JP2010218917A - X-ray tube device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable X-ray tube device. <P>SOLUTION: The X-ray tube device has an X-ray tube 1 including an anode 11, a cathode 10 having a filament 17 and a grid 18, and a vacuum envelope 19, a cabinet 20, an insulating oil 9, a receptacle 16a having a filament terminal 31 and a grid terminal 32, a filament circuit 3, and a grid circuit 4. A discharge starting voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 is less than an insulation breakdown voltage between the filament terminal 31 and the grid terminal 32 of the receptacle 16a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an X-ray tube apparatus.

  In general, X-ray tube apparatuses are used in medical diagnosis systems, industrial diagnosis systems, and the like. The X-ray tube device includes an X-ray tube that emits X-rays, a housing that houses the X-ray tube, and insulating oil that is filled in the housing. The X-ray tube has a cathode having a filament and a grid for emitting electrons, an anode for emitting X-rays when the electrons emitted from the filament collide, and a vacuum envelope containing the cathode and the anode. ing.

  An anode receptacle and a cathode receptacle are respectively attached to the casing (see, for example, Patent Document 1). For example, a receptacle for a cathode has a filament terminal and a grid terminal.

  A filament circuit is connected to the filament, and the filament circuit is drawn out of the X-ray tube and is connected to the filament terminal through the insulating oil. A grid circuit is connected to the grid, and the grid circuit is drawn out of the X-ray tube and connected to the grid terminal through the insulating oil.

An anode voltage is supplied to the anode from a high-voltage power source through an anode-fed high-voltage cable and an anode receptacle. Filament voltage is supplied to the filament from the negative side of the high voltage power source via the cathode-fed high voltage cable, the filament terminal, and the filament circuit. A grid voltage is supplied to the grid from the negative side of the high-voltage power source via a cathode-fed high-voltage cable, a grid terminal, and a grid circuit. For this reason, the cathode-fed high-voltage cable includes two core conductors insulated from each other. A bias voltage is further supplied to the grid.
JP-A-5-152093

  By the way, discharge may occur between the grid and the anode. When discharge occurs, a high voltage is induced in the grid, so that a large potential difference is generated between the filament (filament circuit). The potential difference between the grid and the filament at the moment when the discharge occurs reaches the value of the high-voltage power supply voltage at the maximum. For this reason, there is a possibility that dielectric breakdown may occur between the grid terminal and the filament terminal in the cathode receptacle.

In order to withstand this, in order to increase the dielectric strength between the grid terminal and the filament terminal, a sufficient distance is provided between the grid terminal and the filament terminal, a material with high dielectric strength is used, or the filament circuit and the grid circuit It is conceivable to take measures by means such as incorporating a surge absorber such as a varistor or arrester in between. However, it is practically difficult to adopt the above means because of dimensional restrictions or the durability and reliability of the surge absorber. In order to provide a highly reliable X-ray tube apparatus, it is required to reliably prevent dielectric breakdown between the grid terminal and the filament terminal.
The present invention has been made in view of the above points, and an object thereof is to provide a highly reliable X-ray tube apparatus.

In order to solve the above problems, an X-ray tube apparatus according to an aspect of the present invention provides:
An anode that emits X-rays when struck by electrons, a filament that emits electrons that collide with the anode, a cathode having a grid provided around an orbit of electrons from the filament toward the anode, and An X-ray tube including a vacuum envelope containing an anode and a cathode;
A housing containing the X-ray tube;
Insulating oil filled in the housing;
An insulating receptacle attached to the housing, having a filament terminal for supplying a filament voltage to the filament and a grid terminal for supplying a grid voltage to the grid;
A filament circuit connected to the filament and drawn out of the X-ray tube and connected to the filament terminal through the insulating oil;
A grid circuit connected to the grid and drawn out of the X-ray tube, connected to the grid terminal through the insulating oil, and
A discharge start voltage between the filament circuit and the grid circuit via the insulating oil is less than a breakdown voltage between the filament terminal and the grid terminal of the receptacle.

  According to this invention, a highly reliable X-ray tube apparatus can be provided.

Hereinafter, an X-ray tube apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIGS. 1, 2, and 3, the X-ray tube device includes an X-ray tube 1, a housing 20, an insulating oil 9, an anode connector 14, a cathode connector 16, an anode-fed high-voltage cable 13, and a cathode-fed high-voltage cable. 15, a filament circuit 3, a grid circuit 4, and a high voltage power supply 12 are provided. In this embodiment, the X-ray tube 1 is a rotary anode type X-ray tube.

The X-ray tube 1 includes a rotating body 5, a fixed body 6, a cathode 10, an anode 11, and a vacuum envelope 19.
The rotating body 5 is formed in a cylindrical shape, and one end thereof is closed. The rotating body 5 extends along a rotation axis that is a central axis of the rotating operation of the rotating body. The rotating body 5 is rotatable around the rotation axis. The rotating body 5 is made of a material such as Fe (iron) or Mo (molybdenum).

  The fixed body 6 is formed in a column shape. The diameter of the fixed body 6 is smaller than the inner diameter of the rotating body 5. The fixed body 6 is provided coaxially with the rotating body 5 and extends along the rotation axis. The fixed body 6 is formed of a material such as Fe or Mo. The fixed body 6 is fitted to the rotating body 5 and is fixed to the vacuum envelope 19. Although not shown, the gap between the rotating body 5 and the fixed body 6 is filled with a metal lubricant such as gallium, indium, tin alloy (GaInSn). For this reason, the X-ray tube 1 uses a sliding bearing.

  The anode 11 is disposed to face one end of the fixed body 6 in a direction along the rotation axis. The anode 11 has a target layer 11a located on the outer surface of the anode. The anode 11 is fixed to the closed end of the rotating body 5 with a nut 7. The anode 11 has an annular shape and is formed of a material such as heavy metal. The anode 11 is made of Mo, for example.

  The anode 11 is provided coaxially with the rotating body 5 and the fixed body 6. The anode 11 is rotatable around a rotation axis. The anode 11 emits X-rays when electrons emitted from the cathode 10 collide. A relatively positive voltage is supplied to the anode 11.

  The cathode 10 has a filament 17 and a grid 18. The cathode 10 is disposed to face the target layer 11a of the anode 11 with a space therebetween. The filament 17 emits electrons that collide with the anode 11. The grid 18 is provided so as to surround an electron trajectory from the filament 17 toward the anode 11. A relatively negative voltage and current are applied to the filament 17 and the grid 18. As a result, the filament 17 emits electrons (thermoelectrons) as described above.

  The vacuum envelope 19 contains the anode 11 and the cathode 10. The vacuum envelope 19 is formed of an insulating material such as glass and ceramic, or a combination of an insulating material and a conductive member such as metal. The vacuum envelope 19 is sealed and the inside is maintained in a vacuum state. The vacuum envelope 19 has an X-ray transmission window 19 a that transmits X-rays in the vicinity of the target layer 11 a facing the cathode 10.

  The housing 20 accommodates the X-ray tube 1, the filament circuit 3, and the grid circuit 4. The housing 20 has an X-ray transmission window 20 a that transmits X-rays in the vicinity of the target layer 11 a facing the cathode 10. The housing 20 contains the X-ray tube 1 and the like, and is filled with insulating oil 9 as a coolant.

  For this reason, the X-ray tube 1, the filament circuit 3, the grid circuit 4 and the like are immersed in the insulating oil 9. Although not shown, a stator coil that rotates the rotating body 5 is also housed inside the housing 20.

  The anode connector 14 has a receptacle 14a and a plug 14b. The receptacle 14a and the plug 14b are detachable. The receptacle 14a is attached to the housing 20 in an airtight manner. The receptacle 14a is made of, for example, a resin as an insulating material. The anode connector 14 is connected to the anode 11 and supplies an anode voltage to the anode 11.

  The cathode connector 16 has a receptacle 16a and a plug 16b. The receptacle 16a and the plug 16b are detachable. The receptacle 16a is airtightly attached to the housing 20 independently of the receptacle 14a. The receptacle 16a is formed of, for example, a resin as an insulating material.

  The receptacle 16 a has a filament terminal 31 that supplies a filament voltage to the filament 17 and a grid terminal 32 that supplies a grid voltage to the grid 18. The filament terminal 31 is connected to the filament 17 and supplies a filament voltage to the filament 17. The grid terminal 32 is connected to the grid 18 and supplies a grid voltage to the grid 18.

  The filament circuit 3 is connected to the filament 17 and pulled out to the outside of the X-ray tube 1, passes through the insulating oil 9, and is connected to the filament terminal 31. The grid circuit 4 is connected to the grid 18, drawn out to the outside of the X-ray tube 1, passed through the insulating oil 9, and connected to the grid terminal 32.

  The high voltage power supply 12 is for supplying a high voltage to the anode 11 and the cathode 10. In this embodiment, the high voltage power supply 12 supplies a voltage of 70 kV to the anode 11 side and supplies a voltage of −70 kV to the cathode 10 side. The high voltage power supply 12 includes two power supply units 12a. In order to make the electric field strength constant, the conducting wire between the power supply units 12a is grounded.

  The anode-fed high-voltage cable 13 is connected to the positive side of the high-voltage power supply 12 and the anode connector 14. The anode-fed high-voltage cable 13 supplies an anode voltage from the high-voltage power supply 12 to the anode connector 14.

  The cathode power supply high voltage cable 15 is connected to the negative side of the high voltage power supply 12 and the cathode connector 16. More specifically, the cathode-fed high-voltage cable 15 includes two core conductors that are insulated from each other. One end of these core conductors is connected to the negative side of the high voltage power supply 12. One end of the core conducting wire is connected to the filament terminal 31, and the other end of the core conducting wire is connected to the grid terminal 32. The cathode power supply high voltage cable 15 supplies the filament voltage from the high voltage power supply 12 to the filament terminal 31 and the grid voltage to the grid terminal 32.

  A filament power supply 22 is connected to the core conductor connected to the filament terminal 31. A bias power source 21 is connected to the core conductor connected to the grid terminal 32. Therefore, a negative bias voltage of about 3 kV is supplied to the grid 18 with respect to the filament 17.

  The X-ray tube 1 further includes a stem portion 2 that is in contact with the insulating oil 9 and to which the filament circuit 3 and the grid circuit 4 are attached. The filament circuit 3 includes an insulating portion 24a attached to the stem portion 2, and a filament lead wire 25a surrounded by the insulating portion 24a. The grid circuit 4 includes an insulating portion 24b attached to the stem portion 2, and a grid lead wire 25b surrounded by the insulating portion 24b. The insulating parts 24a and 24b are made of, for example, a plurality of ceramic materials. The lead wires 25a and 25b are made of nickel, for example.

  The discharge start voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 is less than the dielectric breakdown voltage between the filament terminal 31 and the grid terminal 32 of the receptacle 16a. More specifically, the discharge start voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 and the two insulating portions 24a and 24b is less than the breakdown voltage between the filament terminal 31 and the grid terminal 32 of the receptacle 16a. In other words, the discharge start voltage is a dielectric breakdown voltage along the surface of the insulating portions 24 a and 24 b that insulate the filament circuit 3 and the grid circuit 4.

Next, the stem part 2 will be described in detail.
A Kovar ring 29 is welded to the glass bulb 28. The end of the Kovar ring 29 is airtightly joined to the cathode holder 27. The cathode holder 27, the glass bulb 28, and the Kovar ring 29 constitute a part of the vacuum envelope 19. An insulating portion 24a is implanted in the stem substrate 23 by welding and brazing via a metal insulating portion holder 26a. Similarly, an insulating portion 24b is implanted in the stem substrate 23 by welding and brazing via a metal insulating portion holder 26b.

  The lead wires 25a and 25b penetrate the central portions of the insulating portions 24a and 24b, and can supply power to the grid 18 and the filament 17 inside the X-ray tube 1 while maintaining insulation from each other. Since the X-ray tube 1 is placed in the insulating oil 9 filling the housing 20, the insulating portions 24 a and 24 b are also in the insulating oil 9 filling the housing 20. Thereby, sufficiently high insulation is obtained between the insulating portions 24a and 24b.

  The value of the discharge start voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 and both insulating parts 24a and 24b is determined by the height of the insulating parts 24a and 24b and the characteristics of the insulating oil 9, and the grid 18 In addition, it is set (designed) so as to obtain an insulation capability that can sufficiently withstand a bias voltage of 3 kV applied between the filaments 17.

  Normally, when a discharge occurs between the grid 18 and the anode 11 inside the X-ray tube 1, a potential difference close to a high-voltage power supply voltage is generated between the grid 18 and the filament 17, but the cathode holder 27 including the stem substrate 23 has a grid. 18 are connected so as to have the same potential as 18, the insulating portions 24 a and 24 b are directly exposed to this induced voltage. On the other hand, since the value of the discharge start voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 and both insulating parts 24a and 24b is lower than this value, dielectric breakdown (discharge) in the insulating oil 9 is induced. Can be made.

  In this embodiment, the height of the insulating portions 24a and 24b is 2.2 mm. The range in which the discharge start voltage is distributed between the filament circuit 3 and the grid circuit 4 when the high voltage power supply 12 outputs a DC voltage is 17 to 23 kV, which is a sufficiently high value (range) for the bias voltage 3 kV. It has become. On the other hand, the dielectric breakdown voltage between the filament terminal 31 and the grid terminal 32 of the receptacle 16a is in the range of 35 to 49 kV. Since the value of the breakdown voltage between the filament terminal 31 and the grid terminal 32 completely exceeds the value of the discharge start voltage between the filament circuit 3 and the grid circuit 4, it is possible to completely prevent the breakdown of the receptacle 16a. it can.

Next, a case where X-rays are emitted using the X-ray tube apparatus configured as described above will be described.
First, the high voltage power supply 12 supplies an anode voltage to the anode 11, supplies a filament voltage to the filament 17, and supplies a grid voltage to the grid 18. The bias power supply 21 supplies a bias voltage to the grid 18.

  Thereby, an X-ray tube voltage (hereinafter referred to as tube voltage) is applied between the filament 17 and the anode 11. More specifically, the value of the X-ray tube current (hereinafter referred to as tube current) flowing from the filament 17 to the focal point of the target layer 11 a is controlled by the filament current, and the tube current is turned on by the bias voltage applied to the grid 18. / OFF is controlled.

For this reason, the electrons emitted from the filament 17 are accelerated and collide with the target layer 11 a of the anode 11. The anode 11 emits X-rays when colliding with electrons, and the emitted X-rays are emitted to the outside of the housing 20 through the X-ray transmission windows 19a and 20a.
As described above, the X-ray tube device can emit X-rays.

  According to the X-ray tube apparatus configured as described above, the X-ray tube apparatus includes the X-ray tube 1 having the stem portion 2, the casing 20, the insulating oil 9, the filament terminal 31, and the grid terminal 32. The receptacle 16a having the above structure, the filament circuit 3, and the grid circuit 4 are provided. The filament circuit 3 includes an insulating portion 24a attached to the stem portion 2 and a lead wire 25a surrounded by the insulating portion 24a. The grid circuit 4 includes an insulating portion 24b attached to the stem portion 2 and a lead wire 25b surrounded by the insulating portion 24b.

  The discharge start voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 is less than the dielectric breakdown voltage between the filament terminal 31 and the grid terminal 32 of the receptacle 16a. More specifically, the discharge start voltage between the filament circuit 3 and the grid circuit 4 via the insulating oil 9 and the two insulating portions 24a and 24b is less than the breakdown voltage between the filament terminal 31 and the grid terminal 32 of the receptacle 16a.

When a discharge occurs between the grid 18 in the X-ray tube 1 and the anode 11, a dielectric breakdown occurs along the surface of the insulating portions 24 a and 24 b in the oil. Since the insulation recovers once the condition is cured, the function as the X-ray tube apparatus is not impaired at all. Here, when the inventors of the present application investigated using the X-ray tube device described above, there was no accident that the receptacle 16a was broken down. As described above, the X-ray tube apparatus can prevent the dielectric breakdown of the receptacle 16a that cannot be recovered by utilizing the recoverable breakdown in oil.
As described above, a highly reliable X-ray tube apparatus can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

The schematic block diagram which shows the X-ray tube apparatus which concerns on embodiment of this invention. It is sectional drawing which shows a part of X-ray tube apparatus shown in FIG. 1, and is a figure which extracts and shows especially an X-ray tube, a housing | casing, insulating oil, a filament circuit, a grid circuit, and a receptacle. The expanded sectional view which shows the stem part shown in FIG.

  DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... Stem part, 3 ... Filament circuit, 4 ... Grid circuit, 5 ... Rotating body, 6 ... Fixed body, 9 ... Insulating oil, 10 ... Cathode, 11 ... Anode, 11a ... Target layer, 12 DESCRIPTION OF SYMBOLS ... High voltage power supply, 13 ... Anode feeding high voltage cable, 14 ... Anode connector, 14a ... Receptacle, 14b ... Plug, 15 ... Cathode feeding high voltage cable, 16 ... Cathode connector, 16a ... Receptacle, 16b ... Plug, 17 ... Filament, 18 DESCRIPTION OF SYMBOLS ... Grid, 19 ... Vacuum envelope, 20 ... Housing, 21 ... Bias power supply, 22 ... Filament power supply, 23 ... Stem substrate, 24a, 24b ... Insulation part, 25a, 25b ... Lead wire, 31 ... Filament terminal, 32 ... grid terminal.

Claims (2)

An anode that emits X-rays when struck by electrons, a filament that emits electrons that collide with the anode, a cathode having a grid provided around an orbit of electrons from the filament toward the anode, and An X-ray tube including a vacuum envelope containing an anode and a cathode;
A housing containing the X-ray tube;
Insulating oil filled in the housing;
An insulating receptacle attached to the housing, having a filament terminal for supplying a filament voltage to the filament and a grid terminal for supplying a grid voltage to the grid;
A filament circuit connected to the filament and drawn out of the X-ray tube and connected to the filament terminal through the insulating oil;
A grid circuit connected to the grid and drawn out of the X-ray tube, connected to the grid terminal through the insulating oil, and
The X-ray tube device, wherein a discharge start voltage between the filament circuit and the grid circuit via the insulating oil is less than a breakdown voltage between the filament terminal and the grid terminal of the receptacle. The X-ray tube further includes a stem portion in contact with the insulating oil, to which the filament circuit and the grid circuit are attached,
The filament circuit has an insulating portion attached to the stem portion, and a filament lead wire surrounded by the insulating portion,
The grid circuit has an insulating portion attached to the stem portion, and a grid lead wire surrounded by the insulating portion,
2. The X-ray tube apparatus according to claim 1, wherein a discharge start voltage between the filament circuit and the grid circuit via the insulating oil and both insulating portions is less than a breakdown voltage between the filament terminal and the grid terminal of the receptacle. .

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