SLIDING ELEMENT

Description

Technical Field

[0001] The present invention relates to a sliding member suitable for, for example, mechanical seals, bearings, and other slide parts. In particular, the present invention relates to a sliding member such as a sealing ring or a bearing required to reduce friction on sliding surfaces and to prevent leakage of the fluid from the sliding surfaces.Background Art

[0002] In a mechanical seal which is an example of a sliding member, in order to maintain sealing performance in the long term, there is a technique for balancing conflicting conditions of "sealing" and "lubrication". For example, in a pair of sliding members that slide relative to each other, those in which a spiral groove is provided on a sliding surface of a sliding component, and using a pumping action of the spiral groove, a sealed fluid that is likely to leak to a low-pressure fluid side is pushed back to the sealed fluid side, thereby improving sealing function of the sliding surface are known (for example, see JP S61 - 82 177 U) . US 3 466 052 A discloses a sealing structure having similar features. JP S57 - 146 955 A, WO 2018 / 034 197 A1, JP H03 - 41 267 U and JP 2011 - 185 292 A disclose further prior art.SUMMARY OF THE INVENTIONProblem to be Solved by the Invention

[0003] However, in the above technique, the pumping action of the spiral groove is exhibited only at above a certain rotating speed, and therefore a low-speed rotating equipment could not obtain sufficient sealing effect even if the spiral groove is provided on the sliding surface.

[0004] The present invention has an object to provide a sliding member that can exhibit a pumping action even at low-speed rotation and can exhibit sealing function and lubrication function.Means for Solving Problem

[0005] The above object is solved by a pair of sliding members according to claim 1 of the present invention.

[0006] According to the invention, the shape of the dynamic pressure generation mechanism is such that the curvature is small at the inlet opening of the dynamic pressure generation mechanism (the curvature radius is large) and the curvature is increased in proportion to the flow path length from the inlet opening of the dynamic pressure generation mechanism (the curvature radius is small). Thereby, the difference between the angle at which the fluid flows into the dynamic pressure generation mechanism and the angle of the inlet opening of the dynamic pressure generation mechanism can be reduced. Moreover, as the fluid within the dynamic pressure generation mechanism flows to the flow path downstream side, the rotational velocity of the fluid is efficiently converted into the radial velocity. Thereby, it is possible to reduce a loss in inflow when the fluid flows into the inlet opening of the dynamic pressure generation mechanism, and it is possible to generate a pumping action even at low-speed rotation.

[0007] The pair of sliding members according to dependent claim 2 is characterized in that the angle between an inner circumferential edge of the sliding surface and the inlet opening of the dynamic pressure generation mechanism is set to from 0° to 45°.

[0008] Accordingly, an angle θ 1 between an inner circumferential edge 5b of the sliding surface S and the inlet opening of the dynamic pressure generation mechanism is 0° ≤ θ 1 ≤ to 45°, thereby it is possible to extremely reduce a loss in inflow when the fluid flows into the dynamic pressure generation mechanism.

[0009] The pair of sliding members according to dependent claim 3 is characterized in that the shape of the flow path is represented by the following formulas: P = P 0 + h ∫ 0 S e jϕ dS ϕ = ϕ 0 + ϕ v S + ϕ u S 2 S = s h 0 < S < 1 where P is a position vector of a point on the dynamic pressure generation mechanism, P 0 is a position vector of the inlet opening of the dynamic pressure generation mechanism, s is a flow path length from P 0 to P, h is an entire length of the flow path of the dynamic pressure generation mechanism, S is what s is normalized by h, ϕ is a tangential angle at P, i = √-1 is an imaginary unit, ϕ 0 is a tangential angle at P 0 , ϕ v is an increment of the tangential angle to ϕ 0 in h in a circular arc of the length h having ϕ 0 , and ϕ u is an increment of the tangential angle to ϕ v in h.

[0010] Accordingly, easily by means of the above formulas, it is possible to reduce a loss in inflow when the fluid flows into the inlet opening of the dynamic pressure generation mechanism, and it is possible to generate a pumping action even at low-speed rotation.

[0011] The pair of sliding members according to dependent claim 4 is characterized in that the flow path is such that one end communicates with a leakage side and the other end is surrounded by a land portion.

[0012] Accordingly, since the dynamic pressure generation mechanism exhibits a pumping action even at low-speed, even when dynamic pressure by the dynamic pressure generation mechanism is not sufficiently generated at low-speed, the fluid flowed into the dynamic pressure generation mechanism can generate positive pressure by a wedge effect, and therefore it is possible to maintain the sliding surface at a fluid lubrication state even at low-speed rotation.

[0013] The pair of sliding members according to dependent claim 5 is characterized in that the flow path is made of a groove portion.

[0014] Accordingly, the dynamic pressure generation mechanism can be easily constituted from the groove portion.

[0015] The pair of sliding members according to dependent claim 6 is characterized in that the flow path is a pseudo flow path made of a dimple group consisting of a plurality of dimples.

[0016] Accordingly, the dynamic pressure generation mechanism can be easily constituted from the dimple group.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a vertical cross-sectional view showing an example of a mechanical seal including a sliding member according to the present invention. FIG. 2 is a drawing showing a sliding surface of the sliding member taken along the arrow W-W in FIG. 1. FIG. 3 is a drawing for explaining a difference between a dynamic pressure generation mechanism according to the present invention and a conventional spiral-shaped dynamic pressure generation mechanism. DESCRIPTION OF EMBODIMENTS

[0018] Hereinafter with reference to the drawings, modes for carrying out the present invention will be described illustratively based on an embodiment. However, the dimensions, materials, shapes, relative arrangements, and others of components described in the embodiment are not intended to limit the scope of the present invention only to them unless otherwise described explicitly.

[0019] Referring to FIG. 1 to FIG. 3, as to a sliding member according to the present invention, a mechanical seal which is an example of the sliding member will be described. In a first embodiment, the outer circumferential side of the sliding member constituting the mechanical seal is described as a sealed fluid side and the inner circumferential side is described as a leakage side.

[0020] A mechanical seal 1 in FIG. 1 includes a rotating-side sealing ring 3 integrally rotatable with a sleeve 2 mounted on a rotating shaft 9 side, a circular-ring shaped stationary-side sealing ring 5 which is the other slide component provided in a state of being axially movable to a casing 4 and non-rotatable, a coiled wave spring 6 axially biasing the stationary-side sealing ring 5, and a bellows 7 which seals the stationary-side sealing ring 5, and mirror-finished sliding surfaces S slide in close contact with each other.

[0021] In the mechanical seal 1, the rotating-side sealing ring 3 and the stationary-side sealing ring 5 have the sliding surfaces S formed radially, and the mechanical seal 1 prevents a sealed fluid from flowing out from the outer circumferential side of the sliding surface S to the leakage side on the inner circumferential side at each other's sliding surfaces S.

[0022] In addition, in FIG. 1, a case where the width of the sliding surface of the rotating-side sealing ring 3 is wider than the width of the sliding surface of the stationary-side sealing ring 5 is shown, but the present invention is not limited thereto, and of course can be applied to the opposite case.

[0023] Although the materials of the rotating-side sealing ring 3 and the stationary-side sealing ring 5 are selected from silicon carbide (SiC) excellent in wear resistance, carbon excellent in self-lubricity and the like, for example, both may be SiC or combinations of SiC as the rotating-side sealing ring 3 and carbon as the stationary-side sealing ring 5 are possible.

[0024] As shown in FIG. 2, on the sliding surface S of the stationary-side sealing ring 5, a predetermined number (eighteen in the embodiment of FIG. 2) of dynamic pressure generation mechanisms 11 are arranged. The dynamic pressure generation mechanism 11 is an arcuate groove portion which is convexed toward the leakage side of the sliding surface S, communicates with the leakage side via an inlet opening 11a opened to a circumferential edge 5b on the leakage side, and has a toe part 11b surrounded by a land portion at the sealed fluid side and thus is isolated from the sealed fluid side.

[0025] The dynamic pressure generation mechanism 11 has a shape in which the curvature of the dynamic pressure generation mechanism 11 continuously increases toward the toe part 11b (the downstream side) from the inlet opening 11a (the upstream side) . The shape of a center line of the dynamic pressure generation mechanism 11 expressed in polar coordinate system is represented by the following Formula (1) to Formula (3): P = P 0 + h ∫ 0 S e jϕ dS ϕ = ϕ 0 + ϕ v S + ϕ u S 2 S = s h 0 < S < 1 where P 0 is a position vector of a starting point (the inlet opening 11a of the dynamic pressure generation mechanism 11), P is a position vector of a point on the dynamic pressure generation mechanism 11, s is a length (m) of a curved line from P 0 to P, h is an entire length (m) of a flow path of the dynamic pressure generation mechanism 11, S is what s is normalized by the entire length h of the flow path, ϕ is a tangential angle (rad) at P of the dynamic pressure generation mechanism 11, i = √-1 is an imaginary unit, ϕ 0 is an initial direction (a tangential angle (rad) of the dynamic pressure generation mechanism 11 at P 0 ), ϕ v is an increment (rad) of the tangential angle to ϕ 0 in h in a circular arc of the length h having the initial direction ϕ 0 , and ϕ u is an increment (rad) of the tangential angle to ϕ v in h of the dynamic pressure generation mechanism 11. That is, the tangential angle ϕ = ϕ 0 + ϕ v + ϕ u in h (S=1).

[0026] For example, the dynamic pressure generation mechanism 11 is defined by the above four parameters h, ϕ 0 , ϕ v , and ϕ u . In addition, when both ϕ o and ϕ v are zero, the dynamic pressure generation mechanism 11 coincides with an equiangular spiral. When ϕ v and ϕ u are positive values, the dynamic pressure generation mechanism 11 forms a curved line convexed toward the leakage side of the sliding surface S. In order to define the shape of the dynamic pressure generation mechanism 11 according to the present invention, ϕ v and ϕ u are set within the ranges of 0 ≤ ϕ v ≤ 2 and 0 ≤ ϕ u ≤ 1. Moreover, when ϕ v and ϕ u are negative values, the dynamic pressure generation mechanism 11 forms a curved line concaved toward the leakage side of the sliding surface S. In FIG. 3A, by means of Formula (1) to Formula (3), the shape of the dynamic pressure generation mechanism 11 is defined using the vector when ϕ 0 is zero. That is, the shape of the dynamic pressure generation mechanism 11 is set in such a manner that the curvature is small at the inlet opening 11a of the dynamic pressure generation mechanism 11 (the curvature radius is large) and the curvature is increased according to the flow path length from the inlet opening 11a of the dynamic pressure generation mechanism 11 (the curvature radius is small).

[0027] As shown in FIG. 3, when the sliding member (the rotating-side sealing ring 3) on the opposite side rotates in a predetermined direction (a clockwise direction in FIG. 3), the fluid, due to its viscosity, moves by following the moving direction of the rotating-side sealing ring 3 and flows into the dynamic pressure generation mechanism 11. For example, as shown in FIG. 3A, when the flow of the fluid from the stationary-side sealing ring 5 is observed, a velocity Vi of the fluid flowing into the dynamic pressure generation mechanism 11 is obtained by combining a circumferential velocity u according to the rotational velocity of the rotating-side sealing ring 3 with a radial velocity Vp by a pumping action of the dynamic pressure generation mechanism 11.

[0028] In FIG. 3A, the effect of the circumferential velocity u is large and the radial velocity is low, and therefore an angle α at which the fluid flows into the dynamic pressure generation mechanism 11 is very small. On the other hand, the initial curvature at the inlet opening 11a of the dynamic pressure generation mechanism 11 is set to zero, and therefore the angle between the inner circumferential edge 5b of the sliding surface S and a surface on the convex side of the dynamic pressure generation mechanism 11, that is, an inlet angle of the inlet opening 11a of the dynamic pressure generation mechanism 11 also is zero. Thereby, the difference between the angle α at which the fluid flows into the dynamic pressure generation mechanism 11 and the angle of the inlet opening 11a of the dynamic pressure generation mechanism 11 is very small, and therefore it is possible to reduce a loss in inflow when the fluid flows into the inlet opening 11a of the dynamic pressure generation mechanism 11. Moreover, the circumferential velocity u of the fluid within the dynamic pressure generation mechanism 11 is efficiently converted into the radial velocity Vp toward the flow path downstream side, and therefore it is possible to generate a pumping action for sucking the fluid into the sliding surface S from the leakage side even at low-speed rotation.

[0029] On the other hand, FIG. 3B shows a state that the fluid flows into a conventional spiral-shaped dynamic pressure generation mechanism 12. In a case of the spiral-shaped dynamic pressure generation 12, the difference between the angle α at which the fluid flows into the dynamic pressure generation mechanism 12 and an angle θ 2 of the inlet opening 11a of the dynamic pressure generation mechanism 12 is very large, and therefore a loss in inflow when the fluid flows into the dynamic pressure generation mechanism 12 is very large. Therefore, a pumping action for sucking the fluid into the sliding surface S from the leakage side is not generated till at high-speed rotation.

[0030] Thus, the sliding member having the dynamic pressure generation mechanism 11 according to the present invention can exhibit a pumping action even at low-speed rotation (around 10rpm) and suck the fluid from the leakage side when the rotating-side sealing ring 3 begins to rotate, and can push back, to the sealed fluid side, the sealed fluid that is likely to leak to the low-pressure fluid side, and therefore it is possible to improve sealing performance. Specifically, the angle θ 1 between the inner circumferential edge 5b of the sliding surface S and the inlet opening 11a of the dynamic pressure generation mechanism 11 is 0° ≤ θ 1 ≤ 45°, preferably 0° ≤ θ 1 ≤ 10°, and therefore it is possible to extremely reduce a loss in inflow when the fluid flows into the dynamic pressure generation mechanism 11. Here, θ 1 corresponds to ϕ 0 in Formula 2.

[0031] Moreover, since the dynamic pressure generation mechanism 11 exhibits a pumping action even at low-speed, even when dynamic pressure by the dynamic pressure generation mechanism 11 is not sufficiently generated at low-speed, positive pressure can be generated by a wedge effect at the toe part 11b of the dynamic pressure generation mechanism 11, and therefore it is possible to maintain the sliding surface S at a fluid lubrication state even at low-speed rotation.

[0032] As described above, the sliding member according to the present invention exhibits the following effects. 1. Since the shape of the dynamic pressure generation mechanism 11 is set such that the curvature thereof is increased in proportion to the flow path length of the dynamic pressure generation mechanism 11 from the inlet opening 11a, the difference between the angle α at which the fluid flows into the dynamic pressure generation mechanism 11 and the inlet angle of the inlet opening 11a of the dynamic pressure generation mechanism 11 can be set extremely small, and therefore it is possible to extremely reduce a loss in inflow when the fluid flows into the dynamic pressure generation mechanism 11. Moreover, the circumferential velocity u of the fluid within the dynamic pressure generation mechanism 11 is efficiently converted into the radial velocity Vp toward the flow path downstream side, and therefore it is possible to generate a pumping action for sucking the fluid into the sliding surface S from the leakage side even at low-speed rotation. 2. The dynamic pressure generation mechanism 11 is set to have the shape in Formulas (1) to (3), thereby capable of easily designing the dynamic pressure generation mechanism 11 with low loss. 3. Since the dynamic pressure generation mechanism 11 exhibits a pumping action even at low-speed, even when dynamic pressure by the dynamic pressure generation mechanism 11 is not sufficiently generated at low-speed, positive pressure can be generated by a wedge effect at the toe part 11b of the dynamic pressure generation mechanism 11, and therefore it is possible to maintain the sliding surface S at a fluid lubrication state even at low-speed rotation.

[0033] Hereinbefore, although the embodiment of the present invention has been described by the drawings, its specific configuration is not limited to the embodiment, and any changes and additions made without departing from the scope of the appended claims are included in the present invention.

[0034] In the above embodiment, the dynamic pressure generation mechanism 11 is made up of the groove portion, but the present invention is not limited thereto. For example, the dynamic pressure generation mechanism may be made up of a pseudo flow path in which minute dimples are arranged adjacent to each other.

[0035] Although the outer circumferential side is described as the sealed fluid side and the inner circumferential side is described as the leakage side, the present invention is not limited thereto, and is also applicable to a case where the inner circumferential side is the sealed fluid side and the outer circumferential side is the leakage side. For example, the inlet opening 11a of the dynamic pressure generation mechanism 11 is assumed as the outer circumferential edge of the sliding surface, and ϕ v and ϕ u are set within the ranges of -2 ≤ ϕ v ≤ 0 and -1 ≤ ϕ u ≤ 0, thereby capable of defining the dynamic pressure generation mechanism 11.

[0036] Moreover, the dynamic pressure generation mechanism 11 is provided on the sliding surface S of the stationary-side sealing ring 5, but may be provided on the sliding surface S of the rotating-side sealing ring 3.Reference Signs List

[0037] 1 mechanical seal 2 sleeve 3 rotating-side sealing ring 5 stationary-side sealing ring 6 coiled wave spring 7 bellows 8 packing 9 casing 10 rotating shaft 11 dynamic pressure generation mechanism 11a inlet opening 11b toe part 12 dynamic pressure generation mechanism S sliding surface

Claims

1. A pair of sliding members (3, 5) that slide relative to each other on sliding surfaces (S), wherein: at least one of the sliding surfaces (S) includes a dynamic pressure generation mechanism (11), the dynamic pressure generation mechanism (11) is an arcuate groove portion which is convexed or concaved toward the leakage side of the sliding surface (S), communicates with a leakage side via an inlet opening (11a) opened to a circumferential edge (5b) on the leakage side, and has a toe part (11b) surrounded by a land portion at the sealed fluid side and thus is isolated from the sealed fluid side, the dynamic pressure generation mechanism (11) extends from the inlet opening (11a) toward a downstream side of a rotating direction of an opposing sliding surface, and the curvature of the dynamic pressure generation mechanism (11) continuously increases according to the flow path length toward the toe part (11b) from the inlet opening (11a) of the dynamic pressure generation mechanism (11).

2. The pair of sliding members (3, 5) according to claim 1, characterized in that the angle between a circumferential edge of the sliding surface (S) and the inlet opening (11a) of the dynamic pressure generation mechanism (11) is set to from 0° to 45°.

3. The pair of sliding members (3, 5) according to claim 1 or 2, characterized in that the shape of the dynamic pressure generation mechanism (11) is represented by the following formulas: P = P 0 + h ∫ 0 S e jϕ dS ϕ = ϕ 0 + ϕ v S + ϕ u S 2 S = s h 0 < S < 1 where P is a position vector of a point on the dynamic pressure generation mechanism (11), P0 is a position vector of the inlet opening (11a) of the dynamic pressure generation mechanism (11), s is a flow path length from P0 to P, h is an entire length of the flow path of the dynamic pressure generation mechanism (11), S is what s is normalized by h, φ is a tangential angle at P, i = √-1 is an imaginary unit, φ0 is a tangential angle at P0, φv is an increment of the tangential angle to φ0 in h in a circular arc of the length h having φ0, and φu is an increment of the tangential angle to φv in h.

4. The pair of sliding members (3, 5) according to any one of claims 1 to 3, characterized in that the dynamic pressure generation mechanism (11) is such that one end communicates with a leakage side and the other end is surrounded by a land portion.

5. The pair of sliding members (3, 5) according to any one of claims 1 to 3, characterized in that the dynamic pressure generation mechanism (11) is such that one end is surrounded by a land portion and the other end communicates with a sealed fluid side.

6. The pair of sliding members (3, 5) according to any one of claims 1 to 3, characterized in that the dynamic pressure generation mechanism (11) is surrounded by a land portion.

7. The pair of sliding members (3, 5) according to any one of claims 1 to 6, characterized in that the dynamic pressure generation mechanism (11) is made of a groove portion.

8. The pair of sliding members (3, 5) according to any one of claims 1 to 6, characterized in that the dynamic pressure generation mechanism (11) is a pseudo flow path made of a dimple group consisting of a plurality of dimples.