X-ray thickness gauge

Abstract

Provided is an X-ray thickness gauge in which measurement error caused by contamination of an X-ray transmission window can be suppressed. The X-ray thickness gauge according to an embodiment comprises: an X-ray generation unit capable of generating X-rays; a housing for housing the X-ray generation unit; an X-ray transmission window disposed on a wall surface of the housing and capable of transmitting X-rays; an X-ray detection unit disposed facing the outer surface of the X-ray transmission window and capable of detecting the dose of X-rays radiated through the X-ray transmission window; an air purge device capable of spraying a gas along the outer surface of the X-ray transmission window; a liquid purge device capable of spraying a liquid toward the outer surface of the X-ray transmission window; and a control unit for controlling at least one of the spraying of the liquid toward the outer surface of the X-ray transmission window by the liquid purge device or the spraying of the gas along the outer surface of the X-ray transmission window by the air purge device on the basis of the dose of the X-rays detected by the X-ray detection unit before and after the measurement of the thickness of a measurement target.

Description

X-ray thickness gauge

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to an X-ray thickness gauge.

[0002] A conventional technique is known in which the thickness of an object is measured by irradiating the object with X-rays and measuring the attenuation of the X-rays as they pass through the object. Such a technique for measuring thickness using X-rays is used, for example, to measure the thickness of steel plates in a rolling process for steel plates and the like.

[0003] Generally, X-ray thickness gauges irradiate the object to be measured with X-rays through an X-ray transmission window provided in a housing that houses an X-ray generator. Therefore, if the X-ray transmission window becomes dirty, the dirt will attenuate the X-rays, causing errors in the measurement.

[0004] Japanese Patent Laid-Open No. 3-167493 Japanese Patent Laid-Open No. 2004-230315 Japanese Patent Laid-Open No. 2016-200480 Japanese Patent Laid-Open No. 7-173996

[0005] As described above, conventional X-ray thickness gauges have a problem in that measurement errors can occur when dirt adheres to the X-ray transmission window provided in the housing that houses the X-ray generator. An object of the present invention is to provide an X-ray thickness gauge that can suppress measurement errors caused by dirt on the X-ray transmission window.

[0006] An X-ray thickness gauge according to an embodiment is an X-ray thickness gauge that measures the thickness of a plate-shaped object by irradiating the object with X-rays. The X-ray thickness gauge according to the embodiment includes an X-ray generation unit capable of generating X-rays, a housing that houses the X-ray generation unit, an X-ray transmission window disposed on a wall surface of the housing and capable of transmitting X-rays, an X-ray detection unit disposed opposite the outer surface of the X-ray transmission window and capable of detecting the amount of X-rays emitted through the X-ray transmission window, an air purge device that can inject gas along the outer surface of the X-ray transmission window, a liquid purge device that can inject liquid toward the outer surface of the X-ray transmission window, and a control unit that controls at least one of the liquid purge device to inject liquid toward the outer surface of the X-ray transmission window and the air purge device to inject gas along the outer surface of the X-ray transmission window based on the amount of X-rays detected by the X-ray detection unit before and after measuring the thickness of the object.

[0007] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and is not to be limited to the disclosed exemplary embodiments.

[0008] (Configuration of the embodiment) Hereinafter, an X-ray thickness gauge of the embodiment will be described in detail with reference to the drawings. Fig. 1 is a diagram showing the appearance of an X-ray thickness gauge 1 according to the embodiment. Fig. 2 is a block diagram showing the configuration of the X-ray thickness gauge 1 according to the embodiment.

[0009] As shown in FIG. 1 , the X-ray thickness gauge 1 of the embodiment includes a housing 11 , an X-ray detector 12 , an X-ray transmission window 13 , and a purge device 30 .

[0010] The housing 11 is a structure that houses the functional elements of the X-ray thickness gauge and enables the irradiation of X-rays to the object to be measured. The housing 11 is configured with an opening in the movement direction T of the object to be measured so that the object to be measured can pass through the space G where X-rays are irradiated. The housing 11 is configured to be able to reciprocate, for example, in one direction (direction M) perpendicular to the movement direction (direction T) in which the object to be measured flows. The housing 11 holds an X-ray detector 12 on one side of the thickness direction of the object to be measured that passes in the direction T. Similarly, the housing 11 houses an X-ray generator 14 on the other side of the thickness direction of the object to be measured that passes in the direction T.

[0011] 1, the housing 11 includes an upper frame 11a that extends horizontally when the housing 11 is installed, a lower frame 11b that is arranged parallel to the upper frame 11a, and a vertical frame 11c that connects the upper frame 11a and the lower frame 11b at one end thereof. That is, the housing 11 is configured so that the upper frame 11a, the lower frame 11b, and the vertical frame 11c surround a measurement object that moves in the T direction.

[0012] 1 , the housing 11 has, for example, an X-ray detector 12 disposed on the lower wall surface of the upper frame 11a. Similarly, the housing 11 has an X-ray generator housed in the lower frame 11b. An X-ray transmissive window 13 is disposed on the wall surface (upper wall surface) of the lower frame 11b facing the X-ray detector 12 disposed on the upper frame 11a. That is, the upper and lower frames 11a and 11b, which are arranged in parallel, have the X-ray transmissive window 13 and the X-ray detector 12 disposed opposite each other, enabling X-ray radiation (X in the figure) perpendicular to the object to be measured passing between them in the T direction.

[0013] The X-ray thickness gauge 1 irradiates a predetermined range of an object to be measured passing through the space G in the T direction with X-rays through an X-ray transmission window 13. The X-rays that have passed through the object to be measured are detected by an X-ray detector 12. The X-ray thickness gauge 1 calculates the thickness of the object to be measured based on the detected X-ray amount. An example of the object to be measured is a plate-shaped steel plate. Such an X-ray thickness gauge 1 is placed, for example, on a production line for the steel plate, which is the object to be measured, and on a transport path along which the steel plate is transported in one direction.

[0014] The X-ray detector 12 is a functional element capable of detecting the amount of X-rays. The X-ray detector 12 is configured to convert the detected amount of X-rays into a detection signal and transmit the signal to the control device 20. The X-ray detector 12 is disposed on the lower wall surface of the upper frame 11a, facing the outer surface of the X-ray transmission window 13. The X-ray detector 12 can be realized by, for example, an ionization chamber.

[0015] The X-ray transmissive window 13 is a window member made of a material that is transmissive to X-rays. In this embodiment, the X-ray transmissive window 13 is disposed on the upper wall surface of the lower frame 11b on a straight line connecting the X-ray generator 14 and the X-ray detector 12, which will be described later.

[0016] 2, the X-ray generator 14 is a functional element housed in the lower frame 11b of the housing 11 and capable of generating X-rays. The X-ray generator 14 is disposed in a position where it can irradiate X-rays toward the X-ray detector 12 through the X-ray transmission window 13. The X-ray generator 14 is configured to be able to irradiate X-rays at a predetermined reference dose when a predetermined tube voltage and tube current are supplied. The dose of X-rays generated by the X-ray generator 14 can be controlled externally by an X-ray generator control signal Xg.

[0017] The purging device 30 is a functional element that cleans the outer surface of the X-ray transmissive window 13 that faces the object to be measured. The purging device 30 cleans (purges) the outer surface of the X-ray transmissive window 13 using at least one of a gas (air) and a liquid (water). In the following description, cleaning using air is referred to as air purging, and cleaning using water is referred to as water purging. The purging device 30 includes an air purging device 30a that performs air purging and a water purging device 30b that performs water purging.

[0018] The air purge device 30a has an air supply source 31, an air purge nozzle 32, an air pipe 33, and an electromagnetic valve 34. The air purge device 30b has a water supply source 35, a water purge nozzle 36, a water pipe 37, and an electromagnetic valve 38.

[0019] The air supply source 31 is, for example, a tank that stores gas (air) for air purging. The air supply source 31 is filled with air at a predetermined pressure so that air can be supplied at the predetermined pressure during air purging. The air supply source 31 can be housed, for example, within the housing 11.

[0020] The air purge nozzle 32 is a spray nozzle that purges the outer surface of the X-ray transparent window 13 with air. The air purge nozzle 32 is configured to be able to blow air along the outer surface of the X-ray transparent window 13. The air purge nozzle 32 is disposed on the upper wall surface of the lower frame 11b, around the periphery of the outer surface of the X-ray transparent window 13. The air purge nozzle 32 acts to blow away dirt on the outer surface of the X-ray transparent window 13 along the outer surface of the X-ray transparent window 13. The air purge nozzle 32 is connected to the air supply source 31 via an air pipe 33.

[0021] The solenoid valve 34 is a valve device disposed in the air pipe 33 that connects the air purge nozzle 32 and the air supply source 31. The solenoid valve 34 can be controlled to open and close from the outside by an air valve control signal a. The solenoid valve 34 can also control the amount of air supplied to the air purge nozzle 32 by the air valve control signal a.

[0022] The water supply source 35 is, for example, a tank that stores a liquid (water) for water purging. The water supply source 35 may include a pump (not shown) to supply water at a predetermined pressure during water purging. The water supply source 35 may be housed within the housing 11, for example.

[0023] The water purge nozzle 36 is a spray nozzle that purges the outer surface of the X-ray transparent window 13 with water. The water purge nozzle 36 is configured to spray water toward the outer surface of the X-ray transparent window 13 from a direction at a predetermined angle θ relative to the outer surface of the X-ray transparent window 13. That is, the water purge nozzle 36 is disposed on the upper wall surface of the lower frame 11b, around the periphery of the outer surface of the X-ray transparent window 13. Furthermore, the water purge nozzle 36 is disposed in a position and orientation that allows it to spray water toward the X-ray transparent window 13 at the predetermined angle θ. The water purge nozzle 36 acts to blow away dirt with the liquid directed toward the outer surface of the X-ray transparent window 13. The water purge nozzle 36 is connected to a water supply source 35 via a water pipe 37.

[0024] The angle θ formed by the water purge nozzle 36 and the X-ray transmission window 13 may be any angle that allows the water jetted from the water purge nozzle 36 to be jetted directly onto the outer surface of the X-ray transmission window 13 .

[0025] The solenoid valve 38 is a valve device disposed in a water pipe 37 that connects the water purge nozzle 36 and the water supply source 35. The solenoid valve 38 can be externally controlled to open and close by a water valve control signal w. The solenoid valve 38 can also control the amount of water supplied to the water purge nozzle 36 by the water valve control signal w.

[0026] In air purging, if air is blown directly onto the X-ray transparent window 13, it may catch surrounding dirt and make it impossible to remove dust and other debris from the outer surface of the X-ray transparent window 13. Therefore, air purging nozzle 32 is disposed in a position and orientation that allows air to be blown parallel to the outer surface of the X-ray transparent window 13. In other words, air purging nozzle 32 is configured so that air is not blown directly onto the outer surface of the X-ray transparent window 13.

[0027] On the other hand, in the water purge using water, which has a greater mass than air, it is possible to remove heavy contaminants. Therefore, the water purge nozzle 36 is disposed in a position and oriented so that water can be sprayed directly onto the outer surface of the X-ray transmissive window 13.

[0028] In the X-ray thickness gauge 1 of the embodiment, in addition to air purging, water purging can be performed on the X-ray transmission window 13. According to the X-ray thickness gauge 1 of the embodiment, by adding water purging, it is possible to remove oil and scale stains that cannot be removed by air alone.

[0029] The control device 20 shown in Fig. 2 is a functional element that realizes measurement control as an X-ray thickness gauge and purging control by the purging device 30. As shown in Fig. 2, the control device 20 includes a dose acquisition unit 21, a calculation unit 22, a storage unit 23, and a valve control unit 24. The control device 20 is electrically connected to the X-ray detector 12, the X-ray generator 14, and the solenoid valves 34 and 38. The control device 20 can be realized by a computer including a CPU, a main storage device, an auxiliary storage device, etc.

[0030] The dose acquisition unit 21 is a functional element that receives the detection result (detection signal Xd) from the X-ray detector 12. The dose acquisition unit 21 may include an amplifier that amplifies the detection signal Xd detected by the X-ray detector 12 and a conversion unit that converts the detection signal into a signal that can be processed by the calculation unit 22.

[0031] The calculation unit 22 is a functional element that executes a program deployed in a memory serving as a main storage device (not shown). The calculation unit 22 can be realized, for example, by a CPU or the like. The storage unit 23 is an information storage medium serving as an auxiliary storage device. The storage unit 23 is a functional element that can store the X-ray dose and detection signals acquired by the dose acquisition unit 21, measurement results as an X-ray thickness gauge, etc. The storage unit 23 can be realized, for example, by a hard disk drive (HDD) or a solid-state disk (SSD).

[0032] The calculation unit 22 has a function of calculating the thickness of the object to be measured by calculating the detection signal acquired by the dose acquisition unit 21. Specifically, the calculation unit 22 stores a calibration curve for the entire measurement range, which has been created in advance using a calibration reference plate, as a calibration curve in the storage unit 23. The calculation unit 22 calculates the plate thickness of the object to be measured by applying the detection signal, which is obtained by the X-ray detector 12 after passing through the object to the calibration curve.

[0033] The calculation unit 22 also has a function of detecting contamination on the outer surface of the X-ray transmissive window 13. Contamination detection can be achieved by comparing the radiation dose (detection signal) before and after measurement of the object to be measured. Specifically, the calculation unit 22 first stores a reference radiation dose (detection signal X0) in the storage unit 23. The reference radiation dose (detection signal X0) is the radiation dose (detection signal) detected by the X-ray detector 12 through the X-ray transmissive window 13 of X-rays emitted by the X-ray generator 14 in advance, without the object to be measured passing through the space G.

[0034] After storing the reference dose in the memory unit 23, the calculation unit 22 measures (calculates) the thickness of the object to be measured. After measuring the thickness of the object to be measured, the calculation unit 22 causes the X-ray detector 12 to detect X-rays emitted by the X-ray generator 14 through the X-ray transmission window 13 without allowing the object to pass through the space G again, thereby obtaining the X-ray dose (detection signal X1). The calculation unit 22 compares the reference dose (detection signal X0) with the dose (detection signal X1) obtained after measuring the thickness of the object to be measured. The difference between these values ​​serves as an indicator of contamination of the outer surface of the X-ray transmission window 13 during the thickness measurement of the object to be measured. If the difference exceeds a predetermined value as a result of the comparison, the calculation unit 22 can determine that the X-ray transmission window 13 is contaminated.

[0035] Furthermore, the calculation unit 22 has a function of controlling the amount of X-rays generated by the X-ray generator 14. The calculation unit 22 can transmit an X-ray generator control signal Xg to control the tube voltage and tube current that cause the X-ray generator 14 to generate X-rays.

[0036] The valve control unit 24 is a functional element that controls the opening and closing of the solenoid valves 34 and 38. The valve control unit 24 transmits an air valve control signal a to the solenoid valve 34 to control the opening and closing of the solenoid valve 34. For example, when air purging is performed using the air purge nozzle 32, the valve control unit 24 transmits the air valve control signal a to open the valve to the solenoid valve 34. Upon receiving the air valve control signal a to open the valve, the solenoid valve 34 opens the valve and supplies air from the air supply source 31 to the air purge nozzle 32.

[0037] Similarly, the valve control unit 24 transmits a water valve control signal w to the solenoid valve 38 to control the solenoid valve 38. For example, when performing water purging using the water purge nozzle 36, the valve control unit 24 transmits a water valve control signal w to open the valve to the solenoid valve 38. Upon receiving the water valve control signal w to open the valve, the solenoid valve 38 opens the valve and supplies water from the water supply source 35 to the water purge nozzle 36.

[0038] That is, the valve control unit 24 can switch between injection control of the air purge device 30a to inject air from the air purge nozzle 32 and injection control of the water purge device 30b to inject water from the water purge nozzle 36.

[0039] (Operation of the embodiment) Next, the operation of the X-ray thickness gauge 1 of the embodiment will be described with reference to Figures 1 to 3. Figure 3 is a flowchart for explaining the operation of the X-ray thickness gauge according to the embodiment.

[0040] Contamination such as oil and scale, which can cause measurement errors, adheres to the surface of the X-ray transmissive window 13 during steel measurement. Therefore, the dose is measured in a state where no object to be measured is present before thickness measurement in order to obtain a detection signal that serves as a reference for use in detecting contamination on the X-ray transmissive window 13. The dose acquisition unit 21 acquires the X-ray dose of the X-ray generator 14 detected by the X-ray detector 12 through the X-ray transmissive window 13 as a detection signal X0 (S110).

[0041] The calculation unit 22 stores the detection signal X0 acquired by the dose acquisition unit 21 in the storage unit 23 as a reference dose (detection signal) (S120).

[0042] Next, the thickness of the object 100 is measured while the object 100 moves in the direction T through the space G (while passing through the space G). The calculation unit 22 calculates the thickness of the object 100 based on the detection signal Xd acquired by the dose acquisition unit 21 and the calibration curve stored in the storage unit 23 (S130). The calculation unit 22 stores the thickness calculation result in the storage unit 23 as the measurement result.

[0043] After the thickness measurement of the object to be measured is completed, the dose is measured in a state where the object to be measured is not present in the space G. The dose acquisition unit 21 acquires the X-ray dose of the X-ray generator 14 detected by the X-ray detector 12 through the X-ray transmission window 13 as a detection signal X1 (S140).

[0044] The calculation unit 22 reads out the reference dose (detection signal X0) from the storage unit 23 and compares it with the dose (detection signal X1) acquired in S140 (S150). If the difference between the reference detection signal X0 and the detection signal X1 acquired in S140 is equal to or less than a predetermined value (if the dose has not decreased by a predetermined amount) (No in S150), it determines that the contamination on the object to be measured is equal to or less than the specified level, and continues measuring the thickness of the object to be measured (S130).

[0045] If the difference between the reference dose (detection signal X0) and the dose (detection signal X1) acquired in S140 exceeds a predetermined value (if the dose has decreased by a predetermined amount) (Yes in S150), the valve control unit 24 transmits a water valve control signal w to the solenoid valve 38 to open it. The solenoid valve 38 opens the valve in response to the water valve control signal w. The water purge nozzle 36 sprays water from the water supply source 35 toward the outer surface of the X-ray transmissive window 13 to perform water purging (S160). After a predetermined time has elapsed since the water was sprayed, the valve control unit 24 transmits a water valve control signal w to the solenoid valve 38 to close it. The solenoid valve 38 closes the valve in response to the water valve control signal w, stopping the supply of water.

[0046] When the water purge in S160 is completed, the valve control unit 24 transmits an air valve control signal a to the solenoid valve 34 to open it. The solenoid valve 34 opens the valve in response to the air valve control signal a. The air purge nozzle 32 sprays air sent from the air supply valve 31 along the outer surface of the X-ray transmissive window 13 to perform air purging (S170). After a predetermined time has elapsed since the air was sprayed, the valve control unit 24 transmits an air valve control signal a to the solenoid valve 34 to close it. The solenoid valve 34 closes the valve in response to the air valve control signal a, stopping the supply of air.

[0047] In the above description, the air purge is performed after the water purge, but this is not limited to this. If the result of the determination by the calculation unit 22 in S150 is that the decrease in dose is relatively small, the water purge may be omitted and only the air purge may be performed.

[0048] However, when water purging is performed, there is a risk that the purging water will remain on the surface of X-ray transmissive window 13, which may lead to measurement errors. Therefore, when water purging is performed, it is desirable to subsequently perform air purging to remove water remaining on the surface of X-ray transmissive window 13.

[0049] In the above description, the detection signals X0 and X1 of the X-ray detector 12 are acquired before and after measuring the thickness of the object to be measured, but this is not limiting. Even during the thickness measurement of the object to be measured, air purging alone may be performed at regular intervals. It is preferable not to perform water purging during the thickness measurement of the object to be measured, as this may cause X-ray attenuation and reduce measurement accuracy.

[0050] The X-ray thickness gauge according to the embodiment has been described as having the X-ray generator 14 housed in the lower frame 11b of the housing 11 and the X-ray transparent window 13 disposed on the upper wall surface of the lower frame 11b, but is not limited to this. The X-ray generator 14 may be exposed from the frame 11b of the housing 11 and the X-ray transparent window 13 may be disposed on the upper wall surface of the X-ray generator 14. Even in this case, the arrangement and positional relationship between the air purge nozzle 32 and the water purge nozzle 36 and the X-ray transparent window 13 remains the same.

[0051] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied 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 modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0052] DESCRIPTION OF SYMBOLS 1...X-ray thickness gauge 11...housing, 11a...upper frame, 11b...lower frame, 11c...vertical frame 12...X-ray detector 13...X-ray transmission window 14...X-ray detector 20...controller 21...dose acquisition unit, 22...calculation unit, 23...storage unit, 24...valve control unit 30...purging device, 30a...air purging device, 30b...water purging device 31...air supply source, 32...air purging nozzle, 33...air pipe, 34...solenoid valve 35...water supply source, 36...water purging nozzle, 37...water pipe, 38...solenoid valve 100...steel material G...space X...X-ray a...air valve control signal w...water valve control signal Xg...X-ray generator control signal Xd...X-ray detection signal

Claims

1. An X-ray thickness gauge for irradiating a plate-shaped object to be measured with X-rays to measure the thickness of the object to be measured, comprising: - an X-ray generating unit capable of generating the X-rays; - a housing for housing the X-ray generating unit; - an X-ray transmission window disposed on a wall surface of the housing and capable of transmitting the X-rays; - an X-ray detection unit disposed to face an outer surface of the X-ray transmission window and capable of detecting the dose of the X-rays radiated through the X-ray transmission window; - an air purge device capable of injecting gas along the outer surface of the X-ray transmission window; - a liquid purge device capable of injecting liquid toward the outer surface of the X-ray transmission window; and - a control unit configured to execute at least one of control of injection of the liquid toward the outer surface of the X-ray transmission window by the liquid purge device and control of injection of the gas along the outer surface of the X-ray transmission window by the air purge device based on the dose of the X-rays detected by the X-ray detection unit before and after measurement of the thickness of the object to be measured.

2. The X-ray thickness gauge according to claim 1, wherein the measurement of the thickness of the object to be measured is performed while the object to be measured is passing between the outer surface of the X-ray transmission window and the X-ray detection unit.

3. The X-ray thickness gauge according to claim 1, wherein the control unit executes at least one of the injection control of the liquid and the injection control of the gas based on a difference value between the dose of the X-rays detected by the X-ray detection unit before measurement of the thickness of the object to be measured and the dose of the X-rays detected by the X-ray detection unit after measurement of the thickness of the object to be measured.

4. The X-ray thickness gauge according to claim 1, wherein the control unit executes the injection control of the gas after executing the injection control of the liquid.

5. The X-ray thickness gauge according to claim 1, wherein the gas is air and the liquid is water.

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