| 摘要 |
Provided in series between pump and tank in a control device for a hydraulic control motor are two throttle devices, between which a line leading to the control motor branches off. One of the throttle devices is made up of a controllable throttle valve having a piston, of which one side supports a valve head, which forms the boundary of an annular gap between an inflow duct and an outflow duct. The pressure drop at the annular gap is continuously controllable by a throttle needle, which is arranged on the other side of the piston, in a hydraulic control path. The hydraulic control path extends from the inflow duct through the throttle opening to the tank, running through a precontrol bore in the piston. When the control device functions according to the open-center principal, an unwanted leakage fluid stream through the precontrol bore to the tank is formed when the annular gap is completely opened. In order to prevent this, one end of the precontrol bore at the annular gap in the region of the inflow duct is positioned in such manner, that it even remains opened in the case of a closed annular gap, and the other end of the precontrol bore on the other side of the piston is arranged where the piston, in response to the controllable throttle valve being completely opened, pushes against a stop face and, in so doing, automatically closes this other end.
|
