ASf11003
Figure 11-3.--Reciprocating open compressor.
SUCTION
VALVE
COMPRESSOR
ASf11005
Figure 11-5.--Reciprocating hermetic compressor.
DISCHARGE
VALVE
used on mobile air-conditioners. The A/M32C-21 unit
uses this style in the 6-cylinder model.
The hermetic compressor (fig. 11-5) is a
motor-compressor combination encased within a
gastight, welded casing that cannot be opened for
servicing except in refrigeration component overhaul
shops. The hermetic compressors are used on
refrigerators, freezers, window air-conditioners, and
other small units.
ASf11004
Figure 11-4.--Reciprocating semi-hermetic compressor.
The operation of all reciprocating compressors is
basically the same. The piston and connecting rod are
pressor (fig. 11-3) is driven from an external power
attached to a crankshaft, which is turned by the driving
source through V belts, gears, or a flexible coupling. It
force. As the piston moves down toward its lowest
is used on mobile air-conditioners powered by diesel
position, a low-pressure area is formed within the
engines and electric motors.
cylinder. As indicated in view A of figure 11-6, the
suction (intake) valve opens when the pressure within
The semi-hermetic compressor (fig. 11-4) is a
the cylinder becomes less than the pressure in the
motor-compressor combination enclosed within a
suction line leading to the cylinder. When the intake
common housing. It is provided with access plates and
valve opens, the cylinder is filled with low-pressure
can be serviced in the field if necessary. This
refrigerant vapor.
compressor, in multi-cylinder versions (four or six), is
PRESSURE IN DISCHARGE
PRESSURE IN CYLINDER
PRESSURE IN CYLINDER
DOWNSTROKE OF PISTON
LINE HOLDS DISCHARGE
HOLDS SUCTION
RAISES DISCHARGE VALVE.
CREATES VACUUM IN CYLINDER.
VALVE CLOSED.
VALVE CLOSED.
VAPOR FLOWS INTO
PRESSURE IN SUCTION LINE
DISCHARGE PIPE.
FORCES SUCTION VALVE OPEN.
PISTON ON
PISTON ON
DOWNSTROKE
UPSTROKE
ASf11006
A
B
Figure 11-6.--Operating cycle of a reciprocating compressor.
11-10