jcb JS300 Service Manual page 986

Brake Valve
Brake Function
When control valve A is returned to neutral, the
pressurised oil from the pump is blocked, and pressure at
P1 and P2 becomes equal, and the plunger tries to return
to neutral position by the spring. When the plunger moves,
F-9
the plunger diaphragm opening becomes smaller and
because the piston motor continues to rotate due to inertia
(motor pumping function), the pressure at M2 port side
rises and braking occurs. At this time, when the M2 port
side pressure attains the relief valve set pressure, the relief
valve works and allows oil to escape to M1 port side,
absorbs shock pressure caused by inertia of M2 port side
while also preventing M1 port side cavitation.
A
P1
M2
Fig 4.
9813/5100-1
Section F - Transmission
Traction Motor / Reduction Gear
P2
M1
Operation
C076860
F-9