Hydraulic system of an automatic transmission with a plurality of valve devices

摘要

It is a hydraulic system (1) with a plurality of valve means (2 to 5) and with a hydraulically operable parking brake unit (6) is described. In a first axial position of a valve slide (8) of a park blocking valve (2) is provided on the parking brake unit (6) an actuating pressure (pb) can be applied, to which a parking lock in the inserted operating state. In addition, at the valve spool (8) a in the direction of a with a second operating state of the park blocking valve (2) corresponding second axial position of the valve slide (8) can be a pressure signal (pa), in which at the parking brake unit (6) a the parking lock in the exposed operating state by means of which the actuating pressure (pb) can be applied. The actuating pressure (pb) additionally rests against a further control surface (13) of the valve slide (8) on. The resulting actuating force acts in the direction of the second axial position, while in the region of an additional control surface (14) of the valve slide (8) a further pressure signal (pmv) can be applied, this is the direction of the first axial position of the valve slide (8) engages on this. The control surfaces (10, 13, 14) and said spring means (9) are matched to each other such that in the case in the region of the control surfaces (10, 13, 14) adjacent and mutually corresponding pressures (pa, pb, pmv), at the valve slide (8) a the valve spool (8) into its first axial position displacing the total force component acts.