Kawasaki Hybrid Supercharged Motorcycle Patent

We’ve known for some time that Kawasaki is working on a hybrid motorcycle, but a recently published patent suggests it may be combined another Kawasaki technology, a supercharger. More specifically, the patent describes an electrically-powered supercharger, with a motor capable of driving both the motorcycle and the supercharger’s impeller.

While notable on its own, the concepts in a patent don’t always manifest in an actual product, but a trademark application Kawasaki filed earlier this year suggests that a hybrid motorcycle with an electric supercharger may have already moved past the conceptual stage. On March 29, Kawasaki filed to trademark “E-BOOST” in Japan for a number of uses, including for hybrid and electric motorcycles. While we initially assumed the “boost” referred to an electrically assisted hybrid mode, we now believe it may in fact refer to the electric supercharger.

Kawasaki’s had supercharged motorcycles in its lineup for several years now, with the H2, H2R, H2 SX and Z H2, but they all use a compressor driven by the engine’s crankshaft via a chain. Instead of using a mechanical connection to the engine, an electric supercharger uses an electric motor to spin the impeller. In theory, an electric supercharger would work instantaneously, avoiding any delay in waiting for the engine to get up to speed.

The downside is an electric supercharger requires more parts, with a motor and a battery large enough to provide a supercharged boost as needed. For a gas-powered motorcycle, that’s a lot of added weight for what may be a marginal gain. With a hybrid motorcycle, however, those parts are already in place. If a hybrid is going to be heavier, Kawasaki figures, it may as well give those additional parts a secondary use.

The patent describes the different modes a vehicle could use a combination of a gas-powered engine, electric motor and a supercharger. The motor has an output shaft that is directly connected to the supercharger. The output shaft is also connected to the transmission’s input shaft via a one-way clutch. The clutch controls whether the motor can drive the input shaft, with the motorcycle working in either an electric or hybrid electric mode.

In hybrid electric mode, the engine (E in the diagrams) and motor (M) are both driving the input shaft. In electric mode, an actuator (#15) disengages the main clutch and the engine stops, leaving the motor to drive the input shaft alone. In either HEV or EV mode, inertial forces from deceleration turns the motor into regeneration mode. It’s important to note that in either mode, the electric motor is “upstream” of the transmission and the motorcycle can still switch gears even in electric mode unlike most electric motorcycles that operate with a single gear.

In the “normal” mode, the internal combustion motor becomes the primary drive source with the electric motor working in regeneration mode. In both normal and HEV modes, the motor spins at about 5500 rpm or slower, running the compressor in what the patent describes as “weak supercharging,” providing some added boost to the engine. Things pick up in supercharging mode, with the electric motor’s clutch disengaging from the input shaft in order to devote its full output (from 6000 to about 15,000 rpm) to drive the supercharger.

According to the patent, the motorcycle can switch between modes manually via rider input or automatically, choosing the mode based on various factors such as the engine speed, traveling speed, acceleration, gear selection and battery level.

Again, we have to reiterate, a patent filing doesn’t mean that we’ll see a hybrid supercharged Kawasaki motorcycle any time soon; it only tells us that Kawasaki has been working on one. The trademark filing for “E-BOOST” indicates development on its hybrid project has progressed to the point that Kawasaki decided to give it a name. It’s been a while since Kawasaki provided an update on its hybrid motorcycle project, but recent comments from Kawasaki indicate the company is committed to the technology.

Earlier this week, Kawasaki announced a $265 million investment in expanding its factory in Nebraska and in building a new facility in Mexico. In the announcement, Hiroshi Ito, president of Kawasaki Heavy Industry’s Motorcycle and Engine Company, said the company “is also increasing investments in new product development which will be available in the near future, especially in the growing MULE, ATV and JetSki markets as well as innovative new street motorcycles, our new electric, hybrid, and hydrogen power source projects and off-road motorcycles.”

We expect Ito to further elaborate on those plans in October when Kawasaki’s Motorcycle and Engine business will officially be spun off into its own company.


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