JPH10172483A - Rotary anode type x-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of displacement and inclination of a rotary center axis and enable fast rotation by setting an axial length of a fixer small diameter part to a specific dimensional rate of an external diameter of a fixer large diameter part. SOLUTION: In the case of an X-ray anode type X-ray tube for circulator photography in which an input heat capacity of an anode target is about 2.5MHU, a fixer small diameter part 15a in which radial direction dynamic pressure type slide bearings 18 and 19 are formed is defined to be 100mm in its axial length Lr and 20mm in its diameter Dr. On the contrary, a fixer large diameter 15b in which a thrust direction dynamic pressure type slide bearings 23 and 24 are formed is defined to be 40mm in its diameter Ds'. Here, an axial length Lr of the fixer small diameter part is set to 1.2 times or more of a diameter Ds of the fixer part or more preferably to a dimensional rate from 1.5 times to 5 times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotating anode X-ray tube.

[0002]

2. Description of the Related Art As is well known, a rotating anode type X-ray tube supports a disk-shaped anode target by a rotating body having a bearing portion and a fixed body, and energizes an electromagnetic coil of a stator disposed outside a vacuum vessel. While rotating at a high speed, the electron beam emitted from the cathode is applied to the anode target surface to emit X-rays. The bearing part is a rolling bearing such as a ball bearing, and a spiral groove is formed on the bearing surface and gallium (G)
a) or gallium-indium-tin (Ga-In-S)
n) It is composed of a hydrodynamic plain bearing in which a bearing gap is filled with a liquid metal lubricant such as an alloy.

As a rotating anode type X-ray tube using the latter dynamic pressure type sliding bearing, a rotating anode type sliding bearing in which a radial dynamic pressure type sliding bearing is formed in a small diameter portion and a thrust direction dynamic pressure type sliding bearing is formed in a large diameter portion. The X-ray tube is, for example, Japanese Patent Publication No. 3-776.
No. 17, JP-A-2-244545, JP-A-2-227
947, JP-A-2-227948, JP-A-4-36
No. 3,845, JP-A-5-290770, and US Pat. No. 5,504,797.

The rotating anode type X disclosed in each of the above publications
In the wire tube, the bearing surfaces of all the hydrodynamic sliding bearings in the radial and thrust directions formed by the spiral grooves of the herringbone pattern are configured to maintain a bearing gap of, for example, 20 μm. The agent is filled. The spiral groove of each bearing is approximately 20 μm
Of depth.

A rotary anode type X-ray tube having a dynamic pressure sliding bearing of this type has a bearing with a rotary resistance of about 3000 r.
An operation is performed so as to perform X-ray irradiation while rotating at a relatively low rotation speed of about pm.

However, if the rotation speed of the anode target is low, the input load to the anode target cannot be naturally increased, and a solution to this problem is to use a large heat capacity, that is, a large and heavy anode target. . In addition, for example, X
2. Description of the Related Art In a line imaging apparatus, there are many cases where an object to be imaged is imaged from various directions and quickly changed in position.
As a result, a large acceleration is applied to the anode target, and thus a large load in various directions and a large load is randomly applied to the hydrodynamic bearing.

[0007] As described above, it is necessary to stably support a large load in each direction with a bearing. For example, Japanese Patent Application Laid-Open No. 4-36
An X-ray tube having radial and thrust dynamic pressure bearings between a simple cylindrical fixed body and a rotating body fitted thereto, as described in Japanese Patent No. 3845, has a diameter of the fixed body. It is possible to provide a bearing performance that can sufficiently withstand loads in each direction as the value is increased. Further, as described in the specification of US Pat. No. 5,504,797, a structure in which a large-diameter portion is provided in a fixed body and a dynamic pressure bearing in the thrust direction is formed here has an advantage that the diameter of the thrust-direction bearing can be arbitrarily increased. Has become practical.

[0008]

By the way, a rotating anode type X-ray tube using a conventional dynamic pressure bearing of this kind has sufficient bearing performance to withstand a large load in each direction. However, this is because the larger the diameter of the fixed body that fits with the rotating body and the longer its axial length, the greater the rotational resistance of the bearing and the higher the speed of rotation. Requires very large rotational drive power.

On the other hand, if the axial length of the fixed body fitted to the rotating body is shortened, the rotation resistance can be reduced correspondingly, but the rotation center axis of the rotating body is likely to be shifted. That is, as shown in FIG. 6, the rotation center axis R of the anode target 11 and the rotating body 12 easily shifts and tilts with respect to the center axis C of the fixed body 15, and precession movement easily occurs. In such a state, the fixed body and the rotating body come into contact with each other at various places, and the bearing gap becomes non-uniform at various places, so that normally balanced dynamic pressure is not generated in the bearings.
Although the figure shows the bearing gap and the inclination of the rotating body in an exaggerated manner, the fixed body large-diameter portion 15b which constitutes a thrust bearing in a rotating anode type X-ray tube which is conventionally practically used is constructed.
Is smaller than 1.2 times the axial length L of the fixed body diameter portion constituting the radial bearing with respect to the diameter D.

Reference numerals 18 and 19 in the figure denote two sets of radial dynamic pressure bearings and a herringbone pattern spiral groove formed on the fixed body, and 15b denotes a fixed body large-diameter portion.
5c is an anode support portion, 23 and 24 are two sets of thrust dynamic pressure bearings having upper and lower surfaces of one of the larger fixed body diameters as one bearing surface, and a circular herringbone pattern spiral formed on the larger fixed body diameter portion. The groove 12b represents the copper cylinder of the rotating body. The spiral groove and the bearing gap of each bearing are filled with a liquid metal lubricant (not shown).

According to the conventional structure, as described above, the fixed body and the rotating body may come into contact with each other at various places, and the bearing may not operate normally due to unevenness and fluctuation of the bearing gap.
In particular, as the rotation speed increases, such inconvenience becomes more remarkable. Also, if the diameter D of the large-diameter fixed body portion 15b constituting the thrust bearing is large, the rotational resistance between the large-diameter portion and the rotating body becomes particularly large, making high-speed rotation difficult.

The present invention solves the above-mentioned disadvantages, makes it difficult for the rotation center axis to be displaced or tilted, and suppresses the rotational resistance so as to be capable of rotating at a high speed exceeding, for example, 6000 rpm. The purpose is to provide a tube.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a rotary anode type X-ray tube in which a radial and thrust dynamic bearing is formed between a fixed body having a small diameter part and a large diameter part and a rotating body. , The axial length of the fixed body small diameter portion where the radial dynamic pressure type sliding bearing is formed is at least 1.2 times the outer diameter of the fixed body large diameter portion where the thrust direction dynamic pressure type sliding bearing is formed. Rotating anode type X with the dimension ratio of
It is a wire tube.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same parts are denoted by the same reference numerals. A disk-shaped anode target 11 made of heavy metal has a rotating shaft 13 protruding from one end of a rotating body 12 having a substantially bottomed cylindrical shape.
Are integrally fixed by a nut 14. Rotating body 1
2, an inner cylinder 12a made of an iron alloy and an outer cylinder 12b made of copper are fitted and fixed doubly. A substantially cylindrical fixed body 15 made of an iron alloy is inserted inside the rotating body 12.

The fixed body 15 has a small-diameter portion 15a having a small diameter Dr at the upper part in the figure, a large-diameter part 15b having a large diameter Ds at a lower part thereof, and an anode support part 15c at a lower end.
In the fitting portion between the rotating body 12 and the fixed body 15, a dynamic pressure type spiral groove slide bearing in the radial direction and the thrust direction as described in each of the above-mentioned publications is formed. That is, two pairs of herringbone pattern helical grooves 16 and 17 are formed on the outer peripheral bearing surface of the small diameter portion 15a, and the dynamic bearings 18 and 19 in the radial direction are formed together with the inner peripheral bearing surface of the inner cylinder 12a of the rotating body. Is composed.

A herringbone pattern spiral groove 2 is formed in a circular shape on the upper bearing surface in the figure of the large diameter portion 15b of the fixed body.
0 is formed. And the inner cylinder 12a of the rotating body
So that the lower end opening of the thrust ring 2 is substantially closed.
1 is screwed. On the upper bearing surface of this thrust ring 21 which is in contact with the illustrated lower bearing surface of the fixed body large diameter portion 15b, the herringbone pattern spiral groove 2 is also formed in a circle.
2 are formed. These two sets of spiral grooves 20, 2
2, and a bearing surface of a fixed body or a rotating body which is close to and opposed to each other, form thrust-direction dynamic pressure-type sliding bearings 23, 24.

For this reason, for example, a rotating anode type X for circulatory organ photography in which the input heat capacity of the anode target is about 2.5 MHU.
In the case of a wire tube, radial dynamic pressure type sliding bearings 18, 19
The fixed body diameter small portion 15a in which is formed has an axial length Lr of 100 mm and a diameter Dr of 20 mm. On the other hand, the fixed body large diameter portion 15b on which the thrust direction dynamic pressure type slide bearings 23 and 24 are formed,
The diameter Ds is set to 40 mm.

In particular, the axial length Lr of the fixed body diameter small portion
Is set to a dimensional ratio in the range of 1.2 times or more, more preferably 1.5 times to 5 times the diameter Ds of the large diameter of the fixed body. When the dimensional ratio (Lr / Ds) of the two is less than 1.2 times, the above-described displacement or inclination of the rotating shaft of the rotating body is apt to occur, and when too large, the rotational resistance in the small diameter portion is undesired. It becomes big.

Further, it is desirable that the diameter Dr of the large diameter portion of the fixed body is set to a dimensional ratio in the range of 1.5 to 5 times the diameter Ds of the small diameter portion of the fixed body. When these dimensional ratios are 1.5
If it is less than twice, the dynamic pressure of the thrust bearing cannot be obtained sufficiently and sufficiently compared to the dynamic pressure of the radial bearing. If it exceeds five times, the rotational resistance due to the large diameter portion becomes relatively large, and high speed rotation It becomes difficult to make it.

Further, the average clearance Gs of the thrust-direction dynamic pressure-type sliding bearings 23 and 24 is larger than that of the dynamic-pressure-type sliding bearings formed by the bearing surfaces of the rotating body and the fixed body. Pressure slide bearings 18, 19
Are set to be larger than the average bearing gap Gr. Note that the average bearing gap is the overall average value of the bearing portions in the axial direction and the circumferential direction in the radial dynamic pressure type sliding bearings 18 and 19, and is large in the thrust direction dynamic pressure type sliding bearings 23 and 24. It is the average value of the bearing gap both above and below the part. That is, it does not represent a part of the bearing gap such as when the bearing is offset in a specific direction.

In the case of the rotating anode type X-ray tube described above, the average bearing gap Gr between the radial sliding bearings 18 and 19 is 1
It is set in the range of 0 μm to 20 μm, for example, 15 μm. On the other hand, the average bearing gap Gs between the thrust slide bearings 23 and 24 is set in a range of 30 μm to 60 μm, for example, 45 μm. In addition, each spiral groove 16,17,
Each of the depths 20 and 21 is approximately 20 μm.

Note that the fixed body 15 is provided with a lubricant housing chamber 31 having a hole having a diameter of 3 mm whose central shaft is hollowed out along the axial direction. This lubricant storage chamber 31
The illustrated upper end opening 31a communicates with the radial dynamic pressure type sliding bearing 18 via the upper space Sa in the illustration. Further, four radial passages 32 communicating from the lubricant accommodating chamber 31 to the circumferential space Sb are formed symmetrically at intervals of 90 degrees. Thereby, the lubricant containing chamber 31 communicates with the circumferential space Sb through the radial passage 32, and further communicates therewith with the two sets of radial dynamic pressure type sliding bearings 18 and 19 located at the top and bottom in the figure.

A liquid metal lubricant L such as a Ga alloy is supplied to the inside of the spiral groove of each bearing portion, the bearing gap, the lubricant accommodating chamber, the radial passage, and each space. In addition, the filling amount of the lubricant is preferably the above-described bearing portions and bearing gaps,
20% to 80% of the volume of the space including the lubricant containing chamber, the radial passage, and each internal space, for example, about 50%
Is the volume amount corresponding to

In the rotating anode type X-ray tube having such a structure, a relatively small rotating resistance can be obtained. Therefore, the rotating body and the anode target are continuously rotated at a rotating speed exceeding 6000 rpm or at a high speed during X-ray irradiation. Can be done. That is, for example, 3000 to 6000 rpm at the time of shooting standby
Is continuously rotated at an arbitrary number of rotations during the period, and when X-ray imaging is performed by X-ray exposure, 9000 to 10000 r
X-ray imaging can be performed by increasing the rotation speed to pm. In this manner, when necessary, X-ray imaging can be performed by increasing the rotation speed to a high speed at which X-ray irradiation can be performed instantaneously. In addition, even with such a high-speed rotation, the occurrence of a shift or an inclination of the rotation axis of the rotating body is suppressed, and a stable operation is obtained.

In the embodiment shown in FIG. 4, the fixed-body large-diameter portion 1 in which the thrust-direction hydrodynamic slide bearings 23 and 24 are formed.
The outer peripheral wall 15d of 5b is a surface which is not or hardly wet with the liquid metal lubricant. Therefore, a lubricant wetting prevention layer 35 made of a material that repels the lubricant with little or no liquid metal lubricant, such as a ceramic thin film made of titanium oxide, adheres to the outer peripheral wall surface 15d of the large diameter portion. It is formed. Of course, the lubricant wetting prevention layer 35 is not formed on the bearing surface of the dynamic pressure type sliding bearing including the spiral grooves 20 and 22. The lubricant wetting prevention layer may be made of a material other than those described above, or any material having such a property that the surface of the base material itself having a large diameter of the fixed body does not wet with the lubricant. However, the bearing surface on which the spiral groove is formed must be a surface that is wetted by the lubricant.

According to this embodiment, the rotation resistance between the large diameter portion of the fixed body and the rotating body can be reduced by the lubricant wetting prevention layer 35. That is, when the wetting prevention layer 35 is not provided, the space Q between the outer peripheral wall surface 15d of the large diameter portion of the fixed body located farthest from the center axis of rotation and the peripheral wall surface of the rotating body which is close to and opposed to the fixed body diameter is provided. The contact resistance due to the wettability with the intervening liquid metal lubricant acts relatively largely as rotational resistance. However, according to this embodiment, the contact resistance between this surface and the liquid metal lubricant existing in the space Q is reduced by forming the lubricant wetting prevention layer 35 here. As a result, rotation resistance is reduced, which is advantageous for high-speed rotation.

The embodiment shown in FIG. 5 shows a large-diameter fixed body portion 15 in which thrust-direction dynamic pressure type sliding bearings 23 and 24 are formed.
The lubricant wetting prevention layer 35 is formed by adhering to the inner peripheral wall surface of the rotating body 12 surrounding the outer peripheral edge portion b. The lubricant wetting prevention layer 35 may be formed on the outer peripheral wall 15d of the large diameter portion of the fixed body as shown in FIG. Also,
The lubricant wetting prevention layer 35 is formed of the dynamic pressure type sliding bearing 23,
In order not to impair the bearing performance of the bearing 24, it is desirable not to form it in a region functioning as a dynamic pressure type sliding bearing.
According to this embodiment, the rotation resistance can be reduced as described above, which is advantageous for high-speed rotation.

[0028]

As described above, according to the present invention,
The rotating body can be rotated at a high speed without causing the displacement or inclination of the rotating shaft.

[Brief description of the drawings]

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

FIG. 2 is a side view showing a part of the fixed body of FIG. 1;

FIG. 3 is a top view showing the thrust ring of FIG. 1;

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

FIG. 5 is a longitudinal sectional view of a main part showing still another embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing a conventional structure and operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Anode target 12 ... Rotating body 15 ... Fixed body 15a ... Fixed body diameter small part 15b ... Fixed body diameter large part 16, 17, 20, 22 ... Helical groove 18, 19 ... Radial direction dynamic pressure type sliding bearing 23, 24 ... Thrust direction dynamic pressure type sliding bearing 35 ... Lubricant wetting prevention layer M ... Liquid metal lubricant Lr ... Axial length of fixed body diameter small part Dr ... Outside diameter of fixed body diameter small part Ds ... Outside of fixed body diameter large part Diameter Gr: Average bearing clearance of radial-direction sliding bearing Gs: Average bearing clearance of thrust-dynamic sliding bearing

Claims (7)

[Claims] A fixed body having a small-diameter portion and a large-diameter portion; a rotating body fitted around an outer periphery of the fixed body with a bearing gap therebetween and an anode target partially fixed to the fixed body; A radial dynamic pressure type sliding bearing configured between the small diameter portion and the rotating body; a thrust direction dynamic pressure type sliding bearing configured between the large diameter portion of the fixed body and the rotating body; In the rotating anode type X-ray tube including the sliding bearing and the liquid metal lubricant supplied to the bearing gap, the axial length of the fixed body small diameter portion in which the radial dynamic pressure type sliding bearing is formed is as described above. 1. The outer diameter of the large diameter portion of the fixed body on which the thrust direction dynamic pressure type sliding bearing is formed.
A rotating anode type X-ray tube having a dimension ratio of twice or more. 2. A fixed body having a small-diameter portion and a large-diameter portion, a rotator fitted around the outer periphery of the fixed body with a bearing gap therebetween, and an anode target partially fixed to the fixed body, A radial dynamic pressure type sliding bearing configured between the small diameter portion and the rotating body; a thrust direction dynamic pressure type sliding bearing configured between the large diameter portion of the fixed body and the rotating body; In a rotating anode type X-ray tube comprising a sliding bearing and a liquid metal lubricant supplied to the bearing gap, an average bearing gap of the thrust direction dynamic pressure type sliding bearing is:
A rotating anode type X-ray tube, wherein the dimension is set to be larger than the average bearing clearance of the radial dynamic pressure type plain bearing. 3. An average bearing gap of the thrust direction dynamic pressure type sliding bearing is set to be larger than an average bearing gap of the radial direction dynamic pressure type sliding bearing.
The rotating anode type X-ray tube according to claim 1. 4. The rotary anode type according to claim 1, wherein the average bearing gap of the thrust direction dynamic pressure type slide bearing is 1.5 times or more the average bearing gap of the radial direction dynamic pressure type slide bearing. X-ray tube. 5. An average bearing gap of the thrust direction dynamic pressure type sliding bearing is in a range of 30 μm to 60 μm, and an average bearing gap of the radial direction dynamic pressure type sliding bearing is 10 μm.
The rotating anode type X-ray tube according to claim 1 or 2, wherein the diameter is in a range of m to 20 µm. 6. The outer peripheral wall surface of the large diameter portion of the fixed body and at least one wall surface of the inner peripheral wall of the rotating body which is close to and opposed to the outer peripheral wall surface of the large diameter fixed portion are hardly or hardly wet with the liquid metal lubricant. 3. The rotating anode X-ray tube according to claim 1, wherein the rotating anode type X-ray tube has a surface. 7. The axial length of the fixed-body small-diameter portion on which the radial-direction dynamic-pressure sliding bearing is formed is equal to the outer diameter of the fixed-body-diameter large portion on which the thrust-direction dynamic-pressure sliding bearing is formed. 2. The rotating anode type X-ray tube according to claim 1, wherein the dimensional ratio ranges from 1.5 times to 5 times.