Section E - Hydraulics
Operation Description
Transmission Pump Operation - Series 2 Machines
E-19 E-19
9803-9340-8
Transmission Pump Operation - Series 2 Machines
The transmission pump P1 is a variable displacement axial
piston pump 10, and associated control circuits.
Forward/reverse control is provided by a solenoid
operated directional control valve 3, which acts on the
swash angle control piston 2. This switches the swash
plate 11 in the pump from one direction to the other.
Swivelling the swash plate over centre changes the
direction of flow smoothly. The swash angle is also
affected by the displacement angle control valve (DA) 6,
which compensates for changes in load, e.g. ‘pull down’ of
the engine speed due to increased load or a hydraulic
service demand.
Oil is drawn through suction strainer S from hydraulic tank
T by the charge pump 8 which is an engine driven single
stage hydraulic gear pump. The charge pump is part of the
transmission pump assembly and provides the control
pressure for the pump operation. The charge pressure is
regulated by charge pressure relief valve 7.
Oil flow to drive the transmission motor(s) leaves via port
A and returns via port B or vice versa, depending on the
direction of drive, and forms a closed circuit.
Oil returns to tank from port T, the transmission motor case
drain, via the oil cooler C.
For a more detailed explanation of pump operation refer to
pages E6-4 and E6-5.
T004510-1
Fig 11.
Key
E Engine
P2 Main Services Pump
2 Control Piston
3 Direction Control Valve
4 Pressure Cut-off Valve
5 High Pressure Relief Valves
6 Displacement Angle Control Valve (DA)
7 Charge Pressure Relief Valve
8 Charge Pump
10 Variable Displacement Axial Piston Pump
11 Swash Plate
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