Patent ID: 9077276
Filing Date: 2015-07-07
Classification: A61C,H02P

Abstract:
1. A motor control apparatus for a dental handpiece, the dental handpiece having a motor that rotationally drives a cutting tool, the motor control apparatus comprising: a load torque detecting section that detects a load torque applied to the cutting tool; a rotational speed detecting section that detects a rotational speed of the motor; and a control section that controls the rotational speed and a motor current of the motor, wherein the control section limits the motor current to a first limit current while the motor is energized, when the load torque detected by the load torque detecting section exceeds a preset limit torque value, wherein the first limit current is non-zero, and when the load torque exceeds the limit torque value and the rotational speed detecting section detects that the motor has stopped rotating while the motor is energized, gradually reduces the motor current over a period of time after the motor has stopped rotating and while the motor remains energized, to be equal to or lower than a second limit current, which is lower than the first limit current, and then stops power supply to the motor or makes the motor rotate in a reverse direction upon determining that the motor current becomes equal to or lower than the second limit current, wherein at an initial stage where the load torque applied to the cutting tool does not exceed the preset limit torque value, the motor control apparatus controls the rotational speed of the motor based on a feedback control so as to be set at a desired constant speed.