the piston arrangement (3) during a push-out movement of the gas spring (1), and wherein the sealing element (12) is arranged and displaceable in a radially outer annular space (23) of the piston packet such that the sealing element (12) can be pressed against the cylinder (2) with a first pressing force during a push-out movement of the gas spring (1), and can be pressed against the cylinder (2) with a second, lower pressing force during a push-in movement of the gas spring (1).

Description

[0001] Gas spring system with at least one gas spring

[0002] The invention relates to a gas spring system with at least one gas spring with a cylinder closed at a first end, a piston arrangement displaceably arranged in the cylinder, which divides the cylinder into a first working chamber near the first end and a second working chamber remote from the first end and a piston rod arranged on one side of the piston arrangement, which projects through the second working chamber and is led out of the cylinder concentrically to the longitudinal axis of the cylinder at a second end opposite the first end, sealed by a seal and a piston rod guide.

[0003] Gas spring systems with a gas spring are well known. Gas springs are used primarily for force support, but also for damping and locking. In addition to lifting, they can also be used to specifically dampen a movement at a defined speed. Gas spring systems are used, for example, in flap systems with two end positions, such as vehicle tailgates, which need to be conveniently adjusted from a closed to an open position. Depending on the application, the limitation of a flap opening angle or the provision of different flap opening angles is desired.

[0004] The gas springs known for these applications typically have a direction-dependent piston valve with a piston seal. This valve is closed by a spring force during the gas spring's automatic extension movement and opens in a holding area in response to a force acting in the opening direction, depending on the pressure. This piston seal with the spring-loaded valve, known, for example, from DE 33 01 544 A1, has proven to be disadvantageous, particularly with regard to frictional resistance and temperature dependence. Likewise, the use of a piston valve can be disadvantageous with regard to noise emissions.

[0005] A gas spring with a springless piston assembly is known, for example, from DE 25 13302 A1. High friction of the sealing elements has proven to be disadvantageous. Therefore, the object of the invention is to propose an improved gas spring system with at least one simply constructed gas spring.

[0006] The object is achieved according to the invention by a gas spring system according to claim 1. The gas spring system according to the invention comprises at least one gas spring with a cylinder closed at a first end, a piston arrangement displaceably arranged in the cylinder, which piston arrangement divides the cylinder into a first working chamber near the first end and a second working chamber remote from the first end, and a piston rod arranged on one side of the piston arrangement, which extends through the second working chamber and is led out of the cylinder concentrically to the longitudinal axis of the cylinder at a second end opposite the first end, sealed by a seal and a piston rod guide.The cylinder has at least one overflow channel that can be connected to the working chambers for the automatic extension movement of the gas spring. At least one holding region of the cylinder is provided, interrupting the overflow channel, to limit the stroke of the piston assembly and blocking the automatic extension movement. The piston assembly is designed as a directionally sealed piston assembly. Furthermore, the piston assembly is springless and has at least one annular sealing element, which is provided to seal between the holding region of the cylinder and the piston assembly during an extension movement of the gas spring.The sealing element is arranged and displaceable in a radially outer annular space of the piston assembly in such a way that the sealing element can be pressed against the cylinder with a first contact force during an extension movement of the gas spring and against the cylinder with a second, lower contact force during a retraction movement of the gas spring.

[0007] In this context, a directionally closed piston assembly means that no additional force, such as a spring force, is required to close the piston assembly during an extension movement. By eliminating a valve spring, the design of the piston assembly can be significantly simplified, thus optimizing the cost of the gas spring system and reducing design effort due to the significantly simplified design.

[0008] Likewise, the gas spring system is more temperature-independent due to the elimination of the valve spring. In conventional gas springs with valve springs, the holding force decreases with increasing temperature. To compensate for this, it is therefore necessary to use a stronger valve spring, which in turn leads to increased adjustment forces at medium and especially at lower temperatures. In the gas spring with the piston assembly according to the invention, although the extension force increases with increasing temperature, the holding force of the piston assembly increases simultaneously, so compensation in this regard is not necessary.

[0009] A reduced contact force of the sealing element during an insertion movement also leads to a reduction in friction.

[0010] The system according to the invention thus allows for improved adjustment comfort, particularly in the medium and lower temperature range, due to a smaller spread of an adjustment force.

[0011] According to an advantageous embodiment of the invention, the piston package has a further sealing element which is provided for static sealing between the piston arrangement and the piston rod.

[0012] These two annular sealing elements allow for one- or two-sided static sealing as well as a gas-tight design of the piston package, which can achieve lower friction of the sealing elements.

[0013] A particularly simple construction of the piston package is preferably achieved in that the piston package has a piston and a stop disc, wherein the piston rests against the stop disc with a projection extending in the axial direction relative to the longitudinal axis in such a way that the radially outer annular space is formed.

[0014] The stop disc rests on a shoulder of the piston rod, with a piston rod extension protruding through the piston assembly and attaching the piston assembly to the piston rod.

[0015] The stop disc is preferably substantially cylindrical and has a radial collar which bears against the shoulder of the piston rod and which has at least one radially outer recess, the piston bearing against a side of the collar facing away from the piston rod with the projection.

[0016] Preferably, the piston has an annular recess for receiving the further annular sealing element for sealing the piston relative to the piston rod.

[0017] If the piston assembly reaches the holding area of ​​the cylinder that interrupts at least one overflow channel during the extension movement, a seal between the piston and the piston rod or between the piston and the cylinder is easily ensured. The projection tapers on its outer side in such a way that the sealing element is displaced towards the piston during an extension movement and a sealing connection with the holding area of ​​the cylinder that interrupts the overflow channel is ensured. During a retraction movement, the sealing element is displaced towards the collar of the stop disk, allowing overflow. The tapering of the projection advantageously reduces the contact force of the sealing element against the cylinder and thus the frictional force.

[0018] Preferably, the collar has a dimpled structure on the side facing away from the piston rod. These dimples allow for good flow and ensure pre-positioning of the sealing element toward the piston. Flow through the recess of the stop disc can be easily ensured.

[0019] According to an advantageous embodiment of the invention, the at least one overflow channel is designed as an axial groove, with the groove profile being provided for adjusting a stroke-dependent, controllable extension speed. This allows, for example, a flat start of the automatic extension movement of the gas spring.

[0020] Preferably, at least two overflow channels are provided and designed as an axial groove, with the cylinder holding area interrupting the overflow channels being provided for adjusting the stroke limit. This allows multiple opening angles to be realized when used in a flap system.

[0021] According to an advantageous embodiment of the gas spring system, it comprises an additional gas spring. Depending on the application, the two gas springs can have an identical or differently constructed piston assembly, or differ in the design of the transfer channels.

[0022] The gas spring system according to the invention can preferably be used for a flap system, in particular a tailgate system. It can also be used for a front hood system. Brief Description of the Drawings

[0023] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0024] Examples include:

[0025] Fig. 1 shows a gas spring of a gas spring system according to the invention in longitudinal section;

[0026] Fig. 2 shows an extension force characteristic of the gas spring according to Fig. 1.

[0027] Embodiment of the invention

[0028] Figure 1 shows a longitudinal section of a gas spring 1 of a gas spring system according to the invention. The gas spring system can preferably be used for a flap system (not shown), in particular a tailgate system. It can also be used for a front hood system.

[0029] The gas spring 1, which is shown in a not completely retracted state, comprises a cylinder 2 closed at a first end (not shown), and a piston assembly 3 slidably arranged in the cylinder 2, which divides the cylinder 2 filled with compressed gas into a first working chamber 5 near the first end and a second working chamber 6 remote from the first end. A piston rod 7 arranged on one side of the piston assembly 3, which extends through the second working chamber 6, is led out of the cylinder 2 concentrically to the longitudinal axis L of the cylinder 2 or the gas spring 1 at a second end 4 opposite the first end, sealed by a seal 8 and a piston rod guide (not shown in detail). The cylinder 2 has at least one overflow channel 9 which can be connected to the working chambers 5, 6 and for the automatic extension movement of the gas spring.If the piston assembly 3 is located in this area of ​​the cylinder 2, the overflow dynamically dampens the extension movement. If the piston assembly 3 reaches a holding area 10 of the cylinder 2 during the movement, which interrupts the overflow channel 9, the automatic extension movement of the piston assembly 3 is blocked. In other words, the holding area 10 of the cylinder 2, which is indicated by two dashed lines, is intended to limit the stroke of the piston assembly 3.

[0030] If a further overflow channel 21 is provided as shown, a second area with automatic extension movement follows the holding area 10 in the further course of the extension movement.

[0031] The piston arrangement 3 is designed as a directionally closed, springless piston assembly. In this context, a directionally closed piston assembly means that no additional force, such as a spring force, is required to close the piston assembly during an extension movement. By eliminating the conventional valve spring, the design of the piston assembly can be significantly simplified, thereby optimizing the cost of the gas spring system and reducing design effort due to the significantly simplified design. Likewise, the elimination of the valve spring makes the gas spring system less temperature-independent, so that a smaller spread of the adjustment force overall allows for improved adjustment comfort, particularly in the medium and lower temperature ranges.

[0032] As can be seen from Figure 1, the piston assembly has an annular sealing element 12 and a further sealing element 11, which are provided during an extension movement in the holding area 10 of the cylinder 2 interrupting the overflow channels 9, 21 for sealing between the cylinder 2 and the piston assembly, as well as between the piston assembly and the piston rod 7. The piston assembly comprises a piston 13 and a stop disk 14, wherein the stop disk 14 rests against a shoulder 15 of the piston rod 7, a piston rod extension 16 extends through the piston assembly and additionally fastens the piston assembly to the piston rod 7, for example by riveting. Together with the piston arrangement 3, the piston rod 7 forms a piston-piston rod unit.

[0033] The piston 13 can advantageously be made of plastic.

[0034] The stop disc 14, as can be seen from Figure 1, is essentially cylindrical and has a radial collar 17 which bears against the shoulder 15 of the piston rod 7 and which has at least one radially outer recess 18. The piston 13 bears against a side of the collar 17 facing away from the piston rod 7 with a projection 19 extending in the axial direction - relative to the longitudinal axis L of the gas spring 1 or the cylinder 2.

[0035] Furthermore, the piston 13 has a radially inner, annular recess 20 for

[0036] Accommodates the further annular sealing element 11 for sealing the piston 13 against the piston rod 7 or the piston rod extension 16 and forms with its projection 19 and the collar 17 of the stop disk 14 a radially outer annular space 23 for receiving the annular sealing element 12. If the piston package reaches the holding area 10 of the cylinder 2 interrupting the overflow channels 9, 21 during the extension movement, a seal between the piston 13 and the piston rod extension 16 or between the piston 13 and the cylinder 2 is thereby ensured in a simple manner.

[0037] The sealing element 12 is arranged and displaceable in the radially outer annular space 23 such that it can be pressed against the cylinder 2 with a first contact force during an extension movement of the gas spring 1 and with a second, lower contact force during a retraction movement of the gas spring 1 against the cylinder 2. The first contact force is significantly higher, for example, at least twice as large as the second contact force.

[0038] For this purpose, the projection 19 tapers on its outer side in such a way that the sealing element 12 is displaced toward the piston 13 during an extension movement, ensuring a sealing engagement with the cylinder's holding area 10, which interrupts the transfer channels 9, 21. As can be seen from Figure 1, the sealing element 12 bears against a radial and an axial piston surface 24, 25 of the piston 13 with high contact pressure.

[0039] During an insertion movement, the sealing element 12 shifts toward the collar 17 of the stop disc 14, allowing overflow via the sealing element 12 from the working chamber 5 toward the working chamber 6. Since the sealing element 12 no longer seals against the radially and axially formed piston surfaces 24, 25, the gas can flow between the piston 3 and the sealing element 12 and enters the working chamber 6 via the recess 18.

[0040] The displacement of the sealing element 12 in the direction of the stop disc 14 results in a reduced contact force of the sealing element 12 on the cylinder 2, so that significantly lower friction is the result.

[0041] A nub structure with nubs 22 on the side of the collar 17 facing away from the piston rod 7 allows for good flow over and ensures pre-positioning of the sealing element 12 in the direction of the piston 13. In other words, the nubs 22 prevent a further displacement of the sealing element 12 in the direction of the stop plate 14. Sealing of the recess 18 can be reliably prevented. The overflow channels 9, 21 are designed as axial grooves in the embodiment shown, wherein the groove profile is provided for adapting a stroke-dependent, controllable extension speed. In this case, for example, a flat start of the automatic extension movement of the gas spring 1 is possible. Other groove profiles not shown are also conceivable within the scope of the invention.By providing two overflow channels 9, 21 with an intermediate holding area 10 which interrupts the overflow channels 9, 21, for example, two opening angles of the flap system can be realized.

[0042] Figure 2 shows an extension force characteristic of the gas spring 1, wherein at a first point 1 on the characteristic curve the piston rod 7 with the piston assembly is pushed in, i.e. in the drawing it is in a right-hand end position. In this state a tailgate hinged to the gas spring, for example, is closed. When the tailgate is opened, the piston assembly is initially in the area of ​​the first overflow channel 9 and gas flows via the groove of the first overflow channel 9 from the second working chamber 6 into the first working chamber 5. Since a filling pressure is selected such that the weight of the tailgate is overcome, the gas spring 1 extends automatically. The extension force Fout decreases linearly until the piston assembly reaches the holding area 10, at which a first opening angle of the tailgate is reached. In this area the piston assembly is statically sealed so that the holding or stopping function of the tailgate is ensured.The extension force Fout drops to a minimum due to the gas compression.

[0043] If the tailgate is to be opened further, the gas spring 1 or its piston-piston rod unit can be moved, usually manually, into the area of ​​the second overflow channel 21 by means of an adjustable release force, so that the piston rod 7 extends again automatically until a left end position shown in the drawing with the point 2 is reached, in which a second opening angle of the tailgate is reached.

[0044] The gas spring 1, and thus the gas spring system, exhibits significantly improved temperature behavior. To overcome the release force or overpressure force, the piston-piston rod unit must be displaced against a developing pressure cushion in the second working chamber 6 until the sealing element 12 reaches the area of ​​the second overflow channel 21 and the pressure cushion can be dissipated.

[0045] As the piston assembly moves, the second working chamber 6 in front of the piston assembly becomes smaller, and the pressure continues to rise. The increase corresponds to the ratio of the volume when the holding range 10 is reached to the volume when the end of this range is reached. If the starting pressure increases due to an increase in temperature, the absolute pressure increase at the end will be greater than at a lower starting pressure. This effect counteracts the decreasing overpressure force at higher temperatures by increasing the extension force and can neutralize this undesirable effect.

[0046] A gas spring system according to the invention can comprise the described gas spring 1 and a further gas spring. The further gas spring can be constructed identically to the gas spring 1. Alternatively, the further gas spring can be designed differently than the gas spring 1 and, for example, have a non-static seal and / or a reduced groove cross-section and / or only travel-dependent damping.

[0047] To improve frictional resistance, the additional gas spring can have a piston assembly with a piston ring that offers improved sliding properties. A PTFE ring, for example, can be used here. In this case, the holding function would be ensured exclusively by the gas spring 1 described above.

Claims

Claims 1. A gas spring system comprising at least one gas spring (1) with a cylinder (2) closed at a first end, a piston assembly (3) displaceably arranged in the cylinder, which divides the cylinder (2) into a first working chamber (5) close to the first end and a second working chamber (6) remote from the first end, and a piston rod (7) arranged on one side of the piston assembly (3), which extends through the second working chamber (6) and is led out of the cylinder (2) concentrically to the longitudinal axis (L) of the cylinder (2) at a second end (4) opposite the first end, sealed by a seal (8) and a piston rod guide, wherein the cylinder (2) has at least one overflow channel (9) connectable to the working chambers (5, 6) for the automatic extension movement of the gas spring (1), wherein at least one holding region (10) of the cylinder (2) interrupting the overflow channel (9) is provided to limit the stroke of the piston assembly (3),in which the automatic extension movement is blocked, wherein the piston arrangement (3) is designed as a directionally closed piston assembly, wherein the piston assembly is designed without springs and has at least one annular sealing element (12) which is provided for sealing between the holding area (10) of the cylinder (2) and the piston arrangement (3) during an extension movement of the gas spring (1), and wherein the sealing element (12) is arranged and displaceable in a radially outer annular space (23) of the piston assembly such that the sealing element (12) can be pressed against the cylinder (2) with a first contact force during an extension movement of the gas spring (1) and against the cylinder (2) with a second, lower contact force during a retraction movement of the gas spring (1).

2. Gas spring system according to claim 1, characterized in that the piston assembly has a further annular sealing element (11) which is provided for static sealing between the piston assembly (3) and the piston rod (7).

3. Gas spring system according to claim 2, characterized in that the piston package has a piston (13) and a stop disc (14), wherein the piston (13) bears against the stop disc (14) with a projection (19) extending in the axial direction relative to the longitudinal axis (L) in such a way that the radially outer annular space (23) is formed.

4. Gas spring system according to claim 3, characterized in that the stop disc (14) rests against a shoulder (15) of the piston rod (7), wherein a piston rod extension (16) projects through the piston assembly and fastens the piston assembly to the piston rod (7).

5. Gas spring system according to claim 4, characterized in that the stop disc (14) is substantially cylindrical and has a radial collar (17) which bears against the shoulder (15) of the piston rod (7) and which has at least one radially outer recess (18), the piston (13) bearing against a side of the collar (17) facing away from the piston rod (7) with the projection (19).

6. Gas spring system according to claim 5, characterized in that the piston (13) has an annular recess (20) for receiving the further annular sealing element (11) for sealing the piston (13) relative to the piston rod (7).

7. Gas spring system according to claim 6, characterized in that the collar (17) has a knob structure (22) on the side facing away from the piston rod (7).

8. Gas spring system according to claim 7, characterized in that the at least one overflow channel (9) is designed as an axial groove, wherein the groove profile is provided for adapting a stroke-dependent controllable extension speed.

9. Gas spring system according to claim 8, characterized in that at least two overflow channels (9, 21) are provided and are designed as an axial groove, wherein the holding region of the cylinder (2) interrupting the overflow channels (9, 21) is provided for adjusting the stroke limitation.

10. Gas spring system according to one of the preceding claims 1 to 9, characterized in that the gas spring system comprises a further gas spring.

11. Gas spring system according to claim 10, characterized in that the gas spring system comprises a further gas spring, wherein the gas springs (1) have an identical or a differently constructed piston package.

12. Gas spring system according to claim 10 or 11, characterized in that the gas spring system comprises a further gas spring, wherein the gas springs (1) have differently designed overflow channels (9, 21).

13. Gas spring system according to one of the preceding claims 1 to 12 for use for a flap system, in particular a tailgate system.

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