The present invention relates to a rotary/linear drive comprising a rotary drive device which has magnets for generating a torque in a manner which is free of axial forces.
In a combined motor for rotary movement and axial movement, that is to say in a rotary/linear drive, it is advantageous for control reasons for the motor part which generates the rotary movement to not give rise to any axial forces. In addition, the excitation of oscillating torques should be reduced, these oscillating torques originating, in the case of a permanent-magnet synchronous machine (PM synchronous machine), from the interaction between harmonic force waves of the rotor field and control value fluctuations in the used stator. High oscillating torques have an adverse effect on the rotation of the rotary drive.
The object of the present invention is therefore to simultaneously satisfy both conditions, namely of keeping the axial forces of the rotary drive as low as possible and at the same time reducing oscillating torques to the greatest possible extent.
According to the invention, this object is achieved by a rotary/linear drive comprising a rotary drive device which has magnets for generating a torque, wherein at least one magnet has at least two magnet sections which run in an inclined manner with respect to the axial direction of the rotary drive device, or a plurality of magnets are designed to form at least two magnet arrangements which run in an inclined manner and are arranged symmetrically with respect to a line which runs in the circumferential direction of the rotary drive device. The oscillating torques are advantageously reduced by the magnet sections which run in an inclined manner and the axial forces are canceled out by the symmetrical design of said magnet sections.
In accordance with a further embodiment of the present invention, said object is achieved by a rotary/linear drive comprising a rotary drive device which has magnets for generating a torque, wherein the magnets are distributed in a non-uniform manner over the circumference of the rotor and/or of the stator of the rotary drive device.
According to the invention, provision is also made of a rotary/linear drive comprising a rotary drive device which has magnets for generating a torque, wherein the smallest common multiple of the number of slots and the number of poles of the rotary drive device is greater than the number of slots multiplied by three. The oscillating torques are advantageously minimized on account of the smallest common multiple of the number of slots and the number of poles being selected to be as high as possible.
In accordance with one preferred refinement of the present invention, the magnets are realized by permanent magnets of the rotor. However, the magnets may also be electromagnets of the stator. In either case, the objective of the invention of eliminating axial forces and reducing oscillating torques can be achieved by appropriate design and/or arrangement of the magnets.
In the embodiment with the magnet sections which run in an inclined manner, permanent magnets are preferably used which are V-shaped and are arranged on the rotor of the rotary drive device such that their vertex points in the circumferential direction of the rotor. On account of this V shape, the north poles and south poles can be arranged in line in a favorable manner.
However, a plurality of permanent magnets can also be combined to form one of a large number of V-shaped magnet units of the north-pole or south-pole type, with the vertex of each magnet unit pointing in the circumferential direction of the rotor. For this embodiment, permanent magnets with standard shapes, for example square or rectangular, can be used.
The present invention will now be explained in greater detail with reference to the attached drawings, in which:
The embodiments which are described in greater detail in the text which follows represent preferred exemplary embodiments of the present invention.
The combined drive or rotary/linear drive illustrated in
The rotary drive R is realized as a PM synchronous machine. Its permanent magnets PR are fixed on the internal rotor I.
In order to ensure that no axial forces occur in the event of pure rotary movement by the rotary drive, neither the stator ST nor the rotor I of the rotary drive R may be inclined, or they must be inclined such that the axial forces are compensated for. In this case, the term “inclined” means that sections of the magnets, be they the electromagnets or the permanent magnets, run in an inclined manner in relation to the axis of the rotary drive R.
In accordance with a first embodiment, the permanent magnets PR of the rotary drive R are designed with an arrow-like inclination according to
The oscillating torques are reduced by the limbs, which run in an inclined manner, of each magnet. Furthermore, the axial forces are canceled out by the magnets being symmetrical with respect to the center line, which runs in the circumferential direction, of the magnet arrangement. In
A further embodiment of the magnet arrangement according to the invention is illustrated in
Instead of providing the individual magnets with an arrow-like inclination, the inclination can also be achieved by a large number of individual magnets, which have a square or rectangular contour for example, being arranged to form a contour which runs in an inclined manner. In this case too, oscillating torques are reduced by virtue of the inclined offset of the individual magnets with respect to the axial direction. As a result of a symmetrical arrangement again in relation to a circumferential line, the axial forces are superposed such that they are eliminated.
However, the oscillating torques can also be reduced by the smallest common multiple of the number 2p of poles of the rotor and the number N1 of slots of the stator being selected to be as high as possible. Favorable results can be achieved as early as when this smallest common multiple is greater than 3×N1. One example of a magnet arrangement in which the oscillating torques are sufficiently low would be: N1=27 and 2p=8. The smallest common multiple would then be 8×27=216.
Number | Date | Country | Kind |
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10 2004 056 210.5 | Nov 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/56002 | 11/16/2005 | WO | 00 | 5/22/2007 |