Linear drive for a lift system

Abstract

The invention relates to a linear drive (4) for a lift system (1) comprising: a magnet track (5), which comprises at least one row (16, 17) of permanent magnets (8, 8a, 8b), the permanent magnets (8, 8a, 8b) being mounted rotatably about their own rotation axis (r) in a carrier (7); a force-transfer member (6); the magnet track being fixable to a lift shaft (2) and the force-transfer member being fixable to a lift car (3), or vice versa, so that: the permanent magnets in the same row are arranged successively in the direction of a displacement axis (z); the magnet track and the force-transfer member are displaceable relative to one another in the direction of the displacement axis; the magnet track and the force-transfer member are opposite one another in an overlap region (9), a permanent magnet located in the overlap region being separated from the force-transfer member opposite it by an air gap (s); a rotary drive (11), which is designed to rotate the permanent magnets so that, due to the superimposition of the magnetic fields of the rotating permanent magnets, a travelling field travelling in the direction of the displacement axis is generated.

Description

[0001] LINEAR DRIVE FOR AN ELEVATOR SYSTEM

[0002] The present invention relates to a linear drive for an elevator system. Furthermore, the invention relates to an elevator system equipped with such a linear drive.

[0003] Elevator cabins in elevator systems, such as those used to transport people or goods in multi-story buildings, are typically coupled to an electric motor via suspension elements such as ropes or belts. The rotary motion of the electric motor's drive shaft is converted into a translation of the suspension elements and thus of the elevator cabin along the elevator shaft.

[0004] There are also elevator systems whose elevator cars can be moved along the elevator shaft via a linear motor. Such a linear motor can comprise several electromagnets. The strength of the current flowing through the coils of the electromagnet, and thus of the generated magnetic field, is usually limited to avoid excessive heat generation.

[0005] WO 98 / 58866 describes an example of an elevator system with a linear motor in the form of a switched reluctance machine.

[0006] There may be a need for a linear actuator for an elevator system that allows for increased force density without excessive heat generation in the elevator shaft. Furthermore, there may be a need for a correspondingly improved elevator system.

[0007] These needs can be met by the subject matter of the independent claims. Advantageous embodiments are set forth in the dependent claims, the following description, and the accompanying figures.

[0008] A first aspect of the invention relates to a linear drive for an elevator system. The elevator system comprises an elevator shaft and an elevator car that can be displaced in the direction of a displacement axis in the elevator shaft. The linear drive comprises a magnetic track comprising at least one row of permanent magnets, wherein the or each permanent magnet is mounted in a support so as to be rotatable about its own axis of rotation. Furthermore, the linear drive comprises a force transmission element made of an electrically conductive material. The magnetic track can be fixed to the elevator shaft, while the force transmission element can be fixed to the elevator car. Alternatively, the force transmission element can be fixed to the elevator shaft, while the magnetic track can be fixed to the elevator car. In both cases, the magnetic track and the force transmission element can be fixed such that:

[0009] - the permanent magnets of the same row are arranged one behind the other in the direction of the displacement axis;

[0010] - the magnetic track and the force transmission element can be displaced relative to each other in the direction of the displacement axis;

[0011] - the magnetic track and the force transmission member are located opposite each other in an overlapping region, wherein the or each permanent magnet located in the overlapping region is separated from the force transmission member opposite it by an air gap.

[0012] Furthermore, the linear drive comprises a rotary drive which is designed to rotate the permanent magnets about their axes of rotation in such a way that, by superimposing the magnetic fields of the rotating permanent magnets, a traveling field moving in the direction of the displacement axis is generated for displacing the force transmission element relative to the magnetic track.

[0013] A second aspect of the invention relates to an elevator system comprising an elevator shaft, an elevator car that is displaceable in the direction of a displacement axis within the elevator shaft, and a linear drive as described above and below. The magnetic track is fixed to the elevator shaft, while the power transmission member is fixed to the elevator car. Alternatively, the power transmission member is fixed to the elevator shaft, while the magnetic track is fixed to the elevator car.

[0014] Electric linear motors are typically based on the generation of a traveling magnetic wave by exciting a coil arrangement with (multiphase) currents. This principle is comparable to a stadium wave ("Mexican wave") of spectators in a stadium: The coil currents pulsate at a specific rate, similar to standing and seated spectators, thus generating a moving magnetic wave. The part of the linear drive containing the coils is usually referred to as the armature, which can be stationary or movable. The other part of the linear drive, referred to below as the non-armature part, interacts electromagnetically with the traveling wave generated by the armature, causing opposing but equal forces to act on both parts. Depending on the configuration of the armature, a distinction can be made between synchronous machines, asynchronous machines, or synchronous reluctance machines.For applications with very long strokes, synchronous machines are generally too expensive, as large quantities of rare earth elements or copper may be required for the correspondingly long non-armature section. For such applications, rails made of magnetically passive and easily available materials, such as steel or aluminum, with a simple structure are generally preferred. Designs suitable for very long strokes are therefore usually asynchronous or synchronous reluctance machines.

[0015] In both cases, the (sinusoidal) traveling wave can be decomposed into two orthogonal, oscillating components (direct and quadrature current) for control purposes. These components can be independently varied by the resulting decomposed currents to obtain the desired electromechanical behavior of the machine. This means that propulsive forces and attractive forces can be independently controlled via these orthogonal components. The magnitude of these forces depends to some extent on the amplitude of the traveling wave. The force density is therefore limited by the thermal constraints of the armature coils.

[0016] The force density of an electrical machine based on the traveling wave principle can therefore be limited by the ability of the current-carrying coils to generate a magnetic field. The extent to which the coils can generate a magnetic field is directly proportional to the strength of the current flowing through the coils. For example, if the coils are wound from conventional materials with electrical resistance, the dissipative properties of the coils limit the maximum current and thus the torque or force density of the electrical machine.

[0017] Long-stroke translational movements can be generated using the direct or indirect drive principle. The direct drive principle is based on linear electric machines, which enable forces to be generated between two magnetic structures of the electric machine, i.e. the stator and rotor, separated by an air gap. The force is transferred between these two structures without contact, as the magnetic traveling wave propagates in the direction of the translational movement. Thus, in principle, a direct drive can have an unlimited stroke, which is particularly advantageous when the stroke is several orders of magnitude greater than the shortest link in the machine. In practice, however, the force capacity of the machine is limited by the available installation space in conjunction with the maximum permissible heat dissipation per unit volume.

[0018] For example, the power density can be increased locally by choosing an indirect drive, which, however, results in a significantly reduced stroke. An indirect drive can comprise a rotating machine in conjunction with a mechanical gearbox that converts the rotation into translation. Since the rotating machine is usually spatially separated from the gearbox, the heat dissipated by the machine's coils does not have a significant impact on the gearbox. However, frictional heat is generated in the gearbox, albeit to a lesser extent. Furthermore, mechanical gearboxes are inherently susceptible to wear and can cause unwanted noise and vibration.

[0019] In the direct drive described above, increasing the power density is generally one of the goals in the design phase of the electric machine, as this allows for a reduction in the amount and mass of material used and a corresponding increase in cooling capacity. To increase the power density, cooling methods can be used that keep the coil temperature within an acceptable range. However, such cooling methods can be relatively complex.

[0020] There are also linear transverse flux machines, flux-switched machines, and switched reluctance machines, which abandon the principle of the magnetic traveling wave in favor of increased force density. However, these approaches can result in increased force ripple and noise. Controlling such machines can be complex.

[0021] To minimize power loss in the coils, superconducting coils, for example, can be used. However, such coils require a carefully shielded cryogenic environment at very low temperatures below 100 K, which can only be implemented in practice with considerable effort.

[0022] The approach proposed here makes it possible to at least partially overcome the limitations and undesirable effects described above. The power transmission of the linear drive is based on the traveling wave principle, i.e., it is contactless, and the traveling wave is generated by rotating permanent magnets, which can be driven by a rotating electric machine. This improves heat dissipation. Furthermore, the use of permanent magnets instead of coils allows the magnetic field strength to be increased.

[0023] Optionally, the permanent magnets can be driven independently of each other. This enables field-oriented control, meaning that propulsive forces parallel to the displacement axis and attractive forces perpendicular to the displacement axis between the force transmission element and the permanent magnets can be controlled independently of each other. With an appropriately configured rotary drive, the same orthogonal decomposition of the force components can be achieved as in a conventional synchronous, asynchronous, or synchronous reluctance machine, while increasing force density and reducing power loss.

[0024] In other words, rotating permanent magnets, as used in the present approach, are capable of generating higher field strengths with a smaller volumetric footprint in a nearly non-dissipative manner.

[0025] The use of permanent magnets also offers the advantage that the attractive forces between the magnetic track and the power transmission element are maintained even in the event of a power failure. This increases the operational reliability of the elevator system.

[0026] Without limiting the scope of the invention in any way, embodiments of the invention may be considered to be based on the ideas and findings described below.

[0027] The permanent magnets can, for example, each be rod-shaped, in particular cylindrical. The axis of rotation of a permanent magnet can correspond to its longitudinal or central axis. The permanent magnets can each be magnetized in specific magnetization directions, for example orthogonal to the axis of rotation, and can be positioned relative to one another via the rotary drive such that the magnetization directions of adjacent permanent magnets - in the rotating and / or non-rotating state - are aligned at a defined angle to one another. This angle can be kept constant during operation of the linear drive, i.e., while the permanent magnets are rotating, or it can be varied within a specific angular range, for example in order to modify the amplitude and / or phase shift of the traveling wave.The angular range can be, for example, plus / minus 40 degrees, preferably plus / minus 30 degrees, in particular plus / minus 20 degrees, particularly preferably plus / minus 10 degrees, in particular plus / minus 5 degrees. The rotary drive can, for example, comprise an electric motor with a rotating drive shaft and a gear designed to convert the rotary movement of the drive shaft into corresponding rotary movements of the individual permanent magnets. The gear can, for example, comprise gears, belts, and / or chains that positively and / or non-positively couple the axes of rotation of the permanent magnets to one another and / or to the drive shaft. The synchronization of the rotary movements of the individual permanent magnets can thus take place via the gear.

[0028] Alternatively, a design is conceivable in which each permanent magnet is rotated by its own electric motor. This has the advantage that the permanent magnets can be controlled independently of each other. In this case, synchronization can be achieved by simultaneously controlling the individual electric motors, for example, via a higher-level elevator control system.

[0029] The linear drive can also comprise more than one magnetic track and / or more than one power transmission element. For example, when the elevator system is in operation, the magnetic track and the power transmission element can be arranged on opposite sides of the elevator car. However, a single-sided drive of the elevator car is also possible.

[0030] According to one embodiment, the rotary drive can be designed to rotate adjacent permanent magnets of the same row such that the magnetic fields of the rotating adjacent permanent magnets of the same row are offset by 90 degrees from one another. "Orientation" here and below can be understood as a magnetization direction in which the respective permanent magnet is magnetized. In this way, for example, it can be achieved that the traveling field is increased on a side of the magnetic track facing the force transmission member and / or reduced on a side of the magnetic track facing away from the force transmission member. This has the advantage that smaller permanent magnets can be used without the resulting magnetic forces necessarily being reduced.

[0031] According to one embodiment, the orientation of the magnetic field of each rotating permanent magnet, preceded by a neighboring rotating permanent magnet of the same row and followed by a neighboring rotating permanent magnet of the same row, can be equal to a 90-degree clockwise rotation of the magnetic field of the preceding permanent magnet and equal to a 90-degree counterclockwise rotation of the magnetic field of the following permanent magnet. Thus, the magnetic track can be implemented as a Halbach array or quasi-Halbach array. For example, the orientations in a reference position can have the following sequence: left, top, right, bottom, left, top, etc. The orientations can also follow one another in reverse order.Starting from the reference position, the permanent magnets can then be rotated so that the initial alignment of adjacent orientations to each other is maintained throughout the permanent magnets' rotation. As mentioned above, a (minor) variation of the angular deviations during the permanent magnets' rotation is also possible.

[0032] According to one embodiment, the rotary drive can be designed to rotate adjacent permanent magnets of the same row such that the magnetic fields of the rotating adjacent permanent magnets of the same row have opposite orientations, i.e., they differ from each other by 180 degrees. This can be the case, for example, if the force transmission member is arranged in the overlap region between a first row and a second row of permanent magnets (see also below) and the axes of rotation of the permanent magnets of the first row are offset relative to the axes of rotation of the permanent magnets of the second row in the direction of the displacement axis, for example, are offset centrally, so that - viewed in the direction of the displacement axis - the distance between adjacent axes of rotation of different rows is equal to half the distance between adjacent axes of rotation of the same row.

[0033] According to one embodiment, the magnetic track can comprise a first row and a second row of permanent magnets. The force transmission member can be arranged in the overlap region between the first row and the second row, i.e., run through an air gap between the first row and the second row. The rotary drive can be designed to rotate adjacent permanent magnets of different rows such that the magnetic fields of the rotating adjacent permanent magnets of different rows are offset from one another by a defined angle. For example, the first row can comprise the same number of permanent magnets as the first row. Alternatively, the first and second rows can comprise different numbers of permanent magnets. As mentioned above, the first and second rows can be offset from one another (see also below).A design is also possible in which the permanent magnets of different rows – viewed transversely to the displacement axis – are arranged opposite each other in pairs, whereby the permanent magnets of the same pair, or more precisely their rotational axes, have the same longitudinal position relative to the displacement axis, and the permanent magnets of different pairs have different longitudinal positions relative to the displacement axis. The rotary drive can, for example, be designed to drive the permanent magnets of the first row independently of the permanent magnets of the second row.

[0034] According to one embodiment, the defined angle can be 0 degrees, 90 degrees, or 180 degrees. If the first and second rows are each designed as a (quasi-)Halbach array and the permanent magnets of different rows are arranged opposite one another in pairs (see above), the orientations of the magnetic fields of adjacent permanent magnets of different rows can, for example, be alternately offset by 180 degrees and 0 degrees from one another, i.e., alternately opposite and in the same direction. If the axes of rotation of different rows are offset from one another in the direction of the displacement axis (see above), the orientations of the magnetic fields of adjacent permanent magnets of different rows can, for example, be offset from one another by 90 degrees. In this case, for example, the magnetic fields of adjacent permanent magnets of the same row can be opposite in orientation.

[0035] According to one embodiment, the rotation axes of the permanent magnets in the first row can be offset relative to the rotation axes of the permanent magnets in the second row in the direction of the displacement axis. For example, the rotation axes of the permanent magnets in the first row can be centrally offset relative to the rotation axes of the permanent magnets in the second row in the direction of the displacement axis. In other words, the distance between adjacent rotation axes of different rows—viewed in the direction of the displacement axis—can be equal to half the distance between adjacent rotation axes of the same row.

[0036] According to one embodiment, the rotary drive can be designed to rotate the permanent magnets of the first row at a different rotational speed and / or in a different rotational direction than the permanent magnets of the second row. In principle, all permanent magnets of the same row should be rotated at the same rotational speed and in the same rotational direction. To achieve the desired superposition of the magnetic fields in the form of a traveling wave, the permanent magnets of the first row can be rotated in a direction opposite to the rotational direction of the permanent magnets of the second row. By changing the rotational speed of the permanent magnets of the first row (which rotate at the same speed) compared to the rotational speed of the permanent magnets of the second row (which rotate at the same speed), a phase-shifted traveling wave can be generated, for example.According to one embodiment, the rotary drive can be configured to rotate the permanent magnets of the same row simultaneously at the same rotational speed and / or in the same direction. This allows the amplitude of the traveling wave to be kept more constant.

[0037] According to one embodiment, the permanent magnets of the same row can alternately comprise first permanent magnets and second permanent magnets. The rotary drive can be configured to rotate the first permanent magnets independently of the second permanent magnets. In other words—viewed in the direction of the displacement axis—at least one second permanent magnet can always be arranged between two first permanent magnets and / or at least one first permanent magnet can always be arranged between two second permanent magnets. The rotary drive can therefore be configured to rotate the first permanent magnets at a different rotational speed and / or in a different rotational direction than the second permanent magnets.Additionally, the rotary drive can be configured to rotate all first permanent magnets simultaneously at the same rotational speed and / or in the same rotational direction and / or to rotate all second permanent magnets simultaneously at the same rotational speed and / or in the same rotational direction. Additionally, the rotary drive can be configured to rotate the first permanent magnets together with the second permanent magnets.

[0038] According to one embodiment, the permanent magnets can be divided into at least two cylindrical segments of different polarity along their rotational axes. The segments can be separated from each other, for example, by an air gap. The segments can be rigidly connected to each other. In other words, the segments can be coupled in such a way that one segment always rotates at the same speed and in the same direction as the other segment(s). This can reduce drive force fluctuations of the linear drive.

[0039] According to one embodiment, the axes of rotation can run parallel to each other and / or orthogonal to the displacement axis.

[0040] According to one embodiment, the power transmission element can be designed in a ladder-like configuration with a plurality of rungs. The rungs can, for example, extend transversely or obliquely to the longitudinal direction of the ladder-like power transmission element. The rungs can be separated from each other by air gaps. For example, the power transmission element can resemble a squirrel-cage rotor, as used for asynchronous machines. This allows the weight of the power transmission element to be reduced.

[0041] Additionally or alternatively, the force transmission element can be formed by a soft magnetic structure, which in particular has slots. The slots allow the magnetic properties of the force transmission element to be locally modified, comparable to the rotor of a reluctance motor.

[0042] Additionally or alternatively, the force transmission element can be designed as a plate or band. For example, a force transmission element in the form of a flexible metallic belt, band, or plate is possible, which, when the linear drive is in operation, runs at least partially through the elevator shaft along the displacement axis. The plate- or band-like force transmission element can optionally have a plurality of through openings, for example in the form of slots arranged in a row in the direction of the displacement axis, in order to locally modify the magnetic properties of the force transmission element, comparable to the rotor of a reluctance motor.

[0043] According to one embodiment, a gap between adjacent rungs can be at least partially filled with a soft magnetic material. The soft magnetic material can be, for example, (soft) iron, steel, a nickel-iron, cobalt-iron, or aluminum-iron alloy. This allows the magnetic properties of the force transmission element to be further improved.

[0044] Advantageous embodiments of the invention are further explained below with reference to the accompanying drawings, wherein neither the drawings nor the explanations are to be interpreted as limiting the invention in any way.

[0045] Fig. 1 shows an elevator system according to an embodiment of the invention.

[0046] Fig. 2 shows a section of a linear drive according to an embodiment of the invention with a single-row magnetic track.

[0047] Fig. 3 shows a section of a linear drive according to an embodiment of the invention with a two-row magnetic track whose permanent magnets are arranged opposite each other in pairs. Fig. 4 shows a section of a linear drive according to an embodiment of the invention with a two-row magnetic track whose permanent magnets are offset from each other.

[0048] Fig. 5 shows a section of a linear drive according to an embodiment of the invention with several double-row magnetic tracks.

[0049] Fig. 6 shows a section of a ladder-like force transmission element of a linear drive according to an embodiment of the invention.

[0050] The figures are merely schematic and not to scale. The same reference numerals designate the same or equivalent features in the various drawings.

[0051] Fig. 1 shows an elevator system 1 in whose elevator shaft 2 an elevator car 3 is mounted so that it can be moved along a vertical displacement axis z between different floors of a building. A horizontal or inclined displacement axis z is also possible.

[0052] The elevator car 3 is driven by a linear drive 4, which comprises at least one magnetic track 5 and at least one force transmission member 6 made of an electrically conductive material, for example a metallic material such as iron, steel or aluminum.

[0053] The magnetic track 5 is formed by one or more supports 7 in which several permanent magnets 8 are arranged in a row, each mounted for rotation about its own axis of rotation r. The permanent magnets 8 can be arranged in one or more rows.

[0054] The magnetic track 5 can, as shown by way of example in Fig. 1, be fixed to a side wall of the elevator shaft 2 via the support 7, while the force transmission member 6 can be fixed laterally to the elevator car 3. However, an embodiment is also possible in which, conversely, the support 7 is fixed to the elevator car 3, while the force transmission member 6 is fixed to the side wall of the elevator shaft 2.

[0055] In both cases, the magnetic track 5 and the force transmission member 6 are arranged such that the permanent magnets 8 belonging to the same row are arranged in the direction of the displacement axis z, i.e. vertically in this case, and the magnetic track 5 and the force transmission member 6 are opposite each other in an overlapping area 9.

[0056] In the overlapping region 9, the permanent magnets 8 and the force transmission member 6 are each separated from one another by an air gap (not shown) which is dimensioned such that the permanent magnets 8 and the force transmission member 6 are in magnetic interaction with one another.

[0057] Because the force transmission member 6 is fixed to the elevator car 3, it can be displaced together with the elevator car 3, ie the magnetic track 5 and the force transmission member 6 can be displaced relative to one another in the direction of the displacement axis z, in this case in the vertical direction.

[0058] The axes of rotation r of the permanent magnets 8 of the same row can, for example, lie in a common vertical plane and be aligned parallel to each other, ie run horizontally and thus orthogonally to the (vertical) displacement axis z.

[0059] If the magnetic track 5 comprises several rows of permanent magnets 8 (see also Fig. 3 to Fig. 5), the axes of rotation r of different rows can, for example, lie in two or more than two parallel vertical planes and each run horizontally.

[0060] The permanent magnets 8 are each magnetized in a specific magnetization direction (the magnetization direction can be understood as an orientation of a magnetic field generated by the respective permanent magnet 8).

[0061] If the permanent magnets 8 are cylindrical bar magnets, the magnetization direction of each permanent magnet 8 can, for example, be orthogonal to the longitudinal or central axis of the permanent magnet 8. The longitudinal or central axis can correspond to the rotation axis r of the permanent magnet 8.

[0062] In order to generate a magnetic field moving in the direction of the displacement axis z, in this case either from bottom to top or from top to bottom, which causes a corresponding displacement of the force transmission member 6 relative to the magnetic track 5 and thus of the elevator car 3, the linear drive 4 comprises a rotary drive 11 which is designed to set the permanent magnets 8 in a suitable manner into rotary movements, ie in such a way that by superimposing the magnetic fields of the rotating permanent magnets 8 a traveling field moving along the magnetic track 5, in this case vertically, results in magnetic interaction with the force transmission member 6.

[0063] The rotary drive 11 can, for example, be arranged at least partially outside the elevator shaft 2. Thus, mechanical or thermal influences of the rotary drive 11 on components of the elevator system 1 located in the elevator shaft 2 can be reduced.

[0064] In principle, the rotary drive 11 can comprise an electric motor 12 with a rotating drive shaft 13, which can be coupled to the individual permanent magnets 8 via a gear 14. The electric motor 12 can, for example, be arranged outside the elevator shaft 2. The gear 14 can be arranged partly outside and partly inside the elevator shaft 2.

[0065] For example, the rotary drive 11 can be configured to rotate the permanent magnets 8 of one and the same row simultaneously in the same direction and at the same rotational speed. This ensures that the permanent magnets 8 maintain their initial orientation relative to each other in the rotating state.

[0066] Optionally, each permanent magnet 8 can be divided in the direction of its rotation axis r into two cylindrical segments 15 of different polarity, i.e. into a north pole and a south pole segment.

[0067] The two segments 15 can be separated from each other, for example, by an axial air gap. This configuration can reduce the torque ripple required for the drive, i.e., the rotation of the permanent magnets 8.

[0068] Contrary to the illustration shown in Fig. 1, the magnetic track 5 and the force transmission element 6 can be arranged on opposite sides of the elevator car 3. In other words, the elevator car 3 can be driven on both sides by the linear drive 4.

[0069] Fig. 2 shows a section of a linear drive 4 in which the permanent magnets 8 are arranged in only one row and opposite one and the same side of the force transmission member 6. The permanent magnets 8 are each separated from the force transmission member 6 by an air gap s. In this example, the permanent magnets 8 are aligned with each other in a reference position in which the orientations (indicated by arrows in Fig. 2 to Fig. 4) of the magnetic fields of adjacent permanent magnets 8 are each offset by 90 degrees from each other.

[0070] In particular, the permanent magnets 8 can be aligned with each other in the reference position such that the orientation of the magnetic field of each permanent magnet 8, preceded by an adjacent permanent magnet 8 and followed by an adjacent permanent magnet 8, is equal to a 90-degree clockwise rotation of the magnetic field of the preceding permanent magnet 8 and equal to a 90-degree counterclockwise rotation of the magnetic field of the following permanent magnet 8. The force transmission member 6 thus hovers above the magnetic track 5.

[0071] By arranging the permanent magnets 8 with mutually orthogonal magnetization directions on only one side, manufacturing costs can be reduced compared to a two-row magnetic track 5 (see Fig. 3 and Fig. 4). Furthermore, this allows greater freedom of movement of the force transmission element 6 transversely to the displacement axis, for example.

[0072] Fig. 3 shows a section of a linear drive 4 with a first row 16 of permanent magnets 8 and a second row 17 of permanent magnets 8, which is opposite the first row 16. The force transmission element 6 can run in an air gap s between the two rows 16, 17.

[0073] The permanent magnets 8 are here aligned to one another in a reference position in which, on the one hand, the orientations of the magnetic fields of adjacent permanent magnets 8 of the first row 16 are orthogonal to one another and, on the other hand, the orientations of the magnetic fields of adjacent permanent magnets 8 of the second row 17 are orthogonal to one another.

[0074] The permanent magnets 8 are also arranged in pairs so that - viewed transversely to the displacement axis z - each permanent magnet 8 of the first row 16 is opposite exactly one of the permanent magnets 8 of the second row 17.

[0075] Furthermore, the permanent magnets 8 of each row 16, 17 can comprise first permanent magnets 8a and second permanent magnets 8b, which alternate—viewed in the direction of the displacement axis z. Each first permanent magnet 8a of the first row 16 can be opposite exactly one of the first permanent magnets 8a of the second row.

[0076] This can apply correspondingly to the second permanent magnets 8b.

[0077] In this case, the reference position can, for example, be such that the magnetic fields of the first permanent magnets 8a of the same longitudinal position with respect to the displacement axis z have opposite orientations, i.e., offset by 180 degrees, parallel to the displacement axis z, and the magnetic fields of the second permanent magnets 8b of the same longitudinal position with respect to the displacement axis z have the same orientations, i.e., offset by 0 degrees, orthogonal to the displacement axis z. The arrangement of the permanent magnets 8, 8a, 8b shown in Fig. 3 can also be referred to as a (quasi-)Halbach array.

[0078] By appropriately rotating the permanent magnets 8, 8a, 8b, two orthogonally aligned pulsating magnetic fields can be generated, which overlap to form a traveling wave, i.e., a traveling magnetic wave. Control of the traveling wave with respect to commutation angle and amplitude can largely resemble the control in conventional machines using phase currents projected onto two mutually orthogonal axes via dqO decomposition.

[0079] The dqO decomposition of the currents makes it possible to control the driving and attractive forces independently of each other via the quadrature and direct current, respectively. Controlling the direct current also allows for field weakening to extend the speed range of the electric machine. A similar technique can be applied here, albeit with limitations, but mechanically rather than electrically.

[0080] Since the pulsating fields of the two rows 16, 17 are orthogonal, a mechanical change in their relative phase shift has a similar effect to changing the quadrature and direct current. One difference can be seen in the fact that the amplitudes of the pulsating fields in coil-based electric machines can be controlled independently of each other via the current, which is not the case here. To still allow better control over the amplitude of the two pulsating fields, the first permanent magnets 8a can be driven independently of the second permanent magnets 8b of the same row 16 or 17.

[0081] Fig. 4 shows a two-row arrangement of the permanent magnets 8, in which the permanent magnets 8 of the first row 16 are arranged offset relative to the permanent magnets 8 of the second row 17 in the direction of the displacement axis z, in such a way that - viewed in the direction of the displacement axis z - exactly one of the permanent magnets 8 of the other row 16 or 17 lies between adjacent permanent magnets 8 of one row 16 or 17.

[0082] In this case, the reference position may, for example, be such that the magnetic fields of adjacent permanent magnets 8 of the first row 16 have opposite orientations parallel to the displacement axis z and the magnetic fields of adjacent permanent magnets 8 of the second row 17 have opposite orientations orthogonal to the displacement axis z.

[0083] This also enables field-oriented control of the linear drive 4, as is realized in conventional electrical machines by controlling the current components of the coil current.

[0084] In other words, the second row 17, hereinafter referred to as the upper armature, may have a vertically oriented, alternating north-south magnetization pattern. When the permanent magnets 8 of the upper armature all rotate synchronously and in the same direction, the power transmission member 6 is exposed to a pulsating magnetic field.

[0085] The first row 16, hereinafter referred to as the lower armature, can be constructed similarly to the upper armature, with the difference that the north-south magnetization pattern is aligned horizontally, i.e. shifted by 90 degrees to the magnetization pattern of the upper armature.

[0086] In addition, the rotation axes r of the permanent magnets 8 belonging to the lower armature are horizontally shifted relative to the rotation axes r of the permanent magnets 8 belonging to the upper armature, so that they are located exactly in the middle between adjacent permanent magnets 8 of the upper armature.

[0087] When the permanent magnets 8 of the lower armature are rotated synchronously with those of the upper armature, but in opposite directions, the force transmission element 6 is subjected to an additional pulsating magnetic field, now emanating from the lower armature. The two pulsating magnetic fields overlap to form a traveling wave, the direction of motion of which is determined by the direction of rotation of the permanent magnets 8 in both armatures. In this example, the angle between the alignment of the magnetization patterns of the upper and lower armatures is maintained at 90 degrees during rotation. However, this is not absolutely necessary. By varying this angle, the traveling wave can be modified in a similar way to field-oriented control. Instead of changing the direct and quadrature currents, the angle between the upper and lower magnetization patterns is changed to serve a similar purpose.In this way, the attraction and propulsion forces can be controlled.

[0088] It should be noted that the reference positions described above can refer to a rotating and / or a non-rotating state of the permanent magnets 8, 8a, 8b.

[0089] The rotary drive 11 can be designed to rotate the permanent magnets 8 such that the reference position related to the non-rotating state is maintained in the rotating state or is varied within certain limits.

[0090] For example, the rotary drive 11 can be designed to rotate the permanent magnets 8 of the first row 16 in a different direction of rotation and / or at a different rotational speed than the permanent magnets 8 of the second row 17.

[0091] Additionally or alternatively, the rotary drive 11 can be designed to drive the first permanent magnets 8a of each row 16, 17 independently of the second permanent magnets 8b of the same row 16 or 17.

[0092] The single-row embodiment of the magnetic track 5 shown in Fig. 2 can also comprise alternating first permanent magnets 8a and second permanent magnets 8b, wherein the first permanent magnets 8a can be rotatable independently of the second permanent magnets 8b. The levitation and propulsion forces can thus be controlled by controlling the angles and rotational speeds of the two sets of permanent magnets.

[0093] As shown in Fig. 2 to Fig. 5, the force transmission member 6 can be designed, for example, in a band- or plate-shaped manner. Additionally, the band- or plate-shaped force transmission member 6 can have a series of, for example, slot-shaped openings 18 for influencing the magnetic flux.

[0094] Alternatively, the force transmission member 6 can be ladder-like with a plurality of

[0095] Rungs 19 may be designed as shown in Fig. 6. In the case of an asynchronous machine, the power transmission member 6 may be formed, for example, by a double, rolled, cage-like or ladder-like structure made of electrically conductive material.

[0096] The spaces between the rungs 19 may be empty or, optionally, at least partially filled with a soft magnetic material.

[0097] Alternatively, in the case of a synchronous reluctance machine, the force transmission member 6 may be formed by a soft magnetic structure which may have corresponding slots in order to locally change the magnetic properties, ie the reluctance.

[0098] Fig. 5 shows a design with four magnetic tracks 5 with mutually orthogonal longitudinal axes, arranged opposite one and the same side of the force transmission member 6 and separated from it by an air gap. This allows displacement of the force transmission member 6 in mutually orthogonal directions (indicated by two double arrows).

[0099] The four magnetic tracks 5 can optionally be arranged on both sides of the force transmission element 6, whereby the magnetic tracks 5 on different sides can be arranged opposite each other in pairs. The linear drive 4 can thus comprise a total of eight magnetic tracks 5.

[0100] Finally, it should be noted that terms such as "having," "comprising," etc., do not exclude other elements or steps, and indefinite articles such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with features or steps described with reference to other of the above embodiments. Reference signs in the claims are not to be considered as limitations.

Claims

Claims 1. Linear drive (4) for an elevator system (1), wherein the elevator system (1) comprises an elevator shaft (2) and an elevator car (3) that can be displaced in the elevator shaft (2) in the direction of a displacement axis (z), wherein the linear drive (4) comprises: a magnetic track (5) comprising at least one row (16, 17) of permanent magnets (8, 8a, 8b), wherein the permanent magnets (8, 8a, 8b) are rotatably mounted in a support (7) about their own axis of rotation (r); a force transmission element (6) made of an electrically conductive material; wherein either the magnetic track (5) can be fixed to the elevator shaft (2) and the force transmission element (6) to the elevator car (3) or the force transmission element (6) can be fixed to the elevator shaft (2) and the magnetic track (5) to the elevator car (3) such that: the permanent magnets (8, 8a, 8b) of the same row (16, 17) are arranged one behind the other in the direction of the displacement axis (z);the magnetic track (5) and the force transmission element (6) are displaceable relative to each other in the direction of the displacement axis (z); the magnetic track (5) and the force transmission element (6) are opposite each other in an overlap region (9), wherein the permanent magnet (8, 8a, 8b) located in the overlap region (9) are separated from the force transmission element (6) opposite it by an air gap (s); and a rotary drive (11) configured to rotate the permanent magnets (8, 8a, 8b) about their axes of rotation (r) such that, by superposition of the magnetic fields of the rotating permanent magnets (8, 8a, 8b), a traveling field moving in the direction of the displacement axis (z) is generated to displace the force transmission element (6) relative to the magnetic track (5).

2. Linear drive (4) according to claim 1, wherein the rotary drive (11) is configured to rotate adjacent permanent magnets (8, 8a, 8b) of the same row (16, 17) such that the magnetic fields of the rotating adjacent permanent magnets (8, 8a, 8b) of the same row (16, 17) are offset in their orientation by 90 degrees to each other.

3. Linear drive (4) according to claim 2, wherein the orientation of the magnetic field of each rotating permanent magnet (8, 8a, 8b) preceded by a rotating adjacent permanent magnet (8, 8a, 8b) of the same row (16, 17) and a rotating adjacent Permanent magnet (8, 8a, 8b) of the same row (16, 17) is configured to rotate adjacent permanent magnets (8, 8a, 8b) of the same row (16, 17) such that the magnetic fields of the preceding permanent magnet (8, 8a, 8b) are rotated 90 degrees clockwise and the magnetic fields of the following permanent magnet (8, 8a, 8b) are rotated 90 degrees counterclockwise. Linear drive (4) according to claim 1, wherein the rotary drive (11) is configured to rotate adjacent permanent magnets (8, 8a, 8b) of the same row (16, 17) such that the magnetic fields of the rotating adjacent permanent magnets (8, 8a, 8b) of the same row (16, 17) have opposite orientations.Linear drive (4) according to one of the preceding claims, wherein the magnetic track (5) comprises a first row (16) and a second row (17) of permanent magnets (8, 8a, 8b); wherein the force transmission element (6) is arranged in the overlap region (9) between the first row (16) and the second row (17); wherein the rotary drive (11) is configured to rotate adjacent permanent magnets (8, 8a, 8b) of different rows (16, 17) such that the magnetic fields of the rotating adjacent permanent magnets (8, 8a, 8b) of different rows (16, 17) are offset in their orientation by a defined angle to each other. Linear drive (4) according to claim 5, wherein the defined angle is 0 degrees, 90 degrees, or 180 degrees. Linear drive (4) according to claim 5 or 6, wherein the axes of rotation (r) of the permanent magnets (8, 8a, 8b) of the first row (16) are offset relative to the axes of rotation (r) of the permanent magnets (8, 8a, 8b) of the second row (17) in the direction of the displacement axis (z).Linear drive (4) according to one of claims 5 to 7, wherein the rotary drive (11) is configured to rotate the permanent magnets (8, 8a, 8b) of the first row (16) at a different rotational speed and / or in a different direction of rotation than the permanent magnets (8, 8a, 8b) of the second row (17). Linear drive (4) according to any one of the preceding claims, wherein the rotary drive (11) is configured to rotate the permanent magnets (8, 8a, 8b) of the same row (16, 17) simultaneously at the same rotational speed and / or in the same direction of rotation. Linear drive (4) according to any one of the preceding claims, wherein the permanent magnets (8, 8a, 8b) of the same row (16, 17) alternately comprise first permanent magnets (8a) and second permanent magnets (8b); wherein the rotary drive (11) is configured to rotate the first permanent magnets (8a) independently of the second permanent magnets (8b). Linear drive (4) according to any one of the preceding claims, wherein the permanent magnets (8, 8a, 8b) are divided in the direction of their axes of rotation (r) into at least two cylindrical segments (15) of opposite polarity. Linear drive (4) according to one of the preceding claims, wherein the rotation axes (r) are parallel to each other and / or orthogonal to the displacement axis (z).Linear drive (4) according to one of the preceding claims, wherein the force transmission element (6) is formed in a ladder-like manner with a plurality of rungs (19) and / or by a soft magnetic structure, which in particular has slots. Linear drive (4) according to claim 13, wherein a space between adjacent rungs (19) is at least partially filled with a soft magnetic material. Elevator system (1) comprising: an elevator shaft (2); an elevator car (3) which is displaceable in the direction of a displacement axis (z) in the elevator shaft (2); and a linear drive (4) according to one of the preceding claims, wherein either the magnetic track (5) is fixed to the elevator shaft (2) and the force transmission element (6) is fixed to the elevator car (3), or the force transmission element (6) is fixed to the elevator shaft (2) and the magnetic track (5) is fixed to the elevator car (3).

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