Sealing device and method for forming a transfer film

Abstract

To provide a sealing device capable of forming a transfer film excellent in low friction property, and a method for forming the transfer film.SOLUTION: The sealing device includes a resin material filled with carbon fiber and fluororesin, and the resin material is thermoplastic polyether ether ketone. It is preferable that the sealing device has a substantially constant frictional coefficient between sliding distances of 1MPa and 95MPa when a pin-on-disk test is performed under hydrogen gas environments of 0M or more and 4000M or less. A method of forming a PTFE transfer film on a structure to be sealed includes the steps of placing a sealing device in contact with the structure to be sealed, placing the sealing device in a hydrogen gas atmosphere between 1MPa and 95MPa, and sliding the sealing device against the structure to be sealed to form a PTFE transfer film on the structure to be sealed.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sealing device and a method for forming a transfer membrane. [Background technology]

[0002] Hydrogen energy and fuel cell vehicles that use it are attracting attention as a clean energy source that can replace fossil fuels. To popularize fuel cell vehicles, infrastructure development is required, such as hydrogen stations for filling vehicles with hydrogen. High-pressure gas compressors in hydrogen stations use composites containing self-lubricating tetrafluoroethylene (PTFE) as piston ring material.

[0003] For example, Patent Document 1 discloses a technology in which a sliding member is sealed with a seal, and a tetrafluoroethylene resin is slid over the sliding member while high-purity hydrogen gas is enclosed, thereby forming a tetrafluoroethylene resin transfer film on the sliding member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-290398 Summary of the Invention [Problem to be solved by the invention]

[0005] It would be desirable to find a seal that can form a transfer film with even lower friction than the prior art. [Means for solving the problem]

[0006] In order to solve the above problems, a sealing device according to one aspect of the present disclosure includes a resin material filled with carbon fiber and fluororesin, and the resin material is thermoplastic polyether ether ketone.

[0007] A method for forming a transfer film according to one embodiment of the present disclosure includes the steps of contacting a sealing device, which includes a resin material filled with carbon fiber and a fluororesin, and the resin material is thermoplastic polyether ether ketone, with a sealed structure; exposing the sealing device to a hydrogen gas environment of 1 MPa or more and 95 MPa or less; and sliding the sealing device against the sealed structure to form a transfer film containing a fluororesin on the sealed structure. [Effects of the Invention]

[0008] According to the present disclosure, a transfer film having even lower friction than conventional films can be formed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram schematically illustrating a portion of a compressor equipped with a sealing device according to the present embodiment. [Figure 2] FIG. 2 is an enlarged view of a portion of the compressor of FIG. 1. [Figure 3] FIG. 2 is a flow diagram illustrating a method for forming a transfer film according to the present embodiment. [Figure 4] Schematic diagram of a pin-on-disk friction tester. [Figure 5] 10 is a graph showing test results of a friction test. [Figure 6] 10 shows the results of observing the surface of a transfer film formed on a disk test piece using the first embodiment. [Figure 7] 10 shows the results of observing the surface of a transfer film formed on a disk test piece using the second embodiment. [Figure 8] 1 shows the results of observing the surface of a transfer film formed on a disk test piece using the first comparative example. [Figure 9] 10 shows the results of observing the surface of a transfer film formed on a disk test piece using the second comparative example. [Figure 10] 10 is an XPS result for carbon in a transfer film according to a first comparative example. [Figure 11] 10 is an XPS result for carbon in the transfer film according to the second comparative example. [Figure 12] 1 shows an XPS result regarding fluorine in the transfer film according to the first embodiment. [Figure 13] 10 shows an XPS result regarding fluorine in the transfer film according to the second embodiment. [Figure 14] 10 shows an XPS result for carbon in the transfer film according to the first embodiment. [Figure 15] 10 shows an XPS result for carbon in the transfer film according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the dimensions or scale of each part in the drawings may differ from the actual dimensions, and some parts are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to the following embodiments unless otherwise specified in the following description.

[0011] A. Embodiment 1. Compressor 100 with sealing device 4 Fig. 1 is a diagram that also schematically shows a portion of a compressor 100 that is equipped with a sealing device 4 according to this embodiment. The compressor 100 shown in Fig. 1 is used, for example, in a hydrogen station for filling hydrogen into vehicles such as fuel cell vehicles.

[0012] The compressor 100 includes a housing 2, a shaft 3, and a sealing device 4. The housing 2 is a case having a space for accommodating various components (not shown), including the shaft 3. The shaft 3 is an example of a "sealed structure." The shaft 3 is a rod-shaped member that is movable relative to the housing 2. Specifically, the shaft 3 is movable back and forth in the X1 direction and the X2 direction. Materials of the housing 2 and the shaft 3 include stainless steel.

[0013] The sealing device 4 is an elastic shaft seal. The sealing device 4 is fixed to the housing 2, is slidable relative to the shaft 3, and provides a seal between the housing 2 and the shaft 3. The outer surface of the shaft 3 is a mating surface 30 that faces the sealing device 4. The mating surface 30 is cylindrical, and the sealing device 4 is annular with an inner wall surface that corresponds to the cylindrical shape.

[0014] The compressor 100 is used, for example, as a high-pressure gas compressor in a hydrogen station. The shape of the sealing device 4 is not limited to the shape shown in the figure and is arbitrary. The sealing device 4 may be used for purposes other than shaft sealing as long as it has a structure that seals between two members including a "sealed structure."

[0015] Fig. 2 is an enlarged view of a portion of the compressor 100 in Fig. 1. As shown in Fig. 2, a transfer film 5 formed by the transfer of some of the components of the sealing device 4 is provided on the mating surface 30 of the shaft 3. The transfer film 5 is formed in the range of the mating surface 30 of the shaft 3 where the sealing device 4 slides.

[0016] 2. Sealing device 4 The sealing device 4 described above includes a resin material filled with carbon fiber and fluororesin, and the resin material is thermoplastic polyether ether ketone (PEEK). That is, the sealing device 4 includes carbon fiber, fluororesin, and a resin material, and the resin material is the main material. The content of the main resin material is 50% or more.

[0017] The sealing device 4 slides against the mating surface 30 of the shaft 3 as the "sealed structure," thereby forming a transfer film 5 containing fluororesin on the mating surface 30. The transfer film 5 exhibits excellent low friction. Therefore, a compressor 100 equipped with the sealing device 4 and the shaft 3 as the "sealed device" having the mating surface 30 on which the transfer film 5 is formed can ensure excellent sealing properties while also ensuring excellent sliding properties of the sealing device 4 against the shaft 3.

[0018] The sealing device 4 is made of a resin material filled with carbon fiber and fluororesin, but may contain trace amounts of materials other than these materials to the extent that the above-mentioned effects of the sealing device 4 are not impaired.

[0019] Furthermore, thermoplastic PEEK is used as the resin material, which makes it easier to manufacture a sealing device 4 with excellent sliding properties compared to when other materials are used.

[0020] Examples of fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and perfluoroethylenepropene copolymer (FEP). Among these, the fluororesin is preferably PTFE. When the fluororesin is PTFE, it is easier to form a transfer film 5 with excellent low friction properties compared to other materials.

[0021] 3. Method for forming transfer film 5 The transfer film 5 is formed by the following method. Fig. 3 is a flow diagram showing the method for forming the transfer film 5 of this embodiment. As shown in Fig. 3, the method for forming the transfer film 5 includes a contact step S1, a step S2 of placing the sealing device 4 in a gas environment, and a step S3 of forming the transfer film 5. These steps are performed in this order.

[0022] In the contact step S1, a sealing device 4 made of thermoplastic PEEK filled with carbon fiber and fluororesin is brought into contact with a shaft 3 as a "sealed structure." In the step S2 of placing the sealing device 4 in a gas environment, the sealing device 4 is placed in a hydrogen gas environment of 1 MPa to 95 MPa. Then, in the step S3 of forming a transfer film 5, the sealing device 4 is slid over the shaft 3, and a transfer film 5 containing fluororesin is formed on the shaft 3.

[0023] By placing the sealing device 4 in a high-pressure environment of 1 MPa to 95 MPa and in a hydrogen gas atmosphere, the transfer film 5 containing fluororesin can be suitably formed under the influence of the high-pressure environment and hydrogen.

[0024] In particular, the fluororesin is preferably PTFE, since PTFE makes it easier to form the transfer film 5 compared to other materials. [Example]

[0025] Examples of the present invention will be described below. Friction tests were carried out using a pin-on-disk type friction tester.

[0026] A. Preparation of Pin Test Specimens for Sealing Devices A-1. Example First, a pin test piece for the sealing device of the example was prepared. The composition of the pin test piece of the example was as follows: Carbon fiber: 5 parts by weight PTFE as fluororesin: 20 parts by weight Thermoplastic PEEK: 75 parts by weight

[0027] The carbon fiber and PTFE-filled thermoplastic PEEK was extruded into rods and then dried to produce cylindrical pin specimens with a diameter of 6 mm and a length of 15 mm.

[0028] A-2. Comparative example A pin test piece for a sealing device of a comparative example was manufactured. The composition of the pin test piece of the comparative example was as follows. Note that the comparative example was the same as the example except for using the following materials. Carbon fiber: 30 parts by weight Thermoplastic PEEK: 70 parts by weight

[0029] B. Preparation of disc specimen with mating surface A disk-shaped test piece having a through hole in the center is prepared. The material of the test piece is austenitic stainless steel SUS316L. The test piece has an outer diameter of 56 mm, an inner diameter of 20 mm, and a thickness of 3 mm. The arithmetic mean roughness RA of the mating surface of the test piece is 0.05 mm. The test pieces used in the examples and comparative examples have the same configuration.

[0030] C. Friction test Friction tests were carried out using a pin-on-disk type friction tester. Specifically, tests were carried out under atmospheric pressure and under high pressure.

[0031] 4 is a schematic diagram of a pin-on-disc type friction tester 6. As shown in FIG. 4, the pin-on-disc type friction tester 6 has a pin holder 61, a support member 62, and a disc holder 63.

[0032] The pin holder 61 secures a pin test piece 71. The pin holder 61 is connected to a support member 62 and supported by the support member 62. The pin holder 61 rotates integrally with the support member 62. The disk holder 63 secures a disk test piece 72. Although not shown, the disk holder 63 is fixed to the load shaft via a thrust bearing and rotates around the axis A1.

[0033] In the pin-on-disc friction tester 6, the pin test piece 71 and the disk test piece 72 are each placed so that the pin test piece 71 abuts against the mating surface 720 of the disk test piece 72. When the disk holder 63 rotates around the axis A1, the disk test piece 72 rotates and moves in a sliding manner while in contact with the pin test piece 71. The pin-on-disc friction tester 6 is placed in a chamber (not shown).

[0034] Tests under atmospheric pressure are conducted in a chamber at atmospheric pressure of 0.1 MPa. Tests under high pressure are conducted in a chamber at high pressure of 40 MPa. For both tests, the chamber is evacuated to a high vacuum, filled with hydrogen gas, and then set to the appropriate pressure. For both tests, the sliding conditions are a sliding speed of 0.25 m / s, an average contact pressure of 1.8 MPa when a load of 50.89 N is applied, and a temperature of 100°C near the test piece. The total sliding distance is 4,500 m.

[0035] D. Friction test results Figure 5 is a graph showing the results of the friction test. Hereinafter, the example in which the pin test specimen of the embodiment was used to test under atmospheric pressure will be referred to as "First Example βA," and the example in which the pin test specimen of the embodiment was used to test under high pressure will be referred to as "Second Example βH." Furthermore, the example in which the pin test specimen of the comparative example was used to test under atmospheric pressure will be referred to as "First Comparative Example αA," and the example in which the pin test specimen of the comparative example was used to test under high pressure will be referred to as "Second Comparative Example αH."

[0036] Under atmospheric pressure conditions, the friction of the first comparative example αA increased up to a sliding distance of approximately 1000 m, and then showed a decreasing trend. A similar trend was confirmed for the first example βA. On the other hand, under high-pressure conditions, the friction of the second comparative example αH and the second example βH increased immediately after the start, and then tended to remain at a constant friction coefficient.

[0037] The second example βH exhibited a lower coefficient of friction than the second comparative example αH. Furthermore, the coefficient of friction of the second comparative example αH changed significantly as the sliding distance increased from 0 m to 4000 m, whereas the second example βH exhibited a nearly constant coefficient of friction over the sliding distance range from 0 m to 4000 m.

[0038] As can be seen from the results of the friction test shown in Figure 5, when the sealing device of the example is used under high pressure, it exhibits superior low friction compared to the comparative example and can maintain that low friction. In other words, by using a sealing device containing thermoplastic PEEK filled with carbon fiber and fluororesin, it is possible to improve the low friction of the sealing device against the mating surface.

[0039] The above explanation also shows the results of pin-on-disk tests conducted in a hydrogen gas environment of 40 MPA. In addition, when pin-on-disk tests were conducted in a hydrogen gas environment of 1 MPa to 95 MPa, the results showed similar trends to those of pin-on-disk tests conducted in a hydrogen gas environment of 40 MPA.

[0040] Specifically, when a pin-on-disk test was conducted in a hydrogen gas environment of 1 MPa to 95 MPa, the coefficient of friction remained nearly constant over a sliding distance of 0 to 4000 m. The term "nearly constant" not only means that the coefficient of friction is strictly constant, but also that the change in the coefficient of friction falls within a range of 0.001 to 0.01.

[0041] Therefore, it was found that by using a sealing device containing thermoplastic PEEK filled with carbon fiber and fluororesin, low friction can be maintained in a hydrogen gas environment of 1 MPa to 95 MPa, and excellent low friction can be maintained for a long period of time.

[0042] Furthermore, when pin-on-disk tests were conducted in a hydrogen gas environment of 10 MPA to 95 MPA, the friction coefficient was 0.17 or less for sliding distances of 0 to 4,000 m. In other words, by using a sealing device containing thermoplastic PEEK filled with carbon fiber and fluororesin, a low friction coefficient of 0.17 or less could be achieved.

[0043] E. Other Evaluations Furthermore, the disk specimens after the friction test were subjected to surface observation using a laser microscope, Raman spectroscopy, FT-IR analysis, and X-ray photoelectron spectroscopy (XPS).

[0044] E-1. Results of surface observation using a laser microscope 6 to 8 show the results of surface observation of a disk test piece using a laser microscope. FIG. 6 shows the results of surface observation of a transfer film formed on a disk test piece using the first example βA. FIG. 7 shows the results of surface observation of a transfer film formed on a disk test piece using the second example βH. FIG. 8 shows the results of surface observation of a transfer film formed on a disk test piece using the first comparative example αA. FIG. 9 shows the results of surface observation of a transfer film formed on a disk test piece using the second comparative example αH.

[0045] In all of the examples shown in Figures 6 to 8, the formation of a film, i.e., the formation of a transfer film, was confirmed. Furthermore, as shown in the first example βA in Figure 6 and the first comparative example αA in Figure 8, the formation of a relatively thick film was confirmed under atmospheric pressure conditions. In the first comparative example αA in Figure 8, the formation of a particularly thick film was confirmed. Furthermore, in the second example βH in Figure 7, the formation of a thin film was confirmed. Furthermore, in the second example βH in Figure 7 and the first comparative example αH in Figure 9, the formation of a thin film was confirmed.

[0046] E-2. Raman spectroscopy and FT-IR analysis Raman spectroscopy and FT-IR analysis of the surface of the pin test specimen revealed a Raman spectrum derived from the carbon fiber and an IR spectrum derived from PEEK. This suggests that a tribofilm consisting of at least PEEK and carbon fiber was formed on the surface of the pin test specimen due to friction.

[0047] Furthermore, when the surface of the disk test piece was subjected to Raman spectroscopy, the Raman spectrum derived from the carbon fiber was detected in the same manner as on the surface of the pin test piece.

[0048] E-3.X-ray photoelectron spectroscopy (XPS) FIG. 10 shows the XPS results for carbon in the transfer film of the first comparative example αA. FIG. 11 shows the XPS results for carbon in the transfer film of the second comparative example αH. FIG. 12 shows the XPS results for fluorine in the transfer film of the first example βA. FIG. 13 shows the XPS results for fluorine in the transfer film of the second example βH. FIG. 14 shows the XPS results for carbon in the transfer film of the first example βA. FIG. 15 shows the XPS results for carbon in the transfer film of the second example βH. In each figure, 0s, 27s, and 459s are energy levels. The larger the value, the deeper the XPS results from the surface.

[0049] XPS analysis was performed to analyze the composition of the film formed on the surface of the disk specimen. As shown in Figures 10 and 11, a significantly high carbon-C-C bond peak was detected in the first comparative example αA and the second comparative example αH. In other words, the transfer film formed using the comparative pin specimen made of carbon fiber and thermoplastic PEEK exhibited a significantly high carbon-C-C bond peak both under atmospheric pressure and high pressure.

[0050] Furthermore, in Example 1 βA, which was measured under atmospheric pressure, a slight fluorine peak derived from the metal fluoride was detected, as shown in Figure 12, and a high carbon-C-C bond peak was detected, as shown in Figure 14. On the other hand, in Example 2 βH, which was measured under high pressure, clear peaks derived from C-F bonds were confirmed in the carbon and fluorine detection range, as shown in Figures 13 and 15. This suggests the presence of fluorine derived from PTFE with C-F bonds in the transfer film formed using pin test specimens made of PTFE, carbon fiber, and thermoplastic PEEK under high-pressure hydrogen gas. Note that, since the comparative example was made of carbon fiber and thermoplastic PEEK, no fluorine peak was detected in the transfer film formed using this comparative example.

[0051] It is known that carbon fibers can improve sliding properties. Therefore, it is believed that the carbon derived from the carbon fibers mainly contributes to the friction behavior in the transfer films of Example βA and Comparative Example αA. As a result, there is no difference in the results of the friction test shown in Figure 5 between Example βA and Comparative Example αA.

[0052] In addition, sliding the pin test piece against the disk test piece under high pressure filled with hydrogen gas changes the surface characteristics of the disk test piece. Furthermore, because the second example βH contains PTFE as a fluororesin, the lubricating effect of PTFE is thought to have contributed to the low friction of the second example βH compared to the second comparative example αH.

[0053] Although the sealing device and the transfer film forming method have been described above based on preferred embodiments, the present disclosure is not limited to the above-described embodiments. Furthermore, the configurations of the above-described parts can be replaced with any configuration that performs the same function as the above-described embodiments, and any configuration can be added.

[0054] 3. Notes For example, the following aspects can be understood from the above embodiment and modified examples.

[0055] A sealing device according to a first aspect that is a suitable example of the present disclosure includes a resin material filled with carbon fiber and fluororesin, and the resin material is made of thermoplastic polyether ether ketone.

[0056] According to this first aspect, a transfer film having even lower friction than conventional films can be formed.

[0057] In the second aspect, which is a preferred example of the first aspect, when a pin-on-disk test is conducted in a hydrogen gas environment of 1 MPa or more and 95 MPa or less, the coefficient of friction is approximately constant over a sliding distance of 0 m to 4000 m.

[0058] This sealing device can maintain low friction in a hydrogen gas environment of 1 MPa or more and 95 MPa or less, and therefore can exhibit excellent low friction for a long period of time.

[0059] In a third aspect which is a preferred example of the first aspect, when a pin-on-disk test is conducted in a hydrogen gas environment of 1 MPa or more and 95 MPa or less, the coefficient of friction is 0.17 or less over a sliding distance of 0 m to 4000 m.

[0060] By using a sealing device containing the thermoplastic PEEK filled with the aforementioned carbon fiber and fluororesin, it is possible to achieve low friction with a friction coefficient of 0.17 or less.

[0061] In a fourth aspect which is a preferred example of the first aspect, a transfer film containing a fluororesin is formed on a mating surface by sliding against the mating surface.

[0062] The formation of the transfer film ensures excellent sealing performance and also ensures excellent sliding properties of the sealing device against the mating surface.

[0063] In a fifth aspect which is a suitable example of the first aspect, the fluororesin is polytetrafluoroethylene.

[0064] This makes it easier to form a transfer film with excellent low friction properties compared to other materials.

[0065] A sixth aspect of the method for forming a transfer film, which is a preferred example of the present disclosure, includes a resin material filled with carbon fiber and fluororesin, and includes the steps of: bringing a sealing device made of thermoplastic polyether ether ketone into contact with a sealed structure; exposing the sealing device to a hydrogen gas environment of 1 MPa or more and 95 MPa or less; and sliding the sealing device against the sealed structure to form a transfer film containing fluororesin on the sealed structure.

[0066] According to the sixth aspect described above, by placing the sealing device in a high-pressure environment in the range of 1 MPa to 95 MPa and in a hydrogen gas atmosphere, it is possible to suitably form a transfer film containing fluororesin under the influence of the high-pressure environment and hydrogen.

[0067] In a seventh aspect which is a suitable example of the sixth aspect, the fluororesin is polytetrafluoroethylene.

[0068] This makes it easier to form a transfer film with excellent low friction properties compared to other materials. [Explanation of symbols]

[0069] 2...housing, 3...shaft, 4...sealing device, 5...transfer film, 6...disc-type friction tester, 30...counter surface, 61...pin holder, 62...support member, 63...disc holder, 71...pin test piece, 72...disc test piece, 100...compressor, 720...counter surface, A1...shaft.

Claims

1. It includes a resin material filled with carbon fiber and fluororesin, The sealing device, wherein the resin material is thermoplastic polyether ether ketone.

2. 2. The sealing device according to claim 1, wherein when a pin-on-disk test is conducted in a hydrogen gas environment of 1 MPa or more and 95 MPa or less, the friction coefficient is approximately constant over a sliding distance of 0 m to 4000 m.

3. 2. The sealing device according to claim 1, wherein, when a pin-on-disk test is conducted in a hydrogen gas environment of 1 MPa or more and 95 MPa or less, the friction coefficient is 0.17 or less over a sliding distance of 0 m to 4000 m.

4. The sealing device according to claim 1 , wherein a transfer film containing a fluororesin is formed on a mating surface by sliding against the mating surface.

5. The sealing device according to claim 1 , wherein the fluororesin is polytetrafluoroethylene.

6. contacting a sealing device with a sealed structure, the sealing device including a resin material filled with carbon fiber and a fluororesin, the resin material being thermoplastic polyetheretherketone; placing the sealing device in a hydrogen gas environment of 1 MPa or more and 95 MPa or less; sliding the sealing device against the sealed structure to form a transfer film containing a fluororesin on the sealed structure; A method for forming a transfer film, comprising:

7. 7. The method for forming a transfer film of claim 6, wherein the fluororesin is polytetrafluoroethylene.

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