Komatsu ecot3 PC300LC-8 Shop Manual page 242

SEN01995-01
Function
This valve reduces the swing back generation
q
in the swing body by the inertia of the swing
body, the backlash and rigidity of the machin-
ery system, and the compression of the
hydraulic oil when the swing is stopped.
q The valve contributes in preventing collapsing
of load when the swing is stopped and also
contributes in reducing cycle time (enhances
the positioning performance, enabling you to
proceed to the next work quicker than ever).
Operation
1. When port (MB) brake pressure is gener-
ated
q Pressure (MB) is conducted to chamber (d) via
notch (g).
The pressure compresses spring (6) by use of
q
the difference in areas of circles (
spool (5) and moves spool (5) to the left side.
o
q Port (MB) chamber (e) will be intercon-
nected.
q Since pressure (MA) is lower than the set pres-
sure of spring (3), spool (2) does not move and
the pressurized oil is kept in. Thus the braking
force is ensured.
50
10 Structure, function and maintenance standard
2.
q
q
q
q
q
φ φ
D1 > D2) of
When motor is stopped temporarily
The motor rotation is reversed by the closing
pressure generated at port (MB). (1st time:
reverse rotation)
Reversing pressure is generated on port (MA).
Pressure (MA) is conducted to chamber (a).
The pressure compresses spring (3) by use of
the difference in areas of circles (
spool (2) and moves spool (2) to the right side.
o
Port (MA) chamber (b) will be intercon-
nected.
Then ports (b) and (f) will be interconnected
through the drilled hole (h) on spool (5). This
interconnection bypasses the reversing pres-
sure on port (MA) to port (T), thereby prevent-
ing the reverse rotation of the 2nd time.
φ φ
D3 > D4) of
PC300, 350-8