Ball screw mechanism and electrically powered steering device utilizing the same

摘要

A ball screw mechanism (20) compact in size, employing a minimized number of component parts and having a high load capacity includes a rotary nut (22) having an internally threaded helical groove (26) and a mounting hole (30) both defined therein, and a simplified bridge member (24) mounted in the rotary nut (22). The bridge member (24) has a plurality of connecting grooves (28) defined on an inner surface thereof each operable to communicate neighboring convolutions of the internally threaded helical groove (26). The bridge member (24) has its opposite side edges formed with respective guide walls (36) protruding in a direction radially outwardly of the rotary nut (22) that are crimped to allow the bridge member (24) to be fixedly retained within the mounting hole (30).