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Journal bearing

Journal bearing

Journal bearings are used to carry radial loads, for example, to support rotating shafts. A simple journal bearing consists of two rigid cylinders, of which the outer cylinder (bearing) wraps the inner rotating bearing journal (shaft).

The new thin film flow interface in the "CFD Module" can be used for lubrication analysis and complete elastohydrodynamic simulation. This case describes the pressure distribution of lubricating oil in a journal bearing, where the bearing extends around the rotating bearing journal. When solving the Reynolds equation around the lubricating oil surface of the bearing neck, the model uses the convergent and divergent lubricating oil thickness to simulate the eccentric position of the bearing neck in the bearing gap.

Journal bearing

Journal bearings are actually rolling bearings. The outer ring of its bearing is generally thicker and has a strong ability to withstand radial forces. It is more commonly used on modern machine tool rail pairs. It is often used in groups. It is usually installed under the slide plate to replace the previous sliding rail surface. According to the structure, rolling bearings can also be divided into deep groove ball bearings, self-aligning ball bearings, needle roller bearings and so on. The structure of deep groove ball bearings is relatively simple, and it is also very convenient to use. Deep groove ball bearings are mainly used to bear radial load, but also can bear certain axial load. Generally used in automobiles, tractors, machine tools, motors, water pumps, agricultural machinery, textile machinery, etc. The self-aligning ball bearing has two rows of steel balls and two raceways in the inner ring. Because the raceway of the outer ring of the self-aligning ball bearing is inner spherical, it also has the function of self-aligning and can automatically compensate for the Coaxiality errors caused by bending and shell deformation are generally used in agricultural machinery such as combine harvesters, blowers, paper machines, textile machinery, woodworking machinery, traveling wheels and drive shafts of bridge cranes.

Nowadays, journal bearings are mostly used in the field of automobile technology, and the general structure is: one hole, one shaft, clearance fit, the hole is a tile, and the shaft is a journal. Because it is a sliding bearing, it has strict and high lubrication requirements, so the bush and the neck are mostly high-pressure hydraulic lubrication, so that the journal basically does not contact the bush during the rotation of the shaft, and try to achieve the ideal zero wear .

Journal bearing

Journal bearing is a kind of precision mechanical component that changes the sliding friction between the running shaft and the shaft seat into rolling friction, thereby reducing friction loss. Rolling bearings are generally composed of four parts: inner ring, outer ring, rolling elements and cage. The function of the inner ring is to cooperate with the shaft and rotate with the shaft; the function of the outer ring is to cooperate with the bearing seat and play a supporting role; The cage evenly distributes the rolling elements between the inner ring and the outer ring, and its shape, size and quantity directly affect the performance and life of the rolling bearing; the cage can evenly distribute the rolling elements and guide the rolling elements to rotate for lubrication.

effect:
Support the rotating shaft and parts on the shaft, and maintain the normal working position and rotation accuracy of the shaft. The journal bearing is convenient to use and maintain, reliable in work, good starting performance, and high load capacity at medium speed. Compared with sliding bearings, rolling bearings have larger radial dimensions, poorer vibration damping capabilities, low service life at high speeds, and greater noise.

Journal bearing

structure:
The structure of rolling bearings consists of parts
1. Outer ring-installed in the bearing seat hole, generally does not rotate
2. Inner ring-installed on the journal, rotating with the shaft
3. Rolling element-the core element of rolling bearing
4. Cage-evenly separate the rolling elements to avoid friction
Lubricant is also considered to be the fifth largest component of rolling bearings. It mainly plays a role in lubrication, cooling, cleaning, etc.
Rolling bearing features:
1. Specialization
In the processing of bearing parts, a large number of special bearing equipment is used. For example, steel ball processing uses ball mills, grinders and other equipment. Specialization is also reflected in the production of bearing parts, such as a steel ball company specializing in the production of steel balls and a miniature bearing factory specializing in the production of miniature bearings.
2. Advancement
Due to the large-scale requirements of bearing production, it is possible to use advanced machine tools, tooling and technology. Such as CNC machine tools, three-jaw floating chuck and protective atmosphere heat treatment.
3. Automation
The specialization of bearing production provides conditions for its production automation. In production, a large number of fully automatic, semi-automatic special and non-dedicated machine tools are used, and production automatic lines are gradually popularized and applied. Such as automatic heat treatment line and automatic assembly line.

Journal bearing

Basic Features:
benefit:
(1). Significant energy saving. Due to the characteristics of the rolling bearing's own motion, the friction force is much smaller than that of the sliding bearing, which can reduce the power consumption in frictional resistance, so the energy saving effect is significant. From theoretical analysis and production practice, general small ball mills with rolling bearings as main bearings can save energy up to 30%~35%, medium ball mills can save electricity up to 15%~20%, and large ball mills can save electricity up to 10%~20%. Since the ball mill itself is a major energy consuming consumer in production, this will mean a considerable saving in costs.
(2). Easy maintenance and reliable quality. The use of rolling bearings can save a series of complex maintenance processes such as smelting, casting and scraping of babbitt alloy materials, as well as oil supply and water supply cooling systems, so the maintenance amount is greatly reduced. And because the rolling bearing is manufactured by a professional manufacturer, the quality is often guaranteed. It also brings convenience to manufacturers who use ball mills.

Journal bearing
advantage:
1. Low friction resistance, low power consumption, high mechanical efficiency and easy start;
2. The size is standardized, interchangeable, easy to install and disassemble, and easy to maintain;
3. Compact structure, light weight, and reduced axial size;
4. High precision, large load, small wear and long service life;
5. Some bearings have self-aligning performance;
6. Suitable for mass production, with stable and reliable quality and high production efficiency;
7. The transmission friction torque is much lower than the hydrodynamic bearing, so the friction temperature rise and power consumption are lower;
8. Starting friction torque is only slightly higher than rotating friction torque;
9. The sensitivity of bearing deformation to load changes is less than that of hydrodynamic bearings;
10. Only a small amount of lubricant is needed for normal operation, and lubricant can be provided for a long time during operation;
11. The axial size is smaller than the traditional hydrodynamic bearing;
12. It can bear combined radial and thrust loads at the same time;
13. In a large load-speed range, the unique design can obtain excellent performance;
14. Bearing performance is relatively insensitive to fluctuations in load, speed and operating speed.
Disadvantages:
1. Loud noise.
2. The structure of the bearing seat is more complicated.
3. Higher cost.
4. Even if the bearings are well lubricated, installed correctly, dust-proof and moisture-proof, and running normally, they will eventually fail due to fatigue of the rolling contact surface.

Journal bearing

The difference with sliding bearings:
Basic difference:
The difference between rolling bearings and sliding bearings is first expressed in structure. Rolling bearings support the rotating shaft by the rotation of rolling elements, and the contact part is a point. The more rolling elements, the more contact points; the sliding bearing relies on smooth surfaces. To support the rotating shaft, so the contact part is a surface. Secondly, the movement mode is different. The movement mode of the rolling bearing is rolling; the movement mode of the sliding bearing is sliding, so the friction situation is completely different.
Sliding bearing:
Sliding bearing (slidingbearing), a bearing that works under sliding friction. Sliding bearings work smoothly, reliably, and noiselessly. Under liquid lubrication conditions, the sliding surfaces are separated by lubricating oil without direct contact, and friction loss and surface wear can be greatly reduced. The oil film also has a certain vibration absorption capacity. But the starting frictional resistance is relatively large. The part of the shaft supported by the bearing is called the journal, and the parts matching the journal are called the bearing bush.
In order to improve the friction properties of the bearing pad surface, the anti-friction material layer cast on the inner surface is called the bearing liner. The materials of bearing bushes and bearing linings are collectively referred to as sliding bearing materials. Commonly used sliding bearing materials include bearing alloys (also called Babbitt alloys or white alloys), wear-resistant cast iron, copper-based and aluminum-based alloys, powder metallurgy materials, plastics, rubber, hardwood and carbon-graphite, polytetrafluoroethylene (PTFE) ), modified polyoxymethylene (POM), etc. Sliding bearing applications are generally under low-speed and heavy-duty conditions, or operating parts where maintenance and lubrication are difficult.

Journal bearing
Rolling bearings:
The radial bearing in the rolling bearing (mainly bearing radial force) is usually composed of 4 parts: inner ring, outer ring, rolling element and rolling element cage. The inner ring is tightly sleeved on the journal and rotates with the shaft, and the outer ring is installed in the bearing seat hole. Raceways are formed on both the outer circumference of the inner ring and the inner circumference of the outer ring. When the inner and outer rings rotate relatively, the rolling elements roll on the raceways of the inner and outer rings. They are separated by the cage to avoid mutual friction. Thrust bearing is divided into two parts: tight ring and live ring. The tight ring and the shaft sleeve are tight, and the live ring is supported on the bearing seat. Rings and rolling elements are usually made of rolling bearing steel with high strength and good wear resistance, and the surface hardness after quenching should reach HRC60-65. The cage is mostly made of mild steel stamping, and it can also be made of copper alloy laminated bakelite or plastic.

Status and role:
Rolling bearings are important mechanical basic parts that are widely used and are widely used in various fields of national economy and national defense.
The invention of rolling bearings has a long history. According to the archaeological relics found in Yongji County, Shanxi Province, China, there were bronze rolling bearings as early as 221-207 BC (Qin Dynasty); according to the archaeological relics found in Lake Nimi, Italy, 12-41 AD There were also bronze rolling bearings. The birth of the modern bearing industry was marked by the invention of the world's first ball grinding machine in 1883 in Germany, which entered the era of industrialized production of steel balls. Rolling bearings developed vigorously along with the bicycle and automobile industries during the second industrial revolution. It has gradually become a highly specialized industrial industry worldwide, and has a very important position and role in modern industry.

Journal bearing
The importance of rolling bearings is mainly reflected in the following aspects:
(1) In the national economy-rolling bearings are called the "joint of industry". As the basic industry and backbone industry of the machinery industry, the bearing industry's development level often represents or restricts the development level of a country's machinery industry and other related industries. In Japan, people often refer to the bearing industry as the food of the industry. The bearing industry is called "the core industry of the machinery industry" and "the basic industry that improves people's lives". It is protected and supported by the Japanese government's revitalization policy. There are 14 specific One of the "machinery industry" industries. In China, rolling bearings are one of the 11 types of specific revitalized machinery products identified by the state, and 33 bearing companies are listed as specific revitalized industries. Among the 520 key enterprises newly identified by the country, 6 are in the bearing industry. Car bearings, railway rolling stock, precision bearings and high-speed bearing manufacturing are included.
(2) In the national defense industry-rolling bearings are necessary armaments. Without bearings, missiles cannot be launched, aircraft cannot be launched, warships cannot go to sea, tanks cannot attack... Bearings are important or core components in many military equipment; in wars, bearing manufacturers are hostile countries Included as one of the key targets; during the Cold War, special bearing equipment was one of the embargoed materials that Western countries imposed economic blockade on socialist countries. So far, many bearing products and technologies are still included in the technical blockade by many military powers.
(3) In terms of technical status-bearing steel is the steel grade that requires the most technical indicators and the most stringent among various alloy steels. The world recognizes that the smelting level of bearing steel is a sign of the level of metallurgical technology in a country. In China, among many special steels such as stainless steel, high-speed steel, gear steel, valve steel, spring steel, etc., bearing steel is one of the few steel types that require production licenses so far. Rolling bearings are also an important application field for many new materials such as engineering ceramics and engineering plastics.
The rolling bearing industry is one of the first industrial fields to carry out standardization activities and adopt reliability technology.

Date

26 October 2020

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Journal bearing

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