Skytrak 6036 Service Manual Bedienungsanleitung PDF herunterladen (Seite 161)

Section 9 Hydraulic System

Model 6036/6036T S/N 9B0500 thru 14833

9-11

Fig. 9.7 Inlet Section - Sectional View

either of the two pulsar solenoids, one for each

function. The pulsar solenoids are energized 33

times per second by PWM signals from the

controller to generate control pressure which is

proportional to the PWM on-off cycle, Fig. 9.8.

The pulsar solenoids are fitted with matched

orifice plates and seals at the return. Oil leaving a

pulsar solenoid is restricted by the orifice plate to

result in proportional back pressure which is

applied to either end of the main spool in the

corresponding control chamber.

The position of the main spool is determined by

the centering spring and the differential pressure

between the two chambers at either end of the

spool. In the static condition there is no differential

pressure, the main spool is centered, there is no

flow at the cylinder ports, and the reservoir and

cylinder pressure passages are at reservoir

pressure. If no PWM signals are sent to the pulsar

solenoids, both valve sections are static, load

sensing pressures are vented back to the reser-

voir, and the inlet compensator valve flow is

bypassed to the reservoir at approximately 200 psi

(13,8 bar).

When one of the pulsar solenoids is energized by

PWM signals, control pressure is applied to one of

the control chambers. The differential pressure

between the chambers shifts the main spool to

allow oil flow across the spool lands to the corre-

sponding cylinder port. Initial metered oil flow

occurs at 60 psi

(4,1 bar) differential pressure with

full flow at 132 psi

(9,1 bar). Unused oil is by-

passed to the reservoir at approximately 200 psi

(13,8 bar) over load pressure.

c. Working Sections - Main Spool Control

Pilot pressure is supplied to two pulsar solenoids,

Fig, 9.8, in the pilot stage of each working section.

The main spool in the main stage is actuated by

b. Inlet Unloading Pressure Compensation

and Relief

The inlet section bypass spool, Fig. 9.7, is bal-

anced between the system pressure and the load

plus spring force pressures. Under static condi-

tions the valve remains closed until the supply oil

pressure in the supply passage reaches approxi-

mately 200 psi

(13,8 bar) and overcomes the

compensator spring force. This shifts the spool to

open the valve and bypass the oil to return. When

a working section is actuated, the combined

compensator spring force and load pressure in the

load sense cavity shift the bypass spool to close

the valve. The spool will shift to open the valve

and bypass excess oil to the reservoir once the

working sections are supplied with the selected

flow rate at the required pressure. Pressure

supplied to the working sections is 200 psi

(13,8

bar) over load pressure. The bypass pressure can

be adjusted with the adjustment plug and seat.

The pilot-operated relief valve maintains load

pressure at a preset maximum allowable value.

Whenever the load pressure exceeds the poppet

spring force, the poppet cone, Fig. 9.7, will unseat

causing the bypass spool to relieve flow to the

reservoir. The relief valve setting can be adjusted

with the setscrew. Refer to paragraph 9.6.2.m for

control valve adjustments.

BYPASS

ADJUSTMENT

PLUG AND SEAT

COMPENSATOR

SPRING

RETURN

PASSAGE

RELIEF

VALVE

SETSCREW

POPPET

SPRING

POPPET

CONE

LOAD

SENSE

CAVITY

BYPASS

SPOOL

SUPPLY

PASSAGE

MK0050

1 2 ... 156 157 158 159 160 161 162 163 164 165 166 ... 341 342

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