Honda to add new dedicated hybrid model with i-MMD in US in 2018; hybrid system to expand to light trucks
Honda will produce a new dedicated hybrid model in the US for nationwide in 2018, as part of the Honda Electrification Initiative, which will expand the company’s portfolio of electrified vehicles. Honda set a global target for two-thirds of all sales to come from electrified models by 2030 and to halve its total company CO2 emissions from 2000 levels by 2050.
The new, dedicated hybrid vehicle will utilize Honda’s second-generation two-motor hybrid system, which is currently deployed in the Accord Hybrid (earlier post). The new model will be produced at an existing plant in the United States. Additional details on the vehicle and its manufacturing will be announced closer to launch.
The second-generation Intelligent Multi-Mode Drive (i-MMD) two-motor hybrid powertrain as applied in the Accord includes a propulsion motor and a generator motor, both of which were upgrade from the previous generation i-MMD for more power, smaller size and lighter weight.
Both motors utilize segment conductor winding, where the coil is inserted from the axial direction of the stator core, as well as square copper wire versus the previous round wire, providing a denser and more compact stator. These changes enable the electric motors to be significantly smaller and more than 23% lighter than the previous motors.
An additional improvement in the motors is the replacement of two larger rotor magnets with three smaller and lighter magnets. The three magnets are arranged in an arc pattern that creates six magnetic poles, which helps to improve torque multiplication.
These changes result in significantly increased output performance. The propulsion motor’s maximum power was raised by 14.8 horsepower to 181 horsepower (135 kW) and torque is increased by 6 lb-ft to 232 lb-ft (315 N·m). The generator motor’s power was raised to 142 horsepower (106 kW) from 140.8 with torque remaining at 62.7 lb-ft (85 N·m).
The intelligent Power unit (IPU) packages a DC-DC converter and a 1.3 kWh Li-Ion battery pack. Significant changes to the IPU provide the same capacity and output but in a much more compact and lighter package. This was achieved by utilizing VDA-standard, high-energy density Li-Ion battery cells, unifying the battery ECU and cell voltage sensor into one component and utilizing a single rather than dual cooling duct. These changes reduced the overall volume of the IPU by more than 30% to 2.26 cubic feet from 3.32 cubic feet and reduced the weight by almost 13% to 99.2 lbs (45 kg) from 113.8 lbs (52 kg).
The battery pack is recharged by the propulsion motor operating in regenerative braking mode, and by the generator motor, which is powered by the gasoline engine. Battery temperature is controlled by a fan system that pulls air from the interior of the vehicle via vents located beneath the left rear seat bottom.
The Power Control Unit (PCU)—the brains of the i-MMD system—dictates the power management strategy of the two-motor hybrid system, including motor power and battery recharge. In addition, the PCU increases the electric voltage up to 700 volts, enabling the propulsion motor to realize output as high as 181 horsepower.
The new design PCU reduced the component weight by 27% and reduced its size by almost 23%. This, in turn, increased the power density 25% by volume. The new floating structure of the PCU’s reactor greatly reduced vibration and high frequency noise.
Along with the greatly reduced size, overall i-MMD component packaging was improved by directly mounting the PCU to the transmission and utilizing a three-phase connector, which eliminated the need for the previous frame mounting bracket and connection cable.
i-MMD is not equipped with a conventional mechanical transmission. Instead, motive force transfer is accomplished through the interaction of the engine and two electric motors. Coordinated by the IPU, this form of drive force transfer offers smooth and predictable acceleration matched with efficient low-rpm highway cruising when the gasoline engine is in operation. Gasoline engine shutdown is seamlessly integrated into the operation when appropriate.
The drive force transfer system operates without the need for a torque converter, mechanical pulley or belt. It instead uses two motors for driving and generating power. The system is optimally and rapidly able to control both engine and electric motor rotation in order to deliver higher fuel efficiency and quicker engine response in each driving mode.
When cruising at mid- or high-speeds in the high-efficiency range of the engine, a lock-up clutch is engaged, connecting the drive motor to the generator motor to transmit engine torque directly to the drive wheels as efficiently as possible. In EV Drive operation, when the battery-powered drive motor is used for either acceleration or regenerative braking, a clutch disengages the stopped gasoline engine from the drivetrain to eliminate efficiency loss from mechanical friction in the engine.
Improving efficiency and reducing weight and size, the drive force transfer system of the second-generation i-MMD integrates the torque limiter within the flywheel.
The i-MMD offers three operating modes: EV Drive, Hybrid Drive and Engine Drive. Detailed energy management for each component, as controlled by the Power Control Unit (PCU), enables the system to make the best use of both the electric propulsion motor and the gasoline engine to seamlessly provide smooth and responsive performance along with fuel efficiency.
Honda also announced it will expand the use of its two-motor hybrid powertrain from passenger cars to its light truck lineup in the future.
Half of the all-new models Honda will launch in the United States in the coming two years will be electrified vehicles. In the long term, electrified vehicles are key to the future of carbon-free mobility.—Takahiro Hachigo, President & CEO of Honda Motor Co., Ltd.
In December 2016, Honda began the launch of its new Clarity series of electrified vehicles, starting with the Clarity Fuel Cell. The Clarity Fuel Cell is available through select California Honda dealers and boasts the highest range of any zero-emissions vehicle in America with its 366-mile EPA range rating. This year, Honda will launch the Clarity Electric and the Clarity Plug-In Hybrid, as the two remaining models in its Clarity series of premium midsize electrified vehicles.