Bonding method for conductor of electric wire and electric wire

Abstract

A bonding method for a conductor of an electric wire includes a conductor formed of a plurality of strands and a sheath covering the conductor such that the conductor is exposed to a predetermined length. The bonding method ultrasonically bonds the plurality of strands of the electric wire to each other using an anvil and a horn. When the strands are ultrasonically bonded to each other by clamping a part of the conductor exposed from the sheath between the anvil and the horn throughout a predetermined length and ultrasonically vibrating the horn, a distance from the anvil or the horn to the sheath of the electric wire is shorter than a length of the strands when the strand vibrates in a primary mode by ultrasonic vibration.

What is claimed is: 
     
         1 . A bonding method for a conductor of an electric wire including a conductor formed of a plurality of strands and a sheath covering the conductor such that the conductor is exposed to a predetermined length, the bonding method ultrasonically bonding the plurality of strands of the electric wire to each other using an anvil and a horn, wherein
 when the strands are ultrasonically bonded to each other by clamping a part of the conductor exposed from the sheath between the anvil and the horn throughout a predetermined length and ultrasonically vibrating the horn, a distance from the anvil or the horn to the sheath of the electric wire is shorter than a length of the strands when the strand vibrates in a primary mode by ultrasonic vibration.   
     
     
         2 . The bonding method for a conductor of an electric wire according to  claim 1 , wherein an outer diameter of a middle portion of the conductor, positioned between the bonded portion formed by the ultrasonic bonding and a portion covered with the sheath, gradually decreases toward the bonded portion from the portion of the conductor covered with the sheath,
 a maximum value of an intersection angle between an upper surface of the bonded portion or a longitudinal direction of the electric wire and the strands of the middle portion of the conductor is smaller than a predetermined angle, and   the predetermined angle is an angle at which breakage of the strands is prevented when the ultrasonic bonding is performed.   
     
     
         3 . The bonding method for a conductor of an electric wire according to  claim 2 , wherein the anvil and the horn are provided with an inclined surface contacting a portion of the middle portion of the conductor on a side of the bonded portion throughout a predetermined length. 
     
     
         4 . The bonding method for a conductor of an electric wire according to  claim 1 , wherein, after the bonded portion is formed, a bonding state of the bonded portion is inspected by performing at least one of allowing a fluid having a flow rate exceeding a predetermined speed to flow to the bonded portion and applying an acceleration exceeding a predetermined magnitude to the bonded portion. 
     
     
         5 . The bonding method for a conductor of an electric wire according to  claim 1 , wherein a part of the sheath is held when the strands are ultrasonically bonded to each other.