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An alternative to hydraulic automatic transmissions,...
An alternative to hydraulic automatic transmissions, the Double Dry Clutch transmission features one clutch for even gears and one clutch for odd gears. This provides the comfort of an automatic transmission and the fuel efficiency of a manual transmission.
Valeo offers a double dry clutch that provides comfort when shifting gears and fuel economy when compared to other automatic transmissions.ergie.
The double clutch gearbox offers the automotive industry a future automatic transmission solution that provides a combination of comfort of use and reduced vehicle fuel consumption. Valeo offers a double dry clutch developed using its manual gearbox experience. When coupled with electro-mechanical actuator technology, this concept offers significantly higher performance than that of the hydraulically actuated double clutch systems currently fitted in double clutch production vehicles.
The double dry clutch is designed to offer maximum comfort when shifting gears. This comfort is provided by ensuring controlled slipping of the plates in both clutches during gear changes. Valeo handles this harsh clutch use by offering an integrated clutch and
actuator solution. This solution couples technologies already tried and tested in series production, such as bonded rather than riveted linings, with specially-developed technologies ensuring double-clutch strength and reliability, such as travel adjustment integrated within the actuators.
he double dry clutch offered by Valeo contains three plates. The central clutch plate is fixed axially and its rotation is linked to the engine’s flywheel. A disk presses on each side of the central plate, and a moving plate presses in turn on the disks. The disk on the plate’s motor side engages both when starting and when shifting to odd gears. The plate on the plate’s gearbox side engages only when shifting to even gears and reverse. The plates transmit torque to two coaxial shafts: one of them is hollow and is used for even gears, and the other passes inside it and is used for odd gears. The plates are engaged by an electromechanical actuator applying a force, via a release
To obtain maximum comfort during gearshifts, sufficient controlled slip from both plates is required. When one plate is disengaging, the other is engaging, meaning that the mechanism must withstand a high thermal load applied for a very short time. This heat is
absorbed through a careful choice of materials. The slipping movement also increases plate wear. Valeo therefore utilizes its Tripod® plates with bonded linings (already in use in single clutches) offering a longer clutch plate life. This exclusive patented technology
allows the total thickness of both plates to be reduced and thereby optimizes the thermal mass, which is key in efficient double dry clutch operation.
The engaging of a clutch requires the balancing of the forces applied by the diaphragm and those by the actuator. In order to reduce the demands made on the electric motor, the actuator includes an assisting spring. This utilizes a cam to apply a force almost equal to that applied by the diaphragm. The electric motor then provides the additional force required to control the plate engaging and disengaging actions, thereby consuming less energy. 15 Amperes electric current are required during gearshifts, and only 1 Ampere is required between gearshifts to keep both clutches closed. This contributes to Valeo’s double dry clutch exceptional efficiency. Lastly, the actuators include a bi-directional travel adjustment mechanism that adjusts for disk wear and also adjusts automatically to compensate for production tolerances. This last point simplifies the vehicle assembly process.
If requested, Valeo can alternatively supply an automotive manufacturer with its electro-mechanical actuators alone, for fitting to wet friction clutches.
The double dry clutch can be fitted in conjunction with a dual mass flywheel if required for particular diesel or gasoline engines. The permitted torque range for a transverse gearbox varies from 200 to 350 Nm depending on the clutch plate diameter defined by the space available, the vehicle weight and the gearing reduction in the gearbox’s first gear.
Valeo offers a highly efficient mechanism, providing exceptional performance:
The customer enjoys not only better performance and improved fuel economy but also improved comfort and driving pleasure :
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