JP2003194234A - Manufacturing method for rotating shaft seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a rotating shaft seal, in which seal element using polytetrafluoroethylene as its main ingredient is bonded to a metal case with high adhesive strength, capable of being manufactured highly efficiently and in a short time with a small number of processes and easy management of each process and simple manufacturing equipment. <P>SOLUTION: Fluororesin having a hydroxyl group in molecules is inserted in between the seal element 3 using the polytetrafluoroethylene as its main ingredient and the metal case 2, and an loaded object 20 is heated and compressed. The loaded object is then cooled under a loading condition to melt and solidify the thermoplastic fluororesin. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a rotary shaft seal using a seal element containing polytetrafluoroethylene as a main component.

[0002]

2. Description of the Related Art Conventionally, as a seal used for an engine shaft of an automobile, a combination of a rubber seal element and an annular metal fitting (metal case) has been used. However, in recent years, due to the demand for higher durability of the seal due to the high-speed rotation of the engine shaft and the rise in the operating environment temperature, polytetrafluoroethylene (which has high heat resistance and low friction resistance as a seal element) Hereinafter, it is also referred to as PTFE) is being used.

However, the seal element made of rubber (fluorine rubber) can be integrated with the metal case by molding the rubber (fluorine rubber) so as to cover the metal case. However, the seal element made of PTFE is PTFE. Since it cannot be molded to cover the metal case, in general, use a fixing bracket separately from the metal case, sandwich the sealing element between the metal case and the fixing bracket, and bend the end of the metal case (caulking). ) Is fixed. And
At this time, the rubber elastic body is sandwiched together with the PTFE sealing element to prevent the sealing element from moving and rotating. Therefore, the seal (hereinafter, also referred to as “clamp type seal”) requires a metal component and a rubber elastic body for sandwiching the seal element in addition to the metal case. It takes time (manufacturing time becomes long), management of manufacturing equipment is complicated, and productivity is low. In addition, since it is fixed only by the compressive force, the seal element is displaced from the metal case due to deterioration of the rubber elastic body, etc. in the long-term use, which causes leakage of sealing fluid from other than the shaft seal part. There is also a problem.

Therefore, the present inventors tried to adhesively fix the PTFE sealing element to the metal case using an epoxy resin adhesive. However, a fluororesin such as PTFE has a small surface free energy and is inactive as compared with other resins, and in order to obtain good adhesiveness, the surface of the seal element is treated with metallic sodium ( Pre-treatment to modify the surface of the seal element by performing plasma treatment or exposure to the air to introduce hydroxyl groups etc. after the immersion in sodium solution is essential. Since these surface treatment methods use a special gas or solvent, special equipment and working environment are essential, and the equipment and management costs rise. Epoxy resin adhesives are liquid at room temperature, so it is possible to manage the working conditions (ambient temperature, discharge pressure, time, measurement, prevention of liquid dripping / liquid clogging) etc. for applying adhesive to metal cases. There is the problem of complexity. Therefore, in order to apply to mass production (industrial production), the number of processes is large, the equipment is complicated, and work management in each process is not easy,
Since the manufacturing time becomes long, it cannot be said to be an efficient manufacturing method. Further, the rotary shaft seal obtained by such a method is one in which the metal case and the seal element are bonded to each other with a somewhat high adhesive force, but the thermal expansion coefficient between the epoxy resin adhesive and polytetrafluoroethylene is Because of the difference
When used in a high temperature environment, the adhesive force between the metal case and the seal element may be reduced, and leakage of the sealing fluid from other than the shaft seal portion may occur.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has a small number of steps, easy control of each step, and simple manufacturing equipment, and a sealing element containing polytetrafluoroethylene as a main component has a metal element. An object of the present invention is to provide a method of manufacturing a rotary shaft seal, which can efficiently manufacture a rotary shaft seal adhered to a case with high adhesive force in a short time.

[0006]

In order to achieve the above object, the present invention has the following features. (1) A method of manufacturing a rotary shaft seal in which a seal element having polytetrafluoroethylene as a main component is integrated with a metal case, wherein a seal element having polytetrafluoroethylene as a main component and the metal case are provided. ,
A fluororesin having a hydroxyl group in the molecule, the melting point of which is lower than the melting point of the polytetrafluoroethylene that constitutes the sealing element, is sandwiched, the resulting stack is heated and compressed, and then the stack Cool the object under load to melt the fluororesin with hydroxyl group in the molecule.
A method for manufacturing a rotary shaft seal, which comprises solidifying. (2) The method for producing a rotary shaft seal according to (1) above, wherein the fluororesin having a hydroxyl group in the molecule is a film-shaped molded product. (3) The method for producing a rotary shaft seal according to (1) above, wherein the difference between the melting point of the fluororesin having a hydroxyl group in the molecule and the melting point of the polytetrafluoroethylene forming the seal element is 10 ° C. or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The rotary shaft seal manufactured in the present invention means one side of the longitudinal direction of the rotary shaft of the fluid sealed around the rotary shaft in the engine shaft, the air conditioner compressor, the supercharger, the turbocharger, etc. It is used by being attached to the rotating shaft in order to prevent leakage to the polytetrafluoroethylene (PTFE).
The seal element whose main component is is fixed to the metal case,
It is an integrated structure. Examples of the sealed fluid include engine oil for engine shafts, lubricating oil and refrigerant for compressors for air conditioners, and high temperature / high pressure gas for superchargers and turbochargers. The sealing element that contains polytetrafluoroethylene (PTFE) as its main component has mechanical properties even under high temperature use environment of the rotating shaft due to the excellent heat resistance, oil resistance, chemical resistance and low friction property of PTFE. (Strength, elongation) is less likely to deteriorate and the frictional resistance is small, so that good sealing properties can be maintained for a long period of time with respect to the above sealing fluid.

In the present invention, "a seal element containing polytetrafluoroethylene (PTFE) as a main component"
The term means a seal element formed by molding PTFE alone or a seal element formed by molding a composition in which PTFE is mixed with an additive such as a filler. In addition, "polytetrafluoroethylene (PTFE)" here is
Modified PTFE (TF) prepared by copolymerizing a small amount of perfluoroalkyl vinyl ether with polytetrafluoroethylene.
The content of E is 99.0 mol% or more). Examples of the perfluoroalkyl vinyl ether in the modified PTFE include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl and the like.

The "sealing element containing PTFE as a main component" used in the present invention is, for example, PTFE or a known compound such as PTFE, a filler and other additives to be added as necessary, such as a Henschel mixer. The mixture obtained by mixing with a mixing device and processed into a desired shape by a method such as compression molding, sintering, and cutting is used. Also, a commercially available seal element can be used.

The method for manufacturing a rotary shaft seal according to the present invention is the same as the above-mentioned seal element containing PTFE as a main component, without being subjected to any special surface treatment (activation treatment such as plasma treatment or metal sodium treatment). A fluororesin having a hydroxyl group in the molecule is sandwiched between the untreated seal element and the metal case (first step), and the stack is heated / compressed (second step). It is characterized by cooling under load (third step), whereby the fluororesin having a hydroxyl group in the molecule is melted and solidified, and is fused to the metal case and the seal element, and the metal case and the seal. A rotary shaft seal is obtained in which the element and the element are integrated through a fusion layer of a fluororesin having a hydroxyl group in the molecule.

In the present invention, the fluororesin having a hydroxyl group in the molecule means a fluororesin having no hydroxyl group in the molecule (a conventionally known general fluororesin), for example, represented by the following formula (I). Is a copolymer of a fluorine-containing ethylene-based monomer having a hydroxyl group, such as

Formula (I): CX ₂ ═CX ¹ —R _f —CH ₂ OH (In the formula, X and X ¹ may be the same or different and each represents a hydrogen atom or a fluorine atom, and R _f is the number of carbon atoms. A divalent alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having 1 to 40 carbon atoms in an ether bond, or a fluorine-containing oxy group having 1 to 40 carbon atoms in an ether bond. Represents an alkylene group.)

In the present invention, preferred specific examples of the compound represented by the formula (I) include perfluoro- (1,
1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol).

Examples of the fluororesin having no hydroxyl group in the molecule (conventional publicly known general fluororesin) include, for example, tetrafluoroethylene, perfluoroalkyl vinyl ether, chlorotrifluoroethylene, vinylidene fluoride and hexafluoro. A polymer (copolymer) having at least one fluorine-containing ethylene monomer selected from the group consisting of propylene as a constituent unit, or constituting at least one fluorine-containing ethylene monomer and ethylene. A unit copolymer may be used.

In the present invention, as the fluororesin having a hydroxyl group in the molecule, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA) described in WO97 / 21778 has a fluorine-containing ethylene having a hydroxyl group. Ethylene-tetrafluoroethylene copolymer obtained by further copolymerizing a fluorinated ethylene-based monomer having a hydroxyl group with tetrafluoroethylene-hexafluoropropylene copolymer (FEP) Those in which (ETFE) is further copolymerized with a fluorine-containing ethylene-based monomer having a hydroxyl group can be preferably used, and those in which PFA is further copolymerized with a fluorine-containing ethylene-based monomer (hereinafter, referred to as “hydroxyl group”). Also referred to as "containing PFA") is particularly preferable.

In the present invention, the fluororesin having a hydroxyl group in the molecule includes a fluorine-containing ethylene monomer having a hydroxyl group and a fluorine-containing ethylene monomer having no hydroxyl group (a conventionally known hydroxyl group in the molecule. It can be obtained by copolymerizing with a fluororesin-containing monomer) which does not have a known polymerization method. The polymerization method is preferably a method by radical copolymerization, as the radical polymerization initiator, heat,
Known radical polymerization initiators that generate radicals by irradiation with light or ionizing radiation can be used. The polymerization method is also not particularly limited, and solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization and the like can be used without limitation. The molecular weight is controlled by the concentration of the monomer used for the polymerization, the concentration of the polymerization initiator, the concentration of the chain transfer agent, the temperature, etc., and the composition of the copolymer produced can be controlled by the composition of the charged monomer.

The fluororesin having a hydroxyl group in the molecule used in the present invention has a melting point of polytetrafluoroethylene (320 to 360) constituting the seal element.
℃). In the cooling process after heating and compressing the fluororesin having a hydroxyl group in the molecule between the metal case and the seal element, before the polytetrafluoroethylene forming the seal element is solidified, This is because the fluororesin having a hydroxyl group is first solidified to fix the seal element and suppress the heat shrinkage of the seal element. If the present inventors cannot sufficiently suppress such heat shrinkage, residual strain occurs in the seal element portion of the manufactured rotary shaft seal, unintentional deformation (corrugation, etc.) occurs, or adhesive strength decreases. It has been found that problems such as peeling may occur even with a slight increase in the operating environment temperature. Therefore, in order to sufficiently exert the heat shrinkage suppression effect of the seal element, the fluororesin having a hydroxyl group in the molecule has a melting point lower than that of polytetrafluoroethylene constituting the seal element to be used by 10 ° C. or more. Is preferably used, and one lower than 15 ° C. is particularly preferable. If the melting point of the fluororesin having a hydroxyl group in the molecule is too low, the heat resistance of the resin itself will be insufficient, and the adhesive strength will decrease when used in a high temperature environment (specifically, 150 ° C. or higher). The problem that the sealing element peels off and the sealing fluid leaks easily occurs. Therefore, it is preferable that the fluorine resin having a hydroxyl group in the molecule has a melting point of 260 ° C. or higher.

The fluororesin having a hydroxyl group in the molecule usually has a copolymerization amount of the fluorine-containing ethylene monomer having a hydroxyl group of 0.05 to 30 per the whole polymer (resin).
It is mol%, preferably 0.1 to 10 mol%.
Copolymerization amount of fluorinated ethylene monomer is 0.05 mol%
If the amount is less than 30%, it is difficult to obtain a sufficiently high adhesive force with respect to the seal element and the metal case, and if it exceeds 30 mol%, the heat resistance decreases, so coloring and foaming occur during heating / compression-cooling. Etc. and the adhesive strength is reduced. In addition, as described later, it is formed into a film,
When it is used, it tends to cause coloring, foaming, decomposition, etc. at the time of its molding, resulting in a decrease in the adhesiveness of the molded film, which is not preferable.

In the present invention, the fluororesin having a hydroxyl group in the molecule is blended with various additives such as fillers and pigments within a range that does not impair the adhesiveness, heat resistance, chemical resistance and the like of itself. You can also do it.

In the present invention, the fluororesin having a hydroxyl group in the molecule may be in the form of powder, or a molded product formed into a pellet, rod or film form. From the viewpoint of handleability (handling property) when sandwiching between the seal element and the metal case, a rod-shaped or film-shaped one is preferable, and a film-shaped one is particularly preferable. In addition, if it is formed into a film, the fusion layer obtained by melting and solidifying is excellent in uniformity of properties, and the metal case and the sealing element are more firmly bonded. Furthermore, the setting of the fusing area for the seal element is also possible by
This is preferable because there is an advantage that it can be easily performed only by changing the size. Therefore, the fusion layer obtained by melting and solidifying is formed in a state of protruding from the shaft-side end portion (the peripheral edge of the circular through hole through which the shaft is inserted) of the metal case, and the contact state of the sealing surface changes, It is possible to avoid the problem that the sealing performance is deteriorated. When a fluororesin having a hydroxyl group in the molecule is formed into a film, the fluororesin is melted by a heat method; an extrusion method; a cutting method; a solvent casting; an aqueous or organic solvent dispersion (dispersion) is used as a base material. It may be prepared according to a known resin film forming method such as a method of coating the above with a continuous film and peeling it from the substrate.

The amount of the fluororesin having a hydroxyl group in the molecule is such that the thickness of the fusion layer formed by melting and solidifying between the metal case and the seal element is generally 5 to 10.
The amount is about 0 μm, preferably about 10 to 70 μm.

In the present invention, the stacking product in which the fluororesin having a hydroxyl group in the molecule is sandwiched between the sealing element and the metal case is heated and compressed. At this time, in order to obtain a high adhesive force, the seal is used. At the boundary between the element and the fluororesin having a hydroxyl group in the molecule (the layer), it is necessary to form a fused part in which the polytetrafluoroethylene in the sealing element and the fluororesin having a hydroxyl group in the molecule are melted together There is a PTF that constitutes the sealing element to be used at the heating temperature during heating and compression of stacks.
The temperature is set to a temperature equal to or higher than the melting point of E, preferably 5 ° C. or more higher than the melting point, and particularly preferably 30 ° C. or higher higher than the melting point. When the heating temperature is 400 ° C. or higher, PTFE constituting the sealing element is thermally decomposed, so the heating temperature is preferably lower than 400 ° C.

The compressive force (load) during heating and compression is usually
It is in the range of 0.01 to 10 MPa, preferably 0.0
1 to 5 MPa, particularly preferably 0.05 to 1 MPa. The heating / compressing time is generally about 5 to 30 minutes, preferably about 5 to 15 minutes, although it varies depending on the heating temperature, the compressive force (load) and the like.

Further, in the present invention, in order to achieve a high adhesive force, it is important to heat and compress the stack and then cool the stack as it is (cool under load). is there. That is, compressive force (load) during heating and compression
The adhesive strength is improved by cooling the product while it is still applied. Therefore, the load during cooling is usually 0.01 to 10
The range of MPa, preferably 0.01-5 MPa,
It is particularly preferably 0.05 to 1 MPa.

The metal case used in the present invention is a member for holding and fixing the seal element so that the seal element is brought into contact with the rotary shaft in a predetermined pressed state.
Iron, aluminum, stainless steel, steel (carbon steel, special steel)
It can be obtained by appropriately processing a metal material such as the above into a shape and a size according to the purpose by a metal press or the like. The portion where the fluororesin layer having a hydroxyl group in the molecule is fused (fused portion) may be surface-roughened by a known method such as sandblasting, sanding, or acid / alkali cleaning. Further, the surface of the metal case may be subjected to rustproofing treatment by a known method. The surface treatment applied to the metal case is preferably one having heat resistance at the heating temperature at the time of fusing the fluororesin having a hydroxyl group in the molecule.

FIG. 1 is a radial cross-sectional view of a metal case, which is a simplified example of the rotary shaft seal manufactured by the method of the present invention. The drawing shows a radial portion on one side in contact with the shaft of the seal, and the other radial portion in contact with the shaft (not shown) has the same structure. In the rotary shaft seal 1, the metal case 2 includes a cylindrical peripheral wall portion 4 and a flange portion 5 protruding from one end of the peripheral wall portion 4 in the axial direction toward the inner space of the peripheral wall portion.
Have and. The flange portion 5 is formed at the one end portion over the entire area of the peripheral wall portion 4 in the circumferential direction, whereby a circular through hole 11 through which the shaft is inserted is defined.
The layer 10 of fluororesin having a hydroxyl group in the molecule is fused to the metal case 2 and the seal element 3, whereby the seal element 3 and the metal case 2 are bonded and integrated. The seal element 3 is mainly composed of PTFE, and one end thereof is adhered to the surface of the collar portion 5 on the other side in the axial direction through a fluororesin layer 10 having a hydroxyl group in the molecule, and the other end side ( The seal lip 8) is bent toward the sealed fluid R side and pressed against the shaft 12,
It prevents the fluid from leaking from the contact surface with. A sealant 15 is provided on the outer peripheral side (back side) of the metal case 2, and the seal 1 tightly fits the seal 1 between the shaft 12 and the housing 13. The sealant 15 is, for example, a method of extruding rubber such as acrylic rubber or fluororubber, applying a paste of the rubber with a solvent, drying it, or winding a resin tape. Is formed by.

In the present invention, the sealing element is PT
When the FE is composed of a composition containing an additive such as a filler, the filler is preferably an inorganic fiber, a solid lubricant, a hard copper alloy powder, or the like, and the inorganic fiber is, for example, soda glass, Non-alkali glass, glass fiber such as silica glass, ceramic fiber such as rock wool, metal fiber of metal such as steel, iron, aluminum, nickel, copper, whiskers such as potassium titanate, carbon fiber, carbon graphite fiber, etc. Of these, glass fibers are preferable, and alkali-free glass fibers are particularly preferable.

In addition, the tensile strength of the single fiber of the inorganic fiber is 2
00 kgf / mm ² or more, particularly 300 kgf / mm ² or more, and an average fiber diameter of 50 μm or less, especially 10
It is preferably μm or less. The average length of the inorganic fiber is 1
0 to 1000 μm, particularly 50 to 150 μm is suitable, and the aspect ratio is 1 to 80, particularly 5 to 50.

When inorganic fibers are added, PTFE100
It is preferably used in the range of 1 to 60 parts by weight, more preferably 3 to 30 parts by weight, based on parts by weight. If the amount of the inorganic fibers is less than 1 part by weight relative to 100 parts by weight of PTFE, it tends to be difficult to sufficiently obtain the effect of improving the wear resistance, and if it exceeds 60 parts by weight, the elongation of the sealing element tends to decrease. However, the sealing performance may be deteriorated, which is not preferable.

The solid lubricant may be used without limitation as long as it is a known compound capable of imparting lubricity, and among them, soap, mica, soap stone, zinc white, molybdenum compound and the like are preferable, and molybdenum compound is preferable. Is particularly preferable. As the molybdenum compound, there are various molybdenum disulfides and organic molybdenum compounds, and examples thereof include natural hexagonal compounds and trigonal compounds. In addition, the hexagonal compound has a purity of 9 obtained by a method such as flotation from ore.
Examples include high-grade concrete for lubrication of 9% or more and ferroalloy products with a purity of around 85%. Further, molybdenum disulfide may be a synthetic orthorhombic substance, a hexagonal substance obtained by heating the orthorhombic substance, or the like. Examples of the organic molybdenum compound include molybdenum dialkyl diphosphate and molybdenum dialkyl dithiocarbamate.

The amount of the solid lubricant is preferably 1 to 20 parts by weight, particularly preferably 2 to 5 parts by weight, based on 100 parts by weight of PTFE. The amount of solid lubricant is PTF
If the amount is less than 1 part by weight with respect to 100 parts by weight of E, the effect of improving the lubricity tends to be insufficient, and 2
If it exceeds 0 parts by weight, mechanical properties (tensile strength, elongation) tend to be deteriorated, which is not preferable.

The hard copper alloy powder is effective in improving the creep property (load deformation resistance) of the seal element. For example, various copper alloy powders such as bronze, brass, phosphor bronze, nickel silver and lead bronze are used. Of these, bronze powder is particularly preferable. The amount of the hard copper alloy powder is preferably 10 to 200 parts by weight, and particularly preferably 15 to 150 parts by weight, based on 100 parts by weight of PTFE. The amount of hard copper alloy powder is PT
If it is less than 10 parts by weight with respect to 100 parts by weight of FE, a sufficient effect of improving the creep property cannot be obtained, and if it exceeds 200 parts by weight, the tensile strength and elongation of the seal element tend to be lowered, which is not preferable.

The above-mentioned solid lubricant and hard copper alloy powder are used in the form of fine powder or fine powder. Generally, those having a particle size of 100% passing through a Tyler standard sieve 100 mesh, and particularly preferably passing through a Tyler standard sieve 200 mesh at 100% are preferable.

If desired, the PTFE may further contain additives other than the above-mentioned fillers, and examples thereof include heat resistant resin powders and pigments. As heat-resistant resin powder, polyphenylene sulfide (PP
S), polyimide resin (PI), aromatic polyester resin (LCP) and the like are preferable, and as the pigment, red iron oxide, cobalt blue, titanium oxide and the like are preferable. These are used in a range that does not impair the wear resistance and oil resistance of PTFE.

A specific procedure of the method of manufacturing the rotary shaft seal of the present invention will be described in detail below with reference to an example of manufacturing the rotary shaft seal 1 shown in FIG.

First, as shown in FIG. 2 (a), the cylindrical peripheral wall portion 4 and the flange portion 5 (the flange portion) protruding from the end portion on one axial side of the peripheral wall portion 4 to the inner space side of the peripheral wall portion. 5 is formed over the entire area in the circumferential direction of the peripheral wall portion 4.), and has a hydroxyl group in the molecule, which is formed by molding and processing a fluororesin having a hydroxyl group in the molecule. Circular ring-shaped film 10 made of fluororesin
A circular ring-shaped sealing element 3 made of A and PTFE (or a PTFE composition) is prepared (note that
In FIG. 1, the sealant layer is shown on the back side of the annular metal case 2, but it is not shown here. ), So that the centers of the circular through holes of these members are aligned on the same axis.

Next, as shown in FIG. 2B, a circular ring-shaped film 10A made of a fluororesin having a hydroxyl group in the molecule is formed on the surface 5A of the collar portion 5 of the annular metal case 2 on the inner side of the case. The circular ring-shaped sealing element 3 is placed on top of it, and the circular ring-shaped film 10A made of fluororesin having a hydroxyl group in the molecule is sandwiched between the metal case 2 and the circular ring-shaped sealing element 3. Then, the stack 20 is created.

Next, a thermostatic chamber 17 in which a pair of upper and lower press plates 15A and 15B whose flat surfaces face each other in parallel are installed is prepared, and a cylindrical compression jig is preliminarily set in the thermostatic chamber 17. 21 is heated to a temperature approximately the same as the melting point of PTFE that constitutes the seal element 3, and the above-mentioned stack 20 is placed in a constant temperature bath 17 that has a temperature approximately equal to the melting point of PTFE that constitutes the seal element. Then, the columnar compression jig 21 is placed on the circular ring-shaped sealing element 3 of the stack 20, and then the inside of the thermostatic chamber is above the melting point of PTFE constituting the sealing element 3 and below 400 ° C. Is set to a desired temperature within the range, and the stack 20 on which the compression jig 21 is placed is sandwiched between the press plates 15A and 15B,
By holding for a predetermined time, heating / compression is performed. here,
The press plates 15A and 15B are connected to a means (not shown) for moving them by, for example, hydraulic pressure, pneumatic pressure, or the like. In addition, the columnar compression jig 21 is
Is used so that the pressure from the press plates 15A and 15B is evenly transmitted (especially uniformly to the seal element), and is usually obtained by processing a metal such as steel or aluminum. The cylindrical peripheral wall portion 4 of the metal case 2 has an outer diameter
The inner diameter is smaller than the inner diameter and is larger than the outer diameter of the circular ring-shaped sealing element 3.

Next, with the compression jig 21 and the stack 20 being sandwiched between the press plates 15A and 15B, the stack structure (press plates 15A and 15B, the compression jig 21 and The stack 20) is taken out from the constant temperature bath 17 and left to stand naturally (air cooling), or the stack structure is brought into contact with a cooling jig such as a metal plate, or the stack structure is removed. Perform forced cooling such as water cooling. The cooling is carried out until the temperature becomes equal to or lower than the melting point of the fluororesin having a hydroxyl group in the molecule. This is because the heat shrinkage of the seal element is fixed by sufficiently cooling and solidifying the fluororesin having a hydroxyl group in the molecule. If forced cooling is performed, the cooling time can be shortened, which is more effective in shortening the manufacturing time.

After that, when the press plates 15A and 15B and the compression jig 21 are removed, the circular ring-shaped sealing element 3 is bonded to the annular metal case 2 by the fusion layer of the fluororesin having a hydroxyl group in the molecule. A fixed rotary shaft seal 1 is obtained.

Although FIGS. 1 to 3 show a seal in which a seal element 3 having a seal lip portion is adhered to a surface 5A of the collar portion 5 of an annular metal case 2 on the inner side of the case. When attaching another seal element having a dust lip portion or the like, the outer surface 5B (face 5) of the collar portion 5 is attached.
On the surface opposite to A), a fluororesin having a hydroxyl group in the molecule is intervened to form a stack of other sealing elements, and the stack is heated and compressed. And cooling is applied.

In addition, here, heating and compression of the stack are
Although it was carried out by pressing (compressing) the stacked products in a constant temperature bath, it may be carried out by hot pressing the stacked products using a known hot press device equipped with a heating plate.

The melting point of PTFE and the melting point of a fluororesin having a hydroxyl group in the molecule in the present specification are values by DSC analysis.

[0044]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.

Example 1 Using a fluororesin film having a hydroxyl group in the molecule, a steel case and PTFE were manufactured according to the manufacturing procedure shown in FIGS.
A rotary shaft seal was produced by adhering and integrating the seal element.

The steel case has an annular shape, and the inner diameter of the cylindrical peripheral wall portion (D1 in FIG. 2) is 58.5 mmφ and the inner diameter of the circular through hole defined by the collar portion (D2 in FIG. 2) is 46. 0.5 mm
φ, the wall thickness (D3 in FIG. 2) 0.8 mm, and the height of the cylindrical peripheral wall portion (D4 in FIG. 2) 7.0 mm were used.
The PTFE sealing element is a PTFE compound (containing 5 parts by weight of molybdenum disulfide (solid lubricant) and 5 parts by weight of glass fiber per 100 parts by weight of PTFE).
Thickness (D5 in FIG. 2) 0.8 mm × outer diameter (D6 in FIG. 2) 58.45 mmφ × inner diameter (D7 in FIG. 2)
35.0mmφ circular ring sheet (no surface treatment)
It was used. Melting point of PTFE: 327 ° C. A fluorine resin film having a hydroxyl group in the molecule was formed into a film shape by hydroxyl group-containing PFA (melting point: 310 ° C.) manufactured by Daikin Industries, Ltd., and the thickness (D8 in FIG. 2) 85 μm × outer diameter ( A film processed into a circular ring shape having D9) 56.50 mmφ × inner diameter (D10 in FIG. 2) 50.50 mmφ in FIG. 2 was used.

The compression jig has a height of 15 mm and an outer diameter (φ).
A cylinder made of 58.4 mm steel and weighing 500 g was used.

Heating / compression is 360 ° C. × 0.06 MPa
× 30 minutes. For cooling after heating and compression, the pressing jig and
The mixture was air-cooled for about 5 minutes until it reached 0 ° C. Hydroxyl group-containing PF with respect to the adhered surface of the collar portion of the metal case in the finished product (that is, the surface 5A of the collar portion 5 inside the case in FIG. 2)
The size (area) of the fusion bonding region of A was 98.0%.

The shear peeling torque between the metal case and the seal element of the finished rotary shaft seal was measured at room temperature (20 ° C.) using the jig shown in FIG. as a result,
The jig slipped from the sealing element before the sealing element peeled from the metal case. Since the torque when the slip occurred was 800 kgf · cm, the shear peeling torque between the metal case and the seal element was determined to be 800 kgf · cm or more.

The shear peeling torque measuring jig shown in FIG. 4 comprises an outer jig 31 for fixing a metal case, jigs 32 and 33 for tightening and rotating the seal element, and a tightening bolt 34. That is, the outer jig 31 has a cylindrical shape with a size into which the metal case 2 can be fitted, and the metal case 2 is fitted into the outer jig 31 and fixed with a vise or the like to fix the rotary shaft seal 1. To be done. The jigs 32 and 33 for tightening and rotating the seal element are such that the lower jig 33 is mounted on the disk-shaped substrate 33a having an outer diameter slightly smaller than the inner diameter of the outer jig 31 for fixing the metal case. A cylindrical protrusion 33b of a size (larger than the through hole of the seal element 3) to be inserted into the through hole of the seal element 3, and a protrusion 33c of a size to be inserted into the through hole of the seal element 3 on the protrusion 33b. Upper jig 3
2 is a seal element 3 on the disk-shaped substrate 32a having an outer diameter slightly smaller than the inner diameter of the cylindrical peripheral wall portion 4 of the metal case 2.
The cylindrical protrusion 32b is larger than the through hole of the metal case 2 but smaller than the through hole of the metal case 2.
The tightening bolt 34 is adapted to be screwed into a screw hole formed in the shaft center of the upper jig 32 and the lower jig 33. By rotating the bolt 34 by screwing the screw 34, Only the seal element 3 is sandwiched (tightened) by the cylindrical protrusion 32b of the upper jig 32 and the cylindrical protrusion 33b of the lower jig 33, and a rotational torque is generated.

Example 2 A rotary shaft seal was produced in the same manner as in Example 1 except that a steel annular case (having the same dimensions as in Example 1) whose surface was sanded was used. The size (area) of the fusion region of the hydroxyl group-containing PFA with respect to the adhered surface of the collar portion of the metal case in the finished product was 98.0%. The shear separation torque between the metal case and the seal element of the finished rotary shaft seal was measured in the same manner as in Example 1. As a result, the jig slipped from the seal element before the seal element separated from the metal case. It was Since the torque when the slip occurred was 800 kgf · cm, the shear peeling torque between the metal case and the seal element was determined to be 800 kgf · cm or more.

Example 3 The same as Example 1 except that the annular case was replaced with an aluminum case having the same dimensions as the steel case used in Example 1 and having no surface treatment (as machined). Then, a rotary shaft seal was produced. The size (area) of the fusion region of the hydroxyl group-containing PFA with respect to the adhered surface of the collar portion of the metal case in the finished product was 98.0%. The shear separation torque between the metal case and the seal element of the finished rotary shaft seal was measured in the same manner as in Example 1. As a result, the jig slipped from the seal element before the seal element separated from the metal case. It was Since the torque when this slip occurred was 800 kgf · cm,
The shear separation torque between the metal case and the seal element was determined to be 800 kgf · cm or more.

Comparative Example 1 A PTFE sheet treated with metallic sodium (Example 1)
The PTFE sheet used in 1. was treated with metallic sodium), the same metal case as in Example 1 was used, and the epoxy resin adhesive (BANI-62) was used.
0T (Maruzen Petrochemical Co., Ltd.)
It was heated and compressed under the conditions of 0 ° C. × 0.06 MPa × 5 minutes, and then reheated at 170 ° C. for 15 hours. Note that P
The metallic sodium treatment of the TFE sheet was carried out by immersing the PTFE sheet in Tetra Etch (manufactured by Junkosha Co., Ltd.) for 30 seconds and then washing it with acetone and then with water. When the shear separation torque between the metal case and the seal element of the completed rotary shaft seal was measured in the same manner as in Example 1, only the seal element rotated at 500 kgf · cm.

Comparative Example 2 As shown in FIG. 5, an inner case 41 made of steel and a rubber elastic body 42 made of acrylic rubber were used, and the metal case 2 and the sealing element 3 were the same as those in the first embodiment. A clamp type rotary shaft seal was manufactured. The shear separation torque between the metal case and the seal element of the completed rotary shaft seal was measured in the same manner as in Example 1, and it was 250 kgf · cm, and only the seal element rotated.

Next, the following heat resistance test and cold resistance test were conducted on the rotary shaft seals of Examples 2 and 3 and Comparative Example 1 produced above.

[Heat resistance test] The rotary shaft seal was subjected to the same shear peel test as above in an atmosphere of 150 ° C. to measure the peel torque.

[Cold Resistance Test] The rotary shaft seal was subjected to the same shear peel test as described above in an atmosphere of −40 ° C. to measure the peel torque.

Table 1 shows the above test results.

[0059]

[Table 1]

[0060]

As is apparent from the above description, according to the present invention, it is possible to manufacture a rotary shaft seal in which a seal element is bonded and integrated with a metal case with a small number of steps, and a conventional clamp type seal can be manufactured. In comparison, the manufacturing time can be greatly reduced. In addition, it does not require heating for a long time as in the case of using an epoxy resin adhesive, which is generally known as a heat-resistant adhesive that also adheres to metal, and the work of applying the adhesive Since there is no complexity of managing conditions and equipment, industrial production can be performed efficiently. Furthermore, the adhesive force between the seal element and the metal case has higher resistance to temperature changes than that using an epoxy resin adhesive, and a more reliable rotary shaft seal can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in a radial direction of a metal case, showing a simplified example of a rotary shaft seal manufactured by the present invention.

FIG. 2A and FIG. 2B are cross-sectional views showing an operation of sandwiching a fluororesin having a hydroxyl group in a molecule between a metal case and a seal element in the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view showing a step of heating / compressing a stacked product in which a fluororesin having a hydroxyl group in a molecule is sandwiched between a metal case and a seal element in the manufacturing method of the present invention.

FIG. 4 is a sectional view showing a shear peeling torque measuring jig in a simplified manner.

FIG. 5 is a simplified cross-sectional view showing a conventional clamp type rotary shaft seal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 rotating shaft seal 2 metal case 3 seal element 10 fusion layer 10A of fluororesin having hydroxyl group in molecule circular ring-shaped film 15A, 15B made of fluororesin having hydroxyl group in molecule press plate 17 thermostat 20 stack 21 Compression jig

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ken Baba             663 Minoshima, Arita-shi, Wakayama Mitsubishi Electric Works             Minoshima Works Co., Ltd. F-term (reference) 3J006 AE14 AE30 AE51 CA04 CA05

Claims (3)

[Claims] 1. A method of manufacturing a rotary shaft seal in which a seal element containing polytetrafluoroethylene as a main component is integrated with a metal case, wherein a seal element containing polytetrafluoroethylene as a main component and the metal case are provided. In between, a fluororesin having a hydroxyl group in the molecule, the melting point of which is lower than the melting point of the polytetrafluoroethylene constituting the seal element is sandwiched, after heating and compressing the resulting stack, A method for producing a rotary shaft seal, characterized in that the stacked product is cooled under a load to melt and solidify the fluororesin having a hydroxyl group in the molecule. 2. A fluororesin having a hydroxyl group in the molecule,
The method for producing a rotary shaft seal according to claim 1, which is a molded product formed into a film. 3. The method for producing a rotary shaft seal according to claim 1, wherein the difference between the melting point of the fluororesin having a hydroxyl group in the molecule and the melting point of the polytetrafluoroethylene constituting the seal element is 10 ° C. or more.