DE102015220101A1 - Rotary anode bearing assembly and rotary anode for an X-ray tube - Google Patents

Abstract

The invention relates to a rotary anode bearing assembly for an X-ray tube comprising: - a rotor shaft extending along a longitudinal axis from a first axial end to a second axial end and rotatably supported about the longitudinal axis; wherein - the rotor shaft has an anode receptacle in the region of the first axial end; - With a first rolling bearing in the region of the first axial end and a second rolling bearing in the region of the second axial end; wherein - the rolling bearings have at least one bearing inner ring, which is applied to the rotor shaft or is formed by, and at least one bearing outer ring; - With rolling elements between the at least one bearing inner ring and the at least one bearing outer ring of the rolling bearing. The invention is characterized in that at least one of the rolling bearings is designed as a multi-row roller bearing or as a roller bearing.

Description

The present invention relates to a rotary anode bearing assembly for an X-ray tube and a rotary anode with a corresponding rotary anode bearing assembly according to the preambles of the independent claims.

Rotary anodes in x-ray tubes - for example, for a computed tomography (CT) scanner - require bearing assemblies that control the high rotational speeds of the rotary anode about the longitudinal axis of its own rotor shaft. These speeds are for example up to 9000 revolutions per minute or more. In addition, when the rotary anode is mounted in an X-ray tube of a CT scanner, the rotary anodes must withstand the significant stresses of rotating the X-ray tube about the scanner axis, with 40 times the gravitational acceleration due to the X-ray tube orbit about the scanner axis on the X-ray tube so that the rotary anode bearing arrangement can act.

Conventional Drehanodenlageranordnungen whose structure, for example, as in 1 shown designed, these requirements can no longer meet satisfactorily. Especially with a larger weight of the so-called target, so the anode material on the rotary anode, the allowable load capacity of known rotary anode storage arrangements is exceeded.

For example, results in the in the 1 illustrated embodiment increased wear in the raceways of the two bearings 1 . 2 at the two axial ends 4 . 5 the rotor shaft 3 , And operating in a wider speed range, there is a risk of bearing excitation or the excitation of the system and an undesirable noise.

The present invention has for its object to provide a rotary anode bearing assembly and a rotary anode for an X-ray tube, in particular for a CT scanner, which are designed with respect to the said prior art improved in their capacity, higher speeds at a rotation of the rotor shaft over its longitudinal axis and allow in particular the entire rotary anode on the scanner axis of rotation and allow advantages in the adjustment of the excitation frequencies, and advantageously reduce the operating noise.

The object of the invention is achieved by a rotary anode bearing arrangement having the features of claim 1 and a rotary anode having the features of claim 17. In the dependent claims advantageous and particularly expedient embodiments of the invention are given.

An inventive rotary anode bearing arrangement for an X-ray tube, in particular in a CT scanner, has a rotor shaft which extends along a longitudinal axis from a first axial end to a second axial end and is rotatably mounted over the longitudinal axis. The rotor shaft has an anode receptacle in the region of the first axial end and is mounted by means of a first rolling bearing in the region of the first axial end and a second rolling bearing in the region of the second axial end.

At the anode receptacle, the actual anode, that is, the anode material, for example, on an anode plate, are connected. During operation of the x-ray tube, this anode material is bombarded with electrons from the anode associated cathode, whereby the desired x-ray radiation is generated. The x-ray tube usually has a vacuum container, for example of glass, in which the cathode and the rotary anode are positioned opposite one another. Accordingly, the rotor of the rotary anode is also positioned within the vacuum vessel and is typically circulated by a stator positioned outside the vacuum vessel surrounding the rotor so that the anode material rotates under the electron beam.

According to the invention, the roller bearings have at least one bearing inner ring, which is applied to the rotor shaft or is formed by them. The rolling bearings also have at least one bearing outer ring, for example, a common bearing outer ring. In particular, however, each bearing has at least one (own) bearing outer ring. Thus, it is possible that a single bearing inner ring, for example formed by the rotor shaft, facing a plurality of bearing outer rings or are enclosed by them.

Between the at least one bearing inner ring and the bearing outer rings rolling elements of the rolling bearings are introduced. In this case, the design or the choice of material of the at least one bearing inner ring, the rolling elements and the bearing outer rings advantageously such that they are in electrically conductive connection with each other, so that an electrical voltage can be transmitted via the bearing assembly on the rotary anode or constructed between the cathode and the rotary anode can be.

According to the invention, at least one of the rolling bearings is now designed as a multi-row rolling bearing or as a roller bearing.

A multi-row roller bearing is characterized by a plurality of rows of rolling elements positioned one behind the other in the direction of the longitudinal axis, which are each arranged distributed within a row over the circumference of the bearing. A roller bearing is characterized by a line contact, in contrast to a point contact as in a ball bearing, between the bearing inner ring and each rolling element on one side and the rolling element and the bearing outer ring on the other side.

All alternative measures according to the invention, which can also be combined with one another, considerably increase the load-bearing capacity of the rotary anode bearing arrangement. In particular, the load capacity and the life can be increased, and also the running noise can be reduced because the bearing clearance can be comparatively reduced. Thus, different excitation frequencies of the bearing can be set specifically.

Particularly advantageously, the at least one multi-row roller bearing, which in the present case is understood to mean a double-row roller bearing, but the invention is not limited thereto, a bearing outer ring divided in the direction of the longitudinal axis, with a plurality of axial sections by means of a removable spacer in the axial direction are supported against each other. In particular, two axial sections are provided per rolling bearing, which are supported by a single interposed spacer in the axial direction against each other.

The spacing element may, for example, be designed as a ring closed over the circumference of the longitudinal axis, but advantageously designed as an interrupted ring over the circumference of the longitudinal axis, for example as a so-called C-ring. The name of the C-ring refers to its shape viewed in the direction of the longitudinal axis.

The one or more bearing outer rings is / are advantageously made closed over its circumference.

According to an advantageous embodiment, the spacer element is elastically deformable, so that it can be slid over the rotor shaft in the radial direction and mounted in at least one already applied to the rotor shaft bearing outer ring or axial sections of a bearing outer ring, so to speak clipped.

It is favorable if the spacer element is made of a different material than the bearing outer race (s). For example, the at least one bearing outer ring and in particular the at least one bearing inner ring made of a hardenable material, that is made of a tempered steel, whereas the material of the spacer element does not have to be curable and may have a correspondingly low carbon content, for example, of 0.2 wt. % Or less. However, this does not exclude that, according to an alternative embodiment, the spacer element is made of a hardenable material, in particular tempered steel.

According to an advantageous embodiment of the invention, the spacer has a larger coefficient of thermal expansion than the at least one bearing outer ring and in particular as the at least one bearing inner ring. As a result, a particularly favorable temperature behavior of the rotary anode bearing arrangement can be achieved, in particular with regard to the variation in the bearing clearance during the transition from the cold state into the warm state. According to one embodiment, the spacer element has a thermal expansion coefficient of at least 14 × 10 ^-6 1 / K, advantageously 15 × 10 ^-6 1 / K or 16 × 10 ^-6 1 / K. The bearing outer ring or rings and in particular the at least one bearing inner ring advantageously has a maximum thermal expansion coefficient of <14 × 10 ^-6 1 / K and in particular of 13 × 10 ^-6 1 / K or 12 × 10 ^-6 1 / K or less.

According to one embodiment, the at least one bearing inner ring and the at least one bearing outer rings are made of the same material. For example, for the bearing inner ring and the entire rotor shaft AISI M62 into consideration, as well as for the bearing or the outer rings. However, the components mentioned can also be made of different materials.

The spacer element is made of aluminum or an aluminum alloy according to one embodiment.

According to one embodiment of the invention, the spacer element, which has at least one bearing inner ring and / or the at least one bearing outer ring, is / is made of a cobalt-free material, that is to say a material which has less than 0.3 wt.% Cobalt.

The at least one bearing outer ring of the first rolling bearing and the at least one bearing outer ring of the second rolling bearing advantageously have a free distance from one another in the direction of the longitudinal axis of the rotor shaft, that is, a distance in which no spacer element or the like is provided.

In a multi-row roller bearing provided according to the invention, this can be used as an employee Bearings be designed with an X-arrangement or with an O-arrangement. However, other arrangements are also possible, for example a tandem arrangement.

If a roller bearing is designed as a roller bearing, then this may be provided as a cylindrical roller bearing, but comes in accordance with an alternative embodiment, a tapered roller bearing or a needle bearing into consideration. Also, a corresponding roller bearing can be provided either with the axis of rotation of the rollers parallel to the longitudinal axis of the rotor shaft or hired for this purpose, that is enclosing an angle.

According to one embodiment of the invention, the rotary anode bearing assembly is provided as a bearing assembly without thrust bearing or with a one-sided thrust bearing, that is support only in one direction of the longitudinal axis. According to an advantageous embodiment, the first rolling bearing and the second rolling bearing are each designed as a multi-row roller bearings, in particular double-row roller bearings. As a result, a particularly large load rating can be achieved. An alternative embodiment provides that the first rolling bearing is designed as a multi-row, in particular double-row roller bearing, the second rolling bearing, however, as a single-row roller bearing. In both embodiments, the use of ball bearings as rolling bearings is considered, but not mandatory. The arrangement of the double-row roller bearing in the region of the first axial end of the rotor shaft is favorable, since here the comparatively larger radial forces occur when the anode is connected at this axial end.

According to an alternative embodiment, instead of the double-row roller bearing at the first axial end, a roller bearing is provided at the first axial end, combined with a single-row roller bearing, in particular ball bearing, at the second axial end of the rotor shaft.

A rotary anode according to the invention has a rotor and a stator circumferentially surrounding the rotor at a distance, wherein the rotor and the stator are in electromagnetic interaction with each other, such that the rotor is displaceable by applying an electromagnetic field by means of the stator in circulation over the longitudinal axis , The rotor is cup-shaped and encloses the rotor shaft, is connected to the first axial end of the rotor shaft and thereby stored on the rotor shaft flying.

There is further provided an anode plate, which is also connected in the region of the first axial end to the rotor shaft and / or on the rotor and cantilevered and is provided with an anode material.

The rotor shaft of the rotary anode is mounted by means of the illustrated rotary anode bearing arrangement according to the invention in a stationary housing which is enclosed by the stator.

Both the rotor and the stationary housing, the latter at least partially, are advantageously located within the vacuum vessel described above.

The invention will be described by way of example with reference to exemplary embodiments and the figures.

Show it:

1 a rotary anode bearing assembly according to the prior art;

2 an embodiment of a rotary anode according to the invention;

3 an example of a rotary anode bearing arrangement according to the invention, as for example in the rotary anode in the 2 is provided;

4 a different design of a rotary anode bearing assembly according to the invention;

5 a further embodiment with double row and single row rolling bearing;

6 an embodiment with a combination of a single row ball bearing and a single row roller bearing;

7 - 9 Examples of possible employment of multi-row roller bearings with regard to the line of force before and after installation.

In the 2 an embodiment of a rotary anode according to the invention is shown, comprising a rotary anode bearing assembly with a rotor shaft 3 having a first axial end 4 and second axial end 5 having. The rotor shaft 3 is over its longitudinal axis 6 rotatable within a stationary housing 8th stored. The stationary housing 8th in turn carries a vacuum container 9 or is connected to this pressure-tight, which also includes a cathode not shown here in addition to the rotary anode.

Outside the vacuum container 9 is a stator 10 provided by means of which the rotor 11 , at the first axial end 4 flying on the rotor shaft 3 is stored, non-contact through the wall of the vacuum vessel 9 is drivable through, so that it over the longitudinal axis 6 circulates. At its first axial end 4 carries the rotor shaft 3 also the anode plate 12 that with an anode material 13 is provided and with the rotor 11 or the rotor shaft 3 circulates. The anode material 13 is bombarded by the cathode, not shown here with an electron beam, so that the X-radiation is generated and from the vacuum container 9 exit.

The anode recording 14 for receiving the anode plate 12 or here also the rotor 11 is shown only schematically as Axialflansch and could of course be designed differently.

The in the 2 shown rotary anode bearing assembly is in the 3 shown again in their details. Corresponding components are designated by corresponding reference numerals in all figures.

In the 3 one recognizes especially the here selected O-arrangement of each of the first rolling bearing 1 and the second rolling bearing 2 , Both bearings 1 . 2 are designed as double-row bearings in the form of ball bearings and the employment is such that the power flow lines through the bearings 1 . 2 have a pressure center outside of the rows of rolling elements, at least outside the axial center thereof. In an arrangement with the center of pressure between the rows of rolling elements, however, an X-arrangement is present. The O-arrangement can absorb a comparatively larger tilting moment than the X-arrangement.

Adjusting the power flow lines during assembly of the bearings 1 . 2 is based on the 7 to 9 shown again, in the 7 an O arrangement in the 9 an X arrangement and in the 8th In addition, a so-called tandem arrangement is provided. In such a tandem arrangement, the center of pressure of both rows of bearings is on the same side outside a radial section through the center of the rolling elements, in particular outside of the rows of rolling elements.

In the embodiment according to the 3 has each rolling bearing 1 . 2 a bearing outer ring 15 on, with two axial sections 15.1 . 15.2 by means of a spacer element 16 in the direction of the longitudinal axis 6 supported against each other and spaced from each other. Alternatively, can be dispensed with the spacer element. The rotor shaft 3 on the other hand, it forms the bearing inner ring itself 17 , However, this could be different. For example, a common bearing inner ring for both rolling bearings 1 . 2 on the rotor shaft 3 be applied or for each rolling bearing 1 . 2 could be a bearing inner ring or could be provided more bearing inner rings.

The facing sections 15.2 the bearing outer rings 15 are with a clear distance 18 positioned to each other, that is, free from a support to each other or free from an interposition of a spacer.

The spacer element 16 between the sections 15.1 and 15.2 can, as shown in the introduction, advantageously by selecting a suitable coefficient of thermal expansion relative to the thermal expansion coefficient of the bearing outer ring 15 a thermal compensation, that is cause a compensation of the linear expansion. In addition, the spacer element allows 16 , as is evident from the presentation in the 3 results in a slight assembly of the bearing outer rings 15 if the spacer element 16 after mounting the bearing outer rings 15 or the sections 15.1 and 15.2 on the rotor shaft 3 is mounted, in particular in the form of a C-ring.

In the embodiment according to the 3 has a section 15.1 of the first rolling bearing 1 a covenant 19 on, which protrudes in the radial direction and the front side of the stationary housing 8th can be connected, see the illustration in the 2 ,

In the embodiment according to the 4 was on a corresponding fret 19 waived. Incidentally, the description of the 3 directed.

The embodiment according to the 5 is largely identical to the embodiment according to the 4 , Deviating is as a second rolling bearing 2 However, a single-row roller bearing, here also in the form of a ball bearing, provided. In the illustrated embodiment, the bearing outer ring 15 also a free distance 18 to the bearing outer ring 15 of the first rolling bearing, or to its sections 15.1 . 15.2 on. Due to the Einreihigkeit can the second rolling bearing 2 to dispense with a spacer element.

While in the embodiments according to the 3 . 4 and 5 as a rolling element 20 Balls, which are made for example of the same material as bearing inner and / or outer bearing ring and coated with lead or silver as a lubricant, have been used, in particular in the first rolling bearing 1 as well as in the second rolling bearing 2 is in the embodiment according to the 6 as the first rolling bearing 1 a roller bearing provided here with cylindrical rollers whose axis of rotation 21 parallel to the longitudinal axis 6 runs. Of course, could also be another role form, such as tapered roller shape and / or a position of the axis of rotation 21 opposite the longitudinal axis 6 to get voted.

Because of that, the first rolling bearing 1 and the second rolling bearing 2 are each designed as a single-row roller bearing is on spacers 16 waived. However, in this embodiment shown, a corresponding free distance 18 between the bearing outer rings 15 intended. However, this is not mandatory. Also, a spacer element between the two bearing outer rings 15 be provided with which they are supported against each other. The same applies to the statements made in 2 to 5 are shown.

Claims (17)

Rotary anode bearing arrangement for an X-ray tube 1.1 with a rotor shaft ( 3 ) extending along a longitudinal axis ( 6 ) from a first axial end ( 4 ) to a second axial end ( 5 ) and rotatable about the longitudinal axis ( 6 ) is stored; where 1.2 the rotor shaft ( 3 ) an anode uptake ( 14 ) in the region of the first axial end ( 4 ) having; 1.3 with a first rolling bearing ( 1 ) in the region of the first axial end ( 4 ) and a second rolling bearing ( 2 ) in the region of the second axial end ( 5 ); where 1.4 the rolling bearings ( 1 . 2 ) at least one bearing inner ring ( 17 ) acting on the rotor shaft ( 3 ) is applied, or is formed by these, and at least one bearing outer ring ( 15 ); 1.5 with rolling elements ( 20 ) between the at least one bearing inner ring ( 17 ) and the at least one bearing outer ring ( 15 ) of rolling bearings ( 1 . 2 ); characterized in that 1.6 at least one of the rolling bearings ( 1 . 2 ) is designed as a multi-row roller bearing or as a roller bearing. Rotary anode bearing arrangement according to claim 1, characterized in that the at least one multi-row rolling bearing ( 1 . 2 ) one in the direction of the longitudinal axis ( 6 ) subdivided bearing outer ring ( 15 ), with a plurality of axial sections ( 15.1 . 15.2 ), which by means of an intermediate spacer element ( 16 ) in the direction of the longitudinal axis ( 6 ) are supported against each other. Rotary anode bearing arrangement according to claim 2, characterized in that the spacer element ( 16 ) than over the circumference of the longitudinal axis ( 6 ) interrupted ring is executed. Rotary anode bearing arrangement according to one of claims 2 or 3, characterized in that the spacer element ( 16 ) is made of a different material than the bearing outer rings ( 15 ). Rotary anode bearing arrangement according to one of claims 1 to 4, characterized in that the bearing outer ring ( 15 ) of the first rolling bearing ( 1 ) and the bearing outer ring ( 15 ) of the second rolling bearing ( 2 ) in the direction of the longitudinal axis ( 6 ) are arranged at a distance from each other. Rotary anode bearing arrangement according to one of claims 2 to 5, characterized in that the spacer element ( 16 ) has a larger thermal expansion coefficient than the at least one bearing outer ring ( 15 ) having. Rotary anode bearing arrangement according to one of claims 2 to 6, characterized in that the spacer element ( 16 ) has a larger thermal expansion coefficient than the at least one bearing inner ring ( 17 ) or the rotor shaft ( 3 ) having. Rotary anode bearing arrangement according to one of claims 1 to 7, characterized in that the at least one bearing inner ring ( 17 ), the rolling elements ( 20 ) and the at least one bearing outer ring ( 15 ) are in electrically conductive connection with each other. Rotary anode bearing arrangement according to one of claims 1 to 8, characterized in that the multi-row rolling bearing ( 1 . 2 ) is executed as a staffed warehouse with X-arrangement or with O-arrangement. Rotary anode bearing arrangement according to one of claims 1 to 9, characterized in that the at least one bearing inner ring ( 17 ) and the at least one bearing outer ring ( 15 ) are made of tempered steel. Rotary anode bearing arrangement according to claim 10, characterized in that the spacer element ( 16 ) is made of a low carbon steel having a carbon content of 0.2% by weight or less. Rotary anode bearing arrangement according to one of claims 1 to 11, characterized in that the at least one bearing outer ring ( 15 ), which has at least one bearing inner ring ( 17 ) and in particular the spacer element ( 16 ) are made of a cobalt-free material, with a cobalt content of less than 0.3 wt .-%. Rotary anode bearing arrangement according to one of claims 1 to 12, characterized in that the first rolling bearing ( 1 ) and the second rolling bearing ( 2 ) are each designed as a double-row roller bearing. Rotary anode bearing arrangement according to one of claims 1 to 12, characterized in that the first rolling bearing ( 1 ) is designed as a double-row roller bearing and the second rolling bearing ( 2 ) is designed as a single-row roller bearing. Rotary anode bearing arrangement according to one of claims 1 to 14, characterized in that the rolling bearing ( 1 . 2 ) are designed as ball bearings. Rotary anode bearing arrangement according to one of claims 1 to 15, characterized in that the bearing inner ring ( 17 ) through the rotor shaft ( 3 ) is formed. Rotary anode for an X-ray tube 17.1 with a rotor ( 11 ) and one the rotor ( 11 ) Stator enclosing at a distance in the circumferential direction ( 10 ), wherein the rotor ( 11 ) and the stator ( 10 ) are in electromagnetic interaction with each other such that the rotor ( 11 ) by applying an electromagnetic field by means of the stator ( 10 ) is displaceable in circulation, wherein the rotor ( 11 ) is designed cup-shaped, a roller bearing roller bearing ( 3 ) in the circumferential direction and at a first axial end ( 4 ) of the rotor shaft ( 3 ) connected; 17.2 with an anode plate ( 12 ), which at an axial end of the rotor ( 11 ) and with anode material ( 13 ), wherein the anode plate ( 12 ) in the region of the first axial end ( 4 ) on the rotor shaft ( 3 ) and / or the rotor ( 11 ) connected; characterized in that 17.3 the rotor shaft ( 3 ) by means of a rotary anode bearing arrangement according to one of claims 1 to 16 in a stationary housing ( 8th ), which from the stator ( 10 ) is stored, is stored.

Images