Toyota Motor Corp showed a concept model of a fuel-cell vehicle (FCV) at Tokyo Motor Show 2017, which was open to the public from Oct 28 to Nov 5, 2017.
The FCV, "Fine-Comfort Ride," uses an in-wheel motor (IWM) for each of the four wheels. It realizes a drive range of 1,000km (approx 621 miles) with a large-capacity hydrogen tank and an FC (fuel-cell) stack having a high fuel-electricity conversion efficiency.
Toyota released the "Mirai" FCV in 2014. For the concept car exhibited this time, the company made improvements to the technologies developed for the Mirai and increased drive range per charge by about 50% from 650km to 1,000km (under the JC08 test mode). The drive range is more than twice as long as that of Nissan Motor Co Ltd's "Leaf" electric vehicle (EV).
The drive range of 1,000km is realized by (1) employing an IWM to increase the installation space for the hydrogen tank, (2) improving the fuel-electricity conversion efficiency of the FC stack and (3) reducing traveling resistances such as air resistance and rolling resistance.
By using an IMW for each of the four wheels, the need for a large-size driving motor can be eliminated, creating extra space in the vehicle and enabling to increase the size of hydrogen tank. This time, Toyota employed a vertically-long cylindrical hydrogen tank and installed it under the floor (in the center of the vehicle) in the direction of the vehicle's length.
"The problems of IWM are the increase in the mass of wheel and the control of motor," said an engineer who is developing FCVs at Toyota.
The mass of the motor ranges from 20-25kg, and the mass distribution around the wheel drastically changed from that of the previous FCV.
As the mass around a wheel increases, so does the deformation of the tire. This time, Toyota developed a wheel in cooperation with Sumitomo Rubber Industries Ltd and employed an airless tire whose spoke is made of plastic. The tire does not need to be inflated.
By replacing the hollow rubber part with the spoke, the tire can reduce the deformation caused by the increase of mass, making it easier to control the IWM. The reduction of the heat loss caused by the deformation also contributes to reducing rolling resistance. Toyota has been developing the IWM to be combined with the tire for about 10 years.
Furthermore, the fuel-electricity conversion efficiency of the FC stack was improved.
"We improved the efficiency by 10-20%, compared with the Mirai," Toyota said.
The key is a catalyst technology. A team specialized in catalysts is developing it at the company.
Toyota designed the shape of the auto body so that it can reduce air resistance and realize a spacious interior space. With the design, which the company calls "diamond cabin," the space for the second row of seats is the largest. Whether the FCV is seen from a side or top view, the second row looks as if it is expanding. The large interior space enables seats to move widely.
The Fine-Comfort Ride has three rows of seats. Its riding capacity is six people. Its dimensions are 4,830 (L) x 1,950 x (W) x 1,650mm (H), and its wheelbase is 3,450mm. Compared with Toyota's "Noah" minivan, the FCV is 135mm longer, 255mm wider and 175mm lower.