Sliding component

Abstract

A sliding component has an annular mating ring and an annular seal ring opposite to each other and causing respective sliding surfaces thereof to slidably rotate relative to each other, to seal a sealed fluid present on radially inner or outer side of the sliding surfaces. In the sliding surface of the seal ring, a plurality of dynamic pressure recesses is formed separately arranged in a circumferential direction, the dynamic pressure recesses generating a dynamic pressure by a relative sliding rotation between the mating ring and the seal ring. In the sliding surface of the mating ring, a plurality of static pressure recesses is formed in the circumferential direction at positions where the static pressure recesses cooperate with the dynamic pressure recesses to enable the sealed fluid to flow the static pressure recesses to the dynamic pressure recesses. The static pressure recesses is deeper than the dynamic pressure recesses.

Claims

1. A sliding component comprising a first seal ring and a second seal ring that are opposite to each other and having respective sliding surfaces thereof configured to slidably rotate relative to each other, and configured to seal a sealed fluid on a radially inner or outer side of the sliding surfaces of the first and second seal rings, wherein in the sliding surface of the first seal ring, a plurality of dynamic pressure recesses is formed to be separately arranged in a circumferential direction, the dynamic pressure recesses for generating a dynamic pressure upon a relative sliding rotation between the first seal ring and the second seal ring, in the sliding surface of the second seal ring, a plurality of static pressure recesses is formed in the circumferential direction at positions where the static pressure recesses cooperate with the dynamic pressure recesses, the static pressure recesses being deeper than a deepest part of the dynamic pressure recesses and deeper than 10 μm, and each of the static pressure recesses is formed in a rectangular shape, a U-shape or a V-shape in a cross section.

2. The sliding component according to claim 1, wherein the plurality of dynamic pressure recesses and the plurality of static pressure recesses at least overlap with each, other in a radial direction.

3. The sliding component according to claim 1, wherein the dynamic pressure recesses are open toward the radially inner or outer side where the sealed fluid is intended to be present.

4. The sliding component according to claim 3, wherein each of the dynamic pressure recesses has a strip shape.

5. The sliding component according to claim 1, wherein each of the static pressure recesses is a dimple.

6. The sliding component according to claim 1, wherein each of the dynamic pressure recesses has a strip shape extending in the circumferential direction in a plan view, and each of the static pressure recesses is a dimple.

7. The sliding component according to claim 1, wherein the dynamic pressure recesses are arranged only on the radially inner or outer side where the sealed fluid is intended to be present.

8. The sliding component according to claim 7, wherein the dynamic pressure recesses are arranged only in a region of one quarter or less of the sliding surface of the first seal ring on the radially inner or outer side where the sealed fluid is intended to be present.

9. The sliding component according to claim 1, wherein the static pressure recesses are arranged in an entire region of the sliding surface of the second seal ring.

10. The sliding component according to claim 1, wherein the static pressure recesses have a depth dimension larger than a maximum opening diameter dimension of the static pressure recesses in the plan view.

11. The sliding component according to claim 1, wherein the sealed fluid can be a high-pressure liquid of 0.1 MPa or more.

12. The sliding component according to claim 2, wherein the dynamic pressure recesses are open toward the radially inner or outer side where the sealed fluid is intended to be present.

13. The sliding component according to claim 12, wherein each of the dynamic pressure recesses has a strip shape.

14. The sliding component according to claim 12, wherein each of the static pressure recesses is a dimple.

15. The sliding component according to claim 2, wherein each of the dynamic pressure recesses has a strip shape extending in the circumferential direction in a plan view, and each of the static pressure recesses is a dimple.

16. The sliding component according to claim 3, wherein each of the static pressure recesses is a dimple.

17. The sliding component according to claim 3, wherein each of the dynamic pressure recesses has a strip shape extending in the circumferential direction in a plain view, and each of the static pressure recesses is a dimple.

18. The sliding component according to claim 4, wherein each of the static pressure recesses is a dimple.

19. The sliding component according to claim 2, wherein the dynamic pressure recesses are arranged only on the radially inner or outer side where the sealed fluid is intended to be present.

20. The sliding component according to claim 19, wherein the dynamic pressure recesses are arranged only in a region of one quarter or less of the sliding surface of the first seal ring on the radially inner or outer side where the sealed fluid is intended to be present.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a sectional view showing a sliding component as a mechanical seal for general industrial machinery, according to a first embodiment of the present invention.

(2) FIG. 2 is a plan view showing a sliding surface of a seal ring in which dynamic pressure recesses are formed in the first embodiment of the present invention.

(3) FIG. 3 is a plan view showing a sliding surface of a mating ring as another seal ring arranged opposite the seal ring shown in FIG. 2, in which static pressure recesses are formed.

(4) FIG. 4 is a cross-sectional view of the seal ring and the mating ring in FIGS. 2 and 3 during non-rotation, taken in a radial direction.

(5) FIG. 5 is a schematic cross-sectional view for describing generation of dynamic pressure by the seal ring and the mating ring in FIGS. 2 and 3 during rotation, taken in a circumferential direction.

(6) FIGS. 6A and 6B are cross-sectional views showing modifications of the static pressure recesses according to the first embodiment.

(7) FIGS. 7A to 7G are plan views showing a sliding surface of a seal ring of a sliding component according to a second embodiment of the present invention, in which dynamic pressure recesses are formed.

(8) FIGS. 8A to 8F are plan views showing a sliding surface of a mating ring of a sliding component according to a third embodiment of the present invention, in which static pressure recesses are formed.

DESCRIPTION OF EMBODIMENTS

(9) Modes for implementing a sliding component according to the present invention will be described below based on embodiments.

First Embodiment

(10) A sliding component according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. In the first embodiment, a mechanical seal, which is an example of the sliding component, will be described. In addition, a radially outer peripheral side of sliding parts constituting the mechanical seal is described as a sealed fluid side, and a radially inner peripheral side thereof as an atmosphere side.

(11) The mechanical seal for general industrial machinery shown in FIG. 1 is of an inside type of sealing a sealed fluid that tends to leak from the outer peripheral side to the inner peripheral side of a sliding surface. The mechanical seal mainly includes a mating ring 20 as an annular sliding part provided via a sleeve 2 on the side of a rotating shaft 1 in a state of being integrally rotatable with the rotating shaft 1, and a seal ring 10 as an annular sliding part provided at a seal cover 5, which is fixed to a housing 4 of the installed equipment, in a non-rotating state and in an axially movable state. The seal ring 10 is axially biased by a bellows 7, so that a sliding surface 11 of the seal ring 10 and a sliding surface 21 of the mating ring 20, which are mirror-finished by lapping or the like, slide in close contact with each other. Note that the sealed fluid in the present embodiment is a high-pressure liquid of 0.1 MPa or more.

(12) The seal ring 10 and the mating ring 20 are typically formed of SiC (regarded as hard material) or a combination of SiC (regarded as hard material) and carbon (regarded as soft material), but not limited thereto, and any sliding material can be applied as long as it is used as a sliding material for a mechanical seal. The SiC includes a sintered compact with boron, aluminum, carbon or the like as sintering aids, as well as a material composed of two or more phases having different components and compositions, for example, SiC in which graphite particles are dispersed, reaction-sintered SiC composed of SiC and Si, SiC—TiC, SiC—TiN, and the like. As carbon, carbon in which a carbonaceous material and a graphite material are mixed, as well as resin-molded carbon, sintered carbon, and the like, can be used. In addition to the sliding materials described above, metal materials, resin materials, surface modification materials (or coating materials), composite materials, and the like are also applicable.

(13) As shown in FIG. 2, the seal ring 10 has a sliding surface 11 at one axial end which has an annular shape when viewed from the front in an axial direction, i.e., in a plan view. The sliding surface 11 is a flat surface, in which a plurality of recessed grooves 12 as circumferentially separated dynamic pressure recesses are formed. The sliding surface 11 can be also a land portion with respect to the recessed grooves 12.

(14) The recessed grooves 12 are each defined by a bottom 12A formed as a plane parallel to the sliding surface 11, radial walls 12B and 12C formed as wall surfaces perpendicular to the bottom 12A, and a circumferential wall 12D formed as a wall surface perpendicular to the bottom surface 12A and the radial walls 12B and 12C. Each of the recesses grooves 12 has an opening 12E which has a substantially rectangular shape when viewed from the side and is open in a radially outward direction, on the sealed fluid side. The recessed grooves 12 are formed as grooves which have a strip shape extending in a circumferential direction of the sliding surface 11 when viewed from the front in the axial direction. In addition, the recessed grooves 12 according to the present embodiment are formed by laser processing, but not limited to this, and may be formed by other methods.

(15) Further, twelve recessed grooves 12 are arranged at equal intervals in the circumferential direction of the sliding surface 11. The number and interval of the recessed grooves 12 are not limited to this. However, if the number of the recessed grooves 12 is too large, the generated dynamic pressure is large, and if the number is too small, the change in dynamic pressure acting in the circumferential direction of the sliding surface 11 is large. Therefore, it is preferable that 6 to 24 recessed grooves 12 are arranged at equal intervals.

(16) Further, the circumferential length of the recessed grooves 12 and the length (i.e., interval) between the recessed grooves 12, 12 adjacent to each other in the circumferential direction are substantially the same. Note that the circumferential length and interval of the recessed grooves 12 in the sliding surface 11 are not limited to this.

(17) Further, the axial depth of the recessed grooves 12 is less than 5 μm, preferably 1 μm or more, and the radial length R12 of the recessed grooves 12 is one half or less, preferably one quarter or less, of the radial length R11 of the sliding surface 11 (see FIG. 2). As a result, the total force (buoyancy) of all the dynamic pressures generated in the recessed grooves 12 does not become too large. The recessed grooves 12 are also arranged only in a region on the radially outer side in a radial direction of the sliding surface 11. In addition, it is preferable that the recessed grooves 12 are not arranged on the radially inner side of the sliding surface 11. This makes the radially outer side of the sliding surface 11 unlikely to directly come into contact with the opposite sliding surface 21 during the relative rotation between the seal ring 10 and the mating ring 20, thereby preventing poor lubrication on the radially outer side with a high rotation speed. Furthermore, the circumferential length c12 of the recessed grooves 12 (see FIG. 5) is formed to be longer than the radial length R12 of the recessed grooves 12 (see FIG. 2).

(18) As shown in FIG. 3, the mating ring 20 has the annular sliding surface 21 that is opposite the sliding surface 11 of the seal ring 10 in the axial direction. The sliding surface 21 is a flat surface in which a plurality of dimples 22 as static pressure recesses is formed in the entire surface in the circumferential direction. The sliding surface 21 can be also a land portion with respect to the dimple 22.

(19) Further, the radial length w21 of the sliding surface 21 of the mating ring 20 is formed to be longer than the radial length w11 of the sliding surface 11 of the seal ring 10 (i.e., w11<w21) as shown in FIG. 4. This reduces the maximum radial length r12 of the recessed grooves 12 arranged on the radially outer side of the sliding surface 11 of the seal ring 10.

(20) The dimples 22 are formed in a semi-spheroidal shape having a circular shape (see FIG. 3) when viewed from the front in the axial direction, a substantially elliptical cross section in the radial direction (see FIG. 4), and a substantially elliptical cross section in the circumferential direction (see FIG. 5), and six dimples are radially arranged in a zigzag manner in the entire region of the sliding surface 21. Note that the entire region of the sliding surface 21 indicates a surface region that is capable of substantially sliding with the sliding surface 11. In addition, the dimples 22 in this embodiment are formed by laser processing, but is not limited to this, and may be formed by other methods.

(21) Further, the depth dimension h22 of the dimples 22 is formed to be larger than the maximum opening diameter dimension r22 of the dimples 22 when viewed from the front (i.e., r22<h22) as shown in FIG. 4. This can improve the function of the dimples 22 supplying the sealed fluid to the opposite recessed grooves 12, and can improve the function of the dimples 22 holding the sealed fluid therein at locations where the dimples 22 are not opposite the recessed grooves 12. The depth dimension h22 of the dimples 22 may be also formed to be smaller than or substantially the same as the maximum opening diameter dimension r22 of the dimples 22 when viewed from the front. In addition, the axial depth of the dimples 22 is preferably 10 μm or more at which the wedge effect does not sufficiently act.

(22) As shown in FIG. 4, the depth dimension h22 of the dimples 22 is formed to be larger than the depth dimension h12 of the recessed grooves 12 (i.e., h12<h22). In addition, the maximum radial length r12 of the recessed grooves 12 is formed to be longer than the maximum radial length r22 of the dimples 22 (i.e., r22<r12). Furthermore, as shown in FIG. 5, the maximum circumferential length c12 of the recessed grooves 12 is formed to be longer than the maximum circumferential length c22 of the dimples 22 (i.e., c22<c12). Thus, the recessed grooves 12 and the dimples 22 at least overlap in the radial direction between the sliding surfaces 11 and 21.

(23) Next, generation of dynamic pressure between the sliding surfaces 11 and 21 will be described hereinafter. As shown in FIG. 5, when the seal ring 10 and the mating ring 20 rotate relative to each other with a rotating direction being a direction indicated by a white arrow from the side of the radial wall 12B to the side of the radial wall 12C in FIG. 5, a negative pressure is generated on an end point side of the rotating direction of the recessed grooves 12 (that is, on the side of the radial wall 12C in FIG. 5), while the positive pressure is generated on a start point side of the counter rotating direction (that is, on the side of the radial wall 12B in FIG. 5). The positive pressure is increased by the wedge effect of the radial wall 12B on the start point side of the counter rotating direction of the recessed grooves 12, and the positive pressure acts as a whole to obtain large buoyancy. In addition, the sealed fluid is supplied from the dimples 22 to the recessed grooves 12 through the opposite portion or the vicinity of the opposite portion of the dimples 22 deeper than the recessed grooves 12, so that the dynamic pressure can be reliably generated without poor lubrication. At this time, the recessed grooves 12 mainly function to generate a dynamic pressure between the sliding surfaces 11 and 21 to adjust a contact surface pressure between the sliding surfaces 11 and 21, and the dimples 22 mainly function to supply the sealed fluid held therein to the side of the recessed grooves 12 and to introduce a static pressure from the sealed fluid side on the radially inner side of the sliding surface 11 in which the recessed grooves 12 are not formed. Furthermore, the static pressure by the sealed fluid is introduced into the recessed grooves 12 from an opening 12E which has a substantially rectangular shape when viewed from the side and is open in a radially outward direction, on the sealed fluid side, so that the recessed grooves 12 contribute to generate the dynamic pressure between the sliding surfaces 11 and 21. As schematically shown in FIG. 5, the sliding surfaces 11 and 21 microscopically have a wavy shape due to surface roughness, undulation, and deformation due to dynamic pressure.

(24) As described above, the cooperation between the recessed grooves 12 and the dimples 22 generates a dynamic pressure to such an extent that the seal ring 10 and the mating ring 20 do not completely float relative to each other. Thus, the sliding surfaces 11 and 21 are brought into mixed lubrication in which hydrodynamic lubrication and boundary lubrication are mixed, and are brought into a state of being partially in contact with each other. Therefore, while both sliding surfaces 11 and 21 are in contact with each other, the contact surface pressure is reduced, so that a sliding component with less leakage of the high-pressure sealed fluid and low torque can be obtained. Furthermore, the low torque allows the surface roughness of the sliding surfaces 11 and 21 to be reduced. Unlike the first embodiment, a conventional dynamic pressure generating groove generates a fluid film serving as fluid lubrication.

(25) As a modification of the recessed grooves 12 according to the first embodiment, the radial walls 12B and 12C may not be perpendicular to the bottom 12A, and may, for example, intersect with the bottom 12A in an inclined state. In addition, the bottom 12A may not be parallel to the sliding surface 11, and may be, for example, an inclined surface. Furthermore, the bottom 12A may not be a flat surface, and may be, for example, a curved surface.

(26) As a modification of the dimples 22 according to the first embodiment, the cross-sectional shape of the dimples 22 may be formed in a rectangular shape as shown in FIG. 6A and a conical shape as shown in FIG. 6B.

Second Embodiment

(27) Next, a sliding component according to a second embodiment of the present invention will be described with reference to FIG. 7. The same constitutional elements as those shown in the embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

(28) The sliding component according to the second embodiment will be described. As shown in FIG. 7A, a recessed groove 212 as one of dynamic pressure recesses is formed in a sliding surface 211 of a seal ring 210 and has a semicircular shape when viewed from the front in the axial direction. The recessed groove 212 is open in a radially outward direction, on the sealed fluid side.

(29) Further, as shown in FIG. 7B, spiral grooves 312 as dynamic pressure recesses are formed in a sliding surface 311 of a seal ring 310. The spiral grooves 312 are open in the radially outward direction, on the sealed fluid side, and are closed on a radially inner side.

(30) Further, as shown in FIG. 7C, a recessed groove 412 as one of dynamic pressure recesses is formed in a sliding surface 411 of a seal ring 410 and has a substantially rectangular shape when viewed from the front in the axial direction. The recessed groove 412 is continuously surrounded by a land portion and is thus not open in the radially outward direction, on the sealed fluid side.

(31) Further, as shown in FIG. 7D, a Rayleigh step 512 as one of dynamic pressure recesses is formed in a sliding surface 511 of a seal ring 510 and has a substantially L shape when viewed from the front in the axial direction. In the Rayleigh step 512, grooves extending in the radial direction and the circumferential direction have the same depth, and the groove extending in the radial direction is open in the radially outward direction, on the sealed fluid side.

(32) Further, as shown in FIG. 7E, a Rayleigh step 612 as one of dynamic pressure recesses is formed in a sliding surface 611 of a seal ring 610 and has a substantially L shape when viewed from the front in the axial direction. In the Rayleigh step 612, a deep groove 631 extending in the radial direction are continuously formed with a groove 630 extending in the circumferential direction, and the deep groove 631 is open in the radially outward direction, on the sealed fluid side.

(33) Further, as shown in FIG. 7F, a recessed groove 712 as one of dynamic pressure recesses is formed in a sliding surface 711 of a seal ring 710 and has a substantially rectangular shape when viewed from the front in the axial direction. The recessed groove 712 is constituted by a deep groove 730 formed substantially at the center of the recessed groove 712 in the circumferential direction and a pair of inclined grooves 731 and 732 are continuously formed on both sides of the deep groove 730 in the circumferential direction. The entire recessed groove 712 is open in the radially outward direction, on the sealed fluid side.

(34) Further, as shown in FIG. 7G, dimples 812 as dynamic pressure recesses having a circular shape when viewed from the front in the axial direction are formed in a sliding surface 811 of a seal ring 810. The dimples 812 are arranged only on the radially outer side of the sliding surface 811 of the seal ring 810. Although not shown, for convenience of explanation, the maximum radial length of the dimples 812 is formed to be larger than the maximum radial length of the dimples 22 formed in the sliding surface 21 of the mating ring 20.

(35) Note that the depth of the respective dynamic pressure recesses in FIGS. 7A to 7G in the axial direction of the seal rings is formed to be shallow so that dynamic pressure can be sufficiently generated.

Third Embodiment

(36) Next, a sliding component according to a third embodiment of the present invention will be described with reference to FIG. 8. The same constitutional elements as those shown in the embodiments described above are denoted by the same reference numerals, and redundant description will be omitted.

(37) The sliding component according to the third embodiment will be described. As shown in FIG. 8A, a plurality of dimples 222 as static pressure recesses having a circular shape when viewed from the front in the axial direction is formed in a sliding surface 221 of a mating ring 220. The dimples 222 are arranged in the radial direction and the circumferential direction throughout the entire surface of the sliding surface 221.

(38) Further, as shown in FIG. 8B, a plurality of dimples 322 as static pressure recesses having a rectangular shape when viewed from the front in the axial direction is formed in a sliding surface 321 of a mating ring 320. The dimples 322 are arranged in the radial direction and in the circumferential direction in a zigzag manner throughout the entire surface of the sliding surface 321.

(39) Further, as shown in FIG. 8C, spiral grooves 422 as dynamic pressure recesses are formed in a sliding surface 421 of a mating ring 420. The spiral grooves 422 are arranged in the entire surface of the sliding surface 421, and are open in the radially outward direction i.e., toward the sealed fluid side, and in the radially inward direction.

(40) Further, as shown in FIG. 8D, a plurality of recessed grooves 522 as static pressure recesses which are adjacent to each other in the circumferential direction and have a rectangular shape when viewed from the front in the axial direction is formed in a sliding surface 521 of a mating ring 520. The recessed grooves 522 are arranged only on the radially outer side of the sliding surface 521, and are open in the radially outward direction, on the sealed fluid side.

(41) Further, as shown in FIG. 8E, a recessed groove 622 as one of static pressure recesses is formed in a sliding surface 621 of a mating ring 620 and has a semicircular shape when viewed from the front in the axial direction. The recessed groove 622 is open in the radially outward direction, on the sealed fluid side.

(42) Further, as shown in FIG. 8F, a recessed groove 722 as one of static pressure recesses is formed in a sliding surface 721 of a mating ring 720 and has a substantially rectangular shape when viewed from the front in the axial direction. The recessed groove 722 is open in the radially outward direction, on the sealed fluid side.

(43) Note that the axial depth of the respective static pressure recesses formed in the mating rings in FIGS. 8A to 8F is formed so deep that the dynamic pressure is not sufficiently generated, so that a sealed fluid can be supplied and held.

(44) Although the embodiments according to the present invention have been described above with reference to the drawings, specific configurations are not limited to these embodiments, and changes and additions without departing from the scope of the present invention are also included in the present invention.

(45) Further, in the embodiments described above, the case where the sliding component is a mechanical seal has been described as an example. However, the present invention is not to be construed as being limited to this, and without departing from the scope of the present invention, various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art.

(46) For example, as a sliding component, a mechanical seal for general industrial machinery has been described as an example, however, other mechanical seals for a water pump, or the like may be used. In addition, a mechanical seal may be of an outside type.

(47) Further, in the embodiments described above, an example in which the dynamic pressure recesses are provided in the seal ring, and the static pressure recesses are provided in the mating ring, however, the static pressure recesses may be provided in the seal ring, and the dynamic pressure recesses may be provided in the mating ring.

(48) Further, although a mechanical seal has been described as an example of a sliding component, a sliding component other than a mechanical seal such as a sliding bearing may be applicable.

REFERENCE SIGNS LIST

(49) 1 Rotating shaft

(50) 2 Sleeve

(51) 4 Housing

(52) 5 Seal cover

(53) 7 Bellows

(54) 10 Seal ring (First or Second seal ring)

(55) 11 Sliding surface

(56) 12 Recessed groove (dynamic pressure recess)

(57) 12A Bottom

(58) 12B, 12C Radial wall

(59) 12D Circumferential wall

(60) 12E Opening

(61) 20 Mating ring (Second or First seal ring)

(62) 21 Sliding surface

(63) 22 Dimple (static pressure recess)

(64) 210 to 810 Seal ring (sliding part)

(65) 211 to 811 Sliding surface

(66) 212 Recessed groove (dynamic pressure recess)

(67) 220 to 710 Mating ring (sliding part)

(68) 221 to 721 Sliding surface

(69) 222 Dimple (static pressure recess)

(70) 312 Spiral groove (dynamic pressure recess)

(71) 322 Dimple (static pressure recess)

(72) 412 Recessed groove (dynamic pressure recess)

(73) 422 Spiral groove (static pressure recess)

(74) 512 Rayleigh step (dynamic pressure recess)

(75) 522 Recessed groove (static pressure recess)

(76) 612 Rayleigh step (dynamic pressure recess)

(77) 622 Recessed groove (static pressure recess)

(78) 712 Recessed groove (dynamic pressure recess)

(79) 722 Recessed groove (static pressure recess)

(80) 812 Dimple (dynamic pressure recess)