(12) United States Patent ao) Patent No.: us 6,399,915 Bi
Mori et al. (45) Date of Patent: Jun. 4,2002
(54) METHOD AND APPARATUS FOR
DETERMINING QUALITY OF WELDING AT
WELD BETWEEN WORKING MATERIAL
PIECES
(75) Inventors: Kiyokazu Mori; Yasuo Kqjima, both of Kanagawa (JP)
(73) Assignee: Nissan Motor Co., Ltd., Kanagawa (JP)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 09/526,752
(22) Filed: Mar. 16, 2000
(30) Foreign Application Priority Data
Mar. 23, 1999 (JP) 11-077505
(51) Int. CI.7 B23K 26/00
(52) U.S. CI 219/121.83
(58) Field of Search 219/121.61, 121.62,
219/121.63, 121.64, 121.83, 121.85
(56) References Cited
U.S. PATENT DOCUMENTS
5,085,509 A * 2/1992 Gaffard et al 219/121.79
5,674,415 A * 10/1997 Leong et al 219/121.64
5,847,356 A * 12/1998 Santhanam 219/121.64
5,925,268 A 7/1999 Britnell
5,961,858 A 10/1999 Britnell
6,005,717 A 12/1999 Neuberger et al.
6,018,689 A 1/2000 Kumura et al.
FOREIGN PATENT DOCUMENTS
JP 10-6051 1/1998
JP 11226766 * 8/1999 219/121.64
In a method for determining a quality of welding at a weld between working material pieces, an emission intensity of a visible light emitted from the weld during a laser welding using a laser device emitting a laser having a wavelength falling in a range of the wavelengths of near infra-red rays is detected, a first detection signal indicating the light emission intensity of the visible light is outputted, an intensity of a reflected light of the laser from the weld during the laser welding is detected, a second detection signal indicating the light intensity of the reflected light is outputted, frequencies of the first and second detection signals are analyzed and a determination is made whether a result of the laser welding falls in a favorable range of welding and an identification of a cause of welding failure of the weld if the determination that the result of the laser welding falls out of the favorable range is made on the basis of signal intensities of a first frequency component of each of the first and second detection signals lower than an arbitrary frequency in a range from 50 Hz to 200 Hz and of a second frequency component of each of the first and second detection signals higher than the arbitrary frequency.
12 Claims, 14 Drawing Sheets
