Apr. 2007
6
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DSC48
1.3.1 VALVE PLATE OF HYDRAULIC
BLOCK DH
The oil sucked through the oil fi lter from the oil tank by the
hydraulic pumps (equipped with two hoses) is carried to
the PD and PH ports of the hydraulic block DH.
The hydraulic block DH has the following components:
• Variable relief valve (controlling the hydraulic brake's
pressure)
• Low pressure relief valve (limiting the hydraulic brake's
maximum pressure)
• High pressure relief valve (reaping unit)
• Clutch check valve, reaping unit height check valve,
and orifi ce
A. VARIABLE RELIEF VALVE
It changes the pressure (braking power) applied to the
piston of the steering clutch cylinder by controlling the
pressure of the oil returned to the valve unit (hydraulic
block B port) from the steering clutch cylinder. As the rod is
pressed down, the pressure increases. However, the maxi-
mum pressure is limited by the low pressure relief valve.
This valve is operated through the power brake cable by
the power steering lever.
417W607A
(1) Rod
(2) Poppet
(A) R port (to oil tank)
(B) From direction control cylinder
B. REAPING UNIT HEIGHT CHECK VALVE
To lift the reaping unit, the oil sent from the B port of the
direction control solenoid valve pushes and opens the pop-
pet of the reaping unit height check valve. Then, the oil
fl ows to the reaping unit cylinder.
To lower the reaping unit, the oil from the reaping unit cylin-
der passes through the orifi ce and fl ows to the P port of the
reaping unit lowering solenoid valve.
417W608A
(1) Orifi ce
(2) Line fi lter
(3) Poppet
(A) To reaping unit cylinder
(B) From B port of direction control solenoid valve
(C) To P port of reaping unit lowering solenoid valve
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