METHOD AND APPARATUS FOR CONTROLLING THE WORKING PRESSURE OF A HYDRAULIC MEDIUM SUPPLIED TO A THRUST PISTON UNIT

摘要

A recess in a workpiece is honed by a honing tool that is reciprocated in a succession of strokes back and forth in the recess as it is rotated about an axis of the recess. The stones of the honing tool are pressed by at least one hydraulic cylinder against the workpiece with a pressure that is incrementally increased after each stroke. To this end a pilot-controlled primary pressure-limiting valve is connected between a pump and the cylinder, and a plurality of multiway valves can connect any of a plurality of differently preset secondary pressure-limiting valves to the pilot port of the primary valve. The cylinder piston can have a pair of unequal effective faces each exposed in a respective cylinder compartment so that during a first operation stage both compartments are pressurized to the same extent for differential action and during a second operation stage only one of the compartments is pressurized.