Bearing device for crankshaft of internal combustion engine

Abstract

Provided is a bearing device for a crankshaft of an internal combustion engine, the bearing device being less susceptible to damage even when a bearing housing is ovalized during operation. According to the present invention, there is provided a bearing device comprising a crankshaft, a bearing housing, and a sliding bearing comprising a pair of half bearings, each half bearing having an inner peripheral surface and an outer peripheral surface, and at least one of the half bearings having an oil hole extending so as to pass through the thickness of the half bearing, a transition surface is formed between the outer peripheral surface of the half bearing and the peripheral edge of the outer peripheral surface side opening of the oil hole. In a non-mounted state in which the sliding bearing is not mounted to the bearing holding hole of the bearing housing, the peripheral edge of the outer peripheral surface-side opening of the oil hole is positioned closer to the center of curvature of the outer peripheral surface than the outer peripheral surface. The depth of the transition surface continuously increases from a position adjacent to the outer peripheral surface toward a position adjacent to the peripheral edge of the outer peripheral surface side opening, and 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 its journal portion by a main bearing composed of a pair of half-split bearings in the lower part of the cylinder block of the internal combustion engine. For lubrication of the main bearing, lubricating oil discharged from 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 via an oil passage formed in the cylinder block wall. Further, a first lubricating oil passage is formed penetrating in the diameter direction of the journal portion, and both ends of the first lubricating oil passage are opened and communicated with the lubricating oil groove of the main bearing. Further, a second lubricating oil passage penetrating through the crank arm portion is formed branching from the first lubricating oil passage of the journal portion, and the second lubricating oil passage is communicated with a third lubricating oil passage formed penetrating in the diameter direction along the crank pin. Therefore, the lubricating oil fed into the lubricating oil groove formed in the inner peripheral surface of the main bearing through the through hole from the oil passage in the cylinder block wall is supplied to between the sliding surface of the crank pin and the sliding surface of a connecting rod bearing composed of a pair of half-split bearings via the first lubricating oil passage, the second lubricating oil passage, and the third lubricating oil passage from a discharge port opened at the end of the third lubricating oil passage (for example, refer to Patent Document 1). Thus, 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 is supplied to between the piston and the cylinder liner through a through hole formed in the wall of the connecting rod bearing and a lubricating oil passage formed in the connecting rod wall.

[0003] The main bearing and the connecting rod bearing respectively composed of a pair of half-split bearings are respectively 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 forms the bearing holding hole when combined. The half-split bearing is held on the semi-cylindrical surface.

[0004] However, in recent internal combustion engines, in order to achieve low fuel consumption, weight reduction is sought, and thus, there is a tendency for the rigidity of bearing housing portions such as connecting rods and engine cylinders to become low. Therefore, during operation of the internal combustion engine, due to the inertial force applied to the bearing housing and the dynamic load from the crankshaft, an elastic deformation in which the inner diameter in the vertical direction is larger than the inner diameter in the horizontal direction and an elastic deformation of restoring to a cylindrical shape are repeatedly performed in the bearing holding hole of the cylindrical bearing housing (elliptical phenomenon, Japanese: クローズイン現象). Here, the horizontal direction refers to the direction connecting the two split surfaces of the housing split body of the bearing housing when viewed from the axial direction of the bearing holding hole. Further, the vertical direction refers to the direction orthogonal to the direction connecting the two split surfaces of the housing split body. Due to this phenomenon, a load that varies repeatedly in the circumferential direction is applied to the half-split bearings held in each housing split body. In a semi-split bearing composed of a back metal layer and a sliding layer made of an iron alloy, in order to prevent the sliding layer adjacent to the opening of the through hole (oil hole) from cracking due to the load that repeatedly changes in the circumferential direction of the semi-split bearing, a scheme of removing the sliding layer adjacent to the opening of the through hole (oil hole) has been proposed (for example, refer to patent document 2).

[0005] As described in the above-mentioned patent document 2, when the bearing housing undergoes elliptical deformation during operation of the internal combustion engine, the back metal layer adjacent to the through hole of the sliding bearing having a half-split bearing in which the sliding layer adjacent to the opening of the through hole (oil hole) has been removed is easily damaged (cracked) due to the change in the load applied along the circumferential direction of the half-split bearing. In addition, the through hole (oil hole) undergoes plastic deformation, and the holding force of the bearing housing on the sliding bearing is easily reduced. Prior art literature Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 8-277831 Patent Document 2: Japanese Patent Application Laid-Open No. 2009-41724 Summary of the Invention

[0007] An object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine that is less likely to be damaged during operation of the internal combustion engine.

[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 retaining hole; and a cylindrical sliding bearing mounted to the inner peripheral surface of the bearing retaining hole. The sliding bearing is composed of a pair of half-split bearings, each having a semi-cylindrical shape, each half-split bearing having a back metal layer extending on the outer diameter side and a sliding layer extending on the inner diameter side. In addition, each half-split bearing has an inner peripheral surface, an outer peripheral surface, and two circumferential end surfaces. The inner peripheral surface of the half-split bearing supports the crankshaft. The pair of half-split bearings have the same axial length. At least one of the pair of half-split bearings has one or more oil holes extending through the wall thickness of the half-split bearing, and the inner peripheral surface opening and the outer peripheral surface opening of the oil hole both have a circular shape. A transition surface is formed between the outer peripheral surface of the half-split bearing and the peripheral edge of the outer peripheral surface side opening of the oil hole. In the non-installed state where the sliding bearing is not installed on the inner circumferential surface of the bearing retaining hole, the peripheral edge of the outer circumferential surface side opening of the half-split bearing is located at a position on the side of the curvature center of the outer circumferential surface relative to the outer circumferential surface of the half-split bearing in the direction of the axial center line of the oil hole. As a result, the depth of the transition surface from the outer circumferential surface in the direction perpendicular to the outer circumferential surface continuously increases from the position adjacent to the outer circumferential surface toward the position adjacent to the peripheral edge of the outer circumferential surface side opening. The depth of the transition surface at the position adjacent to the peripheral edge of the outer circumferential surface side opening is 5 to 50 μm. In any radial direction of the axial center line of the oil hole, the length of the transition surface from the position adjacent to the outer circumferential surface to the position adjacent to the peripheral edge of the outer circumferential surface side opening is 100 to 300 μm. Furthermore, in a state where the sliding bearing is mounted to the inner peripheral surface of the bearing holding hole, the outer peripheral surface and the transition surface of the half-split bearing are in contact with the inner peripheral surface of the bearing holding hole without a gap.

[0009] According to a specific example of the present invention, in the non-installed state, the ratio (D1 / L2) of the depth (D1) of the transition surface at a position adjacent to the peripheral edge of the outer peripheral surface opening to the length (L2) of the transition surface can be 0.05 to 0.20. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram showing a bearing device for a crankshaft. Figure 2 This is a diagram showing the sliding bearing according to the first embodiment of the present invention in a non-mounted state as viewed from the axial direction. Figure 3 Observed from the axis Figure 2 Diagram of the upper side of a half-split bearing shown. Figure 4 Viewed from the inner side Figure 2 A top view of the half-split bearing from the upper side is shown. Figure 5 Observed from the outer side Figure 2 A top view of the half-split bearing is shown from the upper side. Figure 6 It shows Figure 2 The diagram near the opening of the oil hole of the half-split bearing shown ( Figure 3 A-direction view). Figure 7 It is along Figure 5 A cross-sectional view along line BB of a half-split bearing is shown. Figure 8 It is a diagram showing a bearing housing. Figure 9 FIG. 1 is a diagram showing the bearing housing during elastic deformation. Figure 10This is a diagram showing a sliding bearing and a bearing housing according to a first embodiment of the present invention as viewed from the axial direction. Figure 11 yes Figure 10 An enlarged cross-sectional view of section C of the sliding bearing and bearing housing is shown. Figure 12A This is a diagram for explaining the effects of the present invention. Figure 12B This is a diagram for explaining the effects of the present invention. Figure 13 This is a diagram showing a sliding bearing according to a second embodiment of the present invention in a non-mounted state as viewed from the axial direction. Figure 14 Observed from the axis Figure 13 Diagram of the upper side of a half-split bearing shown. Figure 15 Observed from the outer side Figure 14 A top view of a half-split bearing is shown. Figure 16 It is along Figure 15 A cross-sectional view along line DD of a half-split bearing is shown. Figure 17 yes Figure 16 An enlarged view of section E of a half-split bearing is shown. DETAILED DESCRIPTION

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

[0012] (First embodiment) Figure 1 Schematically illustrates a bearing assembly 1 for an internal combustion engine. This assembly 1 includes a crankshaft journal 6, which is supported at the bottom of a cylinder block; a crankpin 5, which is integrally formed with the journal 6 and rotates about the journal 6; and a connecting rod 2, which transmits reciprocating motion from the internal combustion engine to the crankpin 5. The bearing assembly 1 also includes a main bearing 4 and a connecting rod bearing 3, serving as sliding bearings supporting the crankshaft. The main bearing 4 rotatably supports the journal 6, while the connecting rod bearing 3 rotatably supports the crankpin 5.

[0013] In addition, although the crankshaft has a plurality of journals 6 and a plurality of crank pins 5, here, for the sake of convenience, one journal 6 and one crank pin 5 are shown in the figure for description. Figure 1 In the figure, with respect to the positional relationship in the depth direction of the paper, the journal portion 6 is located on the depth side of the paper, and the crank pin 5 is located on the front side.

[0014] The journal 6 is axially supported by the bearing housing 10 (cylinder or housing split 101 and cover or housing split 102) at the lower part of the cylinder block of the internal combustion engine through the main bearing 4 composed of a pair of half-split bearings 41 and 42. Figure 1 The upper half-split bearing 41 has an oil groove 41a formed along the entire length of its inner circumference. Furthermore, the journal 6 has a lubricating oil passage 6a extending radially therethrough. As the journal 6 rotates in the direction indicated by arrow X, the inlet openings 6c at both ends of the lubricating oil passage 6a alternately communicate with the oil groove 41a of the main bearing 4.

[0015] The crankpin 5 is axially supported by the bearing housing 21 of the connecting rod 2 (the rod side big end housing or housing split body 22A and the cover side big end housing or housing split body 22B) through the connecting rod bearing 3 composed of a pair of half-split bearings 31 and 32, and rotates in the arrow Z direction.

[0016] The bearing housing 10 is composed of a pair of housing segments 101 and 102. The housing segments 101 and 102 have a semi-cylindrical inner peripheral surface 24. When the split surfaces 26 of the pair of housing segments 101 and 102 are butted together, the inner peripheral surface 24 forms a cylindrical bearing holding hole 23 (see Figure 8 The outer circumference of the pair of half-split bearings 41 and 42 that constitute the main bearing 4 is slightly greater than the inner circumference of the bearing retaining hole 23 of the bearing housing 10. Therefore, after installation, circumferential compressive stress is generated in the pair of half-split bearings 41 and 42, and a compressive pressure is generated between the outer circumferential surfaces 8 of the half-split bearings and the inner circumferential surface 24 of the bearing retaining hole 23, thereby securing the pair of half-split bearings 41 and 42 to the bearing retaining hole 23 of the bearing housing 10.

[0017] Similarly, the bearing housing 21 is composed of a pair of housing segments 22A and 22B. The housing segments 22A and 22B have a semi-cylindrical inner peripheral surface 24. When the split surfaces 26 of the pair of housing segments 22A and 22B are butted together, the semi-cylindrical inner peripheral surface 24 forms a cylindrical bearing holding hole 26 (see FIG. Figure 8 The outer circumference of the pair of half-split bearings 31 and 32 that constitute the connecting rod bearing 3 is slightly greater than the inner circumference of the bearing retaining hole 23 of the large end housing (bearing housing) 21. Therefore, after installation, circumferential stress is generated in the pair of half-split bearings 31 and 32, and compressive pressure is generated between the outer circumferential surfaces 8 of the half-split bearings and the inner circumferential surface 24 of the bearing retaining hole 23, thereby securing the pair of half-split bearings 31 and 32 to the bearing retaining hole 23 of the large end housing (bearing housing) 21.

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

[0019] In addition, a first lubricating oil passage 6a is formed to penetrate along the diameter direction of the journal portion 6, and an inlet opening 6c of the first lubricating oil passage 6a is formed to be able to communicate with the lubricating oil groove 41a. In addition, a second lubricating oil passage 5a is formed to branch off from the first lubricating oil passage 6a of the journal portion 6 and penetrate the crank arm portion (not shown). The second lubricating oil passage 5a is communicated with a third lubricating oil passage 5b formed to penetrate along the diameter direction of the crank pin 5.

[0020] Thus, 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 crankpin 5 and the connecting rod bearing 3.

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

[0022] In recent years, internal combustion engines have been lightweighted for the purpose of reducing fuel consumption. As a result, there is a tendency for the rigidity of the bearing housing parts such as the connecting rod 2 and the engine cylinder 101 to decrease. Therefore, when the internal combustion engine is running, due to the inertial force applied to the bearing housing 10 and the bearing housing 21 and the dynamic load from the crankshaft, the bearing retaining hole 23 of the cylindrical bearing housing 10 and the bearing housing 21 undergoes elastic deformation such that the vertical inner diameter DV becomes larger than the horizontal inner diameter DH (see Figure 9 ) and elastic deformation to return to cylindrical shape (refer to Figure 8 ) repeatedly occurs (ovalization phenomenon). Here, the horizontal direction refers to the direction connecting the two split surfaces 26 of the housing segments 101, 102, and the housing segments 22A, 22B of the bearing housing 10 and the bearing housing 21, when viewed from the axial direction of the bearing retaining hole 23. Furthermore, the vertical direction refers to the direction orthogonal to the direction connecting the two split surfaces 26 of the housing segments 101, 102, and the housing segments 22A, 22B of the bearing housing 10 and the bearing housing 21, when viewed from the axial direction of the bearing retaining hole 23.

[0023] Hoop stress (stress compressing the circumference of the sliding bearings 3 and 4) is applied to the sliding bearings 3 and 4 held in the bearing holding holes 23 of the bearing housings 10 and 21. Consequently, a concentration of hoop stress forms around the oil holes 3H and 4H of the sliding bearings 3 and 4. When the inner diameter of the bearing retaining hole 23 of the bearing housing 10 or 21 increases vertically, the circumference of the inner peripheral surface of the bearing retaining hole 23 increases, reducing the circumferential stress applied to the sliding bearings 3 or 4. On the other hand, when the inner diameter of the bearing retaining hole 23 of the bearing housing 10 or 21 elastically deforms to return to a cylindrical shape, the circumferential stress applied to the sliding bearings 3 or 4 increases. During operation of the internal combustion engine, the circumferential stress applied to the sliding bearings 3 or 4 fluctuates repeatedly.

[0024] In a prior art sliding bearing (for example, see Patent Document 2) that includes a half-split bearing in which the sliding layer adjacent to the opening of the oil hole on the inner circumferential surface side has been removed, when the bearing housing undergoes an ovalization phenomenon during operation of the internal combustion engine, the back metal layer adjacent to the oil hole is easily damaged (cracked) due to changes in the circumferential stress applied to the half-split bearing. In addition, the oil hole (the back metal layer adjacent to the oil hole) undergoes plastic deformation, and the circumferential length of the half-split bearing is reduced, so that the holding force of the bearing housing on the sliding bearing is easily reduced.

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

[0026] Figure 2 3 shows the connecting rod bearing 3 of the present invention, which is composed of the half-split bearings 31 and 32 of the present invention, in a state where the circumferential end faces 76 overlap each other in the non-mounted state, as viewed from the axial direction. Figure 3 Observed from the axis Figure 2 A diagram of the upper half-split bearing 31 is shown. Figure 4 Viewed from the inner side Figure 2 A top view of the upper half-split bearing 31 is shown. Figure 5 Observed from the outer side Figure 2 A top view of the upper half-split bearing 31 is shown.

[0027] like Figures 2 to 4As shown, the connecting rod bearing 3 of this embodiment is formed by butting the circumferential end faces 76 of a pair of semi-cylindrical half-split bearings 31 and 32 together to form a cylindrical shape. The half-split bearings 31 and 32 have a back metal layer 91 extending on the outer diameter side and a sliding layer 92 extending on the inner diameter side. The back metal layer 91 can be made of an iron alloy such as hypoeutectoid steel or stainless steel. The sliding layer 92 can be made of a copper bearing alloy, an aluminum bearing alloy, or the like. In addition, the inner circumferential surface 7 and the outer circumferential surface 8 of the cylindrical shape may also have a surface portion composed of any one of bismuth, tin, and lead, which are softer than the bearing alloy, or a surface portion composed of an alloy mainly composed of these metals, or a surface portion composed of a resin composition mainly composed of a synthetic resin.

[0028] The half-split bearings 31 and 32 have an inner peripheral surface 7, an outer peripheral surface 8, two circumferential end surfaces 76 and 76, and two axial end surfaces 7E and 7E. The inner diameter and outer diameter of the half-split bearings 31 and 32 are the same as each other, and the axial length L1 is the same.

[0029] The half-split bearing 31 has an oil hole 3H extending through the thickness T of the half-split bearing 31 . The inner peripheral surface opening 34 and the outer peripheral surface opening 33 of the oil hole 3H have circular shapes when viewed from the axis CL of the oil hole.

[0030] Figure 6 It shows Figure 3 FIG. 3A and FIG. 3B near the outer peripheral surface opening 33 of the oil hole 3H of the half-split bearing 31 ( FIG. Figure 3 A-direction view), Figure 7 yes Figure 5 A cross-sectional view along line BB of a half-split bearing is shown.

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

[0032] In this embodiment, the wall thickness T1 of the half-split bearing 31 and the thickness T2 of the back metal layer 91 are constant throughout the entire circumference, excluding the transition surface 81 region. Furthermore, the thickness T3 of the sliding layer 92 is constant throughout the entire circumferential length of the half-split bearings 31 and 32. Alternatively, the wall thickness T1 of the half-split bearing 31 and the thickness T3 of the sliding layer may be greatest at the circumferential center of the half-split bearings 31 and 32 and decrease toward the two circumferential end surfaces 76. Furthermore, in the case of a bearing device for a small internal combustion engine, such as a passenger car, the wall thickness T1 of the half-split bearings 31 and 32 may be 1 to 3 mm, the thickness T2 of the back metal layer may be 0.75 to 2.85 mm, and the thickness T3 of the sliding layer may be 0.15 to 0.3 mm. However, the wall thickness T1, the thickness T2 of the back metal layer, and the thickness T3 of the sliding layer of the half-split bearings 31 and 32 are not limited to these values and may also be of other dimensions.

[0033] Furthermore, the inner circumferential surfaces 7 of the half-split bearings 31 and 32 may also have squeeze reliefs (not shown) at both circumferential ends. These squeeze reliefs are formed by radially reducing the wall thickness from the original inner circumferential surface 7 at the circumferential end regions of the half-split bearings 31 and 32. These surfaces are designed to absorb any misalignment and deformation that may occur between the circumferential end surfaces 76 of the half-split bearings 31 and 32 when assembled into the bearing housing. Therefore, the center of curvature of the squeeze relief surface is located at a different position than that of the inner circumferential surface 7 in other regions (see SAE J506 (Items 3.26 and 6.4), DIN 1497, Section 3.2, and JISD 3102). Generally, in bearings for small internal combustion engines used in passenger cars, the depth of the squeeze relief at the circumferential end surfaces of the half-split bearings (the distance from the original inner circumferential surface to the squeeze relief at the circumferential end surface 76) is approximately 0.01 to 0.05 mm.

[0034] Furthermore, in this embodiment, the half-split bearing 31 has a single oil hole 3H, but may also have multiple oil holes 3H. Furthermore, in this embodiment, only one (upper) half of the pair of half-split bearings 31 and 32 has the oil hole 3H, but the other (lower) half-split bearing 32 may also have the oil hole 3H.

[0035] Figure 10 This is a diagram showing the sliding bearing and the large end portion of the connecting rod according to the first embodiment of the present invention as viewed from the axial direction. Figure 11 yes Figure 10 The enlarged cross-sectional view of the sliding bearing and the large end of the connecting rod shown in FIG. Figure 10 As shown, in the state of being mounted to the bearing retaining hole 23 of the large end housing 21, circumferential compressive stress is generated in the pair of half-split bearings 31 and 32, and the circumferential end faces 76 are in contact with each other without a gap. Figure 11 The dashed line adjacent to the outer peripheral surface 8 shows the imaginary transition surface 81A and the outer peripheral surface side opening 33A when not displaced by installation. In the actual installation state, the circumferential end surfaces 76 of the pair of half-split bearings 31 and 32 push against each other due to circumferential compressive stress, so that the transition surface 81 moves radially outward ( Figure 11 The outer peripheral surface 81 is displaced in the direction of the white arrow in FIG. 8 , thereby contacting the inner peripheral surface 24 of the bearing holding hole 23 without a gap, just like the outer peripheral surface 81.

[0036] In addition, if Figure 11 As shown, when mounted in the bearing retaining hole 23 of the large-end housing 21, the transition surface 81 of the half-split bearing 31 is displaced radially outward, causing the inner circumferential surface 7 in the area corresponding to the transition surface 81 and the inner circumferential surface opening 34 of the oil hole 3H to also be displaced radially outward. As a result, the transition inner circumferential surface 71 is formed adjacent to the inner circumferential surface opening 34 of the oil hole 3H of the half-split bearing 31.

[0037] Furthermore, if the depth D1 of the transition surface 81 at a position adjacent to the peripheral edge 33e of the outer peripheral surface opening 33 in the unmounted state is less than 5 μm, or if the length L2 of the transition surface 81 is less than 100 μm, the transition surface 81 elastically deforms when the bearing retaining hole 23 of the bearing housing 10 or 21 becomes ovalized, thereby insufficiently relieving the circumferential compressive pressure applied around the oil hole 3H. Furthermore, if the depth D1 of the transition surface at a position adjacent to the peripheral edge 33e of the outer peripheral surface opening 33 in the unmounted state exceeds 50 μm, or if the length L2 of the transition surface 81 exceeds 300 μm, when the bearing retaining hole 23 of the bearing housing 10 or 21 becomes ovalized, oil passing through the oil hole 3H may sometimes enter between the outer peripheral surface 8 of the half-split bearing 31 and the inner peripheral surface 24 of the bearing retaining hole 23 of the bearing housing 10 or 21. If oil enters between the outer peripheral surface 8 of the half-split bearing 31 and the inner peripheral surface 24 of the bearing retaining hole 23, the holding force of the bearing retaining hole 23 on the sliding bearing 3 will be reduced, and the sliding bearing 3 will rotate together with the rotating shaft (crank pin 5), and sometimes it will be unable to support the rotating shaft (crank pin 5, shaft neck 6).

[0038] Next, the function of the present invention will be described. As described above, when the internal combustion engine is running, due to the inertial force applied to the bearing housing 10 and the bearing housing 21 and the dynamic load from the crankshaft, the bearing retaining hole 23 of the cylindrical bearing housing 10 and the bearing housing 21 undergoes elastic deformation such that the vertical inner diameter DV becomes larger than the horizontal inner diameter DH (see Figure 9 ) and elastic deformation to return to cylindrical shape (refer to Figure 8 ) is a phenomenon that occurs repeatedly (elliptical phenomenon). Figure 12A The bearing holding hole 23 of the bearing housing 21 is elastically deformed by the ovalization phenomenon so that the inner diameter DV in the vertical direction is larger than the inner diameter DH in the horizontal direction when viewed from the axial direction (see FIG. Figure 9 ) is an enlarged sectional view of the oil hole 3H near the half-split bearing 31 in the installed state, Figure 12B The bearing holding hole 23 of the bearing housing 21 is elastically deformed to return to a cylindrical shape when viewed from the axial direction (see FIG. Figure 8 ) is an enlarged sectional view near the oil hole 3H of the half-split bearing 31 in the installed state. like Figure 12A As shown, when the bearing retaining hole 23 of the bearing housing 21 is elastically deformed in such a manner 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 circumferential surface 24 of the bearing retaining hole 23 becomes larger, the circumferential stress applied to the half-split bearing 31 is reduced, and the transition surface 81 is elastically deformed in such a manner that it is separated from the inner circumferential surface 24 of the bearing retaining hole 23. On the other hand, Figure 12B As shown, when the inner diameter of the bearing retaining hole 23 of the bearing housing 21 is elastically deformed in a manner that returns to a cylindrical shape, the circumferential stress applied to the half-split bearing 31 increases, and the transition surface 81 is elastically deformed in a manner that contacts the inner circumferential surface 24 of the bearing retaining hole 23 without a gap. When ovalization occurs, just before the circumferential load applied to the oil hole 3H increases, a portion of this load is dissipated by the elastic deformation of the transition surface 81. This prevents damage (cracking) to the sliding layer 92 and back metal layer 91 adjacent to the oil hole 3H, and prevents plastic deformation of the oil hole (i.e., the sliding layer and back metal layer adjacent to the oil hole) that would otherwise reduce the circumferential length of the half-split bearing. This maintains the bearing housing's holding force on the sliding bearing.

[0039] (Second embodiment) Hereinafter, another non-limiting embodiment of the present invention will be described.

[0040] Figure 13 This is a diagram showing a connecting rod bearing 3 composed of half-split bearings 31 and 32 in a state where circumferential end surfaces 76 overlap each other, as viewed from the axial direction in a non-mounted state according to the second embodiment of the present invention. Figure 14 Observed from the axis Figure 13 A diagram of the half-split bearing 31 is shown on the upper side. Figure 15 Observed from the outer side Figure 14 A top view of the half-split bearing 31 is shown. Figure 16 yes Figure 15 A cross-sectional view of the half-split bearing 31 along line DD is shown, Figure 17 yes Figure 16 An enlarged view of portion E of the half-split bearing 31 is shown.

[0041] The bearing device of the second embodiment differs from the bearing device of the first embodiment only in the structure of the half-split bearing 31 on the upper side of the sliding bearing (connecting rod bearing 3). The remaining structure is the same as that of the bearing device of the first embodiment. The description of the structure common to the first embodiment is omitted.

[0042] A chamfer 34C is formed between the peripheral edge 34e of the inner peripheral opening 34 of the oil hole 3H of the half-split bearing 31 and the inner peripheral surface 7. During the manufacture of the half-split bearing 31, burrs may form on the edge of the inner peripheral opening 34 of the oil hole 3H. Chamfer 34C is formed to remove these burrs. In this embodiment, the surface of chamfer 34C is flat, but it can also be curved.

[0043] A chamfer 33C is formed between the peripheral edge 33e of the outer peripheral surface side opening 33 of the oil hole 3H of the half-split bearing 31 and the outer peripheral surface 8. When manufacturing the half-split bearing 31, burrs are sometimes formed at the edge of the outer peripheral surface side opening 33 of the oil hole 3H. The chamfer 33C is formed to remove the burrs. In this embodiment, the chamfer 33C is formed into a curved surface (arc surface), but it can also be a flat surface. In addition, when the half-split bearing 31 is mounted on the bearing retaining hole 23 of the bearing housing 21, the chamfer 33C does not contact the inner peripheral surface 24 of the bearing retaining hole 23. When the chamfer 33C is too large, the strength of the back metal layer 91 adjacent to the outer peripheral surface side opening 33 of the oil hole 3H will be reduced. In order to reduce the influence on the strength of the back metal layer 91 adjacent to the outer peripheral surface side opening 33 of the oil hole 3H, the length L3 of the chamfer 33C is preferably set to be less than 15% of the length L2 of the transition surface 81, wherein the length L3 of the chamfer 33C is defined as the radial distance from the position adjacent to the outer peripheral surface 8 to the position adjacent to the peripheral edge 33e of the outer peripheral surface side opening 33 with respect to the axis CL (refer to Figure 17 ).

[0044] While the above description uses the bearing device of the present invention as an example of a connecting rod bearing supporting the crankpin of a crankshaft of an internal combustion engine, the bearing device of the present invention can also be applied to a main bearing supporting the journal portion of a crankshaft. Furthermore, the half-split bearing may also include, for example, an oil groove or a positioning notch. Furthermore, the half-split bearing may also include chamfers at locations adjacent to the axial end faces on the outer circumference and at locations adjacent to the axial end faces on the inner circumference. Explanation of symbols

[0045] 1 bearing device; 10. Bearing housing (for main bearing); 101 shell segment (lower part of cylinder block); 102 housing segment (bearing cover); 2 connecting rods; 21 bearing housing (for connecting rod bearing); 22A housing split body (rod side large end housing); 22B shell split body (cover side large end shell); 23 bearing retaining hole; 24 inner circumference; 25 lubrication oil circuit; 3 connecting rod bearings; 31, 32 semi-split bearings; 3H oil hole; 33 outer peripheral side opening; 33e periphery; 34 inner peripheral surface side opening; 34e periphery; 4 main bearings; 41, 42 semi-split bearings; 41a oil tank; 4H oil hole; 5 crank pin; 5a, 5b lubrication oil circuit; 5c discharge outlet; 6-axis neck; 6a lubricating oil circuit; 6c entrance opening; 7 inner circumference; 71 transition inner peripheral surface; 7E axis direction end face; 76 circumferential end face; 8 outer peripheral surface; 81 transition surface; 81A imaginary transition surface; 91 back metal layer; 92 sliding layer; C1 is the center of curvature of the peripheral surface; The center of C2 oil hole; The axis of the CL oil hole; D1 is the depth of the transition surface; L1 is the axial length of the half-split bearing; L2 The length of the transition surface; L3 chamfer length; T1 half-split bearing wall thickness; T2 thickness of the back metal layer; T3 thickness of sliding layer; The rotation direction of the X-axis neck; Z is the direction of rotation of the 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 retaining hole; and a cylindrical sliding bearing mounted to an inner peripheral surface of the bearing retaining hole. The sliding bearing is composed of a pair of half-split bearings, each having a semi-cylindrical shape, each half-split bearing having a back metal layer extending on the outer diameter side and a sliding layer extending on the inner diameter side. In addition, each half-split bearing has an inner peripheral surface, an outer peripheral surface and two circumferential end surfaces, the inner peripheral surface of the half-split bearing supports the crankshaft, the pair of half-split bearings have the same axial length as each other, and at least one of the pair of half-split bearings has one or more oil holes extending through the wall thickness of the half-split bearing, and the inner peripheral surface side opening and the outer peripheral surface side opening of the oil hole both have a circular shape. The bearing device is characterized in that A transition surface is formed between the outer peripheral surface of the half-split bearing and the peripheral edge of the outer peripheral surface side opening of the oil hole. The cam is provided with a plurality of grooves, and the grooves are provided with a plurality of grooves, and the grooves are connected to the grooves of the cam, and the grooves are connected to the grooves of the cam. Furthermore, in a state where the sliding bearing is mounted to the inner peripheral surface of the bearing holding hole, the outer peripheral surface and the transition surface of the half-split bearing are in contact with the inner peripheral surface of the bearing holding hole without a gap.

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

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