| 摘要 |
PURPOSE:To detect a true position of a weld zone, and also to detect the position in the same way even after cutting of a bead by detecting a position of the weld zone from a surface temperature distribution in the vicinity of the weld zone. CONSTITUTION:A lens 9 and an infrared ray detector 10 are placed so that two very small areas in the vicinity of a weld zone 3 form an image on each infrared ray detector 10. In this state, voltage signal outputs VA, VB corresponding to a surface temperature of a point A and a point B of positions on the surface of an electric welded tube 4 are obtained from the infrared ray detector 10. The voltage signal outputs VA, VB are proportional to infrared ray radiation quantity of the positions A, B on the electric welded tube 4, the surface temperature of the electric welded tube 4 has a temperature distribution being higher enough than the ambient temperature, and the highest temperature position O is on the weld zone 3. Accordingly, a shift of the center position of the electric welded tube 4 for forming an image on the infrared ray detector 10 is found from the polarity of VB-VA by a signal processing part 6, and also a shift quantity from the highest temperature position is found from the amplitude of VB-VA. |
