rotary joint

Abstract

To provide a rotary joint capable of suppressing the mixture of foreign matters into sealed fluid while rotatably supporting a rotary shaft.SOLUTION: A rotary joint 1 includes a cylindrical case body 2 having an outside flow path 23a where sealed fluid flows, a rotary shaft 4 arranged in the case body 2 and having an inside flow path 4a where the sealed fluid flows, a mechanical seal 6 having static sealing rings 61, 62 provided on the case body 2, a rotary sealing ring 63 provided on the rotary shaft 4 in opposition to the static sealing rings 61, 62 in the axial direction, and a communication flow path 64 linking the outside flow path 23a to the inside flow path 4a for sealing a space between the static sealing rings 61, 62 and the rotary sealing ring 63, and a gas bearing 5 provided in the case body 2 for rotatably supporting the rotary shaft 4 in no contact therewith using pressurized gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotary joint. [Background technology]

[0002] A rotary joint is used to connect a flow path of a fixed member to a flow path of a rotating member. For example, in a CMP (Chemical Mechanical Polishing) apparatus used to polish the surface of a semiconductor wafer, sealed fluids such as polishing liquid, pressurizing air, cleaning water, pure water, inert gases such as nitrogen, air for air blowing, and polishing residue liquid flow between the rotating member (turntable or top ring) and the fixed member (CMP apparatus main body) that supports it. The rotary joint described in Patent Document 1 is used to allow these sealed fluids to flow between the rotating member and the fixed member.

[0003] The rotary joint of Patent Document 1 includes a cylindrical case body (main body), a rotating shaft rotatably disposed within the case body, and a plurality of mechanical seals arranged axially in an annular space between the case body and the rotating shaft. A plurality of fluid passages are formed radially penetrating the case body. The rotating shaft is formed with the same number of fluid passages as the fluid passages in the case body, opening on the outer circumferential side of the rotating shaft. A plurality of communication passages are formed in the annular space, connecting each fluid passage in the case body with each fluid passage in the rotating shaft. These communication passages are sealed by a plurality of mechanical seals. The rotating shaft is rotatably supported relative to the case body via rolling bearings. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-084691 Summary of the Invention [Problem to be solved by the invention]

[0005] In a rotary joint configured as described above, the inside of the rolling bearing that rotatably supports the rotating shaft is lubricated with a lubricant such as grease. When the rotating shaft rotates, the lubricant inside the rolling bearing may splash out of the rolling bearing. In this case, the splashed lubricant may get mixed into the sealed fluid, which may adversely affect the semiconductor manufacturing process, etc.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a rotary joint that can rotatably support a rotating shaft while preventing foreign matter from being mixed into the sealed fluid. [Means for solving the problem]

[0007] (1) The present disclosure relates to a rotary joint including: a cylindrical case body having an outer flow passage through which a sealed fluid flows; a rotating shaft disposed within the case body and having an inner flow passage through which the sealed fluid flows; a stationary seal ring provided in the case body; a rotary seal ring provided on the rotating shaft axially opposite the stationary seal ring; a mechanical seal having a communicating flow passage connecting the outer flow passage and the inner flow passage and providing a seal between the stationary seal ring and the rotary seal ring; and a gas bearing provided in the case body for rotatably supporting the rotating shaft without contact using pressurized gas.

[0008] According to the rotary joint of the present disclosure, the rotating shaft is rotatably supported without contact by the gas bearings provided in the case body. Because the gas bearings do not require lubricant, it is possible to prevent foreign matter (lubricant) from being mixed into the sealed fluid flowing through the outer flow path, the communication flow path, and the inner flow path.

[0009] (2) In the rotary joint of (1), it is preferable that the gas bearing has a radial bearing portion that supports the outer peripheral surface of the rotating shaft in a non-contact manner, and a thrust bearing portion that supports the axial end face of the rotating shaft in a non-contact manner. In this case, neither the radial bearing, which supports the outer peripheral surface of the rotating shaft without contact, nor the thrust bearing, which supports the end face in the axial direction without contact, requires lubricant, which further prevents foreign matter (lubricant) from being mixed into the sealed fluid.

[0010] (3) In the rotary joint of (1) or (2), the mechanical seal is preferably a non-contact mechanical seal that generates static pressure or dynamic pressure between the stationary seal ring and the rotating seal ring by a seal gas, thereby sealing the gap while maintaining a non-contact state with the seal gas. In this case, the stationary seal ring and the rotating seal ring of the mechanical seal are kept in a non-contact state by the seal gas, which prevents wear debris from being generated between the stationary seal ring and the rotating seal ring, thereby further preventing foreign matter (wear debris) from being mixed into the sealed fluid.

[0011] (4) In the rotary joint of (3) above, the mechanical seal is preferably a hydrostatic non-contact mechanical seal that generates hydrostatic pressure between the stationary seal ring and the rotary seal ring by the seal gas. In this case, the generation of wear debris between the stationary seal ring and the rotating seal ring can be suppressed more effectively than with a dynamic pressure type non-contact mechanical seal, which further suppresses the intrusion of foreign matter (wear debris) into the sealed fluid.

[0012] (5) In the rotary joint of (3) or (4) above, the seal gas is preferably the same type of gas as the pressurized gas. In this case, the pressurized gas for the gas bearing can be used as the seal gas for the mechanical seal, so that the running costs can be reduced.

[0013] (6) In the rotary joint of any one of (3) to (5) above, the case body preferably has a common discharge passage for discharging both the pressurized gas and the seal gas. In this case, it is not necessary to provide separate discharge paths for the pressurized gas and the seal gas in the case body, which reduces the manufacturing costs of the case body. [Effects of the Invention]

[0014] According to the rotary joint of the present disclosure, it is possible to rotatably support the rotary shaft while preventing foreign matter from being mixed into the sealed fluid. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing a rotary joint according to an embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a gas bearing. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a mechanical seal. [Figure 4] FIG. 10 is an enlarged cross-sectional view showing a modified example of the gas bearing. [Figure 5] FIG. 10 is an enlarged cross-sectional view showing another modified example of the gas bearing. DETAILED DESCRIPTION OF THE INVENTION

[0016] Next, preferred embodiments will be described with reference to the accompanying drawings. [Overall configuration] FIG. 1 is a cross-sectional view showing a rotary joint 1 according to an embodiment. The rotary joint 1 includes a cylindrical case body 2 and a rotating shaft 4. The case body 2 is attached to a stationary member of a rotating device (for example, the main body of a CMP device). The rotating shaft 4 is attached to a rotating member of the rotating device (for example, the turntable of a CMP device). In this embodiment, the case body 2 and the rotating shaft 4 are arranged with their axial directions aligned vertically.

[0017] In this disclosure, the term "axial direction" refers to a direction along the center line C of the rotary joint 1 (including a direction parallel to the center line C). In addition, in this disclosure, the term "radial direction" refers to a direction perpendicular to the center line C of the rotary joint 1, and the term "circumferential direction" refers to a direction around the center line C of the rotary joint 1. Furthermore, the orientation of the rotary joint 1 may be other than that shown in FIG. 1, but for ease of explanation, in this embodiment, the upper side of FIG. 1 will be referred to as the "upper side" of the rotary joint 1, and the lower side of FIG. 1 will be referred to as the "lower side" of the rotary joint 1.

[0018] [Case body] The case body 2 is configured by stacking a first flange 21, a second flange 22, a third flange 23, a fourth flange 24, a fifth flange 25, and a sixth flange 26 in this order from the bottom up. The first flange 21 to the fifth flange 25 are all formed in an annular shape. The sixth flange 26 is formed in a disk shape. All of the flanges 21 to 26 are fixed in a vertically stacked state by a plurality of bolts 27 (only one is shown in FIG. 1). As a result, the case body 2 as a whole is formed in a cylindrical shape with a top.

[0019] The gap between the first flange 21 and the second flange 22, the gap between the second flange 22 and the third flange 23, the gap between the third flange 23 and the fourth flange 24, and the gap between the fourth flange 24 and the fifth flange 25 are each sealed by an O-ring 28.

[0020] An outer flow passage 23a, through which the sealed fluid flows, is formed at a predetermined circumferential position of the third flange 23 and extends radially. Examples of the sealed fluid include polishing liquid, pressurizing air, cleaning water, pure water, inert gas such as nitrogen, air for air blowing, and polishing residue liquid. The outer flow passage 23a opens on both the inner and outer circumferential surfaces of the third flange 23. The openings on the outer circumferential surface of the third flange 23 serve as connection ports to which the piping of the fixed-side member is connected. As described above, the case body 2 has the outer flow passage 23a through which the sealed fluid flows.

[0021] Rotation Axis The rotating shaft 4 is formed in a cylindrical shape. The rotating shaft 4 is disposed on the inner peripheral side of the case body 2. The rotating shaft 4 has an inner flow passage 4a through which the sealed fluid flows. Specifically, the inner flow passage 4a through which the sealed fluid flows is formed extending in the axial direction inside the rotating shaft 4. The upper end of the inner flow passage 4a opens on the outer peripheral surface 4b of the rotating shaft 4 at a height position corresponding to the outer flow passage 23a of the case body 2. Although not shown in the figure, the lower end of the inner flow passage 4a opens on the lower end surface of the rotating shaft 4. The piping of the rotating-side member is connected to the opening on this lower end surface.

[0022] [Gas bearings] Rotary joint 1 includes gas bearing 5 that rotatably supports rotating shaft 4 without contact. Gas bearing 5 in this embodiment is provided on fifth flange 25 of case body 2, and supports the upper end of rotating shaft 4. Specifically, an annular fitting groove 25e that opens upward is formed in the center of fifth flange 25. Gas bearing 5 is fitted into fitting groove 25e from above.

[0023] Figure 2 is an enlarged cross-sectional view of gas bearing 5. In Figure 2, gas bearing 5 is, for example, a hydrostatic gas bearing, and employs a multiple-hole, inherently restrictor type. Gas bearing 5 has a radial bearing portion 51 and a thrust bearing portion 52. Radial bearing portion 51 supports outer peripheral surface 4b of rotating shaft 4 in a non-contact manner. Thrust bearing portion 52 supports an axially upper end face 4c of rotating shaft 4 in a non-contact manner.

[0024] The thrust bearing portion 52 is made of, for example, a disk-shaped member. The thrust bearing portion 52 has an annular protrusion 52a that protrudes upward. The protrusion 52a is fitted into a recess 26a formed in the center of the lower surface of the sixth flange 26. The upper surface of the protrusion 52a abuts against the bottom surface of the recess 26a. The outer peripheral surface of the thrust bearing portion 52 is fitted into and fixed to the inner peripheral surface of the fitting groove 25e of the fifth flange 25.

[0025] Radial bearing portion 51 is made of, for example, a cylindrical member. Radial bearing portion 51 protrudes downward from the radially outer portion of thrust bearing portion 52. The outer peripheral surface of radial bearing portion 51 is fitted into and fixed to the inner peripheral surface of fitting groove 25e of fifth flange 25. The inner diameter of radial bearing portion 51 is slightly larger than the outer diameter of rotating shaft 4. As described above, gas bearing 5 is formed as a whole in the shape of a closed cylinder. The upper end of rotating shaft 4 is inserted into gas bearing 5 from below.

[0026] A circumferential groove 51a is formed around the entire outer periphery of the radial bearing portion 51. A plurality of ejection holes 53 communicating with the circumferential groove 51a are formed to penetrate the radial bearing portion 51 in the radial direction. The plurality of ejection holes 53 are formed at equal intervals around the circumferential direction of the radial bearing portion 51. Each ejection hole 53 ejects pressurized gas between the inner circumferential surface 51b of the radial bearing portion 51 and the outer circumferential surface 4b of the rotating shaft 4. Each ejection hole 53 has, in order from the outside in the radial direction, a large diameter portion 53a, a throttle portion 53b, and a small diameter portion 53c.

[0027] The large diameter portion 53a opens at the bottom surface of the circumferential groove 51a of the radial bearing portion 51. The small diameter portion 53c is formed to have a smaller diameter than the large diameter portion 53a. The small diameter portion 53c opens at the inner circumferential surface 51b of the radial bearing portion 51. The opening of the small diameter portion 53c serves as an ejection port 53d for ejecting pressurized gas. The throttle portion 53b is formed so as to gradually reduce in diameter from the radial inner end of the large diameter portion 53a to the radial outer end of the small diameter portion 53c.

[0028] A supply passage 25c is formed in the fifth flange 25 to supply pressurized gas from outside the rotary joint 1 to the plurality of ejection holes 53. In this embodiment, the supply passage 25c is a hole formed radially penetrating the fifth flange 25 at a predetermined location in the circumferential direction. The supply passage 25c communicates with the circumferential groove 51a of the radial bearing portion 51. As a result, the supply passage 25c communicates with each of the plurality of ejection holes 53 via the circumferential groove 51a.

[0029] A plurality of ejection holes 54 for ejecting pressurized gas are formed in the thrust bearing portion 52 between its lower surface 52b and the upper end surface 4c of the rotary shaft 4. Each ejection hole 54 is formed to penetrate in the up-down direction, radially inward of the protruding portion 52a of the thrust bearing portion 52. Each ejection hole 54 has, in order from top to bottom, a large diameter portion 54a, a throttle portion 54b, and a small diameter portion 54c.

[0030] The large diameter portion 54a opens at the upper surface of the thrust bearing portion 52. The small diameter portion 54c is formed to have a smaller diameter than the large diameter portion 54a. The small diameter portion 54c opens at the lower surface 52b of the thrust bearing portion 52. The opening of the small diameter portion 54c serves as an ejection port 54d for ejecting pressurized gas. The throttle portion 54b is formed so as to gradually decrease in diameter from the lower end of the large diameter portion 54a to the upper end of the small diameter portion 54c.

[0031] There are no particular limitations on the pressurized gas used in the radial bearing portion 51 and the thrust bearing portion 52 as long as it is gaseous. In this embodiment, compressed air is used as the pressurized gas.

[0032] A supply passage 26b is formed in the center of the sixth flange 26, through which pressurized gas is supplied from outside the rotary joint 1 to the plurality of ejection holes 54. In this embodiment, the supply passage 26b is a hole formed in the sixth flange 26, penetrating in the vertical direction from the top surface thereof to the bottom surface of the recessed portion 26a. The supply passage 26b is in communication with each of the plurality of ejection holes 54.

[0033] In gas bearing 5 configured as described above, pressurized gas is supplied from supply passage 25c of fifth flange 25 to multiple ejection holes 53 via circumferential groove 51a of radial bearing portion 51. The pressurized gas supplied to each ejection hole 53 is ejected from ejection port 53d into between inner circumferential surface 51b of radial bearing portion 51 and outer circumferential surface 4b of rotating shaft 4. This ejected pressurized gas rotatably supports outer circumferential surface 4b of rotating shaft 4 without contacting inner circumferential surface 51b of radial bearing portion 51.

[0034] Further, pressurized gas is supplied from supply passage 26b of sixth flange 26 to the plurality of ejection holes 54 of thrust bearing portion 52. The pressurized gas supplied to each ejection hole 54 is ejected from ejection port 54d into a gap between lower surface 52b of thrust bearing portion 52 and end face 4c of rotating shaft 4. This ejected pressurized gas rotatably supports end face 4c of rotating shaft 4 without contacting lower surface 52b of thrust bearing portion 52.

[0035] An O-ring 55 is provided between the upper surface of the protruding portion 52a and the bottom surface of the recessed portion 26a, radially outward of the protruding portion 52a of the thrust bearing portion 52. The O-ring 55 prevents the pressurized gas supplied from the supply passage 25c to the ejection holes 53 of the radial bearing portion 51 and the pressurized gas supplied from the supply passage 26b to the ejection holes 54 of the thrust bearing portion 52 from leaking outside the case body 2.

[0036] A discharge passage 25d is formed in fifth flange 25, which discharges the pressurized gas ejected from each of ejection holes 53, 54 of gas bearing 5 to the outside of rotary joint 1. Discharge passage 25d is formed in fifth flange 25 below circumferential groove 51a of gas bearing 5. Discharge passage 25d in the present embodiment is a hole formed radially penetrating fifth flange 25 at a predetermined location in the circumferential direction (a location different from supply passage 25c).

[0037] [Mechanical seal] In Figure 1, the rotary joint 1 further includes a mechanical seal 6. The mechanical seal 6 in this embodiment is a hydrostatic non-contact mechanical seal. The mechanical seal 6 has a first stationary seal ring 61, a second stationary seal ring 62, a rotary seal ring 63, a communicating passage 64, a first elastic member 65, and a second elastic member 66. The first stationary seal ring 61 and the second stationary seal ring 62 are stationary seal rings provided on the inner circumferential side of the case body 2. The rotary seal ring 63 is provided on the outer circumferential side of the rotary shaft 4 so as to be rotatable integrally with the rotary shaft 4.

[0038] Figure 3 is an enlarged cross-sectional view of the mechanical seal 6. In Figure 3, a first stationary seal ring 61 and a second stationary seal ring 62 are arranged as a pair above and below with a rotary seal ring 63 sandwiched between them. As a result, the first stationary seal ring 61 and the second stationary seal ring 62 are each arranged opposite the rotary seal ring 63 in the axial direction. The first stationary seal ring 61 and the second stationary seal ring 62 are each formed in an annular shape.

[0039] The first stationary seal ring 61 is attached to the first flange 21 of the case body 2. Specifically, an annular mounting groove 21a that opens upward is formed in the first flange 21 radially inward of the second flange 22. The first stationary seal ring 61 is fitted into this mounting groove 21a. A seal surface 61a is formed around the entire periphery on the end face of the upper surface of the first stationary seal ring 61.

[0040] The second stationary seal ring 62 is attached to the fifth flange 25 of the case body 2. Specifically, an annular mounting groove 25a that opens downward is formed in the fifth flange 25 radially inward of the fourth flange 24. The second stationary seal ring 62 is fitted into this mounting groove 25a. A seal surface 62a is formed around the entire circumference of the lower end face of the second stationary seal ring 62.

[0041] An engagement hole 61b is formed on the underside of the first stationary seal ring 61. A pin 21b fixed to the bottom surface of the mounting groove 21a is engaged with the engagement hole 61b. An engagement hole 62b is formed on the upper side of the second stationary seal ring 62. A pin 25b fixed to the bottom surface of the mounting groove 25a is engaged with the engagement hole 62b. This makes the first stationary seal ring 61 and the second stationary seal ring 62 unable to rotate relative to the case body 2 and will not rotate together with the rotating seal ring 63.

[0042] The rotary seal ring 63 is formed in an annular shape. The rotary seal ring 63 is fitted onto and fixed to the outer peripheral surface 4b of the rotary shaft 4 at a height position corresponding to the opening of the inner flow passage 4a of the rotary shaft 4. This allows the rotary seal ring 63 to rotate integrally with the rotary shaft 4. A seal surface 63a is formed over the entire periphery on the upper end face of the rotary seal ring 63. The seal surface 63a is arranged axially opposite the seal surface 61a of the first stationary seal ring 61. A seal surface 63b is formed over the entire periphery on the lower end face of the rotary seal ring 63. The seal surface 63b is arranged axially opposite the seal surface 62a of the second stationary seal ring 62. In this embodiment, each of the seal surfaces 63a, 63b is coated with, for example, a ceramic coating.

[0043] The communicating passage 64 of the mechanical seal 6 is a passage that connects the outer passage 23a of the third flange 23 and the inner passage 4a of the rotary shaft 4. In this embodiment, a plurality of communicating passages 64 are formed at intervals in the circumferential direction of the rotary seal ring 63 (see also FIG. 1). Each communicating passage 64 is formed to penetrate the rotary seal ring 63 in the radial direction so as to open on the outer peripheral surface and the inner peripheral surface thereof, respectively. The radially inner opening of each communicating passage 64 is arranged opposite the opening of the inner passage 4a on the outer peripheral surface 4b of the rotary shaft 4. The radially outer opening of each communicating passage 64 is arranged opposite the opening of the outer passage 23a on the inner peripheral surface of the third flange 23.

[0044] An annular space 67 is formed between the outer peripheral surface of the rotary seal ring 63 and the inner peripheral surface of the third flange 23. Each of the communicating passages 64 of the rotary seal ring 63 communicates with the outer passage 23a of the third flange 23 via the annular space 67. As a result, the outer passage 23a of the third flange 23 and the inner passage 4a of the rotary shaft 4 are connected by the annular space 67 and the communicating passage 64. The annular space 67 is sealed by O-rings 72 and 75 (described below) arranged on both the top and bottom sides thereof. The gap between the inner peripheral surface of the rotary seal ring 63 and the outer peripheral surface 4b of the rotary shaft 4 is sealed by a pair of upper and lower O-rings 68 arranged on either side of the communicating passage 64.

[0045] In Fig. 1, the first elastic member 65 is made of, for example, a coil spring. The first elastic member 65 is provided in a compressed state in the mounting groove 21a of the first flange 21. Although not shown, a plurality of first elastic members 65 are provided at intervals in the circumferential direction of the mounting groove 21a. One end (upper end) of the first elastic member 65 abuts against the first stationary seal ring 61. As a result, the first stationary seal ring 61 is pressed upward against the case body 2, towards the rotary seal ring 63, by the elastic restoring force of the first elastic member 65. Note that the first elastic member 65 may be an elastic member other than a coil spring.

[0046] The second elastic member 66 is made of, for example, a coil spring. The second elastic member 66 is provided in a compressed state in the mounting groove 25a of the fifth flange 25. Although not shown, a plurality of second elastic members 66 are provided at intervals in the circumferential direction of the mounting groove 25a. One end (lower end) of the second elastic member 66 abuts against the second stationary seal ring 62. As a result, the second stationary seal ring 62 is pressed downward toward the rotary seal ring 63 with respect to the case body 2 by the elastic restoring force of the second elastic member 66. Note that the second elastic member 66 may be an elastic member other than a coil spring.

[0047] 3, a static pressure generating groove 61c having an annular shape is formed around the entire periphery of the seal surface 61a of the first stationary seal ring 61. The static pressure generating groove 61c is a groove for generating static pressure between the seal surface 61a of the first stationary seal ring 61 and the seal surface 63a of the rotary seal ring 63. In this embodiment, the static pressure generating groove 61c is formed to have, for example, a V-shaped cross section.

[0048] An air supply hole 61d is formed at a predetermined position in the circumferential direction of the first stationary seal ring 61. The air supply hole 61d is a hole for supplying seal gas to the static pressure generating groove 61c. In Figure 3, the air supply hole 61d is simplified and indicated by a two-dot chain line. The air supply hole 61d is formed so as to open at the outer peripheral surface of the first stationary seal ring 61 and at the static pressure generating groove 61c.

[0049] An annular static pressure generating groove 62c is formed around the entire circumference of the seal surface 62a of the second stationary seal ring 62. The static pressure generating groove 62c is a groove for generating static pressure between the seal surface 62a of the second stationary seal ring 62 and the seal surface 63b of the rotary seal ring 63. The static pressure generating groove 62c in this embodiment is formed, for example, with a V-shaped cross section.

[0050] An air supply hole 62d is formed at a predetermined position in the circumferential direction of the second stationary seal ring 62. The air supply hole 62d is a hole for supplying seal gas to the static pressure generating groove 62c. In Figure 3, the air supply hole 62d is simplified and indicated by a two-dot chain line. The air supply hole 62d is formed so as to open at the outer peripheral surface of the second stationary seal ring 62 and at the static pressure generating groove 62c.

[0051] There are no particular limitations on the seal gas supplied to the static pressure generating grooves 61c, 62c of the first stationary seal ring 61 and the second stationary seal ring 62. In this embodiment, compressed air, which is the same type of gas as the pressurized gas in the gas bearing 5, is used as the seal gas.

[0052] A supply passage 22a is formed in the second flange 22 to supply seal gas from the outside of the rotary joint 1 to the air intake hole 61d of the first stationary seal ring 61. In this embodiment, the supply passage 22a is a hole formed radially penetrating the second flange 22 at a predetermined location in the circumferential direction. An annular space 71 is formed between the outer peripheral surface of the first stationary seal ring 61 and the inner circumferential surface of the second flange 22. As a result, the air intake hole 61d of the first stationary seal ring 61 communicates with the supply passage 22a of the second flange 22 via the annular space 71.

[0053] The gap between the outer peripheral surface of the first stationary seal ring 61 and the inner peripheral surface of the second flange 22 is sealed by a pair of upper and lower O-rings 72 arranged on either side of the annular space 71. As a result, the annular space 71 is sealed by the pair of upper and lower O-rings 72. The gap between the inner peripheral surface of the first stationary seal ring 61 and the inner peripheral surface of the mounting groove 21a of the first flange 21 is sealed by an O-ring 73.

[0054] A supply passage 24a is formed in the fourth flange 24 to supply seal gas from the outside of the rotary joint 1 to the air intake hole 62d of the second stationary seal ring 62. In this embodiment, the supply passage 24a is a hole formed radially penetrating the fourth flange 24 at a predetermined location in the circumferential direction. An annular space 74 is formed between the outer peripheral surface of the second stationary seal ring 62 and the inner circumferential surface of the fourth flange 24. As a result, the air intake hole 62d of the second stationary seal ring 62 communicates with the supply passage 24a of the fourth flange 24 via the annular space 74.

[0055] The gap between the outer peripheral surface of the second stationary seal ring 62 and the inner peripheral surface of the fourth flange 24 is sealed by a pair of upper and lower O-rings 75 arranged on either side of an annular space 74. As a result, the annular space 74 is sealed by the pair of upper and lower O-rings 75. The gap between the inner peripheral surface of the second stationary seal ring 62 and the inner peripheral surface of the mounting groove 25a of the fifth flange 25 is sealed by an O-ring 76.

[0056] In the mechanical seal 6 configured as described above, before the rotating shaft 4 starts to rotate, seal gas is supplied from the supply passage 22a of the second flange 22 to the static pressure generating groove 61c via the annular space 71 and the air inlet 61d of the first stationary seal ring 61. The seal gas supplied to the static pressure generating groove 61c generates static pressure between the seal surface 61a of the first stationary seal ring 61 and the seal surface 63a of the rotary seal ring 63. This static pressure holds the first stationary seal ring 61 slightly spaced downward from the rotary seal ring 63 against the elastic restoring force of the first elastic member 65. As a result, the seal gas seals the gap between the two seal surfaces 61a, 63a while maintaining a non-contact state between them.

[0057] Furthermore, before the rotating shaft 4 starts to rotate, seal gas is supplied from the supply passage 24a of the fourth flange 24 to the static pressure generating groove 62c via the annular space 74 and the air inlet 62d of the second stationary seal ring 62. The seal gas supplied to the static pressure generating groove 62c generates static pressure between the seal surface 62a of the second stationary seal ring 62 and the seal surface 63b of the rotary seal ring 63. This static pressure holds the second stationary seal ring 62 slightly spaced above the rotary seal ring 63 against the elastic restoring force of the second elastic member 66. As a result, the seal gas seals the gap between the two seal surfaces 62a, 63b while maintaining a non-contact state between them.

[0058] As described above, the rotating shaft 4 is rotated relative to the case body 2 in a state where the seal surfaces 61a, 63a of the first stationary seal ring 61 and the rotary seal ring 63, and the seal surfaces 62a, 63b of the second stationary seal ring 62 and the rotary seal ring 63 are sealed in a non-contact state. This makes it possible to suppress the generation of wear debris between the seal surfaces 61a, 63a and between the seal surfaces 62a, 63b when the rotating shaft 4 starts to rotate and during rotation.

[0059] The seal gas supplied to the static pressure generating groove 61c of the first stationary seal ring 61 passes between the two seal surfaces 61a, 63a, then passes between the outer peripheral surface 4b of the rotating shaft 4 and the inner peripheral surface of the first stationary seal ring 61, and between the outer peripheral surface 4b of the rotating shaft 4 and the inner peripheral surface of the first flange 21, and is discharged below the case body 2.

[0060] The seal gas supplied to the static pressure generating groove 62c of the second stationary seal ring 62 passes between both seal surfaces 62a, 63b, and then flows upward, passing between the outer peripheral surface 4b of the rotating shaft 4 and the inner peripheral surface of the second stationary seal ring 62, and between the outer peripheral surface 4b of the rotating shaft 4 and the inner peripheral surface of the fifth flange 25. The seal gas that has flowed upward in this manner is discharged to the outside of the rotary joint 1 through the discharge path 25d that discharges the pressurized gas of the gas bearing 5, as shown in FIG. 1 . Therefore, the discharge path 25d in this embodiment is a shared discharge path that discharges both the pressurized gas of the gas bearing 5 and the seal gas of the mechanical seal 6 to the outside of the rotary joint 1.

[0061] [Effects of the embodiment] As described above, according to the rotary joint 1 of this embodiment, the rotating shaft 4 is rotatably supported in a non-contact manner by the gas bearing 5 provided in the case body 2. The gas bearing 5 does not require a lubricant such as grease. This makes it possible to prevent foreign matter (lubricant) from being mixed into the sealed fluid flowing through the outer flow path 23a of the case body 2, the communicating flow path 64 of the mechanical seal 6, and the inner flow path 4a of the rotating shaft 4. Furthermore, because the sliding resistance of the rotating shaft 4 against the gas bearing 5 is nearly zero, the rotary joint 1 of this embodiment can be used in high-speed rotating equipment in which a rotating member rotates at high speed relative to a fixed member.

[0062] Gas bearing 5 has a radial bearing portion 51 that supports outer peripheral surface 4b of rotating shaft 4 without contact, and a thrust bearing portion 52 that supports upper end face 4c of rotating shaft 4 without contact. Neither radial bearing portion 51 nor thrust bearing portion 52 requires lubricant, which can further prevent foreign matter (lubricant) from being mixed into the sealed fluid.

[0063] Furthermore, the mechanical seal 6 is a non-contact mechanical seal. Therefore, the seal surfaces 61a, 62a of the stationary seal rings 61, 62 and the seal surfaces 63a, 63b of the rotary seal ring 63 are maintained in a non-contact state by the seal gas. As a result, the generation of wear debris between the seal surfaces 61a, 63a and between the seal surfaces 62a, 63b can be suppressed. This further suppresses the intrusion of foreign matter (wear debris) into the sealed fluid.

[0064] Furthermore, the mechanical seal 6 is a hydrostatic non-contact mechanical seal that generates hydrostatic pressure using a seal gas. Therefore, compared to a hydrodynamic non-contact mechanical seal, it is possible to suppress the generation of wear debris between the seal surfaces 61a and 63a and between the seal surfaces 62a and 63b when the rotating shaft 4 starts to rotate. This further suppresses the intrusion of foreign matter (wear debris) into the sealed fluid.

[0065] Furthermore, the seal gas used in mechanical seal 6 is the same type of gas as the pressurized gas used in gas bearing 5. This allows the pressurized gas for gas bearing 5 to be used as the seal gas for mechanical seal 6, thereby reducing running costs.

[0066] Furthermore, the case body 2 has a common exhaust path 25d that exhausts both the pressurized gas and the seal gas. This eliminates the need to provide separate exhaust paths for the pressurized gas and the seal gas in the case body 2, thereby reducing the manufacturing cost of the case body 2.

[0067] [others] The rotary joint 1 in this embodiment may be disposed upside down in the axial direction, or may be disposed so that the axial direction is horizontal. Furthermore, the rotary joint 1 can be applied to other devices, such as sputtering devices and etching devices, in addition to CMP devices. Furthermore, the rotary joint 1 is not limited to use in the semiconductor field. Furthermore, the rotary joint 1 may be a multi-port rotary joint having multiple sets of flow paths (outer flow path 23a, communicating flow path 64, inner flow path 4a).

[0068] The mechanical seal 6 may be a dynamic pressure contact type mechanical seal that seals at least one of the seal surfaces 61a, 63a and the seal surfaces 62a, 63b without contact by dynamic pressure. Alternatively, the mechanical seal 6 may be a contact type mechanical seal that seals by contacting at least one of the seal surfaces 61a, 63a and the seal surfaces 62a, 63b.

[0069] The communicating flow passage 64 of the mechanical seal 6 is not limited to this embodiment. For example, the rotary seal ring 63 may be divided into two, upper and lower, and the gap formed between the divided rotary seal rings 63 may serve as the communicating flow passage 64. The case body 2 may have a dedicated discharge passage for discharging only the seal gas to the outside. Furthermore, the seal gas may be a different type of gas from the pressurized gas in the gas bearing 5.

[0070] Gas bearing 5 in this embodiment supports the upper end of rotating shaft 4, but in addition to this or instead, it may support a portion other than the upper end of rotating shaft 4. Gas bearing 5 may have at least one of radial bearing portion 51 and thrust bearing portion 52. For example, gas bearing 5 may have only radial bearing portion 51. In that case, end face 4c of rotating shaft 4 may be rotatably supported in contact with it by a sliding bearing or the like.

[0071] The gas bearing 5 of this embodiment employs a multi-hole, inherently restricting type hydrostatic gas bearing. However, a multi-hole, orifice-restricting type as shown in FIG. 4 or a porous type as shown in FIG. 5 may also be employed. In the orifice-restricting type gas bearing 5 shown in FIG. 4, each of the ejection holes 53 of the radial bearing portion 51 has an throttling portion 53e midway in the radial direction (the left-right direction in FIG. 4). Similarly, each of the ejection holes 54 of the thrust bearing portion 52 has an throttling portion 54e midway in the up-down direction. In the porous type gas bearing 5 shown in FIG. 5, the radial bearing portion 51 has a porous member 56 provided in each of the ejection holes 53. Similarly, the thrust bearing portion 52 has a porous member 57 provided in each of the ejection holes 54. Each of the porous members 56, 57 has a large number of fine holes formed therein for ejecting pressurized gas. The gas bearing 5 of this embodiment is not limited to an hydrostatic gas bearing and may be, for example, a spiral groove type hydrodynamic gas bearing.

[0072] 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]

[0073] 1 rotary joint 2 Case body 4 rotation axes 4a Inner flow channel 4b Outer surface 4c end face 5 Gas bearings 6 Mechanical seal 23a Outside channel 25d Exhaust channel 51 Radial bearing section 52 Thrust bearing part 61 First stationary sealing ring (static sealing ring) 62 Second stationary sealing ring (static sealing ring) 63 Rotating seal ring 64 Connecting flow path

Claims

1. a cylindrical case body having an outer flow path through which a sealed fluid flows; a rotating shaft disposed inside the case and having an inner flow passage through which a sealed fluid flows; a mechanical seal having a stationary seal ring provided on the case body, a rotary seal ring provided on the rotary shaft axially opposite the stationary seal ring, and a communication flow path connecting the outer flow path and the inner flow path, and sealing between the stationary seal ring and the rotary seal ring; a gas bearing provided in the case body and rotatably supporting the rotating shaft in a non-contact manner by pressurized gas, the mechanical seal is a non-contact mechanical seal that generates static pressure or dynamic pressure between the stationary seal ring and the rotary seal ring by a seal gas, thereby sealing the gap while maintaining a non-contact state with the seal gas, A rotary joint, wherein the seal gas is the same type of gas as the pressurized gas.

2. A cylindrical case body having an outer flow path through which a sealed fluid flows; a rotating shaft disposed inside the case and having an inner flow passage through which a sealed fluid flows; a mechanical seal having a stationary seal ring provided on the case body, a rotary seal ring provided on the rotary shaft axially opposite the stationary seal ring, and a communication flow path connecting the outer flow path and the inner flow path, and sealing between the stationary seal ring and the rotary seal ring; a gas bearing provided in the case body and rotatably supporting the rotating shaft in a non-contact manner by pressurized gas, the mechanical seal is a non-contact mechanical seal that generates static pressure or dynamic pressure between the stationary seal ring and the rotary seal ring by a seal gas, thereby sealing the gap while maintaining a non-contact state with the seal gas, The rotary joint, wherein the case body has a common discharge path for discharging both the pressurized gas and the seal gas.

3. 3. The rotary joint according to claim 1, wherein the gas bearing comprises a radial bearing portion that supports an outer peripheral surface of the rotating shaft in a non-contact manner, and a thrust bearing portion that supports an axial end face of the rotating shaft in a non-contact manner.

4. 3. The rotary joint according to claim 1, wherein the mechanical seal is a hydrostatic non-contact mechanical seal that generates hydrostatic pressure between the stationary seal ring and the rotary seal ring by the seal gas.

5. A rotary joint as described in claim 1 or claim 2, wherein the gas bearing has a porous member having a large number of fine holes formed therein through which the pressurized gas is ejected.

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