| THE SCOPE OF APPLICATION Household appliances:Air conditions, wash machines,musical instruments, microwave ovens, vacnum cleaners,exhaust devices. Office equipment: Printers, mappers, electronic data-processing equipments, coppies, facsimiles, currency counting machines. Electric appliance:Small generatous, smallmotors, synchromotors, electric tools, conveyors. Electronics equipment: Television cameras, recorders, video cassetterecorders, oscillographs, power meters, radar equipments, plotting instruments, mobile, computer. Optical instruments:film pojectors, slide projectors, lasers. Medical instrument: dental drills, electrocardio gram recorders, test instrumerts. Machinery: quantitative packagers, NC machines, transportation equipments, gearshifts, Highfrequemly spindles, Packing machines, washing machines. Others: amateur sports apparatuses small-sized driving devices, textilc machines, automobile, automatic elevator, etc. STUCTURE FORM AND CHARACTERISTICS HTMR can produce small single row deep groove ball bearings. The bearings can sustain radial load in either direction. The bearings have low triction, low vibration and low noise. These characteristics make them to be available for situations of high speed, high precision, low friction and low noise operations. HTMR bearings can be devided into open type and closed type. The colsed type can be devided into shielded and sealed bearings. Deep groove ball bearings often have shields or seals installed on both sides and are packed with a lubricant. The use of such bearings simplifies the structure of installation. It also eliminates the need for relubrication and therefore reduces maintenance costs. HTMR closed bearfings have four basic types:shielded, contact sealed, non-contact sealed and light contact sealed bearings. (a).shielded bearings -zz(-z) Shielded bearings are protected by two or one shield polate of pressed steel. The shields can be made of either low carbon steel or stainless steel. (b).Contact sealed bearings: Sealed bearings have superior sealing effectiveness compared to shielded bearings, particularly, the contact type sealed bearings which prevent the intrusion of dust from outside because the seal plate lip slides on a seal groove in the inner ring. The torque is, however,high due to the friction of seal lip. There are two types of contact seals:-2RS(-RS), -2LS(-LS). (C).Non-contact sealed bearings -2RZ(-RZ) Bearings with low friction seals which provide efficient sealing together with low friction torque. The speed and low friction abilities of non-contact sealed bearings are similar to shielded bearings. However, when high speed and low friction are critical, the shielded bearings may show slight advantage due to possible excentricity. Lip contact may occur between seal and shoulder of inner ring for the non-sealed bearings. (d).Light contact sealed bearing-LL(-L) The sealed structure of this type bearing is similar to the contact sealed bearing, and sealed lip lightly slides on a seal groove, so it has a some sealed effect and lower friction. HTMR can also produce mixed closed bearings by combination of shielded and/or sealed structures. ZL- One side is shielded and other is lightly contact sealed. LV- One side is lightly contact sealed and other is non-contact sealed. LD- One side is lightly contact sealed and other is contact sealed. DV- One side is contact sealed and other is non-contact sealed. HTMR may produce open bearing or one side shield bearing with a block groove on out ring. HTMR can also design and maufacture the other gypes of deep groove ball bearings according to customersi needs. CAGE STRUCTURE In general, the cages used in deep Groove ball bearings are pressed steel ribbon cages and snap cages. Pressed steel ribbon cages are generally used in the larger bearings and pressed snap cages in the smaller ones. For extra-high speed-applications, synthetic-resin cages or plastic cages are used. In recent years, plastic cages which have the advartages of low torgue, and low noise are used in many kinds of miniature bearings. HTMR can manufactur bearings with all above types of cages. SELECTION OF BEARING SIZE (1)Bearing life Bearing life, in a broad sense of the term, is the period during which bearings continue to operate and to satisfy their required function. This bearing life may be definde as noise life, abrasion life, grease life, or rolling fatique life, depending on which one causes loss of bearing service. Rolling fatique life is represented by the total number of revolutions before the bearing surface will start flaking due to stress.This is called fatique life. Even for seemingly identical bearings which are of the same type, size, and materials and receive the same heat treatment and other processing, the rolling fatigue life varies greatly even under identical operating conditions. This is because flaking of materials due to fatigue subject to many other variables. Consequently, "rating fatique lifei, in which rolling fatique life is treated as a statistical phenomnon, is used in preference to actual rolling fatique life. Suppose a number of bvearings of the same type are operated in dividually under the same conditions. After a certain period of time, 10%of themfail as the result of flaking caused by rolling fatique, in this case, the total number of revolutions is defined as the rating fatique life is often expressed by the total number of operation hours completed when 10% of the bearings become inoperable due to flaking. (2)Basic rating life The basic rating life of a single bearing or of a group of apparently identical bearings operating in identical conditions is the life corresponding to a reliability of 90%. Basic rating life is marked sith L10(millions of revolutions) or L10h(operating hours). For radial ball bearings L10=(Cr/Pr)3 where:L10-basic rating Life millions of revolutions. Cr-radial basic dynamic load ruting, N Pr-dynamic equivalent radial load, N The basic dynamic load rating is defined as the constant load applied on bearing with stationary outer rings that the inner rings can endue for a rating life of one million revolutions. The basic dynanucl load rating of radial bearings is defined as a central radial load of constant direction and magnitude. The radial basic dynamic load rating Cr is listed in bearing tables. While the radial and exial load. acting simultaneously, the radial equivalent dynamic bearing load can be caculated using the following equations. Pr=Fr for pure radial load. Pr=xFr+YFa for combined load. Were Fr-the radial component of the load, N Fa-the axial componment of the load, N Values of the coefficients X and Y can be found in following table. Radial load factor and axial load factor.
L10=106/60n(Cr/Pr)3 Where: n--rotational speed, r/min When determining the bearing size it is necessary to base the calculations on the rating life corresponding to the purpose of operation. It usually depends on the machine type, service life and the requiremints regarding operational safety. (3) Static load rating and static equivalem load. Static radial load rating Cor is considered in case of low speeds, low oscillating movements or in the stationary case. According to ISO76(GB/T4662) static radial load rating Cor is defined as the corresponding radial static load to a calculated contact stress in the center of the contact area between the most heavily loaded rolling element and the raceway. 4200 MPa(deep groove ball bearings) This stress preduces a permanent deformation of the 0.0001 rolling element diameter. The static equivalent radial load Por is a hypothetical load that produces a contact stress equal under actucel loaded conditions, in the center of the contact area between the most heavily loaded rolling element and raoeway. The greater of the two values calculated from the following equations should be adopted as the static equivalent radial load on radial ball bearings. Pr=XoFr+YoFa Pr=Fr where: Por static equivalent radial load Fr: radial load (N) Fa: axial load (N) Xo: static radial load factor (0.6) Yo: static axial load factor (0.5) The permissible static equivalent radial load on bearings varies depending on the basic static load rating and also their application and operating conditions. LIMITING SPEEDS Values for the limiting speed are listed in the bearing tables. The limiting speeds in the tables are applicable to bearings of standard design and subjected to normal loads, (c/p¡Ý12 and Fa/Fr¡Ü0.2) approximately. The limiting speeds for oil lubrication listed in the bearing tables are for conventional oil bath lubrication. When speeds are more than 70% of the listed limiting speed, oil or grease used in bearing lubrication must have high speed characteristics. BEARING TOLERANCE The accuracy of HTMR deep groove ball bearings is divided into three grades of tolerances with National Standard of P.R. of china: GB/T307.1-94 which compares with the ISO standard, etc is in the following table.
The radial clearances of HTMR deep groove ball bearings are according with National standard of P.R of china: GB4604-93 which is adopted from ISO5753-1991 equivalently, dividing into five groups as shown in the following table.
RADIAL CLEARANCE OF MOTOR BEARING
In general, the lubricating methods are divided into oil or grease lubrication Oil Lubrication (1)Suitable for extremely high operating speeds. (2)Good for assembly where the bearings are located in the same housing with oil lubricated components. (3)Suitable for extremely high operationg temperatures. (4)Good where a central oil system is used for auxiliary machine parts. (5)Good where bearing torque requirements are a consideration. Grease Lubrication (1)Grease may be retained in the bearing without an elaborate enclosure. (2)Grease give long service without renewal or inspection. (3)Grease increases the effectiveness of dirt exclusion in the enclosure. (4)Enclosed sealed bearings are lubricated at the factory. Technical Installation Conditions
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