JP2024003557A - Method for manufacturing x-ray tube - Google Patents

Abstract

To provide a method for manufacturing an X-ray tube for obtaining an X-ray tube with high reliability that can maintain stable withstand voltage performance.SOLUTION: In an X-ray tube, a vacuum envelope comprises: an insulating envelope formed of ceramics, a cathode-side metal envelope provided on one end face of the insulating envelope and supporting a cathode filament, an anode-side metal envelope provided on the other end face of the insulating envelope and joined to a substrate to support the substrate, a high-voltage cable connected with the substrate and applying high voltage to an anode target, an electrically insulating radiator arranged around the high-voltage cable, and an electrical insulator made of resin and filling the space between the radiator and the high-voltage cable. The electrical insulator is obtained by injecting resin material in a molten state and subsequently curing it by heating, and the step of curing by the injection and the heating is performed multiple times to fill the space.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing an X-ray tube.

Fixed anode X-ray tubes are generally known as X-ray tubes. A fixed anode X-ray tube includes a vacuum envelope, an anode target, a cathode filament, a support, a heat sink, an electrical insulator, and a high voltage cable. An output window that transmits X-rays is provided in a flat portion at one end of the vacuum envelope.

The anode target is located inside the vacuum envelope and faces the output window. The cathode filament is placed inside the vacuum envelope and emits electrons that irradiate the anode target. A support is provided within the vacuum envelope, and one end of the support supports an anode target.

A high voltage cable and a heat sink are connected to the other end of the support. The high voltage cable is for applying high voltage to the anode target. A heat sink is disposed around the high voltage cable at the other end of the support and is for dissipating heat generated at the anode target and transferred to the support. An electrical insulator is filled between the high voltage cable and the heat sink at the end of the support.

Patent No. 6440192

However, during the manufacturing process of X-ray tubes and during use in the market, defects such as cracks, voids, and peeling occur in the electrical insulator, resulting in a significant decline in the withstand voltage performance of the X-ray tube. .

The present invention has been made in view of the above points, and an object thereof is to provide a method for manufacturing an X-ray tube for obtaining a highly reliable X-ray tube that can maintain stable withstand voltage performance.

In order to solve the above problems, a method for manufacturing an X-ray tube according to an aspect of the present invention includes: a vacuum envelope in which an output window that transmits X-rays is formed; An X-ray tube comprising an anode target facing a window, a support for the anode target, and a cathode filament provided in the vacuum envelope and emitting electrons to irradiate the anode target. The envelope includes an insulating envelope made of ceramics, a cathode-side metal envelope provided on one end surface of the insulating envelope and supporting the cathode filament, and provided on the other end surface of the insulating envelope, an anode-side metal envelope joined to the support to support the support; a high-voltage cable connected to the support to apply a high voltage to the anode target; and a high-voltage cable arranged around the high-voltage cable. It includes an electrically insulating heat radiator and an electrical insulator made of a resin material filled in a space between the heat radiator and the high voltage cable, and the electrical insulator is made of a resin material after the resin material is injected in a molten state. This is a method for manufacturing an X-ray tube that is cured by heating, and is filled by performing the steps of injection and curing by heating a plurality of times.

According to the present invention, it is possible to prevent the occurrence of defects in the electrical insulator, and it is possible to obtain a highly reliable X-ray tube that can maintain stable withstand voltage performance.

FIG. 1 is a sectional view showing a schematic configuration of an X-ray tube manufactured by the method for manufacturing an X-ray tube according to the first embodiment. FIG. 2 is an enlarged view of section B shown in FIG. FIG. 3 is a cross-sectional view of the method for manufacturing an X-ray tube according to the first embodiment, showing a state before being filled with an electrical insulator in FIG. FIG. 4 is a cross-sectional view of the method for manufacturing an X-ray tube according to the first embodiment, showing a state in which the first molten resin material is injected in FIG. FIG. 5 is a cross-sectional view showing the method of manufacturing an X-ray tube according to the second embodiment, showing a state in which the second molten resin material is injected in FIG. FIG. 6 is a cross-sectional view showing a method of manufacturing an X-ray tube according to a third embodiment, showing a state in which the second molten resin material is injected in FIG. FIG. 7 is a cross-sectional view showing a method of manufacturing an X-ray tube according to a fourth embodiment, showing a state in which the first molten resin material is injected in FIG. 2.

Hereinafter, a fixed anode X-ray tube will be described in detail as an X-ray tube according to an embodiment with reference to the drawings. In addition, in order to make the explanation more clear, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is just an example, and the drawings do not reflect the present invention. It does not limit interpretation. In addition, in this specification and each figure, the same reference numerals are given to components that perform the same or similar functions as those described above with respect to the existing figures, and overlapping detailed explanations may be omitted as appropriate. .

As shown in FIG. 1, the fixed anode X-ray tube 1 includes a vacuum envelope 3, an anode target 5, a support 7, a cathode filament 9, an insulating envelope 11, a tube container 13, It includes a heat sink 15 and a high voltage cable 17.

The vacuum envelope 3 maintains a vacuum inside, has a cylindrical shape with an outer diameter gradually tapered at its tip, and is provided with an output window 19 that transmits X-rays in a flat portion of the tip surface.
The output window 19 is made of, for example, beryllium (Be), which is a material with low attenuation of X-rays.

Inside the vacuum envelope 3, an anode target 5 is arranged facing the output window 19, and a cathode filament 9 is arranged on the outer peripheral side of the anode target 5. Note that a focusing electrode 21 is provided between the anode target 5 and the cathode filament 9.

Furthermore, a tip 7a of the support 7 is disposed at the center of the vacuum envelope 3. The tip 7a of the support 7 is disposed on the inner peripheral side of the focusing electrode 21 and supports the anode target 5 at the tip. The other end 7b of the support body 7 is provided protruding from the other end side of the insulating envelope 11, and a bonded body (anode side metal envelope) 23 is brazed to the bonded body 23 to form an insulating envelope. The vessel 11 and the support body 7 are coupled in a sealed state. In other words, the bonded body 23 supports the anode target 5.
Further, a metal film 36 is formed on the tip end surface (one end surface) 11b of the insulating envelope 11, and a cathode-side metal envelope 24 that supports the cathode filament 9 is brazed to the metal film 36.

An exhaust pipe 27 for evacuating the inside of the vacuum envelope 3 through an exhaust path 25 formed inside the support 7 is provided on the end face of the other end 7b of the support 7. A power supply section 29 is provided to which a high voltage cable 17 for applying high voltage is connected.

The heat sink 15 has electrical insulation properties. The heat sink 15 has a cylindrical shape, and has a female threaded portion 31 (see FIG. 3) formed on its inner peripheral surface. This female threaded portion 31 is screwed into a male threaded portion 32 formed on the other end 7b of the support body 7, and one end surface 15a of the heat sink 15 is in contact with the joined body 23. As is clear from FIGS. 2 and 3, the female screw portion 31 of the heat sink 15 is formed on the entire inner peripheral surface of the heat sink 15, and is screwed into the male screw portion 32 of the support body 7. This is only the part located on the support body 7 side.
The heat sink 15 is made of ceramics having high thermal conductivity of 20 W/m·K or more and high voltage insulation of 10 kV/mm or more. For example, by using aluminum nitride, a high thermal conductivity of 90 W/m·K or more can be obtained. It will be done.

The high-voltage cable 17 is located on the inner peripheral side of the heat radiator 15 and the electrical insulator 33 and is drawn out to the outside of the insulator 33 .

As shown in FIG. 3, a space K surrounded by the rear end surface 7c of the support body 7, the heat sink 15, and the high voltage cable 17 is filled with an electrical insulator 33 (see FIG. 2). In other words, the electrical insulator 33 is filled between the inner peripheral surface of the cylindrical heat sink 15 and the high voltage cable 17. The electrical insulator 33 is, for example, a potting material such as silicone resin.
The details and filling method of this electric insulator 33 will be described later.

As shown in FIG. 1, another electric insulator 34 is filled between the insulating envelope 11, the joined body 23, and the heat sink 15 on the inner peripheral side of the tube container 13. The other electrical insulator 34 is made of a potting material such as silicone resin, like the electrical insulator 33.

A cooling section 35 is provided on the outer surface of the tube container 13. For this cooling unit 35, an air-cooled type, a liquid-cooled type, or a heat pipe type can be selected depending on the input from the fixed anode X-ray tube 1, but an air-cooled type or a heat pipe type is preferable because it is easy to maintain. . The cooling unit may be a radiator.

Heat radiation in this embodiment will be explained.
Heat is generated by the collision of electrons with the anode target 5, and the heat of the anode target 5 is transmitted to the support 7, and is transferred to the insulating envelope via the bonded body 23 connected to the other end 7b of the support 7. It is radiated and conducted to the heat sink 11, the electrical insulator 33, and the heat radiator 15, and is radiated and conducted to the other electrical insulator 34, the tube vessel 13, etc. via the heat radiator 15. The heat conducted to the tube container 13 from the other electrical insulators 34 and the heat radiator 15 is released by the cooling section 35 that cools the outer surface of the tube container 13. In this embodiment, since the heat radiator 15 is directly connected to the other end 7b of the support 7, the heat generated in the anode target 5 and transferred to the support 7 can be radiated more efficiently.

Next, filling of the electrical insulator 33 will be explained.
The electrical insulator 33 is, for example, in a molten state at about 50°C and hardened by heating at about 100°C. In this embodiment, the electrical insulator 33 is filled into the space K (see FIG. 4) by performing the steps of injecting a molten resin material and curing by heating a plurality of times. In this embodiment, the electrical insulator 33 is filled in two steps. The first resin material (molten resin material) 33a to be injected for the first time and the second resin material (molten resin material) 33b to be injected for the second time are both made of the same silicone resin as the main component. Furthermore, fine particles of an inorganic substance (for example, silica, etc.) may be blended into the silicone resin material, which is the main component of the first resin material 33a, which is injected first, in order to improve thermal conductivity and X-ray shielding ability. , the coefficient of thermal expansion may be smaller than that of the second resin material 33b that is injected later.
For example, the coefficient of thermal expansion of silicone alone is 270×10 ⁻⁶ /K, but when fine particles are blended, the coefficient of thermal expansion can be increased to about 200 to 270×10 ⁻⁶ /K.

Filling of the electrical insulator 33 is performed in the following order.
(1) As shown in FIG. 3, connect the high voltage cable 17 to the power supply part 29 of the support body 7, and screw the female thread part 31 of the heat sink 15 into the male thread part 32 of the other end 7b of the support body 7. At the same time, the heat dissipating body 15 spirally moves until one end surface 15a abuts on the joined body 23.
Thereby, a space K surrounded by the high voltage cable 17, the other end 7b of the support body 7, and the heat sink 15 is formed. This space K is a space filled with the electrical insulator 33.

(2) As shown in FIG. 4, the first resin material 33a is applied to the female screw portion 31 (see FIG. 3) of the heat sink 15, and is heated and hardened.
The first resin material 33a is applied to the female threaded portion 31 using a brush, for example, and is applied so that the thread groove of the female threaded portion 31 is filled. The resin material is applied in a molten state at, for example, 50° C., and then placed in a furnace and heated to about 100° C. to be cured.

(3) Next, as shown in FIG. 4, after the first resin material 33a is hardened, the second resin material 33b is poured into the space (remaining space) K1 inside the first resin material 33a (see FIG. 2). At this time, the second resin material 33b in a molten state is filled into the space K1 from above with the support body 7 facing downward (upside down from the state shown in FIG. 4), and then placed in a furnace and heated to harden.

(4) Finally, the first resin material 33a and the second resin material 33b are cooled to room temperature in a hardened state to become the electrical insulator 33.

The effects of the first embodiment will be explained.
According to the first embodiment, the electrical insulator 33 is filled in multiple times by applying the first resin material 33a and then heating and hardening it, and then injecting the second resin material 33b and then heating and hardening it. Since the volume of the electrical insulator formed each time is reduced, it is possible to alleviate the residual stress inside the electrical insulator that occurs due to phase changes during the manufacturing process (molten resin → heat curing → cooling). can. In particular, since the volume to be filled is divided and reduced, the adverse effects of volumetric contraction that occurs during cooling can be reduced.

That is, the electrical insulator 33 hardens in an expanded state and then contracts in volume when cooled, and the members of the X-ray tube to which the electrical insulator 33 is adjacent contract at different contraction rates. Internal stress occurs in the resin material of the electrical insulator 33, but since the volume of the electrical insulator 33 that undergoes phase change is made small, it is possible to alleviate the residual stress that occurs inside the electrical insulator. It becomes possible to prevent the occurrence of defects in 33. This makes it possible to obtain a highly reliable X-ray tube that can maintain stable withstand voltage performance.

Furthermore, by applying the first resin material 33a to the female screw portion 31 of the heat sink 15, the first resin material 33a is the only resin material that comes into contact with the heat sink 15, and the second resin material 33b is in contact with the heat sink 15. Since there is no need to be affected by contact (effects due to differences in expansion coefficients), it is also possible to prevent defects in the electrical insulator 33 between the high voltage cable 17 and the heat sink 15. For example, regarding the first resin material 33a, the coefficient of thermal expansion of silicone alone is 270×10 ⁻⁶ /K, whereas the coefficient of thermal expansion of aluminum nitride forming the heat sink 15 is 4 to 5×10 ^-6 /K.

Other embodiments will be described below, but in the embodiments described below, the same reference numerals will be given to parts that have the same effects as those of the above-mentioned embodiment, and detailed explanations of those parts will be omitted. However, in the following description, the main points that are different from one embodiment will be explained.

FIG. 5 shows a second embodiment. In this second embodiment, the resin material constituting the electrical insulator 33 is filled in three times, and specifically, the first resin material 33a, the second resin material 33b, and the third resin material 33c are filled. Divide and inject in this order. The first resin material 33a is heated and hardened after being applied to the female threaded portion 31 of the heat sink 15 in the same manner as in the first embodiment, and the second resin material 33b is thickened on the inner peripheral side of the first resin material 33a. The third resin material 33c is applied in a layered manner and then cured by heating, and the remaining space K2 is filled with the third resin material 33c and then cured by heating.

According to the second embodiment, since the resin materials 33a, 33b, and 33c constituting the electrical insulator 33 are filled in three times, the volume of phase change per time is greater than that in the case of dividing into two times. Since it is also possible to reduce the size, defects in the electrical insulator 33 between the high-voltage cable 17 and the heat sink 15 can be further prevented from occurring.

FIG. 6 shows a third embodiment. In this third embodiment, similarly to the second embodiment, the resin material constituting the electrical insulator 33 is filled in three times. The first resin material 33a is applied to the female threaded portion 31 of the heat sink 15 and cured by heating, as in the first embodiment, and the second resin material 33b is cured by heating after being applied to the outer circumferential surface of the high-voltage cable 17. After filling the remaining space K3 between the first resin material 33a and the second resin material 33b with the third resin material 33c, the third resin material 33c is heated and cured.

In the third embodiment, the first resin material 33a and the second resin material 33b are applied to the interface between the high-voltage cable 17 covering material (silicone resin, etc.) and the heat sink 15 (aluminum nitride, etc.) and are then cured. Since the third resin material 33c of the same composition is injected into the space K3 between the first resin material 33a and the second resin material 33b, the third resin material 33c has the same composition on the boundary surface, so it is compatible with the third resin material 33c. Therefore, the occurrence of defects in the electrical insulator 33 can be further prevented. In this case as well, the first resin material 33a and the second resin material 33b that contact the interface with the high voltage cable 17 and the interface with the heat sink 15 should have a smaller coefficient of thermal expansion than the third resin material 33c. is desirable.

FIG. 7 shows a fourth embodiment.
In the fourth embodiment, as shown in FIG. 7, the support body 7 is turned upside down with the other end 7b facing down, and the first resin material 33a and the second resin material 33b are stacked vertically in the space K. Fill them sequentially. In this embodiment, an example is shown in which the electrical insulator 33 is filled in two parts, the first resin material 33a and the second resin material 33b, but the electrical insulator 33 may be filled in three or four parts.

In this fourth embodiment as well, by filling the electrical insulator 33 with the resin materials 33a and 33b in multiple steps, the volume that undergoes a phase change during the manufacturing process (molten resin→heat curing→cooling) can be divided and made smaller. Therefore, defects in the electrical insulator 33 between the high voltage cable 17 and the heat sink 15 can be prevented from occurring.
Further, the resin materials 33a, 33b, etc., which are to be filled in a plurality of times, can be injected sequentially one above the other, making it easy to fill.

It should be noted that the present invention is not limited to the above-described embodiments as they are, but can be implemented by modifying the constituent elements within the scope of the invention at the implementation stage. Moreover, various inventions can be formed by appropriately combining the plurality of components disclosed in the above embodiments.
For example, some components may be deleted from all the components shown in the embodiments.

DESCRIPTION OF SYMBOLS 1... Fixed anode type X-ray tube, 3... Vacuum envelope, 5... Anode target, 7... Support body, 9... Cathode filament, 11... Insulating envelope, 15... Heat sink, 17... High voltage cable, 23... Joined body (anode side metal envelope), 31...female screw, 32...male screw, 33...electric insulator, 33a...first resin material, 33b...second resin material, K...resin filling space.

Claims (4)

a vacuum envelope formed with an output window that transmits X-rays;
an anode target provided in the vacuum envelope and facing the output window; and a support for the anode target;
An X-ray tube comprising a cathode filament that is provided in the vacuum envelope and emits electrons to irradiate the anode target,
The vacuum envelope includes an insulating envelope made of ceramic, a cathode-side metal envelope provided on one end surface of the insulating envelope and supporting the cathode filament, and a cathode-side metal envelope provided on the other end surface of the insulating envelope. an anode side metal envelope that is provided and joined to the support to support the support; a high voltage cable connected to the support to apply a high voltage to the anode target; and a high voltage cable around the high voltage cable. comprising an electrically insulating heat radiator arranged and an electrical insulator filled in a space between the heat radiator and the high voltage cable,
The electric insulator is injected with a resin material in a molten state and then cured by heating, and the method for manufacturing an X-ray tube is filled by performing the steps of injection and curing by heating a plurality of times. The support body has a male threaded part, the heat sink has a female thread part, and the female thread part is formed over the entire inner peripheral surface of the heat sink, and only a part of the heat sink is formed on the support body. is screwed into the male threaded portion of the
The electrical insulator is formed by applying a first molten resin material to the female threaded portion of the heat radiator that is not screwed into the male threaded portion of the support, and then hardening by heating, and then applying the next molten resin material to the The method for manufacturing an X-ray tube according to claim 1, wherein the material is cured after being injected into the space between the heat sink and the high-voltage cable. 3. The method for manufacturing an X-ray tube according to claim 1, wherein the main component of the resin material injected in multiple doses is the same silicone resin. 4. The method for manufacturing an X-ray tube according to claim 3, wherein the resin material is injected in multiple steps, and the coefficient of thermal expansion of the resin material injected first is smaller than the coefficient of thermal expansion of the resin material injected later. .

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