DE102014214511A1 - Device with a gantry - Google Patents

Abstract

The invention relates to a device (2), in particular a computer tomograph (2), comprising a gantry (4) with a stator (6) and with a rotor (10) which rotates about an axis of rotation (Fig. 40) is rotatable, wherein the rotor (10) has an annular support (12), wherein the rotor (10) by means of a number of magnet units (20) in a radial direction (30) and in the axial direction (26) magnetically on Stator (6) is mounted and wherein the carrier (12) has a bearing surface (28) whose surface normal to the radial direction (30) and against the axial direction (26) is tilted and at least one of the magnet units (20) is associated in that this magnet unit (20) contributes to the mounting of the carrier (12) both in the radial direction (30) and in the axial direction (26).

Description

The invention relates to a device, in particular a computer tomograph, comprising a gantry with a stator and with a rotor which is rotatable about an axis of rotation extending in an axial direction, the rotor having an annular support and wherein the rotor by means of a number of Magnetic units is mounted in a radial direction and in the axial direction magnetically on the stator.

Current computer tomographs typically include a gantry with a stator and a rotor rotatable relative to the stator. The rotor usually has a mass in the range 800 kg to 1600 kg and rotates in operation at a rotational speed of up to 240 U / min. As a result, the requirements for the storage of the rotor on the stator are quite high, so that a corresponding classical mechanical bearing is complicated and expensive to manufacture.

An alternative to the classical mechanical storage is a magnetic storage and in the document DE 10 201 015 061 A1 is described a computed tomography or computed tomography device, in which the rotor of a gantry is magnetically mounted on the stator of the gantry.

Proceeding from this, the object of the invention is to provide a device in which the rotor of a gantry is advantageously mounted on the stator of the gantry.

This object is achieved by a device having the features of claim 1. The dependent claims include in part advantageous and in part self-inventive developments of this invention.

A corresponding device is in particular a computer tomograph and comprises a gantry with a stator and with a rotor. The rotor in turn has an annular support and is rotatable about an axis of rotation extending in an axial direction, wherein the rotor is magnetically supported on the stator by means of a number of magnet units in a radial direction and in an axial direction. For this purpose, the carrier has a bearing surface, the surface normal is tilted against the radial direction and against the axial direction and the at least one of the magnet units is assigned, so that the magnet unit contributes to the support of the carrier both in the radial direction and in the axial direction.

Thus, while the magnetic units contribute in a magnetic bearing according to the prior art either for storage in the radial direction or for storage in the axial direction and accordingly with these a force effect is achieved either in the radial direction or in the axial direction, carries that magnet unit of the presented here Device for magnetic bearing both in the axial direction and in the radial direction and, accordingly, with this magnet unit also a force in the radial direction on the one hand and in the axial direction on the other hand realized.

On the other hand, the orientation of the surface normal of the bearing surface relative to the radial direction on the one hand and the axial direction on the other hand determines the ratio of the forces acting in the axial direction or in the radial direction, the sum of the two directional components corresponding to the total force action. The orientation of the surface normal and thus the ratio of the directional components is further constructive, so given by the design of the support of the rotor, and is typically adapted to the expected occurring bearing forces.

Thus, since the axial bearing and the radial bearing is no longer realized by separate magnet units and thus no longer by quasi two separate magnetic bearings, the number of required components, in particular the number of required magnet units, this is one or more permanent magnets and / or reduced by one or more electromagnets, in the device presented here compared to the prior art. This not only saves costs, moreover, less space is required for the components of the magnetic bearing, so that as a result, a larger work space can be realized, so a larger diameter patient.

In an advantageous embodiment, two flanking bearing surfaces are given on the carrier, the surface normal is tilted in each case against the radial direction and against the axial direction and each bearing surface is assigned at least one magnet unit, each of these magnet units for supporting the carrier both in the radial direction and in axial Direction contributes. The structure is also preferably symmetrical and accordingly, a substantially identical ratio of the directional components for the respective force effect is given for the two flanking magnet units and the associated bearing surfaces. Thus, then the angle between the respective surface normal and the axial direction and the radial direction is substantially identical.

With the help of such a symmetrically constructed magnetic bearing can be a particularly smooth running of the rotor realize, since in this case, inter alia, typically no tilting moment occurs. The positioning of the magnet units in the region of the flanks of the carrier also requires a more favorable accessibility of these modules, which facilitates both the production and a maintenance or repair. It is also a very stable and low-vibration construction in which due to the predetermined force application points favorable leverage ratios are given. Moreover, the location of the magnet units is also favorable in terms of electromagnetic compatibility, among other things because the magnet units are positioned relatively far from electronic components which are often positioned in the rotor and secured to the carrier. It should be remembered that the carrier typically represents a kind of basic framework to which, for example, in the case of a computer tomograph, an X-ray source, an X-ray detector and various electronic components, for example an electronic control system, are attached.

Furthermore, the magnet units are preferably arranged in pairs, so that in each case two magnet units are arranged spaced from each other in the axial direction at the same angular position. In addition, the magnet units are preferably arranged with respect to the distribution about the rotation axis in the manner of a common division, so that there is a uniform and symmetrical distribution of the magnet units, whereby the realization of a stable magnetic bearing is simplified.

In the simplest case, only three pairs of magnet units are arranged with respect to the distribution about the axis of rotation in the manner of a common division, so that overlooked over the circumference of the rotor three attack points or more precisely three attack areas are given. In this case, the number of components required for the magnetic bearing is particularly low.

It is also advantageous if the magnet units are designed as controllable magnet units and in particular as actively controlled electromagnets. In this way, a calibration of the magnetic bearing can be carried out, inter alia, after the completion of the device and / or after maintenance work. In addition, however, a permanent active control preferably takes place during operation of the device, ie during the rotation of the rotor, in which typically the relative position and the relative position of the rotor relative to the stator are detected by measurement and in the case of the measurement data acquired in this way Magnetic units, ie in particular the electromagnets, takes place, so that, inter alia, vibrations are suppressed.

In this case, further preferably serve the controllable magnet units, so the electromagnets, only for fine tuning of the magnetic bearing and to specify a basic magnetic field passive magnet units, so permanent magnets are used. In this case, so then integrated in the structure passive permanent magnets take over the storage of the base load and the Grundkippmoments and the electromagnets are then used to compensate for minor fluctuations during rotation of the rotor. Alternatively, the use of passive magnet units is dispensed with, in which case also the bearing of the basic weight load and the basic overturning moment is taken over by the activatable magnet units. Of course, these have to be adapted with regard to their dimensioning.

In addition, the device advantageously has at least one fishing camp, which takes over the storage in the event of a disturbance of the magnetic storage quasi provisionally. This is typically designed as a simple mechanical roller bearing. In normal operation, however, the safety bearing does not contribute to the storage.

According to an advantageous embodiment, the carrier is further constructed in several parts and has a base and at least one bearing ring, which flanks the base in the axial direction and forms a bearing surface. In this way, for example, different parts of the carrier made of different materials.

The bearing ring is advantageously constructed of sheets, which are lined up in the axial direction and accordingly form a kind of laminated core. The sheets are formed here, for example, as ring segments or as rings. In addition, the sheets are separated by an insulating material, such as a resin layer or a paint coating, from each other, so that can be reduced by means of this structure eddy current losses. In an advantageous embodiment of the bearing ring is designed as a sheet-metal laminate and is bolted or glued as a prefabricated component with the base.

It is also advantageous if the bearing ring is made of a ferromagnetic material, ie in particular of ferromagnetic sheets, whereas the base is preferably at least largely made of a non-ferromagnetic material, such as aluminum or other light metals, non-magnetic stainless steels, plastics or composite materials ( CFK, GFK, ...). In this case, the magnetic interaction with the magnet units is on the bearing ring limited and by using the non-ferromagnetic material, in particular aluminum, magnetic emissions can be minimized.

Are two flanking bearing surfaces provided for the carrier, it is expedient to provide two bearing rings, which then flank the base on both sides in the axial direction and are constructed substantially the same.

Embodiments of the invention will be explained in more detail with reference to a schematic drawing. Show:

1 in a first sectional view of a computer tomograph with a gantry,

2 in a second sectional view with a sectional plane perpendicular to the sectional plane of the first sectional view of the gantry and

3 in the second sectional view, an alternative embodiment of the gantry.

Corresponding parts are provided in all figures with the same reference numerals.

An example described below and in 1 sketched device is as a computer tomograph 2 trained and designed for X-ray imaging according to a known principle for use in the medical field.

It includes a gantry 4 with a stator 6 standing at a rack 8th (English: gantryframe) is attached, and with a rotor 10 , which is magnetic on the stator 6 is stored and as a carrier 12 (English: drum) for various components of the computer tomograph 2 serves. Are indicated in the representation of 1 an example of an x-ray tube 14 and an x-ray detector 16 on the carrier 12 are fixed and in operation with the carrier 12 and thus with the rotor 10 around a patient table 18 rotate. Other components or assemblies, such as controllers, are not explicitly illustrated, but are also typically on the carrier 12 attached and become during the rotation of the rotor 10 carried.

The magnetic bearing of the rotor 10 at the stator 6 is done with the help of magnet units 20 , wherein passive magnet units, ie permanent magnets 22 , are used to generate a basic magnetic field that carries the base load in the magnetic storage, and actively driven magnet units, ie electromagnets 24 , are used to make a permanent fine adjustment.

For this purpose, there is also a permanent sensory monitoring of the magnetic bearing, on the basis of which an adapted control of the electromagnets is carried out, so that, for example, smaller imbalances are compensated and a low-vibration rotation of the rotor 10 is possible.

In the exemplary embodiment, the sensory monitoring of the magnetic bearing is carried out by a current or voltage measurement to the electromagnet itself, on the basis of which then on the distance between the respective electromagnet and the rotor 10 is closed back. Alternatively, separate sensors, such as Hall sensors, for a distance measurement can be used, which are then positioned, for example in the field of electromagnets.

The control of the electromagnets takes place in the embodiment also starting from a stored base line or a stored base control signal in response to the sensor data, so that in the context of active control only small adjustments of the base control signal must be made, through which smaller time-varying fluctuations during rotation of the rotor 10 be compensated. The baseline or base control signal for the solenoids is typically determined during calibration following completion of the computed tomography 2 and if necessary after maintenance or repairs is made.

For this calibration, the computer tomograph 2 a non-illustrated special separate electronic unit, which is used only for the calibration and the determination of the base line and the base control signal. During the calibration, the rotor becomes 10 in rotation and during which the relative position of the rotor 10 and its relative orientation sensory monitored and evaluated. The sensory monitoring of storage is preferably carried out with the same sensors as the sensory monitoring during normal operation of the computer tomograph 2 , So here in the embodiment by a voltage or current monitoring of the electromagnets 24 ,

The magnet units 20 are how out 2 shows, arranged in pairs in the exemplary embodiment, so that each two magnet units 20 in an axial direction 26 spaced apart at the same angular position on the stator 6 are attached. Three pairs are from electromagnets 24 formed, these pairs in the manner of a common division over the circumference of the stator 6 distributed and thus positioned offset by 120 ° to each other.

Each magnet unit 20 is still a storage area 28 assigned their surface normal against the axial direction 26 and against a radial direction 30 is tilted, so every magnet unit 20 both for storage in the axial direction 26 as well as radial direction 30 contributes. So that means that the force effect of the magnet units 20 each a directional component in the axial direction 26 as well as a directional component in the radial direction 30 or rather can be decomposed into corresponding directional components. The ratio of the directional components depends on the angle between the surface normal and the axial direction 26 or the radial direction 30 from and is given according to the expected occurring bearing forces constructive. In the exemplary embodiment, an angle of 45 ° was chosen.

To the number of used magnet units 20 As low as possible, the magnetic bearing is not based on the interaction between two magnet units 20 but on the interaction between a magnet unit 20 and a storage area 28 , which is formed by a component made of a ferromagnetic material. In the exemplary embodiment, all magnet units are now 20 at the stator 6 attached and the rotor 10 is partially made of a ferromagnetic material.

As in 2 implied, is the carrier 12 designed in several parts and has a base made of aluminum 32 as well as two bearing rings 34 on top of the storage areas 28 for the magnet units 20 form. This shows the base 32 on their flanks annular recesses with triangular profile, in which the bearing rings 34 are inserted and glued. Alternatively or additionally, an attachment of the bearing rings 34 by means of screw connections.

Every bearing ring 34 is here designed as a sheet-metal laminate and made of several ferromagnetic sheets 36 made, which are glued together, being between the individual sheets 36 a thin insulating layer, not shown, is given. The individual sheets 36 are again designed annular, wherein the individual rings have an identical inner diameter but different outer diameter.

To avoid major damage to the gantry 4 in the event of a fault in the magnetic bearing, additional mechanical safety bearings 38 at the stator 6 attached, which is the bearing of the rotor 10 if necessary take over provisionally. These are designed as simple rolling bearings. The fishing camp 38 are also arranged in pairs and act in the area of the bearing rings 34 so that also by the catch camp 38 a storage in the axial direction 26 and in the radial direction 30 occurs when the magnetic bearing is disturbed.

A modified version of the gantry 4 of the computer tomograph 2 is in 3 shown. This design differs in the number and position of the permanent magnets 22 and the fishing camp 38 , In contrast to the embodiment according to 1 this embodiment has only three pairs of backup bearings 38 on, wherein one of these pairs the position of the pair of permanent magnets 22 out 1 occupies. The pair of permanent magnets 22 out 1 again it is replaced by a single permanent magnet 22 , which only in the radial direction 30 acts and in the axial direction 26 seen approximately midway between the flanks of the wearer 12 at the stator 6 is attached. In addition to this, the carrier points 12 in the embodiment according to 3 an additional bearing ring 34 on, which is also designed as a sheet-metal laminate, but has a rectangular cross-section and the permanent magnet 22 opposite to the carrier 12 in a complementary bulge in the base 32 of the carrier 12 is positioned.

Through the magnet units 20 on the one hand and the Fanglanger 38 On the other hand, a certain space requirement is now given, which is based on the dimensions of the stator 6 effect. This has particular impact on the space requirement in the radial direction 30 whereas in the circumferential direction, depending on the number of magnet units used 20 and the number of used bearings 38 inevitably remains unused space, which can then be used for other components, such as sensors, without this additional space requirements is generated. Accordingly, preferably as many components and assemblies as possible, and in particular all components and assemblies required for the magnetic bearing, are placed in these regions, in order to realize as compact a structure as possible and a highly integrated magnetic bearing for the computer tomograph 2 implement. This applies in an analogous manner to the rotor 10 or on the carrier 12 to.

For example, the components for an electric rotary drive, with the help of the rotor 10 around a rotation axis 40 is rotatable, integrated into these areas, so as to keep the structure as compact as possible. Also integrated in corresponding room areas will continue to be an electrical interface to the slip ring 42 , which is for power transmission and / or data transmission between the stator 6 and the rotor 10 serves. Furthermore, an integration of a sensor arrangement is provided, with the aid of which the rotational position and / or the rotational frequency of the rotor 10 metrologically recorded.

The invention is not limited to the embodiment described above. Rather, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the exemplary embodiment can also be combined with each other in other ways, without departing from the subject matter of the invention.

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

• DE 10201015061 A1 [0003]

Claims (11)

Contraption ( 2 ), in particular a computer tomograph ( 2 ), comprising a gantry ( 4 ) with a stator ( 6 ) and with a rotor ( 10 ) extending in an axial direction ( 26 ) extending axis of rotation ( 40 ) is rotatable, wherein the rotor ( 10 ) an annular support ( 12 ) and wherein the rotor ( 10 ) by means of a number of magnet units ( 20 ) in a radial direction ( 30 ) as well as in the axial direction ( 26 ) magnetically on the stator ( 6 ), characterized in that the carrier ( 12 ) a storage area ( 28 ) whose surface normal against the radial direction ( 30 ) as well as against the axial direction ( 26 ) is tilted and the at least one of the magnet units ( 20 ), so that this magnet unit ( 20 ) for storage of the carrier ( 12 ) both in the radial direction ( 30 ) as well as in the axial direction ( 26 ) contributes. Contraption ( 2 ) according to claim 1, characterized in that on the carrier ( 12 ) two flanking storage areas ( 28 ) whose surface normal in each case against the radial direction ( 30 ) as well as against the axial direction ( 26 ) and that each storage area ( 28 ) at least one of the magnet units ( 20 ), so that each of these magnet units ( 20 ) for storage of the carrier ( 12 ) both in the radial direction ( 30 ) as well as in the axial direction ( 26 ) contributes. Contraption ( 2 ) according to claim 1 or 2, characterized in that the magnet units ( 20 ) are arranged in pairs, so that two magnet units ( 20 ) in the axial direction ( 26 ) spaced from each other at the same angular position are arranged. Contraption ( 2 ) according to one of claims 1 to 3, characterized in that the magnet units ( 20 ) with respect to the distribution about the axis of rotation ( 40 ) are arranged in the manner of a common division. Contraption ( 2 ) according to claims 1 and 3, characterized in that three pairs of magnet units ( 20 ) with respect to the distribution about the axis of rotation ( 40 ) are arranged in the manner of a common division. Contraption ( 2 ) according to one of claims 1 to 5, characterized in that a plurality of magnet units ( 20 ) as controllable magnet units ( 24 ) are formed. Contraption ( 2 ) according to one of claims 1 to 6, characterized in that the carrier ( 12 ) is constructed in several parts with a base ( 32 ) and at least one bearing ring ( 34 ), which is the basis ( 32 ) in the axial direction ( 26 flanked and the storage area ( 28 ) trains. Contraption ( 2 ) according to claim 7, characterized in that the at least one bearing ring ( 34 ) of sheets ( 36 ) is constructed in the axial direction ( 26 ) are strung together. Contraption ( 2 ) according to claim 8, characterized in that the at least one bearing ring ( 34 ) is designed as a sheet-metal laminate. Contraption ( 2 ) according to one of claims 7 to 9, characterized in that the at least one bearing ring ( 34 ) is made of a ferromagnetic material. Contraption ( 2 ) according to one of claims 7 to 10, characterized in that the base ( 32 ) is made of aluminum.

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