JP2023129836A - Sliding bearing - Google Patents

Abstract

To provide a sliding bearing for a crank shaft, in which cavitation erosion hardly occurs in the slide surface of the sliding bearing.SOLUTION: In the slide surface of a first half bearing, a partial groove extending in the peripheral direction and a recessed portion are formed. The recessed portion is in a place including the end on the peripheral center portion side of the partial groove. The recessed portion surface includes a center region on the center side, and an edge region on the side adjacent to the peripheral edge of the recessed portion, and an inflection part exists in the boundary. The center region on the recessed portion surface forms a convex curb on the outer diameter side of the first half bearing. The edge region on the recessed portion surface forms a convex curve on the inner diameter side of the first half bearing. A groove center line of the peripheral groove in the recessed portion inclines with respect to a perpendicular line toward the groove axial center of the recessed portion. A groove inclination angle in the edge region is the smallest at the peripheral edge, and becomes continuously larger as coming closer to the inflection portion. A groove inclination angle in the center region is the smallest at the groove axial center of the recessed portion, and becomes continuously larger as coming closer to the inflection portion.SELECTED DRAWING: Figure 8

Description

The present invention relates to a cylindrical sliding bearing that supports a crankshaft of an internal combustion engine and includes a pair of half bearings.

A crankshaft of an internal combustion engine is supported at its journal portion by a lower portion of a cylinder block of the internal combustion engine via a main bearing consisting of a pair of half bearings. For the main bearing, lubricating oil discharged by the oil pump flows from the oil gallery formed in the cylinder block wall, through the through hole formed in the main bearing wall, and along the inner circumferential surface of the main bearing. The lubricant is fed into the lubricating oil groove. Further, a first lubricating oil passage is formed through the journal portion in the diametrical direction, and openings at both ends of the first lubricating oil passage communicate with the lubricating oil groove of the main bearing. Furthermore, a second lubricating oil passage passing through the crank arm part is branched from the first lubricating oil passage of the journal part, and this second lubricating oil passage is connected to a third lubricating oil passage formed through the crank pin in the diametrical direction. It is connected to the oil line. 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, through the first lubricating oil passage, the second lubricating oil passage and The oil is supplied through the third lubricating oil passage from a discharge port opened at the end of the third lubricating oil passage between the sliding surfaces of a connecting rod bearing consisting of a crank pin and a pair of half bearings (for example, see Patent Document 1) . Oil is supplied between the surface of the crankshaft and the sliding surfaces of the main bearing and connecting rod bearing.

Conventionally, in order to prevent cavitation erosion at the ends of the partial grooves formed in the circumferential direction on the sliding surface of the half bearing, a half bearing having a recess communicating with the end of the partial groove has been proposed. (For example, see Patent Document 2 and Patent Document 3).

However, since the concave portion of the conventional technology is formed with only a convex curved surface extending from the sliding surface toward the outer diameter side of the half bearing (it does not have an inflection part like the present invention), the periphery of the concave portion and the sliding The connection part with the surface becomes a discontinuous shape (unsmooth connection part). Therefore, a turbulent flow of lubricating oil occurs at the connection part, and a cavity is generated as the lubricating oil pressure fluctuates. As a result, cavitation erosion occurs on the sliding surface of the half bearing on the front side in the rotational direction of the crankshaft from the periphery of the recess. Further, in the conventional recess, since a circumferential groove is not formed on the surface of the recess, it is difficult for the lubricating oil in the recess to flow in the circumferential direction. Therefore, when a cavity is generated on the front side in the axial rotation direction of the end of the partial groove that communicates with the recess, the cavity is likely to spread outward in the axial direction of the half bearing within the recess. This has caused a problem in that cavitation erosion is likely to occur on the surface of the recess near the axially outer peripheral edge of the recess where the gap with the crankshaft is narrow.

Japanese Patent Application Publication No. 8-277831 Publication No. 53-47438 Publication No. 63-67604

An object of the present invention is to provide a sliding bearing for a crankshaft of an internal combustion engine in which cavitation erosion is less likely to occur on the sliding surface near the periphery of a recess that communicates with a partial groove of a half bearing.

In order to solve the above problems, the present invention provides a sliding bearing for rotatably supporting the crankshaft of an internal combustion engine, comprising:
The sliding bearing has first and second half bearings that are combined with each other to form a cylindrical shape, and the first and second half bearings have sliding surfaces on the inside in the radial direction,
The first and second half bearings have circumferential end faces on both sides in the circumferential direction,
A partial groove extending in the circumferential direction is formed in the sliding surface of the first half bearing, and the partial groove is located on the rear side in the rotational direction of the crankshaft among both circumferential end surfaces of the first half bearing. Open only on the direction end face,
The end of the partial groove on the circumferential center side of the first half bearing slides between the circumferential center of the first half bearing and the circumferential end surface on the rear side in the rotational direction of the crankshaft. located on the surface,
An oil groove extending in the circumferential direction is formed in the sliding surface of the second half bearing, and the oil groove is located at least on the front side in the rotational direction of the crankshaft of both circumferential end surfaces of the second half bearing. Opening on the circumferential end surface,
The groove width centers of the partial groove and the oil groove are aligned with each other, and the partial groove and the oil groove are in fluid communication with each other,
A recess is formed in the sliding surface of the first half bearing, and the recess is located at a position that includes the end of the partial groove on the circumferential center side;
The periphery of the recess on the sliding surface is circular or oval,
The peripheral edge of the recess is not in contact with either the circumferential end face or the axial end face of the first half bearing and is located within the sliding surface,
The recess has a recess surface that is recessed from the sliding surface toward the outer diameter side of the first half bearing,
The recess surface includes a central region on the center side and an edge region on a side adjacent to the periphery of the recess,
There is an inflection section at the boundary between the central region and the edge region.
The central region of the recessed surface forms a curved line convex toward the outer diameter side of the first half bearing in any cross-sectional view perpendicular to the sliding surface of the first half bearing;
The edge region of the recessed surface forms a convex curve toward the inner diameter side of the first half-bearing in a cross-sectional view in any direction perpendicular to the sliding surface of the first half-bearing,
The width of the recess in the axial direction is larger than the groove width of the partial groove at the end on the circumferential center side of the partial groove,
The end of the partial groove on the circumferential center side is located in the central region of the recess surface,
The axial width center of the recess and the groove width center of the partial groove are aligned with each other,
A plurality of circumferential grooves are formed adjacent to each other on the recess surface, the plurality of circumferential grooves are formed over the entire circumferential length of the recess surface, and the plurality of circumferential grooves are formed over the entire width of the recess surface. The circumferential groove has a curved groove surface when viewed in cross section in the axial direction of the first half bearing, and a top portion is formed between adjacent groove surfaces. The curve connecting the tops represents the concave surface.
The groove width of a circumferential groove is defined as the length of an imaginary straight line that connects the tops of both sides of the circumferential groove, and the groove center line passes through the center of the length of the imaginary straight line with respect to the imaginary straight line. The groove depth of a circumferential groove is defined as a line extending vertically, and the groove depth of a circumferential groove is defined as the length perpendicular to an imaginary line from the imaginary line to the point where the groove surface is furthest apart. The position of the maximum groove depth is located above the groove center line,
The area enclosed by the virtual straight line and the groove surface is defined as the groove cross-sectional area,
The groove width, groove depth, and groove cross-sectional area of the plurality of circumferential grooves are the same, and the groove width, groove depth, and groove cross-sectional area of the circumferential grooves are the same at any position in the circumferential direction. The same is true for
The angle between the groove center line and a perpendicular line extending perpendicularly from the sliding surface toward the axis of the half bearing is defined as the groove inclination angle θ1,
The groove center line in the recess is inclined with respect to the perpendicular line toward the center of the width of the recess in the axial direction, and the groove inclination angle θ1 in the edge region is minimum at the periphery and continuously increases as it approaches the inflection part. Thus, a sliding bearing is provided in which the groove inclination angle θ1 in the central region becomes minimum at the center of the axial width of the recessed portion and continuously increases as it approaches the inflection portion.

In another embodiment of the invention, the length L1C of the central region of the recess is greater than or equal to 25% and less than or equal to 75% of the length L1 of the recess.

In another embodiment of the present invention, the plain bearing according to claim 1 or 2, wherein the width W2C of the central region of the recess is 25% or more and 75% or less of the width W2 of the recess.

In another embodiment of the invention, the depth D2 of the recess is greater than or equal to 0.1 mm and less than or equal to 0.5 mm.

In another embodiment of the invention, the groove depth D3 of the circumferential groove is greater than or equal to 1.5 μm and less than or equal to 10 μm.

In another embodiment of the invention, the groove width W3 of the circumferential groove is 0.05 or more and 0.25 mm or less.

In another embodiment of the present invention, when the central region is viewed in an axial section including the point where the depth D2 of the recess is maximum, the groove inclination angle θ1 of the circumferential groove closest to the inflection portion is The groove inclination angle θ1 of the circumferential groove closest to the width center of is larger than the groove inclination angle θ1 by a value in the range of 0.01° or more and 20° or less.

In another embodiment of the present invention, when the edge region is viewed in an axial cross section including the point where the depth D2 of the recess is maximum, the groove inclination angle θ1 of the circumferential groove closest to the inflection portion is The groove inclination angle θ1 of the circumferential groove closest to the circumferential edge of is larger than the groove inclination angle θ1 by a value in the range of 0.01° or more and 20° or less.

In another embodiment of the present invention, the first and second half bearings have two crush reliefs formed on the inner peripheral surface side adjacent to both end surfaces in the circumferential direction.

In another embodiment of the invention, the first half-bearing includes another partial groove extending in the circumferential direction on the sliding surface of the first half-bearing, and the another partial groove is formed in the first half-bearing. Of both circumferential end faces of the split bearing, only the front end face in the circumferential direction in the rotational direction of the crankshaft is open, and the end of the other partial groove on the circumferential center side of the first half bearing is open. Another recess is formed in the sliding surface of the first half bearing, located on the sliding surface between the circumferential center of the first half bearing and the circumferential end surface on the front side in the rotational direction of the crankshaft. The other recess is located at a position that includes the end of the other partial groove on the circumferential center side.

In another embodiment of the present invention, the oil groove of the second half bearing opens on both circumferential end surfaces of the second half bearing.

FIG. 2 is a schematic diagram showing a crankshaft bearing device. FIG. 2 is a diagram of a sliding bearing according to a first specific example of the present invention, viewed from the axial direction of the bearing. FIG. 3 is a plan view of the first half bearing of FIG. 2 viewed from the sliding surface side. FIG. 3 is a plan view of the second half bearing of FIG. 2 viewed from the sliding surface side. 4 is a sectional view taken along line AA in FIG. 3. FIG. 5 is a sectional view taken along line A'-A' in FIG. 4. FIG. 4 is a sectional view taken along line BB in FIG. 3. FIG. FIG. 3 is an enlarged view of the vicinity of the recess viewed from the sliding surface side. 7 is a sectional view taken along line CC in FIG. 6. FIG. FIG. 3 is an enlarged cross-sectional view of a circumferential groove near the center of the width of the recess and near the periphery of the recess. FIG. 3 is an enlarged cross-sectional view of a circumferential groove near a bent portion of a recess. FIG. 3 is a cross-sectional view for explaining the operation of the present invention. FIG. 3 is a plan view for explaining the operation of the present invention. FIG. 3 is a cross-sectional view for explaining the operation of the present invention. FIG. 3 is a plan view for explaining the operation of the present invention. It is a component exploded view of the oil flow F1 near the center of the width of the recess and near the periphery of the recess. It is a component decomposition diagram of the oil flow F1 near the recessed part inflection part. FIG. 3 is a cross-sectional view of a recess with a flat portion. FIG. 7 is a diagram of a half-split bearing according to a second specific example of the present invention viewed from the axial direction of the bearing. FIG. 7 is a diagram of a sliding bearing according to a third specific example of the present invention viewed from the axial direction of the bearing. FIG. 15 is a plan view of the second half bearing of FIG. 14 viewed from the sliding surface side. FIG. 15 is a plan view of the first half bearing of FIG. 14 viewed from the sliding surface side.

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

FIG. 1 schematically shows a bearing device 1 for an internal combustion engine. This bearing device 1 includes a journal part 6 supported at the lower part of a cylinder block 8, a crank pin 5 that is formed integrally with the journal part 6 and rotates around the journal part 6, and a reciprocating engine connected to the crank pin 5 from an internal combustion engine. A connecting rod 2 that transmits motion is provided. The bearing device 1 further includes a main bearing 4 that rotatably supports the journal portion 6 and a connecting rod bearing 3 that rotatably supports the crank pin 5 as a sliding bearing that supports the crankshaft.

Although the crankshaft has a plurality of journal parts 6 and a plurality of crank pins 5, here, for convenience of explanation, one journal part 6 and one crank pin 5 will be illustrated and explained. In FIG. 1, the positional relationship in the depth direction of the paper is such that the journal portion 6 is on the back side of the paper and the crank pin 5 is on the front side.

The journal portion 6 is pivotally supported by a lower cylinder block 82 of the internal combustion engine via a main bearing 4 constituted by a pair of half bearings 41 and 42. In the half bearing 42 located on the upper side in FIG. 1, an oil groove 42a is formed over the entire length of the inner peripheral surface. Further, the journal portion 6 has a lubricating oil passage 6a that penetrates in the diametrical direction, and when the journal portion 6 rotates in the direction of arrow 42a.

The crank pin 5 is connected to the big end housing 21 (the rod side big end housing 22 and the cap side big end housing 23) of the connecting rod 2 via the connecting rod bearing 3 configured by a pair of half bearings 31 and 32. It is pivoted.

As described above, the lubricating oil discharged by the oil pump to the main bearing 4 flows from the oil gallery formed in the cylinder block wall to the inside of the main bearing 4 through the through hole formed in the wall of the main bearing 4. The oil is fed into the oil groove 42a formed along the circumferential surface.

Furthermore, a first lubricating oil passage 6a is formed through the journal part 6 in the diametrical direction, and an inlet opening 6c of the first lubricating oil passage 6a can communicate with the lubricating oil groove 42a, so that the journal part 6 A second lubricating oil passage 5a is formed that branches from the first lubricating oil passage 6a and passes through a crank arm portion (not shown), and the second lubricating oil passage 5a is formed to penetrate in the diametrical direction of the crank pin 5. The third lubricating oil passage 5b is connected to the third lubricating oil passage 5b.

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

Conventionally, in order to prevent cavitation erosion at the circumferential ends of the partial grooves formed in the circumferential direction on the sliding surface of the connecting rod bearing 3, a half-split is provided with a recess that communicates with the circumferential ends of the partial grooves. Bearings have been proposed. However, since the concave portion of the conventional technology is formed with only a convex curved surface extending from the sliding surface toward the outer diameter side of the half bearing (it does not have an inflection part like the present invention), the periphery of the concave portion and the sliding The connection part with the surface becomes a discontinuous shape (unsmooth connection part). Therefore, a turbulent flow of lubricating oil occurs at the connection part, and a cavity is generated as the lubricating oil pressure fluctuates. As a result, cavitation erosion occurs on the sliding surface on the front side in the rotational direction of the crankshaft from the periphery of the recess. Further, in the conventional recess, since a circumferential groove is not formed on the surface of the recess, it is difficult for the lubricating oil in the recess to flow in the circumferential direction. Therefore, when a cavity is generated at the circumferential end of the partial groove that communicates with the recess, the cavity is likely to diffuse outward in the axial direction within the recess. This has caused a problem in that cavitation erosion is likely to occur on the surface of the recess near the axially outer peripheral edge of the recess where the oil clearance is narrow.

The present invention addresses these problems of the prior art.

An example in which the sliding bearing of the present invention is applied to a connecting rod bearing 3 will be described below. However, the present invention is not limited to the connecting rod bearing 3, but can also be applied to the main bearing 4.

FIG. 2 shows a first specific example of the sliding bearing (connecting rod bearing 3) according to the present invention. The connecting rod bearing 3 is formed by abutting circumferential end surfaces 76 of a pair of first half bearing 31 and second half bearing 32 and combining them into a cylindrical shape as a whole. The surface forming the inner peripheral surface of the cylindrical shape is the sliding surface 7, and the surface forming the outer peripheral surface is the back surface.

Note that the wall thicknesses of the first half bearing 31 and the second half bearing 32 are constant in the circumferential direction. However, the wall thickness may be maximum at the circumferential center and continuously decrease toward both circumferential end surfaces 76, 76.

Here, the outer diameter of the first half bearing 31 and the second half bearing 32 is 150 mm, the width in the axial direction is 50 mm, and the wall thickness is 5 mm. Note that these dimensions are just examples, and other dimensions can be used.

FIG. 3 is a diagram of the first half bearing 31 viewed from the sliding surface side. A partial groove 71 extending in the circumferential direction is formed in the sliding surface 7 of the first half bearing 31 . The partial groove 71 is open only in the circumferential end surface 76 on the rear side in the rotational direction Z of the crank pin, of both circumferential end surfaces 76, 76 of the first half bearing 31. An end 71E of the partial groove 71 on the circumferential center side is located between the circumferential center of the first half bearing 31 and the circumferential end surface 76 on the rear side in the rotation direction Z of the crank pin. . Further, a recess 72 is formed in the sliding surface 7 of the first half bearing 31, and the recess 72 is located at a position that includes the end 71E of the partial groove 71 on the circumferential center side. The peripheral edge 723 of the recessed portion 72 is located within the sliding surface 7, not in contact with any of the circumferential end surfaces 76, 76 and the axial end surfaces 7E, 7E of the first half bearing 31. A peripheral edge 723 of the recess 72 on the sliding surface 7 is elliptical. However, the periphery 723 may also be circular.

FIG. 4 is a diagram of the second half bearing 32 viewed from the sliding surface side. The second half bearing 32 has an oil groove 32a formed in the sliding surface 7 and extending in the circumferential direction. The oil groove 32a is open only in the circumferential end surface 76 on the front side in the rotational direction Z of the crank pin, of both circumferential end surfaces 76, 76 of the second half bearing 32. The other end 32aE is located between the circumferential center of the second half bearing 32 and the circumferential end surface 76 on the rear side in the rotation direction Z of the crank pin. However, the oil groove 32a may be opened on both circumferential end surfaces 76, 76.

The groove width center 71C of the partial groove 71 and the groove width center 32C of the oil groove 32a are aligned with each other, and the partial groove 71 and the oil groove 32a are in fluid communication with each other.

FIG. 5A shows a cross-sectional shape of the partial groove 71 in the axial direction, taken along the line AA in FIG. FIG. 5B shows a cross-sectional shape of the oil groove 32a in the axial direction taken along the line A'-A' in FIG. The partial groove 71 and the oil groove 32a have a rectangular cross section with a groove width W1 and a groove depth D1. Note that the groove width W1 is the distance parallel to the sliding surface 7 in a cross section perpendicular to the rotational direction Z of the crankpin (the circumferential direction of the first half bearing 31 and the second half bearing 32). is defined as Further, the groove depth D1 is defined as the distance in the vertical direction from the sliding surface 7 in a cross section perpendicular to the rotational direction Z of the crank pin. In the communication portion between the circumferential end surface 76 of the partial groove 71 and the oil groove 32a, the groove width W1 and the groove depth D1 of the partial groove 71 and the oil groove 32a are formed to have the same dimensions. Here, the groove width W1 is 10 mm, and the groove depth D1 is 2.5 mm. Further, at the end portion 71E of the partial groove 71 in the communicating portion with the recess 72, the groove width W1 of the partial groove 71 is 10 mm. Note that these dimensions are just examples, and other dimensions can be used.

The groove depth D1 of the oil groove 32a is maximum at the portion communicating with the partial groove 71, and gradually decreases toward the rear side in the rotation direction Z of the crank pin. Further, the groove depth D1 of the partial groove 71 is maximum at the communicating portion with the oil groove 32a, and gradually decreases toward the front side in the rotation direction Z of the crank pin. In addition, in the end portion 71E of the partial groove 71 in the communication portion with the recess 72, the groove depth D1 at the groove width center 71C is 0.1 mm. Note that this dimension is just an example, and other dimensions can be used.

Next, the cross-sectional shape of the recess 72 formed in the first half bearing 31 in the circumferential direction will be described in detail with reference to FIG.

FIG. 6 is a cross section taken along line BB in FIG. 3, and shows the cross-sectional shape of the recess 72 in the circumferential direction. The recess 72 has a recess surface 72S that is recessed from the sliding surface 7 toward the outer diameter side of the first half bearing 31. The recess surface 72S includes a central region 721 on the circumferential center side and edge regions 722, 722 on the side adjacent to the peripheral edge 723 of the recess 72. The edge regions 722 are located at one location at the front and rear of the center region 721 in the circumferential direction. The boundaries between the central region 721 and the edge regions 722, 722 each have one inflection portion 72P, 72P. The central region 721 has a curved line that is convex toward the outer diameter side of the first half bearing 31 . The edge regions 722 , 722 have curves that are convex toward the inner diameter side of the first half bearing 31 .

The recess 72 communicates with the partial groove 71 of the first half bearing 31 (the recess 72 and the partial groove 71 overlap). Although the surface 72S of the recess 72 does not actually exist on the rear side in the rotational direction Z of the crank pin from the communication portion, for convenience, an imaginary line of the recess surface 72S when the partial groove 71 is not formed is shown. .

The length L1 of the recess 72 is defined as the distance between both peripheral edges 723, 723 of the recess 72 in the circumferential direction. The direction of the length L1 is orthogonal to a straight line 72C1 connecting the outer diameter center of the first half bearing 31 and the deepest part in the circumferential cross section of the recess 72. Further, the length L1 of the recess 72 is divided into the length L1C of the central region 721 and the lengths L1E, L1E of the edge regions 722, which are located at each of the front and rear circumferential regions of the central region 721. Here, the length L1 of the recess is 20 mm. The length L1C of the central region is "the length L1 of the recessed part x 0.5". The lengths L1E, L1E of the edge regions are "(length L1 of the recessed part-length L1C of the central region)/2". Note that these dimensions are just examples, and other dimensions can be used.

Next, the cross-sectional shape of the recess 72 formed in the first half bearing 31 in the axial direction will be described in detail with reference to FIGS. 8, 9A, and 9B.

FIG. 8 is a cross section taken along the line 72C1 in FIG. 6, showing the cross-sectional shape of the recess 72 in the axial direction. The recess 72 has a recess surface 72S that is recessed from the sliding surface 7 toward the outer diameter side of the first half bearing 31. The recess surface 72S includes a central region 721 on the axial center side and edge regions 722, 722 on the side adjacent to the peripheral edge 723 of the recess 72. The edge regions 722, 722 are located one each on the left and right sides of the center region 721. The boundaries between the central region 721 and the edge regions 722, 722 each have one inflection portion 72P, 72P.

The width W2 of the recess is defined as the distance between both peripheral edges 723, 723 of the recess 72 in the axial direction, parallel to the sliding surface 7. Further, the width W2 of the recessed portion 72 is divided into the width W2C of the central region 721 and the widths W2E and W2E of the edge regions 722, one on each side of the central region 721. Here, the width W2 of the recess is 30 mm. The width W2C of the central region is "width W2 of the recessed portion x 0.5". The widths W2E, W2E of the edge regions are “(width W2 of the recessed portion−width W2C of the central region)/2”. The width W2C of the central region is wider than the groove width W1 (=10 mm) at the end 71E of the partial groove 71. Note that these dimensions are just examples, and other dimensions can be used.

The central region 721 has a curved line that is convex toward the outer diameter side of the first half bearing 31 . The edge regions 722 , 722 have curves that are convex toward the inner diameter side of the first half bearing 31 . Further, the depth D2 of the recess is maximum at the width center 72C2 of the recess 72, and becomes smaller toward the peripheral edges 723, 723. Note that the width center 72C2 is aligned with the groove width center 71C of the partial groove 71 in the axial direction. Further, the depth D2 of the recess is defined as the length in the direction perpendicular to the sliding surface 7 from the sliding surface 7 to the recess surface 72S. Here, the depth D2 of the recess is 0.2 mm, which is deeper than the groove depth D1 (=0.1 mm) at the groove width center 71C of the end 71E of the partial groove 71. Note that these dimensions are just examples, and other dimensions can be used.

A plurality of circumferential grooves 73 are formed adjacent to each other on the recess surface 72S of the first half bearing 31. The plurality of circumferential grooves 73 extend parallel to the circumferential direction and are formed over the entire circumferential length of the recess surface 72S. Moreover, the circumferential groove 73 is formed over the entire width of the recess surface 72S. Note that the circumferential groove 73 is allowed to be slightly inclined (up to 1°) with respect to the circumferential direction of the first half bearing 31. Note that, in order to facilitate understanding, the circumferential groove 73 is exaggerated in each drawing.

The circumferential groove 73 has a curved groove surface 731 when viewed in cross section in the axial direction of the first half bearing 31 . A top portion 732 is formed between the concave surfaces 731 of adjacent circumferential grooves 73 . A curved line connecting the top portions 732 represents the recess surface 72S. When viewed microscopically, there is no flat region on the recess surface 72S.

9A and 9B show enlarged views of the circumferential groove 73 of FIG. 8. FIG. 9A shows the shape of the circumferential groove 73 near the width center 72C2 in the central region 721 of the recess 72 and the shape of the circumferential groove 73 near the periphery 723 of the edge region 722. FIG. 9B shows the shape of the circumferential groove 73 near the bending part 72P in the central region 721 of the recess 72, and the shape of the circumferential groove 73 near the bending part 72P in the edge region 722. The groove width W3 of the circumferential groove 73 is defined as the length of an imaginary straight line 733 that linearly connects the top portions 732 on both sides of the circumferential groove 73. A groove center line 734 is defined as a line that passes through the center of the length of the virtual straight line 733 and extends perpendicularly to the virtual straight line 733. The groove depth D3 of the circumferential groove 73 is defined as the length from the imaginary straight line 733 to the position where the groove surface 731 is the most distant from the imaginary straight line 733 in the direction perpendicular to the imaginary straight line 733. The position of the maximum groove depth D3 of the circumferential groove 73 is located above the groove center line 734.

The area surrounded by the virtual straight line 733 and the groove surface 731 is defined as the groove cross-sectional area 73A. The groove width W3, groove depth D3, and groove cross-sectional area 73A of each circumferential groove 73 are the same. Furthermore, the groove width W3, the groove depth D3, and the groove cross-sectional area 73A of the circumferential groove 73 are the same at any position in the circumferential direction.

Further, the shape of the groove surface 731 of each circumferential groove 73 is formed symmetrically with respect to the groove center line 734. Two groove cross-sectional areas obtained by dividing the groove cross-sectional area 73A of each circumferential groove 73 by the groove center line 734 are the same.

The angle between the perpendicular line VL extending vertically from the sliding surface 7 toward the axis of the first half bearing 31 and the groove center line 734 of the circumferential groove 73 is defined as the groove inclination angle θ1. The groove center lines 734 of all the circumferential grooves 73 in the recess 72 are inclined toward the width center 72C2 of the recess 72 with respect to the perpendicular VL.

In the central region 721 of the recess 72, the circumferential groove 73 closest to the width center 72C2 has the smallest groove inclination angle θ1 (see FIG. 9A), and the circumferential groove 73 closest to the inflection part 72P has the largest groove. It has an inclination angle θ1 (see FIG. 9B). Therefore, the groove inclination angle θ1 continuously increases as it approaches the bending portion 72P from the width center 72C2 (as it goes outward in the axial direction).

In the edge region 722 of the recess 72, the circumferential groove 73 closest to the inflection part 72P has the largest groove inclination angle θ1 (see FIG. 9B), and the circumferential groove 73 closest to the circumferential edge 723 has the smallest groove. It has an inclination angle θ1 (see FIG. 9A). Therefore, the groove inclination angle θ1 becomes continuously smaller as it approaches the peripheral edge 723 from the bending portion 72P (as it goes outward in the axial direction).

As understood from the circumferential cross-sectional shape of the recess 72 in FIG. 6 and the axial cross-sectional shape of the recess 72 in FIG. Also, the central region 721 of the recess surface 72S forms a convex curve toward the outer diameter side of the first half bearing 31, and the edge region 722 of the recess surface 72S forms a convex curve toward the outer diameter side of the first half bearing 31. A convex curve is formed on the inner diameter side.

Next, the circumferential positional relationship between the recess 72 and the partial groove 71 formed in the first half bearing 31 will be explained using FIG. 7. FIG. 7 is an enlarged view of the vicinity of the recess 72 viewed from the sliding surface 7 side. As shown in FIG. 7, an end 71E of the partial groove 71 on the circumferential center side is located in the center region 721 of the recess 72. As shown in FIG.

The connecting rod bearing 3 of this embodiment is formed by abutting circumferential end surfaces 76 of a pair of first half bearing 31 and second half bearing 32 and combining them into a cylindrical shape as a whole. The half bearings 31, 32 can have a sliding layer that is a Cu bearing alloy or an Al bearing alloy. Alternatively, a sliding layer of Cu bearing alloy or Al bearing alloy can be provided on the Fe alloy backing layer. In addition, bearings made of a Cu bearing alloy or an Al bearing alloy and one of soft Bi, Sn, and Pb, or an alloy mainly composed of these metals, and a resin composition mainly made of synthetic resin. The sliding layer may include a surface portion disposed closer to the sliding surface than the alloy.

Next, the operation of the first half bearing 31 of the present invention will be described with reference to FIGS. 10A to 11D.

During operation of an internal combustion engine, the gap S between the surface of the crank pin 5 and the sliding surface 7 of the first half bearing 31 is always maintained due to the effects of explosion pressure in the cylinder and centrifugal force accompanying the rotation of the crankshaft. It's changing. In addition, at the end 71E of the partial groove 71, since the end 71E and the recess 72 are connected by a discontinuous surface, a turbulent flow of lubricating oil occurs at the front side of the end 71E in the rotational direction Z of the crank pin. occurs, and a cavity 9 is created in the lubricating oil due to pressure fluctuations in the lubricating oil.

Here, FIG. 10A shows a cross-sectional view near the end portion 71E, and when the internal combustion engine is operating, the sliding surface 7 of the first half bearing 31 and the surface of the crank pin 5 change from a separated state to a relative position. This shows a state in which the robot moves in close proximity to the target. FIG. 10A shows a circumferential cross section of the first half bearing 31 taken along the line BB in FIG. 3. FIG. When the sliding surface 7 and the surface of the crank pin 5 move relatively close to each other from a separated state, the lubricating oil present in the gap S is pressed toward the sliding surface 7 side. Therefore, the cavity 9 generated on the front side in the rotational direction Z of the crank pin at the end portion 71E is pushed together with the lubricating oil toward the inside of the recess 72 (towards the outer diameter side of the first half bearing 31). Move to.

FIG. 10B is a diagram of FIG. 10A viewed from the sliding surface side. As the crank pin 5 rotates, the lubricating oil in the partial groove 71 mainly flows toward the front side in the rotation direction Z of the crank pin. Since the cavity 9 is formed wider than the above, the generated cavity 9 mainly flows into the central region 721 of the recess 72 .

FIG. 11A is a cross section taken along the line DD in FIG. 10B, and is a partial sectional view of the recess 72 in the axial direction. When the surface of the crank pin 5 approaches the sliding surface 7, the oil flowing circumferentially in the recess 72 is directed into the inside of the plurality of circumferential grooves 73 of the recess 72 (recess surface 731) by the surface of the crank pin 5. being pushed towards. The pressure of the oil in each circumferential groove 73 increases as it is pushed by the oil that flows in from behind, so that it not only flows circumferentially within the circumferential groove 73 but also flows toward the recess 72 (backflow ), an oil flow F1 is formed. Here, the groove center line 734 of each circumferential groove 73 of the recess 72 is inclined toward the width center 72C2 of the recess 72. Therefore, the oil flow F1 flowing out from inside the circumferential groove 73 mainly flows obliquely toward the surface side of the crank pin 5 and toward the width center 72C2 of the recess 72. Also, at this time, an oil flow F2 is formed that accompanies the surface of the rotating crank pin 5 and flows circumferentially through the recess 72 (see FIG. 11B. 31 as seen from the sliding surface side).

The cavity 9 generated on the front side in the rotation direction Z of the crank pin at the end portion 71E is carried along with the lubricating oil to the front side in the rotation direction Z of the crank pin in the recess 72 by the oil flow F1 and the oil flow F2. Since the central region 721 of the recess 72 in which the cavity 9 exists has a convex curve toward the outer diameter side of the first half bearing 31, the oil flow F1 has the following components.

As shown in FIGS. 11C and 11D, the oil flow F1 is decomposed into a component F1 (v) that goes toward the surface side of the crankshaft 5 and a component F1 (h) that goes toward the width center 72C2 side. . In the central region 721, the oil flow F1 flowing out from the circumferential groove 73 near the width center 72C2 of the recess 72 has a relatively large F1(v), as shown in FIG. 11C.

On the other hand, in the central region 721, the oil flow F1 flowing out from the circumferential groove 73 near the bending portion 72P of the recess 72 has a relatively large F1(h), as shown in FIG. 11D.

In the central region 721, the flow component of the oil flow F1 flowing out from the circumferential groove 73 existing between the width center 72C2 and the bending part 72P flows from the width center 72C2 toward the bending part 72P (first half). (toward the axially outer side of the bearing 31), the flow component changes continuously from the flow component shown in FIG. 11C to the flow component shown in FIG. 11D. With this structure, the oil flow F1 in the central region 721 of the recess 72 directs the lubricating oil present in the central region 721 together with the cavity 9 in the direction of the width center 72C2 of the recess 72 and in the direction of the surface of the crank pin 5. and press. Since the pressure of the lubricating oil in the pressed central region 721 increases, the cavity 9 contained in the lubricating oil collapses within the central region 721 due to the return pressure. Therefore, the cavity 9 is prevented from flowing out from the inside of the recess 72 to the sliding surface 7, and cavitation erosion is prevented from occurring on the sliding surface 7. Moreover, at this time, the cavity 9 in the central region 721 is pushed up near the surface of the crank pin 5 together with the lubricating oil, and is spaced apart from the recess surface 72S. Furthermore, the depth D2 of the recess is the deepest near the width center 72C2 where the cavity 9 is pressed and moved. Therefore, when the cavity 9 collapses within the central region 721, cavitation erosion is prevented from occurring on the recess surface 72S and the groove surface 731 of the central region 721.

Furthermore, since the edge region 722 of the recess 72 has a curve convex toward the inner diameter side of the first half bearing 31, the oil flow F1 has the following components.

In the edge region 722, the oil flow F1 flowing out from the circumferential groove 73 near the bending portion 72P of the recess 72 has a relatively large F1(h), as shown in FIG. 11D.

On the other hand, in the edge region 722, the oil flow F1 flowing out from the circumferential groove 73 near the periphery 723 of the recess 72 has a relatively large F1(v), as shown in FIG. 11C.

Therefore, even if the cavity 9 does not all flow into the central region 721 and a part of it flows into the edge region 722, the cavity 9 will flow into the width center 72C2 of the recessed portion 72 along with the lubricating oil near the bending portion 72P of the edge region 722. being pushed towards. This has the effect of pushing the cavity 9 flowing into the edge region 722 into the central region 721 . Further, even if the cavity 9 reaches the vicinity of the periphery 723 of the edge region 722, the cavity 9 is pressed toward the surface side of the crank pin 5 together with lubricating oil near the periphery 723 of the edge region 722, and the return pressure causes the cavity 9 to reach the vicinity of the periphery 723 of the edge region 722. It is possible to cause the cavity 9 to collapse early. In this way, the cavity 9 is prevented from flowing out onto the sliding surface 7. Further, at this time, the cavity 9 near the peripheral edge 723 of the edge region 722 is pushed up near the surface of the crank pin 5 together with the lubricating oil, and is separated from the recess surface 72S. Therefore, when the cavity 9 collapses near the periphery 723 of the edge region 722, cavitation erosion is prevented from occurring on the recess surface 72S and the groove surface 731 of the edge region 722.

Note that when the sliding surface 7 and the surface of the crank pin 5 change from being close to each other to being separated during operation of the internal combustion engine, the cavity 9 existing in the gap S will absorb the surface of the crank pin 5 together with the lubricating oil. The crank pin 5 moves in a direction away from the sliding surface 7 (toward the surface side of the crank pin 5). Furthermore, since the gap S is also enlarged, the cavity 9 within the central region 721 or the edge region 722 will collapse at a position sufficiently spaced from the recess surface 72S, the groove surface 731, and the sliding surface 7. Cavitation erosion does not occur on the recess surface 72S, the groove surface 731, and the sliding surface 7.

Further, as shown in FIG. 10A, an edge region 722 having a convex curve on the inner diameter side of the first half bearing 31 is formed near the peripheral edge 723 on the front side in the rotation direction Z of the crank pin. , the connection portion between the edge region 722 and the sliding surface 7 has a smooth (continuous) shape. Therefore, no turbulent flow of lubricating oil occurs at the connection portion, and therefore, the formation of cavities 9 is prevented. This prevents the cavity 9 from flowing into the sliding surface 7 and the occurrence of cavitation erosion at the connection portion.

Unlike the configuration of this embodiment, if the concave surface 72S of the concave portion 72 does not have an inflection portion 72P and is formed only by a convex curve on the outer diameter side, the surface of the crank pin 5 approaches the sliding surface 7. When this occurs, although there is an effect of pushing the lubricating oil and cavity 9 toward the surface of the crank pin 5, since the connection between the peripheral edge 723 of the recess 72 and the sliding surface 7 is formed by a discontinuous surface, the connection A cavity 9 is generated on the front side in the rotational direction, and cavitation erosion occurs on the sliding surface.

Further, unlike the configuration of this embodiment, when the groove center line 734 of the circumferential groove 73 is inclined toward the peripheral edge 723 side rather than toward the width center 72C2 side with respect to the perpendicular line VL, the surface of the crank pin 5 When approaching the sliding surface 7, although there is an effect of pushing up the lubricating oil and the cavity 9 towards the surface side of the crank pin 5, there is a flow that pushes the lubricating oil and the cavity 9 outward in the axial direction. easily flows out from the recess 72 to the sliding surface 7.

Further, unlike the configuration of this embodiment, when a flat portion 72F exists between the circumferential grooves 73 of the recessed portion 72 as shown in FIG. In addition, the oil flow F1 flowing toward the recessed portion 72 (flowing backward) is not formed in the flat portion 72F. Therefore, the lubricating oil and the cavity 9 are not easily pressed toward the surface side of the crank pin 5 and the width center 72C2 side of the recess 72, and the cavity 9 is collapsed at a position close to the recess surface 72S and the groove surface 731. Therefore, cavitation erosion is likely to occur on the recess surface 72S and the groove surface 731. Further, since the pressure in the cavity 9 is difficult to recover, the cavity 9 cannot completely collapse within the recess 72 and flows into the sliding surface 7, which tends to cause cavitation erosion on the sliding surface 7.

The length L1C of the central region of the recess 72 is preferably 25% or more and 75% or less of the length L1 of the recess. If the length L1 of the recess is less than 25%, the cavity 9 that has flowed into the central region 721 is pushed up to the front edge region 722 in the rotational direction Z of the crank pin 5 before being pushed up toward the front surface of the crank pin 5. The cavitation surface 72S and the groove surface 731 are easily reached, and cavitation erosion may occur there. Furthermore, if the length of the recess exceeds 75% of the length L1, the connection between the edge region 722 and the sliding surface 7 is difficult to become smooth, causing a turbulent flow of lubricating oil at the connection, and creating a cavity 9. There is.

The width W2C of the central region of the recess 72 is preferably 25% or more and 75% or less of the width W2 of the recess. If the width W2 of the recess is less than 25%, when the width W2C of the central region is made larger than the groove width W1 at the end 71E of the partial groove 71, the width W2 of the recess becomes relatively excessive, and the recess An oil film may run out at 72, and seizure may occur on the front side of the recess 72 in the direction of rotation Z of the crank pin. If it exceeds 75% of the width W2 of the recess, the connection between the edge region 722 in the axial direction and the sliding surface 7 is difficult to become smooth, causing turbulent flow of lubricating oil there, and creating a cavity 9. There is.

The depth D2 of the recess is preferably 0.1 mm or more and 0.5 mm or less. If the depth D2 of the recess exceeds 0.5 mm, the oil film may run out in the recess 72, and seizure may occur on the front side of the recess 72 in the rotational direction Z of the crank pin. If the depth D2 of the recess is less than 0.1 mm, cavitation erosion may occur on the recess surface 72S.

The groove depth D3 of the circumferential groove 73 is preferably 1.5 μm or more and 10 μm or less. The groove width W3 of the circumferential groove 73 is preferably 0.05 mm or more and 0.25 mm or less. When the groove depth D3 of the circumferential groove 73 exceeds 10 μm or when the groove width W3 exceeds 0.25 mm, the oil flow F1 becomes weak. Further, when the groove depth D3 of the circumferential groove 73 is less than 1.5 μm, or when the groove width W3 is less than 0.05 mm, the oil flow F1 flowing from each circumferential groove 73 to the recess 72 The amount of Therefore, the cavity 9 may not be pressed sufficiently.

When looking at the central region 721 in the axial cross section including the point where the depth D2 of the recess is the maximum, the groove inclination angle θ1 of the circumferential groove 73 closest to the inflection portion 72P is at the width center 72C2 of the recess 72. It is preferable that the groove inclination angle θ1 of the nearest circumferential groove 73 is larger than the groove inclination angle θ1 by a value in the range of 0.01° or more and 20° or less. When the groove inclination angle θ1 of the circumferential groove 73 closest to the inflection portion 72P is larger than the groove inclination angle θ1 of the circumferential groove 73 closest to the width center 72C2 of the recessed portion 72 by a value of less than 0.01°, The F1(h) component of the oil flow F1 flowing out from the circumferential groove 73 in the central region 721 becomes too small. Therefore, the cavity 9 is less likely to be pressed toward the width center 72C2, and the cavity 9 is more likely to flow out into the edge region 722. Further, when the groove inclination angle θ1 of the circumferential groove 73 closest to the inflection portion 72P is larger than the groove inclination angle θ1 of the circumferential groove 73 closest to the width center 72C2 of the recessed portion 72 by a value exceeding 20°, The F1(v) component of the oil flow F1 flowing out from the circumferential groove 73 in the central region 721 becomes too small. Therefore, the cavity 9 is not easily pressed toward the surface of the crank pin 5, and the cavity 9 is likely to collapse near the recess surface 72S and the groove surface 731 in the central region 721.

When looking at the edge region 722 in the axial cross section including the point where the depth D2 of the recess is the maximum, the groove inclination angle θ1 of the circumferential groove 73 closest to the inflection portion 72P is the closest to the peripheral edge 723 of the recess 72. It is preferable that the groove inclination angle θ1 of the adjacent circumferential groove 73 is larger by a value in the range of 0.01° or more and 20° or less. If the groove inclination angle θ1 of the circumferential groove 73 closest to the inflection part 72P is larger than the groove inclination angle θ1 of the circumferential groove 73 closest to the circumferential edge 723 of the recessed part 72 by a value less than 0.01°, the edge The F1(h) component of the oil flow F1 flowing out from the circumferential groove 73 near the bending portion 72P of the region 722 becomes too small. Therefore, it is difficult to push the cavity 9 into the central region 721, and the cavity 9 is likely to collapse within the edge region 722. If the groove inclination angle θ1 of the circumferential groove 73 closest to the bending portion 72P is larger than the groove inclination angle θ1 of the circumferential groove 73 closest to the circumferential edge 723 of the recess 72 by a value exceeding 20°, the cavity 9 It is difficult to be pushed up toward the surface of the crank pin 5. Therefore, when the cavity 9 collapses within the edge region 722, the cavity 9 tends to collapse near the recess surface 72S and the groove surface 731 of the edge region 722.

At any position in the circumferential direction, each circumferential groove 73 formed in the recess 72 has the same groove depth D3, groove width W3, and groove cross-sectional area 73A. Since the groove depth D3, groove width W3, and groove cross-sectional area 73A of each circumferential groove 73 of the recess 72 are the same, the surface of the crankshaft 5 approaches the sliding surface 7 during operation of the internal combustion engine. At this time, the pressure of the oil pressed and flowing into each circumferential groove 73 becomes equally high almost simultaneously, and an oil flow F1 flowing backward from each circumferential groove 73 toward the recess 72 is formed almost simultaneously. Therefore, since the cavity 9 is evenly pressed toward the width center 72C2 of the recess, the cavity 9 is easily collapsed on the surface side of the crankshaft 5 at the width center 72C2 of the recess.

Unlike this embodiment, when the groove depth D3, groove width W3, and groove cross-sectional area 73A of each circumferential groove 73 of the recess 72 are not constant, when the surface of the crankshaft 5 approaches the sliding surface 7, The pressure of the oil that is pressed and flows into each circumferential groove 73 does not become the same pressure at the same time, and the oil flow F1 that flows backward from each circumferential groove 73 toward the recess 72 is not formed at almost the same time. . Alternatively, among the plurality of circumferential grooves 73, a circumferential groove 73 having a relatively large groove depth D3, groove width W3, and groove cross-sectional area 73A has a relatively large groove depth D3, a groove width W3, and a groove cross-sectional area 73A. is not formed (oil flows circumferentially within the circumferential groove 73). Therefore, it is difficult for the cavity 9 to be stably pressed against the surface side of the crankshaft 5 at the width center 72C2 of the recess, and cavitation erosion may occur on the recess surface 72S, the groove surface 731, and the sliding surface 7.

Hereinafter, non-limiting specific examples of other embodiments of the present invention will be described.

Second Specific Example FIG. 13 shows a diagram of a first half bearing 31 and a second half bearing 32 according to a second specific example of the present invention, viewed from the axial direction of the bearings. The half bearings 31 and 32 have two crush reliefs 70 formed on the inner peripheral surface side adjacent to both end surfaces 76 and 76 in the circumferential direction. The other configurations are the same as those of the first half bearing 31 and the second half bearing 32 that have already been described. The surface of the crush relief 70 constitutes a part of the sliding surface 7.

Note that the crush relief 70 is formed by reducing the thickness of the wall portion in the circumferential end region of the first half bearing 31 and the second half bearing 32 from the original sliding surface 7 in the radial direction. This refers to the positional deviation of the circumferential end surface 76 of the half bearings that may occur when the pair of first half bearings 31 and second half bearings 32 are assembled to the connecting rod 2, for example. Formed to absorb deformation. Therefore, the center of curvature position of the surface of the crush relief 70 is different from the center of curvature position of the sliding surface 7 in other areas (SAE J506 (item 3.26 and item 6.4), DIN1497, section 3.2, JIS D3102 reference). Generally, in the case of a bearing for a small internal combustion engine for a passenger car, the depth of the crush relief 70 on the circumferential end face of the half bearing (the distance from the original sliding surface to the crush relief 70 on the circumferential end face 76) is It is approximately 0.01 mm to 0.05 mm.

Note that the recess 72 is formed on the sliding surface 7 excluding the crush relief 70.

Third Specific Example FIG. 14 shows a first half bearing 41 and a second half bearing 42 according to a third specific example of the present invention, viewed from the axial direction of the bearings. In this specific example, the present invention is applied to the main bearing 4 shown in FIG.

FIG. 16 is a diagram of the first half bearing 41 viewed from the sliding surface side. The first half bearing 41 includes another partial groove 71' extending in the circumferential direction on the sliding surface 7 of the first half bearing 41. Another partial groove 71' is open only in the circumferential end surface 76 on the front side in the rotational direction of the crankshaft among both circumferential end surfaces 76, 76 of the first half bearing 41. An end 71E' of another partial groove 71' on the side of the circumferential center of the first half bearing 41 is connected to the circumferential center of the first half bearing 41 and the front side of the crankshaft in the rotational direction. It is located on the sliding surface 7 between the direction end surface 76. Further, another recess 72' is formed in the sliding surface 7 of the first half bearing 41. Another recess 72' is located at a position that includes an end 71E' on the circumferential center side of another partial groove 71'. The peripheral edge 723' of another recess 72' is not in contact with either the circumferential end surfaces 76, 76 or the axial end surfaces 7E, 7E of the first half bearing 41, and is located within the sliding surface 7. are doing. The periphery 723' of the further recess 72' in the sliding surface 7 is elliptical. However, the periphery 723' may also be circular.

FIG. 15 is a diagram of the second half bearing 42 viewed from the sliding surface side. The second half bearing 42 has an oil groove 42a formed in the sliding surface 7 and extending in the circumferential direction. The oil groove 42a is open to both end surfaces 76, 76 in the circumferential direction of the second half bearing 42.

The groove width center 71C' of the other partial groove 71' and the groove width center 42C of the oil groove 42a are aligned with each other, and the other partial groove 71' and the oil groove 42a are in a fluid communication relationship. The other configurations are the same as those of the half bearings 31 and 32 already described.

In this configuration, even if the first half bearing 41 is erroneously assembled to the cylinder block lower part 82 in the opposite direction, the effects of the present invention can be produced.

An oil hole may be provided at the position where the partial groove 71 of the first half bearing 31, 41 is formed, and an oil hole may be provided at the position where the oil groove 32a, 42a of the second half bearing 32, 42 is formed. It may also have an oil hole.

The axial cross sections of the partial grooves 71 of the first half bearings 31, 41 and the oil grooves 32a, 42a of the second half bearings 32, 42 are not limited to rectangular shapes, but may also be shaped into inverted trapezoids or curved surfaces. good.

1 Bearing device 2 Connecting rod 3 Connecting rod bearing 4 Main bearing 5 Crank pins 5a, 5b Lubricating oil passage 5c Discharge port 6 Journal portion 6a Lubricating oil passage 6c Inlet openings 31, 41 First half bearing 32, 42 Second half bearing Bearings 32a, 42a Oil grooves 32C, 42C Groove width center 32aE End 7 Sliding surface 7E Axial end face 70 Crush relief 71 Partial groove 71C Groove width center 71E End 71' Another partial groove 71C' Groove width center 71E' End Part 72 Recessed part 72' Another recessed part 721 Central region 722 Edge region 723 Peripheral edge 72C1 Straight line 72C2 Width center 72F Flat part 72P Inflection part 72S Recessed part surface 73 Circumferential groove 731 Groove surface 732 Top part 733 Virtual straight line 734 Groove center line 73A Groove cut Area 76 Circumferential end face 8 Cylinder block 81 Cylinder block upper part 82 Cylinder block lower part 9 Cavity D1 Groove depth D2 Recess depth D3 Groove depth L1 Recess length L1C Center region length L1E Edge region length S Gap VL Perpendicular line W1 Groove width W2 Width of the recess W2C Width of the central region W2E Width of the edge region W3 Groove width of the circumferential groove X Rotation direction of the journal Z Rotation direction of the crank pin θ1 Groove inclination angle

Claims (11)

A sliding bearing for rotatably supporting the crankshaft of an internal combustion engine,
The sliding bearing has first and second half bearings that are combined with each other to form a cylindrical shape, and the first and second half bearings have sliding surfaces on the inside in the radial direction,
The first and second half bearings have circumferential end faces on both sides in the circumferential direction,
A partial groove extending in the circumferential direction is formed in the sliding surface of the first half bearing, and the partial groove is formed in the sliding surface of the first half bearing in the circumferential direction. opening only on the circumferential end surface on the rear side of the direction,
The end of the partial groove on the circumferential center side of the first half bearing is connected to the circumferential center of the first half bearing and the circumferential end face on the rear side in the rotational direction of the crankshaft. located on the sliding surface between;
An oil groove extending in the circumferential direction is formed in the sliding surface of the second half bearing, and the oil groove is formed on at least one of the circumferential end surfaces of the second half bearing. opening in the circumferential end surface on the front side in the rotational direction;
The groove width centers of the partial groove and the oil groove are aligned with each other, and the partial groove and the oil groove are in fluid communication with each other,
A recess is formed in the sliding surface of the first half bearing, and the recess is located at a position that includes an end of the partial groove on the circumferential center side;
The circumference of the recess on the sliding surface is circular or elliptical,
The peripheral edge of the recess is not in contact with either the circumferential end face or the axial end face of the first half bearing and is located within the sliding surface,
The recess has a recess surface that is recessed from the sliding surface toward the outer diameter side of the first half bearing,
The recess surface includes a central region on the center side and an edge region on a side adjacent to the peripheral edge of the recess,
There is an inflection part at the boundary between the central region and the edge region,
The central region of the surface of the recessed portion forms a curve convex toward the outer diameter side of the first half-bearing in a cross-sectional view in any direction perpendicular to the sliding surface of the first half-bearing. and
The edge region of the recess surface forms a curve convex toward the inner diameter side of the first half bearing in a cross-sectional view in any direction perpendicular to the sliding surface of the first half bearing. and
The width of the recess in the axial direction is larger than the groove width of the partial groove at an end on the circumferential center side of the partial groove,
An end of the partial groove on the circumferential center side is located in the center region of the recess surface,
The center of the width of the recess in the axial direction and the center of the groove width of the partial groove are aligned with each other,
A plurality of circumferential grooves are formed adjacent to each other on the surface of the recess, the plurality of circumferential grooves are formed over the entire circumferential length of the surface of the recess, and the plurality of circumferential grooves are formed on the surface of the recess. The circumferential groove is formed over the entire width of the recess surface, and the circumferential groove has a curved groove surface when viewed in cross section in the axial direction of the first half bearing, and the circumferential groove has a curved groove surface. A top is formed in between, and a curve connecting the tops represents the surface of the recess,
The groove width of the circumferential groove is defined as the length of an imaginary straight line that linearly connects the tops on both sides of the circumferential groove, and the groove center line passes through the center position of the length of the imaginary straight line. Defined as a line extending perpendicularly to an imaginary straight line, the groove depth of the circumferential groove is defined as a line extending perpendicularly to the imaginary straight line, and the groove depth of the circumferential groove is defined as a line extending perpendicularly to the imaginary straight line, from the imaginary straight line to a position where the groove surface is furthest apart. a maximum groove depth of the circumferential groove is located above the groove centerline;
The area surrounded by the virtual straight line and the groove surface is defined as a groove cross-sectional area, and the groove width, the groove depth, and the groove cross-sectional area of the plurality of circumferential grooves are each the same. , the groove width, the groove depth, and the groove cross-sectional area of the circumferential groove are the same at any position in the circumferential direction,
The angle between the groove center line and a perpendicular line extending perpendicularly from the sliding surface toward the axis of the half bearing is defined as a groove inclination angle θ1,
The groove center line in the recess is inclined with respect to the perpendicular line toward the center of the width of the recess in the axial direction, and the groove inclination angle θ1 in the edge region is minimum at the peripheral edge, and the groove inclination angle The groove inclination angle θ1 in the central region continuously increases as it approaches the curved portion, becomes minimum at the center of the width of the concave portion in the axial direction, and continuously increases as it approaches the curved portion. . The plain bearing according to claim 1, wherein a length L1C of the central region of the recess is 25% or more and 75% or less of the length L1 of the recess. The plain bearing according to claim 1 or 2, wherein a width W2C of the central region of the recess is 25% or more and 75% or less of the width W2 of the recess. The sliding bearing according to any one of claims 1 to 3, wherein the depth D2 of the recess is 0.1 mm or more and 0.5 mm or less. The sliding bearing according to any one of claims 1 to 4, wherein a groove depth D3 of the circumferential groove is 1.5 μm or more and 10 μm or less. The sliding bearing according to any one of claims 1 to 5, wherein a groove width W3 of the circumferential groove is 0.05 or more and 0.25 mm or less. When the central region is viewed in an axial section including the point where the depth D2 of the recess is maximum, the groove inclination angle θ1 of the circumferential groove closest to the inflection portion is equal to the width of the recess. The plain bearing according to any one of claims 1 to 6, wherein the groove inclination angle θ1 of the circumferential groove closest to the center is larger by a value in a range of 0.01° or more and 20° or less. When the edge region is viewed in an axial cross section including a point where the depth D2 of the recess is maximum, the groove inclination angle θ1 of the circumferential groove closest to the inflection portion is equal to the circumferential edge of the recess. The plain bearing according to any one of claims 1 to 7, wherein the groove inclination angle θ1 of the circumferential groove closest to the groove is larger by a value in a range of 0.01° or more and 20° or less. The slide according to any one of claims 1 to 8, wherein the first and second half bearings have two crush reliefs formed on the inner circumferential surface side adjacent to both circumferential end surfaces. bearing. The first half-bearing includes another partial groove extending in the circumferential direction on the sliding surface of the first half-bearing, and the another partial groove is formed in the sliding surface of the first half-bearing. Of both end faces in the circumferential direction, only the end face in the circumferential direction on the front side in the rotational direction of the crankshaft is opened, and the end of the another partial groove on the side of the center part in the circumferential direction of the first half bearing is located on the sliding surface between the circumferential center of the first half bearing and the circumferential end face on the front side in the rotational direction of the crankshaft, and the sliding surface of the first half bearing The plain bearing according to any one of claims 1 to 9, wherein another recess is formed in the surface, and the another recess is located at a position that includes an end on the circumferential center side of the another partial groove. . The sliding bearing according to any one of claims 1 to 10, wherein the oil groove of the second half bearing is open to both circumferential end faces of the second half bearing.