Dual Mass Flywheel (DMF) for Cars

At high engine speeds, the centrifugal load pushes the springs against the spring guides and creates friction.

Due to this friction, the active number of coil springs is reduced, therefore, the effective spring stiffness is increased and filtering capacity is reduced.

In DMFs with inner springs, small straight springs are integrated in the drive plate. Less sensitive to the centrifugal load, they are able to filter the vibrations.

For some extremely demanding applications, especially on rear wheel drive (RWD) vehicles, achieving an extremely low vibration level at the gearbox entry level is necessary.

Valeo’s long travel damper (LTD) technology, developed for automatic transmission damping, is integrated inside the DMF to reach this target.

Long travel damper DMF : The LTD DMF significantly reduces perceived vibrations and engine noise, representing a major step forward in powertrain filtration technologies.

This advance is especially important as the fuel-saving engines now being developed have higher torque and, consequently, generate greater vibrations, particularly at low speeds.

The LTD DMF absorbs torque vibrations generated by the engine before they reach the transmission, thereby increasing passenger comfort.

Two compact filtration devices give the LTD DMF the qualities needed to become an essential component in tomorrow's conventional high-performance engines as well as for hybrid powertrains, which have the strictest installation constraints.

The LTD technology is based on two sets of three springs operating in series and synchronised by a back plate.

The straight springs are less sensitive to the centrifugal load than the curved springs, providing less friction, and thus better filtering than with curved springs.

In addition to common Dual Mass Flywheel technology, the LTD DMF integrates a long travel damper developed by Valeo for torque converters on automatic transmissions.

This combination allows for optimal filtration, especially during startup, thanks to a maximum angular displacement of 80° and exceptional performance with all engine types.

Valeo’s long travel damper Dual Mass Flywheel offers previously impossible comfort levels on the most fuel-efficient engines.

The performance, comfort, and safety of any vehicle is defined by its powertrain. The major factors driving demand in the passenger powertrain market are the rising popularity of automated transmissions and the growing trend of engine downsizing. Engine downsizing, in particular, can reduce fuel consumption and emissions, providing the performance of a larger engine while preserving cabin comfort. 

To reduce fuel consumption, car makers add gears, axles, and increased automation to the gearbox, generating more noise and vibrations.

Downsizing is thus key to reducing pollution and keeping performance by reducing engine cylinder size or the piston count to generate less noise and vibrations. 

The common element here is the clutch, which must be redesigned to adapt to all these constraints whilst keeping noise and vibrations at an acceptable level. 

For some years now, a special type of flywheel, called the Dual Mass Flywheel (DMF), has been used in car powertrains to protect the transmission and the rest of the driveline from engine vibrations. 

Recently, DMFs with pendulum technology have been introduced on vehicles with the most powerful engines, where a standard DMF isn’t enough to reduce vibrations to an acceptable level. Adding a pendulum to the DMF reduces total vibration by about 10%.

As with any tuned mass absorber, a centrifugal pendulum absorber’s function is based on absorption rather than damping. This distinction is significant since dampers reduce the vibration amplitude by converting vibration energy into heat. Absorbers store the energy and return it to the vibration system at the appropriate time.

Like tuned mass absorbers, centrifugal pendulum absorbers are not part of the force/torque flow. The absorption range of the centrifugal pendulum absorber differs from the tuned mass absorber and is effective over an entire order instead of a narrow frequency range.