JPH0414742A - Bearing device and x-ray tube therewith - Google Patents

Abstract

PURPOSE:To allow high-speed rotation, heavy load and low-level noise by providing fixed rings respectively on both axial sides of a rolling bearing in no contact with a rotating member, forming spiral grooves in at least one of the inner periphery of the fixed rings and the outer periphery of the rotating member corresponding to the fixed rings and using liquid metal as lubricant for the rolling bearing. CONSTITUTION:A shaft 2 as a rotating member is pivotally supported by an anode fixing base 1 as a fixing member via a rolling bearing 13 with rotation allowable. On both axial sides of the rolling bearing 13, fixed rings 71, 72 are respectively fitted in no contact with the shaft 2. In the outer periphery of the shaft 2 corresponding to the fixed rings 71, 72, spiral grooves 101, 102 are formed. Liquid metal is used as lubricant 8 for the rolling bearing 3, and the lubricant 8 is prevented from being leaked to the outside by the fixed rings 71, 72. In this way, stable lubrication is maintained even in a vacuum at a high temperature.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a bearing device and an X-ray tube using the same.

(Prior Art) Conventionally, a bearing device used, for example, in a rotating anode type X-ray tube is configured as shown in FIG. It is rotatably supported by an anode fixing base 1 which is a fixing member. The rolling bearing 3 includes an outer race 4 fixed to the anode fixed base 1 and a plurality of balls 5 rotatably disposed between the outer race 4 and the rotation shaft 2.

In addition, generally at least one of the rotating shaft 2, the outer ring 4, and the balls 5
A solid lubricant film made of lubricant such as silver or lead is formed on each friction surface, and in the example shown in FIG. 3, a solid lubricant film 6 is formed on the surface of the ball 5.

A rotating anode X-ray tube using such a bearing device has conventionally been constructed as shown in FIG. An anode target 12 is arranged to face the anode target 12 . The anode target 12 is fixed to a support column 11a that projects integrally from the covered rotating cylinder 11, and a rotating shaft 2 is integrally provided inside the rotating cylinder 11 along its axis. A bottomed cylindrical anode fixing base 1 is disposed between the rotating shaft 2 and the rotating cylinder 11, and a sealing ring 14 is attached to the bottom side of the anode fixing base 1.
．． It is fixed to the vacuum envelope 10 via 15. -Furthermore, the rotating shaft 2 is rotatably supported by the anode fixing base 1 via two rolling bearings 3 shown in FIG. This rolling bearing 3 is, of course, comprised of an outer race 4, a plurality of balls 5, and a solid lubricant film 6.

During operation, the rotating cylinder 11 rotates together with the rotating shaft 2 by a rotating magnetic field generated by a magnetic field generator (not shown) provided outside the vacuum envelope 10, thereby rotating the anode target 12.

(Problem to be Solved by the Invention) In a vacuum, when oil is used as a lubricant, the degree of vacuum decreases, so conventionally a solid lubricant film 6 has been used as described above, but compared to the case of oil, At the same rotation speed and under the same load, a stable lubrication state cannot be maintained, which has the disadvantage of significantly shortening the service life. Therefore,
In a conventional bearing device using a solid lubricant film 6, the rotation speed,
The applied load could only be allowed to be about 1/3 to 1/1 of that in the case of oil. Furthermore, since the solid lubricant film 6 has extremely low damping characteristics, the rotational noise is significantly greater than in the case of oil lubricant.

Further, even in a rotating anode type X-ray tube using the conventional bearing device as described above, there are naturally the above-mentioned drawbacks of the bearing device. Furthermore, the phenomenon described below makes the above drawbacks even more serious. That is, in a rotating anode X-ray tube, when electrons emitted from the cathode collide with the anode target 12,
At the same time as the X-rays are generated, the anode target 12 becomes hot. Since the anode target 12, the rotating cylinder 11, and the rotating shaft 2 are directly connected thermally, the rotating shaft 2 is
The temperature will be ~500°C. For this reason, the solid lubricant film 6 of the rolling bearing 3 is also softened due to the high temperature of 300 to 500'C, so that it cannot withstand the contact pressure between the balls 5 and the rotating shaft 2, and between the balls 5 and the outer ring race 4, and the solid lubricant film 6 decreases in film thickness. As a result, the balls 5 and the rotating shaft 2, and the balls 5 and the outer race 4 come into direct contact with each other, causing seizure wear and significantly shortening the service life.

These drawbacks become more serious as the heat input increases as the capacity of the X-ray tube increases.

Regarding a bearing device using liquid metal as a lubricant, there is a technique disclosed in Japanese Patent Laid-Open No. 167125/1983. This is a configuration in which a spiral groove is formed in the ball holder to force the liquid metal toward the ball. However, with this structure, the number of rotations of the cage is always smaller than the number of rotations of the rotating shaft. It is thought that it is difficult to obtain a sufficient lubricant sealing effect by a spiral groove provided in a cage having a low relative rotational speed. In addition, since the retainer has a structure in which spiral grooves are formed on both sides, it is difficult to maintain even minute gaps between these surfaces and the inner and outer races, making it difficult to obtain a stable sealing effect. It's difficult.

Furthermore, it is considered difficult to assemble the inner race, the outer race, the balls, and the retainer.

This invention can maintain stable lubrication even when used at high temperatures and in vacuum, and can rotate at higher speeds than before.
It is an object of the present invention to provide a bearing device that can realize high loads and low noise, has a long life, and prevents lubricant made of liquid metal from leaking to the outside due to a fixing ring, and an X-ray tube using the bearing device.

[Structure of the invention]

(Means for Solving the Problems) This invention provides fixing rings on both sides of a rolling bearing in the axial direction without contacting the rotating member, and further includes an inner periphery of the fixed ring and an outer periphery of the rotating member corresponding to the fixed ring. This is a bearing device in which a spiral groove is formed in at least one of the bearings, and a liquid metal is used as a lubricant for the rolling bearing.

The present invention also provides a cathode and anode target arranged oppositely in a vacuum envelope, a rotating cylinder integrally fixed to the anode target and having a rotating shaft, and a rotary cylinder rotatably supported by the rotating shaft. X comprising the bearing device of Tako's invention
It is a wire tube.

(Function) According to this invention, even when used at high temperatures and in a vacuum, it is possible to maintain a stable lubrication state, achieve higher speed rotation, higher load, lower noise than before, and have a longer service life. .

Furthermore, since the fixing ring is provided, the lubricant made of liquid metal will not leak to the outside. Furthermore, since the rotating anode type X-ray tube of this invention also uses the above-mentioned bearing device,
It is possible to achieve higher rotation speed, higher load, lower noise, and longer life than before, and it is also possible to maintain a stable lubrication state even when heat input is increased.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The bearing device according to the present invention is constructed as shown in FIG. 1, and the same parts as in the conventional example (FIG. 3) are given the same symbols. The anode fixed base 1 is rotatably supported. The rolling bearing 13 is composed of an outer race 4 fixed to the anode fixed base 1 and a plurality of balls 5 rotatably disposed between the outer race 4 and the rotating shaft 2. In this invention, fixing rings 71 and 72 are fitted on both sides of the rolling bearing 13 in the axial direction, respectively, without contacting the rotating shaft 2. A helical groove 101, 102 is formed on the outer periphery of the rotating shaft 2 corresponding to this fixing ring 71, 72. Liquid metal is used as the lubricant 8 of the rolling bearing 3, and this lubricant 8 is applied to the fixed ring 71.7.
2 prevents leakage to the outside.

Now, a rotating anode X-ray tube using the bearing device of the present invention as described above is constructed as shown in FIG. Inside the envelope 10, a cathode (not shown) that emits thermoelectrons and an anode target 12 are disposed to face each other. The anode target 12 is fixed to a support column 11a that projects integrally from the covered rotating cylinder 11, and a rotating shaft 2 is integrally provided inside the rotating cylinder 11 along its axis. A bottomed cylindrical anode fixing base 1 is disposed between the rotating shaft 2 and the rotating cylinder 11, and the bottom side of the anode fixing base 1 is connected to the vacuum envelope via sealing rings 14 and 15. It is fixed at 10.

Furthermore, the rotating shaft 2 has two rolling bearings 13 shown in FIG.
It is rotatably supported by the anode fixing base 1 via.

Of course, this rolling bearing 13 includes an outer race 4, a plurality of balls 5, a lubricant 8 made of liquid metal, and a fixing ring 71, 72.
It is composed of

In the above case, the balls 5 of the rolling bearing 13, the outer ring race 4
For example, silicon nitride is used as the material of the fixing ring 7.
1.72. For example, molybdenum is used as the material for the rotating shaft 2. In addition, examples of liquid metals include Ga, I
An alloy of n and Sn is used. During operation, when electrons emitted from a cathode (not shown) collide with the anode target 12 rotating at high speed, X-rays are generated. The anode target 12 becomes high in temperature due to the collision of electrons, and the rolling bearing 13 also becomes high in temperature due to radiation and heat conduction from the rotating cylinder 11 and the rotating shaft 2. In particular, in a large-capacity X-ray tube, the temperature of the rolling bearing 13 is over 400°C, but the liquid metal lubricant 8
Even at this temperature, as described below, no problematic characteristic changes occur, so excellent rotational characteristics can be maintained stably.

That is, the liquid metal lubricant 8 has a very low equilibrium vapor pressure of about 10-8 Torr even at a high temperature of 500° C., and does not cause a decrease in the degree of vacuum. The viscosity coefficient is also approximately 1c even at 500℃
The ball 5 made of silicon nitride, the outer race 4 and the fixing ring 71.72 made of molybdenum hold a value of approximately p.
Since there is almost no change in the wettability with the rotating shaft 2 from that at room temperature, the rolling bearing 13 can continue to maintain good lubrication. Since the material of the part that comes into contact with the liquid metal lubricant 8 is silicon nitride and molybdenum, the friction surface will not be damaged by corrosion even at a high temperature of 500°C.

As mentioned above, the same heat input as the conventional one can be achieved by rolling bearings.
3, the life of the rolling bearing 13 can be significantly increased, and at the same time, noise can be reduced. In addition, the rotation speed of the anode target 12 has been reduced by about 3 compared to the conventional one.
Even if the rotation speed is increased to 10,100,000 rpm, the rotational life does not occur, so it is possible to make the focal shape of the electron beam from the cathode smaller than before, making it possible to achieve a finer X-ray focal point. In addition, compared to the conventional bearing temperature (300 to 400℃), the temperature of the bearing part is higher (4
Since it is possible to maintain stable rotational characteristics even at temperatures (00 to 500°C), it is possible to use it with higher heat input than before. Also, compared to the conventional method, the anode target 12
Even if the weight of the anode target 12 is increased by about twice, the rotational life will not deteriorate, so it is possible to increase the heat capacity of the anode target 12 and increase the heat input compared to the conventional one.

(Modified example) In the above examples, Ga is used as the liquid metal lubricant.

Although the case where an alloy of In and Sn is used has been described, any single metal or alloy having any melting point can be used depending on the lower limit of the operating temperature of the bearing.

Furthermore, in the above embodiment, silicon nitride was used as the material for the balls 5 of the rolling bearing 13 and the outer ring race 4, and molybdenum was used as the material for the fixing rings 71 and 72 and the rotating shaft 2. The material may be other ceramic materials with excellent corrosion resistance, refractory metals such as tungsten or tungsten-molybdenum alloys, or high-speed tool steel, which has poor corrosion resistance but is easy to process. After forming, the surface may be coated with other ceramic materials or refractory metals having excellent corrosion resistance.

Further, in the above embodiment, a bearing without a retainer was used as the rolling bearing 13, but the present invention can also be applied to any rolling bearing such as a ball bearing or a roller bearing provided with a retainer. is possible.

In addition, in the above embodiment, a bearing in which spiral grooves 101 and 102 were formed on the rotating shaft 2 without using an inner ring was used, but a structure in which an inner ring race was used and the inner ring race was attached to the rotating shaft 2 was used. You may do so.

In addition, in the above embodiments, it is assumed that all of the above are used in a vacuum, but as mentioned above, the operating temperature is not limited to a vacuum.
It can be applied to any bearing device in which the temperature exceeds 0° C. and the use of oil lubricant becomes impossible.

Further, in the above embodiment, the spiral grooves 101, 102 are formed on the outer periphery of the rotating shaft 2, but they may be formed on the inner periphery of the fixed ring 71, 72, or on the rotating shaft 2 and the fixed ring 71.
72 may be formed.

[Effects of the Invention] As explained above, according to the present invention, in the bearing device, fixing rings are provided on both sides of the rolling bearing in the axial direction without contacting the rotating member, and furthermore, fixing rings are provided on the inner circumference of the fixing ring and on the fixing ring. A spiral groove is formed on at least one of the outer peripheries of the corresponding rotating member, and a liquid metal is used as the lubricant for the rolling bearing, so it maintains a stable lubrication state even when used at high temperatures and in a vacuum. It is possible to achieve higher rotation speed, higher load, lower noise than before, and has a longer life. Furthermore, since the fixing ring is provided, the lubricant made of liquid metal will not leak to the outside.

In addition, since the rotating anode type X-ray tube of the present invention uses the above-mentioned bearing device, it can achieve higher rotation speed, higher load, lower noise, and longer life than before, and can also increase thermal manpower. It is also possible to maintain a stable lubrication state.

[Brief explanation of drawings]

¥, Figure 1 is a cross-sectional view showing a bearing device according to an embodiment of the present invention, Figure 2 is a cross-sectional view showing a rotating anode type X-ray tube using the bearing device of the present invention, and Figure 3 is a cross-sectional view showing a conventional bearing device. FIG. 4 is a sectional view showing a rotating anode type X-ray tube using a conventional bearing device. DESCRIPTION OF SYMBOLS 1... Anode fixed base, 2... Rotating shaft, 4... Outer race, 5... Balls, 8... Lubricant, 10... Vacuum envelope, 11... Rotating cylinder, 12...Anode target,...Rolling bearing, 2...Fixing ring, 1, 2...Spiral groove.

Claims (2)

[Claims] (1) In a bearing device in which a rotating member is rotatably supported by a fixed member via a plurality of rolling bearings, fixing rings are provided on both sides of the rolling bearing in the axial direction without contacting the rotating member, Further, a spiral groove is formed on at least one of the inner periphery of the fixed ring and the outer periphery of the rotating member corresponding to the fixed ring, and a liquid metal is used as a lubricant for the rolling bearing. Bearing device. (2) A cathode and anode target arranged to face each other in a vacuum envelope, a rotating cylinder that is integrally fixed to the anode target and has a rotating shaft, and a bearing that rotatably supports the rotating shaft. An X-ray tube comprising: an X-ray tube, wherein the bearing device is the bearing device according to claim 1.