May 20, 2014 Toyota City, Japan – Toyota is using one of the hardest materials in nature after diamonds to develop a semiconductor chip it hopes will improve the fuel efficiency of its hybrids, such as the Prius, by as much at 10 percent.
The company and its partners announced today that they have developed a silicon carbide (SiC) power semiconductor for use in automotive power control units. Toyota plans to begin test-driving vehicles with the technology on public roads in Japan within a year.
The chips, made from carbide – one of the hardest materials in nature, theoretically have superior characteristics such as one-tenth the electrical power loss and 10 times the drive frequency. Toyota said the chips would also allow it to reduce the size of current automotive power control units by 80 percent.
The automaker said it has already achieved a 5 percent improvement in fuel efficiency in test vehicles and aims to commercialize the technology by 2020.
The new chips, along with improved engines and aerodynamics, are key steps the company is taking to continue advancing hybrid powertrains, a technology it pioneered nearly 17 years ago.
Toyota Develops New Series of Gas Engines That Will Boost Fuel Efficiency At Least 10%
The new engines leverage combustion and loss-reduction technologies Toyota has refined in its dedicated hybrid engines. Two engines will form the base of the new series. The first is a 1.3-liter gasoline engine using the Atkinson cycle normally used in dedicated hybrid vehicles that achieves a maximum thermal efficiency of 38 percent — top-level among mass-produced engines. The second is a 1.0-liter gasoline engine, jointly developed with Daihatsu Motor Co., Ltd., that has achieved maximum thermal efficiency of 37 percent.
The new engines will be used in models scheduled for partial redesign in the near future, and a total of 14 engine variations will be introduced globally by 2015.
1Numerical expression showing how much of the thermal energy generated by burning fuel is converted into effective power. The higher the thermal efficiency, the lower the fuel consumption.
Toyota Develops Engines with Improved Thermal, Fuel Efficiency
One of the engines is a 1.3-liter gasoline engine in which Toyota is employing the Atkinson cycle3―normally used in dedicated hybrid engines. Use of the Atkinson cycle provides an increased expansion ratio and reduces waste heat through a high compression ratio (13.5), resulting in superior thermal efficiency. Toyota aims to further improve the fuel efficiency of the engine by utilizing other innovations including an intake port with a new shape that generates a strong tumble flow (whereby the air-fuel mixture flows in a vertical swirl) inside the cylinder, and a cooled exhaust gas recirculation (EGR) system paired with Variable Valve Timing-intelligent Electric (VVT-iE) technology to improve combustion and reduce loss. As a result, the new engine will have a maximum thermal efficiency of 38 percent4―top-level among mass-produced engines. The new features, combined with idling stop and other functions, will lead to fuel efficiency gains of approximately 15 percent2 by comparison with current vehicles.
Meanwhile, a 1.0-liter engine jointly developed with Daihatsu Motor Co., Ltd. has achieved maximum thermal efficiency of 37 percent4 due to a similar tumble flow-generating intake port, a cooled EGR system, and a high compression ratio. Combination with the idling-stop function and various other fuel consumption reduction technologies allows vehicles to achieve a maximum fuel efficiency improvement of approximately 30 percent2 over current vehicles.
1Numerical expression showing how much of the thermal energy generated by burning fuel is converted into effective power. The higher the thermal efficiency, the lower the fuel consumption.
2Under the Japanese Ministry of Land, Infrastructure, Transport and Tourism’s (MLIT) JC08 test cycle
3Combustion cycle in which thermal efficiency is improved by making the expansion ratio larger than the compression ratio, thereby improving fuel efficiency
4Based on in-house calculations
Toyota Develops New Silicon Carbide Power Semiconductor with Higher Efficiency
Toyota City, Japan, May 20, 2014―Toyota Motor Corporation, in collaboration with Denso Corporation (Denso) and Toyota Central R&D Labs., Inc. (Toyota CRDL), has developed a silicon carbide (SiC) power semiconductor for use in automotive power control units (PCUs). Toyota will begin test driving vehicles fitted with the new PCUs on public roads in Japan within a year.
Through use of SiC power semiconductors, Toyota aims to improve hybrid vehicle (HV) fuel efficiency by 10 percent under the Japanese Ministry of Land, Infrastructure, Transport and Tourism’s (MLIT) JC08 test cycle and reduce PCU size by 80 percent compared to current PCUs with silicon-only power semiconductors. SiC power semiconductors have low power loss when switching on and off, allowing for efficient current flow even at higher frequencies. This enables the coil and capacitor, which account for approximately 40 percent of the size of the PCU, to be reduced in size.
PCUs play an important role in hybrids and other vehicles with an electrified powertrain: they supply electrical power from the battery to the motor to control vehicle speed, and also send electricity generated during deceleration to the battery for storage. However, PCUs account for approximately 25 percent of the total electrical power loss in HVs, with an estimated 20 percent of the total loss associated with the power semiconductors alone. Therefore, a key way to improve fuel efficiency is to improve power semiconductor efficiency, specifically by reducing resistance experienced by the passing current. Since launching the “Prius” gasoline-electric HV in 1997, Toyota has been working on in-house development of power semiconductors and on improving HV fuel efficiency.
As SiC enables higher efficiency than silicon alone, Toyota CRDL and Denso began basic research in the 1980s, with Toyota participating from 2007 to jointly develop SiC semiconductors for practical use. Toyota has installed the jointly developed SiC power semiconductors in PCUs for prototype HVs, and test driving on test courses has confirmed a fuel efficiency increase exceeding 5 percent under the JC08 test cycle.
In December last year, Toyota established a clean room for dedicated development of SiC semiconductors at its Hirose Plant, which is a facility for research, development and production of devices such as electronic controllers and semiconductors.
In addition to improved engine and aerodynamic performance, Toyota is positioning high efficiency power semiconductors as a key technology for improving fuel efficiency for HVs and other vehicles with electrified powertrains. Going forward, Toyota will continue to boost development activities aimed at early implementation of SiC power semiconductors.
Toyota will exhibit the technology at the 2014 Automotive Engineering Exposition, to be held from May 21 to May 23 at the Pacifico Yokohama convention center in Yokohama.