| 摘要 |
PURPOSE:To obtain simplified and small-sized structure of a valve mechanism by arranging a valve plate to slide for making switching control of operation oil by the relative rotation with a worm shaft. CONSTITUTION:A cylinder 2 is partitioned by a piston 1 into the first operation chamber 3 and the second operation chamber 4. A rack 5 is engaged with a selector gear 5a of a sector shaft 5 to drive a steering link, and selectively charges or discharges the first and the second operation chambers 3 and 4 with operation oil via a supply hole 7 and a discharge hole 8 provided in a rear housing 6 to close the one end of the cylinder 2 for assisting the rotation of the sector shaft 5. In the initial state of the rotation of a stub shaft 13, the torsion angle of a torsion bar 17 causes a relative rotation between a worm shaft 9 and a valve plate 20 in one body with a drive pin 13b, and the difference of oil pressures between the first and the second operation chambers gives the assisting force to the rotation of the sector shaft 5. |
