Zeroshift has devised a multi-speed gearbox for electric cars that needs no clutch – a damper inside the gear hubs and electronic control of the motor make ratio changes seamless.
Having more than one gear ratio and the ability to shift without interrupting torque means the motor runs at higher efficiency, extending range and batteries’ life expectancy by up to 10 percent.
The innovation could enable manufacturers to downsize electric cars’ electric motors, keeping them running longer at the medium loads and speeds where peak efficiency of over 95 percent is possible. For drivers, that could mean more performance, greater range and longer lasting batteries.
Zeroshift’s concept prevents any torque interruptions during ratio changes and does not require a clutch, issues that have so far deterred electric car manufacturers from fitting multi-speed gearboxes. Current electric cars instead use a single-speed transmission, but the motor then spends more of its time outside of its optimum efficiency range.
The improved efficiency offered by Zeroshift’s concept could also extend electric cars’ in-service battery life. Current range limitations often lead electric car drivers to drain the cells to the maximum allowable level of discharge in order to reach their destination; the deeper cycling affects batteries’ life expectancy. Improving the motor efficiency uses less of the energy stored for a given journey, easing the discharge-recharge cycles and reducing recharge time.
