JPH11108199A - Sliding ring for mechanical seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent initial leakage by conforming (sliding surface of a sliding member on a rotating side with a sliding surface of a sliding member on a static side in a short time in a initial operation after mounting to a device. SOLUTION: A DLC membrane is formed by a deposition at an end face which acts as a sliding surface in a surface of a ring-like substrate member formed for a seal ring and/or a mating ring, and the surface of the DLC membrane is planed by a lap. Because the DLC has an intermediate property (texture) of a graphite carbon burning member and a diamond, an initial abrasion of a sliding surface of a mechanical seal can be reduced and further a starting torque can be reduced, whereby conforming of sliding surfaces can be smoothly done.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member used as a sealing element on a rotating shaft side or a stationary sealing element sliding on the rotating shaft side in a mechanical seal for sealing a fluid around a rotating shaft of an apparatus. .

[0002]

2. Description of the Related Art A mechanical seal is an end face in which a sliding member provided on a rotating shaft side and rotating with the rotating shaft and a stationary sliding member provided on a non-rotating housing side are orthogonal to the axis. By sliding closely together, leakage of fluid around the shaft is prevented, and the sliding material is required to have excellent wear resistance and sliding characteristics. For this reason, as the material of the sliding material, a hard material having excellent wear resistance, a hard material such as silicon carbide or alumina, or carbon having excellent self-lubricating properties is used. It is desirable that both sliding surfaces of the rotating side sliding material and the stationary side sliding material are both extremely smooth, except for a case where lubricating liquid is intentionally supplied between the sliding surfaces. Order flatness is required.

[0003] The sliding surfaces of the rotating sliding member and the stationary sliding member may be deformed by pressure or may not be in a completely sealed sliding state at the beginning of use, and may be deformed at the time of startup and operation. By a synergistic effect such as a thermal deformation and a lubricating action of the sealing liquid that has entered between the sliding surfaces, the state gradually shifts to an appropriate sealed sliding state. This process is called “familiar” .If the device on which the mechanical seal is actually installed is one that generates a certain level of vibration or shaft runout, such as a rotating device such as general industrial machinery, In such a case, “fit-in” is unlikely to occur, and therefore, an improper sealing sliding state continues, often causing leakage of the fluid to be sealed (initial leakage).

As a method for preventing initial leakage due to improper sliding between sliding surfaces in the initial stage of use as described above, the following means have conventionally been adopted. (1) The sliding surfaces of the rotating sliding member and the stationary sliding member are machined as smoothly and as precisely as possible. (2) Attach to the equipment by rubbing the sliding surfaces of the rotating side sliding member and the stationary side sliding member with each other so that the close contact state is as appropriate as possible. (3) After mounting on the equipment, perform the running-in operation for the required time, and use the sliding surfaces after they have been properly sealed and slid. (4) Apply oils and fats or liquid to be sealed in advance on the sliding surface.

[0005]

However, the prior art described above
The following problems are pointed out in (1) to (4). Method (1): No matter how smooth and high-precision the sliding surface is, small undulations and inclinations on the sliding surface are inevitable. Method (2) ··········································································································································································· 熟 · Method (3) ······································································· Method (4) ... The formation of a lubricating film with oils and fats and the liquid to be sealed does not necessarily promote familiarization.

SUMMARY OF THE INVENTION The present invention has been made under the above circumstances, and a technical problem thereof is that a rotary sliding member and a stationary sliding member are used in an initial operation after mounting on a device. The purpose of the present invention is to prevent the initial leakage by adapting the respective sliding surfaces to each other in a short time.

[0007]

As a means for effectively solving the above-mentioned technical problems, a sliding ring for a mechanical seal according to the present invention includes a sliding ring of a mechanical seal (seal ring and / or mating). A DLC film is applied to an end surface serving as a sliding surface among the surfaces of the annular base material formed for the ring), and the surface of the DLC film is formed smoothly. Here, “DLC” is an abbreviation for diamond-like carbon, and as will be described in detail later, intermediate properties (structure) between high-purity calcined carbon containing graphite (hereinafter, referred to as graphite carbon calcined body) and diamond ), Which is harder than a carbon material or the like used as a normal mechanical seal sliding material. In addition, the DLC film has a function of filling and smoothing minute unevenness existing on the end surface of the base material serving as a sliding surface. For this reason, the initial wear of the mechanical seal sliding surface is small, and the starting torque is suppressed low, so that the sliding surface can be smoothly adapted.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION "DLC" as used in the present invention is defined as follows by Raman spectrum analysis.

In measuring the Raman spectrum of a carbon-based sample, the surface of the sample is irradiated with an argon laser beam, and the spectrum of the Raman scattered light from the sample surface is measured by a spectroscope. As shown in FIG. 1, the Raman spectrum obtained in this manner shows a sharp peak only in the graphite band (hereinafter, referred to as G band) near 1680 cm ^{−1 in} the case of single crystal graphite, and shows a general mechanical seal sliding material. In the case of graphite carbon fired body used as
A sharp peak appears in both of the diamond bands around 1370 cm ^-1 (hereinafter referred to as D band). On the other hand, in the case of natural diamond, a sharp peak appears only in the D band.

A non-crystalline graphite film containing a large amount of hydrogen (hereinafter referred to as a-CH film) and a hard film containing diamond structure (hard DLC film) are 1680 cm.
^It has peaks in both the G band near ^-1 and the D band near 1370 cm ^-1, and one or both of them are significantly broader than the spectral peaks of single crystal graphite, graphite carbon fired product or natural diamond. , And the spectral intensity between both peaks is large as a whole.
The DLC referred to in the present invention includes all carbon-based materials having such a spectral pattern, and has a property (structure) intermediate between graphite carbon fired body and diamond. Relatively hard. The sliding ring for a mechanical seal of the present invention can reduce the initial wear and the starting torque by applying such a DLC film to the sliding surface.

It has been experimentally found that the larger the thickness of the DLC film, the longer the film retention time becomes. However, when the thickness exceeds 5 μm, the film tends to be easily worn. For this reason,
The thickness of the DLC film is within 5 μm, preferably about 2 μm. As a method of applying the DLC film, for example, an ion beam evaporation method is employed for a hard carbon film containing a diamond structure, and for an a-CH film, for example, plasma CVD (chemical vapor deposition) is employed.

When the base material of the sliding ring is made of a fired graphite carbon material or a cemented carbide, the DLC film is bonded to the carbon structure on the base material surface, so that the DLC film is adhered with high bonding strength. When it is made of a material that does not contain a large amount of carbon, it is difficult to obtain a large adhesion strength. Therefore, in such a case, the DLC film is applied via an intermediate layer that contains unbonded carbon and silicon particles and has good bondability with the base material. This intermediate layer is typically made of SiO ₂ or TiC
It consists of That is, DLC is placed on the intermediate layer.
Is deposited, carbon of DLC is bonded to unbonded carbon and silicon particles contained in the intermediate layer, and a film is formed using these carbon and silicon particles as nuclei. For this reason, the carbon or silicon particles can function as an anchor between the DLC film and the intermediate layer, and can improve the adhesion strength with the base material.

[0013]

【Example】

Example 1 A base material of a seal ring for a mechanical seal made of a graphite carbon fired body was formed, a dry lap was applied to an end surface serving as a sliding surface with a mating ring, and after cleaning, a plasma CVD method was performed under the following conditions. An a-CH film as a DLC film was deposited on the end face. Deposition conditions: Acetylene gas flow rate ··· 3.01 / min Oxygen flow rate ··· 3.01 / min Acetylene gas / Oxygen mixture ratio 1.21 Base material temperature 800C Film thickness ...・ ・ ・ ・ 0.5μm

The seal ring of Example 1 in which the a-CH film was formed on the sliding surface by the above-described method, and the seal ring as Comparative Example 1 made of a graphite carbon fired body having no film formed on the sliding surface, respectively. It was assembled in a mechanical seal and subjected to a sliding test under the following conditions to measure the change over time in the friction coefficient. FIG. 2 shows the measurement results. Test conditions Material of mating ring of mating partner: Cemented carbide Slide surface pressure: 4 kgf / cm ² Liquid to be sealed ···················································· 8 liters / min.・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Room temperature Number of rotations ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・... 2,000 rpm.

As is clear from FIG. 2, in the case of the mechanical seal using the seal ring as Comparative Example 1, the state where the coefficient of friction continues to be high for about 80 minutes immediately after the start, and then the progress of the familiarization of the sliding surface progresses. With the transition to a proper sealed sliding state, the coefficient of friction gradually decreased, whereas the seal ring of Example 1 having an a-CH film formed on the sliding surface was used. In the case of the mechanical seal, it can be seen that the coefficient of friction is kept low from the start. Further, in Example 1, a slight increase in the friction coefficient was observed with time, and the friction coefficient in Example 1 was almost equal to the friction coefficient in Comparative Example 1 approximately 200 minutes after the start of operation. This is because the a-CH film on the sliding surface was almost worn at the time.

Example 2 A base material of a mechanical sealing mating ring made of a cemented carbide is formed, a wet lap is applied to an end surface serving as a sliding surface with a mating seal ring, and after washing, the following is performed by an ion beam evaporation method. Under the conditions described above, a hard film containing a diamond structure was deposited on the end face. Vapor deposition conditions; Raw materials: Amorphous carbon plate Sputter gas:・ ・ ・ Argon and hydrogen mixed gas Thickness ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 0.1μm

The mating ring of Example 2 in which a hard film containing a diamond structure was formed on the sliding surface by the above-mentioned method, and a comparative example 2 in which a hard film made of a cemented carbide not forming the hard film on the sliding surface was used. Each of the toting rings was incorporated into a mechanical seal, and a test was performed under the following conditions, and a sliding state during operation and a sliding surface after operation were observed. Material ........ graphite carbon test conditions counterpart sealing ring fired body sliding surface pressure ···················· 10 kgf / cm ² sealed liquid・ ・ ・ ・ ・ ・ ・ ・ ・ Shimizu Flow rate ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 8 liters / Min. Temperature ········· 80 ° C Number of rotations ········ ········ 2,000rpm. Operating time ········· 180 min.

In FIG. 3, (A) shows the sliding surface properties of the mating ring according to Example 2 after the hard coating containing a diamond structure is applied, and (B) shows the mating ring according to Comparative Example 2. Is the sliding surface properties after operation.
As is clear from this figure, relatively large tissue destruction and striations were observed on the sliding surface of the comparative example, while the sliding surface properties of Example 2 were good. Further, in Comparative Example 2, a sliding noise caused by a stick-slip phenomenon due to insufficient lubrication occurred during operation, whereas in Example 2, such abnormal noise did not occur.

[0019]

According to the sliding ring for mechanical seal of the present invention, the initial wear can be reduced and the starting torque can be suppressed low by applying the DLC film to the sliding surface. It is possible to smoothly transition to a sealed sliding state, and effectively prevent stick-slip motion and initial leakage due to an increase in the starting torque.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a Raman spectrum pattern of a carbon-based material for defining DLC used in the present invention.

FIG. 2 shows a time-dependent change in friction coefficient of a seal ring of Example 1 in which an a-CH film is formed on a sliding surface and a seal ring of Comparative Example 1 in which a film is not formed on a sliding surface in a sliding test. It is an explanatory view showing the result.

FIG. 3 shows a mating ring of Example 2 in which a hard film containing a diamond structure is formed on a sliding surface, and a mating ring of Comparative Example 2 made of a cemented carbide not forming the hard film on the sliding surface. It is explanatory drawing which shows the sliding surface property after a sliding test.

Claims (2)

[Claims] 1. A surface of an annular base material formed for a sliding ring of a mechanical seal has a sliding surface with an end face serving as a sliding surface.
A sliding ring for a mechanical seal, wherein an LC film is applied and the surface of the DLC film is formed smoothly. 2. The mechanical seal according to claim 1, wherein the DLC film is applied via an intermediate layer containing unbonded carbon or silicon particles and having good bonding properties with a base material. Sliding ring.