JP2006194282A - Mechanical seal mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanical seal mechanism excellent in sliding characteristics of sealing rings, low in friction resistance, and excellent in a service life, at low cost. <P>SOLUTION: In an embodiment, hard carbon thin film 10 composed of DLC and containing 20 atom % or less hydrogen is formed on a seal surface of a rotary seal ring 4 attached on a side of a rotor 12, or a opposite seal surface of a fixed seal ring 7 attached on a side of a housing 13 storing the rotor 12, or both seal surfaces, and mixture of glycol of one kind, two kinds or more glycol is contained in liquid to be sealed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mechanical seal mechanism that is used to prevent leakage of liquid such as oil or water from between a housing and a shaft that rotates in the housing.

For example, in a mechanical seal of equipment used underwater such as a water pump, the rotary seal ring attached to the rotary shaft side is silicon carbide, and the fixed seal ring attached to the housing side located around the rotary shaft is It is common to use a carbon material.
That is, silicon carbide is used for the rotary seal ring because it has high hardness and excellent wear resistance and is not corroded even when exposed to high-temperature and high-pressure water vapor. On the other hand, the reason why the carbon material is used for the fixed sealing ring is to have excellent self-lubricating properties and to suppress abnormal wear and abnormal noise generation (so-called “squeal”) even when the lubrication state is deteriorated.

In some cases, silicon carbide is used for both the rotating seal ring and the stationary seal ring. In this case, in order to prevent the generation of abnormal noise when the lubrication state by the sealing liquid deteriorates, porous silicon carbide is used. It is necessary to apply (refer patent document 1).
JP 2002-323142 A

  As described above, silicon carbide is a suitable material as a sliding material for mechanical seals, but is an expensive material. Therefore, as described in Patent Document 1, particularly, a rotary seal ring, a fixed seal is used. When applied to both rings, there is a problem that the material cost will rise. Moreover, the sliding material using silicon carbide has become a mature technology, and it is technically difficult to reduce the frictional resistance.

  The present invention has been made by paying attention to the above-mentioned problems in conventional sliding materials for mechanical seals. The purpose of the present invention is to provide excellent sliding characteristics between sealing rings, low friction resistance, and long service life. It is to provide an excellent mechanical seal mechanism at low cost.

  In order to achieve the above-mentioned problems, the present inventors have studied various sliding materials suitable for a sealing ring of a mechanical seal, and combinations with a sealing liquid that will be interposed on the sliding surface of these sliding materials. As a result of intensive studies on the above, as a result of containing a glycol such as ethylene glycol or propylene glycol in the sealing liquid, diamond-like carbon (hereinafter, “ It has been found that by applying a coating with a hard carbon thin film such as “DLC”, it is possible to achieve both wear resistance and low frictional resistance, and the present invention has been completed.

  That is, the mechanical seal mechanism of the present invention is based on the above knowledge, and in the mechanical seal mechanism for preventing the outflow and inflow of liquid from between the housing and the rotating body rotatably accommodated in the housing. A rotating seal ring that is attached to the rotating body and has a seal surface on one end side, and a fixed seal ring that is attached to the housing side and has an opposing seal surface that is in sliding contact with the seal surface of the rotary seal ring. And at least one of the sealing surface of the rotary sealing ring and the opposing sealing surface of the stationary sealing ring is covered with a hard carbon thin film, the liquid contains at least one glycol, and the hard The carbon thin film has a hydrogen content of 20 atomic% or less.

  According to the present invention, a hard carbon thin film such as DLC is coated on at least one of the seal surface of the rotary seal ring in the mechanical seal and the opposed seal surface of the fixed seal ring that is in sliding contact with the seal surface, and Since the liquid to be sealed by the sealing mechanism contains glycol such as ethylene glycol and propylene glycol, the friction performance of both seal surfaces is improved, the frictional resistance and the amount of wear are reduced, and excellent sealing performance is achieved. In addition to being able to be exhibited over a long period of time, the use of an inexpensive material brings about an excellent effect that significant cost reduction is possible.

  Hereinafter, the present invention will be described in more detail. In this specification, “%” indicates mass percentage unless otherwise specified.

  1A and 1B show an example in which the mechanical seal mechanism of the present invention is mounted on a water pump used in a cooling system for an automobile engine. The mechanical seal 1 of the present invention has a tip portion. Is mounted between a shaft (rotary body) 12 having an impeller 11 attached thereto and a pump housing 13 that houses the shaft 12, and coolant outside the housing does not flow into the housing 13 (between the shaft 12). Is sealed.

  The mechanical seal 1 includes a match ring (rotating seal ring) 4 attached to the shaft 12 via a stainless steel sleeve 2 and a synthetic rubber gasket 3 as shown in FIG. In addition, a seal ring (fixed sealing ring) 7 attached to the housing 13 via a stainless steel cartridge 5 and a synthetic rubber bellows 6 is also provided. The seal ring 7 is made of stainless steel for springs. The opposing seal surface of the seal ring 7 is slidably contacted with the seal surface of the match ring 4 that is pressed against the match ring 4 by the coil spring 8 and rotates integrally with the shaft 12, thereby blocking the flow of the inside and outside, and the coolant It can be sealed.

A hard carbon thin film 10 is formed on at least one of the two seal surfaces, that is, the seal surface of the match ring 4 and the opposite seal surface of the seal ring 7, in this example, the seal surface of the match ring 4. The friction coefficient of the sealing surface is reduced, the frictional resistance is reduced, the wear amount is reduced, and the service life is improved.
At this time, it is possible to form a hard carbon thin film on the opposing seal surface of the seal ring 7 or to form a hard carbon thin film on both of these seal surfaces, and the same effect can be obtained.

Here, examples of the hard carbon thin film include a crystalline or amorphous thin film containing carbon, particularly a diamond thin film and a DLC thin film.
This DLC material can be formed by, for example, a CVD method (chemical vapor deposition method) or a PVD method (physical vapor deposition method), and is an amorphous material mainly composed of carbon atoms, The bonding form between carbons consists of both a diamond structure (SP ³ bond) and a graphite bond (SP ² bond).

  Specifically, aC (amorphous carbon) consisting only of carbon elements, aC: H (hydrogen amorphous carbon) containing hydrogen, and some metal elements such as titanium (Ti) and molybdenum (Mo). In the present invention, the hydrogen content is preferably as low as possible. In the present invention, the hydrogen content is preferably 20 atomic% or less, preferably 10 atomic% or less, particularly 0.5 atom. % Or less, and a-C (amorphous carbon) material which does not contain hydrogen can be preferably used.

  That is, when the hydrogen content in the hard carbon thin film increases, the friction coefficient increases. Therefore, in the present invention, the upper limit of the hydrogen content needs to be 20 atomic%, but the friction coefficient during sliding is sufficiently reduced. In order to secure more stable sliding characteristics, it is desirable that the content be 10 atomic% or less, and further 0.5 atomic% or less.

In general, the amount of hydrogen contained in the hard carbon thin film depends on the film forming method, and such a hard carbon thin film having a low hydrogen content is substantially free of hydrogen or a hydrogen-containing compound such as a sputtering method or an ion plating method. It is obtained by forming a film by a PVD method that is not used in the process.
In this case, in addition to using a gas not containing hydrogen at the time of film formation, in some cases, the film may be formed after sufficiently baking the reaction vessel or the base material holder or cleaning the surface of the base material. It is desirable to reduce the amount of hydrogen.

  In addition, the surface roughness of the base material before coating the hard carbon thin film has a large influence on the roughness of the film surface even after film formation because the film thickness of the hard carbon thin film is considerably thin. The roughness Ra (centerline average roughness) is preferably 0.1 μm or less. That is, when the surface roughness Ra of the substrate is more than 0.1 μm, the protrusion due to the roughness of the film surface increases the local contact surface pressure with the counterpart material, and the film cracks. By increasing the chance of triggering.

  In the mechanical seal mechanism of the present invention, as a material for the sealing ring, silicon carbide or a carbon material can be basically used as in the conventional case, but a hard carbon thin film is formed on at least one seal surface. Therefore, since the friction characteristics (low friction property, wear resistance) between the sealing rings are improved, various inexpensive materials corresponding to the characteristics of the fluid to be sealed are not limited to the above materials. It can be used, and a significant cost reduction is possible.

For example, as a base material in the case of coating a hard carbon thin film on a rotating seal ring, it is only necessary to have a certain degree of hardness and corrosion resistance, so in addition to stainless steel, if the entire exposed surface is coated with a hard carbon thin film, An aluminum alloy, steel, or the like can be used, which is preferable because cost can be further reduced.
On the other hand, the base material of the fixed seal ring is required to have lower hardness than the rotary seal ring and to be excellent in corrosion resistance, wear resistance, and low friction. Therefore, in addition to the carbon material, polyphenylene sulfide ( PPS), aromatic polyamide, polyethersulfone (PES), polyterimide (PEI) and other resins, especially fiber reinforced resin materials in which these resins are reinforced with glass fiber or carbon fiber to ensure wear resistance Is preferred.

  Thus, when a base material having a lower hardness than the rotating seal ring is used for the fixed seal ring, the hard carbon thin film having a high hydrogen atom content of 0.5 atomic% or less is coated with the rotary seal ring. In addition, it is more preferable to cover the fixed sealing ring with a hard carbon thin film having a hydrogen atom content of 0.5 atomic% or less, which has a slightly low hardness, in order to ensure wear resistance.

Next, the liquid sealed by the mechanical seal mechanism of the present invention contains at least one glycol as described above, and such liquid is interposed between the sealing surfaces of both sealing rings, The friction characteristics will be greatly improved.
Here, the glycol is not particularly limited, and for example, ethylene glycol, propylene glycol, trimethylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol and the like alone or in combination of two or more thereof. Of these, ethylene glycol or propylene glycol or a mixture thereof is used because of flow characteristics, cooling efficiency, availability in the market, and price. It is desirable.

  Moreover, as content of the said glycol, it is desirable to set it as 0.1 to 97% of range as the total amount of the 1 type (s) or 2 or more types. That is, if the glycol content is less than 0.1%, the effect of reducing the frictional resistance cannot be obtained sufficiently, and if it exceeds 97%, the added components may become insoluble, which is not preferable.

  Examples of components other than glycol include water and alcohol. In addition to this, for the purpose of rust prevention of metal materials in contact with the liquid, addition of triazoles, thiazoles, phosphates, carboxylic acids, etc. The total amount of the agent can be added within a range of 10% or less.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited only to these Examples.

[Friction and wear test]
As shown in FIG. 2, a cylinder-on-disk single-piece reciprocating friction test was performed using a cylindrical test piece 21 as a sliding side test piece and a disk-like test piece 22 as a counterpart test piece. Then, the coefficient of friction after 10 minutes was measured.
Friction test conditions Test equipment: Cylinder-on-disk single-piece reciprocating friction test equipment Sliding side test piece: φ15 × 22 mm cylindrical test piece Counterpart test piece: φ24 × 7.9 mm disc-shaped test piece Load: 100 N (sliding side test piece Pressing load)
Amplitude: 1.0 mm
Frequency: 50Hz
Test temperature: 80 ° C
Measurement time: 10 minutes

Example 1
From the SUJ2 steel defined as a high carbon chromium bearing steel in JIS G4805, a disk-shaped test piece base material having a diameter of 24 mm and a thickness of 7.9 mm as described above is cut out, and a PVD arc is formed on the upper sliding surface of the base material. A DLC thin film having a hydrogen content of 0.5 atomic% or less, a Knoop hardness Hk = 2170 kg / mm ² , and a surface roughness Ry = 0.03 μm is formed to a thickness of 0.5 μm by an ionic ion plating method, A disk-shaped test piece 22 was prepared and used as a counterpart test piece (disk-type test piece) of this example. The surface roughness Ra on the DLC film-forming surface of the substrate was 0.01 μm.
On the other hand, a cylinder-shaped test piece 21 having a diameter of 15 mm × 22 mm was formed from the baked carbon material, and this was used as a sliding side test piece, and a friction test was performed under the above conditions. In addition, in the said Example, the said friction test was implemented in the state which apply | coated the liquid which uses ethylene glycol as a base material to the sliding side test piece 21. FIG. Such material combinations are summarized in Table 1 and the results are shown in FIG.

(Example 2)
As shown in Table 1, the same friction test as in Example 1 was performed except that a liquid based on propylene glycol instead of ethylene glycol was applied to the sliding test piece (cylindrical test piece 21). The results are shown in FIG.

(Example 3)
Except that the cylindrical test piece 21 formed by forming a DLC thin film on the surface of a cylindrical test piece base material having a diameter of 15 mm × 22 mm under the same conditions as in Example 1 was used as the sliding test piece. Then, the same friction test as in Example 1 was performed. The results are also shown in FIG.

Example 4
As shown in Table 1, the same friction test as in Example 3 was performed except that a liquid based on propylene glycol instead of ethylene glycol was applied to the sliding side test piece (cylindrical test piece 21). The results are shown in FIG.

(Comparative Example 1)
The same friction test as in Example 1 was performed, except that the counterpart test piece (disk-shaped test piece 22) of the same size made of SiC (silicon carbide) was used. The results are also shown in FIG.

(Comparative Example 2)
A friction test similar to that of Example 2 was performed, except that a counterpart test piece (disk-shaped test piece 22) of the same size made of SiC (silicon carbide) was used. The results are also shown in FIG.

(Comparative Example 3)
The same friction test as in Example 1 was performed except that the counterpart test piece (disc-like test piece 22) was made of the same size made of alumina ceramics. The results are also shown in FIG.

(Comparative Example 4)
The same friction test as in Example 2 was carried out except that the counterpart test piece (disk-shaped test piece 22) of the same size made of alumina ceramics was used. The results are also shown in FIG.

(A) It is sectional explanatory drawing which shows the example which applied the mechanical seal mechanism of this invention to the water pump. (B) It is an expanded sectional view of the mechanical seal mechanism shown to Fig.1 (a). It is the schematic which shows the structure of the cylinder on disk single-piece | unit reciprocating friction test machine used for the Example of this invention. It is a graph which compares and shows the friction coefficient of an Example and a comparative example.

Explanation of symbols

1 Mechanical seal 4 Match ring (Rotating seal ring)
7 Seal ring (fixed seal ring)
10 Hard carbon thin film 12 Shaft (Rotating body)
13 Housing

Claims (6)

  A mechanical seal mechanism for preventing outflow or inflow of liquid from between a housing and a rotating body rotatably accommodated in the housing, the rotating seal ring having a seal surface on one end side and attached to the rotating body And a fixed sealing ring having an opposing seal surface slidably contacting the sealing surface of the rotating seal ring and attached to the housing, and at least one of the seal surface of the rotating seal ring and the opposing seal surface of the fixed seal ring A mechanical seal mechanism characterized in that the surface is coated with a hard carbon thin film, the liquid contains at least one glycol, and the hydrogen content of the hard carbon thin film is 20 atomic% or less.   2. The mechanical seal mechanism according to claim 1, wherein the hydrogen content of the hard carbon thin film is 10 atomic% or less.   The mechanical seal mechanism according to claim 1, wherein the hydrogen content of the hard carbon thin film is 0.5 atomic% or less.   The mechanical seal mechanism according to claim 1, wherein the hard carbon thin film does not substantially contain hydrogen.   The mechanical seal mechanism according to any one of claims 1 to 4, wherein the surface roughness of the base material before coating with the hard carbon thin film is 0.1 µm or less in terms of Ra.   The mechanical seal mechanism according to any one of claims 1 to 5, wherein the liquid contains ethylene glycol and / or propylene glycol.

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