For each bearing, it has its own limit speed, and the speed plays a key role in the bearing heating factor. If the speed of a bearing exceeds the limit speed, it will cause the bearing temperature to rise, the lubricant will dry, or even Stuck the bearing. Therefore, we are rotating the appropriate bearing type according to the speed of the bearing, then we need to understand what are the requirements for selecting the bearing under the speed
The rotation speed of the bearing is mainly limited by the temperature rise caused by the internal frictional heat of the bearing. When the rotation speed exceeds a certain limit, the bearing will not continue to rotate due to burns, etc.
Requirements for selecting bearings according to speed:
1. Ball bearings have a higher limit speed and rotation accuracy than roller bearings, so ball bearings should be preferred at high speeds.
2. Under the condition of the same inner diameter, the smaller the outer diameter, the smaller the rolling element, and the smaller the centrifugal inertial force of the rolling element on the outer raceway during operation, so it is suitable for working at higher speed . Therefore, at high speeds, bearings with smaller outer diameters in the same diameter series should be used. If a bearing with a smaller outer diameter is used and the load carrying capacity does not meet the requirements, the same bearing can be installed in parallel, or a wide series of bearings can be considered.
3. The material and structure of the cage have a great influence on the bearing speed. The solid cage allows a higher rotation speed than the stamping cage, and the bronze solid cage allows a higher rotation speed.
Generally speaking, deep groove ball bearings, angular contact bearings, and cylindrical roller bearings should be used in higher speed working occasions; tapered roller bearings can be used in lower speed working situations. The limit speed of tapered roller bearings is generally about 65% of deep groove ball bearings, 70% of cylindrical roller bearings, and 60% of angular contact ball bearings. Thrust ball bearings have a low limit speed and can only be used in lower speed applications.
Note: Depending on the type and brand of lubricant. Some lubricants may have good performance but are not suitable for high-speed rotation. Therefore, if the bearing speed exceeds 80% of the limit speed stated in the dimension table, please contact the bearing manufacturer.
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Bearing speed limit:
The limit speed of the bearing refers to the limit value of the speed at which the frictional heat does not cause burns and can rotate continuously. Therefore, the limit speed of the bearing depends on various factors such as the shaft type, size, tolerance, lubrication method, quality and quantity of lubricant, cage material and type, and load conditions.
The limit speeds of various types of bearings for grease lubrication and oil lubrication (oil bath lubrication) are shown in each bearing size table. Speed limit.
Experience has shown that even if the bearings are operated under the most favorable load and friction conditions, the cost required to maintain stable working conditions for a certain period of time due to technical reasons or too high should not exceed the maximum speed.
The limit speeds listed in the product list apply to the basic bearing design. In the case where the limit speed is higher than the reference speed, the operating temperature may be significantly higher than the reference value. Under these conditions, appropriate measurements may be required (retainers, seals, pre-tightening, and whether the lubricant can withstand high temperatures). If these measurements are not sufficient, you need to verify the internal clearance of the bearing and the accuracy of the bearing seat and the journal, and make appropriate adjustments to meet more demanding working conditions.
In addition, it must be considered whether the materials in the bearing system meet the requirements of bearing operating temperature and required service life. When the stable operating temperature is higher than the maximum temperature recommended for the bearing material stability series (for example, for SN series, the recommended high temperature is 120 ° C), a bearing with a higher stability level may be required to maintain the installation stress and the bearing interior Play.
For grease, other factors should also be considered, such as the lubrication conditions of the guide surface of the cage and the consistency of the grease at the operating temperature.
The friction of some open ball bearings is very low, and the reference speed listed in the product table may be higher than the limit speed. Therefore, it is necessary to calculate the adjusted reference speed and compare it with the limit speed, and then take the lower value between the two. In some special cases, for example, for some cylindrical roller bearings, if other cages are selected, the bearings can be operated above the standard limit speeds listed in the table.
If the bearing needs to run at a speed higher than the limit speed in the product list, it is necessary to improve some factors that limit the speed. If you want to modify the bearing, lubrication system or application. The modifications may include improving the bearing rotation accuracy; changing the cage material and structure, lubrication conditions, and heat dissipation methods.
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