X-ray inspection device

Abstract

To provide an X-ray inspection device that can prevent a reduction in inspection processing capacity even when it continues executing an inspection in a low-voltage condition.SOLUTION: An X-ray inspection device 1 comprises: an X-ray irradiation unit 6 that applies a first voltage between a cathode 57 and an anode 56 in an X-ray tube 50 to generate an X-ray, and irradiates an article G to be conveyed with the X-ray; an X-ray detection unit 7 that detects the X-ray with which the article is irradiated by the X-ray irradiation unit 6; an inspection unit 40 that creates an X-ray transmission image on the basis of a result of the detection performed by the X-ray detection unit 7, and inspects the article G; and a control unit 40 that changes the voltage applied between the cathode 57 and the anode 56. Before starting the irradiation with the X-ray that is generated by application of the first voltage, or after the completion of the irradiation with the X-ray that is generated by application of the first voltage, the control unit 40 applies a second voltage higher than the first voltage between the cathode 57 and the anode 56.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] One aspect of the present invention relates to an X-ray inspection apparatus. [Background technology]

[0002] There is known an X-ray inspection device that includes a conveying section that conveys an article, an X-ray irradiation section that irradiates the article conveyed by the conveying section with X-rays, and an X-ray detection section that detects the X-rays that have passed through the article (for example, Patent Document 1). In such an X-ray inspection device, the voltage value applied to the X-ray tube is adjusted according to the type of article to be inspected, and the X-ray output value is appropriately switched. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-2023 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such an X-ray inspection device, if inspection is continued under low voltage conditions, for example, with a voltage value in the range of 15 kV to 50 kV, a defect may occur due to X-rays not being properly radiated in part of the acquired X-ray transmission image (abnormal discharge occurring in the X-ray tube). In this case, it is necessary to reacquire the X-ray transmission image, which reduces the inspection processing capacity of the X-ray inspection device.

[0005] Therefore, an object of one aspect of the present invention is to provide an X-ray inspection apparatus that can suppress a decrease in inspection processing capacity even when inspection is continuously performed under low voltage conditions. [Means for solving the problem]

[0006] (1) An X-ray inspection device according to one aspect of the present invention includes an X-ray irradiation unit that generates X-rays by applying a first voltage between a cathode and an anode in an X-ray tube and irradiates the X-rays onto an object being transported, an X-ray detection unit that detects the X-rays irradiated from the X-ray irradiation unit, an inspection unit that generates an X-ray transmission image based on the detection result of the X-ray detection unit and inspects the object, and a control unit that changes the voltage applied between the cathode and the anode, wherein the control unit applies a second voltage higher than the first voltage between the cathode and the anode before starting irradiation of the X-rays generated by applying the first voltage or after finishing irradiation of the X-rays generated by applying the first voltage.

[0007] When the X-ray inspection device is continuously used under low voltage conditions, a defect occurs due to X-rays not being properly radiated in a part of the acquired X-ray transmission image. The inventor of the present application considered that this is because, when the voltage applied between the cathode and the anode is low, the force pulling electrons from the cathode to the anode is weak, and the surplus electrons that do not hit the target are retained in the X-ray tube. Therefore, the inventor considered that, if a high voltage is applied between the cathode and the anode, these surplus electrons will hit the target and be expelled from the X-ray tube, and X-rays will be properly radiated from the X-ray tube. Therefore, the control unit applies a second voltage higher than the first voltage between the cathode and the anode before starting irradiation of X-rays generated by applying the first voltage, or after finishing irradiation of X-rays generated by applying the first voltage. This suppresses abnormal discharge occurring in the X-ray tube, and suppresses a decrease in inspection processing capacity even when the inspection is continuously performed under low voltage conditions.

[0008] (2) In the X-ray inspection apparatus described in (1) above, the first voltage may be in the range of 15 kV to 50 kV, and the second voltage may be in the range of 60 kV to 150 kV. In this configuration, even if the X-ray inspection apparatus is continuously used under a low voltage condition in the range of 15 kV to 50 kV, by periodically applying a high voltage in the range of 60 kV to 150 kV, it is possible to suppress the occurrence of defects caused by X-rays not being appropriately radiated to a part of the acquired X-ray transmission image.

[0009] (3) In the X-ray inspection apparatus described in (1) or (2) above, the second voltage may be twice or more the first voltage. In this configuration, by periodically applying the second voltage twice or more the first voltage, it is possible to suppress the occurrence of defects caused by X-rays not being properly irradiated to a part of the acquired X-ray transmission image.

[0010] (4) In the X-ray inspection device according to any one of (1) to (3) above, the control unit may determine at least one of the intensity and application time of the second voltage based on at least one of the number of abnormal discharges that occur in the X-ray irradiator and the irradiation time of X-rays in the X-ray irradiator, starting from the start of use of the X-ray tube or the previous application of the second voltage. With this configuration, excess electrons in the X-ray tube can be appropriately removed.

[0011] (5) In the X-ray inspection device described in any one of (1) to (4) above, the control unit may store the number of abnormal discharges that occur in the X-ray irradiation unit when the X-ray tube is first used or when the second voltage was last applied, and may determine whether or not to apply the second voltage based on the number of abnormal discharges. The time required to apply the second voltage, which is unrelated to obtaining an X-ray transmission image, eats into the time available for inspection, causing a decrease in inspection processing capacity. In this configuration, the second voltage is applied as needed, so that the decrease in inspection processing capacity can be kept to a minimum.

[0012] (6) In the X-ray inspection device described in any one of (1) to (5) above, the control unit may store the X-ray irradiation time in the X-ray irradiation unit from the start of use of the X-ray tube or the previous application of the second voltage as a starting point, and determine whether or not to apply the second voltage based on the irradiation time. The time required to apply the second voltage, which is not related to obtaining an X-ray transmission image, eats into the time available for inspection, causing a decrease in inspection processing capacity. In this configuration, the second voltage is applied as needed, so that the decrease in inspection processing capacity can be kept to a minimum.

[0013] (7) In the X-ray inspection apparatus according to any one of (1) to (6) above, the control unit may apply the second voltage when the power is turned on. In this configuration, since excess electrons in the X-ray tube are periodically and appropriately removed, even when the inspection is continuously performed under low-voltage conditions, it is possible to suppress a decrease in the inspection processing capacity. Effect of the Invention

[0014] According to one aspect of the present invention, even when tests are continuously performed under low voltage conditions, a decrease in test processing capacity can be suppressed. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a configuration diagram of an X-ray inspection apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing the internal configuration of the shielding box shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram showing a schematic configuration of the X-ray irradiation unit shown in FIG. [Figure 4] FIG. 4 is a graph showing the number of times abnormal discharge occurred per day during continuous operation with a voltage of 30 kV (8 mA) applied between the anode electrode and the cathode electrode. [Diagram 5] FIG. 5 is a graph showing the number of times abnormal discharges occurred per day when operation was continued by applying a voltage of 30 kV (8 mA) after applying a voltage of 75 kV (4 mA) between the anode and cathode electrodes for 10 minutes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an X-ray inspection apparatus 1 according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted.

[0017] 1 and 2, the X-ray inspection device 1 includes an apparatus main body 2, support legs 3, a shielding box 4, a transport conveyor 5, an X-ray irradiation unit 6, an X-ray detection unit 7, an LCD display 8, and a controller (control unit) 10. The X-ray inspection device 1 obtains an X-ray transmission image of an article G while transporting the article G, and performs inspection of the article G (for example, inspection of the number of items stored, inspection of foreign matter contamination, inspection of missing items, inspection of cracks and chips, etc.) based on the X-ray transmission image.

[0018] The X-ray inspection apparatus 1 is connected to an external power source (not shown) that supplies power to the X-ray inspection apparatus 1. In the X-ray inspection apparatus 1, an X-ray generator 100 is configured with an X-ray irradiation unit 6, an LCD display 8, and a controller 10. An item G before inspection is carried into the X-ray inspection apparatus 1 by a carry-in conveyor 9A, and an item G after inspection is carried out from the X-ray inspection apparatus 1 by an unloading conveyor 9B. An item G determined to be a defective item by the X-ray inspection apparatus 1 is sorted out of the production line by a sorting device (not shown) arranged downstream of the unloading conveyor 9B, and an item G determined to be a non-defective item by the X-ray inspection apparatus 1 passes through the sorting device as is.

[0019] The device main body 2 houses a controller 10 and the like. The support legs 3 support the device main body 2. The shielding box 4 is provided on the device main body 2 and prevents leakage of X-rays. The shielding box 4 is formed with an entrance 4a and an exit 4b. An item G before inspection is carried into the shielding box 4 from the carry-in conveyor 9A via the entrance 4a, and an item G after inspection is carried out from the shielding box 4 to the exit conveyor 9B via the exit 4b. An X-ray shielding curtain (not shown) for preventing leakage of X-rays is provided at each of the entrance 4a and the exit 4b.

[0020] The transport conveyor 5 is disposed within the shielding box 4, and transports the article G from the carry-in entrance 4a to the carry-out exit 4b along the transport direction A. The transport conveyor 5 is, for example, a belt conveyor stretched between the carry-in entrance 4a and the carry-out exit 4b.

[0021] The X-ray irradiation unit 6 is disposed in the shield box 4, and irradiates X-rays onto the object G transported by the transport conveyor 5. The X-ray irradiation unit 6 has at least an X-ray tube 50 (see FIG. 3) that irradiates X-rays. The X-ray irradiation unit 6 will be described in detail later.

[0022] The X-ray detection unit 7 is disposed in the shield box 4, and detects the X-rays irradiated from the X-ray irradiation unit 6 and transmitted through the article G and the transport conveyor 5. The X-ray detection unit 7 constitutes an X-ray detection device. The X-ray detection unit 7 is configured as, for example, a line sensor. Specifically, the X-ray detection unit 7 has a plurality of photodiodes arranged one-dimensionally along a horizontal direction perpendicular to the transport direction A, and a scintillator arranged on the X-ray incident side of each photodiode. In this case, in the X-ray detection unit 7, the X-rays incident on the scintillator are converted into light, and the light incident on each photodiode is converted into an electrical signal.

[0023] The LCD display 8 is provided on the device body 2. The LCD display 8 has a display screen as a touch panel and a speaker. The LCD display 8 functions as an operation input unit that accepts input of various conditions via the display screen. The LCD display 8 functions as a display unit that displays the inspection results of the X-ray inspection device 1 via the display screen.

[0024] The controller 10 is disposed in the device body 2 and controls the operation of each part of the X-ray inspection device 1. The controller 10 includes a processor such as a CPU (Central Processing Unit), memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and a storage such as an SSD (Solid State Drive). A program for controlling the X-ray inspection device 1 is recorded in the ROM. The controller 10 can be configured as software in which a program stored in the ROM is loaded onto the RAM and executed by the CPU. The controller 10 may be configured as hardware such as an electronic circuit. Note that the characteristic control contents of the controller 10 in this embodiment will be described in detail later.

[0025] The storage unit 10A is configured with any one or more of a RAM, an HDD (Hard Disk Drive), a flash memory, etc. The storage unit 10A stores the generated X-ray transmission image, the detection time of the abnormal discharge, the normal driving conditions (applied voltage for each article G, application time of the voltage for each article G, conveying speed), etc.

[0026] The X-ray generating device 100 is a device that generates X-rays, and includes an X-ray irradiation unit 6, a controller 10, and an LCD display 8, as shown in Fig. 1. As shown in Fig. 3, the X-ray irradiation unit 6 includes an X-ray tube 50, a tube power supply 51, a filament power supply 52, a tank 53, an abnormal discharge detection circuit 54, and a current monitoring mechanism 71. The X-ray tube 50 includes an X-ray tube body 55 made of stainless steel and ceramics, an anode electrode 56 (positive electrode) that is disposed inside the X-ray tube body 55 and includes a target T, and a cathode electrode 57 (negative electrode) that is disposed inside the X-ray tube body 55 and includes a filament F. The X-ray tube body 55 is formed with an X-ray irradiation window 58 that transmits X-rays.

[0027] The tube power supply 51 is connected to an external power supply, and generates a predetermined DC voltage by boosting the input voltage with an inverter or the like (not shown). The tube power supply 51 has a positive output terminal connected to the anode electrode 56 and a negative output terminal connected to the cathode electrode 57. The tube power supply 51 applies (supplies) a predetermined voltage to each of the anode electrode 56 and the cathode electrode 57, generating a potential difference between the anode electrode 56 and the cathode electrode 57.

[0028] Filament power supply 52 supplies a filament current to cathode electrode 57. When a filament current is supplied from filament power supply 52 to cathode electrode 57 in a state in which a predetermined potential difference is generated between anode electrode 56 and cathode electrode 57 as described above, cathode electrode 57 is heated in X-ray tube 50, and thermoelectrons are emitted from cathode electrode 57, and the thermoelectrons emitted from cathode electrode 57 collide with anode electrode 56 (see dashed arrow). As a result, X-rays are generated that are irradiated to the outside of X-ray tube 50 through X-ray emission window 58 (see dashed-dotted arrow X).

[0029] Tank 53 contains X-ray tube 50, tube power supply 51, and filament power supply 52. ​​Inside tank 53, there are arranged a first electric circuit 59 which is an electric circuit connecting tube power supply 51 and anode electrode 56 (i.e., an electric circuit including anode electrode 56), and a second electric circuit 60 which is an electric circuit connecting tube power supply 51 and cathode electrode 57 (i.e., an electric circuit including cathode electrode 57).

[0030] Insulating oil 61 is sealed inside tank 53. Insulating oil 61 has electrical insulation properties and ensures electrical insulation between each part having a potential difference in the space inside tank 53 (for example, between first electric circuit 59 and second electric circuit 60, or between first electric circuit 59 or second electric circuit 60 and tank 53 or X-ray tube main body 55). Insulating oil 61 plays a role in cooling X-ray tube 50, which generates high heat when generating X-rays. Note that instead of or in addition to insulating oil 61, a solid insulator such as epoxy or silicone may be sealed inside tank 53.

[0031] The abnormal discharge detection circuit 54 is a circuit for detecting abnormal discharge occurring within the X-ray tube 50. Abnormal discharge caused by the structure of the X-ray tube 50 occurs within the X-ray tube 50 due to factors such as electrons emitted from the cathode electrode 57 remaining within the X-ray tube 50 without colliding with the anode electrode 56. More specifically, examples of abnormal discharge caused by the structure of the X-ray tube 50 include discharge caused between the anode electrode 56 and the cathode electrode 57 when gas inside the X-ray tube 50 is ionized by electrons emitted from the cathode electrode 57, and discharge caused within the X-ray tube 50 when electrons emitted from the cathode electrode 57 temporarily accumulate on the insulating X-ray tube wall and reach saturation.

[0032] The abnormal discharge detection circuit 54 is connected to the first electric circuit 59, the second electric circuit 60, and the controller 40. The abnormal discharge detection circuit 54 includes a first detection unit that outputs a pulse in response to a change (sudden drop) in the voltage value in the first electric circuit 59, a second detection unit that outputs a pulse in response to a change (sudden drop) in the voltage value in the second electric circuit 60, an XOR circuit, an AND circuit, etc. When a change (sudden drop) in the voltage value occurs in at least either the first electric circuit 59 or the second electric circuit 60, the abnormal discharge detection circuit 54 detects this and outputs a signal to the controller 10.

[0033] The current monitoring mechanism 71 has a function of monitoring the current flowing through the X-ray tube 50. The current monitoring mechanism 71 can be configured by, for example, a current detector. The location of the current monitoring mechanism 71 is not particularly limited, but the current monitoring mechanism 71 here is located between the tube power supply 51 and the anode electrode 56.

[0034] The controller 10 controls the X-ray irradiation unit 6. The controller 10 changes the voltage applied between the anode electrode 56 and the cathode electrode 57. Specifically, when the type of the object G to be inspected is selected (reserved) via the LCD display 8, the controller 10 reads out a voltage value (tube voltage) stored in association with the type of the object G from the memory unit 10A, and applies the read-out voltage between the anode electrode 56 and the cathode electrode 57 when inspecting the object G. As a result, a current (tube current) corresponding to the applied voltage flows through the X-ray tube 50, and the object G is irradiated with X-rays of an intensity suitable for X-ray inspection (suitable for obtaining a clear X-ray transmission image). The controller 10 receives a signal output from the X-ray detection unit 7 and A / D converted. The controller 10 functions as an inspection unit that generates an X-ray transmission image of the object G based on the signal and inspects the object G based on the X-ray transmission image.

[0035] In the X-ray inspection apparatus 1 of this embodiment, in order to improve the inspection performance for a thin object or a soft foreign object, the tube voltage can be set in a low voltage range of 15 kV to 50 kV. That is, the controller 10 can apply a voltage in the range of 15 kV to 50 kV (hereinafter also referred to as a "first voltage") between the anode electrode 56 and the cathode electrode 57 during inspection of the object G.

[0036] The controller 10 detects abnormal discharge based on changes in the voltage values ​​in both the first electric circuit 59 and the second electric circuit 60. The controller 10 determines that abnormal discharge has occurred when a change (sudden drop) in the voltage values ​​is detected in both the first electric circuit 59 and the second electric circuit 60. The controller 10 stores information relating to the time when it is determined that abnormal discharge has occurred in the memory unit 10A.

[0037] The controller 10 periodically applies a voltage in the range of 60 kV to 150 kV (hereinafter also referred to as a "second voltage"), which is higher than a voltage in the range of 15 kV to 50 kV, between the anode electrode 56 and the cathode electrode 57. More specifically, the controller 10 applies the second voltage between the anode electrode 56 and the cathode electrode 57 before starting irradiation of X-rays generated by applying a voltage in the range of 15 kV to 50 kV, or after finishing irradiation of X-rays generated by applying a voltage in the range of 15 kV to 50 kV.

[0038] The controller 10 applies a second voltage stored in the memory unit 10A in association with the first voltage. The second voltage applied by the controller 10 of this embodiment is set to be at least twice the first voltage. For example, the controller 10 operates the X-ray irradiation unit 6 at a tube voltage of 75 kV (tube current at this time is 1 mA) for one minute before operating the X-ray irradiation unit 6 at a tube voltage of 30 kV (tube current at this time is 8 mA).

[0039] Examples of timing before starting to irradiate X-rays generated by applying the first voltage include the timing when the X-ray inspection device 1 is started up every morning (immediately after the X-ray inspection device 1 is turned on), immediately before the type of item G to be inspected is selected (reservation settings are changed) and calibration is performed under those conditions, immediately after the inspection start button is pressed and before irradiation of X-rays generated by applying the first voltage starts, etc.

[0040] Further, examples of the later timing for starting the irradiation of X-rays generated by applying the first voltage include the timing for stopping the X-ray inspection device 1 every evening (just before the power to the X-ray inspection device 1 is turned off), before the type of item G to be inspected is set (just after the button for starting to change the reservation setting is pressed), and after the item G is discharged from the transport conveyor 5 (just after the inspection is completed), etc.

[0041] The effects of the X-ray inspection device 1 of the above embodiment will be described. If the X-ray inspection device 1 is used continuously under the condition that the voltage applied between the anode electrode 56 and the cathode electrode 57 is a low voltage of 15 kV to 50 kV, a defect (e.g., multiple streaks) may occur due to X-rays not being properly radiated in a part of the acquired X-ray transmission image. The inventors of the present application found that the cause is that when the voltage applied between the anode electrode 56 and the cathode electrode 57 is low, the force pulling electrons from the cathode electrode 57 to the anode electrode 56 is weak, and surplus electrons that did not hit the target T are retained in the X-ray tube 50. Therefore, they thought that if a voltage (high voltage) in the range of 60 kV to 150 kV is applied between the anode electrode 56 and the cathode electrode 57, these surplus electrons will hit the target T and be expelled from the X-ray tube 50, and X-rays will be properly radiated from the X-ray tube 50.

[0042] In the X-ray inspection apparatus 1 of the present embodiment, the controller 10 applies a second voltage higher than the first voltage between the anode electrode 56 and the cathode electrode 57 before starting irradiation of X-rays generated by applying the first voltage, or after finishing irradiation of X-rays generated by applying the first voltage. This suppresses abnormal discharge occurring in the X-ray tube 50, and suppresses a decrease in inspection processing capacity even when inspection is continued under conditions of applying a voltage (low voltage) in the range of 15 kV to 50 kV.

[0043] Here, the occurrence of abnormal discharge when the first voltage was continuously applied between the anode electrode 56 and the cathode electrode 57 was confirmed. In the X-ray inspection device 1 as shown in Figs. 1 to 3, the number of occurrences of abnormal discharge per day was obtained when operation was continued (after electricity was continued) with a voltage of 30 kV (8 mA) applied between the anode electrode 56 and the cathode electrode 57. In this case, as shown in Fig. 4, it was confirmed that the number of occurrences of abnormal discharge per day increased rapidly after a predetermined electricity-passing time had elapsed. Therefore, at the timing when the abnormal discharge started to increase rapidly, a voltage of 75 kV (4 mA), which is higher than the voltage of 30 kV (8 mA), was applied between the anode electrode 56 and the cathode electrode 57 for 10 minutes.

[0044] The number of abnormal discharges occurring per day was obtained when a voltage of 75 kV (4 mA) was applied, followed by a voltage of 30 kV (8 mA) was applied. In this case, as shown in Fig. 5, it was confirmed that the number of abnormal discharges occurring per day could be reduced. This confirmed that, by applying a second voltage higher than the first voltage between the anode electrode 56 and the cathode electrode 57, abnormal discharges occurring in the X-ray tube 50 could be reduced, and a reduction in inspection processing capacity could be suppressed, even when inspections were continued under low voltage conditions of 15 kV to 50 kV.

[0045] In the X-ray inspection apparatus 1 of the present embodiment, the first voltage range is 15 kV to 50 kV, and the second voltage range is 60 kV to 150 kV. In this configuration, even if the X-ray inspection apparatus is continuously used under a low voltage condition in the range of 15 kV to 50 kV, by periodically applying a high voltage in the range of 60 kV to 150 kV, it is possible to suppress the occurrence of defects caused by X-rays not being appropriately radiated to a part of the acquired X-ray transmission image.

[0046] In the X-ray inspection apparatus 1 of the present embodiment, the second voltage is set to be twice or more the first voltage. In this configuration, by periodically applying the second voltage twice or more the first voltage, it is possible to suppress the occurrence of defects caused by X-rays not being appropriately irradiated to a part of the acquired X-ray transmission image.

[0047] In the X-ray inspection apparatus 1 of the present embodiment, the controller 10 can apply the second voltage when the power is turned on. With this configuration, excess electrons in the X-ray tube 50 are properly removed periodically, so that even if the inspection is continuously performed under a low voltage condition in the range of 15 kV to 50 kV, the number of times that abnormal discharge occurs in the X-ray tube 50 is reduced, and therefore the deterioration of the inspection processing capacity can be suppressed.

[0048] Although one embodiment has been described above, one aspect of the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit and scope of the invention.

[0049] In the X-ray inspection device 1 of the present embodiment, the second voltage applied by the controller 10 is the second voltage stored in the memory unit 10A, that is, a set value set for the first voltage (in other words, set for each article G), but the present invention is not limited to this. For example, the controller 10 may apply a variable value that varies depending on various conditions (operating conditions) set in the X-ray irradiation unit 6 as the second voltage. For example, the controller 10 may determine at least one of the intensity and application time of the second voltage based on at least one of the number of abnormal discharges that occur in the X-ray irradiation unit 6 and the irradiation time of X-rays in the X-ray irradiation unit 6, starting from the start of use of the X-ray tube 50 or the previous application of the second voltage. The number of abnormal discharges that occur in the X-ray irradiation unit 6 and the irradiation time of X-rays in the X-ray irradiation unit 6 are stored in the memory unit 10A.

[0050] In order to apply the second voltage and expel excess electrons in the X-ray tube 50 from the X-ray tube 50 in a shorter time, the shortest application time of the second voltage may be determined based on the maximum voltage (e.g., 75 kV) that can be set in the X-ray inspection device 1. However, in this case, the burden on the X-ray tube 50 or the X-ray detection unit 7 increases. For this reason, when there is sufficient time to apply the second voltage (e.g., after the end of production for the day), a voltage lower than the maximum voltage (e.g., 60 kV) may be set and applied for a time longer than the shortest application time to expel excess electrons in the X-ray tube 50 from the X-ray tube 50. This allows the second voltage to be applied while suppressing deterioration of each component.

[0051] In the above embodiment and the above modified example of the X-ray inspection apparatus 1, the second voltage is applied periodically at the timing described above, but the present invention is not limited to this. For example, the controller 10 may determine whether or not to apply the second voltage every time at the timing described above.

[0052] As an example of a method of determination, the controller 10 may determine whether or not to apply the second voltage based on the number of abnormal discharges that occur in the X-ray irradiation unit 6 from the start of use of the X-ray tube 50 or the previous application of the second voltage as a starting point. The controller 10 can obtain the number of abnormal discharges from the storage unit 10A.

[0053] As another example of the determination method, the controller 10 may determine whether or not to apply the second voltage based on the X-ray irradiation time of the X-ray irradiator 6 from the start of use of the X-ray tube 50 or the previous application of the second voltage. The controller 10 can obtain the above-mentioned irradiation time from the memory unit 10A.

[0054] With the configuration of this modified example, it is possible to appropriately remove excess electrons in the X-ray tube 50. Furthermore, while periodically applying the second voltage would consume the time required to apply the first voltage and perform the inspection, with the configuration of this modified example, it is possible to minimize the number of times the second voltage is applied. As a result, it is possible to minimize the decrease in the inspection processing capacity of the X-ray inspection apparatus 1.

[0055] In the above embodiment and the above modified X-ray inspection apparatus 1, an example has been described in which a voltage twice or more as high as the first voltage is applied when the second voltage is applied, but if the first voltage is set to 15 kV to 50 kV and the second voltage is set to 60 kV to 150 kV, the condition of applying a voltage twice or more as high as the first voltage when the second voltage is applied may be removed. Also, even if the first voltage is not set to a range of 15 kV to 50 kV and the second voltage is not set to a range of 60 kV to 150 kV as in the above embodiment and the above modified X-ray inspection apparatus 1, the controller 10 may be configured to apply a voltage twice or more as high as the first voltage when the second voltage is applied.

[0056] In the above embodiment and the above modified X-ray inspection device 1, the X-ray detection unit 7 has been described as having a plurality of photodiodes arranged one-dimensionally along the horizontal direction (width direction) perpendicular to the conveying direction A, but may have a plurality of photodiodes arranged in a plane (two-dimensionally) in the conveying direction A and the width direction. The X-ray detection unit 7 may be, for example, a sensor (multi-energy sensor) that detects X-rays in each of a plurality of energy regions that penetrate the article G. In the above embodiment and the above modified X-ray inspection device 1, the scintillator arranged on the X-ray entrance side of each photodiode has been described as having a scintillator, but the scintillator may be omitted and the X-ray detection unit 7 may be replaced with a direct conversion type detection unit capable of detecting X-rays by a photon counting method. [Explanation of symbols]

[0057] 1...X-ray inspection equipment, 2...main body of equipment, 4...shielding box, 5...transport conveyor, 6...X-ray irradiation unit, 7...X-ray detection unit, 10...controller (control unit), 10A...memory unit, 40...controller (inspection unit / control unit), 50...X-ray tube, 54...abnormal discharge detection circuit, 56...anode electrode (positive electrode), 57...cathode electrode (negative electrode), 100...X-ray generator, A...transport direction, G...item, T...target.

Claims

1. an X-ray irradiation unit that generates X-rays by applying a first voltage between a cathode and an anode of an X-ray tube and irradiates the transported object with the X-rays; an X-ray detection unit that detects the X-rays irradiated from the X-ray irradiation unit; an inspection unit that generates an X-ray transmission image based on a detection result of the X-ray detection unit and inspects the article; A control unit that changes a voltage applied between the cathode and the anode, The control unit applies a second voltage higher than the first voltage between the cathode and the anode before starting irradiation of X-rays generated by applying the first voltage or after finishing irradiation of X-rays generated by applying the first voltage.

2. 2. The X-ray inspection apparatus of claim 1, wherein the first voltage ranges from 15 kV to 50 kV and the second voltage ranges from 60 kV to 150 kV.

3. 3. The X-ray inspection apparatus according to claim 1, wherein the second voltage is at least twice as high as the first voltage.

4. 3. The X-ray inspection device according to claim 1, wherein the control unit determines at least one of an intensity and an application time of the second voltage based on at least one of a number of abnormal discharges occurring in the X-ray irradiator and an irradiation time of the X-rays in the X-ray irradiator, the number of abnormal discharges occurring in the X-ray irradiator being determined from a start point of use of the X-ray tube or a previous application of the second voltage.

5. 3. The X-ray inspection device according to claim 1, wherein the control unit stores the number of abnormal discharges that occur in the X-ray irradiation unit from the start of use of the X-ray tube or the previous application of the second voltage, and determines whether or not to apply the second voltage based on the number of abnormal discharges.

6. 3. The X-ray inspection device according to claim 1, wherein the control unit stores an irradiation time of the X-rays in the X-ray irradiation unit from a time when the X-ray tube is started to be used or a time when the second voltage was last applied as a starting point, and determines whether or not to apply the second voltage based on the irradiation time.

7. The X-ray inspection apparatus according to claim 1 , wherein the control unit applies the second voltage when a power source is turned on.

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