Multi - Plate Clutch Operation
WARNING: This page does not describe the selected car, but rather 212 other vehicles, including the 2012 BMW 750i, 2012 BMW 750Li, 2011 BMW M3, 2011 BMW 750i, and 2011 BMW 750Li. However, it is still accessible from the selected car via links, so may be relevant.
In order to carry out a shift in ratio, fluid needs to be applied or released from the Multi - Plate Clutch (or Brake). As shown in the example at the right, the following sequence occurs:
- Fluid from a shift valve in the valve body is applied to the clutch assembly.
- Fluid pressure builds behind the apply piston and overcomes the resistance from the diaphragm spring.
- The friction and steel discs are compressed together and become locked, preventing any slippage between them.
- Two planetary members are now locked together.
- When fluid pressure is released, the steel and friction discs are allowed to unlock.
- The diaphragm spring pushes against the apply piston and returns the piston back to the rest position.
- The check ball in the apply piston is unseated by centrifugal force which allows the clutch to drain completely. See Fig 1.