JPH05166480A - Power feed mechanism to rotary unit - Google Patents

Abstract

PURPOSE:To suppress a temperature rise in the inside of an envelope by constituting a power feed mechanism of a rotary unit provided in the envelope, filament for emitting a thermion, anode for receiving the thermion from this filament and a radiator for releasing generated heat from the filament to the outside. CONSTITUTION:An annular radiator 13, arranged so as to surround the periphery of an anode 3, consisting of material of high thermal conductivity, is fitted to be inserted through an envelope 10, and radiating fins 16 having a water path 14 of circulating cooling water in the inside are left as provided in a part protruded to the outside. A black color coating is left as formed on an internal peripheral surface 17 of the radiator 13, opposed to the anode 3, and similarly on also an external peripheral surface 18 of the anode 3 opposed to the internal peripheral surface 17, and a recessed part 4 of the anode 3 is mirror-finished or to apply silver and gold plating. A mechanism is thus constituted, and radiation heat from a filament 5 is reflected by the recessed part 4 and absorbed to a black color surface of the radiator 13 in an opposed position and to water in the water path 14 or released to the outside from the fins 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power feeding mechanism for a rotating body which is used for feeding power to a rotary cathode provided in a rotary cathode X-ray tube device.

[0002]

2. Description of the Related Art Recently, a rotary cathode X-ray tube device has been proposed in which a vacuum envelope having a shape surrounding the entire circumference of a subject is provided.
A magnetically levitated ring-shaped rotary cathode and a ring-shaped fixed anode that is installed and fixed are opposed to each other. A filament that emits thermoelectrons toward the fixed anode is attached to the rotary cathode. When the rotating cathode is rotated at high speed while emitting thermoelectrons from the filament toward the fixed anode, X-rays are irradiated from the entire circumferential direction of the fixed anode toward the subject, and scanning is performed at high speed.

In such a rotary cathode X-ray tube device, electric power for heating the filament which rotates integrally with the rotary cathode at high speed is supplied, and thermoelectrons are emitted toward the fixed anode. It is necessary to apply a high direct current voltage between the rotating cathode and the fixed anode. A generally well-known power feeding mechanism is a ring-shaped slip ring that is connected to a lead wire of a filament and integrally rotates with a rotating cathode, and is brought into contact with the slip ring while sliding. It is composed of a power supply brush that supplies electric power from a power source installed outside the vacuum envelope to the filament.

However, according to such a power feeding mechanism,
The power feeding brush wears down significantly due to the frictional force at the contact surface between the slip ring of the rotating cathode rotating at high speed and the power feeding brush.
The wear powder generated by this wear causes the following problems. (1) Abrasion powder may scatter in the vacuum envelope and enter the orbit of the thermoelectrons extracted from the filament.
Then, the abrasion powder of the power supply brush, which is a conductor, also collides with the fixed anode together with the thermoelectrons. The collision point between the thermoelectrons and the fixed anode becomes the X-ray generation point, but if the abrasion powder of the power feeding brush intervenes there, the X-ray generation rate will significantly decrease. Further, the abrasion powder collides with the fixed anode, which may damage the fixed anode. (2) The abrasion powder causes discharge in the vacuum envelope, which deteriorates the withstand voltage characteristics of the rotary cathode X-ray tube and reduces the vacuum degree of the vacuum envelope. (3) The service life of the power supply brush is significantly reduced due to frictional heat, and frequent replacement work is required, resulting in high costs.

Therefore, there has been proposed a power feeding mechanism for the rotating body in which the wear is prevented from occurring in the power feeding portion. One such example is shown in FIG. 5 and described below.

A ring-shaped anode 3 is integrally attached to the surface of the rotating cathode 1 opposite to the surface on which the filament 2 is mounted. A recess 4 as shown in the drawing is formed in the anode 3, and a filament 5 for emitting thermoelectrons and a grid 6 are provided inside the recess 4. A heating power source 7 for heating the filament 5 and a high voltage power source 9 for applying a DC high voltage between the rotating cathode 1 and the fixed anode 8 are connected to the filament 5. Reference numeral 10 indicates an envelope that is evacuated, and 11 indicates an electromagnet device that magnetically levitates the rotating cathode 1.

The filament 5 is driven by the current of the heating power source 7.
When is heated, thermoelectrons are emitted from it. The thermoelectrons are accelerated by the heating power source 7 so as to be attracted to the positively charged grid 6, and are accelerated toward the anode 3 to form a thermoelectron flow between the filament 5 and the anode 6. A current flows due to this thermionic flow, and a potential difference due to the high voltage power source 9 appears between the rotating cathode 1 and the fixed anode 8. If the filament 2 attached to the rotating cathode 1 is heated by the method described below, thermoelectric electrons are emitted from the filament 2 toward the fixed anode 8 due to the potential difference, and X-ray irradiation is performed.

For heating the filament 2, a storage battery attached to the rotating cathode 1 is used, or a solar cell is attached to the rotating cathode 1 to apply power from the outside by applying light.
A method in which a generator is provided in the rotating cathode 1 or a method in which electric power is supplied from the outside in a non-contact manner using a rotating transformer is used.

[0009]

In the power feeding mechanism as illustrated and described above, when the voltage drop between the filament 5 and the anode 3 is large, the voltage between the rotating cathode 1 and the fixed anode 8 is correspondingly increased. The potential difference becomes small, resulting in a decrease in the amount of electrons emitted from the filament 2 attached to the rotating cathode 1 and a concomitant decrease in the generated X-ray dose. Therefore, as shown in the figure, in practice, a recess 4 is formed in the anode 3, a filament 5 is arranged inside the recess 4, and a device for widening a range for receiving thermoelectrons emitted from the filament 5 is further provided. A measure is taken to increase the amount of thermoelectrons to increase the current flowing between the filament 5 and the anode 3. Regarding the latter, for example, the heating temperature of the filament 5 is increased,
Will be adopted.

However, if the heating temperature of the filament 5 is increased or the number of the filaments 5 installed is increased, the heat generated by the filament 5 causes the following problems. (1) The anode 3 close to the filament 5 may be heated and thermally expanded, and the gap length between the filament 5 and the anode 3 may be narrowed, so that they may come into contact with each other. Then, the filament 5 is broken or damaged by the anode 3 which rotates integrally with the rotating cathode 1 at a high speed.

(2) Further, the heat conduction from the anode 3 causes the temperature of the rotating cathode 1 to rise, causing thermal expansion. When the rotating cathode 1 that is rotating is deformed due to thermal expansion, the position of the filament 2 attached thereto is displaced, and the position of the X-ray focal point formed on the fixed anode 8 is displaced. Along with the displacement of the X-ray focal point, there is a problem that the irradiation angle of the X-ray toward the subject and the distance from the X-ray focal point to the subject change, which significantly impairs the image quality of the tomographic image. (3) Due to the heat generation of the filament 5 and the heat radiation from the heated anode 3, the temperature inside the envelope 10 rises, and the internal gas of the equipment provided inside the envelope 10 is released. The degree of vacuum decreases. Then, the dielectric strength in the envelope 10 is lowered, and a discharge occurs between the fixed anode 8 kept at a high potential and the envelope 10.

The present invention has been made in view of the above circumstances, and is capable of suppressing the temperature rise inside the envelope and promoting the practical application of a power feeding mechanism mediated by thermoelectrons. The purpose is to provide a power supply mechanism to the.

[0013]

In order to achieve the above object, the present invention has the following constitution. That is, according to the present invention, a rotating body that rotates in an envelope, a thermoelectron emission filament fixedly installed in the envelope, and a heat from the filament that is integrally attached to the rotating body. An anode that receives electrons and a radiator that is attached to the envelope and that emits heat generated from the filament to the outside of the envelope are provided.

[0014]

The function of the present invention is as follows. When thermoelectrons are emitted from the filament installed in the envelope, the anode attached to the rotating body receives it, and a thermoelectron flow is formed between the filament and the anode. While supplying electric power to the rotating body through such thermoelectrons, the radiator dissipates heat generated by the filament at the time of thermoelectron emission to the outside of the envelope and suppresses temperature rise inside the envelope.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view of a rotary cathode X-ray tube device showing a power feeding mechanism for a rotating body according to this embodiment. In FIG. 1, the same reference numerals as those in FIG. 5 used in the conventional example indicate the same components. Rotating cathode 1 filament 2
A support 12 made of a material having low thermal conductivity such as ceramic is attached to the surface opposite to the surface on which the ring-shaped anode 3 is mounted. The anode 3 and the rotary cathode 1 are electrically connected by the lead wire 15.

An annular radiator 13 arranged so as to surround the outer periphery of the anode 3 is attached so as to penetrate the envelope 10. The radiator 13 is made of a material having high thermal conductivity such as copper, and the radiator fin 16 is formed in a portion protruding to the outside of the envelope 10, and a water passage 14 for circulating cooling water is formed inside the radiator fin 16. Has been done. As shown in a partially enlarged view of FIG. 2, the inner peripheral surface 17 of the radiator 13 facing the anode 3 is coated in black, and the outer peripheral surface 18 of the anode 3 facing the inner peripheral surface 17 is similarly processed. It is coated in black. On the other hand, the recess 4 of the anode 3 is mirror-finished,
It is plated with silver and gold.

A heating power source 7 is provided for a filament 5 for emitting thermoelectrons installed inside the hemispherical recess 4 of the anode 3.
When heated by, thermoelectrons are emitted from it. The thermoelectrons are accelerated by the grid 6 toward the anode 3,
A thermoelectron stream is formed between the filament 5 and the anode 6. A current due to this thermionic flow flows through the lead wire 15 to the rotating cathode 1, and the potential difference due to the high-voltage power supply 9 causes the rotating cathode 1 to flow.
And the fixed anode 8 appear.

By the heating at this time, the filament 5
The radiant heat emitted from is reflected by the mirror surface or the plated surface of the recess 4 and is absorbed by the black surface of the radiator 13 located at the opposite position. The heat absorbed by the radiator 13 is conducted inside and is absorbed by the cooling water flowing back through the water passage 14, or is radiated from the radiator fin 16 to the outside of the envelope 10.
The radiant heat reflected by the mirror surface or plating surface of the hemispherical recess 4 irradiates the filament 5 located at the center of the radiator 13 in the process of traveling toward the radiator 13 to heat it. This also has the side effect of saving the amount of power for heating the filament 5.

Part of the radiant heat that is not reflected by the mirror surface or the plated surface of the recess 4 is absorbed by the anode 3, conducted inside, and emitted from the outer peripheral surface 18, which is a black surface.
Since the anode 3 is supported by the support 12 having a low thermal conductivity, and the recess 4 is a mirror surface or a plated surface, heat is released from the outer peripheral surface 18 which is the other portion. The heat release is promoted by making the outer peripheral surface 18 a black surface. The radiant heat emitted from the outer peripheral surface 18 is absorbed by the black surface of the radiator 13 located around the outer peripheral surface 18 and is emitted to the outside of the envelope 10.

<Modification> (1) As shown in FIG. 3, the cross section of the recess 4 of the anode 3 is changed to a parabolic shape, and the filament 5 is discharged by utilizing the geometrical properties of the shape. Radiant heat is reflected in parallel. That is, if the radiator 13 is configured to concentrate and cool only the surface 20 that receives the radiant heat reflected in parallel, efficient heat radiation can be performed. As an example, as shown in the figure, the surface 20 is a black surface, and a cooling water passage 21 through which cooling water circulates is formed on the inner surface for intensive cooling.

(2) As shown in FIG. 4, the cross-sectional shapes of the anode 3 and the radiator 13 are changed so as to draw one ellipse. The geometrical property of this shape, that is, the property of converging the reflected wave to a certain focal point may be utilized, and the radiator 13 may be arranged at the focal point to intensively cool the portion.

[0022]

As is apparent from the above description, according to the power feeding mechanism for the rotating body of the present invention, the heat generated from the filament for thermionic emission is radiated to the outside of the envelope, and the inside of the envelope is discharged. Since it is equipped with a radiator that suppresses the temperature rise, the problem of the power feeding mechanism to the rotating body mediated by the thermoelectrons flowing between the filament and the anode is solved, and the practical application of the power feeding mechanism is promoted. .

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary cathode X-ray tube showing an embodiment of a power feeding mechanism according to the present invention.

FIG. 2 is a partially enlarged view thereof.

FIG. 3 is a main-portion cross-sectional view showing a modification of the power feeding mechanism.

FIG. 4 is a diagram showing another modification.

FIG. 5 is a cross-sectional view of a rotary cathode X-ray tube showing an example of a power feeding mechanism already proposed in a conventional example.

[Explanation of symbols]

 1 ... Rotating cathode 2 ... Filament 3 ... Anode 5 ... Thermionic emission filament 10 ... Enclosure 13 ... Radiator

Claims (1)

[Claims] 1. A rotating body that rotates in an envelope, and a filament for thermoelectron emission fixedly installed in the envelope,
An anode integrally attached to the rotating body to receive thermoelectrons from the filament, and a radiator attached to the envelope to radiate heat generated from the filament to the outside of the envelope. A power supply mechanism for a rotating body.