Drawn cup needle roller bearings are assemblies, there are two types of open type and closed type. The assembly includes a thin-walled drawn cup, needle roller and cage assembly.
The outer ring of the drawn cup needle roller bearings are formed by precision stamping of thin steel plate, which has a small structure space and a large load capacity. It is suitable for occasions where the installation space is limited and the housing hole is not suitable for the raceway. And no further axial positioning is required after being pressed into the bearing seat hole.
Structural composition of drawn cup needle roller bearings
- Outer ring: installed in the bearing seat hole, generally does not rotate.
- Inner ring: bearing neck, which rotates with the shaft.
- Stamping body.
- Cage: The stamping body is evenly spaced to reduce friction.
Features of drawn cup needle roller bearings
- Low friction resistance, low power consumption, high mechanical efficiency, easy to start.
- Standardized size, interchangeable, easy to install and disassemble, easy to maintain.
- Compact structure, light weight, and reduced axial size.
- High precision, high speed, low wear and long service life.
- Some bearings have self-aligning performance.
- It is suitable for mass production, with stable and reliable quality and high production efficiency.
There are two types of drawn cup needle roller bearings: perforated type and sealed type. Drawn cup needle roller bearings have no inner ring, and the needle directly contacts the surface of the shaft, so the machining accuracy and heat treatment hardness of the shaft should be the same as the inner ring of the bearing.
Scope of application: Drawn cup needle roller bearings with cages are suitable for high speed and heavy load, and are mostly used in the transmission of machine tools, automobiles, motorcycles or textile machinery. Cageless drawn ferrule needle roller bearings are suitable for oscillating working conditions under heavy loads due to their full needle rollers. Such as the frame of the aircraft, the shaft end of the main wing of the missile, etc.
Heat treatment of integral drawn cup needle roller bearings
The first step in the heat treatment of the overall drawn cup needle roller bearings is to process the needle rollers, that is, the needle rollers are heated, quenched and tempered in a roller furnace. During heating, the carbon potential in the furnace is CP=1.0～1.1%, and the heating temperature ( 845～870)℃±5℃, use fast bright quenching oil, oil temperature 80℃, core quenching hardness 760+80HV, surface hardness 780+160HV, tempering temperature 160～180℃, hardness after tempering ≥ 810HV, the metallographic structure is tempered cryptocrystalline, fine crystalline or small acicular martensite, uniformly distributed fine residual carbides and a small amount of residual austenite.
The needle rollers after heat treatment are ground, polished, etc., and then sorted by an automatic high-speed sorting machine. The frame and the stamped outer ring are assembled on a fully automatic assembly and sealing machine to become an integral stamped needle roller bearing.
Finally, they are carburized (carbonitriding) quenching in the mesh belt furnace. The quenching cooling medium is graded quenching oil. Potential CP =0.9%～1.2%, carburizing time is generally 30～100min according to technical requirements, carburizing layer depth of stamping outer ring is 0.08～0.33mm, carburizing and quenching hardness is 840～900HV; carburizing layer depth of cage is 0.02 ～0.12mm, carburizing and quenching hardness 410～550HV.
For needle rollers, the metallographic structure before carburizing and quenching is tempered hidden needles, fine crystalline or small acicular martensite, uniformly distributed fine residual carbides and a small amount of retained austenite, which are in the second carburizing. During quenching, because of the short time, for high carbon chromium bearing steel, the structure will not be coarse, but it can make the structure finer and more uniform, and improve the contact fatigue strength. At this time, the quenching hardness is ≥910HV, and the hardness after tempering ≥810HV.
After the heat treatment, cleaning and drying of the integral stamped needle roller bearing is completed, its size will be reduced by 0.01 ~ 0.05mm. For this reason, 100% enveloping circle detection is required for the integral stamped bearing. For a very small number of out of tolerance, it needs to be squeezed. Only after correction can be put into storage.
Drawn cup needle roller bearings are needle roller bearings with a thin drawn cup outer ring. Its main feature is that the section height is very low and the load bearing capacity is high. It is mainly used for the bearing configuration with compact structure and low price, and the inner hole of the bearing box cannot be used as the raceway of the needle roller cage assembly. Bearings and bearing housings must be installed with an interference fit. If the axial positioning functions such as the box shoulder and the stop ring can be omitted, the inner hole of the bearing box can be made extremely simple and economical.
The drawn cup needle roller bearings mounted on the shaft end are of double-sided open type and single-sided closed type. The base end face of the closed drawn outer ring can bear little axial guiding force. Drawn cup needle roller bearings generally do not have an inner ring.
The hardened steel outer ring of drawn cup needle roller bearings cannot be separated from the needle roller cage assembly. Free space for lubricant storage allows extended relubrication intervals. Bearings generally use a single-row design. Except for the wider bearing series 1522, 1622, 2030, 2538 and 3038, which are equipped with two needle roller cage assemblies. There are lubricating oil holes in the outer ring of the bearing. According to user needs, all single row drawn cup needle roller bearings with shaft diameter greater than or equal to 7mm can be equipped with an outer ring with lubricating oil holes.
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