User Manual
Table Of Contents
- Content
- 1 Overall hydraulic system
- 2 Steering hydraulics
- System concept
- Fully hydraulic steering (Emergency steering)
- Orbitrol axle = Floating axle (1), the rigid axle (2) is tracked by electro-hydraulic means
- Orbitrol axle = Rigid axle (2), the floating axle (1) is tracked by electro-hydraulic means
- The floating axle (1) and the rigid axle (2) are steered electro- hydraulically - the Orbitrol steering circuit is closed.
- Steering valve VI
- 3 Working hydraulics
000 293 646 0 - SYS-H XERION 3300 - 04/05 17
1 Overall hydraulic system
PFC pump
391
Description of function All control units are in their neutral position. At the beginning of this example, the
swash plate (17) is in its maximum end position (see also Engine OFF).
When the engine is started, the pump feeds the maximum volume flow via the
pump output (20) up to the spools of all control units.
Since the spools block the flow completely, the pressure rises and is applied to
the right face end of the volume flow controller (772) which is moved to the left
against the compression spring (margin pressure) (21). In this process, the
control edge (25) is opened so that the pressure gains access to the top side of
the variable-displacement pump hydraulic cylinder (377). Now the swash plate
(17) is moved to the "Minimum volume flow" position against the control spring
(15). This process takes only 10 milliseconds.
In this pump position, the following happens: Volume flow is generated only to
such an extent that leakage losses are compensated. The pressure required for
initial actuation of a consumer is maintained.
When all control units are set to their neutral positions, the load pressure input
(7) is pressureless. To move the volume flow controller (772), the pump pressure
must overcome the compression spring (margin pressure) (21) and the LS
residual pressure. The pressure required for this is 20 + X bar and is referred to
as "Low-pressure standby". The "Low-pressure standby" is slightly higher than
the "Margin pressure" of 20 bar. As a function of the setting of the volume flow
controller (772) and of the pump leakage, "Low-pressure standby" and "Margin
pressure" may be almost identical. However, the "Margin pressure" can never be
higher. The low-pressure standby cannot be adjusted and may therefore vary
from machine to machine. It changes as the leakage rate in the pump or in the
system rises. The pump remains in the "Low-pressure standby" position until a
control unit is actuated. In this operating position, the pump only requires little
drive energy.