DE102014219832A1 - Computer tomography device with a direct drive - Google Patents

Abstract

For a particularly powerful, at the same time high-quality and cost-effective drive has a computer tomography device a stator and a rotatable relative thereto annular rotor, the computed tomography device has a high-pole permanent-magnet direct electrical drive to generate the rotational movement of the rotor, the stator as active components at least one stator segment with current flowing through Windings and the rotor has at least one rotor segment, each having at least one multi-pole component, wherein the current-carrying windings magnetically interact with the respective multi-pole component via an air gap between the stator and rotor, and wherein each multi-pole component is formed such that it has an upper side and a lower side a first magnetic pole having a surface on top, a second magnetic pole having a surface adjacent in a tangential direction the first magnetic pole on the upper side, and a soft magnetic device having a recess between the first magnetic pole and the second magnetic pole, wherein a vertical direction is directed from the upper side to the lower side perpendicular to a tangential direction, and wherein the first magnetic pole has a permanent magnet with a magnetization in one direction and the second magnetic pole has no permanent magnet.

Description

The invention relates to a computed tomography device having a stator and a rotor rotatable relative thereto and a high-pole permanently excited direct electrical drive for generating the rotational movement of the rotor according to claim 1.

A computed tomography (CT) device i.A. both an annular stator and an annular rotor, wherein on the rotor, an X-ray source and a fan-shaped X-ray detector are arranged. The rotor has to rotate around a centrally arranged object of investigation with very high precision and high speed in order to meet the necessary requirements for high-quality X-ray imaging. For example, the X-ray detector has to rotate on a circular path of about 1 m in diameter and at a speed of about 200 to 400 rpm around the examination subject. The rotating arrangement has e.g. a mass of about 500 to 600 kg.

In known computed tomography devices, the drive of such an arrangement is effected by means of a toothed belt drive or a direct drive according to the prior art. A belt drive is relatively inexpensive, but also requires a high maintenance and has low dynamics. A CT with a known (electric) direct drive is e.g. The ring-shaped stator has at least one stator segment (also: primary part), which is designed as laminated cores equipped with energizable coils, on the annular and generally faceted rotor permanent magnets are applied (also: secondary part). This results in the following disadvantages: The permanent magnets must i.A. are glued to the annular rotor carrier; if the rotor carrier has facets, cuboidal magnets can be mounted on the rotor carrier ring, which is very expensive; If the rotor carrier has no facets, bent shell magnets must be mounted on the rotor arm, which are also very expensive. Overall, the need for temperature-resistant rare earth magnets is very high.

From the non-prepublished patent application EP 14175245 is known multi-pole component for a novel direct drive, which component has at least two magnetic poles, one of which has a permanent magnet and the other no permanent magnet.

It is an object of the present invention to provide a computed tomography device with a drive, which avoids the problems of the prior art.

The object is achieved by a computed tomography device with a direct drive according to claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

The computed tomography device according to the invention has a stator and a rotatable relative to annular rotor, the computed tomography device has a high-pole permanent-magnet electric direct drive to generate the rotational movement of the rotor, the stator as active components at least one stator, in particular at least two diametrically opposed stator segments, with current flowing through Windings and the rotor at least one, in particular at least two rotor segments, each having at least one multi-pole component, wherein the current-carrying windings magnetically interact with the respective multi-pole component via an air gap between the stator and rotor, and wherein each multi-pole component is designed such that it a top and a bottom, a first magnetic pole having a surface on top, a second magnetic pole having a surface in a tange and a soft magnetic device having a recess between the first magnetic pole and the second magnetic pole, wherein a vertical direction from the top to the bottom perpendicular to a tangential direction and wherein the first magnetic pole has a permanent magnet with a magnetization in one direction and the second magnetic pole has no permanent magnet.

The rotor of the computed tomography device according to the invention generally carries an X-ray detector, e.g. a fan-shaped X-ray detector, and an X-ray source (X-ray source), and rotates to receive a plurality of X-ray images around an examination subject disposed inside the annular rotor.

In addition, advantageously a cost-effective multipolar component can have a small proportion of cost-intensive parts despite high demands on the quality of an electric drive with mehrpoligem component. Costly components are e.g. Permanent magnets.

A magnetic pole, in particular the first magnetic pole or the second magnetic pole, is a location in the vicinity of which the magnetic field strength is particularly high. This is advantageously achieved in the first magnetic pole, the first magnetic pole has a permanent magnet. For this purpose, the second magnetic pole advantageously comprises a soft-magnetic material which is magnetically more conductive than the surroundings of the second magnetic pole.

For this purpose, the second magnetic pole can advantageously have high-quality ferromagnetic metals such as iron, cobalt, nickel or ferromagnetic alloys such as iron-silicon alloys (sheet metal, dynamo sheet) or iron-cobalt alloys, for example, in order to increase the magnetic field in the concentrate second magnetic pole. The ferromagnetic metals or alloys can advantageously be inexpensively produced in high quality, e.g. be made by forming and / or punching in the required dimensions. The relative permeability of ferromagnetic materials is significantly greater than 1. Advantageously, iron or certain ferromagnetic iron alloys, such as e.g. Iron-silicon alloys, a relative permeability greater than 300. Thus, advantageously, cost-effective, high quality iron or certain ferro-ferromagnetic iron alloys, e.g. Iron-silicon alloys that focus magnetic field in the second magnetic pole.

Advantageously, the second magnetic pole does not necessarily have to have a winding which generates a magnetic field which is essentially constant over time. Thus, a permanent magnet can advantageously be dispensed with in the case of the second magnetic pole.

The soft magnetic device may conduct a magnetic flux between the first and second magnetic poles. Thus, the second magnetic pole may be made of a soft magnetic material.

Since permanent magnets are generally formed by costly rare-earth magnets, the need for such permanent magnets is halved with almost constant performance, the production costs for a CT according to the invention with such a direct drive are thus significantly lower.

In the computed tomography device according to the invention with the multi-pole components used, the rotor segments can be built and applied particularly simple and without loss of the quality of the drive force and form fit to the curvature of the annular rotor. For this purpose, the multi-pole components are advantageously adapted and arranged at least along their underside to the curvature of the annular rotor. This is possible with conventional direct drives only if elaborate shell magnets were used or already the annular rotor by additional processing, e.g. Milling, a faceted outer surface for bonding cuboid permanent magnet receives, but both are very complex. In the computed tomography device according to the invention can be used in the manufacture of the rotor quite simply an annular carrier with a rounded outer surface on which the rotor segments are attached.

The computed tomography device according to the invention or the direct drive used is very easy to maintain compared to a maintenance-intensive toothed belt drive and also has a long service life without any outlay.

The magnetic return in known direct drives via the annular, generally made of solid steel rotor. In the computed tomography apparatus according to the present invention, the magnetic flux can be made integral with the rotor segment by the presence of the soft magnetic device (e.g., plate, dynamo plate, e.g., a lamellar laminated core). This leads to the advantage that the iron losses in the rotor are reduced compared to the known CT direct drives with solid iron yoke.

The stator segment (s) may be e.g. be arranged in a stationary warehouse. A typical stator segment may have the shape of a ring segment extending in the circumferential direction over an angle of about 20 °, but also be formed smaller or larger. The stator segments can also form a complete ring together. The torque of the drive can be scaled by the number of stator segments as needed.

According to one embodiment of the invention, the multi-pole component has a further first magnetic pole without permanent magnets, which has a surface on the top, wherein in tangential directions of the first magnetic pole is between the other first magnetic pole and the second magnetic pole. Thus, areas without permanent magnets can be made available on both sides of the permanent magnet to save space with little additional space required in addition to the arrangement of magnetic poles.

According to a further embodiment of the invention, each multi-pole component has at least one further first magnetic pole which has a surface on the upper side, and at least one further second magnetic pole which has a surface in a tangential direction adjacent to the first magnetic pole on the The upper side has, wherein the at least one further first magnetic pole has a permanent magnet and the at least one further second magnetic pole has no permanent magnet, and wherein the first and the second magnetic poles are arranged in the tangential direction in an alternating sequence, wherein the soft magnetic device respectively has a recess between the magnetic poles. In this way, the multi-pole component comprises a plurality of magnetic poles in order to minimize the assembly effort in the manufacture or maintenance of the rotor segments. Particularly advantageously, each multi-pole component has a plurality of first magnetic poles and a plurality of second magnetic poles, in particular exactly four first magnetic poles and five second magnetic poles.

According to a further embodiment of the invention, the stator has at least one pair, in particular at least two pairs, of in each case diametrically arranged stator segments. With more than one stator segment, higher torque requirements can be met if required. The stator segments can be dimensioned depending on the application. For example, a typical stator segment can again assume a tangential extension along the circumference of approximately 20 °, but can also be smaller or larger. The stator segments need not all be arranged symmetrically with respect to each other, but it is advantageous for a uniform drive if they are arranged in pairs diametrically opposite each other.

According to a further embodiment of the invention, the annular rotor along its circumference on a plurality, in particular at least six, rotor segments, each having at least one multi-pole component. As a result, a computed tomography device with a high-quality drive and high performance can be provided. The torque-forming active track width, ie the extent of the magnetic poles of the multipolar components or the rotor segments in the axial direction may typically be about 10 to 30 mm. In order to increase the torque, however, along the circumference of the rotor, two or more rotor segments can also be arranged next to one another in the axial direction, and thus the active track width can be doubled or multiplied. The track width may then be corresponding to about 20 to 60 mm or more. Corresponding to the track width of the rotor, the corresponding track width or axial width of the stator segments must also be increased.

Advantageously, the second magnetic pole protrudes from the upper side with respect to the first magnetic pole. Thus, the overhang, which results from the protruding of the second magnetic pole, protect the permanent magnet advantageous, in particular against mechanical action, for example, from contamination in the air gap and the overhang can additionally increase the feed force.

According to a further embodiment of the invention, the multi-pole components are mounted on the annular rotor by gluing.

The invention and further advantageous embodiments according to features of the subclaims are explained in more detail below with reference to schematically illustrated embodiments in the drawing, without thereby limiting the invention to these embodiments. Show it:

1 a view of a multi-pole (3-pin) component of a computed tomography device according to the invention;

2 a view of another multi-pin (9-pin) component of a computed tomography device according to the invention;

3 a view of a stator-rotor assembly of a computed tomography device according to the invention;

4 an annular rotor with rotor segments of a computed tomography device according to the invention;

5 a view of a stator segment of a computed tomography device according to the invention; and

6 a detail of a stator and an opposite rotor segment of a computed tomography device according to the invention.

1 shows an embodiment of a multi-pole (3-pin) component 10 , The multipolar component 10 includes a top 11 , a bottom 12 and a first magnetic pole 13 that a surface 14 on the top 11 has. Furthermore, the multipole component comprises 10 a second magnetic pole 15 that a surface 16 in a tangential direction 22 adjacent to the first magnetic pole 13 on the top 11 has, and a soft magnetic device 17 , this device 17 a recess 18 between the first magnetic pole 13 and the second magnetic pole 15 having. A vertical direction 19 is from the top 11 to the bottom 12 perpendicular to a tangential direction 22 directed. The multipolar component 10 extends in an axial direction 26 , the perpendicular to the tangential directions 22 . 24 and the vertical directions 19 . 25 runs. The tangential directions 22 . 24 run in a sectional plane perpendicular to the axial direction 26 and indicate in the cutting plane in the embodiment according to 1 slightly different directions. This is due to the fact that the surface 14 of the first magnetic pole 13 and the surface 16 of the second magnetic pole 15 not in the cutting plane or not completely parallel to each other.

A first tangential direction 22 runs in the direction of a tangent to the surface 14 of the first magnetic pole 13 in the cutting plane. Another tangential direction 24 runs in a direction of a tangent to the surface 16 of the second magnetic pole 15 , Accordingly, there is a vertical direction 25 from the top 11 to the bottom 12 perpendicular to the first tangential direction 22 directed and a vertical direction 25 from the top 11 to the bottom 12 perpendicular to the other tangential direction 24 , The first magnetic pole 13 has a permanent magnet 20 with a magnetization in one direction 21 on. The second magnetic pole 15 has no permanent magnet. The direction 21 the magnetization of the permanent magnet 20 runs mostly on a line 23 parallel to a vertical direction 19 , The permanent magnet 20 thus has its first axial end on the surface 14 of the first magnetic pole 13 a north pole and on the opposite side at its second axial end of a south pole.

The permanent magnets can, for example, with an adhesive (eg, a 2k structural adhesive) on the soft magnetic device 17 be glued. The second magnetic pole 15 may be opposite to the first magnetic pole 13 from the top 11 protrude to minimize its wear. In 1 You can see that well, that a corner of the permanent magnet 20 opposite one in the tangential direction 22 adjacent corner of the second magnetic pole 15 is reset. The recess 18 runs along the direction 21 the magnetization. The recess is in the embodiment of 1 empty and thus has a low relative permeability, which is less than 2. The soft magnetic device 17 consists of in the axial direction 26 layered sheets of a ferromagnetic metal and has the second magnetic pole 15 formed from the sheets on.

The multipolar component 10 has another second magnetic pole 15 without permanent magnets on, which has a surface on top 11 possesses, being in tangential directions 22 . 24 the first magnetic pole 13 between the other second magnetic pole 15 and the second magnetic pole 15 located.

The bottom 12 and / or the entire multi-pole component can advantageously be designed such that it is adapted to the annular rotor on which it is applied, so in particular slightly curved. The components can be attached to the ring-shaped rotor in a particularly simple and effective manner, for example by gluing. In addition, because of the adhesive gap between the rotor and the multi-pole component or rotor segment, for example, small nubs may be arranged on the underside.

In the 2 is another multi-pole, in this case 9-pin component 10 shown which four first magnetic poles 13 and five second magnetic poles 15 having. The first magnetic poles 13 in turn are made of permanent magnets 20 formed and alternate in their sequence with the second magnetic poles 15 which part of the soft magnetic device 17 are starting from, starting with a second magnetic pole 15 , To illustrate the tangential design of the multipole component and the curved bottom 12 for better adaptation to the rotor 2 is the rotor 2 also shown indicated. A rotor segment 4 is formed by one or more mutually joined in the circumferential direction of the rotor multi-pole components, and it is also possible, for example, for a larger track width and thus a higher torque, two or more multi-pole components 10 in the axial direction 26 to arrange next to each other.

3 shows a computed tomography device according to the invention or an embodiment of the arrangement of the stator segments of such a device. The computed tomography device has a stator 1 which is generally arranged statically, and an annular rotor 2 which is generally rotatable with respect to the stator 1 is arranged and about a rotation axis 5 can be rotated. The stator has at least two stator segments arranged diametrically opposite one another 3 in the case shown, for example, two pairs of diametrically opposed stator segments 3 on, which may be arranged for example in a stationary support. Between the stator 1 and the rotor 2 there is an air gap 30 , The annular rotor 2 is generally located inside the stator. Each stator segment 3 has at least one current-carrying winding. In the 5 is the arrangement of a stator segment 3 relative to the annular rotor 2 shown again by way of example, with a laminated core 6 , a headband 7 and a winding 8th are indicated.

In the 4 is a rotor 2 a computer tomography device according to the invention shown in more detail, which on its outer circumference a plurality of rotor segments 4 having. Each of the rotor segments has at least one multi-pole component according to the above description. In the case shown, each rotor segment has exactly one multi-pole component, wherein a multi-pole component has exactly 9 magnetic poles, as in FIG 2 shown. Of the 9 magnetic poles, four are each formed by permanent magnets and five by magnetic poles without permanent magnets (soft magnetic poles). By along the circumference uninterruptible arrangement of multi-pole components, the total number of poles can reduce, since the soft magnetic pole of a first component and the soft magnetic pole of a directly adjacent second component forms a single pole. For example, 25 rotor segments of the rotor can be arranged without interruption along the circumference of the rotor in order to realize a 200-pole motor (2p = 100). Further, other training with more or less rotor segments and more or less poles are possible at any time.

In the 5 a section of a rotor-stator assembly of a computed tomography device according to the invention is shown, wherein the rotor is arranged annularly within the stator. The stator has two diametrically opposed stator segments, of which only one stator segment is shown in the drawing. The stator segment extends along the circumference over a sector of, for example, about 20 °, but may also be formed larger or smaller. The second stator segment corresponds in size and extent approximately to the first stator segment and is arranged along the circumference diametrically thereto. If required, an arrangement of more than two stator segments, for example four or six stator segments, can be provided for rapid acceleration and faster achievement of the final speed of the rotor, wherein these are preferably arranged in pairs diametrically opposite each other. It can also be a full occupancy of the stator can be provided with stator segments, ie a stator assembly with the geometrically maximum possible number of stator segments on the circumference.

6 shows for further clarification, the relative position between the stator 3 and multipole component 10 a rotor segment, of which only sections are shown. Between the stator segment 3 and the rotor segment is an air gap 30 present, which allows the magnetic interaction between stator segment and rotor segment. A typical structure of a stator segment 3 is shown in sections. Thus, the stator segment has a base body 31 with at least one, generally a plurality of teeth 28 on. Between the teeth 28 there are grooves 29 , On the teeth 28 are each current-carrying windings 27 wound. The windings 27 For example, they can be designed as tooth coil windings. In an operation of the computed tomography device, the windings can 27 that are in different grooves 29 are energized, for example, with alternating currents of different phases of a three-phase AC power source, such as an inverter, to generate a tangential in the tangential direction along the stator segment changing magnetic field that causes a relative rotational movement of the rotor in the tangential direction.

In one embodiment, the rotor segments are potted, so that the respective remaining between the permanent magnet and the second magnetic pole recess 18 is filled. The potting can consist of a PU potting compound.

In one embodiment, the permanent magnets of the rotor segment are divided along the circumference (in the tangential direction) at least twice, in order to reduce the eddy current losses in the permanent magnets and thus their thermal load.

The invention can be briefly summarized in the following way: For a particularly powerful, high-quality and cost-effective drive has a computed tomography device a stator and a rotatable relative thereto annular rotor, the computed tomography device has a high-pole permanent-magnet electric direct drive to generate the rotational movement of the rotor, the stator has as active components at least one stator segment, in particular two stator segments arranged diametrically opposite one another, with current-carrying windings and the rotor has at least one rotor segment, in particular at least six rotor segments, each having at least one multi-pole component, wherein the current-carrying windings with the respective multi-pole component via a Air gap between the stator and rotor magnetically cooperate, and wherein each multipolar device is formed such that it has an upper side and a lower side e, a first magnetic pole having a surface on the upper side, a second magnetic pole having a surface in a tangential direction adjacent to the first magnetic pole on the upper side, and a soft magnetic device having a recess between the first magnetic pole Pol and the second magnetic pole, wherein a vertical direction is directed from the top to the bottom perpendicular to a tangential direction, and wherein the first magnetic pole having a permanent magnet with a magnetization in one direction and the second magnetic pole having no permanent magnet.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 14175245 [0004]

Claims (9)

Computer tomography device with a stator ( 1 ) and a rotatable annular rotor ( 2 ), wherein the computed tomography device is a high-pole permanent-magnet electric direct drive for generating the rotational movement of the rotor ( 2 ), wherein the stator ( 1 ) as active component at least one stator segment ( 3 ) with current-carrying windings ( 8th . 27 ) and the rotor ( 2 ) at least one rotor segment ( 4 ) each having at least one multi-pole component ( 10 ), wherein the current-carrying windings ( 8th . 27 ) with the respective multi-pole component ( 10 ) via an air gap ( 30 ) between stator ( 1 ) and rotor ( 2 ) interact magnetically, and wherein each multipole component ( 10 ) is designed such that - a top side ( 11 ) and a bottom ( 12 ), - a first magnetic pole ( 13 ), which has a surface ( 14 ) on the top ( 11 ), - a second magnetic pole ( 15 ), which has a surface ( 16 ) in a tangential direction ( 22 . 24 ) adjacent to the first magnetic pole ( 13 ) on the top ( 11 ), and - a soft magnetic device ( 17 ), which has a recess ( 18 ) between the first magnetic pole ( 13 ) and the second magnetic pole ( 15 ), wherein - a vertical direction ( 19 . 25 ) from the top ( 11 ) to the bottom ( 12 ) perpendicular to a tangential direction ( 22 . 24 ), and - wherein the first magnetic pole ( 13 ) a permanent magnet ( 20 ) with a magnetization in one direction ( 21 ) and the second magnetic pole ( 15 ) have no permanent magnet. Computed tomography device according to claim 1, wherein the multipolar component ( 10 ) a further first magnetic pole ( 13 ) without permanent magnets having a surface ( 14 ) on the top ( 11 ), wherein in tangential directions the first magnetic pole ( 13 ) between the further first magnetic pole ( 13 ) and the second magnetic pole ( 15 ) is located. Computed tomography device according to claim 1 or 2, wherein each multi-pole component ( 10 ) at least one further first magnetic pole ( 13 ), which has a surface ( 14 ) on the top ( 11 ), and at least one further second magnetic pole ( 15 ), which has a surface ( 16 ) in a tangential direction ( 22 . 24 ) adjacent to the first magnetic pole ( 13 ) on the top ( 11 ), wherein the at least one further first magnetic pole ( 13 ) a permanent magnet ( 20 ) and the at least one further second magnetic pole ( 15 ) has no permanent magnet, and wherein the first and the second magnetic poles in the tangential direction ( 22 . 24 ) are arranged in alternating sequence, wherein the soft magnetic device each have a recess ( 18 ) between the magnetic poles. Computed tomography device according to claim 3, wherein each multipole component ( 10 ) a plurality of first magnetic poles ( 13 ) and a plurality of second magnetic poles ( 15 ), in particular exactly four first magnetic poles ( 13 ) and five second magnetic poles ( 15 ), having. Computed tomography device according to one of the preceding claims, wherein the stator ( 1 ) at least one pair, in particular two pairs, of in each case diametrically arranged stator segments (US Pat. 3 ) having. Computed tomography device according to one of the preceding claims, wherein the annular rotor ( 2 ) along its circumference a plurality, in particular at least six, rotor segments ( 4 ) each having at least one multi-pole component ( 10 ) having. Computed tomography device according to one of the preceding claims, wherein the second magnetic pole ( 15 ) with respect to the first magnetic pole ( 13 ) from the top ( 11 ) stands out. Computed tomography device according to one of the preceding claims, wherein the multipolar components ( 10 ) along its underside to the curvature of the annular rotor ( 2 ) are arranged adjusted. Computed tomography device according to one of the preceding claims, wherein the multipolar components ( 10 ) on the annular rotor ( 2 ) are attached by gluing or casting.

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