JPS6120730B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ball joint having an annular seal member (hereinafter simply referred to as a seal member) that has excellent high temperature resistance, low temperature resistance, and chemical resistance and can be used in a wide range of areas. The seal member is an important component of the ball joint.In order to smooth the rotation between the spherical inner cylinder and the outer cylinder, it is necessary that the coefficient of friction between the sliding members be small. In terms of functionality, the impermeability of the sealing member itself, thermal stability,
Mechanical strength and appropriate rigidity are desired. In addition, the seal member needs to have a compressor and compression recovery properties. Among conventional seal member materials, seal members made of asbestos or rubber have problems in lubricity, sealing performance, thermal stability, and compression recovery. Seal members made of polymeric materials such as polytetrafluoroethylene (PTFE) have excellent lubricity, but have problems with temperature stability and mechanical strength. When a ball joint equipped with a sealing member made of a polymeric material such as PTFE is used under normal temperature conditions, there are not many practical problems. However, if such a ball joint is used in an extremely low temperature region (such as when flowing liquefied petroleum gas LPG or liquefied natural gas LNG) or in high temperature fluids (e.g. 250℃ or higher), Due to the thermal deformation of polymeric materials, due to the high coefficient of expansion,
Leakage occurs in the seal member. Furthermore, when heated to a high temperature of several hundred degrees Celsius or higher, such as during a fire, polymer materials decompose thermally.
This decomposed gas is highly toxic and corrosive. Conversely, in extremely low temperature regions, they shrink or break. Furthermore, PTFE causes cold flow due to pressure, making it difficult to maintain sealing.
About cm ² is an acceptable range. In order to improve these shortcomings, PTFE has been filled with asbestos, glass fiber, carbon, graphite, bronze, molybdenum disulfide, and carbon fiber, but this slightly improves heat resistance and mechanical strength. It's nothing more than that. Carbon materials used as solid lubricants are
Although it has excellent heat resistance, it is permeable and has poor mechanical strength, so it has defects such as insufficient sealing surface pressure and relatively high wear. In order to eliminate these defects, filling the voids or pores of carbon materials with synthetic resins such as phenolic resin has already been carried out as a means of reinforcing carbon materials, but the effect can only be maintained if Normally, it can be used at a temperature of up to 200°C, and even if it has been heat-treated to improve its heat resistance, the upper limit of its use is 300°C. The purpose of the present invention is to eliminate such conventional drawbacks,
It is an object of the present invention to provide a ball joint equipped with a sealing member that has a number of excellent advantages that cannot be completely satisfied with the materials used in conventional sealing members for ball joints. That is, the ball joint of the present invention has an inner cylinder having a spherical shape, an accommodation case that houses the inner cylinder and has a concentric spherical inner peripheral surface, and a ball joint located between the inner cylinder and the accommodation case. from the group consisting of an annular seal member in which the contact portion of the annular seal member with the storage case is (a) a compression molded product of expanded graphite, and (b) a compression molded product of a composite of expanded graphite and an inorganic binder. A group in which the parts selected and in contact with the inner cylinder are (c) a composite of a carbon material (excluding expanded graphite) and a metal, and (d) a composite of a carbon material (excluding expanded graphite) and an inorganic binder. It is characterized by being selected from. Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.
Explain in detail. FIG. 1 is a longitudinal sectional front view of an example of the ball joint of the present invention. FIGS. 2A to 2I are longitudinal sectional front views showing different examples of the sealing member. FIG. 3 is a vertical cross-sectional view of a main part showing a state in which the seal member shown in FIG. 2H is assembled into a ball joint. In Fig. 1, 1 is a seal member, 2 is a storage case,
3 is an inner cylinder, 4 is a stopper, and 5 and 6 are flanges. 2A to 2I, 11 is a contact member with the storage case 2 in the sealing member of the present invention, 12 is a contact member with the inner cylinder 3, and 13 is externally fitted on the contact member 12 with the inner cylinder. Reinforcement ring, 1
4 is an annular groove, and 15 is an auxiliary ring. The subscripts a, b, c, . . . attached to each reference numeral indicate that the indicated member is in a different embodiment starting from FIG. 2A. In FIGS. 2A and 2D, the contact members 11a and 11b with the storage case are fitted into annular grooves provided across the outer surfaces of the inner cylinder contact members 12a and 12d and the reinforcing rings 13a and 13d. The outer surface of the contact member 12a is fixed to the inner cylinder.
12d and the reinforcing rings 13a, 13d. In Figures 2B, 2E, 2G, 2H, and 2I, contact members 11b, 11e...
are fitted and fixed in annular grooves attached to the outer surfaces of the contact members 12b, 12e, . In FIGS. 2C and 2F, the contact members 11c and 11f with the storage case have a flat annular shape,
It is adhered to the outer surface of the contact members 12c and 12f with the inner cylinder. Contact member 11 with the storage case in FIG. 2D
d is tapered inward in order to improve load distribution and to improve its own compression resilience. Contact member 11 with the storage case in FIG. 2E
A plurality of concentric annular irregularities are provided on the outer surface of e for the purpose of dispersing surface pressure and improving sealing performance. In FIG. 2G, the contact member 11g with the storage case is divided into two pieces so that good sealing performance can be obtained even with low surface pressure. The contact surface of the inner cylinder contact member 12 with the inner cylinder 3 is as follows:
Except for 12b, which is a flat surface, the other parts are formed into arcuate surfaces that generally correspond to the inner cylinder 3. An annular groove 14 extending in the circumferential direction is carved on the contact surface with the inner cylinder 3 of the inner cylinder contact members 12d-12i. These annular grooves are rectangular except for 14h and 14i, one for 14d, two for 14e, and one for 14f.
This book includes auxiliary rings 15f made of the same material as the contact member 15f with the storage case, 2 pieces of 14g, each with 15g of auxiliary rings similar to 15f.
14h opens in the centrifugal direction with respect to the flow path, and 14i has a shallow V shape. In the ball joint of the present invention, the material of the contact member 11 of the seal member with the storage case is as follows.
Selected from (a) and (b). (a) Compression molded product of expanded graphite, (b) Compression molded product of composite of expanded graphite and inorganic binder. The expanded graphite compacted body has impermeability and a spring function, and exhibits a sealing function when the sealing member is tightened between the housing case and the inner cylinder. Expanded graphite has excellent heat resistance and does not lose its functionality even at low temperatures, so it can be used from high temperatures of several 100 degrees Celsius, such as during fires, to extremely low temperatures, such as LPG and LNG. Furthermore, the mechanical strength, compression recovery rate,
In order to improve density and impermeability, it is preferable to use (b), ie, a blend of expanded graphite and an inorganic binder, as a compression-molded graphite composite. In particular, when ball joints are used for high-pressure fluids, a composite of expanded graphite with an inorganic binder has a higher density, superior compressive strength, and is superior to a composite of expanded graphite with an inorganic binder at the same molding pressure. This is preferred because a permeable molded article can be obtained. The contact member 11 with the storage case made of such a material has a small coefficient of thermal expansion, and has a temperature range of -250°C to 3600°C.
The shape and dimensions are stable over a wide temperature range, the properties do not change, and there is no problem even with rapid heating. Further, the contact member with the storage case has excellent self-lubricating properties and excellent corrosion resistance against acids, alkalis, and organic compounds. Furthermore, other characteristics of the contact member with the storage case can be controlled by specifying its specific gravity. The specific gravity is preferably 1.1 to 2.1, preferably 1.4 to 2.1.
It is 1.8. If the specific gravity is less than 1.1, the strength and other properties will decrease, and if the specific gravity exceeds 2.1, the hardness will increase too much and the compression recovery property will decrease. Specific gravity can be adjusted by adjusting the pressure during compression molding of expanded graphite,
This can be achieved by adjusting temperature and time appropriately. When using an inorganic binder, the specific gravity can be adjusted by adjusting its type or amount. As the inorganic binder, graphite oxide, aluminum phosphate, boric acid, water glass, and colloidal silica can be used. Particularly preferred are graphite oxide, aluminum phosphate, and boric acid. The amount of the inorganic binder used is 1 to 20 parts by weight, preferably 2 to 15 parts by weight, and more preferably 3 to 10 parts by weight, based on 100 parts by weight of expanded graphite. If the amount of the inorganic binder used is less than 1 part by weight, the strength of the composite compression molded product will be insufficient, and if it exceeds 20 parts by weight, the hardness will increase too much and the compression recovery property will be poor. Note that expanded graphite refers to one obtained in the following manner. Graphite such as natural graphite, pyrolytic graphite, and hardwood graphite is treated with a strong oxidizing agent such as concentrated sulfuric acid, concentrated nitric acid, a mixture of concentrated nitric acid and potassium chlorate, a mixture of concentrated sulfuric acid and potassium permanganate, or a halogen compound such as aluminum chloride. to form an intercalation compound. When the graphite particles that have formed this intercalation compound are rapidly heated to a high temperature of 1000℃ or higher, the intercalation compound decomposes and generates gas, and the gas pressure increases the graphite interlayer distance (C-axis direction) by 10 to 300 times. Expanded graphite is obtained in particulate form. A composite of expanded graphite and an inorganic binder is obtained as follows. The expanded graphite and inorganic binder solution are mixed, dried, compressed, and heated if necessary. Graphite oxide is preferably used in the form of a colloidal aqueous solution. Boric acid can be used as a solution in a solvent such as methanol, ethanol, acetone, water, or the like. The amount of solvent used is such that it saturates the boric acid at room temperature. To remove the solvent, either natural drying or heat drying may be used, but after natural evaporation, the mixture is heated slowly and then stirred and heated above the boiling point of the solvent to completely drive out the solvent. The method is preferred. When aluminum phosphate is used as a binder, its components include A ₂ O ₃ , 3P ₂ O ₅ .
6H ₂ O, A ₂ O ₃・3P ₂ O ₅ , A ₂ O ₃・P ₂ O ₅ , A
Aluminum phosphates represented by (H ₂ PO ₄ ) ₃ , A ₂ (HPO ₄ ) ₃ , APO ₄ or A(PO ₃ ) ₃ , or aluminum phosphates containing sodium, potassium, ammonium, chlorine, etc. Refers to salts and compositions containing two or more of these salts. The method for producing a graphite composite using these as a binder is the same as in the case of boric acid. Other inorganic binders that can be used include water glass and colloidal silica, and in that case, the graphite composite can be produced in the same manner as described above. The pressure for manufacturing (a) and (b) above is 20Kg/
^cm2 to 2000Kg/ ^cm2 . When using boric acid, the appropriate heating temperature is at least 600°C or higher, preferably 1000 to 2400°C. Note that aluminum phosphate, graphite oxide, water glass, or colloidal silica can be molded at room temperature, but materials other than graphite oxide are preferably heat-treated at 500°C or higher, preferably 600 to 1300°C, after molding. The contact member 12 with the inner cylinder is made of one of the following materials (c) to (d). (c) A composite of a carbon material other than expanded graphite and a non-ferrous metal or an alloy thereof. (d) A carbon material other than expanded graphite impregnated with at least one of the above inorganic binders. In the present invention, "carbon material" If it is called,
This includes both graphite (crystalline) and carbonaceous (amorphous) materials. It is preferable to use graphite when the main focus is on sliding properties, and carbonaceous when the main focus is on wear resistance. However, this graphite does not include modified graphite such as expanded graphite and oxidized graphite. In the carbon-metal composite material (c), the volume ratio of the carbon material to the metal is preferably 90 to 60%. That is, when the carbon material content is less than 60%, the lubricity decreases and the coefficient of friction with the metal valve body increases. Moreover, when the carbon material exceeds 90%, mechanical strength decreases. As for mechanical strength, bending strength is 1000Kg/cm ²
It is preferable to try to achieve the above. As a carbon material raw material, fine powder of pitch coke, oil coke, coal, carbon black, natural graphite or artificial graphite with a particle size of 149μ or less, preferably 105μ or less, or these fine powders mixed with tar, pitch, or other organic matter. After adding and mixing the binder,
Re-powdered (hereinafter referred to as re-powdered) and molded 800
A carbon sintered body heat-treated at ℃~3000℃ is used. The melting point of metals used in composite materials is 200°C to 1300°C.
metals are preferable, and Al or Al alloys, Cu or Ni alloys are preferable from the viewpoint of heat resistance. However, if the operating temperature is 400°C or less, Sb or Sb alloy may be used. As the non-ferrous metal or alloy, for example, the following are preferable. Al, Zn, Cu, Al−Cu, Al−Mg, Al−Mn, Al
−Si, Al−Zn, Al−Cu−Mg, Al−Cu−Si, Al
−Zn−Mg, Cu−Be, Cu−Mg, Cu−Mn, Cu−
Pb, Cu−Si, Cu−Zn, Cu−Zn−Sn, Cu−Sn−
P, Cu-Sn, Cu-Sn-Pb, Cu-Sn-Ni, Cu-
Pb−Si, Cu−Ni−Si, Zn−Al, Zn−Cu, Zn−
Al−Cu, Sn−Zn, Sn−Al, Sn−Pb, Sn−Pb−
Sb, Sn−Sb−Cu, Pt−Cd, Pb−Sb−Sn, Ag−
Al, Ag−Cu and Ag−Sn. When forming a composite of the metal and carbon material, it is important that the metal has good wettability with the carbon material. In the case of Al or an Al alloy, since Al itself is a metal that wets well with carbon materials, any alloy can be put to practical use. In the case of Cu or Ni, it has poor wettability with carbon materials, so it is used in the form of an alloy with Sn, Zn, Si, P, etc.
Furthermore, in order to ensure sufficient wetting with the carbon material, the effect is enhanced by adding 0.5 to 25 wt% of a Ti or Zr wetting agent to the metal or alloy. However, experiments have shown that even up to 25% of these ingredients can be effective. Next, the method of compounding will be described. In the case of the above-mentioned fine powder raw material, the fine carbon powder is filled in a container made of thin steel plate, the lid is placed on the container, and the material is suspended in an autoclave so that the impregnated metal reaches a temperature of 50 to 200 degrees above its melting point.
When the temperature of the molten metal reaches a temperature higher than 0.degree. C., the object to be impregnated is immersed in the molten metal and pressurized to 50 to 150 Kg/cm ² with an inert gas such as N ₂ . As a result, the molten metal enters through the gap between the container and the lid, and the fine carbon powder in the container is compressed and molded by a type of isostatic pressure phenomenon, forming a composite rigid body. When using a carbon sintered body, the carbon sintered body is similarly suspended in an autoclave, and the pressure inside the tank is reduced to degas the air in the pores in the carbon sintered body. The degree of vacuum at this time is
It is necessary to be 5 mmHg or less. Next, as in the case of the fine powder raw material described above, the object to be impregnated is immersed in molten metal and pressurized with N ₂ gas or the like. A composite of the carbon material and at least one of the inorganic binders described in (d) above is obtained by mixing and molding the carbon material raw material and the binder in the same manner as in (b) above, and further adding as necessary. It can be hardened or fired to form a molded body. Alternatively, after forming the carbon material in advance and impregnating the pores with a binder solution under reduced pressure and normal pressure or reduced pressure and increased pressure,
It can also be obtained by evaporating water at 200°C and then dehydrating and curing at 500 to 1300°C. Through this process, the amount of water that is removed is
In theory, voids remain, but these can be resolved by repeated impregnation operations. In practice, it is preferable to repeat the impregnation at least three times to obtain sufficient air impermeability. The latter method of blending an inorganic binder is preferable because it contributes to improving wear resistance. The amount of inorganic binder impregnated with the carbon material is 0.5~
30wt%, preferably 5 to 20wt%. At that time, the bending strength is 600 as mechanical strength.
Preferably, Kg/cm ² is achieved. In this case, unlike (b) above, the inorganic binder is not just a binder, but has an action as a filler for the voids of the carbon material. The void filling rate in this case is 70 to 100%, preferably 85 to 100%. As preferred inorganic binders, aluminum phosphate, boric acid or colloidal silica can be used, particularly preferred is aluminum phosphate or colloidal silica. Compared to the carbon material itself, carbon material impregnated with an inorganic binder has improved wear resistance, improved mechanical strength, improved impermeability by filling the voids in the carbon material with binder, and improved heat resistance. etc. can be obtained. Manufacturing Examples 1 to 4 of seal members, comparative examples, and test examples in which the seal members were incorporated into ball joints Table 1 shows seal members for a ball joint with a nominal diameter of 2 inches (50A) having the structure shown in Figure 1. We prepared the structure and material shown in . In the following description, unless otherwise indicated, parts are parts by weight. In Table 1: (1) Stainless steel (SUS316) was used for the reinforcing ring. (2) The carbon material used in the sliding contact portion with the inner cylinder in Production Examples 1 to 4 was obtained by the following method. Coke manufactured by Nippon Steel Chemical Co., Ltd. (99.01% fixed carbon,
Volatile content: 0.61%, ash content: 0.25%) was pulverized to a maximum particle size of 40μ or less. This finely pulverized coke
Add 43 parts of a binder consisting of 1 part tar and 9 parts pitch to 100 parts, and mix this mixture with a Banbury mixer to give 1 kg of mixture.
It was mixed with 10kw power. The obtained mixture was allowed to cool to room temperature, and then re-pulverized and sieved to a particle size of 149 μm or less. The re-ground feed material is put into a mold and molded under pressure.
It was molded at 2t/cm ² to 4t/cm ² . The temperature of this molded article was raised at a rate of 5° C. per hour in a nitrogen gas atmosphere furnace. The bulk specific gravity of the obtained fired product (carbon material) was as shown in Table 2. This carbon material was placed in an autoclave at a pressure of 80 kg/cm ² and a temperature of 450 to 900.
A sliding contact member was obtained by impregnating the alloy shown in Table 1 at ℃. Table 2 shows various properties of the obtained sliding contact member. (3) The expanded graphite molded body and expanded graphite composite used in the contact portion with the storage case in Production Examples 1 to 4 were obtained by the following method. Expanded graphite for use in Production Examples 1 to 4 is
It was manufactured as follows. Natural graphite (-24~+
48 mesh (70-90%) is reacted in a mixture of 920 parts of concentrated sulfuric acid and 50 parts of sodium nitrate. The reaction time was approximately 16 hours. The acid-treated natural graphite particles are washed with sufficient water.
Next, the washed particles are dried at 100°C to evaporate the water. After this drying, the particles are heat-treated at a temperature of 1300
The treatment was carried out under the conditions of temperature and heat treatment time of 5 to 10 seconds. As a result, particles expanded to about 300 times the original size of the graphite particles in the C direction were obtained. This was compression molded at 100 kg/cm ² to obtain a contact member (used in Production Example 1). The method for producing graphite oxide as a binder was as follows. Mix 80 parts of natural graphite particles (95% less than 300 mesh), 3422 parts of concentrated sulfuric acid, and 40 parts of sodium nitrate, keep the liquid temperature below 0℃ with dry ice, and add potassium permanganate every hour. Add 30 parts each to make a total of 240
I continued doing this until I became a member of the department. This is then stirred for 18 hours, and the liquid temperature is gradually raised to room temperature. After the temperature of the liquid has returned to room temperature, the mixture is diluted with water while removing heat with ice. Next, in order to reduce permanganate to manganese salt, approximately 10% hydrogen peroxide solution was added until the purplish color of KMnO ₄ disappeared. Thereafter, washing with water was repeated several times until the liquid became neutral. Add water to 1 part of graphite oxide thus produced.
20 parts of the dispersed graphite oxide was mixed with 10 parts of the expanded graphite used in the above production example, which was then dried at 130°C and compression molded to produce a contact member. The compression molding pressure was 100 Kg/cm ² (used in Production Example 2). A 50% methanol solution of boric acid was mixed with 100 parts of expanded graphite manufactured for the production example so that the amount of boric acid added was 10 parts, and the molding pressure was 200 kg/cm ² and the temperature was
A contact member was obtained by compression molding at 1300°C for 10 minutes (used in Production Example 3). A 50% aqueous solution of monobasic aluminum phosphate was added to 100 parts of expanded graphite produced for the production example so that the amount added was 10 parts,
Compression molding at a molding pressure of 200Kg/ ^cm2 , then 600℃,
A contact member was obtained by heat treatment for 2 hours (used in Production Example 4). (4) In Manufacturing Example 4, the member corresponding to 15 in Fig. 2G is the same member as the contact portion with the storage case. The properties of each material are shown in Tables 2 to 4. As is clear from Table 2, each material of the manufacturing example has a much wider heat-resistant temperature range, a smaller coefficient of thermal expansion, a smaller coefficient of friction, and a better balance of other physical properties than the comparative example. is removed and satisfies the numerical values required for a sealing member. Next, these seal members were assembled into ball joints and various performance evaluation tests were conducted. (1) Low-temperature test The ball joint was maintained at -55°C and the air pressure was 6Kg/cm ² and a leakage test was conducted. In the ball joint of the comparative example, leakage was significant due to shrinkage of tetrafluoroethylene, which is a material of the sealing member. The rest passed with no omissions observed. (2) Water pressure test As a seal water leak test, 18, 21, 53,
Tests were conducted at pressures of 105 and 155 kg/cm ² . Apply water pressure equivalent to the nominal pressure inside the ball joint, seal it, and apply each of the above test pressures.
After holding for a minute, water leakage and bleeding from the seal portion were measured. In both the production example and the comparative example, no leakage was observed and the test was passed. (3) Air test Attach a blind flange to the ball joint (flange section 6 in Figure 1) and apply pressures of 2, 6, 10, 16, and 20 from the other end (flange section 5 in Figure 1). (Kg/cm ² ) of air pressure was applied to seal the container, and leakage from the sealed portion was measured. As a result, all tests passed with no leakage observed. (4) Water vapor test As water vapor, 6Kg/cm ² (158℃), 10Kg/cm ²
(179℃), 15Kg/cm ² (197℃), 20Kg/cm ² (211℃)
The ball joint was heated until the entire ball joint became almost isothermal, and leakage from the seal was tested. In the comparative example, when the pressure was 10 kg/cm ² or more, thermal deformation of the sealing member occurred and leakage was observed. In all other cases, there was no thermal deformation of the sealing member, and no leakage was observed at all, making the test pass. In addition, no burning of the sliding contact portions was observed except for the comparative examples.

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【table】 [Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a ball joint showing one embodiment of the present invention, FIGS. 2A to 2I are longitudinal sectional front views showing different examples of the annular seal member in the ball joint of the present invention, and FIG. 2H is a longitudinal sectional view of a main part showing a state in which the annular seal member shown in FIG. 2H is assembled into a ball joint. FIG. DESCRIPTION OF SYMBOLS 1... Annular seal member, 2... Accommodation case, 3... Inner cylinder, 11... Contact part of annular seal member with accommodation case, 12... Contact part with inner cylinder of annular seal member.

Claims (1)

[Scope of Claims] 1. An inner cylinder having a spherical shape, an accommodation case that houses the inner cylinder and has a spherical inner peripheral surface concentric with the inner cylinder, and an annular seal located between the inner cylinder and the accommodation case. the contact portion of the annular seal member with the housing case is selected from the group consisting of (a) a compression molded product of expanded graphite, and (b) a compression molded product of a composite of expanded graphite and an inorganic binder; and the contact portion with the inner cylinder is selected from the group consisting of (c) a composite of a carbon material (excluding expanded graphite) and a metal, and (d) a composite of a carbon material (excluding expanded graphite) and an inorganic binder. A ball joint characterized by being 2. The ball joint according to claim 1, wherein the specific gravity of (a) is 1.1 or more. 3. The ball joint according to claim 1, wherein the specific gravity of (b) is 1.1 or more. 4. Claim 1, wherein the inorganic binder in (b) above is selected from the group consisting of graphite oxide, aluminum phosphate, and boric acid.
Ball joint as described in section. 5. The ball joint according to claim 1, wherein the amount of the inorganic binder used in (b) is 1 to 20% by weight based on the expanded graphite. 6. The ball joint according to claim 1, wherein the metal in (c) has a melting point of 200 to 1300°C. 7. The ball joint according to claim 1, wherein the amount of metal in (c) is 10 to 40% of the amount of metal in terms of volume ratio. 8. Claim 1, wherein the inorganic binder in (d) above is selected from the group consisting of aluminum phosphate and colloidal silica.
Ball joint as described in section. 9 The amount of inorganic binder used in (d) above is
The ball joint according to claim 1, wherein the weight ratio is 0.5 to 30% based on the carbon material.