With the popularity of the refrigerator industry, refrigerators appear in more and more residents' homes. The compressor is one of the main components of the refrigerator. It is called the heart of the refrigerator. If it fails, it will cause serious consequences, which will bring great inconvenience to users. Refrigerator compressors generally use a small fully closed reciprocating piston structure. When the refrigeration system of the refrigerator breaks down, it must be determined whether it is caused by the compressor. This article is about to introduce the fault diagnosis and repair method of the refrigerator compressor, as follows:

First, the fault judgment of the compressor

The fault of the refrigerator may be caused by the refrigeration system or the electrical system. When judging the fault of the compressor, it is necessary to first confirm whether the electrical system is working normally. There are two main aspects: one is to check whether the power plug and the power switch are in good contact, whether the fuse is blown and disconnected, whether the power wiring is correct and disconnected, and whether the power supply voltage is too high or too low; the second is to check the placement of the thermostat. Whether the orientation is correct, whether the working value in the temperature sensor leaks, whether the temperature adjustment is suitable, whether the induction action fails, etc.

1. Motor winding fault

The compressor shell has three terminals, namely C (common end), S (starting end), M (working end), and the starting winding (S-C) and the working winding (M-C) are connected inside, and the starting winding and the working winding have one end each. Connect them together to the common terminal C, and the other terminal is connected to the S and M terminals respectively. The motor winding fault is generally judged by the resistance measurement method, and it should be judged that the power supply, the generator (PTC or gravity type) or the thermal protector are normal. carried out later.

(1) The winding is open. Use a multimeter to measure the resistance value between the three terminals. If the resistance value appears infinite at one time, it means that the winding is open circuit when it is checked that the terminal is not loose, oxidized, or corroded to cause poor touch.

(2) The winding is short-circuited. The arrangement of the three terminals of various types of compressors in China and abroad is irregular, but there is a certain resistance value between each two terminals, and it is satisfactory: Rms= Rmc+Rsc and Rsm> Rsc> Rmc. Generally, the three resistance values ​​of Rms, Rsc and Rmc do not exceed 100Ω (for example, the RMS=84Ω of the British "GEC" compressor); the small ones are only rare ohms (such as the Rms=7Ω of the German PWTN18 compressor), use a multimeter to measure the three The resistance values ​​of the terminals are R1, R2, and R3 (it is not necessary to determine which of Rms, Rmc, and Rsc). If the three resistances cannot satisfy the above two relations, it means that the winding has a short-circuit fault (except for a small number of compressor windings) . It is worth noting that sometimes when the winding part is short-circuited, the measured R1, R2, and R3 will also satisfy the above two relations, because the multimeter can only measure the resistance change of the winding part short-circuit. However, when the winding is partially short-circuited, the current when energized is larger than the normal value.

(3) The winding is short-circuited or leaked to the ground (case). Use a megohmmeter to measure the insulation resistance between the terminal and the casing. If the resistance value tends to zero, it means that the working winding or the starting winding is short-circuited to the ground.

2. Work stuck fault

There are many manifestations of stuck faults, including stuck casings, stuck cylinders, shafts, and shaking shafts. The phenomenon is that the compressor does not run after the power is turned on, the casing is hot and accompanied by a "hum" sound, and then the thermal relay (protector) acts with a "click" to cut off the power supply. When the power supply voltage, motor winding, and engine are normal, the motor does not roll, that is, the compressor and other work are stuck.

(1) The oil circuit is not smooth. The oil circuit of the compressor is blocked by dirt, the oil supply system is not dredged, and the parts are worn and stuck.

(2) The parts are rubbed against each other. The fixing bracket is deformed, the fixing screw is loose, the cooperation between the parts is too tight, the gap is too small, and they rub against each other during work.

(3) The rotor is skewed. After the paint on the winding enameled wire is corroded and peeled off, it sticks to the cylinder and piston, or the rotating shaft and the bearing sleeve are worn and loosened. After power-on, the rotor is magnetically attracted to one side and deviates from the center line, so that it cannot roll.

When a stuck fault occurs, generally the engine should be stopped first and then tried to start. If it still does not roll, you can try the percussion start method, the supercharged force start method, the capacitor start method, the pressure relief start method and the gas impulse start method to start.

3. Abnormal noise fault

When the compressor is working, there is a "dangdang" metal impact noise in the casing, and the working noise faults mostly occur in the cylinder, crankcase and shock absorption equipment.

(1) Shock absorption failure. After the shock-absorbing spring is cracked, dislocated or deformed, the shock-absorbing effect is lost, so that the body hits the inner wall of the casing to generate noise during operation.

(2) Knock the cylinder. The top of the piston and the exhaust valve collide, that is, the gap between the two is too small, and the phenomenon of "cylinder knocking" occurs.

(3) The valve plate is abnormal. The valve plate tightening screw or the nut on the piston connecting rod is loose, and the valve plate is cracked or severely worn due to poor raw materials and improper operation.

(4) The piston is damaged. Piston badly worn or stuck. Note: Refrigerator compressors generally do not have piston rings.

(5) The connecting rod is faulty. The connecting rod nut is loose, and the gap between the big end of the connecting rod and the crank or between the crank and the main bearing is too large.

(6) The bearing is dry and stuck. The amount of lubricating oil in the bearing is lacking, and impurities are mixed in the oil.

(7) The flywheel is loose. The cooperation between the flywheel and the bearing is loose.

(8) Hydraulic hammer (also known as cylinder flushing, cylinder knocking or wet stroke). The main reason is that the suction valve is opened too large and too fast, resulting in a sharp and strong suction, which causes the refrigerant liquid in the evaporator to be sucked into the compressor without evaporation, resulting in liquid hammer noise. Hydraulic hammer damage is very big, in addition to the noise, it may also break the suction and exhaust valves, and in the worst case, the connecting rod, piston, crankshaft will be distorted and deformed, and even the cylinder head will be cracked. The main reasons for liquid shock caused by non-compressors are: too much refrigerant charge, too thick frosting in the evaporator, too much internal oil accumulation, too small transpiration area or too large cooling capacity, etc.

4. Exhaust failure

(1) The exhaust pressure is too high. One is that the heat transfer tube of the condenser is severely fouled, which leads to a decrease in conduction power; the other is that the system is overfilled with refrigerant; the third is that the system is mixed with non-condensable gas.

(2) The exhaust pressure is low. After the refrigerant leakage, capillary and filter blockage are removed, the exhaust system is faulty, which is manifested as the condenser is not hot or slightly hot, there is a slight airflow sound in the compressor, and the compressor works for a long time and the refrigeration effect is not good. Reasons: First, the high-pressure exhaust pipe is cracked or the sealing gasket is broken down, so that the refrigerant is shunted to form an internal circulation, and the airflow sound is generated, which makes the refrigeration effect worse; The fouling is not closed tightly; the third is that the gap between the compressor piston and the cylinder is too large due to wear and tear, so that the compressor displacement is insufficient; the fourth is the lack of refrigerant; the fifth is the condenser condensation speed is too fast.

2. Repair of the compressor

For the compressor that is judged to be faulty, it is necessary to open the casing for repair, remove the compressor from the refrigerator, pour out the oil, and check the oil quantity (depending on the type, the compressor oil quantity is generally 250-350ml), color (whether it has changed, Opaque, blackening), odor (with or without burnt odor), etc., to analyze the overheating or wear of the compressor. Depending on the shape of the compressor shell, the shell can be opened by machine tool (circular socket), gas welding (flanging butt weld), hacksaw sawing (oval socket), etc. Use a sander to grind the seal and open the shell.

1. Disassembly and assembly of the shock-absorbing spring

After opening the compressor casing, first unplug the compressor inner lead plug from the socket, and then loosen the high-pressure output pipe screw and clip, and the body can be removed from the shock-absorbing spring. Generally, the compressor has two sets of upper and lower shock-absorbing springs: there are three upper suspension springs, which are evenly distributed at 120°. When disassembling, use needle-nose pliers to rotate counterclockwise, and use concave screwdriver to rotate clockwise when installing; There are four lower seat springs, and the body can be taken out directly from the housing. If the tension spring is found to be deformed or cracked, it should be replaced. When reassembling, make sure that the suspension spring and the seat spring are fundamentally level. The dismantled parts are cleaned with gasoline, coated with anti-rust oil, and covered with dust.

2. Troubleshooting of stuck

After fully immersing the body in diesel oil (usually 24 hours), turn the motor rotor by hand. If the shaft and the frame are found to be loose, check whether the fixing screws of the bracket are loose and whether the bearings are worn. Then remove the connecting rod and crankshaft fixing bolts to separate the connecting rod from the crankshaft (connecting rod type compressor); or remove the cylinder, slide pipe and slider (sliding tube type compressor). Check the piston and cylinder, if there is any scratch, you can carefully grind off the burr, and clean the attached dirt. Then check the cooperation gap between the cylinder and the piston. The operation method is: insert the piston into the cylinder after coating the refrigerated oil, block the end face of the cylinder with one palm, and pull the piston with the other hand. After the pulling piston is opened, if the piston is sucked into the cylinder, it means that the cooperation gap between the two is basically appropriate. ·When assembling, it should be noted that the end face of the piston cannot touch the low pressure valve plate.