Automatic screw tightening control method and device

Abstract

In an electric driver configured such that a driver bit is coupled to a drive output shaft of an electric motor via a clutch mechanism to perform screw tightening operations, an automatic screw tightening control method and a device in which setting is performed such that an appropriate screw tightened state and various inappropriate screw tightened states in a screw tightening operation can be confirmed and determined, simply and reliably are provided. In a screw tightening operation by an electric driver, at start of a predetermined screw tightening operation, a rotation amount Rm of an electric motorat a clutch operation time by a clutch mechanismis detected, this rotation amount is set to be a target rotation amount (including a permissible range) Rm±α, and in the subsequent screw tightening operations, a rotation amount Rtof the electric motor at the clutch operation time is detected and compared with the target rotation amount, respectively, so that acceptability of the respective screw tightened states is determined.