Bearing device for a crankshaft of an internal combustion engine

Abstract

To provide a bearing device for a crank shaft of an internal combustion engine which is excellent in foreign matter burying property and in a bearing of which seizure hardly occurs.SOLUTION: The outer peripheral face of each half-split bearing in a non-mounted state consists of first and second curved faces (81, 82) formed along the two types of circular arcs different in curvature radius. In a mounted state, the peripheral end faces of the pair of half-split bearings contact each other with no space, and the first curved face and the second curved face of the outer peripheral faces of the pair of half-split bearing contact the inner peripheral face of a bearing holding hole with no space. A third curved face in a region corresponding to the second curved face is displaced to the radial outside, and then a fourth curved face (72) is formed at a position adjacent to each of the peripheral ends of the inner peripheral faces of the pair of half-split bearings. A thickness (T3) of a slide layer is constant over the whole length in the peripheral direction of the half-split bearing or maximum at the peripheral center of the inner peripheral face, and continuously becomes smaller toward the peripheral end of the half-split bearing.SELECTED DRAWING: Figure 2

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 split bearings at its journal part. To lubricate the main bearing, lubricating oil discharged by an oil pump is sent into an 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. A first lubricating oil passage is formed to penetrate in the diameter direction of the journal part, and both ends of the first lubricating oil passage are communicated with the oil groove of the main bearing. Further, a second lubricating oil passage passing through the crank arm part is branched from the first lubricating oil passage of the journal part and communicated with a third lubricating oil passage formed to penetrate in the diameter direction of the crank pin. Therefore, the lubricating oil sent into the 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 lubricating oil passage, the second lubricating oil passage, and the third lubricating oil passage, and is also supplied from a discharge port opened at the end of the third lubricating oil passage between the sliding surface of the connecting rod bearing composed of a pair of split bearings and the crank pin (see, for example, Patent Document 1). In this way, oil is supplied between the crankshaft surface, the sliding surface of the main bearing, and the sliding surface of the connecting rod bearing.

[0003] Conventionally, as the main bearing and the connecting rod bearing, a sliding bearing composed of a pair of split bearings has been adopted. In the sliding bearing, a crush relief is formed adjacent to the contact surface between the split bearings. The crush relief is a wall thickness reduction region formed such that the wall thickness of a region adjacent to the circumferential end surface of the split bearing becomes thinner toward the circumferential end surface. The crush relief is formed in anticipation of absorbing the displacement and deformation of the butting surface of the split bearings in a state where the pair of split bearings are assembled to a bearing housing (see, for example, Patent Document 2).

[0004] In addition, in order to prevent foreign matter mixed in the oil supplied to the sliding bearing from entering the sliding surface of the sliding bearing, a sliding bearing has been proposed in which the clearance between the chamfer and the chamfered portion and the crankshaft surface is used as a foreign matter discharge path (see, for example, Patent Document 3).

[0005] By the way, in recent years, the oil pump of the internal combustion engine has been miniaturized, and the amount of oil supplied to the sliding bearing has decreased. Along with this, the bearing clearance between the surface of the crankshaft and the inner peripheral surface (sliding surface) of the sliding bearing tends to be set small in order to reduce the amount of oil leaking out from this bearing clearance to the outside. Even under such circumstances, among the foreign matter mixed in the inner peripheral surface of the sliding bearing along with the oil, foreign matter smaller than the bearing clearance will flow away with the oil even if it enters the bearing clearance, so it is difficult to embed in the inner peripheral surface of the sliding bearing and has little influence on the bearing performance.

[0006] On the other hand, among the foreign matter mixed in the inner peripheral surface of the sliding bearing, foreign matter larger than the bearing clearance, when a chamfer relief is formed on the inner peripheral surface of the split bearing, is discharged from the oil supply path to the chamfer relief portion where the clearance is larger than the bearing clearance. Regarding the foreign matter discharged into this chamfer relief portion, that is, the relief clearance between the chamfer relief surface and the crankshaft surface, some of the foreign matter is discharged together with the oil leaking out from the relief clearances at both ends in the width direction of the split bearing, but the remaining foreign matter is pushed into the bearing alloy on the surface of the chamfer relief by the surface of the crankshaft.

[0007] However, since the conventional crush relief is a wall thickness reduction region formed by cutting (removal of the bearing alloy which is the sliding layer) so that the wall thickness becomes thinner than the original inner peripheral surface (major arc), in the region adjacent to the circumferential end of the split bearing of the crush relief, the thickness of the bearing alloy layer is too small, the ability to hold foreign matter is low, and the embedded foreign matter easily falls off. For this reason, foreign matter tends to be concentrated and embedded in the region adjacent to the inner peripheral surface of the crush relief where the bearing alloy layer is thick and the ability to hold foreign matter is high. Thus, when a local large amount of foreign matter embedding part is formed in the region adjacent to the inner peripheral surface of the crush relief, there is a risk of seizure occurring on the inner peripheral surface of the split bearing in the vicinity adjacent to the crush relief due to heat generation caused by the contact between the foreign matter and the surface of the crankshaft.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine that is excellent in foreign matter embedding property and is less likely to cause seizure in the bearing.

Means for Solving the Problems

[0010] To solve the above problems, the present invention is a bearing device for supporting a crankshaft of an internal combustion engine, and the bearing device includes a crankshaft, a bearing housing having a cylindrical bearing holding hole, a sliding bearing and has The sliding bearing consists of a pair of half bearings, Each of the pair of half bearings has an inner circumferential surface, an outer circumferential surface, and two circumferential end faces, The pair of half bearings have the same axial length as each other, The pair of half bearings each have a backing layer on the outer diameter side and a sliding layer on the inner diameter side, In a bearing device, the pair of half bearings are mounted on the inner circumferential surface of a bearing holding hole, and the inner circumferential surfaces of the pair of half bearings support a crankshaft. The outer circumferential surface of each half bearing in the non-mounted state consists of a first and a second curved surface formed along two types of arcs with different curvatures. The first curved surface is a region including the circumferential central portion of the outer circumferential surface, and the second curved surface is the remaining two regions of the outer circumferential surface that are continuous with the first curved surface and extend toward the circumferential end face of the half bearing. The relationship between the center of the first arc forming the first curved surface and the center of the second arc forming the second curved surface is that the center of the second arc is on a perpendicular line to the bearing outer diameter center line passing through the center of the first arc and is offset to the inner side, that is, the side closer to the circumferential central portion of the outer circumferential surface, relative to the center of the first arc. The second curved surface is formed in a range where the circumferential angle measured from the circumferential end face of the half bearing with the center of the first arc as the center is from a minimum value of 10° to a maximum value of 30°. The radial length of the half bearing between the second curved surface and the virtual outer circumferential surface when the first and second curved surfaces of the outer circumferential surface of the half bearing are extended to the circumferential end of the half bearing at the circumferential end of the half bearing is 10 - 60 μm. The inner circumferential surface of each half bearing in the non-mounted state consists of a third curved surface formed along one type of arc. In the mounted state, the circumferential end faces of the pair of half bearings are in contact with each other without a gap, and the first and second curved surfaces of the outer circumferential surfaces of the pair of half bearings are in contact with the inner circumferential surface of the bearing holding hole without a gap. When the second curved surface is in contact with the inner circumferential surface of the bearing holding hole without a gap in the mounted state, the third curved surface in the region corresponding to the second curved surface is displaced radially outward, thereby forming a fourth curved surface at a position adjacent to each circumferential end of the inner circumferential surface of the pair of half bearings. The thickness of the sliding layer is constant over the entire circumferential length of the split bearing, or the thickness of the sliding layer is maximum at the circumferential center of the inner peripheral surface and continuously decreases towards the circumferential ends of the split bearing, and the thickness at the circumferential ends of the split bearing is 90% or more of the thickness at the circumferential center, and a bearing device is provided.

[0011] In another embodiment of the present invention, when a plane where the circumferential end faces of a pair of split bearings contact each other is defined as a dividing plane, in the non-mounted state, the circumferential end faces of the split bearings are parallel to the dividing plane.

[0012] In another embodiment of the present invention, when a plane where the circumferential end faces of a pair of split bearings contact each other is defined as a dividing plane, in the non-mounted state, the circumferential end faces of the split bearings contact the dividing plane at the radially outer ends and are inclined so as to be spaced apart from the dividing plane closer to the radially inner ends, and the inclination angle between the circumferential end faces of the split bearings and the dividing plane is 3×10 -2 ° to 15×10 -2 °.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

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Figure 14

Figure 15(A)

Figure 15(B)

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Figure 18

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0015] (First Embodiment) Figure 1 schematically shows a bearing device 1 for a crankshaft of an internal combustion engine. Figure 6 shows a view of the large end housing of the connecting rod as seen in the axial direction. Figure 7 shows a cross-sectional view taken along line A-A of the large end housing of the connecting rod shown in Figure 6. This bearing device 1 has a journal portion 6 supported at the lower part of the cylinder block, a crankpin 5 formed integrally with the journal portion 6 and rotating about the journal portion 6, and a connecting rod 2 for transmitting a reciprocating motion from the internal combustion engine to the crankpin 5. Further, as a sliding bearing for supporting the crankshaft, the bearing device 1 further has a main bearing 4 for rotatably supporting the journal portion 6 and a connecting rod bearing 3 for rotatably supporting the crankpin 5.

[0016] Note that the crankshaft has a plurality of journal portions 6 and a plurality of crankpins 5. Here, for the sake of convenience of explanation, one journal portion 6 and one crankpin 5 are illustrated and described. In Figure 1, the positional relationship in the depth direction of the paper surface is such that the journal portion 6 is on the back side of the paper surface and the crankpin 5 is on the front side.

[0017] The journal portion 6 is pivotally supported by a split-type bearing housing 10 composed of a lower part 101 of the cylinder block of the internal combustion engine and a bearing cap 102 via a main bearing 4 constituted by a pair of half bearings 41, 42. Note that the half bearings 41, 42 constituting the main bearing 4 are conventional half bearings. In the lower part 101 of the cylinder block and the bearing cap 102, bearing holding holes having a semi-cylindrical surface shape are respectively formed. The half bearing 41 is inserted into the bearing holding hole having a semi-cylindrical surface shape of the lower part 101 of the cylinder block, the half bearing 42 is inserted into the bearing holding hole having a semi-cylindrical surface shape of the bearing cap 102, and then the lower part 101 of the cylinder block and the bearing cap 102 are fastened by bolts (not shown) so that the pair of half bearings 41, 42 are held in the cylindrical bearing holding hole. An oil groove 41a is formed over the entire length of the inner peripheral surface of the half bearing 41 on the upper side in Figure 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.

[0018] The crankpin 5 is pivotally supported on the large end housing 21 of the connecting rod 2 via a connecting rod bearing 3 composed of a pair of half bearings 31 and 32. As shown in FIGS. 6 and 7, the large end housing (bearing housing) 21 consists of a rod side large end housing 22A and a cap side large end housing 22B. The rod side large end housing 22A and the cap side large end housing 22B each have a semi-cylindrical surface 27, and when the pair of semi-cylindrical surfaces 27 are butted against the dividing surface of the rod side large end housing 22A and the cap side large end housing 22B, they form a cylindrical bearing holding hole 23.

[0019] The outer peripheral length of the pair of half bearings 31 and 32 is slightly larger than the inner peripheral length of the bearing holding hole 23 of the large end housing 21. After installation, a pressure is generated by the outer peripheral surface 8 of the pair of half bearings 31 and 32 pressing against the inner peripheral surface 24 of the bearing holding hole 23, and thus the pair of half bearings 31 and 32 are fixed to the bearing holding hole 23 of the large end housing 21. Note that the large end housing 21 is shown as an example of a split-type bearing housing, but it is not limited to this, and a large end housing 21 that is an integral type may also be used. The integral type large end housing 21 means a bearing housing having a configuration in which the inner peripheral surface 24 of the bearing holding hole 23 is not divided into a plurality of parts.

[0020] A second lubricating oil passage 5a is formed that branches off from the first lubricating oil passage 6a of the journal portion 6 and passes through a crank arm portion (not shown). This second lubricating oil passage 5a communicates with a third lubricating oil passage 5b formed to penetrate in the diameter direction of the crankpin 5.

[0021] Therefore, as described above, the lubricating oil discharged by the oil pump passes from the oil gallery formed in the cylinder block wall through the through hole 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, and is supplied to the gap formed between the journal portion 6 and the main bearing 4.

[0022] On one hand, the lubricating oil is also 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 through the first lubricating oil passage 6a, the second lubricating oil passage 5a, and the third lubricating oil passage 5b.

[0023] 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 should be understood that the bearing device of the present invention is not limited to the application to the connecting rod bearing portion, and may be applied to the main bearing portion having the main bearing housing.

[0024] FIG. 2 shows a view of the connecting rod bearing 3 composed of the half 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 half bearing 31 (32) shown in FIG. 2 as viewed from the axial direction. FIG. 4 is a plan view of the half bearing 31 (32) shown in FIG. 2 as viewed from the inner peripheral surface side. FIG. 5 is a plan view of the half bearing 31 (32) shown in FIG. 2 as viewed from the outer peripheral surface side.

[0025] 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 half bearings 31 and 32 having a semi-cylindrical shape and combining them into a cylindrical shape as a whole. The half bearings 31 and 32 have a backing layer 91 on the outer diameter side and a sliding layer 92 on 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 inner peripheral surface 7 and the outer peripheral surface 8 of the cylindrical shape 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. Note that 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 92, which will be described later, are defined as the thicknesses not including the surface portion.

[0026] The split bearings 31 and 32 have an inner circumferential surface 7, an outer circumferential surface 8, two circumferential end faces 76, 76, and two axial end faces 7E, 7E. The pair of split bearings 31 and 32 have the same inner diameter dimension, outer diameter dimension, and axial length L1. The outer circumferential surfaces 8 of the split bearings 31 and 32 in the non-mounted state are composed of a first curved surface 81 and a second curved surface 82 formed along two types of arcs with different curvatures (which may be elliptical arcs). The first curved surface 81 is a region including the circumferential central portion CP of the outer circumferential surface 8. The second curved surface 82 is the remaining two regions of the outer circumferential surface 8 that are continuous with the first curved surface 81 and extend toward the circumferential end faces 76 of the split bearings 31 and 32. The relationship between the center C1 of the first arc forming the first curved surface 81 and the center C2 of the second arc forming the second curved surface 82 is that the center C2 of the second arc is on the perpendicular line CL to the bearing outer diameter center line passing through the center C1 of the first arc, and is offset to a position closer to the circumferential central portion CP of the outer circumferential surface 8, that is, inside the center C1 of the first arc.

[0027] The second curved surface 82 is formed in a range where the circumferential angle θ1 measured from the circumferential end faces 76 of the split bearings 31 and 32 around the center C1 of the first arc is from a minimum value of 10° to a maximum value of 30°. In the case of a bearing device for a small internal combustion engine for a passenger car (for example, an internal combustion engine with a crankshaft shaft diameter of 30 to 100 mm), the radial length L2 of the split bearings 31 and 32 between the second curved surface 82 and the virtual outer circumferential surface 83 when the first curved surface 81 and the second curved surface 82 at each circumferential end face 76 of the split bearings 31 and 32 are extended to the circumferential end faces 76 of the split bearings is 10 to 60 μm. Furthermore, the relationship between the circumferential angle θ1 and the length L2 (L2 / θ1) is preferably 1 to 2 (μm / °).

[0028] In this embodiment, the wall thickness T1 of the split bearings 31 and 32 and the thickness T2 of the backing layer in the region of the first curved surface 81 are constant over the circumferential direction. The thickness T3 of the sliding layer is constant over the entire circumferential length of the split bearings 31 and 32 (both the region of the first curved surface 81 and the region of the second curved surface 82). In the case of a bearing device for a small internal combustion engine such as a passenger car, the wall thickness T1 of the split bearings 31 and 32 in the region of the first curved surface 81 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 split bearings 31 and 32, the thickness T2 of the backing layer, and the thickness T3 of the sliding layer are not limited to these and can be other dimensions.

[0029] The inner peripheral surfaces 7 of the split bearings 31 and 32 in the non-mounted state are composed of a third curved surface 71 formed along one type of arc. The center C3 of the arc of the third curved surface 71 in this embodiment is concentric with the center C1 of the first arc forming the first curved surface 81.

[0030] Also, in this embodiment, when a plane where the circumferential end faces of the pair of split bearings contact each other is defined as a dividing plane HP, in the non-mounted state, the circumferential end faces 76 of the split bearings 31 and 32 are parallel to the dividing plane HP.

[0031] FIG. 8 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. 9 is an enlarged view of portion B of the sliding bearing and the large end portion of the connecting rod shown in FIG. 8. As shown in FIGS. 8 and 9, after the pair of split bearings 31 and 32 are mounted in the bearing holding hole 23 of the large end housing 21 (mounted state), circumferential compressive stress is generated in the pair of split bearings 31 and 32, and the circumferential end faces 76 come into contact with each other without a gap. Further, the dotted line continuous with the first curved surface 81 shown in FIG. 9 indicates a virtual second curved surface 82A in the case where there is no displacement due to mounting. After mounting (mounted state), due to the circumferential compressive stress, the circumferential end faces 76 of the pair of split bearings 31 and 32 are pressed against each other, and the second curved surface 82 is displaced in the radially outer direction (the direction of the white arrow in FIG. 9). The second curved surface 82 on the outer peripheral surface 8 of the pair of split bearings 31 and 32 comes into contact with the inner peripheral surface 24 of the bearing holding hole 23 without a gap, similarly to the first curved surface 81. Therefore, it becomes difficult for the oil supplied to the bearing device during the operation of the internal combustion engine and the sludge contained in the oil to enter between the outer peripheral surface 8 of the pair of split bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23.

[0032] Also, the dotted line continuous with the third curved surface 71 shown in FIG. 9 indicates a virtual third curved surface 72A when it does not displace due to mounting. After mounting (mounted state) in the bearing holding hole 23 of the large end housing 21, the second curved surface 82 on the outer peripheral surface 8 of the split bearings 31, 32 displaces radially outward, so that the third curved surface 71 in the region corresponding to the second curved surface 82 also displaces radially outward. As a result, the fourth curved surface 72 is formed at a position adjacent to each circumferential end of the inner peripheral surfaces of the pair of split bearings 31, 32. For this reason, the fourth curved surface 72, like the second curved surface 82, is formed in a range where the circumferential angle θ1 measured from the circumferential end surface 76 of the split bearings 31, 32 is from a minimum value of 10° to a maximum value of 30°. Also, the radial length L3 of the split bearings between the fourth curved surface 72 and the virtual inner peripheral surface 72A at each circumferential end surface 76 of the split bearings 31, 32 is the same as the radial length L2 of the split bearings 31, 32 between the second curved surface 82 and the virtual outer peripheral surface 83 in the non-mounted state, and is 10 to 60 μm. The gap between the fourth curved surface 72 and the surface of the crankshaft functions as a crush relief. The thickness T3 of the sliding layer (bearing alloy) 92 in the region of the fourth curved surface 72 is the same as the thickness T3 of the sliding layer (bearing alloy) on the third curved surface 71.

[0033] In addition, when the formation range of the second curved surface 82 is less than 10° or when the radial length L2 of the split bearings 31, 32 between the second curved surface 82 and the virtual outer peripheral surface 83 at each circumferential end surface 76 of the split bearings 31, 32 is less than 10 μm, the function as a crush relief by the fourth curved surface 72 becomes insufficient.

[0034] In addition, when the formation range of the second curved surface 82 exceeds 30°, or when the radial length L2 of the half bearings 31 and 32 between the second curved surface 82 and the virtual outer peripheral surface 83 at the circumferential end faces 76 of the half bearings 31 and 32 exceeds 60 μm, a (partial) gap may be formed between the second curved surface 82 of the outer peripheral surface 8 of the pair of half bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23 after mounting. When such a gap is formed, sludge enters this gap together with the oil supplied to the bearing device during the operation of the internal combustion engine, and the sludge is likely to accumulate locally. When a local sludge accumulation part is formed between the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23, the inner peripheral surface 7 of the half bearings 31 and 32 at the position of this accumulation part bulges toward the inner diameter center side, and damage is likely to occur due to strong contact with the surface of the crankshaft.

[0035] Next, the operation of the present invention will be described. In recent years, the oil pump of an internal combustion engine has been miniaturized, and the amount of oil supplied to the sliding bearing 3 has decreased. Along with this, the bearing clearance between the surface of the crankshaft 5 and the inner peripheral surfaces 7 (third curved surfaces 71) of the half bearings 31 and 32 tends to be set small in order to reduce the amount of oil leaking out from this bearing clearance to the outside. Among the foreign matters mixed into the inner peripheral surfaces 7 of the half bearings 31 and 32, foreign matters larger than the bearing clearance are discharged to the fourth curved surface portion where the clearance is larger than the bearing clearance from the oil supply passage. Regarding the foreign matter F discharged into the relief clearance, that is, the clearance between the fourth curved surface 72 and the surface of the crankshaft 5, a part of the foreign matter F is discharged together with the oil leaking out from the relief clearances at both ends in the width direction of the half bearings 31 and 32, but the remaining foreign matter F is pushed onto the surface of the fourth curved surface 72 by the surface of the crankshaft 5. FIG. 10 shows an enlarged view of the vicinity of the circumferential end portion of the half bearing 31 in the mounted state as viewed from the axial direction. Since the thickness T3 of the sliding layer (bearing alloy) 92 in the region of the fourth curved surface 72 is made the same as the thickness T3 of the sliding layer (bearing alloy) on the third curved surface 71, the region of the fourth curved surface 72 has a high ability to hold the foreign matter F embedded over the entire circumferential direction, and the embedded foreign matter F is difficult to fall off. For this reason, the foreign matter F becomes dispersed and buried over the entire circumferential direction of the fourth curved surface 72, and a buried portion of a large amount of local foreign matter F is not formed.

[0036] Here, for comparison with the operation of the present invention, the configuration and operation of the prior art will be described with reference to FIGS. 11 to 14. FIG. 11 is a view of a conventional half bearing 131 as viewed from the axial direction. FIG. 12 is an enlarged view of part D in FIG. 11. FIG. 13 is a view taken in the direction of arrow Y1 in FIG. 12. FIG. 14 shows an enlarged view of the vicinity of the circumferential end portion of the conventional half bearing 131 in the mounted state as viewed from the axial direction.

[0037] A conventional split bearing 131 has a backing layer 191 on the outer diameter side and a sliding layer 192 on the inner diameter side. The outer peripheral surface 18 of the split bearing 131 is composed of a curved surface formed along one type of arc. A curved surface 171 and a crush relief 170 are formed on the inner peripheral surface 17 of the split bearing 131. The curved surface 171 includes the circumferential center portion CP of the split bearing 131 and is formed along an arc having a center C13 concentric with the center C11 of the outer peripheral surface 18. The crush relief 170 is formed in a region adjacent to each circumferential end face 176. The thickness T12 of the backing layer is constant over the circumferential direction. The wall thickness T11 of the split bearing 131 and the thickness T13 of the sliding layer are constant in the circumferential direction except in the region of the crush relief 170.

[0038] The crush relief 170 is a wall thickness reduction region formed by cutting (removing the sliding layer 192) so that the wall thickness is thinner than the original inner peripheral surface 173 (dotted line in FIG. 12). The thickness T13' of the sliding layer (bearing alloy) in the crush relief 170 is maximum at a position adjacent to the curved surface 171 and continuously decreases toward the circumferential end face 176 side. In the region 170L (see FIG. 13) adjacent to the circumferential end face 176 of the crush relief 170, the thickness of the sliding layer (bearing alloy) 192 is too small and the ability to hold foreign matter F is low. For this reason, as shown in FIG. 14, the foreign matter F (dotted circle F) embedded in the surface of the region 170L adjacent to the circumferential end face 176 of the crush relief 170 easily falls off. For this reason, the foreign matter F becomes concentrated and embedded in the region 170U (see FIG. 13) adjacent to the curved surface 171 of the crush relief 170 where the thickness of the sliding layer (bearing alloy) 192 is large and the ability to hold foreign matter F is high. Thus, when a local large amount of foreign matter F embedding portion is formed in the region 170U adjacent to the curved surface 171 of the crush relief 170, there is a risk of seizure occurring on the curved surface 171 in the vicinity adjacent to the crush relief 170 due to heat generation caused by contact between the foreign matter F and the surface of the crankshaft 5.

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

[0040] FIG. 15(A) and FIG. 15(B) show views of the half bearings 31(32) constituting the connecting rod bearing 3 of the second embodiment according to the present invention as seen in the axial direction.

[0041] The bearing device of the second embodiment differs only in the configuration of the inner peripheral surfaces 7 and the sliding layers 92 of the half bearings 31 and 32 that constitute the sliding bearing (connecting rod bearing 3), and the 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 is omitted.

[0042] The inner peripheral surface 7 of the half bearing 31(32) in the non-mounted state is composed of a third curved surface 71 formed along one type of elliptical arc. The relationship between the center C1 of the first arc forming the first curved surface 81 of the outer peripheral surface 8 of the half bearing 31(32) and the center C3 of the third arc forming the third curved surface 71 of the inner peripheral surface 7 is such that the center C3 of the third arc is on the perpendicular line CL with respect to the bearing outer diameter center line passing through the center C1 of the first arc, and is offset to a position outside the center C1, that is, on the side farther from the circumferential center portion CP' of the inner peripheral surface 7. The distance between the center C1 of the first arc forming the first curved surface 81 of the outer peripheral surface 8 of the half bearing 31(32) and the inner peripheral surface 7 is the minimum R3C at the position of the circumferential center portion CP' of the inner peripheral surface 7, and is the maximum R3E at both ends in the circumferential direction.

[0043] In this embodiment, the wall thickness T1 of the split bearings 31 and 32 in the region of the first curved surface 81 is maximum at the position of the circumferential center portion CP' of the inner circumferential surface 7, and continuously decreases toward the circumferential end surface 76. The thickness of the sliding layer 92 is maximum at the circumferential center portion CP' of the inner circumferential surface 7 (the third curved surface 71), and continuously decreases toward the circumferential end surface 76 of the split bearing 8. The thickness T3E at the circumferential end surface 76 of the split bearing 31 (32) is 90% or more of the thickness T3C at the circumferential center portion CP' of the inner circumferential surface 7 (T3E ≧ T3C × 0.90). Since the thickness T3E is 90% or more of the thickness T3C (T3E ≧ T3C × 0.90), the thickness T3 of the sliding layer (bearing alloy) can be increased over the entire circumferential direction of the fourth curved surface 72 formed in the mounted state, and the holding ability of the embedded foreign matter can be enhanced.

[0044] (Third Embodiment) Hereinafter, other non-limiting embodiments of the present invention will be described.

[0045] FIG. 16 shows a view of the connecting rod bearing 3 composed of the split bearings 31 and 32 of the third embodiment of the present invention with the circumferential end surfaces 76 facing each other in the non-mounted state, as viewed from the axial direction. FIG. 17 shows a view of the split bearing 31 (32) shown in FIG. 16 as viewed from the axial direction. FIG. 18 is an enlarged view of part C of the split bearing 31 (32) shown in FIG. 17.

[0046] The bearing device of the third embodiment is different only in the configuration of the circumferential end surfaces 76, 76 of the split bearings 31 and 32 that constitute the connecting rod bearing 3, and the 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.

[0047] As shown in the enlarged view of FIG. 18, when a plane where the circumferential end faces of a pair of half bearings contact each other is defined as a dividing plane HP, the circumferential end faces 76, 76 of the half bearings 31, 32 in the non-mounted state are in contact with the dividing plane HP at the radially outer end 76O, and are inclined so as to be separated from the dividing plane HP as they approach the radially inner end 76I. The inclination angle θ2 between the circumferential end faces 76, 76 of the half bearings 31, 32 and the dividing plane HP is 3×10 -2 ° to 15×10 -2 °. When the circumferential end faces 76, 76 of the half bearings 31, 32 have the inclination angle θ2, the formation range of the second curved surface 82 is defined as the circumferential angle θ1 measured from the radially outer end 76O of the circumferential end face 76 of the half bearings 31, 32 with the center C1 of the first arc as the center.

[0048] When the circumferential end faces 76, 76 of the half bearings 31, 32 have the inclination angle θ2, in the mounted state, the circumferential end faces 76 contact each other without a gap. Also, the second curved surface 82 becomes more likely to be displaced in the radially outer direction, and the pressure (pushing pressure) between the second curved surface 82 and the inner circumferential surface 24 of the bearing holding hole 23 becomes larger. For this reason, it becomes more difficult for the oil supplied to the bearing device during the operation of the internal combustion engine and the sludge contained in the oil to enter between the outer circumferential surface 8 of the pair of half bearings 31, 32 and the inner circumferential surface 24 of the bearing holding hole 23.

[0049] When the inclination angle θ2 between the circumferential end faces 76, 76 of the half bearings 31, 32 and the dividing plane HP is less than 3×10 -2 °, it becomes difficult to obtain the effect of increasing the pressure between the second curved surface 82 and the inner circumferential surface 24 of the bearing holding hole 23 in the mounted state. Also, when the inclination angle θ2 exceeds 15×10 -2 °, when mounted in the bearing holding hole 23 of the large end housing (bearing housing) 21, a large displacement may occur between the circumferential end faces 76, 76 of the half bearings 31, 32.

[0050] The above description has been made using an example in which the bearing device of the present invention is applied to a connecting rod bearing portion that supports a crank pin of a crankshaft of an internal combustion engine. However, the bearing device of the present invention can also be applied to a main bearing portion that supports a journal portion of the crankshaft. Further, the half bearing may further have, for example, an oil hole, an oil groove, or a notch for positioning. Further, the half bearing may have a chamfer at a position where the outer peripheral surface and each end surface in the axial direction are adjacent, or at a position where the inner peripheral surface and each end surface in the axial direction are adjacent. Further, it may have a chamfer at a position where the inner peripheral surface and each circumferential end surface are adjacent. In the case of having these chamfers, the wall thickness of the half bearing, the thickness of the backing layer, and the thickness of the sliding layer related to the configuration of the present invention are defined as the thickness in the case where no chamfer is formed.

Explanation of Signs

[0051] 1 Bearing device 10 Bearing housing (main bearing) 101 Lower part of cylinder block 102 Bearing cap 2 Connecting rod 21 Big end housing, bearing housing 22A Rod side big end housing 22B Cap side big end housing 23 Bearing holding hole 24 Inner peripheral surface 27 Semi-cylindrical surface 3 Connecting rod bearing 31, 32 Half bearings 4 Main bearing 41, 42 Half bearings 41a Oil groove 5 Crank pin 5a, 5b Lubricating oil passage 5c Discharge port 6 Journal portion 6a Lubricating oil passage 6c Inlet opening 7 Inner peripheral surface 7E Axial end surface 70 Crush relief 71 Third curved surface 72 Fourth curved surface Virtual third camber surface when there is no displacement of 72A 76 Circumferential end face 76I Inner end 76O Outer end 8 Outer peripheral surface 81 First camber surface 82 Second camber surface 82A Virtual second camber surface when there is no displacement 83 Virtual outer peripheral surface 91 Backing layer 92 Sliding layer C1 Center of the first arc C2 Center of the second arc C3 Center of the third arc CL Perpendicular line to the bearing outer diameter center line CP Circumferential central part CP´ Circumferential central part F Foreign matter HP Dividing plane L1 Axial length of the half bearing L2 Length L3 Length T1 Wall thickness of the half bearing T2 Thickness of the backing layer T3 Thickness of the sliding layer T3C Thickness of the sliding layer at the circumferential center T3E Thickness of the sliding layer at the circumferential end X Rotation direction of the journal part Z Rotation direction of the crank pin θ1 Circumferential angle θ2 Inclination angle

Claims

【Claim 1】 A bearing device (1) for supporting a crankshaft of an internal combustion engine, wherein the bearing device (1) comprises: a crankshaft (5, 6); a bearing housing (10, 21) having a cylindrical bearing holding hole (23); a sliding bearing (3, 4); and has the sliding bearing consists of a pair of split bearings (31, 32; 41, 42); each of the pair of split bearings has an inner peripheral surface (7), an outer peripheral surface (8), and two circumferential end surfaces (76, 76); the pair of split bearings have the same axial length (L1) with respect to each other; each of the pair of split bearings has a backing layer (91) on the outer diameter side and a sliding layer (92) on the inner diameter side; the pair of split bearings are mounted on the inner peripheral surface (24) of the bearing holding hole, and in the bearing device (1), the inner peripheral surfaces of the pair of split bearings support the crankshaft; in the non-mounted state, the outer peripheral surface of each split bearing consists of a first and a second curved surface (81, 82) formed along two arcs with different curvatures. The first curved surface is a region including the circumferential central portion (CP) of the outer peripheral surface. The second curved surface is the remaining two regions of the outer peripheral surface that are continuous with the first curved surface and extend toward the circumferential end surface of the split bearing. The relationship between the center (C1) of the first arc forming the first curved surface and the center (C2) of the second arc forming the second curved surface is such that the center (C2) of the second arc is on a perpendicular line (CL) to the bearing outer diameter center line passing through the center (C1) of the first arc, and is offset to a position inside, that is, closer to the circumferential central portion of the outer peripheral surface, than the center (C1) of the first arc; the second curved surface is formed in a range where the circumferential angle (θ1) measured from the circumferential end surface of the split bearing around the center (C1) of the first arc is from a minimum value of 10° to a maximum value of 30°; the radial length (L2) of the split bearing between the second curved surface and a virtual outer peripheral surface (83) when the first curved surface and the second curved surface of the outer peripheral surface of the pair of split bearings are extended to the circumferential end of the split bearing at the circumferential end of the split bearing is 10 to 60 μm; in the non-mounted state, the inner peripheral surface of each split bearing consists of a third curved surface (71) formed along one type of arc; in the mounted state, the circumferential end surfaces of the pair of split bearings are in contact with each other without a gap, and the first curved surface and the second curved surface of the outer peripheral surface of the pair of split bearings are in contact with the inner peripheral surface of the bearing holding hole without a gap. When the second curved surface is in contact with the inner peripheral surface of the bearing holding hole without a gap in the mounted state, the third curved surface in the region corresponding to the second curved surface is displaced radially outward, whereby a fourth curved surface (72) is formed at a position adjacent to each circumferential end of the inner peripheral surface of the pair of half bearings. The thickness (T3) of the sliding layer is constant over the entire circumferential length of the half bearing, or the thickness (T3) of the sliding layer is maximum at the circumferential center of the inner peripheral surface and continuously decreases toward the circumferential ends of the half bearing, and the thickness (T3E) at the circumferential ends of the half bearing is 90% or more of the thickness (T3C) at the circumferential center (T3E ≧ T3C × 0.90). The bearing device (1) is characterized by this. **Claim 2** When a plane where the circumferential end faces of the pair of half bearings are in contact with each other is defined as a dividing plane (HP), in the non-mounted state, the circumferential end faces of the half bearings are parallel to the dividing plane (HP). The bearing device (1) according to claim 1. **Claim 3** When a plane in which the circumferential end faces of the pair of half bearings are in contact with each other is defined as a dividing plane (HP), in the non-mounted state, each circumferential end face of the half bearing is in contact with the dividing plane at the radially outer end (76O), and is inclined so as to be separated from the dividing plane (HP) closer to the radially inner end (76I). The inclination angle θ2 between each circumferential end face of the half bearing and the dividing plane is 3×10 －２ ° to 15×10 －２ °, and the bearing device (1) according to claim 1.

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