Disk brake apparatus for motor vehicle

A hydraulically operated disk brake apparatus for motor vehicles comprising a brake disk, a caliper-like brake housing having a pair of caliper arms and disposed to straddle over said brake disk, a pair of brake pad assemblies disposed in said caliper housing in opposition to each other with said brake disk being interposed therebetween, said brake pad assemblies being movable toward and from said brake disk, a cylinder chamber formed in one of said caliper arms and filled with a hydraulic medium, a first piston member disposed slidably in said cylinder chamber adjacent to an associated one of said brake pad assemblies, a second piston member disposed slidably in said cylinder chamber with a space from said first piston member, means for sliding said second piston member toward said first piston member upon application of said brake while simultaneously rotating said second piston member, thereby to produce a hydraulic pressure within said cylinder chamber under which said first piston member and said associated brake pad assembly are caused to more toward said brake disk;

• a reservoir for containing hydraulic medium;
• and means actuated by rotation of said second piston member for permitting flow of medium from said reservoir into said cylinder chamber when said second piston member is in its rest state, whereby compensation for wear of said brake pad assemblies is automatically achieved.