Steering column vibration reduced by cylinder pressure shaping

[SomptingGuy]

According to this:

https://www.hondarandd.jp/point.php?pid=1033&lang=en

During development of the 2014 model-year Accord Hybrid, for which the SPORT HYBRID i-MMD new model hybrid system was adopted, 2nd-order vibration transmitted to the steering became an issue. This occurred because the vehicle has higher engine net torque than a gasoline engine vehicle, so that there is larger crankshaft revolution 2nd-order fluctuation, which is the source of the vibration. There is concern that using only reduction of engine net torque as the means to lessen crankshaft revolution 2nd-order fluctuation could cause an increase in the brake-specific fuel consumption. Therefore the combustion control parameters, such as ignition timing and valve operation timing, were changed as a way of optimizing crankshaft revolution 2nd-order fluctuation, engine net torque, and brake-specific fuel consumption. These measures achieved the steering vibration target while also determining the optimal point where the amount of engine net torque reduction could be lessened by 5 Nm and 1% of the increase in brake-specific fuel consumption could be recovered.

...P&E engineers have allowed fundamental changes to breathing and combustion to reduce steering column vibration. I haven't read the actual article, but it sounds a little far-fetched. Interested to hear similar anecdotes.

- Steve

 

[GregLocock]

That report makes very little sense.

So, could you modify the combustion pressure such that the second order component is reduced, and yet the torque (the integral of all the harmonics) stays the same?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[ivymike]

sure, you probably could (we're talking flywheel-averaged torque, and you can definitely change noise noticeably through injection rate shaping while maintaining power output) ... but could you still meet emissions and combustion noise targets?

If this is a hybrid vehicle with a flywheel-centric electric motor, why not just actively cancel the undesired vibrations electrically?

 

[SomptingGuy]

I was just thrown by the source (Official Honda) and how exacting it was. Reducing combustion noise by rate shaping (or just simple retarding) isn't new, but even that upsets everyone else. And if it's total blue-sky stuff, why not something like steer by wire? I'm still totally missing the point here? There must be some other agenda.

- Steve

 

[ivymike]

protective publication, perhaps? maybe they got wind of a competitor doing something, and wanted to make sure it wasn't patented?

 

[SomptingGuy]

Oops, forgot to add the point that combustion noise isn't going to affect steering vibration. To do that you're going to need to do something serious about the fundamental inertial/gas forces. And tiddling with combustion isn't going to do that.

- Steve

 

[ivymike]

looks like the engine used in the i-MMD system is a 2-liter 4-cylinder ... so 2nd order is the firing frequency ... off the cuff it would seem that the way to change 2nd order flywheel vibration magnitude would be to reduce peak cylinder pressure (while attempting to maintain BMEP), so a longer combustion duration would be necessary?