Half-split thrust bearing

Abstract

To provide a half-split thrust bearing which is hardly damaged (fatigued) during the operation of an internal combustion engine, for receiving the axial force of a crank shaft.SOLUTION: A half-split thrust bearing which has a constant bearing wall thickness between a slide surface and a back surface, has an almost flat central area and two end areas on both peripheral sides of the central area. Each of the end areas extends from each peripheral end to the peripheral center of the half-split thrust bearing over a circumferential angle of 5° or more and 35° or less. When the reference surface is defined as a virtual plane which is perpendicular to the axial direction of the half-split thrust bearing and parallel to the slide surface in the central area and located away from the slide surface, an axial distance between the slide surface and the reference surface is minimum in the central area, and continuously longer as extending from the central area side to the peripheral end side in the peripheral direction at any position in the radial direction in each end area.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] The crankshaft of an 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 formed by combining a pair of half bearings into a cylindrical shape. 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. The half thrust bearing is disposed for the purpose of receiving the axial force generated in the crankshaft, i.e., for supporting the axial force input to the crankshaft when the crankshaft and the transmission are connected by the clutch, etc.

[0003] In general, the sliding surface of a half thrust bearing that receives an axial force and its opposite back surface are parallel to a plane perpendicular to the axial direction of the half thrust bearing, and the thickness between the sliding surface and the back surface is constant. In addition, thrust reliefs are 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 ends. In general, thrust reliefs are formed so that the thrust relief length from the circumferential ends of the half thrust bearing to the sliding surface and the thrust relief depth at the circumferential ends are constant regardless of the radial position. The thrust reliefs are 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).

[0004] In the past, in consideration of the flexural deformation of the crankshaft during operation of an internal combustion engine, it has been proposed to provide a curved crowning surface on at least the outer diameter side of the sliding surface of a half thrust bearing, thereby reducing the local contact stress between the sliding surface of the half thrust bearing and the crankshaft (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-201145 [Patent Document 2] JP 2013-19517 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the diameter of the crankshaft has been reduced to reduce the weight of the internal combustion engine, and the crankshaft has become less rigid than a conventional crankshaft. As a result, the crankshaft is more likely to bend during operation of the internal combustion engine, and the crankshaft tends to vibrate more. The inclination of the thrust collar surface relative to the sliding surface near the circumferential center of the half thrust bearing becomes particularly large. Therefore, the sliding surface near the circumferential center of the half thrust bearing and the thrust collar surface of the crankshaft come into local contact, making damage (fatigue) more likely to occur.

[0007] Even if a curved crowning surface is provided on at least the outer diameter side of the sliding surface as described in Patent Document 2 in order to prevent contact between the sliding surface near the circumferential center of the half thrust bearing and the thrust collar surface of the crankshaft, making them more susceptible to damage (fatigue), it is difficult to prevent damage (fatigue) from occurring when the sliding surface near the circumferential center of the half thrust bearing comes into contact with the thrust collar of the crankshaft, especially when the vibration caused by the bending of the crankshaft described above is large.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to address the above problems and provide a half thrust bearing that is less susceptible to damage (fatigue) during operation of an internal combustion engine. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a substantially semicircular ring-shaped half thrust bearing for receiving an axial force from a crankshaft of an internal combustion engine, this half thrust bearing having a sliding surface that receives the axial force and a back surface on the opposite side, and a bearing wall thickness between the sliding surface and the back surface is constant. In addition, the half thrust bearing has the following features: a substantially flat central region including a circumferential central portion of the half thrust bearing; two end regions on both circumferential sides of the central region, the end regions extending from each circumferential end of the half thrust bearing toward the circumferential central portion over a circumferential angle of 5° or more and 35° or less; has. The reference surface is defined by an imaginary plane that is perpendicular to the axial direction of the half thrust bearing, parallel to the sliding surface in the central region of the half thrust bearing, and located on the sliding surface side of the half thrust bearing, away from the sliding surface, and in this case, the axial distance between the sliding surface and the reference surface is smallest in the central region, and in each end region, at any radial position, continuously increases in the circumferential direction from the central region side to the circumferential end side.

[0010] According to one embodiment of the present invention, the difference between the axial distance between the sliding surface and the reference surface in the central region and the axial distance between the sliding surface and the reference surface at the circumferential end portion is 10 to 60 μm.

[0011] According to one embodiment of the present invention, two thrust reliefs are formed on the sliding surface, adjacent to both circumferential ends of the half thrust bearing.

[0012] Furthermore, according to one embodiment of the present invention, at least one oil groove is formed in the sliding surface.

[0013] According to one embodiment of the present invention, the oil groove has a groove portion extending radially of the half thrust bearing and one or two radially extending inclined portions formed adjacent to one or both circumferential ends of the groove portion, and the inclined portions are inclined so that the wall thickness of the half thrust bearing decreases from the sliding surface side towards the groove portion side when viewed in a cross section of the half thrust bearing cut in the circumferential direction of the sliding surface. Effect of the Invention

[0014] According to the half thrust bearing of the present invention, even if the inclination angle of the thrust collar surface of the crankshaft with respect to the sliding surface near the circumferential center of the half thrust bearing becomes large due to bending of the crankshaft during operation of the internal combustion engine, the sliding surfaces near both circumferential ends of the half thrust bearing will come into contact with the thrust collar surface of the crankshaft, preventing only the sliding surface near the circumferential center of the half thrust bearing from coming into contact with the thrust collar surface of the crankshaft and making damage to the sliding surfaces of the half thrust bearing less likely to occur. [Brief description of the drawings]

[0015] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 1 is a front view of a half thrust bearing according to the prior art; [Diagram 5] FIG. 5 is a side view of the half thrust bearing of the conventional art shown in FIG. 4 as seen from the Y2 arrow. [Figure 6] FIG. 1 is a side view for explaining the operation of a half thrust bearing according to the prior art. [Figure 7] FIG. 2 is a front view of the half thrust bearing of the first embodiment. [Figure 8] 8 is a cross-sectional view taken along line AA of the half thrust bearing in FIG. 7. [Figure 9] 8 is a bottom view of the half thrust bearing of FIG. 7 as seen from the Y1 arrow. [Figure 10] FIG. 2 is a cross-sectional view of a half thrust bearing according to a first embodiment for explaining the operation of the present invention. [Figure 11] FIG. 2 is a cross-sectional view of a half thrust bearing according to a first embodiment for explaining the operation of the present invention. [Figure 12] FIG. 11 is a front view of a half thrust bearing according to a second embodiment. [Figure 13] 13 is a side view of the half thrust bearing of FIG. 12 as viewed from the Y3 arrow. [Figure 14] FIG. 11 is a front view of a half thrust bearing according to a third embodiment. [Figure 15] 15 is a BB cross-sectional view of the half thrust bearing of FIG. 14. [Figure 16] FIG. 11 is a front view of a half thrust bearing according to another embodiment of the present invention. [Figure 17] 17 is a side view of the half thrust bearing in FIG. 16 near its circumferential end portion. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] (Overall configuration of the bearing device) First, the overall configuration of the bearing device 1 will be described with reference to Figs. 1 to 3. As shown in Figs. 1 to 3, a bearing housing 4 formed by attaching a bearing cap 3 to the lower part of a cylinder block 2 has a bearing hole (retaining hole) 5, which is a circular hole penetrating between both side surfaces, and annular recessed seats 6, 6 are formed on the periphery of the bearing hole 5 on the side surface. Half bearings 7, 7 that rotatably support a journal part 11 of a crankshaft are assembled and fitted into the bearing hole 5 in a cylindrical shape. A lubricating oil groove 71 extending in the circumferential direction is formed on the inner peripheral surface of the half bearing 7 on the upper side (cylinder block 2 side), and lubricating oil is supplied to the lubricating oil groove 71 through a through hole 72 formed in the bearing wall of the half bearing 7. Half thrust bearings 8, 8 that receive an axial force f (see Fig. 3) via a thrust collar surface 12 of the crankshaft are assembled and fitted into the seats 6, 6 in a circular shape.

[0018] (Prior Art) Next, problems with the conventional half thrust bearing 18 will be described with reference to FIGS. Fig. 4 shows a front view of a conventional half thrust bearing 18, and Fig. 5 shows a side view of the half thrust bearing 18 shown in Fig. 4, as viewed from the Y2 arrow. The sliding surface 181 and back surface 184 of the conventional half thrust bearing 18 are flat surfaces perpendicular to the axial direction of the half thrust bearing 18, and the bearing wall thickness T between the sliding surface 181 and the back surface 184 is constant.

[0019] 6 is a cross-sectional view showing a state in which the inclination angle of the thrust collar surface 12 of the crankshaft relative to the sliding surface 181 near the circumferential center of the conventional half thrust bearing 18 becomes large due to bending of the crankshaft during operation of the internal combustion engine (reference numeral 183 indicates a circumferential end surface). Since the sliding surface 181 and the back surface 184 of the conventional half thrust bearing 18 are flat surfaces perpendicular to the axial direction, when the inclination angle of the thrust collar surface 12 of the crankshaft relative to the sliding surface 181 near the circumferential center of the half thrust bearing 18 becomes large, only the sliding surface 181 near the circumferential center of the half thrust bearing 18 comes into strong contact with the thrust collar surface 12 of the crankshaft, which causes a problem that the sliding surface 181 near the circumferential center is easily damaged (fatigue). EXAMPLES

[0020] (Configuration of half thrust bearing) Next, the configuration of the half thrust bearing 8 of the first embodiment of the present invention will be described with reference to Figs. 7 to 11. Fig. 7 shows a front view of the half thrust bearing 8, Fig. 8 shows a cross-sectional view of the half thrust bearing shown in Fig. 7 taken along line AA, and Fig. 9 shows a bottom view of the half thrust bearing 8 shown in Fig. 7 taken along line Y1. The half thrust bearing 8 of this embodiment is formed in an approximately semicircular ring shape by a bimetal in which a thin bearing alloy layer is bonded to a steel backing layer (the half thrust bearing 8 is called "approximately" semicircular ring shape because it is curved in the direction perpendicular to the paper surface of Fig. 7 as described later). The half thrust bearing 8 has a sliding surface 81 facing the axial direction, and the sliding surface 81 is made of a bearing alloy layer. The half thrust bearing 8 has a back surface 84 on the opposite side of the sliding surface 81.

[0021] The sliding surface 81 may have an oil groove 81a to improve the oil retention of the lubricating oil. Although two oil grooves 81a, 81a are shown in Fig. 7 and Fig. 2, unlike this embodiment, one oil groove 81a, or three or more oil grooves 81a may be formed in the sliding surface 81. However, when the oil groove 81a is formed, the "sliding surface 81" in the portion of the oil groove 81a becomes a virtual surface on the assumption that the oil groove 81a does not exist.

[0022] The half thrust bearing 8 has a central region 8C including a circumferential central part C of the half thrust bearing 8, and two end regions 8E each extending from each circumferential end 86 of the half thrust bearing 8 toward the circumferential central part C over a circumferential angle θ1 (circumferential length) of 5° or more and 35° or less. Note that in this embodiment, the circumferential angle θ1 of the end region 8E is constant between the radially inner end 8i and the radially outer end 8o, but is not limited thereto, and the circumferential angle θ1 of the end region 8E may change between the radially inner end 8i and the radially outer end 8o and may not be constant (see Example 2).

[0023] The sliding surface 81 in the central region 8C is substantially flat (substantially planar). The sliding surfaces 81 in the two end regions 8E are both curved in a convex shape from the back surface side 84 toward the sliding surface 81 in the circumferential direction of the half thrust bearing 8. Here, "curved" means that the sliding surfaces 81 in each end region 8E are curved to be one curved surface as a whole as shown in FIG. 8, and the curvature of the curved surface may change in the circumferential direction (this also applies to other embodiments). In this case, the back surface 84 is parallel to the sliding surface 81. That is, since the bearing wall thickness T in the direction perpendicular to the sliding surface 81 between the sliding surface 81 and the back surface 84 is constant, the back surface 84 in the central region 8C and the end region 8E has a shape corresponding to the sliding surface. The bearing wall thickness T may be slightly distorted (15 μm or less) due to, for example, processing accuracy.

[0024] A reference plane 90 as a plane perpendicular to the axial direction of the half thrust bearing 8 is defined as follows. That is, the reference plane 90 is an imaginary plane located away from the sliding surface 81 of the half thrust bearing 8 so that the sliding surface 81 faces the reference plane 90, and the sliding surface 81 of the central region 8C of the half thrust bearing 8 is defined as an imaginary plane parallel to the reference plane 90. Here, the axial direction is a direction perpendicular to the reference plane 90, the axis is an imaginary line passing through the center of the half thrust bearing 8 and extending in the axial direction, and the axial distance is the separation distance between two objects in the axial direction.

[0025] When the reference surface 90 is defined in this way, the axial distance L between the sliding surface 81 and the reference surface 90 is minimum (L1) and constant in the central region 8C, and in each end region 8E, at any position in the radial direction, it continuously increases (maximum L2) (in the circumferential direction) from the position 8X of the edge portion adjacent to the central region 8C toward the circumferential end 86 of the sliding surface 81 (see Figs. 8 and 9). At this time, the axial distance between the back surface 84 of the half thrust bearing 8 and the reference surface 90 is also minimum in the central region 8C at any position in the radial direction, and in each end region 8E, it continuously increases (in the circumferential direction) from the position 8X of the edge portion adjacent to the central region 8C toward the circumferential end of the back surface 84 at any position in the radial direction. Since the sliding surface 81 and the back surface 84 are parallel, it goes without saying that the same relationship is also established for the back surface 84.

[0026] Specifically, when used in a crankshaft (having a journal portion with a diameter of about 30 to 100 mm) of a small internal combustion engine for a passenger car or the like, the difference L3 (L3=L2-L1) between the axial distance L1 between the sliding surface 81 and the reference surface 90 in the central region 8C of the half thrust bearing 8 and the axial distance L2 between the sliding surface 81 and the reference surface 90 at the circumferential end 86 is, for example, 5 to 100 μm, more preferably 10 to 60 μm. If the difference L3 in the axial distance is less than 5 μm, when the inclination angle of the thrust collar surface 12 of the crankshaft with respect to the sliding surface 81 near the circumferential center C of the half thrust bearing 8 becomes large, the sliding surface 81 near the circumferential end 86 will not come into contact with the thrust collar surface 12 of the crankshaft, and only the sliding surface 81 near the circumferential center C of the half thrust bearing 8 will be likely to come into contact with the thrust collar surface 12. Furthermore, if the difference in axial distance L3 exceeds 100 μm, when the inclination angle of the thrust collar surface 12 of the crankshaft with respect to the sliding surface 81 near the circumferential center C of the half thrust bearing 8 becomes large, the load applied to the sliding surface 81 near the circumferential end portion 86 becomes too large, which may result in damage. However, these dimensions are merely one example in the above-mentioned usage example, and the difference in axial distance L3 is not limited to the above-mentioned dimensional range.

[0027] In the half thrust bearing 8 of this embodiment, the sliding surface in the central region 8C (and the back surface 84 corresponding thereto) is entirely parallel (i.e. flat) to the reference surface 90. However, without being limited thereto, the sliding surface 81 and the back surface 84 in the central region 8C may have a curved shape (a single convex shape with a height difference of 15 μm or less) that protrudes slightly from the back surface 84 side toward the sliding surface 81 side when viewed in a cross section cut in the radial direction due to, for example, machining accuracy, or a curved shape (a single convex shape with a height difference of 15 μm or less) that protrudes slightly from the sliding surface 81 side toward the back surface 84 side, or may have other curved shapes. When the sliding surface 81 in the central region 8C is curved in the radial direction, the state in which the half thrust 8 is arranged so that the axial distance L1 between the sliding surface 81 at the radially outer end 8o of the central region 8C and the reference surface 90 is the same as the axial distance L1 between the sliding surface 81 at the radially inner end 8i of the central region 8C and the reference surface 90 corresponds to a state in which the radial center line CL of the sliding surface 81 in the central region 8C is parallel to the reference surface 90. The axial distance L1 at the radially inner end 8i and the radially outer end 8o of the sliding surface 81 in the central region 8C in this arrangement state is defined as the "axial distance L1 between the sliding surface 81 in the central region 8C and the reference surface 90."

[0028] Furthermore, in the half thrust bearing 8 of this embodiment, at the circumferential end 86, the sliding surface 81 (i.e., the circumferential edge) of the end region 8E is parallel to the reference surface 90. However, without being limited thereto, the sliding surface 81 (circumferential edge) at the circumferential end 86 may be slightly inclined with respect to the reference surface 90 (the difference in distance from the reference surface 90 is 15 μm or less), for example, due to machining accuracy. When the sliding surface 81 (circumferential edge) at the circumferential end 86 is inclined with respect to the reference surface 90, the axial distance L2 is defined as the axial distance at the position where the axial distance L from the reference surface 90 is maximum on the sliding surface 81 (circumferential edge) at the circumferential end 86.

[0029] The half thrust bearing 8 is arranged so that its back surface 84 faces the seat 6 of the cylinder block 2, and its sliding surface 81 is adapted to receive an axial force f (see FIG. 3) via the thrust collar surface 12 of the crankshaft. 10 is a cross-sectional view of the half thrust bearing 8 when the back surface 84 of the central region 8C at the circumferential center C of the half thrust bearing 8 and the back surfaces 84 of the end regions 8E of each circumferential end 86 are arranged to face the seat 6 of the cylinder block 2. As shown in the cross-sectional view, an axial gap S2 is formed between the back surface 84 of the half thrust bearing 8 and the seat 6, and this gap S2 is continuously enlarged in the central region 8C from the position where it contacts the seat 6 at the circumferential center C toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E), and in the end region 8E, it is continuously enlarged from the position where it contacts the seat 6 near each circumferential end 86 toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E). In addition, for the sliding surface 81 in the central region 8C of the half thrust bearing 8, the amount of axial displacement in the direction in which the sliding surface 81 faces is smallest at the circumferential center C of the half thrust bearing 8, and increases continuously toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E), and for the sliding surface 81 in the end region 8E of the half thrust bearing 8, the amount of axial displacement in the direction in which the sliding surface 81 faces is smallest at the circumferential end 86 of the half thrust bearing 8, and increases continuously toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region).

[0030] (action) Next, the operation of the half thrust bearing 8 of this embodiment will be described with reference to FIG. 11 shows a state in which the inclination angle of the thrust collar surface 12 of the crankshaft relative to the sliding surface 81 near the circumferential center C of the half thrust bearing 8 has increased due to bending of the crankshaft during operation of the internal combustion engine. The amount of axial displacement of the sliding surface 81 in the central region 8C of the half thrust bearing 8 in the direction in which the sliding surface 81 faces (toward the thrust collar surface 12) continuously increases toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E). For this reason, even if the inclination angle of the thrust collar surface 12 of the crankshaft relative to the sliding surface 81 near the circumferential center C of the half thrust bearing 8 becomes large, the entire sliding surface 81 in the central region 8C and the sliding surface 81 in the area adjacent to the central region 8C in the end region 8E come into contact with the thrust collar surface 12 of the crankshaft, thereby preventing only the sliding surface 81 near the circumferential center C of the half thrust bearing 8 from coming into contact with the thrust collar surface of the crankshaft. As described above, in this embodiment, there is an axial gap S2 between the back surface 84 of the half thrust bearing 8 and the seat 6, and in the central region 8C, the gap S2 continuously increases from the position where the seat 6 contacts the seat 6 at the circumferential center C toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E), and in the end region 8E, the gap S2 continuously increases from the position where the seat 6 contacts the seat 6 near each circumferential end 86 toward the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E). When the sliding surface 81 near the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E) comes into contact with the thrust collar surface 12 of the crankshaft, the half thrust bearing 8 elastically deforms toward the gap S2 near the position 8X where the central region 8C and the end region 8E of the half thrust bearing 8 are adjacent (the boundary between the central region 8C and the end region 8E), and the axial displacement of the sliding surface 81 becomes small. Therefore, it is also possible to prevent only the sliding surface 81 near the position 8X where the central region 8C and the end region 8E are adjacent (the boundary between the central region 8C and the end region 8E) from coming into contact with the thrust collar surface 12 of the crankshaft. Therefore, the half thrust bearing 8 of the present invention is less susceptible to damage over the entire sliding surface 81. EXAMPLES

[0031] A half thrust bearing 8 of a different embodiment from that of the first embodiment will be described with reference to Figures 12 and 13. Note that the same reference numerals will be used to denote the same or similar parts as those described in the first embodiment.

[0032] FIG. 12 shows a front view of the sliding surface 81 side of the half thrust bearing 8 of the second embodiment, and FIG. 13 shows a side view of the half thrust bearing 8 of FIG. 12 as viewed from the Y3 arrow.

[0033] (composition) The configuration of the half thrust bearing 8 of this embodiment is generally similar to that of the first embodiment, except for the configuration of the end region 8E and the configuration of the thrust reliefs 82, 82.

[0034] In this embodiment, the circumferential angle θ1 (circumferential length) of each end region 8E of the half thrust bearing 8 varies between the radially inner end 8i and the radially outer end 8o. As a result, in each end region 8E, a position 8X adjacent to the central region 8C is parallel to a plane (thrust bearing division plane HP) that passes through both circumferential end faces 83 of the half thrust bearing 8.

[0035] Further, the half thrust bearing 8 of this embodiment is provided with thrust reliefs 82, 82 in areas adjacent to the end faces 83, 83 on both circumferential sides.

[0036] The thrust relief 82 is a wall thickness reducing region formed in an area on the sliding surface 81 side adjacent to both circumferential end faces 83, 83 so that the bearing wall thickness T of the half thrust bearing 8 gradually becomes thinner towards the end face, and extends over the entire radial length of the circumferential end face 83 of the half thrust bearing 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, which may occur due to misalignment when the half thrust bearing 8 is assembled into the split bearing housing 4.

[0037] In this case, the sliding surface 81 is defined to include a virtual surface on the assumption that the oil groove 81a and the thrust relief 82 do not exist. Therefore, the sliding surface 81 in the central region 8C is approximately flat, and the sliding surface 81 in the end region 8E is curved so that the entire sliding surface 81 in the circumferential direction of the half thrust bearing 8 forms a single convex curved surface that protrudes from the back surface 84 side toward the sliding surface 81 side (FIG. 13).

[0038] As shown in FIG. 12, the thrust relief 82 has a constant thrust relief length L5 between the radially inner end 8i and the radially outer end 8o of the half thrust bearing 8. When used on a crankshaft (with a journal diameter of about 30 to 100 mm) of a small internal combustion engine for a passenger car or the like, the thrust relief length L5 from the circumferential end face 83 of the half thrust bearing 8 is set to 3 to 25 mm.

[0039] Here, the thrust relief length L5 is defined as the length measured vertically from a plane (thrust bearing dividing plane HP) passing through both circumferential end faces 83 of the half thrust bearing 8. In particular, the thrust relief length L5 at the radially inner end 8i is defined as the vertical length from the circumferential end face 83 of the half thrust bearing 8 to the point where the thrust relief surface 82 intersects with the sliding surface 81.

[0040] Furthermore, the thrust relief 82 of the half thrust bearing 8 can be formed so as to have a constant depth RD1 at the circumferential end face 83 between the radially inner end 8i and the radially outer end 8o of the half thrust bearing 8. The depth RD1 of this thrust relief 82 can be set to 0.1 to 1 mm (FIG. 13).

[0041] Here, the depth of the thrust relief 82 means the distance from the sliding surface 81 of the half thrust bearing 8 to the surface of the thrust relief 82 in a direction perpendicular to the sliding surface 81. In other words, the depth is the distance measured perpendicularly from an imaginary sliding surface obtained by extending the sliding surface 81 onto the thrust relief 82 to the surface of the thrust relief 82. Therefore, the depth RD1 of the thrust relief 82 at the circumferential end face 83 is particularly defined as the depth from the surface of the thrust relief 82 at the circumferential end face 83 of the half thrust bearing 8 to the imaginary sliding surface.

[0042] However, these dimensions of the thrust relief length L5 and the depth RD1 of the thrust relief 82 are merely examples and are not limited to the above-mentioned dimensional ranges. Also, the dimensions of the thrust relief length L5 and the depth RD1 of the thrust relief 82 may be formed so as to vary between the radially inner end 8i and the radially outer end 8o of the half thrust bearing 8. Note that, although the thrust relief 82 is formed within the end region 8E in this embodiment, the thrust relief 82 may be formed so as to include a central region 8C adjacent to the end region 8E.

[0043] As described above, when the thrust relief 82 is formed, the axial distance L2 is defined as the axial distance between the imaginary sliding surface at the circumferential end 86 and the reference surface 90 when the thrust relief 82 is not formed. EXAMPLES

[0044] 14 and 15, a half thrust bearing 8 according to another embodiment different from Example 1 will be described. Note that the same reference numerals will be used to denote the same or similar parts as those described in Example 1.

[0045] FIG. 14 shows a front view of the sliding surface 81 side of the half thrust bearing 8 of the third embodiment, and FIG. 15 shows a BB cross-sectional view of the half thrust bearing 8 of FIG.

[0046] (composition) First, the configuration will be described. The configuration of the half thrust bearing 8 of this embodiment is generally similar to that of the first embodiment, except for the configuration of the oil groove 81a and the configuration of the inclined surfaces 85F and 85R.

[0047] In this embodiment, too, the sliding surface 81 (including the imaginary surfaces at the portions of the oil groove 81a and the inclined surfaces 85F, 85R that would be formed if they did not exist) is approximately flat in the central region 8C, and in the end region 8E, the entire surface is curved in the circumferential direction of the half thrust bearing 8 so as to form a single convex curved surface extending from the back surface 84 side toward the sliding surface 81 side.

[0048] 15, the sliding surface 81 and the back surface 84 are drawn parallel to a plane perpendicular to the axial direction of the half thrust bearing 8. The half thrust bearing 8 of this embodiment is provided with four oil grooves 81a extending radially (from the center of the half thrust bearing) on ​​the sliding surface 81 side.

[0049] The half thrust bearing 8 further includes inclined surfaces 85F, 85R adjacent to the circumferential ends 81aE, 81aE of the oil groove 81a on the sliding surface 81 side. The inclined surfaces 85F, 85R are wall thickness reducing regions formed so that the wall thickness T of the half thrust bearing 8 gradually becomes thinner from the sliding surface 81 toward the circumferential ends 81aE, 81aE of the oil groove 81a and has a minimum thickness T1 at the circumferential end 81aE of the oil groove 81a, and extend over the entire radial length of the half thrust bearing 8. The inclined surfaces 85F, 85R are formed to increase the pressure of the oil flowing through the gap between the inclined surfaces 85F, 85R and the thrust collar surface 12 during operation of the internal combustion engine, thereby increasing the load capacity of the half thrust bearing 8.

[0050] The depth D0 of the inclined surface, defined as the length perpendicular to the sliding surface 81 from the sliding surface 81 to the inclined surfaces 85F, 85R at a position adjacent to the circumferential end 81aE of the oil groove 81a, may be 5 to 80 μm. The length of each of the inclined surfaces 85F, 85R parallel to the circumferential direction of the half thrust bearing 8 (circumferential length) may be a length corresponding to a circumferential angle of 5° to 25°. However, these dimensions of the depth D0 of the inclined surface and the length of the inclined surface are merely examples and are not limited to the above-mentioned dimensional ranges.

[0051] In addition, without being limited to this embodiment, it is also possible to form only the inclined surface 85F adjacent to the front circumferential end 81aE of the oil groove 81a in the rotational direction X (the direction of the X arrow in FIG. 14) of the thrust collar surface 12, and not to form the inclined surface 85R adjacent to the rear circumferential end 81aE of the oil groove 81a in the rotational direction X of the crankshaft (thrust collar surface 12).

[0052] In addition, when an oil groove 81a is formed at a position including the circumferential end 86 of the sliding surface 81 in the end region 8E, the axial distance L2 is defined as the axial distance between the imaginary sliding surface and the reference surface 90 when the oil groove 81a is not formed at the circumferential end 86.

[0053] Although the embodiments of the present invention have been described in detail above with reference to the drawings, it should be understood that the specific configurations are not limited to these embodiments, and that design changes that do not depart from the gist of the present invention are included in the present invention.

[0054] For example, in the embodiment, a bearing device 1 of a type in which the half bearing and the half thrust bearing are separate has been described, but the present invention is not limited to this and can also be applied to a bearing device 1 of a type in which the half bearing and the half thrust bearing are integrated.

[0055] 16, the half thrust bearing may be provided with a protrusion 88 that protrudes radially outward for positioning and rotation prevention. Note that the protrusion 88 does not have to satisfy the configuration of the axial distances L1, L2 and the bearing wall thickness T described above. 16 and 17, the circumferential length of the half thrust bearing may be formed to be shorter by a predetermined length S1 from the position of the circumferential end face of the half thrust bearing 8 shown in the first embodiment (thrust bearing dividing plane HP). Furthermore, the inner circumferential surface of the half thrust bearing may be cut out in an arc shape of radius R near both circumferential ends. Also, a back surface relief 82B may be formed in an area adjacent to the back surface 84 and the circumferential end face 83 of the half thrust bearing.

[0056] Also, a chamfer may be formed along the circumferential direction on the radially outer edge and / or the radially inner edge of the sliding surface of the half thrust bearing. In this case, the bearing wall thickness T of the half thrust bearing can be represented by the bearing wall thickness when no chamfer is formed.

[0057] In the above embodiment, four half thrust bearings are used in the bearing device, but the present invention is not limited to this, and the desired effect can be obtained by using at least one half thrust bearing according to the present invention. In the bearing device, the half thrust bearing of the present invention may be integrally formed on one or both axial end faces of the half bearing that rotatably supports the crankshaft. [Explanation of symbols]

[0058] 1 Bearing device 11 Journal Section 12 Thrust collar surface 2 Cylinder block 3 Bearing cap 4 Bearing housing 5 Bearing hole (retaining hole) 6 catch seat 7 Half bearing 71 Lubricant groove 72 Through hole 8. Half Thrust Bearing 8C central area 8E End area 8X adjacent positions 81 Sliding surface 81a Oil groove 82 Thrust relief 82B Rear relief 83 Circumferential end face 84 Back 85F Slope 85R slope 86 Circumferential end 88 Protrusion 90 Reference plane C Circumferential center HP Thrust Bearing Split Plane L1 Axial distance L2 Axial distance L3 Axial distance difference L4 Axial distance L5 Thrust relief length RD1 Thrust relief depth T Bearing wall thickness T1 Bearing wall thickness X Rotation Direction θ1 Circumferential angle

Claims

1. A roughly semicircular ring-shaped half thrust bearing (8) for receiving an axial force of a crankshaft of an internal combustion engine, The half thrust bearing has a sliding surface (81) that receives the axial force and a back surface (84) on the opposite side thereof, and a bearing wall thickness (T) between the sliding surface (81) and the back surface (84) is constant; the half thrust bearing (8) has a substantially flat central region (8C) including a circumferential central portion (C) of the half thrust bearing (8), and two end regions (8E) on both circumferential sides of the central region (8C), each end region (8E) extending from each circumferential end portion (86) of the half thrust bearing (8) toward the circumferential central portion (C) over a circumferential angle (θ1) of 5° or more and 35° or less, a reference surface (90) is defined by an imaginary plane that is perpendicular to the axial direction of the half thrust bearing (8), parallel to the sliding surface (81) in the central region (8C) of the half thrust bearing (8), and located on the sliding surface (81) side of the half thrust bearing (8), away from the sliding surface (81), and at this time, an axial distance (L) between the sliding surface (81) and the reference surface (90) is a minimum (L1) in the central region (8C), and in each end region (8E), continuously increases in the circumferential direction from the central region (8C) side toward the circumferential end (86) side, at any radial position.

2. 2. The half thrust bearing according to claim 1, wherein a difference between an axial distance (L1) between the sliding surface (81) and the reference surface (90) in the central region (8C) and an axial distance (L2) between the sliding surface (81) and the reference surface (90) at the circumferential end portion (86) is 10 to 60 μm.

3. 3. The half thrust bearing according to claim 1, further comprising two thrust reliefs (82) formed on the sliding surface (81) and adjacent to each of the circumferential ends (86) of the half thrust bearing (8).

4. 3. The half thrust bearing according to claim 1, further comprising at least one oil groove (81a) formed in the sliding surface (81).

5. 5. The half thrust bearing according to claim 4, wherein the oil groove (81 a) has a groove portion extending radially of the half thrust bearing (8) and one or two radially extending inclined portions formed adjacent to one or both circumferential ends (81 aE) of the groove portion, and the inclined portions are inclined such that a wall thickness of the half thrust bearing (8) decreases from the sliding surface (81) side toward the groove portion side when viewed in a cross section of the half thrust bearing (8) cut in the circumferential direction.

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