Compressor HVAC: Description and Operation
DKS-17CH Type CompressorDESCRIPTION AND OPERATION
The compressor performs two main functions:
It compresses low-pressure and low-temperature refrigerant vapor from the evaporator into high pressure and high-temperature refrigerant vapor to the condenser. And it pumps refrigerant and refrigerant oil through the air conditioning system.
This vehicle is equipped with swash plate type compressor (DKS-17CH: L4 Engine) or vane rotary type compressor (DKV-14D: V6 Engine).
The oil used in the HFC-134a system compressor differs from that used in R-12 systems.
Also, compressor oil to be used varies according to the compressor model. Be sure to avoid mixing two or more different types of oil.
If the wrong oil is used, lubrication will be poor and the compressor will seize or malfunction.
When servicing the compressor, keep dirt or foreign material from getting on or into the compressor parts and system. Clean tools and a clean work area are important for proper service. The compressor connections and the outside of the compressor should be cleaned before any "On-Vehicle" repair, or before removal of the compressor. The parts must be kept clean at all times and any parts to be reassembled should be cleaned with Trichloroethane, naphtha, kerosene, or equivalent solvent, and dried with dry air. Use only lint free cloths to wipe parts.
The operations described below are based on bench overhaul with compressor removed from the vehicle, except as noted. They have been prepared in order of accessibility of the components. When the compressor is removed from the vehicle for servicing, the oil remaining in the compressor should be discarded and new compressor oil added to the compressor.
Compressor malfunction will appear in one of four ways: noise, seizure, leakage or low discharge pressure. Resonant compressor noises are not cause for alarm; however, irregular noise or rattles may indicate broken parts or excessive clearances due to wear. To check seizure, de-energize the magnetic clutch and check to see if the drive plate can be rotated. If rotation is impossible, the compressor is seized. Low discharge pressure may be due to a faulty internal seal of the compressor, or a restriction in the compressor. Low discharge pressure may also be due to an insufficient refrigerant charge or a restriction elsewhere in the system. These possibilities should be checked prior to servicing the compressor. If the compressor is inoperative, but is not seized, check to see if current is being supplied to the magnetic clutch coil terminals.
The compressor oil used in the HFC-134a system compressor differs from that used in R-12 systems. Also, compressor oil to be used varies according to the compressor model. Be sure to avoid mixing two or more different types of oil.
If the wrong oil is used, lubrication will be poor and the compressor will seize or malfunction.
Swash plate compressors have a swash (slanted) plate mounted on the shaft. When the shaft turns, the rotation of the swash plate is converted to reciprocating piston motion which sucks in and compresses the refrigerant gas.
Shaft seal (Lip type) is installed between the valve plate and shaft & cylinder head to prevent refrigerant gas leaks. A specified amount of compressor oil is contained in the oil pan.
This oil is supplied to the cylinders, bearings, etc., by an oil pump which is connected to the swash plate shaft.
With some compressors the differential between the intake pressure and discharge pressure generated while the compressor is operating is used for lubrication instead of an oil pump.
Three pistons are arranged at 120° intervals around the center of the swash plate shaft. These pistons are connected to the ends of the swash plate through shoe disks and balls.
The rotation of the swash plate causes reciprocating movement of the piston inside the cylinders, with each piston operating as two cylinders. Because of that, the compressor operates as through it has 6 cylinders.