Friday, June 26, 2020

Here's How Kia's Clutch-by-Wire Technology Works


When Kia pulled the wraps off the refreshed 2021 Rio, one of the more unique things about it is the so-called intelligent Manual Transmission or iMT. Unlike a traditional manual which uses a mechanical linkage for the clutch, this one uses a “clutch-by-wire system” and is paired to their mild-hybrid powertrain.

At the time, the Korean automaker didn’t delve into much detail on how it works. Now, they have.

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. This improves overall fuel efficiency and can reduce emissions by around three percent 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 says the iMT was developed particularly for the European market who still prefer the engagement of a manual transmission. They say it’s an ideal solution for electrified models because it offers the same feel and familiarity of a MT gearbox, but with added fuel efficiency benefits.

Moreover, 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.

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