Toyota Motor Corporation has developed a new continuously variable transmission (CVT) featuring a launch gear; a new 6-speed manual transmission; a new 2.0-liter engine with 40% thermal efficiency (41% in hybrid applications); a new 2.0-liter hybrid system; and new 4WD systems—one for gasoline-engined cars, one for hybrids—based on the Toyota New Global Architecture (TNGA).
Toyota intends to expand the number of models equipped with the newly announced powertrain units globally from this spring onward. The powertrain units will not only contribute to improved environmental and driving performance of conventional gasoline engine vehicles, but the core technologies will be reflected in the performance improvement of electrified vehicles, including hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), and fuel cell electric vehicles (FCEVs).
Direct Shift-CVT: A New Type of Continuously Variable Transmission
The basic function of any transmission system is to achieve transmission efficiency, high-efficiency engine ranges, and highly responsive gear changes. To improve these functions, Toyota has striven to reduce mechanical loss, adopt a wider gear range, and improve shift tracking. These initiatives have resulted in a direct and smooth driving experience with superior fuel efficiency, which has been improved by 6% over the existing transmission system.
Reduced mechanical loss. The new powertrain unit features the first launch gear in a passenger vehicle CVT, which facilitates improved transmission efficiency in lower gear ratios where belt efficiency is poor. By adopting launch gears, it is possible to improve belt efficiency and increase ratio spread by 15% without performance deterioration.
The transmission system utilizes gear drive when starting from a full stop, resulting in powerful acceleration while at the same time resolving the momentary sluggish feeling that was previously present during accelerator operation. Both smooth and comfortable launch performance are realized. When switching from gear drive to belt drive, the transmission system uses highly responsive gear change control technologies cultivated from AT technology.
Conversion to wider gear ranges. In line with the adoption of a launch gear, belt use is now specified for higher gear ratios. This new setup not only improves the efficiency of belt use, but also enables the adoption of wider gear ranges, thereby realizing a class-leading gear ratio range of 7.5 for the 2.0-liter class.
Improved shift tracking. The adoption of launch gears results in reduced input load. This enables the size of both belt and pulley components to be reduced. The belt angle has been narrowed and pulley diameters reduced, resulting in shifting speeds that are 20% faster. Both powerful and rhythmic acceleration are realized. Shift responsiveness has improved through downsizing of the pulley and reduction of inertia by 40%.
New 6-speed Manual Transmission (6MT)
Toyota has also developed a new manual transmission in response to global needs, particularly those in Europe. Compared to the existing version, the mass of the new system has been reduced by 7 kg (15.4 lbs) and total length by 24 millimeters (0.9 inces). This makes it one of the world’s smallest transmissions, and its small size contributes to improved fuel efficiency.
The 6MT also offers leading transmission efficiency, while the use of iMT (Intelligent Manual Transmission) controls, which automatically adjust engine rotations when changing gears, ensures smooth gear shifting free of uncomfortable recoils.
2.0-liter Dynamic Force Engine, a New 2.0-liter Direct-injection, Inline 4-cylinder Gasoline Engine
Toyota’s new Dynamic Force Engine adopts high-speed combustion technologies and a variable control system. It also achieves greater thermal efficiency, resulting in high output, due to a reduction in energy loss associated with exhaust and cooling systems, the movement of mechanical parts, and other aspects.
As a result, the newly developed 2.0-liter gasoline vehicle and hybrid vehicle engines achieve world-leading thermal efficiencies of 40% and 41% respectively. In addition, compared to existing engines, the new engines achieve increased torque at all engine speeds—from low to high rotations—and will comply with expected future exhaust regulations in each country in advance.
Some of the new technologies applied in the 2.0-liter engine include:
Piston with laser pit skirt. By subjecting the skirt sliding surface to mirror finishing, reduced friction is realized. On the skirt surface, narrow crosshatch grooves created by lasers improve scuff resistance.
Cylinder head. Adopting a laser clad valve seat for the intake valve seat to make the intake port compatible with strong tumble flow (fuel consumption performance) and intake flow rate (output performance).
To improve thermal efficiency and fuel economy, the high-speed combustion technology in the engine features a long stroke; a widened angle between the intake and exhaust valves; a high-efficiency intake port with a laser-cladded valve seat; a high compression ratio (14); high-energy ignition coil; new D-4S injection; and a multi-hole direct injector.
A variable cooling system utilizes a motor-driven water pump and heated thermostat.
2.0-liter Toyota Hybrid System (THS II)
Toyota has developed a new hybrid system for 2.0-liter engines, which applies the same size-reducing, weight-reducing, and loss-reducing technologies used in the fourth-generation Prius. The new system realizes improved driving performance while retaining superior fuel efficiency. When accelerating, the hybrid system reduces engine rotations while drawing increased electric power from the battery, thereby delivering a linear and lengthened sense of acceleration.
The new Power Control Unit (PCU) is 20% smaller, and 10% lighter than the conventional 1.8-liter model, which allows it to be placed directly above the transaxle.
The new transaxle motor features a new rolling-coil structure with fewer wires, and also uses a newly developed magnetic steel. A new parallel reduction gear format helps to reduce the loss in the transaxle. The two-motor mechanical power split transaxle offers maximum motor output of 80 kW and maximum motor torque of 202 N·m.
The new system uses a 1.4 kWh NiMH pack with 180 cells (6.5 Ah, 212 V).
New Dynamic Torque Vectoring AWD and E-Four 4WD Systems
Toyota has developed two new 4WD systems with the aim of improving fuel efficiency and achieving high 4WD handling, stability, and off-road performance.
The new Dynamic Torque Vectoring AWD system is used in gasoline engine vehicles. By adopting a torque vectoring mechanism, which independently distributes torque to the left and right rear wheels according to driving conditions, the Dynamic Torque Vectoring AWD system enables the driver to steer the vehicle exactly as intended. It achieves high off-road performance even on the toughest roads.
It also incorporates a disconnect mechanism, which features the first ratchet-type dog clutches on both the front and rear wheel shafts. These clutches stop the drive system rotations, which transmit driving force to rear wheels when in 2WD mode, significantly reducing energy loss and improving fuel efficiency.
The new E-Four system will be used in hybrid vehicles. The system increases total torque to the rear wheels—which are electrically driven—by 30% compared to existing versions. By adopting a new control system that optimally distributes torque to the rear wheels based on the driving conditions, the E-Four system offers high off-road performance, handling, and stability.
Moreover, both the Dynamic Torque Vectoring AWD system and the new E-Four system feature AWD Integrated Management (AIM), which harmonizes engine, transmission, braking, and 4WD systems to offer superb handling and stability regardless of road surface conditions.
Regarding TNGA-based powertrains, Toyota has already announced plans to introduce 17 versions of nine engines, 10 versions of four transmissions, and 10 versions of six hybrid systems by the end of 2021. The new continuously variable transmission, 6-speed manual transmission, 2.0-liter engine, and 2.0-liter hybrid system represent four of the planned components.
Within the next five-years to the end of 2023, Toyota aims to have TNGA-based powertrain units installed in approximately 80 percent of Toyota-brand and Lexus-brand vehicles sold annually in Japan, the United States, Europe, and China. Toyota forecasts that the TNGA-based powertrain units alone will improve fuel efficiency enough to reduce CO2 emissions from Toyota vehicles by more than 18%.