Bendix Commercial Vehicle Systems BENDIX 720CC COMPRESSOR - Manual (Page 5)

5
NON-COMPRESSION OF AIR (UNLOADED)
COMPRESSOR AND AIR DRYER SYSTEM
(REFER TO FIGURE 6)
Air delivery to the vehicle’s air system is controlled either
by the governor and the air dryer, or with a separate
discharge line unloader valve. The governor is plumbed
to the component (e.g. air dryer or DLU valve) in order to
control when the air is delivered to the vehicles air system.
When air pressure in the supply reservoir reaches the cut-
out setting of the governor, the governor delivers system air
to the discharge line unloader style (DLU) air dryer’s control
port. This allows the discharge air from the compressor to
flow out the exhaust port of the air dryer.
Note: The Bendix ® 720cc compressor is a discharge
line unloader-style (DLU-style) unit. This means that the
compressor functions in a continuous pumping mode;
regardless of whether the brake system requires air. It
requires a downstream device (e.g. turbo cut-off-style air
dryer and discharge line unloader valve) to unload the
system when air requirements have been met as described
in the previous paragraph.
LUBRICATION
The vehicle's engine provides a continuous supply of oil
to the compressor. Oil is routed from the engine to the
compressor's oil inlet. Note: There is no external oil supply
line; the oil delivery is located at the engine to compressor
mounting face. (See Figure 7.) This pressurized oil flows
to the precision front sleeve main bearing, and — via an oil
passage in the crankshaft — routes pressurized oil to the
connecting rod bearings and the rear journal associated
with the end cover. Spray lubrication of the cylinder bore
and connecting rod wrist pin bushing is obtained as oil is
forced out around the crankshaft journals by engine oil
pressure. Oil then falls to the bottom of the compressor
crankcase and is returned to the engine through the
opening at the compressor mounting flange.
COOLING
The Bendix 720cc twin cylinder compressor is cooled both
by air flowing through the engine compartment as it passes
the compressor's cast-in cooling fins, and by the flow of
engine coolant through the cylinder head assembly and
the water jacket around the cylinder bore of the crankcase.
Coolant supplied by the engine cooling system passes
through connecting lines into the cylinder head, cooling
plate, valve plate assembly, and into the crankcase water
jacket. It returns through the same components — out of
the coolant outlet port of the cylinder head — and returns
to the engine. Figure 7 illustrates the approved coolant
flow connections. Proper cooling is important in minimizing
discharge air temperatures – see the tabulated technical
data on page 13 of this manual for specific requirements.
FIGURE 7 - BENDIX ® 720
CC
TWIN CYLINDER COMPRESSOR PORT IDENTIFICATION
Discharge Port
Inlet
Port
Head
Bolt (8)
CYLINDER HEAD PORT IDENTIFICATION
The cylinder head connection ports are
identified with “cast in” numerals as follows:
AIR IN . . . . . . . . . . . . . 0
Compressed AIR OUT . . . . . 2
Coolant IN . . . . . . . . . . . 9
Coolant OUT. . . . . . . . . . 9
Safety
Valve Port
Coolant Port
(In or Out)
Coolant Port
(In or Out)
Oil
Supply