GB2524490A

GB2524490A - Bearing shell

Info

Publication number: GB2524490A
Application number: GB1405188.2A
Authority: GB
Inventors: Hervã Galand
Original assignee: Mahle International GmbH; Mahle Composants Moteur France SAS; Mahle Engine Systems UK Ltd
Current assignee: Mahle International GmbH; Mahle Composants Moteur France SAS; Mahle Engine Systems UK Ltd
Priority date: 2014-03-24
Filing date: 2014-03-24
Publication date: 2015-09-30
Anticipated expiration: 2034-03-24
Also published as: GB2524490B; GB201405188D0

Abstract

A bearing shell 100 having a concave bearing surface 108 and a convex outer surface, opposed axial end faces 110A, 110B and joint faces 120. The shell comprises an oil distribution groove 116A in the concave bearing surface that has a first groove portion 116A that extends along the bearing surface along a medial plane M that is substantially parallel with and equidistant from the axial end faces. An oil supply hole (112 fig. 1B) extends between the outer and inner surface and connects to the first groove portion to provide fluid communication with an oil supply channel in a housing that is offset so it is centred closer to one axial end face than the other. The oil supply hole can be a circular hole with a radius of curvature where the centre of curvature is spaced apart from the medial plane by at least the radius of curvature. The distribution groove can comprise a second groove portion 116B connecting the oil supply hole and the first groove portion. The second groove can be axially excursive and the distribution groove can have a substantially uniform cross-sectional area.

Description

BEARING SHELL

FIELD OF INVENTION

The present invention relates to bearing shells for sliding bearings having both an oil supply hole and an oil distribution groove, to which the oil supply hole is coupled, and in particular to bearing shells for use in bearing assemblies and bush assemblies of internal combustion engines.

BACKGROUND

In typical internal combustion engines, pairs of hollow semi-cylindrical bearing shells (also known as "half bearings") are used as linings in a housing to support rotation of the crankshaft in both main bearing assemblies and connecting rod bearing assemblies. Main bearing assemblies are provided where the engine block and engine cap form a housing to support the main (axial) crankshaft journal. Connecting rod bearing assemblies are provided at the "big end" of a connecting rod, where it connects onto a crankshaft pin.

In use, the bearing assemblies are lubricated with oil. Commonly, in modern engines, the lubricating oil is fed to the bearing clearance of each of the main bearing assemblies through oil supply channels in the engine block or engine cap (collectively forming the housing of the main bearing assembly, and being fed from an oil gallery manifold). The engine block and engine cap form a housing for each main engine bearing assembly, which has a pair of bearing shells, with an oil supply channel coupled to an oil supply hole extending through a bearing shell and connecting to an oil distribution groove. In a pair of bearing shells in a bearing assembly, the oil supply hole and oil distribution groove are typically provided in an unloaded bearing shell, and most commonly in main engine bearing assemblies.

The oil distribution groove extends circumferentially around the concave bearing surface of the bearing shell. Although the oil distribution groove enhances the circumferential distribution of oil around the bearing assembly, the axial width of the oil distribution groove is restricted, to maximise the surface area across which the load to the bearing shell is distributed.

Channels, known as "drillings", typically run through the crankshaft of modern engines, extending between drilling ports in the respective journal surfaces, to conduct lubricating oil from bearing clearances in main engine bearing assemblies to the bearing clearances in other bearing assemblies downstream (e.g. connecting rod bearing assemblies). The oil distribution groove also enhances oil flow between the bearing clearance and any associated crankshaft drilling.

In normal operation, commencing shortly after starting the engine, the crankshaft journal and bearing shell are spaced apart by a high pressure, wedge-shaped cushion-like film of oil, which is drawn between them, in a condition known as "hydrodynamic lubrication".

However, the bearing shell risks becoming damaged by high peak loads and low oil film thickness (e.g. due to low oil viscosity through excessive oil temperature or oil degradation).

Accordingly, the performance of the bearing shell is highly sensitive to oil flow through the bearing clearance, which is affected by the design of the concave bearing surface of the bearing shell.

The bearing shell provides a pattern of oil flow in the bearing clearance of each bearing assembly that is substantially axially symmetrical (i.e. symmetrical about a plane parallel with, and equidistant between, the axial end faces), by the symmetrical location of each oil supply channel, oil supply hole, oil distribution groove and (any associated) crankshaft drilling hole midway between the axial end faces of the corresponding bearing shell. The axially symmetric oil flow minimizes the risk of preference towards the oil starvation in either axial end of each bearing assembly, which could otherwise result in direct physical contact between the crankshaft journal and the bearing shell through failure of the intervening oil film, leading to increased rates of abrasion and heating of the bearing shell, in use, which can lead to seizure. W02012069192A1 illustrates an exemplary bearing shell having an oil supply hole and an groove that are each located midway between the axial end faces of the bearing shell, with the oil distribution groove extending between the opposed joint faces, and parallel with the axial end faces, in an arrangement that is mirror symmetric about a plane perpendicular to the axis of the rotation of the associated journal, in use.

Bearing bushes are hollow cylindrical bearing liners, that may be solid sleeve bushes, split bushes (in which a strip is formed into a cylinder with butt-jointed ends) or clinch bushes (like split bushes, additionally provided with mutual engagement features on the ends of the strip). Bearing bushes are used at the small end of the connecting rod, to connect onto the piston pin (also known as a gudgeon pin or wrist pin), and may be used elsewhere in an engine.

SUMMARY OF THE DISCLOSURE

According to a first aspect, there is provided a bearing shell having a concave bearing surface and a convex outer surface, opposed axial end faces and joint faces, comprising: an oil distribution groove in the concave bearing surface, having a first groove portion that extends along the bearing surface along a medial plane substantially parallel with and equidistant between the axial end faces, and an oil supply hole extending between the convex outer surface and the concave bearing surface and connecting to the first groove portion, wherein the oil supply hole is configured to provide fluid communication with an oil supply channel in a housing that is centred closer to one axial end face than the other axial end face.

According to a second aspect, there is provided a blank configured to form a bearing shell according to the first aspect.

According to a third aspect, there is provided an internal combustion engine comprising a bearing assembly having a bearing shell according to the first aspect.

The oil supply hole may comprise a curved portion having a centre of curvature that is closer to one axial end face than the other.

The curved portion may have a radius of curvature, and the centre of curvature may be spaced apart from the medial plane by at least the radius of curvature. The curved portion may have a radius of curvature, and the centre of curvature may be spaced apart from the medial plane by at least twice the radius of curvature. The centre of curvature may be spaced apart from the medial plane by at least 5% of the axial width of the bearing shell.

The oil supply hole may be a circular hole located closer to one axial end face than to the other axial end face.

The oil distribution groove may comprise a second groove portion, which connects between the oil supply hole and the first groove portion, and the second groove portion extends transversely to the medial plane. The second groove portion may extend perpendicular to the medial plane. The second groove portion may extend non-perpendicularly to the medial plane.

The second groove portion may be an excursive second groove portion, and each end of the second groove portion connects to the first groove portion. The excursive second groove portion follows a path that deviates axially away from the medial plane, intermediate the ends of the second groove portion.

The second groove portion may comprise a pair of groove portions dividing from a common connection to the first groove portion.

The oil distribution groove may have a substantially uniform cross-sectional area along the length of the oil distribution groove.

The oil supply hole may be an elongate hole with a direction of elongation transverse to the medial plane. The direction of elongation of the oil supply hole may be perpendicular to the medial plane.

The bearing shell may comprise a plurality of oil supply holes. The bearing shell may comprise one, two or four oil supply holes.

The oil supply holes may each be closer to a common axial end face than to the other axial end face.

The bearing shell is configured to cooperate with a journal rotating about a journal axis, and the bearing shell may be two-fold rotationally symmetric about a rotational symmetry axis that is perpendicular to the journal axis (i.e. the bearing shell may appear identical when rotated by 1800).

The bearing shell may be hollow substantially semi-cylindrical, e.g. of the type commonly used in main engine bearing assemblies and connecting rod bearing assemblies. The bearing shell may be hollow substantially cylindrical, e.g. of the type commonly used in bearing bushes.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: * Figure 1A shows a perspective view of a bearing shell having an oil supply hole, and an oil distribution groove having a circumferential portion and a transverse, spur-like groove portion; * Figure lB shows a plan viewofa blankforforming the bearing shell of Figure 1A; * Figure 2 shows a plan view of a blank for forming a bearing shell having two oil supply holes, and an oil distribution groove having a circumferential portion and two transverse, spur-like groove portions; * Figure 3 shows a plan view of a blank for forming a bearing shell having two oil supply holes, and an oil distribution groove having a circumferential portion connecting with two excursive groove portions; * Figure 4 shows a plan view of a blank for forming a bearing shell having four oil supply holes, and an oil distribution groove having a circumferential portion connecting with two pairs of excursive groove portions; and * Figure 5 shows a plan view of a blank for forming a bearing shell having two slot-like oil supply holes connecting with a circumferential oil distribution groove.

DETAILED DESCRIPTION

In the described embodiments, like features have been identified with like numerals, albeit in some cases having one or more of increments of integer multiples of 100; and suffix letters.

For example, in different figures, 100', 200', 300', 400' and 500' indicate a blank for forming a bearing shell.

Figure 1A schematically illustrates a bearing shell 100 (e.g. a bearing shell in a main engine bearing) for lining a bearing housing in a bearing assembly with a shaft. The bearing shell 100' is in the form of a hollow semi-cylindrical bearing shell, which is also commonly referred to as a "half bearing". Figure 1 B schematically illustrates a plan view of a flat blank 100' from which the semi-cylindrical bearing shell 100 is formed, by being deformed into a substantially semi-cylindrical shape.

The bearing shell 100 typically comprises coatings on the concave inner surface of a backing. In an exemplary embodiment, the bearing shell 100 has a substrate comprising a strong steel backing 102 and a bearing lining layer 104 (e.g. an aluminium-tin alloy layer) on the concave inner surface of the backing. An optional "overlay" layer 106 (e.g. a plastic polymer-based composite layer of a plastic polymer matrix with particulate distributed throughout the matrix) is provided on the lining layer 104. The overlay layer 106 is configured to provide a bearing surface 108 (i.e. the running surface) over the lifetime of the bearing shell 100. The overlay layer 106 is the innermost layer of the bearing shell 100, which is configured to face a cooperating moving part in a bearing assembly (e.g. the overlay layer receives a journaled shaft in an assembled bearing, which mutually cooperate, with an intervening film of lubricating oil).

M indicates a medial plane that is parallel with, and equidistant between, the axial end faces 11 OA and 11DB of the bearing shell 100 (and the corresponding flat blank 100').

An oil supply hole 112 extends through the bearing shell 100, and has a centre of curvature o to one side of the medial plane M, being closer to a first axial end face 11OA than the second axial end face 11DB. The oil supply hole is asymmetrically positioned to couple with a correspondingly positioned outlet (indicated in Figure lB by broken circle 114) of an oil supply channel that supplies lubricating oil through the associated bearing housing, when the formed semi-cylindrical bearing shell is in use. The centre C of the oil supply hole 112 may be spaced apart from the medial plane M by at least 5% of the axial width of the bearing shell, or by a distance that is greater than the radius of curvature of the oil supply hole.

The oil supply hole 112 may be provided in either a loaded or an unloaded bearing shell 100, in an unequally loaded bearing assembly. The oil supply hole 112 may be provided in a region of the bearing shell 100 away from where peak loads typically occur, for example being provided ahead of where the peak loads occur, with respect to the rotation of a joumal, which draws oil around the bearing shell.

An oil distribution groove 116 extends across the concave bearing surface 108 of the bearing shell 100, and comprises first and second groove portions 116A and 1168. The first groove portion liSA extends substantially circumferentially (in the formed, semi-cylindrical bearing shell 100) around the bearing surface 108 towards the joint faces 120 (which are joined with a further semi-cylindrical bearing shell, in use, to form a hollow cylindrical lining to the housing of a bearing assembly), and is equidistant between the axial end faces 11 OA and 11DB (i.e. the mid-line of the first groove portion 116A extends substantially coplanar with the medial plane M). The second groove portion 1 16B provides a spur extending transversely to the medial plane M, and connecting between the first groove portion 116A and the asymmetrically located oil supply hole 112.

Bearing shells according to the present invention provide an oil supply hole that is configured, in use with a mating housing, to couple with an oil supply channel that is located closer to one axial end face of the bearing shell than the other axial end face, whilst maintaining an oil distribution groove portion that is substantially symmetrically located between the axial end faces. This enables the use of established engine blocks and engine caps, in which the housings for the engine main bearing assemblies have been modified to increase their axial width, by extension at one axial end, without the need to modify the established locations of the oil supply channels, and whilst maintaining a generally symmetrical distribution of oil through the bearing clearance between the bearing shell and a journal, in use. Accordingly, this enables existing engine designs to be modified to increase the surface area across which the loads are distributed in bearing assemblies.

In the illustrated embodiment, the second groove portion 1 16B is shown extending axially (i.e. perpendicular to the medial plane M, in the formed semi-cylindrical bearing shell).

However, alternatively, the spur-like second groove portion 116B may extend both axially and circumferentially (i.e. at a non-perpendicular angle to the medial plane M, in the formed semi-cylindrical bearing shell). Advantageously, a non-perpendicular connection between the second groove portion and the first groove portion may enhance the flow of oil from the oil supply hole 112 to the circumferential first groove portion liSA, in particular where the corresponding bearing shell is used with a journal that rotates exclusively or predominantly in only one direction. Advantageously, an enhanced supply of lubricating oil provides superior cooling of the bearing shell, resulting in lower temperature operation of the corresponding bearing assembly and lubricating oil, increasing the durability of the bearing shell, as well as increasing the lifespans of both the bearing shell and the lubricating oil.

Figure 2 illustrates a flat blank 200' for forming a semi-cylindrical bearing shell, which differs from the bearing shell 100 and blank 100' of Figures 1A and lB by providing two spur-like second groove portions 216B extending transversely to the medial plane M, and connecting between the first groove portion 216A and two asymmetrically located oil supply holes 212.

The oil supply holes 212 are located closer to different axial end faces 210A and 210B and joint faces 220, in an arrangement that is two-fold rotationally symmetric when rotated 1800 about a rotational symmetry axis perpendicular to the centre Z of the bearing shell blank 200', which is the midpoint of the crown of the bearing shell (i.e. the rotational symmetry axis is perpendicular to the journal axis, about which a cooperating journal rotates, in use).

Advantageously, providing a bearing shell (or a blank for forming a bearing shell) having an arrangement of oil supply holes that is two-fold rotationally symmetric about the midpoint of the crown of the bearing enables the bearing shell to be fitted into a housing with an asymmetric oil supply channel in either of the two possible rotational orientations.

Figure 3 illustrates a flat blank 300' for forming a semi-cylindrical bearing shell that has an oil distribution groove 316 having a first groove portion 316A extending circumferentially (in the formed semi-cylindrical bearing shell) and being equidistant between the axial end faces 310A and 310B, and excursive second groove portions 316B, which deviate axially away from the medial plane M, to connect oil supply holes 312 to the first groove portion. The excursive second groove portions 316B deviate axially away from the medial plane M, and each end connects with the first groove portion 316A. The oil supply holes 312 are each located closer to one axial end face 31 OA and 31DB than the other axial end face.

Figure 4 illustrates a flat blank 400' for forming a semi-cylindrical bearing shell, which differs from the blank 300' of Figure 3 by having four excursive groove portions arranged as two pairs of excursive second groove portions 416B1 and 416B2, in which one of each pair is closer to one axial end face 410A and the other of each pair is closer to the other axial end face 41DB.

In the embodiments of Figures 3 and 4, the excursive second groove portions are illustrated extending both axially and circumferentially (i.e. not perpendicular to the medial plane M), which may advantageously enhance oil flow from the oil supply holes to the circumferential first groove portion. At each end, the excursive second groove portions are illustrated connecting with the first groove portion, which may advantageously enhance oil flow along the length of each second groove portion, in use.

The cross-sectional area may be substantially constant along the length of the oil distribution groove. So, in the case of an oil distribution groove that is undivided along its length, e.g. Figure 3, the first and second groove portions 316A and 316B may have substantially equal cross-sectional areas perpendicular to their length (i.e. along lines Xl and X2). In the case of an oil distribution groove that divides into a plurality of minor grooves, e.g. Figure 4, the cross-sectional area of the first groove portion 416A (i.e. along line Yl) may be substantially equal to the sum of the cross-sectional areas of the pairs of excursive second groove portions 416B1 and 416B2 (i.e. along line Y2). Advantageously, a substantially constant cross-sectional area may enhance oil flow through the oil distribution groove. Further, a bearing shell having a substantially constant cross-sectional area may be particularly suitable for manufacturing by an embossing process, such that any axial deformation of the bearing shell blank during the embossing process is substantially uniform, along the circumferential length of the bearing shell, thereby providing a manufacturing process and mating with the corresponding bearing assembly housing that are more accurately controllable.

Figure 5 illustrates a flat blank 500' for forming a semi-cylindrical bearing shell that has an oil distribution groove 516 that extends circumferentially (in the formed semi-cylindrical bearing shell) and is equidistant between the axial end faces 510A and 5103, and oil supply holes 512 that are transversely elongate (e.g. slot-like) that intersect the oil distribution groove.

The oil supply holes 512 have a direction of elongation that is transverse to the medial plane M, e.g. the elongation is perpendicular to the medial plane M in the illustrated embodiment.

The curved ends 512E of the supply holes 512 each have a respective centre of curvature C that is located to one side of the medial plane M, being closer to one axial end face 510A and SlOB than the other axial end face.

Advantageously, as with the asymmetrically located oil supply holes in Figure 1A to 4, the transversely elongate oil supply holes 512 in the embodiment of Figure 5 are each shaped to couple with an asymmetrically positioned outlet (indicated by broken circle 514) of an oil supply channel that supplies lubricating oil through the associated bearing housing, when the formed semi-cylindrical bearing shell is in use.

The embodiments of bearing shells and blanks for bearing shells illustrated in the Figures show bearing shells and blanks for bearing shells having one, two or four oil supply holes connected to a circumferential portion of an oil distribution groove that is equidistant between the opposed axial end faces. However, blanks and corresponding bearing shells according to the present invention are not limited to these combinations of oil supply holes, and may each have one or a plurality of oil supply holes.

In Figures 2 and 3, a plurality of oil supply holes have been illustrated in arrangements that are two-fold rotationally symmetric, but not mirror symmetric. In use with a housing in which the oil supply channel(s) are all closer to one axial end face than the other, redundant oil supply holes may introduce unnecessary, small perturbations into the oil flow across the bearing surface and within the bearing clearance.

Alternatively, the oil supply holes may all be provided on the same side of the medial plane M, which may enable the corresponding bearing shell to couple to a greater number of housing oil supply channels, in the case of a bearing housing having more than one oil supply channel, which are each closer to a common axial end face (e.g. where a symmetric bearing assembly has been axially extended on one side). Advantageously, providing oil supply holes only in locations corresponding with oil supply channels through the bearing assembly housing may reduce turbulence in the oil flow within the bearing clearance, enhancing oil flow and reducing drag on the corresponding, rotating journal.

In exemplary bearing shells having axial widths up to 150mm, circumferential oil distribution grooves are provided having maximal widths (adjacent the bearing surface) of 0.5 to 10mm, with groove sides that slope at an angle of at least 45°, relative to the bearing surface. The depth to the bottom of the oil distribution groove (e.g., as opposed to the variable depth of the sides of the groove, which may be non-perpendicular to the bearing surface) may be approximately 0.5mm, and the thickness (radially) of the bearing at the bottom of the groove may be at least 0.5mm.

In the illustrated embodiment, the oil distribution grooves extend all the way around the concave inner bearing surface of the bearing shell or flat blank for a bearing shell, between the joint faces. Alternatively, the oil distribution groove may extend only part way around the bearing surface, for example stopping shod of one or each joint face by up to 60°.

The Figures illustrate hollow substantially semi-cylindrical bearing shells and corresponding blanks. However, the present invention can also be applied to hollow substantially cylindrical bearing shells (e.g. bearing bushes) provided with an oil supply hole and an oil distribution groove.

The figures provided herein are schematic and not to scale.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS1. A shell having a concave bearing surface and a convex outer surface, opposed axial end faces and joint faces, comprising: an oil distribution groove in the concave bearing surface, having a first groove portion that extends along the bearing surface along a medial plane substantially parallel with and equidistant between the axial end faces, and an oil supply hole extending between the convex outer surface and the concave bearing surface and connecting to the first groove portion, wherein the oil supply hole is configured to provide fluid communication with an oil supply channel in a housing that is centred closer to one axial end face than the other axial end face.
2. A bearing shell according to claim 1, wherein the oil supply hole comprises a curved portion having a centre of curvature that is closer to one axial end face than the other.
3. A bearing shell according to claim 2, wherein the curved portion has a radius of curvature, and the centre of curvature is spaced apart from the central plane by at least the radius of curvature.
4. A bearing shell according to any one of claims 1, 2 or 3, wherein the oil supply hole is a circular hole located closer to one axial end face than to the other axial end face.
5. A bearing shell according to any preceding claim, wherein the oil distribution groove comprises a second groove portion, which connects between the oil supply hole and the first groove portion, and the second groove portion extends transversely to the medial plane.
6. A bearing shell according to claim 5, wherein the second groove portion is an axially excursive second groove portion, and each end of the second groove portion connects to the first groove portion.
7. A bearing shell according to claim 6, wherein the second groove portion comprises a pair of groove portions dividing from a common connection to the first groove portion.
8. A bearing shell according to any preceding claim, wherein the oil distribution groove has a substantially uniform cross-sectional area along the length of the oil distribution groove.
9. A bearing shell according to any one of claims 1 to 3, wherein the oil supply hole is an elongate hole with a direction of elongation transverse to the medial plane.
10. A bearing shell according to any preceding claim, wherein the bearing shell comprises a plurality of oil supply holes.
11. A bearing shell according to claim 10, wherein the oil supply holes are each closer to a common axial end face than to the other axial end face.
12. A bearing shell according to any one of claims 1 to 10, wherein the bearing shell is configured to cooperate with a journal rotating about a journal axis, and the bearing shell is two-fold rotationally symmetric about a rotational symmetry axis that is perpendicular to the journal axis.
13. A blank configured to form a bearing shell according to any preceding claim.
14. An internal combustion engine comprising a bearing assembly having a bearing shell according to any one of claims ito 12.
15. A bearing shell substantially as hereinbefore described with reference to theaccompanying description and the Figures.
16. A blank configured to form a bearing shell substantially as hereinbefore described with reference to the accompanying description and the Figures.
17. An internal combustion engine comprising a bearing shell substantially as hereinbefore described with reference to the accompanying description and the Figures.