Patent ID: 9592593
Date: 2017-03-14
CPC Classifications: B25B

Claim:
1. A hand-held rotatable impact tool, comprising a housing; a powering unit comprising a motor and an impact mechanism driven by the motor, and the impact mechanism being configured to generate an intermittently increasing torque; an adjusting unit configured to set a first torsion value and generate a corresponding first torsion signal; a detecting unit positioned on the motor, the detecting unit being capable of detecting a rotational speed of the powering unit and generating a corresponding first rotational speed signal; a control unit configured to generate a control signal for controlling the output of the rotational speed of the powering unit, the control unit comprising an electronic switch connected in series with the motor, the control unit generating a second rotational speed signal according to the first torsion signal outputted by the adjusting unit, comparing the first rotational speed signal with the second rotational speed signal, generating a control signal enabling the rotational speed of the powering unit to approach a speed corresponding to the second rotational speed signal while the powering unit outputs a torque approaching a torque corresponding to the first torsion value set by the adjusting unit, substituting the first rotational speed signal and the second rotational speed signal into a PID increment algorithm and generating a PWM control signal according to its result, wherein the electronic switch receives the PWM signal and thereby controls a duty ratio of electrical current flowing through the motor, to maintain a constant speed and torque; the control unit further comprising a trigger switch operable coupled to the motor, wherein the motor starts to operate when the trigger switch is pressed and stops when the trigger switch is released.