9-26
ㆍWhen the main circuit pressure is lower than the regulated pressure:
when the main circuit pressure is lower than the pressure regulated a port B, the sequential valve
work to increase the pressure at port P to maintain the regulated pressure.
When the solenoid is switched on, in the same way as mentioned in the previous paragraph,
passage(18) and chamber(10) are interconnected and a part of the fluid delivered from the pump is
branched and flows from port B to the cylinder. A the same time, the branched off fluid is let into
sequential valve spring chamber(8) through passage(9).
Here, the force imposed upon the left side of sequential valve spool(612) is the pressure in
chamber(13), and on the right side of the spool the pressure in chamber(8) and the force of
spring(622) are imposed. While chambers(13 and 8) have the same pressure, the spool is pushed
leftwards by the force of spring(622) and closes orifice(24). Then the pressure at port P increases.
When the pressure at port B reaches 15kgf/cm(213 psi), pressure-reducing valve spool(611) shifts
itself to close orifice(16) and the pressure in chamber(8) is also maintained at 15kgf/cm
2
(213 psi)
to maintain the pressure-reducing valve secondary pressure at the regulated level. The pressure at
port P is balanced at a pressure that is higher by the pressure equivalent to the force of spring(622):
approx.3kg/cm
2
(43 psi), so the pressure at port B becomes approx.18kgf/cm
2
(256 psi).
In this way even when the main circuit pressure is lower than the regulated level , the pressure at
port P (the pump delivery pressure) is elevated to the specified level, making it possible for the
clutch to be engaged in the same way as mentioned in the previous paragraph.
Fig.9-33
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