“Clutch by wire” for mild hybrid Kias

Kia Motors today reveals more details of its new intelligent Manual Transmission (iMT), which has been designed for a range of mild-hybrid electric vehicles (MHEVs) from Kia. It represents a world-first application of a 48V mild-hybrid powertrain with a ‘clutch-by-wire’ transmission. The technology is engineered to boost fuel efficiency and reduce CO2 emissions of Kia’s MHEVs, while retaining the driver engagement of a conventional manual transmission. The iMT strengthens Kia’s leading role in developing a comprehensive range of electrified powertrains for drivers at all price points.

Instead of a mechanical linkage, the iMT’s clutch operates purely electronically, and is integrated seamlessly with a 48V MHEV powertrain. The iMT works with the mild-hybrid starter generator (MHSG) to switch off the engine earlier than Kia’s Idle Stop & Go start-stop system when coasting to a halt. It also enables brief periods of ‘engine-off’ coasting at speeds of up to 125 km/h (77 mph), seamlessly reactivating when the driver pushes the accelerator or clutch pedal. The system can improve overall fuel efficiency and can reduce CO2 emissions by around three per cent in real-world driving conditions.

The chosen gear remains engaged even with the engine off. The engine restarts in the same gear as soon as the driver presses either the brake or accelerator pedals thanks to the burst of power provided by the MHSG. The transmission restarts the engine in neutral (with an open clutch) if the driver pushes the clutch pedal to change gear, or if the vehicle speed is too low for the current engaged gear.

How it works – step-by-step

The driver leaves the car in-gear as it starts to coast, gently slowing the car down (e.g. for a corner, junction, or traffic)
While in-gear, the iMT sends an electronic signal to the gearbox and MHSG to seamlessly switch off the engine and open the clutch
With the engine switched off, the car continues coasting, with the open clutch limiting deceleration and allowing the car to make the most of its kinetic energy
As the driver pushes the accelerator to pick up speed, or engages the clutch to change gear, the MHSG restarts the engine in the driver’s selected gear, or in neutral (with an open clutch)
Electric power from the MHSG and 48V battery instantly brings the engine and transmission up to the correct speed
If the car drops below a certain speed, the engine restarts with assistance from the MHEV system, and the clutch closes, to avoid labouring the engine in the engaged gear
Kia’s new iMT has been developed at the Hyundai Motor Europe Technical Centre in Offenbach, Germany, overseen by Dr Michael Winkler, Head of Powertrain. Dr Winkler comments: “We are always looking at new ways to improve powertrain efficiency and performance, and the iMT is one such innovation. An automatic or a dual-clutch transmission suits a lot of drivers, but European drivers in particular still love changing gear for themselves. Alongside the increasing demand for electrified models, the iMT is a result of us exploring ways to electrify the ‘classic’ manual transmission.”

Dr Winkler continues: “Electrification is an overarching development theme across our European powertrain division, and our work encompasses the development of 48V mild-hybrid powertrains, through to the new ‘clutch-by-wire’ iMT as a complementary technology. We want to continue providing drivers with a familiar and engaging manual gear change, so this is an ideal solution for the new range of MHEV powertrains we are rolling out across Europe in the months ahead.”

The familiarity of a conventional manual transmission
Although the iMT introduces a new clutch-by-wire technology in place of a mechanical link between driver and transmission, it retains the same operation and driver engagement as a conventional manual. The new system allows drivers to enjoy the uniquely engaging drive that comes from using a manual transmission. The clutch pedal operates in the same manner as a conventional manual, with greater controllability due to the electromechanical control of the clutch and a ‘biting point’ that enables drivers to change gears smoothly.

The iMT will be fitted to the upgraded Kia Rio EcoDynamics+, due on-sale in Europe during the third quarter of 2020 with a new 1.0-litre T-GDi petrol mild-hybrid powertrain. The new transmission will be adopted across a number of future Kia models, with the brand set to introduce a range of new engines and MHEV powertrains later in 2020.