Mechanical seal

Abstract

A mechanical seal according to the present disclosure comprises: a stationary unit having a seal case that is fixed to a casing, and a stationary seal ring disposed in the seal case and divided in the circumferential direction; and a rotary seal ring that is integrally rotatably mounted on a rotary shaft surrounded by the casing and slides against the stationary seal ring. The stationary unit has an annular seal member that fastens the stationary seal ring from a radially outer side and seals a space between the seal case and the stationary seal ring to form a sealed space for sealing a fluid-to-be-sealed on the radially outer side of a sliding portion between the rotary seal ring and the stationary seal ring in the seal case.

Description

Mechanical seal

[0001] This application claims priority to Japanese Patent Application No. 2024-026432, filed February 26, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] A mechanical seal described in Patent Document 1 is known as a shaft sealing means used in large pumps and the like. This mechanical seal includes a rotary unit having a rotary seal ring that rotates with the rotary shaft, and a stationary unit having a stationary seal ring divided in the circumferential direction and fixed to the casing. The rotary seal ring and the stationary seal ring have sealing surfaces that come into close contact with each other. The stationary unit includes a holder that holds the stationary seal ring in a state in which it is tightened from the radially outward direction to prevent leakage of the sealed fluid from the divided parts of the stationary seal ring.

[0003] The stationary unit further includes a retainer and an O-ring for setting a balance ratio (the ratio between the force that tries to close the gap between the seal surfaces of the rotary seal ring and the stationary seal ring and the force that tries to open the gap between the seal surfaces). The retainer is positioned so as to press the stationary seal ring toward the rotary seal ring. The O-ring is attached to the outer peripheral surface of the retainer and seals between the retainer and the casing. The balance ratio is set by adjusting the radial position of the outer peripheral surface of the retainer (the attachment position of the O-ring) relative to the contact position between the seal surfaces of the rotary seal ring and the stationary seal ring. For this reason, the retainer is formed into a complex shape that takes the balance ratio into consideration.

[0004] Japanese Patent Application Laid-Open No. 2020-020424

[0005] The static unit of the mechanical seal needs to include not only the circumferentially divided stationary seal rings, but also a holder for holding the stationary seal rings, and a retainer and O-ring for setting the balance ratio, which increases the number of parts in the static unit and leads to an increase in manufacturing man-hours.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a mechanical seal that can simplify the configuration of a stationary unit that includes a stationary seal ring that is divided in the circumferential direction.

[0007] (1) A mechanical seal disclosed herein comprises a seal case fixed to a casing, a stationary unit disposed within the seal case and having a stationary seal ring divided circumferentially, and a rotary seal ring provided on a rotating shaft surrounded by the casing so as to be rotatable integrally with the rotating shaft and sliding on the stationary seal ring, wherein the stationary unit has an annular seal member that tightens the stationary seal ring from the radially outward direction and seals between the seal case and the stationary seal ring to form a sealed space that seals the sealed fluid radially outward of the sliding portion between the rotary seal ring and the stationary seal ring within the seal case.

[0008] According to the mechanical seal of the present disclosure, in a sealed space formed in a seal case for sealing the sealed fluid, fluid pressure from the sealed fluid acts on the seal members, which clamp the circumferentially divided stationary seal ring from the radially outward direction. This fluid pressure causes the seal members to deform and expand on both sides in the radial direction, thereby increasing the clamping force of the seal members against the stationary seal ring. Furthermore, since the fluid pressure from the sealed fluid acts directly on the stationary seal ring itself from the radially outward direction, this directly acting fluid pressure can further clamp the stationary seal ring from the radially outward direction. As a result, the stationary seal ring can be held in a state of being clamped from the radially outward direction without using a conventional holder. Therefore, the conventional holder is no longer necessary, simplifying the configuration of the stationary unit.

[0009] (2) In the mechanical seal of (1), the stationary seal ring preferably has a fitting surface formed on the outer periphery of the stationary seal ring, on which the seal member is fitted, and an annular seal end surface against which the rotary seal ring slides, and the outer diameter of the fitting surface is smaller than the outer diameter of the seal end surface and larger than the inner diameter of the seal end surface. In this case, when forming the stationary seal ring, the balance ratio can be set by setting the outer diameter of the fitting surface against which the seal member is fitted to be smaller than the outer diameter of the seal end surface and larger than the inner diameter. Therefore, the seal member that tightens the stationary seal ring also serves as the seal member for setting the balance ratio, further simplifying the configuration of the stationary unit.

[0010] (3) In the mechanical seal of (2), the stationary unit further includes an elastic member for pressing the stationary seal ring toward the rotary seal ring, and a transmission member interposed between the elastic member and the stationary seal ring for transmitting the pressing force of the elastic member to the stationary seal ring, the transmission member preferably being formed in an annular plate shape. In this case, the transmission member for transmitting the pressing force of the elastic member to the stationary seal ring is formed in an annular plate shape, so that the shape can be simpler than that of a conventional retainer for transmitting a pressing force to a stationary seal ring. As a result, the configuration of the stationary unit can be further simplified.

[0011] (4) In the mechanical seal of (3), the transmission member is preferably divided in the circumferential direction, which makes it easy to assemble the transmission member.

[0012] (5) In the mechanical seal of any one of (1) to (4), it is preferable that a notched groove for hooking a finger is formed on the inner periphery of the stationary seal ring. In this case, an operator can hook a finger into the notched groove when assembling the stationary seal ring. This allows the operator to easily assemble the stationary seal ring even when the gap between the inner periphery of the stationary seal ring and the outer periphery of the rotating shaft is narrow.

[0013] (6) In the mechanical seal of (5), the stationary unit further has a restricting member that engages with the stationary seal ring to restrict co-rotation of the stationary seal ring with the rotary seal ring, and an engagement groove into which the restricting member engages is formed on the inner periphery of the stationary seal ring, and the engagement groove is preferably the notched groove. In this case, the notched groove for hooking a finger also serves as the engagement groove into which the restricting member that restricts co-rotation of the stationary seal ring engages, further simplifying the configuration of the stationary unit.

[0014] According to the present disclosure, it is possible to simplify the configuration of a stationary unit that includes a stationary seal ring that is divided in the circumferential direction.

[0015] Fig. 1 is a cross-sectional view showing a mechanical seal according to an embodiment of the present disclosure; Fig. 2 is an enlarged cross-sectional view showing the periphery of a stationary seal ring; Fig. 3 is a front view of the stationary seal ring as viewed from the other axial side; Fig. 4 is a front view of a transmission member as viewed from the axial direction; Fig. 5 is a graph showing test results of a static pressure test; Fig. 6 is a graph showing test results of a rotation test;

[0016] Next, preferred embodiments will be described with reference to the accompanying drawings. [Overall Configuration] Fig. 1 is a cross-sectional view showing a mechanical seal according to an embodiment of the present disclosure. In Fig. 1, the mechanical seal 1 of this embodiment is a large-sized mechanical seal that seals a sealed fluid (solvent, water, oil, etc.) inside a large rotating device such as a pump or a mixer. The mechanical seal 1 is disposed along the axial direction of the rotating shaft 71 between a rotating shaft 71 of the rotating device and a casing 72 surrounding the rotating shaft 71.

[0017] Hereinafter, in this specification, the "axial direction" refers to the direction along the axis X of the rotating shaft 71. In addition, in this specification, the "radial direction" refers to the direction perpendicular to the axis X of the rotating shaft 71, and the "circumferential direction" refers to the direction around the axis X of the rotating shaft 71. In addition, in this specification, for convenience, the left side (outside the machine) in Fig. 1 will be referred to as one axial side, and the right side (inside the machine) in Fig. 1 will be referred to as the other axial side.

[0018] The mechanical seal 1 of this embodiment is a so-called inside-type mechanical seal. The mechanical seal 1 includes a rotating unit 2 that is integrally rotatable with a rotating shaft 71, and a stationary unit 3 that is mounted on a casing 72.

[0019] [Rotating Unit] The rotating unit 2 is disposed within a seal case 31 (described later) of the stationary unit 3. The rotating unit 2 includes a first retainer 11, a second retainer 12, a third retainer 13, and a rotary seal ring 14. The first retainer 11, the second retainer 12, and the third retainer 13 are each formed in an annular shape. The first retainer 11 is fitted into an annular groove 71a formed on the outer periphery of the rotating shaft 71. The first retainer 11 is fixed to the rotating shaft 71 by a plurality of set screws 15 being radially fastened therein.

[0020] The second retainer 12 and the third retainer 13 are fixed to the radially outer and inner sides, respectively, of one axial side of the first retainer 11. A seal (secondary seal) is formed between the first retainer 11 and the second retainer 12 by an O-ring 16. A seal (secondary seal) is formed between the first retainer 11 and the third retainer 13 by an O-ring 17.

[0021] The rotary seal ring 14 is held between the second retainer 12 and the third retainer 13 on one axial side of the first retainer 11. The rotary seal ring 14 is made of, for example, silicon carbide (SiC), which has excellent wear resistance and sealing performance. A seal end face 14a is formed on one axial side of the rotary seal ring 14. Relative rotation of the rotary seal ring 14 with respect to the first retainer 11 is restricted by a pin 18 fixed to the first retainer 11. An O-ring 19 provides a secondary seal between the rotary seal ring 14 and the second retainer 12.

[0022] [Stationary Unit] The stationary unit 3 includes a seal case 31 fixed to the casing 72. The seal case 31 has an annular first case body 311, a cylindrical second case body 312, an annular third case body 313, an annular fourth case body 314, and an annular fifth case body 315. The first case body 311 is fixed to the casing 72 by bolts 51 while abutting against one axial side of the casing 72. The inner peripheral surface of the first case body 311 is close to the outer peripheral surface of the rotating shaft 71. An O-ring 41 provides a seal (secondary seal) between the first case body 311 and the casing 72.

[0023] The second case body 312 and the third case body 313 are arranged in this order on one axial side of the first case body 311. The second case body 312 and the third case body 313 are fixed to the first case body 311 by bolts 52. An O-ring 42 seals (secondary seal) between the first case body 311 and the second case body 312. An O-ring 43 seals (secondary seal) between the second case body 312 and the third case body 313.

[0024] The inner diameter of the second case body 312 is larger than the outer diameter of the first retainer 11. The inner diameter of the third case body 313 is smaller than, for example, the outer diameter of the rotary seal ring 14. The rotary unit 2 is housed in an annular space formed between the first case body 311 and the third case body 313 and between the second case body 312 and the rotary shaft 71.

[0025] The fourth case body 314 and the fifth case body 315 are arranged in this order on one axial side of the third case body 313. The inner diameters of the fourth case body 314 and the fifth case body 315 are smaller than the inner diameter of the third case body 313. The inner peripheral surfaces of the fourth case body 314 and the fifth case body 315 are close to the outer peripheral surface of the rotating shaft 71.

[0026] The fourth case body 314 is fixed to the third case body 313 by bolts 53. An O-ring 44 provides a seal (secondary seal) between the third case body 313 and the fourth case body 314. The fourth case body 314 has a protruding portion 314b that protrudes along the inner circumferential surface of the third case body 313 toward the other axial direction. The protruding portion 314b is formed in a cylindrical shape. A notch 314a that opens toward one axial direction is formed on the inner periphery of the fourth case body 314. The notch 314a is formed in an annular shape around the entire circumference of the fourth case body 314.

[0027] The fifth case body 315 is fixed to the fourth case body 314 by bolts 54. An O-ring 45 provides a seal (secondary seal) between the fourth case body 314 and the fifth case body 315. A notch 315a that opens to the other axial side is formed on the inner periphery of the fifth case body 315. The notch 315a is formed in an annular shape around the entire circumference of the fifth case body 315. The notch 315a of the fifth case body 315 communicates with the notch 314a of the fourth case body 314.

[0028] The stationary unit 3 further includes a stationary seal ring 32 , a seal member 33 , a plurality of regulating members 34 , a plurality of elastic members 35 , a transmission member 36 , an adapter ring 37 , and a segment ring 38 arranged in the seal case 31 .

[0029] Figure 2 is an enlarged cross-sectional view showing the periphery of the stationary seal ring 32. Figure 3 is a front view of the stationary seal ring 32 as viewed from the other axial side. In Figures 2 and 3, the stationary seal ring 32 is disposed radially inward of the third case body 313 within the seal case 31, and is disposed alongside on one axial side of the rotary seal ring 14. The stationary seal ring 32 is made of, for example, silicon carbide (SiC), which has excellent wear resistance and sealing performance, similar to the rotary seal ring 14.

[0030] The stationary seal ring 32 is divided in the circumferential direction. In this embodiment, the stationary seal ring 32 is divided into two circumferentially, and is composed of a first segment 321 and a second segment 322 formed in a semicircular arc shape. End faces 321 a on both circumferential sides of the first segment 321 and end faces 322 a on both circumferential sides of the second segment 322 are in surface contact with each other.

[0031] The stationary seal ring 32 has a main body portion 32a and a nose portion 32b. The main body portion 32a is formed into an annular shape by a first segment 321 and a second segment 322. The nose portion 32b protrudes from the radially outer side of the other axial end portion of the main body portion 32a toward the other axial side. The nose portion 32b is also formed into an annular shape by the first segment 321 and the second segment 322. The end face on the other axial side of the nose portion 32b serves as an annular seal end face 32c against which the seal end face 14a of the rotary seal ring 14 slides.

[0032] A connecting surface 32f is formed around the entire circumference of the main body 32a on the other axial side of the outer periphery. The connecting surface 32f connects to the outer periphery of the nose 32b. The outer diameter of the connecting surface 32f is the same as the outer diameter of the nose 32b (seal end surface 32c). A fitting surface 32d, to which the seal member 33 is fitted, is formed around the entire circumference of the main body 32a on one axial side of the outer periphery.

[0033] The outer diameter D1 of the fitting surface 32d of the main body 32a is smaller than the outer diameter D2 of the seal end surface 32c and larger than the inner diameter D3 of the seal end surface 32c. In this embodiment, the outer diameter D1 of the fitting surface 32d is smaller than the outer diameter D2 of the seal end surface 32c and larger than the inner diameter D3 of the seal end surface 32c. An annular stepped surface 32e is formed on the outer periphery of the main body 32a between the fitting surface 32d and the connection surface 32f. The fluid pressure of the sealed fluid in the sealed space 73 (described below) acts on the stepped surface 32e.

[0034] The seal member 33 is an annular member made of an elastic material. In this embodiment, the seal member 33 is, for example, an O-ring. The inner circumferential side of the seal member 33 is fitted into the fitting surface 32d of the main body 32a, and holds the circumferentially divided stationary seal ring 32 in a tightened state from the radially outward direction. This keeps the end faces 321a, 322a of the first segment 321 and the second segment 322 in close contact with each other, thereby preventing leakage of the sealed fluid from between these end faces 321a, 322a.

[0035] The seal member 33 is disposed at a position where the axial distance L1 from the cross-sectional center of the seal member 33 to the seal end face 32c is 60% or more and 80% or less of the axial length dimension L2 of the stationary seal ring 32. This ensures a pressure-receiving area on the outer peripheral surface of the stationary seal ring 32 that receives the fluid pressure of the sealed fluid in the sealed space 73.

[0036] With the inner circumferential side of the seal member 33 tightening the stationary seal ring 32 from the radially outward direction, the outer circumferential side of the seal member 33 is in close contact with the inner circumferential surface of the third case body 313. As a result, the gap between the stationary seal ring 32 and the seal case 31 is sealed (secondary seal) by the seal member 33.

[0037] The seal member 33 is disposed between the protrusion 314b of the fourth case body 314 and the stepped surface 32e of the stationary seal ring 32. The protrusion 314b and the stepped surface 32e are both located radially inward of the third case body 313. Therefore, the seal member 33 is restricted from slipping out of its tight contact with the inner circumferential surface of the third case body 313 to either side in the axial direction of the third case body 313.

[0038] A notched groove 32g is formed on the inner periphery of the main body portion 32a. A plurality of notched grooves 32g are formed at equal intervals in the circumferential direction on the inner periphery of the main body portion 32a. The notched grooves 32g are formed in a shape that allows an operator's fingers to be hooked when the stationary seal ring 32 is assembled between the seal case 31 and the rotating shaft 71. In this embodiment, the notched grooves 32g are formed, for example, in a concave shape when viewed from the front in FIG. 3. The notched grooves 32g are formed over the entire axial direction of the main body portion 32a.

[0039] After the stationary seal ring 32 is assembled, the notched grooves 32g are used as engagement grooves into which the restricting members 34 are engaged. For this reason, the inner periphery of the main body 32a is formed with the same number of notched grooves 32g as the number of restricting members 34 (four in FIG. 3). Hereinafter, the notched grooves 32g will also be referred to as engagement grooves 32g.

[0040] The restricting member 34 is formed, for example, by a cylindrical pin member. A male thread 34a is formed on the outer periphery of one axial end of the restricting member 34. The male thread 34a of the restricting member 34 is screwed into a threaded hole 314c formed on the inner periphery of the fourth case body 314. The other axial end of the restricting member 34 protrudes further axially to the other side than the fourth case body 314 and engages with an engaging groove 32g of the stationary seal ring 32 (main body portion 32a). The restricting member 34 prevents the stationary seal ring 32 from rotating relative to the seal case 31, and restricts co-rotation with the rotary seal ring 14.

[0041] 1 and 2 , the elastic member 35 is a member that presses the stationary seal ring 32 toward the other axial side (toward the rotary seal ring 14). In this embodiment, the elastic member 35 is, for example, a compression coil spring. The elastic member 35 is inserted into a through hole 314d formed in the inner periphery of the fourth case body 314. The through holes 314d are formed in the fourth case body 314 at different circumferential positions relative to the threaded hole 314c and are formed at equal intervals in the circumferential direction. An elastic member 35 is inserted into each of the multiple through holes 314d. The other axial end of the elastic member 35 protrudes further toward the other axial side than the fourth case body 314 and abuts against a side surface of the transmission member 36 on one axial side.

[0042] Figure 4 is a front view of the transmission member 36 as viewed from the axial direction. In Figures 1, 2, and 4, the transmission member 36 is interposed between the elastic members 35 and the stationary seal ring 32. The transmission member 36 is formed in an annular plate shape and transmits the pressing forces of the multiple elastic members 35 evenly around the entire circumference of the stationary seal ring 32. The transmission member 36 in this embodiment is divided in the circumferential direction. Specifically, the transmission member 36 is divided into two in the circumferential direction and is composed of a first divided plate 361 and a second divided plate 362 formed in a semicircular arc shape. End faces 361a on both circumferential sides of the first divided plate 361 and end faces 362a on both circumferential sides of the second divided plate 362 are in surface contact with each other.

[0043] The other axial side surface of the transmission member 36 abuts against the one axial side surface of the stationary seal ring 32 (main body 32 a). The same number of grooves 36 a as the number of stationary seal rings 32 are formed on the inner periphery of the transmission member 36. The other axial end portion of the restriction member 34 passes through the grooves 36 a of the transmission member 36 and engages with the engagement groove 32 g of the stationary seal ring 32.

[0044] 1 and 2, the adapter ring 37 is formed in an annular shape and is fitted into the notch 314a of the fourth case body 314. The adapter ring 37 is fixed to the fourth case body 314 with bolts (not shown). One axial end of the elastic member 35 abuts against the other axial side surface of the adapter ring 37. By fitting and fixing the adapter ring 37 into the notch 314a of the fourth case body 314, the elastic member 35 is compressed in the axial direction.

[0045] The segment ring 38 is formed in an annular shape and is fitted into the notch 315a of the fifth case body 315. The other axial side of the segment ring 38 abuts against the one axial side of the adapter ring 37. Relative rotation of the segment ring 38 with respect to the adapter ring 37 is restricted by a pin 46 fixed to the adapter ring 37.

[0046] With the above configuration, the elastic member 35 presses the stationary seal ring 32 toward the other axial side, so that the seal end surface 32c of the stationary seal ring 32 closely contacts the seal end surface 14a of the rotary seal ring 14. As a result, when the rotary seal ring 14 rotates together with the rotary shaft 71, the seal end surface 14a of the rotary seal ring 14 slides against the seal end surface 32c of the stationary seal ring 32 while closely contacting it.

[0047] Therefore, within the seal case 31, a sealed space 73 for sealing the sealed fluid is formed radially outward from the sliding portion between the seal end surface 14a of the rotary seal ring 14 and the seal end surface 32c of the stationary seal ring 32, and on the other axial side of the seal member 33. The fluid pressure of the sealed fluid within the sealed space 73 acts on the seal member 33. This fluid pressure causes the seal member 33 to deform so as to expand on both sides in the radial direction, thereby improving the tightening force of the seal member 33 against the stationary seal ring 32 and the sealing performance between the stationary seal ring 32 and the seal case 31.

[0048] Furthermore, because the seal member 33 seals between the stationary seal ring 32 and the seal case 31, the balance ratio of the mechanical seal 1 can be set by the shape of the stationary seal ring 32. The balance ratio is the ratio of the force that tries to close the gap between the seal end faces 14a, 32c of the rotary seal ring 14 and the stationary seal ring 32 to the force that tries to open the gap between the seal end faces 14a, 32c. As described above, the shape of the stationary seal ring 32 is formed so that the outer diameter D1 of the fitting surface 32d, into which the seal member 33 is fitted, is smaller than the outer diameter D2 of the seal end face 32c and larger than the inner diameter D3. This allows the balance ratio of the mechanical seal 1 to be set.

[0049] 1 and 2, a method for assembling the stationary unit 3 to the casing 72 will be described. First, the worker fixes the first case body 311 of the seal case 31 to the casing 72 with the bolts 51. Next, the worker assembles the rotating unit 2 to the rotating shaft 71, and then fixes the second case body 312 and the third case body 313 of the seal case 31 to the first case body 311 with the bolts 52.

[0050] Next, the worker inserts the stationary seal ring 32 from one axial side into the annular space formed between the inner peripheral surface of the third case body 313 and the outer peripheral surface of the rotary shaft 71. At this time, the worker inserts the first segment 321 and the second segment 322 of the stationary seal ring 32 separately, which makes it possible to easily insert the stationary seal ring 32, which is a large, heavy object, into the annular space.

[0051] Furthermore, an operator can easily insert the first segment 321 and the second segment 322 into the annular space by hooking their fingers into the notched groove 32g (see FIG. 3 ). In particular, in this embodiment, the balance ratio is set based on the shape of the stationary seal ring 32, which may narrow the gap between the inner circumferential surface of the main body portion 32a of the stationary seal ring 32 and the outer circumferential surface of the rotating shaft 71. In such cases, the notched groove 32g is more effective. For example, as shown in FIG. 2 , if the balance ratio is set by making the outer diameter D1 of the fitting surface 32d of the stationary seal ring 32 smaller than the outer diameter D2 of the seal end surface 32c, the inner diameter of the main body portion 32a must be reduced to ensure the radial thickness of the main body portion 32a. In such cases, the narrow gap makes the notched groove 32g, which allows the operator's fingers to be hooked, more effective.

[0052] Furthermore, with conventional mechanical seals, the worker must assemble the stationary seal ring together with the holder and retainer as a unit into the casing, and there is a risk that the stationary seal ring may come into contact with the holder or the like and be damaged during this unitization process. In contrast, in the present embodiment, the worker does not need to unitize the stationary seal ring 32 with other components when inserting the stationary seal ring 32 into the annular space, so damage to the stationary seal ring 32 can be suppressed.

[0053] Next, the worker pushes the seal member 33 from one axial side into the annular seal gap formed between the inner circumferential surface of the third case body 313 and the fitting surface 32d of the stationary seal ring 32. At this time, the worker can push the seal member 33 into the seal gap while visually checking the seal member 33 from one axial side of the third case body 313. This makes it possible to reduce assembly errors of the seal member 33 (such as twisting of the seal member 33 or protrusion of the seal member 33 from the seal gap).

[0054] Next, the worker inserts the transmission member 36 into the annular space and abuts the transmission member 36 against one axial side surface of the stationary seal ring 32. At this time, the worker inserts the first divided plate 361 and the second divided plate 362 of the transmission member 36 separately, which makes it possible to easily insert the large transmission member 36 into the annular space.

[0055] Next, the worker fixes the fourth case body 314 to the third case body 313 with the bolts 53. Then, the worker tightens the male threads 34a of each restricting member 34 into the respective screw holes 314c of the fourth case body 314 to engage the other axial end of each restricting member 34 with the engagement groove (notched groove) 32g of the stationary seal ring 32. In this way, by assembling each restricting member 34 separately from the fourth case body 314, damage to the stationary seal ring 32 caused by the restricting member 34 coming into contact with the stationary seal ring 32 can be suppressed.

[0056] Next, the worker inserts the elastic members 35 into each through-hole 314d of the fourth case body 314 from one axial side thereof, and then fits and secures the adapter ring 37 into the notch 314a of the fourth case body 314 from one axial side thereof. This causes the elastic member 35 to be compressed in the axial direction, and presses the stationary seal ring 32 toward the rotary seal ring 14 via the transmission member 36. Next, the worker abuts the segment ring 38 against the side surface on one axial side of the adapter ring 37, and then brings the fifth case body 315 close to the fourth case body 314 from one axial side thereof and fits the segment ring 38 into the notch 315a of the fifth case body 315. Finally, the worker fixes the fifth case body 315 to the fourth case body 314 with the bolts 54.

[0057] [Effectiveness Confirmation Test] The inventors of the present application conducted a static pressure test and a rotation test to confirm the effects of the mechanical seal 1 of this embodiment. In the static pressure test, the fluid pressure of the sealed fluid in the sealed space 73 was increased without rotating the rotary seal ring 14, and the amount of leakage of the sealed fluid radially inward from the divided portion of the stationary seal ring 32 (between the end faces 321 a, 322 a) was measured.

[0058] 5 is a graph showing the results of the static pressure test. As shown in FIG. 5, in the initial stage when the fluid pressure of the sealed fluid in the sealed space 73 begins to increase, the rate of increase in the leakage rate of the sealed fluid is large. However, once the increase in fluid pressure exceeds the initial stage, the rate of increase in the leakage rate of the sealed fluid becomes smaller than in the initial stage. This change in the rate of increase indicates that the fluid pressure acts on the seal member 33 and the stationary seal ring 32, increasing the clamping force of the seal member 33 and the stationary seal ring 32 due to the fluid pressure. Therefore, it was confirmed that the fluid pressure of the sealed fluid in the sealed space 73 increases the clamping force of the seal member 33 and the fluid pressure.

[0059] In the rotation test, the change in torque of the rotary seal ring 14 and the change in the amount of leakage of the sealed fluid radially inward from the dividing portion of the stationary seal ring 32 (between the end faces 321a, 322a) were measured while the rotary seal ring 14 was rotating. Here, the rotation test was carried out under the following conditions A and B. In both cases of conditions A and B, the rotation speed of the rotary seal ring 14 was 700 rpm (min －１ Condition A: Fluid pressure of the sealed fluid in the sealed space 73 = 0.45 MPaG Condition B: Fluid pressure of the sealed fluid in the sealed space 73 = 0.70 MPaG

[0060] 6 is a graph showing the results of the rotation test. As shown in FIG. 6, in both the low fluid pressure condition A and the high fluid pressure condition B, the changes in torque and leakage amount were small and no sudden changes were observed, confirming that the sealing performance was stable.

[0061] [Effects of the Embodiment] According to the mechanical seal 1 of this embodiment, in the sealed space 73 formed in the seal case 31 for sealing the sealed fluid, the fluid pressure of the sealed fluid acts on the seal members 33, which clamp the circumferentially divided stationary seal rings 32 from the radially outward direction. This fluid pressure causes the seal members 33 to deform and expand radially in both directions, thereby increasing the clamping force of the seal members 33 against the stationary seal rings 32. Furthermore, since the fluid pressure of the sealed fluid acts directly on the stationary seal rings 32 from the radially outward direction, this directly acting fluid pressure can further clamp the stationary seal rings 32 from the radially outward direction. As a result, the stationary seal rings 32 can be held in a state of being clamped from the radially outward direction without using a conventional holder. Therefore, the conventional holder is no longer necessary, and the configuration of the stationary unit 3 can be simplified.

[0062] When forming the stationary seal ring 32, the balance ratio can be set by setting the outer diameter D1 of the fitting surface 32d, into which the seal member 33 is fitted, to be smaller than the outer diameter D2 of the seal end surface 32c and larger than the inner diameter D3. Therefore, the seal member 33 that fastens the stationary seal ring 32 also serves as a seal member for setting the balance ratio, further simplifying the configuration of the stationary unit 3.

[0063] The transmission member 36 that transmits the pressing force of the elastic member 35 to the stationary seal ring 32 is formed in an annular plate shape, so it can have a simpler shape than a conventional retainer that transmits pressing force to a stationary seal ring. As a result, it is possible to further simplify the configuration of the stationary unit 3. In addition, because the transmission member 36 is divided in the circumferential direction, it can be easily assembled.

[0064] A notched groove 32g for hooking fingers is formed on the inner periphery of the stationary seal ring 32. As a result, even if the gap between the inner periphery of the stationary seal ring 32 and the outer periphery of the rotary shaft 71 is narrow, the worker can easily assemble the stationary seal ring 32 by hooking their fingers into the notched groove 32g.

[0065] The notched groove 32g into which the operator's fingers are hooked when assembling the stationary seal ring 32 also serves as an engaging groove into which the restricting member 34 engages, restricting co-rotation of the stationary seal ring 32. This allows the configuration of the stationary unit 3 to be further simplified.

[0066] [Others] The stationary seal ring 32 in the above embodiment is divided into two in the circumferential direction, but it may be divided into three or more. The notched groove 32g of the stationary seal ring 32 does not have to also serve as an engagement groove with which the restricting member 34 engages. The seal member 33 may be a seal member other than an O-ring. The elastic member 35 may be an elastic member other than a compression coil spring. The transmission member 36 is divided into two in the circumferential direction, but it may not be divided, or may be divided into three or more. Furthermore, the transmission member 36 may have a shape other than an annular plate.

[0067] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof.

[0068] REFERENCE SIGNS LIST 1 Mechanical seal 3 Stationary unit 14 Rotating seal ring 31 Seal case 32 Stationary seal ring 32c Seal end face 32d Fitting face 32g Notched groove (engagement groove) 33 Seal member 34 Restricting member 35 Elastic member 36 Transmission member 71 Rotating shaft 72 Casing 73 Sealed space D1 Outer diameter of fitting face D2 Outer diameter of seal end face D3 Inner diameter of seal end face

Claims

1. A mechanical seal comprising: a seal case fixed to a casing, a stationary unit having a stationary seal ring arranged within the seal case and divided circumferentially; and a rotary seal ring provided on a rotating shaft surrounded by the casing so as to be rotatable integrally with the rotating shaft and sliding on the stationary seal ring, wherein the stationary unit tightens the stationary seal ring from the radially outward direction and has an annular seal member that seals between the seal case and the stationary seal ring to form a sealed space for sealing the sealed fluid radially outward of the sliding portion between the rotary seal ring and the stationary seal ring within the seal case.

2. A mechanical seal as set forth in claim 1, wherein the stationary seal ring has a fitting surface formed on the outer periphery of the stationary seal ring and into which the seal member is fitted, and an annular seal end surface against which the rotary seal ring slides, and the outer diameter of the fitting surface is smaller than the outer diameter of the seal end surface and larger than the inner diameter of the seal end surface.

3. A mechanical seal as described in claim 2, wherein the stationary unit further comprises an elastic member for pressing the stationary seal ring toward the rotary seal ring, and a transmission member interposed between the elastic member and the stationary seal ring for transmitting the pressing force of the elastic member to the stationary seal ring, the transmission member being formed in the shape of an annular plate.

4. A mechanical seal according to claim 3, wherein the transmission member is divided in the circumferential direction.

5. A mechanical seal according to any one of claims 1 to 4, wherein a notched groove for hooking a finger is formed on the inner periphery of the stationary seal ring.

6. A mechanical seal as set forth in claim 5, wherein the stationary unit further has a restricting member that engages with the stationary seal ring to restrict co-rotation of the stationary seal ring with the rotating seal ring, and an engaging groove into which the restricting member engages is formed on the inner circumference of the stationary seal ring, and the engaging groove is the notched groove.

Images