Volt Drivetrain Patent and info

That's my understanding, except that the ICE is never locked by anything. Closing the valves (which can't be done, only the timing can change) would not lock the ICE. Closing the throttle just minimizes engine drag by reducing pumping loss, if torque from the HSD is spinning it.

There is a fixed ratio between the ICE and MG1 torques. If there's no torque on the ICE, then there cannot be any torque from MG1 (at steady state) and vice versa. No torque ==> no power no matter how fast it's spinning.

It's like an open differential. In a diff, the output torques (to each wheel) are always the same...the ratio between them is 1. The HSD planetary system is similar, but the ratio is not 1...but it's still a fixed ratio.

If they could lock the ICE at 0 RPM, then they could get power out of MG1 in EV mode (and regen from it).

 

Yeah, I'm not quite sure how they achieve the 0 RPM on ICE. I was guessing it could be passive or perhaps actively maintained by minor inputs to MG1.

 

I too agree with your understanding. There will be a shock felt because MGa come to abrupt stop which would affect the speed of MGb which in turn will affect the wheel. It may even over-speed the MGb out of spec depending on how fast Volt is travelling. MGa is used to keep MGb RPM low.

 

"You" refers to multiple/plural, not AG itself only. Both were in, I'm happy now

Superior design er um? To be honest, like you did, I have to disagree, but we are free to do it.
"Superior design" is where you have KIS approach, or from the technical point of view, a Lean Design. Clutches mean more moving parts and debris, as I said before (small amount in oil severy increases wear of bearings and gearing, doesn't it?). If it were applied to the HSD, I would certainly be surprised, cause of superior complexity also. If there were great advantages, at least?

 

How do you explain lower kWh per mile of the PHV Prius? PHV Prius is 41% more efficient than Volt in EV mode.

Volt's MGa is also "wasted" because MGb is rated 150 hp (per MT diagram in post #1) and Volt's total peak power is also 150 hp. You would be right if both MGa and MGb are 75hp each.

 

I don't follow 100%. How does that happen in Voltec?

 

Easiest way to see it is to use the Prius Simulator. Set the ICE to 1,500 RPM. Slide MG2 up and down to notice the "seesaw" effect. You can lower MG1 rpm by increasing MG2 rpm.

For the Volt, just remap the components. ICE=Wheel, MG1=MGb and MG2=MGa. There is a direct relation between MGa and MGb rpm. You increase one to lower the other.

To correct myself, I don't think MGb will over-spin out of spec since in EV mode, it can reach the top speed by itself.

 

How do you calculate that ?

Anyway, Volt is heavier and works in EV mode at high speeds.

 

Imagine a sprinter and a marathoner. Someone times the sprinters average pace at the second lap of an 800, then they compare that to the average pace of the marathoner on a marathon. The sprinter looks like a much better athlete if you only look at those numbers. I believe figures like 41% more efficient is from comparing two different tests between the two cars. e.g. your edmunds test tested the volt running the whole course, but ran the prius twice, once with a full battery and once empty. It then tried to guess how many miles the prius traveled on electric from the gas usage. This is not a good test.

The phv prius can not be kept in EV mode with reasonable speeds and accelerations. The volt has the hardware to be put in blended mode, but does not have software to do it. I would prefer both had both modes. It is easy to see if you spin a motor versus not spinning it that there are losses. Toyota has been good at removing these losses, so it is not idle speculation that toyota may remove the losses again in the next rev of the prius. I am comparing apples to apples.

The volt has only slightly worse kwh/100 miles than the leaf (36 vs 34) which I believe is efficient in EV mode.

I assume this is not for me, but in case it is, I don't think MGa or MG1 are wasted, my opinion is the oposite. In fact I think it would be a more elegant design if the volts traction motor had enough power at higher speeds to not need the help of the generator.

 

On the question of clutches, everyone is stating the pros and the cons.

So with everything I've gathered on the Voltec powertrain, I hypothesize that the clutches will never significantly wear out because with the planetary gearing setup, it can usually stop the ring gear or rev-match to the ring gear first before applying the clutches.

Examples

1 Motor Mode to 2 Motor Mode
C2 Clutches, connecting MGa to Ring Gear
C1 Uncluches, unlocking ring gear from case
Now MGa is clutched to the ring gear, initially at 0 rpm, and can now add torque to planetary carrier (wheels)
Since the ring gear is intitially at 0 RPM, there is very little slip in the time it takes to release C1


2 Motor Mode to 1 Motor Mode
Electronics force MGa to decrease RPM to 0, simultaneously increasing MGb RPM to maintain Planetary Carrier speed (wheel speed)
Once ring gear is at 0 RPM, C1 clutches, locking ring gear to case
Now ring gear is locked, C2 unclutches, disconnecting MGa
Since ring gear was forced to 0 rpm, there is very little slip, hence minimal wear on C1

Series Mode Start
Both ICE and MGa are not spinning, both are at 0 rpm
C3 clutches, connecting ICE to MGa, MGa used to start ICE, so now MGa can generate electricty from the ICE. Electricty is sent via electrical pathway to MGb. Since both ICE and MGa were at 0 rpm when C3 engaged, there is no slip and little wear on C3.

Series Mode End
Ignition off, ICE stops spinning, and so does the connected MGa, until 0 rpm reached. C3 unclutches, disconnecting ICE from MGa. Since both ICE and MGa are at 0 rpm, there is no slip and little wear on C3.

1 Motor Mode to Output Split Mode
C3 clutches, connecting ICE to MGa
C2 clutches, connecting MGa to Ring Gear
C1 unclutches unlocking ring gear
Ring Gear, ICE and MGa start at 0 rpm (Ring gear was locked), so there is little slip, hence minimal wear on C1
ICE then spins up to 1000 RPMs and then ignition

2 Motor Mode to Output Split Mode
C3 clutches, connecting ICE to MGa
This one is more tricky because, assuming MGa is already adding its torque to the planetary carrier (wheels), it is spinning, and C3 would have to slip a little while the clutch is fully applied. The ICE is stopped and must be clutched to MGa before it can start.

Ok, technically, we could do this:
Go from Two Motor Mode to One Motor Mode, then going to Output Split Mode. (See 2 Motor Mode to 1 Motor Mode, and 1 Motor Mode to Output Split Mode above)

It is probably best to stop MGa to allow it to clutch to a stopped ICE.

Series Mode to Output Split Mode
C2 clutches, connecting MGa to Ring Gear
C1 unclutches, unlocking ring gear from case
Ring Gear was at 0 RPM, so little to no slip to cause wear to C1


Output Split to Series Mode
Turn ICE ignition off (it's still spinning and connected to MGa)
Use MGa to force Ring Gear RPM to 0, while adjusting MGb RPM to maintain planet carrier RPMs
C1 clutches, locking ring gear to case
C2 unclutches disconnecting MGa from the Ring Gear
Restart ICE using MGa to generate electricity

Output Split to Neutral
At first, everything is spinning and C2 and C3 are clutched in
First, turn ICE ignition off, so no torque from engine, except it is still free spinning
So now this is like Two Motor Mode, except the ICE is clutched to MGa, while fuel is cut.
We proceed to do the same as Two Motor Mode to One Motor Mode transition, the only difference is fuel-cut ICE is clutched to MGa
MGa forced to spin down to 0 RPM, whle MGb spun up to maintain plantery carrier RPM (wheel speed)
Ring gear now stationary, C2 unclutches, disconnecting MGa from Ring Gear
C3 unclutches, disconnecting ICE from MGa (optional)

I'm not saying this is the best way to go into neutral from output split, but technically I suppose this will work.


1 Motor Mode to Neutral
No clutches needed
MGb free spins

2 Motor Mode to Neutral
Go from 2 Motor Mode to 1 Motor Mode, then to Neutral


Series to Neutral
C1 unclutches, unlocking ring gear from case
Ring Gear was locked so 0 rpm, no slip or wear on clutches


Neutral to Two Motor Mode
The best way to come out of neutral is into Two Motor Mode, since the ring gear is spinning, and this only involves applying C2. Doing this avoids having to stop the ring gear somehow.

My thought is MGa is rev-matched to RPMs of the spinning ring gear, so C2 can engage. This connects MGa to the spinning ring gear, and minimizes wear on C2. Once in two motor mode, it can enter any other mode.




OK, so unless I am way of base, the Volt's computers can manage the mode transitions in non-emergency situations with minimal wear on the clutches.


Just so were clear on what the clutches do:

C1
Clutched - Locks Ring Gear to Case
Unclutched - Unlocks Ring Gear to Case

C2
Clutched - Connects ICE/MGa to Ring Gear
Unclutched - Disconnects ICE/MGa to Ring Gear

C3
Clutched - Connects ICE to MGa
Unclutched - Disconnects ICE to MGa

And how the Voltec power split is set up

Ring Gear (is either locked to the case, or not locked to the case; it is also either connected to MGa/ICE or not connected to MGa/ICE)
Planetary Carrier is the output to the differential
Sun Gear is the input from MGb

The ICE only can clutch to MGa. MGa can only clutch to the Ring Gear. The Ring Gear can either be locked to the case, or unlocked to accept input from MGa/ICE.


OK, so I'm not saying that any of the above actually happens, it's just speculation on my part. Feel free to double check my analysis, in case I made a mistake.

 

I was using data from InsideLine's comparison test.

Comparison Test: 2011 Chevrolet Volt vs. 2010 Toyota Prius PHV

 

Well, no. They clearly stated their test procedure.

We measured gasoline mpg by driving test loops with a discharged battery — pretty standard stuff. But we also measured electricity consumption by driving a known distance and then using a special meter to determine how many kilowatt-hours of juice passed through the charge cord during the subsequent battery recharge.​

PHV Prius can be driven in EV for a very reasonable speed and acceleration around where I live. Did you see the videos? Do you honestly think it is not reasonable?

I totally agree. It is actually Volt's weakness because it is trying to pretend as an EV. A vehicle that drives like an EV but it has a tailpipe. That's like a chick with a d*ck. Please excuse my language .

PHV Prius' gas engine does not spin below 62 mph so the losses are the same with the Volt. Both can have the planetary gearsets with two MGs spinning.

Above 62 mph, Prius will spin the gas engine. You'll want to anyway because the EV range will be greatly reduced due to air resistance. Gas engine is very efficient at highway speed. PHV Prius taps into synergy by running the gas engine and continue to discharge the PHV battery. This is an example of PHV Prius intelligently select the best combination of hybrid powertrain.

In this situation, Volt will only use the battery (even climbing mountain) and take the EV range in the chin. It will then run on premium gas @37 MPG. That's not intelligent.

Volt is a compact car but Leaf is a midsize. Volt should get at least 30 kWh/100 miles so it guzzles 20% extra electricity.

InsideLine test showed PHV Prius (midsize) consumed only 23.2 kWh/100 miles where Volt consumed 39 kWh/100 miles.

Both MGa and MGb are the same size. If MGb is 150hp, then why isn't the peak hp 300? That indicates 150hp MGa is wasted. You saw the seesaw effect right? Both MGa and MGb cannot reach peak power at the same time. That is probably the limiting factor.

 

What does "reasonable" mean? Cruising along at 55 was effortless with the PHV. Accelerating in the burbs (to 45) was a pure joy, only electricity was used and it was surprisingly quick.

So what if the engine comes on at times? It's really clean & efficient anyway.
.

 

I was critizing the idea that

A) the EV modes are the same. In the prius will turn on its engine, the volt willl not under normal circumstances.

B) That the numbers are from the same test.

I am in agreement that the prius engine is efficient and low poluting, I even bought one. But, you can not compare electrical efficiencies unless they are tested in the same way. IMHO chevy should allow software for a blended mode, and the phv prius should implement an ev mode. Until they do that a more efficient electrical phv prius is a bad point. For most of us interested in a PHEV, having the capability of going all electric trumps the electrical efficiency of blended mode. Some of course disagree, although most of those are not really interested in a PHEV. Its good to have choices of the volt, prius, and when it comes out the phv prius.

 

Now it is "normal" that is vague. What does that mean?

When I was driving the PHV the same way I drive my 2010, the engine certainly didn't turn on... even when accelerating up long & steep hill from a dead stop to 40.
.

 

Actually they were called on that "procedure" and further explained in their comments that they ran two loops, one in CS and one with charged battery. Both used gas, then they used their meter, and guestimated gas. How accurately do you think they measured the gasoline? Do you think that it is a fair test? Blended mode will definitely run more efficiently, shouldn't they have tried to keep the prius engine off, stopped when it turned on, and followed at those slow speeds with the volt. That would have been more reasonable, but still unfair.

No I do not think a normal driver is going to patiently watch the meter and accelerate 0-60 in 30 or 40 seconds. It is unreasonable to drive the prius without the engine turning on. Will the driver still be able to do even this with the airconditioner or heater on? A good argument might be blended mode is useful, but it is a bad argument that a reasonable driver would keep the engine off.

Well I actually have to drive on highways often with 65 and 75 mph speeds. MG1 always needs to turne, and yes the ice will turn. Toyota already uses clutches in at least one hybrid (Lexus gs450h) and it is reasonable that in a gen IV when the batteries are good enough to drive on American highway speeds that the prius gets a clutch and stops spinning in these modes. Do you really think the phv prius is perfect and they won't even try to improve it and add a real ev mode?

Well actually I was thinking about efficiency in terms of CdA,
rolling resistance, and vehicle weight. I believe these are the engineering challenges. I don't think we should be one size fits all.

Edmunds numbers are the results of drastically different tests. I believe the blended mode would be more efficnt, but as in my story you should not test a marathoners speed on a marathon and a sprinters speed on the sprint and compare. They should at a minimum tried to let the volt sprint in the same test, the phv prius can not do a marathon. To me your harping on this suspect test is a fixation. Can you not see why some of us want a PHEV that can keep the motor off?

Like the tesla's first iteration the traction motor does not provide as much power at higher rpms as the manufacturer would like. Tesla had a two speed transmission, then properly specified the motor and made it a one speed again. GM is using the generator mainly to work with the universal gear to put the traction motor in a more efficient range. The generator motor does provide some power, but it is likely limited by the software, battery pack, and inverter. In the phv prius the mg2 is also limited by these factors and not its power rating.

If GM allowed a blended mode in software the ice could contribute and bring the total power closer to 200hp. There are some constraints, and I believe gm does not go into this mode bellow 30mph, so you would not be able to hit this extra power until a threshold speed. The porsche prototype phev 918 does have software to allow the driver to select from all these modes

 

It is unfair in the sense both were not driven with the same acceleration or speed.

It is fair because both were driven with the acceleration / speed that the car allows them to. That demonstrate the efficient usage of the battery. The intelligent car would use the battery wisely. The other, just brute force.

Yes, the A/C was set to 72 deg F in the entire test drive. I would prefer to drive without the gas engine but that's what EVs are for. For a hybrid, I prefer to use both powertrains. For a plugin hybrid, I still want to use both to get what I paid for. Would you buy a V8 and use only 4 cylinders at full throttle? That's what the Volt does. PHV Prius use all "cylinders" and it is a good thing. A hybrid that uses both powertrains at the same time is normal / natural.

There is room for improvement when the battery price drop and energy/power density increases. Until then, I believe PHV Prius is making the best of what we have today, to provide the best bang for our buck.

I can see it and I want it also. However, the trade-offs resulting from it are too much (compromises).

 

Um, No absolutely not. The prius used gas the volt did not. The prius was not driven in electric mode at the same distance or speed. Edmunds clearly stated in comments they could not drive it in ev mode for a reasonable test.

I don't really want to give anthropamorphic brain powers to the car. The phv does not have the capacity to do what the volt did on the test. It is not intelligence to not do things that are made impossible because of the design.

So no, you can not draw your conclusion from the edmunds test. All you can draw is an ev driving at lower speeds and less acceleration will be more efficient than one driving faster with more acceleration. Toyota has clearly stated they have the smaller battery because of costs not to cripple the EV speed and acceleration. These are design trade offs. You may like the phv prius's trade off, but it is intellectually dishonest to think the volts batteries and motors were tested in the same way that the prius's were.

When we have races and you don't finish you get a dnf. I give the prius a dnf on the test. This is not a victory. Now one thing you can do is figure out some kind of gasoline electrical equivalance. Then you could compare the efficiency. Edmunds chose an equivalance of energy price and trip distance of 100 miles, and if that is your measure then the phv prius is more efficient. If you choose a different metric like 40 mile trips and energy equivalence between electricity and gasoline the volt is more efficient. Reasonable people can disagree about metrics and have these discussions. I don't think reasonable people would look at the electrical efficiency add different speeds distances and acceleration and think its a valid test.

 

AG, the result speaks for itself. You have issue with how PHV Prius use the battery or gasoline. You need to get your head around the concept of gasoline engine running during the charge depletion (CD) mode. CD mode doesn't have to be in pure EV mode.

If you prefer how Volt uses the battery or gasoline, do you like the result?

EV-mode electricity consumption (*kWh/100 miles) *unlike mpg, smaller is better:

Volt 39.0
Prius PHV 23.2

HV-mode (hybrid vehicle) gasoline fuel economy (mpg):

Volt 31.1
Prius PHV 47.2

EV-mode electric range (miles):

Volt 33.9
Prius PHV 14.6

Driven the same way, our Prius PHV used 34 percent less gasoline in gasoline-hybrid mode and 41 percent less electricity in EV mode than the Volt.​

 

Is that like asking what the definition of is is? I mean the median portion of the population. I really doubt more than 5% of people buying a car between 20K=50K drive as slow with as low of acceleration in their driving. {sarcasm on} yes I'm calling your driving not normal {sarcasm off}

This is where I would love a like, don't like button, to see if most on the forum believe the phv prius is designed for ev operation, or if they agree with me and the magazines and the epa that it is a blended phev.