Sealing device and method for forming transfer film

Abstract

A sealing device according to the present invention includes a resin material that has been filled with carbon fibers and a fluororesin, said resin material being a thermoplastic polyether ether ketone. When the sealing device is subjected to a pin-on-disc test in a 1-95 MPa hydrogen gas environment, it is preferable for the friction coefficient to be substantially constant for sliding distances from 0-4000 M. Furthermore, a method for forming a transfer film according to the present invention comprises: a step in which a structure to be sealed is brought into contact with the sealing device which includes a resin material that has been filled with carbon fibers and a fluororesin, said resin material being a thermoplastic polyether ether ketone; a step in which the sealing device is placed in a 1-95 MPa hydrogen gas environment; and a step in which a PTFE transfer film is formed on the structure to be sealed by sliding the sealing device across the structure to be sealed.

Description

Sealing device and method for forming a transfer membrane - Patents.com

[0001] SUMMARY The present disclosure relates to sealing devices and methods for forming transfer membranes.

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

[0003] For example, Patent Document 1 discloses a technique for forming a tetrafluoroethylene resin transfer film on a sliding member by sealing the sliding member with a seal and sliding tetrafluoroethylene resin on the sliding member while sealing in high-purity hydrogen gas.

[0004] JP 2008-290398 A

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

[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: bringing a sealing device, which includes a resin material filled with carbon fiber and a fluororesin and in which the resin material is thermoplastic polyether ether ketone, into contact with a sealed structure; placing the sealing device in a hydrogen gas environment of 1 MPa or more and 95 MPa or less; and sliding the sealing device over the sealed structure to form a transfer film containing the fluororesin on the sealed structure.

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

[0009] 1 is a schematic diagram of a portion of a compressor equipped with a sealing device according to an embodiment of the present invention; FIG. 2 is an enlarged view of a portion of the compressor of FIG. 1; FIG. 3 is a flow chart showing a method for forming a transfer film according to an embodiment of the present invention; FIG. 4 is a schematic view of a pin-on-disk type friction tester; FIG. 5 is a graph showing test results of a friction test; FIG. 6 is a surface observation result of a transfer film formed on a disk test piece using the first embodiment; FIG. 7 is a surface observation result of a transfer film formed on a disk test piece using the second embodiment; FIG. 8 is a surface observation result of a transfer film formed on a disk test piece using the first comparative example; FIG. 9 is a surface observation result of a transfer film formed on a disk test piece using the second comparative example; FIG. 10 is an XPS result for carbon in the transfer film according to the first comparative example; FIG. 11 is an XPS result for carbon in the transfer film according to the second comparative example; FIG. 12 is an XPS result for fluorine in the transfer film according to the first embodiment; FIG. 13 is an XPS result for fluorine in the transfer film according to the second embodiment; FIG. 14 is an XPS result for carbon in the transfer film according to the first embodiment;

[0010] Preferred embodiments of the present disclosure 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 forms unless otherwise specified in the following description.

[0011] 1. Embodiment 1-1. Compressor 100 equipped with sealing device 4 Fig. 1 is a diagram schematically showing a portion of a compressor 100 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 capable of reciprocating movement in the X1 direction and the X2 direction. The 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 a shaft seal 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] 1-2. 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, with the resin material being 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] The resin material used is thermoplastic PEEK, which makes it easier to manufacture a sealing device 4 with excellent sliding properties compared to other materials.

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

[0021] 1-3. Method for Forming the 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 the shaft 3 as the "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 ranging from 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 the transfer film 5 can be formed more easily using PTFE than using other materials.

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

[0026] A. Preparation of Pin Test Pieces for Sealing Devices A-1. Example First, a pin test piece for a sealing device of the example is prepared. The composition of the pin test piece of the example is 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 is as follows. The comparative example is the same as the example except for the use of the following materials: Carbon fiber: 30 parts by weight Thermoplastic PEEK: 70 parts by weight

[0029] B. Preparation of a disk test piece with a mating surface A disk-shaped test piece with a through hole in the center was prepared. The material of the disk test piece was austenitic stainless steel SUS316L. The disk test piece had 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 disk test piece was 0.05 mm. The disk test pieces used in the examples and comparative examples had 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 the 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 disk holder 63.

[0032] The pin holder 61 secures the pin test piece 71. The pin holder 61 is connected to and supported by a support member 62. The pin holder 61 is rotated integrally with the support member 62. The disk holder 63 secures the 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 each pressure. The sliding conditions for both tests 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 near the test piece of 100°C. 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 tested under atmospheric pressure using the pin test specimen of the embodiment will be referred to as "First Example βA," and the example tested under high pressure using the pin test specimen of the embodiment will be referred to as "Second Example βH." Furthermore, the example tested under atmospheric pressure using the pin test specimen of the comparative example will be referred to as "First Comparative Example αA," and the example tested under high pressure using the pin test specimen of the comparative example 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 coefficient of friction of Example βH was lower than that of Comparative Example αH. Furthermore, the coefficient of friction of Comparative Example αH changed significantly as the sliding distance increased from 0 to 4000 m, whereas Example βH maintained a nearly constant coefficient of friction as the sliding distance increased from 0 to 4000 m. The range from 0 to 4000 m refers to a range from 0 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 excellent 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 with respect to the mating surface.

[0039] In addition, the above description 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 the 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 friction coefficient was found to be approximately constant over a sliding distance of 0 m to 4000 m. The term "approximately constant" refers not only to the case where the friction coefficient is strictly constant, but also to the case where the change in the friction coefficient 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 a pin-on-disk test was 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 4000 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 test pieces 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 Figures 6 to 8 each show the results of surface observation of a disk test piece using a laser microscope. Figure 6 shows the results of surface observation of a transfer film formed on a disk test piece using the first example βA. Figure 7 shows the results of surface observation of a transfer film formed on a disk test piece using the second example βH. Figure 8 shows the results of surface observation of a transfer film formed on a disk test piece using the first comparative example αA. Figure 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. The formation of a particularly thick film was confirmed in the first comparative example αA in Figure 8. Furthermore, the formation of a thin film was confirmed in the second example HB in Figure 7. Furthermore, the formation of a thin film was confirmed in the second example βH in Figure 7 and the first comparative example αH in Figure 9.

[0046] E-2. Raman Spectroscopic Analysis and FT-IR Analysis Raman spectroscopic analysis 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 composed of at least PEEK and carbon fiber 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) Figure 10 shows XPS results for carbon in the transferred film of the first comparative example αA. Figure 11 shows XPS results for carbon in the transferred film of the second comparative example αH. Figure 12 shows XPS results for fluorine in the transferred film of the first example βA. Figure 13 shows XPS results for fluorine in the transferred film of the second example βH. Figure 14 shows XPS results for carbon in the transferred film of the first example βA. Figure 15 shows XPS results for carbon in the transferred film of the second example βH. In each figure, 0 s, 27 s, and 459 s indicate etching times, with larger values ​​representing XPS results from deeper portions from the surface.

[0049] XPS analysis was performed to analyze the composition of the film formed on the surface of the disk test 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 test 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 HB, which was measured under high pressure, a clear peak derived from the C-F bond was confirmed in the detection range of carbon and fluorine, as shown in Figures 13 and 15. This suggests the presence of fluorine derived from the PTFE having C-F bonds in the transfer film formed using the pin test specimen composed of PTFE, carbon fiber, and thermoplastic PEEK under high-pressure hydrogen gas. Note that, since the comparative example was composed 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 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 the first example βA and the first comparative example αA. As a result, it is believed that there was no difference in the results of the friction test shown in Figure 5 between the first example βA and the first 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. And, because the second example βH contains PTFE as a fluororesin, it is thought that the lubricating effect of PTFE made the second example βH lower in friction than 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] 2. Supplementary Notes The following aspects, for example, can be understood from the above-described embodiments and modifications.

[0055] A sealing device according to a first aspect, which 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 the first aspect, a transfer film having even lower friction than conventional films can be formed.

[0057] In a second aspect, which is a preferred example of the first aspect, the coefficient of friction measured when a pin-on-disk test is performed in a hydrogen gas environment of 1 MPa or more and 95 MPa or less 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 over a long period of time.

[0059] In a third aspect which is a preferred example of the first aspect, the coefficient of friction measured when a pin-on-disk test is carried out in a hydrogen gas environment of 1 MPa or more and 95 MPa or less 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 carbon fiber and fluororesin described above, 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 the 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 the steps of bringing a sealing device, which includes a resin material filled with carbon fiber and a fluororesin and is made of thermoplastic polyether ether ketone, into contact with a sealed structure, placing the sealing device in a hydrogen gas environment of 1 MPa or more and 95 MPa or less, and sliding the sealing device over the sealed structure to form a transfer film containing a 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 a 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.

[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. A sealing device comprising a resin material filled with carbon fiber and fluororesin, wherein the resin material is thermoplastic polyetheretherketone.

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

3. A sealing device as described in claim 1, wherein the coefficient of friction measured when conducting a pin-on-disk test in a hydrogen gas environment of 1 MPa or more and 95 MPa or less is 0.17 or less for sliding distances of 0 m to 4000 m.

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

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

6. A method for forming a transfer film, comprising the steps of: bringing a sealing device containing a resin material filled with carbon fiber and fluororesin, the resin material being thermoplastic polyether ether ketone, into contact with a sealed structure; placing the sealing device in a hydrogen gas environment of 1 MPa or more and 95 MPa or less; and sliding the sealing device over the sealed structure to form a transfer film containing fluororesin on the sealed structure.

7. The method for forming a transfer film according to claim 6, wherein said fluororesin is polytetrafluoroethylene.

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