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Mr. John Smith

Job title



Title: Efficient disconnect for electric drivetrains Car electrification era sees more and more four wheel drive (4WD) cars coming on the market as the customer wants more safety, fun to drive but also less range anxiety for less cost. Unfortunately, about 60% to 70% of the time the vehicle is in 4 x 2 mode and its rear axle will generate losses especially with a permanent magnet motor. As known, reducing transmission losses is key for the CO2 emissions (HEV) and the range quest (BEV). One way to do so is to disconnect as many rotating parts as possible in the gearbox and e-motor on the rear axle through a dedicated device. A disconnect device can save from 5% to 10% in transmission losses in low and high voltage applications. It will become the main trend for permanent magnet rear axles. In the first step, different concepts will be compared in terms of efficiency. In a second step the chosen concept will be improved for main functional performance but also for constraint functions as mass, volume, assembly and remanufacturing. Electromagnetic simulations with a dedicated software will be shown in detail as it is the main design driver for the actuator performance, opening and closing time. Electro-magnetic simulation tool was correlated with measurements on the first concept so as to get confidence for future studies. Magnetic field leakage, sensor location choice and safety have also to be considered. The disconnect can be operated at 0 km/h so clunk noise at the end stroke was taken into account through a piston impact force simulation. In addition to electro-magnetic and dynamical aspects, integration of a disconnect in a reducer; volume optimisation, reparability and CO2 have been taken into account. The study is centered on solenoids coaxial to the transmission shaft. It can be extended to a solenoid parallel to the shaft but it will not include other actuator concepts like motor+screw. This is the second generation of an existing concept. Design steps and optimisation methodology will be shown for the first time. New, improved disconnects are needed for the future HEV and BEV 4x4 applications to come. The Valeo coaxial solenoid disconnect has a lower mass and energy consumption than the first disconnect generation and takes into account today's CO2 constraints. Dipl ing Roel VERHOOG, Valeo Dipl ing Christophe MOLLIER, Valeo Dr Alexandre RENAULT, Valeo

Dipl.-Ing. Roel VERHOOG, R+I Manager, Valeo

Efficient disconnect for electric dirvetrains

FWC2023-PPE-009 • Propulsion, power & energy efficiency


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