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Optymalizacja charakterystyk zawieszeń i sterowania samochodu przednionapędowego w celu szybszego pokonania łuku drogi

Maniowski M.

Czasopismo Techniczne. Mechanika

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2012

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R. 109, z. 5-M

35--50

PL

Artykuł dotyczy zwiększania osiągów samochodów przystosowywanych do sportu poprzez optymalizację charakterystyk elementów sprężystych i tłumiących w zawieszeniach kół. Parametry te są zwykle dobierane najczęściej metodami prób i błędów. W celu przyspieszenia tego procesu zastosowano wielokryterialną optymalizację modelu symulacyjnego samochodu, o 26 współrzędnych stanu i kilkuset parametrach, opartą na algorytmach ewolucyjnych. Wektor zmiennych decyzyjnych o 31 składowych zawiera także parametry odpowiedzialne za sterowanie kierowcy. Przykład numeryczny dotyczy wyścigowego przejazdu odcinka drogi asfaltowej typu prosta–łuk–prosta samochodem Ford Focus ST170. Przedstawiono możliwości poprawienia osiągów układu samochód-kierowca w pierwszej, najtrudniejszej fazie manewru.

EN

Paper deals with increasing of sports car performance through optimization of spring and damper modules in car suspensions. Typically, these parameters are chosen based on many road test with trial and error methods. In order to fasten this process a multi-criteria optimization algorithm is applied to a virtual car with 26 state variables and hundreds of parameters. The design vector includes also parameters responsible for the driver actions. Numerical example considers extreme negotiation of a corner with Ford Focus ST170. Performance enhancements the of car-driver system are described for turn-in phase.

2

Wpływ mikrogeometrii na parametry pracy łożysk stożkowych

Raczyński A.

Tribologia

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2000

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nr 1

90-110

PL

W artykule przedstawiono badanie wpływu korekcji i geometrii styku na biezni pomocniczej łożyska stożkowego na tarcie i naciski kontaktowe przy różnej makrogeometrii i różnych obciążeniach. Metoda obliczeń jest opisana w poprzednim artykule autora. Charakterystyki momentu tarcia i nacisków kontaktowych służą określeniu optymalnych wartości parametrów mikrogeometrycznych. Są przedstawione zależności tych optymalnych parametrów od makrogeometrii łożyska. Podane zalecenia mogą być bezpośrednio wykorzystane do projektowania kształtu powierzchni roboczych łożyska stożkowego, charakteryzującego się zmniejszonymi oporami ruchu i większą prędkością graniczną.

EN

The following work represents the continuation of the former articles written by the same author: "Purposes and Possibilities of the Use of Correction in Roller Bearings" and "The Method of Analysis of Pressures and Friction in Roller Bearings from the Aspect of the Contact Correction". .In order to do research work on the influence of microgeometrical dimensions (beta,hi, ho, hw, delta, Rk) on friction lisses and contact pressure the author worked out the computer programme based on method shown in (L.6). In the programme, equations of equilibrium are solved first, then running parameters are calculated (primarily the moment of friction of a bearing and contact pressures) for given bearing dimensions and axial load Fa. The choice of correction of main bearing races and main surface of roller. Research was carried out for ten bearing sizes. For each size, 306 correction combinations were determined. For each combination calculations in the range of angle beta from (βn - 4') to (βn + 4') ware made to obtain the smallest moment M(T) value. Relative load was assumed at P/C =0,35 level. In all series with a contact angle α less then 17° the smallest values of M(T) are achieved at the correction system that is hi=hw>0 ho=0. Only in the 313 series (α=28°48'39") the smallest values of M(T) are achieved at the correction system: hi=hw>0, ho(…)2hi.The proper correction value depends and its dimensional proportions. Therefore, the choice of correction value was solved by means of non-dimensional method for fictitious bearings with different macrogeometry. The results of these calculations are illustrated in DRAWING 4. The characteristics of the most favourable correction values depending on bearing macrogeometry is shown in DRAWING 5. The choice of angle β. Drawing 6 present an example of characteristics of a moment of friction for a certain macrogeometrical case. The most favourable value β is about 1°59'55". Taking working tolerance into consideration, it was assumed that the tolerance range of angle β should lie between -4" and +26". As result of the calculations of the friction moment for other variants of macrogeometry, depedence of recommended angle β deviations on quotient Lw/Dw was determined, which is shown in DRAWING 7. The choice of angle δ an radius Rk. The studies of the influence of these parameters on pressure in a roller 's contact with a side flange and on the friction moment of a bearing were jointly conducted by means of a non-dimensional method. One of the resultant diagrams is demonstrated in DRAWING 8. On exceeding a certain value of Rk the moment of friction rapidly rises as a result of extension of the contact area, which starts on the edge of the roller end. This causes an increase in friction force and makes the formation of an oil film difficult. The successive curves attributed to the increasing values of an angle δ are displaced downwards and to the left. The value of the angle is compromising due to the friction and contact pressures and it is enclosed in the range of 89°40'÷89°45'. The minimum moment of friction occurs at Rk=0,95÷0,96 value. Owing to the analogus calculations made for others macrogeometrical variants, the dependence of the most favoruable values δ and Rk on macrogeometry parameters was obtained. It is shown in DRAWING 10 in a form of diagrams. At the end an example of the correction choice is presented. On comparing the results with the recommendation stated in work (L.2), it was assumed that there was a little difference between them. On the other hand, using the above described method one can divide the recommended in (L.2) sum of correction between a bearing roller and bearing rings.

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Korekcja styku wałeczków i bieżni łożysk baryłkowych poprzecznych

Raczyński A.

Tribologia

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2000

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nr 6

1009-1125

PL

W artykule jest przedstawione badanie wpływu korekcji styku na bieżniach głównych łożyska baryłkowego na tarcie i naciski kontaktowe przy różnych obciążeniach i dwóch różnych rodzajach korekcji. Metoda obliczeń jest opisana w jednym z poprzednich artykułów autora. Uzyskane charakterystyki momentu tarcia i nacisków kontaktowych służą do określenia optymalnych wartości parametrów mikrogeometrycznych. Zaprezentowana na jednym przykładzie metoda postępowania może być zastosowana do konstruowania dowolnego łożyska baryłkowego dwurzędowego. Analiaza wyników obliczeń wykazała, że przy obciążeniach małych i średnich (P/C<0,2) wystarcza zastosowanie jednołukowej korekcji wałeczków. Przy większych obciążeniach pożądana jest korekcja dwułukowa ze względu na spiętrzenia nacisków kontaktowych.

EN

The present article is the fourth of a series by this author concerning the microgeometry of roller bearings.published in "Tribology". The previous had the following titles "Purpose and possibilities of the use of correction in roller bearings" ,"The Method of analysis of pressures and friction in roller bearings in aspect of contact correction" and "The effect of microgeometry on running parameters of taper roller bearings". In order to investigate the effect of the microgeometrical dimensions of the spherical roller bearings on power losses and contact pressures, the author has written a special computer program. It is base on the methodology presented in paper(L11). In the program, equations of balance are solved first. Then, contact pressures the skew of the roller and the moment of frictionof the bearing for the pre-set dimensions and load are computed. One significant checking parameter is the roller skew self-stabilisation angle.Its absolute value shows whether the roller presses against the side flange during the rolling(L8). The operation of a bearing is considered correct if the rollers are in the state of self-stabilisation without any contact with the side flange (L.3). In such a case, the microgeometry of the spherical roller bearing resolves itself to the form of adhesion of the roller profile to the inner and outer ring profile. This form results from the correction of an appropriate contact. In practice, two kinds of correction of spherical roller bearings are possible (FIG.1a) and two-arc correction (FIG. 1b). In the analyses made so far, the attention was paid only to the importance of correction for the uniform distribution of pressures in the contact, and not to the resistance to motion of the bearing. The aim of the calculations presented herein is to investigate the effect of the spherical roller bearing microgeometry on the contact capacity and the resistance to motion. These properties of the bearings are practically defined by two parameters: the maximum contact pressures and the moment of friction. The sample calculations refer to one type bearing only, namely 22316. Two levels of the relative load of the bearing was assumed P/C=0.1 (average load) and P/C = 0.35 (large load).The calculation results are presented in the form of graphs which show the characteristics of the greatest unit pressures at the contact of the roller and the rings p(max.w) and p (max.z) as a function of the radius R(BW), the characteristics of the self-stabilisation angle Θ 0 for the loaded rollers and the characteristics of the moment of friction of the bearing. Owing to these graphs the most favourable values of R(BW) can be selected; the minimum of the moment of friction and the smallest values of pressures should be aimed at; at the same time, the self-stabilisation angles Θ 0 of the loaded rollers should be kept within -0.006rad - +0.006rad. An analysis of the results of the computer computations has shown that spherical roller bearings with the rollers made without two-arc correction can be satisfactority used under small and medium loads (P/C<0.2). By using the selected dimensions R(B) and R(BW),the concentraction of stresses can be avoided and a satisfactory compromise beteween the minimisation of the resistance to motion and the minimisation of contact stresses achieved. If the relative load of the bearing is geater than 0.2, the concentration of stresses is formed, first of all at the contact of the roller and the outer ring (due to the greater adhesion coefficient). In this situation, the correction of the rollers is necessary. Analyses have proved that the two-arc correction of the parameters conformant with the results of the work is effective (L.7). The same radii, R(B) and R(BW), which turned out to be the most favourable in the case of the roller made without two-arc correction can be used here as the main radii of the lateral generatrix of the roller and the race of the outer ring. The method of finding the most favourable dimensions of the bearing of reference number 22316 can be used for any type and size of a spherical roller bearing. Thus, it is a practical method for the engineering shaping of the working surfaces of double -row spherical roller bearings.

4

Cele i mozliwości stosowania korekcji w łożyskach wałeczkowatych

Raczyński A.

Tribologia

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1999

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nr 1

55-70

PL

Korekcja wałeczków i bieżni pierścieni łożysk wałeczkowych jest od dawna stosowana w celu wyrównania nacisków kontaktowych. Mniej są znane inne możliwości, jakie może dać korekcja. Poprzez korekcję bieżni głównych i wałeczków można wpływać na rozkład prędkości ślizgania. w efekcie można wywołać taki moment sil stycznych. że wspomaga on właściwe toczenie wałeczków po bieżniach. W kontakcie wałeczków z bieżnia pomocniczą dzięki korekcji czoła wałeczka i tej bieżni można osiągnąć hydrodynamiczny film olejowy i w rezultacie tarcie płynne. Tak więc dzięki korekcji można zmniejszyć prace tarcia w łożysku.

EN

It is well-known that the distribution of contact pressures is improved by the correction of working surfaces of roller bearings, since edge concentrations of these pressures are reduced. However, there are various kinds of correction of different degrees of manufacturing difficulties and different effects. Arc correction, chord correction and logarithmic correction with modification are most frequently used. In the paper, comparisons of the three correction types taken from the literature are quoted. In the comparisons different loads of contact and the tilt of the roller with respect to the raceway axis that can occur in practice have been taken into consideration. The diagram of the ,,contact load capacity" proves that logarithmic correction with modification generally gives the best effects. The second purpose of using correction is to reduce the friction work at the contact of the rollers with the side flange. Correction of this contact can consist in: - deflecting the generatrix of the side flange from the roller end plane, - replacing the flat roller end with the convex end, - introducing a convex generatrix of the side flange. In the article different forms of corrected contact have been analysed (basing on the figures given) and their advantages in the aspect of the formation of fluid friction on the roller end have been shown. The best conditions for the formation of an hydrodynamic oil film occur when the convex roller end and the side flange of the slightly tilted generatrix are combined. This is the case of a small sensitivity to the manufacturing errors and load changes. The possibility of the easy formation of an oil film has been assessed on the grounds of the shape of the bearing interspace and the rate of the lubricant inflow to the contact area. The third aim of using correction is the possibility to modify the moments of tangent forces acting upon the roller from the side of raceway of the inner and outer ring. This refers to bearings of the tilted axis of the rollers in relation to the bearing axis, since the correction of these raceways and the correction of the lateral surface of the roller affects the contact length, the distribution of the rubbing speed and the distribution of unitary tangent forces. By modifying moments of tangent forces one can control the tendency of the roller to skew and there by affect friction work in the bearing. In barrel bearings a reduction in the tendency to skew results in the so called self-stabilisation of the roller, i.e. the loss of the pressure force between the roller and the side flange. The preservation of such a state during operation of the bearing greatly decreases friction work. In cone bearings there is a tendency of the roller to skew, caused by the friction force on the side flange. The moments of friction deliberately generated and determined by the correction on the main raceways can compensate this tendency. This also results in a decrease in the total friction work. However, in order to achieve this goal a certain perturbation of the kinematic conformity in the cone bearing is necessary. In view of the purposes being so different, it is not easy to select the proper magnitude of correction. A certain compromise is necessary and it is for the designer of the bearing to decide about it.