The Toyota Hybrid System in its 4th generation
by Raf Schuermans
Technological evolution of 4 generations – Technical highlights of the latest system in the Toyota Prius – Nearly 20 years of Full Hybrid experience in the global market
Since the 1st market introduction nearly 20 years ago, Toyota’s full hybrid technology has been continuously improved through 3 generations that are described in the presentation for reference. The main content of their presentation at the CTI Symposium will describe the Toyota Hybrid System in its 4th generation in more detail, as available in the market in the New Prius. The new hybrid system is more compact and lighter. The new hybrid battery offers higher energy density. Whilst its total power was maintained, its size has been reduced so that it is located entirely beneath the rear seats, avoiding any intrusion in the load space. It can now absorb more energy in the same amount of time, which means that it charges faster than before. Cooling efficiency and regeneration range have been improved too. The electric motors are smaller in size, yet also provide a better power-to-weight ratio. Higher motor speed and new forced water-convection cooling in place of air cooling improve the efficiency. The new multi-shaft transaxle design is more compact, which allowed to relocate the 12V battery of the vehicle back into the engine compartment and further improve load space as a result.
Careful attention has been paid to the NVH behaviour of the transmission in combination with the power control unit (PCU) sitting on top of it. The PCU itself has been totally redesigned, resulting in a reduction in size, weight and electrical losses. Updates to the hybrid system software allow to accelerHybrid Systemate the car in a low engine rev range and in less dependency on the combustion engine at higher speeds, improving fuel economy. The fuel economy achieved by the new Prius on a vehicle level marks the largest improvement between generations of the hybrid model, achieved thanks to improvements in the hybrid system and efficiency improvements throughout the car. This accomplishment reflects Toyota’s philosophy of refining existing technology – the concept of having something good, then making it better. The main attributes that have made Toyota hybrids popular with drivers across the globe are their fuel efficiency, and the relaxed and carefree drive that they provide. Variations of the technology are used in a whole range of vehicles from the Toyota and Lexus brands, with several vehicle models being assembled in Europe.