Patent Application
20250146897
The present invention relates to a rubber product, a test jig and a test apparatus for a sealing member, and a leak detection member. More specifically, the present invention relates to a rubber product such as a sealing product for sealing pipes and the like, a test jig and a test apparatus for a sealing member, and a leak detection member.
Conventionally, rubber products using rubber as a main raw material are used in many fields, and for example, the sealing member such as packings and gaskets are widely used in automobiles and electric appliances. More specifically, for example, a cell assembly in a fuel cell is sealed with a gasket (rubber) (see, for example, Patent Document 1).
The gasket prevents hydrogen leakage in the fuel cell, and there are concerns that hydrogen leakage may cause various problems. Therefore, inspection (seal inspection) before assembling the fuel cell is particularly important, and it is required in the seal inspection to confirm the presence or absence of leakage and a position of the leakage.
In such a seal inspection, a method of detecting a hydrogen leak using a chromic material has been proposed (see, for example, Patent Document 2).
However, the sheet described in Patent Document 2 needs to be stuck to a gasket or the like to be inspected at the time of seal inspection. Further, after the inspection is completed, it is necessary to peel off the sheet from the gasket to be inspected, and there is a concern that the inspection target is damaged when the sheet is peeled off.
Further, when the sheet described in Patent Document 2 is attached to an inspection target, a slight gap may occur between the sheet and the inspection target, and if gap is present, parts around the gap may be discolored widely. Therefore, although leakage is observed, there is a concern that an accurate position of the leakage cannot be detected. Thus, there is still room for improvement for even the sheet described in Patent Document 2.
The present invention has been made in view of the prior art, and an object of the present invention is to develop a rubber product, a test jig member and a test apparatus for a sealing member, and a leak detection member, which are capable of preventing the inspection target from being damaged at the time of seal inspection, and further capable of easily and accurately detecting the presence or absence of leakage and a position of the leakage.
According to the present invention, there is provided a rubber product, a test jig and a test apparatus for a sealing member, and a leak detection member, described below.
The rubber product according to the present invention has an effect of being able to easily and accurately detect the presence or absence of leakage and a position of the leakage. Here, the rubber product, when used as a sealing member (sealing product), has an effect of being able to prevent the inspection target from being damaged during the seal inspection, and further easily and accurately detect the presence or absence of leakage and a position of the leakage.
The test tool for a sealing member according to the present invention has an effect of being able to easily and accurately detect the presence or absence of leakage in the sealing member and a position of the leakage.
The test apparatus for a sealing member according to the present invention has an effect of being able to easily and accurately detect the presence or absence of leakage in the sealing member and a position of the leakage.
The leak detection member according to the present invention has an effect of being able to easily and accurately detect the presence or absence of leakage of gas or the like from such pipes and a position of the leakage.
Embodiment according to the present invention will be described below referring to the drawings. It should be understood that the present invention is not limited to the following embodiment, and modifications, improvements, and the like can be made as appropriate based on ordinary knowledge of a person skilled in the art without departing from the spirit of the present invention.
An embodiment of a rubber product according to the present invention includes a gas chromic material that changes a color thereof reversibly or changes an electric resistance value thereof, due to oxidation-reduction reaction. This rubber product can easily and accurately detect the presence or absence of leakage and a position of leakage.
The gas chromic material is a material that changes a color thereof reversibly or changes an electric resistance value thereof, due to oxidation-reduction reaction. Such a gas chromic material can be, for example, transition metal oxides such as tungsten oxide, vanadium oxide, niobium oxide, tantalum oxide, zirconium oxide, and chromium oxide, as described below. In order to accelerate the reaction, it is preferable to further load a catalyst such as platinum or chromium. For example, tungsten oxide and platinum are more preferably contained.
In the rubber product according to the present invention, light transmittance is changed (that is, transmittance in a specific wavelength band is greatly changed) due to oxidation-reduction reaction, which leads to change of appearance of a color thereof.
The rubber used as the material of the rubber product may be any conventionally known rubber, and usage of the rubber product is not particularly limited, and may be used as a sealing product such as a sealing member.
The rubber product according to the present invention can be produced, for example, as follows. First, a solid material containing platinum (Pt) and tungsten oxide (WO3) is synthesized by a conventionally known process (see, for example, JP 2017-181996A). The synthesized solid material is then ground. Here, examples of grinding means for the solid material include a bead mill, a jet mill, and a mortar. In order to improve the dispersibility of Pt and WO3 in the rubber product, a surface treatment may be performed using any dispersant.
The ground solid material (sometimes referred to as “Pt/WO3”) is then mixed with raw rubber along with other ingredients. The timing of the mixing is not particularly limited as long as it is at a stage before the rubber is vulcanized, such as at the time of kneading or at the time of promoting for introduction of a vulcanizing agent. The mixing device is not particularly limited, and a general device used for kneading rubber such as a kneader or a roll can be employed. When liquid rubber is used as the raw rubber, it may be mixed manually without using a device. Then, a rubber material in which Pt/WO3 is mixed is formed into an arbitrary form and vulcanized, whereby the rubber product can be produced.
An embodiment of a rubber product according to the present invention is a sealing product 10 shown in
Such a sealing product 10 can easily and accurately detect the presence or absence of leakage and a position of leakage. The sealing product 10 is a device for preventing leak of a fluid from the inside to the outside of a machine, and specifically the sealing product 10 can be an oil seal, a rubber gasket, an O ring, and the like.
Here, a sealing product such as an O-ring or a gasket is a device that is installed at a bond position between two machines to prevent a fluid or gas inside the machines from leaking to the outside. However, there is a concern that leakage may occur due to insufficient airtightness caused by such as disturbances and sudden defects.
When leakage occurs, its cause is investigated and countermeasures are taken, which requires identification of the leak position. However, when the sealed medium is a colorless gas (e.g., hydrogen, etc.), it tends not to be easy to accurately identify the leak position visually.
Therefore, a method of observing variation in an applied pressure value, a method of measuring a flow rate of an applied gas, and the like are generally employed. However, in these methods, only the presence or absence of leak is determined, and there is a tendency that the leak position cannot be sufficiently specified.
For this reason, as a method of specifying a leak position, there is a method of finely dividing a pressure measurement area and specifying a leak position from individual pressure fluctuations. However, it cannot be determined which part of the contact line where the leak occurs. Therefore, as a method of inspecting a leak position more finely, there is also a method of specifying a leak position by applying a gas such as He and scanning a probe connected to a detector such as a leak detector in the vicinity of the test object. However, even in this method, since He diffuses prior to reaching the probe, it tends to be difficult to measure when an amount of leak is small as in the case of a sealing product.
Next, as a method for visualizing a leak position, there is a foaming method in which an inspection liquid is applied to a seal portion, tightened with a transparent member such as an acrylic plate, and bubbles generated when pressure is applied are observed to identify the leak portion. However, even in this method, when an amount of leak is small, there is a concern that it is difficult to observe the bubbles, or that the inspection liquid itself becomes an auxiliary agent for sealing and stops the leak.
In addition, among gases that are sealed media, there are gases that are highly permeable for objects, such as H2 and He. Of these gases, H2 is widely known to be at risk of explosion due to reaction with O2. Therefore, it is difficult to completely eliminate leakage of H2 to the outside, but from the viewpoint of ensuring safety, it is required to keep an amount of leak to be minimum. In particular, a sealing product used to fill a gap between fastened portions is often formed by an elastomer with a relatively low density, which may result in transmission leakage.
In the present invention, it has been found that a sealing product itself can be utilized as a sensor by mixing a gas chromic material with a polymer material such as a resin.
When the sealing product itself is used as a sensor in this manner, it becomes easy to accurately identify a part where leak occurs, and further it is possible to save a trouble for installing another sensor device. That is, when a rubber product (specifically, a sealing product) according to the present invention is used, it is possible to detect leak while maintaining usage of members around it as they are.
Further, since the gas chromic material has reversibility, the gas chromic material can be used repeatedly in the same product, and thus is excellent in economical efficiency. Note that the time of the reversible reaction can be adjusted by using a polymer material having a low gas permeability or by forming two layers of a polymer material on top of each other. As the polymer material to be used, a material suitable for specifications and an environment for observing leak can be appropriately selected.
In addition, small leak (e.g., very small leak such as below 0.1 cc/min) can also be detected in the present invention. This is because a detection method such as image processing of an image acquired by a camera or acquisition of an electric signal can be selected, whereby gas chromism color development performance (color tone and maintenance time) and resistance value change performance can be controlled in a use environment.
Furthermore, the sealing product of the present embodiment can be applied not only to specify a leak position but also to visualize a flow of gas. For example, it is possible to apply the sealing product of the present embodiment to visualization of unevenness of a flow rate of hydrogen flowing through a power generation surface of a cell for a fuel cell. That is, there is a flow of hydrogen inside the sealing product, the closer to a region, where a flow rate of hydrogen is large, an inner surface portion of the sealing product is, the more strongly (more darkly) a color of the inner surface portion of the sealing product changes, and the farther from the region having the large flow rate of hydrogen an inner surface portion of the sealing product is, the more lightly a color of the inner surface portion of the sealing product changes. Therefore, a check of a degree of discoloration of an inner surface portion of the sealing product makes it possible to obtain a distribution of a flow rate of hydrogen.
Such a sealing product (i.e., rubber product) can be used as a sealing member in contact with hydrogen gas and can be applied, for example, to a sealing member in a cell for a fuel cell and to a seal or a gasket for an engine that burn (explode) hydrogen, a hydrogen tank/pipe, and a hydrogen pipe in a plant.
When an elastic material in which a gas chromic material is mixed is applied to a sealing product (a sealing member used in a cell for a fuel cell and in contact with hydrogen in the cell), it is considered that hydrogen can be converted into water in the rubber (sealing product) due to an oxidation-reduction reaction caused by the gas chromic material. That is, since it is conceivable that hydrogen is converted into water before the hydrogen leaks to the outside, it is possible to prevent hydrogen leak and reduce a risk of an accident due to hydrogen leak. Here, it is considered that there is a small amount of oxygen penetrate inside the sealing product on the low-pressure side of the sealing product, and a part of hydrogen immediately before leak is converted to water by the reduction reaction with the oxygen.
Further, there is a process of confirming the presence or absence of leak from a sealing product at a manufacturing stage of the sealing product, but in this confirmation process, it is desired that the presence or absence of leak can be accurately detected.
In the sealing product of the present embodiment, a gas chromic material is contained in the sealing product itself, and the sealing product itself directly changes in response to leak, so that a position of the leak can be detected more accurately and easily. In addition, when hydrogen gas is used, hydrogen leak can be prevented, and a risk of an accident due to hydrogen leak can be reduced. Here, when a hydrogen detection sheet (for example, refer to Patent Document 2) is separately used, a gap may occur between a leak detection target and the hydrogen detection sheet, and in this case, there is a concern that a position of leak cannot be accurately detected. That is, since the part where the gap exists is widely discolored, the presence of the leak can be recognized, but there is a tendency that it is insufficient to accurately confirm the location of the leak. On the other hand, in the sealing product of the present embodiment, since the leak detection target (the sealing product itself) is discolored as described above due to the occurrence of the leak, the position of the leak can be accurately grasped. In addition, since adoption of a separate member such as the above-mentioned hydrogen detection sheet for a leak detection target and direct attachment of the separate member to the leak detection target are avoided, it is possible to avoid damaging the inspection target (that is, the leak detection target) at the time of seal inspection.
The sealing product of the present embodiment has elasticity, and the material thereof is not particularly limited, and examples thereof include vinyl methyl silicone rubber (VMQ), vinylidene fluoride rubber (FKM), ethylene propylene diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), and the like. The sealing product of the present embodiment may be transparent. If it is transparent, leak due to cracks or the like inside the sealing product can be reliably confirmed from the outside by the discoloration. As long as the inside of the sealing product can be visually recognized, it can be colored or colorless, but it is preferable that it is colorless. In the present specification, being “transparent” includes being transparent to the extent that light is transmitted (being translucent) in addition to being completely transparent.
The gas chromic material is a material that changes a color thereof reversibly or changes an electric resistance value thereof, due to oxidation-reduction reaction. Such a gas chromic material can be, for example, transition metal oxide such as tungsten oxide, vanadium oxide, niobium oxide, tantalum oxide, zirconium oxide, and chromium oxide. In order to accelerate the reaction, it is preferable to further load a catalyst such as platinum or chromium. For example, tungsten oxide and platinum are more preferably contained.
Note that the reaction of the gas chromic material is a reversible oxidation-reduction reaction, and the higher the hydrogen concentration is, the higher change performance thereof is such that the more easily a color thereof develops or the lower an electric resistance value thereof is. Further, the higher the oxygen concentration is, the lower change performance thereof about development of a color thereof or an electric resistance value thereof. In addition, the higher the temperature is, the more easily the reaction is activated, which leads to increase of responsiveness about development of a color thereof or an electric resistance value thereof. Moreover, also when an amount of the gas chromic material contained in the polymer material is increased, the change performance is increased.
There is no particular limitation on a condition in which the sealing product 10 is used, and the sealing product 10 is used in a temperature environment of, for example, 60° C. to 230° C. and accurately detects the presence or absence of leakage and a position of leakage in such a temperature environment.
The fluid to be detected is not particularly limited, and an example thereof is a gas other than the atmosphere, specifically hydrogen or the like. For example, hydrogen is used as a fuel gas of a solid polymer fuel cell, and the hydrogen is sealed in the cell using a sealing product. There is also a concern that such hydrogen may leak very slightly when the battery is subjected to shock, vibration, or the like. Therefore, by using the sealing product of the present embodiment, it is possible to reliably and easily detect the presence or absence of leak and a position of leak.
As shown in
The test apparatus 100 can be used to test the presence or absence of leak in the sealing product 10, and when the sealing product 10 has leak, a discolored portion 27 is confirmed over the entire width direction of the sealing product 10, as shown in
After the sealing product 10 is disposed in a fastening portion such as a pipe, it is possible to easily confirm leak due to aging or the like which occurs during use, and a position where the leak occurs.
One embodiment of a test jig according to the present invention is a test jig 50 shown in
The test jig 50 for a sealing member can easily and accurately detect the presence or absence of leakage in the sealing member and a position of leakage. In addition, since in the test jig 50, the sealing member is mounted on the mounting table 31 at the time of the seal inspection, it is possible to avoid damaging the inspection target at the time of the seal inspection.
Here, as shown in
In the same way as the above mentioned sealing product, the sealing member is a device for preventing leak of a fluid from the inside to the outside of a machine, and specifically the sealing member can be an oil seal, a rubber gasket, an O ring, and the like.
The mounting table 31 has a mounting surface 31a on which the sealing member 15 is mounted. As long as the mounting table 31 has a mounting surface 31a as described above, its material, shape, size, and the like are not particularly limited.
The material of the mounting table 31 is not particularly limited, and any material may be used as long as it does not leak a test fluid when the mounting table 31 holds the sealing member. Examples of the material of the mounting table 31 include a resin, glass, steel material such as stainless steel, and aluminum.
The upper disposed member 33 is disposed on the upper side of the sealing member mounted on the mounting table 31. A material, shape, size, and the like of the upper disposed member 33 are not particularly limited and can be appropriately determined.
A material of the upper disposed member 33 is not particularly limited in the same way as the mounting table 31 as long as the material does not allow a test fluid to leak when the sealing member is held. Examples of the material of the upper disposed member 33 include resin, glass, a steel material such as stainless steel, and aluminum.
More specifically, the upper disposed member 33 may be made of resin or glass, and in the case of resin, may be made of a transparent material. Specific examples of the transparent material include acrylic resins and polycarbonates. When the upper disposed member 33 is transparent as described above, a state of the sealing member 15 during a test can be checked and recorded by a photographing unit (photographing unit 23) such as a camera, from the upper side of the test jig 50.
The leakage detection member 35 is positioned on the outer side of the sealing member 15 mounted on the mounting table 31, and includes a gas chromic material that changes a color thereof reversibly or changes an electric resistance value thereof, due to oxidation-reduction reaction. Note that the leakage detection member 35 and the sealing member 15 may be disposed so as to be in contact with each other or may be disposed so as to be spaced apart from each other by a gap.
A material of the leakage detection member 35 is not particularly limited, but may be, for example, resin, rubber, or the like.
A position of the leakage detection member 35 is not particularly limited as long as it is located on the outer side of the sealing member 15. For example, the leakage detection member 35 may be positioned, as a sheet member 37, on the mounting table 31 or the upper disposed member 33, or may be positioned, as a protrusion 39, on the mounting table 31. The leakage detection member 35 may be both the sheet member 37 and the protrusion 39. In this way, it is possible to more accurately confirm the presence or absence of leak and a position of leak.
The test jig 50 may further include a sheet member 37 having a sheet shape that is disposed on at least one side of the mounting table 31 side and the upper disposed member 33 side of the sealing member 15, and a sealing member is disposed to be positioned on the outer side of the sheet member 37 during a leak test for the sealing member. The sheet member 37 on the at least one side may constitute at least a part of the leakage detection member 35. Here, the sheet member 37 has a sheet shape, which includes “a shape of a thin film”.
A state in which the sheet member 37 is positioned is not particularly limited, and a range where the sheet member 37 is positioned (a film forming range when the sheet member having a shape of a thin film is formed) may be the entire surface of the mounting table 31 or the like, or a part of the entire surface of the mounting table 31 such as an edge (a boundary) region thereof with a contact surface of the sealing member.
Note that the sheet member 37 may be a single layer sheet, or a multi-layer sheet in which a thin film in which the gas chromic material is dispersed using a polymer material as a binder, and a further polymer material film on the thin film are arranged may be used.
The test jig 50 may further include a protrusion 39 that protrudes from the mounting surface 31a of the mounting table 31, and the protrusion 39 may constitute at least a part of the leakage detection member 35 when the sealing member 15 is disposed in contact with the inner surface of the protrusion 39 to be tested.
The protrusion 39 may be a continuous ring as shown in
The protrusion 39 may be formed integrally with the mounting table 31 or may be formed separately from the mounting table 31. In the case of being formed separately from the mounting table 31, it is preferably fixed to the mounting table 31.
The protrusion 39 may be made of an elastic material, and the material thereof is not particularly limited, and examples thereof include fluororubber and the like.
One embodiment of a test apparatus according to the present invention is a test apparatus 200 for a sealing member shown in
The test apparatus 200 includes the above-described test jig 50, a photographing unit that records changes of the leakage detection member 35 in the test jig 50, a test fluid supplying unit 25, and a leak amount measuring unit 60. The test jig 50 and the test fluid supplying unit 25 are connected by pipes. The test jig 50 functions as a test unit. The test fluid supplying unit 25 is, for example, a reservoir for supplying a test fluid such as hydrogen to the test jig 50 which is a test unit.
The test apparatus 200 for a sealing member includes the above-described test jig 50, whereby the presence or absence of leakage in the sealing member 15 and a position of leakage can be easily and accurately detected, and further, the leak amount measuring unit 60 can measure a leak amount of the leaking fluid, thereby improving effect of the leakage countermeasure.
When a change in color of the sealing member 15 is checked, there are a first method in which the test jig 50 is disassembled after the test to check it, and a second method in which it is checked during the test by using the test jig 50 a part of which is made of a transparent member. In addition, when it is difficult to visually determine a change in color, it is possible to identify a leak position by analyzing an image captured by the imaging unit 23 such as a camera.
In the test apparatus 200 shown in
The imaging unit 23 is not particularly limited as long as it is capable of recording the presence or absence of leakage and a position of leakage in the sealing member 15, and a predetermined device can be adopted as appropriate.
The leak amount measuring unit 60 measures a leak amount of the leaking fluid, and includes a dispersed rubber sheet 38 that is a probe disposed between the sealing member 15 to be tested and the protrusion 39 (the leak detecting member 35). Specifically, the leak amount measuring unit 60 may be a pressure gauge, a flow rate gauge, a leak detector, or the like, and a leak amount may be detected by a change in an electric resistance value of the dispersed rubber sheet 38. Incidentally, it is not possible to grasp a leak amount by the above-described test jig 50 alone in which only a change in color can be confirmed, but if combined with the leakage amount measuring unit 60, it is possible to distinguish a portion where a large leak amount of leak is likely to occur and a portion where minute leak is likely to occur. Since cause of leak may be different depending on a leak amount, use of the combination of the leakage amount measuring unit 60 and the test jig 50 makes it possible to take more effective countermeasures against leak.
A leak detection member according to the present invention includes a cylindrical elastic portion having a cylindrical shape that is formed by an elastic material including a gas chromic material that changes a color thereof reversibly or changes an electric resistance value thereof, due to oxidation-reduction reaction, and at least one pair of electrodes that are disposed on an outer peripheral surface of the cylindrical elastic portion. Such a leak detection member can easily and accurately detect the presence or absence of a leak of gas or the like from a pipe or the like and a position of leak.
Such a leak detection member 70 can easily and accurately detect the presence or absence of leak of gas or the like from a pipe or the like and a position of leak.
Here, as shown in
The cylindrical elastic portion 72 has a cylindrical shape and is formed by an elastic material including a gas chromic material that changes a color thereof reversibly or changes an electric resistance value thereof, due to oxidation-reduction reaction
The cylindrical elastic portion 72 is not particularly limited in a size thereof and a shape of an opening thereof as long as it is cylindrical, and they can be appropriately determined in accordance with a shape and a size of a pipe or the like to which the leak detection member 70 is attached. Specifically, the cylindrical elastic portion 72 may have a circular cylindrical shape or the like. The cylindrical elastic portion 72 may have slits or notches formed in the central axis direction thereof. This is because formation of the slits and the notches facilitates piping work or the like. Here, it should be noted that the cylindrical elastic portion 72 that lacks a part thereof due to formation of a notch should be taken as still having a “cylindrical shape”.
A material of the elastic material of the cylindrical elastic portion 72 is not particularly limited, and examples thereof include vinyl methyl silicone rubber (VMQ), vinylidene fluoride rubber (FKM), ethylene propylene diene rubber (EPDM), and acrylonitrile-butadiene rubber (NBR).
The pair of electrodes 80 are respectively disposed on one end surface 73 side and on the other end face 75 side of an outer peripheral surface of the cylindrical elastic portion 72.
As for the pair of electrodes 80, conventionally known electrodes can be employed, and the positions of the electrodes are not particularly limited and can be appropriately determined.
Note that each electrode may be an annular electrode disposed along the outer peripheral surface of the cylindrical elastic portion 72, and may lack a part of the annular structure.
As shown in
A rubber product according to the present invention can be adopted as a sealing member in each of joint portions (fastening portions) of pipes or the like. A test jig and a test apparatus for a sealing member according to the present invention can be used as a jig or an apparatus for testing the presence or absence of leakage in the sealing member in each of the joint portions of the pipes or the like. A leak detection member according to the present invention can be used to detect the presence or absence of leakage in each of the joint portions of the pipes or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-178658 | Nov 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/037574 | 10/7/2022 | WO |
