Komatsu 830E-AC Shop Manual page 682

PRINCIPLE OF OPERATION
Full Pump Volume:
Control piston (1, Figure 4-10) controls the angle of
the swashblock (4). When the control piston moves
to the full right position, the pump is at maximum
pumping capacity.
The driveshaft turns the splined housing (2) which
contains the pumping pistons (3). When the housing
is rotated, the pistons move in and out of their bores
and the piston shoes "ride" against the angled
swashblock (4).
As the cylinder rotates, the individual piston bores
are connected, alternately to the left (port A) and
right (port B) crescent shaped ports in the valve
plate. While connected to left side (suction) port A,
each piston moves outward, drawing fluid from port A
into the piston bore until its outermost stoke is
reached. At that point the piston bore passes from
the left crescent port to the right crescent port.
While rotating across the right side crescent, each
piston moves downward on the angled swashblock
face. Thus, each piston is forced inward. Each piston
displaces fluid through the right side crescent to port
B until it's innermost stroke is reached. At that point,
the piston bore again passes from the right to the left
side crescent and the operating cycle is repeated.
Half Pump Volume:
Figure 4-11 shows that the position of the control pis-
ton (1) is near the center of its travel. The swash-
block is not angled as steep as before, and therefore
the pistons have a shorter stroke. As the piston
stroke gets shorter, the pump output also decreases.
L4-18
FIGURE 4-10. PUMP AT FULL VOLUME
1. Control Piston
2. Housing
FIGURE 4-11. PUMP AT HALF VOLUME
1. Control Piston
2. Housing
Steering Circuit
3. Piston
4. Swashblock
3. Piston
4. Swashblock
L04048