When purchasing rolling bearings, do you doubt that the higher the bearing speed, the better the performance? The faster, the more expensive? Is that really the case? We will provide a detailed explanation of the bearing speed and the factors that affect it in the following content:
For each bearing, it has its own limit speed, which is mainly limited by the temperature rise caused by friction heating inside the bearing. When the speed exceeds a certain limit, the bearing will be burned and unable to continue rotating, or even get stuck in the bearing. Therefore, we are rotating the appropriate bearing type based on the rotational speed of the bearing, so we need to choose the requirements of the bearing. In some applications, other factors are more important than the limit speed. Such as low speed, reciprocating oscillation, etc.
The maximum speed of a bearing refers to the boundary value of friction heating and continuous rotation that does not cause burns. Therefore, the maximum speed of a bearing depends on factors such as the type, size, and accuracy of the bearing, lubrication method, quality and quantity of lubricant, material and type of cage, and load conditions.
The maximum speed provided by the bearing manufacturer generally refers to the highest speed that can be achieved under the agreed conditions, such as a bearing tolerance of 0; The bearing clearance is 0 groups; The bearing load is 10% of the rated load; Lubrication and cooling conditions are normal; Radial bearings only bear radial loads, while thrust bearings only bear axial loads; The outer ring temperature shall not exceed 100 ℃.
The speed range required for the usage scenario helps determine what type of bearing to use. Most bearing manufacturers' product catalogs provide the maximum speed values of their products. Practice has proven that it operates below 90% of the maximum speed limit.
1. Select bearing category based on rotational speed
a. The maximum speed and rotational accuracy of ball bearings are higher than those of roller bearings, so ball bearings should prioritize high speed.
b. In the case of the same inner diameter, the smaller the outer diameter, the smaller the rolling element, and the smaller the centrifugal inertia force exerted by the rolling element on the foreign raceway, which is suitable for high-speed operation. Therefore, on highways, bearings with smaller outer diameters in the same diameter series should be selected. If bearings with smaller outer diameters cannot meet the required load-bearing capacity, the same bearings can be installed or wide series bearings can be considered.
c. The material and structure of the cage have a significant impact on the bearing speed.
The allowable rotational speed of the solid cage is higher than that of the stamped cage, and the allowable rotational speed of the bronze solid cage is even higher.
Deep groove ball bearings, ball bearings, motor bearings, automotive bearings, electric tool bearings, angular contact ball bearings;
Rolling bearings can be used in low-speed working environments.
Factors affecting bearing speed
The factors that affect the maximum speed of bearings include the magnitude of external loads, stress direction, type and quantity of lubricants, manufacturing accuracy of bearings, bearing tolerance level, and bearing clearance.
In addition, lubricants may have better performance than others, but are not suitable for high-speed rotation.
The factors affecting the maximum speed of bearings are related to the type, load, accuracy, size, lubrication, clearance, cage, and cooling conditions of the bearings. However, the most important factor is the allowable working temperature or lubricant of the bearing material.
A typical high-speed bearing refers to a bearing with a speed of up to 60 meters per second. The high speed, medium speed, and low speed of bearings are not determined by rotational speed but by linear velocity. A small bearing that rotates tens of thousands of revolutions per minute is not considered a high-speed bearing, while a large bearing that rotates hundreds of revolutions per minute is considered a high-speed bearing. In sliding bearings, liquid static pressure bearings, liquid dynamic pressure bearings, gas static pressure bearings, and gas dynamic pressure bearings are all suitable for high-speed rotation.
High speed bearings and ordinary bearings: installation fit and adjustment of high-speed bearings
1. When considering the fit and clearance of high-speed bearings, the following two points should be taken into account:
(1) The changes in size and hardness when rising from room temperature to high temperature;
(2) The changes in force system and shape caused by centrifugal force at high speeds.
In short, it is difficult to maintain the accuracy and performance of bearings in terms of fit and clearance selection under high-speed and high-temperature conditions.
In order to ensure that the deformation of the raceway after bearing installation is small and the interference fit of the ball bearing is not too large, the centrifugal force at high speed and the thermal expansion at high temperature, or the normal pressure on the mating surface, can be offset. Or it may cause the mating surface to loosen, so the interference fit must be carefully calculated while considering the above two factors. Effective interference fit at room temperature and speed may be ineffective for high-speed bearings.
If the contradiction in the calculation result is too great (usually only at ultra-high speeds), only a dual lubrication measure of using both under ring lubrication and static pressure lubrication can be adopted, which may make the DMN value of the bearing exceed the 3 million mark.
Thermal expansion at high temperatures, or offsetting the normal pressure on the mating surface. Or it may cause the mating surface to loosen, so the interference fit must be carefully calculated while considering the above two factors. Effective interference fit at room temperature and speed may be ineffective for high-speed bearings.
When considering the clearance of high-speed bearings, not only the above factors should be taken into account, but also the influence of shaft thermal elongation on clearance. It is required that the bearing has the best clearance under working conditions, that is, at working temperature, and this clearance is formed in a state of precise alignment of the center of the inner and outer ring ball grooves. Due to the efforts of high-speed bearings to reduce relative sliding and internal friction, it is best not to adjust the clearance of ball bearings by using the method of axial relative displacement of the inner and outer rings.
When considering the fit interference and clearance of bearings, attention should be paid to the characteristics of materials becoming soft and easily deformed at high temperatures, as well as the possibility of permanent deformation caused by multiple temperature changes from room temperature to high temperature.
2. Requirements for host related components
High speed bearings require precise dynamic balancing of the rotating system where the bearings are located. The parts where the bearings are installed on the shaft and seat hole should have dimensional and positional accuracy higher than the general requirements, especially the coaxiality and perpendicularity of the shoulder to the seat hole or shaft neck. When considering these issues, attention must also be paid to the high-speed and high-temperature factors during bearing operation.
The shaft support system requires both high rigidity and minimal weight. To overcome this contradiction, measures such as reducing surface roughness and improving surface strengthening can be taken to increase support stiffness, and hollow shafts can be used to reduce system weight.

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