JP2006250307A - Axial flow seal device and shaft sealing device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial flow seal device capable of controlling properly the seal gas amount supplied from a seal gas supply passage and of exerting a good sealing function at all times. <P>SOLUTION: The axial flow seal device 4 is structured so that a pair of segment seals 11 are mounted in a ring-shaped seal chamber 10 formed at the inside surface of a seal case 1, which is furnished with the seal gas supply passage 13 to supply the seal gas 12 to between two seals 11, and thereby the area between regions B and C is shielded and sealed by flowing the seal gas 12 out to the both side regions B and C of the seal chamber 10 from the space between the confronting peripheral surfaces of the segment seals 11 and the rotary shaft 2, wherein the seal gas supply passage 13 is furnished with an orifice 17 as a throttle for the rate of gas flow. The segment seals 11 are formed by tying together segments 11a in the shape of circular arc using a garter spring 14 in a ring-shaped form. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an axial flow sealing device used in a rotary device such as a compressor, and is held in a sealed state in a seal case in an annular seal chamber formed in an inner peripheral portion of the seal case through which the rotary shaft penetrates. In addition, a pair of axial flow seals inserted into the rotary shaft is loaded, and a seal gas supply passage for supplying a seal gas between both axial flow seals is formed in the seal case, and the seal gas is supplied to each axial flow seal. The axial flow sealing device is configured to shield and seal both sides of the sealing chamber by allowing the gas to flow into the both sides of the seal chamber from between the opposed peripheral surfaces of the rotating shaft and the rotary shaft. The present invention relates to a shaft seal device used as a next seal.

  As a conventional axial flow sealing device, for example, it rotates in a state where it is pressed and contacted with a sealing surface which is an axially opposed wall surface in an annular sealing chamber formed in an inner peripheral portion of a sealing case through which a rotating shaft penetrates. A pair of segment seals inserted into the shaft, and a seal gas supply path for supplying seal gas to a space surrounded by the segment case, the inner wall surface of the seal chamber, and the outer peripheral surface of the rotating shaft in the seal case A segment seal device configured to shield and seal both side regions of the seal chamber is known. In such a segment seal device, each segment seal is composed of one seal ring (an arc-shaped segment is annularly bound by a garter spring (extension spring)) (for example, see Patent Document 1), and each segment Some seals are configured by a pair of seal rings (see, for example, FIG. 7 of Patent Document 2).

  Such a conventional axial flow seal device (segment seal device) is a gas that is slightly higher in pressure than both sides of the seal chamber as a seal gas, and does not leak into the both sides. On the other hand, by using inert and harmless nitrogen gas or the like, the both side regions can be well shield-sealed.

Japanese Utility Model Publication No. 03-017471 Japanese Utility Model Publication No. 05-040656 (FIG. 7)

However, in such a conventional axial flow seal device, there is a possibility that the amount of seal gas (seal gas supply amount) supplied from the seal gas supply path becomes excessive or insufficient (insufficient). In some cases, the proper sealing function was not exhibited. Further, the leak amount of seal gas (seal gas leak amount) from the gap between the axial flow seal and the rotating shaft increases as the gap increases (particularly, under certain seal conditions, the gap increase amount is the third power). In general, the clearance increases in proportion to the safety factor in order to avoid damage due to contact between the axial seal and the rotating shaft. Increases more than necessary, and the running cost increases.
Furthermore, when the axial flow seal device is used under high temperature conditions, the gap may increase due to the difference in thermal expansion coefficient due to the difference in material between the axial flow seal and the rotating shaft. In addition, the consumption of the seal gas increases more than necessary and the running cost increases. Such a problem occurs not only when the axial flow sealing device is used as a primary seal, but also with a shaft sealing device that uses the axial flow sealing device as a secondary seal.

  The present invention provides an axial flow seal device that can appropriately control the amount of seal gas supplied from the seal gas supply path without causing such problems, and can always exhibit a good sealing function. An object of the present invention is to provide a shaft sealing device that can exhibit a good sealing function by using the axial flow sealing device as a secondary seal.

  A first aspect of the present invention is a pair of axial flows that are held in a sealed state in a seal case and fitted into a rotary shaft in an annular seal chamber formed in the inner peripheral portion of the seal case through which the rotary shaft penetrates. In addition to loading the seal, a seal gas supply path for supplying a seal gas between both axial flow seals is formed in the seal case, and the seal gas is passed between the opposed peripheral surfaces of each axial flow seal and the rotary shaft in the seal chamber. In order to achieve the above object, in the axial flow sealing device configured to shield and seal both side regions by flowing out to both side regions, in particular, a gas flow restrictor is provided in the seal gas supply path. It is suggested to keep. As described at the beginning, the seal gas supplied from the seal gas supply path is a gas that is slightly higher in pressure than the both sides of the seal chamber and leaks into both sides of the gas (generally, the both sides Nitrogen gas that is inert and harmless to the fluid in the area is used. As the gas flow restrictor, generally, an orifice having a diameter of 0.3 to 5.0 mm is used.

  In such an axial flow sealing device, an annular partition wall located between the axial flow seals is projected on the inner peripheral portion of the seal case, and the downstream end of the seal gas supply path is connected to the inner periphery of the partition wall. It is preferable to open the surface.

  In a preferred embodiment, the axial flow sealing device is pressed into contact with a sealing surface, which is an axially opposed wall surface, in an annular sealing chamber formed in an inner peripheral portion of a sealing case through which a rotating shaft penetrates. A pair of segment seals inserted into the rotating shaft in a state is loaded, and a seal gas supply passage for supplying a seal gas to the seal chamber is formed in the seal case so as to shield and seal both sides of the seal chamber The segment seal device is configured. In such a segment seal device, each segment seal is constituted by one seal ring in which an arc segment is annularly bound by a garter spring, or each arc segment is annularly bound by a garter spring. A pair of seal rings. In addition, a spring holding hole penetrating in the axial direction without intersecting the seal gas supply passage is formed in the annular partition wall positioned between the two segment seals, and the two segment seals are separated in the spring holding hole. It is preferable that both the segment seals are pressed and contacted with the seal surface of the seal chamber by inserting and holding the spring that presses and biases, and the partition wall does not intersect the seal gas supply path in the axial direction. It is preferable that the drive pins extending in the direction are supported through, and both end portions of the drive pins are engaged with the opposing surfaces of the segment seals to prevent relative rotation of the segment seals with respect to the seal case. .

  Secondly, according to the present invention, a primary seal and a secondary seal are arranged in parallel in the axial direction between a seal case and a rotary shaft penetrating the seal case, and the sealed fluid region and the two seals are separated by the primary seal. In the shaft seal device configured to shield and seal the intermediate region and the intermediate region and the non-sealed fluid region by the secondary seal, the axial seal device described above is used as the secondary seal. Propose. In such a shaft seal device, a seal gas discharge passage communicating with the intermediate region is formed in the seal case, and the seal gas leaking from the axial flow seal device to the intermediate region is primarily sealed from the seal gas discharge passage. It is preferable that the fluid is discharged while accompanying fluid leaking to the intermediate region. Further, when the fluid in the sealed fluid region is a gas, a non-contact mechanical seal configured so that the opposing seal rings relatively rotate in a non-contact state is used as the primary seal. As a non-contact type mechanical seal, for example, a sealing ring on the seal case side (case side sealing ring) and a sealing ring on the rotating shaft side (rotating shaft side sealing ring) are provided on the sealing end surface which is the opposite end surface of both sealing rings. A fluid pressure type configured to be held in a non-contact state by a dynamic pressure generated by one formed dynamic pressure generating groove, a sealed fluid region from a seal gas supply passage penetrating a seal case and a case side sealing ring A high-pressure seal gas is supplied between the sealed end faces, and a static pressure is generated between the sealed end faces, thereby holding both sealed rings in a non-contact state, or a case-side sealed ring and a rotating shaft. Inductive ring type, etc., in which a floating ring is interposed between the side sealing rings and the opposing sealing rings (rotating shaft side sealing ring and induction ring) are held in a non-contact state by the dynamic pressure generated therebetween. used.

  In the axial flow sealing device of the present invention, the amount of seal gas supplied from the seal gas supply passage is controlled by a gas flow restrictor such as an orifice disposed in the supply passage, so that an appropriate amount without excess or deficiency is obtained. Seal gas can be supplied and a good sealing function is always exhibited. In addition, even when the gap between the axial seal and the rotating shaft becomes large due to the difference in thermal expansion coefficient due to the material of both, or when designed with a safety factor in mind, the sealing gas consumption is reduced by the throttle function of the gas flow restrictor. However, the running cost can be reduced as much as possible.

  Further, according to the shaft seal device of the present invention, the axial flow seal device that exhibits an appropriate sealing function as described above is used as the secondary seal, and the leakage fluid from the primary seal is accompanied by the seal gas from the intermediate region. Since the seal gas is discharged from the seal gas discharge passage to the outside of the shaft seal device, a good and reliable shaft seal function can be obtained even when the sealed fluid is a toxic gas or the like that should avoid leakage into the non-sealed fluid region. It can be demonstrated.

  FIG. 1 is a longitudinal side view of the upper half portion showing a case where the shaft sealing device according to the present invention is applied as a shaft sealing means of a compressor, and FIG. 2 is a longitudinal side view showing the lower half portion of the coaxial sealing device, FIG. 3 is an enlarged view of the main part of FIG. 1 (an axial flow sealing device according to the present invention).

  The shaft seal device shown in FIGS. 1 and 2 includes a primary seal 3 and a second seal between a seal case 1 attached to a compressor housing (not shown) and a rotating shaft (turbine shaft) 2 penetrating therethrough. The secondary seal 4 is arranged in parallel in the axial direction, and the primary seal 3 shields and seals the sealed fluid region (compressor's in-machine region) A and the intermediate region B between the seals 3 and 4 and the secondary seal 4. The intermediate region B and the non-sealed fluid region (compressor outside region) C are shield-sealed to completely prevent leakage of the fluid (gas) in the sealed fluid region A to the non-sealed fluid region C. It is composed of.

  As shown in FIGS. 1 and 2, the primary seal 3 is provided on the rotary shaft 2 so as to face the stationary ring 5 and a stationary ring (case-side sealing ring) 5 held in the seal case 1 so as to be movable in the axial direction. The rotating ring (sealing shaft side sealing ring) 6, the spring 7 (see FIG. 2) interposed between the seal case 1 and the stationary ring 5, and the sealing rings 5 and 6 are held under pressure. And by generating a dynamic pressure between the rotary ring 6 and the idle ring 8 by a dynamic pressure generating groove 6a formed on the sealing end face of the rotary ring 6. This is a floating ring type non-contact type mechanical seal configured to shield and seal the sealed fluid region A and the intermediate region B while maintaining a non-contact state. The rotary shaft 2 includes a main body shaft 2a and a plurality of sleeves 2b fitted and fixed thereto, and the rotary ring 6 is fitted and fixed to the sleeves 2b. The stationary ring 5 is prevented from rotating relative to the seal case 1 by engaging a drive pin 5 a attached thereto with an engagement hole provided in the seal case 1. The guide ring 8 is prevented from rotating relative to the stationary ring 5 by engaging a drive pin 5 b attached to the stationary ring 5 with an engagement hole provided in the idle ring 8. The stationary ring 5 and the induction ring 8 are secondarily sealed by an O-ring 9 interposed therebetween.

  The secondary seal 4 is an axial flow sealing device according to the present invention. This axial flow sealing device 4 is provided in an annular seal chamber 10 formed on the inner peripheral portion of the seal case 1 as shown in FIGS. A pair of segment seals 11, 11 as axial flow seals are loaded, and a seal gas supply passage 13 for supplying the seal gas 12 to the seal chamber 10 is formed in the seal case 1. B is a segment seal device configured to shield and seal B and the non-sealed fluid region C.

  An annular partition wall 1a that bisects the seal chamber 10 in the axial direction projects from the inner peripheral portion of the seal case 1, and each segment seal 11 is loaded between the partition wall 1a and each seal surface 10a. Has been.

  Each segment seal 11 is composed of one seal ring 11a divided into a plurality of portions (arc-shaped segments) in the circumferential direction. That is, as shown in FIGS. 1 to 3, the seal ring 11 a is formed by binding a plurality of arc segments in a ring shape with a garter spring 14, and is fitted into the rotary shaft 2 (sleeve 2 b). . As shown in FIG. 2, the segment seals 11 and 11 are urged to be separated in the axial direction by a suitable number (only one is shown) of springs (compression coil springs) 15 interposed therebetween. That is, the side end surface of each segment seal 11, that is, the seal ring 11 a is pressed against the seal surface 10 a by the spring 15. The partition wall 1a is formed with a spring holding hole 10c penetrating in the axial direction without intersecting a seal gas supply path 13 described later, and a spring 15 is inserted and held in the spring holding hole 10c. Further, as shown in FIG. 2, an appropriate number of drive pins 16 (only one is shown) extending in the axial direction without intersecting the seal gas supply passage 13 are penetrated and supported in the partition wall 1a. By engaging both ends of the pin 16 with engagement holes formed on the opposing surfaces of the seal rings 11a and 11a, relative rotation of the seal rings 11a with respect to the seal case 1 is prevented.

  As shown in FIGS. 1 and 3, the seal gas supply path 13 passes through the seal case 1 in the radial direction and is opened at the inner peripheral portion of the partition wall 1 a, and is slightly larger than the side regions B and C of the seal chamber 10. A high-pressure seal gas 12 is supplied to the seal chamber 10. As the sealing gas 12, harmless nitrogen gas or the like that is inert to the fluid in each of the regions A to C and does not interfere with the leakage into the non-sealed fluid region C is used.

  Thus, the gas flow restrictor 17 is disposed in the seal gas supply path 13. In this example, as shown in FIG. 1 and FIG. 3, an annular plate 17a is arranged at an appropriate position of the seal gas supply passage 13 and in the vicinity of the seal gas supply passage portion passing through the partition wall 1a. An orifice formed by a central hole (0.3 to 5.0 mm diameter) is used as the restrictor 17.

  Further, as shown in FIGS. 1 and 3, the seal case 1 is formed with a seal gas discharge passage 18 communicating with the intermediate region B. From the seal gas discharge passage 18, the axial flow seal device 4 is connected to the intermediate region B. The seal gas 13 leaking to B is discharged while accompanying the fluid (gas) leaking from the primary seal (floating ring type non-contact mechanical seal) 3 to the intermediate region B.

  In the shaft seal device configured as described above, the fluid in the sealed fluid region A (gas as the sealed fluid) is sealed by the floating ring-type non-contact mechanical seal 3 as the primary seal. At this time, since the primary seal 3 is a non-contact type mechanical seal that allows leakage, the sealed fluid leaks into the intermediate region B from between the stationary ring 6 and the idle ring 8 although the amount is small.

  On the other hand, in the axial flow seal device (segment seal device) 4 that is the secondary seal configured as described above, both the segment seals 11 and 11 are in pressure contact with the seal surfaces 10 a and 10 a that are both side walls of the seal chamber 10. In this state, the seal gas 12 is inserted into the rotary shaft 2 and is supplied to the seal chamber 10 through the seal gas supply path 13 from the intermediate region B and the non-sealed fluid region C. At this time, the seal gas 12 supplied to the seal chamber 10 is divided and leaked from between the opposing peripheral surfaces of the segment seals 11 and 11 and the rotary shaft 2 to both regions B and C. Therefore, the intermediate region B and the non-sealed fluid region C are surely shielded and sealed. The seal gas 12 leaked to the intermediate region B is discharged from the seal gas discharge path 18 while accompanying the leaked fluid from the primary seal 3 to the intermediate region B. Therefore, leakage of the sealed fluid from the sealed fluid region A to the non-sealed fluid region C is surely prevented, and it is undesirable for the sealed fluid to be discharged into the unsealed fluid region C as it is (existent). Even in the case of a poison gas or the like, it can be satisfactorily and safely sealed.

  Thus, the seal gas 12 is squeezed by the orifice 17 disposed in the seal gas supply path 13 and then supplied to the seal chamber 10, so that the differential pressure and pressure between the side regions B and C of the seal chamber 10 are increased. Even under varying sealing conditions, the amount of seal gas supplied from the seal gas supply passage 13 to the seal chamber 10 (seal gas supply amount) becomes excessive, or conversely, becomes too small and the intermediate region B (or not) The backflow phenomenon from the sealed fluid region C) to the seal chamber 10 does not occur, and an appropriate amount of seal gas 12 is always supplied to the seal chamber 10, and sealing by the axial flow seal device 4 is performed. The function will be exhibited well. That is, when the seal gas supply amount is excessive, the seal gas supply amount and the seal gas leakage amount from the seal chamber 10 (the amount of seal gas flowing out from the segment seals 11 and 11 to both regions B and C) are unbalanced. As a result, the pressure in the seal chamber 10, that is, the pressure in the portion downstream of the orifice 17 in the seal gas supply passage 13 increases, the amount of gas passing through the orifice 17 decreases, and the seal gas supply amount is adjusted appropriately (decrease). ) On the contrary, when the seal gas supply amount becomes too small, the seal gas supply amount and the seal gas leakage amount become imbalanced, and the pressure in the seal chamber 10 (the portion on the downstream side of the orifice 17 in the seal gas supply passage 13). ) Decreases, the amount of gas passing through the orifice 17 increases, and the seal gas supply amount is adjusted (increased) appropriately. In this way, the seal gas supply amount is automatically adjusted and controlled by the function of the orifice 17, so that an appropriate seal gas supply amount is always obtained, and the sealing function by the axial flow sealing device 4 is satisfactorily exhibited.

  Further, the amount of seal gas leakage from between each segment seal 11 and the rotary shaft 2 is to prevent the axial flow seal 11 from being broken when the gap between the two and 11 becomes large due to a difference in thermal expansion coefficient or the like. Even if the clearance is set large in consideration of the safety factor, the orifice function does not increase more than necessary. Therefore, even when the axial flow seal 4 is used under high temperature conditions, the amount of seal gas consumption does not increase more than necessary and the running cost does not increase. In addition, the gap can be designed to be large without increasing the amount of seal gas consumption, and the axial flow seal 11 can be prevented from being broken to exhibit a highly reliable sealing function.

  The shaft sealing device and the axial flow sealing device according to the present invention are not limited to the above-described embodiments, and can be appropriately improved and changed without departing from the basic principle of the present invention.

  For example, when the axial flow seal device 4 is a segment seal device, as shown in FIG. 4, the segment seal 11 serving as each axial flow seal can be constituted by a pair of seal rings 11a and 11a. is there. Further, each axial flow seal 11 may be a circumferential seal, a fixed bush seal, a Rayleigh step seal, etc. in addition to the above-described segment seal (floating ring seal). The axial flow seal device 4 can also be used as a primary seal. However, in a shaft seal device that uses the axial flow seal device 4 as a secondary seal, the primary seal 3 has the above-described induction ring type non-contact type. Even in the case of non-contact type mechanical seals other than mechanical seals (for example, dynamic pressure type non-contact type mechanical seals, static pressure type non-contact type mechanical seals, etc.), the case side sealing ring and the rotary shaft side sealing ring are in relative rotational sliding contact. It may be an end surface contact type mechanical seal or a floating ring type mechanical seal in which the floating ring and the rotary shaft side sealing ring are in relative rotational sliding contact.

It is a vertical side view which shows the upper half part of the shaft seal apparatus which concerns on this invention. It is a vertical side view which shows the lower half part of a coaxial sealing apparatus. It is an enlarged view of the principal part (axial flow sealing apparatus) of FIG. It is a vertical side view equivalent to FIG. 3 which shows the modification of the axial flow sealing apparatus which concerns on this invention.

Explanation of symbols

1 seal case 1a partition wall 2 rotating shaft 3 primary seal
4 Secondary seal (Axial flow seal device)
5 Stationary ring 6 Rotating ring (opposing seal ring)
7 Spring 8 Free ring (opposing seal ring)
DESCRIPTION OF SYMBOLS 10 Seal chamber 10a Seal surface 11 Segment seal 11a Seal ring 12 Seal gas 13 Seal gas supply path 14 Garter spring 15 Spring 16 Drive pin 17 Orifice (gas flow restrictor)
18 Seal gas discharge path A Sealed fluid area B Middle area (both sides of the seal chamber)
C Unsealed fluid area (both sides of the seal chamber)

Claims (9)

A pair of axial flow seals that are held in a sealed state in the seal case and fitted into the rotation shaft are loaded into an annular seal chamber formed in the inner peripheral portion of the seal case through which the rotation shaft passes, and the seal case In addition, by forming a seal gas supply path for supplying a seal gas between the two axial flow seals, by allowing the seal gas to flow out between the opposed peripheral surfaces of each axial flow seal and the rotary shaft to both sides of the seal chamber, An axial flow sealing device configured to shield and seal the both side regions, wherein a gas flow restrictor is disposed in a seal gas supply path. An annular partition wall located between the axial flow seals protrudes from the inner peripheral portion of the seal case, and the downstream end of the seal gas supply path is opened to the inner peripheral surface of the partition wall The axial flow sealing device according to claim 1. The axial flow seal device according to claim 1 or 2, wherein each axial flow seal is a segment seal that is pressed into contact with a seal surface that is a side wall surface of a seal chamber and is fitted into a rotary shaft. . The axial flow sealing device according to claim 3, wherein each segment seal is constituted by one seal ring formed by binding an arcuate segment in a ring shape with a garter spring. By forming a spring holding hole penetrating in the axial direction without intersecting the seal gas supply path in the partition wall, and inserting and holding a spring that presses and urges both segment seals in the spring separating hole, The axial flow seal device according to claim 2, 3 or 2, and 4, wherein both the segment seals are configured to be brought into press contact with the seal surface of the seal chamber. 6. The axial flow seal device according to claim 1, 2, 3, 4, or 5, wherein the gas flow restrictor is an orifice. A primary seal and a secondary seal are arranged in parallel in the axial direction between the seal case and the rotary shaft that penetrates the seal case, and the primary seal shields and seals the sealed fluid region and the intermediate region between the two seals. And a shaft seal device configured to shield and seal the intermediate region and the non-sealed fluid region with a secondary seal,
A shaft seal device, wherein the secondary seal is the axial flow seal device according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6. A seal gas discharge path communicating with the intermediate area is formed in the seal case, and a seal gas leaking from the axial flow sealing device to the intermediate area is leaked from the primary seal to the intermediate area from the seal gas discharge path. The shaft seal device according to claim 7, wherein the shaft seal device is configured to be discharged while being accompanied. The primary seal is a non-contact type mechanical seal configured such that the opposing seal rings rotate relative to each other in a non-contact state, and the fluid in the sealed fluid region is a gas. Item 9. The shaft seal device according to Item 8.