Analysis of Bearings in Mine Truck Application

In recent years, under the background of tight international energy supply, China has increased investment in new energy fields represented by wind energy, which has gradually increased the output of new energy. However, for a long time, China’s coal-based energy sources The structure will continue. Compared with underground coal mining, open-pit coal mining has high productivity, low accident rate, and easy equipment maintenance and other objective advantages. Whether at home or internationally, vigorous development of open pit mining is a major trend. Mine trucks, one of the important equipment necessary for open pit mining, will also have a bright future with the development of open pit mines.

The tapered roller bearings produced by TIMKEN Bearings have decades of application history in mining trucks and have accumulated considerable application experience. This article will briefly analyze the problems that should be paid attention to when using tapered roller bearings for mining trucks. It is hoped that it will help the majority of mine truck designers and users to better select and use bearings and improve the reliability of mining trucks.

In addition to the factors of system design matching and installation adjustment, there are three main factors that determine the performance of tapered roller bearings: 1) the material of the bearing 2) the roughness of the bearing raceway 3) the surface modification of the bearing raceway . Next, a detailed analysis of the factors that should be considered in these three aspects of bearing selection during mine truck conditions.

First, the material of the bearing

Two considerations are taken into account when considering the material of the bearing: the purity of the steel and the heat treatment process of the steel.

The time it takes for the bearing to run is its fatigue life. The occurrence of spalling is mainly due to the presence of non-metallic inclusions inside the bearing steel. When the bearing is working, non-metallic inclusions will cause stress concentration inside the steel, resulting in weak points. As the bearing runs day after day, these weak points gradually develop into fine cracks, which eventually cause the surface of the raceway to peel off. Therefore, the purity of the steel is critical to the bearing. The smaller the particle size of the inclusions inside the steel, the smaller the number of particles, the smaller the probability of crack occurrence and the higher the fatigue life of the bearing.

With the development of modern smelting technology, the bearing manufacturers of world-class brands have reached a very high level in the purity of bearing steel. In addition to bearing materials that meet ISO and ABMA standards, they also use materials that are cleaner than pure steel to improve the reliability of bearings under high loads. With the hub bearing application in a mining truck, the bearing carries a very high force. Taking the load of 200 tons as an example, the whole vehicle is about 350 tons after full load, and the force of the one-side rear wheel hub bearing reaches about 120 tons. Therefore, if a standard material bearing is selected, its size will be very large. In order to minimize the size of the hub and make the design more compact, bearings with high purity precision materials are often used in this position. Even so, the inner diameter of the bearing is about 500mm.

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The importance of bearing grease stability

Proper use of bearing grease requires knowledge of the movement of the grease in the bearing. Guarantee the stability of the grease. The movement of the grease filled in the rolling bearing can be roughly divided into two stages as the SKF bearing rotates.

By the way, by the way, when lubricating the bearing, pay attention to the amount of grease. For details, please refer to the article "Introduction of the amount of grease used in lubrication of SKF bearings".

In general, the amount of grease in the SKF bearing always exceeds the actual amount of lubrication directly involved in the lubrication, on the frame and in the cavity of the bearing cover, and forms a contour on the periphery of the rolling element. In this process, the bearing temperature rises rapidly due to the resistance of excess grease. Although most of the excess grease is squeezed out at the beginning of the run, the grease that is squeezed into the raceway attachment may still be carried by the rolling element into the raceway. In the initial stage of the bearing crucible, most of the grease is squeezed out of the raceway very quickly (less than one minute), and the accumulated grease is discharged a small amount while circulating along with the bearing rotating body. At this time, the bearing temperature continues to rise until the excess bearing grease is completely discharged, which can be called the walking phase of the grease. According to the grease quality and filling amount in the bearing structure, this time may last for more than ten. Minutes, even hours.

After the remaining bearing grease is completely discharged, the remaining small amount of grease forms a thin layer of grease film on the mutual contact surface of the rolling element, the raceway and the cage, thereby entering the normal bearing of the bearing. stage. At this time, the temperature gradually drops and reaches equilibrium. In other words, long-term lubrication is mainly borne by this layer of grease film. In addition, during the long-term operation of the bearing, the contour of the rolling element and the raceway and the grease on the cage are shrunk to separate a part of the base oil, and after flowing into the raceway, the lubrication is also supplemented. .

Different bearing greases are not the same in the contours of the bearings. It is necessary to form a contour that is relatively straightforward. The running time is short. In the long-term operation, the bearing temperature is low and stable. This is an ideal one. Grease is especially important for grease channeling.

Some so-called eddy-flow greases are not easy to form contours, and even if they are contoured, they are easy to collapse. At this time, the excess grease repeatedly returned to the raceway is in a state of being strongly stirred for a long time, and the bearing torque is large and the temperature is high. Unbalanced, noise may also be generated, and grease is also prone to deterioration and loss.

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