Force multiplication of PS
Force multiplication of PS
(OP)
Will the force multiplication of hydraulic power steering (feel) be directly influenced by hydraulic line pressure ?
Or is it a design function of the relative areas in spool valve and rack piston ?
I realise that there needs to be sufficient pump pressure to generate enough basic rack force, but above that, does increased line pressure effect overall force multiplication ?
Or is it a design function of the relative areas in spool valve and rack piston ?
I realise that there needs to be sufficient pump pressure to generate enough basic rack force, but above that, does increased line pressure effect overall force multiplication ?





RE: Force multiplication of PS
RE: Force multiplication of PS
RE: Force multiplication of PS
At less than 4 degrees then you get a reduced level of assistance from the pump. The shape of the curve of boost vs bar angle is critical, as is the stiffness of the bar itself, and the maximum bar angle.
The relationship between those and other parameters is extremely complex, you may find some useful stuff if you look around for literature by Bishop.
Further complexity is added when you have variable ratio and speed dependent systems.
If you increase the blow-off valve setting then you will get a reduction in steering wheel efforts, and a subjective mismatch between the torsion bar's stiffness and that of the hydraulic circuit. You'd get a similar effect by fitting a larger rack (ie piston).
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Force multiplication of PS