JP4094176B2 - mechanical seal - Google Patents

Description

【００３１】
【発明の効果】
上記試験結果からも明らかなように、本発明によると、結合材に固体潤滑材料を配合した摺動皮膜を、硬質で変形しにくく熱伝導性の良い基材の表面にコーティングすることによって、液体潤滑膜が形成されない乾燥摺動条件でも優れた潤滑性を発揮すると共に、著しい耐摩耗性の向上が実現できる。しかも、摺動皮膜の大部分が摩滅した場合でも上記効果が持続されるので、特に、摩耗粉等による異物の発生を極力防止する必要のある機器において、乾燥状態で摺動されるメカニカルシールとして、優れた効果を実現することができる。
【図面の簡単な説明】
【図１】 本発明に係る摺動材の評価を行うための摺動試験に用いたメカニカルシールをハウジング及び回転軸と共に軸心を通る平面で切断して示す断面図である。
【符号の説明】
１１ 静止側密封要素
１１ａ，１４ａ 摺動面
１４ 回転側密封要素[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mechanical seal having a stationary-side sealing element and a rotating-side sealing element that slide in a non-lubricated state in which a fluid film is not formed between sliding surfaces .
[0002]
[Prior art]
The mechanical seal is provided on the rotating shaft side and rotates with the rotating shaft (rotating side sealing element), and a stationary sliding material (stationary side sealing element) provided on the non-rotating housing side. Is a material that is excellent in low friction and wear resistance for the sliding material because it prevents fluid leakage around the shaft by sliding closely between the end faces orthogonal to the shaft center. The In particular, a sliding material that is slid in a non-lubricated state where no fluid lubrication film is supplied between the sliding surfaces is required to have excellent self-lubrication and wear resistance. For example, carbon materials, graphite, and glass have been conventionally used. A material made of a tetrafluoroethylene resin blended with an aggregate mainly composed of fiber, carbon fiber, metal powder or the like is used.
[0003]
[Problems to be solved by the invention]
However, in the case of a carbon material, in an atmosphere such as a vacuum, a reducing gas, or dry air having a low dew point temperature, the lubricity of the carbon may be lost and significant wear may occur.
[0004]
Moreover, in the tetrafluoroethylene resin sliding material which mix | blended the aggregate, although it is comparatively hard to receive the influence by the said atmosphere, slight abrasion generate | occur | produces. Especially for agitators used in the production process of foods and pharmaceuticals, it is necessary to prevent foreign substances from entering as much as possible from the viewpoint of hygiene and product characteristics. Therefore, mechanical seals used in such devices are also manufactured. In order to prevent the wear powder from being mixed into the food and the like as much as possible, it is necessary to eliminate the generation of the wear powder due to the wear of the sliding material even in a non-lubricated state or to make it extremely small. From such a point of view, in the tetrafluoroethylene resin sliding material, various studies have been made on the types and blending ratios of aggregates to be blended to improve the wear resistance.
[0005]
However, the tetrafluoroethylene resin sliding material has about 70% of the tetrafluoroethylene resin that has lubricity but poor wear resistance, so there is a limit in improving the wear resistance and can be used. The range is limited. In recent years, ceramics containing a self-lubricating substance such as carbon or metal materials containing a self-lubricating substance may be used as a non-lubricated sliding material, but conditions such as vacuum and pressure are repeated. In such a case, “squealing” or the like caused by poor lubrication occurs on the sliding surface, and wear powder is generated. In terms of design, an attempt has been made to reduce the burden of the sliding material by providing a groove on the sliding surface so that a gas film is formed between the sliding surfaces during sliding. In addition, when conditions such as a vacuum state and a pressurized state are repeated as described above, sufficient effects are not exhibited.
[0006]
The present invention has been made in view of the above problems, and the main technical problem is that it is excellent in an atmosphere where there is no lubricating oil or liquid, or in environmental conditions where lubrication with a fluid cannot be expected. An object of the present invention is to provide a mechanical seal having a sliding material capable of exhibiting slidability and wear resistance.
[0007]
[Means for Solving the Problems]
In order to effectively solve the technical problems described above, the mechanical seal according to the present invention has a stationary side sealing element and a rotary side sealing element that slide in a non-lubricated state in which a lubricant film is not formed between the sliding surfaces. In addition, each of the stationary side sealing element and the rotary side sealing element has at least one kind of self-lubricating material made of ethylene tetrafluoride resin, molybdenum disulfide, graphite, tungsten disulfide, or graphite fluoride on the surface of the substrate. A mechanical seal made of a sliding material having a sliding film coated with a mixed liquid of a solid lubricant material selected and a binder made of an epoxy resin, a polyimide resin, or a polyamide-imide resin. Both of the stationary side sealing element and the rotary side sealing element are made of silicon carbide or carbon, and the surface of the sliding side end surface of the base material is a surface of the mixed liquid. Before coating, it is characterized in that after the surface roughening by a diamond paper or diamond abrasive grains, leaving the fine recesses tip of the fine protrusions are polished flat.
[0008]
That is, in the present invention, ceramics and carbon used as a substrate are excellent in corrosion resistance, hardly elastically deformed , excellent in thermal conductivity, and themselves have a required self-lubricating property. The basis of the selection is first to prevent the sliding film due to corrosion of the joint interface with the sliding film to be coated. Secondly, it is intended to make it difficult to be deformed by a load such as a pressure of the use atmosphere, and thereby, it is easy to maintain the initial surface roughness of the sliding coating, and to reduce the change of the friction coefficient. Thirdly, because of the good thermal conductivity, the heat generated by sliding can be easily dissipated, and the thermal load of the sliding film can be reduced. Fourth, the sliding film wears over time. Even when the thickness is reduced, the base material exposed to the sliding surface due to wear does not significantly impair the lubricity, and the remaining portion of the sliding coating can be in a sliding state that assists the lubricity on the base material surface.
[0009]
In addition, the solid lubricating material and the binder constituting the sliding coating have low friction coefficients but poor wear resistance, so they are not suitable as sliding materials by themselves, and are usually only used as lubricating aids or simple binders. Although used, according to the inventor's research, such a mixture of solid lubricating material and binder is coated on the surface of a substrate made of ceramic, carbon, etc., which is hard and not easily deformed, and has good thermal conductivity. As a result, a significant improvement in wear resistance was achieved.
[0010]
That is, according to the present invention, as a result of the base material compensating for the hardness and thermal conductivity that the solid lubricating material and the binder constituting the sliding coating do not originally have, the wear resistance can be improved. is there. As will be described later, since the progress of wear is remarkably suppressed due to excellent wear resistance, a film thickness of 10 to 30 μm is sufficient.
[0011]
In order to improve the bonding property of the sliding film to the substrate surface, a certain degree of surface roughness is required on the surface of the substrate. If the tip of the saw-toothed hard base material is exposed to the sliding surface due to the progress of wear, the mating sliding surface may be scraped off and wear may be accelerated. In the present invention, the surface of the substrate to be coated is polished so that the protrusions of the fine protrusions in the surface roughness become flat. Even if the portion is exposed, it becomes less aggressive against the mating material and is polished while leaving a fine recess, so that good bondability with the sliding film is also ensured.
[0012]
In the mechanical seal according to the present invention, both the stationary- side sealing element and the rotating-side sealing element that slides on the stationary- side sealing element are made of the sliding material . As a result, even in a dry lubrication atmosphere in which no fluid lubricating film is formed, the wear resistance of the stationary side sealing element and the rotary side sealing element is significantly improved, and generation of wear powder can be effectively suppressed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment according to the present invention, ceramics such as silicon carbide, alumina, silicon nitride, zirconia, sialon, or carbon can be used for the base material. Although not limited to this depending on thermal conductivity, corrosion resistance, surface roughness of the coating surface, hardness, etc., silicon carbide is a particularly preferred material in view of these points.
[0014]
The surface of the base material forming the sliding surface is provided with fine irregularities in advance and polished by lapping or the like so that the tips of the fine convex portions in the surface roughness are flattened to ensure flatness. For the formation of fine irregularities, when the base material is ceramics or the like, a softer material is blended into the ceramics, and the soft part is preferentially scraped off by sandblasting or the like. A method of performing sand blasting by applying the masking, a method of polishing with diamond coarse grains, and the like are employed. In addition, pore-dispersed ceramics having an infinite number of spherical or irregular fine pores are preferable because appropriate surface roughness is imparted by pores exposed on the surface.
[0015]
In the case of a substrate made of carbon, the surface roughness tends to be rough, so care must be taken not to roughen it more than necessary. This is because if the surface roughness is too rough, the thickness of the sliding film to be coated becomes thin. Sandblasting with ceramic abrasive grains is effective as a method for imparting surface roughness to a base material made of a metal material, but care must be taken so that the surface roughness does not become rough.
[0016]
The sliding film coated on the surface of the substrate is made of a material obtained by blending a solid lubricant material with a binder . The solid lubricant material is typically selected from one or more well-known self-lubricating substances such as ethylene tetrafluoride resin, molybdenum disulfide, graphite, tungsten disulfide, graphite fluoride, etc. From the viewpoint of excellent self-lubricating property and being hardly affected by the atmospheric fluid, ethylene tetrafluoride resin is most preferable.
[0017]
Further, the binder to be fixed on the surface of a substrate while binding the particles of the solid lubricant material as slide film, heat resistance, bond strength, it has excellent film-forming properties and abrasion resistance are required. Typically, it is selected from an epoxy resin, a polyimide resin, or a polyamide-imide resin, and is used by being dissolved or dispersed in a medium such as an appropriate solvent. The selection of the binder and the blending ratio with the solid lubricant material are appropriately determined in consideration of the use conditions such as the thermal conditions and the type of fluid to be sealed, and the type of the solid lubricant material.
[0018]
The method of coating the surface of the base material with the sliding film is not particularly specified, and various methods such as spraying with a spray, application with a brush, or immersion in a mixed liquid of the above-described solid lubricating material and a binder . The method can be adopted. Thus, the coating layer adhering to the surface of the substrate in the form of a film is cured by a curing process including a heat treatment and becomes a sliding film.
[0019]
The sliding material having the above structure has a sliding film having excellent self-lubricating properties and excellent wear resistance due to hardness compensation by the base material. By using it for both stationary and rotating side sealing elements of mechanical seals mounted on shaft seals such as multi-function filter dryers that perform solid-liquid separation, washing and drying at Abrasion is improved, and generation of wear powder is effectively suppressed.
[0020]
FIG. 1 schematically shows a mechanical seal 1 used in a sliding test described below. The mechanical seal 1 is held on the inner periphery of the housing 2 that surrounds the outer peripheral side of the rotary shaft 3 via an O-ring 12 and is prevented from rotating via an engaging means 13. An element 11, a rotary side sealing element 14 that is disposed on the outer periphery of the rotary shaft 3 via a packing 15 so as to be axially movable, and is opposed to the stationary side sealing element 11 in the axial direction, and the rotary side sealing element A coil spring 16 that presses 14 against the stationary-side sealing element 11 to apply an appropriate close load between the sliding surfaces 11a, 14a, and an intermediate ring 17 disposed between the coil spring 16 and the rotary-side sealing element 14. And a collar 18 that supports the coil spring 16 and transmits the rotational force of the rotary shaft 3 to the rotary side sealing element 14 through the intermediate ring 17.
[0021]
That is, in this mechanical seal 1, the sliding surface 14 a of the rotating side sealing element 14 rotated together with the rotating shaft 3 is in close contact with the sliding surface 11 a of the non-rotating stationary side sealing element 11 held in the housing 2. This provides a shaft seal function that seals the gas.
[0022]
In the case where the sliding material of Examples 1 to 5 which will be described later is incorporated as the stationary side sealing element 11 and the rotation side sealing element 14 and the case where the sliding material of Comparative Examples 1 and 2 is incorporated in the mechanical seal 1 described above. Were subjected to a sliding test under the following conditions, and the results were compared.
[Test conditions]
Sliding surface peripheral speed: 1 m / s
Surface pressure of sliding surface: 0.7 kgf / cm ²
Atmosphere: N ₂ gas 2 kgf / cm ² G
Test time: 100 hours [0023]
[Example 1]
Using a silicon carbide sintered body (specific gravity 3.10), the inner diameter φ1 = 58.6 mm of the annular convex portion forming the sliding surface 11a, the outer diameter φ2 = 66.1 mm of the annular convex portion, and the ring inner diameter φ3 = An annular body for the stationary-side sealing element 11 having a diameter of 56 mm, a ring outer diameter of φ4 = 81 mm, and an axial length L1 = 27 mm was manufactured. Also, with the same material as this, the inner diameter (ring inner diameter) φ5 = 56.5 mm of the portion that becomes the sliding surface 14a, the outer diameter φ6 = 75mm of the portion that becomes the sliding surface 14a, the outer diameter of the ring φ7 = 77mm, the shaft An annular body for the rotation-side sealing element 14 having a directional length L2 = 26.5 mm was manufactured. Next, by polishing and lapping the end surfaces which become the sliding surfaces 11a and 14a in both annular bodies, the surface roughness of the end surfaces is set to 0.05 μmRa, and thereafter, the surface is roughened by 9 μm diamond paper, and further 3 μm. By polishing with a diamond dispersion, the top of the fine convex portion on the surface was cut flat, and the surface roughness was 0.3 μmRa. Next, an enameled epoxy resin containing 40 wt% of tetrafluoroethylene resin having an average particle size of 5 μm was applied to the end face by air spray, and after drying, a curing treatment was performed at 180 ° C. for 30 minutes. Furthermore, in order to obtain the flatness of the sliding surface, polishing was performed with a 3 μm diamond dispersion liquid to obtain a test sample. The film thickness was about 15 μm.
[0024]
[Example 2]
An annular body for the stationary side sealing element 11 and an annular body for the rotary side sealing element 14 were manufactured in the same shape as in Example 1. Next, the end surfaces of both annular bodies that become the sliding surfaces 11a and 14a are roughened with 9 μm diamond abrasive grains, and then polished with a 3 μm diamond dispersion liquid, whereby the tops of the fine convex portions on the surface are obtained. Was cut flat and the surface roughness was 0.3 μmRa. Next, an enamel-like polyamideimide resin containing 30 wt% of tetrafluoroethylene resin having an average particle size of 5 μm was applied to the end face by air spraying, and after drying, a curing treatment was performed at 260 ° C. for 30 minutes. Next, in order to obtain the flatness of the sliding surface, polishing was performed with a 3 μm diamond dispersion to prepare a test sample. The film thickness was about 20 μm.
[0025]
[Example 3]
For the annular body for the stationary side sealing element 11 and the rotary side sealing element 14 by a silicon carbide sintered body containing 3 wt% of carbon powder having an average particle size of 15 μm and having irregular pores (average diameter 20 μm) exposed on the surface. An annular body of the same shape as in Example 1 was produced. And the surface roughness was set to 0.08 micrometer Ra by polishing with the 3 micrometers diamond dispersion liquid to the end surface used as the sliding surfaces 11a and 14a in both annular bodies. Thereafter, an enamel-like polyamideimide resin containing 30 wt% of tetrafluoroethylene resin having an average particle size of 5 μm was applied to the end face by air spray, dried, and then subjected to a curing treatment at 260 ° C. for 30 minutes. Thereafter, in order to obtain the flatness of the sliding surface, polishing was performed with a 3 μm diamond dispersion liquid to obtain a test sample. The film thickness was about 20 μm.
[0026]
[Example 4]
For the annular body for the stationary side sealing element 11 and the rotary side sealing element 14 by a silicon carbide sintered body containing 3 wt% of carbon powder having an average particle size of 15 μm and having irregular pores (average diameter 20 μm) exposed on the surface. An annular body of the same shape as in Example 1 was produced. And the surface roughness was set to 0.08 micrometer Ra by polishing with the 3 micrometers diamond dispersion liquid to the end surface used as the sliding surfaces 11a and 14a in both annular bodies. Thereafter, an enamel-like polyamideimide resin containing 30 wt% of tetrafluoroethylene resin having an average particle size of 5 μm was applied to the end face by air spray, dried, and then subjected to a curing treatment at 260 ° C. for 30 minutes. Thereafter, the film having a film thickness of about 20 μm formed in this manner is scraped off with a diamond dispersion liquid having an average particle size of 3 μm to leave only a part of the film only in the fine recesses due to the irregular pores. A sliding film was formed in a dispersed manner on about 10% of the entire surface, and used as a test sample.
[0027]
[Example 5]
Using a hard carbon material having a hardness of 110, an annular body for the stationary-side sealing element 11 was manufactured in the same shape as in Example 1. And the surface roughness was set to 0.20 μmRa by polishing the end surface which becomes the sliding surface 11 a in this annular body with a 6 μm diamond dispersion. Thereafter, an enameled epoxy resin containing 40 wt% of a tetrafluoroethylene resin having an average particle size of 5 μm was applied to the end face by air spraying, dried, and then subjected to a curing treatment at 180 ° C. for 30 minutes. Then, in order to obtain the flatness of the sliding surface, the sliding surface was polished with a 3 μm diamond dispersion liquid to obtain a stationary test sample. The test sample on the rotating side was manufactured in the same manner as in Example 3.
[0028]
[Comparative Example 1]
The stationary side sealing is achieved by using the same silicon carbide sintered body as used in Examples 3 and 4, which contains 3 wt% of carbon powder having an average particle size of 15 μm and further has irregular pores (average diameter of 20 μm) exposed on the surface. An annular body for the element 11 and an annular body for the rotary side sealing element 14 were produced in the same shape as in Example 1. A coating was not applied to the end surfaces of the two annular bodies that would become the sliding surfaces 11a and 14a, and polishing was performed with a 3 μm diamond dispersion to obtain a flatness of the sliding surfaces, thereby preparing test samples.
[0029]
[Comparative Example 2]
An annular body for the stationary-side sealing element 11 is manufactured in the same shape as in Example 1 by using a tetrafluoroethylene resin sliding material containing 15 wt% of carbon fibers (short fibers having an average thickness of 10 μm and an average length of 100 μm). A normal surface finish was applied to the sliding surface 11a to obtain a stationary test sample. A test sample on the rotating side was made of an alumina sintered body having a purity of 99.5% and having the same shape as in Example 1, and a normal surface finish was applied to the sliding surface 14a.
[0030]
Table 1 below shows the results of the sliding test. As is apparent from Table 1, in Examples 1 to 5, the amount of wear on the sliding surface after sliding for 100 hours is 0 or extremely small, and the temperature of the sliding surface due to heat generated by sliding is zero. Also, it was confirmed that the temperature was significantly lower than those of Comparative Examples 1 and 2. Moreover, even in Example 4 in which the sliding film remained in about 10% of the entire sliding surface due to the fine recesses due to the irregular pores, the amount of wear was 0, so that most of the sliding film was worn out. After that, it was confirmed that the effect was sustained. On the other hand, in the comparative example in which the sliding film is not formed, in addition to the occurrence of a certain amount of wear, the temperature of the sliding surface is high, and in comparative example 1, the frictional sound called “squeal” caused by insufficient lubrication is generated. There was an outbreak.
[Table 1]

[0031]
【The invention's effect】
As is apparent from the above test results, according to the present invention, a liquid coating is obtained by coating a hard and hard-to-deform surface of a base material having a good thermal conductivity with a sliding film in which a solid lubricating material is blended with a binder. While exhibiting excellent lubricity even under dry sliding conditions in which a lubricating film is not formed, a significant improvement in wear resistance can be realized. Moreover, even if most of the sliding film wears out, the above effect is maintained, so as a mechanical seal that is slid in a dry state, especially in equipment that needs to prevent the generation of foreign matter due to wear powder and the like as much as possible. , it is possible to realize an excellent effect.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a mechanical seal used in a sliding test for evaluating a sliding member according to the present invention cut along a plane passing through an axis together with a housing and a rotating shaft.
[Explanation of symbols]
11 Static side sealing element 11a, 14a Sliding surface 14 Rotation side sealing element

Claims (1)

Having a stationary-side sealing element and a rotating-side sealing element that slide in a non-lubricated state in which a fluid film is not formed between the sliding surfaces;
The stationary side sealing element and the rotary side sealing element are each selected from one or more kinds of self-lubricating materials made of tetrafluoroethylene resin, molybdenum disulfide, graphite, tungsten disulfide, or graphite fluoride on the substrate surface. A mechanical seal made of a sliding material having a sliding film coated with a mixed solution of a solid lubricating material and a binder that is an epoxy resin, a polyimide resin, or a polyamide-imide resin,
The substrate is made of silicon carbide or carbon for both the stationary side sealing element and the rotary side sealing element,
The surface of the sliding side end surface of the base material is subjected to surface roughening with diamond paper or diamond abrasive grains before coating with the mixed solution, and then the protruding end of the fine convex portion is polished flat, leaving a fine concave portion. A mechanical seal characterized by

Images