Roll Pins And Bidirectional Thrust Cylindrical Roller Composite Bearings

1. Product Definition and Positioning​

Needle and double-directional thrust cylindrical roller combined bearings are highly integrated composite bearing units. By coaxially and rigidly integrating a radial needle roller load-bearing unit and a double-directional thrust cylindrical roller load-bearing unit, they achieve synchronous and efficient bearing of both radial loads and double-directional axial loads. Their core positioning is to solve the load-bearing challenges of small and medium-sized precision machinery in scenarios featuring "frequent switching of axial force directions + limited installation space". They replace the traditional split combination scheme of "needle roller bearings + double-directional thrust bearings", simplifying equipment structure and improving transmission accuracy. As such, they are key supporting components for core equipment in precision manufacturing, automation, new energy, and other fields.​

The core value of these bearings lies in "integration of double-directional load-bearing" and "maximization of space utilization". Compared with traditional split bearing combinations, they can reduce axial installation space by over 40% and radial installation space by more than 30%, while increasing transmission accuracy by 20%-30%. They perfectly meet the development needs of modern equipment for "miniaturization, high precision, and high reliability".​

2. Core Structure and Component Details​

(1) Overall Structural Layout​

Adopting a "radial-axial coaxial integration" design, the bearing has an overall cylindrical structure. The radial needle roller unit is located in the middle, and the double-directional thrust cylindrical roller units are symmetrically distributed on both sides of the radial unit. Rigid connection is achieved through positioning steps, retaining rings, or bolts to form an non-separable integral structure. Some sealed models are equipped with sealing rings/dust covers at both ends, forming a fully enclosed or semi-enclosed protective structure. The overall structure is compact, with a clear load-bearing path.​

(2) Technical Characteristics of Key Components​

Radial Needle Roller Unit​

Needle Rollers: Made of high-purity bearing steel (SUJ2 or GCr15SiMn) and subjected to integral quenching, with a hardness of HRC60-62. The diameter accuracy is controlled within ±0.002mm, and the length tolerance is ±0.05mm. The surface undergoes ultra-precision grinding, with a roughness of Ra ≤ 0.02μm, reducing frictional loss with the raceway. Both ends of the needle rollers are designed with arc chamfers (R0.1-R0.3mm) to avoid early wear caused by stress concentration.​

Cages: Mainly made of brass (H62 brass) through stamping or machining. For scenarios requiring lightweight design, reinforced nylon (PA66+GF30) is used. The pocket size accuracy of the cage reaches IT8 grade, ensuring uniform distribution of needle rollers. The gap between the pockets and the needle rollers is controlled at 0.01-0.03mm to prevent noise caused by needle roller movement. The surface of metal cages is galvanized or passivated to improve rust resistance.​

Inner Ring (Optional): Some models are equipped with independent inner rings, made of the same material as the needle rollers. The inner hole of the inner ring adopts an interference fit with the shaft (fit tolerance H7/k6), and the outer raceway is ultra-precision ground, with a roundness error of ≤ 0.003mm. Inner ring-free models need to be directly matched with the shaft journal, which requires the shaft journal surface to have a hardness of ≥ HRC58 and a roughness of Ra ≤ 0.04μm to replace the function of the inner ring raceway.​

Double-Directional Thrust Cylindrical Roller Unit​

Thrust Washers: Composed of 3 washers (1 middle fixed washer + 2 side movable washers), made of high-carbon chromium bearing steel subjected to vacuum quenching, with a hardness of HRC58-60. The working surface of the washers undergoes ultra-precision grinding, with a flatness error of ≤ 0.005mm, a parallelism error of ≤ 0.003mm, and a roughness of Ra ≤ 0.016μm. The outer circle of the middle fixed washer is provided with a positioning step, adopting a transition fit with the bearing housing (H7/js6). The inner holes of the side movable washers adopt a transition fit with the shaft (H7/h6) to ensure synchronous rotation.​

Thrust Cylindrical Rollers: Made of the same bearing steel as the needle rollers, with a diameter accuracy of ±0.003mm and a length tolerance of ±0.04mm. The roller surface is subjected to crown modification (logarithmic crown), with a modification amount of 0.005-0.01mm, avoiding excessive local stress caused by edge contact. The contact area between the two ends of the rollers and the thrust washers is controlled at over 80%, improving the efficiency of axial load transmission.​

Cages: Made of brass or reinforced nylon, with an integral or split structure. The number of pockets matches the number of rollers, and the pocket gap is 0.02-0.04mm. The cage is equipped with a guiding structure, forming positioning with the middle fixed washer or the side movable washers to ensure stable operation of the rollers under axial load.​

Protective and Connecting Components​

Sealing Rings/Dust Covers: Sealing rings are made of nitrile rubber (NBR) or fluororubber (FKM). NBR is suitable for a temperature range of -30℃-120℃, while FKM is suitable for high-temperature scenarios of -20℃-200℃. The lip of the sealing ring adopts a multi-lip structure (2-3 lips), and the interference between the lip and the shaft journal is controlled at 0.1-0.2mm to improve the sealing effect. Dust covers are made of thin steel plates (0.3-0.5mm) through stamping, with a galvanized surface. They are connected to the bearing outer ring through snaps or interference fit to prevent dust intrusion.​

Positioning and Connecting Components: The height of the positioning step is 2-5mm, with a tolerance controlled within ±0.01mm to ensure the coaxiality of the radial and axial units (coaxiality error ≤ 0.01mm). Retaining rings are made of spring steel (65Mn) subjected to quenching, with a hardness of HRC45-50. They are connected to the bearing outer ring or inner ring through grooves to prevent axial movement of the axial unit. Some large-sized models adopt bolt connection, with bolts made of stainless steel (A2-70). The pre-tightening torque is controlled at 5-20Nm depending on the model.​

3. Performance Parameters and Technical Indicators​

(1) Core Load-Bearing Parameters

(2) Environmental Adaptability Parameters

 (3) Friction and Service Life Parameters

4.Product application scenarios

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