Sliding component

Abstract

Provided is a sliding component having high lubricity during low-speed relative rotation.　This sliding component is disposed between a housing 4 and a shaft 1 inserted through the housing 4, and has a pair of sliding surfaces 11, 21 that partition a sealed fluid space S1 and a leakage space S2, wherein one sliding surface 11 includes: dynamic pressure generating grooves 13 that communicate with the sealed fluid space S1; a storage groove 12 that is disposed closer to the leakage space S2 side than the dynamic pressure generating grooves 13 and that extends in the circumferential direction; first negative pressure generating grooves 14 that are disposed closer to the leakage space S2 side than the storage groove 12 and that do not communicate with the storage groove 12; and second negative pressure generating grooves 15 that are disposed closer to the leakage space S2 side than the storage groove 12 and that communicate with the storage groove 12.

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] Mechanical seals, for example, are shaft sealing devices that prevent leakage of sealed fluids and are equipped with a pair of annular sliding components that rotate relative to one another and have sliding surfaces that slide against each other. In recent years, there has been a demand for reducing the energy lost due to sliding in such mechanical seals, for environmental reasons.

[0003] For example, in the mechanical seal disclosed in Patent Document 1, the outer diameter sides of the rotating ring and stationary ring are the high-pressure fluid side, and the inner diameter sides are the low-pressure fluid side. An annular pressure release groove and a plurality of dimples extending in the circumferential direction are provided on the sliding surface of the stationary ring. The pressure release groove is in communication with the high-pressure fluid side. The dimples are provided on the sliding surface closer to the low-pressure fluid side than the pressure release groove. The pressure release groove and the dimples are radially separated by a land.

[0004] During relative rotation between the rotating ring and the fixed ring, negative pressure is generated at the upstream end of the dimple, and the high-pressure fluid between the sliding surfaces is sucked into the dimple, preventing the high-pressure fluid from leaking into the low-pressure fluid. The high-pressure fluid sucked into the dimple moves to the downstream end of the dimple and is discharged over the land into the pressure release groove, thereby maintaining the dimple's ability to generate negative pressure.

[0005] WO 2014 / 050920 (page 13, Figure 15)

[0006] In a mechanical seal such as that described in Patent Document 1, the dimples can recover high-pressure fluid that attempts to leak to the low-pressure fluid side, but when the relative rotational speed of the rotating ring and the fixed ring is low, it is difficult for a liquid film to be formed by the Rayleigh step, which is a positive pressure generating mechanism, so high-pressure fluid is difficult to supply from the pressure release groove to the dimples, which could result in poor lubrication.

[0007] The present invention has been made in view of these problems, and has as its object to provide a sliding part that has high lubrication properties during low-speed relative rotation.

[0008] In order to solve the above problems, the sliding component of the present invention is a sliding component having a pair of sliding surfaces that are arranged between a housing and a shaft inserted through the housing and that partition a sealed fluid space and a leakage space, wherein one of the sliding surfaces is provided with: a dynamic pressure generating groove that communicates with the sealed fluid space, a reservoir groove that is arranged closer to the leakage space than the dynamic pressure generating groove and extends in the circumferential direction, a first negative pressure generating groove that is arranged closer to the leakage space than the reservoir groove and does not communicate with the reservoir groove, and a second negative pressure generating groove that is arranged closer to the leakage space than the reservoir groove and communicates with the reservoir groove. According to this, the sealed fluid is introduced into the second negative pressure generating groove from the reservoir groove, thereby improving lubrication during low relative rotation speeds.

[0009] The total volume of the second negative pressure generating groove may be smaller than the total volume of the first negative pressure generating groove, whereby during high speed forward rotation, the first and second negative pressure generating grooves function to recover the sealed fluid, and during reverse rotation, the total volume of the second negative pressure generating groove is smaller than the total volume of the first negative pressure generating groove, thereby reducing the amount of sealed fluid that flows toward the leakage side.

[0010] A plurality of the second negative pressure generating grooves may be arranged in the circumferential direction, and a plurality of the first negative pressure generating grooves may be arranged between adjacent ones of the second negative pressure generating grooves, thereby improving the lubrication and fluid recovery capability of the sliding surface in a balanced manner in the circumferential direction.

[0011] The first negative pressure generating groove and the second negative pressure generating groove may extend in a radial direction, and an end of the second negative pressure generating groove facing the leakage space may be disposed closer to the storage groove than an end of the first negative pressure generating groove facing the leakage space. This allows the end of the second negative pressure generating groove facing the leakage space to be spaced apart from the leakage space, thereby preventing leakage of the sealed fluid from the second negative pressure generating groove into the leakage space during relative rotation in the reverse direction.

[0012] The first negative pressure generating groove may be provided on an extension line of the second negative pressure generating groove on the leakage space side, at a distance therefrom, so that the sealed fluid recovered by the first negative pressure generating groove provided on the extension line at a distance therefrom can be easily recovered by the second negative pressure generating groove and returned to the reservoir groove.

[0013] The second negative pressure generating groove may overlap an end of the first negative pressure generating groove on the sealed fluid space side in the circumferential direction, whereby the fluid collected by the first negative pressure generating groove can be easily collected by the second negative pressure generating groove and returned to the reservoir groove.

[0014] A flow impeding means may be provided which provides resistance to the sealed fluid flowing through the second negative pressure generating groove toward the leakage space side. In this way, the flow impeding means can impede the sealed fluid from flowing from the second negative pressure generating groove toward the leakage side, thereby suppressing the sealed fluid from flowing toward the leakage side during reverse rotation.

[0015] The flow obstructing means may be a protrusion extending at an angle toward the communicating portion between the second negative pressure generating groove and the reservoir groove, whereby the protrusion allows the sealed fluid to flow from the second negative pressure generating groove to the reservoir groove and restricts the flow of the sealed fluid from the reservoir groove to the second negative pressure generating groove.

[0016] The flow obstructing means may be a wall rising in a depth direction against the flow of the sealed fluid toward the leakage space, whereby the wall allows the flow of the sealed fluid from the second negative pressure generating groove to the storage groove and restricts the flow of the sealed fluid from the storage groove to the second negative pressure generating groove.

[0017] The one sliding surface may be provided with dimples on the leakage space side of at least the first and second negative pressure generating grooves, whereby the sealed fluid stored in the dimples can ensure lubrication on the leakage space side of the first and second negative pressure generating grooves, which tend to be poorly lubricated.

[0018] The other sliding surface facing the one sliding surface may be provided with dimples at least closer to the leakage space than the first and second negative pressure generating grooves, whereby the sealed fluid stored in the dimples can ensure lubrication on the leakage space side of the first and second negative pressure generating grooves, which tend to be poorly lubricated.

[0019] 4 is a longitudinal sectional view showing an example of a mechanical seal according to a first embodiment of the present invention; FIG. 5 is a view of the sliding surface of the stationary seal ring according to the first embodiment, as viewed from the axial direction; FIG. 6 is an enlarged view of a main part of the sliding surface of the stationary seal ring, as viewed from the axial direction, when the rotating seal ring is rotating forward; FIG. 7 is an enlarged view of a main part of the sliding surface of the stationary seal ring, as viewed from the axial direction, when the rotating seal ring is rotating backward; FIG. 8 is a sectional view taken along line A-A in FIG. 4; FIG. 9 is an enlarged view of a main part of the sliding surface of the stationary seal ring according to a second embodiment of the present invention, as viewed from the axial direction; (a) is an enlarged view of a main part of the sliding surface of the stationary seal ring according to a third embodiment of the present invention, as viewed from the axial direction; (b) is a schematic diagram showing the flow of the sealed fluid during forward rotation; and (c) is a schematic diagram showing the flow of the sealed fluid during reverse rotation. (a) is an enlarged view of a main part of the sliding surface of the stationary seal ring according to a fourth embodiment of the present invention, as viewed from the axial direction; and (b) is an enlarged view of a main part showing a modification of (a). (a) is an enlarged view of a main part of the sliding surface of a stationary seal ring in embodiment 5 of the present invention, as viewed from the axial direction, (b) is a cross-sectional view taken along line B-B of (a), and (c) is a cross-sectional view showing a modified example of (b). Fig. 1 is a view of the sliding surface of a rotary seal ring in embodiment 6 of the present invention, as viewed from the axial direction. Fig. 2 is a schematic view of the sliding surface of a stationary seal ring, as viewed from the axial direction, in a state where a pair of sliding surfaces are overlapped. Fig. 3 is a view of the sliding surface of a stationary seal ring in embodiment 7 of the present invention, as viewed from the axial direction. Fig. 4 is a view of the sliding surface of a rotary seal ring in embodiment 8 of the present invention, as viewed from the axial direction. Fig. 5 is a view showing a modified example of the mechanical seal in embodiment 1 of the present invention.

[0020] 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.

[0021] A sliding component according to a first embodiment will be described with reference to Figures 1 to 5. In this embodiment, a mechanical seal will be used as an example of the sliding component. In the mechanical seal of this embodiment, a high-pressure sealed fluid, such as oil, exists in an outer space S1, which serves as a sealed fluid space, and an inner space S2, which serves as a leakage space, communicates with the low-pressure atmosphere. For ease of explanation, grooves and the like formed on the sliding surface may be indicated by dots in the drawings.

[0022] The mechanical seal shown in FIG. 1 is an inside type that seals against a sealed fluid that attempts to leak from the outer diameter side to the inner diameter side of the sliding surface.

[0023] The mechanical seal is mainly composed of a stationary seal ring 10 and a rotary seal ring 20. The stationary seal ring 10 is annular and is mounted on a seal cover 5 fixed to a housing 4 of the device to which it is attached in a non-rotating state but movable in the axial direction. The rotary seal ring 20 is annular and is mounted on a rotary shaft 1 via a sleeve 2 in a state in which it can rotate together with the rotary shaft 1.

[0024] The stationary seal ring 10 is biased in the axial direction by the elastic member 7. The sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotary seal ring 20 are adapted to slide closely against each other. The sliding surface 21 of the rotary seal ring 20 is flat, and this flat surface does not have any recesses such as grooves.

[0025] The stationary seal ring 10 and the rotating seal ring 20 are typically formed from a combination of SiC (hard material) or SiC (hard material) and carbon (soft material), but any sliding material used as a sliding material for mechanical seals 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.

[0026] 2, the rotary seal ring 20 slides mainly counterclockwise relative to the stationary seal ring 10 as shown by the solid arrow. The rotation direction can also be switched to clockwise relative sliding as shown by the dashed arrow. In the following description, the direction of the solid arrow indicates the forward rotation direction of the rotary seal ring 20, and the direction of the dashed arrow indicates the reverse rotation direction of the rotary seal ring 20.

[0027] As shown in FIGS. 2 and 3, the sliding surface 11 of the stationary seal ring 10 is provided with a reservoir groove 12, a dynamic pressure generating groove 13, a first negative pressure generating groove 14, and a second negative pressure generating groove 15.

[0028] The reservoir groove 12 is composed of an annular groove portion 12A and a plurality of (six in this embodiment) inlet / outlet groove portions 12B. The annular groove portion 12A is provided approximately concentrically with the sliding surface 11 at approximately the center of the sliding surface 11 in the radial direction.

[0029] The lead-in / out grooves 12B extend in an arc shape inclined in the reverse rotation direction from the annular groove 12A toward the outer diameter side. The outer diameter ends 12Ba of the lead-in / out grooves 12B communicate with the external space S1, and the inner diameter ends 12Bb communicate with the annular groove 12A. The lead-in / out grooves 12B are evenly spaced in the circumferential direction. Note that the lead-in / out grooves 12B are not limited to being arc-shaped, and may extend linearly or radially without inclining in the circumferential direction. Furthermore, the number of lead-in / out grooves 12B can be freely changed.

[0030] The annular groove 12A and the lead-in groove 12B are formed to the same depth, which is deeper than the dynamic pressure generating groove 13, the first negative pressure generating groove 14, and the second negative pressure generating groove 15, which will be described later. The annular groove 12A and the lead-in groove 12B may be formed to different depths.

[0031] The dynamic pressure generating groove 13 extends in an arc shape while inclining in the forward rotation direction from the outer diameter side toward the inner diameter side. In other words, the dynamic pressure generating groove 13 is a so-called spiral groove having a radial component and a circumferential component.

[0032] The outer diameter end 13a of the dynamic pressure generating groove 13 communicates with the external space S1, and the inner diameter end 13b is closed. That is, lands 16 are present on both circumferential sides of the dynamic pressure generating groove 13 between the inner diameter end 13b of the dynamic pressure generating groove 13 and the annular groove portion 12A.

[0033] The dynamic pressure generating grooves 13 extend substantially parallel to the inlet / outlet groove portion 12B. The dynamic pressure generating grooves 13 are not limited to being arc-shaped, but may extend linearly. Furthermore, the dynamic pressure generating grooves 13 are not limited to being spiral grooves, but may also be in the form of Rayleigh steps, dimples, or the like.

[0034] A plurality of dynamic pressure generating grooves 13 (five in this embodiment) are equally spaced between adjacent inlet / outlet groove portions 12B in the circumferential direction. The number of dynamic pressure generating grooves 13 can be freely changed.

[0035] Furthermore, the dynamic pressure generating grooves 13 are formed shallower than the reservoir grooves 12 .

[0036] A plurality of first negative pressure generating grooves 14 and a plurality of second negative pressure generating grooves 15 are provided on the inner diameter side of the annular groove portion 12A.

[0037] The first negative pressure generating groove 14 extends in an arc shape while inclining in the reverse rotation direction from the outer diameter side to the inner diameter side. In other words, the first negative pressure generating groove 14 is a so-called spiral groove having a radial component and a circumferential component.

[0038] The outer diameter end 14a and the inner diameter end 14b of the first negative pressure generating groove 14 are closed ends. That is, the first negative pressure generating groove 14 is surrounded by the land 16 and does not communicate with the annular groove portion 12A and the internal space S2.

[0039] The second negative pressure generating groove 15 extends in an arc shape inclined in the counter-rotation direction from the outer diameter side toward the inner diameter side, and is substantially parallel to the first negative pressure generating groove 14. In other words, the second negative pressure generating groove 15 is a so-called spiral groove having a radial component and a circumferential component. The second negative pressure generating groove 15 is longer in the extension direction than the first negative pressure generating groove 14. A portion of the second negative pressure generating groove 15 circumferentially overlaps with the outer diameter end 14a, which is the end of the first negative pressure generating groove 14 on the sealed fluid space side.

[0040] The outer diameter end 15a of the second negative pressure generating groove 15 is connected to the annular groove portion 12A, and the inner diameter end 15b is a closed end. That is, lands 16 are present between the inner diameter end 15b of the second negative pressure generating groove 15 and the internal space S2, on both circumferential sides of the second negative pressure generating groove 15.

[0041] The second negative pressure generating grooves 15 (six in this embodiment) are arranged at equal intervals in the circumferential direction. The outer diameter end 15a of each second negative pressure generating groove 15 is located downstream in the forward rotation direction of the inner diameter end 12Bb of the inlet / outlet groove portion 12B. The number of second negative pressure generating grooves 15 can be freely changed.

[0042] A plurality of first negative pressure generating grooves 14 (five in this embodiment) are equally spaced between circumferentially adjacent second negative pressure generating grooves 15. The number of first negative pressure generating grooves 14 can be freely changed.

[0043] The first negative pressure generating groove 14 and the second negative pressure generating groove 15 are both formed to the same depth as the dynamic pressure generating groove 13. That is, the first negative pressure generating groove 14 and the second negative pressure generating groove 15 are formed shallower than the storage groove 12 (see FIG. 5). The first negative pressure generating groove 14 and the second negative pressure generating groove 15 may have a different depth from the dynamic pressure generating groove 13. Furthermore, the first negative pressure generating groove 14 and the second negative pressure generating groove 15 may have different depths.

[0044] The second negative pressure generating grooves 15 are longer in the extension direction than the first negative pressure generating grooves 14, but are fewer in number than the first negative pressure generating grooves 14, and the total area AR2 of the second negative pressure generating grooves 15 on the sliding surface 11 when viewed in the axial direction is smaller than the total area AR1 of the first negative pressure generating grooves 14 on the sliding surface 11 (AR2 < AR1).

[0045] Furthermore, since the first negative pressure generating groove 14 and the second negative pressure generating groove 15 have the same depth, the total volume VL2 of the second negative pressure generating groove 15 is smaller than the total volume VL1 of the first negative pressure generating groove 14 (VL2<VL1).

[0046] Next, a state in which the rotary seal ring 20 rotates relative to the stationary seal ring 10 in the forward direction will be described.

[0047] As shown in FIG. 3, when the rotary seal ring 20 rotates relative to the stationary seal ring 10 in the forward direction, the fluid moves in each groove in accordance with the direction of rotation of the rotary seal ring 20 .

[0048] Specifically, when the rotating seal ring 20 and the stationary seal ring 10 are rotating in the forward direction at a low speed, the sealed fluid in the outer space S1 is introduced from the outer diameter end 12Ba of the lead-in / out groove 12B and moves toward the annular groove 12A, and the sealed fluid in the annular groove 12A moves in the forward rotation direction. As a result, the sealed fluid flows out between the sliding surfaces 11 and 21 from the lead-in / out groove 12B and the annular groove 12A.

[0049] In addition, in the dynamic pressure generating groove 13, the sealed fluid in the outer space S1 is introduced from the outer diameter end 13a and moves toward the inner diameter end 13b. As a result, the sealed fluid flows out from the dynamic pressure generating groove 13 between the sliding surfaces 11 and 21. During forward rotation at low speed, almost no dynamic pressure is generated at the inner diameter end 13b. As a result, the lubrication of the area of ​​the sliding surface 11 from the annular groove portion 12A to the outer diameter side is improved.

[0050] In addition, in the first negative pressure generating groove 14, the fluid in the first negative pressure generating groove 14 moves from the inner diameter end 14b toward the outer diameter end 14a and flows out between the sliding surfaces 11 and 21. Also, the sealed fluid between the surrounding sliding surfaces 11 and 21 is introduced into the first negative pressure generating groove 14. Note that the sealed fluid and the air in the internal space S2 may be mixed in the first negative pressure generating groove 14. Furthermore, during forward rotation at low speeds, almost no dynamic pressure is generated in the first negative pressure generating groove 14.

[0051] In the second negative pressure generating groove 15, a part of the sealed fluid flows out between the sliding surfaces 11 and 21. The sealed fluid between the peripheral sliding surfaces 11 and 21 is introduced into the second negative pressure generating groove 15. Furthermore, during slow forward rotation, almost no dynamic pressure is generated in the second negative pressure generating groove 15. Specifically, at rotation speeds slower than the low speeds, the shearing force acting between the sliding surfaces 11 and 21 is small, and the sealed fluid mainly moves from the second negative pressure generating groove 15 in the circumferential direction and flows out between the sliding surfaces 11 and 21, thereby supplying the sealed fluid from the annular groove 12A to the second negative pressure generating groove 15. At rotation speeds faster than the low speeds, the shearing force acting between the sliding surfaces 11 and 21 is large, and the sealed fluid in the second negative pressure generating groove 15 moves from the inner diameter end 15b toward the outer diameter end 15a, and a part of it is discharged into the annular groove 12A (as shown by the white arrow in FIG. 3).

[0052] Since the second negative pressure generating groove 15 communicates with the annular groove portion 12A, the lubrication of the area of ​​the sliding surface 11 on the inner diameter side of the annular groove portion 12A is improved during low relative rotation speeds.

[0053] As mentioned above, the second negative pressure generating grooves 15 are evenly spaced in the circumferential direction, and the first negative pressure generating grooves 14 are evenly spaced between adjacent second negative pressure generating grooves, so that the lubrication of the sliding surface 11 can be improved in a balanced manner in the circumferential direction.

[0054] When the rotating seal ring 20 and the stationary seal ring 10 are rotating in the forward direction at high speed, positive pressure is generated at the inner diameter end 13b of the dynamic pressure generating groove 13, and positive pressure is generated at the outer diameter end 14a of the first negative pressure generating groove 14. This causes the sliding surfaces 11, 21 to separate, allowing a large amount of sealed fluid to be introduced from the outer space S1, improving slidability.

[0055] Furthermore, a relative negative pressure is generated at the inner diameter end 14b of the first negative pressure generating groove 14 and the inner diameter end 15b of the second negative pressure generating groove 15. As a result, the sealed fluid that would otherwise leak over the annular groove 12A into the internal space S2 is collected in the first negative pressure generating groove 14 and the second negative pressure generating groove 15. The sealed fluid collected in the first negative pressure generating groove 14 is returned to the annular groove 12A over the land 16, and the sealed fluid collected in the second negative pressure generating groove 15 is returned to the annular groove 12A through the outer diameter end 15a, thereby preventing leakage of the sealed fluid.

[0056] As mentioned above, the second negative pressure generating grooves 15 are evenly spaced in the circumferential direction, and the first negative pressure generating grooves 14 are evenly spaced between adjacent second negative pressure generating grooves, so that the fluid recovery capacity can be increased in a balanced manner in the circumferential direction of the sliding surface 11.

[0057] In addition, a part of the inner diameter end 15b of the second negative pressure generating groove 15 circumferentially overlaps with the outer diameter end 14a of the first negative pressure generating groove 14. As a result, the sealed fluid collected in the first negative pressure generating groove 14 is easily guided to the second negative pressure generating groove 15 and is easily returned to the reservoir groove 12 via the second negative pressure generating groove 15.

[0058] As shown in FIG. 4, when the rotary seal ring 20 and the stationary seal ring 10 rotate in opposite directions, the sealed fluid in the annular groove 12A is discharged from the outer diameter end 12Ba of the inlet / outlet groove 12B into the outer space S1.

[0059] In the hydrodynamic pressure generating groove 13, the sealed fluid moves from the inner diameter end 13b toward the outer diameter end 13a and is discharged into the outer space S1. At this time, the surrounding sealed fluid is also collected. In this way, the sealed fluid is prevented from being introduced into between the sliding surfaces 11 and 21 from the outer space S1, and a large amount of the sealed fluid is stored in the storage groove 12, preventing poor lubrication.

[0060] In the first negative pressure generating groove 14, the fluid in the first negative pressure generating groove 14 moves from the outer diameter end 14a toward the inner diameter end 14b. However, since the first negative pressure generating groove 14 is not connected to the annular groove portion 12A and the amount of movement is small, the sealed fluid is unlikely to leak from the inner diameter end 14b toward the internal space S2.

[0061] Since the second negative pressure generating grooves 15 communicate with the annular groove portion 12A, the sealed fluid is supplied from the annular groove portion 12A to the outer diameter end 15a and discharged from the inner diameter end 15b toward the internal space S2. On the other hand, as described above, the total area AR2 of the second negative pressure generating grooves 15 on the sliding surface 11 is smaller than the total area AR1 of the first negative pressure generating grooves 14 on the sliding surface 11, and the total volume VL2 of the second negative pressure generating grooves 15 is smaller than the total volume VL1 of the first negative pressure generating grooves 14.

[0062] As a result, during high speed forward rotation, the first negative pressure generating groove 14 and the second negative pressure generating groove 15 perform the function of recovering the sealed fluid, and during reverse rotation, the amount of sealed fluid heading toward the internal space S2 is reduced, making it less likely to leak.

[0063] As shown in FIG. 5, the annular groove portion 12A is formed deeper than the second negative pressure generating groove 15, and a side wall 12Ac on the second negative pressure generating groove 15 side rises in the depth direction.

[0064] The side wall 12Ac is configured to provide resistance to most of the sealed fluid flowing from the annular groove 12A toward the second negative pressure generating groove 15 during reverse rotation. That is, the side wall 12Ac functions as a flow obstruction means in this embodiment. On the other hand, during forward rotation, the flow of the sealed fluid from the second negative pressure generating groove 15 toward the annular groove 12A is permitted.

[0065] In this way, the flow of the sealed fluid from the second negative pressure generating groove 15 to the annular groove portion 12A is permitted, and the flow of the sealed fluid from the annular groove portion 12A to the second negative pressure generating groove 15 is restricted, so that the fluid recovery capacity during forward rotation is increased while leakage of the sealed fluid during reverse rotation is reduced.

[0066] Next, a sliding element according to a second embodiment will be described with reference to Fig. 6. Note that the description of the same configuration as in the first embodiment will be omitted.

[0067] 6 , the second negative pressure generating groove 215 of the second embodiment has a shorter length in the extension direction than the second negative pressure generating groove 15 of the first embodiment. In other words, the inner diameter end 215b of the second negative pressure generating groove 215 is located on the outer diameter side of the inner diameter end 214b of the first negative pressure generating groove 214.

[0068] This allows the inner diameter end 215b of the second negative pressure generating groove 215 to be spaced radially away from the internal space S2, making it difficult for the sealed fluid to leak from the inner diameter end 215b into the internal space S2 during reverse rotation.

[0069] In addition, the inner diameter end 215b of the second negative pressure generating groove 215 is positioned on the outer diameter side of the inner diameter end 214b of the first negative pressure generating groove 214. In other words, the second negative pressure generating groove 215 of this embodiment 2 is shorter and has a smaller volume than the second negative pressure generating groove 15 of embodiment 1, so that the flow of the sealed fluid to the second negative pressure generating groove 215 is reduced, making it difficult for dynamic pressure to be generated, and as a result, floating of the sliding surface is suppressed and leakage is suppressed.

[0070] Further, a groove 214' serving as a first negative pressure generating groove is provided on the inner diameter side in the extension direction of an inner diameter end 215b of the second negative pressure generating groove 215, the periphery of which is closed by a land 216. This groove 214' functions in the same manner as the first negative pressure generating groove 214. As a result, during forward rotation, the sealed fluid recovered in the groove 214' provided at a distance on the extension line can be easily recovered by the second negative pressure generating groove 215 and returned to the annular groove portion 212A.

[0071] Next, a sliding element according to a third embodiment will be described with reference to Fig. 7. Note that the description of the same configuration as in the first embodiment will be omitted.

[0072] As shown in FIG. 7A, the second negative pressure generating groove 315 of the third embodiment has protrusions 315c and 315d, which function as flow obstruction means, provided on opposite sides in the width direction at a position close to the annular groove portion 312A.

[0073] The protrusion 315c extends inward in the width direction from the side wall 315e of the second negative pressure generating groove 315 toward the annular groove 312A. The protrusion 315d extends inward in the width direction from the side wall 315f of the second negative pressure generating groove 315 toward the annular groove 312A. The tips of these protrusions 315c, 315d are spaced apart in the width direction. The side walls of these protrusions 315c, 315d are continuous with the bottom surface of the second negative pressure generating groove 315. Although the protrusions 315c, 315d are flush with the land 16, it is acceptable for them to be recessed further than that.

[0074] 7B, during forward rotation, the sealed fluid flows from the inner diameter side to the outer diameter side of the second negative pressure generating groove 315, passing between the protrusions 315c and 315d and flowing toward the annular groove 312A. At this time, the sealed fluid flows smoothly along the protrusions 315c and 315d while being guided toward the annular groove 312A.

[0075] 7C, during reverse rotation, the sealed fluid flows from the outer diameter side toward the inner diameter side of the second negative pressure generating groove 315. At this time, resistance is applied to the sealed fluid by the protrusions 315c, 315d, and the sealed fluid is retained between the protrusions 315c, 315d and the side walls 315e, 315f, so that the flow rate from the annular groove 312A toward the inner diameter end 315b of the second negative pressure generating groove 315 is reduced. Because the amount of introduced sealed fluid is reduced, dynamic pressure is less likely to be generated, which results in suppression of floating of the sliding surfaces and therefore leakage.

[0076] In this way, during forward rotation, the flow of sealed fluid from the second negative pressure generating groove 315 to the annular groove portion 312A is permitted, so the fluid recovery capacity of the second negative pressure generating groove 315 is high, and during reverse rotation, the flow of sealed fluid from the annular groove portion 312A to the inner diameter end 315b of the second negative pressure generating groove 315 is restricted, so leakage into the internal space S2 can be efficiently suppressed.

[0077] In the third embodiment, the protrusions 315c and 315d are provided on both sides of the second negative pressure generating groove 315 in the width direction so as to face each other, but they may be arranged offset in the extension direction of the second negative pressure generating groove.

[0078] Furthermore, in this embodiment 3, the protrusions 315c, 315d are exemplified as extending linearly toward the annular groove portion 312A, but this is not limited to this. For example, the protrusions may be formed into an approximately L-shape by a piece that intersects with the extension direction of the second negative pressure generating groove and a piece that extends from the intersecting piece toward the annular groove portion.

[0079] Next, a sliding element according to a fourth 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.

[0080] 8A, the second negative pressure generating groove 415 of the fourth embodiment is provided with a throttle portion 415g. The throttle portion 415g has a smaller flow path cross-sectional area than another portion 415h of the second negative pressure generating groove 415 located radially inward of the throttle portion 415g. The other portion 415h is provided radially inward of the throttle portion 415g and bulges outward upstream in the forward rotation direction. In other words, the land 416 located upstream of the throttle portion 415g in the forward rotation direction and the side wall 412Ac of the annular groove 412A function as a flow obstruction means.

[0081] As a result, during low-speed rotation, lubrication can be improved by the sealed fluid in the second negative pressure generating groove 415 that communicates with the annular groove portion 412A, and during reverse rotation, the land 416 restricts the flow of the sealed fluid from the annular groove portion 412A to other portions 415h, making it difficult for dynamic pressure to be generated, and as a result, lift-up between the sliding surfaces can be suppressed, and leakage into the internal space S2 can be suppressed.

[0082] In the fourth embodiment, the other portion 415h is provided so as to bulge upstream in the forward rotation direction on the inner diameter side of the throttle portion 415g. However, as shown in FIG. 8B, the other portion 415h' may be provided so as to bulge downstream in the forward rotation direction on the inner diameter side of the throttle portion 415g'. In other words, the land 416' may be provided downstream of the throttle portion 415g' in the forward rotation direction. In this embodiment, the land 416' downstream of the throttle portion 415g' in the forward rotation direction and the side wall 412Ac' of the annular groove 412A' function as the flow obstruction means.

[0083] 8(a) and 8(b), the configuration in Fig. 8(a) is preferable. Specifically, in the configuration in Fig. 8(a), the side wall 415k extending in the circumferential direction in the other portion 415h extends upstream in the forward rotation direction from the inner diameter end of the throttle portion 415g. In other words, since the throttle portion 415g is disposed in the forward rotation direction relative to the side wall 415k, the sealed fluid in the other portion 415h easily flows in the forward rotation direction along the side wall 415k, and the sealed fluid can be smoothly introduced into the throttle portion 415g.

[0084] On the other hand, in the configuration shown in Fig. 8(b), a side wall 415k' of the other portion 415h' extends downstream in the forward rotation direction from the inner diameter end of the throttle portion 415g'. In other words, the throttle portion 415g' is disposed in the reverse rotation direction relative to the side wall 415k'. As a result, during forward rotation, the sealed fluid in the other portion 415h' moves in a direction away from the throttle portion 415g', and is therefore more likely to stagnate near the side wall 415k' and is less likely to be introduced into the throttle portion 415g' than in the configuration shown in Fig. 8(a).

[0085] Next, a sliding element according to a fifth 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.

[0086] 9(a) and 9(b), the second negative pressure generating groove 515 of the fifth embodiment has a bottom surface 515j that is inclined so that the depth becomes shallower from the inner diameter end 515b to the outer diameter end 515a. The deepest portion of the second negative pressure generating groove 515 in FIG. 9(b) is the same depth as the second negative pressure generating groove 15 of the first embodiment.

[0087] During reverse rotation, the side wall 512Ac of the annular groove 512A functions as a flow obstruction means, and in addition, the cross-sectional area of ​​the flow path near the outer diameter end 515a is further reduced by the portion 515k of the second negative pressure generating groove 515 which is shallower than that of the first embodiment, making it difficult for the sealed fluid in the annular groove 512A to flow into the second negative pressure generating groove 515. This makes it difficult for dynamic pressure to be generated, and as a result, lifting between the sliding surfaces is suppressed, thereby suppressing leakage.

[0088] 9(c), the bottom surface 515j' of the second negative pressure generating groove 515' may be stepped so as to become shallower from the inner diameter end 515b' to the outer diameter end 515a'. In this case, the side wall 512Ac' of the annular groove 512A' functions as a flow obstruction means. In addition, the cross-sectional area of ​​the flow path near the outer diameter end 515a' is further reduced by the shallower portion 515k' of the second negative pressure generating groove 515' compared to the first embodiment, making it difficult for the sealed fluid in the annular groove 512A' to flow into the second negative pressure generating groove 515'. This makes it difficult for dynamic pressure to be generated, thereby suppressing lift-up between the sliding surfaces and thereby suppressing leakage.

[0089] Next, a sliding element according to a sixth embodiment will be described with reference to Figures 10 and 11. Note that a description of the same configuration as in the first embodiment will be omitted.

[0090] 10 , in the sliding component of the sixth embodiment, a band-shaped dimple group 622A consisting of a plurality of dimples 622 is arranged in an annular pattern on the sliding surface 621 of a rotary seal ring 620. In the dimple group 622A, the plurality of dimples 622 are arranged in a staggered pattern in the circumferential direction. The dimples 622 are of such a depth that the dynamic pressure generated during relative rotation can be almost ignored.

[0091] 11, the dimple group 622A is arranged on the sliding surface 611 of the stationary seal ring 610 so as to overlap in the axial direction with the land 616 on the leakage side, i.e., the inner diameter side of the first negative pressure generating groove 614 and the second negative pressure generating groove 615. In FIG. 11, the formation area of ​​the dimple group 622A is indicated by dots.

[0092] In this way, since multiple dimples 622 are provided on the sliding surfaces 611, 621 on the inner diameter side of the first negative pressure generating groove 614 and the second negative pressure generating groove 615, the sealed fluid stored in the multiple dimples 622 can ensure lubrication of the land 616 on the inner space S2 side relative to the first negative pressure generating groove 614 and the second negative pressure generating groove 615, which are prone to poor lubrication.

[0093] Furthermore, the multiple dimples 622 are positioned on the inner diameter side of the first negative pressure generating groove 614 and the second negative pressure generating groove 615, in other words, they are not positioned so as to overlap circumferentially with the first negative pressure generating groove 614 and the second negative pressure generating groove 615, and therefore are unlikely to affect the function of the first negative pressure generating groove 614 and the second negative pressure generating groove 615.

[0094] In some cases, a mixture of a low-boiling-point fluid and a lubricating fluid is enclosed as the sealed fluid. In such cases, the low-boiling-point fluid and the lubricating fluid normally flow between the sliding surfaces 611 and 621 and are returned to the outer diameter side by the first negative pressure generating groove 614 and the second negative pressure generating groove 615, thereby achieving both sealing and lubrication. When the temperature between the sliding surfaces 611 and 621 and the surrounding area is high, the low-boiling-point fluid evaporates, but the lubricating fluid remains between the sliding surfaces 611 and 621 and is stored in the dimples 622, thereby ensuring lubrication. During relative sliding, the low-boiling-point fluid and the lubricating fluid flow between the sliding surfaces 611 and 621 as needed. However, as the low-boiling-point fluid evaporates, only the lubricating fluid tends to remain on the inner diameter side of the first negative pressure generating groove 614 and the second negative pressure generating groove 615, ensuring lubrication.

[0095] Next, a sliding element according to a seventh 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.

[0096] 12, in the sliding component of the seventh embodiment, a band-shaped dimple group 717A consisting of a plurality of dimples 717 is arranged in an annular pattern on the inner diameter side, i.e., leakage side, of the first negative pressure generating groove 714 and the second negative pressure generating groove 715 on the sliding surface 711 of the stationary seal ring 710. In the dimple group 717A, the plurality of dimples 717 are arranged in a staggered pattern in the circumferential direction. The dimples 717 are of such a depth that the dynamic pressure generated during relative rotation can be almost ignored. The sliding surface 721 of the rotary seal ring 720 is flat.

[0097] In this way, multiple dimples 717 are provided between the sliding surfaces 711, 721 on the inner diameter side of the first negative pressure generating groove 714 and the second negative pressure generating groove 715, so that the sealed fluid stored in the multiple dimples 717 can ensure lubrication of the land 716 on the inner space S2 side of the first negative pressure generating groove 714 and the second negative pressure generating groove 715, which are prone to poor lubrication.

[0098] Furthermore, the multiple dimples 717 are positioned on the inner diameter side of the first negative pressure generating groove 714 and the second negative pressure generating groove 715, in other words, they are not positioned so as to overlap circumferentially with the first negative pressure generating groove 714 and the second negative pressure generating groove 715, and therefore are unlikely to affect the function of the first negative pressure generating groove 714 and the second negative pressure generating groove 715.

[0099] In some cases, a mixture of a low-boiling-point fluid and a lubricating fluid is enclosed as the sealed fluid. In such cases, the low-boiling-point fluid and the lubricating fluid normally flow between the sliding surfaces 711 and 721 and are returned to the outer diameter side by the first negative pressure generating groove 714 and the second negative pressure generating groove 715, thereby achieving both sealing and lubrication. When the temperature between the sliding surfaces 711 and 721 and the surrounding area is high, the low-boiling-point fluid evaporates, but the lubricating fluid remains between the sliding surfaces 711 and 721 and is stored in the dimples 717, thereby ensuring lubrication. During relative sliding, the low-boiling-point fluid and the lubricating fluid flow between the sliding surfaces 711 and 721 as needed. However, as the low-boiling-point fluid evaporates, only the lubricating fluid tends to remain on the inner diameter side of the first negative pressure generating groove 714 and the second negative pressure generating groove 715, ensuring lubrication.

[0100] Next, a sliding element according to an eighth embodiment will be described with reference to Fig. 13. Note that the description of the same configuration as in the first embodiment will be omitted.

[0101] 13, in the sliding component of the eighth embodiment, a band-shaped dimple group 817A is arranged in an annular pattern in a sliding region of a sliding surface 821 of a rotary seal ring 820 that faces the entire sliding surface 11 (see FIG. 2) of the stationary seal ring 10. In the dimple group 817A, a plurality of dimples 817 are arranged in a staggered pattern in the circumferential direction.

[0102] The multiple dimples 817 at least partially overlap in the axial direction with the reservoir groove 12, dynamic pressure generating groove 13, first negative pressure generating groove 14, and second negative pressure generating groove 15 (see Figure 2) provided on the sliding surface 11 of the stationary seal ring 10.

[0103] In this way, since multiple dimples 817 are provided over almost the entire sliding area between the sliding surfaces 11 and 821, the sealed fluid stored in the multiple dimples 817 can ensure lubrication of the land 816 on the inner space S2 side relative to the first negative pressure generating groove 14 and the second negative pressure generating groove 15, which are prone to poor lubrication.

[0104] Furthermore, it is preferable that the dimples 817 be formed to a depth that does not affect the dynamic pressure generating capacity of the dynamic pressure generating grooves 13, the first negative pressure generating grooves 14, and the second negative pressure generating grooves 15, for example, a depth that is 1 / 10 or less of the depth of the dynamic pressure generating grooves 13, the first negative pressure generating grooves 14, and the second negative pressure generating grooves 15.

[0105] Furthermore, dimples may be provided in areas on the sliding surface 11 of the stationary seal ring 10 other than the reservoir groove 12 , the dynamic pressure generating groove 13 , the first negative pressure generating groove 14 , and the second negative pressure generating groove 15 .

[0106] 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.

[0107] For example, in the first to eighth embodiments, mechanical seals have been described as examples of sliding components, but other mechanical seals for general industrial machinery, automobiles, water pumps, etc. may also be used. Furthermore, the sliding components are not limited to mechanical seals, and may be sliding bearings or other sliding components other than mechanical seals.

[0108] Furthermore, in the first to eighth embodiments, the first and second negative pressure generating grooves are spiral grooves, but the present invention is not limited to this and may be Rayleigh steps, dimples, or the like.

[0109] Furthermore, in Examples 1 to 8, the total area of ​​the second negative pressure generating grooves on the sliding surface is smaller than the total area of ​​the first negative pressure generating grooves, and the total volume of the second negative pressure generating grooves is smaller than the total volume of the first negative pressure generating grooves. However, this is not limiting. For example, if the total area of ​​the second negative pressure generating grooves on the sliding surface is smaller than the total area of ​​the first negative pressure generating grooves, the total volume of the second negative pressure generating grooves may be larger than the total volume of the first negative pressure generating grooves. Furthermore, if the total volume of the second negative pressure generating grooves is smaller than the total volume of the first negative pressure generating grooves, the total area of ​​the second negative pressure generating grooves on the sliding surface may be larger than the total area of ​​the first negative pressure generating grooves.

[0110] Furthermore, in Examples 1 to 8, the storage groove has an annular groove portion, but instead of the annular groove portion, multiple arc-shaped grooves or C-shaped grooves when viewed in the axial direction may be used, as long as they are deeper than the first negative pressure generating groove and the second negative pressure generating groove.

[0111] In addition, in the above-described first to eighth embodiments, the sealed fluid space is the outer space S1 and the leakage space is the inner space S2, but as shown in Fig. 14, the sealed fluid space may be the inner space S2 and the leakage space may be the outer space S1. In this case, the inlet / outlet groove 112B and the dynamic pressure generating groove 113 may be located radially inward of the annular groove 112A, and the first negative pressure generating groove 114 and the second negative pressure generating groove 115 may be located radially outward of the annular groove 112A.

[0112] Furthermore, although the sealed fluid side has been described as the high pressure side and the leakage side as the low pressure side, the sealed fluid side and the leakage side may be at approximately the same pressure.

[0113] In the first to eighth embodiments, the sealed fluid is described as a high-pressure lubricating oil, but it is not limited to this and may be a gas or a low-pressure liquid, or a mist mixture of liquid and gas. Also, two or more types of fluids may be mixed, such as a low-boiling point fluid and a lubricating fluid.

[0114] In addition, in the above-described Examples 1 to 8, the fluid on the leaking side was described as low-pressure gas, i.e., atmospheric air, but the fluid is not limited to this and may be a liquid or high-pressure gas, or a mist-like mixture of liquid and gas. Furthermore, two or more types of fluid may be mixed, such as a low-boiling-point fluid and a lubricating fluid.

[0115] In addition, in Examples 6 to 8, the dimples were arranged in a staggered pattern, but the dimple arrangement pattern can be freely changed. The shape and depth of the dimples can also be freely changed. Dimples may also be provided on the sliding surface of the stationary seal ring and the sliding surface of the fixed seal ring.

[0116] Furthermore, in Examples 6 to 8, a configuration in which a plurality of dimples are provided is exemplified, but for example, a single annular dimple or a single arc-shaped dimple may be provided closer to the leakage space than the first and second negative pressure generating grooves. The number of dimples can be freely changed.

[0117] Furthermore, in the seventh embodiment, a form was exemplified in which dimples were provided on the sliding surface of the stationary seal ring closer to the leakage space than the first and second negative pressure generating grooves, but dimples may also be provided in portions of the sliding surface of the stationary seal ring other than the reservoir groove, dynamic pressure generating groove, first negative pressure generating groove and second negative pressure generating groove, for example, in a portion between the reservoir groove and the dynamic pressure generating groove or a portion between the reservoir groove and the first negative pressure generating groove.

[0118] DESCRIPTION OF SYMBOLS 1 Rotating shaft 4 Housing 10 Stationary seal ring 11 Sliding surface (one of the sliding surfaces) 12 Reservoir groove 12A Annular groove portion 12B Inlet / outlet groove portion 13 Dynamic pressure generating groove 14 First negative pressure generating groove 14a Outer diameter end (end portion on the sealed fluid space side) 14b Inner diameter end (end portion on the leakage space side) 15 Second negative pressure generating groove 15a Outer diameter end (end portion on the sealed fluid space side) 15b Inner diameter end (end portion on the leakage space side) 16 Land 20 Rotating seal ring 21 Sliding surface (other of the sliding surfaces) AR1 Total area AR2 Total area S1 Outer space (sealed fluid space) S2 Inner space (leakage space) VL1 Total volume VL2 Total volume

Claims

1. A sliding component arranged between a housing and a shaft inserted through the housing, and comprising a pair of sliding surfaces which partition a sealed fluid space and a leakage space, wherein one of the sliding surfaces is provided with: a dynamic pressure generating groove communicating with the sealed fluid space, a storage groove which is arranged on the leakage space side of the dynamic pressure generating groove and extends in the circumferential direction, a first negative pressure generating groove which is arranged on the leakage space side of the storage groove and does not communicate with the storage groove, and a second negative pressure generating groove which is arranged on the leakage space side of the storage groove and communicates with the storage groove.

2. A sliding component according to claim 1, wherein the total volume of the second negative pressure generating grooves is smaller than the total volume of the first negative pressure generating grooves.

3. A sliding component according to claim 1, wherein a plurality of the second negative pressure generating grooves are arranged in the circumferential direction, and a plurality of the first negative pressure generating grooves are arranged between adjacent pairs of the second negative pressure generating grooves.

4. A sliding component as described in claim 1, wherein the first negative pressure generating groove and the second negative pressure generating groove extend in a radial direction, and an end of the second negative pressure generating groove on the leakage space side is positioned closer to the storage groove than the end of the first negative pressure generating groove on the leakage space side.

5. A sliding component according to claim 4, wherein the first negative pressure generating groove is provided on an extension line of the second negative pressure generating groove on the leakage space side, at a distance therefrom.

6. A sliding component according to claim 4, wherein the second negative pressure generating groove overlaps in the circumferential direction with an end of the first negative pressure generating groove on the side of the sealed fluid space.

7. A sliding component according to claim 1, further comprising flow impeding means for providing resistance to the sealed fluid flowing through said second negative pressure generating groove into said leakage space.

8. A sliding component according to claim 7, wherein the flow obstruction means is a protrusion extending at an angle toward the communicating portion between the second negative pressure generating groove and the reservoir groove.

9. A sliding component according to claim 7, wherein said flow obstructing means is a wall rising in the depth direction against the flow of the sealed fluid towards said leakage space.

10. A sliding component according to claim 1, wherein said one sliding surface is provided with dimples at least closer to said leakage space than said first negative pressure generating groove and said second negative pressure generating groove.

11. A sliding component according to claim 1, wherein the other sliding surface opposite to the one sliding surface is provided with dimples at least closer to the leakage space than the first negative pressure generating groove and the second negative pressure generating groove.

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