Waterproof joint section forming method and wire harness provided with waterproof joint section formed by the method

A waterproof joint section forming method, comprising:

• forming slits for peeling in leading end sides of a plurality of insulated wires to be electrically connected with each other;
• providing a waterproof rubber lid having opposite front and rear faces and a plurality of through holes extending through the water proof rubber lid from the front face to the rear face, the waterproof rubber lid having and outer circumferential surface and a waterproof sealing lip extending around the outer circumferential surface;
• providing a resin molded protection cap having a tubular side wall, a closed bottom wall and an opening end opposite the closed bottom wall, the bottom wall being free of openings therethrough, a positioning rib extending around an inner periphery of the tubular side wall at a distance from the opening end substantially equal to a distance between the front and rear faces of the waterproof rubber lid;
• inserting the leading ends of the insulated wires respectively through the through holes formed in the waterproof rubber lid so that portions of outer circumferential surfaces of insulating coatings of the respective wires are held in close contact with inner circumferential surfaces of the respective through holes of the waterproof rubber lid for sealing,
• peeling off the insulating coatings at the ends of the wires from the slits after being passed through the through holes to expose cores,
• connecting the exposed cores directly to one another by welding, fusion-bonding, soldering, or fastening by a crimping terminal to form a terminal joint section,
• inserting the terminal joint section through the opening end in the protection cap, and
• fitting the waterproof rubber lid in the opening end of the protection cap so that the front face of the waterproof rubber lid contacts the positioning rib and so that the waterproof seal lip formed on the outer circumferential surface of the waterproof rubber lid is pressed into contact with an inner circumferential surface of the tubular side wall of the protection cap between the opening end of the protection cap and the positioning rib for sealing the terminal joint section in the protection cap without injecting a waterproofing agent into the protection cap.