Bendix Commercial Vehicle Systems INLET REG VALVE COMP 3/04 - Manual (Page 2)

2
FIGURE 3 - COMPRESSOR EITHER LOADED OR
UNLOADED WITH LOW TURBOCHARGER PRESSURE
OUTLET
T O
COMPRESSOR
temperature o-rings, seals, seats, and lubricant are used
throughout the IRV
™ valve to provide compatibility with
incoming turbocharger air temperatures up to 250°F. The
unitized valve and piston assembly consists of the piston
housing, two o-rings and control piston with its permanently
affixed valve plate. The cavity below the piston is vented to
atmosphere. The ring spacer holds the piston housing in
place and rests on the supply cap nut along with the valve
spring. The steel cap nut contains the supply port and retains
an o-ring which serves as the valve seat. A hex socket plug
with a through drilled vent along with a spring and steel ball
valve comprise the safety valve.
OPERATION
GENERAL
The IRV ™ valve maintains a low pressure at the compressor
inlet (10 psi or less) regardless of turbocharger supply air
pressure. The air flow through the IRV
™ valve is throttled by
the valve which varies in position from fully open to closed.
Valve position and, therefore, the degree of throttling is
controlled by both turbocharger supply pressure and
compressor air flow demand. The operation of the IRV
™ valve
is described for each of four functional conditions.
COMPRESSOR EITHER LOADED OR UNLOADED LOW
TURBOCHARGER PRESSURE (Figure 3)
For both loaded and unloaded compressor operation at low
turbocharger pressure (Less than 5 psi) the IRV
™ valve
remains fully open. Air is supplied to the compressor at
turbo supply pressure. The position of the piston/valve plate
assembly is determined by the pressure forces acting on
the top of the piston, on the upper and lower valve plate
surfaces, and by the spring force. At low supply pressure
the thrust of the pressure forces is insufficient to overcome
the spring force.
COMPRESSOR LOADED HIGH TURBOCHARGER
PRESSURE (Figure 4)
Air at turbocharger supply pressure is continually supplied
to the chamber above the IRV
™ valve piston. At pressures
above 5 psi the force on the piston is sufficient to partially
close the valve. With the compressor loaded (compressing
air) the resulting pressure drop across the valve lowers the
delivery pressure to the compressor. This lower pressure is
effective over the upper surface of the valve plate, tending to
open the valve. The pressure drop across the valve increases
with increased compressor flow (higher compressor RPM).
The position of the valve is thus affected by both turbo
supply pressure and compressor air demand. High turbo
supply pressure coupled with low compressor air demand
will tend to close the valve.
COMPRESSOR UNLOADED HIGH TURBOCHARGER
PRESSURE (Figure 5)
TURBOCHARGER
SUPPLY
PISTON
VALVE
PLATE
SPRING
SEAT
FIGURE 4 - COMPRESSOR LOADED-
HIGH TURBOCHARGER PRESSURE
OUTLET
T O
COMPRESSOR
TURBOCHARGER
SUPPLY
PISTON
VALVE
PLATE
SPRING
SEAT
FIGURE 5 - COMPRESSOR UNLOADED-
HIGH TURBOCHARGER PRESSURE
OUTLET
T O
COMPRESSOR
TURBOCHARGER
SUPPLY
PISTON
VALVE
PLATE
SPRING
SEAT