Toyota Hybrids for Environment
Companies that develop, produce and sell automobiles cannot avoid environmental issues. Against the backdrop of dwindling petroleum resources and the company’s desire to help reign in global warming, Toyota has been actively developing various new technologies that help achieve energy security and diversify energy sources.
One solution developed by the company to address these issues is the widespread use of internal combustion hybrids. Hybrid systems combine an engine and a motor to distribute drive power efficiently and recover kinetic energy during deceleration, converting it to electrical energy for storage in a battery, which greatly improves fuel efficiency and makes cleaner exhaust emissions possible. In addition, hybrid technologies can be adapted for fuel cell vehicles and are key technologies for the development of the ultimate eco car.
A Leap of Faith
Early in the 1990s, Toyota sought to answer two important questions: “What are the requirements of motor vehicles for the 21st century?” and “What sort of vision must Toyota have to meet the challenges of the new era?” To answer these questions, the company assembled staff members from various departments to develop a totally new type of vehicle.
They set a target of a 50 percent increase in fuel efficiency (1.5 times that of existing vehicles). Akihiro Wada, a Toyota executive vice president at the time who was responsible for the project, felt that this was inadequate. The team’s first plans were drastically changed, as the initial technologies being considered would not be capable of reaching this level.
In January 1994, a full-fledged project began, and in 1997, Toyota declared the start of the Toyota Eco Project. As part of this effort, Toyota decided to tackle the international challenge of reducing CO2 emissions in order to prevent global warming and accelerated the development of a hybrid vehicle with the goal of achieving twice the fuel efficiency of conventional vehicles. Then, in March of the same year, Toyota announced the completion of a new power train called the Toyota Hybrid System (THS) for use in passenger vehicles. This power train combines a gasoline engine and an electric motor and does not require external charging. This system also achieves nearly twice the fuel efficiency of conventional gasoline engines.
THS was first installed in Toyota’s Prius passenger vehicle and introduced to the Japanese market in December 1997 as the first mass-produced hybrid passenger vehicle in the world. In 2000, after further improving THS, overseas marketing of the Prius began.
What Is a Hybrid System?
Automobile hybrid systems combine two power sources, such as an internal combustion engine and an electric motor.
Hybrid systems possess the following four characteristics:
- Energy-loss reduction — The system automatically stops the idling of the engine (idling stop), thus reducing the energy that would normally be wasted.
- Energy recovery and reuse — The energy that would normally be wasted as heat during deceleration and braking is recovered as electrical energy, which is then used to power the starter and the electric motor.
- Motor assist — The electric motor assists the engine during acceleration.
- High-efficiency operation control — The system maximizes the vehicle’s overall efficiency by using the electric motor to run the vehicle under operating conditions in which the engine’s efficiency is low and by generating electricity under operating conditions in which the engine’s efficiency is high.
In Pursuit of the World’s Highest Fuel Efficiency
The new hybrid system THS II is based essentially on THS. In a bid for even higher efficiency, the new system adopts a high-voltage power circuit between the motor and generator, and greatly reduces energy loss during energy transmission to deliver optimal energy efficiency. THS II significantly increases the use of the electric motor, and under conditions in which the engine experiences poor efficiency, the engine is stopped and the vehicle runs using only power from the electric motor.
THS, which is a series parallel hybrid, contains a power split device that splits power into two paths. In one path, the power from the gasoline engine is directly transmitted to the vehicle’s wheels. In the other path (electrical path), the power from the engine is converted into electricity by a generator to drive an electric motor or to charge the battery. This unique configuration achieves idling stop, stopping of the gasoline engine while the vehicle is running, running of the vehicle using the electric motor, motor assist at any speed, and highly efficient energy regeneration, without using a clutch or transmission. This is achieved through the use of a motor having large low-speed torque and large output.
Expanding Sales of Hybrid Vehicles
Toyota believes that promoting the widespread use of vehicles with high environmental performance will require the introduction of hybrid vehicles into popular market segments. The applicability of hybrid technology is broad and can be used not only on gasoline vehicles, but also with diesel and alternative fuel engines, and is even effective in combination with fuel cell technologies. If the hybrid system can increase performance regardless of the energy source, it will remain a core technology in the development of the ultimate eco car.
With the recent launch of the two hybrid SUVs, Toyota
