X-ray emitter

Abstract

An X-ray emitter has a rotating anode rotatably mounted inside an X-ray tube by way of a multi-sliding surface bearing. The multi-sliding surface bearing has an inner and an outer sliding surface which are mounted so they can rotate relative to each other about an axis of rotation such that a gap is formed between the inner and outer sliding surfaces. A contour of the inner sliding surface, in a plane running perpendicular to the axis of rotation, is formed at least in certain sections by arc-shaped segments which are each centered around center points that are offset from each other.

Claims

1. An X-ray emitter, comprising: a rotating anode disposed inside an X-ray tube; a multi-sliding surface bearing rotatably mounting said rotating anode inside said X-ray tube; said multi-sliding surface bearing having an inner sliding surface and an outer sliding surface that are mounted for rotation relative to each other about an axis of rotation and forming a gap between said inner and outer sliding surfaces; said inner sliding surface, in a plane running perpendicular to the axis of rotation, having a contour formed at least in certain sections by arc-shaped segments that are each centered around center points arranged so as to be offset from one another.

2. The X-ray emitter according to claim 1, wherein said outer sliding surface is centered around the axis of rotation and at least one of said arc-shaped segments of said inner sliding surface is centered around a center point that is eccentrically offset from the axis of rotation.

3. The X-ray emitter according to claim 1, wherein all center points of said arc-shaped segments are arranged eccentrically offset at an equal radial spacing distance in respect of the axis of rotation.

4. The X-ray emitter according to claim 1, wherein the center points of said arc-shaped segments are arranged at regular angular positions circumferentially around the axis of rotation.

5. The X-ray emitter according to claim 4, wherein the center points arranged at regular angular positions are offset from each other by an angle matching a quotient of 360 divided by a number of said arc-shaped segments of the inner sliding surface.

6. The X-ray emitter according to claim 1, wherein said arc-shaped segments of said inner sliding surface have a radius and the radii of all said arc-shaped segments of said inner sliding surface assume the same value.

7. The X-ray emitter according to claim 1, wherein said inner sliding surface has at least two said arc-shaped segments.

8. The X-ray emitter according to claim 1, wherein said inner sliding surface of said multi-sliding surface bearing runs parallel to the axis of rotation.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a rotating anode rotatably mounted in an X-ray tube in a schematic sectional view;

(2) FIG. 2 shows a multi-sliding surface bearing for mounting the rotating anode according to a first exemplary embodiment in a schematic sectional view;

(3) FIG. 3 shows the gap height of the first exemplary embodiment as a function of the angular position;

(4) FIG. 4 shows a multi-sliding surface bearing for mounting the rotating anode according to a second exemplary embodiment in a schematic sectional view;

(5) FIG. 5 shows the gap height of the second exemplary embodiment as a function of the angular position;

(6) FIG. 6 shows a multi-sliding surface bearing for mounting the rotating anode according to a third exemplary embodiment in a schematic sectional view;

(7) FIG. 7 shows the gap height of the third exemplary embodiment as a function of the angular position.

(8) Mutually corresponding parts are provided with the same reference numerals in all figures.

DETAILED DESCRIPTION OF THE INVENTION

(9) Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a rotating anode 1 of an X-ray emitter 10. The anode 1 is rotatably mounted about an axis of rotation D and is illustrated in a schematic sectional view. In a manner known per se the rotating anode 1 has a target surface for impingement by with an electron beam e.sup.. During operation the rotating anode 1 is caused to rotate in order to distribute a build-up of heat that has occurred during operation over the entire surface and therefore be able to tolerate higher intensities. In the illustrated exemplary embodiment, the rotating anode 1 has a hollow shaft by which it is rotatably mounted on a fastening element 3. The fastening element 3 is arranged in a rotationally fixed manner in respect of an X-ray tube 5, which is only indicated in highly schematic form for reasons of clarity. In addition to rotatable mounting, the fastening element 3 is used for axial fixing of the rotating anode. A multi-sliding surface bearing 4 is formed between the fastening element 3 and the rotating anode 1 in the regions of the hollow shaft shown in broken lines in FIG. 1.

(10) The multi-sliding surface bearing 4 is located inside the evacuated X-ray tube 5. Lubrication of the components guided so as to be rotatable relative to each other under high vacuum is subject to specific requirements, so suitability of a particular bearing geometry or design in this regard can only generally be defined by simulations and/or test runs.

(11) Arranged in the region of the multi-sliding surface bearing 4 is an outer surface of the fixed fastening element 3 at the minimum radial spacing from an inner surface of the rotating hollow shaft. The outer surface of the fastening element 3 has an MSB structuring and forms an inner sliding surface 41 of the multi-sliding surface bearing 4. The one outer sliding surface 42 of the multi-sliding surface bearing 4 is formed by the inner surface of the hollow shaft. The structural design of the multi-sliding surface bearing 4, in particular the MSB structuring of the inner sliding surface 41 will be illustrated below with reference to preferred exemplary embodiments.

(12) FIG. 2 shows the multi-sliding surface bearing 4 according to a first exemplary embodiment of the invention in a sectional view. The illustrated section runs in a plane that runs perpendicular to the axis of rotation D. The multi-sliding surface bearing 4 comprises the inner sliding surface 41 and the outer sliding surface 42. Both the inner sliding surface 41 and the outer sliding surface 42 run parallel to the axis of rotation D that runs perpendicular to the drawing plane.

(13) The outer sliding surface 42 is circular ring-shaped. In the illustrated first exemplary embodiment the inner sliding surface 41 comprises three sections A which each have an arc-shaped profile. Formed between the inner sliding surface 41 and the outer sliding surface 42 therefore is a variable gap 43 which is filled with lubricant. Each arc-shaped segment A extends over an angular range of about 120 around the axis of rotation D.

(14) The arc-shaped segments A have a constant radius of curvature and are centered around center points M which are eccentrically arranged in respect of the axis of rotation D. The center points M are therefore located on a circular line having radial spacing R.sub.ex from axis of rotation D. All sections A are arranged in the same radius R.sub.kon from the associated center point M in each case. The outer sliding surface 42 surrounds the inner sliding surface 41 and is formed in the manner of a circular ring having a radius R.sub.B. The center points M are arranged at predefined angular positions w in respect of the axis of rotation D. In the first exemplary embodiment three sections curved in an arc-shaped manner are arranged at regular spacings from each other; the center points M respectively associated with the sections are therefore arranged offset by an angle of 120 from each other.

(15) The eccentric arrangement of the sections A curved in an arc-shaped manner means a gap having variable gap height d is formed between the inner sliding surface 41 and the outer sliding surface 42. FIG. 3 shows the characteristic of this gap.

(16) FIG. 3 schematically shows the gap height d of the gap 43 formed in the first exemplary embodiment as a function of the angular position w. The gap height d varies between a minimum and a maximum value. The minimum gap height d.sub.MIN or the maximum gap height d.sub.MAX is in each case assumed at three different angular positions w. The points corresponding thereto are designated by P.sub.MIN and P.sub.MAX in FIG. 1.

(17) FIG. 3 shows with a dotted line a slightly modified design in which the ratio of the variables influencing the bearing geometry has been varied slightly. These variables are essentially predefined by the radial spacing R.sub.ex and the radii R.sub.B and R.sub.kon.

(18) FIG. 4 shows a second exemplary embodiment of the invention in which the inner sliding surface 41 is formed by four arc-shaped segments A that are each arranged offset from each other by 90. In the axial direction running perpendicular to the drawing plane extends the inner sliding surface 41 and the outer, circular ring-shaped sliding surface 42 parallel to the axis of rotation D. The sections A of the inner sliding surface 41 extend around center points M which are eccentrically arranged in respect of the axis of rotation D. The eccentricity of the arrangement is predefined by the radial spacing R.sub.ex which therefore assumes the same value for all sections A. Furthermore, the four arc-shaped segments A of the inner sliding surface 41 have the same radius of curvature that is predefined by the radius R.sub.kon.

(19) FIG. 5 illustrates the gap height d of the gap 43 of the second exemplary embodiment. Since in the second exemplary embodiment a total of four arc-shaped segments A is provided, the minimum gap height d.sub.MIN or the maximum gap height d.sub.MAX is assumed at a total of four angular positions w. FIG. 3 shows the points P.sub.MIN or P.sub.MAX corresponding hereto. FIG. 5 likewise shows two curves, illustrated by way of example, which correspond to different parameter values of the influencing factors predefined in terms of construction by the bearing. This essentially corresponds to the eccentricity of the arc-shaped segments A which is predefined by the value of the radial spacing R.sub.ex and the size of the radius R.sub.kon in the ratio to the radius R.sub.B of the outer sliding surface 42.

(20) FIG. 6 shows a third exemplary embodiment of the invention which essentially differs from the exemplary embodiments illustrated in FIGS. 2 and 4 in that the gap is not mirror-symmetrical in design. However, the variation in the arrangement and extent of the sections A of the inner sliding surface 41, curved in an arc-shaped manner, results in the lubricating wedge lengths, i.e. the length of those gap regions in which the gap height d tapers in the circumferential direction, being significantly lengthened. The lubricating wedge lengths are, in particular, crucially responsible for generation of the hydrodynamic load-bearing pressure, so a variation of this kind enables particular adjustment to a specific loading condition.

(21) Furthermore, the design of the third exemplary embodiment essentially matches that of the first exemplary embodiment shown in FIG. 2. In particular, the inner sliding surface 41 has a total of three sections A which are curved in an arc-shaped manner and extend parallel to the axis of rotation D. The sections A are each arranged offset from each other by 120. Each arc-shaped segment A extends in the radius R.sub.kon around a center point M which is eccentrically arranged in respect of the axis of rotation D.

(22) FIG. 7 illustrates the dependency of the gap height d of the third exemplary embodiment. The gap height d also varies here between a minimum and a maximum value. The minimum gap height d.sub.MIN and the maximum gap width d.sub.MAX are each assumed at three different angular positions w. These angular positions match the points P.sub.MIN and P.sub.MAX shown in FIG. 6. In contrast to the first two exemplary embodiments, the characteristic of the gap height d is not symmetrical. The third exemplary embodiment has a gap region here in which the gap height d changes significantly in a relatively small angular range.

(23) Although the invention has been illustrated and described in detail with reference to the preferred exemplary embodiments, it is not limited hereby and a person skilled in the art can derive other variations and combinations herefrom without departing from the fundamental idea of the invention.