Piston pump having a helical gear as a power brake pressure generator of a hydraulic vehicle power brake system

A hydraulic block for a hydraulic unit of an hydraulic vehicle power brake system, comprising:

• a helical gear as a power brake pressure generator of a hydraulic vehicle power brake system;
• a piston displaceable in a cylinder, wherein:
• the helical gear includes a spindle that is connected to the piston or is rotationally drivable and a nut that is rotationally drivable or connected to the piston for displacing the piston in the cylinder for generating a hydraulic brake pressure;
• the nut includes:
• a plastic body with a nut threat and
• a metal sleeve covering the plastic body;
• the helical gear is situated coaxially to the cylinder and is supported rotatably with a spindle bearing on the hydraulic block, which supports the helical gear axially on the hydraulic block;
• and
• the hydraulic block includes at least one of the following features (a)-(g):
• (a) the plastic body and the metal sleeve are each tubular and are form-fitted to each other;
• (b) the metal sleeve is arranged relative to the plastic body such that the plastic body is prevented from radially expanding due to impingement of the plastic body against the metal sleeve;
• (c) the metal sleeve is arranged at a radial position that is between a radial position of the plastic body and a radial position of the piston;
• (d) the metal sleeve encloses the plastic body at a circumference of the plastic body without any space between the plastic body and the metal sleeve;
• (e) the metal sleeve includes an inward corrugation inserted in a groove of the plastic body of the nut
• (f) the plastic body of the nut has a rib inserted in an outward corrugation of the metal sleeve;
• and
• (g) the metal sleeve and the plastic body of the nut have corresponding ring steps for an axially fixed connection between the metal sleeve and the plastic body of the nut in a direction of the pressure-generating forward stroke of the piston.