JPH01163948A - Rotating anode type x-ray tube - Google Patents

Abstract

PURPOSE:To sharply reduce surface roughening of a sliding part by forming at least the inside face of an anode fixing base which contacts with the outer ring race of a bearing, out of material which has almost the same hardness as that of the outer ring race. CONSTITUTION:An anode fixing base 9 is divided into two and composed of an anode fixing base main body 25 at the outside and an anode fixing base inner wall 26 at the inside and united by a screw 20. And the inner wall 20 contacts with each outer ring race 17 of bearings 19, 14, and the inner wall 26 is formed of quenched and tempered material of high speed tool steel SKH. The quenched and tempered material of high speed tool steel SEH is more than HRC60 at Rockwell hardness and almost the same hardness as the outer ring races 17 of the bearings 19, 14. Hereby, the surface roughening of a sliding part by fretting can be reduced sharply and made into low vibration and low noise enabing the life to be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a rotating anode type X-ray tube, and particularly to improvements in its rotation mechanism.

(Prior art) X-ray tubes are generally used for medical purposes, for example, for X-ray diagnosis, but in cases such as gastric examination, an X-ray tube as shown in Fig. 3 has been conventionally used. .

This X-ray tube is a so-called rotating anode type.
An anode is disposed on one side of the envelope 1, and a cup f3 having a built-in cathode filament and a focusing electrode that emits thermoelectrons is provided eccentrically. In addition, near the center of the envelope 1,
A substantially umbrella-shaped anode target 4 is disposed facing the cathode l. This anode target 4 creates a high potential difference between the cathodes and accelerates the electrons emitted from the cathode filament to collide with each other, generating X-rays by controlled radiation and generating a large amount of heat at that time. It is designed to store and dissipate heat, and can be rotated at high speeds to effectively expand the heat generation area. Such an anode target 4 is attached to a covered rotating cylinder (
rotor) 6. This rotating cylinder 6 generates a rotational force by receiving a rotating magnetic field generated by a stator 7 disposed outside the envelope 1, and together with the stator 7 forms an induction motor. Note that the support column 5 and the rotating cylinder 6 are integrated. A rotating shaft 8 is disposed inside the rotating cylinder 6 along the axis, and one end of the rotating shaft 8 is fixed to the rotating cylinder 6 with a screw or the like (not shown). This rotating shaft 8
A bottomed cylindrical anode fixing base 9 is provided between the rotary cylinder 6 and the rotary cylinder 6.
are arranged coaxially, and one end is fixed to the envelope 1 via a sealing ring 10.11. Note that this anode fixing base 9 is partially exposed outside the tube and also serves to support and fix the entire X-ray tube to the outside. Bearings 12, 13 are interposed between the anode fixing base 9 and the rotating shaft 8, so that the rotating shaft 8 can rotate freely.

Normally, this bearing 12, 13 is composed of a metal inner race, an outer race, and a large number of goals.In order to suppress wear between these, a solid lubricant such as Pb or Ag is applied to the surface of the goals. is attached. When the X-ray tube is in operation, the vicinity of the bearings 12 and 13 reaches a high temperature of several hundred degrees Celsius due to conduction heat from the anode target 4. Among the pair of bearings 12 and 13, the bearing 12 that is closer to the anode target 4 in terms of thermal path tends to be at a higher temperature than the one that is farther away.

As described above, due to the difference in thermal expansion of the anode structure due to the temperature distribution that exists in the anode structure including the bearing 12.13, and the deformation due to heat, the proper contact between the inner race and the outer race of the guru is impaired, resulting in extreme If this occurs, it may become impossible to rotate.

In order to prevent such inconvenience, a pair of angular contact type bearings 19.1 are installed as shown in FIG.
4, and is provided with a roll spring 18 that contacts the bearing 14 located far from the anode target so as to apply preload in the thrust direction. And this roll spring 1
Even if a thermal expansion difference occurs in the anode structure due to the preload of 8, will the bearing fail? - In many cases, the structure is such that appropriate contact between the inner race 16 and the outer race 17 of the wheel 15 is maintained.

FIG. 5 shows an enlarged view of the vicinity of the bearing 14 to which the preload is applied, and a temperature distribution occurs in the anode structure due to the heat generated in the anode target during operation. This temperature distribution causes a difference in thermal expansion in the structure.

This difference in thermal expansion impairs proper contact between the balls 15 of the bearing 14 and the inner race 16 and outer race 17, but as in this example, the inner race 16 is fixed and the outer race 17 is subjected to thrust preload. When the ball 15, the inner race 16, and the outer race 17 are deformed in the thrust direction, the preload from the roll spring 18 causes the outer race 17 to slide on the inner wall of the anode fixing base 9 and move to the position indicated by the broken line. Distortion and misalignment are eliminated, and appropriate contact properties are maintained.

In addition, in FIGS. 4 and 5, 23 is a cylindrical spacer, and 24 is a nut.

(Problems to be Solved by the Invention) In order to maintain appropriate contact properties, the outer race 17 needs to slide smoothly along the inner wall of the anode fixing base 9. This is done against the frictional force between the outer ring race 17 and the inner wall of the anode fixing base 9 in a vacuum, and requires a very large force. If the preload force is smaller than this frictional force, the outer ring race 17 will not move.
Preload is disabled. On the other hand, if the preload force is greater than the frictional force, the outer race 17 will slide smoothly, but the outer race 17 will press the ball 15 more than necessary, causing the Pb+Ag solid that adheres to the surface of the goal 15 to form. This has the drawback of accelerating the consumption of the lubricant and damaging the base of the seal 1b, which tends to shorten its life. Also, in order to reduce the frictional force, there is a method of providing a slight clearance between the outer ring race 17 and the inner wall of the anode fixing base 9, but if this clearance is too large, the rotation formed by the anode targut and the rotor will be reduced. This has the drawback that it disturbs the balance of the system, and as a result, the entire Fixture and IS tube vibrates so much that it cannot withstand use. In addition, such a clearance naturally changes due to the difference in thermal expansion of the anode structure between when the X-ray tube is in operation and when it is stopped.In the worst case, the outer ring race 1
7 will bite into the inner wall of the anode fixing base 9, and it can be predicted that a problem will occur in which the preload becomes ineffective. As described above, in the preloaded structure, selection of the preload force and the above-mentioned clearance is technically a very difficult problem.

Furthermore, in the conventional structure, the inner surface of the anode fixing base 9, which is in contact with the outer peripheral surface of the sliding outer ring race 17, is a straight flat surface, as is clear from the figure, and is in contact with the entire outer peripheral surface of the outer ring race 17. There is. Therefore, in order for the outer race 17 to slide smoothly, the surface of the sliding portion on the inner surface of the anode fixing base 9 must be maintained in a smooth state without irregularities at all times during operation.

However, in the conventional structure, the material of the outer ring race 17 is not made of high-speed tool steel because it is a high-temperature bearing and requires hardness at high temperatures, and the material of the sliding part on the inner surface of the anode fixing base 9 is made of stainless steel. The hardness of the outer ring race 17 is about three times higher than that of the sliding part on the surface of the anode fixing base 9V'3.

Due to this unbalanced hardness, vibrations generated by repeated high-speed rotation during operation can cause retching (fine wear) between the outer race 17 and the sliding part on the inner surface of the anode fixing base 9. Surface roughness occurred on the sides, and as the bearings were used repeatedly, the surface roughness progressed to the point where it became impossible to slide, and the bearings were likely to be damaged, resulting in short lifespans.

When we investigated the surface roughness of the sliding part on the inner surface of the anode fixing base 9 of the X-ray tube, which had a short life due to the above reasons, we found that the unevenness became pleated, and the surface roughness was approximately RmaX = 10 An. It was found that large fretting had occurred.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotating anode a-X-ray tube that significantly reduces surface roughness of sliding parts due to fretting, has low vibration and noise, and has a long life.

[Structure of the Invention] (Means for Solving the Problems) This invention provides that at least the inner wall of the anode fixing base in contact with the outer race of the bearing located far from the anode targut is made of a material having a hardness comparable to that of the outer race. It is a rotating anode type X-ray tube with a well-shaped structure.

(Function) According to the present invention, it is possible to significantly reduce the surface roughness of the sliding portion due to 7-retching, and as a result, it is possible to achieve a long life with low vibration and low noise.

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

The main parts of the rotating anode type XM tube according to the present invention are constructed as shown in FIG. 1, and the same parts as in the conventional example (FIG. 4) are given the same reference numerals.

That is, between the rotating cylinder 6 to which the anode target 4 is fixed and the rotating shaft 8 coaxially fixed to the inside of this rotating circle @g, there is a pair of bottomed cylindrical anode fixing bases. bearings 19.14 are arranged.

In this case, the anode fixing base is divided into nine parts, and the outer anode fixing base main body 25 and the inner anode fixing base inner wall 26 are integrated together by screws 20. The inner wall 26 of the anode fixing base is connected to each outer race 1 of the bearing 19.14.
Although it is close to 7.

In this invention, the anode fixing base inner wall 26 is made of high speed tool steel SK.
It is made of H quenched and tempered material.

The quenched and tempered material of the high speed tool steel SEH has a Rockwell hardness of HRC60 or higher, and has a hardness comparable to that of the outer race 17 of the bearing 19.14. High speed tool steel S
There are two types of quenched and tempered KH materials: tungsten-based and molybdenum-based, but molybdenum-based is preferred because of its low cost, and among these, high-speed tool steel S is preferred from the viewpoint of grindability and toughness.
KHs z is highly preferred.

In the rotating anode type XIfiA tube manufactured according to the present invention, after 100,000 uses, the surface roughness of the sliding part of the anode fixed base inner wall 26 is approximately Rma = 2 μm, compared to the conventional structure. 1/! 5, there were no problems with rotational life, and the long-life effect was confirmed.

The rotary anode type X-ray tube of the present invention has the same structure as the conventional example (FIGS. 3 and 4) except for the above, and therefore detailed explanation will be omitted.

(Modification) FIG. 2 shows a modification of the present invention, which provides the same effects as the above embodiment. That is, in FIG. 2, the anode fixing base inner wall 26 in the above embodiment is divided into two parts: an upper anode fixing base inner wall 26a and a lower anode fixing base inner wall 26b, which is in contact with the outer race 17 of the bearing 14.

Only this lower anode fixing base inner wall 26b is formed of a hardened and tempered material of high speed tool steel SKH.

Note that the lower anode fixing base inner wall 26h and the lower anode fixing base inner wall 26b are welded.

[Effects of the Invention] According to the present invention, at least the inner wall of the anode fixing base in contact with the outer race of the bearing located far from the anode tardut is formed of a quenched and tempered material of high-speed tool steel SKH. 7. Surface roughness of sliding parts due to retching can be significantly reduced.

As a result, appropriate contact between the goal and the inner and outer races is maintained even during long-term use, regardless of whether the X-ray tube is in operation or at rest, resulting in low vibration and noise, and a long service life. It is possible to aim for

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of a rotating anode type X-ray tube according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a modified example of the present invention, and FIG. A cross-sectional view showing a wire tube,
FIG. 4 is a cross-sectional view showing the vicinity of a rotating mechanism in a conventional rotating anode X-ray tube with a preloaded structure, and FIG. 5 is a cross-sectional view showing an enlarged main part of FIG. 4. 4... Anode target, 6... Rotating cylinder, 8...
Rotating shaft, 9... Anode fixed base, 14... Bearing, 15... M-rule, 16... Inner ring race, 17... Outer ring v-, <. 18... Roll spring, 25... Anode fixing base body,
26...Anode fixed base inner wall. Applicant's Representative Patent Attorney Takehiko Suzue Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) A rotating cylinder to which an anode target is fixed, a rotating shaft coaxially fixed to the inside of this rotating cylinder, and a bottomed cylindrical anode fixing device disposed between this rotating shaft and the rotating cylinder. a base, a pair of bearings interposed between the anode fixing base and the rotating shaft, an outer race of the bearing farthest from the anode target of the pair of bearings, and a stepped portion of the anode fixing base; In the rotating anode mass X-ray tube equipped with a roll spring disposed between the anode target and the anode target, the material of at least the inner wall of the anode fixing base in contact with the outer race of the bearing located far from the anode target has a Rockwell hardness of H_RC60 or higher. A rotating anode type X-ray tube characterized by being made of hard metal. (2) The rotating anode X-ray tube according to claim 1, wherein the anode fixing base is divided into two or more parts and integrated. (3) The rotating anode lid X-ray tube according to claim 1 or 2, wherein the high hardness metal having a Rockwell hardness of H_RC60 or more is high speed tool steel.