Bearing arrangement for a crankshaft of an internal combustion engine

Abstract

To provide a split type bearing device for a crankshaft hardly causing a wiping phenomenon of lubricating oil due to generation of a step on a bearing inner peripheral surface in the whole period from starting to regular operation of an internal combustion engine.SOLUTION: According to the present invention, in the split-type bearing device, the first half bearing and the second half bearing each have the back metal layer made of steel and the bearing alloy layer, only the second half bearing further has the coating layer, and the rigidity of the first housing split body is lower than the rigidity of the second housing split body. In a non-mounted state in which the split-type sliding bearing is not mounted in the split-type bearing housing, the first half bearing and the second half bearing have an outer diameter and a width equal to each other, and the back metal layer and the bearing alloy layer of the first half bearing have thicknesses equal to those of the back metal layer and the bearing alloy layer of the second half bearing, respectively, at symmetrical positions with respect to a butting plane when the first half bearing and the second half bearing are butted against each other.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a bearing device that supports a crankshaft of an internal combustion engine. [Background technology]

[0002] The crankshaft of an internal combustion engine is supported at its journal portion on the lower part of the cylinder block of the 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 and into a lubricating oil groove formed along the inner surface of the main bearing. A first lubricating oil passage is formed through the journal portion in the radial 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 is formed branching from the first lubricating oil passage in the journal portion and passing through the crank arm portion, and this second lubricating oil passage is connected to a third lubricating oil passage formed through the crank pin in the radial direction. As a result, lubricating oil is sent from the oil gallery in the cylinder block wall through the through hole into the lubricating oil groove formed in 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 opening at the end of the third lubricating oil passage to between the sliding surfaces of the crankpin and the connecting rod bearing, which is made up of a pair of half bearings (see, for example, Patent Document 1). In this way, oil is supplied between the surface of the crankshaft and the sliding surfaces of the main bearing and connecting rod bearing.

[0003] A split plain bearing for an internal combustion engine crankshaft is formed into a cylindrical shape by assembling a pair of half bearings into a bearing housing, i.e., by assembling them into a housing segment that is part of the engine block and a housing segment that is a bearing cap. Before assembling the pair of half bearings, the bearing retaining hole in the bearing housing is machined in a single operation to make it perfectly round, with the pair of housing segments fastened together with bolts. In recent years, it has become common for passenger vehicle internal combustion engines to use aluminum alloy engine blocks to reduce the engine's weight. In this case, a split-type bearing housing for a crankshaft typically has one housing segment that is part of the aluminum alloy engine block and the other housing segment that is an iron alloy bearing cap.

[0004] On the other hand, the half bearings of a split plain bearing for a crankshaft are generally made of a steel backing metal and a bearing alloy layer. The circumferential length of the outer surface of a split plain bearing for a crankshaft, which is made up of a pair of half bearings, is formed to be larger by a predetermined length than the circumferential length of the inner surface of the bearing retaining hole in the split bearing housing. Due to this dimensional relationship, when the pair of half bearings are assembled into the split bearing housing, circumferential compressive stress and radial stress are generated in the pair of half bearings. As a result, the pair of half bearings are tightly fixed against the inner surface of the bearing retaining hole in the split bearing housing, and the split bearing housing elastically deforms and expands radially, increasing the inner diameter of the bearing retaining hole.

[0005] Here, the relationship between the split bearing housing and the split plain bearing for a crankshaft, which is comprised of a pair of half bearings assembled therein, will be described with reference to FIGS. Figure 15 shows a split-type bearing housing 10 for a crankshaft, which is made up of a cylinder block lower part 101, which is part of the engine block, and a bearing cap 102 (made of, for example, an iron alloy). With the bearing cap 102 attached to the cylinder block lower part 101 with bolts 103, the bearing retaining hole 23, which has a perfect circular cross section, is formed by machining at room temperature. The subsequent bearing device assembly work is performed by removing the bolts 103 from the bearing housing 10, fitting the half bearings 141 and 142 that form the split-type plain bearing along the inner surfaces 104 and 105 of the bearing retaining hole 23, and then fastening the cylinder block lower part 101 to the bearing cap 102 again with the bolts 103.

[0006] In the low-rigidity split bearing housing 10 that has become common in recent years, if bolts 103 are tightened so that the same level of stress as in conventional split plain bearings is generated in the split plain bearing to fit and secure it, the amount of expansion and deformation of the split bearing housing's inner diameter will be large. Furthermore, because the cylinder block lower part 101 and bearing cap 102 that make up the split bearing housing have different rigidities, the stress used to secure the split plain bearing will cause a difference in the amount of expansion and deformation of inner circumferential surfaces 104, 105. This appears as a step g between inner circumferential surfaces 104, 105 within fastening plane 106 between cylinder block lower part 101 and bearing cap 102 (the split bearing housing's dividing surface), and also creates a step g1a on the bearing inner circumferential surfaces 7 of half bearings 141, 142 (see Figure 16).

[0007] Furthermore, in this split bearing housing, when the temperature rises due to operation of the internal combustion engine and reaches the temperature of normal operation, due to the different thermal expansion coefficients of aluminum alloy and iron alloy, the inner diameter of housing segment 101, which is made of aluminum alloy and has a relatively high thermal expansion coefficient, located on the engine block side becomes larger than the inner diameter of housing segment 102, which is made of iron alloy and has a relatively low thermal expansion coefficient. For this reason, as shown in Figure 18, the difference in the amount of expansion and deformation is compounded by the difference in the amount of thermal expansion, forming a step g' on inner circumferential surfaces 104, 105 of the bearing retaining hole within fastening plane 106, and a step g3b on inner circumferential bearing surfaces 7 of half bearings 141, 142.

[0008] Meanwhile, in recent internal combustion engines, the downsizing of oil pumps has reduced the amount of lubricating oil supplied to the inner surface of the crankshaft plain bearing. In response to this, the bearing clearance between the inner surface of the crankshaft plain bearing and the surface of the crankshaft 6 has been set smaller to reduce the amount of lubricating oil leaking from the bearing clearance. However, under normal operating conditions, when a step g3b that is relatively large relative to the bearing clearance Cr is formed on the inner surface of the bearing at the fastening plane of the cylinder block lower part 101 and the bearing cap 102 as shown in FIG. 18, the ratio of the step area that acts as a barrier to the lubricating oil flow to the cross-sectional area of ​​the lubricating oil flow path becomes relatively high compared to when the bearing clearance is set larger in the past (see FIG. 19), and the step g3b causes a wiping phenomenon of the lubricating oil (see FIG. 20), which increases the amount of lubricating oil leaking and causes poor lubricating oil supply to the bearing sliding surface.

[0009] Patent Document 2 teaches the step g of a split bearing housing having housing segments with different rigidity, and here, when a pair of half bearings are assembled into the split bearing housing, a difference in bearing thickness is set at the mating end faces of the pair of half bearings so as to offset the step that occurs on the inner surface of the bearing due to the difference in rigidity of the housing segments.

[0010] Furthermore, Patent Document 3 teaches the step g' of a split bearing housing having housing segments with different thermal expansion coefficients, and here, a difference in bearing thickness is set at the mating end faces of a pair of half bearings so as to cancel out the step that occurs on the inner circumferential surface of the bearing due to the difference in the amount of thermal expansion of the split bearing housing when the temperature of the split bearing housing rises due to operation of the internal combustion engine. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 8-277831 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-156373 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-156374 Summary of the Invention [Problem to be solved by the invention]

[0012] Patent Document 2 teaches a means for offsetting a step g1a that occurs on the inner peripheral surface of the bearing at the mating end faces of the half bearings when the pair of half bearings are assembled (at start-up) to a pair of housing segments of a split bearing housing that have different rigidities (see FIG. 21). However, Patent Document 2 does not consider at all the problem of wiping of the lubricating oil caused by the difference in thermal expansion between the pair of half bearings assembled to a pair of housing segments that have different thermal expansion coefficients, and then the temperature of the split bearing housing rising as the internal combustion engine operates, and the difference in thermal expansion occurs at the mating end faces of the half bearings in the intermediate temperature range from start-up to normal operation (see FIG. 22). Furthermore, at the temperature during normal operation, a step g2b that is relatively large relative to the bearing clearance Cr occurs at the mating end faces of the split bearings (see FIG. 23).

[0013] Patent Document 3 teaches a means for offsetting a step that occurs when the temperature of the split bearing housing rises due to operation of the internal combustion engine (during normal operation) caused by a step g4b (see FIG. 25) that occurs on the mating end faces of the half bearings when the pair of half bearings are assembled (at start-up) to a pair of housing segments that make up a split bearing housing for the crankshaft of an internal combustion engine, due to a difference in bearing thickness on the bearing inner peripheral surface (see FIG. 27). However, Patent Document 3 does not consider at all the problem of wiping of lubricating oil occurring due to a step g4a that occurs due to a difference in the thermal expansion of the housing segments in the intermediate temperature range from start-up to normal operation when the temperature of the split bearing housing rises due to operation of the internal combustion engine (see FIG. 26). Furthermore, at the temperature during startup, a step g4b that is relatively large relative to the bearing clearance Cr occurs on the mating end faces of the half bearings (see FIG. 25).

[0014] Therefore, an object of the present invention is to provide a split-type bearing device for an internal combustion engine crankshaft that is less likely to cause the wiping phenomenon of lubricating oil due to steps occurring on the inner circumferential surface of the bearing, throughout the entire period from start-up to normal operation of the internal combustion engine. [Means for solving the problem]

[0015] According to the present invention, there is provided a split-type plain bearing device for a crankshaft of an internal combustion engine, comprising: a cylindrical split plain bearing having a first half bearing and a second half bearing that are abutted against each other; A split bearing housing having a first housing segment on which a first half bearing is mounted and a second housing segment on which a second half bearing is mounted, wherein a bearing retaining hole for retaining the split plain bearing is formed by fastening the first housing segment and the second housing segment together; and the first half bearing and the second half bearing each have a steel backing layer and a bearing alloy layer; of the first half bearing and the second half bearing, only the second half bearing further has a coating layer containing a synthetic resin and a solid lubricant; The first housing section has lower rigidity than the second housing section, When the split plain bearing is not mounted in a split bearing housing: the first half bearing and the second half bearing have equal outer diameters and widths; at positions symmetrical with respect to an abutment plane (a plane including the axial end face 76) when the first half bearing and the second half bearing are abutted together, the back metal layer and the bearing alloy layer of the first half bearing have thicknesses equal to those of the back metal layer and the bearing alloy layer of the second half bearing, respectively; When a split plain bearing is mounted in a split bearing housing and the first and second housing segments are fastened together with bolts, a difference in the amount of deformation between the first and second housing segments, which arises from the difference in rigidity, causes a step to form in the radial direction in the bearing retaining hole within the fastening plane between the first and second housing segments, and A split-type plain bearing device is provided in which, when the first and second housing halves are each at a temperature in the intermediate temperature range of 40 to 80°C from the time the internal combustion engine is started until it is in normal operation, the coating layer has a low thermal conductivity relative to the backing metal layer and the bearing alloy layer, so that the second housing halve on the second bearing side, which has the coating layer, has a higher temperature than the first housing halve, and as a result, the first and second housing halves deform to eliminate the step in the fastening plane due to the difference in thermal expansion that occurs based on the temperature difference.

[0016] The coating layer of the second half bearing may have a thickness in the range of 2 μm to 12 μm.

[0017] The coating layer may have a thermal conductivity of 3 W / m·° C. or less. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing a bearing device for a crankshaft of an internal combustion engine. [Figure 2] FIG. 2 is a view of the big end housing of the connecting rod as seen from the axial direction. [Figure 3] 1 is a view of a sliding bearing according to a first embodiment of the present invention in an unmounted state, viewed from the axial direction. [Figure 4] 4 is a view of the first half bearing shown in FIG. 3 as seen from the inner peripheral surface side. FIG. [Figure 5] FIG. 4 is a cross-sectional view of the first half bearing taken along line AA in FIG. [Figure 6] FIG. 4 is a plan view of the second half bearing shown in FIG. 3, viewed from the inner peripheral surface side. [Figure 7] FIG. 6 is a BB cross-sectional view of the second half bearing shown in FIG. 5. [Figure 8] 1 is a front view showing a state in which a split plain bearing for a crankshaft of an internal combustion engine according to a first embodiment of the present invention is mounted in a split bearing housing made up of bearing housings with different rigidity. FIG. [Figure 9] 9 is an enlarged view of a step forming portion C in FIG. 8. FIG. [Figure 10] 10 is a plan view of the inner circumferential surface of the stepped portion in FIG. 9. FIG. [Figure 11] FIG. 9 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 8, in a state in which the temperatures of the housing segments have risen due to operation of the internal combustion engine, and the butting end faces of the half bearings have been aligned at a certain temperature in the intermediate temperature region from start-up to normal operation. [Figure 12] 12 is an enlarged view of a step forming portion D in FIG. [Figure 13] FIG. 9 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 8, in a state in which the temperature of the housing segments has risen due to operation of the internal combustion engine and reached the temperature during normal operation. [Figure 14] 14 is an enlarged view of a step-forming portion E in FIG. 13. FIG. [Figure 15] 1 is an explanatory diagram showing a split bearing housing consisting of a pair of bearing housings with different rigidities in an assembled state; [Figure 16] FIG. 1 is a front view showing a split plain bearing for a crankshaft of an internal combustion engine according to the prior art, mounted in a split bearing housing made up of bearing housings with different rigidity. [Figure 17] FIG. 17 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 16, showing a state in which the temperature of the housing segments rises due to operation of the internal combustion engine, and the state is in an intermediate temperature range from start-up to normal operation. [Figure 18] FIG. 17 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 16, showing a state in which the temperature of the housing segments has risen due to operation of the internal combustion engine and reached the temperature during normal operation. [Figure 19] 19 is an enlarged view of a step forming portion F in FIG. 18. FIG. [Figure 20]20 is a plan view of the inner circumferential surface of the stepped portion in FIG. 19. FIG. [Figure 21] FIG. 1 is a front view showing a split plain bearing for a crankshaft of an internal combustion engine according to Patent Document 2, mounted in a split bearing housing made up of bearing housings with different rigidity. [Figure 22] FIG. 22 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 21, showing a state in which the temperature of the housing segments rises due to operation of the internal combustion engine, and the state is in an intermediate temperature range from start-up to normal operation. [Figure 23] FIG. 22 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 21, showing a state in which the temperature of the housing segments has risen due to operation of the internal combustion engine and reached the temperature during normal operation. [Figure 24] 24 is an enlarged view of a step forming portion H in FIG. 23. [Figure 25] FIG. 10 is a front view showing a split plain bearing for a crankshaft of an internal combustion engine according to Patent Document 3, mounted in a split bearing housing made up of bearing housings with different rigidity. [Figure 26] FIG. 26 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 25, showing a state in which the temperature of the housing segments rises due to operation of the internal combustion engine, and the state is in an intermediate temperature range from start-up to normal operation. [Figure 27] FIG. 26 is a front view of the split-type plain bearing for a crankshaft of an internal combustion engine shown in FIG. 25, showing a state in which the temperature of the housing segments has risen due to operation of the internal combustion engine and reached the temperature during normal operation. [Figure 28] FIG. 26 is an enlarged view of a step-forming portion I in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] (First embodiment) Fig. 1 shows a schematic diagram of a bearing device 1 for a crankshaft of an internal combustion engine. Fig. 15 shows a view of the bearing housing as seen from the axial direction. This bearing device 1 has a journal portion 6 supported on the lower part of a cylinder block, a crankpin 5 formed integrally with the journal portion 6 and rotating around the journal portion 6, and a connecting rod 2 that transmits reciprocating motion from the internal combustion engine to the crankpin 5. The bearing device 1 also has, as sliding bearings that support the crankshaft, a main bearing 4 that rotatably supports the journal portion 6, and a connecting rod bearing 3 that rotatably supports the crankpin 5.

[0021] Although the crankshaft has multiple journals 6 and multiple crankpins 5, for ease of explanation, only one journal 6 and one crankpin 5 are shown here. In Fig. 1, the positional relationship in the depth direction of the page is such that the journals 6 are at the back side of the page and the crankpins 5 are at the front side.

[0022] The journal portion 6 is journaled in a split bearing housing 10, which is made up of a cylinder block lower portion 101 and a bearing cap 102 of the internal combustion engine, via a main bearing 4 composed of a pair of half bearings 41, 42. 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 in the cylinder block lower portion 101, and the half bearing 42 is inserted into the semi-cylindrical bearing retaining hole in the bearing cap 102. The cylinder block lower portion 101 and the bearing cap 102 are then fastened together with bolts (not shown) to retain the pair of half bearings 41, 42 in the cylindrical bearing retaining holes. The half bearing 41, which is on the upper side in Figure 1, has an oil groove 41a formed along the entire length of its inner circumferential surface. The journal portion 6 also has a lubricating oil passage 6a that penetrates in the diameter direction, and when the journal portion 6 rotates in the direction of arrow X, the inlet openings 6c at both ends of the lubricating oil passage 6a alternately communicate with the oil groove 41a of the main bearing 4.

[0023] The crankpin 5 is journaled in the big-end housing 21 of the connecting rod 2 via a connecting rod bearing 3 composed of a pair of half bearings 31, 32. As shown in Figure 2, the big-end housing (bearing housing) 21 consists of a rod-side big-end housing 22A and a cap-side big-end housing 22B. The rod-side big-end housing 22A and the cap-side big-end housing 22B each have semi-cylindrical inner circumferential surfaces 27a, 27b, and when the split surfaces of the rod-side big-end housing 22A and the cap-side big-end housing 22B are butted together, the pair of inner circumferential surfaces 27a, 27b form a cylindrical bearing retaining hole 23a.

[0024] 3 is slightly larger than the inner peripheral length of the bearing retaining hole 23 of the bearing housing 10. After installation, pressure is generated between the outer peripheral surfaces 8 of the pair of half bearings 41, 42 and the inner peripheral surfaces 104, 105 of the bearing retaining hole 23, thereby fixing the pair of half bearings 41, 42 in the bearing retaining hole 23.

[0025] A second lubricating oil passage 5a is formed, branching 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 to penetrate the crank pin 5 in the diameter direction.

[0026] 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 the 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.

[0027] 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.

[0028] Hereinafter, an embodiment in which the bearing device 1 of the present invention is applied to a main bearing will be described. However, it will be understood that the application of the bearing device of the present invention is not limited to main bearings, and it may also be applied to a connecting rod bearing having a connecting rod bearing housing.

[0029] Fig. 3 shows a view from the axial direction of a main bearing 4 made up of half bearings 41, 42 of the present invention in an unmounted state with circumferential end faces 76 abutting against each other. Fig. 4 shows the half bearing 41 shown in Fig. 3 as seen from the inner circumferential surface side. Fig. 5 shows a cross-sectional view of the half bearing 41 shown in Fig. 4 taken along line AA. Fig. 6 shows the half bearing 42 shown in Fig. 3 taken from the inner circumferential surface side. Fig. 7 shows a cross-sectional view of the half bearing 42 shown in Fig. 6 taken along line BB.

[0030] As shown in Figures 3 to 7, the main bearing 4 of this embodiment is formed by abutting the circumferential end faces 76 of a pair of semi-cylindrical half bearings 41, 42 together to form an overall cylindrical shape. The upper half bearing 41 has a backing metal layer 91 on the outer diameter side and an alloy layer 92 on the inner diameter side. The lower half bearing 42 has a backing metal layer 91 on the outer diameter side and an alloy layer 92 and a coating layer 93 on the inner diameter side. The backing metal layer 91 can be made of an Fe alloy such as hypoeutectoid steel or stainless steel. The alloy layer 92 can be made of a Cu bearing alloy, an Al bearing alloy, or the like. The coating layer 93 is formed of a resin binder and a solid lubricant. While known resins can be used as the resin binder, highly heat-resistant materials such as polyamideimide, polyimide, or polybenzimidazole are preferred. Alternatively, the resin binder may be a resin composition obtained by mixing a highly heat-resistant resin such as polyamideimide, polyimide, or polybenzimidazole with a resin such as polyamide, epoxy, or polyethersulfone. Examples of solid lubricants that can be used include molybdenum disulfide, tungsten disulfide, graphite, polytetrafluoroethylene, and boron nitride. The solid lubricant is preferably added in an amount of 20 to 80% by volume relative to the resin binder. To enhance the wear resistance of the coating layer 93, the coating layer 93 may contain hard particles such as ceramics or intermetallic compounds. The coating layer 93 preferably has a thermal conductivity of 3 W / m°C or less. 5 and 7, in the case of a small internal combustion engine bearing for a passenger car, the thickness t1 of the steel backing layer of half bearings 41 and 42 can be 0.7 to 1.3 mm, and the thickness t2 of the bearing alloy layer can be 0.2 to 0.7 mm, although the thickness t1 of the steel backing layer and the thickness t2 of the bearing alloy layer can also be other dimensions.

[0031] According to a first aspect of the present invention, there is provided a split-type plain bearing device for a crankshaft of an internal combustion engine as described below. A split-type plain bearing device 1 for a crankshaft of an internal combustion engine, a cylindrical split plain bearing 4 having a first half bearing 41 and a second half bearing 42 that are abutted against each other; A split bearing housing 10 having a first housing segment 101 on which a first half bearing is mounted and a second housing segment 102 on which a second half bearing is mounted, in which a bearing retaining hole 23 for retaining the split plain bearing is formed by fastening the first housing segment and the second housing segment together. and The first half bearing and the second half bearing each have a steel backing layer 91 and a bearing alloy layer 92; of the first half bearing and the second half bearing, only the second half bearing further has a coating layer containing a synthetic resin and a solid lubricant; The first housing section 101 has lower rigidity than the second housing section 102, In the unmounted state where the split plain bearing 4 is not mounted in the split bearing housing 10: The first half bearing 41 and the second half bearing 42 have the same outer diameter and width; At positions symmetrical with respect to the butt plane when the first half bearing 41 and the second half bearing 42 are butted together, the back metal layer 91 and the bearing alloy layer 92 of the first half bearing 41 have thicknesses t1 and t2 equal to those of the back metal layer 91 and the bearing alloy layer 92 of the second half bearing 42, respectively, and the coating layer of the second half bearing 42 has a thickness t3b; When the split plain bearing 4 is mounted in the split bearing housing 10 and the first housing section 101 and the second housing section 102 are fastened together with bolts, a step g is formed in the radial direction of the bearing retaining hole 23 within the fastening plane 106 between the first housing section 101 and the second housing section 102 due to the difference in the amount of deformation between the first housing section 101 and the second housing section 102, which is caused by the difference in rigidity. When the first and second housing halves 101, 102 are bolted together with the first and second half bearings 41, 42 attached, and the temperature of the first and second housing halves 101, 102 rises as the internal combustion engine operates, and reaches 40 to 80°C, which is the intermediate temperature range from start-up to normal operation, the coating layer 93 has an extremely low thermal conductivity compared to the backing metal layer 91 and the bearing alloy layer 92. Therefore, the heat storage capacity of the first and second half bearings 41, 42 differs depending on whether or not the coating layer 93 is present. The temperature of the second housing section 102 on the second half bearing 42 side becomes higher than that of the first housing section 101, and within the fastening plane 106, a step caused by the difference in the amount of thermal expansion of the first and second housing sections 101, 102 due to the difference in temperature occurs in a direction that cancels out the step g caused by the difference in the amount of deformation of the first and second housing sections 101, 102 due to the difference in rigidity, thereby bringing the inner surfaces 7, 7 of the first and second half bearings 41, 42 into alignment, resulting in a split-type plain bearing device.

[0032] Here, heat storage capacity refers to the resistance of the split bearing housings to a drop in temperature caused by heat from the split bearing housings 101, 102 being transferred to the engine oil through the bearings and the alloy layer 92 or coating layer 93 on the bearing surface. As a result, even if the split bearing housings 101, 102 are each subjected to the same amount of heat when the internal combustion engine is operating, the high-rigidity split bearing housing 102, which has a relatively high heat storage capacity, will have a relatively higher temperature, and the low-rigidity split bearing housing 101, which has a relatively low heat storage capacity, will have a relatively higher temperature. Here, the "matching state of the inner peripheral surface" will be described. This matching does not mean that the inner peripheral surfaces of the half bearings are perfectly geometrically aligned with each other, but rather that the difference in the amount of expansion deformation of the inner diameter of the bearing retaining hole at the butting end faces of the pair of housing halves when the pair of housing halves are fastened together with bolts is calculated using, for example, the "expansion deformation difference calculation formula" shown below, The temperature of the high-rigidity split bearing housing 102 on the second half bearing side, at which the amount of thermal expansion and deformation of the inner diameter of the bearing retaining hole at the butt end face of the second half bearing housing segment 102, which occurs in a direction that cancels out the difference in the amount of expansion and deformation, becomes equal to the difference in the amount of expansion and deformation, is calculated as a target temperature in the intermediate temperature range from start-up to normal operation as the temperature of the housing segments rises due to operation of the internal combustion engine, for example, using the "thermal expansion amount calculation formula" shown below, The thickness of the coating layer 93 required for the split bearing housing 102 so that the second half bearing housing 102 reaches the target temperature is calculated, for example, using the "film thickness calculation formula" shown below: By setting this value as the thickness t3b of the coating layer of the second half bearing, the heat storage capacity of the second half bearing is increased compared to the first half bearing, and when the temperature reaches a certain temperature in the intermediate temperature range from start-up to normal operation, the step g1a is offset by the amount of thermal expansion of the second bearing housing segment, An allowance is made for errors determined by the machining accuracy during manufacturing of the split plain bearing and split bearing housing.

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[0045] 8 is a front view showing a split plain bearing consisting of a pair of half bearings 41, 42 of the present invention mounted within the inner circumferential surfaces 104, 105 of a bearing retaining hole in a split bearing housing 10 for an internal combustion engine crankshaft. The split bearing housing 10 is made up of a low-rigidity split bearing housing 101 that forms part of an aluminum alloy engine block, and a high-rigidity split bearing housing 102 that serves as an iron alloy bearing cap, and both housing halves 101, 102 are fastened together with bolts 103. The bearing retaining hole 23 in the split bearing housing 10 is formed by machining a cylindrical hole with a perfect circle in cross section after the housing halves 101, 102 have been assembled using bolts 103, without a split plain bearing being mounted. The figure shows the split bearing housing 10 disassembled after the inner surfaces 104, 105 of the bearing retaining holes have been formed by machining as described above, and the half bearings 41, 42 have been fitted along the inner surfaces of the housing halves 101, 102, which have then been reassembled together with bolts 103. In their initial state before being assembled into the split bearing housing 10, the half bearings 41, 42 have the same outer diameter, and only the half bearing 42 on the high-rigidity split bearing housing side has a coating layer, compared to the half bearing 41 on the low-rigidity split bearing housing side.

[0046] However, when the housing halves 101, 102 are joined together with the bolts 103, as explained above and as shown in Figure 16, the amount of expansion and deformation at the butt end of the low-rigidity split bearing housing 101 is greater than the amount of expansion and deformation at the butt end of the high-rigidity split bearing housing 102. This means that the inner diameters of the bearing retaining holes 104, 105 will be different between the two housing halves 101, 102, and a step g1a as shown in Figure 16 may occur between the butt end faces 76 of the two half bearings 141, 142. However, in this embodiment, the half bearings 41, 42 have the same outer diameter and width dimensions in their initial state, the back metal layers 91 and alloy layers 92 of the half bearings 41, 42 have the same thickness at corresponding positions in the circumferential direction (i.e., at symmetrical positions with respect to the butt plane when the first half bearing 41 and the second half bearing 42 are butted together), and only the half bearing 42 on the high-rigidity split bearing housing side has a coating layer compared to the half bearing 41 on the low-rigidity split bearing housing side (FIGS. 5 and 7). As a result, the temperatures of the housing halves 101, 102 rise as the internal combustion engine operates, and at a certain temperature (FIG. 11) in the intermediate temperature range between startup (FIG. 8) and normal operation (FIG. 13), the high-rigidity split bearing housing 102, which has the coating layer 93, becomes hotter than the low-rigidity split bearing housing 101, and a step due to the difference in temperature appears at the mating end surfaces of the pair of housing halves 101, 102, resulting from the difference in the amount of thermal expansion of the two housing halves, in a direction that cancels out the step due to the difference in deformation of the two housing halves caused by the difference in rigidity. This cancels out the step g1a on the inner surfaces of the two half bearings 41, 42, and this embodiment is designed so that the inner surfaces 7 of the two half bearings at the mating end surface 76 are aligned, resulting in the condition of the mating end surface 76 as shown in FIG. 12. During normal operation, the temperature of the high-rigidity split bearing housing 102 becomes even higher than that of the low-rigidity split bearing housing 101, and a step g2a occurs at the mating end surfaces of the pair of housing segments 101, 102 due to the difference in temperature, which causes a step due to the difference in the amount of thermal expansion of the two housing segments in a direction that cancels out the step due to the difference in the amount of deformation of the two housing segments caused by the difference in rigidity.However, because the step g2a is small compared to the bearing clearance Cr, wiping of the lubricating oil is unlikely to occur (Figures 13 and 14).

[0047] 16 is a front view of a conventional example showing a split plain bearing consisting of a pair of half bearings 141, 142, in which, unlike the present invention, both the first and second half bearings have a coating layer, mounted within the inner surfaces 104, 105 of the bearing retaining hole of a split bearing housing 10 for an internal combustion engine crankshaft. The split bearing housing 10 is formed from a low-rigidity split bearing housing 101 that forms part of an aluminum alloy engine block and a high-rigidity split bearing housing 102 that serves as an iron alloy bearing cap, and both housing halves 101, 102 are fastened together with bolts 103. The bearing retaining hole 23 of the split bearing housing 10 is formed by machining a cylindrical hole with a perfect circle in cross section after the housing halves 101, 102 have been assembled using bolts 103, without the split plain bearing being mounted. The figure shows the split bearing housing 10 disassembled after the inner peripheral surfaces 104, 105 of the bearing retaining holes have been formed by machining in this way, and the half bearings 141, 142 are fitted along the inner peripheral surfaces of the housing halves 101, 102, and the housing halves 101, 102 are then reassembled together with bolts 103. The half bearings 141, 142 have the same outer diameter in the initial state before being assembled into the split bearing housing 10.

[0048] However, when the housing halves 101, 102 are joined together with the bolts 103, as explained above and as shown in Figure 16, the amount of expansion and deformation at the butt end of the low-rigidity split bearing housing 101 is greater than the amount of expansion and deformation at the butt end of the high-rigidity split bearing housing 102, so the inner diameter of the bearing retaining hole 23 differs between the two housing halves 101, 102, and a step g1a, as shown in Figure 16, may occur between the butt end faces 76 of the two half bearings 141, 142. However, if the outer diameters and widths of the half bearings 141, 142 in the initial state are the same, the thicknesses of the back metal layers 191 and alloy layers 192 of the half bearings 141, 142 are the same at corresponding positions in the circumferential direction, and both the half bearing 141 on the low-rigidity split bearing housing side and the half bearing 142 on the high-rigidity split bearing housing side have coating layers 193, the temperature of the housing halves 101, 102 will rise during operation of the internal combustion engine, and the temperature of the housing halves 101, 102 will rise during the period from start-up (FIG. 16) to normal operation (FIG. 18). In the intermediate temperature range (FIG. 17) where the high-rigidity split bearing housing 102 is at the same temperature as the low-rigidity split bearing housing 101, a step resulting from the difference in the amount of thermal expansion of the pair of housing halves 101, 102 at their butted end faces, due to the difference in thermal expansion coefficients, occurs in the same direction as the step g1a resulting from the difference in the amount of deformation of the housing halves due to the difference in rigidity, resulting in a step g3a on the inner circumferential surfaces of the two half bearings 141, 142. Furthermore, during normal operation, the step g3a increases further due to the difference in thermal expansion coefficients (see step g3b in FIG. 19), making the step g3b larger than the bearing clearance Cr, which could result in wiping of the lubricating oil at the butted end faces 76 of the two half bearings 141, 142 (FIG. 20).

[0049] 21 is a front view showing a split plain bearing made up of a pair of half bearings 241, 242 mounted within the inner circumferential surfaces 104, 105 of a bearing retaining hole in a split bearing housing 10 for an internal combustion engine crankshaft, which, unlike the present invention, sets a difference in bearing thickness at the butting end faces of the half bearings when the pair of half bearings 241, 242 are assembled to a pair of housing segments of the split bearing housing that have a difference in rigidity, as taught in Patent Document 2. The split bearing housing 10 is formed from a low-rigidity split bearing housing 101 that forms part of an aluminum alloy engine block, and a high-rigidity split bearing housing 102 that serves as an iron alloy bearing cap, and both housing segments 101, 102 are fastened together with bolts 103. The bearing retaining hole 23 in the split bearing housing 10 is formed by machining a cylindrical hole with a perfect circular cross section after the housing halves 101, 102 have been assembled using bolts 103, without a split plain bearing being installed. The split bearing housing 10 having the bearing retaining hole 23 formed by machining in this way is disassembled, and half bearings 241, 242 are installed along the inner surfaces of the housing halves 101, 102, and the housing halves 101, 102 are then reassembled together using bolts 103, as shown in the figure. The half bearings 241, 242 have the same outer diameter in the initial state before being assembled into the split bearing housing 10.

[0050] However, when the housing halves 101, 102 are joined together with the bolts 103, as explained above and as shown in Figure 16, the amount of expansion and deformation at the butt end of the low-rigidity split bearing housing 101 is greater than the amount of expansion and deformation at the butt end of the high-rigidity split bearing housing 102, so the inner diameter of the bearing retaining hole 12 is different between the two housing halves 101, 102, and a step g1a may occur between the butt end faces 76 of the two half bearings 141, 142.However, with regard to this step in the split bearing housings, which have different rigidity from each other, by setting a difference in bearing thickness at the butt ends of the half bearings when a pair of half bearings are assembled to a pair of housing halves of the split bearing housing, which have different rigidity from each other, the step g1a that occurs on the inner circumferential surface of the bearing due to the difference in rigidity of the split bearing housings is offset (Figure 21). However, the outer diameter and width dimensions of the half bearings 241, 242 are equal in the initial state, and as the temperature of the housing halves 101, 102 rises as the internal combustion engine operates, the temperature of the high-rigidity split bearing housing 102 becomes equal to the temperature of the low-rigidity split bearing housing 101 in the intermediate temperature range (FIG. 22) between startup (FIG. 21) and normal operation (FIG. 23). This causes a step due to the difference in the amount of thermal expansion of the two housing halves at the mating end faces of the pair of housing halves 101, 102, resulting in a step g2b on the inner circumferential surfaces of the half bearings 241, 242. Furthermore, during normal operation, the difference in thermal expansion coefficients further increases the step g2b (see step g2c in FIG. 24), making the step g2c larger compared to the bearing clearance Cr. This may result in wiping of the lubricating oil at the mating end faces 76 of the half bearings 241, 242.

[0051] 25 is a front view showing a split plain bearing comprising a pair of half bearings 341, 342 mounted in a bearing retaining hole 23 of a split bearing housing 10 for an internal combustion engine crankshaft. This split bearing housing 10 sets a difference in bearing thickness at the butt-joint end faces of the half bearings when the pair of half bearings 341, 342 are assembled to a pair of housing segments of the split bearing housing that have different thermal expansion coefficients, as taught in Patent Document 3, unlike the present invention. The split bearing housing 10 is formed by a low-rigidity split bearing housing 101 that forms part of an aluminum alloy engine block and a high-rigidity split bearing housing 102 that serves as an iron alloy bearing cap, and both housing segments 101, 102 are fastened together with bolts 103. The bearing retaining hole 23 of the split bearing housing 10 is formed by machining a cylindrical hole with a perfect circle in cross section after the housing segments 101, 102 are assembled using bolts 103, without a split plain bearing being mounted. The figure shows the split bearing housing 10 disassembled after the bearing retaining holes 23 have been formed by machining in this way, and the half bearings 41, 42 are fitted along the inner surfaces of the housing halves 101, 102, which are then reassembled together with bolts 103. The half bearings 341, 342 have the same outer diameter in the initial state before being assembled into the split bearing housing 10.

[0052] Here, when the temperature of the split bearing housing rises due to operation of the internal combustion engine and the engine enters normal operation, as explained above and as shown in Figure 18, the amount of thermal expansion and deformation at the butt end of the low-rigidity split bearing housing 101 is greater than the amount of thermal expansion and deformation at the butt end of the high-rigidity split bearing housing 102, so the inner diameter of the bearing retaining hole 12 differs between the two housing halves 101, 102, and a step g3b as shown in Figure 18 may occur between the butt end faces 76 of the two half bearings 141, 142. However, when the temperature of the split bearing housing rises due to operation of the internal combustion engine, and the engine enters normal operation, a difference in bearing thickness at the mating end faces of the half bearings is set, which offsets the step g3b that occurs on the inner surface of the bearing due to the difference in the amount of thermal expansion of the split bearing housing (Figure 27). Meanwhile, the outer diameters and widths of the half bearings 341, 342 are equal in the initial state, and as the temperature of the housing halves 101, 102 rises during operation of the internal combustion engine, a difference occurs between a step due to the difference in the amount of thermal expansion of the housing halves 101, 102 and a step due to the difference in bearing thickness at the mating end faces of the pair of housing halves 101, 102 due to the difference in thermal expansion coefficients, and a step due to the difference in bearing thickness, resulting in a step g4a on the inner circumferential surfaces of the half bearings 341, 342. Furthermore, at startup, the difference in thermal expansion coefficients increases the difference between the step due to the difference in the amount of thermal expansion of the housing halves and the step due to the difference in bearing thickness (see step g4b in FIG. 25). This increases the step g4b at the mating end faces 76 of the half bearings 341, 342 compared to the bearing clearance Cr, potentially causing wiping of the lubricating oil.

[0053] The bearing retaining hole inner diameter D (mm) is the dimension at the bearing retaining hole machining temperature T1 (°C) of the split bearing housing, and bearing retaining hole machining is usually performed in the room temperature range (20 to 25°C). In addition, for a typical passenger internal combustion engine, the temperature at startup is around 20 to 25°C, and the temperature during normal operation is around 120°C. Therefore, the temperature in the intermediate temperature range is above the temperature at startup and below the temperature during normal operation. In Example 1, the target temperature T2 (°C) of the high-rigidity side split bearing housing that is consistent in the intermediate temperature range of the internal combustion engine varies depending on the specifications of the internal combustion engine, but in the case of an internal combustion engine for a typical passenger car, it is set to approximately 40 to 80°C, which is a range slightly lower than the median between the temperature at startup and the temperature during normal operation.The reason for this is that in the low temperature range of the housing segments 101, 102 from startup, the amount of thermal expansion of the housing segments 101, 102 is small, so the bearing clearance Cr between the inner surface of the crankshaft sliding bearing and the surface of the crankshaft becomes small, making the flow of lubricating oil more susceptible to steps and making wiping more likely to occur.Therefore, within the temperature range from startup to normal operation, it is given priority to mitigate steps in the lower temperature range. The thickness of the coating layer is roughly determined by the materials of the low-rigidity split bearing housing and the high-rigidity split bearing housing, and the wall thickness, outer diameter, and width specifications of the half bearings. For example, in a combination of split bearing housings made of aluminum alloy and iron alloy, where the half bearing wall thickness is 1.5 to 2.0 mm, the outer diameter is 30 to 100 mm, and the width is 10 to 40 mm, the thickness of the coating layer will be in the range of 2 μm to 12 μm. Furthermore, in order to provide heat storage within the limited range of coating layer thickness, it is preferable that the thermal conductivity of coating layer 93 be 3 W / m·°C or less, as determined by Equation 8. Furthermore, split bearing housings 101, 102, which have relatively different thermal expansion coefficients, are fastened together with bolts 103, and compressive stress occurs perpendicular to the butt end faces 76 of split bearing housings 101, 102, with the butt end face 76 of split bearing housings 101, which has a relatively low thermal expansion coefficient, acting as a resistance to the thermal expansion deformation of butt end face 76 of split bearing housing 102, which has a relatively high thermal expansion coefficient. When split bearing housings made of aluminum alloy and iron alloy, which have relatively different thermal expansion coefficients, are combined, the difference in the amount of thermal expansion deformation of the inner diameter of the bearing retaining hole at the split surface of the split bearing housing is mitigated to about one-third of the difference in the amount of thermal expansion deformation when each split bearing housing thermally expands in a free state (thermal expansion deformation mitigation coefficient K = 1 / 3).

[0054] In reality, to configure the inner circumferential surfaces of the two half bearings 41, 42 so that they align with each other at a certain temperature in the intermediate temperature range as described above, the actual split bearing housings 101, 102 (cylinder block and bearing cap), or a model of only the split bearing housing portion created to imitate the actual parts, is used. A pair of half bearings 141, 142 of the same shape and dimensions are mounted in the bearing retaining holes 104, 105 of the split bearing housing, and the two half bearings are fastened together with bolts 103. The step size of the inner diameter at the butting end faces of the pair of half bearings is measured using a measuring machine such as a roundness measuring machine, and the step g1a due to the difference in rigidity is found. In addition, a pair of half bearings 141, 142 of the same shape and dimensions are mounted in the bearing retaining holes of the split bearing housings 101, 102, and both housing halves are fastened together with bolts 103. With this in place, the high-rigidity split bearing housing is heated to a temperature in the intermediate temperature range between the start-up and normal operation of the internal combustion engine, and the step dimensions of the inner diameters at the butting end faces of the pair of half bearings are measured using a measuring device such as a roundness measuring device, and the temperature difference between the split bearing housings 101, 102 at which the step is reduced is determined. In addition, by assembling half bearings 41, 42 with and without a coating layer into split bearing housings 101, 102, tests were conducted using a testing machine created to simulate an actual machine, and the temperature of the back surface of the bearing in the intermediate temperature range from start-up to normal operation was measured, and the thickness of the coating layer at which a temperature difference occurs between the first half bearing and the second half bearing was determined. Using these measurements, the thickness t3b of the coating layer of the half bearing to be mounted on the relatively high-rigidity split bearing housing can be set to the dimensional value actually measured using the actual object or a model.

[0055] Alternatively, for simplicity, the coating layer thickness t3b of the half bearing to be mounted in the high-rigidity split bearing housing can be set to the thickness of coating layer 93 calculated using equations 1 to 12. In this case, when calculating the housing mass, it is possible to assume that the housing outer diameter is 1.5 times the bearing retaining hole inner diameter D and that the housing width is equivalent to the bearing width L1. Furthermore, when calculating the shaft mass, it is possible to assume that the shaft width is equivalent to the bearing width L1.

[0056] (calculation example) When an aluminum alloy housing segment (Young's modulus 74.5 (GPa), Poisson's ratio 0.3) and an iron alloy housing segment (Young's modulus 205.9 (GPa), Poisson's ratio 0.33) are fastened with iron alloy bolts together with a half bearing (Young's modulus 205.9 (GPa), Poisson's ratio 0.33, alloy thickness 0.3 mm, backing thickness 1.7 mm), and the split bearing housing has a bearing retaining hole dimension of 50 mm, interference of 0.1 mm, and a relaxation coefficient of 1 / 3, the difference in the amount of expansion deformation is calculated from formulas 1 to 6 as follows: BB=((1-0.3)+(1+0.3)×(1-2×(1.7mm+0.3mm / 3) / 50mm)^2) / (205.9GPa×4×(1-2×(1.7mm+0.3mm / 3) / 50mm×(1-(1.7mm+0.3mm / 3) / 50mm))=0.064mm2 / N BH(L)=((1-0.33)+(1+0.33)×(50mm×1.5 / 50mm)^2) / (74.5GPa×((50mm×1.5 / 50mm)^2-1))=0.039mm2 / N BH(H)=((1-0.3)+(1+0.3)×(50mm×1.5 / 50mm)^2) / (205.9GPa×((50mm×1.5 / 50mm)^2-1))=0.014mm2 / N ΔD(L)=0.039mm2 / N / (0.064mm2 / N+0.0039mm2 / N)×0.1mm=0.038mm ΔD(H)=0.014mm2 / N / (0.064mm2 / N+0.014mm2 / N)×0.1mm=0.018mm Expansion deformation difference = (0.038 mm - 0.018 mm) x 1 / 3 = 0.007 mm This becomes: The target temperature T2 of the high-rigidity split bearing housing required to cancel out the difference in the amount of expansion deformation due to the amount of thermal expansion is calculated from Equation 7, assuming that the thermal expansion coefficient of the iron alloy housing segment is 1.2 x 10^-5 / ℃ and the temperature at start-up is 20℃. T2=(0.007mm / 1000+50mm / 1000×20℃×1.2×10^-5×1 / 3) / (50mm / 1000×1.2×10^-5 / ℃×1 / 3)=55℃ This becomes: The thickness t3b (mm) of the coating layer 93 of the half bearing required to generate the target temperature T2 of the high-rigidity split bearing housing is calculated from equations 8 to 12, assuming that the reference temperature during normal operation is 120°C, the diameter of the journal is 46 mm, the width of the half bearing is 16 mm, the thermal conductivity of the coating layer is 2.4 (W / m·°C), the specific heat of the iron alloy housing segment and journal is 461 (J / kg·°C), the density is 7.874 (g / cm3), and the specific heat of the aluminum alloy housing segment is 900 (J / kg·°C), and the density is 2.7 (g / cm3). Q(H)=(((50mm×1.5 / 2)^2-(50mm / 2)^2)×π / 2×16mm) / 1000×7.874g / cm3) / 1000×461J / kg・℃×(120℃-20℃)=7127J Q(L)=(((50mm×1.5 / 2)^2-(50mm / 2)^2)×π / 2×16mm) / 1000×2.7g / cm3) / 1000×900J / kg・℃×(120℃-20℃)=4771J Q(S)=((46mm / 2)^2×π×16mm) / 1000×7.874g / cm3) / 1000×461J / kg・℃×(120℃-20℃)=9652J Q=7127J+4771J+9652J=21151J t3b=2.4W / m·℃×(50mm×π / 2×16mm) / 1000000×(55℃-20℃) / (21151J / 1s)=0.005mm This becomes: The thickness t3b of the coating layer of the half bearing attached to the housing segment 102 with relatively high rigidity is set to 0.005 mm. This gives the high-rigidity split bearing housing 102 a greater heat storage capacity than the low-rigidity split bearing housing 101. As a result, when the temperatures of the housing segments rise during engine operation, the temperature of the high-rigidity split bearing housing 102 is greater than that of the low-rigidity split bearing housing 101, causing the high-rigidity split bearing housing 102 to expand more thermally than the low-rigidity split bearing housing 101. The step g1a that occurs between the mating end faces 76 of the two half bearings 41, 42 due to the difference in rigidity of the housing segments at startup is offset by the thermal expansion of the high-rigidity split bearing housing 102 at a certain temperature in the intermediate temperature range from startup to normal operation, and the two bearing segments are aligned. As a result, during normal operation, the temperature of the high-rigidity split bearing housing 102 becomes even higher than that of the low-rigidity split bearing housing 101, which further cancels out the difference in thermal expansion caused by the difference in thermal expansion coefficients of the split bearing housings.Even if a step g2a occurs, the step g2a is small compared to the bearing clearance Cr, so the wiping phenomenon of the lubricating oil is unlikely to occur (Figures 13 and 14).

[0057] In the embodiment, the thickness t1 of the steel backing of the first and second half bearings 41, 42, the thickness t2 of the bearing alloy layer, and the thickness t3b of the coating layer of the second half bearing 42 are constant in the circumferential and axial directions (width direction) (of the half bearings). However, without being limited to this, the thickness t2 of the bearing alloy layer may be greatest at the circumferential center of the first and second half bearings 41, 42 and continuously decrease toward both circumferential ends (so that the thickness t of the half bearing is greatest at the circumferential center and continuously decrease toward both circumferential ends).

[0058] Furthermore, while the embodiment is applied to a split bearing housing for a crankshaft, in the case of a bearing housing 21 for a connecting rod shaft (Figure 2), this patent can be applied by taking into account differences in housing shape, with split bearing housing 22B being the low-rigidity split bearing housing to which the first half bearing is assembled, and 22A being the high-rigidity split bearing housing to which the second half bearing is assembled. In this case, to take into account differences in rigidity due to shape, it is also possible to simply multiply BH(L) by a relaxation coefficient K = 1 / 3. [Explanation of symbols]

[0059] 1 Bearing device 10 Bearing housing (main bearing) 101 First housing segment, cylinder block lower portion 102 Second housing segment, bearing cap 103 volts 104, 105 Inner surface of bearing retaining hole 106 Fastening plane (split surface of split bearing housing) 2 connecting rods 21 Big end housing, bearing housing 22A Rod side big end housing 22B Cap side big end housing 23, 23a Bearing retaining hole 27a Inner surface 27b Inner surface 3 Connecting rod bearing 31, 32 Half bearings 4 Main bearing 41, 42 Half bearing according to Example 1 of the present invention 141, 142 Half bearings according to the prior art 241, 242 Half bearing according to Patent Document 2 341, 342 Half bearing according to Patent Document 3 41a Oil groove 43 Circumferential end 5 crank pin 5a, 5b Lubrication oil path 5c outlet 6 Journal Section 6a Lubrication oil path 6c Inlet opening 7 Inner surface 76 Circumferential end face of half bearing 8 Outer surface 91 Underground Gold 92 alloy layer 93 Covering layer 191 Backing metal layer of half bearing according to prior art 192 Alloy layer of half bearing according to prior art 193 Coating layer of half bearing according to prior art Cr Clearance between bearing and shaft g Steps that occur at the joints of the housing due to differences in the amount of expansion and deformation g' Steps that occur at the joints of the housing due to differences in thermal expansion and deformation g1a Step that occurs at the joint of the half bearing due to difference in expansion deformation g2a, g2b, g2c Steps that occur at the joints of half bearings due to differences in thermal expansion g3a, g3b Steps that occur at the joints of half bearings due to differences in expansion and thermal deformation g4a, g4b Steps that occur at the joints of half bearings due to differences in bearing thickness L1 Axial length of half bearing t Thickness of half bearing t1 Backing layer thickness of the half bearing supported by the low-rigidity side and light-synthetic side split bearing housing t2 Thickness of alloy layer of half bearing supported by low-rigidity and high-rigidity split bearing housings t3b Coating thickness of half bearing supported by high-rigidity split bearing housing X Rotation direction of journal Z Crank pin rotation direction

Claims

1. A split-type plain bearing device for a crankshaft of an internal combustion engine, comprising: a cylindrical split plain bearing having a first half bearing and a second half bearing that are abutted against each other; a split bearing housing having a first housing section to which the first half bearing is attached and a second housing section to which the second half bearing is attached, wherein a bearing retaining hole for retaining the split plain bearing is formed by fastening the first housing section and the second housing section together; and the first half bearing and the second half bearing each have a steel backing layer and a bearing alloy layer; only the second half bearing of the first half bearing and the second half bearing further has a coating layer containing a synthetic resin and a solid lubricant, the first housing section has lower rigidity than the second housing section; In an unmounted state in which the split plain bearing is not mounted in the split bearing housing: the first half bearing and the second half bearing have equal outer diameters and widths; the back metal layer and the bearing alloy layer of the first half bearing have the same thickness as the back metal layer and the bearing alloy layer of the second half bearing at positions symmetrical with respect to a butt plane when the first half bearing and the second half bearing are butted together, When the split plain bearing is mounted in the split bearing housing and the first housing section and the second housing section are fastened together with bolts, a difference in deformation between the first housing section and the second housing section, which is caused by the difference in rigidity, causes a step to be formed in the bearing retaining hole in the radial direction within the fastening plane between the first housing section and the second housing section, and A split-type plain bearing device in which, when the first and second housing halves are each at a temperature within a range of 40 to 80°C, which is an intermediate temperature region, between the time when the internal combustion engine is started and the time when the engine is in normal operation, the coating layer has a lower thermal conductivity than the backing metal layer and the bearing alloy layer, and therefore the second housing halve on the second bearing side, which has the coating layer, has a higher temperature than the first housing halve, and as a result, the first and second housing halves deform to eliminate the step in the fastening plane due to the difference in thermal expansion that arises based on the difference in temperature.

2. 2. The split plain bearing device according to claim 1, wherein the coating layer of the second half bearing has a thickness in the range of 2 μm to 12 μm.

3. 2. The split plain bearing device according to claim 1, wherein the coating layer has a thermal conductivity of 3 W / m·°C or less.

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