JPS6345755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a packing formed by molding expanded graphite into a ring shape.

Due to the characteristics of expanded graphite, this type of packing has excellent flexibility, chemical resistance, heat resistance, and low temperature resistance. There is a drawback that the coefficient of friction between the shaft material increases rapidly over time, causing seizure, and if the mating shaft material is made of iron-based alloy, etc., the potential difference with the mating shaft material increases. This may lead to pitting corrosion.

Therefore, attempts have been made to add various lubricants such as oils or solid lubricants, passivation promoters, and various anticorrosive agents such as sacrificial metals to expanded graphite, but these efforts have not overcome the above-mentioned drawbacks. The problem has not yet been solved satisfactorily, and the current situation is that it actually has an adverse effect on the strength characteristics of expanded graphite itself.

The present invention has been made in view of the above points, and
The purpose is to provide a ring-shaped expanded graphite packing that can effectively prevent problems such as seizure and pitting due to potential difference without sacrificing the flexibility and other advantages of the packing.

In order to achieve the above object, the packing of the present invention is a packing formed by molding expanded graphite into a ring shape, and includes at least one kind of low melting point metal selected from lead, zinc, tin, and antimony only on the inner diameter surface of the packing. The film is formed by vapor deposition to a thickness in the range of 500 Å to 5 μm.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows an example of an apparatus for obtaining a packing according to the present invention, and shows a vacuum evaporation apparatus. That is, in FIG. 1, reference numeral 1 denotes a vacuum container, which is equipped with a supply pipe 2 for supplying an inert gas such as argon, and an intake pipe 3 connected to a vacuum suction pump (not shown). Reference numeral 4 denotes a holding stand supported within the vacuum container 1, which includes a cylindrical holding wall 5 and a lid 6 that covers the upper surface of the holding wall 5. Reference numeral 7 denotes a packing base material formed by molding expanded graphite into a ring shape having a rectangular cross section, and an appropriate number of packing base materials 7, 7, . . . are stacked concentrically on the holding table 4. This loaded packing base material 7,
7 are held by the retaining wall 5 in a fit-in manner, and are also pressed and held by the lid body 6. 8 is a cylindrical porous body pre-infiltrated with at least one kind of low melting point metal selected from lead, zinc, tin, and antimony, and is held in a state where it can be inserted concentrically into the packing base materials 7, 7... It is held on stand 4. 9
is a heating body made of tungsten wire or the like, and the porous body 8
This is to heat the inside of the machine. 10 is a shutter that can be opened and closed between the packing base materials 7, 7, . . . and the porous body 8, and 11 is an applied voltage between the packing base materials 7, 7, .

According to such a vacuum evaporation apparatus, when the shutter 10 is opened, the low melting point metal evaporated from the porous body 8 by the heating body 9 is transferred to each packing base material 7.
A plurality of packings according to the present invention as shown in FIG. 2 can be obtained by vapor-depositing only on the inner diameter surface 7a of the packing.

This packing has a low melting point metal film 12 of an appropriate thickness on the inner diameter surface 7a of a packing base material 7 made of expanded graphite.
is uniformly deposited. Note that the applied voltage (500V to 5KV) 11 can further strengthen the adhesion of the low melting point metal film 12 to the packing base material 7.

In the packing of the present invention manufactured by the manufacturing method described above, since the inner diameter portion of the packing that directly contacts the mating shaft material is the low-melting point metal film 12, wear powder of expanded graphite etc. does not come into contact with the mating shaft material. It is very effective to prevent adhesion, and when the contact part with the mating shaft material generates heat, the low melting point metal film 12 melts and forms a fluid film between it and the mating shaft material. The coefficient of friction does not increase rapidly, and therefore seizure, which is a fatal drawback of expanded graphite packings, can be effectively prevented.

Furthermore, since a low melting point metal is interposed between the expanded graphite and the mating shaft material, corrosion due to potential difference is effectively prevented even when the mating shaft material is an iron-based alloy or the like.

In addition, since the low melting point metal film 12 is only formed on the part that directly contacts the mating shaft material, that is, the inner diameter part of the packing, the presence of this low melting point metal film 12 makes it possible for the expanded graphite packing to It does not take away any of the advantages of flexibility it has. Incidentally, the thickness of the low melting point metal film 12 can be arbitrarily determined by controlling the evaporation time and evaporation source temperature using the vacuum evaporation apparatus, but it is possible to In order not to impair flexibility, it is necessary to keep the thickness within the range of 500 Å to 5 μm. In other words, if the low melting point metal film thickness is less than 500 Å, the amount of melting due to heat generation with the mating shaft material will be too small, so there is a risk that it will completely flow out in a single time.
If it exceeds this, although there is an advantage of being melted and lubricated for a long time, the strength of the metal film becomes stronger, and the original flexibility of expanded graphite is impaired. In other words, expanded graphite has excellent properties such as low stress relaxation and large stress conversion coefficient, which are essential properties for packing, but when the thickness of the low melting point metal film exceeds 5 μm, it becomes an inhibiting factor. The effects of this will be promoted. In addition, when the above-mentioned vapor deposition means is used on a commercial basis, it is preferable that the heating element 9 evaporates the low melting point metal at a temperature of 1000° C. or less.

Further, as described above, the surface of the low melting point metal film 12 formed by vacuum deposition (including ion deposition) can be made extremely smooth, so when a sacrificial metal addition method such as powder mixing is used, In comparison, its specific surface area is small, so it wears out slowly, exhibits a good sealing function over a long period of time, and has a corrosion-preventing effect.

Next, an embodiment of the packing according to the present invention will be shown.

〔Example〕

In the vacuum evaporation apparatus shown in Fig. 1, the inside of the vacuum container 1 is made into an argon atmosphere, and the degree of vacuum is set to 10 ^-2 to ^{10 -5} torr.
, select lead as the low melting point metal to be infiltrated into the porous body 8, set the applied voltage 11 to -1 to -5 KV, and deposit a lead film 12 with a thickness of 2 μm on the inner diameter surface 7a of the packing base material 7. I let it happen.

In the packing thus obtained, the lead film 12 in contact with the mating shaft material melts due to frictional heat and a fluid film is formed between it and the mating shaft material.
Unlike conventional expanded graphite packings, the coefficient of friction does not suddenly decrease over time and is stable without increasing, eliminating the conventional seizure phenomenon and maintaining good sealing performance over a long period of time. It was confirmed that it can be maintained.

This can be easily understood from the experimental results shown in FIG.

In other words, this experiment compared a first sample made of expanded graphite formed into a tape shape (thickness 0.38 mm, width 6 mm) and a second sample made with a 2 μm lead film deposited on one side of the first sample. As shown in FIG. 4, each sample 13 is wound around a drum 14, a weight W (500gr) is connected to one end of the sample 13, and the drum 14 is moved at a constant angular velocity (1787r.) in the direction of the arrow. pm), the tensile force F acting on the other end of each sample 13 was measured. The results of this experiment are
After converting the tensile force F into a friction coefficient μ, the third
In the figure, the first sample is indicated by a broken line and the second sample is indicated by a solid line. The conversion formula is F=W·e〓〓, that is, μ=1/φln (F/W), where φ is the contact angle of each sample 13 to the drum 14.

Therefore, as is clear from FIG. 3, the friction coefficient of the first sample made only of expanded graphite increases over time, while the friction coefficient of the second sample with a lead film deposited increases over time. The coefficient decreases over time, and after a certain period of time it stabilizes with almost no change. This is because the lead film is melted by frictional heat with the drum 14 and forms a fluid film between the lead film and the drum 14.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a vacuum evaporation apparatus for obtaining a packing according to the present invention, FIG. 2 is a partially cutaway perspective view showing a packing according to the present invention, FIG. 3 is a graph showing experimental results, and FIG. The figure is a schematic diagram of the experimental apparatus. 7... Packing base material, 7a... Inner diameter surface, 12... Low melting point metal film.

Claims (1)

[Claims] 1. In a packing formed by molding expanded graphite into a ring shape, at least one kind of low melting point metal film selected from lead, zinc, tin, and antimony is vapor-deposited only on the inner diameter surface to a thickness in the range of 500 Å to 5 μm. Patsukin is characterized by having done.