1、 Reference number ISO/TR 27507:2010(E) ISO 2010TECHNICAL REPORT ISO/TR 27507 First edition 2010-07-15 Plain bearings Recommendations for automotive crankshaft bearing environments Paliers lisses Recommendations pour les environnements des paliers de vilebrequins pour automobiles ISO/TR 27507:2010(E)
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5、IGHT PROTECTED DOCUMENT ISO 2010 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below
6、or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2010 All rights reservedISO/TR 27507:2010(E) ISO 2010 All rights reserved i
7、iiContents Page Foreword iv Introduction.v 1 Scope1 2 Crankshafts1 2.1 Surface finish.1 2.2 Grinding1 2.3 Journal diameter tolerance.2 2.4 Diametral tolerance for taper, hourglass and barrel shape 2 2.5 Axial contour irregularities.2 2.6 Ovality or roundness.3 2.7 Lobing and chatter 3 2.8 Squareness
8、 of thrust faces 4 2.9 Shaft alignment4 2.10 Shaft bow4 3 Housings 5 3.1 General .5 3.2 Surface finish.5 3.3 Bore diameter tolerance .5 3.4 Diametral tolerance for taper, hourglass and barrel shape 5 3.5 Ovality or roundness.5 3.6 Main bearing bore alignment .6 3.7 Rod bore alignment.6 3.8 Lubricant
9、 hole alignment6 3.9 Location of housing caps.6 4 Conclusion .6 ISO/TR 27507:2010(E) iv ISO 2010 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standa
10、rds is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also tak
11、e part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is
12、 to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In exceptional circumstances, when a
13、 technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informa
14、tive in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or al
15、l such patent rights. ISO/TR 27507 was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 3, Dimensions, tolerances and construction details. ISO/TR 27507:2010(E) ISO 2010 All rights reserved vIntroduction The successful functioning of thin-walled crankshaft bearings for aut
16、omotive engines depends on numerous parameters. For an initial appraisal, it is necessary to consider those parameters producing the basic operational conditions of the bearings, i.e. principally those of load and lubricant film thickness. Technology has progressed and computer techniques have been
17、developed which enable these variables to be calculated to a sufficiently accurate degree such that comparative assessments can be made, enabling the bearing designer to predict, in general terms, the potential performance of crankshaft bearings. Unfortunately, the bearing designer has no knowledge
18、of how meticulously the engine will be built, how contaminated the lubricant will be, how much distortion will take place in the associated components, or of any of a number of other conditions which are each influential in their effect on the bearings performance. The influences of these “subsidiar
19、y” parameters are, furthermore, unquantifiable in general terms since their effect depends largely on the prevailing operating conditions, i.e. the magnitude of the load and the thickness of the lubricant film. For example an engine with very low loads and very thick lubricant films is able to accep
20、t greater misalignment (of its crankshaft) without sustaining edge loading fatigue or local surface wiping, than an engine where loads and films are critical. It is, therefore, impossible to write a list of recommendations or environmental conditions which serve as a general specification. Strictly
21、speaking, it is necessary for each case to be considered individually with reference to the loading and lubrication characteristics which are peculiar to that engines design. However, the bearing designer is very often asked for an opinion on the bearing environment and for advice on the limits and
22、deviations from perfect which can be tolerated in associated components. In such cases, the bearing designer calls upon the experience of what has produced satisfactory operation in the past and, of necessity, compromises with what is reasonably achievable in terms of production methods. The trend o
23、ver the past few years for engine operating conditions to become more and more arduous has resulted in the crankshaft bearing conditions becoming more critical, and accordingly, it is often necessary to incorporate associated components of greater accuracy than previously used. However, as rates of
24、mass production of engine components tend to increase, economically, it is not simple to improve the quality of components in an attempt to meet the more critical bearing conditions. In fact, there is a tendency for some manufacturers to look for a relaxation of tolerances to ease production difficu
25、lties. The recommendations in this Technical Report are made in an attempt to detail the various dimensions and conditions that most engine manufacturers can achieve with current production machinery in order to produce crankshaft bearing environments, which generally do not themselves lead to beari
26、ng problems. For the reasons outlined above some recommendations might not be adequate for certain applications where design specifications can require greater precision components of high quality. It is the responsibility of the user to have discussions with the supplier, who might be able to link
27、more closely the environmental conditions with the bearing performance characteristics. TECHNICAL REPORT ISO/TR 27507:2010(E) ISO 2010 All rights reserved 1Plain bearings Recommendations for automotive crankshaft bearing environments 1 Scope This Technical Report gives recommendations for automotive
28、 crankshaft bearing environments. It specifies the various dimensions and conditions that most engine manufacturers can achieve with current production machinery in order to produce crankshaft bearing environments, which, generally, do not lead to bearing problems. It is possible that some recommend
29、ations in this Technical Report are not adequate for certain applications where design specifications can require greater precision components of high quality. 2 Crankshafts 2.1 Surface finish Clearly the rougher the surface of the shaft, the greater will be the disruptive effect on the lubricant fi
30、lm with the likelihood of asperity contact, and accordingly the higher the wear rate. Indeed a pour surface finish may reduce the lubricant film thickness to the extent where overheating and even seizure occurs. Normally crankpins and journals should be no rougher than 0,25 m Ra. Thrust faces should
31、 never be rougher than 0,4 m Ra but experience and testing has shown that the load that can be carried by a thrust washer is inversely proportional to the surface finish value of the mating surface, and it may therefore be necessary to finish a thrust cheek to a very much lower figure than 0,4 m Ra.
32、 2.2 Grinding During the grinding of modular cast iron shafts, graphite nodules are exposed to, and removed from, the material surface with “filaments” or “tongues” of the iron matrix material formed at these sites. These “filaments” embed into the bearing alloy during operation and cause severe wea
33、r and damage after only a short period. It is normal practice therefore to polish the crankshaft subsequent to grinding in order to remove these protruding “tongues” of material. Their orientation on the shaft surface depends upon the direction of rotation during the grinding and polishing operation
34、s. It is important that the “filaments” lie (i.e. point) in the opposite direction to shaft rotation during operation in order to minimise their effect on the bearing performance. Tests indicated that the optimum procedure for the finishing of modular cast iron shafts is to grind with the crankshaft
35、 rotating in the same direction of rotation as in service, followed by polishing in this same direction of rotation. In practice a number of engine manufacturers grind with the reverse direction of rotation to that recommended and then polish in the opposite (i.e. “recommended”) direction. Experienc
36、e has shown that control of the polishing operation is important and that both insufficient and excessive polishing can be detrimental to the bearing performance. The object of the polishing operation is to remove the “filaments” produced during grinding without generating further “filaments” by exp
37、osing significant further graphite to the shaft surface. ISO/TR 27507:2010(E) 2 ISO 2010 All rights reserved2.3 Journal diameter tolerance Tighter tolerances are easier to hold on a journal than in the bore, so the greater share of bearing clearance control falls on the journal tolerance. For journa
38、ls up to 75 mm the recommended diametral tolerance is 13 m. For larger journals a tolerance of 25 m is acceptable. For tighter control of the bearing clearance range, decrease the journal diameter tolerance. 2.4 Diametral tolerance for taper, hourglass and barrel shape The limits tabulated below app
39、ly to both connecting rod and main bearing journals. In addition, axial waviness should be held within 2,5 m peak to valley. As with the housing bore, in a very heavily loaded application with short bearings there is virtually no tolerance for profile variations (see Figure 1). taper hourglass barre
40、l Figure 1 Shaft shape of the journal Table 1 Diameter tolerance Bearing length Medium duty diametral tolerance Heavy duty diametral tolerance up to 25 mm 5 m 2,5 m 25 to 50 mm 10 m 5 m over 50 mm 12,5 m 7,5 m 2.5 Axial contour irregularities Irregularities in axial profile which follow no clear pat
41、tern will also produce uneven loading along the bearing. In such cases it is not possible to specify limits for such irregularities since they are likely to be very inconsistent and will need to be investigated by profile measurement. Axial contour deviations which are circumferentially consistent a
42、re less likely to cause damage than those which are inconsistent from one part of the shaft circumference to another, but this is dependent on the severity of the defect (see Figure 2). Waviness Figure 2 Waviness ISO/TR 27507:2010(E) ISO 2010 All rights reserved 32.6 Ovality or roundness If a cranks
43、haft has running surfaces of an oval form there will be an effect on the hydrodynamic wedge action of the oil film and some reduction of minimum film thickness is likely. Roundness is more critical for the journal than the bore because to some extent bearing break-in will compensate for the defect i
44、s in the bore geometry, whereas significant journal wear is usually pined by catastrophic failure. Recommended limits for journal out- of round are given in Table 2 (see Figure 3). Table 2 Ovality Journal diameter Medium duty diametral O-O-R limit Heavy duty diametral O-O-R limit up to 75 mm 12,5 m
45、5 m 75 to 125 mm 12,5 m 7,5 m over 125 mm 25 m 10 m O-O-R = Out of round Polygon Figure 3 Roundness 2.7 Lobing and chatter Journal lobing and chatter are also out of round conditions. A lobe protrudes from the running surface, and with its tight radius, acts as an lubricant scraper. Lobing can cause
46、 a disruption to the generated lubricant films and produce high bearing wear rates or in severe cases, seizure. As the number of lobes increases, so does the curvature difference and the frequency of passage. Chatter is high frequency lobbing (see Figure 4). Chatter Figure 4 Chatter ISO/TR 27507:201
47、0(E) 4 ISO 2010 All rights reservedRecommendations for the limit of these surface inaccuracies are shown in Figure 5. This gives a maximum allowable radial peak to valley height or amplitude, against the number of lobes. Amplitude (Yj) um Lobing/Chatter Graph Frequency (Xj) Amplitude (Y) 360 Order W
48、here J = Series order from 2 to 100 Formula for limiting amplitude: () 5 . 0 6 . 1 50 Yj 5 . 2 + + = XjFigure 5 Lobing and chatter graph for main and pin journals in circumferential direction 2.8 Squareness of thrust faces Out of squareness of the thrust collar with the journal will result in uneven
49、 wear of the thrust bearing surface and run-out of thrust faces should not exceed 0,3 m per mm diameter of thrust face. 2.9 Shaft alignment As for main bearing bores, overall misalignment should be held to 50 m for moderate loads and 25 m for heavy applications. The maximum allowable misalignment for adjacent journals is 25 m. On a crankshaft, crankpin and main journals should be parallel within 12,5 m for heavy duty units. Thrust faces should be flat and square (or perpendicular) to the main journal axi
