General
This section contains a description and repair
procedures for a electro-hydraulic main control
valve with variable displacement pump used in the
hydraulic system for this series of lift trucks.
The electro-hydraulic (E-Valve) main control valve
is controlled electronically. It is mounted to the
cowl using three mounting bolts. See Figure 1.
NOTE:
MAJOR COMPONENTS NOT SHOWN FOR
CLARITY. VIEW IS FROM THE FRONT.
1. COWL
2. INSERT
3. WASHER
4. MOUNTING CAPSCREW
5. MAIN CONTROL VALVE
6. FRAME
Figure 1. Main Control Valve Mounting
The E-Valve with variable displacement pump
(VDP) is electronically-controlled, closed-center,
single function compensated, and utilizes parallel
hydraulic circuitry. Load sensing is done through
the VDP. Operating multiple functions
simultaneously will result in a non-proportionate
increase in pump flow to functions which receive
the lowest amount of pressurized fluid. The
hydraulic circuitry will incorporate dual pressure
relief logic.
Lift function pressure is regulated by the pump
pressure compensator. The pump compensator will
be set to the maximum system pressure and a
clipper relief valve will be present in the transition
section of the valve and set slightly higher. The
clipper relief valve adjustment is tamper proof. Tilt
and auxiliary functions are on secondary relief
pressure setting. Lift pressure is not affected by
secondary relief operation.
The electronic main control valve with variable
displacement pump assembly is divided into the
following sections (see Figure 2):
• Steering Control Unit (SCU)
• Transition section
• Lift/Lower section
• Tilt section
• Auxiliary section(s)
• Outlet section
2000 SRM 1899
General
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