OPERATING TEMPERATURES OF THE BEARING SYSTEM OF GRINDER SPINDLE

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1 -011 T R I B O L O G I A 157 Stanisław STRZELECKI *, Zdisław SOCA * OPERATING TEMPERATURES OF TE BEARING SYSTEM OF GRINDER SPINDLE TEMPERATURY PRACY UKŁADU ŁOŻYSK WRZECIENNIKA SZLIFIERKI Key words: theory of hydrodynamic lubrication, journal bearings, oil film temerature Słowa klucowe: teoria smarowania hydrodynamicnego, łożyska śligowe, temeratura filmu smarowego Abstract The ground for the safe oeration of multilobe journal bearings at roer oil film temerature is the full knowledge of bearing thermal erformances articularly the oil film temerature distribution and its maximum value. This aer describes the theoretical and exerimental investigation into the oerating temeratures of ericycloid, -lobe journal bearings * Research Develoment Centre of Textile Machinery POLMATEX-CENARO, Łódź, Poland.

2 158 T R I B O L O G I A -011 suorting the sindle of grinding machine. The oil film ressure, temerature and viscosity fields have been obtained by iterative solution of the Reynolds', energy and viscosity equations. Adiabatic, laminar oil film and the static equilibrium osition of the journal were assumed. Exerimental investigation consisted in the measurements of temeratures in the bearings. INTRODUCTION ydrodynamic journal bearings can roerly oerate in the strictly determined range of rotational seeds. The ermissible temerature of oeration and the ossibilities of heat conduction determine the uer boundary of the range, but the lower boundary determines the occurrence of fluid friction. The multilobe journal bearings [L. 1 ], mostly used in slightly loaded, high seed rotating machines are characterised by good cooling roerties, daming of vibrations and the stability. Industry alies different tyes of -lobe journal bearings. One of these tyes of bearings is the -lobe journal bearing with the ericycloid rofile ( wave bearing) [L., ] that is characterised by the continuous rofile of the bearing sleeve. An examle of the alication of such bearings is the bearing system of a grinder sindle. The oil film temerature distribution and its maximum value are very imortant bearing characteristics [L. 4 5]. An excessive temerature of oil film causes the degradation of lubricant and bearing material. igh temerature gradients may cause cracking and ratcheting, while unequal thermal growth of bearing comonents can cause the seiure of bearing material. The aer describes the theoretical and exerimental investigation into the oerating temeratures of the journal bearings suorting the sindle of grinding machine. The theoretical art includes the determination of oil film ressure, temerature, and viscosity distributions. These distributions were obtained from the solution of the Reynolds energy and viscosity equations. All calculations were carried-out on the assumtion of adiabatic, laminar oil film and the static equilibrium osition of journal. The develoed code of calculations uses the finite difference method [L., 5]. The exerimental art of the investigation consisted in the measurements of temeratures generated in the journal bearings of the grinder

3 -011 T R I B O L O G I A 159 sindle. The test rig was designed on the basis of a real bearing system [L. 4]. Each bearing of the sindle was equied in three doubled thermocoules laced in the centre of bearing lobes about 0. mm below their oerating surface. GEOMETRY OF OIL FILM The geometry of the oil film ga of ericycloid journal bearings (Fig. 1) is described by Equation (1) [L. 1 ]. Fig. 1. Geometry of -lobe journal bearings; a) geometry of the oil film of -lobe ericycloid and -lobe classic journal bearings; O b, O j, O L, R, r, R centres and radii of bearings, journal, the lobe of classic bearing and ericycloid bearing, s oil suly ressure, 1,, lobe number Rys. 1. Geometria łożysk śligowych wieloowierchniowych; łożysko -owierchniowe arysem erycykloidalnym i -owierchniowe symetrycne (klasycne); O b, O j, O L, R, r, R środki i romienie łożysk, coa, łożyska klasycnego i erycykloidalnego, s ciśnienie asilania olejem, 1,, numery segmentów = 1 ε cos( ϕ α) λ * (1 cos n ϕ) (1) where: ε relative eccentricity, ϕ eriheral co-ordinate, α attitude angle of centres line, λ * ericycloid eccentricity, n multily of ericycloid.

4 T R I B O L O G I A OIL FILM PRESSURE AND TEMPERATURE DISTRIBUTION The journal bearing erformances for the adiabatic model of oil film can be determined by the numerical solution of the oil film geometry, and Reynolds energy and viscosity equations. The oil film ressure distribution was defined from transformed Reynolds Equation () [L. ]. φ ϕ ϕ ϕ L D 1 6 = () where: D, L bearing diameter and length (m), = h/(r-r) dimensionless oil film thickness, h oil film thickness (µm), dimensionless oil film ressure, = ψ /( ω), oil film ressure (MPa), r, R journal and sleeve radius (m), ϕ, eriheral and dimensionless axial co-ordinates, φ dimensionless time, φ = ω t, t time (sec), ω angular velocity (sec -1 ), dimensionless viscosity, ψ bearing relative clearance, ψ = R/R ( ), R bearing clearance, R = R-r (m). It has been assumed for the ressure region that on the bearing edges and in the regions of negative ressures the oil film ressure (ϕ, ) = 0. The oil film ressure distribution comuted from Equation () was ut in the transformed energy Equation () [L. 4, 5]. L D T L D T T L D T Pe ϕ ϕ ϕ ϕ = = where: T dimensionless oil film temerature, Pe Peclet number. Oil film temerature and viscosity fields were obtained by numerical solving of Equation () and Equation (). The temerature T(ϕ, ) on the ()

5 -011 T R I B O L O G I A 161 bearing edges ( = ± 1 ) was comuted by the method of arabolic aroximation [L., 5]. The develoed rogram of numerical calculation [L. ] solves all the above-mentioned equations. RESULTS OF CALCULATIONS The calculations included the non-dimensional load caacity S 0 and journal dislacement ε, the static equilibrium osition angles α eq, and oil film ressure and temerature distributions. The assumed value of bearing length to diameter ratios was L/D = 1.0 at the bearing relative clearance ψ = 0.4 and the ericycloid relative eccentricity λ* = 0.5. Rotational seed of journal was n = 1500 rm. The temerature of feeding oil was equal to the ambient temerature T 0. Calculations of oil film ressure and temerature distributions were carried out for the range of relative eccentricities ε = 0.1 to ε = 0.8. It was assumed that the load is directed vertically between the lobes (Fig. lobe No. and ). Exemlary results of calculated oil film ressure and temerature distributions in ericycloid -lobe journal bearing are showed in Fig. at the determined value of relative eccentricity ε and the static equilibrium osition angle α eq. Fig.. Oil film ressure and temerature distribution in ericycloid -lobe journal bearing at determined value of static equilibrium osition angle α eq Rys.. Rokład ciśnienia i temeratury w filmie smarowym -owierchniowego śligowego łożyska erycykloidalnego dla ałożonej wartości kąta statycnego ołożenia równowagi α eq

6 16 T R I B O L O G I A -011 In case of the load alied between the lobes of bearing, the maximum oil film ressure and temerature occur on the lobe No. (Fig. ). On the lobe No. 1 and No., the temeratures have almost equal values (Fig. ). The considered case of calculation corresonds to the load and orientation of bearing A of the grinder sindle. EXPERIMENTAL INVESTIGATION INTO TE OIL FILM TEMPERATURE OF BEARING The scheme of side view of the grinder sindle is showed in Fig. and the layout of sindle with the bearings, and the osition of the rotor of electric motor shows Fig. 4 [L. 4]. Fig.. Side view of test rig; 1 casing, taer end of sindle, electric motor, 4, 5 journal bearings, 6, 7 rolling bearings Rys.. Widok bocny stanowiska; 1 korus, stożek wreciona, silnik elektrycny, 4, 5 łożyska śligowe, 6, 7 łożyska tocne The grinder sindle assembly (Fig. 5 and Fig. 6) was fixed to the frame made of heavy grey cast elements. The schemes of the ericycloid -lobe journal bearings of grinding sindle are showed in Fig. 8. Each bearing was equied in three doubled thermocoules NiCr-NiAl laced in the centre of bearing lobe about 0. mm below its surface (Fig. 7). Two additional thermocoules were alied for the measurements of temeratures of bearing casings. The bearings system was lubricated with the oil Velol 9 of the kinematic viscosity 9 11 mm /sec at 40ºC. The oil was sulied from the ressurised, central lubricating system (Fig. 5). The rotational seed of sindle was 1500 rm at the rated ower of electric motor 7.5 kw. The acquisition system that was couled with the

7 -011 T R I B O L O G I A 16 comuter has allowed for the continuous measurements of temeratures during the assumed eriod of time. The loading device (Fig. 6) has allowed for the vertical load in the uer direction by means of tightening the bolts that was fixed to the dynamometer [L. 4]. Fig. 4. Journal bearings system of the sindle of grinding machine; A, B ericycloid -lobe journal bearings, C axial ball bearing, D dee groove ball bearing, W rotor of electric motor, T grinding wheel Rys. 4. Układ łożysk śligowych wreciennika; b A, B -owierchniowe łożyska arysem erycyckloidalnym, C łożysko wdłużne, D łożysko kulkowe, W wirnik, T ściernica Fig. 5. Side view of the sindle assembly of grinding machine SPE-40; 1 casing, sindle, electric motor, 4 oil suly system, 5 control system Rys. 5. Widok bocny stanowiska badawcego temeratury racy łożysk wreciennika slifierki SPE-40; 1 korus, wreciono, silnik elektrycny, 4 układ asilania olejem, 5 układ sterowania

8 164 T R I B O L O G I A -011 Fig. 6. Face view of the sindle assembly with the loading device; 1 sindle, casing of ball bearing, dynamometer, 4 gri, 5 uer gri Rys. 6. Widok cołowy stanowiska układem obciążania łożysk wreciennika; 1 wreciono, obudowa łożyska tocnego, dynamometr, 4 uchwyt, 5 uchwyt górny The temerature measuring system consists of the following elements (Fig. 8): 1. Grinding sindle assembly JOTES. Card SENSOR SENSOR,. Notebook AMILO L100 Fujitsu-Siemens, 4. Thermocoules TP-0K CZAKI 5. Amlifiers modules of thermocoules of K tye SENSOR, 6. Measuring card DAQcard-604E National Instruments, 7. Program of measuring card NIDAQ740 National Instruments, 8. Program of data acquisition KSD-400 SENSOR.

9 -011 T R I B O L O G I A 165 Fig. 7. Arrangement of thermocoules in the ericycloid -lobe journal bearings of the sindle of grinding machine SPE-40 Rys. 7. Układ cujników temeratury w łożyskach -owierchniowych arysem erycykloidalnym wreciennika slifierki SPE-40 The series of the measurements consisting of 19 readings were made every seconds. In each series, the temerature measurement was made in 6 oints times. The results that are showed in Fig. 9 include 400 series of measurements Fig. 8. Layout of the temerature measuring system alied for the grinding sindle journal bearings Rys. 8. Układ omiarowy temeratury łożysk wreciennika Exemlary results of oerating temerature measurements are showed in Fig. 9. It results from Fig. 9 that the lowest temerature was registered on the lobe No. of A bearing and the highest on the lobe No. 5 of B bearing (Fig. 7).

10 166 T R I B O L O G I A -011 Fig. 9. Runs of temeratures measured on the oerating surfaces of the ericycloid -lobe journal bearings of grinding sindle SPE-40; thermocoule No. 7 casing of bearing A Rys. 9. Prebiegi temeratur mieronych na owierchniach robocych łożysk -owierchniowych arysem erycykloidalnym wreciennika SPE-40; cujnik temeratury nr 7 obudowa łożyska A FINAL REMARKS The aer summarises the results of the calculations and exerimental investigation of the oil film temeratures of ericycloid -lobe journal bearings that were alied in the real mechanical system of the grinding sindle. The calculated temeratures were obtained for a single bearing. In a real bearing system, the temeratures of oil film are affected by many factors, e.g., casing design, temerature of sulied oil and its ressure. owever, the results that were obtained from the theory and exeriment show the correct values on the bearing lobes. There is good agreement in, e.g. maximum oil film temeratures on the oerating lobes of bearings (Fig. and Fig. 9). In the steady-state conditions of grinder sindle oeration, the measured temeratures are in the range of 8 4ºC (Fig. 9), and they corresond to the calculated temeratures (Fig. ). Exerimental investigations certify the correct oeration of develoed code of calculations. Rewiever Jan SIKORA

11 -011 T R I B O L O G I A 167 Strescenie Wieloowierchniowe łożyska śligowe [L. 1 ], stosowane są w lekko obciążonych, wysokoobrotowych masynach wirnikowych. W raktyce stosowane są łożyska śligowe -owierchniowe erycykloidalnym arysem anewki (łożysko falowe wave ) [L., ]. Prykładem ich astosowania jest układ łożyskowania wreciennika slifierki lub łożyska satelitów rekładni lanetarnej [L. ]. W cęści teoretycnej wynacono rokłady ciśnienia i temeratury w filmie smarowym -owierchnowego łożyska arysem erycykloidalnym rowiąując równania Reynoldsa, energii i lekości środka smarowego. Oblicenia rerowadono metodą różnic skońconych [L. ] dla ryadku adiabatycnego filmu. W doświadcalnej cęści badań omierono temeratury na owierchniach robocych -owierchniowych łożysk arysem erycykloidalnym. Stanowisko badawce skonstruowano na baie recywistego układu łożysk śligowych [L. 4]. Każde łożysk śligowych wyosażono w try cujniki temeratury umiescone w środkowej łascyźnie łożyska w odległości około 0, mm od owierchni robocej anewki. Pomierone wartości temeratur orównano wartościami wynaconym teoretycnie.