Electrically operated disc brake

An electrically operated disc brake comprising:

• a caliper having a caliper body;
• an electric motor mounted within the caliper body;
• a piston supported by the caliper body and operatively connected to the electric motor, said piston having a threaded section;
• a ball/ramp mechanism disposed within the caliper body and including an axially movable member, said axially movable member having a threaded section threadably engaged with the threaded section of the piston, said ball/ramp mechanism being operable to convert rotary motion of the electric motor to linear motion and transmit the linear motion to the piston so that the piston is advanced in response to operation of the electric motor to urge a pair of friction pads against opposite sides of a disc rotor to thereby produce a braking force;
• a pad wear adjusting mechanism disposed within the caliper body, said pad wear adjusting mechanism being operable to threadably move the threaded section of the piston relative to the threaded section of the axially movable member in response to the amount of pad wear;
• a dust boot connected between the piston and the caliper body;
• a holder associated with the caliper body to collectively define a caliper housing within which the electric motor, the ball/ramp mechanism and the pad wear adjusting mechanism are contained, said holder having an opening through which the piston extends;
• and
• a seal disposed in the opening of the holder,
• said piston having a smooth section extending from the threaded section toward the disc rotor, said smooth section of the piston being slidably received in the seal.