Transmissions Focussed On Newer Efficiencies For Better Tomorrow

Cover Story October 2019 Transmissions Focus Newer Efficiencies

The automotive transmission space globally has been witnessing significant advancements focussed on addressing the ever-increasing need for greater fuel economy, emission reduction and improved driving experience

The area of automotive transmissions has been witnessing an increase in the number of gears (progressing from three speed gearboxes to 10-speed gearboxes), variation in ratios as well as different types of clutch systems supporting these advanced gears, all aimed at ensuring an efficient power transfer from the engine to the wheels. There is an increasing industry focus on environmentally-friendly powertrains, while at the same time ensuring they are able to maintain vehicle dynamics and support active safety systems. There is little doubt that the future gearbox will have to be much smarter so that it delivers higher efficiency without compromising on the fun-to-drive experience of vehicle users.

GLOBAL AUTOMOTIVE TRANSMISSION TRENDS

The auto industry has been witnessing adoption of different transmission technologies across the globe. The Chinese transmission market is dominated by continuously variable transmissions (CVTs), dual clutch transmissions (DCTs), and conventional automatic transmission. All these transmission technologies enjoy an equal presence because the Chinese market has been growing so fast that no single technology could bridge the demand gap, thus resulting in consumers lapping up all these technologies. In the US, conventional automatic transmissions are firmly entrenched, while the transmission story in Europe is also about conventional automatics but are increasingly moving towards dual clutch transmissions (DCTs). As far as Japan is concerned, continuously variable transmissions (CVTs) rule the roost, which is hardly surprising since CVTs were invented there.

INDIAN TRANSMISSION STORY

Manual transmissions (MTs) enjoy an overwhelming penetration in India (enjoy a penetration of over 80 %) owing to the low-cost advantage it offers. Optimisation and performance enhancements of MTs going forward will be largely driven by transmission efficiency improvements, cost & weight reduction, gear shift convenience as well as increasing gear span that increase fuel economy.

Automatic transmissions (ATs) had first arrived in the Indian market with Hyundai rolling the i10 in 2008, and a few years later Maruti Suzuki came up with AT-equipped A-Star in 2010. Even as ATs were rolled out in India, it is important to understand that the advent of ATs in India has been taken with a pinch of salt because it was generally felt that the shift from MTs to ATs was an expensive affair. The price difference between MT and AT was anywhere in the range of Rs 100,000 - Rs 120,000 and fuel efficiency of AT was also lower by around 10-20 % as compared to MT. Further, there was also a perception that maintenance costs of AT-equipped vehicles would be higher.

The perception about ATs subsequently changed with the arrival of automatic manual transmission (AMT) called the auto gear shift (AGS) technology launched by Maruti Suzuki in 2014 (AGS was rolled out on its Celerio). The AMT is essentially a manual gearbox that features an electronic or hydraulic actuator that monitors the driving behaviour and shifts between gears. For price-conscious Indian consumers, who accord a high level of importance to Kitna Degi or fuel efficiency, AMT was seen as a better option owing to the low-cost advantage it offers - the price difference between manual transmission and automatic manual transmission was around Rs 50,000-60,000. In fact, both MT and AMT offer more or less same fuel efficiency because the basic structure is that of a manual shift transmission. AMTs have proved to be a huge success since it was seen as a good option for Indian consumers, who wanted some level of ‘comfort’ while driving without having to shell out more as they would have in case of opting for ATs.

There is a line of thought that the transition from MT to AT (all forms of automatic – AT, AMT, DCT, CVT, etc) could happen quickly in India like it has happened in China. The AT penetration in the Indian mass market is around 5-6 % and is poised to go up to 35-40 % over the next five years and this will be largely driven by AMT and dual clutch transmission (DCT) technologies.

PROMINENCE OF DCT TECHNOLOGY

DCTs despite being expensive are fast emerging as the go-to technology as it offers higher efficiency and power shifts aimed at offering drivers a fun-to-drive experience. The DCT technology divides between odd gears and even gears and this ensures friction losses occur from one clutch at a time. DCTs have two technologies – dry clutch DCT and wet clutch DCT. A dry clutch DCT operates with an electromechanical shift, where electromechanical solemnities perform the shifting. Dry clutch DCTs are deployed in smaller torque engines, achieve better fuel economy and is much cheaper to make. But it subsequently lost out on popularity because it had judder issues, unfavourable wear and flip characteristics as well as service maintenance issues. On the other hand, wet clutch DCTs are deployed in higher torque engines, operate with an electro hydraulic shifting and ensure smooth flip characteristics as well as higher durability. Wet clutch DCTs are however, not without shortfalls – it has drag losses and is less fuel efficient than dry clutch DCTs. DCTs in general, across the globe have proved to be highly efficient than the conventional automatic transmission.

DCTs are steadily penetrating into the Indian mass market, especially in sports utility vehicles (SUVs) – Jeep Compass and MG Hector are prime examples. The DCT technology gets more prominence for vehicles above 1.5 l engine vehicles as they are better equipped to handle a wider gear ratio spread coupled with higher slip efficiency. With the Indian auto industry working moving to BS VI and CAFÉ norms, there will be a need to expand the ratio spread and this is where DCTs will play a crucial role.

CVT TECHOLOGY

The CVT technology is a good offering for 1.2-1.5 l petrol engine vehicles, but it is susceptible to monopoly pricing as only globally there are currently only two suppliers. So supply chain security is a challenge for adoption of CVTs However, CVTs are good for handling a narrow gear ratio spread of up to 1.5 l engine vehicles (its slip efficiency decreases beyond 1.5 l engine vehicles) and cannot be deployed effectively above 1.5 l petrol engine vehicles.

GLOBAL PASSENGER & COMMERCIAL VEHICLE TRENDS

Although the two-wheeler industry has not witnessed considerable advancements in the area of transmissions, the passenger vehicle segment has seen significant advancements over the years steadily moving away from manual gearboxes to various types of semi-automated and fully-automatic transmissions (AT) depending on the segments. It is globally observed that passenger vehicles largely come with automatic transmissions (it could be either torque converter, DCT or CVT). The improved performance of ATs can be attributed to improved electronics and this is where various electronic control units play a big role – all these ensure a satisfactory drive as well as fuel economy.

Commercial vehicles (CVs) globally have been witnessing significant developments in the area of transmissions – the bus segment has embraced ATs in more advanced countries in Europe, North America and the Asia-Pacific region. MTs are widely used for buses in developing markets, with AMTs also penetrating these markets.

Under CVs, the truck segment across the globe has been adopting ATs with the most common being six and eight-speed transmissions because they largely operate at a specific speed without having too many halts, which also ensure decent fuel efficiency, in contrast to AT-equipped passenger vehicles. But off-road vehicles such as mining tippers opt for AMTs since this works well for trucks continuously operating at low speeds over an extremely challenging terrain for long hours (sometimes 20-22 hours in a day) and invariably featuring full payloads.

ROUND-UP

The future of mobility is steadily transitioning towards electrification and this transition will cover hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), wherein the electric motor can be integrated into ATs, DCTs, CVTs by adding a hybrid module. Further, there is development work going on around dedicated hybrid transmissions that is said to have lower mechanical complexities than conventional multi-speed transmissions. There is also a lot of work going around reversible variable transmission that offers a new way of transmitting power and contains no clutch or other slipping components and uses the engine at its best efficiency curve at all times – this technology offers substantial fuel savings and Co2 reduction along with pleasant driving experience.

Automotive transmissions are rapidly evolving and one can be rest assured of one thing – going forward, the automotive industry will deal with transmissions that will deliver higher fuel economy, substantial Co2 reduction and even more better driving experience.

(With inputs from Divgi TTS and Greaves Cotton)

TEXT: Suhrid Barua

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