Bearing device for a crankshaft of an internal combustion engine

Abstract

To provide a bearing device for a crankshaft of an internal combustion engine that is less likely to be damaged even if a closing phenomenon occurs in the bearing housing during operation. 【Solution means】According to the present invention, there is provided a bearing device having a crankshaft, a bearing housing, and a sliding bearing composed of a pair of half bearings. Each half bearing has an inner peripheral surface and an outer peripheral surface. At least one of the half bearings has an oil hole extending through the wall thickness of the half bearing, and a transition surface is formed between the outer peripheral surface of the half bearing and the periphery of the outer peripheral surface side opening of the oil hole. In a non-mounted state where the sliding bearing is not mounted in the bearing holding hole of the bearing housing, the periphery of the outer peripheral surface side opening of the oil hole is located closer to the center of curvature of the outer peripheral surface than the outer peripheral surface. As a result, the depth of the transition surface continuously increases from a position adjacent to the outer peripheral surface toward a position adjacent to the periphery of the outer peripheral surface side opening. In the mounted state, the outer peripheral surface and the transition surface of the half bearing are in contact with the inner peripheral surface of the bearing holding hole without a gap.

Description

Technical Field

[0001] The present invention relates to a bearing device for supporting a crankshaft of an internal combustion engine.

Background Art

[0002] The crankshaft of an internal combustion engine is supported at the lower part of the cylinder block of the internal combustion engine via a main bearing composed of a pair of half bearings at its journal part. For lubrication of the main bearing, lubricating oil discharged by an oil pump is fed into a lubricating oil groove formed along the inner peripheral surface of the main bearing through a through hole formed in the wall of the main bearing from an oil gallery formed in the cylinder block wall. Further, a first lubrication oil passage is formed penetrating in the diameter direction of the journal part, and both ends of the first lubrication oil passage are in communication with the lubricating oil groove of the main bearing. Further, a second lubrication oil passage branching from the first lubrication oil passage of the journal part and passing through the crank arm part is formed, and this second lubrication oil passage communicates with a third lubrication oil passage formed penetrating in the diameter direction of the crank pin. Therefore, the lubricating oil fed into the lubricating oil groove formed on the inner peripheral surface of the main bearing through the through hole from the oil gallery in the cylinder block wall passes through the first lubrication oil passage, the second lubrication oil passage, and the third lubrication oil passage, and is supplied from a discharge port opened at the end of the third lubrication oil passage between the sliding surfaces of the crank pin and the connecting rod bearing composed of a pair of half bearings (see, for example, Patent Document 1). In this way, oil is supplied between the surface of the crankshaft and the sliding surfaces of the main bearing and the connecting rod bearing. The lubricating oil supplied to the connecting rod bearing passes through a through hole formed in the wall of the connecting rod bearing and a lubrication oil passage formed in the connecting rod wall and is supplied between the piston and the cylinder liner.

[0003] The main bearing and the connecting rod bearing each composed of a pair of half bearings are held in a cylindrical bearing holding hole of a bearing housing. The bearing housing is composed of a pair of housing split bodies, and each housing split body has a semi-cylindrical surface that becomes a bearing holding hole when combined. The half bearing is held on this semi-cylindrical surface.

[0004] Incidentally, in recent internal combustion engines, weight reduction has been pursued for the purpose of improving fuel efficiency, and as a result, the rigidity of bearing housing parts such as connecting rods and engine blocks has a tendency to decrease. For this reason, during the operation of an internal combustion engine, due to the inertial force applied to the bearing housing and the dynamic load from the crankshaft, the bearing holding holes of the cylindrical bearing housing repeatedly experience elastic deformation where the inner diameter in the vertical direction becomes larger than that in the horizontal direction, and elastic deformation that returns to a cylindrical shape (the closing-in phenomenon) (here, the horizontal direction refers to the direction connecting the two split surfaces of the housing split body of the bearing housing as viewed from the axial direction of the bearing holding hole. The vertical direction refers to the direction perpendicular to the direction connecting the two split surfaces of the housing split body). Due to this phenomenon, a load that repeatedly fluctuates in the circumferential direction is applied to the half bearings held by each housing split body. In a half bearing composed of a backing layer and a sliding layer made of an Fe alloy, in order to prevent cracking of the sliding layer in the vicinity adjacent to the opening of the through hole (oil hole) due to a load that repeatedly fluctuates in the circumferential direction applied to the half bearing, there has been a proposal to remove the sliding layer in the vicinity adjacent to the opening of the through hole (oil hole) (see, for example, Patent Document 2).

[0005] In a sliding bearing equipped with a half bearing in which the sliding layer in the vicinity adjacent to the opening of the through hole (oil hole) has been removed, as described in Patent Document 2 above, when the closing-in phenomenon occurs in the bearing housing during the operation of an internal combustion engine, damage (cracking) is likely to occur in the backing layer in the vicinity adjacent to the through hole due to the fluctuation of the load applied in the circumferential direction of the half bearing, and the through hole (oil hole) is likely to undergo plastic deformation, resulting in a decrease in the holding force of the sliding bearing by the bearing housing.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine in which such damage is unlikely to occur during operation of the internal combustion engine.

Means for Solving the Problems

[0008] According to the present invention, there is provided a bearing device for supporting a crankshaft of an internal combustion engine, comprising a crankshaft, a bearing housing having a cylindrical bearing holding hole, and a cylindrical sliding bearing mounted on an inner peripheral surface of the bearing holding hole. The sliding bearing is composed of a pair of half bearings each having a semi-cylindrical shape. Each half bearing has a backing layer extending to the outer diameter side and a sliding layer extending to the inner diameter side. Each half bearing also has an inner peripheral surface, an outer peripheral surface, and both end surfaces in the circumferential direction. The inner peripheral surface of the half bearing supports the crankshaft. The pair of half bearings have the same axial length as each other. At least one of the pair of half bearings has one or more oil holes extending through the wall thickness of the half bearing. Both the inner peripheral surface side opening and the outer peripheral surface side opening of the oil hole have a circular shape. In the bearing device, A transition surface is formed between the outer peripheral surface of the half bearing and the periphery of the outer peripheral surface side opening of the oil hole. In a non-mounted state where the sliding bearing is not mounted on the inner peripheral surface of the bearing holding hole, the periphery of the outer peripheral surface side opening of the oil hole of the half bearing is located on the curvature center side of the outer peripheral surface in the direction of the axis of the oil hole rather than the outer peripheral surface of the half bearing. Thereby, the depth of the transition surface from the outer peripheral surface in the direction perpendicular to the outer peripheral surface continuously increases from a position adjacent to the outer peripheral surface to a position adjacent to the periphery of the outer peripheral surface side opening. The depth of the transition surface at a position adjacent to the periphery of the outer peripheral surface side opening is 5 to 50 μm. In any radial direction of the axis of the oil hole, the length of the transition surface from a position adjacent to the outer peripheral surface to a position adjacent to the periphery of the outer peripheral surface side opening is 100 to 300 μm. Also, In a mounted state where the sliding bearing is mounted on the inner peripheral surface of the bearing holding hole, the outer peripheral surface and the transition surface of the half bearing are in contact with the inner peripheral surface of the bearing holding hole without a gap. A bearing device is provided.

[0009] According to a specific example of the present invention, in the non-mounted state, the ratio (D1 / L2) of the depth (D1) to the length (L2) of the transition surface at a position adjacent to the periphery of the outer peripheral surface side opening may be 0.05 to 0.20.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 12A

Figure 12B

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Figure 17

Mode for Carrying Out the Invention

[0011] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

[0012] (First Embodiment) FIG. 1 schematically shows a bearing device 1 of an internal combustion engine. This bearing device 1 includes a journal portion 6 of a crankshaft supported at the lower part of a cylinder block, a crank pin 5 of the crankshaft formed integrally with the journal portion 6 and rotating about the journal portion 6, and a connecting rod 2 that transmits a reciprocating motion from the internal combustion engine to the crank pin 5. 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 for supporting the crankshaft.

[0013] The crankshaft has a plurality of journal portions 6 and a plurality of crank pins 5. Here, for the sake of convenience of explanation, one journal portion 6 and one crank pin 5 are illustrated and described. In FIG. 1, in the positional relationship in the depth direction of the paper surface, the journal portion 6 is on the back side of the paper surface and the crank pin 5 is on the front side.

[0014] The journal portion 6 is pivotally supported by a bearing housing 10 (cylinder block or housing split body 101 and cap or housing split body 102) at the lower part of the cylinder block of the internal combustion engine via a main bearing 4 composed of a pair of half bearings 41 and 42. An oil groove 41a is formed over the entire length of the inner peripheral surface of the upper half bearing 41 in FIG. 1. Further, the journal portion 6 has a lubricating oil passage 6a penetrating in the diameter direction, and when the journal portion 6 rotates in the direction of arrow X, the inlet openings 6c at both ends of the lubricating oil passage 6a communicate with the oil groove 41a of the main bearing 4 alternately.

[0015] The crankpin 5 is pivotally supported on a bearing housing 21 (rod-side large-end housing or housing split body 22A and cap-side large-end housing or housing split body 22B) of the connecting rod 2 via a connecting rod bearing 3 constituted by a pair of half bearings 31, 32, and is adapted to rotate in the direction of arrow Z.

[0016] The bearing housing 10 is composed of a pair of housing split bodies 101, 102. The housing split bodies 101, 102 have semi-cylindrical inner peripheral surfaces 24, and when the split surfaces 26 of the pair of housing split bodies 101, 102 are butted against each other, a cylindrical bearing holding hole 23 is formed (see FIG. 8). The outer peripheral lengths of the pair of half bearings 41, 42 constituting the main bearing 4 are slightly larger than the inner peripheral length of the bearing holding hole 23 of the bearing housing 10. Therefore, after mounting, circumferential compressive stress is generated in the pair of half bearings 41, 42, and a pressure is generated that presses the outer peripheral surface 8 against the inner peripheral surface 24 of the bearing holding hole 23, whereby the pair of half bearings 41, 42 are fixed to the bearing holding hole 23 of the bearing housing 10.

[0017] Similarly, the bearing housing 21 is composed of a pair of housing split bodies 22A, 22B. The housing split bodies 22A, 22B have semi-cylindrical inner peripheral surfaces 24, and when the split surfaces 26 of the pair of housing split bodies 22A, 22B are butted against each other, a cylindrical bearing holding hole 26 is formed (see FIG. 8). The outer peripheral lengths of the pair of half bearings 31, 32 constituting the connecting rod bearing 3 are slightly larger than the inner peripheral length of the bearing holding hole 23 of the large-end housing (bearing housing) 21. Therefore, after mounting, circumferential stress is generated in the pair of half bearings 31, 32, and a pressure is generated that presses the outer peripheral surface 8 against the inner peripheral surface 24 of the bearing holding hole 23, whereby the pair of half bearings 31, 32 are fixed to the bearing holding hole 23 of the large-end housing (bearing housing) 21.

[0018] As described above, for lubricating the main bearing 4, the lubricating oil discharged by the oil pump passes from the oil gallery formed in the cylinder block wall through the oil hole 4H formed in the wall of the main bearing 4 and is fed into the oil groove 41a formed along the inner peripheral surface of the main bearing 4.

[0019] Furthermore, a first lubricating oil passage 6a is formed to penetrate in the diameter direction of the journal portion 6, and an inlet opening 6c of the first lubricating oil passage 6a is configured to communicate with the lubricating oil groove 41a. Also, a second lubricating oil passage 5a is formed which branches from the first lubricating oil passage 6a of the journal portion 6 and passes through a crank arm portion (not shown), and the second lubricating oil passage 5a communicates with a third lubricating oil passage 5b formed to penetrate in the diameter direction of the crank pin 5.

[0020] In this way, the lubricating oil passes through the first lubricating oil passage 6a, the second lubricating oil passage 5a, and the third lubricating oil passage 5b, and is supplied from the discharge port 5c at the end of the third lubricating oil passage 5b to the gap formed between the crank pin 5 and the connecting rod bearing 3.

[0021] Furthermore, an oil hole 3H is formed to penetrate the wall of the connecting rod bearing 3 and communicates with a lubricating oil passage 25 formed to penetrate the wall of the connecting rod 2. The lubricating oil passes through the oil hole 3H of the connecting rod bearing 3 and the lubricating oil passage 25 of the connecting rod 2 and is supplied to the gap formed between a piston (not shown) and a cylinder liner (not shown).

[0022] In recent internal combustion engines, weight reduction is being pursued for the purpose of improving fuel efficiency, and as a result, the rigidity of bearing housing parts such as the connecting rod 2 and the engine block 101 tends to decrease. For this reason, during the operation of the internal combustion engine, due to the inertial force applied to the bearing housing 10;21 and the dynamic load from the crankshaft, the bearing holding hole 23 of the bearing housing 10;21 having a cylindrical shape undergoes an elastic deformation (see Fig. 9) in which the inner diameter DV in the vertical direction becomes larger than the inner diameter DH in the horizontal direction, and an elastic deformation (see Fig. 8) that returns to the cylindrical shape, and a phenomenon (closing-in phenomenon) in which these deformations repeat occurs. Here, the horizontal direction is the direction connecting the two split surfaces 26 of the housing split bodies 101, 102;22A, 22B of the bearing housing 10;21 as viewed from the axial direction of the bearing holding hole 23. The vertical direction is the direction orthogonal to the direction connecting the two split surfaces 26 of the housing split bodies 101, 102;22A, 22B of the bearing housing 10;21 as viewed from the axial direction of the bearing holding hole 23.

[0023] A circumferential stress (a stress in the direction of compressing the circumference of the sliding bearing 3;4) is applied to the sliding bearing 3;4 held in the bearing holding hole 23 of the bearing housing 10;21. For this reason, a concentration portion of the circumferential stress is formed around the oil holes 3H;4H of the sliding bearing 3;4. When the inner diameter of the bearing holding hole 23 of the bearing housing 10;21 becomes larger in the vertical direction, the circumference of the inner peripheral surface of the bearing holding hole 23 becomes larger, and the circumferential stress applied to the sliding bearing 3;4 becomes smaller. On the other hand, when the inner diameter of the bearing holding hole 23 of the bearing housing 10;21 elastically deforms so as to return to the cylindrical shape, the circumferential stress applied to the sliding bearing 3;4 becomes larger. During the operation of the internal combustion engine, the circumferential stress applied to the sliding bearing 3;4 fluctuates repeatedly.

[0024] In a conventional sliding bearing having a split bearing in which a sliding layer in the vicinity adjacent to the opening of the oil hole on the inner peripheral surface side is removed (see, for example, Patent Document 2), when a closing phenomenon occurs in the bearing housing during operation of an internal combustion engine, due to fluctuations in the circumferential stress applied to the split bearing, damage (cracks) is likely to occur in the backing layer in the vicinity adjacent to the oil hole, and the oil hole (the backing layer in the vicinity adjacent to the oil hole) is plastically deformed, and the circumferential length of the split bearing decreases, so that the holding force of the sliding bearing by the bearing housing is likely to decrease.

[0025] Hereinafter, an embodiment in which the bearing device 1 of the present invention is applied to the connecting rod bearing portion will be described. However, it will be understood that the bearing device of the present invention is not limited to application to the connecting rod bearing portion, and may also be applied to a main bearing portion having a main bearing portion housing.

[0026] FIG. 2 shows a view of the connecting rod bearing 3 composed of the split bearings 31 and 32 of the present invention with the circumferential end faces 76 aligned in the non-mounted state, as viewed from the axial direction. FIG. 3 is a view of the upper split bearing 31 shown in FIG. 2 as viewed from the axial direction. FIG. 4 is a plan view of the upper split bearing 31 shown in FIG. 2 as viewed from the inner peripheral surface side. FIG. 5 is a plan view of the upper split bearing 31 shown in FIG. 2 as viewed from the outer peripheral surface side.

[0027] As shown in FIGS. 2 to 4, the connecting rod bearing 3 of the present embodiment is formed by butting the circumferential end faces 76 of a pair of split bearings 31 and 32 having a semi-cylindrical shape and combining them into a cylindrical shape as a whole. The split bearings 31 and 32 have a backing layer 91 extending to the outer diameter side and a sliding layer 92 extending to the inner diameter side. For the backing layer 91, an Fe alloy such as hypoeutectoid steel or stainless steel can be used. For the sliding layer 92, a Cu bearing alloy, an Al bearing alloy, etc. can be used. Further, the cylindrical inner peripheral surface 7 and outer peripheral surface 8 may have a surface portion made of any one of Bi, Sn, and Pb, which is softer than the bearing alloy, or a surface portion made of an alloy mainly composed of these metals, or a surface portion made of a resin composition mainly composed of a synthetic resin.

[0028] The half bearings 31 and 32 have an inner peripheral surface 7, an outer peripheral surface 8, two circumferential end surfaces 76, 76, and two axial end surfaces 7E, 7E. The pair of half bearings 31 and 32 have the same inner diameter dimension, outer diameter dimension, and axial length L1 with respect to each other.

[0029] The half bearing 31 has an oil hole 3H penetrating through the wall thickness T of the half bearing 31. The inner peripheral surface side opening 34 and the outer peripheral surface side opening 33 of the oil hole 3H have a circular shape when viewed from the direction of the axial center line CL of the oil hole.

[0030] FIG. 6 is a view showing the vicinity of the outer peripheral surface side opening 33 of the oil hole 3H of the half bearing 31 shown in FIG. 3 (view taken along arrow A in FIG. 3), and FIG. 7 is a cross-sectional view taken along line B - B of the half bearing shown in FIG. 5.

[0031] In the non - mounted state, the periphery 33e of the outer peripheral surface side opening 33 of the oil hole 3H of the half bearing 31 is located closer to the center of curvature C1 of the outer peripheral surface (i.e., the inner peripheral surface 7 side) than the outer peripheral surface 8 in the direction of the axial center line CL of the oil hole 3H. A transition surface 81 is formed between the outer peripheral surface 8 and the periphery 33e of the outer peripheral surface side opening 33 of the oil hole 3H. The depth of the transition surface 81 defined as the distance in the direction perpendicular to the outer peripheral surface 8 from the outer peripheral surface 8 to the transition surface 81 continuously increases from the position adjacent to the outer peripheral surface 8 to the position adjacent to the periphery 33e of the outer peripheral surface side opening 33 in any radial direction with respect to the center C2 of the oil hole 3H. The depth D1 of the transition surface at the position adjacent to the periphery 33e of the outer peripheral surface side opening 33 is 5 to 50 μm. Also, the length L2 of the transition surface 81 defined as the radial distance with respect to the center C2 of the oil hole 3H from the position adjacent to the outer peripheral surface 8 to the position adjacent to the periphery 33e of the outer peripheral surface side opening 33 is 100 to 300 μm in any radial direction with respect to the center C2 of the oil hole 3H. Furthermore, the ratio (D1 / L2) of the depth D1 of the transition surface to the length L2 of the transition surface at the position adjacent to the periphery 33e of the outer peripheral surface side opening 33 is preferably 0.05 to 0.20.

[0032] In this embodiment, the wall thickness T1 of the half bearing 31 and the thickness T2 of the backing layer 91 are constant over the circumferential direction except in the region of the transition surface 81. Also, the thickness T3 of the sliding layer 92 is constant over the entire circumferential length of the half bearings 31 and 32. Alternatively, without being limited thereto, the wall thickness T1 of the half bearing 31 and the thickness T3 of the sliding layer may be maximum at the circumferential center of the half bearings 31 and 32 and decrease toward both circumferential end faces 76. In the case of a bearing device for a small internal combustion engine such as for a passenger car, the wall thickness T1 of the half bearings 31 and 32 can be 1 to 3 mm, the thickness T2 of the backing layer can be 0.75 to 2.85 mm, and the thickness T3 of the sliding layer can be 0.15 to 0.3 mm. However, the wall thickness T1 of the half bearings 31 and 32, the thickness T2 of the backing layer, and the thickness T3 of the sliding layer are not limited thereto and can be other dimensions.

[0033] Also, the inner circumferential surfaces 7 of the half bearings 31 and 32 may have a crush relief (not shown) at both circumferential ends. The crush relief is a surface formed by reducing the wall thickness in the radial direction from the original inner circumferential surface 7 in the circumferential end regions of the half bearings 31 and 32, and this is formed to absorb, for example, the circumferential misalignment or deformation between the circumferential end faces 76 of the half bearings that may occur when a pair of half bearings 31 and 32 are assembled to a bearing housing. 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 circumferential surface 7 in other regions (see SAE J506 (items 3.26 and 6.4), DIN1497, section 3.2, JIS D3102). Generally, 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 face of the half bearing (the distance from the original inner circumferential surface to the crush relief at the circumferential end face 76) is about 0.01 to 0.05 mm.

[0034] Also, in this embodiment, the half bearing 31 has one oil hole 3H, but may have a plurality of oil holes 3H. Also, in this embodiment, among the pair of half bearings 31 and 32, only one (upper side) half bearing 31 has the oil hole 3H, but the other (lower side) half bearing 32 can also be made to have the oil hole 3H.

[0035] FIG. 10 is a view of the sliding bearing and the large end portion of the connecting rod according to the first embodiment of the present invention as viewed in the axial direction. FIG. 11 is an enlarged cross-sectional view (enlarged cross-section of portion C) of the sliding bearing and the large end portion of the connecting rod shown in FIG. 10 at a position near the oil hole 3H. As shown in FIG. 10, in the mounted state where the bearing holder holes 23 of the large end housing 21 are mounted, circumferential compressive stress is generated in the pair of split bearings 31, 32, and the circumferential end faces 76 thereof come into contact with each other without a gap. Further, the dotted line adjacent to the outer peripheral surface 8 shown in FIG. 11 indicates the virtual transition surface 81A and the outer peripheral surface side opening 33A when there is no displacement due to mounting. In the actual mounted state, due to the circumferential compressive stress, the circumferential end faces 76 of the pair of split bearings 31, 32 are pressed against each other, so that the transition surface 81 is displaced in the radially outer direction (the direction of the white arrow in FIG. 11), and thereby comes into contact with the inner peripheral surface 24 of the bearing holder hole 23 without a gap, similar to the outer peripheral surface 81.

[0036] Also, as shown in FIG. 11, in the mounted state where the bearing holder hole 23 of the large end housing 21 is mounted, when the transition surface 81 of the split bearing 31 is displaced radially outward, the inner peripheral surface 7 in the region corresponding to the transition surface 81 and the inner peripheral surface side opening 34 of the oil hole 3H are also displaced radially outward. As a result, the transition inner peripheral surface 71 is formed at a position adjacent to the inner peripheral surface side opening 34 of the oil hole 3H of the split bearing 31.

[0037] In addition, when the depth D1 of the transition surface 81 at a position adjacent to the periphery 33e of the outer peripheral surface side opening 33 in the non-mounted state is less than 5 μm, or when the length L2 of the transition surface 81 is less than 100 μm, when the close-in phenomenon occurs in the bearing holding hole 23 of the bearing housing 10; 21, the transition surface 81 elastically deforms, resulting in an insufficient effect of relaxing the circumferential compressive stress applied around the oil hole 3H. Further, when the depth D1 of the transition surface at a position adjacent to the periphery 33e of the outer peripheral surface side opening 33 in the non-mounted state exceeds 50 μm, or when the length L2 of the transition surface 81 exceeds 300 μm, when the close-in phenomenon occurs in the bearing holding hole 23 of the bearing housing 10; 21, the oil passing through the oil hole 3H may enter between the outer peripheral surface 8 of the half bearing 31 and the inner peripheral surface 24 of the bearing holding hole 23 of the bearing housing 10; 21. When oil enters between the outer peripheral surface 8 of the half bearing 31 and the inner peripheral surface 24 of the bearing holding hole 23, the holding force of the sliding bearing 3 by the bearing holding hole 23 becomes small, and the sliding bearing 3 may rotate together with the rotating shaft (crank pin 5), and the rotating shaft (crank pin 5; journal portion 6) may not be supported.

[0038] Next, the operation of the present invention will be described. As described above, during the operation of the internal combustion engine, due to the inertial force applied to the bearing housing 10; 21 and the dynamic load from the crankshaft, the bearing holding hole 23 of the cylindrical bearing housing 10; 21 repeatedly undergoes an elastic deformation in which the inner diameter DV in the vertical direction becomes larger than the inner diameter DH in the horizontal direction (see FIG. 9) and an elastic deformation that returns to the cylindrical shape (see FIG. 8) (close-in phenomenon). FIG. 12A shows an enlarged cross-sectional view of the vicinity of the oil hole 3H of the half bearing 31 in the mounted state when the bearing holding hole 23 of the bearing housing 21 elastically deforms such that the inner diameter DV in the vertical direction becomes larger than the inner diameter DH in the horizontal direction (see FIG. 9) due to the close-in phenomenon, as viewed from the axial direction, and FIG. 12B shows an enlarged cross-sectional view of the vicinity of the oil hole 3H of the half bearing 31 in the mounted state when the bearing holding hole 23 of the bearing housing 21 elastically deforms to return to the cylindrical shape (see FIG. 8), as viewed from the axial direction. As shown in Fig. 12A, when the bearing holding hole 23 of the bearing housing 21 elastically deforms such that the inner diameter DV in the vertical direction is larger than the inner diameter DH in the horizontal direction, the circumference of the inner peripheral surface 24 of the bearing holding hole 23 increases, the circumferential stress applied to the split bearing 31 decreases, and the transition surface 81 elastically deforms so as to be separated from the inner peripheral surface 24 of the bearing holding hole 23. On the other hand, as shown in Fig. 12B, when the inner diameter of the bearing holding hole 23 of the bearing housing 21 elastically deforms so as to return to a cylindrical shape, the circumferential stress applied to the split bearing 31 increases, and the transition surface 81 elastically deforms so as to be in contact with the inner peripheral surface 24 of the bearing holding hole 23 without a gap. When the close-in phenomenon occurs, immediately before the circumferential load applied around the oil hole 3H increases, a part of the load is consumed by the elastic deformation of this transition surface 81, thereby preventing damage (cracking) of the sliding layer 92 and the backing layer 91 in the vicinity adjacent to the oil hole 3H, or plastic deformation of the oil hole (that is, the sliding layer and the backing layer in the vicinity adjacent to the oil hole), and a decrease in the circumferential length of the split bearing. As a result, the holding force of the sliding bearing by the bearing housing can be maintained.

[0039] (Second Embodiment) Hereinafter, other non-limiting embodiments of the present invention will be described.

[0040] Fig. 13 is a view of the connecting rod bearing 3 composed of split bearings 31 and 32 with their circumferential end faces 76 aligned in the non-mounted state of the second embodiment of the present invention, as viewed from the axial direction. Fig. 14 is a view of the upper split bearing 31 shown in Fig. 13, as viewed from the axial direction. Fig. 15 is a plan view of the split bearing 31 shown in Fig. 14, as viewed from the outer peripheral surface side. Fig. 16 is a cross-sectional view of the split bearing 31 shown in Fig. 15, taken along line D-D, and Fig. 17 is an enlarged view of part E of the split bearing 31 shown in Fig. 16.

[0041] The bearing device of the second embodiment differs only in the configuration of the upper split bearing 31 of the sliding bearing (connecting rod bearing 3), and other configurations are the same as those of the bearing device of the first embodiment. The description of the configurations common to the first embodiment will be omitted.

[0042] A chamfer 34C is formed between the peripheral edge 34e of the inner circumferential surface side opening 34 of the oil hole 3H of the half bearing 31 and the inner circumferential surface 7. There may be burrs formed on the edge of the inner circumferential surface side opening 34 of the oil hole 3H when manufacturing the half bearing 31. The chamfer 34C is formed to remove this burr. In this embodiment, the surface of the chamfer 34C is flat, but it may also be curved.

[0043] A chamfer 33C is formed between the peripheral edge 33e of the outer circumferential surface side opening 33 of the oil hole 3H of the half bearing 31 and the outer circumferential surface 8. There may be burrs formed on the edge of the outer circumferential surface side opening 33 of the oil hole 3H when manufacturing the half bearing 31. The chamfer 33C is formed to remove this burr. In this embodiment, the chamfer 33C is curved (arc-shaped), but it may also be flat. Note that this chamfer 33C is configured not to contact the inner circumferential surface 24 of the bearing holding hole 23 when the half bearing 31 is mounted in the bearing holding hole 23 of the bearing housing 21. If the chamfer 33C is made too large, the strength of the backing layer 91 in the vicinity adjacent to the outer circumferential surface side opening 33 of the oil hole 3H will be reduced. In order to minimize the impact on the strength of the backing layer 91 in the vicinity adjacent to the outer circumferential surface side opening 33 of the oil hole 3H, the length L3 of the chamfer 33C, defined as the radial distance with respect to the axis line CL from the position adjacent to the outer circumferential surface 8 to the position adjacent to the peripheral edge 33e of the outer circumferential surface side opening 33, is preferably 15% or less of the length L2 of the transition surface 81 (see Fig. 17).

[0044] The above description has been made using an example in which the bearing device of the present invention is applied to the connecting rod bearing portion that supports the crank pin of the crankshaft of an internal combustion engine. However, the bearing device of the present invention can also be applied to the main bearing portion that supports the journal portion of the crankshaft. Further, the half bearing may further have, for example, an oil groove or a notch for positioning. Further, the half bearing may have a chamfer at a position where the outer circumferential surface and each end surface in the axial direction are adjacent, or at a position where the inner circumferential surface and each end surface in the axial direction are adjacent.

Description of Reference Numerals

[0045] 1 Bearing device 10 Bearing housing (for main bearing) 101 Housing Split Body (Lower Cylinder Block) 102 Housing Split Body (Bearing Cap) 2 Connecting Rod 21 Bearing Housing (For Connecting Rod Shaft) 22A Housing Split Body (Large End Housing on Rod Side) 22B Housing Split Body (Large End Housing on Cap Side) 23 Bearing Retaining Hole 24 Inner Peripheral Surface 25 Lubrication Oil Passage 3 Connecting Rod Bearing 31, 32 Half Bearings 3H Oil Hole 33 Outer Peripheral Surface Side Opening 33e Periphery 34 Inner Peripheral Surface Side Opening 34e Periphery 4 Main Bearing 41, 42 Half Bearings 41a Oil Groove 4H Oil Hole 5 Crank Pin 5a, 5b Lubrication Oil Passages 5c Discharge Port 6 Journal Part 6a Lubrication Oil Passage 6c Inlet Opening 7 Inner Peripheral Surface 71 Transition Inner Peripheral Surface 7E Axial Direction End Face 76 Circumferential Direction End Face 8 Outer Peripheral Surface 81 Transition Surface 81A Virtual Transition Surface 91 Backing Metal Layer 92 Sliding Layer C1 Curvature Center of Outer Peripheral Surface C2 Center of Oil Hole CL Axis Line of Oil Hole D1 Depth of Transition Surface L1 Axial Direction Length of Half Bearing L2 Length of Transition Surface L3 Chamfer Length T1 Wall Thickness of Half Bearing T2 Thickness of Backing Metal Layer Thickness of the T3 sliding layer Rotational direction of the X journal part Rotational direction of the Z crank pin

Claims

1. A bearing device for supporting a crankshaft of an internal combustion engine, comprising a crankshaft, a bearing housing having a cylindrical bearing holding hole, and a cylindrical sliding bearing mounted on an inner peripheral surface of the bearing holding hole, wherein the sliding bearing is composed of a pair of half bearings each having a semi-cylindrical shape, each half bearing has a backing layer extending to the outer diameter side and a sliding layer extending to the inner diameter side, and each half bearing has an inner peripheral surface, an outer peripheral surface, and both circumferential end faces, the inner peripheral surface of the half bearing supports the crankshaft, the pair of half bearings have the same axial length, and at least one of the pair of half bearings has one or more oil holes extending through the wall thickness of the half bearing, and both the inner peripheral surface side opening and the outer peripheral surface side opening of the oil hole have a circular shape, in the bearing device, a transition surface is formed between the outer peripheral surface of the half bearing and the periphery of the outer peripheral surface side opening of the oil hole, in a non-mounted state where the sliding bearing is not mounted on the inner peripheral surface of the bearing holding hole, the periphery of the outer peripheral surface side opening of the oil hole of the half bearing is located on the curvature center side of the outer peripheral surface in the direction of the axis of the oil hole with respect to the outer peripheral surface of the half bearing, whereby the depth of the transition surface from the outer peripheral surface in a direction perpendicular to the outer peripheral surface continuously increases from a position adjacent to the outer peripheral surface to a position adjacent to the periphery of the outer peripheral surface side opening, the depth of the transition surface at a position adjacent to the periphery of the outer peripheral surface side opening is 5 to 50 μm, and in any radial direction of the axis of the oil hole, the length of the transition surface from a position adjacent to the outer peripheral surface to a position adjacent to the periphery of the outer peripheral surface side opening is 100 to 300 μm, and in a mounted state where the sliding bearing is mounted on the inner peripheral surface of the bearing holding hole, the outer peripheral surface and the transition surface of the half bearing are in contact with the inner peripheral surface of the bearing holding hole without a gap, a bearing device characterized thereby.

2. The bearing device according to claim 1, wherein in the non-mounted state, the ratio (D1 / L2) of the depth (D1) of the transition surface at a position adjacent to the periphery of the outer peripheral surface side opening to the length (L2) of the transition surface is 0.05 to 0.20.

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