Mechanical seal

Abstract

Provided are sliding components capable of reducing leakage of a sealed fluid and arranging sliding surfaces to be spaced apart from each other in a balanced manner.　On at least one sliding surface 11 of a pair of sealing rings 10, 20, a supply hole 10b for supplying a barrier fluid G to between the sliding surfaces 11, 21 is formed. On the sliding surface 21, an introducing groove 23 which overlaps the supply hole 10b in an axial direction and extends in a circumferential direction is formed, and a bypass groove 25 of which both ends 252, 253 in the circumferential direction extend toward the introducing groove 23 is formed on a leakage side S2 from the introducing groove 23.

Description

[Technical Field]

[0001] The present invention relates to a sliding component that rotates relative to one another, and more particularly to a mechanical seal used in a shaft sealing device that seals the rotating shaft of a rotary machine in, for example, an automobile, general industrial machinery, or other sealing fields. [Background technology]

[0002] Mechanical seals, for example, are shaft sealing devices that prevent leakage of sealed fluids and are equipped with a pair of annular sliding components that rotate relative to one another and have sliding surfaces that slide against each other. In recent years, there has been a demand for reducing the energy lost due to sliding in such mechanical seals, for environmental reasons.

[0003] For example, in the mechanical seal shown in Patent Document 1, a fluid supply passage is formed in the stationary seal ring, connecting the seal surface with an external fluid supply source. The rotary seal ring is also provided with a fluid guide groove extending in the circumferential direction into which a gas such as nitrogen gas is introduced from the fluid supply passage, a plurality of dynamic pressure generating grooves extending from the fluid guide groove to the high pressure side, and a plurality of dynamic pressure generating grooves extending from the fluid guide groove to the low pressure side.

[0004] When gas is supplied from the fluid supply source, the gas flows into the fluid guide groove and is uniformly distributed as static pressure in the circumferential and radial directions between the relative sliding surfaces by the dynamic pressure generating grooves on the high-pressure and low-pressure sides, and this static pressure can separate the sliding surfaces. Furthermore, during relative rotation, dynamic pressure is generated in the dynamic pressure generating grooves in addition to the static pressure, so the sliding surfaces can be further separated from each other, effectively reducing friction that occurs during relative rotation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-022834 A (page 6, Figure 3) Summary of the Invention [Problem to be solved by the invention]

[0006] In a mechanical seal such as that disclosed in Patent Document 1, the dynamic pressure generating grooves on the high-pressure and low-pressure sides generate static and dynamic pressures approximately uniformly in the circumferential and radial directions between the opposing sliding surfaces, thereby separating the sliding surfaces in a balanced manner, but the configuration makes it easy for gas to leak from the dynamic pressure generating groove on the low-pressure side to the low-pressure side, which raises the risk of gas leaking from the dynamic pressure generating groove on the low-pressure side between the sliding surfaces and the sealed fluid on the high-pressure side leaking into the space on the low-pressure side.

[0007] The present invention has been made in view of these problems, and has as its object to provide a sliding component which reduces leakage of sealed fluid and can separate sliding surfaces in a balanced manner. [Means for solving the problem]

[0008] In order to solve the above problems, the mechanical seal of the present invention comprises: A mechanical seal is disposed between a housing and a rotary shaft that rotates relative to the housing, wherein a stationary seal ring fixed to the housing and a rotary seal ring fixed to the rotary shaft rotate relative to each other, separating a sealed fluid space from a leakage space, A mechanical seal in which a supply hole for supplying a barrier fluid between the sliding surfaces is formed in at least one of the sliding surfaces of the pair of seal rings, and an introduction groove overlapping with the supply hole in the axial direction and extending in the circumferential direction is formed in at least one of the sliding surfaces of the pair of sliding rings, A bypass groove is formed on the leakage side of the introduction groove, with both circumferential ends extending toward the introduction groove. With this, the bypass groove extending from the leakage side toward the introduction groove recovers the fluid on the leakage side of the introduction groove, thereby reducing leakage of the sealed fluid and enabling the sliding surfaces to be spaced apart in a balanced manner.

[0009] The bypass groove may have inclined portions at both ends in the circumferential direction, and the inclined portion on the upstream side in the relative rotation direction may be inclined upstream in the relative rotation direction toward the introduction groove, and the inclined portion on the downstream side in the relative rotation direction may be inclined downstream in the relative rotation direction toward the introduction groove. This makes it easy to introduce and extract the barrier fluid between the bypass groove and the introduction groove. In addition, because a positive pressure is generated at the leakage side end of the upstream inclined portion and a negative pressure is generated at the downstream inclined portion, the leakage side is also lifted in a balanced manner, and the fluid flowing out to the leakage side is easily collected.

[0010] A peripheral portion extending in the circumferential direction may be provided between the upstream inclined portion and the downstream inclined portion in the circumferential direction. With this, the circumferentially extending peripheral portion becomes the negative pressure generating portion, so that the fluid that flows out to the leakage side from the introduction groove when the pair of sliding rings rotates relative to each other can be more easily recovered.

[0011] Both ends of the bypass groove may be in communication with the introduction groove. With this, the barrier fluid can be introduced from the introduction groove into the bypass groove when the pair of sliding rings are rotating relative to each other or when they are stationary, thereby separating the sliding surfaces from each other.

[0012] A branch groove may extend from the introduction groove toward the sealed fluid side. This allows pressure to be generated in a well-balanced manner in the radial direction, and the sliding surfaces can be stably separated from each other.

[0013] The branch groove may have a dynamic pressure generating portion extending in the direction of relative rotation of the pair of seal rings. This improves the lifting force between the sliding surfaces due to the dynamic pressure generated during relative rotation in addition to the static pressure of the barrier fluid. Also, since a large amount of barrier fluid can be discharged to the sealed fluid side, leakage of the sealed fluid into the leakage side space can be suppressed.

[0014] The branch groove may be disposed between both ends of the bypass groove in the circumferential direction. According to this, the bypass groove and the branch groove are provided at positions where they overlap in the radial direction, so that the sliding surfaces can be separated from each other more stably.

[0015] The introduction groove may be an endless ring. This allows pressure to be generated in a well-balanced manner in the circumferential direction, enabling the sliding surfaces to be stably separated from each other. Furthermore, during rotation, dynamic pressure is less likely to be generated locally in the circumferential direction of the introduction groove. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a vertical cross-sectional view showing an example of a mechanical seal according to a first embodiment of the present invention. [Figure 2] 3 is a view of the sliding surface of the rotary seal ring in the first embodiment as viewed from the axial direction. FIG. [Figure 3] FIG. 3 is a partially enlarged view of FIG. 2. [Figure 4] (a) is a cross-sectional view taken along the line AA, and (b) is a cross-sectional view taken along the line BB. [Figure 5] FIG. 2(a) is a schematic diagram showing the state of static pressure acting on the sliding surface in Example 1, and FIG. 2(b) is a schematic diagram showing the state of dynamic pressure acting on the sliding surface in Example 1. [Figure 6] FIG. 10 is a view of the sliding surface of the rotary seal ring in the second embodiment according to the present invention, as viewed from the axial direction. [Figure 7] FIG. 7 is a partially enlarged view of FIG. 6. [Figure 8] (a) is a CC cross-sectional view, and (b) is a DD cross-sectional view. [Figure 9] 10(a) is a schematic diagram showing the state of static pressure acting on the sliding surface in Example 2, and (b) is a schematic diagram showing the state of dynamic pressure acting on the sliding surface in the same manner. [Figure 10] FIG. 10 is a view of an introduction groove and branch grooves in a third embodiment according to the present invention, as viewed from the axial direction. [Figure 11] FIG. 10 is a view of an introduction groove and branch grooves in a fourth embodiment according to the present invention, as viewed from the axial direction. [Figure 12]FIG. 10 is a view of an introduction groove and branch grooves in a fifth embodiment according to the present invention, as viewed from the axial direction. [Figure 13] FIG. 13 is a view of an introduction groove and branch grooves in a sixth embodiment according to the present invention, as viewed from the axial direction. [Figure 14] FIG. 13 is a view of an introduction groove and branch grooves in a seventh embodiment of the present invention, as viewed from the axial direction.

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mechanical seal according to the present invention will be described below with reference to the following examples. Example 1

[0018] A mechanical seal according to a first embodiment will be described with reference to FIGS. 1 to 5. FIG.

[0019] The mechanical seal shown in FIG. 1 is an inside type that seals against a sealed fluid F that attempts to leak from the outer diameter side to the inner diameter side of the sliding surface.

[0020] Specifically, the sealed fluid F exists in the outer space S1 of the mechanical seal, and the atmosphere A exists in the inner space S2. In this embodiment, the outer diameter side of the sliding components constituting the mechanical seal will be described as the sealed fluid space side (high pressure side), and the inner diameter side will be described as the leakage space side (low pressure side). For ease of explanation, grooves formed on the sliding surfaces may be marked with dots in the drawings.

[0021] The mechanical seal is mainly composed of a stationary seal ring 10 as the other annular sliding ring, and a rotary seal ring 20 as one annular sliding ring. The rotary seal ring 20 is mounted on the rotating shaft 1 via a sleeve 2 so as to be rotatable together with the rotating shaft 1. The stationary seal ring 10 is mounted on the inner diameter side of the housing 4 of the device to which it is attached so as to be non-rotating and movable in the axial direction.

[0022] Two O-rings 5 ​​are arranged axially spaced apart between the housing 4 and the stationary seal ring 10. A through-hole 4a is formed in the housing 4, penetrating it in the radial direction. The inner diameter opening of the through-hole 4a communicates with a space 6 partitioned by the housing 4, the stationary seal ring 10, and the two O-rings 5, and the outer diameter opening of the through-hole 4a communicates with a static pressure gas supply source 9 arranged externally. In addition, a cover 8 is fixed to the housing 4, and is arranged on the opposite side of the stationary seal ring 10 from the rotary seal ring 20.

[0023] An elastic member 7 is disposed between the cover 8 and the stationary seal ring 10. The stationary seal ring 10 is biased in the axial direction by the elastic member 7, so that the sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotating seal ring 20 slide closely against each other.

[0024] Additionally, the stationary seal ring 10 is formed with a plurality of passages 10a in the circumferential direction, extending from the outer peripheral surface to the sliding surface 11. The opening on one end of the passages 10a communicates with the space 6, and the opening on the other end, a supply hole 10b, communicates with an introduction groove 23 (described later) of the rotary seal ring 20. The sliding surface 11 of the stationary seal ring 10 is configured as a flat surface except for the supply holes 10b.

[0025] The stationary seal ring 10 and the rotating seal ring 20 are typically formed from a combination of SiC (hard material) or SiC (hard material) and carbon (soft material), but this is not limited thereto; any sliding material used 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 graphite materials, resin-molded carbon, and sintered carbon. In addition to the above sliding materials, metal materials, resin materials, surface-modified materials (coating materials), and composite materials are also applicable.

[0026] 2 and 3, the rotary seal ring 20 is able to slide clockwise and counterclockwise relative to the mating seal ring, the stationary seal ring 10. The solid arrows and chain arrows in Figures 2 and 3 indicate the relative rotation direction of the stationary seal ring 10 with respect to the rotary seal ring 20. Note that hereinafter, the direction of the solid arrows in Figures 2 and 3 may be referred to as the forward rotation direction, and the direction of the chain arrows as the reverse rotation direction.

[0027] The sliding surface 21 of the rotary seal ring 20 is provided with an introduction groove 23 and a plurality of bypass grooves 25. The areas other than the introduction groove 23 and the bypass groove 25 form a flat land 22. Furthermore, the portion of the inner diameter part of the rotary seal ring 20 where the sleeve 2 fits is not shown in the figure.

[0028] The introduction groove 23 is provided concentrically with the rotary seal ring 20. That is, the introduction groove 23 has an endless annular shape.

[0029] On the inner diameter side of the introduction groove 23, bypass grooves 25 are arranged at equal intervals in the circumferential direction (for example, eight in this embodiment).

[0030] The bypass groove 25 has a generally U-shape when viewed in the axial direction. Specifically, the bypass groove 25 is composed of a circumferential portion 251 and inclined portions 252 and 253. The bypass groove 25 has an overall shape in which the circumferential length is longer than the radial length.

[0031] The circumferential portion 251 extends in the circumferential direction at a position spaced radially inward from the introduction groove 23. The circumferential portion 251 is substantially parallel to the introduction groove 23.

[0032] The inclined portions 252, 253 extend from both ends of the circumferential portion 251 in directions away from each other toward the introduction groove 23. The inclined portions 252, 253 are connected to the introduction groove 23. More specifically, the inclined portion 252 is located upstream in the forward rotation direction. The inclined portion 252 has a pair of walls in the circumferential direction. This pair of walls extends linearly from the circumferential portion 251 toward the introduction groove 23 in the radial direction and from the circumferential portion 251 toward the upstream side in the forward rotation direction in the circumferential direction. That is, the inclined portion 252 extends linearly from the circumferential portion 251 toward the introduction groove 23, inclined toward the upstream side in the forward rotation direction. The inclined portion 253 is located downstream in the forward rotation direction. The inclined portion 253 has a pair of walls in the circumferential direction. This pair of walls extends linearly from the circumferential portion 251 toward the introduction groove 23 in the radial direction and from the circumferential portion 251 toward the downstream side in the forward rotation direction in the circumferential direction. That is, the inclined portion 253 extends linearly from the circumferential portion 251 toward the introduction groove 23, inclining toward the downstream side in the forward rotation direction. During reverse rotation, the upstream and downstream sides of the inclined portions 252 and 253 are reversed, but the inclination direction remains the same. That is, the upstream inclined portion is inclined toward the upstream side, and the downstream inclined portion is inclined toward the downstream side. The pair of circumferential walls that make up the inclined portion 252 and the pair of circumferential walls that make up the inclined portion 253 may be other than straight, and may be, for example, curved, bent, or other shapes.

[0033] The bypass groove 25 has a symmetrical shape with respect to a line α that extends in the radial direction and passes through the circumferential center of the circumferential portion 251. In the following description, the line α that extends in the radial direction will be simply referred to as a radial line α.

[0034] 4(a), the depth D1 of the introduction groove 23 is deeper than the depth D2 of the inclined portion 253 (D1>D2). Specifically, the depth D1 is about twice the depth D2.

[0035] As shown in FIG. 4(b), the depth D2 of the inclined portion 253 is the same as the depth D2' of the circumferential portion 251 and the depth D2'' of the inclined portion 232 (D2=D2'=D2''). That is, the bypass groove 25 has a constant depth.

[0036] Next, the pressure acting on the sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotary seal ring 20 will be described.

[0037] When static pressure gas G is supplied as a barrier fluid from the static pressure gas supply source 9, the static pressure gas G passes through the through hole 4a of the housing 4, the space 6, the passage 10a of the stationary seal ring 10, and the supply hole 10b, and is introduced into the introduction groove 23 of the rotary seal ring 20 (see FIG. 1). Note that the static pressure gas G is at a higher pressure than the sealed fluid F.

[0038] As shown in Fig. 5(a), the static pressure gas G introduced into the introduction groove 23 flows into each bypass groove 25. As a result, the static pressure of the static pressure gas G acts on the sliding surfaces 11 and 21, separating the sliding surfaces 11 and 21 in the axial direction. In this way, the static pressure of the static pressure gas G acts not only on the introduction groove 23 but also on the bypass grooves 25 branching off from the introduction groove 23 in the radial direction, so that the sliding surfaces 11 and 21 can be separated in a balanced manner. In addition, the static pressure of the static pressure gas G can prevent the sealed fluid F flowing between the sliding surfaces 11 and 21 from moving toward the inner diameter side.

[0039] 5(b), when the sliding surfaces 11, 21 rotate relative to each other in the forward rotation direction, the static pressure gas G in the introduction groove 23 and the bypass groove 25 moves in the forward rotation direction. In the bypass groove 25, the static pressure gas G flows from the introduction groove 23 into the inclined portion 252, flows through the circumferential portion 251 and the inclined portion 253, and then returns to the introduction groove 23.

[0040] The flow of the static pressure gas G in the bypass groove 25 due to this shearing makes it possible to recover the fluid on the inner diameter side of the introduction groove 23, making it difficult for the static pressure gas G to leak into the internal space S2. Therefore, the sealed fluid F is unlikely to leak into the internal space S2 together with the static pressure gas G.

[0041] Specifically, a relative negative pressure is generated in the inclined portion 253 and the circumferential portion 251 located downstream of the bypass groove 25 because the fluid in the inclined portion 253 is drawn into the flow of the static pressure gas G in the introduction groove 23, which is the main stream. On the other hand, the static pressure gas G in the introduction groove 23 flows into the inclined portion 252 located upstream of the bypass groove 25, so the relative pressure is higher there than in the inclined portion 253 and the circumferential portion 251. As a result, in the bypass groove 25, the circumferential portion 251, where a relative negative pressure is generated, easily recovers the fluid in its vicinity. Note that, although the relative negative pressure in the circumferential portion 251 and the inclined portion 253 is higher than that in the inclined portion 252, the static pressure of the static pressure gas G in the introduction groove 23 and the inclined portion 252 is dominant, and therefore this has almost no effect on the force separating the sliding surfaces 11 and 21.

[0042] Furthermore, the flow of the static pressure gas G in the bypass groove 25 is relatively faster in the circumferential portion 251 than in the inclined portions 252 and 253. This is because the extension direction of the inclined portions 252 and 253 intersects with the direction of the shear force, and the influence of the shear force is relatively smaller in the inclined portions 252 and 253 than in the circumferential portion 251. Also, the flow in the inclined portion 252 is obstructed by the bending point between the inclined portion 252 and the circumferential portion 251. In addition, the flow in the inclined portion 253 is obstructed by the static pressure in the introduction groove 23. For these reasons, the flow in the inclined portions 252 and 253 is slower than in the circumferential portion 251.

[0043] Furthermore, the inclined portion 252 of the bypass groove 25 is inclined in the reverse rotation direction from the circumferential portion 251 toward the introduction groove 23, and the inclined portion 253 is inclined in the forward rotation direction from the circumferential portion 251 toward the introduction groove 23. Therefore, during forward rotation, the static pressure gas G is easily introduced from the introduction groove 23 to the inclined portion 252, and the static pressure gas G is easily discharged from the inclined portion 253 to the introduction groove 23. Furthermore, dynamic pressure is generated at the leakage-side end 252a of the inclined portion 252 on the upstream side in the forward rotation direction, i.e., near the bending point between the inclined portion 252 and the circumferential portion 251, so that the leakage side can also be floated in a balanced manner.

[0044] Furthermore, since the static pressure gas G returns from the inner diameter side of the introduction groove 23 toward the introduction groove 23, the static pressure gas G is less likely to leak from the inner space S2.

[0045] Moreover, since the inclined portions 252, 253 communicate with the introduction groove 23, it is easy to introduce and release the static pressure gas G between the inclined portions 252, 253 and the introduction groove 23. Furthermore, even when the sliding movement of the sliding surfaces 11, 21 relative to each other is stopped, the static pressure gas G can be introduced from the introduction groove 23 into the bypass groove 25, so the sliding surfaces 11, 21 can be separated from each other.

[0046] Furthermore, the inclined portions 252, 253 extend linearly and have no inflection points, allowing the static pressure gas G to flow smoothly inside the inclined portions 252, 253. Therefore, dynamic pressure is less likely to be generated near the inclined portions 252, 253 during relative rotation, and leakage of the static pressure gas G into the internal space S2 can be reduced.

[0047] Furthermore, because the introduction groove 23 has an annular shape, pressure is generated in a well-balanced manner in the circumferential direction, and it is possible to stably separate the sliding surfaces 11, 21. Furthermore, during relative rotation, dynamic pressure is unlikely to be generated locally in the circumferential direction of the introduction groove 23.

[0048] Furthermore, since the bypass groove 25 has a symmetrical shape with respect to the radial line α, the fluid recovery ability of the bypass groove 25 does not change depending on the rotational direction of the rotary seal ring 20. Furthermore, during reverse rotation, dynamic pressure can be generated at the leakage side end 253a of the inclined portion 253 on the upstream side in the reverse rotation direction, i.e., near the bending point between the inclined portion 253 and the circumferential portion 251.

[0049] In this embodiment, the depth D1 of the introduction groove 23 is approximately twice the depth D2 of the inclined portion 253, but these depths can be freely changed. For example, the depth D2 may be the same as or deeper than the depth D1.

[0050] Furthermore, in this embodiment, the bypass groove 25 has a constant depth, but it may have different depths in the extending direction.

[0051] In addition, in this embodiment, both ends of the circumferential portion 251 are the inclined portions 252, 253, but both ends of the circumferential portion 251 may extend in the radial direction.

[0052] Furthermore, in this embodiment, the bypass groove 25 has been exemplified as having a symmetrical shape with respect to the longitudinal line α, but it may have an asymmetrical shape with respect to the longitudinal line. Example 2

[0053] Next, a mechanical seal according to a second embodiment will be described with reference to Figures 6 to 9. Note that a description of the same configuration as in the first embodiment will be omitted.

[0054] 6 and 7, a sliding surface 221 of a rotary seal ring 220 of the second embodiment is provided with an introduction groove 223, outer diameter side dynamic pressure generating mechanisms 224, 224' which are branch grooves, and a bypass groove 225. The introduction groove 223 and the bypass groove 225 have the same configuration as the introduction groove 23 and the bypass groove 25 of the first embodiment.

[0055] Sets of outer diameter side dynamic pressure generating mechanisms 224, 224' are equally spaced in the circumferential direction (e.g., eight sets in this embodiment) on the outer diameter side of the introduction groove 223. The outer diameter side dynamic pressure generating mechanisms 224, 224' are arranged between the inclined portions 225A, 225B at both ends of the bypass groove 225 in the circumferential direction.

[0056] The outer diameter side dynamic pressure generating mechanism 224 has a so-called Rayleigh step shape and is composed of a radial groove 224A and a circumferential groove 224B that serves as a dynamic pressure generating portion. The radial groove 224A extends in the outer diameter direction from the introduction groove 223. The circumferential groove 224B extends in the forward rotation direction from the outer diameter end of the radial groove 224A, substantially parallel to the introduction groove 223.

[0057] Furthermore, the outer diameter side dynamic pressure generating mechanism 224' is disposed at a distance in the opposite rotational direction from the outer diameter side dynamic pressure generating mechanism 224. The outer diameter side dynamic pressure generating mechanism 224' has a symmetrical shape to the outer diameter side dynamic pressure generating mechanism 224 with respect to the radial line α.

[0058] As shown in FIG. 8(a), the depth D10 of the introduction groove 223 is the same as the depth D20 of the radial groove 224A of the outer diameter side dynamic pressure generating mechanism 224 (D10=D20).

[0059] Furthermore, the depth D20 of the radial groove 224A is deeper than the depth D30 of the bypass groove 225 (D20>D30). Specifically, the depth D30 is about half the depth D20. Note that the depth D30 can be freely changed as long as it is shallower than the depth D20.

[0060] As shown in FIG. 8(b), the bottom surface 224b of the circumferential groove 224B is an inclined surface that gradually becomes shallower from the bottom surface 224a of the radial groove 224A toward the land 222.

[0061] 9(a), the static pressure gas G introduced into the introduction groove 223 flows into each of the outer diameter side dynamic pressure generating mechanisms 224, 224' and each of the bypass grooves 225. As a result, the static pressure of the static pressure gas G acts on the sliding surfaces 11 and 21, separating the sliding surfaces 11 and 21 in the axial direction. In this way, the static pressure of the static pressure gas G acts not only on the introduction groove 223 but also on each of the outer diameter side dynamic pressure generating mechanisms 224, 224' and each of the bypass grooves 225 that branch off radially from the introduction groove 23, so that the sliding surfaces 11 and 21 can be separated in a balanced manner.

[0062] 9(b), when the sliding surfaces 11, 21 rotate relative to each other in the forward rotation direction, the static pressure gas G in the introduction groove 223, the outer diameter side dynamic pressure generating mechanisms 224, 224', and the bypass groove 225 moves in the forward rotation direction. As a result, dynamic pressure is generated near the end 224c of the circumferential groove 224B and near the leakage side end 225a of the inclined portion 225A on the upstream side of the bypass groove 225 in the forward rotation direction, i.e., near the intersection of the inclined portion 225A and the circumferential portion 225C, and the fluid around the bypass groove 225 can be recovered. That is, in addition to the static pressure of the static pressure gas G, dynamic pressure also acts on the sliding surfaces 11, 21 on both the sealed fluid side and the leakage side of the introduction groove 223, so that the sliding surfaces 11, 21 can be further separated from each other.

[0063] Furthermore, since the groove volumes V224, V224' of the outer diameter side dynamic pressure generating mechanisms 224, 224' are larger than the groove volume V225 of the bypass groove 225, sufficient static pressure gas G can be discharged from one side of the outer diameter side dynamic pressure generating mechanisms 224, 224' to between the sliding surfaces 11, 21, and the sealed fluid F flowing between the sliding surfaces 11, 21 can be prevented from moving toward the inner diameter side.

[0064] Furthermore, the outer diameter side dynamic pressure generating mechanisms 224, 224' are disposed between the inclined portions 225A, 225B at both ends of the bypass groove 225. In other words, the outer diameter side dynamic pressure generating mechanisms 224, 224' and the bypass groove 225 are provided at positions where they overlap in the radial direction. This allows pressure to be generated at positions where they overlap in the radial direction, so that the sliding surfaces 11, 21 can be separated from each other more stably.

[0065] During forward rotation, dynamic pressure is generated by the outer diameter side dynamic pressure generating mechanism 224, and during reverse rotation, dynamic pressure can be generated by the outer diameter side dynamic pressure generating mechanism 224' and the leakage side end 225b of the inclined portion 225B on the upstream side during reverse rotation of the bypass groove 225, i.e., near the intersection of the inclined portion 225B and the circumferential portion 225C. In other words, dynamic pressure can be generated regardless of the rotation direction of the rotary seal ring 220.

[0066] In this second embodiment, an example is given in which the outer diameter side dynamic pressure generating mechanisms 224, 224' are arranged between the inclined portions 225A, 225B at both ends of the bypass groove 225, but the branch groove may be arranged circumferentially offset from the bypass groove.

[0067] In addition, in the second embodiment, the outer diameter side dynamic pressure generating mechanisms 224, 224′ are configured with the radial grooves 224A and the circumferential grooves 224B, but may be, for example, spiral grooves having circumferential and radial components. Also, the branch grooves may be configured only with radial grooves. Example 3

[0068] Next, the mechanical seal according to Example 3 will be described with reference to FIG. 10. The description of the same configuration as that of Example 2 will be omitted.

[0069] As shown in FIG. 10, in the rotary seal ring 320 of the present Example 3, the radial grooves 324A, 324A' of the outer diameter side dynamic pressure generating mechanisms 324, 324' and the inclined portions 325A, 325B at both ends of the bypass groove 325 are not in communication with the introduction groove 323. The outer diameter side dynamic pressure generating mechanisms 324, 324' of the present Example are formed to have a constant depth.

[0070] Specifically, the radial width L40 of the land 322a partitioning between the radial groove 324A and the introduction groove 323 is shorter than the radial width L50 of the introduction groove 323 (L40 < L50). The radial width L40 only needs to be shorter than the radial width L50, and preferably, it is 1 / 5 times or less.

[0071] Similarly, the radial width L41 of the land 322b partitioning between the inclined portions 325A, 325B and the introduction groove 323 is shorter than the radial width L50 of the introduction groove 323 (L41 < L50). The radial width L41 only needs to be shorter than the radial width L50, and preferably, it is 1 / 5 times or less.

[0072] According to this, the static pressure gas G is supplied from the introduction groove 423 to the outer diameter side dynamic pressure generating mechanisms 324, 324' and the bypass groove 325 across the lands 322a, 322b.

[0073] In this way, in the mechanical seal of the present invention, the branch groove and the bypass groove whose both ends are connected to the introduction groove only need to be such that the static pressure gas can move between the introduction groove, the branch groove, and the bypass groove. Even if the branch groove and the bypass groove are not in communication with the introduction groove as in the present Example, it is acceptable.

Example 4

[0074] Next, the mechanical seal according to Example 4 will be described with reference to FIG. 11. The description of the same configuration as that of Example 2 will be omitted.

[0075] As shown in FIG. 11, in the rotary seal ring 420 of the fourth embodiment, the bypass groove 425 is V-shaped when viewed in the axial direction.

[0076] Specifically, the bypass groove 425 has an apex 425C provided at approximately the center in the circumferential direction, and the inclined portions 425A and 425B extend in directions away from each other toward the introduction groove 423. That is, the bypass groove 425 of the fourth embodiment does not have the circumferential portion 251 of the first embodiment.

[0077] As described above, the mechanical seal of the present invention only needs to allow the barrier fluid to move between the introduction groove and the bypass groove, and the shape of the bypass groove can be freely changed as in this embodiment. Example 5

[0078] Next, a mechanical seal according to a fifth embodiment will be described with reference to Fig. 12. Note that the description of the same configuration as in the second embodiment will be omitted.

[0079] As shown in FIG. 12, the rotary seal ring 520 of the fifth embodiment is provided with an outer diameter side dynamic pressure generating mechanism 524, and is not provided with the outer diameter side dynamic pressure generating mechanism 224' of the second embodiment.

[0080] In this way, the mechanical seal of the present invention may be adapted to only the forward rotation direction. Example 6

[0081] Next, a mechanical seal according to a sixth embodiment will be described with reference to Fig. 13. Note that a description of the same configuration as in the second embodiment will be omitted.

[0082] 13, in the rotary seal ring 620 of this sixth embodiment, the introduction groove 623 is divided at one location in the circumferential direction. In this way, the introduction groove 623 is not limited to an annular groove, and may be substantially C-shaped.

[0083] The introduction groove is not limited to a C-shape, but may be divided into a plurality of grooves in the circumferential direction, or may have an annular wave shape or an annular angular shape. Example 7

[0084] Next, a mechanical seal according to a seventh embodiment will be described with reference to Fig. 14. Note that a description of the same configuration as in the second embodiment will be omitted.

[0085] The mechanical seal to which the rotary seal ring 720 of this seventh embodiment is applied is an outside type in which the atmosphere A communicates with the outer space S1 of the sliding surface 721 and the sealed fluid F is sealed on the inner space S2 side.

[0086] In this seventh embodiment, the dynamic pressure generating mechanisms 724 and 724 ′ are disposed on the inner diameter side of the introduction groove 723 , and the bypass groove 725 is disposed on the outer diameter side of the introduction groove 723 .

[0087] In this way, the mechanical seal of the present invention may be applied to an environment in which the sealed fluid space is located on the inner diameter side of the sliding surface and the leakage space is located on the outer diameter side of the sliding surface.

[0088] 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.

[0089] For example, in the above-described first to seventh embodiments, the mechanical seal for industrial machinery has been described as an example, but other mechanical seals such as those for automobiles may also be used.

[0090] In addition, in the above-described embodiments 1 to 7, the sealed fluid is described as a high-pressure gas, but it is not limited to this and may be a liquid or a low-pressure gas, or a mist-like mixture of liquid and gas.

[0091] In addition, in the above-described Examples 1 to 7, the fluid on the leakage space side was described as being atmospheric air, which is a low-pressure gas, but this is not limited thereto, and the fluid may be a liquid or a high-pressure gas, or a mist-like mixture of liquid and gas, as long as it has a lower pressure than the sealed fluid.

[0092] In addition, in the above-described first to seventh embodiments, the sealed fluid space side is the high pressure side and the leakage space side is the low pressure side, but the sealed fluid space side and the leakage space side may be at approximately the same pressure.

[0093] In addition, in the above-described Examples 1 to 7, the barrier fluid is supplied between the sliding surfaces from the stationary seal ring side, but the barrier fluid may be supplied between the sliding surfaces from the rotating seal ring side. Note that the supply hole and the introduction groove may be formed in the same seal ring.

[0094] In addition, in the above-described Examples 1 to 7, the rotary seal ring is provided with an inlet groove and a bypass groove, but the inlet groove and the bypass groove may be provided on the stationary seal ring, or the rotary seal ring may be provided with one of the inlet groove and the bypass groove, and the stationary seal ring may be provided with the other of the inlet groove and the bypass groove. Furthermore, the branch groove may be provided on either the stationary seal ring or the rotary seal ring. Furthermore, the branch groove having the dynamic pressure generating portion may be a spiral shape other than a Rayleigh step.

[0095] In the above-described Examples 1 to 7, the bypass groove has both ends formed by inclined portions, but for example, both ends of the bypass groove may extend radially from both ends of the circumferential portion and form approximately right angles with the circumferential portion. [Explanation of symbols]

[0096] 9. Static gas supply source 10 Stationary seal ring (other seal ring) 11 Sliding surface 20 Rotating seal ring (one of the seal rings) 21 Sliding surface 23 Introduction groove 25 Bypass ditch 224,224' Outer diameter dynamic pressure generating mechanism (branch groove) A. Atmosphere F Sealed fluid G Hydrostatic gas (barrier fluid) S1 Outside space (sealed fluid side space) S2 internal space (leak side space)

Claims

1. A mechanical seal is disposed between a housing and a rotary shaft that rotates relative to the housing, wherein a stationary seal ring fixed to the housing and a rotary seal ring fixed to the rotary shaft rotate relative to each other, separating a sealed fluid space from a leakage space, A mechanical seal in which a supply hole for supplying a barrier fluid between the sliding surfaces is formed in at least one of the sliding surfaces of the pair of seal rings, and an introduction groove overlapping with the supply hole in the axial direction and extending in a circumferential direction is formed in at least one of the sliding surfaces of the pair of sliding rings, The mechanical seal has a bypass groove formed on the leakage side of the introduction groove, the bypass groove having both circumferential ends extending toward the introduction groove.

2. 2. The mechanical seal according to claim 1, wherein the bypass groove has inclined portions at both ends in the circumferential direction, the inclined portion on the upstream side in the relative rotation direction inclining upstream in the relative rotation direction toward the introduction groove, and the inclined portion on the downstream side in the relative rotation direction inclining downstream in the relative rotation direction toward the introduction groove.

3. The mechanical seal according to claim 2, wherein a peripheral portion extending in the circumferential direction is provided between the upstream inclined portion and the downstream inclined portion in the circumferential direction.

4. 4. The mechanical seal according to claim 1, wherein both ends of said bypass groove communicate with said introduction groove.

5. 2. The mechanical seal according to claim 1, wherein a branch groove extends from said introduction groove toward the sealed fluid side.

6. 6. The mechanical seal according to claim 5, wherein the branch groove has a dynamic pressure generating portion extending in the direction of relative rotation of the pair of seal rings.

7. 6. The mechanical seal according to claim 5, wherein the branch groove is disposed between both ends of the bypass groove in the circumferential direction.

8. 2. The mechanical seal according to claim 1, wherein the introduction groove is an endless annular groove.

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