Kubota KX080-4 Workshop Manual page 446

KX080-4, WSM
Evaporator outlet temperature
When low (when cooling load is low)
When high (when cooling load is high)
(1) Evaporator
The pressure of the gas in the diaphragm chamber drops, reducing the volume and moving the
heat-sensitive rod to the right, which constricts the needle valve and reduces the flow of refrigerant
to the evaporator.
The pressure of the gas in the diaphragm chamber rises, increasing the volume and moving the
heat-sensitive rod to the left, which opens the needle valve and supplies more refrigerant to the
evaporator.
A : Diaphragm
B : Heat-Sensitive Rod
C : Spring
Expansion Valve
[Functions]
The expansion valve works in the following two
ways.
1. By spraying the liquid refrigerant, which is hot and
under high pressure, it makes it expand rapidly,
producing a low-temp, low-pressure refrigerant
vapor.
2. It adjusts the amount of refrigerant according to the
vaporized state of the refrigerant in the evaporator.
In order to take full advantage of the capabilities of
the evaporator, a state must always be maintained in
which the liquid refrigerant takes on the ambient
heat, then it is completely vaporized at the outlet of
the evaporator. In order to do so, the expansion
valve automatically adjusts the volume of refrigerant
in response to changes in the cabin temperature
(cooling load) and changes in the compressor RPM.
[Structure (box type)]
• The expansion valve is composed of a diaphragm,
heat-sensing rod, and a needle valve (ball) and the
refrigerant gas is enclosed upstream of the
diaphragm. The downstream side of the diaphragm
is pressurized by the evaporator outlet pressure.
[How it Works]
• The heat-sensitive rod senses the temperature of the
refrigerant passing to the evaporator and the
temperature at that point is communicated to the
refrigerant gas on the upstream side of the
diaphragm via the heat-sensitive rod. As such, the
pressure of the gas varies with the temperature, thus
moving the heat-sensitive rod directly connected to
the diaphragm and adjusting the opening of the
needle valve.
Operation
D : Body
E : Needle Valve
5-M9
CABIN
(a) From Receiver
(Hi-Pressure)
(b) To Compressor
(Lo-Pressure)
(c) To Evaporator
(d) From Evaporator
RY9212001CAM0014US0
KiSC issued 08, 2015 A