Request for anyone who is currently bench testing a lexus CVT

[Jacobsmess]

Recently I saw a video of the (if I remember correctly) Subaru CVT made by Toyota, in which the engineer shows how the CVT aspect of the gearbox works. Essentially, spinning mg2 forwards and mg1 backwards achieves a higher output rpm than just mg2.

It would make sense as they are called Continuously variable transmissions, rather than just a motor that they have the ability to modulate the rpm dynamically.... this makes me think.... is it possible with the Lexus (and other Toyota maybe) CVTs.

Unfortunately I'm still in the planning phase but I was wondering if anyone might have a Lexus/Toyota CVT setup on the bench that they could confirm if this is their actual function. If so, it could potentially open up their use quite a bit.

Thanks for reading all!

[Aragorn]

They do this to modulate the ENGINE rpm. When its being used as a standalone motor the power split isnt connected to an engine, and thus either needs to be locked up or otherwise disabled. Either by locking up the PSD input shaft, or by welding up the PSD gears.

MG2 is directly connected to the rear output flange, its speed is thus solely dictated by the road speed (and in the case of the L110, which ever gear is selected)

MG1 is connected to both the engine, and the rear output flange, via the PSD. In the original hybrid application this is where all the CVT "magic" happens, applying negative torque to MG1 did two things, it absorbs energy from the engine (which was recirculated either to the battery or to MG2) and it allowed the system to "set" a gear ratio for the mechanical part of the PSD, which allows direct mechanical transfer of power from the engine to the rear output.
None of that applies when using it as a standalone motor, as there is no engine. You either weld up the PSD, locking the MG1 and carrier together, which means MG1 runs at the same RPM as the output shaft, or you lock the engine input shaft from rotating, allowing the PSD to rotate, which then means MG1 spins faster than the output shaft by the ratio of the PSD.

This simulator might help you visualise:
http://eahart.com/prius/psd/

[Jacobsmess]

They do this to modulate the ENGINE rpm. When its being used as a standalone motor the power split isnt connected to an engine, and thus either needs to be locked up or otherwise disabled. Either by locking up the PSD input shaft, or by welding up the PSD gears.

MG2 is directly connected to the rear output flange, its speed is thus solely dictated by the road speed (and in the case of the L110, which ever gear is selected)

MG1 is connected to both the engine, and the rear output flange, via the PSD. In the original hybrid application this is where all the CVT "magic" happens, applying negative torque to MG1 did two things, it absorbs energy from the engine (which was recirculated either to the battery or to MG2) and it allowed the system to "set" a gear ratio for the mechanical part of the PSD, which allows direct mechanical transfer of power from the engine to the rear output.
None of that applies when using it as a standalone motor, as there is no engine. You either weld up the PSD, locking the MG1 and carrier together, which means MG1 runs at the same RPM as the output shaft, or you lock the engine input shaft from rotating, allowing the PSD to rotate, which then means MG1 spins faster than the output shaft by the ratio of the PSD.

This simulator might help you visualise:
http://eahart.com/prius/psd/

Thanks, that helps clear it up, so you would need a third motor controlling the input shaft in order to get overdrive and CVT function.

[Jacobsmess]

Out of curiosity, what sort of output torque do you think would arise or what would the sum of torque be if running an input motor putting out say 100nm into the input shaft and using mg1 to modulate the speed. Would the input motor need to have a greater torque than mg1 or does it not matter?