DE102011082685A1 - Anode device, useful for X-ray tube, comprises anode body comprising focal spot range, receiving device that is attached at anode body in area adjacent to focal spot range, and latent heat storage element arranged in receiving device - Google Patents

Abstract

The anode device comprises an anode body (2), which comprises a focal spot range (3) and is adapted to produce an X-ray radiation at an impinging of an electron ray on the focal spot range, a receiving device (4), which is attached at the anode body in an area adjacent to the focal spot range, and a latent heat storage element (4a), which is arranged in the receiving device. The anode body is a rotating anode plate for a rotating anode X-ray tube. The focal spot range is a focal path circulating in an outer region of the rotating anode plate on a first surface of the rotating anode plate. The anode device comprises an anode body (2), which comprises a focal spot range (3) and is adapted to produce an X-ray radiation at an impinging of an electron ray on the focal spot range, a receiving device (4), which is attached at the anode body in an area adjacent to the focal spot range, and a latent heat storage element (4a), which is arranged in the receiving device. The anode body is a rotating anode plate for a rotating anode X-ray tube. The focal spot range is a focal path circulating in an outer region of the rotating anode plate on a first surface of the rotating anode plate. The receiving device comprises: an annular structure, which is arranged on a second surface of the rotating anode plate in an outer region of the rotating anode plate opposite to the first surface; an outward dense housing; and a foam material with pores taken up in the housing. The latent heat storage element comprises a phase change material that is injected into the pores of the foam material, hollow spheres taken up in the housing, where the spheres are filled with the phase change material, and composite particles, which comprise a core from the phase change material and a casing from an inert material opposite to the phase change material. The phase change material comprises a metallic alloy such as a eutectic alloy, a salt hydrate, a carbonate mixture, an ionic liquid or paraffin. The phase change material is coupled with the rotating anode plate to receive heat that is generated by an irradiation of the rotating anode plate with the electron ray. An independent claim is included for a method of producing an anode device.

Description

The present invention relates to an anode device with heat storage for X-ray tubes, a method of manufacturing an anode device for an X-ray tube, and an X-ray tube with heat-storing anode device.

State of the art

X-ray tubes are usually in evacuated housings in which a cathode and an anode are housed. The cathode emits an electron beam, which impinges on the anode at a defined location, the so-called focal spot. As a result, X-ray radiation is emitted from the material of the anode.

Only a small part of the energy introduced in the focal spot of the anode is actually converted into X-radiation, the considerably larger proportion of about 99% being converted into heat energy. This heat energy heats up the anode very quickly. As a result, high temperatures can occur in the focal spot which damage the anode material, for example by melting and successive deformation of the anode material or by cyclic thermal stresses, which can then lead to increased failure rates of the X-ray tube.

The problem is aggravated by the fact that the heat generated in the anode can be removed with difficulty. The evacuated housing, which is usually cooled by cooling fluid, is in heat-conducting contact with the anode only via the electrical contacts and the attachment. The release of heat radiation, however, is too slow to release the resulting heat quickly enough. Particularly with medical-technical X-ray tubes, depending on the application, longer irradiation times can occur, so that the heat input into the anode material can be considerable. Typical irradiation times are in the range of computed tomography at a few seconds, in the area of fluoroscopy or angiography at a few minutes.

The publication DE 199 45 416 A1 discloses a cooling device for a housing of an X-ray tube, which comprises a phase change material.

An object of the present invention is therefore to provide an anode device for an X-ray tube, with the overheating of the anode avoided and thus the operating time of the X-ray tube can be increased without damaging the X-ray tube.

Summary of the invention

One aspect of the present invention is therefore an anode device for an X-ray tube, comprising an anode body having a focal spot region and adapted to generate X-radiation when an electron beam strikes the focal spot region, a capture device located on the anode body in one The region adjacent to the focal spot region is attached, and at least one latent heat storage element, which is arranged in the receiving device.

In another aspect, the invention provides an x-ray tube having an anode device according to the invention.

According to a further aspect, the invention relates to using a phase change material coupled to a rotary anode plate for absorbing heat which is produced when the rotary anode plate is irradiated with an electron beam.

According to a further aspect, the invention provides a method for producing an anode device for an x-ray tube, comprising the steps of attaching a receiving device to a rotary anode plate, and arranging at least one latent heat storage element in the receiving device.

An essential basic idea of the invention consists in dissipating the heat energy occurring when an anode of an X-ray tube is irradiated into a latent heat store near the focal spot area. As a result, heating of the anode beyond a phase transition temperature of the latent heat accumulator can advantageously be avoided or at least delayed, and the safe operating time of the x-ray tube can be extended.

An advantage of the invention is that the storage density of latent heat storage is very high and the total weight of the anode body can be kept low. This is advantageous in particular for rotary anodes since the moment of inertia of the rotary anode plate can be minimized.

Another advantage of the invention is that the latent heat storage can be adapted to the particular application to other parts of the anode device such as plain bearings of a rotary anode can be protected against overheating.

In an advantageous embodiment, the anode device may be a rotary anode plate and the focal spot region may be one in one Exterior of the rotary anode plate on a first surface of the rotary anode plate rotating focal path. In this case, the receiving device may have an annular structure which is arranged on a second surface of the rotary anode plate opposite the first surface in an outer region of the rotary anode plate. With this arrangement, a good thermal connection to the focal spot area can be achieved and at the same time a symmetrical mass distribution of the latent heat accumulator can be achieved.

According to an advantageous embodiment, the receiving device may comprise an outwardly sealed housing and a foam material accommodated in the housing with a plurality of pores. In this case, the at least one latent heat storage element may comprise a phase change material which is injected into the pores of the foam material. In this way, when the phase change material melts, a weight shift and therefore a center of gravity displacement of the phase change material can be avoided, so that the occurrence of an imbalance of the rotary anode plate during operation can be prevented.

According to an advantageous embodiment, the receiving device may comprise a housing which is sealed to the outside, and the at least one latent heat storage element may have a multiplicity of hollow spheres accommodated in the housing, which are filled with a phase change material. This offers the advantage that the phase change material remains securely trapped in the hollow balls and can not escape from the receiving device. In addition, a center of gravity shift can be effectively avoided when melting the phase change material.

According to a further advantageous embodiment, the at least one latent heat storage element may comprise a multiplicity of composite particles which have a core of a phase change material and a sheath of a material which is inert to the phase change material.

Advantageously, the phase change material may comprise a metallic alloy, preferably a eutectic alloy, a salt hydrate, a carbonate mixture, an ionic liquid or paraffin. In this way, a melting point can be adapted to the particular application or guaranteed as unchanged as possible melting behavior after a long Gesamtbestrahlzeit.

Further modifications and variations will be apparent from the features of the dependent claims.

Brief description of the figures

Various embodiments and embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, in which: FIG

1 a schematic representation of an X-ray tube according to an aspect of the invention;

2 a schematic representation of an anode device for an X-ray tube according to a further aspect of the invention;

3 a schematic representation of an anode device for an X-ray tube according to a further aspect of the invention;

4 a diagram of the temperature dependence of the heat capacity of different substances;

5 a diagram of a temporal temperature profile during operation of an X-ray tube; and

6 a schematic representation of a method for producing an anode device according to another aspect of the invention shows.

The described embodiments and developments can, if appropriate, combine with one another as desired. Further possible refinements, developments and implementations of the invention also include combinations, not explicitly mentioned, of features of the invention described above or below with regard to the exemplary embodiments.

The accompanying drawings are intended to provide further understanding of the embodiments of the invention. They illustrate embodiments and, together with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the stated advantages will become apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale to each other. The same reference numerals designate the same or similar components.

Detailed description of the invention

1 shows a schematic representation of an X-ray tube 10 , In the exemplary embodiment in FIG 1 is the x-ray tube 10 shown as rotary anode X-ray tube. It should be understood, however, that other types of x-ray tubes, such as stannous x-ray tubes, are also encompassed by the invention.

The x-ray tube 10 has a housing 6 on which can be evacuated. A cathode 7 has a filament 8th on which an electron beam 8a on an anode device 1 emitted. The anode device 1 is shown as a rotary anode, wherein the anode device 1 However, it can also be designed as a standing or fixed anode. The anode device 1 has an anode body 2 , an anode storage 5 and one or more recording devices 4 on. The anode body 2 and the anode layer 5 For example, you can have a rotary anode plate 2 form, which about the axis of the pivot bearing 5 rotates.

In operation of the X-ray tube 10 is the anode body 2 arranged such that the electron beam 8a on a focal spot 2a incident, from which X-radiation 9 from the anode body 2 is emitted. The anode body 2 For example, with zirconium and titanium alloyed molybdenum, copper, carbon, ceramic or rhodium. In the case of a rotary anode, the anode body 2 a focal spot area 3 which is annular in an outer region of the anode body 2 on a first page around its circumference. The focal spot area 3 may for example have a tungsten or tungsten / rhenium coating. By the rotation of the rotary anode about the axis of the pivot bearing 5 the focal spot wanders 2a evenly over the focal spot area 3 , so that a uniform heating of the anode body 2 he follows.

At an underside of the anode body 2 or the rotary anode plate 2 can be a recording device 4 to be appropriate. The recording device 4 For example, by soldering or welding with the rotary anode plate 2 be connected. It is important that a thermally good conductive connection between the receiving device 4 and the anode body 2 is created.

The recording device 4 will be described below with reference to the exemplary embodiments in the 2 and 3 explained in more detail. 2 shows a schematic representation of three views of an anode device 1 , For example, the anode device 1 out 1 , The view (a) is a plan view, the view (b) is a view of the bottom and the view (c) is a sectional view of the anode device 1 ,

View (a) shows a first surface of the anode body 2 , on the outer periphery of the focal spot area 3 is arranged. Indicated by a dashed line is that under the anode body 2 lying pivot bearing 5 , View (b) shows a view of the bottom of the anode body 2 , In an annular structure around the pivot bearing 5 around is a recording device 4 arranged. The recording device 4 can in an outdoor area of the bottom of the anode body 2 be arranged so that the receiving device 4 as close as possible to the focal spot area arranged on the opposite surface 3 lies. This can be achieved that heat by irradiating the focal spot area 3 created with an electron beam, fast and short ways to the receiving device 4 can be directed.

In the recording device 4 is how in 2 schematically indicated at least one latent heat storage element 4a added. The latent heat storage element 4a For example, the receiving device 4 fully fill. For this purpose, the recording device 4 For example, have a fluid-tight housing, in which the latent heat storage element 4a is included. In the embodiment of the anode body 2 as a rotary anode plate 2 it may be advantageous to the receiving device 4 as well as the latent heat storage element 4a rotationally symmetrical about the axis of the pivot bearing 5 arrange so that the center of gravity of the entire anode device 1 in the axis of rotation, in order to produce no imbalance in the operation of the rotary anode.

For this purpose, it may be advantageous to use the latent heat storage element 4a according to the embodiment in 3 in the receiving device 4 to arrange. The anode device 1 in 3 differs from the anode device 1 in 2 essentially only in that a plurality of latent heat storage elements 4a as evenly as possible in the receiving device 4 are distributed. Thereby, a structure can be achieved in which the latent heat storage elements during operation of the anode device 1 remain localized within an X-ray tube even after a phase transition within the receiving device, so that the center of gravity of the entire arrangement with respect to the axis of the pivot bearing 5 not or only insignificantly changes. Thus, the occurrence of imbalance during the operation of the rotary anode can be effectively avoided.

The latent heat storage elements 4a can have a phase change material. The phase change material may comprise, for example, a metallic alloy, preferably a eutectic alloy, a salt hydrate, a carbonate mixture, an ionic liquid or paraffin. The phase change material can be characterized in that it undergoes a phase transformation at a certain phase transition temperature T _P and thereby absorbs or releases latent heat. This behavior is reflected in a jump in the temperature curve of the heat capacity c, as exemplified in the diagram 40 in 4 is shown.

The diagram 40 in 4 shows the behavior of the heat capacity c as a function of the temperature. The curve 41 shows the course of the heat capacity c for a sensitive heat storage, the curve 42 those for a latent heat storage. As can be seen, the curve points 42 at the phase transition temperature T _P a jump .DELTA.c, which is an indication of a first-order phase transition. The curve 41 however, it runs steadily with the temperature T.

When using a latent heat storage device for an anode device, therefore, the latent heat accumulator can absorb heat that is generated when the anode device is irradiated by an electron beam, for example in an x-ray tube, without the temperature of the latent heat accumulator changing. The resulting temperature profile during an operating cycle of an X-ray tube is exemplified in diagram 50 in 5 shown.

The diagram 50 shows the temperature profile of the temperature T of an anode in an X-ray tube with the operating time t. The curve shows 51 the temperature profile of an anode without latent heat storage, the curve 52 a possible temperature profile of an anode with latent heat storage elements. While the curve 51 during the irradiation of the anode increases steadily steadily up to a maximum value and then steadily drops again, the curve shows 52 at the phase transition temperature T _P a kink. In this case, a time interval Δt ₁ occurs during an irradiation phase during which the temperature T of the anode does not change. This is because the heat is bound as latent heat in the latent heat storage. Thereafter, the temperature rises only up to a maximum value T _M , which is well below the maximum value of the temperature of the curve 51 lies. After switching off the X-ray tube, the temperature T decreases again up to the phase transition temperature T _P , at which the latent heat storage reversibly releases the stored heat. As a result, there is no change in temperature T during a second time period Δt _2. Overall, this can reduce the maximum temperature of the anode during one operating cycle at the expense of an extended cooling process. Conversely, this means that the X-ray tube can go through a prolonged operating cycle without the anode overheating and being damaged.

As latent heat storage elements 4a For example, phase change materials that can be injected into a foam material are suitable. For example, the receiving device 4 a foam material such as Al ₂ O ₃ or Si ₃ N ₄ , which has relatively fine and open pores. Since foam material can be closed fluid-tight on the outer walls of a housing. In the pores of the foam material then a phase change material can be injected. The foam material may comprise a material which is inert with respect to the phase change material.

Alternatively, it may be possible to produce hollow spheres from a material which is inert to a phase change material and to fill these hollow spheres with the phase change material. For example, for this purpose, a cold solidifying material such as a hydraulic binder such as refractory cement may be used. It may further be provided that the hollow spheres are sealed after filling with phase change material by means of a sol-gel process or a glazing.

Another alternative offers the possibility of producing composite particles in a thermal spraying process. The composite particles form a so-called core-shell structure, ie a core-shell structure in which a core of phase change material is enveloped by a material that is inert to the phase change material. The composite particles are thereby produced by simultaneous injection of the two materials in powder form, for example as nanoparticles.

All alternatives have the advantage that phase change material can be processed by a uniform distribution in a quasi-homogeneous latent heat storage. This offers particular advantages in the prevention of imbalances in rotary anode devices, since the quasi-homogeneous latent heat storage are not subject to any shift of the center of gravity even with a melting of the phase change material.

6 shows a schematic representation of a method 20 for producing an anode device for an X-ray tube, for example the anode device 1 in the 1 to 3 , In a first step 21 An attachment of a receiving device is carried out 4 on a rotary anode plate 2 , In a second step 22 a placement of at least one latent heat storage element takes place 4a in the cradle 4 ,

The invention relates to an anode device for an X-ray tube, comprising an anode body having a focal spot region and adapted to generate X-radiation when an electron beam strikes the focal spot region, a recording device attached to the anode body in an area adjacent to the focal spot region is, and at least one latent heat storage element, which is arranged in the receiving device.

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 19945416 A1 [0005]

Claims (14)

Anode device ( 1 ) for an X-ray tube ( 10 ), comprising: an anode body ( 2 ), which has a focal spot area ( 3 ), and which is adapted, upon impact of an electron beam ( 8a ) on the focal spot area ( 3 ) X-radiation ( 9 ) to create; a recording device ( 4 ), which on the anode body ( 2 ) in a focal spot area ( 3 ) adjacent area is attached; and at least one latent heat storage element ( 4a ), which in the receiving device ( 4 ) is arranged. Anode device ( 1 ) according to claim 1, wherein the anode body ( 2 ) is a Drehanodenteller for a rotating anode X-ray tube. Anode device ( 1 ) according to claim 2, wherein the focal spot area ( 3 ) one in an outer region of the rotary anode plate ( 2 ) on a first surface of the rotating anode plate ( 2 ), and wherein the receiving device ( 4 ) has an annular structure which on a second, opposite the first surface surface of the rotating anode plate ( 2 ) in an outer area of the rotary anode plate ( 2 ) is arranged. Anode device ( 1 ) according to one of claims 1 to 3, wherein the receiving device ( 4 ) comprises an outwardly sealed housing and a foam material received in the housing and having a plurality of pores. Anode device ( 1 ) according to claim 4, wherein the at least one latent heat storage element ( 4a ) comprises a phase change material injected into the pores of the foam material. Anode device ( 1 ) according to one of claims 1 to 3, wherein the receiving device ( 4 ) comprises an outwardly sealed housing, and wherein the at least one latent heat storage element ( 4a ) has a plurality of hollow spheres accommodated in the housing, which are filled with a phase change material. Anode device ( 1 ) according to one of claims 1 to 3, wherein the at least one latent heat storage element ( 4a ) comprises a plurality of composite particles comprising a core of a phase change material and a shell of a material that is inert to the phase change material. Anode device ( 1 ) according to one of claims 5 to 7, wherein the phase change material comprises a metallic alloy, in particular a eutectic alloy, a salt hydrate, a carbonate mixture, an ionic liquid or paraffin. X-ray tube ( 10 ), comprising: an anode device ( 1 ) according to one of claims 1 to 8. Using one with a rotating anode plate ( 2 ) coupled phase change material ( 4a ) for absorbing heat which, when irradiating the rotary anode plate ( 2 ) with an electron beam ( 8a ) arises. Procedure ( 20 ) for producing an anode device ( 1 ) for an X-ray tube ( 10 ), with the steps: attaching ( 21 ) a receiving device ( 1 ) on a rotating anode plate ( 2 ); Arrange ( 22 ) at least one latent heat storage element ( 4a ) in the receiving device ( 4 ). Procedure ( 20 ) according to claim 11, wherein the arranging of the receiving device ( 4 ) a welding or soldering of the receiving device ( 4 ) to the rotary anode plate ( 2 ). Procedure ( 20 ) according to one of claims 11 and 12, wherein the receiving device ( 4 ) comprises an outwardly sealed housing and a foam material accommodated in the housing with a plurality of pores, and wherein arranging the latent heat storage element ( 4a ) comprises injecting a phase change material into the foam material. Procedure ( 20 ) according to one of claims 11 and 12, wherein arranging the latent heat storage element ( 4a ) comprises encasing hollow phase spheres filled with a phase change material in a composite material.

Images