Zahnradfabrik Friedrichshafen, Ag.

Peter Hartig

Friedrich J Ehrlinger

In a pressure-control device for affecting the closing behavior of powershift clutches (K.sub.1 -K.sub.X) in a powershift transmission, a regulating valve (1) cooperates with a damping device (2) as pressure-control valve. Chokes (4, 40, 400) for a more or less smooth connection are arranged in combination with pressure lines (P.sub.S, P.sub.R) over the pressure cycle when the clutch concerned (K.sub.1 -K.sub.X) is engaged. The travel of the damper piston (21) in a direction toward the regulating valve (1) is shortened by a pressurizing piston device (3) cooperating with the piston (21) of the damping device (2). Thus the time for the slipping phase in the engaged clutch concerned is shortened and, together with a higher initial pressure after the clutch is filled, the friction is limited. The limitation of the friction can also be obtained by adding a second choke in parallel in the control pressure line (Pr) by which the choked cross section is increased.

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Ravensburg, Germany

Peter Hartig