54
Power transmission
M
Safety valve
In the event of a breakdown, this means that
the vehicle can be towed without the engine
running and with the axle raised off the
ground.
Torque is developed at the coupling depen-
ding on the driving situation.
Pressure modulation is induced by means of
the control valve (hydraulic proportional
valve), whose opening cross-section is altered
by a slide valve.
The slide valve is activated by a rack and a
stepping motor.
The control unit together with its software are
located in the immediate vicinity of the step-
ping motor.
A safety valve opens at very higher inner pres-
sure to prevent the coupling from being
damaged.
The hydraulics
Torque is transmitted to the rear axle drive by
means of the plate coupling .
The necessary coupling pressure is generated
via the two annular piston pumps. The annu-
lar piston (also known as axial piston) is
driven by an axial piston pump.
The speed at which this pump rotates is the
difference between coupling input and output
speeds.
An even pressure curve is ensured by three
phase-shifted pump strokes.
The annular pistons runs in floating bearings.
They are driven by the pressure generated by
the pre-pressurising pump (an electrically
driven gear pump).
The pre-pressurising pump only operates if
the ignition has been turned on and engine
speed is greater than 460 rpm.
SSP207/12
Two parallel annular
piston pumps
Pre-pressurising
pump
Control valve
Oil filling
Working piston
Plate set
Cam disc
Input
Output
