JPH1050243A - Rotary anode type x-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adequately retain the positional relation of a inner ring, a ball and an outer ring to maintain the rotation performance of a bearing, by constituting an outside spacer, fixed to the outer side of a ball bearing, with a material having a thermal expansion coefficient higher than that of the material of a rotation shaft. SOLUTION: Ball bearings 8 and 9 are interposed between the anode fixing base part 7 and rotary shaft 5, fixed to a rotary anode type X-ray tube, and the inner ring sides of the ball bearings 8 and 9, are retained at given intervals from an inner spacer 10, and are fixed by a fixing ring 11. The outer ring sides of the ball bearings 8 and 9, are retained at given intervals by an outer spacer 16 and a C type spacer 15, and the outer spacer 16 is constituted of material having a thermal expansion coefficient higher than that of the rotary shaft 5. When an X-ray is generated, the rotation shaft 5 is expanded in axial and diameter directions, and since the thermal expansion coefficient of the spacer 16 is high, the difference between the axial direction expansion quantity of the shaft 5 and the total expansion quantity in the bearing direction of the outer rings of the rearings 8 and 9, the outer spacer 16, and the C-type spacer 15; is reduced. In concrete, the shaft 5 is to be constituted of iron alloy, and the whole or part of the outer spacer 16 is to be copper material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, X-ray tubes are used for medical purposes, for example, for X-ray diagnosis. In the case of, for example, examination of the stomach, a rotating anode X-ray tube is used. In this rotary anode type X-ray tube, a cathode and a substantially umbrella-shaped anode target are installed opposite to each other in a vacuum envelope, and the cathode is installed at a position eccentric from a central axis. It is installed and supported by a rotation mechanism so that it can rotate. Further, a stator is provided outside the vacuum envelope in correspondence with the rotating mechanism, and drives the rotating mechanism.

The rotating mechanism includes, for example, a rotating cylinder to which an anode target is fixed, a rotating shaft coaxially fixed inside the rotating cylinder, and a coaxial fitting between the rotating shaft and the rotating cylinder. Cylindrical anode fixing portion having a bottom, two bearings disposed between the anode fixing portion and the rotating shaft and arranged at an interval from each other, and an interval between these two bearings on the outer ring side is set. It consists of an outer conical or spacer fitted for retention.

The anode becomes extremely hot due to the collision of thermoelectrons from the cathode during X-ray generation. For example, the temperature of the anode target changes from about 1500 ° C. to 2500 ° C., and the heat conduction causes the rotating shaft and the inner ring of the bearing to approach 500 ° C. Further, heat is transmitted to the bearing outer ring, the outer ring, and the bottomed cylindrical anode fixing portion via the bearing ball. At this time, the bearing outer ring and outer
From 50 ° C to about 400 ° C.

That is, a maximum temperature difference of about 150 ° C. occurs between the rotating shaft and the outer ring and the outer ring. for that reason,
A non-negligible difference in thermal expansion occurs between the rotating shaft and the outer ring and the outer ring. Generally, ball bearings require high precision in shape, fit, and the like. Therefore, the above-mentioned difference in expansion changes the positional relationship between the bearing inner ring and the bearing outer ring, and significantly reduces bearing performance.

In order to solve this problem, the rotating shaft and the bearing are generally made of an iron alloy having a small coefficient of thermal expansion. Further, there is a rotation mechanism in which an outer ring and a spring are arranged in combination between two bearing outer rings, and the thermal expansion of the rotation shaft is slid by the outer ring by the spring to keep the positional relationship between the inner ring and the outer ring constant. .

[0007]

However, it is difficult to maintain the accuracy of the bearing simply by forming the rotating shaft and the bearing with a material having a small coefficient of thermal expansion. It is necessary to suppress the amount of thermal expansion. However, in this case, there is a disadvantage that the rigidity of the rotating shaft is reduced. Further, in the case of a rotating mechanism that tries to keep the positional relationship between the inner ring and the outer ring constant by sliding the outer ring with the above-mentioned spring, the outer ring may not slide properly at high temperatures.

SUMMARY OF THE INVENTION The present invention solves the above problems, and provides a rotating anode type X-ray tube in which the difference in thermal expansion between a rotating shaft, a bearing outer ring and an outer ring is reduced, and the rotating performance of the bearing is maintained. The purpose is to do.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a whole or a part of an outer kanza which is fitted to a pair of ball bearings disposed between a fixed body and a rotating body so as to keep an interval between the outer rings. Is a rotating anode type X-ray tube made of a material having a larger coefficient of thermal expansion than the material forming the rotating shaft. More specifically, the rotation shaft is made of an iron alloy, and the whole or part of the outer kanza is made of a copper material.

[0010]

An embodiment of the present invention will be described below in detail with reference to the drawings. The rotary anode type X-ray tube according to the present invention is configured as shown in FIG. 1, reference numeral 1 denotes a rotating cylinder, on which a supporting column 2 is coaxially and integrally protruded by brazing, and an anode target 3 is fixed to the supporting column 2 by screws 4. Have been. A rotating shaft 5 has a screw 6 inside the rotating cylinder 1.
Are coaxially fixed. The rotating cylinder 1, the supporting column 2, and the rotating shaft 5 constitute a rotating body as a whole.

A bottomed cylindrical anode fixing base 7 as a fixed body is coaxially fitted between the rotating shaft 5 and the rotating cylinder 1. The anode fixing base 7 is a rotating anode type X-ray tube. Is fixed to a vacuum envelope (not shown). This anode fixing base 7
A pair of ball bearings 8 and 9 are interposed between the shaft and the rotating shaft 5, and these ball bearings 8 and 9 are fixed at predetermined intervals on the inner ring side by an inner Kanza 10 formed of a cylindrical spacer. It is fixed by a ring 11. Also, the outer ring side is kept at a predetermined interval by an outer Kanza 16 and a C-type Kansa 15 formed of a cylindrical spacer.

The outer ring of the ball bearing 9 is pressed by an outer ring support 18 and a spring 17 so that it can slide in the axial direction. Therefore, the outer Kanza 16 is made of a material having a higher coefficient of thermal expansion than the rotating shaft 5.

In the case of the above-mentioned rotary structure, the inner and outer rings forming the bearings 8 and 9 are 10 μm in the axial and radial directions with the ball.
The rotation performance is improved by providing a gap (play) of m to several tens of μm. When X-rays are generated in this state, the rotating shaft 5 rises to near 500 ° C. and expands in the axial and radial directions. On the other hand, the outer rings of the bearings 8 and 9, the outer Kansa 16 and the C-type Kansa 15 are about 350 ° C., but the thermal expansion coefficient of the outer Kansa 16 is large, so that the axial expansion amount of the rotary shaft 5 and the bearing 8 , 9 are smaller than the sum of the expansion amounts in the bearing direction of the outer ring 16, the outer ring 16, and the C-shaped ring 15, that is, the inner ring and the outer ring forming the bearings 8, 9 have a ball clearance of 10 to several tens μm. Kept at the value.

For example, when the rotary shaft 5, the bearing, the outer Kansa 16 and the C-type Kanza 15 are made of an iron alloy having a linear expansion coefficient of 12.0 × 10 ^-6 , the bearing outer ring, the outer Kansa 16 and the C-type Kansa 15 are used. Is 350 ° C., the sum of the expansion amounts when the rotating shaft 5 is set to 500 ° C. is about 70%.

Here, the outer Kanza 16 has a linear expansion coefficient of 20.
If a copper material (copper or copper alloy) of 0 × 10 ⁻⁶ is used, the length of the outer Kanza 16 is 30 mm, the length of the outer ring of the bearing) is 6 mm, and the length of the C-type Kanza 15 is 8 mm. Approximately, the expansion amount becomes 95% or more of the expansion amount when the rotating shaft 5 is set to 500 ° C., and the thermal expansion amounts of the two are almost equal.

Since the sum of the expansion amount and the length ratio of the bearing outer ring, the outer Kanza 16 and the C-type Kanza 15 and the temperature naturally change, the length ratio must be obtained in advance by calculation. That is, the effect of the present invention can be obtained by changing the length ratio of the outer Kanza 16 and the C-type Kanza 15. Also,
The same applies to the case where the outer can is made of a material having an appropriate expansion coefficient. Further, the distance between the bearings 8 and 9 may be changed.

[0017]

According to the present invention, the positional relationship between the inner race, the ball and the outer race of the bearing can be appropriately maintained, and as a result, the rotational performance of the bearing is not impaired.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an entire rotating mechanism of a rotating anode type X-ray tube according to an embodiment of the present invention.

[Explanation of symbols]

1 ... rotating cylinder, 3 ... anode target, 5 ... rotating shaft, 7 ...
Anode fixing base, 8, 9 ... Bearing, 12 ... Ball, 13 ... Inner ring, 14 ... Outer ring, 16 ... Outer ring, 18 ... Outer ring support.

Claims (2)

[Claims] A rotating body to which an anode target is fixed;
A rotating shaft extending from the rotating body on its inner central axis, a fixed body coaxially fitted to the rotating body,
A pair of ball bearings disposed between the fixed body and the rotating body and arranged at an interval from each other, and an outer kanza fitted to maintain an interval between the pair of bearings on the outer ring side. The rotating anode X-ray tube according to claim 1, wherein the whole or a part of the outer kanza is made of a material having a higher coefficient of thermal expansion than the material forming the rotating shaft.
Wire tube. 2. The rotating anode type X-ray tube according to claim 1, wherein the rotating shaft is made of an iron alloy, and the whole or part of the outer kanza is made of a copper material.