There are many variants in design for this type of valve but they all follow the same basic working principle.
Inside the expansion valve you will typically find the following main components

• The valve body, this holds the components and has an orifice inside to restrict the flow of refrigerant
• The diaphragm which is a strong, thin flexible material, typically metal, which can flex to apply pressure to the pin.
• The pin, or needle, which moves up and down to vary the size of the opening within the orifice to control the refrigerant flow.
• The spring which counteracts the force of the pin
• The sensing bulb and capillary line which measures the refrigerant temperature, at the evaporator exit, and reacts to causes the valve to open or close.