Patent ID: 6880680

Claim:
An electrically actuatable disc brake comprising: a disc rotor; brake pads for engaging with said disc rotor; an electric motor having a rotor; a reduction mechanism for reducing a rotation of said rotor of said electric motor, and for generating a reduced rotation; a converting mechanism for converting the reduced rotation of said reduction mechanism to a linear motion, and for causing said brake pads to engage with said disc rotor so as to generate a braking force; wherein said reduction mechanism comprises an eccentric shaft connected to said rotor of said electric motor, a gear member rotatably attached to said eccentric shaft, said gear member including a set of external input teeth and a set of output teeth adapted to rotate unitarily with each other, a fixed ring gear having internal teeth adapted to mesh with said external input teeth of said gear member, and a ring gear adapted to mesh with said output teeth of said gear member and to operate said converting mechanism; wherein said eccentric shaft has a coaxial hollow space of a circular cross-section therein so that the hollow space extends into said rotor of said electric motor by a predetermined distance; and wherein the hollow space of said eccentric shaft extending into said rotor by the predetermined distance allows for mass added to said rotor by said eccentric shaft to be subtracted at an eccentric position of said rotor so as to achieve rotational balance for said rotor.