Shift Elements: Multi-disc Clutches and Brakes
The purpose of the shift elements is to perform shifts under load without the tractive flow being interrupted. The shift elements consist of the following.
The shift elements are engaged hydraulically. The pressurized oil reaches the space between the cylinder and piston, as a result the discs are compressed. The clutch/brake is engaged when the oil pressure drops, the cup spring acting on the piston presses the piston back into its initial position. The clutch/brake is now released again.
Depending on the gear, the multi-disc clutches B and E supply the engine torque to the planetary gear train, with multi-disc brakes C, D and F directing the torque into the housing.
The dynamic pressure at clutches B and E is equal: i.e. the dynamic pressure in front of and behind the piston is equal. This equalizing effect is achieved in the following way.
The space between the baffle plate and piston is filled with unpressurized oil. A dynamic pressure dependent on the engine speed builds up. The space between pressure also builds up. However, there is simultaneously a static pressure, which causes the clutch to engage. If the static pressure is relieved, the cup spring is able to force the piston back into its original position.
The advantages of this dynamic pressure equalization are:
- Reliable clutch opening in all speed ranges
- Smoother shifts.