Komatsu ecot3 PC300LC-8 Shop Manual page 230

SEN01995-01
Brake valve
The brake valve consists of check valves (14),
q
counterbalance valve (15) and safety valve
(16).
q Functions and operations of respective compo-
nents shall conform to the following.
1. Counterbalance valve and check valve
Function
When traveling downhill, the machine travel
q
speed tends to get faster than the motor
(engine) speed because of the downward force
generated from its own weight.
If the machine travels with the engine at low
q
speed, the motor may rotate without load,
causing the machine to run away, resulting in a
very dangerous situation.
q These valves are used to prevent above by
controlling the machine to travel according to
the engine speed (pump delivery).
38
10 Structure, function and maintenance standard
Operation when pressurized oil is supplied
Operating the travel lever conducts the pres-
q
surized oil from the control valve to port (PA).
q The pressurized oil push-opens check valve
(14A) and then flows to motor outlet port (MB)
via motor inlet port (MA).
q The motor outlet side is closed by check valve
(14B) and spool (24), so the pressure at the
supply side rises.
PC300, 350-8