JPH0562622A - Rotating anode X-ray tube - Google Patents

Abstract

(57) [Summary] [Object] To provide a structure for shielding radiative heat transfer from a target of a rotating anode X-ray tube to a rotor. [Structure] A target has a heat shield plate supported by an envelope on the back side of the target and having an opening inside, and an aperture diameter changing means for changing the aperture diameter of the heat shield plate. The former includes a plurality of metal plates rotatably supported by the envelope and a movable ring that rotates the metal plates, and the inner diameter of the opening changes as the movable ring rotates. The latter transmits a driving force from a driving unit provided outside the envelope to a movable ring by a driving rod via a metal bellows.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary anode X-ray tube,
In particular, the present invention relates to a rotary anode X-ray tube having a structure in which the amount of heat transferred from the target of the anode to the rotor is minimized.

[0002]

2. Description of the Related Art In an X-ray tube, due to its characteristics, almost all of the electric power given to it turns into heat, and heats the target which is a component of the anode. In particular, in an X-ray tube for X-ray CT or circulatory organ diagnosis, the target temperature reaches 1000 ° C during use. The heat of the target is dissipated to the surroundings by radiation,
Most are absorbed in the envelope. Part of the heat is absorbed by the rotor, which is one of the components of the anode, and the heat is transferred to the inside of the rotor, which raises the temperature of the bearing, which is the rotating mechanism. Since the bearing is used in a vacuum, a soft metal such as silver, lead, gold, or molybdenum disulfide is used as a lubricant, and the practical temperature of these lubricants is 300 to 500 ° C.
It is a low temperature. In addition, the steel material used for the bearing is 50
If the temperature exceeds 0 ° C, annealing will occur, resulting in a decrease in hardness, impairing load bearing capacity, and failure in bearing function. Therefore, various improvements have been made to prevent the temperature of the bearing portion from rising. As a means of improving the structure, a structure that shields the heat radiation from the target to the rotor is adopted.

In the conventional rotary anode X-ray tube, a donut-shaped heat shield plate protruding from the envelope is provided on the back side of the target as a structure for shielding radiant heat transfer from the target to the rotor, and the rotor. There is a structure in which a heat shield is attached to a portion close to the target. In the former, the radiant heat transfer from the target to the rotor is reduced by making the inner diameter side opening of the donut-shaped heat shield plate as small as possible. In the latter, since the heat shield rotates with the rotor, it is closely attached to the rotor. On the other hand, since the target is fixed and supported by the protruding shaft of the rotor, the heat from the target also flows into the rotor due to heat conduction. In order to radiate such heat, the outer surface of the rotor itself is blackened to radiate heat.

[0004]

In the case of an X-ray tube having a conventional structure in which the envelope is provided with a donut-shaped heat shield plate, a high voltage is applied between the target (including the rotor) and the envelope. Is applied, it is necessary to make the inner diameter of the opening large enough to prevent discharge from occurring between the anode inner surface of the envelope and the anode. Was enough. Also, in the case of a structure in which the heat shield is attached to the rotor, the heat shield is in close contact with the rotor, so a sufficient heat shield effect cannot be obtained. There is also a drawback that the area of the processing portion becomes small, and conversely the heat dissipation characteristics of the rotor itself deteriorate. In the present invention, in order to solve the above problems, heat is shielded by a shield provided on the envelope side of the non-rotating portion, and the structure is improved.

[0005]

In consideration of the fact that a high voltage is applied only when X-rays are exposed to an X-ray tube, the heat shield plate provided in the envelope on the back side of the target is movable. When the X-ray exposure is stopped, the inner diameter of the opening of the heat shield plate can be reduced to sufficiently shield the heat, and the inner diameter of the opening of the heat shield plate can be increased to secure the withstand voltage during X-ray exposure. I did it. The heat shield plate is composed of multiple metal plates. One of the metal plates is supported by the envelope and the other is connected to the movable ring. The inner diameter of the formed opening is changed. The heat shield plate is driven from the outside of the X-ray tube, a metal bellows is attached to the envelope, and the movable ring is moved by the driving force from the drive unit installed outside the envelope through the metal bellows. I decided to rotate it.

[0006]

With the above-described structure, the opening of the heat shield plate is wide open only during photographing, that is, when a high voltage is applied, and the distance between the anode and the envelope is sufficiently secured. The opening of the heat shield plate becomes small and blocks heat from the target from entering the rotor.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a vertical cross section of an X-ray tube showing an embodiment of the present invention. FIG. 2 is a cross-sectional view of the same X-ray tube, showing a movable state of the heat shield plate, which is a main part of the present invention. Figure 2 (a)
Shows a state in which the opening is narrowed, and FIG. 2B shows a state in which the opening is opened.

In FIG. 1, a target 1 is fixed and supported by a protruding shaft of a rotor 2, and the rotor 2 is rotatably supported by a bearing 3 via a rotating shaft 2a. The heat generated in the target 1 is radiated to the surroundings and radiated, but the heat is also absorbed by the rotor 2. A heat shield plate 4 is attached to the envelope 5 to shield the radiant heat from the target 1 absorbed by the rotor 2. Although the heat shield plate 4 is attached to the outside of the rotor 2 in FIG. 1, the heat shield plate 4 may be attached so as to surround the protruding shaft of the rotor 2 in order to enhance the heat shield effect.

As shown in FIG. 2, the heat shield plate 4 is composed of a plurality of metal shield blades 4a, and each shield blade 4a is an envelope 5.
It is attached to the shielding plate support 10 so that it can rotate about one point. Further, all the shield blades 4a are linked to the movable ring 6, and by rotating the movable ring 6, the shield blades 4a move, and the opening of the heat shield plate 4 becomes large or small in a substantially circular shape. However, the heat shield area changes. The drive system of the movable ring 6 is pulled out from the vacuum to the outside of the envelope 5 by a metal bellows 7 and is operated by a linear motion mechanism using electromagnetic coupling. In the embodiment of FIG. 2, a permanent magnet 11 is fixed to the tip of a drive rod 8 connected to the movable ring 6, and an electromagnet (or permanent magnet) 9 is provided around the permanent magnet 11.
The movable ring 6 can be driven by arranging and moving the permanent magnet 11 attached to the tip of the drive rod 8 by the electromagnet (or permanent magnet) 9. In addition, since a voltage of 1/2 of the high voltage applied to the X-ray tube is applied between the anode (including the target 1 and the rotor 2) and the envelope 5, the gap between the two is It is necessary to ensure the distance required to insulate this voltage.

Next, the operation of the heat shield plate 4 will be described. The heat shield plate 4 is in the most closed state when the photographing is not performed, that is, the heat shield plate 4 is close enough not to contact the rotor 2 of the anode (state of FIG. 2A). The shield blades 4a of the heat shield plate 4 can be rotated within a certain angle range with the fixing pin 12 fixed to the shield plate support 10 of the envelope 5 as a fulcrum. First, when a rotor drive voltage is applied to a stator winding (not shown) arranged outside the X-ray tube on the rotor 2 of the anode by the image capturing start signal, a rotating magnetic field is generated and a starting torque is applied to the rotor 2. Rotate. At the same time, the movable ring 6 rotates to the right when the drive rod 8 moves to the right due to the electromagnetic coupling provided outside the envelope 5. As the movable ring 6 rotates, the shield blade 4a rotates outward with the pin 13 fixed to the movable ring 6 and the groove 14 of the heat shield plate 4 fitted therein as a guide. As a result, the opening of the heat shield plate 4 becomes large (state of FIG. 2B). In this state, a high voltage is applied to the X-ray tube to generate X-rays, and a series of imaging work is performed. When the high voltage application is stopped at the end of a series of photographing operations and the drive rod 8 is moved to the left by an electromagnetic coupling provided outside the envelope 5, the movable ring 6 is rotated in the opposite direction. The opening of the heat shield plate 4 is narrowed, the radiant heat from the target 1 is shielded by the heat shield plate 4, and the incident heat to the rotor 2 is reduced.

Further, if control is performed such that the opening amount of the heat shield plate 4 is made as small as necessary according to the voltage applied to the X-ray tube, heat radiation to the rotor 2 can be limited even during photographing. ..

[0012]

By applying the present invention, the heat radiation from the high temperature target after the X-ray photography is shielded by the heat shield plate, the heat incident on the rotor is extremely reduced, and the temperature of the bearing portion is reduced. Therefore, the hardness of the material of the bearing is not reduced, the evaporation of the lubricant is reduced, and the long life of the bearing can be expected.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an X-ray tube showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an X-ray tube showing an embodiment of the present invention, showing a movable state of a heat shield plate, (a) showing a state in which an opening is narrowed, and (b) showing an opening. The department is in an open state.

[Explanation of symbols]

 1 Target 2 Rotor 3 Bearing 4 Heat Shielding Plate 4a Shielding Blade 5 Envelope 6 Movable Ring 7 Bellows 8 Drive Rod 9 Electromagnet 10 Shielding Plate Support 11 Permanent Magnet 12 Fixed Pin 13 Pin 14 Groove

Claims (3)

[Claims] 1. A target is supported by an envelope on the back side of the target,
A rotary anode X-ray tube comprising a heat shield plate having an opening inside and an aperture diameter changing means for changing the aperture diameter of the heat shield plate. 2. A plurality of metal plates, wherein the heat shield plate is rotatably supported by an envelope, and a plurality of metal plates engaged with each other to give a rotational movement force to the metal plates and to be rotatable about the envelope. A movable ring supported, wherein the plurality of metal plates are integrally formed to form an opening, and an inner diameter of the opening is changed by rotation of the movable ring. The rotating anode X-ray tube according to item 1. 3. The opening changing means comprises a driving portion provided outside the envelope, and a driving force transmitting portion connected to the driving portion at one end through a movable ring and at the other end through a metal bellows.
The rotary anode X-ray tube according to claim 1, wherein the movable ring is rotated by a driving force from the driving unit to change an opening diameter of the heat shield plate.