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Mazda was granted a new U.S. patent this week for the design of an offset wheel-mounted motor for electric and hybrid vehicles. In previous wheel/hub motor configurations, the motor has typically been mounted concentric with the wheel. The essence of the patent is that the motor is offset from the wheel axis, with a gearset installed to provide drive torque to the hub.

Usually, a hub motor consumes most of the space inside the wheel, limiting the possible mounting locations for the suspension links and compromising ride and handling. In theory, Mazda's new arrangement provides more room in the wheel and flexibility for the suspension geometry. However, the gearset hardware at the wheel will increase unsprung mass and degrade the ride and handling accordingly.

There is another possible benefit of this type of installation, however. It provides Mazda with the flexibility to do either a through-the-road hybrid, by having motors on one axle and mechanical drive at the other end, or a power-split hybrid. By offsetting the motor, drive from an engine could still come in through the hub and the gearset could be used for torque blending. Whether this is actually better than the traditional power-split hybrid used by Toyota and Ford is debatable. Finally, there could be a simpler explanation: The real motivator for this patent might be to create a hybrid system that doesn't conflict with patents held by numerous other automakers. Thanks for the tip, Charlie!

[Source: Free Patents Online]

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    • 1 Second Ago
      • 5 Years Ago
      I could see this being useful in the next-generation Miatas, providing optional fwd drive traction for bad weather and launches, and part-time all electric cruising while not interfering with the front engine/rear drive design. Or maybe it would only be used on the back axle exclusively. Also might be very smart on the Mazdaspeed 3, providing much needed off the line control.
        • 5 Years Ago
        I was thinking more of a possible next-gen RX7/8 than the Miata which will probably remain a lightweight RWD car.

        If Mazda's hints are accurate and the next RX7/8 and Miata share a common platform, this would be an easy way to distinguish the two sporty cars - one stays simple and affordable, one offers AWD and/or hybrid power and goes higher-end in terms of performance and price.
      • 5 Years Ago
      This isn't specific to the Mazda patent, but I really think wheel mounted motors are a terrible idea. An axle is a pretty lightweight and inexpensive part to add to move the motors inboard, and the reduction in unsprung weight would be huge.
      • 5 Years Ago
      I've many electric bicycles that drive the wheel from the outside tire, and also drive from the hub, look at Schwinn and Rayos


      The Rayos is offset drive, looks like a Patent infringment. Idea was already done and in production.
      • 5 Years Ago
      Having read the patent claims it does seem fairly obvious, but I probably falls under the traditional category of an improvement on an existing invention as I cannot think of anything else similar.

      The patent specifically is written around a RWD IRS vehicle whereby this device allows the addition of electric motor drive to the existing engine/shaft drive power. It's a *very* specifically-written patent that is limited to an IRS utilizing upper/lower a-arm suspension with a fixed toe link - meaning someone could knock this off using McPherson struts or a torsion beam and probably get their own patent.
      • 5 Years Ago
      Isn't this basically what the Hummer H1 does

        • 5 Years Ago
        Hummer wasn't the first to use such a system, actually, it was about 30 years late to the party.

        Czechoslovak 1953 Praga V3S was the first one (a 6x6 truck).


        • 5 Years Ago
        Excuse me?
        • 5 Years Ago
        • 5 Years Ago
        Electric motors on a Hummer? Oh no you dit'n !!
        • 5 Years Ago
        No, the H1 is geared at each wheel, but there's no electric motors involved.
      • 5 Years Ago
      There French Jamais Contente "never satisfied" was the first vehicle to ever go over 60 mph and had a design similar to this:

      I think sometimes patents sometimes limit creativity and progress for other companies but I guess I also see why they are important.

      • 5 Years Ago
      That is why Mazda has use a Power Train Frame to mount the Rear Diff to Transmission in their RWD MX-5 and RX-8, helps to reduce rear sprung weight.
      I think Mazda know what they are doing here, they are more innovative than any other car maker out there.
      • 5 Years Ago
      Seriously, is there anything you can't patent in this country? How does this not fail the obviousness test?
      • 5 Years Ago
      "However, the gearset hardware at the wheel will increase unsprung mass and degrade the ride and handling accordingly. "

      it may, but it also depends on if the reduction gearing allows them to downsize the motor enough to offset at least some of it. Most of an electric motor's mass is in the iron and copper in the armature and stator; with an aluminum gearcase, the hit might not be so bad.

      think of it kind of like the reduction geared starters that Chrysler used, vs. the direct-drive Delco starters. The Chrysler starters did the same job but weight a ton less.
      • 5 Years Ago
      I say this is BS. Mounting electric motors in wheels is a no brainer, and done before in experimental/concept type vehicles... and even in the mars rover. Offsetting the mottor a bit is no great big discovery nor progress... patent on something like that shouldn't be allowed. Whats next? patent for motor offset by 5cm, then patent on motor offset by 20cm, etc? maybe we can patent a motor offset axialy AND laterally?... then patent a motor that has a been painted pink.... this is pure BS....
        • 5 Years Ago
        you should do it.. since you come off as smarter than the mazda engineers.
        • 5 Years Ago
        go read the patent before you spout off again. The patent covers the specific design they came up with to integrate the gearbox into the suspension.

        I really wish people would read, then speak.
        • 5 Years Ago
        I, apparently alone, agree with you. When is Mazda going to start suing the builders of the remote control cars I played with as a kid? More than one ran off a geared, offset motor.
        • 5 Years Ago
        This isn't novel. I give it 0% chance of standing up in court. Dumb.

        Proof? Go look at a locomotive traction motor. Same damned setup since the dawn of time.

        Jeez, you guys are sure gullible.
      • 5 Years Ago
      For those that have mentioned the weight issue. I am sure Mazda engineers have been fielding that issue. But, I presume they would not be making something if it were not for profit.

      Or, it could be that it will work, but have a flaw (Renesis motor, but horrible mpg)
      • 5 Years Ago
      If unsprung weight is the only argument.... there's really no down side to wheel motors at all then.

      Unsprung weight is just some term out of a book on race car suspension. It has NOTHING to do with road cars.

      Every car with a live rear axle (inc ALL NASCARS) have the entire rear transmission 'unsprung'. The only side effect seems to be the occasional wheel hop under heavy braking when tire traction is broken.

      Any wheel motor set up would be significantly lighter than hanging an entire diff center, diff housing, drive shafts and tail shaft on long (read Heavy) trailing arms.

      The Michelin Active wheel set-up actually REDUCES unsprung weight because the brake system (read: CAST IRON ROTOR) is deleted.

      Anyone who comes out with the 'unsprung weight' argument a) Has a negative personality b) Doesn't know what they are talking about.
        • 5 Years Ago
        Nothing to do with read cars?
        Will you explain how road cars defy the laws of physics please?
        Very few road cars have solid axles nowadays.
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