Hardening method and hardening device

A hardening device for hardening a shaft vertically extending from a flat plate of a work and an inner wall of a hole formed on the flat plate, comprising:

• a work rotating means for rotating the work around the hole;
• a first heating coil adapted to be moved closer to the shaft and for heating the shaft by induction;
• and
• a second heating coil having at least a portion to be inserted into the hole and for heating the inner wall of the hole by induction,
• wherein the work rotating means comprises a driving shaft for rotating the work and a work eccentrically holding means to be secured to the driving shaft and for holding one selected from the shaft of the work and an extended portion of the shaft with an axis of the one aligned with a point eccentrically located relative to the axis of rotation of the driving shaft,
• the holding means having an eccentricity relative to the driving shaft equal to a length between the hole and the shaft of the work, so that the work is held by the holding means so as to align a center of the hole with an axis of the driving shaft,
• the device further comprising an energization means for energizing the first heating coil and the second heating coil, and
• the device revolving the shaft of the work around the hole by rotation of the driving shaft so as to move the first heating coil together with the revolution to of the shaft, and
• energizing the first heating coil and the second heating coil so as to heat the shaft and the inner wall of the hole of the work respectively and simultaneously.

A hardening device for hardening a shaft vertically extending from a flat plate of a work and an inner wall of a hole formed on the flat plate, comprising:

• a work rotating means for rotating the work around the shaft;
• a first heating coil adapted to be moved closer to the shaft and for heating the shaft by induction;
• a second heating coil having at least a portion to be inserted into the hole and for heating the inner wall of the hole by induction;
• and
• a coil revolving means for revolving the second heating coil around the shaft,
• wherein the work rotating means comprises a driving shaft for rotating the work, the driving shaft having a rotational axis aligned with a rotational axis of the coil revolving means,
• wherein the second heating coil has a revolving radius equal to a length between the hole and the shaft of the work and is adapted to revolve by driving by the coil revolving means,
• the device further comprising an energization means for energizing the first heating coil and the second heating coil, the energizing means for energizing the second heating coil being adapted to excite an induction current to the second heating coil by electromagnetic induction, and
• the device revolving the hole around the shaft of the work by rotation of the driving shaft of the work rotating means and revolving the second heating coil by the coil revolving means so as to move the second heating coil together with the revolution of the hole, and
• energizing the first heating coil and the second heating coil so as to heat the inner wall of the hole and the shaft of the work respectively and simultaneously.