Haldex question

[rplines at pacifier.com]

>Jens wrote:
>I tried going to
>www.haldex-traction.com
>look for yourself(s).
>(No helpful info on the mother site www.haldex.com)

>BTW: Is it a clutch or a coupling? And what is the difference?

www.haldex-traction.com is an excellent site.
We studied the Haldex device quite a bit as they are a competitor of ours...
The way it works is very cool.  It is essentially a multi-plate clutch that gets
compressed by hydraulic pressure.  The hydrualic pressure can be generated one of
two ways.  1) Relative motion between the front and rear of the vehicle (wheel-slip)
will create a pumping action to generate hydraulic pressure.  2) There is also an
electric "feeder pump" that generates a small amount of pressure regardless of wheelslip.
 Now the neat thing is that this pressure is applied to the clutch by set of valves
controlled by a computer (also built into the unit).  The computer communicates with
other onboard systems (ABS, engine ECU, TCS, etc...) through what is called a CAN
(controller area network) bus.  So regardless of wheel-slip, the computer can also
go from full lock to full release if it is programmed to do so.  One example is the
ABS panic stop where the device must release completely to prevent torque transfer
from interfering with proper ABS function.  The Haldex is one of the fastest acting
devices out there.  It is the cutting edge AWD technology right now.
-Peter