Psd

It allows the engine RPMs to vary (almost) at will without a clutch or any shifting.
It allows the Computers to extract the optimal performance without interference from the driver.
It integrates three power sources/drains seamlessly.
It eliminates the need for a separate starter and alternator.

Without a large battery, MG1 and MG2 have to exactly balance electrical power, you are going to need a MUCH larger engine, which will have to run at whichever RPM exactly meets your electrical needs. Your HV Battery acts a electrical 'spring' allowing the power to be momentarily out of balance. Without the ability to drain or add to the battery, the computers will have much fewer choices. (this is why you don't normally see the SOC completely full, you would be all out of 'spring travel')

If you read up on 2 mode (many clutches) or IMA (motor limited to engine RPMs) transmissions, PSD looks pretty good.

 

Power Split Device works very well in a hybrid. It is the same architecture, different design, used in the Ford hybrids.

It is more efficient than an ordinary CVT type transmission. Check the Honda hybrids and compare their performance with the equivalent Toyota PDS hybrids.

Yes, less maintenance because the PSD transmission does not include a clutch or as many parts under high power and friction.

The Power Split Device transmission requires some means to transfer part of the motive power from the engine side to the drive side. This can be done with hydraulic motors. So far, I haven't read of anyone doing the hard work it would take to make this happen.

Only 28% of the power passes through the electrical path and 72% via the gears. Because electrical path energy is a fraction of the total engine power, the total electrical losses are roughly the same as the mechanical path losses. Do not forget that the mechanical path has losses too.

Bob Wilson

 

Ola Nuno

I have missed your presentation.
Welcome!
note (In Portugal we have a nice forum, also, although with much less mileage completed...)

 

Understanding Contents

This site is great to understand how Prius PSD works.

 

Something that wasn't already mentionned:

The PSD design solves a dilemna:
1. Use a parrallel design, with its deficiencies (often designed in a way [replacing the flywheel] that the motor cannot by itself propel the car, at least not without turning the ICE)
OR
2. Use a serial hybrid design, with its inefficiencies (too much conversions, with losses, like the ~36 MPG GM's Volt compared to the Prius 50 MPG).

The PSD makes it both a serial AND a parallel design, leveraging the advantages of both designs and avoiding most of their deficiencies. It also use the best of both the ICE limited efficient range and of the motor torque.

And yes, you could design a car with the PSD design, with its ICE and two motors/generators (mechanical path from ICE to wheels and electrical path from ICE to wheels), all without a battery... maybe you wouldn't be able to do reverse though... (would you?).

 

You have identified several important energy losses that the traction battery avoids. Losing these features would burn substantially more fuel:

• ability to move on electric power under low power conditions instead of burning fuel in the engine. In fact the engine will cycle ON-OFF to stay in high efficiency power regions to charge the battery while the car continues at a low speed. If the engine were throttled back to sustain this speed, the throttle plate, pumping losses and other inefficiencies would burn more fuel per kilometer traveled.
• loss of energy recovery from regenerative braking - we burned fuel to reach a given speed so regenerative braking saves some of it for when we need to accelerate later.

But there are other critical functions the traction battery provides:

• starting and stopping the engine - the traction battery provide power in both cases and Prius engine starting takes less than 250 milliseconds. This is substantially faster than 12 V starter systems.
• shifting to 'over drive' - there are several other terms for this, "energy recirculate" and "heretical mode," but it means the vehicle switches MG1 from being a generator to a motor that lowers the engine RPM and effectively shifts to a higher gear for higher speeds and less fuel consumption. This is not a trivial operation and there are a few brief seconds when the traction battery supplies the power needed for this transition. Without the traction battery, the engine and all power would have to be removed, a noticable shift-point.
• extra power for passing and hill climb - the traction battery provides the extra energy so the relatively small gas engine and the traction battery perform like a vehicle with a much larger and less fuel efficient engine.

Is there something about the traction battery that is a concern?

Bob Wilson

 

Without a battery, the engine has to be strong enough to accelerate as fast as the driver wants. (in the Prius it steals from the battery and recharges it once cruising, when HP needs are lower) The engine is 76 HP but appears to be 110 HP in the 2004 to 2009. (with battery powering MG2) The engine is 98 HP but appears to be 134 HP in the 2010. (with battery powering MG2) The power comes on much lower in the RPM range in the electric motor, so the power train appears to have much more torque than the ICE alone.

Without a large battery MG1 has to generate exactly the amount of electricity to match the amount of electricity MG2 uses each instant to propel the car. With the large battery, they only need to average out over time. In the Prius all power ultimately comes from the engine, but the battery allows you to average that over time.

 

It seems to me what the Original Poster is asking is this:

Would the planetary/ring/sun gear setup of the PSD be adaptable to a one-input, one-output setup (eg: ICE -> differential -> drive wheels) and, if so, would there be any tangible benefit over, say a belt-driven or toroidal CVT?

Or, to put it another way:

Parece-me o que o poster original está perguntando é este: A instalação planetária/do anel/sol engrenagem do PSD seria adaptávela a uma um-entrada, instalação da um-saída (por exemplo: ICE - > diferencial - > as rodas da movimentação) e, em caso afirmativo, haveria algum benefício real, diz um CVT movido a correia ou toroidal?

 

If you were on the electrical grid but preferred to use a gasoline engine, MG1 and MG2 could make unequal amounts of power as they do in a Prius, you just either feed the grid or buy power from the grid.

 

The US broke away from England while they were still using old units of measure. (the French were about to invent the Metric system) Sadly, the US has never adopted any Metric system, let alone the current SI Metric system. I can look up the metric equivalents, but I had the English measures in my head. The US stand almost alone in not using a metric system of measures, it cripples us in trade.

 

Power curve of an electric motor. (not the one used in a Prius, so just look at the shape)
An electric motor produces maximum torque near 0 RPMs, and max Power at low RPMs, then fades.
http://www.electricmotorsport.com/store/images/EV_Parts/motors/motor_ac_induction_curve.jpg

The Prius engine has an almost flat torque curve that peaks at 4200 RPM, and a power curve that starts at 0 and peaks at the 5000 RPM redline.
http://priuschat.com/forums/attachm...ving-methods-toyota-nhw20-prius-engine_05.gif

When you superimpose these curves you get more low end torque and power than many engines, and more peak power than the engine alone would make. (But later you will need to recharge the battery)

 

Ahhh, I see what you are asking:

We typically see the traction battery as an integral part of the PSD. You are asking if as a transmission, ignoring all other benefits, a PSD would be a good transmission? You really don't care about the vehicle efficiency but just the transmission alone?

Ok, I'll simply offer that a PSD has fewer moving parts, no clutch and about as heavy as other automatic transmissions with similar efficiency.

Bob Wilson

 

In fact, "the use of the metric system [was] made legal in the United States by the Metric Act of 1866 (Public Law 39-183). This law made it unlawful to refuse to trade or deal in metric quantities." (A chronology of the metric system)

But then yes, you are alsmost alone not to use it, along with two other thriving coutries: Myanmar (Burma) and Liberia.

 

It can work but it will be expensive with little benefit. You won't have the battery but you'll still need the 650v inverter and cooling for it.

The generator will need to be more powerful to make up for the lack of HV battery.

ICE will not be able to stay in the most efficient range. It will be at the mercy of the driver accelerator and no HV battery to "buffer" additional power.

As you have mentioned, there won't be regen power captured.

Atkinson cycle ICE will not have enough peak power (due to the lack of HV battery) so you'll need to switch to Otto cycle or need a bigger ICE. You'll loose 15% efficiency in Otto cycle or introduce more pumping loss from the bigger ICE.

 

It can but the loss of functionality would be a challenge.

Bob Wilson