JP2008157076A - Reciprocating gas compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniform surface pressure of a piston ring of each stage, solve a problem such as partial wear of a high-pressure side piston ring, elongate the life of the piston rings, and reduce a maintenance cost of a reciprocating gas compressor with simple structure, in a reciprocating gas compressor. <P>SOLUTION: A high-pressure gas compressor compresses gas by reciprocating a piston 18 in a cylinder. In the high-pressure gas compressor, the piston rings 23 are fitted to the piston in a multi-stage manner, a part of each of the piston rings is cut out to form a clearance, the clearances are formed so that the clearance gets smaller from the high-pressure side toward the low-pressure side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reciprocating gas compressor for compressing a gas to a high pressure, and more particularly to an oil-free reciprocating compressor for compressing a gas such as natural gas.

  As a compressor that compresses a gas such as natural gas to a high pressure, there is a compressor in which a plurality of cylinders are connected in series, and the compression pressure is sequentially increased for each cylinder in each stage to obtain a desired high pressure.

  An example of such a high pressure gas compressor is shown in FIG.

  A plurality of crosshead guides 2 are provided radially on the crankcase 1, and a cylinder 3 is provided concentrically with the crosshead guide 2 at the tip of the crosshead guide 2. A crosshead 4 is slidably provided on the crosshead guide 2, and a piston 5 is slidably provided on the cylinder 3. The piston 5 and the crosshead 4 are concentric via a piston rod 9. It is connected to.

  A crankshaft 6 is rotatably provided in the crankcase 1, and the crosshead 4 is connected to the crankshaft 6 via a connecting rod 7, and the crankshaft 6 is connected to a motor (not shown).

  The cylinder head of the cylinder 3 is provided with an intake / exhaust valve unit 8, and an intake / exhaust pipe (not shown) is connected to the intake / exhaust valve unit 8. The intake / exhaust valve units 8 and 8 are connected by the pipe via a cooler (not shown), and the exhaust gas from the low pressure side cylinder 3 is cooled by the cooler to be high pressure side cylinder 3. It is designed to be led to the air intake.

  By rotating the crankshaft 6 by a motor (not shown), the piston 5 is reciprocated through the connecting rod 7 and the crosshead 4 to perform intake and compression, and further, the pressure is increased in multiple stages by each cylinder 3. As a result, the high-pressure gas is finally exhausted.

  The piston 5 is provided with a piston ring so that the inside of the cylinder is an airtight chamber. Also, when the gas to be pressurized is natural gas or the like, it is not preferable that lubricating oil be mixed in. Therefore, the piston ring is made of a synthetic resin that has self-lubricating properties and can be operated without lubrication. Is done.

  FIG. 6 shows a conventional piston 5 and a piston ring group 11 fitted to the piston 5.

  The piston 5 is provided at the tip of the piston rod 9, and the piston ring group 11 is provided on the piston 5.

  The piston 5 is provided with ring grooves 12 at predetermined intervals at predetermined intervals, and piston rings 13 are respectively fitted into the ring grooves 12, and the piston rings 13 are arranged in a plurality of stages (12 stages in FIG. 6). 11 is configured.

  The piston ring 13 is cut at one portion of the ring and is fitted in a state where the diameter is slightly reduced, and a certain gap is formed at the cut portion. In the operating state, a surface pressure is applied to the piston ring 13 by a high-pressure gas, and the piston ring 13 is in sliding contact with the inner surface (cylinder liner) of the cylinder 3 with a required surface pressure. The piston ring 13 is made of a synthetic resin, has a self-lubricating property, has no oil supply, and has wear resistance and sealing properties.

  Here, the surface pressure acting between the piston ring 13 and the cylinder liner is determined by the pressure difference between the high pressure side and the low pressure side with the piston ring 13 interposed therebetween, and the piston rings 13 are provided in multiple stages. By making sliding contact with the cylinder liner, the pressure drops for each stage of the piston ring 13 and a high pressure difference is sealed.

  FIG. 7 shows the result of analyzing the pressure in the ring gap 14 formed between the rings in the conventional piston ring group 11.

  From the high pressure side, the first stage ring gap 14-1, the second stage ring gap 14-2, the third stage ring gap 14-3, the fourth stage ring gap 14-4,..., The eleventh stage ring The gap 14-11 is shown, and the same reference numerals are given to the curves showing the pressure of each gap in FIG. In FIG. 7, the vertical axis represents pressure, and the horizontal axis represents crank angle.

  According to the analysis results, the pressure drops greatly in the first-stage ring gap 14-1, the second-stage ring gap 14-2, and the third-stage ring gap 14-3. No pressure drop was observed.

  As described above, since the surface pressure acting between the piston ring 13 and the cylinder liner is determined by the pressure difference between the high pressure side and the low pressure side, the first stage piston ring 13 and the second stage piston ring A large surface pressure acts on 13. For this reason, it is considered that the load on the first stage piston ring 13 and the second stage piston ring 13 is large and wear progresses, and the life of the piston ring group 11 is also the first stage piston ring 13, the second stage piston ring 13. This is influenced by the wear state of the piston ring 13.

  When the piston ring 13 is actually operated, the piston ring group 11 is worn by the first and second piston rings 13 because the first and second piston rings 13 are significantly worn. The maintenance period is also determined by the wear of the plurality of piston rings 13 on the high pressure side such as the first stage and the second stage.

  The piston 5 is provided with a passage communicating the ring groove 12 and the compression chamber, and a back pressure caused by a compressed gas is applied to the inner peripheral surface of the piston ring 13 so that the piston ring 13 and the piston Patent Document 1 discloses that the surface pressure acting between cylinder liners is reduced.

  However, it is troublesome to drill a large number of passages in the piston, and it is more troublesome to change the diameter of the passages in order to reduce the back pressure stepwise.

JP-A-8-270557

  In view of such circumstances, the present invention has a simple configuration and gradually reduces the pressure in the gap formed between the rings, equalizes the surface pressure of the piston ring at each stage, and the high-pressure side piston ring is locally worn. It is intended to eliminate problems such as to extend the life of the piston ring and to reduce the maintenance cost of the reciprocating gas compressor.

  The present invention provides a high-pressure gas compressor in which a piston is reciprocated in a cylinder to compress gas, and a piston ring is fitted into the piston in multiple stages, and the piston ring is partially cut away to form a gap. And the gap is large on the high pressure side and small on the low pressure side.

  Further, the present invention relates to a reciprocating gas compressor in which the gap decreases toward the low pressure side. In the gap, the pressure between the rings drops for each stage, and the amount of pressure drop is equal or substantially equal. The present invention relates to a reciprocating gas compressor set as described above.

  According to the present invention, in a high-pressure gas compressor in which a piston reciprocates in a cylinder to compress gas, the piston ring is fitted into the piston in multiple stages, and the piston ring is partially cut off. Thus, the gap is large on the high pressure side and small toward the low pressure side, so that the piston ring on the high pressure side is prevented from being locally worn, and the life of the piston ring can be extended. In addition, since the piston is not required to be processed and only the gap between the piston rings needs to be changed, the manufacturing cost can be reduced, and the present invention can be applied to an existing reciprocating gas compressor.

  Further, according to the present invention, the gap decreases toward the low pressure side, or the gap is such that the pressure between the rings drops at each stage and the amount of pressure drop becomes equal or substantially equal. As a result, the pressure between the rings is equalized, the surface pressure of the piston ring in all stages is averaged, the wear of the piston ring is also averaged, the life of the piston ring is extended, and the reciprocating gas is further increased. Excellent effects such as reduction of compressor maintenance costs.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 shows a piston to which the present invention is applied. The reciprocating gas compressor in which the present invention is implemented is the same as the reciprocating gas compressor illustrated in FIG. Further, in FIG. 1, the same components as those shown in FIG.

  A piston core shaft 15 extends from the piston rod 9 to the cylinder head side, and a piston washer 16, a base rider ring 17, a piston 18, from the base end (crank shaft 6 side end, see FIG. 5) side to the piston core shaft 15. The front end rider ring 19 is sequentially fitted, and the nut 21 is screwed to the front end (cylinder head side end) of the piston core shaft 15.

  If the nut 21 is tightened and an initial tension is generated in the piston core shaft 15, it is possible to prevent a decrease in the tightening force at the time of temperature expansion or to increase the apparent rigidity.

  Ring grooves 22 are engraved in multiple stages (17 stages in the figure) at predetermined intervals in the piston 18, and piston rings 23 are fitted into the ring grooves 22, respectively, and a multistage piston ring group 24 is constituted by the piston rings 23. Is done. As the material of the piston ring 23, a synthetic resin having lubricity, for example, a tetrafluoride resin (PTFE) is used. The base rider ring 17 and the distal end rider ring 19 have a guide function for the piston ring group 24. Even when the piston ring 23 is worn, the piston 18 is attached to the inner surface (cylinder liner) of the cylinder 3. There is no contact.

  As shown in FIG. 2, the piston ring 23 is cut at one portion of the ring, and the piston ring 23 is fitted in the ring groove 22 so that a gap 25 is formed at the cut portion. It has become.

  Also, the size of the gap 25 is different at the position of the groove in which the piston ring 23 is fitted. The size of the gap 25 is set so as to gradually decrease from the high pressure side to the low pressure side in the fitted state.

  If the piston rings fitted in the ring groove 22 are piston rings 23-1, 23-2, 23-3, 23-4,..., 23-17 from the high pressure side, the size of the gap 25 is, for example, As shown in FIG.

  In addition, the value of the gap 25 shown in FIG. 3 shows an average value and shows an example. The gap 25 is set so that the pressure descending from the piston ring 23 becomes equal and substantially equal for each stage of the piston ring 23.

  4 shows the pressure in the ring gaps 26-1, 26-2,... When the gap 25 of the piston ring 23 is gradually reduced from the high pressure side toward the low pressure side. In FIG. 4, the vertical axis represents pressure, and the horizontal axis represents crank angle.

  From the high pressure side, a ring gap 26-1 between the first-stage piston ring 23 and the second-stage piston ring 23, a ring gap 26-2 between the second-stage piston ring 23 and the third-stage piston ring 23, 3 A ring gap 26-3 between the stage-stage piston ring 23 and the fourth-stage piston ring 23,..., And a curve indicating the pressure of the gap of each stage in FIG. .

  As shown in FIG. 4, the pressure drop when the gap 25 is gradually reduced from the high pressure side to the low pressure side is dispersed by each stage piston ring 23, and the pressure drop for each stage is It is almost equal. In particular, it is preferable that the pressure drop amount is uniform and substantially uniform at the maximum pressure.

  For this reason, the surface pressure between the piston ring 23 and the cylinder liner is also equalized for each stage, and the wear of the piston ring 23 is also distributed to all stages, thereby extending the life.

  In particular, by increasing the gap 25 of the high-pressure side piston ring 23 relative to the low-pressure side, the surface pressure of the high-pressure side piston ring 23 is reduced, and the high-pressure side piston ring 23 is locally worn. That can be avoided.

  For the low pressure side, two piston rings 23 may be fitted in one ring groove 22 in order to improve the sealing performance.

  In the present invention, the surface pressure of the piston rings 23 in all stages can be averaged only by changing the gap 25 of the piston ring 23 in accordance with the provided position, and processing and manufacture are easy. Further, since the piston does not need to be processed, it can be applied to an existing reciprocating gas compressor.

It is sectional drawing which shows the piston and piston ring which are used for the reciprocating gas compressor which concerns on this invention. (A) Front view of the piston ring, (B) Side view of the piston ring. It is a figure which shows the relationship between the position of a piston ring, and the clearance gap formed in this piston ring. It is a diagram which shows the pressure between rings which concern on this invention. It is sectional drawing which shows a reciprocating gas compressor. It is sectional drawing which shows the conventional piston and piston ring. It is a diagram which shows the pressure between rings in the conventional reciprocating gas compressor.

Explanation of symbols

3 Cylinder 9 Piston rod 15 Piston core shaft 18 Piston 22 Ring groove 23 Piston ring 25 Clearance

Claims (3)

  In a high-pressure gas compressor in which a piston reciprocates in a cylinder to compress gas, a piston ring is fitted into the piston in multiple stages, and the piston ring is partially cut away to form a gap, The reciprocating gas compressor is characterized in that the gap is large on the high pressure side and small on the low pressure side.   The reciprocating gas compressor according to claim 1, wherein the gap decreases toward the low pressure side.   The reciprocating gas compressor according to claim 1, wherein the gap is set so that the pressure between the rings drops for each stage and the amount of pressure drop is equal or substantially equal.

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