Hyundai HX140L, Manual

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2-81
2. FUNCTIONS
FUNDAMENTAL FUNCTIONS
The pilot valve is a valve that controls the spool stroke, direction, etc of a main control valve. This
function is carried out by providing the spring at one end of the main control valve spool and apply-
ing the output pressure (secondary pressure) of the pilot valve to the other end.
For this function to be carried out satisfactorily, the pilot valve is composed of the following ele-
ments.
Inlet port (P) where oil is supplied from hydraulic pump.
Output ports (1, 2, 3 & 4) to apply pressure supplied from inlet port to ends of control valve spools.
Tank port (T) necessary to control the above output pressure.
Spool to connect output port to inlet port or tank port.
Mechanical means to control output pressure, including springs that work on the above spools.
FUNCTIONS OF MAJOR SECTIONS
Item numbers are based on the type M1.
The functions of the spool (3) are to receive the supply oil pressure from the hydraulic pump at its
port P, and to change over oil paths to determine whether the pressure oil of port P is led to output
ports 1, 2, 3 & 4 or the output port pressure oil to tank port T.
The spring (5) works on this spool to determine the output pressure.
The change the deflection of this spring, the push rod (9) is inserted and can slide in the plug (8).
For the purpose of changing the displacement of the push rod through the swash plate (16) and
adjusting nut (17) are provided the handle assy (20) that can be tilted in any direction around the
fulcrum of the universal joint (15) center.
The spring (7) works on the case (1) and spring seat (6) and tries to return the push rod (9) to the
zero-displacement position irrespective of the output pressure, securing its resetting to the center
position.
This also has the effect of a reaction spring to give appropriate control feeling to the operator.
1)
(1)
(2)
(3)
(4)
(5)
2)