Описание
(1) реле давления
(2) бачок осушителя
(3) компрессор
(4) конденсатор
(5) редуктор
(6) испаритель
R134a is drawn into the compressor (3) as gas under low pressure
It leaves it as gas under high pressure, then it is drawn to the condensor (4) where it changes to a liquid under high pressure due to its cooling caused by external air blown by the fans
The R134a is then brought to the pressure relief valve where the great drop in pressure which it experiences leads to a very great drop in its temperature
It leaves the pressure relief valve (5) as a mixture of low pressure gas and liquid
As it passes into the evaporator (6) this causes the cooling and dehumidifying of the air which enters the passenger compartment
It leaves the evaporator as a low pressure gas and returns to the compressor (3) to start a new cycle
The pressure switch (1) ensures the safety of the circuit in relation to high pressures
The dehydrator reservoir (2) has the task of absorbing the humidity in the circuit
Компрессор
The compressor puts the R134a liquid under pressure
It operates on the principle of a pump with 7 pistons controlled by a sloping plate driven by the motor
The basic operating principle of an air conditioning circuit with a variable capacity compressor does not differ from that for a circuit with a fixed capacity compressor
However, to reduce the cyclic phenomenon, the variable capacity compressor varies its capacity according to
- The requirement for cold air in the passenger compartment
- The temperature of the air passing across the evaporator
- The humidity of the air passing across the evaporator
The variation in capacity is caused by changing the angle of the piston-bearing plate
This angle of the piston-bearing plate is a function of the high and low pressures of the refrigerant
These high and low pressures, controlled by the regulation valve (8) change the pressure in the compressor casing and determine the angle of the piston-bearing plate
Положение максимального объема цилиндров
Положение минимального объема цилиндра
ПримечаниеThe safety of this type of circuit is always ensured by a pressure switch and an evaporator temperature sensor
Full principles of operation are being produced and will be distributed later
Редуктор
(A) high pressure liquid
(B) low pressure liquid/gas
(C) low pressure gas which returns to the compressor
(7) thermostatic bulb or capsule
The pressure relief valve causes the sudden drop in pressure of the liquid refrigerant
It also has the role of adjusting the flow (of refrigerant) according to the requirement for cold air in the passenger compartment
Safety/regulation
The safety of this type of circuit is ensured by two main elements
- The pressure switch (positioned in the high pressure part of the circuit)
- Датчик температуры в испарителе
The pressure switch has a safety function in relation to the high pressures; it operates on the electrical supply to the compressor
The evaporator temperature sensor has a regulation role according to the temperature of the evaporator
It therefore prevents the evaporator becoming blocked due to the freezing of condensation on it
The sensor resistance is read and interpreted by the electronic thermostat which controls the supply to the compressor
Заключение
Passenger compartment temperature regulation is obtained by successive impulses of the electrical supply to the compressor (cycllical operation of the compressor)
This phenomeneon leads to a deterioration in driveability by causing engine hesitation when the electrical supply to the compressor recommences
This problem is lessened by the use of a compressor with variable capacity