JP2006250713A - Method and apparatus for detecting necking of molded object after press molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a necking detecting method for rapidly and certainly detecting whether necking is caused in a molded object after press molding, and a necking detector therefor. <P>SOLUTION: The surface to be detected of the molded object is photographed at the different points of time by an infrared camera from the point of time when the in-plane to be detected of the molded object is heated by a current supply heating system for allowing a current to flow to the in-plane of the molded object from one side thereof to the other side thereof and the difference between the images mutually obtained by photographing the in-plane of the molded object at the different points of time is taken to calculate the temperature rising quantities after the start of heating of the respective parts of the molded object while an abnormal part is detected on the basis of the temperature rising quantities. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for quickly and reliably detecting whether or not necking has occurred in a molded body after press molding.

  In a press line for manufacturing automobile parts and the like from a metal plate by press forming, a defect called necking may occur in the formed body after press forming. As shown in FIG. 7, necking is a portion that has been subjected to unstable plastic deformation from the maximum stress to fracture in the relationship between strain and tensile stress of the metal material. Therefore, the abnormal part caused by necking compared to the normal part is a part that requires a larger amount of processing during press molding. The abnormal part caused by such necking is a local thin part including minute cracks, but it is a problem that cannot be overlooked as it is. ing.

However, the press line is highly productive, and the above-described abnormal parts are difficult to detect visually, so that they may be revealed during the painting process or the actual vehicle test. In order to prevent such a situation, it is necessary to arrange many skilled inspectors on the press line for inspection, but the feasibility is low.
Therefore, a heating type detection device has been proposed that detects whether or not necking has occurred in the molded body after the molded body after press molding is once taken out of the press device and heated by heating means. (Patent Document 1).

The panel crack and thickness change part detection device of Patent Document 1 is a hot air generator that uniformly blows and heats hot air from one side to the corner of the panel, and an infrared that detects the temperature distribution on the other side of the corner. When a detector such as a temperature detector and an image processing device are provided, and a defect such as a crack or necking has occurred in the corner, heat is transferred by the amount that the plate thickness has decreased or the corner has penetrated. Therefore, the defect portion is detected by increasing the temperature of the portion where the crack or necking has occurred to the portion where the other plate thickness is not reduced.
JP-A-4-184248

However, in the abnormal part detection device of Patent Document 1, hot air is blown to heat the object, and the temperature distribution of the panel is detected after a certain period of time, so that defects such as cracks and necking occur quickly in the corner part. There is a problem that it is difficult to detect whether or not.
Moreover, in the abnormal part detection apparatus of patent document 1, since it does not mention at which time point the temperature distribution of a panel is detected from the time of starting a heating, when a detection time becomes late, it becomes difficult to detect a defect. There was a problem.

  An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method and an apparatus for quickly and reliably detecting whether or not necking has occurred in a molded product after press molding. To do.

The inventor diligently studied about the necking detection technology of a molded body, and found that the above problem can be solved by detecting the amount of temperature increase immediately after the start of heating using an infrared camera with a short imaging interval. It came to be accomplished.
That is, the present invention is as follows.
1. A heating method of the molded body after press molding is a necking detection method, in which the heating difference between the abnormal part and the normal part is revealed by an energizing heating system in which current flows from one side to the other side of the surface of the molded body, After the inside of the detection surface is heated, the surface to be detected of the molded body is imaged at different time points by an infrared camera, and the difference between the images obtained at different time points is taken to start heating each part of the molded body A method for detecting necking after press forming, wherein an abnormal portion is detected based on the amount of temperature rise.
2. Above 1. The necking detection method according to claim 1, wherein a current-carrying terminal having flexibility is brought into contact with one side and the other side in the surface of the molded body to detect an abnormal portion. .
3. Above 1. Or 2. The necking detection method according to claim 1, wherein the imaging interval of the infrared camera is 1 to 10 ms.
4). Above 1. ~ 3. In the necking detection method according to any one of the above, after the press forming, the isothermal curve is displayed around the image of the abnormal part based on the image signal from the infrared camera, and the abnormal part is detected. Necking detection method.
5. A heating type necking detection device for a molded body after press molding, wherein the current-carrying terminal for flowing current from one side of the surface of the molded body to the other side and the detected surface of the molded body are imaged at different points in time. An infrared camera, an image processing device that processes an image signal from the infrared camera, and an image display device that displays a result processed by the image processing device, and the image processing device captures images at different points in time. The difference between the images obtained in this way is taken to determine the amount of temperature rise after the start of heating of each part of the molded body, and an abnormal portion is detected based on the amount of temperature rise. Necking detection device after press molding.

  ADVANTAGE OF THE INVENTION According to this invention, it can be detected rapidly and reliably whether necking has generate | occur | produced in the molded object after press molding.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a characteristic diagram illustrating the method of the present invention, and FIG. 2 is a graph illustrating the temperature measurement principle of the method of the present invention. FIG. 3 is a conceptual diagram of an apparatus suitable for carrying out the present invention.
In FIG. 1, t0, t1, t2, and t3 indicate the time points when the surface of the molded body after press molding is imaged with an infrared camera. a shows the temperature rise in the abnormal part immediately after the start of heating, and b shows the temperature rise in the normal part just after the start of heating. The temperature rise amount a in the abnormal part immediately after the start of heating is
Larger than the temperature rise b in the normal part immediately after the start of heating.

  In other words, the abnormal portion having a locally thin thickness has a higher electrical resistance than a normal portion having a small thickness, and therefore, the rate of temperature rise immediately after the start of heating by the energization heating method is high. However, when a certain period of time has passed immediately after the start of heating, there is no difference in the temperature increase rate between the abnormal part and the normal part. Therefore, the present invention is characterized in that, as shown in FIG. 1, a temperature increase amount immediately after the start of heating of each portion of the molded body is obtained, and an abnormal portion is detected based on the temperature increase amount. In this case, after the imaging time t1, the difference in temperature increase rate between the abnormal part and the normal part is small. Note that even after t3, the surface of the molded body can be imaged at the imaging interval Δt.

Here, as shown in FIG. 2, since there is a one-to-one relationship between the amount of infrared radiation radiated from the object surface and the temperature of the object surface, the molded object is imaged by imaging the surface of the molded object with an infrared camera. The temperature of each part can be detected.
The reason for taking the difference between images obtained at different points in time is that the image obtained by taking an infrared camera includes a temperature disturbance such as a high temperature body or illumination light in a place where necking detection of the molded body is performed, oil or Since emissivity disturbances such as surface properties are included, by removing differences between images, temperature disturbances and emissivity disturbances are removed, and only infrared rays from each part of the molded body are detected, and each of the molded body is detected. This is because the temperature rise amount of the portion is obtained accurately.

For example, as shown in FIGS. 3 (a) and 3 (b), the compact after completion of press molding for detecting necking is arranged in contact with the lower terminals of the current-carrying terminals 4A and 4B having flexibility. The surface to be detected is uniformly heated in the plane between the energization terminals 4A and 4B. An infrared camera 1 that can capture images at different points in time is arranged opposite to the detection surface between the energization terminals 4A and 4B.
In FIG. 3, reference numeral 2 denotes an image processing device that processes an image, and 3 denotes an image display device such as a CRT that displays the result of the image processing device 2. In addition, 4A, 4B shows the energization terminal which consists of metal chain blinds as an example, 5 shows the direction through which an electric current flows. Instead of a metal chain, a copper wire mesh tape, an energizing copper roller, or the like may be used. W1 is a normal part, and W2 is an abnormal part whose thickness is locally reduced by necking.

By the way, a steel plate is often used as a metal plate for press forming. The thermal conductivity of the steel sheet is 50 W / m · K, which is as large as about 50 times the thermal conductivity of concrete or silicon. For this reason, after starting heating, it is important to image the surface of the molded body with an infrared camera when the difference in temperature increase between the abnormal part and the normal part does not become small.
Therefore, the imaging interval Δt of the infrared camera is preferably set to 1 to 10 ms. This is because the thermal conductivity of the metal plate is larger than that of concrete, silicon, or the like, so that when the imaging interval Δt is larger than 10 ms, the image interval Δt becomes excessive, and the temperature distribution is caused by the heat conduction in the width direction. Uniformity may occur, and it may not be possible to reliably detect whether or not necking has occurred in the molded body after press molding. On the other hand, when the imaging interval Δt of the infrared camera is smaller than 1 ms, the imaging interval Δt is too small, the amount of temperature rise in each part of the molded body is less than the temperature detection accuracy of the infrared camera, and the molded body after press molding is completed. It may not be possible to quickly detect whether or not necking has occurred. Therefore, the imaging interval Δt of the infrared camera is preferably set to 1 to 10 ms. For example, when a high-performance camera (for example, an infrared camera manufactured by CEDIP) that can shorten the imaging interval Δt is used as an infrared camera, imaging can be performed with the imaging interval Δt set to 10 ms or less.

As described above, according to the necking detection method of the present invention, by appropriately setting the imaging interval Δt of the infrared camera that can shorten the imaging interval Δt, the detected surface is heated by the energization heating method. In combination, it is possible to detect whether or not necking has occurred in the compact after press molding quickly and reliably.
The necking detection apparatus according to the embodiment of the present invention shown in FIG. 3A includes energization terminals 4A and 4B for flowing current from one side to the other side in the surface of the molded body W, and the molded body W. An infrared camera 1 capable of imaging a detection surface at different points in time, an image processing device 2 that processes an image signal from the infrared camera 1, and an image display device 3 that displays a result processed by the image processing device 2 are provided. ing. The energizing terminals 4A and 4B are preferably flexible terminals such as metal mesh belts and copying rollers. This is because the lower end portion of the energization terminal can be uniformly brought into contact with the molded body W following the surface shape of the molded body W.

  Further, the image processing apparatus 2 obtains a temperature rise amount immediately after the start of heating of each part of the molded body W by taking a difference between images obtained at different time points, and detects an abnormal portion based on the temperature rise amount. Is configured to do. For example, as shown in FIG. 4, the image processing apparatus 2 receives the image signal from the infrared camera 1 by the image input unit 4 and temporarily holds it in the first image holding unit. When the next image signal is received, the image in the first image holding unit is moved to the second image holding unit, and at the same time, the next image is held in the first image holding unit. Subsequently, the image difference calculation unit calculates an image difference between the image in the second image holding unit and the image in the first image holding unit, and sends the image difference data to the abnormal part extraction / identification unit. The abnormal part extraction / identification part extracts and identifies an abnormal part based on the image difference data, and sends the result as an image signal to the image display device 3 such as a CRT. Therefore, the surface of the molded body W can be imaged at different time points by the infrared camera 1, and the difference in the obtained images can be taken to determine the amount of temperature rise of each part of the molded body W. Reference numeral 9 denotes an image data storage unit.

According to the necking detection device having such a configuration, images as shown in FIGS. 5 and 6 can be displayed quickly and reliably on the screen of the image display device 3. In FIG. 5, 12 indicates an image of a normal part, and 13 indicates an image of an abnormal part. Moreover, in FIG. 6, 14 shows an isothermal curve.
In the present invention, it is preferable to detect the abnormal portion 13 by displaying an isothermal curve 14 around the image 13 of the abnormal portion based on the image signal captured by the infrared camera 1 as shown in FIG. The reason for this is whether or not necking has occurred in the molded body W after press molding by displaying the isothermal curve 14 like a ripple around the abnormal portion 13 as well as the abnormal portion 13 on the screen. This is because the inspector can be surely notified.

  Further, in the present invention, in order to increase the temperature rising rate of the surface to be inspected of the molded body, when the interval between the one side and the other side where the lower end portions of the energizing terminals are in contact is narrowed, the molded body after press molding is completed. It is also possible to detect whether or not necking has occurred in the molded body after press molding while continuously moving W.

It is a characteristic view explaining the method of this invention. It is a graph explaining the principle of the temperature measurement by the method of this invention. It is a conceptual diagram of an apparatus suitable for implementing the present invention. It is a conceptual diagram of the arithmetic processing unit suitable for implementing this invention. It is a conceptual diagram of the image displayed by this invention. It is another conceptual diagram of the image displayed by the present invention. It is a characteristic view explaining the generation | occurrence | production mechanism of necking.

Explanation of symbols

t0, t1, t2, t3 First to fourth imaging time points Δt Imaging interval a Temperature rise in abnormal part b Temperature rise in normal part 1 Infrared camera 2 Image processing device 3 Image display device 4A, 4B Energizing terminal 5 Current Flow direction W Molded body W1 Normal part W2 Abnormal part 12 Normal part image 13 Abnormal part image 14 Isothermal curve

Claims (5)

It is a heating method necking detection method of a molded body after press molding,
The detected surface of the molded body from the time when the detected surface is heated by revealing the heating difference between the abnormal part and the normal part by an energization heating method in which a current flows from one side to the other side in the surface of the molded body. Are picked up at different points of time by an infrared camera, and the difference between the images obtained at different points in time is taken to determine the amount of temperature rise after the start of heating of each part of the molded body. A method for detecting necking after press forming, characterized in that:   The necking detection method according to claim 1, wherein a current-carrying terminal having flexibility is brought into contact with one side and the other side in the surface of the molded body, and an abnormal portion is detected. Necking detection method.   The necking detection method according to claim 1 or 2, wherein an imaging interval of the infrared camera is 1 to 10 ms.   The necking detection method according to any one of claims 1 to 3, wherein an isothermal curve is displayed around an image of an abnormal part based on an image signal from the infrared camera to detect the abnormal part. Necking detection method after press forming.   A heating type necking detection device for a molded body after press molding, wherein the current-carrying terminal for flowing current from one side of the surface of the molded body to the other side and the detected surface of the molded body are imaged at different points in time. An infrared camera, an image processing device that processes an image signal from the infrared camera, and an image display device that displays a result processed by the image processing device, and the image processing device captures images at different points in time. The difference between the images obtained in this way is taken to determine the amount of temperature rise after the start of heating of each part of the molded body, and an abnormal portion is detected based on the amount of temperature rise. Necking detection device after press molding.

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