JPH0414844Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a rotating anode type X-ray tube, and particularly to improvements in its rotation mechanism. [Technical background of the invention] Generally, X-ray tubes are used for medical purposes, for example, for X-ray diagnosis, but in cases such as gastric examination,
Conventionally, an X-ray tube as shown in FIG. 4 has been used. This X-ray tube is of a so-called rotating anode type, and an anode 2 is disposed on one side of an envelope 1.
A cup 3 containing a cathode filament for emitting thermoelectrons and a focusing electrode is provided eccentrically.
Further, near the center of the envelope 1, a substantially umbrella-shaped anode target 4 is arranged opposite to the cathode 2 . This anode target 4 establishes a high potential difference between it and the cathode 2 , accelerates electrons emitted from the cathode filament, causes them to collide, and generates X-rays through controlled radiation, and at the same time It is designed to store and dissipate heat, and is designed to rotate at high speeds to effectively expand the heat generation area. Such an anode target 4
is a covered rotating cylinder (rotor) 6 via a support column 5
is connected to. 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). A bottomed cylindrical anode fixing base 9 is coaxially disposed between the rotating shaft 8 and the rotating cylinder 6, and one end is fixed to the envelope 1 via sealing rings 10 and 11. ing. A portion of this anode fixing base 9 is exposed outside the tube, and also serves to support and fix the entire X-ray tube to the outside.
Bearings 12 and 13 are interposed between the anode fixing base 9 and the rotating shaft 8, so that the rotating shaft 8 can rotate freely. Normally, these bearings 12 and 13 are composed of a metal inner race, an outer race, and a large number of balls.In order to suppress wear between these balls, the surfaces of the balls are coated with solid lubricant such as Pb or Ag. material 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.
Of the pair of bearings 12 and 13, the bearing 12 is particularly close to the anode target 4 in terms of thermal path.
The temperature tends to be about 100 degrees Celsius or more higher than those located further away. As described above, due to the difference in thermal expansion of the structure due to the temperature distribution that exists in the anode structure including the bearings 12 and 13, and deformation due to heat, proper contact between the balls and the inner race and the outer race is impaired.
In extreme cases, it may become impossible to rotate. In order to prevent such inconveniences, a pair of angular contact type bearings 19 and 14 are used, as shown in Fig. 5, and are brought into contact with the bearing 14 located far from the anode target so as to apply preload in the thrust direction. A coil spring 18 is provided. Even if a thermal expansion difference occurs in the anode structure due to the preload of the coil spring 18, the structure maintains appropriate contact between the balls 15 in the bearing 14 and the inner race 16 and the outer race 17. In many cases, it is. FIG. 6 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 at 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 When thrust preload is applied,
Due to the preload from this coil spring 18, the outer race 17 slides on the inner wall of the anode fixing base 9 and moves to the position indicated by the broken line, eliminating deformation and misalignment between the ball 15, inner race 16, and outer race 17 in the thrust direction. This will ensure that appropriate contact is maintained. In addition, in FIGS. 5 and 6, 23 is a cylindrical spacer, and 24 is a nut. [Problems with Background Art] In order to maintain proper contact, 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 is smaller than this frictional force, the outer race 17 will not move and the preload will be ineffective. Conversely, 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 and Ag attached to the surface of the ball 15 to
This accelerates the consumption of the solid lubricant of the ball 15.
The disadvantage is that it damages the base material and tends to shorten its lifespan. Also, in order to reduce the frictional force, there is a method of providing a slight clearance between the outer race 17 and the inner wall of the anode fixing base 9.
If this clearance is too large, the balance of the rotating system consisting of the anode target and the rotor will be disturbed, and the vibration of the entire X-ray tube will increase, making it unusable. In addition, such 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, and in the worst case, the outer race 17 may bite into the inner wall of the anode fixing base 9, causing the preload to increase. It can be predicted that the inconvenience of invalidation will occur. As described above, in the preloaded structure, selection of the preload force and the above-mentioned clearance has been technically a very difficult problem. In addition, in the conventional structure, the sliding outer ring race 17
As is clear from the figure, the inner surface of the anode fixing base 9, which the outer circumferential surface of the anode fixing base 9 contacts, was a straight flat surface, and was in contact with the entire outer circumferential surface of the outer race 17. For this reason, both edged edges of the outer ring race 17 bite into the inner surface of the anode fixing base 9 and get stuck.
There were cases where the bearing 14 could not be moved. [Purpose of the invention] The purpose of this invention was made in view of the above circumstances. Under high temperatures during operation, the outer ring race moves smoothly along the inner wall of the anode fixing base with a small preload from the coil spring, and the ball and the An object of the present invention is to provide a rotating anode type X-ray tube having a rotation mechanism that maintains appropriate contact with an outer race, has low vibration, and has a long life. [Summary of the invention] In the rotating anode X-ray tube of this invention, at least the inner surface of the anode fixed base that contacts the outer race of the bearing located far from the anode target is self-lubricating by friction or high-temperature heating in vacuum. Fe-Mo with high Mo and high S compositions can segregate in the surface layer and achieve low friction on the surface.
-Made of S ternary alloy. [Embodiment of the invention] The main parts of the rotating anode type X-ray tube according to this invention are constructed as shown in FIG. 1, and the same parts as in the conventional example (FIG. 5) are given the same reference numerals. That is, a bottomed cylindrical anode fixing base 9 is disposed between a rotating cylinder 6 to which an anode target 4 is fixed and a rotating shaft 8 coaxially fixed to the inside of this rotating cylinder 6. A pair of bearings 19 and 14 are disposed between this anode fixing base 9 and the rotating shaft 8. In this case, the anode fixing base 9 is divided into two parts, an outer anode fixing base main body 25 and an inner intermediate cylindrical member 26, which are integrated by screws 20. The intermediate cylindrical member 26 is the bearing 1
9 and 14 , but in this design, the intermediate cylindrical member 26 is made of a high Mo, high S composition.
It is made of a Fe-Mo-S ternary alloy, for example, a Fe-22.1Mo-2.61S alloy. This Fe-Mo-S ternary alloy with a high Mo and high S composition is formed into a self-lubricating Mo-S compound (MoS1.8 in the case of Fe-22.1Mo-2.61S alloy) by friction or high-temperature heating in vacuum. ) is known to segregate in the surface layer, significantly lowering the surface friction coefficient. Such a Fe-Mo-S ternary alloy is applied to the outer race 1 of the bearing 14 far from the anode target 4.
The material used for the inner surface of the anode fixing base 9 , that is, the intermediate cylindrical member 26 in contact with the outer ring race 1
7. It is highly effective for smooth sliding. Furthermore, the segregation of the self-lubricating Mo-S compound into the surface layer can be easily achieved by vacuum heat treatment for the purpose of degassing before assembling the X-ray tube, or by heating during the exhaust process. Another big advantage is that it does not require . In this way, the solid lubricant segregated on the surface of the intermediate cylindrical member 26 reduces the friction between the inner surface of the intermediate cylindrical member 26 and the outer race 17, making it easier for them to slide, and even during operation, the solid lubricant is solid lubricant. Lubricant is supplied to the surface and good sliding performance can be maintained for a long time. The rotary anode type X-ray tube of this invention has the same structure as the conventional example (Figs. 4 and 5) except for the above.
Detailed explanation will be omitted. [Effects of the invention] In the rotating anode X-ray tube of this invention, there is a space between the outer ring race of the bearing far from the anode target and the anode fixing base body.
An intermediate cylindrical member made of a ternary alloy of Fe-Mo-S containing Mo and S is interposed. As a result, the self-lubricating Mo-S compound is segregated on the surface due to high temperature heating due to friction during operation, and the outer race 17 slides extremely smoothly along the inner surface of the anode fixing base 9 . As a result, appropriate contact between the balls 15 and the inner race 16 and the outer race 17 is maintained regardless of whether the X-ray tube is in operation or at rest, resulting in low vibration and noise, resulting in a long life. In addition, since the intermediate cylindrical member is composed of a ternary alloy of Fe-Mo-S, which is mainly composed of Fe and also contains Mo and S, its coefficient of thermal expansion is approximately the same as that of the anode fixing base body, and it can be easily used during operation. , there is no possibility of an undesirably wide gap occurring between the two, and stable movement of the outer race can be achieved. [Modification of the invention] FIGS. 2 and 3 show a modification of this invention, which provides the same effects as the above embodiment. That is, in FIG. 2, the intermediate cylindrical member 26 in the above embodiment is divided into two parts: an upper intermediate cylindrical member 26a and a lower intermediate cylindrical member 26b in contact with the outer race 17 of the ball bearing 14 . Only 26b is formed from a Fe-Mo-S ternary alloy. In addition, the upper intermediate cylindrical member 26
a and the lower intermediate cylindrical member 26b are welded. Further, in FIG. 3, the intermediate cylindrical member 26 is divided into two parts, an upper intermediate cylindrical member 26a and a lower intermediate cylindrical member 26b, as in the case of FIG. 2, but in this case, the two are not in close contact with each other. Lower intermediate cylindrical member 26b
is fixed to the outer race 17 of the ball bearing 14 . It moves together with the outer race 17 and is slidable along the inner surface of the anode fixing base main body 25. It goes without saying that only the lower intermediate cylindrical member 26b is formed of the Fe--Mo--S ternary alloy.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the main parts of a rotating anode type X-ray tube according to an embodiment of this invention, Figs. 2 and 3 are sectional views showing a modification of this invention, and Fig. 4 is a sectional view of a conventional A cross-sectional view showing a rotating anode type X-ray tube. Figure 5 is a cross-sectional view showing the vicinity of the rotation mechanism in a rotating anode type X-ray tube with a conventional preload structure. Figure 6 is an enlarged view of the main parts of Figure 5. FIG. 4... Anode target, 6... Rotating cylinder, 8...
... Rotating shaft, 9 ... Anode fixed base, 14 ... Bearing, 15 ... Ball, 16 ... Inner race, 1
7...Outer race, 18...Coil spring, 25...
...Anode fixing base body, 26...Intermediate cylindrical member.

Claims (1)

[Claims for Utility Model Registration] A rotating cylinder to which an anode target is fixed, a rotating shaft coaxially fixed inside the rotating cylinder,
A plurality of balls are installed between a bottomed cylindrical anode fixing base body disposed between the rotating shaft and the rotating cylinder, an inner race and an outer race, and the anode fixing base body and the A pair of bearings are interposed between the rotating shaft and the outer race of the bearing that is far from the anode target, and the bearing is provided so as to apply a pressing force in a direction away from the other bearing. In a rotary anode type X-ray tube equipped with a coil spring, an Fe
Fe-Mo- which mainly contains Mo and S
A rotating anode type X characterized by an intervening intermediate cylindrical member made of a ternary alloy of S
wire tube.