Rolling Pin And Thrust Combined Bearing

Needle and thrust combined bearings are composite bearing units that integrate radial needle roller bearings and axial thrust bearings. Their core function is to simultaneously withstand radial loads and axial loads (unidirectional or bidirectional) in compact spaces. Through structural integration, they simplify the assembly process and save installation space. Widely used in mechanical transmission systems that require strict space constraints and combined load-bearing capacity, they are key supporting components for small and medium-sized precision equipment.​

1. Core Structural Design: Integrated Load-Bearing Layout​

Different from single-function bearings, their structure is specifically designed around the "radial + axial" combined load-bearing requirement, with a typical structure including three core components:​

Radial Load-Bearing Unit: Composed of high-precision needle rollers (diameter: 2-8mm, length: 5-20mm) and cages (plastic or metal material). Some models are equipped with inner rings or outer rings (inner ring-free/outer ring-free models need to be directly matched with shafts/bearing housings to save radial space). It bears radial loads through the line contact between needle rollers and raceways, with a radial rated dynamic load of up to 5-80kN.​

Axial Load-Bearing Unit: Arranged coaxially with the radial unit, it commonly adopts the structure of "thrust ball" or "thrust roller" - the thrust ball unit is suitable for medium-low axial loads (≤15kN) and uses high-precision steel balls and hardened washers; the thrust roller unit (thrust cylindrical/tapered roller) is suitable for medium-high axial loads (≤50kN). It improves load-bearing capacity through roller line contact, and the washer surface is ground with a flatness error of ≤0.005mm.​

Integrated Assembly Structure: The radial and axial units are connected by positioning steps, snap rings, or bolts to form an non-separable integral unit. Some models are equipped with seals (rubber seal rings or dust covers) to prevent impurity intrusion and retain grease, making them suitable for harsh working conditions.​

2. Key Performance Advantages: Efficient Load-Bearing in Compact Spaces​

Based on the integrated structure, their performance advantages focus on "space utilization" and "combined load-bearing efficiency", with the following core highlights:​

Ultra-High Space Utilization: The radial dimension is only 60%-70% of that of deep groove ball bearings with the same load-bearing capacity (for example, when bearing a radial load of 10kN, the radial width of the combined bearing is ≤15mm, while that of traditional deep groove ball bearings needs to be ≥25mm). The axial dimension is reduced by more than 30% through unit integration, making it suitable for compact space scenarios such as motors and gearboxes.​

Combined Load-Bearing Capacity: It can withstand both radial and axial loads, with flexible load combinations - radial loads are borne by the needle roller unit, and axial loads are borne by the thrust unit, without mutual interference. Moreover, the direction of axial loads can be adjusted by the type of thrust unit (unidirectional thrust units bear unidirectional axial loads, and bidirectional units bear bidirectional axial loads).​

High Precision and Low Friction: The radial needle roller unit is processed with P5-P6 grade tolerance, with radial runout ≤0.01mm; the thrust unit washer has high flatness, with axial movement ≤0.008mm, ensuring precise transmission of equipment. The friction coefficient is low (≤0.002 under grease lubrication), and the operating temperature rise is lower than that of traditional split bearing combinations, reducing energy consumption by 5%-10%.​

Simplified Assembly and Maintenance: The integrated structure reduces the number of parts (by 40% compared with split bearing combinations). During assembly, there is no need to separately adjust the coaxiality of radial and axial bearings, reducing assembly difficulty. Some models have reserved lubrication holes for regular grease replenishment, extending the maintenance cycle to 2000-5000 hours.​

3. Main Application Scenarios: Combined Load-Bearing Requirements in Space-Constrained Environments​

According to the load-bearing capacity and structural form, the product is mainly suitable for four categories of precision machinery scenarios, covering the automotive, home appliance, and industrial equipment fields:​

Automotive Transmission Systems: Suitable for gearbox synchronizers, clutch release bearings, and motor end cover supports. For example, the synchronizer of Volkswagen DSG gearboxes adopts inner ring-free needle-thrust ball combined bearings (model: NKX series), which bear radial shifting loads and axial synchronization loads, and the space occupation is reduced by 25% compared with traditional split bearings.​

Home Appliances and Office Equipment: Used in washing machine dehydration shafts, printer roller shafts, and air conditioning compressor crankshafts. For example, the dehydration shaft of drum washing machines adopts combined bearings with plastic cages (model: RNAX series), with radial load ≤8kN and axial load ≤3kN, meeting the lightweight and miniaturization needs of home appliances.​

Industrial Precision Equipment: Applied in servo motor output ends, small reducers, and robot joints. For example, 600W servo motors adopt sealed needle-thrust roller combined bearings (model: KZT series), with radial runout ≤0.008mm, meeting the high-precision transmission requirements of motors.​

Agricultural Machinery and Construction Machinery: Suitable for small tractor gearboxes and harvester reel shafts. It adopts a metal cage + dust-proof seal structure to withstand the dusty field environment, with a radial rated dynamic load ≥20kN and axial load ≥10kN, adapting to intermittent impact loads.​

4. Key Technical Parameters: Multiple Specifications Covering Different Needs​

The core parameters form a hierarchical system around "size-load-bearing-precision". The typical parameter ranges are as follows：

 In addition, the product can also be customized in terms of materials (such as corrosion-resistant stainless steel) and seal forms (double-sided dust covers/seal rings) according to requirements, to adapt to special environments (such as stainless steel bearings for food-grade equipment).

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