Patent ID: 6961984
Filing Date: 2005-11-08
Classification: B21J,Y10T

Abstract:
1. In a self-piercing rivet setting machine wherein a self-piercing rivet comprising a flange-shaped head and an annular leg extending downward from said head is driven into a plurality of workpieces by a punch and a die to outwardly expand and deform the edge of said leg while piercing said workpieces with said leg, so as to connect said workpieces with each other between said deformed leg and said head, a method for detecting a setting defect of the self-piercing rivet comprising the steps of: plotting a normal upper limit curve defining the upper limit of a normal setting range and a normal lower limit curve defining the lower limit of the normal setting range on a graph having X-Y coordinates representing a rivet driven stroke and a rivet driving load; during driving of the rivet, measuring the rivet driven strokes and rivet driving loads of the self-piercing rivet to plot them on said graph; and determining whether said plotted values would deviate from the values between said normal upper limit curve and said normal lower limit curve to detect a first setting defect of said self-piercing rivet, and wherein said method further comprises the steps of: plotting a defect upper limit curve and a defect lower limit curve between said normal upper and lower limit curves on said graph, said defect upper and lower limit curves being obtained from a second setting defect different from said first setting defect; and determining whether said plotted value of said driven self-piercing rivet lies between said defect upper limit curve and said defect lower limit curve to detect said second setting defect of said self-piercing rivet.