PACKING SEAL FOR A PISTON COMPRESSOR AND METHOD FOR OPERATING SAME

Abstract

The packing seal for a piston compressor, having a longitudinal axis L as well as, following one after the other in the direction of the longitudinal axis L, a fastening part and a cylindrical part, wherein a magnetic bearing and at least one chamber ring with a sealing ring arranged therein are arranged following one after the other in the direction of the longitudinal axis L in the cylindrical part, wherein the magnetic bearing includes at least one controllable electromagnet.

Claims

1. A packing seal for a piston compressor, comprising a longitudinal axis L and, following one after another in the direction of the longitudinal axis L a fastening part and a cylindrical part, wherein in the cylindrical part a magnetic bearing and a seal are arranged, wherein the magnetic bearing comprises a controllable electromagnet, wherein the seal is designed as a chamber ring with a sealing ring arranged therein, the sealing ring being radially displaceable with respect to the longitudinal axis L in the chamber ring, and wherein in the cylindrical part, after the fastening part, following one after the other in the direction of the longitudinal axis L, the magnetic bearing and the chamber ring are arranged.

2. The packing seal according to claim 1, wherein the magnetic bearing comprises at least two controllable electromagnets which are arranged opposite each other with respect to the longitudinal axis L in the cylindrical part.

3. The packing seal according to claim 1, comprising at least two emergency bearings which are mutually spaced in the direction of the longitudinal axis L.

4. The packing seal according to claim 3, wherein the magnetic bearing is arranged in the direction of the longitudinal axis L between the two emergency bearings.

5. The packing seal according to claim 1, characterized in that it further comprising a sensor designed to measure a radial position of a piston rod passing through the packing seal with respect to the longitudinal axis L.

6. The packing seal according to claim 5, wherein the sensor is arranged in the direction of the longitudinal axis L between the two emergency bearings.

7. The packing seal according to claim 6, wherein the sensor is arranged in the direction of the longitudinal axis L along the magnetic bearing.

8. The packing seal according to claim 1, wherein said fastening part is flange-shaped, and said packing seal further comprising cooling channels, said cooling channels having ports arranged on a front side of the flange-shaped fastening part.

9. The packing seal according to claim 8, wherein the cooling channels extend in the direction of the longitudinal axis L along the entire length of the magnetic bearing.

10. The packing seal according to claim 1, wherein the chamber rings are arranged in the direction of the longitudinal axis L along an end portion L.sub.2, said end portion L.sub.2 being located at an opposite end of the packing seal with respect to the fastening part.

11. The packing seal according to claim 10, having an overall length L.sub.1 in the direction of the longitudinal axis L, the end section L.sub.2 having an end section length L.sub.3, the end section length L.sub.3 being less than 50% of the overall length L.sub.1.

12. The packing seal according to claim 1, wherein a plurality of chamber rings are arranged in the direction of the longitudinal axis L along an end portion L.sub.2 of the packing seal, the end portion L.sub.2 being located at an opposite end of the packing seal with respect to the fastening part.

13. The packing seal according to claim 1, wherein the packing seal comprises cooling channels extending inside an outer casing of the packing seal and/or inside a coil core of the magnetic bearing.

14. A piston compressor comprising a packing seal according to claim 1.

15. A method for operating a piston compressor comprising the steps: moving a piston back and forth in the direction of a longitudinal axis within a cylinder, the piston being driven via a piston rod, and comprising a packing seal with a controllable magnetic bearing and a seal, wherein the piston rod extends through the packing seal, and exerting a controllable magnetic force F.sub.m acting at least perpendicular to the longitudinal axis L on the piston rod via the controllable magnetic bearing, wherein the piston rod is sealed in the seal by a chamber ring with a sealing ring arranged therein, and the piston rod is sealed between the piston and the magnetic bearing, and moving the piston rod radially with respect to the longitudinal axis L by the magnetic bearing, thereby reducing a contact force of the piston supported on an inner surface of the cylinder, the piston rod bearing against the sealing ring, and the sealing ring being radially displaced with respect to the longitudinal axis L with respect to the chamber ring.

16. The method according to claim 15, wherein a state variable (Z) of the piston compressor is detected, the magnetic force F.sub.m is controlled as a function of the state variable (Z), and a force F.sub.h is thereby exerted on the piston via the piston rod.

17. The method according to claim 16, wherein the state variable (Z) is measured within the packing seal, and the controllable magnetic bearing acts in a centering manner via the piston rod on the position of the piston within the cylinder.

18-19. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings used to explain the embodiments show:

[0027] FIG. 1 a schematically simplified longitudinal section through a piston compressor;

[0028] FIG. 2 a schematic illustration of a control device;

[0029] FIG. 3 an exemplary progression of the magnetic force as a function of a state variable, namely the angle of rotation of a drive shaft;

[0030] FIG. 4 a longitudinal section through a known packing seal;

[0031] FIG. 5 a longitudinal section through a packing seal according to the invention;

[0032] FIG. 6 a radial magnetic bearing;

[0033] FIG. 7 An inclined piston compressor, for example on a ship with wave motion;

[0034] FIG. 8 a simplified illustration of a packing seal with magnetic bearing.

[0035] In principle, the same parts are given the same reference signs in the drawings.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0036] FIG. 1 shows a piston compressor 1 for compressing a gas, comprising a cylinder 2 extending in the horizontal direction and comprising a piston 3 movable within the cylinder 2 in the direction of extension of the cylinder 2 respectively in the longitudinal direction L. The piston compressor 1 also comprises a piston rod 16, a packing seal 12, a magnetic bearing 13, a crosshead 17 with a linear guide 18, a push rod 19 and a drive, for example a crank 20 with a drive shaft 21. In the exemplary embodiment shown, the piston 3 is of double-acting design and comprises sealing or piston rings 4 as well as a guide ring 5, the piston 3 dividing the interior of the cylinder 2 into a first interior space 6 and a second interior space 7, these two interior spaces each having an inlet valve 8, 9 and an outlet valve 10, 11. The cylinder 2 is connected to a housing 15 via an intermediate piece 14, with the packing seal 12 and the magnetic bearing 13 also being arranged in the intermediate piece. The magnetic bearing 13 exerts a magnetic force F.sub.m on the piston rod 16 at least in the vertical direction. A control device 22 detects a state variable Z of the piston compressor 1 via a signal line 24 and a sensor not shown, for example the displacement path s(t) of the piston in the cylinder 7 as a function of time, the displacement path s(t) of the piston rod 16 and/or an angle of rotation α(t) of the drive shaft 21 as a function of time. The control device 22 controls, via a signal line 25, the current in the electromagnets of the magnetic bearing 13 and thereby the magnetic force exerted by the magnets on the piston rod 16.

[0037] In a simple embodiment, the drive device 22 can be operated in a drive mode in which a state variable Z is measured, and the magnetic force F.sub.m is modified as a function of the state variable Z. In this case, feedback can be dispensed with. FIG. 3 shows an example of such a control mode in which the progression of a curve K1 is specified, the curve K1 specifying the relationship between the state variable Z, in the present case the angle of rotation α of the drive shaft 21, and the magnetic force F.sub.m to be generated as a function of the angle of rotation α. In the illustrated exemplary embodiment, the angle α=0° corresponds to the bottom dead center and α=180° to the top dead center of the piston 3 with respect to the second interior space 7, the magnetic force F.sub.m being smallest at the bottom dead center, because the lever arm formed by the piston rod 16 between the center of gravity S of the piston 3 and the magnetic bearing 13 is shortest, and wherein the magnetic force F.sub.m is largest at the top dead center because the lever arm formed by the piston rod 16 between the center of gravity S of the piston 3 and the magnetic bearing 13 is longest. The angle of rotation α is measured by a sensor not shown and fed to the control device 22 via the signal line 24. The curve progression K1 can be predetermined, for example, on the basis of empirical values. This embodiment is particularly preferred if, as shown in FIG. 1, a piston 3 having a guide ring 5 is used, wherein the guide ring 5 bears against the inner surface of the cylinder 2, and wherein the magnetic force F.sub.m serves to reduce the bearing force of the guide ring 5 against the inner surface of the cylinder 2, thereby in particular reducing wear of the guide ring 5. The curve K1 shown in FIG. 3 only shows the progression of the magnetic force F.sub.m as a function of the crankshaft angle α between 0° and 180°. In the subsequent section between 180° and 360°, which is not shown, the force F.sub.m, starting from the value at 180°, runs in the reverse direction to the value of F.sub.m at the angle of 0°, this value being identical to the value at the angle of 360°.

[0038] In a further preferred embodiment, a measuring device, for example a sensor 26, is provided to measure the position of the piston rod 16 and/or the piston 3 at least in the vertical direction. FIG. 2 shows an embodiment which measures the position of the piston rod 16 in the vertical direction. In a preferred embodiment, the sensor 26 is arranged close to the magnetic bearing 13 or even inside the magnetic bearing 13, wherein the sensor 26 preferably measures the distance D between an upper coil core 13a of the magnetic bearing 13 and the surface of the piston rod 16. Preferably, the magnetic bearing 13 comprises at least an upper coil core 13a with coil 13b and a lower coil core 13c with coil 13d. As shown in FIG. 6, the magnetic bearing 13 can also be designed as a radial magnetic bearing with a plurality of electromagnets 13f distributed in the circumferential direction, wherein their coils 13b, 13d can preferably be controlled individually so that the direction of the magnetic force F.sub.m exerted on the piston rod 16 can be determined by a corresponding control of the coils 13b, 13d.

[0039] In a preferred operating method, a setpoint for the distance D is predetermined for the control device 22 via the setpoint specification 28, with the control device 22 driving the coils 13b, 13d with current via the signal line 25 in such a way that the piston rod 16 has an essentially unaltered, constant distance D with respect to the upper coil core 13a, irrespective of the stroke s(t) or the crankshaft angle α(t). The piston rod 16 thereby acts as a magnetic armature of the two coil cores 13a, 13b. Preferably, the magnetic bearing 13 can exert both an upward force and a downward magnetic attraction force on the piston rod 16, so that the position of the piston rod 16 relative to the magnetic bearing 13 can be controlled particularly precisely.

[0040] The piston compressor 1 is thus preferably operated in such a way that a controllable magnetic force F.sub.m is exerted on the piston rod 16, so that a force F.sub.m acting at least in the vertical direction, or a relief force F.sub.h, is exerted on the piston 3 via the piston rod 16, which counteracts the force of gravity F, the magnetic force F.sub.m being controlled or varied as a function of a state variable Z such as, for example, the distance D, the stroke s(t) or the angle of rotation α(t). The arrangement described in FIGS. 1 to 3 and the method described are also suitable for operating or controlling a piston compressor with a cylinder extending in the vertical direction and a piston moving in the vertical direction.

[0041] FIG. 7 shows a further example of a piston compressor which, in comparison with the piston compressor 1 shown in FIG. 1, is provided with a cylinder 2 or an interior of a cylinder extending essentially in the vertical direction, with a piston rod 16 extending essentially in the vertical direction, and with a piston 3 movable in this direction. FIG. 7 also shows a packing seal 12 in which the radial bearing 13 is integrated. The radial bearing 13 is supplied with power via line 25 and is connected to a coolant circuit via line 27. In FIG. 7, the piston compressor 1 is arranged on a ship heeled with a heel angle, which is why the cylinder 2 and the piston rod 16 have an angle of inclination β with respect to the vertical V. The piston compressor 1 is preferably arranged in the ship in such a way that the cylinder 2 and the piston rod 16 are exactly in the vertical direction or at least approximately in the vertical direction when the sea is absolutely calm. The piston compressor 1 could of course also be arranged on land, and the cylinder 2 and the piston rod 16 preferably extend exactly in vertical direction or at least approximately in vertical direction. Preferably, the angle of inclination β with respect to the vertical V is measured by a sensor 26 not shown, the angle of inclination β preferably being measured as a function of time t. The magnetic bearing 13 is controlled via the control device 22 in such a way that a magnetic force F.sub.m is exerted on the piston rod 16, and that the piston rod 16 transmits a relief force F.sub.h to the piston 3, so that, due to the acting relief force Fri, the position of the piston 3 within the cylinder 2 is influenced, if possible.

[0042] As a state variable Z for controlling the magnetic bearing 13, at least one of the following variables is suitable, in addition to or instead of the state variables Z already mentioned: Angle of inclination β of the cylinder relative to the vertical V, gap width between the inner surface of the cylinder and the side surface of the piston, location of a mutual point of contact between the piston and the cylinder.

[0043] Preferably, the magnetic bearing 13 is controlled in such a way that the mutual distance between the piston rod 16 and the magnetic bearing 13 and/or the distance between the cylinder inner surface and the piston side surface, perpendicular to the longitudinal direction L, is kept constant or substantially constant. Preferably, the piston 3 is held without wall contact in the cylinder 7. Preferably, the angle of inclination β(t) assumed between the vertical V and the longitudinal direction L is also measured as a function of time t as the state variable Z. Particularly preferred, in the case of a piston compressor arranged on a ship, the magnetic force F.sub.m is controlled by means of a predictive control. Preferably, the state variable Z comprises the inclination angle β(t) as a function of time t, such that the state variable Z is dependent on time t. In a preferred embodiment, the state variable Z comprises, in addition to the inclination angle β(t) as a function of time t, at least one further state variable mentioned herein, so that such a resulting state variable consists of a combination of at least two state variables mentioned herein. For example, a resulting state variable could comprise the state variable Z of the movement of the piston rod perpendicular to the longitudinal direction L, and be combined with the state variable Z of the inclination angle β(t) as a function of time t, so that with the aid of the predictive control and the knowledge of the state variable Z of the angle of inclination β(t) as a function of the time t, the expected movement of the piston rod perpendicular to the longitudinal direction L caused by the angle of inclination β(t) at the time t+Δt can be predicted, and the magnetic bearing 12 can be controlled with this predictive state variable Z.sub.V (t+Δt).

[0044] Preferably, a predictive state variable Z.sub.V (t+Δt) is calculated from the state variable Z(t) depending on the angle of inclination β(t) for a future point in time t+Δt, and the magnetic force F.sub.m is controlled at the current point in time t depending on the predictive state variable Z.sub.V (t+Δt).

[0045] Particularly preferred, the piston compressor according to the invention comprising the controllable magnetic bearing is used in combination with a transport ship used for transports over the sea.

[0046] The longitudinal section shown in FIG. 4 shows a packing seal 12 known per se, comprising a plurality of chamber rings 12a in which sealing rings 12b are arranged. In addition, the packing seal 12 comprises a fastening part 12c designed as a flange, to which all chamber rings 12a are fastened in a manner not shown in detail. The packing seal 12 is connected to a cylinder housing 2a of a cylinder 2 via the fastening part 12c, wherein a piston rod 16 extends through the packing seal 12. The cylinder housing 2a has a recess which corresponds to an outer contour 12d of the packing seal 12, so that the entire packing seal 12 can be inserted into this recess and, if necessary, the entire packing seal 12 can be replaced as a complete unit, preferably after the fastening part 12c has been detached from the cylinder housing 2a.

[0047] FIG. 5 shows a longitudinal section through a packing seal 12 according to the invention comprising a magnetic bearing 13. FIG. 6 shows a partial section of the magnetic bearing 13, which is designed as a radial bearing and comprises, for example, eight coil cores 13a, 13c, the two opposing coil cores 13a, 13c being provided with reference signs. The coil cores 13a, 13c are wound with coils 13b, 13d. In addition, the end face 13e of the coil core 13a facing the piston rod 16 is shown. The packing seal 12 according to FIG. 5 preferably comprises two chamber rings 12a in which sealing rings 12b are arranged. The packing seal 12 could also have only a single chamber ring 12a or more than two chamber rings 12a with sealing ring 12b arranged therein. The packing seal 12 also includes two emergency bearings 12f, 12g each having a bearing surface 12h, 12i. In the event of a power failure of the magnetic bearing 13 or, for example, when the piston compressor is switched off, the piston rod 16 can rest on the emergency bearings 12f, 12g. Preferably, the packing seal 12 further comprises a holder 12k for a sensor 26, wherein preferably at least one sensor 26 is arranged at the top, and wherein preferably a plurality of sensors 26 are arranged mutually spaced in the circumferential direction. In addition, the packing seal 12 comprises a fastening part 12c, to which preferably all components shown in FIG. 5 are connected and preferably held firmly together by fastening means not shown, such as screws. The packing seal 12 has an outer contour 12d. In a preferred embodiment, the outer contour 12d of the packing seal 12 according to the invention is similarly or identically dimensioned to the known packing seal 12 shown in FIG. 4, so that the packing seal 12 according to the invention can be used in existing piston compressors 1 having the known packing seal 12. Preferably, a piston compressor 1 upgraded with the packing seal 12 according to the invention is also provided with a control device 22, so that existing piston compressors 1 can also be provided with the device according to the invention or existing piston compressors 1 can be operated with the process according to the invention.

[0048] In a further, preferred embodiment, the packing seal 12 according to the invention, as shown in FIG. 5, also comprises cooling channels 121, which run, for example, inside the outer casing 12e and/or inside the coil cores 13a, 13c, the cooling channels forming part of a cooling circuit in order to cool the magnetic bearing 13 and/or the packing seal 12. The cooling circuit is shown only schematically, the supply lines and the discharge lines of the cooling circuit preferably running through the mounting part 12c in such a way that the mounting part 12c has connections 12m for the cooling circuit which are accessible from the outside, preferably on its end face, and in that the cooling circuit inside the packing seal 12 is predefined and fully configured, so that after installation of the packing seal 12 only the external coolant supply from the outside needs to be connected to the fastening part 12c in order to supply the cooling circuit inside the packing seal 12 with coolant. In FIG. 5, in particular, the connecting channels arranged inside the emergency bearing 12g and mutually connecting the cooling channels 121 in a fluid-conducting manner are not shown.

[0049] FIG. 8 shows in a simplified representation and partially in section a packing seal 12 with integrated magnetic bearing 13. The packing seal 12 comprises a flange-like fastening part 12c and a cylindrical body part 12p, which are firmly connected to each other by retaining means 12o. The fastening part 12c can preferably be fastened to the cylinder housing 2a by means of fastening means 12n. The packing seal 12 preferably comprises at least one sealing ring 12b, and preferably comprises all components shown in FIG. 5, which are not shown in detail in FIG. 8. In the piston compressor 1 shown in FIG. 7, the packing seal 12 is arranged as shown in FIG. 8. The packing seal 12 could be arranged in a variety of different piston compressors 1, for example also in the piston compressor 1 shown in FIG. 1.

[0050] The packing seal 12 for a piston compressor 1 shown in FIGS. 5 and 8 comprises a longitudinal axis L, and in succession in the direction of the longitudinal axis L a flange-shaped mounting part 12c and a cylindrical part 12p, wherein a magnetic bearing 13 and at least one chamber ring 12a with a sealing ring 12b arranged therein are arranged in succession in the direction of the longitudinal axis L in the cylindrical part 12p, wherein the magnetic bearing 13 comprises at least one single controllable electromagnet 13f.

[0051] Preferably, the magnetic bearing 13 comprises at least two controllable electromagnets 13f, which are arranged opposite each other in the cylindrical part 12 with respect to the longitudinal axis L, as shown in FIG. 6.

[0052] Preferably, the packing seal comprises at least two emergency bearings 12f, 12g, which are arranged mutually spaced apart in the direction of the longitudinal axis L.

[0053] Preferably, the magnetic bearing 13 is arranged in the direction of the longitudinal axis L between the two emergency bearings 12f, 12g.

[0054] Preferably, the packing seal further comprises a sensor 26 configured to measure the radial position of a piston rod 16 extending through the packing seal with respect to the longitudinal axis L.

[0055] Preferably, the sensor 26 is arranged in the direction of the longitudinal axis L between the two emergency bearings 12f, 12g, wherein the sensor 26 is preferably arranged in the direction of the longitudinal axis L along the magnetic bearing 13.

[0056] The packing seal preferably comprises cooling channels 121, which preferably have connections 12m arranged on the end face of the flange-shaped mounting part 12c. Preferably, the cooling channels 121 run in the direction of the longitudinal axis L along the entire length of the magnetic bearing 13.

[0057] Preferably, the chamber rings 12a are arranged in the direction of the longitudinal axis L along an end portion L2 of the packing seal 12, the end portion L2 being located at the opposite end of the packing seal with respect to the fastening part 12c.

[0058] Preferably, the packing seal 12 has an overall length L1 in the direction of the longitudinal axis L, and the end section L2 has an end section length L3, the end section length L3 being less than 50% of the overall length L1, preferably less than 25%, and particularly preferably less than 10%. This embodiment has the advantage that a substantial part of the total length L1 is available for the magnetic bearing 13. A piston rod 16 extending through the packing seal 12 is preferably in contact with the sealing rings 12b and thus touches them, whereas the piston rod 16 along the remaining total length L1 preferably does not touch the packing seal 12. This embodiment has the advantage that within the remaining total length L1 a deflection or movement of the piston rod 16 radially to the longitudinal axis L is possible, wherein the maximum possible path of movement is of course limited by the inner cross-section of the passage of the packing seal 12 provided for the piston rod 16. In contrast to the exemplary embodiment according to FIG. 4, the piston rod 16 is thus slightly movable in radial direction with respect to the packing seal 12 within the remaining total length L1, so that the position of the piston rod 16 in radial direction can be corrected particularly well with the aid of the magnetic bearing 13.

[0059] Particularly preferred, this also allows the position of the piston 3 connected to the piston rod 16 to be corrected with respect to the interior of the cylinder 2, at least in the radial direction. In a preferred embodiment, the sealing rings 12b are displaceable radially with respect to the longitudinal direction L in the chamber ring 12a. In a further embodiment, the directional rings 12b are not displaceable or are only slightly displaceable in this radial direction in the chamber ring 12a. This embodiment has the advantage that the chamber ring or rings 12a form a kind of pivot point with respect to which the piston rod 16 is slightly rotatable when the piston rod 16 is displaced in the radial direction by the magnetic bearing 13 in the region of the remaining overall length L1, so that the piston 3 connected to the piston rod 16 is preferably displaced in the opposite direction within the cylinder 2. This slight displacement of the piston 3 or at least the application of a force acting in the radial direction to the piston 3 preferably takes place at a relatively high frequency, for example at 10, 100 or 1000 Hz, so that the piston 3 is preferably held continuously and preferably in a central position with respect to the interior of the cylinder 2.

[0060] The piston compressor comprises a piston which is moved back and forth in the direction of a longitudinal axis within a cylinder, the piston being driven by a crosshead via a piston rod, and comprising a packing seal with a controllable magnetic bearing and at least one chamber ring 12a with a sealing ring 12b arranged therein, wherein the piston rod 16 extends through the packing seal 12, and wherein a controllable magnetic force F.sub.m acting at least perpendicularly to the longitudinal axis L is exerted on the piston rod 16 via the controllable magnetic bearing 13.

[0061] Preferably, a state variable Z of the piston compressor 1 is detected, wherein the magnetic force F.sub.m is controlled as a function of the state variable Z, and wherein a force F.sub.h is thereby exerted on the piston 3 via the piston rod 16.

[0062] Preferably, the state variable Z is measured within the packing seal 12, with the controllable magnetic bearing 13 having a centering effect on the position of the piston 3 within the cylinder 7 via the piston rod 16.

[0063] In the embodiment shown in FIG. 1, a piston compressor 1 comprising a piston 3 with piston rings or sealing rings 4 and a guide ring 5 is shown. The guide ring 5 could be dispensed with. In another embodiment, not shown, the piston 3 could also be designed as a labyrinth piston, wherein this labyrinth piston preferably does not touch the inner wall of the cylinder 2.

[0064] Embodiments of piston compressors and methods of operation are described below.

[0065] Item 1: A piston compressor 1 for compressing a gas, comprising a cylinder 2, a piston 3, a piston rod 16, a packing seal 12, a crosshead 17, a magnetic bearing 13, and a drive 21, wherein the piston 3 is arranged movably in a longitudinal direction L within the cylinder 2, wherein the piston 3 is connected to the crosshead 17 via the piston rod 16, wherein the packing seal 12 is arranged between the piston 3 and the crosshead 17, through which the piston rod 16 extends, wherein the crosshead 17 is driven by the drive 21, the magnetic bearing 13 being arranged between the piston 3 and the cross head 17, and the magnetic bearing 13 being capable of exerting a magnetic force F.sub.m on the piston rod 16 at least perpendicularly to the longitudinal direction L, a sensor 26 being arranged for detecting a state variable Z of the piston compressor 1, the magnetic bearing 13 being designed as a controllable magnetic bearing 13, and a control device 22 controlling the magnetic force F.sub.m exerted by the magnetic bearing 13 on the piston rod 16 as a function of the state variable Z.

[0066] Item 2: A piston compressor according to item 1, with the cylinder 2 extending in a substantially horizontal direction.

[0067] Item 3: A piston compressor according to item 1, with the cylinder 2 extending in a substantially vertical direction.

[0068] Item 4: A piston compressor according to one of items 1 to 3, wherein the sensor 26 is designed to detect at least one of the following variables as a state variable Z: displacement path of the piston in the cylinder, displacement path of the piston rod in the direction of extension of the piston rod, displacement path of the piston rod perpendicular to the running direction of the piston rod, movement of the piston perpendicular to the running direction of the piston rod, angle of rotation of the drive shaft, gap width within the magnetic bearing 13 between the piston rod 16 and a magnet of the magnetic bearing 13.

[0069] Item 5: A piston compressor according to any one of items 1 to 4, wherein the sensor 26 is configured to detect at least one of the following parameters: Angle of inclination β of the longitudinal direction L with respect to the vertical V, gap width between the inner surface of the cylinder and the side surface of the piston, location of a mutual contact point of the piston and the cylinder.

[0070] Item 6: A piston compressor according to any one of items 1 to 5, wherein the packing seal 12 is configured as a replacement part, and wherein the packing seal 12 comprises both at least one seal ring 23 and the magnetic bearing 13.

[0071] Item 7: A piston compressor according to any one of items 1 to 6, wherein the piston 3 is designed as a labyrinth piston.

[0072] Item 8: A piston compressor according to any one of items 1 to 6, wherein the piston 3 comprises a plurality of seal rings 4 and preferably also a guide ring 5.

[0073] Item 9: A piston compressor according to any one of items 1 to 8, wherein the packing seal 12 and the magnetic bearing 13 comprise cooling channels 121 for a coolant.

[0074] Item 10: A piston compressor according to any one of items 1 to 9, wherein the packing seal 12 comprises, arranged sequentially in the longitudinal direction L, at least one fastening part 12c, the magnetic bearing 13, and at least one chamber ring 12a with a seal ring 12b arranged therein.

[0075] Item 11: A piston compressor according to item 10, wherein the packing seal 12 comprises at least two emergency bearings 12f, 12g which are mutually spaced in the longitudinal direction L.

[0076] Item 12: A method for operating a piston compressor 1 comprising a piston 3, which is moved back and forth in a longitudinal direction L within a cylinder 7, wherein the piston 3 is driven via a piston rod 16, and wherein a magnetic force F.sub.m acting at least perpendicular to the longitudinal direction L is exerted on the piston rod 16, wherein a state variable Z of the piston compressor 1 is detected, wherein the magnetic force F.sub.m is controlled as a function of the state variable Z, and wherein a force F.sub.h is thereby exerted on the piston 3 via the piston rod 16.

[0077] Item 13: A method according to item 12, wherein the longitudinal direction L is substantially in the horizontal direction.

[0078] Item 14: A method according to item 12, wherein the longitudinal direction L is substantially in the vertical direction.

[0079] Item 15: A method according to item 12, wherein the longitudinal direction L has an angle of inclination β in the range of +/−10° with respect to the vertical V.

[0080] Item 16: A method according to any one of items to 15, wherein the state variable Z comprises at least one of the following variables, displacement path of the piston 3 in the cylinder 7, displacement path of the piston rod 16 in the longitudinal direction L, movement of the piston rod 16 perpendicular to the longitudinal direction L, movement of the piston 3 perpendicular to the longitudinal direction L, angle of rotation of a drive shaft 21 driving the piston rod 16; gap width within the magnetic bearing 13 between the piston rod 16 and a magnet of the magnetic bearing 13.

[0081] Item 17: A method according to any one of items 12 to 15, wherein the mutual position of the piston rod 16 and the magnetic bearing 13, perpendicular to the longitudinal direction L of the piston rod 16, is measured as the state variable Z.

[0082] Item 18: A method according to any one of items 12 to 15, wherein as a state variable Z at least one of the following variables: Inclination angle β of the cylinder with respect to the vertical V, gap width between the inner surface of the cylinder and the side surface of the piston, location of a mutual contact point of the piston and the cylinder.

[0083] Item 19: A method according to any one of items 12 to 18, wherein the mutual distance of piston rod 16 and magnetic bearing 13 and/or the distance of the inner surface of the cylinder and the piston side surface, perpendicular to the longitudinal direction L, is kept constant.

[0084] Item 20: A method according to any one of items 12 to 19, wherein the piston 3 is held in the cylinder 7 without wall contact.

[0085] Item 21: A method according to any one of items 12 to 20, wherein, moreover, as a state variable Z, the angle of inclination β(t) assumed between the vertical V and the longitudinal direction L is measured as a function of time t.

[0086] Item 22: A method according to any one of items 12 to 21, wherein the magnetic force F.sub.m is controlled by means of a predictive control system.

[0087] Item 23: A method according to item 22, where the state variable Z comprises the inclination angle β(t) as a function of time t, such that the state variable Z is dependent on time t.

[0088] Item 24: A method according to item 23, wherein a predictive state variable Z.sub.V (t+Δt) is calculated from the state variable Z(t) as a function of the inclination angle β(t) for a future point in time t+Δt, and in that the magnetic force F.sub.m is controlled at the current point in time t as a function of the predictive state variable Z.sub.V (t+Δt).

[0089] Item 25: A method according to any one of items 12 to 20, wherein the magnetic force F.sub.m is fixedly predetermined as a function of the state variable Z.