JPH0696474B2 - Seal mechanism - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a seal mechanism used in a mechanical seal, a floating seal, or the like. More specifically, the present invention relates to a seal mechanism which is used in a mechanical seal, a floating seal or the like and has stable friction characteristics when a load changes.

[Prior Art] As a mechanism to prevent leakage from the part of the shaft that rotates at high speed under high temperature and pressure and to prevent foreign matter such as water, mud, and sand from entering from the outside, the shaft is fixed to the shaft. A seal mechanism such as a mechanical seal or a floating seal, in which a rotating ring (driven ring) that rotates together with the fixed ring (seat ring) that faces the rotating ring slide against each other to prevent leakage, is used. It is widely used in internal combustion engine driven transmissions, upper and lower guide rollers for guiding the sash of tracked vehicles, guide wheels, speed reducers for traveling, and the like.

As an example of such a conventional sealing mechanism, a floating seal used for a lower traveling wheel such as a hydraulic excavator will be described with reference to FIG.

In the figure, reference numeral 1 denotes a cylindrical stationary casing fixed to a frame 3 of a hydraulic excavator or the like with a bolt 7 through a screw hole 5. A rotating side casing 9 is disposed on the other end side of the stationary side casing 1, and a track link 11 as a cover is brought into contact with the outer peripheral surface of the rotating side casing. When the bandage is driven, the rotating casing 9 rolls around the shaft 13. A space 16 for storing the lubricating oil 15 is provided inside the rotating casing 9. A wear-resistant sleeve 17 is inserted at the interface between the rotating casing 9 and the shaft 13.

Further, 19 is an end portion 1B of each of the casings 1 and 9 facing each other,
A floating seal mounted on the inner peripheral side of 9B. The seal 19 prevents the lubricating oil in each casing 1, 9 from leaking to the outside, and keeps dirt, sewage, rainwater, etc. in each casing 1, 9 To prevent it from entering.

The present inventors have previously devised and applied for a sealing device as shown in FIG. 5 (see Japanese Utility Model Application No. 60-140577).

In the figure, 21 and 21 are seal rings arranged on the inner surface side of the end portions 1B and 9B of the respective casings 1 and 9, and each seal ring 21 is formed of a corrosion resistant light alloy material such as an aluminum alloy and a zinc alloy, On the surfaces facing each other in the axial direction, annular grooves 21A, 21A formed in a U-shaped cross section are provided near the outer peripheral side. Then, in each of the annular grooves 21A, SiC, Al ₂ O ₃ , Z
A sliding member 22 made of a ceramic material having corrosion resistance and wear resistance such as rO and Si ₃ N ₄ is joined by an elastic adhesive 23 to form a sliding seal surface. Further, the outer peripheral surface 21B of each seal ring 21 is formed in a concave curved shape and inclined outward in the axial direction.
When each O-ring 25 is sandwiched between the inner peripheral surface 1C and 9C of
By the elastic force of each O-ring 25, a pressing force is applied to each sliding seal surface to provide sealing property.
This O-ring also has a function of buffering the transmission of shaft runout to the closely contacted sliding seal surfaces.

A seal ring having such a sliding member made of ceramics is less expensive to manufacture than a seal ring made of a special cast iron material to which a high-grade material such as molybdenum or vanadium is added, and the sliding surface is There is an advantage that the surface contact state can be maintained at all times.

[Problems to be Solved by the Invention] However, ceramic sliding members are subject to heat generation due to high load fluctuation, shock load and abnormal friction at initial load, seizure and local loss of sliding surface, and damage to mating member. Limited range of use.

Ceramic is a sintered body of fine particles having high hardness, low elasticity and low toughness, and generally has a cross-sectional shape as shown in FIG. As shown in the figure, the surface of the ceramic is a non-smooth surface having a large number of voids and irregularities and also waviness in a microscopic view.

Therefore, when the respective sliding members are brought into sliding contact with each other, as shown in FIG. 7, the sliding contact surfaces of the rotary side sliding member and the fixed side sliding member have convex portions abutting each other or convex portions. It will be fitted into the recess. For this reason, since the friction coefficient fluctuates depending on the load, the initial friction characteristic and the friction characteristic when the load fluctuates are unstable, a high frictional force is locally generated, and uneven rotation occurs.

Furthermore, due to the low toughness of the ceramic when locally loaded, fine deficient grains may occur, which causes a significant increase in local load when it enters the sliding seal surface, sometimes causing damage to the mating member. Become. In addition, since ceramics are generally low heat-conducting materials, the heat generated by localized high friction is less likely to diffuse or dissipate, which not only causes deterioration of sliding characteristics and seizure, but also causes the O-ring to be aged and deformed. is there.

Therefore, an object of the present invention is to provide a seal mechanism having stable friction characteristics when the load changes.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the seal mechanism of the present invention is arranged on the inner surface side of a relatively rotating casing, and the surfaces opposed to each other in the axial direction are sliding seals. In a seal mechanism consisting of a pair of seal rings that form a surface, and means for applying a pressing force to at least one of the seal rings,
At least one sliding seal surface of the seal ring,
It is formed of a metal film plated on a ceramics wear-resistant sliding member by an electroless plating method, and the thickness of the plated metal film is 0.5 to 3 of the sliding surface roughness Rmax of the sliding member.
It is in the double range.

The seal mechanism of the present invention is preferably used for mechanical seals and / or floating seals.

[Operation] As described above, in the sealing mechanism of the present invention, the metal film is plated on the sliding surface of the ceramic wear-resistant sliding member.
While fully exhibiting the basic characteristics such as high load resistance, high wear resistance, low friction and high corrosion resistance that the ceramic sliding member that serves as the plating substrate originally possesses, high toughness, high lubricity, and high The corrosion resistance and high thermal conductivity of the metal film dramatically improve sliding characteristics, sealing resistance, durability and reliability.

It is particularly preferable to form the metal film by electroless plating. It has been discovered that the electrolessly plated metal is amorphous and therefore has excellent filling and bonding properties on the surface of the ceramic sliding member, and is also satisfactory in terms of "compatibility" at low temperatures. The electroless plating method itself is a known and well-known plating method, but it was first discovered by the present inventors that it is effective as a means for forming a metal film on the sliding surface of a ceramic-based sliding member such as a seal ring. Was done. In fact, the electroless plating method has conventionally been used as a plating means for a metal on a ceramic substrate only for electrical applications, and the present invention is the first to be applied to sliding members.

Japanese Unexamined Patent Publication (Kokai) No. 63-246505 discloses a sliding member in which a metal film lubricating layer is formed on the sliding surface of a ceramic member. However, the metal coating lubrication layer is formed by transferring the metal on the sliding surface of the metal sliding member to the ceramic member during sliding between the ceramic and the metal. In order to ensure the formation of the metal coating lubrication layer by this transfer, the metal sliding member used is one or more of Mo.Co, Ti, W,
Moreover, it must be contained in a predetermined amount or more, and is required to be used in a high temperature environment. Therefore, according to the present invention, a structure other than "ceramics member / transfer metal coating lubrication layer / metal sliding member" cannot be implemented. The "metal film" of the present invention is formed by the electroless plating method and is not formed by transfer. Therefore, it is completely unnecessary to use a metal sliding member having a specific composition. Further, since it is not necessary to promote the transfer, it can be sufficiently used in a low temperature environment, and can be used as "ceramics member / electroless plating metal film / ceramics member" or "ceramics member / electroless plating metal film /
Either configuration of "metal sliding member" is also possible.

Further, in the sliding member of the above publication, when the metal sliding member and the ceramic member are slid for the first time, the metal film lubricating layer is not yet formed on the surface of the ceramic member. Therefore, in order to prevent "galling" etc. due to initial sliding, the average surface roughness of the ceramic member sliding surface is 0.2 μm, and the average surface roughness of the metal sliding surface is 0.1 to 0.2 μm.
You have to finish to a certain degree. The electroless plating metal film of the present invention does not require a finishing treatment for flattening the surface and can be used as it is, and its surface roughness may be about 6.6 to 8.9 μm. Similarly,
The sliding member of the present invention can be used only at a low load of about 1 kgf / cm2 at a steady load in order to prevent the occurrence of "galling" due to initial sliding. The seal member of the present invention can be used even under a high load of about 5 kgf / cm2.

According to the above publication, the metal sliding member must continue to form a transfer metal coating lubricating layer having a thickness of about 0.5 μm or more by sliding with the ceramic member, while the metal sliding member is continuously Continue to wear. For this reason, the life of metal sliding members such as engine members is relatively short and must be replaced frequently. In the present invention, a metal film having a desired thickness can be immediately and easily formed by the electroless plating method, and no wear of the metal sliding member is required, so that the life of the metal sliding member is not impaired.

As described above, the sliding member described in JP-A-63-246505 is completely different from the sealing mechanism of the present invention.

Embodiment An example of the seal mechanism of the present invention will be described in more detail with reference to the drawings. In the following embodiments, the same components as those of the prior art shown in FIGS. 4 and 5 are designated by the same reference numerals.

FIG. 1 is a schematic sectional view of an example of a seal member used in the seal mechanism of the present invention.

As shown in the drawing, an annular groove having a substantially U-shaped cross section is formed on the surfaces of the annular seal ring 21 which face each other in the axial direction.
21A is provided, and a flat ring-shaped sliding member 22 is joined to this groove via an elastic adhesive 23. A metal film 27 is plated on the sliding seal surface of this sliding member. Further, the outer peripheral surface 21B of the seal ring 21 is concavely curved,
Moreover, it is formed so as to be inclined outward in the axial direction.

The material of the seal ring itself is not an essential requirement of the present invention.
It can be composed of a commonly used corrosion-resistant metal material such as an aluminum alloy, a zinc alloy, die cast, and stainless. Special cast iron or steel, which is a conventional seal ring forming material, can also be used. Besides, reinforced plastics or engineering plastics can also be used.

The sliding member is made of a ceramic material such as SiC, Al ₂ O ₃ , ZrO, Si ₃ N ₄ and sialon, which has corrosion resistance and wear resistance. Not only ceramic materials but also other wear resistant materials can be used, but ceramics are most preferable in terms of price and ease of manufacture.

As the adhesive for joining the sliding member to the seal ring, for example, a silicone-based elastic adhesive or the like can be used. This adhesive can be elastically deformed according to the load stress applied to the sliding member. Elastic adhesives other than silicone adhesives can of course be used. Such adhesives are well known to those skilled in the art. The adhesive used in the present invention preferably has oil resistance and heat resistance in addition to elasticity. The effect of using the elastic adhesive is described in detail in the above-mentioned Japanese Patent Application No. 60-140577.

The metal film is preferably plated on the surface of the sliding member by electroless plating. The electroless plating method is a method of depositing metal ions in a metal salt aqueous solution on the surface of a support by a substitution reaction or a redox reaction without using electric energy. For example, a reducing agent can be added to the aqueous solution of Ni salt, and Ni can be precipitated by its reducing power. Other than Ni,
Metals such as Co, Pd, Au, Ag, Sn, Cu and Zn can also be deposited.

When a metal is plated by the reduction method electroless plating, a film having no pinhole and having a substantially uniform thickness and excellent in corrosion resistance and abrasion resistance is formed regardless of the shape of the base material or the substrate. . It can also be applied to non-conductors such as ceramics and products made by powder metallurgy. As the metal, not only the single metal as described above, but also alloys can be plated.

The reducing electroless plating bath composition is composed of three kinds of metal salts, a reducing agent, and a buffering agent. As metal salts, metal chlorides, sulfates, carbonates, nitrates, cyanides and the like can be used. As the reducing agent, sodium hypophosphite, sodium hyposulfite, anhydrous sodium sulfite, hydrazine chloride, hydroquinone, formalin and the like are used. Further, as the buffer, acetic acid, propionic acid, butyric acid, valeric acid, lactic acid,
Combinations of alkali salts such as glycolic acid, tartaric acid, citric acid, succinic acid, malonic acid, glutaric acid, adipic acid, formic acid are used. Regarding these concentrations, it depends on the operating conditions of the bath and the material to be plated.
It is necessary to determine the optimum concentration.

The optimum value of the thickness of the plated metal film is determined by the operating conditions, but in general, the sliding surface roughness Rmax of the sliding member used is
It is preferable that the thickness is within a range of 0.5 times to 3 times.
When the thickness of the plated metal film is 0.5 times the Rmax at the end, the temperature rises during sliding and it is likely to bite, which is not preferable. On the other hand, when the thickness of the plated metal film is more than 3 times Rmax,
The durability of the metal film decreases.

The seal members shown in FIG. 1 are used as a left and right pair in a seal mechanism such as that shown in FIG. 2 (a). As shown in the figure, the plated metal films 27, 27 are in sliding contact with each other to ensure the sealing property. O-ring as pressing means
25 is made of metal, plastic, asbestos, synthetic rubber or tetrafluoroethylene resin. In the illustrated example, both seal rings have a plated metal film, but a sealing mechanism in which only one of the fixed side ring and the rotating side ring has a plated metal film can be implemented depending on the usage conditions.

The pressing means of the seal ring is not limited to the O-ring type as shown in FIG. 2 (a). For example, FIG. 2 (b)
The driven ring 31 can be pressed by the spring 30 as shown in FIG. Therefore, the spring 30 is attached to the rotary shaft 32.
A stopper 33 for use is screwed on. In the figure, 34 is a casing, 35 is a fixed seat ring, and 36 and 37 are packings.

Further, as shown in FIG. 2C, the driven ring 31 can be pressed by the bellows 38. The bellows 38 is fixed to the stopper 39 by a ring spring 40.
The material of the bellows is synthetic rubber, tetrafluoroethylene resin, metal or the like. Although those shown in FIGS. 2B and 2C press the driven ring, the seal ring 35 on the fixed side can also be pressed. In addition, magnetic force, fluid pressure, etc. can be used as the pressing means.

As shown in FIGS. 2 (a) to 2 (c), the shape of the seal member used in the seal mechanism of the present invention can be appropriately changed depending on the application and / or the specific configuration of the seal mechanism. . Regarding classification of mechanical seals, Akira Washida “New Mechanical Seals”, Nikkan Kogyo Shimbun, Showa 57
Please refer to the details on December 6 of the year, p.6 to p.27.

The condition of temperature change of the sliding portion of the seal mechanism of the present invention shown in FIG. 2 (a) was measured.

Ring-shaped ceramic plate made of Al ₂ O ₃ (thickness: 1.5 mm) 4
The sheets were electrolessly plated with Ni. The composition of the plating bath is Ni30 sulfate
g / 1, Sodium hypophosphite 12g / 1, Sodium acetate 60g / 1, Temperature 95〜
It was 98 ° C and pH 5.6. The plating results are summarized in Table 1 below.

The thickness of the metal film plated on the No. 1 and No. 2 ceramic plates is about 2.15 to 0.93 times the sliding surface roughness (Rmax), which is within the range of the present invention. On the other hand, the thickness of the metal film plated on the No. 3 and No. 4 ceramic plates is about 0.38 to 0.32 times the sliding surface roughness (Rmax), which is outside the scope of the present invention. Therefore, the No. 1 and No. 2 ceramic plates are combined to form the sealing mechanism of the present invention as shown in FIG. 2 (a), and the No. 3 and No. 4 ceramic plates are combined to make a comparative seal. The mechanism was constructed. The gap between the casings
4.0 mm, load surface pressure 0.4 to 0.5 MPa, relative rotation speed 1.3 m / s
The seal test was performed for 18 hours under the test conditions of. A hole is formed from the outer peripheral surface side of the seal ring to reach the ceramic plate, and the thermocouple is inserted into this hole so that the tip of the thermocouple comes into contact with the ceramic plate. The temperature change was measured. The measurement results are summarized in Table 2 below.

As is clear from the results shown in Table 2, the plating thickness of the plated metal film of the seal member used in the sealing mechanism of the present invention was 8 and 14 μm, and the surface of the plated metal film was flattened after plating. Since no finishing treatment is applied, the plating surface roughness
Rmax is 6.6 and 8.9 μm, and the flatness of the sliding surface is 40
And 18 μm, which was considerably bad, there was no oil leakage, seizure, or other damage at the end of the test, and the plating film remained on the entire sliding surface. Also, there is no sudden temperature rise immediately after the start of the test, the temperature rises steadily with a maximum fluctuation of about 3.0 ° C, and the steady state is reached in just 2 hours and 40 minutes. On the other hand, the sealing member of the comparative example has a plating film thickness of
Since it is as thin as 1.5 μm and cannot cover the irregularities on the surface of the ceramic sliding member, it is possible to see the temperature change for a long time (1 to 1.5 hours) in addition to the temperature rise within a short time for 6 hours immediately after the start of the test. To be However, the rapid temperature change (about 15
(0-200 ℃), the fluctuation is relatively small. Although this is 1.5 μm thick, it is plated almost evenly over the entire surface of the ceramic sliding member, so local contact is prevented and heat is diffused. It seems that it corresponds to the change of the surface. It is probable that the plated metal on the contact surface of the convex part was worn at the beginning of the test and entered the concave part. It is presumed that the wear metal powder was small and relatively soft, so damage to the contact surface was prevented, the contact surface expanded with the elapse of the test time, and reached a stable state in about 6 hours.

Although the load condition is constant in the above test, it is estimated that a high surface pressure on the local sliding surface cannot be prevented during a sudden high surface pressure or rotational movement, so it is estimated that a certain amount of plating thickness is required. It However, it is preferable that the plating thickness is as thin as possible in order to take advantage of the characteristics of ceramics against an average high surface pressure and high-speed sliding.

A sealing mechanism comprising the above-mentioned sealing member of No. 1 and No. 2 of the present invention and a sealing mechanism using a sealing member made of an Al ₂ O ₃ ceramics sliding member having no plating film are provided.
It was used as a floating seal as shown in the figure and the temperature change of the sliding surface was measured. The method for measuring the temperature was the same as that used in the above test. The reference interval of the casing was 3 mm, the seal set load was 80 to 100 kg, and the rotation speed was 240 rpm. 5 minutes forward-5 minutes reverse-5
A cycle of reverse rotation for 5 minutes, stop for 5 seconds, and forward rotation for 5 minutes was repeated for 10 hours. The measurement results are shown in FIG.

As is clear from the figure, in the case of the floating seal using the seal member of the present invention, the saturating temperature (97.5 ° C) is smoothly reached after the start of the test without showing any abnormal temperature change. On the other hand, in the case of the floating seal composed of the seal member of the control example having no plating film, a fricative noise started to be heard immediately after the start of the test, and a rapid temperature rise occurred, reaching 145 ° C.
During this time, the creaking noise continued all the time, and as the temperature dropped, this creaking noise also disappeared. afterwards,
The saturating temperature (97.5 ° C) was gradually reached.

It should be noted that in the above-mentioned embodiment, the description has been centered on the electroless plating of the seal ring, but the sliding characteristics can be improved by electroless plating of the ceramic bearing.

[Effects of the Invention] As described above, in the sealing mechanism of the present invention, a metal film is plated on the surface of a sliding member made of a wear resistant material such as ceramics by an electroless plating method, and this plated metal film is deposited. Is used as a sliding seal surface. Therefore, while exhibiting the basic characteristics such as high load resistance, high wear resistance, low friction resistance, and high corrosion resistance that the ceramic sliding member that serves as the plating substrate originally possesses, high toughness and high lubrication are achieved. The metal film having high heat resistance, high corrosion resistance and high thermal conductivity dramatically improves sliding characteristics, sealing resistance, durability and reliability.

The seal member having such an electroless plated metal film can remarkably improve the sliding characteristics even if the surface flatness is poor. Therefore, in the present invention, it is possible to omit the flattening finishing treatment of the plated metal film surface after plating.

On the surface of the ceramic sliding member, there are many microscopically small voids and irregularities. A conventional sealing member composed of only a ceramics sliding member has deteriorated sliding characteristics due to voids and irregularities on the surface of the ceramics. In the present invention, the voids on the surface of the ceramic are filled by electroless plating, and the projections are buried in the plating film.

Therefore, the sealing mechanism of the present invention is preferably used for a mechanical seal or a floating seal in a place where the usage conditions are severe, such as muddy water. In particular, in the floating seal, foreign matter is likely to enter through the gap between the casings. The foreign matter once entering the sliding surface will roughen the sliding surface for a long time. On the other hand, in the seal member of the present invention, even if a minute foreign matter enters the sliding sealing surface of the plating film through the gap of the casing, the foreign matter is foreign to the plated film because it is softer than the foreign matter. The risk of the sliding surface being roughened by being embedded in the plating film is reduced.

Although not particularly confirmed by experiments, since the seal mechanism of the present invention has excellent lubricity, it can be optimally used for a non-lubricated sliding surface in outer space.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a seal member used in the seal mechanism of the present invention, and FIG. 2 (a) is a schematic cross-sectional view showing an example of the seal mechanism of the present invention. (B) and FIG. 2 (c) are schematic cross-sectional views respectively showing another example of the seal mechanism of the present invention, and FIG. 3 is a seal member used in the seal mechanism of the present invention and a seal member of a comparative example. Is a characteristic diagram showing the temperature change of each sliding surface when sliding,
4 is a partially cutaway sectional view showing an example of an apparatus using a floating seal, FIG. 5 is a schematic sectional view showing an example of a sealing apparatus devised by the present inventor earlier, and FIG. 6 is a ceramic slide. FIG. 7 is an enlarged schematic sectional view of the moving member, and FIG. 7 is an enlarged schematic sectional view showing a sliding contact state of each sliding surface of the ceramics sliding member. 1,9 …… Casing, 1C, 9C …… Inner peripheral surface, 25 …… O ring, 21 …… Seal ring, 21A …… Annular groove, 21B …… Outer peripheral surface, 22 …… Ceramics sliding member, 23… … Elastic adhesive, 27…
... Plating metal film

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-63-246505 (JP, A) JP-A-63-103884 (JP, A) JP-A-63-95183 (JP, A) JP-A 51- 11807 (JP, A) Actually opened Sho 59-80460 (JP, U)

Claims (3)

[Claims] 1. A pair of seal rings, which are respectively disposed on the inner surface sides of relatively rotating casings and whose axially opposite surfaces are sliding seal surfaces, and a pressing force is applied to at least one of the seal rings. In a seal mechanism consisting of a means for applying, at least one sliding seal surface of the seal ring,
It is formed of a metal film plated on a ceramics wear-resistant sliding member by electroless plating, and the thickness of the plated metal film is the sliding surface roughness Rmax of the sliding member.
The seal mechanism is characterized by being in the range of 0.5 to 3 times. 2. The seal mechanism according to claim 1, which is used as a mechanical seal. 3. The seal mechanism according to claim 1, wherein the seal mechanism is used as a floating seal.