User Manual

8/12 Bosch Rexroth AG
LLC Load Limiting Control
RE 95310/01.09
The LLCB electronic load limiting control functions in basically
the same way as the LLCA variant, but is designed to control
only one pump instead of two.
In addition, the valve for the slew drive is controlled in such a
way that the flow rate for the slew drive motor is maintained
irrespective of the diesel engine speed. As a result, the slew
drive always turns at the same speed regardless of the speed
at which the diesel engine is running.
The electronic load limiting control is designed for controlling
variable displacement pumps in an open hydraulic circuit.
The following hydraulic concept can be used for control pur-
poses:
• The hydraulic system consists of the axial piston pumps
A8VO or A11VO with a hydraulic or electrohydraulic power
controller and load limiting controller (LA1, LG1, LE) together
with a control block (e.g. M7) with a pressure reduction valve
(DRE) on the slew drive spool.
The RC2-2/20 controller controls the pump controller and
the pressure reduction valve in the control block.
The following diesel engine configuration can be used:
• Diesel engine with or without CAN-bus interface
The controller receives the specified speed for the diesel
engine from an angle sensor (accelerator pedal position as
specified speed). The actual speed is measured using a
speed sensor on the starter gear rim.
The LLCB variant does not evaluate the CAN bus.
Functional description
The diagram below illustrates how the load limiting control
works:
• From the specified speed value and the diesel characteristic,
the load limiting control calculates the current speed drop of
the diesel engine.
• The load limiting control compares the current speed drop
with the parameterizable limit values. Different limit values
can be parameterized for different specified speeds.
• As long as the total of the hydraulic powers does not exceed
the installed diesel power, the speed drop will not exceed
the parameterized limit values. The load limiting control will
not intervene.
• If, however, the diesel engine speed drop exceeds the limit
value, the load limiting controller will intervene and reduce
the pump power.
• The maximum permissible speed drop of the diesel engine
can be adjusted in three steps using the "power mode"
switches.
Figure 6: Configuration for LLCB
RC2-20 controller
with LLCA software
Error
lamp
BODAS service
PC software
Speed sensor
Diesel engine with
or without CAN-bus
interface
Angle
sensor
Pumps
A8VO... LA1..F.4 or
A11VO...LE / LG1
Slew drive
GFB
Slew drive
shaft in
control block
M7
Variant LLCB