Thrust generator and disk brake

A disk brake comprising:

• a drive source which outputs rotational force;
• a pressing member generating thrust in an axial direction to press a brake pad against a disk;
• and
• a ball-and-ramp mechanism converting rotational force transmitted from the drive source into rectilinear motion to propel the pressing member;
• the ball-and-ramp mechanism comprising:
• a pair of ramp members each having a plurality of sloped grooves sloped along a circumferential direction, each sloped groove having an arcuate diametrical cross-section;
• and
• a rolling member interposed between each pair of mutually opposing ones of the sloped grooves of the ramp members to transmit force from one of the pair of ramp members to the other of the pair of ramp members;
• the sloped grooves each having a track area where the rolling member contacts the sloped groove and having regions in the track area that vary in curvature radius of the diametrical cross-section.