Abstract: According to the working principle and working conditions of scroll compressor for automobile air conditioner, the structure of sealed deep groove ball bearing for scroll compressor is designed to make the performance of sealed deep groove ball bearing meet the operating requirements of compressor.
Keywords: sealed bearing; Deep groove ball bearing; Automobile bearing; Structure; Design
At present, the advanced automotive air conditioner compressor is a scroll compressor, which is the core component of the air conditioner. Sealed deep groove ball bearing is one of the main supporting bearing products. The dynamic characteristics of vehicle operation and changeable external environment make the working environment of air conditioner compressor very bad. This puts forward high requirements for sealed deep groove ball bearings, which not only have good life reliability and sealing performance, but also have low vibration, low friction, low noise and high temperature resistance.
1. Structural design of low vibration and low noise deep groove ball bearing
The reasons affecting bearing vibration and noise are relatively complex: ① The influence of design parameters and structures, such as the number of steel balls, ring structure, clearance, cage structure, seal structure and form, etc. ② The influence of manufacturing error of bearing parts includes dimensional tolerance, geometric tolerance and surface quality of parts. The domestic and foreign test research shows that the steel ball has the greatest influence on the bearing vibration and noise, followed by the inner and outer rings. The main influencing factors are roundness, waviness, surface roughness, surface bumps and cleanliness. In addition, lubricating grease and installation accuracy will also affect vibration and noise.
1.1 Selection of steel ball
The quality of steel ball has the greatest influence on bearing vibration and noise. The surface quality of steel ball, such as spherical deviation, waviness and roughness, is the primary factor affecting vibration and noise. Therefore, G10 steel balls with high accuracy, low vibration and good spherical deviation, waviness and roughness should be selected.
1.2 Selection of precision, clearance and main parameters
The accuracy, main parameters and clearance of bearing have great influence on the vibration and noise of bearing, so the reasonable selection of the accuracy, main parameters and clearance of bearing is the most basic condition to ensure low vibration and noise of bearing. The spindle accuracy of the air conditioner compressor is required to be high, so the bearing accuracy, especially the rotation accuracy, will directly affect the vibration and noise of the compressor spindle. The bearing accuracy shall be higher than P5. Clearance is another important technical parameter of bearing design, which affects the load distribution, vibration, noise, friction and life of bearings. The bearing is interference fit, especially when the scroll compressor works normally, the temperature is high (up to 120 ℃), which reduces the clearance. In order to prevent the bearing from being stuck, large C3 group clearance shall be selected during design. At the same time, a reasonable ball filling angle is used to make the bearing assembly easier, and a transition chamfer is added at the junction of the ring groove and the rib to reduce the scratch on the surface of the inner and outer rings and the steel ball when the bearing is sleeved.
1.3 Selection of radius of curvature of inner and outer ring grooves
The unequal curvature design of the inner and outer ring grooves can maximize the inner and outer rings. The contact stress is basically the same. The reduction of the curvature radius coefficient f i of the inner ring groove can increase the tightness of the bearing, reduce the stress and extend the service life. At the same time, properly increasing the groove curvature radius coefficient fe of the outer ring can reduce the friction torque, help to form the lubricating oil film, improve the dynamic performance, increase the limit speed, reduce the vibration and noise of the bearing, and extend the service life of the bearing. In order to control the bearing clearance more effectively, the tolerance is symmetrically distributed, and the groove curvature radius tolerance is compressed (the tolerance is ± 0.01 mm in design). Since the curvature radius coefficients f i ≈ 0.53 for the inner ring groove and f e ≈ 0.55 for the outer ring groove in the design are beyond the range of f i=0.515 and f e=0.525, the load coefficient Fe in the rated dynamic load will be affected.
The calculation results show that the load factor Fc is reduced by about 20%. Considering that the deep groove ball bearing is mainly used as an auxiliary support, although the rated dynamic load is reduced by about 20%, the load capacity can still meet the operating requirements, and will not affect its performance.
1.4 Design of plastic cage
Compared with the pressed steel plate cage, the plastic cage not only vibrates. The utility model has the advantages of small movement, low noise, long service life, good elasticity, good self lubrication, light weight, etc; At the same time, it is not easy to wear in case of poor lubrication, which will not degrade the lubricating grease, thus prolonging the burn resistance life of the bearing. Suitable for automobile air conditioner compressor bearing. However, because compressor bearings are generally light series standard bearings with narrow width, the traditional design is open. After the plastic cage is used and the seal ring is added, the bearing sealing space is relatively small. In order to reduce the vibration and noise caused by the cage, the following measures are taken during the erection of the plastic cage: (1) The true round pocket is used to reduce the displacement of the steel ball in the cage pocket. (2) The size of the cage adopts one-way dimensional tolerance, the inner diameter adopts one-way plus tolerance, and the outer diameter adopts one-way minus tolerance to control the cage width and avoid the friction with the inner and outer rings caused by the movement inside the bearing, resulting in noise, etc. (3) Improve the precision of plastic cage.
2 Sealing structure
The sealing performance of the bearing is one of the important indicators to measure the sealed bearing, and the reliability of the seal is the premise for the sealed bearing to achieve a long life. The early damage of sealed bearings is often caused by poor bearing sealing, pollutants entering the bearings and gradual failure of lubricating grease. The air conditioner bearing is a small bearing, and its sealing groove has a narrow seam width. When the assembly pressure is high, the sealing groove will crack. During assembly, the sealing ring adopts the positioning and matching method of axial positioning and lateral compression, which is characterized by small assembly pressure and easy assembly. The compression amount between the seal groove bottom of the bearing outer ring and the outer diameter of the seal ring shall be strictly controlled. The diameter tolerance of the seal groove bottom of the outer ring and the outer diameter tolerance of the seal ring shall be changed to symmetrical tolerance to avoid too much or too little compression to ensure the reliability of the seal.
The general structure that the inner ring of sealed deep groove ball bearing matches with the seal ring is that the inner ring does not have a seal groove, and its sealing effect is not as good as that of the inner ring with a seal groove. In order to make it have a good sealing effect, the sealing structure of inner ring with sealing groove is adopted in the design. Considering that the cage of the bearing is plastic and the internal space of the bearing is small, the double lip seal structure with arc groove on the inner ring is adopted. One sealing lip is a light contact seal and the other is a non-contact seal. Its characteristics are: ① The friction torque of light contact seal is small, the sealing lip is not easy to wear, and the sealing stability is good. ② The sealing space is small and will not collide with the cage. ③ The seal clearance is long. The sealing structure has good sealing effect.
3 Test verification
Take QK - 85 automobile air conditioner scroll compressor as an example, simulate the actual working condition according to the air conditioning industry standard JB/T6915 - 1993 "Test Method for Automotive Air Conditioning Refrigeration Compressors", carry out the durability test of scroll compressor at low speed, heavy load and high speed, light load. After 500 hours of operation at low speed, heavy load and high speed, light load respectively, no abnormal bearing conditions, bearing vibration, noise The performance of preventing medium leakage can meet the supporting requirements of the host.
More about SUNSPEED Deep Groove Ball Bearing:
Deep groove ball bearing is the most widely used type of bearing, with a wide range of applications. They have low friction and are optimized for low noise and low vibration to achieve high speeds. They can withstand radial and axial loads in both directions, are easy to install, and require less maintenance than other bearing types.
Features and benefits:
Low friction and operating temperature, low noise and vibration;
High operating speed;
The ability to provide high quality and performance for your applications;
Bearing radial load and axial load in two directions;
Various greases for most conditions, including food grade greases, high temperature greases and solid oils;
Improves reliability and provides longer bearing and lubricant life.