Half bearings and plain bearings

Abstract

To provide a half bearing constituting a slide bearing hardly damaged in an operation of an internal combustion engine.SOLUTION: A half bearing includes at least one projection, and the projection projects to a radial outer side from an outer peripheral surface. A recessed portion recessed to a radial inner side from the outer peripheral surface, is formed over the whole circumferential length between the projection and a circumferential end surface of the half bearing. Two radial grooves are formed on the circumferential end surfaces of the half bearings to the projection in a state of respectively being adjacent to each of recessed portion side surfaces. The radial grooves extend in a radial direction along the recessed portion side surfaces and separate from the recessed portion in the middle of the extension. An inner peripheral surface-side end portion in an extending direction of the radial groove is positioned between a recessed portion bottom surface and an inner peripheral surface of the half bearing. A groove width and a groove depth of the radial groove are reduced from a position separating from the recessed portion toward the inner peripheral surface-side end portion and become zero at the inner peripheral surface-side end portion.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present invention relates to a half bearing constituting a plain bearing that supports a crankshaft of an internal combustion engine. The present invention also relates to a cylindrical plain bearing that supports the crankshaft of an internal combustion engine and includes the half bearing. [Background technology]

[0002] The crankshaft of the internal combustion engine is supported at its journal portion on the lower part of the cylinder block of the internal combustion engine via a main bearing consisting of a pair of half bearings. Lubricating oil discharged from an oil pump is sent from an oil gallery formed in the cylinder block wall to a lubricating oil groove formed along the inner circumferential surface of the main bearing through a through hole formed in the wall of the main bearing. A first lubricating oil passage is formed through the journal portion in the diametrical direction, and both ends of the first lubricating oil passage are connected to the lubricating oil groove of the main bearing. A second lubricating oil passage is formed by branching from the first lubricating oil passage of the journal portion and passing through the crank arm portion, and this second lubricating oil passage is connected to a third lubricating oil passage formed through the crank pin in the diametrical direction. In this way, the lubricating oil is sent from the oil gallery in the cylinder block wall through the through hole into the lubricating oil groove formed on the inner peripheral surface of the main bearing, passes through the first lubricating oil passage, the second lubricating oil passage, and the third lubricating oil passage, and is supplied from the discharge port opening at the end of the third lubricating oil passage between the crank pin and the sliding surface of the connecting rod bearing consisting of a pair of half bearings (see, for example, Patent Document 1). Oil is supplied between the surface of the crankshaft and the sliding surfaces of the main bearing and the connecting rod bearing.

[0003] The main bearing and the connecting rod bearing, which are made up of a pair of half bearings, are held in a cylindrical bearing retaining hole of a bearing housing. The bearing housing is made up of a pair of housing segments, each of which has a semi-cylindrical surface that becomes the bearing retaining hole when assembled. The half bearings are held in this semi-cylindrical surface. The half bearings include a protrusion that protrudes radially outward from the outer circumferential surface near the circumferential end surface. A recess having a rectangular cross-sectional shape that is recessed radially inward from the outer circumferential surface is formed between the protrusion and the circumferential end surface. The bearing retaining hole (semi-cylindrical surface) of the housing segments has a groove (recess) that extends circumferentially from the circumferential end of the semi-cylindrical surface. The protrusion of the half bearing is accommodated in the groove of the bearing retaining hole, so that the half bearing is arranged at a predetermined position in the axial direction in the bearing retaining hole of the bearing housing (see, for example, Patent Documents 2, 3, and 4).

[0004] In recent internal combustion engines, weight reduction is being attempted in order to improve fuel efficiency, and as a result, the rigidity of the bearing housing parts, such as the connecting rod and the engine block, tends to decrease. For this reason, during operation of the internal combustion engine, due to the inertial force applied to the bearing housing and the dynamic load load from the crankshaft, the bearing retaining hole of the cylindrical bearing housing undergoes a phenomenon (close-in phenomenon) in which the bearing retaining hole repeats elastic deformation in which the inner diameter in the vertical direction becomes larger than the inner diameter in the horizontal direction, and elastic deformation in which the bearing retaining hole returns to the cylindrical shape (here, the horizontal direction refers to the direction connecting both split surfaces of the housing segments of the bearing housing as viewed from the axial direction of the bearing retaining hole. Also, the vertical direction refers to the direction perpendicular to the direction connecting both split surfaces of the split bearing housing). When the inner diameter of the bearing retaining hole of the bearing housing increases in the vertical direction, a gap may be momentarily formed between the split surfaces of the pair of housing segments of the bearing housing. When the split surfaces of the housing segments come into contact with each other again, the circumferential end faces of the half bearings held by the housing segments are strongly pressed against each other, and a large load is applied near the circumferential end faces of the half bearings.

[0005] Conventional half bearings having protrusions and recesses for positioning in the bearing housing, as described in the above Patent Documents 2 to 4, are prone to damage (cracks) near the recesses on the circumferential end faces due to the load applied to the circumferential end faces when the close-in phenomenon occurs in the bearing housing during operation of the internal combustion engine. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-277831 [Patent Document 2] Japanese Patent Publication No. 59-50226 [Patent Document 3] JP 2019-190551 A [Patent Document 4] JP 2013-11333 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a half bearing that constitutes a plain bearing for a crankshaft of an internal combustion engine that is less susceptible to such damage during operation of the internal combustion engine, and a plain bearing including the half bearing. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a half bearing constituting a plain bearing that supports a crankshaft of an internal combustion engine, the half bearing having a semi-cylindrical shape and having an inner circumferential surface and an outer circumferential surface, The half bearing includes at least one protrusion, the protrusion protruding radially outward from an outer circumferential surface, a recess is formed over the entire circumferential length between the projection and the circumferential end face of the half bearing, the recess being recessed radially inward from the outer circumferential surface; The projection is located between both axial end faces of the half bearing, when viewed in a cross section parallel to the circumferential end faces, the recess has a recess bottom surface that is parallel to the axial direction of the half bearing, two recess side surfaces that are perpendicular to the axial direction of the half bearing at both ends of the recess in the axial direction of the half bearing, and two recess curved surfaces that connect the recess side surfaces and the recess bottom surface, Two radial grooves are formed in a circumferential end surface of the half bearing with respect to the protrusion, and the two radial grooves are adjacent to respective recess side surfaces, The extension length (L3) of the radial groove is greater than the depth (D1) of the recess, the radial groove extends radially from an outer peripheral surface to an inner peripheral surface of the half bearing along a side surface of the recess, and the radial groove is separated from the recess midway along its extension; an inner peripheral surface side end portion in an extension direction of the radial groove is located between a bottom surface of the recess portion and an inner peripheral surface of the half bearing, A half bearing is provided in which the groove width (W3) and groove depth (D2) of the radial groove decrease from a position away from the recess toward the inner circumferential surface end, and become zero at the inner circumferential surface end.

[0009] In another embodiment of the present invention, the groove depth (D2) of the radial groove at a position away from the recess is 0.03 to 0.15 mm.

[0010] In another embodiment of the present invention, the groove width (W3) of the radial groove at a position away from the recess is 0.1 to 0.3 mm.

[0011] In another embodiment of the present invention, the extension length (L3) of the radial groove is 0.05 to 0.8 mm greater than the depth (D1) of the recess.

[0012] Another aspect of the present invention provides a cylindrical plain bearing for supporting a crankshaft of an internal combustion engine, comprising the above-mentioned half bearing.

[0013] In another embodiment of the present invention, the plain bearing is configured by combining a pair of the above-mentioned half bearings. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a schematic diagram showing a bearing device for a crankshaft. [Diagram 2] FIG. 1 is a perspective view of a half bearing according to an embodiment of the present invention. [Figure 2A] FIG. 2 is a perspective view of a protrusion, recess, and radial groove according to one embodiment of the present invention. [Diagram 3] 3 is a diagram of a protrusion, a recess, and a radial groove according to an embodiment of the present invention, as viewed from a direction perpendicular to a circumferential end face (as viewed from an arrow Y1 in FIG. 2). [Figure 4] 3 is a diagram of a protrusion, a recess, and a radial groove according to one embodiment of the present invention, as viewed in the axial direction (as viewed in the direction of the Y2 arrow in FIG. 2). [Diagram 5] 3 is a diagram of a protrusion, a recess, and a radial groove according to one embodiment of the present invention, as viewed from the outer circumferential surface side (as viewed in the direction of the Y3 arrow in FIG. 2). [Figure 6] FIG. 13 is a view of a radial groove at a position away from a recess, as viewed in an axial cross section of the half bearing. [Figure 7] FIG. [Figure 8] FIG. 4 is a diagram showing a bearing housing during elastic deformation. [Figure 9] FIG. 2 is a diagram illustrating the operation of the present invention. [Figure 10] FIG. 1 is a diagram of a recess in the prior art. [Figure 11] FIG. 13 is a diagram of a recess in a comparative example. [Figure 12] FIG. 13 is a diagram of a recess in another comparative example. [Figure 13] FIG. 13 is a diagram of a recess in another comparative example. [Figure 14] FIG. 13 is a diagram of a recess in another comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

[0016] A bearing device 1 for an internal combustion engine is shown diagrammatically in Fig. 1. This bearing device 1 comprises a journal portion 6 supported on the lower portion of a cylinder block, a crank pin 5 formed integrally with the journal portion 6 and rotating about the journal portion 6, and a connecting rod 2 that transmits reciprocating motion from the internal combustion engine to the crank pin 5. The bearing device 1 further comprises, as a sliding bearing that supports the crankshaft, a main bearing 4 that rotatably supports the journal portion 6, and a connecting rod bearing 3 that rotatably supports the crank pin 5.

[0017] Although the crankshaft has multiple journal portions 6 and multiple crank pins 5, for ease of explanation, only one journal portion 6 and one crank pin 5 are illustrated here. In Fig. 1, the positional relationship in the depth direction of the page is such that the journal portions 6 are at the rear side of the page and the crank pins 5 are at the front side.

[0018] The journal portion 6 is journaled in a bearing housing 10 (cylinder block 101 and cap 102) at the bottom of the cylinder block of the internal combustion engine via a main bearing 4 consisting of a pair of half bearings 41, 42. An oil groove 41a is formed along the entire length of the inner circumferential surface of the half bearing 41, which is on the upper side in Fig. 1. The journal portion 6 also has a lubricating oil passage 6a penetrating in the diameter direction, and when the journal portion 6 rotates in the direction of the arrow X, the inlet openings 6c at both ends of the lubricating oil passage 6a alternately communicate with the oil groove 41a of the main bearing 4.

[0019] The crank pin 5 is journalled in the bearing housing 21 (the rod-side big-end housing 22 and the cap-side big-end housing 23 ) of the connecting rod 2 via a connecting rod bearing 3 constituted by a pair of half bearings 31 , 32 .

[0020] The bearing housing 10 consists of a pair of housing halves 101, 102. The housing halves 101, 102 have semi-cylindrical surfaces 27, which become cylindrical bearing retaining holes 26 when the divided surfaces 25 of the pair of housing halves 101, 102 are butted together. Half bearings 41, 42 are retained by each of the semi-cylindrical surfaces 27.

[0021] Similarly, the bearing housing 21 is made up of a pair of housing halves 22, 23. The housing halves 22, 23 have semi-cylindrical surfaces 27, which become cylindrical bearing retaining holes 26 when the divided surfaces 25 of the pair of housing halves 22, 23 are butted together. Half bearings 31, 32 are retained by each of the semi-cylindrical surfaces 27.

[0022] As described above, lubricating oil discharged by the oil pump to the main bearing 4 is sent from the oil gallery formed in the cylinder block wall through a through hole formed in the wall of the main bearing 4 and into the oil groove 41a formed along the inner surface of the main bearing 4.

[0023] Furthermore, a first lubricating oil passage 6a is formed extending through the journal portion 6 in the radial direction, and an inlet opening 6c of the first lubricating oil passage 6a is capable of communicating with the lubricating oil groove 41a. A second lubricating oil passage 5a is formed branching off from the first lubricating oil passage 6a in the journal portion 6 and passing through the crank arm portion (not shown), and the second lubricating oil passage 5a is connected to a third lubricating oil passage 5b formed extending through the crank pin 5 in the radial direction.

[0024] In this way, the lubricating oil is supplied to the gap formed between the crank pin 5 and the connecting rod bearing 3 from the discharge port 5c at the end of the third lubricating oil passage 5b through the first lubricating oil passage 6a, the second lubricating oil passage 5a and the third lubricating oil passage 5b.

[0025] In recent internal combustion engines, weight reduction is being attempted for the purpose of improving fuel efficiency, and as a result, the rigidity of the bearing housing parts such as the connecting rod 2 and the engine block 101 tends to decrease. For this reason, during operation of the internal combustion engine, due to the inertial force applied to the bearing housing 10;21 and the dynamic load load from the crankshaft, the bearing retaining hole 26 of the cylindrical bearing housing 10;21 repeats a phenomenon (close-in phenomenon) in which the bearing retaining hole 26 repeats elastic deformation (see FIG. 8) in which the inner diameter DV in the vertical direction becomes larger than the inner diameter DH in the horizontal direction, and elastic deformation (see FIG. 7) in which the bearing retaining hole 26 returns to the cylindrical shape. Here, the horizontal direction refers to the direction connecting both the divided surfaces 25 of the housing segments 101, 102; 22, 23 of the bearing housing 10;21 as viewed from the axial direction of the bearing retaining hole 26. The vertical direction refers to the direction perpendicular to the direction connecting both the divided surfaces 25 of the housing segments 101, 102; 22, 23 of the bearing housing 10;21 as viewed from the axial direction of the bearing retaining hole 26.

[0026] When the inner diameter of the bearing retaining hole 26 of the bearing housing 10; 21 increases in the vertical direction, a gap may momentarily form between the divided surfaces 25 of the pair of housing halves 101, 102; 22, 23 of the bearing housing 10; 21. When the divided surfaces 25 of the housing halves 101, 102; 22, 23 come into contact with each other again, the circumferential end faces 76 of the half bearings 41, 42; 31, 32 held by the respective housing halves 101, 102; 22, 23 are pressed strongly against each other, and a large load is applied near the circumferential end faces 76 of the half bearings 41, 42; 31, 32.

[0027] The half bearing of the prior art includes a protrusion 72A protruding radially outward from an outer circumferential surface 71 near a circumferential end surface 76. A recess 8A having a rectangular cross-sectional shape recessed radially inward from the outer circumferential surface 71 is formed between the protrusion 72A and the circumferential end surface 76. A groove (recess) extending circumferentially from a circumferential end of the semi-cylindrical surface is formed in the bearing retaining hole (semi-cylindrical surface) of the housing segment. The protrusion 72A of the half bearing is accommodated in the groove of the bearing retaining hole, so that the half bearing is disposed at a predetermined axial position within the bearing retaining hole (see, for example, Patent Documents 2, 3 and 4).

[0028] Fig. 10 shows a projection 72A and a recess 8A having a rectangular cross section of a conventional half bearing, viewed from a direction perpendicular to the circumferential end faces 76. When the close-in phenomenon occurs in the bearing housing 10;21, the circumferential end faces 76 of the half bearings are pressed strongly against each other, and a large load is applied near the circumferential end faces 76 of the half bearings, stress is concentrated in the corners (see the dashed circle in Fig. 10) formed by the recess bottom face 81A and the recess side face 82A in the conventional half bearing, making the corners susceptible to damage (cracks).

[0029] The present invention addresses these problems of the prior art.

[0030] Hereinafter, an example will be described in which the half bearing of the present invention is applied to the connecting rod bearing 3. However, the present invention is not limited to the connecting rod bearing 3, and can also be applied to a half bearing that constitutes the main bearing 4.

[0031] Of the pair of half bearings that constitute the connecting rod bearing 3 or the main bearing 4, both half bearings may be the half bearings of the present invention. Alternatively, one half bearing may be the half bearing of the present invention, and the other may be a conventional half bearing that does not have any projections or recesses on its outer circumferential surface.

[0032] 2 shows a specific example of a half bearing (connecting rod bearing 3) according to the present invention. The connecting rod bearing 3 is formed by butting circumferential end faces 76 of a pair of half bearings 31, 32 together and assembling them into an overall cylindrical shape. The surface that forms the inner circumferential surface 70 of the cylindrical shape is the sliding surface.

[0033] The thickness of the half bearings 31, 32 is constant in the circumferential direction. However, the thickness may be greatest at the circumferential center and continuously decrease toward both circumferential end faces 76. The inner circumferential surface 70 may have crush reliefs at both circumferential ends.

[0034] The crush relief is a surface formed by radially reducing the thickness of the wall in the circumferential end region of the half bearings 31, 32 from the original inner peripheral surface 70, and is formed to absorb misalignment and deformation of the circumferential end surface 76 of the half bearing that may occur when, for example, the pair of half bearings 31, 32 are assembled to the connecting rod 2. Therefore, the position of the center of curvature of the surface of the crush relief is different from the position of the center of curvature of the inner peripheral surface 70 in other regions (see SAE J506 (items 3.26 and 6.4), DIN1497, section 3.2, and JIS D3102). In general, in the case of a bearing for a small internal combustion engine for a passenger car, the depth of the crush relief at the circumferential end surface of the half bearing (the distance from the original inner peripheral surface to the crush relief at the circumferential end surface 76) is about 0.01 to 0.05 mm.

[0035] FIG. 2A is a perspective view of the protrusion, recess, and radial groove according to an embodiment of the present invention. FIG. 3 is a view of the protrusion, recess, and radial groove as viewed from a direction perpendicular to the circumferential end surface 76 (Y1 arrow direction in FIG. 2). FIG. 4 is a view of the protrusion, recess, and radial groove as viewed from the axial direction (Y2 arrow direction in FIG. 2). FIG. 5 is a view of the protrusion, recess, and radial groove according to an embodiment of the present invention as viewed from the outer circumferential surface side (Y3 arrow direction in FIG. 2). Of course, the present invention is not limited to this embodiment. For ease of understanding, the protrusion 72, recess 8, and radial groove 9 are exaggerated in each drawing.

[0036] Each of the half bearings 31 and 32 includes at least one protrusion 72, which protrudes radially outward from the outer circumferential surface 71 on the side of one circumferential end surface 76. The protrusion 72 is formed between both axial end surfaces 77, 77 of the half bearings 31 and 32. However, the protrusion 72 is not formed in contact with the axial end surface 77. In other words, the protrusion 72 is formed at a distance from the axial end surface 77. The protrusion 72 has protrusion side surfaces 722 parallel to the circumferential direction of the half bearings 31 and 32 at both ends in the width direction (axial direction of the half bearings 31 and 32). The protrusion 72 also has a protrusion circumferential surface 721 parallel to the circumferential end surface 76 of the half bearings 31 and 32 at the circumferential end portion on the side of the circumferential end surface 76 of the half bearings 31 and 32.

[0037] The protrusion side surface 722 may be inclined with respect to the circumferential direction of the half bearings 31, 32. The protrusion circumferential surface 721 may be inclined with respect to the circumferential end surfaces 76 of the half bearings 31, 32.

[0038] In this embodiment, one protrusion 72 and one recess 8 are provided on only one circumferential end face side of the half bearings 31, 32. However, this is not limited to this, and one or more protrusions 72 and recesses 8 may be provided on each circumferential end face side of the half bearings 31, 32.

[0039] In the case of a small internal combustion engine for a passenger car, the width W1 of the projection 72 is 1.5 to 5.5 mm, and the height L1 of the projection 72 is 0.5 to 3 mm. The height L1 of the projection 72 is defined as the radial length between the outer circumferential surface 71 at the circumferential end face 76 of the half bearings 31, 32 and the position of the projection 72 farthest in the radial direction (see FIG. 4). The length L4 in the direction perpendicular to the circumferential end face 76 between the circumferential end face 76 of the half bearings 31, 32 and the end of the projection 72 on the circumferential center side of the half bearings 31, 32 is 2 to 7 mm. The projection 72 is not limited to the above dimensions, and may have other dimensions.

[0040] A recess 8 is formed over the entire circumferential length between the projection 72 (projection circumferential surface 721) and the circumferential end surface 76 of the half bearings 31, 32, recessed radially inward from the outer circumferential surface 71. When viewed in a cross section parallel to the circumferential end surface 76, the recess 8 has a recess bottom surface 81 parallel to the axial direction of the half bearings 31, 32, two recess side surfaces 82 perpendicular to the axial direction of the half bearings 31, 32 at both ends of the recess 8 in the axial direction of the half bearings 31, 32, and two recess curved surfaces 83 (curved surfaces convex toward the inner diameter side of the half bearings 31, 32) connecting the recess side surfaces 82 and the recess bottom surface 81. The recess 8 is also open to the circumferential end surface 76 of the half bearings 31, 32.

[0041] The recess bottom surface 81, recess side surface 82, and recess curved surface 83 of the recess 8 extend perpendicularly to the circumferential end surface 76 of the half bearings 31, 32. The end surface of the recess 8 on the protrusion 72 side is in the same plane as the protrusion circumferential surface 721. In FIG. 3, the dashed dotted line indicates the position of the outer circumferential surface 71 on the protrusion circumferential surface 721 in a case where the outer circumferential surface 71 on the protrusion circumferential surface 721 is also present on the protrusion 72. In FIG. 3, the surface surrounded by the dashed dotted line, the recess bottom surface 81, the recess side surface 82, and the recess curved surface 83 is the end surface of the recess 8 on the protrusion 72 side.

[0042] The width W2 of the recess 8 is the same as the width W1 of the protrusion 72. The width W2 of the recess 8 may be slightly smaller than the width W1 of the protrusion 72. In the case of a small internal combustion engine for a passenger car, the length L2 of the recess 8 is 0.5 to 3 mm, and the depth D1 of the recess is 0.3 to 2 mm (however, the depth D1 of the recess 8 is 60% or less (D1≦T×0.6) of the thickness T at the circumferential end face 76 of the half bearings 31 and 32). The length L2 of the recess 8 is defined as the length in the direction perpendicular to the circumferential end face 76 between the circumferential end face 76 of the half bearings 31 and 32 and the end face of the recess 8 on the protrusion 72 side (see FIG. 4). The depth D1 of the recess is defined as the radial length between the outer circumferential surface 71 at the circumferential end face 76 of the half bearings 31 and 32 and the bottom surface 81 of the recess (see FIG. 4). The recess 8 is not limited to the above dimensions, and may have other dimensions.

[0043] Two radial grooves 9 are formed on the circumferential end faces 76 of the half bearings 31 and 32 for the protrusions 72. The two radial grooves 9 are adjacent to the respective recess side faces 82. The radial grooves 9 extend radially along the recess side faces 82 from the outer peripheral faces 71 to the inner peripheral faces 70 of the half bearings 31 and 32. When two or more protrusions 72 are provided on the half bearings 31 and 32, two radial grooves 9 are formed on the circumferential end faces 76 of the half bearings 31 and 32 for each protrusion 72. The extension length L3 of the radial grooves 9 is greater than the depth D1 of the recess 8. The radial grooves 9 are separated from the recess 8 (recess curved surface 83) in the middle of their extension. An inner peripheral surface side end 91 of the radial grooves 9 in the extension direction is located between the recess bottom face 81 and the inner peripheral surface 70 of the half bearings 31 and 32.

[0044] The groove depth of the radial groove 9 decreases from the outer circumferential surface 71 toward a position P away from the recess 8 (recess curved surface 83). The groove width W3 and groove depth D2 of the radial groove 9 decrease from the position P away from the recess 8 (recess curved surface 83) toward the inner circumferential surface end 91, and become zero at the inner circumferential surface end 91. FIG. 6 is a diagram of the radial groove 9 at a position P (AA part in FIG. 3) away from the recess 8, as seen in a cross section in the axial direction of the half bearings 31 and 32. In this embodiment, the cross-sectional shape of the radial groove 9 is V-shaped, but it may be R-shaped. The extension direction of the radial groove 9 may be inclined with respect to the radial direction of the half bearings 31 and 32.

[0045] In the case of a small internal combustion engine for a passenger car, the groove depth D2 of the radial groove 9 at the position P away from the recess 8 may be 0.03 to 0.15 mm. The groove width W3 of the radial groove 9 at the position P away from the recess 8 may be 0.1 to 0.3 mm. The extension length L3 of the radial groove 9 may be 0.05 to 0.8 mm larger than the depth D1 of the recess 8. However, it is preferable that the extension length L3 of the radial groove 9 is less than 75% of the thickness (wall thickness) T of the circumferential end face 76 of the half bearing. In other words, it is preferable that no radial groove is formed and a circumferential end face having 25% or more of the thickness T of the half bearing is secured between the inner peripheral surface side end portion 91 and the inner peripheral surface 70.

[0046] The groove depth D2 of the radial groove 9 at the position P away from the recess 8 is defined as the length perpendicular to the circumferential end face 76 from the circumferential end face 76 to the deepest position of the radial groove 9. The groove width W3 of the radial groove 9 at the position P away from the recess 8 is defined as the length of the radial groove 9 at the circumferential end face 76 in a direction parallel to the axial direction of the half bearings 31, 32. The extension length L3 of the radial groove 9 is defined as the radial length between the outer circumferential surface 71 at the circumferential end face 76 and the inner circumferential surface side end 91 of the radial groove 9. The radial groove 9 is not limited to the above dimensions and may have other dimensions.

[0047] The connecting rod bearing 3 of this embodiment is formed by butting the circumferential end faces 76 of a pair of half bearings 31, 32 together and assembling them into an overall cylindrical shape. When the protrusions 72 and the recesses 8 are formed only on one of the circumferential end faces 76, the pair of half bearings 31, 32 are generally assembled by butting the circumferential end faces 76 on which the protrusions 72 and the recesses 8 are formed. At this time, the recesses 8 on the circumferential end face 76 of one half bearing 31 (32) are not in contact with the recesses 8 on the circumferential end face 76 of the other half bearing 32 (31) (the recesses 8 are in contact with the circumferential end face 76 at the location where the recesses 8 are not formed). The half bearings 31, 32 may have a sliding layer made of a Cu bearing alloy or an Al bearing alloy. Alternatively, the sliding layer made of a Cu bearing alloy or an Al bearing alloy may be formed on a backing metal layer made of an Fe alloy. In addition, the sliding surface, which is the cylindrical inner surface 70, and the outer surface 71 may have a surface portion made of one of Bi, Sn, and Pb, which are softer than the bearing alloy, or an alloy mainly made of these metals, or a surface portion made of a resin composition mainly made of synthetic resin.

[0048] The reason why damage (cracks) are less likely to occur near the recess 8 of the circumferential end face 76 in the half bearings 31, 32 of the present invention as described above will be explained below.

[0049] As described above, when the close-in phenomenon occurs in the bearing housing 21 during operation of the internal combustion engine, the circumferential end faces 76 of the half bearings 31, 32 are strongly pressed against each other. However, the recess 8 of the present invention has a recess curved surface 83 between the recess bottom surface 81 and the recess side surface 82, so that no point where stress is concentrated like the corners of the prior art is formed, and the stress is dispersed over the entire recess curved surface 83. Furthermore, a load applied near the recess curved surface 83 elastically deforms the bearing material near the recess curved surface 83 toward the space created by the radial groove 9, thereby easing the stress applied to the bearing material near the recess curved surface 83.

[0050] In detail, when a load is applied near the recessed curved surface 83, the bearing material (see the approximately triangular hatched area in FIG. 9) near the circumferential end face of the portion surrounded by the position P where the radial groove 9 separates from the recessed curved surface 83, the radial groove 9, the recessed bottom surface 81, and the recessed curved surface 83 elastically deforms toward the space created by the radial groove 9 (in the direction of the hollow arrow in FIG. 9), thereby reducing the stress applied to the bearing material of the recessed curved surface 83. This makes it less likely that damage will occur near the recesses on the circumferential end faces of the half bearings 31, 32.

[0051] 11 is a view of the vicinity of the recess 8A on the circumferential end face of the half bearing of the comparative example, as viewed from a direction perpendicular to the circumferential end face. The recess 8A of this comparative example has a radial groove 9A, but the recess bottom face 81A and the recess side face 82A of the recess 8A are directly connected, and does not have a recess curved face 83. For this reason, when the close-in phenomenon occurs in the bearing housing 21 and the circumferential end faces 76 of the half bearing are strongly pressed against each other, and a large load is applied to the vicinity of the circumferential end face 76 of the half bearing, stress is concentrated in the corner of the recess 8A formed by the recess bottom face 81A and the recess side face 82A (see the dashed circle in FIG. 11), and the corner is likely to be damaged.

[0052] 12 is a view of the vicinity of the recess 8A on the circumferential end face of a half bearing of another comparative example, as viewed from a direction perpendicular to the circumferential end face. The recess 8A of this comparative example has a recess curved surface 83A between the recess bottom surface 81A and the recess side surface 82A of the recess 8A, but does not have a radial groove 9. For this reason, when the close-in phenomenon occurs in the bearing housing 21, the circumferential end faces 76 of the half bearing are strongly pressed against each other, and a large load is applied to the vicinity of the circumferential end face 76 of the half bearing, the bearing material near the recess curved surface 83A cannot elastically deform into the space created by the radial groove 9, so that stress is concentrated on the recess curved surface 83A (see the dashed circle in FIG. 12), and the recess curved surface 83A is likely to be damaged.

[0053] 13 is a view of the vicinity of the recess 8A on the circumferential end face of a half bearing of another comparative example, as viewed from a direction perpendicular to the circumferential end face. The recess 8A of this comparative example has a recess curved surface 83A between the recess bottom surface 81A and the recess side surface 82A of the recess 8A, and has two radial grooves 9A. However, the extension length L3 of the radial groove 9A is smaller than the depth D1 of the recess 8A. For this reason, when the close-in phenomenon occurs in the bearing housing 21, the circumferential end faces 76 of the half bearing are strongly pressed against each other, and a large load is applied to the vicinity of the circumferential end faces 76 of the half bearing, the bearing material near the curved surface 83A is not elastically deformed into the space created by the radial groove 9A insufficiently or not at all, so that stress is concentrated on the curved surface 83A (see the dashed circle in FIG. 13), and the curved surface 83A is easily damaged.

[0054] FIG. 14 shows a perspective view of the vicinity of the recess 8A on the circumferential end surface of a half bearing of another comparative example. In the recess 8A of this comparative example, the recess bottom surface 81A and the recess side surface 82A of the recess 8A are directly connected, and the recess curved surface 83 is not included. In addition, one radial groove 9A is present, and the radial groove 9A has a width larger than the width of the recess 8A, and has a trapezoidal cross section. The groove width and groove depth of the radial groove 9A are maximum on the outer peripheral surface, and become smaller toward the inner peripheral surface. The radial groove 9A has an end 91A at the end on the inner peripheral surface side, which is parallel to the axial direction of the half bearing. In the half bearing of this comparative example, when the close-in phenomenon occurs in the bearing housing 21, the circumferential end surfaces 76 of the half bearing are strongly pressed against each other, and a large load is applied near the circumferential end surfaces 76 of the half bearing, stress is concentrated at the corner formed by the recess bottom surface 81A and the recess side surface 82A, and the corner is likely to be damaged. Furthermore, stress is concentrated at the corners (see the dashed circle in FIG. 14) where the inner peripheral side end 91A of the radial groove 9A and the width direction end face 92A of the radial groove 9A are connected, making them more susceptible to damage.

[0055] Although the above explanation shows an example in which the half bearing of the present invention is applied to a connecting rod bearing that supports the crank pin of the crankshaft of an internal combustion engine, the half bearing of the present invention can also be applied to one or both of a pair of half bearings that constitute a main bearing that supports the journal portion of the crankshaft. The half bearing may also have oil holes and oil grooves. [Explanation of symbols]

[0056] 1 Bearing device 2 Connecting rod 3 Connecting rod bearing 4 Main bearing 5 Crank pin 5a, 5b Lubrication oil path 5c outlet 6. Journal Section 6a Lubrication oil path 6c Inlet opening 10 Bearing housing 101 Housing division body 102 Housing division body 21 Bearing housing 22 Housing division body 23 Housing division body 25 Split plane 26 Bearing retaining hole 27 Semi-cylindrical surface 31, 32 Half bearing 41, 42 Half bearing 41a Oil groove 70 Inner surface 71 Outer surface 72 Protrusion 721 Projection circumferential surface 722 Projection side 76 Circumferential end face 77 Axial end face 8 Recess 81 Bottom of recess 82 Recessed side 83 Concave Surface 9 Radial groove 91 Inner peripheral surface end of radial groove D1 Recess depth D2 Groove depth of radial groove DH Horizontal inner diameter of bearing retaining hole DV Vertical inside diameter of bearing retaining hole P Separate position W1 Protrusion width W2 Recess width W3 radial groove width L1 Protrusion height L2 Recess length L3 Radial groove extension length L4 Length of protrusion and recess T Thickness of half bearing at circumferential end face Z Crank pin rotation direction X Rotation direction of journal

Claims

1. A half bearing constituting a plain bearing that supports a crankshaft of an internal combustion engine, the half bearing having a semi-cylindrical shape and an inner peripheral surface and an outer peripheral surface, The half bearing includes at least one protrusion, the protrusion protruding radially outward from the outer circumferential surface, a recess recessed radially inward from the outer circumferential surface over an entire circumferential length between the protrusion and a circumferential end surface of the half bearing, The protrusion is located between both axial end faces of the half bearing, when viewed in a cross section parallel to the circumferential end faces, the recess has a recess bottom surface that is parallel to the axial direction of the half bearing, two recess side surfaces that are perpendicular to the axial direction of the half bearing at both ends of the recess in the axial direction of the half bearing, and two recess curved surfaces that connect the recess side surfaces and the recess bottom surface, Two radial grooves are formed in the circumferential end surface of the half bearing with respect to the protrusion, and the two radial grooves are adjacent to the respective recess side surfaces, The extension length (L3) of the radial groove is greater than the depth (D1) of the recess, the radial groove extends radially along a side surface of the recess from the outer circumferential surface to the inner circumferential surface of the half bearing, and the radial groove is separated from the recess midway along its extension, an inner peripheral surface side end portion in an extension direction of the radial groove is located between a bottom surface of the recess portion and the inner peripheral surface of the half bearing, A half bearing, wherein a groove width (W3) and a groove depth (D2) of the radial groove become smaller from a position away from the recess toward the inner circumferential surface end portion, and become zero at the inner circumferential surface end portion.

2. The half bearing according to claim 1, wherein the groove depth (D2) of the radial groove at a position away from the recess is 0.05 to 0.15 mm.

3. The half bearing according to claim 1 or 2, wherein the groove width (W3) of the radial groove at a position away from the recess is 0.1 to 0.3 mm.

4. The half bearing according to any one of claims 1 to 3, wherein the extension length (L3) of the radial groove is 0.05 to 0.8 mm greater than the depth (D1) of the recess.

5. 5. A cylindrical plain bearing for supporting a crankshaft of an internal combustion engine, comprising the half bearing according to claim 1.

6. 6. A sliding bearing according to claim 5, which is constructed by combining a pair of said half bearings.

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