Sliding component

Abstract

Provided is a sliding component capable of smoothly shifting from lubrication due to a high-viscosity fluid to lubrication due to a low-viscosity fluid.　This sliding component is disposed at a position where a pair of sliding surfaces 11, 21 are rotated relative to each other, and partitions a high-viscosity space S1 in which a high-viscosity fluid F having relatively high viscosity is present and a low-viscosity space S2 in which a low-viscosity fluid A having relatively low viscosity is present, wherein: the one sliding surface 11 includes a low-viscosity-side dynamic pressure generation groove 13 provided on the low-viscosity space S2 side; and between the pair of sliding surfaces 11, 21, a land 11A on the high-viscosity space S1 side is farther away in the axial direction than a land 11B on the low-viscosity space S2 side.

Description

Sliding parts

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

[0002] 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, Patent Document 1 discloses a mechanical seal in which the sliding surface of one of the sliding rings is provided with a plurality of Rayleigh steps that communicate with an outer diameter space where a liquid is present and a plurality of inclined grooves that communicate with an inner diameter space where a gas is present. One of the sliding rings is biased toward the other sliding ring by a biasing means. When the pair of sliding rings rotate relatively at low 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. The sliding surfaces are slightly separated from each other by the dynamic pressure generated by the Rayleigh steps, and the sliding surfaces are liquid-lubricated.

[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. At high relative rotational speeds of the pair of sliding rings, the dynamic pressure generated in the inclined grooves is dominant, causing the sliding surfaces to separate slightly, and the sliding surfaces are gas-lubricated. 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] JP 2024-19026 A (pages 8 to 10, Figure 2)

[0006] In a mechanical seal such as that described in Patent Document 1, the biasing force of the biasing means is adjusted to ensure sufficient dynamic pressure using gas through the inclined grooves, thereby ensuring gas lubrication between the sliding surfaces at high relative rotational speeds. However, during relative rotation of a pair of sliding rings, fluid shear resistance occurs between the sliding surfaces due to the viscosity of the liquid and gas. Fluid shear resistance is calculated by (fluid viscosity × relative rotational speed × sliding area) ÷ axial clearance between the sliding surfaces. In other words, when transitioning from liquid lubrication to gas lubrication, as the relative rotational speed increases, the fluid shear resistance due to the highly viscous liquid increases, generating large torque, which could prevent a smooth transition from liquid lubrication to gas lubrication.

[0007] The present invention has been made in view of these problems, and has as its object to provide a sliding part that can smoothly transition from lubrication with a high viscosity fluid to lubrication with a low viscosity fluid.

[0008] In order to solve the above problems, the sliding component of the present invention is a sliding component that is arranged at a location where a pair of sliding surfaces rotate relative to each other and that partitions a high-viscosity space where a relatively high-viscosity fluid exists and a low-viscosity space where a relatively low-viscosity fluid exists, wherein one of the sliding surfaces has a low-viscosity-side dynamic pressure generating groove provided on the low-viscosity space side, and between the pair of sliding surfaces, the land on the high-viscosity space side is spaced apart in the axial direction from the land on the low-viscosity space side. With this, since the lands on the high-viscosity space side are spaced apart in the axial direction, an increase in fluid shear resistance due to the high-viscosity fluid is suppressed when the relative rotational speed increases, and a smooth transition from lubrication by the high-viscosity fluid to lubrication by the low-viscosity fluid can be achieved.

[0009] The lands on the high viscosity space side may be spaced apart in the axial direction over the circumferential direction, thereby enabling the fluid shear resistance caused by the high viscosity fluid to be suppressed in a balanced manner over the circumferential direction.

[0010] At least one of the sliding surfaces on the high-viscosity space side may be provided with a high-viscosity dynamic pressure generating groove, which generates dynamic pressure in the high-viscosity dynamic pressure generating groove as well, thereby separating the sliding surfaces even at low speeds.

[0011] The spacing between the lands on the high-viscosity space side may be smaller than the depth of the low-viscosity dynamic pressure generating grooves, so that the lands on the high-viscosity space side are not spaced apart excessively, allowing dynamic pressure from the high-viscosity dynamic pressure generating grooves to act reliably.

[0012] The high-viscosity hydrodynamic grooves may be Rayleigh steps, which allow the high-viscosity fluid to be efficiently introduced between the lands on the high-viscosity space side.

[0013] The one sliding surface may have a stepped shape with different heights. In this case, since the one sliding surface on which the high-viscosity-side dynamic pressure generating groove is provided has a stepped shape with different heights, it is possible to reliably reduce fluid shear resistance regardless of radial positional deviation between the pair of sliding surfaces.

[0014] The land on the high-viscosity space side of the one sliding surface may have a smaller radial width than the land on the low-viscosity space side of the one sliding surface, thereby allowing dynamic pressure to be generated efficiently by the low-viscosity-side dynamic pressure generating groove.

[0015] FIG. 3 is a longitudinal sectional view showing an example of a mechanical seal according to a first embodiment of the present invention. FIG. 4 is a view of the sliding surface of the stationary seal ring according to the first embodiment from the axial direction. FIG. 5 is a sectional view taken along line A-A in FIG. 2. FIG. 6 is an explanatory view of the movement of fluid in each dynamic pressure generating groove during relative rotation as viewed from the axial direction. (a) to (c) are sectional views schematically showing the state of a pair of sliding components at each relative rotation speed. FIG. 3 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. FIG. 4 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. FIG. 5 is a schematic sectional view showing a pair of sliding components according to a fourth embodiment of the present invention. FIG. 6 is a schematic sectional view showing a pair of sliding components according to a fifth embodiment of the present invention. FIG. 6 is a schematic sectional view showing a pair of sliding components according to a sixth embodiment of the present invention. FIG. 7 is a schematic sectional view showing a pair of sliding components according to a seventh embodiment of the present invention. FIG. 7 is a view of the sliding surface of a stationary seal ring according to a modified example as viewed from the axial direction.

[0016] 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.

[0017] 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. A liquid serving as a high-viscosity fluid exists in the outer space of the mechanical seal, and a gas serving as a low-viscosity fluid exists in the inner space. The outer diameter side of the sliding component constituting the mechanical seal will be described as the liquid side (and high-pressure side), and the inner diameter side as the gas side (and low-pressure side). For ease of explanation, grooves and the like formed on the sliding surface may be indicated by dots in the drawings.

[0018] The mechanical seal shown in FIG. 1 is an inside type that seals against liquid F leaking from an outer space S1 on the outer diameter side of the sliding surface toward an inner space S2 on the inner diameter side, and the inner space S2 is connected to the atmosphere.

[0019] 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 so as to be rotatable together with the rotary shaft 1. The stationary seal ring 10 is axially biased by an elastic member 7. The sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotary seal ring 20 slide closely against each other. The sliding surface 21 of the rotary seal ring 20 is flat and does not have any recesses such as grooves.

[0020] 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.

[0021] As shown in FIG. 2, the rotary seal ring 20 slides relative to the stationary seal ring 10 in the counterclockwise direction as indicated by the solid arrow.

[0022] As shown in Figures 2 and 3, the sliding surface 11 of the stationary seal ring 10 includes an annular land 11A on the outer space S1 side and an annular land 11B on the inner space S2 side. The lands 11A and 11B are the portions that substantially slide against the sliding surface 21 of the rotary seal ring 20. Furthermore, when the engine is not in operation, the land 11B abuts against the sliding surface 21 of the rotary seal ring 20, while the land 11A is very slightly spaced from the sliding surface 21 of the rotary seal ring 20. Specifically, the land 11A is located axially farther away from the rotary seal ring 20 than the land 11B. That is, the sliding surface 11 has a stepped shape in which the lands 11A and 11B have different heights. Note that hereinafter, the land 11A may be referred to as the lower side and the land 11B as the higher side. Furthermore, as will be described later, the land 11A is the portion where a fluid film can be formed between the land 11A and the opposing sliding surface 21 for liquid lubrication with the liquid F.

[0023] The axial end faces (hereinafter sometimes referred to as "top faces") of the lands 11A and 11B are substantially parallel. A side face 11C of the land 11B connecting the top faces of the lands 11A and 11B is perpendicular to the top faces of the lands 11A and 11B. The top face of the land 11A is not limited to a flat face, but may be an inclined face or a curved face.

[0024] The radial width W1 of the land 11A is smaller than the radial width W2 of the land 11B (W1<W2). In this embodiment, the radial width W1 is approximately half the radial width W2.

[0025] A land 11A on the sliding surface 11 has a plurality of first dynamic pressure generating grooves 12 (four in this embodiment) arranged at equal intervals in the circumferential direction as high viscosity side dynamic pressure generating grooves.

[0026] The first dynamic pressure generating groove 12 is mainly composed of a deep groove portion 121 and a shallow groove portion 122 as a Rayleigh step.

[0027] The deep groove portion 121 has an outer diameter end that communicates with the outer space S1 and extends inward at a constant depth D3. The deep groove portion 121 is not limited to a constant depth, and may gradually become shallower inward. Furthermore, the bottom surface of the deep groove portion 121 can be freely modified, such as an inclined surface, a curved surface, or a stepped surface. For ease of explanation, the depth D3 of the deep groove portion 121 is shown in FIG. 3 as being shallower than it actually is.

[0028] The shallow groove portion 122 extends counterclockwise from the inner diameter end of the deep groove portion 121, i.e., extends circumferentially in an arc shape with a constant depth D4 toward the downstream side of the relative rotation of the rotary seal ring 20 (see FIG. 5A). The depth D4 of the shallow groove portion 122 is shallower than the depth D3 of the deep groove portion 121. In this embodiment, the shallow groove portion 122 has a depth of about 1 / 10 of the deep groove portion 121.

[0029] Furthermore, the shallow groove portion 122 is not limited to a constant depth, and may be gradually shallower toward the downstream side in the direction of relative rotation. Furthermore, the bottom surface of the shallow groove portion 122 can be freely changed to an inclined surface, a curved surface, a stepped surface, or the like.

[0030] A plurality of second dynamic pressure generating grooves 13 (24 in this embodiment) serving as low-viscosity dynamic pressure generating grooves are uniformly arranged in the circumferential direction on the land 11B of the sliding surface 11.

[0031] The second dynamic pressure generating groove 13 is a spiral groove that extends from the inner space S2 toward the outer diameter side at an incline in the circumferential direction. The depth D1 of the second dynamic pressure generating groove 13 is constant in the extending direction. The depth D1 of the second dynamic pressure generating groove 13 is the same as or slightly shallower than the depth D4 of the shallow groove portion 122 (D1≦D4).

[0032] The second dynamic pressure generating groove 13 is not limited to a constant depth, and may be gradually shallower toward the downstream side in the direction of relative rotation. Furthermore, the bottom surface of the second dynamic pressure generating groove 13 may be freely modified to have an inclined surface, a curved surface, a stepped surface, or the like. The depth D1 of the second dynamic pressure generating groove 13 may be different from the depth D4 of the shallow groove portion 122.

[0033] The height difference D2 between the lands 11A and 11B on the sliding surface 11 (i.e., the height of the side surface 11C) is shallower than the depth D1 of the second dynamic pressure generating groove 13 (D1>D2). In this embodiment, the height difference D2 between the lands 11A and 11B is about 1 / 10 of the depth D1 of the second dynamic pressure generating groove 13.

[0034] Next, the flow of fluid during relative rotation between the stationary seal ring 10 and the rotating seal ring 20 will be explained using Figure 4. Note that the flow of fluid in Figure 4 is shown simply and schematically without specifying the relative rotational speed of the rotating seal ring 20.

[0035] First, we will explain the flow of liquid F within the first hydrodynamic groove 12. As shown in Figure 4, when the rotating seal ring 20 rotates relative to the stationary seal ring 10, the liquid F within the deep groove portion 121 of the first hydrodynamic groove 12 moves from the outer diameter end toward the inner diameter end as shown by the white arrow L1, and the liquid F within the shallow groove portion 122 moves from the start end 122A toward the end end 122B of the shallow groove portion 122 as shown by the white arrow L1'.

[0036] The liquid F that has moved toward the end 122B is subjected to increased pressure at and near the end 122B, and flows out between the sliding surfaces 11 and 21 as indicated by the white arrow L2.

[0037] Next, we will explain the flow of gas A within the second dynamic pressure generating groove 13. When the rotating seal ring 20 rotates relative to the stationary seal ring 10, gas A within the second dynamic pressure generating groove 13 moves from the starting end 13A toward the ending end 13B as shown by the black arrow L3.

[0038] The gas A that has moved toward the end 13B is pressurized at and near the end 13B, and flows out between the sliding surfaces 11 and 21 as shown by the black arrow L4.

[0039] Next, changes in the force that separates the sliding surfaces 11, 21 will be described with reference to Fig. 5. In order to clearly show changes in a first force F1 and a second force F2, which will be described later, Fig. 5 shows a schematic cross-sectional view in which cross sections of the first dynamic pressure generating groove 12 and the second dynamic pressure generating groove 13 taken in the longitudinal direction are arranged at the same position in the axial direction.

[0040] First, when the mechanical seal is not in operation and the rotating seal ring 20 is not rotating, the stationary seal ring 10 is urged axially toward the rotating seal ring 20 by the elastic member 7, so the sliding surfaces 11, 21 are in contact with each other, and almost no liquid F leaks out between the sliding surfaces 11, 21 into the internal space S2.

[0041] Furthermore, a gap S10 is formed on the land 11A side between the sliding surfaces 11 and 21 due to the step between the lands 11A and 11B (see FIG. 5A). The gap S10 is in communication with the external space S1, so the liquid F flows into it.

[0042] At low speeds immediately after the rotating seal ring 20 begins to rotate relative to the stationary seal ring 10, as shown in Figure 5(a), the sliding surfaces 11, 21 are in a so-called liquid lubrication state due to the liquid F in the gap S10, and positive pressure is generated at the end 122B of the first hydrodynamic groove 12 as indicated by the white arrow L2. A first force F1 caused by the positive pressure generated at the end 122B of the first hydrodynamic groove 12 causes the sliding surfaces 11, 21 to separate slightly in the axial direction. The separation distance between the sliding surfaces 11, 21 at this time is defined as a separation width Δa.

[0043] The biasing force of the elastic member 7 is adjusted in advance so that the separation width Δa between the sliding surfaces 11 and 21 at this time is wide enough to allow a second force F2 due to the positive pressure generated in the second dynamic pressure generating groove 13 at high relative rotation speeds, which will be described later, to act between the sliding surfaces 11 and 21.

[0044] As a result, more liquid F flows from the outer space S1 into the gap S10 on the outer diameter side between the sliding surfaces 11 and 21, which has been widened by the separation width Δa. The presence of liquid F between the sliding surfaces 11 and 21 in this way improves lubrication even during low-speed rotation, and makes it possible to suppress wear between the sliding surfaces 11 and 21. Furthermore, because the separation distance between the sliding surfaces 11 and 21 is small, liquid F does not leak into the inner space S2.

[0045] On the other hand, in the second dynamic pressure generating grooves 13, when the relative rotation speed between the rotary seal ring 20 and the stationary seal ring 10 is low, the gas A does not become sufficiently dense and high positive pressure is not generated, and the second force F2 (not shown in FIG. 5A) due to the positive pressure generated by the second dynamic pressure generating grooves 13 is relatively smaller than the first force F1. Therefore, when the rotary seal ring 20 is rotating at low speed, the first force F1 mainly separates the sliding surfaces 11, 21 from each other.

[0046] At this time, fluid shear resistance due to the liquid F acts between the sliding surfaces 11 and 21. The fluid shear resistance is calculated by (fluid viscosity × relative rotation speed × sliding area) ÷ axial clearance between the sliding surfaces. In the state of Figure 5(a), the relative rotation speed is low, so the fluid shear resistance due to the liquid F is small.

[0047] When the relative rotation speed of the rotary seal ring 20 increases, the positive pressure increases at the terminal end 13B of the second dynamic pressure generating groove 13, as shown in FIG. 5(b).

[0048] A second force F2 is applied by the positive pressure generated at the end 13B of the second hydrodynamic groove 13, causing the sliding surfaces 11, 21 to move further apart compared to Figure 5(a). As a result, gas A within the second hydrodynamic groove 13 flows between the sliding surfaces 11, 21, as indicated mainly by the black arrow L4. The separation distance between the sliding surfaces 11, 21 at this time is defined as a separation width Δb (Δb > Δa).

[0049] The gas A in the second dynamic pressure generating groove 13 indicated by the black arrow L4 acts to push the liquid F near the end 13B back toward the outer space S1, so that the liquid F does not leak into the inner space S2.

[0050] Furthermore, the separation distance between the sliding surfaces 11 and 21 becomes a separation width Δb, and the separation between the sliding surfaces 11 and 21 becomes greater (Δb>Δa) compared to FIG. 5(a), so that the first force F1' becomes smaller compared to FIG. 5(a).

[0051] Since an axial gap S10 is formed in advance on the outer diameter side between the sliding surfaces 11 and 21, i.e., between the land 11A and the sliding surface 21, even if the relative rotational speed between the sliding surfaces 11 and 21 increases, the fluid shear resistance due to the liquid F acting between the sliding surfaces 11 and 21 hardly increases or increases only slowly.

[0052] When the relative rotational speed of the rotary seal ring 20 increases further and reaches a high rotation speed, i.e., a steady operating state, as shown in Figure 5(c), the amount of gas A drawn into the second dynamic pressure generating grooves 13 increases further, generating a high positive pressure, increasing the second force F2', and causing the sliding surfaces 11, 21 to separate further from each other compared to Figure 5(b). The separation distance between the sliding surfaces 11, 21 at this time is defined as a separation width Δc (Δc > Δb).

[0053] In this embodiment, when the separation distance increases due to high-speed rotation of the rotary seal ring 20, the positive pressure generated in the first dynamic pressure generating grooves 12 becomes negligibly small. Therefore, when the rotary seal ring 20 rotates at high speed, the second force F2' mainly separates the sliding surfaces 11, 21. In other words, when the rotary seal ring 20 rotates at high speed, the sliding surfaces 11, 21 are in a so-called gas lubrication state.

[0054] As described above, in the mechanical seal of this embodiment, the transition from liquid lubrication to gas lubrication between the sliding surfaces 11 and 21 can be made smoothly.

[0055] Specifically, in such a mechanical seal, the biasing force of the elastic member 7 is adjusted in advance to ensure gas lubrication of the sliding surfaces 11, 21. In other words, the biasing force of the elastic member 7 is adjusted in advance to prevent the sliding surfaces 11, 21 from separating excessively when the sliding surfaces 11, 21 are liquid lubricated.

[0056] As in the past, when the mechanical seal was not in operation and both sliding surfaces were in contact with each other over almost the entire surface, the separation width of the sliding surfaces when liquid lubricated was set to be small. As a result, as the relative rotational speed increased, the fluid shear resistance of the liquid F increased, and when the transition from liquid lubrication to gas lubrication occurred, a large load was momentarily applied between the sliding surfaces.

[0057] In the mechanical seal of this embodiment, the sliding surfaces 11, 21 are spaced further axially on the outer space S1 side than on the inner space S2 side. In other words, because a gap S10 is provided on the outer space S1 side between the sliding surfaces 11, 21, i.e., on the liquid space side where the liquid F is present, an increase in fluid shear resistance due to the liquid F is suppressed when the relative rotational speed increases, and a smooth transition from liquid lubrication to gas lubrication can be achieved between the sliding surfaces 11, 21.

[0058] Furthermore, since the gap S10 is provided in the circumferential direction, the fluid shear resistance due to the liquid F can be suppressed in a balanced manner in the circumferential direction, thereby preventing the relative tilt of the sliding surfaces 11, 21 from occurring due to differences in the fluid shear resistance due to the liquid F in the circumferential direction.

[0059] In addition, a first dynamic pressure generating groove 12 is provided between the sliding surfaces 11 and 21 on the external space S1 side, and the first dynamic pressure generating groove 12 also generates dynamic pressure, which can separate the sliding surfaces 11 and 21, resulting in high lubricity during low relative rotational speeds.

[0060] Furthermore, since the axial width of the gap S10, i.e., the difference D2 in height between the lands 11A and 11B, is shallower than the depth D1 of the second dynamic pressure generating groove 13, dynamic pressure from the first dynamic pressure generating groove 12 can be reliably applied, allowing smooth liquid lubrication.

[0061] Furthermore, the first dynamic pressure generating groove 12 has a shallow groove portion 122 which is a Rayleigh step, and the shallow groove portion 122 extends circumferentially along the relative rotation direction of the rotating seal ring 20. This allows the liquid F to easily move within the shallow groove portion 122 in response to the relative rotation of the rotating seal ring 20, resulting in a high dynamic pressure generation effect and enabling the liquid F to be efficiently introduced into the gap S10.

[0062] Furthermore, the sliding surface 11 on which the first dynamic pressure generating groove 12 and the second dynamic pressure generating groove 13 are formed has a stepped shape with lands 11A and 11B of different heights. Therefore, even if the sliding surfaces 11 and 21 are displaced radially, a gap S10 is reliably formed on the external space S1 side, thereby reliably reducing the fluid shear resistance caused by the liquid F.

[0063] Furthermore, the radial width W1 of the land 11A is smaller than the radial width W2 of the land 11B, and the second dynamic pressure generating groove 13 can be secured to be large in the radial direction, which allows dynamic pressure to be generated more efficiently by the second dynamic pressure generating groove 13. In other words, gas lubrication can be reliably achieved between the sliding surfaces 11, 21, and a smooth transition from liquid lubrication to gas lubrication can be achieved, resulting in good floating balance.

[0064] Furthermore, since the radial width W2 of the land 11B is ensured to be approximately 2 / 3 or more of the radial width of the sliding surface 11, it is possible to stabilize the contact state between the sliding surfaces 11, 21 when the mechanical seal is not in operation. Note that it is preferable that the radial width W2 of the land 11B be ensured to be approximately 1 / 2 or more of the radial width of the sliding surface 11.

[0065] In this embodiment, the lands 11A, 11B are annular when viewed in the axial direction and are concentric with the stationary seal ring 10, but the outer shape of the land 11B may be sinusoidal or elliptical when viewed in the axial direction. Also, the outer shape of the land 11B may be rectangular or polygonal when viewed in the axial direction.

[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] As shown in FIG. 6, a land 211A of the sliding surface 211 of the stationary seal ring 210 is provided with a plurality of first dynamic pressure generating grooves 212 evenly spaced in the circumferential direction (only one groove is shown in FIG. 6).

[0068] The first dynamic pressure generating groove 212 is composed of a deep groove portion 212A and shallow groove portions 212B and 212C.

[0069] The deep groove portion 212A has an outer diameter end that communicates with the outer space S1 and extends in the inner diameter direction.

[0070] The shallow groove portion 212B extends in an arc shape in the circumferential direction counterclockwise from the inner diameter end of the deep groove portion 212A.

[0071] The shallow groove portion 212C extends in an arc shape in the circumferential direction clockwise from the inner diameter end of the deep groove portion 212A.

[0072] In the area of ​​the land 211B of the sliding surface 211, a plurality of second dynamic pressure generating grooves 213 are arranged evenly in the circumferential direction.

[0073] The second dynamic pressure generating groove 213 is composed of an inclined groove 213A that extends from the inner space S2 toward the outer diameter side at an incline in the circumferential direction and a reverse groove 213B that is formed continuously with the outer diameter side of the inclined groove 213A and extends at an incline in the opposite circumferential direction to the inclined groove 213A, forming a generally L-shape in the axial direction. In other words, the second dynamic pressure generating groove 213 has a so-called herringbone shape. The connection portion between the inclined groove 213A and the reverse groove 213B on the forward rotation direction side forms a corner 213C that tapers in the forward rotation direction.

[0074] When the rotating seal ring 20 rotates relative to the stationary seal ring 210 in the positive rotation direction, i.e., counterclockwise, a positive pressure is generated near the closed end 212Ba of the shallow groove portion 212B of the first dynamic pressure generating groove 212, and a relative negative pressure is generated near the closed end 212Ca of the shallow groove portion 212C. This allows the liquid F in the gap S210 to flow smoothly in the positive rotation direction.

[0075] In the second dynamic pressure generating groove 213, the gas A in the inclined groove 213A and the gas A in the reverse groove 213B move toward the corner 213C, generating a positive pressure near the corner 213C. Furthermore, a relative negative pressure is generated near the inner diameter end of the inclined groove 213A and near the outer diameter end of the reverse groove 213B, allowing the liquid F present in the surrounding areas to be recovered.

[0076] When the rotating seal ring 20 rotates in the reverse rotation direction, i.e., clockwise, relative to the stationary seal ring 210, a positive pressure is generated near the closed end 212Ca of the shallow groove portion 212C of the first dynamic pressure generating groove 212, and a relative negative pressure is generated near the closed end 212Ba of the shallow groove portion 212B. This allows the liquid F in the gap S210 to flow smoothly in the reverse rotation direction.

[0077] In addition, in the second dynamic pressure generating groove 213, the gas A in the reverse groove 213B moves toward the outer diameter end of the reverse groove 213B, generating a positive pressure near the outer diameter end of the reverse groove 213B and a relative negative pressure on the side of the inclined groove 213A, thereby making it possible to recover the liquid F present around the vicinity of the inclined groove 213A.

[0078] In this way, in the mechanical seal of this embodiment 2, even when the rotating seal ring 20 rotates in the opposite direction relative to the stationary seal ring 210, the sliding surfaces 211, 21 can be separated from each other by the positive pressure generated near the closed end 212Ca of the first dynamic pressure generating groove 212 and the positive pressure generated near the outer diameter end of the reverse groove 213B.

[0079] 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.

[0080] 7, a plurality of axially recessed recesses 314 are provided at intervals in the circumferential direction in the region on the outer space S1 side of the sliding surface 311 of the stationary seal ring 310 in this embodiment 3. The recesses 314 are disposed between the first hydrodynamic grooves 312 that are adjacent in the circumferential direction.

[0081] The recess 314 communicates with the external space S1. The bottom surface of the recess 314 serves as a land 311A. The remaining portion of the sliding surface 311 other than the recess 314, the first dynamic pressure generating groove 312, and the second dynamic pressure generating groove 313 serves as a land 311B.

[0082] A gap S310 is formed between the sliding surfaces 311 and 21 due to the step between the lands 311A ​​and 311B.

[0083] In this way, a plurality of gaps S310 are formed in the circumferential direction on the outer space S1 side between the sliding surfaces 311 and 21, which suppresses an increase in fluid shear resistance due to the liquid F when the relative rotation speed increases, and enables a smooth transition from liquid lubrication to gas lubrication between the sliding surfaces 311 and 21. In addition, the floating ability of the sliding surfaces due to the dynamic pressure of the first dynamic pressure generating grooves 312 can be improved.

[0084] Although the third embodiment exemplifies a configuration in which the recess 314 is provided on the sliding surface 311 of the stationary seal ring 310, a recess may be provided on the liquid space side of the sliding surface of the rotary seal ring.

[0085] 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.

[0086] As shown in FIG. 8, the sliding surface 411 of the stationary seal ring 410 of the fourth embodiment is inclined so that a side surface 411C between the lands 411A and 411B becomes shallower toward the inner diameter side.

[0087] This allows the liquid F in the gap S410 to be easily introduced along the side surface 411C between the land 411B of the sliding surface 411 and the sliding surface 21, thereby improving the lubricity during liquid lubrication.

[0088] The side surface 411C is not limited to being annular when viewed in the axial direction, and may be, for example, sinusoidal or rectangular when viewed in the axial direction. Alternatively, one sliding surface may be flat, the other sliding surface may be stepped, and the side surface between lands of different heights on the other sliding surface may be tapered. Alternatively, both sliding surfaces may be stepped, and the side surfaces between lands of different heights on both sliding surfaces may be tapered.

[0089] 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.

[0090] As shown in FIG. 9, the sliding surface 511 of the stationary seal ring 510 of this fifth embodiment has a land 511A that is flat in the radial direction except for the first dynamic pressure generating grooves 512 and the second dynamic pressure generating grooves 513 .

[0091] The opposing sliding surface 521 of the rotary seal ring 520 has a stepped shape in which the outer space S1 side is spaced apart from the sliding surface 511 in the axial direction.

[0092] That is, a gap S510 communicating with the external space S1 is formed on the external space S1 side between the sliding surfaces 511 and 521. This gap S510 overlaps with the first dynamic pressure generating groove 512 in the axial direction.

[0093] In this way, a gap S510 is provided axially on the outer space S1 side between the sliding surfaces 511 and 521, which suppresses the increase in fluid shear resistance due to the liquid when the relative rotational speed increases, and allows for a smooth transition from liquid lubrication to gas lubrication.

[0094] Next, a sliding element according to Example 6 will be described with reference to Fig. 10. Note that a description of the same configuration as in Example 1 will be omitted. Note that the inclination of the inclined surface is shown exaggerated in order to make the description easier to understand.

[0095] 10 , the inner space S2 side of the sliding surface 611 of the stationary seal ring 610 of this sixth embodiment forms an inclined surface 615 that inclines in a direction away from the sliding surface 21 of the rotary seal ring 20 as it moves toward the inner diameter side. Second dynamic pressure generating grooves 613 are formed on this inclined surface 615. The vicinity of the terminal end 613B of the second dynamic pressure generating groove 613 is in contact with the sliding surface 21 of the rotary seal ring 20, so the dynamic pressure generating capacity of the second dynamic pressure generating groove 613 is ensured.

[0096] This allows for a high degree of design freedom, as the contact area between the sliding surface 611 and the sliding surface 21 is small, allowing for a high surface pressure and enabling the biasing force of the elastic member 7 (see FIG. 1) to be set small.

[0097] Next, a sliding element according to Example 7 will be described with reference to Fig. 11. Note that a description of the same configuration as in Example 1 will be omitted. Note that the inclination of the inclined surface is shown exaggerated in order to make the description easier to understand.

[0098] 11 , the inner space S2 side of the sliding surface 721 of the rotary seal ring 720 of this embodiment 7 forms an inclined surface 715 that inclines in a direction away from the sliding surface 11 of the stationary seal ring 10 as it moves toward the inner diameter side. The vicinity of the terminal end 13B of the second dynamic pressure generating groove 13 contacts the sliding surface 721 of the rotary seal ring 720, so the dynamic pressure generating capacity of the second dynamic pressure generating groove 13 is ensured.

[0099] This allows for a high degree of design freedom, as the contact area between the sliding surface 11 and the sliding surface 721 is small, allowing for a high surface pressure and enabling the biasing force of the elastic member 7 (see FIG. 1) to be set small.

[0100] 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.

[0101] For example, in the above-described Examples 1 to 7, the outer diameter side of the sliding surface is described as the high-viscosity space side and the inner diameter side as the low-viscosity space side, but as shown in Figure 12, the outer space S1 may be the low-viscosity space where gas A resides, and the inner space S2 may be the high-viscosity space where liquid F resides. In this case, it is sufficient that a lower land 811A is provided on the inner space S2 side of the sliding surface 811, and a higher land 811B is provided on the outer space S1 side. In other words, it is sufficient that the inner diameter sides of the sliding surfaces are spaced apart in the axial direction.

[0102] In addition, in the above-described Examples 1 to 7, the liquid is at high pressure and the gas is at low pressure, but the liquid may be at low pressure and the gas at high pressure, or the liquid and the gas may be at approximately the same pressure. In particular, when the liquid is at low pressure and the gas is at high pressure, this is useful for bearings, etc.

[0103] In addition, in Examples 1 to 4, 6, and 7, one sliding surface is stepped, and in Example 5, the other sliding surface is stepped, thereby forming a gap on the high-viscosity space side between the sliding surfaces. However, both sliding surfaces may be stepped so as to form a gap on the high-viscosity space side between the sliding surfaces. In other words, in the sliding component of the present invention, the high-viscosity space side between the pair of sliding surfaces is farther apart in the axial direction than the low-viscosity space side, and one sliding surface may have a low-viscosity-side dynamic pressure generating groove provided at a position farther apart in the axial direction, i.e., closer to the low-viscosity space side than the side surface that forms the step between the sliding surfaces.

[0104] In addition, in Example 6, the low-viscosity space side of one sliding surface is an inclined surface, and in Example 7, the low-viscosity space side of the other sliding surface is an inclined surface, but the low-viscosity space sides of both sliding surfaces may be inclined in directions that move away from each other in the axial direction as they approach the outer diameter side.

[0105] In addition, in the first and third to seventh embodiments, the low-viscosity dynamic pressure generating grooves are spiral grooves, and in the second embodiment, they are herringbone grooves. However, the present invention is not limited to this, and the shape of the low-viscosity dynamic pressure generating grooves can be freely changed. For example, they may be Rayleigh step grooves.

[0106] In addition, in the above-described Examples 1 to 7, the high-viscosity-side dynamic pressure generating grooves have been described as having a Rayleigh step configuration, but the configuration of the high-viscosity-side dynamic pressure generating grooves is not limited to this and can be freely changed. For example, they may have a spiral groove, a herringbone groove, or the like.

[0107] The number of low-viscosity side dynamic pressure generating grooves and high-viscosity side dynamic pressure generating grooves may be freely changed depending on the usage environment, etc.

[0108] Furthermore, in Examples 1 to 7, the gap width between the sliding surfaces on the high-viscosity space side was shallower than the depth of the low-viscosity side dynamic pressure generating groove, but the gap width may be equal to or deeper than the depth of the low-viscosity side dynamic pressure generating groove.

[0109] Furthermore, in Examples 1 to 7, the land on the high-viscosity space side has a smaller radial width than the land on the low-viscosity space side, but the radial width of the land on the high-viscosity space side may be equal to or larger than the radial width of the land on the low-viscosity space side.

[0110] Furthermore, in the above-described Examples 1 to 7, sliding parts used in mechanical seals for automobiles, general industrial machinery, etc. have been described, but the sliding parts may also be used in thrust bearings, radial bearings, plain bearings, etc.

[0111] Furthermore, the liquid F may be in the form of a mist in which a liquid and a gas are mixed. The gas A may be in the form of a mist in which a liquid and a gas are mixed. In other words, it is sufficient that the viscosity of the liquid F is higher than the viscosity of the gas A. In other words, as long as there is a difference in viscosity, both liquids and both gases may exist in the outer space and the inner space.

[0112] DESCRIPTION OF SYMBOLS 1 Rotating shaft 4 Housing 7 Elastic member 10 Stationary seal ring 11 Sliding surface (one sliding surface) 11A, 11B Land 11C Side surface 12 First dynamic pressure generating groove (high viscosity side dynamic pressure generating groove) 13 Second dynamic pressure generating groove (low viscosity side dynamic pressure generating groove) 20 Rotating seal ring 21 Sliding surface (other sliding surface) 122 Shallow groove portion (Rayleigh step) A Gas F Liquid S1 Outer space (high viscosity space) S10 Gap S2 Inner space (low viscosity space)

Claims

1. A sliding component in which a pair of sliding surfaces are arranged at a position where they rotate relative to each other, and which partitions a high-viscosity space in which a relatively high-viscosity fluid exists and a low-viscosity space in which a relatively low-viscosity fluid exists, wherein one of the sliding surfaces has a low-viscosity side dynamic pressure generating groove provided on the low-viscosity space side, and between the pair of sliding surfaces, the land on the high-viscosity space side is farther away in the axial direction than the land on the low-viscosity space side.

2. A sliding component according to claim 1, wherein the lands on the high viscosity space side are spaced apart in the axial direction along the circumferential direction.

3. A sliding component according to claim 1, wherein at least one of the sliding surfaces on the high viscosity space side is provided with a high viscosity side dynamic pressure generating groove.

4. A sliding component according to claim 3, wherein the spacing between the lands on the high viscosity space side is smaller than the depth of the dynamic pressure generating grooves on the low viscosity space side.

5. A sliding component according to claim 3, wherein the high-viscosity hydrodynamic groove is a Rayleigh step.

6. A sliding element according to claim 3, wherein said one sliding surface has a stepped shape with different heights.

7. A sliding component according to claim 1, wherein the land on the high viscosity space side of said one sliding surface has a smaller radial width than the land on the low viscosity space side of said one sliding surface.

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