WO2008061750A1

WO2008061750A1 - Gas spring device

Info

Publication number: WO2008061750A1
Application number: PCT/EP2007/010128
Authority: WO
Inventors: Jan Hasenkamp; Kai Lunau
Original assignee: Ixetic Bad Homburg Gmbh
Priority date: 2006-11-23
Filing date: 2007-11-22
Publication date: 2008-05-29
Also published as: DE112007002283A5; DE112007002281A5; WO2008061748A1

Abstract

The invention relates to a gas spring device, for example for supporting the opening movement of a tailgate of a motor vehicle or for keeping said tailgate open. Said gas spring device comprises a cylinder-piston unit (5), a gas spring accumulator (23), a fluid conveying unit (2), a valve unit (15) including a control piston (21) that is movably received in a control compartment (47) against the force of readjusting springs (17, 19), and a pressure limiting unit.

Description

Gas fueling

description

The invention relates to a gas spring device, for example, to support the opening movement or to keep open a motor vehicle tailgate.

Gas spring devices of the type discussed here are known. They serve, for example, to support the applied manual force for opening or closing a tailgate. Such gas spring devices also allow automatic opening or closing, for example, a tailgate without the use of manual power. It has been found in the known gas spring devices that may result in a disability of the movement of a motor vehicle tailgate, damage to the gas spring device or injury to persons. To avoid this, overpressure valves can be used, but this increases the cost of such a gas spring device and its space requirements.

It is therefore an object of the invention to provide a gas spring device which avoids the disadvantages mentioned.

To solve this problem, a gas spring device is proposed, which has the features mentioned in claim 1. The gas spring device has a cylinder-piston device, a gas spring reservoir, a fluid delivery device, such as a pump, and a valve device, for example a pressure-controlled 5/3-way valve. The fluid delivery device is preferably driven by an electric motor. The valve device comprises a control chamber in which a control piston against the Force of return springs is movably mounted. In addition, the gas spring device has a pressure limiting device. The gas spring device is characterized in that the pressure limiting device is integrated into the valve device of the gas spring device. Due to the advantageous integrated pressure limiting device, the gas spring device is protected against overloading, whereby outside the valve device arranged pressure limiting valves, a motor current monitoring device or the like are superfluous. So there are no additional components needed, so that the gas spring device requires very little space. The pressure limiting device prevents excessive force or pressure effects on the components of the gas spring device, but in particular serves to prevent damage: If, for example, the motor vehicle tailgate is automatically opened in a low garage, it strikes against the ceiling of the garage. so that the pump builds up an increasing pressure, which can lead to damage in the gas spring device and on the tailgate. The pressure limiting device ensures that in such a case, only a certain maximum pressure can be built, which is harmless both for the gas spring device and for the other parts, ie here for the motor vehicle tailgate. At least greater damage is avoided. The same applies in the event that a person gets into the range of movement of the closing motor vehicle tailgate. If the tailgate is blocked, for example, by pinching a person, the pressure provided by the fluid delivery device increases, so that damage can occur inside the gas spring device and in particular also injury to the person. To avoid this, the pressure limiting direction provided which limits the forces built up by the gas spring device.

Particularly preferred is a gas spring device, which is characterized in that the return springs act on the ends of the control piston, which is movably mounted in the control chamber of the valve device.

Further preferred is a gas spring device, which is characterized by a valve device, that it has a control spring, and that the control piston encompasses at least two partial pistons. The control spring is arranged between the at least two partial pistons and preferably has a higher spring stiffness than the return springs.

A further preferred gas spring device has at least one partial piston which has a section designed as a hollow cylinder, in the wall of which there is a passage and in whose outer surface at least one groove is introduced, into which the passage opens. This embodiment makes it possible that a fluid flow passes through the opening in the hollow cylindrical part piston to an opening of the control chamber. Two cooperating partial pistons preferably have mutually facing stop surfaces.

Furthermore, a gas spring device is preferred in which the valve device has two partial pistons, which are constructed identically and are arranged in mirror image relative to one another in the control chamber. This embodiment allows a particularly simple construction of the gas spring device. In a further preferred gas spring device, the control chamber has at least two openings connected to the cylinder-piston device. In addition, the control chamber of the valve device has at least two with the fluid delivery device, for example a pump designed as a reversible pump, and at least one opening connected to the gas spring accumulator. The openings are each connected via lines to the respective components of the gas spring device.

Also preferred is a gas spring device, which is characterized in that the control chamber of the valve device comprises two control pressure chambers receiving the return springs, each of which is delimited on one side by the portion of the control piston designed as a hollow cylinder.

Further preferred is a gas spring device, which is characterized in that the control piston assumes a neutral position within the valve device. In this neutral position, a first control pressure chamber is connected via a first opening to the fluid delivery device, for example to a reversing pump, and a second control pressure chamber of the valve device is likewise connected to the fluid delivery device via a second opening. The opening of the control chamber connected to the gas spring accumulator is connected to the openings communicating with the cylinder-piston device. The openings of the control chamber, which are connected to the cylinder-piston device, are also connected to each other. The fluid delivery device, which can be driven for example via an electric motor, is not in operation in this position of the control piston. When opening or closing a tailgate with pure hand force the gas spring device acts in neutral position the control piston according to the gas spring characteristic with a constant Ausschiebekraft on the tailgate. The Ausschiebekraft based on the pressure in the gas spring accumulator and is superimposed on the hand force supportive.

In a further preferred gas spring device, the control piston in the control chamber assumes a first delivery position. The first delivery position of the control piston results from the fact that the fluid delivery device is driven by an electric motor in a first direction of rotation. In the first delivery position, the first control pressure chamber is acted upon by the fluid delivery device with a pressurized fluid. In this case, the cylinder-piston device is supplied by the pressurized fluid, so that a hydraulic piston and a piston rod of the cylinder-piston device move in a first direction. Particularly preferably, the cylinder-piston device is supplied via the first control pressure chamber with pressurized fluid. In addition, in this first conveying position of the control piston, the cylinder-piston device is connected to the gas spring accumulator and to the fluid delivery device. The second control pressure chamber is preferably connected via an opening of the control chamber with the fluid conveying device.

Also preferred is a gas spring device, which is characterized in that the control piston assumes a second delivery position. The second delivery position of the control piston results from the fact that the fluid delivery device is driven by an electric motor in a second direction of rotation. In this second delivery position, the second control pressure chamber is acted upon by the fluid delivery device with a pressurized fluid. The cylinder The piston device is also supplied with the pressurized fluid, so that move the hydraulic piston and the piston rod of the cylinder-piston device in a second direction. Preferably, the cylinder-piston device is supplied via the second control pressure chamber with pressurized fluid. In addition, in this second conveying position of the control piston, the cylinder-piston device is connected to the gas spring accumulator and to the fluid delivery device. The first control pressure chamber is preferably connected via an opening of the control chamber with the fluid conveying device.

Finally, a gas spring device is preferred, which is characterized in that the control piston assumes a fail-safe position. The starting position of the control piston is the first or second delivery position of the control piston. In the fail-safe position of the control piston there is a short circuit between the openings of the control chamber, which are connected to the fluid delivery device via the opening of the control chamber, which is connected to the gas spring accumulator. At the same time there is a connection between the openings of the control chamber, which are connected to the piston-cylinder device. Should an excessive force or pressure be exerted on the gas spring device during the electrohydraulically assisted operation of the gas spring device due to a hindrance of the movement of the motor vehicle tailgate, the control piston moves from the first or second delivery position into fail-safe described above. Position, so over the opening of the control chamber, which is connected to the gas spring accumulator, there is a short circuit between the suction and pressure side of the fluid conveyor and so pressure-bearing components of the gas spring device are relieved. Thus, in the valve direction integrated pressure relief device, which is realized by displacement of the control piston within the valve device in a fail-safe position.

The invention will be explained in more detail below with reference to the drawing. Show it:

1 shows a gas spring device with switched off Fluidför- device and control piston in neutral position;

FIG. 2 shows a structural design of the valve device of the gas spring device shown in FIG. 1;

FIG. 3 shows a gas spring device with connected fluid delivery device and a first delivery position of the control piston;

FIG. 4 shows a gas spring device with connected fluid delivery device and a second delivery position of the control piston;

FIG. 5 shows a structural design of the valve device of the gas spring device shown in FIG. 3; and

Figure 6 shows a structural design of a valve device with

Control piston in fail-safe position of a gas spring device according to FIG. 3.

FIG. 1 shows a gas spring device 1 which is filled with a fluid, for example hydraulic oil, and comprises a fluid delivery device 2 which can be driven, for example, by an electric motor 3. The direction of rotation of the electric motor 3 is the Förderrich- tion of the fluid conveyor 2 before. This is preferably designed as a re versierpumpe. In the case of the gas spring device 1 illustrated in FIG. 1, the electric motor 3 does not drive the fluid delivery device 2, ie it is switched off, so that no hydraulic oil is conveyed through the fluid delivery device 2.

The gas spring device 1 further comprises a cylinder-piston device 5, which has a hydraulic piston 7 and a piston rod 9, which are movably mounted in the cylinder-piston device 5. The cylinder-piston device 5 also comprises two cylinder chambers 11 and 13, which are arranged spatially separated from each other by the hydraulic piston 7. The hydraulic piston 7 is movably mounted with the piston rod 9 in the cylinder-piston device 5. The hydraulic piston 7 has a smaller effective area 14a and a larger effective area 14b. The smaller effective area 14a corresponds to the effective area 14b minus the cross-sectional area of the piston rod 9.

The gas spring device 1 in Figure 1 also includes a valve means 15. This is, for example, as shown in Figure 1, designed as a pressure-controlled 5/3-way valve. The valve device 15 has, inter alia, two return springs 17 and 19 and a control piston 21, shown schematically here by means of switching symbols.

The gas spring device 1 in FIG. 1 also has a gas spring accumulator 23 which serves, in conjunction with the hydraulic piston 7, to obtain the characteristic of a gas spring. The gas spring accumulator 23 is under a pressure also referred to as biasing pressure and stores excess hydraulic oil, which the result of the arranged in the cylinder chamber 11 piston rod 9 different maximum capacity of the two cylinder chambers 11 and 13 results.

The fluid delivery device 2 is connected via lines 25 and 27 with here only indicated openings 29 and 31 of a control chamber of the valve device 15, not shown. The gas spring accumulator 23 is connected via a line 33 with a again only indicated opening 35 of the control chamber of the valve device 15. The cylinder-piston device 5 is connected via lines 37 and 39 with interpreted openings 41 and 43 of the control chamber of the valve device 15. In this case, the line 37 establishes a connection between the opening 41 of the valve device 15 and the cylinder chamber 11, while the line 39 establishes a connection between the opening 43 and the cylinder chamber 13.

Also recognizable in FIG. 1 is a leakage line 45, which connects the gas spring accumulator 23 to the fluid delivery device 2. This serves to keep the pretensioning pressure of the fluid delivery device 2 at a certain level, for example 100 bar.

FIG. 2 shows a structural design of the valve device 15 of the gas spring device 1 shown in FIG. 1. The openings 29 and 31 connected to the fluid delivery device 2 are clearly visible in the control chamber 47. In addition, the opening 35 connected to the gas spring accumulator 23 is shown as well as the openings 41 and 43, which are connected to the cylinder-piston device 5.

Figure 2 also shows the return springs 17 and 19, which act on one end 49 and 51 of the control piston 21 respectively. The valve device 15 has a control spring 53, which is mounted in the control chamber 47 of the valve device 15. The control piston 21 comprises two partial pistons 55 and 57, between which the control spring 53 is arranged. The control spring 53 has a higher spring stiffness than the restoring springs 17 and 19.

The two sub-pistons 55 and 57 are constructed identically in the embodiment of Figure 2 and arranged in mirror image to each other in the control chamber 47. The sub-pistons 55 and 57 also have two facing abutment surfaces 59 and 61.

The sub-pistons 55 and 57 have on their the abutment surfaces 59, 61 opposite side each formed as a hollow cylinder portion 63. In the wall of the portions 63, two passages 65 and 67 are introduced and in the outer surface of the wall in each case a groove 69 and 71, into each of which a passage 65, 67 opens.

The control chamber 47 also has two control pressure chambers 73 and 75, in which the return springs 17 and 19 are arranged, and which are each bounded on one side by the portion 63 of the control piston 21 formed as a hollow cylinder.

In the neutral position of the valve device 15 shown in FIG. 2, the electric motor 3 does not drive the fluid delivery device 2. As a result, the control piston 21 is in the control chamber 47 in a neutral position. The spring forces of the return springs 17 and 19 provide for a centering of the control piston 21 within the control chamber 47. While the return spring 17, the sub-piston 55 and thus the control spring 53 is acted upon by spring force, the sub-piston 57 and thus also the control spring 53 with the spring force of the return spring 19 acted upon. Characterized in that the control spring 53 has a higher spring stiffness than the return springs 17 and 19, this is not significantly compressed by the force of the return springs 17 and 19. Starting from the same spring forces of the return springs 17 and 19, the control piston 21 is thus urged into a middle position or neutral position.

In this neutral position of the control piston 21, the control pressure chamber 73 is connected to the fluid delivery device 2 via the passage 67 in the partial piston 55 and the opening 29. Accordingly, the control pressure chamber 75 is connected to the fluid delivery device 2 via the passage 67 in the partial piston 57 and the opening 31. Because the electric motor 3 does not drive the fluid delivery device 2, for example a reversing pump, the control pressure chambers 73 and 75 are not subjected to pressurized fluid, for example hydraulic oil.

Furthermore, in the neutral position of the control piston 21, the openings 41 and 43 connected to the cylinder-piston device 5 are connected to one another via a region 77 of the valve device 15. The region 77 is arranged between the two sub-pistons 55 and 57. Also, in this position of the control piston 21 connected to the gas spring accumulator 23 opening 35 is connected via the region 77 with the openings 41 and 43 of the control chamber 47.

By existing in neutral position connection between the openings 41 and 43 are the two cylinder chambers 11 and 13 of the cylinder-piston device 5 with each other.

In the above-described neutral position of the control piston 21, ie in non-driven fluid delivery device 2, which is located Gas spring device 1 in purely manual "gas spring operation", ie a manual operation of the tailgate is possible. When the piston rod 9 is pressed in a first direction, for example downward with manual force, corresponding to a closing movement of the tailgate, the fluid present in the cylinder chamber 13, for example a hydraulic oil, via the opening 43 and the opening 35 of the valve device 15 to the gas spring accumulator 23 on the one hand, and on the other hand via the opening 43 and the opening 41 to the cylinder chamber 11 conveyed. Due to the fact that the cylinder chamber 13 has a greater maximum capacity than the cylinder chamber 11, characterized in that in the cylinder chamber 11, the piston rod 9 occupies a portion of the volume, the excess hydraulic oil in the gas spring accumulator 23 must be cached. If the piston rod 9 is now pulled up with manual force, corresponding to an opening movement of the tailgate, hydraulic oil is in turn directed out of the cylinder chamber 11 via the opening 41 and the opening 43 to the cylinder chamber 13. Since the capacity of the cylinder chamber 13 is greater than that of the cylinder chamber 1 1, the resulting difference volume with hydraulic oil from the gas spring accumulator 23 must be compensated.

The piston rod 9 of the cylinder-piston device 5 experiences a permanent Ausschiebende force component resulting from the system-internal pressure, which acts on the different sized effective surfaces 24 a and 24 b of the cylinder-piston device 5. Thus, if the valve device 15 is in the neutral position described above, with the electric motor 3 not driving the fluid delivery device 2, then the gas spring device 1 has the typical characteristic of a gas spring and the deploying force component is superimposed on the manual force. FIG. 3 shows a gas spring device 1 with connected fluid delivery device 2 and a first delivery position of the control piston 21. The same parts are provided with the same reference numerals, so that reference is made to the preceding figures. In the gas spring device 1 in FIG. 3, the electric motor 3 drives the fluid delivery device 2 in a first direction of rotation. The pump thus conveys fluid in the direction of arrow 79 via line 25 and openings 29 and 41 of valve device 15 via line 37 into cylinder chamber 11 pressed, so that the volume of the cylinder chamber 13 is reduced and there existing hydraulic oil via line 39 and the opening 43 to the valve means 15 and transported from there on the one hand via the opening 35 to the gas spring accumulator 23, and on the other hand via the opening 31 to the suction side of the fluid conveyor 2 becomes. The cylinder-piston device 5 is thus connected on the one hand to the fluid delivery device 2 and on the other hand to the gas spring accumulator 23.

The first direction of rotation of the fluid delivery device 2 shown in FIG. 3 causes a downward movement of the piston rod 9 in the cylinder-piston device 5 and thus an automatic closing movement of a tailgate.

FIG. 4 shows a gas spring device 1 with connected fluid delivery device 2 and a second delivery position of the control piston 21. The same parts are provided with the same reference numerals, so that reference is made to the preceding figures. The electric motor 3 drives the fluid delivery device 2 in a second direction of rotation. As a result, a fluid, for example a hydraulic oil, in Direction of the arrow 81 via the line 27, the openings 31 and 43 of the valve means 15 and conveyed via the line 39 into the cylinder chamber 13. By acting on the hydraulic piston 7 with hydraulic oil under pressure, the latter is pressed upwards, so that the volume of the cylinder chamber 11 is reduced and any hydraulic oil present there is displaced via the line 37 and the opening 41 to the valve device 15 and from there via the Opening 29 and the line 25 to the suction side of the Fluidförde- device 2 passes. Due to the volume flow additionally required in the cylinder chamber 13, the hydraulic oil temporarily stored in the gas spring accumulator 23 is now partially added to the fluid flow flowing out of the cylinder chamber 11.

The movement of the fluid delivery device 2 in a second direction of rotation by means of the electric motor 3 causes an extension of the piston rod 9 and thus an automatic opening movement of a tailgate.

FIG. 5 shows a structural design of the valve device 15 shown in FIG. 3. The same parts are provided with the same reference numerals, so that reference is made to the preceding figures. The first delivery position of the control piston 21 shown in FIG. 5 results from the drive of the fluid delivery device 2 by the electric motor 3 in the first direction of rotation, whereby the fluid delivery device 2 conveys hydraulic oil via the line 25, not shown, to the opening 29 of the control chamber 47. The pressurized hydraulic oil thus passes through the opening 29 in the control pressure chamber 73. This is acted upon by the hydraulic oil under pressure, so that the sub-piston 55 and 57 and the control spring 53 moves against the force of the return spring 19 become. The sub-piston 57 is pressed against the force of the return spring 19 to a stop 83 of the control chamber 47.

Due to the preferably much higher rigidity of the control spring 53, this is not or only slightly compressed in the operating state described here, so that the distance between the sub-piston 55 at a nominal operating pressure, which acts on the sub-piston 55, at best only slightly changes.

In the first delivery position of the control piston 21 shown in FIG. 5, there is now a connection between the opening 29, which is connected to the pressure side of the fluid delivery device 2, via the control pressure chamber 73 with the passage 65 of the hollow cylindrical section 63 of the partial piston 55 65 in turn communicates with the opening 41 of the control chamber 47, which is connected to the cylinder chamber 11 of the cylinder-piston device 5. The cylinder-piston device 5 is thus supplied via the first control pressure chamber 73 with the funded by the fluid conveyor 2, pressurized hydraulic oil.

At the same time in this first conveying position of the control piston 21, a connection between the connected to the cylinder-piston device 5 opening 43 via the region 77 of the control chamber 47 on the one hand via the opening 35 with the gas spring accumulator 23 and on the other hand via the opening 31 with the suction side of Fluid delivery device 2. The cylinder-piston device 5 is thus connected to the fluid delivery device 2 and to the gas spring accumulator 23.

If the pressure in the control pressure chamber 73 decreases, for example due to a reduced motor current and thus reduced delivery rate the fluid delivery device 2, the sub-piston 55, 57 and the control spring 53 are pushed back by the force of the return spring 19, so that the neutral position of the control piston 21 described in Figures 1 and 2 results.

The second delivery position of the control piston 21 shown in Figure 4 is not shown here as a structural design, however, corresponds to their basic operation of the shown in Figure 5. In this case, the electric motor 3 drives the fluid delivery device 2 in the second direction of rotation, whereby the control pressure chamber 75 is acted upon by a pressurized fluid and the sub-piston 55 and 57 are pressed with the control spring 53 against the force of the return spring 17 until the sub-piston 55 to a Stops stop 85 of the control chamber 47.

Due to the displacement of the control piston 21, a connection between the opening 31 connected to the fluid delivery device 2 and the opening 43 is released, which in turn is connected to the cylinder chamber 13. The hydraulic piston 7 with the piston rod 9 are pushed upward by the application of pressurized fluid, whereby the hydraulic oil present in the cylinder chamber 11 is displaced to the opening 41. From there, the fluid passes via the opening 29 to the suction side of the fluid delivery device 2. In addition, the gas spring accumulator 23 discharges a portion of the hydraulic oil stored there via the opening 35 in the region 77 to the fluid flow flowing into the cylinder chamber 13. If the pressure in the control pressure chamber 75 decreases, the control piston 21, ie the partial pistons 55, 57 and the control spring 53, is pushed back with the force of the return spring 17, so that the control piston 21 is displaced into its neutral position. FIG. 6 shows the structural design of a valve device 15 in a fail-safe position, starting from a first delivery position of the control piston 21 according to FIG. 5. The same parts are provided with the same reference numerals, so that reference is made to the preceding figures.

If, starting from a first delivery position of the control piston 21, ie in the first direction of rotation of the fluid delivery device 2, the operating pressure in the control pressure chamber 73 exceed a maximum allowable operating pressure, the control piston 21 is urged into the fail-safe position. This may be the case, for example, when holding the tailgate by hand. In this case, the hydraulic piston 7 is held in the cylinder-piston device 5 in a fixed position, but the fluid conveyor 2 promotes constantly pressurized hydraulic oil through the valve means 15 to the cylinder-piston device 5. The pressurization of the piston 55 of the Valve device 15 is so large that it is displaced so far against the force of the control spring 53, is pressed down in Figure 6, that the two stop surfaces 59 and 61 of the sub-piston 55 and 57 abut each other.

As can be clearly seen from FIG. 6, in the fail-safe position of the control piston 21 there is a connection between the opening 29 and the opening 31 via the opening 35 of the control chamber 47. The connection is established via the passage 67 and the groove 71 of the partial piston 55. As can be seen from FIG. 6, the opening 35 is connected to the region 77 of the control chamber 47 by the positioning of the partial piston 55. The positioning of the partial piston 55 in the fail-safe position of the control piston 21 thus creates a short circuit between the pressure side and the suction side of the fluid piston. Also formed via the above-described way a connection between the two connected to the cylinder-piston device 5 openings 41 and 43 and thus a connection between the two cylinder chambers 11 and 13th

If, for example, a holding of the tailgate with hand force is necessary and pressure-bearing components of the gas spring device 1 are loaded too heavily, a short circuit results on the one hand from the pressure side to the suction side of the fluid delivery device 2 and on the other hand a connection between the two via the openings 41 and 43 connected cylinder chambers 11 and 13.

Reduces the existing in the control pressure chamber 73 operating pressure back to a nominal operating pressure and thus leads to a normal pressurization of the sub-piston 55, the sub-piston 55 is pushed back with the force of the control spring 53. The control piston 21 then resumes its position according to FIG. 5, that is to say a first conveying position.

Due to the symmetrical design of the valve device 15, a fail-safe position is also possible starting from the second delivery position of the control piston 21 according to FIG. 4 without further ado. A corresponding structural design is not shown here.

Starting from the second delivery position according to FIG. 4, ie when the electric motor of the fluid delivery device 2 is driven in a second direction of rotation, the partial piston 57 is pressed against the force of the control spring 53 when the permissible operating pressure in the control pressure chamber 75 is exceeded, so that the stop surfaces 59 and 61 of the two sub-pistons 55 and 57 are pressed against each other and the control piston 21 is again in a fail-safe position. In this fail-safe position of the control piston 21, there is a short circuit between the openings 29 and 31 connected to the fluid delivery device 2 via the opening 35. In addition, there is again a connection between the openings 41 and 43 connected to the cylinder-piston device 5 via the opening 35.

The overpressure limiting device with the control spring 53, which is arranged between two sub-pistons 55 and 57, enables a particularly simple, space-saving and cost-effective realization of an overpressure function, which can be integrated directly into a valve device. The permissible maximum operating pressure, which acts on pressure-carrying components of the gas spring device 1, can be adjusted, for example, via the spring stiffness of the control spring 53.

Overall, a gas spring device 1 can be seen, which can be operated on the one hand manually with gas spring characteristic. The control piston 21 of the valve device 15 is in a neutral position, and the fluid delivery device 2 is not driven by the electric motor 3. On the other hand, an automatic operation of the gas spring device 1 is possible, which allows, for example, an automatic opening or closing a tailgate without the use of manual power. The electric motor 3 drives the fluid delivery device 2 either in the first direction of rotation or in the second direction of rotation, which respectively urges the control piston 21 into a first or second delivery position, so that the hydraulic piston 7 and the piston rod 9 either downwards or downwards move upward, whereby a motor vehicle tailgate is opened or closed.

In the case of excessive loading of the gas spring device 1, that is to say when the maximum operating pressure is exceeded, for example by a hand force exceeding the electrohydraulic force, which hinders the movement of the motor vehicle tailgate, the control piston 21 becomes in a fail-safe position displaced so that a short circuit between the pressure and suction side of the Fluidför- device 2 and the gas spring accumulator 23 on the one hand and on the other hand a connection between the two cylinder chambers 11 and 13 of the cylinder-piston device 5 is formed so that pressure-bearing components are relieved.

It thus turns out that the proposed gas spring device 1 has a particularly simple and compact design and in this case comprises an effective pressure limiting device which can be integrated directly into the valve device. Thus, it requires no additional components, such as pressure relief valves or a motor current monitoring device, which otherwise requires additional electronics. In the event of an emergency, the tailgate can be kept open with manual force during a closing process effected by the fluid conveyor without the gas spring device 1 thereby being damaged or persons being injured. LIST OF REFERENCE NUMBERS

Gas spring means

Fluid delivery device

electric motor

Cylinder-piston means

hydraulic pistons

piston rod

cylinder chamber

Cylinder chamber a effective area b effective area

valve means

Return spring

spool

Gas spring

management

management 29 opening

31 opening

33 line

35 opening

37 line

39 line

41 opening

43 opening

45 Leakage line

47 control room

49 end (Steuerkc

51 end (Steuerkc

53 control spring

55 partial pistons

57 partial piston

59 stop surface

61 stop surface 63 section (Hohlzy

65 holes

67 passage

69 groove

71 groove

73 control pressure chamber

75 control pressure chamber

77 area

79 arrow

81 arrow

83 stop

85 stop

Claims

claims

1. Gas spring device (1), for example, to support the opening movement or to keep open a motor vehicle tailgate, with a cylinder-piston device (5), comprising a gas spring accumulator (23), a fluid conveying device (2), a valve device (15) a in a control chamber (47) against the force of return springs (17,19) movably mounted control piston (21) and with a pressure limiting device, characterized in that the pressure limiting device in the valve means (15) can be integrated.

2. Gas spring device according to claim 1, characterized in that the return springs (17,19) act on the ends (49,51) of the control piston (21).

3. Gas spring device according to one of the preceding claims, character- ized in that the valve device (15) has a control spring (53), that the control piston (21) comprises at least two partial pistons (55,57) that the control spring (53) between the at least two partial piston (55,57) can be arranged and that the control spring (53) has a higher spring stiffness than the restoring springs (17,19).

4. Gas spring device according to claim 3, characterized in that at least one partial piston (55,57) has a hollow cylinder formed as portion (63), and in that in the wall of the hollow cylinder at least one passage (65,67) and in the Außenflä - At least one groove (69,71) is introduced, in which the passage (65,67) opens.

5. Gas spring device according to claim 3 or 4, characterized in that at least two cooperating partial pistons (55,57) stop surfaces (59,61).

6. Gas spring device according to one of claims 3 to 5, characterized in that the valve device (15) has two partial pistons

(55,57), which are constructed identically and mirror images of each other in the control chamber (47) are arranged.

7. Gas spring device according to one of the preceding claims, characterized in that the control chamber (47) at least two with the cylinder-piston device (5), at least two with the FIu- idfördereinrichtung (2), and at least one with the gas spring accumulator (23 ) has associated openings (29,35,31, 41, 43).

8. Gas spring device according to one of the preceding claims, characterized in that the control chamber (47) has two restoring springs (17,19) receiving control pressure chambers (73,75) which in each case on one side of the formed as a hollow cylinder portion (63 ) of the control piston (21) are limited.

9. Gas spring device according to claim 8, characterized in that in a neutral position of the control piston (21) a first control pressure chamber (73) via a first opening (29) with the Fluidförderein- direction (2) is connected, that a second control pressure chamber ( 75) is connected to the fluid delivery device (2) via a second opening (31), that the opening (35) of the control chamber (47) connected to the gas spring accumulator (23) communicates with the openings connected to the cylinder piston device (5) (41, 43), and the openings (41, 43) of the control chamber (47) connected to the cylinder-piston device (5) are interconnected.

10. Gas spring device according to claim 8 or 9, characterized in that in a first conveying position of the control piston (21) of the first control pressure chamber (73) from the fluid conveying device (2) is acted upon by a pressurized fluid, and that the cylinder piston Device (5) is supplied with the pressurized fluid, so that a hydraulic piston (7) and a piston rod (9) of the cylinder-piston device (5) move in a first direction.

11. Gas spring device according to claim 10, characterized in that the cylinder-piston device (5) via the first control pressure chamber (73) is supplied with the pressurized fluid.

12. Gas spring device according to one of claims 10 or 11, character- ized in that in the first delivery position of the control piston (21), the cylinder-piston device (5) with the fluid delivery device (2) and with the gas spring accumulator (23) is connected ,

13. Gas spring device according to one of claims 10 to 12, characterized in that in the first delivery position of the control piston (21) of the second control pressure chamber (75) via an opening (31) of the control chamber (47) connected to the fluid conveying device (2) is.

14. Gas spring device according to one of claims 7 to 13, characterized in that in a second conveying position of the control piston (21), the second control pressure chamber (75) of the fluid conveying device (2) with a pressurized fluid beauf- is hit and that the cylinder-piston device (5) is supplied with the pressurized fluid, so that the hydraulic piston (7) and the piston rod (9) of the cylinder-piston device (5) move in a second direction.

15. Gas spring device according to claim 14, characterized in that the cylinder-piston device (5) via the second control pressure chamber (75) is supplied with the pressurized fluid.

16. Gas spring device according to one of claims 14 or 15, character- ized in that in the second conveying position of

Control piston (21), the cylinder-piston device (5) with the fluid delivery device (2) and with the gas spring accumulator (23) is connected.

17. Gas spring device according to one of claims 14 to 16, character- ized in that in the second conveying position of the first

Control pressure chamber (73) via an opening (29) of the control chamber (47) with the fluid conveying device (2) is connected.

18. Gas spring device according to one of claims 7 to 17, characterized in that in a fail-safe position of the control piston (21) a short circuit between the openings (29, 31) of the control chamber (47) connected to the fluid conveying device ( 2) are connected, via the opening (35) of the control chamber (47) which is connected to the gas spring accumulator (23), and a connection between the openings (41, 43) with the cylinder-piston device (5 ).