JP2010007643A - Reciprocating compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reciprocating compressor capable of compatibly materializing sealing performances in both directions in a suction stroke and a compression stroke and durability of a piston ring. <P>SOLUTION: This compressor include a first piston ring 30 installed in a first ring groove 25 at an outer circumference side of a piston 14 and sealing a section between the piston and a cylinder in the suction stroke of the piston 14, and a second piston ring 31 installed in a second ring groove 26 at an outer circumference side of the piston 14 and sealing a section between the piston and the cylinder in the compression stroke of the piston 14. A bottom part 25a of the first ring groove 25 and a bottom part 26a of the second ring groove 26 have mutually opposite tapered shapes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reciprocating compressor.

  A reciprocating compressor that compresses gas has a cylindrical cylinder on which a cylinder head is mounted, and a piston that is slidably inserted into the cylinder and defines a compression chamber between the cylinder head. The piston is reciprocated in the cylinder by the eccentric motion of the crank provided in the crank chamber, so that the compression chamber is expanded and the gas is sucked in, the compression chamber is contracted and the gas is compressed and discharged. is there. In such a reciprocating compressor, a piston ring is provided on the outer peripheral side of the piston in order to seal the gap between the piston and the cylinder, in other words, between the compression chamber and the crank chamber.

  In such a reciprocating compressor, in order to improve the sealing performance of the piston ring in the compression stroke, a ring groove having a tapered bottom is formed on the outer peripheral side of the piston, and an O-ring is attached to the ring groove. In some cases, a piston ring is arranged on the outer peripheral side of the O-ring (see, for example, Patent Document 1). As a result, when the piston ring and the O-ring move in the ring groove to the opposite side of the compression chamber due to sliding resistance with the cylinder in the compression stroke, the diameter is expanded by the taper shape of the ring groove, and the contact force to the cylinder is increased. This will improve the sealing performance.

Further, in the reciprocating compressor, in order to improve the sealing performance of the piston ring in both the compression stroke and the suction stroke, two piston rings having lip portions extending in the opposite directions are provided on the outer peripheral side of the piston. There are some (see, for example, Patent Document 2). As a result, the piston ring having the lip portion extending to the compression chamber side in the compression stroke is expanded in diameter by receiving the gas pressure, and the contact force to the cylinder is increased to improve the sealing performance, and compression is performed in the suction stroke. The piston ring having a lip portion extending to the opposite side of the chamber is expanded in diameter by receiving the gas pressure, and the contact force to the cylinder is increased to improve the sealing performance.
JP-A-61-38180 Japanese Utility Model Publication No. 63-12669

  When the above-described piston having a ring groove with a tapered bottom is used, the sealing performance in the compression stroke can be improved, but the sealing performance is lowered in the suction stroke. For this reason, blow-by in which the gas on the crank chamber side enters the compression chamber occurs in the suction stroke, which causes a decrease in the purity of the compressed gas and a load fluctuation of the piston due to a change in the internal pressure of the crank chamber.

  In addition, when two piston rings having opposite lip portions as described above are used, the problem of blow-by hardly occurs, but since the piston ring is always in sliding contact with the inner surface of the cylinder, wear durability is reduced. There was a problem.

  Therefore, an object of the present invention is to provide a reciprocating compressor that can achieve both the sealing performance of the suction stroke and the compression stroke and the improvement of the durability of the piston ring.

  In order to achieve the above object, the present invention provides a first piston ring that is mounted in a first ring groove on an outer peripheral side of a piston and seals between the cylinder during a suction stroke of the piston, A second piston ring that is attached to the second ring groove on the outer peripheral side and seals between the piston and the cylinder during the compression stroke of the piston, and the bottom of the first ring groove and the second ring The bottoms of the grooves are inversely tapered.

  According to the present invention, it is possible to achieve both the sealing performance of the suction stroke and the compression stroke and the improvement of the durability of the piston ring.

“First Embodiment”
A reciprocating compressor according to a first embodiment of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the reciprocating compressor 11 of the first embodiment includes a cylindrical cylinder 13 on which a cylinder head 12 is mounted, a piston 14 slidably fitted in the cylinder 13, A connecting rod 15 having one end connected to the piston 14 is provided.

  Here, although not shown, the other end of the connecting rod 15 is connected to a crank that is eccentrically moved by the driving force of the electric motor, and the piston 14 is moved into the cylinder 13 via the connecting rod by the eccentric movement of the crank. To reciprocate.

  The piston 14 defines a compression chamber 20 between the piston 14 and the cylinder head 12, and defines a crank chamber 21 in which the crank is disposed on the opposite side of the cylinder head 12. The piston 14 reciprocates to expand and contract the volume of the compression chamber 20. Although illustration is omitted, when the compression chamber 20 is enlarged, a suction valve provided in the cylinder head 12 is opened, gas is sucked into the compression chamber 20, and the compression chamber 20 is contracted to be provided in the cylinder head 12. The discharged discharge valve is opened and the gas in the compression chamber 20 is discharged while being compressed.

  As shown in FIG. 2, an annular first ring groove 25 is formed on the outer peripheral side of the piston 14 on the compression chamber 20 side (upper side in FIG. 2), and compression of the first ring groove 25 is performed. An annular second ring groove 26 is formed on the side opposite to the chamber 20.

  The first ring groove 25 is a tapered first taper part 25a whose diameter increases toward the compression chamber 20 side, and the bottom part of the second ring groove 26 contracts toward the compression chamber 20 side. A tapered second tapered portion 26a is formed. That is, the first tapered portion 25a at the bottom of the first ring groove 25 and the second tapered portion 26a at the bottom of the second ring groove 26 are opposite to each other so as to form a V shape. It has a tapered shape. Here, the first taper portion 25a of the first ring groove 25 and the second taper portion 26a of the second ring groove 26 have the same groove width, minimum diameter, and maximum diameter. As a result, the taper angle with respect to the cylinder axis is the same, and only the taper direction is reversed. Further, the first ring groove 25 and the second ring groove 26 are separated from each other in the cylinder axis direction, and therefore, a partition wall 27 having a larger diameter than these is provided between them.

  The first ring groove 25 is fitted with a first piston ring 30 that is in sliding contact with the inner surface of the cylinder 13 and seals the gap between the piston 14 and the cylinder 13. In other words, the first piston ring 30 partitions the compression chamber 20 and the crank chamber 21. The inner surface of the first piston ring 30 is a tapered first abutting portion 30 a that matches the first tapered portion 25 a of the first ring groove 25. Here, as shown in FIG. 1, the first piston ring 30 is formed with an abutment portion 30b so as to be cut out in a substantially L shape at a midway portion in the circumferential direction, and is sealed by the abutment portion 30b. It is possible to expand and contract while maintaining the properties. The first contact portion 30a has at least the same taper angle as the first taper portion 25a.

  The second ring groove 26 is fitted with a second piston ring 31 that is in sliding contact with the inner surface of the cylinder 13 and seals the gap between the piston 14 and the cylinder 13. The second piston ring 31 also defines the compression chamber 20 and the crank chamber 21. The inner surface of the second piston ring 31 is a tapered second abutting portion 31 a that matches the second tapered portion 26 a of the second ring groove 26. Here, as shown in FIG. 1, the second piston ring 31 is also formed with an abutting portion 31b so as to be cut out in a substantially L shape at a middle portion in the circumferential direction, and is sealed by the abutting portion 31b. It is possible to expand and contract while maintaining the properties. The second contact portion 31a also has the same taper angle as that of at least the second taper portion 26a.

  Note that the first piston ring 30 and the second piston ring 31 have an outer diameter that is smaller than the inner diameter of the cylinder 13 in a natural state. Used in reverse.

  In the suction stroke in which the piston 14 expands the compression chamber 20, the first piston ring 30 is placed in the first ring groove 25 on the compression chamber 20 side (see FIG. 3) due to sliding resistance with the cylinder 13. 3) and the second piston ring 31 also moves to the compression chamber 20 side in the second ring groove 26. Then, the first piston ring 30 increases in diameter following the expansion of the first taper portion 25a of the first ring groove 25 that comes into contact with the first contact portion 30a, and the contact force to the cylinder 13 is increased. Is tightly contacted to seal with the cylinder 13. On the other hand, the second piston ring 31 can be reduced in diameter following the reduced diameter of the second taper portion 26a of the second ring groove 26 that comes into contact with the second contact portion 31a, and its own elastic restoring force Thus, a gap is formed between the cylinder 13 and the cylinder 13. That is, during the suction stroke of the piston 14, the first piston ring 30 seals between the cylinder 13, and the second piston ring 31 does not exhibit sealing performance.

  Conversely, in the compression stroke in which the piston 14 reduces the compression chamber 20, the second piston ring 31 is moved into the compression chamber 20 within the second ring groove 26 as shown in FIG. 4 due to sliding resistance with the cylinder 13. The first piston ring 30 also moves in the first ring groove 25 to the opposite side to the compression chamber 20. Then, the second piston ring 31 expands in accordance with the diameter expansion of the second taper portion 26a of the second ring groove 26 that comes into contact with the first contact portion 30a, and the contact force to the cylinder 13 is increased. Is tightly contacted to seal with the cylinder 13. On the other hand, the first piston ring 30 can be reduced in diameter in accordance with the reduced diameter of the first taper portion 25a of the first ring groove 25 that comes into contact with the first contact portion 30a, and its own elastic restoring force Thus, a gap is formed between the cylinder 13. That is, during the compression stroke of the piston 14, the second piston ring 31 seals between the cylinder 13 and the first piston ring 30 does not exhibit sealing performance.

  In the suction stroke, after the first piston ring 30 starts sealing with the cylinder 13, the second piston ring 31 finishes sealing with the cylinder 13, and in the compression stroke, The first piston ring 30, the second piston ring 30, and the second piston ring 31 end the seal with the cylinder 13 after the second piston ring 31 starts the seal with the cylinder 13. The dimensional relationship among the piston ring 31, the first tapered portion 25a, and the second tapered portion 26a is set.

  According to the first embodiment described above, the first taper portion 25a of the first ring groove 25 and the second taper portion 26a of the second ring groove 26 are reversely tapered. The first abutting portion 30a of the first piston ring 30 has a tapered shape that matches the first tapered portion 25a, and the second abutting portion 31a of the second piston ring 31 is the second tapered portion. 26a, the first piston ring 30 and the second piston ring 31 are sealed and the other is separated from the cylinder 13 and compressed in the suction stroke as described above. In the stroke, the other side is sealed and the one side is separated from the cylinder 13. Therefore, since the sealing performance between the cylinder 13 and the piston 14 can be ensured not only in the compression stroke but also in the suction stroke, the occurrence of blow-by can be suppressed, and the first piston ring 30 and the second piston ring 31 are suppressed. In any case, since either one of the suction stroke and the compression stroke mainly exhibits a sealing property, durability can be improved.

  The first piston ring 30 abuts against the inner surface of the cylinder 13 during diameter expansion following the first taper portion 25a and seals between the cylinder 13 and the piston 14, while the first taper portion 25a A gap is formed between the second piston ring 31 and the inner surface of the cylinder 13 at the time of diameter expansion following the second taper portion 26a. While sealing between the piston 13 and the piston 14, a gap is formed between the inner surface of the cylinder 13 when the diameter is reduced following the second taper portion 26a. it can.

“Second Embodiment”
A reciprocating compressor according to a second embodiment of the present invention will be described below mainly with reference to FIG. 5 with a focus on differences from the first embodiment. Note that the same parts as those in the first embodiment have the same names and the same reference numerals, and description thereof will be omitted.

  In the second embodiment, the arrangement of the first ring groove 25 and the second ring groove 26 of the piston 14 is opposite to that of the first embodiment. In other words, the second ring groove 26 having a tapered second taper portion 26a whose diameter increases toward the side opposite to the compression chamber 20 is formed on the compression chamber 20 side, and the diameter increases toward the compression chamber 20 side. A first ring groove 25 having a tapered first taper portion 25 a is formed on the opposite side of the second ring groove 26 from the compression chamber 20. As a result, the first taper portion 25a of the first ring groove 25 and the second taper portion 26a of the second ring groove 26 have two first ring grooves 25 and two second ring grooves 26. They are mutually reverse tapered so as to form a letter shape.

“Third Embodiment”
A reciprocating compressor according to a third embodiment of the present invention will be described below with reference mainly to FIG. 6 focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment have the same names and the same reference numerals, and the description thereof will be omitted.

  In the third embodiment, the first ring groove 25 and the second ring groove 26 have different taper angles at the bottom of each other. That is, the first taper portion 25a of the first ring groove 25 and the second taper portion 26a of the second ring groove 26 have the same minimum diameter and maximum diameter, and the second taper portion. The groove width of the portion 26a is wider than that of the first taper portion 25a, and the taper angle of the second taper portion 26a is smaller than that of the first taper portion 25a. As a result, the timing of expanding the diameter in the suction stroke is advanced, and the timing of expanding the diameter in the compression stroke is delayed, so that the occurrence of the incomplete seal state of the first piston ring 30 and the second piston ring 31 is suppressed. It has become.

  In the first to third embodiments, the materials of the first piston ring 30 and the second piston ring 31 may be different. For example, when the gas to be compressed is a special gas such as nitrogen gas, depending on the type of gas, the wear of the piston ring may be deteriorated, so that a high-cost special material piston ring may have to be used. In the case of handling such a gas, only the second piston ring 31 that performs sealing during the compression stroke needs to be expensive, and the cost can be reduced. If the structure of 2nd Embodiment is employ | adopted at this time, it will become difficult to expose the 1st piston ring 30 which seals by a suction stroke to the atmosphere of the compression chamber 20, and is more preferable.

  In the first to third embodiments, the shapes of the first piston ring 30 and the second piston ring 31 are not limited to the above. For example, as shown in FIG. Or an elliptical cross section (or a circular shape) as shown in FIG.

It is a fragmentary sectional view showing the reciprocating compressor of a 1st embodiment of the present invention. It is a fragmentary sectional view which shows the piston and piston ring in the reciprocating compressor of 1st Embodiment of this invention. It is a fragmentary sectional view which shows the piston and piston ring of the suction stroke in the reciprocating compressor of 1st Embodiment of this invention. It is a fragmentary sectional view which shows the piston and piston ring of the compression stroke in the reciprocating compressor of 1st Embodiment of this invention. It is a fragmentary sectional view which shows the piston and piston ring in the reciprocating compressor of 2nd Embodiment of this invention. It is a fragmentary sectional view which shows the piston and piston ring in the reciprocating compressor of 3rd Embodiment of this invention. It is a fragmentary sectional view which shows the modification of the piston ring in the reciprocating compressor of 1st-3rd embodiment of this invention. It is a fragmentary sectional view which shows another modification of the piston ring in the reciprocating compressor of 1st-3rd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Reciprocating compressor 12 Cylinder head 13 Cylinder 14 Piston 20 Compression chamber 25 1st ring groove 25a 1st taper part (bottom part)
26 2nd ring groove 26a 2nd taper part (bottom part)
30 1st piston ring 30a 1st contact part (inner peripheral surface)
31 2nd piston ring 31a 2nd contact part (inner peripheral surface)

Claims (3)

A cylinder mounted with a cylinder head;
In a reciprocating compressor having a piston slidably inserted into the cylinder and defining a compression chamber between the cylinder head and reciprocating,
A first piston ring that is mounted in a first ring groove on the outer peripheral side of the piston and seals between the piston and the cylinder during a suction stroke;
A second piston ring that is mounted in a second ring groove on the outer peripheral side of the piston and seals between the piston during the compression stroke of the piston;
A reciprocating compressor characterized in that a bottom portion of the first ring groove and a bottom portion of the second ring groove are reversely tapered. The first piston ring has an abutment portion and is mounted in the first ring groove so that the diameter of the first piston ring can be increased or decreased. The first piston ring contacts the inner surface of the cylinder when the diameter is increased following the bottom of the first ring groove. In contact with and sealing between the cylinder and forming a gap with the cylinder inner surface at the time of diameter reduction following the bottom of the first ring groove,
The second piston ring has an abutment portion and is mounted in the second ring groove so that the diameter of the second piston ring can be expanded and contracted. 2. The reciprocating compressor according to claim 1, wherein a space is formed between the cylinder and an inner surface of the cylinder when the diameter is reduced following the bottom of the second ring groove. .   The reciprocating compressor according to claim 1, wherein the first ring groove and the second ring groove have different taper angles at the bottom.

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