Piston compressor of an apparatus for supplying pressurized air, in particular in commercial vehicles, with a valve plate active as a valve support, which is arranged between a cylinder housing and a cylinder head of the piston compressor, and which, in addition to a suction valve and a pressure valve, has a relief valve for connection as needed of a working chamber embodied in the cylinder housing to a relief chamber arranged in the cylinder head and further has a cooling channel, first and foremost for water cooling of the pressure valve, characterized by the following features: a) a three-part design of the valve plate with a base plate at the cylinder, a cover plate at the top and a core plate arranged between these, b) a design of the core plate made of a material with high thermal conductivity, c) a design of the base plate and of the cover plate made of a material with high heat resistance, d) a design of the suction valve as a lamellar valve with a plurality of circular-arc-shaped entry channels arranged in the valve plate valve plate and a valve lamella provided with a central recess covering the entry channels, which is arranged within a cylinder-side recess of the base plate, e) a design of the pressure valve as a lamellar valve with at least one exit channel arranged radially in the valve plate within an arc formed by the placement of the entry channels and a valve lamella covering this exit channel, said valve lamella being arranged on the head-side outer wall of the cover plate, f) a design of the relief valve as a sliding plate valve with at least one relief duct arranged in the valve plate between the entry channels and the exit channel and a sliding plate mounted in articulated manner on the one side covering the at least one relief duct, which is arranged in the cylinder-side recess of the base plate between the valve lamella of the suction valve and the inner wall of the recess, g) an axially movable arrangement of a pneumatically actuable control piston of an actuator connected to the sliding plate at its end opposite the articulated mounting in a bore of the core plate, and h) an arrangement of at least one cooling channel in the core plate, which at least partially winds around the exit channel. a) a three-part design of the valve plate with a base plate at the cylinder, a cover plate at the top and a core plate arranged between these, b) a design of the core plate made of a material with high thermal conductivity, c) a design of the base plate and of the cover plate made of a material with high heat resistance, d) a design of the suction valve as a lamellar valve with a plurality of circular-arc-shaped entry channels arranged in the valve plate valve plate and a valve lamella provided with a central recess covering the entry channels, which is arranged within a cylinder-side recess of the base plate, e) a design of the pressure valve as a lamellar valve with at least one exit channel arranged radially in the valve plate within an arc formed by the placement of the entry channels and a valve lamella covering this exit channel, said valve lamella being arranged on the head-side outer wall of the cover plate, f) a design of the relief valve as a sliding plate valve with at least one relief duct arranged in the valve plate between the entry channels and the exit channel and a sliding plate mounted in articulated manner on the one side covering the at least one relief duct, which is arranged in the cylinder-side recess of the base plate between the valve lamella of the suction valve and the inner wall of the recess, g) an axially movable arrangement of a pneumatically actuable control piston of an actuator connected to the sliding plate at its end opposite the articulated mounting in a bore of the core plate, and h) an arrangement of at least one cooling channel in the core plate, which at least partially winds around the exit channel.