Featured Your Engine May Also Become A Generator

GM is known for overly complex approaches with little in return. How many here remember BAS or e-Assist ?

 

My first takes:

Pro: by harvesting some electricity at the cylinder instead of downstream at a generator shaft, some loads on bearings and any gears are reduced, avoiding a bit of friction losses along the way.

Cons: Longer thermal path to the cylinder jacket cooling. Piston magnet must maintain its field at higher temperatures than other generator magnets. Increased piston mass from the added magnet means more vibration to be damped, more bearing pressures. Metal portion of cylinder is effectively a 'shorted turn', adding some electrical loss, though a nonconductive ceramic cylinder liner between magnets and coils will greatly reduce this.

And a nit to pick with the headline: "GM wants to ..." A patent doesn't mean they want to bring this to market soon, or ever. It only means they are protecting their ideas. Maybe for their own use, or for the future, or simply to build up a larger IP portfolio for licensing or trading with others. The patent itself doesn't give any hint to their market plans.

 

I agree GM is a mess , this patent is brilliant if it can be made.

 

I would also add most pistons are aluminum, a poor magnet and the high temperatures of a cylinder wall are a poor place for temperature sensitive magnets and the cylinder walls need cooling. Now if the piston pin were a high-temperature tolerant magnet and adjacent pistons were not 180 degrees out of phase, manufacturing costs would still be too much. This changes with a free-piston, engine generator.

The Honda IMA that makes the flywheel into also a motor/generator makes a lot more sense. It can eliminate the starter, alternator, and avoids a huge number of thermal and mechanical problems. But it would need a significantly higher voltage battery that a 48 V LiON battery might handle (i.e., 1 hp = 746 W, 15 A @48 V.) It could also help with momentary, low rpm, engine torque.

Bob Wilson

 

Generally pistons are made as light as possible because of the high stresses of acceleration and decellerating that the piston experiences on every rotation of the engine. Putting magnets in the pistons would make them heavier. Where would you locate these magnets. The piston ring area can't be moved or the piston pin location. Possibly at right angles to the piston pin at the same height? The diecast manufacturing process to assure the same magnetic pole is facing out on both sides of the piston is doable but it would be more complex.

The suggestion that the magnets be placed in the piston pin would be easier and simplify manufacturing but it would still add weight to the reciprocating end of the piston assembly.

 

A bar magnet in the piston pin is at the wrong orientation to the illustrated cylinder coils, so all the fields would cancel out and not allow any energy harvest.

A bar magnet would have to placed in the same direction as the cylinder, making a fairly tall piston, which I take to be a nonstarter. The piston rod could be used, but the large gap to the coils reduces effectiveness.

The best magnet configuration for this concept is a ring in the piston, as close to the cylinder wall as practical. One magnetic pole on the outside of the ring, the other on the inside.

 

good ol' GM ..... as long as we keep burning fuels in cylingers to make juice .... sounds so good it makes me wana junk our solar

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Generator Magnets?

 

Pretty sure our Honda already has magnets


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Not sure where their program is now, but Toyota has one working on a linear generator.
Toyota R&D continues work on free piston linear generators for EVs; novel resonant pendulum control method - Green Car Congress
GM's system is just sticking it into the cylinder of a typical engine instead of making it a generator only.

Mild hybrids are going to outnumber full ones in the near future. Ford has five models with such coming out in Europe, and Volvo's plan to go all electrified means anything without a plug will be a mild hybrid.

GM is still using the 3rd gen system in China.

 

That was called missing the point and casting out a red-herring. Now, it is a "What about?"

 

Adding the weight of magnets to the pistons would add additional stress to the bearings and possibly limit rpm. Doesn't it make more sense to follow Honda's lead and mount the magnets on the engine flywheel and leave the engine to do what it was intended to do. I can't imagine repairs of coils inside the block.

 

call me dim - but I must have missed the point also -

yes, BAS provides mediocre but still improved mileage, by simply adding a start/stop system. Pretty simple .... but your complaint against GM here, is that they are overly complex? Aren't these GM complaints kinda mixed up? BAS is pretty cheap.
Just saw a luxury European car come up next to me, & the engine turned off - then back on when the light turned green. So this IS still a solution for improved efficiency. Tho it's not some folks' cup of tea, as a hybrid, it seems to be catching on.
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i wonder how they hold up. i suppose if theyre german, it doesnt matter

 

You referred to BAS/eAssist as an "overly complex approach". It is actually a mechanical simplification as two components, starter and alternator, and replaced with one, a motor/generator. It is far less complex than a full hybrid.

It has also been copied by Hyundai/Kia for the front end of their full hybrids in the HSG(hybrid starter generator), and the first gen 48v mild hybrid systems nearly everyone is adopting, which I guess I should have spelled out earlier.

Now, I concur, the early iterations of BAS were costly for the benefit, though I won't discount greed on GM's part, but they have improved over time. Which is why the 48v systems are being adopted, as they cost less than a full hybrid system. In terms of batteries used, more mild hybrids could lead to greater reduction of carbon emissions than fewer full hybrids.

I assume the expected use for this system by GM would be in a hybrid. In which case, a low rpm limit wouldn't be much of a limitation. It could be an ideal solution for a parallel hybrid as it might work as a starter for the engine, completely eliminating the HSG, and improve the efficiency for recharging the battery while cruising, depending on output. For less than full hybrids, it could mean greater shifting of moving accessories, like A/C, to electric.

Sounds GM has designed this to be easily added to existing engine designs. The coil is a slip in insert. So repair should be simple.

Parents' Acura has start/stop. Ford introduced it with the current Fusion, and think all the F150s have it now. The Malibu we test drove had it, and I caught it on a Jeep next to me. They are becoming widespread in the US.

A mild hybrid has a more power HSG, which allows a higher engine rpm before starting. That lessens wear and tear, while providing a smoother start. They also add some regen braking to help with efficiency. The Ram 1500 has a 48v system standard on the V6, and optional on the V8, in the US.

 

Stop/start is already the norm in Europe, as I have heard on the street corners while traveling there:

 

This might have an application in power generation. Tiny plants, like those on dairy farms, use piston engines for the generator.