MB split copper cage self-aligning roller bearing is a special bearing that combines self-aligning performance, copper cage characteristics, and split design. Its working principle achieves high load capacity, high stability, and long service life through structural innovation and material optimization. Here is a detailed analysis:
1. Core structure and components
1. Basic structure of self-aligning roller bearing
Outer ring: outer spherical design, allowing for an automatic self-aligning angle of 1 °~2.5 ° between the inner and outer rings, compensating for installation errors or shaft bending induced deflection, and avoiding edge stress concentration.
.Inner ring: Double raceway design, forming line contact with rollers, dispersing loads, and improving load-bearing capacity.
Roller: Symmetrical drum shaped roller, with edge trimming design (rounded transition) at both ends to reduce stress concentration and prevent friction damage between the roller end and the raceway edge.
.Retainer: Made of copper alloy material (such as H62 brass or QSn6.5-0.1 tin bronze), it has high strength, good thermal conductivity, and wear resistance, which can effectively guide the rollers to be evenly distributed and reduce sliding friction.
.2. MB Split Design Features
Outer Ring Split Structure: The outer ring is connected by two symmetrical parts through bolts or snap rings. During installation, there is no need to disassemble the shaft or adjacent components. The outer ring is directly inserted into the shaft and closed for fixation, simplifying the assembly process.
.Copper cage: The cage is formed by integral stamping process, and the surface is polished to reduce the friction coefficient with the roller (μ ≤ 0.003). At the same time, the thermal conductivity of copper (about 401 W/(m · K)) can quickly dissipate frictional heat, preventing deformation of the cage.
.2. Step by step analysis of working principle
1. Load transmission and dispersion
Radial load: The load is transmitted to the inner race raceway through the rollers, and then dispersed to the outer race through the contact surface between the rollers and the outer race raceway.
. The line contact design of drum shaped rollers ensures a more uniform load distribution and avoids local crushing caused by point contact (for example, the point contact stress of deep groove ball bearings can reach 3000MPa, while that of self-aligning roller bearings can be reduced to below 1500MPa).Axial load: Spherical roller bearings can withstand a certain axial load (usually 15%~20% of the radial load), and achieve axial force transmission through the contact between the roller and the inclined surface of the raceway.
.2. Implementation of centering function
Skewness compensation mechanism: When the shaft bends or is installed at an angle, the centerline of the inner and outer raceway is offset (Δθ).
. The drum shaped roller automatically adjusts its position during the rolling process, causing the contact point between the roller and the raceway to move along the axial direction of the roller, maintaining a stable contact area and avoiding edge stress concentration (as shown in Figure 1). For example, in a certain wind turbine gearbox, the MB split copper insulated self-aligning roller bearing can still maintain over 85% of its rated life even when the shaft is skewed by 1.5 °.3. The role of copper cage
Roller guidance and positioning: The pocket design of copper cage (such as straight or inclined pocket) precisely controls the roller spacing, prevents roller tilting or jamming, and ensures uniform distribution of rolling elements.
. Friction and temperature rise control: Copper has a low friction coefficient and good thermal conductivity, which can quickly transfer the heat generated by the friction between the roller and the cage to the bearing seat, avoiding the cage from getting stuck due to thermal expansion (measured data shows that the operating temperature of copper cage bearings is 5-8 ℃ lower than that of steel cage bearings). Corrosion resistance: Copper alloy surfaces can form dense oxide films (such as Cu ₂ O), which are more resistant to corrosion in humid or corrosive environments (such as chemical equipment) than steel cages.4. Advantages of Split Structure
Installation and Maintenance Convenience: In large equipment such as rolling mills and shield machines, traditional integral bearings require disassembly of the shaft or adjacent components to be installed, while MB split bearings can be directly fitted into the shaft and the outer ring can be closed, reducing installation time by more than 60%.
. Interchangeability and maintainability: The split design of the outer ring allows for the replacement of damaged outer half rings separately, without the need to replace the entire bearing, reducing maintenance costs (for example, the maintenance cost of a rolling mill bearing in a certain steel plant is reduced by 40%).III. Key Performance Parameters and Influencing Factors
1. Basic Rated Dynamic Load (C)
Calculation Formula:
C=bm ⋅ fh ⋅ fm ⋅ (i ⋅ L ⋅ cos α) 7/9 ⋅ Z3/4 ⋅ Dw29/27
bm: Material Coefficient (1.2-1.5 for copper bearings and 1.0 for steel bearings);
;fh: life coefficient;
i: number of roller rows;
L: Effective length of roller;
α: contact angle;
Z: number of rollers; Dw: Roller diameter.
The influence of copper cage: The friction coefficient of copper cage is low, which can reduce energy loss and increase the actual bearing capacity by 10%~15% compared to the theoretical value.
.2. Limit of self-aligning performance
Maximum self-aligning angle: usually 1.5 °~2.5 °. Exceeding this angle will cause a sharp increase in contact stress between the roller and the raceway edge (as shown in Figure 2), leading to a sharp decrease in lifespan.
.Compensation capability verification: By simulating shaft deflection conditions through finite element analysis (FEA), the roller trimming curve and raceway curvature radius are optimized to ensure uniform stress distribution at the ultimate centering angle.
.3. Speed and temperature rise control
Limit speed (n ₘₐₓ): The limit speed of copper bearing is 10%~15% lower than that of steel bearing, because the density of copper (8.9g/cm ³) is greater than that of steel (7.85g/cm ³), and the centrifugal force is greater.
. However, by optimizing the cage structure (such as hollow design), wind resistance can be reduced, and some models can achieve 90% of the rotational speed of steel bearings.Temperature rise curve: After continuous operation for 2 hours, the temperature rise of copper insulated bearings stabilizes at 40-50 ℃, which is 8-12 ℃ lower than that of steel insulated bearings and suitable for high-temperature environments (such as continuous casting machines in the metallurgical industry).
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