Electric power tool provided with motor controller controlling motor including limiter for limitting current contributing to torque generation
View Patent ↗An electric power tool is provided with a permanent magnet synchronous motor, and a controller. The controller is configured to control an operation of the permanent magnet synchronous motor. The controller includes a limiter that limits a current contributing to torque generation by the permanent magnet synchronous motor to a predetermined maximum set value based on a predetermined tightening torque. The controller calculates the maximum set value of the current that contributes to the torque generation by changing one of a rotation speed and an angular speed of the permanent magnet synchronous motor.
1. An electric power tool comprising:
a permanent magnet synchronous motor; and
a controller configured to control an operation of the permanent magnet synchronous motor,
wherein the controller comprises a limiter that limits a current contributing to torque generation by the permanent magnet synchronous motor to a predetermined maximum set value based on a predetermined tightening torque.
2. The electric power tool as claimed in claim 1 ,
wherein the controller calculates the maximum set value of the current that contributes to the torque generation by changing one of a rotation speed and an angular speed of the permanent magnet synchronous motor.
3. The electric power tool as claimed in claim 2 ,
wherein the controller calculates a maximum set value i δ * max of the current that contributes to the torque generation using an equation of
i δ * max =K ( T−J·d ω)/ dt+T 0)
wherein K and J are constants, dω/dt is a differential value of the angular speed of the permanent magnet synchronous motor, T is a predetermined target tightening torque, and T0 is a predetermined loss torque.