JP7448139B2 - X-ray CT imaging method and X-ray CT imaging device for automobile body - Google Patents

Description

The present invention relates to an X-ray CT imaging method and an X-ray CT imaging apparatus for an automobile body.

There are many welds and joints in an automobile body, and there is technology that can check the adhesion of the plates, the caulking of rivets, the spread of adhesive, the welding status of spot welding, etc. in three-dimensional images. It has been demanded. The internal condition of welds and joints cannot be determined by visual inspection. Therefore, it is conceivable to obtain a three-dimensional image of the interior using X-ray CT technology.

As shown in Patent Documents 1 and 2, normal X-ray CT imaging is performed by fixing an X-ray source and a detector facing each other and rotating a workpiece placed between them by 360 degrees. However, when the workpiece is large, such as an automobile body, it is impossible to rotate it 360 degrees. Therefore, a technique is required to take X-ray CT images of each part while keeping the workpiece fixed.

Note that Patent Document 3 describes a device that rotates a set of an X-ray source and a detector while keeping a workpiece fixed. However, in order to locally inspect welds, joints, etc. of an automobile body using this method, it is necessary to rotate the X-ray source or detector within a narrow space inside the body. Therefore, such a photographing method cannot be adopted.

Japanese Patent Application Publication No. 2007-163254 Japanese Patent Application Publication No. 2008-224692 Japanese Patent Application Publication No. 2006-023187

Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to provide an X-ray CT scan of an automobile body that can confirm the internal condition of local parts such as welds and joints of an automobile body as a three-dimensional image. An object of the present invention is to provide an imaging method and an X-ray CT imaging device.

In order to solve the above-mentioned problems, the method of X-ray CT imaging of an automobile body of the present invention involves inserting a detector inside the imaging region of the automobile body and supporting it so that it does not move relative to the automobile body. The feature is that an X-ray source placed outside the area to be imaged is rotated while irradiating X-rays toward the area to be imaged, and the resulting image of the area to be imaged is reconstructed to obtain a three-dimensional image of the area to be imaged. That is.

Note that the X-ray source is preferably rotated in a plane parallel to the screen of the detector, and the angle at which the X-ray source is rotated is preferably 180 degrees or more.

Furthermore, the X-ray CT imaging apparatus for an automobile body according to the present invention, which has been made to solve the above-mentioned problems, has a detector support means for inserting the detector inside the imaging region of the automobile body and supporting it so that it does not move relative to the automobile body. a detector supported by the detector support means; an X-ray source support means for supporting and rotating the X-ray source outside the imaging region of the car body; The device is characterized by comprising an X-ray source that irradiates X-rays toward the site.

Note that it is preferable that both the detector support means and the X-ray source support means are robot arms. Further, it is preferable that the X-ray source support means is rotated using rotation of a sixth axis of the robot.

According to the present invention, the detector is inserted and fixed inside the imaged area of the car body, and the X-ray source is rotated outside the imaged area of the car body. It is possible to check the internal situation of local parts such as joints and joints as a three-dimensional image.

Further, by using a configuration in which the detector is supported using a robot arm and the X-ray source is rotated using the robot arm, accuracy and practicality can be improved.

FIG. 2 is a diagram explaining the principle of an X-ray CT imaging method. FIG. 3 is an explanatory diagram of an image taken by a detector. FIG. 2 is an explanatory diagram of an embodiment of an X-ray CT imaging method. FIG. 3 is an explanatory diagram of a state in which the rotation angle of the X-ray source is limited. FIG. 3 is an explanatory diagram of an image taken by a detector and a reconstructed image. FIG. 1 is an explanatory diagram showing an embodiment of an X-ray CT imaging device. FIG. 3 is an explanatory diagram of the positional relationship between an X-ray source and a detector. It is an explanatory view of other embodiments. FIG. 3 is an explanatory diagram of screen alignment of a master image and a photographed image. FIG. 3 is a diagram showing criteria for determining quality. It is a drawing of a rivet connection part.

FIG. 1 is an explanatory diagram of the principle of the X-ray CT imaging method of the present invention. Reference numeral 10 denotes an automobile body, and in this figure, a joint 13 where a steel plate 11 and a resin member 12 are bonded together with an adhesive is shown as an imaged part. Reference numeral 14 denotes a detector inserted into the inside of the imaging site, which is supported by, for example, a robot arm, as will be described later, and fixed to the car body 10 so as not to move.

Reference numeral 15 denotes an X-ray source placed outside the imaged region of the automobile body 10. The X-ray source 15 rotates as shown in the figure and irradiates X-rays toward the junction 13, which is the imaging site, to perform X-ray CT imaging. It is preferable that the rotation center axis 16 of the X-ray source 15 is perpendicular to the screen 17 of the detector 14. In other words, it is preferable that the X-ray source 15 is rotated in a plane parallel to the screen 17 of the detector 14. . It is preferable that the rotation center axis 16 coincides with the joint portion 13, which is the imaging site.

When X-ray CT imaging is performed in this manner, a 360-degree image of the joint 13 sandwiched between the steel plate 11 and the resin member 12 is formed into a shape centered on the imaging center O of the detector 14, as shown in FIG. Being photographed. The technique of reconstructing a three-dimensional image of the same object from X-ray CT images taken from various angles is well known and can be implemented using a commercially available program.

When photographing the joint 13, it is possible to obtain an image of a circular photographing range centered on the target joint center. The content of the joint 13 is a joining method such as an adhesive, spot welding, or rivet joining, as will be described later. This part can be inspected. From the captured image centered on this joint 13, it is determined whether it is OK or NG. The determination method is often to compare a normal captured image with a captured image of the part of the product to be inspected. An example of an adhesive case is shown in FIG. 9, which will be described later.

As shown in FIG. 3, the detector 14 has to be inserted into a narrow space inside the car body 10, but the X-ray source 15 can be rotated 360 degrees within the space outside the car body 10. In many cases it is possible to do so. However, as shown in FIG. 4, the region to be imaged is close to a bent portion of the automobile body 10, and the X-ray source 15 may not be able to be rotated 360 degrees due to interference with the automobile body 10. The photographed image in such a case is shown in FIG. 5, but if the angle of rotation of the X-ray source 15 can be set to 180 degrees or more, it is possible to reconstruct a three-dimensional image of the object. be. However, if the rotation is less than 180 degrees, the reconstructed three-dimensional image will become unclear, so it is preferable to rotate the rotation by at least 180 degrees.

FIG. 6 is an explanatory diagram showing an embodiment of the X-ray CT imaging apparatus of the present invention. In addition to the above-described detector 14 and X-ray source 15, the X-ray CT imaging apparatus also includes a detector support means 20 for inserting and supporting the detector 14 inside the photographed region of the automobile body 10, and a detector support means 20 for supporting the detector 14 by inserting it inside the photographed region of the automobile body 10. The X-ray source support means 21 supports and rotates the X-ray source 15. These can be designed and manufactured individually, but in practice it is preferable to use a robot arm as shown in the figure.

The robot arm of the first robot used as the detector support means 20 supports the detector 14 inside the imaging region, and the robot arm of the second robot used as the X-ray source support means 21 supports the detector 14 outside the imaging region. Rotate the source 15. At this time, as shown in FIGS. 6 and 7, it is preferable that the center of the detector 14, the center of the imaging region, and the rotation center axis of the X-ray source 15 coincide.

The first robot and the second robot each have teaching coordinates, and are taught to have the positional relationship shown in FIG. 6. The teaching coordinates can be taken out from the controller of the robot, and the rotation radius r of the X-ray source 15 can be determined from the installation offset amount of the X-ray source 15. From the teaching coordinates, the A dimension (distance from the center of the detector 14 to the center of the imaged area) and the B dimension (distance from the center of the imaged area to the rotation center of the X-ray source 15) can be found, so as shown in FIG. The amount of deviation R from the center of the detector 14 to the projected image can be determined. These values are input to the reconstruction program as necessary parameters when reconstructing a three-dimensional image of the object from the X-ray CT image.

Most of the robots currently used in industry are six-axis robots, the sixth axis of which is used as the detector support means 20 and the X-ray source support means 21. Although each robot is taught to take the positional relationship shown in FIG. 6, its stopping accuracy is not high. The robot arm of the first robot used as the detector support means 20 only supports the detector 14 and therefore does not require high positional accuracy, but the robot arm of the second robot used as the X-ray source support means 21 The positional accuracy of is important.

However, since the rotation of the sixth axis is rotation of only one axis, the rotation accuracy is sufficiently high. Therefore, even if the positional accuracy of the sixth axis is not sufficient, the rotation of the X-ray source 15 by the sixth axis itself can be performed with high precision, and there will be no major hindrance to implementing the present invention. do not have.

Note that it is also possible to tilt the central axis of the X-ray source 15 with respect to the rotational central axis of the X-ray source 15, as shown in FIG. In this case, the tilt angle is input into a program for reconstructing a three-dimensional image.

Next, image alignment and quality determination will be explained with reference to FIGS. 9 and 10. Here, an example is shown in which the shape of the adhesive at a certain joint is inspected by X-ray CT photography. The master image drawn on the left side of FIG. 9 shows the regular shape of the adhesive at the bonded portion. On the other hand, in the photographed image drawn on the right side of FIG. 9, the shape and angle of the adhesive are shifted from the master image. As shown in the lower part of FIG. 9, these images are superimposed, and the coordinates are rotated and enlarged/reduced to obtain the image shown in FIG. 10.

As shown by broken lines in FIG. 10, the MAX and MIN ranges of the adhesive are set on both sides of the outline of the master image, and if the actual image taken falls within these ranges, it is a good product. However, as shown in the figure, if a part of the adhesive protrudes beyond the MAX range of the adhesive or conversely does not reach the MIN range, it can be automatically determined as a defective product.

By performing X-ray CT imaging using a robot in this manner, it becomes possible to automatically inspect many welds, joints, etc. of the automobile body 10. Since these are areas that have conventionally been difficult to inspect, the present invention has high practical value.

In the above-described embodiment, the photographed region was a joint, but it goes without saying that the present invention can also be applied to a riveted joint or a welded region, as shown in FIG. Internal cracks may also occur in rivet joints as shown on the right side of FIG. 11, and according to the present invention, such internal defects can also be confirmed as a three-dimensional image.

As explained above, according to the present invention, it is possible to accurately confirm the internal conditions of localized parts such as welds and joints of an automobile body, which were difficult to inspect in the past, as three-dimensional images. , can contribute to improving the quality of automobile bodies.

10 Automobile body 11 Steel plate 12 Resin member 13 Joint portion 14 Detector 15 X-ray source 16 Rotation center shaft 17 Detector screen 20 Detector support means 21 X-ray source support means

Claims (6)

The detector is inserted inside the area to be imaged on the car body and supported so that it does not move relative to the car body , and the X-ray source placed outside the area to be imaged on the car body is rotated to emit X-rays towards the area to be imaged. An X-ray CT imaging method for an automobile body, characterized in that a three-dimensional image of the imaging region is obtained by irradiating the imaging region and reconstructing the obtained image of the imaging region. 2. The method for X-ray CT imaging of an automobile body according to claim 1, wherein the X-ray source is rotated in a plane parallel to a screen of a detector. 3. The method for X-ray CT imaging of an automobile body according to claim 1, wherein the angle at which the X-ray source is rotated is 180 degrees or more. A detector support means for inserting a detector inside an imaged area of a car body and supporting it so that it does not move relative to the car body , a detector supported by the detector support means, and an X-ray source outside the imaged area of the car body. An automobile body comprising: an X-ray source support means for supporting and rotating; and an X-ray source supported by the X-ray source support means and rotating while emitting X-rays toward a region to be imaged. X-ray CT imaging device. 5. The X-ray CT imaging apparatus for an automobile body according to claim 4, wherein the detector support means and the X-ray source support means are both robot arms. 6. The X-ray CT imaging apparatus for an automobile body according to claim 5, wherein the X-ray source support means is rotated using rotation of a sixth axis of a six-axis robot.

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