Bearing device for crankshaft of internal combustion engine

Abstract

The present invention addresses the problem of providing a split-type bearing device for a crankshaft in which the wiping phenomenon of lubricating oil due to the generation of a step on the inner peripheral surface of a bearing is less likely to occur during the entire period from the start-up of an internal combustion engine to the normal operation of the internal combustion engine. In the split bearing device according to the present invention, a first half bearing and a second half bearing each have a steel back metal layer and a bearing alloy layer, only the second half bearing further has a cover layer, and the rigidity of a first housing split body is lower than the rigidity of a second housing split body. In a non-mounted state in which the split sliding bearing is not mounted to the split bearing housing, the first half bearing and the second half bearing have the same outer diameter and width as each other, and the first half bearing and the second half bearing are arranged in a symmetrical position that is symmetrical with respect to a butt-joint plane when the first half bearing and the second half bearing are in butt joint. The back surface metal layer and the bearing alloy layer of the first half bearing have the same thickness as the back surface metal layer and the bearing alloy layer of the second half bearing, respectively.

Description

Technical Field

[0001] This invention relates to a bearing device for supporting the crankshaft of an internal combustion engine. Background Technology

[0002] The crankshaft of the internal combustion engine is supported at its journal by a main bearing consisting of a pair of split bearings in the lower part of the engine block. For lubrication of the main bearing, lubricating oil discharged by an oil pump is delivered from an oil passage 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 in the diametrical direction, with its two ends communicating with the lubricating oil groove of the main bearing. Then, a second lubricating oil passage branches off from the first lubricating oil passage at the journal, passing through the crank arm, and communicates with a third lubricating oil passage formed through the crank pin in the diametrical direction. Therefore, lubricating oil, supplied from the oil passages within the cylinder wall through a through-hole to the lubricating oil groove formed on the inner circumferential surface of the main bearing, is supplied via the first, second, and third lubricating oil passages, and from the outlet opening at the end of the third lubricating oil passage to the sliding surface between the sliding surface of the crankpin and the sliding surface of the connecting rod bearing, which is composed of a pair of split bearings (see, for example, Patent Document 1). Thus, oil is supplied between the surface of the crankshaft and the sliding surfaces of the main bearing and the connecting rod bearing.

[0003] The split-type sliding bearing for the crankshaft of an internal combustion engine is formed into a cylindrical shape by assembling a pair of split bearing halves onto the bearing housing, that is, assembling them onto a housing split body that is part of the engine cylinder and a housing split body that is a bearing cover. Before assembling the pair of split bearing halves, the bearing retaining hole of the bearing housing is machined into a perfect circle in a single machining operation while the pair of housing split bodies are fastened with bolts. In recent years, aluminum alloy engine cylinders have been widely used in passenger car internal combustion engines to reduce engine weight. In this case, a common combination in split bearing housings for crankshafts is that one housing segment is part of an aluminum alloy engine cylinder, and the other housing segment is a steel alloy bearing cap.

[0004] On the other hand, the split-type sliding bearings for crankshafts typically consist of a steel backing metal and a bearing alloy layer. The circumference of the outer surface of a split-type sliding bearing for a crankshaft, consisting of a pair of split-type bearings, is formed to be a predetermined length longer than the circumference of the inner circumference of the bearing retaining hole in the split-type bearing housing. Based on this dimensional relationship, when a pair of split-type bearings are assembled into the split-type bearing housing, circumferential compressive stress and radial stress are generated on the pair of split-type bearings. As a result, the pair of split-type bearings are tightly fixed to the inner circumferential surface of the bearing retaining hole in the split-type bearing housing, and the split-type bearing housing undergoes elastic deformation and expands radially, increasing the inner diameter of the bearing retaining hole.

[0005] Here, refer to Figure 15 , 16 Articles 18 and 19 describe the relationship between the split bearing housing and the split sliding bearing for the crankshaft, which consists of a pair of half-split bearings, assembled thereon. Figure 15 A split-type bearing housing 10 for a crankshaft is shown. The bearing housing 10 is formed by a lower cylinder block 101, which is part of an engine cylinder, and a bearing cap 102 (e.g., made of an iron alloy). With the bearing cap 102 assembled to the lower cylinder block 101 by bolts 103, a bearing retaining hole 23 with a circular cross-section is machined at room temperature. The subsequent bearing assembly is performed as follows: the bolts 103 are removed from the bearing housing 10, and the split bearings 141 and 142, forming a split-type sliding bearing, are installed along the inner circumferential surfaces 104 and 105 of the bearing retaining hole 23. The lower cylinder block 101 is then fastened to the bearing cap 102 again by bolts 103.

[0006] In the widely used low-rigidity split bearing housing 10 in recent years, bolts 103 are tightened to generate the same level of stress on the split sliding bearing as before in order to fit and fix the split sliding bearing. However, this results in a larger expansion deformation of the inner diameter of the split bearing housing. Furthermore, the lower cylinder 101 and bearing cap 102 constituting the split bearing housing have different rigidities. Therefore, due to the stress of fixing the split sliding bearing, a difference in expansion deformation occurs on the inner circumferential surfaces 104 and 105. This manifests as a step g on the inner circumferential surfaces 104 and 105 within the fastening plane 106 (the split surface of the split bearing housing) between the lower cylinder 101 and bearing cap 102. A step g1a also occurs on the inner circumferential surface 7 of the half-split bearings 141 and 142 (see reference). Figure 16 ).

[0007] Furthermore, in this type of split bearing housing, when the temperature rises due to the operation of the internal combustion engine and reaches the normal operating temperature, the coefficients of thermal expansion of aluminum alloy and iron alloy are different. Therefore, compared to the inner diameter of the housing split 102 on the bearing cap side made of iron alloy, which has a relatively lower coefficient of thermal expansion, the inner diameter of the housing split 101 on the engine cylinder side made of aluminum alloy, which has a relatively higher coefficient of thermal expansion, becomes larger. Thus, as... Figure 18 As shown, the difference in expansion deformation plus the difference in thermal expansion forms a step g' on the inner circumferential surfaces 104 and 105 of the bearing retaining hole within the fastening plane 106, and a step g3b is also generated on the inner circumferential surface 7 of the half-split bearings 141 and 142.

[0008] On the other hand, in recent years, due to the miniaturization of oil pumps in internal combustion engines, the amount of lubricating oil supplied relative to the inner circumferential surface of the crankshaft sliding bearing has decreased. Correspondingly, in order to reduce lubricating oil leakage from the bearing clearance between the inner circumferential surface of the crankshaft sliding bearing and the surface of the crankshaft 6, the bearing clearance is set to be smaller. However, under normal operating conditions, such as... Figure 18 As shown, if a step g3b with a larger size than the bearing clearance Cr is formed on the inner circumferential surface of the bearing at the fastening plane of the lower cylinder 101 and the bearing cap 102, the ratio of the step area that obstructs the flow of lubricating oil to the cross-sectional area of ​​the lubricating oil flow path becomes relatively high compared to the case where the bearing clearance is set to be larger in the past (refer to...). Figure 19 The phenomenon of lubricating oil smearing caused by step g3b occurs (refer to...). Figure 20 This leads to increased lubricant leakage and poor lubricant supply relative to the bearing sliding surface.

[0009] Regarding the step g of a split bearing housing having housing segments with different rigidities, Patent Document 2 teaches that the difference in bearing thickness is set at the mating end faces of a pair of split bearings to offset the step generated on the inner circumferential surface of the bearing due to the difference in rigidity of the housing segments when assembling a pair of split bearings into a split bearing housing.

[0010] Furthermore, regarding the step g' of a split bearing housing with different coefficients of thermal expansion, Patent Document 3 teaches that a difference in bearing thickness is set at the mating end faces of a pair of split bearings to offset the step generated on the inner circumferential surface of the bearing due to the difference in thermal expansion of the split bearing housing when the temperature of the split bearing housing rises due to the operation of the internal combustion engine. Existing technical documents Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 8-277831 Patent Document 2: Japanese Patent Application Publication No. 2010-156373 Patent Document 3: Japanese Patent Application Publication No. 2010-156374 Summary of the Invention The technical problem that the invention aims to solve

[0012] Patent document 2 teaches the following mechanism: when assembling a pair of split bearings into a pair of housing segments with a difference in rigidity (at startup), the mating end faces of the split bearings counteract the step g1a (refer to) generated on the inner circumferential surface of the bearing. Figure 21 However, when a pair of split bearings are assembled into a pair of housings with different coefficients of thermal expansion, and the temperature of the split bearing housing rises due to the operation of the internal combustion engine, a step g2b is generated at the mating end face of the split bearings due to the difference in thermal expansion in the intermediate temperature range from start-up to normal operation (see reference). Figure 22 At normal operating temperatures, a step g2c, which is larger than the bearing clearance Cr, is generated at the mating end face of the split bearing (refer to...). Figure 23 This leads to lubricant wiping, a problem that is not addressed in Patent Document 2.

[0013] Patent document 3 teaches the following mechanism: when assembling a pair of split bearings into a pair of housing segments constituting a split bearing housing for an internal combustion engine crankshaft (at startup), at the mating end faces of the split bearings, a step g4b (refer to) is generated on the inner circumferential surface of the bearing due to the difference in bearing thickness. Figure 25 This compensates for the temperature rise in the split bearing housing due to the operation of the internal combustion engine (during normal operation) that causes a step-up (refer to...). Figure 27 However, the temperature of the split bearing housing rises due to the operation of the internal combustion engine. In the intermediate temperature range from start-up to normal operation, a step g4a is generated due to the difference in thermal expansion between the split housing sections (see reference). Figure 26 At startup temperature, a step g4b with a larger size than the bearing clearance Cr is generated at the mating end face of the split bearing (refer to...). Figure 25 This results in lubricant wiping, a problem that is not addressed in Patent Document 3.

[0014] Therefore, the object of the present invention is to provide a split bearing device for the crankshaft of an internal combustion engine, which is less prone to lubricant smearing due to steps on the inner circumferential surface of the bearing during the entire period from the start-up of the internal combustion engine to normal operation. Means for solving technical problems

[0015] According to the present invention, a split-type sliding bearing device is provided, which is a split-type sliding bearing device for the crankshaft of an internal combustion engine, comprising: A cylindrical, segmented sliding bearing, comprising a first segmented bearing and a second segmented bearing mating with each other; and A split bearing housing has a first housing segment for mounting a first split bearing and a second housing segment for mounting a second split bearing, and a bearing retaining hole for retaining the split sliding bearing is formed by fastening the first housing segment and the second housing segment. The first and second split bearings each have a steel back metal layer and a bearing alloy layer, respectively. Of the first and second split bearings, only the second split bearing also has a covering layer containing synthetic resin and solid lubricant. The rigidity of the first shell segment is lower than that of the second shell segment. In the non-installed state, where the split sliding bearing is not mounted on the split bearing housing: The first and second split bearings have equal outer diameters and widths. At a symmetrical position symmetrical about the mating plane (including the plane of axial end face 76) when the first and second split bearings are mated, the back metal layer and bearing alloy layer of the first split bearing have the same thickness as the back metal layer and bearing alloy layer of the second split bearing. When the split sliding bearing is installed on the split bearing housing and the first and second housing split bodies are bolted together, the difference in deformation between the first and second housing split bodies due to their different rigidity causes a step to form radially in the bearing retaining hole within the fastening plane between the first and second housing split bodies. During the period from the start-up of the internal combustion engine to normal operation, when the first housing segment and the second housing segment are in the intermediate temperature range, i.e., 40 to 80°C, the thermal conductivity of the cover layer is lower than that of the back metal layer and the bearing alloy layer. Therefore, the temperature of the second housing segment on the bearing side of the second half of the cover layer is higher than that of the first housing segment. As a result, the first housing segment and the second housing segment deform in a way that eliminates the step in the fastening plane due to the difference in thermal expansion caused by the temperature difference.

[0016] The thickness of the cover layer of the second half-split bearing can be in the range of 2μm to 12μm.

[0017] In addition, the thermal conductivity of the covering layer can be below 3 W / m·℃. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the bearing assembly of the crankshaft of an internal combustion engine. Figure 2This is a diagram of the outer casing at the large end of the connecting rod, viewed from the axial direction. Figure 3 This is a diagram of the sliding bearing of the first embodiment of the present invention viewed from the axial direction in its non-installed state. Figure 4 Viewed from the inner circumferential side Figure 3 The diagram shows the first half of the split bearing. Figure 5 yes Figure 3 The first half of the bearing is shown in sectional view AA. Figure 6 Viewed from the inner circumferential side Figure 3 The top view of the second half of the split bearing is shown. Figure 7 yes Figure 5 The BB section view of the second half-split bearing is shown. Figure 8 This is a front view showing the state in which the crankshaft of the internal combustion engine according to Embodiment 1 of the present invention is mounted with a split-type sliding bearing on a split-type bearing housing composed of bearing housings having different rigidities. Figure 9 yes Figure 8 Enlarged view of step-forming part C in the image. Figure 10 It is observation Figure 9 A top view of the inner circumferential surface of the step-forming part. Figure 11 yes Figure 8 The front view of the split-type sliding bearing for the crankshaft of the internal combustion engine shown is in the following state: the temperature of the split housing rises due to the operation of the internal combustion engine, and the mating ends of the split bearing are aligned at a certain temperature in the intermediate temperature range from start-up to normal operation. Figure 12 yes Figure 11 Enlarged view of step-forming part D in the image. Figure 13 yes Figure 8 The front view shown is of the crankshaft of the internal combustion engine using a split-type sliding bearing in the following state: the temperature of the housing split body has risen to the normal operating temperature due to the operation of the internal combustion engine. Figure 14 yes Figure 13 Enlarged view of step-forming part E in the diagram. Figure 15 This is an explanatory diagram showing a split bearing housing composed of a pair of bearing housings with different rigidities, in its assembled state. Figure 16 This is a front view showing the state in which the crankshaft of a prior art internal combustion engine is mounted with a split-type sliding bearing on a split-type bearing housing consisting of bearing housings with different rigidities. Figure 17 It is shown Figure 16 The front view of the crankshaft of the internal combustion engine with a split sliding bearing is shown in the following state: the temperature of the split housing increases due to the operation of the internal combustion engine, and the state is in the intermediate temperature range from the start-up to normal operation. Figure 18 It is shown Figure 16 The front view shown is of the crankshaft of the internal combustion engine using a split-type sliding bearing in the following state: the temperature of the housing split body has risen to the normal operating temperature due to the operation of the internal combustion engine. Figure 19 yes Figure 18 Enlarged view of the step-forming part F in the diagram. Figure 20 It is observation Figure 19 A top view of the inner circumferential surface of the step-forming part. Figure 21 This is a front view showing the state in which the crankshaft of the internal combustion engine of Patent Document 2 is mounted with a split-type sliding bearing on a split-type bearing housing composed of bearing housings with different rigidities. Figure 22 yes Figure 21 The front view of the crankshaft of the internal combustion engine with a split sliding bearing is shown in the following state: the temperature of the split housing increases due to the operation of the internal combustion engine, and the state is in the intermediate temperature range from the start-up to normal operation. Figure 23 It is shown Figure 21 The front view shown is of the crankshaft of the internal combustion engine using a split-type sliding bearing in the following state: the temperature of the housing split body has risen to the normal operating temperature due to the operation of the internal combustion engine. Figure 24 yes Figure 23 Enlarged view of the step-forming part H in the diagram. Figure 25 This is a front view showing the state in which the crankshaft of the internal combustion engine of Patent Document 3 is mounted with a split-type sliding bearing on a split-type bearing housing composed of bearing housings with different rigidities. Figure 26 It is shown Figure 25 The front view of the crankshaft of the internal combustion engine with a split sliding bearing is shown in the following state: the temperature of the split housing increases due to the operation of the internal combustion engine, and the state is in the intermediate temperature range from the start-up to normal operation. Figure 27 It is shown Figure 25 The front view shown is of the crankshaft of the internal combustion engine using a split-type sliding bearing in the following state: the temperature of the housing split body has risen to the normal operating temperature due to the operation of the internal combustion engine. Figure 28 yes Figure 25 Enlarged view of step-forming part I in the diagram. Symbol Explanation 1. Bearing assembly; 10. Bearing housing (main bearing); 101 First outer shell segment, lower part of cylinder block; 102 Second outer casing segment, bearing cover; 103 bolts; The inner circumferential surface of the retaining hole for bearings 104 and 105; 106 Fastening plane (segmentation surface of split bearing housing); 2-link linkage; 21. Large end housing, bearing housing; 22. Large end housing on the side of the rod; 22B Cover side large end shell; 23, 23a bearing retaining holes; 27a Inner circumferential surface; 27b Inner circumferential surface; 3-link bearing; 31 and 32 are split bearings; 4. Main bearings; 41, 42 The semi-split bearing of Embodiment 1 of the present invention; 141, 142 Existing split bearings; The split bearings in patent documents 241 and 242; The semi-split bearings in patent documents 341 and 342; 41a Oil tank; 43. Circumferential end; 5 crank pins; 5a and 5b lubrication circuits; 5c discharge port; 6-axis journal; 6a Lubrication circuit; 6c Inlet opening; 7. Inner circumferential surface; The circumferential end face of a 76-segment bearing; 8. Outer perimeter; 91. Backside metal layer; 92 alloy layer; 93. Covering layer; 191. The back metal layer of the prior art split bearing; 192. Alloy layer of existing split bearings; 193. Covering layer of existing split bearings; The clearance between the Cr bearing and the shaft; g is a step that occurs at the joint of the outer shell due to the difference in expansion and deformation. g' is a step formed at the joint of the outer shell due to the difference in thermal expansion deformation; The step formed at the joint of the split bearing due to the difference in expansion deformation of g1a. Steps are formed at the joint of the split bearings g2a, g2b, and g2c due to the difference in thermal expansion. The step formed at the joint of the split bearings g3a and g3b due to the difference in expansion deformation and thermal expansion deformation. The step formed at the joint of the split bearings g4a and g4b due to the difference in bearing thickness. The axial length of the L1 split bearing; The thickness of the t-segment bearing; t1 is the thickness of the back metal layer of a semi-segmented bearing supported by a bearing housing divided by a low-rigidity side and a high-rigidity side. t2 is the alloy layer thickness of a semi-segmented bearing supported by a bearing housing divided by a low-rigidity side and a high-rigidity side. The thickness of the cover layer of the t3b semi-split bearing supported by a high-rigidity side-split bearing housing; The direction of rotation of the X-axis journal; The direction of rotation of the Z crank pin. Detailed Implementation

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

[0020] (First Implementation) Figure 1 The bearing assembly 1 for the crankshaft of an internal combustion engine is shown in a schematic diagram. Figure 15 The diagram shows the bearing housing viewed from the axial direction. The bearing assembly 1 includes: a journal 6 supported on the lower part of the cylinder block; a crank pin 5 integrally formed with the journal 6 and rotating around the journal 6; and a connecting rod 2 that transmits reciprocating motion from the internal combustion engine to the crank pin 5. Furthermore, the bearing assembly 1 also includes a main bearing 4 and a connecting rod bearing 3 as sliding bearings supporting the crankshaft, the main bearing 4 supporting the journal 6 for free rotation, and the connecting rod bearing 3 supporting the crank pin 5 for free rotation.

[0021] Furthermore, although the crankshaft has multiple journals 6 and multiple crank pins 5, for ease of explanation, only one journal 6 and one crank pin 5 are illustrated here. Figure 1 In the paper, regarding the positional relationship in the depth direction, the journal 6 is located on the depth side of the paper, and the crank pin 5 is located on the near front side.

[0022] The journal 6 is supported by a main bearing 4, consisting of a pair of split bearings 41 and 42, within a split bearing housing 10 of an internal combustion engine, which is formed by a lower cylinder block 101 and a bearing cap 102. Semi-cylindrical bearing retaining holes are formed in both the lower cylinder block 101 and the bearing cap 102. The split bearing 41 is inserted into the semi-cylindrical bearing retaining hole in the lower cylinder block 101, and the split bearing 42 is inserted into the semi-cylindrical bearing retaining hole in the bearing cap 102. The lower cylinder block 101 and the bearing cap 102 are then fastened together with bolts (not shown), thereby retaining the pair of split bearings 41 and 42 in the cylindrical bearing retaining holes. Figure 1 At the upper half-split bearing 41, an oil groove 41a is formed along the entire length of the inner circumference. In addition, the journal 6 has a lubrication oil passage 6a that runs through the diameter direction. If the journal 6 rotates in the direction of arrow X, the inlet openings 6c at both ends of the lubrication oil passage 6a alternately communicate with the oil groove 41a of the main bearing 4.

[0023] The crank pin 5 is supported by a connecting rod bearing 3, which consists of a pair of split bearings 31 and 32, on the large end housing 21 of the connecting rod 2. For example... Figure 2 As shown, the large end housing (bearing housing) 21 is composed of a rod-side large end housing 22A and a cap-side large end housing 22B. The rod-side large end housing 22A and the cap-side large end housing 22B each have semi-cylindrical inner circumferential surfaces 27a and 27b, respectively. When the dividing surfaces of the rod-side large end housing 22A and the cap-side large end housing 22B are aligned, the pair of inner circumferential surfaces 27a and 27b form a cylindrical bearing retaining hole 23a.

[0024] Figure 3 The outer perimeter of the pair of split bearings 41 and 42 shown is slightly larger than the inner perimeter of the bearing retaining hole 23 of the bearing housing 10. After installation, a mutual pressing pressure is generated between the outer peripheral surface 8 of the pair of split bearings 41 and 42 and the inner peripheral surface 104 and 105 of the bearing retaining hole 23, thereby fixing the pair of split bearings 41 and 42 to the bearing retaining hole 23.

[0025] A second lubrication passage 5a branches off from the first lubrication passage 6a of the journal 6 and passes through the crank arm (not shown). This second lubrication passage 5a communicates with a third lubrication passage 5b that extends through the crank pin 5 in the diametrical direction.

[0026] Therefore, as described above, the lubricating oil discharged by the oil pump passes through the oil passage formed in the cylinder wall, through the through hole formed in the wall of the main bearing 4, and is fed into the oil groove 41a formed along the inner circumferential surface of the main bearing 4, and is supplied to the gap formed between the journal 6 and the main bearing 4.

[0027] On the other hand, lubricating oil is also supplied from the outlet 5c at the end of the third lubricating oil passage 5b to the gap formed between the crank pin 5 and the connecting rod bearing 3 via the first lubricating oil passage 6a, the second lubricating oil passage 5a and the third lubricating oil passage 5b.

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

[0029] Figure 3 The diagram shows the main bearing 4, which consists of the split bearings 41 and 42 of the present invention, viewed from the axial direction, with the circumferential end faces 76 abutting each other in the non-installed state. Figure 4 Viewed from the inner circumferential side Figure 3 The diagram shows the split bearing 41. Figure 5 It is shown Figure 4 The cross-sectional view of the split bearing 41 along line AA is shown. Figure 6 Viewed from the inner circumferential side Figure 3 The diagram shows the split bearing 42. Figure 7 It is shown Figure 6 The cross-sectional view of the split bearing 42 along line BB is shown.

[0030] like Figures 3-7 As shown, the main bearing 4 in this embodiment is formed by joining the circumferential end faces 76 of a pair of semi-cylindrical bearings 41 and 42 together to form a cylindrical shape. The upper semi-cylindrical bearing 41 has a back metal layer 91 on the outer diameter side and an alloy layer 92 on the inner diameter side. Furthermore, the lower semi-cylindrical bearing 42 has a back metal layer 91 on the outer diameter side and an alloy layer 92 and a cover layer 93 on the inner diameter side. The back metal layer 91 can be made of ferroalloys such as hypoeutectoid steel or stainless steel. The alloy layer 92 can be made of copper bearing alloys, aluminum bearing alloys, etc. The cover layer 93 is formed of a resin binder and a solid lubricant. Known resins can be used as the resin binder, but polyamide-imide, polyimide, polybenzimidazole, etc., which have high heat resistance, are preferred. Alternatively, a resin composition formed by mixing a resin with high heat resistance such as polyamide-imide, polyimide, or polybenzimidazole with a resin such as polyamide, epoxy resin, or polyethersulfone can also be used as the resin binder. As a solid lubricant, molybdenum disulfide, tungsten disulfide, graphite, polytetrafluoroethylene, boron nitride, etc., can be used. The addition ratio of the solid lubricant to the resin binder is preferably 20-80% by volume. Furthermore, to improve the wear resistance of the cover layer 93, the cover layer 93 can contain hard particles such as ceramics or intermetallic compounds. Additionally, the thermal conductivity of the cover layer 93 is preferably below 3 W / m·℃. like Figure 5 , Figure 7 As shown, in the case of small internal combustion engine bearings for passenger cars, the thickness t1 of the steel back metal layer of the split 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. However, the thickness t1 of the steel back metal 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, a split-type sliding bearing device for the crankshaft of an internal combustion engine, as shown below, is provided. A split-type sliding bearing device, specifically a split-type sliding bearing device 1 for the crankshaft of an internal combustion engine, comprising: A cylindrical, segmented sliding bearing 4, comprising a first segmented bearing 41 and a second segmented bearing 42 mating together; and The split bearing housing 10 has a first housing split body 101 for mounting a first split bearing and a second housing split body 102 for mounting a second split bearing, and a bearing retaining hole 23 for retaining the split sliding bearing is formed by fastening the first housing split body and the second housing split body. The first and second split bearings each have a steel back metal layer 91 and a bearing alloy layer 92, respectively. Of the first and second split bearings, only the second split bearing also has a covering layer containing synthetic resin and solid lubricant. The rigidity of the first outer shell partition 101 is lower than that of the second outer shell partition 102. In the non-installed state where the split sliding bearing 4 is not installed in the split bearing housing 10: The first half-split bearing 41 and the second half-split bearing 42 have equal outer diameters and widths. At a symmetrical position relative to the mating plane of the first half-split bearing 41 and the second half-split bearing 42, the back metal layer 91 and the bearing alloy layer 92 of the first half-split 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-split bearing 42, respectively, and the cover layer of the second half-split bearing 42 has a thickness t3b. When the split-type sliding bearing 4 is installed on the split-type bearing housing 10 and the first housing split body 101 and the second housing split body 102 are bolted together, due to the difference in deformation between the first housing split body 102 and the second housing split body 102 caused by their different rigidity, a step g is formed radially in the bearing retaining hole 23 within the fastening plane 106 between the first housing split body 101 and the second housing split body 102. With the first half-bearing 41 and the second half-bearing 42 installed, the bolts are tightened to secure the first housing segment 101 and the second housing segment 102. The temperature of the first housing segment 101 and the second housing segment 102 rises due to the operation of the internal combustion engine. When the temperature reaches the intermediate range of 40–80°C from startup to normal operation, the thermal conductivity of the cover layer 93 is extremely low compared to the thermal conductivity of the back metal layer 91 and the bearing alloy layer 92. Therefore, the presence or absence of the cover layer 93 results in a difference in the heat storage capacity of the first half-bearing 41 and the second half-bearing 42. The temperature of the second housing segment 102 on the side of the second half-split bearing 42 with the cover layer 93 is higher than that of the first housing segment 101. Within the fastening plane 106, due to the temperature difference, a step is generated in the direction of eliminating step g caused by the difference in thermal expansion between the first housing segment 101 and the second housing segment 102. As a result, the inner peripheral surfaces 7, 7 of the first half-split bearing 41 and the second half-split bearing 42 are aligned. The step g is caused by the difference in deformation between the first housing segment 101 and the second housing segment 102 due to the difference in rigidity.

[0032] Furthermore, the heat storage capacity here refers to the tolerance to the following situation: heat from the split bearing housings 101 and 102 is transferred to the engine oil through the bearing and the alloy layer 92 or cover layer 93 on the bearing surface, thereby reducing the temperature of the bearing housing. Therefore, even if the split bearing housings 101 and 102 each receive the same amount of heat due to the operation of the internal combustion engine, the temperature of the high-rigidity side split bearing housing 102, which has relatively higher heat storage capacity, is relatively higher, and the temperature of the low-rigidity side split bearing housing 101, which has relatively lower heat storage capacity, is relatively lower. Here, we will explain the "alignment status of the inner circumferential surface". This alignment does not mean that the inner circumferential surfaces of the split bearings are geometrically identical, but rather indicates the following: For example, the difference in expansion deformation of the bearing retaining hole inner diameter at the mating end faces of the two split housings when bolting a pair of housing splits can be calculated using the "Expansion Deformation Difference Calculation Formula" shown below. For example, using the "thermal expansion calculation formula" shown below, the temperature of the high-rigidity side split bearing housing 102 on the second half-split bearing housing side, where the thermal expansion deformation of the bearing retaining hole inner diameter at the mating end face of the second half-split bearing housing split body 102 becomes equal to the thermal expansion deformation difference in the direction of eliminating the expansion deformation difference, is calculated as a target temperature in the intermediate temperature region. This intermediate temperature region is the area where the temperature of the housing split body rises due to the operation of the internal combustion engine from startup until normal operation. For example, the thickness of the cover layer 93 required for the split bearing housing 102 to reach the target temperature can be determined using the "film thickness calculation formula" shown below. By setting this value to the thickness t3b of the cover layer of the second half-bearing, the heat storage capacity of the second half-bearing is made higher than that of the first half-bearing. When it reaches a certain temperature in the intermediate temperature range from startup to normal operation, the step g1a is offset by the thermal expansion of the second bearing housing segment. Moreover, this alignment allows for errors determined by the machining precision required when manufacturing the split sliding bearing and the split bearing housing.

[0033] [Mathematical Expression 1] ΔD={ΔD(L)-ΔD(H)}×K…Mathematical Formula 1 Symbol explanation: ΔD: Difference in expansion deformation (mm) ΔD(L): Expansion deformation (mm) of the bearing retaining bore inner diameter in a low-rigidity side-split bearing housing. ΔD(L): Expansion deformation of the bearing retaining bore inner diameter in a high-rigidity side-split bearing housing (mm) K: Bolt relaxation coefficient

[0034] [Mathematical Expression 2] Symbol explanation: B B : Coefficient related to the rigidity of the semi-segmented bearing within the combined cylinder (mm) 2 / N) B H (L): Coefficient (mm) relating to the rigidity of the low-rigidity side-split bearing housing within the combined cylinder. 2 / N)σ: Interference fit (outer diameter of half-split bearing - inner diameter of bearing retaining hole) (mm)

[0035] [Mathematical Expression 3] Symbol explanation: t: Thickness of the split bearing (mm) D: Bearing retaining bore inner diameter (mm) E B Young's modulus (GPa) of a split bearing ν B Poisson's ratio of a split bearing

[0036] [Mathematical Expression 4] Symbol explanation: ν H (L): Poisson's ratio D of low-rigidity side-split bearing housing H (L): Outer diameter of the housing of a low-rigidity, side-split bearing (mm) E H (L): Young's modulus (GPa) of low-rigidity side-split bearing housing.

[0037] [Mathematical Expression 5] Symbol explanation: B H (H): Coefficient (mm) relating to the rigidity of the high-rigidity side-split bearing housing within the combined cylinder. 2 / N)

[0038] [Mathematical Expression 6] Symbol explanation: ν H (H): Poisson's ratio of the housing of a high-rigidity side-split bearing. D H (H): Outer diameter of the high-rigidity side-split bearing housing (mm) E H (H): Young's modulus (GPa) of high-rigidity side-split bearing housing.

[0039] [Mathematical Expression 7] ΔD=D×(T2-T1)×a(H)×K…Mathematical expression 7 Symbol explanation: ΔD: Difference in thermal expansion (mm) D: Bearing retaining bore inner diameter (mm) T1: Machining temperature of the bearing retaining hole for split bearing housings and reference temperature during startup (°C) T2: Target temperature (°C) of the bearing housing on the high-rigidity side required to eliminate the difference in expansion deformation due to thermal expansion. α(H): Coefficient of thermal expansion of the split bearing housing on the high-rigidity side ( / ℃) K: Bolt relaxation coefficient

[0040] [Mathematical Expression 8] Q / 1=k×A×(T2-T1) / t3b…Mathematical expression 8 Symbol explanation: Q / 1: Reference heat (J / s) per unit time required to raise the bearing assembly to its normal operating temperature. A: Sliding surface area of ​​the semi-split bearing on the rigid side (m²) 2 ) κ: Thermal conductivity of the capping layer (W / m·℃) t3b: Film thickness (m) of the resin coating on the high-rigidity side of the split bearing.

[0041] [Mathematical Expression 9] Q = Q(H) + Q(L) + Q(S)... Mathematical formula 9 Symbol explanation: Q: Reference heat (J) required to raise the bearing assembly to its normal operating temperature. Q(H): Reference heat (J) required to raise the housing of a high-rigidity split bearing to the reference temperature for normal operation. Q(L): Reference heat (J) required to raise the housing of a low-rigidity split bearing to the reference temperature for normal operation. Q(S): Reference heat (J) required to raise the journal diameter (limited to the bearing area) to the reference temperature for normal operation.

[0042] [Mathematical Expression 10] Q(H)=m(H)×c(H)×(T3-T1)… Mathematical formula 10 Symbol explanation: m(H): Mass (g) of the housing of a high-rigidity side-split bearing. c(H): Specific heat of the housing of a high-rigidity side-split bearing (J / g·℃) T3: Reference temperature during normal operation (°C)

[0043] [Mathematical Expression 11] Q(L)=m(L)×c(L)×(T3-T1)… Mathematical formula 11 Symbol explanation: m(L): Mass (g) of the housing of a low-rigidity, side-split bearing. c(L): Specific heat of the housing of a low-rigidity side-split bearing (J / g·℃)

[0044] [Mathematical Expression 12] Q(S)=m(S)×c(S)×(T3-T1)… Mathematical expression 12 Symbol explanation: m(S): Mass (g) of the journal portion limited to the bearing range. c(S): Specific heat of the journal (J / g·℃)

[0045] Figure 8This is a front view showing the state in which the split-type sliding bearing of the present invention, consisting of a pair of half-split bearings 41 and 42, is installed in the inner peripheral surfaces 104 and 105 of the bearing retaining hole of the split-type bearing housing 10 for the crankshaft of an internal combustion engine. The split-type bearing housing 10 is formed by a low-rigidity side split bearing housing 101 that forms part of an aluminum alloy engine cylinder and a high-rigidity side split bearing housing 102 that serves as a bearing cover made of iron alloy. The two housing splits 101 and 102 are integrally fastened by bolts 103. The bearing retaining hole 23 of the split-type bearing housing 10 is formed by machining a cylindrical hole with a perfectly circular cross-section in the state in which the housing splits 101 and 102 are assembled with bolts 103 without the split-type sliding bearing installed. The figure shows the following state: the split bearing housing 10, after the inner circumferential surfaces 104 and 105 of the bearing retaining holes are formed by machining as described above, is disassembled; half-split bearings 41 and 42 are installed along the inner circumferential surfaces of the housing splits 101 and 102; and the housing splits 101 and 102 are then integrally assembled again by bolts 103. In their initial state before being installed in the split bearing housing 10, the half-split bearings 41 and 42 have equal outer diameters; relative to the half-split bearing 41 on the low-rigidity side of the split bearing housing, only the half-split bearing 42 on the high-rigidity side of the split bearing housing has a cover layer.

[0046] Furthermore, when the outer casing segments 101 and 102 are integrally assembled using bolts 103, as described above, the following also applies: Figure 16 As shown, because the expansion deformation at the mating end of the low-rigidity side-split bearing housing 101 is greater than that at the mating end of the high-rigidity side-split bearing housing 102, the inner diameters of the bearing retaining holes 104 and 105 differ between the two housing splits 101 and 102. This difference may occur between the mating end faces 76 of the two half-split bearings 141 and 142. Figure 16 The steps g1a shown are as shown. However, in this embodiment, the outer diameter and width dimensions of the split bearings 41 and 42 are equal in the initial state. The back metal layer 91 and alloy layer 92 of the split bearings 41 and 42 are of equal thickness at corresponding positions in the circumferential direction (i.e., symmetrical positions about the mating plane when the first split bearing 41 and the second split bearing 42 are mated). The split bearing 41 on the low-rigidity side split bearing housing side has a covering layer only on the high-rigidity side split bearing housing side of the split bearing 42. Figure 5 , Figure 7 Therefore, the temperature of the outer casing sections 101 and 102 rises due to the operation of the internal combustion engine, especially during startup. Figure 8 When it reaches normal operation ( Figure 13 A certain temperature in the intermediate temperature range between ) Figure 11Under these conditions, the temperature of the high-rigidity side-split bearing housing 102 with the covering layer 93 is higher than the temperature of the low-rigidity side-split bearing housing 101. At the mating end faces of the pair of housing splits 101 and 102, due to the temperature difference, a step is generated in the direction that eliminates the step caused by the difference in deformation of the two housing splits due to the difference in rigidity. Thus, in this embodiment, the step g1a of the inner circumferential surfaces of the two half-split bearings 41 and 42 is canceled out, and the inner circumferential surfaces 7 of the two half-split bearings at the mating end face 76 become aligned and become Figure 12 The mating end face 76 is as shown. Furthermore, during normal operation, the temperature of the high-rigidity side-split bearing housing 102 is further higher than the temperature of the low-rigidity side-split bearing housing 101. At the mating end face of the pair of housing splits 101 and 102, due to the temperature difference, a step is further generated in the direction that eliminates the step caused by the difference in deformation of the two housing splits due to the difference in rigidity. Therefore, even if a step g2a is generated, since step g2a is smaller than the bearing clearance Cr, lubricant smearing is less likely to occur. Figure 13 , Figure 14 ).

[0047] Figure 16 This is a front view showing a conventional example where a split-type sliding bearing consisting of a pair of split bearing halves 141 and 142 is installed within the inner circumferential surfaces 104 and 105 of the bearing retaining hole of the split-type bearing housing 10 for the crankshaft of an internal combustion engine, unlike the present invention. Both the first and second split bearing halves have a cover layer. The split-type bearing housing 10 is formed by a low-rigidity side-split bearing housing 101, which forms part of an aluminum alloy engine cylinder, and a high-rigidity side-split bearing housing 102, which serves as a bearing cap made of iron alloy. The two housing halves 101 and 102 are integrally fastened by bolts 103. The bearing retaining hole 23 of the split-type bearing housing 10 is formed by machining a cylindrical hole with a perfectly circular cross-section in the state where the housing halves 101 and 102 are assembled using bolts 103 without the split-type sliding bearing installed. The figure shows the following state: the split bearing housing 10, after the inner circumferential surfaces 104 and 105 of the bearing retaining holes are formed by machining as described above, is disassembled. Half-split bearings 141 and 142 are installed along the inner circumferential surfaces of the housing splits 101 and 102, and then the housing splits 101 and 102 are reassembled into a single unit using bolts 103. In their initial state before being installed into the split bearing housing 10, the half-split bearings 141 and 142 have equal outer diameters.

[0048] Furthermore, when the outer casing segments 101 and 102 are integrally assembled using bolts 103, as described above, the following also applies: Figure 16As shown, because the expansion deformation at the mating end of the low-rigidity side-split bearing housing 101 is greater than that at the mating end of the high-rigidity side-split bearing housing 102, the inner diameter of the bearing retaining hole 23 differs between the two housing splits 101 and 102. This may result in a gap between the mating end faces 76 of the two half-split bearings 141 and 142. Figure 16 The steps g1a shown are as shown. However, if the outer diameter and width dimensions of the split bearings 141 and 142 are equal in their initial state, and the thicknesses of the corresponding circumferential positions of the back metal layer 191 and alloy layer 192 of the split bearings 141 and 142 are equal, and both the split bearing 141 on the low-rigidity side of the split bearing housing and the split bearing 142 on the high-rigidity side of the split bearing housing have a cover layer 193, then the temperature of the housing split bodies 101 and 102 will rise due to the operation of the internal combustion engine, starting from the start ( Figure 16 When it reaches normal operation ( Figure 18 The intermediate temperature range between ( ) Figure 17 Under these conditions, the temperature of the high-rigidity side-split bearing housing 102 is equal to the temperature of the low-rigidity side-split bearing housing 101. At the mating end faces of the pair of housing split bodies 101 and 102, due to the difference in thermal expansion coefficients, a step is formed in the same direction as the step g1a caused by the difference in deformation of the two housing split bodies due to their different rigidity. Thus, a step g3a is formed on the inner circumferential surfaces of the two split bearings 141 and 142. Furthermore, during normal operation, due to the difference in thermal expansion coefficients, step g3a further expands (see reference...). Figure 19 Because of the larger step g3b compared to the bearing clearance Cr, lubricant smudging may occur at the mating end faces 76 of the two split bearings 141 and 142. Figure 20 ).

[0049] Figure 21This is a front view showing a split-type sliding bearing consisting of a pair of split bearings 241, 242 installed in the inner peripheral surfaces 104, 105 of the bearing retaining hole of the split-type bearing housing 10 for the crankshaft of an internal combustion engine, unlike the present invention but as taught in Patent Document 2. When the pair of split bearings 241, 242 are assembled into a pair of housing segments of the split-type bearing housing with a difference in rigidity, a difference in bearing thickness is set at the mating end faces of the split bearings. The split-type bearing housing 10 is formed by a low-rigidity side split bearing housing 101 that forms part of an aluminum alloy engine cylinder and a high-rigidity side split bearing housing 102 that serves as a bearing cap made of iron alloy. The two housing segments 101, 102 are integrally fastened by bolts 103. The bearing retaining hole 23 of the split bearing housing 10 is formed by machining a cylindrical hole with a perfectly circular cross-section, in the state where the housing segments 101 and 102 are assembled with bolts 103 without the split sliding bearings installed. The figure shows the following state: the split bearing housing 10, after the bearing retaining hole 23 has been machined as described above, is disassembled, and the half-split bearings 241 and 242 are installed along the inner circumferential surfaces of the housing segments 101 and 102. The housing segments 101 and 102 are then reassembled into a single unit using bolts 103. The half-split bearings 241 and 242 have equal outer diameters in their initial state before being installed in the split bearing housing 10.

[0050] Furthermore, when the outer casing segments 101 and 102 are integrally assembled using bolts 103, as described above, the following also applies: Figure 16 As shown, because the expansion deformation at the mating end of the low-rigidity side-split bearing housing 101 is greater than that at the mating end of the high-rigidity side-split bearing housing 102, the inner diameter of the bearing retaining hole 12 is different between the two housing splits 101 and 102. This may result in a step g1a between the mating end faces 76 of the two half-split bearings 141 and 142. However, regarding the step on the split bearing housing with different rigidities, by setting the difference in bearing thickness at the mating end face of the half-split bearing when assembling a pair of half-split bearings onto a pair of housing splits with different rigidities, the difference in rigidity of the split bearing housing can offset the step g1a generated on the inner circumferential surface of the bearing. Figure 21 ). However, the outer diameter and width of the split bearings 241 and 242 are equal in their initial state. The temperature of the split housings 101 and 102 rises due to the operation of the internal combustion engine, starting from startup ( Figure 21 When it reaches normal operation ( Figure 23 The intermediate temperature range between ( ) Figure 22Under these conditions, the temperature of the high-rigidity side-split bearing housing 102 is equal to the temperature of the low-rigidity side-split bearing housing 101. At the mating end faces of the pair of housing splits 101 and 102, due to the difference in their coefficients of thermal expansion, a step is generated caused by the difference in the thermal expansion of the two housing splits, resulting in a step g2b on the inner circumferential surfaces of the two half-split bearings 241 and 242. Furthermore, during normal operation, due to the difference in thermal expansion coefficients, the step g2b further expands (see reference...). Figure 24 Because of the step g2c, compared with the bearing clearance Cr, the step g2c is larger, and the lubricating oil may be wiped at the mating end face 76 of the two half-split bearings 241 and 242.

[0051] Figure 25 This is a front view showing a split-type sliding bearing consisting of a pair of split bearings 341, 342 installed in the bearing retaining hole 23 of the split-type bearing housing 10 for the crankshaft of an internal combustion engine, unlike the present invention and as taught in Patent Document 3. When the pair of split bearings 341, 342 are assembled into a pair of housing segments of the split-type bearing housing with a difference in their coefficients of thermal expansion, a difference in bearing thickness is set at the mating end faces of the split bearings. The split-type bearing housing 10 is formed by a low-rigidity side split bearing housing 101, which forms part of an aluminum alloy engine cylinder, and a high-rigidity side split bearing housing 102, which serves as a bearing cap made of iron alloy. The two housing segments 101, 102 are integrally fastened by bolts 103. The bearing retaining hole 23 of the split-type bearing housing 10 is formed by machining a cylindrical hole with a perfectly circular cross-section in the state where the housing segments 101, 102 are assembled using bolts 103 without the split-type sliding bearing installed. The figure shows the following state: the split bearing housing 10, after being machined to form the bearing retaining hole 23 as described above, is disassembled. Half-split bearings 341 and 342 are installed along the inner circumferential surfaces of the housing split bodies 101 and 102. The housing split bodies 101 and 102 are then reassembled into a single unit using bolts 103. In their initial state before being installed into the split bearing housing 10, the half-split bearings 341 and 342 have equal outer diameters.

[0052] Here, when the temperature of the split bearing housing rises due to the operation of the internal combustion engine and reaches normal operating temperature, as described above, it is also as follows: Figure 18 As shown, because the thermal expansion deformation at the mating end of the low-rigidity side-split bearing housing 101 is greater than that at the mating end of the high-rigidity side-split bearing housing 102, the inner diameter of the bearing retaining hole 12 differs between the two housing splits 101 and 102. This may result in a difference between the mating end faces 76 of the two half-split bearings 141 and 142. Figure 18 The steps g3b shown are as shown. However, when the temperature of the split bearing housing rises due to the operation of the internal combustion engine and reaches normal operating temperature, a difference in bearing thickness at the mating end face of the split bearing is set, thereby offsetting the step g3b generated on the inner circumferential surface of the bearing by the difference in thermal expansion of the split bearing housing. Figure 27 ). On the other hand, the outer diameter and width dimensions of the semi-split bearings 341 and 342 are equal in their initial state. The temperature of the housing split bodies 101 and 102 rises due to the operation of the internal combustion engine, starting from startup ( Figure 25 When it reaches normal operation ( Figure 27 The intermediate temperature range between ( ) Figure 26 At the mating end faces of a pair of housing segments 101 and 102, due to the difference in their coefficients of thermal expansion, a difference arises between the step caused by the difference in the thermal expansion of the two housing segments and the step caused by the difference in bearing thickness, thus creating a step g4a on the inner circumferential surfaces of the two semi-segmented bearings 341 and 342. Furthermore, during startup, due to the difference in their coefficients of thermal expansion, the difference between the step caused by the difference in the thermal expansion of the two housing segments and the step caused by the difference in bearing thickness widens (see reference). Figure 25 Because of the step g4b), at the mating end face 76 of the two split bearings 341 and 342, the step g4b is larger than the bearing clearance Cr, which may cause the lubricating oil to wipe.

[0053] The bearing retainer bore inner diameter D (mm) is the dimension of the bearing retainer bore in a split bearing housing at the machining temperature T1 (°C). Bearing retainer bore machining is typically performed within the room temperature range (20–25°C). Furthermore, in the case of a typical passenger vehicle internal combustion engine, the starting temperature is approximately 20–25°C, and the normal operating temperature is approximately 120°C. Therefore, the temperature range in the intermediate temperature zone represents the range exceeding the starting temperature but below the normal operating temperature. In Embodiment 1, the target temperature T2 (°C) of the high-rigidity side-segment bearing housing that matches the intermediate temperature range of the internal combustion engine varies depending on the specifications of the internal combustion engine. However, in the case of a typical passenger car internal combustion engine, it is set to a range slightly lower than the midpoint between the starting temperature and the normal operating temperature, i.e., about 40 to 80°C. The reason is that in the region of lower temperature of the housing segments 101 and 102 starting from the start, the thermal expansion of the housing segments 101 and 102 is smaller. Therefore, the bearing clearance Cr between the inner circumferential surface of the crankshaft sliding bearing and the surface of the crankshaft becomes smaller. Since the flow of lubricating oil is easily affected by the step, swiping is likely to occur. Therefore, in the temperature range from the start to the normal operating temperature, the step is mitigated preferentially in the region of lower temperature. The thickness of the cover layer is roughly determined based on the materials of the low-rigidity and high-rigidity split bearing housings, as well as the wall thickness, outer diameter, and width specifications of the split bearing. For example, in a combination of split bearing housings made of aluminum alloy and iron alloy, with a split bearing wall thickness of 1.5–2.0 mm, an outer diameter of 30–100 mm, and a width of 10–40 mm, the cover layer thickness ranges from 2 μm to 12 μm. Furthermore, the split bearing housings 101 and 102, with relatively different coefficients of thermal expansion, are fastened by bolts 103. This generates compressive stress in the mating end faces 76 of the split bearing housings 101 and 102 in a direction perpendicular to the mating end faces. The mating end face 76 of the split bearing housing 101, with a relatively lower coefficient of thermal expansion, becomes a resistance to the thermal expansion deformation of the mating end face 76 of the split bearing housing 102, with a relatively higher coefficient of thermal expansion. If it is a combination of split bearing housings made of aluminum alloy and iron alloy with relatively different coefficients of thermal expansion, the difference in thermal expansion deformation of the bearing retaining hole inner diameter at the split surface of the split bearing housing is mitigated to about one-third of the difference in thermal expansion deformation when the split bearing housings are thermally expanded in a free state (the mitigation coefficient for thermal expansion deformation K = 1 / 3).

[0054] In practice, to align the inner circumferential surfaces of the two split bearings 41 and 42 at a certain temperature within the intermediate temperature range as described above, actual split bearing housings 101 and 102 (cylinder and bearing cap) are used, or a model of only the split bearing housing portion is made, imitating the actual housing. With a pair of split bearings 141 and 142 of the same shape and size installed in the bearing retaining holes 104 and 105 of the split bearing housing, and the two split bearings fastened with bolts 103, the step size of the inner diameter at the mating end face of the pair of split bearings is measured using a roundness measuring machine or similar measuring machine, and the step g1a caused by the rigidity difference is determined. In addition, with a pair of half-split bearings 141 and 142 of the same shape and size installed in the bearing retaining holes of the split bearing housings 101 and 102, and the two housing splits fastened by bolts 103, the high-rigidity side split bearing housing is heated to the temperature of the intermediate temperature range between the start-up of the internal combustion engine and normal operation. The step size of the inner diameter at the mating end face of the pair of half-split bearings is measured using a roundness measuring machine or similar measuring machine, and the temperature difference of the split bearing housings 101 and 102 with the step being mitigated is calculated. In addition, by assembling split-type bearing housings 101 and 102 with half-split bearings 41 and 42 that differ in whether they have a cover layer or not, a test is conducted using a test machine that imitates the actual machine. The temperature on the back of the bearing is measured in the intermediate temperature range between startup and normal operation, and the thickness of the cover layer that produces the temperature difference between the first half-split bearing and the second half-split bearing is determined. These measurements can be used to set the thickness t3b of the cover layer of the semi-split bearing, which should be installed in a relatively high-rigidity side-split bearing housing, to a dimensional value actually measured using a physical object or model.

[0055] Alternatively, the thickness t3b of the cover layer of the half-split bearing to be installed in the high-rigidity side-split bearing housing can be simply set to the thickness of the cover layer 93 calculated based on formulas 1 to 12. In this case, in the calculation of the housing mass, it can be assumed that the outer diameter of the housing is 1.5 times the inner diameter D of the bearing retaining hole, and that the width of the housing is equal to the width L1 of the bearing. Furthermore, in the calculation of the shaft mass, it can also be assumed that the width of the shaft is equal to the width L1 of the bearing.

[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 while a half-segment bearing (Young's modulus 205.9 GPa, Poisson's ratio 0.33, alloy thickness 0.3 mm, back metal thickness 1.7 mm) is installed, and a half-segment bearing housing (Young's modulus 205.9 GPa, Poisson's ratio 0.33, alloy thickness 0.3 mm, back metal thickness 1.7 mm) is installed, the difference in expansion deformation is calculated according to mathematical formulas 1 to 6, assuming a bearing retaining hole size of 50 mm, an interference fit of 0.1 mm, and a relaxation coefficient of 1 / 3. B B =((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))=0.064mm 2 / N B H (L)=((1-0.33)+(1+0.33)×(50mm×1.5 / 50mm)^2) / (74.5GPa ×((50mm×1.5 / 50mm)^2-1))=0.039mm 2 / N B H (H)=((1-0.3)+(1+0.3)×(50mm×1.5 / 50mm)^2) / (205.9GPa ×((50mm×1.5 / 50mm)^2-1))=0.014mm 2 / N ΔD(L)=0.039mm 2 / N / (0.064mm 2 / N+0.0039mm 2 / N)×0.1mm=0.038mm ΔD(H)=0.014mm 2 / N / (0.064mm 2 / N+0.014mm 2 / N)×0.1mm=0.018mm The difference in expansion deformation is calculated as (0.038mm - 0.018mm) × 1 / 3 = 0.007mm. The target temperature T2 of the high-rigidity side-split bearing housing required to eliminate the difference in expansion deformation through thermal expansion is calculated based on the following conditions: the coefficient of thermal expansion of the iron alloy housing split body is 1.2 × 10⁻⁵ / ℃, and the starting temperature is 20℃. According to mathematical formula 7: The result is T2 = (0.007mm / 1000 + 50mm / 1000 × 20℃ × 1.2 × 10^-5 × 1 / 3) / (50mm / 1000 × 1.2 × 10^-5 / ℃ × 1 / 3) = 55℃. The reference temperature during normal operation is 120℃, the journal diameter is 46mm, the width of the split bearing is 16mm, the thermal conductivity of the cover layer is 2.4 (W / m·℃), the specific heat of the iron alloy housing split and journal is 461 (J / kg·℃), and the density is 7.874 (g / cm³). 3 The aluminum alloy shell segment has a specific heat of 900 (J / kg·℃) and a density of 2.7 (g / cm³). 3 In the case of ), the thickness t3b of the cover layer 93 of the half-split bearing required to generate the target temperature T2 of the high-rigidity side-split bearing housing is determined according to mathematical formulas 8-12: 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 / cm 3 ) / 1000×900J / kg·℃×(120℃-20℃)=4771J Q(S)=((46mm / 2)^2×π×16mm) / 1000×7.874g / cm 3 ) / 1000×461J / kg ·℃×(120℃-20℃)=9652J Q=7127J+4771J+9652J=21151J It becomes t3b-t3a=2.4W / m·℃×(50mm×π / 2×16mm) / 1000000×(55℃-20℃) / (21151J / 1s)=0.005mm. The thickness t3b of the cover layer of the half-split bearing installed on the relatively high-rigidity side of the housing split 102 is set to 0.005 mm. As a result, the heat storage capacity of the high-rigidity side split bearing housing 102 is greater than that of the low-rigidity side split bearing housing 101. Therefore, when the temperature of the housing split rises due to the operation of the internal combustion engine, the temperature of the high-rigidity side split bearing housing 102 is greater than that of the low-rigidity side split bearing housing 101. Consequently, the thermal expansion of the high-rigidity side split bearing housing 102 is greater than that of the low-rigidity side split bearing housing 101. During startup, the step g1a generated between the mating end faces 76 of the two half-split bearings 41 and 42 due to the difference in rigidity of the housing split is offset by the thermal expansion of the high-rigidity side split bearing housing 102 at a certain temperature in the intermediate temperature range from startup to normal operation, thus achieving alignment. Therefore, during normal operation, the temperature of the high-rigidity side-split bearing housing 102 is further higher than that of the low-rigidity side-split bearing housing 101, thereby further eliminating the difference in thermal expansion caused by the difference in the thermal expansion coefficients of the split bearing housings. Thus, even if a step g2a is generated, since the step g2a is smaller than the bearing clearance Cr, the lubricating oil smudging phenomenon is less likely to occur. Figure 13 , Figure 14 ).

[0057] In this embodiment, the thickness t1 of the steel back metal of the first half-split bearing 41 and the second half-split bearing 42, the thickness t2 of the bearing alloy layer, and the thickness t3b of the cover layer of the second half-split bearing 42 are constant in the circumferential and axial directions (width direction) of the half-split bearings. However, it is not limited to this; the thickness t2 of the bearing alloy layer may be the largest at the circumferential center of the first half-split bearing and the second half-split bearing of the half-split bearings 41 and 42, and continuously decrease towards the two circumferential ends (therefore, the thickness t of the half-split bearing is the largest at the circumferential center and continuously decreases towards the two circumferential ends).

[0058] Additionally, the embodiment applies to split-type bearing housings for crankshafts, but not to the case of bearing housing 21 for connecting rod shafts ( Figure 2Based on the different housing shapes, the split bearing housing 22B is a low-rigidity side-split bearing housing for assembling the first half-split bearing, and the split bearing housing 22A is a high-rigidity side-split bearing housing for assembling the second half-split bearing, thus making this application applicable. At this time, considering the difference in rigidity caused by the shape, B can also be simply... H (L) multiplied by the mitigation factor K = 1 / 3.

Claims

1. A split-type sliding bearing device, which is a split-type sliding bearing device for the crankshaft of an internal combustion engine, comprising: A cylindrical, segmented sliding bearing, comprising a first segmented bearing and a second segmented bearing mating with each other; and A split bearing housing has a first housing segment for mounting a first split bearing and a second housing segment for mounting a second split bearing, and a bearing retaining hole for retaining the split sliding bearing is formed by fastening the first housing segment and the second housing segment. The first and second split bearings each have a steel back metal layer and a bearing alloy layer, respectively. Of the first and second split bearings, only the second split bearing also has a covering layer containing synthetic resin and solid lubricant. The rigidity of the first housing segment is lower than that of the second housing segment. In the non-installed state, where the split sliding bearing is not mounted on the split bearing housing: The first and second split bearings have equal outer diameters and widths. At a symmetrical position symmetrical about the mating plane when the first and second split bearings are mated, the back metal layer and the bearing alloy layer of the first split bearing have the same thickness as the back metal layer and the bearing alloy layer of the second split bearing. When the split sliding bearing is installed on the split bearing housing and the first and second housing split bodies are bolted together, the difference in deformation between the first and second housing split bodies due to their different rigidity causes a step to form radially in the bearing retaining hole within the fastening plane between the first and second housing split bodies. During the period from the start-up of the internal combustion engine to normal operation, when the first housing segment and the second housing segment are in the intermediate temperature range, i.e., 40 to 80°C, the temperature of the second housing segment on the bearing side of the second half of the housing with the cover layer is higher than that of the back metal layer and the bearing alloy layer because the thermal conductivity of the cover layer is lower than that of the back metal layer and the bearing alloy layer. As a result, the first housing segment and the second housing segment deform in a way that eliminates the step in the fastening plane due to the difference in thermal expansion caused by the temperature difference.

2. The segmented sliding bearing device according to claim 1, characterized in that, The thickness of the cover layer of the second half-split bearing is in the range of 2μm to 12μm.

3. The segmented sliding bearing device according to claim 1, characterized in that, The thermal conductivity of the covering layer is below 3 W / m·℃.

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