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 a sliding bearing that is less susceptible to wear when press-fitted into a bearing holding hole of an integrated bearing housing. 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. The second curved surface is formed in a range in which a circumferential angle ([theta] 1) measured from the circumferential end surface of the half bearing, centered on the center (C1) of the first arc, is from a minimum value of 10 DEG to a maximum value of 30 DEG. The length (L2) in the radial direction of the half bearing between the second curved surface at the circumferential end of the half bearing and an imaginary outer circumferential surface (83) when the first curved surface extends to the circumferential end of the half bearing is 5-30 [mu] m. 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.

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 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 an 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 open and communicate with the oil groove of the main bearing. Further, a second lubricating oil passage penetrating through the crank arm portion is formed branching from the first lubricating oil passage of the journal portion, and the second lubricating oil passage communicates with a third lubricating oil passage formed penetrating in the diameter direction along the crank pin. Therefore, the lubricating oil fed into the oil groove formed in 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 bearings and the crank pin through the first lubricating oil passage, the second lubricating oil passage, and the third lubricating oil passage, and from the discharge port opening 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, in the case where the bearing housing holding the main bearing or the connecting rod bearing is of an integral type, a pair of half bearings constituting the main bearing or the connecting rod bearing are simultaneously pressed into from one opening in the axial direction of the cylindrical bearing holding hole of the bearing housing (for example, refer to Patent Document 2). Prior Art Documents Patent Documents

[0004] Patent Document 1: Japanese Patent Laid-Open No. 8-277831 Patent Document 2: Japanese Utility Model Laid-Open No. 11-236923 Summary of the Invention

[0005] The conventional sliding bearing composed of a pair of half bearings has the following problems: When simultaneously pressed into from one opening of the bearing holding hole of the integral type bearing housing, first, the circumferential end faces of the pair of half bearings are offset from each other immediately after the start of pressing, and the circumferential end portion near the outer circumferential surface of the half bearing strongly interferes with the edge of the opening of the bearing holding hole, so that the outer circumferential surface of the half bearing is cut, and when further pressing is performed, due to the material of the outer circumferential surface of the half bearing adhering to the edge of the opening of the bearing holding hole, the outer circumferential surface of the half bearing is liable to wear (damage in multiple axial directions).

[0006] Accordingly, an object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine, the bearing device for the crankshaft of the internal combustion engine having a sliding bearing that is not easily worn when pressed into a bearing holding hole of an integral bearing housing.

[0007] 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; An integral bearing housing having a cylindrical bearing holding hole; and A sliding bearing, The sliding bearing is composed of a pair of half-segment bearings, Each of the pair of half-segment bearings has an inner peripheral surface, an outer peripheral surface, and two circumferential end faces, The pair of half-segment bearings have the same axial length in the axial direction, The pair of half-segment bearings are simultaneously pressed into the inner peripheral surface of the bearing holding hole from one opening in the axial direction of the bearing holding hole, and the inner peripheral surfaces of the pair of half-segment bearings support the crankshaft, The outer peripheral surface of each half-segment bearing in the non-mounted state is composed of a first curved surface and a second curved surface formed by two arcs with different curvatures. The first curved surface is a region including the circumferential central portion of the outer peripheral surface, and the second curved surface is the remaining two regions of the outer peripheral surface that are connected to the first curved surface and extend toward the circumferential end faces of the half-segment 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 circumferential central portion of the outer peripheral surface, compared 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-segment 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-segment bearing between the second curved surface at the circumferential end of the half-segment bearing and the imaginary outer peripheral surface when the first curved surface is extended to the circumferential end of the half-segment bearing is 5 to 30 μm, An extrusion release portion is formed at each circumferential end of the inner peripheral surface of each half-segment bearing, In the mounted state, the circumferential end faces of the pair of half-segment bearings are in contact with each other without a gap, and the first curved surface and the second curved surface of the outer peripheral surfaces of the pair of half-segment bearings are in contact with the inner peripheral surface of the bearing holding hole without a gap.

[0008] In another embodiment of the present invention, when the plane in which the circumferential end faces of the pair of half-segment bearings are in contact with each other is defined as the dividing plane, in the non-mounted state, the circumferential end faces of the half-segment bearings are parallel to the dividing plane.

[0009] In yet another embodiment of the present invention, when a plane in which the circumferential end faces of a pair of half-split bearings contact each other is defined as a split plane, in the non-mounted state, the circumferential end faces of the half-split bearings contact the split plane at the radially outer ends, and are inclined so as to be 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

[0010] 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 a view when observed from the axial direction Figure 2 of the half-split bearing shown. Figure 4 is a top view when observed from the inner circumferential surface side Figure 2 of the half-split bearing shown. Figure 5 is a top view when observed from the outer circumferential surface side Figure 2 of the half-split bearing shown. Figure 6 is a view when observed from the axial direction of the large end housing of the connecting rod. Figure 7 is Figure 6 a cross-sectional view along line A-A of the large end housing of the connecting rod shown. Figure 8 is a view when observed from the axial direction of the sliding bearing and the large end of the connecting rod according to the first embodiment of the present invention. 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 a view when observed from the axial direction of a sliding bearing according to a second embodiment of the present invention in the non-mounted state. Figure 11 is a view when observed from the axial direction Figure 10 of the half-split bearing shown. Figure 12 is Figure 11 an enlarged view of part C of the half-split bearing shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

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

[0012] (First Embodiment) Figure 1 A bearing device 1 for a crankshaft of an internal combustion engine is schematically shown. Figure 6 A view showing the large-end housing of a connecting rod as viewed in the axial direction. Figure 7 is Figure 6 A cross-sectional view taken along line A-A of the large-end housing of the connecting rod shown. The bearing device 1 has: a journal portion 6 that is supported at the lower part of the cylinder block; a crankpin 5 that is integrally formed with the journal portion 6 and rotates about the journal portion 6; and a connecting rod 2 that transmits reciprocating motion from the internal combustion engine to the crankpin 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 crankpin 5 to rotate freely.

[0013] In addition, although 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 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 crankpin 5 is located on the front side.

[0014] The journal portion 6 is pivotally supported by a main bearing 4 composed of a pair of half-split bearings 41, 42 in a split-type bearing housing 10 of the internal combustion engine formed by a lower part 101 of the cylinder block and a bearing cap 102. In addition, the half-split bearings 41, 42 constituting the main bearing 4 are conventional half-split bearings. Semi-cylindrical bearing holding holes are respectively formed in the lower part 101 of the cylinder block and the bearing cap 102. The half-split bearing 41 is inserted into the semi-cylindrical bearing holding hole of the lower part 101 of the cylinder block, and the half-split bearing 42 is inserted into the semi-cylindrical bearing holding hole of the bearing cap 102. 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-split bearings 41, 42 are held in a cylindrical bearing holding hole. In Figure 1 the upper half-split bearing 41 located in the upper side is formed with an oil groove 41a over the entire length of the inner circumferential surface. In addition, 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.

[0015] The crankpin 5 is pivotally supported by a connecting rod bearing 3 composed of a pair of half-split bearings 31, 32 in the large-end housing 21 of the connecting rod 2. As shown in Figure 6 and Figure 7As shown, the large-end housing (bearing housing) 21 is of an integral type and has a bearing holding hole 23 with a cylindrical shape. The fact that the large-end housing 21 is of an integral type means that the inner circumferential surface 24 of the bearing holding hole 23 is not divided into a plurality (usually two). A pair of split bearings 31, 32 are simultaneously pressed into the bearing holding hole 23 of the large-end housing 21 from one opening 25 in the axial direction of the bearing holding hole 23 while the circumferential end faces 76 are made to coincide with each other. The outer circumferences of the pair of split bearings 31, 32 before pressing are slightly larger than the inner circumference of the bearing holding hole 23 of the large-end housing 21. After pressing, compressive pressure is generated between the outer circumferential surfaces 8 of the pair of split bearings 31, 32 and the inner circumferential surface 24 of the bearing holding hole 23, so that the pair of split bearings 31, 32 are installed (fixed) in the bearing holding hole 23 of the large-end housing 21.

[0016] 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 shaft neck portion 6. The second lubricating oil passage 5a communicates with a third lubricating oil passage 5b formed penetrating in the diametrical direction of the crank pin 5.

[0017] Therefore, as described above, the lubricating oil discharged by the oil pump passes through the through-hole formed in the wall of the main bearing 4 from the oil passage formed in the cylinder block wall and is fed 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 shaft neck portion 6 and the main bearing 4.

[0018] On the other hand, the lubricating oil is also supplied to the gap formed between the crank pin 5 and the connecting rod bearing 3 from the discharge port 5c at the end of the third lubricating oil passage 5b via the first lubricating oil passage 6a, the second lubricating oil passage 5a, and the third lubricating oil passage 5b.

[0019] In an existing sliding bearing having a pair of split bearings whose outer circumferential surfaces are formed of curved surfaces along an arc (which may also be an elliptical arc), there are the following problems. When a pair of split bearings are simultaneously pressed into one opening of the bearing holding hole of an integral large-end housing, first, immediately after the start of pressing, the circumferential end faces of the pair of split bearings are displaced from each other. Then, the circumferential end portion near the outer circumferential surface of the split bearing strongly interferes with the edge of the opening of the bearing holding hole, and the outer circumferential surface of the split bearing is cut. When further pressing is performed, due to the material of the outer circumferential surface of the split bearing adhering to the edge of the opening of the bearing holding hole, the outer circumferential surface of the split bearing is liable to wear (damage in a plurality of axial directions).

[0020] The present invention is for dealing with the above-mentioned problems of the prior art. Hereinafter, an embodiment in which the bearing device 1 of the present invention is applied to a 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 a main bearing portion having an integral main bearing housing.

[0021] Figure 2 Fig. 3 shows the connecting rod bearing 3 formed by the semi-segmented bearings 31 and 32 of the present invention in a state where the circumferential end faces 76 are overlapped with each other in the non-mounted state (before press-fitting), as viewed from the axial direction. Figure 3 as viewed from the axial direction Figure 2 a view of the semi-segmented bearing 31 (32) shown. Figure 4 as viewed from the inner circumferential surface side Figure 2 a top view of the semi-segmented bearing 31 (32) shown. Figure 5 as viewed from the outer circumferential surface side Figure 2 a top view of the semi-segmented bearing 31 (32) shown.

[0022] 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 and 32 to form an integral cylindrical shape. The semi-segmented bearings 31 and 32 can have a sliding layer made of a Cu bearing alloy or an Al bearing alloy. Alternatively, a sliding layer made of a Cu bearing alloy or an Al bearing alloy can be provided on the back metal layer made of an Fe alloy. In addition, the inner circumferential surface 7 and the outer circumferential surface 8 of the cylindrical shape can also have a surface portion made of any one of bismuth, tin, and lead, 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 synthetic resin.

[0023] The semi-segmented 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 inner diameter dimensions, outer diameter dimensions, and axial length L1 of the pair of semi-segmented bearings 31 and 32 are the same. The outer circumferential surface 8 of each semi-segmented bearing 31 and 32 in the non-mounted state is composed of a first curved surface 81 and a second curved surface 82 formed along two arcs (which can also be elliptical arcs) with different curvatures. 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 connected to the first curved surface 81 and extend toward the circumferential end faces 76 of the semi-segmented 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 circumferential central portion CP of the outer circumferential surface 8, compared to the center C1 of the first arc.

[0024] The second curved surface 82 is formed within a range where the circumferential angle θ1 measured from the circumferential end surface 76 of the half-split bearings 31 and 32 with the center C1 of the first circular 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 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 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 surface 76 at each circumferential end surface 76 of the half-split bearings 31 and 32 is 5 to 30 μm. Additionally, the relationship between the circumferential angle θ1 and the length L2 (L2 / θ1) is preferably 0.5 to 1.2 (μm / °).

[0025] In the present embodiment, the wall thickness of the half-split bearings 31 and 32 in the region of the first curved surface 81 is fixed in the entire circumferential direction. However, it may also be that the wall thickness in the region of the first curved surface 81 reaches the maximum at the circumferential center portion CP and continuously decreases as it approaches the circumferential end surface 76 side.

[0026] An extrusion relief portion 70 is formed in a region of the inner circumferential surface 7 of the half-split bearings 31 and 32 adjacent to the circumferential end surface 76. The extrusion relief portion 70 is formed as a wall thickness reduction region that is thinner than the original inner circumferential surface 7 (major circular arc) through machining (machining to remove the sliding layer). The extrusion relief portion 70 is provided to form a gap for absorbing the circumferential end surface 76 position offset and deformation in a state where a pair of half-split bearings 31 and 32 are assembled to the bearing housing (for example, refer to SAE J506 (Items 3.26 and 6.4), DIN 1497 (Section 3.2), JIS D3102). Generally, in the case of a bearing for a small internal combustion engine for a passenger car, the depth of the extrusion relief portion at the circumferential direction end surface of the half-split bearing (the distance from the original inner circumferential surface to the actual inner circumferential surface) is about 0.01 to 0.075 mm, and its length (the length in the direction perpendicular to the end surface from the circumferential direction end surface of the half-split bearing to the upper edge portion of the extrusion relief portion 70) is about 3 to 7 mm.

[0027] Furthermore, in the present embodiment, when the plane where the circumferential end surfaces of a pair of half-split bearings are in contact with each other is defined as the split plane HP, in the non-mounted state, the circumferential end surfaces of the half-split bearings are parallel to the split plane HP.

[0028] As described above, the outer peripheral surface 8 of the half-split bearing used in the bearing device of the present invention is composed of the first curved surface 81 and the second curved surface 82 formed along two circular arcs with different curvatures in the non-mounted state. Hereinafter, the reason for reducing bearing damage by this half-split bearing will be described.

[0029] As described above, in the present invention, the first curved surface 81 is a region including the circumferential central portion CP of the outer circumferential surface 8, and the second curved surface 82 is the remaining two regions of the outer circumferential surface 8 that are connected to the first curved surface 81 and extend toward the circumferential end surface of the half-split bearing. The relationship between the center C1 of the first circular arc forming the first curved surface 81 and the center C2 of the second circular arc forming the second curved surface 82 is that the center C2 of the second 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 inward, that is, toward the side closer to the circumferential central portion CP of the outer circumferential surface 8, compared to the center C1 of the first circular arc. The second curved surface 82 is formed in the range where the circumferential angle θ1 measured from the circumferential end surface 76 of the half-split bearings 31, 32 is from a minimum value of 10° to a maximum value of 30°. The radial length L2 of the half-split bearing between the second curved surface 82 on the circumferential end of the half-split bearings 31, 32 and the imaginary outer circumferential surface 83 when the first curved surface 81 is extended to the circumferential end of the half-split bearings 31, 32 is 5 to 30 μm.

[0030] Under this structure, a gap is formed between the second curved surface 82 of the outer circumferential surface 8 of the half-split bearings 31, 32 and the imaginary outer circumferential surface 83 when the first curved surface 81 is extended to the circumferential end surface 76 of the half-split bearings 31, 32 (see Figure 2 and Figure 3 ). Therefore, when the pair of half-split bearings 31, 32 are simultaneously pressed into one opening 25 of the bearing holding hole 23 of the integral large-end housing 21, even if the circumferential end surfaces 76 of the pair of half-split bearings 31, 32 are offset from each other at the beginning of the pressing, the second curved surface 82 of the outer circumferential surface 8 of the half-split bearings 31, 32 is less likely to strongly interfere with the edge of the opening 25 of the bearing holding hole 23, so that the second curved surface 82 of the outer circumferential surface 8 does not wear (damage in multiple axial directions).

[0031] Figure 8 is a view of the sliding bearing and the large end of the connecting rod according to the first embodiment of the present invention as viewed 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 in Figure 8 and Figure 9 As shown, after being pressed into the bearing holding hole 23 of the integral large-end housing 21 (in the installed state), circumferential compressive stress is generated in the pair of half-split bearings 31, 32, and the circumferential end surfaces 76 are in contact with each other without a gap. In addition, Figure 9 the dashed line shown in Figure 9 represents the imaginary second curved surface 82A when not displaced due to pressing (installation). After pressing (in the installed state), the circumferential end surfaces 76 of the pair of half-split bearings 31, 32 are pressed against each other by the circumferential compressive stress, and the second curved surface 82 moves in the radially outward direction ( Figure 9It is displaced in the direction of the white arrow). The second curved surface 82 of the outer peripheral surface 8 of the pair of half-split bearings 31 and 32 is in contact with the inner peripheral surface 24 of the bearing holding hole 23 without clearance, just like the first curved surface 81. Therefore, it is difficult for the oil supplied to the bearing device during the operation of the internal combustion engine and the waste residues contained in the oil to enter between 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.

[0032] In addition, when the formation range of the second curved surface 82 is less than 10° or 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 at the circumferential end faces 76 of the half-split bearings 31 and 32 is less than 5 μm, when the pair of half-split bearings are simultaneously pressed into from the opening 25 side of one of the bearing holding holes 23 of the integral large-end housing 21, the second curved surface 82 of the outer peripheral surface of the half-split bearing may strongly interfere with the edge of the opening of the bearing holding hole 23, resulting in the cutting of the outer peripheral surface of the half-split bearing and wear (damage in multiple axial directions).

[0033] Furthermore, when the formation range of the second curved surface 82 exceeds 30° or 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 at the circumferential end faces 76 of the half-split bearings 31 and 32 exceeds 30 μm, after pressing, a (local) gap may sometimes be formed between the second curved 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, the waste residues enter this gap together with the oil supplied to the bearing device, and the waste residues are likely to accumulate locally. When a local accumulation part of the waste residues is formed between the second curved 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 this accumulation part bulges toward the inner diameter center side and strongly contacts the surface of the crankshaft, thus easily causing damage.

[0034] (Second Embodiment) Hereinafter, another non-limiting embodiment of the present invention will be described.

[0035] Figure 10 Fig. shows a connecting rod bearing 3 composed of the half-split bearings 31 and 32 of the second embodiment of the present invention in a state where the circumferential end faces 76 are overlapped with each other in the non-mounted state (before pressing), as viewed from the axial direction. Figure 11 Fig. shows a view as viewed from the axial direction Figure 10 of the half-split bearing 31 (32) shown. Figure 12 is Figure 11 an enlarged view of part C of the half-split bearing 31 (32) shown.

[0036] The bearing device of the second 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 2, 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.

[0037] As Figure 12 shown in the enlarged view of, when the plane in which 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 °. In addition, 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.

[0038] When the circumferential end faces 76, 76 of the half split bearings 31, 32 have the inclination angle θ2, in the mounted state (after press-fitting), 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 circumferential surface 24 of the bearing holding hole 23 becomes greater. Therefore, it becomes more 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, 32 and the inner circumferential surface 24 of the bearing holding hole 23.

[0039] In addition, 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 circumferential surface 24 of the bearing holding hole 23 in the mounted state. In addition, when the inclination angle θ2 exceeds 15×10 -2 °, the circumferential end faces 76, 76 of the half split bearings 31, 32 are displaced from each other at the beginning of press-fitting, and the second curved surface 82 of the outer circumferential surface 8 of the half split bearings 31, 32 may strongly interfere with the edge of the opening 25 of the bearing holding hole 23 and cause wear (damage in multiple axial directions).

[0040] The above description is given by taking as an example the application of the bearing device of the present invention to the connecting rod bearing portion that supports the crank pin of the crankshaft of an internal combustion engine. However, the bearing device of the present invention can also be applied to the main bearing portion that supports the journal portion of the crankshaft. 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. Symbol Explanation

[0041] 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; 23 Bearing holding hole; 24 Inner peripheral surface; 25 Opening; 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; 76 Circumferential end face; 76I Inner side end; 76O Outer side end; 8 Outer peripheral surface; 81 First curved surface; 82 Second curved surface; 82A Hypothetical second curved surface when not displaced; 83 Hypothetical outer peripheral surface; C1 Center of the first circular arc; C2 Center of the second circular arc; CL Perpendicular line to the center line of the bearing outer diameter; CP Circumferential central portion; HP Division plane; L1 Axial direction length of the semi-segmented bearing; L2 Length; Rotation direction of the X-axis neck Rotation direction of the Z crank pin Circumferential angle θ1 Tilt angle θ2

Claims

1. A bearing device (1), the bearing device (1) supporting a crankshaft of an internal combustion engine, and comprising: Crankshaft (5, 6); An integrated 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 are simultaneously pressed into the inner peripheral surface (24) of the bearing retaining hole from an opening (25) on one side of the axial direction of the bearing retaining hole, and the inner peripheral surface of the pair of half-split bearings supports the crankshaft. The bearing device (1) 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 5 to 30 μm, A squeeze release portion (70) is formed at each circumferential end portion of the inner circumferential surface of each half-split bearing. In the installed state, the circumferential end surfaces 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 surfaces of the pair of half-split bearings are in contact with the inner circumferential surface of the bearing holding hole without a gap.

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 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-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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