[torsen] RE: Torsen differential

Keith Maddock Keith.Maddock at trw.com
Wed Nov 20 06:30:03 EST 2002


Dave,

WRT " you could achieve it with a haldex lsc, all you need is an integrated
differential.  it interests me that no-one has done one yet."

GKN has done it, it's called Visco-Lok. 
 Uses shear pumps instead of gerotors, but otherwise the same principle.  They also put a small mechanical preload on the clutch to get some coupling before slip occurs. (no electronic control though)
Currently available on some ATV's, and the M3 ("Variable M Differential Lock")
http://www.gkndrivetech.com/Motorsport-Cat/Motorsport.pdf  (look at page 14)

As a rear diff, its phenomenal, I don't think anyone is using it as a center diff yet though it could be done!

The unit is capable of enough clamping/locking to propel a 6000lb 2wd pickup up a 20% grade with one drive wheel on glare ice.

WRT 
"my description of the use of the feeder pump in abs operation is that the
pump is opened (and presumably disabled) by the ecu on abs operation, as the
throttle valve is connected to it."

That explanation seems to be odds with the following graph: 
http://www.haldex-traction.com/bilder/pictures/enlarge/graph_deactivation.gif

which shows a residual pressure of 4 bar which I am assuming is from the pump, as it is also seen here on a ice launch:
http://www.haldex-traction.com/bilder/pictures/enlarge/graph_acceleration.gif

If the pump is off in the ABS case, where is the 4 bar coming from?  

Guess I have a lot of questions for the Haldex guy when I get chance to see him up north!

Keith

****************************************************************
Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> "Dave.Eaton" <Dave.Eaton at clear.net.nz> 11:30:54 20.11.2002 >>>
well, i'd say technically and functionally "part-time" awd, and marketing
"full-time" awd :)

the key thing for me is that, in normal operation, there is no engagement
until slip occurs, and therefore no torque distribution until slip.  my
definition of "full-time awd" is a nominal torque distribution in the static
case.  you could achieve it with a haldex lsc, all you need is an integrated
differential.  it interests me that no-one has done one yet.

as i understand it, the pump (called a "feeder pump" by haldex) is used to
prime the clutch on full throttle starts (prior to slip), but is primarily
used (as you've quoted from the haldex web-site) to keep the 2 main
(pumping) pistons closed up to the rollers, to reduce the engagement time.
my description of the use of the feeder pump in abs operation is that the
pump is opened (and presumably disabled) by the ecu on abs operation, as the
throttle valve is connected to it.

however, the feeder pump does not make the haldex an active clutch, not does
it make it capable of "full-time" awd - as per my description above.

i've enjoyed the discussion, thanks.

dave
'95 rs2
'90 ur-q






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