TM 5-2410-240-23-1
0007
HYDRAULIC SYSTEMS CONTINUED
Left Side Hydrostatic Pump Operation
0007
When the engine is running, the shaft (Figure 4, Item 12) and barrel (Figure 4, Item 9) rotate. The port plate
(Figure 4, Item 7) and swashplate (Figure 4, Item 11) are stationary within the pump housing. The spring (Figure 4,
Item 8) maintains a force against the barrel and port plate. There are nine pistons (Figure 4, Item 10) in the barrel.
When the barrel is rotating, each piston follows the angle of the swashplate. If the angle of the swashplate is zero,
pistons do not move in and out of the barrel and there is no oil flow.
Pilot oil from the fan motor maintains oil pressure in the pump in order to perform the following tasks:
Keep the barrel (Figure 4, Item 9) full of oil.
Provide makeup oil for internal loss of oil due to leakage.
Lubricate the pump components.
Provide oil to the proportional solenoid valve (Figure 4,Item 4) in order to shift the actuator piston (Figure 4,
Item 1) and change the angle of the swashplate (Figure 4, Item 11).
Release the parking brake.
The actuator piston (Figure 4, Item 1) determines the position of the swashplate (Figure 4, Item 11) accordingly.
The machine Electronic Control Module (ECM) interprets signals from the speed and direction control and sends
pulse width modulated signals to the solenoids (Figure 4, Item 2) on either side of the proportional solenoid valve
(Figure 4, Item 4). As the proportional solenoid valve shifts to either direction, signal oil from the passage (Figure 4,
Item 3) is directed to the corresponding end of the actuator piston (Figure 4, Item 1). As the actuator piston begins
to move, the angle of the swashplate begins to increase. As the piston (Figure 4, Item 10) follows the swashplate,
pistons begin to move in and out of the barrel (Figure 4, Item 9). As the piston moves out of the barrel, oil is drawn
from the passage of port (Figure 4, Item 5) of the drive loop through the port plate (Figure 4, Item 7). As the piston
follows the swashplate and the piston moves into the barrel, oil is pushed through the port plate into the passage to
port (Figure 4, Item 6) of the drive loop. As the angle of the swashplate increases, the output flow of the pump also
increases.
0007-4
