JP2008025597A - Rotary joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary joint which enables stable and good flowing between relative rotary members of high specific resistance value water (having a specific resistance value of 5 MΩcm or more) such as ultrapure water or pure water similar to this, functional water, etc., over a long period of time. <P>SOLUTION: A fluid passage 2 to make ultrapure water 1 flow communicates with a first passage 24 formed in a rotary shaft body 4 and a second passage 26 formed in a joint main body 3 to rotatably connect and support the rotary shaft body 4 via connection spaces 25, 27. The connection spaces 25, 27 are sealed by an end contact type mechanical seal 5 formed to relatively make a first sealing ring 11 made of silicon carbide and mounted in the rotary shaft body 4 side and a second sealing ring 12 made of silicon carbide and mounted in a case body 3 side be slidably in contact with. A sliding surface 11a of the first seal ring 11 is coated with silicon carbide chemical vapor deposition 30 having a specific resistance value of 1 Ωcm or less, which effectively prevents static electricity from producing and accumulating by a friction contact of both the seal rings 11, 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes one or more fluidized ultrapure water (including water having a specific resistance value of 5 MΩ · cm or more, such as pure water similar to these or functional water such as hydrogen water and ozone water). The present invention relates to a rotary joint having a plurality of fluid passages, wherein the relative rotational connection portion of the fluid passage is sealed with an end surface contact type mechanical seal.

  In semiconductor manufacturing factories and nuclear power facilities, etc., high cleanliness and avoidance of contamination are required, so ultrapure water or similar pure water is used as cleaning water, cooling water, etc. Production and purification of functional water (such as ultrapure water, hydrogen water, ozone water, etc.) made from raw materials, etc. is performed, but in rotating equipment used in processes that handle such ultrapure water, A rotary joint may be used to flow ultrapure water or the like between the relative rotating members.

  As such a rotary joint, for example, a connection space in which a first passage formed in a rotating shaft body and a second passage formed in a joint body that rotatably connects and supports the rotating shaft body is formed between the two bodies. A fluid passage formed in communication with the first and second silicon carbide sealing rings provided on the rotating shaft body side and the silicon carbide second sealing ring provided on the joint body side. It is well known that it is devised to seal with an end-face contact type mechanical seal that is configured to make a relative rotational sliding contact. However, in such a rotary joint, contamination such as ultrapure water that flows in the fluid passage is known. In order to avoid this, both sealing rings are made of silicon carbide (see, for example, Patent Document 1).

JP-A-11-248072

However, in such a rotary joint, the fluid flowing through the fluid passage is water having a high specific resistance value such as ultrapure water, pure water similar to this, hydrogen water, ozone water, etc. In the case of 18.2 MΩ · cm water (for example, the specific resistance value of ultrapure water is about 18 MΩ · cm), the surface of the silicon carbide sealing ring that seals the connection space, in particular, the sliding with the other sealing ring A phenomenon (white powder generation) in which the moving surface (sealed end surface) turns white may be observed. The white substance (white powder) generated on the sliding surface is known to be SiO ₂ according to X-ray diffraction or the like, and such whitening phenomenon is due to oxidative corrosion of silicon carbide, and the other party is sealed. This is because static electricity is generated and accumulated on the sliding surface due to contact friction with the ring. That is, in an electrically insulating fluid having an extremely high specific resistance value such as ultrapure water, static electricity generated on the sliding surface is accumulated without being discharged, and as a result, is contained in static electricity and ultrapure water, etc. The silicon carbide constituting the sliding surface is corroded by the battery action of oxygen.

Thus, when such a whitening phenomenon occurs, that is, when SiO ₂ that is a white substance is generated, it contaminates ultrapure water or the like as a foreign substance, leading to abnormal wear of the sliding surface. Become. Further, depending on the degree of oxidative corrosion of the sliding surface, the sealing ring itself may be destroyed. That is, the grain boundary of silicon carbide is significantly eroded by such oxidative corrosion, and when this erosion progresses, the silicon carbide particles may be peeled off to cause erosion wear, and the sealing ring may be broken. Therefore, the above-described rotary joint cannot be stably and satisfactorily sealed for a long time with the mechanical seal of the relative rotational connection portion (connection space) of the fluid passage, and cannot be used for applications handling ultrapure water or the like. It was a thing. In addition, even when the seal ring does not break, contaminants in the ultrapure water etc. (the above-mentioned white matter and wear powder generated by sliding the seal ring) will be adsorbed and accumulated by electrostatic action, It will cause severe contamination.

  The present invention solves the above-described problem when the relative rotational connection portion of the fluid passage is sealed by an end face contact type mechanical seal using a silicon carbide sealing ring, and provides ultrapure water or a similar pure water. To provide a rotary joint capable of stably and satisfactorily flowing a high specific resistance water such as water or functional water (having a specific resistance value of 5 MΩ · cm or more) between relative rotating members over a long period of time. It is intended.

  The present invention has at least one fluid passage through which ultrapure water flows, and the fluid passage is provided in a joint body that rotatably connects and supports the first passage formed in the rotating shaft body and the rotating shaft body. The formed second passage is connected in communication through a connection space formed between the two bodies, and this connection space is provided on the first sealing ring made of silicon carbide provided on the rotating shaft side and on the joint body side. In order to achieve the above-described object, in the rotary joint sealed by the end surface contact type mechanical seal configured to make relative rotational sliding contact with the second seal ring made of silicon carbide, in particular, the first seal ring And / or the second sealing ring is coated with a silicon carbide chemical vapor deposition film (hereinafter referred to as “CVD-SiC film”) having a specific resistance value of 1 Ω · cm or less on at least a sliding surface with the counterpart sealing ring. It is intended to propose a door. The term “ultra pure water” in the present invention is a concept including general ultra pure water (resistivity value: about 18 MΩ · cm) and water showing a similar high specific resistance value (5 MΩ · cm or more). However, in the following description, for the sake of convenience, the former is referred to as “ultra pure water” and the latter is referred to as “high specific resistance water”. Specific examples of high specific resistance water include, for example, pure water having a specific resistance value of 5 to 18.2 MΩ · cm, or hydrogen water produced and purified using such pure water or ultrapure water, ozone. There is functional water such as water.

In such a rotary joint, the CVD-SiC film can be formed on a surface portion other than the sliding surface of the sealing ring, and the fluid (ultra pure water or high ratio flowing in the fluid passage) on the surface of the sealing ring. It is preferable to coat the portion (including the sliding surface) that comes into contact with the (resistance value water). In addition, the CVD-SiC film is preferably strongly oriented on the (220) plane in the Miller index display so that the specific resistance value is 1 Ω · cm or less. Here, the strong orientation in the (220) plane means that the X-ray diffraction peak intensity of the (220) plane measured by an X-ray diffractometer is the X of the (111) plane and all other crystal planes in the Miller index display. In order to increase the specific resistance value to 1 Ω · cm or less, the orientation ratio of the (220) plane to the (111) plane is 10 to 1000 (preferably 100 to 1000). ) Is preferably oriented (strongly oriented) in the (220) plane. The orientation ratio of the (220) plane to the (111) plane being δ means that the X-ray diffraction peak intensity of the (220) plane is δ times the X-ray diffraction peak intensity of the (111) plane. (The X-ray diffraction peak intensity is corrected by the powder X-ray diffraction value based on the US ASTM standard). Since the degree of orientation of the crystal plane is the highest in the (111) plane and the (220) plane follows this, when strongly oriented in the (220) plane, the peak of the X-ray diffraction intensity is (220). Most crystal planes other than the plane and the (111) plane do not appear. In order to set the specific resistance value of the CVD-SiC film to 1 Ω · cm or less, as described above, it is optimal to strongly orient the CVD-SiC film on the (220) plane. The specific resistance value of the CVD-SiC film can be reduced to 1 Ω · cm or less also by doping a trace amount (several ppm) of N ₂ .

The base of the sealed ring on which the CVD-SiC film is formed is preferably a dense silicon carbide sintered body having a density of 3.00 g / cm ³ or more and a silicon carbide purity of 80% or more.
The silicon carbide sintered body can be obtained by pressureless sintering, hot press sintering, hot isostatic pressing or the like using β-type silicon carbide or α-type silicon carbide as a raw material. The thickness of the CVD-SiC film is preferably 10 μm to 2 mm, and the silicon carbide purity of the CVD-SiC film is preferably 99.99% or more.

In the rotary joint of the present invention, as a first seal ring and / or a second seal ring made of silicon carbide, a good conductor film (CVD-SiC) having at least a sliding surface with a specific resistance of 1 Ω · cm or less. When the seal ring is used in a state where it is in contact with an electrically insulating fluid (ultra pure water or high specific resistance water) having a high specific resistance value, Effectively prevents the generation and accumulation of static electricity due to contact friction with the mating seal ring, and can effectively prevent whitening caused by static electricity, and wear powder generated by sliding of the seal ring It is possible to achieve a high degree of cleanliness and contamination-free without adsorbing and accumulating the contaminants. Therefore, according to the present invention, water contamination (contamination of ultrapure water or high specific resistance water flowing in the fluid passage) due to the generation of white matter (SiO ₂ ) in the sealing ring or damage to the sealing ring does not occur. In addition, there is no adsorption or accumulation of wear powder on the surface of the sealing ring due to static electricity, and it can exhibit a clean, good and reliable sealing function (the sealing function of the fluid passage by a mechanical seal) for a long time. The flow of ultrapure water and high specific resistance water between the relative rotating members of a rotary device such as a pump installed in a semiconductor manufacturing apparatus or the like that requires high cleanliness and no contamination can be performed well. A practical rotary joint that can be provided can be provided.

  FIG. 1 is a longitudinal side view showing an example of a rotary joint according to the present invention, and FIG. 2 is a detailed view showing an enlarged main part of FIG.

  As shown in FIG. 1, the rotary joint in this embodiment includes ultrapure water and high water between relative rotating members of rotating equipment (CMP (Chemical Mechanical Polishing) device, etc.) used in semiconductor manufacturing factories and nuclear facilities. A joint body that has one fluid passage 2 for flowing an electrically insulating fluid 1 such as specific resistance water, and is attached to a fixed side member (for example, a CMP apparatus body) that is one of the relative rotating members. 3, a rotating shaft body 4 attached to a rotating side member (for example, a top ring or a turntable of a CMP apparatus) which is the other of the relative rotating members, and an end face contact type interposed between the both bodies 3 and 4. And a mechanical seal 5. In the following description, the top and bottom mean the top and bottom in FIG.

  As shown in FIG. 1, the joint body 3 has a cylindrical shape with the upper end closed, and is attached to the cylindrical side wall 6 having a circular inner peripheral portion and to close the upper end thereof. End wall 7 formed. The side wall 6 has a vertically divided structure.

  As shown in FIG. 1, the rotating shaft body 4 has a cylindrical shape arranged concentrically in the side wall 6 of the joint body 3 except for the lower end portion. The bearings 8 and 8 are rotatably connected.

  As shown in FIGS. 1 and 2, the mechanical seal 5 includes a first seal ring 11 provided at the upper end portion of the rotary shaft body 4, a second seal ring 12 provided at the upper end portion of the joint body 3, 2 Rotation prevention means 13 and 14 and a spring member 15 interposed between the sealing ring 12 and the joint body 3 are provided.

As shown in FIGS. 1 and 2, the first sealing ring 11 includes an annular main body 16 and a cylindrical fitting portion 17 formed integrally with the lower end portion thereof. By being fitted to the fitted portion 18, which is the upper end portion of the rotating shaft body 4, the rotating shaft body 4 is fitted and fixed concentrically with the rotating axis. The front end surface (upper end surface) of the main body 16 is a sealed end surface 11a that is a smooth annular plane orthogonal to the axis. The fitting portion 17 and the fitted portion 18 are connected to each other through an O-ring 19 and a drive pin 20 so as not to be relatively rotatable.

  As shown in FIGS. 1 and 2, the second sealing ring 12 includes an annular main body portion 21 and a cylindrical holding portion 22 formed integrally with the upper end portion thereof. By fitting into a holding hole 26a (which constitutes an inner side passage opening of the second passage 26 described later) provided in the wall 7, it moves concentrically with the first sealing ring 11 and moves axially to the joint body 3. Held possible. The fitting portion between the holding portion 22 and the holding hole 26a is secondarily sealed by an O-ring 23 held on the inner peripheral portion of the holding hole 26a. The main body portion 21 has a larger diameter than the holding portion 22, and the front end surface (lower end surface) is a smooth annular plane orthogonal to the axis, and abuts on the sealed end surface 11 a of the first seal ring 11. It is set as the sealing end surface 12a.

  As shown in FIGS. 1 and 2, the rotation prevention means is arranged at the lower end portion of the end wall 7 of the joint body 3 in the outer peripheral region of the holding hole 26a, so that one or more locking pins 13 are located downward. And projecting toward one another, forming one or a plurality of engaging recesses 14 on the outer peripheral portion of the main body 21 of the second sealing ring 12, and engaging the locking pins 13 with the engaging recesses 14, The second sealing ring 12 is locked and held so as not to rotate relative to the joint body 3 while allowing movement in the axial direction.

  As shown in FIGS. 1 and 2, the spring member 15 is interposed between the outer peripheral portion of the main body portion 21 of the second sealing ring 12 and the lower end portion of the end wall 7 of the joint main body 3 facing this. It comprises a plurality of coil springs and presses and urges the second sealing ring 12 toward the first sealing ring 11 so that both the sealing end faces 11a and 12a are pressed against each other.

  The mechanical seal 5 configured as described above has a connection space (sealing ring) which is an inner peripheral side region of the relative rotational sliding contact portion by the relative rotational sliding contact action of the sealing end faces 11a and 12a accompanying the rotation of the rotary shaft body 4. 11 and 12 in the center holes 25 and 27) and the outer peripheral side region thereof, and exhibits the same sealing function as a well-known end-face contact type mechanical seal.

  The fluid passage 2 is formed by connecting the first passage 24 formed in the rotating shaft body 4 and the second passage 26 formed in the joint body 3 between the bodies 3 and 4 and sealed by the mechanical seal 5. As shown in FIGS. 1 and 2, the rotating shaft body 4 is formed so as to penetrate the shaft center portion, and the upper end portion of the rotating shaft body 4. A first passage 24 in which an inner side passage opening 24a that opens to a central hole (a through hole formed in the central portion of the main body portion 16) 25 of the first sealing ring 11 is communicated, and an end wall of the joint main body 3 7 is formed in the center hole of the second sealing ring 12 (in the center of the main body portion 21 and the holding portion 22). The second passage 26 communicated with the through hole 27) is connected to the mechanical seal 5 Series in formed by connecting communication Ri. That is, the fluid passage 2 is connected between the inner side passage port 24a of the first passage 24 and the inner side passage port 26a of the second passage 26 via the connection spaces 25 and 27 which are the inner spaces of both the sealing rings 11 and 12. Thus, the fluid 1 can be made to flow between the passages 24 and 26 without causing any leakage. An oil seal 28 is provided between the bodies 3 and 4 to partition the region where the mechanical seal 5 is disposed and the region where the bearings 8 and 8 are disposed. In addition, a drain path 29 that opens to a region where the mechanical seal 5 is disposed is formed in the side wall 6 of the joint body 3.

  Thus, the first and second sealing rings 11 and 12 are the bases (the main sealing part 11 and the fitting part 17 for the first sealing ring 11, and the main body part 21 and the holding part for the second sealing ring 12. 22) is composed of silicon carbide, and the CVD-SiC film 30 (and / or 31) is coated on the entire surface of the first sealing ring 11 and / or the second sealing ring 12 or a part thereof. ing.

In this example, as shown in FIG. 2, a CVD-SiC film 30 is coated on the sealing end face 11a which is the surface of the first sealing ring 11 and is a sliding surface with the other sealing ring (second sealing ring 12). is there. That is, the bases 16 and 17 of the first seal ring 11 are sintered silicon carbide obtained by pressureless sintering, hot press sintering, hot isostatic pressing, or the like using β-type silicon carbide or α-type silicon carbide as a raw material. In particular, a dense silicon carbide sintered body having a density of 3.00 g / cm ³ or more and a silicon carbide purity of 80% or more. The end surface of the main body portion 16 of the first sealing ring 11 is coated with a CVD-SiC film 30, and the CVD-SiC film 30 is subjected to surface polishing to form the sealing end surface 11a. As described above, the CVD-SiC film 30 causes the CVD-SiC film 30 to be strongly oriented in the (220) plane (for example, the orientation ratio of the (220) plane to the (111) plane is 10 to 1000 (preferably 100 to 100). 1000), or by doping a very small amount (several ppm) of N ₂ so that the specific resistance is 1 Ω · cm or less, and the silicon carbide purity is 99.99%. It is the above thing and shall have thickness of 10 micrometers-2 mm. The second sealing ring 12 is formed of a silicon carbide sintered body that is the same quality as the bases 16 and 17 of the first sealing ring 11, and is formed into a sealing end surface 12a by subjecting the end surface of the main body 21 to surface polishing. is there. Of the rotary joint constituent members, the portions (excluding the sealing rings 11 and 12) in contact with the fluid 1 are preferably made of a material that does not generate contamination due to contact with the fluid 1. That is, the rotating shaft body 4 and the end wall 7 in which the passages 24 and 26 are formed, depending on the use conditions, may cause elution of metal components and dust generation such as wear powder due to contact with the fluid 1. In addition, it is preferably made of a plastic having heat resistance, corrosion resistance, or chemical resistance. For example, particles are not generated by contact with the fluid 1, and dimensional stability, heat resistance, etc. are obtained by processing. It can be made of engineering plastics such as PEEK, PES, PC, etc., which are excellent, and fluorine plastics such as PTFE, PFA, FEP, PVDF, etc., which are excellent in corrosion resistance, chemical resistance, etc. The O-rings 19 and 23 that may be in contact with the fluid 1 are not only general rubber but also fluorine-based resin or fluorine rubber (for example, “Viton” or “Kalrez” manufactured by DuPont). It is preferable to use what is constructed. In this example, the rotating shaft 4 and the end wall 7 are made of PEEK, the joint body portion other than the end wall 7 is made of metal, and all the O-rings including the O-rings 19 and 23 are made of fluorine rubber. It is.

  According to the rotary joint configured as described above, the sealing ring 11 made of silicon carbide is used as a sealing means for the relative rotational connection portion of the fluid passage 2 (the relative rotational connection portion between the first passage 24 and the second passage 26). , 12 adopts the end surface contact type mechanical seal 5 that makes relative rotational sliding contact, but without causing the problems as described at the beginning, the electrically insulating fluid (ultra pure water or high Specific resistance water) can be stably and satisfactorily performed.

  That is, one of the silicon carbide sealing rings 11 and 12 (first sealing ring 11) that makes relative rotational sliding contact (first sealing ring 11) (a sliding surface that may generate static electricity due to contact friction with the other sealing ring 12). Is composed of a CVD-SiC film 30 which is a good conductor film having a specific resistance value of 1 Ω · cm or less, so that generation and accumulation of static electricity due to frictional contact (relative rotational sliding contact) of the sealing rings 11 and 12 is effective. Is prevented. As a result, adsorption of foreign matter such as abrasion powder generated on the sealed end surfaces 11a and 12a due to generation and accumulation of static electricity is effectively prevented, and abnormal wear and water contamination of the sealed end surfaces 11a and 12a are prevented as much as possible. The Further, the above-mentioned whitening phenomenon (oxidation corrosion of silicon carbide) due to static electricity does not occur, and there is no fear that the sealing rings 11 and 12 are destroyed by oxidation corrosion. Therefore, according to the rotary joint, it is possible to exhibit a clean, good and reliable sealing function (sealing function of the fluid passage 2 by a mechanical seal) for a long period of time, and a high degree of cleanliness and contamination-free are required. It is possible to satisfactorily flow ultrapure water or high specific resistance water between relative rotating members such as a CMP apparatus.

  By the way, such an effect is obtained by forming a CVD-SiC film similar to the above on the sliding surface (sealed end surface) 12a of the second seal ring 12 which is the other seal ring, and further, the sealed end surfaces 11a and 12a. The surface portion other than the above (particularly, the surface portion in contact with the fluid 1) is more remarkably exhibited by coating the same CVD-SiC film. For example, as shown in FIG. 3, a CVD-SiC film having a specific resistance value of 1 Ω · cm or less on all the portions (including the sealed end faces 11a and 12a) in contact with the fluid 1 on the surfaces of both sealed rings 11 and 12 By coating 30 and 31, trouble caused by static electricity can be avoided more effectively.

  In addition to the rotary joint described above, the present invention provides a seal sealed by a single mechanical seal (hereinafter referred to as “end face side mechanical seal”) disposed between the opposing end faces in the axial direction of the joint body and the rotary shaft body. One fluid passage sealed by two fluid passages (hereinafter referred to as “end face opening type fluid passage”) and a pair of mechanical seals (hereinafter referred to as “peripheral surface side mechanical seals”) disposed between the opposing peripheral surfaces of both bodies. (Hereinafter referred to as “circumferential opening type fluid passage”) (for example, JP-A-11-257561, JP-A-11-287371, JP-A-11-287372, or JP-A-2000-9237). ), And a rotary having one peripheral surface opening type fluid passage sealed by a pair of peripheral surface side mechanical seals Joint (see, for example, Japanese Patent Laid-Open Nos. 11-141771, 2001-4083 or 2001-208258), a plurality of peripheral surface openings sealed by a plurality of concentrically arranged end face side mechanical seals A rotary joint having a fluid passage (see, for example, Japanese Patent Application Laid-Open No. 2002-5365 or Japanese Patent Application Laid-Open No. 2004-183901) or a plurality of peripheral surface-opening body passages sealed by a plurality or a plurality of pairs of peripheral surface side mechanical seals. The present invention can be applied to a rotary joint having any structure such as a joint (see, for example, Japanese Patent Application Laid-Open No. 2002-5380), and can exhibit the same effects as those of the above-described rotary joint. In the case of a rotary joint having a plurality of fluid passages, when at least one of the fluid passages is used for flowing ultrapure water or high resistivity water, the ultrapure water, high ratio The present invention is applied to a mechanical seal for sealing a fluid passage for resistance water.

  As an example, a first sealing ring in which a base is made of a dense silicon carbide sintered body made of β-SiC and a sealed end face is made of a CVD-SiC film formed by chemical vapor deposition of β-SiC, Five rotary joints (rotary joints shown in FIGS. 1 and 2, hereinafter referred to as “example joints”) incorporating a second sealing ring made of a dense silicon carbide sintered body of the same quality were manufactured.

In the example joint, the density of the silicon carbide sintered body constituting the base body of the first sealing ring and the second sealing ring was 3.05 g / cm ³ and the silicon carbide purity was 97%.

The CVD-SiC film is deposited by a low pressure CVD method (reaction gas: SiCl ₄ (Si source) and C ₃ H ₈ (C source), carrier gas: H ₂ )), and the deposition conditions ( By controlling the reaction gas flow rate, molar ratio, reduction ratio with carrier gas, vapor deposition temperature, vapor deposition rate, etc., the (220) plane is strongly oriented so that the specific resistance value is 1 Ω · cm or less. It is. That is, the orientation ratio of the (220) plane to the (111) plane in the CVD-SiC film was 150, and the specific resistance value was 0.2 Ω · cm. The film thickness of the CVD-SiC film after surface polishing of the CVD-SiC film (after formation of the sealed end face of the first sealing ring) was 50 μm. Further, the CVD-SiC film has a silicon carbide purity of 99.99% or more, and impurities contained therein are Na: 7 ppb, K: less than 20 ppb, Cr: less than 40 ppb, Mn: less than 2 ppb, Fe: 5 ppb , Co: less than 2 ppb, Cu: less than 10 ppb, Zn: less than 20 ppb, Mo: less than 20 ppb, W: less than 7 ppb.

  Further, as Comparative Example 1, five rotary joints (hereinafter referred to as “first comparative example joints”) having the same configuration as the example joints except that the properties of the CVD-SiC film in the first sealing ring are different. Produced. The CVD-SiC film of the first sealed ring is deposited by the same reduced pressure CVD method as the CVD-SiC film of the first sealed ring in the example joint except that the deposition conditions are different. It had a non-oriented crystal structure that was not oriented on the plane, and the specific resistance value was 1.2 Ω · cm. The film thickness of the CVD-SiC film after surface polishing was 50 μm, which is the same as that in the example joint.

  Further, as Comparative Example 2, a rotary joint (hereinafter referred to as “second comparative example”) having the same configuration as that of the example joint except that the first sealing ring does not have a CVD-SiC film like the second sealing ring. 5 joints) were manufactured. The sealed end face of the first seal ring was formed by surface polishing of a silicon carbide sintered body in the same manner as the second seal ring, and the specific resistance value was 10 Ω · cm.

  Thus, each of the joints of each of the examples was made to pass 3 under constant conditions (100 rpm × 0.2 MPa) while continuously passing ultrapure water (specific resistance value: 18 MΩ · cm) from the second passage to the first passage. We have been operating continuously for several months.

  In addition, each of the first and second comparative example joints was also continuously operated for three months under the same conditions in which the same ultrapure water as that of the example joint was continuously passed.

  After three months, each example joint and each first and second comparative example joint were disassembled, and the state of the sliding surface (sealed end surface) of the sealing ring in each joint was visually observed.

  As a result, in all of the joints of the example joints, the sealing rings were not damaged, and no whitening phenomenon was observed at all on the sliding surfaces (sealing end surfaces). On the other hand, for the first comparative joint, no damage to the seal ring was observed in all five units, but in one of the first comparative example joints, although there was a very small amount on the sliding surface of the seal ring, Was recognized. Moreover, about the 2nd comparative example joint, white powder had generate | occur | produced on the sliding surface of the sealing ring in all five sets, and the clear whitening phenomenon was recognized. Moreover, in the two second joints of the second comparative example, breakage of the sealing ring was observed.

  Moreover, about the Example joint, all 5 units | sets were continuously operated for another 6 months on the same conditions as the above, and the state of the sealing ring was visually confirmed again. As a result, no damage to the sealing ring and whitening phenomenon on the sliding surface were observed in any of the joints of Examples.

  From these facts, the joint of the first sealing ring is of course the same as the joint of the second comparative example in which the sealing end face of the first sealing ring is not composed of the CVD-SiC film. Although the CVD-SiC film is coated, the specific resistance of the film is slightly higher than 1 Ω · cm (1.2 Ω · cm). It was confirmed that the seal ring can be effectively prevented from being damaged and that it exhibits a good joint function over a long period of time.

It is a vertical side view which shows an example of the rotary joint which concerns on this invention. FIG. 2 is an enlarged detailed view showing a main part of FIG. 1. It is a vertical side view equivalent to FIG. 2 which shows a modification.

Explanation of symbols

1 Ultrapure water, etc. (Ultrapure water)
2 Fluid passage 3 Joint body 4 Rotating shaft 5 Mechanical seal 11 First seal ring 11a Seal end surface (sliding surface)
12 Second seal ring 12a Seal end face (sliding surface)
16 Main body (first sealing ring base)
17 Fitting part (base of first sealing ring)
21 Body (second sealing ring base)
22 Holding part (base of second sealing ring)
24 1st passage 25 Center hole (connection space) of 1st sealing ring 11
26 Second passage 27 Center hole (connection space) of second seal ring 12
30 CVD-SiC film 31 CVD-SiC film

Claims (5)

The fluid passage has at least one fluid passage for flowing ultrapure water, and the fluid passage is formed in the joint body that rotatably connects and supports the first passage formed in the rotating shaft body and the rotating shaft body. Are connected through a connection space formed between the two bodies, and this connection space is made of a silicon carbide first sealing ring provided on the rotating shaft body side and a silicon carbide made on the joint body side. In a rotary joint that is sealed by an end surface contact type mechanical seal configured to be in relative rotational sliding contact with the second sealing ring,
A rotary characterized in that the first sealing ring and / or the second sealing ring is formed by coating a silicon carbide chemical vapor deposition film having a specific resistance value of 1 Ω · cm or less on at least a sliding surface with the other sealing ring. Joint. 2. The rotary joint according to claim 1, wherein the silicon carbide chemical vapor deposition film is coated on at least a portion in contact with ultrapure water on the surface of the sealing ring. The silicon carbide chemical vapor deposition film is strongly oriented on the (220) plane in the Miller index display so that the specific resistance value thereof is 1 Ω · cm or less. The rotary joint described in 2. The sealed ring substrate on which the silicon carbide chemical vapor deposition film is coated is a silicon carbide sintered body having a density of 3.00 g / cm ³ or more and a silicon carbide purity of 80% or more. The rotary joint in any one of Claims 1-3. 5. The rotary joint according to claim 1, wherein a thickness of the chemical vapor deposition film is 10 μm to 2 mm, and a silicon carbide purity of the film is 99.99% or more.

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