ISO TR 17606-2014 Plain bearings - Lubrication characteristics of crosshead pin bearings for low-speed marine diesel engines《滑动轴承 船用低速柴油发动机十字头销轴承的润滑特性》.pdf

1、 ISO 2014 Plain bearings Lubrication characteristics of crosshead pin bearings for low-speed marine diesel engines Paliers lisses Caractristiques de lubrification des paliers de crosse pour moteurs diesels marins vitesse faible TECHNICAL REPORT ISO/TR 17606 First edition 2014-06-15 Reference number

2、ISO/TR 17606:2014(E) ISO/TR 17606:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2014 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photoco

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4、7 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ISO/TR 17606:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Crosshead pin bearing and its symbols 1 3 Oil supply method on bearing sliding surfaces 3 4 Shape of a bearing . 3 4.1 Beari

5、ng inside diameter, bearing width, height, circumferential groove, and an upper bearing . 3 4.2 Wall thickness of a bearing and shape of its bore . 4 4.3 Oil supply Lubrication characteristics . 5 Bibliography 8 ISO/TR 17606:2014(E) Foreword ISO (the International Organization for Standardization) i

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12、lain bearings, Subcommittee SC 7, Special types of plain bearings.iv ISO 2014 All rights reserved ISO/TR 17606:2014(E) Introduction For crosshead pin bearings, with which a shaft oscillates when a load is applied mainly in a downward direction, it is difficult to generate an appropriate lubricating

13、film; therefore, they are subject to unfavourable lubricating conditions. For better lubrication of crosshead pin bearings, which have a high rate of damage, two types of bearing structures are mainly used as oil supply methods for sliding surfaces at present. The characteristics of those bearings a

14、re compared and the concept of design approaches is standardized. ISO 2014 All rights reserved v Plain bearings Lubrication characteristics of crosshead pin bearings for low-speed marine diesel engines 1 Scope This Technical Report specifies lubrication characteristics of grooves and pockets on cros

15、shead pin bearings for low-speed marine diesel engines. It is applicable to the design of axial oil groove and pocket types as an oil supply method. 2 Crosshead pin bearing and its symbols The crosshead pin bearing and changes in specific load and angular velocity during one cycle are schematically

16、illustrated in Figures 1 and 2. Table 1 shows the symbols and their descriptions. Figure 1 Crosshead pin bearing TECHNICAL REPORT ISO/TR 17606:2014(E) ISO 2014 All rights reserved 1 ISO/TR 17606:2014(E) 0 Figure 2 Changes in specific load and angular velocity during one cycle Table 1 Symbols and the

17、ir descriptions Symbol Description e eccentricity hmin minimum oil film thickness l subtended taper length L axial width O b center of bearing O j center of journal p oil film pressure P1 pad 1 P2 pad 2 P3 pad 3 P rspecific load r shaft radius F bearing load circumferential pitch angle circumferenti

18、al width angle taper depth oscillation angle attitude angle circumferential angular coordinate 2 1 effective angular extent of bearing arc angular velocity2 ISO 2014 All rights reserved ISO/TR 17606:2014(E) 3 Oil supply method on bearing sliding surfaces There are two oil supply methods. One is for

19、bearings with a few (normally four) axial grooves. Oil is supplied to the sliding surface at normal pressure through these oil grooves. The other is for bearings with two oil pockets symmetrically located relative to the central part of each bearing. Oil is supplied to the oil pockets at high pressu

20、re to provide a hydrostatic bearing mechanism (see Figure 3). Figure 3 Bearings with axial grooves and oil pockets 4 Shape of a bearing 4.1 Bearing inside diameter, bearing width, height, circumferential groove, and an up- per bearing The diameter of a crosshead pin is set by consideration of streng

21、th design taking into account such as cylinder bore diameter and explosion pressure. The inside diameter of the bearing is based on the diameter of its crosshead pin. The bearing width is set within the allowable specific pressure range for its bearing material in consideration of the durability and

22、 strength of the material. Normally, single wide (integral structure) bearings are commonly used with respect to each cylinder. Some bearings may be axially divided into two parts for the reason of production of their bearing materials. The height of the bearing should be set to ensure adequate inte

23、rference fit. The height measurement method is the same as for smaller sized half-bearings. The crosshead housing can be checked for deformation due to the tightening of the bearing by conducting an assembly test using a housing (it might affect bearing clearance). In the case of a bearing with more

24、 than one axial groove, it may be provided with a circumferential groove around (part of) the entire circumference. The upper bearing on the unloaded side is provided with a relatively wide opening to allow the crosshead pin, which is connected to a piston rod, and the crosshead pin bearing to oscil

25、late relative to each other. ISO 2014 All rights reserved 3 ISO/TR 17606:2014(E) 4.2 Wall thickness of a bearing and shape of its bore The wall thickness of a bearing is set in consideration of its bore clearance. 4.2.1 Influence of the clearance ratio on the minimum oil film thickness The clearance

26、 ratio is the value of the radial clearance divided by the bearing radius. If the clearance ratio is too low, it has a small wedge effect; it tends to have a relatively small oil film thickness. Conversely, if the clearance ratio is gradually increased, it has a larger wedge effect; it tends to have

27、 a larger oil film thickness until the clearance ratio is around 0,000 5. However, if the clearance ratio is too high, oil film pressure is concentrated on the central part of the bearing, resulting in severer lubricating condition; it tends to have a very small oil film thickness. 4.2.2 Influence o

28、f the clearance ratio on the maximum oil film pressure If the clearance ratio becomes higher, the bearing load is concentrated on the central pad on the loaded side and there is an increase in the maximum oil film pressure as a result. If the clearance ratio becomes lower, the bearing load tends to

29、be distributed to some pads on the loaded side and there is a decrease in the maximum oil film pressure as a result (see Figure 4). a) Distribution of oil film pressure with high clearance ratio b) Distribution of oil film pressure with low clearance ratio Figure 4 Distributions of oil film pressure

30、 4.2.3 Guideline for bearing design In consideration of the effects of a clearance ratio on its maximum oil film pressure and minimum oil film thickness, the maximum oil film pressure could be decreased by using a concept of contact arc with a clearance ratio of zero (see Figure 5). When there is a

31、decrease in the minimum oil film thickness as a result of the clearance ratio in the vicinity of zero, the wedge effect could be improved by providing 4 ISO 2014 All rights reserved ISO/TR 17606:2014(E) the small and appropriate taper on both ends of the axial oil grooves to increase the minimum oil

32、 film thickness. a) Normal circular bearing with a middle clear- ance ratio b) Contact arc (120) with a clearance ratio of zero Figure 5 Normal circular bearing with a middle clearance ratio and contact arc with a clearance ratio of zero 4.3 Oil supply Lubrication characteristics 4.3.1 Axial oil gro

33、oves 4.3.1.1 Influence of oil groove pitch angle and design standards It is necessary to ensure satisfactory oil film formation by making the oil grooves circumferential pitch angle, , smaller than the crosshead pins oscillation angle, . In recent years, attempts have been made to decrease the maxim

34、um oil film pressure at the central pad by widening its circumferential angle range allowing for tendency to increase bearing loads. 4.3.1.2 Cross-sectional shape of an oil groove The cross-sectional shape of a standard oil groove is semicircular. Oil grooves either with the same cross-sectional sha

35、pe along the axial direction or with chamfers (bleed groove) at the axial ends of the groove for supplying an appropriate amount of oil to sliding surfaces are commonly used. Both types produce a cooling effect from the introduction of fresh oil through the oil grooves see Figures 6 a) and b). 4.3.1

36、.3 Effectiveness of tapered oil grooves If the clearance ratio becomes lower, the maximum oil film pressure is decreased and the bearing load tends to be distributed to some pads on the loaded side, and there is a decrease in the wedge effect; it might become difficult to maintain an appropriate min

37、imum oil film thickness. By providing the small and appropriate taper on both ends of the axial oil grooves, the wedge effect could be improved to ISO 2014 All rights reserved 5 ISO/TR 17606:2014(E) increase the minimum oil film thickness. As a result, the disadvantage of having a smaller wedge effe

38、ct due to a decreased bearing clearance would be offset to some extent by such tapers at both ends of the oil grooves see Figure 6 (c). Figure 6 Cross-sections of 3 types of oil grooves 4.3.2 Oil pocket 4.3.2.1 Influence of oil supply pressure with hydrostatic crosshead pin bearings The load capabil

39、ity of a bearing is increased by supplying oil to its oil pocket at high pressure due to the recovery of oil film thickness near the bottom dead centre of the piston. However, a high-pressure oil supply mechanism is needed, resulting in increased production costs. 4.3.2.2 Influence of area of oil po

40、cket For the area of the oil pocket, its axial length L and circumferential width angle, , should be set correctly in consideration of the bearings load capability. The larger the axial length L, the higher the static pressure. On the other hand, if the circumferential width angle, , becomes too lar

41、ge, there is little increase in the static pressure acting in vertical directions, which are effective in lifting the crosshead pin; conversely, the load capability could become lower. 4.3.2.3 Influence of pitch angle of oil pocket The pitch angle, , should be set correctly in consideration of the b

42、earings load capability. There is an increase in the area of the central part of the bearing, which facilitates squeeze action, by increasing the oil pockets pitch angle, . However, if the pitch angle, , becomes too large, there is little increase in the 6 ISO 2014 All rights reserved ISO/TR 17606:2

43、014(E) static pressure acting in vertical directions, which are effective in lifting the crosshead pin; conversely, the load capability could become lower. In the case of a hydrostatic crosshead pin bearing, the oil film thickness is recovered near the bottom dead centre of the piston and the oil fi

44、lm thickness is satisfactorily maintained on the sliding surface of the bearing. Thus, it is not necessary to make the circumferential pitch angle, , smaller than the crosshead pins oscillation angle, . As a result, the central part of the bearing has a large area to facilitate squeeze action. ISO 2

45、014 All rights reserved 7 ISO/TR 17606:2014(E) Bibliography 1 ISO 4381, Plain bearings Tin casting alloys for multilayer plain bearings 2 ISO 4383, Plain bearings Multilayer materials for thin-walled plain bearings 3 Kitahara T., & Nakahara D. Accurate Measurement of Oil Film Thickness Using LIF Method to Improve Load Carrying Capacity of Crosshead Bearings. 25th CIMAC Paper, Vienna, No.42, 2007, pp. 1-148 ISO 2014 All rights reserved ISO/TR 17606:2014(E) ISO 2014 All rights reserved ICS 21.100.10 Price based on 8 pages