Infiniti F50. Manual — part 123
REFRIGERATION SYSTEM
ATC-17
C
D
E
F
G
H
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L
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A
B
ATC
REFRIGERATION SYSTEM
PFP:KA990
Refrigerant Cycle
EJS00077
REFRIGERANT FLOW
The refrigerant flows in the standard pattern, that is, through the compressor, the condenser with liquid tank,
through the evaporator, and back to the compressor. The refrigerant evaporation through the evaporator coil is
controlled by an externally equalized expansion valve, located inside the evaporator case.
FREEZE PROTECTION
Under usual operating conditions, when the A/C is switched on, the compressor runs continuously, and the
evaporator pressure, and therefore, temperature is controlled by the V-6 variable displacement compressor to
prevent freeze up.
Refrigerant System Protection
EJS001Y3
REFRIGERANT PRESSURE SENSOR
The refrigerant system is protected against excessively high or low pressures by the refrigerant pressure sen-
sor, located on the liquid tank. If the system pressure rises above, or falls below the specifications, the refriger-
ant pressure sensor detects the pressure inside the refrigerant line and sends the voltage signal to the ECM.
ECM makes the A/C relay go OFF and stops the compressor when pressure on the high-pressure side
detected by refrigerant pressure sensor is over about 2,746 kPa (28 kg/cm
2
, 398 psi), or below about 134 kPa
(1.4 kg/cm
2
, 20 psi).
PRESSURE RELIEF VALVE
The refrigerant system is also protected by a pressure relief valve, located in the rear head of the compressor.
When the pressure of refrigerant in the system increases to an unusual level [more than 3,727 kPa (38 kg/cm
2
, 540 psi)], the release port on the pressure relief valve automatically opens and releases refrigerant into the
atmosphere.
RJIA0849E
ATC-18
REFRIGERATION SYSTEM
V-6 Variable Displacement Compressor
EJS001Y4
GENERAL INFORMATION
1.
The V-6 variable compressor differs from previous units. The vent temperatures of the V-6 variable com-
pressor do not drop too far below 5
°
C (41
°
F) when:
Evaporator intake air temperature is less than 20
°
C (68
°
F).
Engine is running at speeds less than 1,500 rpm.
This is because the V-6 compressor provides a means of
″
capacity
″
control.
2.
The V-6 variable compressor provides refrigerant control under varying conditions. During cold winters, it
may not produce high refrigerant pressure discharge (compared to previous units) when used with air
conditioning systems.
3.
A
″
clanking
″
sound may occasionally be heard during refrigerant charge. The sound indicates that the tilt
angle of the wobble (swash) plate has changed and is not a problem.
4.
For air conditioning systems with the V-6 compressor, the clutch remains engaged unless: the system
main switch, fan switch or ignition switch is turned OFF. When ambient (outside) temperatures are low or
when the amount of refrigerant is insufficient, the clutch is disengaged to protect the compressor.
REFRIGERATION SYSTEM
ATC-19
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D
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A
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ATC
DESCRIPTION
General
The variable compressor is basically a swash plate type that changes piston stroke in response to the required
cooling capacity.
The tilt of the wobble (swash) plate allows the piston's stroke to change so that refrigerant discharge can be
continuously changed from 14.5 to 184 cm
3
(0.885 to 11.228 cu in).
Operation
1.
Operation Control Valve
–
By changing high-pressure valve lift amount, built-in compressor control valve executes the following:
•
Controls high-pressure valve discharge amount.
•
Changes crankcase pressure in compressor.
•
Changes angle of wobble (swash) plate.
RJIA1260E
ATC-20
REFRIGERATION SYSTEM
–
Amount of high-pressure valve loft is determined by factors below.
•
Low pressure applied to diaphragm
•
Spring load of set spring
•
Balance of magnetic force generated in magnet coil
–
Electronic control valve (ECV) magnet coil receives electric signal (duty control) from auto amplifier. Then,
magnetic force generated by electric current is changed to control high-pressure valve lift amount.
2.
Maximum Cooling
High-pressure valve is closed by magnetic force generated by electric signal sent from automatic ampli-
fier. At this time, cylinder moves full stroke due to pressure balance between inside crankcase (Pc) and
suction line (Ps).
Under this condition, the wobble (swash) plate is set to the maximum stroke position.
3.
Capacity Control
When no electric signal is sent from automatic amplifier (current: OFF), high-pressure valve is opened by
spring force.
Since suction pressure is low, it makes the suction port close and the discharge port open. Thus, crank-
case pressure becomes high as high pressure enters the crankcase.
–
The force acts around the journal pin near the wobble (swash) plate, and is generated by the pressure dif-
ference before and behind the piston.
The drive lug and journal pin are located where the piston generates the highest pressure. Piston pres-
sure is between suction pressure Ps and discharge pressure Pd, which is near suction pressure Ps. If
crankcase pressure Pc rises due to capacity control, the force around the journal pin makes the wobble
(swash) plate angle decrease and also the piston stroke decrease. In other words, crankcase pressure
RJIA0851E
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