X-ray thickness measuring device

Abstract

To provide an X-ray thickness measurement apparatus which can shorten the calibration time and improve the reliability of calibration accuracy.SOLUTION: An X-ray thickness measurement apparatus includes: an X-ray generator; an X-ray detector on which the X-ray radiated from the X-ray generator is incident and which outputs a detection signal depending on the intensity of the incident X-ray; a calibration device which is arranged between the X-ray generator and the X-ray detector, and has several reference plates and a first movement part that is provided for each of the multiple reference plates and can move the reference plate to a position through which the X-ray radiated from the X-ray generator can pass; a first acceleration sensor which is provided in the calibration device; and a controller which is electrically connected to the X-ray generator, the X-ray detector, the first movement part and the first acceleration sensor and stores data of the calibration curve that defines the relationship between the value of the detection signal output from the X-ray detector and the thickness of a measurement object and data of the thickness of each of the multiple reference plates.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] Embodiments of the present invention relate to an X-ray thickness measuring apparatus. [Background Art]

[0002] For example, in rolling lines for ferrous and non-ferrous metals that operate 24 hours a day, there are X-ray thickness measuring apparatuses that online measure the thickness of rolled plates. Such an X-ray thickness measuring apparatus includes an X-ray generator that irradiates X-rays onto a plate material as a measurement object, and an X-ray detection unit that detects X-rays attenuated after transmitting through the plate material.

[0003] Here, the relationship between the value of the detection signal from the X-ray detection unit and the thickness of the plate material is non-linear. Therefore, data of a calibration curve defining the relationship between the value of the detection signal from the X-ray detection unit and the thickness of the plate material is stored in advance in a controller of the X-ray thickness measuring apparatus. However, the value of the detection signal from the X-ray detection unit may fluctuate due to disturbance factors and the like. Therefore, a calibration device is provided in the X-ray thickness measuring apparatus for calibrating the calibration curve.

[0004] The calibration device is provided with a plurality of reference plates. When calibrating the calibration curve, a reference plate is appropriately selected and moved to a position where X-rays emitted from the X-ray generator transmit through. In this case, if reference plates with different thicknesses are appropriately selected and superimposed at the position where X-rays transmit through, a plurality of points on the calibration curve can be calibrated.

[0005] However, moving the reference plate causes the reference plate to vibrate. When the reference plate vibrates, the X-ray transmission length in the reference plate changes, which reduces the reliability of calibration accuracy. Therefore, in general, calibration is performed after the elapse of an expected time during which the vibration of the reference plate is expected to converge.

[0006] However, the time it takes for the vibration of the reference plate to subside varies depending on the thickness (mass) of the reference plate. For example, the time it takes for the vibration of a thick (high-mass) reference plate to subside is longer than the time it takes for the vibration of a thin (low-mass) reference plate to subside. In this case, if calibration is performed using the time it takes for the vibration of a thick reference plate to subside, the calibration time will be longer. If calibration is performed using the time it takes for the vibration of a thin reference plate to subside, the reliability of the calibration accuracy may decrease. Therefore, there was a need for the development of an X-ray thickness measuring device that could shorten calibration time and improve the reliability of calibration accuracy. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-198708 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is to provide an X-ray thickness measuring device that can shorten calibration time and improve the reliability of calibration accuracy. [Means for solving the problem]

[0009] The X-ray thickness measuring apparatus according to the embodiment includes an X-ray generator capable of irradiating X-rays, an X-ray detection unit into which the X-rays irradiated from the X-ray generator are incident and capable of outputting a detection signal corresponding to the intensity of the incident X-rays, a calibration apparatus provided between the X-ray generator and the X-ray detection unit and having a plurality of reference plates, and a first moving unit provided for each of the plurality of reference plates and capable of moving the reference plates to a position through which the X-rays irradiated from the X-ray generator pass, a first acceleration sensor provided in the calibration apparatus, and a controller electrically connected to the X-ray generator, the X-ray detection unit, the first moving unit, and the first acceleration sensor, and storing calibration curve data that defines the relationship between the value of the detection signal output from the X-ray detection unit and the thickness of the object to be measured, and thickness data for each of the plurality of reference plates. The controller can calibrate the calibration curve data using the value of the detection signal output from the X-ray detection unit and the data of the thickness of the reference plate through which the X-rays have passed, when the X-rays that have passed through the reference plate are incident on the X-ray detection unit. If the controller determines that the vibration of the reference plate at the position through which the X-rays have passed has converged, based on the value of the detection signal output from the first acceleration sensor and a first threshold value determined in advance, it starts calibrating the calibration curve data. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram of the X-ray thickness measuring device according to this embodiment. [Figure 2] This is a schematic perspective view illustrating the appearance of the calibration device. [Figure 3] Figure 2 is a schematic cross-sectional view of the calibration device in the direction of line AA. [Figure 4] This is a schematic perspective view illustrating the operation of the moving part. [Modes for carrying out the invention]

[0011] The embodiments will be illustrated below with reference to the drawings. In each drawing, similar components are denoted by the same reference numerals, and detailed descriptions will be omitted as appropriate.

[0012] Figure 1 is a block diagram of the X-ray thickness measuring device 100 according to this embodiment. As shown in Figure 1, the X-ray thickness measuring device 100 includes, for example, an X-ray generator 1, an X-ray detection unit 2, a frame 3, an X-ray power supply 4, a circuit unit 5, a calibration device 6, and a controller 7.

[0013] The X-ray generator 1 is electrically connected to the X-ray power supply 4 via the circuit unit 5. When power is supplied from the X-ray power supply 4, the X-ray generator 1 generates X-rays 14. The X-ray generator 1 irradiates the object to be measured 200 with the generated X-rays 14. The object to be measured 200 is, for example, a plate material containing metals such as iron or non-ferrous metals. There are no particular limitations on the type of X-ray generator 1. For example, the X-ray generator 1 can be a fixed anode X-ray tube, a rotating anode X-ray tube, etc. The X-ray generator 1 illustrated in Figure 1 is a fixed anode X-ray tube. In the following, as an example, the case in which the X-ray generator 1 is a fixed anode X-ray tube will be described.

[0014] The X-ray generator 1 includes, for example, an X-ray tube 11, a filament 12, and a target 13. The X-ray tube 11 can be, for example, a tubular body capable of maintaining a vacuum inside. The filament 12 and the target 13 are located inside the X-ray tube 11. The filament 12 is located near one end of the X-ray tube 11. The target 13 is located near the other end of the X-ray tube 11. The filament 12 and the target 13 face each other. The filament 12 and the target 13 are formed using, for example, tungsten. For example, the filament 12 serves as the cathode. For example, the target 13 is embedded in the end of the anode, which is formed using copper.

[0015] The filament 12 is electrically connected to a heating circuit 51 provided in the circuit section 5. The filament 12 and the target 13 are electrically connected to a high-voltage circuit 52 provided in the circuit section 5. When current flows through the filament 12 via the heating circuit 51, the filament 12 is heated and thermionic electrons are generated. When a high voltage is applied to the heated filament 12 and the target 13 via the high-voltage circuit 52, the thermionic electrons generated in the filament 12 are accelerated and collide with the target 13. X-rays 14 are generated when the thermionic electrons collide with the target 13, and the generated X-rays 14 are irradiated onto the object to be measured 200.

[0016] The X-ray detection unit 2 is positioned opposite the X-ray generator 1, with the calibration device 6 in between. For example, the X-ray generator 1 and the calibration device 6 can be positioned below the position where the object to be measured 200 is transported. For example, the X-ray detection unit 2 can be positioned above the position where the object to be measured 200 is transported.

[0017] X-rays 14 that have passed through the object to be measured 200 are incident on the X-ray detection unit 2. The X-ray detection unit 2 outputs a detection signal of at least one of the values ​​of a detection voltage and a detection current, according to the intensity of the X-rays 14 that have been attenuated by passing through the object to be measured 200. The detection signal output from the X-ray detection unit 2 is input to the controller 7 via a conversion unit 21. The conversion unit 21 is, for example, an AD converter. The conversion unit 21, being an AD converter, converts the detection signal, which is an analog signal, into a digital signal and inputs it to the controller 7. Note that the conversion unit 21 is not necessarily required, and the controller 7 may convert the detection signal into a digital signal. The X-ray detection unit 2 is not particularly limited as long as it can convert the intensity of the incident X-rays 14 into an electrical signal. The X-ray detection unit 2 can be, for example, an ionization chamber.

[0018] The frame 3 includes, for example, a base portion 31, an arm 32, and a support portion 33. The base portion 31 has a box shape and is provided, for example, on a floor at a location where the X-ray thickness measurement apparatus 100 is installed. The arm 32 has a box shape and is provided at a position facing the base portion 31. A space through which the measurement object 200 is conveyed is provided between the base portion 31 and the arm 32. The support portion 33 has a columnar shape, and one end thereof is connected to the vicinity of one end of the base portion 31. The other end of the support portion 33 is connected to the vicinity of one end of the arm 32. That is, the support portion 33 supports the arm 32 in a cantilever manner.

[0019] Note that a pair of support portions 33 may be provided to support the vicinity of both ends of the arm 32. However, if the arm 32 is supported in a cantilever manner, size reduction can be achieved for the frame 3, and consequently for the X-ray thickness measurement apparatus 100. Further, the X-ray thickness measurement apparatus 100 can be installed on an apparatus that conveys the measurement object 200 from a side of the apparatus that conveys the measurement object 200. Therefore, installation of the X-ray thickness measurement apparatus 100 is facilitated.

[0020] Inside the base portion 31, for example, the X-ray generator 1, the circuit unit 5, and the calibration apparatus 6 can be provided. Inside the arm 32, the X-ray detection unit 2 can be provided. When the arm 32 is supported in a cantilever manner, the X-ray detection unit 2 can be provided near the free end of the arm 32.

[0021] The X-ray power supply 4 includes, for example, a filament power supply 41 and a high-voltage power supply 42. The filament power supply 41 is provided to heat the filament 12 to generate thermoelectrons. The high-voltage power supply 42 is provided to accelerate the thermoelectrons generated from the filament 12. For example, the anode side of the high-voltage power supply 42 can be electrically connected to the target 13, and the cathode side of the high-voltage power supply 42 can be electrically connected to the filament 12. In this case, the high-voltage power supply 42 can also be electrically connected to the filament 12 or the target 13. However, if the high-voltage power supply 42 is electrically connected to both the filament 12 and the target 13, the tube voltage (acceleration voltage) can be increased, so the intensity of the generated X-rays 14 can be increased. The X-ray power supply 4 is electrically connected to an external power supply such as a commercial power supply, for example.

[0022] The circuit unit 5 includes a heating circuit 51 and a high-voltage circuit 52. The heating circuit 51 electrically connects the filament power supply 41 of the X-ray power supply 4 and the filament 12 of the X-ray generator 1. The heating circuit 51 includes a transformer 51a. The primary side of the transformer 51a is electrically connected to the filament power supply 41 of the X-ray power supply 4. The secondary side of the transformer 51a is electrically connected to the filament 12 of the X-ray generator 1.

[0023] The high-voltage circuit 52 electrically connects the high-voltage power supply 42 of the X-ray power supply 4, and the filament 12 and the target 13 of the X-ray generator 1. The high-voltage circuit 52 includes a transformer 52a, a booster circuit 52b, and a booster circuit 52c. The primary side of the transformer 52a is electrically connected to the high-voltage power supply 42 of the X-ray power supply 4. The secondary side of the transformer 52a is electrically connected to the filament 12 and the target 13 of the X-ray generator 1. The booster circuit 52b is electrically connected between the secondary side of the transformer 52a and the filament 12. The booster circuit 52c is electrically connected between the secondary side of the transformer 52a and the target 13.

[0024] Here, the relationship between the attenuation of the X-rays 14 that have passed through the object 200 and the thickness of the object 200 is nonlinear. Therefore, a calibration curve that defines the relationship between the value of the detection signal from the X-ray detection unit 2 and the thickness of the object 200 has been determined in advance. Therefore, by applying the value of the detection signal from the X-ray detection unit 2 to the calibration curve, the thickness of the object 200 can be determined.

[0025] However, the value of the detection signal from the X-ray detection unit 2 may fluctuate due to external disturbances. These disturbances include, for example, temperature changes of the cooling medium that cools the X-ray generator 1, temperature and humidity changes of the atmosphere in which the X-ray generator 1 and the X-ray detection unit 2 are installed, and the intrusion of foreign matter (e.g., water, oil, scale, etc.) between the X-ray generator 1 and the X-ray detection unit 2. Therefore, it is necessary to calibrate the predetermined calibration curve as needed or periodically.

[0026] The calibration device 6 is provided for calibrating the calibration curve. The calibration device 6 is located between the X-ray generator 1 and the X-ray detection unit 2. The calibration device 6 may have, for example, multiple reference plates 63 of different thicknesses. Calibration by the calibration device 6 is performed when there is no object 200 to be measured between the X-ray generator 1 (calibration device 6) and the X-ray detection unit 2. When performing calibration by the calibration device 6, the reference plate 63 of the calibration device 6 is moved between the X-ray generator 1 and the X-ray detection unit 2. For example, the reference plate 63 of the calibration device 6 is moved to a position 6a through which the X-rays 14 irradiated from the X-ray generator 1 pass. The X-rays 14 irradiated from the X-ray generator 1 pass through the reference plate 63 and enter the X-ray detection unit 2. Since the thickness of the reference plate 63 is known, the relationship between the value of the detection signal from the X-ray detection unit 2 and the thickness of the reference plate 63 can be determined. By performing the above procedure while changing the thickness of the reference plate 63, multiple points on the pre-determined calibration curve can be calibrated. Further details regarding the configuration, operation, and effects of the calibration device 6 will be described later.

[0027] The controller 7 controls the operation of each element provided in the X-ray thickness measuring device 100. The controller 7 includes, for example, a computing device such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), and a storage device such as semiconductor memory or a hard disk drive. The controller 7 is, for example, a computer. The storage device of the controller 7 stores a control program, a thickness calculation program, a calibration curve calibration program, a pre-determined calibration curve, thresholds used to determine the vibration state of the reference plate 63 and frame 3 (corresponding to an example of a first threshold and a second threshold), and data on the thickness of the reference plate 63. The control program is, for example, a program for controlling the operation of each element provided in the X-ray thickness measuring device 100. The thickness calculation program is, for example, a program for calculating the thickness of the object to be measured 200 using the value of the detection signal from the X-ray detection unit 2 and the calibration curve. The calibration curve calibration program is a program used to calibrate the calibration curve stored in the memory device when performing calibration using the calibration device 6, by using the relationship between the value of the detection signal from the detection unit 2 and the thickness of the reference plate 63.

[0028] Furthermore, the controller 7 can be electrically connected to an external device controller 300. For example, if the controller 300 is a control device that controls the operation of a rolling mill, the controller 300 provides feedback control of the operation of the rolling mill based on the thickness of the object to be measured 200 calculated by the controller 7. Detailed explanations of the control program, thickness calculation program, calibration curve calibration program, and calibration curve are omitted because known techniques can be applied to them.

[0029] Next, we will explain the calibration device 6 in more detail. Figure 2 is a schematic perspective view illustrating the external appearance of the calibration device 6. To avoid complexity, Figure 2 only depicts the external appearance of the calibration device 6. Figure 3 is a schematic cross-sectional view of the calibration device 6 in Figure 2 in the direction of line AA. Figure 4 is a schematic perspective view illustrating the operation of the movable part 65. To avoid complexity, only the two movable parts 65 are shown in Figure 4.

[0030] As shown in Figures 2 and 3, the calibration device 6 includes, for example, a housing 61, a transmissive window 62, a reference plate 63, a shielding plate 64, a moving part 65, a circuit part 66, an acceleration sensor 67, and a temperature sensor 68.

[0031] The housing 61 is box-shaped and has a space inside for housing a reference plate 63, a shielding plate 64, a movable part 65, a circuit part 66, and an acceleration sensor 67 (corresponding to an example of a first acceleration sensor). As shown in Figure 2, the external shape of the housing 61 can be, for example, a rectangular parallelepiped. However, the external shape of the housing 61 is not limited to a rectangular parallelepiped. The housing 61 can be formed from a material capable of shielding X-rays 14. A material capable of shielding X-rays 14 is, for example, lead. In this case, the housing 61 may have a box-shaped body made of a metal such as iron, and a shielding plate containing lead or the like that covers at least one of the inner and outer walls of the box-shaped body. The housing 61 can have an airtight structure that can maintain the internal atmosphere. The internal space of the airtight housing 61 can be filled with nitrogen gas.

[0032] A pair of transmission windows 62 can be provided. As shown in Figure 2, the pair of transmission windows 62 are positioned opposite each other in the direction from the X-ray generator 1 to the X-ray detection unit 2 (the irradiation direction of the X-rays 14). For example, one transmission window 62 can be provided on the side of the housing 61 facing the X-ray generator 1. For example, the other transmission window 62 can be provided on the side of the housing 61 facing the X-ray detection unit 2. The pair of transmission windows 62 are positioned so that the X-rays 14 traveling from the X-ray generator 1 to the X-ray detection unit 2 pass through them. The pair of transmission windows 62 are plate-shaped and can be formed from a material that can transmit X-rays 14. An example of a material that can transmit X-rays 14 is beryllium.

[0033] The reference plate 63 is plate-shaped and can be made from the same material as the object to be measured 200. Multiple reference plates 63 can be provided. There is no particular limit to the number of reference plates 63, but increasing the number of reference plates 63 allows for more points to be used to calibrate the calibration curve. Therefore, the accuracy and reliability of the calibration curve can be improved. Multiple reference plates 63 can have the same thickness, or at least one reference plate 63 can have a different thickness from the other reference plates 63. If reference plates 63 with different thicknesses are provided, it becomes easier to arbitrarily set the interval between points to calibrate the calibration curve. The thickness of the reference plate 63 can be appropriately selected, for example, within the range of 0.1 mm or more and 5 mm or less.

[0034] When viewed from the direction from the X-ray generator 1 toward the X-ray detection unit 2 (the irradiation direction of the X-rays 14), the dimensions of the reference plate 63 can be made larger than the dimensions of the area where the X-rays 14 are incident on the reference plate 63 (the spot diameter of the X-rays 14).

[0035] The shielding plate 64 is plate-shaped and can be formed from a material capable of shielding X-rays 14. Examples of materials capable of shielding X-rays 14 include lead. The thickness of the shielding plate 64 is not particularly limited as long as it can shield X-rays 14. When viewed from the direction from the X-ray generator 1 toward the X-ray detection unit 2 (the irradiation direction of X-rays 14), the dimensions of the shielding plate 64 can be, for example, the same as or larger than the dimensions of the transmission window 62.

[0036] Multiple movable units 65 can be provided. One movable unit 65 can be provided for each of the reference plate 63 and the shielding plate 64 (corresponding to examples of the first and second movable units). As shown in Figures 3 and 4, the movable unit 65 moves the positions of the reference plate 63 and the shielding plate 64 between the position 6a through which the X-rays 14 pass and the position 6b separated from the position 6a through which the X-rays 14 pass (retracted position).

[0037] The moving part 65 includes, for example, a drive unit 65a and an arm 65b. The drive unit 65a is not particularly limited as long as it can move the positions of the reference plate 63 and the shielding plate 64. The drive unit 65a can be, for example, a solenoid, an air cylinder, a rotary solenoid, a rotary air cylinder, a control motor such as a stepping motor, etc. The drive unit 65a illustrated in Figures 3 and 4 is a rotary solenoid. If the drive unit 65a is a rotary solenoid, it is possible to simplify the control of the drive unit 65a and to miniaturize the calibration device 6.

[0038] The arm 65b has a plate-like shape and extends in one direction. The arm 65b can be, for example, a rectangular plate-like body. Near one end of the arm 65b, it is connected to the drive unit 65a. Near the other end of the arm 65b, a reference plate 63 or a shielding plate 64 is provided. The arm 65b on which the reference plate 63 is provided can be formed from, for example, a material that can transmit X-rays 14. A material that can transmit X-rays 14 is, for example, beryllium. Alternatively, the arm 65b on which the reference plate 63 is provided can be formed from a metal such as iron and have a hole through which X-rays 14 can pass at the position where the reference plate 63 is provided. The arm 65b on which the shielding plate 64 is provided can be the same as the arm 65b on which the reference plate 63 is provided, or it can have a material or configuration that suppresses the transmission of X-rays 14.

[0039] As shown in Figures 3 and 4, in the direction from the X-ray generator 1 to the X-ray detection unit 2 (the irradiation direction of the X-rays 14), each of the multiple arms 65b is positioned at a distance from one another. For example, as shown in Figure 4, the position of the arms 65b can be changed by changing the length of the drive shaft 65a1 for each of the multiple drive units 65a. Alternatively, the position of the arms 65b can be changed by changing the mounting position of the arms 65b to the drive shaft 65a1, or by providing spacers of different thicknesses between the housing 61 and the drive units 65a.

[0040] The distance between adjacent arms 65b is greater than the thickness of the reference plate 63 and the thickness of the shielding plate 64. Therefore, multiple reference plates 63 can be selectively moved to the position 6a through which the X-rays 14 pass. In this way, multiple reference plates 63 can be used in combination during calibration, so that multiple points on the calibration curve can be calibrated.

[0041] Furthermore, the shielding plate 64 can be moved to the position 6a through which the X-rays 14 pass without having to retract the reference plate 63. In this case, the shielding plate 64 can be installed on at least one of the arms 65b located closest to the X-ray generator 1 and the arms 65b located closest to the X-ray detection unit 2. In this way, it is possible to suppress the entry of X-rays 14 into the housing 61 and to suppress the leakage of X-rays 14 that have entered the housing 61 to the outside of the housing 61.

[0042] The circuit unit 66 can be installed, for example, inside the housing 61. The circuit unit 66 is equipped with a control circuit that individually controls the multiple movable parts 65. The circuit unit 66 includes, for example, a circuit board and electrical components that constitute the control circuit. The circuit unit 66 is electrically connected to the multiple movable parts 65 and the controller 7.

[0043] Here, when the reference plate 63 is moved by the moving part 65 to the position 6a through which the X-rays 14 pass, vibration occurs in the arm 65b and the reference plate 63. When the reference plate 63 vibrates, it tilts, which changes the transmission length of the X-rays 14 through the reference plate 63. When the transmission length of the X-rays 14 changes, the attenuation of the X-rays 14 changes, which reduces the calibration accuracy. Therefore, calibration is generally performed after the expected time for the vibration of the reference plate 63 to subside has elapsed.

[0044] However, the time it takes for the vibration of the reference plate 63 to subside varies depending on the thickness (mass) of the reference plate 63. For example, the time it takes for the vibration of a reference plate 63 with a thickness of 5 mm to subside is longer than the time it takes for the vibration of a reference plate 63 with a thickness of 0.1 mm to subside. In this case, if calibration is started using the time it takes for the vibration of the 5 mm thick reference plate 63 to subside, the calibration time will be longer. If calibration is started using the time it takes for the vibration of the 0.1 mm thick reference plate 63 to subside, the reliability of the calibration accuracy may decrease.

[0045] Therefore, the X-ray thickness measuring device 100 is provided with an acceleration sensor 67. The acceleration sensor 67 is electrically connected to the controller 7. The acceleration sensor 67 can be installed, for example, inside the housing 61. If the acceleration sensor 67 is installed inside the housing 61, vibrations generated in the moving part 65 are more easily transmitted to the acceleration sensor 67, making it easier to detect the vibration state of the reference plate 63. In this case, as shown in Figure 3, if the acceleration sensor 67 is installed in the circuit part 66, it becomes easier to electrically connect the acceleration sensor 67 to the controller 7.

[0046] The controller 7 determines the vibration state of the reference plate 63 based on the value of the detection signal from the acceleration sensor 67. For example, if the value of the detection signal from the acceleration sensor 67 exceeds a predetermined threshold, the controller 7 can determine that the vibration of the reference plate 63 has not converged. For example, if the value of the detection signal from the acceleration sensor 67 falls below the threshold, the controller 7 can determine that the vibration of the reference plate 63 has converged. The threshold used to determine the vibration state of the reference plate 63 can be determined in advance by conducting experiments or simulations. The determined threshold can be stored in the memory of the controller 7.

[0047] By initiating calibration based on the detection signal value from the acceleration sensor 67, the convergence of the vibration of the reference plate 63 is guaranteed, thereby improving the reliability of the calibration accuracy. Furthermore, even if the thickness of the reference plate 63 used for calibration changes and the vibration state of the reference plate 63 changes, there is no need to add extra waiting time. Therefore, the calibration time can be shortened.

[0048] When the controller 7 determines that the vibration of the reference plate 63 at position 6a through which the X-rays 14 pass has converged, it starts calibrating the calibration curve data. The controller 7 uses the value of the detection signal output from the X-ray detection unit 2, which receives the X-rays 14 that have passed through the reference plate 63, and the data of the thickness of the reference plate 63 through which the X-rays 14 have passed, to calibrate the calibration curve data stored in the memory.

[0049] Furthermore, by determining the vibration state of the reference plate 63 based on the value of the detection signal from the acceleration sensor 67, the effects of external vibrations (e.g., earthquakes) can be eliminated. For example, if the controller 7 determines that the vibration of the reference plate 63 at position 6a through which the X-rays 14 pass has increased after the start of calibration of the calibration curve data, it can stop the calibration of the calibration curve data.

[0050] For example, if the value of the detection signal from the acceleration sensor 67 exceeds a predetermined threshold after the calibration has started, the controller 7 may stop the calibration. If the calibration is stopped, the obtained data may be discarded. Also, if the value of the detection signal from the acceleration sensor 67 falls below the threshold after the calibration has been stopped, the controller 7 may, for example, restart the calibration or start the calibration again from the beginning. By eliminating the effects of external vibrations in this way, the reliability of the calibration accuracy can be improved.

[0051] The threshold used to determine when to terminate calibration can be determined in advance through experiments or simulations. The determined threshold can be stored in the memory of the controller 7. The threshold used to determine when to terminate calibration may be the same as, or different from, the threshold used to determine when to start calibration as described above.

[0052] Here, if external vibrations are applied to the X-ray thickness measuring device 100, at least one of the X-ray generator 1, calibration device 6, and X-ray detection unit 2 may vibrate. When these vibrate, the relative positions of the X-ray generator 1, calibration device 6, and X-ray detection unit change, which may cause a change in the transmission direction of the X-rays 14 in the reference plate 63. If the transmission direction of the X-rays 14 in the reference plate 63 changes, the transmission length of the X-rays 14 changes, which may reduce the reliability of the calibration accuracy.

[0053] Therefore, the acceleration sensor 67 can also be provided on at least one of the X-ray generator 1, the X-ray detection unit 2, and the frame 3 (corresponding to an example of a second acceleration sensor). If the acceleration sensor 67 is provided on at least one of the X-ray generator 1, the X-ray detection unit 2, and the frame 3, the vibration state of the X-ray thickness measuring device 100 can be detected. In this case, as shown in Figure 1, the X-ray detection unit 2 is provided near the free end of the arm 32. Therefore, if the acceleration sensor 67 is provided on the X-ray detection unit 2, it becomes easier to detect external vibrations.

[0054] When the acceleration sensor 67 is installed on the frame 3, it is preferable to install the acceleration sensor 67 on the base 31 in the part where the calibration device 6 is installed, or on the arm 32 in the part where the X-ray detection unit 2 is installed. This makes it easier to detect external vibrations transmitted to the calibration device 6, and to detect changes in the positional relationship between the X-ray generator 1, the calibration device 6, and the X-ray detection unit 2.

[0055] If the acceleration sensor 67 is provided on at least one of the X-ray generator 1, the X-ray detection unit 2, and the frame 3, the influence of external vibrations can be eliminated, thereby improving the reliability of calibration accuracy.

[0056] In this case, the controller 7 can determine the external vibration applied to the X-ray thickness measuring device based on the value of the detection signal from the acceleration sensor 67 provided on at least one of the X-ray generator 1, the X-ray detection unit 2, and the frame 3, and a predetermined threshold value, either before or after the start of calibration. For example, if the value of the detection signal output from the acceleration sensor 67 exceeds the threshold value, the controller 7 can determine that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring device 100 and either not start the calibration of the calibration curve data or cancel the calibration of the calibration curve data.

[0057] The threshold used to detect external vibrations can be determined in advance through experiments or simulations. The determined threshold can be stored in the memory of the controller 7. The threshold used to detect external vibrations may be the same as, or different from, the threshold used to determine the start of calibration and the threshold used to determine the termination of calibration, as described above.

[0058] When calibration is performed using the calibration device 6, X-rays 14 are emitted from the X-ray generator 1. Therefore, if the frame 3 tilts due to external vibrations such as an earthquake, there is a risk that the X-rays 14 may be emitted in an unintended direction.

[0059] In this case, the controller 7 can determine that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring device 100 if the value of the detection signal from the acceleration sensor 67 provided on at least one of the X-ray generator 1, the X-ray detection unit 2, and the frame 3 exceeds a predetermined threshold. When the controller 7 determines that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring device 100, it controls the movement unit 65 of the calibration device 6 to move the shielding plate 64 to the position 6a through which the X-rays 14 pass. In this way, the X-rays 14 irradiated from the X-ray generator 1 are shielded by the shielding plate 64, thereby suppressing irradiation of the X-rays 14 in unintended directions. Therefore, the safety of the X-ray thickness measuring device 100 can be improved.

[0060] Furthermore, if the controller 7 determines that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring device 100, it can control the X-ray power supply 4 to stop the irradiation of X-rays 14 from the X-ray detection unit 2. In this way, it is possible to suppress the irradiation of X-rays 14 in an unintended direction. Therefore, the safety of the X-ray thickness measuring device 100 can be improved.

[0061] When the drive unit 65a located inside the housing 61 is operated, heat is generated in the drive unit 65a and the circuit unit 66. In addition, heat is transferred between the atmosphere in which the X-ray thickness measuring device 100 is located and the housing 61. As a result, the internal temperature of the housing 61 may change. Since a reference plate 63 is provided inside the housing 61, a change in the internal temperature of the housing 61 will cause a change in the temperature of the reference plate 63. A change in the temperature of the reference plate 63 will change the thickness of the reference plate 63, which in turn changes the attenuation of the X-rays 14 on the reference plate 63. A change in the attenuation of the X-rays 14 may reduce the calibration accuracy.

[0062] Therefore, the calibration device 6 can be equipped with a temperature sensor 68. The temperature sensor 68 is not particularly limited as long as it is capable of measuring the internal temperature of the housing 61. The temperature sensor 68 can be, for example, a thermocouple, a resistance thermometer, a thermistor, etc. The temperature sensor 68 is electrically connected to the controller 7. The temperature sensor 68 can be installed, for example, inside the housing 61. If the temperature sensor 68 is installed inside the housing 61, it becomes easy to detect the internal temperature of the housing 61. In this case, as shown in Figure 3, if the temperature sensor 68 is installed in the circuit section 66, it becomes easy to electrically connect the temperature sensor 68 to the controller 7.

[0063] The controller 7 corrects the data on the thickness of the reference plate 63 stored in the controller 7's memory based on the value of the detection signal from the temperature sensor 68. For example, the controller 7 can correct the thickness data of the reference plate 63 using the following formula. Tx' = Tx · {1 + α(t - t0)} 2 In this case, Tx' is the thickness (mm) of the reference plate 63 after temperature correction. Tx is the thickness (mm) of the reference plate 63 before temperature compensation. α is the coefficient of linear thermal expansion of the material of the reference plate 63 (10 -6 It is / ℃). t is the temperature (°C) detected by the temperature sensor 68. t0 is the temperature (°C) at the time the thickness data of the reference plate 63 stored in the memory was acquired. By correcting the thickness data of the reference plate 63 based on the value of the detection signal from the temperature sensor 68, the reliability of the calibration accuracy can be improved.

[0064] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other. [Explanation of Symbols]

[0065] 1 X-ray generator, 2 X-ray detection unit, 3 frame, 4 X-ray power supply, 6 calibration device, 6a position, 6b position, 7 controller, 14 X-ray, 31 base, 32 arm, 61 housing, 62 transmission window, 63 reference plate, 64 shielding plate, 65 moving unit, 65a drive unit, 65b arm, 66 circuit unit, 67 acceleration sensor, 68 temperature sensor, 100 X-ray thickness measuring device, 200 object to be measured

Claims

1. An X-ray generator capable of irradiating with X-rays, An X-ray detection unit receives the X-rays irradiated from the X-ray generator and is capable of outputting a detection signal corresponding to the intensity of the incident X-rays, A calibration device comprising: an X-ray generator and an X-ray detection unit, provided between them, a plurality of reference plates, and a first movable part provided for each of the plurality of reference plates, which is capable of moving the reference plates to a position through which the X-rays irradiated from the X-ray generator pass; The calibration device includes a first acceleration sensor, A controller electrically connected to the X-ray generator, the X-ray detection unit, the first moving unit, and the first acceleration sensor, which stores calibration curve data defining the relationship between the value of the detection signal output from the X-ray detection unit and the thickness of the object to be measured, and data for the thickness of each of the plurality of reference plates, Equipped with, The aforementioned controller, When X-rays that have passed through the reference plate are incident on the X-ray detection unit, the data of the calibration curve can be calibrated using the value of the detection signal output from the X-ray detection unit and the data of the thickness of the reference plate through which the X-rays have passed. An X-ray thickness measuring device that, based on the value of the detection signal output from the first acceleration sensor and a first threshold value determined in advance, determines that the vibration of the reference plate at the position through which the X-rays pass has converged, and starts calibrating the calibration curve data.

2. The X-ray thickness measuring apparatus according to claim 1, wherein the controller determines, after the start of calibration of the calibration curve data, that the vibration of the reference plate located at the position through which the X-rays pass has increased, and then stops the calibration of the calibration curve data.

3. The frame on which the X-ray generator, the X-ray detection unit, and the calibration device are provided, A second acceleration sensor is provided on at least one of the X-ray generator, the X-ray detection unit, and the frame, and is electrically connected to the controller. Furthermore, The X-ray thickness measuring apparatus according to claim 1 or 2, wherein the controller determines, based on the value of the detection signal output from the second acceleration sensor and a pre-determined second threshold, that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring apparatus, and either does not start the calibration of the calibration curve data or cancels the calibration of the calibration curve data.

4. The calibration apparatus includes a shielding plate capable of blocking the X-rays, and a second movable part capable of moving the shielding plate to a position through which the X-rays pass. Furthermore, The X-ray thickness measuring apparatus according to claim 3, wherein the controller determines that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring apparatus, and controls the second moving part to move the shielding plate to a position through which the X-rays pass.

5. The X-ray thickness measuring apparatus according to claim 3, wherein the controller determines that an external vibration of a predetermined magnitude has been applied to the X-ray thickness measuring apparatus, and stops the irradiation of X-rays from the X-ray generator.

6. The calibration device further includes a temperature sensor, The X-ray thickness measuring apparatus according to claim 1 or 2, wherein the controller corrects the thickness data of each of the plurality of reference plates based on the value of the detection signal from the temperature sensor.

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