JP2007032359A - Oscillation type compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent stick or the like of a joint due to welding by changing material composition of a piston ring and increasing pressure of compressed fluid. <P>SOLUTION: The piston ring 21 is installed in a ring groove 18A of a piston part 18 to seal a gap between the piston part 18 and a cylinder 7 even when an oscillation piston 14 of the piston part 18 reciprocates while oscillating in the cylinder 7. The piston ring 21 contracts and expands in relation to the ring groove 18A by approach and separation of a joint part. Material of the piston ring 21 is modified PTFE of which grade name is called 70-J. In an embodiment, 10-30 weight% powder material composed of copper or bronze, 5-15 weight% nodular carbon and 3-7 weight% molybdenum disulfide are contained in the material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oscillating compressor that is suitably used to compress a fluid such as air.

  Generally, as a small oil-free compressor that compresses fluid such as air, a swinging piston called a rocking piston is used, and the swinging type is configured to reciprocate while swinging in a cylinder. A compressor is known (see, for example, Patent Documents 1 and 2).

  This type of conventional oscillating compressor includes a cylindrical cylinder, an oscillating piston that reciprocates while oscillating in the cylinder, and that defines a compression chamber in the cylinder. The seal member is provided and seals between the cylinder and the swing piston.

  And this sealing member is comprised by the cyclic | annular lip ring which makes a substantially circular cup shape, and this lip ring uses polytetrafluoroethylene (PTFE) as a base material in order to improve heat resistance, abrasion resistance, etc. It is molded using a composite material.

  On the other hand, as a non-lubricated compressor, there is a reciprocating compressor configured to connect a crankshaft and a piston by a connecting rod (connecting rod) in order to reciprocate the piston without swinging in the cylinder. Are known. And in this compressor, it is set as the structure which mounts a piston ring in the ring groove formed in the outer peripheral side of a piston, and seals between the said cylinder and piston by this piston ring (for example, patent document 3). reference).

JP-A-8-28469 Japanese Patent Laid-Open No. 10-148178 Japanese Patent Laid-Open No. 11-270680

  By the way, in the oscillating compressor according to the above-described prior art, an annular lip ring is used as a seal member provided on the oscillating piston. On the high pressure side of the compressor, the lip ring is likely to be thermally deformed due to heat effects such as compression heat and frictional heat. In some cases, the lip ring is damaged, the sealing function is lost, and a problem such as leakage of compressed air occurs.

  Therefore, the present inventors examined using a piston ring instead of an annular lip ring as a seal member provided on the swing piston. However, when a piston ring known from the past (for example, Patent Document 3) is used, for example, a joint portion provided for expanding and reducing the diameter of the piston ring is welded due to heat and sealed. May lose itself.

  In other words, the joint portion of the piston ring may rub against each other as the piston ring expands and contracts when the compressor is continuously operated, and may be welded and fixed due to heat effects such as compression heat and friction heat. is there. When the compression operation is stopped in this state, the piston ring gradually heat-shrinks and the ring diameter (outer diameter) becomes smaller than the cylinder diameter. Moreover, there is an unsolved problem that the elastic expansion and contraction of the piston ring becomes difficult due to the fixing of the joint portion, and the original sealing function is lost.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to increase the pressure of the compressed fluid by changing the material composition of the piston ring used as the seal member. An object of the present invention is to provide a oscillating compressor that can improve reliability, life and the like by preventing welding and sticking.

  In order to solve the above-described problems, the present invention is provided with a cylindrical cylinder, a swinging piston that reciprocates while swinging in the cylinder, and defines a compression chamber in the cylinder, and the swinging piston is provided in the swinging piston. The present invention is applied to an oscillating compressor including a sealing member that seals between the cylinder and the oscillating piston.

  A feature of the configuration adopted by the invention of claim 1 is that the seal member is configured by a piston ring having an abutment portion that is mounted in an annular ring groove provided in the swinging piston so as to expand and contract. The piston ring is made of polytetrafluoroethylene having a permanent deformation rate of 3% or less after a load of 14 MPa is applied for 24 hours at room temperature, and the substrate is made of at least copper or bronze powder. The present invention has a configuration in which it is formed of a composite material to which a powder substance, spherical carbon, and molybdenum disulfide are added.

  According to a second aspect of the present invention, the composite material includes, in addition to the polytetrafluoroethylene, 10 to 30% by weight of the powder substance, 5 to 15% by weight of the spherical carbon, and 3 of the molybdenum disulfide. It is set as the structure contained in -7weight%.

  Furthermore, according to the invention of claim 3, the polytetrafluoroethylene serving as the base material of the composite material is composed of PFA-modified PTFE in which a fluorinated alkoxyethylene (PFA) group is added to polytetrafluoroethylene (PTFE). is doing.

  As described above, the invention described in claim 1 uses a piston ring having an abutment portion as a sealing member, and this piston ring has a polytetrafluoroethylene base material with a permanent deformation rate of 3% or less. Since it is formed of a composite material containing at least a powder material made of copper or bronze powder, spherical carbon and molybdenum disulfide, the heat resistance and wear resistance of the piston ring made of such a composite material can be improved. It is possible to prevent the joint portion of the piston ring from being welded and brought into a fixed state under the influence of heat such as compression heat and frictional heat. And this piston ring can seal well between a rocking | fluctuation piston and a cylinder over a long period of time.

  In this case, the polytetrafluoroethylene used as the base material for the piston ring has a permanent deformation rate of 3% or less after a load of 14 MPa is applied for 24 hours at room temperature, and the creep (permanent deformation) due to thermal expansion can be reduced. In addition to improving the heat resistance of the piston ring, it is possible to prevent the joint portion of the piston ring from being welded under the influence of heat during the compression operation and becoming stuck when the operation is stopped, thereby preventing the joint portion from sticking. Further, even when the operation is resumed thereafter, it is possible to compensate for the elastic expansion and contraction of the piston ring, ensuring the sealing performance and realizing a long-term maintenance-free operation.

  In addition, since the composite material used for the piston ring is added with at least a powder substance made of copper or bronze powder, spherical carbon and molybdenum disulfide to the base material (polytetrafluoroethylene), the thermal conductivity of the piston ring Etc., heat at the time of compression operation can be released to the cylinder side, and excellent lubricity can be secured to improve wear resistance. Thereby, the sealing performance at the time of the compression operation can be sufficiently secured, and for example, a fluid such as compressed air can be compressed to a high pressure up to a pressure of 3 MPa or more. For example, even when applied to the high-pressure side of a two-stage compressor, the durability and life of the piston ring can be increased and the reliability can be improved.

  In addition to the polytetrafluoroethylene, the invention described in claim 2 includes 10 to 30% by weight of a powder substance made of copper or bronze powder, 5 to 15% by weight of spherical carbon, and 3 to 7 of molybdenum disulfide. A piston ring can be formed using a composite material contained in the range of wt%, and the heat conductivity and wear resistance can be improved by increasing the thermal conductivity of the piston ring.

  In this case, when the content of the powder substance made of copper or bronze powder is less than 10% by weight, the thermal conductivity of the piston ring is deteriorated, and the thermal conductivity can be improved by increasing the content to 10% by weight or more. On the other hand, when the powder substance exceeds 30% by weight, the discharge amount (air amount) of compressed air or the like decreases. This is presumably because the content of the powder substance is excessively increased, the wear is excessively reduced, and the conformability as a piston ring is deteriorated, resulting in a decrease in sealing performance.

  Spherical carbon does not have an edge like carbon fiber, and can reduce wear by suppressing the aggressiveness to the mating surface (cylinder wall surface). However, if the spherical carbon content is less than 5% by weight, the aggressiveness to the mating surface (cylinder wall surface) becomes too small to smooth the surface, so that the wear on the outer periphery of the piston ring tends to increase. On the other hand, when the amount of spherical carbon is more than 15% by weight, on the contrary, the aggression against the mating surface is increased, which causes, for example, increased wear on the cylinder wall surface.

  Moreover, when the content of molybdenum disulfide is less than 3% by weight, the lubricity as a piston ring tends to be lowered and the sliding characteristics tend to be deteriorated. Conversely, when molybdenum disulfide exceeding 7% by weight is contained. This tends to decrease the polytetrafluoroethylene content and increase wear.

  According to the invention described in claim 3, the polytetrafluoroethylene serving as the base material of the composite material is composed of PFA-modified PTFE in which a fluorinated alkoxyethylene (PFA) group is added to polytetrafluoroethylene (PTFE). Therefore, creep (permanent deformation) due to thermal expansion can be suppressed to a small level, the heat resistance and wear resistance of the piston ring can be increased, and the durability and life can be improved.

  Hereinafter, a case where the oscillating compressor according to the embodiment of the present invention is applied to an air compressor will be described as an example and described in detail with reference to the accompanying drawings.

  Here, FIG. 1 to FIG. 5 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes a crankcase of an air compressor. The crankcase 1 defines a crank chamber 2 therein, and a crank 5 and a balance weight are connected to the crank chamber 2 via an output shaft 4 described later. 6 is rotatably provided.

  Reference numeral 3 denotes an electric motor as a drive source provided in parallel with the crankcase 1. The electric motor 3 includes a stator 3B fixed in the motor case 3A and a radial inner side of the stator 3B, which will be described later. The rotor 3 </ b> C is rotatably configured via the output shaft 4.

  Reference numeral 4 denotes an output shaft that rotates integrally with the rotor 3C of the electric motor 3. The output shaft 4 is rotatably supported on one side in the axial direction by a motor case 3A via a bearing, and the other side in the axial direction is a crank. The case 1 is rotatably supported via a bearing or the like. The other side of the output shaft 4 protrudes and extends into the crank chamber 2, and the crank 5 and the balance weight 6 are attached to the outer peripheral side so as to rotate integrally within the crank chamber 2.

  Reference numeral 7 denotes a cylindrical cylinder mounted on the crankcase 1, and the cylinder 7 is formed as a cylindrical body by subjecting a molded product made of, for example, an aluminum alloy to anodization. One side (base end side) of the cylinder 7 is opened (communication) into the crank chamber 2, and the other side (tip end side) of the cylinder 7 is closed by a valve seat plate 8 described later. In the cylinder 7, a compression chamber 19 described later is defined between the valve seat plate 8 and the swing piston 14 (piston portion 18).

  Reference numeral 8 denotes a valve seat plate provided on the front end side of the cylinder 7. The valve seat plate 8 is provided with a suction hole 8A and a discharge hole 8B spaced apart from each other as shown in FIGS. A suction hole 8 </ b> A of the valve seat plate 8 communicates a suction chamber 11 </ b> A described later to the compression chamber 19. Further, the discharge hole 8B of the valve seat plate 8 communicates the compression chamber 19 with a discharge chamber 11B described later.

  Reference numeral 9 denotes a cylinder head mounted on the cylinder 7 via the valve seat plate 8. The cylinder head 9 is provided with a partition wall 10 located between the valve seat plate 8 and the partition wall 10. The inside of the cylinder head 9 is divided into two chambers, a suction chamber 11A and a discharge chamber 11B.

  The cylinder head 9 is provided with an intake port 9A for allowing outside air (air) to flow into the suction chamber 11A and a discharge port 9B for discharging compressed air from the discharge chamber 11B to the outside. The valve seat plate 8 and the cylinder 7 and the valve seat plate 8 and the cylinder head 9 are hermetically sealed by a gasket (not shown), respectively.

  A suction valve 12 is provided between the suction chamber 11A and the compression chamber 19 and is provided in the valve seat plate 8. The suction valve 12 is attached to the valve seat plate 8 so as to open and close the suction hole 8A. It has been. The suction valve 12 opens when a piston portion 18 of the swing piston 14 to be described later moves from the top dead center to the bottom dead center (intake stroke), and moves from the bottom dead center to the top dead center ( The valve is closed during the compression stroke.

  A discharge valve 13 is provided between the discharge chamber 11B and the compression chamber 19 and is provided on the valve seat plate 8. The discharge valve 13 is attached to the valve seat plate 8 so as to open and close the discharge hole 8B. It has been. The discharge valve 13 opens in the compression stroke of the swing piston 14 and closes in the suction stroke.

  Reference numeral 14 denotes a swinging piston as a locking piston that is fitted in the cylinder 7 so as to be able to reciprocate. The swinging piston 14 is positioned at one end side in the crank chamber 2 and is rotatable to the crank 5 via a bearing 15. The connected ring portion 16, a rod-shaped piston rod 17 integrally formed with the ring portion 16 and extending into the cylinder 7, and a piston portion 18 as a disk portion integrally formed on the other end side of the piston rod 17. It is comprised by.

  The piston portion 18 is formed in a substantially disk shape with an outer diameter dimension smaller than the inner diameter dimension of the cylinder 7, and swings up and down while swinging left and right in the cylinder 7 as the crank 5 rotates. It reciprocates. Further, a ring groove 18A having a U-shaped cross section is formed on the outer peripheral side of the piston portion 18 over the entire circumference. A piston ring 21 described later is mounted in the ring groove 18A.

  Reference numeral 19 denotes a compression chamber defined in the cylinder 7, and this compression chamber 19 is formed between the valve seat plate 8 in the cylinder 7 by the piston portion 18 of the swing piston 14. The piston portion 18 of the swing piston 14 sucks air into the compression chamber 19 through the suction valve 12 in the above-described suction stroke, and compresses the air while compressing the air in the compression chamber 19 in the compression stroke. Air is discharged through the discharge valve 13.

  Reference numeral 20 denotes a cooling fan that generates cooling air. The cooling fan 20 is provided on the front end side of the output shaft 4 that extends in the axial direction in the crank chamber 2, and is driven to rotate integrally with the crank 5 by the output shaft 4. The cooling fan 20 cools the crankcase 1, the electric motor 3, the cylinder 7, etc. by circulating cooling air toward the crank chamber 2.

  21 is a piston ring as a seal member for sealing between the piston portion 18 of the swing piston 14 and the cylinder 7, and the piston ring 21 is made of a composite material described later in order to improve heat resistance, wear resistance, and the like. For example, as shown in FIGS. 3 to 5, it is formed as a ring body that can be reduced and expanded. The piston ring 21 is formed with cutouts 21A and 21B cut out in a substantially L shape at a midway portion in the circumferential direction.

  In this case, the piston ring 21 is mounted in the ring groove 18A of the piston portion 18, and the diameters of the ring portion 18A are reduced and expanded with respect to the ring groove 18A when the joint portions 21A and 21B approach and separate from each other. And as for the piston ring 21, the outer peripheral surface protrudes from the ring groove 18A to radial direction as shown in FIGS. 1-3, and it contacts the inner peripheral surface of the cylinder 7 elastically. As a result, the piston ring 21 moves between the outer peripheral surface of the piston portion 18 and the inner peripheral surface of the cylinder 7 even when the swing piston 14 (piston portion 18) reciprocates while swinging in the cylinder 7. It keeps hermetically sealed.

  Here, the material of the piston ring 21 is made of, for example, polytetrafluoroethylene (hereinafter referred to as PTFE) whose grade name is “70-J” as a base material, and a powder substance made of at least copper or bronze powder on the base material, It is formed using a composite material to which spherical carbon and molybdenum disulfide are added.

  PTFE (grade name is “70-J”) which is the base material of the composite material is also called PFA-modified PTFE, and is constituted by so-called modified PTFE in which a PFA (alkoxyfluorinated ethylene) group is added to PTFE. ing. Further, as shown in Table 1 to be described later, this modified PTFE has a permanent deformation rate of 3% or less (for example, 2.6%) after applying a load of 14 MPa for 24 hours at a room temperature of 23 ° C., for example. ) And permanent deformation at room temperature can be kept small.

  Moreover, this modified PTFE has a permanent deformation rate of 20.7% even when the same test is performed at a high temperature of 150 ° C., for example, and the creep (permanent deformation) due to thermal expansion can be suppressed to a low level. For this reason, the heat resistance can be improved by using modified PTFE as the material of the piston ring 21.

  The composite material used as the material of the piston ring 21 is 10 to 30% by weight of a powder substance made of copper or bronze powder, 5 to 15% by weight of the spherical carbon, 3 to 7% by weight of the molybdenum disulfide, The modified PTFE and inevitable impurities are contained in the range of 48 to 82% by weight. And as for the composition ratio of the composite material, when the content of the modified PTFE is 55 to 80% by weight, the remaining 20 to 45% by weight is composed of the powder substance, spherical carbon and molybdenum disulfide. Is preferred.

  In this case, the composite material used as the material of the piston ring 21 is dry-mixed with the above-described components using a mixer such as a Henschel mixer, and the resulting powder is molded (compressed) at a pressure of 40 to 78 MPa using a mold. Molding). The molded product is fired at a high temperature (for example, a maximum temperature of 370 ° C.) for about 4 hours, and then subjected to necessary machining or the like to provide the abutting portions 21A and 21B as shown in FIGS. A piston ring 21 is formed.

  The air compressor according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

  First, when the crank 5 in the crank chamber 2 is rotationally driven by the output shaft 4 of the electric motor 3, the piston portion 18 of the swing piston 14 reciprocates while swinging in the cylinder 7. Thereby, the piston portion 18 of the swing piston 14 sucks air from the suction chamber 11A into the compression chamber 19 and compresses the air in the compression chamber 19 and discharges it as compressed air to the discharge chamber 11B. Repeat the compression operation.

  When the piston portion 18 is performing compression operation in the cylinder 7, the piston ring 21 has a diameter from the ring groove 18 </ b> A of the piston portion 18 as the piston portion 18 swings (tilts) to the left and right. Repeated expansion and contraction so as to project in the direction. As a result, the outer peripheral surface of the piston ring 21 continues to be in sliding contact with the inner peripheral surface of the cylinder 7, and the space between the piston portion 18 and the cylinder 7 can be hermetically sealed, and the air in the cylinder 7 (compression chamber 19). The compression efficiency can be increased.

  On the other hand, when power supply to the electric motor 3 is stopped and the compression operation is interrupted, the reciprocating motion of the swing piston 14 (piston portion 18) also stops together with the electric motor 3. For example, when the oscillating piston 14 stops in the compression stroke in which the air in the compression chamber 19 is compressed, the compressed air remains in the compression chamber 19.

  However, in the middle of the piston ring 21 in the circumferential direction, there are joint portions 21A and 21B formed by cutting out in a substantially L shape, and between the ring groove 18A of the piston portion 18 and the inner periphery of the piston ring 21. An annular space is formed. For this reason, the compressed air remaining in the compression chamber 19 gradually leaks into the crank chamber 2 through the gap between the piston ring 21 and the ring groove 18A.

  After that, when the air compressor is restarted, the pressure in the cylinder 7 (compression chamber 19) is reduced to a state close to the atmospheric pressure. For this reason, when the air compressor is restarted, an extra load does not act on the electric motor 3 and the like, and a smooth restart can be performed.

  By the way, while the piston portion 18 of the oscillating piston 14 performs the compression operation in the cylinder 7, the piston ring 21 becomes a high temperature state due to the compression heat and frictional heat in the cylinder 7, and the piston ring 21 is expanded. There is a possibility that the joint portions 21A and 21B provided for reducing the diameter are welded due to thermal effects and lose their original sealing function.

  That is, the joint portions 21A and 21B of the piston ring 21 rub against each other in the directions indicated by arrows a and b in FIG. 5 as the piston ring 21 expands and contracts when the compressor is continuously operated. , May be welded and fixed due to thermal effects such as frictional heat. When the compression operation is stopped in this state, the piston ring 21 gradually shrinks and the ring diameter (outer diameter) becomes smaller than the cylinder diameter (inner diameter of the cylinder 7). , 21B makes it difficult to elastically expand and contract the piston ring 21, and the original sealing function may be lost.

  Therefore, in the present embodiment, the composite material as the material of the piston ring 21 is based on a modified PTFE (polytetrafluoroethylene) whose grade name is “70-J” as shown in Table 1, for example, The base material is composed of a composite material obtained by adding at least a powder substance made of copper or bronze powder, spherical carbon and molybdenum disulfide.

  The composite material used as the material of the piston ring 21 is 10 to 30% by weight of a powder substance made of copper or bronze powder, 5 to 15% by weight of the spherical carbon, 3 to 7% by weight of the molybdenum disulfide, The modified PTFE and inevitable impurities are contained in the range of 48 to 82% by weight. And as for the composition ratio of the composite material, when the content of the modified PTFE is 55 to 80% by weight, the remaining 20 to 45% by weight is composed of the powder substance, spherical carbon and molybdenum disulfide. Is preferred.

  As a result, as can be confirmed from test data (see Tables 2 and 3) described later, wear of the piston ring 21 and adhesion of the joint portions 21A and 21B can be suppressed. Problems such as a decrease in the amount of air can be prevented.

  In this case, the modified PTFE (grade name is “70-J”) serving as the base material of the piston ring can suppress creep (permanent deformation) due to thermal expansion to a small level. For this reason, while being able to improve the heat resistance as piston ring 21, it suppresses that joint part 21A, 21B of piston ring 21 is welded by the heat influence at the time of compression operation, and will be in a fixed state at the time of operation stop, joint part 21A, It is possible to prevent 21B from sticking. Further, even when the operation is resumed thereafter, the piston ring 21 can be compensated for elastic expansion and contraction, ensuring a sealing performance and realizing a long-term maintenance-free operation.

  Further, since the composite material used for the piston ring 21 is added with a powder material made of copper or bronze powder, spherical carbon and molybdenum disulfide to the modified PTFE serving as a base material, the heat conduction of the piston ring 21 It is possible to improve the properties and the like, and to release heat at the time of the compression operation to the cylinder 7 side, and it is possible to secure excellent lubricity and improve wear resistance.

  Thereby, the sealing performance at the time of the compression operation can be sufficiently secured, and for example, a fluid such as compressed air can be compressed to a high pressure up to a pressure of 3 MPa or more. For example, even when applied to a piston ring provided on the high-pressure side of a two-stage compressor, the durability and life of the piston ring 21 can be increased and the reliability can be improved.

  Further, the composite material as the material of the piston ring 21 contains a powder substance made of copper or bronze powder in the range of 10 to 30% by weight, the spherical carbon in the range of 5 to 15% by weight, and the two It is set as the structure which contains 3 to 7weight% of molybdenum sulfide. Thereby, the heat conductivity of piston ring 21 can be improved and heat resistance and wear resistance can be improved.

  In this case, if the content of the powder substance made of copper or bronze powder is less than 10% by weight, for example, the thermal conductivity of the piston ring 21 is deteriorated, and the thermal conductivity is improved by increasing it to 10% by weight or more. Can do. On the other hand, when the powder substance exceeds 30% by weight, the discharge amount of compressed air or the like decreases. This is presumably because the content of the powder substance is excessively increased, the conformability as the piston ring 21 is deteriorated, and the sealing performance is deteriorated.

  Moreover, the spherical carbon mentioned above does not have an edge like a carbon fiber, and can suppress wear by suppressing the aggressiveness to the other surface (inner peripheral surface of the cylinder 7). However, when the spherical carbon content is less than 5% by weight, the aggression on the mating surface (the inner peripheral surface of the cylinder 7) becomes too small and smoothing is not smoothed, so that the wear on the outer periphery of the piston ring 21 tends to increase. There is. On the other hand, when the amount of spherical carbon is more than 15% by weight, on the contrary, the attacking property to the mating surface is increased, and for example, the wear on the inner peripheral surface of the cylinder 7 is increased.

  Further, when the content of molybdenum disulfide is less than 3% by weight, the lubricity as the piston ring 21 is lowered, and the sliding characteristics tend to be deteriorated. On the other hand, when molybdenum disulfide exceeding 7% by weight is contained, the content of modified PTFE or the like is decreased by this, and there is a tendency for wear to increase.

  In addition, when the content of modified PTFE (polytetrafluoroethylene) is less than 55% by weight, the strength as the piston ring 21 is insufficient, and it is difficult to ensure sufficient wear resistance and sealability. On the other hand, when the content of the modified PTFE exceeds 80% by weight, the amount of other additives (containing components) is insufficient, and the effect of reducing wear cannot be obtained sufficiently.

  For this reason, the composite material used as the material of the piston ring 21 is a powder material made of copper or bronze powder, three materials of spherical carbon and molybdenum disulfide within the range of 20 to 45% by weight, and the modified PTFE is 55%. It is preferable to make it contain in the range of -80 weight%. Thereby, the heat resistance and wear resistance of the piston ring 21 can be increased, and its reliability and life can be improved.

  Examples of the present invention are shown below together with comparative examples. The present invention is not limited to these examples.

  Here, PTFE (grade name is “70-J”) used in the examples is also called PFA-modified PTFE. This modified PTFE is, for example, 24 at room temperature of 23 ° C. as shown in Table 1 below. The permanent deformation rate after applying a 14 MPa load over time is 2.6%, and the permanent deformation at room temperature is small. Moreover, this modified PTFE has a permanent deformation rate of 20.7% even when the same test is performed at a high temperature of 150 ° C., for example, and the creep (permanent deformation) due to thermal expansion can be suppressed to a low level.

  On the other hand, a general-purpose PTFE used in a comparative example to be described later has a grade name “7-J”, and has a permanent deformation rate of 6.2 after applying a 14 MPa load for 24 hours at a room temperature of 23 ° C., for example. For example, at a high temperature of 150 ° C., the permanent deformation rate increases to 32.6%.

  In this case, in the example, after the components of the composite material (modified PTFE, copper powder, spherical carbon, and molybdenum disulfide) that are the raw materials of the piston ring 21 are blended at a weight ratio (% by weight) shown in Table 2 below. As described above, the piston ring 21 provided with the abutting portions 21A and 21B as shown in FIG. 4 is formed by using compression molding, firing means or the like.

  The piston ring 21 is mounted in the ring groove 18A of the swinging piston 14 (piston portion 18) as shown in FIGS. 1 to 3, and the air compressor is continuously operated at a discharge pressure of 3 MPa in this state (for example, For 30 minutes), after cooling the compressor until the temperature in the compression chamber 19 drops to room temperature, the above-mentioned continuous operation (30 minute operation) is repeated for a total of 1000 cycles, for example. When the operation time reaches 500 hours, it is confirmed whether there is no abnormality in the piston ring 21 or the like and the compression operation is possible.

  Here, as shown in Table 2 below, the composite material employed in the piston ring 21 of the example is 75% by weight of modified PTFE (70-J), 10% by weight of powdered material (copper powder), and spherical carbon. It contains 10% by weight and 5% by weight of molybdenum disulfide.

  On the other hand, the composite material employed in the piston ring of the comparative example uses general-purpose PTFE (7-J) instead of modified PTFE (70-J). That is, as shown in Table 2, the composite material employed in the comparative example was 75 wt% PTFE (7-J), 10 wt% copper powder, 10 wt% spherical carbon, and 5 wt% molybdenum disulfide. Contains.

  Further, the piston ring of the comparative example is formed by using the same compression molding and firing means as those of the example by using the composite material having the composition ratio shown in Table 2. The piston ring according to the comparative example is also mounted in the ring groove 18A of the oscillating piston 14 (piston portion 18), and in this state, the air compressor is continuously operated at a discharge pressure of 3 MPa (for example, operation for 30 minutes). It is what I did.

  Thus, as is apparent from the test data in Table 3, the air compressor using the piston ring 21 according to the example has an air amount of 75 (liters / minute) at the initial stage of operation, and the air is continuously operated for 30 minutes. The amount was 71 (liters / minute). And in the case of the Example, it was confirmed that there was almost no abrasion of the piston ring 21, and adhesion of the joint parts 21A and 21B etc. can be prevented.

  On the other hand, in the case of the comparative example, although the air amount is 70 (liters / minute) in the continuous operation for 30 minutes, the joint portion of the piston ring is melted and fixed and becomes NG (unusable) thereafter. The test became impossible. The reason for this is considered to be the use of general-purpose PTFE (7-J) in the comparative example, not the modified PTFE (70-J) as in the examples.

  Therefore, according to the present embodiment, the modified PTFE whose grade name is “70-J” is used as the base material for the composite material that is the material of the piston ring 21, thereby reducing creep (permanent deformation) due to thermal expansion. It is possible to suppress such a problem that the joint portions 21A and 21B are melted and fixed when the operation is stopped.

  In addition, the composite material used as the material of the piston ring 21 is blended by adding an appropriate amount of a powder material made of copper or bronze powder, spherical carbon and molybdenum disulfide to a base material made of modified PTFE. The wear resistance of the piston ring 21 and the cylinder 7 can be improved, the life as an air compressor can be increased, and long-term maintenance-free operation can also be realized.

  In the above embodiment, the case where the joint portions 21A and 21B of the piston ring 21 are formed in a substantially L shape as shown in FIGS. 4 and 5 has been described as an example. However, the present invention is not limited to this. For example, an abutting portion may be formed by cutting a middle portion of the piston ring obliquely downward at a certain angle, and may be cut into a substantially U-shape. A joint portion may be formed.

  Moreover, in the said embodiment, the case where the oscillating compressor was applied to the air compressor was described as an example. However, the present invention is not limited to this, and may be applied to an oscillating compressor that compresses a fluid such as a gas such as nitrogen or hydrogen or a refrigerant.

It is a longitudinal section showing an air compressor by an embodiment of the invention. It is sectional drawing which looked at the air compressor from the arrow II-II direction in FIG. It is sectional drawing of the same position as FIG. 2 which shows the state which the piston moved to the bottom dead center. It is a perspective view which shows the piston ring in FIG. 1 alone. It is a front view which expands and shows the piston ring in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crankcase 4 Output shaft 5 Crank 7 Cylinder 8 Valve seat board 9 Cylinder head 14 Oscillating piston 16 Ring part 17 Piston rod 18 Piston part 18A Ring groove 19 Compression chamber 21 Piston ring 21A, 21B Abutment part

Claims (3)

A cylindrical cylinder, a oscillating piston that reciprocates while oscillating in the cylinder and defines a compression chamber in the cylinder, and a seal provided between the cylinder and the oscillating piston provided in the oscillating piston In the oscillating compressor comprising a sealing member that
The seal member is constituted by a piston ring having an abutment portion mounted so as to be able to expand and contract in an annular ring groove provided in the swing piston,
This piston ring has a base material made of polytetrafluoroethylene having a permanent deformation rate of 3% or less after a load of 14 MPa is applied for 24 hours at room temperature, and the base material is a powder substance made of at least copper or bronze powder. An oscillating compressor characterized in that it is formed of a composite material to which spherical carbon and molybdenum disulfide are added.   The composite material includes, in addition to the polytetrafluoroethylene, 10 to 30% by weight of the powder substance, 5 to 15% by weight of the spherical carbon, and 3 to 7% by weight of the molybdenum disulfide. The oscillating compressor according to claim 1.   The said polytetrafluoroethylene used as the base material of the said composite material is comprised by the PFA modified PTFE which added the fluorinated alkoxyethylene (PFA) group in the polytetrafluoroethylene (PTFE). Oscillating compressor.

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