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SYSTEMS OPERATION
Transmission Control. Valve
This control valve comprises accumulator valve
2, inching valve 5, differential valve 6, direc
tional selector valve 4 and speed selector valve 3.
(1) Accumulator valve 2 gradually rises the oil
pressure in the clutch piston chamber to
insure smooth clutch engagement (smooth
starting).
(2) Differential valve 6 keeps the pressure ap
plied to the directional clutches (forward
and reverse clutches) lower than the pres
sure applied to the speed clutches (1st-
speed, 2nd-speed and 3rd-speed clutches)
by 2 kgf/cm2 (28 psi) [0.2 MPaJ. Conse
quently, the speed clutch is engaged earlier
than the directional clutch and the direc
tional clutch serves to transmit the power.
(3) Directional selector valve 4 directs the oil to
either forward clutch piston chamber or
reverse clutch piston chamber.
(4) Speed selector valve 3 directs the oil to any
of the 1st-speed, 2nd-speed and 3rd-speed
clutch•ports.
(5) Inching valve 5, actuated by the inching
pedal, reduces the pressure in the forward
or reverse clutch piston chamber to control
the clutch in transition from full engage
ment to full disengagement for moving the
machine in an inching manner.
(6) Main relief valve 1 maintains the pressure
of oil discharged from the pump. Because
of this valve, the pressure applied to the
clutch piston chambers is always constant
and full-flow oil is supplied to the lubrica
tion circuit except when oil is supplied to
clutch piston chambers.
1
Main relief valve
4
Directional selector valve
6
Differential valve
2
Accumulator valve
5
Inching valve
7 Neuiral switch
3
Speed
selector
valve
22
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