JP2015011766A - X-ray generator and x-ray inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an X-ray generator compact.SOLUTION: An X-ray generator 8 has a housing 10 filled with an insulating oil 14 in which an X-ray tube 11 is immersed. In the housing, a sheet-like insulator 20 is arranged between the inner surface of the housing and the X-ray tube. The insulator has each cylindrical peripheral wall 21 the upper surface of which is open 23, and a bottom wall 22 covering the bottom surface of the housing excepting the base 12. When considering insulation performance only by the insulating oil, discharge is prevented reliably even if the distance between the housing and the X-ray tube is not sufficient, because the housing and X-ray tube are separated by the insulator. The housing is not up-sized even if the tube voltage of the X-ray tube is set higher. The housing can be down-sized than the prior art for the same tube voltage.

Description

  The present invention relates to an X-ray generator that houses an X-ray tube inside a housing filled with insulating oil, emits X-rays generated from the X-ray tube to the outside of the housing, and is used for various purposes, and X-ray generation The present invention relates to an X-ray inspection apparatus that inspects an object to be inspected using the apparatus, and in particular, adopts a structure that suppresses the occurrence of discharge between an X-ray tube and a housing, thereby reducing the size of the entire apparatus. The present invention relates to a line generator.

  The following Patent Document 1 discloses an invention of an X-ray generator aimed at improving the cooling efficiency to reduce the size of the device and improving the reliability of sealing. The X-ray generator of the present invention includes a housing 11 filled with an insulating oil 13 that houses an X-ray tube 12 that generates X-rays and that immerses the X-ray tube 12, and an opening 11 a of the housing 11. The lid body 17 having heat conductivity to be sealed, the heat radiation fins 18 provided outside the lid body 17, the heat transfer plate 19a attached inside the lid body 17, and the heat transfer plate 19a are provided and insulated. An endothermic fin 19b immersed in the oil 13 is provided. According to the present invention, heat generated from the X-ray tube 12 is absorbed from the insulating oil 13 by the heat absorbing fins 19b and the heat transfer plates 19a and transmitted to the lid body 17 and the heat radiating fins 18, so that sufficient cooling efficiency is obtained. This makes it possible to reduce the size of the X-ray generator. Further, the heat dissipation structure (such as cooling fins) provided on the lid 17 is not provided through the lid 17 itself, but is provided on the upper surface of the lid 17 as described above. Since the heat dissipating fins 18 and the heat transfer plates 19a and the heat absorbing fins 19b provided on the bottom surface of the lid body 17 are separately provided, the opening 11a of the housing 11 by the lid body 17 is surely closed. The reliability of sealing the casing 11 by the lid 17 is improved.

JP 2004-22459 A

  In the X-ray generator described above, a high tube voltage of several tens to several hundreds kV is applied to the X-ray tube housed in the housing depending on the application. Therefore, in such an X-ray generator, in order to prevent discharge between the X-ray tube and the housing due to a high tube voltage, the distance between the X-ray tube housed in the housing and the inner surface of the housing (creepage) Need to be set to a sufficiently large dimension according to the tube voltage. Because of these circumstances, when trying to meet the demand to reduce the size of the X-ray generator, it is not possible to secure a sufficient creepage distance simply by reducing the size of the housing, causing discharge. The risk of being increased. In addition, there may be a need to increase the tube voltage in order to provide a larger output X-ray generator. In such a case, the creepage distance described above must be set large, The size as a device becomes large. However, even when output improvement is required in this way, there are many cases where it is required to make the apparatus compact by avoiding an increase in size of the apparatus.

  The present invention has been made in view of the above-described problems in the conventional X-ray generator, and has as its main purpose to reduce the size of the X-ray generator. For example, an X-ray generator that does not need to be made larger than before even if the tube voltage applied to the X-ray tube is set larger, and can be made smaller than before if the tube voltage is the same. An object of the present invention is to provide an X-ray inspection apparatus provided with such an X-ray generation apparatus as an X-ray source.

The X-ray generators 8, 81, 82 described in claim 1 are:
An X-ray tube 11 for generating X-rays;
A housing 10 that houses the X-ray tube 11 and is filled with an insulating oil 14 that immerses the X-ray tube 11;
Sheet-like insulators 20, 30, 40, 50 disposed between the inner surface of the housing 10 and the X-ray tube 11 in the housing 10;
It is characterized by comprising.

The X-ray generation device 8, 81, 82 according to claim 2 is the X-ray generation device 8, 81, 82 according to claim 1,
The insulators 20, 30, 40 and 50 are arranged so as to surround the X-ray tube 11, and at least a part thereof is supported on the inner surface of the housing 10.

The X-ray inspection apparatus 1 according to claim 3 is:
X-ray inspection in which X-rays are emitted from the X-ray generators 8, 81, 82 to the inspection object, and the inspection object is inspected based on the transmission amount of the X-ray transmitted through the inspection object In device 1,
The X-ray generators 8, 81, 82 are
An X-ray tube 11 for generating X-rays;
A housing 10 that houses the X-ray tube 11 and is filled with an insulating oil 14 that immerses the X-ray tube 11;
Sheet-like insulators 20, 30, 40, 50 disposed between the inner surface of the housing 10 and the X-ray tube 11 in the housing 10;
It is characterized by comprising.

  According to the X-ray generator described in claim 1, when considering only the insulating performance by the insulating oil alone, the inner surface of the housing and the X-ray are not required even if the creepage distance between the inner surface of the housing and the X-ray tube is not sufficient. Since the tube is separated by the sheet-like insulator, the discharge between the X-ray tube and the housing can be reliably prevented. Therefore, even if the tube voltage of the X-ray tube is set higher, the case does not increase in size, and the case can be made smaller than before if the tube voltage is the same.

  According to the X-ray generator described in claim 2, the sheet-like insulator is arranged so as to surround a part of the surface of the X-ray tube that is particularly likely to cause discharge with respect to the inner surface of the housing. In addition, since at least a part of the insulator can be supported on the inner surface of the housing so that the position does not shift, insulation between the inner surface of the housing and the X-ray tube can be achieved more reliably. .

  According to the X-ray inspection apparatus recited in claim 3, when considering only the insulating performance of the insulating oil alone, the inner surface of the housing and the X-ray are not required even if the creepage distance between the inner surface of the housing and the X-ray tube is not sufficient. Since the tube is separated by the sheet-like insulator, the discharge between the X-ray tube and the housing can be reliably prevented. Therefore, even if the tube voltage of the X-ray tube is set higher, the case does not increase in size, and if the tube voltage is the same, it can be made smaller than before. As a whole, it can be configured compactly.

It is a schematic perspective view of the X-ray inspection apparatus in 1st Embodiment of this invention. (A) is a typical perspective view of the X-ray generator in 1st Embodiment, (b) is a typical perspective view of the conventional X-ray generator in which tube voltage is equivalent to the X-ray generator of (a). FIG. It is a perspective view of the insulator used with the X-ray generator of 2nd Embodiment. It is a typical perspective view of the X-ray generator of 3rd Embodiment. It is a typical perspective view of the X-ray generator of 4th Embodiment.

The X-ray inspection apparatus according to the first embodiment will be described with reference to FIGS. 1 and 2.
FIG. 1 is a schematic perspective view of an X-ray inspection apparatus 1 according to this embodiment. The X-ray inspection apparatus 1 includes an X-ray shielding main body 2, a conveyor 3 for conveying an inspection object such as raw meat, fish, processed food, and medicine into the main body 2, and the conveyor 3 A foreign object detector 4 for inspecting whether or not the object to be inspected contains foreign substances by X-rays.

  The conveyor 3 is composed of a drive motor (not shown) and a belt 5 that is circulated and driven by this drive motor. It can be carried out of the main body 2. The foreign matter detection unit 4 is configured by an X-ray generator 8 provided above the conveyor 3 in the main body 2 and an X-ray detector 9 provided at a position directly below the belt 5 above the conveyor 3 in the main body 2. The X-ray generator 8 emits X-rays from the X-ray generator 8 to the inspected object conveyed by the conveyor 3 and the X-ray detector 9 By detecting with this, it is possible to inspect whether or not the object to be inspected contains foreign matter.

  FIG. 2A is a schematic perspective view of the X-ray generator 8 of the present embodiment. FIG. 2B is a schematic perspective view of a conventional X-ray generator 8b in which the tube voltage is equivalent to that of the X-ray generator 8 of the embodiment. It is shown for comparison of size.

First, with reference to FIG. 2A, a portion common to the conventional X-ray generator 8b in the configuration of the X-ray generator 8 of the present embodiment will be described.
As shown in FIG. 2A, the X-ray generator 8 of the present embodiment has a substantially rectangular parallelepiped casing 10. The housing 10 is made of stainless steel or iron, and although not shown, the wall surface is provided with an X-ray shielding material. A cylindrical X-ray tube 11 serving as an X-ray source is accommodated in the housing 10. The X-ray tube 11 has a cathode provided at one end in the cylindrical axial direction and an anode provided at the other end, and the anode is provided with a target made of tungsten or the like. Yes. By applying a high voltage to the anode, an electron beam is extracted from the cathode, and electrons are projected onto the target to generate X-rays.

  As shown in FIG. 2A, the lower side of the peripheral surface of the X-ray tube 11 and the bottom surface of the housing 10 are connected by a base 12 having a hollow frustoconical shape, whereby the X-ray tube 11 is cylindrical. Is supported at a substantially central position of the housing 10 in a posture in which the axis of the horizontal axis is horizontal. The upper end of the base 12 surrounds the X-ray emission port and is connected to the X-ray tube 11, and the lower end of the base 12 surrounds the window 13 made of Be or the like provided on the bottom surface of the housing 10. It is connected to the bottom surface of the body 10. Therefore, X-rays radiated from the target when the X-ray tube 11 is driven are radiated from the radiation port provided on the peripheral surface of the X-ray tube 11 to the inside of the base 12 and further from the window 13 of the housing 10. Radiated to the outside. Further, the inside of the casing 10 configured as described above is filled with insulating oil 14 except for a slight air layer at the top, and the X-ray tube 11 and the base 12 are immersed in the insulating oil 14. ing. The insulating oil 14 maintains the insulation between the housing 10 and the X-ray tube 11 and also functions as a cooling medium that transmits heat generated by the X-ray tube 11 to the heat dissipation mechanism (not shown) during driving.

Next, a configuration unique to the X-ray generator 8 of the present embodiment, which is different from the conventional X-ray generator 8, will be described with reference to FIG.
As shown in FIG. 2 (a), according to the X-ray generator 8 of the present embodiment, the inside of the housing 10 filled with the insulating oil 14 is between the inner surface of the housing 10 and the X-ray tube 11. The sheet-like insulator 20 is disposed at the position. The insulator 20 is perpendicular to the bottom surface of the housing 10 and has a rectangular cylindrical peripheral wall portion 21 formed of four flat plates that are orthogonal to each other and a bottom wall that is in contact with the bottom surface of the housing 10. Part 22. An opening 23 is provided above the peripheral wall portion 21 so as not to prevent the movement of the insulating oil 14 inside the housing 10. That is, when the X-ray tube 11 releases heat during use of the apparatus, the insulating oil 14 can be convected between the inside and outside of the insulator 20 by this heat, and the heat is efficiently conducted to a heat dissipation mechanism (not shown). be able to. The bottom wall portion 22 is at least partially continuous with the peripheral wall portion 21, and a portion excluding the central circular through hole 24 through which the base 12 portion is inserted covers the bottom surface of the housing 10. And this bottom wall part 22 is supported or fixed to the bottom face of the housing | casing 10 by arbitrary methods and structures, As a result, the position in the housing | casing 10 of the surrounding wall part 21 is fixed, and the inner surface of the housing | casing 10 is fixed. The distance between the X-ray tube 11 and the peripheral wall portion 21 is kept constant.

  According to the X-ray generator 8 of the present embodiment, the sheet-like insulator 20 disposed between the inner surface of the housing 10 and the X-ray tube 11 has a high breakdown voltage and charges are difficult to accumulate. A function of preventing discharge from being generated between the applied X-ray tube 11 and the housing 10 is provided. As described above, the inside of the casing 10 is filled with the insulating oil 14 because the casing 10 is filled with the insulating oil 14 whose dielectric breakdown voltage is higher than that of air. This is for preventing discharge from occurring between the tube 11 and the housing 10, but according to the present embodiment, in addition to the insulating oil 14, it is further provided between the inner surface of the housing 10 and the X-ray tube 11. By disposing the sheet-like insulator 20, no discharge occurs even if the distance between the X-ray tube 11 and the inner surface of the housing 10 (referred to as a creepage distance) is made smaller than before, while maintaining the tube voltage. be able to. That is, if the same tube voltage is used, an effect that the device can be made smaller than before can be obtained. Therefore, the X-ray generator 8 having a desired tube voltage can be reduced in size while ensuring necessary insulation performance. Further, since this insulator is in the form of a sheet, it can be easily installed in an arrangement that surrounds the X-ray tube 11 inside the housing 10, and a flexible design for downsizing the X-ray generator 8 described above. And efficient production becomes possible.

  FIG. 2B is a schematic perspective view of a conventional X-ray generator 8b having a tube voltage equivalent to that of the X-ray generator 8 of the embodiment shown in FIG. As can be understood by comparing the conventional X-ray generator 8b shown in FIG. 2B with the X-ray generator 8 of the embodiment shown in FIG. 2A, the tube voltage, the insulation performance, and other conditions are the same. Then, the X-ray generator 8 (FIG. 2A) according to the embodiment including the sheet-like insulator 20 has a shorter creepage distance than the conventional X-ray generator 8b (FIG. 2B). Thus, the housing 10 can be made smaller than the conventional housing 10b, and the entire apparatus can be downsized.

  Next, in the X-ray generator 8, in order to prevent discharge between the inner surface of the housing 10 and the X-ray tube 11, a method for calculating a creepage distance corresponding to the insulating oil 14 to be used is specifically described. Further, a specific example of the sheet-like insulator 20 used together with the insulating oil 14 and the effect of shortening the creeping distance by providing this will be described more specifically.

  First, as described above, in the design of the X-ray generator, in order to prevent discharge from occurring between the X-ray tube 11 to which a high voltage is applied and the metal casing 10 that houses the X-ray tube 11. It is necessary to ensure a creepage distance according to the applied voltage. Further, in order to conduct and dissipate heat generated by the X-ray tube 11 to which a high voltage is applied, it is also necessary to fill the housing 10 with the insulating oil 14 and immerse the X-ray tube 11 in the insulating oil 14. .

  As characteristic values indicating the insulating performance of the insulating oil 14, a dielectric breakdown voltage (kV / mm) and a test method thereof are defined in JISC2101 (electric insulating oil test method). Usually, a commercially available insulating oil has a dielectric breakdown voltage measured according to this standard, and the value is described in a data sheet for each product issued by the product manufacturer. The insulation oil can be selected in consideration of the breakdown voltage described in the data sheet, but it is not necessary to simply select one having a high breakdown resistance. Since it is necessary to consider heat dissipation as well, the options are limited in practice.

In consideration of other factors including heat dissipation, when insulating oil with the highest dielectric breakdown resistance is selected as much as possible, the breakdown voltage (kV) required by the X-ray generator and the Calculate the minimum creepage distance from the dielectric breakdown voltage (kV / mm) of the insulating oil.
[Required breakdown voltage (kV) / dielectric breakdown voltage (kV / mm)] x (margin) = minimum creepage distance (mm)

Insulating oil deteriorates when exposed to air or moisture, and the dielectric breakdown voltage decreases. Therefore, it is preferable to set the margin ratio (safety factor) to a large value. If an example of calculation when the margin ratio (safety factor) is determined in the range of about 5 to 10 is shown, for example, the tube voltage of the X-ray generator, which is a required breakdown voltage, is 50 (kV), and is used. When the dielectric breakdown voltage of the insulating oil is 20 (kV / mm) and the safety magnification is 10, the minimum creepage distance (mm) is as follows.
[50 (kV) / 20 (kV / mm)] × 10 = 25 (mm)

  In an actual X-ray generator, the protrusions and corners exist at specific positions due to the structure of the X-ray tube and the housing, which causes insulation oil to stay in the housing, resulting in poor insulation performance depending on the location. It may be uniform. Therefore, in consideration of such circumstances, it is preferable that the margin rate is set larger than that described above.

  In the design of the X-ray generator, the creepage distance can be set as described above, but in this embodiment, in addition to the insulating oil 14, the gap between the inner surface of the housing 10 and the X-ray tube 11 is further increased. The creeping distance is shortened as much as possible by arranging the sheet-like insulator 20. As the sheet-like insulator 20, a mylar sheet, a mica plate, a laminated composite material in which minute mica pieces are bonded to the surface with an epoxy resin or the like can be used. The dielectric breakdown voltage of such an insulator 20 is at least as a test result by JISC2151 (electrical plastic film test method), JISC2116 (electrical mica product test method), JISK6911 (thermosetting plastic general test method), etc. It is preferable that the voltage is about several kV / mm to several tens of kV / mm. However, in consideration of other factors including heat dissipation, by selecting the insulator 20 having the highest dielectric breakdown voltage as much as possible, the calculation example described above is used. It is possible to further reduce the minimum creepage distance set as shown.

  Further, since the sheet-like insulator 20 arranged between the inner surface of the housing 10 and the X-ray tube 11 is less likely to deteriorate as compared with the insulating oil 14, such an insulator 20 is provided. Based on the premise, the margin rate can be estimated small when performing the calculation as exemplified above. Further, the sheet-like insulator 20 can be easily processed and mounted in the housing 10 and can be locally disposed only at a necessary position in the housing 10. Therefore, the required insulation performance can be achieved efficiently.

The insulator 30 of the second embodiment will be described with reference to FIG. FIG. 2 is used for the configuration of the housing 10 and the X-ray tube 11.
FIG. 3 is a perspective view showing a sheet-like insulator 30 in the X-ray generator of the second embodiment. Similar to the insulator 20 of the first embodiment, the insulator 30 includes a rectangular tube-shaped peripheral wall portion 31 having an open top. The peripheral wall 31 has the same shape as that of the first embodiment, but the structure of the bottom wall 32 that contacts the bottom surface of the housing 10 is different from that of the first embodiment. The bottom wall portion 32 of the present embodiment includes two pieces 35 and 35 respectively connected to the lower edges of the two opposing surfaces of the peripheral wall portion 31. A semicircular cutout 36 is formed at the center of the free end of each piece 35. When the two pieces are arranged on the bottom surface of the housing 10, the base 12 of the X-ray tube 11 is placed. An encircling circular through hole 34 is formed.

Since the insulator 30 according to the present embodiment has the above-described structure, it can be attached to the inside of the housing 10 after the X-ray tube 11 is attached to the inside of the housing 10. That is, the X-ray tube 11 is opened in a state where the upper surface of the housing 10 to which the X-ray tube 11 is attached is opened and the two pieces 35 and 35 are lifted along the inner surface of the peripheral wall 31. The peripheral wall portion 31 is placed in the housing 10 so as to surround. Then, the two pieces 35 and 35 are overlaid on the bottom surface of the housing 10. Since the two pieces 35 and 35 overlapped on the bottom surface of the housing 10 have a through hole 34 formed by notches 36 and 36 so as not to interfere with the base 12 that supports the X-ray tube 11. The bottom surface of the casing 10 around the base 12 is covered with a piece 25 of the insulator 30. Then, the overlapping portions of the pieces 35 and 35 are fixed by an arbitrary means, and are also fixed to the bottom surface of the housing 10 as necessary. As a result, the insulator 30 is fixed to the housing 10 at a predetermined position.
Other configurations and effects are the same as those of the first embodiment.

The X-ray generator according to the third embodiment will be described with reference to FIG.
FIG. 4 is a perspective view of the X-ray generator 81 of the third embodiment. The sheet-like insulator 40 in this embodiment has a cylindrical peripheral wall portion 41 having an open upper surface, a diameter equivalent to that of the peripheral wall portion 41, and the window portion 13 so as not to interfere with the base 12 portion. And a circular bottom wall portion 42 having a through hole 44 having the same shape and size. The peripheral wall 41 can be manufactured by rounding a belt-like sheet and connecting both ends. A slit (not shown) that reaches the through hole 44 is formed in the bottom wall portion 42 so that the X-ray tube 11 and the base 12 are attached to the inside of the housing 10 and can be attached to the inside of the housing 10. It may be.
Other configurations and effects are the same as those of the first embodiment.

With reference to FIG. 5, the X-ray generator of 4th Embodiment is demonstrated.
FIG. 5 is a perspective view of the X-ray generator 82 of the fourth embodiment. The sheet-like insulator 50 in this embodiment has two wall portions 51 and 52 each having a semi-cylindrical shape that is obtained by bending a rectangular sheet. The first wall 51 includes a housing 10 so as to cover the X-ray tube 11 from above in a positional relationship such that the substantially semi-cylindrical busbar substantially coincides with the busbar of the cylindrical X-ray tube 11. It is arranged and fixed on the bottom of the. Accordingly, the anodes and cathodes at both ends of the cylindrical shape of the X-ray tube 11 face the openings at both ends of the first wall portion 51. The second wall portion 52 is a first wall portion in which the substantially semi-cylindrical busbar is orthogonal to the busbar of the cylindrical X-ray tube 11 and the anode of the X-ray tube 11 is disposed. 51 is disposed and fixed on the bottom surface of the housing 10 so as to cover the opening at one end of the casing 51. According to this embodiment, while having a simple structure using the two sheet-like walls 51 and 52 as the insulator 50, the anode side in the X-ray tube 11, which has a high risk of discharge, is enclosed. The effect that it can shield reliably with respect to the body 10 and can suppress the danger of discharge low is acquired.
Other configurations and effects are the same as those of the first embodiment.

DESCRIPTION OF SYMBOLS 1 ... X-ray inspection apparatus 8, 81, 82 ... X-ray generator 10 ... Housing 11 ... X-ray tube 12 ... Base 13 ... Window part 14 ... Insulating oil 20, 30, 40, 50 ... Insulator

Claims (3)

An X-ray tube (11) for generating X-rays;
A housing (10) filled with insulating oil (14) for housing the X-ray tube and immersing the X-ray tube;
A sheet-like insulator (20, 30, 40, 50) disposed between the inner surface of the housing and the X-ray tube in the housing;
An X-ray generator (8, 81, 82) characterized by comprising: The insulator (20, 30, 40, 50) is disposed so as to surround the X-ray tube (11), and at least a part thereof is supported on the inner surface of the housing (10). The X-ray generator (8, 81, 82) according to claim 1. X-rays are applied to the inspection object from the X-ray generator (8, 81, 82), and the inspection object is inspected based on the transmission amount of the X-ray transmitted through the inspection object. In line inspection equipment,
The X-ray generator (8, 81, 82)
An X-ray tube (11) for generating X-rays;
A housing (10) filled with insulating oil (14) for housing the X-ray tube and immersing the X-ray tube;
A sheet-like insulator (20, 30, 40, 50) disposed between the inner surface of the housing and the X-ray tube in the housing;
An X-ray inspection apparatus (1) comprising:

Images