Needle roller bearings Features
Needle roller bearings with an outer ring of precision stamping of sheet steel, and cage and needle the entire group, whose radial cross-sectional thickness is very small, and has a large load capacity, especially suitable for the requirements of the economy high-volume products.
Kind of needle bearing outer ring and bearing housing interference fit, no axial fixtures. Even at high speed, high load conditions, but also to ensure their effective performance. In addition, due to the volume of seal fat, can ensure long lubrication intervals. Typically, single row Needle roller bearings without lubrication hole and then double row bearings with lubrication holes.
This class generally do not have an inner ring needle roller bearings. If you need to use the inner ring, the choice of IR-type inner.
Needle roller bearings into the bearing ends of perforation (HK-type) and closed end bearings (BK-type). Compared with perforation drawn cup needle roller bearings, bearing the seal one end of the closed type, suitable for shaft end and can withstand small axial travel power.
Spherical Plain Bearings Overview
Joint bearing mainly by a spherical inner ring and an inner spherical outer ring, can withstand a greater load. According to their different types and structures to withstand radial load, axial load or radial, axial joint load. Since the inner surface of the outer sphere inlaid with composite materials, so the bearings can be produced in the work of self-lubricating. Generally used for slower swing movement, but also for a certain tilt angle range of motion, when the bearing shaft and housing bore axis misalignment is large, can still work. Self-lubricating auxiliary bearing joints used in water conservancy, specialized machinery and other industries.
Joint bearings are widely used in hydraulic engineering, metal forming machine tools, engineering machinery, automation equipment, automotive shock absorbers, irrigation machinery and other industries. Introduction and classification of joint bearing joint bearing is spherical plain bearings, spherical basic model is a sliding spherical contact surface The inner and outer ring. Depending on the structure and type, can withstand the radial load, axial load, or radial, axial joint load. Because large spherical plain bearings sliding contact area, tilt angle, but also because most of the articular bearing to a special process treatment, such as surface phosphate, zinc, chrome or outside the sliding surface lining, insert pad, such as spraying. Therefore, greater load capacity and impact resistance, and has anti-corrosion, abrasion-resistant, self-aligning, self-lubricating lubrication or no lubrication good dirt pollution characteristics, even dislocation can be installed to work properly. Therefore, joint bearings are widely used for slower swing motion, tilt movement and rotation.
Principles of bearing selection and application
Rolling bearing arrangement includes not only, but also with bearing-related components, such as shafts and housings. A very important part of the lubricant is bearing arrangement, since the lubricant to the anti-wear anti-corrosion, so the bearing to fully play its role. In addition, also a very important component, the seal performance of the seal member cleaning is essential for the lubricant. Cleanliness has a profound effect on bearing life, which is why lubricants and seals have become part of the SKF business reason.
In order to design Rolling command,
- Select the appropriate bearing type
- Determine the appropriate bearing size,
But this is not enough. Also consider other aspects:
- Such as the bearing arrangement suitable form and design of other components,
- The right fit and bearing internal clearance or preload
- Fixing means,
- Appropriate seals,
- Lubricant type and dose, and
- Installation and removal methods.
Each individual's decision will affect the bearing arrangement of performance, reliability and economy.
The basic performance requirements of bearing steel
Rolling bearing parts timber including timber and cage, rivets and other supporting material. The vast majority of rolling bearings and parts made of steel, bearing steel is usually high carbon chromium steel and hardened steel. With the increasing amount of development and the use of modern science and technology of rolling bearings, bearing the increasingly high demand, such as precision, long life and high reliability. For some special purpose bearings, bearing materials also requires a high temperature, corrosion-resistant, non-magnetic, ultra-low temperature, radiation and other properties. In addition, the bearing material further includes alloys, non-ferrous metals and non-metallic materials. In addition, the ceramic material of the bearing has been applied to locomotives, cars, subways, aviation, aerospace, chemical and other fields.
Rolling basic material requirements depends largely on the performance of the bearing. Select the manufacturer of rolling bearings material is appropriate, it will have a significant impact on its performance and life. Under normal circumstances, the main damage is in the form of a rolling bearing deposit under varying stress fatigue spalling, and wear due to friction loss leaving precision bearings. In addition, crack, indentation, corrosion and other causes of non-normal damage bearings. Therefore, the bearing should have a high resistance to plastic deformation, less friction and wear, good rotation accuracy, good dimensional accuracy and stability, and long contact fatigue life. And many of the performance is made of a material and heat treatment of the common decision.
Detailed analysis of internal bearing clearance
Bearing in operation, the temperature rise so that the outer ring temperature changes, will install clearance reduction, while the load is applied to the rolling bodies and rings elastically deformed, will increase the clearance. Operating clearance is slightly larger than usual installation clearance, in order to get the most satisfactory work performance, you should select the appropriate clearance work.
Bearing through a certain amount of negative clearance requirement may have some bearing preload, aims to improve the rigidity of the bearing, the bearing life can be improved; when the preload exceeds the upper limit of the optimum range, bearing rigidity increment little friction and heat has increased dramatically, but also a sharp decline in bearing life. When clearance is too large, the load-bearing rolling elements fewer, larger body to withstand the maximum load of the rolling bearing life will be reduced.
Therefore, the choice of internal clearance, should be considered in addition to bearing operating conditions (such as load, speed, temperature, etc.) and bearing the use of performance requirements (such as vibration and noise, friction torque, rotation accuracy, etc.), but also consider bearing installation shrinkage after clearance work the effects of temperature on clearance.
The working principle and characteristics of oil-bearing
Oil bearing, also known as porous bearing (Porous Bearing). It is a metal powder as the main raw material, produced by powder metallurgy sintered body, which has always been porous, but also in the manufacturing process can be more free to adjust the number, size, shape and distribution of pores and so on.
1, the use of sliding friction sleeve bearings, use of lubricants as a lubricant and DRA
2, beginning with Operation when using low noise, low manufacturing costs, but the wear and tear is serious, there is a big gap between life than ball bearings;
3, when over time, due to the seals, the oil will gradually be volatile, and the dust will enter the bearings, causing the device speed slows down, the noise increases and other issues.
The porous nature of the material or the use of oil-bearing parent and the characteristics of lubricating oil in the bearing before installation, so that oil infiltration bearing materials, during the bearing can not add or longer without oil.
Oil bearing in the non-operation state, lubricant filled pore, during operation, the shaft rotation due to friction and heat, thermal expansion bush make pores decreases, so oil overflowed into the bearing clearance. When the shaft stops rotating, bearing cooling, pore recovery, lubricating oil has been sucked back into the pores. Although there may be oil bearing form a complete film, but most of the occasion, the bearing oil film is in an incomplete state of mixed friction.
You can take advantage of the porous nature of the material, the lubricating oil filled porosity oil bearing bush materials: wood, grow cast iron, copper alloy and powder metallurgy antifriction material; can take advantage of an affinity with the lubricating properties of the material, uniformly dispersed in the lubricating oil oil-bearing materials, mostly polymer bearing materials, such as oil phenolic resin.