Sliding component

Abstract

Provided is a sliding component having high floating effect.　A sliding component 3 is disposed between a housing 2 and a shaft 1 inserted into the housing 2, and has a pair of sliding surfaces 11, 21 that rotate relatively. At least one sliding surface 11 includes a dynamic pressure generation groove 13 having an introduction part 14 on one side communicating with one space S1 and an introduction part 15 on the other side communicating with the other space S2, and a tip part 17B where both introduction parts 14, 15 merge on a relative rotation downstream side. The dynamic pressure generation groove 13 is shallower at the tip part 17B than at the introduction part 14 on one side and the introduction part 15 on the other side.

Description

Sliding parts

[0001] The present invention relates to a sliding part that rotates relative to another sliding part, such as a sliding part used in a shaft sealing device that seals the rotating shaft of a rotating machine in an automobile, general industrial machine, or other sealing field, or a sliding part used in a bearing of a machine in an automobile, general industrial machine, or other bearing field.

[0002] Some bearing devices that support a rotating shaft have thrust bearings that rotatably support the rotating shaft in the thrust direction. In recent years, there has been a demand for reducing the energy lost due to sliding in such thrust bearings, for environmental reasons.

[0003] For example, the thrust bearing disclosed in Patent Document 1 includes an annular sliding ring fixed to a rotating shaft and an annular sliding ring provided on the housing side. A plurality of herringbone-shaped dynamic pressure grooves, which are generally V-shaped when viewed in the axial direction, are formed circumferentially on the sliding surface of the housing-side sliding ring. The dynamic pressure grooves have a constant depth, with their apexes facing downstream of relative rotation. Their outer diameter ends communicate with an outer diameter space, and their inner diameter ends communicate with an inner diameter space. The outer diameter space and the inner diameter space, i.e., the housing, are filled with lubricating oil.

[0004] When the rotating shaft rotates, lubricating oil is supplied from the outer and inner diameter ends of the dynamic pressure grooves, generating dynamic pressure at the top of the dynamic pressure grooves. This dynamic pressure effect causes the sliding ring on the rotating shaft to float slightly above the sliding ring on the housing in the direction of separation between the sliding surfaces, allowing lubricating oil to flow in, thereby improving lubrication.

[0005] JP 2007-327545 A (page 7, Figure 2)

[0006] In thrust bearings such as those described in Patent Document 1, large positive pressure can be generated by increasing the circumferential length of the dynamic pressure grooves and introducing a large amount of lubricating oil from the outer diameter side space and the inner diameter side space. However, positive pressure is generated at the top of the dynamic pressure grooves, and the locations where positive pressure is generated on the sliding surface are dispersed in the circumferential direction, which could prevent a sufficient floating effect from being obtained.

[0007] The present invention has been made in view of these problems, and has as its object to provide a sliding part with a high floating effect.

[0008] In order to solve the above problems, the sliding component of the present invention is a sliding component that is arranged between a housing and a shaft inserted through the housing and has a pair of sliding surfaces that rotate relative to one another, at least one of the sliding surfaces having a dynamic pressure generating groove that has an inlet on one side that communicates with one space and an inlet on the other side that communicates with the other space, and a tip end where both the inlets join downstream of the relative rotation, and the dynamic pressure generating groove is shallower on the tip end side than on the inlet on one side and the inlet on the other side. This increases the pressure of the fluid introduced from the inlet on one side and the inlet on the other side as it moves toward the tip end, making it possible to increase the positive pressure over a wide range in the circumferential direction.

[0009] The dynamic pressure generating groove may be gradually shallower from at least one of the introduction portions toward the tip portion, thereby allowing the pressure to be gradually increased.

[0010] The bottom surface of the tip portion may be curved in the circumferential direction relative to the land, which makes it easier to guide the fluid flowing in the circumferential direction.

[0011] The bottom surface of the tip portion may be curved in a radial direction relative to the land, which makes it easier to guide the fluid flowing in the circumferential direction in the radial direction as well.

[0012] The angle of inclination of the bottom surface of at least one of the introduction portions may be larger than the angle of inclination of the bottom surface of the tip portion. This makes it easier to introduce the fluid from the introduction portion to the tip portion, and ensures that the tip portion where positive pressure is generated is large in the circumferential direction.

[0013] At least one of the introduction portions may be disposed along the radial direction, and the tip portion may be disposed along the circumferential direction, thereby ensuring a wide tip portion in the circumferential direction where positive pressure is generated.

[0014] The tip portion may be tapered in the forward rotation direction, thereby generating a large positive pressure at the tip of the tip portion.

[0015] The one-side introduction portion may be wider and longer than the other-side introduction portion, whereby the volume of the one-side introduction portion is larger than the volume of the other-side introduction portion, allowing a larger amount of fluid to be introduced into the one space.

[0016] The tip portion may be deeper on the one introduction port side than on the other introduction port side, which allows a larger amount of fluid to be introduced from the one introduction port and makes it easier to generate positive pressure on the other side of the tip portion.

[0017] 4 is a longitudinal sectional view showing an example of a thrust bearing according to a first embodiment of the present invention; FIG. 4 is a view of the sliding surface of the stationary ring according to the first embodiment from the axial direction; FIG. 4 is an enlarged view of the sliding surface of the stationary ring according to the first embodiment from the axial direction; FIG. 4 is a schematic sectional view taken along the line from the inner diameter-side inlet groove to the tip of the tip-side groove in the first embodiment; (a) is a sectional view taken along the line A-A in FIG. 4, and (b) is a sectional view taken along the line B-B in FIG. 4; FIG. 4 is an explanatory view of the movement of fluid in the dynamic pressure generating groove during forward rotation, as viewed from the axial direction, for the sliding surface of the stationary ring according to the first embodiment; and FIG. 4 is an explanatory view showing the pressure distribution in the dynamic pressure generating groove in the first embodiment. (a) is a schematic sectional view taken along the line from the inner diameter-side inlet groove to the tip of the tip-side groove in the second embodiment of the present invention; (b) is a sectional view taken along the line C-C in FIG. 4; and (c) is a sectional view taken along the line D-D in FIG. 4; and FIG. 4 is an enlarged view of the sliding surface of the stationary ring according to the third embodiment of the present invention from the axial direction. FIG. 10 is an enlarged view of the inner peripheral surface of a radial bearing according to a sixth embodiment of the present invention, as viewed from the axial direction.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sliding element according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0019] A sliding component according to a first embodiment will be described with reference to Fig. 1 to Fig. 7. In this embodiment, the sliding component is a thrust bearing, and the same lubricating oil is present in both the inner and outer spaces of the thrust bearing.

[0020] As shown in FIG. 1, the bearing device of this embodiment is mainly composed of a rotating shaft 1, a housing 2, a thrust bearing 3, and a radial bearing 4.

[0021] The housing 2 is cylindrical and has the rotating shaft 1 inserted therethrough. A radial bearing 4 is disposed axially between the rotating shaft 1 and the housing 2. The radial bearing 4 allows the rotating shaft 1 to rotate while restricting tilt.

[0022] A thrust bearing 3 is disposed on one axial side of the radial bearing 4 on the rotating shaft 1. The thrust bearing 3 is mainly composed of an annular stationary ring 10 and an annular rotating ring 20 as sliding components.

[0023] The rotating ring 20 is mounted on the rotating shaft 1 in a state where it can rotate together with the rotating shaft 1. The stationary ring 10 is fixed to the housing 2 in a non-rotating state. The sliding surface 11 of the stationary ring 10 and the sliding surface 21 of the rotating ring 20 are adapted to slide closely against each other. The sliding surface 21 of the rotating ring 20 is flat, and this flat surface does not have any recesses such as grooves.

[0024] The stationary ring 10 and the rotating ring 20 are typically formed of SiC (hard material) or a combination of SiC (hard material) and carbon (soft material), but are not limited thereto; any sliding material used as a sliding material for bearings can be used. Examples of SiC include sintered bodies using boron, aluminum, carbon, or other sintering aids, as well as materials consisting of two or more phases with different components and compositions, such as SiC with dispersed graphite particles, reaction-sintered SiC consisting of SiC and Si, SiC-TiC, and SiC-TiN. Examples of carbon include a mixture of carbonaceous and graphitic materials, resin-molded carbon, and sintered carbon. In addition to the above sliding materials, metal materials, resin materials, surface-modified materials (coating materials), composite materials, and the like can also be used.

[0025] 2 and 3, the rotating ring 20, which is a mating sliding part, slides counterclockwise relative to the stationary ring 10 as shown by the solid arrow. In the following description, the rotation direction of the solid arrow is assumed to be the forward rotation direction.

[0026] A plurality of dynamic pressure generating grooves 13 (ten in this embodiment) are evenly arranged in the circumferential direction on the sliding surface 11 of the stationary ring 10. The portion of the sliding surface 11 other than the dynamic pressure generating grooves 13 forms a land 12 that forms a flat surface.

[0027] The dynamic pressure generating groove 13 is composed of an outer diameter side inlet groove portion 14 as an inlet portion on one side, an inner diameter side inlet groove portion 15 as an inlet portion on the other side, and a tip side groove portion 17, and is a so-called herringbone-shaped groove that is roughly V-shaped when viewed in the axial direction.

[0028] As shown in FIG. 3, the outer diameter side introduction groove portion 14 communicates with the outer space S1 as one space, and extends in the inner diameter direction while inclining in the forward rotation direction when viewed in the axial direction.

[0029] The outer diameter side introduction groove 14 has a generally arcuate shape that is convex toward the inner diameter side when viewed in the axial direction. The inner diameter end 14a of the outer diameter side introduction groove 14 faces the generally forward rotation direction and is wider than the outer diameter end 14b.

[0030] The curvature of the side wall 14c on the downstream side of the relative rotation in the outer diameter side introduction groove portion 14 is greater than the curvature of the side wall 14d on the upstream side of the relative rotation in the outer diameter side introduction groove portion 14. Note that the curvature here refers to the average curvature. The same applies hereinafter.

[0031] The radial length L10 of the side wall 14c is shorter than the radial length L11 of the side wall 14d. In this embodiment, the side wall 14c has an inflection point, whereas the side wall 14d does not have an inflection point and has a substantially constant curvature. The curvatures of the side walls 14c and 14d may be constant or may vary.

[0032] The inner diameter side introduction groove portion 15 communicates with the inner space S2 as the other space, and extends in the outer diameter direction while inclining in the forward rotation direction when viewed in the axial direction.

[0033] The inner diameter side introduction groove 15 has a generally arcuate shape that is convex toward the outer diameter side when viewed in the axial direction. The outer diameter end 15a of the inner diameter side introduction groove 15 faces the generally forward rotation direction and is wider than the inner diameter end 15b.

[0034] Specifically, the curvature of the side wall 15c of the inner diameter side introduction groove 15 on the downstream side in the relative rotation direction is greater than the curvature of the side wall 15d of the inner diameter side introduction groove 15 on the upstream side in the relative rotation direction.

[0035] The radial length L20 of the side wall 15c is shorter than the radial length L21 of the side wall 15d. In this embodiment, the side wall 15c has an inflection point, whereas the side wall 15d has no inflection point and has a substantially constant curvature. The side walls 14d and 15d are connected in a substantially V-shape when viewed in the axial direction. The curvatures of the side walls 15c and 15d may be constant or may vary.

[0036] The tip groove 17 includes a confluence 17A where the inner diameter end 14a of the outer diameter introduction groove 14 and the outer diameter end 15a of the inner diameter introduction groove 15 join, and a tip 17B extending in the forward rotation direction from the confluence 17A. Note that, in this embodiment, the tip 17B is a positive pressure generating region, as described below, and the confluence 17A is a non-positive pressure generating region located upstream of the tip 17B in the relative rotation direction.

[0037] The tip groove 17 tapers in the forward rotation direction from the confluence 17A to the tip 17B when viewed in the axial direction. A tip 17Ba of the tip 17B is located near the center of the sliding surface 11 in the radial direction.

[0038] The tip side groove 17 has a larger circumferential component than the radial component than the outer diameter side inlet groove 14 and the inner diameter side inlet groove 15, and the outer diameter side inlet groove 14 and the inner diameter side inlet groove 15 have a larger radial component than the circumferential component than the tip side groove 17. In other words, the outer diameter side inlet groove 14 and the inner diameter side inlet groove 15 are disposed radially more than the tip side groove 17, and the tip side groove 17 is disposed circumferentially more than the outer diameter side inlet groove 14 and the inner diameter side inlet groove 15. Therefore, the circumferential dimension L1 of the outer diameter side inlet groove 14 and the circumferential dimension L1' of the inner diameter side inlet groove 15 can be reduced, and the circumferential dimension L2 of the tip side groove 17 can be made longer in the circumferential direction than the circumferential dimensions L1 and L1' (see FIG. 2 ). This allows for more dynamic pressure generating grooves 13 to be disposed circumferentially.

[0039] The outer diameter side wall 17a of the tip side groove 17 is generally arc-shaped and convex toward the outer diameter side, and the curvature of the side wall 14c of the outer diameter side introduction groove 14 is smaller and gentler than the curvature of the side wall 14d of the outer diameter side introduction groove 14. The curvature of the side wall 17a of the tip side groove 17 is also smaller and gentler than the curvature of the side wall 14d of the outer diameter side introduction groove 14.

[0040] The inner diameter side wall 17b of the tip side groove 17 is generally arc-shaped and convex toward the outer diameter side, and the curvature of the side wall 15c of the inner diameter side introduction groove 15 is smaller and gentler than the curvature of the side wall 15d of the inner diameter side introduction groove 15. The curvature of the side wall 17b of the tip side groove 17 is also smaller and gentler than the curvature of the side wall 15d of the inner diameter side introduction groove 15.

[0041] 4 is a cross-sectional view of the region from the inner diameter side introduction groove portion 15 to the tip end 17B of the tip end groove portion 17 along the extension direction. Note that the shape of the outer diameter side introduction groove portion 14 in the depth direction is substantially the same as the shape of the inner diameter side introduction groove portion 15 in the depth direction, and therefore a detailed description thereof will be omitted.

[0042] As shown in FIG. 4, the hydrodynamic groove 13 is shallower on the tip end portion 17B side than on the inner diameter side introduction groove portion 15.

[0043] Specifically, the bottom surface 15e of the inner diameter side introduction groove 15 is inclined so as to become gradually shallower toward the bottom surface 17c of the tip side groove 17. That is, the inner diameter side introduction groove 15 is deepest at the inner diameter end 15b. This bottom surface 15e is flat.

[0044] The bottom surface 17c of the tip groove portion 17 is inclined so as to become gradually shallower toward the land 12. The bottom surface 17c is flat.

[0045] The bottom surface 17c of the tip groove 17 is continuous in a smooth curve in the circumferential direction with the land 12. In other words, no surface rising in the depth direction is formed between the tip groove 17 and the land 12 located in the forward rotation direction of the tip groove 17.

[0046] The inclination angle θ1 of the bottom surface 15e of the inner diameter side introduction groove 15 is larger than the inclination angle θ2 of the bottom surface 17c of the tip side groove 17. The same applies to the bottom surface 14e of the outer diameter side introduction groove 14. In other words, the depth of the tip side groove 17 can be made shallow, and a wide positive pressure generation region is ensured, as will be described later.

[0047] As shown in FIG. 5A, the cross section of the inner diameter side introduction groove portion 15 in the width direction is substantially rectangular.

[0048] As shown in FIG. 5B, the cross section of the tip groove portion 17 in the width direction is substantially rectangular.

[0049] Next, the operation of the stationary ring 10 and the rotating ring 20 during relative rotation will be described with reference to Figures 6 and 7. In Figure 7, the pressure distribution is shown by the density of the dot pattern, and the darker the dot pattern, the higher the pressure.

[0050] As shown in FIG. 6, when the rotating ring 20 rotates relative to the stationary ring 10 in the forward rotation direction, the fluid in the dynamic pressure generating grooves 13 moves in the forward rotation direction of the rotating ring 20 due to shearing with the sliding surface 21 .

[0051] As a result, the fluid in tip groove 17 moves from confluence 17A toward tip 17Ba of tip portion 17B, and the fluid in outer diameter side inlet groove 14 and inner diameter side inlet groove 15 moves toward confluence 17A. Also, fluid is introduced from outer space S1 into outer diameter side inlet groove 14, and fluid is introduced from inner space S2 into inner diameter side inlet groove 15.

[0052] The bottom surface 14e of the outer diameter side inlet groove portion 14 and the bottom surface 15e of the inner diameter side inlet groove portion 15 are inclined so as to gradually become shallower toward the bottom surface 17c of the tip side groove portion 17, so that it is easy to guide fluid from the inner diameter end 14a of the outer diameter side inlet groove portion 14 and the outer diameter end 15a of the inner diameter side inlet groove portion 15, which are relatively deeper than other parts of the dynamic pressure generating groove 13, toward the tip side groove portion 17.

[0053] Furthermore, since the inclination angle θ2 of the bottom surface 17c of the tip groove portion 17 is smaller than the inclination angle θ1 of the bottom surface 14e of the outer diameter side inlet groove portion 14 and the bottom surface 15e of the inner diameter side inlet groove portion 15, the depth of the tip groove portion 17 can be made shallow over a wide range in the circumferential direction, and a wide positive pressure generation area can be secured in the circumferential direction.

[0054] Furthermore, the bottom surface 14e of the outer diameter side introduction groove 14 and the bottom surface 15e of the inner diameter side introduction groove 15 are flat surfaces, which allows the fluid to flow smoothly through the outer diameter side introduction groove 14 and the inner diameter side introduction groove 15.

[0055] Furthermore, the curvature of the side wall 14c of the outer diameter side inlet groove portion 14 and the side wall 15c of the inner diameter side inlet groove portion 15 is greater than the curvature of the side wall 14d of the outer diameter side inlet groove portion 14 and the side wall 15d of the inner diameter side inlet groove portion 15, and the inner diameter end 14a of the outer diameter side inlet groove portion 14 and the outer diameter end 15a of the inner diameter side inlet groove portion 15 face approximately in the positive rotation direction, so that fluid can be efficiently introduced in the positive rotation direction.

[0056] Furthermore, the outer diameter side inlet groove portion 14 and the inner diameter side inlet groove portion 15 are arranged radially more closely than the tip side groove portion 17, and the tip side groove portion 17 is arranged circumferentially more closely than the outer diameter side inlet groove portion 14 and the inner diameter side inlet groove portion 15. Therefore, the circumferential lengths L1, L1' of the outer diameter side inlet groove portion 14 and the inner diameter side inlet groove portion 15 can be reduced, and the circumferential length L2 of the tip side groove portion 17, i.e., the positive pressure generation area, can be made large.

[0057] Furthermore, since the radial lengths L10, L20 of the side walls 14c and 15c are shorter than the radial lengths L11, L21 of the side walls 14d and 15d, fluid can be easily introduced into the tip groove portion 17 from the outer space S1 and the inner space S2.

[0058] The bottom surface 17c of the tip side groove 17 gradually becomes shallower from the confluence 17A toward the tip end 17B, so that the pressure of the fluid in the tip side groove 17 gradually increases toward the tip end 17B.

[0059] In addition, the bottom surface 17c of the tip groove portion 17 is connected to the land 12 in a smooth curve in the circumferential direction, making it easy to guide fluid from the tip 17Ba of the tip portion 17B of the tip groove portion 17 in the circumferential direction, i.e., from the tip portion 17B toward the adjacent land 12 in the circumferential direction.

[0060] Furthermore, since the tip portion 17B is tapered in the forward rotation direction, a large positive pressure can be generated at the tip 17Ba of the tip portion 17B.

[0061] This allows positive pressure to be generated at the tip end 17B of the dynamic pressure generating groove 13 and over a wide range in the circumferential direction in the vicinity thereof.

[0062] Specifically, as shown in Figure 7, the greatest positive pressure occurs near the tip 17Ba of the tip portion 17B of the dynamic pressure generating groove 13, and the positive pressure gradually decreases as it spreads around the tip 17Ba. In particular, the range in which positive pressure occurs is larger upstream of the tip 17Ba of the tip portion 17B of the tip-side groove 17 than downstream of the tip 17Ba in the relative rotation. Furthermore, almost no positive pressure occurs near the confluence 17A. This prevents the flow of fluid from the outer diameter inlet groove 14 and the inner diameter inlet groove 15 to the confluence 17A from being obstructed, generating positive pressure over a wide circumferential range.

[0063] The force of the positive pressure generated at and near the tip 17B of the dynamic pressure generating groove 13 causes the sliding surfaces 11 and 21 to be slightly spaced apart, and fluid is introduced between the sliding surfaces 11 and 21, improving lubrication.

[0064] Furthermore, since a wide positive pressure generating region is ensured, positive pressure can be generated over a wide circumferential range between the sliding surfaces 11 and 21. Therefore, when the rotating ring 20 floats relative to the stationary ring 10 in the direction in which the sliding surfaces 11 and 21 are separated from each other, there is little shaking, and the sliding between the sliding surfaces 11 and 21 is stable.

[0065] Furthermore, the curvature of the side walls 17a, 17b of the tip groove portion 17 is smaller than the curvature of the side wall 14d of the outer diameter side inlet groove portion 14 and the curvature of the side wall 15d of the inner diameter side inlet groove portion 15, and they extend in an almost straight line, so that a wide land 12 can be secured around the positive pressure generating region, and shaking is small when the rotating ring 20 floats up relative to the stationary ring 10 in the direction separating the sliding surfaces 11, 21, and sliding between the sliding surfaces 11, 21 is stable.

[0066] Furthermore, the side walls 14d and 15d are connected in a generally V-shape when viewed in the axial direction, and the tip 17Ba of the tip portion 17B of the dynamic pressure generating groove 13 is located downstream in the positive rotation direction at approximately the same radial position as the valley between the side walls 14d and 15d. This prevents the fluid discharged from the tip 17Ba of the tip portion 17B of the dynamic pressure generating groove 13 in the positive rotation direction, i.e., onto the land 12, from being immediately recovered in the downstream outer diameter side inlet groove 14 and inner diameter side inlet groove 15, thereby ensuring the generation of positive pressure between the dynamic pressure generating grooves 13 adjacent in the circumferential direction.

[0067] In this embodiment, the cross-sectional shapes of the outer diameter side introduction groove portion 14 and the inner diameter side introduction groove portion 15 are exemplified as being approximately the same, but they may have different depths or different bottom shapes, for example, one may be flat and the other may be curved.

[0068] Furthermore, the bottom surface 14e of the outer diameter side inlet groove portion 14 and the bottom surface 15e of the inner diameter side inlet groove portion 15 are not limited to being flat surfaces, but may be convex or concave on one side in the axial direction when viewed in cross section so that the grooves become shallower toward the tip, or may be stepped so that the grooves become shallower toward the tip.

[0069] Furthermore, in this embodiment, the tip 17Ba of the tip portion 17B is disposed near the center in the radial direction of the sliding surface 11, but it may be disposed closer to one side in the radial direction.

[0070] Next, a sliding element according to a second embodiment will be described with reference to Fig. 8. Note that the description of the same configuration as in the first embodiment will be omitted.

[0071] As shown in FIG. 8A, the cross-sectional shape of the dynamic pressure generating groove 213 of this embodiment 2 along the extension direction from the inner diameter side introduction groove portion 215 to the tip end portion 217B of the tip end side groove portion 217 is substantially the same as that of the dynamic pressure generating groove 13 of embodiment 1.

[0072] 8(b), the widthwise cross section of the inner diameter side inlet groove 215 is substantially U-shaped. The widthwise side walls 215c, 215d of the inner diameter side inlet groove 215 have rounded portions 215cr, 215dr at their upper portions, and are connected in smooth curves to the lands 212 located on both widthwise sides. This makes it easy to introduce fluid into the inner diameter side inlet groove 215 from both widthwise sides of the inner diameter side inlet groove 215.

[0073] Furthermore, the side walls 215c, 215d are also smoothly curved and continuous with the bottom surface 215e of the inner diameter side introduction groove 215. This makes it difficult for the fluid to stagnate near the bottom surface 215e of the inner diameter side introduction groove 215, allowing the fluid to flow smoothly in the forward rotation direction.

[0074] 8(c), the widthwise cross section of the tip side groove 217 is generally U-shaped. The widthwise side walls 217a, 217b of the tip side groove 217 have rounded portions 217ar, 217br at their upper portions, and are connected in a smooth curve to the lands 212 located on both sides in the widthwise direction. As a result, the fluid flowing circumferentially through the tip side groove 217 is gradually pressured toward the tip 217Ba of the tip side groove 217 while also being guided to both radial sides, effectively increasing the positive pressure and improving the levitation effect.

[0075] Furthermore, the side walls 217a and 217b are also smoothly curved and connected to the bottom surface 217c of the tip groove 217. This makes it difficult for the fluid to stagnate near the bottom surface 217c of the tip groove 217, allowing the fluid to flow smoothly in the forward rotation direction.

[0076] In the second embodiment, the cross sections of the bottom surface 215e of the inner diameter side introduction groove 215 and the bottom surface 217c of the tip side groove 217 are generally U-shaped, but they may be generally V-shaped. Also, the cross sections are not limited to being symmetrical in the width direction, and may be asymmetrical.

[0077] Next, a sliding element according to a third embodiment will be described with reference to Fig. 9. Note that the description of the same configuration as in the first embodiment will be omitted.

[0078] As shown in FIG. 9, in the dynamic pressure generating groove 313 of the third embodiment, the side walls 314c and 314d of the outer diameter side introduction groove portion 314 extend substantially parallel to each other, and the side walls 315c and 315d of the inner diameter side introduction groove portion 315 extend substantially parallel to each other.

[0079] This makes it possible to stabilize the flow of fluid in the outer diameter side inlet groove portion 314 and the inner diameter side inlet groove portion 315.

[0080] Next, a sliding element according to a fourth embodiment will be described with reference to Fig. 10. Note that the description of the same configuration as in the first embodiment will be omitted.

[0081] 10 , in the dynamic pressure generating groove 413 of the fourth embodiment, the bottom surface 415 e of the inner diameter side introduction groove portion 415 (i.e., the bottom surface 414 e of the outer diameter side introduction groove portion 414) and the bottom surface 417 e of the tip side groove portion 417 are connected at the same inclination angle. This makes it possible to adjust the size of the positive pressure generating region according to the circumferential length of the dynamic pressure generating groove 413.

[0082] Next, a sliding element according to a fifth embodiment will be described with reference to Fig. 11. Note that the description of the same configuration as in the first embodiment will be omitted.

[0083] 11, the lubricating oil in the outer space S1 of the stationary ring 510 in this embodiment 5 is at a higher pressure than the lubricating oil in the inner space S2. In addition, in FIG. 11, the change in the depth of the dynamic pressure generating grooves 513 is shown schematically by the darkness of the dot pattern, with the darker the dot pattern, the deeper the groove.

[0084] In the dynamic pressure generating groove 513 of the fifth embodiment, the outer diameter side inlet groove portion 514 is wider and longer in the extending direction than the inner diameter side inlet groove portion 515. In other words, the volume of the high-pressure side outer diameter side inlet groove portion 514 is larger than the volume of the low-pressure side inner diameter side inlet groove portion 515. Therefore, high-pressure lubricating oil is more easily introduced into the tip side groove portion 517, and the dynamic pressure generation effect is enhanced.

[0085] The outer diameter side wall 517a of the tip groove 517 has a larger curvature than the inner diameter side wall 517b. The tip groove 517 is wider in the radial direction, in other words, in the direction perpendicular to the extending direction, compared to the tip groove 17 of the first embodiment.

[0086] The dynamic pressure generating groove 513 gradually deepens from the tip 517Ba of the tip portion 517B of the tip side groove 517 toward the outer diameter side introduction groove 514 and the inner diameter side introduction groove 515. More specifically, the dynamic pressure generating groove 513 gradually deepens from the tip 517Ba toward the outer diameter side introduction groove 514 and the inner diameter side introduction groove 515, with the higher pressure side increasing. In other words, the dynamic pressure generating groove 513 deepens from the inner diameter side toward the outer diameter side and upstream in the forward rotation direction, in other words, obliquely relative to the circumferential direction. The tip side groove 517 is partitioned by the outer space S1 and the inner space S2 and the land 512, and is in communication with the outer space S1 and the inner space S2 via the outer diameter side introduction groove 514 and the inner diameter side introduction groove 515. Therefore, during relative rotation, high-pressure lubricating oil is efficiently introduced along side wall 517a of tip groove 517, and positive pressure is relatively easily generated on the side wall 517b side of tip groove 517. Furthermore, compared to the embodiment 1, the positive pressure generated at tip 517Ba of tip portion 517B is larger, and the positive pressure generation region is narrower.

[0087] Next, a sliding element according to a sixth embodiment will be described with reference to Fig. 12. Note that the description of the same configuration as in the first embodiment will be omitted.

[0088] 12 , a plurality of dynamic pressure generating grooves 613 are formed on the inner peripheral surface 640a of the radial bearing 640 (only one is shown in FIG. 12 ). This dynamic pressure generating groove 613 includes a one-side introduction groove 614 that communicates with one space S10 on one axial side, a second-side introduction groove 615 that communicates with the second space S20 on the other axial side, and a tip-side groove 617 that extends downstream in the relative rotation direction from the one-side introduction groove 614 and the second-side introduction groove 615. The tip-side groove 617 gradually becomes shallower from the one-side introduction groove 614 and the second-side introduction groove 615 side toward the tip 617Ba.

[0089] Although the radial bearing is fixed to the housing in the above example, it may be fixed to the rotating shaft. In this case, it is sufficient that dynamic pressure generating grooves are provided on the outer circumferential surface of the radial bearing.

[0090] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0091] For example, in Examples 1 to 6, the hydrodynamic grooves gradually become shallower from the introduction portion toward the tip portion, but the introduction portion may be a deep groove with a constant depth, and the tip portion may be a shallow groove with a constant depth. In other words, the hydrodynamic groove may have at least one portion with a different depth, and the tip portion may be shallower than the introduction portion.

[0092] Furthermore, in the above-described Examples 1 to 6, the outer diameter side inlet portion is in communication with the outer space and the inner diameter side inlet portion is in communication with the inner space, but as long as the fluid can be introduced from between the sliding surfaces, at least one of the outer diameter side inlet portion and the inner diameter side inlet portion may not be in communication with the outer space or the inner space.

[0093] Furthermore, in Examples 1 to 6, the tip end of the dynamic pressure generating groove and the land are smoothly connected in the circumferential direction, but a surface rising in the depth direction may be formed between the tip end of the dynamic pressure generating groove and the land.

[0094] Furthermore, in Examples 1 to 6, the outer diameter side introduction portion and the inner diameter side introduction portion were generally arc-shaped when viewed in the axial direction. However, for example, the outer diameter side introduction portion and the inner diameter side introduction portion may extend linearly while inclined in the forward rotation direction, or one may be linear and the other arc-shaped.

[0095] Furthermore, in the above-described Examples 1 to 6, the dynamic pressure generating grooves are arranged at 10 equal intervals in the circumferential direction, but this may be freely changed depending on the usage environment, etc.

[0096] Furthermore, in the first to sixth embodiments, the sliding member is annular, but the present invention is not limited to this and may be, for example, a disk-shaped sliding member.

[0097] Furthermore, in the above-described first to sixth embodiments, the sliding parts used in thrust bearings have been described, but the sliding parts may also be used in mechanical seals for automobiles, general industrial machinery, and the like, or in plain bearings.

[0098] The fluid used for lubrication may be liquid or gas, or may be a mist of a mixture of liquid and gas.

[0099] Furthermore, in the above-described Examples 1 to 6, the same fluid is present in the outer space and the inner space, but different fluids that are allowed to be mixed may be present, or the pressures may be different.

[0100] Furthermore, in the above-described first to sixth embodiments, a configuration in which no positive pressure is generated at the confluence of the tip groove portion has been exemplified, but a positive pressure may also be generated at the confluence.

[0101] REFERENCE SIGNS LIST 1 rotating shaft 3 thrust bearing (sliding part) 10 stationary ring 11 sliding surface 12 land 13 hydrodynamic pressure generating groove 14 outer diameter side introduction groove portion (introduction portion) 14e bottom surface 15 inner diameter side introduction groove portion (introduction portion) 15e bottom surface 17 tip side groove portion 17A merging portion 17B tip portion 17Ba tip 17c bottom surface S1 outer space S2 inner space θ1, θ2 inclination angle

Claims

1. A sliding part arranged between a housing and a shaft inserted into the housing, with a pair of sliding surfaces rotating relative to one another, wherein at least one of the sliding surfaces is provided with a dynamic pressure generating groove having an introduction portion on one side communicating with one space and an introduction portion on the other side communicating with the other space, and a tip portion where both introduction portions join downstream of the relative rotation, wherein the dynamic pressure generating groove is shallower on the tip side than on the introduction portion on one side and the introduction portion on the other side.

2. A sliding component according to claim 1, wherein the dynamic pressure generating groove becomes gradually shallower from at least one of the introduction portions toward the tip portion.

3. A sliding component according to claim 1, wherein the bottom surface of the tip portion is continuous in a curved line with respect to the land in the circumferential direction.

4. A sliding component according to claim 1, wherein the bottom surface of the tip portion is continuous in a curved shape in the radial direction relative to the land.

5. A sliding component according to claim 2, wherein the inclination angle of the bottom surface of at least one of said introduction portions is larger than the inclination angle of the bottom surface of said tip portion.

6. A sliding component according to claim 1, wherein at least one of said introduction portions is disposed along the radial direction, and said tip portion is disposed along the circumferential direction.

7. A sliding component according to any one of claims 1 to 6, wherein the tip portion is tapered in the forward rotation direction.

8. The sliding component according to claim 1, wherein the introduction portion on one side is wider and longer than the introduction portion on the other side.

9. The sliding component according to claim 8, wherein the tip portion is deeper on the side of the introduction portion on the one side than on the side of the introduction portion on the other side.

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