JP7702469B2 - Bearing arrangement for a crankshaft of an internal combustion engine - Google Patents

Description

The present invention relates to a bearing device that supports the crankshaft of an internal combustion engine.

The crankshaft of an internal combustion engine is supported at its journal portion on the lower part of the cylinder block of the internal combustion engine via a main bearing consisting of a pair of half bearings. To lubricate the main bearing, lubricating oil discharged by an oil pump is sent from an oil gallery formed in the cylinder block wall through a through hole formed in the wall of the main bearing into a lubricating oil groove formed along the inner circumferential surface of the main bearing. A first lubricating oil passage is formed through the journal portion in the diametrical direction, and both end openings of this first lubricating oil passage are connected to the lubricating oil groove of the main bearing. Furthermore, a second lubricating oil passage that passes through the crank arm portion is formed by branching off from the first lubricating oil passage of the journal portion and is connected to a third lubricating oil passage that is formed through the crank pin in the diametrical direction. Therefore, the lubricating oil sent from the oil gallery in the cylinder block wall through the through hole into the lubricating oil groove formed on the inner peripheral surface of the main bearing passes through the first, second and third lubricating oil passages, and is supplied from the discharge port at the end of the third lubricating oil passage to between the sliding surface of the connecting rod bearing, which is made up of a pair of half bearings, and the crank pin (see, for example, Patent Document 1). In this way, oil is supplied between the crankshaft surface and the sliding surface of the main bearing and the sliding surface of the connecting rod bearing.

Conventionally, when the bearing housing that holds the main bearing or connecting rod bearing is one-piece, a pair of half bearings that make up the main bearing or connecting rod bearing are simultaneously pressed into one of the axial openings of the cylindrical bearing retaining hole in the bearing housing (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 8-277831 Japanese Utility Model Application Publication No. 11-236923

Conventional sliding bearings consisting of a pair of half bearings have the problem that when they are simultaneously pressed into one of the openings of a bearing retaining hole in a one-piece bearing housing, first, the circumferential end faces of the pair of half bearings become misaligned immediately after the start of the press-fitting, and the peripheral surface of the half bearing near the circumferential end strongly interferes with the edge of the opening of the bearing retaining hole, causing the peripheral surface of the half bearing to be scraped off, and as the press-fitting continues, the material of the peripheral surface of the half bearing that has adhered to the edge of the opening of the bearing retaining hole tends to cause scoring (multiple axial scratches) on the peripheral surface of the half bearing.

Therefore, the object of the present invention is to provide a bearing device for a crankshaft of an internal combustion engine that has a sliding bearing that is less likely to cause galling when pressed into a bearing retaining hole in a one-piece bearing housing.

In order to solve the above problems, the present invention provides 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 retaining hole;
A plain bearing,
The plain bearing is made up of a pair of half bearings,
Each of the pair of half bearings has an inner circumferential surface, an outer circumferential surface, and two circumferential end surfaces,
The pair of half bearings have the same axial length,
A bearing device in which a pair of half bearings are simultaneously press-fitted into an inner circumferential surface of a bearing retaining hole from one axial opening 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 made up of first and second curved surfaces formed along two types of arcs having different curvatures, the first curved surface being a region including a circumferential central portion 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 face of the half bearing, and 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 such that the center of the second arc is offset inward from the center of the first arc, i.e., toward the side closer to the circumferential central portion of the outer peripheral surface, on a line perpendicular to the bearing outer diameter center line that passes through the center of the first arc,
the second curved surface is formed such that a circumferential angle measured from a circumferential end face of the half bearing about the center of the first arc is in a range from a minimum of 10° to a maximum of 30°;
a radial length of the half bearing between the second curved surface at the circumferential end of the half bearing and a virtual outer circumferential surface when the first curved surface is extended to the circumferential end of the half bearing is 5 to 30 μm;
A crush relief is formed on each circumferential end of the inner peripheral surface of each half bearing,
The present invention provides a bearing device characterized in that, 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 on 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.

In another embodiment of the present invention, when the plane where the circumferential end faces of a pair of half bearings meet is defined as the division plane, in the unmounted state, each circumferential end face of the half bearing is parallel to the division plane.

In another embodiment of the present invention, when the plane where the circumferential end faces of a pair of half bearings contact is defined as the division plane, in the unmounted state, each circumferential end face of the half bearing contacts the division plane at its radially outer end and is inclined so as to move away from the division plane closer to its radially inner end, and the inclination angle between each circumferential end face of the half bearing and the division plane is 3× ¹⁰⁻² ° to 15× ¹⁰⁻² ° when viewed from the axial direction.

1 is a schematic diagram showing a bearing device for a crankshaft of an internal combustion engine; FIG. 1 is a view of a sliding bearing according to a first embodiment of the present invention in an unmounted state, as viewed from the axial direction. FIG. 3 is a view of the half bearing shown in FIG. 2 as viewed from the axial direction. 3 is a plan view of the half bearing shown in FIG. 2 as viewed from the inner peripheral surface side. FIG. 3 is a plan view of the half bearing shown in FIG. 2 as viewed from the outer circumferential surface side. FIG. FIG. 4 is a view of a big end housing of the connecting rod as viewed from the axial direction. 7 is a cross-sectional view of the big end housing of the connecting rod shown in FIG. 6 along line AA. 1 is a view showing a plain bearing and a big end of a connecting rod according to a first embodiment of the present invention, as viewed from the axial direction. FIG. FIG. 9 is an enlarged view of a portion B of the sliding bearing and the big end of the connecting rod shown in FIG. 8 . FIG. 11 is a view showing a sliding bearing according to a second embodiment of the present invention in an unmounted state, as viewed from the axial direction. FIG. 11 is a view of the half bearing shown in FIG. 10 as viewed from the axial direction. FIG. 12 is an enlarged view of a portion C of the half bearing shown in FIG. 11 .

The following describes an embodiment of the present invention with reference to the drawings.

First Embodiment
FIG. 1 shows a schematic diagram of a bearing device 1 for a crankshaft of an internal combustion engine. FIG. 6 shows a view of a big end housing of a connecting rod as viewed in the axial direction. FIG. 7 shows a cross-sectional view of the big end housing of the connecting rod shown in FIG. 6 taken along line A-A. This bearing device 1 has a journal portion 6 supported on the lower part of a 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 that transmits reciprocating motion from the internal combustion engine to the crank pin 5. The bearing device 1 further has, as a sliding bearing that supports the crankshaft, a main bearing 4 that rotatably supports the journal portion 6, and a connecting rod bearing 3 that rotatably supports the crank pin 5.

The crankshaft has multiple journals 6 and multiple crank pins 5, but for ease of explanation, only one journal 6 and one crank pin 5 are illustrated here. In FIG. 1, the positional relationship in the depth direction of the page is such that the journals 6 are at the back of the page and the crank pins 5 are at the front.

The journal portion 6 is supported by a split bearing housing 10 consisting of a cylinder block lower portion 101 and a bearing cap 102 of an internal combustion engine via a main bearing 4 consisting of a pair of half bearings 41, 42. The half bearings 41, 42 constituting the main bearing 4 are conventional half bearings. The cylinder block lower portion 101 and the bearing cap 102 each have a semi-cylindrical bearing retaining hole. The half bearing 41 is inserted into the semi-cylindrical bearing retaining hole of the cylinder block lower portion 101, and the half bearing 42 is inserted into the semi-cylindrical bearing retaining hole of the bearing cap 102. The cylinder block lower portion 101 and the bearing cap 102 are then fastened by bolts (not shown) to retain the pair of half bearings 41, 42 in the cylindrical bearing retaining hole. The half bearing 41 on the upper side in FIG. 1 has an oil groove 41a formed along the entire inner peripheral surface. In addition, the journal portion 6 has a lubricating oil passage 6a that penetrates in the diametrical direction, and when the journal portion 6 rotates in the direction of the arrow X, the inlet openings 6c at both ends of the lubricating oil passage 6a alternately communicate with the oil groove 41a of the main bearing 4.

The crank pin 5 is supported by the big end housing 21 of the connecting rod 2 via a connecting rod bearing 3 consisting of a pair of half bearings 31, 32. As shown in Figures 6 and 7, the big end housing (bearing housing) 21 is one-piece and has a cylindrical bearing retaining hole 23. The big end housing 21 being one-piece means that the inner circumferential surface 24 of the bearing retaining hole 23 is not divided into multiple parts (usually two). The pair of half bearings 31, 32 are simultaneously pressed into the bearing retaining hole 23 of the big end housing 21 from one of the axial openings 25 with their circumferential end faces 76 aligned. The outer circumferential length of the pair of half bearings 31, 32 before pressing is slightly larger than the inner circumferential length of the bearing retaining hole 23 of the big end housing 21. After press-fitting, a pressure is generated between the outer peripheral surface 8 of the pair of half bearings 31, 32 and the inner peripheral surface 24 of the bearing retaining hole 23, and the pair of half bearings 31, 32 are attached (fixed) to the bearing retaining hole 23 of the big end housing 21.

A second lubricating oil passage 5a is formed, branching off from the first lubricating oil passage 6a in the journal portion 6 and passing through the crank arm portion (not shown). This second lubricating oil passage 5a is connected to a third lubricating oil passage 5b formed diametrically through the crank pin 5.

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

Meanwhile, the lubricating oil is also supplied to the gap formed between the crank pin 5 and the connecting rod bearing 3 through the first lubricating oil passage 6a, the second lubricating oil passage 5a, and the third lubricating oil passage 5b, and from the discharge port 5c at the end of the third lubricating oil passage 5b.

Conventional sliding bearings, which are made up of a pair of half bearings whose outer circumferential surfaces are curved surfaces formed along a single arc (or an elliptical arc), have the following problems. When a pair of half bearings are simultaneously pressed into one opening of a bearing retaining hole in a one-piece big-end housing, first, the circumferential end faces of the pair of half bearings become misaligned immediately after the start of the press-fitting. Then, the circumferential end area of the outer circumferential surface of the half bearing strongly interferes with the edge of the opening of the bearing retaining hole, causing the outer circumferential surface of the half bearing to be scraped. As the press-fitting progresses further, the material of the outer circumferential surface of the half bearing that has adhered to the edge of the opening of the bearing retaining hole is likely to cause scoring (multiple axial scratches) on the outer circumferential surface of the half bearing.

The present invention addresses these problems with the conventional technology. Below, an embodiment in which the bearing device 1 of the present invention is applied to a connecting rod bearing portion will be described. However, it will be understood that the application of the bearing device of the present invention is not limited to connecting rod bearing portions, but may also be applied to main bearing portions having an integral main bearing portion housing.

Figure 2 shows a connecting rod bearing 3 made up of half bearings 31, 32 of the present invention, viewed from the axial direction, with the circumferential end faces 76 mated in an unmounted state (before press-fitting). Figure 3 shows the half bearing 31 (32) shown in Figure 2, viewed from the axial direction. Figure 4 is a plan view of the half bearing 31 (32) shown in Figure 2, viewed from the inner peripheral surface side. Figure 5 is a plan view of the half bearing 31 (32) shown in Figure 2, viewed from the outer peripheral surface side.

As shown in Figures 2 to 4, the connecting rod bearing 3 of this embodiment is formed by butting the circumferential end faces 76 of a pair of half bearings 31, 32 together and combining them into an overall cylindrical shape. The half bearings 31, 32 can have a sliding layer made of a Cu bearing alloy or an Al bearing alloy. Alternatively, they can have a sliding layer made of a Cu bearing alloy or an Al bearing alloy on a backing metal layer made of an Fe alloy. In addition, the cylindrical inner surface 7 and outer surface 8 may have a surface portion made of one of Bi, Sn, and Pb, which are softer than the bearing alloy, or a surface portion made of an alloy mainly made of these metals or a resin composition mainly made of a synthetic resin.

The half bearings 31 and 32 have an inner peripheral surface 7, an outer peripheral surface 8, two circumferential end surfaces 76 and 76, and two axial end surfaces 7E and 7E. The pair of half bearings 31 and 32 have the same inner diameter dimension, outer diameter dimension, and axial length L1. The outer peripheral surface 8 of each half bearing 31 and 32 in the unmounted state consists of a first curved surface 81 and a second curved surface 82 formed along two types of arcs (which may be elliptical arcs) with different curvatures. The first curved surface 81 is a region including the circumferential center 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 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 offset on a line CL perpendicular to the bearing outer diameter centerline that passes through the center C1 of the first arc, toward the inside of the center C1 of the first arc, that is, toward the side closer to the circumferential center CP of the outer peripheral surface 8.

The second curved surface 82 is formed such that the circumferential angle θ1 measured from the circumferential end surface 76 of the half bearings 31, 32 around the center C1 of the first arc is in the range of a minimum of 10° to a maximum of 30°. In the case of a bearing device for a small internal combustion engine (e.g., an internal combustion engine with a crankshaft diameter of 30 to 100 mm) for a passenger car or the like, the radial length L2 of the half bearings 31, 32 between the second curved surface 82 at each circumferential end surface 76 of the half 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 bearings is 5 to 30 μm. Furthermore, it is preferable that the relationship between the circumferential angle θ1 and the length L2 (L2/θ1) is 0.5 to 1.2 (μm/°).

In this embodiment, the wall thickness of the half bearings 31, 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 center portion CP and continuously decrease toward both circumferential end faces 76.

A crush relief 70 is formed in an area adjacent to the circumferential end face 76 of the inner peripheral surface 7 of the half bearings 31, 32. The crush relief 70 is a wall-thickness-reduced area formed by cutting (removal of the sliding layer) so that the wall thickness is thinner than the original inner peripheral surface 7 (main arc). The crush relief 70 is provided with the intention of forming a gap to absorb the positional deviation and deformation of the circumferential end face 76 when the pair of half bearings 31, 32 are assembled in the bearing housing (see, for example, SAE J506 (items 3.26 and 6.4), DIN 1497 (section 3.2), and JIS D3102). Generally, for small internal combustion engine bearings for passenger cars, the depth of the crush relief at the circumferential end face of the half bearing (the distance from the original inner circumferential surface to the actual inner circumferential 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 relative to that end face) is about 3 to 7 mm.

In this embodiment, when the plane where the circumferential end faces of the pair of half bearings meet is defined as the division plane HP, in the unmounted state, each circumferential end face of the half bearing is parallel to the division plane HP.

As described above, the outer peripheral surface 8 of the half bearing used in the bearing device of the present invention, when not mounted, consists of first and second curved surfaces 81, 82 formed along two types of arcs with different curvatures. The reason why this half bearing reduces bearing damage is explained below.

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 a remaining region of the outer peripheral surface 8 that is connected to the first curved surface 81 and extends 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 perpendicular to the center line of the outer diameter of the bearing that passes through the center C1 of the first arc and the center C2 of the first arc. 1, that is, it is offset toward the side closer to the circumferential center CP of the outer peripheral surface 8, and the second curved surface 82 is formed such that the circumferential angle θ1 measured from the circumferential end surface 76 of the half bearings 31, 32 is in the range of a minimum of 10° to a maximum of 30°, and the radial length L2 of the half bearing between the second curved surface 82 at the circumferential end of the half bearings 31, 32 and the imaginary outer peripheral surface 83 when the first curved surface 81 is extended to the circumferential end of the half bearings 31, 32 is 5 to 30 μm.

With this configuration, a gap is formed between the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31, 32 and the imaginary outer peripheral surface 83 when the first curved surface 81 is extended to the circumferential end surface 76 of the half bearings 31, 32 (see Figures 2 and 3). Therefore, when the pair of half bearings 31, 32 are simultaneously pressed into one opening 25 of the bearing retaining hole 23 of the one-piece big end housing 21, even if the circumferential end surfaces 76 of the pair of half bearings 31, 32 are misaligned with each other immediately after the start of the press-in, the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31, 32 is unlikely to strongly interfere with the edge of the opening 25 of the bearing retaining hole 23, and galling (multiple axial scratches) is not generated on the second curved surface 82 of the outer peripheral surface 8.

Figure 8 is a view of the sliding bearing and the big end of the connecting rod according to the first embodiment of the present invention, viewed from the axial direction. Figure 9 is an enlarged view of part B of the sliding bearing and the big end of the connecting rod shown in Figure 8. As shown in Figures 8 and 9, after being pressed into the bearing retaining hole 23 of the one-piece big end housing 21 (mounted state), a pair of half bearings 31, 32 are subjected to circumferential compressive stress, and the circumferential end faces 76 come into contact with each other without any gaps. The dotted line shown in Figure 9 indicates a virtual second curved surface 82A when not displaced by press-fitting (mounting). After being pressed in (mounted state), the circumferential compressive stress causes the circumferential end faces 76 of the pair of half bearings 31, 32 to press against each other, and the second curved surface 82 is displaced radially outward (in the direction of the white arrow in Figure 9). The second curved surface 82 of the outer peripheral surface 8 of the pair of half bearings 31, 32, like the first curved surface 81, comes into contact with the inner peripheral surface 24 of the bearing retaining hole 23 without any gaps. Therefore, the oil supplied to the bearing device during operation of the internal combustion engine and the sludge contained in the oil are less likely to get between the outer peripheral surface 8 of the pair of half bearings 31, 32 and the inner peripheral surface 24 of the bearing retaining hole 23.

If the range of the second curved surface 82 is less than 10°, or if the radial length L2 of the half bearings 31, 32 between the second curved surface 82 and the imaginary outer circumferential surface 83 at each circumferential end surface 76 of the half bearings 31, 32 is less than 5 μm, when a pair of half bearings are simultaneously pressed into one of the openings 25 of the bearing retaining hole 23 of the one-piece big end housing 21, the second curved surface 82 of the outer circumferential surface of the half bearing may strongly interfere with the edge of the opening of the bearing retaining hole 23, causing the outer circumferential surface of the half bearing to be scraped off, resulting in scoring (multiple axial scratches).

In addition, if the range of the second curved surface 82 exceeds 30°, or if the radial length L2 of the half bearings 31, 32 between the second curved surface 82 and the virtual outer circumferential surface 83 at each circumferential end surface 76 of the half bearings 31, 32 exceeds 30 μm, a (partial) gap may be formed between the second curved surface 82 of the outer circumferential surface 8 of the pair of half bearings 31, 32 and the inner circumferential surface 24 of the bearing retaining hole 23 after press-fitting. If such a gap is formed, sludge enters the gap together with the oil supplied to the bearing device during operation of the internal combustion engine, and the sludge is likely to accumulate locally. If a localized sludge deposit is formed between the second curved surface 82 of the outer circumferential surface 8 of the half bearings 31, 32 and the inner circumferential surface 24 of the bearing retaining hole 23, the inner circumferential surface 7 of the half bearings 31, 32 at the position of the deposit rises toward the inner diameter center, and is likely to be damaged by strong contact with the surface of the crankshaft.

Second Embodiment
Other non-limiting embodiments of the present invention will now be described.

Figure 10 shows a connecting rod bearing 3 made up of half bearings 31, 32 according to a second embodiment of the present invention, viewed from the axial direction, with the circumferential end faces 76 aligned in an unmounted state (before press-fitting). Figure 11 shows a view of the half bearing 31 (32) shown in Figure 10, viewed from the axial direction. Figure 12 is an enlarged view of part C of the half bearing 31 (32) shown in Figure 11.

The bearing device of the second embodiment differs only in the configuration of the circumferential end faces 76, 76 of the half bearings 31, 32 that make up the connecting rod bearing 3, and the other configurations are the same as those of the bearing device of the first embodiment. Explanations of the configurations common to the first embodiment will be omitted.

As shown in the enlarged view of Fig. 12, when the plane where the circumferential end faces of the pair of half bearings are in contact is defined as the division plane HP, each circumferential end face 76, 76 of the half bearings 31, 32 in the unmounted state contacts the division plane HP at the radially outer end 76O, and is inclined so as to move away from the division plane HP as it approaches the radially inner end 76I. The inclination angle θ2 between each circumferential end face 76, 76 of the half bearings 31, 32 and the division plane HP is 3 x ^10-2 ° to 15 x ^10-2 ° as viewed from the axial direction. When each circumferential end face 76, 76 of the half bearings 31, 32 has an inclination angle θ2, the formation range of the second curved surface 82 is defined as a circumferential angle θ1 measured from the radially outer end 76O of the circumferential end face 76 of the half bearings 31, 32 with the center C1 of the first arc as the center.

When the circumferential end faces 76, 76 of the half bearings 31, 32 have an inclination angle θ2, the circumferential end faces 76 come into contact with each other without any gaps when mounted (after press-fit). In addition, the second curved surface 82 is more likely to be displaced radially outward, and the pressure (pushing pressure) between the second curved surface 82 and the inner peripheral surface 24 of the bearing retaining hole 23 becomes greater. As a result, the oil supplied to the bearing device during operation of the internal combustion engine and the sludge contained in the oil are less likely to get between the outer peripheral surface 8 of the pair of half bearings 31, 32 and the inner peripheral surface 24 of the bearing retaining hole 23.

If the inclination angle θ2 between each of the circumferential end faces 76, 76 of the half 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 retaining hole 23 in the mounted state. If the inclination angle θ2 exceeds 15×10 ^-2 °, a misalignment will occur between the circumferential end faces 76, 76 of the half bearings 31, 32 immediately after the start of press-fitting, and the second curved surface 82 of the outer peripheral surface 8 of the half bearings 31, 32 will strongly interfere with the edge of the opening 25 of the bearing retaining hole 23, causing scoring (multiple axial scratches).

The above explanation is given using an example in which the bearing device of the present invention is applied to a connecting rod bearing portion that supports the crank pin of the crankshaft of an internal combustion engine, but the bearing device of the present invention can also be applied to a main bearing portion that supports the journal portion of the crankshaft. The half bearing may further have, for example, an oil hole, an oil groove, or a notch for positioning. The half bearing may also have chamfers at positions where the outer circumferential surface and each axial end face are adjacent, or at positions where the inner circumferential surface and each axial end face are adjacent.

1 Bearing device 10 Bearing housing (main bearing)
Reference Signs List 101 Lower part of cylinder block 102 Bearing cap 2 Connecting rod 21 Big end housing, bearing housing 23 Bearing retaining hole 24 Inner peripheral surface 25 Opening 3 Connecting rod bearing 31, 32 Half bearing 4 Main bearing 41, 42 Half bearing 41a Oil groove 5 Crank pin 5a, 5b Lubricating oil passage 5c Discharge port 6 Journal portion 6a Lubricating oil passage 6c Inlet opening 7 Inner peripheral surface 7E Axial end face 70 Crush relief 76 Circumferential end face 76I Inner end 76O Outer end 8 Outer peripheral surface 81 First curved surface 82 Second curved surface 82A Virtual second curved surface 83 in the case of no displacement Virtual outer peripheral surface C1 Center of first arc C2 Center of second arc CL Perpendicular line CP to bearing outer diameter center line Circumferential center HP Split plane L1 Axial length L2 of half bearing Length X Rotation direction Z of journal portion Rotational direction of crank pin θ1 Circumferential angle θ2 Inclination angle

Claims (3)

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);
A sliding bearing (3, 4),
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. The bearing device (1) according to claim 1, in which, when the plane where the circumferential end faces of the pair of half bearings meet is defined as a division plane (HP), in the unmounted state, each circumferential end face of the half bearing is parallel to the division plane (HP). The bearing device (1) according to claim 1, wherein, when a plane where the circumferential end faces of the pair of half bearings are in contact is defined as a division plane (HP), in an unmounted 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 the radially inner end (76I), and an inclination angle θ2 between each circumferential end face of the half bearing and the division plane is 3× ¹⁰⁻² ° to 15× ¹⁰⁻² ° when viewed from the axial direction.