18/56 Product description
Bosch Rexroth AG, A22VG Series 40, RE 93221-01-B/07.2013
5.2.2 Functional description
Torque and rotational speed are applied to the drive shaft (1) by an diesel engine.
The drive shaft is connected by splines to the cylinder(8) to set this in motion. With
every revolution, the pistons (9) in the cylinder bores execute one stroke whose
magnitude depends on the setting of the cradle(11). The pistons hold the slipper
pads (10) onto the glide surface of the cradle with the retainer plate (2) and guide
them along. The swashplate setting during a rotation causes each piston to move
over the bottom and top dead centers and back to its initial position. Here, hydraulic
fluid is fed in and drained out through the two control slots in the control plate(7)
according to the stroke displacement. On the high-pressure side (5) the hydraulic
fluid is pushed out of the cylinder chamber and into the hydraulic system by the
pistons. At the same time, hydraulic fluid flows into the growing piston chamber on
the low-pressure side(6). In a closed circuit, supported by the return and boost
pressure.
The four high-pressure relief valves protect the hydrostatic transmission (pump and
engine) against overloading. They limit the maximum pressure in the relevant
high-pressure line and at the same time act as boost valves.
High-pressure relief valves are not working valves and are only suitable for pressure
spikes or high rates of pressure change.
In order to replenish internal leakage in the variable double pump and consumers,
portG must be connected to an external source of boost pressure.
The boost pressure-relief valve is integrated.
The boost pump continuously supplies a volume of fluid (boost volume) from a
reservoir to the low-pressure side of the closed circuit via a check valve to replenish
the internal leakage of the variable double pump and consumers.
The boost pump is an internal gear pump, driven directly
via the drive shaft.
Pressure portG
2
on the boost pump must be externally piped up by the customer
to portG (or G
1
on the version with DA control valve). Suction or pressure
filtration must be provided by the customer.
The swivel angle of the cradle (11) is steplessly varied. Controlling the swivel angle
of the swashplate changes the piston stroke and therefore the displacement.
Adjusting the swashplate through the neutral position will change the direction of
flow (making reversing operation possible). The swivel angle is controlled
hydraulically by means of the stroking piston. The cradle is mounted in swivel
bearings for easy motion and the neutral position is spring-centered.
Increasing the swivel angle increases the displacement; reducing the angle results in
a corresponding reduction in displacement.
Various control devices are available depending on requirements. Information
about this can be found in data sheet 93221.
Pump
High-pressure safeguarding
Version without boost
pump
Version with boost pump
(optional)
Control
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