Shift Elements: Multi-disc Clutches and Brakes

The shift elements perform shifts under load without interrupting the tractive flow. The illustration identifies the following components:

1. Snap Ring
2. Steel Disc
3. Lined Disc
4. Cup Spring
5. Oil Supply to Dynamic Pressure Equalizer
6. Baffle Plate
7. Disc Carrier
8. Oil Supply to Clutch
9. Input Shaft
10. Cylinder
11. Piston
12. Spring Disc

The shift elements are engaged hydraulically. The pressurized oil reaches the space between the cylinder and the piston, which compresses the discs. The clutch/brake is engaged when the oil pressure drops and the cup spring acts on the piston, pressing the piston back into the initial position. This releases the clutch/brake again.

Depending on the gear, the multi-disc clutches B and E supply the engine torque to the planetary gear train. The multi-disc brakes C, D, and F direct the torque into the housing.

The dynamic pressure at clutch B is equal to the pressure at clutch E, that is, the dynamic pressure in front of the piston equals the pressure behind the piston. This equalizing effect occurs in the following way:

1. The space between the baffle plate and the piston is filled with unpressurized oil.
2. A dynamic pressure dependent on the engine speed builds up.
3. The space between pressure also builds up.
4. Simultaneously a static pressure occurs, which causes the clutch to engage.
5. If the static pressure is relieved, the cup spring is able to force the piston back into the original position.

The advantages of this dynamic pressure equalization are reliable clutch openings in all speed ranges, and smoother shifts.