Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-04-20
2001-05-08
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S430000
Reexamination Certificate
active
06227709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a bearing shell with at least one retaining cam, which comprises an outer contour which is rectangular when the partial surface of the bearing shell is viewed from above and an indentation on the inside of the bearing shell. The invention also relates to a method of producing cams in bearing shells by pressing outwards into a rectangular die a small portion of the bearing shell wall in the area of the partial surface.
2. Description of Related Art
Retaining cams on bearings shells have the task of easing installation of the bearing shell, by defining the installation position in the bearing housing in cooperation with a recess provided therein. When the partial surface
2
of the bearing shell
1
is viewed from above, such retaining cams
3
, known for example from DE-AS 1477052, comprise, as shown in
FIG. 1
, a rectangular outer contour and a rectangular inner contour. The retaining cam
3
is provided so as to position itself in the milled-out portion
5
on insertion into the bore in the bearing housing
4
. In the region of the retaining cam
3
, the partial surface
2
then lies in the plane of the partial surface
6
of the bearing housing and then rests against the closed parting plane of the second housing half. This not only results in fixing of the installation position but also in the prevention of rotation of the bearing shell within the housing bore during operation.
The retaining cams
3
may be beaten by means of a blade or, as described in DE-AS 1477052, produced in the gap in a roll pair. However, a disadvantage of all known retaining cams is the small transition area
7
a,b
between the cam
3
and the adjacent bearing wall. The transition area should be understood to mean the area between the base
8
a,b
of the cam and the indentation
9
. In general, the material of the bearing shell is torn or even sheared off in this area, such that material detachment may occur there during operation. To prevent this, in many instances the inside of the bearing shell is adjusted by milling in the area of the indentation
9
. In the case of heavily loaded bearings, the cam may possibly tear away under the action of the forces and vibrations arising during operation owing to the only slight connection with the rest of the bearing shell in the upper area.
It has therefore already been proposed to provide pin-shaped elevations in the bearing housing, which engage in corresponding bores in the bearing shell. This is described, for example, in the Clevite brochure “Mechanics Engine Bearing Reference Manual, First Edition, 1954”. This solution is only possible, however, with bearing housings which have a suitably thick wall.
U.S. Pat. No. 2,124,060 discloses a retaining cam with round inner and outer contour, which projects only slightly outwards, however, such that it cannot adequately fulfill its function as a rotation prevention device. In the production of round cams which do project sufficiently far outwards, it has been found that the nominal width, which is predetermined by the milled-out portion in the bearing housing, cannot be maintained because of gentle transition areas. It is thus impossible to locate the bearing shell cleanly against the housing and position and fix it with axial precision.
These disadvantages may be prevented if the cam is produced only in the area of the bearing backing, in order thereby not to damage the running surface. DE 3230700 C2 discloses so-called upset cams, wherein, by the exertion of pressure directed perpendicularly at a radially outer, axially defined area of the partial surface and with appropriate bracing at the bearing inner surface, material is displaced radially outwards. Between the indentation arising through material displacement and the inner surface there remains a supporting strip of material. This method may, however, only be used with thick bearing shells with wall thicknesses >2 mm.
Since developments in engine construction are moving in the direction of thinner walled, i.e. lighter, bearing housings and also of thinner bearing shells, which additionally are exposed to ever higher loads, for instance speeds of up to 17000 rpm in racing, alternatives to the known solutions are being sought.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a bearing shell whose retaining cams exhibit greater stability. Another object of the invention is to provide a method by which retaining cams may be produced which are more stable and which may possibly, for instance depending on the flow behaviour of the composite bearing material used, obviate the need for further processing of the inside of the bearing shell.
This object is achieved with a bearing shell according to claim
1
. The production method constitutes the subject matter of claim
7
. Advantageous embodiments are described in the subclaims.
The invention comprises combining a rectangular outer contour of the cam with an inner contour which, in contrast to the prior art, is not similarly rectangular, but rather follows such a course that the indentation is at its greatest in the centre of the cam. A contour shape is preferred, in which the indentation increases continuously in degree from the edge to the center M of the cam.
The rectangular outer contour has the advantage that existing dies may be used for production and in particular that the sufficiently large locating surface of the cam ensures clean axial positioning and fixing in the bearing housing as well as, in special cases such as racing engines, the prevention of rotation. The inner contour according to the invention ensures that a large and in particular undamaged transition area is present which guarantees stability of the cam even under heavy loading. The depth of the indentation in the center of the cam may be greater than is the case with conventional cams, which is not disadvantageous, however, insofar as the loading of the cam is at its greatest not in the center but in the edge area, where a correspondingly large transition area remains. This embodiment of the retaining cam is thus also possible in particular in the case of thin bearing shells with a wall thickness amounting to <2 mm.
The indentation preferably increases continuously from its edge to the center of the cam. The indentation may in principle have any contour, for example it may even be triangular. However, a round, advantageously arcuate, contour is preferred.
The indentation may also comprise a round portion and straight lateral portions. The lateral portions do not in this instance extend over half the bearing shell wall thickness, such that a sufficiently large transition area remains.
The width B
v
of the indentation preferably corresponds approximately to the width B
n
of the cam.
The method of producing retaining cams provides for the production of an indentation, by outwards pressing, which is greatest in the area of the center of the cam. The material displacement is thus at its slightest in the edge area of the indentation, such that the retaining cam cannot tear away. Detachment of the bearing material thus does not occur at all or occurs only to a limited degree, depending on the flow behaviour of the composite bearing material used, such that further processing, i.e. milling out and removal of the bearing material, is unnecessary. This method is gentle on the material while at the same time a stable cam is produced which withstands heavy loads when in operation.
The outwards pressing is preferably effected by means of a round blade.
The indentation may be beaten or embossed.
REFERENCES:
patent: 2124060 (1938-07-01), Gilman
patent: 3576353 (1971-04-01), Barker et al.
patent: 4845817 (1989-07-01), Wilgus
patent: 5727885 (1998-03-01), Ono et al.
patent: 3230700 (1984-03-01), None
patent: 1477052 (1984-03-01), None
Lehmann Uwe
Lill Michael
Glyco-Metall-Werke Glyco B.V. & Co. KG
Hannon Thomas R.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
LandOfFree
Bearing shell with retaining cam and method for production... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bearing shell with retaining cam and method for production..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bearing shell with retaining cam and method for production... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2490540