JPH06325706A - Rotary anode type x-ray tube - Google Patents

Abstract

PURPOSE:To obtain a rotary anode type X-ray tube which can maintain a dynamic pressure type slide bearing operation with a high reliability for a long period, by preventing a scattering of a liquid metallic lubticate from a slide bearing to a space in a vacuum container, and at the same time, preventing a piling of the liquid metallic lubricate in a narrow spatial passage between the slide bearing and the space. CONSTITUTION:The wall surface of a spatial passage G connecting a dynamic pressure slide bearing interval 28 composed by the extension 18a of a fixed body and the extensions 19 and 35 of rotary bodies provided coaxial to the fixed body, and the internal space of a vacuum container 23, is made as a surface not wet with a liquid metallic lubricate. On the way of the spatial passage G composed of a surface not wet with such a lubricant, at least one of trap hollow bodies 36 and 38 to grasp the lubricant leaking through the passage is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary anode type X-ray tube, and more particularly to improvement of a rotary structure thereof.

[0002]

2. Description of the Related Art As is well known, a rotary anode type X-ray tube supports a disk-shaped anode target with a rotating body having a bearing and a fixed body, and energizes an electromagnetic coil of a stator arranged outside a vacuum container to achieve high speed. While rotating, the electron beam emitted from the cathode is applied to the anode target surface to emit X-rays. The bearing may be a rolling bearing such as a ball bearing, or a metal lubricant that forms a spiral groove on the bearing surface and is liquid in operation such as gallium (Ga) or gallium-indium-tin (Ga-In-Sn) alloy. It is composed of a dynamic pressure type sliding bearing using. Examples of the latter slide bearing are disclosed, for example, in JP-B-60-21463 and JP-A-60-113.
817, JP-A-60-117531, JP-A-2-2
No. 27948, JP-A-2-244545, or European Patent Publication Nos. 479194 and 479.
No. 198 is disclosed in each specification and the like.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In the rotary anode type X-ray tube provided with the dynamic pressure type slide bearing using the liquid metal lubricant disclosed in the above publications, the rotary body can be rotated at a high speed with respect to the fixed body. At the same time, in order to discharge the gas generated in the bearing part to the outside of the bearing part without leakage of the lubricant, a narrow passage leading from the bearing gap to the space inside the vacuum container is required between the fixed body and the rotating body. And If the liquid metal lubricant leaks out from the bearing, the lubricant in the plain bearing will be insufficient, and the stable dynamic pressure bearing action for a long time cannot be obtained. The dispersion of the agent causes a fatal obstacle that the withstand voltage performance is significantly impaired.

In order to prevent the occurrence of such a failure,
For example, in the rotary anode type X-ray tube disclosed in the above-mentioned JP-A-2-244545 and European Patent Publication Nos. 479194 and 479198, the spatial passage from the plain bearing to the space inside the vacuum container is a liquid. It is composed of a wall surface of a material that is well wetted and reacted with the lubricant so that the metal lubricant immediately adheres. Part of this passage is 0.1 m
It has a narrow gap of about m and constitutes a part of the lubricant leakage prevention means. If the lubricant leaked from the bearing part adheres to this narrow passage wall and causes a reaction, the gap will be further narrowed, and if lubricant leaks later, it will be accumulated in this narrow passage and the passage will be accumulated. There is a possibility that the rotating body and the fixed body may be mechanically brought into close contact with each other in an extreme case. When such a state is reached, stable rotation performance cannot be obtained.

The present invention solves the above inconveniences, prevents the liquid metal lubricant from scattering from the sliding bearing portion into the space inside the vacuum container more reliably, and prevents the liquid metal lubricant from flowing into the narrow spatial passage between them. It is an object of the present invention to provide a rotating anode type X-ray tube capable of preventing metal lubricant from accumulating and maintaining a highly reliable dynamic pressure type sliding bearing operation for a long time.

[0006]

SUMMARY OF THE INVENTION The present invention connects a dynamic pressure slide bearing gap constituted by an extension of a fixed body and an extension of a rotating body arranged coaxially with the extension and a space inside a vacuum container. At least one trap that traps the lubricant leaking through the passage in the middle of the spatial passage formed by the surface that is not wetted by the liquid metal lubricant as the wall surface of the spatial passage It is a rotary anode type X-ray tube provided with a cavity.

[0007]

According to the present invention, even if the liquid metal lubricant leaks out from the bearing portion, the lubricant is reliably caught in the trap cavity without adhering to the wall surface of the narrow spatial passage, It is possible to more reliably prevent scattering to the space inside the X-ray tube vacuum container outside the space. Therefore, it is possible to obtain the rotary anode type X-ray tube provided with the dynamic pressure type slide bearing in which the lubricant is not accumulated in the narrow spatial passage and the reliable rotation performance is maintained for a long time.

[0008]

Embodiments will be described below with reference to the drawings.
The same parts are represented by the same symbols. The embodiment shown in FIGS. 1 to 3 has the following configuration. That is, the disk-shaped anode target 11 made of a heavy metal has a cylindrical rotating body 12
It is fixed at one end. The rotating body 12 includes an inner cylinder 13, an intermediate cylinder 14, a copper outer cylinder 15, and a rotating shaft 16 projecting from the intermediate cylinder, which are coaxially fitted to each other. The anode target 11 is attached to the nut 1 on the rotating shaft 16.
It is fixed at 7. A cylindrical fixed body 18 is inserted into the inner side of the inner cylinder 13 from the rotary body opening 12a and fitted coaxially therewith. The fixed body 18 has a fixed body extending portion 18a having a reduced outer diameter near the lower end of the fixed body 18 in the figure, that is, near the rotary body opening 12a. A ring-shaped thrust ring 19 that surrounds the fixed body extension 18a and substantially closes the opening 12a is fixed to the rotary body opening 12a with a plurality of bolts 20. An auxiliary support member 21 is fixed to the tip end of the fixed body extension 18a by welding, and this is airtightly joined to the glass portion of the vacuum container 23 via a sealing metal ring 22. Inside the vacuum container 23, a cathode 24 is provided facing the anode target 11, and a window 25 for X-ray emission is provided in a part of the vacuum container. A stator electromagnetic coil 26 is arranged around the rotating body 12 outside the vacuum container.

Two sets of dynamic pressure type radial slide bearings 27 and two sets of dynamic pressure type thrust slide bearings 28 as shown in the above-mentioned respective publications are formed at the fitting portion of the cylindrical rotary body 12 and the fixed body 18. ing. Therefore, the herringbone pattern spiral grooves 29, 30 as described in the above-mentioned publications are formed on the outer peripheral surface and the tip surface of the fixed body, which are the sliding bearing surfaces on the fixed body side, and the upper surface of the thrust ring 19. ing. The sliding bearing surface on the rotor side facing this may be a simple smooth surface, or may have a spiral groove formed if necessary. Each plain bearing is configured to maintain a bearing clearance of approximately 20 micrometers during rotary operation. Also, the fixed body 1 on the rotation axis
8 is provided with a lubricant accommodating chamber 31 whose center portion is a hole hollowed out in the axial direction. The lubricant containing chamber 31 has an upper end opening 31a in the drawing communicating with the bearing gap of the thrust bearing 28 on the target side, and a terminating end 31b on the lower side in the drawing extending to the fixed body extension 18a. A slightly cut small diameter portion 32 is formed on the outer peripheral wall of the intermediate portion of the fixed body 18, and four radial passages 33 opening from the lubricant containing chamber 31 to the small diameter portion 32 are 90 degrees. It is formed axisymmetrically at intervals. A liquid metal lubricant such as Ga alloy is supplied to the spiral groove of the plain bearing, the bearing gap, the lubricant accommodating chamber 31, the space formed by the small diameter portion 32, and the passage 33.

A small-diameter circumferential recess 34 is provided in the portion of the small-diameter fixed body extension 18a close to the thrust bearing 28. Thrust ring 19 has
A thrust ring cylindrical portion 19a is integrally formed so as to surround and surround the fixed body extension portion 18a. These fixed body extensions 1
8a and thrust ring 19 allow thrust bearing 2
A part of a spatial passage G from 8 to the internal space of the vacuum container 23 is configured. Further, the thrust ring 19 includes a thrust ring cylindrical portion 19a and a fixed body extension portion 18
A rotating body cover 35 that coaxially surrounds a part of a is fixed. The rotating body cover 35 has an outer cylindrical portion 35a having a large diameter and an inner cylindrical portion 35b having a small diameter. The inner cylindrical portion 35b has an inner diameter equal to that of the thrust ring cylindrical portion 19a and closely surrounds the fixed body extension portion 18a,
Further, a taper portion 35c that expands outward at the upper and lower ends thereof,
35d is formed. Thus, the fixed body extension portion 18
Further, a part of the spatial passage G extending from the thrust bearing 28 to the internal space of the vacuum container 23 is also constituted by a and the inner cylindrical portion 35b of the rotary body cover. Thrust ring cylindrical portion 19a, outer cylindrical portion 3 of the rotor cover
5a and a part of the inner cylindrical portion 35b constitute a ring-shaped first trap cavity 36 on the outer circumference of the thrust ring cylindrical portion. Then, the end surface of the thrust ring cylindrical portion 19a and the taper portion 35 of the inner cylindrical portion 35b of the rotating body cover.
The tip surface of d constitutes the opening Q1 of the first trap cavity 36. The thrust ring cylindrical portion 19a and the rotor cover 35 constitute a rotor extension that coaxially surrounds the fixed body extension.

The auxiliary support member 21 fixed to the outer periphery of the fixed body extension portion 18a has its tapered portion 21a spaced from and close to the tapered portion 35d of the inner cylindrical portion 35b of the rotary body cover to maintain a narrow passage G as well. Are arranged. On the outer periphery of the auxiliary support member 21, a fixed body cover 37 having a substantially U-shaped half-section is brazed and fixed so as to surround a part of the rotary body cover 35. The fixed body cover 37 constitutes a second trap cavity 38 having a large diameter. Fixed body cover 3
The inner cylindrical portion 37a of 7 is the outer cylindrical portion 3a of the rotor cover.
5a, the inner cylindrical portion 35b, and the tapered portion 35d have an inner shape conforming to the outer shapes, and these also form a part of the narrow passage G. Further, the auxiliary support member 21 and the end surface of the inner cylindrical portion 37a of the fixed body cover which faces the auxiliary support member 21 in close proximity to each other form an opening Q2 of the second trap cavity 38. The passage G is folded back upward from the front of the opening Q2 and extends in a meandering shape in a vertical section, and terminates at an opening R to the space inside the vacuum container. The wall surface forming each passage G described above is formed of the lubricant wetting prevention layer 43.

On the inner surfaces of the first and second trap cavities 36 and 38, the raw material surfaces of iron or a similar iron alloy such as stainless steel constituting them are exposed as they are and are wet with a lubricant. Inner surface condition. in addition,
Inside the first trap cavity 36 and inside the second trap cavity 38, there are arranged nets 39 and 40 for adhering a lubricant, which are formed by knitting thin copper wires that are well wetted with a lubricant into a substantially cylindrical shape. There is. The one net 39 constitutes the inner peripheral wall of the outer cylindrical portion 35a of the rotating body cover 35 forming a part of the first trap cavity, and the other net 40 constitutes a part of the second trap cavity. Fixed body cover 37
It is attached to the inner peripheral wall of the outer cylindrical portion and the horizontal wall of the auxiliary supporting member 21, respectively. Further, a ventilation duct 41 having a minute diameter is formed so as to directly connect the lower end portion 31b of the lubricant containing chamber and the second trap cavity so as to allow ventilation. The ventilation duct 41 is protected by a sponge-like plug 42 made of a material that repels the lubricant so that the lubricant does not pass therethrough and is not blocked by the lubricant. When the gas is generated or reaches the lubricant accommodating chamber 31, the ventilation duct 41 discharges the gas to the second trap cavity having a large internal volume without leaking the lubricant, and the gas pressure is increased here. It is for lowering and further discharging this gas into the space inside the vacuum container through the passage G leading to the opening R.

Therefore, from the thrust bearing 28 to the vacuum container 2
A lubricant wetting prevention layer 43, which is a material that does not wet with the liquid metal lubricant but repels the lubricant, is attached to the wall surface of each member forming the spatial passage G reaching the inner space of 3. The lubricant wetting prevention layer 43 is attached to the wall surface of almost the entire area of the passage G, as shown by the dotted line in FIGS. 1 and 2 and the solid line in FIG. The lubricant wetting prevention layer 43 includes zirconium oxide (ZrO ₂ ), indium oxide (In ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ).
₃ ), or those coated with titanium carbide (TiC) or the like by coating, spraying, vapor deposition, sputtering, or thermal spraying are suitable. The passages G whose opposite wall surfaces are covered with the lubricant wetting prevention layer 43 each have a passage gap of about 0.1 mm. A spiral groove pump may be provided near the circumferential recess 34 close to the thrust bearing 28 so that the lubricant leaking near the circumferential recess is pushed back toward the thrust bearing 28. Good.

In the rotating anode type X-ray tube having such a structure, during operation, the liquid metal lubricant should pass from the bearing portion to the passage G.
When it leaks to the above, since the wall surface of the passage G is formed of the lubricant wetting prevention layer 43, it rolls and moves in a small particle state without adhering to the passage wall surface. Then, as shown in FIG. 3, when reaching the vicinity of the opening Q1 of the first trap cavity 36, the rotating body rotates at a high speed, so that the lubricant is centrifugally applied to the inside of the first trap cavity 36. It is repelled and adheres to the net 39 or the inner wall surface of the trap cavity. First
The lubricant splashed into the trap cavity 36 adheres to the net 39 or the inner wall surface of the cavity and reacts therewith, so that it is reliably captured here, and there is no room for entering the passage G again. The lubricant which is not trapped by the first trap cavity 36 and further moves the passage G downward in the drawing moves in the passage G downward in the drawing as it is in a small particle state, and the taper portion 35d of the rotary body cover.
It rolls in the passage G between the auxiliary support member 21 and the centrifugal force as shown by the arrow, and is blown from the opening Q2 into the second trap cavity 38 and attached to the inner wall of the cavity or the net 40 to be captured. To be done. Since the passage G near the opening R leading to the space inside the vacuum container is folded back upward in the drawing from before reaching the opening Q2 and extends in a meandering shape, the passage G is opened from the opening R through the passage G on the terminal side. The probability that the lubricant will leak into the inner space is extremely small.

In this way, even if the liquid metal lubricant leaks from the bearing portion, the lubricant will be reliably caught in the trap cavity without adhering to the wall surface of the narrow spatial passage, and the X outside the passage will be prevented. Scattering into the space inside the vacuum tube is more reliably prevented.

In the embodiment shown in FIG. 4, the first trap cavity 36 is formed at the tip of the passage G extending along the direction of the rotation axis. That is, the metal ring 44 having an L-shaped half-section is brazed and fixed to the auxiliary support member 21, and the first trap cavity 36 is formed around the fixed body extension portion 18a. A lubricant wetting prevention layer 43 is formed on the wall surface of the passage G up to the opening Q1 of the first trap cavity 36.
Further, the second trap cavity 38 is formed on the outer periphery of the passage G extending in the lateral direction. And the second trap cavity 3
A lubricant wetting prevention layer 43 is formed on substantially the entire wall surface of each passage G leading to the opening Q2 to the opening 8 and the opening R to the vacuum space.

According to this embodiment, the first trap cavity 36 is provided at the end of the passage G linearly extended from the thrust bearing 28, and the passage G extended further in the lateral direction.
Since the second trap cavity 38 is formed on the outer periphery of the, the lubricant moving in the passage G can be more reliably trapped in the trap cavity. Therefore, it is possible to more reliably prevent the lubricant from leaking into the space inside the vacuum container.

In the embodiment shown in FIGS. 5 and 6, inside the opening of the fixed body cover 37, the outer periphery of the seal ring 45 made of a thin metal disk is fixed with the screw 46. The peripheral surface is the vertical surface 3 of the rotor cover 35.
5e. The seal ring 45 is, for example, about 50 micrometers thick, for example tungsten (W), Ni-Cr-F known as Inconel.
It is made of a material having excellent wear resistance and relatively high elasticity, such as an e alloy or spring steel. The seal ring 45 has a plurality of fixing holes 45 on its outer peripheral portion.
a. A number of narrow ventilation slits 45b through which the lubricant cannot pass due to its surface tension are spirally formed on the inner peripheral portion. As a result, the seal ring 45 is in contact with the vertical surface 35e of the rotary body cover 35 while being slightly pressed by the elastic force of itself. The fixed body inner ring 47 having an L-shaped half-section forms a narrow passage G between the inner ring 47 and the outer peripheral wall of the inner cylindrical portion 35b of the rotary body cover. 43 is formed. In addition, a rod 48 having a large number of minute holes of a size that prevents lubricant from entering due to the surface tension of the lubricant is driven into the ventilation duct 41 that connects the lubricant containing chamber 31b and the second trap cavity so as to allow ventilation. It is fixed. The rod 48 may be made of a material that repels the lubricant, in which case there is an advantage that the inner diameter of the through hole can be made relatively large.

According to this embodiment, even if the liquid metal lubricant leaks from the bearing portion, the lubricant is trapped in the trap cavity without adhering to the wall surface of the narrow spatial passage G. At the same time, in particular, the passage G can be ventilated to the space inside the vacuum container by the seal ring, but the lubricant cannot be leaked out, so that the leakage of the lubricant into the space inside the vacuum container is surely prevented. It

The present invention also relates to a rotary anode type X-ray tube having a structure in which a substantially cylindrical rotating body is arranged on the central axis and a cylindrical fixed body having a bottom is coaxially fitted and arranged on the outer periphery of the rotating body. Applicable. The number of trap cavities may be one, or three or more. Furthermore, the lubricant wetting prevention layer of the passage G may be an oxide film obtained by oxidizing the surface of the metal forming the passage G, or instead of forming a coating film, the passage G
The material itself constituting the material may be composed of a material such as alumina or other ceramics that repels without getting wet with a lubricant.

Furthermore, the liquid metal lubricant is Ga, Ga
-In alloy or G such as Ga-In-Sn alloy
The material mainly composed of a can be used, but is not limited thereto, and for example, Bi-In-containing a relatively large amount of bismuth (Bi).
Pb-Sn alloy or In containing a relatively large amount of In
-Bi alloy or In-Bi-Sn alloy may be used.
Since these have a melting point of room temperature or higher, it is desirable to preheat the metal lubricant to a temperature equal to or higher than the melting point before rotating the anode target and then rotate the target.

[0022]

As described above, according to the present invention,
Even if the liquid metal lubricant leaks from the bearing portion into the narrow spatial passage G, the lubricant is surely captured in the trap cavity without adhering to the wall surface of the passage, and the inside of the X-ray tube vacuum container is prevented. It can be more surely prevented from scattering in the space. Therefore, it is possible to obtain a rotary anode type X-ray tube including a dynamic pressure type slide bearing which can maintain a highly reliable rotation performance for a long time.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an enlarged view of an essential part of FIG.

FIG. 4 is a longitudinal sectional view of a main part showing another embodiment of the present invention.

FIG. 5 is an enlarged vertical sectional view of an essential part showing still another embodiment of the present invention.

6 is a perspective view of a main part of FIG.

[Explanation of symbols]

 11 ... Anode target, 12 ... Rotating body, 18 ... Fixed body, 18a ... Fixed body extension, 23 ... Vacuum container, 19, 35 ... Rotating body extension, 27, 28 ... Sliding bearing, G ... Passage 36, 38 ... Trap cavity, 31 ... Lubricant storage chamber, 41 ... Ventilation duct, 43 ... Lubricant wetting prevention layer.

Claims (3)

[Claims] 1. An anode target provided in a vacuum container, a rotating body having a rotating shaft to which the anode target is fixed, and a coaxially fitted arrangement with respect to the rotating body to rotate the rotating body. A slide bearing having a spiral groove provided in the fitting portion of the rotating body and the fixed body, and a liquid metal lubricant supplied to the spiral groove and the bearing gap of the slide bearing. In the rotating anode X-ray tube, a spatial passage that connects the bearing gap formed by the extension of the fixed body and the extension of the rotation body arranged coaxially with the fixed body and the space inside the vacuum container The wall surface is a surface that is not wetted by the lubricant, and at least one trap cavity that traps the lubricant that leaks through the passage is provided in the middle of the spatial passage that is formed by the surface that is not wetted by the lubricant. What is done Rotating anode X-ray tube according to claim. 2. The rotating anode type X-ray tube according to claim 1, wherein the inner wall surface of the trap cavity is made of a material to which a lubricant easily adheres. 3. A lubricant accommodating chamber is provided in a fixed body or a rotating body on a central axis of rotation, and the lubricant accommodating chamber and the trap cavity are connected by a ventilation duct that does not allow lubricant to pass therethrough. The rotary anode type X-ray tube according to claim 1.