Bearing device for a crankshaft of an internal combustion engine

Abstract

To provide a bearing device for a crank shaft of an internal combustion engine having a sliding bearing in which biting hardly occurs when pressed into a bearing holding hole of an integral type bearing housing.SOLUTION: The outer peripheral face of each half-split bearing in a non-mounted state consists of first and second curved faces (81, 82) formed along the two types of circular arcs different in curvature radius. A circumferential angle (θ1) of the second curved face, measured from the peripheral end face of the half-split bearing while centering on a center (C1) of a first circular arc, is formed in a range from a minimum value 10° to a maximum value 30°. When extending the second curved face and the first curved face at the peripheral end of the half-split bearing to the peripheral end of the half-split bearing, a length (L2) from a virtual outer peripheral face (83) in the radial direction of the half-split bearing is 5-30 μm. In a mounted state, the peripheral ends of the pair of half-split bearings contact each other with no space, and the first curved face and the second curved face of the outer peripheral faces of the pair of half-split bearings contact the inner peripheral face of the bearing holding hole with no space.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

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

[0003] Conventionally, when a bearing housing for holding a main bearing and a connecting rod bearing is of an integral type, a pair of split bearings constituting the main bearing and the connecting rod bearing are simultaneously press-fitted from one opening in the axial direction of the cylindrical bearing holding hole of the bearing housing (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In a conventional sliding bearing composed of a pair of split bearings, when press-fitting them simultaneously from one opening of the bearing holding hole of an integral bearing housing, first, immediately after the start of press-fitting, a deviation occurs between the circumferential end faces of the pair of split bearings, and the circumferential end portion near the outer peripheral surface of the split bearing strongly interferes with the edge of the opening of the bearing holding hole, resulting in the outer peripheral surface of the split bearing being scraped. Further, as the press-fitting progresses, there is a problem that the outer peripheral surface of the split bearing is likely to be bitten (multiple axial scratches) by the material of the outer peripheral surface of the split bearing adhering to the edge of the opening of the bearing holding hole. [Means for Solving the Problems]

[0006] Therefore, an object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine having a sliding bearing in which biting is less likely to occur when press-fitting into a bearing holding hole of an integral bearing housing.

[0007] To solve the above problems, the present invention is a bearing device for supporting a crankshaft of an internal combustion engine, the bearing device comprising: a crankshaft; an integral bearing housing having a cylindrical bearing holding hole; a sliding bearing and having the sliding bearing is composed of a pair of split bearings, the pair of split bearings each have an inner peripheral surface, an outer peripheral surface, and two circumferential end faces, the pair of split bearings have the same axial length as each other, the pair of split bearings are simultaneously press-fitted from one opening in the axial direction of the bearing holding hole and mounted on the inner peripheral surface of the bearing holding hole, and the inner peripheral surfaces of the pair of split bearings support the crankshaft, in the bearing device. The outer peripheral surface of each half bearing in the non-mounted state is composed of a first and a second curved surface formed along two types of arcs with different curvatures. The first curved surface is a region including the circumferential central part of the outer peripheral surface, and the second curved surface is the remaining two regions of the outer peripheral surface that are continuous with the first curved surface and extend toward the circumferential end surface of the half bearing. The relationship between the center of the first arc forming the first curved surface and the center of the second arc forming the second curved surface is that the center of the second arc is on the perpendicular line to the bearing outer diameter center line passing through the center of the first arc, and is offset to the inner side, that is, the side closer to the circumferential central part of the outer peripheral surface, relative to the center of the first arc. The second curved surface is formed in a range where the circumferential angle measured from the circumferential end surface of the half bearing around the center of the first arc is from a minimum value of 10° to a maximum value of 30°. The radial length of the half bearing between the second curved surface and the virtual outer peripheral surface when the first and second curved surfaces of the outer peripheral surface of the half bearing are extended to the circumferential end of the half bearing at the circumferential end of the half bearing is 5 - 30 μm. Crush reliefs are formed at each circumferential end of the inner peripheral surface of each half bearing. 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 and second curved surfaces of the outer peripheral surfaces of the pair of half bearings are in contact with the inner peripheral surface of the bearing holding hole without a gap, and a bearing device is provided.

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

[0009] In another embodiment of the present invention, when a plane where the circumferential end surfaces of the pair of half bearings are in contact with each other is defined as a dividing plane, in the non-mounted state, the circumferential end surfaces of the half bearings are in contact with the dividing plane at the radially outer end, and are inclined so as to be separated from the dividing plane as they approach the radially inner end. The inclination angle between the circumferential end surface of the half bearing and the dividing plane is 3×10 -2 ° to 15×10 -2 ° when viewed from the axial direction.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

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

[0012] (First Embodiment) FIG. 1 schematically shows a bearing device 1 for a crankshaft of an internal combustion engine. FIG. 6 shows a view of the large end housing of the connecting rod as seen in the axial direction. FIG. 7 shows a cross-sectional view taken along line A-A of the large end housing of the connecting rod shown in FIG. 6. This bearing device 1 has a journal portion 6 supported at the lower part of the cylinder block, a crank pin 5 formed integrally with the journal portion 6 and rotating about the journal portion 6, and a connecting rod 2 for transmitting a reciprocating motion from the internal combustion engine to the crank pin 5. Further, the bearing device 1 further has a main bearing 4 for rotatably supporting the journal portion 6 and a connecting rod bearing 3 for rotatably supporting the crank pin 5 as a sliding bearing for supporting the crankshaft.

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

[0014] The journal portion 6 is pivotally supported by a split-type bearing housing 10 composed of the lower part 101 of the cylinder block of the internal combustion engine and a bearing cap 102 via a main bearing 4 constituted by a pair of half bearings 41 and 42. Note that the half bearings 41 and 42 constituting the main bearing 4 are conventional half bearings. In the lower part 101 of the cylinder block and the bearing cap 102, bearing holding holes having a semi-cylindrical surface shape are respectively formed. The half bearing 41 is inserted into the bearing holding hole having a semi-cylindrical surface shape of the lower part 101 of the cylinder block, the half bearing 42 is inserted into the bearing holding hole having a semi-cylindrical surface shape of the bearing cap 102, and then the lower part 101 of the cylinder block and the bearing cap 102 are fastened by bolts (not shown) so that the pair of half bearings 41 and 42 are held in the cylindrical bearing holding hole. An oil groove 41a is formed in the entire length of the inner peripheral surface of the half bearing 41 on the upper side in FIG. 1. 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 communicate with the oil groove 41a of the main bearing 4 alternately.

[0015] The crankpin 5 is pivotally supported on the large-end housing 21 of the connecting rod 2 via a connecting-rod bearing 3 composed of a pair of split bearings 31 and 32. As shown in FIGS. 6 and 7, the large-end housing (bearing housing) 21 is of an integral type and has a cylindrical bearing holding hole 23. The fact that the large-end housing 21 is of an integral type means that the inner peripheral surface 24 of the bearing holding hole 23 is not divided into a plurality (usually two) parts. The pair of split bearings 31 and 32 are simultaneously press-fitted into one opening 25 in the axial direction of the bearing holding hole 23 of the large-end housing 21 with their circumferential end faces 76 facing each other. The outer peripheral length of the pair of split bearings 31 and 32 before press-fitting is slightly larger than the inner peripheral length of the bearing holding hole 23 of the large-end housing 21. After press-fitting, a pressure is generated that presses the outer peripheral surfaces 8 of the pair of split bearings 31 and 32 against the inner peripheral surface 24 of the bearing holding hole 23, whereby the pair of split bearings 31 and 32 are mounted (fixed) in the bearing holding hole 23 of the large-end housing 21.

[0016] A second lubricating oil passage 5a is formed that branches off from the first lubricating oil passage 6a of the journal portion 6 and passes through a crank arm portion (not shown). This second lubricating oil passage 5a communicates with a third lubricating oil passage 5b formed to penetrate in the diametrical direction of the crankpin 5.

[0017] Therefore, as described above, the lubricating oil discharged by the oil pump passes from the oil gallery formed in the cylinder block wall through the through-hole formed in the wall of the main bearing 4 and is fed into the oil groove 41a formed along the inner peripheral surface of the main bearing 4, and is supplied to the gap formed between the journal portion 6 and the main bearing 4.

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

[0019] In a conventional sliding bearing having a pair of split bearings whose outer peripheral surfaces are formed by a curved surface along one arc (which may be an elliptical arc), there were the following problems. When simultaneously press-fitting a pair of split bearings from one opening of the bearing holding hole of the integral large-end housing, first, a deviation occurs between the circumferential end faces of the pair of split bearings immediately after the start of press-fitting. Then, the vicinity of the circumferential end of the outer peripheral surface of the split bearing strongly interferes with the edge of the opening of the bearing holding hole, and the outer peripheral surface of the split bearing is scraped. As the press-fitting further progresses, due to the material of the outer peripheral surface of the split bearing adhering to the edge of the opening of the bearing holding hole, notches (multiple axial scratches) are likely to occur on the outer peripheral surface of the split bearing.

[0020] The present invention addresses such problems of the prior art. Hereinafter, an embodiment in which the bearing device 1 of the present invention is applied to the connecting rod bearing portion will be described. However, it will be understood that the bearing device of the present invention is not limited to application to the connecting rod bearing portion, and may also be applied to a main bearing portion having an integral main bearing housing.

[0021] FIG. 2 shows a view of the connecting rod bearing 3 composed of the split bearings 31 and 32 of the present invention with the circumferential end faces 76 aligned in the non-mounted state (before press-fitting), as viewed from the axial direction. FIG. 3 is a view of the split bearing 31 (32) shown in FIG. 2 as viewed from the axial direction. FIG. 4 is a plan view of the split bearing 31 (32) shown in FIG. 2 as viewed from the inner peripheral surface side. FIG. 5 is a plan view of the split bearing 31 (32) shown in FIG. 2 as viewed from the outer peripheral surface side.

[0022] As shown in FIGS. 2 to 4, the connecting rod bearing 3 of the present embodiment is formed by butting the circumferential end faces 76 of a pair of split bearings 31 and 32 and combining them into a cylindrical shape as a whole. The split bearings 31 and 32 can have a sliding layer made of a Cu bearing alloy or an Al bearing alloy. Alternatively, they can have a sliding layer of a Cu bearing alloy or an Al bearing alloy on a backing layer made of an Fe alloy. Further, the cylindrical inner peripheral surface 7 and outer peripheral surface 8 may have a surface portion made of any one of Bi, Sn, and Pb, which is softer than the bearing alloy, or a surface portion made of an alloy mainly composed of these metals or a resin composition mainly composed of a synthetic resin.

[0023] The half bearings 31 and 32 have an inner peripheral surface 7, an outer peripheral surface 8, two circumferential end surfaces 76, 76, and two axial end surfaces 7E, 7E. The pair of half bearings 31 and 32 have the same inner diameter dimension, outer diameter dimension, and axial length L1. The outer peripheral surfaces 8 of the respective half bearings 31 and 32 in the non-mounted state are composed of a first curved surface 81 and a second curved surface 82 formed along two types of arcs (which may be elliptical arcs) having 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 continuous with the first curved surface 81 and extend toward the circumferential end surfaces 76 of the half 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 such that the center C2 of the second arc is on the perpendicular line CL with respect to the bearing outer diameter center line passing through the center C1 of the first arc, and is offset to a position closer to the center C1 of the first arc, that is, closer to the circumferential central portion CP of the outer peripheral surface 8, i.e., on the inner side.

[0024] The second curved surface 82 is formed in a range where the circumferential angle θ1 measured from the circumferential end surfaces 76 of the half bearings 31 and 32 around the center C1 of the first arc is from a minimum value of 10° to a maximum value of 30°. In the case of a bearing device for a small internal combustion engine for a passenger car (for example, an internal combustion engine with a crankshaft shaft diameter of 30 to 100 mm), the radial length L2 of the half bearings 31 and 32 between the second curved surface 82 and the virtual outer peripheral surface 83 when the second curved surface 82 and the first curved surface 81 at each circumferential end surface 76 of the half bearings 31 and 32 are extended to the circumferential end surfaces 76 of the half bearings is 5 to 30 μm. Further, 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 bearings 31 and 32 in the region of the first curved surface 81 is constant in the circumferential direction. However, the wall thickness in the region of the first curved surface 81 may be maximum at the circumferential central portion CP and continuously decrease toward both circumferential end surface 76 sides.

[0026] In a region adjacent to the circumferential end face 76 of the inner peripheral surface 7 of the half bearings 31 and 32, a crush relief 70 is formed. The crush relief 70 is a wall thickness reduction region formed by cutting (removing the sliding layer) so that the wall thickness is thinner than the original inner peripheral surface 7 (major arc). The crush relief 70 is provided with the intention of forming a gap for absorbing the displacement and deformation of the circumferential end face 76 in a state where the pair of half bearings 31 and 32 are assembled to the bearing housing (see, for example, SAE J506 (items 3.26 and 6.4), DIN1497 (section 3.2), JIS D3102). Generally, in the case of a bearing for a small internal combustion engine for a passenger car, the depth of the crush relief at the circumferential end face of the half bearing (the distance from the original inner peripheral surface to the actual inner peripheral surface) is about 0.01 to 0.075 mm, and the length (the vertical length from the circumferential end face of the half bearing to the upper edge of the crush relief 70 with respect to the end face) is about 3 to 7 mm.

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

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

[0029] As described above, in the present invention, the first curved surface 81 is a region including the circumferential center portion CP of the outer peripheral surface 8, and the second curved surface 82 is the remaining two regions of the outer peripheral surface 8 that are continuous with the first curved surface 81 and extend toward both circumferential ends of the half bearing. 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 such that the center C2 of the second arc is on the perpendicular line CL to the bearing outer diameter center line passing through the center C1 of the first arc, and is offset to a position closer to the center C1 of the first arc, that is, closer to the circumferential center portion CP of the outer peripheral surface 8. The second curved surface 82 is formed in a range where the circumferential angle θ1 measured from the circumferential end surface 76 of the half bearings 31, 32 is from a minimum value of 10° to a maximum value of 30°. The radial length L2 of the half bearing between the second curved surface 82 and the virtual outer peripheral surface 83 when the first curved surface 81 and the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31, 32 are extended to the circumferential end surfaces 76 of the half bearings 31, 32 is 5 to 30 μm.

[0030] With this configuration, a gap is formed between the second curved surface 82 and the virtual outer peripheral surface 83 when the first curved surface 81 and the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31, 32 are extended to the circumferential end surfaces 76 of the half bearings 31, 32 (see FIGS. 2 and 3). Therefore, when the pair of half bearings 31, 32 are simultaneously press-fitted from one opening 25 of the bearing holding hole 23 of the integral large-end housing 21, even if a displacement occurs between the circumferential end surfaces 76 of the pair of half bearings 31, 32 immediately after the start of press-fitting, the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31, 32 is less likely to strongly interfere with the edge of the opening 25 of the bearing holding hole 23, and no gouging (multiple axial scratches) occurs on the second curved surface 82 of the outer peripheral surface 8.

[0031] FIG. 8 is a view of the sliding bearing and the large end portion of the connecting rod according to the first embodiment of the present invention as viewed in the axial direction. FIG. 9 is an enlarged view of portion B of the sliding bearing and the large end portion of the connecting rod shown in FIG. 8. As shown in FIGS. 8 and 9, in the state where the pair of split bearings 31 and 32 are press-fitted (mounted state) into the bearing holding hole 23 of the integral large end housing 21, circumferential compressive stress is generated in the pair of split bearings 31 and 32, and the circumferential end faces 76 come into contact with each other without a gap. Further, the dotted line shown in FIG. 9 indicates a virtual second curved surface 82A in the case where it does not displace due to press-fitting (mounting). After press-fitting (mounted state), due to the circumferential compressive stress, the circumferential end faces 76 of the pair of split bearings 31 and 32 press against each other, and the second curved surface 82 is displaced in the radially outer direction (the direction of the white arrow in FIG. 9). The second curved surface 82 of the outer peripheral surface 8 of the pair of split bearings 31 and 32 comes into contact with the inner peripheral surface 24 of the bearing holding hole 23 without a gap, similar to the first curved surface 81. Therefore, it becomes difficult for the oil supplied to the bearing device during the operation of the internal combustion engine and the sludge contained in the oil to enter between the outer peripheral surface 8 of the pair of split bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23.

[0032] In addition, when the formation range of the second curved surface 82 is less than 10°, or when the radial length L2 of the split bearings 31 and 32 between the second curved surface 82 and the virtual outer peripheral surface 83 at the circumferential end faces 76 of the split bearings 31 and 32 is less than 5 μm, when the pair of split bearings are simultaneously press-fitted from one opening 25 side of the bearing holding hole 23 of the integral large end housing 21, the second curved surface 82 of the outer peripheral surface of the split bearing strongly interferes with the edge of the opening of the bearing holding hole 23, and the outer peripheral surface of the split bearing may be scraped and nicked (a plurality of axial scratches) may occur.

[0033] Further, when the formation range of the second curved surface 82 exceeds 30°, or when the radial length L2 of the split bearings 31 and 32 between the second curved surface 82 and the virtual outer peripheral surface 83 at each circumferential end surface 76 of the split bearings 31 and 32 exceeds 30 μm, a (partial) gap may be formed between the second curved surface 82 of the outer peripheral surface 8 of the pair of split bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23 after press-fitting. When such a gap is formed, sludge enters this gap together with the oil supplied to the bearing device during the operation of the internal combustion engine, and the sludge is likely to accumulate locally. When a local sludge accumulation part is formed between the second curved surface 82 of the outer peripheral surface 8 of the split bearings 31 and 32 and the inner peripheral surface 24 of the bearing holding hole 23, the inner peripheral surface 7 of the split bearings 31 and 32 at the position of this accumulation part bulges toward the inner diameter center side, and damage is likely to occur due to strong contact with the surface of the crankshaft.

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

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

[0036] The bearing device of the second embodiment is different only in the configuration of the circumferential end surfaces 76, 76 of the split bearings 31 and 32 that constitute the connecting rod bearing 3, and other configurations are the same as those of the bearing device of the first embodiment. The description of the configurations common to the first embodiment will be omitted.

[0037] As shown in the enlarged view of FIG. 12, when a plane where the circumferential end faces of a pair of split bearings contact each other is defined as a split plane HP, the circumferential end faces 76, 76 of the split bearings 31, 32 in the non-mounted state are in contact with the split plane HP at the radially outer end 76O, and are inclined so as to be spaced apart from the split plane HP as they approach the radially inner end 76I. The inclination angle θ2 between the circumferential end faces 76, 76 of the split bearings 31, 32 and the split plane HP is 3×10 -2 ° to 15×10 -2 °. When the circumferential end faces 76, 76 of the split bearings 31, 32 have the inclination angle θ2, the formation range of the second curved surface 82 is defined as the circumferential angle θ1 measured from the radially outer end 76O of the circumferential end face 76 of the 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 split bearings 31, 32 have the inclination angle θ2, in the mounted state (after press-fitting), the circumferential end faces 76 contact each other without a gap. Also, the second curved surface 82 becomes more likely to be displaced in the radially outer direction, and the pressure (pushing pressure) between the second curved surface 82 and the inner peripheral surface 24 of the bearing holding hole 23 becomes larger. For this reason, it becomes more difficult for the oil supplied to the bearing device during the operation of the internal combustion engine and the sludge contained in the oil to enter between the outer peripheral surface 8 of the pair of split bearings 31, 32 and the inner peripheral surface 24 of the bearing holding hole 23.

[0039] If the inclination angle θ2 between the circumferential end faces 76, 76 of the split bearings 31, 32 and the split plane HP is less than 3×10 -2 °, it becomes difficult to obtain the effect of increasing the pressure between the second curved surface 82 and the inner peripheral surface 24 of the bearing holding hole 23 in the mounted state. Also, if the inclination angle θ2 exceeds 15×10 -2 °, displacement may occur between the circumferential end faces 76, 76 of the split bearings 31, 32 immediately after the start of press-fitting, and the second curved surface 82 of the outer peripheral surface 8 of the split bearings 31, 32 may strongly interfere with the edge of the opening 25 of the bearing holding hole 23, resulting in galling (multiple axial scratches).

[0040] The above description has been made using an example in which the bearing device of the present invention is applied to a connecting rod bearing portion that supports a crank pin of a crankshaft of an internal combustion engine. However, the bearing device of the present invention can also be applied to a main bearing portion that supports a journal portion of the crankshaft. Further, the split bearing may further have, for example, an oil hole, an oil groove, or a notch for positioning. Further, the split bearing may have a chamfer at a position where the outer peripheral surface and each end surface in the axial direction are adjacent, or at a position where the inner peripheral surface and each end surface in the axial direction are adjacent.

Description of Symbols

[0041] 1 Bearing device 10 Bearing housing (main bearing) 101 Lower part of cylinder block 102 Bearing cap 2 Connecting rod 21 Big end housing, bearing housing 23 Bearing holding hole 24 Inner peripheral surface 25 Opening 3 Connecting rod bearing 31, 32 Split bearings 4 Main bearing 41, 42 Split 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 end surface 70 Crash relief 76 Circumferential end surface 76I Inner end 76O Outer end 8 Outer peripheral surface 81 First curved surface 82 Second curved surface 82A Virtual second curved surface when not displaced 83 Virtual outer peripheral surface C1 Center of the first arc C2 Center of the second arc Vertical line with respect to the center line of the outer diameter of the CL bearing Central part in the circumferential direction of CP HP Split plane Axial length of the half bearing of L1 Length of L2 Rotational direction of the journal part of X Rotational direction of the crank pin of Z Circumferential angle of θ1 Inclination angle of θ2

Claims

1. A bearing device (1) for supporting a crankshaft of an internal combustion engine, the bearing device (1) comprising: A crankshaft (5, 6), An integral bearing housing (10, 21) having a cylindrical bearing retaining hole (23); Plain bearings (3, 4) having The sliding bearing is composed of a pair of half bearings (31, 32; 41, 42), Each of the pair of half bearings has an inner circumferential surface (7), an outer circumferential surface (8), and two circumferential end surfaces (76, 76), The pair of half bearings have the same axial length (L1), The pair of half bearings are simultaneously press-fitted into an inner circumferential surface (24) of the bearing retaining hole from one axial opening (25) of the bearing retaining hole, and the inner circumferential surfaces of the pair of half bearings support a crankshaft, The outer peripheral surface of each half bearing in an unmounted state is composed of first and second curved surfaces (81, 82) formed along two types of arcs having different curvatures, the first curved surface being a region including a circumferential center portion (CP) of the outer peripheral surface, and the second curved surface being two remaining regions of the outer peripheral surface that are connected to the first curved surface and extend toward the circumferential end surface of the half bearing, and the relationship between a center (C1) of the first arc forming the first curved surface and a center (C2) of the second arc forming the second curved surface is such that the center (C2) of the second arc is offset inward from the center (C1) of the first arc, i.e., to the side closer to the circumferential center portion of the outer peripheral surface, on a perpendicular line (CL) to the bearing outer diameter center line that passes through the center (C1) of the first arc, the second curved surface is formed such that a circumferential angle (θ1) measured from the circumferential end surface of the half bearing about the center (C1) of the first arc is in a range from a minimum of 10° to a maximum of 30°, A radial length (L2) of the half bearing between the second curved surface at the circumferential end of the half bearing and a virtual outer circumferential surface (83) when the first curved surface is extended to the circumferential end of the half bearing is 5 to 30 μm, A crush relief (70) is formed at each circumferential end of the inner circumferential surface of each half bearing, In an installed state, the circumferential end faces of the pair of half bearings are in contact with each other without any gaps, 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 retaining hole without any gaps.

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

3. When a plane where the circumferential end faces of the pair of half bearings are in contact with each other is defined as a division plane (HP), in a non-mounted state, each circumferential end face of the half bearing is in contact with the division plane at a radially outer end (76O) and is inclined so as to move away from the division plane (HP) as it approaches a radially inner end (76I). The inclination angle θ2 between each circumferential end face of the half bearing and the division plane is 3×10° as viewed from the axial direction. －２ °~15×10 －２ 2. The bearing device (1) according to claim 1, wherein the axial length of the bearing 1 is 1.degree.

Images