Servo control, especially power steering for motor vehicles

Servo control arrangement, adapted for power steering for motor vehicles, comprising:

• a shaft which serves as an actuating member and which is subdivided a first shaft part and a second shaft part,
• a spring arrangement drivingly connecting the first and second shaft parts while allowing a relative rotation between the first and second shaft parts,
• a servo-valve arrangement working in dependence on the relative rotation of the first and second shaft parts, comprising an inflow connection connected to a pressure source, an outflow connection connected to an essentially pressureless reservoir, and two working connections which are connected to a servomotor and between which working connections a pressure difference (P.sub.1 -P.sub.2) is generated dependent on the amount and direction of the relative rotation of the first and second shafts, and
• a fluidic reaction control for generating a reaction force counteracting a particular direction of actuation of the first and second shaft parts, said reaction control including a bush part surrounding a portion of the first shaft part, said bush part being rotatably fixed with the second shaft part, said bush part and portion of the first shaft forming a double-acting rotary-blade unit with oppositely acting chambers, in which the pressure in one chamber seeks to bring about a relative rotation of the bush part and the portion of the first shaft part in one direction and the pressure in the other chamber seeks to bring about a relative rotation in the bush part and the portion of the first shaft part in the other direction,
• wherein the rotary-blade unit has two chambers, each of said chambers being connectable to the reservoir via a throttle and to an inflow via a controllable slot between mutually cooperating control edges on the bush part and on the portion of the first shaft part,
• and wherein the two slots are both at least virtually closed in a middle position of the bush part and portion of the first shaft part, while respective ones of said slots opens in the event of a relative rotation between the bush part and portion of the first shaft part.