ISO/TR 27507:2010
(Main)Plain bearings — Recommendations for automotive crankshaft bearing environments
Plain bearings — Recommendations for automotive crankshaft bearing environments
ISO/TR 27507:2010 gives recommendations for automotive 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.
Paliers lisses — Recommendations pour les environnements des paliers de vilebrequins pour automobiles
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 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
Reference number
ISO/TR 27507:2010(E)
©
ISO 2010
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ISO/TR 27507:2010(E)
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ii © ISO 2010 – All rights reserved
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ISO/TR 27507:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Crankshafts.1
2.1 Surface finish.1
2.2 Grinding.1
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 of thrust faces .4
2.9 Shaft alignment.4
2.10 Shaft bow.4
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 hole alignment.6
3.9 Location of housing caps.6
4 Conclusion .6
© ISO 2010 – All rights reserved iii
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ISO/TR 27507:2010(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards 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 take 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 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 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
informative 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 all such patent rights.
ISO/TR 27507 was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 3,
Dimensions, tolerances and construction details.
iv © ISO 2010 – All rights reserved
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ISO/TR 27507:2010(E)
Introduction
The successful functioning of thin-walled crankshaft bearings for automotive 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 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 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
“subsidiary” 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 accept 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 speaking, it is necessary for each case to be considered individually with
reference to the loading and lubrication characteristics which are peculiar to that engine's design.
However, the bearing designer is very often asked for an opinion on the bearing environment and for advice
on the limits and 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 over 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 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 difficulties.
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 bearing 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 more closely
the environmental conditions with the bearing performance characteristics.
© ISO 2010 – All rights reserved v
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TECHNICAL REPORT ISO/TR 27507:2010(E)
Plain bearings — Recommendations for automotive crankshaft
bearing environments
1 Scope
This Technical Report gives recommendations for automotive 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 recommendations 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 film 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.
Normal
...
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