Toyota unveils new TNGA-based engines and transmissions and improved hybrid systems; deployment begins in 2017
In Japan, Toyota Motor Corporation unveiled new advanced engines and transmissions and further evolved hybrid systems based on the Toyota New Global Architecture (TNGA). Toyota intends to deploy these new powertrain units in a rapidly broadening range of vehicle models, starting in 2017. The new units will feature in 60% or more of vehicles sold annually in Japan, United States, Europe and China in 2021, reducing CO2 emissions in those markets by 15% or more.
Within the five years to the end of 2021, Toyota plans to introduce 17 versions of nine new engines; 10 versions of four transmissions, including multi-geared automatic transmissions and a new kind of continuously variable transmission; and 10 versions of six hybrid systems.
Using TNGA, Toyota has been changing the automobile from its very structure, lowering hood heights, lowering the center of gravity and implementing other innovations to improve driving performance. To enhance fundamental vehicle performance in terms of running, turning and stopping, it initiated a comprehensive review centered on vehicle platforms and is now, since the release of the fourth-generation Prius in 2015, expanding the use of new platforms throughout its product lineup. At the same time, it has been developing new powertrain units that significantly improve both driving and environmental performance.
|Powertrain evolution targeted by TNGA, based on improving and maximizing the efficiency of powertrain systems (engines, transmissions and hybrid systems). Click to enlarge.|
Toyota’s newly developed powertrain units are light and compact and have a low center of gravity. Reconsideration of fundamental vehicle performance has resulted in engines with high-speed combustion and in highly efficient multi-geared transmissions. Furthermore, to standardize the basic structure of these new units, Toyota used modular design (unified design).
While it was a given that the new powertrain units would be designed to have a high level of environmental performance, development focused on achieving driving performance that would “change how Toyota cars drive”, under the theme “Direct & Smooth.”
The new powertrain units provide approximately 10% better power performance (in terms of the time needed for a gasoline-powered vehicle to accelerate from 0-60 mph and for a hybrid vehicle to accelerate from 25-43.5 mph) and approximately 20% better fuel economy. Combining the new powertrain units with the overall evolution of the vehicle body, including aerodynamics, weight reduction and others, can open the way to even greater power performance and fuel economy.
Dynamic Force Engines. Toyota has named its new line of internal-combustion power plants “Dynamic Force Engines”. The engines are based on a three-fold development concept: 1) loss reduction (exhaust, cooling, pumping, friction); 2) improved combustion quality; and 3) improved intake efficiency.
The first announced member of the lineup is a 2.5-liter engine that has one of the world’s best thermal efficiencies: 40% when used in gasoline-powered vehicles and 41% when used in hybrid vehicles (HEVs). This new, thoroughly reconsidered and greatly evolved engine features numerous new technologies, such as technologies for minute control that make it highly responsive and allow it to generate ample torque at all speeds.
The gasoline engine employs high-speed combustion technology and a variable control system. Both strong tumble flow and high intake air volume are achieved by redesigning the stroke-bore ratio (Stroke/Bore≈1.2), widening the angle of the valve (to approx. 41˚) and a high-efficiency intake port with laser-cladded valve seat with new seat materials with high wear and heat resistance.
A high compression ratio (13:1 in the conventional engine, 14:1 for the variant used with a hybrid system), high energy ignition coil, new D-4S injection systems and new multi-hold direct injector all contribute to the high thermal efficiency of 40%.
|Performance of new engines. Click to enlarge.|
Other contributors to the greater thermal efficiency are the reductions in energy losses associated with, among others, exhaust and cooling systems and the movement of mechanical parts.
|Technologies used in the new Dynamic Force Engines. Click to enlarge.|
New 8-speed and 10-speed automatic transmissions. Toyota has developed two new automatic transmissions: the 8-speed Direct Shift-8AT and the 10-speed Direct shift-10AT. For both, various measures were taken to minimize energy loss and heighten transmission efficiency. Gear tooth surfaces were processed using a new technique for a lower coefficient of friction when the gears engage, and the configuration of the friction material used inside the clutch was optimized to reduce clutch torque loss by approximately 50% during rotation (compared to a conventional 6-speed transmission).
These and other efforts resulted in achieving one of the world’s best transmission efficiencies. The new automatic transmissions are more compact and lighter than comparative conventional transmissions, lowering a vehicle’s fuel requirements. And their lower center of gravity results in both improved straight-driving stability and better cornering stability.
Furthermore, widened gears and a newly developed high-performance compact torque convertor combine for a broader gear lockup range. The resulting quick and smooth response to accelerator pedal operation creates an “as desired” direct driving feel.
In the case of the Direct Shift-10AT, even though the number of gears has been increased to 10 (compared to eight gears in the case of the Direct Shift-8AT), the use of close-ratio gears optimizes the range of use of each gear, particularly in the low-to-mid speed range. The resulting smooth gear changes, which are among the world’s quickest, create a rhythmical and comfortable sensation that is suitable for a premium rear-wheel-drive vehicle.
Through such measures, fundamental vehicle performance in practical driving situations ranging from driving around town to driving on the highway has been improved to a degree that drivers can distinctly experience. Smooth response to accelerator pedal operation enables “as desired” vehicle departure and, in overtaking maneuvers, it allows lag-free and rhythmical acceleration that meets driver expectations, even in cases of sudden and heavy accelerator pedal use.
Advancement of Toyota Hybrid System II (THS-II). Applying size-reducing, weight-reducing and loss-reducing technologies used in the fourth-generation Prius, Toyota has enhanced its hybrid system for the new Dynamic Force 2.5-liter engines and developed a new, high-performance Multistage THS II for rear-wheel-drive vehicles.
New low-loss components in the power control unit (PCU) help reduce electrical loss by approximately 10%. The new PCU is smaller and lighter, allowing it to be mounted directly above the transaxle. The transaxle itself features a motor with a new rolling coil structure with fewer wires and a newly developed magnetic steel. A new parallel reduction gear format helps reduce losses, while a new multi-axis structure for MG1 and MG2 reduces the size and weight of the system. The new transaxle is also approximately 30 mm shorter.
THS II for 2.5-liter engines excels in both power and fuel-economy performance due to the synergistic effect of size-reducing, weight-reducing and loss-reducing technologies coupled with the high thermal efficiency and output of the new Dynamic Force engine. Acceleration time is 10% shorter than the current system (2AR-FXE + THS II) and fuel economy (JC08) is 20% better.
Multistage THS II—newly developed for rear-wheel-drive passenger vehicles—adds a Multi-Stage Shift Device to THS, resulting in major improvements in system output and transmission efficiency across the entire range. By adopting the Multi-Stage Shift Device to THS, the engine is able to operate in a wider speed range; both engine torque and MG torque are reinforced.
In addition to improving system efficiency at high speeds, intermittent use of the engine at high speeds has also been made possible, further improving high-speed fuel economy.
The system for plug-in hybrid vehicles (PHVs) has also been enhanced. A new dual-mode drive system allows the electric motor, which was hitherto used only as a generator, to provide direct driving power, resulting in powerful driving, even when in EV mode. The one-way clutch stops reverse engine rotation to implement normal direction rotation with no drag.
Further enhancing the system for PHVs is a large-capacity lithium-ion battery that largely increases the EV-mode cruising range to 60 kilometers (37 miles) or more in the JC08 test cycle.
Roll-out of new powertrain units. Through TNGA-based modular development, Toyota will roll out numerous types of new powertrain units within a short timeframe, successively introducing them in various vehicle models, starting with the launch of a new-model vehicle in 2017.
By the end of 2021, Toyota aims to have the new powertrain units feature in 60%or more of Toyota-brand and Lexus-brand vehicles sold annually in Japan, the United States, Europe and China. Toyota forecasts that Toyota and Lexus vehicles sold that year in those markets will account for a CO2 reduction in those markets of 15% or more, counting the fuel-efficiency-improvement contributions made by the new powertrain units alone.
Review and strengthening of development structure of Powertrain Company. Toyota intends to review and strengthen the development structure of its in-house Powertrain Company. Conventional engine-powered vehicles account for the vast majority of vehicles currently on the market, and HEVs and PHEVs—the advance of which is expected to continue—also have internal-combustion engines. In addition to promoting development of engines and transmissions, which are seen to remain mainstay for some time to come, toward the coming electrification of vehicles, Toyota is accelerating its development of hybrid technologies (electrification technologies), such as those used in electric motors, batteries and power control units (PCUs).
Toyota has long conducted research and development of key technologies and systems based on its stance to “acquire through in-house creation”. However, Toyota acknowledges that it would be difficult to heighten the pace of development and commercialization of electrification technologies for further reducing CO2 emissions if Toyota addressed such as it has done until now, relying only on its own resources.
Toyota will continue to carefully select that which it deems necessary to “acquire through in-house creation”. But, from now on, it will also promote the sharing of technologies within the Toyota Group and increase the number of fields covered by joint research. It will strengthen joint development that uses cross-group obeya (project rooms with displays for sharing and reviewing goals, policies, timelines, progress and problems, etc.), efficiently use group resources to quickly establish advanced technologies and aim for increases in three areas: in the collective ability of the Toyota Group; in the speeding of development; and in the scale of proliferation and expansion of environmental technologies.
Strengthening the development structure for hybrid technologies. Key hybrid technologies, such as those found in electric motors, batteries and PCUs, are also key technologies used in vehicles that are powered by electricity, such as PHVs, FCVs and EVs. For the electrification of vehicles, to greatly accelerate the development of hybrid technologies, which Toyota positions as the core technologies of environmental technology development, Toyota plans to increase its number of hybrid technology-development personnel.
Specifically, it plans to reorganize its development structure starting in 2017 and increase its number of people involved in hybrid technology development by approximately 30% within the five years to the end of 2021. Beyond then, as well, it plans to further strengthen its human resources for hybrid technology development as needed.
Toyota aims to reduce new-vehicle CO2 emissions by 90% (compared to 2010 levels) by 2050. Based on its principle policy of conserving energy, which is the cornerstone of its development of environment-friendly technologies, by furthering the evolution of engines and transmissions and by promoting widespread use of HEVs and PHEVs, Toyota is endeavoring to improve fuel efficiency as a means of reducing CO2 emissions. And with a view to the future and an eye on limiting the consumption of fossil fuels centered on petroleum, to respond to the diversification of energy sources, Toyota is advancing its development of zero-emission vehicles, such as FCVs, which use hydrogen, and EVs.