JPH08254178A - Reciprocating compressor - Google Patents

Abstract

PURPOSE: To prevent early wear of a piston ring by reliably opening and closing a communication hole through which a space part, partitioned by a cylinder, a piston, and a piston ring, is communicated with the interior of a crank case. CONSTITUTION: A communication hole 20 through which a space part S and the interior of a crank case are intercommunicated is provided and a pressure adjusting valve 24 having a each valve part to open and close each communication hole 20 is arranged on the inner peripheral side of a piston 14, and a pressure in the space part S is adjusted by the pressure adjusting valve 24. Thus, even when a pressure in a compression chamber 15 is low, a communication passage 20 is cutoff through the pressure adjusting valve 24 and leak of compression to a chamber A on the crank case side. Further, even when a pressure in the compression chamber 15 is high, at a point of time when a pressure in the space part S attains a given value, the pressure adjusting valve 24 is opened and each communication hole 20 is communicated with the chamber A on the crank case side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocating compressor preferably used for compressing and discharging a gas such as air.

[0002]

2. Description of the Related Art Generally, a reciprocating compressor is used to compress and discharge a gas such as air, and when the gas is compressed to a high pressure, the pressure is increased stepwise. A reciprocating compressor is used.

A multistage reciprocating compressor of this type (for example, a two-stage reciprocating air compressor) has a crankcase,
A crankshaft rotatably provided on the crankcase; low-pressure side and high-pressure side cylinders mounted on the crankcase; low-pressure side and high-pressure side cylinder heads mounted on the cylinders; A low-pressure side piston and a high-pressure side piston that are reciprocally provided in each cylinder and define a compression chamber between each cylinder head, and a base end side is connected to the crankshaft, and a tip end side is connected to each It is composed of a connecting rod connected to the piston and an intermediate pipe connecting the discharge side of the low pressure side cylinder head to the suction side of the high pressure side cylinder head.

Further, at least the high-pressure side piston among the above-mentioned pistons is fitted with first and second piston rings and the like in order to prevent the pressure from the compression chamber from leaking to the crankcase side. ing.

This two-stage reciprocating air compressor is
When the crankshaft is rotationally driven by a drive source such as an electric motor, the piston reciprocates in the low-pressure side cylinder and the high-pressure side cylinder via a connecting rod connected to the crankshaft. As a result, the air sucked into the cylinder through the suction chamber of the cylinder head on the low pressure side is compressed in the cylinder and discharged from the discharge chamber into the intermediate pipe, and the compressed air is compressed into high pressure through the intermediate pipe. Side cylinder, and is re-compressed in the cylinder to be discharged as high-pressure compressed air. The compressed air discharged from the cylinder head on the high pressure side is stored in the air tank through the discharge pipe.

Since each piston ring seals between the compression chamber and the chamber on the crankcase side, the piston ring has an upper side (compression chamber side) and a lower side (crankcase side). A differential pressure is generated on the pistons, and the differential pressure at this time acts as a back pressure, whereby each piston ring is pressed against the inner surface (sliding surface) of the cylinder, thus ensuring sealing performance.

However, in the cylinder on the high pressure side, since compressed air from the low pressure side is supplied into the cylinder during the intake stroke of the piston, the upper pressure of the first piston ring located on the compression chamber side is the lower pressure. It may be temporarily smaller than that of the first piston ring, and the back pressure of the first piston ring may be reduced to be in a free state.

As a result, the first piston ring is separated from the cylinder, and the pressure on the compression chamber side acts as the upper pressure on the second piston ring located on the crankcase side (lower side). The pressure difference between the upper side pressure and the lower side pressure of the second piston ring becomes large, a large back pressure acts on the second piston ring, and the second piston ring is strongly pressed against the cylinder and wears early. I will end up.

Therefore, for example, a multi-stage compressor described in Japanese Patent Laid-Open No. 5-141344 (hereinafter referred to as other prior art).
Then, in order to prevent wear of the second piston ring,
The wall of the concave groove (ring groove) with which the lower surface of the first piston ring abuts is provided with a passage that communicates the concave groove with the inside of the crankcase (the chamber on the inner peripheral side of the piston). When the upper pressure of the ring becomes smaller than the lower pressure and the first piston ring is pushed up and is in the free state, the lower pressure is released to the crankcase side through the passage to reduce the lower pressure to the upper side. Less than pressure,
By pressing the first piston ring against the cylinder by the back pressure, the pressure on the compression chamber side is prevented from acting as the upper pressure on the second piston ring, and the pressure between the first piston ring and the second piston ring is prevented. The amount of wear is made approximately uniform.

[0010]

However, in the other prior art described above, since the passage is opened and closed by the first piston ring, the air sucked into the cylinder on the high pressure side in the suction stroke. When the pressure of is low, the force that presses the first piston ring into the passage is weak,
There is a problem that the sealing property of the passage is insufficient and the pressure in the compression chamber leaks to the crankcase side during the intake stroke, and it takes time to pressurize the compressed air to a desired pressure during the compression operation.

Further, when the pressure of the air sucked in the suction stroke is high, the force pressing the first piston ring against the passage is too strong and the sealing property of the passage becomes excessive, so that the cylinder,
There is a problem that the pressure in the space defined by the piston and each piston ring cannot be released to the crankcase side.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to surely open and close a communication hole that communicates the space defined by the cylinder, the piston and each piston ring with the inside of the crankcase. Thus, it is an object of the present invention to provide a reciprocating compressor capable of preventing early wear of the piston ring.

[0013]

In order to solve the above problems, a reciprocating compressor according to the present invention has a crankcase, a cylinder mounted on the crankcase, and a cylinder mounted on the crankcase. A cylinder head, and a piston that is reciprocally provided in the cylinder and defines a compression chamber between the cylinder head, and the piston is provided with a plurality of annular ring grooves on the outer peripheral side thereof. Piston rings that seal between the piston and the cylinder are inserted into the ring grooves.

A feature of the structure adopted by the invention of claim 1 is that the piston has a space portion located between the piston and the cylinder and defined between the piston rings. There is provided a communication hole for communicating with the inside and a pressure adjusting valve for adjusting the pressure in the space by opening and closing the communication hole.

According to the second aspect of the present invention, the communication hole allows the other ring groove of the ring grooves except the ring groove closest to the compression chamber side to communicate with the inner peripheral side of the piston. Is located on the bottom side of the ring groove and is bored in the radial direction of the piston, and the pressure adjusting valve is a thin plate valve that is attached to the inner peripheral side of the piston and that opens and closes the communication hole with a spring property. It is preferably constructed by the body.

[0016]

According to the structure of the invention of claim 1, the communication hole can be closed by the pressure regulating valve even when the suction pressure is low in the suction stroke, while the cylinder, the piston and the piston rings are defined even when the suction pressure is high. When the pressure in the created space becomes high, the pressure control valve can be opened to release the pressure in the space from the communication hole to the crankcase side, and the communication hole can be opened without affecting the pressure in the compression chamber. Can be opened and closed.

According to the second aspect of the present invention, the communication hole can be easily provided by forming the piston in the radial direction, and the pressure adjusting valve made of a thin plate-shaped valve body has a mounting space. Is small and can be easily mounted on the inner circumference side of the piston.

[0018]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 7 by taking an oilless two-stage reciprocating air compressor as an example of a reciprocating compressor.

First, FIGS. 1 to 5 show a first embodiment of the present invention.

In the figure, 1 is an air tank (not shown)
A crankcase 2 mounted on the above constitutes a main body of the reciprocating air compressor, and one end side of the crankcase 2 is a crankshaft rotatably disposed in the crankcase 1 via a bearing (not shown), The other end of the crankshaft 2 projects outside the crankcase 1, and a pulley 28 described later is attached to the projecting end. Also, crankcase 1
Is formed as a closed box whose upper side has a mountain shape by a pair of hypotenuses 1A, 1A.

Reference numeral 3 denotes a low-pressure side cylinder provided on the left oblique side 1A of the crankcase 1 in the figure. Inside the cylinder 3, there is a sliding surface 3A on which a piston 6 described later slides.

Reference numeral 4 denotes a cylinder head mounted on the cylinder 3 via a valve plate 5. Inside the cylinder head 4, a suction chamber and a discharge port located on the valve plate 5 and having a suction port 4A. Discharge chamber (not shown)
And are formed. Further, the valve plate 5 is provided with a suction hole for communicating the suction chamber with the inside of the cylinder 3 and a discharge hole for communicating the discharge chamber with the inside of the cylinder 3, and the suction valve is provided in the suction hole and the discharge hole is provided in the discharge hole. A discharge valve (none of which is shown) is provided so that it can be opened and closed. The construction and operation of the suction chamber, the discharge chamber, the discharge port, the suction hole, the discharge hole, the suction valve and the discharge valve of the valve plate 5 of the cylinder head 4 will be described later. , Discharge chamber 10B, discharge port 10D, suction hole 11A of valve plate 11,
The discharge hole 11B, the suction valve 12, and the discharge valve 13 are substantially the same.

Reference numeral 6 denotes a piston which is reciprocally inserted into the cylinder 3 and defines a compression chamber 7 between the piston and the valve plate 5, and the piston 6 and the cylinder 3 are provided on the outer peripheral side of the piston 6. A piston ring that hermetically seals between the sliding surface 3A and a rider ring that smoothly slides the piston 6 relative to the sliding surface 3A (neither shown),
The piston ring and rider ring are made of a material having self-lubricating property.

Reference numeral 8 denotes a connecting rod whose base end side is connected to the crankshaft 2 and whose tip end side is connected to the piston 6. The connecting rod 8 has its base end side pivoted by the crankshaft 2 so that the tip end side is connected. The piston 6 connected to the cylinder 3
Reciprocate inside.

On the other hand, reference numeral 9 indicates a cylinder on the high pressure side provided on the oblique side 1A of the crankcase 1 on the right side in the drawing, and inside the cylinder 9 is a sliding surface 9 on which a piston 14 described later slides.
A.

Reference numeral 10 denotes a cylinder head mounted on the cylinder 9 via a valve plate 11, and the cylinder head 1
As shown in FIG. 2, inside 0, a suction chamber 10A and a discharge chamber 10B are formed on the valve plate 11. Further, the cylinder head 10 is provided with a suction port 10C for sucking air into the suction chamber 10A and a discharge port 10D for discharging the compressed air in the discharge chamber 10B to the outside. On the other hand, the valve plate 11 has a suction hole 11A for communicating the suction chamber 10A with the inside of the cylinder 9, and the discharge chamber 1
A discharge hole 11B for communicating 0B with the inside of the cylinder 9 is bored, and a suction valve 12 is provided in the suction hole 11A, and a discharge hole 11B.
A discharge valve 13 is provided in the valve so that it can be opened and closed.

Reference numeral 14 denotes a piston that is reciprocally inserted in the cylinder 9 and defines a compression chamber 15 between the valve plate 11 and the cylinder. The piston 14 includes a cylinder portion 14A and a lid portion 14B. It is formed into a shape and is connected to a connecting rod 25 to be described later via the cylindrical portion 14A.

16 is located on the side of the compression chamber 15 and is located on the piston 1
No. 4, a first ring groove formed on the outer peripheral side of the cylindrical portion 14A, 1
Reference numeral 7 denotes a second ring groove formed on the lower side of the first ring groove 16, and each of the ring grooves 16 and 17 is formed as an annular rectangular groove having a rectangular cross section as shown in FIG. ing.

Reference numerals 18 and 18 denote a pair of annular projections provided so as to project inward from the inner circumference of the cylindrical portion 14A of the piston 14, and the spaces between the respective annular projections 18 are located on the inner circumference side of the second ring groove 17. It is a valve body mounting groove 19 in which a pressure adjusting valve 24, which will be described later, is mounted.

The pistons 20 and 20 are arranged so that the second ring groove 17 and the valve body mounting groove 19 communicate with each other as shown in FIG.
4 shows two communication holes formed in the cylindrical portion 14A in the radial direction, and each communication hole 20 communicates a space S described later with a chamber A on the crankcase 1 side.

Reference numeral 21 indicates a first piston ring inserted into the first ring groove 16, and 22 indicates a second piston ring inserted into the second ring groove 17, respectively. 22 receives the pressure of the compressed air in the compression chamber 15 as a back pressure on the inner peripheral surface thereof, thereby bringing the outer peripheral surface into close contact with the sliding surface 9A of the cylinder 9 to obtain a sealing property. And each piston ring 21,
22 is formed of, for example, a material having a self-lubricating property.

Reference numerals 23 and 23 denote the cylinder portion 1 of the piston 14.
Two rider rings are provided on the outer peripheral side of 4A, and each rider ring 23 allows the piston 14 to smoothly slide on the sliding surface 9A. And each rider ring 23
Is formed of a material having a self-lubricating property, like the piston rings 21 and 22.

Reference numeral 24 denotes a pressure adjusting valve which is located on the inner peripheral side of the cylindrical portion 14A of the piston 14 and is fitted in the valve body fitting groove 19. The pressure adjusting valve 24 is formed by bending a strip-shaped thin plate into a C-shape. The valve portions 24A, 24A on both ends thereof are formed into the communication hole 2
It is arranged in the valve body mounting groove 19 so as to close 0 and 20. The pressure adjusting valve 24 has a spring property in the radially outward direction (a direction in which the diameter is expanded), and the spring force is defined by the sliding surface 9A of the cylinder 9, the piston 14 and the piston rings 21, 22. When the pressure in the formed space S becomes higher than the pressure in the compression chamber 15 in the suction stroke, the valves are opened as shown in FIGS. 4 and 5, and the piston rings 21 and 22 are optimally adapted to the sliding surface 9A. The valve is set to close when the back pressure that is pressed by a certain pressing force reaches a pressure that acts.

The base end of 25 is connected to the crankshaft 2,
The tip side shows a connecting rod connected to the piston 14, and the connecting rod 25 reciprocates the piston 14 connected to the tip side in the cylinder 9 when the base side is swung by the crankshaft 2. Is.

Reference numeral 26 is a discharge port of the low pressure side cylinder head 4 and a suction port 10C of the high pressure side cylinder head 10.
An intermediate pipe provided between the discharge pipe 10 and the discharge pipe 10D is connected to the discharge port 10D of the cylinder head 10 on the high pressure side, and the other end of the discharge pipe 27 is connected to an air tank.

Reference numeral 28 denotes a pulley mounted on the protruding end side of the crankshaft 2, and the pulley 28 is connected via a belt to an electric motor (not shown) serving as a rotation source. When the electric motor is driven to rotate, the crankshaft 2 is rotated.

The two-stage reciprocating air compressor according to this embodiment has the above-mentioned structure, and when the crankshaft 2 is rotationally driven by the electric motor, the cylinder 3 on the low pressure side is driven.
In the inside, the air sucked into the compression chamber 7 by the reciprocating motion of the piston 6 is discharged to the intermediate pipe 26, and is supplied through the intermediate pipe 26 into the compression chamber 15 on the high pressure side at an intermediate pressure. Then, the compressed air sucked into the compression chamber 15 is
It is recompressed by the piston 14, discharged through the discharge pipe 27 into the air tank, and stored in the air tank.

Further, during the compression operation, in the high pressure side cylinder 9, the compressed air in the compression chamber 15 gradually leaks from the gap of the first piston ring 21 to the space S side and is accumulated in the space S. As a result, the pressure in the space S rises, and the lower pressure of the first piston ring 21 (pressure in the space S) may become higher than the upper pressure (pressure in the compression chamber 15) in the suction stroke.

However, in this embodiment, the lower pressure of the first piston ring 21, that is, the pressure of the space S, is the compression chamber 15
When the pressure becomes larger than this, each valve portion 24A of the pressure regulating valve 24 is opened by this pressure as shown by the chain double-dashed line in FIG. 4, and the compressed air in the space S is indicated by the arrow in FIG. As described above, the pressure in the space S can be quickly reduced because it is made to flow out into the chamber A on the crankcase 1 side through each communication hole 20.

In addition, the compressed air in the space S is connected to each communication hole 2
From 0 to the chamber A on the crankcase 1 side, and when the pressure in the space S comes to act as a back pressure for optimally pressing the piston rings 21 and 22 against the sliding surface 9A of the cylinder 9, Since each valve portion 24A of the pressure regulating valve 24 is closed by the spring force to shut off each communication hole 20, the sliding surface 9A of the cylinder 9 is constantly pressed with the optimum pressing force for each piston ring 21, 22. Can be pressed against.

Further, by opening / closing each communication hole 20 with the pressure adjusting valve 24, each communication hole 20 can be surely shut off even if the pressure of the air sucked in the suction stroke is low, and the suction hole is sucked in the suction stroke. Even if the air pressure is high,
Each communication hole 20 can be opened and closed by the pressure of the space S regardless of the pressure of the compression chamber 15.

Thus, according to this embodiment, the cylinder 9
Sliding surface 9A, piston 14 and each piston ring 2
The pressure in the space S defined by 1 and 22 is adjusted by the pressure adjusting valve 24.
Since the back pressure acting on the first piston ring 21 and the second piston ring 22 can be made substantially uniform, the second piston ring 22 can be adjusted to a desired pressure.
Only this can prevent premature wear. Moreover, in this embodiment, by providing the pressure regulating valve 24 on the inner peripheral side of the piston 14 to open and close each communication hole 20, compression leakage to the chamber A on the crankcase 1 side due to insufficient sealing of each communication hole 20. Can be prevented, the pressure in the compression chamber 15 can be quickly increased, and even if the pressure in the compression chamber 15 becomes high, the communication holes 20 can be communicated with the chamber A on the crankcase 1 side. The inside of the space S can be maintained at an appropriate pressure, and the life of each piston ring 21, 22 can be further extended.

By adjusting the pressure of the space S by the pressure adjusting valve 24, the piston rings 21, 2 are
Since the back pressure acting on 2 can be optimized, the sealability between the sliding surface 9A of the cylinder 9 and the piston 14 can be further improved, and the compression leakage can be suppressed to the reciprocating compression. The volumetric efficiency of the machine can be improved.

Further, each communication hole 20 is provided by piercing in the radial direction of the cylinder portion 14A of the piston 14, and the pressure regulating valve 24 is formed by bending a strip-shaped thin plate into a C-shape to form the cylinder of the piston 14. Since it is mounted in the valve body mounting groove 19 provided on the inner peripheral side of the portion 14A, each communication hole 20 can be easily provided by performing a drilling process in the radial direction of the cylindrical portion 14A of the piston 14. By mounting the pressure adjusting valve 24 in the valve body mounting groove 19 in a reduced diameter state, the pressure adjusting valve 24 can be easily mounted.

Next, FIG. 6 shows a second embodiment of the present invention. The characteristic feature of this embodiment is that two pressure regulating valves are provided for three piston rings. In this embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 31 denotes a piston according to this embodiment, which is substantially the same as the piston 14 described in the first embodiment, and is formed of a tubular portion 31A and a lid portion 31B in a tubular shape with a lid. Has been done.

32 is located on the side of the compression chamber 15 and is located on the piston 3
The first ring groove formed on the outer peripheral side of the first cylindrical portion 31A, 3
Reference numeral 3 indicates a second ring groove formed below the first ring groove 32, and 34 indicates a third ring groove formed below the second ring groove 33, respectively. Groove 32,
33 and 34 are formed as annular square grooves having a rectangular cross section.

Reference numerals 35, 35, and 35 denote the cylindrical portion 3 of the piston 31.
Three annular projections projecting inward from the inner circumference of 1A, and the spaces between the respective annular projections 35 are located on the inner circumference side of the second ring groove 33 to form the first valve body mounting groove 36, Third ring groove 3
The second valve body mounting groove 37 is located on the inner peripheral side of the groove 4.

Reference numeral 38 is a first communication hole radially formed in the cylindrical portion 31A of the piston 31 so as to connect the second ring groove 33 and the first valve body mounting groove 36, and 39 is a third communication hole. The 2nd communicating hole bored in the cylinder part 31A of the piston 31 in the radial direction so that the ring groove 34 and the 2nd valve body mounting groove 37 may communicate is shown, and the 1st communicating hole 38 is a space part mentioned later. S1 communicates with the chamber A on the crankcase 1 side, and the second communication hole 39 communicates with a space S2 described later and the chamber A on the crankcase 1 side.

Reference numeral 40 is a first piston ring inserted into the first ring groove 32, 41 is a second piston ring inserted into the second ring groove 33, and 42 is a third ring groove 3.
4 shows a third piston ring inserted into the piston 4, and the piston rings 40, 41, 42 seal between the sliding surface 9A of the cylinder 9 and the piston 31.

Reference numeral 43 denotes a first pressure adjusting valve which is located on the inner peripheral side of the cylindrical portion 31A of the piston 31 and is mounted in the first valve body mounting groove 36, and 44 is positioned on the inner peripheral side of the cylindrical portion 31A of the piston 31. The second pressure adjusting valve mounted in the second valve body mounting groove 37 is shown respectively, and the first pressure adjusting valve 43 adjusts the pressure in the space S1 through the first communication hole 38. The second pressure control valve 44 controls the pressure in the space S2 through the second communication hole 39. Each of the pressure adjusting valves 43 and 44 is formed by bending a strip-shaped thin plate into a C shape, and its spring force is set to be substantially the same as that of the pressure adjusting valve 24 according to the first embodiment.

Thus, even in this embodiment having the above-mentioned structure, the same operational effect as that of the first embodiment can be obtained. In particular, the present embodiment is the same as the first embodiment. It is suitable for use in a compressor that discharges compressed air having a pressure higher than that of the compressor described in (1).

In each of the above embodiments, each pressure regulating valve 2
Although it has been described that the 4, 43, and 44 are formed to be curved in a C shape, for example, as in a modification shown in FIG. The engaging protrusions 51A and 51A may be formed. In this case, when the pressure adjusting valve 51 is attached to the piston, the pressure adjusting valve 51 is attached by engaging a jig with each engaging protrusion 51A. The diameter can be easily reduced, and the mounting work can be further facilitated.

In each of the above-mentioned embodiments, a two-stage reciprocating air compressor is used as an example of the reciprocating compressor.
It may be applied to a multi-stage reciprocating compressor of three stages or more, and in this case, a communication hole and a pressure adjusting valve may be provided in the second and third stages.

Further, even when two or more reciprocating compressors are connected in series, the piston of the high-pressure side compressor may be provided with a communication hole and a pressure adjusting valve.

On the other hand, the present invention may be applied to a refueling type multistage reciprocating compressor in which the crankcase is filled with lubricating oil.

[0057]

As described in detail above, according to the first aspect of the present invention, a communication hole for communicating the space defined by the cylinder, the piston and each piston ring with the inside of the crankcase is provided, and the communication is performed. By providing a pressure adjusting valve for adjusting the pressure in the space through the hole, the communication hole can be closed by the pressure adjusting valve even when the pressure in the compression chamber is low, while
Even when the pressure in the compression chamber is high, when the pressure in the space defined by the cylinder, piston and each piston ring becomes high, the pressure control valve is opened to release the pressure in the space from the communication hole to the crankcase side. Therefore, it is possible to open and close the communication hole without being affected by the pressure of the compression chamber, and it is possible to reliably prevent the opening and closing of the communication hole and extend the life of each piston ring. Moreover,
By adjusting the pressure in the space with the pressure control valve, the back pressure acting on each piston ring can be optimally maintained, so the sealability between the cylinder and piston can be improved, and compression leakage can be prevented. Can be suppressed and the volume efficiency of the reciprocating compressor can be improved.

According to the second aspect of the invention, the communication hole can be easily provided by forming the piston in the radial direction, and the pressure adjusting valve made of a thin plate-shaped valve body has a mounting space. Is small and can be easily attached to the inner circumference of the piston, which improves workability during machining and assembly work, and prevents the piston from increasing in size.
The whole can be configured compactly.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an oil-free two-stage reciprocating air compressor according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of essential parts showing a cylinder, a piston and the like on the high pressure side in FIG.

FIG. 3 is a vertical cross-sectional view showing an enlargement of a portion indicated by an arrow a in FIG.

FIG. 4 is a lateral cross-sectional view showing a cylinder, a piston, etc. in an enlarged manner from the direction of IV-IV shown in FIG.

FIG. 5 is a vertical cross-sectional view showing the opened state of the pressure regulating valve at the same position as in FIG.

FIG. 6 is a vertical sectional view showing a piston, a piston ring, a pressure adjusting valve and the like according to a second embodiment of the present invention.

FIG. 7 is an external perspective view showing a pressure regulating valve according to a modified example of the present invention.

[Explanation of symbols]

 1 Crankcase 3 Low Pressure Side Cylinder 4,10 Cylinder Head 6,14,31 Piston 7,15 Compression Chamber 9 High Pressure Side Cylinder 10A Suction Chamber 10B Discharge Chamber 10C Suction Port 10D Discharge Port 16,32 First Ring Groove 17 , 33 Second ring groove 20 Communication hole 21, 40 First piston ring 22, 41 Second piston ring 24, 51 Pressure adjusting valve 26 Intermediate pipe 34 Third ring groove 38 First communication hole 39 Second Communication hole 42 Third piston ring 43 First pressure adjusting valve 44 Second pressure adjusting valve A Crankcase side chamber S, S1, S2 Space section

Claims (2)

[Claims] 1. A compression chamber between a crankcase, a cylinder mounted on the crankcase, a cylinder head mounted on the cylinder, and a cylinder head reciprocally provided in the cylinder. And a plurality of annular ring grooves are provided on the outer peripheral side of the piston, and piston rings for sealing between the piston and the cylinder are inserted into the respective ring grooves. In the reciprocating compressor, the piston has a communication hole for communicating a space defined between the piston and the cylinder and defined between the piston rings with each other in the crankcase, and the communication hole. A reciprocating compressor, comprising: a pressure adjusting valve for adjusting the pressure in the space by opening and closing. 2. The communication hole is located on the bottom side of the ring groove so that other ring grooves of the ring grooves except the ring groove closest to the compression chamber side communicate with the inner peripheral side of the piston. 3. The pressure regulating valve is a thin plate-shaped valve body that is attached to the inner peripheral side of the piston and opens and closes the communication hole with a spring property. The reciprocating compressor described in.