Volt Drivetrain Patent and info

Is the 3 clutch pack in the Volt configuration inherently any more susceptible to "grenading" than the multiclutch packs found in any generic modern transmission ?

I don't think so.

Does the presence of the 3 clutches automatically mean the design is less reliable than the clutchfree Prius, as you tend to imply ?

I don't think so either since clutches are well understood and mature automotive technology. The complexity of the Volt packs is nothing compared to the 1000-speed transmissions found in modern automobiles these days.

 

Clutches are great for smooth transitions from one mode to another.

 

Adrianblack,

Clutches are common components in all transmissions. Their presence in the Volt does not bother me or anyone who's not a Prius purist.

Now, do they lead to a shortened life expectancy of the transmission ? Apparently, Toyota themselves do not think so, given their usage of clutches in the Lexus HSD's.

 

I don't know. Auto tranny has torque converter between engine and transmission gears but Volt doesn't. When all 3 clutches are engaged, two electric motors (up to 10k RPM), the gas engine and the wheels will be grounded to the transmission case.

Yes, generally more moving parts = less reliability. KISS principle implies that simpler design is better than the complicated one.

 

Two stage HSD used in powerful Lexus hybrids simply changes the gear ratio between MG2 and the wheels. There is no possible way of grounding it to a transmission case, like the Volt.

 

It can work the opposite as well. A badly driven manual transmission car can feel jerky due to the clutch timing. 2-mode hybrid was not so great during the mode transition. In fact, it lagged power delivery during shifting (see video around 40 MPH). It may not be the same with the Volt but it was based on the 2-mode hybrid.

 

I try to keep all my statements as objective as possible. I reference them from reputable sources.

It is not a secret that I am a fan of HSD and specifically the Prius. Don't let that bother you.

 

You are backtracking. So, now the KISS principle only applies if it bolsters your argument.

Nice.

If you are truly objective, you have to conclude that the Toyota Prius HSD is better than the Lexus ones.

I'm not hearing that. Instead, I read excuses for the Lexus Clutched HSD design.

 

and what happens then in this hypothetical failure scenario ?

Here, let me answer it for you.

Nothing. The car simply stalls.

 

Yes, HSD is better in Prius than in Lexus higher power designs, with that clutch added.
But far from Volt design.

Do you follow that, or trying to put LSD and Voltec in the same bag?

 

Have you seen or done it in the Volt? What happens to the electric motors? Do they stall too? Can they still be repaired? Share more with us because we have never seen all 3 clutches in the Volt engaged at the same time. We knew it was a possibility.

Lexus hybrid has 5.0 liter V8 ICE and the electric motors. A clutch was added for the second stage as it was tuned for power and performance. On the other hand, the Volt has 1.4 liter 4 cylinder gas engine with 3 clutches.

3 clutches can be justified if it improves fuel economy and beat the Prius 50 MPG but 37 MPG does not cut it. Even the assist hybrid (Insight II) with 15 hp electric motor gets better MPG than the Volt.

 

Clutches have been used for years. They aren't horrible things, but they aren't desirable either. Being clutchless is one of the elegant and desirable things about the Prius HSD.

All other factors being equal, one would prefer a design without a clutch. Obviously, all of the other factors aren't equal when it comes to the Prius and Volt. Whether the Volt system is worth the extra mechanical complexity, only time will tell.

Tom

 

Agree.

Clutches have been used since always, on a dry and separate housing for manual transmissions.
Clutches in the transmission oil have been used for some years in automatic aplications or overdrive gear sets, and motorcycle gearboxes. But have't been consensual, due to the debris that naturally are washed by the oil. There is no such thing as a 100% filter for these particles. Draining the oil is the best periodic "solution". But with time, wear of rotating parts is inavoidable, because the release of particules is always present.
I would say that time WILL TELL, unfortunately not so good for Volt.

 

This is a purely hypothetical argument and proves nothing for nor against the Volt. What about the Prius main computer going bad and spinning the ICE at full RPM while instantly applying maximum counter torque to it then engaging the park pawl?... Both mechanical and software designs are tested before being put in production. The only useful argument would be that software doesn't worn over time.

 

Indeed .... the drivetrain in the Prius is much more likely to destroy itself due to

computer failure than the transmissions in a conventional vehicle.

 

I would have to disagree, if you have proof of those "much more likely" events. Surely, after 2 million units sold and driven much around the globe, you can find enough evidence to support your post.

Well, at least, transmissions in a conventional vehicle are human operated, which I agree, since we are error-proof. LOL

 

I can do better than statistics, facts.

quote: "If the Traction Control System detects ... , the torque would be so great that damage could occur to the transaxle."

 

It doesn't have clutches that can lock everything up to grenade like the Volt.

2 million Priuses, 14 years and counting (plus Ford hybrids). Power Split hybrid has proven to be extremely reliable.

Do you have the source where you got that idea?

 

I don't have a source, but it has been brought here, Priuschat, many times that the traction control has more to do with protecting the drive train than traction control. I and others have actually had the traction control hinder us in getting out of slick conditions. Most other cars equipped with it have an easy way of disabling it.

The limits might be over protective, or the drive train has been improved in a way that over revving isn't as large a threat.