CN216929723U

CN216929723U - Motor for use in external magnetic field

Info

Publication number: CN216929723U
Application number: CN202121870659.4U
Authority: CN
Inventors: 格奥尔格·泽格雷尔
Original assignee: Siemens Healthineers AG
Current assignee: Siemens Healthineers AG
Priority date: 2020-08-11
Filing date: 2021-08-11
Publication date: 2022-07-08
Anticipated expiration: 2031-08-11
Also published as: DE202020104661U1

Abstract

The utility model relates to a motor (1) for use in an external magnetic field (2), comprising: a disk (4), the disk (4) having windings (5) which are distributed uniformly in the circumferential direction of the disk (4), wherein a rotor axis (10) runs through the center of the disk (4) and perpendicular to the disk (4), wherein the windings (5) are insulated from one another such that they are electrically separated from one another; at least one first frame (6) having magnetic cores (8), wherein the first frame (6) and the magnetic cores (8) are arranged such that the magnetic cores (8) are distributed uniformly around the rotor axis (10) in a circumferential direction, wherein the disc (4) and the first frame (6) are rotatable relative to one another, wherein the magnetic cores (8) are arranged distributed over the first frame (6) such that, independently of the position of the disc (4) and the first frame (6) relative to one another, two magnetic cores (8) adjacent on the first frame (6) are each associated with a different winding (5) in a direction parallel to the rotor axis (10).

Description

Motor for use in external magnetic field

Technical Field

The present invention relates to a motor for use in an external magnetic field and to the use of such a motor in an external magnetic field.

Background

The use of electric motors in external magnetic fields can be problematic for different reasons. The external magnetic field generally affects the different components of the motor, in particular the magnetizable components, such as the iron laminations, which can cause: the motor experiences higher losses and has lower power in the external magnetic field than in the absence of the external magnetic field. In particular, electric motors, which usually have a stationary stator and a movable, usually rotating rotor, usually react sensitively to external magnetic fields, in particular when they use magnets for their operation, as is the case, for example, in disk rotor motors.

This problem is particularly important for electric motors that should operate in the vicinity of the magnets of a Magnetic Resonance Tomography (MRT). In the direct vicinity of the MRT, stray fields of the order of 10mT to 100mT are usually present during the operation of the MRT, depending on the exact position. However, the space in the direct vicinity of the MRT is intended for electrical and mechanical components, in order to thereby achieve a space-saving configuration. In particular, it is also desirable to install an electric motor in this region, which is provided, for example, for operating a fan which can deliver fresh air to the patient in the interior of the MRT and ensure cooling of the electrical circuit. In addition, a motor for driving the examination table (i.e., the examination table) is required. The motor-driven adjustable mechanism in the local coil, for example in the head coil, requires a motor, which in this case may even have to be operated in the magnetic field of 1.5T to 7T in the interior of the MRT.

The method used so far is to position the motor at a location where the stray field has a particularly low value. However, such locations in the vicinity of the MR device are limited. Still other components are sensitive to external magnetic fields and thus compete very strongly for the corresponding sites. Furthermore, a large number of tests are required for such a solution, in which tests it is necessary to ascertain: whether the respective motor and its positioning and the external magnetic field present there are working properly.

Another approach is to shield the motor from external magnetic fields by means of a housing made of, for example, iron laminations, especially when structural space with sufficiently low stray fields cannot be found for the motor. However, such a housing has a high weight, is expensive and generates high mechanical forces when it is placed in a stray field.

A further alternative is to position the motor relatively far from the MR device and, for example in the case of a fan motor, to direct the air flow to the desired location through a duct. However, a hose having a relatively large diameter (10cm or more) must be installed for this purpose. However, the additional space required thereby results in a less compact size of the entire MR system. Furthermore, such hoses must usually be installed at the point of use during the installation of the MR system, which increases the expenditure on installation, which in turn leads to a further source of errors at the installation and increases the risk of incorrect installations.

It is therefore desirable to be able to place the motor directly, for example measurably, at the magnet of the MR device. The motor can thus be pre-installed. Furthermore, the components of the MR device can already be tested in advance and time can be saved when installed at the place of use.

SUMMERY OF THE UTILITY MODEL

It is therefore an object of the present invention to provide a motor that can be used in an external magnetic field.

This object is achieved by a motor and a use of such a motor.

According to a first aspect of the utility model, the motor is configured to be used in an external magnetic field. The motor comprises a disk with windings distributed uniformly in the circumferential direction of the disk, wherein the rotor axis passes through the middle point of the disk and runs perpendicular to the disk, wherein the windings are insulated from each other such that they are electrically separated from each other. Furthermore, the motor comprises at least one frame with magnetic cores, wherein the frame and the magnetic cores are arranged such that the magnetic cores are evenly distributed around the rotor axis in the circumferential direction, wherein the disc and the first frame are rotatable relative to each other, and wherein the magnetic cores are arranged distributed over the first frame such that, independently of the position of the disc and the first frame relative to each other, two magnetic cores adjacent on the first frame are each associated with a different winding in a direction parallel to the rotor axis.

An external magnetic field is to be understood here to mean, in particular, a magnetic field at a location at which the motor is to be positioned during its use. The external magnetic field is present here independently of the motor itself and can be generated, for example, by one or more electromagnetic coils which are not part of the motor itself. It is also conceivable that the external magnetic field is generated by a permanent magnet, which is likewise not part of the motor. In particular, the external magnetic field can be generated by a medical device, for example an MR device. Preferably, the external magnetic field is a stray field of the MR magnet. The external magnetic field can have field lines that run continuously and substantially uniformly in one direction. This can be the case at least at the location where the motor is provided.

The disk can be a disk element on which the windings are arranged and/or in which the windings are integrated. In particular, the disc can be substantially constituted by the winding itself. A particularly material-saving design is therefore possible. Furthermore, when such a disk is rotated while the motor is running, the motor can start faster, more efficiently and with lower energy losses, since the small weight can result in less torque required to put the disk in motion. Thus, the motor itself is more energy efficient. Preferably, the disk is formed by a winding, which is arranged such that it substantially results in a disk shape, wherein the winding is fixed in said shape. Thus, the disc can be formed mainly of windings. In other words, at least 70% of the disc is constituted by windings, preferably at least 80% is constituted by windings. For example, the windings can be provided in epoxy. Preferably, this is a nonconductive epoxy resin. This advantageously enables a simple and fast but at the same time also efficient manufacture of a disc which also has good durability and robustness. However, it is also conceivable to fasten the winding to a disk separate from the winding, for example by welding, gluing and/or clamping, or to hold the winding in a disk-shaped housing, for example by hooking, hanging, gluing and/or welding or otherwise fastening. The disk can therefore advantageously be adapted to the desired configuration or shape of the motor, while the windings can be arranged partially independently of the configuration of the disk or possibly only limited by the circumference of the disk. In this context, disk-like can mean an expansion substantially in two spatial directions. The expansion in the third spatial direction can be significantly smaller. Preferably, the expanded configuration of the disk, which is greater in both spatial directions, is circular or approximately circular. This makes it possible to achieve a particularly uniform operation of the motor in an advantageous manner if the disk has the function of a rotor of the motor. However, it is also conceivable for the disk to have a different configuration than a circular shape in the two spatial directions, for example in order to save material. In particular, if the disk has the function of a stator of the motor, i.e. does not rotate during operation of the motor, it is conceivable for the disk to have a configuration in the two spatial directions which differs from a circular shape. For example, it can be expedient to adjust the configuration of the disk such that the disk can be fixed as effectively as possible or the current supply to the winding can be achieved particularly well. The disks can be formed rotationally symmetrically about the rotor axis. Furthermore, the disk can have a variable thickness along the rotor axis. Preferably, the thickness of the disc decreases from the rotor axis towards the radially outer edge of the disc. This is particularly advantageous if the disk is used as a rotor of a motor, since a weight saving is thereby possible. The windings can also be referred to as coils.

The winding can be an electrically conductive wire. The windings can be insulated from each other such that the windings are electrically separated from each other. The insulation can be achieved, for example, by spacing the windings apart from each other. It is also conceivable that the windings are insulated from one another by a non-conductive material. For example, it is conceivable for the winding to be covered by an insulating material. Preferably, the winding is embedded in a non-conductive material. For example, the winding can be surrounded by a non-conductive epoxy. This enables a compact and relatively easy to manufacture construction. The winding can in particular be an electrically conductive conductor ring having an extension in the radial direction of the disk. The radial direction can be a direction beamwise directed outward from a midpoint of the disk. Preferably, the windings are single windings which can be arranged in sequence, side by side or offset, uniformly in the circumferential direction of the disc. The offset arrangement offers the following advantages: the windings can be arranged on the disc with a large bending radius. Furthermore, the copper filling level (in case the winding contains copper) can be increased, which improves the effective power of the motor during operation. In other words, each winding can preferably be formed by a conductor loop or a wire which is guided in a completely or partially closed circuit (Umlauf), in particular in the radial direction and back again. The disks can have holding devices for one winding each. A winding can be placed or wound around each holding device. The windings can thus be easily installed and easily replaced in the event of servicing. A uniform distribution in the circumferential direction of the disk can here mean a uniform distribution along the angle of rotation around the middle of the disk. The rotor axis can extend through the midpoint of the disk. A uniform distribution can in particular mean: the angular spacing between adjacent windings is the same or substantially the same, respectively. Preferably, each winding is insulated from any other winding. The windings preferably each have at least two terminals via which a voltage can be applied to the windings. Preferably, the terminals are located at the beginning and end of the respective winding, respectively. Further, the terminals are located in an interior region of the tray. Wherein the inner region of the disc can be the part of the disc comprising the face of the disc which lies within a circle having a radius which is less than half the radius of the entire disc, preferably less than one third of the radius of the entire disc. The windings can be partially connected to one another at their ends, which can be designed as electrical terminals. Thus, a winding pair can be formed, which is composed of at least two windings. In particular, the ends of the windings, which are each connected to the same pole of the current source (for example, the positive or negative pole of the current source), can also be connected to one another. In particular, the windings can also be connected in series.

In one embodiment, the windings are arranged side by side in the circumferential direction. This is a structurally particularly simple arrangement which at the same time enables efficient motor operation. This arrangement can be relatively easy to manufacture, since the windings only have to be arranged side by side in a circular manner. Furthermore, in such an arrangement, the windings can be insulated from each other more easily, for example by spacing. In an alternative, preferred embodiment, it is provided that the windings are arranged with a smaller offset in the circumferential direction than their extent in the circumferential direction. The windings can be offset in the direction perpendicular to the disk (i.e., parallel to the rotor axis). The windings can thus be arranged partially one after the other and/or overlapping. Furthermore, it is conceivable that each winding defines a winding region on the disk, which winding region can be at least partially surrounded by a winding. In one embodiment, the winding areas of the respective windings do not overlap, in an alternative embodiment, the winding areas partially or even completely overlap. It is thus conceivable, for example, for a first winding region of the first winding to begin, as viewed in the circumferential direction, and for at least one second winding region to begin before the end of this winding region. Viewed in the circumferential direction, the first winding region can end before the second winding region ends. It is thus advantageously possible to arrange a particularly large number of windings in a narrow space, which makes it possible to drive the motor particularly efficiently. In particular, the bending radius of the region with radially outwardly extending windings and the degree of filling of the winding material can be achieved particularly advantageously.

The frame can be a member or element adapted to hold the magnetic core in a circumferential direction around the rotor axis. For example, the frame can also be a stent. The magnetic cores can be distributed uniformly in the circumferential direction. Preferably, the magnetic cores are distributed uniformly here, similar to the distribution of the windings. The number of windings and the number of magnetic cores can be different. The magnetic core can also be referred to as a core. The magnetic core can in particular serve as a flux guide which concentrates the magnetic flux caused by the external magnetic field and intensifies and/or guides it in a certain direction in its surroundings. In this sense, a magnetic core or a part of a magnetic core can also be understood as a pole shoe which guides and/or reinforces magnetic lines of force, for example of an external magnetic field or of a permanent magnet. The magnetic core can be made of a ferromagnetic metal, such as cobalt, iron or nickel, or of a ferromagnetic metal alloy. Which can be magnetized particularly efficiently and which can produce a suitably large magnetic flux density. In this sense, these materials can be magnetized particularly effectively, so that they have a magnetic permeability of significantly more than 1, in particular of a majority of orders of magnitude. The generated magnetic flux density is expediently large in this context if it is significantly greater, preferably a multiple of the same and particularly preferably at least one order of magnitude greater, than the magnetic flux density which would be caused by the external magnetic field alone without the magnetic core. However, the use of ferromagnetic materials, such as ferrites or magnetites, is also conceivable. Preferably, the magnetic core is formed of soft magnetic iron so that the magnetic core can be driven to magnetic saturation by an external magnetic field of about 10 mT. This can also be applied in the following case: the magnetic circuit is not closed in the region of the motor. In other words, the magnetic core is designed such that it aligns the magnetic field in a specific shape to the winding (i.e. leads through the winding) such that a torque acts on the winding due to the lorentz force. There may be an air gap between the winding and the core. The magnetic core can be designed in such a way that it guides the magnetic field to the air gap and brings about a matching shape of the magnetic field in the air gap. The air gap can describe the area through which the magnetic field stretches through the air.

In the absence of an external magnetic field, the core is not necessarily magnetized. However, due to the remanent magnetic properties of the magnetic core, the magnetic core may also be magnetized in the absence of an external magnetic field, wherein in this case the magnetic core may be magnetized more weakly than when the external magnetic field is switched on. The magnet can be magnetized by an external magnetic field. As a result, a magnetic flux density can be generated in the region of the disk or the winding, which is significantly greater than the magnetic flux density generated solely by the external magnetic field. The magnetic core preferably generates a magnetic flux density in the range from 0.2T to 3T, and particularly preferably in the range from 1T to 1.7T, if the magnetic core is saturated by an external magnetic field. The frame can for example form a housing or a part of a housing that can accommodate the disc. The magnetic flux density produced by a saturated magnetic core can be related to the material of the magnetic core. Preferably, the magnetic core is configured such that the magnetic flux density generated by the magnetic core is stronger than that of the external magnetic field.

The tray and the first frame are rotatable relative to each other. In this case, the disk or the first frame can be arranged rotatably about the rotor axis, while the respective other component can be arranged fixedly. Preferably, the disk and the first frame can be offset from one another in the direction of the rotor axis, wherein the spacing between the two from one another can preferably lie in the order of magnitude of the thickness of the disk. Preferably, the ratio of the radius of the disc to the spacing between the disc and the frame is in the range from 0.01 to 0.5, preferably in the range from 0.05 to 0.25, particularly preferably in the range from 0.07 to 0.1. An effective operation of the motor can thus be ensured while maintaining sufficiently high tolerances, so that costs can be saved during production.

According to the utility model, two magnetic cores adjacent on the first frame are respectively associated with different windings, independently of the position of the disc and the first frame relative to each other. Adjacent can here mean adjacent in the circumferential direction. In other words, the magnetic core can be associated with at least one winding. In other words, two magnetic cores arranged side by side in the circumferential direction are not allowed to be associated with the same winding. The association can here mean: one of the magnetic cores interacts electromagnetically with the plurality of associated windings or with one associated winding during operation of the motor. Further, association can mean: the magnetic flux density increased by at least one of the magnetic cores magnetized by the external magnetic field is particularly strongly present in the region of the winding. The expression "behaves particularly strongly" can be understood here as: the magnetic flux density in the respective region is at or near maximum. Furthermore, the association can be represented in the spatial vicinity. Thus, the magnetic core can be opposed to at least a portion of at least one winding with a gap therebetween. In particular, the magnetic core can be arranged opposite the associated winding along a line running parallel to the rotor axis. In other words, the associated magnetic core can be located at the same radial and/or angular position relative to the rotor axis as its associated winding. The position of the magnetic core and of the winding or of a part of the winding, in particular of a part of the winding which extends radially away from or towards the rotor axis, can therefore only be distinguished by a positioning in a direction parallel to the rotor axis. The magnetic core can be magnetized by an external magnetic field or an external magnetic field. The external magnetic field can be substantially unidirectional. This can be applied in particular to the region in which the magnetic core is arranged in an external magnetic field. Thus, the magnetic flux in the region of the disk that can be induced or enhanced by the magnetization of the magnetic core can be oriented in the same direction or substantially in the same direction at the location where the associated winding is provided. Another magnetic core may be provided adjacent to the magnetic core provided in the circumferential direction in the radial direction. Thus, radially adjacent magnetic cores can be arranged along one or more associated windings (i.e. along a radial section thereof). The magnetic cores can, for example, each have a cylindrical shape, the height of which extends parallel to the rotor axis. Such magnets are generally readily commercially available and relatively inexpensive. Furthermore, when the radially extending conductor sections of the respective winding enter the region of the magnetic core and leave it again, a continuously increasing and decreasing torque can thus be achieved in relation to each individual winding. Furthermore, the magnetic core can have an oval shape, the major axis of the oval shape extending in the radial direction. A circular segment-like shape or pie-chart shape can also be envisaged, which enables an optimum utilization of the available space and thus a particularly efficient operation of the motor. Any type of core can be suitable as long as two circumferentially adjacent cores are associated with different windings, respectively.

Preferably, during operation, the motor is oriented or arranged in the external magnetic field such that the external magnetic field is oriented parallel to the rotor axis. In other words, the field lines of the external magnetic field can extend parallel to the rotor axis. Accordingly, the external magnetic field can extend perpendicularly to the disk, whereby the magnetic flux that can be generated by the magnetic core can also extend perpendicularly to the disk. If a current is now conducted through the winding, which runs substantially in the plane of the disk and thus perpendicularly to the magnetic flux caused by the magnetic core, a lorentz force can act on the winding. The lorentz force can be related to the direction of current flow or the direction of current flow and the magnetic flux density. In the case of the intensity I of the current flowing through the winding and the length x of the orientation of the wire sections of the winding, i.e. the vector x of the values which describe the length and direction of the current wires, the magnetic flux density B can generate lorentz forces F on the respective wire sections of the winding_LI (x × B). For radially extending sections of the winding, the lorentz forces can act tangentially with respect to the disk. Depending on the direction of the current and the direction of the magnetic field or the magnetic flux density associated therewith, the force can be directed clockwise or counterclockwise. Thus, the rotation direction of the disk or the frame can be controlled. By means of the ring-shaped configuration of the winding, the winding can have a region in which the current flows radially outward and another region in which the current flows radially inward, respectively. Depending on the extension of the winding and the magnetic core in the circumferential direction and with suitable switching in of the current, it is possible to derive a situation in which the current flows only in the radial direction (only outwards or only inwards) in the region of influence of the magnetic flux density of the magnetic core, permanently or at least in some positions of the disk relative to the frame. By appropriately switching in the current, lorentz forces acting opposite to the desired direction of rotation can be prevented. That is, if a section of the winding enters (by rotating the disc or the frame) the area of influence of the magnetic core, in which area of influence the current flows in the radial direction with the electricity in the section of the winding previously in the area of influence of the magnetic coreThe flow is oppositely stretched, the direction of the current through the winding can always be reversed. The area of influence of the core can be the area where the magnetic flux generated by the core is maximal or approximately maximal. Sections of the winding can be associated with the magnetic core similar to the definitions given above. By switching the current direction in this way it can be ensured that: the lorentz forces acting on the conductor sections always point in the same rotational direction. In other words, continuous rotation based on the lorentz force can be achieved without the magnetic cores having different polarizations.

The motor according to the utility model therefore differs from the disk rotor motors known from the prior art in that, during operation of the motor, the windings are not associated with two circumferentially adjacent magnetic cores or magnets at any point in time and an external magnetic field can be used for operating the motor. Thus, in contrast to the disk rotor motors known in the prior art, two circumferentially adjacent magnetic cores can have the same polarization (i.e. the field lines generated or enhanced by the adjacent magnetic cores point in the same direction).

Furthermore, a magnetic core is used instead of the permanent magnet according to the present invention. In the case of prior art disc rotor motors, it is common and expedient to arrange the magnets alternately in a circumferential direction around the rotor axis, so that adjacent magnets each generate a magnetic flux density running parallel to the rotor axis in opposite directions (i.e. adjacent magnets have different polarizations). Here, the section of the winding in which the current flows radially outward is associated with a magnet and the section of the winding in which the current flows radially inward is associated with an adjacent magnet, which produces a magnetic flux density that is opposite to the magnetic flux density of the first magnet. In the absence of an external magnetic field, this arrangement results in an efficient motor, since the radially inwardly and radially outwardly extending sections of the windings contribute to the torque of the rotor. This configuration is disadvantageous in the case of strong external magnetic fields, since it switches the polarity of the magnets, thereby limiting the function of the motor.

In particular, the motor can be operated without restriction in an external magnetic field by the arrangement according to the utility model of the magnetic core. The magnetic shielding of the motor is not necessary for the motor according to the utility model, since an external magnetic field can be used for the function of the motor. The motor can thus be arranged at any location around the MR system and can be operated without problems during operation of the MR system. The motor according to the utility model therefore does not compete with other magnetic field-sensitive components for the installation position when mounted on an MR system.

According to a preferred embodiment, each winding of the motor has: two radial sections extending substantially radially over the disc; and at least one circumferential section which extends substantially in the circumferential direction of the disk, wherein the radial sections of each winding have a limited first angular distance from one another, and wherein two circumferentially adjacent magnetic cores each have a limited second angular distance from one another, wherein the value of the second angular distance is greater than the value of the first angular distance, preferably at least twice as great as the value of the first angular distance.

Substantially radial here can mean: the radial sections do not necessarily extend in a braid-like manner from the inner region of the disk outwards or from the outside towards the inner region of the disk, but rather slightly different, for example slightly curved or curved, extensions are also conceivable. This can be achieved more easily, for example, in terms of production, in particular in order to be able to form the winding in a ring-like manner and without bending. The circumferential section can extend with a curvature corresponding to the curvature of a circle at a point of the circumferential section, the midpoint of which coincides with the midpoint of the disk. However, the circumferential section can also run straight or with a stronger or weaker curvature than a circle at the point of the circumferential section, the midpoint of which can coincide with the midpoint of the disk. Preferably, the radial section is as large as possible (i.e. has as large an extension as possible) relative to the circumferential section. Since, during operation of the motor, only the lorentz forces acting on the radially extending winding sections (i.e. acting on the radial sections) contribute to the rotation of the disk or the frame, the efficiency of the motor can advantageously be increased by a large fraction of the radially extending winding sections. Lorentz forces acting tangentially in the circumferential direction with respect to the disk can rotationally drive the disk (in the case where the disk is a rotor), or forces in the opposite direction of the generated lorentz forces can rotationally drive the frame (in the case where the frame is a rotor).

The radial segments have a limited angular distance from one another, which can be expressed in particular by: the angular spacing is greater than 0 °. The angular distance is understood here to mean the size of the angle in the circumferential direction, wherein the first angular distance is preferably less than 180 ° and particularly preferably less than 90 °. Preferably, the first angular distance can also be significantly smaller than 90 °, for example in the range from 1 ° to 15 °, in order to be able to provide a plurality of magnetic cores, and thus to be able to realize a more efficient motor. In a preferred embodiment, the first angular distance is approximately 45 °, wherein the windings can optionally overlap in this case.

An arrangement in which the value of the second angular spacing between adjacent magnetic cores is greater than the value of the first angular spacing between two radial sections of a respective winding can advantageously be implemented: the windings are associated with only one core each at any one time. The width of the magnetic core can correspond to an angular spacing that is less than a difference between the second angular spacing and the first angular spacing. If the second angular spacing is twice as large as the first angular spacing, then one winding is associated with only one magnetic core at any one time if the angular extent over which each magnetic core extends substantially corresponds to the first angular spacing. A particularly efficient and constant working process of the motor can thus be ensured.

According to one embodiment, the first frame and the magnetic core can be arranged such that the magnetic core is arranged on a circle concentric with the rotor axis. By arranging the magnetic cores on a circle concentric with the rotor axis, a particularly constant operation of the motor is advantageously achieved. Particularly preferably, the center point of the magnetic core can be arranged on a circle concentric to the rotor axis. All the magnetic cores can have the same shape, which corresponds to a particularly uniform arrangement. Each magnetic core can have a substantially cylindrical shape, wherein each magnetic core can be arranged on the frame such that a longitudinal axis of each magnetic core extends parallel to the rotor axis. Furthermore, the magnetic core can be arranged such that it is associated with a region of the disk (i.e. the winding arranged there), which can be spaced from the rotor axis by a value greater than half the radius of the disk.

According to an advantageous embodiment, a second frame with magnetic cores can be provided on the other side of the disk, so that the disk can be inserted between the first frame and the second frame, wherein the second frame and the magnetic cores can be provided such that the magnetic cores are distributed uniformly around the rotor axis in the circumferential direction, wherein the magnetic cores of the respective one first frame and the magnetic cores of the second frame can lie on the same straight line running parallel to the rotor axis, and wherein the first frame and the second frame can be fixedly arranged relative to one another. Preferably, the magnetic cores of the first frame and the second frame are arranged in mirror image with respect to a mirror plane defined by the disk or with respect to a mirror plane running centrally through the disk and perpendicular to the rotor axis. The magnetic core of the first frame and the magnetic core of the second frame can interpose a winding associated with both magnetic cores in between. The second frame can be fixed to the first frame, but the second frame can also be arranged on the motor independently of the first frame. The first frame and the second frame may be integrally or integrally formed. The additional magnetic core of the second frame makes it possible to achieve a stronger magnetic flux density, in particular, for example, twice as strong, in the region of the disks, and thus a more powerful motor. The magnetic resistance can therefore also be reduced if, optionally, permanent magnets or electromagnets are additionally used for magnetizing the core. Since a larger share of the magnetic field lines generated by the permanent magnets can extend through the well-permeable magnetic core, rather than through the low-permeability air (air gap). It is thus possible to provide less strong permanent magnets in order to put the core completely in saturation. Therefore, providing the second frame has the following advantages: the magnetic resistance (magnetic reluctance) in the magnetic circuit can be reduced, in particular by a given geometry, for example to one eighth, because the air gap in the magnetic circuit is shorter.

In one embodiment, the motor can comprise at least one permanent magnet, which can magnetize the magnetic core such that the field lines generated by the magnetized magnetic core point in the same direction at least in the region of the disk, respectively. The permanent magnet can also be configured as a coil, which can generate a magnetic field by suitable control. In this case, the coil can act like a permanent magnet. The coil offers the following advantages: the coils can be selectively operated and do not have to be energized in the presence of an external magnetic field. In other words, the coils can be operated only when there is no external magnetic field and the motor should still be operated. In particular, the motor can be positioned such that the field lines generated by the permanent magnets point in the same direction as the external magnetic field, at least in the region of the magnetic core. This can advantageously be achieved: the motor is also operated if the external magnetic field is switched off, i.e. for example if the magnet of the MRT in which the motor is arranged is not operating. For example, the electronics of the MRT and the table can therefore be operated at least at reduced power, even if the MR magnetic field is switched off. This eases commissioning, maintenance and testing in the laboratory.

Preferably, the at least one permanent magnet is designed to magnetize the magnetic core until saturation. Because the magnetic core can be magnetized by the permanent magnet until saturation, the following can be realized: the magnetic flux in the region of the disk is present substantially constantly with and without an external magnetic field, and therefore the motor power is also substantially constant, since the core can be magnetized until saturation and the magnetic flux is determined substantially by the magnetization of the core. Thus, the motor can be operated under any circumstances.

Preferably, the two magnetic cores, which are arranged opposite one another on both sides of the disk in the direction of the rotor axis, are connected via a connecting region which runs parallel to the rotor axis and at a distance from the disk in the radial direction, so that the two magnetic cores are connected by means of a substantially U-shaped connection. The connection region can be composed of the same material as the magnetic core. This can cause effective magnetization. When optionally additionally using permanent magnets or electromagnets to magnetize the core, the magnetic resistance can thereby be reduced even further. Since a significantly larger fraction of the magnetic field lines generated by the permanent magnets can extend through a well-permeable magnetic core, rather than through air of low permeability. Therefore, a significantly lower strength permanent magnet is required. In particular, the second frame can be substantially formed by the connection region or a part of the connection region. Preferably, the two oppositely arranged magnetic cores together with the connecting region result in a U-shaped or horseshoe-shaped overall magnetic core. The magnetic circuit can thus be closed outside the motor (i.e. outside the area where the disc is located) by the connection area. Thus, in this embodiment, the magnetic core can be placed in saturation with a small permanent magnet and without an external magnetic field. Therefore, the entire torque of the motor can be generated. In this case, however, a correspondingly oriented external magnetic field can counteract the magnetic field acting in the connecting region at the connecting region. However, since the field in the connecting region is not used for operating the motor, the function of the motor is not disturbed, since the torque is only generated in the region of the core.

In other words, a first region can be defined in which the connection region is provided and in which the magnetic circuit is closed. In the first region, the field lines induced by the magnetic core can run opposite to the field lines of the external magnetic field. However, since the first region is radially spaced from the disc, this has no negative effect on the operation of the motor. Furthermore, a second region can be defined in which the magnetic core and the winding are arranged. In the second region, the field lines induced by the magnetic core run along the field lines of the external magnetic field. The magnetic core induced field lines in the second region can be used to drive the disk or the frame. In other words, by means of the connection region it can be ensured that: the first area is located outside an area where the disc is located. Thus, efficient operation of the motor can be ensured.

According to one embodiment, the disk is designed as a rotor, wherein the winding is supplied with a direct current, in particular via at least one commutator having a plurality of sliding contacts, wherein the number of sliding contacts preferably corresponds to twice the number of magnetic cores on the first frame and/or the second frame. In this embodiment, the frame can serve as a stator, which is fixed and thus non-rotatable. This embodiment has the following advantages: the magnetic core does not have to be moved in the external magnetic field, and the problems of possible force and eddy current losses can be avoided accordingly. The sliding contact portion can realize: the windings are supplied with current without the input wires having to rotate with the disc. The sliding contact can be arranged in the frame of the commutator such that, when the disk rotates, one end of each winding is connected to the positive pole and the other end is connected to the negative pole or to ground. Further, as the disk rotates, the windings can periodically switch polarity such that current flow is periodically reversed. It is thus possible to ensure: the current of the wire section running in the radial direction and just associated with the magnetic core always flows in the same direction, so the resulting lorentz force is always oriented in the same direction. Preferably, the number of sliding contacts corresponds to twice the number of magnetic cores, since the polarity reversal can thus be achieved at a suitable frequency which is directly related to the number of magnetic cores. Each winding can have a section in which current flows outwards and a section in which current flows inwards. Hereby, the current flow in the winding can be switched in polarity at least once when said core and said winding run past each other. This can be achieved by means of a given number of sliding contacts. The supply current supplied to the motor can be a direct current, and due to this arrangement the current flowing through the winding periodically changes its direction during operation.

According to an alternative embodiment, the first frame or possibly also the second frame can be designed to serve as a rotor, wherein the motor can further comprise a control unit, which is designed to supply each winding with an alternating current having a predetermined alternating frequency, wherein the alternating frequency can correspond to a mathematical product of the rotational frequency of the motor and twice the number of magnetic cores of the frame. In this embodiment, the disc can be used as a stator, i.e. fixed and non-rotatable. While the frame is rotatable around a rotor axis, wherein the rotor axis is preferably located at the center of the magnetic core. In this case, force interactions can be used, which serve to: by means of a corresponding opposing force of the lorentz force, a force is also exerted on the magnetic core, which force is in particular equivalent to the lorentz force exerted on the winding. This embodiment has the following advantages: sliding contacts, which may produce spark formation or brush sparks on the slip ring, which are detrimental for MR devices, are not required. In order to still be able to ensure a current direction in the winding that alternates over time, the winding can be supplied with an alternating current, wherein the alternating current frequency can be adapted to the geometry of the motor and to the desired rotational frequency or rotational speed of the motor. For example, a frequency converter can be used to control the current. In this case, it is preferred that the frame is likewise of substantially disk-shaped design, which facilitates uniform rotation of the frame.

According to a preferred embodiment of the motor, the magnetic core may be a laminated sheet. The magnetic core can be formed from thin laminated sheets or films, which are insulated from one another. Eddy currents, which would impair the power of the motor, can thus be avoided or minimized. Alternatively, it is also conceivable to use powder cores for the same purpose, in which the powder particles are isolated from one another. It is also conceivable to use ferrite cores or other ferromagnetic materials which, due to their low electrical conductivity, have only very low eddy current losses.

According to one embodiment, the motor can be designed to intermittently switch the current supply to the winding on and off in addition to the ac frequency during operation, so that a higher switching frequency, in particular a switching frequency of at least 1kHz, is achieved. In other words, at a predetermined polarity switching frequency, for example 100Hz, the winding can be switched on and off several times, for example ten times, within one cycle in order to always reach a high switching frequency, for example 1 kHz. Such a switching frequency is not necessary for the operation of the motor. For this purpose, the motor can have a control unit, which can be designed to switch the current supply to the winding such that a switching frequency of at least 1kHz is reached.

In an alternative embodiment, it is also conceivable for the windings to overlap. Additionally, the number of magnetic cores can optionally be less than the number of windings. The motor can be designed here such that a plurality of windings can be supplied with current simultaneously. In this embodiment, the windings can be switched relatively frequently. In particular, the windings can be switched at a frequency corresponding to the motor frequency or to the mathematical product of the rotation frequency of the frame and twice the number of cores. Alternatively, the windings can also be switched at a frequency that corresponds to the mathematical product of the motor frequency or the rotational frequency of the frame and the number of windings. It is thus possible to derive a switching frequency which is significantly greater than the actual rotational frequency of the disk or frame. If the rotational frequency of the disk or the frame is, for example, 33.3Hz, the winding can be switched, for example, at every 1/30 revolutions of the frame or disk, resulting in a switching frequency of approximately 1 kHz.

These embodiments for controlling the switching frequency can be advantageous when using a motor in the vicinity of the MR system, since the measurement or MR imaging reacts sensitively to magnetic disturbances, in particular a slight modulation of the magnetic field in the field of view, in the range of 1Hz to 1 KHz. The exact frequency range of the highest interference sensitivity is associated with the selected sequence of the MR imaging. While the interference of magnetic fields above 1kHz is far less critical for MR imaging. By the arrangement according to this embodiment, switching in this critical frequency range (i.e. due to commutation) can be avoided without having to increase the rotational speed of the motor itself, which is undesirable for several purposes, such as running one or more fans or moving the examination table in a controlled manner. To this end, the control unit can have a Delta-Sigma digital-to-analog converter (Delta-Sigma modulator), which can ensure that: low frequencies below 1kHz are avoided even if the pole change frequency is low for the desired rotational speed, e.g. 100 Hz. In this case, the clock frequency of the Delta Sigma modulator can be selected such that the noise rises from 1kHz and a sinusoidal signal is not output, but white noise is output as a valid signal. For the operation of the motor, a signal can therefore be obtained which has almost no power density at 1 kHz. The output of the Delta Sigma modulator can be rectangular, so the energization of the windings only has to be switched on and off.

Alternatively, it is also conceivable for the motor according to one of the preceding embodiments to be synchronized with the pulse frequency or the measurement frequency of the MRT. In particular, the switching frequency of the winding can correspond to the measurement frequency of the MRT, at which the MRT emits pulses and measures, or the switching frequency of the winding can be a multiple of this measurement frequency. The disturbance of the MRT measurement may be caused by a spatially slightly shifted MRT image. For example, the MRT image can thus be shifted by 0.1mm to 2 mm. By synchronizing, the offset can advantageously be constant or remain constant. Thus, a sharp image can be derived with only an absolute shift.

In other words, each MRT imaging sequence can have its own duration in which the HF pulses and the measurement of the MRT signals are repeated, for example every 30 milliseconds (═ 33.3 Hz). The magnetic field disturbance due to the operation of the motor has no or hardly any influence if it has the same frequency or an integer multiple of said frequency. Then if the windings are switched every 5ms (six times the frequency) (in the case of e.g. 12 windings on the disc, the disc can be 16.66 revolutions per second or 1000 revolutions per minute), the magnetic field disturbance caused by the motor (period 5ms) and the measurement of the MRT (i.e. slices with a period of 30 ms) must be phase-synchronized (i.e. the starting time points are not shifted from each other over the duration of the entire sequence, which duration is e.g. 5 minutes). The magnetic field disturbance therefore has the same effect in each measurement. The effect of the small superimposed magnetic field is typically due to: the gradient (slice selection, phase encoding or frequency encoding gradient) is slightly curved. The assumed position of the MRT signal is slightly shifted. This appears to be at a particular location in the MRT image, not actually at that location, but with a small amount (e.g., about 1/10mm to about 2mm) of spatial offset. Since the magnetic field disturbance is synchronized with the rhythm of the image generation of the MRT, this shift is always the same, so that the image remains sharp and there is only a small error in the absolute spatial position.

In another example, in case the interval between two MRT measurements (HF pulses) is 66Hz, the current through the winding can be switched every 5.077ms, which can correspond to a frequency of 13 times. This may result in 16.4 revolutions per second or 985 revolutions per minute. In the case of fans, the speed variation (i.e. compared to the above-mentioned speed) is tolerable, for example.

Another aspect of the utility model proposes the use of a motor according to one of the described embodiments in an external magnetic field, wherein the motor is oriented in the external magnetic field such that the field lines of the external magnetic field run parallel to the rotor axis. All advantages and embodiments described for the motor also apply to the application of the motor and vice versa.

In one embodiment, the motor is used in a Magnetic Resonance (MR) system (MRT). The problems described in the general part with respect to placing the motor in the vicinity of the MR system can thus be solved and the motor can utilize the stray magnetic field of the MR magnet.

It is particularly preferred that the motor used in the external magnetic field or in or at the MR system is designed to drive the fan.

Drawings

Embodiments are described below with reference to the drawings.

Fig. 1 shows a front view of a disc rotor motor as known in the prior art;

FIG. 2 illustrates a front view of one embodiment of a motor according to the present invention;

fig. 3 shows a side view of a second embodiment of a motor according to the utility model;

fig. 4 shows a third embodiment of the motor according to the utility model; and

FIG. 5 shows a side view of the motor of FIG. 4 along section A-A; and

fig. 6 shows a motor according to the utility model, which is arranged in the direct vicinity of the MR system.

Detailed Description

Fig. 1 shows a front view of a disc rotor motor 100 according to the prior art. The disk rotor motor 100 has eight windings 105, which are arranged uniformly on the rotor 104 in the circumferential direction about the rotor axis 110. The rotor 104 is rotatably supported about a rotor axis 110. In addition, motor 100 has eight stationary magnets 109, which are offset axially along rotor axis 110 and which are each associated with two windings 105 or two radially extending conductor sections 112 of two different windings 105. Adjacent magnets 109 of the arrangement are respectively differently polarized, meaning that in the circumferential direction the north poles of the magnets 109 always alternately point towards or away from the image plane. The direction of current flow in winding 105 is indicated by the arrows in fig. 1. The current flow directions of the sections of the winding 105 respectively associated with the magnets 109 point in the same direction. The directions are opposite in the winding sections 112 associated with adjacent magnets 109 and are switched in adjacent magnets 109 according to the alternating orientation of the magnets 109.

However, the constant external magnetic field 2 can disturb the operation of the motor 100. In particular, if the external magnetic field is oriented along the rotor axis 110, the effect of the magnets 109 is reduced or even reversed in polarity, thereby rendering the motor 1 inoperative or at least reducing its power. Due to the differently oriented and alternating magnetic fields, different current flow directions in all radially extending wire sections of the winding can be used to put the rotor into rotation.

Fig. 2 shows a front view of the motor 1 according to an embodiment of the present invention. The motor 1 has a disk 4 which is rotatable about a rotor axis 10 and has eight windings 5, each of which has two radial sections 12 and a circumferential section 14. In this case, the windings 5 are arranged next to one another in the circumferential direction for a better overview, but it is also feasible and advantageous for the windings 5 to be arranged in an overlapping manner. At the end of each radial section 12 there is a sliding contact 18, so that each winding 5 has two sliding contacts 18. The windings 5 can alternatively also be connected in series or in parallel if the windings 5 are arranged such that they always have the same switching point in time for the current. This can save the sliding contact portion. In the exemplary embodiment with 4 cores offset by 90 °, this is in each case a winding 5 arranged offset by exactly 90 ° on the disk 4. The sliding contact 18 is connected to a current source, so that current can be supplied to the winding via this. In one embodiment, in each position of the motor 1, one sliding contact 18 of the winding 5 is in contact with the positive pole of the current terminal, respectively, and the other sliding contact 18 of the winding 5 is in contact with the negative pole of the current terminal, respectively. Depending on the position of the disk 4, a current flow through the respective winding 5 in one direction or the opposite direction is thus induced. The current flow direction is indicated by the arrow at winding 5 in fig. 2 for the current position of the disc 4.

Furthermore, the motor 1 comprises four magnetic cores 8, which are arranged on a stationary, non-rotatable first frame 6 (not shown in fig. 2). In this position, each magnetic core 8 is associated with two radial sections 12 of two different windings. The current flow directions of the two radial sections 12 associated with the magnet core 8 each point in the same direction during operation of the motor 1. Only one radial section 12 in each winding 5 is associated with the magnetic core 8. Each further radial segment 12 is not associated with a magnetic core 8. This furthermore leads to: each two adjacent magnetic cores 8 are not associated with the same winding 5, thereby avoiding: the magnet 9 is associated with two windings having different current flow directions. A first angular distance 16, which describes the width of the winding 5 in the circumferential direction or the angular distance of two radial sections 12 of the winding 5, is smaller than half of a second angular distance 17, which describes the distance of two adjacent magnetic cores 8 in the circumferential direction, in this exemplary embodiment. In this case, the distance between two adjacent magnetic cores 8 in the circumferential direction is measured between the midpoints of the magnetic cores 8. In order to ensure a particularly efficient distribution of the windings 5 and the magnetic cores 8, the second angular distance 17 is preferably exactly twice as large as the first angular distance 16.

For the operation of the motor 1, it is proposed that the motor be oriented in an external magnetic field 2, the external magnetic field 2 being oriented substantially parallel to the rotor axis 10. In this case the magnetic field lines of the external magnetic field 2 run perpendicular to and away from the image plane of fig. 2. This causes the magnetic core 8 to be magnetized in the direction of the external magnetic field 2. The magnetic flux density in the region of the disk 5 is thereby significantly increased at the location of the disk 5 associated with the magnetic core 8. In this example, here, the region of the disk 5 that is located on the same plane as the core 8 in the image plane is associated with the core 8. At each time point, the respective setting of the sliding contact 18 ensures: the current in the radial section 12 just associated with the magnetic core 8 flows radially outwards. Since the magnetic flux density caused by the external magnetic field is significantly lower than the magnetic flux density that is increased in the region of the magnetic core 8, a substantially clockwise torque is obtained by the lorentz force. The lorentz forces acting on the radial sections 12 not associated with the magnetic core, although pointing in opposite directions, are significantly lower due to the lower magnetic flux density of the external magnetic field there, and thus have no significant effect on the total torque. The sum of the torques induced on the individual radial segments 12 respectively associated with the magnetic cores 8, which torques are all directed in the same direction of rotation, results in a total torque of the motor 1 in the clockwise direction, so that the disk 4 rotates about the rotor axis 10 and is driven as a rotor of the motor. The lorentz forces also act on the circumferential section 14, but are very weak, since they are not associated with the magnetic core 8 and are oriented perpendicular to the direction of rotation of the disk, i.e. in the direction in which the disk cannot move. In addition, the lorentz forces acting on the different circumferential sections cancel each other out, since the forces acting on the opposing circumferential sections are directed in opposite directions. Likewise, if the current is controlled such that it flows radially inward in the radial section associated with the magnetic core, the rotor is also able to rotate counterclockwise.

Fig. 3 shows a side view of a further embodiment of the motor according to the utility model in an external magnetic field 2, which extends from left to right in the image plane. The disc 4 can be seen, from which angle the windings 5 of the disc are not visible. The rotor axis 10 runs parallel to the external magnetic field 2. Furthermore, a first frame 6 is visible, to which a magnetic core 8 is fastened, which is located on the right side of the disk 4. A further magnetic core 8 is fastened to the second frame 7, which is fastened to the first frame 6 via a connecting region 20, said further magnetic core being situated opposite the magnetic core 8 fastened to the first frame 6 and being situated to the left of the disk 4. In this case, the connection region 20 is integrally formed with the first frame 6 and the second frame 7. Further, the connection region 20 is formed of the same material as the magnetic core 8. This results in a monolithic magnetic core which is formed in the shape of a horseshoe and which advantageously enables a stronger magnetization by the permanent magnet 19, which in this embodiment is fixed to the magnetic core 8 of the first frame. Here, the motor is oriented such that the field lines (not shown) of the permanent magnets 19 point in the same direction as the field lines of the external magnetic field 2. This can be achieved: the motor 1 can be operated even in the case where the external magnetic field 2 is switched off. Advantageously, the permanent magnet 19 is strong enough to magnetize the core 8 to saturation. In a further embodiment, which is not shown, the permanent magnet 19 is configured as a coil, which is able to generate a magnetic field by applying a voltage. Therefore, the magnetic flux density in the region of the disk 4 associated with the magnetic core 8 is not significantly different when the external magnetic field is turned on from when the external magnetic field is turned off. This is due to: the magnitude of the magnetic flux density is essentially determined by the magnetized magnetic core 8, while the contribution caused by the external magnetic field 2 and the permanent magnets is only small. Since the magnetic core 8 is in any case magnetized to saturation, the magnetic flux density in the region associated with the magnetic core does not change significantly when the external magnetic field 2 is switched on. Thus, the motor 1 works reliably and independently of the external magnetic field 2.

Fig. 4 and 5 show a further embodiment of the motor 1 according to the utility model, fig. 5 here showing a side view along the sectional axis a-a shown in fig. 4. In this embodiment, the first frame 6 with the magnetic core 8 is rotatably supported, while the disc 4 with the winding 5 is fixed. In fig. 4, the first frame 6 is not shown for the sake of overview. Also in this case, the external magnetic field is oriented parallel to the rotor axis 10. Since the direction of the current flow through the winding 5 cannot be changed by means of the sliding contact 18, an alternating voltage is applied to the winding 5, which alternating voltage corresponds to eight times the rotational frequency of the motor 1, depending on twice the number of magnetic cores 8. In this case, too, the first angular distance 16 is greater than the second angular distance 17, but, owing to the relatively small magnetic core 8 here, is less than twice the second angular distance 17. In this embodiment, the magnetic core 8 is a laminated sheet. In another embodiment, not shown, all the electrically conductive components of the motor 1 are laminated (see definition above) in order to limit losses caused by eddy currents.

Fig. 6 shows a motor 1 according to the utility model, which is arranged in the direct vicinity of the MR system 3 and is used there. Since in the vicinity of the MR system 3 the motor is in the influence range of the external magnetic field 2 caused by the MR system 3. In this case, the motor 1 is used to drive the fan 15. The current through the windings 5 of the disc of the motor is controlled by a control unit 11.

Claims

1. A motor for use in an external magnetic field, the motor comprising:

a disk (4), the disk (4) having windings (5) which are distributed uniformly in the circumferential direction of the disk (4), wherein a rotor axis (10) runs through the center of the disk (4) and perpendicular to the disk (4), wherein the windings (5) are insulated from one another such that they are electrically separated from one another,

at least one first frame (6) having a magnetic core (8), wherein the first frame (6) and the magnetic core (8) are arranged such that the magnetic core (8) is distributed uniformly around the rotor axis (10) in a circumferential direction,

wherein the disc (4) and the first frame (6) are rotatable relative to each other,

it is characterized in that the preparation method is characterized in that,

the magnetic cores (8) are distributed over the first frame (6) in such a way that, independently of the position of the disk (4) and the first frame (6) relative to one another, two magnetic cores (8) adjacent to one another on the first frame (6) are each associated with a different winding (5) in a direction parallel to the rotor axis (10).

2. The motor as set forth in claim 1, wherein the motor is a motor,

it is characterized in that the preparation method is characterized in that,

each winding (5) has: two radial sections (12) extending radially on the disc (4); and at least one peripheral section (14) extending in a peripheral direction of the disk (4),

wherein the radial sections (12) of each winding (5) have a limited first angular spacing (16) from each other, and

wherein two magnetic cores (8) adjacent in the circumferential direction each have a limited second angular distance (17) from one another,

wherein the value of the second angular spacing (17) is greater than the value of the first angular spacing (16).

3. The motor as set forth in claim 2, wherein the motor is a motor,

it is characterized in that the preparation method is characterized in that,

the value of the second angular distance (17) is twice as large as the value of the first angular distance (16).

4. The motor according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the first frame (6) and the magnetic core (8) are arranged such that the magnetic core (8) is arranged on a circle concentric with the rotor axis (10).

5. The motor of any one of the preceding claims,

the motor (1) is arranged in an external magnetic field (2) during operation such that field lines of the external magnetic field (2) extend parallel to the rotor axis (10).

6. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

a second frame (7) having a magnetic core (8) is provided on the other side of the disk (4) such that the disk (4) is inserted between the first frame (6) and the second frame (7),

wherein the second frame (7) and the magnetic core (8) are arranged such that the magnetic core (8) is evenly distributed around the rotor axis (10) in a circumferential direction,

wherein one magnetic core (8) of the first frame (6) and one magnetic core (8) of the second frame (7) can each lie on a same line extending parallel to the rotor axis (10), and

wherein the first frame (6) and the second frame (7) are fixedly arranged relative to each other.

7. The motor as set forth in claim 6, wherein the motor is a motor,

it is characterized in that the preparation method is characterized in that,

two magnetic cores (8) which are arranged opposite one another on both sides of the disk (4) in the direction of the rotor axis (10) are connected via a connecting region (20) which extends parallel to the rotor axis (10) and at a distance from the disk (4) in the radial direction, so that the two magnetic cores (8) are connected by means of a U-shaped connecting section.

8. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the motor (1) comprises at least one permanent magnet (19) which magnetizes the magnetic core (8) in such a way that the field lines generated by the magnetized magnetic core (8) point in the same direction at least in the region of the disk (4).

9. The motor as set forth in claim 8, wherein the motor is a motor,

it is characterized in that the preparation method is characterized in that,

the at least one permanent magnet (19) is designed to magnetize the magnetic core (8) until saturation.

10. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the disc (4) is configured to act as a rotor,

wherein the winding (5) is supplied with a direct current via at least one commutator having a plurality of sliding contacts (18),

wherein the number of the sliding contact portions (18) corresponds to twice the number of the magnetic cores (8) on the first frame (6).

11. The motor according to any one of claims 1 to 9,

it is characterized in that the preparation method is characterized in that,

the first frame (6) is configured to act as a rotor,

wherein the motor (1) further comprises a control unit configured for supplying each winding (5) with an alternating current having a predetermined alternating frequency,

wherein said alternating frequency corresponds to a mathematical product of the rotational frequency of said motor (1) and twice the number of said magnetic cores (8) of the frame.

12. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the magnetic core (8) is laminated.

13. The motor as set forth in claim 11, wherein the motor is a motor,

it is characterized in that the preparation method is characterized in that,

the motor (1) is designed to intermittently switch the current supply to the winding (5) on and off in addition to the AC frequency during operation, so that a higher switching frequency of at least 1kHz is achieved.

14. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the motor is oriented in the external magnetic field (2) such that the field lines of the external magnetic field (2) run parallel to the rotor axis (10).

15. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the motor is used in or at a magnetic resonance system.

16. The motor of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the motor (1) is designed to drive a fan.