Transmitting More Than Torque

Decoding Technology Transmission Torque

Transmissions are major enablers and candidates for reducing carbon footprint, improving vehicle fuel economy, reducing total cost of ownership and enhancing the driving experience.

The evolution of transmissions in the early days of mobility was more focused on higher efficiency in transmitting power from the engine as torque to the wheels with a good drive and shifting feel for the occupants. As that phase progressed, cost and light weighting became the new focus areas for developers. With the advent of hybrids and alternate mobility powertrains, the seamless integration of an electric motor inside the powertrain assembly became a priority and a necessity due to vehicle packaging constraints and the costs associated to modify body-in-white along with associated components. This sandwiched motor between the engine and transmission introduced new challenges of powertrain dynamics, thermal management, longevity, robustness and serviceability of the powertrain. It also introduced a new dimension of reliability in torque delivery on driver demand. In parallel, at this time, compactness and light weighting were also top attributes of focus.

Over the years, to ensure a better driving experience, and with advancing engine technologies, vehicle options and driver demands, transmissions were developed in different architectures – manual, automatic, semi-automatic, electric, hydrostatic, hydrodynamic, direct shift gearboxes with dual-clutch and continuous variable transmissions. These have been integrated in the vehicle based on market needs, engine configurations and costs. Due to the huge costs in development and integration of a transmission, the designers utilise the opportunity to optimise transmission behaviour during calibration, shift scheduling, sensing & actuation, and the electronics in conjunction with controls.

With the evolution of transmission architectures, the regulations and norms in different parts of the world, vehicle styling and characteristics were changing too. The focus gradually shifted to transmissions being the enablers for other attributes in the vehicle such as end of life, lifecycle and environment aspects.

It was obvious that a transmission with high efficiency, lower frictional & thermal losses, and lesser weight contributes majorly to the fuel efficiency of the vehicle and a cleaner tail pipe in vehicles. The transmission architecture along with the controls strategy, can decide the shift behaviour and torque required from the engine. It is, in turn, dependent on driver demand and driving behaviour.

In the global outreach and markets, the powertrain and vehicles are expected to be interchangeable not only due to norms and regulations but also due to the driving conditions and the local ecosystem of traffic patterns. These aspects severely affect the functionality of vehicles, impacting fuel economy and emissions. In addition, the effect on end of life of vehicle significantly differs in different operating environments.

Innovative as well as conventional strategies have been used for thermal management, compacting, reduction of hardware & weight, gear layouts, the composition of lubricants & lubrication layouts, newer technologies for different types of transmissions, the sensor technologies, networking and control strategies. Many of the technological features have become a standard in the new age vehicles due to competition and consumer demand. Even techniques for grinding of gears, hobbing as well as other manufacturing processes have come a long way as they impact the sustainable life, heat generation and noise in transmissions.

The transmissions are not merely subsystems that transmit torque to the wheels. They are the key lever to a long-term reliable driving experience and sustainable mobility. Transmissions provide the competitive edge to automotive manufacturers globally.