JPH089985B2 - Oil-free reciprocating compressor and expander - Google Patents

Description

The present invention relates to an oil-free reciprocating compressor and an expander, and more particularly to a piston body fitted with a piston ring formed of a self-lubricating material and a metal-made piston body. The present invention relates to an oil-free reciprocating compressor including a cylinder and an expander.

“Prior Art” Conventionally, in order to ensure smooth slidability between a piston and a cylinder, for example, as shown in FIG. 3, from the top side of the piston 10 formed of aluminum or other metal material to the skirt side. Ring groove 11 in a multi-step shape over almost the entire outer peripheral surface
1a, 111b, 111c are recessed, piston rings 105a, 105b and a rider ring 106 made of fluororesin or other self-lubricating resin are annularly provided in the ring groove, and the ring outer diameter is set to the land portion 102 of the piston ( The ring-shaped protrusion that holds the piston ring above and below the ring groove) By setting the diameter slightly larger than the outer diameter, the self-lubricating piston rings 105a, 105
Only oilless compressors and expanders are known that are configured so that only b and the rider ring 106 (hereinafter referred to as the ring body) come into contact with the cylinder, which ensures smooth slidability between the piston and cylinder. Is.

In the case of such a fluid machine, since the cylinder is made of a metal material harder than the piston ring, if the ring body wears due to the sliding contact and the wear limit is exceeded due to long-term operation, the outer circumference of the piston (land portion) ) May directly contact the cylinder, causing galling and the like.

In particular, in the case of a compressor having a compression ratio of 5 kgf / cm ² or more, thermal expansion occurs because the compression heat of around 300 ° C is applied to the top surface of the piston at the time of maximum compression, and even if the ring body slightly wears This causes the problem of rubbing against the cylinder.

In order to eliminate such drawbacks, in a known compressor, a polytetrafluoroethylene (PTFE) resin material with good sliding performance is used for the ring body, and the piston / cylinder clearance is set to the piston outer diameter. For 1
~ 2% (0.5-1mm for 50mmφ piston outer diameter) is set.

However, if such a configuration is adopted, the clearance between the piston and the cylinder becomes unnecessarily large at the initial stage of compression or at the time of intermittent operation, and the compression rate is likely to decrease correspondingly.

In order to eliminate such drawbacks, a technique has been started to prevent self-lubricating resin from being applied on the surface of a piston made of aluminum so as to prevent galling even when the outer circumference of the piston slides on the cylinder. However, since the heat-resistant strength of the self-lubricating resin such as PTFE, which has been widely used in conventional piston rings, etc., is around 200 to 250 ° C, when the adiabatic compression is increased to 5 kgf / cm ² or more as described above. In addition, the heat of compression easily exceeds the heat resistant temperature of the PTFE, deterioration and deformation of the piston surface coating, further peeling due to the difference in the coefficient of thermal expansion between the piston body made of aluminum material, etc. Since cracks and the like may occur, this technique has a drawback that it cannot be applied to a low-pressure compressor that has a small temperature rise due to compression heat.

Further, in any of the above-mentioned prior arts, the piston itself is made of a metal material, particularly an aluminum material in order to achieve weight reduction. However, since the aluminum material has a high thermal conductivity, the compression received by the top surface of the piston The heat is transmitted to the entire piston, and especially the pin hole that transmits the movement of the connecting rod that drives the piston via the piston pin also becomes high temperature, and in the case of an oilless compressor, means such as oil cooling of the piston pin is required. Since it is impossible, it is necessary to use bearing parts etc. having heat resistance, and the piston pin portion has a large load per unit area as compared with other bearings, resulting in heat resistance Since a bearing having a load bearing property must be used, the cost increase and the deterioration of durability are likely to occur.

In general, a reciprocating compressor has a C-shape in which one end of a circular ring is cut in order to allow a piston ring that performs an airtight seal to be inserted into a ring groove. In this case, as described above, the clearance between the piston and the cylinder is larger than that in the oil-filled compressor, so that gas leakage is likely to occur from the joint (abutment) between the ring ends.

For this reason, similar to a normal compressor, even in an oil-free compressor, it is necessary to discriminate the shape of the abutment part into a shape such as a step cut, and the rings are arranged in multiple stages so that the abutment of each ring is a shaft. The positions are shifted in the circumferential direction so that they do not coincide with the same position in the direction, but even with this configuration, there is a ring-shaped gap between the piston land and the cylinder that exists between the upper and lower piston rings. Since there is a clearance, the abutments of the adjacent rings communicate with each other through the clearance, and gas leakage cannot be prevented.

In order to solve such a drawback, there is a technique of arranging a pin or other fixing means for the piston ring in the ring groove of the piston and fixing the position of the abutment portion on the side thrust side in close contact with the cylinder during the compression process. Conceivable. (This technology is used in the field of refueling type compressors.
No. 60-26236, it is new in the field of oilless compressors. ) However, in the oilless compressor, since the piston maintains the non-contact state with the cylinder as described above, even if it is attempted to seal the side thrust side close to the cylinder with the mating portion of the piston ring, As long as there is an abutment that is cut in the direction, it cannot be completely sealed, and since the piston ring used in oilless compressors is not made of metal, it is resin resistant. It is difficult to take a structure in which a part is cut out and engaged with the pin, and if a pin is provided at a position corresponding to the abutment portion, the abutment portion is separated and gas leakage occurs from the separated portion. I will end up.

[Problems to be Solved by the Invention] In view of the drawbacks of the prior art, it is an object of the present invention to provide an oil-free reciprocating compressor / expander that does not cause galling or decrease in compression efficiency (expansion efficiency). To do.

Another object of the present invention is to provide an oil-free reciprocating pressure welding machine in which deformation or deterioration of the piston does not occur even when high compression heat comes into contact with the top of the piston.

Another object of the present invention is to provide an oil-free reciprocating compressor / expander capable of maintaining high compression efficiency (expansion efficiency) for a long period of time without causing gas leakage or galling from the ring gap. To provide.

[Means for Solving the Problem] A. Invention according to claim 1) (first invention) In order to achieve such an object, the first invention is a thermosetting condensed polycyclic polynuclear aromatic compound recently developed. A resin (hereinafter referred to as COPNA resin) is used as a molding material, and a heat-resistant material that enhances slidability, for example, graphite and a material that enhances strength such as carbon fiber, if necessary, are mixed into the resin to improve heat resistance and strength. Resin-based composite material (self-lubricating composite material) with improved self-lubricating property
Is used to form a piston body from the composite material.

According to this invention, the heat distortion temperature of the COPNA resin itself is 250 ° C. or higher and the molding resin is molded by adding a material having higher heat resistance such as graphite, so that the heat resistance is 300 In order to maintain around ℃ or more,
Even if the adiabatic compression ratio is set to 5 kgf / cm ² or more (compression heat is around 300 ° C), the piston does not undergo any thermal deformation and heat deterioration does not occur over a long period of time.

Further, since the composite material is formed by mixing graphite etc., which enhances slidability, it has a self-lubricating function by itself, and as a result, no galling occurs even if the piston itself comes in sliding contact with the cylinder. Smooth sliding performance can be obtained.

Furthermore, since the coefficient of thermal expansion is several steps lower than that of aluminum material, there is no problem even if the clearance between the piston and the cylinder is made small, and it is possible to improve the compression efficiency rather. In this case, in order to obtain a high compression efficiency without causing galling due to thermal expansion, the most preferable clearance is a range where galling does not occur, so that it can be fitted tightly, more specifically about 0.1 to 0.5% at room temperature with respect to the piston diameter. It is better to set to, and since the thermal conductivity of the piston is smaller than that of aluminum material in particular, the amount of heat of compression heat stored at the top of the piston is large and the thermal expansion coefficient at the top and bottom of the piston is different during compression operation. , The clearance between the piston and the cylinder becomes non-uniform, and the compression efficiency is likely to be adversely affected. Therefore, it is preferable that the diameter of the upper side of the piston is relatively smaller than the diameter of the lower side, and preferably, it is formed in an inverse tapered shape.

On the other hand, the fact that the thermal conductivity of the composite material is several orders of magnitude lower than that of the aluminum material has a preferable effect on the piston pin side bearing portion.

That is, since the piston made of composite material has a low thermal conductivity, the compression heat received at the top surface of the piston is released from the metal cylinder rather than being transferred from the top to the piston pin side. Since the temperature of the pin hole portion is suppressed, as a result, the piston pin portion can be formed without taking heat resistance into consideration, and a special bearing member is provided because the piston itself has a self-lubricating function. It is possible to directly fit the piston pin without any problem.

As a result, the number of parts can be reduced and the cost can be reduced, and since the pin hole portion is not exposed to high temperature, the durability can be improved.

Further, the pin hole portion receives a shock when the piston moves from the ascending step to the descending step or from the descending step to the ascending step, and in a structure using a conventional bearing, the impact causes deterioration of the bearing or the like. Since the piston itself made of the composite material having elastic force functions as the bearing, the impact can be absorbed by the piston and the durability can be improved.

B. Outline of the second invention described in claim holes 2) and 3) In the above invention, since the piston itself has a lower heat conduction than the aluminum material, it is possible to prevent the piston pin from becoming highly heated.
On the contrary, high heat is accumulated on the top of the piston, and the compression efficiency may be reduced even if the heat resistant temperature of the composite material itself is not exceeded.

Therefore, in the invention described in claim 2), a smooth sliding function between the cylinder and the piston pin portion and discharge /
Separates the heat-resistant (thermoelectric carrying) function on the top facing the suction valve, in other words the top of the piston that comes into contact with compression heat, and at least the portion of the outer periphery that slides on the cylinder and the piston pin hole are self-lubricating By forming a heat-resistant material and the piston top part with a good heat conductive material such as aluminum, respectively, and providing the good heat conductor on the piston top side substantially extending to the back side of the piston top part, the above-mentioned drawbacks Is intended to be resolved.

According to this structure, since the piston top side that comes into contact with the compression heat is made of a material such as aluminum, the top portion is deformed or deformed even if the adiabatic compression ratio is increased and the compression heat rises up to around 300 ° C. Without deterioration, the top portion is cooled by touching cold air at the time of suction, so that compression heat is easily discharged through the discharged air without being accumulated.
As a result, the self-lubricating heat-resistant material is made of, for example, a fluororesin having a low heat-resistant temperature, without increasing the heat transfer temperature to the portion formed of the self-lubricating heat-resistant material located below the heat-transfer temperature to a position close to the compression heat. Even if formed, it can be easily maintained at a heat resistant temperature or lower.

Further, in the invention described in claim 3), particularly in this case, the heat dissipation effect is further improved by forming the top land portion where the compression heat is most easily transmitted together with the piston top portion by using a good heat conductor, It is even possible to use fluororesin with a lower heat resistant temperature. In this case, set the outer diameter of the top land to be slightly smaller than the piston diameter below it to avoid rubbing against the cylinder side. With this configuration, it is possible to prevent galling of the top land portion and ensure smooth piston sliding performance. That is, at least the outer peripheral surface side of the piston main body that slides against the cylinder is formed of a self-lubricating heat resistant material, and since the outer peripheral surface side avoids heat transfer of compression heat as described above as much as possible, It becomes easy to secure smooth sliding property even with a low material.

Therefore, the self-lubricating heat resistant material according to the present invention is not necessarily limited to the COPNA resin composite material, and it is also possible to form a polytetrafluoroethylene (PTFE) resin or its composite material, and further a fluororesin. Is.

The structure of the present invention is, as shown in FIG. 4, a piston formed by integrally molding the composite material around the piston core formed of a metal material. With the core made of metallic material exposed, the outer circumference of the piston that is in sliding contact with the cylinder and the pin hole part may be integrally formed into a thick wall using the composite material. While forming with material
A metal body having good heat conductivity may be disposed at least on the top side of the piston facing the discharge valve, and the two may be integrated by using any fixing means.

In this case, the good thermal conductor on the top of the piston is extended to the back side of the top of the piston either directly or through a connecting body such as a rivet, so that heat is dissipated from the inside of the piston and the piston slides. It is possible to reduce the heat transfer to the surface side and avoid the temperature rise on the outer peripheral side as much as possible to ensure smooth slidability between the piston and the cylinder.

C. Summary of Third Invention of Claims 4) to 6) The present invention is based on the following idea in order to prevent gas leakage at the mating portion of the piston ring as described above.

First, even if you try to seal the side thrust side that is in close contact with the cylinder during the compression process with the abutment part of the pinton ring, as long as there is an abutment part that is cut in the axial direction, it is possible to completely seal it. In the conventional oil-free compressor, the piston and the cylinder are kept in non-contact with each other, so it is necessary to seal only at the aforesaid joint. There is a problem that the condition is bad.

Therefore, in the present invention, the piston or its sliding surface is formed of a self-lubricating composite material as in the first aspect of the present invention to enable sliding contact with the cylinder of the piston itself, and to provide a side thrust portion in close contact with the cylinder during the compression process. The first feature is that the sliding surface of the piston itself located allows a substantially airtight seal.

In this case, the piston sliding surface facing the cylinder may be formed of a self-lubricating composite material, or only the cylinder side or both of the cylinder and the piston or the surface layer portion thereof may be formed of a self-lubricating composite material. .

However, even if configured as described above, if a ring groove exists in the side thrust portion, the sealing is dependent on the piston ring, in other words, the sealing condition depends on the mating portion of the piston ring existing at the ring groove position. Resulting in.

Therefore, in the present invention, without providing a ring groove at the side thrust position, the ring groove is formed in a C shape separated by the side thrust portion so that the piston peripheral surface itself can be sealed.

And, as a function of preventing rotation of the mating end of the piston ring, the separated portion formed at the side thrust position is used to form a circular shape in the combination of the separated portion of the ring groove and the piston ring, and the seal circle is used. As a result, the cylinder can be hermetically sealed.

The present invention is not limited to the single-stage compressor according to claim 4), and may include the oil-free single-stage reciprocating expander according to claim 5) and the oil-free multi-stage reciprocating compression according to claim 6). In the case of the former expander, the piston itself located in the side thrust portion that is in close contact with the cylinder during the expansion process can be configured as described above, and in the case of the latter multistage reciprocating compressor, The above configuration may be applied to the side thrust portion that is in close contact with the cylinder during the piston raising process on the stage side, and to both side thrust portions during the piston raising process and the descending process on the high stage side.

That is, at least the outer peripheral surface side of the piston body that slides against the cylinder is formed of a self-lubricating composite material, and as described above, heat transfer of compression heat is avoided as much as possible, so that the smooth sliding described above is performed. It becomes easy to secure the sex.

Further, in the case of the expander according to claim 5), since it is not necessary to consider heat resistance, the molding material of the piston body is COPNA.
The material is not limited to the resin or its composite material (self-lubricating composite material), and it can be formed of a PTFE resin or its composite material.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be exemplarily described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only thereto, but merely illustrative examples. Nothing more than.

First, referring to FIG. 1, a description will be given of a main part configuration of an oilless compressor to which the present invention is applied. Reference numerals 2 and 3 are a cylinder and a cylinder head made of aluminum or another metal having good conductivity. A spacer 4 in which a discharge valve 4A and a suction valve 4B are incorporated is sandwiched between the two. The inside of the cylinder head 3 is divided by a partition wall 3A, and a corresponding suction chamber is provided with a suction port 3B communicating with the suction valve 4B and a discharge port 3C communicating with the discharge valve 4A.

On the other hand, a piston 1 having a piston ring 5 installed therein is fitted in the cylinder 2, and the connecting rod 6 and the piston pin 7 (second
The piston 1 reciprocates via the suction valve 4B, whereby the air sucked into the top space of the piston 1 via the suction valve 4B is adiabatically compressed and discharged from the discharge valve 4A to the discharge port 3C side. The compression operation is performed. Since such an operation is already well known, its explanation is omitted.

Now, FIG. 2 is an embodiment of the first invention showing the essential structure of the piston and cylinder part incorporated in the oilless compressor.

The cylinder 2 is made of an aluminum alloy, as is well known, and has a fin 2a on the outer peripheral surface and a hard alumite treatment on the piston sliding portion on the inner peripheral surface side.

Next, before explaining the shape of the piston 1, the piston 1
The manufacturing procedure will be described in detail.

This piston 1, as shown in USP 4,758,653, is a COPNA resin formed by bridging between condensed polycyclic aromatic compounds with a benzene ring having two methylene chains, one at the para position (Japanese Patent Resin material (trade name SK resin: SUMITOMO METALS CO.
LTD) and graphite powder are mixed at a ratio of 6: 4, and the molding material is molded at a molding temperature of 170 to 220 ° C. and a molding pressure of 200 to 3
Molding is carried out under the molding conditions of 00 KG / cm ² and curing time of 1 min / 1 mm thickness by the compression molding means or injection molding means similar to the known phenol resin molding.

The piston 1 thus formed has physical properties such as a thermal expansion coefficient of 4.4X10 ^-5 / deg and a thermal conductivity of 1.12 kcal / m / .hr ° C. : 2.3X10 ^-5 /
deg, thermal conductivity: 0.013 kcal / m / .hr ℃), the thermal expansion coefficient is 1.9 times and the thermal conductivity is 1/86 times that of the piston 1 formed with
A piston 1 having high heat insulation and heat storage could be formed.

Next, the shape of the piston 1 will be described. The outer diameter shape has a taper shape that spreads downward to a skirt portion below the piston top portion 13 with a dimensional difference considering a thermal gradient. For example, thermal expansion of the piston 1 and the cylinder 2 is performed. The difference in rate Δb is 2.
Since it is 1X10 ^-5 / deg, if the temperature difference between the upper and lower parts of piston 1 is Δt and the outer diameter of piston 1 is P, then Δt · P
If the taper difference is set to (2.1X10 ^-5 / deg), the clearance of piston 1 / cylinder 2 during compression operation can be maintained uniformly.

Further, since the clearance receives the compression heat of about 300 ° C. at the piston top 13, the clearance is set to about 0.1 to 0.5% with respect to the diameter of the piston 1 at room temperature without causing galling during the compression operation, and The clearance between 1 / cylinder 2 can also be kept to the minimum value that does not interfere with reciprocating motion, and as a result, the entire outer circumference of piston 1 can function as a sliding surface with the surface of cylinder 2, so the graphite of the piston can be used in the cylinder. By transferring, the sliding property and the sealing property are further improved. As a result, the piston ring 5
Gas leakage that occurs through the peripheral surface of the piston 1 can be greatly reduced from the contact portion 5a, etc., and the compression efficiency can be improved.

Further, a ring groove 11 and a pin hole 12 are sequentially formed from the top side of the piston 1.

The ring groove 11 is formed as a ring circle in the vicinity of the piston top portion 13 as much as possible, and the piston ring 5 made of PTFE resin is fitted into the ring groove 11.

In this embodiment, since the piston itself has a certain degree of sealing effect, it is not necessary to provide two piston rings 5 as in the conventional apparatus, and one piston can obtain a predetermined sealing effect.

The pin hole 12 is provided at a substantially intermediate position of the piston 1 and is ground so that the pin hole 12 directly functions as a bearing.

Then, the piston pin 7 is mounted in the pin hole 12, and the piston 1 is driven by the rotary motion of the crankshaft through the connecting rod 6.
Exercise up and down.

In this case, when the piston 1 is moved from the ascending step to the descending step or from the descending step to the ascending step, an impact is received, and in a structure using a conventional bearing, the impact causes deterioration of the bearing, but in the present invention, the elastic force is used. Since the piston 1 itself having the function as a bearing functions as the bearing, the impact can be absorbed by the piston 1 and the durability can be improved.

In such an embodiment, the oilless compressor is provided with a third
The one using the conventional piston 101 shown in the figure and the one using the piston 1 according to the present embodiment (piston diameter 50 mm)
After carrying out continuous load operation of 7 kgf / cm ² and disassembling and confirming each under load operation for 1000 hours, it was found that the conventional compressor was 10
It was confirmed that a biting mark was seen on the land part of the piston 1 after running for 00 hours, and the bearing fitted in the pin hole 12 of the piston pin 7 part was also worn and the noise during load operation became loud. It was On the other hand, in the case of this embodiment, after 1000 hours have passed, the sliding surface of the piston 1 shows some marks, but no galling occurs, and the pin hole 12 has a slight degree of wear. It was confirmed that there was no backlash between them. In terms of temperature, a reduction of 25 ° C was seen at the piston.

FIG. 4 shows a piston 1 according to an embodiment of the second invention used in the compressor, which is a piston core 10A made of a metal material.
The composite material 10B is integrally molded around the periphery to form a thick piston
Is formed.

Briefly describing the specific configuration, the piston core body 10A is formed of an aluminum alloy, the upper surface thereof is formed in a flat shape, and fin-shaped projections are provided on the inner peripheral surface side along the axial direction.

Then, the composite material 10B is integrally formed thickly on the outer periphery of the piston core 10A and the piston pin hole 12 to form the piston 10.

That is, with the piston core 10A exposed at the top of the piston, the plurality of members 10B are thickly surrounded by the outer periphery of the piston 10 slidingly contacting the cylinder 2 and the pin hole 12 portion.

The composite material 10B has a wall thickness of 50φ for the piston 10,
It is preferable that the pin hole 12 has a thickness of 1 to 3 mm and the outer peripheral portion has a thickness of about 2 to 3 mm.

According to this embodiment, the same effect as that of the first embodiment can be obtained, and the piston top portion and the inner peripheral surface side, which have the highest temperature, are formed of an aluminum alloy having good thermal conductivity. The generated compression heat is radiated through the inner peripheral surface of the piston 10 and the high pressure compressor can be used, and the compression efficiency can be improved.

For example, in Example 1 shown in FIG. 2 in which the entire piston 1 is formed of a composite material, and with respect to the piston 10 of this example, the temperature rise of each part is checked after 1H load operation at 7 kgf / cm ² , In the first embodiment, the back side of the piston 1 is 125 to 1
In contrast to the temperature rise of 30 ° C., that of the present embodiment is 80 to 90.
℃ was significantly reduced, and even at the piston pin hole 12 part, a temperature decrease of about 10 ℃ was seen from that of Example 1,
It can be estimated that the durability is improved accordingly.

FIG. 5 shows a modified example of the above embodiment, in which the entire outer peripheral portion of the piston 20 is made of the heat resistant composite material 21B, and the head portion 21A surrounded by the 21B is made of an aluminum alloy. A piston 1 in which a large number of downwardly radiating fins 21C are provided on the surface side is disclosed. According to such an embodiment, in addition to the effects of the aforementioned embodiment, the heat dissipation of the piston top portion 13 is achieved by the aforementioned radiating fins 21C. Further, the cooling effect of the piston 1 is further enhanced, and since the entire outer peripheral portion 21B is formed of the self-lubricating heat resistant composite material, the sliding friction between the head portion 1A and the cylinder 2 is completely cut off.

In the second embodiment, since the resin material is also present in the 14 parts of the top land that directly receives the compression heat, there is no other choice but to use the above-mentioned high heat resistant Copna resin composite material as the resin material. .

Therefore, FIG. 6 shows a ring groove in order to eliminate the above-mentioned drawback.
A piston head 30A made of an aluminum material in which the upper top land 14 of 11 parts and the piston top 13 are formed with a predetermined thickness,
It is composed of a piston body 30B made of a self-lubricating heat resistant material integrally formed with the head 30A.

Top land 14 above ring groove 11 and piston top
The head 30A side including 13 having a predetermined thickness is formed of an aluminum material, and the piston main body 30B including the ring groove 11 therebelow is integrally molded. Then, the head 30A sets the outer diameter of the top land 14 part to be slightly smaller than the diameter of the piston body 30B below it, and bends the lower end side 31 inward in a key shape in section to form a combination with the piston body 30B. We are trying to make it easier.

The piston body 30B is formed by using a molding material in which graphite is mixed with SK resin 40% in the same manner as in the above-mentioned embodiment, and by performing casting molding integrally with the head 30A that has been previously molded and cured using the molding material. It is good, but the piston top 13
Since the heat on the side does not directly contact the resin body, it is possible to use the same PTFE resin as the piston ring 5 or a composite material thereof.

Further, according to such an embodiment, since the head 30A having good thermal conductivity is formed up to the top land 14 where the compression heat is most easily transmitted together with the piston top portion 13, the heat dissipation effect is further improved, and the piston main body side has the above-mentioned structure. Since the material is used, the heat-resistant temperature is 300 ° C. or higher, and it is possible to form a good piston 1 with less thermal deformation.

FIG. 7 shows another embodiment using a rivet coupling means, in which the piston body 40B and the head 40A are individually formed, and then they are integrally fixed by a rivet 41.

That is, the head 40A causes the piston 1 to move into the ring groove 11
A disk-like plate having a shape cut horizontally from the upper surface side is formed, and its diameter is formed to be slightly smaller than the diameter of the piston body 40B made of a self-lubricating resin material located below, and the head 40A. Between the piston body 40B and the piston body 40B, as shown in FIGS. 7 (b) and (C), the four rivets 41 having good thermal conductivity are integrally fixed, and the rivet end 41a extends to the rear surface side of the piston top portion 13. Configure to extend. In this embodiment, it is possible to obtain the same effect as that of the above embodiment. That is, as a result, the compression heat transferred to the head 40A side can be dissipated to the lower side of the piston 1 via the rivet 41 or diffused to the entire piston main body 40B. It can eliminate thermal problems.

FIG. 8 and FIG. 9 show the essential configuration of a single-stage oilless reciprocating compressor to which the third invention is applied.

As in the case of the first embodiment, the piston 50 is a compounded granular resin having a resin skeleton of COPNA resin) and graphite.
It is formed by integrally molding a molding material mixed with 40%, and as shown in FIG.
A pin hole 12 for inserting a piston pin is cut or drilled.

The ring groove 51 has a U-shaped cross section without chamfering the upper and lower end portions and side end portions, and the ring shape is formed circumferentially with respect to the entire circumferential surface of the piston 1. Instead, it is formed in a C shape, and the portion where the ring groove 51 is not formed (spaced portion 52) is formed so as to be located on one line orthogonal to the inserting direction of the pin hole 12.

In other words, the entire circumferential surface of the piston 1 is the ring groove 51.
The position of the ring groove 51 is set so as to be continuous in the axial direction only on the one orthogonal line without being divided by.

On the other hand, the piston ring 5 is formed of PTFE resin as is well known, and its cross-sectional shape is matched with the ring groove 51 to have a rectangular cross-section without chamfering the upper and lower end portions and side end portions, and its planar shape is Formed so that the ring 5 has the same shape as the ring groove 51 when it is fitted / compressed and deformed in the ring groove 51, and the mating port 5a at the end of the ring 5 is closely attached to the end of the ring groove 51. To do.

Then, after the piston ring 5 is fitted to the piston 1, the inside of the cylinder 2 is positioned so that the separated portion 52 is located in the side thrust portion S ₁ -S ′ ₁ which is in close contact with the cylinder 2 during the compression process (raising process). Incorporate piston 50 into.

According to this embodiment, since the separated portion 52 of the piston is located at the side thrust portion that comes into close contact with the cylinder 2 during the compression process, the side thrust portion is sealed by the peripheral surface of the pistrin 50 itself including the separated portion 52. The piston ring 5 does not move in the circumferential direction, and the abutment portion 50 is held in position at the separated portion 52. Therefore, an inscribed circle having the separated portion 52 as a contact point with the piston 50. It can be formed with the piston ring 5.

As a result, although the piston 50 and the cylinder 2 are separated from each other in the parts other than the side thrust parts S ₁ -S ′ ₁ ,
At that portion, since the piston ring 5 is inscribed in the circumferential surface of the cylinder 2, the combination of the separated portion 52 of the ring groove 51 and the piston ring forms a circular shape that is sealed over the entire circumference of the cylinder 2, The cylinder 2 can be configured to be hermetically sealed by using the sealing circle.

FIG. 10 shows another embodiment in which the third invention is applied to an oil-free single-stage reciprocating expander. In the case of the compressor, the crankshaft 7 rotates to receive compressed air on the upper surface of the piston 50. When the direction is counterclockwise, the side thrust portion S ₁ -S ′ ₁ exists on the left side. However, in the case of the expander, unlike the compressor, the expansion step exists during the piston descending step, so the crankshaft 7 When the rotation direction is counterclockwise, that is, when the rotation direction is counterclockwise, the side thrust portion S ₁ -S ′ ₁ is present on the right side. As a result, in the case of an expander, the separation portion 52 is located on the opposite side of the compressor. Formed on the circumferential surface of the piston.

In the case of the expander, since it is not necessary to consider heat resistance, the molding material of the piston body is not limited to COPNA resin or its composite material, but polytetrafluoroethylene (PTFE) resin or its composite material. It is also possible to form with.

FIG. 11 is another embodiment in which the present invention is applied to an oil-free two-stage reciprocating compressor, in the case of a two-stage compressor, the air pressure compressed on the low pressure side is applied to the high pressure side piston even during the suction step, As a result, the side thrust part S ₁ − in the suction process
_'Side thrust unit in _one compression step S _{1 -S'} S ₁
It will be located on the opposite side 180 degrees away from.

Therefore, it is necessary to provide an airtight seal between the piston 50A / cylinder 2A on the high-pressure side in both the suction process and the compression process. Therefore, in this embodiment, the ring groove 51A,
Two upper and lower 51B are provided and the ring grooves 51A and 51B are
Piston rings 5A and 5B, which are formed in the same manner as in the above-described embodiment, are fitted to each other by being cut symmetrically at 0 °.

As a result, for example, the side thrust portion 53A on the side of the top ring 5A is sealed during the suction process on the high stage side (see FIG. 11A), and the second ring is pressed on the compression process on the high stage side (see FIG. 11B). The side thrust portion 53B on the 5B side is sealed, and as a result, reliable sealing is possible in both the suction process and the compression process.

[Advantages of the Invention] As described above, according to the first aspect of the present invention, by using the thermosetting condensed polycyclic polynuclear aromatic, it is possible to use a resin or a sliding resin which has been impossible in a conventional industrial compressor. A compressor using a piston with the entire moving part made of resin becomes possible, the above-mentioned effects due to the weight reduction of the piston, simplification of the structure by the formation of the sliding surface of the material, and the durability of the piston are greatly improved. Even if the wear progresses due to long-term use, maintenance can be done for a long time without causing fatal defects, and there is no galling or compression efficiency (expansion efficiency) reduction. Oil-free reciprocating compressor / expander Can be provided.

According to the second aspect of the present invention, the smooth sliding function with the cylinder and the heat-resistant function on the top of the piston facing the discharge / suction valve, in other words, on the top of the piston that comes into contact with the compression heat are separated to separate the outer peripheral portion. At least the part that slides against the cylinder is made of a self-lubricating heat resistant material, and the piston top is made of a good heat conductive material having a higher heat conductivity than the heat resistant material such as aluminum. Even if high compression heat comes into contact with the piston top without lowering, the piston top is repeatedly cooled by cold air during intake, so the temperature of the piston top can be reduced, and therefore the piston outer circumference and piston hole that become the sliding surface It is possible to provide an oil-free reciprocating compressor in which deformation or deterioration of the piston does not occur due to suppression of temperature rise due to temperature propagation to the piston.

Further, according to the third aspect of the present invention, as compared with the conventional oil-free type fluid machine, the gas leakage from the piston ring mating port is completely sealed, and the separated portion functioning as a rotation stopper for the piston ring is also provided. Since it is formed integrally with the piston itself, not only the structure is extremely simple and permanent deterioration does not occur, but also it becomes compatible with use for many years, and high compression efficiency can be maintained over a long period of time.

It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is a sectional view showing an oilless reciprocating compressor to which the present invention is applied, and FIG. 2 is a sectional view showing a main part configuration of an oilless reciprocating compressor according to an embodiment of the first invention, and FIG. Is a cross-sectional view showing the structure of a main part of a conventional oil-free reciprocating compressor, FIG. 4, FIG.
FIG. 6 and FIG. 6 are sectional views showing pistons according to respective embodiments of the second invention. FIG. 7 shows a piston according to another embodiment, (a) is a judgment surface view, (b) is a bottom view and a sectional view taken along the line AA '. FIG. 8 is a front sectional view and an AA ′ line sectional view showing one embodiment in which the third invention is applied to an oil-free single-stage reciprocating compressor.
FIG. 9 is a perspective view of an essential part showing the peripheral surface shape of the piston, and FIG.
The drawing is a schematic view showing another embodiment in which the third invention is applied to an oil-free type single-stage reciprocating expander and a sectional view taken along the line BB '. First
FIG. 11 is a schematic view showing another embodiment in which the present invention is applied to an oilless type two-stage reciprocating compressor, and (A) shows a suction process on the high stage side.
(B) shows a sliding contact state between the piston and the cylinder in the high-stage compression process.

Claims (6)

[Claims] 1. An oil-free reciprocating compressor and expander comprising a piston body fitted with a piston ring formed of a self-lubricating material and a metal cylinder, wherein the piston body is a thermosetting condensed polycyclic polynuclear Aromatic resin,
It is formed of a self-lubricating composite material containing graphite and other heat-resistant materials that enhance slidability, and at least the clearance between the piston and the cylinder near the top of the piston is 0.1 to 0.5 at room temperature with respect to the piston diameter.
%, The diameter of the upper part of the piston was made smaller than the diameter of the lower part, and the piston pin was directly supported in the pin hole penetrating the body of the piston body without a bearing. Oil-free reciprocating compressor and expander characterized 2. A self-lubricating reciprocating compressor and expander comprising a piston body fitted with a piston ring formed of a self-lubricating material and a metal cylinder, wherein at least the cylinder of at least the outer peripheral portion of the piston body is slidable. The part to be rubbed and the piston pin hole are made of a self-lubricating heat resistant material, and the piston top is made of a good heat conductive material, and the good heat conductor on the top side is extended substantially to the back side of the piston top. Oil-free reciprocating compressor and expander characterized by being installed 3. A self-lubricating reciprocating compressor and expander comprising a piston body fitted with a piston ring made of a self-lubricating material and a metal cylinder, wherein at least the cylinder is slidable on at least the outer peripheral portion of the piston body. The part to be rubbed and the piston pin hole are made of a self-lubricating heat resistant material, and the top part of the piston including the top land part above the piston ring is made of a good heat conductive material, and the outer diameter of the top ramp part is Set slightly smaller than the piston diameter, and the piston top and the piston body are integrated by using any fixing means, and an oil-free reciprocating compressor and an expander are provided. 4. An oil-free single-stage reciprocating compressor including a piston fitted with a piston ring formed of a self-lubricating material, wherein at least a sliding surface of the piston or / and the cylinder is formed of a self-lubricating composite material. At the same time, the ring groove formed on the peripheral surface of the piston is formed in a C shape with its both ends being separated by a small distance, and the separated portion is a side thrust portion that is in close contact with the cylinder during the compression process. An oil-free single-stage reciprocating compressor characterized in that a piston is incorporated so as to be positioned, and the cylinder can be hermetically sealed in a combination of the separated portion and the piston ring. 5. In an oil-free single-stage reciprocating expander including a piston fitted with a piston ring formed of a self-lubricating material, at least the sliding surface of the piston or / and the cylinder is formed of a self-lubricating heat resistant material. In addition, the ring groove formed on the peripheral surface of the piston is formed in a C shape in which both ends thereof are separated from each other by a small distance, and the separated portion is a side thrust portion that is in close contact with the cylinder during the expansion process. An oil-free single-stage reciprocating expander characterized in that a piston is incorporated so as to be positioned, and a corresponding cylinder can be hermetically sealed in a combination of the separated portion and a piston ring. 6. An oil-free multistage reciprocating compressor including a piston fitted with a piston ring formed of a self-lubricating material on both the low-stage side and the high-stage side, at least the low-stage side and the high-stage side. Also forms the sliding surface of the piston and / or the cylinder with a self-lubricating composite material, and forms a ring groove formed on the peripheral surface of the piston in a C shape in which both ends thereof are separated by a small distance. However, on the low-stage side, the above-mentioned separated parts should be located in the side thrust parts that are in close contact with the cylinder during the piston rising process, and on the high-stage side, in the side thrust parts during both the piston rising process and the descending process. The oilless multistage reciprocating compressor characterized in that the corresponding cylinders can be hermetically sealed in the combination of the separated portion and the piston ring.