Half thrust bearing

Abstract

To provide a half-split thrust bearing in which a burnout during operation of an internal combustion engine is suppressed.SOLUTION: A half-split thrust bearing includes two oil grooves on a slide surface. A straight line perpendicular to an axial direction of the half-split thrust bearing and passing through a semi-circle center and a circumferential center is defined as a vertical center line, and a straight line perpendicular to the axial direction of the half-split thrust bearing passing through each circumferential end surface is defined as a horizontal center line. The oil grooves extend in parallel with the vertical center line, and opens on an inner peripheral-side edge part and an outer peripheral-side edge part of the half-split thrust bearing. The oil groove includes a groove bottom surface of a constant groove width, a constant bottom surface width, and a constant groove depth. The two oil grooves are arranged away from the vertical center line symmetrically with respect to the vertical center line. In a cross-sectional view vertical to a slide surface and in parallel with the vertical center line, the groove bottom surface of the oil groove is formed of a convex-concave surface having a plurality of projections and a plurality of recesses that continuously project and recess without a flat part, and a ridge line of each convex and a trough line of each concave extend in parallel with the horizontal center line. A difference in height of the convex-concave surface is 5% or more and 20% or less of the groove depth.SELECTED DRAWING: Figure 4

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, and more particularly to a half thrust bearing that has oil grooves for supplying lubricating oil to sliding surfaces. [Background technology]

[0002] The crankshaft of an internal combustion engine is rotatably supported at its journal portion on the lower part of the cylinder block of the internal combustion engine via a main bearing formed 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 is intended to bear the axial force generated in the crankshaft, i.e., to support the axial force input to the crankshaft when the crankshaft and transmission are connected by the clutch.

[0005] The crankshaft of an internal combustion engine is supported at its journal portion on the lower part of the cylinder block of the engine via a main bearing consisting of a pair of half bearings. Lubricating oil is supplied from the oil gallery in the cylinder block wall through a through-hole in the wall of the main bearing and into an oil groove formed along the inner surface of the main bearing. In this way, lubricating oil is supplied into the oil groove of the main bearing and then to the half thrust bearing.

[0006] An oil groove is formed on the sliding surface of the half thrust bearing to supply lubricating oil to the sliding surface (see FIG. 1 of Patent Document 1).

[0007] In recent years, oil pumps for supplying lubricating oil to internal combustion engines have become smaller, resulting in a decrease in the amount of lubricating oil supplied to bearings. This has led to a decrease in the amount of lubricating oil leaking from the end faces of the main bearings, and a corresponding decrease in the amount of lubricating oil supplied to half thrust bearings. To address this issue, a technology has been proposed that improves the oil retention of lubricating oil by, for example, forming multiple narrow grooves in parallel on the sliding surface of the half thrust bearing (see Patent Document 2). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-201145 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-323928 Summary of the Invention [Problem to be solved by the invention]

[0009] Furthermore, in recent years, the diameter of crankshafts has been reduced to reduce the weight of internal combustion engines, resulting in lower rigidity than conventional crankshafts. This makes the crankshaft more susceptible to bending during operation of the internal combustion engine, increasing the tendency for the crankshaft to vibrate. This increases the inclination of the thrust collar surface relative to the sliding surface near the circumferential center of the half thrust bearing. This causes direct contact between the sliding surface near the circumferential center of the half thrust bearing and the thrust collar surface of the crankshaft, making it more susceptible to damage (seizure).

[0010] Patent Document 2 discloses a configuration in which lubricating oil is supplied to almost the entire surface of the bearing surface by providing a plurality of narrow grooves on the sliding surface. However, even if the technology of Patent Document 2 is adopted, it is difficult to prevent the sliding surface near the circumferential center of the half thrust bearing from coming into contact with the thrust collar of the crankshaft when vibration caused by the bending of the crankshaft described above is large. When the vibration of the crankshaft increases during operation of an internal combustion engine, the sliding surface of the half thrust bearing and the collar surface of the crankshaft repeatedly move toward and away from each other. When the sliding surface of the half thrust bearing and the collar surface of the crankshaft move toward each other, oil in the lubrication oil groove is pressed against the collar surface of the crankshaft and leaks out from the openings on the outer and inner sides of the lubrication oil groove. This results in insufficient lubrication oil being supplied to the sliding surface near the center of the half thrust bearing in the circumferential direction, which can cause the sliding surface of the half thrust bearing to seize.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a half thrust bearing that is less likely to seize during operation of an internal combustion engine. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a semi-annular half thrust bearing for receiving the axial force of an internal combustion engine crankshaft. This half thrust bearing has a sliding surface that receives the axial force and a back surface that is parallel to the opposite sliding surface, and the sliding surface has two oil grooves. Here, a line that passes through the center and circumferential center of the semi-annular shape and is perpendicular to the axial direction of the half thrust bearing is defined as a vertical centerline, and a line that passes through each circumferential end face and is perpendicular to the axial direction of the half thrust bearing is defined as a horizontal centerline. Each oil groove extends parallel to the vertical centerline and opens at the inner and outer peripheral edges of the half thrust bearing. Each oil groove has a groove bottom and has a constant groove width, a constant bottom width, and a constant groove depth. The two oil grooves are located symmetrically about the vertical centerline and spaced apart from the vertical centerline. When viewed in a cross section perpendicular to the sliding surface and parallel to the vertical center line LV, the bottom surface of the oil groove is an uneven surface consisting of a plurality of continuously undulating peaks and valleys without any flat portions, the ridge line of each peak and the valley line of each valley extend parallel to the horizontal center line, and the height difference of the uneven surface is 5% to 20% of the groove depth.

[0013] According to one embodiment of the present invention, the height difference of the uneven surface is preferably 5% or more and 15% or less of the groove depth.

[0014] According to one embodiment of the present invention, the pitch between the ridgelines of adjacent mountains on the bottom surface of the groove in the direction parallel to the vertical center line is preferably 1 to 3 mm.

[0015] According to one embodiment of the present invention, the oil groove is preferably spaced apart from the vertical center line by a circumferential angle θ in the range of 20° to 45°.

[0016] According to one embodiment of the present invention, it is preferable that the sliding surface further has another oil groove. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. 2 is a front view of a half bearing and a thrust bearing. [Figure 4] FIG. 2 is a front view of the half thrust bearing of the first embodiment. [Figure 5] 5 is a cross-sectional view of the half thrust bearing taken along line AA in FIG. 4. [Figure 6] FIG. 5 is a BB cross-sectional view of the half thrust bearing of FIG. 4. [Figure 7A] FIG. 6 is an enlarged view of the vicinity of the groove bottom surface in FIG. 5. [Figure 7B] FIG. 7B is an enlarged view of the view taken along arrow C in FIG. 7A. [Figure 8] FIG. 2 is a front view of a half thrust bearing for explaining the operation of the present invention. [Figure 9] 9 is a cross-sectional view of the half thrust bearing taken along line CC of FIG. 8 for explaining the operation of the present invention. FIG. [Figure 10] FIG. 1 is a front view of a half thrust bearing according to the prior art. [Figure 11] 11 is a cross-sectional view of the half thrust bearing taken along the line A1-A1 in FIG. 10. [Figure 12] FIG. 10 is a diagram for explaining the operation of the prior art. [Figure 13] FIG. 10 is a diagram for explaining the operation of the prior art. [Figure 14] FIG. 10 is a front view of a half thrust bearing of another embodiment. [Figure 15] 15 is a view of the half thrust bearing of FIG. 14 as seen from the Y1 arrow. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will now be described with reference to the drawings.

[0019] (Overall configuration of bearing device) First, the overall configuration of a bearing device 1 having a half thrust bearing 8 of the present invention will be described using Figures 1 to 3. As shown in Figures 1 to 3, a bearing housing 4 formed by attaching a bearing cap 3 to the bottom 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 surfaces. Half bearings 7, 7 that 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 that receive axial force f (see Figure 2) via a thrust collar 12 of the crankshaft are assembled and fitted in a circular shape into the seats 6, 6.

[0020] As shown in Figure 3, of the half bearings 7 that make up the main bearing, the half bearing 7 on the cylinder block 2 side (upper side in the figure) has a lubricating oil groove 71 formed in its inner peripheral surface, and a through-hole 72 that penetrates through to the outer peripheral surface is formed within the lubricating oil groove 71. Note that lubricating oil grooves can also be formed in both the upper and lower half bearings.

[0021] (Configuration of half thrust bearing) Next, the configuration of the half thrust bearing 8 of the embodiment will be described with reference to Figures 4 to 7. Figure 4 is a front view of the half thrust bearing 8 of the embodiment 1, Figure 5 is a cross-sectional view taken along line AA in Figure 4, Figure 6 is a cross-sectional view taken along line BB in Figure 4, Figure 7A is an enlarged view of the vicinity of the groove bottom surface in Figure 5, and Figure 7B is a view seen from the direction of arrow C in Figure 7A. The half thrust bearing 8 of this embodiment is formed into a semicircular flat plate using a bimetal, for example, a steel backing layer with a thin bearing alloy layer bonded thereto. The half thrust bearing 8 has a sliding surface 81, which is the surface of the bearing alloy layer and supports the thrust collar 12, and a back surface 82, which is the surface of the backing layer opposite the side to which the bearing alloy layer is bonded; the sliding surface 81 and back surface 82 are parallel. Two oil grooves 81a, 81a are formed in the sliding surface 81 to supply lubricating oil to the sliding surface 81.

[0022] The vertical centerline LV is the centerline that intersects perpendicularly with the axial direction of the half thrust bearing 8 and passes through the center O of the semicircular ring shape and the circumferential center CP, while the horizontal centerline LH is the centerline that intersects perpendicularly with the axial direction of the half thrust bearing 8 and passes through each circumferential end face 83. Here, the axial direction of the half thrust bearing 8 is perpendicular to the sliding surface, and the circumferential center CP is the position where the circumferential angle from both circumferential end faces 83 is equal. The vertical centerline LV and the horizontal centerline LH are perpendicular to each other. The oil groove 81a extends parallel to the vertical centerline LV (roughly speaking, ignoring the unevenness described below) and opens at the radially inner end (inner peripheral edge) 8i and the radially outer end (outer peripheral edge) 8o of the half thrust bearing 8. The oil groove 81a has a groove bottom surface 90 that is parallel to the sliding surface 81 in a cross-sectional view perpendicular to the sliding surface 81 and parallel to the horizontal center line LH. The groove width W1 and bottom width W2 of the oil groove 81a are constant in the direction in which the oil groove 81a extends (see FIG. 6). The two oil grooves 81a have the same groove width W1 and groove bottom width W2. The groove width W1 of the oil groove 81a is defined as the length of the oil groove 81a in a direction parallel to the horizontal center line LH at the position of the sliding surface 81, and the bottom width W2 is defined as the length of the groove bottom surface 90 in a direction parallel to the horizontal center line LH.

[0023] The two oil grooves 81a, 81a are formed in the sliding surface 81 symmetrically with respect to the vertical center line LV and spaced apart from the vertical center line LV. The oil groove 81a can be spaced apart from the vertical center line LV by a circumferential angle θ1 in the range of 20° to 45° (see FIG. 4). Here, the angle of separation of the oil groove 81a from the vertical center line LV is represented by the circumferential angle (centered at the center O of the semicircular ring shape) at the position of the groove end portion on the circumferential center side of the half thrust bearing 8 at the position of the outer peripheral edge 8o of the oil groove 81a.

[0024] The groove bottom surface 90 of the oil groove 81a is an uneven surface consisting of multiple continuously undulating peaks 91 and multiple valleys 92 without any flat portions, in a cross section perpendicular to the sliding surface 81 and parallel to the vertical center line LV. The groove depth D of the oil groove 81a is defined as the depth from the sliding surface 81 to the deepest points 92P of the valleys 92 in the direction perpendicular to the sliding surface (see FIG. 7A). The dashed lines in FIGS. 5 and 7A indicate imaginary lines connecting the deepest points 92P of the valleys 92, and the distance from the sliding surface 81 to this imaginary line (groove depth D) is constant in the extension direction of the oil groove 81a. The groove depth D of the oil groove 81a may vary slightly in the extension direction of the oil groove 81a. The ridge line 91L of each peak 91 and the valley line 92L of each valley 92 extend parallel to the horizontal center line LH. The ridge line 91L of each peak 91 is defined as a line connecting the peaks 91P of the peaks 91, and the valley line 92L of each valley 92 is defined as a line connecting the deepest parts 92P of the valleys 92 (points with the greatest depth from the sliding surface 81) (see FIG. 7B . In FIG. 7B , the dashed-dotted lines indicate the ridge lines 91L, the broken lines indicate the valley lines 92L, and the H arrow indicates a direction parallel to the horizontal center line).

[0025] The pitch P1 between the ridge lines 91L of adjacent mountains 91 in the direction parallel to the vertical center line LV is preferably 1 to 3 mm, but is not limited to this and may be other dimensions.

[0026] The height difference of the uneven surface, i.e., the height h of the peaks 91, is 5% or more and 20% or less of the groove depth D. It is more preferable that the height h of the peaks 91 is 5% or more and 15% or less of the groove depth D. It is preferable that the height h of the peaks 91 is constant in the extension direction of the ridge line 91L, but it may vary slightly in the extension direction of the ridge line as long as it is within a range in which the relationship between the groove depth D and the height h of the peaks 91 is established.

[0027] (action) Next, the operation of the half thrust bearing 8 of this embodiment will be described with reference to FIGS.

[0028] Figure 8 shows a front view of the half thrust bearing 8 when the sliding surface 81 and the surface of the thrust collar 12 are closest together, with X indicating the rotation direction of the crankshaft (thrust collar 12), and the arrows flowing out from the oil groove 81a indicating the flow of oil from the oil groove 81a into the gap between the sliding surface 81 and the surface of the thrust collar 12. Figure 9 shows a CC cross section of the half thrust bearing 8 of Figure 8, with the hollow arrows indicating the flow of oil toward the groove bottom surface 90 and the solid arrows indicating the flow of oil along the groove side surface 93 (reverse flow).

[0029] As described above, when vibrations caused by bending of the crankshaft increase during operation of the internal combustion engine, the surface of the thrust collar 12 of the crankshaft repeatedly moves toward and away from the sliding surface 81 of the half thrust bearing 8 while changing its inclination angle or undulating, with the surface of the thrust collar 12 coming closest particularly near the circumferential center of the half thrust bearing 8. When the sliding surface 81 of the half thrust bearing 8 and the surface of the thrust collar 12 of the crankshaft move from a separated state to a relatively closer state, the oil in the gap between the groove bottom surface 90 of the oil groove 81a of the half thrust bearing 8 and the surface of the thrust collar 12 of the crankshaft is compressed, increasing its pressure, and flows as if being forced toward the groove bottom surface 90. In a cross-sectional view perpendicular to the sliding surface 81 and parallel to the vertical center line LV, the groove bottom surface 90 of the oil groove 81 is an uneven surface consisting of multiple continuously undulating peaks 91 and multiple valleys 92 with no flat portions, and the ridge lines 91L of each peak and the valley lines 92L of each valley extend parallel to the horizontal center line LH. Therefore, the high-pressure oil flowing toward the groove bottom surface 90 of the oil groove 81a flows along the valleys 92 because the peaks 91 provide flow resistance in the direction of the oil groove extension (direction parallel to the vertical center line LV), and flows toward both ends in the width direction of the groove bottom surface 90 (the ends in the direction of extension of the valley lines 92L). Then, due to the inertial force, the oil flows back along the groove side surfaces 93 of the oil groove 81a and flows out into the gap between the sliding surface 81 and the surface of the thrust collar 12. This leaked oil adheres to the surface of the thrust collar 12 and is sent to the sliding surface 81 near the circumferential center of the half thrust bearing 8, thereby preventing damage (seizure) to the sliding surface 81 near the circumferential center of the half thrust bearing 8.

[0030] The above action is mainly due to the oil groove 81a (the oil groove 81a on the left side of the paper in FIG. 4) that is rearward in the rotational direction of the crankshaft (thrust collar 12) with respect to the circumferential center CP of the half thrust bearing 8. The rotational direction X of the thrust collar surface relative to the half thrust bearings 8, 8 arranged on the seat 6 on the left side of the paper in FIG. 2 is opposite to the rotational direction X of the thrust collar surface relative to the half thrust bearings 8, 8 arranged on the seat 6 on the right side of the paper. For the half thrust bearing 8 arranged on the side that is opposite the rotational direction (counterclockwise rotation) of the thrust collar 12 shown in FIG. 2, the oil groove 81a on the right side of the paper in FIG. 4 is mainly involved in the action.

[0031] It is preferable that the oil groove 81a (the end of the groove width W1 on the circumferential center side of the half thrust bearing 8 at the position of the outer peripheral edge 8o of the oil groove 81a) be spaced apart from the vertical center line LV at a circumferential angle θ1 in the range of 20° to 45°. When the crankshaft bends during operation of the internal combustion engine and vibration of the crankshaft increases, the inclination of the surface of the thrust collar 12 relative to the sliding surface 81 near the circumferential center of the half thrust bearing 8 becomes particularly large, narrowing the gap between the two surfaces. If the oil groove 81a is spaced at a circumferential angle θ1 of less than 20° from the vertical center line LV, the gap between the sliding surface 81 adjacent to the oil groove 81a and the surface of the thrust collar 12 may become too narrow, making it difficult for the oil in the oil groove 81a to flow into the gap. Furthermore, if the oil groove 81a is spaced apart from the vertical center line LV at a circumferential angle θ1 of more than 45°, the oil that flows out from the oil groove 81a into the gap between the sliding surface 81 adjacent to the oil groove 81a and the surface of the thrust collar 12 will, due to the action of centrifugal force, flow out from the outer peripheral edge 8o side of the half thrust bearing 8 before it reaches the sliding surface 81 near the circumferential center, which may result in an insufficient amount of oil flowing to the sliding surface 81 near the circumferential center.

[0032] Furthermore, the height difference of the uneven surface, i.e., the height h of the peaks, is 5% to 20% of the depth D of the oil groove 81a. If the height h of the peaks is less than 5% of the depth D of the oil groove 81a, the high-pressure oil that has flowed toward the groove bottom surface 90 of the oil groove 81a will also tend to flow in the extension direction of the oil groove 81a (the direction parallel to the vertical center line) and will leak out from the opening on the outer peripheral edge 8o side or the opening on the inner peripheral edge 8i side of the oil groove 81a, resulting in an insufficient amount of oil flowing to the sliding surface 81 near the circumferential center.

[0033] Generally, when laminar oil flow becomes turbulent, pressure loss occurs, resulting in mechanical losses in the internal combustion engine. Even during normal operation of the internal combustion engine, small deflections and vibrations occur in the crankshaft, but if the height h of the ridge exceeds 20% of the depth D of the oil groove 81a, this small vibration causes the sliding surface 81 of the half thrust bearing 8 and the surface of the thrust collar 12 to approach each other, and oil is more likely to flow along the groove side surface 93 of the oil groove 81a into the gap between the sliding surface 81 and the surface of the thrust collar 12. When this oil flow collides (merges) with the oil flow (laminar flow) that flows along the surface of the thrust collar 12 and through the gap between the sliding surface 81 and the surface of the thrust collar 12, the oil becomes turbulent, resulting in increased mechanical losses in the internal combustion engine. If the groove depth D of the oil groove 81a is 20% or less, oil will not flow along the groove side surface 93 of the oil groove 81a into the gap between the sliding surface 81 and the surface of the thrust collar 12 when the sliding surface 81 of the half thrust bearing 8 and the surface of the thrust collar 12 come close to each other due to small deflections and vibrations of the crankshaft during normal operation of the internal combustion engine. This makes it possible to prevent an increase in mechanical loss during normal operation of the internal combustion engine.

[0034] In contrast to this, when the ridge lines 91L of the peaks 91 and the valley lines 92L of the valleys 92 on the groove bottom surface 90 of the oil groove 81a are inclined with respect to the horizontal center line LV, unlike in the embodiment, the greater the inclination angle, the smaller the resistance to the flow of high-pressure oil in the extension direction of the oil groove 81a (the direction parallel to the vertical center line LV) that has flowed toward the groove bottom surface 90. This makes it easier for the oil to leak out from the opening on the outer peripheral edge 8o side and the opening on the inner peripheral edge 8i side of the oil groove 81a, making it difficult for the oil to be delivered to the sliding surface 81 near the circumferential center of the half thrust bearing 8, and therefore makes the sliding surface 81 near the circumferential center of the half thrust bearing 8 more susceptible to damage (seizure).

[0035] Next, the configuration and operation of a conventional half thrust bearing 18 will be described using Figures 10, 11, 12, and 13. Figure 10 is a front view of the sliding surface side of half thrust bearing 18, Figure 11 is a cross-sectional view taken along the line A1-A1 in Figure 10, Figure 12 is a front view of the sliding surface 181 of half thrust bearing 18 and the surface of thrust collar 12 at their closest position, with X indicating the direction of rotation of the crankshaft (thrust collar 12) and the white arrow indicating the flow of oil, and Figure 13 is a cross-sectional view taken along the line C1-C1 in Figure 12 of half thrust bearing 18, with the white arrow indicating the flow of oil.

[0036] The half thrust bearing 18 of the prior art has the same configuration as the half thrust bearing 8 of the embodiment, except for the groove bottom surface 190 of the oil groove 181a. The groove bottom surface 190 of the oil groove 181a of the half thrust bearing 18 of the prior art is a flat surface parallel to the sliding surface 181 in a cross section perpendicular to the sliding surface 181 and parallel to the vertical center line LV (see FIG. 11). When the sliding surface 181 of the half thrust bearing 18 and the surface of the thrust collar 12 of the crankshaft move from a spaced apart state to a relatively closer state, the oil in the gap between the groove bottom surface 190 of the oil groove 181a of the half thrust bearing 18 and the surface of the thrust collar 12 of the crankshaft flows as if being pushed toward the groove bottom surface 190. Because the groove bottom surface 190 of the oil groove 181a is a flat surface, the oil that flows toward the groove bottom surface 190 of the oil groove 181a flows along the groove bottom surface 190 in the extension direction of the oil groove 181a (parallel to the vertical center line) and flows out to the outside from the opening on the outer peripheral edge 18o side of the oil groove 181a or the opening on the inner peripheral edge 18i side. As a result, the oil cannot flow out into the gap between the sliding surface 181 adjacent to the oil groove 181a and the surface of the thrust collar 12, and the oil becomes difficult to supply to the sliding surface 181 near the circumferential center of the half thrust bearing 18.

[0037] Although the embodiments of the present invention have been described above in detail 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.

[0038] FIG. 14 shows a front view of a half thrust bearing 8 of another embodiment, and FIG. 15 shows a view taken along the Y1 arrow of the half thrust bearing 8 of FIG. 14. For example, as shown in FIG. 14, the half thrust bearing 8 may be provided with a protrusion 88 that protrudes radially outward for positioning and rotation prevention. Also, as shown in FIGS. 14 and 15, thrust reliefs 84 may be formed at both circumferential ends of the sliding surface 81 of the half thrust bearing 8, and back surface reliefs 84B may be formed at both circumferential ends of the back surface 82. Furthermore, the circumferential length of the half thrust bearing 8 may be shorter by a predetermined length S1 than the position of the circumferential end face 83 (thrust bearing dividing plane HP) of the half thrust bearing 8 shown in the first embodiment. Furthermore, the half thrust bearing 8 may have an inner peripheral surface cut out in the shape of an arc with a radius R near the circumferential end.

[0039] Furthermore, the half thrust bearing 8 may have other oil grooves in addition to the two oil grooves described above. The other oil grooves may be arranged in any manner and have any structure. For example, they may be oil grooves that extend parallel to the vertical center line LV at the circumferential center CP of the sliding surface 81.

[0040] Furthermore, although the above description has been given of a case in which four half thrust bearings are used in the bearing device, the present invention is not limited to this, and the desired effect can be achieved by using at least one half thrust bearing according to the present invention. Furthermore, in the bearing device of the present invention, the half thrust bearings may be formed integrally with one or both axial end faces of the half bearing that rotatably supports the crankshaft. [Explanation of symbols]

[0041] 1 Bearing device 11 Journal Department 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 8i Inner edge 8o Outer edge 81 Sliding surface 81a Oil groove 82 Back 83 Circumferential end faces 84 Thrust Relief 84S Rear Relief 90 Groove bottom surface 91 mountains 91L Ridgeline 91P Top 92 Valley 92L Valley line 92P Deepest 93 Groove side CP circumferential center D Groove depth h Mountain height HP thrust bearing split plane LH horizontal center line LV vertical centerline O center P1 Pitch W1 Groove width W2 Bottom width X rotation direction θ1 Circumferential angle H Parallel to the horizontal center line LH

Claims

1. A semicircular half thrust bearing (8) for receiving an axial force of a crankshaft of an internal combustion engine, the half thrust bearing having a sliding surface (81) that receives the axial force and a back surface (82) that is parallel to the sliding surface on the opposite side, and having two oil grooves (81 a) on the sliding surface; If a straight line that is perpendicular to the axial direction of the half thrust bearing and passes through the center (O) and circumferential center (CP) of the semicircular ring shape is defined as a vertical center line (LV), and a straight line that is perpendicular to the axial direction of the half thrust bearing and passes through each circumferential end face is defined as a horizontal center line (LH), each oil groove extends parallel to the vertical center line (LV) and opens to an inner peripheral edge portion (8i) and an outer peripheral edge portion (8o) of the half thrust bearing, Each oil groove has a groove bottom surface (90), a constant groove width (W1) and a constant bottom width (W2), In the half thrust bearing (8), the two oil grooves (81 a) are positioned symmetrically with respect to the vertical center line (LV) and spaced apart from the vertical center line (LV), In a cross-sectional view perpendicular to the sliding surface (81) and parallel to the vertical center line (LV), the groove bottom surface (90) of the oil groove (81a) is an uneven surface consisting of a plurality of continuously undulating peaks (91) and a plurality of valleys (92) without any flat portion, and when the depth of the deepest part (92P) of each valley (92) is defined as a groove depth (D), each of the oil grooves has a constant groove depth (D); The ridge line (91L) of each peak (91) and the valley line (92L) of each valley (92) extend parallel to the horizontal center line (LH), A half thrust bearing, characterized in that the height difference (h) of the uneven surface is 5% or more and 15% or less (excluding 15%) of the groove depth (D).

2. 2. The half thrust bearing according to claim 1, wherein a pitch (P1) between the ridge lines (91L) of adjacent peaks (91) on the groove bottom surface (90) in a direction parallel to the vertical center line (LV) is 1 to 3 mm.

3. 2. The half thrust bearing according to claim 1, wherein the oil groove (81a) is spaced from the vertical center line (LV) at a circumferential angle θ in the range of 20° to 45°.

4. 2. The half thrust bearing according to claim 1, further comprising another oil groove on said sliding surface.

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