Bearings

Details Bearings Bearings

1999-10-29

2001-08-28

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Plain bearing

C384S429000, C384S294000, C384S626000, C029S898047, C029S898070, C029S898090

Reexamination Certificate

active

06280091

ABSTRACT:

The present invention relates to half-shell bearings for internal combustion engines.
Half-shell sliding bearings generally employ a so-called “nick” or “notch” to provide axial location of the bearing shells in their housings, usually in either the connecting rod (conrod) housings and/or the main bearing housings, in the engine. The nick is a small portion of the bearing wall adjacent the joint face and either at one end face or intermediate the bearing end faces which is sheared and moved in a radially outwardly direction relative to the bearing circumference and which locates in a machined recess in the bearing housing. As mentioned above, the purpose of the nick is to provide accurate axial location of the bearing in its housing and, in some cases, to provide a fool-proof assembly method, for example to prevent a cap half-shell being fitted to the block and vice versa where the two half shells differ. The nick is not intended to prevent rotation of the bearing within the housing, rotation being prevented in most cases by the degree of interference between the bearing back and the housing.
However, it is becoming increasingly common for production engines to employ “nickless” bearings.
The absence of a nick presents problems in the case of racing engines. Racing engines operating at high rotational speeds suffer from distortion of the housing due to the high loads generated and in this instance the nick not only provides axial location but also does provide some measure of resistance to circumferential movement of the bearing shells relative to their housing. Racing engine designers are not therefore, prepared to use nickless bearings in racing engines. In some racing applications bearings employing two nicks are used.
Where rotation of the bearing has been experienced, fracture of the nick portion can occur and there is a case for nicks having an increased projected area to resist rotational force to be used, however, for manufacturing reasons this is rarely possible.
There are however disadvantages in having a nick in the bearing and these disadvantages are accentuated in the case of racing engines.
Firstly, the recess in the bearing bore due to the nick can cause breakdown of the hydrodynamic oil film which, in any case, is frequently significantly thinner than on normal production engines.
Secondly, the presence of the nick disrupts the bearing joint face and therefore causes a localised region of poor clamping between the bearing halves with a consequential reduction in contact pressure on the bearing back in this area.
Thirdly, the recess required in the bearing housing to accommodate the nick can act as a stress raiser and cracking in this region between the recess and the bolt hole is not unknown. Again, this particular problem is exacerbated in racing engines due to the greater stresses involved.
Thus, it is an object of the present invention to provide a bearing or a bearing and housing assembly wherein the bearing has greater resistance to rotation relative to its housing whilst not incurring the above mentioned disadvantages of nicks.
According to a first aspect of the present invention, there is provided a combination of a bearing and a housing for the bearing, the bearing comprising two substantially semi-cylindrical half bearings each retained in a corresponding housing part about a joint face split-line wherein the housing has at least one circumferential locking plate inserted in said joint face split-line, said at least one circumferential locking plate extending radially inwardly to lie between opposed joint faces of the two bearing halves.
In one embodiment of the combination of bearing and housing according to the present invention the at least one circumferential locking plate would extend over the housing joint face area and have a hole therein for the retaining bolt to pass therethrough.
The bearing and housing assembly may have a locking plate on one half of the joint face or there may be a locking plate on both sides of the joint face split line about the bearing axis.
A dowel may also be provided in the joint face region to prevent angular displacement of the circumferential locking plate about the retaining bolt and ensure the face of the circumferential locking plate between the bearing joint faces remains substantially parallel to the bearing axis.
The thickness of the circumferential locking plate may be accommodated in several different ways.
The joint faces of the housing may be machined to accommodate the thickness of the circumferential locking plate and to ensure that the bore of the retained half-bearings remains truly circular. The bearing joint faces also require machining in a corresponding manner.
In a first alternative method the housing parts and bearings may be used in their “standard” form except for being provided with a thicker layer of bearing material which is bored after assembly of the bearings into the housing with the circumferential locking plates in place. Such boring may take account of the need to provide a so-called overlay coating by electroplating, for example, after boring.
In a second alternative method the housing may be bored with “false” circumferential locking plates in place at the joint faces to produce a circular bore and assembled using standard bearings inserted with new circumferential locking plates extending into the joint face region between the bearings although the bearing is manufactured to suit a slightly smaller diameter than the sing bore, the free-spread of the bearing (that excess diameter of the bearing over and above the housing diameter when the bearing is free-standing outside the housing) would enable the bearing to be used. Alternatively, bearings having increased free-spread may be manufactured.
Clearly, in all alternatives, the shaft journal diameter would be made to suit the actual bearing bore.
The circumferential locking plates may be provided with bearing material applied to their end faces which face the co-operating shaft journal in use. In order that the present invention may be more fully understood, examples will now be described by way of illustration only with reference to the accompanying drawings, of which:
FIG. 1
shows a perspective view of a conventional half-bearing shell;
FIG. 2
shows a schematic end view of a bearing and bearing housing according to a first embodiment of the present invention;
FIG. 3
shows a housing of a combination according to a second embodiment of the present invention; and
FIG. 4
which shows a third embodiment of a bearing and housing according to the present invention.


REFERENCES:
patent: 949910 (1910-02-01), Perkins
patent: 1391886 (1921-09-01), Fritz
patent: 1453518 (1923-01-01), Price
patent: 1561745 (1925-11-01), Redfield
patent: 1635753 (1927-07-01), Johnson
patent: 1736998 (1929-11-01), Darrach, Jr.
patent: 2082944 (1937-06-01), Evans
patent: 2720794 (1955-10-01), Morris
patent: 3071419 (1963-01-01), Lower et al.
patent: 4270813 (1981-06-01), Wiggins
patent: 19501999 (1995-01-01), None
patent: 956845 (1963-04-01), None
patent: 1016913 (1966-01-01), None
patent: 1025669 (1966-04-01), None
patent: 1462261 (1977-01-01), None
patent: 2157779A (1985-10-01), None
International Search Report for Application No. EP 999307961.5-2309-dated Oct.19,200.
English Abstract from Derwent for DE 19501999.

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