Oil change adjustment for EV usage versus ICE usage

the engine stays off when your foot is off the gas or when you're in ev mode in all prius. that's part of what makes it so efficient.
every generation has increased the speed at which the engine stays off. it's now 84 mph or something.
the clutch has nothing to do with it. it's the design of the ecvt.

 

It doesn't have to turn in Ev mode. The torque can be balanced between the two MGs so that it just sits there with the planets spinning but not rotating.

The same has been true of the Prius family since its inception.

Go fiddle with this.

Toyota Prius - Power Split Device

 

My understanding is that synthetics do a better job of producing a protective ("lubricative," if that's a word) film over moving parts. That can be important if the engine rotates while the oil is still viscous (i.e., engine still cold).

 

To drive from both MGs with the engine stationary, MG1, the one on the sun gear, has to turn much faster than MG2, the one on the ring gear. That is why, on Gen-2 for example, the engine has to turn above ~42MPH: MG1 hits its rotational-speed limit.

If they intended the engine not to turn at all in EV mode, then it certainly would have been easier and higher-reliability to clutch the engine completely stationary, rather than create a comparatively complex unidirectional clutch, allowing it to turn forward but not backward.

 

it is stationary up to 84 mph on prime, is it not?

 

Yes.

 

A sprag clutch is a highly reliable, low friction, low cost thing. There's one on every device that has a pull start, like a lawn mower, and on the back wheel of every bike.

 

I, for one, hope that's true, but how do you know? Is that documented somewhere?

And again, why put in a one-way clutch if it's not to turn either direction? A brake is simpler.

 

That's how a Prius PSD works. The engine doesn't rotate up to some speed at which the sun pinon (or mg1 which powers it) can't go any faster backward. At that point the engine has to turn to reduce the speed on mg1.

And a brake is an active device, requiring an actuator which makes it more expensive and less reliable. A sprag clutch is passive, and therefore cheaper and more reliable.

 

where does bob wilson get documentation, argon labs or somewhere?

the pip can go 62 mph on ev, but the ice starts spinning around 45. maybe the clutch on prime allows 84?

 

The clutch on the Prime is there to allow both M/Gs to be used for propulsion. Without it, the ICE would spin backwards when M/G1 tried to add to M/G2 for that.

Spinning the ICE while under EV propulsion is done to prevent damage to M/G1 from over revving. The top speed for that point has gotten higher with each generation.

 

The word "forwards" is missing in the above IMO to make your explanation complete...so I added it with your permission

 

Reasonable point regard active vs passive devices.

Not clear what the sprag clutch is for, in that usage. It would only be useful in cases where MG1 is more than keeping up with MG2.

 

The sprag clutch allows MG1 to provide torque to the wheels through spinning the planets. Without the clutch, that torque would spin the engine backwards. With it, it can augment the Ev mode power available.

 

The nomogram cited by Lee Jay several posts ahead is showing speeds not torques.
Now let's see, you want to accelerate in EV with both MGs as motors, low car speed. MG1's windings are excited so it produces torque (i.e. acts as motor), without the one way clutch this torque would spin the ICE shaft (planets carrier) backwards, with it this torque is joining forces with MG2 to propel the car.
Now car gathers speed to a point where MG1 (as a motor) reachs its max allowable speed (backwards) at this point ICE shaft is allowed to spin (forward) to enable MG1 to perform as motor without overspinning. Up to here - dual motors drive.
When 84 mph is reached, ICE fires to join and as a result MG1 changes to a generator to convert part of the ICE torque to electricity so no dual motors at this stage.
It seems that the best element chosen by Toyota to make sure ICE shaft will not spin backwards while be free to spin forward is this Sprag clutch.

 

So, the premise is that MG2 is spinning forward at r1/r2 times the speed MG1 is moving backward, where r2 is the radius of the ring gear connected to MG2, and r1 is the radius of the sun gear connected to MG1. That is, they're matching each other, meaning that the engine is not rotating.

So then, you're suggesting a scenario where only MG1 is supplying power?

 

No, where MG1 adds its torque capacity to that being produce by MG2. The sprag clutch has to lock up to react this torque and thus allow it to pass into the spinning (but not orbiting) planets and on into the ring gear which propels the car.

Toyota calls this "dual motor" mode. It allows the Ev power to be increased from 53kW on the G4 liftback to 76kW on the Prime.

 

Yes, I understand the usage Lee Jay is describing. But the sprag clutch is not needed for that scenario, because MG2 already prevents the ICE spinning backward in that scenario.

The best rationale I can come up with for the sprag clutch (and I'm still pondering this to see whether I buy it) is not related to speeds (angular velocities), but to torques: MG1 cannot exert a torque unless it has something stationary to push against (or more accurately, to twist -- torque -- against), and the sprag clutch provides that. Again, still pondering to what degree I buy that...

 

Did you understand the usage I was describing?

 

No it doesn't.

The torque on the planet carrier is the torque applied by MG1 (times a gear ratio). If MG1 applies a torque, it's against the engine. If the engine is running, MG1 can apply a (backwards) torque to act as a generator, with the torque reacted against the engine. If the engine is not running and thus not producing torque, MG1's applied torque is also against the engine. In one direction, it starts the engine acting as a starter motor. In the other direction, it spins the engine backwards. But if that torque is reacted by the clutch instead of the engine, that torque is transmitted through the planets (not the carrier - the planets) to the annulus (ring) gear and on to the wheels.