Electric wire connection structure

An electric wire connection structure comprising:

• one or more copper-based conductor covered electric wires having a copper-based conductor covered part in which a copper-based conductor made of copper or a copper alloy is covered with an insulating cover and a copper-based conductor exposed part in which a part of the insulating cover is stripped by a predetermined length to expose the copper-based conductor;
• and
• one or more aluminum-based conductor covered electric wires having an aluminum-based conductor covered part in which an aluminum-based conductor made of aluminum or an aluminum alloy is covered with an insulating cover and an aluminum-based conductor exposed part in which a part of the insulating cover is stripped by a predetermined length to expose the aluminum-based conductor, wherein
• an ultrasonic joint part is provided at a conductor stacked part in which the copper-based conductor exposed part and the aluminum-based conductor exposed part are superposed, and
• a joint interface of the ultrasonic joint part satisfies a relational expression of
• (x/L)×100≤10%
• where a total contacting length which is a summed length of a part at which the copper-based conductor exposed part and the aluminum-based conductor exposed part contact is L and a summed length of a contour line of a space formed at a part at which the copper-based conductor exposed part and the aluminum-based conductor exposed part are separate is x based on cross-section observation, and
• wherein the joint interface of the ultrasonic joint part is provided by only the aluminum-based conductor covered electric wire being melted in a space unjoined which is formed between the copper-based conductor exposed part and the aluminum-based conductor exposed part forming the joint interface so as to fill the space of the copper-based conductor covered electric wire based on cross-section observation,
• strands of the aluminum-based conductor exposed part are connected to each other and integrated,
• strands of the copper-based conductor exposed part are connected to each other with a gap formed,
• the space is filled with aluminum in the aluminum-based conductor exposed part, and
• a difference in tensile strength between the copper-based conductor and the aluminum-based conductor is 100 MPa or more.