Mechanical seal and method for adjusting fluid pressure of mechanical seal

Abstract

To provide a mechanical seal which enables adjustment of a leakage amount of sealed fluid from between seal surfaces of a rotary seal ring and a stationary seal ring, and to provide a fluid pressure adjustment method of the mechanical seal.SOLUTION: A stationary side unit 3 of a mechanical seal 1 includes: a retainer 34 which is attached to the casing 72 side so as to be movable in an axial direction and retains a stationary seal ring 35; a first fluid chamber 61 which is formed communicating with a device internal area 73 so that sealed fluid is introduced thereinto and the retainer 34 is pressed to one axial side by a fluid pressure P1 of the sealed fluid; a second fluid chamber 62 which is formed independently from the device internal area 73 and the first fluid chamber 61 so that the seal fluid is introduced thereinto and the retainer 34 is pressed to the other axial side by a fluid pressure P2 of the seal fluid; and a pressure regulating valve 4 which may adjust the pressure fluid P2 of the seal fluid.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mechanical seal and a method for adjusting fluid pressure in a mechanical seal. [Background technology]

[0002] For example, in high-load mechanical seals, in order to cope with high pressure and high peripheral speed conditions, the balance ratio (the ratio between the force that tries to close the gap between the two seal faces of the stationary seal ring and the rotating seal ring and the force that tries to open the gap between the two seal faces) is set to a smaller value than usual (0.6 to 0.75), allowing a certain amount of sealed fluid to leak from between the two seal faces. This causes a lubricating film to be formed by the sealed fluid between the two seal faces, ensuring lubrication between the two seal faces (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-101361 Summary of the Invention [Problem to be solved by the invention]

[0004] When the balance ratio is reduced as described above, the pressing force that presses the seal faces together due to the fluid pressure of the sealed fluid is reduced. This reduced pressing force makes it easier for the static seal ring to lose compliance due to disturbances during operation of the mechanical seal. When compliance of the static seal ring is reduced, for example, foreign matter may become lodged between the seal faces, potentially causing a large amount of sealed fluid to leak from between the seal faces in excess of the specified amount.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a mechanical seal that can adjust the amount of sealed fluid leaking from between the seal faces of a rotary seal ring and a stationary seal ring, and a method for adjusting the fluid pressure of a mechanical seal. [Means for solving the problem]

[0006] (1) The present invention is a mechanical seal comprising: a rotary seal ring provided on a rotating shaft so as to be rotatable together with the rotating shaft and having a seal surface formed on one axial side; and a stationary seal unit provided in a casing surrounding the rotating shaft and having a stationary seal ring formed on the other axial side with a seal surface opposing the seal surface of the rotary seal ring, wherein the rotary seal ring and the stationary seal ring seal a sealed fluid into an inboard area, wherein the stationary unit is attached to the casing so as to be axially movable and has a retainer that holds the stationary seal ring; a first fluid chamber formed in communication with the inboard area so that the sealed fluid is introduced therein and the fluid pressure of the sealed fluid presses the retainer to the one axial side; a second fluid chamber formed independently of the inboard area and the first fluid chamber so that a seal fluid is introduced therein and the fluid pressure of the seal fluid presses the retainer to the other axial side; and a pressure regulating valve capable of adjusting the fluid pressure of at least one of the sealed fluid and the seal fluid.

[0007] According to the present invention, the force pressing the retainer to the other axial direction can be adjusted by adjusting the fluid pressure of at least one of the sealed fluid introduced into the first fluid chamber and the seal fluid introduced into the second fluid chamber with the pressure regulating valve. This makes it possible to adjust the pressing force with which the seal surface of the stationary seal ring held by the retainer presses against the seal surface of the rotary seal ring, thereby regulating the amount of sealed fluid leaking from between the seal surfaces of the rotary seal ring and the stationary seal ring.

[0008] (2) It is preferable that the stationary unit further has an introduction passage that introduces a portion of a flushing fluid for cooling both seal surfaces of the rotary seal ring and the stationary seal ring into the second fluid chamber as the seal fluid. In this case, part of the flushing fluid that cools both seal surfaces can be used as the seal fluid, thereby simplifying the structure of the mechanical seal.

[0009] (3) It is preferable that the in-machine region is formed radially outward of both seal surfaces of the rotary seal ring and the stationary seal ring, the retainer has a pressing surface that presses only the radially inner portion of the end face on one axial side of the stationary seal ring toward the other axial side, and the pressure regulating valve is capable of adjusting the fluid pressure of the seal fluid. In this case, even if the portion of the stationary seal ring radially outward from the seal surface on the other axial side is pressed by the fluid pressure of the sealed fluid in the in-machine region, the radially inward portion of the end face on one axial side of the stationary seal ring is pressed by the pressing surface of the retainer to counteract that fluid pressure. Therefore, by adjusting the fluid pressure of the seal fluid with the pressure regulating valve and adjusting the pressing force of the stationary seal ring by the pressing surface of the retainer, the seal surface of the stationary seal ring can be uniformly pressed radially against the seal surface of the rotary seal ring. This prevents uneven wear of the seal surface of the stationary seal ring in the radial direction due to the fluid pressure of the sealed fluid, thereby preventing a deterioration in the sealing performance of the mechanical seal.

[0010] (4) The retainer has a first pressure-receiving surface that receives the fluid pressure of the sealed fluid in the first fluid chamber from the other axial side, and a second pressure-receiving surface that receives the fluid pressure of the sealing fluid in the second fluid chamber from the one axial side, and it is preferable that the area of ​​the first pressure-receiving surface is equal to or larger than the area of ​​the second pressure-receiving surface. In this case, by making the area of ​​the first pressure-receiving surface of the retainer equal to or larger than the area of ​​the second pressure-receiving surface, the balance diameter of the stationary seal ring can be made smaller than when the area of ​​the first pressure-receiving surface is made smaller than the area of ​​the second pressure-receiving surface. This makes it possible to reduce the pressing force on the stationary seal ring by the pressing surface of the retainer and the peripheral speed of the pressing surface. This is particularly effective in high-load mechanical seals used under high pressure and high peripheral speed conditions.

[0011] (5) The fluid pressure adjusting method for a mechanical seal according to (1) adjusts the at least one fluid pressure by the pressure adjusting valve so as to satisfy the following relationship: P1×B1 <P2×B2 Here, the definitions of the variables in the above formula are as follows: P1: Fluid pressure of the sealed fluid in the first fluid chamber B1: Area of ​​the first pressure-receiving surface of the retainer that receives the fluid pressure of the sealed fluid in the first fluid chamber from the other axial side P2: Fluid pressure of the seal fluid in the second fluid chamber B2: Area of ​​the second pressure-receiving surface of the retainer that receives the fluid pressure of the seal fluid in the second fluid chamber from one axial side

[0012] In this case, the force relationship of the above formula is maintained, so that a force pressing the retainer toward the other axial direction is always applied to the retainer, thereby making it possible to adjust the force pressing the retainer toward the other axial direction while suppressing movement of the retainer toward the one axial direction. [Effects of the Invention]

[0013] According to the mechanical seal of the present invention, it is possible to adjust the amount of leakage of the sealed fluid from between the seal faces of the rotary seal ring and the stationary seal ring. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing a mechanical seal according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a main part of FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing the periphery of a stationary seal ring. [Figure 4] FIG. 10 is a cross-sectional view illustrating the wear state of the seal surface of the stationary seal ring in a reference example in which the pressing surface of the retainer is changed. [Figure 5] 5 is a cross-sectional view illustrating the state of wear on the seal surface of the stationary seal ring in the reference example of FIG. 4. FIG. [Figure 6] FIG. 4 is a cross-sectional view showing a mechanical seal according to a second embodiment of the present invention. [Figure 7] FIG. 3 is an enlarged cross-sectional view of a main part of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings. [First embodiment] Fig. 1 is a cross-sectional view showing a mechanical seal according to a first embodiment of the present invention. In Fig. 1, mechanical seal 1 is used in rotating equipment such as pumps and agitators, and seals a sealed fluid (solvent, water, oil, etc.) inside the rotating equipment. Mechanical seal 1 is disposed between a rotating shaft 71 of the rotating equipment and a casing 72 surrounding the rotating shaft 71, along the axial direction of the rotating shaft 71 (hereinafter simply referred to as the "axial direction").

[0016] The mechanical seal 1 of this embodiment is used under high load conditions such as high pressure and high peripheral speed, and includes a rotating side unit 2 that is mounted on a rotating shaft 71 so as to be rotatable integrally therewith, and a stationary side unit 3 that is mounted on a casing 72. For convenience, the left side of Fig. 1 will be referred to as one axial side, and the right side of Fig. 1 will be referred to as the other axial side in this specification (the same applies to Figs. 2 to 7).

[0017] <Rotating unit> The rotating side unit 2 includes a sleeve 11, a stopper ring 12, a rotary seal ring 13, and a retainer 14. The sleeve 11 has a cylindrical sleeve main body 11a fitted and fixed to the outer periphery of the rotary shaft 71, an annular portion 11b extending radially outward from the other axial end of the sleeve main body 11a, and a cylindrical portion 11c extending axially from the radial outer end of the annular portion 11b.

[0018] A key groove 11d is formed at a predetermined location in the circumferential direction on the inner periphery of one axial end of the sleeve body 11a. A key member 15 is inserted between the key groove 11d and the outer circumferential surface of the rotating shaft 71. A stopper ring 12 is fitted onto the outer periphery of the rotating shaft 71 on one axial side of the sleeve body 11a to prevent the key member 15 from slipping out to that axial side. The other axial end of the stopper ring 12 is fitted onto the outer periphery of one axial end of the sleeve body 11a, and a set screw 16 is radially tightened into this fitted portion. In this way, the sleeve 11 is fixed to the rotating shaft 71. An O-ring 17 provides a seal (secondary seal) between the inner periphery of the other axial end of the sleeve body 11a and the outer periphery of the rotating shaft 71.

[0019] A rotary seal ring 13 is disposed between the sleeve main body 11a and the cylindrical portion 11c. A seal surface 13a is formed on one axial end face of the rotary seal ring 13. The rotary seal ring 13 is concentrically attached to the cylindrical portion 11c via a cylindrical retainer 14. Specifically, the outer peripheral surface of the rotary seal ring 13 is fitted and fixed to the inner peripheral surface of the retainer 14, and the outer peripheral surface of the retainer 14 is fitted to the inner peripheral surface of the cylindrical portion 11c. A protrusion 14a (see FIG. 2) that protrudes radially outward is integrally formed on a portion of the outer peripheral surface of the retainer 14 in the circumferential direction. The protrusion 14a is inserted into a recessed groove 11e (see FIG. 2) formed on a portion of the inner peripheral surface of the cylindrical portion 11c in the circumferential direction. This restricts rotation of the retainer 14 and the rotary seal ring 13 relative to the sleeve 11. An O-ring 18 is disposed on the other axial end of the retainer 14. The O-ring 18 provides a seal (secondary seal) between the inner peripheral surface of the cylindrical portion 11c and the outer peripheral surface of the rotary seal ring 13.

[0020] <Stationary unit> The stationary side unit 3 includes a seal case 30, a retainer 34, and a stationary seal ring 35. The seal case 30 has an annular first case body 31 fixed to the casing 72, an annular second case body 32 fixed to the first case body 31, and a cylindrical third case body 33 fixed to the second case body 32.

[0021] The radially outer portion of the first case body 31 is fixed to the casing 72 by bolts 36 while abutting against a side surface on one axial side of the casing 72. An annular groove 31a is formed on the radially inner side of the first case body 31. An O-ring 38 provides a seal (secondary seal) between the side surface on the other axial side of the first case body 31 and the side surface on one axial side of the casing 72.

[0022] The second case body 32 is fitted into the annular groove 31a of the first case body 31 and fixed to the first case body 31 by bolts 39. An O-ring 40 provides a seal (secondary seal) between the outer circumferential surface of the second case body 32 and the inner circumferential surface of the annular groove 31a.

[0023] Fig. 2 is an enlarged cross-sectional view of a main portion of Fig. 1. As shown in Fig. 2, the third case body 33 has a case main body 33a and a connecting tubular portion 33b extending from the case main body 33a to one side in the axial direction. The outer peripheral surface of the case main body 33a is fitted into the inner peripheral surface of the casing 72. O-rings 41 and 42 seal between the inner peripheral surface of the casing 72 and both axial sides of the outer peripheral surface of the case main body 33a, respectively.

[0024] The connecting cylinder portion 33b is formed in a cylindrical shape and has a diameter smaller than the outer circumferential surface of the case main body 33a. One axial side of the connecting cylinder portion 33b is fixed with a screw 43, with its inner circumferential surface fitted to the outer circumferential surface of the second case body 32. Furthermore, one axial side of the connecting cylinder portion 33b is fitted into the annular groove 31a of the first case body 31, with the connecting cylinder portion 33b fixed to the second case body 32.

[0025] The retainer 34 has a retainer body 340 formed in an annular shape, a first cylindrical portion 341 extending from the inner circumferential end of the retainer body 340 to the other axial side, and a second cylindrical portion 342 extending from the inner circumferential end of the retainer body 340 to one axial side. The retainer body 340 is disposed axially movably on the inner circumferential side of the third case body 33. An O-ring 44 provides a seal (secondary seal) between the outer circumferential surface of the retainer body 340 and the inner circumferential surface of the third case body 33.

[0026] A pin 45 is fixed to a first side surface 340a on the other axial side of the retainer body 340, protruding toward the other axial side. A pin 46 is fixed to a second side surface 340b on one axial side of the retainer body 340, protruding toward one axial side. The pin 46 is inserted into a pin groove 32a formed in the second case body 32. As a result, the retainer 34 is attached to the seal case 30 on the casing 72 side so as to be movable in the axial direction, and relative rotation with respect to the seal case 30 is restricted.

[0027] 1, a plurality of springs 47 (only one is shown in FIG. 1) are provided at predetermined intervals in the circumferential direction between the second case body 32 and the retainer body 340. The springs 47 bias the retainer body 340 toward the other axial side relative to the second case body 32.

[0028] 2, the outer diameter of the first cylindrical portion 341 is larger than the outer diameter of the second cylindrical portion 342. As a result, the area B1 of the first side surface 340a of the retainer body 340 is smaller than the area B2 of the second side surface 340b. The second cylindrical portion 342 is inserted into the inner circumferential side of the second case body 32. An O-ring 48 provides a seal (secondary seal) between the outer circumferential surface of the second cylindrical portion 342 and the inner circumferential surface of the second case body 32.

[0029] The stationary seal ring 35 is disposed on the other axial side of the retainer 34. An annular nose portion 35a that protrudes toward the other axial side is formed radially inward at the other axial end of the stationary seal ring 35. The end face on the other axial side of the nose portion 35a forms a seal surface 35b that can face and come into contact with the seal surface 13a of the rotary seal ring 13. As a result, an in-machine region 73 in which the sealed fluid is sealed is formed radially outward of both the seal surfaces 13a, 35b of the rotary seal ring 13 and the stationary seal ring 35 within the casing 72.

[0030] Because the mechanical seal 1 of this embodiment is used under high-load conditions as described above, the shape of the stationary seal ring 35 is determined so that the balance ratio (the ratio of the force that tries to close the gap between the seal faces 13a, 35b of the rotating seal ring 13 and the stationary seal ring 35 to the force that tries to open the gap between the seal faces 13a, 35b) is small (e.g., 0.6 to 0.75). Therefore, by reducing the balance ratio, the mechanical seal 1 of this embodiment allows a certain amount of sealed fluid to leak from between the seal faces 13a, 35b. This allows a lubricating film to be formed by the sealed fluid between the seal faces 13a, 35b, ensuring lubrication between the seal faces 13a, 35b.

[0031] A pin groove 35c is formed on the radially outer side of one axial end of the stationary seal ring 35. A pin 45 fixed to the retainer body 340 is inserted into the pin groove 35c. As a result, the stationary seal ring 35 is held by the retainer 34, and relative rotation with respect to the retainer 34 is restricted.

[0032] 3 is an enlarged cross-sectional view showing the periphery of the stationary seal ring 35. As shown in FIG. 3, the end face 35d on one axial side of the stationary seal ring 35 is composed of a first end face 35d1, a second end face 35d2, and a third end face 35d3, which are formed in this order from the radially inner side to the radially outer side. An end face 341a on the other axial side of the first cylindrical portion 341 of the retainer 34 abuts against the first end face 35d1. The second end face 35d2 is formed to protrude toward one axial side beyond the first end face 35d1. A first circumferential surface 35e is formed between the first end face 35d1 and the second end face 35d2. The other axial end of the first cylindrical portion 341 is inserted into the inner periphery of the first circumferential surface 35e.

[0033] The third end face 35d3 is formed to protrude further toward one axial direction than the second end face 35d2. A second circumferential surface 35f is formed between the second end face 35d2 and the third end face 35d3. An O-ring 49 provides a seal (secondary seal) between the inner circumferential surface of the second circumferential surface 35f and the outer circumferential surface of the first cylindrical portion 341. The third end face 35d3 is disposed with a gap on the other axial direction side relative to the first side surface 340a of the retainer body 340. With the above configuration, the retainer 34 (end face 341a of the first cylindrical portion 341) abuts only against the radially inner portion (first end face 25d1) of the end face 35d on one axial side of the stationary seal ring 35.

[0034] As will be described later, the force relationship of equation (1) is always maintained, so that the retainer 34 is always pressed toward the other axial direction. Therefore, the end face 341a of the retainer 34 functions as a pressing surface that presses the first end face 35d1 of the stationary seal ring 35 toward the other axial direction. Hereinafter, the end face 341a of the retainer 34 will also be referred to as the pressing surface 341a.

[0035] <Flushing channel> 1 and 2, a flushing flow path 74 through which a flushing fluid flows is formed in the casing 72. The flushing fluid is introduced into the in-machine area 73 to cool both the seal surfaces 13a, 35b of the rotary seal ring 13 and the stationary seal ring 35, and is the same fluid as the sealed fluid.

[0036] The flushing passage 74 is formed to extend radially at a predetermined position in the circumferential direction of the casing 72. The radial outer end of the flushing passage 74 is connected to a first pipe 75 arranged outside the casing 72. The first pipe 75 is a pipe that supplies the sealed fluid in the in-machine region 73 to the flushing passage 74 as a flushing fluid.

[0037] The seal case 30 has a communication flow path 50 that communicates the flushing flow path 74 with the in-machine area 73. The communication flow path 50 has an annular flow path 51, a first supply flow path 52, and a second supply flow path 53 formed in the third case body 33. The annular flow path 51 is formed in an annular shape in the circumferential direction of the third case body 33. The annular flow path 51 opens at the outer periphery of the third case body 33 and communicates with the radially inner end of the flushing flow path 74. The annular flow path 51 in this embodiment is formed, for example, with a rectangular cross section.

[0038] The first supply flow passage 52 is a flow passage that connects the annular flow passage 51 with the in-machine region 73 and supplies flushing fluid to both seal surfaces 13a, 35b of the rotary seal ring 13 and the stationary seal ring 35. A plurality of first supply flow passages 52 are formed at predetermined intervals in the circumferential direction of the third case body 33. Each first supply flow passage 52 is formed in the third case body 33 so as to incline from the annular flow passage 51 toward the other axial side and radially inward so that the flushing fluid is supplied toward both seal surfaces 13a, 35b.

[0039] The second supply flow path 53 is a flow path that connects the annular flow path 51 and the in-machine region 73 and supplies flushing fluid to a first fluid chamber 61, which will be described later. Similar to the first supply flow path 52, a plurality of second supply flow paths 53 are formed at predetermined intervals in the circumferential direction of the third case body 33. Each second supply flow path 53 is formed radially outside the first fluid chamber 61 in the third case body 33 so that the flushing fluid is supplied toward the first fluid chamber 61.

[0040] <1st fluid chamber> 2, the stationary side unit 3 includes a first fluid chamber 61 formed in communication with the in-machine region 73. The first fluid chamber 61 is formed between the retainer 34 and the stationary seal ring 35. Specifically, the first fluid chamber 61 is formed by gaps formed between the first side surface 340a of the retainer body 340 and the second end face 35d2 and the third end face 35d3 of the stationary seal ring 35. The radial inside of the first fluid chamber 61 is sealed by the O-ring 49 described above.

[0041] The first fluid chamber 61 communicates with the in-machine region 73 at its radially outer side. As a result, the flushing fluid (sealed fluid) supplied from the second supply flow path 53 to the in-machine region 73 is introduced into the first fluid chamber 61. The flushing fluid introduced into the first fluid chamber 61 presses the first side surface 340a of the retainer body 340 toward one axial direction due to its fluid pressure. Therefore, the first side surface 340a functions as a first pressure-receiving surface that receives the fluid pressure of the flushing fluid in the first fluid chamber 61 from the other axial direction. Hereinafter, the first side surface 340a of the retainer body 340 will also be referred to as the first pressure-receiving surface 340a.

[0042] <Second fluid chamber> The stationary side unit 3 includes a second fluid chamber 62 formed independently of the in-machine area 73 and the first fluid chamber 61. The second fluid chamber 62 is defined by the second case body 32, the third case body 33, and the retainer 34. Specifically, the second fluid chamber 62 is defined by a gap formed between the other axial end face of the second case body 32 and the second side surface 340b of the retainer body 340, and a gap formed between the inner peripheral surface of the connecting tube portion 33b and the outer peripheral surface of the retainer body 340.

[0043] One axial side of the second fluid chamber 62 is sealed by the O-rings 40 and 48. The other axial side of the second fluid chamber 62 is sealed by the O-ring 44. As a result, the second fluid chamber 62 is formed independently of the in-machine region 73 and the first fluid chamber 61.

[0044] <Inlet flow path> 1 and 2, the stationary unit 3 includes an introduction flow path 55 that introduces sealing fluid into the second fluid chamber 62. In this embodiment, a portion of the flushing fluid flowing through the first piping 75 is used as the sealing fluid. The introduction flow path 55 includes a first introduction flow path 55a formed in the first case body 31, a second introduction flow path 55b formed between the first case body 31 and the third case body 33, and a third introduction flow path 55c formed in the third case body 33.

[0045] The first introduction flow path 55a is formed with a substantially L-shaped cross section at a predetermined location in the circumferential direction of the first case body 31. One end of the first introduction flow path 55a opens at the outer peripheral surface of the first case body 31 and is connected to a second pipe 76 branching off from the first pipe 75. This allows a portion of the flushing fluid flowing through the first pipe 75 to pass through the second pipe 76 as seal fluid and be supplied to the introduction flow path 55, thereby simplifying the configuration of the mechanical seal. The other end of the first introduction flow path 55a opens at a side surface on the other axial side of the first case body 31, radially inward from the casing 72.

[0046] The second inlet flow path 55b is formed in an annular shape between a side surface on one axial direction side of the case main body 33a of the third case body 33 and a side surface on the other axial direction side of the first case body 31 opposing the side surface, and is in communication with the first inlet flow path 55a. The other axial side of the second inlet flow path 55b is sealed by the O-ring 41. The third inlet flow path 55c is formed to penetrate radially at a predetermined location in the circumferential direction of the connecting cylindrical portion 33b of the third case body 33, and connects the second inlet flow path 55b and the second fluid chamber 62.

[0047] With the above configuration, the seal fluid flowing through the second pipe 76 passes through the first introduction flow path 55a, the second introduction flow path 55b, and the third introduction flow path 55c in this order before being introduced into the second fluid chamber 62. The seal fluid introduced into the second fluid chamber 62 presses the second side surface 340b of the retainer body 340 toward the other axial direction due to its fluid pressure. Therefore, the second side surface 340b functions as a second pressure-receiving surface that receives the fluid pressure of the seal fluid in the second fluid chamber 62 from one axial direction side. Hereinafter, the second side surface 340b of the retainer body 340 is also referred to as the second pressure-receiving surface 340b.

[0048] <Discharge flow path> 1, the stationary side unit 3 is provided with a discharge flow path 56 that discharges the sealing fluid introduced into the second fluid chamber 62 to the outside. The discharge flow path 56 has a first discharge flow path 56a formed in the first case body 31, a second discharge flow path 56b formed between the first case body 31 and the third case body 33, and a third discharge flow path 56c formed in the third case body 33.

[0049] The first discharge flow path 56a is formed with a generally L-shaped cross section at a predetermined location (a location different from the first introduction flow path 55a) in the circumferential direction of the first case body 31. One end of the first discharge flow path 56a opens at the outer peripheral surface of the first case body 31 and is connected to a third pipe 77 arranged outside the casing 72. The other end of the first discharge flow path 56a opens at a side surface on the other axial side of the first case body 31, radially inward from the casing 72.

[0050] The second discharge flow path 56b is a flow path that communicates with the first discharge flow path 56a. In this embodiment, the first discharge flow path 56a communicates with the annular second inlet flow path 55b, and the second inlet flow path 55b also serves as the second discharge flow path 56b. The third discharge flow path 56c is formed to penetrate radially through a predetermined circumferential location (a location different from the third inlet flow path 55c) of the connecting cylindrical portion 33b of the third case body 33. As a result, the third discharge flow path 56c communicates between the second discharge flow path 56b (second inlet flow path 55b) and the second fluid chamber 62.

[0051] With the above configuration, the sealing fluid in the second fluid chamber 62 passes through the third discharge flow path 56c, the second discharge flow path 56b, and the first discharge flow path 56a in this order, and is discharged to the third pipe 77. Note that the second discharge flow path 56b may be formed independently of the second introduction flow path 55b.

[0052] <Pressure Regulating Valve> The mechanical seal 1 further includes a pair of pressure regulating valves 4 capable of adjusting the fluid pressure of the sealing fluid, and a check valve 5. The check valve 5 is provided in the second pipe 76 and prevents the sealing fluid in the second pipe 76 from flowing back into the first pipe 75. The pair of pressure regulating valves 4 is composed of a first pressure regulating valve 4A provided in the second pipe 76 closer to the introduction flow path 55 than the check valve 5, and a second pressure regulating valve 4B provided in the third pipe 77.

[0053] The first pressure regulating valve 4A can manually adjust the fluid pressure of the sealing fluid introduced into the second fluid chamber 62 through the second pipe 76. The second pressure regulating valve 4B can manually adjust the fluid pressure of the sealing fluid discharged from the second fluid chamber 62 through the third pipe 77.

[0054] <How to adjust the fluid pressure of the seal fluid> In Figures 1 and 2, the force exerted by fluid pressure on the first pressure-receiving surface 340a and the second pressure-receiving surface 340b of the retainer 34 must always maintain the force relationship of the following equation (1) using the areas B1 and B2 of both pressure-receiving surfaces 340a and 340b. P1×B1 <P2×B2 (1) Here, P1 is the fluid pressure of the flushing fluid (sealed fluid) in the first fluid chamber 61 (in-machine region 73), and P2 is the fluid pressure of the sealing fluid in the second fluid chamber 62.

[0055] By constantly maintaining the force relationship of the above formula (1), a force constantly acts on the retainer 34 pressing it toward the other axial side, preventing the retainer 34 from moving toward one axial side. This prevents the O-ring 49 from falling off from between the retainer 34 and the stationary seal ring 35 due to movement of the retainer 34 toward one axial side, thereby preventing the sealed fluid in the in-machine region 73 from leaking outside the machine.

[0056] The force relationship of the above formula (1) must be maintained at all times when adjusting the fluid pressure P2 of the sealing fluid by the pair of pressure adjustment valves 4. In this embodiment, as described above, the area B1 of the first pressure receiving surface (first side surface) 340a is smaller than the area B2 of the second pressure receiving surface (second side surface) 340b. Therefore, the fluid pressure P2 of the sealing fluid is adjusted by the pair of pressure adjustment valves 4 to be smaller than the fluid pressure P1 of the flushing fluid so that the force relationship of the above formula (1) is maintained at all times based on the size relationship between the areas B1 and B2.

[0057] As described above, the retainer 34 is biased toward the other axial direction by the spring 47 (see FIG. 1), but because the mechanical seal 1 of this embodiment is used under high load (high pressure) conditions, the fluid pressures P1 and P2 are also high. Therefore, the forces on the right and left sides of the above formula (1) are significantly greater than the biasing force of the spring 47, so there is no problem even if the biasing force of the spring 47 is ignored in the above formula (1).

[0058] By adjusting the fluid pressure P2 of the seal fluid with the pair of pressure regulating valves 4 so that the force relationship of the above formula (1) is always maintained, it is possible to adjust the force with which the pressing surface 341a (see FIG. 3) of the retainer 34 presses the stationary seal ring 35 in the other axial direction. By adjusting this pressing force, it is possible to adjust the pressing force with which the seal surface 35b of the stationary seal ring 35 presses the seal surface 13a of the rotary seal ring 13. This makes it possible to appropriately adjust the amount of leakage of the sealed fluid from between the seal surfaces 13a, 35b of the rotary seal ring 13 and the stationary seal ring 35.

[0059] As shown in Fig. 3, the outer periphery of the stationary seal ring 35 radially outward of the seal surface 35b is pressed toward one axial side and radially inward by fluid pressure P1 of the sealed fluid. When fluid pressure P1 acts in this manner, a rotational moment M1 is generated in the stationary seal ring 35 in the clockwise direction in Fig. 3 about the center of gravity G of its cross section. For this reason, as shown in Fig. 4, for example, if the pressing surface of the retainer 34 that presses the stationary seal ring 35 is the first side surface 340a instead of the end surface 341a, and the first side surface 340a presses the third end surface 35d3 of the stationary seal ring 35, that is, if the retainer 34 presses the stationary seal ring 35 in a manner that promotes the generation of rotational moment M1, the following problem occurs.

[0060] 4, when rotational moment M1 is generated, the radially outer portion of seal surface 35b of stationary seal ring 35 is pressed more strongly against seal surface 13a of rotary seal ring 13 than the radially inner portion, and the radially outer portion wears preferentially. As a result, as shown in FIG. 5, the radially outer portion of seal surface 35b of stationary seal ring 35 cannot be pressed against seal surface 13a of rotary seal ring 13, and there is a risk of a large amount of sealed fluid leaking from in-machine region 73.

[0061] In contrast, as shown in Fig. 3, in this embodiment, due to the fluid pressure P2 of the sealing fluid (see Fig. 2), the end face (pressing surface) 341a of the retainer 34 presses the first end face 35d1, which is located radially inward of the center of gravity G of the stationary seal ring 35, toward the other axial direction. In other words, the pressing surface 341a of the retainer 34 presses the first end face 35d1 of the stationary seal ring 35 so as to face the fluid pressure P1 of the sealed fluid. Due to this pressing force F1, a rotational moment M2 is generated in the stationary seal ring 35 in the counterclockwise direction in Fig. 3 about the center of gravity G. As a result, rotational moments M1 and M2 are generated in the stationary seal ring 35 in mutually opposite directions.

[0062] Therefore, by adjusting the fluid pressure P2 of the seal fluid with the pair of pressure regulating valves 4 and adjusting the pressing force F1 on the stationary seal ring 35 by the pressing surface 341a of the retainer 34, it is possible to make the two rotational moments M1 and M2 cancel each other out. This allows the seal surface 35b of the stationary seal ring 35 to be pressed uniformly in the radial direction against the seal surface 13a of the rotary seal ring 13. As a result, it is possible to prevent the seal surface 35b of the stationary seal ring 35 from wearing unevenly in the radial direction, and therefore to prevent a deterioration in the sealing performance of the mechanical seal 1.

[0063] [Second embodiment] 6 is a cross-sectional view showing a mechanical seal according to a second embodiment of the present invention. The mechanical seal 1 of this embodiment differs from the first embodiment in the second pipe 76, the size relationship between the areas B1 and B2 of the first and second pressure-receiving surfaces 340a and 340b of the retainer 34, and the method of adjusting the fluid pressure of the seal fluid.

[0064] The second pipe 76 of this embodiment is provided independently of the first pipe 75. The same fluid as the flushing fluid (sealed fluid) flowing through the first pipe 75 flows through the second pipe 76 as a sealing fluid. Note that a fluid different from the flushing fluid may also flow through the second pipe 76 as a sealing fluid.

[0065] Fig. 7 is an enlarged cross-sectional view of a main portion of Fig. 6. As shown in Fig. 7, in the retainer 34 of this embodiment, the outer diameter of the first cylindrical portion 341 is smaller than the outer diameter of the second cylindrical portion 342. As a result, the area B1 of the first pressure-receiving surface 340a of the retainer body 340 is larger than the area B2 of the second pressure-receiving surface 340b. Therefore, the fluid pressure P2 of the sealing fluid is adjusted by the pair of pressure adjustment valves 4 to be greater than the fluid pressure P1 of the flushing fluid so that the force relationship of the above formula (1) is always maintained based on the size relationship between the areas B1 and B2.

[0066] In this embodiment, the area B1 of the first pressure-receiving surface 340a of the retainer body 340 is larger than the area B2 of the second pressure-receiving surface 340b. Therefore, compared to when area B1 is smaller than area B2 (see FIG. 2), the balance diameter D1 of the stationary seal ring 35 (the outer diameter of the retainer 35 (first cylindrical portion 341) that presses against the stationary seal ring 35 in this embodiment) can be made smaller. Note that it is sufficient that the area B1 of the first pressure-receiving surface 340a is equal to or larger than the area B2 of the second pressure-receiving surface 340b. Since other configurations of this embodiment are similar to those of the first embodiment, the same reference numerals are used and their description will be omitted.

[0067] As described above, also in this embodiment, the force with which the pressing surface 341a of the retainer 34 presses the stationary seal ring 35 in the other axial direction can be adjusted by adjusting the fluid pressure P2 of the seal fluid with the pair of pressure regulating valves 4. By adjusting this pressing force, the pressing force with which the seal surface 35b of the stationary seal ring 35 presses the seal surface 13a of the rotary seal ring 13 can be adjusted. This makes it possible to appropriately adjust the amount of leakage of the sealed fluid from between the seal surfaces 13a, 35b of the rotary seal ring 13 and the stationary seal ring 35.

[0068] Furthermore, because the area B1 of the first pressure-receiving surface 340a of the retainer 34 is larger than the area B2 of the second pressure-receiving surface 340b, the balance diameter D1 of the stationary seal ring 35 can be made smaller than when the area B1 is smaller than the area B2. This makes it possible to reduce the pressing force of the pressing surface 341a of the retainer 35 on the stationary seal ring 35 and the peripheral speed of the pressing surface 341a. This is particularly effective in a high-load mechanical seal 1 used under high-pressure and high-peripheral-speed conditions, as in this embodiment.

[0069] [others] Although the pressure regulating valve 4 in each of the above embodiments can manually adjust the fluid pressure P2, it may also adjust the fluid pressure P2 automatically. In this case, for example, a sensor may detect the amount of sealed fluid leaking from between the seal surfaces 13a, 35b of the rotary seal ring 13 and the stationary seal ring 35, and if the amount of leakage is outside a predetermined range in a control unit that receives the detection information, the pressure regulating valve 4 may be controlled to automatically adjust the fluid pressure P2.

[0070] In each of the above embodiments, the pressure regulating valve 4 regulates the fluid pressure P2 of the sealing fluid. However, in addition to or instead of this, a pressure regulating valve 4 may be provided in the first pipe 75 to manually or automatically regulate the fluid pressure P1 of the flushing fluid (sealed fluid). In this case, the pressure regulating valve 4 provided in the first pipe 75 regulates the fluid pressure P1 to a range greater than the fluid pressure P2 in the first embodiment, and regulates the fluid pressure P1 to a range less than the fluid pressure P2 in the second embodiment. Note that, when adjusting the fluid pressure P1 using the pressure regulating valve 4 in the first embodiment, it is preferable to provide a mechanism for increasing the fluid pressure P1. For example, a floating ring may be provided between the rotating shaft 71 and the casing 72 on the other axial side of the rotating-side unit 2, and the gap for the flushing fluid flowing between this floating ring and the rotating shaft 71 may be reduced to increase the fluid pressure P1.

[0071] The second pipe 76 in the first embodiment branches off from the first pipe 75, but similar to the second embodiment, it may be provided independently of the first pipe 75. In this case, the sealing fluid flowing through the second pipe 76 may be the same fluid as the flushing fluid (sealed fluid) flowing through the first pipe 75, or may be a different fluid.

[0072] The second pipe 76 in the second embodiment is provided independently of the first pipe 75, but may branch off from the first pipe 75 in the same manner as in the first embodiment. The mechanical seal of the present invention can also be used under conditions other than high load conditions. In such cases, the force relationship in the above formula (1) can be set to take into account the biasing force of the spring 47.

[0073] 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 all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0074] 1 Mechanical seal 3 Stationary unit 4. Pressure Regulating Valve 13 Rotating seal ring 13a sealing surface 34 Retainer 35 Stationary sealing ring 35b sealing surface 35d1 1st end face (end face) 55 Inlet channel 61 1st fluid chamber 62 2nd fluid chamber 71 Rotation axis 72 Casing 340a First side surface (first pressure receiving surface) 340b Second side surface (second pressure receiving surface) 341a End face (pressing surface) B1 Area of ​​the first pressure receiving surface B2 Area of ​​the second pressure receiving surface P1 Fluid pressure of the flushing fluid (sealed fluid) P2 Fluid pressure of the sealing fluid

Claims

1. a rotary seal ring provided on the rotary shaft so as to be integrally rotatable therewith and having a seal surface formed on one axial side thereof; a stationary side unit provided in a casing surrounding the rotary shaft, the stationary side unit having a stationary seal ring with a seal surface formed on the other axial side thereof opposed to the seal surface of the rotary seal ring, A mechanical seal that seals a sealed fluid in an in-machine region by the rotating seal ring and the stationary seal ring, The stationary side unit is a retainer that is attached to the casing side so as to be movable in the axial direction and that holds the stationary seal ring; a first fluid chamber formed in communication with the in-machine region so that the sealed fluid is introduced thereinto and the fluid pressure of the sealed fluid presses the retainer to one side in the axial direction; a second fluid chamber formed independently of the in-machine region and the first fluid chamber so that a seal fluid is introduced thereinto and a fluid pressure of the seal fluid presses the retainer toward the other axial direction; a pressure regulating valve capable of regulating the fluid pressure of at least one of the sealed fluid and the sealing fluid, The in-machine region is formed radially outward of both seal surfaces of the rotary seal ring and the stationary seal ring, the retainer has a pressing surface that presses only a radially inner portion of an end face on the one axial direction side of the stationary seal ring toward the other axial direction, The pressure regulating valve is capable of adjusting the fluid pressure of the sealing fluid.

2. 2. The mechanical seal according to claim 1, wherein the stationary unit further comprises an introduction passage for introducing a part of a flushing fluid for cooling both of the seal surfaces into the second fluid chamber as the seal fluid.

3. The retainer includes: a first pressure receiving surface that receives the fluid pressure of the sealed fluid in the first fluid chamber from the other axial direction; a second pressure receiving surface that receives the fluid pressure of the seal fluid in the second fluid chamber from one axial side, 3. The mechanical seal according to claim 1, wherein an area of ​​the first pressure-receiving surface is equal to or larger than an area of ​​the second pressure-receiving surface.

4. 2. The method for adjusting fluid pressure in a mechanical seal according to claim 1, further comprising adjusting the at least one fluid pressure by the pressure regulating valve so as to satisfy the following relationship: P1×B1<P2×B2 Here, the variables in the above formula are defined as follows: P1: Fluid pressure of the sealed fluid in the first fluid chamber B1: Area of ​​the first pressure receiving surface of the retainer that receives the fluid pressure of the sealed fluid in the first fluid chamber from the other axial side P2: Fluid pressure of the sealing fluid in the second fluid chamber B2: Area of ​​the second pressure receiving surface of the retainer that receives the fluid pressure of the seal fluid in the second fluid chamber from one axial side

Images