Explanation Of Operation; Material Handling Valve; Pressure Compensation Mechanism - Toyota 7FBEF 15 Service Manual

9-10
I Explanation of Operation

Material handling valve

1. Pressure compensation mechanism

When pressure compensation mechanism is ON
When solenoid C1 is euergized and non-leak valve is closed, the pressure compensation mechanism
operates as follows:
Pressure oil flowing from port P flows from chamber (a) through orifice A to chamber (b), then flows
through orifice B to chamber (c).
The opening aperture of oil passage E is determined by the equilibrium of chamber (b), chamber (c)
and spring 1.
This controls the oil pressure of chamber (a) at a fixed pressure higher than the oil pressure in
chamber (c).
Pressure oil that has flowed through the pressure reducing valve flows to chamber (f), then flows
through orifice D to chamber (e).
The pressure oil in chamber (c) flows into chamber (d) and the pressure compensation valve is
operated by the equilibrium of chamber (c), chamber (d) and spring 2.
This controls the oil pressure of chamber (d) at a fixed pressure higher than the oil pressure in
chamber (e).
Chamber (d) and chamber (c) are connected by orifice C, so they have the same oil pressure, and the
pressure differential between chamber (a) and chamber (f) is kept constant by operation of the unload
valve and the pressure compensation valve.
This pressure differential is detertimed by spring 1 and spring 2.
When the oil pressure in chamber (a) becomes high, the oil drains from the pilot relief valve of the
unload valve.
Accordingly, the maximum oil pressure of chamber (a) is detertimed by the installation load of spring 3.
Pressure compensating function (sectional view of inlet section)
Main flow/excess flow
Pilot flow
Unload valve
Port T1
(b)
(f)
(e)
E A (a) B
Port P
Spring 2
Spring 1
(c)
When the pilot relief valve is opened
When the pilot relief valve is closed
C
(d)
Non-leak valve
Pressure compensation valve
Spring 3
Solenoid C1