JPH0658793B2 - Rotating anode for X-ray tube - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improvement of a rotary anode X-ray tube that emits X-rays while rotating a portion of an anode target.

[Background of the Invention]

A rotating anode X-ray tube (hereinafter referred to as an X-ray tube) generates X-rays by projecting high-speed electrons emitted from a cathode onto a target portion of a rotating anode. In this case, the target portion becomes high temperature due to the collision of high-speed electrons emitted from the cathode and eventually melts, so that the target plate made of a disc-shaped high melting point metal is rotated at high speed. Then, the collision position of high-speed electrons is moved to prevent local temperature rise of the anode.

FIG. 1 shows a rotary anode type X-ray tube, in which a cathode 2 is disposed on one side of an envelope 1, and the cathode 2 has a cathode filament and a focusing electrode built-in (not shown). A substantially umbrella-shaped disk-shaped target 3 is arranged near the center of the envelope 1 so as to face the cathode 2 and rotates with the rotor 4 and the rotating shaft 5 by bearings 6a and 6b with respect to the anode fixing portion 7. It is freely supported and normally rotates at about 3000 to 9000 rpm. As described above, the X-ray tube in which the target portion of the anode is rotated at a high speed is often used for an extremely short time of X-ray photography in which the load time is within several seconds, and the stator attached to the external station of the X-ray tube is often used. A current is passed through the rotor 8, and the rotating magnetic field generated thereby is used to rotate the rotor 4 which is arranged in the X-ray tube and is connected to the target plate 3.
This rotor usually reaches a specified high speed rotation in about 1 second, and is loaded only for a short time within about several seconds in the specified high speed rotation state. Then, at the same time when this short-time load ends, the stator current is cut off,
The anode rotor and target portions continue to rotate for about several minutes to tens of minutes by inertia, and then stop.

By the way, in the conventional X-ray tube as described above, the rotating torque applied to the rotor 4 by using the rotating magnetic field is transmitted to the target plate 3 through the rotating shaft 5 so that the rotor 4, the rotating shaft 5 and the target plate 3 move together at high speed. It rotates. However, the target plate 3 is made of an alloy mainly composed of tungsten or tungsten in order to increase the X-ray generation capacity and to endure the heat generated at that time, or by combining these metals with another refractory metal. There is. In addition, since the target plate 3 is required to have a large diameter and a large thickness, the stationary torque becomes large, and when it is rotated at high speed in a short time, it is added between the rotary shaft 5 and the target plate 3. Torsional moments are extremely difficult. On the other hand, for the purpose of use, it is necessary for the X-ray tube that the vibration, vibration, and rotation noise of the rotating part be as small as possible when the anode is rotated, that the rotating part has a long life, and that it be able to withstand repeated start and stop of multiple rotations. Therefore, it is required that the target plate 3 and the rotary shaft 5 are firmly connected to each other, and that they are unlikely to change with time due to repeated use.

As a method of connecting the target plate and the rotary shaft, for example, as disclosed in Japanese Utility Model Laid-Open No. 53-151378, the rotary shaft is fitted to the target plate, and the fitting part is fixed in order to fix each other in a fixed direction. A method is known in which a stepped portion eccentric from the center of rotation is provided, and a nut screwed to the end of the rotation shaft is used to tighten and fix the rotation shaft and the target plate.

However, in order to increase the X-ray output, when the target plate is made large and it is attempted to rotate it at a higher speed, there is a problem that fixing is likely to be insufficient, and the X-ray tube has a long life and high output performance. There was a limit in producing.

[Object of the Invention]

An object of the present invention is to provide a rotating anode for an X-ray tube having a structure in which a target plate and a rotating shaft are firmly fixed. At the same time, the heat generated in the target plate when X-rays are generated is suppressed from being transmitted to the rotary shaft side, which reduces the burden on the bearing and prolongs the service life.

[Outline of Invention]

In order to achieve the above-mentioned object, according to the present invention, the direction and magnitude of the rotating torque are different between when the X-ray tube is rotated at high speed and when the rotation is stopped, and the looseness between the target plate and the rotating shaft is the rotating direction. It was made by paying attention to the fact that it is likely to occur and that the suppression is most necessary, and the feature is that the fitting part between the target plate and the rotary shaft has a high precision fitting part and a relatively loose precision screw. The point is that a joint portion is provided side by side, and a screw that rotates in the opposite direction to the screw of the target plate is provided in a part of the rotating portion so that the target is screwed and the target plate and the rotary shaft are fastened and fixedly fixed.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. In the present invention, first, when fitting the target plate 3 and the rotary shaft 5,
When the X-ray tube operates, the target plate 3 reaches a very high temperature of about 1,000 ° C., so that the mutual thermal expansion coefficients are made equal to each other. Normally, molybdenum or a molybdenum alloy is used as the rotating shaft 5, but for the purpose of the present invention, the target plate 3 is made of a material (for example, tungsten) which is suitable for the purpose of the X-ray emitting portion 9 for the X-ray emitting purpose. The same material as that of the rotating shaft 5 is used for at least the fitting portion of the rotating shaft 3 of the portion 10. Next, as the geometrical dimensions of the fitting portion of the target plate 3 and the rotary shaft 5, the high precision fitting portion 11 and the loose precision screwing portion 1 are formed.
Installed with 2 The high-precision fitting portion 11 is such that the diameter of each of the hole provided in the target plate 3 and the shaft provided in the rotary shaft 5 is as high as possible in terms of machining, and the length of the fitting portion is the same as the thickness of the target plate 3. Shorten to about 1/3 or less. On the other hand, the loose precision screwing portion 12 is a loose fitting such that the screw hole provided in the target plate 3 and the screw provided in the rotary shaft 5 slightly rattle, and for example, a clearance 13 is formed in the diametrical direction of the fitting portion. To do. The thread should be a large screw with a pitch of at least 1 mm, and should be dimensioned to withstand a large torque when starting the anode rotation, even if the screw fitting is not tight. Target plate 3 is rotating shaft 5
On the other hand, after the screws are screwed together with a torque that is at least larger than the anode rotation start torque, the nut 15 is tightened and fixed via the washer 14. Rotating shaft 5 and nut 15
The fitting of the threaded portion 16 with and is performed with high precision by tight fitting, and the screw end 17 is crushed to prevent rotation. Further, the respective screws of the loose precision screwing portion 12 and the nut screwing portion 16 have their rotation directions opposite to each other so that the fixing loosening is unlikely to occur when the anode is rotated. Further, in this embodiment, the screw rotation direction of the loose precision screwing portion 12 is formed in the direction opposite to the anode rotation start direction.

FIG. 2 shows another embodiment. The high-precision fitting portion 11 has a shape in which the rotary shaft flange portion 18 fits into the target plate 3, and the others are the same as in the example of FIG.

FIG. 3 shows still another embodiment. Collar 1 of rotating shaft 5
8 and the target plate 3 are joined together by a taper fitting portion 19
Are provided, and the others are similar to those in FIG. Even in this case, the high precision fitting portion 11 and the taper fitting portion 19
It is preferable to shorten the thickness of the target plate 3 to about one third or less of the thickness of the target plate 3. The stepped portion 20 is provided on the target plate 3,
If the length of the loose precision screwing portion is increased, the fixing of the fitting portion can be made firm even when the target plate 3 becomes large in size.

4 and 5, the target plate 3 is provided with a small hole as an auxiliary means for facilitating a large torque when screwing the rotary shaft 5 against the rotary shaft 5, and a screwdriver 2 is provided.
It is one. The shape and the number of the holes are not limited to the shapes and the numbers shown in the figure, but it is sufficient that the holes are arranged in proportion to each other without being biased in a specific direction with respect to the central axis of the target plate 3. FIG. 6 shows the notch 22 in the stepped portion 20 of the target plate 3.
Is provided so that the same function as that of the example of FIGS. 4 and 5 is performed.

[Advantages of the Invention] According to the present invention, since the fitting portion between the target plate and the rotary shaft is firmly fixed, it is possible to manufacture an X-ray tube using a large and heavy target plate. Since the anode is rotated at extremely high speed, it can withstand many uses even if a large torque is applied. Furthermore, even if the target plate glows red when X-rays are generated, the heat conduction from the target plate to the rotating shaft is relatively small, so that the temperature rise of the bearing supporting the rotating shaft is suppressed, resulting in the rotation of the bearing. It has a great effect such as a long life.

[Brief description of drawings]

FIG. 1 is a sectional view showing a side surface of a fitting portion between a target plate and a rotary shaft of a rotary anode for an X-ray tube showing an embodiment of the present invention, and FIGS. 2 and 3 are fittings showing other embodiments. 4 is a side cross-sectional view of FIG. 4, and FIG. 4 is a top view showing a screwdriver provided on a fitting portion between the target plate and the rotary shaft.
FIG. 6 is a bottom view showing a notch provided in a stepped portion of a target plate, and FIG. 7 is a side view with a partial cross section showing a schematic structure of a conventional X-ray tube. 3 ... Target plate, 5 ... Rotation axis, 11 ... High precision fitting portion, 12 ... Loose precision screwing portion, 19 ... Tapered fitting portion, 20 ... Stepped portion, 21 ... Screwdriver Hanging, 2
2 ... Stepped part notch.

Claims (4)

[Claims] 1. A cathode and a rotating anode are arranged to face each other in an envelope,
In an X-ray tube in which a substantially umbrella-shaped disc-shaped target plate of the anode is rotated by a rotor via a rotation shaft, the target plate has the same material as that of the fitting portion with the rotation shaft as the material of the rotation shaft. The rotary anode for an X-ray tube, wherein the target plate and a rotary shaft are fastened together with a fitting portion and a screwing portion provided side by side with the fitting portion. 2. The rotary anode for an X-ray tube according to claim 1, wherein a counter-rotating screw is formed in a threaded portion between the target plate and the rotary shaft with respect to a rotating direction of the target plate. 3. The rotary anode for an X-ray tube according to claim 1, wherein the target plate has a stepped portion. 4. The X-ray according to claim 3, wherein the stepped portion of the target plate is provided with a notch as an auxiliary means for screwing the target plate onto a rotary shaft. Rotating anode for tubes.