Patent Application
20210355926
The present invention relates to a gas compressor that compresses gas and to a method for manufacturing the gas compressor.
A gas compressor that compresses gas includes a cylinder liner and a piston member. The piston member includes a piston and piston rod. The piston reciprocates in an inner space of the cylinder liner. The piston rod is connected to the piston. Resin-made rings that generate low friction force are used at parts where the piston member contacts with the cylinder liner. The resin-made rings are a piston ring, a rider ring, rod packing, and the like, for example.
The rider ring is a sliding member for preventing metal contact between the piston and the cylinder liner. The piston ring is a sliding member having a function of sealing for preventing leakage of compressed gas. These sliding members are provided on an outer circumference of the piston. The rod packing is a sliding member having a function of sealing for preventing gas leakage along the piston rod.
An oil-free gas compressor is used as the gas compressor in order that gas compressed by the gas compressor is prevented from containing an oil component. No lubrication oil is thus supplied to surfaces of the piston ring, the rider ring, and the rod packing. For this reason, the piston ring, the rider ring, and the rod packing are formed of a material having a low friction coefficient to reduce friction with a subjected-to-sliding member, i.e., a reception member that receives sliding. Examples used as this material are resins such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), and polyimide. These materials have low friction with the metal-made reception member, thus lengthening wear lives.
A reciprocation compressor used under a high-pressure operation condition includes a sliding surface. Wear resistance of the sliding surface can be maintained for a long period of time by a known sealing element (Japanese Patent Application Laid-open Publication No. 2011-38107), for example.
Specifically, the sealing element is constituted by a wear-resistant polymer matrix. Examples of the polymer matrix include PEEK, polybutadiene-styrene (PBS), and PTFE. The polymer matrix includes a plurality of dispersed microcapsules inside. The microcapsules enclose lubricants inside.
However, the sealing element cannot be used in an oil-free gas compressor because of the lubricants dispersed inside the sealing element. Particularly when hydrogen is compressed to high pressure by the compressor and charged in a fuel cell vehicle, application of the above-described sealing element is inappropriate because of a request for high-purity quality of the hydrogen.
An object of the present disclosure is, in view of the above, to provide a gas compressor and a gas compressor manufacturing method that enable compressed gas of high purity to be sent out when compressing the gas and can extend a sliding-member replacement life attributed to wear.
One aspect of the present disclosure is a gas compressor that compresses gas. The gas compressor includes:
a cylinder liner;
a piston member including,
An amorphous carbon film is formed on a sliding surface of each of the first sliding member and the reception member.
A carbon content in the amorphous carbon film formed on each of the sliding surfaces is larger in a surface part than in an inner part on an inner side of the surface part, the surface part and the inner part belonging to the amorphous carbon film.
Preferably, the first sliding member is formed of a resin material containing an additive that contains sulfur, the amorphous carbon film formed on each of the sliding surfaces is free of sulfur, and a pipe connected to a hydrogen gas source is connected to a compression chamber of the gas compressor.
Preferably, the first sliding member is formed of a resin material containing an additive that contains sulfur, and the amorphous carbon film formed on each of the sliding surfaces is free of sulfur.
Preferably, the first sliding member is formed of a resin material containing fluorine, and a fluorine content in the amorphous carbon film formed on each of the sliding surfaces is smaller in the surface part than in the inner part on an inner side of the surface part.
Preferably, the first sliding member is a desulfurized member.
Another aspect of the present disclosure is a gas compressor that compresses gas. The gas compressor includes:
a cylinder liner;
a piston member including
a first sliding member made of a resin, having a ring shape, and provided on one of the piston member and the cylinder liner, the first sliding member configured to slide relatively against a reception member while another of the piston member and the cylinder liner serves as the reception member that receives sliding; and
a second sliding member having a ring shape and provided on the one of the piston member and the cylinder liner, the second sliding member configured to slide relatively against the reception member and thereby supply graphite for forming an amorphous carbon film, a graphite content in the second sliding member being larger than in the first sliding member.
Still another aspect of the present disclosure is a method for manufacturing a gas compressor configured to compress gas. The gas compressor includes: a cylinder liner; a piston member including a piston configured to reciprocate in an inner space of the cylinder liner, and a piston rod connected to the piston; and a first sliding member made of a resin, having a ring shape, and provided on one of the piston member and the cylinder liner, the first sliding member configured to slide relatively against a reception member while another of the piston member and the cylinder liner serves as the reception member that receives sliding,
The method for manufacturing the gas compressor includes:
forming a carbon film on a surface of the first sliding member or the reception member, the carbon film containing carbon as a main component; and
driving the piston member so as to slide the first sliding member relatively against the reception member, thereby causing an amorphous carbon film to be formed, from the carbon film, on a sliding surface of the first sliding member and a sliding surface of the reception member, the amorphous carbon film being more hardened than the carbon film.
Yet another aspect of the present disclosure is a method for manufacturing a gas compressor configured to compress gas. The gas compressor includes: a cylinder liner; a piston member including a piston configured to reciprocate in an inner space of the cylinder liner, and a piston rod connected to the piston; a first sliding member made of a resin, having a ring shape, and provided on one of the piston member and the cylinder liner, the first sliding member configured to slide relatively against a reception member while another of the piston member and the cylinder liner serves as the reception member that receives sliding; and a second sliding member made of a resin, having a ring shape, and configured to slide relatively against the reception member, a carbon content in the second sliding member being larger than in the first sliding member.
The method for manufacturing the gas compressor includes driving the piston member so as to slide the first sliding member and the second sliding member relatively against the reception member, thereby causing an amorphous carbon film to be formed on a sliding surface of the reception member, a sliding surface of the first sliding member, and a sliding surface of the second sliding member, the amorphous carbon film being formed of carbon derived from the second sliding member.
Preferably, a graphite content in the second sliding member is larger than in the first sliding member, and the second sliding member supplies the graphite, thereby forming the amorphous carbon film.
Preferably, the method includes exposing the second sliding member to a hydrogen atmosphere before incorporating the second sliding member into the gas compressor.
Preferably, the method includes exposing the first sliding member to a hydrogen atmosphere before incorporating the first sliding member into the gas compressor.
Preferably, the first sliding member is formed of a resin material containing an additive that contains sulfur, and the amorphous carbon film formed on each of the sliding surfaces is free of sulfur.
Preferably, the gas compressor sucks hydrogen gas, compresses the sucked hydrogen gas, and sends out the compressed hydrogen gas.
The gas compressor and the gas compressor manufacturing method described above enable compressed gas of high purity to be sent out, and can extend a sliding-member replacement life attributed to wear.
The following describes a gas compressor according to one embodiment, with reference to the drawings.
The gas compressor 10 includes a cylinder 16 and a piston 18. The cylinder 16 includes a compression chamber 14 (an inner space of the cylinder) connected to a tank (gas source) via a suction pipe 12. The piston 18 is arranged inside the cylinder 16 so as to be reciprocally slidable. Specifically, the cylinder 16 includes a cylinder liner inside, and the piston 18 reciprocates in an inner space of the cylinder liner. Reciprocal sliding of the piston 18 causes gas stored in the tank such as hydrogen gas to be sucked into the compression chamber 14 of the cylinder 16 and compressed to high pressure (e.g., in a range of 20 to 80 MPa). A cylinder head 24 is provided on an upper side of the compression chamber 14. The cylinder head 24 is provided with a suction valve and a discharge valve for gas. The compressed gas is sent out through the discharge valve and a discharge pipe 20. The discharge pipe 20 is provided with a cooler 22 for cooling the compressed gas. The tank is a hydrogen gas source that stores hydrogen gas.
The drive unit 3 includes a piston rod 31, a crosshead 33, a connecting rod 34, a crankshaft 36, a power transmission mechanism 37, and a drive motor 38.
One end of the piston rod 31 is connected to a base end of the piston 18.
The crosshead 33 is connected to the other end of the piston rod 31 and arranged inside a crosshead guide 32 so as to be reciprocally slidable.
One end of the connecting rod 34 is connected to the crosshead 33.
The other end of the connecting rod 34 is connected to the crankshaft 36. The crankshaft 36 is supported by rotary bearings of a crankcase 35.
The power transmission mechanism 37 includes pulleys and a belt.
The drive motor 38 is connected to the crankshaft 36 via the power transmission mechanism 37 so as to enable power transmission. Rotational force of the drive motor 38 accordingly causes rotation of the crankshaft 36 and reciprocal sliding of the crosshead 33 in the crosshead guide 32, consequently causing reciprocal sliding of the piston 18 inside the cylinder 16.
The piston 18 is provided with a plurality of piston rings 52. The piston ring 52 is provided on the piston 18 so as to prevent compressed gas inside the compression chamber 14 from leaking toward rod packing 54. The piston ring 52 is a ring-shaped member made of a resin and closely contacting with the cylinder liner 17. The piston ring 52 slides relatively against the cylinder liner 17 while the cylinder liner 17 serves as a reception member. The piston ring 52 is arranged in a groove provided on the outer circumference of the piston 18.
The cylinder 16 is provided with a plurality of pieces of the rod packing 54. The rod packing 54 is a ring-shaped member made of a resin. The rod packing 54 is provided on a bottom side so as to prevent compressed gas inside the compression chamber 14 from leaking to a lower side in
In other words, the rider ring 50, the piston ring 52, and the rod packing 54 are the ring-shaped resin-made sliding members that slide relatively against the reception members while the cylinder liner 17 and the piston rod 31 serve as the reception members.
The sliding member is made of a resin to reduce a coefficient of friction with the reception member. Examples of the resin used for the sliding member include polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), and polyimide. These resins each contain an additive containing a sulfur component to improve durability. Examples of the additive include a polyphenylene sulfide (PPS) resin and molybdenum disulfide.
An amorphous carbon film is formed on sliding surfaces of both the sliding member and the reception member.
A carbon content in the amorphous carbon film formed on each of these sliding surfaces is larger in its surface part than in its inner part on an inner side of the surface part. The amorphous carbon film has a high affinity with the resin and is less likely to be peeled off than a metal-made member. This amorphous carbon film is diamond-like carbon and has high hardness. The diamond-like carbon has a low friction coefficient. The amorphous carbon film accordingly has a low coefficient of friction with the reception member, resulting in that a sliding-member life length attributed to wear is extended.
Such an amorphous carbon film is made by forming a carbon film and driving the piston 18. Specifically, the carbon film yet to turn into the amorphous carbon film is formed on one or both of the sliding surface of the sliding member and the sliding surface of the reception member, and the piston 18 is then driven inside the cylinder liner 17 for hydrogen gas as compression target gas, as described below.
A composition of the amorphous carbon film can be examined by X-ray photoelectron spectroscopy (XPS). The XPS is measurement for a sample on which an amorphous carbon film has been formed. The measurement includes irradiating the sample with an X ray in a vacuum, thereby causing photoelectrons to be emitted from an inside of the sample. The measurement includes measuring kinetic energy of the emitted photoelectrons by spectroscopy, thereby enabling analysis of constituent elements of the sample and electron states of the constituent elements.
The line L1 in
The region in the vicinity of 170 [eV] illustrated in
Thus, even when the sliding member is formed of a resin material containing fluorine, a fluorine content in the amorphous carbon film formed on each of the sliding surfaces is preferably smaller in its surface part than in its inner part on an inner side of the surface part to prevent the amorphous carbon film from containing impurities such as fluorine and sulfur. Even when the sliding member is formed of a resin material containing an additive that contains sulfur, the amorphous carbon film formed on each of the sliding surfaces is preferably free of sulfur.
Methods as illustrated in
Specifically, a carbon film containing carbon as a main component (the main component is a component whose percentage mass content exceeds 50%) is formed on a surface of the sliding member or the reception member. The piston member is then driven, causing the sliding member to slide relatively against the reception member. As a result, an amorphous carbon film hardened more than the carbon film is formed on the sliding surface of the sliding member and the sliding surface of the reception member.
Thereby, a carbon content in the amorphous carbon film can be made larger in its surface part than in its inner part on an inner side of the surface part.
Also in this case, forming the carbon film 62 on the sliding surface of the cylinder liner 17 enables the amorphous carbon film as diamond-like carbon to be efficiently formed on an outer circumferential surface of the piston ring 52 and an inner circumferential surface of the cylinder liner 17.
When the gas compressor is made to operate without formation of either the carbon film 60 or the carbon film 62 on the sliding surface of the piston ring 52 or the cylinder liner 17, the amorphous carbon film having a low friction coefficient fails to be formed on the entire sliding surfaces by the tribochemical reaction. This applies even when wear of the piston ring 52 made of a resin results in separation of a carbon component included in additive components of the resin. In addition, the amorphous carbon film of which carbon content is higher in its surface part than in its inner part as illustrated in
A surplus of the carbon film 60 does not constitute the amorphous carbon films, and is sent out to an outside along with generated compressed gas.
Such a carbon film 60 or 62 may be formed by adhering of flake graphite powder or amorphous graphite powder. The flake graphite powder and the amorphous graphite powder are obtained by pulverizing and granulating natural graphite. The carbon component of the carbon film 60 or 62 is not limited to graphite carbon, and may be glassy carbon. The carbon film 60 or 62 can be formed by making powder carbon adhere to the sliding surface of the piston ring 52 or the cylinder liner 17, or also by applying and drying a slurry-like liquid that contains graphite or the like. The carbon film 60 or 62 can also be formed by chemical vapor deposition (CVD).
According to one embodiment, the piston rings 50 and 52 are preferably desulfurized members from the viewpoint of preventing compressed gas from containing impurities. Before the piston rings 50 and 52 are incorporated into the gas compressor, the piston rings 50 and 52 are preferably subjected to the desulfurization treatment. For example, this treatment exposes the piston rings 50 and 52 to a hydrogen atmosphere. Sulfur that is among sulfur contained in PPS or the like in the piston rings 50 and 52 and that is contained in low molecules reacts with hydrogen in the hydrogen atmosphere. The sulfur thereby turns into hydrogen sulfide gas, and is then easily released to an outside. Removing such sulfur from the piston rings 50 and 52 can suppress compressed gas from containing, as impurities, the gas that contains the sulfur derived from the piston rings 50 and 52. Particularly, when the gas compressor is driven for hydrogen gas as gas to be compressed, sulfur in the piston rings 50 and 52 easily reacts with the hydrogen so as to generate a hydrogen sulfide gas to be contained as impurities in the hydrogen gas. For example, when the compressed hydrogen gas is used in a fuel cell vehicle, the standard (ISO-14687-2: 2012) requests that a concentration (a value determined based on that all sulfur compounds are regarded as hydrogen sulfide) of total sulfur compounds be equal to or smaller than 0.004 ppm. From this point, the piston rings 50 and 52 are preferably desulfurized members. For example, the piston rings 50 and 52 are preferably exposed to a hydrogen atmosphere before being incorporated into the gas compressor. Further, the rider ring 50 and the rod packing 54 are also preferably desulfurized members for the similar reason. For example, the rider ring 50 and the rod packing 54 are preferably exposed to a hydrogen atmosphere before being incorporated into the gas compressor. The hydrogen atmosphere is an atmosphere of 200° C. and 5.5 MPa, for example. The piston rings 50 and 52, the rider ring 50, and the rod packing 54 are left in the hydrogen atmosphere for 7 hours, for example. As a hydrogen atmosphere pressure and a hydrogen atmosphere temperature are higher, reaction between the hydrogen and the sulfur is more promoted. A high pressure and a high temperature are thus preferable. When a hydrogen atmosphere temperature is excessively high, resins of the piston rings 50 and 52, the rider ring 50, and the rod packing 54 are, however, easily damaged. From this point, a hydrogen atmosphere temperature is preferably in a range of 100° C. to 200° C.
As described above, the piston rings 50 and 52, the rider ring 50, and the rod packing 54 are desulfurized, for example, exposed to a hydrogen atmosphere. This can significantly postpone a timing of replacing a filter. The filter conventionally uses activated carbon or the like to secure high-purity compressed gas.
According to one embodiment, the sliding member is formed of a resin material containing fluorine, as described above. However, a fluorine content in the amorphous carbon film formed on each of the sliding surfaces is smaller in its surface part than in its inner part on an inner side of the surface part. The surface part of the amorphous carbon film accordingly contains less fluorine than the inner part, and contains a large content of carbon. The amorphous carbon film containing a small content of impurities can be thus formed, and a wear property is also improved.
According to one embodiment, the sliding member is formed of a resin material containing an additive that contains sulfur, while the amorphous carbon film formed on each of the sliding surfaces is free of sulfur. Thus, the amorphous carbon film containing a small content of impurities, i.e., a diamond-like carbon film can be formed, and a wear property is improved.
Further, the sliding member is a desulfurized member, for example, a member that has been previously exposed to a hydrogen atmosphere. The sliding member contains, in the resin, the additive containing sulfur. The additive is, for example, a reinforcing material for improving wear resistance. In some cases, a part of this sulfur, however, turns into impurity gas in compressed gas. Particularly when hydrogen gas is the compressed gas, a part of the sulfur easily reacts with the hydrogen to turn into hydrogen sulfide gas. For this reason, the sliding member is desulfurized in order that impurity gas is then hardly generated. For example, the sliding members that have been previously exposed to a hydrogen atmosphere are used as the rider ring 50, the piston ring 52, and the rod packing 54.
According to one embodiment, a ring-shaped sliding member (second sliding member) of which carbon content is larger than that of the different sliding member (first sliding member) is provided also as the sliding member. The ring-shaped sliding member slides relatively against the reception member. The ring-shaped sliding member containing a large content of carbon is worn by sliding, thereby separating a resin. A carbon component in the separated resin can stably form into the amorphous carbon films of a certain film thickness by the tribochemical reaction.
Further, the ring-shaped sliding member (second sliding member) containing a large content of carbon is preferably a desulfurized member. For example, the ring-shaped sliding member is preferably exposed to a hydrogen atmosphere before being incorporated into the gas compressor, from the viewpoint that compressed gas can be thereby prevented from containing impurities.
The gas compressor and the gas compressor manufacturing method according to the present invention are described above in detail. As a matter of course, the present invention is, however, not limited to the above-described embodiments. Various improvements and modifications may be made without departing from the essence of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-005223 | Jan 2019 | JP | national |
This application is a National Stage Entry application of PCT International Application No. PCT/JP2020/000944, filed on Jan. 15, 2020, which claims the priority benefit of Japanese Patent Application No. 2019-005223, filed on Jan. 16, 2019, the entire contents of both of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/000944 | 1/15/2020 | WO | 00 |
