Patent ID: 6702702
Filing Date: 2004-03-09
Classification: F16H,Y10S,Y10T

Abstract:
An automatic gearbox, comprising:a control device configured to select a gearbox driving position, the control device including: a spool valve configured to connect a pressure connection to a consumer; a shift valve configured to shift a pressure connection from a pressure supply of the control device to the spool valve to actuate the spool valve; and a retaining device configured to fix the spool valve in at least one control position and to retain a selected gearbox driving position in accordance with a failure of the shift valve; wherein the retaining device includes a hydraulic retaining device; and wherein the retaining device includes a changeover valve configured to enable a pressure connection between the pressure supply and a pressure chamber on the spool valve when the shift valve is activated and to change over and prevent a return flow from the pressure chamber when the shift valve is subsequently deactivated.