The DDCT dual-clutch gearbox, consisting of a C635 6-speed mechanical gearbox, two clutch discs and an electro-hydraulic control, this solution allows 'powershift' shifts, i.e. without interruption of power exchange to the ground.

The DDCT transmission can be used in both semi-automatic mode (MANUAL) and automatic mode (AUTO).

The control lever is replaced by 'P (Parking), R (Retro), N (Neutral), D (Drive)' controls on a special joystick on the dashboard.

Operation

The whole system works thanks to the oil pressure in the system, and the TCU gearbox in the passenger compartment under the floor covering in front of the passenger seat, which controls the EVs for selecting and engaging gears and clutch actuators.

Constructively, each clutch is connected to a specific primary shaft: in dual-clutch gearboxes there are two coaxial primary shafts:

• The K1 'odd' clutch connects the engine to odd gears 1,3,5
• The K2 'even' clutch connects the engine to even gears 2,4,6
• The RM can be connected to one clutch or another depending on the design.

Cueing is done in the 'traditional' way by engaging the K1 'odd' clutch with the first gear engaged on its synchroniser.

When changing gears, the next gear is first engaged with the clutch still disengaged, then this clutch is engaged in modulated mode, and at the same time the clutch of the previous gear is disengaged in modulated mode.

In this way, the engine can always transmit torque to the ground, as in automatic transmissions (AT).

Click on the following link for a brief example of the shift phase: tct example shift 1 - 2 gear

The DCU clutch kitconsists of a clutch mechanism cover K1 odd gears (1)the K1 clutch drive disc in odd gears (2)a K1 clutch plate pusher spring in odd gears (3), an intermediate flywheel (4)a K2 clutch plate retaining spring even gears (5), a K2 clutch disc pusher spring in even gears (6)a K2 clutch mechanism cover even gears (7) and the K2 clutch drive disc in even gears (8).

The Electro-hydraulic unit (Complete Actuation System C.A.S.), includes:

• the hydraulic power unit consisting of an electric pump and accumulator, which provides hydraulic power for the actuation of both gear engagement/selection and CSCs.

• The solenoid valve actuating unit that converts hydraulic energy into mechanical energy by interfacing the engagement pistons with the control rods. It is responsible for controlling and managing the position of the clutches, gear selection and engagement.

On behalf of the Technical Help Desk team, I thank you for your attention and wish you good work.