Patent ID: 9111708
Filing Date: 2015-08-18
Classification: H01H

Abstract:
1. A fusible link comprising: a fuse portion that has a first electrical resistance portion and a second electrical resistance portion which are formed of a fusible metal conductor, wherein the first electrical resistance portion has a first resistance value and the second electrical resistance portion has a second resistance value, and wherein the first electrical resistance portion has a fusible portion which is provided in proximity to a connecting portion of the first electrical resistance portion with the second electrical resistance portion and which is adapted to be fused and cut off when the fusible portion is heated up by an overcurrent; a metal chip whose melting point is lower than a melting point of the fusible metal conductor, and which is adapted to be fused to be dispersed into the fusible portion for formation of an alloy phase when the metal chip is heated up by the overcurrent; and a holding portion that is provided in proximity to the fusible portion for holding the metal chip, wherein the first resistance value is greater than the second resistance value such that a ratio of the first resistance value and the second resistance value ranges from 2 to 1 to 5 to 1 so that a temperature of the first electrical resistance portion is increased by the overcurrent in a rare-short-circuit range; and wherein the second electrical resistance portion is shorter in length than the first electrical resistance portion, wherein the second electrical resistance portion has a first end part connected to the first electrical resistance portion and a second end part connected to a heat dissipating portion, the first end part being opposite to the second end part, wherein the heat of the fusible portion increased by the overcurrent in the rare-short-circuit range is conducted to the heat dissipating portion so that the heat of the fusible portion of the first electrical resistance portion is decreased so as not to fuse the metal chip while maintaining a temperature of a part of the first electrical resistance portion that does not include the fusible portion of the first electrical resistance portion, wherein a width of the heat dissipating portion is greater than a width of a portion of the second electrical resistance portion other than the holding portion, and wherein the rare-short-circuit range of the overcurrent is greater than a rated value and is smaller than a predetermined current that is twice as large as the rated value.