Sliding component

Abstract

Provided is a sliding component capable of reducing a friction force that is generated during relative sliding, even in reverse rotation.　The sliding component is provided in a position where a pair of sliding surfaces 11, 21 rotate relative to each other, and partitions a leakage side space S1 and a sealed fluid side space S2. One sliding surface 11 is provided with: a plurality of inclined grooves 12, 13 that extend from the leakage side space S1 to a relative rotational direction forward rotation side and toward the sealed fluid side space S2 side, and that have closed ends 12b, 13b; circumferential direction grooves 14 that communicate with the sealed fluid side space S2 and extend toward the relative rotational direction forward rotation side; and reverse circumferential direction grooves 15 that communicate with the sealed fluid side space S2 and extend toward a relative rotational direction reverse rotation side. The plurality of inclined grooves 12, 13 include some long inclined grooves 13.

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] In rotary machines, a mechanical seal consisting of a pair of annular sliding rings that rotate relative to each other and whose sliding surfaces slide against each other is known as a sliding component for preventing leakage of a sealed fluid around a rotating shaft. In recent years, there has been a demand for reducing the energy lost due to sliding, for example, in order to protect the environment, and some mechanical seals have dynamic pressure generating grooves on the sliding surfaces of the sliding rings.

[0003] For example, the sliding surface of one of the sliding rings of the mechanical seal shown in Patent Document 1 is provided with a plurality of Rayleigh steps that communicate with an outer diameter space where liquid is present, and a plurality of inclined grooves that communicate with an inner diameter space where gas is present. When the pair of sliding rings are rotating at a low relative speed, liquid in the outer diameter space is introduced into the Rayleigh steps, and gas in the inner diameter space is introduced into the inclined grooves, causing the sliding surfaces to slightly separate from each other mainly due to the dynamic pressure generated by the Rayleigh steps, and liquid flows between the sliding surfaces.

[0004] As the relative rotational speed of the pair of sliding rings increases, the dynamic pressure generated in the inclined grooves becomes dominant, causing the sliding surfaces to separate. When the pair of sliding rings are rotating at high relative rotational speeds, the dynamic pressure generated in the inclined grooves is the main force, slightly separating the sliding surfaces, and gas flows between the sliding surfaces. At this time, liquid flowing from the outer diameter space between the sliding surfaces is pushed back toward the outer diameter by the dynamic pressure generated in the inclined grooves, preventing the liquid from leaking into the inner diameter space.

[0005] The plurality of inclined grooves also includes a long inclined groove that extends further toward the outer diameter space than the other inclined grooves, which allows dynamic pressure to be generated at different positions in the radial direction, making it easier to separate the sliding surfaces while maintaining them approximately parallel to each other.

[0006] WO 2023 / 026755 (page 20, Figure 12)

[0007] In a mechanical seal such as that described in Patent Document 1, the frictional force generated by the relative sliding of the sliding surfaces is reduced by the liquid during low-speed rotation, and the frictional force generated by the relative sliding of the sliding surfaces is reduced by the gas during high-speed rotation, but it does not support reverse rotation, and there is a risk of large frictional force being generated during reverse rotation.

[0008] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a sliding component that can reduce the frictional force generated during relative sliding even in reverse rotation.

[0009] To solve the above problem, the present invention provides a sliding element that is arranged at a location where a pair of sliding surfaces rotate relative to each other and that separates a leakage-side space and a sealed fluid-side space, wherein one of the sliding surfaces comprises a plurality of inclined grooves that extend from the leakage-side space toward the forward rotation side in the relative rotation direction and toward the sealed fluid-side space and have closed ends, a Rayleigh step that communicates with the sealed fluid-side space and extends toward the forward rotation side in the relative rotation direction, and a reverse Rayleigh step that communicates with the sealed fluid-side space and extends toward the reverse rotation side in the relative rotation direction, and some of the inclined grooves have long inclined grooves. With this, during reverse rotation, the sealed fluid is introduced into the reverse Rayleigh step, generating positive pressure in the reverse Rayleigh step. This dynamic pressure causes the sliding surfaces to slightly separate, making it possible to reduce the frictional force generated by the fluid flowing between the sliding surfaces due to their relative sliding. Furthermore, during reverse rotation, the negative pressure generated in the long inclined grooves makes it easier to guide the sealed fluid to the inverse Rayleigh step, which makes it easier to generate high dynamic pressure in the inverse Rayleigh step.

[0010] The long inclined groove may extend at least to the same radial position as the end of the reverse Rayleigh step on the reverse rotation side in the relative rotation direction, whereby a larger negative pressure is generated in the long inclined groove during reverse rotation, making it easier to generate a high dynamic pressure in the reverse Rayleigh step.

[0011] The closed end of the long inclined groove may be provided at the same radial position as the end of the reverse Rayleigh step, whereby during reverse rotation, negative pressure generated in the long inclined groove makes it easier to more efficiently guide the sealed fluid into the reverse Rayleigh step, making it easier to generate high dynamic pressure in the reverse Rayleigh step.

[0012] An inclined groove shorter than the long inclined groove may be disposed circumferentially between the end of the inverted Rayleigh step and the long inclined groove. This makes it possible to achieve both the effect of guiding the sealed fluid to the inverted Rayleigh step by the negative pressure generated by the two inclined grooves during reverse rotation and the dynamic pressure effect of the inverted Rayleigh step.

[0013] The reverse Rayleigh step may have a communicating groove communicating with the sealed fluid-side space and extending in the radial direction, and a reverse circumferential groove extending from the reverse-rotation side of the communicating groove to the reverse-rotation side of the relative rotation direction, and a circumferential length between the long inclined groove and the end of the reverse Rayleigh step may be longer than the circumferential length of the reverse circumferential groove. This makes it possible to achieve both the effect of guiding the sealed fluid to the reverse Rayleigh step by the negative pressure generated in the long inclined groove during reverse rotation and the dynamic pressure effect of the reverse Rayleigh step.

[0014] The Rayleigh step and the reverse Rayleigh step may be disposed between adjacent long inclined grooves, and the circumferential length between the long inclined groove and the end of the reverse Rayleigh step may be shorter than the circumferential length between another long inclined groove and the end of the Rayleigh step. This makes it possible to suppress the dynamic pressure effect of the reverse Rayleigh step during reverse rotation more effectively than the dynamic pressure effect of the Rayleigh step during forward rotation. As a result, at low speeds, contaminants trapped in the reverse Rayleigh step are less likely to be discharged to the land during reverse rotation.

[0015] The circumferential groove of the Rayleigh step and the reverse circumferential groove of the reverse Rayleigh step that are adjacent in the circumferential direction may communicate with the same communicating groove that communicates with the sealed fluid-side space. This makes it easier for the sealed fluid to flow from the Rayleigh step to the reverse Rayleigh step during reverse rotation, reducing the amount of sealed fluid that flows from the sealed fluid-side space into the communicating groove. This makes it possible to prevent foreign matter from flowing between the sliding surfaces through the communicating groove.

[0016] The circumferential groove, the communication groove, and the reverse circumferential groove may have the same depth, which allows the sealed fluid to more smoothly flow from the circumferential groove to the reverse circumferential groove during reverse rotation.

[0017] FIG. 1 is a longitudinal cross-sectional view showing an example of a mechanical seal according to a first embodiment of the present invention. FIG. 1 is a view of the sliding surface of a stationary seal ring as viewed from the axial direction. (a) is a schematic cross-sectional view for explaining the depth of inclined grooves, and (b) is a schematic cross-sectional view for explaining the depths of communicating grooves and reverse circumferential grooves. FIG. 2 is an enlarged view of a main portion of FIG. 2 during forward rotation. FIG. 2 is an enlarged view of a main portion of FIG. 2 during reverse rotation. FIG. 1 is a view of the sliding surface of a rotary seal ring of another embodiment as viewed from the axial direction. FIG. 2 is an enlarged view of a main portion of the sliding surface of a stationary seal ring according to a second embodiment of the present invention. FIG. 3 is an enlarged view of a main portion of the sliding surface of a stationary seal ring according to a third embodiment of the present invention. FIG. 4 is an enlarged view of a main portion of the sliding surface of a stationary seal ring according to a fourth embodiment of the present invention. FIG. 5 is an enlarged view of a main portion of the sliding surface of a stationary seal ring according to a fifth embodiment of the present invention. (a) is a schematic cross-sectional view for explaining the depth of inclined grooves in the fifth embodiment, and (b) is a schematic cross-sectional view for explaining the depths of communicating grooves and reverse circumferential grooves in the fifth embodiment. FIG. 1 is a view of the sliding surface of a stationary seal ring 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 Figures 1 to 6. In this embodiment, a mechanical seal will be used as an example of the sliding component. For ease of explanation, grooves formed on the sliding surface may be indicated by dots in the drawings.

[0020] The mechanical seal shown in Fig. 1 separates an inner space S1 as a leakage-side space from an outer space S2 as a sealed fluid-side space. Atmospheric air exists as a gas A in the inner space S1. A liquid F, which is a sealed fluid such as oil, exists in the outer space S2. In other words, the mechanical seal is an inside type that seals off the liquid F that attempts to leak from the outer space S2 toward the inner space S1. Note that this embodiment illustrates a configuration in which the gas A is at a lower pressure than the liquid F. The types of gas A and liquid F may be changed as appropriate.

[0021] The mechanical seal comprises a stationary seal ring 10 and a rotary seal ring 20. The stationary seal ring 10 is fixed to 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 attached to a sleeve 2 fixed to a rotary shaft 1 and is rotatable together with the rotary shaft 1.

[0022] 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, which serves as one sliding surface, and the sliding surface 21 of the rotary seal ring 20, which serves as the other sliding surface, are adapted to slide closely against each other. The sliding surface 21 of the rotary seal ring 20 is a flat surface, and does not have any recesses such as grooves.

[0023] 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 are not limited to this. 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.

[0024] As shown in FIG. 2, the rotary seal ring 20 is slidable relative to the stationary seal ring 10 in the counterclockwise direction as indicated by the solid arrow, and in the clockwise direction as indicated by the dashed arrow.

[0025] In this embodiment, the counterclockwise sliding of the rotary seal ring 20 relative to the engine is referred to as forward rotation, and the clockwise sliding of the rotary seal ring 20 relative to the engine is referred to as reverse rotation. Furthermore, in this embodiment, the description will be given assuming forward rotation unless otherwise specified. Furthermore, during forward rotation, the clockwise side of the target position will be referred to as the upstream side in the forward rotation direction, and the counterclockwise side of the target position will be referred to as the downstream side in the forward rotation direction. Furthermore, during reverse rotation, the clockwise side of the target position will be referred to as the downstream side in the reverse rotation direction, and the counterclockwise side of the target position will be referred to as the upstream side in the reverse rotation direction.

[0026] The sliding surface 11 of the stationary seal ring 10 is provided with spiral grooves 12 and 13 as 24 inclined grooves, three circumferential grooves 14, three reverse circumferential grooves 15, and three communicating grooves 16. The portion of the sliding surface 11 other than the spiral grooves 12 and 13, the circumferential groove 14, the reverse circumferential groove 15, and the communicating grooves 16 is a land 17 forming a flat surface.

[0027] The spiral grooves 12 and 13 have different lengths in the extension direction. In the following description, the spiral groove 12 may be referred to as a first spiral groove 12, and the spiral groove 13, which is an inclined groove longer than the first spiral groove 12, may be referred to as a second spiral groove 13.

[0028] The 24 spiral grooves 12, 13 are equally spaced. Of these, 18 first spiral grooves 12 are provided. Also, 6 second spiral grooves 13 are provided. Specifically, three first spiral grooves 12 are provided between two circumferentially adjacent second spiral grooves 13 in the circumferential direction.

[0029] The first spiral groove 12 has an open end 12a on the inner diameter side that communicates with the internal space S1 and extends in an arc shape while inclining from the open end 12a toward the outer diameter side and downstream in the positive rotation direction. The first spiral groove 12 has an arc shape that protrudes toward the outer diameter side and upstream in the positive rotation direction. The outer diameter side end of the first spiral groove 12 is a closed end 12b that is closed so as not to communicate with the external space S2.

[0030] In the following description, the upstream side in the forward rotation direction may be simply referred to as the "upstream side," and the downstream side in the forward rotation direction may be simply referred to as the "downstream side."

[0031] 3A, the first spiral groove 12 has a substantially constant depth D1, i.e., a substantially constant axial length, from the open end 12a to the closed end 12b. Note that in FIG. 3A, a cross section cut radially is shown schematically to clearly show the depth of the first spiral groove 12 and other components.

[0032] The depth of the first spiral groove 12 may be gradually shallower or may vary from the open end 12 a to the closed end 12 b. The cross-sectional shape of the first spiral groove 12 is rectangular, but may also be U-shaped, semicircular, triangular, or any other suitable shape. The same applies to the other grooves 13, 14, 15, and 16.

[0033] 2 , the second spiral groove 13 has substantially the same shape as the first spiral groove 12, and therefore a redundant description will be omitted or simplified. The length of the second spiral groove 13 in the extension direction from the open end 13 a to the closed end 13 b is longer than that of the first spiral groove 12. In other words, the closed end 13 b of the second spiral groove 13 is located radially outer than the closed end 12 b of the first spiral groove 12.

[0034] The depth and width, i.e., the circumferential length, of the second spiral groove 13 are substantially the same as those of the first spiral groove 12. Note that the second spiral groove may be different from the first spiral groove in at least one of the depth and width.

[0035] The single circumferential groove 14 and the single reverse circumferential groove 15 are arranged on both circumferential sides of the same single communicating groove 16. The circumferential grooves 14, 15 communicate with the communicating groove 16. These are sometimes referred to as one set, simply as "grooves 14, 15, 16" in the following description.

[0036] A total of three sets of grooves 14, 15, 16 are provided and equally spaced on the sliding surface 11. On the sliding surface 11, regions where one set of grooves 14, 15, 16 is formed between two circumferentially adjacent second spiral grooves 13 and regions where none of the grooves 14, 15, 16 is formed between two circumferentially adjacent second spiral grooves 13 are alternately provided.

[0037] In addition, two or more sets of grooves 14, 15, 16 may be provided circumferentially between two adjacent second spiral grooves 13, and areas where grooves 14, 15, 16 are formed and areas where they are not formed may not be provided alternately, and only areas where grooves 14, 15, 16 are formed may be provided, and the arrangement of one set of grooves 14, 15, 16 may be changed as appropriate.

[0038] 3, the depth D2 (see FIG. 3(b)) of the grooves 14, 15, and 16 is substantially the same as the depth D1 (see FIG. 3(a)) of the spiral grooves 12 and 13 (D1 = D2). Note that the depth D2 of the grooves 14, 15, and 16 and the depth D1 of the spiral grooves 12 and 13 may be different.

[0039] 4, the communication groove 16 is a groove that extends radially and has a constant depth, and the outer diameter side end thereof communicates with the external space S2. The inner diameter side end of the communication groove 16 is closed.

[0040] The circumferential groove 14 is a groove of constant depth that extends circumferentially from the open end 14a toward the downstream side, with its upstream end being connected to the downstream side of the inner diameter end of the communicating groove 16. The downstream end of the circumferential groove 14 is a closed end 14b. The circumferential groove 14 and the communicating groove 16 form a Rayleigh step.

[0041] The reverse circumferential groove 15 is a groove of constant depth that extends circumferentially from the open end 15a toward the upstream side, with its downstream end being connected to the upstream side of the inner diameter side end of the communicating groove 16. The upstream end of the reverse circumferential groove 15 is a closed end 15b. The circumferential groove 14 and the communicating groove 16 form an inverse Rayleigh step.

[0042] The circumferential groove 14 and the reverse circumferential groove 15 are provided at approximately the same radial position as the closed end 13b of the second spiral groove 13. The circumferential groove 14 and the reverse circumferential groove 15 have approximately the same volume, i.e., approximately the same length, depth, and width in the extension direction, but at least one of these may be different.

[0043] Next, the sealing between the inner space S1 and the outer space S2 by the stationary seal ring 10 and the rotary seal ring 20 will be described with reference to Figures 4 and 5. The fluid flow in Figure 4 is shown schematically assuming that the rotary seal ring 20 is rotating forward at a low speed.

[0044] When the mechanical seal is not in operation and the rotary seal ring 20 is not rotating, the sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotary seal ring 20 are in contact with each other, thereby preventing the liquid F from leaking into the internal space S1.

[0045] First, the operation during forward rotation at low speed will be described. At low speed immediately after the rotating seal ring 20 starts to rotate forward relative to the stationary seal ring 10, the gas A in the first spiral groove 12 tries to move in the direction of rotation of the rotating seal ring 20 due to shear with the sliding surface 21, as shown by the outline arrow in Figure 4.

[0046] The gas A is guided along the first spiral groove 12 to the closed end 12b and is supplied between the sliding surfaces 11 and 21 from the closed end 12b and its vicinity. The gas A moves mainly toward the outer diameter side and downstream. Positive pressure is generated at the closed end 12b and its vicinity. The same applies to the second spiral groove 13.

[0047] 4, the liquid F in the circumferential groove 14 is guided along the circumferential groove 14 to the closed end 14b and is supplied between the sliding surfaces 11 and 21 from the closed end 14b and its vicinity. The liquid F flows mainly downstream. Positive pressure is generated at the closed end 14b and its vicinity.

[0048] The circumferential groove 14 can introduce the liquid F from the communication groove 16 to efficiently generate dynamic pressure.

[0049] As shown by the black arrows in Figure 4, the liquid F in the reverse circumferential groove 15 is guided along the reverse circumferential groove 15 to the open end 15a and flows into the communicating groove 16. A relative negative pressure is generated on the upstream side of the reverse circumferential groove 15. This negative pressure increases as it approaches the closed end 15b. In other words, the force sucking the liquid F becomes stronger. Hereinafter, the relative negative pressure will be simply referred to as "negative pressure."

[0050] During forward rotation at low speeds, the sliding surfaces 11, 21 can be slightly separated by the positive pressure generated mainly by the circumferential grooves 14. This allows liquid F and gas A to flow between the sliding surfaces 11, 21. Furthermore, because the positive pressure generated by the spiral grooves 12, 13 at low speeds is small, liquid F is more likely to flow into the inner diameter side between the sliding surfaces 11, 21 at low speeds. In other words, the sliding surfaces 11, 21 are primarily liquid lubricated, and the frictional force due to relative sliding is reduced.

[0051] The liquid F upstream of the reverse circumferential groove 15 is easily sucked into the reverse circumferential groove 15 due to the negative pressure generated in the reverse circumferential groove 15 located downstream.

[0052] The liquid F that has flowed into the reverse circumferential groove 15 is accompanied by a flow, and therefore is likely to flow into the circumferential groove 14 through the connected communicating groove 16. This makes it possible to reduce the amount of liquid F that flows into the communicating groove 16 from the outer space S2. Note that the communicating groove 16 contains liquid F that flows out to the outer space S2 and liquid F that flows in from the outer space S2.

[0053] Furthermore, the closed end 12b of the first spiral groove 12 and the closed ends 13b, 14b of the second spiral groove 13 and the circumferential groove 14 can generate positive pressure at different radial positions, which makes it easier to separate the sliding surfaces 11, 21 while maintaining them substantially parallel to each other.

[0054] The liquid F that has moved toward the inner diameter side will now be described. The liquid F that has moved toward the inner diameter side of the grooves 14, 15, and 16 is returned toward the outer space S2 by the positive pressure generated at and near the closed end 12b of the first spiral groove 12. The liquid F also moves toward the outer space S2 by moving together with the gas A within the spiral grooves 12 and 13.

[0055] The closed end 13b of the second spiral groove 13 is located close to the external space S2, making it easier to discharge the liquid F from the closed end 13b into the external space S2.

[0056] In addition, since the second spiral groove 13 extends from the inner diameter edge of the sliding surface 11 to approximately the same radial position as the circumferential groove 14, liquid F that has moved downstream of the first spiral groove 12 and the circumferential groove 14 can easily flow in.

[0057] Next, the operation during forward rotation and high speed rotation will be described. When the relative rotation speed of the rotary seal ring 20 further increases and reaches high speed rotation, i.e., a steady operating state, the positive pressure generated at high speed becomes greater than the positive pressure generated at low speed.

[0058] In particular, the positive pressure generated by each spiral groove 12, 13 increases, and the force pushing the liquid F back toward the external space S2 increases, causing the gas A to flow into the outer diameter side between the sliding surfaces 11, 21. In other words, the sliding surfaces 11, 21 are primarily gas lubricated, and the frictional force due to relative sliding is reduced. At this time, the sliding surfaces 11, 21 are spaced apart more than at low speeds, and the positive pressure due to the circumferential groove 14 decreases.

[0059] Next, the reverse rotation of the rotary seal ring 20 will be described with reference to Figure 5. Note that the description of the same as that of the forward rotation will be simplified or omitted. In addition, the relative rotation speed during reverse rotation in this embodiment is approximately the same as that during forward rotation, but may be changed as appropriate.

[0060] 5, the gas A in the first spiral groove 12 is guided along the first spiral groove 12 to the open end 12a and discharged into the internal space S1. As a result, a negative pressure that increases toward the closed end 12b is generated on the upstream side of the first spiral groove 12 in the reverse rotation direction. The same applies to the second spiral groove 13.

[0061] 5, the liquid F in the reverse circumferential groove 15 is guided along the reverse circumferential groove 15 to the closed end 15b and is supplied between the sliding surfaces 11 and 21 from the closed end 15b and its vicinity. The liquid F flows mainly downstream in the reverse rotation direction. In addition, a positive pressure is generated at the closed end 15b and its vicinity.

[0062] The reverse circumferential groove 15 can introduce the liquid F from the communication groove 16 to efficiently generate dynamic pressure.

[0063] 5, the liquid F in the circumferential groove 14 is guided along the circumferential groove 14 to the open end 14a and flows into the communicating groove 16. On the upstream side of the circumferential groove 14 in the reverse rotation direction, the closer to the closed end 14b, the greater the negative pressure generated.

[0064] As described above, during reverse rotation, the sliding surfaces 11, 21 can be slightly separated from each other by the positive pressure generated by the reverse circumferential groove 15. This reduces the frictional force generated by the relative sliding between the sliding surfaces 11, 21.

[0065] Furthermore, the liquid F in the reverse circumferential groove 15 is sucked toward the second spiral groove 13 by the negative pressure generated in the second spiral groove 13, which is located close to the reverse circumferential groove 15 and downstream of the reverse circumferential groove 15 in the reverse rotation direction. In other words, by guiding the liquid F from the circumferential groove 14 or the communicating groove 16 to the reverse circumferential groove 15, the amount of liquid F flowing in the reverse circumferential groove 15 increases, thereby increasing the dynamic pressure generated in the reverse circumferential groove 15. This makes it easier to increase the positive pressure generated at and near the closed end 15b and the negative pressure generated in the circumferential groove 14.

[0066] Furthermore, the closed ends 12b of the two first spiral grooves 12 are located in close proximity to the closed ends 15b of the reverse circumferential grooves 15. Specifically, one closed end 12b is located on the inner diameter side at approximately the same circumferential position as the closed end 15b. The other closed end 12b is located downstream in the reverse rotation direction and on the inner diameter side of the closed end 15b of the reverse circumferential groove 15. The negative pressure generated by these also can guide the liquid F into the reverse circumferential groove 15, thereby increasing the dynamic pressure within the reverse circumferential groove 15.

[0067] Furthermore, the liquid F upstream of the circumferential groove 14 in the reverse rotation direction is easily sucked into the circumferential groove 14 due to the negative pressure generated in the circumferential groove 14. Furthermore, the negative pressure generated in the circumferential groove 14 is increased by the negative pressure generated in the spiral grooves 12 and 13, thereby increasing the efficiency of recovering the liquid F.

[0068] The liquid F that has flowed into the circumferential groove 14 is accompanied by a flow, and therefore is likely to flow into the reverse circumferential groove 15 through the connected communicating grooves 16. This makes it possible to reduce the amount of liquid F that flows into the communicating grooves 16 from the outer space S2. Note that the communicating grooves 16 contain liquid F that flows out to the outer space S2 and liquid F that flows in from the outer space S2.

[0069] Contaminants may be mixed into the liquid F that flows between the sliding surfaces 11 and 21. Hereinafter, the contaminants that flow between the sliding surfaces 11 and 21 will be described with reference to Figures 4 and 5. Note that the foreign matter may be slurry and is not limited to contaminants.

[0070] 4, when the rotary seal ring 20 rotates forward, contaminants present between the land 17 and the sliding surface 21 move downstream as the rotary seal ring 20 rotates, and are likely to be collected in one of the downstream grooves 12, 13, 14, 15, and 16. This prevents contaminants from remaining between the land 17 and the sliding surface 21 for a long period of time.

[0071] Contaminants in the first spiral groove 12 move toward the closed end 12b due to the flow of gas A in the first spiral groove 12 and shear with the sliding surface 21. The contaminants are then discharged from the closed end 12b and its vicinity toward the external space S2. Contaminants in the vicinity of the closed end 12b are pushed toward the external space S2 by gas A supplied from the closed end 12b between the sliding surfaces 11 and 21. The same applies to the second spiral groove 13.

[0072] Since the closed end 13b of the second spiral groove 13 is located close to the external space S2, contaminants can be easily discharged from the closed end 13b and its vicinity into the external space S2. This prevents contaminants from remaining between the sliding surfaces 11 and 21 for a long period of time.

[0073] Furthermore, contaminants present downstream of the closed end 13 b are likely to be collected into the reverse circumferential groove 15 due to the negative pressure generated at the closed end 15 b of the reverse circumferential groove 15, the flow of the liquid F in the reverse circumferential groove 15, and the shear force acting on the liquid F between the sliding surfaces 11 and 21.

[0074] Contaminants in the reverse circumferential groove 15 move downstream due to the flow of the liquid F in the reverse circumferential groove 15 and shear with the sliding surface 21, and flow into the communicating groove 16. The contaminants taken into the reverse circumferential groove 15, the communicating groove 16, and the circumferential groove 14 are trapped in these grooves 14, 15, and 16. As a result, the contaminants in the grooves 14, 15, and 16 are less likely to be discharged to the land 17, and are more likely to be discharged from the communicating groove 16 into the external space S2. This so-called trapping effect is more pronounced because the distance between the sliding surfaces 11 and 21 becomes shorter as the relative rotational speed decreases.

[0075] Furthermore, the contaminants discharged from the closed end 14b to the land 17 are easily collected in the second spiral groove 13 located downstream thereof. The contaminants collected in the second spiral groove 13 are discharged from the second spiral groove 13 toward the external space S2 by the high dynamic pressure generated during high-speed rotation.

[0076] Referring to FIG. 5, when the rotary seal ring 20 rotates in the reverse direction, contaminants present between the land 17 and the sliding surface 21 move downstream in the reverse rotation direction in response to the rotation of the rotary seal ring 20, and are likely to be collected in one of the grooves 14, 15, or 16 located downstream in the reverse rotation direction.

[0077] Furthermore, since the flow direction of the gas A changes between forward and reverse rotation, even if contaminants get mixed into the grooves 12 and 13, they are unlikely to accumulate in a specific location. This also applies to the grooves 14, 15, and 16.

[0078] Furthermore, contaminants present downstream of the closed end 13b in the reverse rotation direction are easily collected into the circumferential groove 14 due to the negative pressure generated at the closed end 14b of the circumferential groove 14, the flow of the liquid F in the circumferential groove 14, and the shear force acting on the liquid F between the sliding surfaces 11, 21. Furthermore, the efficiency of collecting contaminants is increased by the negative pressure generated in the circumferential groove 14 and the negative pressure generated in the spiral grooves 12, 13.

[0079] Contaminants in the circumferential groove 14 move downstream in the reverse rotation direction due to the flow of the liquid F in the circumferential groove 14 and shear with the sliding surface 21, and flow into the communicating groove 16. The contaminants taken into the circumferential groove 14, the communicating groove 16, and the reverse circumferential groove 15 become trapped in these grooves 14, 15, and 16. As a result, the contaminants in the grooves 14, 15, and 16 are less likely to be discharged to the land 17, and are more likely to be discharged from the communicating groove 16 into the external space S2.

[0080] Furthermore, if the relative rotational speed during reverse rotation of the rotary seal ring 20 is low, the distance between the sliding surfaces 11, 21 during reverse rotation is shorter than the distance between the sliding surfaces 11, 21 during high speed rotation. For this reason, contaminants trapped in the grooves 14, 15, 16 are difficult to remove by the land 17, particularly at low speeds.

[0081] Furthermore, the contaminants discharged from the closed end 15b to the land 17 are easily collected in the second spiral groove 13 located downstream in the reverse rotation direction.

[0082] As described above, in the mechanical seal of this embodiment, during reverse rotation, the liquid F in the outer space S2 is introduced into the reverse circumferential groove 15 in the reverse Rayleigh step, and dynamic pressure is generated in the reverse circumferential groove 15. This dynamic pressure causes the sliding surfaces 11, 21 to slightly separate from each other, and the liquid F and gas A that have flowed between the sliding surfaces 11, 21 can reduce the frictional force generated by the relative sliding between the sliding surfaces 11, 21.

[0083] Furthermore, the second spiral groove 13 extends at least to the same radial position as the closed end 15b downstream in the reverse rotation direction of the reverse circumferential groove 15. This makes it easier to guide the liquid F into the reverse circumferential groove 15 due to the negative pressure generated in the second spiral groove 13 during reverse rotation, making it easier to generate high dynamic pressure in the reverse circumferential groove 15.

[0084] Furthermore, the closed end 13b of the second spiral groove 13 is located circumferentially downstream in the reverse rotation direction from the closed end 15b of the reverse circumferential groove 15 and at the same radial position as the closed end 15b. This makes it easier to more efficiently guide the liquid F into the reverse circumferential groove 15 due to the negative pressure generated in the second spiral groove 13 during reverse rotation, making it easier to generate high dynamic pressure in the reverse circumferential groove 15.

[0085] 4 , the circumferential length between the closed ends 13b, 15b of the second spiral groove 13 and the reverse circumferential groove 15 that are adjacent in the circumferential direction, i.e., the closest second spiral groove 13 located upstream of the single reverse circumferential groove 15, is defined as length L1. The circumferential length of the first spiral groove 12 is defined as length L2. The length L1 is approximately 9 / 5 of the length L2 (L1 = L2 × 9 / 5), i.e., is between 1 and 2 times the length L2.

[0086] Furthermore, two spiral grooves 12, 13 including the second spiral groove 13 are arranged on the reverse rotation side of the reverse circumferential groove 15. In other words, one spiral groove 12 is provided between the reverse circumferential groove 15 and the second spiral groove 13 in the circumferential direction.

[0087] This makes it possible to achieve both the effect of guiding liquid F to the reverse circumferential groove 15 by the negative pressure generated in the spiral grooves 12, 13 during reverse rotation, and the dynamic pressure effect of the reverse circumferential groove 15, i.e., the dynamic pressure of the liquid F that has flowed out between the sliding surfaces 11, 21, to secure an area that separates the sliding surfaces 11, 21.

[0088] Furthermore, during forward rotation, the negative pressure generated in the reverse circumferential groove 15 is less likely to interfere with the effect of discharging liquid F and contaminants from the closed end 13b of the second spiral groove 13 to the external space S2, and with the dynamic pressure effect of the second spiral groove 13.

[0089] The length L1 may be from 1 to 3 times the length L2, but is preferably from 1 to 2 times the length L2 in order to achieve both the effect of guiding the liquid F to the reverse circumferential groove and the dynamic pressure effect of the reverse circumferential groove, as described above.

[0090] The length of the reverse circumferential groove 15 in the extension direction from the open end 15a to the closed end 15b is defined as length L3. Length L3 is shorter than length L1 (L1 > L3). This allows for both the effect of guiding the liquid F to the reverse circumferential groove 15 by the negative pressure generated in the second spiral groove 13 during reverse rotation and the dynamic pressure effect of the reverse circumferential groove 15.

[0091] Furthermore, during forward rotation, the negative pressure generated in the reverse circumferential groove 15 is less likely to interfere with the effect of discharging liquid F and contaminants from the closed end 13b of the second spiral groove 13 to the external space S2, and with the dynamic pressure effect of the second spiral groove 13.

[0092] Furthermore, the circumferential length between the closed ends 13b, 14b of the second spiral groove 13 and the circumferential groove 14 that are adjacent in the circumferential direction, i.e., the closest second spiral groove 13 located downstream of one circumferential groove 14, is defined as length L4. Length L4 is longer than length L1 (L4>L1).

[0093] This makes it possible to suppress the dynamic pressure effect of the reverse circumferential grooves 15 of the reverse Rayleigh step during reverse rotation compared to the dynamic pressure effect of the circumferential grooves 14 of the Rayleigh step during forward rotation. As a result, contaminants trapped in the grooves 14, 15, and 16 are less likely to be discharged to the land 17 during reverse rotation, particularly at low speeds.

[0094] Furthermore, by making the length L4 longer than the length L1, it becomes easier to recover the liquid F and contaminants from the second spiral groove 13 to the reverse circumferential groove 15 in the reverse Rayleigh step during forward rotation. In addition, it becomes easier to introduce the liquid F into the reverse circumferential groove 15 due to the negative pressure generated in the second spiral groove 13 during reverse rotation.

[0095] Furthermore, the circumferential groove 14 and the reverse circumferential groove 15 that are adjacent in the circumferential direction communicate with the same communicating groove 16. This makes it easier for the liquid F to flow from the circumferential groove 14 to the reverse circumferential groove 15 during reverse rotation, and it is possible to reduce the amount of liquid F that flows from the outer space S2 into the communicating groove 16. This makes it possible to prevent contaminants from flowing between the sliding surfaces 11, 21 through the communicating groove 16.

[0096] The communicating groove 16 has approximately the same depth as the circumferential groove 14 and the reverse circumferential groove 15. This allows the liquid F to more smoothly flow from the circumferential groove 14 into the reverse circumferential groove 15 during reverse rotation. Furthermore, compared to a configuration in which the communicating groove is deeper than the circumferential groove 14 and the reverse circumferential groove 15, contaminants are less likely to flow between the sliding surfaces 11 and 21 from the outer space S2 through the communicating groove 16.

[0097] The sliding surface may be provided with a plurality of inclined grooves of the same type, for example, the first spiral grooves 12, arranged in the circumferential direction. Even with this configuration, the liquid F can be guided to the closed ends 15b of the reverse circumferential grooves 15 as described above.

[0098] On the other hand, from the viewpoint of being able to generate dynamic pressure at different radial positions and from the viewpoint of the efficiency of discharging liquid F and contaminants, it is preferable to provide multiple types of grooves with different lengths in the extension direction, such as spiral grooves 12 and 13.

[0099] In addition, from the viewpoint of making it easier to collect the liquid F downstream in the reverse rotation direction from the reverse circumferential groove 15 during reverse rotation and thus more effectively guiding the liquid F to the closed end 15 b of the reverse circumferential groove 15, the long inclined groove may be extended toward the outer space S2 further than the closed end 15 b of the reverse circumferential groove 15.

[0100] Furthermore, from the viewpoint of achieving a greater effect of guiding the liquid F to the closed end 15b of the reverse circumferential groove 15 by negative pressure, it is preferable that the closed end of a long inclined groove, such as the closed end 13b of the second spiral groove 13, be located at a circumferential position downstream in the reverse rotation direction from the closed end 15b of the reverse circumferential groove 15 and at the same radial position as the closed end 15b.

[0101] In this embodiment, the sliding surface 21 of the rotary seal ring 20 is described as not being provided with recesses such as grooves. However, as in the sliding surface 121 of a rotary seal ring 120 of another embodiment shown in FIG. 6 , a plurality of third spiral grooves 122 (24 in this embodiment) may be evenly arranged circumferentially on the inner diameter side.

[0102] With this configuration, gas A is also supplied between the sliding surfaces 11, 121 from the third spiral groove 122 during forward rotation, so that it is possible to shift from liquid lubrication to gas lubrication when the relative rotational speed of the rotary seal ring 120 is slower than the above-mentioned high speed. Furthermore, it is possible to increase the efficiency of discharging contaminants into the outer space S2.

[0103] On the other hand, from the viewpoint of preventing the liquid F from leaking into the internal space S1 during reverse rotation, it is preferable that the mating sliding surface does not have recesses such as grooves, like the sliding surface 21 of the rotary seal ring 20.

[0104] Next, a sliding element according to a second 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.

[0105] 7, spiral grooves 212 and 213 are formed on a sliding surface 211 of a stationary seal ring 210 on the inner diameter side of the grooves 14, 15, and 16. In other words, the spiral grooves 212 and 213 in this embodiment have a shorter length in the extension direction than the spiral grooves 12 and 13 in the first embodiment, and therefore a smaller volume.

[0106] Furthermore, the closed end 213b of the second spiral groove 213 is provided at approximately the same circumferential position as, and faces in the radial direction, the closed end 15b of the reverse circumferential groove 15. Even with this configuration, the negative pressure generated in the second spiral groove 213 during reverse rotation makes it easier to guide the liquid F to the closed end 15b of the reverse circumferential groove 15, thereby generating high dynamic pressure.

[0107] On the other hand, from the viewpoint of the larger positive or negative pressure generated at the same relative rotation speed, the spiral grooves 12 and 13 in the first embodiment are preferable.

[0108] Furthermore, from the viewpoint of making it easier to discharge contaminants outside the sliding surfaces 11 and 21, it is preferable that the second spiral groove 13 in Example 1 has a closed end 13b located closer to the external space S2 than the second spiral groove 213 in Example 2.

[0109] Next, a sliding element according to a third 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.

[0110] 8 , the circumferential groove 314 provided on the sliding surface 311 of the stationary seal ring 310 of the third embodiment has an opening end 314a that narrows toward the communicating groove 16. In addition, the reverse circumferential groove 315 has an opening end 315a that narrows toward the communicating groove 16.

[0111] As a result, during forward rotation, the open end 314 a of the circumferential groove 314 functions as a trap, making it difficult for contaminants that have flowed into the communication groove 16 to flow into the circumferential groove 314 .

[0112] Furthermore, during reverse rotation, the open end 315 a of the reverse circumferential groove 315 functions as a trap, making it difficult for contaminants that have flowed into the communication groove 16 to flow into the reverse circumferential groove 315 .

[0113] As a shape that functions as a trap, a shape in which the opening end narrows toward the communicating groove has been exemplified, but the communicating groove may be deeper than the circumferential groove or the reverse circumferential groove, and the shape may be changed as appropriate as long as it functions as a trap.

[0114] Next, a sliding element according to a fourth 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.

[0115] 9 , the sliding surface 411 of the stationary seal ring 410 of the fourth embodiment is provided with a communicating groove 418 communicating with the circumferential grooves 414, and a communicating groove 419 communicating with the reverse circumferential grooves 415. In other words, in this embodiment, a Rayleigh step constituted by the circumferential groove 414 and the communicating groove 418, and a reverse Rayleigh step constituted by the reverse circumferential groove 415 and the communicating groove 419 are individually provided.

[0116] As a result, during forward rotation, contaminants in the reverse circumferential groove 415 are more likely to be discharged to the external space S2 through the communicating groove 419. In other words, contaminants in the reverse Rayleigh step can be prevented from flowing into the Rayleigh step.

[0117] Furthermore, during reverse rotation, contaminants in the circumferential grooves 414 are more likely to be discharged to the external space S2 through the communicating grooves 418. In other words, contaminants in the Rayleigh step can be prevented from flowing into the reverse Rayleigh step.

[0118] On the other hand, during forward rotation, the liquid F tends to flow from the outer space S2 into the communicating groove 418, which causes contaminants to flow between the sliding surfaces 411 and 21 together with the liquid F. Furthermore, during reverse rotation, the liquid F tends to flow from the outer space S2 into the communicating groove 419, which causes contaminants to flow between the sliding surfaces 411 and 21 together with the liquid F. From this perspective, a structure in which the circumferential groove and the reverse circumferential groove communicate with the same communicating groove, as in Example 1, is preferable.

[0119] Next, a sliding element according to a fifth 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.

[0120] 10 and 11 , the depth D52 of the grooves 514, 515, and 516 provided in the sliding surface 511 of the stationary seal ring 510 of the fifth embodiment is greater than the depth D1 of the spiral grooves 12 and 13. In other words, the grooves 514, 515, and 516 have a larger volume than the grooves 14, 15, and 16 of the first embodiment.

[0121] This allows the positive pressure generated in the circumferential groove 514 and the reverse circumferential groove 515 to be greater than the positive pressure generated in the circumferential groove 14 and the reverse circumferential groove 15 at the same relative rotation speed.

[0122] The volume of the circumferential groove or the reverse circumferential groove may be increased by making the width, i.e., the radial length or the extension length, longer than the circumferential groove 14 or the reverse circumferential groove 15. On the other hand, it is preferable to adjust the depth or width, since this does not affect the number or arrangement of the second spiral grooves 13.

[0123] 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.

[0124] As shown in FIG. 12, in this embodiment, an inner space S61 is a sealed fluid side space in which a liquid F exists, and an outer space S62 is a leakage side space in which a gas A exists.

[0125] Spiral grooves 612, 613 provided on a sliding surface 611 of the stationary seal ring 610 communicate with the outer space S62 and extend inclined downstream and radially inward.

[0126] The circumferential groove 614 extends from the downstream side of the outer diameter end of the communicating groove 616 toward the downstream side. The reverse circumferential groove 615 extends from the upstream side of the outer diameter end of the communicating groove 616 toward the upstream side. The communicating groove 616 communicates with the internal space S61. The circumferential groove 614 and the communicating groove 616 form a Rayleigh step. The reverse circumferential groove 615 and the communicating groove 616 form a reverse Rayleigh step.

[0127] As a result, during forward rotation, positive pressure is generated by the spiral grooves 612, 613 and the circumferential groove 614, slightly separating the sliding surfaces 611, 612 from each other, thereby reducing frictional force. Also, while contaminants can be collected in the grooves 612, 613, 614, 615, and 616, they can be discharged to the internal space S61 side by the second spiral groove 613 and the communicating groove 616.

[0128] During reverse rotation, the reverse circumferential groove 615 generates positive pressure, slightly separating the sliding surfaces 611 and 21, thereby reducing frictional force. Also, the grooves 614, 615, and 616 can collect contaminants.

[0129] 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.

[0130] For example, in the first to sixth embodiments, a liquid is present in the sealed fluid-side space, but the present invention is not limited to this. The liquid may be a gas or a mist of a mixture of liquid and gas. The same applies to the leakage-side space. In other words, the same fluid may exist in both the sealed fluid-side space and the leakage-side space.

[0131] Furthermore, in the above-described Examples 1 to 6, the gas A is at a lower pressure than the liquid F, but the liquid may be at a lower pressure and the gas at a higher pressure, or the liquid and the gas may be at approximately the same pressure.

[0132] In addition, in the first to sixth embodiments, one of the sliding surfaces is described as being the sliding surface of a stationary seal ring, but this is not limitative and it may be the sliding surface of a rotary seal ring.

[0133] In addition, in Examples 1 to 6, spiral grooves are used as inclined grooves, but this is not limited to this and the inclined grooves may extend linearly toward the closed end, or may be modified as appropriate.

[0134] Furthermore, in the first to sixth embodiments, mechanical seals are used as examples of sliding parts, but the present invention is not limited to this and may be a thrust bearing, a radial bearing, a sliding bearing, or the like.

[0135] DESCRIPTION OF SYMBOLS 10 Stationary seal ring 11 Sliding surface (one of the sliding surfaces) 12 First spiral groove (inclined groove) 12b Closed end 13 Second spiral groove (long inclined groove) 13b Closed end 14 Circumferential groove 14b Closed end (end on the forward rotation side of the relative rotation direction) 15 Reverse circumferential groove 15b Closed end (end on the reverse rotation side of the relative rotation direction) 16 Communication groove 20 Rotary seal ring 21 Sliding surface (the other of the sliding surfaces) 120 Rotary seal ring 121 Sliding surface (the other of the sliding surfaces) 210, 310, 410, 510, 610 Stationary seal ring 211, 311, 411, 511, 611 Sliding surface (one of the sliding surfaces) 212, 612 First spiral groove (inclined groove) 213, 613 Second spiral groove (inclined groove) 213b Closed end 314, 414, 514, 614 Circumferential groove 315, 415, 515, 615 Reverse circumferential groove 418, 419, 616 Communication groove A Gas F Liquid S1 Inner space (leakage side space) S2 Outer space (sealed fluid side space) S61 Inner space (sealed fluid side space) S62 Outer space (leakage side space)

Claims

1. A sliding component arranged at a location where a pair of sliding surfaces rotate relative to each other, separating a leakage-side space and a sealed fluid-side space, wherein one of the sliding surfaces comprises a plurality of inclined grooves extending from the leakage-side space toward the forward rotation side in the relative rotation direction and toward the sealed fluid-side space, each having a closed end, a Rayleigh step communicating with the sealed fluid-side space and extending toward the forward rotation side in the relative rotation direction, and a reverse Rayleigh step communicating with the sealed fluid-side space and extending toward the reverse rotation side in the relative rotation direction, and wherein some of the plurality of inclined grooves have a long inclined groove.

2. A sliding element according to claim 1, wherein the long inclined groove extends at least to the same radial position as the end of the reverse Rayleigh step on the side opposite to the relative rotation direction.

3. A sliding element according to claim 2, wherein the closed end of the long inclined groove is provided at the same radial position as the end of the inverse Rayleigh step.

4. A sliding element according to claim 2, wherein an inclined groove shorter than the long inclined groove is disposed between the end of the inverse Rayleigh step and the long inclined groove in the circumferential direction.

5. A sliding component as described in claim 2, wherein the reverse Rayleigh step has a communicating groove that communicates with the sealed fluid side space and extends in the radial direction, and a reverse circumferential groove that extends from the reverse rotation side of the communicating groove to the reverse rotation side of the relative rotation direction, and the circumferential length between the long inclined groove and the end of the reverse Rayleigh step is longer than the circumferential length of the reverse circumferential groove.

6. A sliding component as described in claim 3, wherein the Rayleigh step and the inverse Rayleigh step are arranged between adjacent long inclined grooves, and the circumferential length between the long inclined groove and the end of the inverse Rayleigh step is shorter than the circumferential length between another long inclined groove and the end of the Rayleigh step.

7. A sliding component according to any one of claims 1 to 6, wherein the circumferential groove of the Rayleigh step and the reverse circumferential groove of the reverse Rayleigh step that are adjacent in the circumferential direction are connected to the same connecting groove that is connected to the sealed fluid side space.

8. A sliding component according to claim 7, wherein the circumferential groove, the communicating groove, and the reverse circumferential groove have the same depth.

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