TSE DPT40-B, Owner'S Manual

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9
Series 90 Functional Description 2
2.4.1 Charge Pump
The charge pump is necessary to supply cool fluid to
the system, to maintain positive pressure in the main
system loop, to provide pressure to operate the
control system, and to make up for internal leakage.
Charge pressure must be at its specified pressure
under all conditions of driving and braking to prevent
damage to the transmission.
The charge pump is a fixed-displacement, gerotor
type pump installed in the variable displacement
pump and driven off the main pump shaft. Charge
pressure is limited by a relief valve (Sec. 2.4.2).
The standard charge pump will be satisfactory for
most applications. However, if the charge pump sizes
available for the given main pump size are not ad-
equate, a gear pump may be mounted to the auxiliary
mounting pad
(Sec. 2.4.8) and supply the required
additional charge flow. For repairs to the charge
pump see
Sec. 9.2.4 .
2.4.2 Charge Relief Valve
The charge relief valve on the pump serves to main-
tain charge pressure at a designated level. A direct-
acting poppet valve relieves charge pressure when-
ever it surpasses a certain level. This level is nomi-
nally set referencing case pressure at 1775 rpm. This
nominal setting assumes the pump is in neutral (zero
flow); in forward or reverse charge pressure will be
lower. The charge relief valve setting is specified on
the model code of the pump
(Sec. 8.1.1) . For repairs
to the pump charge relief valve see Sec. 9.2.3 .
2.4.3 System Check Valves
The system check valves allow pressurized flow from
the charge pump to enter the low pressure side of the
loop whenever system pressure dips below a certain
level. This is needed as the pump will generally lose
system pressure due to leakage and other factors.
Since the pump can operate in either direction, two
system check valves are used to direct the charge
supply into the low pressure lines. The system check
valves are poppet valves located in the multi-function
valve assembly (next section).
PV with Charge Pump
90000243
90000349
Charge Pump Components
Pump Charge System
Case
Drain
Line
Charge Relief
Charge
Pump
System
Check
Valves
Input
Inlet Filter
Reservoir
PV PF
90000804
2.4 Pump Features
CONTENTS