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Open circuit
Variable-speed operation
Product description | SYDFED-2X, SYDFED-3X, SYHDFED-1X
5 Product description
5.1
PERFORMANCE DESCRIPTION
The SY(H)DFED control system is designed and built for the electrohydraulic
control of swivel angle, pressure and power/torque of an axial piston unit. It is
intended for stationary applications.
Please refer to the data sheet and order confirmation for the technical data,
operating conditions and operating limits of the SY(H)DFED control system.
5.2
DEVICE DESCRIPTION
The SY(H)DFED control system is based on an axial piston variable displacement
pump of swashplate design for hydrostatic drives in the open circuit. The flow is
proportional to drive speed and displacement. The flow can be steplessly varied
by adjusting the swashplate.
In an open circuit, the hydraulic fluid flows from the tank to the variable
displacement pump and is transported from there to the consumer via a
directional valve. From the consumer, the hydraulic fluid flows via the directional
valve back to the tank.
In the regenerative operating mode (see chapter 5.3.4.1 "Regenerative operation"
on page 24) the hydraulic fluid can also flow from the consumer through the
pump to the tank.
For the control system SY(H)DFED we offer the order option "variable-speed
operation". Variable speed operation is an additional function, which determines
the optimum drive speed for the motor in dependence on the current working
point and passes it on to the drive. In addition, this additional function allows
power losses to be reduced.
5.2.1
Functional description, section of SY(H)DFED
The numbers in the description below refer to the numbers in brackets in Fig. 3, 4
and 5 on pages 19 and 20.
The pressure and swivel angle of the A10VSO variable displacement pump of the
SY(H)DFED control system is controlled using an electrically operated proportional
valve (2). The proportional valve determines the position of the swashplate (1)
by means of the actuating piston (4). The displaced flow is proportional to the
position of the swashplate. The counter-piston (3), which is preloaded by a spring
(5), is permanently pressurized to pump pressure.
While the pump is not rotating and the actuating system is depressurized, spring
(5) holds the swashplate in position +100 %. With a driven pump and a de-
energized proportional solenoid (8) the system swivels to zero stroke pressure
as the valve spool (9) is pushed to the initial position by the spring (10) and,
therefore, pump pressure p is applied to the actuating piston (4) via valve port
"A". A balance between the pump pressure on the actuating piston and the spring
force (5) is achieved at a pressure of 8 to 12 bar. This basic position (= zero stroke
operation) is obtained e.g. when the valve electronics is de-energized.
In contrast to this, a pump with external supply swivels to the negative limit
stop (regenerative operation). See also section 5.3.4.1 "Regenerative
operation" on page 24.
RE 30017-B, Edition 11.2021, Bosch Rexroth AG
17/96
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