Patent ID: 8779608

Claim:
A construction machine comprising: a lower driving structure capable of traveling; an upper swing structure mounted on an upper portion of the lower driving structure and provided with a working device; a swing ring gear fixed to the lower driving structure; a swing ring gear cover fixed to the upper swing structure and engaged with the swing ring gear to perform a rotational operation; a permanent magnet installed on one of the swing ring gear and the swing ring gear cover; an induction coil installed on the other of the swing ring gear and the swing ring gear cover; a hydraulic swing motor that is rotatable using an inflow and outflow of hydraulic fluid supplied from a hydraulic pump; a pinion gear that is rotated by the hydraulic swing motor, wherein the pinion gear is engaged with the swing ring gear to rotate the upper swing structure; a pressure sensor sensing hydraulic pressure in the hydraulic swing motor and outputting an electrical signal; a control lever manipulating the upper swing structure in a swing operation state or in a swing stop state; a control unit receiving signals of the pressure sensor and the control lever and making the induction coil generate induction current in the case where it is judged that the hydraulic swing motor is in a speed reduction state; and a control switch formed between the control unit and the induction coil to be short-circuited in the case where the generation of the induction current is desired and to be open in the case where the generation of the induction current is not desired; wherein induction current is generated in the induction coil in accordance with the rotational operation of the swing ring gear cover.