SANY LATIN AMERICA
4-99
SY195/205/215/225C9 Crawler Hydraulic Excavator
Structure and Function
Shop Manual - June 2013
●
The counterbalance valve and the relief
valve forms the braking circuit. When the
main valve is neutralized position, hydrau-
lic oil from the main pump is cut off, and
pressure at port P1 and P2 is the same.
As a result, piston (1) moves to the neutral
position, and the opening area of circuit B
decreases. At the same time, because of
the inertia of external force, the motor does
not stop rotating (pump effect), and pres-
sure at port M2 rises and serves as the
braking force of motor rotation. When the
pressure at port M2 reaches the set pres-
sure of relief valve (8), cone valve (8-1) at
port M1 overcomes the force of spring (8-
2) and moves to the left, and hydraulic oil
fl
ows the port M1. In this way, the impact-
ing force due to inertia at port M2 is under
control, and vacuum at port M1 is avoided.
D. Braking of motor
ZX215-1002096
6-2
7-2
5-2
4-2
2-2
2-1
4-1
5-1
7-1
6-1
8-2
8
8-1
3
1
M1
P1
P2
M2
Circuit B
Circuit C2
Damper chamber A2
Orifice D4
Spring chamber 2
Circuit C1
Orifice D1
Damper chamber A1
Orifice D2
Spring chamber 1
Orifice D3
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