Patent ID: 7736270

Claim:
A control valve arrangement for controlling a start clutch of an automatic transmission, the control valve arrangement comprising a clutch control valve ( 3 , 37 , 41 , 48 , 49 ) for controlling at least one clutch activation apparatus ( 4 , 40 ), during normal operation of the transmission, depending one of a pilot pressure (P_VST, P_VST 1 , P_VST 2 ) and an electric pilot signal (S), and the clutch control valve ( 3 , 37 , 41 , 48 , 49 ) converting a supply pressure (P_V 1 , P_V 2 ) into a clutch activation pressure (P_K, P_K 1 , P_K 2 ) enabling control of the clutch activation apparatus ( 4 , 40 ); an emergency operation of the transmission being initiated by a failure of a pilot pressure (P_VST, P_VST 1 , P_VST 2 ) which is due to a failure of at least one of an electric pilot signal (S), a motor rotational speed, a transmission input revolution speed, a transmission output revolution speed, a motor torque and a transmission torque, with consideration given to an extent of vehicle travel; an activation pressure (P_A), during the emergency operation of the transmission, being exerted upon one of the clutch control valve ( 3 , 37 41 , 48 , 49 ) or directly upon the clutch activation apparatus ( 4 , 40 ) such that the clutch activation apparatus ( 4 , 40 ) is maintained in a closed position, until at least one of the motor output rotational speed and the transmission output rotational speed is respectively less than a predetermined threshold speed; the clutch control valve ( 3 , 41 ), which is controlled by the pilot pressure (P_VST, P_VST 1 , P_VST 2 ), comprises a short slide valve and an axially aligned long slide valve, a first face of the short slide valve ( 34 , 92 ), remote from a reset spring ( 33 ), is subjected to the activation pressure (P_A), a second face of the short slide valve ( 34 , 92 ) and a first face of the long slide valve ( 19 , 90 ), remote from the reset spring ( 33 ) and axially adjacent the second face of the short slide valve ( 34 , 39 ), both being subjected to the pilot pressure (P_VST, P_VST 1 , P_VST 2 ), and a second face of the long slide valve ( 19 , 90 ) communicating with and is biased by the reset spring.