Discussion on the relationship between motor bearing load and limiting speed

1. Basic functions and types of motor bearings
The main function of motor bearings is to support the rotating shaft, reduce friction resistance, and ensure rotation accuracy and stability. According to the different structures and working principles, motor bearings can be divided into two categories: rolling bearings and sliding bearings. Among them, rolling bearings are widely used in motors due to their high efficiency, low friction, and easy maintenance. The rolling bearing contains rolling elements (such as steel balls, rollers), inner rings, outer rings, and cages. The load is transmitted through the rolling of the rolling elements to achieve the rotation of the shaft.

2. The influence of load on internal friction and wear of motor bearings
During the working process, motor bearings need to withstand radial loads, axial loads, or combined loads from the motor rotor. The size of the load directly affects the stress distribution inside the bearing, the contact pressure between the rolling element and the raceway, and the lubrication state. When the load increases, the contact area between the rolling element and the raceway decreases, the contact pressure increases, resulting in local temperature increases, thinning or even rupture of the lubricating film, thereby exacerbating friction and wear.

The increase in friction not only consumes additional energy and reduces the efficiency of the motor, but also generates heat, further accelerating the fatigue damage of the bearing material. Wear directly leads to an increase in bearing clearance, affecting rotation accuracy and stability. In severe cases, it may even cause vibration and noise, shortening the service life of the bearing.

3. Relationship between load and limit speed
The limit speed refers to the maximum speed at which the bearing can work stably for a long time under specific conditions. It is affected by many factors such as bearing type, material, lubrication method, load size and environmental conditions. Under the condition that other conditions remain unchanged, the greater the load, the more serious the friction and wear inside the bearing, the worse the lubrication effect, and the increased heat generated by the bearing. These factors work together to make the temperature of the bearing higher when it reaches thermal equilibrium, the material performance decreases, and the limit speed decreases accordingly.

Specifically, high load will cause the contact stress between the rolling element and the raceway to exceed the allowable stress of the material, accelerating material fatigue damage; at the same time, poor lubrication will aggravate dry friction, generate a lot of heat, increase the bearing temperature, and make the grease or lubricating oil fail, further limiting the high-speed operation ability of the bearing.

4. Optimization measures and application suggestions
In order to improve the limit speed of motor bearings under heavy loads, the following measures can be taken:

Select high-performance bearing materials: such as ceramic rolling elements, because of their low density, high hardness and good wear resistance, they can effectively reduce the friction coefficient and increase the limit speed.
Optimize the lubrication system: Use appropriate lubricants to ensure good lubrication and reduce friction and wear. For high-speed and heavy-load applications, consider using oil mist lubrication or oil-gas lubrication.
Accurate calculation and selection: According to the load characteristics in the actual application, accurately calculate the required bearing type and size to avoid overload.
Enhance cooling and heat dissipation: By designing an effective cooling system, timely remove the heat generated by the bearing and maintain a suitable operating temperature.
Regular inspection and maintenance: Regularly inspect the bearings to promptly detect and deal with wear, looseness and other problems to extend the service life of the bearings.