Komatsu PC20R-8 Shop Manual page 46

OPERATION
1. Pump operation
1 - The cylinder block (7) rotates together with the
shaft (1), and the shoe (5) slides on the flat sur-
face A.
At this time, the rocker cam (4) moves along
the cylindrical surface B, so the angle
tween the center line X of the rocker cam (4)
and the inclination of the cylinder block (7) in
the axial direction changes.
a
This angle is called the swash plate angle.
2 - When the center line X of the rocker cam (4)
maintains the swash plate angle
to the axial direction of the cylinder block (7),
the flat surface A acts as a cam for the shoe
(5).
By this, the piston (6) slides on the inside of
the cylinder block (7), creates a difference be-
tween capacities E and F, then suction and
discharge of oil for the amount of this differ-
ence (F ± E) will be carried out.
In other words, oil is discharge as the capacity
of the chamber F decreases when the cylinder
block (7) rotates.
In the mean time, the capacity of the chamber
E increases, and the oil is sucked at this pro-
cess.
(The figure shows the state of the pump when
suction of the chamber F and discharge of the
chamber E have completed).
3 - When the center line X of the rocker cam (4)
becomes in line with the axial direction of the
cylinder block (7) (swash plate angle = 0),
the difference between capacities of E and F
inside the cylinder block (7) becomes 0, so
the pump does not carry out any suction or dis-
charge action of oil.
(In actual fact, the swash plate angle never be-
comes 0).
4 - In other words, discharge amount of the pump
is directly proportional to the swash plate an-
a
gle .
10-28
a
be-
a
in relation
X
X
4 5
1
B
4
= 0
A F
7
6
E
RKP01240
F
7
E
RKP01260
PC20R-8 PC27R-8