Motor shaft dampers?

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hobbit

hobbit

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Do any EVs have damper clutches between motors and the rest of the drivetrain, like the plate that the
Prius ICE connects through and can absorb sudden torque shocks without breaking stuff? And possibly
help self-correct minor axial misalignments, or the "too many bearings" rigidity problem that has been
discussed about the Konas and Niros. In heavy accel or regen, bumps in the road can make huge torque
peaks that likely can't change the speed of the heavy motor rotor very fast, and it would be nice to have
something in between that could slip just a bit when needed and relieve the drivetrain stress.

_H*
 
hobbit said:
Do any EVs have damper clutches between motors and the rest of the drivetrain, like the plate that the
Prius ICE connects through and can absorb sudden torque shocks without breaking stuff? And possibly
help self-correct minor axial misalignments, or the "too many bearings" rigidity problem that has been
discussed about the Konas and Niros. In heavy accel or regen, bumps in the road can make huge torque
peaks that likely can't change the speed of the heavy motor rotor very fast, and it would be nice to have
something in between that could slip just a bit when needed and relieve the drivetrain stress.

_H*
Click to expand...
Closest EV I can find would be the dual speed EV gearbox used in Porsche Taycan which incorporates a clutch.
Better details here showing comparison to its single speed counterpart.
 
Both my BMW i3 and the Tesla Model 3 handle it electronically. The BMW applies acceleration smoothing over about 500-750 ms. In my Tesla, I run it in 'calm' mode which solves a lot of 'power jerking' symptoms

Sad to say, my first 2014 BMW i3 suffered a motor mount failure due to me taking speed bumps at suspension dampening speeds. Happily it was a warranty repair.

Suspensions are a mass, spring, and resistance dampening system. It turns out that speed bumps all but disappear if taken at a fast enough speed. But the mounting points can become be the weak link.

Bob Wilson
 
Both my Solterra and Ioniq 6 have dampened torque onsets when tromping the pedal and when letting off with regen. Makes for smoother driving. The dampening may be just a fraction of a second, but it is noticeable although probably has minimal impact to performance numbers. This is in direct contrast to my old 2019 Kona EV (and a 2023 that I test drove) which provides instant torque both on acceleration and regen. Of course you can modulate that onset of torque with the pedal, but is built in with the Solterra and Ioniq 6.

These comparisons are all in ECO drive mode which I use almost exclusively. The only time I use Normal or Sport mode is when I want to demonstrate the power and acceleration to a friend. I find that ECO mode is more than enough for all my acceleration needs, incl the Kona which has a lot less power (but lots of torque).

The only other EV comparison I have is my son's Tesla M3. He always has it in full stop one pedal mode, which I don't really like. I find it jerky for take off and when coming to a full stop. I am sure you can get use to that by modulating the pedal better. I can go full stop one pedal in my Ioniq 6, too. But after trying it a couple times, I don't like it either. I prefer stepping on the brake for that final stop to prevent creeping forward, very much like an ICE car. YMMV.
 
Algorithms help, I suppose, but what I'm talking about here is a mechanical slip element to prevent transmitting
the really damaging peak torque differentials across the whole powertrain, but non-slippy enough to send full
expected normal drive and regen torque through. Maybe that's impossible, not sure.

_H*
 
hobbit said:
Algorithms help, I suppose, but what I'm talking about here is a mechanical slip element to prevent transmitting
the really damaging peak torque differentials across the whole powertrain, but non-slippy enough to send full
expected normal drive and regen torque through. Maybe that's impossible, not sure.

_H*
Click to expand...
A mechanical dampener would add to the cost of the vehicle, require additional engineering to incorporate it, require additional space to contain it, and add a new point of possible failure.

The ECM in my MINI Cooper SE electronically controls the torque to prevent wheel-slip (which it does very well). There's a dashboard switch to reduce the effect of the anti-wheel-slip programming, but it can't be turned completely off. I believe BMW had problems with the original i3 breaking parts of the drivetrain and they used the ECM to solve those problems rather than a mechanical dampener.
 
hobbit said:
Algorithms help, I suppose, but what I'm talking about here is a mechanical slip element to prevent transmitting
the really damaging peak torque differentials across the whole powertrain, but non-slippy enough to send full
expected normal drive and regen torque through. Maybe that's impossible, not sure.

_H*
Click to expand...
Why use a mechanical solution when the software can do it instead, and maybe better. It saves not only the drive train parts but also the motor mounts.
 
One early problem with some EVs were speed bumps. Taken too quickly, the drive wheels would suddenly go to no torque load. In the 10s to 100s of milliseconds to hit the road, the motor could accelerate the wheels and lead to a significant torque overload. This was documented in the BMW i3 forums.

Bob Wilson
 
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