Abstract: Bearings, as one of the most important parts, play a very important role in mechanical equipment. This paper mainly from the sliding bearing and rolling bearing composition, characteristics and disassembly and lubrication, to a comprehensive understanding of the bearing, unveil its mystery.
Keywords: sliding bearings; rolling bearings; lubrication
0 Introduction
Bearings are a common and important component. In mechanical equipment and daily life, it is widely used. Its main function is to support the rotation of the shaft, reduce the friction during its movement, and ensure the rotary accuracy.
Bearings are divided into two main categories according to their different forms of friction: one is sliding bearings that produce sliding friction, and the other is rolling bearings that produce rolling friction.
1 Sliding bearings
When working, the bearing and journal support surface between the formation of sliding friction bearings, called sliding bearings.
1.1 Types and characteristics of sliding bearings
Sliding bearings are mainly divided into: radial load bearing radial sliding bearings and axial load bearing thrust sliding bearings.
Compared with rolling bearings, sliding bearing bearing capacity, good vibration resistance, smooth work, noise and radial size, long service life, and can be made into a split type, easy to install and dismantle, so suitable for high speed, high precision, heavy load and have a large impact on the occasion, but also applied to the unimportant low-speed machine, but the sliding bearing has a large start friction resistance, maintenance complex and other disadvantages.
1.2 The structure of the shaft tile
Shaft tile is the most important part of the sliding bearing, it is directly in contact with the journal, work with the journal there is a certain relative sliding speed. Shaft tile structure is reasonable, the performance of the sliding bearing has a great impact, there are mainly integral and split type two types.
(1) overall type
Integral sliding bearing is commonly known as the sleeve, is also the simplest form of sliding bearing, but wear can not adjust the clearance, and installation inconvenience. Installation, the main use of pressure and hammering method, special occasions using hot installation method, most of the sleeve is made of copper or cast iron, assembly of shaft tile and bearing using interference with the pressure, whether knocked into or pressed into must prevent tilt, and let the oil groove and oil hole in the required position, in order to facilitate lubrication.
(2) Split type
Split type bearings, also known as open bearings, have a simple structure, easy to adjust and dismantle the characteristics. Shaft tile is generally made of bimetallic materials, in order to improve the frictional nature of the surface of the shaft tile, often cast in its inner surface of a layer or two layers of friction reducing material, usually called bearing lining. And in the non-load bearing area of the shaft tile, or the pressure of the smaller area to open oil holes and oil grooves, so that the lubricant can be evenly distributed to the entire work surface. In order to improve the bearing capacity of the shaft tile, to prevent axial runout, both ends also have a flange structure.
1.3 Installation and maintenance of sliding bearings
In the installation and maintenance of the sliding bearing, one is to ensure that the journal in the bearing hole rotation flexible, accurate, smooth. Second, the tile back and bearing seat hole to repair scraping fit, pay attention to clean, each repair scraping after cleaning and oiling, shaft tile profile to be 0.05 ~ 0.1mm higher, in order to press. Third, to ensure that the main oil circuit is smooth, the oil circuit and oil tank connected. And to frequently check the lubrication, heat, vibration and other issues.
2 Rolling bearings
The rolling bearing is a precision mechanical component that turns the sliding friction between the running shaft and the shaft seat into rolling friction, thus reducing the friction loss.
2.1 The basic structure and application characteristics of rolling bearings
(1) The basic structure of rolling bearings
The basic structure of rolling bearing mainly contains: inner ring, outer ring, rolling body, cage. The role of the inner ring is to cooperate with the shaft, and rotate with the shaft. The role of the outer ring is to cooperate with the bearing seat, play a supporting role. The rolling body is evenly distributed between the inner ring and outer ring with the help of the cage, and its shape, size and number directly affect the performance and life of the rolling bearing. Keep frame can make rolling body evenly distributed, prevent rolling body off, guide rolling body rotating lubrication role.
(2) The application characteristics of rolling bearings
Rolling bearings rely on rolling contact between components to bear the load, compared with sliding bearings, has a small frictional resistance, easy to start, high efficiency, small axial size, lubrication and maintenance and other advantages. But the impact resistance is poor; high speed is easy to noise, radial size, the structure can not be divided, the working life is short.
2.2 The basic type of rolling bearing
In order to facilitate the study of rolling bearing characteristics, often in accordance with different ways to classification.
(1) according to the rolling bearing can bear the load direction is different, can be divided into: bear radial load to the heart of the bearing, bear axial load thrust bearing and at the same time bear radial, axial load to the heart of the thrust bearing.
(2) according to the rolling body shape, and can be divided into: ball bearings and roller bearings.
(3) according to the bearing in the work can adjust the heart, can also be divided into: non-signaling bearings and spherical bearings.
(4) according to a single bearing in the rolling body of the number, can be divided into: single, double and multi-row bearing.
2.3 Rolling bearing disassembly and assembly
As the rolling bearing is a standard part, so the inner ring and shaft using the base hole system, outer ring and box seat hole using the base shaft system. They should be cleaned before mounting. When installing, do not directly hammer the bearing end face and non-stressing surface, should use special tools to press the bearing flat and evenly, do not pass through the rolling body pressure installation.
To dismantle the bearing, use a special dismantling tool – a pulling horse. In the event of difficulties, special tools can be used to pull outward while pouring hot oil on the inner ring, so that the inner ring of the bearing expands, thus making it easier to fall off.
3 Lubrication of bearings
Whether it is a sliding bearing or a rolling bearing, lubrication is required in the process of use, which is to reduce friction and wear inside the bearing, prolong the service life of the bearing, enhance the performance of the bearing, and also to prevent rust and corrosion due to the intrusion of foreign matter inside the bearing. The following ways are generally used:
First, manual lubrication, which is the most primitive method, in the case of insufficient lubricating oil in the bearing, with the oiler to supply oil. But this method is difficult to keep the oil quantity certain, usually only used for light load, low speed or intermittent movement occasions.
The second is the drop point lubrication, usually used for line speed not more than 4 ~ 5m/s light load, medium load bearing, from the container by hole, needle, valve, etc. supply roughly for the quantitative lubricating oil.
Three is the oil ring lubrication, rely on hanging in and can rotate the ring, the oil pool of lubricating oil to the bearing, applicable to the journal more than 50mm in the middle speed and high speed bearings.
Four is oil rope lubrication, relying on the capillary tube of the oil rope and siphon effect will oil cup in the lubricating oil led to the bearing, mainly used for circumferential speed less than 4-5m / s light load and medium load bearing, in addition the oil rope in the whole process can play a filtering role.
Five is the oil bath lubrication, this kind of lubrication is part of the bearing into the lubricant, commonly used in the vertical axis of the thrust bearing.
Six is splash lubrication, relying on the oil tank in the rotating parts of the clap and splash up the lubricating oil supply bearings, suitable for higher speed bearings.
Seven is spray lubrication, the lubricating oil atomization after spraying in the friction surface lubrication method, suitable for high-speed bearings.
Eight is pressure lubrication, by the pressure of the lubrication pump to the bearing oil supply, from the bearing out of the lubricating oil recovery to the oil pool in order to recycle, is the most amount of oil supply and the most stable lubrication methods, suitable for high-speed, heavy-duty sliding bearings.
For example, in motor vehicles, gearbox gear lubrication is splash lubrication, engine oil pump lubrication to the camshaft lubrication is pressure lubrication.
4 Conclusion
Industry, agriculture, national defense, science and technology and household appliances and other areas of the host, its precision, performance, life, reliability and economic indicators, have a close relationship with the bearing, and the development of the bearing industry is also related to China’s major technical equipment manufacturing level and the export capacity of machinery and equipment. It can be seen that bearings cover a wide range and play a large role. Through the introduction of this thesis, we can initially understand bearings, know bearings, and lay a solid theoretical foundation for the safe use and scientific disassembly of bearings in mechanical equipment.
