JP4638808B2 - X-ray generator - Google Patents

Description

  The present invention relates to an X-ray generation device, and more particularly to an X-ray generation device used for nondestructive inspection for detecting foreign matter in an object to be inspected, such as food and medicine.

  In a production line for foodstuffs and pharmaceuticals, continuous inspection of all products is performed for the presence or absence of foreign substances in the product, and non-destructive inspection using X-rays is performed as the means. In this inspection, X-rays radiated from the X-ray generator are irradiated onto an object to be inspected, and foreign matter is detected by image processing the amount of transmission.

  The structure of an X-ray generator used for inspection is shown in FIG. FIG. 4 is a cross-sectional view from the side of the X-ray generator.

  The X-ray generator is mainly composed of a metal enclosure 3 having an opening on the upper surface for storing the X-ray tube 1 and the insulating oil 2, and the heat transfer device 4 and the radiator 5 close the opening. It is attached to do.

  The X-ray tube 1 applies a high voltage by a high voltage generator (not shown) between the anode 6 and the cathode 7 sealed in the vacuum glass, and collides thermal electrons from the cathode 7 with the anode 6. X-rays 9 are emitted from the X-ray emission port 8. In order to reduce the size of the X-ray generator, the X-ray tube 1 is usually a small and high performance cathode grounding type.

  In order to prevent leakage of X-rays from other than the X-ray emission port 8, the surface of the X-ray tube 1 is covered with a cylindrical lead shielding cover 10 except for the X-ray emission port 8.

  The insulating oil 2 is filled in the enclosure 3 and cools the X-ray tube 1 that generates heat with the radiation of the X-rays 9, and the anode 6 and the cathode 7 of the X-ray tube 1 and the grounded enclosure It serves to insulate the container 3.

  In the X-ray generator having such a structure, the insulating oil 2 is exposed to the air in the manufacturing process, the air enters the inside due to poor airtightness of the enclosure 3 during use, There is a problem that a minute amount of moisture is mixed into the insulating oil 2 and the dielectric breakdown voltage is lowered due to the precipitation of moisture from the components of the high voltage generator (not shown).

  When the dielectric breakdown voltage of the insulating oil 2 decreases, the dose of X-rays 9 emitted by the occurrence of discharge inside the enclosure 3 decreases, so that it is erroneously detected as a foreign object in the inspection object in image processing. Therefore, the accuracy of the nondestructive inspection is lowered, which causes the production efficiency of the production line to be lowered.

  Therefore, at present, in the manufacturing process of the X-ray generator, after injecting the insulating oil 2, a method of reducing the amount of water mixed in the insulating oil 2 as much as possible by repeatedly performing aging by continuous operation and new replacement of the insulating oil 2. Has been taken.

  Further, since the ground voltage difference between the anode 6 and the cathode 7 is lower than the ground potential difference between the anode 6 and the cathode grounded X-ray tube 1, the neutral point grounded X-ray is not generated. A tube 1 is also employed.

  However, the above method has a problem that the number of manufacturing steps of the X-ray generator increases and the amount of insulating oil used increases, resulting in an increase in manufacturing cost.

  In addition, the neutral point grounded X-ray tube has a problem in that it is difficult to obtain high-quality X-rays because the method of applying a high voltage is more complicated than the grounded cathode type.

  Furthermore, since it is not possible to cope with the mixing of moisture into the insulating oil when the X-ray generator is used, there has been a problem that the accuracy of the initial nondestructive inspection cannot be maintained due to the occurrence of discharge.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a highly accurate X-ray generator that can prevent the occurrence of discharge and can be manufactured at low cost. Is.

  In order to achieve the above object, the present invention provides an X-ray comprising an X-ray tube, an insulating oil in which the X-ray tube is immersed, and an enclosure that contains the X-ray tube and the insulating oil. A generator, wherein the insulating oil includes a water-absorbing agent.

  With such a configuration, moisture mixed in the insulating oil can be selectively absorbed by the water-absorbing agent to prevent a decrease in the dielectric breakdown voltage of the insulating oil and prevent the occurrence of discharge.

  The water-absorbing agent may be activated carbon, zeolite, molecular sieves, silica gel and activated alumina, or a combination thereof. In particular, it is desirable to use molecular sieves in view of temperature conditions and adsorption capacity.

  In actual use, it is preferable to use molecular sieves having adsorption holes of a size that selectively absorbs moisture in a water-permeable bag.

  In the present invention, since the X-ray generator is configured to include a water absorbent such as molecular sieves in the insulating oil, the water absorbed in the insulating oil is adsorbed by the water absorbent to prevent the breakdown voltage from being lowered. Occurrence can be prevented.

  Thereby, since the manufacturing process of an X-ray generator can be simplified and the usage-amount of insulating oil can also be reduced, manufacturing cost can be reduced.

  By storing and using this water-absorbing agent in a bag or the like, handling at the time of manufacture and after the end of the product life is facilitated.

  In addition, the moisture mixed in the insulating oil at the time of manufacture of the X-ray generator and the water mixed in the insulating oil at the time of use can be adsorbed, so that the accuracy of the non-destructive inspection can be maintained. Production efficiency can be increased.

  Furthermore, since the dielectric breakdown voltage of the insulating oil can be prevented from being lowered during the period of use of the X-ray generator, the amount of insulating oil to be sealed can be reduced, and the X-ray generator can be miniaturized. Is possible.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a first embodiment according to the present invention. FIG. 1 is a cross-sectional view showing the structure of the X-ray generator according to the first embodiment. In addition, the same code | symbol is attached | subjected to the same part as FIG.

  The X-ray generator according to the first embodiment includes a water-absorbing agent 20 in the enclosure 3 of the conventional X-ray generator shown in FIG. Therefore, the description about the same part is abbreviate | omitted.

  The water-absorbing agent 20 is housed inside the water-permeable bag 21 and is placed so as to straddle the shielding cover 10 while being immersed in the insulating oil 2.

  As the water-absorbing agent 20, a substance having a large moisture adsorption ability, such as activated carbon, zeolite, molecular sieves, silica gel, activated alumina, or the like can be used. In particular, the temperature of the insulating oil 2 when using the X-ray generator (about 20 to 100 ° C.), the amount of moisture mixed in the insulating oil 2 (about 5 to 60 ppm), and various conditions such as electrical insulation In view of the above, it is preferable that the molecular sieve is an insulator having a high adsorption ability in the temperature range. In order for the molecular sieves to selectively adsorb moisture, it is preferable to use molecular sieves having an effective pore diameter of about 0.3 nm, specifically a product type of 3A.

  The shape of the water-absorbing agent 20 may be any shape such as a bead shape, a pellet shape, or a powder shape, but is preferably a pellet shape because a large surface area can be obtained. Moreover, the bag body 21 which accommodates the water absorbing agent 20 can be made from a nonwoven fabric made of polyethylene, for example.

  Note that the water absorbing agent is not limited to the bag body 21 and may be a box made of water-permeable ceramics, for example.

  The place where the water-absorbing agent 20 accommodated in the bag body 21 is placed is preferably a place where the circulating convection of the insulating oil 2 generated in the enclosure 3 is applied, for example, on the shielding cover 10 as shown in FIG. .

  The operation of the X-ray generator according to the first embodiment having the above configuration will be described below.

When a high voltage is applied between the anode 6 and the cathode 7 of the X-ray tube 1 by a high voltage generator (not shown), X-rays 9 are emitted from the X-ray tube 1. A convection phenomenon occurs in the insulating oil 2 due to a temperature difference due to heat generated in the X-ray tube 1 due to the radiation of the X-ray 9 and a Coulomb force due to a strong electric field generated in the enclosure 3. Due to this convection phenomenon, heat generated in the X-ray tube 1 is transmitted from the insulating oil 2 to the heat transfer device 4 and is radiated to the outside through the heat dissipation device 5.

  At this time, the insulating oil 2 that convects in the sealed container 3 flows through the bag body 21 and comes into contact with the water-absorbing agent 20, so that the mixed moisture is adsorbed by the water-absorbing agent 20.

  In this way, it is possible to prevent the dielectric breakdown voltage of the insulating oil 2 from being lowered over the period of use of the X-ray generator.

  Moreover, since the water absorbing agent 20 is accommodated in the bag body 21, the water absorbing agent 20 can be easily handled at the time of manufacture of the X-ray generator and after the end of its life.

  For the absorbent 20 collected after the end of its life, for example, in the case of molecular sieves, the adsorbed moisture can be released and reused by heat treatment in a reduced pressure environment for a certain period of time. In addition, the manufacturing cost can be further reduced.

  A second embodiment according to the present invention is shown in FIG. FIG. 2 is a cross-sectional view showing the structure of the X-ray generator according to the second embodiment.

  In the second embodiment, a water absorbent 20 on a film or thin plate is attached to the inner surface of the enclosure 3. The water absorbing agent 20 may be attached by an adhesive or a mechanical method using screws or the like. The mounting location is preferably a location where the circulating convection of the insulating oil 2 generated in the enclosure 3 is applied, for example, the upper part of the inner surface of the enclosure 3 as shown in FIG.

  Instead of attaching the water absorbing agent 20 as it is, a method of adhering or applying a fine powdered form mixed with a solvent to the inner surface of the enclosure 3 or the like may be used.

  A third embodiment according to the present invention is shown in FIG. FIG. 3 is a sectional view showing the structure of the X-ray generator according to the third embodiment.

  In the third embodiment, the water absorbing agent 20 is not stored in the bag body 21 or the like, but is dispersed as it is in the insulating oil 2.

  The shape of the water-absorbing agent 20 may be any of a bead shape, a pellet shape, a powder shape, and the like, but is preferably a bead shape or a pellet shape from the viewpoint of easy handling.

  In the present embodiment, the manufacturing cost can be reduced in that the bag body 21 and the like are not necessary, and the contact area between the water-absorbing agent 20 and the insulating oil 2 can be maximized. The voltage drop can be further prevented.

It is sectional drawing which shows the structure of the X-ray generator which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the X-ray generator which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the X-ray generator which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the conventional X-ray generator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray generator 2 Insulating oil 3 Enclosed container 4 Heat exchanger 5 Radiator 6 Anode 7 Cathode 8 X-ray emission port 9 X-ray 10 Shielding cover 20 Water absorbing agent 21 Bag body

Claims (4)

An X-ray tube;
Insulating oil in which the X-ray tube is immersed;
An X-ray generator comprising an X-ray tube and an enclosure containing the insulating oil,
An X-ray generator comprising a water absorbing agent in the insulating oil. The X-ray generator according to claim 1, wherein the water-absorbing agent comprises at least one of activated carbon, zeolite, molecular sieves, silica gel, and activated alumina. The X-ray generator according to claim 1, wherein the absorbent contains water-absorbing molecular sieves in a water-permeable bag. An X-ray tube;
Insulating oil in which the X-ray tube is immersed;
An enclosure containing the X-ray tube and the insulating oil and having an opening at the top;
A heat exchanger that closes the opening;
In an X-ray generator comprising a heat radiator installed on the heat exchanger,
An X-ray generation apparatus comprising a water-permeable bag body containing water-absorbing molecular sieves in the enclosure.

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