JP2013044272A - Reciprocating compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reciprocating compressor having a piston ring causing no welding at a piston ring abutment part by heat generation caused by operation in the reciprocating compressor having the piston ring subjected to abutment working so as to be expandable and contractible in diameter.SOLUTION: The reciprocating compressor includes a compressor body for compressing air by the reciprocating motion of a piston mounted with the piston ring, inside a cylinder, and a motor for driving the compressor body. The piston ring has an abutment part expandable and contractible in diameter, uses PTFE (polytetrafluoroethylene) as a base material with copper powder filled therein, and has particle diameters of the filled copper powder being distributed to have at most 10% of 100 μm or more.

Description

  The present invention relates to a reciprocating compressor provided with a piston ring.

  The piston ring for an air compressor described in Patent Document 1 is characterized in that PTFE is used as a base material and a lubricant and a spherical carbon material are filled.

  In addition, the sealing material for an air compressor described in Patent Document 2 has a powdery hard material having an old Mohs hardness of 6 to 8 and an average particle size of 100 μm or less, a polytetrafluoroethylene resin and / or a four-fluid material. Composed of a composite material containing a fluorinated ethylene / perfluoroalkoxyethylene resin, and the hard material is one or more selected from diatomaceous earth, tourmaline, silicate mineral, metal oxide, and tetrafluoroethylene The perfluoroalkoxyethylene resin has a molecular weight of 5 million or more and is non-thermoplastic.

Japanese Patent Application No. 10-78045 Japanese Patent Application No. 2004-135785

  The ring materials described in the above two patent documents improve wear resistance. However, when the compressor is further reduced in size and pressure, welding of the piston ring joint becomes a major issue.

  Therefore, in view of the above problems, the present invention provides a reciprocating compressor having a piston ring that can be expanded and contracted and subjected to joint processing, and has a piston ring that does not cause welding at the piston ring joint portion due to heat generated by operation. The purpose is to provide.

  The present invention includes a compressor main body that compresses air by reciprocating a piston having a piston ring in a cylinder, and a motor that drives the compressor main body. And a reciprocating compressor characterized in that the particle size distribution of the filled copper powder is 100 μm or more and 10% or less using PTFE as a base material. .

  ADVANTAGE OF THE INVENTION According to this invention, the reciprocating compressor which has a piston ring in which the fusion part of a piston ring does not generate | occur | produce welding by the heat_generation | fever by a driving | operation of a compressor can be provided.

It is a sectional side view of the compressor main body which concerns on Example 1 of this invention. It is a piston ring which concerns on Example 1 of this invention. It is a mixing | blending of the piston ring which concerns on Example 1 of this invention. It is the size and ratio of the filler which concerns on Example 1 of this invention. It is a test result of the welding confirmation which concerns on Example 1 of this invention. It is an enlarged view of the piston ring joint part which concerns on Example 1 of this invention. It is a mixing | blending of the piston ring which concerns on Example 2 of this invention. It is the size and ratio of the filler which concerns on Example 2 of this invention. It is a test result of the welding confirmation which concerns on Example 2 of this invention.

  An air compressor body and piston ring material according to an embodiment of the present invention will be described in detail with reference to the drawings.

  First, the structure of the compressor main body that compresses air in the air compressor according to Embodiment 1 of the present invention will be described below with reference to FIG. In addition, although the present Example demonstrates by the compressor which compresses air, when compressing other fluids, the same effect can be show | played.

  Reference numeral 1 denotes a compressor body that compresses air. The compressor body 1 includes a crankcase 1A and cylinders 18A and 18B attached to the crankcase 1A. A shaft (rotary shaft) 6A of the motor 6 passes through the crankcase 1A.

  A crankcase 1A covers the compressor body 1 and the motor 6. A stator 2 is directly fixed to one end side of the crankcase 1A and a bearing 3 is mounted. A bearing box 5 to which a bearing 4 is mounted is fitted on the opposite side of the stator 2 from the mounting side. ing. A key 12 is provided at the center of the shaft 6A penetrating the crankcase 1A. In addition, a piston 14 fitted with a piston ring 24 for sealing air and a piston 25 fitted with a lip ring 26 for sealing air are inserted together with a balance 17 via an eccentric 16 eccentric with the bearing 15. The The piston 14, the piston 25, and the balance 17 are supported from both sides by the two bearings 3 and 4 attached to the crankcase 1 </ b> A and the bearing housing 5. In this embodiment, the piston ring 24 is provided only for the piston 14 that reciprocates in the high-pressure side cylinder 18A, but the piston ring 24 is similarly provided for the piston 25 that reciprocates in the low-pressure side cylinder 18B. May be.

  Reference numeral 6 denotes a motor for driving the compressor body 1. The motor 6 includes a stator 2, a bearing 3, a shaft 6A, a key 7, a rotor 8, and a washer 9. A cooling fan 10 is provided at an end of the shaft 6A. A rotor 8 is attached to one end side of the shaft 6A via a key 7. The rotor 8 is fixed in the axial direction by a fan shaft 11 for attaching a washer 9 and a cooling fan 10.

  Reference numeral 10 denotes a cooling fan for cooling components of the air compressor such as the stator 2, the cylinders 18A and 18B, and the cylinder heads 21A and 21B. The cooling fan 10 is provided at the end of the shaft 6 </ b> A by the fan shaft 11 and is driven by the motor 6.

  18A is a high-pressure side cylinder attached to the crankcase. In this embodiment, two cylinders 18A and 18B are provided on the high and low pressure sides, and the pair of cylinders 18A and 18B are attached so as to face each other with the crankcase interposed therebetween. The cylinder 18A includes a flange 19A, an air valve 20A, and a through bolt 22A. The cylinder head 21A and the crankcase 1A are provided with a flange 19A for mounting the cylinder 18A. The cylinder 18A, the air valve 20A, and the cylinder head 21A are fixed to the flange 19A by a through bolt 22A, and the compression chamber 23A is formed. Forming.

  Similarly, 18B is a low-pressure side cylinder attached to the crankcase. The cylinder 18B includes a flange 19B, an air valve 20B, and a through bolt 22B. The cylinder head 21B crankcase 1A is provided with a flange 19B for mounting the cylinder 18B. The cylinder 18B, the air valve 20B, and the cylinder head 21B are fixed to the flange 19B by a through bolt 22B to form a compression chamber 23B. is doing.

  The operation of the compressor body 1 in this embodiment will be described with reference to FIGS. In the compressor body 1 in this embodiment, when the shaft 6A is rotated by driving the rotor 8, the piston 25 having the lip ring 26 is reciprocated while the lip ring 26 slides with the cylinder 18B in the compression chamber 23B by the eccentric 27. To do. The piston 25 having the lip ring 26 sucks air into the compression chamber 23B through the crankcase 1A and the cylinder 19B in the suction process from the top dead center toward the bottom dead center, and conversely in the discharge process toward the top dead center. The compressed air is discharged through the air valve 20B and the cylinder head 21B while being compressed to about 0.7 MPa, and the discharged compressed air is sent to the cylinder head 21A on the high pressure side through the pipe 28. Similarly to the low pressure side, the shaft 6A is rotated by driving the rotor 8, and the piston 14 having the piston ring 24 is reciprocated in the compression chamber 23A by the eccentric 16 while the piston ring 24 slides on the cylinder 18A. The compressed air sent from the low-pressure side cylinder 18A is sucked into the compression chamber 23A through the cylinder head 21A and the air valve 20A in the suction process in which the piston 14 having the piston ring 24 moves from the top dead center to the bottom dead center. As an example of high compression in the discharge process toward the top dead center, it is compressed again to about 4.2 MPa. The compressed air passes through the pipe 29 and is stored in the air tank 30. Thus, the compressor main body 1 of the present embodiment is a two-stage compressor that compresses air in two stages. In the two-stage compressor, the pressure ratio on the low-pressure side and the high-pressure side is smaller than that in the case of the single-stage compression. Therefore, the heat generated in the compression section can be reduced by improving the efficiency. However, since this compressor is an oil-free compressor and does not use lubricating oil, the piston ring 24 has PTFE as a base material and is highly slidable filled with molybdenum disulfide, copper powder, carbon, etc. A member with excellent wear resistance is used. Therefore, the temperature of the compression part tends to be higher than that of the oil supply type. In addition, since this compressor compresses high-pressure air of 4.0 MPa or higher, the compression heat generated by compression is higher than that of a standard compressor that compresses air to about 1.0 MPa, and the compression section Temperature tends to rise.

  Next, the welding of the piston ring 24 according to the first embodiment of the present invention will be described below with reference to FIGS.

  As the piston ring used in the first embodiment, a leak cut piston ring 24A shown in FIG. 3 or a step cut piston ring 24B shown in FIG. 4 is mainly used. The leak-cut piston ring 24A and the step-cut piston ring 24B have a joint portion 31, and the joint portion 31 freely expands and contracts, so that the piston ring 24 is deformed according to the shape of the cylinder 18A during the compression process. Thus, the cylinder 18A and the piston ring 24 are sealed.

  As described above, since this compressor is an oil-free compressor and a high-pressure compressor, the temperature of the compression section is higher than that of an oil-provided compressor or a low-pressure compressor of about 1.0 MPa. Furthermore, as the needs of products, the size and pressure of compressors are increasing, and there is a problem that the temperature of the compression section rises accordingly. When the temperature of the compression part rises, the piston ring 24 based on PTFE, which is a thermoplastic resin, softens. When the piston ring abutment portions 25 are pressed against each other with the compressed air generated by the operation of the compressor while being cooled, the piston ring abutment portions are welded. This occurs because PTFE, which is the main material of the piston ring, is a thermoplastic resin, so that the abutment portions adhere to each other when the ring is softened, and PTFE is cured when the ring temperature is lowered. Note that when the joint portions are pressed against each other at a higher pressure, for example, 4.0 MPa or more, the joint portions are more easily welded. As described above, the leak-cut piston ring 24A and the step-cut piston ring 24B have the abutment portion 31, and the abutment portion 31 freely expands and contracts so that the piston ring seals with the cylinder 18B. When the parts are welded, the piston ring does not expand or contract (because the joint portions are fixed and the ring diameter does not change), the compressor does not increase in pressure even when the operation is performed. For this reason, up to now, the efficiency of cooling of the compressor body 1 has been improved, but it is indispensable to establish means effective for this problem when aiming at further higher pressure and smaller size in the future. Therefore, this problem was solved not by improving the cooling performance but by improving the materials shown below.

  Conventionally, in an oil-free reciprocating compressor, in order to improve slidability and heat dissipation, for example, PTFE (polytetrafluoroethylene) mixed with graphite or the like is used for the piston ring 24. In some cases, PTFE is mixed with molybdenum disulfide or bronze powder. However, in the piston ring 24 having the joint portion such as the step cut piston ring 24B and the leak cut piston ring 24A, there is a problem that the joint portion of the piston ring 24 is welded as described above.

  Therefore, a specific embodiment of the present invention that solves the above problem will be described below. First, PTFE as a base material, spherical carbon to improve the strength of the ring, copper powder to dissipate the heat of the piston ring by operating the compressor, disulfide to improve the slidability of the ring and cylinder Piston rings (Comparative Example 1 and Examples 1 and 2) were prepared by compression molding, heat treatment, and cutting a mixture of molybdenum in the types and ratios shown in the columns of Comparative Example 1 and Examples 1 and 2 in FIG. Obtained. In addition, the particle size distribution of the mixed copper powder is shown in FIG. Here, as shown in FIG. 6, the particle size distribution of the copper powders of Comparative Example 1 and Examples 1-2 is at least 15% or more in 100 μm in Comparative Example 1, and 100 μm or more in Example 1. Is 10%, and in Example 2, 100% or more is 0%.

  Then, the piston ring is mounted on the compressor shown in FIG. 1 and continuously operated at a high temperature and a high load (4.2 MPa). After the temperature has been saturated, the compressor is cooled to room temperature with the load applied. A welding reproduction test was conducted. The result is shown in FIG.

  From the results of FIG. 7, it can be seen that welding occurred in Comparative Example 1, and the welding could be prevented in Examples 1 and 2. That is, it can be seen that the occurrence of welding can be prevented by setting the particle size distribution of the copper powder filled in PTFE to be 10% or less when the particle size is 100 μm or more. This is because when the piston ring 24 having a reduced diameter portion such as the step cut piston ring 24B or the leak cut piston ring 24A is cut, the copper powder is dropped from the processed surface, and the generation of the hole 33 shown in FIG. 9 can be prevented. is there. The joint portion of the piston ring 24 is processed with a blade, but if the copper powder 32 filled in the piston ring 24 is present on the processed surface, the copper powder 32 may fall off during processing as shown in FIG. . When the copper powder 32 falls off during processing, a large number of holes 33 as shown in FIGS. 8 and 9 are generated in the piston ring joint portion 31, and when the piston ring joint portions are pressed against each other by compressed air generated by operation. Since the area where the piston ring abutment portions contact each other is smaller than in the prior art, the surface pressure of the abutment contact surface increases and welding is likely to occur.

  Therefore, by reducing the particle size of the filled copper powder, it is difficult for the copper powder to fall off during ring processing, and even if the copper powder falls off, the hole is small, preventing an increase in surface pressure at the joint. Can do.

Thus, when the distribution of the particle size of the copper powder filled in the PTFE of the piston ring is such that the particle size of 100 μm or more is 10% or less, welding of the piston ring joint can be prevented as follows. There is an effect like this.
(1) Piston ring joint can be produced at low cost without the need for special coating treatment (2) Highly reliable piston ring even if temperature rises due to downsizing and high pressure of the compressor Can be provided.
(3) The piston ring joint portion need not be polished in a separate process and can be produced at low cost.
(4) The running-in operation for wearing the piston ring joint portion is not required, and the productivity can be improved.

1 Compressor body 1A Crankcase 6 Motor 6A Shaft 10 Cooling fan 18 Cylinder 21 Cylinder head 24 Piston ring

Claims (6)

A compressor body that compresses air by reciprocating a piston having a piston ring in the cylinder;
A motor for driving the compressor body,
The piston ring has a joint portion that can be expanded and contracted, PTFE is used as a base material, copper powder is filled, and the particle size distribution of the filled copper powder is 100 μm or more and 10% or less. A reciprocating compressor characterized.   The reciprocating compressor according to claim 1, wherein the compressor body is an oil-free type that does not use lubricating oil during compression.   The reciprocating compressor according to claim 1, wherein the compressor body is boosted to a pressure of 4.0 MPa or more.   2. The reciprocating compressor according to claim 1, wherein the compressor main body performs two-stage compression in which the air compressed by the low pressure side cylinder and the piston is further compressed by the high pressure side cylinder and the piston. .   The reciprocating compressor according to claim 4, wherein a lip ring is attached to the low pressure side piston, and the piston ring is attached to the high pressure side piston.   The reciprocating compressor according to claim 1, wherein the piston ring is filled with molybdenum disulfide, copper powder, and carbon.

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