This paper evaluates two mild hybrid drive trains for a mid-class passenger car with a gasoline engine by means of Computer simulation. The term mild hybrid is used for vehicles without sustained electric propulsion. The mild hybrid drive trains both have a Continuously Variable Transmission (CVT) with a Van Doorne metal V-belt and a torque assist device used to enhance fuel economy driveability, comfort and emissions at minimal additional costs. The aim is to carry out an objective analysis of the electrical and mechanical torque assist systems on acceleration performance with equally efficient engine operation. In the electrical torque assist system, a 4,5 kW (10 kW peak) starter-alternator with NiMH battery is added to the CVT drive train and the mechanical torque assist system connects a 0,4 kgm2 flywheel inertia in parallel to the CVT using a power splitting planetary gear set. The acceleration performance of the drive train experienced by the driver is determined by the total acceleration time, maximum acceleration level and the dead time between pedal deflection and persistent acceleration response. It is shown that driving fuel-efficiently tends to deteriorate the acceleration response, while total acceleration time and final acceleration level are virtually unchanged. The poor driveability associated with fuel-efficient engine operation is therefore linked to the acceleration response, more than anything else. In view of this understanding, the electrical or mechanical torque assist should be directed especially towards improving the initial acceleration response. Both torque assist Systems manage to enhance the acceleration response while tracking the E-line, but excel at different vehicle speeds, having a break-even performance slightly above 30 km/h. Below the breakeven speed, the electrical system is somewhat ahead of the mechanical system. Above this speed, the mechanical torque assist system starts to outperform the electrical torque assist system on acceleration response.


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    Title :

    Mild hybrids with CVT: Comparison of electrical and mechanical torque assist


    Contributors:

    Published in:

    Publication date :

    2001


    Size :

    15 Seiten, 8 Bilder, 5 Tabellen, 7 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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