JPH10228875A - Rotating anode x-ray tube with metal envelope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage to a vacuum envelope during a manufacturing process or when used. SOLUTION: A vacuum envelope 1 is constitution of a cathode side envelope 2 made of an insulating material such as hard glass, a metal envelope 3 and positioned in the intermediate part, and an anode side envelop 4 made of a similar insulating material to that of the envelope 2. A cathode 5 and an anode containing an umbrella type target 7 are installed in one end and the other end of the vacuum envelope, respectively, ad sealed air-tightly in vacuum on the opposite to each other. The metal envelope is constituted of an intermediate envelope 11 and a ring substrate 12 facing to the rear side of the umbrella target. The ring base plate is a flat plate-like ring made of a relatively thick stainless steel and connected to the anode side envelope by putting a cylindrical ring 22 made of a material having approximately the same thermal expansion coefficient as that of the material for the anode side envelope. The thin plate- like ring has a bent part A25 and the cylindrical ring has a bent part B28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating anode X-ray tube having a metal envelope, and more particularly to a rotating anode X-ray tube having an improved structure and manufacturing method of a metal envelope to improve hermetic reliability. About pipes.

[0002]

2. Description of the Related Art A first example of a rotating anode X-ray tube having a metal envelope is disclosed in Japanese Patent Application Laid-Open No. Sho 54-96985. The middle part of the vacuum envelope of the X-ray tube is made of metal, and the stator for rotating the anode of the X-ray tube is arranged close to the umbrella-shaped target, and high-voltage discharge between the stator and the anode terminal is performed. Preventing. In this known technique, a portion of the metal envelope corresponding to the back surface of the target is a metal ring made of a material having good heat conductivity such as copper. Since the metal ring is substantially flat and made of copper or the like, the metal ring is subjected to a force applied to the vacuum envelope due to a pressure difference between the inside of the vacuum X-ray tube and the outside of the atmospheric X-ray tube. However, since the metal ring is easily deformed, the diameter of the metal ring cannot be increased so much that it cannot be applied to a large-capacity X-ray tube having a large target diameter. When a metal ring is brought close to the anode, when a high voltage is applied between the anode and the junction (earth potential) extending from the metal ring and connected to the glass envelope part, However, since the high-voltage discharge occurs and the joint is broken and a vacuum failure is likely to occur, the joint must be provided at a position away from the anode, and eventually the distance between the stator and the target is reduced. They also had the problem of being restricted.

As a second conventional example which addresses the above problem, Japanese Utility Model Laid-Open Publication No. 63-18756 discloses a rotating anode X-ray tube shown in FIG. In this rotary anode X-ray tube, the portion of the metal envelope facing the back surface of the X-ray tube anode target is formed into a flat plate using a metal having excellent mechanical strength even at a high temperature, and is connected to a glass envelope. And a shield that electrically shields the junction to be formed from the anode. The configuration of FIG. 5 will be briefly described below. In FIG. 5, a vacuum envelope 1 of a rotating anode X-ray tube is the same as a cathode envelope 2 made of an insulating material such as glass, a metal envelope 3 located in the middle, and a cathode envelope 2. It is constituted by an anode-side envelope 4 made of an insulating material. A cathode 5 is connected to one end of the vacuum envelope 1.
However, an anode 6 is sealed at the other end while maintaining the vacuum airtightness.
An umbrella-shaped target 7 is rotatably supported on the anode 6 by a rotation support mechanism including a rotor. A stator 8 for rotating the rotor is provided on the outer periphery of the anode-side envelope 4 by an insulating cylinder 9.
Are arranged through. The metal envelope 3 is an intermediate envelope 11
And a substrate 12 facing the back surface of the target 7, and a hollow portion 13 through which the anode 6 is inserted is provided in the center of the substrate 12. At the connecting portion 10 slightly closer to the outer periphery than the diameter of the hollow portion 13, the anode-side envelope 4 and the substrate 12
Is connected. Further, a metal shielding tube 14 is provided in the hollow portion 13 so as to protrude longer than the connection portion 10. The shielding tube 14 electrically shields the connection portion 10 between the substrate 12 and the anode-side envelope 4 with respect to the anode 6.

Here, the substrate 12 is made of stainless steel (having a thermal expansion coefficient of 14.14 × 10 ⁶ /
deg) and a heat-resistant high-strength material such as a flat plate. If the thickness of the substrate 12 is 3 to 6 mm, it can withstand heat radiation from the target 7 and withstand a pressure difference between vacuum and atmospheric pressure. Therefore, by applying this configuration, it is possible to employ a target having a large diameter as the X-ray tube anode, apply a high voltage, and shorten the distance between the target and the stator.

[0005]

In a second conventional example shown in FIG. 5, a connecting portion 10 between a substrate 12 and an anode side envelope 4 has a substrate 12 made of stainless steel and an anode side made of hard glass. The envelope 4 is connected by a ring 15 sealed in hard glass. In the X-ray tube, hard glass such as borosilicate glass is used in consideration of heat resistance. For this reason, Kovar having a thermal expansion coefficient substantially equal to that of borosilicate glass is used as a material of the ring 15. . For this reason, in the connection between the substrate 12 and the ring 15, there is a problem that the thermal expansion coefficients of the two materials are greatly different from each other, and stress is generated in the connection portion 10 due to thermal strain and the anode-side envelope 4 is damaged. there were. By increasing the length of the ring 15, the thermal stress is slightly relieved, but it is still insufficient, and if the length of the ring 15 is further increased, X
Another problem is that the total length of the wire tube becomes longer.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a rotary anode X-ray tube having a short overall length without damaging the vacuum envelope during the manufacturing process and use. And

[0007]

In order to achieve the above object, a metal envelope rotating anode X-ray tube according to the present invention has a vacuum envelope having a middle portion made of metal and both ends made of a heat-resistant insulator. In the vessel, a cathode and an umbrella-shaped target are supported by the heat-resistant insulator and disposed opposite to each other, and a heat-resistant high-strength portion is provided at a portion of the metal part of the vacuum envelope facing the back surface of the target. A metal envelope rotating anode X-ray tube in which a flat ring substrate made of a metal material is provided, and one end of a heat-resistant insulator A on the anode side is connected to the inner diameter of the ring substrate. A thin plate-shaped ring connected to the ring substrate and a cylindrical ring connected to the heat-resistant insulator A are interposed between the inner diameter portion of the substrate and the heat-resistant insulator A on the anode side. The material has a thermal expansion coefficient substantially equal to that of the heat-resistant insulator A. That the metal and then, in which the connecting portion of the thin plate ring and the cylindrical ring are joined by welding (claim 1).

In this configuration, a thin plate ring and a cylindrical ring are interposed between the ring substrate of the metal envelope and the anode side envelope, and the thermal expansion coefficient of the material of the cylindrical ring is reduced by the anode side envelope. Since it is almost equal to the material of the vessel, the influence from the ring substrate and the influence from the connection between the thin plate ring and the cylindrical ring on the connection between the anode side envelope and the cylindrical ring are reduced, During the manufacturing process and use of the X-ray tube, the connection between the anode-side envelope and the cylindrical ring does not break due to thermal stress or the like, and the hermetic reliability of the X-ray tube is improved.

Further, in the metal anode rotating anode X-ray tube according to the present invention, the material of the heat-resistant insulator A is borosilicate glass, the material of the ring substrate is stainless steel, and the thin ring and the cylindrical ring are used. Is Kovar (claim 2). In this configuration, the material of the thin plate ring and the cylindrical ring is changed to Kovar having a thermal expansion coefficient close to that of borosilicate glass, which is a material of the anode side envelope, and the anode side envelope and the cylindrical ring are formed. This further reduces the stress applied to the connection with the substrate.

In the metal anode rotating anode X-ray tube according to the present invention, the thin plate ring is brazed to the ring substrate on the inner diameter side, and the outer diameter end is smaller than a right angle toward the anode side. The cylindrical ring has a bent portion A bent at a bending angle, one end of the cylindrical ring is brazed or welded to the heat-resistant insulator A, and the other end faces a flange portion and an outer peripheral portion thereof toward the anode side. And has a bent portion B bent at the same bending angle as the bending angle of the thin plate-shaped ring. The bent portion B is fitted inside the bent portion A, and the ends of both bent portions are joined by welding. (Claim 3).

In this configuration, a bent portion is provided in the thin ring and the cylindrical ring to increase the distance between the ring substrate and the anode-side envelope without increasing the overall length of the vacuum envelope. , Reducing the influence of the metal envelope on the anode-side envelope

[0012] In the metal anode rotating anode X-ray tube according to the present invention, the bending angle of the bent portion A of the thin plate ring is further changed by the bending angle B of the thin plate ring at the time of single processing, and the bending angle at the time of welding. The bending angle of the bent portion A is returned to the bending angle A from the bending angle B when the ring substrate and the thin ring are brazed (claim 4).

In this configuration, since the bent portion of the thin ring is deformed by residual stress when brazing the ring substrate and the thin ring, the bent portion is processed before brazing in consideration of the deformation. This contributes to improving the processing accuracy of the vacuum envelope and preventing damage to the anode-side envelope.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As for the reference numerals in the figure, those having the same functions as those of the prior art are used for the same reference numerals. FIG. 1 shows a first embodiment of a rotating anode X-ray tube of a metal envelope according to the present invention. In FIG. 1, a vacuum envelope 1 includes a cathode-side envelope 2 made of an insulator such as hard glass, a metal envelope 3 located at an intermediate portion, and an insulator similar to the cathode-side envelope 2. And an anode-side envelope 4 made of A cathode 5 is sealed at one end of the vacuum envelope 1 and an anode 6 is sealed at the other end while maintaining vacuum tightness. An umbrella-shaped target 7 is rotatably supported on the anode 6 by a rotation support mechanism (not shown) including a rotor 23. The cathode 5 and the umbrella-shaped target 7 are arranged to face each other in the metal envelope 3. A stator (not shown) for rotating the rotor 23 is provided on the outer periphery of the anode-side envelope 4 by an insulating cylinder (not shown).
Is located through

The metal envelope 3 comprises an intermediate envelope 11 and a ring substrate 12 facing the back of the umbrella-shaped target 7. The intermediate envelope 11 is formed in a cylindrical shape, and the ring substrate 12 is formed in a flat plate shape. Both are stainless steel (for example, SUS304 or the like) having high mechanical strength even at a high temperature, or a heat resistant material having similar thermal characteristics and mechanical strength. It is made of heat-resistant and high-strength materials such as steel and titanium alloy.
Stainless steel has a coefficient of thermal expansion of 14 × 10 ⁶ / deg.
Degree, thermal conductivity 0.17 cal / cm · sec · de
It has thermal characteristics of about g. The main role of the ring substrate 12 is to receive heat radiated from the umbrella-shaped target 7 and dissipate the heat into the surrounding insulating oil, and to withstand the pressure difference between vacuum and atmospheric pressure. The thickness of the ring substrate 12 needs to be increased as the diameter of the umbrella-shaped target 7 increases, but in the case of an X-ray tube using the umbrella-shaped target 7 having a diameter of about 150 mm, the thickness is 3 to 6 mm. Sufficient function can be exhibited thermally and mechanically.

The ring-side substrate 12 is connected to the anode-side envelope 4. Further, a hollow portion 13 for inserting the anode 6 is provided at a central portion of the ring substrate 12. The outer diameter of the anode-side envelope 4 is larger on the side connected to the ring substrate 12 than on the anode end side. This is because the withstand voltage between the anode and the ground is reduced by increasing the distance between the connection portion (ground potential) between the ring substrate 12 and the anode side envelope 4 (ground potential) and the rotor 23 (anode potential) of the anode 6. It is a thing to consider not to do. A thin plate-shaped ring 21 and a cylindrical ring 22 are arranged at a connection portion between the ring substrate 12 and the anode-side envelope 4. FIG. 2 shows details of the structure. The thin plate-shaped ring 21 has a flat plate portion 24 and a bent portion A25.
And is joined to the ring substrate 12 by brazing at the inner diameter portion 26 of the flat plate portion 24. The cylindrical ring 22 includes a cylindrical portion 27, a flange portion 32, and a bent portion B2.
And the anode side envelope 4 at the tip portion 29 of the cylindrical portion 27.
It is connected to the. In addition, the inside diameter of the bent portion A25 of the thin ring 21 is attached to the bent portion B2 of the cylindrical ring 22.
8 are fitted, the bent part A25 and the bent part B
The thin plate-like ring 21 and the cylindrical ring 22 are connected by joining the tip portion 30 of the thin plate-like member 28 with a welding portion 28 by welding.

With respect to the connection between the cylindrical ring 22 and the anode-side envelope 4, a hard glass such as borosilicate glass is used as the material of the anode-side envelope 4, and the material of the cylindrical ring 22 is Kovar or the like. And a material having a thermal expansion coefficient substantially equal to that of borosilicate glass is used. In X-ray tubes, during manufacture and use, the cylindrical ring 22
Since the temperature of the connection between the and the anode-side envelope 4 becomes high, it is important that both materials have substantially the same thermal expansion coefficient so that a large thermal stress does not occur. Also in this embodiment, Kovar is used as the material of the cylindrical ring 22 in consideration of this point. Needless to say, other materials may be used as long as they are heat-resistant and high-strength metal materials having a thermal expansion coefficient close to that of Kovar. Here, after the distal end portion 29 of the cylindrical ring 22 is glass-wrapped with borosilicate glass, which is the material of the anode-side envelope 4, the cylindrical ring 22 is connected to the anode-side envelope 4.

The shape of the thin plate-like ring 21 is
The reason why the length of the vacuum envelope 1 is determined at the position of the flat plate portion 24 is to make the connection between the ring substrate 12 and the anode side envelope 4 as short as possible. And the cylindrical ring 22 at the bent portion A25.
The ring substrate 12 and the anode-side envelope 4 are connected to each other by welding with the bent portion B28 of FIG. Therefore, the bent portion A25 of the thin plate ring 21 is not limited to the shape shown in FIG. 2 as long as it has a shape that allows the bent portion B28 of the cylindrical ring 22 to be fitted. You may.

The thin ring 21 and the cylindrical ring 2
The length 2 is better when the thermal stress generated at the connection with the anode side envelope 4 is taken into consideration, and the longer the thickness, the better. However, in consideration of mechanical strength, the thickness is preferably larger and the length is preferably shorter. Therefore, the thickness and length are determined in consideration of both thermal stress and mechanical strength. It is appropriate that both the thin ring 21 and the cylindrical ring 22 have a thickness of about 0.5 to 2 mm and a length of about 20 to 40 mm.

As the material of the thin plate-like ring 21, a metal material having a thermal expansion coefficient approximately equal to or larger than the material of the cylindrical ring 22 (Kovar in this embodiment) is used.
This is to reduce the thermal stress applied to the weld between the thin ring 21 and the cylindrical ring 22. In this embodiment, Kovar is used. Therefore, the thermal stress at the welded portion and the thermal stress at the connection between the cylindrical ring 22 and the anode-side envelope 4 are also reduced.

Next, the ring substrate 12 and the thin ring 21
Will be described with reference to FIGS. 3 and 4. FIG. 3 and 4, the ring substrate 12 and the thin ring 2
1 shows a structural view before and after brazing with No. 1. In FIG.
The inner diameter 2 of the thin ring 21 is attached to the inner diameter of the ring substrate 12.
6 is provided with a stepped portion for fitting, and the brazing material 31 is placed there,
The inner diameter portion 26 of the thin ring 21 is fitted thereon.
Copper brazing or silver copper brazing is used as the brazing material 31, and the temperature is raised to about 700 to 1100 ° C. during brazing. Bending part A25 of thin ring 21 before brazing
Is formed so as to be substantially perpendicular to the flat plate portion 24, after the brazing, the bent portion A25 is slightly opened to the outer peripheral side and inclined as shown in the figure. This is the ring substrate 1
Since the thermal expansion coefficient of stainless steel, which is the material of No. 2, is larger than that of Kovar, which is the material of the thin plate-shaped ring 21, when the brazed portion is cooled, the contraction of the ring substrate 12 is large, Tensile stress acts and deforms. Therefore, in order for the bent portion A25 of the thin plate ring 21 to be substantially perpendicular to the flat plate portion 24 after brazing, as shown in FIG. The bent angle of the bent portion A25 with respect to the flat plate portion 24 is not a right angle, but is larger than the right angle, and slightly inclined toward the inner peripheral side. In the present embodiment, if it is tilted by about 4 °, it becomes a substantially right angle after brazing. This angle of inclination may be slightly larger in consideration of the fitting allowance between the thin ring 21 and the cylindrical ring 22, and is preferably about 4 ° to 8 °.

The flat plate portion 2 after brazing the bent portion A25
It is desirable that the bending angle with respect to 4 is substantially a right angle when viewed from the viewpoint of strength. However, as described above, the bending angle is made smaller than the right angle and inclined toward the outer peripheral side in accordance with the bent portion B28 of the cylindrical ring 22 to be fitted. In such a case, the bent portion A25 of the thin plate-like ring 21 before brazing may be used.
May be processed so as to be larger than the bending angle of the bent portion B28 of the cylindrical ring 22 by about 4 ° so that the bending angles match after brazing.

As the anode-side envelope 4, ceramics such as alumina porcelain may be used in addition to borosilicate glass. In this case, the tip portion 29 of the cylindrical ring 22 and the anode-side envelope 4 are connected to each other. Are joined by brazing. The end surface of the anode-side envelope 4 is subjected to a metallizing process for brazing, and then brazed to the distal end portion 29 of the cylindrical ring 22.

[0024]

As described above, according to the present invention, a thin ring and a cylindrical ring are provided between a ring substrate of a metal envelope and an anode-side envelope to form a vacuum envelope. In the final step, the thin plate ring and the cylindrical ring are joined by welding, so that the connection between the anode side envelope and the cylindrical ring does not receive excessive stress during the manufacturing process and during use Therefore, it is possible to provide a highly airtight and reliable vacuum envelope that does not cause breakage of an insulating member such as glass. As a result, a highly reliable and long-life rotating anode X-ray with high assembling accuracy can be provided. A tube is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a metal envelope rotating anode X-ray tube according to the present invention.

FIG. 2 is a view showing details of a connection portion between a ring substrate and an anode-side envelope.

FIG. 3 is an example of a structural diagram before and after brazing a ring substrate and a thin plate ring.

FIG. 4 is another example of a structural diagram before and after brazing a ring substrate and a thin ring.

FIG. 5 is a diagram showing a conventional example of a metal envelope rotating anode X-ray tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum envelope 2 Cathode envelope 3 Metal envelope 4 Anode envelope 5 Cathode 6 Anode 7 Umbrella-shaped target 11 Intermediate envelope 12 Ring substrate 13 Hollow part 21 Thin ring 22 Cylindrical ring 23 Rotor 24 Flat plate part 25 Bend part A 26 Inner diameter part 27 Cylindrical part 28 Bend part B 29 Tip part 30 Tip part 31 Brazing material 32 Flange part

Claims (4)

[Claims] A cathode and an umbrella-shaped target are disposed opposite to each other while being supported by the heat-resistant insulator in a vacuum envelope whose intermediate portion is made of metal and whose both ends are made of a heat-resistant insulator. A flat ring substrate made of a heat-resistant high-strength metal material is disposed on a portion of the metal intermediate portion of the vacuum envelope facing the back surface of the target, and a heat-resistant material on the anode side is provided on the inner diameter portion of the ring substrate. A thin plate connected to the ring substrate between the inner diameter of the ring substrate and the heat-resistant insulator A on the anode side in a metal envelope rotating anode X-ray tube to which one end of the conductive insulator A is connected A cylindrical ring connected to the heat-resistant insulator A and a metal having a thermal expansion coefficient substantially equal to that of the heat-resistant insulator A. That the connecting parts of the ring are joined by welding A rotating anode X-ray tube for a metal envelope, characterized in that: 2. The metal envelope rotating anode X-ray tube according to claim 1, wherein the material of the heat-resistant insulator A is borosilicate glass, the material of the ring substrate is stainless steel, A metal anode rotating anode X-ray tube, wherein the material of the cylindrical ring is Kovar. 3. A metal anode rotating anode X-ray tube according to claim 1 or 2, wherein said thin plate-shaped ring is brazed to said ring substrate at an inner diameter side, and an anode at an outer diameter side end. The cylindrical ring has one end brazed or welded to the heat-resistant insulator A, and the other end has a flange portion and an outer peripheral portion thereof. A bent portion B bent toward the anode side at the same bending angle as the bending angle of the thin plate-shaped ring. The bent portion B is fitted inside the bent portion A, and the ends of both bent portions are provided. A rotating anode X-ray tube for a metal envelope, the parts of which are joined by welding. 4. The metal anode rotating anode X-ray tube according to claim 3, wherein the bending angle of the bent portion A of the thin plate-shaped ring at the time of single processing of the thin plate-shaped ring is welded. Metal, wherein the bending angle of the bent portion A returns to the bending angle A from the bending angle B when the ring substrate and the thin ring are brazed. Envelope rotating anode X-ray tube.