JP3026252B2 - Sliding material for mechanical seal - Google Patents

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, it prevents fluid leakage around the shaft.
Excellent wear resistance and sliding characteristics are required. 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.

When sliding flat surfaces under lubrication with an isothermal incompressible fluid, if the flat surfaces are extremely smooth, a fluid lubricating film is theoretically not formed between the sliding surfaces in a steady state ( JNAnno and JAWalowit and CMAlle
n, Journal of Lubrication Technology, ASME, Series
F, vol. 90, No. 2, pp. 351-355 (1968)), but in actual mechanical seals, small undulations generated on sliding surfaces,
It is said that a fluid lubricating film is formed due to factors such as surface roughness. However, during sliding, the waviness and the surface roughness change due to frictional heat and the like, and the change in the thickness of the fluid lubricating film accompanying this change also changes the friction coefficient and the calorific value on the sliding surface. RRPaxton and H.T.Hulbert, L
ubrication Engineering, vol.36, No.1, pp89-95 (19
80) reported a sliding test using a combination of carbon and a smooth sliding material such as dense silicon carbide, alumina, cemented carbide, etc. Has an unstable friction coefficient, and its maximum value is at least twice the average value. When such a sliding material is used under severe conditions such as a higher PV value, the average value and the maximum value of the coefficient of friction and the amount of heat generated by sliding further increase. As a result, minute deterioration or destruction of the sliding surface progresses.

That is, generally, when a hard sliding material such as silicon carbide is used in combination with a sliding material made of carbon having self-lubricating properties, a frictional heat called a blister is formed on a sliding surface on the carbon side due to frictional heat. It is known that worm-like abnormal wear due to swelling often occurs, and when sliding members made of silicon carbide are slid,
It has been pointed out that there is a problem of generating an unpleasant rubbing noise called squeal on the sliding surface at the time of starting, a sticking phenomenon called linking, and a heat crack. In addition, when a mechanical seal that slides a sliding material made of cemented carbide and a carbon sliding material is used as a shaft sealing device of a refrigerator compressor, a high PV value is required, and the rotating shaft of the refrigerator compressor is required. It has been pointed out that a large thermal shock is applied at the time of start-up due to repeated rotation and stop, which causes a heat crack on a sliding surface and a blister on a carbon sliding material.

[0005] In recent years, in order to improve the sliding characteristics, a porous sliding material having a large number of pores at a predetermined ratio has been developed. As a typical example, for example, a porous sliding member made of silicon carbide is disclosed in Japanese Patent Publication No. 5-69066.
And a porous sliding member made of tungsten carbide (a cemented carbide) is disclosed in Japanese Patent Application Laid-Open No. 1-283479. According to this kind of porous sliding material, it is possible to effectively prevent the occurrence of sliding noise and linking on the sliding surface, or the occurrence of blisters and heat cracks. This is because the fine dimples due to the large number of pores present on the sliding surface function as a lubricating liquid pool, and the hydrodynamic lubricating liquid film is formed on the sliding surface of silicon carbide or cemented carbide without self-lubrication. This is because stabilization is achieved and lubrication and cooling of the sliding surface are promoted.

Further, Japanese Patent Publication No. 58-28466 discloses a technique in which dents (dimples) are formed only on a sliding surface without using a porous sliding material. Its features are:
A large number of depressions are provided only on the inner peripheral side (atmospheric side) of the sliding surface, and the outer peripheral side (the fluid side to be sealed) of the sliding surface is a smooth land portion. The fluid to be sealed that has passed through the portion is scraped off by the dent, and the fluid pressure generated inside the dent exerts an action of pushing the scraped fluid back to the land portion, thereby obtaining a sealing effect.

[0007]

However, the porous sliding member has a problem that the strength is reduced due to the presence of a large number of pores inside. In order to prevent leakage due to penetration of the fluid to be sealed, The pores inside the sliding member need to exist independently of each other, and therefore, there is a limit in stabilizing the lubricating liquid film by increasing the porosity.
In order to form a more stable lubricating liquid film, it is effective to give dimples on the sliding surface with an appropriate shape and direction, but in the case of dimples utilizing pores, such shapes and directions are effective. Could not be given.

On the other hand, the technology described in Japanese Patent Publication No. 58-28466 is intended only to improve the sealing performance. However, when such a technique is applied to a mechanical seal having a combination of sliding materials that easily causes instability of the fluid lubricating film described above, leakage does not occur, instead of interposing between sliding surfaces. Since even a small amount of fluid is removed, insufficient lubrication is promoted, and the wear of the sliding surface due to an increase in the coefficient of friction and the amount of heat generated by the sliding is accelerated.

The present invention has been made in view of the above circumstances, and the technical problem thereof is that dimples on the sliding surface can be formed without causing a decrease in the strength of the material itself or permeation leakage. It is an object of the present invention to obtain a more stable lubricating liquid film depending on the shape and directionality, improve slidability, and maintain stable sealing properties.

[0010]

As a means for effectively solving the above-mentioned technical problems, a sliding member for a mechanical seal according to the present invention is made of a high-density hard material, and is provided over the entire sliding surface . A large number of substantially elliptical or substantially rectangular dimples having a width of 50 μm or more and 1,000 μm or less and a longitudinal length of 2,000 μm or less and having a substantially constant cross-sectional shape are formed. Is sliding
It is assumed that they are aligned at substantially right angles to the direction .
In this case, as the high-density hard material, silicon carbide,
It is made of a material selected from carbides such as titanium carbide and tungsten carbide, or selected from nitrides such as silicon nitride and titanium nitride, or oxides such as alumina and zirconia .

Here, the term "hard material" refers to a material generally used as a hard material, such as a sintered material such as so-called ceramics or cemented carbide, and "high density" refers to This means that the material is not porous, that is, the material does not have pores therein, or at least does not intentionally form pores.

Of the many dimples formed on the entire sliding surface, the dimple group located near the outer periphery of the sliding surface has an effect of increasing penetration of the liquid to be sealed from the outer periphery into the space between the sliding surfaces. On the other hand, the dimple group existing in the area near the inner circumference has an action of removing the intruding liquid to be sealed to the outer circumference side, and both actions cause a hydrodynamic lubricating liquid film between the sliding surfaces. Intervening as liquid (liquid to be sealed)
And the lubricating liquid film can be stabilized. The sliding material is made of high-density material and has low porosity. Dimples are not formed using the pores of the sliding material. Does not occur. The material of the sliding material is selected from hard materials such as carbides, nitrides, and oxides, and furthermore, since a stable lubricating liquid film is formed, the abrasion of the sliding surface is extremely reduced. Is not easily worn away, and its function as a lubricating fluid reservoir is maintained for a long time.

The reason why the width of the dimple is specified to be 50 μm or more is that the minimum diameter which can control the processing shape is about 50 μm, and that the dimple having a width of less than 50 μm has a small function as a lubricating liquid pool, and a sliding test. From the result of, the width 50
This is because it has been found that the best slidability can be obtained in the range from μm to 100 μm . Also, if the width is 1,00
0 μm or less, the length in the longitudinal direction is specified as 2,000 μm or less, when the width is more than 1,000 μm and the length in the longitudinal direction is more than 2,000 μm When dimples are provided,
This is because the leakage of the sealing target liquid interposed as the lubricating liquid film between the sliding surfaces becomes an allowable amount or more, and the mechanical seal easily leaks via these dimples even when the mechanical seal is stationary (when not sliding). . Moreover, for large dimples,
It has also been found that the opening edge has a steep shape, the aggressiveness against the mating sliding surface is increased, and the amount of wear is increased. For these reasons, the upper limit of the size of the dimple is set as described above. Stipulated.

By forming the dimples so that the longitudinal direction thereof is aligned in a direction perpendicular to the sliding direction, that is, by forming the dimples with directivity in the radial direction, the dynamic pressure of the fluid held in the dimples increases. The thickness of the lubricating liquid film formed between the sliding surfaces can be increased .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The formation of dimples on a sliding surface is as follows.
It can be formed by sandblasting using a known photosensitive film for sandblasting as a protective mask. That is, first, a photosensitive film for sandblasting is adhered to the surface to be processed (sliding surface) of the sliding material, and a photo-transfer pattern in which circular transfer patterns arranged in a lattice pattern corresponding to the dimple pattern are drawn thereon. A mask pattern corresponding to a photosensitive portion and a non-photosensitive portion by the transfer pattern is formed on the photosensitive film for sand blasting by a method such as bringing a mask (positive film) into close contact, exposing and developing. Then, by performing a sandblasting process of spraying fine abrasive grains from above the photosensitive film for sandblasting, an exposed portion of the processing target surface by the mask pattern is eroded by the abrasive grains, so that the abrasive pattern corresponds to the mask pattern. Dimples are formed.

In the case of a sliding material made of silicon carbide, silicon nitride, or the like, a method for forming dimples is disclosed in
The methods disclosed in 198078, JP-A-4-325479 or JP-A-4-325480 can also be employed. That is, in this method, a metal thin film such as stainless steel is attached to the surface to be processed,
Forming a dimple corresponding to the pattern of the metal thin film by causing a chemical reaction between the metal thin film and the silicon carbide by heat and, after cooling, removing the reaction product from the surface to be processed by applying a slight impact; It is. As the metal thin film, a metal thin film or a method of forming by vapor deposition, electrodeposition or coating of metal powder can be applied,
For the patterning, an etching method or the like can be applied.

[0017]

FIG . 3 shows the results of a sliding test of Example 1 and Comparative Example 1 described below, using a mechanical seal tester, under the following test conditions. As shown in FIG. 2 , a mechanical seal tester includes a casing 11 for supporting a stationary ring 1 as a sample through a gasket 12 in a non-rotating state, and a rotating shaft rotatably inserted through the inner periphery of the casing 11. 13, a rotating ring 15 supported on the outer periphery of the rotating shaft 13 via a packing 14 so as to be movable in the axial direction, and opposed to the fixed ring 1 in the axial direction, and biasing the rotating ring 15 in the axial direction. A spring 16 for bringing the sliding surface into close contact with the sliding surface of the fixed ring 1;
The liquid W to be sealed is sealed in the sealed space defined by the rotating ring 15.

[0018]Example 1  The stationary ring 1 is made of a high-density silicon carbide sliding material,Figure
1As shown in the figure, the sliding surface 1a is shortened by a reaction method with a metal film.
Depth 1 with a substantially elliptical shape with a diameter of 70 μm and a major diameter of 200 μm
The dimple 1c of 0 μm has its major axis in the sliding direction.
Direction perpendicular to, that is, the radial direction of the sliding surface
With 400 μm in the circumferential direction and in the radial direction
Slid in an array pattern arranged at intervals of 200 μm
What was formed at a rate of about 25% with respect to the area of the surface 1a
Using. Comparative Example 1 The stationary ring 1 was made of a high-density silicon carbide sliding material.
A moving surface formed on a smooth surface without dimples
Using.

In this sliding test, the stationary ring 1 and the rotating ring 15 were slid by combining the same sliding materials, and the other conditions were as follows. Test conditions (1) Liquid W to be sealed Water (2) Peripheral speed of sliding surface 7.8 m / s (3) Sliding time 100 hr. (4) The temperature of the liquid W to be sealed is 60 ° C. (5) The pressure of the liquid W to be sealed is 0.686 MPa. When the relative wear amount was set to 1 , the wear amount of the fixed ring sliding surface having the elliptical dimple of Example 1 was about 0.15.

FIGS. 4 to 11 are described below .
9 shows the results of performing a sliding test on Examples 2 and 3 and Comparative Examples 1 to 3 using the same mechanical seal tester as described above with reference to FIG. 2 under the test conditions and test methods described below. .

[0021]Example 2  The stationary ring 1 is made of a high-density silicon carbide sliding material,
50 μm width (short diameter) over the entire area of the moving surface 1 a, length in the longitudinal direction
(Longer diameter) Depth 8.6 μm with a substantially elliptical shape of 200 μm
Of the dimple 1c with respect to the sliding direction
At right angles, that is, with a direction that matches the radial direction of the sliding surface.
hand,StaggeredWith the area of the sliding surface 1a.
And what was formed at a rate of about 8% was used.Example 3  The stationary ring 1 is made of a high-density silicon carbide sliding material,
50 μm width (short diameter) over the entire area of the moving surface 1 a, length in the longitudinal direction
(Longer diameter) Depth 12.2μ with a substantially elliptical shape of 200μm
m dimple 1c, the major axis direction is
At a right angle, that is, a direction that matches the radial direction of the sliding surface.
WhatFIG.Are arranged in the sliding direction and radial direction as shown in
In an array pattern of lattice points, the area of the sliding surface 1a is
What was formed at a rate of about 8% was used.

Comparative Example 1 As described above, the stationary ring 1 was made of a high-density silicon carbide sliding material and the sliding surface was formed to be a smooth surface free of dimples. Comparative Example 2 As the fixed ring 1, a dimple having a depth of 10.1 μm having a substantially circular shape with a diameter of 60 μm and having a depth of 10.1 μm was formed only in a region close to the inner periphery of the sliding surface. The array pattern was formed at a rate of about 8% with respect to the sliding surface area of the above-mentioned region, and the region near the outer periphery of the sliding surface was finished smoothly. Comparative Example 3 A stationary ring 1 made of a porous silicon carbide sliding material having a large number of closed cells inside and having dimples formed at random on the sliding surface due to part of the closed cells being exposed. Using.

Test conditions (1) Sliding material Fixed ring 1 (hard material); various silicon carbide materials (inner diameter φ36 × outer diameter φ54.1 × thickness 8.5) Rotating ring 15 (soft material); resin impregnated firing Carbon (inner diameter 35.2 x outer diameter 49.65 x thickness 8) (2) Surface roughness Fixed ring 1; Rz 0.3 Rotating ring 15; Rz 0.5 (3) Flatness 1 HLB or more (4) Liquid W to be sealed Tap water (5) Temperature of liquid W to be sealed 25 ± 5 ℃ (6) Flow rate 3,000cm³/ Min (7) Surface pressure of sliding surface 1.10MPa (calculated from the following numerical value) Pressure of liquid W to be sealed; 1.02MPa Load of spring 16; 89.2N Sliding area: 4.56cm²  1.38 (8) Peripheral speed of sliding surface 869 cm / s 4,000 rpm (9) Test time 48h

Measurement method (1) Sliding surface temperature Measured with a JIS-TYPE-K thermocouple attached to the side of the stationary ring 1 at 1 mm from the sliding surface on the atmosphere side. (2) Friction coefficient Calculated from sliding torque ( 3) Data recording Each data was sampled every 12 seconds, and the obtained data was recorded on a hard disk of a computer and then subjected to various data processing.

As shown in FIGS. 4 and 5 , as a result of the above-described sliding test, Comparative Example 2 in which dimples were formed in a region near the inner periphery of the sliding surface showed the friction coefficient and sliding The surface temperature shows the highest value , and the transition of the sliding surface temperature and the friction coefficient shown in FIG. 10 are also unstable. This is probably because in Comparative Example 2, dimples near the inner periphery of the sliding surface eliminated the lubricating liquid film interposed between the sliding surfaces, thereby promoting insufficient lubrication.

Further, according to the above test results, the embodiment in which the dimples are arranged in a direction to increase the dynamic pressure is shown.
2 and 3, than Comparative Example 3 in which dimples are formed at random on the sliding surface by the closed cells of the porous silicon carbide,
The coefficient of friction and the temperature of the sliding surface are further reduced .
As is clear from FIG. 8 and FIG. 8 , the undulation of the friction coefficient and the sliding surface temperature is small, and it is found that the sliding surface is stabilized. Especially real
In Example 3 , the average value and the maximum value of the friction coefficient are remarkably reduced to about 40% of Comparative Example 3, and the standard deviation is reduced to about 25% of Comparative Example 3.

In the above embodiment, silicon carbide was used as the material of the sliding member. However, as described above, the present invention is applicable to other carbides such as titanium carbide and tungsten carbide, silicon nitride, titanium nitride and the like. Also, the present invention can be applied to a sliding material made of a nitride such as, or an oxide such as alumina or zirconia. In the above embodiment, the present invention is applied to the sliding surface on the stationary ring 1 side, but dimples may be formed on the sliding surface on the rotating ring 15 side. In addition, the substantially elliptical dimple 1c can provide substantially the same effect even when the dimple 1c is formed as a substantially rectangular dimple.

[0029]

According to the sliding material for a mechanical seal of the present invention, the following effects are realized. (1) Aligned so that the longitudinal direction is substantially perpendicular to the sliding direction
This dimple is formed by a substantially elliptical or substantially rectangular dimple.
Since the dynamic pressure generated in the sample is the largest, the lubricant film
Can stably enhance the effect of suppressing wear. (2) Since the sliding material has a high density and does not form dimples due to pores on the sliding surface, the strength of the sliding material itself does not decrease, so that the wear resistance is improved. (3) Since the sliding material is not made porous, leakage due to penetration of the fluid to be sealed does not occur.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an enlarged part of a sliding surface of a sliding member for a mechanical seal according to a first embodiment of the present invention.

FIG. 2 is a schematic half cross-sectional view of a mechanical seal tester used for a sliding test of a sliding material for a mechanical seal, cut along a plane passing through an axis.

FIG. 3 is an explanatory diagram showing sliding test results of Example 1 and Comparative Example 1.

FIG. 4 is an explanatory diagram showing a standard deviation, an average value and a maximum value of a friction coefficient by sliding tests of Examples 2 and 3 and Comparative Examples 1 to 3.

FIG. 5 is an explanatory diagram showing a standard deviation, an average value, and a maximum value of sliding surface temperatures in sliding tests of Examples 2 and 3 and Comparative Examples 1 to 3.

FIG. 6 is an explanatory diagram showing an enlarged part of a sliding surface of a sliding member for a mechanical seal according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram showing transition of measured values of a sliding surface temperature and a friction coefficient in a sliding test process of Example 2 .

FIG. 8 is an explanatory diagram showing transition of measured values of a sliding surface temperature and a friction coefficient in a sliding test process of Example 3 .

FIG. 9 is an explanatory diagram showing transition of measured values of a sliding surface temperature and a friction coefficient in a sliding test process of Comparative Example 1.

FIG. 10 is an explanatory diagram showing transition of measured values of a sliding surface temperature and a friction coefficient in a sliding test process of Comparative Example 2.

FIG. 11 is an explanatory diagram showing transition of measured values of a sliding surface temperature and a friction coefficient in a sliding test process of Comparative Example 3.

[Explanation of symbols]

 1 Fixed ring (sliding material) 1a Sliding surface 1b, 1c Dimple

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-161368 (JP, A) JP-B 5-69066 (JP, B2) JP-B-58-28466 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) F16J 15/34-15/38

Claims (5)

(57) [Claims] 1. A substantially elliptical cross section made of a high-density hard material and having a width of 50 μm or more and 1,000 μm or less and a length of 2,000 μm or less in a longitudinal direction over the entire sliding surface. Numerous elongated dimples are formed
This dimple has a longitudinal direction with respect to the sliding direction.
A sliding material for a mechanical seal, wherein the sliding material is arranged at substantially right angles . 2. A substantially rectangular cross-section having a width of 50 μm or more and 1,000 μm or less and a length of 2,000 μm or less in the longitudinal direction, which is made of a high-density hard material and has a substantially constant cross-sectional shape. Have numerous elongated dimples formed
This dimple has a longitudinal direction with respect to the sliding direction.
A sliding material for a mechanical seal, wherein the sliding material is arranged at substantially right angles . 3. A sliding material for a mechanical seal, wherein the high-density hard material according to claim 1 is selected from carbides such as silicon carbide, titanium carbide and tungsten carbide. . 4. A sliding material for a mechanical seal, wherein the high-density hard material according to claim 1 is selected from nitrides such as silicon nitride and titanium nitride. 5. A sliding material for a mechanical seal, wherein the high-density hard material according to claim 1 is selected from oxides such as alumina and zirconia.