During Normal Operation (Contact Point Is On)
When the refrigerant pressure is applied from inside the housing to the seal film, a force is exerted from the stopper, guide head, high pressure disc and high pressure internal lid to the low pressure disc to set the low pressure guide pin free, causing the moving contact to be ON.
Dual Switch Function - During Normal Operation (Contact Point Is On). Scheme 115
During Abnormal Low-Pressure Operation
If the refrigerant pressure falls, the pressure on the seal film is lost, and the force exerted from the stopper, guide head, high pressure disc and high pressure internal lid to the low pressure disc decreases, and the low pressure disc rotates back, pressing the guide pin down and causing the moving contact to be OFF.
Dual Switch Function - During Abnormal Low-Pressure Operation. Scheme 116
During Abnormal High-Pressure Operation
If the refrigerant pressure becomes abnormally high, a force is exerted from the seal film to the guide head and press guide, and the high pressure disc rotates back, pressing the guide pin down and causing the moving contact to be OFF.
Dual Switch Function - During Abnormal High-Pressure Operation. Scheme 117
An airstream produced by a blower passes through the cooling fins and tubes. This air is warmer than the refrigerant and gives up its heat to the fins, tubes and then to the refrigerant itself. As the low pressure refrigerant moves through the evaporator, heat given up by the air passing through the evaporator causes the refrigerant to begin to boil. By the time the refrigerant has passed through the evaporator, it becomes a vapor. As the heat is absorbed by the boiling refrigerant, the fins and tubes turn cold and in turn cool the air passing over them. Moisture contained in the air condenses to water drops as it passes around the cooling tubes and fins of the evaporator. Water and dirt are then discharged outside the vehicle through the drain hose.
The evaporator is a laminated type and consists of thin, rectangular aluminum plates arranged in many layers and fins that are attached between them. The operation of the evaporator is as follows
Misty refrigerant (very close to liquid form) from the expansion valve at a low pressure, enters the lower tube of the evaporator, where it soaks up heat from the compartment. The refrigerant boils and vaporizes quickly due to the rapid heat exchange. Then the refrigerant is pushed upward by the force of the bubble generated during the exchange and passes evaporating into the upper tube. When it reaches to upper tank, the refrigerant is in a thoroughly vaporized form.
The evaporator has a single tank, and its surface has been given a multiple treatment.
Scheme 118
- Rustproof treatment
- Waterproof treatment
- Moldproof treatment (Scheme 118): Identifying Evaporator Mechanism Function
The expansion valve is attached to the evaporator inlet and outlet pipe. It converts high pressure liquid refrigerant which comes from the liquid tank to misty, low pressure refrigerant, and delivers to the evaporator. Being at low pressure and low temperature, the liquid refrigerant evaporates in the evaporator removing heat from the compartment. It automatically controls the flow rate of refrigerant to obtain the necessary cooling ability required by the fluctuating heat load.
The refrigerant temperature is sensed by the temperature sensing element installed at the low pressure refrigerant passage in the expansion valve, and the flow rate of the refrigerant is controlled by changing the lift of the valve ball at the high pressure side.
Identifying Expansion Valve Mechanism Components. Scheme 119
If the heat load of the air conditioner system increases, the refrigerant temperature at the evaporator outlet rises and therefore increases the pressure P 1 at around the temperature sensing area. As this pressure P 1 becomes higher than the resultant force of evaporator outlet (low pressure side) pressure P 2 and the spring force F (P 1 > P 2 + F), the diaphragm is pressed down, opening the valve ball connected to the diaphragm to increase the flow of the refrigerant.
If the heat load decreases, the action contrary to the one mentioned above takes place, closing the valve to decrease the flow of the refrigerant.
