Roller hemming device and preliminary bending method using the device

A roller hemming device comprising:

• a backing metal comprising an upper surface,
• an abutment surface, and
• a guide surface extending along the upper surface of the backing metal, the guide surface opposite to the abutment surface, the abutment surface being configured to be brought into abutment against a first panel member among the first panel member and a second panel member superimposed with the first panel member;
• a guide roller configured to be moved in an extending direction of the guide surface with abutting against the guide surface;
• a bending roller disposed below the guide roller, the bending roller configured to, with being moved synchronously with the guide roller, press a bent peripheral edge portion of the first panel member via the backing metal such that the bent peripheral edge portion of the first panel member is pinched between the bending roller and the guide roller, and fold the bent peripheral edge portion of the first panel member back to a periphery edge portion of the second panel member;
• a pressing unit biasing the guide roller toward the bending roller so as to press the bending roller toward the backing metal, wherein the pressing unit is configured to change and adjust a distance between the guide roller and the bending roller, and wherein the pressing unit comprises either (1) a servo motor and a gear mechanism or (2) an air cylinder;
• and
• a swinging unit attached to the guide roller, the bending roller, and the pressing unit, wherein
• when viewed in a moving direction of the guide roller, at least one of the guide surface or an outer peripheral surface of the guide roller configured to be brought into abutment against the guide surface is a curved surface that is convex in a direction in which the bent peripheral edge portion of the first panel member is pinched between the bending roller and the guide roller, and
• the swinging unit is configured to swing the guide roller and the bending roller integrally in a plane perpendicular to the moving direction of the guide roller, with the guide surface and the outer peripheral surface abutting against each other.