Properties of Typical Low Noise Sealed Bearing Greases
In the study, we selected several lubricating greases commonly used by domestic sealed bearing production companies, and tested the apparent viscosity, centrifugal oil separation and other general physical and chemical indicators respectively, and then used the speed type BVT-IA bearing vibration measuring instrument, BANT Bearing abnormal sound analyzer and acceleration type 50910-1 bearing vibration measuring instrument for analysis (we selected several data from the National Testing Laboratory of Hangzhou Bearing Test and Research Center aided by the United Nations (CNALNO.L0309) and Yanhua Group Tianjin Lubricating Grease Co., Ltd The data obtained from the master’s thesis research project jointly cooperated by the company. For several foreign products, the final data of the same test standard may appear to be different from the original index of the product manufacturing company. At this time, our test data is for whom)
1. Physical and chemical indicators
Its commonly used physical and chemical indicators are shown in Table 1 and Table 2o
2. Rheology and colloidal properties
Use dynamic centrifugal oil separator testing machine, apparent viscosity testing machine, flow pressure tester and electronic scanning microscope to test and analyze the selected grease, and calibrate the rheological properties of grease from numerous grease noise test studies. Colloid stability.
The following test conditions have an important impact on the vibration performance of the bearing. They are 60 ℃, x500rl/nin centrifugal oil separation, 20 ℃, shear rate = 10000 times s-1, apparent viscosity, 20 ℃ flow pressure, 40 ℃ See Table 3 for the specific data of grease base oil viscosity, etc. It can be seen from the data in Table 3 that:
(l) Under the same consistency, high-temperature lubricating greases, no matter compound keloid-based or polyurea-type high-temperature lubricating greases, their thickener crystals have higher hardness, strong binding ability to base oil, and less dynamic centrifugal oil separation. Low. However, the dynamic colloidal performance of the thickener fiber is relatively soft, and the dynamic colloidal properties of the carton-based grease can be adjusted in a larger range through different processes. The influence of the difference of the thickener on the dynamic oil separation is directly reflected in the change of the vibration performance of the related bearing.
(2) The apparent viscosity of lubricating grease has a strong correlation with the base oil. The higher the viscosity of the base oil, the greater the apparent viscosity. Under the same base oil viscosity, the similar viscosity of composite file or poly grease is much higher than that of file base grease.
(3) The flow pressure of lubricating grease also belongs to the category of rheological behavior. It is listed here to comprehensively analyze the relationship between the rheology of lubricating grease and the vibration performance of bearings in combination with the similar viscosity of lubricating grease. From the above data it was found that similar viscosities of greases have no correlation with flow pressure.
(4) Grease base oil viscosity is listed in this table as a factor in the overall analysis. There is a strong correlation between the base oil viscosity and apparent viscosity and dynamic oil separation performance of grease, but it is definitely not a one-to-one correspondence.
Noise Analysis of Typical Low Noise Sealed Bearing Grease
1. Test instrument
Measuring instruments include BVT series (velocity type) bearing vibration measuring instrument, BANT series bearing abnormal noise measuring instrument and acceleration type bearing vibration measuring instrument.
Aiming at the typical low-noise lubricating greases mentioned above, the acceleration type bearing vibrometer was used to analyze the vibration and noise. In the test, for the comprehensiveness and pertinence of the results, miniature bearings (608), small bearings (6201, 6204) and medium bearings (6308) were tested separately. In the selection of bearing grades, the grades of bearings are deliberately selected, and strive to cover bearings with different surface processing quality levels
2. Vibration and noise performance test of typical low-noise sealed bearing grease on 608 miniature bearings
l) The vibration reduction effect of various greases in the test bearing is not obvious, especially after the bearing has been running for a few minutes, the vibration value is almost unchanged. This is mainly because the area of the Hertzian contact area between the steel ball and the channel of the miniature bearing is small, the amount of grease required to form an oil film is low, and the small amount of oil separation and lubricant return can meet the needs of sufficient lubrication. In addition, the higher surface machining accuracy of micro-miniature bearings is also an important reason for the above results.
(2) In this type of bearing, the influence of grease on the vibration performance of the bearing is more prominent. The difference is manifested in the level of the start-up value. The high apparent viscosity and low dynamic oil separation of high-temperature grease make the oil supply in the contact area of the bearing short-lived at the beginning of starting. After a certain period of time, as the temperature rises, the grease in the boundary area The stability of the shear force makes the grease quickly enter the stable period in the dynamic space of the bearing, and the vibration value decreases.
(3) In the description of noise, the high-temperature bearing grease has much worse noise than the general-purpose bearing grease. This has nothing to do with the colloidal and rheological properties of the grease, it is mainly due to the thickener of the grease and the impurity content in it. Compared with medium-sized bearings, the noise of micro-sized bearings is more sensitive to the content of impurities and the particle size of thickener.
.3 Vibration and noise test of typical low-noise sealed bearing grease on 620, bearing
The vibration of grease in small bearings is basically the same as that in miniature bearings, but there are also differences. During the noise test, some lubricating greases will produce an indeterminate creaking sound, which is basically absent at the beginning, and becomes more apparent after 1-2 minutes. High temperature grease and grease with high base oil viscosity have a much higher chance of creaking noise, such as Mobil HP222 and Jinzhi low-noise grease, but bearings with high processing precision are not obvious to the type of grease, such as No. 1 and No. 2 grease. We understand this sound as the sound caused by the vibration of the cage caused by poor lubrication of the grease to the bearing. When the apparent viscosity of the grease is high, the flow and migration of the grease in several mutual moving elements becomes difficult. If there is not enough grease separation to alleviate this oil-poor phenomenon, the lubricating oil film between the cage and the rolling elements, the rolling elements and the raceways, the raceways and the cages will be extremely unstable, and the cage and the rolling elements will be extremely unstable. The increase of the friction torque between the cages will cause the vibration frequency of the cage to be unstable.
4 Vibration and noise performance test of bearing grease on 6204 small bearings.
In the 6204 bearing, it can be clearly seen that the apparent viscosity of the grease controls the change of the vibration value, and the dynamic oil separation of the grease has little influence on the vibration value. The synergistic SRL with lower base oil viscosity has smaller values at high frequency and intermediate frequency, and the grease with higher apparent viscosity has higher indication value besides the pointer fluttering. This phenomenon shows that the oil separation of the grease in the contact area has little effect on increasing the thickness of the oil film and maintaining a stable oil film. The main contradiction in controlling the lubrication stability of the lubricated bearing is that the resistance of the grease when it is sheared in the bearing is small. It is beneficial to the flow of lubricating grease between moving parts and improves the phenomenon of poor lubrication.
5. Test of typical low-noise sealed bearing grease on 6308 medium-sized bearings
(l) For medium and large sealed bearings, the dynamic oil separation and rheological properties of grease will have an important impact on reasonable lubrication. From the data in the table, it can be seen that the ideal bearing vibration performance cannot be obtained only by controlling the above two indicators.
(2) The increase of the inner diameter of the bearing will bring about the movement of the rolling elements and other components in the axial direction. Alleviating or damping this movement is as important as controlling the radial vibration. Here, the effect of the fiber structure of the thickener can be reflected. The dense and lubricating fiber can relieve the axial movement of the bearing to a certain extent, coupled with good dynamic oil separation and proper apparent viscosity of the grease in the shear zone, the grease with this performance is relatively low compared to other lubricants. In terms of grease, it has better vibration and noise performance.
Development of Lubricating Grease for Bearings
Due to the expansion of bearing applications and the advancement of bearing technology, high speed, long life, precision, low noise, and energy saving will become important directions for the development of bearing technology. The development of bearing technology will inevitably drive the development of grease, because in all Grease lubrication accounts for 80% of the bearings, such as grease for computer hard disk bearings. With the development of computer technology, especially the development of hard disk technology, the number of rotations and capacity of hard disks have greatly increased. Therefore, hard disk bearings have relatively high requirements for grease such as vibration damping, lubricity, oxidation stability, long life, low noise, and low rotational torque, which promotes the development and upgrading of grease. As we all know, bearings are used in a wide range of applications, from general environments such as automobiles, metallurgy, and machinery to special environments such as electronic components, liquid crystals, semiconductors, vacuum equipment, and chemical industries. Bearings are involved. Therefore, the lubricating grease that can adapt to these environments will be the kind that will be needed in the future.
(l) When the consistency of the grease and the viscosity of the base oil are the same, the dynamic centrifuge oil separation of the high-temperature grease, no matter the compound file type or the polysulfide type grease, is lower than that of the carton-based grease, and the similar viscosity is higher.
(2) There is a certain correlation between the fiber condition of the grease thickener and the apparent viscosity of the grease, but it is not a deterministic correspondence. Under the same conditions, increasing the fiber concentration of the thickener can significantly increase the apparent viscosity of the grease during flow and reduce its dynamic oil separation.
(3) In the low-noise miniature bearings, the vibration reduction effect of various greases in the test bearings is not obvious, and the high apparent viscosity and low dynamic oil separation make the bearings show high values at the beginning. In miniature bearings, the degree of influence of dynamic centrifuge oil separation is much more important than that of rheology.
(4) The poor oil phenomenon makes the high-temperature grease and the grease with high base oil viscosity have a much higher probability of creaking in small bearings. In small bearings, the key to the rationality of grease lubrication should be a reasonable combination of a certain range of dynamic oil separation and an appropriate matching apparent viscosity. In the 6204 bearing, it can be clearly seen that the apparent viscosity of the grease controls the change of the vibration value, and the dynamic oil separation of the grease has little influence on the vibration value.
(5) For medium and large sealed bearings, the fibers that are dense and lubricating can alleviate the axial movement of the bearing to a certain extent, coupled with good dynamic oil separation and proper apparent viscosity of the grease in the shear zone, The grease with this property has better vibration and noise performance than other greases.
(6) The analysis of grease vibration reduction, noise reduction and abnormal sound removal in this paper is still a preliminary result. Further analysis requires the combination of three-band BVT series speed-type bearing vibration measuring instrument and BANT series bearing abnormal sound measuring instrument for comprehensive analysis and research. This paper Due to space limitation, it is omitted.