Fitting one-way clutch to GS450h input shaft

[Miyuki]

Hi,
As the stock MG1 limit is just about 7000 RPM, I wonder if somebody considered fitting a one-way clutch to the input shaft.
I was looking it up, and Toyota already uses this at PHEVs to extract power from MG1 at low speeds and prevent the engine from rotating backward.
So it looks like a proven solution, just on a different platform.

[jrbe]

Once way bearings don't handle much power and when they fail they can make a mess.

[Miyuki]

They use this
https://toyota-club.net/files/2023/23-0 ... w52_en.htm
But this MG1 has only 40Nm, so it is tiny
Does anybody know the rating of GS450h? I see everywhere just wild guesses.
But even if it would be about 100Nm, then it is about 3 times more at the engine shaft and 300Nm sprag-type clutches are readily available.

[Jacobsmess]

Why not use an electromagnetic clutch? Then it is just on or off no? The hybrid Subaru uses one in its eCVT to disengage and engage the rear drive I believe.

[TongueTester]

Hi Miyuki,

I am interested to know what you are wanting to achieve by fitting a one way clutch vs fixing the input shaft as others have done?
Is it so you can keep the ICE and gain the ability to drive both elec motors in an EV only mode?

Thanks

[Miyuki]

Yes, mainly it is for the possibility to use both motors and switch to ICE when wanted.
And also I am a little concerned with the high speed of MG1 as it has a bigger diameter than MG2. I know many people let it spin fast, but how long will it last?
I still wonder what is its torque rating as in its original use it sees just less than one-third of ICE torque and the inverter part is also half the size compared to the main motor part. If it is a significant performance boost to worth using it.

[TongueTester]

Hey Miyuki,

Thanks for starting such a great conversation. It took me down the rabbit hole for sure! (I have similar PHEV related interests).

What I discovered was that under normal operation, the THS (Toyota Hybrid System) in a normal hybrid (non PHEV) rotates MG1 backward in certain circumstances. For example at high speed and max engine RPM and possibly engine based decel when the battery is fully charged.

A Sprag clutch may work to lock the input to MG1 and allow you to use it as a motor (not just a generator), but the sprag clutch 'may' also prevent the hybrid system operating correctly and would likely result in a bunch of CEL (check engine light) errors or maybe even a physical limitation such as limiting max speed.

Getting a GS450H hybrid to work in 'EV only mode' above 40mph (~60kph) is a very interesting problem when you drill down into it. Holding the input shaft still may even be necessary to run on just MG2 above 60kph (to prevent MG1 spinning too fast).

I personally don't think an electromagnetic clutch is practical because (presumably) you would need to replace the input dampener assembly which I feel Toyota put in for a reason, but conceivably you could mount an electromagnetic 'locking pin' on the outside of the bellhousing to engage with the dampener assembly to achieve the same result.

My original plan to run in 'EV mode' with MG2 only (above 60kph) was to 'brake' MG1 electrically with its inverter to limit its RPM. But I am still learning about the PSD to know whether this would actually work and it would be quite a waste of battery power (unless it could be used to feed power back to MG2).