2016 – MX-5 – HVAC

EXPANSION VALVE

Purpose, Function

• The expansion valve rapidly depressurizes the liquid refrigerant to form it into a mist.

• The expansion valve adjusts the liquid refrigerant flow volume sent to the evaporator.

Construction

• The expansion valve consists of the following parts.

Operation

• The expansion valve adjusts the liquid refrigerant flow volume using the opening angle of the ball valve in the expansion valve.

• The opening angle adjustment is performed according to the balance of the following forces:

  

• Refrigerant pressure (Pd) in diaphragm

• Refrigerant gas pressure (PI) of evaporator under diaphragm

• Spring force (Fs) pushing up ball valve

• If the gaseous refrigerant temperature from the evaporator increases, the expansion valve increases the amount of refrigerant according to the following operations.

  

• The temperature of the temperature sensor tightly sealed against the diaphragm increases.

• The refrigerant in the diaphragm warms and the Pd increases.

• If this Pd increases more than PI + Fs, the diaphragm is pressed down.

• The shaft installed to the temperature sensor end presses down the ball valve.

• The amount of refrigerant is increased.

• If the gaseous refrigerant temperature from the evaporator decreases, the expansion valve decreases the amount of refrigerant flow according to the following operation.

  

• The temperature of the temperature sensor tightly sealed against the diaphragm decreases.

• The refrigerant temperature in the diaphragm decreases and the Pd decreases.

• The Pd decreases less than PI + Fs.

• The ball valve installed to the temperature sensor end is pressed up.

• The amount of refrigerant is decreased.

Fail-safe

• Not applicable

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