Journal bearing

Abstract: A journal bearing for internal combustion engines having a semi-cylindrical bearing shell (20) with an inwardly facing bearing surface (30), adapted to surround a journal, and which is preferably divided circumferentially into a concentric central portion (32) and a pair of eccentric end portions (36). The eccentric end portions extend outwardly from the opposite ends (40) of the concentric central portion a progressively increasing distance to the outer ends (42) of the bearing shell to form a split line relief portion. An eccentric lubricant supply groove (44) is formed in the inwardly facing bearing surface tapering from a point of maximum depth at the central portion of the bearing shell to terminate within each of the eccentric end portions thereby forming lubricant metering orifices (48) at the interface of the concentric central portion, the eccentric end portions and the eccentric lubricant supply groove to control the flow of lubricant to the split line and reduce the pressure loss through the journal bearing.

Description: The present invention relates to a journal bearing for an internal combustion engine and, more particularly, to a journal bearing having an eccentric lubricant supply groove which meters the flow of lubricant through the journal bearing. Typical internal combustion engines utilize journal bearings to mount the crankshaft in the block and to secure the connecting rods to the crank pin journals. The journal bearings typically comprise a pair of semicircular or semi-cylindrical inserts or bearing shells which are retained in a cylindrical bore in the connecting rod or block, wherein half of the bore is formed by a removable cap provided to permit assembly of the journal and the bearing shells within the bore. Recesses formed at the split line between the two semicircular inserts are provided to prevent excessive wear or failure of the insert caused by "close-in" or slight misalignment of the shells during assembly. Without such split line recess, the reduction in bearing clearance at the split line may result in excessive wear or failure of the insert. Also typical of journal bearings used in internal combustion engines, is the provision of a lubricant supply groove formed in the upper bearing shell which is connected, through a lubricant supply passage, to the oil gallery of the engine. The lubricant supply groove assures an adequate supply of oil to establish a lubricating film between the journal and the inner face of the bearing shell. The lubricant supply groove will typically extend along the entire inner circumference of the bearing shell resulting in a substantial flow path of lubricant to the split line and a correspondingly substantial oil pressure penalty which affects the engine's entire lubricating system. Such an arrangement is disclosed in US Patent No. 3,743,367. A journal bearing in accordance with the present invention is characterised by the features specified in the characterising portion of Claim 1. In a preferred embodiment in accordance with the present invention, a journal bearing for use in an internal combustion engine is disclosed. The journal bearing supports a rotatable journal within a cylindrical opening which is defined by a pair of semicircular or semi-cylindrical bearing shells which are maintained in endwise abutment at a split line. The inwardly facing bearing surfaces of the bearing shells are adapted to surround the supported journal in a close fitting bearing relationship with clearance provided therebetween for a load carrying lubricating oil film. The inwardly facing bearing surface of at least one bearing shell is divided circumferentially into a concentric central portion, which is equidistant at all points from the central axis of the journal bearing and which extends circumferentially for a predetermined angular distance, and a pair of eccentric end portions which extend outwardly from the opposite ends of the central portion and which provide a progressively increasing clearance between the supported journal and the inwardly facing bearing surface from the ends of the central portion to the outer ends of the bearing shell. To assure a supply of lubricant adequate to establish the desired load carrying lubricating oil film between the journal and the journal bearing a circumferentially extending lubricant supply groove is formed in the inwardly facing bearing surface. The lubricant supply groove is centred on an axis eccentric from the central axis of the journal bearing, causing the lubricant supply groove to taper from a point of maximum depth at the centre of the bearing shell to terminate within each of the eccentric end portions intermediate the ends of the concentric central portion and the outer ends of the shell. As a result, lubricant metering orifices are formed at the interface of the concentric central portion, the eccentric end portions, and the eccentric lubricant supply groove to control or meter the flow of lubricant from the lubricant supply groove to the split line thereby reducing the pressure loss within the oil gallery of the engine. The volume of lubricant flowing through the journal bearing depends upon the predetermined angular dimensions of the concentric central portion and the lubricant supply groove. By varying these dimensions the flow characteristics can be tailored to the specific engine application. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a sectional view of a crankshaft journal and its associated journal bearing embodying the present invention; Figure 2 is a perspective view of a bearing shell embodying the present invention; Figure 3 is a plan view of the bearing shell of Figure 2, showing the inner bearing surface; Figure 4 is a side view of the bearing shell embodying the present invention; Figure 5 is an enlarged view of the circled area of Figure 4; Figure 6 is a sectional view of the bearing taken along line 6-6 of Figure 4; and Figure 7 is a side view of a second embodiment of a bearing shell embodying the present invention. In Figure 1 there is shown a crankshaft journal 10 rotatably carried within cylindrical bore 12 defined by cylinder block 14 and detachable bearing cap 16. Fixedly secured within each cylindrical bore 12, in rotatable bearing contact with crankshaft journal 10, is a journal bearing, designated generally as 18. The journal bearing 18 comprises a pair of semi-cylindrical bearing shells or inserts 20 and 22 which meet in endwise abutment at split line 24. Clearance is provided between the journal bearing 18 and crankshaft journal 10 for the formation of a load carrying lubricating oil film therebetween, so as to prevent direct contact during rotation. An oil supply channel 26, supplies lubricating oil from the oil gallery of cylinder block 14 or other external source to the journal bearing 18 through a lubricant supply opening 28 in bearing shell 20. In a preferred embodiment, shown in Figures 4 and 5, the inwardly facing bearing surface 30 of bearing shell 20 is divided circumferentially into a concentric central portion 32 which is centred on the central axis 34 of cylindrical bore 12, and a pair of eccentric end portions 36 having an axis 38 eccentric to central axis 34. The concentric central portion 32 is equidistant at all points from the central axis 34 and extends circumferentially for a predetermined angular distance to terminate at concentric end portions 40. The eccentric end portions 36 extend progressively outwardly from each concentric end portion 40 of concentric central portion 32 to terminate at the outer ends 42 of the bearing shell 20. The actual curvature of the eccentric end portions 36 will depend on the location of axis 38. The eccentric end portions 36, which extend the entire axial length of the bearing shell 20, provide a radial relief at the split line 24 which prevents bearing failure due to close-in of the bearing shells 20,22 at the split line, caused by deformation of cylindrical bore 12 due to fluctuating loads, or due to slight misalignments of the outer ends 42 during assembly. To assure an adequate supply of lubricant to establish the required lubricating film between crankshaft journal 10 and journal bearing 18, a lubricant supply groove 44, shown in Figures 2 and 3, is formed in the inwardly facing bearing surface 30 of bearing shell 20. The lubricant supply groove 44 is centred on an axis 46, see Figure 4, which is eccentric to the central axis 34. As a result, the lubricant supply groove 44 tapers from a point of maximum depth, preferably at the centre of the concentric central portion 32, to terminate at a position intermediate the centre of the bearing shell 20 and its outer ends 42. The lubricant supply groove 44 therefore has a predetermined length. To provide an adequate flow of lubricant through the journal bearing 18, thereby preventing dirt and contamination from collecting between the inwardly facing bearing surface 30 and the crankshaft journal 10, (eccentric) axis 46 is located so that lubricant supply groove 44 terminates within each of the eccentric end portions 36 thereby forming lubricant metering orifices 48 at the interface of the concentric central portion 32, the eccentric end portions 36 and the (eccentric) lubricant supply groove 44. The result is a reduction in oil pressure loss normally associated with journal bearings having lubricant supply grooves which extend to the split line, providing an increase in efficiency since less engine power is required to maintain oil pressure. Also, the provision of the lubricant metering orifices 48 allows a controlled or metered flow of lubricating oil to pass through the journal bearing 18 to prevent the build-up of harmful dirt and deposits therein. A principle advantage of the present invention is the ability to tailor the lubricant flow rate through the journal bearing 18 by varying the eccentricity of axis 46 to change the groove termination point and, consequently, the size of lubricant metering orifices 48. The volume of lubricant passing through the lubricant metering orifices 48, and the bearing shell 20, is therefore a predetermined value dependent upon the clearance between the crankshaft journal 10 and the inwardly facing bearing surface 30 at the end of the lubricant supply groove 44. The result is a journal bearing which can be made to suit specific design applications. To further enhance lubricating characteristics, lubricant supply groove 44 may be formed with chamfered edges, as shown in Figure 6. The chamfered edges cause a reduction in the axial dimension of lubricant supply groove 44, see Figure 3, as the depth diminishes. The resulting lubricant supply groove 44 has a relatively large volume near the centre of the bearing shell 20 capable of supplying substantial lubricant and a relatively small volume at each end where the lubricant passes through the lubricant metering orifices 48. The other bearing shell 22 may be of any conventional design, but preferably has a clearance defined by eccentric end portions 70 at its outer ends 72 which substantially correspond to the eccentric end portions 36 of bearing shell 20. A second embodiment of the journal bearing of the present invention is shown in Figure 7. In Figure 7 the bearing shell 50 has an inwardly facing bearing surface 52 having an arcuate cross section which is centred on an axis 54 which is eccentric from the central axis 56. Due to the eccentric offset of the inwardly facing bearing surface 52, the clearance between the crankshaft journal and the inwardly facing bearing surface 52 increases progressively from the centre of the bearing shell 50 to its outer ends 58. The increased clearance eliminates the need for distinct eccentric end portions as described above. Other features of bearing shell 50 are similar to those of bearing shell 20, except those detailed below. Lubricant supply groove 60 is formed in the inwardly facing bearing surface 52, and is centred on axis 62, which is eccentric to the central axis 56 of the journal bearing. Similar to the above embodiment, the lubricant supply groove 60 tapers from a point of maximum depth at the centre of the bearing shell 50 to terminate at a position intermediate the centre of the bearing shell 50 and its outer ends 58. In this embodiment, as the inwardly facing bearing surface clearance increases towards the outer ends 58, it provides a flow path to the split line for the pressurized lubricant within the (tapering) lubricant supply groove 60. By varying the eccentricity of the lubricant supply groove 60, and therefore the distance that the lubricant supply groove extends into the steadily increasing bearing clearance before terminating, the rate of lubricant flow through the journal bearing can be controlled. As a result, pressure loss at the split line due to the lubricant supply groove extending the full length of the bearing shell is reduced while continuing to provide lubricant flow through the journal bearing which is necessary to prevent dirt and contamination from collecting in the journal bearing. Although the above description is to an upper bearing shell of a crankshaft journal bearing, the invention is not limited to that application. The journal bearing of the present invention is useful in any bearing application where lubrication requirements necessitate substantial supply of lubricant to the journal bearing and where it is desirable to reduce the pressure loss normally associated with journal bearings having lubrication supply grooves that extend to the split line.

Claims: A journal bearing (18) for a cylindrical bore (12) in an internal combustion engine or the like within which a journal (10) can be received for rotation about a central axis (34,56), the journal bearing comprising a bearing shell (20) having a semi-cylindrical configuration adapted to be received in the cylindrical bore and an inwardly facing bearing surface (30,52) adapted to surround a portion of the journal in close fitting bearing relationship; a lubricant supply groove (44,60) formed in the inwardly facing bearing surface and tapering from a maximum depth at a point intermediate its ends to define lubricant metering orifices at the ends thereof; and a lubricant supply opening (28) extending through the bearing shell to intersect the lubricant supply groove; characterised by at least a portion (36,52) of the inwardly facing bearing surface being arcuate about an axis (38,54) which is offset from the central axis so as to provide greater clearance between the journal and the inwardly facing bearing surface at the outer ends (42,58) of the bearing shell than at the centre thereof; and in that the lubricant supply groove has a predetermined length with its ends located intermediate the centre of the bearing shell and the outer ends thereof. A journal bearing as claimed in Claim 1, wherein the inwardly facing bearing surface (30) comprises a concentric central portion (32) and a pair of eccentric end portions (36), the concentric central portion extending circumferentially a predetermined angular dimension from the centre of the bearing shell (20) to concentric end portions (40), and being equidistant at all points from the central axis (34); the eccentric end portions extending axially the full width of the bearing shell, extending outwardly from the concentric end portions, and defining the said portion of the inwardly facing bearing surface so that the inwardly facing bearing surface is of progressively increasing distance from the central axis from the concentric end portions towards the outer ends (42) of the bearing shell; and wherein the lubricant metering orifices (48) are at the concentric end portions and open onto the eccentic end portions. A journal bearing as claimed in Claim 1, wherein the said portion of the inwardly facing bearing surface (52) extends the full length of the inwardly facing bearing surface, and is eqidistant at all points from the axis (54) which is offset from the central axis (56) so that the inwardly facing bearing surface is of progressively increasing distance from the central axis from the centre of the bearing shell (50) towards the outer ends (58) of the bearing shell. A journal bearing as claimed in any one of Claims 1 to 3, wherein the edges of the lubricant supply groove (44,60) are chamfered. A journal bearing as claimed in any one of Claims 1 to 4, wherein the point at which the lubricant supply groove (44,60) has its maximum depth is at the centre of the bearing shell (20,50). A journal bearing as claimed in any one of Claims 1 to 5, wherein the lubricant supply opening (28) intersects the lubricant supply groove (44,60) at the point the lubricant supply groove has its maximum depth.

Inventors: HAHN CHARLES J, HAHN, CHARLES J.
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1991
Main classification: F16C9
IPC codes: F16C33, F16C32, F01M1, F16C9