Mechanical seal

Abstract

Provided is a sliding member in which leakage of a fluid to be sealed is reduced and sliding surfaces can be equally separated from each other. A supply hole (10b) for supplying a spacer fluid (G) between the sliding surfaces (11, 21) is formed in at least one of the sliding surfaces (11, 21) of the pair of seal rings (10, 20), an introduction groove (23) that overlaps the supply hole (10b) in the axial direction and extends in the circumferential direction is formed in the sliding surface (21), and branch grooves (24, 25) extend from the introduction groove (23). The groove volume of the branch groove (25) extending to the leakage side (S2) is smaller than the groove volume of the branch groove (24) extending to the sealed fluid side (S1).

Description

Technical Field

[0001] The present invention relates to relatively rotating sliding parts, for example, to a mechanical seal used in a shaft sealing device for sealing a rotating shaft of a rotating machine in an automobile, general industrial machinery, or other sealing fields. Background Art

[0002] As a shaft sealing device that prevents leakage of a sealed fluid, for example, a mechanical seal includes a pair of annular sliding members that rotate relative to each other and slide against each other. In recent years, for environmental reasons, it has been desired to reduce the energy lost due to sliding in such mechanical seals.

[0003] For example, the mechanical seal disclosed in Patent Document 1 has a fluid supply passage formed in a stationary seal ring, connecting the sealing surface with an external fluid supply source. Furthermore, the rotating seal ring is provided with: a circumferentially extending fluid guide groove, into which a gas such as nitrogen is introduced from the fluid supply passage; a plurality of dynamic pressure generating grooves extending from the fluid guide groove toward the high-pressure side; and a plurality of dynamic pressure generating grooves extending from the fluid guide groove toward the low-pressure side.

[0004] When gas is supplied from the fluid supply source, it flows into the fluid guide grooves and, through the dynamic pressure-generating grooves on the high- and low-pressure sides, is evenly distributed as static pressure in the circumferential and radial directions between the opposing sliding surfaces. This static pressure separates the sliding surfaces from each other. Furthermore, during relative rotation, dynamic pressure is generated in the dynamic pressure-generating grooves in addition to the static pressure, further separating the sliding surfaces and effectively reducing friction during relative rotation.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-022834 (page 6, Figure 3 ) Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In a mechanical seal such as that disclosed in Patent Document 1, while the dynamic pressure-generating grooves on the high-pressure and low-pressure sides generate substantially equal static and dynamic pressures in the circumferential and radial directions between the opposing sliding surfaces, thus maintaining a balanced separation between the sliding surfaces, the structure is susceptible to gas leakage from the low-pressure dynamic pressure-generating grooves to the low-pressure side. Consequently, there is a risk that the sealed fluid on the high-pressure side will leak into the low-pressure space along with the gas that leaks from the low-pressure dynamic pressure-generating grooves between the sliding surfaces.

[0010] The present invention has been made in view of such problems, and an object of the present invention is to provide a sliding component that reduces leakage of a sealed fluid and enables sliding surfaces to be separated from each other in a balanced manner.

[0011] Means for solving problems

[0012] In order to solve the above-mentioned problems, the mechanical seal of the present invention is arranged between a housing and a rotating shaft rotating relative to the housing, and a stationary sealing ring fixed to the housing side and a rotating sealing ring fixed to the rotating shaft side rotate relative to each other. The mechanical seal divides the sealed fluid space from the leakage space, and a supply hole for providing an isolation fluid between the sliding surfaces is formed on the sliding surface of at least one of a pair of the sealing rings, and an inlet groove is formed on the sliding surface of at least one of the pair of the sealing rings, which overlaps with the supply hole in the axial direction and extends circumferentially, wherein branch grooves extend from the inlet groove to the sealed fluid side and the leakage side respectively, and the groove volume of the branch groove extending to the leakage side is smaller than the groove volume of the branch groove extending to the sealed fluid side.

[0013] Thus, sufficient barrier fluid is supplied to the branch grooves extending toward the sealed fluid side, and a small amount of barrier fluid is supplied to the branch grooves extending toward the leakage side, thereby reducing leakage of the sealed fluid and achieving balanced separation between the sliding surfaces.

[0014] The average groove depth of the branch grooves extending toward the leakage side may be shallower than the average groove depth of the branch grooves extending toward the sealed fluid side.

[0015] As a result, the opening area of ​​the branch groove facing the mating seal ring can be ensured to be large, making it easier to separate the sliding surfaces from each other.

[0016] A radial end portion of the branch groove extending toward the leakage side may be located at a position radially farther from the introduction groove than a radial end portion of the branch groove extending toward the sealed fluid side.

[0017] This allows pressure to be generated over a wide range in the radial direction on the leakage side.

[0018] The branch groove extending toward the leakage side and the branch groove extending toward the sealed fluid side may communicate with the introduction groove.

[0019] Thus, the barrier fluid can be reliably introduced from the introduction groove into the two branch grooves to separate the sliding surfaces from each other.

[0020] Alternatively, the introduction groove is in an endless ring shape.

[0021] This allows for balanced pressure generation in the circumferential direction, allowing the sliding surfaces to be separated stably. Furthermore, during rotation, dynamic pressure is less likely to be generated locally in the circumferential direction of the guide groove.

[0022] The branch groove may include a dynamic pressure generating portion extending in a relative rotation direction of the pair of seal rings.

[0023] Thus, in addition to the static pressure of the isolation fluid, the buoyancy force between the sliding surfaces is enhanced by utilizing the dynamic pressure generated during the relative rotation.

[0024] An end portion of the dynamic pressure generating portion of the branch groove extending toward the leakage side may extend toward the introduction groove side.

[0025] This can reduce leakage of the sealed fluid into the space on the leakage side together with the spacer fluid leaking from the end of the dynamic pressure generating portion of the branch groove extending toward the leakage side.

[0026] The radial width between the end of the dynamic pressure generating portion of the branch groove extending toward the leakage side and the leakage side may be greater than the radial width between the end of the dynamic pressure generating portion and the introduction groove.

[0027] This can further reduce the sealed fluid from leaking into the space on the leakage side together with the spacer fluid leaking from the tip of the branch groove extending toward the leakage side. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a longitudinal sectional view showing an example of a mechanical seal according to Example 1 of the present invention.

[0029] Figure 2 This is a diagram showing the sliding surface of the rotary seal ring of Example 1 as viewed from the axial direction.

[0030] Figure 3 yes Figure 2 A partial enlarged view of .

[0031] Figure 4 It is a cross-sectional view along line AA.

[0032] Figure 5 (a) is a cross-sectional view along line BB, Figure 5 (b) is a cross-sectional view along line CC.

[0033] Figure 6 (a) is a schematic diagram showing the state of static pressure acting on the sliding surface. Figure 6 (b) is a schematic diagram showing the state of dynamic pressure acting on the sliding surface.

[0034] Figure 7This is a diagram of the introduction groove and the branch groove according to Example 2 of the present invention as viewed from the axial direction.

[0035] Figure 8 This is a diagram showing the introduction groove and branch grooves according to Example 3 of the present invention as viewed from the axial direction.

[0036] Figure 9 This is a diagram showing the introduction groove and branch grooves according to Example 4 of the present invention as viewed from the axial direction.

[0037] Figure 10 This is a diagram showing the introduction groove and branch grooves according to Example 5 of the present invention as viewed from the axial direction.

[0038] Figure 11 This is a diagram of the introduction groove and the branch groove according to Example 6 of the present invention as viewed from the axial direction.

[0039] Figure 12 This is a diagram of the introduction groove and the branch groove according to Example 7 of the present invention as viewed from the axial direction. DETAILED DESCRIPTION

[0040] Hereinafter, modes for implementing the mechanical seal of the present invention will be described based on examples.

[0041] Example 1

[0042] Reference Figures 1 to 6 The mechanical seal of Example 1 will be described.

[0043] Figure 1 The mechanical seal shown is an inside type mechanical seal that seals a sealed fluid F that leaks from the outer diameter side to the inner diameter side of a sliding surface.

[0044] Specifically, a sealed fluid F exists in the outer space S1 of the mechanical seal, and atmosphere A exists in the inner space S2. In this embodiment, the outer diameter side of the sliding member constituting the mechanical seal is described as the sealed fluid space side (high-pressure side), and the inner diameter side is described as the leakage space side (low-pressure side). Furthermore, for ease of explanation, grooves formed on the sliding surface are sometimes indicated with dots in the drawings.

[0045] The mechanical seal mainly consists of an annular rotating seal ring 20, which serves as one seal ring, and an annular stationary seal ring 10, which serves as the other seal ring. The rotating seal ring 20 is mounted on the rotating shaft 1 via a sleeve 2, so that it can rotate along 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 be mounted, so that it does not rotate but can move in the axial direction.

[0046] Two O-rings 5 ​​are axially spaced apart between the housing 4 and the stationary seal ring 10. The housing 4 is formed with a through-hole 4a extending radially therethrough. The inner opening of the through-hole 4a communicates with a space 6 defined by the housing 4, the stationary seal ring 10, and the two O-rings 5, while the outer opening of the through-hole 4a communicates with an external static pressure gas supply source 9. Furthermore, a cover 8 is secured to the housing 4, located on the side of the stationary seal ring 10 opposite the rotating seal ring 20.

[0047] 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, and the sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotating seal ring 20 slide in close contact with each other.

[0048] Furthermore, the stationary seal ring 10 is formed with a plurality of passages 10a extending from the outer peripheral surface to the sliding surface 11 in the circumferential direction. The openings at one end of the passages 10a communicate with the space 6, while the openings at the other end, i.e., the supply holes 10b, communicate with the introduction grooves 23 (described later) of the rotary seal ring 20. Furthermore, the sliding surface 11 of the stationary seal ring 10 is formed as a flat surface except for the supply holes 10b.

[0049] The stationary seal ring 10 and the rotating seal ring 20 are typically formed from a combination of SiC (hard material) and SiC (hard material) or a combination of SiC (hard material) and carbon (soft material), but are not limited to these. Any sliding material that can be used as a sliding material for mechanical seals can be used. SiC includes materials composed of two or more phases with different components and compositions, such as sintered bodies containing boron, aluminum, carbon, etc. as sintering aids. Examples include SiC with dispersed graphite particles, reaction-sintered SiC composed of SiC and Si, SiC-TiC, and SiC-TiN. Carbon includes resin-molded carbon and sintered carbon, such as carbon mixed with carbonaceous and graphite. In addition to the aforementioned sliding materials, metal materials, resin materials, surface-modified materials (coating materials), and composite materials can also be used.

[0050] like Figure 2 and Figure 3 As shown, the rotary seal ring 20 is slidable clockwise and counterclockwise relative to the stationary seal ring 10 as the counterpart seal ring. Figure 2 and Figure 3 The solid arrows and dashed arrows in FIG. 1 show the relative rotation direction of the stationary seal ring 10 relative to the rotating seal ring 20. Figure 2 and Figure 3 The direction of the solid arrow is called the forward direction, and the direction of the dotted arrow is called the reverse direction.

[0051] The sliding surface 21 of the rotary seal ring 20 is provided with an introduction groove 23, outer-diameter-side dynamic pressure generating mechanisms 24, 24', which are branch grooves extending toward the sealed fluid, and inner-diameter-side dynamic pressure generating mechanisms 25, 25', which are branch grooves extending toward the leakage side. The area outside the introduction groove 23, outer-diameter-side dynamic pressure generating mechanisms 24, 24', and inner-diameter-side dynamic pressure generating mechanisms 25, 25' is a flat land portion 22. The inner diameter portion of the rotary seal ring 20, into which the sleeve 2 fits, is not shown.

[0052] The introduction groove 23 is provided concentrically with the rotary seal ring 20. That is, the introduction groove 23 is in the shape of an endless circular ring.

[0053] On the outer diameter side of the introduction groove 23 , sets of outer diameter side dynamic pressure generating mechanisms 24 , 24 ′ (for example, eight sets in this embodiment) are evenly arranged in the circumferential direction.

[0054] The outer diameter-side dynamic pressure generating mechanism 24 has a so-called Rayleigh step shape and is composed of a radial groove 24A and a circumferential groove 24B, which serves as a dynamic pressure generating portion. The radial groove 24A extends radially outward from the introduction groove 23. The circumferential groove 24B extends from the outer diameter end of the radial groove 24A in the forward rotation direction, approximately parallel to the introduction groove 23.

[0055] The outer diameter side dynamic pressure generating mechanism 24' is arranged in the reverse direction away from the outer diameter side dynamic pressure generating mechanism 24. The outer diameter side dynamic pressure generating mechanism 24' is symmetrical with the outer diameter side dynamic pressure generating mechanism 24 with reference to the radially extending line α.

[0056] On the inner diameter side of the introduction groove 23 , sets of inner diameter side dynamic pressure generating mechanisms 25 , 25 ′ (for example, eight sets in this embodiment) are evenly arranged in the circumferential direction.

[0057] The inner diameter side dynamic pressure generating mechanism 25 has a so-called Rayleigh step shape and is composed of a radial groove 25A and a circumferential groove 25B serving as a dynamic pressure generating portion. The radial groove 25A extends radially inward from the introduction groove 23. The circumferential groove 25B extends from the inner diameter end of the radial groove 25A in the forward rotation direction, approximately parallel to the introduction groove 23.

[0058] The inner diameter side dynamic pressure generating mechanism 25' is arranged in the reverse direction away from the inner diameter side dynamic pressure generating mechanism 25. The inner diameter side dynamic pressure generating mechanism 25' is symmetrical with the inner diameter side dynamic pressure generating mechanism 25 with reference to the radially extending line α.

[0059] like Figure 4 As shown, the depth D1 of the introduction groove 23 is the same as the depth D2 of the radial groove 24A of the outer diameter side dynamic pressure generating mechanism 24 ( D1 = D2 ).

[0060] Furthermore, the depth D2 of the radial groove 24A is deeper than the depth D3 of the radial groove 25A of the inner diameter side dynamic pressure generating mechanism 25 (D2>D3). Specifically, the depth D3 is approximately 1 / 2 times the depth D2.

[0061] like Figure 5 As shown in FIG. 2( a ), the bottom surface 24 b of the circumferential groove 24B is an inclined surface that gradually becomes shallower from the bottom surface 24 a of the radial groove 24A toward the land portion 22 .

[0062] And, as Figure 5 As shown in FIG. 2( b ), the bottom surface 25 b of the circumferential groove 25B is an inclined surface that gradually becomes shallower from the bottom surface 25 a of the radial groove 25A toward the land portion 22 .

[0063] return Figure 3 The circumferential length L1 of the circumferential groove 24B is substantially the same as the circumferential length L2 of the circumferential groove 25B ( L1 = L2 ).

[0064] That is, the groove volumes V25 and V25' of the inner diameter side dynamic pressure generating mechanisms 25 and 25' are smaller than the groove volumes V24 and V24' of the outer diameter side dynamic pressure generating mechanisms 24 and 24' (V24=V24'>V25=V25').

[0065] Furthermore, a radial separation width L4 between the circumferential groove 25B and the introduction groove 23 is longer than a radial separation width L3 between the circumferential groove 24B and the introduction groove 23 ( L3 < L4 ).

[0066] 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.

[0067] When the static pressure gas G as the isolation fluid is supplied from the static pressure gas supply source 9, the static pressure gas G is introduced into the introduction groove 23 of the rotating seal ring 20 (see FIG. Figure 1 ). In addition, the static pressure gas G is at a higher pressure than the sealed fluid F.

[0068] like Figure 6 As shown in (a), the static-pressure gas G introduced into the inlet groove 23 flows into the outer-diameter-side dynamic pressure generating mechanisms 24, 24' and the inner-diameter-side dynamic pressure generating mechanisms 25, 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. This static pressure acts not only on the inlet groove 23 but also on the outer-diameter-side dynamic pressure generating mechanisms 24, 24' and the inner-diameter-side dynamic pressure generating mechanisms 25, 25' that branch radially from the inlet groove 23, thereby achieving a balanced separation between the sliding surfaces 11 and 21.

[0069] And, as Figure 6 As shown in (b), when the sliding surfaces 11 and 21 rotate relative to each other in the forward direction, the static pressure gas G within the outer diameter-side dynamic pressure generating mechanisms 24 and 24' and the inner diameter-side dynamic pressure generating mechanisms 25 and 25' moves in the forward direction. This generates dynamic pressure near the end 24c of the circumferential groove 24B and near the end 25c of the circumferential groove 25B. In other words, in addition to the static pressure of the static pressure gas G, dynamic pressure also acts on the sliding surfaces 11 and 21, thereby further separating the sliding surfaces 11 and 21 from each other. Furthermore, although some relative negative pressure is generated in the outer diameter-side dynamic pressure generating mechanisms 24' and the inner diameter-side dynamic pressure generating mechanisms 25', the static pressure of the static pressure gas G dominates.

[0070] As mentioned above, the groove volume of the outer diameter side dynamic pressure generating mechanism 24, 24' is larger than the groove volume of the inner diameter side dynamic pressure generating mechanism 25, 25', so that sufficient static pressure gas G can flow out from the outer diameter side dynamic pressure generating mechanism 24, 24' to between the sliding surfaces 11, 21, and the sealed fluid F flowing into between the sliding surfaces 11, 12 can be suppressed from moving toward the inner diameter side.

[0071] On the other hand, the outer diameter side dynamic pressure generating mechanisms 24, 24' are supplied with a smaller amount of static pressure gas G than the inner diameter side dynamic pressure generating mechanisms 25, 25', so the static pressure gas G is less likely to leak into the inner space S2. Therefore, the sealed fluid F is less likely to leak into the inner space S2 along with the static pressure gas G.

[0072] Furthermore, the groove volumes V25 and V25' of the inner-diameter-side dynamic pressure generating mechanisms 25 and 25' are smaller than the groove volumes V24 and V24' of the outer-diameter-side dynamic pressure generating mechanisms 24 and 24', respectively. The opening areas of the inner-diameter-side dynamic pressure generating mechanisms 25 and 25' are approximately the same as those of the outer-diameter-side dynamic pressure generating mechanisms 24 and 24'. The average depth of the inner-diameter-side dynamic pressure generating mechanisms 25 and 25' is shallower than that of the outer-diameter-side dynamic pressure generating mechanisms 24 and 24'. This ensures a large opening area of ​​the inner-diameter-side dynamic pressure generating mechanisms 25 and 25' facing the sliding surface 11, facilitating balanced separation of the sliding surfaces 11 and 21.

[0073] Furthermore, the outer diameter side dynamic pressure generating mechanisms 24 , 24 ′ and the inner diameter side dynamic pressure generating mechanisms 25 , 25 ′ are connected to the introduction groove 23 , so that the static pressure gas G can be reliably introduced from the introduction groove 23 to the outer diameter side dynamic pressure generating mechanisms 24 , 24 ′ and the inner diameter side dynamic pressure generating mechanisms 25 , 25 ′.

[0074] Furthermore, the separation width L4 between the circumferential groove 25B and the introduction groove 23 is longer than the separation width L3 between the circumferential groove 24B and the introduction groove 23 (L3 < L4). In other words, the inner diameter-side dynamic pressure generating mechanisms 25 and 25' extend radially farther from the introduction groove 23 than the outer diameter-side dynamic pressure generating mechanisms 24 and 24'. This allows pressure to be generated over a wider radial range on the inner space S2 side. Furthermore, to enable pressure to be generated over a wider radial range on the leakage side, the separation width L4 is preferably longer than the separation width L3, but this is not limiting. The separation width L4 may also be less than the separation width L3 (L3 ≥ L4).

[0075] Furthermore, since the introduction groove 23 is annular, it is possible to generate pressure evenly in the circumferential direction, stably separating the sliding surfaces 11 and 21. Furthermore, dynamic pressure is less likely to be generated locally in the circumferential direction of the introduction groove 23 during relative rotation.

[0076] Furthermore, during forward rotation, dynamic pressure can be generated by the outer-diameter-side dynamic pressure generating mechanism 24 and the inner-diameter-side dynamic pressure generating mechanism 25, while during reverse rotation, dynamic pressure can be generated by the outer-diameter-side dynamic pressure generating mechanism 24' and the inner-diameter-side dynamic pressure generating mechanism 25'. In other words, dynamic pressure can be generated regardless of the direction of rotation of the rotary seal ring 20.

[0077] In the present embodiment, the depth D3 of the radial groove 25A is exemplified as being approximately 1 / 2 times the depth D2 of the radial groove 24A. However, the depth D3 can be freely changed as long as it is shallower than the depth D2.

[0078] Furthermore, in the present embodiment, an example is shown in which the depth D1 of the introduction groove 23 is the same as the depth D2 of the radial groove 24A, but these can be freely changed.

[0079] Furthermore, in this embodiment, the bottom surfaces 24b and 25b of the circumferential grooves 24B and 25B are inclined surfaces, but they may also be stepped shapes that become shallower toward the front end. Furthermore, the depth of the circumferential grooves 24B and 25B may be constant along the circumferential direction.

[0080] Furthermore, in this embodiment, the outer diameter side dynamic pressure generating means 24, 24' and the inner diameter side dynamic pressure generating means 25, 25' are constituted by radial grooves and circumferential grooves. However, for example, spiral grooves having circumferential and radial components may be used.

[0081] Example 2

[0082] Next, refer to Figure 7 A mechanical seal according to Example 2 will be described. Note that redundant descriptions of the same structures as those of Example 1 will be omitted.

[0083] like Figure 7As shown, in the rotary seal ring 220 of the second embodiment, the shapes of the inner diameter side dynamic pressure generating mechanisms 225 and 225' are different from those of the inner diameter side dynamic pressure generating mechanisms 25 and 25' of the first embodiment, but the structure otherwise is the same as that of the first embodiment. The inner diameter side dynamic pressure generating mechanisms 225 and 225' have substantially the same structure, so only the inner diameter side dynamic pressure generating mechanism 225 will be described.

[0084] The end portion 225 c , which is the front end of the circumferential groove 225B of the inner diameter side dynamic pressure generating mechanism 225 , extends toward the introduction groove 223 .

[0085] Specifically, the distal end of the circumferential groove 225B is bent so as to incline radially outward. The distance L10 between the end 225c of the circumferential groove 225B and the introduction groove 223 is shorter than the distance L11 between the end 225c of the circumferential groove 225B and the inner circumferential surface 220a of the rotary seal ring 220 ( L10 < L11 ). In other words, the end 225c of the circumferential groove 225B is positioned closer to the introduction groove 223.

[0086] As a result, during relative rotation, the static pressure gas G within the inner diameter side dynamic pressure generating mechanism 225 is guided to flow out from the end portion 225c of the circumferential groove 225B toward the introduction groove 223, thereby making it less likely for the static pressure gas G to leak into the inner space S2. Consequently, leakage of the sealed fluid F into the inner space S2 along with the static pressure gas G can be reduced.

[0087] In addition, in this second embodiment, the front end portion of the circumferential groove 225B is bent so as to be inclined toward the outer diameter side. However, the front end of the circumferential groove may also extend in an arc shape toward the outer diameter side. Furthermore, the circumferential groove is not limited to extending from the middle of the circumferential groove toward the lead-in groove so that the front end of the circumferential groove is close to the lead-in groove. The circumferential groove may also extend from the leakage side end of the radial groove toward the lead-in groove so that the front end of the circumferential groove is close to the lead-in groove.

[0088] Example 3

[0089] Next, refer to Figure 8 A mechanical seal according to Example 3 will be described. Note that redundant descriptions of the same structures as those of Example 1 will be omitted.

[0090] like Figure 8 As shown, the rotary seal ring 320 of the third embodiment is provided with a plurality of outer diameter side dynamic pressure generating mechanisms 324 and inner diameter side dynamic pressure generating mechanisms 325 in the circumferential direction, but the outer diameter side dynamic pressure generating mechanism 24 ′ and inner diameter side dynamic pressure generating mechanism 25 ′ of the first embodiment are not provided.

[0091] The outer diameter side dynamic pressure generating mechanism 324 is composed of a radial groove 324A and a circumferential groove 324B. The radial groove 324A and the circumferential groove 324B have a constant depth.

[0092] The inner diameter side dynamic pressure generating mechanism 325 is composed of radial grooves 325A and circumferential grooves 325B. The radial grooves 325A and circumferential grooves 325B have a constant depth. The depth of the inner diameter side dynamic pressure generating mechanism 325 is shallower than that of the outer diameter side dynamic pressure generating mechanism 324.

[0093] In this way, the mechanical seal of the present invention can also cope with only the forward rotation direction.

[0094] Example 4

[0095] Next, refer to Figure 9 A mechanical seal according to Example 4 will be described. Note that redundant descriptions of the same structures as those of Example 1 will be omitted.

[0096] like Figure 9 As shown, in the rotary seal ring 420 of the fourth embodiment, the radial groove 424A of the outer-diameter dynamic pressure generating mechanism 424 and the radial groove 425A of the inner-diameter dynamic pressure generating mechanism 425 are not connected to the introduction groove 423. The outer-diameter dynamic pressure generating mechanism 424' and the inner-diameter dynamic pressure generating mechanism 425' also have substantially the same structure.

[0097] Specifically, the radial width L20 of the land portion 422a that separates the radial groove 424A from the introduction groove 423 is shorter than the radial width L22 of the introduction groove 423 (L20<L22). The radial width L20 only needs to be shorter than the radial width L22, and is preferably 1 / 5 times or less.

[0098] Similarly, radial width L21 of land portion 422b that separates radial groove 425A from introduction groove 423 is shorter than radial width L22 of introduction groove 423 (L21<L22). Radial width L21 only needs to be shorter than radial width L22, and may be preferably 1 / 5 times or less.

[0099] As a result, the static pressure gas G passes over the land portions 422 a and 422 b and is supplied from the introduction groove 423 to the outer diameter side dynamic pressure generating mechanism 424 and the inner diameter side dynamic pressure generating mechanism 425 .

[0100] Thus, in the mechanical seal of the present invention, the branch groove extending from the inlet groove only needs to allow the static pressure gas to substantially move between the inlet groove and the branch groove. As in this embodiment, the branch groove may not communicate with the inlet groove.

[0101] Example 5

[0102] Next, refer to Figure 10 A mechanical seal according to Example 5 will be described. Note that duplicate descriptions of the same structures as those of Example 1 will be omitted.

[0103] like Figure 10 As shown, the rotary seal ring 520 of the fifth embodiment includes an inlet groove 523, a plurality of outer diameter branch grooves 524 extending radially outward from the inlet groove 523, and a plurality of inner diameter branch grooves 525 extending radially inward from the inlet groove 523. The inner diameter branch grooves 525 are shallower than the outer diameter branch grooves 524.

[0104] During relative rotation, dynamic pressure is generated near the circumferential side surfaces of the outer diameter side branch groove 524 and the inner diameter side branch groove 525. Thus, the branch grooves do not need to have a portion extending in the circumferential direction.

[0105] In addition, in this embodiment 5, a method of generating dynamic pressure near the circumferential side surfaces of the outer diameter side branch groove 524 and the inner diameter side branch groove 525 is illustrated, but these branch grooves can also be formed deeper so that no dynamic pressure is generated during relative rotation.

[0106] Example 6

[0107] Next, refer to Figure 11 A mechanical seal according to Example 6 will be described. Note that redundant descriptions of the same structures as those of Example 1 will be omitted.

[0108] like Figure 11 As shown, in the rotary seal ring 620 of the sixth embodiment, the introduction groove 623 is divided at one point in the circumferential direction. Thus, the introduction groove 623 is not limited to a circular groove, but may also be substantially C-shaped.

[0109] Furthermore, the introduction groove is not limited to the C-shape, and may be divided into a plurality of parts in the circumferential direction, or may be an annular wave shape or an annular polygonal shape.

[0110] Example 7

[0111] Next, refer to Figure 12 A mechanical seal according to Example 7 will be described. Note that redundant descriptions of the same structures as those of Example 1 will be omitted.

[0112] The mechanical seal to which the rotary seal ring 720 of the seventh embodiment is applied is an outer-type mechanical seal that allows the atmosphere A to communicate with the outer space S1 of the sliding surface 721 and seals the sealed fluid F on the inner space S2 side.

[0113] In the seventh embodiment, the groove capacities of the outer diameter side dynamic pressure generating mechanisms 724 and 724 ′ are smaller than the groove capacities of the inner diameter side dynamic pressure generating mechanisms 725 and 725 ′.

[0114] As described above, the mechanical seal of the present invention can also be used in an environment where 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.

[0115] While 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 modifications and additions within the scope that do not depart from the gist of the present invention are also included in the present invention.

[0116] For example, in the above-mentioned embodiments 1 to 7, the mechanical seal for industrial machinery was described as an example, but other mechanical seals such as those for automobiles may also be used.

[0117] Furthermore, in the above-mentioned embodiments 1 to 7, the sealed fluid is described as a high-pressure gas, but the present invention is not limited thereto and may be a liquid or a low-pressure gas, or may be a mist mixture of liquid and gas.

[0118] Furthermore, in the aforementioned embodiments 1 to 7, the case where the fluid on the leakage space side is the atmosphere as a low-pressure gas is described, but it is not limited to this. As long as it is at a lower pressure than the sealed fluid, it can also be a liquid or a high-pressure gas, or it can be a mist mixed with liquid and gas.

[0119] Furthermore, in the above-described embodiments 1 to 7, the sealed fluid space side is described as the high-pressure side and the leakage space side as the low-pressure side. However, the sealed fluid space side and the leakage space side may be at substantially the same pressure.

[0120] Furthermore, in the above-mentioned embodiments 1 to 7, the barrier fluid is supplied from the stationary seal ring to the sliding surfaces. However, the barrier fluid may also be supplied from the rotating seal ring. Furthermore, the supply hole and the introduction groove may be formed in the same seal ring.

[0121] Furthermore, while the aforementioned embodiments 1 to 7 illustrate the provision of an introduction groove and a branching groove on the rotating seal ring, the introduction groove and the branching groove may also be provided on the stationary seal ring. Alternatively, one of the introduction groove and the branching groove may be provided on the rotating seal ring, while the other may be provided on the stationary seal ring. Furthermore, the branching groove, which serves as the dynamic pressure generating portion, may have a spiral shape, in addition to a Rayleigh step.

[0122] Description of labels

[0123] 9: Static pressure gas supply source; 10: Stationary sealing ring (sealing ring on the other side); 11: Sliding surface; 20: Rotating sealing ring (sealing ring on one side); 21: Sliding surface; 23: Inlet groove; 24, 24': Outer diameter side dynamic pressure generating mechanism (the branch groove extending toward the leakage side); 25, 25': Inner diameter side dynamic pressure generating mechanism (branch groove extending toward the sealed fluid side); A: Atmosphere; F: Sealed fluid; G: Static pressure gas (isolating fluid); S1: External space (space on the sealed fluid side); S2: Internal space (space on the leakage side).

Claims

1. A mechanical seal disposed between a housing and a rotating shaft that rotates relative to the housing, wherein a stationary seal ring fixed to the housing and a rotating seal ring fixed to the rotating shaft rotate relative to each other, the mechanical seal partitioning a sealed fluid space from a leakage space, wherein a supply hole for supplying an isolation fluid between the sliding surfaces is formed on the sliding surface of at least one of the pair of seal rings, and an introduction groove is formed on the sliding surface of at least one of the pair of seal rings, overlapping the supply hole in the axial direction and extending in the circumferential direction. in, Branch grooves extend from the inlet groove to the sealed fluid side and the leakage side respectively. A groove volume of the branch groove extending toward the leakage side is smaller than a groove volume of the branch groove extending toward the sealed fluid side.

2. The mechanical seal according to claim 1, wherein: An average groove depth of the branch grooves extending toward the leakage side is shallower than an average groove depth of the branch grooves extending toward the sealed fluid side.

3. The mechanical seal according to claim 1, wherein: A radial end portion of the branch groove extending toward the leakage side is located at a position radially farther from the introduction groove than a radial end portion of the branch groove extending toward the sealed fluid side.

4. The mechanical seal according to claim 1, wherein: The branch groove extending toward the leakage side and the branch groove extending toward the sealed fluid side communicate with the introduction groove.

5. The mechanical seal according to any one of claims 1 to 4, wherein: The introduction groove is in an endless ring shape.

6. The mechanical seal according to claim 1, wherein: The branch groove has a dynamic pressure generating portion extending in a relative rotation direction of the pair of seal rings.

7. The mechanical seal according to claim 6, wherein: An end portion of the dynamic pressure generating portion of the branch groove extending toward the leakage side extends toward the introduction groove side.

8. The mechanical seal according to claim 7, wherein: The radial width between the end of the dynamic pressure generating portion of the branch groove extending toward the leakage side and the leakage side is greater than the radial width between the end of the dynamic pressure generating portion and the introduction groove.

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