In a new patent filing made in Japan, Mazda appears to be developing revolutionary in-wheel electric motors powered by a capacitor for use in future vehicles. The patent appears to be an update to an earlier one filed last year and details a rather complicated powertrain setup.
The latest filing shows a front-engine, rear-wheel drive layout (FR) with two in-wheel electric hub motors for the front axle, a third motor acting as a crankshaft-integrated starter generator (C-ISG), a capacitor, and a small lithium-ion battery.
The specific type of engine used appears to vary for this setup, as last year’s earlier filing had an inline four-cylinder unit at the front, while the diagrams seen here depict the use of a V-type engine of an unknown cylinder count as well as a Wankel rotary engine.
The latter is set to make a return, albeit in a heavily downsized manner as a range extender on the MX-30. However, there has been no clear word from Mazda if a fully rotary-powered sports car will make a return despite the hype surrounding the RX-Vision concept made its debut at the 2015 Tokyo Motor Show.
The new FR platform could be used in the next Mazda 6, and to amortise development costs, more models should receive the underpinnings as well. Potential subjects include the next-generation CX-9, and if the stars align and we are blessed enough, maybe even a production RX-9 (one can dream).
Getting back to the tech, Mazda appears to have a solution to conventional in-wheel electric motors, which historically adds excess unsprung weight that can negatively affect ride and handling. The idea is to have a relatively small motor located at the front wheel hubs that is powered by a double-layer capacitor in the engine bay, with the whole system running on a 120-volt electrical architecture.
A capacitor has the benefit of being able to rapidly discharge its energy and also recover energy from braking more efficiently than a battery. Additionally, running at a higher voltage the motors should be able to make the same power as a lower-voltage solution at lower current, which in turn means wiring and windings can be smaller.
This contributes to a compact, lightweight electric all-wheel drive solution, but due to the mounting of the electric motors at the end of each axle, less torque is expected to be generated due to reduced leverage, as Automobile pointed out.
The setup also uses three inverters to manage the different system voltages, including one linked to the C-ISG between the flywheel-less internal combustion engine (ICE) and driveshaft. The C-ISG is a 25-kW unit that is powered by a 48-volt, 3.5-kWh lithium-ion battery pack that can also drive the rear wheels or support the ICE.
A smaller battery is possible as the capacitor does most of the heavy lifting for the in-wheel electric hub motors at the front, but it can also deliver power to the front axle via a separate inverter if needed.
The battery is mounted in the driveshaft tunnel, taking up the space where a typical transmission might go, requiring a rear transaxle placement that robs less interior space and provides better weight distribution.
It certainly looks like a complex setup and it isn’t confirmed if this will be used for the upcoming Mazda 6, which is more likely to be rear-wheel drive with an inline-six engine and an eight-speed automatic gearbox. This front-engine, all-wheel-drive hybrid powertrain doesn’t exist in Mazda’s current line-up, which primarily consists of mainly front-wheel drive models, with the exception being the MX-5 that uses a more conventional FR setup. Perhaps it is better suited for a new halo car?
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Next gen Mazda 6 is inline6 & RWD
Go, go, go Mazda!! Kipidap with Rotary!!
Rotary engine is not reliable in the long run