JP5728849B2 - Gas seal device - Google Patents

Description

  The present invention relates to a gas seal device.

  In a compressor for compressing a gas such as nitrogen or air, it is necessary to provide a gas seal device for preventing gas leakage and increasing compression efficiency, and a labyrinth seal has been generally used conventionally. Has been. The labyrinth seal has a clearance of, for example, 100 to 200 μm between the housing and the inner peripheral surface of the housing between the stationary side housing and the rotation shaft that is rotatably supported by the housing. A plurality of labyrinth fins are attached to the outer peripheral surface of the rotating shaft, and the high-pressure side gas compressed by the compression blade is prevented from leaking to the low-pressure side (atmospheric pressure side) through the bent flow path formed by the labyrinth fins.

  In the labyrinth seal, when the housing and the labyrinth fin come into contact with each other, there is a possibility that the shaft vibration increases and the operation is stopped. For this reason, an explosion-proof film made of white metal, copper, or a material excellent in machinability is applied to the inner peripheral surface of the housing facing the labyrinth fin.

  However, the gas seal device using the labyrinth fin is a factor that cannot increase the operation efficiency of the compressor because there are many gas leaks due to the gap.

  On the other hand, a gas seal device called a dry gas seal is known as one that can reduce gas leakage (see Patent Documents 1 and 2, etc.).

  The dry gas seal has a rotating ring attached to a rotating shaft and a stationary ring supported by a housing so as to face the rotating ring. A rotating ring is disposed on an opposing surface of the rotating ring facing the stationary ring. As a result of the rotation, a dynamic pressure generating groove extending in a radial curve is formed so as to take in gas from the outer periphery and generate pressure (dynamic pressure) between the stationary ring and the stationary ring. Further, a spring is provided between the stationary ring and the housing, and the stationary ring is pushed by the spring and is in contact with the rotating ring.

  In the dry gas seal, the stationary ring when the rotating shaft is stopped is pressed against the opposite surface of the rotating ring by a spring, and the stationary ring is pressed against the rotating ring even when the rotation of the rotating shaft is activated. When the rotation speed of the rotating ring becomes larger than a predetermined value, the dynamic pressure generated between the opposing surfaces by the dynamic pressure generating groove overcomes the pressing force of the spring, pushes the stationary ring back, and A slight gap (about 2 μm) is formed between them to rotate.

  As described above, a slight seal gap of about 2 μm holding pressure is formed between the rotating ring and the stationary ring, so that the amount of high-pressure side gas leaking to the low-pressure side can be reduced. .

  In this type of conventional gas seal device, the rotating ring is made of, for example, a surface of a stainless steel base material that can maintain the rotational strength, titanium nitride (TiN) coated or sintered material of silicon carbide. In general, carbon (C) having excellent sliding characteristics is used.

JP-A-10-292867 Japanese Patent Laid-Open No. 03-140672

  The dry gas seal rotates with the stationary ring pressed against the rotating ring at the time of starting and stopping, and therefore, there is a problem that the opposed surfaces of the rotating ring and the stationary ring are worn.

For this reason, in Patent Document 1, the stationary ring is made of the same carbon (C) as the conventional one, and the rotating ring is coated with ceramic coating on the opposing surface of the base material made of stainless steel or the like by using a ceramic material. Subsequently, after the surface of the ceramic coating is precision ground, a solid lubricating film made of molybdenum disulfide (MoS ₂ ), diamond-like carbon (DLC), etc. is applied to the surface of the ceramic coating by physical vapor deposition (PVD), chemical vapor deposition. It is made to adhere by (CVD) method etc.

In Patent Document 2, the conventional material of the facing surfaces of the rotating ring and stationary ring is a combination of hard carbon (carbon C) and metal or ceramic, or metal-metal, ceramic-ceramic. Since there is a problem such as seizure due to a high coefficient, the opposite surface between the rotating ring and the stationary ring has a tetrafluoroethylene resin (PTFE), a polyimide resin, molybdenum disulfide (MoS ₂ ), gold or silver. A film is formed by coating a solid lubricant made of a metal such as the above.

  However, as conventionally practiced, when a stationary ring is made of carbon (C), it is necessary to sinter the carbon powder in a sintering furnace maintaining high temperature and high pressure. At present, the size limit of what can be manufactured by a kiln is about 500 mm in diameter.

  For this reason, a stationary ring with a diameter of 500 mm or more applied to a large compressor cannot be manufactured with carbon. Therefore, in order to manufacture a stationary ring with carbon, a stationary ring is formed by dividing the stationary ring into a plurality of segments divided in the circumferential direction and then sintering the sintering segment in a sintering furnace and then assembling the carbon segments into a ring shape. It is possible. However, in the stationary ring formed by assembling the carbon segments into a ring shape, there is a gap between the segments. For this reason, there is a problem that gas cannot leak from the gap to improve the sealing performance.

  On the other hand, as shown in Patent Document 2, a film in which a solid lubricant made of tetrafluoroethylene resin (PTFE) is coated on the opposing surfaces of the rotating ring and the stationary ring is based on a test conducted by the present inventors. It was confirmed that the coating was worn or that the coating attacked the mating member and caused the problem of wearing the mating material to generate wear powder.

  The present invention has been made in view of the above circumstances, and reduces the occurrence of wear due to contact rotation of a rotating ring and a stationary ring, and easily increases the diameter of a dry gas seal while maintaining sealing performance. An object of the present invention is to provide a gas seal device that enables this.

The present invention includes a rotating ring attached to a rotating shaft that includes a compression blade and a stationary ring that is supported by a housing so as to face the rotating ring, and a dynamic pressure generating groove is formed on an opposing surface of the rotating ring. A gas seal device for a compressor, wherein a stationary ring pressed against a rotating ring by a spring is pushed back at a sliding speed of 6 m / s to form a seal interval, on the opposing surface of the stationary ring , The present invention relates to a gas seal device characterized by forming a resin film coated with a polybenzimidazole resin.

  In the gas seal device, it is preferable that the stationary ring is made of a metal substrate, and a polybenzimidazole-based resin film is formed on the opposing surface of the metal substrate.

According to the present invention, since the resin film coated with the polybenzimidazole resin is formed on the opposite surface of the stationary ring facing the rotating ring, it is possible to suppress wear caused by contact rotation between the rotating ring and the stationary ring. Therefore, it is possible to reduce the generation of abrasion powder caused by the contact between the stationary ring and the rotating ring, and to achieve an excellent effect that the diameter of the dry gas seal can be easily increased while maintaining the sealing performance. .

(A) is a cut side view which shows an example of the form of the gas seal apparatus which implements this invention, (b) is a cut side view which shows the state which the rotating shaft of (a) rotated. It is a front view of the stationary ring provided with the polybenzimidazole-type resin film in the opposing surface. It is a front view which shows an example of the dynamic pressure generation groove | channel with which the opposing surface of the rotating ring was equipped. It is a diagram which shows the result of having investigated about the leakage amount ratio with respect to the pressure ratio by the sealing device which equipped the polybenzimidazole-type resin film of this invention in the stationary ring.

  Hereinafter, embodiments for carrying out the present invention will be described together with illustrated examples.

  1 (a), 1 (b), and 2 show an embodiment of the present invention. The features of the illustrated example are as shown in FIGS. 1 (a), 1 (b), and FIG. A polybenzimidazole (PBI) (registered trademark) resin film 14 is formed on the opposing surface 6a of the stationary ring 6 facing the rotating ring 5 of the gas seal device constituting the seal by coating.

  In the case of FIG. 1, the rotating ring 5 may be made of, for example, titanium nitride (TiN) coated on a facing surface 5a of a stainless steel substrate capable of maintaining rotational strength or a sintered material of silicon carbide. Further, a light metal, for example, a titanium base material is used for the stationary ring 6, and a polybenzimidazole-based resin film 14 is formed on the opposing surface 6a of the titanium base material.

  The polybenzimidazole-based resin film 14 can be formed by applying a polybenzimidazole-based resin to the opposed surface 6a of the stationary ring 6 and then baking it by heating, so that the large-diameter stationary ring 6 can be easily formed. Can be manufactured.

  The imidazole resin film 14 may be provided only on the facing surface 6a of the stationary ring 6 as shown in FIGS. 1A and 1B, or may be provided only on the facing surface 5a of the rotating ring 5. Alternatively, it may be provided on the opposing surfaces 5a, 6a of both the stationary ring 6 and the rotating ring 5.

  Further, as shown in FIG. 3, a dynamic pressure generating groove 7 is formed in the facing surface 5a of the rotating ring 5 so as to bend and extend radially outward from the radial center of the facing surface 5a. The dynamic pressure generating groove 7 is formed by groove processing on the facing surface 5 a of the rotating ring 5.

  The operation of the above embodiment will be described below.

  The stationary ring 6 when the rotating shaft 2 is stopped is pressed against the facing surface 5a of the rotating ring 5 by a spring 8 as shown in FIG. Even when the rotation of the rotating shaft 2 is started, the rotating ring 5 rotates with the stationary ring 6 pressed against it. However, when the rotating speed of the rotating ring 5 exceeds a predetermined value, the dynamic pressure generating groove 7 causes the rotating ring 5 to rotate. The dynamic pressure generated between the opposing surfaces 5a and 6a overcomes the pressing force of the spring 8, pushes the stationary ring 6 back as shown in FIG. 1B, and a slight seal (about 2 μm) is provided between the opposing surfaces 5a and 6a. A gap is formed to rotate.

  In this way, a seal gap of several micron level that maintains the pressure is formed between the rotating ring 5 and the stationary ring 6, so that the amount of high-pressure side gas leaking to the low-pressure side is reduced.

  As described above, when the rotation of the rotating ring 5 is started / stopped, the rotating ring 5 starts rotating while the stationary ring 6 is pressed. , 6a may have a problem of wear due to contact rotation.

  However, as shown in FIGS. 1A, 1B, and 2, the formation of the polybenzimidazole resin film 14 on the opposed surface 6 a of the stationary ring 6 can significantly reduce the problem of wear. did it.

  Polybenzimidazole (PBI) is known to have excellent mechanical properties such as wear resistance, heat resistance, and corrosion resistance, and has come to be used in various destinations.

  The inventors of the present invention have shown three types of (A, B, C) resin films made of tetrafluoroethylene resin (PTFE), which are conventionally known, as shown in FIG. Wear test simulating start-up when the polybenzimidazole (PBI) resin film 14 of the present invention is formed on the opposed surface 6 a of the stationary ring 6. And the wear of the resin film was investigated. At this time, the rotating ring 5 used was a stainless steel base material coated with titanium nitride. The test conditions were a sliding speed of 6 m / s, a contact surface pressure of 0.06 MPa, and a start / stop count of about 200.

The survey results are shown in Table 1.

  As a result of the above test, all of the tetrafluoroethylene resin (PTFE) -based coatings produced slight or many abrasion powders, whereas the polybenzimidazole (PBI) coating of the present invention was hardly visually observed. It was extremely small that could not be confirmed. Further, the aggressiveness to the rotating ring as the counterpart material was minimal or large in the change in the tetrafluoroethylene resin (PTFE) type coating, whereas the coating of the polybenzimidazole (PBI) of the present invention. The change was minimal.

  Therefore, as is apparent from Table 1, the polybenzimidazole (PBI) coating of the present invention has been confirmed to have excellent functions such as less wear, no problem of peeling, and little damage to the counterpart material. The present invention can be suitably applied to a wide range of gas seal devices such as a compressor that requires a large-diameter dry gas seal.

  Further, FIG. 4 shows the result of investigation on the leakage ratio with respect to the pressure ratio (PH / PL) by a sealing device provided with the polybenzimidazole resin film of the present invention in a stationary ring. The leakage amount indicated by the solid line X in FIG. 4 was the same as or less than that of a conventional gas sealing device using a dry gas seal.

  As shown in FIGS. 1A and 1B, a structure in which a polybenzimidazole-based resin film 14 is formed on an opposing surface 6a of a stationary ring 6 is formed on a stationary ring 6 provided in a conventional dry gas seal. It can be easily applied to a conventional dry gas seal simply by mounting instead. Further, even if the resin film 14 is worn out due to the operation of the compressor for a long time, it is replaced with a new stationary ring 6 provided with the resin film 14, or the resin film 14 on the opposite surface 6 a of the stationary ring 6. By recoating a new one, it can be easily regenerated and the compressor can be operated.

  Note that the gas seal device of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Housing 2 Rotating shaft 5 Rotating ring 5a Opposing surface 6 Stationary ring 6a Opposing surface 7 Dynamic pressure generating groove 8 Spring 14 Polybenzimidazole (PBI) resin film

Claims (2)

A rotating ring attached to a rotating shaft provided with a compression blade, and a stationary ring that is supported by the housing opposite the rotating ring , and a dynamic pressure generating groove is provided on an opposing surface of the rotating ring, and a spring a gas seal device of a compressor which is adapted stationary ring pressed against the rotary ring to form a seal gap is pushed back at a sliding speed of 6 m / s by the opposing surface of the stationary ring, polybenzimidazole A gas seal device in which a resin film coated with a resin is formed.   2. The gas seal device according to claim 1, wherein the stationary ring is made of a metal base material, and a polybenzimidazole-based resin film is formed on an opposing surface of the metal base material.

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