| 摘要 |
<p>The invention provides a closed center rotary valve and a power-assisted steering mechanism for a motor vehicle incorporating the rotary valve. The closed center rotary valve comprises cooperating relatively rotatable sleeve and core members having cooperating axially-extending grooves therein and means relatively biassing the members towards a neutral position. Said grooves comprise at least one inlet groove connectable to a source of fluid under pressure, a cylinder groove angularly spaced from the inlet groove on each side thereof and connectable to opposite sides of a double-acting piston-and-cylinder, and a return groove in overlapping relation with each of the cylinder grooves in the neutral position of the valve and connectable to a reservoir for the fluid under pressure, the inlet groove being closed from communication with the cylinder and return grooves in the neutral position of the valve. The arrangement is such that on relative angular displacement of the member in either direction from the neutral position the inlet groove is placed in communication with one of the cylinder grooves, the one cylinder groove and its associated return groove move out of their overlapping relation to close communication therebetween, and the overlap between the other cylinder groove and its associated return groove is increased.</p> |
