Patent ID: 7770658
Filing Date: 2010-08-10
Classification: B23P,B25B

Abstract:
1. A control method for an impact type screw fastening device using an electric motor as a rotation driving source, the control method comprising the steps of: driving the motor to rotate by supplying thereto pulse current having a rectangular waveform with a flat peak and a predetermined period so that a speed of the motor becomes an intermittent waveform corresponding to the pulse current in a time axis and, at the same time, torque exerted on a load by rotation of the motor becomes pulse torque corresponding to the pulse current and increases pulse by pulse in succession in the time axis; in a first stage until the pulse torque reaches a first set value, controlling the pulse current so that the pulse torque increases pulse by pulse in succession in increments of a first torque value; and in a second stage starting from when the pulse torque reaches the first set value and until the pulse torque reaches a second set value, controlling the pulse current so that the pulse torque increases pulse by pulse in succession in increments of a second torque value that is smaller than the first torque value.