In which a thin layer of liquid perceives the direct load from the shaft.
Hydraulic and pneumatic bearings are often used for high loads, high speeds, and where a precise shaft fit is required when conventional ball bearings generate too much vibration, too much noise, or are not suitable for compact equipment or durability. They are being used more and more often due to the declining cost. For example, computer hard drives that have an electric motor shaft mounted on hydraulic bearings are quieter and cheaper than those with ball bearings.
Operating principle
Advantages and disadvantages
Advantages
- Hydraulic and pneumatic bearings, in general, have very low coefficients of friction - much lower than mechanical bearings. The main source of friction is the viscosity of a liquid or gas. Since gas has a lower viscosity than liquid, gas-static bearings are among the bearings with the lowest coefficients of friction. However, the lower the viscosity of the liquid, the higher the leakage, which requires additional costs for pumping the liquid (or gas) into the bearing. These bearings also require seals and the better the seal, the higher the frictional forces.
- Under high loads, the clearance between the surfaces in hydraulic bearings changes less than in mechanical bearings. Bearing stiffness can be considered to be a simple function of the average fluid pressure and bearing surface area. In practice, when the load on the shaft is large and the clearance between the bearing surfaces decreases, the fluid pressure under the shaft increases, the fluid resistance force increases greatly, and thus the bearing clearance is maintained.
However, in bearings with a low load, such as bearings in disk drives, the stiffness of rolling bearings is on the order of 10 7 MN / m, while in hydraulic bearings ~ 10 6 MN / m. For this reason, in order to increase the rigidity, some hydraulic bearings, in particular hydrostatic bearings, are designed to be preloaded.
- Due to the way they work, hydraulic bearings often have significant damping properties.
- Hydraulic and pneumatic bearings are generally quieter and generate less vibration than rolling bearings (due to more evenly distributed frictional forces). For example, hard drives made using hydraulic (pneumatic) bearings have a bearing / motor noise level of 20-24 dB, which is not much more than background noise in a closed room. Roller bearing discs are at least 4 dB quieter.
- Hydraulic bearings are cheaper than conventional bearings at the same load. Hydraulic and pneumatic bearings are simple in design. In contrast, rolling bearings contain rollers or balls that have a complex shape and require high manufacturing accuracy - it is very difficult to produce perfectly round and smooth rolling surfaces. In mechanical bearings at high rotational speeds, surfaces are deformed due to centrifugal force, while hydraulic and pneumatic bearings are self-correcting for small deviations in the shape of the bearing parts.
- Hydrostatic and many air bearings are more complex and expensive than hydrodynamic bearings due to the pump.
Flaws
- Fluid dynamic bearings typically dissipate more energy than ball bearings.
- Energy dissipation in bearings, as well as stiffness and their damping properties, are highly temperature dependent, which complicates bearing design and operation over a wide temperature range.
- Hydraulic and air bearings can suddenly jam or collapse in critical situations. Ball bearings often fail gradually, this process is accompanied by the appearance of audible extraneous noise and backlash.
- The imbalance of the shaft and other parts in hydraulic and pneumatic bearings is greater than the imbalance in ball bearings, which leads to more severe precession, leading to a reduction in the life of the bearing and a deterioration in its quality indicators [ ] .
- Another disadvantage of hydraulic and pneumatic bearings is liquid or gas leakage to the outside of the bearing; retaining liquid or gas inside a bearing can be difficult. Hydraulic and air bearing trunnions are often installed in double and triple strings to avoid leakage from one side. Hydraulic bearings that use oil are not used where oil leakage to the environment is unacceptable or where maintenance is not economically feasible.
Application of fluid dynamic bearings
Hydrodynamic bearings are most widely used in machines due to their simplicity of design, although during the periods of starting and stopping, at low speeds, they operate under conditions of boundary lubrication or even "dry" friction.
- One of the main examples of the hydrodynamic friction regime from everyday life is the bearings of the crankshaft and camshaft of an internal combustion engine, in which, during its operation, an oil wedge is constantly held due to the viscosity of the oil and the rapid rotation of the shaft. The main shaft wear occurs at the time of starting and stopping the engine, when the shaft revolutions are insufficient to maintain the oil wedge and friction becomes boundary friction.
- In modern precision machine tools operating under light loads, especially in grinding
- The use of hydrodynamic plain bearings instead of rolling bearings in computer hard drives makes it possible to regulate the spindle rotation speed in a wide range, reduce noise and the effect of vibrations on the operation of devices, thereby increasing the data transfer rate and ensuring the safety of recorded information, as well as creating more compact hard drives. discs (0.8-inch). However, there are a number of disadvantages: high friction losses and, as a consequence, reduced efficiency (0.95 ... 0.98); the need for continuous lubrication; uneven bearing and journal wear; use of expensive materials for the manufacture of bearings.
- In pumps, for example, in the circulation pump of the RBMK-1000 reactor.
- In fans for cooling a personal computer. Using this type of bearing can reduce noise and improve the efficiency of the cooling system. Even initially, a fluid dynamic bearing is quieter than a plain bearing. After the end of a certain period of operation, it does not lose its acoustic properties and does not become noisier, unlike other bearings.
Application of gas dynamic bearings
Notes (edit)
Literature
- Metal-cutting machines: Textbook / V.E. Push, Moscow: Mechanical Engineering, 1986.- 564 p.
The content of the article
BEARING, a structural unit of machines and mechanisms that supports or guides a rotating shaft or axis. If the journal of the shaft in the bearing slides directly on the bearing surface, then it is called a sleeve bearing. If there are balls or rollers between the shaft journal and the bearing surface, then such a bearing is called a rolling bearing. The purpose of the bearing is to reduce friction between the moving and stationary parts of the machine, since friction is associated with energy loss, heating and wear.
Plain bearings.
A plain bearing is a massive metal support with a cylindrical bore, into which a sleeve, or insert, made of antifriction material is inserted. The journal, or trunnion, of the shaft enters the bore of the bearing sleeve with a small clearance. To reduce friction and wear, the bearing is usually lubricated so that the shaft is separated from the bushing by a film of a viscous oily liquid. The performance of a plain bearing is determined by its dimensions (length and diameter) as well as the viscosity of the lubricant and the speed of rotation of the shaft.
Lubrication.
Any sufficiently viscous liquid can be used to lubricate the plain bearing - oil, water, gasoline and kerosene, water and oil emulsions, and in some cases even gases (for example, heated air and combustion products in jet engines) and liquid metals. Also used are plastic and solid ("grease") lubricants, but their lubricating properties are different from those of liquids and gases. In cases where the natural circulation of the lubricant in the bearing is not enough to cool it, a forced circulation system with heat-emitting radiators and heat sinks is provided.
Hydrostatic bearings.
A sleeve bearing in which lubrication is supplied under pressure (usually by an oil pump) from an external source is called a hydrostatic bearing. The bearing capacity of such a bearing is mainly determined by the pressure of the supplied lubricant and does not depend on the peripheral speed of the shaft.
Hydrodynamic bearings.
A lubricated sleeve bearing can be thought of as a pump. In order to move a viscous medium from a low-pressure region to a high-pressure region, it is necessary to expend energy from an external source. The grease adhering to the contact surfaces, when the shaft rotates, resists complete abrasion and is squeezed out into the area where the pressure increases, thereby maintaining a gap between these surfaces. A sleeve bearing, in which a high pressure area is created in the described manner, which holds the load, is called hydrodynamic.
Rolling bearings.
In a rolling bearing, sliding friction is replaced by rolling friction, thereby reducing frictional energy losses and reducing wear.
Ball bearings.
The most common rolling bearing is the ball bearing. The shape of the grooves (raceways) of the inner and outer rings of a rolling bearing must be very precisely controlled during manufacture so that, on the one hand, there is no slippage of the balls relative to the ring, and on the other hand, they have a sufficiently large bearing area. The separator sets the exact position of the balls and prevents their mutual friction. In addition to single-row ball bearings, bearings with two and several rows of balls (double-row, multi-row) are produced, as well as bearings of other designs.
Roller bearings.
Roller bearings in roller bearings are rollers - cylindrical, barrel-shaped, tapered, needle-shaped or twisted. Roller bearing designs are also varied.
Lubrication.
Roller bearing life is determined by the fatigue wear of the balls (rollers) and raceways in the rings, which also require lubrication to reduce friction and wear. The operating temperature is important, since at elevated temperatures, not only does the unequal thermal expansion of the bearing elements affect, which leads to increased slippage, and therefore wear, but also decreases the hardness of the bearing materials.
Bearing materials.
Plain bearings are made from a variety of metals, alloys, plastics, composites and other materials. For a long time, the main bearing material was babbitt, patented by A. Babbitt in 1839. This alloy based on tin or lead with small additions of antimony, copper, nickel, etc. allows a number of composition options that differ in the relative content of components. Babbitt alloys have become, as it were, the standard for evaluating other bearing materials, among which are combinations of materials that have proven themselves well individually: babbitt and steel; babbitt, steel and bronze; lead with indium; silver and steel; graphite and bronze. Nylon and Teflon, which do not require lubrication, stand out among the plastics for plain bearings. Carbon graphite, cermets and composites are also used as materials for sleeve bearing bushings.
The content of the article
BEARING, a structural unit of machines and mechanisms that supports or guides a rotating shaft or axis. If the journal of the shaft in the bearing slides directly on the bearing surface, then it is called a sleeve bearing. If there are balls or rollers between the shaft journal and the bearing surface, then such a bearing is called a rolling bearing. The purpose of the bearing is to reduce friction between the moving and stationary parts of the machine, since friction is associated with energy loss, heating and wear.
Plain bearings.
A plain bearing is a massive metal support with a cylindrical bore, into which a sleeve, or insert, made of antifriction material is inserted. The journal, or trunnion, of the shaft enters the bore of the bearing sleeve with a small clearance. To reduce friction and wear, the bearing is usually lubricated so that the shaft is separated from the bushing by a film of a viscous oily liquid. The performance of a plain bearing is determined by its dimensions (length and diameter) as well as the viscosity of the lubricant and the speed of rotation of the shaft.
Lubrication.
Any sufficiently viscous liquid can be used to lubricate the plain bearing - oil, water, gasoline and kerosene, water and oil emulsions, and in some cases even gases (for example, heated air and combustion products in jet engines) and liquid metals. Also used are plastic and solid ("grease") lubricants, but their lubricating properties are different from those of liquids and gases. In cases where the natural circulation of the lubricant in the bearing is not enough to cool it, a forced circulation system with heat-emitting radiators and heat sinks is provided.
Hydrostatic bearings.
A sleeve bearing in which lubrication is supplied under pressure (usually by an oil pump) from an external source is called a hydrostatic bearing. The bearing capacity of such a bearing is mainly determined by the pressure of the supplied lubricant and does not depend on the peripheral speed of the shaft.
Hydrodynamic bearings.
A lubricated sleeve bearing can be thought of as a pump. In order to move a viscous medium from a low-pressure region to a high-pressure region, it is necessary to expend energy from an external source. The grease adhering to the contact surfaces, when the shaft rotates, resists complete abrasion and is squeezed out into the area where the pressure increases, thereby maintaining a gap between these surfaces. A sleeve bearing, in which a high pressure area is created in the described manner, which holds the load, is called hydrodynamic.
Rolling bearings.
In a rolling bearing, sliding friction is replaced by rolling friction, thereby reducing frictional energy losses and reducing wear.
Ball bearings.
The most common rolling bearing is the ball bearing. The shape of the grooves (raceways) of the inner and outer rings of a rolling bearing must be very precisely controlled during manufacture so that, on the one hand, there is no slippage of the balls relative to the ring, and on the other hand, they have a sufficiently large bearing area. The separator sets the exact position of the balls and prevents their mutual friction. In addition to single-row ball bearings, bearings with two and several rows of balls (double-row, multi-row) are produced, as well as bearings of other designs.
Roller bearings.
Roller bearings in roller bearings are rollers - cylindrical, barrel-shaped, tapered, needle-shaped or twisted. Roller bearing designs are also varied.
Lubrication.
Roller bearing life is determined by the fatigue wear of the balls (rollers) and raceways in the rings, which also require lubrication to reduce friction and wear. The operating temperature is important, since at elevated temperatures, not only does the unequal thermal expansion of the bearing elements affect, which leads to increased slippage, and therefore wear, but also decreases the hardness of the bearing materials.
Bearing materials.
Plain bearings are made from a variety of metals, alloys, plastics, composites and other materials. For a long time, the main bearing material was babbitt, patented by A. Babbitt in 1839. This alloy based on tin or lead with small additions of antimony, copper, nickel, etc. allows a number of composition options that differ in the relative content of components. Babbitt alloys have become, as it were, the standard for evaluating other bearing materials, among which are combinations of materials that have proven themselves well individually: babbitt and steel; babbitt, steel and bronze; lead with indium; silver and steel; graphite and bronze. Nylon and Teflon, which do not require lubrication, stand out among the plastics for plain bearings. Carbon graphite, cermets and composites are also used as materials for sleeve bearing bushings.
The article was written solely to familiarize Internet users with the main types of bearings. It will be useful for students of higher technical educational institutions and, possibly, young specialists.
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The main types of bearings
Bearings are technical devicesbeingpart of the supports for rotating axles and shafts. They perceive radial and axial loads applied to the shaft or axle, and transfer them to the frame, body or other parts of the structure. At the same time, they must also hold the shaft in space, provide rotation, swing or linear movement with minimal energy loss. The efficiency, performance and durability of the machine largely depend on the quality of the bearings.
Currently, bearings are widely used:
contact (having rubbing surfaces) - rolling bearings i and slip;
non-contact (not having rubbing surfaces) - magnetic bearings.
By the type of friction, they are distinguished:
plain bearings, in which the bearing surface of the axle or shaft slides along the working surface of the bearing;
rolling bearingswhich use rolling friction due to the installation of balls or rollers between the moving and stationary bearing rings.
Plain bearings
Schematic diagram of a support with a sleeve bearing
Sleeve bearingis is a body with a cylindrical hole into which an insert or sleeve made of antifriction material is inserted(non-ferrous metals are often used), and a lubricating device. There is a gap between the shaft and the bore of the bearing sleeve, which allows the shaft to rotate freely. For successful bearing operation, the clearance is pre-calculated.
Depending on the design, the peripheral speed of the trunnion, the operating conditions, sliding friction is:
liquid, when the surfaces of the shaft and bearing are separated by a layer of liquid lubricant , there is either no direct contact between these surfaces, or it occurs in separate areas;
boundary - the surfaces of the shaft and bearing are in contact completely or in areas of great length, and the lubricant is in the form of a thin film ;
dry - direct contact between shaft and bearing surfaces along the entire length or over long sections , there is no liquid or gaseous lubricant;
gas - shaft and bearing surfaces are separated by a gas layer, friction is minimal.
Types of sleeve bearing lubrication
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The main types of lubrication |
Lubricants and materials for creating lubricating coatings. Lubrication options |
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In the nanostructured state: C, BN, MoS 2 and WS 2; In the form of nanocomposite coatings: WC / C, MoS 2 / C, WS 2 / C, TiC / C and nanodiamond; In the form of diamond and diamond-like carbon coatings: films of diamond, hydrogenated carbon ( a - C: H ), amorphous carbon ( a -C), carbon nitride ( C 3 N 4 ) and boron nitride ( BN); In the form of hard and superhard coatings from VC, B 4 C, Al 2 O 3, SiC, Si 3 O 4, TiC, TiN, TiCN, AIN and BN, In the form of scaly films of MoS 2 and graphite; In the form of non-metallic films of titanium dioxide, calcium fluoride, glass, lead oxide, zinc oxide and tin oxide, In the form of a film of soft metals: lead, gold, silver, indium, copper and zinc, In the form of self-lubricating composites of nanotubes, polymers, carbon, graphite and cermets, In the form of flake films of carbon compounds: fluorinated graphite and graphite fluoride; Carbon; Polymers: PTFE, nylon and polyethylene, Fats, soap, wax (stearic acid), Ceramics and cermets. |
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Liquid |
Hydrodynamic lubrication: thick-layer and elastohydrodynamic; |
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Thin-film |
Mixed lubricant (semi-fluid); Boundary lubrication. |
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Gas-dynamic lubrication |
There are a large number of design types of plain bearings: self-aligning, segmental, self-lubricating, etc.
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G ) |
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a - appearance,
b - a typical spherical bearing with a sliding surface of the "metal-to-metal" type,
c - a typical spherical bearing with a self-lubricating surface,
d - due to the possibility of self-alignment and the perception of large loads, spherical bearings are used in units of heavy equipment (for example, in an excavator hydraulic cylinder)
Spherical plain bearings are one of the few types of plain bearings that are standardized and mass-produced by the industry
Plain bearingshave the following advantages:
allow high rotation speed;
allow you to work in water, with vibration and shock loads;
economical for large shaft diameters;
possibility of installation on shafts, where the bearing must be split (for crankshafts);
admit regulation different clearance and therefore accurate installation of geometric shaft axis.
a - HDD spindle motor with rolling bearing,
b - HDD spindle motor with hydrodynamic sliding bearing,
c - the location of the hydrodynamic plain bearing in the HDD (Hard Disk Drive)
The use of hydrodynamic plain bearings instead of rolling bearings in computer HDDs (Hard Disk Drive) makes it possible to regulate the spindle rotation speed in a wide range (up to 20,000 rpm), reduce noise and the effect of vibrations on the operation of devices, thereby increasing the data transfer rate, ensuring preservation of recorded information and the service life of the device as a whole (up to 10 years), and also - to create more compact HDD (0.8-inch)
Comparison of bearing types used in HDD (Hard Disk Drive) spindles
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HDD Requirements |
Bearing requirements |
Friction bearing |
Hydrodynamic bearing |
Typical Application |
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hard metal |
made of porous material * |
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Large storage capacity |
Single beats |
Personal computer, server |
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High rotation speeds |
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Low noise level |
Low noise level |
User computer (netbooks, SOHO) |
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Low current consumption |
Low torque |
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Shock resistance |
Shock resistance |
Mobile computers (laptops) |
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Reliability |
Resistance to seizure |
All computers |
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Rigidity |
Rigidity |
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Note:
* - data are given for NTN BEARPHITE;
** - designations: ++ - very good, + - good, o - mediocre.
Disadvantages of sleeve bearings:
high frictional losses and therefore reduced efficiency (0,95... 0,98);
need for continuous lubrication;
uneven bearing and journal wear;
the use of expensive materials for the manufacture of bearings;
relatively high labor intensity of manufacture.
Rolling bearings
Schematic diagram of a support with a rolling bearing
Rolling bearingsoperate mainly with rolling friction and consist of two rings, rolling elements, a separator separating the rolling elements from each other, holding them at an equal distance and directing their movement. On the outer surface of the inner ring and the inner surface of the outer ring (on the end surfaces of the thrust rolling bearing rings), grooves are made - raceways along which the rolling bodies roll during the operation of the bearing.
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d) e) |
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a - with ball rolling elements, b - with short cylindrical rollers, c - with long cylindrical or needle rollers, d - with tapered rollers,
d - with barrel-shaped rollers
Note : only some types of rolling elements are shown
Rolling elements of various shapes are used in rolling bearings.
In some units of machines in order to reduce dimensions, as well as improve accuracy and rigidity, the so-called combined bearings are used: the raceways are made directly on the shaft or on the surface of the body part. Some rolling bearings are manufactured without a cage. Such bearings have a large number of rolling elements and, therefore, a large load capacity. However, the limiting rotational speeds of full complement bearings are significantly lower due to the increased torques of resistance to rotation.
To reduce radial dimensions and weight, “no-break” bearings are used.
Comparison of rolling bearings by performance
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Bearing type |
High speed |
Perception of skew |
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radial |
axial |
combined |
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Ball radial |
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Ball radial double row spherical |
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Angular contact single row ball |
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Angular contact ball double row and single row double ("back to back") |
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Ball four-point contact |
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With short cylindrical rollers without flanges on one of the rings |
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With short cylindrical rollers with flanges on opposite sides of the outer and inner rings |
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Radial needle |
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Spherical roller |
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Tapered roller |
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Thrust ball |
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Thrust with tapered rollers |
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Radial thrust roller spherical |
Note:
* - designations: +++ - very good, ++ - good, + - satisfactory, o - bad, x - unusable.
Compared to sleeve bearings, they have the following advantages:
much less friction loss, and, consequently, higher efficiency (up to 0.995) and less heating;
10 ... 20 times less frictional torque at start;
saving scarce colored materials, which are most often used in the manufacture of plain bearings;
smaller overall dimensions in the axial direction;
ease of maintenance and replacement;
less lubricant consumption;
low cost due to mass production of standard bearings;
ease of machine repair due to the interchangeability of bearings.
e)
a - damage to the inner ring of a spherical roller bearing caused by excessive interference when landing;
b - fretting corrosion inner ring of a radial roller cylindrical bearing caused by vibration;
v - damage to the inner ring of a deep groove ball bearing caused by excessive axial loading;
G - damage to the inner ring of a radial roller cylindrical bearing caused by excessive radial load;
e - traces of rust on the surface of the roller of a spherical roller bearing, caused by the ingress of water into the bearing;
e - damage to the tapered roller bearing cage caused by heavy loads and / or vibrations, and / or improper installation and / or lubrication and / or operation at high speeds
Roller bearing damage
The disadvantages of rolling bearings are:
limited use at very high loads and high speeds;
unsuitability for work under significant shock and vibration loads due to high contact stresses and poor ability to damp vibrations;
significant overall dimensions in the radial direction and weight;
noise during operation due to form errors;
the complexity of the installation and mounting of bearing assemblies;
increased sensitivity to inaccuracy of the installation;
high cost for small-scale production of bearings with unique dimensions.
Magnetic bearings
Principle of operation magnetic bearing (suspension) based on the use of levitation created by electric and magnetic fields. Magnetic bearings allow without physical contact to carry out the suspension of the rotating shaft and its relative rotation without friction and wear.
Children's toy Levitron clearly demonstrates what electromagnetic fields are capable of
Electric and magnetic suspensions, depending on the principle of operation, are usually divided into nine types:
Electrostatic;
on permanent magnets;
active magnetic;
LC - resonant;
induction;
conductive;
diamagnetic;
Superconducting;
Magnetohydrodynamic.
Schematic diagram of a typical active magnetic bearing (AMB) system
The most popular are active magnetic bearings.Active magnetic bearing (AMB) is a controlled mechatronic device in which the rotor position is stabilized by magnetic attraction forces acting on the rotor from the side of electromagnets, the current in which is regulated by an automatic control system according to signals from the rotor displacement sensors. Full non-contact rotor suspension can be carried out using either two radial and one axial AMB, or two conical AMBs. Therefore, the rotor magnetic suspension system includes both the bearings themselves, built into the machine body, and an electronic control unit connected by wires to the windings of electromagnets and sensors. The control system can use both analog and more modern digital signal processing.
Control circuit diagram of a typical active magnetic bearing system
The main advantages of AMP are:
relatively high carrying capacity;
high mechanical strength;
the ability to implement a stable non-contact suspension of the body;
the ability to change the stiffness and damping over a wide range;
the possibility of using at high speeds of rotation, in vacuum, high and low temperatures, sterile technologies ...
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a - diagram of a compressor with rolling bearings,
b - diagram of a compressor with magnetic bearings
The use of magnetic bearings makes it possible to make the structure more rigid, which, for example, makes it possible to reduce the dynamic deflection of the shaft at high speeds.
Currently, an international standard is being created for AMP, for which a special committee ISO TC108 / SC2 / WG7 was created.
AMP can be effectively used in the following equipment:
Turbochargers and turbofans;
Turbomolecular pumps;
Electric spindles (milling, drilling, grinding);
Turbo expanders;
gas turbines and turboelectric units;
inertial energy storage.
Spindles for vacuum machines With active magnetic bearings
However, AMPs require complex and expensive control equipment, an external source of electricity, which reduces the efficiency and reliability of the entire system.Therefore, active work is underway to create passive magnetic bearings (PMB), which do not require complex control systems: for example, based on high-energy permanent magnets NdFeB (neodymium-iron-boron).
Passive magnetic bearing based on high-energy permanent magnets
1
) Albert Kascak,
Robert Fusaro &Wilfredo Morales. Permanent Magnetic Bearing for Spacecraft Applications. NASA / TM-2003-211996;
2)
Ball and Roller Bearings. Сat. No. 2202. NTN, 2001;
3)
Care andMaintenanceof Bearings. Сat. No.3017 NTN;
4) Henrik Strand. Design, Testing and Analysis of Journal Bearings for Construction Equipment. Department of Machine Design. Royal Institute of Technology. Stockholm, Sweden, 2005;
5) ISO Standardization for Active Magnetic Bearing Technology. Published 2005;
6)
Kazuhisa Miyoshi. Solid Lubricants and Coatings for Extreme Environments: State-of-the-Art Survey. NASA, 2007;
7) Needle Roller Bearings. Cat. No. 2300-VII / E. NTN;
8) Needle Roller Bearing Series General Catalog. IKO;
10
) Lei Shi, Lei Zhao, Guojun Yang, etc. DESIGN AND EXPERIMENTS OF THE ACTIVE MAGNETIC
BEARING SYSTEM FOR THE HTR-10. 2nd International Topical Meeting on HIGH TEMPERATURE REACTOR TECHNOLOGY... Beijing, CHINA, September 22-24, 2004;
11)
Linear Motion Rolling Guide Series General Catalog, IKO;
12
) Precision Rolling Bearings. Cat. No. 2260-II / E. NTN;13
) Spherical Plain Bearings. Cat. No. 5301-II / E. NTN;
14) Torbjorn A. Lembke. Induction Bearings. A Homopolar Concept for High Speed Machines. Electrical Machines and Power Electronics. Department of Electrical Engineering. Royal Institute of Technology. Stockholm, Sweden, 2003 ;
15
) Anuryev V.I. Handbook of the constructor-machine builder. M .: Mechanical Engineering, 2001;
16) Zhuravlev Yu. N. Active magnetic bearings: Theory, calculation, application. - SPb .: Polytechnic, 2003;
17
) Orlov P.I. Basics of design / Reference guide in 2 books. M .: Mechanical Engineering, 1988;
18) Chermensky O. N., Fedotov N. N. Rolling bearings.WITH directory directory. M: Mechanical Engineering, 2003.
The utility model relates to units and parts of machines that ensure the normal operation of machines and installations, namely, to sleeve bearings for rotary motion. The claimed device can be used in the spindle bearings of grinding machines. The technical problem to be solved by the claimed device is to improve the manufacturability of the hydrodynamic bearing by simplifying the system for adjusting the mounting clearance between the bearing and the spindle shaft of the machine. This problem is solved due to the fact that the hydrodynamic bearing mounted on the machine spindle shaft contains two support rings connected by pins with a gasket installed between them and three self-aligning support liners, each of which contains a spherical support. In this case, an annular chamfer is made on each of the support rings from the side of their connection, and each of the three support self-aligning liners contains a hemispherical groove. The technical result provided by the specified set of features is to improve the manufacturability of the hydrodynamic bearing, due to the peculiarities of the proposed design of self-aligning bushings and simplified adjustment of the gap between the support rings, by selecting the thickness of the gasket.
The utility model relates to units and parts of machines that ensure the normal operation of machines and installations, namely, to sleeve bearings for rotary motion. The claimed device can be used in the spindle bearings of grinding machines.
The prior art knows the design of a rolling bearing (and.with. SU 1557382, IPC F16C ЗЗ / 38, publ. 15.04.90, bul. 14), containing an inner and an outer ring, rolling elements placed between them and a separator separating them in the form of end washers with protrusions. The free space between the rings is filled with a solid lubricating anti-friction filler.
A disadvantage of the known rolling bearing design is its low operating speed.
Known hydrodynamic radial segment sliding bearing (A.S. 1516640, IPC F16C 17/24, publ. 23.10.89, bul. 39), containing self-aligning segments installed on support elements, united in a closed loop by elastic elements rigidly connected to them, and also a load monitoring and control system including a sensor and an amplifier connected to it.
The disadvantage of the design of the hydrodynamic bearing is the complexity of its operation, associated with the need to manually adjust the mounting clearance for each of the bushings. In addition, the well-known hydrodynamic bearing has low manufacturability due to the presence of complex automation elements in its design.
The technical problem to be solved by the claimed device is to improve the manufacturability of the hydrodynamic bearing by simplifying the system for adjusting the mounting clearance between the bearing and the spindle shaft of the machine.
This problem is solved due to the fact that the hydrodynamic bearing mounted on the machine spindle shaft contains two support rings connected by pins with a spacer installed between them and three self-aligning bushings, each of which contains a spherical support. In this case, an annular chamfer is made on each of the support rings from the side of their connection, and each of the three self-aligning liners contains a hemispherical groove.
The technical result provided by the specified set of features is to improve the manufacturability of the hydrodynamic bearing, due to the peculiarities of the proposed design of self-aligning bushings and simplified adjustment of the gap between the support rings, by selecting the thickness of the gasket.
The utility model is illustrated by drawings, where in FIG. 1 shows a hydrodynamic bearing, FIG. 2 - the location of the self-aligning bearing bushings and the position of the hydrodynamic bearing on the machine spindle.
The hydrodynamic bearing, mounted on the machine spindle shaft, contains two support rings 1 connected by pins 2 with a spacer 3 installed between them and three self-aligning liners 4, each of which contains a spherical support 5. Moreover, on each of the support rings from the side of their connection is made annular chamfer 6, and each of the three self-aligning bushings contains a hemispherical groove 7.
In each of the three self-aligning bearing shells 4, radial grooves are made to a depth of h 1 and h 3, respectively, which is necessary for grinding hemispherical grooves 7 and ensuring accurate installation of spherical bearings 5 with a diameter D C into the self-aligning bearings to a depth of h 2. A groove with a radius R is made in the support rings to secure the spherical supports 5 and prevent them from moving along the chamfers in the support rings 1.
The hole with diameter d 1 in the spherical bearings is designed to ensure their full immersion in the oil layer and to exclude mutual friction of the rings and bushings. The spherical bearings are fixed by two support rings, the outer diameter of which is D 1 and the inner diameter is D 2. A spacer 3 is installed between the support rings, which regulates the diametral gap by. The above-mentioned structural elements of the bearing are connected into a single subassembly using pins 2 with a diameter D 3 and a length L equal to the width of the bearing. The installation of the pins is performed in the holes, the center of which is at a distance D W from the center of the bearing, and at a distance t in the cross section from the edge of the self-aligning insert (Fig. 2).
The bearing is installed on the spindle shaft 8, while the required mounting clearance determines the distance H from the top point of the spherical bearing to the spindle shaft of the machine (Fig. 1).
Hydrodynamic bearing works as follows.
Preliminarily, the required size of the diametrical gap between the support rings 1 is adjusted by selecting the thickness of the gasket 3.
Further, the adjustment of the mounting clearance between the spindle shaft 8 and the self-aligning liners 4. The adjustment is carried out on the shaft, the diameter of which is equal to the diameter of the spindle shaft. With the help of the spacer 3 between the support rings 1, a shift is carried out, moving the spherical bearings 5 up or down, depending on the required size of the mounting gap. Presetting the mounting clearance is necessary due to the complexity of its adjustment directly on the machine spindle shaft.
