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 having excellent burying performance of foreign matters and being difficult to sinter. The outer peripheral surface of each split bearing in a non-mounted state is configured from first and second curved surfaces (81, 82) formed along two types of arcs having different curvatures. In the mounted state, the circumferential end surfaces of the pair of half bearings are in contact with each other without a gap, and the first curved surface and the second curved surface 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. The third curved surface in a region corresponding to the second curved surface is displaced radially outward, so that a fourth curved surface (72) is formed at a position adjacent to each circumferential end surface of the inner circumferential surfaces of the pair of half bearings. The thickness (T3) of the sliding layer is fixed over the entire length of the half bearing in the circumferential direction, or the thickness (T3) is the largest in the center of the inner circumferential surface in the circumferential direction and continuously decreases toward the end of the half bearing in the circumferential direction.

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 circumferential surface of the main bearing through a through-hole formed in the wall of the main bearing from an oil passage formed in the cylinder block wall. 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. In addition, a second lubricating oil passage passing 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 on the inner circumferential 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 connecting rod bearing composed of a pair of half-split bearings and the crank pin 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.

[0003] Conventionally, as the main bearing and the connecting rod bearing, a sliding bearing composed of a pair of half-split bearings has been used. An extrusion relief portion is formed on the sliding bearing in a manner adjacent to the abutting surface between the half-split bearings. The extrusion relief portion is a wall thickness reduction region in which the wall thickness of a region formed adjacent to the circumferential end surface of the half-split bearing becomes thinner toward the circumferential end surface. The extrusion relief portion is formed to absorb the position deviation and deformation of the butting surface of the half-split bearings in a state where the pair of half-split bearings are assembled to the bearing housing (for example, refer to Patent Document 2).

[0004] In addition, in order to prevent foreign matters 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 gap between the extrusion relief portion and the chamfered portion and the surface of the crankshaft is used as a foreign matter discharge path (for example, refer to Patent Document 3).

[0005] However, 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 amount of oil leaking out from the bearing clearance between the surface of the crankshaft and the inner circumferential surface (sliding surface) of the sliding bearing has decreased, and therefore, the bearing clearance is often set to be small. In this situation, among the foreign matters mixed into the inner circumferential surface of the sliding bearing following the oil, the foreign matters smaller than the bearing clearance will flow away together with the oil even if they enter the bearing clearance, and thus, the above foreign matters are not easily buried in the inner circumferential surface of the sliding bearing and have a small influence on the bearing performance.

[0006] On the other hand, in the case where an extrusion release portion is formed on the inner peripheral surface of the semi-split bearing, foreign matter larger than the bearing clearance among the foreign matter mixed into the inner peripheral surface of the sliding bearing is discharged from the oil supply passage to the extrusion release portion having a clearance larger than the bearing clearance. For the foreign matter discharged to this extrusion release portion, that is, the release clearance between the extrusion release surface and the surface of the crankshaft, a part of the foreign matter is discharged from the release clearance at both ends in the width direction of the semi-split bearing together with the oil leaking to the outside, but the remaining foreign matter is pressed into the bearing alloy on the surface of the extrusion release portion by the surface of the crankshaft.

[0007] However, the conventional extrusion release portion is formed by cutting (processing for removing the bearing alloy as the sliding layer) into a wall thickness reduction region having a wall thickness thinner than the original inner peripheral surface (main arc), so that in the region adjacent to the circumferential end of the semi-split bearing of the extrusion release portion, the thickness of the bearing alloy layer is too small, the ability to hold foreign matter is low, and the buried foreign matter is likely to fall off. Therefore, foreign matter is concentrated and buried in the region adjacent to the inner peripheral surface of the extrusion release portion where the thickness of the bearing alloy layer is large and the ability to hold foreign matter is high. Thus, when a local large number of foreign matter burial portions are formed in the region adjacent to the inner peripheral surface of the extrusion release portion, sintering may occur due to the heat generated by the contact between the foreign matter and the surface of the crankshaft on the inner peripheral surface of the semi-split bearing adjacent to the extrusion release portion. Prior Art Documents Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 8-277831 Patent Document 2: Japanese Patent Laid-Open No. 5-71538 Patent Document 3: Japanese Patent Laid-Open No. 2005-69283 Summary of the Invention

[0009] Therefore, an object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine having excellent foreign matter burial property and being difficult to sinter.

[0010] To solve the above technical problems, the present invention provides a bearing device that supports a crankshaft of an internal combustion engine and has: A crankshaft; A bearing housing having a cylindrical bearing holding hole; and A sliding bearing, The sliding bearing is composed of a pair of semi-split bearings, Each of the pair of semi-split bearings has an inner peripheral surface, an outer peripheral surface, and two circumferential end faces, The pair of semi-split bearings have the same axial length, A pair of semi-split bearings each have a back metal layer on the outer diameter side and a sliding layer on the inner diameter side. The pair of semi-split bearings are mounted on the inner circumferential surface of a bearing holding hole, and the inner circumferential surfaces of the pair of semi-split bearings support a crankshaft. The bearing device is characterized in that The outer circumferential surface of each semi-split bearing in the non-mounted state is composed of a first curved surface and a second curved surface formed along two 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 connected to the first curved surface and extend toward the circumferential end faces of the semi-split 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 line perpendicular to the bearing outer diameter center line passing through the center of the first arc and is located at a position offset inward, that is, toward the side closer to the circumferential central portion of the outer circumferential surface, compared with 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 semi-split 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 semi-split bearing between the second curved surface at the circumferential end of the semi-split bearing and the imaginary outer circumferential surface when the first curved surface is extended to the circumferential end of the semi-split bearing is 10 - 60 μm. The inner circumferential surface of each semi-split bearing in the non-mounted state is composed of a third curved surface formed along one kind of arc. In the mounted state, the circumferential end faces of the pair of semi-split bearings are in contact with each other without a gap, and the first curved surface and the second curved surface of the outer circumferential surfaces of the pair of semi-split 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, so that a fourth curved surface is formed at a position adjacent to the circumferential ends of the inner circumferential surfaces of the pair of semi-split bearings. The thickness of the sliding layer is fixed within the entire circumferential length of the semi-split bearing, or the thickness of the sliding layer is the largest at the circumferential center of the inner circumferential surface and continuously decreases toward the circumferential ends of the semi-split bearing, and the thickness at the circumferential ends of the semi-split bearing is 90% or more of the thickness at the circumferential center.

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

[0012] In yet another embodiment of the present invention, when the plane where the circumferential end faces of a pair of half-split bearings are in contact with each other is defined as the split plane, in the non-mounted state, the circumferential end faces of the half-split bearings are in contact with the split plane at the radially outer ends, and are inclined in such a way that they are farther away from the split plane as they approach the radially inner ends. The inclination angle between the circumferential end faces of the half-split bearings and the split plane is 3×10 -2 ° to 15×10 -2 °. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic view showing a bearing device for a crankshaft of an internal combustion engine. Figure 2 is a view of a sliding bearing according to a first embodiment of the present invention when observed from the axial direction in the non-mounted state. Figure 3 is when observed from the axial direction Figure 2 a view of the half-split bearing shown. Figure 4 is when observed from the inner circumferential surface side Figure 2 a top view of the half-split bearing shown. Figure 5 is when observed from the outer circumferential surface side Figure 2 a top view of the half-split bearing shown. Figure 6 is a view of the large end housing of a connecting rod when observed from the axial direction. Figure 7 is Figure 6 a cross-sectional view of the large end housing of the connecting rod shown along line A-A. Figure 8 is a view of the sliding bearing according to the first embodiment of the present invention and the large end of the connecting rod when observed from the axial direction. Figure 9 is Figure 8 an enlarged view of part B of the sliding bearing and the large end of the connecting rod shown. Figure 10 is an enlarged view of the vicinity of the circumferential end of the half-split bearing when observed from the axial direction in the mounted state. Figure 11 is a top view of a conventional half-split bearing when observed from the axial direction. Figure 12 is Figure 11 an enlarged view of part D of the half-split bearing shown. Figure 13 is Figure 12 a view of the half-split bearing shown in the Y1 direction. Figure 14 is an enlarged view of the vicinity of the circumferential end of a conventional half-split bearing when observed from the axial direction in the mounted state. FIG. 15(A) is a view of the half-split bearing of the sliding bearing according to the second embodiment of the present invention in a non-mounted state as viewed from the axial direction. FIG. 15(B) is a view of the half-split bearing of the sliding bearing according to the second embodiment of the present invention in a non-mounted state as viewed from the axial direction. Figure 16 It is a view of the sliding bearing according to the third embodiment of the present invention in a non-mounted state as viewed from the axial direction. Figure 17 It is as viewed from the axial direction Figure 16 a view of the half-split bearing shown. Figure 18 It is Figure 17 an enlarged view of part C of the half-split bearing shown. DETAILED DESCRIPTION

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

[0015] (First Embodiment) Figure 1 A bearing device 1 for a crankshaft of an internal combustion engine is schematically shown. Figure 6 A view of the large end housing of the connecting rod as viewed from the axial direction is shown. Figure 7 It is Figure 6 a cross-sectional view along line A-A of the large end housing of the connecting rod shown. The bearing device 1 has: a journal portion 6, which is supported on the lower part of the cylinder block; a crank pin 5, which is integrally formed with the journal portion 6 and rotates around the journal portion 6; and a connecting rod 2, which transmits the reciprocating motion from the internal combustion engine to the crank pin 5. In addition, the bearing device 1 also has a main bearing 4 and a connecting rod bearing 3 as sliding bearings for supporting the crankshaft, the main bearing 4 supporting the journal portion 6 to rotate freely, and the connecting rod bearing 3 supporting the crank pin 5 to rotate freely.

[0016] In addition, although 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 shown in the drawing for explanation. In Figure 1 terms of the positional relationship in the depth direction of the drawing plane, the journal portion 6 is located on the depth side of the drawing plane, and the crank pin 5 is located on the front side.

[0017] The journal portion 6 is axially supported via a main bearing 4 composed of a pair of split bearings 41 and 42 in a split-type bearing housing 10 of an internal combustion engine, which is composed of a lower cylinder block 101 and a bearing cap 102. Further, the split bearings 41 and 42 constituting the main bearing 4 are conventional split bearings. Semi-cylindrical bearing holding holes are respectively formed in the lower cylinder block 101 and the bearing cap 102. The split bearing 41 is inserted into the semi-cylindrical bearing holding hole of the lower cylinder block 101, and the split bearing 42 is inserted into the semi-cylindrical bearing holding hole of the bearing cap 102. Then, the lower cylinder block 101 and the bearing cap 102 are fastened by bolts (not shown), so that the pair of split bearings 41 and 42 are held in a cylindrical bearing holding hole. In Figure 1 the upper split bearing 41 located on the upper side is formed with an oil groove 41a over the entire length of the inner circumferential surface. Further, the journal portion 6 has a lubricating oil passage 6a penetrating in the diameter direction. 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 are alternately communicated with the oil groove 41a of the main bearing 4.

[0018] The crankpin 5 is axially supported via a connecting rod bearing 3 composed of a pair of split bearings 31 and 32 in a large end housing 21 of the connecting rod 2. As Figure 6 and Figure 7 shown, the large end housing (bearing housing) 21 is composed 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 respectively have semi-cylindrical surfaces 27, and a pair of semi-cylindrical surfaces 27 form a cylindrical bearing holding hole 23 when butted at the split surface of the rod side large end housing 22A and the cap side large end housing 22B.

[0019] The outer circumferences of the pair of split bearings 31 and 32 are slightly larger than the inner circumference of the bearing holding hole 23 of the large end housing 21. After installation, a squeezing pressure is generated between the outer circumferential surface 8 of the pair of split bearings 31 and 32 and the inner circumferential surface 24 of the bearing holding hole 23, so that the pair of split bearings 31 and 32 are fixed to the bearing holding hole 23 of the large end housing 21. Further, the large end housing 21 is shown as an example of a split-type bearing housing, but is not limited thereto, and it may also be an integral-type large end housing 21. The integral-type large end housing 21 refers to a bearing housing having a structure in which the inner circumferential surface 24 of the bearing holding hole 23 is not divided into a plurality of parts.

[0020] A second lubricating oil passage 5a passing through a crank arm portion (not shown) is formed branching off from the first lubricating oil passage 6a of the journal portion 6. The second lubricating oil passage 5a communicates with a third lubricating oil passage 5b formed penetrating in the diameter direction of the crankpin 5.

[0021] Therefore, as described above, the lubricating oil discharged from the oil pump is sent from the oil passage formed in the cylinder block wall, through the through-hole formed in the wall of the main bearing 4, and into the oil groove 41a formed along the inner circumferential 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 the other hand, the lubricating oil is also supplied to the gap formed between the crankpin 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, from the discharge port 5c at the end of 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, the bearing device of the present invention is not limited to being applied to the connecting rod bearing portion, and it should be understood that it can also be applied to the main bearing portion having a main bearing portion housing.

[0024] Figure 2 Fig. shows the connecting rod bearing 3 formed by the semi-segmented bearings 31, 32 of the present invention in a state where the circumferential end faces 76 are overlapped with each other in the non-mounted state, as viewed from the axial direction. Figure 3 is a view from the axial direction Figure 2 of the semi-segmented bearing 31 (32) shown. Figure 4 is a top view of the semi-segmented bearing 31 (32) shown Figure 2 as viewed from the inner circumferential surface side. Figure 5 is a top view of the semi-segmented bearing 31 (32) shown Figure 2 as viewed from the outer circumferential surface side.

[0025] As Figures 2 to 4 shown, the connecting rod bearing 3 of the present embodiment is formed by butt-joining the circumferential end faces 76 of a pair of semi-segmented bearings 31, 32 having a semi-cylindrical shape to form an integral cylindrical shape. The semi-segmented bearings 31, 32 have a back metal layer 91 on the outer diameter side and a sliding layer 92 on the inner diameter side. The back metal layer 91 can be made of ferrous alloys such as hypoeutectoid steel and stainless steel. The sliding layer 92 can be made of copper bearing alloy, aluminum bearing alloy, etc. In addition, the inner circumferential surface 7 and the outer circumferential surface 8 of the cylindrical shape may also have a surface portion made of any one of bismuth, tin, and lead, which is softer than the bearing alloy, or may have a surface portion made of an alloy mainly composed of these metals, or a surface portion made of a resin composition mainly composed of synthetic resin. In addition, the wall thickness T1 of the semi-segmented bearings 31, 32, the thickness T2 of the back metal layer, and the thickness T3 of the sliding layer 92 described later are defined as the thicknesses not including the surface portion.

[0026] The half-split bearings 31 and 32 have an inner peripheral surface 7, an outer peripheral surface 8, two circumferential end faces 76 and 76, and two end faces 7E and 7E in the axial direction. The inner diameter dimensions, outer diameter dimensions, and axial length L1 of the pair of half-split bearings 31 and 32 are the same. The outer peripheral surface 8 of each of the half-split bearings 31 and 32 in the non-mounted state is composed of a first curved surface 81 and a second curved surface 82 formed by two arcs (which may also be elliptical arcs) with different curvatures. The first curved surface 81 is a region including the circumferential central portion CP of the outer peripheral surface 8. The second curved surface 82 is the remaining two regions of the outer peripheral surface 8 that are connected to the first curved surface 81 and extend toward the circumferential end faces 76 of the half-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 vertical line CL with respect to the bearing outer diameter center line passing through the center C1 of the first arc, and is located at a position offset inward, that is, toward the side closer to the circumferential central portion CP of the outer peripheral surface 8, compared to 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 face 76 of the half-split bearings 31 and 32 with the center C1 of the first arc as the center 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 passenger cars, etc. (for example, an internal combustion engine with a crankshaft shaft diameter of 30 to 100 mm), the radial length L2 of the half-split bearings 31 and 32 between the second curved surface 82 and the imaginary outer peripheral surface 83 when the first curved surface 81 is extended to the circumferential end face 76 of the half-split bearings at each circumferential end face 76 is 10 to 60 μm. In addition, the relationship (L2 / θ1) between the circumferential angle θ1 and the length L2 is preferably 1 to 2 (μm / °).

[0028] In the present embodiment, the wall thickness T1 of the half-split bearings 31 and 32 and the thickness T2 of the back metal layer in the region of the first curved surface 81 are fixed in the entire circumference. The thickness T3 of the sliding layer is fixed within the entire circumferential length (both the region of the first curved surface 81 and the region of the second curved surface 82) of the half-split bearings 31 and 32. In addition, in the case of a bearing device for a small internal combustion engine for passenger cars, etc., the wall thickness T1 of the half-split bearings 31 and 32 in the region of the first curved surface 81 can be set to 1 to 3 mm, the thickness T2 of the back metal layer can be set to 0.75 to 2.85 mm, and the thickness T3 of the sliding layer can be set to 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 this, and other dimensions can also be set.

[0029] The inner circumferential surfaces 7 of the half-split bearings 31 and 32 in the non-mounted state are constituted by a third curved surface 71 formed along an arc. The center C3 of the arc of the third curved surface 71 in the present embodiment is concentric with the center C1 of the first arc forming the first curved surface 81.

[0030] In addition, in the present embodiment, when a plane in which the circumferential end faces of a pair of half-split bearings are in contact with each other is defined as a split plane HP, in the non-mounted state, the circumferential end faces 76 of the half-split bearings 31 and 32 are parallel to the split plane HP.

[0031] Figure 8 FIG. 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. Figure 9 is Figure 8 an enlarged view of a portion B of the sliding bearing and the large end portion of the connecting rod shown. As Figure 8 and Figure 9 shown, after being installed in the bearing holding hole 23 of the large end portion housing 21 (in the mounted state), 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. In addition, Figure 9 the dashed line connected to the first curved surface 81 shown represents a hypothetical second curved surface 82A when not displaced due to installation. After installation (in the mounted state), the circumferential end faces 76 of the pair of half-split bearings 31 and 32 are pressed against each other by the circumferential compressive stress, and the second curved surface 82 is displaced in the radially outer direction ( Figure 9 the direction of the white arrow). The second curved surface 82 of the outer circumferential surfaces 8 of the pair of half-split bearings 31 and 32, like the first curved surface 81, is in contact with the inner circumferential surface 24 of the bearing holding hole 23 without a gap. Therefore, it is difficult for the oil supplied to the bearing device during the operation of the internal combustion engine and the waste residue contained in the oil to enter between the outer circumferential surface 8 of the pair of half-split bearings 31 and 32 and the inner circumferential surface 24 of the bearing holding hole 23.

[0032] In addition, Figure 9The dashed line connected to the third bending surface 71 indicates a hypothetical third bending surface 72A when not displaced due to installation. After being installed in the bearing holding hole 23 of the large end housing 21 (in the installed state), the second bending surface 82 of the outer peripheral surface 8 of the half-split bearings 31 and 32 is displaced radially outward, so that the third bending surface 71 in the area corresponding to the second bending surface 82 is also displaced radially outward. As a result, a fourth bending surface 72 is formed at a position adjacent to the circumferential ends of the inner peripheral surfaces of the pair of half-split bearings 31 and 32. Therefore, similar to the second bending surface 82, the fourth bending surface 72 is formed in the range where the circumferential angle θ1 measured from the circumferential end surface 76 of the half-split bearings 31 and 32 is from a minimum value of 10° to a maximum value of 30°. In addition, the radial length L3 of the half-split bearings between the fourth bending surface 72 and the hypothetical inner peripheral surface 72A at the circumferential end surfaces 76 of the half-split bearings 31 and 32 is the same as the radial length L2 of the half-split bearings 31 and 32 between the second bending surface 82 and the hypothetical outer peripheral surface 83 in the non-installed state, and is 10 - 60 μm. The gap between the fourth bending surface 72 and the surface of the crankshaft functions as an extrusion relief portion. The thickness T3 of the sliding layer (bearing alloy) 92 in the area of the fourth bending surface 72 is the same as the thickness T3 of the sliding layer (bearing alloy) in the third bending surface 71.

[0033] In addition, when the formation range of the second bending surface 82 is less than 10° or the radial length L2 of the half-split bearings 31 and 32 between the second bending surface 82 and the hypothetical outer peripheral surface 83 at the circumferential end surfaces 76 of the half-split bearings 31 and 32 is less than 10 μm, the function of the fourth bending surface 72 as an extrusion relief portion is insufficient.

[0034] In addition, when the formation range of the second bending surface 82 exceeds 30° or the radial length L2 of the half-split bearings 31 and 32 between the second bending surface 82 and the hypothetical outer peripheral surface 83 at the circumferential end surfaces 76 of the half-split bearings 31 and 32 exceeds 60 μm, after installation, a (local) gap may be formed between the second bending surface 82 of the outer peripheral surface 8 of the pair of half-split bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23. When the above gap is formed, during the operation of the internal combustion engine, waste residues enter the gap together with the oil supplied to the bearing device, and the waste residues are likely to accumulate locally. When a local waste residue accumulation portion is formed between the second bending surface 82 of the outer peripheral surface 8 of the half-split bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23, the inner peripheral surface 7 of the half-split bearings 31 and 32 at the position of the accumulation portion bulges toward the inner diameter center side and strongly contacts the surface of the crankshaft, thus easily causing damage.

[0035] Next, the operation of the present invention will be described. In recent years, the oil pump of internal combustion engines has been miniaturized, and the amount of oil supplied to the sliding bearing 3 has decreased. Along with this, the amount of oil leaking out to the outside from the bearing clearance between the surface of the crankshaft 5 and the inner circumferential surface 7 (third curved surface 71) of the half-split bearings 31 and 32 has decreased, and therefore, this bearing clearance tends to be set smaller. Foreign matter larger than the bearing clearance among the foreign matter mixed into the inner circumferential surface 7 of the half-split bearings 31 and 32 is discharged from the oil supply passage to the fourth curved surface portion where the clearance is larger than the bearing clearance. For the foreign matter F discharged to this fourth curved surface portion, that is, the release clearance between the fourth curved surface 72 and the surface of the crankshaft 5, a part of the foreign matter F is discharged from the release clearance at both widthwise ends of the half-split bearings 31 and 32 together with the oil leaking out to the outside, but the remaining foreign matter F is pressed into the surface of the fourth curved surface 72 by the surface of the crankshaft 5. Figure 10 is an enlarged view of the vicinity of the circumferential end of the half-split bearing 31 in the installed 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) of the third curved surface 71, the region of the fourth curved surface 72 has a high ability to hold the embedded foreign matter F over the entire circumferential range, and thus the embedded foreign matter F is difficult to fall off. Therefore, the foreign matter F is buried dispersedly over the entire circumferential range of the fourth curved surface 72, and no local buried portion of a large amount of foreign matter F is formed.

[0036] Here, in order to make a comparison with the operation of the present invention, Figures 11 to 14 the structure and operation of the prior art will be described. Figure 11 is a top view of a conventional half-split bearing 131 as viewed from the axial direction. Figure 12 is Figure 11 an enlarged view of part D of Figure 13 is Figure 12 a view in the YI direction of Figure 14 is an enlarged view of the vicinity of the circumferential end of the conventional half-split bearing 131 in the installed state as viewed from the axial direction.

[0037] The conventional half-split bearing 131 has a back metal layer 191 on the outer diameter side and a sliding layer 192 on the inner diameter side. The outer circumferential surface 18 of the half-split bearing 131 is composed of a curved surface formed along a certain arc. A curved surface 171 and an extrusion release portion 170 are formed on the inner circumferential surface 17 of the half-split bearing 131. The curved surface 171 includes the circumferential central portion CP of the half-split bearing 131 and is formed along an arc having a center C13 concentric with the center C11 of the outer circumferential surface 18. The extrusion release portion 170 is formed in a region adjacent to each circumferential end face 176. The thickness T12 of the back metal layer is fixed over the entire circumference. The wall thickness T11 of the half-split bearing 131 and the thickness T13 of the sliding layer are fixed in the circumferential direction except in the region of the extrusion release portion 170.

[0038] The extrusion release portion 170 is formed by machining (machining to remove the sliding layer 192) into a wall thickness reduction region having a wall thickness thinner than the original inner peripheral surface 173 ( Figure 12 dotted line). The thickness T13' of the sliding layer (bearing alloy) at the extrusion release portion 170 reaches the maximum at a position adjacent to the curved surface 171 and continuously decreases as it approaches the circumferential end surface 176 side. In the region 170L (see Figure 13 ) adjacent to the circumferential end surface 176 of the extrusion release portion 170, the thickness of the sliding layer (bearing alloy) 192 is too small, so the ability to hold foreign matter F is low. Therefore, as Figure 14 shown, the foreign matter F (dotted circle F) buried in the surface of the region 170L adjacent to the circumferential end surface 176 of the extrusion release portion 170 easily falls off. Therefore, the foreign matter F will be concentrated and buried in the region 170U (see Figure 13 ) adjacent to the curved surface 171 of the extrusion release portion 170 where the thickness of the sliding layer (bearing alloy) 192 is large and the ability to hold the foreign matter F is high. Thus, when a buried portion of a large amount of local foreign matter F is formed in the region 170U adjacent to the curved surface 171 of the extrusion release portion 170, sintering may occur on the curved surface 171 adjacent to the extrusion release portion 170 due to the heat generated by the contact between the foreign matter F and the surface of the crankshaft 5.

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

[0040] FIG. 15(A) and FIG. 15(B) are views of the half-split bearing 31(32) constituting the connecting rod bearing 3 of the second embodiment of the present invention as viewed from the axial direction.

[0041] The bearing device of the second embodiment is different from the bearing device of the first embodiment only in the structure of the inner peripheral surface 7 and the sliding layer 92 of the half-split bearings 31 and 32 constituting the sliding bearing (connecting rod bearing 3), and the remaining structures are the same as those of the bearing device of the first embodiment. The description of the structures common to the first embodiment is omitted.

[0042] The inner circumferential surface 7 of the semi-split bearing 31(32) in the non-mounted state is composed of a third curved surface 71 formed along an elliptical arc. The relationship between the center C1 of the first circular arc of the first curved surface 81 forming the outer circumferential surface 8 of the semi-split bearing 31(32) and the center C3 of the third circular arc of the third curved surface 71 forming the inner circumferential surface 7 is as follows: The center C3 of the third circular arc is on the vertical line CL with respect to the bearing outer diameter center line passing through the center C1 of the first circular arc, and is located at a position offset to the outside, that is, to the side away from the circumferential central portion CP' of the inner circumferential surface 7. The distance between the center C1 of the first circular arc of the first curved surface 81 forming the outer circumferential surface 8 of the semi-split bearing 31(32) and the inner circumferential surface 7 reaches the minimum R3C at the position of the circumferential central portion CP' of the inner circumferential surface 7 and reaches the maximum R3E at the two circumferential ends.

[0043] In this embodiment, the wall thickness T1 of the semi-split bearings 31, 32 in the region of the first curved surface 81 reaches the maximum at the position of the circumferential central portion CP' of the inner circumferential surface 7 and continuously decreases toward the circumferential end face 76. The thickness of the sliding layer 92 reaches the maximum at the circumferential central portion CP' of the inner circumferential surface 7 (third curved surface 71) and continuously decreases toward the circumferential end face 76 of the semi-split bearing 8. The thickness T3E at the circumferential end face 76 of the semi-split bearing 31(32) is 90% or more of the thickness T3C at the circumferential central 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 range of the fourth curved surface 72 formed in the mounted state, and the holding ability for buried foreign matters can be improved.

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

[0045] Figure 16 FIG. shows a connecting rod bearing 3 constituted by the semi-split bearings 31, 32 of the third embodiment of the present invention in a state where the circumferential end faces 76 are overlapped with each other in the non-mounted state, as viewed from the axial direction. Figure 17 Shows as viewed from the axial direction Figure 16 The semi-split bearing 31(32) shown. Figure 18 Is Figure 17 An enlarged view of part C of the semi-split bearing 31(32) shown.

[0046] The bearing device of the third embodiment is different from the bearing device of the first embodiment only in the structure of the circumferential end faces 76, 76 of the half-split bearings 31, 32 that constitute the connecting rod bearing 3, and the remaining structures are the same as those of the bearing device of the first embodiment. Regarding the structures common to the first embodiment, the description is omitted.

[0047] As Figure 18 shown in the enlarged view of, when the plane where the circumferential end faces of a pair of half-split bearings are in contact with each other is defined as the split plane HP, the circumferential end faces 76, 76 of the half-split bearings 31, 32 in the non-mounted state are in contact with the split plane HP at the radially outer ends 76O, and are inclined so as to be away from the split plane HP as they approach the radially inner ends 76I. The inclination angle θ2 of the circumferential end faces 76, 76 of the half-split bearings 31, 32 with respect to the split plane HP is 3×10 -2 ° to 15×10 -2 °. Additionally, when the circumferential end faces 76, 76 of the half-split bearings 31, 32 have the inclination angle θ2, the formation range of the second curved surface 82 is defined by the circumferential angle θ1 measured from the radially outer end 76O of the circumferential end face 76 of the half-split 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-split bearings 31, 32 have the inclination angle θ2, in the mounted state, the circumferential end faces 76 are in contact with each other without a gap. In addition, the second curved surface 82 becomes more likely to displace in the radially outer direction, and the pressure (extrusion pressure) between the second curved surface 82 and the inner peripheral surface 24 of the bearing holding hole 23 becomes greater. Therefore, when the internal combustion engine is running, the oil supplied to the bearing device and the waste residue contained in the oil become more difficult to enter between the outer peripheral surfaces 8 of the pair of half-split bearings 31, 32 and the inner peripheral surface 24 of the bearing holding hole 23.

[0049] Furthermore, when the inclination angle θ2 of the circumferential end faces 76, 76 of the half-split bearings 31, 32 with respect to the split plane HP is less than 3×10 -2 °, it is difficult to obtain the effect of increasing the pressure between the second curved surface 82 and the inner peripheral surface 24 of the bearing holding hole 23 in the mounted state. In addition, when the inclination angle θ2 exceeds 15×10 -2 °, when mounting to the bearing holding hole 23 of the large end housing (bearing housing) 21, there may be a large offset between the circumferential end faces 76, 76 of the half-split bearings 31, 32.

[0050] The above description is given by taking the bearing device of the present invention applied to the connecting rod bearing portion that supports the crank pin of the crankshaft of an internal combustion engine as an example. 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. In addition, the semi-segmented bearing may also have, for example, an oil hole, an oil groove, and a notch for positioning. Further, the semi-segmented bearing may have chamfers at positions adjacent to the end faces in the axial direction on the outer peripheral surface and at positions adjacent to the end faces in the axial direction on the inner peripheral surface. Further, chamfers may be provided at positions adjacent to the circumferential end faces on the inner peripheral surface. Additionally, in the case of having these chamfers, the wall thickness of the semi-segmented bearing related to the structure of the present invention, the thickness of the back metal layer, and the thickness of the sliding layer are defined as the thickness when no chamfers are formed. Symbolic Explanation

[0051] 1 Bearing device; 10 Bearing housing (main bearing); 101 Lower part of the cylinder block; 102 Bearing cap; 2 Connecting rod; 21 Large end housing, bearing housing; 22A Rod side large end housing; 22B Cap side large end housing; 23 Bearing holding hole; 24 Inner peripheral surface; 27 Semi-cylindrical surface; 3 Connecting rod bearing; 31, 32 Semi-segmented bearings; 4 Main bearing; 41, 42 Semi-segmented bearings; 41a Oil groove; 5 Crank pin; 5a, 5b Lubricating oil passages; 5c Discharge port; 6 Journal portion; 6a Lubricating oil passage; 6c Inlet opening; 7 Inner peripheral surface; 7E Axial direction end face; 70 Extrusion release portion; 71 Third bending surface; 72 Fourth bending surface; 72A Hypothetical third bending surface when not displaced; 76 Circumferential end face; 76I Inner end; 76O Outer end; 8 Outer peripheral surface; 81 First bending surface; 82 Second bending surface; The imaginary second curved surface when 82A is not displaced; The imaginary outer peripheral surface; The back metal layer; The sliding layer; C1 The center of the first circular arc; C2 The center of the second circular arc; C3 The center of the third circular arc; CL The vertical line relative to the center line of the bearing outer diameter; CP The circumferential central part; CP’ The circumferential central part; F Foreign object; HP The dividing plane; L1 The axial direction length of the half-divided bearing; L2 Length; L3 Length; T1 The wall thickness of the half-divided bearing; T2 The thickness of the back metal layer; T3 The thickness of the sliding layer; T3C The thickness of the sliding layer at the circumferential center; T3E The thickness of the sliding layer at the circumferential end; X The rotation direction of the journal; Z The rotation direction of the crank pin; θ1 The circumferential angle; θ2 The inclination angle.

Claims

1. A bearing device (1), the bearing device (1) supporting a crankshaft of an internal combustion engine, and comprising: Crankshaft (5, 6); A bearing housing (10, 21) having a cylindrical bearing retaining hole (23); and Sliding bearings (3, 4), The sliding bearing is composed of a pair of half-split bearings (31, 32; 41, 42). The pair of half-split bearings respectively have an inner peripheral surface (7), an outer peripheral surface (8) and two circumferential end surfaces (76, 76), The pair of half-split bearings have the same axial length (L1). The pair of half-split bearings each have a back metal layer (91) on the outer diameter side and a sliding layer (92) on the inner diameter side. The pair of half-split bearings are mounted on the inner peripheral surface (24) of the bearing retaining hole, and the inner peripheral surface of the pair of half-split bearings supports the crankshaft. The bearing device is characterized in that The outer peripheral surface of each half-split bearing in a non-installed state is composed of a first curved surface and a second curved surface (81, 82) formed along two arcs with different curvatures, the first curved surface is an area including a circumferential center portion (CP) of the outer peripheral surface, and the second curved surface is the remaining two areas of the outer peripheral surface connected to the first curved surface and extending toward the circumferential end surface of the half-split bearing, and 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: the center (C2) of the second arc is located on a perpendicular line (CL) relative to the center line of the outer diameter of the bearing passing through the center (C1) of the first arc, and is located inwardly compared with the center (C1) of the first arc, that is, offset to one side close to the circumferential center portion of the outer peripheral surface, The second curved surface is formed in a range where a circumferential angle (θ1) measured from the circumferential end surface of the half-split bearing with the center (C1) of the first arc as the center is within a minimum range of 10° to a maximum range of 30°, The radial length (L2) of the half-split bearing between the second curved surface at the circumferential end of the half-split bearing and the imaginary outer peripheral surface (83) when the first curved surface is extended to the circumferential end of the half-split bearing is 10 to 60 μm, The inner peripheral surface of each half-split bearing in the non-installed state is composed of a third curved surface (71) formed along a circular arc, In the installed state, the circumferential end faces of the pair of half-split bearings are in contact with each other without a gap, and the first curved surface and the second curved surface of the outer circumferential surface of the pair of half-split bearings are in contact with the inner circumferential surface of the bearing retaining hole without a gap. When the second curved surface contacts the inner peripheral surface of the bearing retaining hole without a gap in the installed state, the third curved surface of the area corresponding to the second curved surface is displaced radially outward, so that the fourth curved surface (72) is formed at a position adjacent to each circumferential end of the inner peripheral surface of the pair of half-split bearings. The thickness (T3) of the sliding layer is fixed over the entire circumferential length of the half-split bearing, or the thickness (T3) of the sliding layer is maximum at the circumferential center of the inner circumferential surface and continuously decreases toward the circumferential end of the half-split bearing, and the thickness (T3E) at the circumferential end of the half-split bearing is more than 90% of the thickness (T3C) at the circumferential center (T3E≥T3C×0.90).

2. The bearing device (1) according to claim 1, characterized in that When a plane where the circumferential end faces of the pair of half-split bearings contact each other is defined as a split plane (HP), in a non-mounted state, the circumferential end faces of the half-split bearings are parallel to the split plane (HP).

3. The bearing device (1) according to claim 1, characterized in that When the plane where the circumferential end faces of the pair of half-split bearings contact each other is positioned as the split plane (HP), in the non-installed state, the circumferential end faces of the half-split bearings contact the split plane at the radially outer end (76O) and are inclined in a manner that the closer they are to the radially inner end (76I), the farther they are from the split plane (HP), and the inclination angle (θ2) between the circumferential end faces of the half-split bearings and the split plane is 3×10 -2 °~15×10 -2 °.

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