Welding gun and methods conducted using the same

• US 6,531,674 B2
• Filed: 08/03/2001
• Issued: 03/11/2003
• Est. Priority Date: 12/01/1998
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Suita, Kazutsugu
• Primary Examiner(s): Dunn, Tom
• Assistant Examiner(s): DUNN, COLLEEN P
• Application Number:
  US09/920,841
• Publication Number:
  US 20010045413A1
• Time in Patent Office: 585 Days
• Field of Search: 219/109, 219/170, 219/86.41, 219/91.1, 73/17.9, 73/10.1
• US Class Current: 219/86.41
• CPC Class Codes: B23K 11/10 Spot welding; Stitch welding
• CPC Class Codes: B23K 11/253 the measured parameter being a displacement or a position
• CPC Class Codes: B23K 11/311 the actuating device comprising an electric motor
• CPC Class Codes: B23K 11/315 with one electrode moving on a linear path

Abstract

An intelligent welding gun is provided with a fixed side sensor in a fixed side portion. The mechanical impedance of the fixed side portion is kept small, which permits the mechanical impedance to be set in a range where the fixed side sensor can effectively detect at least one of a position of a fixed side welding tip and a pressing force imposed on the fixed side welding tip. The fixed side sensor and a moving side sensor constitute a redundant sensor measurement system. Various kinds of methods conducted using the above welding gun include a method of calibrating a sensor (including calibration of a reference point and a gain), a control method of suppressing a welding expulsion, a re-welding feedback control method, a control method of a welding strength, a control method of reducing a clearance between workpieces, a method of correcting a welding robot track, and a method of managing a positional accuracy change at a welding point.

Claims

1. A method of calibrating a sensor conducted using a welding gun which includes (1) a moving side portion including a moving side welding tip and a driving device for driving said moving side welding tip and (2) a fixed side portion including a fixed side welding tip and an arm supporting said fixed side welding tip, wherein a fixed side sensor for detecting at least one of a position of said fixed side welding tip and a pressing force imposed on said fixed side welding tip is provided in said fixed side portion, and a moving side sensor for detecting at least one of a position of said moving side welding tip and a pressing force caused in said moving side welding tip is provided in said moving side portion, said method comprising:

releasing said moving side welding tip from a position of contact with said fixed side welding tip; and

calibrating at least one of a pressing force information and a positional information a reference point of the fixed side sensor.

2. A method of calibrating a sensor conducted using a welding gun which includes (1) a moving side portion including a moving side welding tip and a driving device for driving said moving side welding tip and (2) a fixed side portion including a fixed side welding tip and an arm supporting said fixed side welding tip, wherein a fixed side sensor for detecting at least one of a position of said fixed side welding tip and a pressing force imposed on said fixed side welding tip is provided in said fixed side portion, and a moving side sensor for detecting at least one of a position of said moving side welding tip and a pressing force caused in said moving side welding tip is provided in said moving side portion, said method comprising:

increasing pressure of said moving side welding tip against said fixed side welding tip and plotting a pressing force and/or a positional information to obtain characteristic curves of said moving side sensor and said fixed side sensor using a method of least squares; and

determining gains of said sensors such that the gains of said moving side sensor and said fixed side sensor are equal to each other.