JP2017053630A - X-ray ct apparatus, and ct scanning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus and a CT scanning method that can reduce the processing time taken to test multiple specimens consecutively and have other advantages.SOLUTION: An X-ray CT apparatus 10 is equipped with an X-ray tube 11 arranged in a radiation source chamber 12, a detector 21 arranged in a detecting chamber 22 having openable doors 24a and 24b, and a shutter 44 that partitions the radiation source chamber 12 and the detecting chamber 22 from each other and transmits and intercepts X-rays radiated from the X-ray tube 11. The shutter 44 and the openable doors 24a and 24b are so configured as to operate in an interlocked way. When bringing a work W into a prescribed testing position in the detecting chamber 22 and bringing out the work W from the prescribed testing position, the shutter 44 is closed to intercept X-rays and the radiating operation of the X-ray tube 11 is continued.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an X-ray CT apparatus for nondestructive inspection of an internal structure of a test object such as a die-cast product and a CT inspection method suitable for continuously inspecting a plurality of test objects.

  2. Description of the Related Art Conventionally, an X-ray CT apparatus includes an X-ray source and a detector disposed opposite thereto, and based on an X-ray transmission image obtained by scanning an object (work) from a 360 ° rotation direction, This is an inspection device that reconstructs 3D tomographic images. For example, a medical CT apparatus is generally a gantry type in which an X-ray source and a detector rotate around a subject with a constant radius. On the other hand, for industrial use, an X-ray CT apparatus that scans a transmission image by fixing an X-ray source and rotating an object to be tested is generally used instead of a gantry type. In this type of X-ray CT apparatus, the distance between the X-ray source and the detector can be made variable, whereby the imaging magnification can be adjusted (see, for example, Patent Document 1).

JP 2006-105787 A

  By the way, the X-ray CT apparatus is provided in a room covered with an X-ray shielding wall in order to prevent the inspection worker from being exposed. The test object is set at a predetermined position between the X-ray source and the detector, and the test is performed with the door of the X-ray shielding wall being completely closed. However, an X-ray tube used as an X-ray source of a CT apparatus requires some rise time from when the power is turned on until the output is stabilized. For this reason, there has been a waste of time from when the door is closed until when imaging is actually started.

  Therefore, an object of the present invention is to provide an X-ray CT apparatus and a CT inspection method that can shorten the process time when continuously inspecting a plurality of test objects.

  In order to solve the above problems, the present invention is an X-ray CT apparatus comprising: an X-ray source; and a detector that is disposed opposite to the X-ray source and captures an X-ray transmission image of a test object, An X-ray source is disposed in a source chamber closed with an X-ray shielding wall, and the detector is disposed in an examination room closed with an X-ray shielding wall having an open / close door capable of shielding X-rays. An X-ray CT apparatus in which a chamber and the examination room are partitioned through a shutter that transmits and blocks X-rays emitted from the X-ray source.

  In the above configuration, it is preferable that the shutter and the opening / closing door are configured to perform an interlock operation in which one of the shutter and the opening / closing door does not open unless the other is closed.

  In addition, the X-ray CT apparatus may further include a loading device that loads the test object to a predetermined inspection position in the inspection chamber through the openable door.

  The X-ray CT apparatus may further include a carry-out device that carries the test object at the predetermined examination position out of the examination room through the opened door.

  Further, the X-ray CT apparatus is preferably configured such that the X-ray emission operation by the X-ray source is continued while the carry-in apparatus carries the test object to a predetermined examination position in the examination room. .

  Further, the X-ray CT apparatus is preferably configured such that the X-ray emission operation by the X-ray source is continued while the unloading apparatus unloads the test object from a predetermined inspection position in the inspection room. .

  The open / close doors are preferably provided at two locations on both sides of the X-ray shielding wall of the examination room so as to face each other in a direction orthogonal to the X-ray radiation direction from the X-ray source.

  The X-ray CT apparatus further includes a carry-in device for carrying an object into a predetermined inspection position in the inspection room through a first opening / closing door on one side of the inspection room, and the other side of the inspection room. There may be provided an unloading device for unloading the object at a predetermined inspection position in the inspection chamber through the second opening / closing door.

  The present invention also provides an X-ray source disposed in a source chamber closed with an X-ray shielding wall, a detector disposed in an examination room closed with an X-ray shielding wall, the source chamber, A predetermined inspection in the inspection room is performed through a shutter that partitions the inspection room, transmits and blocks X-rays emitted from the X-ray source, and a first open / close door on one side of the inspection room. A carry-in device for carrying in the position, a carry-out device for carrying out the object at the predetermined inspection position outside the inspection room through a second opening / closing door on the other side of the inspection room, and controlling the operation thereof. A CT inspection method performed in an X-ray CT apparatus comprising: a control means for reconstructing and calculating a tomogram of a test object; after the test object is carried into the predetermined inspection position, the control means , X-rays emitted from the X-ray source during X-ray emission operation by opening the shutter, A first step of scanning an X-ray transmission image of the test object by the detector, and when the scanning is completed, the control means closes the shutter and is emitted from the X-ray source during the X-ray emission operation. A second step of blocking X-rays, and the control means opens the second door and operates the carry-out device to carry out the inspected object out of the examination room, Immediately after the third step of closing the second opening / closing door, the control means opens the first opening / closing door, operates the loading device, and loads a new object into the predetermined inspection position. And immediately after that, the fourth step of closing the first opening / closing door, and the control means opens the shutter with the first and second opening / closing doors completely closed, and the new test object. Scanning the X-ray transmission image with respect to the first step. Repeatedly performing the steps set from a CT examination method.

  According to the present invention, the X-ray emitted from the X-ray source during the X-ray emission operation can be blocked so as not to leak into the examination room by closing the shutter that partitions the radiation source room and the examination room. Thereby, the operation of the X-ray source can be continued while the test object is carried into and / or out of the examination room. Therefore, the rise time of the output of the X-ray source during the examination process, etc. The wasted time can be eliminated.

It is a side view which shows schematic structure of a X-ray CT apparatus. It is a figure for demonstrating the reference | standard of the rotation angle position of a turntable. It is a figure for demonstrating CT imaging operation by 1st embodiment. It is a figure for demonstrating CT imaging operation by 2nd embodiment. It is a figure for demonstrating CT imaging operation by 3rd embodiment. It is a perspective view which illustrates the composition of a source room and an examination room. It is a figure for demonstrating CT imaging process flow.

  FIG. 1 is a side view showing a schematic configuration of an X-ray CT apparatus 10 according to an embodiment of the present invention. In the X-ray CT apparatus 10, an X-ray tube 11, which is an X-ray source, is disposed in the radiation source chamber 12, and an X-ray detector 21 is disposed in the examination chamber 22 so as to face the X-ray tube 11. The source room 12 and the examination room 22 are entirely shielded by X-ray shielding walls 13 and 23 made of lead or the like in order to prevent exposure of workers and the like by X-rays radiated from the X-ray tube 11. Further, the source room 12 and the examination room 22 are similarly partitioned by an X-ray shielding wall 43. The X-ray shielding wall 43 is provided with an openable / closable shutter 44 that transmits and blocks X-rays emitted from the X-ray tube 11. As will be described later, the shutter 44 can be constituted by two shutter pieces that move in opposite directions, for example.

  The X-ray tube 11 radiates cone beam-shaped X-rays horizontally toward the X-ray detector 21, thereby capturing an X-ray transmission image of the test object (hereinafter referred to as “work”) W. . In the present specification, the “X-ray emission direction” refers to the horizontal central axis direction of X-rays emitted from the X-ray tube 11 toward the X-ray detector 21 in a cone beam shape.

  In the inspection room 22, the workpiece W is set at a predetermined inspection position on a rotary table 31 disposed between the X-ray tube 11 and the X-ray detector 21. The turntable 31 is provided to be rotatable around a vertical axis orthogonal to the X-ray radiation direction. That is, when the rotary table 31 on which the workpiece W is installed rotates at a constant speed, the workpiece W can be rotated relative to the X-ray radiation direction. Thereby, it is possible to scan a plurality of X-ray transmission image data in each direction of the work W.

  A control device (not shown) provided outside controls the operation of the X-ray tube 11, the X-ray detector 21, the rotary table 31, and the like, and based on X-ray transmission image data scanned from each direction of the workpiece W. The 3D tomographic image of the workpiece W is reconstructed and calculated.

  Moreover, in this embodiment, the slide means which slide-moves the workpiece | work W on the horizontal surface of the rotary table 31 is provided. As the slide means, for example, a linear motion stage 32 on which the workpiece W can be mounted can be employed. The linear motion stage 32 can be provided on the rotary table 31 such that the radial direction passing through the rotation center axis of the rotary table 31 and the moving direction of the linear motion stage 32 coincide with each other. As will be described later, for example, when the workpiece W is long, it is possible to perform imaging by offsetting to a specific part where the presence of an internal structural defect becomes critical.

  By the way, this type of industrial X-ray CT apparatus is required to be able to inspect workpieces having various shapes and dimensions regardless of the shape of the workpiece. Conventionally, for example, when inspecting for the presence of internal defects in a long die cast product, transmission image data in the thickness direction with a relatively large amount of X-ray transmission and relatively small amount of X-ray transmission A three-dimensional tomographic image was reconstructed using the longitudinal transmission image data together. However, the inventors have found that transmission image data in the longitudinal direction with a relatively small amount of X-ray transmission information does not contribute much to the resolution of the reconstructed three-dimensional tomogram. The inventors have an idea from there, scan the workpiece W within a rotation angle range narrower than 360 °, and have sufficient resolution to withstand the practical use of nondestructive inspection based on the X-ray transmission image. The inventors have come up with the invention of a CT imaging method and a CT apparatus that can obtain a work tomographic image.

(Description of CT imaging method)
The X-ray CT apparatus 10 is used, for example, for inspecting internal defects of a die-cast cast product or the like before finely processing a car engine case part. The X-ray CT apparatus 10 of the present embodiment can cope with inspection of workpieces having various shapes, but here, the description will be generalized assuming that the shape of the target workpiece W is an elongated cylinder. 2 to 5, in order to distinguish the front side and the back side of the workpiece W, concave and convex marks are given to the back side.

  The long workpiece W is set on the rotary table 31 so that the radial direction passing through the rotation center axis of the rotary table 31 and the longitudinal direction of the workpiece W coincide with each other. Here, as shown in FIG. 2, the rotational angle position of the rotary table 31 when the thickness direction of the workpiece W (diameter direction when the workpiece is a cylinder) is orthogonal to the X-ray radiation direction A is 0 ° (reference ).

  In the first embodiment, as shown in FIG. 3, the control device is based on transmission image data scanned in a range of a predetermined rotation angle A (A> −90 °) to B (B <90 °). A tomographic image of the workpiece W is reconstructed. In this case, the range of the predetermined rotation angle is preferably −60 ° to + 60 ° or more. The right side of FIG. 3 illustrates a tomographic image when the scan rotation angle is −60 ° to + 60 °. The tomogram of FIG. 3 has a resolution that can determine the internal defect structure. However, if the scan rotation angle range is −60 ° to + 60 ° or more, the tomogram having at least a resolution higher than that of FIG. Can be obtained.

  In the second embodiment, first, the control device scans the surface side of the workpiece W while rotating the rotary table 31 from the initial position of −30 ° to the rotation angle position of + 30 ° (FIG. 4I). When the rotation angle position of the turntable 31 reaches + 30 °, the control device rotates the turntable 31 by 120 ° and scans the back side of the workpiece W while rotating the rotation table 31 from the rotation angle position of 150 ° to 210 ° ( FIG. 4 (II)). Thus, by reconstructing the tomographic image of the workpiece W based on the transmission image data obtained by scanning both surfaces of the workpiece W in a predetermined rotation angle range, the internal defect structure as shown in FIG. A resolution that can be more clearly discriminated can be obtained in a short time.

  In particular, in order to image a specific part of the long workpiece W, the X-ray CT apparatus 10 of the third embodiment is a slide unit that moves the workpiece W on the rotary table 31 in the rotational radius direction of the rotary table 31. A linear motion stage 32 is provided.

  In the third embodiment shown in FIG. 5, first, the long workpiece W is set on the rotary table 31 at an initial position in which the longitudinal direction of the workpiece W faces the direction of −30 °. At this initial position, the center of the workpiece W in the longitudinal direction is offset by a predetermined distance from the center of the rotation axis of the turntable 31 toward the first side in the longitudinal direction in order to concentrate and image a specific part of the workpiece W. And is held on the linear motion stage 32.

  The control device scans the surface side of the specific part of the workpiece W while rotating the rotary table 31 from the initial position from −30 ° to the rotation angle position of + 30 ° (FIG. 5 (I)). When the rotation angle position of the rotary table 31 reaches + 30 °, the control device drives the linear motion stage 32 to move the center of the workpiece W to the second side opposite to the first side in the longitudinal direction (FIG. 5). (II)). Thereby, the rotation locus | trajectory in which the front-end | tip of the elongate workpiece | work W interferes with others becomes small.

  In this state, the control device rotates the turntable 31 by 120 ° (FIG. 5 (III)). When the rotational angle position of the rotary table 31 reaches + 150 °, the control device drives the linear motion stage 32 to move the workpiece W to the first side in the longitudinal direction by a predetermined distance (FIG. 5 (IV)). In other words, the center of the workpiece W in the longitudinal direction is offset again from the rotation axis center of the rotary table 31 to the first side. The control device scans the back side of the specific part of the workpiece W while rotating the rotary table 31 from the rotation angle position of 150 ° to 210 ° (FIG. 5 (V)).

  Thus, the tomographic image of the workpiece W can be reconstructed based on the transmission image data obtained by offsetting the long workpiece W and scanning it within a predetermined rotation angle range. As a result, a three-dimensional tomographic image having sufficient resolution that can determine the internal defect structure of a specific part of the workpiece W can be obtained in a short time.

  According to the CT imaging method described above, since the workpiece is scanned within a rotation angle range of, for example, 120 °, which is narrower than 360 °, the transmission time for transmitting images can be shortened compared to the conventional method. Further, by using transmission image data with a small amount of information with a narrow scan angle, it is possible to reduce the time required to reconstruct a tomogram and the processing load on the computer. Moreover, in the workpiece | work in which the exposure amount of a X-ray is restrict | limited, the exposure amount can also be suppressed.

  Further, the specific part of the long workpiece can be concentrated and imaged by the offset scanning method of the present embodiment. At the same time, by moving the center of the workpiece to the center of the rotary table by the linear motion stage 32, the interference range when the workpiece is rotated can be reduced. As a result, the examination room can be designed in a compact manner, leading to savings in material costs for the X-ray shielding wall using lead or the like and reduction in equipment costs for the entire apparatus.

(Explanation of CT imaging process flow)
Next, a CT imaging process flow for the purpose of improving time efficiency when a plurality of workpieces are continuously inspected with one X-ray CT apparatus will be described.

  Similar to the above-described embodiment, for example, as shown in FIG. 6, the X-ray tube 11 is arranged in the radiation source chamber 12 closed by the X-ray shielding wall 13. Further, the X-ray detector 21 and the rotary table 31 are disposed in the examination room 22 that is blocked by the X-ray shielding wall 23. The X-ray shielding wall 43 that partitions the radiation source chamber 12 and the examination chamber 22 is provided with an openable / closable shutter 44 that transmits and blocks X-rays. The shutter 44 includes two shutter pieces 44a and 44b that open and close to the left and right opposite to each other.

  The X-ray shielding wall 23 of the inspection chamber 22 is provided with opening / closing doors 24 a and 24 b that allow the work W to be carried into and / or out of the predetermined inspection position of the rotary table 31. As shown in FIG. 7, in the direction orthogonal to the X-ray emission direction, it is preferable that opening / closing doors 24a and 24b are respectively provided at two positions on both sides of the X-ray shielding wall of the examination room 22 to face each other. The shutters 44a and 44b and the open / close door 24a are in an interlocking operation so that the other does not open unless one is closed. Similarly, the shutters 44a and 44b and the open / close door 24b are also in an interlocking operation.

  The X-ray CT apparatus 10 includes a workpiece loading device 25 that loads a workpiece to an inspection position in the inspection chamber 22 through an open / close door 24a that is open on one wall surface side. Further, the X-ray CT apparatus 10 includes a work unloading device 26 that unloads the work at the inspection position out of the inspection chamber 22 through the open / close door 24b opened on the other wall surface side.

  An example of a specific work carry-in / out operation by the X-ray CT apparatus 10 will be described with reference to FIG.

  First, after the workpiece W is set at a predetermined inspection position, the control device opens the shutters 44a and 44b. As a result, a transmission image of the workpiece W is captured by X-rays from the X-ray tube 11 (see FIG. 6) during the X-ray emission operation (FIG. 7 (I)).

  When the imaging is completed, the control device closes the shutters 44a and 44b and blocks X-rays. At this time, the X-ray emission operation (power-on state) of the X-ray tube 11 (see FIG. 6) continues, but since the source chamber 12 is sealed, the X-rays do not leak to the outside and the shutter 44a. , 44b is closed, and no X-rays leak into the examination room 22.

  Then, the control device releases the interlock, opens the open / close doors 24a and 24b, operates the work carry-out device 26, and carries the inspected work W from the inspection position to the outside through the open / close door 24b (FIG. 7). (II)). Immediately thereafter, the control device closes the open / close door 24b, and carries a new workpiece W through the open / close door 24a to a predetermined inspection position (FIG. 7 (III)).

  The control device closes the open / close door 24a after the work W is carried in. The interlock is released with the two open / close doors 24a and 24b completely closed, and the shutters 44a and 44b of the control device are opened. As described above, since the power-on state of the X-ray tube 11 continues and the X-ray radiation operation is stable, imaging of a new workpiece W is started immediately after the shutters 44a and 44b are opened. (FIG. 7 (IV)).

  According to such a CT imaging process, the X-ray emission operation by the X-ray tube 11 is continued even in the process of bringing the workpiece into and out of the inspection position. Therefore, it is possible to eliminate the so-called rise time that was conventionally required until the X-ray radiation output is stabilized. Moreover, the work loading / unloading time can be shortened by arranging the workpiece loading / unloading device 25 and the workpiece loading / unloading device 26 so as to face each other. Further, the imaging time can be shortened by making the scan angle for imaging narrower than 360 °. By accumulating the time reduction of each of these processes, the inspection time per work can be significantly shortened compared to the conventional method, and the time efficiency of the inspection process can be improved.

DESCRIPTION OF SYMBOLS 10 X-ray CT apparatus 11 X-ray tube 12 Source room 13 X-ray shielding wall 21 X-ray detector 22 Inspection room 23 X-ray shielding walls 24a and 24b Open / close door 25 Work carry-in apparatus 26 Work carry-out apparatus 31 Rotary table 32 Direct motion Stage 43 X-ray shielding wall 44 Shutter

Claims (9)

An X-ray CT apparatus comprising: an X-ray source; and a detector that is disposed opposite to the X-ray source and captures an X-ray transmission image of a test object,
The X-ray source is disposed in a source chamber closed by an X-ray shielding wall;
The detector is disposed in an examination room closed by an X-ray shielding wall having an opening / closing door capable of shielding X-rays;
An X-ray CT apparatus in which the source room and the examination room are partitioned through a shutter that transmits and blocks X-rays emitted from the X-ray source.   The X-ray CT apparatus according to claim 1, wherein the shutter and the opening / closing door are configured to perform an interlock operation in which one of the shutter and the opening / closing door does not open unless the other is closed.   The X-ray CT apparatus according to claim 1, further comprising a carry-in device for carrying a test object into a predetermined inspection position in the inspection chamber through the openable door.   The X-ray CT apparatus according to any one of claims 1 to 3, further comprising a carry-out device that carries the test object at the predetermined inspection position out of the inspection room through the openable door.   The X-ray CT apparatus according to claim 3, wherein the X-ray emission operation by the X-ray source is continued while the carry-in apparatus carries a test object to a predetermined examination position in the examination room. .   The X-ray CT apparatus according to claim 4, wherein the X-ray emission operation by the X-ray source is continued while the unloading apparatus unloads a test object from a predetermined inspection position in the inspection room. .   The opening / closing door is provided at two locations on both sides of the X-ray shielding wall of the examination room so as to face each other in a direction orthogonal to the X-ray radiation direction from the X-ray source. The X-ray CT apparatus described.   Through a first opening / closing door on one side of the inspection room, a loading device for carrying an object to a predetermined inspection position in the inspection room, through a second opening / closing door on the other side of the inspection room, The X-ray CT apparatus according to claim 7, further comprising an unloading device that unloads an object at a predetermined inspection position in the inspection room. An X-ray source disposed in a source chamber blocked by an X-ray shielding wall, a detector disposed in an examination room blocked by an X-ray shielding wall, and the source chamber and the examination chamber are partitioned; A carry-in device for carrying an object into a predetermined inspection position in the inspection room through a shutter that transmits and blocks X-rays emitted from the X-ray source and a first opening / closing door on one side of the inspection room. An unloading device for unloading the object at the predetermined inspection position to the outside of the inspection room through the second opening / closing door on the other side of the inspection room, and a tomographic image of the inspection object by controlling these operations A CT inspection method performed in an X-ray CT apparatus comprising:
After the test object is carried into the predetermined inspection position, the control means opens the shutter and emits the X-ray emitted from the X-ray source during the X-ray emission operation by the detector. A first step of scanning an X-ray transmission image of the specimen;
When the scanning is finished, the control means closes the shutter and shuts off the X-rays emitted from the X-ray source during the X-ray emission operation;
The control means opens the second door, operates the carry-out device, carries out the inspected object to the outside of the inspection chamber, and immediately closes the second door. Three steps,
The control means opens the first open / close door, operates the carry-in device to carry a new object into the predetermined inspection position, and immediately after that closes the first open / close door. Steps,
The control means opens the shutter in a state where the first and second doors are completely closed, and scans the X-ray transmission image for the new test object. The CT inspection method is repeatedly executed.