JP2012007560A - Piston ring for reciprocating compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring for a reciprocating compressor, causing no start failure at restart immediately after stop even when the reciprocating compressor is small, preventing joints of a seal ring and a backup ring from overlapping by a simple means without using a pin or the like and not becoming separate when installation.SOLUTION: The piston ring 1 includes the seal ring 2, the backup ring 3 and a tension ring 4. A projection portion 3c complementary to the stepped joint 2c of the seal ring 2 is provided on the outer peripheral surface 3b of the backup ring 3. The seal ring 2 and the backup ring 3 are positioned in the circumferential direction and the axial direction with the projection portion 3c and the stepped joint 2c complemented to each other. A passage 5 for gas vent is provided in all circumference of the corner between the inner peripheral surface 2a and the side surface 2b of the seal ring 2.

Description

  The present invention relates to a piston ring for a reciprocating compressor, and more particularly to a piston ring for a reciprocating compressor that is attached to a piston of an oil-free compressor and seals a gas such as air or an inert gas.

  Generally, in a reciprocating compressor, while a piston reciprocates in a cylinder, in a suction process, gas is sucked into a compression chamber formed in the cylinder via a suction valve, and in the discharge process, the gas is pressurized and the discharge valve is operated. It is made to discharge through. The reciprocating compressor has a piston ring fitted on the outer periphery of the piston so as to seal between the piston and the cylinder, and the piston ring can maintain the airtightness between the piston and the cylinder for a long time. Has been.

  As a conventional piston ring, a piston ring comprising a combination of a seal ring, a backup ring and a tension ring is known. FIG. 4 is an enlarged cross-sectional view of the piston ring attached to the piston, and FIG. 5 is a perspective view of the piston ring. As shown in FIG. 4, a piston ring that contacts the cylinder 6 is disposed between the cylinder 6 and the piston 7 in a groove 8 provided on the outer periphery of the piston 7, and functions as a seal member. A plurality of the grooves 8 may be provided in order to improve sealing performance and durability.

  As shown in FIG. 5, the piston ring 12 includes a seal ring 9 having a stepped mating port 9 a, a backup ring 10 having a mating port 10 a in contact with the inner circumferential surface of the seal ring 9, and an inner circumference of the backup ring 10. The tension ring 11 is in contact with the surface and has an abutment 11a. The piston ring 12 is assembled in the groove 8 so that the position of the piston ring 12 is shifted by, for example, 180 degrees so that the stepped opening 9a and the opening 10a do not overlap. This is because if the abutment 9a and the abutment 10a overlap, gas leaks from the abutment and does not function as a seal member. Further, as a material used for the seal ring 12, a resin composition in which a copper-based or iron-based alloy and carbon fiber are blended with a polytetrafluoroethylene (hereinafter referred to as PTFE) resin is used. What suppresses the aggressiveness to a member and self-abrasion is known.

  In a reciprocating compressor using a piston ring, when the compressor stops, the compression chamber is kept airtight by the piston ring, so high-pressure gas leaks from the discharge valve side to the compression chamber, and the compression chamber May be high pressure. If the reciprocating compressor is started in this state, the compression chamber may be overcompressed, resulting in a starting failure such as a time lag.

  As means for solving this problem, Patent Document 1 proposes a gas vent passage provided at a joint of a piston ring having a stepped joint. Further, as described in the prior art of Patent Document 1, a gap is formed between the suction valve and the suction hole covered by the suction valve, and the gas in the compression chamber is stopped when the compressor is stopped. Have been proposed in which the pressure in the compression chamber is prevented from rising through the suction hole.

  Further, when the piston 7 reciprocates in the cylinder 6, the pressure of the gas, the tension of the tension ring 11, the inclination of the piston 7 with respect to the inner peripheral surface of the cylinder 6, the inner peripheral surface of the seal ring 9 and the outer periphery of the backup ring 10 Due to non-uniform contact with the surface, the seal ring 9, the backup ring 10 and the tension ring 11 are rotated. As a result, in use, the stepped joint 9a of the seal ring 9 and the joint 10a of the backup ring 10 may overlap on the circumference. When they overlap, there is a problem that the gas leaks from the overlapping portion and the sealing performance is lowered.

  With respect to such a problem, in Patent Document 2, as a means for mutually locking the backup ring and the seal ring in the piston ring, (1) it is formed by bending the joint end of the tension ring outward. A locking means for engaging the protruding portion with the concave portion formed on the mating portion of the backup ring and the inner peripheral surface of the seal ring, and (2) formed on the outer peripheral surface of the backup ring and the inner peripheral surface of the seal ring. Locking means using a rotation-preventing pin, (3) a recess or a protrusion formed on the outer peripheral surface of the backup ring, and a recess or a protrusion formed on the inner peripheral surface of the seal ring, respectively. Locking means for engaging with each other has been proposed.

  Further, in Patent Document 3, a seal ring having a stepped opening and a backup ring in contact with the inner periphery of the seal ring are provided, and the seal ring is larger than the diameter of the hole formed in the width direction and is a seal ring. A protrusion obtained by press-fitting a fitting such as a pin having a length less than or equal to the width into the hole is located at a position other than the stepped mating port, and the mating port of the backup ring is locked to the projecting portion. A piston ring has been proposed.

Japanese Utility Model Publication No. 02-096076 Japanese Patent Laid-Open No. 11-063226 JP 2001-032935 A

  However, in a small reciprocating compressor used for an impact driver or an impact wrench, the capacity of the motor is small. Therefore, the technique disclosed in Patent Document 1 and the conventional technique described in Patent Document 1 are sufficient solutions. did not become.

  Further, the protrusions formed by bending outwardly the mating end of the tension ring described in Patent Document 2 are formed into concave portions formed on the mating end of the backup ring and the inner peripheral surface of the seal ring. The use of a tension ring is indispensable for a piston ring having a locking means to be engaged. Moreover, the piston ring which has the latching means by the non-rotating pin formed in the outer peripheral surface of a backup ring and the inner peripheral surface of a seal ring has a danger that a detent pin will remove | deviate. In addition, the seal ring may get over the detent pin. Further, the recesses or projections formed on the outer peripheral surface of the backup ring and the recesses or projections formed on the inner peripheral surface of the seal ring respectively have locking means for engaging the mutual recesses and projections. The piston ring cannot be used unless the seal ring is thick.

  The piston ring described in Patent Document 3 has a risk of disengaging fittings such as pins. If the fitting is disengaged, the seal ring rotates and the mating part of the seal ring and the mating part of the backup ring overlap, and there is a risk that gas leaks from the overlapping part and the sealing performance is lowered. Further, the seal ring may get over a fitting such as a pin. Further, since positioning in the axial direction cannot be performed, the seal ring and the backup ring, or the seal ring, the backup ring, and the tension ring may be separated when assembled in the ring groove.

  The present invention was made to cope with such problems, and even a small reciprocating compressor used for an impact driver, an impact wrench or the like does not cause a start failure in restart immediately after stopping, It is another object of the present invention to provide a piston ring for a reciprocating compressor that does not become disjointed when the joints of the seal ring and the backup ring overlap with each other by simple means without using pins.

  The piston ring for a reciprocating compressor according to the present invention is a piston ring for a reciprocating compressor that is used by being fitted in a groove provided on the outer periphery of the piston so as to seal between the piston and the cylinder. A seal ring that is in sliding contact; and a backup ring that elastically contacts the inner peripheral surface of the seal ring. The seal ring and the backup ring each have an abutment, and an inner peripheral surface and a side surface of the seal ring. A gas venting passage is provided in the entire circumference of the corner of the gas.

Sectional area of the axial section of the gas vent ^passage, characterized in that it is a 0.07 mm 2 to 0.5 mm ^2. Further, the gas vent passage is a chamfered surface of a C surface or an R surface. In addition, the gap between the back-up rings is 2 mm to 6 mm.

  The seal silling and the backup ring are made non-rotatable so that the seal ring and the backup ring do not overlap in the circumferential direction. The mating port of the seal ring is a stepped mating port.

  The backup ring has a protrusion that complements the stepped opening of the seal ring on an outer peripheral surface other than the mating opening, and the protrusion and the stepped opening complement each other so that the seal ring and the backup ring are complementary. The ring is positioned in the circumferential direction and the axial direction.

  The protrusion part of the said backup ring is formed between 45 degree | times and 315 degree | times when an abutment is made into 0 degree | times with respect to the circumferential center point of a backup ring. In particular, it is formed between 170 degrees and 190 degrees.

  The height from the outer peripheral surface of the protrusion of the backup ring is the same as or thinner than the thickness of the seal ring. The height from the outer peripheral surface of the protrusion of the backup ring is 2/3 or more of the thickness of the seal ring.

  The seal ring and the backup ring are made of synthetic resin. The backup ring is injection-molded. In particular, the backup ring is injection-molded into a flat plate shape.

  The backup ring is made of a fluororesin. The fluororesin is a polytetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (hereinafter referred to as PFA) resin, an ethylene-tetrafluoroethylene copolymer (hereinafter referred to as ETFE) resin, tetrafluoroethylene / hexa It is at least one selected from fluoropropylene copolymer (hereinafter referred to as FEP) resin.

  The seal ring is made of a fluororesin. The fluororesin is a PTFE resin.

  A tension ring is provided on the inner periphery of the backup ring. The piston ring seals air or gas.

  The piston ring for a reciprocating compressor according to the present invention is provided with a seal ring having an abutment and a backup ring, and a gas vent passage is provided in the entire periphery of the corner between the inner peripheral surface and the side surface of the seal ring. Therefore, when the compressor is stopped, the high-pressure gas confined in the compression chamber passes through the gap of the back-up ring joint from the venting passage and passes through the lower venting passage. Immediately escaped from the compression chamber. For this reason, even if it restarts, it can be started immediately without starting failure. In particular, even if it is used for a small reciprocating compressor used for a hand tool such as an impact wrench or an impact driver having a small motor capacity, it does not cause a start failure even if it is restarted immediately after stopping.

Sectional area of the axial section of the gas vent passage, since it is 0.07 mm ² to 0.5 mm ^2, can be both opposing effects of discharge of rapid pressure gas when stopping the sealing effect during operation. In addition, since the gap between the back-up rings is 2 to 6 mm, high-pressure gas can be discharged smoothly.

  Since the venting passage is a chamfered surface of the C or R plane, the venting passage can be formed without increasing the number of manufacturing steps.

  Since the joint of the seal ring and the joint of the backup ring are not allowed to rotate with each other so as not to overlap each other in the circumferential direction, if the step joint of the seal ring and the joint of the backup ring overlap Therefore, good sealing performance is maintained. Further, since the mating port of the seal ring is a stepped mating port, the sealing effect during operation is excellent.

  The backup ring has a protrusion that complements the stepped opening of the seal ring on an outer peripheral surface other than the mating opening, and the protrusion and the stepped opening complement each other so that the seal ring and the backup ring are complementary. Since the ring is positioned in the circumferential direction and the axial direction, the stepped joint of the seal ring and the joint of the backup ring do not overlap, and good sealing performance is maintained for a long time. In addition, the assembly time does not come apart and assembly time does not increase.

  Since the protrusion of the backup ring is formed between 45 degrees and 315 degrees when the abutment is 0 degrees with respect to the circumferential center point of the backup ring, the sealing performance is excellent. Furthermore, it is excellent in assemblability by forming the protrusions between 170 degrees and 190 degrees.

  Since the height from the outer peripheral surface of the protrusion of the backup ring is the same as or thinner than the thickness of the seal ring, it is possible to prevent the protrusion from protruding from the seal ring. Moreover, since the height from the outer peripheral surface of the protrusion part of the backup ring is 2/3 or more of the thickness of the seal ring, rotation of the seal ring can be reliably prevented.

  Since the seal ring and the backup ring are made of synthetic resin, they can be used in a non-lubricated atmosphere. Moreover, since the backup ring is injection-molded, the molding is easy even when the protrusion is present. Further, since the backup ring is injection-molded into a flat plate shape, no tension ring is required in the piston ring.

  Since the backup ring is made of a fluororesin, it has excellent lubrication characteristics. Further, since the fluororesin is at least one selected from PFA resin, ETFE resin, and FEP resin, it can be manufactured by injection molding while having excellent lubrication characteristics.

  Since the seal ring is made of a fluororesin, it has excellent lubrication characteristics. Moreover, since the said fluororesin is PTFE resin, it is excellent in a sealing characteristic with a lubrication characteristic.

  Since the tension ring is further provided on the inner periphery of the backup ring, the calculation of the tension between the seal ring and the backup ring can be omitted.

It is a perspective view which shows the component of the piston ring for reciprocating compressors of this invention, and its assembly state. It is an expanded sectional view of the axial direction of the state which mounted | wore the piston with the piston ring for reciprocating compressors of this invention. It is a figure which shows the backup ring shape | molded in flat form. It is an expanded sectional view of the axial direction in the state where the conventional piston ring was mounted on the piston. It is a perspective view which shows the conventional piston ring.

  An example of a piston ring for a reciprocating compressor according to the present invention is shown in FIG. FIG. 1 is a perspective view showing components of a piston ring and its assembled state. As shown in FIG. 1, the piston ring 1 is obtained by assembling a seal ring 2, a backup ring 3, and a tension ring 4 in order from the outer ring to the inner ring. The seal ring 2 is in the outermost layer of the piston ring 1 and contacts an inner wall of a cylinder or the like to seal a gas such as air or an inert gas (see FIG. 2). The backup ring 3 is provided in elastic contact with the inner peripheral surface 2a of the seal ring 2 so that the pressure applied from the gas and the pressing force from the tension ring 4 are uniformly applied to the seal ring 2. The seal ring 2 is formed with an abutment 2c, and the backup ring 3 is formed with an abutment 3a. The backup ring 3 prevents gas leakage from the abutment 2 c of the seal ring 2. The tension ring 4 presses the seal ring 2 and the backup ring 3 toward the outer peripheral direction to further improve the gas sealing performance. In the piston ring 1 of the present invention, the tension ring 4 is not necessarily provided. When the tension ring 4 is not used, the backup ring 3 is designed to replace it. In the above-described configuration, the gas vent passage 5 is provided on the entire circumference of the corner between the inner peripheral surface 2a and the side surface 2b of the seal ring 2.

  The axial cross-sectional shapes of the seal ring 2, the backup ring 3, and the tension ring 4 are arranged such that the backup ring 3 is disposed on the inner peripheral surface of the seal ring 2 and the tension ring 4 is disposed on the inner peripheral surface of the backup ring 3. Any shape that can be used is not particularly limited. Since each ring is easily arranged, it is preferable that each ring has a rectangular cross section as shown in FIGS.

  FIG. 2 shows an enlarged sectional view in the axial direction in a state where the piston ring for a reciprocating compressor of the present invention is mounted on the piston. As shown in FIG. 2, the piston ring 1 is fitted between a cylinder 6 and a piston 7 in a groove 8 provided on the outer periphery of the piston 7 while being in sliding contact with the cylinder 6. It functions as a seal member that seals gas such as. A plurality of grooves 8 may be provided in order to improve sealing performance and durability.

  The venting passage 5 is provided at the corner between the inner peripheral surface 2 a and the side surface 2 b of the seal ring 2. Here, the corner between the inner peripheral surface 2a and the side surface 2b refers to a certain range of the boundary portion (corner portion) between the inner peripheral surface 2a and the side surface 2b. In the embodiment shown in FIG. 2, the gas vent passage 5 has two locations (left and right) of the seal ring 2, that is, a side surface 2 b positioned on the compression chamber side and the atmosphere side of the seal ring 2, and an inner peripheral surface 2 a. Is provided at the corner. Further, the gas vent passage 5 is provided over the entire circumference in the circumferential direction of the seal ring 2.

  The gas vent passage 5 may be provided at least at the corner between the side surface 2b on the compression chamber side and the inner peripheral surface 2a in the seal ring 2, but the assembly of the piston ring 1 and the incorporation into the groove 8 are facilitated. In consideration, it is preferable to provide at the corners on both sides of the compression chamber side and the atmosphere side as in the embodiment shown in FIG.

  The high-pressure gas left in the compression chamber is the gas on the compression chamber side formed around the entire periphery of the inner peripheral surface 2a and side surface 2b of the seal ring 2 from the gap between the seal ring 2 and the groove 8 of the piston. The gas escapes from the cylinder 6 through the clearance passage 5 of the backup ring 3 through the clearance passage 3a of the backup ring 3 and through the gas extraction passage 5 of the atmosphere-side seal ring 2 (see FIGS. 1 and 2). In addition, the air is released from the gas vent passage 5 of the seal ring 2 on the atmosphere side through a gap between the mating port 2 c of the seal ring 2 and a fitting gap between the mating port 2 c and the protrusion 3 c of the backup ring 3.

The degassing passage 5 preferably has a cross-sectional area of an axial cross section of 0.07 to 0.5 mm ² . By setting it as this range, the conflicting effect | action of the sealing effect at the time of a driving | operation and discharge | emission of the high-pressure gas quickly at the time of a stop can be made compatible. If the cross-sectional area of the gas vent passage 5 is smaller than 0.07 mm ² , the high-pressure gas may not be discharged quickly when stopped. Further, if the cross-sectional area of the gas vent passage 5 is larger than 0.5 mm ² , the sealing effect may be reduced and compression failure may occur.

  The shape of the cross section in the axial direction of the gas vent passage 5 can be an arbitrary shape, for example, a rectangular shape (rectangular shape), a triangular shape (C surface), or an arc shape (R surface). Since the venting passage 5 can be formed without increasing the manufacturing process of the seal ring 2, it is preferable to chamfer the C surface or the R surface. For example, when the seal ring 2 is manufactured from a pipe material manufactured by PTFE resin ram extrusion, which will be described later, the inner diameter and the outer diameter are finished with a lathe, and then chamfering is performed simultaneously when parting off from the inner diameter side. Can be formed. Specifically, it is possible to use a cutting tool having chamfered portions on both side surfaces of the cutting tool.

  The shape of the mating port 2c of the seal ring 2 is preferably a stepped mating port that is excellent in sealing performance of the seal, so-called step cut. In particular, as shown in FIG. 1, a step cut with an interval complementary to the protrusion 3 c of the backup ring 3 is preferable. The shape of the abutment 3a of the backup ring 3 is preferably a straight cut as shown in FIG. 1 because it is used as a passage for venting high-pressure gas. Further, the shape of the joint 4a of the tension ring 4 is not particularly limited, and for example, a straight cut as shown in FIG.

  The gap of the abutment 4a of the tension ring 4 is set so that the gap of the abutment does not become zero when the inside of the piston reaches the maximum temperature even if the ring expands in the circumferential direction due to thermal expansion. Further, the gap between the mating ports 3a of the backup ring 3 is set so that at least 1.0 mm is open even when the inside of the piston reaches the maximum temperature.

  It is preferable that the gap of the abutment 3a of the backup ring 3 is 2 to 6 mm. Within this range, the high-pressure gas is discharged smoothly. If the gap between the mating ports 3a is smaller than 2 mm, the mating gap becomes small when thermally expanded, which may hinder the discharge of high-pressure gas. On the other hand, if the gap of the abutment 3a is larger than 6 mm, the abutment gap becomes too large and the sealing effect during operation may be reduced.

  By assembling the mating port 2c of the seal ring 2 and the mating port 3a of the backup ring 3 so as not to overlap each other in the circumferential direction, the seal ring 2 and the backup ring 3 cannot rotate with each other during use. The mating port 2c of the seal ring 2 and the mating port 3a of the backup ring 3 do not overlap with each other, and good sealing performance can be maintained. As a means for preventing the seal ring 2 and the backup ring 3 from rotating relative to each other, any means can be adopted as long as it can prevent the rotation of both rings.

  As a means for preventing the rotation of both rings, as shown in FIG. 1, a protrusion 3 c that complements the stepped opening 2 c of the seal ring 2 is provided on the outer peripheral surface 3 b other than the opening 3 a of the backup ring 3. It is preferable. The circumferential direction and the axial direction positioning of the seal ring 2 and the backup ring 3 are performed by the protrusion 3c and the stepped mating port 2c complementing each other. By adopting such a configuration, it is possible to prevent the stepped joint 2c of the seal ring 2 and the joint 3a of the backup ring 3 from overlapping with a simple means that does not use a pin or the like, and a good sealing property can be obtained for a long time. Can be maintained. In addition, the assembly time does not come apart and assembly time does not increase.

  The protrusion 3c of the backup ring 3 is preferably formed between 45 degrees and 315 degrees when the abutment is 0 degrees with respect to the circumferential center point of the backup ring 3. Here, forming the protrusion 3c between 45 degrees and 315 degrees means that the center of the protrusion 3c in the circumferential direction is positioned between 45 degrees and 315 degrees. In addition, the circumferential direction length of the protrusion 3c is sufficiently small with respect to the entire circumference, and is about 5 to 10 degrees at the above angle. When the position where the protrusion 3c is formed is a position less than 45 degrees or more than 315 degrees, the mating port 2c of the seal ring 2 and the mating port 3a of the backup ring 3 are too close, and seal leakage does not occur in design. However, there may be cases where a sense of security cannot be obtained with respect to seal leakage.

  The position where the protrusion 3c of the backup ring 3 is formed is more preferably between 90 degrees and 270 degrees, and further preferably between 170 degrees and 190 degrees. By setting the position where the protrusion 3c is formed between 170 degrees and 190 degrees, in addition to the sealing performance, the assembling performance is also excellent. The position where the protrusion 3c is formed is most preferably 180 degrees on the side opposite to the joint 3a.

  The height from the outer peripheral surface 3b of the protrusion 3c of the backup ring 3 is preferably set to be the same as or thinner than the thickness of the seal ring 2. By making the height of the protrusion 3 c the same as or thinner than the thickness of the seal ring 2, the protrusion 3 c can be prevented from protruding from the seal ring 2. On the other hand, if the height of the protrusion 3c is too low, the seal ring 2 may rotate over the protrusion 3c. Therefore, in order to reliably prevent the relative rotation between the backup ring 3 and the seal ring 2, the height from the outer peripheral surface 3b of the protrusion 3c of the backup ring 3 is 2/3 or more of the thickness of the seal ring 2. It is preferable.

  The material used for the seal ring 2 is preferably a synthetic resin, and among them, a fluororesin excellent in self-lubricating property, sealing property, heat resistance, chemical resistance and the like is preferable. Fluororesin includes PTFE resin, PFA resin, FEP resin, polychlorotrifluoroethylene resin, ETFE resin, chlorotrifluoroethylene-ethylene copolymer resin, polyvinylidene fluoride resin, tetrafluoroethylene-hexafluoropropylene-par Examples include fluoroalkyl vinyl ether copolymer resins. Among these, it is preferable to use PTFE resin, PFA resin, FEP resin, and ETFE resin because of low frictional resistance with the cylinder. In particular, it is preferable to use a PTFE resin because it is excellent in sealing properties as well as self-lubricating properties.

  The material used for the backup ring 3 is preferably a synthetic resin, and among them, a resin composition that can be injection-molded to form the protrusion 3c is preferable. Examples of the resin composition include PFA resin, FEP resin, ETFE resin, polyether ketone resin, polyether ether ketone (hereinafter referred to as PEEK) resin, polyphenylene sulfide (hereinafter referred to as PPS) resin, aromatic polyester resin, polyamide Examples thereof include resins and polyimide resins. Among these, PFA resin, FEP resin, ETFE resin, PEEK resin, and PPS resin are preferably used because they are excellent in self-lubricating property, sealing property, heat resistance, chemical resistance, and the like. In particular, it is preferably at least one selected from PFA resin, FEP resin, and ETFE resin, which are fluororesins that can be injection molded. In order to prevent the seal ring 2 and the backup ring 3 from adhering to each other, the backup ring 3 needs to use a resin different from the seal ring 2. By using the seal ring 2 and the backup ring 3 made of synthetic resin as described above, the seal ring 2 and the backup ring 3 can be used in a non-lubricated atmosphere.

  As the seal ring 2 and the backup ring 3, only the above-described synthetic resin, that is, 100% synthetic resin not containing a compounding agent can be used. In addition to the synthetic resin, various fillers can be added as necessary. In this case, the blending ratio is preferably 97 to 70% by weight of the synthetic resin and 3 to 30% by weight of the filler so as not to prevent the non-adhesiveness of the synthetic resin.

  The molding method of the seal ring 2 and the backup ring 3 is not particularly limited, and injection molding, extrusion molding, compression molding, or the like can be employed. As a method of molding the seal ring 2 using PTFE resin or the like as a material, for example, a powder mixture in which raw materials are uniformly mixed is molded into a pipe shape by ram extrusion molding or the like, and an inner diameter and an outer diameter are obtained from the obtained pipe material. After finishing with a lathe, chamfering is simultaneously performed when parting off from the inner diameter side, whereby the seal ring 2 having the gas vent passage 5 is obtained.

  As a method of forming the backup ring 3 using PFA resin, FEP resin, ETFE resin or the like as a material, for example, the raw materials are dry-mixed with a Henschel mixer, a ball mixer, a ribbon blender, a Redige mixer, an Ultra Henschel mixer, etc. It can be obtained by melt-kneading with a melt extruder such as a twin screw extruder to obtain pellets for molding and then injection molding.

  The backup ring 3 may be formed into a ring shape as shown in FIG. 1, but may be formed into a flat plate shape as shown in FIG. In the case of a flat plate shape, tension is generated by a restoring force, so that the tension ring 4 can be dispensed with in the piston ring 1.

  The material used for the tension ring 4 may be any material that exhibits a spring shape that can be given a force to press the backup ring 3. For example, stainless steel (SUS), metal materials, such as iron-cobalt, and resin materials are mentioned. Further, by providing the tension ring 4, it is possible to omit the tension calculation of the seal ring 2 and the backup ring 3.

  The piston ring for a reciprocating compressor according to the present invention can be used as a piston ring that is mounted on a piston of an oil-free compressor and seals a gas such as air or an inert gas. In particular, even a small reciprocating compressor used for an impact driver, an impact wrench, or the like can be suitably used as a piston ring for these reciprocating compressors because no starting failure occurs upon restart immediately after stopping.

1 piston ring 2 seal ring 3 backup ring 4 tension ring 5 passage for venting 6 cylinder 7 piston 8 groove

Claims (20)

In a piston ring for a reciprocating compressor used by being fitted in a groove provided on the outer periphery of the piston so as to seal between the piston and the cylinder,
The piston ring includes a seal ring that is in sliding contact with the cylinder, and a backup ring that is in elastic contact with the inner peripheral surface of the seal ring,
The seal ring and the backup ring each have an abutment, and a reciprocating motion characterized in that a gas vent passage is provided around the entire corner of the inner peripheral surface and the side surface of the seal ring. Piston ring for compressor. ^{2. The} piston ring for a reciprocating compressor according to claim 1, wherein a cross-sectional area of an axial section of the gas vent passage is 0.07 to 0.5 mm ² .   The piston ring for a reciprocating compressor according to claim 2, wherein the gas vent passage is a chamfered surface of a C surface or an R surface.   The piston ring for a reciprocating compressor according to claim 1, 2 or 3, wherein the gap of the abutment of the backup ring is 2 to 6 mm.   The seal silling and the backup ring are made non-rotatable so that the seal ring and the backup ring do not overlap in the circumferential direction. The piston ring for reciprocating compressors as described in any one of Claim 1 thru | or 4.   The piston ring for a reciprocating compressor according to claim 5, wherein a mating port of the seal ring is a stepped mating port.   The backup ring includes a protrusion that complements the stepped mating port of the seal ring on an outer peripheral surface other than the mating port, and the projecting portion and the stepped mating port complement each other so that the seal ring and the backup ring are complementary to each other. The reciprocating compressor piston ring according to claim 6, wherein the ring is positioned in the circumferential direction and the axial direction.   8. The reciprocation according to claim 7, wherein the protrusion of the backup ring is formed between 45 degrees and 315 degrees when the abutment is 0 degrees with respect to the circumferential center point of the backup ring. Piston ring for dynamic compressor.   The reciprocation according to claim 8, wherein the protrusion of the backup ring is formed between 170 degrees and 190 degrees when the abutment is 0 degrees with respect to the circumferential center point of the backup ring. Piston ring for dynamic compressor.   The piston ring for a reciprocating compressor according to any one of claims 1 to 9, wherein a height from an outer peripheral surface of the protrusion of the backup ring is equal to or thinner than a thickness of the seal ring. .   11. The piston ring for a reciprocating compressor according to claim 10, wherein a height from an outer peripheral surface of the protrusion of the backup ring is 2/3 or more of a thickness of the seal ring.   The piston ring for a reciprocating compressor according to any one of claims 1 to 11, wherein the seal ring and the backup ring are made of a synthetic resin.   The piston ring for a reciprocating compressor according to claim 12, wherein the backup ring is injection-molded.   The piston ring for a reciprocating compressor according to claim 13, wherein the backup ring is injection-molded into a flat plate shape.   The reciprocating compressor piston ring according to claim 12, 13 or 14, wherein the backup ring is made of a fluororesin.   The fluororesin is at least one selected from polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, ethylene-tetrafluoroethylene copolymer resin, and tetrafluoroethylene-hexafluoropropylene copolymer resin. The piston ring for a reciprocating compressor according to claim 15.   The reciprocating compressor piston ring according to any one of claims 12 to 16, wherein the seal ring is made of a fluororesin.   The piston ring for a reciprocating compressor according to claim 17, wherein the fluororesin is a polytetrafluoroethylene resin.   The reciprocating compressor piston ring according to any one of claims 1 to 18, wherein a tension ring is provided on an inner periphery of the backup ring.   The reciprocating compressor piston ring according to any one of claims 1 to 19, wherein the piston ring seals air or gas.

Images