Honda Working on Complex Hybrid Motorcycle

In the quarter century since the launch of the first Toyota Prius hybrid cars have become commonplace, but the same combination of combustion engine and electric power has yet to make an impact on two wheels. There have been attempts at hybrid bikes in the past and Kawasaki’s upcoming 2024 Ninja hybrid promises to up the ante further, but several new patent applications from Honda show a much more complex and advanced take on the idea.

Honda has a reputation for taking the difficult route when it comes to developing new ideas. This is, after all, the same company that developed oval pistons with twin con-rods and eight valves per cylinder when race regulations said it couldn’t use a V-8. So while it’s “relatively” straightforward to simply bolt an electric motor to an existing combustion engine and transmission to create a hybrid bike—as Piaggio did back in 2008 to create the MP3 plug-in hybrid—Honda is taking a very different path.

Kawasaki’s upcoming Ninja HEV hybrid, due in production in 2024, already promises multiple riding modes. It can work in electric-only mode in cities, as a gas-powered bike while cruising, and with both power units working together when you need maximum performance. It’s also got a push-button-operated, semi-auto transmission to help create a seamless transition between power sources. Clever stuff, but not a patch on what Honda appears to be planning.

The new Honda patents show various layouts for a hybrid that combines a combustion engine with not one but two electric motor/generator units, along with a planetary gearbox and a multi-ratio manual transmission. The designs show the outlines of two possible combustion engines: one that appears similar to the 750cc twin used in the X-ADV and NC750 range, the other a smaller unit, possibly a single. They also illustrate a variety of possible layouts for the positions of the two electric motors, but whichever version is chosen the basics of the operation will be the same.

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Honda connects the two electric motors and the combustion engine together via an epicyclic or “planetary” gearset in a layout that’s very similar to the transmission that was the killer feature of the Prius when it was introduced a quarter of a century ago. There’s no clutch between the engine and transmission, but the planetary gears means the bike can be ridden in pure electric mode with the engine stopped or in pure ICE mode, and in a variety of ways in between.

The main electric motor/generator, labeled MG1 in the drawings, is connected to the ring gear of the planetary gearset. The second motor/generator, labeled MG2, is connected to the sun gear in the middle, and also directly linked to the reduction gearset that drives the front sprocket, so it always turns when the rear wheel is moving, acting either as a generator to replenish the batteries or as a motor to drive the wheel. The combustion engine drives the planet carrier that holds the planetary gears in position between.

On its own, the system creates a continuously variable transmission—the combustion engine can maintain its most efficient speed and the transmission’s output speed is altered by adjusting the speed of the main motor/generator (MG1). In this state, referred to as “eCVT” mode, MG1 is acting as a generator and MG2 and the combustion engine are working together to drive the rear wheel.

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In Honda’s patents, the system is shown in various layouts, all within the silhouette of an X-ADV 750. The layouts also show how the batteries could be arranged, but don’t read too much into the use of the X-ADV’s shape. If this design reaches production, it will be in a bike that’s purpose-made to house it. Given the probable bulk and complexity of the setup, it’s more likely to be suited to a tourer, providing a long range and plenty of power from a partially electrified design, than a smaller, sportier bike. It’s also still clearly a project that’s a long way from production, but if Honda is to hit its self-imposed target of making its motorcycle business carbon-neutral by 2040, it’s the sort of machine the company needs to be making.