Three stepped concepts for the E-Clutch have been developed by Schaeffler depending on the level of automation required. In the MTplus version, the basic principle of transmitting forces hydraulically is maintained but with the addition of an actuator directly in the pressure line. The advantage here is that the demands on actuation times and the number of actuations are lower, resulting in reduced demands on performance.
Even partial automation makes a contribution to reducing fuel consumption when ‘sailing’. During continuous driving, the engine is disconnected from the transmission and is either completely switched off or idles. The MTplus system disconnects the transmission. The driver provides the signal for this indirectly by taking their foot off the accelerator pedal.
Tests conducted using the WLTP consumption measurement cycle and realistic customer cycles have recorded reductions in fuel consumption from 2% (engine goes to idle) to 6% (engine switches off). Using a 1.2 litre petrol engine demonstration vehicle, Schaeffler claims to have shown that it is possible to achieve savings of up to 8% in urban driving conditions.
In the clutch-by-wire concept, the mechanical or hydraulic connection between the pedal and the clutch release system is replaced completely. The opposing force on the pedal from the clutch release system, which is no longer required, is generated by a pedal force adjuster containing an additional sensor that sends a signal on the pedal position to a clutch actuator. The driver is therefore not immediately aware of the automatic engagement but continues to drive as normal with a manual transmission. An intelligent actuator undertakes the opening and closing of the clutch in all driving situations consisting of a basic actuator that includes all the electronics, the e-motor, and a spindle drive. Its modular design is said to be universally applicable, which reduces the development time and overall system costs.
Clutch-by-wire is more powerful than MTplus: the functionality of this clutch release system means that it can accommodate driving conditions with high dynamic requirements, such as rapid gear shifting or emergency braking. The option of electrically tuning the transfer from pedal travel to clutch travel is said to make it possible to have gear-related adaptation or a sport mode option, previously only reserved for automatic transmissions.
The performance of this technology has been demonstrated in the ‘Gasoline Technology Car’ (GTC) co-developed by Schaeffler, Ford and Continental, where reductions in fuel consumption and CO2 emissions of 17% were achieved with the automatic clutch said to make a significant contribution to this.
Electronic Clutch Management (ECM) is based on the same system as clutch-by-wire, but without a clutch pedal. A sensor provides the signal for disengagement when the driver changes gear. Engagement follows automatically once the gear is selected. The high degree of automation in the ECM system provides a basis for integrating an electric motor into the drive train. By using a suitable battery in a 48V on-board electrical system, the ECM system is used to drive the vehicle in all instances when the engine is running inefficiently.
Schaeffler claims its E-Clutch system not only opens up new prospects for manual transmissions, but this also provides a way into new markets and market segments for hybrid transmissions.
