Komatsu Galeo BR380JG-1E0 Shop Manual page 123

10 Structure, function and maintenance standard
2. At hold and when load pressure (P2) is low.
NOTE: When load pressure (P2) is lower than output
pressure (PR) of the self pressure reducing valve.
Valve (2) receives force in the direction to
q
close the passage from port (P1) o (P2) from
spring (3) and pressure (PR) (when the engine
is stopped, the pressure is 0 MPa {0 kg/cm
However, when hydraulic oil flows in from port
q
(P1), the pressure is balanced so that pressure
(P1) = force of spring (7) + (area (Ød) x pres-
sure (PR)), and the opening from port (P1) o
(P2) is adjusted so that pressure (P1) is kept at
a certain value above pressure (PR).
When pressure (PR) goes above the set pres-
q
sure, poppet (5) opens, and the hydraulic oil
flows in the following circuit: port (PR) o hole
(a) inside spool (8) o opening of poppet (5) o
tank port (T).
As a result, a pressure difference is created on
q
both sides of hole (a) inside spool (8), so spool
(8) moves in the direction to close the opening
from port (P1) o (PR). Pressure (P1) is
reduced to a certain pressure (set pressure) by
the amount of opening at this point, and is sup-
plied as pressure (PR). (See Fig. 2)
BR380JG-1E0
3. When load pressure (P2) is high.
If load pressure (P2) increases and the pump
q
discharge amount also increases because of
operations, pressure (P1) also increases
(pressure (P1) > force of spring (7) + (area
(Ød) x pressure (PR)), so valve (2) moves to
2
}). the right to the end of the stroke.
As a result, the amount of opening from port
q
(P1) o (P2) increases and the resistance in
the passage is reduced, so the loss of engine
horsepower is reduced.
If pressure (PR) goes above the set pressure,
q
poppet (5) opens and the hydraulic oil flows in
the following circuit: port (PR) o hole (a) inside
spool (8) o opening of poppet (5) o tank port
(T).
As a result, a pressure difference is created on
q
both sides of hole (a) inside spool (8), so spool
(8) moves in the direction to close the opening
from port (P1) o (PR). Pressure (P1) is
reduced to a certain pressure (set pressure) by
the amount of opening at this point, and is sup-
plied as pressure (PR).
SEN01352-00
(See Fig. 3)
13