SANY LATIN AMERICA
4-102
SY195/205/215/225C9 Crawler Hydraulic Excavator
Structure and Function
Shop Manual - June 2013
Brake valve operation
●
The brake valve consists of suction safety
valve (8A) and counterbalance valve (18).
Functions and operations of respective
components are described below.
1) Counterbalance valve and check valve
Function
●
When the machine is travels downhill, the
weight of the machine tends to make the
travel speed faster than the motor speed.
If the machine travels with the engine at
low speed, the motor may rotate at zero
load, resulting in run away and inviting a
very dangerous situation. These valves are
used to avoid such a situation by control-
ling the machine to travel as per the engine
speed (pump delivery).
Operation when pressurized oil is supplied
●
Operating the travel lever conducts the
pressurized oil from the control valve to
port (PA). The pressurized oil opens suc-
tion safety valve (8A) and then flows to
motor outlet port (MB) via motor inlet port
(MA). The motor outlet side is closed by
suction safety valve (8B) and spool (19),
so the pressure at the supply side rises.
ZX215-1002101
PA
MA
MB
8A
18
PB
Travel control valve
ZX215-1002102
PA
PB
MA
MB
8B
8A
19
Travel control valve
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