Half thrust bearing and bearing arrangement for an internal combustion engine crankshaft

Abstract

To provide a half-split thrust bearing for a crankshaft of an internal combustion engine in which the accumulation and seizure of foreign matters hardly occur at an operation.SOLUTION: A half-split thrust bearing according to this invention is formed of an Fe-alloy back metal layer and a bearing alloy layer, and has a slide face and two thrust reliefs. Each of thrust relief faces has a first region 821 at an end face side in a peripheral direction in which the back metal layer is exposed, a second region 822 in which the bearing alloy layer is exposed, and a third region 823. The slide face has a fourth region 812. An end part region 800 in the peripheral direction composed of the first region and the second region is defined. The bearing alloy layer of the second region has a thickness-equalized part which is constant in a thickness of the bearing alloy layer, and a thickness-reduced part adjoining an inside-diameter side end face, and thinner than the thickness-equalized part in a thickness of the bearing alloy layer at its cross section, and each of the bearing alloy layers of the third region and the fourth region has a thickness-equalized part which is constant in the thickness of the bearing alloy layer, and a thickness-increased part or a thickness-equalized part adjoining the inside-diameter side end face, and thicker than the thickness-equalized part in the thickness of the bearing alloy part at its cross section.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a half thrust bearing that receives axial force from a crankshaft of an internal combustion engine. [Background technology]

[0002] The crankshaft of the internal combustion engine is rotatably supported at its journal portion on a lower portion of a cylinder block of the internal combustion engine via a main bearing configured by combining a pair of half bearings into a cylindrical shape.

[0003] One or both of the pair of half bearings are used in combination with a half thrust bearing that receives the axial force of the crankshaft. The half thrust bearing is disposed on one or both of the axial end faces of the half bearing.

[0004] The half thrust bearing receives the axial force generated in the crankshaft. That is, the half thrust bearing is disposed for the purpose of supporting the axial force input to the crankshaft when the crankshaft and the transmission are connected by the clutch.

[0005] A thrust relief is formed on the sliding surface side near both circumferential ends of the half thrust bearing so that the thickness of the bearing member becomes thinner toward the circumferential end faces. In general, thrust reliefs are formed so that the length from the circumferential end face of the half thrust bearing to the sliding surface and the depth at the circumferential end face are constant regardless of the radial position. The thrust relief is formed to absorb misalignment between the end faces of a pair of half thrust bearings when the half thrust bearings are assembled into a split bearing housing (see FIG. 10 of Patent Document 1).

[0006] The crankshaft of the internal combustion engine is supported at its journal portion on the lower part of the cylinder block of the internal combustion engine via a main bearing consisting of a pair of half bearings. At this time, lubricating oil is fed from an oil gallery in the cylinder block wall through a through hole in the wall of the main bearing into a lubricating oil groove formed along the inner peripheral surface of the main bearing. The lubricating oil is thus supplied into the lubricating oil groove of the main bearing, and then supplied to the half thrust bearing. In addition, a laminated structure in which a sliding layer made of a bearing alloy such as an aluminum bearing alloy or a copper bearing alloy is formed on one surface of a backing metal layer made of an Fe alloy is generally used for a thrust bearing that receives the axial force of the crankshaft of the internal combustion engine. In a conventional half thrust bearing, the thickness of the sliding layer and the thickness of the backing metal layer are set to be constant in the radial direction.

[0007] In a conventional half thrust bearing (having a backing layer and a sliding layer), when an axial force from the crankshaft is input to the sliding surface of the half thrust bearing, the inner diameter side edge of the half thrust bearing adjacent to the thrust relief of the sliding surface of the half thrust bearing may come into local contact (one-sided contact) with the thrust collar surface of the crankshaft. In order to prevent fatigue or seizure of the sliding layer near the local contact area in this case, there has been a proposal to continuously cover the surface and side of the backing layer at least at the inner diameter side edge of the sliding layer of the thrust bearing, provide an arc-shaped part in the continuous part, and form a thin-walled part at least at the inner diameter side edge of the backing layer so that the thickness of this edge part is thinner than the thickness of the radial center part, and make the sliding layer thicker at the thin-walled part than the radial center part (see Fig. 4 of Patent Document 2). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-201145 [Patent Document 2] JP 2014-177968 A Summary of the Invention [Problem to be solved by the invention]

[0009] The oil supplied to the sliding surface of the half thrust bearing is mainly leaked from the crush relief gap (the gap between the crush relief surface and the surface of the journal part of the crankshaft) of the main bearing (a pair of half bearings). The half thrust bearing is designed so that the oil leaking from this crush relief gap flows onto the inner diameter side end face of the thrust relief and the sliding surface part adjacent to the thrust relief, and is then sent to the sliding surface side. If foreign matter is mixed in the oil supplied to the main bearing, the foreign matter will be discharged together with the oil mainly through the crush relief gap, and therefore will likely be sent to the inner diameter side end face of the thrust relief of the half thrust bearing and the portion of the sliding surface adjacent to the thrust relief. The sliding layer (bearing alloy) of a half thrust bearing generally has the ability to embed and contain foreign matter that gets mixed in. In conventional thrust bearings, a large amount of foreign matter was likely to be embedded and accumulated on the surface of the sliding layer (bearing alloy) exposed at the inner diameter side end face of the thrust relief and the portion of the sliding surface adjacent to the thrust relief. Furthermore, as described above, when the inner diameter edge portion of the sliding surface portion adjacent to the thrust relief of the half thrust bearing comes into localized contact (one-sided contact) with the thrust collar surface of the crankshaft, a large amount of foreign matter that has accumulated on the surface of the sliding layer (bearing alloy) exposed at the inner diameter end face of the sliding layer (bearing alloy) simultaneously falls off and is sent to the surface of the thrust relief and the portion of the sliding surface adjacent to the thrust relief, making it easy for seizure to occur on these surfaces.

[0010] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a half thrust bearing for a crankshaft of an internal combustion engine, and a bearing device which are less susceptible to localized accumulation of foreign matter during operation and which are less susceptible to seizure. [Means for solving the problem]

[0011] In order to achieve the above object, according to one aspect of the present invention, there is provided a semi-annular half thrust bearing for receiving an axial force of a crankshaft of an internal combustion engine, comprising: The half thrust bearing has a back metal layer made of an Fe alloy and a bearing alloy layer provided on a surface of the back metal layer, the bearing alloy layer forming a sliding surface that receives an axial force, and the back metal layer forming a back surface parallel to the sliding surface, the half thrust bearing has two thrust reliefs formed adjacent to both circumferential end faces thereof, each thrust relief having a flat thrust relief surface extending between the sliding surface and the circumferential end face, whereby at the thrust relief, the wall thickness of the half thrust bearing becomes thinner from the sliding surface side toward the circumferential end face side; Each thrust relief surface has a first region on a circumferential end side, the first region being a surface where the back metal layer is exposed, and a second region and a third region being a surface where the bearing alloy layer is exposed, the second region being adjacent to the first region and the third region being adjacent to the sliding surface, and the sliding surface has a fourth region between the two third regions, thereby defining a circumferential end region consisting of the first region and the second region; a circumferential end region length (L) from the dividing plane (HP) of the half thrust bearing to the boundary between the second region and the third region, measured perpendicularly to the dividing plane, is constant between the inner diameter side end face and the outer diameter side end face of the half thrust bearing, and corresponds to a circumferential angle (θ1) of at least 10° and at most 35° from the dividing plane toward the circumferential center of the half thrust bearing at the inner diameter side end face, the bearing alloy layer in the second region has a constant thickness portion in which the thickness of the bearing alloy layer is constant in an area including the radial center of the half thrust bearing in any cross section parallel to the dividing plane, and has a reduced thickness portion in an area adjacent to the inner diameter side end face in which the thickness of the bearing alloy layer is smaller than that of the constant thickness portion; the bearing alloy layer in the third region has a constant thickness portion in which the thickness of the bearing alloy layer is constant in an area including the radial center of the half thrust bearing in any cross section parallel to the dividing plane, and has an increased thickness portion or a constant thickness portion in which the thickness of the bearing alloy layer is greater than the constant thickness portion in an area adjacent to the inner diameter side end face, A half thrust bearing is provided in which the bearing alloy layer in the fourth region has a constant thickness portion in which the thickness of the bearing alloy layer is constant in an area including the radial center of the half thrust bearing in any radial cross section including the axis of the half thrust bearing, and has an increased thickness portion or constant thickness portion in which the thickness of the bearing alloy layer is greater than the constant thickness portion in an area adjacent to the inner diameter end face.

[0012] In one embodiment of the half thrust bearing of the present invention, the bearing alloy layer in the second and third regions may further have an increased thickness portion adjacent to the outer diameter end face in any cross section parallel to the dividing plane, in which the thickness of the bearing alloy layer is greater than that of the constant thickness portion.

[0013] In one embodiment of the half thrust bearing of the present invention, the third region length (L3) from the boundary between the second region and the third region to the third region and the fourth region, measured perpendicular to the dividing plane, may be 5 to 25% of the thrust relief length (LT) from the dividing plane to the boundary between the third region and the fourth region at the inner diameter end face.

[0014] In one embodiment of the half thrust bearing of the present invention, the second region length (L2) from the boundary between the first region and the second region to the boundary between the second region and the third region, measured perpendicular to the dividing plane, may be 10 to 40% of the thrust relief length (LT) from the dividing plane to the boundary between the third region and the fourth region at the inner diameter end face.

[0015] In one embodiment of the half thrust bearing of the present invention, the bearing alloy layer in the fourth region may further have an increased thickness portion in which the thickness of the bearing alloy layer is greater than the uniform thickness portion in an area adjacent to the outer diameter side end face in any radial cross section including the axis of the half thrust bearing.

[0016] In one embodiment of the half thrust bearing of the present invention, the center of curvature of the inner diameter side end face of the circumferential end region may be at a position different from the center of curvature of the inner diameter side end face of the fourth region.

[0017] According to another aspect of the present invention, A crankshaft, A pair of half bearings supporting journal portions of a crankshaft, each half bearing having two crush reliefs formed on an inner peripheral surface side adjacent to both circumferential end faces of the half bearing; a bearing housing having a retaining hole formed therethrough for retaining a pair of half bearings; The half thrust bearing according to one aspect of the present invention described above includes at least one semi-annular half thrust bearing disposed on an axial end surface of the bearing housing adjacent to a retaining hole for receiving an axial force of a crankshaft; A bearing device for a crankshaft of an internal combustion engine, comprising: A bearing device is provided in which a circumferential end region length (L) is greater than a crush relief length of the crush relief at an axial end of the half bearing.

[0018] In one embodiment of the bearing device of the present invention, the circumferential end region length (L) of the inner diameter side end face of the half thrust bearing may be 1.5 times or more the crush relief length at the axial end of the half bearing. Effect of the Invention

[0019] The half thrust bearing and the bearing device for the crankshaft of the present invention receive the axial force of the crankshaft of the internal combustion engine. As described above, in the half thrust bearing for the crankshaft, lubricating oil containing foreign matter is supplied to the inner diameter side end face of the thrust relief surface. However, according to the present invention, the bearing alloy layer in the second region of the thrust relief surface has a constant thickness part in which the thickness of the bearing alloy layer is constant in a range including the radial center of the half thrust bearing in any cross section parallel to the dividing plane of the half thrust bearing, and has a reduced thickness part in which the thickness of the bearing alloy layer is smaller than the constant thickness part in a range adjacent to the inner diameter side end face of the half thrust bearing, so that the proportion of the bearing alloy layer exposed on the inner diameter side end face of the second region is small. Therefore, a large amount of foreign matter is unlikely to accumulate on the surface of the bearing alloy layer at the inner diameter side end face of the second region where lubricating oil containing foreign matter is supplied, and at the same time, a large amount of foreign matter is not dropped off and sent to the thrust relief surface, so that seizure is unlikely to occur. [Brief description of the drawings]

[0020] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. 2 is an axial cross-sectional view of the bearing device. [Figure 4] FIG. [Diagram 5] 5 is a bottom view of the half bearing shown in FIG. 4, as viewed from the radially inner side. [Figure 6] FIG. 2 is a front view of the half thrust bearing of the first embodiment. [Figure 7] FIG. 2 is an enlarged front view of the vicinity of a circumferential end of the half thrust bearing of the first embodiment. [Figure 8] 8 is an enlarged side view of the vicinity of a circumferential end of the half thrust bearing of the first embodiment, as viewed from the inside (as viewed in the direction of the Y1 arrow in FIG. 7). [Figure 9] This is a cross-sectional view taken along line AA in FIG. [Figure 10] This is a cross-sectional view taken along line B-B in FIG. [Figure 11] This is a cross-sectional view taken along line CC in FIG. [Figure 12A] FIG. 4 is a front view of a half bearing and a half thrust bearing for explaining the operation of the embodiment. [Figure 12B] 12B is a diagram showing the inner surface of the half bearing and the thrust bearing of FIG. 12A as viewed from the radially inner side. FIG. [Figure 13] FIG. 11 is an enlarged front view of the vicinity of a circumferential end of a half thrust bearing of a second embodiment. [Figure 14] This is a cross-sectional view taken along line A1-A1 of FIG. [Figure 15] This is a cross-sectional view taken along line B1-B1 of FIG. [Figure 16] This is a cross-sectional view taken along line C1-C1 of FIG. [Figure 17] FIG. 11 is a front view of a half thrust bearing according to a third embodiment. [Figure 18] FIG. 11 is a front view of a half thrust bearing according to another embodiment. [Figure 19] FIG. 11 is a side view of the vicinity of a circumferential end of a half thrust bearing according to another embodiment. [Figure 20] FIG. 11 is a side view of the vicinity of a circumferential end of a half thrust bearing according to another embodiment. [Figure 21] FIG. 11 is a front view of the vicinity of a circumferential end of a half thrust bearing according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0022] (Overall configuration of bearing device) First, the overall configuration of a bearing device 1 according to a first embodiment of the present invention will be described with reference to Figures 1 to 3. As shown in Figures 1 to 3, a bearing housing 4 formed by attaching a bearing cap 3 to the lower part of a cylinder block 2 is formed with a bearing hole (retaining hole) 5 which is a circular hole penetrating between both side surfaces, and annular recessed seats 6, 6 are formed around the periphery of the bearing hole 5 on the side surface. Half bearings 7, 7 which rotatably support a journal portion 11 of the crankshaft are assembled and fitted in a cylindrical shape into the bearing hole 5. Half thrust bearings 8, 8 which receive an axial force f (see Figure 3) via a thrust collar 12 of the crankshaft are assembled and fitted in a circular shape into the seats 6, 6.

[0023] 2 to 5, of the half bearings 7 constituting the main bearing, a lubricating oil groove 71 is formed in the inner circumferential surface of the half bearing 7 on the cylinder block 2 side (upper side), and a through hole 72 penetrating the outer circumferential surface is formed in the lubricating oil groove 71. Note that the lubricating oil groove 71 can also be formed in both the upper and lower half bearings.

[0024] Furthermore, crush reliefs 73, 73 are formed on both circumferential ends of the half bearing 7 adjacent to the abutment surfaces between the half bearings 7. The crush reliefs 73 are wall-thickness reducing regions formed so that the wall thickness of the region adjacent to the circumferential end faces of the half bearing 7 gradually becomes thinner toward the circumferential end faces. The crush reliefs 73 are formed with the intention of absorbing misalignment and deformation of the abutting surfaces when the pair of half bearings 7, 7 are assembled.

[0025] (Configuration of half thrust bearing) Next, the configuration of the half thrust bearing 8 of the first embodiment will be described with reference to FIGS. 2, the half thrust bearing 8 of this embodiment has a sliding surface 81 (bearing surface) that extends over a range including the circumferential center and receives an axial force f, and two thrust reliefs 82, 82 formed in areas adjacent to both circumferential end faces 83, 83, and the thrust relief 82 has a flat thrust relief surface (flat surface) 82S. Two oil grooves 81a, 81a are formed in the sliding surface 81 between the thrust reliefs 82, 82 on both sides in order to improve the oil retention of the lubricating oil.

[0026] The thrust relief 82 is a wall thickness reducing region formed over the entire radial length of the half thrust bearing 8 in an area on the sliding surface 81 side adjacent to both circumferential end faces 83 so that the wall thickness of the half thrust bearing 8 gradually becomes thinner toward the circumferential end faces 83 (see also FIG. 8 ). The thrust relief 82 is formed to reduce misalignment between the circumferential end faces 83, 83 of the pair of half thrust bearings 8, 8 that may occur when the half thrust bearing 8 is assembled into the split bearing housing 4.

[0027] As shown in FIGS. 6 and 7, the thrust relief 82 of this embodiment has a thrust relief length LT that is constant between the inner diameter side end face 8i and the outer diameter side end face 8o of the half thrust bearing 8. The thrust relief surface 82S of the thrust relief 82 has a first region 821 consisting of an exposed surface of the back metal layer 84 on the circumferential end face 83 side of the half thrust bearing 8, and also has a second region 822 and a third region 823 consisting of exposed surfaces of the bearing alloy layer 85 adjacent to the first region 821 on the circumferential center side. The second region 822 is adjacent to the first region 821, and the third region 823 is adjacent to the second region 822 and the sliding surface 81. The first region 821, the second region 822 and the third region 823 extend in the same plane, thereby constituting a flat thrust relief surface 82S. The thrust relief length LT from the circumferential end face 83 of the half thrust bearing 8 is a length corresponding to a circumferential angle (θ) of a minimum of 15° and a maximum of 40° from the split plane HP toward the circumferential center of the half thrust bearing at the inner diameter side end face 8i. A second region length L2 of the second region 822, defined as the length from the boundary between the first region 821 and the second region 822 to the boundary between the second region 822 and the third region 823, is preferably 10 to 40% (i.e., L2 / LT = 0.1 to 0.4) of the thrust relief length LT at the inner diameter side end face 8i of the half thrust bearing 8. Moreover, a third region length L3 of the third region 823 is preferably 5 to 25% (L3 / LT = 0.05 to 0.25) of the thrust relief length LT at the inner diameter side end face 8i of the half thrust bearing 8.

[0028] Here, the thrust relief length LT of the thrust relief 82 is defined as a length measured perpendicular to the dividing plane HP, which is a plane including the central axis CP1 of the half thrust bearing 8 and serves as a symmetrical plane when a pair of half thrust bearings are arranged (hereinafter, the dividing plane HP), to the boundary between the thrust relief surface 82S and the sliding surface 81. In this embodiment, since both circumferential end faces 83 are located within the dividing plane HP, the thrust relief length LT at the inner diameter side end face 8i can be defined as a vertical length from the circumferential end face 83 to a point where the thrust relief surface 82S intersects with the inner peripheral edge of the sliding surface 81. It will be understood that the second region length L2 and the third region length L3 of the thrust relief 82 are also defined as lengths measured perpendicular to the dividing plane HP.

[0029] 8, the thrust relief 82 of the half thrust bearing 8 is formed at a circumferential end face 83 so as to have a constant axial depth RD1 between an inner diameter side end face 8i and an outer diameter side end face 8o of the half thrust bearing 8. The axial depth RD1 of the thrust relief 82 may be 0.1 to 1 mm.

[0030] Here, the axial depth of the thrust relief 82 means the axial distance from a plane including the sliding surface 81 of the half thrust bearing 8 to the thrust relief surface 82S. In other words, the axial depth of the thrust relief 82 is the distance measured perpendicularly from an imaginary sliding surface obtained by extending the sliding surface 81 onto the thrust relief 82 to the thrust relief surface 82S. Therefore, the axial depth RD1 of the thrust relief 82 at the circumferential end surface 83 of the half thrust bearing 8 is defined as the distance from the imaginary sliding surface obtained by extending the sliding surface 81 to the intersection point of the thrust relief surface 82S and the circumferential end surface 83.

[0031] Half thrust bearing 8 is formed as a semicircular ring-shaped flat plate using a bimetal in which a thin bearing alloy layer 85 is bonded to an Fe alloy backing layer 84. A Cu bearing alloy, an Al bearing alloy, or the like can be used for the bearing alloy layer 85 forming the sliding surface 81, and steel, stainless steel, or the like can be used for the Fe alloy of the backing layer 84.

[0032] The back metal layer 84 forms a back surface 84 S of the half thrust bearing 8 parallel to the sliding surface 81 on the side opposite to the sliding surface 81 .

[0033] As shown in FIGS. 6 and 7, the sliding surface 81 of the half thrust bearing 8 has a fourth region 812 that includes the circumferential center of the half thrust bearing 8 and extends between the two third regions 823 of each thrust relief surface 82S. The first region 821 and the second region 822 of the thrust relief surface 82S form circumferential end regions 800 on each circumferential side of the half thrust bearing 8. The circumferential end region 800 has a circumferential end region length L that is the length from the circumferential end face 83 to the boundary between the second region 821 and the third region 823, measured perpendicularly to the division plane HP, and this circumferential end region length L is constant between the inner diameter side end face 8i and the outer diameter side end face 8o of the half thrust bearing 8, and corresponds to a circumferential angle (θ1) of at least 10° and at most 35° from the division plane HP toward the circumferential center of the half thrust bearing at the inner diameter side end face 8i. As can be seen, the circumferential end region length L is smaller than the thrust relief length LT at the inner diameter side end face 8i of the half thrust bearing 8. Also, preferably, the circumferential end region length L is 75 to 95% of the thrust relief length LT at the inner diameter side end face 8i of the half thrust bearing 8 (L / LT = 0.75 to 0.95).

[0034] Hereinafter, the arrangement of back metal layer 84 and bearing alloy layer 85 of half thrust bearing 8 will be described with reference to FIGS. 10 showing the cross section BB of Fig. 7, the bearing alloy layer 85 in the third region 823 has only a constant thickness portion 88 which extends over a range including the radial center in a cross section parallel to the parting plane HP and has a constant axial thickness T2. Note that the axial thickness Tb of the half thrust bearing 8 is constant in this cross section.

[0035] 9 showing the cross section AA of FIG. 7, the bearing alloy layer 85 in the second region 822 has, in a cross section parallel to the parting plane HP, a uniform thickness portion 88 extending in a range including the radial center, the uniform thickness portion 88 having a constant axial thickness T3, and a reduced thickness portion 89 adjacent to the inner diameter side end face 8i, the reduced thickness portion 89 having an axial thickness T4 smaller than the thickness T3 of the uniform thickness portion 88. More specifically, the thickness T4 of the reduced thickness portion 89 decreases continuously from the uniform thickness portion 88 toward the inner diameter side end face 8i. Note that the axial thickness Ta of the half thrust bearing 8 is constant in this cross section as well.

[0036] 11 showing the CC cross section of FIG. 7, bearing alloy layer 85 in fourth region 812 has only constant thickness portion 88 whose axial thickness T1 is constant in a radial cross section including the axis of half thrust bearing 8. It is preferable that thickness T1 of constant thickness portion 88 of bearing alloy layer 85 is 0.2 to 0.5 mm. It is preferable that length L5 perpendicular to the axial direction of reduced thickness portion 89 in second region 822 is 0.2 to 1 mm.

[0037] FIG. 8 is a side view of the vicinity of a circumferential end region 800 of the half thrust bearing 8 as viewed from the inner diameter side (as viewed in the direction of the Y1 arrow in FIG. 7). The dotted lines drawn in circumferential end region 800 represent the surfaces where bearing alloy layer 85 contacts back metal layer 84 in constant thickness portion 88, or in other words, the boundaries between bearing alloy layer 85 and back metal layer 84 when reduced thickness portion 89 is not formed in bearing alloy layer 84. The proportion of the area of ​​bearing alloy layer 84 at inner diameter end face 8i of circumferential end region 800 is smaller than in the case where reduced thickness portion 89 is not formed. Of circumferential end region 800, thickness T4 of reduced portion 89 of bearing alloy layer 85 at inner diameter side end face 8i in second region 822 is preferably 5% or more (25% or less) of thickness T3 of uniform thickness portion 88 of bearing alloy layer 85. By having thickness T4 of reduced portion 89 of bearing alloy layer 85 at inner diameter side end face 8i in second region 822 be 5% or more of thickness T3 of uniform thickness portion 88 of bearing alloy layer 85, direct contact between back metal layer 84 of half-shaft thrust bearing 8 and the surface of thrust collar 12 of the crankshaft is prevented.

[0038] An overlay layer may be formed on the sliding surface 81 of the bearing alloy layer 85 of the half thrust bearing 8. As the overlay layer, metals or alloys such as Sn, Sn alloys, Bi, Bi alloys, Pb, Pb alloys, or resin sliding materials may be used. The resin sliding material is formed from a resin binder and a solid lubricant. Although known resins may be used as the resin binder, it is preferable to use one or more of polyamideimide, polyimide, and polybenzimidazole, which have high heat resistance. In addition, a resin composition in which a highly heat-resistant resin made of one or more of polyamideimide, polyimide, and polybenzimidazole is mixed with 1 to 25 volume % of a resin made of one or more of polyamide, epoxy, and polyethersulfone, or a polymer alloyed resin composition may be used as the resin binder. As the solid lubricant, molybdenum disulfide, tungsten disulfide, graphite, polytetrafluoroethylene, boron nitride, etc. may be used. The ratio of the solid lubricant added to the resin sliding material is preferably 20 to 80 volume %. To enhance the wear resistance of the resin sliding material, hard particles such as ceramics and intermetallic compounds may be contained in the resin sliding material in an amount of 0.1 to 10% by volume.

[0039] This overlay layer may be applied not only to the sliding surface 81 of the bearing alloy layer 85 that receives the axial force f of the crankshaft, but also to the thrust relief surface 82S of the thrust relief 82, the surface of the oil groove 81a, the inner diameter side end face 8i, the outer diameter side end face 8o, the back surface 84S, the circumferential end face 83, etc. of the half thrust bearing 8. The thickness of the overlay layer 82b is 0.5 to 20 μm, and preferably 1 to 10 μm. In this specification, the sliding surface 81, thrust relief surface 82S, inner diameter side end surface 8i, outer diameter side end surface 8o, back surface 84S and circumferential end surface 83 are defined as surfaces when the overlay layer 82b is not applied.

[0040] (action) Next, the operation of the thrust bearing 10 of this embodiment will be described with reference to FIGS. 2, 3, 12A and 12B. In the bearing device 1, lubricating oil discharged under pressure from an oil pump (not shown) passes from an internal oil passage of the cylinder block 2 through a through hole 72 penetrating the wall of the half bearing 7, and is supplied to a lubricating oil groove 71 on the inner peripheral surface of the half bearing 7. The lubricating oil supplied to the lubricating oil groove 71 may contain foreign matter, and some of this lubricating oil is supplied to the inner peripheral surface of the half bearing 7, some is sent to the crankpin side through an opening (not shown) for the internal oil passage of the crankshaft provided on the surface of the journal portion 11, and the other part passes through a gap between the surface of the crush relief 73 of the pair of half bearings 7, 7 that constitute the main bearing, and the surface of the journal portion 11 of the crankshaft, and flows out from both axial ends of the half bearings 7, 7 to the outside.

[0041] In this embodiment, the half bearing 7 is arranged concentrically with the half thrust bearing 8, and the plane including both circumferential end faces of the half bearing 7 that constitutes the main bearing coincides with the plane including both circumferential end faces of the half thrust bearing 8, and therefore the position of the crush relief 73 corresponds to the position of the thrust relief 82.

[0042] The operation of the present invention will now be described. The lubricating oil containing foreign matter immediately after leaking out from the crush relief gap of the half bearing 7 flows in the circumferential direction along the surface of the journal portion 11 of the rotating crankshaft, and therefore, due to the force of inertia that tries to move it forward in the rotational direction of the crankshaft, as shown in Figures 12A and 12B (see the dashed arrows in Figures 12A and 12B), flows forward in the rotational direction of the crankshaft from the position of the butt portion (contact portion) of the circumferential end face 83 of one half thrust bearing 8 and the circumferential end face 83 of the other half thrust shaft 8).

[0043] The half thrust bearing 8 of this embodiment has a thrust relief surface 82S consisting of a first region 821, a second region 822 and a third region 823, and a circumferential end region 800 consisting of the first region 821 and the second region 822. Of the circumferential end region 800, the second region 822 has, in a cross section parallel to the division plane HP of the half thrust bearing 8, a constant thickness portion 88 extending over a range including the radial center and having a constant axial thickness T3, and a reduced thickness portion 89 adjacent to the inner diameter side end face 8i and having an axial thickness T4 that is smaller than the thickness T3 of the constant thickness portion 88. Therefore, in the half thrust bearing 8 of the present invention, the ratio of the bearing alloy layer 85, which is easily embedded with foreign matter, is small at the inner diameter side end surface 8i of the circumferential end region 800 into which the lubricating oil containing foreign matter flows (i.e., the ratio of the back metal layer 84, which is difficult to embed with foreign matter, is large). Therefore, a large amount of foreign matter is unlikely to accumulate on the surface (side surface) of the bearing alloy layer 85 at the inner diameter side end surface 8i of the circumferential end region 800, and the accumulated large amount of foreign matter is not dropped off from the surface (side surface) of the bearing alloy layer 85 and sent to the thrust relief 82, so that seizure is unlikely to occur on these thrust relief surfaces 82S. Note that, since the circumferential end region length L is a length corresponding to a minimum of 10° from the division plane HP toward the circumferential center side of the half thrust bearing at the inner diameter side end surface 8i, the lubricating oil containing foreign matter is unlikely to be sent to the inner end surface 8i of the third region 821 adjacent to the circumferential end region 800.

[0044] During operation of an internal combustion engine, particularly under operating conditions where the crankshaft rotates at high speed, the crankshaft is deflected (in the axial direction), causing large vibrations of the crankshaft. This large vibration may cause repeated local contacts with the surface of the thrust collar 12 of the crankshaft at a portion of the sliding surface 81 adjacent to the outer diameter end face 8o and the inner diameter end face 8i of the fourth region 812 located at the circumferential center of the half thrust bearing 8, as well as a portion of the thrust relief surface 82S adjacent to the outer diameter end face 8o of the third region 823 of the thrust relief 82 and a portion of the thrust relief surface 82S adjacent to the inner diameter end face 8i. However, the bearing alloy layer 85 in these portions does not have a reduced thickness portion 89 (it has a uniform thickness portion 88), and therefore has a sufficient thickness, and the load caused by local contact with the surface of the thrust collar 12 is mitigated by the elastic deformation of the soft bearing alloy layer 85. EXAMPLES

[0045] 13 to 16, a half thrust bearing 8 having a fourth region 812 and a circumferential end region 800 in a configuration different from that of Example 1 with respect to the bearing alloy layer 85 will be described below. Note that the same reference numerals will be used to describe the same or equivalent parts as those described in Example 1. Fig. 13 is an enlarged front view of the vicinity of the circumferential end of half thrust bearing 8 of Example 2, Fig. 14 shows the A1-A1 cross section of Fig. 13, Fig. 15 shows the B1-B1 cross section of Fig. 13, and Fig. 16 shows the C1-C1 cross section of Fig. 13.

[0046] (composition) First, the configuration will be described. The configuration of half thrust bearing 8 of this embodiment is generally similar to that of Example 1, except for the shape (thickness) of bearing alloy layer 85 in the above cross section.

[0047] Specifically, the bearing alloy layer 85 in the third region 823 of the thrust relief 82 of the half thrust bearing 8 of this embodiment has, in a cross section parallel to the parting plane HP, a uniform thickness portion 88 extending over a range including the radial center and having a constant axial thickness T2, an increased thickness portion 90 adjacent to the inner diameter side end face 8i and having an axial thickness T5 greater than the thickness T2 of the uniform thickness portion 88, and further, an increased thickness portion 90 adjacent to the outer diameter side end face 8o and having an axial thickness T5 greater than the thickness T2 of the uniform thickness portion 88. In the increased thickness portion 90, the axial thickness of the bearing alloy layer 85 increases continuously from the side in contact with the uniform thickness portion 88 toward the outer diameter side end face 8o (see FIG. 15 ). Furthermore, bearing alloy layer 85 in second region 822 of circumferential end region 800 has, in a cross section parallel to parting plane HP, a constant thickness portion 88 extending over a range including the radial center and having a constant axial thickness T3, a reduced thickness portion 89 adjacent to inner diameter side end face 8i and having an axial thickness T4 smaller than the thickness T3 of constant thickness portion 88, and further an increased thickness portion 90 adjacent to outer diameter side end face 8o and having an axial thickness T5 larger than the thickness T3 of constant thickness portion 88. In increased thickness portion 90, the thickness of bearing alloy layer 85 continuously increases from the side in contact with constant thickness portion 88 toward outer diameter side end face 8o (see FIG. 14). In addition, it is preferable that the length L6 perpendicular to the axial direction of the thickened portion 90 in the second region 822 and the third region 823 adjacent to the outer diameter side end face 8o, and the length L5' perpendicular to the axial direction of the thickened portion 90 in the third region 823 adjacent to the inner diameter side end face 8i are 0.2 to 1 mm. Furthermore, the bearing alloy layer 85 in the fourth region 812 located at the circumferential center of the half thrust bearing 8 has, in a radial cross section including the axis of the half thrust bearing 8, a uniform thickness portion 88 including the radial center and having a constant axial thickness T1, an increased thickness portion 90 adjacent to the inner diameter side end face 8i and having an axial thickness T6 greater than the thickness T1 of the uniform thickness portion 88, and an increased thickness portion 90 adjacent to the outer diameter side end face 8o and having an axial thickness T6 greater than the uniform thickness portion 88. In these increased thickness portions 90, the bearing alloy layer 85 has a thickness that increases continuously from the side in contact with the uniform thickness portion 88 toward the inner diameter side end face 8i and the outer diameter side end face 8o (see FIG. 16). It is preferable that the length L6 of the increased thickness portion adjacent to the outer diameter side end face 8o and the length L5' of the increased thickness portion adjacent to the inner diameter side end face 8i are 0.2 to 1 mm in the radial cross section.

[0048] In Example 2, the configuration in which the bearing alloy layer 85 in the second region 822 of the circumferential end region 800 has a reduced thickness portion 89 adjacent to the inner diameter side end face 8i is the same as in Example 1, and therefore Example 2 has the effect of preventing the accumulation of foreign matter, similar to Example 1. In Example 2, furthermore, the bearing alloy layer 85 in the fourth region 812 and the third region 823 of the half thrust bearing 8 includes thickened portions 90, 90 adjacent to the inner diameter side end face 8i and the outer diameter side end face 8o, respectively, and the bearing alloy layer 85 in the circumferential end region 800 includes a thickened portion 90 adjacent to the outer diameter side end face 8o. Therefore, this half thrust bearing 8 is excellent in the effect of mitigating the load caused by local contact between the surface of the thrust collar 12 and the portion of the sliding surface 81 and the portion of the thrust relief surface 82S adjacent to the inner diameter side end face 8i and the outer diameter side end face 8o when the crankshaft is deflected (in the axial direction) and the vibration of the crankshaft increases. In addition, the bearing alloy layer 85 in the fourth region 812 and the third region 823 of the half thrust bearing 8 in this embodiment has thickened portions 90, 90 adjacent to the inner diameter side end face 8i and the outer diameter side end face 8o, respectively, but may have only the thickened portion 90 adjacent to the outer diameter side end face 8o, or only the thickened portion 90 adjacent to the inner diameter side end face 8i (in this case, it does not have the thickened portion 90 adjacent to the outer diameter side end face 8o of the circumferential end region 800). EXAMPLES

[0049] Hereinafter, a half thrust bearing 8 having an inner diameter side end surface 8i of a circumferential end region 800 in a form different from that of the first embodiment will be described with reference to Fig. 17. Note that the same or equivalent parts as those described in the first embodiment will be described with the same reference numerals. Fig. 17 is a front view of a half thrust bearing 8 of the third embodiment.

[0050] (composition) The configuration of the half thrust bearing 8 of this embodiment is generally similar to that of the first embodiment, except for the inner diameter side end surface 8i of the circumferential end region 800.

[0051] Specifically, the center of curvature CP2 of the inner diameter side end face 8i of each circumferential end region 800 of the half thrust bearing 8 in this embodiment is offset from the center of curvature CP1 (and the center of curvature of the outer diameter side end face 8o) of the inner diameter side end face 8i of the fourth region 812 located in the circumferential center of the half thrust bearing 8. In Example 3, the configuration in which the bearing alloy layer 85 in the second region 822 of the circumferential end region 800 has a reduced thickness portion 89 adjacent to the inner diameter side end face 8i is the same as in Example 1, and therefore Example 3 has the effect of preventing the accumulation of foreign matter, similar to Example 1. EXAMPLES

[0052] Next, a bearing device 1 equipped with a thrust bearing of the present invention will be described with reference to Figures 2 to 8, 12A and 12B. Note that the same or equivalent parts as those described in the above embodiment will be described with the same reference numerals. In this embodiment, a bearing device 1 equipped with the half thrust bearing 8 described in embodiment 1 will be described, but it should be noted that this is not limited to this, and the same action and effect as described below can also be achieved with a bearing device 1 equipped with a half thrust bearing 8 of embodiments 2 to 3.

[0053] As shown in Figures 1 to 3, the bearing device 1 of this embodiment has a bearing housing 4 having a cylinder block 2 and a bearing cap 3, two half bearings 7, 7 that rotatably support the journal portion 11 of the crankshaft, and four half thrust bearings 8 that receive axial forces via thrust collars 12 of the crankshaft.

[0054] A bearing hole 5 serving as a retaining hole for retaining a pair of half bearings 7, 7 is formed through the cylinder block 2 and the bearing cap 3 that constitute the bearing housing 4 at a joint between them. Each half bearing 7 has crush reliefs 73, 73 formed adjacent to both circumferential ends of its inner circumferential surface. The half bearing 7 arranged on the cylinder block 2 side has a lubricating oil groove 71 formed along the circumferential direction near the center in the width direction (axial direction) of the bearing, and a through hole 72 that penetrates from the lubricating oil groove 71 on the inner circumferential surface side to the outer circumferential surface, as shown in Figures 4 and 5.

[0055] A pair of half thrust bearings 8, 8 are disposed on each side in the axial direction of the pair of half bearings 7, 7. Each half thrust bearing 8 is formed in a semicircular ring shape, and the outer diameter of the half bearing 7 and the outer diameter of the half thrust bearing 8 are disposed approximately concentrically. Furthermore, the horizontal plane passing through both circumferential end faces of the half bearing 7 and the horizontal plane (split plane HP) passing through both circumferential end faces of the half thrust bearing 8 are disposed so as to coincide or to be approximately parallel. Therefore, as shown in FIG. 2, the crush relief 73 of the half bearing 7 and the thrust relief 82 of the half thrust bearing 8 are positioned in a one-to-one correspondence.

[0056] As described in the first embodiment, each half thrust bearing 8 has circumferential end regions 800 on both sides in the circumferential direction.

[0057] The half thrust bearing 8 of this embodiment has the following relationship with the half bearing 7. That is, in the half thrust bearing 8 of this embodiment, the circumferential end region length L of the circumferential end region 800 at the inner diameter side end face 8i of the half thrust bearing 8 is greater than the crush relief length CL of the crush relief 73 of the half bearing 7. Here, the crush relief length CL is the height from a horizontal plane to the upper edge of the crush relief 73 when the half bearing 7 is placed on a horizontal plane with both circumferential end faces 74, 74 forming the lower end faces (see FIG. 4). The crush relief lengths of the crush reliefs 73 on both sides of the circumferential ends of the half bearing 7 are the same. Also, unlike this embodiment, the crush relief length of the crush relief 73 of the half bearing 7 may vary in the axial direction of the half bearing 7.

[0058] The operation of this embodiment will now be described. As shown in Figures 12A and 12B, the lubricating oil immediately after flowing out from the crush relief gap of half bearing 7 to the outside flows in the circumferential direction along the surface of the journal portion of the rotating crankshaft, and therefore flows toward the front side in the rotational direction of the crankshaft from the position of crush relief 73 due to the force of inertia that tries to move it forward in the rotational direction of the crankshaft 11 (dashed arrow). In the bearing device 1 of this embodiment, the circumferential end region length L of the circumferential end region 800 at the inner diameter side end face 8i of the half thrust bearing 8 is greater than the crush relief length CL of the crush relief 73 of the half bearing 7. Therefore, the lubricating oil (containing foreign matter) that flows out of the crush relief gap of the half bearing 7 and flows forward in the rotational direction of the crankshaft 11 beyond the position of the crush relief 73 first flows toward the inner diameter side end face 8i of the circumferential end region 800, and therefore the foreign matter contained in the lubricating oil is less likely to accumulate on the surface of the soft bearing alloy layer 85 at the inner diameter side end face 8i.

[0059] As specific dimensions of the crush relief 73 of the half bearing 7, in the case of a crankshaft of a small internal combustion engine for a passenger car, etc. (with a journal diameter of approximately 30 to 100 mm), the crush relief length CL is, for example, 3 to 7 mm, and the depth of the crush relief 73 at the circumferential end face 74 from an imaginary extension plane obtained by extending the sliding surface 75 up to the crush relief is 0.01 to 0.1 mm.

[0060] It is preferable that the circumferential end region length L of the circumferential end region 800 at the inner diameter end face 8i of the half thrust bearing 8 satisfies the formula: L≧1.5×CL, with respect to the crush relief length CL of the crush relief of the half bearing 7 at the corresponding position.

[0061] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0062] For example, as shown in FIG. 18, the present invention can also be applied to a half thrust bearing 8 having a protrusion 8p that protrudes radially outward for positioning and rotation prevention. As shown in FIG. 19, the circumferential length of this half thrust bearing 8 may be shorter than that of the half thrust bearing 8 shown in the first embodiment by a predetermined length S1.

[0063] A chamfer may be formed in the circumferential direction on the outer edge or inner diameter edge of sliding surface 81 of half thrust bearing 8. When a chamfer is formed on the outer edge or inner diameter edge of sliding surface 81, thickness T6 of thickened portion 90 of bearing alloy layer 85 is defined as the thickness measured from sliding surface 81 (surface of bearing alloy layer 85) when no chamfer is formed.

[0064] Similarly, a chamfer may be formed in the circumferential direction on the outer edge or inner diameter edge of thrust relief surface 82S. In particular, when a chamfer is formed on the outer edge or inner diameter edge of second region 822, thicknesses T4, T5 of reduced thickness portion 89 and increased thickness portion 90 of bearing alloy layer 85 are defined as thicknesses measured from second region 822 when no chamfer is formed.

[0065] Furthermore, as shown in FIG. 20, the half thrust bearing 8 can have back reliefs 92 having a shape similar to the thrust relief 82 on the back surface 84S side of the back metal layer 84 adjacent to both circumferential ends 83.

[0066] To prevent incorrect assembly, the circumferential end faces of each half thrust bearing 8 can be formed as inclined end faces 83A at only one of the two butting portions of a pair of half thrust bearings 8, as shown in Fig. 21. In this case, the inclined end face 83A is formed at a predetermined angle θ2 with respect to a plane (division plane HP) passing through the circumferential end face 83 of the other butting portion, which is not inclined. Alternatively, instead of the inclined end face 83A, each circumferential end face can have another shape, such as a corresponding concave-convex shape. In either case, however, it will be understood by those skilled in the art that the thrust relief length LT is defined as the vertical length from the split plane HP of the half thrust bearing 8 to the point where the surface of the thrust relief 82 intersects with the inner circumferential edge of the sliding surface 81. Similarly, the length L of the circumferential end region 800 is defined as the length measured vertically from the split plane HP of the half thrust bearing 8 to the boundary between the circumferential end region 800 and the fourth region 812.

[0067] In addition, in the fourth embodiment, four half thrust bearings 8 are used in the bearing device 1, but the present invention is not limited to this, and the desired effect can be obtained by using at least one half thrust bearing 8 according to the present invention. Also, the half thrust bearing 8 according to the present invention and a conventional half thrust bearing may be paired and used as an annular thrust bearing. Furthermore, in the bearing device 1 of the present invention, the half thrust bearing 8 may be formed integrally with the half bearing 7 on one or both axial end faces of the half bearing 7 that rotatably supports the crankshaft. [Explanation of symbols]

[0068] 1 Bearing device 4 Bearing housing 7 Half bearing 11 Journal Section 12 Thrust collar 71 Lubricant groove 72 Through hole 73 Crash Relief 74 Circumferential end face 75 Sliding surface CL Crash relief length 8. Half Thrust Bearing 81 Sliding surface 81a Oil groove 82 Thrust relief 82S Thrust relief surface 83 Circumferential end face 84 Backing Gold Layer 84S back 85 Bearing alloy layer 800 Circumferential end area 812 4th area 821 1st area 822 Second area 823 Third area 8i Inner diameter side end face 8o Outer diameter end face 88 Equal thickness section 89 Thickening section 90 Thickened section RD1 Thrust relief depth at circumferential end face L Length of the circumferential end area on the inner diameter side LT Length of thrust relief at inner diameter end face L2 Length of the second area on the inner diameter side L3 Length of the third area on the inner diameter side L5 Length of reduced thickness L5' Length of thickened part L6 Length of thickened part Ta Thickness of half thrust bearing T1 Thickness of bearing alloy layer at uniform thickness T2 Thickness of bearing alloy layer at reduced thickness T3 Thickness of bearing alloy layer at uniform thickness T4 Thickness of bearing alloy layer at reduced thickness T5 Thickness of bearing alloy layer in thickened area T6 Thickness of bearing alloy layer in thickened area HP splitting plane CP1 center of curvature CP2 center of curvature

Claims

1. A semi-annular half thrust bearing for receiving an axial force of a crankshaft of an internal combustion engine, the half thrust bearing has a back metal layer made of an Fe alloy and a bearing alloy layer provided on a surface of the back metal layer, the bearing alloy layer forming a sliding surface that receives the axial force, and the back metal layer forming a back surface that is parallel to the sliding surface, the half thrust bearing has two thrust reliefs formed adjacent to both circumferential end faces thereof, each thrust relief having a flat thrust relief surface extending between the sliding surface and the circumferential end face, whereby, at the thrust relief, a wall thickness of the half thrust bearing becomes thinner from the sliding surface side toward the circumferential end face side; Each thrust relief surface has a first region on the circumferential end surface side, the first region being a surface where the backing metal layer is exposed, and a second region and a third region being a surface where the bearing alloy layer is exposed, the second region being adjacent to the first region and the third region being adjacent to the sliding surface, and the sliding surface has a fourth region between the two third regions, thereby defining a circumferential end region consisting of the first region and the second region; a circumferential end region length (L) from a dividing plane (HP) of the half thrust bearing to a boundary between the second region and the third region, measured perpendicular to the dividing plane, is constant between an inner diameter side end face and an outer diameter side end face of the half thrust bearing, and corresponds to a perpendicular distance from the dividing plane to a position on the inner diameter side end face that forms a circumferential angle (θ1) of a minimum of 10° and a maximum of 35° from the dividing plane toward the circumferential center of the half thrust bearing, the bearing alloy layer in the second region has a constant thickness portion in which the thickness of the bearing alloy layer is constant in a range including the radial center of the half thrust bearing in any cross section parallel to the dividing plane, and has a reduced thickness portion in a range adjacent to the inner diameter side end face in which the thickness of the bearing alloy layer is smaller than that of the constant thickness portion; the bearing alloy layer in the third region has a constant thickness portion in which the thickness of the bearing alloy layer is constant in a range including the radial center of the half thrust bearing in any cross section parallel to the dividing plane, and has an increased thickness portion or the constant thickness portion in which the thickness of the bearing alloy layer is greater than that of the constant thickness portion in a range adjacent to the inner diameter side end face, The bearing alloy layer in the fourth region has a constant thickness portion in which the thickness of the bearing alloy layer is constant in a range including the radial center of the half thrust bearing in any radial cross section including the axis of the half thrust bearing, and has an increased thickness portion or the constant thickness portion in which the thickness of the bearing alloy layer is greater than that of the constant thickness portion in a range adjacent to the inner diameter side end face. A half thrust bearing comprising:

2. 2. The half thrust bearing according to claim 1, wherein the bearing alloy layer in the second region and the third region further has a thickened portion in which the thickness of the bearing alloy layer is greater than that of the uniform thickness portion in an area adjacent to the outer diameter side end face in any cross section parallel to the dividing plane.

3. 3. The half thrust bearing according to claim 1, wherein a third region length (L3) from a boundary between the second region and the third region to the third region and the fourth region, measured perpendicular to the dividing plane, is 5 to 25% of a thrust relief length (LT) from the dividing plane to the boundary between the third region and the fourth region, at the inner diameter side end face.

4. 4. The half thrust bearing according to claim 1, wherein a second region length (L2) from a boundary between the first region and the second region to the second region and the third region, measured perpendicular to the dividing plane, is 10 to 40% of a thrust relief length (LT) from the dividing plane to a boundary between the third region and the fourth region, at the inner diameter side end face.

5. 5. A half thrust bearing as claimed in claim 1, wherein the bearing alloy layer in the fourth region further has an increased thickness portion in which the thickness of the bearing alloy layer is greater than the uniform thickness portion in an area adjacent to the outer diameter side end face in any radial cross section including the axis of the half thrust bearing.

6. 6. The half thrust bearing according to claim 1, wherein a center of curvature of an inner diameter side end face of the circumferential end region is located at a position different from a center of curvature of an inner diameter side end face of the fourth region.

7. A crankshaft, a pair of half bearings supporting journal portions of the crankshaft, each half bearing having two crush reliefs formed on an inner peripheral surface side adjacent to both circumferential end faces of the half bearing; a bearing housing having a retaining hole formed therethrough for retaining the pair of half bearings; 7. The half thrust bearing according to claim 1, further comprising: at least one semi-annular half thrust bearing disposed on an axial end surface of the bearing housing adjacent to the retaining hole for receiving an axial force of the crankshaft; A bearing device for a crankshaft of an internal combustion engine, comprising: A bearing device, characterized in that the circumferential end region length (L) is greater than a crush relief length of the crush relief at an axial end of the half bearing.

8. 8. The bearing device according to claim 7, characterized in that the circumferential end region length (L) at the inner diameter side end face of the half thrust bearing is 1.5 times or more the crush relief length at the axial end of the half bearing.

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