Practical scheme for factory screening and inspect

Practical scheme for factory screening and inspection of refrigerator compressor

the compressor is the heart of the refrigerator. A large part of the faults of the refrigerator are compressor faults. Some serious faults will cause the refrigerator to lose its basic function or cause serious consequences. Common serious faults of compressor include: no starting, no exhaust (or small exhaust), poor electrical strength of insulation, abnormal noise, etc. At present, most manufacturers only test the static insulation electrical strength and simple power on start-up inspection of compressors before delivery, which can not completely eliminate the above serious fault products, and it is difficult to meet the quality requirements. This paper attempts to try a new screening method

1 improvement of the factory screening method of compressors that can directly test finished workpieces

the general factory full inspection method cannot reliably detect the following three faults of Compressors:

① small exhaust volume. The common practice is to judge based on the experience of quality inspectors, such as hand feeling, and cannot make quantitative judgment

② abnormal noise. Because the environmental noise at the production site is large, it affects the judgment of quality inspectors

③ poor electrical insulation under operation. When the motor winding warps or the winding touches the non live metal parts, because the stop position of the rotor and the contact condition of the contact point are random, the electrical insulation defects may not be exposed when the compressor core is stationary

in view of the above problems, we have improved the method of compressor factory screening and full inspection

the first is to quantitatively detect the amount of fracture that is more likely to occur in exhaust. The method is to start the compressor at a certain initial equilibrium pressure while starting at a low voltage, and connect a container with a certain volume at the exhaust side; Detect the exhaust pressure that can be reached within the specified time. Set corresponding limit standards for different types of products, and then conduct quantitative full inspection on the exhaust volume

the second is to more accurately identify the abnormal noise when the compressor is running. This requires that the interference of environmental noise on quality inspectors should be eliminated as far as possible by placing the testing process in the sound insulation room and taking silencing or sound insulation measures for the import and export of the production line in the sound insulation room. Practice has proved that as long as the environmental noise is below 43db, the abnormal operation noise of the compressor can be identified by human ears while detecting the exhaust volume

in addition, in order to find dynamic electrical insulation defects, the electrical insulation strength must be tested during the operation of the compressor. The method is to use the isolation transformer with secondary intermediate tap to provide the working voltage to the compressor. In the process of exhaust volume detection, the specified electrical insulation strength test voltage is applied between the secondary intermediate tap of the transformer and the compressor shell for voltage withstand test

2 implementation plan of improvement measures

the first consideration of the implementation plan is the construction, process layout and process flow of the sound insulation room. A section of the finished product packaging inspection line is isolated with a sound insulation room, and 2-3 inspection posts are set in the sound insulation room according to the matching needs of production pace and inspection speed. The sound insulation room is built with sound insulation materials, and the inner wall is covered with sound-absorbing materials. The inlet and outlet of the assembly line and the ventilation outlet of the sound insulation room shall be silenced as much as possible

in the circuit in Figure 2, the lines and components connected to the high voltage side of the withstand voltage test circuit must be well insulated to the ground to avoid false detection and misjudgment

see Figure 3 for the process flow rate of screening inspection. Figure 4 is a ladder diagram of the detection control circuit. (see Figure 3 and Figure 4)

3 discussion of two problems that may be encountered

3.1 the function of full screening is limited, and it is impossible to achieve the effect of laboratory performance testing after all. Exhaust volume measurement can be used as a simplified alternative test of refrigeration volume measurement, but the two cannot be completely equivalent; The human ear only qualitatively distinguishes abnormal noise, but it is unrealistic to reach the quantitative evaluation of noise level. In addition, the working condition of exhaust volume detection is also different from the standard noise test working condition. However, through screening and full inspection, serious defective products can be basically eliminated, which greatly reduces the offline rate of compressors in refrigerator manufacturers

3.2 for some compressor production lines with fast production tempo, a full inspection post on one production line can not meet the tempo requirements, which may be that 2-4 posts are normally required, which increases the labor cost to a certain extent. Therefore, it is suggested that the manufacturer should retain the original means of full factory inspection at the same time, according to the quality reliability of the compressor manufacturing process and the requirements of the user's offline rate, Flexibly decide whether to carry out the factory screening full inspection described in this article

4 summary

increasing the exhaust volume before the refrigerator compressor leaves the factory, the electrical insulation under the working state and the screening and full inspection of abnormal noise can greatly reduce the end of line rate and achieve ppm quality. This paper introduces the corresponding implementation scheme

reference

national standard gb4706.1 safety of household and similar electrical appliances - General requirements