JP6895331B2 - mechanical seal - Google Patents

Description

The present invention relates to a mechanical seal using a carbon-based hard film on a sliding surface.

The mechanical seal is used by being mounted between the housing of the fluid device and the rotating shaft arranged so as to penetrate the housing, and is used by the sliding surface of the static sealing ring fixed to the housing and the rotation. The sliding surface of the rotary sealing ring that rotates with the shaft is brought into sliding contact with the sliding surface to prevent fluid from leaking from the inside to the outside or from the outside to the inside of the fluid device.

In such a mechanical seal, conventionally, as shown in Patent Document 1, one of the sliding surface of the static sealing ring and the sliding surface of the rotating sealing ring that rotates with the rotating shaft has low friction resistance and wear resistance. Some are provided with an excellent hard carbon thin film (see, for example, Patent Document 1).

JP-A-2007-138965 (Page 7, Fig. 1)

However, in a mechanical seal as in Patent Document 1, the rotary sealing ring is made of stainless steel and one surface thereof is coated with a hard carbon thin film to form a sliding surface, and the static sealing ring is made of silicon carbide (SiC). A configuration is shown in which the sliding surface is formed as a main component and one surface thereof is a sliding surface. However, when the sliding surface of the static sealing ring and the sliding surface of the rotary sealing ring are made of hard materials, they are mutually formed. Until the sliding surfaces of the above are scraped into a surface shape that fits smoothly with each other, the friction becomes high, and there is a problem that the low friction property, which is a function of the hard carbon thin film, cannot be fully utilized.

The present invention has been made by paying attention to such a problem, and provides a mechanical seal capable of quickly bringing the sliding surface of the static sealing ring and the sliding surface of the rotary sealing ring into a low friction state. With the goal.

In order to solve the above problems, the mechanical seal of the present invention is used.
A mechanical seal in which one sealing ring in which a base material is coated with a hard carbon thin film and the other sealing ring formed mainly of ceramics slide in relative rotation.
The sliding surface of the other sealing ring is characterized in that it is composed of ceramic particles having a maximum particle diameter of 1.0 μm or less.
According to this feature, the maximum particle size of the ceramic particles constituting the sliding surface of the other sealing ring is 1.0 μm or less, which is an extremely small unit, and the particles easily fall off from the interface of the grain boundary. When and the other sealing ring slide relatively rotationally, the shape of the sliding surface of the other sealing ring quickly becomes a shape that follows the shape of one sealing ring, and one sealing ring and the other seal ring The sliding surface with the sealing ring of the above can be brought into a low friction state at an early stage.

The sliding surface of the other sealing ring is characterized in that it is composed of ceramic particles having an average particle diameter of 0.1 μm to 1.0 μm.
According to this feature, since there is little variation in the size of the ceramic particles, the sliding surface of the other sealing ring tends to be smoothed in a short period of time.

In order to solve the above problems, the mechanical seal of the present invention is used.
A mechanical seal in which one sealing ring in which a base material is coated with a hard carbon thin film and the other sealing ring formed mainly of ceramics slide in relative rotation.
The sliding surface of the other sealing ring is characterized by having an amorphous structure.
According to this feature, the sliding surface of the other sealing ring has an amorphous structure, and the amorphous structure is easily broken in small units, so that one sealing ring and the other sealing ring slide relatively rotationally. At that time, the shape of the sliding surface of the other sealing ring quickly becomes a shape that follows the shape of one sealing ring, and the sliding surface of one sealing ring and the other sealing ring is quickly brought into a low friction state. Can be.

It is sectional drawing which shows the mechanical seal in Example 1. FIG. It is a partially enlarged sectional view which shows the sliding contact structure between the sealing rings in Example 1. FIG. (A) is a partially enlarged cross-sectional view showing the state of the sliding surfaces before the sealing rings rotate relative to each other in the mechanical seal of the first embodiment, and (b) is the sealed rings of the mechanical seal of the first embodiment. An enlarged schematic view showing the state of the sliding surfaces before they rotate relatively, (c) shows the state of the sliding surfaces when the sliding surfaces rotate relative to each other in the mechanical seal of the first embodiment. It is an enlarged schematic view which shows. It is an enlarged schematic view which shows the state of the sliding surfaces when the sealing rings rotate relative to each other in the mechanical seal of the prior art example 1. FIG. It is an enlarged schematic view which shows the state of the sliding surfaces when the sealing rings rotate relative to each other in the mechanical seal of the prior art example 2. FIG. (A) is an enlarged schematic view showing the state of the sliding surfaces before the sealing rings rotate relative to each other in the mechanical seal of the second embodiment, and (b) is the relative of the sealing rings to each other in the mechanical seal of the second embodiment. It is an enlarged schematic view which shows the state of the sliding surfaces at the time of rotational rotation.

A mode for carrying out the mechanical seal according to the present invention will be described below based on examples.

The mechanical seal according to the first embodiment will be described with reference to FIGS. 1 to 4.

FIG. 1 is a vertical sectional view showing an example of a mechanical seal, in which the mechanical seal 1 seals a fluid to be sealed on the machine M side of a fluid device that is about to leak from the outer periphery of the sliding surface toward the inner circumference. This is an inside type, and is provided on the rotating shaft 8 side for driving a pump impeller (not shown) on the high-pressure fluid side via a sleeve 2 so as to be integrally rotatable with the rotating shaft 8. An annular seal ring (rotary sealing ring) 3 which is a sliding component of the above, and an annular May which is the other sliding component provided in the housing 4 of the fluid device in a non-rotating state and in a state where it can move in the axial direction. It has a ting ring (static sealing ring) 5 and.

The mating ring 5 and the seal ring 3 are adapted to slide closely between the sliding surfaces S1 and S2 by the coiled wave spring 6 and the bellows 7 that urge the mating ring 5 in the axial direction. That is, the mechanical seal 1 prevents the fluid to be sealed from flowing out from the outer circumference of the rotating shaft 8 to the atmosphere A side on the sliding surfaces S1 and S2 of the mating ring 5 and the seal ring 3. is there.

In the mating ring 5, the base material 5A (see FIG. 2) is made of hard ceramics (silicon nitride, zirconia, alumina, SiC, etc.), and as shown in FIG. 2, the surface facing the seal ring 3 5a A carbon-based hard film 10 is formed on the surface. In this embodiment, the carbon-based hard film 10 is formed over the entire surface of the facing surface 5a, and the surface 10a of the carbon-based hard film 10 constitutes the sliding surface S1 of the mating ring 5. The carbon-based hard film 10 is made of a carbonaceous material other than diamond, for example, one or more of fullerenes, carbon nanotubes, graphenes, graphites, amorphous carbons, and calvins containing no hydrogen. It is formed by a specific manufacturing method, and is, for example, a DLC (diamond-like carbon) film, a diamond coating, a carbon film, a BNC film, or the like, and is excellent in low friction resistance and abrasion resistance.

On the other hand, the seal ring 3 is made of hard ceramics (silicon nitride, zirconia, alumina, SiC, etc.) like the mating ring 5. The seal ring 3 of this embodiment is obtained by sintering SiC powder (ceramic particles), and the SiC particles on the sliding surface S2 have a maximum particle diameter of 1.0 μm or less and are average particles. The diameter is configured to be 0.1 to 1.0 μm.

As an example of the method for producing the seal ring 3, a sintering aid, a binder, a surfactant, etc. are added to SiC powder to prepare a slurry, and the slurry is dried and granulated with a spray dryer, and the granules are mechanically granulated. Compression molding is performed with a metal mold press or rubber press that is close to the seal shape, and in order to further cure the binder, the molded product is heated at around 120 ° C. for 1 to 2 hours to complete the curing, and this is used for mechanical sealing. Machin to part dimensions. The firing may be carried out at argon under no pressure or preferably at 2050 ° C to 2150 ° C in a vacuum atmosphere. In this embodiment, the embodiment in which the seal ring 3 is formed as the main component of the SiC powder is illustrated, but silicon nitride, zirconia, or the like may be used as the ceramic particles constituting the seal ring 3.

The surface 3a facing the mating ring 5 in the seal ring 3 formed in the above step constitutes a sliding surface S2 that slides on the sliding surface S1 (surface 10a of the carbon-based hard film 10) of the mating ring 5. doing. When the sliding surface S2 of the seal ring 3 was measured, it was confirmed that the maximum particle size was 0.6 μm and the average particle size was 0.5 μm. That is, in the SiC powder having an average particle size of 0.4 μm, the SiC particles, which are the main components of the seal ring 3, are expanded by 20% by firing.

Further, the sliding surface S2 of the seal ring 3 formed in the above step was wrapped to obtain an arithmetic average roughness Ra = 0.01 μm. Similarly, the sliding surface S1 of the carbon-based hard film 10 was also wrapped to obtain an arithmetic mean roughness Ra = 0.01 μm.

Next, a state in which the mating ring 5 and the seal ring 3 rotate and slide relative to each other will be described with reference to FIGS. 3 to 5. In addition, the cross section of FIGS. 3 to 5 is described by taking as an example the cross section of the seal ring 3 having the same angle in the rotation direction. Furthermore, in FIGS. 3 (b) and 3 (c), for convenience of explanation, the fine uneven shape of the sliding surface S1 of the mating ring 5 is omitted and shown on a flat surface.

As described above, the mating ring 5 and the seal ring 3 are made of hard materials, and the sliding surface S1 of the carbon-based hard film 10 and the sliding surface S2 of the seal ring 3 have fine irregularities. Since it is formed, as shown in FIG. 3A, after the mechanical seal 1 is installed in the shaft seal portion of the housing 4 of the fluid device, the mating ring 5 and the seal ring 3 are relatively rotationally slid. In the state where it has begun to occur, the fine irregularities formed on the sliding surface S2 of the seal ring 3 and the surface 10a (sliding surface S1) of the carbon-based hard film 10 coated on the mating ring 5 The shapes do not match and the friction is high. Specifically, since the convex portion formed on the sliding surface S2 of the seal ring 3 locally contacts the sliding surface S1 of the carbon-based hard film 10, the friction is high.

When the mating ring 5 and the seal ring 3 start to rotate and slide relatively, the sliding surface S2 of the seal ring 3 which is softer than the carbon-based hard film 10 as compared with the sliding surface S1 of the carbon-based hard film 10. The SiC particles on the sliding surface S2 of the seal ring 3 have a small particle size, so that the SiC particles are likely to fall off from the interface.

As shown in FIG. 4, for example, in the case of a seal ring 34 composed of ceramic particles 34A having an average particle size of about 5 μm as in the conventional case, the mating ring 5 and the seal ring 34 are relatively rotating slides. When it starts to move, a part of the ceramic particles 34A constituting the sliding surface S21 of the seal ring 34 is scraped by abrasion, and a part of the ceramic particles 34A constituting the sliding surface S21 of the seal ring 34 is scraped from the interface. It will drop out. Since the particle size of the ceramic particles 34A is large, the smoothness of the sliding surface S21 of the seal ring 34 is impaired due to the falling off of the ceramic particles 34A, and the ceramic particles 34A wear for a long time, so that the seal ring 34 slides. It took a long time for the surface S21 and the sliding surface S1 of the carbon-based hard film 10 to become familiar with each other. Further, the ceramic particles 34A constituting the sliding surface S21 of the seal ring 34 may fall off together with the ceramic particles 34A inside the sliding surface S21. In this case, the sliding surface S21 of the seal ring 34 may fall off. The smoothness of the is greatly impaired.

Further, as shown in FIG. 5, for example, in the case of the seal ring 35 composed of ceramic particles 35A having an average particle diameter of about 10 μm, since the ceramic particles 35A are extremely large, the bonding region between the adjacent ceramic particles 35A is also formed. growing. In other words, since the bonding force between the ceramic particles 35A is increased, the seal ring 35 is not easily broken from the grain boundary of the ceramic particles 35A, and the ceramic particles 35A itself forming the convex portion of the sliding surface S22 of the seal ring 35 is worn. Will be scraped. As described above, when the ceramic particles 35A itself is scraped, the vicinity of the convex portion of the sliding surface S22 does not largely fall off, but it takes a long time to scrape the ceramic particles 35A.

On the other hand, in this embodiment, as shown in FIGS. 3 (b) and 3 (c), the seal ring 3 is composed of extremely small ceramic particles 3A, 3A, ... With a maximum particle diameter of 0.6 μm or less. Therefore, the ceramic particles 3A are likely to fall off from the interface of the grain boundaries in extremely small units, and when the mating ring 5 and the seal ring 3 are relatively rotationally slid, the shape of the sliding surface S2 of the seal ring 3 is formed. Early becomes a shape that follows the shape of the sliding surface S1 of the mating ring 5. As a result, the sliding surface S1 and the sliding surface S2 can be brought into a low friction state at an early stage.

Further, since the seal ring 3 is composed of small ceramic particles 3A, the density is higher than that of the conventional seal rings 34 and 35, so that the mating ring 5 and the seal ring 3 rotate relatively. When sliding, the ceramic particles 3A forming the convex portion on the sliding surface S2 are less likely to fall off together with the ceramic particles 3A inside the sliding surface S2. Further, even if the ceramic particles 3A inside the sliding surface S2 fall off together with the ceramic particles 3A forming the convex portion, the smoothness of the sliding surface S2 of the seal ring 3 is not easily impaired.

Further, the ceramic particles 3A, 3A, ... That have fallen off from the seal ring 3 enter into a fine recess formed in the sliding surface S2 of the seal ring 3, thereby increasing the smoothness of the sliding surface S2 and sliding. It also functions as an abrasive for polishing the surface S2, and wear of the sliding surface S2 is promoted. Further, since the maximum particle size of the seal ring 3 is as small as 0.6 μm or less, the mating ring 5 and the seal ring 3 even if the ceramic particles 3A of the seal ring 3 enter the gap between the carbon-based hard film 10 and the seal ring 3. It does not easily affect the sealing property with 3.

Further, since the average particle size of the ceramic particles constituting the seal ring 3 is extremely small at 0.5 μm and the size does not vary much, the seal ring 3 has a large difference in size of the ceramic particles. It is easy to smooth the sliding surface S2 of. In addition, the quality of the seal ring 3 is stable, and the density of the ceramic particles 3A is high, so that the structural strength is also improved.

Experiments have shown that the maximum particle size of suitable ceramic particles 3A for shortening the time required for familiarization is 0.1 μm or less.

Next, the mechanical seal according to the second embodiment will be described with reference to FIG. It should be noted that the description of the same configuration as that of the above embodiment and the overlapping configuration will be omitted.

As shown in FIG. 5A, an amorphous layer 11 is formed on the surface 3a of the seal ring 3 facing the mating ring 5. The amorphous layer 11 is formed by irradiating the surface of the SiC material (opposing surface 3a of the seal ring 3) with an irradiation energy less than the processing threshold using a femtosecond laser. In this embodiment, the amorphous layer 11 is formed with a thickness of 1.0 μm. The surface 11a of the amorphous layer 11 constitutes a sliding surface S20 that slides with the sliding surface S1 of the mating ring 5.

As described above, since the sliding surface S20 of the seal ring 3 that slides with the sliding surface S1 of the mating ring 5 is an amorphous layer 11 having no crystal structure, it slides as compared with the seal ring having a crystal structure. Since the moving surface S20 is easily broken in small units, the sliding surface S20 of the seal ring 3 can be easily smoothed. That is, when the mating ring 5 and the seal ring 3 rotate and slide relative to each other, the shape of the sliding surface S20 of the seal ring 3 quickly follows the sliding surface S1 of the mating ring 5. Therefore, the sliding surface S1 and the sliding surface S20 can be brought into a low friction state at an early stage.

In this embodiment, the same seal ring 3 as in Example 1 (seal ring 3 composed of ceramic particles having a maximum particle diameter of 0.6 μm and an average particle diameter of 0.5 μm) is used. Although the morphology has been illustrated, the present invention is not limited to this, and the size of the ceramic particles constituting the seal ring 3 can be freely changed as long as the amorphous layer 11 is formed.

Further, in this embodiment, the form in which the thickness of the amorphous layer 11 is 1.0 μm is illustrated, but it can be appropriately changed to a desired thickness.

Although examples of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these examples, and any changes or additions within the scope of the gist of the present invention are included in the present invention. Is done.

For example, in the above embodiment, the seal ring 3 illustrates a form composed of ceramic particles 3A, 3A, ... With a maximum particle size of 0.6 μm, but if the maximum particle size is 1.0 μm or less, You may change it freely. Further, the average particle size of the ceramic particles 3A may be freely changed as long as it is 1.0 μm or less.

Further, in the above embodiment, the carbon-based hard film 10 is coated on the mating ring 5, but the carbon-based hard film 10 is one of the facing surfaces of the mating ring 5 and the seal ring 3. It suffices if it is provided in. That is, one surface of the seal ring 3 may be covered.

Further, the carbon-based hard film 10 is not limited to one of the facing surfaces of the mating ring 5 and the seal ring 3, and may be covered over the entire surface of one of the mating ring 5 and the seal ring 3. ..

1 Mechanical seal 3 Seal ring (the other seal ring)
3A Ceramic Particle 5 Mating Ring (One Sealed Ring)
5A Base material 10 Carbon-based hard film (hard carbon thin film)
11 Amorphous layer S1 Sliding surface S2 Sliding surface S20 Sliding surface

Claims (4)

A mechanical seal in which one sealing ring in which a base material is coated with a hard carbon thin film and the other sealing ring formed mainly of ceramics slide in relative rotation.
Wherein the ceramic forming the sliding surface of the other seal ring is a zirconia consists of the following zirconia particles the maximum particle size 1.0 .mu.m,
The hard carbon thin film of the one sealing ring is a mechanical seal characterized by being a diamond-like carbon film formed from graphite. The mechanical seal according to claim 1 , wherein the sliding surface of the other sealing ring is composed of zirconia particles having an average particle diameter of 0.1 μm to 1.0 μm. A mechanical seal in which one sealing ring in which a base material is coated with a hard carbon thin film and the other sealing ring formed mainly of ceramics slide in relative rotation.
The ceramics forming the sliding surface of the other sealing ring are zirconia having an amorphous structure.
The hard carbon thin film of the one sealing ring is a mechanical seal characterized by being a diamond-like carbon film formed from graphite. The mechanical seal according to claim 3 , wherein the amorphous structure is formed by irradiation with a femtosecond laser.

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