Pressure medium actuated method and friction clutch with exclusively axially movable friction discs

A method for engaging and disengaging friction clutches arranged in series with a gearbox section having at least one gearwheel stage with a loose wheel which can be connected to a shaft thereof by a gearwheel clutch, which friction clutches are arranged in a power transmission path between an input shaft and an output shaft of a multi-path gearwheel change-speed gearbox, during a gear change between a previous gear and a new gear where, in the previous gear, a first gearbox section having a gearwheel stage is connected by engagement of both one of its gearwheel clutches and an associated friction clutch having at least one engagement spring and a disengagement actuator and, in the new gear, a second gearbox section having a gearwheel stage is connected in a corresponding manner into a drive connection between the input shaft and the output shaft, comprising the steps of subjecting, on the appearance of a gear change signal, a disengagement actuator of a friction clutch of the new gear to operating pressure at least up to the level of a disengagement pressure value sufficient to overcome at least one engagement spring holding the friction clutch of the near gear;

• engaging, on or after reaching the disengagement pressure value, a gearwheel clutch of a loose wheel of the gearwheel stage of the new gear in the second gearbox section;
• applying, on the appearance of a second gear-change signal, an operating pressure to an engagement actuator of the friction clutch of the previous gear;
• raising the operating pressure of the engagement actuator of the friction clutch of the previous gear to a load pressure value sufficient for transmitting an instantaneous load torque so as to take place, at the latest, on engagement of the gearwheel clutch of the loose wheel of the gearbox stage of the new gear in the second gearbox section;
• subjecting, after reaching the load pressure value of the operating pressure in the engagement actuator of the friction clutch of the previous gear, the disengagement actuator of the previous gear friction clutch to operating pressure up to the level of a disengagement pressure value sufficient to overcome the at least one engagement spring thereof;
• applying, after the load pressure value of the operating pressure in the engagement actuator of the friction clutch of the previous gear is reached, operating pressure to an engagement actuator of the friction clutch of the new gear;
• providing, on an increase of the operating pressure in the engagement actuator of the friction clutch of the new gear above a constant contact pressure value, an intersection control of the operating pressures, in the engagement actuators, of the friction clutches of the previous gear and the new gear;
• initiating, when the operating pressure in the engagement actuator of the friction clutch of the previous gear tends to zero, a control phase during which the operating pressure in the engagement actuator of the friction clutch of the new gear is raised to an essentially constant phase pressure value which is larger than the load pressure value of this operating pressure sufficient for transmitting an instantaneous load torque;
• disengaging, on reaching a load pressure value of the operating pressure in the engagement actuator of the friction clutch of the new gear sufficient for transmitting an instantaneous load torque, the gearwheel clutch of the gearwheel stage of the previous gear;
• switching off, after the disengagement of the gearwheel clutch of the gearwheel stage of the previous gear, the operating pressure of the disengagement actuator of the friction clutch of the previous gear;
• terminating the control phase with increased phase pressure value of the operating pressure in the engagement actuator of the friction clutch of the new gear when the rotational speed of the input shaft has dropped to a rotational speed value dependent on the new gear;
• lowering the operating pressure in the engagement actuator of the friction clutch of the new gear at an end of the control phase with increased phase pressure value to a load pressure value sufficient for transmitting an instantaneous load torque;
• switching off, after the load pressure value of the operating pressure in the engagement actuator of the friction clutch of the new gear has been reached, the operating pressure in the disengagement actuator of the friction clutch of the new gear;
• also switching off, when the operating pressure in the disengagement actuator of the friction clutch of the new gear tends to zero, the operating pressure in the engagement actuator of the new gear friction clutch;
• simultaneously subjecting the disengagement actuator of the friction clutch of the previous gear and the engagement actuator of the friction clutch of the new gear to operating pressure;
• simultaneously switching off the operating pressure in the disengagement actuator of the friction clutch of the previous gear and the operating pressure in the engagement actuator of the friction clutch of the new gear;
• and also simultaneously subjecting the engagement actuator of the friction clutch of the previous gear and the disengagement actuator of the friction clutch of the new gear to operating pressure.