Improve fuel economy - Kia launches intelligent manual transmission

Kia researchers have developed a new intelligent manual transmission (iMT) that improves the manual gearshift experience by arranging advanced clutch-by-wire technology into a compact housing.

As car manufacturers need to ensure that the average CO2 emissions of their models fall to 95 g/km by 2021 (in compliance with EC 443/2009 regulation), they are looking for cost-effective solutions, especially for C-segment manufacturers where profit margins are slim.

Kia, for its part, hopes to meet emissions targets with the newly developed iMT, an advanced electronically controlled clutch system developed by Hyundai Motor's European Technical Center in Offenbach, Germany. Dr. Michael Winkler, head of powertrain development at Kia Europe, said the iMT is still a traditional manual transmission, but the clutch system has been electrified.

iMT can be used to complement Kia's 48V mild hybrid system and will be matched with the Ceed's 1.6L CRDi diesel powertrain and the 1.0L TGDI gasoline engine equipped with RIO EcoDynamics+. Its layout is relatively simple. It does not have a master cylinder mechanically connected to the clutch pedal, nor does it drive the clutch release bearing. Instead, it uses a pedal position sensor connected to the TCU and can control the execution of the electro-hydraulic servo system, which can start the clutch release bearing.

Winkler mentioned that the above development process is not just to electrify the clutch, but there are two main factors. One is comfort - many users like the feeling of manual shifting, but in terms of comfort, manual gears still have some defects. When using the electronic system, Kia's researchers can adjust the bite point of the clutch and handle the engine shutdown characteristics. However, the key factor is to reduce vehicle emissions and improve its fuel consumption. At the same time, under actual driving conditions, the system can achieve a 3% fuel saving target.

working principle

When the driver shifts into gear, the vehicle will coast, and the iMT will shut down the engine and disengage the clutch. When the driver intends to accelerate, the mild hybrid starter generator (MHSG) will restart the engine, and the MHSG and 48 V battery will restore the engine and transmission to their original speed. If the vehicle's running speed decreases, the MHSG will also restart the engine and engage the clutch.

Run rules

When the driver releases the accelerator, the vehicle is usually in a state of coasting or turning deceleration. When the iMT decouples the clutch and stops the engine, the system will have the function of a start/stop system. Once the accelerator pedal is pressed again, the 48V starter/generator system will provide additional torque and enable the engine to be smoothly reconnected. When the driver steps on the brake pedal, the system will take full advantage of the engine braking system. When the brakes are applied, the system does not work, which can effectively save energy when the vehicle is driving in suburban areas. When the driver presses or releases the accelerator, there is no need to use the brakes.

The researchers modified the system using Kia's existing manual transmission, saving a lot of redesign work. Winkler said the iMT retains as many of the same components as possible compared to a traditional manual transmission. Kia's researchers were able to make minimal adjustments to the system, mainly replacing the clutch pedal with a sensor-equipped pedal and adding a control unit and an electro-hydraulic actuator.

The main challenge facing researchers is to arrange the system in a compact engine compartment. Factors such as temperature have an impact, so researchers must take into account the placement of the TCU. From the customer's perspective, Winkler mentioned that the driver's pedal feel is no different than that of a vehicle without an iMT. Kia's researchers complete customer surveys to discover their interests and optimize during the development process to meet their actual needs.

However, there is a slight difference in response speed between the iMT and the mechanical clutch mechanism. Winkler mentioned that the driver will not notice the difference in response during normal driving. In sports driving mode, considering some characteristics of the electro-hydraulic system, if it is used in a high-performance vehicle, it will be limited accordingly.

Cost-effectiveness

From a manufacturing perspective, the integrated system will incur additional costs compared to a manual clutch, but Kia researchers believe that it is reasonable to adopt the system. David Labrosse, head of Kia product planning, mentioned that starting in 2021, each vehicle will cost an additional $107 for every additional 1 g of CO2 emitted, so measures to reduce emissions are of high importance. Consumers can choose to buy a Kia pure electric vehicle or a plug-in hybrid vehicle, and the current light hybrid iMT system can achieve better results at a reasonable cost.