The global trend toward a carbon-neutral society has been accelerating in recent years, and automotive manufacturers have been responding by increasing the ratio of power train electrification in order to reduce CO2 emissions. Honda is focusing its efforts on its own e:HEV with its two-motor hybrid system and engaging in expanded development of electric power trains. Now Honda has developed a new plug-in hybrid (e:PHEV) system for the 2023 new model CR-V that has increased the all-electric range (AER) 12% and improved fuel economy 14% over the previous e:HEV system. The three drive modes of EV mode, hybrid drive mode, and engine drive mode that are unique to Honda have been further advanced and optimized. Enhancing more than just long-range EV driving, the high-capacity battery have also reduced the load on the engine without loss of quietness to yield hybrid driving that realizes exhilarating acceleration together with engine driving that realizes enhancement of towing performance and enhancement of high-quality acceleration performance. The new model e:PHEV system has a 2.0-L direct injection Atkinson-cycle engine, a front drive unit (FDU) consisting of a lock-up clutch system directly linking the engine, further the traction motor, and the generator motor .The lock-up clutch system has two types of gear ratio, a low gear for low speeds and towing, and a high gear for high-speed cruising.It also has a power control unit (PCU) to supply power from the high-capacity battery to the motors and to the 12-V battery, and intelligent power unit (IPU) in which the high-capacity battery are installed, and an on-board charger (OBC) that charges the high-capacity battery from the charging infrastructure. Honda gives an exhilarating driving experience with a hybrid drive mode with a Linear Shift Control that provides drivers the feeling of pleasurable driving matched to their sensations by means of engine sounds that agree with their actual driving as well as rhythmical engine sounds that give the impression of shifting gears. The lockup clutch system with two types of gear ratio was newly adopted to assure towing performance and enhance high-speed driving performance. However, when switching to and from the hybrid drive mode described above, the Linear Shift Control and the engine speed change together with the changing rhythm of gear shifts can be a strange feeling for drivers. Seamless switching between modes therefore becomes an issue. To resolve this issue, a control system has been adopted here that provides optimal timing for control of switching between hybrid drive mode and engine drive mode. As a result, we have achieved a good feeling for the driver with exhilaration and linearity when switching drive modes. The characteristics of the 2.0-L direct injection engine adopted for the Honda e:HEV system and of the hybrid systems are used to advantage so that when towing a trailer and so on, selecting the TOW mode switch optimizes the electric power management. By means of a dedicated operation using the low-ratio side of the lockup clutch system, the load on the traction motor is reduced while assuring 1500 kg of towing performance. When driving at high speeds, another dedicated operation using the high-ratio side of the lockup clutch system causes the battery to assist the traction motor. This realizes 10% greater acceleration performance and 22% greater top speed performance, achieving comfortable cruising when driving at high speeds. By means of the above, the kind of long-range EV driving characteristic of the PHEV is achieved. In addition, the exhilarating driving provided by the Linear Shift Control and the towing performance and high-speed driving performance provided by the dual lockup clutch system are enhanced while achieving low fuel consumption. This paper describes how the e:PHEV power train management control realizes quietness combined with exhilarating and high-quality operation as well as advanced environmental performance at a high level while allowing seamless switching between the three driving modes. The paper also introduces the main technologies involved in control operations for towing and for high-speed driving through the use of Linear Shift Control when driving in hybrid drive mode and the use of the lockup clutch system during engine drive mode, together with the results obtained by these technologies.
Mr. Masatoshi Saito, Assistant Chief Engineer, Honda Motor Co., Ltd.